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Mono- and binuclear cobalt hydrides Ng, Jesse B. 1990

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MONO- AND BINUCLEAR COBALT HYDRIDES by Jesse Burton John NG CHEONG CHUNG B.Sc, Queen's University, 1985 M.Sc, Queen's University, 1986 A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in THE FACULTY OF GRADUATE STUDIES Department of Chemistry We accept this thesis as conforming to the required standard The University of British Columbia July 1990 right © Jesse Burton John NG CHEONG CHUNG, July 1990 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver, Canada Date AuGmXT JZZ , /9«?0-DE-6 (2/88) ii Abstract The homogeneous hydrogenation of arenes with functional groups was studied with allylcobalt complexes containing the bulky chelating diphosphines dippp (1,3-bis(diisopropylphosphino)propane and dippcyp (rran.y-(±)-l,2-bis(diisopropylphos-phino)cyclopentane). The results indicated that these catalyst precursors were unsuitable for the hydrogenation reactions, being too sensitive to the nature of the substrate. From these hydrogenation reactions, the intermediates ( T ) 5 -cyclohexadienyl)Co(dippcyp) (10) and (ri4-2-methoxynaphthalene)Co(H)(dippcyp) (11) were isolated and structurally characterized, thus providing some insight into the mechanism of the hydrogenation reaction. The production of binuclear hydrides such as [(dippp)CoH2]2 (4) and [(dippcyp)CoH.2]2 (9) was observed to lead to the end of the catalysis. An X-ray structural characterization of the blue hydride [(dippp)CoH2]2 (4) showed that in the solid state it is binuclear. Although the complex is diamagnetic in the solid state (6-280 K), in solution its paramagnetic behaviour could only be attributed to an equilibrium with a second species proposed to be mononuclear, (dippp)CoH2. In addition, a cyclic voltammogram of the complex in solution indicated that the predominant species still was the binuclear compound [(dippp)CoH2]2 (4). One of the syntheses of [(dippp)CoH.2]2 (4) gave a product identified as (dippp)CoH3 (5). Based on variable-temperature spin-lattice relaxation time (Ti) measurements and an electrochemical study, this red hydride complex appeared to contain an T ] 2 - H 2 ligand. The relationship of this complex with the blue hydride iii apparently involves the mononuclear species, (dippp)CoH.2. Independent pathways led to the formation of both the blue and red hydrides, and these pathways are discussed in terms of possible mechanisms. iv To my parents, for their love and support throughout all these years V The Road not taken Two roads diverged in a yellow road And sorry that I could not travel both And be one traveler, long I stood And looked down one as far as I could To where it bent in the undergrowth; Then took the other, as just as fair, And having perhaps the better claim, Because it was grassy and wanted wear; Though as for that the passing there Had worn them really about the same, And both that morning equally lay In leaves no step had trodden black. Oh, I kept the first for another day! Yet knowing how way leads on to way, I doubted if I should ever come back. I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I-I took the one less traveled by, And that has made all the difference. Robert Lee Frost (1875 - 1963) vi Contents Page Abstract ii Dedication iv Poem v Contents vi List of Figures xi List of Tables xiii Abbreviations xiv Acknowledgements xvii Foreword xviii Chapter 1 - Introduction 1 1.1 Hydrogenation of arenes 1 1.2 Cobalt complexes as arene hydrogenation catalysts 2 1.2.1 The allylcobalt phosphite system 2 1.2.2 The allylcobalt diphosphine system 4 1.3 From metal hydride to metal-T|2-dihydrogen complexes 4 1.4 T|2-dihydrogen complexes 7 1.5 Scope of present work 10 1.6 References 12 Chapter 2 - Cobalt-phosphine complexes 16 2.1 Introduction 16 2.2 Preparation and characterization of (dippp)CoCl2 (1), [(dippp)Co]2(ti-Cl)2 (2), and [(dippe)Co]2(u.-Cl)2 (2') 16 2.3 Solid state structure of [(dippp)Co]2(p>Cl)2 (2) 21 vii 2.4 Synthesis of allylcobalt complexes 23 2.4.1 Synthesis of (Ti3-C3H5)Co(dippp) (3) 23 2.4.2 Preparation and characterization of (n3-CH2C6H5)Co(dippp) (6) 24 2.4.3 Solid state structure of (n3-CH2C6H5)Co(dippp) (6) 26 2.4.4 Synthesis of r -^allylcobalt complexes using ri3-cyclooctenyl-l,5-cyclooctadienecobalt(I) 30 2.5 References 31 Chapter 3 - Hydrogenation of arenes 34 3.1 Introduction 34 3.2 Phosphine ligands in arene hydrogenation 35 3.3 Hydrogenation results 37 3.4 Isolation of the intermediates (rj5-cyclohexadienyl)Co(dippcyp) (10) and (T]4-2-methoxynaphthalene)Co(H)(dippcyp) (11) 39 3.4.1 Characterization of (Tj4-2-methoxynaphthalene) Co(H)(dippcyp) (11) 42 3.4.2 Solid state structure of (n4-2-methoxynaphthalene) Co(H)(dippcyp) (11) 43 3.4.3 The intermediate (Ti5-cyclohexadiene)Co(dippcyp) (10) 48 3.4.4 Solid state structure of (rj5-cyclohexadiene) Co(dippcyp) (10) 49 3.5 The end of the catalytic cycle 53 3.6 Discussion 54 3.7 References 56 Chapter 4 - The binuclear cobalt complex [(dippp)CoH2]2 59 4.1 Introduction 59 4.2 Synthesis of cobalt-hydride complexes 60 viii 4.3 Characterization of [(dippp)CoH2]2 (4) and [(dippehCoH^k (4') 64 4.3.1 Nmr spectra of [(dippp)CoH2]2 (4) and [(dippe)CoH2]2 (4') 65 4.3.2 UV-visible spectroscopy of [(dippp)CoH2]2 (4) 69 4.3.3 Electrochemical measurements on [(dippp)CoH2]2 (4) 71 4.3.4 Magnetic susceptibility measurements on [(dippp)CoH2]2 (4) 75 4.3.5 Infrared spectroscopy 77 4.3.6 X-ray analysis of [(dippp)CoH2]2 (4) 79 4.4 Reactivity 84 4.5 Discussion 88 4.6 References 90 Chapter 5 - The mononuclear cobalt complex (dippp)CoH3 93 5.1 Introduction 93 5.2 Nmr spectroscopy and Ti measurements 94 5.3 Fluxionality and a trihydrogen intermediate 98 5.4 Infrared data 100 5.5 Electrochemical measurements on (dippp)CoH3 (5) 102 5.6 Proposed mechanism of formation of the red hydride 104 5.7 Reactivity of (dippp)CoH3 (5) 108 5.8 Discussion 111 5.9 References 114 Chapter 6 - Conclusions 116 6.1 Discussion 116 6.2 Future work 113 6.3 References 118 Chapter 7 - Experimental Section 119 ix 7.1 General Procedures 119 7.2 Infrared spectra 119 7.3 UV-visible spectra 119 7.4 NMR spectra 120 7.5 Magnetic susceptibility measurements 120 7.6 Molecular weight measurements 121 7.7 Electrochemical measurements 121 7.8 Hydrogenation reactions 122 7.9 Chemicals 123 7.10 Syntheses 124 7.10.1 l,3-bis(diisopropylphosphino)propane (dippp) 124 7.10.2 trans-(±)-1,2-bis(diisopropylphosphino) cyclopentane (dippcyp) 125 7.10.3 Hydrogenation substrates 127 7.10.4 2-methoxyethoxymethoxynaphthalene 127 7.10.5 2-methoxymethylfuran 128 7.10.6 (dippp)CoCl2 (1) 129 7.10.7 [(dippp)Co]2(u-Cl)2 (2) 130 7.10.8 (Ti3-C3H5)Co(dippp) (3) 131 7.10.9 [(dippp)CoH2]2 (4) 132 7.10.10 [(dippp)]CoH3 (5) 134 7.10.11 (Ti3-CH2C6H5)Co(dippp) (6) 135 7.10.12 [(dippp)Co]2(Lt-ri3:r13-C6H6) (7) 137 7.10.13 (Ti3-C8Hi3)Co(dippcyp) (8) 138 7.10.14 [(dippcyp)CoH2]2 (9) 139 7.10.15 (ri5-Cyclohexadienyl)Co(dippcyp) (10) 139 7.10.16 (Ti4-2-methoxynaphthalene)Co(H)(dippcyp) (11) 141 X 7.10.17 (dippp)Co(H)(CO)2 (12) 142 7.10.18 [(dippp)CoH]2»(2,3-dimethyl-l,3-butadiene) (13) 143 7.10.19 Cn3-C8Hi3)Co(dippp) (14) 145 7.10.20 [(dippe)Co]2Gi-Cl)2 (2') 145 7.10.21 (T|3-C8Hi3)Co(dippe) (3') and [(dippe)CoH2]2 (4') 146 7.10.22 (dippcyp)CoCl2 (5') 147 7.11 Acknowledgements for experimental expertise 148 7.12 References 150 Appendix 152 Vita 197 xi List of Figures Page Fig. 2-1 (a) *H NMR spectrum (300 MHz) of [(dippe)Co]2(Lt-Cl)2 (2')-(b) !H NMR spectrum (300 MHz) of [(dippp)Co]2(Lt-Cl)2 (2). 19 Fig. 2-2 (a) Chem 3D™ view of [(dippp)Co]2(Li-Cl)2 (2). (b) Stereoview of the same molecule. 22 Fig. 2-3 *H NMR spectrum (300 MHz) of (ri3-CH2C6H5)Co(dippp) (6). 25 Fig. 2-4 (a) Selected Chem 3D™ view of (r|3-CH2C6H5)Co(dippp) (6). (b) Stereoview of (Ti3-CH2C6H5)Co(dippp) (6). 27 Fig. 3-1 !H NMR spectrum (400 MHz) of (Ti4-CioH7OMe)Co(H) (dippcyp) (11). 42 Fig. 3-2 The structure of (r|4-CioH7OMe)Co(H)(dippcyp) (11) in the solid state depicting T\4 bonding of the unsubstituted ring of the arene ligand to cobalt. 44 Fig. 3-3 (a) Selected Chem 3D™ view of (ri4-2-methoxynaphthalene) Co(H)(dippcyp) (11) showing the result of coordination on the arene ligand. (b) Stereoview of the same molecule. 45 Fig. 3-4 lH NMR spectrum (400 MHz) of (T|5-cyclohexadienyl) Co(dippcyp) (10) showing distinct resonances for the diastereotopic ring protons. 49 Fig. 3-5 (a) Selected Chem 3D™ view of (T]5-cyclohexadienyl)Co (dippcyp) (10). (b) Stereoview of the same molecule. 50 Fig. 4-1 *H NMR spectrum (400 MHz) of the hydride mixture obtained from the hydrogenation of (r|3-CH2C6H5)Co(dippp) (6). 62 Fig. 4-2 (a) 31P{ !H} NMR spectrum (121.4 MHz) of the hydride mixture formed by the reaction of (dippp)CoCl2 (1) with xii n-BuLi under H2. (b) Variable temperature 31p{lH} nmr spectra of the hydride mixture formed by the hydrogenation of (n3-C3H5)Co(dippp) (3). 66 Fig. 4-3 (a) lH NMR spectrum (300 MHz) of the blue hydride [(dippp)CoH2]2 (4) at 20°C. (b) *H NMR spectrum (400 MHz) of the blue hydride [(dippp)CoH2]2 (4) at -95°C. 67 Fig. 4-4 (a) *H NMR spectrum (300 MHz) of the purple hydride [(dippe)CoH2]2 (4') at 20°C. The spectrum of the purple hydride at -95°C. 68 Fig. 4-5 UV-visible spectra of [(dippp)CoH2]2 (4) at different concentrations in hexanes. 70 Fig. 4-6 Cyclic voltammogram of [(dippp)CoH2]2 (4) at 20°C. 72 Fig. 4-7 [(dippp)CoH2]2 (4): (a) redox couples C/F and D/E. (b) redox couples A/H and B/G. 73 Fig. 4-8 [(dippp)CoH2]2 (4): temperature dependence of ueff. 76 Fig. 4-9 Infrared spectrum of the blue hydride [(dippp)CoH2]2 (4). 78 Fig. 4-10 Solid state structure [(dippp)Co]2(H)(u-H)3 (4) at -155°C. 80 Fig. 4-11 (a) Selected Chem 3D™ view of the blue hydride [(dippp)Co]2 (H)(|i-H)3 (4) at 21°C. (b) Stereoview of the same molecule. 81 Fig. 4-12 *H NMR spectrum (400 MHz) of [(dippp)Co]2(H)2« (2,3-dimethyl-l,3-butadiene) (13). 86 Fig. 5-1 *H NMR spectrum (300 MHz) of (dippp)CoH3 (5). 94 Fig. 5-2 Plot of temperature dependence of Ti for (dippp)CoH3 (5) 97 Fig. 5-3 (a) Infrared spectrum of (dippp)CoH3 (5). (b) Infrared spectrum of (dippp)CoD3. 10: Fig. 5-4 Cyclic voltammogram of the red hydride (dippp)CoH3 (5) at -20°C in THF. 103 xiii List of Tables Page Table 2-1 Selected bond distances (A) with estimated standard deviations in [(dippp)Co]2(u-Cl)2 (2) 21 Table 2-2 Selected bond angles (deg) with estimated standard deviations in [(dippp)Co]2(Li-Cl)2 (2) 21 Table 2-3 Selected bond distances (A) with estimated standard deviations in (Ti3-CH2C6H5)Co(dippp) (6) 29 Table 2-4 Selected bond angles (deg) with estimated standard deviations in (Ti3-CH2C6H5)Co(dippp) (6) 29 Table 3-1 Hydrogenation results 38 Table 3-2 Selected bond distances (A) with estimated standard deviations in (Ti4-Ci0H7OMe)Co(H)(dippcyp) (11) 46 Table 3-3 Selected bond angles (deg) with estimated standard deviations in (Ti4.Ci0H7OMe)Co(H)(dippcyp) (11) 47 Table 3-4 Selected bond distances (A) with estimated standard deviations in (Ti5-C6H7)Co(dippcyp) (10) 51 Table 3-5 Selected bond angles (deg) with estimated standard deviations in (r|5-C6H7)Co(dippcyp) (10) 51 Table 4-1 [(dippp)CoH2]2 (4) - Electrochemical data for the redox couples A/H, B/G, C/F and D/E 71 Table 4-2 Selected bond distances (A) with estimated standard deviations in [(dippp)CoH2]2 (4) at 21° and -155°C 82 Table 4-3 Selected bond angles (deg) with estimated standard deviations in [(dippp)CoH2]2 (4) at 21° and -155°C 82 Table 5-1 Hydrogenation products with (dippp)CoH3 (5) 109 xiv Abbreviations A Ampere A Angstrom anh. anhydrous atm atmosphere BM Bohr Magneton bp boiling point (°C) n-Bu, Bun butyl, -C4H9 t-Bu, Bu1 tertiary butyl, -C(CH 3) 3 °C degree Celsius calcd. calculated COD 1,5-cyclooctadiene COSY correlation spectroscopy (NMR) CV * cychc voltammogram CW continuous wave Cy cyclohexyl,-CgHn dec. decomposition 5 bending mode of vibration (IR) 5 chemical shift (NMR) Avi/2 peak width at half height dil. dilute dippp 1,3-bis(diisopropylphosphino)propane dippe 1,2-bis(diisopropylphosphino)ethane dippcyp trans-(±)-1,2-bis(diisopropylphosphino)cyclopentane DME 1,2-dimethoxyethane AEp separation in peak potentials (CV) e electron E 0 ' formal reduction potential (CV) E p a anodic peak potential (CV) E p c cathodic peak potential (CV) ESR electron spin resonance Et ethyl,-C2H5 XV FT Fourier transform GC gas chromatography Hz hert^  ipa peak current at anode (CV) ipc peak current at cathode (CV) IR infrared J scalar nuclear spin-spin coupling constant (NMR) K Kelvin L litre M mole per litre m metre Me methyl, - C H 3 ML n metal M surrounded by n neutral unidentate ligands L in a transition metal complex MO molecular orbital mol mole mp melting point (°C) MS mass spectroscopy |iA microampere (10"6A) M-eff effective magnetic moment mV millivolt (lO'3 V) min rninimum v scan rate (CV) v stretching mode of vibration (IR) NMR nuclear magnetic resonance o ortho p para Ph phenyl, -C6H5 ppm parts per million i-Pr, Pr1 isopropyl, -CH(CH 3) 2 psi pound per square inch pyr pyridine R, R', R1, etc. substituent (usually implies alkyl) Ra-Ni Raney Nickel RT room temperature reff effective bond length xvi s second sat. saturated SCE standard calomel electrode SQUID superconducting quantum interference device T temperature Ti spin-lattice relaxation time (NMR) THF tetrahydrofuran TMS tetramethylsilane TON turnover number Ts para-toluenesulphonyl, P-CH3C6H4SO2-UV ultraviolet V Volt VIS, vis visible xvii Acknowledgements Over the past four years at UBC, I have had the good fortune of working alongside one fine group of people. I wish to acknowledge their constant support and friendship, without which working on this project would have been very difficult indeed. Among them are: Prof. Mike Fryzuk, my research supervisor for total support and his never-ending enthusiasm in the quest for knowledge; Dr. David J. Berg, for tremendous logical insight especially during his stay in our laboratory, and during the writing of this thesis; Drs. George Richter-Addo and Patrick (Paco) Paglia, Guy Clentsmith and David McConville, for many helpful comments and suggestions while proof-reading the thesis; Drs. Brian Lloyd and Craig Montgomery, and Doug Gin, for their contribution to the project in 1987 and 1988; Dr. Pierre Giguere, for many practical suggestions about experimental organic chemistry; the staff of the mechanical shop, especially Brian Snapkauskas, for his friendship and good advice. Finally, my warmest thanks go to my very close and personal friend, Bobbi (Schram) Massey, for being so spontaneous and unselfish in offering her help in my darkest moments; she is indeed one wonderful and irreplaceable friend. xviii Foreword "Cobalt - from Kobold, the German word for "demon": so-called by miners in part because they believed that goblins had substituted it for silver, and in part because of the harmful arsenic and sulphur with which it was usually combined." Roald Hoffmann (1981 Nobel Prize winner in Chemistry) once suggested that every thesis should contain a section which can be understood by a wider audience.1 The following is an attempt at describing the contents of this thesis in words which a non-scientific person.may understand. This thesis is a study of the chemistry of a selected number of cobalt compounds. Cobalt is a metal also known as a transition element. The chemistry of transition metals (other examples include copper, nickel and iron) is largely concerned with the chemistry of coordination compounds or complexes?- The number of possible coordination compounds in chemistry is almost infinite, as present-day research workers prepare many new complexes every day. A coordination compound or complex is formed when molecules (e.g. water) are bound to the metal via a coordinate bond; an example is haemoglobin, the iron complex which is a carrier of oxygen in blood. These molecules bound to the metal are often called ligands. Among commonly encountered ligands in transition metal chemistry are phosphines. They do not normally participate in chemical reactions involving the complex, but provide the right environment around the metal so that certain kinds of reactions are possible. xix One aim of this thesis was to synthesize molecules as they occur in nature. For example, steroids are naturally-occurring substances which are difficult to synthesize in a laboratory, because they contain groups of molecules joined together in a unique fashion. A good analogy is a jig-saw puzzle: there is only one solution when all the pieces fit together. However, one can control the specificity of chemical reactions necessary to synthesize one such steroid molecule by using a transition metal complex as a template or catalyst. Just like our body metabolism is regulated by biological catalysts called enzymes, transition metal complexes can be modified, usually by changing the ligands, so that reactions proceed in a certain way only. The catalytic reaction studied in this thesis is hydrogenation, that is, adding extra hydrogen atoms to other molecules. Unfortunately, using cobalt-phosphine complexes as catalysts to make the reaction proceed to a predetermined product was not very successful because of low product yields. The cobalt-phosphine catalysts became deactivated quickly under the conditions of the experiment to give cobalt-phosphine-hydride complexes. One of these complexes has been studied in detail because of its recurrence in all hydrogenation experiments. In the solid state, it has a binuclear structure, consisting of two cobalt centres to which four hydrogen atoms and two phosphine molecules are bound. Some of the complex dissociates in solution, to give mononuclear species, i.e. compounds containing one cobalt centre, two hydrogen atoms and one phosphine molecule. Thus, an equilibrium between the two cobalt compounds is established in solution. During the study of the binuclear cobalt compound previously mentioned, a new mononuclear cobalt-phosphine-hydride complex was synthesized. Its structure consists of one cobalt centre to which one phosphine molecule and three hydrogen atoms are bound. The arrangement of the hydrogen atoms in this cobalt compound is somewhat unusual, but it appears that these three cobalt compounds are related to one another. XX The initial aim of a thesis is rarely achieved, largely because research is never predictable. This thesis will serve as background material for future researchers who wish to continue along the same path; with the wealth of new and useful information gleaned from it, they can build, and knowing the negative results I have faced, they can devise alternative paths. References: 1. Hoffmann, R. Amer. Sci. 1987, 75, 418. 2. Nicholls, D. Complexes and First-Row Transition Elements, The MacMillan Press Ltd., London; 1974, p 1. 6 This thesis was produced on an Apple® Macintosh™ SE personal computer using the word processing software Microsoft® Word v. 4.0, and the graphics packages Chem 3D™ and ChemDraw™ 2.1.3. The whole document was printed on an Apple® LaserWriter®. \ Chapter 1 Introduction 1 CHAPTER 1 Introduction 1.1 - Hydrogenation of arenes The homogeneous, catalytic hydrogenation of aromatic rings still remains a challenge despite the work reported in the literature1 (Equation 1-1). This is largely because forcing conditions2'3*4 and poor turnovers have limited the applicability of the known soluble catalysts used, in contrast to conventional heterogeneous systems such as Rh/C or Pd/C.5 (Eqn 1-1) The most efficient catalytic systems claimed to date are [(Ti5-C5Me5)Rh]2([i.-Cl)2 (I)6 and {[(Ti5-C5Me5)Ru]2(lt-Cl)(|i-H)2}+Cl-(II),7 which hydrogenate arenes to give saturated hydrocarbons at 50°C and at 50 atm H2 pressure. However, they do not show good stereoselectivity. For example, using II as catalyst, hexadeuterobenzene, C6D6 was converted to C^D^H.^, with no H-D scrambling, but the product is a mixture of cis and trans isomers. Similarly, xylenes gave an isomeric mixture of dimethylcyclohexanes. References on p. 12 Chapter 1 Introduction 2 1.2 - Cobalt complexes as arene hydrogenation catalysts In contrast to the above catalysts, cobalt-based homogeneous catalysts are more stereoselective. For instance, complete cis stereoselectivity was observed when the allylcobalt complexes (r| 3 - C 3 H 5)Co[P(OMe)3]3 8 and (TJ 3 -C 8 H i 3 ) C o [ ( C 6 H i i)2P(CH2)3P(C6Hn)2]9 were used as catalyst precursors in the hydrogenation of aromatic hydrocarbons such as benzene-dg, toluene-dg and naphthalene at 0-20°C and 1 atm H2 pressure. Unfortunately, in these reactions turnover numbers were low, ranging from 10-100 mol products/mol catalyst before the formation of mono-10 or polynuclear hydrides11 which are inert in arene hydrogenation. To account for the stereoselectivity,12 and because neither cyclohexadiene nor cyclohexene was detected during the hydrogenation of benzene with (n 3-C3Ff5)Co[P(OMe)3]3, a mechanism was proposed in which the C6 moiety remains attached to cobalt throughout the hydrogenation reaction (Scheme 1-1). 1.2.1 - The allylcobalt-phosphite system1 0 A prerequisite for the hydrogenation of a substrate such as benzene by (n,3-C3H5)Co[P(OMe)3]3 is the dissociation of a phosphite ligand to generate a coordinatively unsaturated species Cn3-C3H5)Co[P(OMe)3]2 (Scheme 1-1). The allyl group is then hydrogenated to propane, resulting in a transient 14-electron cobalt-hydride complex "CoH[P(OMe)3]2." Upon coordination of benzene to the latter, an undetected intermediate (rj4-C6H6)Co(H)[P(OMe)3]2, is believed to be formed initially.10 Then, hydride transfer from cobalt to benzene yields (rj3-C6H7)Co[P(OMe)3]2. It will be shown later (Scheme 1-2), that a more likely intermediate is (n5-C6H7)Co[P(OMe)3]2. Subsequent steps involving oxidative addition of H2 to cobalt, followed by hydride transfer from the metal to the organic References on p. 12 Chapter 1 Introduction 3 References on p. 12 Chapter 1 Introduction 4 moiety eventually lead to the production of one molecule of cyclohexane. However, the lifetime of the catalyst is limited. Scheme 1-1 shows that dissociation of the phosphite ligand during the catalytic sequence can also lead to a deleterious sequence of reactions leading to the irreversible formation of hydrides such as HCo[P(OMe)3]4 and H3Co[P(OMe)3]3.1 0 1.2.2 - The allylcobalt-diphosphine system9*11 The first step in the reaction sequence for the hydrogenation of benzene by (Ti3-C 8Hi 3)Co[Cy2P(CH2) 3PCy 2] (Cy = C 6 Hn) is the hydrogenation of the r|3_ cyclooctenyl moiety to cyclooctane (as detected by GC/MS) to form the 14-electron complex "[Cy2P(CH2)3PCy2]CoH" (Scheme 1-2). Reaction of the latter with benzene generates an ri5-cyclohexadienyl-cobalt complex which has been isolated and structurally characterized.11 Hydride transfer from cobalt to the arene moiety leads to the formation of Cn4-cyclohexadiene)Co(H)[Cy2P(CH2)3PCy2]. However, the latter can also be obtained if the Ti5-cyclohexadienyl-cobalt complex is reacted with 1,3-cyclohexadiene, suggesting that an intermediate (rj4-benzene)-cobalt-hydride complex is necessary to facilitate the exchange reaction. The sequence leading to the formation of cyclohexane follows the same route as that described in Scheme 1-1. All hydrogenation ceased upon the formation of a dark blue paramagnetic polynuclear hydride, whose identity has been deduced by molecular weight measurements (cryoscopy) to be [{Cy2P(CH2)3PCy2}CoH2]3.9>11 1.3 - From metal hydride to metal-T\2-dihydrogen complexes As shown in Schemes 1-1 and 1-2, and in all homogeneous catalytic hydrogenation reactions, metal hydride complexes play a pivotal role in the catalytic References on p. 12 Chapter 1 Introduction 5 sequence. The addition of H2 to unsaturated organic substrates is normally mediated by a metal centre.13 Scheme 1-2 C y 2 References on p. 12 Chapter 1 Introduction 6 Scheme 1-3 H — H + M L n H H | | — C — C -1 1 M L n hydride route L n M \ .H H > unsaturate route ML n He H H L n M C — C -H - M L r H I -C-I H I -C-I ML n = metal catalyst In most cases, the metal activates both H 2 and the substrate (an olefin in this case) via either the hydride or unsaturate route,13 and facilitates the formation of the hydrogenated product by migratory insertion and reductive elimination (Scheme 1-3). References on p. 12 Chapter 1 Introduction 7 Until recently, the interaction of H2 with a metal centre in hydrogenation reactions was thought to result in the scission of the H-H bond, either by oxidative addition or heterolytic cleavage, to form a metal-hydride complex. However, the perception of the initial interaction of dihydrogen with the metal was to change following the very important discovery of the Ti2-dihydrogen complex W(H2)(CO)3(PPr i 3)2.18 0 C * „ Pr'3P -W——PPrj3 j ^ C O CO 1.4 - r|2-Dihydrogen complexes The isolation of T]2-dihydrogen or molecular hydrogen complexes LnM(rj2-H2) is, without doubt, of fundamental importance in the interaction of a metal centre with dihydrogen in hydrogenation reactions. These complexes are sometimes called non-classical, because they contain dihydrogen as a CT-bonded ligand. They are related to agostic C-H bonds,14 and the so-called T|2-alkane or a-complexes,15 since in all cases, a o-bond acts as a 2e ligand. H / C H 2 H L N M — I L N M / L N M — I H C H 2 T I 2 - H 2 agostic o-complex The bonding scheme in an T|2-dihydrogen complex can be represented by a Dewar-Chatt-Duncanson model as shown below,16 where the shaded orbitals are occupied. References on p. 12 Chapter 1 Introduction 8 The H-2 ligand acts as a donor into an empty dCT orbital on the metal and the o* orbital of H2 accepts metal dn electrons. Indeed, the formation of dihydride complexes can be accounted for in this model by the complete transfer of electrons from the metal to the o* orbitals of the dihydrogen ligand. Weakly 7t-basic metals are expected to be most suited to form T | 2 - H 2 complexes, and metals in low oxidation state are more likely to form classical hydride complexes because the metal is a better 7i-donor.16«17 The discovery of molecular hydrogen complexes suggests that in all sequences involving hydrogen and a metal, complete rupture of the H-H bond may be preceded by the formation of an Ti2-dihydrogen complex. As an illustration, a typical example taken from Scheme 1-1 is given below. That T i 2 - H 2 complexes represent the first step in H-H scission was demonstrated in W^XCO^CPPr^. Variable-temperature *H NMR studies on d Scheme 1-4 References on p. 12 Chapter 1 Introduction 9 the complex showed that indeed a tautomeric equilibrium exists between dihydrogen and dihydride species.17 Since the first fully characterized ri2-dihydrogen complex was reported in 1984,18 reviews have appeared, 16,17,19 a n Q other examples of T]2-dihydrogen complexes have followed e.g. for chromium,20 molybdenum,21 tungsten,22 manganese,23 rhenium,24 iron,25 ruthenium,26 osmium,27, rhodium,28 iridium,29 and platinum.30 Interesting variations such as chiral molecular hydrogen complexes of ruthenium31 and rhenium,32 and an osmium-porphyrin complex33 have been reported also. However, only one example of a stable cobalt-dihydrogen complex [(TJ2-Although the dihydrogen ligand in this cobalt complex was not located in the X-ray structure, its presence was inferred from NMR data. Diagnostic evidence for the presence of the dihydrogen ligand in the complex were the temperature-dependent Ti data which assume a minimum value of 19 ms at 203 K (300 MHz), and the high value of J H D (27.8 Hz) measured for the isotopomer [(Ti2-HD)Co{P(CH2CH2PPh2)3}]+ Most dihydrogen complexes have been characterized in solution by nuclear magnetic resonance spectroscopy, and in the solid state by X-ray and neutron H2)Co{P(CH2CH2PPh2)3}]+PF6-, is known.34 H H PF 6". 3 4 References on p. 12 Chapter 1 Introduction 10 diffraction methods. A H-H bond distance of 0.8-1.2 A in the dihydrogen ligand is consistent with this formulation in comparison to the H-H bond length of 0.74 A in free H2." 1.5 - Scope of present work The work presented here is a study of the coordination chemistry of cobalt complexes containing bulky, chelating diphosphines of formula Pri2P(CH2)nPPri2 (n=2, l,2-bis(diisopropylphosphino)ethane (dippe); n=3, l,3-bis(diisopropylphosphino)pro-pane (dippp)), and rrart.s-(±)-l,2-bis(diisopropylphosphino)cyclopentane (dippcyp). dippp dippe dippcyp In Chapter 2, the synthesis and characterization of a number of complexes containing the ligands dippp and dippe are described. The performance of allylcobalt complexes of dippp and dippcyp as potential arene hydrogenation catalysts is examined in Chapter 3. The mechanisms presented in Schemes 1-1 and 1-2 are supported by the isolation and characterization of two intermediates, (r)4-2-methoxynaphthalene)Co(H)-(dippcyp) and (Tj5-cyclohexadienyl)Co(dippcyp) from the hydrogenation reactions. Although the initial aim of the thesis was the optimization of hydrogenation turnovers with allylcobalt complexes as catalyst precursors, the recurrence of polynuclear hydrides such as the binuclear cobalt-hydride complex [(dippp)CoH2]2 in these References on p. 12 Chapter 1 Introduction 11 hydrogenation reactions prompted a careful study of its structure and properties. This is discussed in greater detail in Chapter 4. During a synthesis of [(dippp)CoH2]2, a mononuclear dihydrogen complex (dippp)CoH3 was isolated; the mechanism of its formation is considered, and its relevance to the chemistry of [(dippp)CoH2]2 is discussed in Chapter 5. References on p. 12 Chapter 1 Introduction 12 1.6 - References 1. (a) Stuhl, L. S.; Rakowski-Dubois, M.; Hirsekorn, F. J.; Bleeke, J. R.; Stevens, A. E.; Muetterties, E. L. / . Am. Chem. Soc. 1978, 100, 2405. (b) Blum, J.; Amer, I.; Vollhardt, K. P. C; Schwarz, H.; Hohne, G. J.Org. Chem. 1987, 52, 2804. (c) Palmer, G. T.; Basolo, F. / . Am. Chem. Soc. 1985,107, 3122. (d) Fordyce, W. A.; Wilczynski, R.; Halpern, J. / . Organomet. Chem. 1985, 296, 115. (e) Johnson, J. W.; Muetterties, E. L.; / . Am. Chem. Soc. 1977, 99, 7395. (f) Russell, M. J.; White, C.; Maitlis, P. M. / . Chem. Soc. Chem. Commun. 1977, 427. (g) Klabunde, K. J.; Anderson, B. B.; Bader, M.; Radonovich, L. J. / . Am. Chem. Soc. 1978,100, 1313. 2. Muetterties, E. L.; Bleeke, J. R. Acc. Chem. Res. 1979,12, 324, and references therein. 3. Bennett, M. A.; Huang, T.-N.; Smith, A. K.; Turney, T. W. J. Chem. Soc. Chem. Commun. 1978,582. 4. Khand I. U.; Pauson, P. L.; Watts, W. E. / . Chem.. Soc. C. 1968, 2257. 5. (a) Rylander, P. N. Catalytic hydrogenation over Platinum Metals, Academic Press, New York; 1967. (b) Rylander, P. N. Hydrogenation Methods, Academic Press, London; 1985. 6. Maitlis, P. M. Acc. Chem. Res. 1978,11, 301. 7. Bennett, M. A. CHEMTECH 1980,10, AM. 8. Muetterties, E. L.; Hirsekorn, F. J. J. Am. Chem. Soc. 1974, 96, 4063. 9. (a) Jonas, K. Angew. Chem. Int. Ed. Engl. 1985,24, 295. (b) Jonas, K. Pure Appl. Chem. 1984,56, 63. 10. Bleeke, J. R.; Muetterties, E. L. J. Am. Chem. Soc. 1981,103, 556. References on p. 12 Chapter 1 Introduction 13 11. Priemer, H. Hydrocobaltierung und Cobalt-Katalysierte Hydrierung von Aromaten, Universitat Bochum, West Germany; 1987, 321 pp; Dissertation. 12. Muetterties, E. L.; Rakowski, M . C.; Hirsekorn, F. J.; Larson, W. D.; Basus, F. J.; Anet, F. A. L. / . Am. Chem. Soc. 1975, 97, 1266. 13. James, B. R. Compr. Organomet. Chem. 1982, 8, 285. 14. Green, M . L. H.; Brookhart, M . / . Organomet. Chem. 1983,250, 395. 15. (a) Periana, R.; Bergman, R. G. / . Am. Chem. Soc. 1986, 108, 7332. (b) Bullock, R. M. ; Headford, C. E. L.; Hennessy, K. M. ; Kegley, S. E.; Norton, J. R. / . Am. Chem. Soc. 1989, 111, 3897. (c) Gould, G. L.; Heinekey, D. M . / . Am. Chem. Soc. 1989, i i i , 5502. 16. Crabtree, R. H. Acc. Chem Res. 1990,23, 95. 17. Kubas, G. J. Acc. Chem. Res. 1988,21, 120. 18. Kubas, G. J.; Ryan, R. R.; Swanson, B. T.; Vergamini, P. J.; Wasserman, H. J. / . Am. Chem. Soc. 1984,106, 451. 19. Crabtree, R. H.; Hamilton, D. G. Adv. Organomet. Chem. 1988,28, 299. 20. (a) Sweany, R. L.; Moroz, A. / . Am. Chem. Soc. 1989, 111, 3577. (b) Upmacis, R. K.; Poliakoff, M. ; Turner, J. J. / . Am. Chem. Soc. 1986,108, 3645. 21. (a) Kubas, G. J.; Unkefer, C. J.; Swanson, B. I.; Fukushima, E. J. Am. Chem. Soc. 1986,108, 7000. (b) Wasserman, H. J.; Kubas, G. J.; Ryan, R. R. / . Am. Chem. Soc. 1986,108, 2294. (c) Kubas, G. J.; Ryan, R. R.; Wrobleski, D. A. / . Am. Chem. Soc. 1986,108,1339. 22. (a) Ishikawa, Y.; Weersink, R. A.; Hackett, P. A.; Rayner, D. M . Chem. Phys. Lett. 1987,142, 111. (b) ref. 18. (c) ref. 21d. 23. Howdle, S. M. ; Poliakoff, M . / . Chem. Soc. Chem. Commun. 1989, 1099. 24. (a) Kim, Y.; Deng, H.; Meek, D. W.; Wojcicki, A. / . Am. Chem. Soc. 1990,112, 2798. (b) Costello, M. T.; Walton, R. A. Inorg. Chem. 1988,27, 2563. References on p. 12 Chapter 1 Introduction 14 25. (a) Antoniutti, S.; Albertin, G.; Amendola, P.; Bordignon, E. /. Chem. Soc. Chem. Commun. 1989, 229. (b) Cappellani, E. P.; Maltby, P. A.; Morris, R. H.; Schweitzer, C. T.; Steele, M. R. Inorg. Chem. 1989,28, 4431. (c) Bianchini, C.; Peruzzini, M.; Zanobini, F. J. Organomet. Chem. 1988,354, C19. (d) Bautista, M.; Earl, K. A.; Maltby, P. A.; Morris, R. H. /. Am. Chem. Soc. 1988,110, 4056. (e) Gadd, G. E.; Upmacis, R. K.; Poliakoff, M.; Turner, J. J. J. Am. Chem. Soc. 1986.108, 2547. (f) Pipal, J. R.; Grimes, R. N. Inorg. Chem. 1979,18, 263. (g) Bampos, N.; Field, L. Inorg. Chem. 1990,29, 587. 26. (a) Joshi, A. M.; James, B. J. Chem. Soc. Chem. Commun. 1989, 1785. (b) Conroy-Lewis, F. M.; Simpson, S. J. /. Chem. Soc. Chem. Commun. 1986, 506. (c) Amendola, P.; Antoniutti, S.; Albertin, G.; Bordignon, E. Inorg. Chem. 1990, 29, 318. (d) Jia, G.; Meek, D. W. /. Am. Chem. Soc. 1990, 111, 757. (e) Hampton, C.; Cullen, W. R.; James, B. R.; Charland, J. P. /. Am. Chem. Soc. 1988,110, 6918. (f) Arliguie, T.; Chaudret, B.; Morris, R. H.; Sella, A. Inorg. Chem. 1988,27, 598. (g) Chinn, M. S.; Heinekey, D. M. /. Am. Chem. Soc. 1987.109, 5865. (h) Chinn, M. S.; Heinekey, D. M.; Payne, N. G.; Sofield, C. D. Organometallics 1989, 8, 1824. (i) Saburi, M.; Aoyagi, K.; Takahashi, T.; Uchida, Y. Chem. Lett. 1990, 601. 27. (a) Johnson, T. J.; Huffman, J. C; Caulton, K. G.; Jackson, S. A.; Eisenstein, O. Organometallics, 1989, 5, 2073. (b) Esteruelas, M. A.; Sola, E.; Oro, L. A.; Meyer, U.; Werner, H. Angew. Chem Int. Ed. Engl. 1988,27, 1563. 28. (a) Bianchini, C; Mealli, C; Peruzzini, M.; Zanobini, , F. /. Am. Chem. Soc. 1987,109, 5548. (b) Bucher, U. E.; Lengweiler, T.; Nanz, D.; von Philipsborn, W.; Venanzi, L. Angew. Chem. Int. Ed. Engl. 1990,29, 548. 29. (a) Lundquist, E. G.; Folting, K.; Streib, W. E.; Huffman, J. C; Eisenstein, O.; Caulton, K. G. /. Am. Chem. Soc. 1990,112, 855. (b) Mediati, M.; Tachibana, References on p. 12 Chapter 1 Introduction 15 G. N.; Jensen, C. M. Inorg. Chem. 1990,29, 3. (c) Marinelli, G.; Rashidi, I. E. S.; Streib, W. E.; Eisenstein, O.; Caulton, K. G. /. Am. Chem. Soc. 1989, 111, 2346. (d) Crabtree, R. H.; Lavin, M. /. Chem. Soc. Chem. Commun. 1985, 1661. 30. Clark, H. C; Hampden-Smith, M. J. / . Am. Chem. Soc. 1986,108, 3829. 31. Tsukahara, T.; Kawano, H.; Ishii, Y.; Takahashi, T.; Saburi, M.; Uchida, Y.; Akutagawa, S. Chem. Lett. 1988, 2055. 32. Luo, X.- L.; Crabtree, R. H. J. Am. Chem. Soc. 1990,112, 4813. 33. Collman, J. P.; Wagenknecht, P. S.; Hembre, R. T.; Lewis, N. S. /. Am. Chem. Soc. 1990,112, 1294. 34. Bianchini, C; Mealli, C; Meli, A.; Peruzzini, M.; Zanobini, F. /. Am. Chem. Soc. 1988,110, 8725. References on p. 12 Chapter 2 Cobalt-phosphine complexes 16 CHAPTER 2 Cobalt-phosphine complexes 2.1 - Introduction In recent years, the predominant role of steric effects in determining the chemistry of low-valent transition metal complexes has become important.1 A number of 14- and 15-electron complexes have been reported in the literature with bulky phosphines as ancillary ligands. In an effort to minimize phosphine dissociation during reaction, bulky chelating bidentate phosphines have also been employed.2 For example, coordinatively unsaturated complexes of rhodium, palladium, tantalum, and tungsten have been synthesized recently in our laboratories, and have been shown to display a wide array of reactivities.3'5 The present chapter is an investigation of the coordination chemistry of cobalt containing bulky chelating diphosphines, and includes the synthesis and characterization of a number of coordinatively unsaturated cobalt complexes with the diphosphine ligands dippp (l,3-bis(diisopropylphosphino)pro-pane),4 dippe (l,2-bis(diisopropylphosphino)ethane),5 and dippcyp (trans-(±)-l,2-bis(diisopropylphosphino)cyclopentane). 2.2 - Preparation and characterization of (dippp)CoCl2 (1), [(dippp)Co]2(p> Cl)2 (2) and [(dippe)Co]2(H-Cl)2 (2') Addition of dippp to anhydrous CoC^in toluene at 20°C resulted in a blue solution from which blue crystals of the coordinatively unsaturated cobalt-dichloride References on p. 31 Chapter 2 Cobalt-phosphine complexes 17 complex (dippp)CoCl2 (1) were isolated in 85-90% yield. This crystalline material is air-stable in the solid state, soluble in aromatic solvents and THF, but only sparingly soluble in diethyl ether and hexanes. Solutions of 1 are air-sensitive and decompose in a matter of hours. A mass spectrum of the decomposition product showed a molecular ion peak at 421, consistent with a molecular formula of (dippp)CoCl2 plus one oxygen atom. It is known that C0CI2 can be reduced in the presence of triisopropylphosphite to give [(PriO^P^CoCl.6 However, there was no reaction between (dippp)CoCl2 (1) and zinc powder. Only when sodium-amalgam was used, did any reaction occur to give the green chloro-bridged dimer [(chppp)Co]2(|i-Cl)2 (2) (Scheme 2-1). Scheme 2-1 toluene (CH 2 ) n CoCI 2 CoCI 2 + PHaP-CCHgJn-PPr^ 20°C dippe: n=2 . dippp: n=3 Na-Hg 1': n=2, green oil ' 1 : n=3, blue crystals, 89% 2': n=2, green, 20% 2 : n=3, green, 71% References on p. 31 Chapter 2 Cobalt-phosphine complexes 18 In an attempt to understand the lack of reactivity of 1 toward zinc, a cyclic voltammogram of the complex was obtained, and indeed it showed that the potential required to reduce Co(II) to Co(I) in this complex is -1.01 V (Pt bead electrode; 0.1 M (NBun4)+PF6" in THF; scan rate: 0.24 V s"1). Thus, zinc (Zn/Zn2+, reduction potential: -0.76 V) is not the reductant of choice for this reaction. The reaction of C0CI2 with dippe yielded the dichloride complex (dippe)CoCl2 (1'), which was obtained as an emerald-green oil from toluene. Apparently, crystals can be isolated following Soxhlet extraction with ether,7a although this was not attempted. Reduction of this dichloride complex gave green crystals of the chloro-bridged dimer [(dippe)Co]2(u-Cl)2 (2') (Scheme 2-1). The complexes (dippp)CoCl2 (1) and [(dippp)Co]2(p>Cl)2 (2) have been characterized by UV-visible spectroscopy in benzene. Values of the molar extinction coefficients for 1 (1000 - 1600 L mol"1 cm-1) are consistent with tetrahedral geometry about the metal centre, the transition involved being 4 A2 —> 4 T i (P).8 This tetrahedral structure agrees with those reported for analogous cobalt-phosphine compounds, e.g. [Cy2P(CH2)3PCy2]CoCl2,9 [Ph2P(CH2)3PPh2]CoCl2,10 [Ph2P(CH2)2PPh2]CoBr211 and (PPh3)2CoX2, (X= Cl, Br).12>13>14>15 Lower molar extinction coefficient values (160 - 450 L mol"1 cm"1) were measured from the UV-visible spectrum of the chloro-bridged dimer 2 in which the geometry at cobalt in this complex is tetrahedral also. The cobalt complexes 1, 1 ' , 2 and V are paramagnetic. Only the magnetic moments of (dippp)CoCl2 (1) and [(dippp)Co]2(|i-Cl)2 (2) have been measured in solution (Evans' method).16 The dichloride complex 1 has an observed moment (^ ieff) of 3.7(1) BM, consistent with a Co(II) centre with 3 unpaired electrons (spin-only value = 3.87). On the other hand, the moment observed for [(dippp)Co]2(p.-Cl)2 (2) References on p. 31 Chapter 2 Cobalt-phosphine complexes 19 1 JU + 4 0 2/4 i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i 30 20 10 0 ppm 1,3 4/2 J U I I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I I | I I I l | I I I I | I I I I [ I I I l | l l I I j I l I I j I i 60 50 40 30 20 10 0 ppm Figure 2-1. (a) lH NMR spectrum (300 MHz) of [(dippe)Co]2(Lt-Cl)2 (2'). (b) *H NMR spectrum (300 MHz) of [(dippp)Co]2(Lt-Cl)2 (2). Solvent peaks are denoted by (°) for CgDsH, and (*) for hexanes; (+) indicates an impurity. References on p. 31 Chapter 2 Cobalt-phosphine complexes 20 is 3.0(1) BM per dimer. Since in d8 tetrahedral cobalt(I) centres, simple crystal field theory predicts 2 unpaired electrons per cobalt, this result implies that two of the electrons in 2 are magnetically coupled, possibly through the chloride bridges (superexchange).17 The !H NMR spectra of [(dippp)Co]2(u-Cl)2 (2) and [(dippe)Co]2(p>Cl)2 (2') are shown in Figure 2-1. Although both compounds are paramagnetic, proton resonances are readily observed, albeit broadened and highly shifted.18-19 In the absence of any coupling information, peak assignments have been made on the basis of integrated intensities. The dippe methylene and methine protons in [(dippe)Co]2(M--Cl)2 (2') have similar integrated intensities and are not distinguishable. The interpretation of the NMR spectrum of this complex follows from the assignments made for (dippe)FeCl2.7a By the selective deuteration of the methine protons in the latter, it was shown that this signal is furthest downfield. In [(dippe)Co]2(p:-Cl)2 (2'), the methine signal is at 43.0 ppm. Broad singlets observed at -1.90 and 2.91 ppm have been assigned to the isopropyl methyl protons, whereas the methylene resonances of the backbone appear at 4.37 ppm. A similar reasoning applied to the assignments in [(dippp)Co]2(|i-Cl)2 (2) puts the isopropyl methyl protons at -2.00 and 1.95 ppm, and the fi-methylene protons at -0.40 ppm. Both a-methylene and methine protons in [(dippp)Co]2(|J.-C1)2 (2) integrate for the same number of protons, making their assignment ambiguous, although it seems likely that the resonance at 59.52 ppm is due to the methine protons. Attempts to confirm the molecular weight in solution of the chloro-bridged dimer 2 were unsuccessful, as it was unstable under the conditions of the experiment (Signer method).20 The characterization of the complex was completed by an X-ray diffraction study, the results being described in the following section. References on p. 31 Chapter 2 Cobalt-phosphine complexes 21 2.3 - Solid state structure of [(dippp)Co]2(p>Cl)2 (2) In the solid state, complex 2 adopts a dimeric structure of D2h symmetry possessing two chloride bridges (Figure 2-2). The principal features of the structure are: (i) the geometry about each cobalt centre is distorted from tetrahedral, as shown in the values of the angles ZPl-Co-P2 (100.61°), ZPl-Co-Cl' (115.27°), ZPl-Co-Cl (110.95°), ZP2-Co-Cl (116.07°), and ZP2-Co-Cl' (114.21°); (ii) the C02CI2 core defines a perfect plane, almost perpendicular to the PCoP vectors of both cobalt-phosphine fragments which lie in the same plane; (iii) the bridging Co-Cl distance (2.357 A) is longer than a terminal metal-Cl bond distance, as in (dippe)FeCl2 (Fe-Cl: 2.22(l));7a (iv) a Co-Co interatomic distance of 3.008 A in the structure of the complex is rather long, and suggests the absence of bonding interaction between the two metal centres. Selected intramolecular bond distances and angles are shown in Tables 2-1 and 2-2 (see Appendix for more details). Table 2-1. Selected bond distances (A) with estimated standard deviations in [(dippp)Co]2(u-Cl)2 (2) Co—P(l) 2.231(2) Co—P(2) 2.232(2) Co—Cl' 2.342(2) Co—Cl 2.357(2)  interatomic distance: Co—Co* 3.008 Table 2-2. Selected bond angles (deg) with estimated standard deviations in [(dippp)Co]2(!!-Cl)2 (2) P(l)—Co—P(2) 100.61(8) P(2)—Co—Cl' 114.21(7) References on p. 31 Chapter 2 Cobalt-phosphine complexes 22 Figure 2-2. (a) Chem 3D™ view of [(dippp)Co]2(u-Cl)2 (2). (b) Stereoview of the same molecule. References on p. 31 Chapter 2 Cobalt-phosphine complexes 23 PQ)—Co—cr 115.27(8) P(2)—Co—CI 116.07(8) P(l)—Co—CI 110.95(7) CI'—Co—CI 100.42(6) Co—CI—Co* 79.58(6) 2.4 - Synthesis of allylcobalt complexes In the light of the importance of allylcobalt complexes as precursors in hydrogenation reactions (Chapter 1), they were synthesized with the ligands dippp, dippe and dippcyp. The characterization of these complexes is described in this chapter, and assessment of their catalytic potential will follow in Chapter 3. Either (dippp)CoCl2 (1) or rj3-cyclooctenyl-l,5-cycloctadienecobalt(I)21 can be used as starting reagents in the syntheses. 2.4.1 - Synthesis of (n3-C3H5)Co(dippp) (3) When a solution of [(dippp)Co]2(|i-Cl)2 (2) in THF was treated with two equivalents of allylmagnesium chloride, a purple solution was formed, from which the allyl complex (r|3-C3H5)Co(dippp) (3) was obtained in 50-60% yield (Scheme 2-2). Alternatively, the allyl complex 3 was also formed (59%) when two equivalents of the Grignard reagent were added to a solution of (dippp)CoCl2 (1) in THF. The first equivalent of Grignard converted 1 from deep blue to a green solution from which [(dippp)Coh(|-t-Cl)2 (2) was isolated. The complex (ri3-C3H5)Co(dippp) (3) is diamagnetic, and is characterized by a very broad singlet in the 31P{1H} NMR spectrum at 47.1 ppm (Avi/2 = 942 Hz). The *H NMR spectrum of the complex shows a typical allylic pattern,22 at 1.43 (Hantj), 3.38 (Hsyn) and 4.70 ppm (H c e n t r ai), integrating for two, two and one proton(s) respectively. References on p. 31 Chapter 2 Cobalt-phosphine complexes 24 2.4.2 - Preparation and characterization of Cn3-CH2C6H5)Co(dippp) (6) The reaction of [(dippp)Co]2(|J.-Cl)2 (2) with benzylpotassium23 gave the benzyl complex (T|3-CH2C6H5)Co(dippp) (6) as dark brown crystals (Scheme 2-2). Scheme 2-2 -o-Co— ,3 f > C H 2 K THF (62%) Cl Cl . (allyl)MgCI Na-Hg toluene ( 7 1 % ) 3 (50-60%) (allyl)MgCI THF In contrast to the synthesis of (T)3-CH2C6H5)Rh(dippp),24 there was no reaction when dibenzylzinc25 was used. The 3 1P{ 1H} NMR spectrum of 6 contains a very broad singlet at 46.3 ppm (Avi/2= 637 Hz). The interpretation of the *H NMR spectrum of (n3-CH2C6H5)Co(dippp) (6) (Figure 2-3) follows from that of (r|3-CH2C6H5)Rh(dippp), which also shows the same pattern of equivalent resonances for the pairs of protons Ha/HD (1.56 ppm), Hc/Hg (5.21 ppm), and H^/Hf (7.31 ppm) on the References on p. 31 Chapter 2 Cobalt-phosphine complexes 25 NMR time scale at room temperature. These resonances probably become equivalent via a process similar to that shown in Scheme 2-3.26 Scheme 2-3 i I i i 1 1 i 7 6 5 4 3 2 1 ppm Figure 2-3. *H NMR spectrum (300 MHz) of (T|3-CH2C6H5)Co(dippp) ( 6 ) . The asterisks (*) denote a minor product assumed to be an T|5-benzyl complex. Solvent peak is indicated by (°). References on p. 31 Chapter 2 Cobalt-phosphine complexes 26 The mechanism includes an initial rearrangement of the bonding mode of the benzyl group from T) 3 tor]1 to generate a short-lived, undetected 14-electron, o-bonded benzyl intermediate which undergoes rapid 180°-rotation of the phenyl ring. A subsequent Tj1—>T|3 rearrangement restores the original bonding mode.26 Also of interest in the *H NMR of (r|3-CH2C6H5)Co(dippp) (6) (Figure 2-3) are the resonances marked by asterisks(*). Although formed as a minor product (18-20% by NMR), this compound may be tentatively assigned as an isomer of 6, an r|5-benzyl complex. Resonances for the ri5-benzyl complex are assigned as follows: 3.64 ppm (Hi), 3.98 ppm (H4), 5.03 ppm (H2 or H3) and 5.39 ppm (H3 or H2). P = dippp Such a species has a precedent in the literature. The complex ( T ] 5 -C6(CH3)5CH2)(T|5-C5H5)Fe has been synthesized and structurally characterized as an T)5-benzyl complex; the exocyclic double bond can even be hydrogenated by Pd over charcoal at 20°C to give (r|5-C6(CH3)6H)(r|5-C5H5)Fe.27 The possible existence of an equilibrium between the proposed r|5-benzyl-cobalt complex and (r|3-CH2C6H5)Co(dippp) (6) has not been investigated. 2.4.3 - Solid state structure of (Ti3-CH2C6H5)Co(dippp) (6) In order to obtain more information on the structure of (T| 3 -CH2C6H5)Co(dippp) (6), a single crystal X-ray diffraction study of the complex was References oh p. 31 Chapter 2 Cobalt-phosphine complexes 27 Figure 2-4. (a) Selected Chem 3D™ view of (Ti3-CH2C6H5)Co(dippp) (6) showing the unsymmetrical bonding of the organic fragment, (b) Stereoview of (r]3-CH2C6H5)Co(dippp) (6). References on p. 31 Chapter 2 Cobalt-phosphine complexes 28 undertaken. The X-ray crystal structure of (ri3-CH2C6H5)Co(dippp) (6) is shown in Figure 2-4. Selected bond distances and angles are given in Tables 2-3 and 2-4. Details about the structure of 6 are given in the Appendix. The complex is isostructural with (n3-CH2C6H5)Rh(dippp).24 Several features are of note in the structure: the bond distances between cobalt and the organic fragment (Table 2-3) indicate that the a-carbon (C16) is closest to the metal (C0-CI6: 1.989 A; Co-C17: 2.033 A; C0-CI8: 2.207 A) with the C0-CI6 bond distance being 0.218 A shorter than C0-CI8. This is also well displayed in the selected Chem 3D™ view of the structure (Figure 2-4). The unsymmetrical bonding pattern observed in the structure has been attributed to a larger negative charge residing on the a-carbon.28*29 The carbon-carbon bond distances in the benzene ring show an alternation between long and short, consistent with a degree of localization in the bonding. Similar observations have been made in the structures of (T|3-CH2C6H5)Co[P(OCH3)3]329 and ( T | 3 -CH2C6(CH3)5)Rh[P(0-i-C3H7)3]2 2 8 and in other cobalt-benzyl compounds.30 The angle defined by C16, Co and C18 is 70.4°, which is comparable to that observed in (n3-CH2C6H5)Co[P(OCH3)3]3 (65.77°) 2 9 As a result of coordination, some distortion is noted on the angles C16-C17-C18 (117.3°), where all three carbons are within bonding distance of cobalt, and C16-C17-C22 (125.1°), where C22 is not bound to cobalt. Of interest as well in the structure is the almost perfectly square-planar arrangement of atoms Pl, P2, Co, C16 and C18, the dihedral angle between the Pl-Co-P2 and CI6-C0-CI8 planes being 0.95°. A square-planar disposition about rhodium also has been observed in the solid state structure of C n 3 -CH2C6(CH3)5)Rh[P(0-i-C3H7)3]2.28 References on p. 31 Chapter 2 Cobalt-phosphine complexes 29 Table 2-3. Selected bond distances (A) with estimated standard deviations in (r|3-CH2C6H5)Co(dippp) (6). Co(l)—P(l) 2.122(2) C(17)—C(18) 1.431(7) Co(l)—P(2) 2.158(2) C(17)—C(22) 1.420(7) Co(l)—C(16) 1.989(5) C(18)—C(19) 1.405(7) Co(l)—C(17) 2.033(5) C(19)—C(20) 1.348(8) Co(l)—C(18) 2.207(5) C(20)—C(21) 1.413(9) C(16)—C(17) 1.410(7) C(21)—C(22) 1.334(8) Table 2-4. Selected bond angles (deg) with estimated standard deviations in (rj3-CH2C6H5)Co(dippp) (6) P(l)—Co(l)—P(2) 99.06(6) P(l)—Co(l)—C(16) 91.5(2) P(l)—Co(l)—C(17) 125.7(2) P(l)—Co(l)—C(18) 161.9(2) P(2)—Co(l)—C(16) 169.3(2) P(2)—Co(l)—C(17) 130.4(2) P(2)—Co(l)—C(18) 99.0(2) C(16)—Co(l)—C(17) 41.0(2) C(16)—Co(l)—C(18) 70.4(2) C(17)—Co(l)—C(18) 39.2(2) Co(l)—C(16)—C(17) 71.1(3) Co(l)—C(17)—C(16) 67.8(3) Co(l)--C(16)--C(18) 77.0(3) Co(l)--C(16)--C(22) 117.6(3) C(16)--C(17)--C(18) 117.3(5) C(16)--C(17)--C(22) 125.1(5) C(18)--C(17)--C(22) 116.9(5) Co(l)--C(18)--C(17) 63.8(3) Co(l)--C(18)--C(19) 130.1(3) C(17)--CQ8)--C(19) 118.7(5) C(18)--C(19)--C(20) 122.2(5) C(19)--C(20)--C(21) 118.7(5) C(20)--C(21)--C(22) 121.4(5) C(17)--C(22)--C(21) 121.6(5) References on p. 31 Chapter 2 Cobalt-phosphine complexes 30 2.4.4 - Synthesis of T\3-alIyl-cobaIt complexes using rj 3-cyclooctenyl-l,5-cycloctadienecobalt(I) Allylcobalt complexes may also be synthesized by making use of r)3-cyclooctenyl-l,5-cycloctadienecobalt(I)21 (Scheme 2-4). Thus, the complexes C n 3 -C8Hi3)Co(dippp) (14), (Ti3-e8H13)Co(dippe) (3') and (Ti3-C8Hi3)Co(dippcyp) (8) have been prepared by adding the diphosphine ligand to (rj3-C8Hi3)Co(COD) in hexanes, resulting in the displacement of COD by the diphosphine to give the required T|3-allyl complex. Whereas 8 and 14 are purple crystalline materials, (rj3-C8Hi3)Co(dippe) (3') could only be obtained as a purple oil. This route was found to be very convenient for the preparation of (ri3-C8Hi3)Co(dippcyp) (8), because the analogue of (dippp)CoCl2 (1) is (dippcyp)CoCl2 (5'), which was obtained as a green oil, and was difficult to purify. Scheme 2-4 CoCI 2 + pyridine, 0°C Na, THF 4 4 % P hexanes •P, 14: dippp (65%) = 8 : dippcyp (42%) P 3' : dippe (purple oil) References on p. 31 Chapter 2 Cobalt-phosphine complexes 31 2.5 - References 1. (a) McAuliffe, C. A. Compr. Coord. Chem. 1987, 2, 989. (b) Clark, H. C; Hampden-Smith, M. J. Coord. Chem. Rev. 1987, 79, 229. (c) McAuliffe, C. A. Coord. Chem. Rev. 1984, 55, 31. (d) Mason, R.; Meek, D. W. Angew. Chem. Int. Ed. Engl. 1978,17, 183. (e) Tolman, C. A. / . Am. Chem. Soc. 1970, 92, 2956. (f) Collman, J. P. Acc. Chem. Res. 1968,1, 36. 2. (a) Mc Auliffe, C. A.; Levason, W. Phosphine, Arsine and Stibine Complexes of the Transition Elements; Elsevier, New York; 1979. (b) Mc Auliffe, C. A. Transition Metal Complexes of Phosphorus, Arsenic and Antimony Ligands; MacMillan, New York; 1973. (c) Tolman, C. A. Chem. Rev. 1977, 77, 313. 3. Rh: see for example: (a) Piers, W. E. Ph. D. Thesis; The University of British Columbia, Vancouver, B. C, Canada; 1988, 235 pp. (b) Fryzuk, M. D.; Piers, W. E.; Rettig, S. J.; Einstein, F. W. B.; Jones, T.; Albright, T. A. /. Am. Chem. Soc. 1989, 111, 5709. (c) Fryzuk, M. D.; Piers, W. E. Organometallics 1990, 9, 986. Ta: Fryzuk, M. D.; McConville, D. H. M. Inorg. Chem. 1989,28, 1613. W: Fryzuk, M. D.; Kreiter, C. G.; Sheldrick, W. S. Chem. Ber. 1989,122, 851. Pd: Fryzuk, M. D.; Clentsmifh, G. K. B.; Lloyd, B. R.; Rettig, S. J. unpublished results. 4. Tani, K.; Tanigawa, E.; Yatsuno, Y.; Otsuka, S. / . Organomet. Chem. 1985,279, 87. 5. Fryzuk, M. D.; Jones, T.; Einstein, F. W. B. Organometallics, 1984, 3, 185. 6. Rakowski, M. C; Muetterties, E. L. /. Am. Chem. Soc. 1977, 99, 739. 7. (a) Hermes, A. R.; Girolami, G. S. Inorg. Chem. 1988,27, 1775. (b) Hermes, A. R.; Girolami, G. S. Inorg. Chem. 1990,29, 313. References on p. 31 Chapter 2 Cobalt-phosphine complexes 32 8. Banci, L.; Bencini, A.; Benelli, C; Gatteschi, D.; Zanchini, C. Struct. Bond. 1982,52, 37. 9. Issleib, K.; Hohlfeld, G. Z. Anorg. Allgem. Chem. 1961,312, 169. 10. DeW. Horrocks, Jr., W.; Van Hecke, G. R.; DeW. Hall, D. Inorg. Chem. 1967, 6, 694. 11. Chatt, J.; Hart, F. A.; Rosevaar, D. T. /. Chem. Soc. 1961, 5504. 12. Cotton, F. A.; Faut, D. D.; Goodgame, D. M. L.; Holm, R. H. / . Am. Chem. Soc. 1961, 83, 1780. 13. Pignolet, L.; DeW. Horrocks, Jr., W. /. Am. Chem. Soc. 1968, 90, 922. 14. Tomlinson, A. A. G.; Bellitto, C; Piovesana, O.; Furlani, C. / . Chem. Soc. Dalton. Trans. 1972, 350. 15. Sznajder, J.; Jablonski, A.; Wojciechowski, W. /. Inorg. Nucl. Chem. 1979,41, 305. 16. (a) Evans, D. F. /. Chem. Soc. 1959, 2003. (b) Deutsch, J. L.; Poling, S. M. / . Chem. Educ. 1969,46, 167. 17. Hodgson, D. J. Prog. Inorg. Chem. 1975,19, 173. 18. Holm, R. H.; Hawkins, C. J. in NMR of Paramagnetic Molecules, La Mar, G. N.; DeW. Horrocks, Jr., W.; Holm, R. H., Academic Press, New York and London; 1973, pp 243-332. 19. Jesson, J. P.; Trofimenko, S.; Eaton, D. R. /. Am. Chem. Soc. 1967, 89, 3158. 20. (a) Signer, R. Ann. 1930, 478, 246. (b) Clark, E. P. Indust. Eng. Chem., Anal. Chem. 1941,13, 820. (c) Burger, B. J.; Bercaw, J. E. in ACS Symp. Ser. vol. 357: Experimental Organometallic Chemistry, Wayda, A. L.; Darensbourg, M. Y. (Eds); American Chemical Society .Washington, D. C; 1987, pp 79-98. 21. Otsuka, S.; Rossi, M. /. Chem. Soc. A 1968, 2630. References on p. 31 Chapter 2 Cobalt-phosphine complexes 33 22. Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry, University Science Books, Mill Valley, California; 1987, pp 175-182. 23. Schlosser, M.; Hartmann, J. Angew. Chem. Int. Ed. Engl. 1973,12, 508. 24. Fryzuk, M. D.; McConville, D. H.; Rettig, S. J. unpublished results. 25. Schrock, R. R. /. Organomet. Chem. 1976,122, 209. 26. (a) Stille, J. K. in The Chemistry of the Metal-Carbon Bond, Hartley, F. R.; Patai, S. (Eds.); John Wiley and Sons, New York; 1985, pp 625-787. (b) "Becker, Y.; Stille, J. K. /. Am. Chem. Soc. 1978,100, 845. 27. Hamon, J.-R.; Astruc, D.; Roman, E.; Batail, P.; Mayerle, J. J. /. Am. Chem. Soc. 1981,103, 2431. 28. Burch, R. R.; Muetterties, E. L.; Day, V. W. Organometallics 1982,1, 188. 29. Bleeke, J. R.; Burch, R. R.; Coulman, C. L.; Schardt, B. C. Inorg. Chem. 1981, 20, 1316. 30. (a) Cotton, F. A.; Marks, T. J. /. Am. Chem. Soc. 1969, 91, 1339. (b) King, R. B.; Fronzalia, A. /. Am. Chem. Soc. 1966, 55, 709. References on p. 31 Chapter 3 Hydrogenation of arenes 34 CHAPTER 3 Hydrogenation of arenes 3.1 - Introduction A number of homogeneous catalytic systems are known to hydrogenate arenes.1 Among them are allylcobalt complexes described earlier (Chapter 1), which have been shown to be very stereoselective towards simple arenes. An area which has received little attention is the hydrogenation of functionalized aromatic substrates, which is discussed in the present chapter. Although the complex (r|3-C3H5)Co[P(OMe)3]3 has been employed in the hydrogenation of functionalized arenes,2 conversion rates were generally poor. For example, anisole, N,N-dimethylaniline, and ethyl benzoate gave low conversion (2-5%) of fully hydrogenated product. Some substrates such as halobenzenes, nitrobenzene, and benzonitrile were unsuitable since they either contain electron-withdrawing substituents which decrease the 71-donor ability of the aromatic ring, or are good coordinating ligands (e.g. benzonitrile). In addition, acidic substrates such as phenol and benzoic acid were reported to protonate the catalyst thus deactivating it.2 Little is known about the activity of allylcobalt complexes containing chelating diphosphines such as ( T | 3 -CgHi3)Co[(C6Hii)2P(CH2)3P(C6Hn)2], towards arenes containing functional groups in hydrogenation reactions. Hydrogenation results obtained with the allylcobalt References on p. 56 Chapter 3 Hydrogenation of arenes 35 complexes synthesized in Chapter 2 are presented here, and the utility of these complexes is discussed. 3.2 - Phosphine ligands in arene hydrogenation In the early stage of this thesis, it was thought that the incorporation of a chelating diphosphine in the allylcobalt system would overcome some of the obstacles which have plagued the use of (rj3-C3H5)Co[P(OMe)3]3, in particular the requirement for phosphite dissociation. Initial results3 using a bulky chelating diphosphine suggested that a chelate ring size of five or six around cobalt was critical for the success of arene hydrogenation. Therefore, the choice of the ligand dippp was obvious. In addition, the syntheses of dippcyp and a chiral analogue of dippp, (S,S)-2,4-bis(diisopropylphosphino)pentane were undertaken for the following reasons. Some functionalized arenes, e.g. substituted naphthalenes, possess enantiotopic faces. 3 chiral centres References on p. 56 Chapter 3 Hydrogenation of arenes 36 Hydrogenation with an achiral cobalt phosphine catalyst precursor would generate a racemic mixture; however, coordination of an enantiotopic face to a chiral cobalt-diphosphine complex would result in diastereomers which might be formed in unequal amounts, thus resulting in asymmetric synthesis.4 For example, with a chiral catalyst, the hydrogenation of prochiral aromatic substrates (Equations 3-1 and 3-2) yield saturated products with two and three chiral centres respectively. The potential of such a transformation was a good incentive to explore this avenue. The ligand dippcyp was prepared from racemic rra/w-(±)-l,2-bis(dichloro-phosphino)cyclopentane,5 following the procedure for dippe.6 Although dippcyp was resolved using a palladium-dimethyl(a-methylbenzyl)amine complex,7 the chemistry discussed in this chapter concerns the racemic ligand only. Scheme 3-1 YT '"-rr b , w O O 65-80% OH OH 70-75% OTs OTs A: Ra-Ni-(r7, fl;-tartaric acid-NaBr, H 2 (100 psi), 100°C B: TsCI, pyridine, 0°C C: (i) LiPPh 2 > THF, 0°C (ii) NiCI0 4 .6H 2 0, KCNS (iii) CH 2 CI 2 , CF3COOH (iv) (a) NaCN, H 2 0 , reflux ; (b) E t 2 0 D: AICI3, PCI3, 280'C E: PHMgCI, E t 2 0 , -10°C V j ^ y ' E V j ^ y * D ^Y^l' Pr j 2P PPr'2 CI2P PCI2 Ph2P PPh 2 C 3 0 % References on p. 56 Chapter 3 Hydrogenation of arenes 37 The proposed synthetic sequence to (S,S)-2,4-bis(diisopropylphosphino)-pentane is shown in Scheme 3-1. The phosphine (S,S)-2,4-bis(diphenylphosphino)-pentane was first synthesized according to the literature.8 Attempts to remove the phenyl substituents from this phosphine under Friedel-Crafts conditions9 gave very small amounts of the desired tetrachlorodiphosphine (31P{!H} NMR: 197.6 ppm) among a mixture of other compounds. The synthesis of (S,S)-2,4-bis(diisopropylphosphino)pentane was not pursued when preliminary results with allylcobalt complexes indicated that they were not suitable arene hydrogenation catalyst precursors. 3.3 - Hydrogenation results Among all of the allylcobalt complexes synthesized, only (r]3-C3H5)Co(dippp) (3) and ( T \ 3 - C g H i 3)Co(dippcyp) (8) were used as catalyst precursors. The experiments were performed as follows: when the substrate was a liquid, the catalyst precursor was dissolved in the neat substrate. For solid substrates such as 2-methoxynaphthalene, THF was used as solvent. Catalyst precursor/substrate mixtures were placed in a thick-wall glass reactor immersed in an oil bath maintained at 0°C, and stirred under a pressure of 0.9-1.0 atm of H2 , except in the case of benzene where the temperature was 20°C. Each run lasted over a period of 1-2 weeks. The end of the reaction was established by the initial colour of the reaction mixture changing from purple to light brown or blue, and when no more uptake of H 2 was monitored on a mercury manometer. The reaction sequence perhaps follows the cycle given in Schemes 1-1 (p. 3) and 1-2 (p. 5). Results of hydrogenation experiments are given in Table 3-1. Only 2-methoxynaphthalene was found to be a suitable functionalized aromatic substrate. Consistent with the results obtained with the allylcobalt systems (Tl3-C3H5)Co[(POMe3)]3 and (T]3-C8Hi3)Co[Cy2P(CH2)3PCy2] References on p. 56 Chapter 3 Hydrogenation of arenes 38 Table 3-1. Hydrogenation results TON1 substrate: Substrate product: f j Catalyst \ ^ Pr'2 154:1 12 Prj2 8 2098:1 0 Hydrogenation rxns @ 20° C and 0.9-1.0 atm H 2 Hydrogenation rxns @ 0°C and 0.9-1.0 atm H 2 "TON = turnover number = mol product / mol catalyst precursor References on p. 56 Chapter 3 Hydrogenation of arenes 39 (Section 1-2), benzene gave cyclohexane only, but a mixture of products was obtained with 2-methoxynaphthalene, as determined by gas chromatography. Although the products were not isolated, addition of hydrogen was very likely cis, because results with naphthalene using (ri3-C8Hi3)Co[Cy2P(CH2)3PCy2] as catalyst precursor are reported to give a mixture of m-tetralin and c/s-decalin only.3 The catalysts seemed to be very sensitive to the nature of the substrate. For example, anisole, methyl benzoate, o-tolunitrile, 1-indanone, coumarin, furan, and 2-methoxymethylfuran were not hydrogenated. These substrates may not have the right 7t-donor capability to coordinate to cobalt. In the case of anisole, methyl benzoate and coumarin, a hydrogenolysis reaction could lead to products, (e.g.methanol from anisole) which poison the catalyst. Substitution O f the 2-methyl ether protecting group in 2-methoxynaphthalene by 2-methoxyethoxymethyl (2-MEM) results in lack of hydrogenation. The ether functionalities of the side-chain are thought to poison the catalyst by blocking available coordination sites at cobalt. Attempts to isolate the catalyst-substrate adduct with 2-MEMO-naphthalene only gave an intractable green oil. In view of the low activity of the catalysts (Table 3-1), all efforts were directed at isolating intermediates in the hydrogenation sequence in an attempt to elucidate the nature of the reactions presented in Schemes 1-1 and 1-2. 3.4 - Isolation of the intermediates Cn5-cyclohexadienyl)Co(dippcyp) (10) and (rj4-2-methoxynaphthalene)Co(H)(dippcyp) (11) When the catalyst precursor (Tj3-CgHi3)Co(dippcyp) (8) was stirred in benzene at room temperature under H2 , the initial purple colour of the solution rapidly References on p. 56 Chapter 3 Hydrogenation of arenes 40 changed to deep red-brown. As soon as no more H 2 was taken up by the system (as monitored on a mercury manometer), the excess gas was removed. From this solution, reddish-brown crystals of (ri5-cyclohexadienyl)Co(dippcyp) (10) were isolated (69% yield) (Scheme 3-2). Scheme 3-2 10 (69%) 11 (46%) The cyclohexadienyl ligand is labile and when allowed to stand, a solution of the compound in C6D6 yields a complex containing CeD^H (Scheme 3-3). It is important to note that the proton is located at the endo site on the ring, as deduced by References on p. 56 Chapter 3 Hydrogenation of arenes 41 *H NMR spectroscopy, where only the resonance for the endo hydrogen was observed. This exchange process probably occurs via an initial migration of Hendo o n t o cobalt to give an T\ 4- arene intermediate. The complex On 4 -2-methoxynaphthalene)Co(H)(dippcyp) (11) was prepared by taking advantage of this process. Hence, in the presence of an excess of 2-methoxynaphthalene, (rj5-cyclohexadienyl)Co(dippcyp) (10) was transformed into (rj4-2-methoxynaphthalene)Co(H)(dippcyp) (11), which was also isolated as a reddish-brown solid (Scheme 3-2). Scheme 3-3 I Co Earlier in Chapter 1, it was suggested that rj4 binding of the substrate was a requisite before hydrogenation could begin.10 Such a proposal was based on the reluctance of the arene ligand in (r|3-C3H5)(r|6-C6H6)RuCl and (r|3-C3H5)(r|6-C6H5CH3)MoCl to undergo hydrogenation, and the lack of hydrogen transfer in (rj6-C 6H 5CH 3)MoH2(PPh3)2. 1 0 ' 1 1 The isolation of (r|4-2-methoxynaphthalene)Co(H)-(dippcyp) (11) suggests that it may be an important intermediate in the hydrogenation cycle. References on p. 56 Chapter 3 Hydrogenation of arenes 42 3.4.1 - Characterization of (n4-2-methoxynaphthalene)Co(H)(dippcyp) (11) The compound 2-methoxynaphthalene possesses two enantiotopic faces per ring. Since the diphosphine ligand is racemic, each ring bound to cobalt would generate two diastereomeric pairs of enantiomers. i 1 1 1 1 i 1 1 1 1 i 1 1 1 1 i ' • 1 ' i ' i • ' i ' ' ' ' i i 1 1 i i i i • i i • i i i | i i i • i i 1 1 1 | 1 1 1 • 1 1 1 1 1 | 7 6 5 4 3 2 1 ppm Figure 3-1. *H NMR spectrum (400 MHz) of (n4-CioH7OMe)Co(H)(dippcyp) (11) showing the presence of two diastereomers (marked by (a) and (b)). Residual C6D5H is indicated by (°). References on p. 56 Chapter 3 Hydrogenation of arenes 43 From NMR data alone, it is difficult to determine the mode of coordination of the arene ligand to cobalt. The 31P{1H} NMR spectrum of (T|4-2-methoxynaphthalene)-Co(H)(dippcyp) (11) shows two broad singlets at 55.0 (Avi/2 = 531 Hz) and 77.8 (Avi/2= 607 Hz) ppm in a 1:1 ratio, indicating that two products were formed. The *H NMR spectrum of complex 11 is shown in Figure 3-1. At high field, two doublets of doublets are observed for the hydride ligands at -23.6 ( 2JHP. 38, 38 Hz) and at -24.1 ppm (2JHP» 38, 38 Hz) in the two diastereomers. Examination of the rest of the spectrum shows two methyl signals at -3.35 ppm, but the complexity of the ring proton resonances makes their assignments difficult. Proton resonances for the ring bound to cobalt are shifted upfield, and they appear between 3.0 and 3.7 ppm overlapped with the methyl peaks. A COSY experiment was performed to aid in the assignments, but the results were inconclusive. Therefore, an X-ray analysis of 11 was undertaken to determine the coordination mode of 2-methoxynaphthalene to cobalt. 3.4.2 - Solid state structure of (n4-2-methoxynaphthalene)Co(H)(dippcyp) (11) Reddish-brown crystals of (rj4-CioH70Me)Co(H)(dippcyp) (11) were grown from a toluene/hexanes mixture (10:1) at 20°C. There are two molecules per asymmetric unit, each having similar bond distance and bond angle parameters. The X-ray structure of only one of them is shown in Figure 3-2. A stereoview of the molecule is also presented in Figure 3-3, along with a selected Chem 3D™ view. Relevant structural data are given in Tables 3-2 and 3-3 (see Appendix for details). The hydride ligand was located in the difference Fourier map, and it is located 1.35(4) A from cobalt. Figure 3-2 shows that the unsubstituted ring is bound to cobalt through C2 (2.173 A), C3 (2.010 A), C4 (1.988 A), and C5 (2.109 A). The effect of coordination of the arene to cobalt is clearly illustrated in the selected Chem 3D™ References on p. 56 Chapter 3 Hydrogenation of arenes 44 C l l Figure 3-2. The structure of (T)4-CioH70Me)Co(H)(dippcyp) (11) in the solid state depicting r\4 bonding of the unsubstituted ring of the arene ligand to cobalt. References on p. 56 Chapter 3 Hydrogenation of arenes 45 Figure 3-3. (a) Selected Chem 3D™ view of (T]4-2-methoxynaphthalene)Co(H)-(dippcyp) (11) showing the result of coordination on the arene ligand. (b) Stereoview of the same molecule. References on p. 56 Chapter 3 Hydrogenation of arenes 46 view of the molecule (Figure 3-3). The four complexed carbon atoms are coplanar to within 0.63°, but the rest of the aromatic ligand is 30° out of that plane. As a result, the uncomplexed ring retains its aromaticity, as shown in the carbon-carbon bond distances (Table 3-2). Dihedral angles generated by the folding of the T|4-arene ligand vary between 32 and 48° in structures of related compounds.140 Some examples of structurally-characterized metal complexes with an T|4-arene ligand are given below for comparison, with the corresponding dihedral angle in parentheses: (Ti4-naphthalene)TaCl[Me2P(CH2)2PMe2] (43°),1 2 (r|6-C6Me6)(r|4-C6Me6)Ru (40°),13 (Ti6-C 6H6)(Ti 4-C 6Ph 6)Ru (46.8°),14 (ri5-C5H5)(Ti4-C6(CF3)6)Rh (47.9°),15 and [(Ti6-C6Me6)(Tl4-C6H2Me6)Rh]+ PF6' (40°).16 Although naphthalene is T|2-bound to nickel as in (rj2-naphthalene)Ni-(diphosphine) (where the diphosphine is dippe or dippp) leaving the metal coordinatively unsaturated,17 with the same ligands naphthalene is T]4-bound in the analogous cobalt complexes.3'18 Only one other transition metal-2-methoxy-naphthalene complex is known in the literature. In the complex (r|5.C5Me5)('n2-2-methoxynaphthalene)Rh(PMe3), 2-methoxynaphthalene is ri2-bound to the metal centre through the ring containing the 2-methoxy group. The latter apparently stabilizes this T\2-naphthalene complex because of its electron-donating abilities.19 Table 3-2. Selected bond distances (A) and estimated standard deviations in (rj4-CioH7OMe)Co(H) (dippcyp) (11) Co(l)--P(l) 2.170(1) C(l)- -C(10) 1.375(6) Co(l)--P(2) 2.179(1) C(2)- -C(3) 1.409(6) Co(l)--C(2) 2.173(4) C(3)- -C(4) 1.391(6) Co(l)--C(3) 2.010(4) C(4)- -C(5) 1.427(6) Co(l)--C(4) 1.988(4) C(5)- -C(6) 1.460(6) References on p. 56 Chapter 3 Hydrogenation of arenes Co(l)—C(5) 2.109(4) Co(l)—H(l) 1.35(4) C(l)—C(2) 1.454(6) C(l)—C(6) 1.409(6) C(6)—C(7) 1.401(6) C(7)—C(8) 1.410(6) C(8)—C(9) 1.349(8) C(9)—C(10) 1.363(7) Table 3-3. Selected bond angles (deg) and estimated standard deviations in (TJ4-CioH7OMe)Co(H)(dippcyp) (11) P(l)--Co(l)--P(2) 91.88(5) C(4)--Co(l)--C(5) 40.6(2) P(l)--Co(l)--C(2) 112.7(1) C(4)--Co(l)--H(l) 92(1) P(D- -Co(l)--C(3) 102.8(1) C(5)--Co(l)--H(l) 90(1) P(i)--Co(l)--C(4) 121.1(1) C(2)--C(l)--C(6) 114.6(4) P(l)--Co(l)--C(5) 157.6(1) C(2)--C(l)--C(10) 126.4(5) P(i)--Co(l)--H(l) 77(1) C(6)--C(l)--C(10) 119.0(4) P(2)--Co(l)--C(2) 108.2(1) Co(l)--C(2)--C(l) 104.0(3) P(2)--Co(l)--C(3) 147.3(1) Cq(l)--C(2)--C(3) 64.2(2) P(2)--Co(l)--C(4) 145.6(1) C(l)- -C(2)--C(3) 119.7(4) P(2)--Co(l)--C(5) 105.0(1) Co(l)--C(3)--C(2) 76.7(2) P(2)--Co(l)--H(l) 87.(2) Co(l)--C(3)--C(4) 68.8(2) C(2)--Co(l)--C(3) 39.1(2) C(2)--C(3)--C(4) 117.1(4) C(2)--Co(l)--C(4) 69.9(2) Co(l)--C(4)--C(3) 70.5(2) C(2)--Co(l)--C(5) 76.3(2) Co(l)--C(4)--C(5) 74.3(2) C(2)--Co(l)--H(l) 161(1); C(3)--C(4)--C(5) 115.4(4) C(3)--Co(l)--C(4) 40.7(2) Co(l)--C(5)--C(4) 65.1(2) C(3)--Co(l)--C(5) 70.6(2) Co(l)--C(5> -C(6) 104.7(3) C(3)--Co(l)--H(l) 125(2) C(4)--C(5)--C(6) 119.3(4) C(l)- -C(6)--C(5) 115.6(4) References on p. 56 Chapter 3 Hydrogenation of arenes 48 3.4.3 - The intermediate (rj5-cycIohexadienyl)Co(dippcyp) (10) In a number of catalyst systems, the hydrogenation of benzene appears to proceed via a cyclohexadienyl intermediate before the eventual formation of cyclohexane.18'20 Transition metal-cyclohexadienyl complexes are generally prepared by hydrogen abstraction from cyclohexadiene compounds21 or nucleophilic addition to arene complexes.22 In the latter case, the arene becomes activated towards nucleophilic attack by virtue of its coordination to the metal, and the hydride enters an exo position on the ring. On the other hand, the formation of (r|5-cyclohexadienyl)-Co(dippcyp) (10) results from a transfer of hydrogen from cobalt to the endo site of the ring (Scheme 3-3). The main feature of the infrared spectrum of (t]5-cyclohexadienyl)Co(dippcyp) (10) is a band of medium intensity at 2744 cnr1 assigned to v(C-Hex0). This band is diagnostic of T|5-cyclohexadienyl compounds.23'24 The presence of a chiral diphosphine ligand in (T|5-cyclohexadienyl)Co(dippcyp) (10) results in diastereotopic ring protons. The lH NMR spectrum of 10 shows that the ring proton resonances are shifted upfield because of coordination to cobalt (Figure 3-4). The following assignments were made from homonuclear decoupling experiments: the broad, unresolved peak at 5.15 ppm is assigned to H4, although the resonance for this proton is normally shifted furthest downfield in similar complexes.22 The triplets at 4.80 and 5.57 ppm have been assigned to either H3 or H5, and the two triplets at 2.79 and 3.75 ppm to H2 or H6- Of interest are the resonances due to H e x 0 and H e n c i 0 . Coupling to H2 and H.6 is different, leading to an overlapping doublet of triplets for H e x 0 at 2.67 ppm (2J, 12, 12 Hz), and a more complex pattern for H e ndo centered at 2.55 ppm. References on p. 56 Chapter 3 Hydrogenation of arenes 49 3.4.4 - Solid state structure of Cn5-cyclohexadienyl)Co(dippcyp) (10) Red-brown crystals of (T]5-cyclohexadienyl)Co(dippcyp) (10) suitable for X-ray diffraction analysis were obtained from toluene/hexanes (10:1) at -30°C. The X-ray crystal structure of (T|5-C6H7)Co(clippcyp) (10) is shown in Figure 3-5. 1 • 1 • 1 1 1 • 1 1 1 1 1 1 ' 1 1 • • 1 1 1 1 1 1 1 1 1 1 1 1 1 ' 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 5 4 3 2 1 p p m Figure 3-4. ! H NMR spectrum (400 MHz) of (Tj5-cyclohexadienyl)Co(dippcyp) (10) showing distinct resonances for the diastereotopic ring protons. Residual C6D5CD2H is indicated by (°). References on p. 56 Figure 3-5. (a) Selected Chem 3D™ view of (Ti5-cyclohexadienyl)Co(dippcyp) (10). (b) Stereoview of the same molecule. References on p. 56 Chapter 3 Hydrogenation of arenes 51 Structures of analogous cyclohexadienyl complexes are numerous in the literature.3'220'25'26 Of interest is the plane containing the five carbon atoms bound to cobalt. The cobalt-carbon bond distances are: Co-C19, 2.071 A ; Co-C20, 2.096 A ; Co-C21A, 2.06 A ; Co-C22, 2.106 A and Co-C23, 2.122 A. The C-C bond lengths of the bound moiety range from 1.25 to 1.36 A, showing some lengthening upon coordination to cobalt. The uncomplexed carbon C18A is 15° out of the plane defined by C19, C20, C21A, C22 and C23; this is best illustrated in the Chem 3D™ view of (Ti5-C6H7)Co(dippcyp) (10) (Figure 3-5). This distortion from planarity was observed to be 41° in the analogous (ri5-C6H7)Co[Cy2P(CH2)2PCy2].3 Selected bond distances and angles in the structure of 10 are given in Tables 3-4 and 3-5 (see Appendix for details). Table 3-4. Selected bond distances (A) with estimated standard deviations in (r)5-C6H7) Co(dippcyp) (10) Co(l)--P(l) 2.1514(9) C(18A> —C(23) 1.51(1) Co(l)--P(2) 2.148(1) C(18B> -C(19) 1.27(2) Co(l)--C(18B) 2.04(1) C(18B)--C(23) 1.38(2) Co(l)--C(19) 2.071(4) C(19)--C(20) 1.358(7) Co(l)--C(20) 2.096(4) C(20)— -C(21A) 1.25(2) Co(l)--C(21A) 2.06(1) C(20)— -C(21B) 1.59(1) Co(l)--C(22) 2.106(4) C(21A> —C(22) 1.35(2) Co(l)--C(23) 2.122(4) C(21B)--C(22) 1.54(1) C(18A) -C(19) 1.65(1) C(22)— -C(23) 1.353(6) Table 3-5. Selected bond angles (deg) with estimated standard deviations in (r|5-C6H7) Co(dippcyp) (10) P(l)—Co(l)—P(2) 89.92(4) C(19)—C(18A)—C(23) 98.1(7) References on p. 56 Chapter 3 Hydrogenation of arenes 52 P(l)—Co(l)—C(18B) 98.3(4) P(l)—Co(l)—C(19) 104.7(2) P(l)—Co(l)—C(20) 134.6(2) P(l)—Co(l)—C(21A) 168.8(4) P(l)—Co(l)—C(22) 145.9(1) P(l)—Co(l)—C(23) 112.4(1) P(2)—Co(l)—C(18B) 170.7(5) P(2)—Co(l)—C(19) 145.5(2) P(2)—Co(l)—C(20) 111.4(2) P(2)—Co(l)—C(21A) 98.9(4) P(2)—Co(l)—C(22) 104.2(1) P(2)—Co(l)—C(23) 133.6(1) C(18B)—Co(l)—C(19) 35.9(5) C(18B)—Co(l)—C(20) 65.6(4) C(18B)—Co(l)—C(21A) 73.5(5) C(18B)—Co(l)—C(22) 66.5(5) C(18B)—Co(l)—C(23) 38.7(5) C(19)—Co(l)—C(20) 38.0(2) C(19)—Co(l)—C(21A) 64.2(4) C(19)—Co(l)—C(22) 81.1(2) C(19)—Co(l)—C(23) 69.5(2) C(20)—Co(l)—C(21A) 35.1(4) C(20)—Co(l)—C(22) 68.8(2) C(20)—Co(l)—C(23) 81.9(2) C(21A)—Co(l)—C(22) 37.9(5) C(21A)—Co(l)—C(23) 66.1(4) C(22)—Co(l)—C(23) 37.3(2) Co(l)--C(18B)--C(19) 73.4(5) Co(l)--C(18B)--C(23) 73.8(5) C(19)--C(18B> -C(23) 129(1) Co(l)--C(19)-•C(18A) 90.1(5) Co(l)- C(19)--C(18B) 70.8(5) Co(l)--C(19)--C(20) 72.0(3) C(18A) -C(19> —C(20) 121.9(6) C(18B)-C(19)--C(20) 117.3(8) Co(l)--C(20)- C(19) 70.0(3) Co(l)--C(20)— -C(21A) 71.0(5) Co(l)--C(20)--C(21B) 91.2(5) C(19)--C(20)— -C(21A) 114.4(8) C(19)--C(20)— -C(21B) 121.3(7) Co(l)--C(21A> —C(20) 73.9(5) Co(l)--C(21A> —C(22) 72.8(5) C(20)--C(21A> —C(22) 131(1) C(20)--C(21B)-—C(22) 98.6(6) Co(l)--C(22)— -C(21A) 69.3(4) Co(l)--C(22)— -C(21B) 92.0(5) Co(l)--C(22)--C(23) 72.0(2) C(21A) —C(22> —C(23) 114.9(7) C(21B> —C(22> -C(23) 124.4(6) Co(l)--C(23)--C(18A) 92.1(5) Co(l)--C(23)--C(18B) 67.5(5) Co(l)--C(23)--C(22) 70.7(2) C(18A) —C(23) —C(22) 123.2(7) C(18B) —C(23> —C(22) 112.6(7) References on p. 56 Chapter 3 Hydrogenation of arenes 53 Although (ri5-C6H7)Co(dippcyp) (10) was obtained from a solution of (n,3-C3H5)Co(dippp) (3) in benzene under H2, a different product could also be isolated. Dilution of the solution with hexanes precipitated a black powder, which is probably the dinuclear species, [(dippp)Co]2(|i-i13:T|3-C6l-l6) (7) (Scheme 3-4), by analogy to the previously characterized [{(C6Hii)2P(CH2)2P(C6Hii)2}Co]2(|i-Tl3:ri3-p-C6H4(CH3)2).27 The binuclear compound 7 is virtually insoluble in solvents such as toluene, benzene or hexanes, but could be characterized by mass spectrometry (M+: 748). 3.5 - The end of the catalytic cycle During a typical hydrogenation experiment, the formation of polynuclear hydrides would lead to the end of the catalytic cycle (as mentioned previously in Chapter 1). Thus, blue and purple hydrides [(dippp)CoH2]2 (4), and [(dippcyp)CoH2J2 (9) were formed when (ri3-C3H5)Co(dippp) (3), and ( T | 3 -CgHi3)Co(dippcyp) (8) were used as catalysts. The blue and purple hydrides 4 and 9 can also be synthesized by stirring the cobalt-allyl complexes 3 and 8 under hydrogen in a non-aromatic solvent (Schemes 3-2 and 3-4). Attempts to regenerate an active catalytic species by dehydrogenation of the blue hydride 4 with 3,3-dimethylbutene28 have failed (Scheme 3-4). With a smaller molecule like ethylene, adducts of structure [Pri2P(CH2)3PPri2]Co(p:-H)2(|l-C2H4)29 and (n2-C2H4)Co[But2P(CH2)3PBut2]3 have been isolated and structurally characterized. It is worthwhile noting that the analogous allylrhodium complex, (T]3-C3H5)Rh(dippp), reacts with H2 to form the binuclear dihydride [(dippp)Rh]2(p>H)2 with no evidence of hydrogenation of the aromatic solvent.30 The blue hydride [(dippp)CoH2]2 (4) is the focus of discussion in Chapter 4. References on p. 56 Chapter 3 Hydrogenation of arenes 54 Scheme 3-4 7 (24%) no hydrogenation of arene 3.6 - Discussion General conclusions can be drawn from the hydrogenation experiments. Allylcobalt complexes containing chelating diphosphines as homogeneous arene hydrogenation catalysts have not proven to be an improvement over the system (n,3-C3H5)Co[P(OMe)3J3 with monodentate phosphites. Although in both cases, mild conditions of temperature and pressure are an advantage over conventional References on p. 56 Chapter 3 Hydrogenation of arenes 55 heterogeneous systems, the sensitivity of the allylcobalt complexes to many functional groups makes their use practical. Conditions to improve the total turnover numbers to synthetically useful values (> 500) have not yet been found. References on p. 56 Chapter 3 Hydrogenation of arenes 56 3.7 - References 1. Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry, University Science Books, Mill Valley, California; 1987, pp 549-556. 2. Stuhl, L. S.; Rakowski-DuBois, M.; Hirsekorn, F. J.; Bleeke, J. R.; Stevens, A. E.; Muetterties, E. L. /. Am. Chem. Soc. 1978,100, 2405. 3. Priemer, H. Hydrocobaltierung und Cobalt-Katalysierte Hydrierung von Aromaten, Universitat Bochum, West Germany; 1987, 321 pp; Dissertation. 4. See for example: (a) Chaloner, P. A. Handbook of Coordination Catalysis in Organic Chemistry, Butterworths, London; 1986. (b) Knowles, W. S. Acc. Chem. Res. 1983,16, 106. (c) Morrison, J. D. (Ed.) Asymmetric Synthesis, Academic Press, New York; 1985. 5. Allen, D. L.; Gibson, V. C; Green, M. L. H.; Skinner, J. F.; Bashkin, J.; Grebenik, P. D. /. Chem. Soc. Chem. Commun. 1983, 895. 6. Fryzuk, M. D.; Jones, T.; Einstein, F. W. B. Organometallics 1984,3, 184. 7. Roberts, N. K.; Wild, S. B. /. Am. Chem. Soc. 1979,101, 6254. 8. (a) Bakos, J.; Toth, L; Balint, H.; Marko, L. /. Organomet. Chem. 1985,279, 23. (b) MacNeil, P. A.; Roberts, N. K.; Bosnich, B. / . Am. Chem. Soc. 1981,103, 2273. 9. Sommer, K. Z. Anorg. Allg. Chem. 1970,376, 37. 10. Bleeke, J. R.; Muetterties, E. L. /. Am. Chem. Soc. 1981,103, 556. 11. (a) Muetterties, E. L.; Schaeffer, H.; Mink, R. I.; Darensbourg, M. Y.; Millar, M.; Groshens, T.; Klabunde, K. J. Inorg. Chem. 1979,18, 883. (b) Muetterties, E. L.; Bleeke, J. R. Acc. Chem. Res. 1979,12, 324. References on p. 56 Chapter 3 Hydrogenation of arenes 57 12. Albright, J. O.; Datta, S.; Bezube, B,; Kouba, J. K.; Marynick, D. S.; Wreford, S. S.; Foxman, B. M. /. Am. Chem. Soc. 1979,101, 611. 13. Huttner, G.; Lange, S. Acta Cystallogr. Sect. B 1972, B28, 2049. 14. (a) Lucherini, A.; Porri, L. / . Organomet. Chem. 1978, 155, C45. (b) Muetterties, E. L.; Bleeke, J. R.; Wucherer, E. J.; Albright, T. A. Chem. Rev. 1982,82,499. 15. Churchill, M. R.; Mason, R. Proc. R. Soc. London. Ser. A 1966,292, 61. 16. Thompson, M. R.; Day, C. S.; Day, V. W.; Mink, R. I.; Muetterties, E. L. /. Am. Chem. Soc. 1980,102, 2979. 17. (a) Benn, R.; Mynott, R.; Topalovic, I.; Scott, F. Organometallics 1989,8, 2299. (b) Scott, F.; Kruger, C; Betz, P. / . Organomet. Chem. 1990,387, 113. 18. Jonas, K. Angew. Chem. Int. Ed. Engl. 1985, 24, 295. 19. Jones, W. D.; Dong. L. J. Am. Chem. Soc. 1989, 111, 8722. 20. Maklis, P. M. /. Chem. Soc. Dalton Trans. 1984, 1747. 21. (a) Johnson, B. F. G.; Lewis, J.; Yarrow, D. J. /. Chem. Soc. Dalton Trans. 1972, 2084. (b) Birch, A. J.; Cross, P. E.; Lewis, J.; White, D. A.; Wild, S. B. /. Chem Soc. A 1968, 332. (c) Pearson, A. J. /. Chem. Soc. Perkin Trans. 1 1977, 2069. 22. (a) White, C; Maitlis, P. M. /. Chem. Soc. A 1971, 3322. (b) Baudry, D.; Boydell, P.; Ephritikhine, M. J. Chem. Soc. Dalton Trans. 1986, 525. (c) Bailey, N. A.; Blunt, E. H.; Fairhurst, G.; White, C. /. Chem. Soc. Dalton Trans. 1980, 829. (d) Jones, D.; Pratt, L.; Wilkinson, G. / . Chem. Soc. 1962, 4458. (e) Winkhaus, G.; Pratt, L.; Wilkinson, G. /. Chem. Soc. 1961, 3807. (f) Pyke, R. D.; Ryan, W. J.; Carpenter, G. B.; Sweigart, D. A; /. Am. Chem. Soc. 1989, 111, 8535. (g) Baudry, D.; Ephritikhine, M.; Felkin, H.; Jeannin, Y.; Robert, F. / . Organomet. Chem. 1981, 220, C7. (h) Semmelhack, M. F.; Hall, Jr., H. T.; Farina, R.; Yoshifuji, M.; Clark, G.; Bargar, T.; Hirotsu, K.; Clardy, J. /. Am. References on p. 56 Chapter 3 Hydrogenation of arenes 58 Chem. Soc. 1979,101, 3535. (i) Semmelhack, M. F. /. Organomet. Chem. Libr. 1976,1, 371. (j) Grundy, S. L.; Smith, A. J.; Adams, H.; Maitlis, P. M. / . Chem. Soc. Dalton Trans. 1984, 1747. (k) Harman, W. D.; Schaefer, W. P.; Taube, H. /. Am. Chem. Soc. 1990,112, 2682. (1) Khand, I. U.; Pauson, P. L.; Watts, W. E. /. Chem. Soc. C 1968, 2257. 23. (a) ref. 3. (b) ref. 22a. (c) ref. 22e. (d) ref. 22j. 24. Khand, I. U.; Pauson, P. L.; Watts, W. E. /. Chem. Soc. C 1969, 2024. 25. (a) ref. 22h. (b) ref. 22i. 26. (a) Ittel, S. D.; Whitney, J. F.; Chung, Y. K.; Williard, P. G.; Sweigart, D. A. Organometallics 1988, 7, 1323. (b) Bird, P. H.; Churchill, M. R. /. Chem. Soc. C 1967, 2257. (c) Churchill, M. R.; Scholer, F. R. Inorg. Chem. 1969, 8, 1950. 27. Jonas, K.; Kcepe, G.; Schieferstein, L.; Mynott, R.; Kruger, C; Tsay, Y.-H. Angew. Chem. Int. Ed. Engl. 1983,22, 620; Angew. Chem. Suppl. 1983, 920. 28. Crabtree, R. H.; Mellea, M. F.; Mihelcic, J. M.; Quirk, J. M. J. Am. Chem. Soc. 1982,104,107. 29. Jonas, K. personal communication. 30. (a) Fryzuk, M. D.; Piers, W. E. Can. J. Chem. 1989, 67, 883. (b) Fryzuk, M. D.; Piers, W. E.; Rettig, S. J.; Einstein, F. W. B.; Jones, T.; Albright, T. A. / . Am. Chem. Soc. 1989, 111, 5709. References on p. 56 Chapter 4 The binuclear cobalt complex 59 [(dippp)CoH 2 ] 2 CHAPTER 4 The binuclear cobalt complex [(dippp)CoH2]2 a 4.1 - Introduction Transition metal hydrides play an important role in many homogeneous catalytic transformations such as hydrogenation, hydroformylation, hydrosilation, isomerization, and polymerization.1'2 Fundamental processes such as oxidative-addition and reductive elimination in mononuclear hydrides are generally well understood whereas in polynuclear hydrides, the chemistry is more complex. However, simple binuclear systems such as the family of coordinatively unsaturated rhodium-hydride complexes of general formula [{R2P(CH2)nPR2}Rh]2(p>H)2 (n = 2, 3; R = Pr*; n = 3, R = Bul) have been shown to provide much insight into reactions at two metal centres.3 The unsaturation of these rhodium hydride dimers is reflected by their high reactivity with a wide range of small molecules such as dihydrogen,4 olefins5 and dienes,6'7 and imines.8 In this chapter, the chemistry of polynuclear cobalt hydrides is discussed, with an emphasis being put on the characterization of the blue hydride [(dippp)CoH2]2 (4). Although these hydrides are assumed to be dimers, evidence presented later in this chapter will support the formulation. On the basis of the rich chemistry of [(dippp)Rh]2(|i-H)2, it seemed appropriate to compare the properties of the binuclear cobalt- and rhodium-hydride complexes of dippp. References on p. 90 Chapter 4 The binuclear cobalt complex 60 [(dippp)CoH 2 ] 2 4.2 - Synthesis of cobalt-hydride complexes At the end of Chapter 3, it was established that the formation of blue and purple cobalt hydrides led to the end of all catalytic activity during the hydrogenation of arenes. These hydrides also can synthesized by stirring the allylcobalt complexes (ri3-C3H5)Co(dippp) (3), (Ti3-C8Hi3)Co(dippcyp) (8), (ri3-C8Hi3)Co(dippp) (14), or (T]3-C8Hi3)Co(dippe) (8') under H 2 in non-aromatic solvents such as THF or hexanes (Scheme 4-1). Scheme 4-1 purple hydride References on p. 90 Chapter 4 The binuclear cobalt complex 61 [(dippp)CoH2]2 When the ligands were dippe or dippcyp, purple hydrides were formed as the only products, but with dippp a mixture of hydrides was obtained (total yield: 85-90%), the blue hydride [(dippp)CoH2]2 (4) being the major product along with a second product assumed to be a cobalt-hydride complex, "hydride X" (see Figure 4-3). Attempts to separate the two compounds by fractional recrystallization or column chromatography (Florisil) at low temperature (-30 to -40°C) have so far been unsuccessful. Surprisingly, the hydrogenation of (t|3-CH2C6H5)Co(dippp) (6) in T H F also gave a mixture of hydrides except that the ratio of the blue hydride 4 to hydride X is different from that found in the previous reaction (Equation 4-1). Equation 4-1 Hi THF (81%) -o-o + hydride X (major) The 1 H NMR spectrum of this product mixture is shown in Figure 4-1, with peaks due to hydride X labelled by asterisks (*). This reaction appears to be solvent-dependent, because with hexanes hydride X is the minor product. The by-product of the hydrogenation of the cobalt-benzyl complex is toluene, which was detected by GC/MS. The mechanism of the hydrogenation of the cobalt-benzyl complex 6 is thought to proceed as shown in Scheme 4-2. References on p. 90 Chapter 4 The binuclear cobalt complex 62 [(dippp)CoH2]2 Alternative routes to the blue hydride mixture are shown in Equations 4-2 and 4-3. They all gave a blue hydride 4/hydride X product mixture of varying ratio. The reaction of 2 equivalents of M+[BEt3H]- (M = Li, K) with [(dippp)Co]2(Lt-Cl)2 (2) results in brownish-black solutions from which the blue hydride 4/hydride X mixture can be isolated, although in small yields (15-20 %) (Equation 4-2). ppm Figure 4-1. *H NMR spectrum (300 MHz) of the hydride mixture obtained from the hydrogenation of (rj3-CH2C6H5)Co(dippp) (6). Peaks due to hydride X are denoted by asterisks (*). Solvent peaks C6D5H and hexanes are indicated by (°) and (+) respectively. References on p. 90 Chapter 4 The binuclear cobalt complex 63 [(dippp)CoH 2 ] 2 Scheme 4-2 -Or P « u /~~\.I C H 3 Cr Ay \ C o - H 5v C \ / J 2 Equation 4-2 [(dippp)Co]2(u.-Cl)2 + 2M+[J3Et3H] -THF [(dippp)CoH2]2 + hydride X + 2M+CT major product The mechanism of the reaction is not known, but perhaps involves a disproportionation. Reaction of [(dippp)Co]2(u.-Cl)2 (2) with Na-Hg under hydrogen also gave low yields (10-20%) of the blue hydride 4/hydride X mixture (Equation 4-3). Equation 4-3 [(dippp)Co]2(p>Cl)2 + 2Na-Hg-Itlf^[(dippp)CoH2]2 + hydride X + 2Na+Cl" 2 4 major product References on p. 90 Chapter 4 The binuclear cobalt complex 64 [(dippp)CoH 2 ] 2 Another method of producing the blue hydride 4/hydride X mixture is the reaction of (dippp)CoCl2 (1) with two equivalents of an organolithium reagent RLi (R = CH3, n-C4H9, (CH3)3CCH2) under H 2. C \ n CI RLi THF H 2 R: Me, n-butyl, neopentyl Equation 4-4 -V-4 major product \ ,CoH 3 + hydride X 5 30% This reaction not only gave the blue hydride 4/hydride X mixture as the major product, but gave yet another cobalt-containing product (dippp)CoH3 (5), which was isolated as a red solid (30%) (Equation 4-4). This reaction will be examined in greater detail in Chapter 5. From this point on, whenever the blue hydride [(dippp)CoF£2]2 (4) is referred to, it implicitly means the blue hydride 4/hydride X mixture. 4.3 - Characterization of [(dippp)CoH2]2 (4) and [(dippe)CoH2]2 (4') When characterizing hydride complexes, elemental analysis does not afford a practical method for estimating the number of hydride ligands. Chemical reactions with halogens, mineral acids and halogenated hydrocarbons have been employed, but sometimes cannot be relied upon to give a quantitative answer.2 Spectroscopic methods such as infrared and NMR spectroscopy are more reliable in providing References on p. 90 Chapter 4 The binuclear cobalt complex 65 [(dippp)CoH 2 ] 2 qualitative estimates of (i) the number of hydride ligands, and (ii) their stereochemistry in the hydride complex. However, they have limitations, especially when the complexes are paramagnetic such as the blue hydride [(dippp)CoH2]2 (4). A few examples of paramagnetic transition metal hydrides have been reported in the literature; e.g. {[(triphos)Rh]2(u-H)3}(BPh4)29, [CoH(PEt3)(triphos)]+BPh4-10 (triphos = MeC(CH2PPh2)3), OsHChztPBu^Phb,11 [(T|5-C5H5)VH(dmpe)]2(M.-dmpe) (dmpe = Me 2 P(CH 2 )2PMe2), 1 2 [CoHL4]+ X" (where L = P(OPh)3> P(OEt)2Ph, P(OMe)2Ph; X = BF4, PF 6), 1 3 ( n 5 - C 5 H 5 ) 2 N b H 2 , 1 4 [(Tl5-C5H5)W-(C6H5)H]+,15 MH2Cl2[Me2P(CH2)2PMe2] (M = Nb, Ta),16 [FeHCl(Ph2P(CH2)2-PPh2)2]+BF4"17 and iron carbonyl hydrides.18 In most cases, the characterization of these paramagnetic hydrides has involved methods such as esr, X-ray and neutron diffraction analyses. 4.3.1 - Nmr spectra of [(dippp)CoH2]2 (4) and [(dippe)CoH2]2 (4') At 20°C, the 31P{ lR\ spectrum of the blue hydride 4 consists of two very broad peak's at -200 (Avi/2 = 2500 Hz), and 355 ppm (Avi/2 = 6260 Hz), which at -90°C are replaced by a broad singlet centered at 88.3 ppm (Avi/2 = 3760 Hz) (Figure 4-2). Based on spectrum (a) in Figure 4-2, it appears that the peak at -200 ppm can be assigned to hydride X because this species was formed in more significant amounts in that particular reaction than [(dippp)CoH2]2 (4). The *H NMR spectrum of the blue hydride at 20°C is shown in Figure 4-3. It is worthwhile comparing this spectrum and that shown in Figure 4-1, because the product ratios of [(dippp)CoH2]2 (4) to hydride X in the two cases are different. The ligand resonances are shifted only slightly from their normal diamgnetic positions. Assignments have been made for the methyl protons of [(dippp)CoH2]2 (4) at 0.29 and 1.44 ppm. The other peaks in the spectrum References on p. 90 Chapter 4 The binuclear cobalt complex 66 [(dippp)CoH2]2 y \ i i A. 2°'C 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 200 ppm 0 200 Figure 4-2. (a) 31P{1H) NMR spectrum (121.4 MHz) of the hydride mixture formed by the reaction of (dippp)CoCl2 (1) with n-BuLi under H2. The red solid, (dippp)CoH3 is indicated by a peak (•) at 81.7 ppm. The peak at 71.2 ppm (s) is an impurity, (b) Variable temperature 31p{lH} NMR spectra (121.4 MHz) of the hydride mixture formed by the hydrogenation of Cn3-C3H5)Co(dippp) (3). References on p. 90 Chapter 4 The binuclear cobalt complex [(dippp)CoH2J2 6 7 Figure 4-3. (a)  lVL NMR spectrum (300 MHz) of the blue hydride [(dippp)CoH2]2 4 at 20°C. (b)  lH NMR spectrum (400 MHz) of the blue hydride at -95°C. Peaks due to hydride X are marked by asterisks (*), and residual C6D5CD2H is indicated by (°). References on p. 90 Chapter 4 The binuclear cobalt complex 68 [(dippp)CoH2]2 _ 1 1.3 A 1 I 1 ' 1 ' I ' ' ' ' | ' ' ' i ' ' i ' | ' i ' i ; i i i i I I I i i i i i i i I i i i i i i i i i I i i i i i i 5 4 3 2 4 0 ppm I I ' ' ) ' I I ' I I ' I I I I I I I I I I I I I I I I I I I I I I I I I II I I I I I I 4 3 2 ^ 6 ppm Figure 4-4. (a) *H NMR spectrum (300 MHz) of the purple hydride [(dippe)CoH2]2 (4') at 20°C. (b) The spectrum of the purple hydride at -95°C. Residual C6D5CD2H is indicated by (°), and hexanes by (+). References on p. 90 Chapter 4 The binuclear cobalt complex 69 [(dippp)CoH2]2 could not be assigned. Peaks marked by asterisks (*) are due to hydride X. When the sample is cooled to -95°C, the spectrum of [(dippp)CoH2]2 (4) is more indicative of a diamagnetic compound, since the peaks observed for the ligands show resolved coupling, and are within the normal range expected for a diamagnetic complex (Figure 4-3). A broad peak can also be discerned in the hydride region at -95°C. For the purple hydride [(dippe)CoH2]2 (4')> no peaks are observed in the 31P{1H} NMR spectrum at 20°C, but when the sample is cooled to -80°C, two peaks are seen at 133 (Avi/2 = 500 Hz) and 150 ppm (Avi/2 = 1500 Hz), shifting at -95°C to two overlapping signals at 129 ppm (Avi/2 = 619 Hz). The !H NMR spectra of the purple hydride [(dippe)CoH2]2 (4') at 20° and at -95°C are shown in Figure 4-4. Since the complex is paramagnetic, peak assignments were made on the basis of integrated intensities, and by comparison with the assignments made previously for [(dippe)Co]2(p>Cl)2 in Chapter 2. The resonances are consistent for only one product being present, and show behaviour similar to that observed in the spectra of the blue hydride 4, i.e. at low temperature the compound becomes diamagnetic. However, the hydride signal could not be discerned in the low-temperature spectrum. In both cases, the changes are fully reversible, and the weak paramagnetic condition is reestablished when samples of the blue and purple hydrides are warmed to room temperature. 4.3.2 - UV-visible spectroscopy of [(dippp)CoH2]2 (4) In an attempt to distinguish between the two species constituting the blue hydride 4, UV-visible spectra of the complex in hexanes at different concentrations were obtained (Figure 4-5). A feature of the spectrum at high concentration (3.56 x References on p. 90 Chapter 4 The binuclear cobalt complex 70 [(dippp)CoH2]2 10"3 M) is the presence of absorption bands at 495 (e = 700 L moHcnr1), and 617 nm (e = 460 L mol-1 cm"1). Bands at 253 (e = 6200 L mol'1 cm"1) and at 358 nm (e = 2600 L mol-1 cm-1) become observable with dilution (3.56 x 10*4 M). The values of the molar extinction coefficients for the bands at 358, 495 and 617 nm are constant over the three concentrations studied, indicating that the predominant species in solution stays intact over that concentration range. Although the band at 617 nm and the shoulder at 515 nm are present at high concentration (3.56 x 10-3 M), they disappear on dilution, but in fact they may be too weak to be observed. 3.56 x 10' 3 M 7.12 x 10" 3M 3.56x1(f*M wavelength (nm) Figure 4-5. UV-visible spectra of the blue hydride [(dippp)CoH2]2 (4) at different concentrations in hexanes. References on p. 90 Chapter 4 The binuclear cobalt complex 71 [(dippp)CoH 2 ] 2 On the basis of their e values, bands at 253 and at 358 nm have been assigned to charge-transfer transitions.19 However, it is not possible to distinguish between the two components of the blue hydride mixture from these data. Molecular weight measurements on the blue hydride 4 in solution by the isopiestic (Signer) method20 were not reproducible. However, evidence for a binuclear structure for [(dippp)CoH2]2 (4) in solution was provided by an electrochemical study. 4.3.3 - Electrochemical measurements on [(dippp)CoH2]2 (4) The cyclic voltammogram of [(dippp)CoH2]2 (4) at 20°C shows four redox steps as two well-separated pairs at E<>' = -0.18 V (A/H), -0.35 V (B/G), -1.30 V (C/F) and -1.62 V (D/E) (Pt bead electrode; scan rate, 0.38 V s'1) (Figure 4-6). The formal electrode potentials, E 0 ' , were measured with respect to standard calomel electrode (SCE). A more detailed analysis of the separated pairs was carried out and the results are shown in Figure 4-7 with the data presented in Table 4-1. Table 4-1 - [(dippp)CoH2]2 (4) - Electrochemical data for the redox couples A/H, B/G, C/F and D/E scan rate(v) Redox pair (V s-1) E«' (V) AEp (mV) a^/ipc A/H 1.76 -0.22 57 -B/G 1.76 -0.40 52 0.79 A/H 3.52 -0.22 79 -B/G 3.52 -0.39 85 0.88 C/F 0.30 -1.11 60 _ References on p. 90 Chapter 4 The binuclear cobalt complex 72 [(dippp)CoH2]2 D/E 0.30 -1.44 70 0.67 C/F 0.74 -1.21 70 -D/E 0.74 -1.54 80 0.70 o!o ^ 5 ^ 5 E / V Figure 4-6. Cyclic voltammogram of [(dippp)CoH2]2 at 20°C (Pt bead, 0.1 M [Bun4N]PF6 in THF); scan rate: 0.38 V s"1. The asterisks (*) denote the products of slow decomposition of 2 during the experiment. References on p. 90 Chapter 4 The binuclear cobalt complex 73 [(dippp)CoH2]2 a b -0.1 0.0 -0.1 -0.2 -03 -0 4 E/V Figure 4-7. (a) [(dippp)CoH2]2: redox couples C/F and D/E (scan rate: 0.38 V s"1). (b) Redox couples A/H and B/G (scan rate: 0.15 Vs"1). References on p. 90 Chapter 4 The binuclear cobalt complex 74 [(dippp)CoH2]2 Analysis of the redox couples reveal that the peak current ratios ipa/ipc for B/G are close to unity for scan rates of 1.76 and 3.52 V s"1, which is consistent with the chemical reversibility of these reductions. The magnitude of the peak separations (AEp) for each of the four redox waves is close to the theoretical value of 59 mV expected for a one-electron transfer.21-22 The lowering of the ipa/ipc values with decreasing scan rate is indicative of coupled chemical reactions (e.g. decomposition) which follow the electron-transfer steps. Peak current ratios for the redox couples A/H and C/F could not be obtained because satisfactory separation of the individual redox couples within each pair was not achieved. The blue hydride 4 undergoes successive reductions in one-electron steps to species containing increasing negative charge. On this basis, the species formed at each step are shown below (Scheme 4-3). In going from II to III, the potential required for the second reduction is slightly higher than the first electron transfer, presumably because some electron derealization has occurred over the second cobalt nucleus. Similar arguments can be applied to the electron transfer in IV and V. It is significant that these reductions occur as pairs, since this is consistent with stepwise reduction of a binuclear complex without large disruption of the overall structure of the complex. Electrochemical studies on metal polyhydrides are scarce in the literature except for Re2(p>H)4H4(PR-3)4 (PR3 = PPI13, PEtPh2, PEt2Ph),23 and the recently reported rhodium complex {[{CH3C(CH2PPh2)3}Rh]2(|i-H)3}2+(BPh4)2,9 where the redox sequence observed is analogous to that observed for the blue hydride 4. Although two species are known to be present in the blue hydride mixture (by lH NMR), they could not be distinguished electrochemically. The results suggest that they may be very similar in constitution, such as isomers, or that a different species References on p. 90 Chapter 4 The binuclear cobalt complex 75 [(dippp)CoH2]2 such as a monomer (dippp)CoH2 is present in the mixture. In any event, the magnitudes of the peak currents are consistent with the one-electron nature of the redox waves being attributable to a single electrochemically-active species present in the electrochemical cell. Scheme 4-3 +e -e J2 +e -e ->2 J2 III +e -e IV 3-+e -e J2 H 4-->2 V V = dippp 4.3.4 - Magnetic susceptibility measurements on [(dippp)CoH2]2 (4) The magnetic moment p.eff, of the blue hydride 4 as determined in solution by Evans' method24 at 20°C in benzene is 1.3 (± 0.1) BM. A variable-temperature magnetic susceptibility study using toluene as solvent shows that initially at 20°C, the value of |ieff is 1.4 BM, but when the sample is cooled, |Xeff decreases to a value of 0.7 BM at -95°C (Figure 4-8). However, solid-state susceptibility measurements show that except for traces of ferromagnetic impurities, the blue hydride is References on p. 90 Chapter 4 The binuclear cobalt complex 76 [(dippp)CoH2]2 diamagnetic from 6 to 280 K. For example, the presence of a small amount (<1%) of cobalt metal (which is ferromagnetic) is enough to give rise to an observable positive measurement. Recently, the complexes [R2P(CH2)2PR2]FeCl2 (R = C2H5, n-C3H7) were reported to be diamagnetic in the solid state, but paramagnetic in solution.25 The behaviour was rationalized in terms of partial dissociation of the bidentate ligand, but, as shown in the cyclic voltammetric data, this does not occur here. On the other hand, if in solution hydride X was present as a mononuclear species such as (dippp)CoH.2, it would contribute to the observed solution paramagnetism. Then, it can be assumed that a monomer dimer equilibrium exists between [(dippp)CoH2]2 (4) and (dippp)CoH2. More evidence will be presented in Chapter 5 to show that (dippp)CoH2 is a stable species. fietf vs temperature 1.6-1.4-1.2-1.0-0.8-° - 6 1 — • — r — « — j — ' — 1 — 1 — 1 — r — 1 — 1 — , — , — , 160 180 200 220 240 260 280 300 temperature (K) Figure 4-8. [(dippp)CoH2]2 (4): temperature dependence of |ieff between 20 and -95°C (solvent: toluene). References on p. 90 Chapter 4 The binuclear cobalt complex 77 [(dippp)CoH 2] 2 4.3.5 - Infrared spectroscopy In solution (hexanes), a weak and very broad band observed between 1890 and 1900 cnr1 has been assigned to a terminal Co-H stretching mode. In the solid state, the v(Co-H) band is observed at 1981 cnr1 (Figure 4-9), which is shifted in the deuterated analogue,26 but the v(Co-D) band is obscured by the ligand modes. By comparison with the infrared spectrum of the deuterated complex [(dippp)CoD2]2> a bridging Co-H-Co stretch and a terminal Co-H bending mode were identified as a shoulder at 1001 cm-1, and at 756 cm-1 respectively (Figure 4-9). The v(Co-D-Co) band is buried under a band envelope centered at 615 cm-1 in the IR spectrum of [(dippp)CoD2l2» whereas the 5(Co-D) mode was not be detected. Although both bridging and terminal hydride ligands could be inferred from the IR data, the actual number of hydrides present per molecule was deduced by chemical means. When toluene solutions of the blue hydride 4 and (dippp)CoCl2 (1) were mixed, a vigorous reaction occured, with liberation of hydrogen gas and resulting in a green solution from which the chloro-bridged dimer [(dippp)Co]2(|i-Cl)2 (2) was isolated quantitatively (Equation 4-5). Equation 4-5 References on p. 90 Chapter 4 The binuclear cobalt complex [(dippp)CoH2]2 78 5(Co-H) v (Co-H) 2000 1500 1 0 0 0 Wavenumbers (cm" 1 ) 500 Figure 4-9. Infrared spectrum of the blue hydride [(dippp)CoH2]2 (4) in the solid state (KBr pellet). References on p. 90 Chapter 4 The binuclear cobalt complex 79 [(dippp)CoH2]2 Analysis of the evolved gas by Toepler pump gave 1.9 ± 0.2 mole of H2 gas per mole of blue hydride assuming a binuclear formulation. This result suggested that four hydrides were coordinated to two cobalt centres. In order to obtain more information on the structure of this compound, a single crystal X-ray diffraction study was carried out, and the results are described in the following section. 4.3.6 - X-ray analysis of [(dippp)CoH2]2 (4) A single crystal X-ray diffraction study performed at 21°C had elucidated the structure, but in an attempt to locate all the hydride ligands, a second analysis was carried out at -155°C. Unfortunately, no new information could be extracted from this second analysis. The structure of the blue hydride 4 in the solid state at -155°C is shown in Figures 4-10 and at 21°C in Figure 4-11. Relevant bond distances and bond angles are given for the two structures in Tables 4-2 and 4-3 (see Appendix for details). It is important to point out that since the two structures were solved on models assuming the presence of two or three bridging hydride ligands, the cobalt-hydride bond distances are drastically different. The following discussion is mainly about the structure solved at 21 °C. Three bridging hydride ligands were located in the room temperature structure (Figure 4-11), two of which were related by the C2 axis of the molecule. The location of the fourth hydride could not be determined, but it is presumed to be a terminal hydride disordered over four possible sites on the two metal centres. The bridging Co-H distances range from 1.52 to 1.57 A. There is a very short Co-Co bond distance of 2.2811(7) A in the molecule, second only to the Co-Co bond distance reported in the literature for ( T | 5 -References on p. 90 Chapter 4 The binuclear cobalt complex t(dippp)CoH2]2 80 Figure 4-10. Solid state structure of [(dippp)Co]2(H)(u.-H)3 (4) at -155 °C. References on p. 90 Chapter 4 The binuclear cobalt complex 8 \ [(dippp)CoH2]2 Figure 4-11. (a) Selected Chem 3D™ view of the blue hydride [(dippp)Co]2(H)(p> H)3 (4) at 21°C. (b) Stereoview of the molecule. References on p. 90 Chapter 4 The binuclear cobalt complex 82 [(dippp)CoH2]2 C5H5)2Co2[bis(trimethylsilyl)acetylene] (2.185 A) . 2 7 The structure of the latter consists of the bridging acetylene ligand oriented perpendicular to the Co-Co axis, resulting in a short metal-metal bond which has been rationalized in terms of a cobalt-cobalt double bond in the molecule. The short Co-Co bond distance in the blue hydride can be explained by the presence of three bridging hydride ligands,2 or because of multiple bonding,28 as suggested as well in the polyhydrido-bridged cobalt complex {[{(Ph2AsCH2)3CCH3}Co]2(li-H)3}+(BPh4)-.29 There are three bridging hydride ligands in the structure of this complex with the cobalt nuclei 2.377(8) A apart. For comparison, other examples of short Co-Co bonds in binuclear cobalt compounds are: 2.372(2) A in [(PPh 3) 2N][{(i^-CsHs^oh^COhlV 0 2.370(1) A in [(^ 5. C5H5)Co]2(^-CO)(|i-NO),31 2.3272(2) A in [(r|5-C5Me5)Co]2(p:-CO)2(p> CHCH3)32 and 2.327(2) A in [(7i'5-C5Me5)Co]2(H-CO)2.33 Table 4-2. Selected bond distances (A) in [(dippp)CoH2]2 (4) at 21° and at -155°C. T = 21°C Co(l)—Co(l)' 2.2841(7) Co(l)—P(l) 2.1357(8) Co(l)—P(2) 2.1416(8) Co(l)—H(35) 1.57(4) Co(l)—H(36*) 1.52(5) Co(l)—H(36) 1.56(5) T = -155°C Co(l)—Co(l)' 2.2811(10) Co(l)—P(l) Co(l)—P(2) Co(l)—H(l) Co(l)—H(l)' 2.1319(10) 2.1415(10) 1.25(9) 1.41(8) Table 4-3. Selected bond distances in [(dippp)CoH2]2 (4) at 21° and -155°C. T = 21°C T = -155°C P(l)—Co(l)—P(2) 99.36(3) P(l)—Co(l)—P(2) 99.24(4) P(l)—Co(l)—Co(l)' 128.92(3) P(l)—Co(l)—Co(l)' 127.45(4) References on p. 90 Chapter 4 The binuclear cobalt complex [(dippp)CoH2]2 P(2)—Co(l)—Co(l)' 131.55(3) C(l)—P(l)—Co(l) 119.0(1) C(4)—P(l)—Co(l) 115.7(1) C(5)—P(l)—Co(l) 116.1(1) C(3)—P(2)—Co(l) 119.30(9) C(6)—P(2)—Co(l) 116.6(1) C(7)—P(2)—Co(l) 114.7(1) 83 H(35)--Co(l)--Co(l)' 43(1) H(36)--Co(l)--Co(l)' 42(2) H(36)*--Co(l)--Co(l)" 43(2) H(35)--Co(l)--P(l) 98(1) H(36)--Co(l)--P(D 104(2) H(36)*--Co(l)--P(l) 170(2) H(35)--Co(l)--P(2) 145.2(2) H(36)--Co(l)--P(2) 132(2) H(36)*--Co(l)--P(2) 89(2) H(36)--Co(l)--H(35) 71(2) H(36)*--Co(l)--H(35) 72(2) H(36)*--Co(l)--H(36) 72(3) P(2)—Co(l)—Co(l)' C(l)—P(l)—Co(l.) C(4)—P(l)—Co(l) C(5)—P(l)—Co(l) C(3)—P(2)—Co(l) C(6)—P(2)—Co(l) C(7)—P(2)—Co(l) H(l)—Co(l)—Co(l)' H(l)'—Co(l)—Co(l)' 132.64(3) 1.19.60(10) 115.94(11) 115.46(11) 119.59(11) 117.10(11) 113.90(11) 29(3) 33(3) H(l)—Co(l)—P(l) 105(3) H(l)'—Co(l)—P(l) 155(3) H(l)—Co(l)—P(2) 143(3) H(l)'—Co(l)—P(2) 104(3) H(l)'—Co(l)—H(l) 61(5) The dihedral angle between the two C0P2 planes of the blue hydride 4 is 77°. This nearly perpendicular arrangement of the end fragments of the binuclear molecule is a result of the bulky isopropyl substituents on phosphorus, the rather large P-Co-P angle of 99.4°, and the short Co-Co bond, causing these isopropyl substituents to interlock into one another. A similar geometry was found in [{(C6Hn)2P(CH2)3-P(C6Hn)2}Ni]2(u,-H)2,34 where the dihedral angle is 63° and in [{BuWCFJ^-References on p. 90 Chapter 4 The binuclear cobalt complex g4 [(dippp)CoH 2] 2 PBul2}Pt]2 where this angle is 82°.3 5 As a result, the inner core of the molecule is well protected, and this probably accounts for the low degree of reactivity of the blue hydride. For example, attempts to regenerate an active arene hydrogenation catalyst from the blue hydride 4, by dehydrogenation using 3,3-dimethylbutene, have been unsuccessful (Scheme 4-4). 4.4 - Reactivity A few reactions involving [(dippp)CoF£2]2 (4) are shown in Scheme 4-4. The reaction of [(dippp)CoH2]2 (4) with (dippp)CoCl2 (1) to give the chloro-bridged dimer [(dippp)Co]2((i-CT)2 (2) has been discussed earlier (section 4.3.5). The reaction of the blue hydride 4 with CO in hexanes produced a brown product of formula (dippp)CoH(CO)2 (12 ), based on elemental analysis, mass spectral, infrared and NMR data. A broad singlet was observed at 54.0 ppm in the 31P{1H} NMR spectrum of the complex, while the *H NMR spectrum of the complex contained a broad singlet integrating for one hydrogen at -12.0 ppm , indicative of the presence of a hydride ligand. The infrared spectrum of (dippp)CoFf(CO)2 (12) showed two very strong bands at 1960 and 1865 cm-1, corresponding to v(C=0) bands. The mass spectrum of this complex confirmed its identity by the presence of the following peaks: M+ (392), {M-CO)+ (364), and {M-2CO}+ (336). The reaction of [(dippp)CoH-2]2 (4) with borane reagent (BFf3»Me2S) was attempted to convert 4 into a cobalt-borohydride complex; however, only decomposition was observed, with a white solid being isolated in 78% yield. Subsequent analysis of this solid indicated that it is (dippp)»(BH3)2. A four-line References on p. 90 Chapter 4 The binuclear cobalt complex 85 [(dippp)CoH2]2 Scheme 4-4 /~\.*cl«.. / p ~ \ \ C o ^ ^Co > + 2H (PHJ decomposition + PPri 2 ) - (BH 3 ) 2 — ( ) — \ to luene \AA y, BH 3 »Me 2 S hexanes 1. 3,3-dimethylbutene 2. H 2 , C 6 H 6 no hydrogenation of benzene EtoO r-01 C o - H 1 1 3 hexanes CO AA \ CoH(CO) 2 1 2 References on p. 90 Chapter 4 The binuclear cobalt complex 86 [(dippp)CoH2]2 pattern (2JPB, 73 Hz) observed in the 3 1P{1H} NMR spectrum of the latter is indicative of phosphorus-boron coupling.36 When a solution of the blue hydride 4 in diethyl ether was stirred with a ten-fold excess of either 1,3-butadiene, or 2-methyl-l,3-butadiene, or 2,3-dimethyl-l,3-butadiene, brown solutions were obtained. H 1 — A / ' "4 H 2 H 3 x4 •13 -14 x4 4 3 ppm Figure 4-12. lH NMR spectrum (400 MHz) of [(dippp)Co]2(H)2*(2,3-dimethyl-1,3-butadiene (13). References on p. 90 Chapter 4 The binuclear cobalt complex 87 [(dippp)CoH 2] 2 Analysis of the dark brown oils obtained from the reactions with 1,3-butadiene and 2-methyl-l,3-butadiene by *H NMR spectroscopy showed broad, unintelligible peaks. With 2,3-dimethyl- 1,3-butadiene, red-brown crystals were isolated, although the yield was low (15%). Normally, mononuclear hydride complexes react with 1,3-dienes to form allyl complexes.7 Analysis of this complex by *H NMR spectrosocopy showed that no rearrangement had occurred to give the T|3-allyl complex, an observation also made in the 2,3-dimethyl-1,3-butadiene complex (diene)Co(H)(PPh3)2.37 The lH NMR spectrum of complex 1 3 (Figure 4-12) consists of a complicated pattern for the ligand resonances between 0.8 and 2.1 ppm, but two peaks are observed in the hydride region each integrating for one hydrogen, a triplet at -13.66 ( 2 J P H . 58 Hz), and a broad peak at -13.10 ppm. The low field region of the spectrum is very difficult to interpret, except for two sharp singlets at 2.11 and 2.17 ppm for the two methyl groups of the diene fragment, and two unresolved peaks at 5.14 and 5.27 ppm each integrating for one proton. They may be assigned to Hi and H4 of the diene fragment, whereas H 2 and H3 are probably obscured by the ligand resonances. Four broad singlets are observed in the 31P{*H} NMR spectrum of the complex at 39.4, 47.8, 53.2, and 69.9 ppm, indicating a very unsymmetrical structure in this molecule. Other relevant data obtained from the mass spectrum ({M-4H}+, 750), and the carbon and hydrogen analyses of this compound, suggest a formulation consisting of two cobalt-diphosphine moieties and one diene molecule. Unfortunately, crystals suitable for a diffraction analysis could not be obtained. A tentative formula for this complex is [(dippp)Co]2(H)2»(dimethylbutadiene) (13). References on p. 90 Chapter 4 The binuclear cobalt complex 88 [(dippp)CoH2]2 4.5 - Discussion The definitive solution structure for the blue hydride [(dippp)CoH2J2 (4) may never be achieved. Nonetheless, a few conclusions can be made from this study. In the solid state, the molecule is binuclear (as shown in the X-ray analysis) and diamagnetic. The paramagnetic (solution, 20°C)-diamagnetic (solution, -95°C and solid state) behaviour of the blue hydride 4 has been rationalized in terms of a monomer dimer equilibrium in solution. Observations made in solution at ambient temperature (20°C) about the NMR spectra and the magnetic moments are an average of the two species. Consistent with these observations, as the temperature is lowered, the equilibrium shifts toward the binuclear complex. Hence, the blue hydride 4 displays more diamagnetic properties, viz. the decrease in (ieff with temperature, and NMR spectra indicating diamagnetic behaviour. The decrease in |ieff on lowering the temperature suggests that the ratio of the two species is never constant. However, the presence of a trinuclear or other species cannot be excluded to account for the solution paramagnetism. A magnetic spin-state cross-over (singlet triplet) or spin equilibrium38 has been ruled out on the basis that this effect should be observed in the solid state.39 As a good indication, the X-ray crystal structures of the blue hydride at 21° and at -155°C reveal no large discrepancies in the cobalt-phosphorus bond distances. From this study, it is clear that cobalt- and rhodium-hydride complexes of dippp bear little resemblance in their physical and chemical properties. References on p. 90 Chapter 4 The binuclear cobalt complex 89' -[(dippp)CoH2]2 Earlier in this chapter, one of the synthetic routes to the blue hydride (Section 4.2) also produced a cobalt complex, the red hydride (dippp)CoH3 (5). The formation of this complex is puzzling, and its chemistry is presented in the next chapter. References on p. 90 Chapter 4 The binuclear cobalt complex 90 [(dippp)CoH2]2 4.6 - References 1. (a) Teller, R. G.; Bau, R. Struct. Bond. 1981, 44, 1. (b) Bau, R.; Teller, R. G.; Kirtley, S. W.; Koetzle, T. Acc. Chem. Res. 1979,12, 176. (c) Bau, R.; Koetzle, T. Pure Appl. Chem. 1978, 50, 55. (d) Muetterties, E. L. in The Hydrogen Series: Transition Metal Hydrides, Muetterties, E. L. (Ed.); Marcel Dekker, Inc., New York; 1971, vol. 1, pp 11-31. (e) Crabtree, R. H. Compr. Coord. Chem. 1987, 2, 689. (f) Ibers, J. A. Adv. Chem. Ser. 1978,167, 26. (g) James, B. R. Compr. Organomet. Chem. 1982, 5, 285. (h) Kaesz, H. D.; Saillant, R. B. Chem. Rev. 1972, 72, 2318. 2. Moore, D. S.; Robinson, S. D. Chem. Soc. Rev. 1983,12, 415. 3. Fryzuk, M. D. Organometallics 1982,1, 408. 4. Fryzuk, M. D.; Piers, W. E. Can. J. Chem. 1989, 67, 883. 5. Fryzuk, M. D.; Jones, T.; Einstein, F. W. B. Organometallics 1984,3, 185. 6. Fryzuk, M. D.; Piers, W. E. Polyhedron 1988, 7, 1001. 7. Fryzuk, M. D.; Piers, W. E.; Rettig, S. J.; Einstein, F. W. B.; Jones, T.; Albright, T. A. /. Am. Chem. Soc. 1989, 111, 5709. 8. Fryzuk, M. D.; Piers, W. E. Organometallics 1990, 9, 986. 9. Bianchini, C.; Laschi, F.; Masi, D.; Mealli, C.; Meli, A.; Ottaviani, F. M.; Proserpio, D. M.; Sabat, M.; Zanello, P. Inorg. Chem. 1989,28, 2552. 10. Bianchini, C.; Masi, D.; Mealli, C.; Meli, A.; Sabat, M. Gazz. Chim. Ital. 1986, 116,201. 11. Chatt, J.; Leigh, G. J.; Paske, R. J. /. Chem. Soc. Chem. Commun. 1967, 671. 12. Hessen, B.; van Bolhuis, F.; Teuben, J. Ff.; Petersen, J. L. /. Am. Chem. Soc. 1988,110, 295. References on p. 90 Chapter 4 The binuclear cobalt complex 91 [(dippp)CoH2]2 13. Sanders, J. R. /. Chem. Soc. Dalton Trans. 1973, 748. 14. Elson, I. H.; Kochi, J. K. /. Am. Chem. Soc. 1975, 97, 1262. 15. Klinger, R. J.; Huffmann, J. C; Kochi, J. K. J. Am. Chem. Soc. 1980,102,208. 16. Sattelberger, A. P. / . Chem. Soc. Chem. Commun. 1983, 1072. 17. Gargano, M.; Giannoccaro, P.; Rossi, M.; Vasopollo, G.; Sacco, A. / . Chem. Soc. Dalton Trans. 1975, 9. 18. Krusic, P. J. /. Am. Chem. Soc. 1981,103, 2131. 19. Drago, R. S. Physical Methods in Chemistry, W. B. Saunders Co., Toronto; 1977, pp 403-405. 20. (a) Clark, E. P. Ind. Eng. Chem., Anal. Ed. 1941,13, 820. (b) Burger, B. J.; Bercaw, J. E. in ACS Symp. Ser. Wayda, A. L.; Darensbourg, M. Y., American Chemical Society, Washington, D. C; 1987, vol. 357, pp 79-98. 21. Heinze, J. Angew. Chem. Int. Ed. Engl. 1984, 23, 831. 22. Zuckerman, J. J. (ed.) Inorganic Reactions and Methods, VCH Publishers, Inc., Florida; 1986, vol. 15, pp 88-141. 23. Allison, J. D.; Walton, R. A. /. Am. Chem. Soc. 1984,106, 163. 24. (a) Evans, D.F. /. Chem. Soc. 1959, 2003. (b) Deutsch, J. L.; Poling, S. M. / . Chem. Educ. 1969,46, 167. 25. Baker, M. V.; Field, L. D.; Hambley, T. W. Inorg. Chem. 1988,27, 2872. 26. The compound [(dippp)CoD2]2 was synthesized by stirring a solution of ( T | 3 -C3H5)Co(dippp) (3) in hexanes under D2. 27. Eaton, B.; O'Connor, J. M.; Vollhardt, K. P. C. Organometallics 1986,5, 394. 28. Cotton, F. A.; Walton, R. A. Multiple Bonds between Metal Atoms, John Wiley & Sons Inc., New York; 1982. 29. Dapporto, P.; Midollini, S.; Sacconi, L. Inorg. Chem. 1975,14,1643. References on p. 90 Chapter 4 The binuclear cobalt complex 92 [(dippp)CoH2]2 30. Schore, N. E.; Ilenda, C. S.; Bergman, R. G. /. Am. Chem. Soc. 1976, 98, 256; 1977, 99, 1781. 31. Bernal, I.; Korp, J. D.; Reisner, G. M.; Herrmann, W. E. /. Organomet. Chem. 1977,139, 321. 32. Herrmann, W.A.; Huggins, J. M.; Bauer, C.; Ziegler, M. L.; Pfisterer, H. / . Organomet. Chem. 1984,262, 253. 33. Bailey, Jr., W. I.; Collins, D. M.; Cotton, F. A.; Baldwin, J. C; Kaska, W. C. / . Organomet. Chem. 1979,165, 373. 34. (a) Barnett, B. L.; Kriiger, C; Tsay, Y.-H.; Summerville, R. H.; Hoffmann, R. Chem. Ber. 1977,110, 3900. (b) Jonas, K.; Wilke, G. Angew. Chem. Int. Ed. Engl. 1973,12, 943. (c) Jonas, K.; Wilke, G. Angew. Chem. Int. Ed. Engl. 1970, 9,31. 35. Yoshida, T.; Yamagata, T.; Tulip, T. H.; Ibers, J. A.; Otsuka, S. J. Am. Chem. Soc. 1978,100, 2063. 36. FuPstetter, H.; Noth, H.; Wrackmeyer, B.; McFarlane, W. Chem. Ber. 1977, 110,3112. 37. (a) Rinze, P. V. Angew. Chem. Int. Ed. Engl. 1974,13, 336. (b) Eshtiagh-Hosseini, H., Nixon, J. F. /. Organomet. Chem. 1980,192, C9. (c) Lorbeth, J.; Noth, H.; Rinze, P. V. /. Organomet. Chem. 1969,16, Pl. 38. (a) Giitlich, P.; McGarvey, B. R.; Klaui, W. Inorg. Chem. 1980,19, 3704. (b) Gutlich, P. Struct. Bond. 1981,44, 83. (c) Dose, E. V.; Hoselton, M. A.; Sutin, N.; Tweedle, M. F.; Wilson, L. J. /. Am. Chem. Soc. 1978,100, 1141. (d) Sacconi, L. Pure Appl. Chem. 1971,27, 161. 39. (a) Stynes, H. C; Ibers, J. A. Inorg. Chem. 1971,10, 2304. (b) Greenaway, A. M.; Sinn, E. /. Am. Chem. Soc. 1978,100, 8080. References on p. 90 Chapter 5 The mononuclear cobalt complex 93 (dippp)CoH3 CHAPTER 5 The mononuclear cobalt complex (dippp)CoH3 5.1 - Introduction One of the many syntheses of the blue hydride [(dippp)CoH2]2 (4) (Chapter 4) includes the reaction of (dippp)CoCl2 (1) with organolithium reagents under H2. Surprisingly, this reaction (Equation 5-1) also produced a red solid with the empirical formula (dippp)CoH3 (5) in 30% yield. This so-called "red hydride" can be separated from the product mixture due to its low solubility in hexanes. The formation of complex 5 seems to be independent of the organolithium reagent used, similar yields (25-30%) being obtained with methyl-, n-butyl- or neopentyllithium. In this chapter, the characterization of the red hydride is described, and an attempt is made to understand the mechanism of its formation and its relationship to the blue hydride [(dippp)CoH2]2 (4). Equation 5-1 poH 3 + hydride X 1 4 5 R: Me, n-Bu, neopentyl major product 30% red hydride references on p. 114 Chapter 5 The mononuclear cobalt complex 94 (dippp)CoH 3 5.2 - Nmr spectroscopy and T i measurements The 31P{1H) NMR spectrum of (dippp)CoH3 (5) consists of a broad singlet at 81.7 ppm (Avi/2= 224 Hz). In the *H NMR spectrum, a broad and featureless peak (Avi/2= 90 Hz) is observed in the hydride region at -15.0 ppm, upfield from TMS (5 = 0.0 ppm) and integrating for three hydrogens. J JL AV A v 1 / 2 = 90 Hz A. T 4 0 - 4 -8 -12 -16 ppm Figure 5-1. l U NMR spectrum (300 MHz) of (dippp)CoH3 (5). Residual C 7 D 7 H is marked by an asterisk (*). The peaks denoted by (°) are due to an impurity. T references on p. 114 Chapter 5 The mononuclear cobalt complex 95 (dippp)CoH3 Other ligand resonances were also found in their normal, diamagnetic positions (Figure 5-1). Thus, initially it was thought that (dippp)CoH3 was a diamagnetic trihydride complex. However, this hydride signal showed no coupling to the 3 1P nuclei of the diphosphine ligand, and was invariant from 20° to -80°C. These observations suggest that this signal may be due to an r\2-H.2 ligand being present in the molecule.1-2 The peculiarity of the hydride resonance in (dippp)CoH3 (5) prompted a variable-temperature spin-lattice relaxation time (Ti) study on the red hydride. This experiment has been used3'4 to assist in the characterization of dihydrogen complexes, and to help differentiate them from classical hydrides. The Ti criterion is especially useful, although not always diagnostic,23 for dihydrogen complexes where (i) the complex is too fluxional on the NMR time scale for unique dihydrogen resonances to be observed, and (ii) no infrared bands can be assigned unequivocally for the dihydrogen ligand.1'3 The Ti of any resonance in solution can be measured by a standard inversion-recovery pulse sequence. The major contribution to the Ti relaxation is dipole-dipole interaction, whereby after being promoted to an excited state through the pulse sequence, a nucleus is relaxed by other nearby nuclei. This relaxation is dependent on the distance, r, between the dipolar nuclei through the following equation: Equation 5-2 R<D D> - TH5D) " <T7^ v + T T t o V 1 where R(DD): relaxation by dipole-dipole mechanism references on p. 114 Chapter 5 The mononuclear cobalt complex 96 (dippp)CoH3 Ti(DD): Ti relaxation by dipole-dipole mechanism y: gyromagnetic ratio, tc: rotational correlation time (s rad"1) CD: Larmor frequency (rad s"1) r. internuclear distance h: 7yr, h: Planck's constant (6.626 x 10"34 J s) The H-H distance in H2 being very short, and YH being large, the corresponding relaxation is potentially very large. In a dihydrogen complex, the H-H bond is lengthened to a certain extent (0.8 to 1.2 A) because of coordination to the metal centre, but the relaxation time of the protons is still very short (typically in the range 4-100 ms). On the other hand, if the complex were to exist in the classical or dihydride form, the distance between the two protons would be of the order of 1.5 A, and consequently, the Ti of these protons is longer, about 1 s.1'2 M—I J 0.8-1.2 A dihydrogen To make the Ti criterion quantitative, it is best to measure its temperature dependence. Equation 5-2 predicts that the Ti value will go through a minimum when the correlation time tc, is matched with the Larmor frequency, CD; in particular when xc = 0.63/CD. At the minimum Ti, an estimate of the effective H-H distance, reff, can be obtained, assuming that all the observed relaxation can be ascribed to dipole-dipole interaction between the two hydrogen atoms of the H2 ligand. The magnitude of this value will indicate whether the complex is non-classical (r ~ 0.8-1.2 A) or classical (r M / t ~1-5A dihydride references on p. 114 Chapter 5 The mononuclear cobalt complex 97 (dippp)CoH3 >1.2 A). According to equation 5-2, the temperature of the minimum is field-dependent.2'3 A plot of the temperature dependence of Ti values for (dippp)CoH3 is shown in Figure 5-2. The results of the experiment5 are as follows: at 20°C, the value of Ti is 107 ± 2 ms, but when the sample was cooled to -95°C, a V-shaped plot is obtained from which a minimum Ti value of 43 ± 2 ms at -37°C (300 MHz) can be extrapolated. The corrected6 H-H bond distance calculated at Ti(mjn) is 1.06 (2) A. Although no correction was made to allow for the presence of a third (terminal) hydride ligand, these data indicate that an T]2-dihydrogen ligand may be present in the molecule. -1 « 1 « 1 « 1 • 1 3.0 4.0 SJ0 1/temp 10 3 K ' 1 Figure 5-2. Plot of temperature dependence of Ti for (dippp)CoH3 (5). references on p. 114 Chapter 5 The mononuclear cobalt complex 98 (dippp)CoH 3 In many r|2-H2 complexes, labeling experiments with the HD-containing complex have been used to characterize the T]2-dihydrogen ligand, since the HD ligand usually shows large ^ H D couplings of 28-34 Hz diagnostic of H 2 binding.1-2 Attempts to synthesize the complex (dippp)CoHD2 by the reaction of the chloro-bridged dimer [(dipppCo]2(u.-Cl)2 (2) with butyllithium under D2, or stirring (dippp)CoH3 (5) under D2 for two hours, gave products which do not show H-D coupling, although the linewidth Avi/2, increased from 90 at 20°C to 104 Hz at -95°C. 5.3 - Fluxionality and a trihydrogen intermediate In polyhydride complexes, when the hydride resonance is not resolved at any accessible temperature, it usually indicates exchange between classical and non-classical sites at a rate which leads to coalescence at all temperatures. If the lifetime of the hydrogen nuclei at each site is comparable with the Ti values involved, then the effective Ti for the classical proton signal will reflect not only the relaxation of the classical, but also that of the non-classical site(s). Thus in (dippp)CoH3, at 20°C the Ti value for the single, broad high-field resonance at -15.0 ppm is short compared to values of typical classical hydrides, because two of the three sites are non-classical. The presence of quadrupolar nuclei such as 5 9Co can broaden the resonances of protons attached to the quadrupolar nucleus, but this is normally a T2 effect.7 Broad lines normally observed at low temperatures arise from the T2 values becoming much shorter than Ti values. As the temperature is lowered, the Ti of quadrupolar nuclei generally decreases sharply, and at low temperature, <-70°C, line-broadening effects on spin 1/2 nuclei due to quadrupolar effects are generally removed.8 Broadening caused by the quadrupolar nucleus 5 9Co (100% abundant) was ruled out because ^ H D references on p. 114 Chapter 5 The mononuclear cobalt complex 99 (dippp)CoH3 has been measured in the cobalt-dihydrogen complex [(rj2-HD)Co{P(CH2CH2-PPh2)3}]+PF6- (27.8 Hz).18 Complexes containing both hydride and dihydrogen ligands, which do not give rise to readily observable signals in the proton NMR, are thought to go through a rapid scrambling motion where the two ligands exchange atoms. In the light of the temperature-invariant signal observed for (dippp)CoH3, it is proposed that the exchange goes through the intermediacy of a trihydrogen complex (Scheme 5-1). Scheme 5-1 In such a complex, the presence of a transient T]3-H3 moiety bound to a metal centre is believed to exist. According to MO calculations,9'10 open and closed geometries are possible for a coordinated T | 3 - H 3 unit, the lowest-energy structure calculated being that for the open form. Trihydrogen complexes have been proposed recently in the literature.11-12 They appear to be characterized by ^{^P} NMR spectra showing A B 2 peak references on p. 114 Chapter 5 The mononuclear cobalt complex 100 (dippp)CoH3 patterns in the hydride region with abnormally large J A B values which are strongly temperature-dependent and field-independent. Several compounds have been suggested to contain an 7i3-trihydrogen ligand; among them are: [(Ti5-C5H5)IrL(H3)]+ (L= PCy3, PMe2Ph, PP^, AsPh3), l lb [(TI5-C 5H5)RUL(H 3)]+ (L= PCy3, PPri 3), l l e [(7l5-C5Me5)Ru(H3)(PCy3)»CuCl] and [(n5-C5Me5)Ru(H3)(PCy3)2«Cu]+PF6-,13 [(Ti5-C5H4SiMe3)2Nb(H3)] and [{n5-(i,3-SiMe3)C5H3}Nb(H3)],llf [(n5-C5H5)Ir(PMe3)(H3)]+BF4-,14 and (n5-C5H5-nRn)2Nb(H3), (n=l, R=Me or SiMe3; n=2, R=SiMe3).llf The large JAB coupling constants (up to 1500 Hz) observed in these complexes have been interpreted in terms of proton-proton exchange couplings.15 These couplings are not magnetic in origin but are suggested to be exchange couplings between protons, similar to those observed between electrons in radical pairs. 5.4 - Infrared data In the solid state, the infrared spectrum of the red hydride (dippp)CoH3 (5) shows bands at 1741, 1687 and a shoulder at 1612 cm4, assigned to a terminal Co-H stretching mode and antisymmetric (as) and symmetric (s) Co-H2 stretching modes (Figure 5-3). A band at 768 cm-1 has been assigned to a 5(Co-H) mode. The v(H-H) band is absent, a feature not unusual in other infrared studies of dihydrogen complexes.1'2 This band is generally weak and only gains in intensity by coupling to a suitable and intense vibration such as v(C=0).1 When the preparation of the red hydride was performed using the dichloro-complex (dippp)CoCl2 (1) and MeLi under D 2, the isolated product (assumed to be (dippp)CoD3) shows bands at 1239.3 cm-1, consistent with an isotopic shift for the Co-D stretching mode. Unfortunately, overlap with the ligand bands makes the assignment of the individual modes of vibration for references on p. 114 Chapter 5 The mononuclear cobalt complex 101 (dippp)CoH3 residual v(Co-H)? v(Co-D) and Vas/v s(Co-D2) 1700 1100 500 Wavenumbers (cm" 1 ) Figure 5-3. (a) Infrared spectrum of the red hydride (dippp)CoH3. (b) Infrared spectrum of (dippp)CoD3. references on p. 114 Chapter 5 The mononuclear cobalt complex 102 (dippp)CoH 3 the C 0 - D 2 group difficult. The band at 1753 cm-1 in the IR spectrum of (dippp)CoD3 may be due to the presence of a hydrogen-containing complex; its presence is discussed in Section 5.6. The presence of a terminal hydride ligand is supported by the isotopic shift of the bending mode from 768 cm1 to 557 crrr1 upon deuteration. Although crystals of (dippp)CoH3 (5) suitable for X-ray diffraction were obtained, the structure of the complex could not be solved because the carbon atoms of the backbone and the hydrogen ligands were too disordered.16 However, the limited diffraction data indicate that the complex is mononuclear in the solid state. 5.5 - Electrochemical measurements on (dippp)CoH3 Electrochemical measurements have been performed on the red hydride.17 As shown in Figure 5-4, the complex is oxidized at A (-1.1 V) to give a decomposition product B which is oxidized at C. By performing the experiment at different scan rates, it was established that B and E form a redox pair. The oxidation potential of 1.1 V is a value normally associated with a Co(I) species, consistent with the value of -1.01 V obtained when (dippp)CoCl2 was reduced electrochemically (see Chapter 2, section 2.2). One-electron oxidative macroelectrolyses carried out at -20°C on a THF solution of the red hydride under argon have indicated the production of a moderately stable Co(II) species, which could very well be [(dippp)Co(H)(H2)]+ (II) (Scheme 5-2). This complex slowly decomposes to a second species which still contains Co(II). According to ESR measurements, the identity of this species is likely "(dippp)CoH2" (III).17 The latter intermediate can be reduced to IV, the process being references on p. 114 Chapter 5 The mononuclear cobalt complex 103 (dippp)CoH 3 Scheme 5-2 1 + H + I 1 1 1 1 I ' ' i l l "0 .5 -1.0 -1.5 Voltage Figure 5-4. Cyclic voltammogram of the red hydride (dippp)CoH3 (5) at -20°C references on p. 114 Chapter 5 The mononuclear cobalt complex 104 (dippp)CoH 3 electrochemically reversible. Since III is a stable species, these findings lend some support to the earlier hypothesis that the blue hydride mixture may contain the monomer "(dippp)CoH2" (see Chapter 4; Section 4.5). 5.6 - Proposed mechanism of formation of the red hydride The addition of the first equivalent of organolithium reagent, RLi, to (dippp)CoCl2 (1) results in the reduction of the metal from Co(II) to Co(I) to give the chloro-bridged dimer [(dippp)Co]2(p>Cl)2 (2) (as discussed in Chapter 2, the latter is also formed upon reduction of 1 with Na-Hg) (Scheme 5-3). Indeed the use of either (dippp)CoCl2 (1) or [(dippp)Co]2(p>Cl)2 (2) gives identical final results in this reaction. Then, the reaction between [(dippp)Co]2(fi-Cl)2 (2) and the second equivalent of organolithium reagent presumably generates a transient cobalt-alkyl complex 2a (Scheme 5-3). In a separate experiment, variable-temperature nmr measurements on a sample of 2 under H 2 have revealed no coordination of H2 prior to reaction with the second equivalent of RLi. With butyllithium, two pathways are possible (Scheme 5-4): H2 adds to the cobalt-butyl complex to form a Co(I)-butyl-dihydrogen complex 2b, or the cobalt-butyl complex decomposes via P-hydride elimination to form 2c. Loss of olefin from 2c gives a short-lived cobalt-hydride complex "(dippp)CoH", which dimerizes under H2 to yield the blue hydride 4. A P-hydride elimination in 2b gives 2d, which upon displacement of the olefin ligand results in the red hydride (dippp)CoH3 (5). This mechanism is supported by the analysis of the organic products (GC/MS) which shows that 1-butene is the gaseous product formed. references on p. 114 Chapter 5 The mononuclear cobalt complex 105 (dippp)CoH3 Scheme 5-3 R: Me, n-Bu -P 2 ^ c o c i 2 •P, Pr'2 1 -LiCI -R» Pr'-\ RLi Pr Co A . Co' Pr1--LiCI BuLi Pr's D \ C o — R Pr'2 2a Na-Hg In addition, under D 2 the reaction gives a red hydride complex still containing one hydrogen ligand, (dippp)CoHD2, likely formed via a decomposition pathway involving P-hydride elimination. Methyllithium does not possess P-hydrogens; therefore a different mechanism is in effect (Scheme 5-5). With H 2 , the cobalt-methyl complex either forms a cobalt-methyl-dihydrogen complex 2e, or undergoes oxidative addition resulting in a cobalt-methyl-dihydride complex 2f. Reductive elimination of methane from the latter, followed by dimerization of "(dippp)CoH" under H 2 again leads to the blue hydride 4. The cobalt-methyl-dihydrogen complex 2e may undergo oxidative addition of a second references on p. 114 Chapter 5 The mononuclear cobalt complex 106 (dippp)CoH 3 Scheme 5-4 mole of H-2 to give species 2g, which after reductive elimination of methane would result in the formation of the red hydride complex (dippp)CoH3 (5). references on p. 114 Chapter 5 The mononuclear cobalt complex 107 (dippp)CoH 3 Scheme 5-5 The presence of a band at 1753 crrr1 in the infrared spectrum of the (dippp)CoD3 (Figure 5-3) was assigned to the stretching mode (v(Co-H)) of a hydrogen-containing complex. The lH NMR spectrum of (dippp)CoD3 (synthesized from (dippp)CoCl2 (1) and MeLi under D2) also shows a small peak at -15.0 ppm. references on p. 114 Chapter 5 The mononuclear cobalt complex 108 (dippp)CoH 3 The magnitude of the v(Co-H) band in the IR spectrum suggests that a mechanism including oc-hydrogen elimination from the cobalt-methyl complex is also possible (Scheme 5-6). Scheme 5-6 5.7 - Reactivity of (dippp)CoH3 Benzene was hydrogenated to a very small extent with (dippp)CoH3 (5) as catalyst precursor (TON: 1-3), but in the presence of 3,3-dimethylbutene, the turnover number was higher, ~ 48 per mole of catalyst. At the end of the experiment, 3,3-dimethylbutene was completely converted to 2,2-dimethylbutane. The mechanism of the hydrogenation presumably includes an initial displacement of H2 by 3,3-dimethylbutene, or insertion of the olefin in the Co-H bond followed by reductive elimination of alkane, to generate "(dippp)CoH". This is followed by complexation of benzene to the latter, consistent with the mechanism proposed for the hydrogenation of arenes (Chapter 3). With 2-methoxynaphthalene, without the addition of 3,3-dimethylbutene the total turnovers were comparable to those obtained for (rj3-allyl)Co(dippp) (3) and (ri3-cyclooctenyl)Co(dippcyp) (8) (Table 5-1 and see Chapter 3; Table 3-1). A few reactions were found to convert the red hydride (dippp)CoH-3 (5) to the blue hydride [(dippp)CoH2]2 (4) (Scheme 5-8). For example, addition of pyridine to references on p. 114 Chapter 5 The mononuclear cobalt complex 109 (dippp)CoH3 Table 5-1 Hydrogenation products (TON) substrate substrate catalyst .OMe ,OMe 476:1 13 15 58 the red hydride gave the blue hydride. Loss of the H2 ligand may have been induced by coordination of pyridine to cobalt to give the cobalt-hydride complex "(dippp)CoH", which rapidly combined with a second molecule of (dippp)CoH3 to yield [(dippp)CoH2]2 (4). The formation of the blue hydride [(dippp)CoH2]2 (4) when a solution of the red hydride and (ri3-allyl)Co(dippp) (3) was stirred under H2, can be explained likewise. Initial generation of the cobalt-hydride complex "(dippp)CoH" from the hydrogenation of (Tj3-allyl)Co(dippp) (3), could be followed by reaction of the former with the red hydride (dippp)CoH3 (5) to yield the blue hydride (Scheme 5-7). All of the red hydride was consumed at the end of the reaction. Scheme 5-7 2 5 4 80% references on p. 114 Chapter 5 The mononuclear cobalt complex HO (dippp)CoH 3 Scheme 5-8 references on p. 114 Chapter 5 The mononuclear cobalt complex 111 (dippp)CoH3 The red hydride was observed to act as an isomerization catalyst for 1-hexene. The olefin was completely isomerized to a mixture of cis- and trans-2-hexene with trace amounts of 3-hexene. The mixture of hexenes was characterized by *H and 1 3C{!H} NMR spectroscopy, which also showed the absence of hexane. A similar result was reported with the dihydrogen complex [Cn, 2-H2)Co{P(CH2CH 2-PPh2)3 }]+PF6", which isomerized dimethyl maleate to dimethyl fumarate quantitatively.18 Reaction of (dippp)CoFf.3 (5) with (dippp)CbCl2 (1) in toluene gave the chloro-bridged dimer [(dippp)Co]2(M--Cl)2 (2) in 92% yield with evolution of H2 (Scheme 5-8). A similar result was obtained when solutions of 1 and the blue hydride 4 were mixed together (Chapter 4; Section 4.3.5). The hydrogen ligands in (dippp)CoH3 (5) can be exchanged for deuterium by stirring the red hydride in THF under D2. This reaction, however, is very slow, and does not go to complete exchange, perhaps because of H/D exchange with the solvent. Decomposition of the red hydride occurred upon reaction with PMe3 and allene, whereas with 1,3-butadiene and CO, the products were isolated as oils which could not be identified. With ethylene, a reddish-brown solid was obtained (28% by weight of cobalt) but this compound has not been fully characterized. There was no reaction with 2,3-dimethyl-l,3-butadiene, presumably because this molecule is too bulky. 5.8 - Discussion The majority of dihydrogen complexes have been characterized by infrared and nuclear magnetic resonance spectroscopy, although in the solid state, some of them references on p. 114 Chapter 5 The mononuclear cobalt complex \ \2 (dippp)CoH3 have been the subject of X-ray and neutron diffraction studies. Whereas the H - H bond distance in free H 2 is 0.74 A, it is between 0.80 and 1.20 A in molecular hydrogen complexes. For example, the H - H bond length in the first fully-characterized T | 2 -dihydrogen complex, W(H2)(CO)3(PCy3)2, has been measured by X-ray crystallography (0.75(16) A), 2 neutron diffraction (0.84 A), 2 and solid state N M R (0.890(6) A). 1 9 Long H - H bond lengths found in some molecular hydrogen complexes have been explained in terms of the restricted rotation of the H 2 ligand, as in trans-[Os(H)(ri 2-H2){Et2P(CH2)2PEt2}2] +BPh4- (1.12(3) A),6 and [Re (Ti 2 -H 2 )H 4 {PhP-(CH 2 CH 2 CH2PCy2)2}] + SbF 6 -(1.08 (5) A) . 2 0 A n important consideration is the electronic and steric influences of ancillary ligands in stabilizing H2 coordination versus dihydride formation. Increasing the basicity of the metal centre in H2 complexes would be expected to lead to H - H cleavage because of greater M->o* donation. In Mo(CO) x(PR3)5_ x(H2), H2 ligands are present until the strong 7t-acceptor CO's are totally substituted by basic PR3's; thus MoH2(PMe3)5 is a seven-coordinate dihydride complex. 2 1 Strong jc-acceptor ligands such as CO are generally considered to be stabilizing factors in helping the H2 a-orbital donation to the metal and prevent back-donation of the metal to the H2 o* orbitals leading to dihydride formation. 1 ' 2 Their absence in (dippp)CoH3 and many other T] 2 -H2 complexes 2 2 implies that they are not a requirement for dihydrogen complexes to form. Evidence that the red hydride (dippp)CoH3 is a Co(I)-containing species was provided by electrochemical measurements. In combination with the T i data, the results suggest the presence of an r | 2 -H2 ligand in the molecule. The rapid relaxation of the rj2-dihydrogen ligand is diluted by exchange with the slowly relaxing terminal references on p. 114 Chapter 5 The mononuclear cobalt complex 113 (dippp)CoH3 hydride, since all the hydrogen ligands can be brought in close contact with one another.23 The T i ( m i n ) value calculated from the data will still be shorter than for a classical structure, but as calculated, the H-H distance of 1.06 A in (dippp)CoH3 is unusually long because it also includes a contribution from the terminal hydride ligand. In the absence of definite evidence, in solution the possible existence of an rj3-trihydrogen ligand is possible. A high-field temperature-invariant resonance in the NMR spectrum, and the slow exchange of the hydrogen ligands with deuterium cannot be easily explained, although the large dipolar coupling between the H2 atoms of the hydrogen ligands may be responsible for the broad peak observed in the NMR spectrum.2 Some insight into the mechanism of formation of (dippp)CoH3 was obtained after the generation of the blue hydride [(dippp)CoH2J2 (4) from (dippp)CoH3 and (ri3-allyl)Co(dippp) (3) under H2. This result suggests that pathways leading to the formation of the blue and red hydrides are different when (dippp)CoCl2 (1) is treated with an organolithium reagent. The fact that no red hydride was detected during the hydrogenation of Cn3-allyl)Co(dippp) (3) implies that in the reaction between (dippp)CoCl2 (1) and butyl or methyllithium under H2, a mechanism involving an rj2-H2 interaction with cobalt soon after the formation of a 14-electron cobalt-alkyl complex is reasonable. references on p. 114 Chapter 5 The mononuclear cobalt complex 114 (dippp)CoH 3 5.9 - References 1. Crabtree, R. H.; Hamilton, D. G. Adv. Organomet. Chem. 1988,25, 299. 2. Kubas, G. J. Acc. Chem. Res. 1988,21, 120. 3. Hamilton, D. G.; Crabtree, R. H. /. Am. Chem. Soc. 1988,110, 4126. 4. Crabtree, R. H.; Hamilton, D. G.; Lavin, M. in ACS Symp. Ser. Wayda, A. L.; Darensbourg, M. Y. (Eds.); American Chemical Society, Washington, DC; 1987, vol. 357, pp 223-226. 5. Ti measurements were performed on a Varian XL-300 NMR spectrometer equipped with a variable-temperature probe. 6. Bautista, M. T.; Earl, K. A.; Maltby, P. A.; Morris, R. H.; Schweitzer, C. T.; Sella, A. J. Am. Chem. Soc. 1988,110,7031. 7. Becker, E. D. High Resolution NMR, Academic Press, New York; 1969, pp 184-187. 8. Brown, P. R.; Green, M. L. H.; Hare, P. M.; Bandy, J. A. Polyhedron 1988, 7, 1819. 9. Burdett, J. K.; Philips, J. R.; Pourian, M. R.; Poliakoff, M.; Turner, J. J.; Upmacis, R. Inorg. Chem. 1987,26, 3054. 10. (a) Burdett, J. K.; Pourian, M. R. Organometallics 1987, 6, 1684. (b) Jean, Y.; Eisenstein, O.; Volatron, F.; Maouche, B.; Sefta, F. J. Am. Chem. Soc. 1986, 108, 6587. (c) Hay, P. J. J. Am. Chem. Soc. 1987,109, 705. 11. (a) Zilm, K. W.; Heinekey, D. M; Millar, J. M; Payne, N. G.; Neshyba, S. P.; Duchamp, J.C; Szczyrba, J. /. Am. Chem. Soc. 1990,112, 920. (b) Heinekey, D. M.; Millar, J. M.; Koetzle, T. F.; Payne, N. G; Zilm, K. W. / . Am. Chem. Soc. 1990,112, 909. (c) Heinekey, D. M.; Payne, N. G; Schulte, G. K. / . Am. Chem. references on p. 114 Chapter 5 The mononuclear cobalt complex 115 (dippp)CoH3 Soc. 1988,110, 2303. (d) Zilm, K. W.; Heinekey, D. M.; Millar, J. M.; Demou, P. /. Am. Chem. Soc. 1989,111, 3088. (e) Arliguie, T.; Chaudret, B.; Devillers, J.; Poilblanc, R. C. R. Acad. Sci., Ser. 7/1987,505, 1523. (f) Antinolo, A.; Chaudret, B.; Commenges, G; Fajardo, M.; Jalon, F.; Morris, R. H.; Otero, A.; Schweitzer, C. T. /. Chem. Soc. Chem. Commun. 1988, 1210. 12. (a) Sweany, R. L. /. Am. Chem. Soc. 1986,108, 6986. (b) Luo, X.-L.; Crabtree, R. H. / . Chem Soc. Chem. Commun. 1990, 189. 13. Chaudret, B.; Commenges, G.; Jalon, F.; Otero, A. /. Chem. Soc. Chem. Commun. 1989, 210. 14. Bergman, R. G.; Gilbert, T. M. /. Am. Chem. Soc. 1985,107, 3502.. 15. (a) Jones, D. H.; Labinger, J. A.; Weitekamp, D. P. /. Am. Chem. Soc. 1989, i i i , 3087. (b)ref. 11a. (c)ref. lib. 16. Rettig, S. J. personal communication. 17. Bianchini, C. personal communication. 18. Bianchini, C; Mealli, C; Meli, A.; Peruzzini, M.; Zanobini, F. /. Am. Chem. Soc. 1988,110, 8725. 19. Zilm, K.; Merrill, R. A.; Kummer, M. W.; Kubas, G. J. /. Am. Chem. Soc. 1986, 108,7837. 20. Kim, Y.; Deng, H.; Meek, D. W.; Wojcicki, A. /. Am. Chem. Soc. 1990,112, 2798. 21. Lyons, D.; Wilkinson, G.; Thornton-Pett, M.; Hursthouse, M. B. /. Chem. Soc. Dalton Trans. 1984, 695. 22. see for example: Crabtree, R. H. Acc. Chem. Res. 1990, 23, 95 and references therein. 23. (a) Luo, X.- L.; Crabtree, R. H. /. Am. Chem. Soc. 1990,112, 4813. (b) Luo, X. - L.; Crabtree, R. H. Inorg. Chem. 1990,29, 2788. references on p. 114 Chapter 6 Conclusions 116 CHAPTER 6 Conclusions 6.1 - Discussion It is obvious from this thesis that the physical and chemical properties of cobalt and rhodium complexes containing the same chelating bidentate phosphines are vastly different. Results obtained in the homogeneous hydrogenation of functionalized arenes with allylcobalt complexes indicate that they are sensitive to too many variables to have any practical value. More interesting results were uncovered in the characterization of the blue hydride [(dippp)CoH2]2 (4), and the red hydride (dippp)CoH3 (5). Although, the complete solution structure of the blue hydride may never be understood, a few conclusions can be derived from this study. In the solid state, the blue hydride is diamagnetic, binuclear as determined crystallographically, but in solution an equilibrium between the binuclear compound and some other species must exist to account for the solution paramagnetism. The binuclear complex appears to be the predominant species in solution, based on the cyclic voltammetric studies. A monomer dimer equilibrium seems the most reasonable explanation for the observed paramagnetism, although the presence of a trinuclear species has not been excluded. The generation of (dippp)CoH2 during the electrolysis of the red hydride, and the conversion of the red hydride to the blue hydride also lends support to References on p. 118 Chapter 6 Conclusions (dippp)CoH.2 playing an important role in the chemistry of both the blue and red hydrides. 6.2 - Future work Stable anions were generated in the electrochemical studies of the blue hydride [(dippp)CoH2]2 (4); perhaps they can be isolated in further studies related to this work. The formation of the red hydride (dippp) C0H3 (5) may be dependent on the chelate ring size, an effect which has not been examined in this thesis. Preliminary work with cobalt-dippe complexes where the chelate ring size is five (in contrast to six in cobalt-dippp complexes) seemed to show that (dippe)CoH-3 was formed (}H NMR spectra of crude mixtures). On the other hand, smaller and larger chelate rings may introduce electronic effects which would influence the presence or absence of a dihydrogen ligand in the structure. A preliminary report examining the effect of chelating bidentate diphosphines as ancillary ligands in stabilizing the dihydrogen ligand in complexes has been published recently.1 During the synthesis of the cobalt-benzyl complex, (r|3-CH2C6H5)Co(dippp) (6), the formation of a minor product assumed to be (ri5-CH2C6H5)Co(dippp) was suggested. In itself, the presence of this compound raises a number of questions, such as: are the two cobalt-benzyl complexes in equilibrium, and, why was it not observed in the synthesis of the rhodium analogue? This area merits further study, especially since only one other r)5-benzyl complex has been characterized structurally.2 References on p. 118 Chapter 6 Conclusions 118 6.3 - References 1. Saburi, M.; Aoyagi, K.; Takahashi, T.; Uchida, Y. Chem. Lett. 1990, 601. 2. Hamon, J.- R.; Astruc, D.; Roman, E.; Batail, P.; Mayerle, J. J. /. Am. Chem. Soc. 1981,103, 2431. References on p. 118 Chapter 7 Experimental Section 119 CHAPTER 7 Experimental Section 7.1 - General Procedures All manipulations of air-sensitive compounds were performed in Schlenk-type glassware under argon or purified nitrogen using standard vacuum line techniques.1 Operations in the glove-box were carried out in a prescrubbed, circulating atmosphere of purified nitrogen in a Vacuum-Atmospheres HE-553-2 DRI-LAB equipped with a MO-40-2H DRI-TRAIN and a -30°C freezer. 7.2 - Infrared spectra Infrared spectra were recorded on a Pye-Unicam SP-1100 and a Nicolet 5DX Fourier Transform spectrophotometers with the samples as KBr pellets or in solution between 0.1 mm NaCl plates. The abbreviations for the infrared bands are: vs, very strong; s, strong; sh, shoulder; m, medium; w, weak. 7.3 - UV-Visible spectra UV-Visible spectra were recorded at 25°C on a Perkin-Elmer 552A UV-VIS spectrophotometer. The samples were prepared in the glove-box and transferred to a 10 mm cuvette fused to a 4 mm Kontes Hi Vacuum Teflon® valve.2 References on p. 150 Chapter 7 Experimental Section 120 7.4 - NMR spectra NMR spectra were obtained on the following FT-NMR spectrometers: Bruker WP-80, Varian XL-300 and Bruker WH-400. Chemical shifts (5) are reported in units of parts per million (ppm), positive shifts being downfield from tetramethylsilane (TMS) (lH and 1 3 C NMR spectra), and H3PO4 (31P NMR spectra) using benzene-do-, toluene-dg and chloroform-d as solvents. *H NMR spectra were recorded at ambient temperature relative to either C6D5H at 7.15 ppm, or C6D5CD2H at 2.09 ppm, or CHCI3 at 7.24 ppm, unless otherwise noted; 31P{H} NMR spectra at 121.421 MHz in 5 mm NMR tubes with external reference P(OMe)3 at 141.0 ppm from H3PO4; 13C{H} NMR spectra at 75.429 MHz with 1 3C6D6 or 13C7Ds as internal reference at 128.0 ppm. The chemical shifts of the paramagnetic complexes are uncorrected for the paramagnetic shift of the solvent. All coupling constants are reported in hertz, and multiplicities are abbreviated as follows: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br, broad; dd, doublet of doublets. Ti data were obtained by the inversion-recovery method3 on the Varian XL-300, equipped with a variable-temperature probe. 7.5 - Magnetic susceptibility measurements Magnetic susceptibilities were determined in solution at ambient temperature by the Evans' method4-5 using benzene as solvent and reference. The measurements were carried out using a Precision coaxial tube (Wilmad Glass Co.) on a Varian EM-360 CW NMR spectrometer, and are estimated to be accurate to within ±10%. Measurements at variable temperature were performed on the Varian XL-300 using References on p. 150 Chapter 7 Experimental Section 121 toluene as solvent and internal reference. The diamagnetic susceptibilities of benzene and toluene were taken from the literature.6 The magnetic susceptibility of [(dippp)CoH2]2 (4) in the solid state was recorded at the University of California, Berkeley on a SHE SQUID magnetometer at 5 and 40 KG from 6 to 280 K. The samples were loaded in the glove-box and run in KEL-F air-tight containers . Each run required 100 mg of compound ground into a fine powder. 7.6 - Molecular Weight measurements The method described by Signer7 was used.. A typical experiment required 13-17 mg of both sample and reference made up to 1 mL of solution in benzene, and would last 6-8 weeks. The reference used was [(Ph2PCH2SiMe2)2N]NiCl (mw, 622.89).8 Measurements were accurate to ± 20%. 7.7 - Electrochemical measurements The electrochemical measurements were performed on a PAR Model 173 potentiostat equipped with a Model 176 current-to-voltage converter and a Model 178 electrometry probe. The triangular waveform potential required during cyclic voltammetric studies was obtained with a Wavetek Model 143 function generator in conjunction with a unity-gain inverter (±15 V, 50 \xA).9 Cyclic voltammograms were recorded on a Hewlett-Packard Model 7090A X-Y recorder. All potentials are reported versus aqueous saturated calomel electrode (SCE), and E 0 ' values were determined as the average of cathodic and anodic peak potentials, References on p. 150 Chapter 7 Experimental Section 122 i.e. ( E p a + E p c)/2. The solutions employed for each run were typically 5 - 7 x 10 - 4 M in the complex, and 0.1 M in the supporting electrolyte [n-Bu4N]PFg using T H F as solvent, and were maintained under an atmosphere of N 2 . Under these conditions, the Cp2Fe/Cp2Fe+ couple was measured at E 0 ' = +0.46 V vs SCE in T H F and the ratio of the anodic peak current to cathodic peak current (ip a/ipc) was 1. Furthermore, the cathodic peak current of this redox couple increased linearly with v 1 / 2 (v : scan rate). The separation of the cathodic and anodic peak potentials (AE p) increased somewhat with an increase in scan rate changing from 67 at a rate of 0.14 V s - 1 to 78 at a rate of 0.28 V s - 1 ; consequently, redox couples exhibiting behaviour similar to that of the Cp2Fe/Cp2Fe+ couple (which is known to be reversible)10 were considered to be reversible. 7.8 - Hydrogenation reactions Hydrogenation reactions were carried out in thick-wall glass reactors fitted with 4 or 8 mm Kontes Hi Vacuum Teflon® valves.1 The reactor was loaded with 17-30 mg of the catalyst precursor and 5-10 g of substrate. Tetrahydrofuran was then transferred into the reactor by trap to trap distillation. The resulting solution was equilibrated in an oil bath maintained at 0°C, before H2 gas (~ 0.9 atm) was admitted. The uptake of gas was monitored on a mercury manometer. A typical run would be complete after 8-10 days. Hydrogenation of benzene was carried out in the neat substrate at 20° C. The hydrogenation products were analyzed by peak integration of the NMR spectra or using a Hewlett-Packard 5880A Series Gas Chromatograph (flame ionization detector) on a column of intermediate polarity (DB210). References on p. 150 Chapter 7 Experimental Section 123 Mass spectra were obtained through the mass spectroscopy services in the department. Melting points were determined on a Mel-Temp apparatus with the samples sealed in capillary tubes under nitrogen, and are uncorrected. . X-ray crystal structures (at 21°C) were determined at the U B C Crystallographic Services of the department, except for the low-temperature study on [(dippp)C0H2 (4) which was performed at Indiana University. The crystals were loaded in 0.3 or 0.5 mm glass capillaries (Charles Supper Co.) in the glove-box, then sealed under nitrogen. Details of the structure determinations are given in the Appendix. 7.9 - Chemicals Unless otherwise noted, all solvents and reagents were obtained from commercial suppliers and used as received. Tetrahydrofuran (THF), 1,2-dimethoxyethane (DME) and hexanes were predried by refluxing for at least 48 h over CaH2, prior to distillation from sodium-benzophenone ketyl under argon. Benzene, toluene and diethyl ether were dried and distilled from sodium-benzophenone ketyl under argon. The deuterated solvents benzene-dg and toluene-ds were purchased from MSD Isotopes, dried over 4 A molecular sieves and deaerated by three freeze -pump -thaw cycles prior to use. Chloroform-d obtained from the same supplier was dried and distilled under nitrogen from CaH2. Hydrogen gas, supplied by Matheson, was purified by passage through a column of activated 5 A molecular sieves and MnO supported on vermiculite.6c Deuterium gas was obtained from MSD Isotopes. References on p. 150 Chapter 7 Experimental Section 124 C0O2.6H2O was supplied by BDH Chemicals and dehydrated by heating under vacuum at 100°C for 10 h. 7.10 - Syntheses The complex (r|3-cyclooctenyl)(l,5-cyclooctadiene)cobalt(I) was prepared according to a published procedure.11 To ensure the success of the synthesis, it is imperative that sodium sand be used. The latter can be prepared by melting sodium metal (30 g) in refluxing toluene (400 mL) in a thick-wall 3-neck 2-L flask fitted with an overhead stirrer and a heating mantle. When all the sodium has melted and been dispersed into a powder, the heating mantle was replaced by a hot water bath (~ 60°C). While the mixture was still being stirred, ice was added to the hot water bath until the flask was cooled at room temperature. Toluene was removed by cannula, and the light purple sodium sand dried under vacuum. The phosphines l,2-bis(diisopropylphosphino)ethane (dippe)12 and trans-{±)-l,2-bis(dichlorophosphino)cyclopentane13 were prepared according to published procedures. The chlorophosphine l,2-bis(dichorophosphino)ethane, O2PCH2CH2-PCI2, was either purchased from Strem Chemical Co. or synthesized according to the literature.14 The synthesis of l,3-bis(diisopropylphosphino)propane (dippp) has been modified from the existing literature preparation,15 and is described below. 7.10.1 - l,3-bis(diisopropylphosphino)propane, Pr^PCC^bPPr^ - (dippp) Chlorodiisopropylphosphine, Pr^PCl,16 was converted to diisopropylphosphine, Pri2PH with L1AIH4 in ether at 0°C.17 Dry THF (500 mL) was added to Pr^ PH (44.38 References on p. 150 Chapter 7 Experimental Section 125 g, 0.376 mol) in a 3-neck 3-L flask equipped with a 250-mL dropping funnel, and a N2 inlet. The solution was cooled at -30 to -40°C and a solution of n-BuLi (1.6 M) in hexanes (235.0 mL, 0.376 mol) was added dropwise over a period of 2 h (with the temperature kept at ~ -30°C) to give a pale yellow mixture. The latter was warmed to room temperature, stirred for 45 minutes and cooled again. One half an equivalent of 1,3-dibromopropane (19.3 mL, 0.188 mol) was then added dropwise at -10°C over 90 minutes, until the yellow colour dissipated (this step is effectively a titration). After the solution was stirred at room temperature for 30 minutes, most of the solvents were removed under vacuum. The viscous residue was taken up in ether (500 mL), and saturated NH4CI (300 mL) was added to give a white precipitate which rapidly disappeared on stirring. The mixture was separated under N2, and extracted with ether (3 x 100 mL). The combined ether extracts were dried over anh. MgS04 for 30 minutes. The ether solution was then filtered off and the ether removed by distillation. The crude mixture was transferred to a small distillation apparatus, and distilled under vacuum to give dippp as a viscous, colourless liquid; bp, 108-115°C (0.03 mmHg). Yield: 46.0 g (89%) 31p{lH} NMR (C6D6, 121.421 MHz, ppm): 1.35 (s) 7.10.2 - fra/zs-(±)-l,2-bis(diisopropyIphosphino)cyclopentane Pr12PCH(CH2)3CHPPri2 - (dippcyp) Isopropylmagnesium chloride was prepared from magnesium turnings (6.0 g, 0.247 mol) in dry ether (100 mL) and isopropyl chloride (16.2 g, 0.206 mol) in dry ether (150 mL) in a 3-neck 500-mL flask equipped with a condenser and a N2 inlet. The excess Mg turnings were removed by filtration through glass wool and the Grignard solution was standardized with 0.1 M HC1. Then, it was cooled at -5°C and a solution of frattS-(±)-l,2-bis(dichlorophosphino)cyclopentane (10.15 g, 0.0373 mol) in ether References on p. 150 Chapter 7 Experimental Section 126 (50 mL) was added over 1 hour. A white precipitate of MgCl2 resulted. When the addition was complete, the mixture was allowed to warm to room temperature and heated at reflux for 1 hour. The excess Grignard was slowly hydrolyzed with deoxygenated sat. NH4CI (100 mL), and the ether layer separated from the aqueous phase in a separatory funnel under N 2. The aqueous layer was extracted with ether (2 x 50 mL) and the ether extracts combined and dried over MgS04 for 2 hours. The ether extract was filtered into a clean flask, and the ether distilled at atmospheric pressure leaving a pale yellow, viscous residue. Distillation of this residue under vacuum gave rrans-(±)-l,2-bis(diisopropylphosphino)cyclopentane as a colourless liquid ; bp, 76°C (0.02 mm Hg). Yield: 5.89 g (53%) 31p{lH} NMR (C6D6) 121.421 MHz, ppm): 15.0 (s) *H NMR (C6D6, 300 MHz, ppm): HI, H3 , H4, H6: 1.00 - 1.41 (m, complex) H10: 1.62 (overlapped with H2 and H5) H2, H5: 1.62, 1.96 (overlapped with H10) H9.H11: 1.82 (m, complex) H7, H8: 2.07 (br) ^CpH} NMR (C6D6, 75.429 MHz, ppm): CI, C3, C4, C6: 20.6 20.9 21.4 (complex) C2, C5: 22.1 (t) 23.4 (complex) C10: 28.0 (br s) C9,C11: 30.4 C7, C8: 37.5 (complex) References on p. 150 Chapter 7 Experimental Section 127 7.10.3 - Hydrogenation substrates The substrates were prepared or purified as follows: 2-methoxynaphthalene was either sublimed under vacuum (oil bath at 70°C), or recrystallized from diethyl ether; 1-indanone was recrystallized from petroleum ether, coumarin from diethyl ether. 7.10.4 - 2-methoxyethoxymethoxynaphthalene A 2-neck 500-mL flask was charged with a solution of 2-hydroxynaphthalene (p-naphthol) (15.0 g, 0.104 mol) in dry ether (200 mL). Diisopropylethylamine (36.2 mL, 0.208 mol), dried and distilled from CaH2, was added to the flask under N 2. The mixture was stirred for 30 minutes, resulting in a pale yellow solution. The flask was then cooled at 0°C, and methoxyethoxymethyl (MEM) chloride (23.8 mL, 0.208 mol) was slowly added while the temperature was kept at 0"C. White fumes were formed and the solution became decolourized. The progress of the reaction was monitored by TLC and found to reach completion after 12 hours. Water (100 mL) was added and the mixture was extracted with ether (2 x 50 mL). The combined ether extracts were washed with 1 M NaOH (2 x 50 mL) to remove unreacted P-naphthol, and water (1 x 100 mL), then dried over anh. Na2S04 and reduced to a small volume on a rotary evaporator. The residue was distilled under vacuum to give 2-MEMO-naphthalene as a pale yellow liquid ; bp, 122-127°C (0.03 mm Hg). Yield: 14.2 g (59%) References on p. 150 Chapter 7 Experimental Section 128 IH NMR (CDCI3, 400 MHz, ppm): CH30 CH2OCH3 CH2OCH2CH2OCH3 CH2OCH2CH2OCH3 naphthalene: 3.40 (s, 3H) 3.57 (t, J, 6 Hz, 2H) 3.89 (t, J, 6 Hz, 2H) 5.43 (s, 2H) 7.25-7.85 (m) 7.10.5 - 2-methoxymethylfuran Sodium hydride (17.2 g, 0.717 mol) was suspended in dry THF (200 mL) in a 3-neck 1-L flask equipped with a 125-mL dropping funnel, and a N2 inlet. After the mixture was cooled to 0°C, 2-hydroxymethylfuran (furfuryl alcohol) (17.7 mL, 0.219 mol, distilled from Na2C03), was added, and the slurry stirred for 15 minutes. Methyl iodide (19.1 mL, 0.306 mol) was then added, and the pale-yellow mixture stirred at room temperature with periodic monitoring by TLC. The excess NaH was destroyed by the slow addition of dil. acetic acid (~ 100 mL) to give a brown solution. Ether (200 mL) was added to the mixture which was then separated, and extracted with further ether (3 x 50 mL). The combined ether extracts were washed with Na2S2C>3 (1 x 100 mL), NaHC03 (1 x 100 mL) and water (lx 100 mL) before being dried over anh. Na2SC*4 for 2 hours. The ether was removed on a rotary evaporator and the residue distilled at atmospheric pressure to give 2-methoxymethylfuran as a colourless liquid; bp, 118°C. Yield: 15.6 g (64%) !H NMR (CDCI3,300 MHz, ppm): 4 3 CH3: 3.37 (s, 3H) CH2: 4.42 (s, 2H) H3, H4: 6.35 (m) References on p. 150 Chapter 7 Experimental Section 129 H5: 7.43 (m) 7.10.6 - (dippp)CoCl2 (1) Cobalt(II) chloride (5.28g, 0.041 mol) was suspended in dry toluene (200 mL) in a 500-mL round-bottom flask with a side-arm under an inert atmosphere. The ligand, dippp (10.lg, 0.036 mol) was slowly added by syringe and the mixture was stirred for 24 hours to give a deep blue solution. The residual C0CI2 was removed by filtration and the filtrate was concentrated in vacuo. The solution was cooled at -20°C for 24 hours and blue needle-like crystals precipitated. These were separated from the supernatant by cannula, washed with minimum cold hexanes and dried under vacuum. The complex, (dippp)CoCl2 (1), is air-stable in the solid state but decomposes slowly in solution. Yield: 13.1g (89%) Analysis: C0CI2P2C15H34; FW: 406.22 Calcd.: C, 44.35; H, 8.44; CI, 17.46 Found: C, 44.23; H, 8.50; CI, 17.26 mp: 114° C MS: 405 (1.4%, M+) 370 (1.3%, {Co(dippp)-Cl}+) 233 (100%, {dippp-Pr'}+) 191 (16.7%, {Pri2P(CH2)3PH}+) 148 (31.4%, {Prip(CH2)3PH}+) 323 (4400) 609 (1100) 659 (1000) References on p. 150 Chapter 7 Experimental Section 130 737 (1600) CV(Pt ; 0.1 M (NBun4)+PF6-in THF; scan rate: 0.24 V s"1): -1.01 V (irreversible) 7.10.7- [(dippp)Co]2(u-Cl)2 (2) Sodium amalgam was prepared as a slurry (Na, 0.238g (0.100 mol) in 20.0 g of Hg) in a 500-mL round-bottom flask with a side-arm, to which a solution of (dippp)CoCl2 (1) (3.02 g, 0.075 mol) in dry toluene (100 mL) was slowly added. The mixture was stirred for 20 hours resulting in a green solution which was carefully separated from the solids by cannula. Excess solvent was removed in vacuo, and after the solution was cooled at -30°C for 24 h, green crystals of [(dippp)Co]2(|i-Cl)2 (2) were obtained. The supernatant was removed by pipette; then the crystals were washed with minimum cold hexanes and dried in vacuo. Yield: 1.67g(71%) Analysis: C0CI2P4C30H68; FW: 741.58 Calcd.: C, 48.59; H, 9.24; CI, 9.56 Found: C, 48.74; H, 9.20; CI, 9.33 mp: dec. MS: dec. lteff(C6H6): 3.0 ±0.1 BM UV {C6H6, X (nm), e (L moHcnr1)}: 442 (450) 622 (160) 661 (200) 732 (220) *H NMR (C6D6,300 MHz, ppm): H1,H3: -2.00 (br s, 6H) 1.95 (br s, 6H) References on p. 150 131 59.52 (br s, 2H) 19.10 (br s, 2H) -0.40 (br s, IH) 7.10.8- (ri3-C3H5)Co(dlppp) (3) The complex, (dippp)CoCl2 (1), (6.67g, 16.4 mmol) was dissolved in dry THF (150 mL) in a 300-mL glass reactor. The solution was cooled at -20°C, and a solution of allylmagnesium chloride (24.4 mL, 1.7 M , 41.0 mmol) was slowly added. The initial blue colour of the solution changed to green, before eventually turning purple. The mixture was warmed to room temperature and stirred for 20 hours. All solvents were removed in vacuo, the residue taken up in dry hexanes (300 mL), and filtered through a plug of Celite. The purple filtrate was then concentrated in vacuo, and cooled at -30°C. Purple crystals of (Ti3-C3H5)Co(dippp) (3) were obtained overnight. These were separated from the supernatant by pipette, washed with minimum cold hexanes and dried in vacuo. The cobalt-allyl complex may also be purified by sublimation under vacuum (oil bath at 65°C). Yield: 3.63g (59%) Analysis: CoP 2Ci8H 3 9; FW: 376.39 Calcd.: C, 57.44; H, 10.44 Found: C, 56.85; H, 10.31 (satisfactory analyses could not be obtained) mp: 92-94°C MS: 376 (9.3%, M+) 333 (1.1%, {(Ti3-allyl)Co(dippp)-C3H7}+) 233 (100%, {dippp-Pr'}+) 191 (19.1%, {Pri2P(CH2)3PH}+) Chapter 7 Experimental Section H2 or H4: H4 or H2: H5: References on p. 150 Chapter 7 Experimental Section 132 148 (34.6%, {PriP(CH2)3PH}+) IR (KBr, cm-1): vC-H(allyl): 3031 (w) 31p{lH} NMR (C 6D 6 , 121.421 MHz, ppm): l H NMR (C 6D 6 , 300 MHz, ppm): Hanti H 47.1 (br s, Avi/2 = 942 Hz)) 1.43 (d, JHanti-Hcentrai: 9.5 Hz, 2H) 3.38 (br s, 2H) 4.70 (m, IH) 0.60-1.30 (br, complex, 28H) 1.78 (br, unresolved, 4H) 1.92 (br, unresolved, 2H) syn • Hcentral : CH3CHCH3: C H 2 C H 2 C H 2 : C H 2 C H 2 C H 2 : ^CpH} NMR (C 6D 6 , 75.429 MHz, p p m ) : CI: 98.8 (s) C2, C2': 50.2 (s) C 3 , C3' : 28.6 ( d t ) C4: 21.1 (t) C5, C8: 23.5 (t) C6, C7, C9, CIO: 20.3, 20.0, 19.3, 18.6 7.10.9 - [(dippp)CoH2]2 (4) A solution of (ri3-C3H5)Co(dippp) (0.516 g , 1.37 mmol) in dry hexanes (15 mL) in an 80-mL glass reactor was degassed, then stirred under an atmosphere of H 2 for 24 hours. The initial purple colour of the solution turned dark blue instantly after hydrogen was admitted. The solution was filtered through a Celite plug and concentrated and cooled at -30°C. Dark blue crystals of [(dippp)CoH2]2 (4) were collected after 24 hours. Yield: 0.388 g (84%) References on p. 150 Chapter 7 Experimental Section 133 Analysis: C02P4C30H72; FW: 674.66 MS: Calcd.: Found: C, 53.41; H, 10.76 C, 53.73; H, 10.79 674 (0.3%, M+) 673 (1.5%, (M-H}+) 672 (4.6%, (M-2HJ+) 671 (0.2%, (M-3HJ+) 670 (0.5%, {M-4HJ+) 629 (0.2%, (M-2H-Pri}+) 554 (0.7%, {M-2H-Pri2PH}+) 233 (10.0%, {dippp-Pr'}+) 118 (100%, Pri2PH+) IR (KBr, cm-l): v C o - H : 1981 (w ) vco-H-Co: 1001 (m, sh) 8co-H : 756 (w, sh) U - e f f ( C 6 H 6 ) : 1.3 ± 0.1 BM UV {hexanes, X (nm), e (L mol*1 cm-1)}: 253 (6200) 358 (2600) 495 (510) 617 (460) 31P{1H) NMR (C7D8, 121.421 MHz, ppm): (-90°C, C7D8): !H NMR (C7D8, 400 MHz, ppm): CH3CHCH3: 0.29 (br s, 6H) and 1.44 (br s, unknown -1.38 (br s, IH) \ H H f \ _ H 200 (very br s, Avi/2 = 2500 Hz) 355 (very br s, Avi/2 = 6260 Hz) 88.3 (br s, Avi / 2 = 3760 Hz) 6H) References on p. 150 Chapter 7 Experimental Section 134 unknown 0.25 (br s, IH) unknown 1.79 (br s, IH) unknown 4.19 (br s, IH) 7.10.10 - (dippp)CoH3 (5) A solution of (dippp)CoCl2 (1) (1.81 g, 4.44 mmol) in dry THF (100 mL) was placed in a 300-mL thick-wall glass reactor, and degassed by three freeze-pump-thaw cycles. While the solution was frozen, a solution of MeLi (1.4 M) in diethyl ether (7.3 mL, 10.2 mmol) was added under a strong flow of nitrogen. The reactor was evacuated, hydrogen admitted, and after it was thawed out, the solution was vigorously stirred to give a green solution initially. After the solution was stirred for 30 minutes, the colour changed to dark blue. The glass reactor was then sealed with ~ 4 atm of H 2 , and the solution was stirred for an additional 10 hours. All solvents were removed under vacuum, and dry hexanes (150 mL) was added to the residue. This mixture was filtered through a medium porosity frit and the solid LiCI washed with copious amounts of hexanes until the filtrate was colourless. The solution was then reduced in vacuo to a volume of ~ 40 mL and allowed to stand at -30°C for 2 hours. A fine red powder of (dippp)CoH3 (5) was collected on a fine porosity frit, and was recrystallized from toluene/hexanes (10:1). It is difficult to recover the blue hydride [(dippp)CoH2]2 (4) from the filtrate, but the latter can be added to (dippp)CoCl2 (1) to generate [(dipppCo]2(u,-Cl)2 (2) quantitatively. Yield: 0.449g (30%) Analysis: CoP2Ci5H3 7; FW: 338.34 Calcd.: C, 53.25; H, 11.02 Found: C, 52.84; H, 11.00 MS: dec. IR (KBr, cm-1): v C o-H : 1741 (s) References on p. 150 Chapter 7 Experimental Section 135 Vas(Co-H 2): 1687 (s) v s (Co-H 2 ) : 1612 (sh m) 5 C o - H : 768 (w) 3lp{lH} NMR (C 6D 6, 121.421 MHz, ppm): 81.7 (br s, A v i / 2 = 224 Hz) *H NMR (C 7D 8, 300 MHz, ppm): C0H3: -15.0 (br s, 3H, Avi/2 = 90 Hz) CH3CHCH3and C H 2 C H 2 C H 2 : 0.96-1.42 (m, complex, 28H) C H 2 C H 2 C H 2 and C H 3 C H C H 3 : 1.66 (m, 6H) !3C{ iH) NMR (C 6D 6, 75.429 MHz, ppm): C1,C3: 18.8 (s), 19.0 (s) 3A)~ C2 C4 C5 28.8 (complex) s / ^CoHa 23.1 (t) P 22.7 (t) 7.10.11 - (ri3-CH2C6H5)Co(dippp) (6) A solution of [(dippp)CoCl]2 (2) (1.12 g,: 1.51 mmol) in dry THF (50 mL) in a 300-mL glass reactor, was cooled at -40°C. Benzylpotassium18 (0.468 g, 3.59 mmol), dissolved in dry THF (5 mL) was then slowly added, and the solution warmed to room temperature. The colour gradually changed from green initially to brown as the glass vessel was warmed. The brown mixture was stirred for an additional 2 hours. All solvents were then removed in vacuo, hexanes added and KC1 removed when the solution was passed through a plug of Celite. The filtrate was concentrated and dark brown crystals of (ri3-CH2C6H5)Co[Pri2P(CH2)3PPri2] (6) were obtained after the solution was cooled for 24 h at -30°C. References on p. 150 Chapter 7 Experimental Section 136 Yield: 0.400 g (62%) Analysis: C0P2C22H41; FW: 426.45 Calcd.: C, 61.96; H, 9.69 Found: C, 60.79; H, 9.61 (no satisfactory analyses could be obtained) IR (KBr, cm"1): v c = c : 1588 (m), 1518 (m) 31p{lH) NMR (C6D6, 121.421 MHz, ppm): 46.3 (br s, AV1/2 = 637 Hz) iH NMR (C6D6, 300 MHz, ppm): H a, Hb: H c, Hg: He: H d , H f: CH3CHCH3: CH2CH2CH2: C H 3 C H C H 3 : 1.56 (br s, 2H) 5.21 (d, J = 7.2, 2H) 6.72 (t, J = 7.2, IH) 7.31 (t, J =7.2, 2H) 0.75-1.20 (br, 24H) 1.62 (br, 6H) 1.85 (br, 4H) "CpHJ NMR (C6D6, 75.429 MHz, ppm): CI: C2: C3, C7: C4, C6: C5: C8,C10, Cll, C13: C9, C12: C14.C16: C15: 23.1 (s) 111.0 (s) 103.3 (s) 132.5 (s) 120.2 (s) 19.0, 20.3 (complex) 20.7 (br t, J = 8) 27.2, 27.4 (br, complex) 30.3 (complex) 11 10 References on p. 150 Chapter 7 Experimental Section 137 7.10.12 - [(dippp)Co]2(u.-T]3:r|3.C6H6) (7) The complex (r|3-allyl)Co(dippp) (3) (0.238 g, 0.632 mmol) was dissolved in dry benzene (10 mL) in an 80-mL glass reactor, and the solution was stirred under H2 for 2 hours. The initial purple colour turned red within 10 minutes of reaction. When no more H2 was absorbed by the system, the gas was removed, and the solution concentrated under vacuum. After hexanes was added to the residue, [(dippp)Co]2(M--Tl3:'n3-C6H6) (7) was precipitated as a black solid. This product was collected by filtration on a fine porosity frit. It has limited solubility in hexanes, benzene or toluene. IR (KBr, cm-1): vC-H(allyl): 3035 (w) 7.10.13 - (r,3.C8Hi3)Co(dippcyp) (8) The ligand rrarts-(±)-l,2-bis(diisopropylphosphino)cyclopentane (7.0 g, 0.0231 mol) was added to (n3-C8Hi3)Co(COD) (5.95 g, 0.0236 mol) in dry hexanes (100 mL) in a 300-mL glass reactor. The mixture was stirred for 1 day changing from an initial dark brown colour to purple-brown. The solvent and residual 1,5-cycloctadiene was removed under vacuum for 6 hours, and the black residue was dissolved in hexanes (50 mL), then filtered through a Celite plug. After this solution Yield: 0.114 g (24%) MS: 748 (M+) References on p. 150 Chapter 7 Experimental Section 138 was cooled at -20°C for 24 h, purple-brown plates of (r|3-C8Hi3)Co(dippcyp) (8) were obtained. The complex was recrystallized from hexanes to yield purple crystals of8. Yield: 4.52 g (42%) Analysis: C0P2C25H49; FW: 470.54 Calcd.: C, 63.81; H, 10.50 Found: C, 63.71; H, 10.59 MS: 470(6.0%, M+) 361 (2.7%, {M-C8Hi3}+) 259 (90.0%, (dippcyp-Pri}+) 318 (5.7%, {M-C8Hi3-Pri}+) 3lp{ lH} NMR (C6D6, 121.421 MHz, ppm): 67.6 (br s, A v i / 2 = 627 Hz) *H NMR (C6D6, 400 MHz, ppm): Hcentrai: 4.79 (t, J = 8) H s y n : 3.98, 4.29 (m) ligand and cyclooctenyl: 0.70-2.48 (complex) ttCpH} NMR (C6D6, 75.429 MHz, ppm): 13 14 16 CI: C2, C2': C3, C3', C4, C4': C5: C6, C7: C8, C9, C10: C11,C13,C14,C16: C12,C15: 98.2 (s) 58.2, 60.5 (s) ' 31.2,31.4,31.7,33.3 30.4 (t) 49.2, 49.9 (t, overlapping) 24.0-24.8 (complex) 18.4-22.8 (complex) 25.4 (dd), 26.8 (dd) 1 0 R P References on p. 150 Chapter 7 Experimental Section 7.10.14 - [(dippcyp)CoH2]2 (9) 139 A solution of (ri3-C8Hi3)Co(dippcyp) (8) (0.308 g, 0.655 mmol) in dry hexanes (15 mL ) in an 80-mL glass reactor was degassed, then stirred under H2for 24 hours. The colour of the solution remained unchanged throughout the experiment. The solvent was removed under vacuum, and dry pentane (3 mL) was added to this purple residue. The solution was then filtered through a Celite plug, and cooled at -30°C. Purple crystals of [(dippcyp)CoH2J2 (9) were obtained and collected after one week. Yield: 0.102 g (43%) Analysis: CoP2Ci7H38; FW: 363.37 Calcd.: C, 56.19; H, 10.54 Found: C, 56.45; H, 10.71 IR (KBr, cm-1): V C O - H : 1938, 1872, 1739 (overlapping) 7.10.15 - (T]5-cyclohexadienyl)Co(dippcyp) (10) A solution of (rj3-C8Hi3)Co(dippcyp) (8) (0.365 g, 0.776 mmol) in dry benzene (15 mL) in an 80-mL glass reactor was degassed, then stirred under H2. The purple colour of the solution changed to dark red within 15 minutes of reaction. When no more H2 was absorbed by the system, the gas was removed, and the solution stirred at room temperature for 24 hours. The solvent was then removed under vacuum, and toluene (5 mL) was added to the residue. After this solution was cooled at -30°C for 48 h, red-brown crystals of (r|5-C6H7)Co(dippcyp) (10) were obtained. References on p. 150 Chapter 7 Experimental Section Yield: 0.236 g (69%) Analysis: C0P2C23H43; FW: 440.47 140 IR (KBr, cm-*): vC-HeX0: 2744 (w) 31p{lH} NMR (C6D6, 121.421 MHz, ppm): *H NMR (C6D6, 400 MHz, ppm): Calcd.: C, 62.72; H, 9.84 Found: C, 59.62; H, 9.68 (no satisfactory analyses could be obtained) -70.0 (very br s, A v i / 2 = 3870 Hz)) Hexo : Hendo : H2 or H6: H3 or H5: H4: H5 or H3: H6 or H2: H12, H14.H15.H17: H13, H16: H7, H8: H9.H11: H10: -2.67 (dt, J = 12, 12, IH) -2.55 (m, complex, IH) 2.79 (t, J = 5.7, IH) 4.80 (t, J = 5.7, IH) 5.15 (brm, IH) 5.57 (t, J = 5.7, IH) 3.75 (t, J = 5.7, IH) 0.73-1.15 (m, complex) 1.81-2.10 (m, complex 1.55-1.81 (br, complex) 1.15-1.35 (br, complex) 1.35-1.55 (br, complex) iSCpH} NMR (C6D6, 75.4 MHz, ppm): CI: C2, C6: C3, C5: C4: C10: C12, C14, C15, C17: 47.0 (s) 75.7 (s) 87.10 (s) 91.5 (s) 30.3 (m, complex) 18.4 (d), 18.6 (d), 20.1 (d), 21.1 (d) endo References on p. 150 Chapter 7 Experimental Section 141 C13 or C16: 23.9 (d) C9, Cll: 24.4 (d), 24.6 (d) C16orC13: 27.1(d) C7, C8: 48.2 (t) 7.10.16 - (r]4-2-methoxynaphthalene)Co(H)(dippcyp) (11) A solution of (ri3-C8Hi3)Co(dippcyp) (8) (0.327 g, 0.694 mmol) in benzene (15 mL) in an 80-mL glass reactor was degassed, then stirred under H2 to give a dark red solution. As soon as no more H2 was absorbed by the system, the solution was frozen and the gas removed. Under a strong flow of N 2 , a solution of 2-methoxynaphthalene (0.732 g, 4.63 mmol) in benzene (4 mL) was added. The mixture was then warmed to room temperature and stirred for 24 hours. The solvent was then removed and the solid residue transferred to a small sublimator, and excess 2-methoxynaphthalene was removed by sublimation under vacuum (oil bath at 70°C). The crude product was dissolved in a toluene/hexanes (5:1) mixture (3 mL) and passed through a Celite plug. After this solution was cooled at -30°C for 48 h, reddish-brown crystals of (r|4-CinH70Me)Co(H)(dippcyp) (11) were obtained. Yield: 0.167 g (46%) Analysis: C0P2C28H47O; FW: 520.56 Calcd.: C, 64.61; Ff, 9.10 Found: C, 63.46; H, 9.27 (satisfactory analyses could not be obtained) IR (KBr, cm-1): V C O - H : 1925 (m), 1908 (sh), 1847 (w) V C = C : 1580-1593 (overlapped bands) 31p{lH} NMR (C6D6, 121.421 MHz, ppm): 55.0 (br s, Avi/2 = 531 Hz) 77.8 (br s, Avi/2 = 607 Hz) References on p. 150 Chapter 7 Experimental Section 142 IH NMR (C 6 D 6 , 400 MHz, ppm): H i a , H i b : -23.6 (dd, 2 J = 38.2, 38.2) Me(a), Me(b): H2: H3: H4: H5: H6: H7: H8: H9, H10: H11,H13, H15, H18: H12: H14, H16, H17, H19: -24.1 (dd, 2 J = 38.2, 38.2) 3.37, 3.40 (s) 6.20, 6.27 (br s, 2H) 5.95, 5.98 (d, J = 9, 2H) 6.32, 6.42 (d, J = 9, 2H) 3.20, 3.40 (d, J = 9, 2H) 6.46, 6.55 (d, br s, J = 9) obscured 3.48, 3.62 (br s) 2.30 (br, 4H) 1.17-1.63 (m, complex, 16H) 1.77 (complex, 4H) 0.70-1.17 (m, complex, 48H) 16 17 " „ V H, A 1 11 OMe a , b 7.10.17 - (dippp)Co(H)(CO)2 (12) A solution of the blue hydride [(dippp)CoH2]2 (4) (0.341 g, 1.01 mmol) in dry hexanes (15 mL ) in an 80-mL glass reactor, was degassed, then stirred under 1 atm of CO. The colour of the solution changed from dark blue to brown rapidly, and within 30 minutes a brown solid had precipitated. The latter was filtered off (0.263 g), but References on p. 150 Chapter 7 Experimental Section 143 could not be characterized fully due to its insolubility in THF, ether, hexanes or toluene. The brown filtrate was concentrated, then cooled at -20° C. Brown plates of (dippp)Co(H)(CO)2 (12) were obtained after 12 hours. Yield: 0.132 g (17%) Analysis: C0P2C17H35O2; FW: 392.34 Calcd.: C, 52.04; H, 8.99 Found: C, 52.51; H, 8.85 MS: 392(2.4%, M+) 364 (47.2 %, {M - CO}+) 336 (6.1 %, {M - 2CO}+) IR (KBr, cm"1): voo: I960 (vs), 1865 (vs) 31P{1H} NMR (C6D6, 121.421 MHz, ppm): 54.0 (br s) C VH C o - C O Pl N c o lH NMR (C6D6, 300 MHz, ppm): Co-H: -12.0 (br s, IH) C H 3 C H C H 3 and CH2CH2CH2: 0.69-1.12 (complex, 26H) C H 2 C H 2 C H 2 : 1.41 (m, 4H) CH3CHCH3: 1.63 (m, 4H) 7.10.18 - [(dippp)Co]2(H)2»(2,3-dimethyl-l,3-butadiene) (13) To a solution of [(dippp)CoH2]2 (0.354 g, 1.05 mmol) in dry ether (30 mL) in an 80-mL glass reactor, 2,3-dimethyl-l,3-butadiene (1.60 mL, 0.014 mol) was added. The mixture was stirred for 48 hours during which time the initial dark blue colour of References on p. 150 Chapter 7 Experimental Section 144 the solution changed to brown. The brown solution was filtered through a Celite plug, concentrated and cooled at -30° C. Brown crystals of a compound of empirical formula [(dippp)Co]2(H)2,(2,3-dimethyl-1,3-butadiene) ( 1 3 ) were obtained after 2 days. The product was washed with minimum cold solvent and dried in vacuo. Yield : 0.061 g (15%) Analysis: C02P4C36H8O (13); FW: 754.79 Calcd.: C, 57.29; H, 10.68 Found: C, 57.00; H, 10.49 MS: 750 ({M-4H}+) 418 ({Co(dippp)(H)(C6Hio)}+) 335 (0.1%, (Co(dippp)}+) 233 (100%, {dippp-Pri}+) 191 (17.3%, {Pri2P(CH2)3PH}+) 118 (11.4%,Pri2PH+) IR (KBr, cm-1): V C O - H : 1789 (m), 2112 (m) 3lp{ iHJNMR (C6D6, 121.421 MHz, ppm): 39.4, 47.8, 53.2, 69.9 (all br s) !H NMR (C6D6, 400 MHz, ppm): Co-Hl: -13.66 (t, 2 J P H = 58 Hz, IH) Co*-H2: -13.10 (br s, IH) ligand resonances + CH2 (diene): 0.75 - 2.05 (complex, 68H + 2H) CH 3 (diene): 2.11, 2.17 (s, 6H) ? 2.45 (m,lH) C=H. (diene) 5.14 (br m, IH) C=H (diene) 5.27 (br m, IH) ^C^H} NMR (C6D6, 75.429 MHz, ppm): C2, C3: 140.0 (br s) C1,C4: 118.0 (s) Other resonances too complex to interpret f-V-04 (K References on p. 150 Chapter 7 Experimental Section 145 7.10.19 - (Ti3-C8H13)Co(dippp) (14) The ligand l,3-bis(diisopropylphosphino)propane (0.324 g, 1.17 mmol) was added to a solution of (Ti3-cyclooctenyl)Co(COD) (0.296g, 1.17 mmol) in dry pentane (15 mL) in an 80-mL glass reactor. The solution was stirred for 18 hours during which time the initial dark brown colour turned purple. The solution was concentrated and cooled at -30°C and purple crystals of (rj3-C8Hi3)Co(dippp) (14) appeared after 48 hours. Yield: 0.331 g (64%) 3 1P{ 1H} NMR (C 6D 6, 121.421 MHz, ppm): 47.8 (br s, A v i / 2 = 860 Hz) 7.10.20 - [(dippe)Co]2(|i-Cl)2 (2') The ligand l,2-bis(diisopropylphosphino)ethane (1.05 g, 4.0 mmol) was added to a suspension of CoCl 2 (0.64 g, 4.94 mmol) in THF (75 mL) in a 250-mL round-bottom flask with a side-arm, resulting in an emerald-green solution within a few minutes. This mixture was stirred for 30 min; then the supernatant was separated from the excess CoCl 2 by cannula. A solution of MeLi (1.4 M) in ether (5.7 mL, 7.98 mmol) was added, and the mixture stirred for 24 h,during which time the colour changed to greenish-brown. All solvents were removed under vacuum, and the residue taken up in toluene/hexanes (5:1) (60 mL). The solution was concentrated References on p. 150 Chapter 7 Experimental Section 146 and cooled at -30°C, and the chloro-bridged dimer [(dippe)Co]2(|i-Cl)2 (2') was obtained as green crystals. Yield: 0.282 g (20%) Analysis: C02P4CI2C28H64; FW: 713.48 Calcd.: C, 47.14; H, 9.04; Cl, 9.94 Found: C, 47.14; H, 8.91; Cl, 9.75 IH NMR (C6D6, 300 MHz, ppm): HI, H3: -1.90 (br s), 2.91 (br s) (12H) H4: 4.37 (br s, 2H) H2: 43.0 (br s, 2H) ^ y y y 7.10.21 - (n3.C8Hi3)Co(dippe) (3') and [(dippe)CoH2]2 (4') A solution of (r|3.cyclooctenyl)Co(COD) (1.33 g, 5.28 mmol) and 1,2-bis(diisopropylphosphino)ethane (1.31 g, 4.99 mmol) in hexanes (20 mL) was stirred for 8 hours in an 80-mL glass reactor. The initial dark brown colour of the solution changed to deep purple. The solvent was removed by stirring under vacuum for 3 hours. The oily purple residue of (r|3-cyclooctenyl)Co(dippe) (3') could not be induced to crystallize. 31p{lH} NMR (C6D6) 121.421 MHz, ppm): 98.1 (br s) IH NMR (C6D6, 300 MHz, ppm): HI: 4.65 (br s, IH) H2, H2': 4.32 (br s, 2H) D 1 References on p. 150 Chapter 7 Experimental Section 147 The purple residue of (T|3-cyclooctenyl)Co(dippe) (3') was redissolved in hexanes (20 mL), filtered through Celite, and loaded into an 80-mL glass reactor. The solution was stirred under H2 for 24 hours with the colour of the solution remaining unchanged. The solvent and cyclooctane were removed by stirring under under vacuum for 3 hours and pentane (8 mL) was added to the residue. After filtration through Celite, the purple solution was cooled at -30°C. After 1 week, purple crystals of [(dippe)CoH2]2 (4') were isolated. Yield: 0.664 g (41%) Analysis: C02P4C28H68; FW: 323.30 Calcd.: C, 52.01; H, 10.60 Found: C, 51.07; H, 10.38 (pure crystals could not be obtained for elemental analysis) IR (KBr, cm-l): V C O - H : 1961 (sh), 1897 (m), 1752 (m), 1557 (w) 31P{ IH} NMR (-80'C, C 7D 8, 121.421 MHz, ppm): 133 (br s, AV1/2 = 500 Hz) 150 (br s, Avi/2 = 1500 Hz) (-95°C) 129 (br s, Av 1 / 2 = 619 Hz) *H NMR (C6D6, 300 MHz, ppm): HI, H3: 1.06 (d, 6H), 1.23 (d, 6H) H4: H2: 1.63 (br s, 2H) 4.02 (br s, 2H) 7.10.22 - (dippcyp)CoCl2 (5') -*2 The ligand rra«i,-(±)-l,2-bis(diisopropylphosphino)cyclopentane (4.26 g, 0.0141 mol) was added to a suspension of CoCl2(2.76 g, 0.0212 mol) in dry toluene References on p. 150 Chapter 7 Experimental Section 148 (200 mL) in a 500-mL round-bottom flask with a side-arm. The solid dissolved after the mixture was stirred for 10 minutes, giving an emerald-green solution, but the mixture was nonetheless stirred for an additional 24 hours. A blue powder (5.1 g) was filtered off, which showed ligand bands in the IR spectrum, but its identity could not be determined being insoluble in THF, ether, hexanes, EtOH, toluene, and CH2CI2. The green filtrate was concentrated and cooled at -20°C to give a green oil mixed with green cystals. The latter were separated from the oil by the careful removal of the supernatant. The green crystals of (dippcyp)CoCl2 (5') were washed with minimum hexanes, and dried in vacuo. Yield: 0.321g (5%) (pure crystals could not be obtained for elemental analysis) MS: 431 (25.8%, M+) 396 (12.7%, (M-C1}+) 359 (14.2%, {M-2HC1J+) 317 (10.4%, {M-Pr1-2C1-H}+) / ^ x " P \ .,*C1 CI P: C o , 302 (4.0%, {dippcyp}*) 259 (100%, {dippcyp-PrM+J 118 (99.9%, {Pri2PH}+) 7.11 - Acknowledgements for experimental expertise The following individuals are thanked for providing generous experimental assistance: Professor Claudio Bianchini at the Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione (ISSECC), CNR, Firenze, Italy, for electrochemical measurements on the blue hydride [(dippp)CoH2]2 (4) and the red hydride (dippp)CoH3 (5). References on p. 150 Chapter 7 Experimental Section , . 149 Dr. Steven J. Rettig of UBC Crystallographic Services for all the X-ray crystal structures determined at 21°C. Professor John C. Huffman at Indiana University, Indiana, for determining the X-ray crystal structure of [(dippp)CoH2]2 (4) at -155°C. Drs. Nancy J. Christensen and George Richter-Addo for obtaining the cyclic voltammograms of the blue hydride [(dippp)CoH2]2 (4) and (dippp)C0CI2 (1) respectively. Dr. Warren E. Piers at the California Institute of Technology, California, for H2 gas measurement by Toepler pump on [(dippp)CoH2]2-Mr. Phil Matsunaga at the University of Berkeley, California, for solid state magnetic susceptibility measurements on [(dippp)CoH2]2-Mr. Peter Borda (UBC) for all the elemental analyses performed. References on p. 150 Chapter 7 Experimental Section 150 7.12 - References: 1. Most of the techniques used in this work are described in: (a) Wayda, A. L.; Darensbourg, M. Y. (Eds.) ACS Symp. Ser. vol. 357: Experimental Organometallic Chemistry; American Chemical Society .Washington, D. C; 1987. (b) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-Sensitive Compounds ; 2nd edition, John Wiley and Sons, Inc., New York, 1986. 2. Marshall, J. L.; Hopkins, M. D.; Gray, H. B. in 1(a) pp 254-256. 3. (a) Mullen, K.; Pregosin, P. S. Fourier Transform NMR Techniques: A Practical Approach, Academic Press, New York; 1976, pp 62-75. (b) Becker, E. D. High Resolution NMR, Academic Press, New York; 1969. 4. Evans, D. F. / . Chem. Soc. 1959, 2003. 5. Deutsch, J. L.; Poling, S. M. /. Chem. Educ. 1969, 46, 167. 6. Handbook of Chemistry and Physics, 47th Edition, CRC Press, Cleveland, Ohio; 1967, ppE108-113. 7. (a) Signer, R. Ann. 1930,478, 246. (b) Clark, E. P. Indus t. Eng. Chem., Anal. Chem. 1941,13, 820. (c) Burger, B. J.; Bercaw, J. E. in ref. 1(a) pp 79-98. 8. MacNeil, P. A. Ph. D. Thesis, University of British Columbia, Vancouver, B. C, Canada; 1983, 175 pp. 9. Richter-Addo, G. B. Ph. D. Thesis, University of British Columbia, Vancouver, B. C, Canada; 1988, 175 pp. 10. Holloway, J. D.; Geiger, W. E. /. Am. Chem. Soc. 1979,101, 2038. 11. (a) Gosser, L. W.; Cushing, Jr.; M. A. Inorg. Synth. 1977,17, 112. (b) Otsuka, S.; Rossi, M. /. Chem. Soc. A 1968, 2630. 12. Fryzuk, M. D.; Jones, T.; Einstein, F. W. B. Organometallics 1984, 3, 184 References on p. 150 Chapter 7 Experimental Section 151 13. Allen, D. L.; Gibson, V. C.; Green, M. L. H.; Skinner, J. F.; Bashkin, J.; Grebenik, P. D. /. Chem. Soc. Chem. Commun. 1983, 895. 14. (a) Henderson, R. H. Inorg. Synth. 1985, 23, 141. (b) Burt, R. J.;Chatt, J.; Hussain, W.; Leigh, J. G. /. Organomet. Chem. 1979,183, 203. 15. Tani, K.; Tanigawa, E.; Yatsuno, Y; Otsuka, S. /. Organomet. Chem. 1985,279, 87. 16. Voskuil, W.; Arens, J, F. Recueil Trav. Chim. Pays-Bas 1963, 82, 302. 17. Issleib, K.; Krech, F. /. Organomet. Chem. 1968,13, 283. 18. Schlosser, M.; Hartmann, J. Angew. Chem. Int. Ed. Engl. 1973,12, 508. References on p. 150 Appendix Crystallographic Analyses 152 APPENDIX Crystallographic Analyses l-[(dippp)Co]2(u-Cl)2 (2) Crystallographic data for [(dippp)Co]2(u--Cl>2 (2) appear in Table A-I. The final unit-cell parameters were obtained by least-squares on the setting angles for 25 reflections with 28 = 26.7-36.1°. The intensities of three standard reflections, measured every 150 reflections throughout the data collection, remained essentially constant. The data were processed1 and corrected for Lorentz and polarization effects, and absorption (empirical, based on azimuthal scans for four reflections). A total of 5101 reflections was collected on a Rigaku AFC6S diffractometer, of these 4571 were unique (Rint = 0.027) and those 1853 having / £ 3a(7) were employed in the solution and refinement of the structure. The systematic absences (Qkl, k odd, hOl, I odd, and hkO, h odd) uniquely indicate the space group Pbca. The structure was solved by conventional heavy atom methods, the coordinates of the Co, Cl, and P atoms being determined from the Patterson function and those of the remaining non-hydrogen atoms from a subsequent difference Fourier synthesis. The non-hydrogen atoms were refined with anisotropic Appendix Crystallographic Analyses 153 thermal parameters. The hydrogen atoms were fixed in idealized positions (C-H = 0.98 A, fiH = 1.2 ^bonded atom)- Neutral atom scattering factors and anomalous dispersion corrections for all atoms were taken from the International Tables for X-Ray Crystallography.2 Final atomic coordinates and equivalent isotropic thermal parameters \Beq = 4/3£;EjPjj(aj-aj)], bond lengths, and bond angles appear in Tables A-II to AIV, respectively. The structure of [(dippp)Co]2(p>Cl)2 (2) is given in Figure A-I. * Here and e l s e w h e r e , primed atoms have c o o r d i n a t e s r e l a t e d to unprimed atoms by the symmetry o p e r a t i o n : l - x , - ^ , l - z . Figure A-I. Structure of [(dippp)Co]2(|i-Cl)2 (2) Appendix Crystallographic Analyses 154 Table A-I. Crystallographic data for [(dippp)Co]2(p>Cl)2 (2) compound [(dippp)Co]2(u-Cl)2 formula C3oH68Cl2Co2P4 fw 741.53 color, habit red prism crystal size , mm 0.25 x 0.25 x 0.47 crystal system orthorhombic space group Pbca a, A 16.151(3) b, A 21.653(3) c A 11.420(3) v , A 3 3994(1) z 4 T, °C 21 pc, g/cm3 1.233 F(000) 1584 radiation Mo wavelength (A) 0.71069 \i, cm"1 11.40 transmission factors 0.90-1.00 scan type co-20 scan range, deg in co 1.50 + 0.35 tan 0 scan speed, deg/min 8 data collected +h, +k, +1 20max> d e § 55 cryst decay negligible Appendix Crystallographic Analyses 155 total no. of reflections 5101 no. of unique reflections 4571 Rint 0.027 no. of reflcns with / ^ 3a(7) 1853 no. of variables 172 R 0.047 Rw 0.058 gof 1.4 max A/a (final cycle) 0.03 residual density e/A3 -0.52, +0.44 a Temperature 294 K, Rigaku AFC6S diffractometer, graphite monochromator, takeoff angle 6.0°, aperture 6.0 x 6.0 mm at a distance of 285 mm from the crystal, stationary background counts at each end of the scan (scan/background time ratio 2:1), o2(F2) = [S2(C + 4B)+ (0.05F2)2]/Lp2 (S = scan speed, C = scan count, B = normalized background count), function minimized Ew(IF0l-IFcl)2 where w = 4F02/o"2(F02), R = Z\\F0[-\FC\\/L\F0\,RW = (Zw(IF0l-IFcl)2/EwlF0l2)1/2, and gof = [E(IF0l-IFcl)2/(m-n)]1^2. Values given for R, Rw, and gof are based on those reflections with / > 3o(/). Table A-II. [(dippp)Co]2(u,-Cl)2 (2); Bond lengths (A) with estimated standard deviations atom atom distance atom atom distance Co P(l) 2 231(2) C d ) C(2) 1 51(1) Co P(2) 2 232(2) C(2) C(3) 1 53(1) Co C l ' 2 342(2) C(4) C(8) 1 51(1) Co Cl 2 357(2) C(4) C(9) 1 54(1) P C ) C d ) 1 845(7) C(5) C ( l l ) 1 51(1) P(l) C(4) 1 858(7) C(5) CdO) 1 52(1) P(l) C(5) 1 863(B) C(6) C(14 ) 1 50(1) P(2) C(3) 1 847(6) C(6) Cd5) 1 53(1) P(2) C(7) 1 857(6) C(7) C(12) 1 51(1) P(2) C(6) 1 870(7) C(7) C(13) 1 52(1) Appendix Crystallographic Analyses 156 Table A-ITI. Intramolecular bond angles (deg) with,estimated standard deviations in [(dippp)Co]2(^-Cl)2 (2) atom atom atom angle atom atom atom angle P ( l ) Co P(2) 100 .61(8) C(7) P(2) Co 116 6(3) P ( l ) Co C I ' 115 .27(8) C(6) P(2) Co 117 0(2) P d ) Co CI 110 .95(7) C(2) C d ) P d ) 115 8(5) P(2) Co C I ' 114 .21(7) C ( l ) C(2) C(3) 115 0(6) P(2) Co CI 116 .07(8) C(2) C(3) P(2) 116 4(5) C I ' Co CI 100 .42(6) C(8) C(4) C(9) 110 5(8) Co CI Co 79. 58(6) C(8) C(4) P d ) 110 9(5) C ( l ) P d ) C(4 ) 101 .2(3) C(9) C(4) P d ) 114 8(6) C d ) P d ) C(5) 100 .5(4) C d l ) C(5) C d O ) 110 3(8) C d ) P d ) Co 116 .9(2) C ( l l ) C(5) P d ) 110 9(6) C(4) P d ) C(5) 103 .1(4) C d O ) C( 5) P d ) 110 0(6) C(4> P d ) Co 116 .3(3) C(14) C(6) C(15) 110 8(7) C( 5) P d ) Co 116 .4(3) C(14) C(6) P(2) 111 0(6) C(3) P(2) C(7) 101 .4(4) C(15) C(6) P(2) 110 6(5) C(3) P(2) C(6) 102 5(3) C(12) C(7) C(13) 111 8(7) C(3) P(2) Co 115 .2(2) C(12) C(7) P(2) 110 9(5) C(7) P(2) C(6) 101 8(4) C(13) C(7) P(2) 116 5(6) Table A-IV. Final atomic coordinates (fractional) and B e q for [(dippp)Co]2(p>Cl)2 a t o m X y z B e q Co 0 . 4 6 5 7 7 ( 5 ) 0 . 0 6 1 9 6 ( 4 ) 0 . 5 3 4 6 3 ( 8 ) 3 . 4 8 ( 3 ) C I 0 . 5 8 6 5 ( 1 ) 0 . 0 1 0 7 3 ( 9 ) 0 . 5 9 8 1 ( 2 ) 4 . 5 3 ( 8 ) P d ) 0 . 4 9 6 3 ( 1 ) 0 . 1 5 4 0 1 ( 8 ) 0 . 4 5 8 2 ( 2 ) 3 . 6 7 ( 7 ) P ( 2 ) 0 . 3 7 6 6 ( 1 ) 0 . 0 8 9 5 ( 1 ) 0 . 6 7 4 5 ( 2 ) 3 . 8 6 ( 7 ) C ( l ) 0 . 4 4 0 6 ( 4 ) 0 . 2 2 1 4 ( 3 ) 0 . 5 1 8 2 ( 7 ) 4 . 6 ( 3 ) C ( 2 ) 0 . 3 5 5 1 ( 4 ) 0 . 2 0 8 5 ( 4 ) 0 . 5 6 6 9 ( 7 ) 5 . 6 ( 4 ) C ( 3 ) 0 . 3 5 3 9 ( 4 ) 0 . 1 7 3 0 ( 4 ) 0 . 6 8 2 8 ( 7 ) 5 . 0 ( 4 ) C ( 4 ) 0 . 6 0 5 6 ( 4 ) 0 . 1 7 9 7 ( 4 ) 0 . 4 7 2 6 ( 8 ) 5 . 2 ( 4 ) C ( 5 ) 0 . 4 7 5 1 ( 5 ) 0 . 1 6 3 9 ( 4 ) 0 . 2 9 9 0 ( 7 ) 6 . 0 ( 4 ) C ( 6 ) 0 . 2 7 0 8 ( 4 ) 0 . 0 5 4 5 ( 4 ) 0 . 6 6 8 1 ( 7 ) 5 . 1 ( 4 ) C ( 7 ) 0 . 4 0 7 7 ( 5 ) 0 . 0 7 2 7 ( 4 ) 0 . 8 2 7 8 ( 6 ) 5 . 4 ( 4 ) C ( 8 ) 0 . 6 3 2 2 ( 5 ) 0 . 1 8 0 1 ( 4 ) 0 . 5 9 9 7 ( 9 ) 7 . 1 ( 5 ) Appendix Crystallographic Analyses 157 C ( 9 ) 0 . 6 2 5 1 ( 6 ) 0 . 2 4 2 2 ( 5 ) 0 . 4 1 5 ( 1 ) 9 . 9 ( 7 ) C ( 1 0 ) 0 . 5 3 0 0 ( 7 ) 0 . 1 2 0 7 ( 5 ) 0 . 2 2 7 9 ( 7 ) 9 . 0 ( 7 ) C ( l l ) 0 . 3 8 4 8 ( 6 ) 0 . 1 5 2 0 ( 4 ) 0 . 2 7 2 0 ( 7 ) 7 . 1 ( 5 ) C ( 1 2 ) 0 . 4 9 4 3 ( 5 ) 0 . 0 9 6 0 ( 5 ) 0 . 8 5 1 9 ( 7 ) 7 . 2 ( 5 ) C ( 1 3 ) 0 . 3 4 7 2 ( 6 ) 0 . 0 9 2 2 ( 5 ) 0 . 9 2 3 1 ( 7 ) 7 . 8 ( 6 ) C ( 1 4 ) 0 . 2 7 4 8 ( 5 ) - 0 . 0 1 4 4 ( 4 ) 0 . 6 8 2 9 ( 7 ) 6 . 4 ( 5 ) C ( 1 5 ) 0 . 2 2 7 7 ( 4 ) 0 . 0 7 1 6 ( 4 ) 0 . 5 5 3 ( 1 ) 6 . 8 ( 5 ) atom X y z B i s o H ( l ) 0 . 4 7 4 4 0 . 2 3 8 8 0 . 5 8 1 4 5 . 5 H ( 2 ) 0 . 4 3 4 9 0 . 2 5 1 9 0 . 4 5 5 3 5 . 5 H ( 3 ) 0 . 3 2 7 2 0 . 2 4 8 2 0 . 5 7 9 2 6 . 7 H ( 4 ) 0 . 3 2 4 5 0 . 1 8 4 3 0 . 5 0 8 8 6 . 7 H (5) 0 . 2 9 8 6 0 . 1 7 7 8 0 . 7 1 7 0 6 . 0 H ( 6 ) 0 . 3 9 5 0 0 . 1 9 1 9 0 . 7 3 4 6 6 . 0 H (7) 0 . 6 3 9 7 0 . 1 4 8 7 0 . 4 3 2 9 6 . 2 H (8) 0 . 4 8 8 3 0 . 2 0 6 6 0 . 2 7 7 1 7 . 2 H (9) 0 . 2 3 8 1 0 . 0 7 1 5 0 . 7 3 2 9 6 . 1 H (10 ) 0 . 4 1 1 1 0 . 0 2 7 6 0 . 8 3 3 1 6 . 5 H ( l l ) 0 . 6 2 2 0 0 . 1 3 9 3 0 . 6 3 4 2 8 . 6 H ( 1 2 ) 0 . 6 9 1 4 0 . 1 8 9 7 0 . 6 0 4 6 8 . 6 H ( 1 3 ) 0 . 6 0 0 5 0 . 2 1 1 3 0 . 6 4 2 5 8 . 6 H ( 1 4 ) 0 . 6 8 4 3 0 . 2 5 1 1 0 . 4 2 2 4 1 1 . 9 H ( 1 5 ) 0 . 6 1 0 3 0 . 2 4 0 4 0 . 3 3 1 4 1 1 . 9 H ( 1 6 ) 0 . 5 9 3 0 0 . 2 7 4 8 0 . 4 5 3 0 1 1 . 9 H ( 1 7 ) 0 . 5 1 8 3 0 . 0 7 7 8 0 . 2 5 0 0 1 0 . 8 H ( 1 8 ) 0 . 5 1 8 7 0 . 1 2 6 3 0 . 1 4 4 3 1 0 . 8 H ( 1 9 ) 0 . 5 8 8 3 0 . 1 3 0 0 0 . 2 4 3 8 1 0 . 8 H ( 2 0 ) 0 . 3 5 0 4 0 . 1 8 2 0 0 . 3 1 3 8 8 . 5 H ( 2 1 ) 0 . 3 7 5 5 0 . 1 5 6 0 0 . 1 8 7 5 8 . 5 H ( 2 2 ) 0 . 3 7 0 0 0 . 1 1 0 1 0 . 2 9 7 1 8 . 5 H ( 2 3 ) 0 . 5 1 3 1 0 . 0 8 0 5 0 . 9 2 7 9 8 . 6 H ( 2 4 ) 0 . 5 3 1 8 0 . 0 8 1 4 0 . 7 9 0 3 8 . 6 Appendix Crystallographic Analyses 158 atom X y z B i s H ( 2 5 ) 0 . 4 9 4 1 0 . 1 4 1 3 0 . 8 5 2 9 8 . 6 H ( 2 6 ) 0 . 3 4 1 9 0 . 1 3 7 3 0 . 9 2 3 3 9 . 4 H ( 2 7 ) 0 . 2 9 2 9 0 . 0 7 3 5 0 . 9 0 8 0 9 . 4 H ( 2 8 ) 0 . 3 6 7 7 0 . 0 7 8 3 0 . 9 9 9 5 9 . 4 H ( 2 9 ) 0 . 2 1 8 7 - 0 . 0 3 1 5 0 . 6 8 1 9 7 . 7 H ( 3 0 ) 0 . 3 0 7 1 - 0 . 0 3 2 4 0 . 6 1 8 6 7 . 7 H ( 3 1 ) 0 . 3 0 1 4 - 0 . 0 2 4 3 0 . 7 5 7 7 7 . 7 H ( 3 2 ) 0 . 2 2 2 7 0 . 1 1 6 6 0 . 5 4 7 7 8 . 2 H ( 3 3 ) 0 . 2 6 0 4 0 . 0 5 6 1 0 . 4 8 7 1 8 . 2 H ( 3 4 ) 0 . 1 7 2 4 0 . 0 5 2 9 0 . 5 5 1 5 8 . 2 2 - (ri3-benzyl)Co(dippp) (6) Crystallographic data appear in Table A-V. The final unit-cell parameters were obtained by least-squares on the setting angles for 25 reflections with 20 = 22.0-28.9°. The intensities of three standard reflections, measured every 200 reflections throughout the data collection, remained essentially constant. The data were processed1 and corrected for Lorentz and polarization effects, and absorption (empirical, based on azimuthal scans for three reflections). A total of 5828 reflections with 20 < 55° was collected on a Rigaku AFC6S diffractometer, 5538 were unique (Rin( = 0.056) and those 1923 having / ^ 3a(7) were employed in the solution and refinement of the structure. Appendix Crystallographic Analyses 159 The structure was solved by conventional heavy atom methods, the coordinates of the Co and P atoms being determined from the Patterson function and those of the remaining non-hydrogen atoms from a subsequent difference Fourier synthesis. The non-hydrogen atoms were refined with anisotropic thermal parameters. The hydrogen atoms were fixed in idealized positions (C-H = 0.98 A, fijj = 1.2 #bonded atom)- Neutral atom scattering factors and anomalous dispersion corrections for all atoms were taken from the International Tables for X-Ray Crystallography? Final atomic coordinates and equivalent isotropic thermal parameters, bond lengths, and bond angles appear in Tables A-VI to A-VIII, respectively. The structure of (T|3-CH2C6H5)Co(dippp) (6) is shown in Figure A-II. Figure A-II. Structure of (rj3-CH2C6H5)Co(dippp) (6). Appendix Crystallographic Analyses 160 Table A-V. Crystallographic data for (T|3-benzyl)Co(dippp) (6) compound (Ti3-benzyl)Co(dippp) formula C22H4iCoP2 fw 426.45 habit prism crystal size , mm 0.10x0.30x0.50 crystal system monoclinic space group Pl\ln a, A. 10.497(4) b,k 15.268(5) c, A 14.546(3) P° 94.06(2) v , A 3 2326(1) z 4 T, °C 21 Pc g/cm3 1.218 F(000) 920 radiation Mo wavelength (A) 0.71069 u., cm-1 8.74 transmission factors 0.90-1.00 scan type-' co-29 scan range, deg in co 1.31+ 0.35 tan 6 scan speed, deg/min 16 data collected +h, +k, ±1 26max> deg 55 Appendix Crystallographic Analyses 161 cryst decay negligible total no. of reflections 5828 no. of unique reflections 5538 Rint 0.056 no. of reflcns with I £ 3a(7) 1923 no. of variables 226 R 0.040 R w 0.041 gof 1.38 max A/a (final cycle) 0.09 residual density e/A3 -0.26, +0.40 a Temperature 294 K, Rigaku AFC6S diffractometer, graphite monochromator, takeoff angle 6.0°, aperture 6.0 x 6.0 mm at a distance of 285 mm from the crystal, stationary background counts at each end of the scan (scan/background time ratio 2:1), a2(F2) = [S2(C + 4B)+ (0.03F2)2]/Lp2 (S = scan speed, C = scan count, B = normalized background count), function minimized Ew(IF0l-IFcl)2 where w = 4F 0 2/o 2(F 0 2), R = ZIIF0I-IFCII/ZIF0I, Rw = (ZwaFol-IFJ^/XwIFol2)1/2, and gof = [Z(IF0l-IFcl)2/(m-n)]1/2. Values given for R, Rw, and gof are based on those reflections with / > 3G(7). Table A-VI. (ti3-CH2C6H5)Co(dippp) (6); Bond lengths (A) and estimated standard deviations. atom atom d is tance atom atom dis tance C o d ) P ( l ) 2.122(2) C<4) C(9) 1.536(6) C o ( l ) P(2) 2.158(2) C(5) C d O ) 1.519(8) C o d ) C(16) 1.989(5) C(5) C d l ) 1.527(6) C o d ) C(17) 2.033(5) C(6) C(12) 1.515(9) Appendix Crystallographic Analyses 162 c o d ) C d 8 ) 2. 207(5) C(6) C(13) 1 507(8) p d ) C d ) 1. 648(5) C(7) C(14) 1 523(6) p d ) C(4) 1. 663(6) C(7) C(15) 1 535(8) p d ) C(5) 1. 863(6) C d 6 ) C(17) 1 410(7) P(2) C(3) 1. 643(6) C(17) C d B ) 1 431(7) P(2) C(6) 1. 859(6) C(17) C(22) 1 420(7) P(2) C(7) 1. 857(6) C(18) C d 9 ) 1 405(7) C d ) C(2) 1. 509(8) C d 9 ) C(20) 1 348(8) C(2) C(3) 1. 508(9) C(20) C(21) 1 413(9) C(4) C(8) 1 525(8) C(21) C(22) 1 334(8) Table A-VII. (rj3-CH2C6H5)Co(dippp) (6); Bond Angles with estimated standard devviations. a t o n atom atom a n g l e atom atom atom a n g l e P ( l ) C o d ) P ( 2 ) 99 06(6) P d ) C ( 4 ) C ( 9 ) 114 6 (4 ) P d ) C o d ) C ( 1 6 ) 91 5(2) C ( 8 ) C ( 4 ) C ( 9 ) 109 4 (5) P ( l ) C o d ) C ( 1 7 ) 125 7 ( 2 ) P d ) C ( 5 ) C H O I 110 6 (4 ) P ( l ) C o d ) C ( 1 8 ) 161 9 ( 2 ) P d ) C ( 5 ) C d l ) 117 0(4 ) P ( 2 ) C o d ) C ( 1 6 ) 169 3 (2 ) C d O ) C ( 5 ) C ( l l ) 109 7 (5) P ( 2 ) C o d ) C ( 1 7 ) 130 4 (2 ) P ( 2 ) C ( 6 ) C ( 1 2 ) 109 2 (5 ) P (2 ) C o d ) C ( 1 8 ) 99 0 (2) P ( 2 ) C ( 6 ) C ( 1 3 ) 114 2(4) C(16) C o d ) C ( 1 7 ) 41 0(2) C ( 1 2 ) C ( 6 ) C ( 1 3 ) 110 1(6) C ( 1 6 ) C o ( l ) C ( 1 8 ) 70 4(2) P ( 2 ) C ( 7 ) C ( 1 4 ) 110 7(4) C ( 1 7 ) C o d ) C ( 1 8 ) 39 2 (2 ) P ( 2 ) C ( 7 ) C ( 1 5 ) 116 7(5) C o d ) P( 1) C d ) 119 5 (2) C ( 1 4 ) C ( 7 ) C ( 1 5 ) 110 5(6) C o d ) P d ) C ( 4 ) 118 6 (2 ) C o d ) C ( 1 6 ) C ( 1 7 ) 71 1(3) C o d ) P d ) C ( 5 ) 113 4(2) C o d ) C ( 1 7 ) C ( 1 6 ) 67 8 (3) C d ) P d ) C ( 4 ) 98 7 (3 ) C o d ) C ( 1 7 ) C ( 1 8 ) 77 0(3) C d ) P d ) C ( 5 ) 101 3(3) C o d ) C ( 1 7 ) C ( 2 2 ) 117 6 (4 ) C ( 4 ) P d ) C ( 5 ) 102 4(3) C ( 1 6 ) C ( 1 7 ) C d B ) 117 3(5) C o d ) P ( 2 ) C ( 3 ) lie 4(2 ) C ( 1 6 ) C ( 1 7 ) C ( 2 2 ) 125 1(6) C o d ) P ( 2 ) C ( 6 ) 117 2 (2 ) C ( 1 8 ) C ( 1 7 ) C ( 2 2 ) 116 9(5) C o d ) P ( 2 ) C ( 7 ) 114 7 ( 2 ) C o d ) C ( 1 8 ) C ( 1 7 ) 63 8(3) C( 3) P ( 2 ) C ( 6 ) 98 2 (3 ) C o d ) C ( 1 8 ) C ( 1 9 ) 130 1(4) C ( 3 ) P ( 2 ) C ( 7 ) 102 6 (3 ) C ( 1 7 ) C ( 1 8 ) C ( 1 9 ) 118 7(5) C ( 6 ) P ( 2 ) C ( 7 ) 103 1 (3 ) C ( 1 8 ) C ( 1 9 ) C ( 2 0 ) 122 2 (6 ) P(l) C d ) C ( 2 ) 115 5(4) C ( 1 9 ) C ( 2 0 ) C ( 2 1 ) 118 7(6) C d ) C ( 2 ) C ( 3 ) 113 5(5) C ( 2 0 ) C ( 2 1 ) C ( 2 2 ) 121 4(6) P ( 2 ) C ( 3 ) C ( 2 ) 115 3(4) C ( 1 7 ) C ( 2 2 ) C ( 2 1 ) 121 6(6) P ( l ) C ( 4 ) C ( 8 ) 110 8(4) Appendix Crystallographic Analyses 163 Table A-VIII. Final atomic coordinates (fractional) and B e q for C n 3 -CH2C6H5)Co(dippp) (6) a t o m X y z C o ( l ) 0 . 4 2 8 2 8 ( 7 ) 0 . 2 3 1 7 2 ( 4 ) 0 . 1 7 4 8 3 ( 5 ) 3 . 4 0 ( 3 ) P (D 0 . 6 1 0 0 ( 1 ) 0 . 2 8 5 3 ( 1 ) 0 . 2 1 5 7 ( 1 ) 4 . 0 6 ( 7 ) P ( 2 ) 0 . 3 9 1 9 ( 1 ) 0 . 1 6 3 7 ( 1 ) 0 . 3 0 0 4 ( 1 ) 4 . 2 2 ( 7 ) C ( l ) 0 . 6 8 7 9 ( 5 ) 0 . 2 5 6 8 ( 4 ) 0 . 3 2 9 7 ( 4 ) 5 . 4 ( 3 ) C ( 2 ) 0 . 6 5 2 1 ( 7 ) 0 . 1 6 8 8 ( 4 ) 0 . 3 6 7 5 ( 4 ) 6 . 4 ( 4 ) C ( 3 ) 0 . 5 1 6 9 ( 6 ) 0 . 1 6 4 8 ( 4 ) 0 . 3 9 6 0 ( 4 ) 5 . 7 ( 3 ) C ( 4 ) 0 . 6 2 6 9 ( 6 ) 0 . 4 0 6 6 ( 4 ) 0 . 2 2 2 7 ( 4 ) 5 . 3 ( 3 ) C ( 5 ) 0 . 7 3 6 4 ( 5 ) 0 . 2 5 4 5 ( 4 ) 0 . 1 3 8 1 ( 4 ) 5 . 1 ( 3 ) C ( 6 ) 0 . 2 5 7 0 ( 6 ) 0 . 2 0 3 6 ( 4 ) 0 . 3 6 5 1 ( 4 ) 5 . 8 ( 4 ) C ( 7 ) 0 . 3 5 7 0 ( 6 ) 0 . 0 4 5 1 ( 4 ) 0 . 2 8 5 9 ( 4 ) 5 . 4 ( 3 ) C ( 8 ) 0 . 5 3 0 9 ( 7 ) 0 . 4 4 5 5 ( 4 ) 0 . 2 8 5 3 ( 5 ) 7 . 1 ( 4 ) C ( 9 ) 0 . 6 1 5 6 ( 7 ) 0 . 4 5 3 8 ( 4 ) 0 . 1 2 9 2 ( 5 ) 7 . 2 ( 4 ) C ( 1 0 ) 0 . 7 5 4 0 ( 6 ) 0 . 1 5 5 8 ( 4 ) 0 . 1 3 6 5 ( 4 ) 6 . 8 ( 4 ) C ( l l ) 0 . 8 6 6 1 ( 6 ) 0 . 2 9 9 1 ( 5 ) 0 . 1 5 5 3 ( 5 ) 8 . 3 ( 5 ) C ( 1 2 ) 0 . 2 6 9 3 ( 7 ) 0 . 3 0 1 7 ( 5 ) 0 . 3 7 8 6 ( 5 ) 8 . 0 ( 5 ) C ( 1 3 ) 0 . 1 2 6 8 ( 7 ) 0 . 1 8 1 6 ( 5 ) 0 . 3 2 0 7 ( 5 ) 8 . 2 ( 5 ) C ( 1 4 ) 0 . 4 6 1 4 ( 7 ) - 0 . 0 0 0 1 ( 4 ) 0 . 2 3 5 9 ( 5 ) 7 . 1 ( 4 ) C ( 1 5 ) 0 . 3 2 9 0 ( 8 ) - 0 . 0 0 6 0 ( 5 ) 0 . 3 7 3 1 ( 5 ) 9 . 3 ( 5 ) C ( 1 6 ) 0 . , 4 2 8 1 ( 5 ) 0 . 2 8 9 0 ( 3 ) 0 . 0 5 2 0 ( 4 ) 4 . 4 ( 3 ) C ( 1 7 ) 0 . , 3 5 8 5 ( 5 ) 0 . 2 1 0 1 ( 3 ) °-0 4 2 8 ( 3 ) 3 . 7 ( 3 ) C ( 1 8 ) 0 . . 2 4 7 5 ( 5 ) 0 . 2 0 2 2 ( 4 ) 0 . 0 9 4 0 ( 4 ) 4 . 0 ( 3 ) C ( 1 9 ) 0 . . 1 7 6 5 ( 6 ) 0 . 1 2 4 2 ( 4 ) o . 0 8 6 8 ( 4 ) 5 . 2 ( 3 ) C ( 2 0 ) 0 . . 2 1 4 5 ( 7 ) 0 . 0 5 4 5 ( 4 ) 0 . 0 3 ^ 7 ( 5 ) 6 . 1 ( 4 ) C ( 2 1 ) 0. , 3 3 1 0 ( 7 ) 0 . 0 5 9 8 ( 5 ) - 0 . 0 0 4 1 ( 4 ) 6 . 1 ( 4 ) C ( 2 2 ) 0 . . 3 9 9 7 ( 5 ) 0 . 1 3 3 4 ( 4 ) - 0 . 0 0 1 7 ( 4 ) 4 . 9 ( 3 ) a t o m X y z B i so H ( l ) 0. . 7 8 0 5 0 . 2 5 7 3 0 . . 3 2 4 6 6 . 5 H ( 2 ) 0 . 6 6 5 2 0 . 3 0 1 8 0. . 3 7 3 7 6 . 5 H ( 3 ) 0 . 6 6 2 2 0 . 1 2 4 4 0, . 3 1 9 9 7 . 7 H ( 4 ) 0 . 7 1 0 3 0 . 1 5 5 7 0. . 4 2 1 5 7 . 7 H ( 5 ) 0 . 5 0 2 6 0 . 2 1 6 1 0. . 4 3 4 5 6 . 8 Appendix Crystallographic Analyses 164 H(6) 0.5080 0.1114 0.4323 6.8 H(7) 0.7124 0.4190 0.2512 6.3 H(8) 0.7041 0.2714 0.0758 6.1 H(9) 0.2644 .0.1762 0.4262 6.9 H(10) 0.2793 0.0412 0.2446 6.5 H ( l l ) 0.5460 0.5085 0.2921 8.6 H(12) 0.4441 0.4354 0.2581 8.6 H(13) 0.5410 0.4173 0.3460 8.6 H(14) 0.6295 0.5167 0.1386 8.6 H(15) 0.6798 0.4306 0.0899 8.6 H(16) 0.5301 0.4441 0.0993 8.6 H(17) 0.6710 0.1274 0.1229 8.2 H(18) 0.8115 0.1402 0.0888 8.2 H(19) 0.7908 0.1359 0.1967 8.2 H(20) 0.9047 0.2817 0.2158 10.0 H(21) 0.9220 0.2815 0.1074 10.0 H(22) 0.8547 0.3628 0.1536 10.0 H(23) 0.3525 0.3152 0.4103 9.6 H(24) 0.2622 0.3309. 0.3185 9.6 H<25) 0.2012 0.3226 0.4159 9.6 H(26) 0.0610 0.2043 0.3588 9.8 H(27) 0.1168 0.2082 0.2594 9.8 H(28) 0.1182 0.1178 0.3152 9.8 H(29) 0.4355 -0 .0604 0.2208 8.5 H(30) 0.4754 .0.0318 0.1790 8.5 H(31) 0.5408 -0 .0008 0.2757 8.5 H(32) 0.2603 0.0232 0.4035 11.1 H(33) 0.3028 -0 .0658 0.3563 11.1 H(34) 0.4061 -0 .0078 0.4152 11.1 H(35) 0.3813 0.3442 0.0427 5.3 H(36) 0.5093 0.2928 0.0228 5.3 H(37) 0.2216 0.2502 0.1332 4.8 H(38) 0.0968 0.1203 0.1177 6.2 H(39) 0.1623 0.0013 0.0336 7.3 H(40) 0.3618 0.0085 -0 .0362 7.4 H(41) 0.4807 0.1345 -0 .0314 5.9 Appendix Crystallographic Analyses 165 3 - [(dippp)Co]2(H)(u-H)3 (4) 3.1 - Structure solution at 21°C Crystallographic data appear in Table A-IX. The final unit-cell parameters were obtained by least-squares on the setting angles for 25 reflections with 20 = 27.0-34.0°. The intensities of three standard reflections, measured every 150 reflections throughout the data collection, decayed uniformly by 2.3%. The data were processed1 and corrected for Lorentz and polarization effects, decay, and absorption (empirical, based on azimuthal scans for four reflections). A total of 4586 reflections was collected on a Rigaku AFC6S diffractometer, of these 4367 were unique (R;nt = 0.030) and those 2725 having / > 3o(7) were employed in the solution and refinement of the structure. The structure analysis was initiated in the centrosymmetric space group C2/c on the basis of the Patterson function, the choice of space group being confirmed by the subsequent successful solution and refinement of the structure. The structure was solved by conventional heavy atom methods, the coordinates of the Co and P atoms being determined from the Patterson function and those of the remaining non-hydrogen atoms from a subsequent difference Fourier synthesis. The non-hydrogen atoms were refined with anisotropic thermal parameters. The bridging hydrogen atoms were refined with isotropic thermal parameters and all carbon-bound hydrogen atoms were fixed in idealized positions (C-H = 0.98 A, 2?H = 1.2 5bonded atom)- T n e remaining metal hydride atom could not be located and is probably a terminal hydride disordered over four possible sites (two at each metal). Neutral atom scattering factors and anomalous dispersion corrections for all atoms were taken from the International Tables for X-Ray Crystallography.2 Final atomic coordinates and equivalent isotropic Appendix Crystallographic Analyses 166 thermal parameters [Beq = 4/3Zj£jPij(afaj)], bond lengths, and bond angles appear in Tables A-X to A-XIH. The structure of [(dippp)Co]2(H)(u-H)3 (4) at 2VC is shown in Figure A-HI. Figure A-III. Structure of [(dippp)Co]2(H)(}i-H)3 (4) at 21°C. Table A-X. Crystallographic data for [(dippp)Co]2(H)(u-H)3 (4) at 21°C compound [(dippp)CoH2J2 formula C3oH72Co2P4 fw 674.66 color, habit blue prism crystal size , mm 0.20 x 0.30 x 0.35 Appendix Crystallographic Analyses 167 crystal system monoclinic space group C2Jc a, A 11.438(3) b, A 16.458(4) c, A 19.561(3) P, deg 92.37(2) V, A 3 3679(1) z 4 T, °C 21 pc, g/cm3 1.22 F(000) 1464 radiation Mo wavelength (A) 0.71069 u,, cm-1 10.88 transmission factors 0.897-1.00 scan type co-29 scan range, deg in co 1.37 + 0.35 tan 9 scan speed, deg/min 16 data collected +h, +k, ±1 28max> deg 55 cryst decay 2.3% total no. of reflections 4586 no. of unique reflections 4367 Rint 0.030 no. of reflcns with / > 3a(7) 2725 no. of variables 169 R 0.032 Appendix Crystallographic Analyses 168 Rw 0.043 gof 1.27 max A/o (final cycle) 0.16 residual density e/A3 0.37 a Temperature 294 K, Rigaku AFC6S diffractometer, graphite monochromator, takeoff angle 6.0°, aperture 6.0 x 6.0 mm at a distance of 285 mm from the crystal, stationary background counts at each end of the scan (scan/background time ratio 2:1), o2(F2) = [S2(C + 45)+ (0.04F2)2]/Lp2 (5 = scan speed, C = scan count, B = normalized background count), function minimized Ew(IF0l-IFcl)2 where w = 4FQ2/a2(F02), R = ZIIF0I-IFCII/IIF0I, Rw = (£w(IF 0l-IF cl) 2/LwlF 0l 2) 1 / 2, and gof = [Z(IF0l-IFcl)2/(m-n)]1/2. Values given for R, Rw, and gof are based on those reflections with / > 3a(/). Table A-XI. [(dippp)Co]2(H)(u,-H)3 (4) at 21°C; bond lengths (A) with estimated standard deviations. atom atom distance Co P ( l ) 2 .1357(B) Co P(2) 2 .1416(8) Co Co* 2, .2841(7) P ( l ) C U ) 1. .856(3) P<1) C(4) 1. .866(3) P ( l ) C(5) 1. .867(3) P(2) C(3) 1. .853(3) P(2) C(6) 1. .862(3) P(2) C(7) 1. .873(3) C ( l ) C(2) 1. ,519(4) Co H(35) 1. .57(4) atom atom distance C(2) C(3) 1. 525(4) C(4) C(8) 1. .520(5) C(4) C(9) 1. .526(4) C(5) C(10) 1. .520(5) C(5) C ( l l ) 1. 529(4) C(6) C(13) 1. 514(5) C(6) C(12) 1. 530(5) C(7) C(14) 1. 510(5) C(7) C(15) 1. 535(4) Co H(36* 1. .52(5) Co H(36) 1. .56(5) Appendix Crystallographic Analyses 169 Table A-XJJ. [(dippp)Co]2(H)(u-H)3 (4) at 21°C; bond angles (deg) with estimated standard deviations. atom •torn atom angle atom •torn atom angle P<1> Co P(2) 99.36(3) C(2) C<1) P d ) 115.3(2) P d ) Co Co* 128.92(3) C ( l ) C(2) C(3) 113.5(2) P(2) Co Co* 131.55(3) C(2) C(3) P(2) 115.5(2) C(l) P ( l ) C(4) 100.8(1) C(8) C(4) C(9) 110.3(3) C(l) P ( l ) C(5) 100.7(1) C(8) C(4) P ( l ) 110.8(2) C ( l ) P d ) Co 119.0(1) C(9) C(4) P d ) 112.0(2) C<4) P(l) C(5) 101.8(1) CdO) C(S) C d l ) 111.0(3) C(4 ) P ( l ) Co 115.7(1) CdO) C(5) P d ) 110.3(2) CIS) P(l) Co 116.1(1) C d l ) C(5) P d ) 115.0(2) C(3) P(2) C(6) 100.6(1) C(13) C(6) C(12) 111.1(3) C(3> P(2) C(7) 100.9(1) C(13) C(6) P(2) 112.4(2) C(3) P(2) Co 119.30(9) C(12) C(6) P(2) 110.4(2) C(6) P(2) C(7) 102.0(1) C(14) C(7) C(15) 110.B(3) C(6) P(2) Co 116.6(1) C(14) C(7) P(2) 110.7(2) C(7) P(2) Co 114.7(1) C(15) C(7) P(2) 115.1(2) H(36)* Co H(36) 72(3) H(36) Co P(2) 132(2) H(36)* Co H(35) 72(2) H(36) Co Co* 42(2) H(36)» Co P(l ) 170(2) H(35) Co P d ) 98(1) H(36)* Co P(2) 89(2) H(35) Co P(2) 145.2(2) H<36)* Co Co* 43(2) H(35) Co CO* 43d) H(36) Co H(35) 71(2) Co B(35) Co* 93(3) H(36) Co P(l ) 104(2) Co H(36) Co* 96(3) Table A-XIH. Positional parameters and Beq for [(dippp)CoH2]2 (4) at 21 "C. a t o m X y z B ( e q ) Co 0 . 4 5 7 7 3 ( 3 ) 0 . 1 5 1 7 5 ( 3 ) 0 . 1 9 6 0 7 ( 2 ) 3 . 6 6 ( 2 ) P d ) 0 . 5 1 5 4 2 ( 6 ) 0 . 2 1 0 2 9 ( 4 ) 0 . 1 0 6 0 5 ( 3 ) 2 . 9 0 ( 3 ) P ( 2 ) 0 . 3 0 9 6 7 ( 6 ) 0 . 0 8 7 5 0 ( 4 ) 0 . 1 5 2 7 3 ( 3 ) 3 . 0 5 ( 3 ) C d ) 0 . 4 3 5 2 ( 3 ) 0 . 1 9 1 2 ( 2 ) 0 . 0 2 3 2 ( 1 ) 3 . 6 ( 1 ) C ( 2 ) 0 . 3 8 0 9 ( 3 ) 0 . 1 0 7 4 ( 2 ) 0 . 0 1 5 3 ( 1 ) 3 . 8 ( 1 ) C ( 3 ) 0 . 2 7 5 9 ( 2 ) 0 . 0 9 4 3 ( 2 ) 0 . 0 5 9 5 ( 1 ) 3 . 7 ( 1 ) C ( 4 ) 0 . 6 6 8 4 ( 2 ) 0 . 1 8 7 0 ( 2 ) 0 . 0 8 2 8 ( 1 ) 3 . 7 ( 1 ) C ( 5 ) 0 . 5 1 6 5 ( 3 ) 0 . 3 2 3 7 ( 2 ) 0 . 1 0 7 6 ( 1 ) 3 . 9 ( 1 ) Appendix Crystallographic Analyses 170 C ( 6 ) 0 . 3 0 8 7 ( 3 ) - 0 . 0 2 4 7 ( 2 ) 0 . 1 6 4 8 ( 2 ) 4 . 0 ( 1 ) C ( 7 ) 0 . 1 6 5 8 ( 2 ) 0 . 1 1 7 8 ( 2 ) 0 . 1 8 7 4 ( 1 ) 4 . 0 ( 1 ) C ( 8 ) 0 . 6 8 8 5 ( 3 ) 0 . 0 9 5 8 ( 2 ) 0 . 0 8 0 3 ( 2 ) 5 . 1 ( 2 ) C ( 9 ) 0 . 7 5 8 6 ( 3 ) 0 . 2 2 6 9 ( 2 ) 0 . 1 3 1 6 ( 2 ) 5 . 6 ( 2 ) C d O ) 0 . 3 9 7 9 ( 3 ) 0 . 3 5 5 9 ( 2 ) 0 . 1 2 7 3 ( 2 ) 6 . 0 ( 2 ) C ( l l ) 0 . 5 5 5 9 ( 3 ) 0 . 3 6 4 1 ( 2 ) 0 . 0 4 2 1 ( 2 ) 5 . 1 ( 2 ) C(12) 0 . 4 1 6 3 ( 3 ) - 0 . 0 6 2 9 ( 2 ) 0 . 1 3 3 7 ( 2 ) 5 . 6 ( 2 ) C ( 1 3 ) 0 . 3 0 0 4 ( 4 ) - 0 . 0 4 B 6 ( 2 ) 0 . 2 3 9 2 ( 2 ) 6 . 2 ( 2 ) C ( 1 4 ) 0 . 1 4 4 8 ( 3 ) 0 . 2 0 7 7 ( 2 ) 0 . 1 7 7 9 ( 2 ) 5 . 8 ( 2 ) C ( 1 5 ) 0 . 0 6 0 0 ( 3 ) 0 . 0 6 8 6 ( 3 ) 0 . 1 6 0 0 ( 2 ) 5 . 7 ( 2 ) H ( l ) 0 . 3 7 2 3 0 . 2 3 1 5 0 . 0 1 8 1 4 . 3 H ( 2 ) 0 . 4 9 0 1 0 . 1 9 8 5 - 0 . 0 1 3 5 4 . 3 H ( 3 ) 0 . 3 5 5 5 0 . 0 9 9 8 - 0 . 0 3 2 8 4 . 6 H ( 4 ) 0 . 4 4 0 6 0 . 0 6 6 8 0 . 0 2 6 0 4 . 6 H ( 5 ) 0 . 2 3 7 5 0 . 0 4 3 6 0 . 0 4 4 8 4 .4 H ( 6 ) 0 . 2 2 1 8 0 . 1 3 9 9 0 . 0 5 1 5 4 . 4 H ( 7 ) 0 . 6 7 9 5 0 . 2 0 6 8 0 . 0 3 6 9 4 .4 H ( 8 ) 0 . 5 7 2 8 0 . 3 3 9 9 0 . 1 4 4 2 4 . 7 H ( 9 ) 0 . 2 3 9 3 - 0 . 0 4 6 1 0 . 1 3 9 9 4 . 8 H ( 1 0 ) 0 . 1 7 2 1 0 . 1 0 8 2 0 . 2 3 6 9 4 . 8 H ( l l ) 0 . 6 8 0 8 0 . 0 7 2 7 0 . 1 2 6 1 6 . 1 H ( 1 2 ) 0 . 6 3 0 4 0 . 0 7 0 9 0 . 0 4 8 6 6 . 1 H ( 1 3 ) 0 . 7 6 7 3 0 . 0 8 4 9 0 . 0 6 4 7 6 . 1 H ( 1 4 ) 0 . 7 5 1 6 0 . 2 0 4 4 0 . 1 7 7 7 6 . 7 H ( 1 5 ) 0 . 8 3 7 4 0 . 2 1 6 4 0 . 1 1 5 9 6 . 7 H ( 1 6 ) 0 . 7 4 4 7 0 . 2 8 5 7 0 . 1 3 2 6 6 . 7 H ( 1 7 ) 0 . 4 0 2 9 0 . 4 1 4 7 0 . 1 3 4 7 7 . 2 H ( 1 8 ) 0 . 3 3 9 6 0 . 3 4 4 3 0 . 0 9 0 5 7 . 2 H ( 1 9 ) 0 . 3 7 4 8 0 . 3 2 9 3 0 . 1 6 9 5 7 . 2 H(20) 0 . 6 3 2 6 0 . 3 4 2 7 0 . 0 3 0 6 6 . 1 H(21) 0 . 4 9 8 9 0 . 3 5 2 7 0 . 0 0 4 6 6 . 1 H ( 2 2 ) 0 . 5 6 1 6 0 . 4 2 3 0 0 . 0 4 9 1 6 . 1 H ( 2 3 ) 0 . 4 1 1 1 - 0 . 1 2 2 2 0 . 1 3 6 7 6 . 7 Appendix Crystallographic Analyses 171 H(24 ) 0.4195 -0.0466 0.0856 6 . 7 H(25) 0.4872 -0.0442 0.1588 6 . 7 H(26) 0.2310 -0.0233 0.2580 7.4 H(27) 0.2941 -0.1078 0.2427 7.4 H(28) 0.3706 -0.0301 0.2651 7.4 H(29) 0.2132 0.2380 0.1959 6.9 H(30) 0.1321 0.2196 0.1291 6 . 9 H(31) 0.0756 0.2239 0.2025 6 . 9 H(32) -0.0094 0.0841 0.1846 6 .8 H(33) 0.0464 0.0798 0.1111 6 . 8 H(34) 0.0754 0.0105 0.1666 6 . 8 H(35) 1/2 0.217(3) 1/4 8(1) H(36) 0.573(4) 0.121(3) 0.233(3) 12(1) 3.2 - Structure solution at -155°C The original crystal (from the room temperature analysis) was carefully removed from the capillary in which it was sent, and was mounted on the goniostat using standard inert atmosphere handling techniques. The quality of the crystal was checked after it was cooled to -155°C, and it was determined to be adequate. A systematic search of a limited hemisphere of reciprocal space located a set of diffraction maxima with symmetry and systematic absences corresponding to the original C2lc unit cell. Subsequent solution and refinement of the structure confirmed the choice. Data were collected in the usual manner using a continuous 6-29 scan with fixed background. Data were reduced to a unique set of intensities and associated sigmas in the usual manner. An absorption correction was made, with maximum and minimum values of 0.925 to 0.876. Appendix Crystallographic Analyses 172 Full matrix refinement of the non-hydrogen atoms followed by a difference Fourier analysis clearly located all hydrogen atoms. Although the hydride was present in this map, it was left out of the initial refinement. After several cycles, all hydrogen atoms "behaved" normally, and a difference Fourier map was generated. There was one large peak (0.59e/A3) in a proper position to bridge two Co atoms. All other peaks within bonding distance of the cobalt atoms were less than 0.25e/A3 in intensity. Although there was a peak on the 2-fold axis, it was the 14th in the list, with an intensity of 0.21e/A3, and appeared too close to the centre of the Co-Co bond to be a hydride. When the hydride was introduced and refinement concluded, it "behaved" properly, although the thermal parameter is considerably higher than any of the remaining hydrogen atoms. A VERSORT drawing of the structure of [(dippp)CoH2]2 (4) at -155"C is shown in Figure A-IV. Details of the analysis are given in Tables A-XIV to A-XVII. Figure A-IV. Structure of [(dippp)CoH2]2 (4) at -155°C Appendix Crystallographic Analyses 173 Table A-XIV. Crystallographic data for [(dippp)CoH2]2 (4) at -155°C compound empirical formula molecular weight colour of crystal crystal dimensions, mm crystal system space group [(dippp)CoH2]2 Co2C30H70P4 672.64 black 0.15x0.30x0.35 monoclinic Cllc Cell dimensions (at -155°C; 92 reflections): a, A b, A c A P, deg v , A 3 Z (molecules/cell) T, °C calculated density, g/cm3 wavelength (A) 11.304(2) 16.312(3) 19.373(3) 92.64(1) 3568.52 4 -155 1.252 0.71069 linear absorption coefficient, cm-1 11.222 (1/4 u, = 0.2228 mm) The diffractometer utilized for data collection was designed and constructed locally (Indiana University). A Picker four-circle goniostat equipped with a Furnas Monochromator (HOG crystal) and Picker X-ray generator is interfaced to a TI980 minicomputer, with Slo-Syn stepping motors to drive angles. Centering is accomplished using automated Top/Bottom—Left/Right slit assemblies. The Appendix Crystallographic Analyses 174 minicomputer is interfaced by low speed data lines to a CYBER170-855 (NOS operating system) where all computations are performed. Detector to sample distance, cm 22.5 Sample to source distance, cm 23.5 Take off angle (deg) 2.0 Average (0 scan width at half-height (deg) 0.25 Data collection performed usind standard crystal-moving detector technique with the folllowing values: Scan speed, deg/min 4.0 Scan width 2.0 + dispersion Single background time at extremes of scan, s 6 Aperture size, mm 3.0 x 4.0 Minimum 28, deg 5 Maximum 20, 5ey 55 Total number of reflections collected 6429 Number of unique intensities 4088 Number with F > 0.0 3749 Number with F > 2.33 G(F) 3406 R for averaging 0.042 R(F) 0.0491 RW(F) 0.0482 Goodness of fit for the last cycle 1.392 Maximum A/a for the last cycle 0.05 Appendix Crystallographic Analyses 175 Table A-XV. [(dippp)CoH2]2 (4) at -155°C; bond lengths ( A ) with estimated standard deviations A B Distance Co(l) Co(l>' 2 2811(10) Co(l) P<1) 2 1319(10) Co(l) P(2) 2 1415(10) P d ) C( l ) 1 852(3) P d ) C(4) 1 870(3) P( l ) C(7) 1 867(4) P(2) C(3) 1 850(3) P<2) C(10) 1 868(4) P(2) C(13) 1 872(3) C( l ) C(2) 1 535(4) C(2) C(3) 1 531(4) C(4) C(5) 1 532(5) C(4) C(6) 1 521(5) C(7) C(8) 1 531(5) C(7) C(9) 1 529(5) C(10) C d l ) 1 525(5) C(10) C(12) 1 528(5) C(13) C(14) 1 524(5) C(13) C<15) 1 527(5) C(12) H(26) .95(4) C(12) H(27) 1 .00(4) C(12) H(28) .86(4) C(13) H(29) .91(4) C(14) H(30) 1 .01(5) C(14) H(31) •94(4) C(14) H(32) 1 .07(5) C(15) H(33) 94(4) C(15) H(34) .99(4) C(15) H(3S) .89(4) A B Distance C o d ) H d ) 1.25(9) Co(l) H ( l ) ' 1.41(8) C( l ) H(2) .94(4) C( l ) H(3) .97(4) C(2) H(4) .91(3) C(2) H(5) 1.00(3) C(3) H(6)' .92(4) C(3) H(7) .95(4) C(4) H(8) .93(3) C(5) H(9) .93(4) C(5) H(10) .97(4) C(5) H ( l l ) .90(4) C(6) H(12) .89(4) C(6) H(13) .97(4) C(6) H(14) .98(4) C(7) H(15) .95(4) C(8) H(16) .92(5) C(8) H(17) 1.00(4) C(8) H(18) .88(4) C(9) H(19) .98(4) C(9) H(20) .95(4) C(9) H(21) .93(4) C(10) H(22) .93(4) C d l ) H(23) .95(4) C d l ) H(24) .98(5) C d l ) H(25) .96(5) Table A-XVI. [(dippp)CoH2]2 (4) at -155°C; deviations A B C Angle C o ( l ) ' Co(l) P( l ) 127 •45(4) C o d ) ' Co(l) P(2) 132 64(3) P d ) C o d ) P(2) 99 24(4) C o d ) P( l ) C( l ) 119 60(10) C o d ) P d ) C(4) 115 94(11) C o d ) P d ) C(7) 115 46(11) C d ) P d ) C(4) 100 72(15) C d ) P d ) C(7) 100 49(15) C(4) P d ) C(7) 101 79(15) C o d ) P(2) C(3) 119 59(11) C o d ) P(2) C(10) 117 10(11) Co(l) P(2) C(13) 113 90(11) C(3) P(2) C(10) 100 34(16) C(3) P(2) C(13) 101 15(15) C(10) P(2) C(13) 102 01(16) P( l ) C d ) C(2) 114 82(22) C d ) C(2) C(3) 113 40(27) P<2) C(3) C(2) 114 79(22) P d ) C(4) C(5) 110 73(23) P d ) C(4) C(6) 112 06(25) C(5) C(4) C(6) 110 0(3) P(D C(7) C(8) 109 92(25) P( l ) C(7) C(9) 114 60(24) C(8) C(7) C(9) 111 2(3) bond angles (deg) with standard A B C Angle Co( l ) ' Co(l) H(l) 29 (3) C o ( l ) ' Co(l) H d ) ' 33 (3) P d ) Co(l) H(l) 105 (3) P d ) C o d ) H ( l ) ' 155 (3) P(2) Co(l) H(l) 143 (3) P(2) C o d ) H d ) ' 104 (3) H d ) Co(l) H(l ) 61 (5) P d ) C d ) H(2) 108 0(20) P d ) C d ) H(3) 109 0(20) C(2) C d ) H(2) 109 1(21) C(2) C d ) • H(3) 111 3(20) H(2) C( l ) H(3) 104 (3) C d ) C(2) H(4) 105 8(21) C d ) C(2) H(5) 112 1(20) C(3) C(2) H(4) 108 5(21) C(3) C(2) H(5) 111 1(19) H(4) C(2) H(5) 105 4(28) P(2) C(3) H(6) 108 7(24) P(2) C(3) H(7) 107 2(23) C(2) C(3) H(6) 109 7(24) C(2). C(3) H(7) 108 0(23) H(6) . C(3) H(7) 108 (3) P d ) C(4) H(8) 106 1(20) C(5) C(4) H(8) 108 0(20) Appendix Crystallographic Analyses 176 P(2) C(10) C ( l l ) 111. 60(26) P(2) C(10) C(12) 110. 00(23) C ( l l ) C(10) C(12) 111. 6(3) P(2) C(13) C(14) 110. 47(25) P(2) C(13) C(15) 115. 68(24) C(14) C(13) C(15) 110. 9(3) H<19) C(9) H(21) 106 • <3) H(20) C(9) H(21) 106 .(3) P(2) C(10) H(22) 106 .0(23) C ( l l ) C(10) H(22) 108 .3(23) C(12) C(10) H(22) 109 .1(23) C(10) C ( l l ) H(23) 111 .5(25) C(10) C<11) H(24) 112 .2(26) C(10) C ( l l ) H(25) 111 .2(28) H(23) C ( l l ) K(24) 112 .(4) H(23) C ( l l ) H(25) 107 • (4) H(24) C ( l l ) HC25) 102 .(4) C(10) C(12) H(26) 110 9(24) C(10) C(12) H(27) 114 .1(25) C(10) C(12) H(28) 110 3(25) H(26) C(12) H(27) 107 (3) H(26) C(12) H(28) 103 (3) H(27) C<12) H(28) 111 .(3) P(2) C(13) H(29) 106 .4(23) C(14) C(13) H(29) 105 .2(24) C(15) C(13) H(29) 107 .5(23) C(13) C(14) H(30) 114 .2(26) C(13) C(14) H(31) 112 .8(25) C(13) C(14) H(32) 110 .8(26) H(30) C(14) H(31) 105 (3) H(30) C(14) H(32) 109 (4) H(31) C(14) H(32) 104 (4) C(13) C(15) H(33) 108 3(22) C(13) C(15) H(34) 111 .6(24) C(13) C(15) H(35) 112 2(26) H(33) C(15) H(34) 109 .(3) H(33) C(15) H(35) 105 • (3) H(34) C(15) HC35) 110 (4) Co(l) H(l) Co( l ) ' 118. (5) C(6) C(4) H(8) 109. 9(20) C(4) C(5) H(9) 113. 3(26) C(4) C(5) H(10) 112. 1(25) C(4) C(5) H ( l l ) 112. 7(27) H(9) C(5) H(10) 110. (4) H(9) C(5) H ( l l ) 102. (4) H(10) C(5) H ( l l ) 106. (4) C(4) C(6) H(12) 111. 6(26) C(4) C(6) H(13) 112. 4(24) C(4) C(6) H(14) 112, 7(24) H(12) C(6) H(13) 109. (3) H(12) C(6) H(14) 109, (4) H(13) C(6) H(14) 102 (3) P( l ) C(7) H(15) 105 4(22) C(8) C(7) H(15) 104 .8(22) C(9) C(7) H(15) 110 .3(22) C(7) C(8) H(16) 109 .(3) C(7) C(8) H(17) 114 .2(22) C(7) C(8) H(18) 110 .4(28) H(16) C(8) H(17) 106 •(4) H(16) C(8) H(18) 107 .(4) H(17> C(8) H(18) 110 (3) C(7) C(9) H(19) 111 .7(24) C(7) C(9) H(20) 113 .1(26) C(7) C(9) H(21) 112 .2(26) H(19) C(9) M(20) 107 (3) Table A-XVII. Fractional coordinates and isotropic thermal paramaters for [(dippp)CoH2]2 (4) at -155°C. Atom X y z Biso Co(l) 4545.0(4) 1528.4(3) 1962.2(2) 23 P(D 5147(1) 2097(1) 1051.8(4) 14 P(2) 3079(1) 851(1) 1515.1(4) 14 C(D 4357(3) 1900(2) 209(2) 15 C(2) 3807(3) 1042(2) 133(2) 16 C(3) 2732(3) 916(2) 574(2) 17 C(4) 6705(3) • 1861(2) 833(2) 17 C(5) 6919(3) 934(2) 833(2) 21 C(6) 7604(3) 2280(3) 1324(2) 26 C(7) 5153(3) 3242(2) 1060(2) 19 C(8) 3929(3) 3563(3) 1232(2) 27 C(9) 5580(3) 3637(2) 400(2) 23 C(10) 3104(3) -286(2) 1633(2) 18 C(U) 3081(4) -522(3) 2394(2) 27 C(12) 4178(3) -651(2) 1293(2) 22 C(13) 1619(3) 1132(2) 1867(2) 19 C(14) 1368(4) 2042(2) 1757(2) 27 C(15) 564(3) 613(3) 1610(2) 25 Appendix Crystallographic Analyses 177 H(l) 557(6) 145(4) 240(5) 118(6) H(2) 376(3) 230(2) 15(2) 14(6) H(3) 489(3) 201(2) -16(2) 16(7) H(4) 357(3) 99(2) -32(2) 9(6) H(5) 440(3) 60(2) 22(2) 13(6) H(6) 233(3) 45(2) 43(2) 23(7) H(7) 221(3) 137(2) 50(2) 20(7) H(8) 679(3) 205(2) 38(2) 10(6) H(9) 683(4) 69(3) 126(2) 34(8) H(10) 642(4) 65(3) 48(2) 33(8) H(ll) 767(4) 80(3) 75(2) • 31(8) H(12) 748(4) 216(3) 176(2) 29(8) H(13) 842(4) 214(2) .123(2) 29(8) H(14) 761(4) 288(3) ' 127(2) 31(8) H(15) 566(3) 339(2) 145(2) 19(7) H(16) 394(4) 413(3) 121(2) 49(9) H(17) 327(3) 338(2) 90(2) 22(7) H(18) 377(4) 343(3) 166(2) 31(8) H(19) 639(4) 347(3) 31(2) 31(8) H(20) 510(4) 350(3) 0(2) 30(8) H(21) 559(4) 421(3) 43(2) 31(8) H(22) 242(3) -48(2) 141(2) 19(7) H(23) 239(4) -32(2) 260(2) 28(8) H(24) 319(4) -111(3) 247(2) 36(8) H(25) 375(4) -30(3) 265(2) 42(9) H(26) 432(3) -120(3) 145(2) 23(7) 11(27) 410(4) -66(3) 78(2) 35(8) H(28) 481(3) -40(2) 143(2) 22(7) H(29) 170(3) 107(2) 234(2) 19(7) H(30) 204(4) 241(3) 191(2) 38(9) H(31) 121(3) 218(2) 129(2) 26(8) H(32) 59(5) 222(3) 201(3) 55(9) H(33) -12(3) 82(2) 180(2) 19(7) H(34) 45(3) 63(3) 110(2) 28(8) H(35) 62(4) 10(3) 175(2) 26(8) Notes: 1) Fractional coordinates are X 10**4 for non-hydrogen atoms and X 10**3 for hydrogen atoms. Biso values are X 10. 2) Isotropic values for those atoms refined anisotropically are calculated using the formula given by W. C. Hamilton, Acta Cryst., 12,609 (1959) 3) Parameters marked by an asterisk (*) were not varied. 4 - (dippcyp)Co(ri5-C6H7) (10) and (r)4-2-methoxynaphthalene)Co(H)(dippcyp) (11) Crystallographic data for (T|4-2-methoxynaphthalene)Co(H)(dippcyp) (11) and (dippcyp)Co(Ti5-C6H7) (10), appear in Table A-XVIII. The final unit-cell Appendix Crystallographic Analyses 178 parameters were obtained by least-squares on the setting angles for 25 reflections with 20 = 25.3-29.6° for 11 and 30.1-31.9° for 10. The intensities of three standard reflections, measured every 200 reflections throughout the data collections, decayed uniformly by 4.0 and 4.7% respectively for 11 and 10. The data were processed1 and corrected for Lorentz and polarization effects, decay, and absorption (empirical, based on azimuthal scans for four reflections). The structure analysis of 11 was initiated in the centrosymmetric space group Pl on the basis of the f-statistics and the appearance of the Patterson function, this choice being confirmed by the subsequent successful solution and refinement of the structure. Both structures were solved by heavy atom methods, the coordinates of the Co and P atoms being determined from the Patterson functions and those of the remaining non-hydrogen atoms from subsequent difference Fourier syntheses. Both crystal structures were found to be disordered. In both of the two crystallographically independent molecules of 11 the methoxy substituent of the T j 4 - 2 -methoxynaphthalene ligand was disordered over two possible sites and for the molecule containing Co(2) one of the isopropyl groups was also disordered. The methoxy carbon atoms for the molecule containing Co(l) could not be resolved, thus a single full-occupancy atom was refined. The individual site occupancy factors for the disordered atoms of 11 were initially estimated from relative Fourier peak heights and were subsequently adjusted to give nearly equal equivalent isotropic thermal parameters for each site. Anomalous thermal parameters for two carbon atoms (C(18) and C(21)) of the (r|5-C6H7) ligand in 10, along with apparent planarity of the ring, suggested that these atoms were disordered. Both of these atoms were refined using a (1:1) split-atom model. All non-hydrogen atoms of both complexes (with the exception of the low-occupancy atoms O(IB), 0(2B), C(39B), and C(52C) in 11) were refined with anisotropic thermal parameters. The metal hydride atoms in 11 and Appendix Crystallographic Analyses 179 the full-occupancy hydrogen atoms of the (T|5-C6H7) ligand in 10 were refined with isotropic thermal parameters and all other hydrogen atoms except for those associated with the low-occupancy carbon atoms C(39B) and C(52C) in 11 were fixed in idealized positions (C-H = 0.98 A , 2?H = 1.2 #bonded atom)- Corrections for secondary extinction were not applied. Neutral atom scattering factors and anomalous dispersion corrections for the non-hydrogen atoms were taken from the International Tables for X-Ray Crystallography.2 Final atomic coordinates and equivalent isotropic thermal parameters [Beg = 4/3SjEjPij(ai-aj)], selected bond lengths, and selected bond angles appear in Tables AXIX to A-XXIV, respectively. The structures of (r)5-CgH7)Co(dippcyp) (10) and (r|4-2-methoxynaphthalene)Co(H)(dippcyp) (11) are shown in Figures A-V and A-VI respectively. Table A-XVIII. Crystallographic data for (ji5-C6H7)Co(dippcyp) (10) and (r|4-2-methoxynaphthalene)Co(H)(dippcyp) (1 l) a compound (Tl4-CioH7OCH3)Co(H)(dippcyp) (Tl5-C6H7)Co(dippc; formula C2 8H4 6CoOP2 C23H43CoP2 fw 519.55 440.47 color, habit red-brown, irregular brown, prism crystal size , mm 0.40 x 0.40 x 0.50 0.18x0.25x0.50 crystal system triclinic monoclinic space group Pl Plllc a, A 18.231(4) 16.131(2) b, A 18.345(4) 8.850(2) c, A 9.029(2) 16.327(2) a° 100.13(2) 90 P° 101.95(2) 90.55(2) Appendix Crystallographic Analyses 180 7° 101.30(2) 90 v , A 3 2822(1) 2331(1) z 4 4 Pcalc • S/om3 1.223 1.255 F(000) 1116 952 \x(Mo-Ka), cm1 7.34 14.77 transmission factors 0.90-1.00 0.94-1.00 scan type co-29 co-28 scan range, deg in to 1.05+0.35 tan 8 1.31+0.35 tan 8 scan rate, deg/min 32 16 data collected +h,±k,±l +h,+k,±l 2emax> d e S 55 55 cryst decay 4.0% 4.7% total no. of reflections 13794 5907 no. of unique reflections 12968 5707 Emerge 0.022 0.055 reflcns with / > 3a(/ ) 6824 2962 no. of variables 610 277 R 0.046 0.035 Rw 0.057 0.039 gof 1.94 1.35 max A/a (final cycle) 0.08 0.01 residual density e/A3 -0.28 to +0.53 -0.20 to +0.43 a Temperature 294 K, Rigaku AFC6S diffractometer, Mo-A"a radiation (k = 0.71069 A ) , graphite monochromator, takeoff angle 6.0°, aperture 6.0 x 6.0 mm at a distance of 285 mm from the crystal, stationary background counts at each end of the scan Appendix Crystallographic Analyses 181 (scan/background time ratio 2:1, up to 8 rescans), a2(F2) = [S2(C +45) + (0.04F2)2]/Lp2 (5 = scan rate, C = scan count, B = normalized background count), function minimized £w(IF 0l-IF cl) 2 where w = 4F02/a2(F02), R = ZIIF0I-Ifcll/1IF0I, Rw = (ZwOFol-IFcl^/EwlFol2)1/2, and gof = [Z(IF0l-IFcl)2/(m-n)]1/2. Values given for R, Rw, and gof are based on those reflections with / ^ 3a(7). Figure A-V. Structure of (T|5-C6H7)Co(dippcyp) (10). Table A-XIX. (T]5-C6H7)Co(dippcyp) (10); bond lengths (A) with estimated standard deviations. atom atom distance atom atom distance C o d ) P d ) 2.1514(9) C(6) C d O ) 1.513(5) C o d ) P(2) 2.148(1) C(6) C d l ) 1.518(5) C o d ) C d 8 B ) 2.04(1) C(7) C(12) 1.525(5) Appendix Crystallographic Analyses 182 C0(1) C d 9 ) 2 0 7 1 ( 4 ) C ( 7 ) C ( 1 3 ) 1 . 5 3 2 ( 5 ) C o d ) C ( 2 0 ) 2 . 0 9 6 ( 4 ) C ( 8 ) C ( 1 4 ) 1 . 5 3 1 ( 5 ) C o d ) C ( 2 1 A ) 2 0 6 ( 1 ) C ( 8 ) C ( 1 5 ) 1 529(5) C o d ) C ( 2 2 ) 2 1 0 6 ( 4 ) C ( 9 ) C ( 1 6 ) 1 . 5 2 0 ( 5 ) C o d ) C ( 2 3 ) 2 122 (4 ) C ( 9 ) C ( 1 7 ) 1 533(5) P H I C d ) 1 843 (3 ) C(18A) C(19 ) 1 6 5 ( 1 ) P U ) C ( 6 ) 1 8 7 5 ( 3 ) C(18A) C ( 2 3 ) 1 51 (1 ) P U > C ( 7 ) 1 870 (3 ) CI18B) C(19 ) 1 2 7 ( 2 ) P ( 2 ) C ( 2 ) 1 845 (3 ) C ( 1 8 B ) C ( 2 3 ) 1 38 (2 ) P ( 2 ) C ( B ) 1 868 (3 ) C(19 ) C ( 2 0 ) 1 358(7) P ( 2 ) C ( 9 ) 1 868 (3 ) C(20 ) C(21A) 1 2 5 ( 2 ) C d ) C ( 2 ) 1 536(4) C(20 ) C(21B) 1 59 (1 ) C d ) C(5 ) 1 531 (4 ) C(21A) C ( 2 2 ) 1 35 (2 ) C ( 2 ) C( 3) 1 532 (4 ) C(21B) C(22 ) 1 54 (1 ) C ( 3 ) C M ) 1 536(5) C ( 2 2 ) C(23 ) 1 353(6) C M ) C ( 5 ) 1 5 3 9 ( 5 ) Table A-XX. (r|5-C6H7)Co(dippcyp) (10); bond angles (deg) with estimated standard deviations. atom atom atom a n g l e atom atom atom a n g l e P ( l ) C o d ) P ( 2 ) 8 9 . 92 (4 ) C(21A) C o d ) C(23 ) 6 6 . 1 ( 4 ) P d ) C o d ) C(18B) 9 8 . 3 (4 ) C ( 2 2 ) C o d ) C(23 ) 3 7 . 3 ( 2 ) P d ) C o d ) C ( 1 9 ) 104 . 7 ( 2 ) C o d ) P d ) C d ) 1 0 8 . 5 ( 1 P d ) C o d ) C ( 2 0 ) 134 . 6 ( 2 ) C o d ) P d ) C ( 6 ) 1 2 0 . 2 ( 1 P d ) C o d ) C ( 2 1 A ) 168 . 8 ( 4 ) C o d ) P d ) C ( 7 ) 1 1 7 . 6 ( 1 P d ) C o d ) C ( 2 2 ) 145 . 9 ( 1 ) C d ) P d ) C ( 6 ) 1 0 4 . 0 ( 1 P d ) C o d ) C(23 ) 112 . 4 ( 1 ) C d ) P d ) C ( 7 ) 1 0 2 . 9 ( 1 P ( 2 ) C o d ) C(18B) 170 . 7 ( 5 ) C ( 6 ) P d ) C ( 7 ) 1 0 1 . 5 ( 2 P I 2 ) C o d ) C(19 ) 145 . 5 ( 2 ) C o d ) P ( 2 ) C ( 2 ) 1 0 8 . 0 ( 1 P ( 2 ) C o d ) C(20 ) 111 . 4 ( 2 ) C o d ) P ( 2 ) C ( 8 ) 1 1 6 . 8 ( 1 P12) C o d ) C(21A) 9 8 . 9 ( 4 ) C o d ) P ( 2 ) C ( 9 ) 1 2 1 . 0 ( 1 P ( 2 ) C o d ) C(22 ) 104 . 2 ( 1 ) C(2 ) P ( 2 ) C ( 8 ) 1 0 3 . 0 ( 1 P ( 2 ) C o d ) C ( 2 3 ) 133 . 6 ( 1 ) C ( 2 ) P ( 2 ) C ( 9 ) 1 0 4 . 6 ( 1 CI18B) C o d ) C ( 1 9 ) 3 5 . 9 ( 5 ) C ( 8 ) P ( 2 ) C ( 9 ) 1 0 1 . 5 ( 2 C(18B) C o d ) C ( 2 0 ) 6 5 . 6 ( 4 ) P d ) C d ) C ( 2 ) 1 0 9 . 8 ( 2 Appendix Crystallographic Analyses 183 atom atom atom a n g l e atom atom atom a n g l e C(18B) C o d ) C I 2 1 A ) 7 3 . 5 ( 5 ) P d ) C ( l ) C ( 5 ) 1 2 6 . 5 ( 2 ) C(18B) C o l l ) C I 2 2 ) 6 6 . 5 ( 5 ) C ( 2 ) C d ) C ( S ) 1 0 2 . 0 ( 2 ) C ( 1 6 B ) C o l l ) C I 2 3 ) 3 8 . 7 ( 5 ) P I 2 ) C ( 2 ) C d ) 1 1 0 . 1 ( 2 ) C ( 1 9 ) C o l l ) C I 2 0 ) 3 8 . 0 ( 2 ) P ( 2 ) C ( 2 ) C ( 3 ) 1 2 7 . 3 ( 2 ) C ( 1 9 ) C o l l ) C I 2 1 A ) 6 4 . 2 ( 4 ) C d ) C ( 2 ) C ( 3 ) 1 0 2 . 1 ( 2 ) C ( 1 9 ) C o d ) C I 2 2 ) 8 1 . 1 ( 2 ) C ( 2 ) C ( 3 ) C ( 4 ) 1 0 4 . 0 ( 3 ) C ( 1 9 ) C o l l ) C I 2 3 ) 6 9 . 5 ( 2 ) C ( 3 ) C ( 4 ) C ( 5 ) 1 0 6 . 8 ( 2 ) C ( 2 0 ) C o U ) C ( 2 1 A ) 3 5 . 1 ( 4 ) C d ) C ( 5 ) C ( 4 ) 1 0 4 . 3 ( 3 ) C ( 2 0 ) C o d ) C I 2 2 ) 6 8 . 8 ( 2 ) P d ) C ( 6 ) C d O ) 1 1 1 . 1 ( 2 ) C ( 2 0 ) C o l 1) C I 2 3 ) 8 1 . 9 ( 2 ) P d ) C I 6 ) C d l ) 1 1 2 . 0 ( 2 ) C(21A) C o d ) C I 2 2 ) 3 7 . 9 ( 5 ) C d O ) C ( 6 ) C d l ) 1 1 0 . 1 ( 3 ) P d ) C d ) H d ) 105 .64 C ( 1 3 ) C ( 7 ) H(10) 1 0 6 . 5 6 C ( 2 ) C d ) H d ) 1 0 5 . 6 5 P ( 2 ) C ( 8 ) 8 ( 1 1 ) 1 0 6 . 4 2 C ( 5 ) C d ) H d ) 1 0 5 . 6 4 C ( 1 4 ) C ( 8 ) H ( l l ) 106 .42 P ( 2 ) C ( 2 ) H(2 ) 1 0 5 . 1 6 C ( 1 5 ) C ( 8 ) B i l l ) 1 0 6 . 4 3 C ( l ) C I 2 ) H(2 ) 1 0 5 . 1 6 P ( 2 ) C ( 9 ) H(12) 107 .87 C O ) C I 2 ) HI2) 1 0 5 . 1 6 C ( 1 6 ) C ( 9 ) H(12 ) 107 .88 C ( 2 ) C ( 3 ) HI3) 1 1 0 . 8 3 C ( 1 7 ) C ( 9 ) . H ( 1 2 ) 107 .88 C ( 2 ) C ( 3 ) H(4 ) 1 1 0 . 8 3 C ( 6 ) C d O ) HI13) 109 .47 CI4 ) C ( 3 ) H(3) 1 1 0 . 8 3 C ( 6 ) C ( 1 0 ) HI14) 109 .47 C I O C I 3 ) H(4 ) 1 1 0 . 8 3 C ( 6 ) C d O ) HI15) 109 .47 H(3) CI3 ) H(4 ) 1 0 9 . 4 6 H(13) C110 ) H(14) 109 .47 C I 3 ) C I 4 ) HI 5) 1 1 0 . 1 3 H(13) C d O ) HI15) 109 .47 C I 3 ) C ( 4 ) H(6) 110 .13 HI14) C d O ) H(15) 1 0 9 . 4 8 C I 5 ) C H ) HI 5) 1 1 0 . 1 3 C I 6 ) C d l ) H(16) 109 .47 CI 5) C ( 4 ) H(6 ) 1 1 0 . 1 3 C ( 6 ) C d l ) H(17) 109 .47 HI5) C ( 4 ) H(6) 1 0 9 . 4 6 C I 6 ) C ( l l ) H(18) 109 .47 C U ) C ( 5 ) H(7 ) 1 1 0 . 7 5 H(16) C d l ) H(17) 109 .47 C U ) C I 5 ) H(8) 1 1 0 . 7 6 HI16) C d l ) H(18) 109 .47 C U ) C ( 5 ) H(7 ) 1 1 0 . 7 5 HI17) C d l ) HI18) 109 .48 C ( 4 ) C I 5 ) H(8) 1 1 0 . 7 6 C ( 7 ) C ( 1 2 ) H(19) 109 .47 H(7 ) C ( 5 ) B ( 8 ) 1 0 9 . 4 6 C ( 7 ) C I 1 2 ) H(20) 109 .47 P U ) C ( 6 ) H(9 ) 107 .84 C ( 7 ) C ( 1 2 ) H(21) 109 .47 C U O ) C ( 6 ) H(9 ) 1 0 7 . 8 3 H(19) C ( 1 2 ) H(20) 109 .47 C U D C ( 6 ) HI9) 1 0 7 . 8 3 H(19) C ( 1 2 ) H(21) 109 .48 P U ) C ( 7 ) H(10) 1 0 6 . 5 6 H(20) C ( 1 2 ) HI21) 1 0 9 . 4 7 C U 2 ) C ( 7 ) HI10) 106 .54 C ( 7 ) C ( 1 3 ) H(22) 109 .48 C ( I S A ) C I 2 3 ) HI44) 119(3 ) C o d ) C ( 2 1 A ) C ( 2 0 ) 7 3 . 9 ( 5 ) C U 8 B ) C123) HI44) 131 (3 ) C o d ) C ( 2 1 A ) C ( 2 2 ) 7 2 . 8 ( 5 ) C ( 2 2 ) C ( 2 3 ) HI44) 115(3 ) C ( 2 0 ) C I 2 1 A ) C ( 2 2 ) 131(1 ) Appendix Crystallographic Analyses 1 8 4 atom atom atom a n g l e atom atom atom a n g l e C ( 7 ) C ( 1 3 ) H(23) 109 . .46 H(34) C ( 1 7 ) H(35) 109 .47 C ( 7 ) C ( 1 3 ) B ( 2 4 ) 109 . .47 H(34) C ( 1 7 ) H(36) 109 .48 B ( 2 2 ) C I 1 3 I H(23) 109. .47 H(35) C ( 1 7 ) H(36) 1 0 9 . 4 7 B ( 2 2 ) C ( 1 3 ) H(24) 109. .47 C ( 1 9 ) C I 1 8 A ) H(37) 115 (4 ) H(23) C ( 1 3 ) H(24) 109 . .47 C(19 ) C(18A) H(38) 112 .28 C ( 8 ) C ( 1 4 ) H(25) 109, .47 C ( 2 3 ) C(18A) H(37) 108(3) C ( 8 ) C(14 ) H(26) 109, .48 C ( 2 3 ) C ( 1 8 A ) H(38) 1 1 2 . 1 9 C ( 8 ) C ( 1 4 ) H(27) 109 .47 H(37) C(18A) H(38) 110 .90 11(25) C ( 1 4 ) H(26 ) 109 .47 C ( 1 9 ) C(18B) H(37) 126 (3 ) H(25) C ( 1 4 ) H(27) 109 .47 C(23 ) C(18B) H(37) 102 ('3) H(26) C ( 1 4 ) H(27 ) 109 . 47 C(18A) C(19 ) H(39) 108(3) C(8 ) C (15 ) H(28) 109 .48 C(18B) C(19 ) H(39) 115(3) C ( 8 ) C(15 ) H(29) 109 .48 C ( 2 0 ) C ( 1 9 ) H(39) 128 (3 ) C ( 8 ) C(15 ) H( 30) 109 . 47 C(19 ) C ( 2 0 ) H(40) 111 (3 ) H(28) C ( 1 5 ) H(29) 109 .47 CI21A) C(20 ) H(40) 134(3) H(28) C(15 ) H(30) 109 .46 C(21B) C(20 ) H( 40 ) 125(3) H(29) C ( 1 5 ) H(30) 109 .45 C(20 ) C(21A) HI 41 ) 118 (2 ) C(9 ) C(16 ) H(31) 109 .47 C(22 ) C(21A) H(41) 111 (2 ) C ( 9 ) C ( 1 6 ) H(32) 109 .47 C ( 2 0 ) C(21B) H(41) 111(3) C ( 9 ) C ( 1 6 ) H(33) 109 .46 C(20 ) C(21B) H(42) 112 .12 H( 31) C ( 1 6 ) H(32) 109 .48 C(22 ) C(21B) H(41) 114 (2 ) H(31) C(16 ) H(33) 109 .47 C(22 ) C(21B) H(42) 112 .12 H(32) C ( 1 6 ) H(33) 109 .47 H(41) C ( 2 1 B ) H(42) 1 0 9 . 5 5 C ( 9 ) C ( 1 7 ) H(34) 109 .47 C(21A) C(22 ) H(43) 124(2) C ( 9 ) C ( 1 7 ) H(35) 109 .47 C(21B) C(22 ) H(43) 113(2) Cf 9) C ( 1 7 ) H(36) 109 .47 C ( 2 3 ) C(22) H(43) 121(2) P ( l ) C ( 7 ) C ( 1 2 ) 111 . 5 ( 2 ) C ( 2 0 ) C(21B) C(22 ) 9 6 . 6 ( 6 ) P d ) C ( 7 ) C ( 1 3 ) 115 . 6 ( 2 ) C o ( l ) C ( 2 2 ) C(21A) 6 9 . 3 ( 4 ) C ( 1 2 ) C ( 7 ) C ( 1 3 ) 109 . 5 ( 3 ) C o d ) C ( 2 2 ) C(21B) 9 2 . 0 ( 5 ) P ( 2 ) C ( 8 ) C ( 1 4 ) 110 . 5 ( 2 ) C o d ) C ( 2 2 ) C ( 2 3 ) 7 2 . 0 ( 2 ) P ( 2 ) C ( 8 ) C(15 ) 116 . 7 ( 2 ) C(21A) C(22 ) C ( 2 3 ) 1 1 4 . 9 ( 7 ) C ( 1 4 ) C ( 8 ) C(15 ) 109 . 7 ( 3 ) C(21B) C(22 ) C ( 2 3 ) 1 2 4 . 4 ( 6 ) P ( 2 ) C ( 9 ) C ( 1 6 ) 112 . 0 ( 2 ) C o d ) C ( 2 3 ) C ( 1 8 A ) 9 2 . 1 ( 5 ) P ( 2 ) C ( 9 ) C(17 ) 110 . 9 ( 2 ) C o d ) C(23 ) C(18B) 6 7 . 5 ( 5 ) C ( 1 6 ) C ( 9 ) C(17 ) 110 . 2 ( 3 ) C o d ) C(23) C(22 ) 7 0 . 7 ( 2 ) C(19 ) C(18A) C(23 ) 9 8 . 1 ( 7 ) C(18A) C ( 2 3 ) C(22 ) 1 2 3 . 2 ( 7 ) C o d ) C(18B) C(19 ) 7 3 . 4 (5 ) C(18B) C(23 ) C(22 ) 1 1 2 . 6 ( 7 ) C o d ) C ( 1 8 B ) C ( 2 3 ) 7 3 . 8 ( 5 ) CI18B) C(19 ) C ( 2 0 ) . 1 1 7 . 3 ( 8 ) C(19 ) C(18B) C(23 ) 129 (1 ) C o d ) C ( 2 0 ) C(19 ) 7 0 . 0 ( 3 ) C o d ) C(19 ) C(18A) 9 0 . 1 ( 5 ) : c o d ) C ( 2 0 ) C(21A) 7 1 . 0 ( 5 ) C o d ) C ( 1 9 ) C(18B) 7 0 . 8 ( 5 ) C o d ) C(20 ) C ( 2 1 B ) 9 1 . 2 ( 5 ) C o d ) C ( 1 9 ) C ( 2 0 ) 7 2 . 0 (3 ) C(19 ) C ( 2 0 ) C ( 2 1 A ) 1 1 4 . 4 ( 8 ) C ( 1 8 A ) C ( 1 9 ) C ( 2 0 ) 121 . 9 ( 6 ) C ( 1 9 ) C ( 2 0 ) C(21B) 1 2 1 . 3 ( 7 ) Appendix Crystallographic Analyses 185 Table A-XXI. Final atomic coordinates (fractional) and B e q for C6H7)Co(dippcyp) (10) a t o m X y z B eq C o ( l ) 0 . 2 5 1 6 5 ( 3 ) 0 . 1 5 7 2 7 ( 5 ) 0 . 1 3 9 9 9 ( 2 ) 2 . 9 2 ( 2 ) P d ) 0 . 3 3 9 5 8 ( 5 ) 0 . 3 2 9 4 ( 1 ) 0 . 1 0 7 5 2 ( 4 ) 2 . 9 8 ( 3 ) P ( 2 ) 0 . 1 5 9 2 4 ( 5 ) 0 . 2 6 5 6 ( 1 ) 0 . 0 6 4 8 2 ( 5 ) 2 . 9 5 ( 3 ) C ( l ) 0 . 2 8 4 5 ( 2 ) 0 . 4 7 8 8 ( 3 ) 0. 0 5 0 1 ( 2 ) 3 . 0 ( 1 ) C ( 2 ) 0 . 2 1 1 4 ( 2 ) 0 . 4 1 0 0 ( 3 ) 0 . 0 0 2 1 ( 2 ) 3 . 0 ( 1 ) C ( 3 ) 0 . 1 7 2 2 ( 2 ) 0 . 5 4 9 8 ( 4 ) - 0 . 0 3 7 8 ( 2 ) 4 . 0 ( 2 ) C ( 4 ) 0 . 2 4 6 7 ( 2 ) 0 . 6 4 8 7 ( 4 ) - 0 . 0 6 0 5 ( 2 ) 4 . 2 ( 2 ) C ( 5 ) 0 . 3 2 2 1 ( 2 ) 0 . 5 8 5 8 ( 4 ) - 0 . 0 1 3 2 ( 2 ) 4 . 0 ( 2 ) C ( 6 ) 0 . 4 3 0 3 ( 2 ) 0 . 2 8 2 0 ( 4 ) 0 . 0 4 1 3 ( 2 ) 3 . 9 ( 2 ) C ( 7 ) 0 . 3 9 0 9 ( 2 ) 0 . 4 3 6 2 ( 4 ) 0 . 1 9 2 8 ( 2 ) 3 . 9 ( 2 ) C ( 8 ) 0 . 1 0 5 6 ( 2 ) 0 . 1 4 5 5 ( 4 ) - 0 . 0 1 3 4 ( 2 ) 3 . 7 ( 1 ) C ( 9 ) 0 . 0 6 9 8 ( 2 ) 0 . 3 6 7 0 ( 4 ) 0 . 1 1 1 7 ( 2 ) 4 . 1 ( 2 ) C ( 1 0 ) 0 . 4 0 2 7 ( 2 ) 0 . 1 9 9 6 ( 4 ) - 0 . 0 3 5 4 ( 2 ) 4 . 8 ( 2 ) C ( l l ) 0 . 4 9 5 0 ( 2 ) 0 . 1 8 9 4 ( 4 ) 0 . 0 8 7 1 ( 2 ) 5 . 3 ( 2 ) C ( 1 2 ) 0 . 3 2 7 5 ( 2 ) 0 . 5 0 2 0 ( 4 ) 0 . 2 5 1 6 ( 2 ) 5 . 2 ( 2 ) C ( 1 3 ) 0 . 4 5 1 3 ( 2 ) 0 . 5 6 0 4 ( 5 ) 0 . 1 6 6 5 ( 2 ) 5 . 3 ( 2 ) C ( 1 4 ) 0 . 1 6 8 8 ( 2 ) 0 . 0 7 1 9 ( 4 ) - 0 . 0 7 0 3 ( 2 ) 4 . 5 ( 2 ) C ( 1 5 ) 0 . 0 3 7 2 ( 2 ) 0 . 2 2 1 2 ( 5 ) - 0 . 0 6 4 3 ( 2 ) 5 . 3 ( 2 ) C ( 1 6 ) 0 . 0 9 8 1 ( 2 ) 0 . 4 8 3 1 ( 5 ) 0 . 1 7 4 6 ( 2 ) 5 . 5 ( 2 ) C ( 1 7 ) 0 . 0 0 9 3 ( 2 ) 0 . 2 5 5 0 ( 5 ) 0. 1 5 0 5 ( 3 ) 6 . 1 ( 2 ) C ( 1 8 A ) * 0 . 3 4 9 1 ( 8 ) - 0 . 0 3 3 ( 1 ) 0 . 2 2 1 2 ( 7 ) 5 . 0 ( 6 ) C ( 1 8 B ) * 0 . 3 2 9 1 ( 7 ) 0 . 0 2 3 ( 2 ) 0 . 2 0 7 ( 1 ) 6 . 5 ( 7 ) C ( 1 9 ) 0 . 2 8 4 9 ( 5 ) 0 . 0 9 4 5 ( 6 ) 0 . 2 5 8 0 ( 3 ) 6 . 8 ( 3 ) C ( 2 0 ) 0 . 2 0 1 4 ( 4 ) 0 . 0 8 0 5 ( 6 ) 0 . 2 5 0 3 ( 3 ) 6 . 0 ( 3 ) C ( 2 1 A ) * 0 . 1 7 8 2 ( 8 ) - 0 . 0 0 5 ( 1 ) 0. 1 9 3 ( 1 ) 5 . 0 ( 6 ) C ( 2 1 B ) * 0 . 1 6 0 9 ( 8 ) - 0 . 0 6 1 ( 1 ) 0. 2 0 5 7 ( 7 ) 4 . 3 ( 5 ) C ( 2 2 ) 0 . 2 2 1 4 ( 3 ) - 0 . 0 7 3 9 ( 4 ) 0 . 1 3 3 4 ( 2 ) 4 . 9 ( 2 ) C ( 2 3 ) 0 . 3 0 4 8 ( 3 ) - 0 . 0 6 2 0 ( 5 ) 0. 1 4 0 5 ( 3 ) 5 . 1 ( 2 ) * S i t e o c c u p a n c y 0 . 5 0 . Appendix Crystallographic Analyses a t o m x H ( l ) 0.2597 H(2) 0.2367 H(3) 0.1401 H(4) 0.1361 H(5) 0.2565 H(6) 0.2366 H(7) 0.3529 H(8) 0.3591 H(9) 0.4563 H(10) 0.4235 H ( l l ) 0.0791 H(12) 0.0402 H(13) 0.3621 H(14) 0.4508 H(15) 0.3773 H(16) 0.4706 H(17) 0.5421 H(18) 0.5142 H(19) 0.3562 H(20) 0.2959 H(21) 0.2896 H(22) 0.4787 R(23) 0.4931 H(24) 0.4207 H(25) 0.2108 H(26) 0.1404 H(27) 0.1956 H(28) 0.0614 H(29) 0.0107 H(30) -0 .0042 H(31) 0.1267 H(32) 0.1359 H(33) 0.0497 H(34) -0 .0387 186 0 . 5 4 4 1 0 . 0 9 1 7 3 . 6 0 . 3 5 3 9 - 0 . 0 4 3 0 3 . 6 0 . 5 2 1 7 - 0 . 0 8 6 8 4 . 8 0 . 6 0 2 4 0 . 0 0 0 8 4 . 8 0 . 6 4 3 6 - 0 . 1 1 9 6 5 . 0 0 . 7 5 3 8 - 0 . 0 4 4 6 5 . 0 0 . 6 6 7 5 0 . 0 1 3 9 4 . 8 0 . 5 3 0 9 - 0 . 0 5 0 0 4 . 8 0 . 3 7 7 0 0 . 0 2 4 6 4 . 6 0 . 3 6 2 4 0 . 2 2 4 2 4 . 7 0 . 0 6 3 0 0 . 0 1 6 6 4 . 5 0 . 4 2 0 7 0 . 0 6 7 8 4 . 9 0 . 2 6 1 5 - 0 . 0 6 5 3 5 . 8 0 . 1 8 1 0 - 0 . 0 7 0 2 5 . 8 0 . 1 0 3 1 - 0 . 0 2 0 4 5 . 8 0 . 0 9 3 2 0 . 1 0 4 3 6 . 3 0 . 1 6 9 7 0 . 0 5 1 0 6 . 3 0 . 2 4 5 5 0 . 1 3 5 4 6 . 3 0 . 5 4 4 5 0 . 2 9 9 5 6 . 2 0 . 5 8 1 8 0 . 2 2 3 8 6 . 2 0 . 4 2 2 1 0 . 2 6 9 3 6 . 2 0 . 6 0 3 1 0 . 2 1 5 1 6 . 3 0 . 5 1 7 3 0 . 1 3 0 1 6 . 3 0 . 6 4 0 2 0 . 1 3 7 6 6 . 3 0 . 0 1 8 6 - 0 . 0 3 7 5 5 . 4 - 0 . 0 0 0 1 - 0 . 1 0 6 6 5 . 4 0 . 1 5 0 0 - 0 . 1 0 3 3 5 . 4 0 . 3 0 1 4 - 0 . 0 9 7 9 6 . 4 0 . 1 4 5 9 - 0 . 0 9 9 9 6 . 4 0 . 2 6 4 9 - 0 . 0 2 7 6 6 . 4 0 . 4 3 1 8 0 . 2 1 9 9 6 . 6 0 . 5 5 5 1 0 . 1 4 8 8 6 . 6 0 . 5 3 7 3 0 . 1 9 5 6 6 . 6 0 . 3 0 9 9 0 . 1 7 1 7 7 . 3 Appendix Crystallographic Analyses 187 H(35) -0 .0093 0.1820 0.1091 7.3 H(36) 0 .0372 0.2013 0.1955 7.3 H(37) 0 .398(3) - 0 . 0 0 0 ( 6 ) 0 .211(3) 9(2) H(38)* 0 .3519 -0 .1240 0.2555 6.0 H(39) 0 .311(2) 0 .148(4) 0 .290(2) 6(1) H(40) 0 .176(3) 0 .141(5) 0 .285(3) 8(1) H(41) 0 .107(2) - 0 . 0 3 9 ( 4 ) 0 .190(2) 6(1) H(42)* 0 .1615 -0 .1512 0.'2-4,0 3 5.1 H(43) 0 .198(2) - 0 . 1 1 6 ( 4 ) 0 .088(2) 3 .9 (8 ) H(44) 0 .333(2) - 0 . 0 9 8 ( 5 ) 0 .098(3) 7(1) * S i t e o c c u p a n c y 0 . 5 0 . Figure A-VI. Structure of (T|4-2-methoxynaphthalene)Co(H)(dippcyp) (11). Appendix Crystallographic Analyses 188 Table A-XXTI. (Ti4-2-methoxynaphthalene)Co(H)(dippcyp) (11); bond lengths (A) with estimated standard deviations. atom atom distance atom atom distance Co(l) P d ) 2 . 170 (1 ) O d B ) C ( 9 ) 1. 2 2 ( 2 ) C o d ) P U ) 2 . 1 7 9 ( 1 ) O d A ) CX8) 1. 317(6) C o d ) C U ) 2 . 1 7 3 ( 4 ) 0(1A) C U D 1. 513 (9 ) C o d ) C U ) 2 . 0 1 0 ( 4 ) 0(2A) C ( 3 7 ) 1. 34 (1 ) C o d ) C ( 4 ) 1. . 988 (4 ) O U A ) C ( 3 9 A ) 1. . 2 6 ( 2 ) C o d ) C ( 5 ) 2 . . 109(4) 0(2B) C ( 3 6 ) 1. . 2 4 ( 2 ) C o d ) H d ) 1. . 35 (4 ) O U B ) C( 39B) 1. . 5 2 ( 3 ) Co(2 ) P ( 3 ) 2 . 175 (1 ) C U ) C ( 2 ) 1. . 4 5 4 ( 6 ) C o d ) P ( 4 ) 2 . . 183 (1 ) C(l) C ( 6 ) 1. . 4 0 9 ( 6 ) C o d ) C (30 ) 2 . , 176 (5 ) C U ) C U O ) 1. . 3 7 5 ( 6 ) C o d ) C U D 2. , 013 (5 ) C U ) - C ( 3 ) 1, . 4 0 9 ( 6 ) Co(2 ) C( 32 ) 1. ,980(4 ) C U ) C ( 4 ) 1, . 3 9 1 ( 6 ) C o d ) C l 33 ) 2 . , 107 (5 ) C ( 4 ) C ( 5 ) 1, . 4 2 7 ( 6 ) Co l 2) H U ) 1. , 3 5 ( 4 ) C ( 5 ) C(6 ) 1, . 4 6 0 ( 6 ) P d ) C I 1 2 ) 1. . 836 (4 ) C ( 6 ) C ( 7 ) 1 . 4 0 1 ( 6 ) P d ) C( 17 ) 1. . 871 (4 ) C ( 7 ) C ( 8 ) 1, . 4 1 0 ( 7 ) P d ) C(18 ) 1. . 857 (4 ) C ( 8 ) C ( 9 ) 1, . 3 4 9 ( 8 ) P ( 2 ) C(13 ) 1. . 8 3 8 ( 4 ) C ( 9 ) C U O ) 1, . 3 6 3 ( 7 ) P ( 2 ) C(19 ) 1. . 8 6 9 ( 4 ) C U 2 ) C( 13) 1, . 5 3 4 ( 5 ) P d ) C ( 2 0 ) 1. . 8 5 5 ( 4 ) C( 12) C( 16) 1, . 5 1 9 ( 5 ) P ( 3 ) C ( 4 0 ) 1, . 8 4 2 ( 4 ) C U 3 ) C U 4 ) 1. . 5 2 3 ( 5 ) P ( 3 ) C ( 4 5 ) 1. . 6 6 8 ( 5 ) C ( 1 4 ) C U S ) 1, . 5 5 9 ( 6 ) P ( 3 ) C ( 4 6 ) 1, . 8 5 9 ( 6 ) C U 5 ) C ( 1 6 ) 1, . 5 1 8 ( 6 ) P ( 4 ) C ( 4 1 ) 1, . 8 5 4 ( 4 ) C U 7 ) C ( 2 1 ) 1, . 5 3 5 ( 6 ) P<4) C ( 4 7 ) 1, . 8 5 0 ( 5 ) C (17 ) C ( 2 2 ) 1. .498(7 ) P<4) C I 4 8 ) 1. . 8 5 6 ( 5 ) C U B ) C ( 2 3 ) 1, . 5 4 0 ( 6 ) C U B ) C{24) 1. . 4 9 9 ( 6 ) C ( 4 6 ) C ( 5 2 C ) 1, . 6 1 ( 2 ) C I 1 9 I C( 25) 1. . 5 2 4 ( 6 ) C(47 ) CCS?) 1. . 5 0 8 ( 7 ) C d 9 ) C ( 2 6 ) 1. . 5 4 0 ( 6 ) C(47 ) C ( 5 4 ) 1, . 5 2 8 ( 7 ) C ( 2 0 ) C U 7 ) 1. . 5 1 9 ( 6 ) C ( 4 8 ) C ( 5 5 ) 1. . 5 2 0 ( 7 ) C ( 2 0 ) C U 8 ) 1. . 5 4 1 ( 6 ) C(37 ) C(38 ) 1 . 3 5 8 ( 9 ) C ( 2 9 ) C ( 3 0 ) 1. . 4 6 7 ( 6 ) C(40 ) C ( 4 1 ) 1 . 5 1 6 ( 6 ) C ( 2 9 ) C ( 3 4 ) 1 . 4 0 1 ( 7 ) C(40 ) C ( 4 4 ) 1 . 5 2 3 ( 5 ) C ( 2 9 ) C(38 ) 1 . 3 9 4 ( 7 ) C ( 4 1 ) C ( 4 2 ) 1, . 5 4 0 ( 6 ) C ( 3 0 ) C ( 3 1 ) 1 . 3 9 6 ( 7 ) C(42 ) C ( 4 3 ) 1. . 5 5 2 ( 7 ) C(31 ) C U 2 ) , 1 . 3 7 9 ( 8 ) C(43 ) C ( 4 4 ) 1. . 5 2 7 ( 7 ) C<32) C(33 ) 1 . 4 3 4 ( 7 ) C(45 ) C ( 4 9 ) 1. . 4 6 ( 1 ) C(33 ) C(34 ) 1 . 4 4 0 ( 7 ) C ( 4 5 ) C ( 5 0 ) 1. . 4 7 6 ( 9 ) C ( 3 4 ) C l 35 ) 1 . 3 7 8 ( 7 ) C(46 ) C ( 5 1 ) 1. 4 2 ( 1 ) C ( 3 5 ) C l 36) 1 . 4 1 ( 1 ) C(46) C ( 5 2 B ) 1. 5 0 ( 1 ) C(36 ) C U 7 ) 1 . 3 7 ( 1 ) C(46 ) C(52A) 1. 39 (1 ) Appendix Crystallographic Analyses 189 Table XXIH. (Ti4-2-methoxynaphthalene)Co(H)(dippcyp) (11); bond angles (deg) with estimated standard deviations. atom atom atom a n g l e a tom atom atom a n g l e P<1> C o l l ) P ( 2 ) 9 1 . 8 8 ( 5 ) P O ) C o ( 2 ) H(2 ) 7 6 ( 1 ) P U ) C o l l ) C ( 2 ) 1 1 2 . 7 ( 1 ) P ( 4 ) Cot<2) C ( 3 0 ) 1 0 8 . 1 ( 1 ) P U ) C o l l ) C O ) 1 0 2 . 8 ( 1 ) P ( 4 ) C o ( 2 ) C ( 3 1 ) 1 4 6 . 7 ( 2 ) P U ) C o l l ) C ( 4 ) 1 2 1 . 1 ( 1 ) P ( 4 ) C o ( 2 ) C ( 3 2 ) 1 4 4 . 6 ( 2 ) P U ) C o l l i C I S ) 1 5 7 . 6 ( 1 ) P ( 4 ) C o ( 2 ) C ( 3 3 ) 1 0 3 . 9 ( 1 ) P U ) C o l 1) H I D 77 (1 ) P ( 4 ) C o ( 2 ) H ( 2 ) 8 6 ( 1 ) P ( 2 ) C o l l ) C I 2 ) 1 0 8 . 2 ( 1 ) C ( 3 0 ) C o ( 2 ) C ( 3 1 ) 3 6 . 7 ( 2 ) P ( 2 ) C o l l ) C O ) 1 4 7 . 3 ( 1 ) C O O ) C o ( 2 ) C ( 3 2 ) 6 9 . 5 ( 2 ) P ( 2 ) C o l 1) C ( 4 ) 1 4 5 . 6 ( 1 ) C O O ) C o ( 2 ) C ( 3 3 ) 7 6 . 2 ( 2 ) P ( 2 ) C o l l ) C ( 5 ) 1 0 5 . 0 ( 1 ) C O O ) C o ( 2 ) H(2 ) 163 (2 ) P ( 2 ) C o l l ) H I D 87 (2 ) C O D . C o ( 2 ) C ( 3 2 ) 4 0 . 4 ( 2 ) C ( 2 ) C o l l ) C O ) 3 9 . 1 ( 2 ) C O D Cot 2) C ( 3 3 ) 7 0 . 5 ( 2 ) C ( 2 ) C o l l ) C ( 4 ) 6 9 . 9 ( 2 ) C O D C o ( 2 ) H(2 ) 126(2 ) C ( 2 ) Co (1) CI 5) 7 6 . 3 ( 2 ) C ( 3 2 ) C o ( 2 ) C ( 3 3 ) 4 0 . 9 ( 2 ) C ( 2 ) C o d ) H I D 161(1 ) C ( 3 2 ) C o ( 2 ) H(2) 93 (2 ) C ( 3 ) C o l l ) C ( 4 ) 4 0 . 7 ( 2 ) C ( 3 3 ) C o ( 2 ) H(2 ) 91 (1 ) C ( 3 ) C o l l ) C I S ) 7 0 . 6 ( 2 ) C o d ) P d ) C I 1 2 ) 1 0 4 . 6 ( 1 ) C ( 3 ) C o l 1) H I D 125(2 ) C o d ) P d ) C ( 1 7 ) 1 1 8 . 9 ( 1 ) C ( 4 ) C o l l ) C ( 5 ) 4 0 . 6 ( 2 ) C o ( l ) P d ) C ( 1 8 ) 1 1 8 . 8 ( 1 ) C I O C o l l ) H I D 92 (1 ) C ( 1 2 ) P d ) C ( 1 7 ) 1 0 6 . 6 ( 2 ) C ( 5 ) C o l l ) H I D 90 (1 ) C ( 1 2 ) P d ) C d B ) 1 0 2 . 5 ( 2 ) P (3 ) C o l 2) P(4 ) 9 1 . 8 5 ( 5 ) C ( 1 7 ) P d ) C ( 1 8 ) 1 0 2 . 1 ( 2 ) P I 3 ) C o l 2) C O O ) 1 1 3 . 1 ( 1 ) C o d ) P ( 2 ) C ( 1 3 ) 1 0 5 . 8 ( 1 ) P ( 3 ) C o l 2) C O D 1 0 4 . 0 ( 1 ) C o d ) P ( 2 ) C ( 1 9 ) 1 1 6 . 6 ( 1 ) P (3 ) C o l 2) C I 3 2 ) 1 2 2 . 0 ( 2 ) C o d ) P ( 2 ) C I 2 0 ) 1 2 1 . 9 ( 1 ) P (3 ) C o l 2) C I 3 3 ) 1 5 8 . 5 ( 1 ) C ( 1 3 ) P ( 2 ) C ( 1 9 ) 1 0 4 . 9 ( 2 ) C O O ) C ( 2 9 ) C O O 1 1 5 . 6 ( 5 ) P O ) C ( 4 0 ) C I 4 1 ) 1 1 1 . 2 ( 3 ) C O O ) C ( 2 9 ) C O B ) 1 2 4 . 3 ( 6 ) P O ) C ( 4 0 ) C ( 4 4 ) 1 2 5 . 1 ( 3 ) C ( 3 4 ) C I 2 9 ) C O B ) 1 2 0 . 1 ( 5 ) C ( 4 1 ) C ( 4 0 ) C ( 4 4 ) 1 0 3 . 1 ( 3 ) C o ( 2 ) C O O ) C I 2 9 ) 1 0 2 . 8 ( 3 ) P ( 4 ) C ( 4 1 ) C ( 4 0 ) 1 1 0 . 3 ( 3 ) C o ( 2 ) C ( 3 0 ) C O D 6 4 . 3 ( 3 ) P (4 ) C ( 4 1 ) C ( 4 2 ) 1 2 5 . 2 ( 3 ) C I 2 9 ) C O O ) C O D 1 1 8 . 7 ( 5 ) C ( 4 0 ) C ( 4 1 ) C ( 4 2 ) 1 0 4 . 4 ( 3 ) C o ( 2 ) C I 3 1 ) C O O ) 7 7 . 0 ( 3 ) C ( 4 1 ) C ( 4 2 ) C ( 4 3 ) 1 0 4 . 5 ( 4 ) C o ( 2 ) C O D C I 3 2 ) 6 8 . 5 ( 3 ) C ( 4 2 ) C ( 4 3 ) C ( 4 4 ) 1 0 6 . 8 ( 4 ) C O O ) C O D C ( 3 2 ) 1 1 7 . 6 ( 5 ) C ( 4 0 ) C ( 4 4 ) C ( 4 3 ) 1 0 3 . 3 ( 4 ) C o ( 2 ) C ( 3 2 ) C O D 7 1 . 1 ( 3 ) P ( 3 ) C(4S> C I 4 9 ) 1 1 4 . 0 ( 4 ) C o ( 2 ) C I 3 2 ) C ( 3 3 ) 7 4 . 3 ( 3 ) P O ) C I 4 5 ) C ( 5 0 ) 1 1 0 . 7 ( 5 ) C O D C I 3 2 ) C ( 3 3 ) 1 1 5 . 5 ( 5 ) C ( 4 9 ) C I 4 5 ) C ( 5 0 ) 1 0 7 . 7 ( 7 ) C o ( 2 ) C ( 3 3 ) C I 3 2 ) 6 4 . 8 ( 3 ) P O ) C I 4 6 ) C ( 5 1 ) 1 1 4 . 3 ( 5 ) C o ( 2 ) C ( 3 3 ) C O O 1 0 6 . 2 ( 3 ) P ( 3 ) C I 4 6 ) CI52B) 1 0 9 . 9 ( 6 ) Appendix Crystallographic Analyses 190 atom e t o n atom a n g l e C ( 1 3 ) P ( 2 ) C d O ) 104 5(2) C ( 1 9 ) P d ) C ( 2 0 ) 101 5 (2 ) C o ( 2 ) P ( 3 ) C ( 4 0 ) 103 7 ( 1 ) C o ( 2 ) P ( 3 ) C ( 4 5 ) 119 1 (2 ) C o ( 2 ) P ( 3 ) C ( 4 6 ) 122 7 ( 2 ) C<40) P ( 3 ) C ( 4 5 ) 102 4 (2 ) C<40) P ( 3 ) C ( 4 6 ) 104 8 (2 ) C ( 4 5 ) P (3 ) C ( 4 6 ) 101 6 ( 3 ) C o ( 2 ) P ( 4 ) C ( 4 1 ) 105 4(1) C o ( 2 ) P ( 4 ) C147) 120 6 (2 ) C o ( 2 ) P ( 4 ) C ( 4 8 ) 118 3(2) C ( 4 1 ) P (4 ) C ( 4 7 ) 103 8 (2 ) C ( 4 1 ) P ( 4 ) C ( 4 8 ) 105 3(2) C ( 4 7 ) P ( 4 ) C ( 4 8 ) 101 7 (2 ) C(8 ) O d A ) C d l ) 114 . 9 ( 6 ) C ( 3 7 ) 0 ( 2 A ) C ( 3 9 A ) 128 (1 ) C ( 3 6 ) 0 ( 2 B ) C ( 3 9 B ) 119 (2 ) C ( 2 ) C d ) C ( 6 ) 114 . 6 ( 4 ) C ( 2 ) C d ) C d O ) 126 . 4 ( 5 ) C ( 6 ) C d ) C d O ) 119 . 0 ( 4 ) C O ( l ) C d ) C d ) 104 . 0 ( 3 ) C o ( l ) C d ) C ( 3 ) 6 4 . 2(2) C d ) C d ) C ( 3 ) 119 . 7 ( 4 ) C o d ) C ( 3 ) C ( 2 ) 7 6 . 7(2) C o d ) C ( 3 ) C ( 4 ) 6 8 . 3(2) C d ) C ( 3 ) C ( 4 ) 117 . 1 ( 4 ) P d ) C d 7 ) C ( 2 1 ) 117 . 0 ( 3 ) P d ) C d 7 ) C ( 2 2 ) 112 . 4 ( 3 ) C ( 2 1 ) C d 7 ) C ( 2 2 ) 110 . 4 ( 4 ) P d ) C d 8 ) C ( 2 3 ) 109 . 8 ( 3 ) P d ) C d 8 ) C ( 2 4 ) 114 . 2 ( 3 ) C ( 2 3 ) C d 8 ) C ( 2 4 ) 109 - 2 ( 4 ) P d ) C d 9 ) C ( 2 5 ) 110 . 5 ( 3 ) P d ) C d 9 ) C d 6 ) 112 . 6 ( 3 ) C ( 2 5 ) C d 9 ) C ( 2 6 ) 110 . 3 ( 4 ) P d ) C ( 2 0 ) C ( 2 7 ) 111 . 1 ( 3 ) P d ) C ( 2 0 ) C ( 2 8 ) 115 . 0 ( 3 ) C ( 2 7 ) C ( 2 0 ) C ( 2 8 ) 109 . 0 ( 4 ) P ( 3 ) C ( 4 6 ) C ( 5 2 A ) 124 . 4 ( 7 ) P ( 3 ) C ( 4 6 ) C ( 5 2 C ) 117 . 0 ( 8 ) C ( 5 1 ) C ( 4 6 ) C ( 5 2 B ) 112 . 6 ( 7 ) C ( 5 1 ) C ( 4 6 ) C ( 5 2 A ) 109 . 8 ( 8 ) C ( 5 2 A ) C ( 4 6 ) C ( 5 2 C ) 112 (1 ) P ( 4 ) C ( 4 7 ) C<53) 111 . 4 ( 3 ) atom atom atom a n g l e C o d ) C ( 4 ) C ( 3 ) 7 0 . 5 ( 2 ) C o d ) C ( 4 ) . C ( 5 ) 7 4 . 3 ( 2 ) C ( 3 ) C ( 4 ) C ( 5 ) 115 4 (4 ) C o d ) C ( S ) C ( 4 ) 6 5 . 1 ( 2 ) C o d ) C ( 5 ) C ( 6 ) 104 7 (3 ) C ( 4 ) C ( 5 ) C ( 6 ) 119 3 (4) C d ) C ( 6 ) C ( 5 ) 115 6 (4 ) C d ) C ( 6 ) C ( 7 ) 118 8 (4 ) C ( 5 ) C ( 6 ) C ( 7 ) 125 5(4) C ( 6 ) C ( 7 ) C ( 8 ) 119 1 (5 ) 0 ( 1 A ) C ( 8 ) C ( 7 ) 115 9 (6 ) O ( I A ) C ( 8 ) C ( 9 ) 123 1(6) C ( 7 ) C ( 8 ) C ( 9 ) 120 9 (5 ) O ( I B ) C ( 9 ) C ( 8 ) 9 7 ( 1 ) O ( I B ) C ( 9 ) C d O ) 143(1 ) C ( 8 ) C ( 9 ) C d O ) 119 7 ( 5 ) C d ) C d O ) C ( 9 ) 122 3(5) P d ) C ( 1 2 ) C ( 1 3 ) 111 1 (3 ) P d ) C ( 1 2 ) C ( 1 6 ) 127 3(3) C ( 1 3 ) C ( 1 2 ) C ( 1 6 ) 102 9 (3 ) P ( 2 ) C ( 1 3 ) . C ( 1 2 ) 111 1(2) P ( 2 ) C ( 1 3 ) C ( 1 4 ) 125 3(3) C ( 1 2 ) C ( 1 3 ) C ( 1 4 ) 103 8 (3 ) C ( 1 3 ) C(14 ) C ( 1 5 ) 105 4(3) C ( 1 4 ) C ( 1 5 ) C ( 1 6 ) 106 1(3) C ( 1 2 ) C ( 1 6 ) C ( 1 5 ) 102 8 (3 ) C ( 3 2 ) C ( 3 3 ) C ( 3 4 ) 119 0(5) C ( 2 9 ) C ( J 4 ) C ( 3 3 ) 115 0(4) C ( 2 9 ) C ( 3 4 ) C ( 3 5 ) lie 3(6) C ( 3 3 ) C ( 3 4 ) C ( 3 5 ) 126 7 (6 ) C ( 3 4 ) C ( 3 5 ) C ( 3 6 ) lie 9(7 ) 0 ( 2 B ) C ( 3 6 ) C O S ) 121 (1 ) 0 ( 2 B ) C ( 3 6 ) C ( 3 7 ) 116 (1 ) C ( 3 5 ) C ( 3 6 ) C ( 3 7 ) 123 . 4 ( 7 ) 0 ( 2 A ) C ( 3 7 ) C ( 3 6 ) 119 . 3 ( 9 ) 0 ( 2 A ) C ( 3 7 ) C ( 3 B ) 124 d ) C ( 3 6 ) - C ( 3 7 ) C ( 3 8 ) 116 . 5 ( 8 ) C ( 2 9 ) C ( 3 8 ) C ( 3 7 ) 122 8 (7 ) P ( 4 ) C ( 4 7 ) C ( 5 4 ) 1 1 5 . 9 ( 4 ) C ( 5 3 ) C ( 4 7 ) C ( 5 4 ) 109 5 (4 ) P ( 4 ) C ( 4 8 ) C ( 5 5 ) 113 6 ( 3 ) P ( 4 ) C ( 4 8 ) C ( 5 6 ) 111 2 (3 ) C ( 5 5 ) C ( 4 B ) C ( 5 6 ) 109 7 (5 ) Appendix Crystallographic Analyses 191 Table A-XXIV. Final atomic coordinates (fractional) and B e q for (TJ4-2-methoxynaphthalene)Co(H)(dippcyp) (11) a t o m X y z B ( e q ) C o ( l ) 0 . 3 1 5 7 8 ( 3 ) 0 . 2 2 6 8 8 ( 3 ) 0 . 5 7 9 3 5 ( 6 ) 3 . 3 2 ( 2 ) C o ( 2 ) 0 . 7 3 3 3 5 ( 3 ) 0 . 2 7 3 6 7 ( 3 ) 0 . 3 4 5 9 1 ( 7 ) 4 . 2 0 ( 2 ) P d ) 0 . 3 6 4 3 3 ( 6 ) 0 . 3 4 5 1 9 ( 6 ) 0 . 7 0 1 4 ( 1 ) 3 . 5 5 ( 3 ) P ( 2 ) 0 . 2 8 2 2 5 ( 6 ) 0 . 2 5 8 8 4 ( 6 ) 0 . 3 5 8 4 ( 1 ) 3 . 3 9 ( 3 ) P ( 3 ) 0 . 6 7 9 7 4 ( 6 ) 0 . 1 5 5 4 4 ( 6 ) 0 . 2 2 6 6 ( 1 ) 4 . 3 5 ( 4 ) P ( 4 ) 0 . 8 4 4 2 0 ( 6 ) 0 . 2 4 6 9 6 ( 6 ) 0 . 4 2 7 7 ( 1 ) 4 . 0 3 ( 4 ) O d A ) 0 . 0 9 0 8 ( 3 ) - 0 . 0 6 9 3 ( 3 ) 0 . 1 3 7 3 ( 6 ) 7 . 9 ( 2 ) O d B ) 0 . 0 0 7 ( 1 ) - 0 . 0 1 6 ( 1 ) 0 . 2 3 4 ( 2 ) 8 . 7 ( 4 ) 0 ( 2 A ) 0 . 8 5 8 7 ( 4 ) 0 . 4 7 9 5 ( 5 ) 1 . 0 3 2 3 ( 8 ) 1 2 . 3 ( 4 ) 0 ( 2 B ) 0 . 9 2 3 ( 1 ) 0 . 5 5 7 ( 1 ) 0 . 8 6 4 ( 2 ) 1 3 . 3 ( 4 ) C d ) 0 . 1 7 4 3 ( 2 ) 0 . 1 0 9 8 ( 2 ) 0 . 5 1 4 4 ( 5 ) 4 . 6 ( 2 ) C ( 2 ) 0 . 2 1 1 4 ( 2 ) 0 . 1 7 6 3 ( 2 ) 0 . 6 4 0 9 ( 5 ) 4 . 5 ( 2 ) C ( 3 ) 0 . 2 8 1 6 ( 3 ) 0 . 1 7 7 9 ( 2 ) 0 . 7 4 3 9 ( 5 ) 4 . 7 ( 2 ) C ( 4 ) 0 . 3 3 2 8 ( 3 ) 0 . 1 4 2 2 ( 2 ) 0 . 6 8 2 4 ( 5 ) 4 . 8 ( 2 ) C ( 5 ) 0 . 3 0 7 8 ( 2 ) 0 . 1 0 8 7 ( 2 ) 0 . 5 1 9 8 ( 5 ) 4 . 4 ( 2 ) C ( 6 ) 0 . 2 2 5 8 ( 3 ) 0 . 0 7 4 3 ( 2 ) 0 . 4 4 9 2 ( 5 ) 4 . 6 ( 2 ) C ( 7 ) 0 . 1 9 5 6 ( 3 ) 0 . 0 1 1 3 ( 2 ) 0 . 3 2 3 3 ( 6 ) 5 . 8 ( 2 ) C ( 8 ) 0 . 1 1 5 0 ( 4 ) - 0 . 0 1 2 9 ( 3 ) 0 . 2 6 1 8 ( 6 ) 6 . 6 ( 2 ) C ( 9 ) 0 . 0 6 6 7 ( 4 ) 0 . 0 2 1 5 ( 3 ) 0 . 3 2 7 2 ( 7 ) 7 . 5 ( 2 ) C d O ) 0 . 0 9 6 2 ( 3 ) 0 . 0 8 1 7 ( 3 ) 0 . 4 5 2 0 ( 6 ) 6 . 2 ( 2 ) C d l ) 0 . 0 0 4 0 ( 5 ) - 0 . 0 9 5 6 ( 4 ) 0 . 0 7 6 1 ( 9 ) 1 3 . 3 ( 4 ) C ( 1 2 ) 0 . , 3 7 4 0 ( 2 ) 0 . 3 9 6 9 ( 2 ) 0 . 5 4 7 2 ( 5 ) 3 . 8 ( 1 ) C ( 1 3 ) 0 . , 3 0 5 7 ( 2 ) 0 . 3 6 3 7 ( 2 ) 0 . 4 0 3 8 ( 4 ) 3 . 7 ( 1 ) C ( 1 4 ) 0 . , 3 2 2 7 ( 3 ) 0 . 4 1 3 4 ( 2 ) 0 . 2 9 0 8 ( 5 ) 5 . 0 ( 2 ) C d 5 ) 0. . 3 7 8 7 ( 3 ) 0 . . 4 8 9 3 ( 2 ) 0 . , 3 9 3 2 ( 6 ) 5 . 1 ( 2 ) C ( 1 6 ) 0, . 3 8 6 3 ( 2 ) 0 . . 4 8 2 4 ( 2 ) 0 . . 5 6 0 5 ( 5 ) 4 . , 6 ( 2 ) C ( 1 7 ) 0 . 3 1 0 4 ( 3 ) 0. . 3 9 2 7 ( 2 ) 0. . 8 2 8 7 ( 5 ) 5. . 0 ( 2 ) C ( 1 8 ) 0 . 4 6 4 1 ( 2 ) 0. . 3 7 2 5 ( 2 ) 0. . 8 2 8 1 ( 5 ) 4 . . 7 ( 2 ) C ( 1 9 ) 0 . 3 3 5 6 ( 3 ) 0 . 2 3 1 9 ( 2 ) 0, . 2 0 9 5 ( 5 ) 4 , . 5 ( 2 ) C ( 2 0 ) 0 . 1 8 0 9 ( 2 ) 0 . 2 3 0 0 ( 3 ) 0, . 2 3 9 7 ( 5 ) 4 , . 8 ( 2 ) C ( 2 1 ) 0 . 3 5 0 5 ( 3 ) 0 . 4 7 3 8 ( 3 ) 0 . 9 2 4 8 ( 6 ) 6 . 3 ( 2 ) Appendix Crystallographic Analyses 192 C(22) 0. .2298(3) 0. .3897(3) 0, .7428(7) 7. .2(2) C(23) 0. .4650(3) 0. .3425(3) 0. .9772(6) 6, .5(2) C(24) 0. .5225(2) 0. .3452(3) 0, .7519(6) 5, .8(2) C(25) 0. .3108(4) 0. .1462(3) 0. .1410(6) 7, .1(2) C(26) 0. .4239(3) 0. .2574(3) 0 .2744(6) 6 .1(2) C(27) 0. .1271(2) 0, .2589(3) 0, .3309(6) 6 .2(2) C(28) 0, .1680(3) 0, .2546(4) 0 .0835(6) 7 .8(2) C(29) 0. .7515(3) 0, .3781(3) 0 .6368(6) 6 .0(2) C(30) 0, .6907(3) 0, .3106(3) 0 .5475(7) 5 .9(2) C(31) 0 .6458(3) 0, .3140(3) 0 .4046(7) 6 .3(2) C(32) 0 .6810(3) 0 .3569(3) 0 .3164(7) 6 .6(2) C(33) 0 .7612(3) 0 .3936(3) 0 .3830(6) 5 .8(2) C(34) 0 .7877(3) 0 .4224(3) 0 .5487(7) 6 .2(2) C(35) 0 .8456(3) 0 .4863(3) 0 .6263(8) 8 .2(3) C(36) 0 .8674(4) 0 .5033(4) 0 .790(1) 10 .5(4) C(37) 0 .8331(4) 0 .4601(5) 0 .878(1) 9 .7(4) C(38) 0 .7744(3) 0 .3989(4) 0 .7987(8) 8 .0(3) C(39A) 0 .920(1) 0 .527(1) 1 .113(2) 14 .1(8) C(39B) 0 .947(2) 0 .571(2) 1 .040(4) 12 .7(9) C(40) 0 .7625(2) 0 .1132(2) 0 .2134(5) 4 .8(2) C(41) 0 .8264(2) 0 .1420(2) 0 .3620(5) 4 .7(2) C(42) 0 .8883(3) 0 .0985(3) 0 .3343(6) 6 .1(2) C(43) 0 .8429(3) 0 .0247(3) 0 .2109(6) 6 • 3(2) C(44) 0 .7582(3) 0 .0280(2) 0 .1737(6) 6 .1(2) C(45) 0 .6240(3) 0 .1335(3) 0 .0193(6) 6 .6(2) C(46) 0 .6169(3) 0 .0892(3) 0 .3085(7) 7 .0(2) C(47) 0 .8899(3) 0 .2658(3) 0 .6381(5) 5 .6(2) C(48) 0 .9266(2) 0 .2873(3) 0 .3516(6) 5 .5(2) C(49) 0 .6711(5) 0 .1520(7) -0 .0877(8) 16 .4(6) C(50) 0 .5625(6) 0 .1753(5) 0 .001(1) 16 .5(5) C(51) 0 .6503(5) 0 .0856(5) 0 .463(1) 8 .0(4) C(52A) 0 .5712(8) 0 .0176(7) 0 .226(1) 8 .1(5) C(52B) 0 .5392(6) 0 .1070(7) 0 .291(2) 8 .0(6) C(52C) 0 .579(1) 0 .127(1) 0 .440(3) 8 .1(5) Appendix Crystallographic Analyses 193 C(53) 0.8372(3) 0.2249(3) 0.7219(6) 7.2(2) C(54) 0.9695(3) 0.2491(4) 0.6813(7) 8.6(3) C(55) 0.9079(3) 0.2726(4) 0.1753(6) 7.5(3) C(56) 0.9577(3) 0.3728(3) 0.4215(8) 8.5(3) H ( l ) 0.389(2) 0.241(2) 0.562(4) 4.9(9) H(2) 0.751(2) 0.267(2) 0.206(4) 4.9(9) a t o m X y z B ( i s o ) H(3) 0.1876 0.2197 0.6545 5.4 H(4) 0.2938 0.2031 0.8542 5.6 H(5) 0.3825 0.1403 0.7463 5.7 H(6) 0.3453 0.1086 0.4562 5.3 H(7) 0.2302 -0.0156 0.2784 6.9 H(8) 0.0107 0.0032 0.2851 9.0 H(9) 0.0605 0.1058 0.4989 7.4 H(10) -0.0167 -0.0531 0.0478 16.0 H ( l l ) -0.0088 -0.1376 -0.0158 16.0 H(12) -0.0188 -0.1132 0.1566 16.0 H(13) 0.4185 0.3843 0.5130 4.6 H(14) 0.2612 0.3773 0.4363 4.5 H(15) 0.3474 0.3886 0.2163 6.0 H(16) 0.2750 0.4233 0.2345 6.0 H(17) 0.4292 0.4957 0.3690 6.1 H(18) 0.3572 0.5329 0.3755 6.1 H(19) 0.3468 0.5018 0.6030 5.5 H(20) 0.4376 0.5098 0.6258 5.5 H(21) 0.3044 0.3615 0.9050 6.1 H(22) 0.4800 0.4284 0.8583 5.6 H(23) 0.3217 0.2576 0.1251 5.4 H(24) 0.1654 0.1741 0.2158 5.8 H(25) 0.4032 0.4749 0.9800 7.5 H(26) 0.3525 0.5093 0.8556 7.5 H(27) 0.3215 0.4889 1.0003 7.5 Appendix Crystallographic Analyses 194 H(28) •0.2003 0.4046 0.8174 8.6 H(29) 0.2315 0.4248 0.6726 8.6 H(30) 0.2048 . 0.3377 0.6824 8.6 H(31) 0.4265 0.3596 1.0267 7 .7 H(32) 0.4527 0.2866 0.9509 7 .7 H(33) 0.5163 0.3621 1.0489 7.7 H(34) 0.5097 0.2893 0.7260 6.9 H(35) 0.5220 0. 3641. 0.6567 6.9 H(36) 0.5740 0.3645 0.8232 6.9 H(37) 0.2545 0.1307 0.1008 8.5 H(38) 0.3354 0.1337 0.0563 8.5 H(39) 0.3265 0.1191 0.2220 8.5 H(40) 0.4398 0.2305 0.3555 7.3 H(41) 0.4491 0.2455 0.1903 7.3 H(42) 0.4390 0.3125 0.3185 7.3 H(43) 0.1383 0.3147 0.3502 7.4 H( 44 ) 0.0734 0.2373 0.2711 7.4 H(45) 0.1348 0.2433 0.4303 7.4 H(46) 0.1794 0.3104 0.1029 9.4 H(47) 0.2024 0.2359 0.0237 9.4 H(48) 0.1142 0.2331 0.0245 9.4 H(49) 0.6818 0.2641 0.5873 7.1 H(50) 0.5911 0.2868 0.3683 7.6 H(51) 0.6532 0.3620 0.2150 7 .9 H(52) 0.797 3 0.3989 0.3168 7.0 H(53) 0.8712 0.5194 0.5685 9.8 H(54) 0.9093 0.5483 0.8442 12.6 H(55) 0.7471 0.3681 0.8579 9.6 H(56) 0.9648 0.5104 1.0858 16.9 H(57) 0.9201 0.5772 1.0910 16.9 H(58) 0.9236 0.5293 1.2231 16.9 H(59) 0.7840 0.1337 0.1340 5.8 H(60) 0.8049 0.1211 0.4409 5.6 H(61) 0.9273 0.1287 0.2949 7.4 H(62) 0.9134 0.0862 0.4305 7.4 Appendix Crystallographic Analyses 195 H(63) 0.8621 0.0224 0.1169 7.6 H(64) 0.8486 -0 .0203 0.2525 7.6 H(65) 0.7302 0.0013 0.2379 7.3 H(66) 0.7330 0.0057 0.0637 7.3 H(67) 0.5995 0.0788 -0 .0121 8.0 H(68) 0.8969 0.3205 0.6792 6.7 H(69) 0.9682 0.2625 0.3846 6.6 H(70) 0.7124 0.1249 -0 .0784 19.7 H(71) 0.6387 0.1366 -0 .1944 19.7 H(72) 0.6938 0.2072 -0 .0620 19.7 H(73) 0.5858 0.2303 0.0255 19.7 H(74) 0.5307 0.1594 -0 .1060 19.7 H(75) 0.5300 0.1641 0.0724 19.7 H(76) 0.6093 0.0696 0.5135 9.6 H(77) 0.6825 0.0487 0.4605 9.6 H(78) 0.6822 0.1360 0.5204 9.6 H(79) 0.5455 0.1606 0.3411 9.6 H(80) 0.5138 0.0981 0.1803 9.6 H(81) 0.5074 0.0741 0.3401 9.6 H(82) 0.5352 -0 .0018 0.2846 9.7 H(83) 0.5420 0.0220 0.1249 9.7 H(84) 0.6042 -0 .0177 0.2093 9.7 H(85) 0.8589 0.2428 0.8344 8.6 H(86) 0.7861 0.2356 0.6940 8.6 H(87) 0.8323 0.1699 0.6919 8.6 H(88) 0.9647 0.1941 0.6506 10.3 H(89) 1.0038 0.2759 0.6273 10.3 H(90) 0.9912 0.2666 0.7938 10.3 H(91) 0.8687 0.2994 0.1386 9.0 H(92) 0.9548 0.2912 0.1426 9.0 H(93) 0.8881 0.2177 0.1310 9.0 H(94) 0.9701 0.3820 0.5351 10.2 H(95) 1.0045 0.3915 0.3884 10.2 H(96) 0.9185 0.3999 0.3858 10.2 Appendix Crystallographic Analyses 196 References: 1. TEXSAN/TEXRAY structure analysis package which includes versions of the following: DIRDIF, direct methods for difference structures, by P.T. Beurskens; ORFLS, full-matrix least-squares, and ORFFE, function and errors, by W.R. Busing, K.O. Martin, and H.A. Levy; ORTEP n, illustrations, by CK. Johnson. 2. International Tables for X-Ray Crystallography ; Kynoch Press: Birmingham, U.K. (present distributor Kluwer Academic Publishers: Dordrecht, The Netherlands), 1974; Vol. IV. pp. 99-102 and 149. Publications 1. Fryzuk, M. D.; Ng, J. B.; Christensen, N. J.; Rettig, S. J.; Huffman, J. C; Jonas, K. "On the nature of the catalytically inactive cobalt hydride formed upon hydrogenation of aromatic substrates." Inorg. Chem. submitted. 2. Ng, J. B.; Shurvell, H. F.; Petelenz, B. U. "The complementary use of factor analysis and spectral deconvolution in a study of the CD3COOD-D2O system." Can. J. Chem. 1988, 66, 1912. 3. Ng, J. B.; Shurvell, H. F. "Application of factor analysis and band contour resolution techniques to the Raman spectra of acetic acid in aqueous solution" /. Phys. Chem. 1987, 91, 496. 4. Ng, J. B.; Shurvell, H. F. "A study of the self-association of acetic acid in aqueous solution using Raman spectroscopy." Can. J. Spectrosc. 1985,30, 149. 

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