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Trivalent group 13 metal complexes of N-substituted-3-hydroxy-2-methyl-4-pyridinones Simpson, Linda 1990

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TRJVALENT GROUP 13 METAL COMPLEXES OF N-SUBSTTTUTED-3-HYDROXY-2-METHYL-4-PYRTDINONES by LINDA SIMPSON B.Sc. (Honours), McMaster University, Hamilton, Ontario, Canada -1988 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Chemistry) We accept this thesis as conforming to the required standard The University of British Columbia August 1990 © Linda Simpson, 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. The University of British Columbia Vancouver, Canada DE-6 (2/88) ii ABSTRACT The compounds tris(N-n-propyl-3-hydroxy-2-methyl-4-pyridinonato) aluminum(III), -gallium(III), and -indium(III) and tris(N-/i-butyl-3-hydroxy-2-methyl-4-pyridinonato)aluminum(ni), -gallium(III), and -indium(III) were synthesized. All six compounds were prepared via the metal template effect. They were characterized by IR, FAB-MS, *H NMR, 2 7 Al NMR, and elemental analysis. Three of the six complexes were studied by single-crystal X-ray diffraction. They formed trihydrates, unlike their N-methyl and N-ethyl analogues, which formed dodecahydrates. The n-butyl complex Al(CioHi4N02)3-3H20 (1) and -^propyl complexes Al(C9Hi2N02)3-3H20 [2], and Ga(C9Hi2N02)3-3H20 {3} were basically isostructural, crystallizing in the space group P3 with the following crystal parameters for 1, [2], and {3}: a = 15.885 (1) ([15.328 (1)], {15.367 (2)}) A, c = 7.280 (8) ([7.2321 (2)], {7.256 (2)}) A, Z = 2. The data were refined by using 1280 ([1377], {1802}) reflections with I>3a(I) to/? and Rw values of 0.047 ([0.057], {0.055)) and 0.061 ([0.077], {0.081}), respectively. The complexes exist as the rigidly fac geometries with infinite chains of hydrogen bonds parallel to the c axis. iii TABLE OF CONTENTS page Abstract ii Table of Contents iii List of Tables.. iv List of Figures vi List of Abbreviations vii Acknowledgements xi Chapter 1. General Introduction 1 Chapter 2. Experimental 6 2.1 Complex Preparation and Characterization 6 2.1.1 M(npp)3 7 2.1.2 M(nbp)3 7 2.1.3 Infrared Spectroscopy 8 2.1.4 Mass Spectrometry 10 2.1.5 Proton NMR 11 2.1.6 Aluminum-27 NMR 13 2.1.7 Elemental Analysis 14 2.2 X-ray Crystallographic Analysis 15 2.2.1. Choosing a Crystal 15 2.2.2. The Orientation Matrix 15 2.2.3. The Lattice Type, Laue Group, and Crystal System 16 2.2.4. Collecting Data 16 2.2.5. Solution of the Structure 16 Chapter 3. Results and Discussion 24 References 55 Appendix ; 58 iv LIST OF TABLES page Table 2.1.3. Characteristic infrared absorptions 9 Table 2.1.4. Data from FAB-MS spectra of the tris-ligand metal complexes 10 Table 2.1.5. *H NMR data for the tris-ligand metal complexes 11 Table 2.1.6. 2 7 A l NMR data for the tris-ligand metal complexes 13 Table 2.1.7. Elemental analyses of the tris-ligand metal complexes 14 Table 2.2.1. Crystallographic data for the tris-ligand metal complexes 18 Table 2.2.2. Atomic positional and equivalent isotropic thermal parameters 19 Table 2.2.3. Selected bond lengths for the tris-ligand metal complexes 22 Table 2.2.4. Selected bond angles for the tris-ligand metal complexes 23 Table 3.1. Boiling points of some common amines 25 Table 3.2. The pKa's and pKb's of some common amines 26 Table 3.3. M-0 bond lengths for the tris-ligand metal complexes 33 Table 3.4. O-M-O bond angles for the tris-ligand metal complexes 33 Table 3.5. O-C-C bond angles for the tris-ligand metal complexes 35 Table 3.6. C-0 bond lengths for the tris-ligand metal complexes 37 Table 3.7. Ring bond lengths for the tris-ligand metal complexes 38 Table 3.8. Ring bond angles for the tris-ligand metal complexes 38 Table 3.9. N-C bond lengths for the tris-ligand metal complexes 39 Table 3.10. C-N-C bond angles for the tris-ligand metal complexes 39 Table 3.11. Unit cell dimensions for the tris-ligand metal complexes 45 Table 3.12. Hydrogen bonding distances and angles for the tris-ligand metal complexes 48 Table A.l . Crystallographic data for the M(dpp)3 complexes 58 Table A.2. Crystallographic data for the M(mepp)3 complexes 59 Table A.3. Bonding parameters for the M(dpp)3 complexes 60 V LIST OF TABLES CONTD Table A.4. Bonding parameters for the M(mepp)3 complexes 61 Table A.5. Hydrogen bonding parameters for the M(dpp)3 complexes 62 Table A.6. Hydrogen bonding parameters for In(dpp)3 62 Table A.7. Hydrogen bonding parameters for the M(mepp)3 complexes 63 vi LIST OF FIGURES page Figure 1.1. Tris(3-hydroxy-4-pyridinonato)metal(III) complexes 1 Figure 1.2. ORTEP of the unit cell packing of M(dpp)3-12H20 2 Figure 1.3. ORTEP of the unit cell packing of M(mepp)3-12H20 3 Figure 1.4. Scheme for the tris-ligand metal complex one-pot synthesis 5 Figure 2.1.5. Tris-ligand metal complex labelling for NMR studies 12 Figure 3.1. Tris-ligand metal complexes with five-membered chelate rings 24 Figure 3.2. The IR spectra of crude and pure Ga(npp)3 28 Figure 3.3. ORTEP of the Al(nbp)3-3H20 unit 30 Figure 3.4. ORTEP of the Al(npp)3-3H20 unit 31 Figure 3.5. ORTEP of the Ga(npp)3-3H20 unit 32 Figure 3.6. The catecholate and semiquinone ligands 36 Figure 3.7. ORTEP of the unit cell packing of Al(nbp)3-3H20 41 Figure 3.8. ORTEP of the unit cell packing of Al(nbp)3-3H20 42 Figure 3.9. ORTEP stereoview of the unit cell packing of Al(nbp)3-3H20 43 Figure 3.10. ORTEP of the unit cell packing of M(npp)3-3H20 44 Figure 3.11. ORTEP of the unit cell packing of M(mepp)3-12H20 46 Figure 3.12. ORTEP of the unit cell packing of Al(nbp)3-3H20 47 Figure 3.13. ORTEP of the hydrogen bonding of M(npp)3-3H20 50 Figure 3.14. ORTEP of the hydrogen bonding of M(mepp)3-12H20 52 Figure 3.15. ORTEP of the simplified hydrogen bonding of the exoclathrates and trihydrates 53 vii LIST OF ABBREVIATIONS Abbreviation Meaning 0 degrees a length of the unit cell along the x axis A angstrom 2 7 Al aluminum-27 Al(dpp)3 tris(3-h ydroxy-1,2-dimethyl-4-pyridinonato)aluminum(ni) Al(ma)3 tris(3-hydroxy-2-methyl-4-pyronato)aluminum(III) Al(mepp)3 tris(l-ethyl-3-hydroxy-2-methyl-4-pyridmonato)aluniinum(III) Al(nbp)3 tris(l-«-butyl-3-hydroxy-2-memyl-4-pyridinonato)alurriinum(III) Al(npp)3 tris(3-hydroxy-2-methyl-1 -«-propyl-4-pyridinonato)alurninum(III) c length of the unit cell along the z axis °C degrees Celsius cm"1 wave number 8 chemical shift dec decomposed deg degrees Af' real dispersion correction for atomic scattering factors Af1 imaginary dispersion correction for atomic scattering factors F c calculated structure factor F 0 observed structure factor FAB-MS positive ion fast atom bombardment mass spectrometry g grams Ga(dpp)3 tris(3-hydroxy-1,2-dimemyl-4-pyridinonato)gallium(III) Ga(mepp)3 tris(l-ethyl-3-hydroxy-2-methyl-4-pyridinonato)gallium(III) viii LIST OF ABBREVIATIONS CONT'D Abbreviation Meaning Ga(nbp)3 tris( 1 -n-butyl-3-hydroxy-2-methyl-4-pyri&nonato)galU Ga(npp)3 ms(3-hydroxy-2-methyl-l-«-propyl-4-pyrimnonato)galUum(in^ *H proton Hdpp 3-hydroxy-l,2-cUmethyl-4-pyridinone Hmepp 1 -ethyl-3-hydroxy-2-methyl-4-pyridinone Hz hertz I intensity In(dpp)3 tn^ (3-hya^ oxy-l,2-dimeuhyl-4-pyridinonato)indium(ni) ln(nbp)3 ms(l-n-buryl-3-hydroxy-2-memyl-4-pyridinonato)mdium(III) In(npp)3 tris(3-hydroxy-2-methyl-1 -«-propyl-4-pyridinonato)indium(III) /-propylamine isopropylamine IR infrared Jab NMR coupling constant between hydrogens a and b L ligand X wavelength, nm H-butylamine normal butylamine H-hexylamine normal hexylamine n-propylamine normal propylamine p. absorption coefficient M metal maltol 3-hydroxy-2-methyl-4-pyrone M(dpp)3 tris(3-hydroxy-1,2-dimethyl-4-pyridinonato)metal(III) MHz megahertz mL millilitre ix LIST OF ABBREVIATIONS CONTD Abbreviation Meaning M(ma)3 tris(maltolato)metal(III) M(mepp)3 ms(l-ethyl-3-hydroxy-2-met^  M(mhpp)3 tris(l-hexyl-3-hydroxy-2-methyl-4-pyricUnonato)metal(in^  mmol millirnole M(mpp)3 tris(3-hydroxy-2-memyl-4-pyridinonato)metal(III) M(nbp)3 tris(l -n-butyl-3-hydroxy-2-methyl-4-pyridinonato)metal(III) M(npp)3 tris(3-hydroxy-2-methyl- l-«-propyl-4-pyridinonato)metal(III) M06 metal ion with six oxygen donor atoms Mp melting point nm nanometre, 10"9 m NMR nuclear magnetic resonance NSERC Natural Sciences and Engineering Research Council npp" (3-hydroxy-2-methyl-1 -«-propyl-4-pyridinonato)anion co weighting factor ORTEP Oak Ridge Thermal Ellipsoid Plot Pealed calculated density pKa negative logarithm to the base 10 of the acid dissociation constant pKb negative logarithm to the base 10 of the base dissociation constant pKw negative logarithm to the base 10 of the ionic product constant of water ppm parts per million R agreement factor Rw weighted agreement factor a standard deviation X LIST OF ABBREVIATIONS CONT'D ^utylamine tertiarybutylamine vx.y vibrational stretching mode of x-y bond W\i2 peak width at half peak height Z number of molecules in the unit cell (excluding solvent molecules of crystallization) xi ACKNOWLEDGEMENTS I would like to thank the Chemistry Support staff and the technical staff of the Mass Spectrometry, NMR, and Microanalytical labs here at U.B.C. I would especially like to thank Charla Beaulieu, Liane Darge, Marietta Austria, and Peter Borda for their time. The financial assistance in the form of a Teaching Assistantship is gratefully acknowledged, as are operating grants from the NSERC of Canada. Equipe Orvig, je veux dire merci. Similar sentiments to the analogous Trotter ensemble. A resounding word of thanks to Chris Orvig and Jim Trotter, for taking me on as their graduate student, but especially for making them feel like Casey too often. A special note of gratitude to Steve Rettig and Zaihui Zhang; without their help I may never have finished. Infinite appreciation goes out to my newfound mentors Vivien and Deryn, as well as to Miss Kris for her encouragement. A moose definite thank you to a more than nice guy, Graham. Amongst other things, he took me out to a Chinese restaurant one fateful evening last September. Soon thereafter, my graduate career took a turn for the better. xii To my parents, Theresa and Henry, and to that fortune cookie which read: "There is new hope for projects you had almost given up on." 1 Chapter 1. General Introduction The coordination chemistry of Group 13 metals is of great interest because of their varied biological effects. While aluminum1 has been implicated in the occurrence of certain diseases, radioactive isotopes of gallium2»3 and indium^ have proven useful in the diagnosis of disease. Research in these laboratories has focussed on the development of ligands which will bind effectively to these metals, both in vitro and in .vivo. In the course of this work a series of pyridinonato metal complexes with unexpected and novel crystallographic properties was discovered. TrisG -^substituted-3-hydroxy-2-methyl-4-pyridinonato)ligands, initially chosen for their efficiency in binding group 13 metal ions4*5 {see Figure 1.1.}, were found to crystallize in a manner previously unknown amongst inorganic hydrates.6,7 The methyl M C H 3 3 M = Al, Ga, In R= H M(mpp)3 C H 3 M(dpp)3 C-5H5 M(mepp)3 n-C 6 H 1 3 M(mhpp)3 Figure 1.1. Tris(N-substituted-3-hydroxy-2-methyl-4-pyridinonato)metal(III) Complexes. 2 and ethyl derivatives displayed unusual hydrogen bonding in the solid state.8"10 Single crystal X-ray diffraction revealed that these compounds crystallized as dodecahydrates. The water molecules form hydrogen bonded hexagonal channels, which are in turn joined by other water molecules to the oxygen atoms which chelate the metal atom {see Figures 1.2. and 1.3.}. This extensive network bears a closer resemblance to one of the crystalline forms of ice than to the typical structure of inorganic hydrates. Figure 1.2. ORTEP view of the unit cell packing of M(dpp)3-12H20 (M View is down the c axis.8-9 = Al, Ga, In). Figure 1.3. ORTEP view of the unit cell packing of M(mepp)3-12H20 (M = Al, Ga). View is down the c axis.10 These complexes can be viewed as clathrate hydrates turned inside out. Whereas a clathrate hydrate possesses a guest ion or molecule surrounded by a hydrogen bonded water host lattice, in these complexes the guest tris-pyiidinonato metal complexes were held rigidly outside the water channels.8"10 4 The exoclathrate water channels are composed of a series of stacked six-membered water rings. In each water ring the hydrogen bonding is circular and the circle is homodromic 1 1 which means that all of the O-H-0 bonds run in the same direction (counterclockwise when viewed down the c axis as in Figure 1.3.). It has been suggested12 that these homodromic circles should be preferred in water clusters over heterodromic circles because of an inherently lower dipole moment We were interested in exploring the steric constraints imposed by these highly ordered crystalline structures. Structural modification is reasonably straightforward. These pyridinonato complexes can be prepared by a relatively simple route which takes advantage of the metal template effect.13 A variety of metals and primary amines can be employed, as shown in Figure 1.4. This synthesis allows the direct preparation of the tris-ligand metal complexes from commercially available starting materials. The metal-pyrone complex is presumably generated in situ, following which insertion of the primary amine into the pyrone ring forms the appropriate tris-pyridinonato metal complex. The accepted mechanism for this 4-pyrone conversion reaction is nucleophilic attack by a primary amine, followed by ring opening, elimination of water, and ring closure to give the 4-pyridinone.14'15 Increasing the size of the metal atom from aluminum (effective six-coordinate ionic radius16, r = 0.535 A) to gallium (r = 0.62*0 A) to indium (r = 0.800 A) seemed to have little effect upon the intricate hydrogen bonding network.8'9 Also, increasing the size of the nitrogen substituent from a methyl group to an ethyl group left the exoclathrate's extensive hexagonal water channels intact.8-10 It was proposed that by increasing the size of the nitrogen substituent, eventually these exoclathrates would have an altered structure, or perhaps not form at all. The work described herein was undertaken in order to probe the steric limitations of these unusual structures. It was hypothesized that a propyl group as the nitrogen subtituent might form an exoclathrate, but that perhaps the lattice would not accommodate a more 5 R = H M(mpp)3 C H 3 M(dpp)3 C 2 H 5 M(mepp)3 n-C 6 H 1 3 M(mhpp)3 Figure 1.4. Synthesis of tris(N-substituted3-hydroxy-2-metbyI-4pyrid^onato)m complexes. sterically demanding butyl group, and hence a different structure would be found. The synthesis, characterization, and X-ray crystallographic analyses of the tris(3-hydroxy-2-methyl-4-pyridinonato)metal(rn) complexes with an n-propyl or n-butyl group as the nitrogen substituent are described. 6 Chapter 2. Experimental 2.1. Complex Preparation and Characterization The tris-ligand metal complexes were characterized by infrared (IR) spectroscopy, positive ion fast atom bombardment mass spectrometry (FAB-MS), proton ('H) and aluminum-27 (27A1) nuclear magnetic resonance (NMR) spectroscopy, as well as by elemental analysis. IR spectra were recorded with a Perkin Elmer PE 783 spectrometer in the range 4000-200 cm-1. All samples were prepared as potassium bromide (KBr) disks and were referenced to polystyrene. The FAB-MS spectra were recorded with an AEI MS9 spectrometer by the U.B.C. mass spectrometry service. Proton NMR spectra, recorded on a Bruker WP-400 instrument are reported in ppm downfield of tetramethylsilane (TMS) as the internal standard. Aluminum NMR spectra were recorded on a Varian XL-300 instrument and are referenced to hexaquaaluminum(III) {A1(H20)63+}. Elemental analyses were performed by Peter Borda of the U.B.C. Microanalytical Laboratory. All chemicals were reagent grade, were used without further purification, and were received from the following chemical companies: amines and maltol (Sigma); AICI36H2O (Anachemia); Ga(N03)3-9H20 (Johnson Matthey); In(N03)3-5H20 (Alfa). The melting points were measured with a Mel-Temp apparatus and are uncorrected. The reaction conditions were the same for aluminum, gallium, and indium with any given ligand.13 Preparative details are given for the aluminum complexes; only reactant concentrations and yields are given for the corresponding gallium and indium complexes. All yields are calculated based on metal complex trihydrates. The pyrone conversion reaction was monitored by thin layer chromatography (TLC) on silica gel plates with 5 % methanol in methylene chloride as the eluting solvent. Optimum yields were obtained after three days. 7 2.1.1. Tris(3-hydroxy-2-rnethyl-1 -w-propy1-4-pyridinonato)metal Complexes 2.1.1.a Trisr3-hvdroxv-2-methvl-l-/2-propvl-4-pvridinonato')aluminumaiD. Al(npp)3. AICI36H2O (1.68 g, 6.95 mmol) and maltol (2.62 g, 20.7 mmol) were dissolved in distilled deionized water (50 mL). n-Propylamine (10.0 mL, 121 mmol) was added and the reaction mixture was stirred under a nitrogen purge for three days, during which time a precipitate formed. The suspension was filtered, and recrystallization of the solid from hot water yielded a pale yellow-orange solid. This solid was then dissolved in a small volume of hot water and the volume reduced to 10 mL by heating at 70 °C. This suspension was filtered while still hot, to give a pale yellow-orange coloured product. The yield was 2.59 g, 64 % based on aluminum. Mp 300 °C (dec). 2.1.1.b TrisC3-hvdroxy-2-methyl-l-n-propyl-4-pyridinonato)galliumCIII). Ga(npp)3. Ga(N03)3-9H20 (1.00 g, 2.39 mmol) and maltol (0.91 g, 7.22 mmol) were dissolved in water (50 mL). n-Propylamine (5.0 mL, 60.8 mmol) was added. The yield was 1.17 g, 78 % based on gallium. Mp 290 °C (dec). 2.1.1. c Tris(3-hydroxy-2-methyl-l-tt-propvl-4-pvridinonato)indiumniI). In(npp)3. In(N03)3-5H20 (1.00 g, 2.55 mmol) and maltol (1.00 g, 7.93 mmol) were dissolved in water (50 mL). -^Propylamine (5.0 mL, 60.8 mmol) was added. The yield was 1.30 g, 76 % based on indium. Mp 280 °C (dec). 2.1.2. Trisfl-n-butyl-3-hydroxy-2-methyl-4-pyridinonato)metal Complexes 2.1.2.a Trisn-n-butyl-3-hydroxy-2-methvl-4-pyridinonato)aluminum(III'). Al(nbp)3. AICI36H2O (1.68 g, 6.96 mmol) and maltol (2.66 g, 21.1 mmol) were dissolved in distilled deionized water (50 mL). n-Butylamine (13.0 mL, 130 mmol) was added and the reaction mixture was stirred under a nitrogen purge for three days, during which time a precipitate formed. The suspension was filtered, and recrystallization of the solid from hot 8 water yielded a beige solid. This solid was then dissolved in a small volume of hot water and the volume reduced to 10 mL by heating at 70 °C. This suspension was filtered while still hot, to give a beige coloured product The yield was 2.37 g, 55 %. Mp 180 °C (dec). 2.1.2.b Trisfl-n-butvl-3-hvdroxv-2-methvl-4-pvridinonato>)gallium(IID. Ga(nbp)3. Ga(NC»3)3-9H20 (1.03 g, 2.47 mmol) and maltol (0.93 g, 7.38 mmol) were dissolved in water (50 mL). n-Butylamine (5.0 mL, 50 mmol) was added. The yield was 1.19 g, 73 %. Mp 170 °C (dec). 2.1.2. C Tris(l-/i-butyl-3-hydroxy-2-methyl-4-pyridinonato')indium(III'). In(nbp)3. In(N03)3-5H20 (1.01 g, 2.59 mmol) and maltol (1.09 g, 8.67 mmol) were dissolved in water (50 mL). n-Butylamine (5.0 mL, 50 mmol) was added. The yield was 1.60 g, 87 %. Mp 255 °C (dec). 2.1.3. Infrared Spectroscopy Characteristic bands in the infrared spectrum indicated whether or not the desired pyridinone had been obtained from the pyrone conversion reaction. If the anticipated bands were observed in an IR spectrum, then recrystallization and further characterization were attempted. A summary of the relevant IR data is given in Table 2.1.3. The spectra of all of these pyridinone derivatives exhibit four ring-stretching bands between 1650 and 1400 cm"1.17 The spectra of the Al, Ga, and In complexes with any given ligand are very similar above 800 cm"1 (all bands are within ±10 cm"1). Three bands below 800 cm"1 are tentatively assigned as V M - O 1 8 This is the region of the spectra where distinctions due to the difference in mass of the metal ions can be made. At least one of these stretching bands is at a significantly lower energy in the tris-ligand gallium complexes relative to the analogous aluminum complexes. The same is true of the V M - O of the tris-ligand indium complexes relative to the gallium complexes. 9 Table 2.1.3. Characteristic infrared absorptions (cm"1). All bands are sharp and strong except as noted.® Assignment Al(npp)3 Ga(npp)3 In(npp)3 Al(nbp)3 Ga(nbp)3 In(nbp)3 VC-H ring (w) 2970 2965 2970 2960 2965 2960 VCH3(w) 2880 2880 2880 2880 2880 2880 vc=o 1610 1600 1600 1610 1605 1600 and 1560 1550 1540 1560 1550 1540 Vring 1520 1510 1500 1520 1510 1500 1495 1485 1485 1490 1485 1490 VM-0 720 710 705 720 715 705 580 (b) 570 (b) 555 590 (b) 570 (b) 555 (1 470 410 (b) <300 470 (b) 410 (b) <300 @ w, weak; b, broad. 10 2.1.4. Mass Spectrometry Formation of the desired metal complex was confirmed by mass spectrometry. A summary of the FAB-MS spectral data is given in Table 2.1.4. In each case, the base peak was the ML2+ species, formed by the loss of one ligand and the hydrogen atom from the molecular ion HML.3+ which was a lower intensity peak. A peak of much lower intensity attributed to an M2Ls+ species was found in all spectra. This dimer occurred through the canonization of the molecular unit by attachment of an M L 2 + unit {ML3 + M L 2 + -> M2L.5"1"}.19'20 The ML + species is formed by the loss of two ligands and the hydrogen atom from the molecular ion HML3+. This peak was not observable in the Al tris-ligand complex spectra, but was present in the analogous Ga and In spectra. For the Ga complexes, the peaks were in the natural isotopic ratio of 3:2 6 9 Ga to 7 1Ga. The presence of peaks due to the matrix (m-nitrobenzylalcohol) made assignment of the spectra beyond this pointless. Table 2.1.4. Data from FAB-MS spectra of the tris-ligand metal complexes (m/z). M(npp)3 M(nbp)3 Al(npp)3 Ga(npp)3 In(npp)3 Al(nbp)3 Ga(nbp)3 In(nbp)3 M 2 L 5 + 884±1 971 ±2 1062±2 954±1 1040±2 112912 HML3+ 526 568 614 568 610 656 570 612 M L 2 + 359 401 447 387 429 475 403 431 ML+ - 236 281 - 250 295 11 2.1.5. Proton NMR A summary of the lH NMR chemical shifts recorded in deuterated chloroform (CDCI3) at 400 MHz is given in Table 2.1.5. All of the spectra exhibit AB doublets for the ring protons (Jab of 6 to 7 Hz), a singlet for the ring methyl group, and a series of signals for the methylene and methyl protons of the R substituent. Table 2.1.5. *H NMR chemical shifts (8) for the tris-ligand metal complexes (ppm).18 Recorded at 400 MHz in CDCI3. Refer to Figure 2.1.5. for proton labelling. M(npp)3 M(nbp)3 Al(npp)3 Ga(npp)3 In(npp)3 Al(nbp)3 Ga(nbp)3 In(nbp)3 H a (d) 7.06 7.07 7.06 7.07 7.06 7.06 H b (d) 6.54 6.47 6.53 6.48 6.53 6.54 C H 3 c (s) 2.44 2.41 2.46 2.44 2.44 2.47 CH2d(t) 3.83 3.83 3.84 3.86 3.86 3.87 CH2e 1.74 (sx) 1.73 (sx) 1.71 (sx) 1.69 (q) 1.69 (q) 1.67 (q) CH2f 0.94 (t)* 0.95 (t)* 0.91 (t)* 1.37 (sx) 1.36 (sx) 1.33 (sx) C H 3 g (t) 0.96 0.96 0.94 * read CH3f. Abbreviations: s = singlet; d = doublet; t = triplet; q = quintet; sx = sextet 12 - 1 3 R=CH 2 dCH 2 eCH 3 f M(npp)3 R=CH 2 dCH 2 eCH 2 fCH 3 g M(nbp)3 M = Al, Ga, In Figure 2.1.5. Tris-Ligand Metal Complex Labelling for NMR Studies » 13 2.1.6. AIuminurn-27 NMR A summary of the 2 7 A l NMR data recorded in deuterated chloroform (CDCI3) on a 300 MHz spectrometer is given in Table 2.1.6. The presence of aluminum in the probe-head ceramics was corrected for by performing a subtraction of a solvent blank spectrum from the spectrum of the aluminum complex. The chemical shift and peak width at half-height for Al(npp)3 and Al(nbp)3 are as expected for aluminum in a trigonal environment, as can be seen by comparing their values with those of the trigonal tris-ligand aluminum complexes included in Table 2,1.6.18,19 Completely symmetric octahedral and tetrahedral aluminum environments yield sharp peaks with a chemical shift near 0 ppm. Table 2.1.6. 27A1 NMR chemical shifts (8) for the tris-ligand aluminum complexes (ppm) recorded on a 300 MHz spectrometer in CDCI3. Al(ma)3 Al(dpp)3 Al(mepp)3 Al(npp)3 Al(nbp)3 ppm 38 37 37 37 37 900 700 780 730 920 14 2.1.7. Elemental Analyses Satisfactory elemental analyses were obtained for all complexes (refer to Table 2.1.7. for summary). Except as noted, the samples were submitted for analysis under nitrogen because they were hygroscopic. Water was removed from the recrystallized products by heating in vacuo (0.05 torr) at 85 °C for 48 hours. Table 2.1.7. Results of elemental analysis (Found [Calculated]) of the metal complexes. Compound Formula %C % H % N Al(npp)3 [C27H36A1N306] 62.00 [61.70] 7.01 [6.90] 7.97 [8.00] Ga(npp)3 [C 27H3 6GaN 30 6] 57.17 [57.06] 6.44 [6.38] 7.52 [7.39] Ga(npp)3-3H20 * [C27H42GaN309] 51.80 [52.11] 6.67 [6.80] 6.60 [6.75] In (npp)3 [C27H3 6InN306] 52.45 [52.87] 5.85 [5.92] 6.70 [6.85] Al(nbp)3 [C3oH42AlN306] 63.41 [63.48] 7.55 [7.46] 7.51 [7.40] Ga(nbp)3-0.5H2O [C30H43GaN3O6.5] 57.93 [58.17] 6.84 [7.00] 6.45 [6.78] In(nbp)3-1.5H20 [C30H45lnN3O7.5] 52.91 [52.79] 6.37 [6.64] 6.11 [6.16] * air-dried X-ray quality crystals. 15 2.2. X-rav Crystallographic Analysis The structures of Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 were established by single crystal X-ray diffraction. Single crystals of the tris-ligand metal complexes were grown by slow evaporation from dilute aqueous solution. The following pages describe the general steps involved in the collection of the diffraction data and the solution of the solid state structures.21'22 2.2.1. Choosing a Crystal Great care was taken in selecting a crystal suitable for data collection. The average dimension of the three dimensional hexagonal cylindrical, colourless crystals used for analysis was between 0.2 mm and 0.4 mm, such that the crystal did not exceed the size of the beam. Imperfections in the crystal, such as twinning, were usually detected using a set of polarized lenses or from precession photographs. The crystal was mounted on the tip of a glass fibre in a random position. 2.2.2. The Orientation Matrix Using a Rigaku AFC6S diffractometer (with graphite-monochromated Cu-Ka radiation), reflections were found using SEARCH, 2 3 a program designed to locate and center reflections through a systematic search of reciprocal space. If the peak profiles were weak, broad or split at this point, then the crystal was discarded. A zigzag search ensured a wide distribution of reflections in reciprocal space. This, in turn, ensured a good orientation matrix and primitive unit cell parameters. 16 2.2.3. The Lattice Tvpe. Laue Group, and Crystal System The cell reduction program DELAUNEY was applied to the primitive unit cell determined in SEARCH. By this method the new orientation matrix and unit cell parameters, as well as the Bravais lattice, were determined. The program LAUE was then run, in order to confirm the Laue group by checking the intensities of potentially equivalent reflections. The established lattice type, Laue group, and crystal system were thus obtained (P, 3, trigonal). 2.2.4. Collecting Data Data were collected in the unique volume of reciprocal space. Three standard reflections were selected on the basis of good intensity and spatial distribution from the reflections used to determine the orientation matrix. Their intensity and orientation were checked periodically to determine whether or not there was any significant crystal decay or crystal movement. Crystal decay and shifts in the position of the crystal were negligible. At the end of data collection, the effect of absorption on the diffraction intensities of the three most intense reflections with x between 75° and 90° was measured by application of the progam PSI. Using the program PROCESS, the data were corrected for Lorentz and polarization effects, the space group (P3, #147) was indicated by the E_-statistics, the transmission factors for absorption correction were calculated, and a data file was prepared. The absorption correction was applied after data processing. 2.2.5. Solution of the Structure A three dimensional Patterson map was used to locate the metal atom (Al or Ga). The positions of all other non-hydrogen atoms were obtained from subsequent electron 17 density difference Fourier maps. In all three structures, all hydrogen atoms were located and their positions and isotropic thermal parameters were refined, except for the -^propyl derivatives. For the Al(npp)3-3H20 structure, the three hydrogen atoms on the methyl carbon of the n-propyl substituent were placed in calculated positions and their isotropic thermal parameters were fixed at 1.2 times the equivalent isotropic thermal parameter of the carbon atom to which they are bonded. For the Ga(npp)3-3H20 structure, the two hydrogen atoms on the second methylene carbon as well as the three hydrogen atoms on the methyl carbon of the n-propyl substituent were placed in calculated positions and their isotropic thermal parameters were fixed as above. Attempts at refinement of the positions of these hydrogen atoms moved them to chemically unacceptable positions. Further refinement of all parameters, including anisotropic temperature factors for all non-hydrogen atoms, was done by full-matrix least-squares methods and minimized with the function X w( IF0| - \FC\ )2. Neutral atom scattering factors were taken from reference 24. Anomalous dispersion effects were included in Fcalc25; the values for Af and Af' were those of Cromer and Waber.26 A correction for secondary extinction was applied to Al(nbp)3-3H20 (coefficient = 0.29804xl(r5) as well as to Ga(npp)3-3H20 (coefficient = 0.47472x10"5). Refinement was terminated when the maximum shift/error was less than 0.015 and there was only a small peak of residual electron density (refer to Table 2.2.1.). Crystal data and other information related to data collection are given in Table 2.2.1. Atomic positional parameters and isotropic thermal parameters are given in Table 2.2.2. Selected bond distances and angles are given in Table 2.2.3. and Table 2.2.4. Anisotropic thermal parameters, bond lengths and angles involving hydrogen, torsion angles, measured and calculated structure factor amplitudes, and intraannular torsion angles are available as supplementary material upon request to the crystallography laboratory at U.B.C. 18 Table 2.2.1. Crystallographic Data3 for Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20. Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 formula C30H48AIN3O9 C27H42AIN3O9 C27H42GaN30o fw 621.7 525.6 622.36 cryst syst trigonal trigonal trigonal space group P3 P3 P3 a, A 15.885 (1) 15.328 (1) 15.367 (2) c, A 7.280 (8) 7.231 (2) 7.256 (2) V, A3 1591.0 (2) 1471.3 (4) 1484.0 (7) z 2 2 2 Pealed, g cm-3 1.30 1.19 1.39 F(000) 668 560 656 u (Cu-Ko) (cm-1) 9.98 9.25 17.02 cryst dimens, mm 0.15x0.15x0.30 0.15x0.15x0.40 0.25x0.25x0.50 transmission coeff 0.84 - 1.00 0.84 - 1.00 0.80 - 1.00 scan range, deg in co 0.94 + 0.30 tan 6 0.89 + 0.30 tan 9 0.80 + 0.20 tan 9 scan speed, deg/min 8 32 32 l$max (deg) 156.5 155.1 155.3 no. of unique reflcns 1994 2032 2032 reflcns with / > 3a(7) 1280 1377 1802 number of variables 195 165 158 R 0.047 0.057 0.055 Rw 0.061 0.077 0.081 max A/a (final cycle) 0.01 0.01 0.01 residual density, e/A3 0.15 0.44 0.66 P 0.05 0.05 0.04 a Temperature 21 °C, Cu-ATa radiation (kKa = 1.54178 A), graphite-monochromated, to -29 scan, Rigaku AFC6S diffractometer, calculations performed on a VAX-based TEXRAY system (Molecular Structure Corp.), R = LI (Fd - IFC| I /£ IFQ\, Rw = Z(w( IF0| - IFC| )2/Zvv F 0 w = 4F02/a2(F02), o2(F0 2) = [S2(C + R2B) + (pF02)2]/Lp2 where S = scan rate, C = peak count, R = scan time/background time, B = background count, Lp = Lorentz-polarization factor, p = p-factor, function minimized: I w( \F0\ - IFC| )2. 19 Table 2.2.2. Atomic Positional and Equivalent Isotropic Thermal Parameters, fieq for Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20. Al(nbp)3-3H20, C30H4SAIN3O9 atom X y X Btq (A2) Al 2/3 1/3 0 .4392(2) 3.40(3) 0(1) 0 .7076(1) 0.2623(1) 0 .5879(2) 3.95(6) 0(2) 0 .6149(1) 0.2204(1) 0 .2844(3) 4.15(7) 0(3) 0 .8294(2) 0.3628(2) 0 .9260(4) 6.4(1) N 0 .6335(2) 0.0074(2) 0 .5549(3) 4.20(8) C(l) 0 .7207(3) 0.1205(3) 0 .8141(5) 5.3(1) C(2) 0 .6750(2) 0.0995(2) 0 .6287(4) 3.9(1) C(3) 0 .6705(2) 0.1714(2) 0 .5300(4) 3.58(8) C(4) 0 .6216(2) 0.1498(2) 0 .3593(4) 3.77(9) C(5) 0 .5829(2) 0.0559(2) 0 .2876(4) 4.2(1) C(6) 0 .5904(2) -0.0128(2) 0 .3895(5) 4.5(1) C(7) 0 .6316(2) -0.0738(2) 0 .6582(5) 5.0(1) C(8) 0 .7274(3) -0.0723(3) 0 .6464(6) 5.4(1) C(9) 0 .7323(4 ) -0.1439(3) 0 .7751(8) 7.4(2) C(10) 0 .8327(6) -0.1321(6) 0 .787(1 ) 10.0(3) H(1B) 0 .772(4) 0.189(4) 0 .820(7) 9(1) H(1C) 0 .684(4) 0.078(4) 0 .911(8) 11(2) H(1A) 0 .777(5) 0.105(5) 0 .815(8) 12(2) H(3B) 0 .782(4) 0.341(4) 0 .848(8) 9(2) H(3A) 0 .812(4) 0.368(4) 1 .04(1) 11(2) H(5) 0 .552(2) 0.040(2) 0 .167(4) 4.4(6) H(6) 0 .557(3) -0.085(3) 0 .354(5) 5.6(8) H(7A) 0 .609(2) -0.072(2) 0 .786(5) 5.2(7) H(7B) 0 .578(2) -0.133(2) 0 .599(4) 4.4(6) H(8B) 0 .784(3) -0.006(2) 0 .673(5) 5.6(8) H(8A) 0 .735(3) -0.091(3) 0 .497(5) 7(1) H(9A) 0 .711(4) -0.135(3) 0 .921(6) 9(1) H(9B) 0 .677(4 ) -0.210(4) 0 .749(7) 10(1) H(10C) 0 .825(5) -0.193(4) 0 .83(1) 12(2) H(10B) 0 .884(5) -0.063(5) 0 .84(1) 14(2) H(10A) 0 .856(5) -0.135(5) 0 .64(1) 16(3) 20 Table 2.2.2. continued AI(npp)3-3H20, C27H42AIN3O9 «*>m X y z *eq(A2) A l 0 . 6 6 7 0 0 . 3 3 3 2 0 . 4 6 0 8 ( 2 ) 3 . 5 6 ( 4 ) 0 ( 1 ) 0 . 7 1 1 4 ( 2 ) 0 . 2 6 2 3 ( 1 ) 0 . 6 1 0 7 ( 3 ) 3.89(8) 0 ( 2 ) 0 . 6 1 4 9 ( 2 ) 0 . 2 1 6 0 ( 2 ) 0 . 3 0 5 5 ( 3 ) 4 . 1 2 ( 8 ) 0 ( 3 ) 0 . 8 3 8 6 ( 2 ) 0 . 3 7 0 2 ( 2 ) 0 . 9 4 5 0 ( 4 ) 5 . 9 ( 1 ) N 0 . 6 4 2 6 ( 2 ) 0 . 0 0 0 5 ( 2 ) 0 . 5 7 9 5 ( 4 ) 4 . 2 ( 1 ) C ( l ) 0 . 7 3 1 7 ( 4 ) 0 . 1 1 9 4 ( 4 ) 0 . 8 3 8 8 ( 6 ) 5 . 2 ( 2 ) C (2) 0 . 6 8 4 1 ( 2 ) 0 . 0 9 6 4 ( 2 ) 0 . 6 5 3 8 ( 4 ) 4 . 0 ( 1 ) C ( 3 ) 0 . 6 7 5 1 ( 2 ) 0 . 1 6 8 3 ( 2 ) 0 . 5 5 2 9 ( 4 ) 3 . 6 ( 1 ) C(4) 0 . 6 2 4 1 ( 2 ) 0 . 1 4 4 2 ( 2 ) 0 . 3 8 1 7 ( 4 ) 3 . 7 ( 1 ) C ( 5 ) 0 . 5 8 7 1 ( 2 ) 0 . 0 4 7 7 ( 2 ) 0 . 3 1 0 4 ( 5 ) 4 . 1 ( 1 ) C(6) 0 . 5 9 8 0 ( 2 ) - 0 . 0 2 1 6 ( 2 ) 0 . 4 1 3 5 ( 5 ) 4 . 4 ( 1 ) C ( 7 ) 0 . 6 4 9 9 ( 3 ) - 0 . 0 7 9 2 ( 3 ) 0 . 6 8 0 5 ( 7 ) 5 . 1 ( 2 ) C ( 8 ) 0 . 7 5 2 4 ( 4 ) - 0 . 0 7 1 6 ( 4 ) 0 . 6 4 3 6 ( 7 ) 6 . 6 ( 2 ) C ( 9 ) 0 . 7 7 5 3 ( 4 ) - 0 . 1 3 2 0 ( 4 ) 0 . 7 7 5 3 ( 8 ) 8.3(3) H ( 1 A ) 0 . 6 9 9 ( 3 ) 0 . 0 8 1 ( 4 ) 0 . 9 3 1 ( 7 ) 7 ( 1 ) H ( 1 B ) 0 . 7 9 5 ( 4 ) 0 . 1 3 1 ( 4 ) 0 . 8 2 9 ( 7 ) 1 1 ( 2 ) H ( 1 C ) 0 . 7 4 5 ( 4 ) 0 . 1 8 4 ( 5 ) 0 . 8 8 6 ( 7 ) 1 0 ( 1 ) H ( 3 A ) 0 . 8 1 1 ( 3 ) 0 . 3 7 5 ( 3 ) 1 . 0 5 9 ( 6 ) 7 ( 1 ) H ( 3 B ) 0 . 7 9 8 ( 4 ) 0 . 3 5 2 ( 4 ) 0 . 8 5 6 ( 8 ) 9(2) H ( 5 ) 0 . 5 5 0 ( 2 ) 0 . 0 2 6 ( 2 ) 0 . 1 9 1 ( 4 ) 4 . 0 ( 7 ) H ( 6 ) 0 . 5 7 5 ( 3 ) - 0 . 0 8 9 ( 3 ) 0 . 3 8 1 ( 5 ) 6 ( 1 ) H ( 7 A ) 0.643(3) - 0 . 0 7 1 ( 3 ) 0 . 8 1 5 ( 6 ) 5 . 2 ( 9 ) H ( 7 B ) 0 . 5 9 0 ( 3 ) - 0 . 1 4 4 ( 3 ) 0 . 6 2 5 ( 5 ) 5 . 4 ( 8 ) H ( 8 A ) 0 . 7 6 0 ( 3 ) - 0 . 0 8 3 ( 3 ) 0 . 5 1 8 ( 6 ) 7 ( 1 ) H ( 8 B ) 0 . 8 1 4 ( 4 ) - 0 . 0 0 8 ( 4 ) 0 . 6 9 3 ( 6 ) 8 ( 1 ) H ( 9 A ) 0 . 7 1 9 6 - 0 . 2 0 1 9 0 . 7 7 5 5 1 0 . 0 H ( 9 B ) 0 . 8 3 7 5 - 0 . 1 3 0 4 0 . 7 3 7 3 1 0 . 0 H O C ) 0 . 7 8 3 9 - 0 . 1 0 3 7 0 . 8 9 9 9 1 0 . 0 21 Table 2.2.2. continued Ga(npp)3-3H20, C27H42GaN30o atom X y z Beq (A2) GA 0.6666 0 .3333 0.46383(7) 3.31(2) 01 0.7113(2) 0 .2583(2) 0.6169(3) 3.70(7) 02 0.6156(2) 0 .2115(2) 0.3034(3) 3.93(7) 03 0.5274(3) 0 .1592(2) 0.9470(4) 5.8(1) N 0.6419(2) -0 .0026(2) 0.5847(4) 4 . 0 ( 1 ) CI 0.7287(4) 0 .1148(3) 0.8429(6) 5 . 0(1) C2 0.6816(2) 0 .0922(2) 0.6579(4) 3.7(1) C3 0.6744(2) 0 .1645(2) 0.5586(4) 3.4(1) C4 0.6242(2) 0 .1409(2) 0.3843(4) 3.5(1) C5 0.5879(2) 0 .0446(2) 0.3140(4) 4 . 0 ( 1 ) C6 0.5971(2) - 0 .0247(3) 0.4154(5) 4 . 2 ( 1 ) C7 0.6502(3) - 0 .0819(3) 0.6827(6) 5 . 0 ( 1 ) C8 0.7522(4) - 0 .0740(4) 0.6463(7) 6 . 7 ( 2 ) C9 0.7769(5) -0 .1324(5) 0.7728(9) 8 . 1 (3 ) , H1A 0.731(5) 0 .163(5) 0.898(8) 10(2) H1B 0 . 7 7 4 ( 4 ) 0 .106(3) 0.842(6) 6 (1 ) H1C 0 . 6 9 5 ( 3 ) 0 . 074 (3 ) 0 . 9 4 0 ( 6 ) 5 (1) H3A 0 . 5 5 7 ( 3 ) 0 . 176 (3 ) 1 . 0 2 4 ( 6 ) 5 (1) H3B 0 . 5 4 1 ( 4 ) 0 . 199 (4 ) 0.858(7) 7 (1 ) H5 0 . 5 5 9 ( 3 ) 0 . 026 (3 ) 0 . 1 9 5 ( 6 ) 5 . 0 ( 9 ) H6 0 . 5 7 1 ( 2 ) - 0 . 088 (3 ) 0 . 3 7 1 ( 4 ) 3 . 7 ( 7 ) H7A 0 . 6 0 9 ( 4 ) - 0 . 130 (3 ) 0.630(6) 7 (1 ) H7B 0 . 6 3 6 ( 3 ) - 0 . 076 (3 ) 0 . 8 0 0 ( 5 ) 4 . 0 ( 8 ) H8A 0.7517 - 0 .0976 0.5207 8 .1 H8B 0.8044 - 0 .0032 0.6567 8 .1 H9A 0.7815 - 0 .1072 0.8986 9 .7 H9B 0.8415 - 0 .1258 0.7374 9 .7 H9C 0 .7243 - 0 .2032 0.7672 9 .7 22 Table 2.2.3. Selected Bond Lengths (A) for Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. length (A) Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 M -0(1) 1.898 (2) 1.887 (2) 1.965 (2) M - 0(2) 1.921 (2) 1.921 (2) 2.002 (2) 0(1) -C(3) 1.326 (3) 1.326 (3) 1.332 (3) 0(2) - C(4) 1.298 (3) 1.301 (4) 1.297 (4) N - C(2) 1.378 (3) 1.385 (4) 1.374 (4) N - C(6) 1.342 (4) 1.339 (5) 1.365 (4) N - C(7) 1.481 (4) 1.475 (4) 1.471 (4) C(l)-C(2) 1.489 (4) 1.480 (5) 1.482 (5) C(2) - C(3) 1.382 (4) 1.385 (4) 1.375 (4) C(3) - C(4) 1.414 (4) 1.411 (4) 1.430 (4) C(4) - C(5) 1.400 (4) 1.392 (4) 1.391 (4) C(5) - C(6) 1.372 (5) 1.375 (5) 1.360 (5) C(7) - C(8) 1.513 (5) 1.540 (6) 1.533 (6) C(8) - C(9) 1.505 (5) 1.488 (6) 1.460 (6) C(9) - C(10) 1.511 (9) 23 Table 2.2.4. Selected Bond Angles (deg) for Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. angle (deg) Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 0(1) - M - 0(2) 83.83 (9) 83.74 (9) 82.72 (9) 0(1)-M-0(1)' 90.7 (1) 90.5 (1) 90.45 (8) O(l) - M - 0(2)' 97.14 (9) 97.27 (9) 98.39 (9) 0 (2 )^-0(1 )^5 170.49 (7) 171.06 (9) 168.84 (8) 0(2) - M - 0(2)' 89.1 (1) 89.5 (1) 89.62 (9) M-0(l)-C(3) 111.6 (2) 111.8 (2) 111.2 (2) M - 0(2) - C(4) 112.3 (2) 112.1 (2) 111.3 (2) C(2) - N - C(6) 121.3 (2) 121.4(3) 120.9 (3) C(2) - N - C(7) 121.2 (3) 120.2 (3) 121.0 (3) C(6) - N - C(7) 117.5 (3) 118.4 (3) 118.1 (3) N - C(2) - C(l) 120.9 (3) 120.9 (3) 120.3 (3) N - C(2) - C(3) 118.7 (3) 117.7 (3) 118.8 (3) C(l)-C(2)-C(3) 120.4 (3) 121.3 (3) 120.8 (3) 0(1) - C(3) - C(2) 123.8 (2) 122.9 (3) 122.7 (3) 0(1) - C(3) - C(4) 115.8 (2) 116.0 (3) 116.7 (2) C(2) - C(3) - C(4) 120.4 (2) 121.1 (3) 120.6 (3) 0(2) - C(4) - C(3) 115.6 (2) 115.5 (3) 117.1 (3) 0(2) - C(4) - C(5) 125.6 (2) 125.7 (3) 124.7 (3) C(3) - C(4) - C(5) 118.8 (2) 118.8 (3) 118.2 (3) C(4) - C(5) - C(6) 118.6 (3) 118.6 (3) 119.4 (3) N - C(6) - C(5) 122.1 (3) 122.3 (3) 121.9 (3) N - C(7) - C(8) 112.1 (3) 110.4 (3) 111.0 (3) C(7) - C(8) - C(9) 112.6 (4) 113.0 (4) 114.4(4) C(8) - C(9) - C(10) 113.0 (5) 24 Chapter 3. Results and Discussion The N-substituted-3-hydroxy-4-pyridinones have several desirable qualities as ligands for group 13 metals. They behave as bidentate27 Lewis bases28 since the deprotonated 3-hydroxyl moiety as well as the carbonyl oxygen can donate one electron pair to the central metal atom. Both oxygen atoms can also be classified as relatively "hard" bases since they have a small atomic radius and are not very polarizable.28 Consequently, they tend to coordinate to relatively hard Lewis acids, such as the group 13 elements in the +3 oxidation state. This results in a tris-ligand metal complex of neutral charge, in which each ligand forms a five-membered chelate ring27 with the central metal atom (refer to Figure 3.1.). The chelate effect contributes to the thermodynamic stability of these tris-ligand metal complexes. 3 M = Al, Ga, In R = CH 2CH 2CH 3 M(npp)3 CH 2CH 2CH 2CH 3 M(nbp)3 Figure 3.1. Tris-ligand Metal Complexes with Five-membered Chelate Rings. 25 No excess maltol is required to drive the reaction under ambient conditions (refer to Sections 2.1.1. and 2.1.2.), illustrating the ease with which these complexes are formed. It should be noted that in view of the reaction conditions (N2 purge, 3 days), excess amine was used in order to compensate for its relative volatility (refer to Table 3.1.). Table 3.1. Boiling Points of Some Common Amines.29 Amine Boiling Point (°C) ethylamine 16.6 -^propylamine 48-49 /-propylamine 33-34 n-butylamine 78 f-butylamine 44-46 n-hexylamine 130 Attempts to synthesize the /-propylamine and r-butylamine derivatives of tris(N-substituted-3-hydroxy-2-methyl-4-pyridinone)metal(III) complexes proved unsuccessful. Several solvent systems were tried, but only the tris(maltolato)metal(III) products were isolated; that is, the conversion reaction did not take place. It should be noted that this one-pot conversion reaction was successful with methylamine,13 ethylamine,13 n-propylarnine, and n-butylamine. As the basicity of these four amines is comparable to that of /-propylamine and /-butylamine (refer to Table 3.2.), differences in the nucleophilicity of the amine nitrogen in the latter two is considered unlikely to be responsible for their anomalous behaviour. A more likely cause is the steric bulk at nitrogen; it will be observed that each of the successful syntheses involves a linear primary amine. It appears likely that 26 factors retard the conversion reaction in the case of branched amines. In support of this, an extensive study on the conversion reaction for pure ligands concluded that more basic and less hindered amines give the greatest yields of 4-pyridinones.30 Table 3.2. The pKa's and pKb's of Some Common Amines. Amine pK a31 pK b @ methylamine 10.6 3.4 ethylarnine 10.6 3.4 -^propylamine 10.5 3.5 /-propylamine 10.6 3.4 n-burylamine 10.6 3.4 ^ufylamine 10.6 3.4 @ pKb = pKw - pKa = 14.0 - pKa (25°C). The characterization data given in Chapter 2 are consistent with the proposed structures shown in Figure 3.1. {i.e. M(npp)3 and M(nbp)3). The anticipated stretching bands, characteristic of the pyridinone ligand, were observed in the IR spectra (refer to Section 2.1.3.). The similarity of the spectra above 800 cm-1 (all bands ± 10 cm*1) reflects the fact that the vibrations of the pyridinone ring are to a large extent unaffected by the ring substituents (i.e. independent of both metal ion and nitrogen substituent).32 Stretching of the delocalized C=0, C=N, C=C bonds of the pyridinone ring gives rise to a characteristic four-band pattern. It is impossible to assign separately the Vc=o and the higher energy vring stretches in any of the compounds. The bands are extensively coupled and there is no mode which is solely carbonyl in character.33 The highest 27 wavenumber band has the most C=0 character and the relatively low energy of this band (below 1650 cm"1 in all spectra) indicates that it is involved in hydrogen bonding.18,38 IR spectroscopy was used to monitor the purification of the tris-ligand metal complexes. Filtration of the crude precipitate as a hot suspension in water was crucial. This ensured that any salt which had coprecipitated with the desired product was dissolved and thus removed from the final product.18 The IR spectrum of the crude precipitate of Ga(npp)3 (refer to Figure 3.2.) exhibits the distinctive strong sharp IR band of NO3" (marked with an asterisk at 1380 cm"1 in Figure 3.2.). Comparison of this spectrum with that of the final product of Ga(npp)3, in which the nitrate band is no longer evident, indicates that this approach was successful (refer to Figure 3.2.). The metal template synthesis facilitated synthesis of the desired metal complexes, however, it also meant that the free ligands were themselves not available for comparison. A small bathochromic shift of the characteristic four-band pattern is expected but in the absence of the free ligand cannot be directly observed upon chelation. Although the location of the ring stretching frequencies indicated that formation of the tris-ligand metal complex was probable,8"10 confirmation was required. The FAB-MS data afforded confirmation that the tris-ligand metal complexes had indeed been obtained (refer to Section 2.1.4.). The parent ion, in particular, was consistent with formation of the desired metal complex. The proton NMR spectra exhibited chemical shifts typical for complexes of this type, and the peak integrations are consistent with the assignments as given in Table 2.1.5. The inductive effect of the nitrogen atom diminishes with increasing distance; of the two ring protons, H a is therefore assigned to the lowerfield doublet, Hb to the higher.34 Similarly, the series of peaks in the aliphatic region were deshielded, with the extent of the downfield shift reflecting the proximity to the ring nitrogen. The typical chemical shift of water in deuterated chloroform is around 1.4 ppm; this peak is deshielded to about 2.4 ppm in these spectra, indicating hydrogen bonding in solution.18 28 Figure 3.2. The IR spectra of Ga(npp)3 from 1400 - 1200 cm-1. (Crude precipitate on the left; final product on the right.) The single crystal X-ray diffraction studies of Al(nbp)3, Al(npp)3, and Ga(npp)3 showed unequivocally that the tris-ligand metal complexes had been formed. The first crystal suitable for crystallographic analysis formed from a dilute aqueous solution of the Al(nbp)3 complex. Even before the structure was solved, the unit cell parameters indicated that the complicated exoclathrate water network had been perturbed, as hypothesized, by the sterically demanding butyl group. The complex crystallizes in the same space group as the exoclathrates; however, the\jength of the a axis {15.885 (1) A} is shorter than the corresponding axis for the Al(dpp)3 complex {16.600 (2) A},18 which has a much smaller 29 methyl group as the nitrogen substituent. The solved crystal structure revealed that the empirical formula is in fact Al(nbp)3-3H20, as opposed to the dodecahydrate. Subsequent efforts produced X-ray quality crystals of both Al(npp)3 and Ga(npp)3 from dilute aqueous solutions. The crystal structures revealed that they too have the empirical formula M(npp)3-3H20. This indicates that the steric sensitivity of the exoclathrate structure is in fact even greater than originally expected; addition of a single methylene unit to the alkyl nitrogen substituent is sufficient to completely disrupt the water network. Comparison of the crystal structures of Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 reveals that these three complexes are basically isostructural (the Al(nbp)3-3H20 complex, of course, has one more methylene group in the nitrogen substituent than the other two complexes). These structures can therefore be discussed concurrently. The crystal structures revealed that the metal atom is in a distorted octahedral environment, with six oxygen donors from the three bidentate ligands. The tris-chelate complexes are arranged in a facial (fac) geometry. Computer generated ORTEP diagrams of the three structures are given in Figures 3.3., 3.4., and 3.5. The crystallographically imposed threefold symmetry of the fac isomer results in an asymmetric unit consisting of 1/3 of a metal ion, one ligand, and one water molecule. Although the water molecule does not coordinate the metal atom, hydrogen bonding interactions with the chelating oxygen atoms do make an important contribution to the stabilization of the lattice. The threefold symmetry about the central metal atom is common to all of the tris(N-substituted-3-hydroxy-2-methyl-4-pyridinonato)metal(III) complexes, including the exoclathrates.8"10 Hence, comparisons of these three new structures will be made to the exoclathrate structures throughout this discussion. It should be noted that the atomic labelling system for the trihydrates is consistent with the labelling for the exoclathrates throughout these tables to facilitate comparisons. The relevant crystallographic tables for the exoclathrate complexes can be found in the Appendix. 30 Figure 3.3. ORTEP view of the Al(nbp)3-3H20 unit. View is down the c axis. 31 Figure 3.4. ORTEP view of the Al(npp)3-3H20 unit. View is down the c axis. 32 Figure 3.5. ORTEP view of the Ga(npp)3-3H20 unit. View is down the c axis. 33 The distortions from true octahedral geometry around the metal atom are evinced by the metal-oxygen bond lengths and oxygen-metal-oxygen bond angles (refer to Tables 3.3. and 3.4.). Ideal octahedral values would entail equal metal-oxygen bond lengths for NI-CK 1) and M-0(2), as well as O-M-0 bond angles of 90° or 180°. The observed distortions can be attributed to several factors. Table 3.3. Metal-Oxygen Bond Lengths (A) for Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. length (A) Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 M-O(l) 1.898 (2) 1.887 (2) 1.965 (2) M-0(2) 1.921 (2) 1.921 (2) 2.002 (2) difference 0.023 (3) 0.034 (3) 0.037 (3) Table 3.4. Oxygen-Metal-Oxygen Bond Angles (deg) for Al(nbp)3 H20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. angle (deg) Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 O(l)- M - 0(2) 83.83 (9) 83.74 (9) 82.72 (9) O(l)- M - O(l)' 90.7 (1) 90.5 (1) 90.45 (8) O(l)- M - 0(2)' 97.14 (9) 97.27 (9) 98.39 (9) 0(2)- M-OdVtrans 170.49 (7) 171.06 (9) 168.84 (8) 0(2)- M - 0(2)' 89.) (1) 89.5 (1) 89.62 (9) 34 The M-O(l) bond lengths are consistently shorter than the M-0(2) bond lengths. The differences in the lengths can be found in italics in Table 3.3., and they represent part of the distortion from true octahedral geometry. Not surprisingly, despite partial delocalization of the carbonyl formal double bond at 0(2), the deprotonated 3-hydroxy oxygen atom 0(1) tends to form a stonger bond with the central metal atom. An examination of the packing arrangement (which will be discussed in detail later) reveals that the distance between these fac tris-ligand metal units is largely determined by the single water molecule of the asymmetric unit mentioned earlier.38 The oxygen atom of the latter is labelled as 0(3) in the figures. Hydrogen bonds to this water molecule join the chelating oxygen atom 0(1) in one unit cell to a second chelating oxygen atom 0(2) in a neighbouring unit cell. This hydrogen bonding network is parallel with the c axis, which is the C3 symmetry axis, and is an important contributor to the stability of the crystal. The length of these hydrogen bonds does not vary significantly among these three structures, indicating that the tris-ligand metal complex must distort in order to be accommodated by the pocket in the hydrogen bonding network. Similar but stronger distortions are observed in the exoclathrate complexes, in which the hydrogen bond lengths are shorter and much more intricate. Evidence for this statement is found by comparing the length of the c axis for Al(npp)3-3H20 to Al(mepp)3-12H20 : 7.231 (2) A versus 6.827 (1) A respectively. The result is a compression along the C3 axis, a twisting of the chelate plane, and hence further distortion from true octahedral geometry. The compression along the C3 axis is evidenced by the compressed 0(l)-M-0(2) bond angles which are significantly less than the ideal octahedral angle of 90° (refer to Table 3.4.). Among these three complexes, this C 3 compression is greatest for Ga(npp)3-3H20, where the 0(l)-M-0(2) bond angle reaches a minimum value of 82.72 (9)°. When compared to the exoclathrate structures, this 0(l)-M-0(2) bond angle is larger only than that of In(dpp)3-12H20 which has a value of 77.87 (6)°. 35 This decrease in the 0(l)-M-0(2) bond angle is accompanied by a related increase in the exocyclic 0(l)-M-0(2)' bond angle. This increase is accordingly greater for the Ga complex than for the two Al complexes (refer to Table 3.4.). The exocyclic 0(1)-M-0(1)' and 0(2)-M-0(2)' bond angles are close to the ideal values (90 ± 1°). Although the pure ligands with an /i-propyl or n-butyl substituent were not synthesized, it seems improbable that adding one or two methylene groups to the nitrogen substituent would have a significant effect upon the bond angles of the ligand. The 0(1)-C(3)-C(4) and 0(2)-C(4)-C(3) bond angles would in this case be close to 120° (refer to Table 3.5.).18 Chelation causes a compression in the interior angles of the chelate ring, with these O-C-C bond angles decreased in both the Al and Ga complexes. It should be noted that these O-C-C bond angles are comparable to the analogous angles in the exoclathrate structures. The increased size of the metal ion is accompanied by a reduction in chelate ring strain, as evidenced by the degree of compression of the O-C-C bond angles. By this criterion, Ga best fits the npp" anion, as it causes the least deviation from the ideal values for the free ligand. The planarity of the chelate rings (C(3)-0(l)-M-0(2)-C(4)} varies in the opposite direction. Deviation from planarity of this chelate ring is greatest for the Table 3.5. Chelating Oxygen-Carbon-Carbon Bond Angles (deg) for Hdpp, Hmepp, Al(nbp)3-3H.20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. angle (deg) Hdpp18 Hmepp18 Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 0(1)-C(3)-C(4) 119.2(2) 118.8(2) 115.8(2) 116.0(3) 116.7(2) 0(2)-C(4)-C(3) 120.5(3) 121.3(2) 115.6(2) 115.5(3) 117.1(3) 36 Ga(npp)3 complex, in which the mean deviation from the plane is 0.051 A, relative to 0.044 A for Al(npp)3, and 0.047 A for Al(nbp)3. This buckling of the chelate ring, as well as the compression along the C3 axis, actually increases directly with the ionic radius of the metal center. The effective six-coordinate ionic radius16 of gallium is 0.620 A, while that of aluminum is 0.535 A. The increased buckling of the chelate ring (mean deviation from the chelate plane), as well as the compression along the C3 axis (compression of the 0(l)-M-0(2) bond angle), in the Ga complex is due to its larger ionic radius. Indium has an effective six-coordinate ionic radius of 0.800 A, which explains why the In(dpp)3-12H20 complex has a smaller 0(1)-M-0(2) bond angle than this Ga complex. The delocalization in the C-0 bonds is directly related to the difference between the 0(1)-C(3) and 0(2)-C(4) bond lengths. This difference is 0.025 A for Al(npp)3-3H20, 0.028 A for Al(nbp)3-3H20, and 0.035 A for Ga(npp)3-3H20, indicating that the delocalization in the C-0 bonds is slightly greater in the Al complexes than the Ga complex (refer to Table 3.6.). The extent of delocalization is clearly seen by comparing bond lengths with the related dihydroxy ligands, the catechols. The average C-0 distance (calculated from a number of different metal complexes) is 1.36 A for the catecholate anion and 1.29 A for the delocalized semiquinone radical anion (see Figure 3.6.).35 o o. o Figure 3.6. The Catecholate and Semiquinone Ligands.35 37 Table 3.6. Carbon-Oxygen Bond Lengths (A) for Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. length (A) Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 0(1)-C(3) 1.326 (3) 1.326 (3) 1.332 (3) 0(2)-C(4) 1.298 (3) 1.301 (4) 1.297 (4) difference 0.028 (4) 0.025(5) 0.035(5) The 0(1)-C(3) bonds are significantly shorter (mean bond length = 1.328 (7) A) than the catecholate bond, and the 0(2)-C(4) bonds are the same length (mean bond length = 1.299 (6) A) as the semiquinone bond (within the estimated standard deviation). The same trend was observed for the exoclathrate complexes. In each complex the pyridinone ring is slightly nonplanar, the distortion being toward an N-C(4) boat for all three structures. The maximum deviation from the mean plane is 0.019 (3) A for each of the trihydrate structures. There are no significant differences in the ring bond lengths between Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 (refer to Table 3.7.). There are also no significant differences in the ring bond angles between the three complexes (refer to Table 3.8.). These ring bond lengths and bond angles are comparable to those found in the exoclathrate structures, indicating that there is no significant difference in double bond delocalization within the ring between these structures. The geometry about the nitrogen atom is also of interest. The N-C(2) and N-C(6) bond lengths reflect the partial delocalization for the formal double bond character of the C=N unit, while the N-C(7) single bond length is typical (refer to Table 3.9.).36 The 38 3.7. Ring Bond Lengths (A) for Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. length (A) Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 N -C(2) 1.378 (3) 1.385 (4) 1.374 (4) C(2) - C(3) 1.382 (4) 1.385 (4) 1.375 (4) C(3) -C(4) 1.414(4) 1.411(4) 1.430 (4) C(4) -C(5) 1.400 (4) 1.392 (4) 1.391 (4) C(5) - C(6) 1.372 (5) 1.375 (5) 1.360(5) N -C(6) 1.342 (4) 1.339 (5) 1.365 (4) Table 3.8. Ring Bond Angles (deg) for Al(nbp)3-3H2Q, Al(npp)3-3H2Q, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. angle (deg) Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 C(2)-N-C(6) 121.3(2) 121.4(3) 120.9 (3) N - C(2) - C(3) 118.7 (3) 117.7 (3) 118.8 (3) C(2) - C(3) - C(4) 120.4 (2) 121.1 (3) 120.6 (3) C(3) - C(4) - C(5) 118.8 (2) 118.8 (3) 118.2 (3) C(4) - C(5) - C(6) 118.6 (3) 118.6 (3) 119.4 (3) N - C(6) - C(5) 122.1 (3) 122.3 (3) 121.9 (3) 39 bonding around the central nitrogen atom is planar within experimental error, with the three bond angles about the nitrogen atom summing to 360° (refer to Table 3.10.). The C(6)-N-C(7) bond angle is slightly compressed from the ideal value of 120° to allow more room for the C(2) substituent which is a methyl group (C(l)}. Table 3.9. Nitrogen-Carbon Bond Lengths (A) forAl(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. length (A) Al(nbp)3-3H20 Al(npp)3-3H20 Ga(npp)3-3H20 N -C(2) 1.378 (3) 1.385 (4) 1.374 (4) N -C(6) 1.342 (4) 1.339 (5) 1.365 (4) N -C(7) 1.481 (4) 1.475 (4) 1.471 (4) Table 3.10. Carbon-Nitrogen-Carbon Bond Angles (deg) forAl(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. angle (deg) Al(nbp)3-3H2Q Al(npp)3-3H20 Ga(npp)3-3H20 C(2)-N-C(6) C(2) - N - C(7) C(6) - N - C(7) 121.3 (2) 121.2 (3) 117.5 (3) 121.4 (3) 120.2 (3) 118.4 (3) 120.9 (3) 121.0 (3) 118.1 (3) 40 Crystal packing forces, which favour the minirnurn energy lattice, are similar for all three trihydrates. Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 all crystallize in the trigonal space group P3. Specific individual reflections were measured to confirm that the crystal was actually trigonal, and not hexagonal. This is the same space group found for the exoclathrates, which means that the trihydrates are isomorphous with the dodecahydrates. There are two tris-ligand metal units in the unit cell, and it is important to remember that there are three lattice water molecules per metal complex molecule in the unit cell. Figures 3.7. and 3.8. show different views of the packing of the unit cell of Al(nbp)3-3H20, while Figure 3.9. shows a stereoview of this packing. Al(npp)3-3H20 and Ga(npp)3-3H20 pack similarly, the only difference being one less methylene group in the nitrogen substituent. Figure 3.10. shows the packing of the unit cell of M(npp)3-3H20 to assure the reader that this is true. The ligand contains non-polar N-substituted pyridinone rings which can be considered hydrophobic.37 These complexes crystallized such that hydrophobic layers of N-substituted pyridinone rings alternated with hydrophilic layers of water molecules (refer to Figure 3.7.). The packing of these tris-ligand metal units is slightly different from that of the previous exoclathrate structures. Figure 3.11. shows the packing of the unit cell of M(mepp)3-12H20. The important feature to notice about this unit cell is the fact that the hydrophobic ring substituents (the methyl and ethyl groups) are all neatly tucked into the center core of the unit cell, with the hexagonal water channels at each corner. The C(2) methyl substituents are not nearly as crowded toward the center of the unit cell as they may at first appear. One of these methyl groups points up the c axis, while the other points down. However, these hydrophobic ligands are completely enclosed by the ubiquitous water molecules of the exoclathrate. In the trihydrates of interest, Figures 3.8. and 3.10. reveal an obvious difference between these structures and the exoclathrate structures; there are no hexagonal water channels at the corners of the unit cell. The usual spatial constraints 41 Figure 3.7. ORTEP view of the unit cell packing of Al(nbp)3-3H20. View is down the b axis. H atoms omitted (except H on water) for clarity. 42 Figure 3.8. ORTEP view of the unit cell packing of Al(nbp)3-3H20. View is down the c axis. 43 Figure 3.9. ORTEP stereoview of the unit cell packing of Al(nbp)3-3H20. View is down the c axis. 44 Figure 3.10. ORTEP view of the unit cell packing of M(npp)3-3H20. View is down the c axis. 45 still cause the C(2) methyl substituents to pack with one methyl group pointing up the c axis, the other pointing down. The space between the hydrophobic ligand and the hydrophilic water fence (shaded oxygen atoms in Figure 3.11.) in the exoclathrate appears sufficient to accommodate one more methylene group. Rather surprisingly, this is not the case, and the single extra methylene group of the /i-propyl substituent precludes the formation of the extensive hexagonal water channels of the exoclathrates, resulting in a more conventional hydrogen bonding network. Changing the size of the nitrogen substituent had other, less dramatic, effects upon the unit cell. Almost all of the cell parameters listed in Table 3.11. undergo a decrease on changing from the ethyl nitrogen substituent to the ^ -propyl nitrogen substituent. This is expected since the trihydrates contain six water molecules per unit cell, whereas the dodecahydrates contain 24 water molecules per unit cell. However, the length of the c axis increases. This is indicative of the strength of the respective hydrogen bonding networks. The hydrogen bonding of the trihydrates is not only less intricate, but also weaker (longer bond lengths), resulting in a longer c axis. The anticipated increases in all of these parameters occurs on changing the N-substituent from a propyl to a butyl group (or from a methyl to an ethyl group). Table 3.11. Unit Cell Dimensions for Tris-ligand Aluminum Complexes. Al(dpp)38 Al(mepp)310 Al(npp)3 Al(nbp)3 a(A) 16.600 (2) 17.1734 (8) 15.328 (1) 15.885(1) c(A) 6.877 (1) 6.827 (1) 7.231 (2) 7.280 (8) Volume (A3) 1641.3 (3) 1743.7 (3) 1471.3 (4) 1591.0 (2) Pcalcd(gcm-3) 1.33 1.33 1.19 1.30 Figure 3.11. ORTEP view of the unit cell packing of M(mepp)3-12H20. View is down the c axis. 47 The symmetrical disposition of the pyridinone rings suggested the possibility of a n-n type of van der Waals interaction (refer to Figure 3.12.). In this type of interaction the nuclei of one pyridinone aromatic ring attract the n electron density of a neighbouring pyridinone ring. Since twice the contact radius of this type of ring is 3.4 A, and the closest approach of two rings in these structures is 3.5 A, this type of stabilizing interaction appears unlikely. A Figure 3.12. ORTEP view of the packing of Al(nbp)3-3H20. H atoms omitted (except H on water) for clarity. 48 Hydrogen bonding increases the crystal field stabilizaton of the lattice.28 When hydrogen is bonded to an electronegative atom (X), and the bond is polar, the hydrogen atom tends to gain a partial positive charge, or acidic character. This in turn enables the hydrogen atom to be attracted by another electronegative atom (Y), yielding a hydrogen bond, X-H-Y. In general, the X-H bond elongates slighdy and the H-Y distance is much longer than the corresponding H-Y covalent bond distance.38 The water molecules form an extensive and important hydrogen bonding network with the oxygen atoms which chelate the metal atom of the trihydrate crystal. In this case, both X and Y are oxygen atoms, X being the oxygen atom of the water molecule and Y the oxygen atom which chelates the metal atom. Table 3.12. summarizes the bond distances and angles involved in this network. Table 3.12. Hydrogen Bonding Distances and Angles for Al(nbp)3-3H20, Al(npp)3-3H20, and Ga(npp)3-3H20 with Estimated Standard Deviations in Parentheses. Complex 0 - 0 (A) 0-H (A) H-0 (A) O-H-0 (°) Al(nbp)3-3H20 03-02 03-H3A H3A-02 03-H3A-02 2.844 (4) 0.88 (7) 1.97 (7) 176(6) 03-01 03-H3B H3B-01 03-H3B-01 3.044 (4) 0.85 (5) 2.25 (5) 152 (5) Al(npp)3-3H20 03-02 03-H3A H3A-02 03-H3A-02 2.839 (4) 0.94 (5) 1.91 (5) 168 (4) 03-01 03-H3B H3B-01 03-H3B-01 3.026 (4) 0.84 (5) 2.23 (6) 158(5) Ga(npp)3-3H20 03-02 03-H3A H3A-02 03-H3A-02 2.843 (4) 0.68 (4) 2.17 (4) 166(5) 03-01 03-H3B H3B-01 03-H3B -01 3.019 (4) 0.84 (5) 2.19 (5) 170(5) 49 In hydrogen bonding, an oxygen atom can be classified as a hydrogen atom donor, or a hydrogen atom acceptor.38 Since the oxygen atoms which chelate the metal atom in the trihydrate have no hydrogen atoms directly attached to them, they are unambiguously hydrogen atom acceptors. The oxygen atoms of the water molecules are unambiguously hydrogen atom donors. A strong hydrogen bond, as seen in the exoclathrates, is indicated by an O-H--O bond angle which approaches the ideal value of 180° and by 0-0 distances less than the sum of their van der Waals radii (2.8 A). Weaker hydrogen bonds are defined by O-H-O bond angles approaching the ideal value of 180°, and H-0 distances which are significantly less than the sum of the van der Waals radii of hydrogen and oxygen. (The van der Waals radius of H is 1.2 A, that of O is 1.4 A, their sum being 2.6 A.) 3 8 By these criteria,the hydrogen bonding in the trihydrates is substantially weaker than in the exoclathrates. The O-H 0 bond angles observed are all greater than 152°, and the H-0 distances are all significantly less than 2.6 A, whereas in the exoclathrates these angles are all greater than 153°, and the 0-0 distances are near 2.7 A. Comparing the hydrogen bond distances and angles in Table 3.12., there is no significant difference in the water network for the trihydrate structures. The loss in strength of the hydrogen bonds relative to the exoclathrates is not surprising, since in the trihydrates two of the three oxygen atoms involved in the water network are chelating a metal atom. A weak hydrogen bond, however, has an estimated enthalpy of 20 - 30 kJ/mol, so that even the less intricate hydrogen bonding network observed in the trihydrate structures results in substantial stabilization of the lattice.28 This more conventional network is built up of water molecules which hydrogen bond chelating oxygen atoms in neighbouring unit cells. An ORTEP view of this network is given in Figure 3.13. These water molecules form an infinite chain down the c axis. They join the hydroxy 0(1) in one ligand to the carbonyl oxygen 0(2) of a ligand rotated by 120° and translated by one unit cell. The O-H and O-O distances vary from 1.91 (5) 50 Figure 3.13. ORTEP view of a part of the hydrogen bonding network of M(npp)3-3H20. This view is down the a axis; all of the atoms in the M(npp)3 units are omitted except for the M06 octahedral coordination sphere. Note that thick lines denote covalent bonds while thin lines denote hydrogen bonds. 51 to 2.25 (5) A and from 2.839 (4) to 3.044 (4) A respectively. The chelating carbonyl 0(2) consistently forms shorter and hence stronger O-H bonds than the chelating hydroxy 0( 1). This may reflect the delocalization of the formal double bond of the carbonyl C(4)-0(2). It is, however, also consistent with the fact that 0(1) forms stronger bonds with the metal atom than 0(2) {the bond length M-0(1) is consistently shorter than that of M-0(2)}. The structural differences between the trihydrates and the dodecahydrates are exaggerated by the increased complexity of the water network in the latter. The extended hydrogen bonding network of the exoclathrate (refer to Figure 3.14.) can be reduced to that shown in Figure 3.15. by removal of the hexagonal water rings, as well as the bridging water molecules to which they are directly attached. The intricate hydrogen bonding network is thus simplified to an infinite chain down the c axis. The similarity to the infinite chain of hydrogen bonded water molecules of the trihydrate structures is striking; in Figure 3.15., comparison of the simplified exoclathrate and the trihydrate structures shows that in the former the essential features of the trihydrate are reproduced intact. In fact, all of these structures are basically isostructural, except that the exoclathrates have more hydrogen bonds to accommodate. The tris-ligand metal complex with the n-propyl substituent could not distort sufficiently to allow it to be accommodated within the rigid hydrogen bonded hexagonal channels. The complicated, energetically favoured water network of the exoclathrates could distort in any number of ways. The fact that the perturbation of the network resulted in the retention of only the infinite chain of hydrogen bonds down the c axis may account for the rarity of these extensive water networks. The interactions between the larger tris-ligand metal molecules appear to take precedence over those between the smaller water molecules, and this helps to explain why the hydrogen bonding seen in the trihydrate structures is more conventional for inorganic hydrates. 52 Figure 3.14. O R T E P view of a part of the hydrogen bonding network of waters in M(mepp)3-12H20. This view down the a axis shows all of the independent O atoms; all of the atoms in the M(mepp)3 units are omitted except for the MOG octahedral coordination sphere. Note that thick lines denote covalent bonds while dashed lines denote hydrogen bonds.10 Figure 3.15. ORTEP view of a part of the simplified hydrogen bonding network of waters in M(mepp)3-12H20 {on the left} and M(npp)3-3H20 {on the right}. This view down the a axis shows the infinite chains of hydrogen bonds which occur along the c axis in both the exoclathrates and the trihydrates. Note that on the left, thick lines denote covalent bonds in the water molecules and M06 units, while dashed lines denote hydrogen bonds. Note that on the right, once again thick lines denote covalent bonds, while thin lines denote hydrogen bonds.10 54 To summarize, a series of Group 13 tris(3-hydroxy-2-methyl-4-pyridinonato) metal(m) complexes was synthesized, in which the nitrogen substituent was n-propyl or n-butyl. The synthesis utilized the metal template effect to effect a pyrone conversion reaction. The importance of steric factors to this synthesis is indicated by the fact that no reaction took place when the bulkier /-propylamine or f-butylamine were used. The complexes formed from the linear amines were characterized by IR, FAB-MS, *H NMR, 2 7 A l NMR, and elemental analysis; the data were fully consistent with the tris-ligand metal species. The IR and NMR data suggested hydrogen bonding within these species, and single-crystal X-ray diffraction studies on three of the six complexes confirmed this. The hydrogen bonds link the metal complexes in an extended array. The network thus formed is substantially less intricate than had been previously observed for the N-methyl and N-ethyl analogues. The latter crystallized as dodecahydrates; the N-n-propyl and N-n-butyl derivatives crystallized as trihydrates. All of these tris(N-substituted-3-hydroxy-2-methyl-4-pyridinonato)metal(III) complexes are isomorphous, crystallizing in the space group P3. The trihydrates and dodecahydrates have similar bond lengths and angles, the only significant difference between the structures being the absence of the extensive hexagonal water channels in the former. Reducing the number of water molecules in the complex from twelve to three reduces the complexity of the hydrogen bonding network, but the essential nature of the tris-ligand metal complex is unchanged. 55 REFERENCES 1. Ganrot, P. O. Environ. Health Perspect. 1986,65, 363. 2. Green, M. A.; Welch, M. J. Nucl. Med. Biol. 1989,16, 435. 3. Hayes, R. L.; Hubner, K. F. Metal Ions Biol.Syst. 1983,16, 279. 4. Clevette, D. J.; Lyster, D. M ; Nelson, W. Ov, Rihela, T.; Webb, G. A.; Orvig, C. Inorg. Chem. 1990,29, 667. 5. Clevette, D. J.; Orvig, C. Polyhedron 1990, 9, 151. 6. Nelson, W. O.; Rettig, S. J.; Orvig, C. / . Am. Chem. Soc. 1987,109, 4121. 7. ' Charalambous, J.; Dodd, A.; McPartlin, M.; Matondo, S. O. G; Pathirans, N. D.; Powell, H. R. Polyhedron 1988, 7, 2235. 8. Nelson, W. O.; Karpishin, T. B.; Rettig, S. J.; Orvig, C. Inorg. Chem. 1988,27, 1045. 9. Matsuba, C. A.; Nelson, W. O.; Rettig, S. J.; Orvig, C. Inorg. Chem. 1988,27, 3955. 10. Nelson, W. O.; Rettig, S. J.; Orvig, C. Inorg. Chem. 1989,28, 3153. 11. Saenger, W. Nature (London) 1979,279, 343. 12. Saenger, W. Nature (London) 1979, 250, 848. 13. Zhang, Z.; Hui, T. L. T.; Orvig, C. Can. J. Chem. 1989, 67, 1708. 14. Elkaschef, M. A-F; Nosseir, M. H. J. Am. Chem. Soc. 1960, 82, 4344. 15. Brown, R. D. J. Chem. Soc. 1951, 2670. 16. Shannon, R. D. Acta Crystallogr. 1976, A32, 751. 17. Bellamy, L. J. The Infrared Spectra of Complex Molecules Volume 2, 2 n d Ed.; Chapman and Hall: New York, 1980; p. 240. 18. Nelson, W. O. Ph.D. Thesis, University of British Columbia, December, 1988. 19. Finnegan, M. M.; Lutz, T. G.; Nelson, W. O.; Smith, A.; Orvig, C. Inorg. Chem. 1987,26,2171. 20. Wilson, B. W.; Costello, C. E.; Carr, S. A.; Biemann, K.; Orvig, C; Davison, A.; Jones, A. G. Anal. Utt. 1979, 72(A3), 303. 21. Pickworth Glusker, J.; Trueblood, K. N. Crystal Structure Analysis, A Primer, Oxford University Press: New York, U. S. A., 1972. 56 REFERENCES CONTD 22. Stout, G. H.; Jensen, L. H. X-ray Structure Determination, A Practical Guide, 2n^ Ed.; John Wiley and Sons: New York, U. S. A., 1989. 23. TEXSAN - TEXRAY Structure Analysis Package, Molecular Structure Corporation, 1985. 24. Cromer, D. T.; Waber, J. T. International Tables for X-ray Crystallography; Kynoch Press: Birmingham, UK, 1974 (Present distributor D. Reidel; Dordrecht The Netherlands); Vol. IV, Table 2.2A. 25. Ibers, J. A.; Hamilton, W. C. Acta Crystallogr. 1964,17, 781. 26. Cromer, D. T.; Waber, J. T. International Tables for X-ray Crystallography; Kynoch Press: Birmingham, UK, 1974 (Present distributor D. Reidel; Dordrecht The Netherlands); Vol. IV, Table 2.3.1. 27. Cotton, F. A.; Wilkinson, G. W. Advanced Inorganic Chemistry, A Comprehensive Text, 4 t h Ed.; John Wiley and Sons: New York, U. S. A., 1980; pp. 63, 71. 28. Cotton, F. A.; Wilkinson, G. W. Basic Inorganic Chemistry; John Wiley and Sons: New York, U. S. A., 1976; pp. 131, 170, 211. 29. The Merck Index, 10th Ed.; Winholz, M.; Budavari, S., Eds.; Merck and Co., Inc.: Rahway, N. J., U. S. A., 1983. 30. Heyns, K.; Vogelsang, G. Chem. Ber. 1954, 87, 1377. 31. Patai, S. The Chemistry of the Amino Group; John Wiley and Sons: New York, U. S. A., 1968; p. 174. 32. Boulton, A. J.; McKillop, A. Comprehensive Heterocyclic Chemistry Volume 2; Katritzky, A. R., Rees, C. W., Eds; Pergamon Press: New York, U. S. A., 1984; p. 1. 33. Katritzky, A. R.; Taylor, P. J. Physical Methods in Heterocyclic Chemistry Volume TV; Katritzky, A. R., Ed.; Academic Press: New York, 1971; p. 266. 34. White, R. F. M.; Williams, H. Physical Methods in Heterocyclic Chemistry Volume IV; Katritzky, A. R., Ed.; Academic Press: New York, U. S. A., 1984; p. 177. 35. Pierpont, C. G.; Buchanan, R. M. Coord. Chem. Rev. 1981,38, 45. 36. Molecular Structures and Dimensions Volume Al; Kennard, O.; Watson, D. G., Eds.; N. V. A. Oosthoek: Netherlands, 1972; p. 52. 37. Morrison, R. T.; Boyd, R. N. Organic Chemistry; Allyn and Bacon, Inc.: Boston, 1973; p. 1060. .« 57 REFERENCES CONT'D Hamilton, W. C; Ibers, J. A. Hydrogen Bonding in Solids; W. A. Benjamin,. Inc.: New York, New York, 1968; 2, 12, 85. 58 APPENDIX 1 8 Table A.l. Crystallographic data for the M(dpp)3 complexes (recorded with a Enraf-Nonius CAD4-F diflfractometer). compound Al(dpp)3'12H20 Ga(dpp)3.12H20 ln(dpp)3-12H20 formula C21H48AIN3O18 C2iH48GaN30ig C21H48I11N3O18 formula weight 657.6 700.3 745.44 crystal system Trigonal Trigonal Trigonal space group P3 P3 P3 a (A) 16.600 (2) 16.6549 (6) 16.842 (1) c(A) 6.877 (1) 6.8691 (4) 6.8078 (7) V(A3) 1641.3 (3) 1650.1 (1) 1672.3 (2) z 2 2 2 D c (g/cm3) 1.331 1.470 1.480 F(000) 704 740 776 radiation Cu-Ka Cu-K 0 Mo-Ka *Ka (A) 1.540562 1.540562 0.70930 1.54439 1.54439 0.71359 nickel filter nickel filtergraphite monochromator H (cm-') 11.97 17.89 7.67 temperature 22*C 22*C 2 r c 2 6 ^ (deg) 150 150 60 reflections with I £ 3a (I) 1662 1653 2496 number of variables 202 195 190 R; Rw 0.045; 0.051 0.047; 0.055 0.033; 0.037 max A/O (final cycle) 0.17 0.023 0.027 goodness of fit indicator 1.020 1.023 1.492 residual density (e/A3) 0.23 0.48 -0.55 to +0.75 (near In) 59 Table A2. Crystallographic data for the M(mcpp)3 complexes (recorded with a Rigaku AFC6). compound Al(mepp)3'12H20 Ga(mepp)3>12 H2O formula C24H54AIN3O18 C24H54GaN30i8 formula weight 699.7 742.4 crystal system Trigonal Trigonal space group P3 P3 a (A) 17.1734 (8) 172A1 (1) c(A) 6.827 (1) 6.830 (2) V (A3) 1743.7 (3) 1759.4 (1) z 2 2 D c (g/cm3) 1.33 1.40 F(000) 752 788 radiation C u - K a M o - K a XKC (A) 1.54178 0.71069 grap hi te-monochro mated graphite-monochromated H (cm"1) 11.56 8.50 temperature 21'C 21*C 2Qmax (deg) 150.3 55.0 reflections with I £ 3o (I) 1157 1918 number of variables 207 215 R; Rw 0.032; 0.038 0.029; 0.036 max A/o (final cycle) 0.23 0.02 goodness of fit indicator 1.63 1.46 residual density (e/A3) 0.10 0.28 Table A.3. Bonding parameters for the M(dpp)3«12H20 complexes. The bond lengths (A) are in the upper portion and the bond angles (deg) are in the lower portion of the table. Atoms M= Al Ga In M-0(1) 1.893 (2) 1.967 (3) 2.134 (2) M-0(2) 1.923 (2) 1.990 (3) 2.165 (2) CK1)-C(3) 1.327 (3) 1.342 (5) 1.343 (3) 0(2)-C(4) 1.299 (3) 1.304 (5) 1.289 (3) N-C(2) 1.369 (3) 1.372 (5) 1.355 (3) C(2)" C(3) 1.385 (3) 1.382 (6) 1.393 (3) C(3) - C(4) 1.423 (3) 1.409 (6) 1.403 (3) C(4) - C(5) 1.398 (3) 1.403 (6) 1.410 (3) C(5)" C(6) 1.360 (3) 1.359 (6) 1.344 (4) C(6) - N 1.360 (3) 1.349 (5) 1.371 (3) C(2) - C(l) 1.493 (3) 1.486 (7) 1.487 (4) N - C(7) 1.476 (3) 1.470 (6) 1.463 (3) 0(1)- M - 0(2) 84.23 (6) 83.22 (12) 77.87 (6) 0(1) -M-0(1) ' 90.81 (8) 90.90(12) 93.58 (6) O(l) - M - 0(2)' 95.71 (7) 96.65 (12) 97.74 (7) 0 (2 ) -M-0( l ) ' B a n s 0(2) - M - 0(2)' 171.85 (7) 89.83 (8) 170.48 (12) 90.01 (12) 166.18 (6) 92.40 (6) M-0 ( l ) -C (3 ) 112.20(13) 110.7 (2) 110.82 (13) 0(1)-C(3)-C(2) 124.5 (2) 122.4 (4) 120.1 (2) O(l) - C(3) - C(4) 115.3 (2) 116.9 (4) 119.1 (2) 0(2) - C(4) - C(3) 116.0 (2) 117.9(4) 120.0 (2) 0(2) - C(4) - C(5) 125.7 (2) 124.2 (4) 123.0 (2) C(6) - N - C(2) 121.2 (2) 121.1 (4) 120.2 (2) N - C(2) - C(3) 119.0 (2) 118.9 (4) 119.7 (2) C(2) - C(3) - C(4) 120.2 (2) 120.7 (4) 120.8 (2) C(3) - C(4) - C(5) 118.4 (2) 117.9(4) 116.9 (2) C(4) - C(5) - C(6) 119.5(2) 119.7 (4) 120.8 (2) C(5) - C(6) - N C(6) - N - C(7) C(2) - N - C(7) 121.7 (2) 117.7(2) 121.1 (2) 121.7 (4) 117.7 (4) 121.1 (4) 121.6 (2) 117.0 (2) 122.8 (2) N - C(2) - C(l) 119.2 (2) 119.4 (4) 118.8 (2) C(l) -C(2)-C(3) 121.9 (2) 121.7 (4) 121.4 (2) 61 Tabic A.4. Bonding parameters for M(mepp)3l2H20 complexes. The bond lengths (A) are in the upper portion and the bond angles (deg) are in the lower portion of the table. Atoms M= Al Ga M-CKD 1.894 (1) 1.962 (1) M-CX2) 1.930(1) 2.00 (1) CKD-C(3) 1.317 (2) 1.327 (2) 0(2)-C(4) 1.297 (2) 1.303 (2) N - C(2) 1.373 (2) 1.376 (3) C(2)-C(3) 1.388 (2) 1.387 (3) C(3) - C(4) 1.424 (2) 1.422 (3) C(4)-C(5) 1.399 (2) 1.396 (3) C(5) - C(6) 1.380 (3) 1.360 (3) C(6)-N 1.342 (3) 1.349 (3) C(2)-C(l) 1.494 (2) 1.485 (3) N - C(7) 1.485 (2) 1.488 (3) C(7) - C(8) 1.504 (3) 1.500 (4) 0( l ) -M-0(2) 84.23 (5) 83.03 (6) O O ) - M - O ( l ) ' 90.46 (6) 90. 52 (6) 0( l ) -M-0(2) ' 94.87 (5) 95.29 (6) 172.50 (5) 171.34 (5) 0(2) - M - 0(2)' 90.93 (6) 91.79(6) M-0(l ) -C(3) 112.1 (1) 111.2 (1) M - 0(2) - C(4) 111.3 (1) 110.7 (1) 0(1)-C(3)-C(2) 124.0 (2) 122.4 (2) 0(1)-C(3)-C(4) 115.5 (1) 117.0 (2) 0(2) - C(4) - C(3) 116.2 (1) 117.5 (2) 0(2) - C(4) - C(5) 125.6(1) 124.9 (2) C(6)-N -C(2) 121.6(1) 120.9 (2) N - C(2) - C(3) 118.8 (2) 118.8 (2) C(2) - C(3) - C(4) 120.5 (1) 120.6 (2) C(3) - C(4) - C(5) 118.1 (1) 117.6 (2) C(4) - C(5) - C(6) 119.2 (2) 120.1 (2) C(5) - C(6) - N 121.8 (2) 122.0 (2) N-C(2)-C( l ) 120.5 (2) 120.2 (2) C(l) - C(2) - C(3) 120.7 (2) 121.0 (2) C(6) - N - C(7) 117.4 (2) 118.0 (2) C(2) - N - C(7) 121.0 (2) 121.1 (2) N - C(7) - C(8) 112.6 (2) 112.5 (2) 62 Table A.5. H-bond distances (A) and angles for M(dpp)3-12H20. Interaction H O O O O - H - O (deg) M = A l Ga Al Ga Al Ga 0(3)-H(a)-0(l) 1.95(6) 1.98(9) 2.861(3) 2.859(5) 161(4) 165(8) 0(3)-H(b)-0(2) 2.08(4) 2.19(6) 2.849(3) 2.842(6) 164(4) 159(7) 0(4)-H(a)-0(6) 2.12(5) 2.19(6) 2.772(3) 2.765(6) 159(5) 164(10) 0(4)-H(b)-0(4) 1.62(8) 1.58(12) 2.747(3) 2.746(5) 168(5) 154(8) 0(5)-H(a)-0(4) 2.06(10) 2.44(12) 2.802(4) 2.807(7) 150(9) 145(22) 0(5)-H(c)-O(5)* 1.50(13) 1.53(24; 2.793(4) 2.779(7) 174(6) 160(10) 0(5)-H(d)-0(5) 2.17(13) 2.793(4) 149(12) 0(6)-H(a)-0(3) 1.72(4) 1.99(8) 2.729(4) 2.734(7) 174(3) 167(8) 0(6)-H(b)-0(5) 2.00(4) 1.91(7) 2.791(4) 2.778(7) 174(3) 171(6) 8 This interaction involves H(05b) for the Ga compound. Table A.6. Hydrogen bond distances (A) and angles for In(dpp)3-12H20. Atoms Interaction O-H (A) H O (A) O O (A) O - H - O (deg) 0(3)-H(03a)-O(l) 1.00 1.92 2.900(3) 165 0(3)-H(03b)-0(2) 0.87(3) 1.99(3) 2.839(3) 168(3) 0(4)-H(04a)-O(6) 0.70(4) " 2.07(5) 2.744(4) 160(5) 0(4)-H(04b)-0(4) 0.87(9) 1.90(9) 2.755(3) 169(6) 0(4)-H(04c)-O(4) 0.72(8) 2.04(8) 2.755(3) 170(6) 0(5)-H(05a)-0(4) 0.82 1.99 2.789(3) 166 0(5)-H(05b)-0(5) 0.77(5) 2.01(5) 2.782(3) 179(5) 0(6)-H(06a)-O(3) 0.66(4) 2.10(4) 2.759(4) 177(5) 0(6)-H(06b)-O(5) 0.74(4) 2.06(4) 2.780(4) 164(4) 63 Table A.l. Hydrogen bond distances (A) and angles for the M(mepp)3»12 H2O complexes. Interaction O H H O O" O-H -O (deg) Al Ga Al Ga Al Ga Al Ga <X3)-H(1) •0(1) 0.81(5) 0.75(4) 2.10(5) 2.14(4) 2.877(2) 2.883(3) 161(4) 173(4) 0(3)-H(2) •0(2) 0.92(7) 0.77(3) 1.95(7) 2.08(3) 2.838(2) 2.834(3) 163(5) 168(3) 0(4)-H(3) <X6) 0.83(7) 0.85(4) 1.99(7) 1.95(7) 2.795(3) 2.784(3) 166(4) 167(4) 0(4>H(4) 0(4) 0.85(8) 0.71(7) 1.97(7) 2.11(7) 2.811(2) 2.810(3) 170(6) 172(5) CX5>H(6) 0(4) 0.89(1) 0.81(3) 2.04(6) 2.03(4) 2.828(3) 2,821(3) 145.83 164(3) CK5>H(5) <K5) 0.82(6) 0.76(3) 2.02(6) 2.08(4) 2.833(2) 2.835(3) 171(4) 175(4) CK6>H(7) •0(3) 0.91(6) 0.79(4) 1.86(6) 2.00(4) 2.771(3) 2.763(3) 173(4) 165(4) 0(6>H(8) <X5) 0.76(8) 0.77(4) 2.11(8) 2.12(4) 2.859(3) 2.849(4) 168(5) 159(4) 

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