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Heterocumulene insertions with group 6 Diaryl Nitrosyl complexes Brouwer, Eric B. 1992

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HETEROCUMULENE INSERTIONS WITH GROUP 6 DIARYL NITROSYLCOMPLEXESByERIC B. BROUWERB.Sc., Queen's University at Kingston, 1990A THESIS SUBMITTED IN PARTIAL FULFILLMENT OFTHE REQUIREMENTS FOR THE DEGREE OFMASTER OF SCIENCEinTHE FACULTY OF GRADUATE STUDIESDEPARTMENT OF CHEMISTRYWe accept this thesis as conformingto the required standardTHE UNIVERSITY OF BRITISH COLUMBIAAugust 1992© Eric Bertrand Brouwer, 1992In presenting this thesis in partial fulfilment of the requirements for an advanceddegree at the University of British Columbia, I agree that the Library shall make itfreely available for reference and study. I further agree that permission for extensivecopying of this thesis for scholarly purposes may be granted by the head of mydepartment or by his or her representatives. It is understood that copying orpublication of this thesis for financial gain shall not be allowed without my writtenpermission.(Signature)Department of Chemistry The University of British ColumbiaVancouver, CanadaDate^September 15, 1992DE -6 (2/88)llAbstractTreatment of the 16-electron complexes Cp*M(NO)(aryl) 2 (Cp* = i5-05Me5; M =Mo, W; aryl = phenyl, o-tolyl, p-tolyl) with the heterocumulenes carbon dioxide, p-tolylisocyanate, and carbon disulfide leads to the i 2-carboxylate-, i2-amide-, and i2-thiocarboxylate-containing complexes, respectively, in 10-50% yields. Treatment with afourth member of the heterocumulene class, diphenylketene, does not result in an isolableinserted complex, although spectroscopic data suggest that insertion has taken place.Cp*M(NO)(aryl)2 complexes thus insert one heterocumulene molecule into a metal-arylbond; the other metal-aryl bond is inert to further insertion. The resulting complexes arethermally stable and air-stable, and can be described as being 18-electron species.Protonolysis of the representative heterocumulene-inserted complex Cp*W(NO){11 2-N(p-tol)C(0)Ph}Ph releases the functionalized heterocumulene molecule, p-tolylbenzamide.All new complexes have been fully characterized by conventional methods. In addition,Cp*W(NO)(r1 2-S2CPh)Ph reacts with the Lewis base trimethylphosphine to formCp*W(NO){11 2-S2C(PMe3)Ph}Ph which contains a zwitterionic phosphonium-betaine ligand.X-ray crystallographic studies of Cp*W(NO){1.1 2-82C(PMe3)Ph}Ph and Cp*W(N0)(11 2 -0NPh)(NPh)Ph are reported and discussed.111Table of ContentsAbstract ^ iiList of Figures vList of Tables ^ viList of Schemes viiList of Abbreviations ^ viiiAcknowledgements xCHAPTER ONE: Chemistry of Carbon Dioxide ^  11.1. Overview ^  11.2. Carbon Dioxide and the Environment ^  11.3. General Chemistry of Carbon Dioxide  31.4. Carbon Dioxide and Chemical Synthesis ^  41.5. Carbon Dioxide and Transition Metals 71.6. Organometallic Nitrosyl Chemistry ^ 141.7. References ^ 16CHAPTER TWO: Synthesis of Heterocumulene-Inserted Complexes ^ 192.1. Introduction ^ 19Historical Background ^ 19Heterocumulenes 20Present Work ^ 212.2. Experimental Section 212.3. Results and Discussion ^ 33Relative Ease of Insertion 45Mechanistic Considerations ^ 462.4. Summary and Future Work 502.5. References ^ 51ivCHAPTER THREE: Reactivity of Heterocumulene-Inserted Complexes ^ 553.1. Introduction ^ 553.2. Experimental Section ^ 563.3. Results and Discussion 60Reaction of Cp*W(NO){i2-N(p-tol)C(0)Ph}Ph with Protonic Acids ^ 60Heterocumulene-Inserted Products and Lewis Bases ^ 65The Solid-State Molecular Structure of Cp*W(NO){1 2-S2C(PMe3)Ph}Ph ^ 70Treatment of Cp*W(NO)(12-S2CPh)Ph with KH ^ 733.4. Summary and Future Work ^ 743.5. References and Notes 76APPENDIX A: Isolation of Cp*W(1 2-0NPh)(NPh)Ph ^ 78A.1. Introduction ^ 78A.2. Experimental Section 78A.3. Results and Discussion ^ 79A.4. Summary and Future Work 85A.S. References ^ 86APPENDIX B: X-ray Crystallographic Analyses ^ 87B.1. X-ray Crystallographic Analysis of Cp*W(NO){112-S2C(PMe3)Ph}Ph ^ 87B.2. X-ray Crystallographic Analysis of Cp*W(1 2-0NPh)(NPh)Ph ^ 94APPENDIX C: Spectral Appendix ^  101List of FiguresFigure 1.1.Figure 1.2.Figure 1.3.Figure 1.4.Figure 2.1.Figure 2.2.Figure 2.3.Figure 2.4.Figure 2.5.Figure 3.1.Figure 3.2.Figure 3.3.Figure 3.4.Figure A.1.Figure A.2.Figure A.3.Atmospheric Carbon-Dioxide Concentrations ^ 3Catalytic Synthesis of Lactones by Palladium Complex ^ 10Modes of Carbon-Dioxide Coordination ^ 11Compounds Containing Coordinated Carbon Dioxide ^ 11The 300 MHz 1H NMR Spectrum of Cp*W(NO)(P-t01)2 35The 300 MHz 1H NMR Spectrum of Cp*W(N0)(12-S2C-p-tol)(p-tol) ^ 36The 300 MHz 1H NMR Spectrum of Cp*Mo(N0)(12-S2C-p-tol)(p-tol) ^ 38The 300 MHz 1H NMR Spectrum ofCp*W(NO){112-N(p-tol)C(0)Ph}Ph ^ 41The 300 MHz 1H NMR Spectra of Reaction 2.7 ^ 48Reaction 3.5 Monitored by IR Spectroscopy 64The 300 MHz 1H NMR Spectrum ofCp*W(NO) { ri2-S2C (PMe3)Ph} Ph ^ 68The 75 MHz 13C{ 1H} NMR Spectrum ofCp*W(NO){112-S2C(PMe3)Ph}Ph ^ 69The ORTEP of Cp*W(NO){1 2-S2C(PMe3)Ph}Ph ^ 71The 300 MHz 1H NMR Spectrum of Cp*W(r1 2-0NPh)(NPh)Ph ^ 81The 75 MHz 13C{ 1H} NMR Spectrum of Cp*W(112-0NPh)(NPh)Ph ^ 82The ORTEP of Cp*W(r12-0NPh)(NPh)Ph ^ 84viList of TablesTable 1.1. Unsaturated Species X =Y that Oxidatively Couple with CO2 ^ 9Table 2.1. Low-Resolution Mass Spectral Data for Heterocumulene-Inserted Complexes ^ 29Table 2.2. Infrared Data for Heterocumulene-Insertion Complexes ^ 30Table 2.3. 1H and 13C{ 1H} NMR Data for Heterocumulene-Insertion Complexes ^ 30Table 3.1. Infrared and Low-Resolution Mass Spectral Data for ChapterThree Complexes ^ 59Table 3.2. 1H and 13C{ 1H} NMR Data for Chapter Three Complexes ^ 59Table 3.3. Selected Bond Distances and Angles forCp*W(NO) {112-S2C(PMe3)Ph}Ph ^ 72Table A.1. 1H and 13C{ 1H} NMR Data for Cp*W(NO)(12-0NPh)(NPh)Ph ^ 79Table A.2. Selected Bond Distances and Metrical Parameters forCp*W(NO)(12-0NPh)(NPh)Ph ^ 84viiList of SchemesScheme 1.1. Carbon-Dioxide Insertions ^ 12Scheme 2.1. RCactivity of CpW(NO)(CH2SiMe 3)2 ^ 20Scheme 2.2. Insertion of Carbon Dioxide into (PMe3)4Ru(r1 2-0C6H3Me) ^ 47Scheme 2.3. Proposed Mechanism of CO2 Insertion into Cp*M(NO)(aryl) 2 ^ 50Scheme 3.1. Stoichiometric Cycle of Cp*W(NO)C1 2 and Heterocumulenes ^ 65List of AbbreviationsA^angstrom, 10-10 mAr^aryl, phenyl, o-tolyl, or p-tolylarom^aromatic; ortho, meta or pars13C^carbon-1313C{ 1 1.1}^proton-decoupled carbon-13calcd^calculatedC6D6^benzene-d6CD2C12^dichloromethane-d2cm-1^wavenumbersCOSY^correlation spectroscopyCp^ri5-05115Cp*^115-05Me5Cp'^Cp or Cp*5^chemical shift in ppm referenced to Me4Si at 5 0d^doublet (in the NMR spectrum)diars^1,2-bis(dimethylarsino)benzenedppe^(Ph)2PCH2CH2P(Ph)2, 1,2-bis(diphenylphosphino)ethaneEt^CH2CH3, ethylEt20^(CH3CH2)20, ether, diethyl etherEI^electron-impacteV^electron volts1H^protonIR^infraredJ^coupling constant (in the NMR spectrum)LUMO^lowest unoccupied molecular orbitalvii'ixm^multiplet (in the NMR spectrum)M^Mo or Wnilz^mass-to-charge ratio in the mass spectrumMe^CH3, methylmmol^millimoleMO^molecular orbitalMS^mass spectrum, mass spectrometryv^stretching frequency (in IR spectrum)NMR^nuclear magnetic resonanceORTEP^Oak Ridge Thermal Ellipsoid Ploto-tol^C6H4Me, ortho-tolyl31p^phosphorus-31[11 +^parent molecular ion (in the mass spectrum)p-tol^C6H4Me, para-tolylPh^C6H5, phenylq^quartet (in the NMR spectrum)quat^quaternary carbon atoms^singlet (in the NMR spectrum)SCE^standard calomel electrodet^triplet (in the NMR spectrum)tetraglyme tetraethylene glycol dimethyl ether, Me(OCH 2CH2)4OMetriphos^1,1,1-tris((diphenylphosphine)methyl)ethaneTHE^C4H80, tetrahydrofuranxAcknowledgementsThere are many to whom I would like to acknowledge my gratitude. I thank PeterLegzdins for his support, encouragement, and enthusiasm over the course of the last twoyears; I believe I have received an excellent training in chemistry from him. I am alsograteful for interesting discussion, helpful comments, and the friendship of my fellowgraduate students Jeff, Cameron, Penny, Steve, Kevin, Rich, Mike, Darlene, John, andMichelle, as well as post-doctoral fellows Roser and George; I hope we all land choice anddeserving jobs. The Departmental staff, particularly Marietta . Austria and Steve Rettig, havebeen of immense assistance. I also would like to express my gratitude to Danielle Dyck forher deep and supportive friendship. As well, I acknowledge the people of Canada for theircontribution in the form of an NSERC scholarship. Finally, I sincerely thank my parents andfamily for their love and nurture. Specifically, my father for his approach to chemistry andlife, both learning and teaching, and my mother for her wisdom and insight.Chapter One:Chemistry of Carbon Dioxide1.1 OverviewThis Chapter presents an overview of the diverse chemistry of carbon dioxide.General aspects are considered first, followed by details pertinent to the research presented inthis Thesis. Chemical research on CO2 has been motivated by the environmental role ofcarbon dioxide and its use as a feedstock in synthetic chemistry. Both facets will bediscussed with the aim of providing a context for the work presented subsequently. Researchon the interactions of carbon dioxide with transition-metal complexes is surveyed briefly withan emphasis on the salient aspects of this active field of work. Chapter One is concludedwith an introduction to organometallic nitrosyl chemistry and an outline of the workpresented in Chapters Two and Three.1.2 Carbon Dioxide and the EnvironmentLife-sustaining temperatures on Earth are maintained by the planet's ability to trap therequisite amount of solar radiation. The maintenance of Earth's heat balance is governed bythe atmospheric levels of water and carbon dioxide. Known as greenhouse gases, both arestrong absorbers in the far-infrared region of the electromagnetic spectrum. The Earth'satmosphere and surface are heated by incoming solar radiation of short wavelength (visibleand ultraviolet), and the resulting heat is distributed about the planet's surface by oceanic andatmospheric circulation. This solar energy is eventually released to space at longerwavelengths (infrared), a process known as reradiation. Greenhouse gases absorb thedeparting energy and in turn, reradiate it in all directions, including some of it back towardsEarth The trapping of energy by these gases results in the loss of less heat to space andconsequently, warmer surface temperatures. This phenomenon is known as the greenhouseeffect. 1 In the absence of greenhouse gases, Earth would be a planet barren of life with anChapter One^ 2average surface temperature of about -15 °C. Naturally occurring greenhouse gases elevatethe mean temperature of Earth to its present 20 °C. 2As atmospheric concentrations of the greenhouse gases increase above natural levels,so does the efficiency of the reradiation process. This, in turn, leads to a scenario in whichthe Earth traps an inordinate amount of heat, producing an unnatural increase in surfacetemperature—a phenomenon known as global warming. While the study of climate is farfrom exact, two trends are well-documented: (1) the increase in the levels of carbon dioxideand other greenhouse gases (methane, NO R , Freons) in the atmosphere and (2) the increase inthe Earth's surface temperature over the past century. Despite argument over the extent towhich these two phenomena are related, most climatologists predict that, if present trendscontinue, a doubling of atmospheric CO 2 levels will cause a temperature rise over the nexthalf century between 1.5 and 4.5 °C. 2Since the onset of industrial development at the beginning of the nineteenth century,atmospheric concentrations of carbon dioxide have increased from an estimated 250 ppm topresent day levels of 356 ppm CO2 . 2,3 Of particular concern is the growth of atmosphericCO2 levels. In the 1960s, the rate of carbon dioxide increase was roughly 0.8 ppm yr -1 ;currently the annual increase is about 1.5 ppm yr1 . The nearly exponential growth ofatmospheric carbon-dioxide concentrations measured at Mauna Loa Observatory, Hawaii isplotted in Figure 1.1.The extent to which global warming and atmospheric carbon dioxide are linked isuncertain. What is certain is that the Earth's temperatures have risen between 0.3 and 0.6 °Cover the last century. When placed in context with the estimated range of averagetemperature fluctuations over the past 10,000 years of only 2 °C, this becomes markedlymore significant. Furthermore, the eight hottest years of this century have occurred since1980. However, average yearly temperatures have previously risen as much as one-half adegree in a century without apparent human interaction, thereby making the present warmingtrend difficult to correlate strongly with human activity.2360350 -E^340 -NO^330-0320 -Chapter One^ 3310^1950^1960^ '^1970 1980^1990^2000^YearFigure 1.1. Atmospheric Carbon-Dioxide Concentrations (ppm by volume). 21.3 General Chemistry of Carbon DioxideThe increase in carbon-dioxide concentrations since the Industrial Revolution isrelated to society's demand for energy. These energy requirements have, in general, beensated by the versatility and abundance of fossil fuels such as coal, natural gas, oil, andgasoline. Combustion of hydrocarbon-containing materials with oxygen is an easilyaccessible means of releasing energy as the chemical process is very exothermic (eq 1.1).{CH2O} + 02^CO2 + H2O + heatCombustion, as in the above equation, is not strictly a human phenomenon. Carbondioxide is produced and released to the atmosphere by the decay of biomass and respirationof various organisms. There are also natural processes in which carbon dioxide is removedfrom the atmosphere, processes known as fixation of carbon dioxide. Fixation is carried outin two ways, the first of which is the hydrospheric chemical conversion of dissolved CO 2 tobicarbonate (HCO3 -) and carbonate (CO32-) in the form of acid-base equilibria (eqs 1.2-1.3).Chapter One^ 4CO2 + H2O H+ + HCO3 -^(1.2)HCO3- H+ + CO32-^(1.3)Carbonate may undergo further transformations involving (1) reaction with alkaline earthcations to produce calcium carbonate (limestone) and (2) formation of shells by diatoms andshelled organisms. The second means of carbon-dioxide fixation is via photosynthesis (eq1.4). By utilizing the energy of sunlight, algae and green plants convert water and energy-poor carbon dioxide to energy-rich organic molecules and molecular oxygen, 4 the reverse ofreaction 1.1. The active components of photosynthesis involve metal complexes ofmagnesium, manganese, iron, and copper making this form of CO2 fixation the chemicallymore interesting process (vide infra). 5hvCO2 + H2O ---11` {CH20 }^02^ (1.4)Via photosynthesis, glucose is synthesized at a rate of 1 g per hour per square metre of plantsurface. It is estimated that approximately 200 billion tonnes of glucose are produced eachyear by photosynthesis. 31.4 Carbon Dioxide and Chemical SynthesisCarbon dioxide is abundant and inexpensive, two features which render it attractive asa synthetic feedstock. However, the utilization of CO 2 in synthesis is limited by its lowreactivity; this is why carbon dioxide (liquid and solid) was only the number eighteenchemical (by mass) produced in the United States with an annual consumption of 4.7 x 10 6tonnes (1990). 6 Large-scale industrial syntheses using CO 2 as a feedstock generally requirehigh temperatures and pressures and/or the use of catalysts. There are four important large-Chapter One^ 5scale processes that employ CO2 as a reagent in the synthesis of organic molecules: 3(1) the production of urea,(2) the synthesis of cyclic carbonates,(3) salicylic acid synthesis, and(4) the production of methanol.Each synthetic process will be considered in turn.(1) The Production of Urea. The synthesis of urea, an important nitrogen-containingfertilizer, from ammonia and carbon dioxide is presently the largest process which uses CO 2as a reagent. Discovered in 1870, this reaction proceeds at elevated temperatures andpressures (150-200 °C, 150-250 atm) (eq 1.5). In 1990, North-American production ofurea was 9.8 million tonnes; urea is the third most important chemical by weight in theCanadian chemical industry.?CO2 + 2 NH3 9H2NCNH2 + H2O (1.5)(2) The Synthesis of Cyclic Carbonates. Cyclic carbonates are used as high-boilingsolvents in the production of synthetic polymers. The synthesis of cyclic carbonates iscarried out via the Hiils process (eq 1.6), developed in Germany during the Second WorldWar. It combines carbon dioxide with ethylene oxides in the presence of a catalyst./O\H2C —OAR + CO2cat. 0 (0R = H, Me^(1.6)(3) Salicylic Acid Synthesis. Salicylic acid (o-hydroxybenzoic acid) and its derivativesare widely used in the preparation of pharmaceuticals, dyes, and pesticides. Its most familiarderivative, acetylsalicylic acid, is better known by its trade name Aspirin. In the UnitedStates 25,000 tonnes of salicylic acid per year are used in the synthesis of Aspirin (1980).Chapter One^ 6Discovered by Kolbe in 1874 and modified by Schmitt a decade later, the Kolbe-Schmittprocess involves the carboxylation of sodium phenolate under mild (5 atm) CO 2 pressures (eq1.7). CO2 H+(4) The Production of Methanol. Synthesis gas (CO/2H2) is a popular mixture usedin the industrial preparation of methanol (eq 1.8), an important chemical with productionquantities in the United States (1990) of 3.8 x 106 tonnes per year. 6 Some processes whichproduce synthesis gas result in a 1:3 molar carbon monoxide to hydrogen ratio (instead of theusual 1:2 molar ratio), and in these cases carbon dioxide may be introduced to compensatefor the additional mole of hydrogen (eq 1.9).CO + 2 H2^CH3OH^ (1.8)CO2 + 3 H2 -IP- CH3OH + H2O^ (1 .9)Significant non-synthetic industrial uses of carbon dioxide are based on its relativeinertness. CO2 is added to beverages, used in deep freezing as dry ice, and serves as aprotective gas in the manufacture of air-sensitive foods. At pressures of up to 400 atm, CO2is used as a supercritical fluid to extract caffeine from coffee beans to prepare decaffeinatedcoffee. 8 Other uses of carbon dioxide include its use as fire-extinguishing and aerosolpropellant agents. CO2-lasers also make use of carbon dioxide.Since CO2 is a highly oxidized form of carbon, it is perceived to be a very stablemolecule. However, this apparent inertness is frequently due to the kinetics of a particularreaction rather than to the enthalpy change, as the thermodynamic behaviour of CO 2 iscomparable to that of carbon monoxide. 3 Reactions of carbon dioxide often have a highChapter One^ 7energy of activation, and one approach to lowering this barrier has been to activate CO2 at atransition-metal centre. A dramatic illustration of carbon-dioxide activation is that of thephysiological reaction of CO2 and water to produce hydrogen carbonate. This reaction isnormally quite slow, but in the presence of carbonic anhydrase, a zinc-based enzyme, theprocess is accelerated significantly. 9 Carbonic anhydrase is found in animals and humans andis an extremely efficient biocatalyst, functioning at physiological pH and possessing turnoverrates of up to 106 reactions per minute. 5,101.5 Carbon Dioxide and Transition MetalsEfforts to activate carbon dioxide at transition-metal centres were initiated in the1960's. Wilkinson and coworkers oxidatively coupled dioxygen and carbon dioxide on aplatinum centre giving a peroxycarbonato complex (eq 1.10). 11^R3P\ /PR3^ R3P\ 0Pt^+ CO2 + 02 -----'^Pt/^+ 2 PR3^(1.10)R3P/^PR R3P 0Since then, the area of carbon-dioxide activation by organometallic complexes has expandedgreatly. 3 Although the sheer diversity of CO2 reactions defies easy systematization, thereactions of carbon dioxide with transition-metal complexes can be broadly categorized asfollows:(1) electrochemical activation of carbon dioxide,(2) oxidative coupling of CO2 ,(3) carbon dioxide coordination, and(4) insertion of carbon dioxide.Each of these processes will now be considered in turn.Chapter One^ 8(1) Electrochemical Activation of Carbon Dioxide. Direct electrochemical reductionof CO2 is an attractive means to activate carbon dioxide, although this approach is hamperedby rather negative potentials (-2.0 V vs SCE) at which this occurs. 12 Depending on reactionconditions, CO2 reduction affords oxalate, formate, carbonate, and carbon monoxide. Thehigh overpotential of carbon dioxide can be decreased by transition metal-based catalystswhich can additionally offer selectivity to one or more reduction products. Systemscontaining the electron-rich late transition metals (especially Group 10) best facilitate theseendeavours. For example, benzoic acid is formed in nearly quantitative yields fromelectrolysis of bromobenzene and carbon dioxide in the presence of catalytic amounts ofNin(dppe)C12 (dppe = 1,2-bis(diphenylphosphino)ethane) (eq 1.11). 12CO2-^(1.11)Ni(dppe)C 12 -BrElectrochemical reductive activation of CO2 with 1,3-enynes by the catalyst [Ni 11(2,2'-bipyridine)3](BF4)2 leads to the stereoselective production of diene carboxylic acids (eq1.12). 13H><HOOC^H1)Ni cat.+ CO2 ^2) H+(1.12)COOH(2) Oxidative Coupling of CO2. In the coordination sphere of electron-rich transition-metal complexes, carbon dioxide can oxidatively couple with unsaturated substrates to form[2+2+1J-cycloaddition products (eq 1.13). Oxidative coupling may occur by (1) activationof the unsaturated organic fragment X =Y, (2) activation of CO2, or (3) simultaneous(1.13)N4,0X—Y[M] + X=Y + 0=C=0Chapter One 9activation of both substrates at the metal. Examples of oxidative coupling abound 3 (Table1.1), mainly with Ni° systems. In general, the only criterion for the metal centre is that ithave high electron density. Both stoichiometric and catalytic cycles exist. 14Table 1.1. Unsaturated Species X = Y that Oxidatively Couple with CO2 .0-containing N-containing C-containing0=0RN=O0=C =0RHC =0RHC =NRRN=C=NRalkenealkynedieneketeneLactones have been synthesized catalytically from carbon dioxide and 1,3-butadiene in thepresence of palladium complexes. The Pd 11 catalyst precursor is first reduced to Pd°, thencoordinates butadiene, which then undergoes carbon-dioxide insertion. Reductive eliminationaffords lactones and regenerates the active Pd° catalyst (Figure 1.2). 15(3) Carbon-Dioxide Coordination. Carbon dioxide has two potential sites ofreactivity: oxygen and carbon. The electron-rich oxygen atoms are sites for electrophilic(E+) attack and are described as Lewis-base sites. In contrast, the electron-poor carbon atomis a Lewis-acid centre and is susceptible to attack by nucleophiles (Nu -). A metal centre canE+^0=C=0 -310. E— 0—C=0Nw 0=C=0 O-C=0NuChapter One^ 102pd114^pdoi, CO2Figure 1.2. Catalytic Synthesis of Lactones by Palladium Complex.be described as electron-rich or electron-poor, depending on its position in the periodic table,its surrounding ligand field, and whether the complex bears a formal charge. The nature ofthe metal complex determines the mode of interaction with CO 2 . Bonding modes of CO2 aresummarized in Figure 1.3. Complexes containing early transition metals and cationiccomplexes are generally electron-deficient and thus tend to interact with the oxygen lonepairs of CO2 , either in an 12-carboxylate (I) or ri 1-end-on (II) fashion. Conversely, latetransition-metal complexes and anionic complexes are electron-rich and interact with carbondioxide via the electrophilic carbon atom (III). Finally, for those transition-metal complexesthat are intermediate to these extremes, a carbon-oxygen double bond can act as a n-acid in asynergic interaction with the metal (IV).AsThAs /0CI—Rh^CAs^\OAsMo—C0Chapter One^ 110^ 0^/o\ ME-- OCO^M C M—v/< / C \0 0^0Figure 1.3. Modes of Carbon-Dioxide Coordination.There are no examples reported in the literature of transition metal-carbon dioxideadducts with bonding as in mode I. Bonding in an end-on manner (II) is similarly rare,although this mode has been detected at cryogenic temperatures for carbon-dioxide matricescontaining copper and titanium oxide. 16 Carbon-dioxide adducts with i 1 -coordination of theLewis-acidic carbon (III) are marginally more common and form with electron-rich Group 8and 9 metals. One of the few structurally-characterized complexes is Rh(diars) 2C1(r1 1 -0O2)(diars = 1,2-bis(dimethylarsino)benzene) (Figure 1.4). 17 In this molecule, the carbondioxide is trans to the chloride and is thought to be stabilized by intramolecular interaction ofthe oxygen atoms with the hydrogen atoms on the nearby methyl groups of the diars ligands.The bonding of the fourth mode is exemplified in the complex (11 5-051-15)2Mo(12-0O2)(Figure 1.4) in which the carbon dioxide can be viewed as undergoing bifunctionalactivation: at carbon, electron-rich molybdenum behaves as a Lewis base whereas the weaklyacidic hydrogen atoms of the 1 6-05H5 ligand interact with the basic oxygen. 18Figure 1.4. Compounds Containing Coordinated Carbon Dioxide.liM-OCH^0I IM-OCOR0Ivi-CR3).^000R3CO2M- 11MO0M-OCNR2M-NR2OM-OCPR3Chapter One^ 12Scheme 1.1. Carbon-Dioxide Insertions. 3(4) Insertions of Carbon Dioxide. Of particular interest to this work is the insertionof CO2 into metal-ligand bonds, and as shown in Scheme 1.1, carbon dioxide inserts into ahost of metal-ligand bonds. Despite the abundance of examples of such insertions, thegeneral trends and characteristics of CO 2 insertions are not as well developed as those forcarbon monoxide. 19 From a theoretical aspect, there are three bonding orientations that arisefrom CO2 insertion into a metal-carbon bond: 0-bound to the metal giving ri 1 -and 112-metalcarboxylates (A, B) or C-bound to form 1-metalated formate esters (C). Without exception,all of the characterized CO2-inserted complexes are metal carboxylate complexes (A, B).Chapter One^ 130^/ 0^ 0MM-0—CR^ M—C—ORN oA BThe most thoroughly studied insertion of carbon dioxide into metal-hydride bonds hasbeen with the anionic Group 6 complexes, [M(C0)511] - (M = Cr, W), which result in theanionic formate complexes [M(C0)5(CO 2H)] - . 2° Carbon dioxide inserts twice into the W-Hbonds of WH6 (PMe3)3 with loss of H2 to give WI12(/2-02CH)(11 1-02CH)(PMe3)3 , acomplex that has both 1 1- and 12-formate ligands. 21 In both cases, insertion is thought toproceed not by initial ligand (CO or phosphine) dissociation, but by electrophilic attack of theacidic CO2 carbon on the hydridic hydride ligands.Insertion of carbon dioxide into metal-carbon bonds has received much attention, themotivation being the potential of new carbon-carbon bond formation. The ability to study thefundamental first step in carbon-dioxide activation by naturally-occurring transition metalcomplexes is of equal importance. Both early- and late-transition metal complexes withmetal-alkyl or metal-aryl bonds insert CO2 . All inserted products contain the metalcarboxylate linkages with either Ti 1- or 12-coordination. For example, the square planar(PMe3)3Rh(Ph) complex inserts one molecule of CO2 to give first an 1 1-benzoate, then uponloss of phosphine, the 1 2-benzoate (eq 1.14). 22PMe3.„.„ CO2Me3P—Rh —rnPMe3 O^PMe3II^PMe3Me3P— Rh — OCPh Me3P— Rh —0I^, 1PMe3 0^N (1.14)PMe3PhMechanistic studies of carbon-dioxide insertion reactions have been carried out byDarensbourg and coworkers on the anionic [W(CO)5R] - (R = alkyl, aryl) complexes 23 andChapter One^ 14by Bergman's group on a ruthenium system having a 4-memberedmetallacycle with Ru-C, Ru-O, and Ru-N variants. 24 In the tungstencases, insertion proceeds in a concerted manner involving a transition state(left) without any prior dissociation of CO. For the ruthenium system, theinsertion mechanism is dependent on the a-heteroatom in the metallacycle.For the oxygen-containing complex, the general insertion mechanismholds: phosphine dissociation followed by CO2 coordination and migration of the aryl group.The Ru-amide, on the other hand, requires no phosphine dissociation as CO 2 coordinates tothe nitrogen lone pair before inserting into the Ru-amide bond. Unlike CO insertions,carboxylations seem to be only marginally dependent on the nature of the R-group.L = PMe3Carbon-dioxide insertions into metal-carbon bonds also occur for unsaturated speciessuch as coordinated olefins, 25 alkynes, 26 and dienes27 to give 5- and 7-memberedmetallacycles. Metal-nitrogen, 28 -silicon,29 -oxygen30 and -phosphorous31 bonds also insertcarbon dioxide (cf. Scheme 1.1).1.6 Organometallic Nitrosyl ChemistryThe transition-metal complexes used in the activation ofcarbon dioxide and its analogues presented in this Thesis havethe general formula Cp*M(NO)(aryl) 2 (Cp* = Ti5-05Me5 ; M =Mo, W) and are described as nitrosyl complexes due to thepresence of the metal-bound nitrosyl (NO) ligand. Thesecompounds have the monomeric 'three-legged piano stool'structure (right). In this configuration the linear nitrosyl ligandChapter One^ 15acts as strong ic-acid towards the metal centre. 32In organometallic chemistry, a complex is generally most stable when the number ofelectrons in the metal's valence shell (from both the metal itself and from the surroundingligands) totals 1,8 and results in a full valence shell. This is known as the '18-electron rule'.This rule is a rule in name only, as it is best used as a guide to suggest probable stablearrangements of ligands and metals; it cannot predict accurately a stable or unstableelectronic configuration. The electron-counting formalism used in this Thesis considers allligands and metals to be neutral, except where there is an overall charge on the complex.The electron count of the stable complex Cp*W(NO)(CO)2 is considered below:Component^Number of ElectronsCp* 5W^6NO 32 x CO^2 x 2Total: 18OC^CON0Previous research has established the thermal and oxidative stability of theCpM(NO)R2 (Cp = 15-05H5 ; R = bulky alkyl) family, 33 relatively surprising propertiessince these are formally 16-electron complexes. Being both coordinatively and electronicallyunsaturated, this class of complexes displays a rich and varied chemistry reflective of thesebonding characteristics. The recently reported diaryl analogues exhibit preliminary studies ofthe chemical reactivity even greater than the dialkyl family due to the decreased steric bulkand increased electron-withdrawing capabilities of the aryl ligands over their alkylconfreres. 34The research presented in this Thesis utilizes the high potential reactivity ofCp*M(NO)(aryl)2 complexes in the activation of carbon dioxide and analogues of CO2 .Chapter Two deals with the insertion reactions of four heterocumulenes (CO 2 , p-tolylisocyanate, CS2, and diphenylketene) into W- and Mo-aryl bonds. The characteristics of theChapter One^ 16insertion reactions are discussed, complemented by mechanistic proposals and bycomparisons of the relative ease of heterocumulene insertions. Chapter Three contains theresults of the investigation of the subsequent chemistry of the inserted complexes andaddresses the question of what manipulations are necessary and feasible to complete theactivation and functionalization of CO 2 and analogues.1.7 References(1) Manahan, S. E. Environmental Chemistry, 4th ed.; Brooks/Cole: Monterey, CA,1984; Chapter 11.(2) Chem. Eng. News, 1992, 70(17), 7-19.(3) Behr, A. Carbon-Dioxide Activation by Metal Complexes; VCH: Weinheim,Germany, 1988.(4) Bishop, M. B.; Bishop, C. B. J. Chem. Educ. 1987, 64, 302-305.(5) Huheey, J. E. Inorganic Chemistry: Principles of Structure and Reactivity, 3rd ed.;Harper and Row: New York, 1983; pp 853-865.(6) Chem. Eng. News, 1992, 70(15), 16.(7) Chem. Eng. News, 1991, 69(49), 36-60.(8) Alwani, Z. Angew. Chem., Int. Ed. Engl. 1980, 19, 623.(9) Zubay, G. Biochemistry; Addison-Wesley: Don Mills, ON, 1983; pp 236-37.(10) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry, 5th ed.; Wiley: NewYork, 1988; pp 1361-1362.(11) (a) Hayward, P. J.; Blake, D. M.; Nyman, C. J.; Wilkinson, G. J. Chem. Soc.,Chem. Commun. 1969, 987-988. (b) Hayward, P. J.; Blake, D. M.; Wilkinson, G.;Nyman, C. J. J. Am. Chem. Soc. 1970, 92, 5873-5878.(12) Armatore, C.; Jutand, A. J. Am. Chem. Soc. 1991, 113, 2819-2825.(13) Derien, S.; Clinet, J.-C.; Dunach, E.; Perichon, J. J. Organomet. Chem. 1992, 424,213-224.Chapter One^ 17(14) Behr, A. Angew. Chem., Int. Ed. Engl. 1988, 27, 661-678.(15) Braunstein, P.; Matt, D.; Nobel, D. J. Am. Chem. Soc. 1988, 110, 3207-3212.(16) Mascetti, J.; Tranquille, M. J. Chem. Phys. 1988, 92, 2177-2184.(17) Calabrese, J. C.; Herskovitz, T.; Kinney, J. B. J. Am. Chem. Soc. 1983, 105,5914-5915.(18) Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. J. Am. Chem. Soc.1985, 107, 2985-2986.(19) Yamamoto, A. Organotransition Metal Chemistry; Wiley: New York, 1986; Chapter6.(20) Darensbourg, D. J.; Rokicki, A.; Darensbourg, M. Y. J. Am. Chem. Soc. 1981,103, 3223-3224.(21) Lyons, D.; Wilkinson, G. J. Chem. Soc., Dalton Trans. 1985, 587-588.(22) Darensbourg, D. J.; Grotsch, G.; Wiegreffe, P.; Rheingold, A. lnorg. Chem. 1987,26, 3827-3830.(23) Darensbourg, D. J.; Kudaroski-Hanckel, R.; Bauch, C. G.; Pala, M.; Simmons, D.;White, J. N. J. Am. Chem. Soc. 1985, 107, 7463-7473.(24) Hartwig, J. F.; Bergman, R. G.; Anderson, R. A. J. Am. Chem. Soc. 1991, 113,6499-6508.(25) Hoberg, H.; Ballesteros, A.; Sigan, A. J. Organomet. Chem. 1991, 403, C19-C22.(26) Kolomnikov, I. S.; Lobeeva, T. S.; Gorbachevskaya, V. V.; Aleksandrov, G. G.,Struckhov, Y. T.; Vol'pin, M. E. J. Chem. Soc., Chem. Commun. 1971, 972-973.(27) Yasuda, H.; Okamoto, T.; Matsuoka, Y.; Nakamura, A.; Kai, Y.; Kanehisa, N.;Kasai, N. Organometallics 1989, 8, 1139-1152.(28) (a) La Monica, G.; Cenini, S.; Porta, F.; Pizzotti, M. J. Chem. Soc., Dalton Trans.1976, 1777-1782. (b) Cowan, R. L.; Trogler, W. C. J. Am. Chem. Soc. 1989, 111,4750-4761.(29) Campion, B. K.; Heyn, R. H.; Tilley, T. D. Inorg. Chem. 1990, 29, 4355-4356.Chapter One^ 18(30) Darensbourg, D. J.; Sanchez, K. M.; Reibenspies, J. H.; Rheingold, A. L. J. Am.Chem. Soc. 1989, 111, 7094-7103.(31) Vaughan, G. A.; Hillhouse, G. L. Organometallics 1989, 8, 1760-1765.(32) Richter-Addo, G. B.; Legzdins, P. Metal Nitrosyls; Oxford University Press: NewYork; 1992; Chapter 1.(33) (a) Legzdins, P.; Rettig, S. J.; Sanchez, L.; Bursten, B. E.; Gatter, M. G. J. Am.Chem. Soc. 1985, 107, 1411-1413. (b) Legzdins, P.; Rettig, S. J.; Sanchez, L.Organometallics 1988, 7, 2394-2403.(34) Dryden, N. H.; Legzdins, P.; Rettig, S. J.; Veltheer, J. E. Organometallics 1992,11, 2583-2590.Chapter Two:^ 19Synthesis of Heterocumulene-Inserted Complexes2.1 IntroductionHistorical Background. The Cp*M(NO)(aryl)2 (Cp* = 115-05Me5 ; M = Mo, W)systems presented in this Thesis have their historical roots in the 1985 discovery of the 16-electron dialkyl family of complexes: 1M = W; R CH2SiMe3 , CH2CMe3 , CH2CMe2PhMR7N0M = Mo; R = CH2SiMe3These complexes, despite being both coordinatively and electronically unsaturated, displayremarkable thermal and oxidative stability. For example, the solid complexes can be handledin air for short durations without observable decomposition. Both the ease of syntheticaccess to, and the robust nature of, this family of complexes were key to the subsequentdevelopment of their chemistry.Studies conducted on the CpM(NO)R2 (Cp = ii5-05H5) family showed it to possessversatile and diverse reactivity. The coordinative unsaturation and Lewis-acid properties ofthese complexes were utilized successfully in their reactions with a variety of molecules(Scheme 2.1). 2 Of particular relevance to the present work are the facile insertion reactionsof a number of small molecules into the tungsten-alkyl bonds.Until recently, study of the related Cp'M(NO)(aryl) 2 (Cp' = Cp, Cp*) chemistry washampered by the inability to synthesize these complexes in acceptable yields. However, withthe use of different arylating agents and improved methodology, these difficulties wereovercome. 3 The decreased steric bulk and increased electron-withdrawing capabilities of thearyl ligands relative to the alkyl ligands result in a reactivity greater than that displayed bythe analogous dialkyl system, as the diaryl complexes are markedly more potent Lewis acids.R N\ R°•Ame3ON PMe310,R N R0vs Eg2/8 Se2/8 E81120Plote 3vacuumI2 NO•R 161 0—N.RR=CH2SiMe3. R =t—Bu. E=S.SeEIS I i/e S8RA N0■RES•:=•RE N ER0Chapter Two^ 20This feature is illustrated by the different behaviours with the classic Lewis base PMe 3 . Arepresentative dialkyl complex, Cp*W(NO)(CH2SiCH3)2, fails to coordinate the phosphine,whereas Cp*W(NO)(aryl)2 complexes form adducts irreversibly with PMe3. 3Scheme 2.1. Reactivity of CpW(NO)(CH2SiMe3)2.One type of reactivity not yet explored involves the treatment of the Cp'M(NO)R2system with carbon dioxide and analogous molecules. The reactivity of Cp'M(NO)R2 withcarbon dioxide is expected to yield insertion products. However, as described in ChapterOne, carbon dioxide is notoriously difficult, from a synthetic perspective, to activate. Inresponse to this challenge, the high reactivity of the Cp*M(NO)(aryl)2 system was chosen tocountervail the relatively low reactivity of carbon dioxide.Heterocumulenes. Allene, CH2=C =CH2, contains two sites of unsaturationdistributed over three carbon atoms and belongs to the cumulene family of molecules. 4 Theclass of molecules known as heterocumulenes displays similar bonding, with the allene C 1and/or C3 being replaced by non-carbon atoms. Some members of heterocumulene familyare listed below.Chapter Two^ 210=C =0^RN=C =0^R2C=C=NRS =C=0 RN=C=NR R2C=C=SS=C=,^R2C=C =0^RN=C=SThe study of heterocumulenes in organometallic chemistry has been motivated largelyby the fact that they are valence isoelectronic with carbon dioxide and thus, their reactivity isexpected to parallel that of CO2 . 5 Complexes that react with non-carbon dioxideheterocumulenes should, by this analogy, react with carbon dioxide. In some cases thispostulate holds. For example, the Cp 2ZrR2 (R=alkyl, aryl) system reacts with ketenes(R2C =C =0), isocyanates (RN=C =0), carbodiimides (R2N=C=NR 2), as well as carbondioxide to give the corresponding insertion products. 6However, there are instances in which heterocumulenes fail to model the reactivity ofcarbon dioxide. Thus, while [Et4N][W(C0)5(0-2,6-Ph2C6H3)] reacts readily with carbonylsulfide (COS), it is unreactive to CO2, even at pressures of 900 psi. 7 One of the failures ofthe heterocumulene-carbon dioxide analogy is that heterocumulenes are generally morereactive due to increased polarity of the unsaturated linkages over that found in CO2 . 6,8Present Work. The reactivity of the Cp*W(NO)(aryl)2 (M = Mo, W) system withfour heterocumulenes (carbon dioxide, carbon disulfide, p-tolyl isocyanate, anddiphenylketene) is described in this Chapter. These reactions proceed under mild conditionsand result in the insertion of the heterocumulene molecule into one metal-aryl bond; furtherinsertion into the other metal-aryl bond is not observed under these conditions. The insertedproducts display both thermal stability and air-stability and can be described as beingcoordinatively and electronically saturated.2.2 Experimental SectionAll reactions and subsequent manipulations involving organometallic reagents wereperformed under anhydrous conditions in an atmosphere of purified dinitrogen.Chapter Two^ 22Conventional drybox and Schlenk techniques were utilized. 9 The complexes Cp*M(NO)C1 2(M = Mo, W) were prepared by published procedures; 10 Cp*Mo(NO)Cl2 was recrystallizedby Soxhlet extraction with dichloromethane. The syntheses of complexes Cp*M(NO)(aryl) 2(M = W, Mo) were carried out with modifications to published procedures. 3 All reagentswere purchased from Aldrich and used as received unless otherwise specified. Researchgrade carbon dioxide (99.995%) was purchased from Matheson. Diarylmagnesium reagentswere synthesized by established routes 3 , and stoichiometries determined by titration with 0.1N HC1 using the indicator phenolphthalein, or in the case of Ph2Mg•Et20.1/2(dioxane),determined by elemental analysis. Solvents were freshly distilled from appropriate dryingagents under a dinitrogen atmosphere and purged for 5-10 min with argon or were directlyvacuum-transferred from the appropriate drying agent. Tetrahydrofuran (THF), diethyl ether(Et20), and dioxane were distilled from sodium/benzophenone; benzene, hexanes, andpentane were distilled from sodium/benzophenone/tetraglyme. Triethylamine (Et3N) wasdistilled from calcium hydride; dichloromethane (CH 2C12) and carbon disulfide (CS2) weredistilled from P2O5. Deuterated benzene (C6D6) and dichloromethane (CD 2C12) werepurchased from MSD Isotopes, dried on 4 A molecular sieves, and degassed by severalfreeze-pump-thaw cycles.All infrared (IR) spectra were recorded on a Nicolet 5DX FT-IR spectrometer,internally calibrated with a He/Ne laser, as solutions or as Nujol mulls between NaC1 plates.All 1 H, 13C, and 31P nuclear magnetic resonance (NMR) spectra were obtained on VarianAssociates XL-300 or Bruker AC-200 spectrometers. The chemical shifts of the observed 1Hand 13 C resonances are reported in parts per million downfield from Me4Si referenced to theresidual proton (5 7.15, 5.35 ppm) or the natural abundance carbon (5 128.00, 53.80 ppm)signals of C6D6 or CD2C12 , respectively. The 31P resonances are referenced to 85% H 3PO4and chemical shifts are reported in parts per million downfield from this signal. Delay timesof up to 10 s were required to obtain certain 13C resonances. Mrs. M. T. Austria, Ms. L. K.Darge, and Dr. S. 0. Chan assisted in the collection of the NMR data. X-raycrystallographic analyses were performed by Dr. S. J. Rettig. Low-resolution mass spectraChapter Two^ 23(EI, 70 eV) were recorded on a Kratos MS50 spectrometer using the direct-insertion methodby Dr. G. K. Eigendorf and Mr. M. A. Lapawa. All elemental analyses were performed byMr. P. Borda.Preparation of Cp*W(NO)Ph2. Solid Cp*W(NO)C12 (1.51 g, 3.60 mmol) wasweighed in air and transferred to a Schienk tube. The atmosphere was removed, and the tubeand contents were taken into the drybox. Ph2Mg•Et20.1/2(dioxane) (1.09 g, 7.22 mmolPh-) was mixed thoroughly with the dichloride reagent. THE (25 mL) was introduced intothe Schlenk tube by vacuum transfer on a vacuum line. The THE solution was warmed to-30 °C and held at that temperature for one hour as the solution turned an intense royal blue.The solvent then was removed in vacuo. The residue was extracted with diethyl ether (30mL) and then was transferred to the top of a column of Florisil 60-100 (2 x 3 cm) supportedon a sintered glass frit. The column was eluted with Et20 (120 mL), and the resulting royalblue eluate was concentrated and cooled overnight at -30 °C to yield blue crystals (0.83 g,1.6 mmol, 46% yield). Anal. Calcd for C 22H25NOW: C, 52.50; H, 5.01; N, 2.78. Found:C, 52.50; H, 4.93; N, 2.78. IR (Nujol mull) v(NO) 1576 cm -1 . 1H NMR (C6D6) 8 7.99(d, 3JHH = 7.8 Hz, 4 H, o-ArH), 7.18 (t, 3Jmi 7.4 Hz, 4 H, m-ArH), 7.07 (d, 3-/HH7.2 Hz, 2 H, p -ArH), 1.58 (s, 15 H, C5(CH3)5). 13C{ 1H} NMR (C6D6) 8 195.90 (Cipao);135.86, 128.86, 127.81 (Carom); 112.26 (C5(CH3)5); 10.08 (C5(CH3)5)• Low-resolutionmass spectrum (probe temperature 100 °C): m/z 503 [P]+.Preparation of Cp*W(N0)(o-to1)2. As above, violet crystalline Cp*W(N0)(o-to1) 2(39% yield) was synthesized. Anal. Calcd for C24H29NOW: C, 54.25; H, 5.50; N, 2.63.Found: C, 55.15; H, 5.89; N, 2.59. IR (Nujol mull) v(NO) 1545 cm -1 . 1H NMR (C6D6)7.43 (d, 3JHH = 6.9 Hz, 2 H, o-ArH), 7.14 (d, 3.4111 = 6.9 Hz, 2 H, m-ArH), 7.06-6.97(m, 4 H, ArH), 2.87 (s, 6 H, Ar-CH3), 1.57 (s, 15 H, C5(CH3)5). 13C{ 1H} NMR (C6D6)197.80 (Cipso); 151.86, 130.41, 129.05, 128.98, 122.98 (Carom); 112.19 (C5(CH3)5); 27.30(Ar-CH3); 9.90 (C5(CH3)5)• Low-resolution mass spectrum (probe temperature 120 °C):m/z 531 [P]+.Chapter Two^ 24Preparation of Cp*W(N0)(p-to1)2. Violet crystals of Cp*W(N0)(p-to1)2 (49%yield) were prepared according to the above procedure. Anal. Calcd for C24H29NOW: C,54.25; H, 5.50; N, 2.63. Found: C, 54.67; H, 5.70; N, 2.70. IR (Nujol mull) v(NO) 1576cm-1 . 1H NMR (C6D6) 8 8.02 (d, 3JHH = 7.8 Hz, 4 H, o-ArH), 7.00 (d, 3./HH = 7.8 Hz,4 H, m-ArM, 2.01 (s, 6 H, Ar-CH3), 1.66 (s, 15 H, C5(CH3)5). 13C{ 1H} NMR (C6D6) 8193.29 (Cipso); 138.90, 136.26, 128.37 (Carom); 112.08 (C5(CH3)5); 21.87 (Ar-CH3); 10.20(C5(CH3)5)• Low-resolution mass spectrum (probe temperature 80 °C): m/z 531 [1]+.Preparation of Diphenylketene. Diphenylketene was synthesized with modificationsto published procedures. 11 Diphenylacetyl chloride (4.93 g, 2 .1.4 mmol, recrystallized oncefrom hexanes) was weighed in air, transferred to a Schlenk tube, and placed under dynamicvacuum for 20 min. Diethyl ether (25 mL) was added to the white crystalline material, andthe resulting solution was cooled to 0 °C. Triethylamine (3.00 mL, 21.6 mmol) was dilutedin Et20 (15 mL) in a pressure-equalized addition funnel and added dropwise to the stirreddiphenylacetyl chloride solution. The clear and colourless solution immediately turned brightyellow. Precipitation of a white powder (Et3N•HC1)was effected by maintaining the solutionat -30 °C overnight. The supernatant solution was filtered on a column of Celite (3 x 3 cm)supported on a sintered glass frit, and the column was washed with Et20 (80 mL). Removalof the Et20 solvent in vacuo left a yellow-orange oil which was transferred by pipet to a 10-mL round-bottom flask and then distilled under vacuum. The yellow-orange oil (2.2 mL, 13mmol, 59% yield) was stored under a dinitrogen atmosphere at -30 °C. Anal. Calcd forC14H100: C, 86.57; H, 5.19. Found: C, 86.64; H, 5.30. IR (neat) v(C=C=O) 2101cm-1 , 1815 cm-1 , v(C=C) 1753 cm-1 . 1H NMR (C6D6) 5 7.06 (s, 4 H, o-ArH), 7.04 (s, 6H, ArH). 13C{ 1H} NMR (C6D6) 5 201.90 (C=C=O); 131.04, 129.49, 127.93, 126.35(Carom); (C=C =0 not observed). Low-resolution mass spectrum (probe temperature 180°C): m/z 194 [P]i -Preparation of Cp*W(N0)(712-S2CPh)Ph. Solid Cp*W(NO)Ph2 (0.27 g, 0.54mmol) was weighed in a drybox, transferred to a Schlenk tube, and connected to the vacuumline. Enough carbon disulfide (10 mL) to dissolve the blue solid was vacuum transferred intoChapter Two^ 25the flask. The solution was then transferred via cannula to a flask equipped with a 4-mmTeflon stopcock, freeze-pump-thaw degassed twice, and left under partial vacuum. Stirringat room temperature for three days was accompanied by a change in colour from blue topurple. Solvent was removed in vacuo, and the residue was taken up in Et20 (20 mL).Chromatography of the purple solution on a column of neutral Alumina I (3 x 8 cm) gave apurple eluate which was reduced in volume until crystallization was initiated. Coolingovernight at -30 °C resulted in the formation of a purple microcrystalline solid (0.17 g, 0.29mmol, 54% yield). Anal. Calcd for C2 3H25NS2OW: C, 47.67; H, 4.35; N, 2.42; S, 11.06.Found: C, 47.87; H, 4.32; N, 2.41; S, 11.26. MS, IR, and NMR data are compiled inTables 2.1, 2.2, and 2.3.Attempted Preparation of Cp*Mo(N0)(112-S2C-p-tol)(p-tol). Solid Cp*Mo(N0)(p-to1)2 (0.17 g, 0.39 mmol) 3 was weighed in a drybox, transferred to a Schlenk tube, and thetube attatched to a vacuum line. THF (20 mL) and then excess carbon disulfide (5 mL) wereadded by vacuum transfer, and the resulting solution was freeze-pump-thaw degassed twice.Over the course of two days at room temperature, the solution changed to red-brown. Thevolatiles were removed in vacuo and the residue washed with pentane (3 x 5 mL) leaving anorange-brown powder. The powder was dissolved in Et20 (20 mL), and the brown solutionwas chromatographed on Florisil 60-100 (3 x 3 cm) supported on a medium porosity frit.Partial removal of solvent from the eluate followed by cooling overnight at -30 °C led to theformation of a rust-coloured powder (0.13 g, 0.25 mmol, 64% yield). Correct microanalysisfor C25H29NOS2Mo was not obtained. MS, IR, and NMR data are listed in Tables 2.1, 2.2,and 2.3.Preparation of Cp*W(NO){n2-N(p-tol)C(0)Ph}Ph. Solid Cp*W(NO)Ph2 (0.30 g,0.60 mmol) was weighed in the drybox and dissolved in THF (10 mL) in a flask equippedwith a 4-mm Teflon stopcock. To this was added p-tolyl isocyanate (0.30 mL, 2.4 mmol).The deep blue solution was freeze-pump-thaw degassed twice and left under partial vacuum.Over the course of three days at ambient temperatures, the solution changed in colour fromblue to yellow-brown. The THF solvent was removed in vacuo, and the resulting oily brownChapter Two^ 26residue was washed with cold pentane (3 x 4 mL) until the washings were colourless.Crystallization of the remaining orange microcrystalline solid was effected over a week from1:1 pentane/Et20 at -30 °C. Two fractions of the solid were collected and recrystallizedfrom Et20 (0.12 g, 0.19 mmol, 32% yield). Anal. Calcd for C30H 32N202W: C, 56.62; H,5.07; N, 4.40. Found: C, 56.41; H, 5.10; N, 4.47. MS, IR, and NMR data are collectedin Tables 2.1, 2.2, and 2.3.Preparation of Cp*W(N0)(n2-02CPh)Ph. Solid Cp*W(NO)Ph2 (0.84 g, 2.0mmol) was dissolved in benzene (15 mL) in a glass vessel equipped with a 4-mm Teflonstopcock. The blue solution was freeze-pump-thaw degassed three times, and the vessel waspressurized with CO2 (1-2 atm). Heating the solution at 60 °C overnight led to a change incolour to amber-brown. The benzene solution was transferred via cannula to a Schlenk tube,and the solvent was removed in vacuo. The brown residue was dissolved in Et20 (20 mL)and chromatographed on a column of neutral Alumina I (3 x 8 cm). Three bands wereeluted; the first and second bands are discussed in Appendix A. The third band, orange-brown, eluted with THF (50 mL). The THF eluate was evaporated, and the residues weretriturated with pentane, followed by washing with pentane until the washings were clear andcolourless (2 x 10 mL). The resulting yellow powder was dissolved in Et20 and held at -30°C for six days to give Cp*W(N0)(1) 2-02CPh)Ph (0.11 g, 0.20 mmol, 10% yield) as ayellow powder. Anal. Calcd for C23H25NO3W: C, 50.48; H, 4.60; N, 2.56. Found: C,51.35; H, 4.97; N, 2.53. MS, IR, and NMR data are collected in Tables 2.1, 2.2, and 2.3.Preparation of Cp*W(N0)(112-02CPh)C1. Solid Cp*W(NO)C12 (0.42 g, 1.0mmol) and sodium benzoate (0.14 g, 1.0 mmol) were weighed in air and transferred to aSchlenk tube. The flask was evacuated and then cooled to -50 °C with a liquidnitrogen/acetone bath. CH2C12 (30 mL) was added, the bath removed, and the solutionstirred overnight at room temperature. The colour of the solution changed from green tobrown-yellow during this time. The solvent was removed in vacuo. Trituration of theresulting brown residue with pentane (2 x 5 mL) afforded a yellow powder which wasdissolved in CH2C12 (20 mL) and filtered on a column of Celite (3 x 3 cm) supported on aChapter Two^ 27sintered glass frit. The orange eluate was reduced in volume, and hexanes (5 mL) wereadded. Orange crystals formed overnight at -30 °C (0.37 g, 0.73 mmol, 73% yield). Anal.Calcd for C 17H201•103C1W: C, 40.38; H, 3.99; N, 2.77. Found: C, 39.99; H, 4.03, N,2.66. MS, IR, and NMR data are recorded in Tables 2.1, 2.2, and 2.3.Attempted Syntheses of Cp*W(N0)(112-02CPh)Ph: (a) Treatment ofCp*W(N0)(Ph)C1 with NaO2CPh. Solid Cp*W(NO)C12 (0.42 g, 1.0 mmol) was weighedin air and transferred to a Schlenk tube. After the atmosphere was removed, the tube andcontents were taken into the drybox. Ph 2Mg•Et20.1/2(dioxane) (0.15 g, 1.0 mmol Ph -) wasmixed with the dichloride reagent and taken to the vacuum line where THF (15 mL) wasintroduced by vacuum transfer. The THF solution was warmed to -20 °C and was held atthat temperature for 30 min as the solution turned a steel-blue colour. The solvent wasremoved in vacuo, and the remaining powder was titurated with pentane (10 mL). The bluepowder was identified as Cp*W(NO)(Ph)Cl (v(NO) 1591 cm-1 , as Nujol mull). The flaskwas placed under vacuum and taken into the drybox where sodium benzoate (0.15 g, 1.0mmol) was added and mixed. THF (15 mL) was added by vacuum transfer, and the solutionwas warmed to room temperature. Over two hours, the solution turned orange-yellow.Removal of solvent followed by trituration with pentane (2 x 5 mL) resulted in the isolationof a tan-yellow powder, identified by IR spectroscopy and MS as Cp*W(NO)(1 2-02CPh)C1.(b) Treatment of Cp*W(N0)(T12-02CPh)C1 with Ph2Mg•Et20.1/2(dioxane).Solid Cp*W(N0)(11 2-02CPh)C1 (0.30 g, 0.60 mmol) and Ph2Mg•Et 20.1/2(dioxane) (0.10 g,0.60 mmol Ph -) were mixed in a Schlenk tube. THF (20 mL) was added by vacuumtransfer. The solution was warmed to 0 °C and changed colour from yellow to dark greenover the course of one hour. The solvent was then removed, giving a dark green-brown tar.Analysis of the residue by IR spectroscopy and MS revealed no identifiable species.Treatment of Cp*W(N0)(o-to1)2 with CS2. Solid Cp*W(N0)(o-to1) 2 (40 mg,0.075 mmol) was dissolved in C 6D6 (0.6 mL) in an NMR tube equipped with a Teflonstopcock and frozen to liquid nitrogen temperatures. Carbon disulfide (0.3 mL, 6.4 mmol)was added via vacuum transfer, and the contents of the tube were freeze-pump-thaw-degassedChapter Two^ 28twice. The purple solution was heated at 65 °C, and the reaction was monitored by 1H NMRspectroscopy over the course of a week. The reaction led to the quantitative conversion tothe carbon-disulfide insertion product, Cp*W(N0)(71 2-S2C-o-tol)(o-tol). MS and NMR dataare collected in Tables 2.1 and 2.3.Treatment of Cp*W(N0)(p-to1)2 with CS2. As above, Cp*W(N0)(p-to1)2 wastreated with CS2 in C6D6. The room-temperature reaction led to the quantitative synthesis ofCp*W(NO)(12-S2C-p-tol)(p-tol) over three weeks, as monitored by 1H NMR spectroscopy.Anal. Calcd for C251129NS2OW: C, 49.43; H, 4.81; N, 2.30; S, 10.56. Found: C, 49.10;H, 4.60; N, 2.24; S, 10.68. MS, IR, and NMR data are collected in Tables 2.1, 2.2, and2.3.Treatment of Cp*W(NO)Ph2 with Diphenylketene. Solid Cp*W(NO)Ph2 (0.36 g,0.72 mmol) was dissolved in THF (10 mL) in a glass vessel equipped with a 4-mm Teflonstopcock. An excess of diphenylketene (0.75 mL, 4.3 mmol) was added by pipet. Thesolution was freeze-pump-thaw-degassed twice and left under partial vacuum. Heating at 65°C for 16 h resulted in the formation of a brown solution which was transferred to a Schlenktube via cannula. The THF solvent was removed, and the residue was dissolved in Et20 (20mL). Chromatography with Et20 on a column of neutral Alumina I (3 x 8 cm) led to theelution of two bands: the first, amber, was collected and upon removal of the solvent, led toan intractable brown oil. The second fraction was yellow and crystallization from diethylether at -30 °C led to the isolation of white crystals of diphenylmethyl phenyl ketone. Anal.Calcd for C2011 1 80: C, 88.20; H, 5.92. Found: C, 88.40; H, 5.91. IR (Nujol mull) v(CO)1681 cm-1 . 1H NMR (C6D6) 5 7.97 (d, 3./HH = 6.9 Hz, 2 H, o-ArH), 7.23 (d, 3JxH = 6.3Hz, 4 H, o-ArH), 7.10-6.90 (m, 9 H, ArH), 5.87 (s, 1 H, CH). 13C{ 111} NMR (C6D6) S197.72 (C=0); 139.82, 137.69, 132.77, 129.59, 129.12, 128.86, 128.68, 127.18 (Carom);59.62 (Ph2CH). Low-resolution mass spectrum (probe temperature 200 °C): m/z 272 [P] -F,167 [P - PhC0]+, 105 [P - CPh2H]+.Treatment of Cp*W(N0)(p-to1)2 with Diphenylketene. The reaction ofCp*W(N0)(p-to1)2 with diphenylketene was carried out in a manner similar to that above,Chapter Two^ 29leading to the isolation of diphenylmethyl p-tolyl ketone. 1H NMR (C6D6) 6 8.00 (d, 3./HH= 8.2 Hz, 2 H, o-ArH), 7.32 (d, 3JHH = 7.1 Hz, 4 H, o-ArH), 7.20-7.01 (m, 6 H, ArH),6.86 (d, 34111 = 8.0 Hz, 2 H, m-ArH), 5.97 (s, 1 H, C(0)-H), 1.98 (s, 3 H, CH3).13C{ 111} NMR (C6D6) 8 197.00 (C=0), 143.37, 140.04, 135.04, 129.64, 129.42, 129.34,128.82, 127.11 (Carom); 59.54 (Ph2CH); 21.28 (CH3). Low-resolution mass spectrum(probe temperature 190 °C): m/z 286 [P] +, 167 [P - C(0)p-tol] +, 119 [P - Ph2CH]±.Table 2.1. Low-Resolution Mass Spectral Data.Complex Mass Spectral Data (m/z)a Tempb (°C)Cp*Mo(N0)(112-S2C-p-tol)(p-tol) 521 [P]±, 491 [P - N0]± 120Cp*W(N0)(712-S2CPh)Ph 579 [P]+, 549 [P - NO] + 150Cp*W(N0)(12-S2C-o-tol)(o-tol) 607 [P]±, 575 [P - NO]+ 120Cp*W(N0)(12-S2C-p-tol)(p-tol) 607 [11 1- , 575 [P - NO] + 80Cp*W(NO){12-N(p-tol)C(0)Ph}Ph 636 [P] +, 606 [P - NO] + 150Cp*W(N0)(11 2-02CPh)Ph 503 [P - CO2]+ 120Cp*W(N0)(11 2-02CPh)C1 505 [P]+, 475 [P - N0]± 180a m/z values are for the highest intensity peak of the isotopic cluster, i.e., 98Mo and 184W.b probe temperatures.Chapter Two^ 30Table 2.2. Infrared Data (in cm -1 as Nujol mull).Complex v(NO) v(CS2)/v(CO2) v(C = C) 8(CH)Cp*Mo(N0)(n2-S2C-p-to1)(p-tol) 1597 1175 (asym) 1604, 1552 800, 8171020 (sym) 1544, 1480Cp*W(N0)(r12-S2CPh)Ph 1578 1176 (asym) 1592, 1557 768, 730, 7001005 (sym) 1450 689Cp*W(N0)(n 2-S2C-p-tol)(p-tol) 1580 1174 (asym) 1589, 1545 800, 8131021 (sym) 1514Cp*W(NO){12-N(p-to1)C(0)Ph}Ph 1576 1601 v(CN) 1557, 1545 836, 735, 7001397 v(CO) 1508, 1486Cp*W(NO)(12-O2CPh)Ph 1585 1480 (asym) 1558, 1576 755, 735, 7031362 (sym) 1550, 1480 692Cp*W(N0)(n2-02CPh)C1 1597 1508 (asym)1457 (sym)1584, 1493 728, 703Table 2.3. 1H and 13C{ 111} NMR Data (in C6D6).Complex 1H NMR 13C{1in NMRCp*Mo(N0)(n2-S2C-p-tol)(p-tol)a 8.23 (d, 3JHH = 8.4 Hz, 2H, o-ArH) 144.89 (Cipso)8.00 (d, 3JHH = 7.8 Hz, 2H, o-ArH) 138.76 (qpso)7.27 (d, 3JHH = 8.1 Hz, 2H, m-ArH) 129.40 (Carom)6.82 (d, 3JHH = 8.1 Hz, 2H, m-ArH) 128.78 (Carom)2.44 (s, 3H, Ar-p-CH3)b 124.45 (Carom)2.32 (s, 3H, Ar-p-CH3) 111.65 (C5(CH3)5)2.03 (s, 3H, Ar-p-CH3)b 21.44 (Ar-CH3)1.94 (s, 3H, Ar-p-CH3) 21.30 (Ar-CH3)1.61 (s, 15H, C5(CH3)5) 9.85 (C5(CH3)5)Chapter Two^ 31Cp*W(NO)(r12-S2CPh)Ph 8.06 (d, 3JHH = 7.5 Hz, 2H, o-ArH)8.02 (d, 3JHH = 8.4 Hz, 2H, o-ArH)7.34 (t, 3JHH = 7.8 Hz, 2H, m-ArH)7.18 (t, 3JHH = 7.4 Hz, 1H, p-ArH)7.08 (t, 3JHH = 7.5 Hz, 1H, p-ArH)6.90 (t, 3JHH = 7.6 Hz, 2H, m-ArH)236.78 (S2C)169.40 (Cipso)156.75 (Cipso)145.01 (Carom)139.64 (Carom)133.65 (Carom)1.55 (s, 15H, C5(CH3)5) 128.60 (Carom)125.32 (Carom)123.68 (Carom)109.92 (C5(CH3)5)9.62 (C5(CH3)5)Cp*W(NO)(r12-S2C-o-tol)(o-tol) 7.81 (d, 3JHH = 6 Hz, 2H, o-ArH) 153.70 (Cipso)7.21 (d, 3JHH = 6 Hz, 2H, o-ArH) 143.50 (Cipso)7.19 - 6.78 (m, 4H, ArH) 130.75 (Carom)2.62 (s, 3H, Ar-CH3) 127.48 (Carom)2.36 (s, 3H, Ar-CH3) 125.57 (Carom)1.77 (s, 15H, C5(CH3)5) 125.18 (Carom)125.07 (Carom)124.41 (Carom)116.88 (C5(CH3)5)28.58 (Ar-CH3)18.72 (Ar-CH3)10.91 (C5(CH3)5)Cp*W(N0)(12-S2C-p-tol)(p-tol) 8.05 (d, 3JHH = 8.1 Hz, 2H, o-ArH)236.28 (S2C)7.80 (d, 3JHH = 7.8 Hz, 2H, o-ArH) 165.33 (Cipso)7.14 (d, 3JHH = 7.8 Hz, 2H, m-ArH) 144.89 (Cipso)6.98 (d, 3JHH = 8.4 Hz, 2H, m-ArH) 142.98 (Carom)2.33 (s, 3H, Ar-CH3) 139.44 (Carom)2.11 (s, 3H, Ar-CH3) 134.04 (Carom)1.73 (s, 15H, C5(CH3)5) 129.52 (Carom)129.15 (Carom)123.91 (Carom)109.76 (C5(CH3)5)21.86 (Ar-CH3)21.61 (Ar-CH3)9.82 (C5(CH3)5)Chapter Two^ 32Cp*W(NO){112-N(p-to1)C(0)Ph}Ph 8.30 (d, 3JHH = 7.8 Hz, 2H, o-ArH)7.43 (d, 3JHH = 7.5 Hz, 2H, o-ArH)7.35 (d, 3JHH = 7.8 Hz, 2H, o-ArH)176.06 (Cipso)172.11 (Cipso)141.08 (Carom)7.23 (m, 3H, ArH) 137.42 (Carom)6.94 - 6.76 (m, 5H, ArH) 135.06 (Carom)2.02 (s, 3H, ArCH3) 133.38 (C^m)1.56 (s, 15H, C5(CH3)5) 130.92 (C m)129.94 (Carom)128.94 (Carom)128.17 (Carom)125.83 (Carom)125.51 (Carom)111.25 (C5(CH3)5)20.81 (Ar-CH3)9.41 (C5(CH3)5)Cp*W(N0)(r12-02CPh)Ph 7.65 (d, 2JHH = 6.6 Hz, 2H, o-ArH) 168.29 (02C)7.16 (d, 2JHH = 7.5 Hz, 2H, m-ArH) 156.87 (Cipso)7.08 (t, 3JHH = 7.8 Hz, 2H, m-ArH) 142.14 (Cipso)7.05 (t, 3JHH = 7.8 Hz, 1H,p-ArH) 128.51 (Carom)6.93 (d, 2JHH = 8.4 Hz, 2H, o-ArH) 126.83 (Carom)6.76 (t, 3JHH = 6.9 Hz, 1H, p-ArH) 123.65 (Carom)1.72 (s, 15H, C5(CH3)5) 122.86 (Carom)117.08 (C5(CH3)5)10.80 (C5(CH3)5)Cp*W(N0)(r12-02CPh)C1 7.90 (d, 2JHH = 8.1 Hz, 2H, o-ArH) 180.41 (02C)7.03 (t, 3JHH = 7.8 Hz, 1H, p-ArH) 134.15 (Carom)6.90 (t, 3JHH = 7.5 Hz, 2H, m-ArH) 129.19 (Carom)1.72 (s, 15H, C5(CH3)5) 128.52 (Carom)115.38 (C5(CH3)5)9.41 (C5(CH3)5)a major and minor products observed; aryl proton and 13C signals unresolved.b minor product.Chapter Two^ 332.3 Results and DiscussionIn this section the reactivity of four heterocumulene molecules with theCp*M(NO)(aryl)2 (M = Mo, W) complexes is described. Three molecules (carbondisulfide, p-tol; I isocyanate, and carbon dioxide) insert into one metal-aryl bond to affordisolable and stable insertion products. Although no inserted complex was isolated from thereaction with diphenylketene, evidence suggests that insertion does occur. Based onqualitative observations, the heterocumulene to insert most easily is CS2, followed by p-tolylisocyanate and carbon dioxide. This section is concluded by a discussion of the mechanismof heterocumulene insertion into metal-carbon bonds.Preparation of Cp*M(N0)(712-S2CR)R (M = W, R = Ph, o-tol, p-tol; M = Mo,R = p-tol). The prototypic aryl complex, Cp*W(NO)Ph2, reacts with carbon disulfidesolvent at room temperature over three days (eq 2.1). Shorter reaction times are possiblewhen the temperature is increased. The reaction is accompanied by a change in colour fromroyal blue to intense purple. The resulting i1 2-thiobenzoate complex can be isolated inmoderate yields and is soluble in diethyl ether but insoluble in pentane. NMR-tube reactionsof other diaryl species in C6D6 with an excess of CS2 are quantitative and display similarcolour changes. Isolated yields are generally lower than the NMR-tube yields due to thethermal sensitivity and air-sensitivity of Cp*W(NO)(aryl)2. 3 In marked contrast to theirunstable diaryl parents, the 1 2-thiocarboxylate complexes are thermally stable and show nonoticeable decomposition in air as solids over a month. Solutions of Cp*W(N0)(71 2-S2CPh)Ph in refluxing C6D6 show no decomposition as monitored by 1H NMR spectroscopyover several days.C S2Ph7 - Ph^Ph - S/ \ -,, --PhN0N0(2.1)Chapter nvo^ 34Spectroscopic and elemental analyses are consistent with the formulation of thecomplexes as mono-insertedi 2-thiocarboxylate species. 1H and 13C{ 1H} NMR spectra showclearly that carbon disulfide has inserted into one of the tungsten-aryl bonds. The 1H NMRspectra of Cp*W(N0)(p-to1)2 and Cp*W(N0)(12-S2C-p-tol)(p-tol) in C6D6 are shown inFigures 2.1 and 2.2. The p-tolyl groups in the parent diaryl are equivalent, as evidenced byone set of resonances for the ortho-aryl protons (5 8.02 ppm, 4 H), the meta-aryl protons (57.00 ppm, 4 H), and the aryl-methyl (5 2.01 ppm, 6 H). Upon insertion, this equivalency isdestroyed, and two sets of aryl resonances result. The sharp doublet at 5 8.05 ppm and thatat 5 7.14 ppm are assignable to protons on the aryl ligand bonded to tungsten. The doubletsat 8 7.80 ppm and 5 6.98 ppm can be attributed to protons on the CS2-inserted aryl ligand.The resonance at 5 7.80 ppm is somewhat broadened, possibly indicating a degree ofhindered rotation of the p-tolyl group about the C2 axis ofthe i2-thiocarboxylate ligand. Broadening of the ortho-arylproton signal is observed in the 1H NMRspectrum of Cp*W(NO)(1 2-S2CPh)Ph, suggesting thathindered rotation also occurs in this case. The presence of two aryl-methyl resonances (82.33, 2.11 ppm) confirms the p-tolyl group inequivalence and suggests that CS 2 insertion hasoccurred.The 13C{ 1}1} NMR spectra of Cp*W(N0)(p-to1) 2 and Cp*W(N0)(12-S2C-p-tol)(p-tol) differ in the expected manner. The spectrum of the parent complex reveals theequivalent nature of the two p-tolyl groups (four aromatic and one aryl-methyl carbonresonance). These five resonances double to ten (eight aromatic and two aryl-methyl carbonresonances) upon insertion as expected. An additional signal is observed at 8 236.3 ppm,assignable to the carbon of the inserted CS 2 . This compares to carbon resonances in similarthioformate12 and thiocarboxylate 13 complexes and is significantly downfield from that offree CS2 (8 192.8 ppm). The 13C{ 1 1-1} NMR spectra for the phenyl and o-tolyl analogues aresimilar to that of the bis(p-tolyl) complex.r-r-, 1 I 1 1 T-1-1-T-1"--1-ri-i-T -r-t -r-rr-r-r-T-T-r-r- III!! -r-^T^ LT-v-7-m- Till^ r-r 18^7^6^5 4 3^2 1 'PMFigure 2.1. The 300 MHz 1 H NMR Spectrum of Cp*W(N0)(p-to1)2 in C6D6. ^FTTI-1 rrrrTm ITTITI171 i i r r r IT^i 1 11 11 111TIT1TTTIT1 rrjrrrrirrrip 11118.2^8.0^7 8^7.6^7 4^7.2^7.0^6 8 PPMir^II^i rrt -r- j r 1-1-T7-r-1 T-r-r-r r^T - 1 r^F 1 r--r T F 1-1 -7 -1--r-r r-r8 7^6 5 4^3^2^1 PPMFigure 2.2. The 300 MHz 1 H NMR Spectrum of Cp*W(N0)(12-S2C-p-tol)p-tol in C6D6 (inset ö 8.2-6.6 ppm).Chapter Two^ 37The presence of the nitrosyl ligand in the compounds studied in these laboratoriesfacilitates the use of IR spectroscopy in characterization. For the complexes Cp'M(NO)R 2(R = alkyl, aryl), v(NO) stretching frequencies are observed between 1650 and 1500 cm -1 .However, the presence of aryl C=C stretches in the 1650-1430 cm-1 region14 precludesprecise assignment of nitrosyl bands in aryl complexes. Nitrosyl-stretching frequencies are1578 cm-1 for Cp*W(N0)(12-S2CPh)Ph and 1580 cm-1 for Cp*W(NO)(12-S2C-p-tol)(p-tol).These values do not differ significantly from the nitrosyl bands of the parent bis(phenyl)(v(NO) 1576 cm -1 ) and bis(o-tolyl) (v(NO) 1576 cm -1 ) complexes. Electronically saturatednitrosyl complexes are expected to have nitrosyl-stretching frequencies that reflect increasedelectron density at the metal centre. With more electron density at the metal, the degree ofmetal-NO n-back donation is expected to increase accompanied by a concomitant lowering ofthe energy of the nitrosyl-stretching frequency. 15 For example, the 18-electrontrimethylphosphine adduct of the bis(p-tolyl) complex, Cp*W(N0)(p-to1)2(PMe3), has anitrosyl-stretching frequency of 1559 cm -1 reflecting significant a-donation from thephosphine ligand. 3 Despite attaining electronic saturation, the thiocarboxylate complexesdisplay values of v(NO) nearly identical to their electronically unsaturated parent complexes,suggesting that perhaps some degree of synergic bonding with sulfur is operative. 15,16Two C-S stretching modes are observed in the IR spectrum of Cp*W(N0)(11 2-S2CPh)Ph and Cp*W(NO)(r1 2-S2C-p-tol)(p-tol). The higher energy bands at 1176 cm -1 forCp*W(NO)(12-S2CPh)Ph and 1174 cm -1 for the p-tolyl congener are assignable to theasymmetric CS2 stretch. The symmetric CS2 stretching frequencies occur at lower energies(1021 and 1005 cm -1). The assigned CS2 stretching modes are consistent with those of other1-1 2-thiocarboxylate complexes. 13,17 A final feature of the IR spectra is the presence of strongbands in the 840-690 cm -1 region, characteristic of out-of-plane aryl C-H bending. Phenylgroups exhibit two bands whereas o- and p-tolyl groups give rise to only one band. 14 Theassignments of the out-of-plane C-H bending modes are listed in Table 2.2.8 4^8. 2^8.0^7.8^7.6^7. 4^7. 2^7.0^6 8 PPM 61 FT-Tr-TT-7 r T r-r- r-r- 1 r- T I I 1- 1 T T 1 1 r 1 11 1-T1 1 -T 1 T r 1 r f1 r r^1-r -T-7-F -r - T-r - r- i--7-TT-Fr-1-1-7-Tr7-7-TT 7 - I-T18^ 7^ 6^ 5^ 4^ 3^ 2^ 1 PPMFigure 2.3. The 300 MHz 1H NMR Spectrum of Cp*Mo(N0)(12-S2C-p-to1)p-tol in C6D6 (inset 5 8.4-6.6 ppm).Chapter Two^ 39The reaction of Cp*Mo(N0)(p-to1)2 with carbon disulfide is akin to that of itstungsten confrere and leads to the formation of the rust-coloured Cp*Mo(NO)(rl 2-S2C-p-tol)(p-tol) in moderate yield. The i2-thiocarboxylate complex displays similar solubility andstability propel Lies as the tungsten analogues. The 1H NMR spectrum reveals the existenceof two species in a 5:1 ratio (Figure 2.3). The major product displays spectral attributessimilar to the analogous tungsten complex. Inequivalence of the p-tolyl groups is evidencedby four aryl proton doublets (6 8.23, 8.00, 7.27, 6.82 ppm) and two aryl-methyl protonsignals (8 2.32, 1.94 ppm).The nature of the minor product is presently unclear. One possibility is that the extrasignals, assignable to a minor product, are due to an intermediate species in the conversion ofCp*Mo(N0)(p-to1)2 to Cp*Mo(N0)(12-S2C-p-tol)(p-tol). The mechanism forheterocumulene insertion proposed later in this chapter involves initial coordination of theheterocumulene before insertion into the metal-aryl bond can proceed. The formation of anend-on 1.1 1 -SCS complex is inferred from 1H NMR spectralevidence of the reaction of Cp*W(N0)(o-to1) 2 with carbondisulfide (vide infra). A similar species (at right) is consistentwith the spectral features observed for the minor isomer of the 1HNMR spectrum of Cp*Mo(N0)(1 2-S2C-p-tol)(p-tol).The IR spectrum of Cp*Mo(NO)(rl 2-S2C-p-tol)(p-tol) is similar to that of its tungstencongener. The CS 2 modes are observed at 1175 (v(CS2) asym) and 1020 cm -1 (v(CS2)sym)•The nitrosyl stretch is greater in energy than that of the tungsten analogue by 17 cm -1 , andreflects the lower electron density at the molybdenum centre. 3Synthesis of Cp*W(NO){n2-N(p-to1)C(0)Ph}Ph. Cp*W(NO)Ph2 reacts with anexcess of p-tolyl isocyanate in THE at room temperatures over three days to give the mono-insertedri2-amide complex Cp*W(NO){112-N(p-tol)C(0)Ph}Ph in moderate yields (eq 2.2).As a powder, the r12-amide complex is bright yellow, but it crystallizes as an orange solidfrom 1:1 CH2C12/hexanes. It is stable to heat as a solid, but slowly decomposes to anintractable brown powder upon prolonged exposure to air.Chapter Two^ 40Spectral and elemental analyses confirm that the complex is an 712-amide asformulated in eq 2.2. The aryl region of the 1H NMR spectrum is complicated by theexistence of two inequivalent phenyl groups and one p-tolyl group. The ortho-phenyl protonresonances provide a key to the interpretation of this spectrum (Figure 2.4). Of all the ArNCOW.'^Ar =p-tol^(2.2)Phi j- ‘14 --13hN0 ArPh/ - Ph0phenyl protons, the ortho-protons are closest to the metal centre and as such, their resonancesshould be most affected by insertion of the isocyanate. The three signals furthest downfieldare doublets and each integrates for two protons. These resonances are attributable to theortho-aryl protons and suggest that (1) the phenyl groups are inequivalent and (2) oneequivalent of p-tolyl isocyanate has been incorporated. The latter point is reinforced by thepresence of the aryl-methyl resonance at 5 2.02 ppm. The 13C NMR spectrum reveals apattern that corroborates the interpretation of the 1H NMR spectrum. Though the signal dueto the amide carbonyl carbon was not detected, twelve aromatic carbon resonances were,confirming the existence of three different aryl groups. The resonance at 5 20.8 ppm isattributable to the p-tolyl methyl carbon.The IR spectrum of Cp*W(NO){712-N(p-tol)C(0)Ph}Ph as a Nujol mull iscomplicated by the absorption of the three aryl ligands which obscure the nitrosyl andcarbonyl region. The absorbance at 1576 cm -1 is tentatively assigned to the nitrosylstretching mode, and is the same as observed for the parent bis(phenyl) complex. In asituation similar to that of the thiocarboxylate species, the value of v(NO) is affected by the7r* acceptor orbital of the 71 2-amide ligand such that the electronic saturation of the tungstencentre cannot be accurately inferred from the value of v(NO). The band at 1601 cm -1 isassignable to the C-N stretch; the v(CO) is found at 1397 cm-1.J tIrnrinrtpiirirnrli rnlrrrr1rnrrrrrrfrrrrTmil7 6^7. 4^7. 2^7. 0^6. 8 PPM 6 6(1-1-r IITIT r-r T r r rTr r r1--r ^rte" r r-r 7 - T --r-T ITITTI I-1 r T T r 1-1-1-T r r^T 1 r 1 r 1-1-7-7-1-1-1-7-r8^7^6 5^4^3 2^1 PPMFigure 2.4. The 300 MHz 1 H NMR Spectrum of Cp*W(NO){i 2-N(p-tol)C(0)Ph}Ph in C6D6 (inset 8 7.6-6.6 ppm).Chapter Two^ 42Preparation of Cp*W(N0)(12-02CPh)Ph. Benzene solutions of Cp*W(NO)Ph 2 at60 °C react with 1-2 atmospheres of CO2 overnight to give the ri2-benzoate complex,Cp*W(N0)(1-12-02CPh)Ph in low yield (eq 2.3). The yellow solid, like the previousCO2 (2.3)Ph ^Ph0Ph" \b j—PhN0heterocumulene insertion products, is air-stable and thermally stable. It is soluble in diethylether but insoluble in pentane. Although not analytically pure, other characterizationtechniques are consistent with the formulation of Cp*W(NO)(rl 2-02CPh)Ph as a mono-inserted species. The 1H NMR spectrum consists of six separate signals in the aryl region.Analysis of the signal-intensity integration and splitting patterns has led to the assignmentsfound in Table 2.3. The spectrum displays a pattern similar to that of the CS2 analogue,Cp*W(NO)(T12-S2CPh)Ph, but differs in that it lacks a broadened ortho-proton resonance.This suggests that unlike the i 2-thiocarboxylate ligand in Cp *W(N0)(11 2-S2CPh)Ph, theri2-benzoate ligand freely rotates at room temperature, perhaps due to the smaller size of theoxygen atom. In addition to the Cp* and aromatic carbon resonances, the 13C NMRspectrum contains a resonance at S 168.3 ppm, assignable to the carboxylate carbon; thechemical shift is similar to that observed for other aryl- and alkyl-carboxylate carbons. 18The IR spectrum of Cp*W(NO)(r1 2-02CPh)Ph as a Nujol mull contains the symmetricand asymmetric CO2 stretches at 1480 and 1362 cm -1 , and some insight can be gleaned fromthis information. Generally, il-bound carboxylates have v(CO2)asym > 1600 cm-1.19,20 Inthe present spectrum, no bands are present between 1800 and 1600 cm -1 . Furthermore, themagnitude of the energy difference between the symmetric and asymmetric modes (Av(CO2))can be used to distinguish between ill- and i2-carboxylates. Dihapto carboxylates displayAv(CO2) values less than 200 cm - 1 . 18-2° In the case of Cp*W(N0)(71 2-02CPh)Ph, Av(CO2)/R^R0H+^9Ph2HCC-R^(2.4)R = Ph, p-tolPh2C=C=0),R70 PhPhChapter Two^ 43= 118 cm -1 and supports strongly the formulation of an 112-benzoate ligand. An intenseband at 897 cm-1 is assignable to a tungsten-oxygen stretch.Reaction of Cp*W(NO)R2 (R = Ph, p-tol) with Diphenyketene. The fourthheterocumulenc studied in this work is diphenylketene. Unlike the other heterocumulenes,the reaction of diphenylketene with diaryl complexes fails to lead to isolable insertionproducts. However, the results presented below suggest that insertion into one of thetungsten-aryl bonds does indeed occur.Reaction of Cp*W(NO)R2 (R = Ph, p-tol) with an excess of diphenylketene takesplace at 65 °C over 16 h in THE leading to a colour change from dark blue to brown.Subsequent work-up of the reaction solution results in the isolation of diphenylmethyl arylketones, Ph2HCC(0)R (R = Ph, p-tol) from Et 20 as white crystals. The organiccompounds can be viewed as being composed of the parent diphenylketene and 'aryl-H'.The ketones most likely originate from insertion of diphenylketene into one tungsten-arylbond followed by decomposition, possibly hydrolysis due to adventitious water, as depictedin eq 2.4. The fate of the organometallic fragment remains to be ascertained.The failure to isolate a diphenylketene-insertion product may be explained by thesteric demands of the resultant 112-63-ketoalkyl) ligand. Insertion of the ketene would createa highly-crowded molecule due to the presence of two phenyl groups at the a-carbon of thecoordinated ketone. Presumably this renders the molecule highly unstable and thus possiblyreactive to a protonic acid such as water, which could attack at the a-carbon, releasing theketone.Chapter Two^ 449Ph2HCC-R + decomposition productsR = Ph, p-tolAttempts to Synthesize Cp*W(NO)(1 2-02CPh)Ph; Preparation of Cp*W(N0)(92-02CPh)C1. When initial efforts to prepare Cp*W(N0)(12-02CPh)Ph from insertion of CO2into a tungsten-phenyl bond met with little success, other synthetic routes were pursued tohelp identify the expected product and see if it was stable before continuing with CO 2-insertion reactions. Precedent for this strategy was found in the literature. The Cp2Ti(allcyl)system inserts CO2 and other heterocumulenes to give carboxylato and analogousderivatives, 21 complexes which were independently synthesized from Cp 2TiC1 and sodiumcarboxylates. 20aTwo routes to the 1 -12-carboxylate complex can be envisioned. The first involves theformation of the benzoate chloride Cp*W(N0)(9 2-02CPh)C1 upon metathesis ofCp*W(NO)C12 with one equivalent of sodium benzoate. Metathesis of the remainingchloride for a phenyl group could then lead to Cp*W(NO)(r; 2-02CPh)Ph (eq 2.5).NaO2CPh^ 1/2Ph2Mg), W '"'Q'..^ W ''"'Q , .^(2.5)C17^NaC1 C17^0-■-•'—‘' Ph - 1/2MgC12 ph/ \0^PhN N N0 0 0The second pathway involves similar steps, but in the reverse order (eq 2.6).Chapter Two^ 45 1/213h2Mg-1/2MgC12NaO2CPh."'Qi..- NaC1^Ph/N0Cl/N0Ph/ NCIN0(2.6)The reaction of sodium benzoate with Cp*W(NO)C12 proceeds over 18 h at roomtemperature in dichloromethane to give Cp*W(NO)(r12-02CPh)C1 in good yield. The 1H and13C{ 1H} NMR spectra are simple (Table 2.3) and confirm the existence of one phenyl group.The v(CO2) stretching modes are at 1508 (symmetric) and 1457 cm -1 (asymmetric). Thedifference in energy between the two, Av(CO2), is 51 cm-1 and supports the formulation ofthe benzoate ligand as dihapto (vide supra). A strong band at 883 cm -1 is attributable tov(W-O). The nitrosyl stretching frequency (v(NO) 1597 cm -1) is 12 cm -1 higher than inCp*W(NO)(r12-02CPh)Ph and is a result of the chloro ligand being more electronegativethan a phenyl ligand.Unfortunately, reaction of Cp*W(N0)(1 2-02CPh)C1 with Ph2Mg•Et20.1/2(dioxane)(1 equiv of Ph-) results in the decomposition of both reagents. This is not surprising asalkylating and arylating agents are known to react with oxygen-containing species such ascarboxylic acids. 22 In this case, the preferred site of reactivity is clearly the carboxylateligand and not the chloride as desired.Cp*W(NO)(Ph)Cl can be generated and isolated as a crude powder from the reactionof the dichloride precursor with the diphenylmagnesium reagent (0.5 equiv). 23 Addition ofsodium benzoate to a THE solution of the phenyl chloride led to the formation of an orange-brown powder which was identified by IR spectroscopy and MS as the benzoate chloride,Cp*W(N0)(71 2-02CPh)C1, and not the expected Cp*W(NO)(ri 2-02CPh)Ph complex.Relative Ease of Insertion. From the reactions of Cp 2ZrR2 (R = alkyl, aryl) withheterocumulenes, it was concluded that the relative ease of heterocumulene insertion into theChapter Two^ 46zirconium-carbon bond was ketene > isocyanate > carbodiimide > carbon dioxide. 6 Thequalitative description of the ease of heterocumulene insertion presented in this chapter iscarbon disulfide > isocyanate > carbon dioxide, which is consistent with theaforementioned trend. There is no apparent dependence on the nature of the aryl group inthese organometallic compounds.Mechanistic Considerations. Little is known concerning insertion reactions ofCO224 or other heterocumulenes. 25 Two transition-metal systems that insert CO2 have beenstudied to date and reveal disparate mechanisms. Rates of CO 2 insertion with the anionicGroup 6-alkyl and -aryl carbonyl complexes [(CO)5MRJ - are faster than rates of ligand (CO)dissociation. This eliminates, in this case at least, a mechanism involving the creation of avacant coordination site by CO-dissociation followed by coordination of CO2 to the metaland then migration of the alkyl- or aryl-group. 24b Carbon dioxide is postulated to insert viaa concerted mechanism in which the anionic metal centre attacks the electrophilic CO2 carbonas a nucleophile. However, the de-insertion of carbon dioxide from analogous formatecomplexes to form the metal hydride and free CO 2 appears to involve coordinated CO2 ,rendering this mechanism suspect if the principle of microscopic reversibility holds true. 26In contrast to the above system is the ruthenium complex (PMe 3)4Ru(i2-0C6H3Me).A coordination and migration mechanism for the reaction of CO2 with (PMe3)4Ru(112-0C6H3Me) is shown in Scheme 2.2. Kinetic measurements are consistent with reversibledissociation of phosphine preceding the rate-determining step of the reaction. This suggeststhat CO2 inserts by the following mechanism: (1) dissociation of phosphine ligand L, (2)coordination of CO2, (3) migration of aryl group, and (4) association of L. This lattermechanism involves the same steps as does the more extensively-studied insertion of carbonmonoxide into metal-carbon bonds. 27Although no kinetic studies were undertaken in the present work, results of the NMR-tube reaction of CS2 with Cp*W(N0)(o-to1)2 support the second mechanism discussed above.Carbon disulfide inserts into one o-tolyl-tungsten bond over the course of three days at 60 °C(eq 2.7). The reaction was monitored by 1 H NMR spectroscopy and the upfieldk2-1ILA]85°Ck3[CO2]k i fCO2]Chapter Thvo^ 47Scheme 2.2. Insertion of Carbon Dioxide into (PMe.3)41Zu(i 2-0C6H3Me). 244regions of three representative spectra are shown in Figure 2.5. Spectrum (a) is that ofCp*W(N0)(o-to1)2 prior to addition of CS2. The signal integrating for 15 protons at 5 1.57ppm is due to the Cp* proton resonances. The resonance at 5 2.87 ppm arises from the o-tolyl-methyl protons and indicates equivalence of the two aryl ligands. The bottom spectrumC S2 (2.7)(c) is of the completed reaction and shows that carbon disulfide has inserted, as demonstratedby two inequivalent o-tolyl methyl resonances at 5 2.62 and 2.36 ppm. Of particular interestis the middle spectrum (b) which shows signals due to the initial reactant and final product aswell as resonances attributable to some intermediate species. The proposed intermediate is anil—SCS adduct which could exist as cis and trans isomers.Chapter 7Wo^ 48bJIJL___,1Figure 2.5. The 300 MHz 1H NMR Spectra of Reaction 2.7 in C 6D6 (5 4.0-1.0 ppm)Chapter Thvo^ 49-SCS^R= o-tolN^ N S0 0 Ccis transThe two o-tolyl groups of each isomer are in a unique environment and give rise to the fourobserved methyl resonances (5 2.82, 2.81, 2.16, 2.04 ppm). The Cp* resonances, not assensitive to the different chemical environments, overlap at 5 1.61 ppm.Therefore, based on these observations, the mechanism of insertion ofheterocumulenes into the metal-carbon bonds of Cp*M(NO)(aryl) 2 (M = Mo, W) appears tobe consistent with a two-step sequence: First, the heterocumulene coordinates to thecoordinatively unsaturated diaryl complex in an i1-end-on fashion. The most electronegativeend of the polarized molecule forms an adduct with the electropositive Group 6 metal centre.The second step is the insertion of the heterocumulene into one of the tungsten-aryl bonds.After the heterocumulene inserts, it forms a dihapto linkage to the metal centre. Theproposed mechanism for insertion of a specific heterocumulene, CO2 , is depicted in Scheme2.3.The mechanism fits well with the known characteristics of the Cp'M(NO)R2 (M =Mo, W; R = alkyl, aryl) system. Specifically, these complexes possess a low-lying, metal-based LUMO which bisects the R-M-R angle and imparts Lewis acidity to the molecules. 1Furthermore, the diaryl subset readily inserts carbon monoxide into the metal-carbon bond byway of an 18-electron, terminal CO-adduct intermediate species. 28 Thus, the mechanism inScheme 2.3 is supported by evidence from CO-insertion reactions with the Cp*M(NO)(aryl) 2(M = Mo, W) family as well as CO2 insertions in other systems.Chapter Two^ 50Scheme 2.3. Proposed Mechanism of CO 2 Insertion into Cp*M(N0)(ary1) 2 (M = Mo, W).CO2 M. '"0;.,Ar^Ar^Ar/ \OCO0 0N Ar2.4 Summary and Future WorkIn the context of carbon-dioxide activation and functionalization, theCp*M(N0)(ary1)2 (M = Mo, W) system displays facile reactivity with a variety ofheterocumulenes, including carbon dioxide. The preparation of the benzoate complex,Cp*W(N0)(ri2-02CPh)Ph by CO2 insertion into the tungsten-phenyl bond is one of onlyabout a dozen such examples of carbon-dioxide insertion. Three other heterocumulenemolecules react with this organometallic system, demonstrating the depth and scope ofheterocumulene-insertion chemistry.The isolated heterocumulene-inserted products display thermal stability and areoxidatively robust. They demonstrate behaviour typical of 18-electron complexes indicatingelectronic and coordinative saturation. For example, under relatively mild conditions, nofurther reactivity with excess heterocumulene is observed. However, insertion into thesecond metal-aryl bond has been only partially addressed as the reactions undertaken in thiswork were done under mild conditions. A complete study of this possibility would involvereaction of a mono-inserted complex under more forcing conditions than were utilized in thiswork. For example, the reaction with high pressures of CO2 may generate the bis(benzoate)complex (eq 2.8).N0Chapter Two^ 51400"-Ph^CO2^0 W' "^(2.8)N^ N0 0It has been argued in this Thesis that the key to the successful reactivity ofCp*M(NO)(aryl)2 (M = Mo, W) with heterocumulenes is a function of the (1) high Lewis-acidity and (2) low steric requirements of these complexes. The CpM(NO)(aryl)2 (M = Mo,W) system enhances both these attributes as the Cp ligand is both a poor electron-donor andis less bulky than the Cp* ligand. Though these diaryl complexes are more difficult tosynthesize, they are anticipated to exhibit a rich and diverse reactivity with heterocumulenes.A final area that merits further research is extension of heterocumulene insertionchemistry to the mixed-aryl and alkyl-aryl system Cp 1 M(N0)(ary1)(R) (M = Mo, W; R =aryl', alkyl). The potential of two different metal-carbon bonds in which the heterocumulenemay insert may give insight into the fundamental differences and similarities of these bonds.Ph - 0 Ph'^- 02.5 References(1) Legzdins, P.; Rettig, S. J.; Sanchez, L.; Bursten, B. E.; Gatter, M. G. J. Am.Chem. Soc. 1985, 107, 1411-1413.(2) (a) Legzdins, P.; Rettig, S. J.; Sanchez, L. Organometallics 1988, 7, 2394. (b)Legzdins, P.; Sanchez, L. J. Am. Chem. Soc. 1985, 107, 5525-5526.(3) Dryden, N. H.; Legzdins, P.; Rettig, S. J.; Veltheer, J. E. Organometallics 1992,11, 2583-2590.(4) McMurry, J. Organic Chemistry; Brooks/Cole: Belmont, CA, 1984; p 223.Chapter Two^ 52(5) (a) Ibers, J. A. J. Chem. Soc. Rev. 1982, 11, 57-73. (b) Lee, G. R.; Maher, J. M.;Cooper, N. J. J. Am. Chem. Soc. 1987, 109, 2956-2962. (c) Lee, G. R.; Cooper,N. J. Organometallics 1989, 8, 1538-1544. (d) Darensbourg, D. J.; Sanchez, K.M.; Reibenspies, J. H.; Rheingold, A. L. J. Am. Chem. Soc. 1989, 111, 7094-7103.(6) Gambarotta, S.; Strologo, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. Inorg.Chem. 1985, 24, 654-660.(7) Darensbourg, D. J.; Mueller, B. L.; Bischoff, C. J.; Chojnacki, S. S.; Reibenspies,J. H. Inorg. Chem. 1991, 30, 2418-2424.(8) Mealli, C.; Hoffmann, R.; Stockis, A. Inorg. Chem. 1984, 23, 56-65.(9) Shriver, D. F.; Drezdon, M. A. The Manipulation of Air-Sensitive Compounds, 2nded.; Wiley-Interscience: New York, 1986.(10) Dryden, N. H.; Legzdins, P.; Trotter, J.; Yee, V. C. Organometallics 1991, 10,2857.(11) (a) Darling, S. D.; Kidwell, R. L. J. Org. Chem. 1968, 33, 3974-3975. (b) Gall,M.; House, H. 0. Org. Synth. 1972, 52, 36-39.(12) Darensbourg, D. J.; Rokicki, A. Organometallics 1982, 1, 1685-1693.(13) Scott, F.; Kruger, G. J.; Cronje, S.; Lombard, A.; Raubenheimer, H. G.; Benn, R.;Rufinska, A. Organometallics 1990, 9, 1071-1078.(14) Lambert, J. B.; Shurvell, H. F.; Lightner, D.; Cooks, R. G. Introduction to OrganicSpectroscopy; Macmillan: New York, 1987.(15) Richter-Addo, G. B.; Legzdins, P. Metal Nitrosyls; Oxford University Press: NewYork, 1992; Chapter 1.(16) Jorgensen, W. L.; Salem, L. The Organic Chemist's Book of Orbitals; Academic:New York, 1974.Chapter Two^ 53(17) (a) Yaneff, P. V. Coord. Chem. Rev. 1977, 23, 183-220. (b) Werner, H.; Bertleff,W. Chem. Ber. 1980, 113, 267-273. (c) Torres, M. R.; Perales, A.; Ros, J.Organometallics 1988, 7,1223-1224.(18) (a) Cutler, A.; Raja, M.; Todaro, A. Inorg. Chem. 1987, 26, 2877-2881. (b)Darensbourg, D. J.; Grotsch, G.; Wiegreffe, P.; Rheingold, A. L. Inorg. Chem.1987, 26, 3827-3830. (c) Holl, M. M.; Hillhouse, G. L.; Folting, K.; Huffman, J.C. Organometallics 1987, 26, 1522-1527.(19) (a) Smith, S. A.; Blake, D. M.; Kubota, M. Inorg. Chem. 1972, 11, 660-662. (b)Bradley, M. G.; Roberts, D. A.; Geoffroy, G. L. J. Am. Chem. Soc. 1981, 103,379-384.(20) (a) Coutts, R. S. P.; Wailes, P. C. Aust. J. Chem. 1967, 20, 1579-1585. (b)Kolomnikov, I. S.; Gusev, A. 0.; Belopotapova, T., S.; Grigoryan, M. K.; Lysyak,T. V.; Struchkov, Y. T.; Vol'pin, M. E. J. Organomet. Chem. 1974, 69, C10-C12.(21) Klei, E.; Telgen, J. H.; Teuben, J. H. J. Organomet. Chem. 1981, 209, 297-307.(22) March, J. Advanced Organic Synthesis, 3rd ed.; Wiley-Interscience: New York,1985; p 816.(23) Debad, J. D.; Legzdins, P. Organometallics submitted for publication.(24) (a) Behr, A. Angew. Chem., Int. Ed. Engl. 1987, 27, 661-678. (b) Darensbourg,D. J.; Hanckel, R. K.; Bauch, C. G.; Pala, M.; Simmons, D.; White, J. N. J. Am.Chem. Soc. 1985, 107, 7463-7473. (c) Grotsch, G.; Darensbourg, D. J. J. Am.Chem. Soc. 1985, 107, 7473-76. (d) Hartwig, J. F.; Bergman, R. G.; Anderson, R.A. J. Am. Chem. Soc. 1991, 113, 6499-6508.(25) (a) Behr, A. Carbon-Dioxide Activation by Metal Complexes; VCH: Weinheim,Germany, 1988. (b) Braunstein, P.; Nobel, D. Chem. Rev. 1989, 89, 1927-1945.(26) (a) Darensbourg, D. J.; Fischer, M. B.; Schmidt, R. E.; Baldwin, B. J. J. Am.Chem. Soc. 1981, 103, 1297-1298. (b) Merrifield, J. H.; Gladysz, J. A.Chapter Two^ 54Organometallics 1983, 2, 782-784. (c) Darensbourg, A. J.; Wiegreffe, P.; Riordan,C. G. J. Am. Chem. Soc. 1990, 112, 5759-5762.(27) (a) Alexander, J. J. Chemistry of the Metal-Carbon Bond; Patai, S.; Hartley, F. R.,Eds.; Wiley and Sons: New York, 1985; Vol. 2, Chapter 5. (b) Yamamoto, A.Organotransition Metal Chemistry; Wiley: New York, 1986; Chapter 6.(28) Dryden, N. H. Ph.D. Dissertion, University of British Columbia, 1990.11-1----)- HOCR + decomposition products^(3.1)9Chapter Three:^ 55Reactivity of Heterocumulene-Inserted Complexes3.1 IntroductionChapter Two describes the successful synthesis of a number of heterocumulene-containing organometallic complexes, the most significant being the preparation ofCp*W(N0)(12-02CPh)Ph by activation of the normally unreactive CO 2 by Cp*W(NO)Ph2 .In the broad perspective of carbon-dioxide chemistry outlined in Chapter One, thesesyntheses can be viewed as the activation of the often-inert heterocumulene class ofmolecules (specifically carbon dioxide). In other words, the large barrier to reactivity ofcarbon dioxide and related compounds has been lowered with the utilization of an appropriatetransition-metal complex.As described earlier, a goal of carbon-dioxide research in organometallic chemistry isthe employment of CO 2 as a one-carbon synthetic unit. 1 If this goal is to be attained for theCp*M(N0)(ary1)2 (M = Mo, W) system, the heterocumulene-inserted complexes reported inthe previous chapter must display additional reactivity, i.e., further functionalization must befeasible.A frequently-studied reaction of CO 2-inserted complexes is acid-hydrolysis whichleads to the release of a carboxylic acid and, in general, the decomposition of theorganometallic moiety (eq 3.1). 2 An obvious drawback of such a reaction is the loss ofintegrity of the metal-based complex, which cannot be reused for subsequent reactions, eitherin a stoichiometric or catalytic manner.In this Chapter, attempts to further functionalize the heterocumulene-insertedcomplexes prepared in Chapter Two are reported. First, the acid-hydrolysis reactions with avariety of sources of H+ are discussed. Secondly, interactions with Lewis bases are reportedChapter Three^ 56and the results interpreted in the context of the bonding in the heterocumulene-insertedcomplexes. Following next is an account of preliminary reactions with the nucleophile H- onCp*W(N0)(i2-S2CPh)Ph. Chapter Three concludes with thoughts on future work stemmingfrom the work reported herein.3.2 Experimental SectionAll manipulations were performed using the general experimental procedures outlinedin Chapter Two. Trimethylphosphine (PMe 3) was synthesized as published 3 and dried oversodium/benzophenone. The heterocumulene-inserted products were prepared by themethodology outlined in Chapter Two.Reaction of Cp*W(NO){112-N(p-tol)C(0)PhIPh with H2O. Cp*W(NO){12-N(p-tol)C(0)Ph}Ph (0.11 g, 0.17 mmol) was weighed in air, transferred to a Schlenk tube, andplaced under vacuum for 15 min. After filling the flask with nitrogen, Et20 (15 mL) wasadded, giving a yellow solution. Distilled water (0.5 mL, excess) was degassed for fiveminutes and then added to the Et20 solution. The reaction mixture was stirred overnightduring which time the colour changed to pale yellow. The solvent was removed, and theresidue was sublimed under static vacuum at 100 °C for one day to obtain whitemicrocrystallinep-tolylbenzamide (0.025 g, 0.12 mmol, 71% yield). IR, MS, and NMRdata for this compound are presented in Tables 3.1 and 3.2. The unsublimed residue wasidentified by IR spectroscopy and MS as Cp*W(0)2Ph. 4Reaction of Cp*W(NO){112-N(p-to1)C(0)Ph)Ph with DOC(0)CD3.Cp*W(NO){712-N(p-tol)C(0)Ph}Ph (0.035 g, 0.055 mmol) was dissolved in C 6D6 (0.6 mL)in an NMR tube equipped with a Teflon stopcock; to this was added an excess of acetic acid-d4 (0.05 mL, 0.6 mmol). The yellow contents were freeze-pump-thaw degassed three times.The reaction (1 d) led to the products Cp*W(NO)(r1 2-02CCD3)Ph and p-tolylbenzamide-d 1 ,quantitatively by 1H NMR spectroscopy. IR, MS, and NMR data for Cp*W(N0)(r1 2-02CCD 3)Ph are recorded in Tables 3.1 and 3.2.Chapter Three^ 57Reaction of Cp*W(NO){112-N(p-to1)C(0)Ph)Ph with HC1. Cp*W(NO){71 2-N(p-tol)C(0)Ph)Ph (0.11 g, 0.17 mmol) was weighed in air, transferred to a Schlenk tube, andplaced under vacuum for 15 min. THE (20 mL) was added by vacuum transfer and waswarmed to -20 °C yielding an orange solution. A solution of HC1 in Et20 (0.75 mL, 1.0equiv HC1) was added by syringe, and the reaction was monitored by solution IRspectroscopy. After one hour, the colour of the solution had changed to lime-green and theIR spectrum indicated: (1) the decrease of the v(NO) band at 1582 cm -1 to one-half of itsoriginal intensity and (2) the appearance of two new absorbances at 1678 and 1628 cm -1 . Anadditional aliquot of HC1/Et 20 (0.75 mL, 1.0 equiv HC1) was added. After 30 min, thesolution had turned an intense green, and the IR spectrum showed only the signals at 1678and 1628 cm-1 . Solvent was removed, and the brown residue was identified by IRspectroscopy as a mixture of Cp*W(NO)C1 2 and p-tolylbenzamide.Treatment of Cp*W(N0)(T12-02CPh)Ph with CO. Cp*W(N0)(11 2-02CPh)Ph(0.03 g, 0.05 mmol) was dissolved in C6D6 (0.6 mL) in an NMR tube equipped with aTeflon stopcock which was then freeze-pump-thaw degassed three times. An atmosphere ofcarbon monoxide (Linde/Union Carbide) was added to the frozen contents of the NMR tube,and the contents were warmed to room temperature. No reaction was observed at roomtemperature or after two days at benzene reflux, as monitored by 1H NMR spectroscopy. Ina similar manner, both Cp*W(N0)(r12-N(p-tol)C(0)Ph)Ph and Cp*W(N0)(1 2-S2CPh)Phfailed to react with carbon monoxide.Treatment of Cp*W(N0)(T12-02CPh)Ph with PMe3. Cp*W(N0)(i2-02CPh)Ph(0.03 g, 0.05 mmol) was dissolved in C6D6 (0.6 mL) in an NMR tube equipped with aTeflon stopcock which was then freeze-pump-thaw degassed three times. Excess PMe 3 (0.3mL) was added to the frozen contents of the NMR tube via vacuum transfer, and the mixturewas warmed to room temperature. No reaction was observed at room temperature or aftertwo days at benzene reflux, as judged by 1H NMR spectroscopy. Similarly, Cp*W(NO){7 -12-N(p-tol)C(0)Ph}Ph exhibited no reactivity with PMe3.Chapter Three^ 58Synthesis of Cp*W(N0)(i2-S2C(PMe3)Ph)Ph. (a) Cp*W(N0)(1 2-S2CPh)Ph(0.032 g, 0.055 mmol) was dissolved in C 6D6 (0.6 mL) in an NMR tube equipped with aTeflon stopcock and freeze-pump-thaw-degassed three times. Excess PMe3 (0.3 mL) wasadded to the frozen contents of the NMR tube by vacuum transfer. Upon warming to roomtemperature, the colour of the sample changed from purple to gold. The resulting productwas identified by 1H and 13C{ 1H} NMR spectroscopy.(b) Cp*W(N0)(12-S2CPh)Ph (0.115 g, 0.199 mmol) was dissolved in Et20 (15 mL)in a Schlenk tube, and the solution was frozen with liquid nitrogen. An excess of PMe3 wasvacuum transferred to the Schlenk tube, and the contents were warmed to room temperature.A yellow-orange precipitate formed from the the dark purple-red solution within minutes ofthawing. After 30 min the solution was taken to dryness in vacuo, and the peach-colouredpowder was triturated with pentane (3 x 5 mL). The powder was dissolved in CH 2C12 (10mL) to which hexanes (10 mL) was added. Crystallization was effected at -30 °C over thecourse of two weeks giving pale gold crystals (0.08 g, 0.12 mmol, 61% yield). Anal. Calcdfor C26H34NOPS2W: C, 47.62; H, 5.23; N, 2.14. Found: C, 48.02; H, 5.31; N, 2.00. IR,MS, and NMR data are collected in Tables 3.1 and 3.2. 31P{ 1H} NMR (C6D6) 5 28.17(PMe3).Treatment of Cp*W(N0)(12-S2CPh)Ph with KIT. Cp*W(N0)(1)2-S2CPh)Ph (0.36g, 0.56 mmol) was weighed in air, transferred to a Schlenk tube, and taken into the drybox.KH (0.022 g, 0.56 mmol) was added and the contents mixed well. On a vacuum line, THE(25 mL) was introduced by vacuum transfer. The purple solution was stirred for two days atroom temperature; no colour change was observed. The solvent was removed, and an IRspectrum of the residue was identical to that of Cp*W(NO)(fl2-S2CPh)Ph.Chapter Three^ 59Table 3.1. Infrareds and Low-Resolution Mass Spectral Data.Complex v(NO) Other IR bands MS (m/z)bp-tolylbenzamide 1649c 1601, 1578, 1528, 1517, 1406 211 [11+1322, 813, 716, 692, 651Cp*W(NO){712-S2C(PMe3)Ph}Ph 1548 1573, 1563, 1519, 1479, 1450 579 [P- PMe,3]+1290, 963, 743, 736, 706, 700Cp*W(N0)(11 2-02CCD3)Ph 1584 1637, 1557, 1485, 1431, 1393 448 [11+1313, 917, 741, 707, 661a. collected as Nujol mulls; values in cm-1 .b probe temperature 80 °C.v(CO).Table 3.2. 1H and 13C{ 1H} NMR Data (in C6D6).Complex 111 NMR 13C{1H} NMRp-tolylbenzamide 7.18-7.12 (m, 4H, ArH) 174.53 (C=0)6.85 (br s, 1H, NH) 136.76 (Carom)6.70-6.52 (m, 5H, ArH) 136.28 (Carom)1.67 (s, 3H, ArCH3) 133.75 (Carom)131.39 (Carom)129.66 (Carom)127.51 (Carom)120.55 (Carom)20.81 (ArCH3)Chapter Three^ 60Cp*W(NO){712-S2C(PMe3)Ph}Ph 8.20 (br s, 2H, o-ArH)7.84 (d, 3JHH = 8.4 Hz, 2H, o-ArH)173.99 (Cipso)a143.78 (Carom)7.34 (t, 3JHH = 7.2 Hz, 2H, m-ArH) 138.49 (Carom)7.16 (t, 3JHH = 7.2 Hz, 1H, p-ArH) 128.33 (Carom)7.14 (t, 3JHH = 7.2 Hz, 2H, m-ArH) 128.27 (Carom)6.99 (t, 3JHH = 7.2 Hz, 1H, p-ArH) 127.68 (Carom)1.70 (s, 15H, C5(CH3)5) 127.56 (Caron)0.86 (d, 1./pH = 12.6 Hz, 9H,P(CH3)3)127.52 (Carom)123.84 (Carom)110.68 (C5(CH3)5)56.32 (d, 1Jpc = 54Hz, S2 C)10.14 (C5(CH3)5)7.20 (d, 1Jpc = 57Hz, P(CH3)3)Cp*W(N0)(712-02CCD3)Ph 7.90 (d, 3JHH = 7.2 Hz, 2H, o-ArH) 177.74 (C=0)7.33 (t, 3JHH = 7.6 Hz, 2H, m-ArH) 135.60 (Carom)7.17 (t, 3JHH = 7.8 Hz, 1H, p-ArH) 128.62 (Carom)1.51 (s, 15H, C5(CH3)5) 125.90 (Carom)112.35 (C5(CH3)5)19.49 (t, 1Jci3 = 7.8Hz, CD3)9.10 (C5(CH3)5)a in CD2C12 .3.3 Results and DiscussionReaction of Cp*W(NO){n2-N(p-tol)C(0)Ph}Ph with Protonic Acids. A commonmeans of liberating a modified heterocumulene moiety from an organometallic complex is byprotonolysis. 2,5 This method was applied to the heterocumulene-inserted productssynthesized in this work with Cp*W(NO){11 2-N(p-tol)C(0)Ph}Ph being the modelheterocumulene-inserted complex, selected on the basis of (1) its ease of synthesis and (2) itshydrolysis product, p-tolylbenzamide, being innocuous and conducive to handling andspectral identification. The reactions with three protonic acids (water, acetic acid-d4 , andChapter Three^ 61hydrochloric acid) are reported and discussed. In all cases, the hydrolysis product, p-tolylbenzamide, is formed. However, reaction with each acid gives rise to differentorganometallic products and thus, each reaction will be considered in turn.Reactio. ,. of Cp*W(NO){712-N(p-tol)C(0)Ph}Ph with an excess of water leads to theformation of two products, p-tolylbenzamide and Cp*W(0)2Ph (eq 3.2). This reactionpresumably occurs by attack of H+ at the nucleophilic lone-pair electrons on nitrogen andresults in removal of the amide moiety. Further reactivity of the putative 15-electronCp*W(NO)Ph fragment with additional water leads to the stable dioxo species. Theorganometallic product of reaction 3.2, Cp*W(0)2Ph, is typical of the reaction of water withCp'W(NO)R2 (R = aryl). 4 Stoichiometric addition of water to Cp*W(N0){12-N(p-tol)C(0)Ph}Ph was not attempted. 0+ PhCN-ArHAr =p-tol.ii0/ \ -j—PhPh^NN IO ArXS H2O lwoZr I A:IPh(3.2)p-Tolylbenzamide sublimes at 100 °C under static vacuum and is stable to air. It iseasily identified by 1H and 13C{ 1}1} NMR spectroscopy due to the aryl-methyl group whichaffords signals at 8 1.67 (CH3) and 8 20.8 ppm (CH 3), respectively. The IR spectrum of p-tolylbenzamide contains a strong, distinctive band at 1649 cm -1 assignable to the amidev(CO) stretch. 6The reaction of Cp*W(NO)012-N(p-tol)C(0)Ph}Ph with an excess of acetic acid-d4(eq 3.3) confirms that the proton of the resulting amide originates from the protonic acid.The low-resolution mass spectrum of the reaction mixture shows a parent peak for p-tolylbenzamide-d 1 [11+ = 212, one mass unit larger than for the mass spectrum of the non-Chapter Three^ 62deuterated amide. The absence of a broad NH resonance at 6 6.85 ppm in the 1H NMRspectrum supports deuterium incorporation into the functionalized heterocumulene product.0 0W .,,,,u ^WPh/Ph / - \0^+ PhCN-Ar^(3.3)/■10 Ar Ar =p-tolThe organometallic product of reaction 3.3 is the acetate species Cp*W(NO)(r1 2-02CCD3)Ph. 1H NMR spectroscopy is insensitive to deuterons and thus the correspondingspectrum shows only resonances due to one phenyl group and the Cp* ligand. The 13C{ 1H}NMR spectrum has a resonance at 6 177.7 ppm which is attributable to the carboxylatecarbon. 5 ' 7 A triplet at 5 19.5 ppm reveals deuterium-carbon coupling ( 1-1cD = 7.8 Hz) ofthe acetate methyl-d3 group. The IR spectrum of Cp*W(NO)(r1 2-02CCD3)Ph has a strongband at 1584 cm -1 that is assignable to a nitrosyl stretch. It is similar to v(NO) observed inthe i2-benzoate analogue Cp*W(N0)(11 2-02CCPh)Ph described in Chapter Two (v(NO)1585 cm -1 ). Due to the presence of many high-intensity features in the 1640-1380 cm -1region, no definite v(CO 2) assignments are possible. However, by analogy withCp*W(N0)(112-02CPh)Ph, the bonding of the acetate ligand is best formulated as dihapto, astrong linkage which is impervious to excess acetic acid.The addition of one equivalent of hydrochloric acid to Cp*W(NO){i 2-N(p-tol)C(0)Ph}Ph was expected to generate p-tolylbenzamide and the monochloride speciesCp*W(N0)(Ph)C1 (eq 3.4). However, even at low temperatures, the dichloride complexCp*W(NO)C12 is the only organometallic species generated from this reaction with HC1 (eq3.5).Reaction 3.5 was monitored by IR spectroscopy as THE solutions, and three IRspectra of the region 1700-1300 cm -1 are shown in Figure 3.1. The top spectrum (a) is the0Chapter Three^ 63 0+ PhCN-ArHAr =p-tolW^HC1Ph/ - \/%1—--Phfi0 ArPh/ - \ ClO(3.4)()+ PhCN-Ar + C6H6 (3.5)Ar =p-tolW^HC1Ph/ \N —PhN0 ArC1/ \ CI0IR spectrum of Cp*W(NO)tri2-N(p-tol)C(0)Ph}Ph. The strong band at 1582 cm-1 isassignable to the nitrosyl-stretching frequency of the starting material. Upon addition of HC1(1 equiv) and after one hour, this signal decreases to one-half its original intensity, as seen inthe middle spectrum (b). Two new bands are also apparent in this spectrum: the band at1678 cm -1 is the amide v(CO) stretch of the p-tolylbenzamide and that at 1626 cm -1 , equal inintensity to the v(NO) of Cp*W(NO){1-12-N(p-tol)C(0)Ph}Ph, is the v(NO) ofCp*W(NO)C12 . The third spectrum (c) shows the species present after a total of twoequivalents of HC1 have been added. Cp*W(NO){71 2-N(p-tol)C(0)Ph}Ph (v(NO) 1582 cm -1)has all but disappeared, leaving only p-tolylbenzamide and Cp*W(NO)C12 .From these observations, a stoichiometric cycle can be constructed for the activationand functionalization of heterocumulenes (Scheme 3.1). The first step involves the formationof the diaryl complex from the dichloride precursor with a diarylmagnesium reagent.Reaction with a heterocumulene leads to its insertion into one W-aryl bond to give an 18-electron complex. Treatment with hydrochloric acid produces both aryl-H and the arylcarboxylic acid (or analogue) as well as regenerates the starting dichloride compound.aChapter Three^ 64In0N1700^1620^1540^1480^1380^1300WAVENUMBERS <CM-1>Figure 3.1. Reaction 3.5 Monitored by IR Spectroscopy (THF solution).Chapter Three^ 65Scheme 3.1. Stoichiometric Cycle of Cp*W(NO)C12 and Heterocumulene X=C =Y.Ar-HXIIAr-C-YH Ar2Mg^MgCl2WA/N0Ar/ Ar0Though not a catalytic cycle, the series of reactions shown in Scheme 3.1 is significantsince the organometallic complex is regenerated in situ and can be subjected to subsequentcycles. In general, hydrolysis reactions of insertion products result in complete destructionof the organometallic complex upon treatment with a hydrolyzing agent. 2Heterocumulene-Inserted Products and Lewis Bases. Based on spectroscopic data(Chapter Two), the bonding of inserted heterocumulenes appears to be dihapto in nature.However, since no X-ray crystallographic studies were successful, 8 little can be saidconcerning this mode of coordination. For example, the question of the nature of the dihaptolinkage (symmetric or asymmetric) is unanswered. Furthermore, the strength and degree ofsuch bonding remain undetermined in the absence of structural data.(3.7)zo0Cp2Zr0ClTHE Chapter Three^ 66Another way to study the dihapto heterocumulene interaction is to probe its behaviourin the presence of Lewis bases. The basis of this strategy is the following postulate: if the112-heterocumulene ligand is functioning as a 3-electron donor (consisting of a 1-electron 6-bond and a 2-electron dative bond), then an appropriate external source of electron density inthe form of a 2-electron donor ligand may dislodge the 2-electron heterocumulene dativebond. This is illustrated for an i2-carboxylate complex in eq 3.6.+ L: 0L:(3.6)Reaction 3.6 holds true for the formate complex Cp2Zr(C1)(02CH). As a solid or inCH2C12 solution, this complex exists as a mixture of unidentate (1 1-) and bidentate (r1 2-)structures. However, in THF solution, the dominant structure is a THF adduct in which theformate ligand is unidentate. The THF solvent is apparently a sufficiently strong 2-electrondonor to be able to displace the 2-electron oxygen dative bond of the formate. 7aCarbon monoxide (CO) and trimethylphosphine (PMe3 ) were selected as Lewis basesfor the work presented here due to their potency, minimal steric profile, and ease ofhandling. All three isolated heterocumulene-inserted products were treated with CO andPMe3 in benzene-d6 solutions in NMR-tubes. In all but one case both Lewis bases failed toform adducts with the organometallic species, even at refluxing benzene temperatures. These67Chapter Threeobservations suggest that the dihapto linkage is very strong and is bestdescribed as being symmetrical with delocalized bonding over the threenon-metal atoms as shown on the right.The lon successful reaction lends further evidence to the above bonding description.Cp*W(NO)(ri2-S2CPh)Ph reacts in both C6D 6 and Et20 solutions with PMe3 at roomtemperature to give Cp*W(NO){112-S2C(PMe3)Ph}Ph in which the Lewis base has attackednot at the tungsten centre as expected, but rather at the dithiocarboxylate carbon (eq 3.8).Cp*W(NO){112-S2C(PMe3)Ph}Ph can be isolated as orange crystals from 1:1CH2C12/hexanes as a dichloromethane solvate. Redissolving the crystals in solvent (pentane,benzene, or Et20) causes a small degree of dissociation to Cp*W(N0)(i2-S2CPh)Ph andPMe3 as observed by a change in colour to purple and the appearance of signals due to theparent Cp*W(N0)(112-S2CPh)Ph in the 1H NMR spectrum. PMe3 PhPMe3/ \Ph^SN0Ph" \ = "SN0(3.8)The 1H NMR spectrum of Cp*W(NO){1 2-S2C(PMe3)Ph}Ph (Figure 3.2) is asexpected. The inequivalency of the two phenyl groups is demonstrated by two sets of arylresonances in the region 5 8.20-6.99 ppm. One phenyl group displays hindered rotation, asthe signal due to the ortho-protons is broadened significantly (5 8.20 ppm). The doublet at 50.86 ppm, integrating for nine protons, is attributable to the PMe3 protons. The splitting ofthe signal is due to coupling to the 31P nucleus ( 14H = 12.6 Hz). The most interestingfeature of the 13C{ 1H} NMR spectrum of Cp*W(N0){1 2-S2C(PMe3)Ph}Ph (Figure 3.3) isthe resonance at 5 56.3 ppm. This doublet is assignable to the rig-thiocarboxylate carbon andthe coupling ( 1Jpc = 54 Hz) indicates connectivity to phosphorus. The chemical shift of thisrrn-rptiwurpwilipiiiiimiturnmilitipminilittultrup -n-rpirrinTri8. 4^8. 2^8. 0^7. 8^7. 6^7. 4^7. 2^7. 0 PRM 8 rimilf^ r-r-r-T^r-r-r-rr^-r r-r-r-t -1-1 IT T-1 t rrrf 111 t-T r^ -1-8 7^6 5^4^3 2^1 PPMFigure 3.2. The 300 MHz 1 H NMR Spectrum of Cp*W(NO){ig-S2C(PMe 3)Ph}Ph in C6D6 (inset 8 8.5-6.8 ppm).WOOt-t^t 1- t1 8 0^r 1 - 1 - 1^I - 1 - r T - r^r^160 140I-1 1 . nr r^1- I10011 r^I^1-11-1-r-r r- r -t r ri - rr^r-t t -r^r80 60^40 20 PPMTi 1 - 1 - 1120Figure 3.3. The 75 MHz 13C{ 1 H} NMR Spectrum of Cp*W(NO){12-S2C(PMe3)Ph}Ph in CD2C12( • ).Chapter Three^ 70carbon resonance is shifted significantly upfield from the resonance observed in the parentcomplex Cp*W(NO)(r1 2-S2CPh)Ph (8 = 236.8 ppm) and indicates a significant change fromdelocalized bonding to that of a tetrahedral, a-bonded carbon.The IR spectrum of Cp*W(NO){r1 2-S2C(PMe3)Ph}Ph contains four strongabsorbances in the 1600-1500 cm -1 region. The most intense band (1548 cm -1) is tentativelyassigned to the nitrosyl stretch. With respect to the parent complex, v(NO) has shifted tolower energy by 30 cm-1 reflecting a significant increase in electron density at tungsten. Thebonding consequences of this datum will be discussed in detail in the following section.The Solid-State Molecular Structure of Cp*W(NO){112-S2C(PMe3)Ph}Ph. An X-ray study was performed on a single crystal of Cp*W(NO){11 2-S2C(PMe3)Ph}Ph and theORTEP and selected metrical parameters are found in Figure 3.4 and Table 3.3 respectively.The solid-state molecular structure confirms that the phosphine has indeed attacked thedithiolate carbon to form a rare phosphonium betaine ligand.9 The PMe3 unit is distal to theCp* ring suggesting that the proximal electrophilic C(17) site in the parent complex issterically sheltered by the bulky Cp* ligand. The P-C(17) bond length is comparable to thatfound in the structurally-characterized complexes [Ru{S2C(PMe2Ph)11}(PMe2Ph)3PF69a,[(triphos)Co{S2C(PEt3)H}](BPh4)29c, and [(triphos)Rh{S 2C(PEt3)11}KBPh4)29e (triphos =1,1,1-tris((diphenylphosphino)methypethane).The 4-membered metallacycle is both planar and symmetrical, a feature also seen inthe previously-mentioned complexes. The carbon-sulfur bond lengths and angles observed inCp*W(NO){112-S2C(PMe3)Ph}Ph are typical of such complexes. The geometry about C(17)is tetrahedral, a change from the putative planar geometry at this carbon in the parentcomplex. This structural change is in accord with the 13C{ 1H} NMR chemical shifts of thesignals due to the carbon in the two related complexes.The W-NO structural parameters are also of interest. The values for the W-N and N-O bond lengths as well as the W-N-O bond angle are similar to those of tungsten mono-nitrosyl complexes. 10 From these parameters, the bonding characteristics of the nitrosylChapter Three^ 71Figure 3.4. The ORTEP of Cp*W(NO){1 2-S2C(PMe3)Ph}Ph. (33% probability ellipsoidsare shown for the non-hydrogen atoms).ligand are best described as it being a 3-electron donor with degrees of both a-donation toand n*-backdonation from tungsten. 11A bonding description of Cp*W(NO){11 2-S2C(PMe3)Ph}Ph can be inferred from thecrystal structure. In valence-bond terms, the tetrahedral geometry about the phosphorus atomof the dithiol chelate can be accounted for by the placement of a formal positive charge onthe phosphorus atom. However, since an overall neutral charge is maintained, the complexmust be zwitterionic in nature, with the formal negative charge residing on the tungsten atomor distributed over the S-C-S system. The latter locale is unlikely as the W-S distances (ca.2.50 A) are indicative of single bonds. 12 The placement of a formal negative charge attungsten is corroborated by the low v(NO) in the IR spectrum, indicative of significantelectron density at the metal centre.Chapter Three^ 72Table 3.3. Selected Bond Distances and Bond Angles for Cp*W(NO){r1 2-S2C(PMe3)Ph}Ph.Atoms Bond Length (A) Atoms Bond Angles (°)W-CPa 2.061 (4) W-N-O 172.4 (4)W-N 1.753 (4) Sl-W-S2 69.88 (4)W-Cl1 2.208 (4) W-S1-C17 93.4 (1)W-S1 2.494 (1) W-S2-C17 93.4 (1)W-S2 2.503 (1) Sl-C17-S2 102.9 (2)N-0 1.224 (5) Sl-C17-P 106.5 (2)C17-S1 1.833 (4) S2-C17-P 105.9 (2)C17-S2 1.825 (4) P-C17-C21 109.9 (2)C17-C21 1.526 (6) Sl-C17-C21 114.9 (3)C17-P 1.823 (4) S2-C17-C21 115.9 (3)a CP - centre of the ri 5-05(CH3)5 ring.Insight into the bonding of both Cp*W(N0)(11 2-S2CPh)Ph and Cp*W(NO){1 2-S2C(PMe3)Ph}Ph is facilitated by a transition to molecular-orbital theory. As described inthe previous Chapter, the nitrosyl-stretching frequency in the IR spectrum is a sensitive probeof the electron density at the metal centre of an organometallic nitrosyl complex. It wassuggested there that the accuracy of the nitrosyl probe may be compromised by possibledonation of tungsten electron density to sulfur as well as NO it orbitals. In the case ofCp*W(NO)(r1 2-S2CPh)Ph, the carbon atom of the SS' chelate is most likely planar ingeometry. As a result, a great degree of electronic delocalization is possible due to extensiveconjugation of the thiobenzoate (Figure 3.5). Consequently, v(NO) indicates that thetungsten centre of Cp*W(N0)(112-S2CPh)Ph is Lewis-acidic. Furthermore, this bondingmode predicts that the carbon of the dithiolate chelate will be highly electrophilic in nature(i.e., have a low-lying LUMO).Chapter Three^ 73Figure 3.5. The thiobenzoate ligand: planar conjugation.The v(NO) of Cp*W(NO){12-S2C(PMe3)Ph}Ph is 30 cm -1 lower than that of itsparent complex Cp*W(N0)(11 2-S2CPh)Ph indicating that tungsten has become less Lewis-acidic upon reaction with the Lewis base PMe 3 . The carbon of the SS' chelate displaystetrahedral geometry and thus disrupts the type of conjugation possible in Cp*W(N0)(1 2-S2CPh)Ph (Figure 3.6). Though still a formal 3-electron donor, the phosphonium betaineligand is less of a Lewis it-acid than the thiobenzoate ligand. As a result, Cp*W(NO){7 -12-S2C(PMe3)Ph}Ph is less Lewis-acidic than its parent.....!..,...:KPMe3Figure 3.6. The phosphonium betaine ligand: conjugation broken.Treatment of Cp*W(N0)(n2-S2CPh)Ph with KW One of the conclusions toemanate from reaction 3.8 is that the carbon atom of the SS' chelate is electrophilic.Although they failed to react with Lewis bases, Cp*W(N0)(71 2-02CPh)Ph andCp*W(NO){71 2-N(p-tol)C(0)Ph}Ph are, by analogy, thought to possess a similarlyelectrophilic carbon. Further activation of the heterocumulene unit is theoretically possibleH- (3.9)\AT/Ph - S0Chapter Three^ 74by nucleophilic attack at the electrophilic site to generate an anionic complex, as shown in eq3.9.Subsequent reaction of the anion with two equivalents of an electrophile would create acationic complex (eq 3.10). PhH2 H+ (3.10)Unfortunately, the attempts to effect reaction 3.9 met with no success. The reactionmay have been hampered by the low solubility of potassium hydride in THF, although if thereaction were facile, KR would be continually dissolving as H - was consumed. A reagentwith better solubility such as LiBEt3H (Super Hydride) would perhaps be a more effectivesource of hydridic H - . 133.4 Summary and Future WorkTwo approaches to the functionalization of heterocumulene-inserted complexes havebeen reported. The first, reaction with protonic acids, is a means by which to harvest thefunctionalized heterocumulene from insertion compounds. Thus, the activation andChapter Three^ 75functionalization of heterocumulenes can be affected stoichiometrically, mediated byorganometallic complexes. The overall transformation is shown below (eq 3.11).YAr2Mg + X=C=Y + 2 HC1 ^ MgC12 + Ar-H + ArC4CH^(3.11)Chemistry arising from the reaction of heterocumulene-inserted complexes with Lewisbases, the second avenue to functionalization, provides a novel approach to the derivatizationof these compounds. The reaction of Cp*W(NO)(r1 2-S2CPh)Ph and PMe3 to giveCp*W(NO){712-S2C(PMe3)Ph}Ph indicates the potential of the central heterocumulenecarbon as a site of functionalization, complementing hydrolysis reactions in which the metal-chelating heteroatoms are the active sites. In principle, this highly electrophilic carbonshould be susceptible to attacks by nucleophiles and preliminary work in pursuit of this goalhas been described.The bonding characteristics of the heterocumulene-inserted products, as deduced fromtheir reactivity studies, are in harmony with the spectral features reported in Chapter Two.The 4-membered metallacycle of the heterocumulene-inserted product exhibits a relativelyrobust bonding arrangement, as illustrated by their general lack of reactivity with Lewis basesand, in the case of Cp*W(N0)(11 2-02CCD3)Ph, stability in the presence of excess aceticacid.Areas warranting further work include a more extensive investigation of theheterocumulene-inserted complexes by sequential nucleophilic-electrophilic reactivity (cf. eqs3.9-3.10). Another tactic to effect liberation of the derivatized heterocumulene from thetungsten centre involves the use of reducing conditions to induce reductive elimination ofArXC(Y)Ar (eq 3.12).Chapter Three^ 76reductive W^ ArC-XArAr/ \x--„-/—Ar^eliminationNO^Ar = Ph, o-tol, p-tol(3.12)3.5 References and Notes(1) Behr, A. Carbon Dioxide Activation by Metal Complexes; VCH: Weinheim,Germany, 1988.(2) (a) Kolomnikov, I. S.; Gusev, A. 0.; Belopotapova, T. S.; Grigoryan, M. K.;Lysyak, T. V.; Struchkov, Y. T.; Vol'pin, M. E. J. Organomet. Chem. 1974, 69,C10-C12. (b) Klei, E.; Telgen, J. H.; Teuben, J. H. J. Organomet. Chem. 1981,209, 297-307. (c) Gamborotta, S.; Strologo, S.; Floriani, C.; Chiesi-Villa, A.;Guastini, C. Inorg. Chem. 1985, 24, 654-660.(3) Wolfsberger, W.; Schmidbaur, H. Syn. Reactiv. Inorg. Metal-Org. Chem. 1974, 4,149.(4) Legzdins, P.; Lundmark, P. J.; Phillips, E. C.; Rettig, S. J.; Veltheer, J. E.Organometallics in press.(5) Darensbourg, D. J.; Grotsch, G.; Wiegreffe, P.; Rheingold, A. L. Inorg. Chem.1987, 26, 3827-3830.(6) Silverstein, R. M.; Bassler, G. C.; Morrill, T. C. Spectrometric Identification ofOrganic Compounds, 4th ed.; Wiley: New York, 1981; Chapter 3.(7) (a) Cutler, A.; Raja, M.; Todaro, A. Inorg. Chem. 1987, 26, 2877-2881. (b) Holl,M. M.; Hillhouse, G. L.; Folting, K.; Huffman, J. C. Organometallics 1987, 26,1522-1527.(8) Cp*W(N0)(712-S2CPh)Ph was crystallized successfully from benzene/pentane as thebenzene solvate, but single crystals decomposed upon exposure to X-rays.Chapter Three^ 77(9) See for example: (a) Ashworth, T. V.; Singleton, E.; Laing, M. J. Chem. Soc.,Chem. Commun. 1976, 875-876. (b) Werner, H.; Bertleff, W. Chem. Ber. 1980,113, 267-273. (c) Bianchini, C.; Meli, A.; Orlandini, A. Inorg. Chem. 1982, 21,4161-4165. (d) Bianchini, C.; Meli, A.; Orlandini, A. Inorg. Chem. 1982, 21,4166-4169. Bianchini, C.; Meli, A.; Dapporto, P.; Tofanari, A.; Zanello, P.Inorg. Chem. 1987, 26, 3677-3682.(10) For the X-ray structure of CpW(NO)(CH2SiMe3)2 see: Legzdins, P.; Rettig, S. J.;Sanchez, L. Organometallics 1988, 7,2394-2403. For that of Cp*W(N0)(o-to1)2see: Dryden, N. H.; Legzdins, P.; Rettig, S. J.; Veltheer, J. E. Organometallics inpress.(11) Richter-Addo, G. B.; Legzdins, P. Metal Nitrosyls; Oxford University Press: NewYork; 1992; Chapter 1.(12) Legzdins, P.; Sanchez, L. J. Am. Chem. Soc. 1985, 107, 5525-5526.(13) For use of Super Hydride, see: Feng, S. G.; White, P. S.; Templeton, J. L. J. Am.Chem. Soc. 1992, 114, 2951-2960.Appendix A:^ 78Isolation of Cp*W(112-0NPh)(NPh)PhA.1 IntroductionFrom the reaction of Cp*W(NO)Ph 2 with carbon dioxide, a complex that crystallizesfrom Et20 was isolated and fully characterized. The product, Cp*W(ONPh)(NPh)Ph, isbelieved to have resulted from the thermal or air-assisted decomposition of the bis(phenyl)complex, rather than a CO 2-induced transformation. Though incongruous with the theme ofthis Thesis, the result is interesting from the point of view of nitrosyl-bond cleavage and isconsequently presented in this Appendix.A.2 Experimental SectionReaction of Cp*W(NO)Ph2 with CO2. Solid Cp*W(NO)Ph2 (0.84 g, 2.0 mmol)was dissolved in benzene (15 mL) in a glass vessel equipped with a 4-mm Teflon stopcock.The blue solution was freeze-pump-thaw degassed three times, and the vessel was pressurizedwith CO2 (1-2 atm). Heating the solution at 60 °C overnight led to a change in colour toamber-brown. The benzene solution was transferred via cannula to a Schlenk tube, and thesolvent was removed in vacuo. The residue was dissolved in Et 20 (20 mL) andchromatographed on a column of neutral Alumina I (3 x 8 cm). Elution of the column withEt20 (150 mL) resulted in a yellow eluate. The Et20 was removed, and the yellow powderwas washed with pentane (2 x 5 mL) to obtain analytically pure Cp*W(11 2-0NPh)(NPh)Ph(0.10 g, 0.17 mmol, 8.4% yield).Anal. Calcd for C2 8H30N2OW: C, 56.58; H, 5.09; N, 4.71. Found: C, 56.20; H,5.25; N, 4.51. IR (Nujol mull): v(C=C) 1588, 1570 cm -1 ; v(CH) 764, 755, 739, 702, 687cm-1 ; also: 1359, 1202, 1152 cm -1 . Low-resolution mass spectrum (probe temperature 80°C): m/z 594 [P]±, 578 [P-0]+. NMR data for Cp*W(12-0NPh)(NPh)Ph are collected inTable A.1.Appendix A^ 79Further elution of the column with CH2C12 (50 mL) afforded a yellow eluate.Evaporation of the eluate yielded a pale yellow powder which was identified by IRspectroscopy (v(W=O) 936, 897 cm -1) as the known Cp*W(0)2Ph complex. 1 Finally, anorange-brown '.and eluted with THE (50 mL) and upon work-up, Cp*W(N0)(71 2-02CPh)Phwas isolated (Chapter Two).Table A.1. 1H and 13C{ 1H} NMR Data for Cp*W(1 2-0NPh)(NPh)Ph (in C6D6).Complex 1H NMR 13C{111} NMRCp*W(112-0NPh)(NPh)Ph 8.08 (d, 2JHH = 7.9 Hz, 2H, o-ArH) 172.38 (Carom)7.47 (d, 2JHH = 8.5 Hz, 2H, o-ArH) 163.84 (Carom)7.37 (t, 3JHH = 7.5 Hz, 2H, m-ArH) 154.23 (Carom)7.21 (t, 3JHH = 7.3 Hz, 1H, p-ArH) 138.00 (Carom)7.09 (t, 3JHH = 7.0 Hz, 2H, m-ArH) 128.14 (Carom)6.86 (t, 3JHH = 7.8 Hz, 2H, m-ArH) 126.10 (Carom)6.86 (t, 3JHH = 7.3 Hz, 1H, p-ArH) 125.27 (Carom)6.68 (t, 3JHH = 7.4 Hz, 1H, p-ArH) 124.41 (Carom)6.14 (d, 2JHH = 8.4 Hz, 2H, o-ArH) 122.10 (Carom)1.72 (s, 15H, C5(CH3)5) 116.70 (Carom)116.01 (C5(CH3)5)10.95 (C5(CH3)5)A.3 Results and DiscussionA current research interest of these laboratories is that of nitrosyl-bond cleavage. Thefirst reported example of this phenomenon is the water-induced transformation ofCpW(NO)(o-tol)2 to the oxo-imido complex CpW(0)(N-o-tol)(o-tol) (eq A.1). 2 Isotopiclabelling studies demonstrate that the isomerization is intramolecular. Since this initialdiscovery, two different bimetallic species have been characterized by X-ray diffraction; bothindicate cleavage of the nitrosyl bond (eqs A.2, A.3). 32^MoR/ \RN0RI^0Mo N =--- MoV I0XS H2, C6H6 -2 RH (A.2)2^WR7 = NC1N0Appendix A^ 80H2O e .N R0R= o-tolyl%0 i NRR%0 1 0(A.1)R CH2Silvle3(A.3)The isolation and characterization of Cp*W(r1 2-ONPh)(NPh)Phprovides the fourth example of NO-bond cleavage and only the secondexample in which the product of such a transformation ismonometallic.Cp*W(71 2-0NPh)(NPh)Ph is soluble in diethyl ether and isisolable as yellow thermally stable and air-stable crystals from Et20 in low yield. The 1 HNMR spectrum of this complex (Fig A.1) shows clearly the existence of three inequivalentphenyl groups. A 1H, 1H COSY experiment has led to the assignment of the ortho-, meta-,and para-proton resonances of each phenyl group. One set of signals is shifted upfieldI^trillIIII11117111IMITITTITTFMTMTpTITITIITFITTTIMITMUITTFT1711 i II8.2 8 0 7 8 7 6 7.4 7 2 7 0 6.8 6.6 6.4 6.2 MOTT 1-1 r r —r^r r rT^7-7 T- I -^-I- -17 -7- 1-1- 1 TT T 1 r T r—r—r-^—T— r—r—r r 1-1 r—r— T —r r—r e t8 7 6 5^4 3^2 1 r'PMFigure A.1. The 300 MHz 1 H NMR Spectrum of Cp*W(NO)(1 2-0NPh)(NPh)Ph in C6D6 (inset 5 8.8-6.0 ppm).r-ri r .. r vr-rr^rt^r-t rr-i - i . r-rt^Fr. r -I - r- rr ritri - 1 iiriTI^r^r-r . T^1-1^ rl180^160 40 120^100^80 60 40^20 PPMFigure A.2. The 75 MHz 13C{ 1 14} NMR Spectrum of Cp*W(N0)(1 2-0NPh)(NPh)Ph in C6D6.Appendix A^ 83relative to the rest and is tentatively assigned to the nitrosobenzene protons. A similar shift isobserved in the spectrum of the complex Mo(r1 2-0NPh)(S2CNEt2)2 . 4 The upfield shift ofthe signals in the molybdenum complex is indicative of a transfer of electron density to themetal from the nitrosobenzene ligand and is also observed with Group 10 complexescontaining this ligand. 5 The upfield signal (5 1.72 ppm) is attributable to the Cp* methylprotons. The 13C{ 1H} NMR spectrum (Figure A.2) shows the presence of only Cp* andphenyl-carbon resonances.The IR spectrum shows an intense band at 1359 cm -1 as well as two bands of mediumintensity at 1202 and 1152 cm -1 Metal-imido stretching frequencies generally occur in theregion of 1360-850 cm -1 . 6 Furthermore, it is expected that the v(NO) stretch would alsoappear in this region.? Consequently, none of these three bands can be assigned withconfidence. Phenyl C=C stretches are found at 1588 and 1570 cm -1 , whereas CH out-of-plane modes are seen between 765 and 685 cm -1 . 8An ORTEP of Cp*W(ONPh)(NPh)Ph is displayed in Figure A.3. Of interest are theimido and the nitrosobenzene ligands. The W-N bond length of the imido moiety (1.758 (4)A) falls within the range observed for the W-N distance in other tungsten-aryl imidocomplexes (1.73-1.77 A). 6 The imido linkage is essentially linear and is consistent with theimido ligand functioning as a formal 2-electron donor to the tungsten centre. The W-N(1)bond length (2.060 (4) A) is considerably longer than the W-N(2) bond, and is indicative of abond order of one. At 1.975 (4) A, the W-0 distance is best characterized as a single bond.The N(1)-0 bond length (1.432 (6) A) displays single-bond character as well, and the dihaptolinkage to tungsten is best described as it being a metallooxaziridine. 9 Overall, the 12-nitrosobenzene ligand functions as a 2-electron donor to tungsten, and the metal's valenceshell thus contains a total of 16 electrons (Cp* = 5, W = 6, Ph = 1, NPh = 2, ONPh =2).The observed stability of Cp*W(r12-0NPh)(NPh)Ph can be explained by it having achieved:(1) coordinative saturation (7-coordinate) and (2) electronic saturation from some degree of7c-bonding from the lone pair electrons on the two nitrogen and one oxygen atoms.Appendix A^ 84C9Figure A.3. ORTEP of Cp*W(r12-0NPh)(NPh)Ph, (33% probabilility ellipsoids are shownfor the non-hydrogen atoms).Table A.2. Selected Bond Distances and Bond Angles for Cp*W(r1 2-0NPh)(NPh)Ph.Atoms Bond Length (A) Atoms Bond Angle (°)W-CPa 2.082 O-W-N1 41.5 (2)W-N1 2.060 (4) O-W-N2 111.08 (2)W-N2 1.758 (4) W-N2-C23 176.3 (4)W-0 1.975 (4) 0-N1-C17 111.0 (4)W-Cll 2.170 (5) 01-W-C11 81.1 (2)N1-0 1.432 (6) N2-W-C11 94.1 (2)N1-C17 1.435 (7) N1-W-N2 102.5 (2)N2-C23 1.389 (6)a CP - centre of the i5-05(CH3)5 ring.Appendix A^ 85Mechanistic Speculation. The complex Cp*W(0)2Ph is also formed during thisreaction. The dioxo species, Cp'W(0)2R (R = alkyl, aryl), are common isolable products ofthe decomposition of Cp'W(NO)R 2 with dioxygen and water (eq A.4). The mechanism ofreaction A.4 is not well understood, and the species 'RNO' (as required by mass balance) hasyet to be detected. Cp*W(ONPh)(NPh)Ph, relative to is parent complex, contains anadditional 'NPh' group. In the absence of any further and conclusive evidence, this 'NPh'species can only be postulated to arise from a free or an organometallic-bound NPh-containing species. This putative species may, in turn, originate from some process in whichNO-bond cleavage plays a role.02/H20 ),^,W^ W^+ decomposition products^(A.4) 1R/ = R 0 i 0RA.4 Summary and Future WorkThe reaction of Cp*W(NO)Ph2 with CO2 yields, in addition to the expected CO 2-inserted product Cp*W(N0)(712-02CPh)Ph, two species: the familiar Cp*W(0)2Ph complex,and Cp*W(N0)(1 -12-0NPh)(NPh)Ph, now fully characterized. The origin of the lattercomplex is puzzling and the process by which Cp*W(N0)(11 2-0NPh)(NPh)Ph is formedcertainly merits further examination. Of particular intrigue is the possibility that cleavage ofthe nitrosyl ligand, a recently-discovered phenomenon, may be implicated in the formation ofCp*W(N0)(12-0NPh)(NPh)Ph. A key reaction to study in the future would be thebehaviour of Cp*W(NO)Ph 2 in the absence of CO2 under the conditions outlined in theexperimental section; this will ascertain whether the tranformation is induced by carbondioxide. Obviously, the chemistry reported and discussed here is far from complete, andwarrants thorough investigation.N0Appendix A^ 86A.5 References(1) Legzdins, P.; Lundmark, P. J.; Phillips, E. C.; Rettig, S. J.; Veltheer, J. E.Organometallics in press.(2) Legzdins, P.; Rettig, S. J.; Ross, K. J.; Veltheer, J. E. J. Am. Chem. Soc. 1991,113, 4361-4363.(3) (a) Legzdins, P.; Young, M.A.; Batchelor, R. J.; Einstein, F. W. B. Presented atthe 75th Canadian Chemical Society Conference, Edmonton, AB, June, 1992; Poster370. (b) Legzdins, P.; Lundmark; P. J. unpublished observations.(4) Maatta, E. A.; Wentworth, R. A. D. Inorg. Chem. 1980, 19, 2597-2599.(5) Otsuka, S.; Aotani, Y.; Tatsuno, Y.; Yoshida, T. Inorg. Chem. 1976, 15, 656-660.(6) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds. Wiley-Interscience:Toronto, 1988.(7) Boyd, A. S. J.; Browne, G.; Gowenlock, B. G.; McKenna, P. J.Organomet. Chem.1988, 345, 217-220.(8) Lambert, J. B.; Shurvell, H. F.; Lightner, D.; Cooks, R. G. Introduction to OrganicSpectroscopy; Macmillan: New York, 1987.(9)^Liebeskind, L.S.; Sharpless, K. B.; Wilson, R. D.; Ibers, J. A. J. Am. Chem. Soc.1978, 100, 7061-7063.Appendix B^ 87Appendix B:X-ray Crystallographic AnalysesB.1. X-ray Crystallography of Cp*W(NO){772-S2C(PMe3)Ph)Ph.Appendix B^ 88A. Crystal DataEmpirical Formula^ C27 H36 Cl 2 NOPS 2 WFormula Weight 740.44Crystal Color, Habit^ orange, prismCrystal Dimensions^(mm)Crystal SystemNo. Reflections Used for Unit0.300 X 0.400monoclinicX 0.450Cell Determination (29 range) 25^( 35.0 - 40.0°)Omega Scan Peak Widthat Half-height 0.40Lattice Parameters:a = 8.482 (1)Ab 27.410 (2)Ac 13.054 (3)A92.02 (1) °V = 3033 (1)A 3Space Group^ P21 /n (#14)Z value 4Dcalc^ 1.621 g/cm 3F000 1472P (MoKm)^ 42.72 cm-1B. Intensity MeasurementsDiffractometer^ Rigaku AFC6SRadiation MoKa (X = 0.71069 A)Temperature^ 21°CTake-off Angle 6.0°Detector Aperture^ 6.0 mm horizontal6.0 mm verticalAppendix B^ 89Crystal to Detector Distance^285 mmScan TypeScan Rate^ 32.0°/min (in omega)(8 rescans)Scan Width^ (0.91 + 0.35 tan9)°629max 0.0°No. of Reflections Measured^Total: 9580Unique: 8837 (R int^.032)Corrections^ Lorentz-polarizationAbsorption(trans. factors: 0.60 - 1.00)Decay (-18.00% decline)Secondary Extinction(coefficient:^0.148(6) E-06)C^Structure Solution and RefinementStructure Solution^ Patterson MethodRefinement^ Full-matrix least-squaresFunction Minimized^ E w (1Fol - IFcl) 2Least-squares Weights 4Fo 2/a2 (Fo 2 )p-factor^ 0.00Anomalous Dispersion^ All non-hydrogen atomsNo.^Observations^(I>3.00a(I))No. VariablesReflection/Parameter RatioResiduals:^R; RwGoodness of Fit IndicatorMax Shift/Error in Final Cycle537531716.960.029;1.700.21p.027Maximum Peak in Final Diff. Map^0.66 eMinimum Peak in Final Diff. Map^-0.78 e-/AJAppendix B^ 90Table .^Final atomic coordinates (fractional) and Beg (40)*atom x Y z BegfW(1) 0.30894(2) 0.350948(6) 0.42478(1) 2.856(7)S(1) 0.2788(1) 0.41378(4) 0.5608(1) 3.73(5)S(2) 0.5128(1) 0.33854(4) 0.5656(1) 3.84(5)P(1) 0.5900(1) 0.43279(4) 0.6571(1) 4.00(6)0(1) 0.5589(5) 0.3629(2) 0.2730(3) 8.4(3)N(1) 0.4607(4) 0.3606(1) 0.3394(3) 4.6(2)C(1) 0.2955(5) 0.2675(2) 0.4071(4) 4.1(2)C(2) 0.2073(7) 0.2881(2) 0.3238(4) 4.4(2)C(3) 0.0713(6) 0.3099(2) 0.3645(4) 4.2(2)C(4) 0.0772(5) 0.3030(2) 0.4712(4) 3.8(2)C(5) 0.2101(6) 0.2760(2) 0.4981(4) 3.8(2)C(6) 0.4433(7) 0.2374(2) 0.3970(6) 7.6(4)C(7) 0.2404(9) 0.2830(2) 0.2124(4) 7.6(4)C(8) -0.0684(7) 0.3290(2) 0.3033(6) 7.5(4)C(9) -0.0466(7) 0.3190(2) 0.5451(6) 7.2(4)C(10) 0.2478(7) 0.2551(2) 0.6026(4) 6.1(3)C(11) 0.1770(5) 0.4085(1) 0.3402(4) 3.5(2)C(12) 0.2029(6) 0.4165(2) 0.2363(4) 4.3(2)C(13) 0.1188(7) 0.4513(2) 0.1779(4) 5.7(3)C(14) 0.0063(7) 0.4789(2) 0.2230(5) 6.3(3)C(15) -0.0239(7) 0.4732(2) 0.3236(5) 5.7(3)C(16) 0.0586(6) 0.4383(2) 0.3809(4) 4.5(2)C(17) 0.4342(5) 0.3872(1) 0.6445(3) 3.4(2)C(18) 0.6617(6) 0.4497(2) 0.5354(4) 5.4(3)C(19) 0.5200(7) 0.4857(2) 0.7193(4) 5.6(3)C(20) 0.7526(6) 0.4094(2) 0.7317(4) 5.6(3)Appendix BTable^.atomFinal atomic coordinatesx(fractional)z91and Beg (A2 )*BegC(21) 0.3814(6) 0.3720(2) 0.7504(3) 3.8(2)C(22) 0.4530(7) 0.3343(2) 0.8041(4) 5.2(3)C(23) 0.406(1) 0.3218(2) 0.9013(5) 7.1(4)C(24) 0.290(1) 0.3476(3) 0.9450(5) 8.3(5)C(25) 0.2155(9) 0.3851(3) 0.8938(5) 7.8(4)C(26) 0.2595(7) 0.3973(2) 0.7965(4) 5.7(3)Cl(1) 0.3221(3) 0.12491(8) 0.5180(2) 10.6(1)C1(2) 0.1542(4) 0.0372(1) 0.5262(2) 16.4(2)C(27) 0.1941(9) 0.0907(3) 0.5856(6) 8.9(5)*Beg = (8/3)m2 In.i..13 a.*a.*(a.•a.3 )Table^. Bond lengths (A) with estimated standard deviations.*atom^atom^distance^atom^atom^distanceW(1) S(1) 2.494(1) C(2) C(7) 1.497(7)W(1) S(2) 2.503(1) C(3) C(4) 1.405(7)W(1) N(1) 1.753(4) C(3) C(8) 1.499(7)W(1) C(1) 2.301(4) C(4) C(5) 1.383(6)W(1) C(2) 2.318(5) C(4) C(9) 1.516(7)W(1) C(3) 2.416(4) C(5) C(10) 1.504(7)W(1) C(4) 2.458(4) C(11) C(12) 1.399(6)W(1) C(5) 2.428(4) C(11) C(16) 1.413(6)W(1) C(11) 2.208(4) C(12) C(13) 1.400(7)W(1) Cp 2.061(4) C(13) C(14) 1.367(8)Appendix B^ 92S(1) C(17) 1.833(4) C(14) C(15) 1.356(8)S(2) C(17) 1.825(4) C(15) C(16) 1.388(7)P(1) C(17) 1.823(4) C(17) C(21) 1.526(6)P(1) C(18) 1.782(5) C(21) C(22) 1.378(6)P(1) C(19) 1.774(6) C(21) C(26) 1.398(7)P(1) C(20) 1.780(5) C(22) C(23) 1.387(8)0(1) N(1) 1.224(5) C(23) C(24) 1.35(1)C(1) C(2) 1.415(7) C(24) C(25) 1.37(1)C(1) C(5) 1.431(6) C(25) C(26) 1.377(8)C(1) C(6) 1.511(6) C1(1) C(27) 1.704(8)C(2) C(3) 1.420(7) C1(2) C(27) 1.688(8)*Here and elsewhere, Cp refers to the unweighted centroid ofthe C(1-5) cyclopentadienyl ring.Table . Bond angles (deg) with estimated standard deviations.atom atom atom angle atom atom atom angleS(1) W(1) S(2) 69.88(4) C(3) C(4) C(9) 126.2(5)S(1) W(1) N(1) 116.5(1) C(5) C(4) C(9) 124.7(5)S(1) W(1) C(11) 78.5(1) C(1) C(5) C(4) 107.9(4)S(1) W(1) Cp 123.5(1) C(1) C(5) C(10) 126.4(5)S(2) W(1) N(1) 89.1(1) C(4) C(5) C(10) 125.4(5)S(2) W(1) C(11) 142.1(1) W(1) C(11) C(12) 120.2(3)S(2) W(1) Cp 108.4(1) W(1) C(11) C(16) 125.4(4)N(1) W(1) C(11) 86.9(2) C(12) C(11) C(16) 114.3(4)N(1) W(1) Cp 120.0(1) C(11) C(12) C(13) 122.7(5)C(11) W(1) Cp 106.2(1) C(12) C(13) C(14) 119.5(5)W(1) S(1) C(17) 93.4(1) C(13) C(14) C(15) 120.8(5)W(1) S(2) C(17) 93.4(1) C(14) C(15) C(16) 119.4(5)C(17) P(1) C(18) 111.5(2) C(11) C(16) C(15) 123.2(5)Appendix B^ 93C(17) P(1) C(19) 110.4(2) S(1) C(17, S(2) 102.9(2)C(17) P(1) C(20) 110.3(2) S(1) C(17) P(1) 106.5(2)C(18) P(1) C(19) 109.0(3) S(1) C(17) C(21) 114.9(3)C(18) P(1) C(20) 107.4(3) S(2) C(17) P(1) 105.9(2)C(19) P(1) C(20) 108.1(3) S(2) C(17) C(21) 115.9(3)W(1) N(1) 0(1) 172.4(4) P(1) C(17) C(21) 109.9(3)C(2) C(1) C(5) 107.7(4) C(17) C(21) C(22) 121.8(4)C(2) C(1) C(6) 124.6(5) C(17) C(21) C(26) 120.0(4)C(5) C(1) C(6) 127.3(5) C(22) C(21) C(26) 118.2(5)C(1) C(2) C(3) 107.2(4) C(21) C(22) C(23) 121.0(5)C(1) C(2) C(7) 126.7(5) C(22) C(23) C(24) 119.5(6)C(3) C(2) C(7) 125.9(5) C(23) C(24) C(25) 121.1(6)C(2) C(3) C(4) 108.2(4) C(24) C(25) C(26) 119.7(6)C(2) C(3) C(8) 125.8(5) C(21) C(26) C(25) 120.4(6)C(4) C(3) C(8) 125.1(5) C1(1) C(27) C1(2) 111.2(4)C(3) C(4) C(5) 108.9(4)Appendix B^ 94B.2. X-ray Crystallography of Cp*W(ONPh)(NPh)Ph.C9Appendix BA. Crystal DataEmpirical Formula^ C28H 30N2OWFormula Weight 594.41Crystal Color, Habit^ orange, prismCrystal Dimensions (mm)Crystal SystemNo. Reflections Used for Unit0.200 X 0.250orthorhombicX 0.450Cell Determination (29 range) 25^( 36.4 - 42.1°)Omega Scan Peak Widthat Half-height 0.38Lattice Parameters:a = 16.538 (2)Ab = 21.803 (4)Ac = 13.492 (3)AV = 4865 (1)A 3Space Group^ PcabZ value 8Dcalc^ 1.623 g/cm 3F000 235241 (MoKa)^ 48.70 cm-1B. Intensity MeasurementsDiffractometer^ Rigaku AFC6SRadiation Mokm (X = 0.71069 A)Temperature^ 21°CTake-off Angle 6.0°Detector Aperture^ 6.0 mm horizontal6.0 mm verticalCrystal to Detector Distance^285 mm9596w- 2 e32.0°/min (in omega)(8 rescans)(1.10 + 0.35 tane) °55.0°Total: 6195Lorentz-polarizationAbsorption(trans. factors: 0.61 - 1.00)Secondary Extinction(coefficient:^0.32(2) E-07)Appendix BScan TypeScan RateScan Width29maxNo. of Reflections MeasuredCorrectionsC. Structure Solution and RefinementStructure Solution^ Patterson MethodRefinement^ Full-matrix least-squaresFunction Minimized^ I w (IF01 - Irci) 2Least-squares Weights 4Fo 2/a2 (Fo2 )p-factor^ 0. 00Anomalous Dispersion^ All non-hydrogen atomsNo.^Observations^(I>3.00a(I))No. VariablesReflection/Parameter RatioResiduals:^R; RwGoodness of Fit IndicatorMax Shift/Error in Final Cycle299929010.340.026;1.390.030.024Maximum Peak in Final Diff. Map^0.49 e-/A!Minimum Peak in Final Diff. Map -0.44 e-/A 4Appendix B^97Tableatom.^Final atomic coordinatesx(fractional)zand Beg (A2)*BegW(1) 0.35446(1) 0.36028(1) 0.38365(1) 2.426(8)0(1) 0.3803(2) 0.3068(2) 0.2699(3) 3.4(2)N(1) 0.4550(3) 0.3303(2) 0.3076(3) 3.2(2)N(2) 0.3484(3) 0.4378(2) 0.3485(3) 2.8(2)C(1) 0.3159(4) 0.3709(3) 0.5505(4) 2.8(3)C(2) 0.4006(4) 0.3790(3) 0.5469(4) 3.1(3)C(3) 0.4352(4) 0.3218(3) 0.5195(4) 3.3(3)C(4) 0.3716(4) 0.2785(3) 0.5071(4) 3.2(3)C(5) 0.2974(3) 0.3091(3) 0.5284(4) 2.9(3)C(6) 0.2550(4) 0.4159(3) 0.5887(4) 4.1(3)C(7) 0.4472(4) 0.4351(3) 0.5717(5) 4.9(4)C(8) 0.5238(4) 0.3053(4) 0.5135(5) 5.1(4)C(9) 0.3813(4) 0.2124(3) 0.4777(5) 4.9(4)C(10) 0.2159(4) 0.2792(3) 0.5397(4) 4.0(3)C(11) 0.2324(3) 0.3390(3) 0.3359(4) 2.7(3)C(12) 0.2119(4) 0.2811(3) 0.2984(4) 3.9(3)C(13) 0.1321(4) 0.2673(3) 0.2713(4) 4.5(4)C(14) 0.0738(4) 0.3108(4) 0.2811(5) 5.3(4)C(15) 0.0931(4) 0.3680(4) 0.3143(5) 4.3(4)C(16) 0.1709(3) 0.3814(3) 0.3426(5) 3.6(3)C(17) 0.4913(3) 0.3723(3) 0.2388(4) 3.1(3)C(18) 0.5574(4) 0.4069(3) 0.2737(5) 4.6(4)C(19) 0.5962(4) 0.4450(4) 0.2098(6) 5.7(4)C(20) 0.5733(4) 0.4502(3) 0.1132(6) 5.3(4)C(21) 0.5093(4) 0.4158(3) 0.0777(5) 4.4(3)Appendix B^ 98Table^. Final atomic coordinates (fractional) and Beg (A2 )*atom^x^y^z^BegC(22) 0.4687(3) 0.3765(3) 0.1414(4) 3.7(3)C(23) 0.3444(3) 0.5001(2) 0.3272(4) 3.0(3)C(24) 0.3083(4) 0.5413(3) 0.3928(5) 4.7(3)C(25) 0.3037(5) 0.6023(3) 0.3676(7) 5.8(4)C(26) 0.3354(5) 0.6231(3) 0.2812(7) 6.3(5)C(27) 0.3709(5) 0.5836(4) 0.2165(6) 5.8(4)C(28) 0.3754(4) 0.5218(3) 0.2382(5) 4.4(3)*Beg(8/3)n2 ZEU..1)a.*a.]*(a.•a.])Table . Bond lengths^(A) with estimated standard deviations.*atom atom distance atom atom distanceW(1) 0(1) 1.975(4) C(4) C(9) 1.503(8)W(1) N(1) 2.060(4) C(5) C(10) 1.505(8)W(1) N(2) 1.758(4) C(11) C(12) 1.402(8)W(1) C(1) 2.352(5) C(11) C(16) 1.377(7)W(1) C(2) 2.366(6) C(12) C(13) 1.402(8)W(1) C(3) 2.418(6) C(13) C(14) 1.36(1)W(1) C(4) 2.456(6) C(14) C(15) 1.36(1)W(1) C(5) 2.439(6) C(15) C(16) 1.373(8)W(1) C(11) 2.170(5) C(17) C(18) 1.409(8)W(1) Cp 2.082 C(17) C(22) 1.370(8)0(1) N(1) 1.432(6) C(18) C(19) 1.359(9)N(1) C(17) 1.435(7) C(19) C(20) 1.36(1)N(2) C(23) 1.389(6) C(20) C(21) 1.384(9)Appendix B^ 99C(1) C(2) 1.413(7) C(21) C(22) 1.387(8)C(1) C(5) 1.414(8) C(23) C(24) 1.396(8)C(1) C(6) 1.497(8) C(23) C(28) 1.389(8)C(2) C(3) 1.421(8) C(24) C(25) 1.375(9)C(2) C(7) 1.485(8) C(25) C(26) 1.36(1)C(3) C(4) 1.423(8) C(26) C(27) 1.36(1)C(3) C(8) 1.510(8) C(27) C(28) 1.381(9)C(4) C(5) 1.425(8)* Here and elsewhere, Cp refers to the unweighted centroidof the C(1-5) cyclopentadienyl ring.Appendix B^ 100Table . Bond angles^(°) with estimated standard deviations.atom atom atom angle atom atom atom angle0(1) w(1) N(1) 41.5(2) C(1) C(5) C(4) 107.6(5)0(1) W(1) N(2) 111.8(2) C(1) C(5) C(10) 125.8(6)0(1) W(1) C(11) 81.1(2) C(4) C(5) C(10) 126.1(6)0(1) W(1) Cp 132.2 W(1) C(11) C(12) 121.6(4)N(1) W(1) N(2) 102.5(2) W(1) C(11) C(16) 121.6(4)N(1) W(1) C(11) 122.4(2) C(12) C(11) C(16) 116.8(5)N(1) W(1) Cp 108.5 C(11) C(12) C(13) 121.0(6)N(2) W(1) C(11) 94.1(2) C(12) C(13) C(14) 119.5(7)N(2) W(1) Cp 123.2 C(13) C(14) C(15) 120.2(6)C(11) W(1) Cp 106.9 C(14) C(15) C(16) 120.4(6)W(1) 0(1) N(1) 72.4(2) C(11) C(16) C(15) 122.0(6)W(1) N(1) 0(1) 66.1(2) N(1) C(17) C(18) 116.7(6)W(1) N(1) C(17) 117.2(3) N(1) C(17) C(22) 123.4(5)0(1) N(1) C(17) 111.0(4) C(18) C(17) C(22) 119.7(6)W(1) N(2) C(23) 176.3(4) C(17) C(18) C(19) 118.9(6)C(2) C(1) C(5) 109.0(5) C(18) C(19) C(20) 121.7(7)C(2) C(1) C(6) 126.7(6) C(19) C(20) C(21) 120.0(7)C(5) C(1) C(6) 123.5(5) C(20) C(21) C(22) 119.4(6)C(1) C(2) C(3) 107.4(6) C(17) C(22) C(21) 120.3(6)C(1) C(2) C(7) 127.5(6) N(2) C(23) C(24) 121.2(6)C(3) C(2) C(7) 125.0(6) N(2) C(23) C(28) 119.7(5)C(2) C(3) C(4) 108.3(5) C(24) C(23) C(28) 119.1(6)C(2) C(3) C(8) 127.8(6) C(23) C(24) C(25) 119.3(7)C(4) C(3) C(8) 123.6(6) C(24) C(25) C(26) 121.0(7)C(3) C(4) C(5) 107.6(5) C(25) C(26) C(27) 120.4(7)C(3) C(4) C(9) 125.9(6) C(26) C(27) C(28) 120.4(7)C(5) C(4) C(9) 126.4(6) C(23) C(28) C(27) 119.8(7)Appendix C:^ 101Spectral AppendixSpectral IndexThe 300 MHz 1H NMR Spectrum of Cp*W(NO)(r1 2-S2C-p-tol)(p-tol) ^ 102The 75 MHz 13C{ 111} NMR Spectrum of Cp*W(N0)(1 2-S2C-p-tol)(p-tol) ^ 103The IR Spectrum of Cp*W(N0)(1 2-S2C-p-tol)(p-to1) as a Nujol mull  104The 300 MHz 1H NMR Spectrum of Cp*W(NO){i 2-N(p-tol)C(0)Ph}Ph ^ 105The IR Spectrum of Cp*W(NO){71 2-N(p-to1)C(0)Ph}Ph as a Nujol mull ^ 106The 300 MHz 1H NMR Spectrum of Cp*W(NO)(r1 2-02CPh)Ph ^ 107The 75 MHz 13C{ 1H} NMR Spectrum of Cp*W(N0)(9 2-02CPh)Ph  108The IR Spectrum of Cp*W(N0)(112-02CPh)Ph as a Nujol mull ^ 109The 300 MHz 1H NMR Spectrum of Cp*W(N0)(1 2-02CPh)C1  110The IR Spectrum of Cp*W(N0)(1 2-02CPh)C1 as a Nujol mull ^ 111The 300 MHz 1H NMR Spectrum of Cp*W(NO){1 .12-S2C(PMe5)Ph}Ph ^ 112The 75 MHz 13C{ 1H} NMR Spectrum of Cp*W(NO){i2-S2C(PMe3)Ph}Ph ^ 113The IR Spectrum of Cp*W(NO){11 2-S2C(PMe3)Ph}Ph as a Nujol mull  114The 300 MHz 1H NMR Spectrum of Cp*W(r1 2-0NPh)(NPh)Ph ^ 115The 75 MHz 13 C{ 1 H} NMR Spectrum of Cp*W(r12-0NPh)(NPh)Ph  116The IR Spectrum of Cp*W(q 2-0NPh)(NPh)Ph as a Nujol mull ^ 117r-r r r r r -T T-r-r-r-r-r-r -Fr r r 1 r-r- r -r^-TT-TT^F-1 1--T r Fr -TT-1^ III!! 1-T-18^7^6^5 4^3 2 1 PPM8.2^8.0^7 8^7.6^7 4^7.2^7.0^6 8 PPMrr TT-- 1-1- rT 1 I - 1- rr T1 T I 1 I 11" T I r 1 n 1 VT1 r -rr^rrTiri r T - rrr r Fr- 1 - 111-1 reTTrr FTTT r1T1- 11   I TT TT1 rt ITT Frn--T-r -r-rr rp -177-r1220^200^180 .^160^140^120^100^80^60^40^20 PPM^8Nw•ctthN0a0w (TiuZoI- (0Z NfYNin0NwNNN0(N1 leoo. oA1650. 0 1500. 0 1350. 0 1200. 0 1050. 0 900_ 00 750. 00 600. 00WAVENUMBERS (CM-1)^!III, lit rtpi 11111111y irtirt trrritrntrrirrrunrq7.6^7.4^7.2^7.0^6 8 PF-'M 6 6J -J(I -r-r-r-r t T -t-r-r r-T r r-r T 7-1-7^ETTI r I r r T-T T r-l-T r r I 1-1-1-^r T I t r I "1-1-r-r1 r 17^6^5 4^3^2^1 PPM8OOmewSOSin2728.7 1588. 5 1420. 4 1272.2 1124.0 075.81 827.63 879.45 531.28WAVENUMBERS CCM-1)Jrlr^rrj rr^t iTrrri^nt -Tt t^{^I - I I I 11 . 1111 r - ri rrri7 t ,^/ 4^/ 2 1 0 e n PPIAI^ITTLIVIIIIIIIIIII11111111111111119 •^(-; 1 PPIVI_^111111;111f Fr-rT^rri T -r -r-r-i T-T VT -FT if I IT 1-1-7-171-Tr1 1 11-1-111 r1 1111 1 111-rri180^160 140^120^100^80^60^40^20 PPM8001N'ItNN06iniI $I s,iI.-1a)coNmup0)NO6.-E.-.in0Nt■1800. 0III11A1,^ I^8vo1650. 0 1500. 0 1350. 0 1200. 0 1050. 0 900. 00 750. 00 600. 00WAVENUMBERS (CM-1)it1 fri IiiirtIli FT -T-T- 1 1 r^r T I I I T-T r r 1-7^r -F-r r-7 r r^r r j 1.1 r, T r rT r r- 1 -T8^ 7 6^ 5^ 4^ 3^ 2^ 1 PPM•ANNft)to‘1-coWu (T)Z02Z NCeI--N(T)rnU)v-4coN1800. 0 1650. 0 1500. 0 1350. 0 1200. 0 1050. 0 900. 00 750. 00 600. OerWAVENUMBERS (CM-1)ITTIlTruipitT ITTITTII ETT1T1 ITTTIT111^rtITTTTET TTITTTITITITTITTITITTITI8. 4^8 2^8.0^7.8^7.6^7.4^7. 2^7.0 PF8v1 8I I! i i 1-1-1 1-1 -17^ p^ry 1 -1" t r I^T-1^-r-r^ 1 -r-r-r-r-r-8^7 6 5 4^3^2^1 PPM-•yr0C")0Nci)*4.I LT - 1180r - rri trill160I1 1 r I^I^f140^•irrriurrI1201^I^11^1 1100cp1-)lirrfrirriurrrirr - r -fitITTIFIrlIT1 11111 - r -- r -r1t,80^60^40^20 PPM^‘7"'( i 1NIik.—4N00)N 1800. 0I^1650. 0AAII11I I^I^I^I^I^---I1500. 0 1350. 0 1200. 0 1050. 0 900. 00 750. 00 600. 00 -4WAVENUMBERS (CM-1) 8.2 8 0 7 8 7 b 7.4 7.2 7.0 6.8 6.6 6.4 6. 2 PRMO1-T- r- 1 r r- r—r-r r -T—rr r r l ITT r riITI 1111 r i^1- 1-1 1 FT-T^ 1—FT-7-1 11 °PM8^7^6^5 4^3^2rrj^T - r-rry r r r-r-t- r - f - urr^T -1 - 1--- rmr-r -1- 1 - F-T - r"r1_ . _t_rt^rrliTTITprr-11111•11-t-rr-r-r-r-r-r-r-Frrri—r-ri-t-^rr- r-r180 160^40 120^100^80^60^40^PPMONNCO(0TI•wuI-- inF-4 r4Z NacOR, 0.-4yr-WAVENUMBERS CCM-1)NZ,P .0Nz051850. 0 1500. 0 1350. 0 1200. 0 1050. 0 900. 00 750. 00 800. 00 ‘sJ

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