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Gold(II) fluorosulfate derivatives and new gold(I) and platinum(II) carbonyl complexes Hwang, Germaine 1993

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GOLD(II) FLUOROSULFATE DERIVATIVES ANDNEW GOLD(I) AND PLATINUM(II) CARBONYL COMPLEXESbyGERMAINE HWANGB.Sc. (Hons.), The University of British Columbia, 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 COLUMBIASeptember 1993© Germaine Hwang, 1993In 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 ç7 'The University of British ColumbiaVancouver, CanadaDate^/5- oc-t /99'3DE-6 (2/88)ABSTRACTControlled pyrolysis of solid Au(SO3F)3 at gradually increasing temperatures up to145°C produced Au2+ ions as lattice defects. The Au2+ ion was also generated in HSO3Fvia reduction of Au(SO3F)3(solv) by gold metal. Both types of materials obtained werestudied by electron resonance spectroscopy, where spectra indicative of high axialsymmetry are obtained. The similar gis0 values indicate that the same species is present ina similar, near square planar environment both in the solid and in the frozen solution. Insolution, the Au2+ ion is unstable, and disproportionates to give a diamagnetic, mixedvalency compound of the composition AuIituIII(SO3F)4. The orange solid was isolatedand studied by vibrational spectroscopy. Dissolution of AulAu111(--3 F)4 in HSO3Fproduced an ESR active species in a highly unsymmetrical environment, postulated to be[Au(SO3F)4]2-, on account of partly resolved hyperfine splitting to four fluorines. Theseresults have allowed the identification of Au2+ (d9) for the first time.Reductive carbonylation of Au(SO3F)3 in HSO3F, followed by solvolysis of theproduct, Au(CO)S03F, in SbF5 in the presence of CO produced [Au(C0)2][Sb2F11], thefirst example of a linear binary carbonyl cation in a thermally stable isolable compound.The white solid was characterized by vibrational spectroscopy and NMR (19F, 13C)studies. [Au(C0)2][Sb2F11] has a very high average C-0 stretching frequency of2235.5 cm-1, suggesting that CO is behaving primarily as a a donor, and ir-backbonding isgreatly reduced. The Au-C bond is consequently weak, and reaction of a donor solventsuch as acetonitrile with [Au(C0)2][Sb2F1i] displaced CO. Slow solvent evaporation gavecrystals of [Au(NCCH3)2}[SbF6], which were suitable for a single crystal X-ray diffractionstudy.[Au(NCCH3)2][SbF6] has completely linear N-Au-N units, and the anion isoctahedral.iiiReductive carbonylation of Pt(SO3F)4 in HSO3F produced [Pt(C0)4][Pt(SO3F)6],which could be further reduced to cis-Pt(C0)2(SO3F)2 with CO by heating. Solvolysis ofcis-Pt(C0)2(SO3F)2 in SbF5 in the presence of CO yielded [Pt(C0)4][Sb2F1112.[Pt(C0)4][Pt(S03F)6] and [Pt(C0)4][Sb2F11]2 contain the hitherto unknown square planar[Pt(C0)4]2+ cation. The platinum carbonyl complexes were studied by vibrationalspectroscopy, and were found to have very high C-0 stretching frequencies. The averageC-0 stretching frequency for [Pt(CO)4][Sb2F11]2 is 2261 cm-1, and is the highest value sofar reported. It was concluded that 7r-backbonding was essentially absent in all thecarbonyl complexes obtained here.TABLE OF CONTENTSPageAbstract^  iiTable of Contents ^ ivList of Tables viiiList of Figures^ ixList of Symbols and Abbreviations^ xiAcknowledgements^ xiiiCHAPTER 1. GENERAL INTRODUCTION^ 11.1 Gold ^ 11.2 Platinum 31.3 Carbonyl Compounds^ 51.3.1 Classical Transition Metal Carbonyl Complexes ^51.3.2 Non-Classical Transition Metal Carbonyl Complexes^71.4 Vibrational Spectroscopy^ 81.5 Nuclear Magnetic Resonance Spectroscopy ^  111.6 Electron Spin Resonance Spectroscopy  111.7 X-ray Photoelectron Spectroscopy^  131.8 Definitions of Acidity, Basicity, and Superacids^  141.8.1 Acid-Base Definitions ^  141.8.2 Superacids^  151.8.2a Fluorosulfuric Acid^  151.8.2b Antimony Pentafluoride  171.9 Bis(fluorosulfuryl) Peroxide ^  181.10 The Scope of This Work 19References^ 22ivPageCHAPTER 2. EXPERIMENTAL^ 252.1 Chemicals^ 252.2 Apparatus 252.3 Instrumentation ^ 272.3.1 Vibrational Spectra^ 272.3.2 Electron Spin Resonance Spectra^ 272.3.2a Simulations^ 282.3.3 X-ray Crystallographic Data 282.3.4 UV-Visible Spectra^ 292.3.5 X-ray Photoelectron Spectra^ 292.4 Microanalysis ^ 30References^ 31CHAPTER 3. SYNTHESIS AND CHARACTERIZATION OF Au2+ IN THE SOLIDSTATE AND IN SOLUTION^ 323.1 Introduction ^ 323.2 Syntheses 373.2.1 Pyrolysis of Au(SO3F)3^ 373.2.2 Reduction of Au(III) to Au2+ UsingGold Metal^ 383.2.3 Reaction of Cs[Au(SO3F)4] with Gold Metal^ 393.3 Results and Discussion^ 403.3.1 Vibrational Spectra 413.3.1a Pyrolysis of Au(SO3F)3^ 413.3.1b Au(SO3F)2^ 463.3.2 Electron Spin Resonance Spectra^ 48Page3.3.2a Au(SO3F)2.67^ 483.3.2b Au(SO3F)3 Reduced by Gold Metal^ 493.3.2c AuiAuiii(s 03F)4^ 533.3.3 Reaction of Cs[Au(SO3F)4] and Gold Metal^ 543.4 Conclusion^ 55References 56CHAPTER 4. SYNTHESIS AND CHARACTERIZATIONOF [Au(C0)2][Sb2F11]^ 574.1 Introduction ^ 574.2 Synthesis of [Au(C0)2][Sb2F11] ^ 584.3 Results and Discussion^ 584.3.1 Vibrational Spectra 594.3.2 1 3 C NMR Spectra^ 644.4 Conclusion^ 67References 69CHAPTER 5. Crystal Structure of [Au(NCCH3)2][SbF6]^ 715.1 Introduction ^ 715.2 Synthesis of [Au(NCCH3)2][SbF6] ^ 715.3 Results and Discussion^ 735.4 Conclusion^ 77References 78CHAPTER 6. SYNTHESES AND CHARACTERIZATIONS OF [Pt(C0)4][Pt(SO3F)6],Pt(C0)2(SO3F)2, AND [Pt(C0)4][Sb2F11]2^ 796.1 Introduction ^ 79viPage6.2 Syntheses ^  816.2.1 Pt(C0)2(SO3F)3^ 816.2.2 Pt(C0)2(SO3F)2 826.2.3 [Pt(C0)4liSb2F11l2^ 826.3 Results and Discussion 846.3.1 Pt(C0)2(SO3F)3^ 846.3.1a Vibrational Spectra^ 886.3.1b 19F and 13C NMR Spectra 906.3.2 Pt(C0)2(SO3F)2^ 916.3.2a Vibrational Spectra^ 926.3.3 [Pt(C0)4][Sb2F11]2 966.3.3a Vibrational Spectra^ 976.3.3b X-ray Photoelectron Spectra^ 986.3.4 Reaction of Cs[Pt(SO3F)5] andCs2[Pt(SO3F)6] with CO in HSO3F^ 1006.4 Conclusion^ 100References 101viiCHAPTER 7. CONCLUSIONS AND SUGGESTIONS FOR FURTHER WORK ..103viiiLIST OF TABLESPageTable 1-1. Electron Affinities of the Halogens and Gold^ 2Table 3-1. Ionization Potentials (kJ.mol-1) for Group 11 Metals^36Table 3-2. Infrared Spectra of Pyrolyzed, Sublimed, andDiamagnetic Au(SO3F)3^ 45Table 3-3. Vibrational Spectra of Au(SO3F)2 and Au(SO3F)3^46Table 3-4. g Values of Known Gold(II) Species^ 50Table 4-1. Infrared and Raman Data (cm-1) for [Au(C0)2]+and Its Isotopomers^ 60Table 4-2. Comparison of [Au(C0)21+ and [Au(CN)2]- StretchingVibrations^ 61Table 4-3. Stretching Frequencies and Force Constants of COin Some Transition Metal Carbonyls^ 62Table 4-4. Melting Points of Gold Carbonyl Derivatives 63Table 4-5. Vibrational Assignments of [Sb2F1 ir in [Au(C0)2][Sb2F11]and Its Isotopomers^ 64Table 5-1. Selected Crystallographic Data for [Au(NCCH3)2][SbF6] ^72Table 5-2. Bond Lengths (A), Angles CI, and Interionic Distances (A) withEstimated Standard Deviations for [Au(NCCH3)2][SbF6]^75Table 6-1. Average C-0 Stretching Frequencies of Some PlatinumCarbonyl Halides^ 80Table 6-2. Redox Potentials of Selected Metals in Aqueous Acid^86Table 6-3. Vibrational Data for [Pt(C0)4][Pt(SO3F)6], Ba[Pt(SO3F)6],and (C102)2[Pt(SO3F)6]^ 89Table 6-4. NMR Parameters for Some Platinum Carbonyl Complexes^91Table 6-5. Vibrational Data for Pt(C0)2(SO3F)2 and Pd(C0)2(SO3F)2^93Table 6-6. Vibrational Data for [Pt(C0)4][Sb2F1 i]2 ^ 97LIST OF FIGURESixPageFigure 1-1. Bonding in Classical Transition Metal Carbonyls ^ 6Figure 1-2. Infrared Active Modes of cis- and trans-ML2(C0)2 8Figure 1-3. The S03F- Anion^ 9Figure 1-4. Reduced Symmetry of S03F-^ 9Figure 1-5. Vibrational Band Positions for Various Coordination Modesof the Fluorosulfate Group^ 10Figure 1-6. Emission of (a) a photoelectron, and (b) an Auger electron ^ 13Figure 2-1. Reactor Used for Synthesis ^ 26Figure 2-2. Filtration Apparatus 26Figure 2-3. Cuvettes Used for UV-Visible Spectrophotometer Measurements ^29Figure 3-1. Crystal Structure of Au4C18^ 34Figure 3-2. Structure of Au2I2{p,-(CH2)2PMe,2}2^ 35Figure 3-3. Structure of Au(SO3F)3 ^ 43Figure 3-4. Enlarged Diagram of the Au(III) Environment^ 44Figure 3-5. ESR Spectrum of Au(SO3F)2.67 ^ 48Figure 3-6. ESR Spectrum of Frozen Au2+(solv) 49Figure 3-7. Au2+ Simulations with a Nuclear Coupling Constant (a)and Without (b) ^ 49Figure 3-8. ESR Spectra of Ag(SO3F)2 in (a) the solid state, and(b) in BrSO3F^ 51Figure 3-9. ESR Spectrum of Au1Au111(S03F)4 in HSO3F^ 52Figure 3-10. ESR Spectrum of Au2+(solv) with Added Au(SO3F)3^53xPageFigure 4-1. Variable Temperature 13C NMR Spectra of a Mixture of[Au(13C0)]+ and [Au(13C0)2]+ in HSO3F^ 67Figure 5-1. An ORTEP Diagram Showing the Atom Positions in[Au(NCCH3)2][SbF6]^ 74Figure 5-2. Stereoview and Packing in [Au(NCCH3)2][SbF6]^74Figure 6-1. Selected Normal Vibrations of [Pt(SO3F)6]2- 90Figure 6-2. Molecular Structure of Pd(C0)2(SO3F)2^ 94Figure 6-3. Cis Binding Energy of [Pt(CO)4][Sb2F11]2 99LIST OF SYMBOLS AND ABBREVIATIONSv^stretching vibration in cm-1 (vibrational spectra)S^deformation mode in cm' I (vibrational spectra);chemical shift in ppm (NMR)def^deformation (vibrational spectra)p^rocking mode (vibrational spectra)A v^Raman shift (cm-1)IR^infraredRa^Ramanint.^intensitysym^symmetricalas, asym^asymmetricalS^strongm^mediumw^weakv^verysh^shoulderb^broadt^terminalbr^bridgingay., ave^averagek, f ,^force constant (N-m-1)A^reduced mass!Leff^effective magnetic moment (Bohr Magnetons)COffXm^corrected molar magnetic susceptibilityxixiic^speed of light (3.0 x 108 m.s.1)J^coupling constant in Hz (NMR)Xmax^maximum intensity absorption in nm (uv-visible spectra)Anal. calc.^analysis calculated (%)Ref.^reference(s)h^hour(s)(solv)^solvated(s)^solidconj.^conjugateACKNOWLEDGEMENTSI would like to express my appreciation and gratitude to Dr. F. Aubke, who hasprovided me with encouragement, guidance and advice throughout my years of study.Thanks also go to all the members, past and present, of our research group, for theirinteresting discussions, and many valuable suggestions. In particular, I would like to thankChangqing Wang for allowing me to include some of his unpublished results in this thesis.Our collaborators at the University of Hannover, Germany, are thanked for carrying outthe NMR studies and for obtaining some vibrational spectra. Drs. F.G Herringand P.S. Phillips are thanked for their help in obtaining and interpreting the ESR spectra.Thanks go to the technicians, the microanalysis, mechanical engineering, electricalengineering and glassblowing shops for all their assistance. The crystallographers arealso thanked for the help they have given me. Financial support by the North AtlanticTreaty Organization (NATO) and by the Natural Science and Engineering ResearchCouncil of Canada (NSERC) is gratefully acknowledged.1CHAPTER 1. GENERAL INTRODUCTIONThe work discussed in this thesis involves the synthesis and characterization of goldand platinum complexes. First, a brief overview of the relevant chemistry of the twometals will be presented, followed by a discussion of metal carbonyl complexes and thebonding that occurs. Second, a description of the physical methods used to characterizethe complexes synthesized in this thesis is provided. The solvent systems used will bebriefly discussed, along with some definitions of acid and base behaviour. A fewstatements outlining the objectives pursued in this work are also provided.1.1 GoldGold has been treasured since ancient times as a sign of wealth, and even now it isused as a monetary standard. This soft, yellow metal is the most ductile and malleable ofall the metals. The uses of gold by jewelers and dentists are well known, as are its uses inthe electronics and the fine china industries.Gold occurs in nature as the metal, either in the form of flakes or nuggets, or inveins in quartz or iron pyrite [1]. It is called a noble metal because of its resistance tochemical attack. Other noble metals include rhodium, palladium, iridium, and platinum.Gold is the only metal that is not attacked by sulfur or oxygen at any temperature. Thefree atom has the electronic configuration [Xe]4f145d106s1 and belongs to group 11.Listed below are some of the physical properties of gold [2].Au^atomic number: 79atomic weight: 196.97 g.morlmelting point: 1064.43°Cboiling point: 2807°Cdensity (20°C): 19.32 g-cm-3natural abundance (197Au): 100%2nuclear spin: 3/2crystal structure: face-centered cubicThe known oxidation states of gold are -1, 0, +1, +2, +3, and +5. Most goldchemistry involves complexes of Au(T) and Au(III).Gold is capable of gaining an electron and filling its 6s shell, behaviour that hascaused it to be called a pseudohalogen. Compounds of the form MAu (M = alkali metal)with the metal in the -1 oxidation state exist, and this has been confirmed in the case ofCsAu by electrical conductivity measurements [3]. With the exception of the halogens,gold has the highest electron affinity among the elements [4] (Table 1-1).Table 1-1. Electron Affinities of the Halogens and GoldElement^Electron Affinity (kknol-1)F 327.9C l^348.8Br 324.6I^295.3At 270Au^ 222.7Gold(I) complexes have been shown to preferentially exhibit two-fold, linearcoordination, e.g. [NC-Au-CNI, and a effects reportedly dominate bonding, even in thepresence of 7-acid ligands (e.g. CO) [5]. The +2 oxidation state is very rare, and foundfor only a few compounds (see Chapter 3); of the known Au(II) species, little informationregarding the structure is available. All Au(III) complexes reported so far have been foundto be low-spin and diamagnetic. Most of these complexes are square planar, although five-and six-coordinate species are also known [6]. No evidence for the +4 oxidation state hasyet been found, and the +5 oxidation state exists only in AuF5 and [AuF6r [7].3There is a vast area of research involving the chemistry of gold clusters andorganometallic compounds, but the work described in this thesis will involve mono anddinuclear species only.1.2 PlatinumPlatinum has not had as glorious a history as gold. It was discovered in 1735 inSouth America and given the name platina del Pinto, Spanish for "little silver of the PintoRiver" [8]. The pure metal is silvery-white, and is also very malleable and ductile. In1741, platinum was introduced in Europe and over the next 90 years, scientists discoveredthe ease with which Pt(II) formed complexes with donor atoms (e.g. N, CW, P, S) [5].The realisation that the divalent metal had square planar geometry introduced the idea ofcis- and trans- isomerism. With the elucidation of the trans effect in Pt(II) compounds inthe early 20th century, chemists were able to synthesize any Pt(II) complex theywished [8]. The organometallic chemistry of platinum was developing simultaneously,with the preparation of Zeise's salt, K[Pt(C2H4)C13].H20, first reported in 1830. Eventhough the organometallic chemistry of platinum will not be discussed in this thesis, theapplications of these compounds in both homogeneous and heterogeneous catalysis inchemistry are of great importance and continuing interest. There is a great deal of clusterchemistry involving platinum, but this topic will also not be addressed in this thesis.Platinum is usually found in cupronickel ores, but occasionally occurs as the nativeore [8]. This group 10 metal has the electron configuration [Xe]4f145d96s1. Some of itsphysical properties are listed below [2]:Pt^atomic number: 78atomic weight: 195.09 g.mo1-1melting point: 1772°Cboiling point: 3828+100°Cdensity (20°C): 21.45gcm-34NMR active nucleus: 195Ptnatural abundance: 33.8%nuclear spin: 1/2crystal structure: face-centered cubicThe known oxidation states are 0, +1, +2, +4, +5, and +6. Complexes ofplatinum in the zero oxidation state are usually coordination complexes with neutral donorligands, e.g. Pt(PPh3)3 [5]. The +1 oxidation state is rare, with only two compoundsreported: Pt3C13 [9], and Pt3(SnC13)2(C81-112)3 [10]. The diamagnetic +2 oxidation stateis the most common and such complexes preferentially exhibit square planar coordination.There are reports of five-coordinate complexes of Pt(II) with 7-acceptor ligands [11].There are a limited number of platinum compounds in the +3 oxidation state [12]. Pt(III)is expected to show paramagnetic behaviour (d7). Complexes such as [Pt(NH3)2X3](X =CI, Br, I) and [Pt(NH3)4X]2+, where platinum has the formal charge of +3, havebeen shown to be mixed valency compounds of Pt(II) and Pt(IV) [8].The +4 oxidation state for platium is quite common. The metal has an octahedralcoordination sphere, and all Pt(IV) complexes are diamagnetic.Platinum forms a variety of fluoride compounds in both the +5 and +6 oxidationstates. PtF5, Pt0F3, and a number of [PtF61- salts are known, e.g. M[PtF6] (M=alkalimetal), 02+[PtF6]. The known structures of the Pt(V) compounds exhibit octahedralsymmetry, and are paramagnetic [8]. The only known Pt(VI) compound is thehexafluoride, PtF6. It is also believed to have octahedral symmetry, but this is deducedfrom its infrared spectrum, since no molecular structure is available [13]. Platinum hasnever been found in an oxidation state higher than +6.51.3 Carbonyl Compounds Carbonyl complexes are found for almost all d-block transition metals. There arethousands of organometallic carbonyl complexes reported, but only a handful of binarytransition metal carbonyls are known.When free carbon monoxide coordinates to a transition metal center, the C-0stretching frequency can either decrease or increase. This allows the division of carbonylcompounds into classical and non-classical transition metal carbonyl complexes. Thefollowing discussion centers on the bonding characteristics of terminally bound CO in thesetwo types of complexes.1.3.1 Classical Transition Metal Carbonyl ComplexesClassical transition metal carbonyl complexes typically involve metals from thed series in the periodic table, and they are characterized by a decrease in the C-0 stretchingfrequency upon coordination of carbon monoxide to the metal. This is caused bya donation of electron density from the carbon 50- orbital to a metal orbital of appropriatesymmetry, and back donation of electron density from a filled dr orbital on the metal to apir orbital on the carbon monoxide molecule. The second effect is commonly calledw-backbonding. Carbon monoxide becomes a better cr-donor due to the increase ofelectron density in its pir orbital, and a better w-acceptor due to the decrease of electrondensity in the 5a orbital [4][5]. This gives CO the ability to stabilize metals in neutral orlow oxidation states. The two phenomena reinforce each other, and are collectivelyreferred to as synergic bonding (Figure 1-1).The stronger metal-carbon bond and weaker carbon-oxygen bond cause the C-0stretching frequency to decrease from 2143 cm-1 [14] for uncoordinated gaseous carbonmonoxide to the range of 2100 cm-1 to 1850 cm-1 [4] for terminally-bound CO.6EmptyC^0M '.■_.)a donation^7-backdonationFigure 1-1. Bonding in Classical Transition Metal Carbonyls.The easiest method for monitoring the change in vC0 is by infrared spectroscopy,which gives a qualitative measure of the strength of the C-0 bond. The greater thedecrease in CO stretching frequency, the weaker the C-0 bond. A more accurate measureof C-0 bond strength is through the use of force constants, since vibrational coupling ofvC0 to other vibrations of comparable energy and symmetry, different metal centers anddifferent counterions may affect the C-0 stretching frequency. The values of the forceconstants obtained allow quantitative comparisons of C-0 bond strengths among variouscarbonyl compounds. Force constants can be calculated using either the method of Cottonand Kraihanzel [15] or Jones [16].The use of 13C NMR to study labelled samples allows the comparison of chemicalshifts of the compounds described in this thesis to those of related species. It also permits(to a limited degree) the study of the behaviour of these species in solution, and thepossibility of exchange processes taking place. The typical range of 13C chemical shiftsfor classical transition metal carbonyls is 189-220 ppm relative to TMS [17].Preparation of classsical transition metal carbonyl complexes often requires forcingconditions. Binary transition metal carbonyls are most commonly produced by reducingmetal salts in an organic solvent with CO under 200-300 atm pressure and at temperaturesranging from 120-300°C. Direct reaction of metal with CO is possible for nickel and iron,but is feasible only for finely divided nickel, which reacts at room temperature; the7reaction of iron with CO requires high temperatures and pressures [5]. Transition metalcomplexes can be prepared from binary metal carbonyls by using donor ligands (e.g. PR3,NR3; R = alkyl group) to displace a CO molecule. The stoichiometry of these complexescan be predicted using the effective atomic number rule (EAN), which is obeyed by allmonomeric, binary metal carbonyl complexes, except [V(C0)6], which has 17 valenceelectrons [18].The most common geometries found for both neutral and charged, monomericbinary metal carbonyl species are(i) octahedral, e.g. Cr(C0)6, [Mn(C0)6]+;(ii) trigonal bipyramidal, e.g. Fe(C0)5, [Mn(C0)5]-; and(iii) tetrahedral, e.g. Ni(C0)4, [Fe(C0)4]2-.1.3.2 Non-Classical Transition Metal Carbonyl ComplexesNon-classical transition metal carbonyl complexes usually involve the noble metals.Unlike classical metal carbonyls, the C-0 stretching frequency is found in the range2153-2200 cm-1, greater than that of free CO, and it has been postulated that the increasein ',CO is due to decreased 7-backbonding [19]. Again, vibrational and 13C NMRspectroscopy are useful techniques for deducing the structures of these compounds.Prior to the work started by this research group, there was no evidence for eitherlinear or square planar binary metal carbonyls. It was thought that Pd, Pt, and Au did notform binary metal carbonyls [5], but matrix isolation experiments have produced Pd(CO)nand Pt(CO)n (n=1-4) [20], as well as Au(CO)n (n=1,2) [21]. All of these species arethermally unstable. Noble metal carbonyl halides are quite common, the first being threeplatinum species which were reported in 1870 [22].The methods of synthesizing non-classical metal carbonyl complexes require lessforcing conditions than those required in the preparation of classical transition metal8carbonyl complexes. For example, the preparation of Au(CO)C1 [23][24] involves heatinggold(III) chloride from 50°C to 120°C in a stream of carbon monoxide.There is a class of transition metal carbonyl complexes which should be brieflymentioned. These are the carbonylate anions, sometimes called "super-reduced" metalcarbonyls. They are prepared by reacting the neutral binary metal carbonyl with strongreducing agents such as aqueous or alcoholic alkali hydroxides, amines, or sodiumamalgam. These complexes show extensive T-backbonding, and the C-0 stretchingfrequencies are well below 2143 cm"1 [5].1.4 Vibrational SpectroscopyVibrational spectroscopy is used to provide information about the structure andbonding of functional groups within a molecule. Infrared spectroscopy is based onabsorptions caused by irradiation that induce a change in the dipole moment of a molecule,while Raman spectroscopy is based on scattering of the exciting light, causing changes inthe polarizability of the molecule. Structural information about a molecule can be obtainedby examining the vibrational spectra. For example, the cis- and trans- isomers ofML2CO2 (M = metal, L = ligand) can be easily distinguished by infrared spectroscopy.cis-M1_2(C0)2 has two infrared active modes, while trans-ML2(C0)2 only has one(Figure 1-2).cis-ML2(C0)2trans-M1_2(C0)2;ID^ i0L C L 'b /kr /\ m/ \m// \^ / \1,^C/'` 1,^C\ & \ (34fi0L C\/kr / \C^LFigure 1-2. Infrared Active Modes of cis- and trans-ML2(C0)29Since the fluorosulfate and fluoroantimonate anions are of interest to us, a briefoverview of their characteristic vibrations will be given.The S03F- anion has C3v symmetry (Figure 1-3). Upon coordination of one or twooxygen atoms to a metal center, the symmetry can be reduced to Cs or C1 (Figure 1-4).Figure 1-3. The S03F" AnionF00^ F 0I \S/0 / \0 0I^ /^\M M M'Cs symmetry^ C1 symmetryFigure 1-4. Reduced Symmetry of SO3F-All of the SO3F- stretching vibrations are both infrared and Raman active. The twomost common coordination modes of the SO3F- group, monodentate and bidentate, can beeasily determined by examining the vibrational spectra and identifying the characteristicvibrations. Figure 1-5 shows the expected vibrational band positions for variouscoordination modes of fluorosulfate groups [25]. The shaded areas show the positions ofthe diagnostic bands.I-.EE(")BondingorCoordinationModeFrequency Range (cm -9_ .^Stretching Band Deformation Band>,COVALENTTRIDENTATE,,,,,^(5-0) v,„,(s--0) v(S-F)I=8„„^00,0NM Prod,r^1 I I NIEN6„,„ (503)PURELYIONICv.,^(s-o)Li„„,,,(s-o)El.(s-r) 8.^(933) 8 irs, (s03)^p axiDO^0f dcrIONICPERTURBEDv. (soovz?z23 „,,„„00,)UZI,,(s--0)1^1 v (S-F)8„„„„,„(soo72.1.1 (SO2 r)IN113 7(s-r) DY(so, F)nod, (S02)WZACOVALENTMONODENTATEv.^(S02) v(S02)l=11v (S-0)r/Y7772iiov(S-F)it1.4.1 002 r)^Itme, (S02)^C.)ODD^et.„ 0,) r^(s-r)^C--)7 (S02 F)1^ICOVALENTBIDENTATE.0-0vo„^(SO2)riziwzaU.=v„,.„,(S02).(s-F) 81.„,(S07)^7„„,(s-F)^• (so,^()^0  0^0 I=imch (SO,)^1h,fti (SO2 F)t^I r^I1400^1200^1000^800^600^400Figure 1-5. Vibrational Band Positions for Various Coordination Modes of the Fluorosulfate Group [25]11The [Sb2F1i] anion has been shown to have D4h symmetry from single crystalX-ray diffraction studies [26][27]. The Sb-Fax (Fax = axial fluorine atom) vibrations arefound at ca. 700 cm-1, and the Sb-F4eq (F4 ^four equatorial fluorine atoms) stretchesare found between 600 cm-1 and 680 cm-1 [28].If there is some uncertainty in assigning a vibration to a peak, then isotopicsubstitution is used. The stretching frequency of the peak(s) in question should shift. Thiswill occur because vibrational frequencies depend upon the mass of the atoms involved(v(in cm-1) = 1/27cjk/A), and changing the mass of one of the atoms will change thevalue of the reduced mass.1.5 Nuclear Magnetic Resonance SpectroscopyNuclear magnetic resonance (NMR) spectroscopy is a technique commonly used todeduce the structure of molecules. NMR can also be used to study reactions in situ, andidentify intermediate species or exchange processes between two or more moieties in thesample. Isotopic labelling of carbon and oxygen in carbon monoxide permits a comparisonof 13C resonances to related metal carbonyls, and also allows us to determine if exchangeprocesses are occurring. If the species observed in the course of the reaction areidentified, we may be able to propose possible mechanisms for the formation of theproduct.The NMR studies described here were carried out at the University of Hannover,Germany.1.6 Electron Spin Resonance Spectroscopy [29][30]Electron spin resonance (ESR) spectroscopy is the best method available to us forthe study of free radicals. The technique measures the first order Zeeman effect. Amolecule with an unpaired electron in a magnetic field has two energy levels for theelectron spin, given byE = gABBorns^(1) where12E is the energy level,AB is the Bohr Magneton,Bo is the applied magnetic field,m is the electron spin,g is the g-factorFor a free electron, the g value is 2.0023. In isotropic systems (e.g. gases,homogeneous liquids, solutions of low viscosity, crystalline solids with tetrahedral oroctahedral symmetry), the g values can be considered as scalar quantities, since the sampleorientation is independent of direction. In anisotropic systems such as unstable speciesgenerated in situ, matrix isolated complexes, solids, or frozen solutions, the g values aredirection dependent, and must be considered as symmetric tensors. The tensor can bediagonalized to give three g values: gxx, gyy, and gzz. The g values of isotropic samplesare all equal. In anisotropic systems, the three g values may differ, and are averaged togive giso. The magnitude of giso shows whether the unpaired electron is based in transitionmetal or ligand orbitals.If there is a nucleus with I = n/2 (n = integer> 0) near the unpaired electron, thetwo will interact, and equation (1) must be modified by adding a hyperfine coupling term:E = gi.A.BBoms + Amsmi^(2) whereA is the hyperfine coupling constantm1 is the nuclear spin quantum number.The coupling patterns observed in these systems are directly analogous to thoseobtained in NMR. The treatment of the A values is also analogous to that of the g values:in isotropic systems, the A terms are equal and treated as scalar quantities; in systems withlower symmetry, the A values must be treated as symmetric tensors which can bediagonalized to give Axx, Ayy and Azz. All three values can be averaged to give Aiso.The number represented by Aiso is a measure of the line separation in the multipletpattern caused by the interacting nuclei, and has units of MHz. Its magnitude is dependenton the spin density at the nucleus in question, and can indicate the extent to which theunpaired electron is delocalized.^-0-4,--.4-6-0— 2p^-&4-0-0-0-0—c^2p• •^2s / • •^2s• photoelectronphoton—•-•---- I sa)^ b)131.7 X-ray  Photoelectron SpectroscopyX-ray photoelectron spectroscopy (XPS) is also called Electron Spectroscopy forChemical Analysis (ESCA). It is a technique which can be used to study the chemicalcomposition of solid surfaces, and in this work, it is used to determine the oxidation stateof an element in a compound. Each element has a unique spectrum; in a compound, thepeaks observed approximately comprise the sum of the spectra of the individualelements [31]. A spectrum is obtained by irradiating the surface of the sample with X-rays(at one energy level) in a vacuum chamber. The electrons emitted from the core levels ofthe atoms in the compound are sorted according to energy level, and the spectrum is a plotof the number of electrons emitted for a given energy interval against the electrons' kineticenergy. The X-ray sources most commonly used are the Mg Ka (1253.6 eV) and the Al Ka(1486.6 eV). The X-rays, or photons, eject electrons from the surface atoms via thephotoelectric effect. The kinetic energy of the emitted electron is given byK.E. = hp - BE - Os^(3), wherehi, is the energy of the photonsBE is the binding energyOs is the spectrometer work functionThe binding energy is defined as the energy separation between the ionized core level andthe Fermi level.After emission of a photoelectron, the ion left is very energetic, and relaxes byemitting a second electron known as the Auger electron (Figure 1 -6).• Auger electronFigure 1-6. Emission of (a) a photoelectron, and (b) an Auger electron [31]14It can be seen that photoionization produces two electrons per atom: a photoelectronand an Auger electron. Detection of the electrons is achieved by using an electronspectrometer set to a given "pass energy", where only electrons within the range of thepass energy will be detected. Applying a variable electrostatic field allows scanning fordifferent electron energies.1.8 Definitions of Acidity,  Basicity,  and SuperacidsSince the work in this thesis involves the use of highly acidic media in order tocarry out the reactions, it is appropriate to quickly review acid-base chemistry and toclarify some definitions.1.8.1 Acid-Base DefinitionsThe three most commonly used definitions of acids and bases are those ofArrhenius, Bronsted-Lowry, and Lewis [32]. The Arrhenius definition appeared between1880 and 1890 and states that in aqueous solution, an acid causes an increase in theconcentration of hydrogen ion, H+, and a base causes an increase in the concentration ofthe hydroxide ion, OW. However, in the absence of water, this definition was invalid. In1923, two chemists, J. N. Bronsted and T.M. Lowry, proposed a more general definitionfor acids and bases: acids acted as proton donors and bases acted as proton acceptors(equation (4)).^H20 + H20 —> H30+ + OH-^(4)acid^base^conj.^conj.acid^baseThis explanation could only be applied to protonic substances. G.N. Lewis, in the sameyear, proposed that acids were electron pair acceptors and bases were electron pair donors.There is also the solvent system definition, where an acid is a solute capable ofincreasing the relative concentration of the characteristic cation of the pure solvent, and the15base is a solute capable of increasing the relative concentration of the characteristic anionof the pure solvent. For example, if a solvent autoionizes according to2A2B # A3B+ + AB"^(5),then an acid in this system would increase the relative concentration of A3B+ and a basewould increase the relative concentration of AB-. The cation is also called the acidium ionand the anion is called the base ion.1.8.2 SuperacidsThere are several definitions of superacids, a term first coined in 1927 by Conantand Hall [33]. Gillespie's definition [34] is valid primarily for Bronsted and conjugateacids and states that a superacid is any acid that is stronger than 100% sulfuric acid.Superacid strength is measured using the Hammett acidity function, Ho [35]. Olah et al.defined a Lewis superacid as any acid that is stronger than anhydrous AlC13; however, theyencountered difficulties in determining a scale of acid strengths [32].The superacid systems discussed in this thesis are Bronsted-Lewis conjugatesuperacids. These are prepared by the addition of a strong Lewis acid to a strong Bronstedacid. The Lewis acid will shift the equilibrium by complexing and effectively removingthe base ion, e.g.2 HSO3F + SbF5 # H2S03F+ + SbF5(SO3F)-^(7)The addition of the Lewis acid greatly increases the acidity of the system.1.8.2a Fluorosulfuric AcidFluorosulfuric acid is the solvent of choice for most of the reactions described inthis thesis. It is prepared by insertion of SO3 into HF [36]. With its wide liquid range(-88.98 to 162.7°C), reactions can be carried out at different temperatures. Underanhydrous conditions, HSO3F is unreactive towards glass, permitting easy storage and16handling. It is easily purified by double distillation under an atmospheric pressure of N2,thereby removing H2SO4 and HF, the two main impurities, that are formed when the acidcomes into contact with moisture, i.e.HSO3F + H20 # H2SO4 + HF (8)Fluorosulfuric acid is commercially available. Its low viscosity allows easymanipulation in glass reactors. HSO3F often has traces of SO3 and HF present, due to thedecomposition of HSO3F:HSO3F # SO3 + HF^(9)and these impurities are difficult to remove. Some physical properties of HSO3F arelisted below [37].HSO3F: boiling point^162.7 °Cmelting point -88.98 °Cdensity (25°C)^1.726 g.m1 - 1viscosity (25°C) 1.56 cPspecific conductance (25°C)^1.084x10-4 (1- lcm-1The high conductivity of fluorosulfuric acid is postulated as being due to the"proton jump" or Grothius mechanism, and ionic molar conductivities at infinite dilutionand at 25°C are H2S03F-}-: 185; SO3F-: 135 [40]. Both the infrared and Raman spectra ofHSO3F are known [38][39].HSO3F is thought to be one of the strongest simple protonic acids known [40]. Itsacidity, as measured on the Hammett acidity scale, is H0=-15.1. The acidity of HSO3Fcan be greatly increased by the addition of SbF5 or by the addition of SO3 and SbF5 [32].Unfortunately, the resulting Bronsted-Lewis conjugate superacid systems contain manyspecies in solution, and is not suitable as a solvent if we want to identify moietiesgenerated in situ.17Fluorosulfuric acid is also used in solvolysis reactions with alkali metal halides toform the alkali metal flurosulfate, which is then used to prepare the corresponding salts ofhigh valent fluorosulfates [41], e.g.CsC1 + HSO3F --> CsSO3F + HC1 (10)followed byCsSO3F + Au(SO3F)3 --> Cs[Au(SO3F)4] (11)The synthetic reactions described herein start with gold tris(fluorosulfate),Au(SO3F)3, or platinum tetralcis(fluorosulfate), Pt(SO3F)4, in fluorosulfuric acid. Thesetwo compounds have been found to behave as Lewis acids in HSO3F [42][43] by removingthe S03F- anion according toAu(SO3F)3 + 2 HSO3F # H2S03F+ + [Au(SO3F)41-^(13)Pt(SO3F)4 + 4 HSO3F # 2 H2S03F+ + [Pt(SO3F)6]2-^(14)while the cesium salts of these two compounds behave as bases in HSO3F, e.g. forCs[Au(SO3F)4]:HSO3FCs[Au(SO3F)4] --> [Au(SO3F)4 ]- + Cs+^(15)[Au(SO3F)4]- 4=1 Au(SO3F)3(solv) + SO3F- (16).1.8.2b Antimony PentafluorideAntimony pentafluoride, SbF5, is the strongest Lewis acid known, and is preparedby direct fluorination of the metal or the metal trichloride [32]. It is polymeric, withcis-bridged fluorines, and because of a high degree of association, SbF5 is much moreviscous than HSO3F.It is usually less desirable to use SbF5 as a solvent because its high viscosity makesit difficult to remove. Some physical properties of SbF5 are listed below.SbF5^boiling point^142.7°Cmelting point 7°C18density @15°C^3.145 g.m1-1viscosity @20°C^460 cPAntimony pentafluoride can undergo adduct formation (equation 17) or complexanion formation (equation 18) with a suitable Lewis base [32], e.g.SbF5 + SO2 --> 0S0—>SbF5^(17)SbF5 + F- --> [SbF6]-^(18)If SbF5 is present in excess, the complex anion can give rise to polyanions [32], i.e.[SbF6r + excess SbF5 --> [Sb2F11], [Sb3F16]-, etc.^(19)SbF5 can also solvolyze metal fluorosulfates to give the corresponding metalfluoroantimonates [44], e.g.SbF5Ni(SO3F)2 + 6 SbF5 —> Ni(SbF6)2 + 2 Sb2F9S03F^(20)Compared to the fluorosulfate group, the vibrational bands of the fluoroantimonatesappear in a narrow region (< 800 cm-I) and are not as intense [32], so there is less chanceof overlapping fluoroantimonate bands with other vibrations of interest.1.9 Bis(fluorosulfuryl) PeroxideBis(fluorosulfuryl) peroxide, S206F2, was first prepared in 1956 by the AgF2catalyzed reaction of fluorine gas and sulfur trioxide [45]. It can be synthesized in thelaboratory in large quantities, and is easily handled under vacuum in glass reactors.Impurities such as SO3 can be removed from S206F2 quickly and efficiently by washingthe peroxide with H2SO4 in a separatory funnel. Other impurities, e.g. bis(fluorosulfuryl)oxide, S205F2, can be removed by cooling S206F2 to -78°C and pumping in vacuo [46].S205F2 is also a byproduct formed by the reduction of S206F2.The combination of bis(fluorosulfuryl) peroxide and fluorosulfuric acid is excellentfor the clean oxidation of metals to form the corresponding fluorosulfates [47] according to19M + n/2 S206F2 —0 M(SO3F). (M=Ag, Pd, Ir, Pt, Sn, Au; n=1-4)^(21)HSO3F and excess 5206F2 are easily removed from the reaction mixture in vacuo.The fluorosulfate radical, 503F, is easily obtained due to the low dissociationenergy (ca. 23 kcal.morl) [48] of S206F2. Heating 5206F2 to 60°C results in theformation of a brown vapour, which is attributed to the SO3F radical [49] (equation (22)).S206F2 VI 2 SO3F•^(22)One minor drawback is the exothermic reaction of the peroxide with readilyoxidizable materials, e.g. organic compounds, so caution is necessary to ensure thatS206F2 does not come into contact with them.1.10 The Scope of This WorkThe work described in this thesis investigates two topics: the unusual magneticbehaviour of Au(SO3F)3, and the use of the superacid system Au(SO3F)3/HSO3F togenerate and stabilize gold carbonyl cations.Au(SO3F)3 showed different magnetic properties depending upon the method ofpreparation. Oxidation of gold metal by BrSO3F and pyrolysis of the intermediateproduced a slightly paramagnetic product [50], while oxidation of the metal powder byS206F2 in HSO3F yielded the expected diamagnetic product [51]. This unusual magneticbehaviour required closer scrutiny. We wanted to investigate the source of theparamagnetism by controlled heating of a diamagnetic sample of Au(SO3F)3. ESR wasused to study any paramagnetic species that may be produced.Earlier work in our laboratory suggested that a paramagnetic species was alsogenerated by the reduction of Au(SO3F)3 using gold powder in HSO3F, and a moredetailed study of this system was also undertaken.The initial purpose of using the superacid system Au(SO3F)3/HSO3F to protonateCO was to rind evidence of the formyl cation, HC0+, detected in interstellar clouds and asshort-lived intermediates in hydrocarbon combustion reactions. HCO+ has also been20generated in tubes containing H2 and CO by electrical discharge, and its microwavespectrum has been recorded [52]. The reaction of CO with the Au(SO3F)3/HSO3Fsuperacid did not provide any evidence of HC0+, but instead, the Au(SO3F)3 was reducedfrom the +3 to the +1 oxidation state, and Au(CO)S03F was isolated [53]. This outcomewas not entirely surprising since CO is commonly used as a reducing agent in thepreparation of metal carbonyl complexes (vide supra). What was surprising, however, wasevidence of the hitherto unknown linear cation [Au(CO)2] + as a reaction intermediate [53].The product, Au(CO)S03F, also had an extremely high C-0 stretching frequency(ave. 2195 cm-1), and solution studies of the intermediate indicated that the C-0 stretchingfrequency of [Au(CO)2} ± was even higher [53]. However, Au-C vibrations were obscuredby fluorosulfate vibrations. In order to clarify the assignment of Au-C vibrations, the useof a more weakly basic anion, e.g. [SbF6]- or [Sb2F1 if, was recommended. Both of theseanions have been found to be among the weakest nucleophiles [54]. One of the goals ofthis thesis was to try to isolate the [Au(CO)2] + cation as the fluoroantimonate salt.Once the study of the reaction between CO and the Au(SO3F)3/HSO3F system iscompleted, the action of CO upon the Pt(SO3F)4/HSO3F superacid system will be studiedto see whether analogous complexes will be formed under similar reaction conditions.The complete assignment of bands in the vibrational spectra of [Au(C0)2]-4-,detected only in solution so far, and [Pt(C0)4]2+, which is unknown, may be difficultbecause there is nothing with which to compare them. However, carbon monoxide and thecyanide anion are isoelectronic, and [Au(CN)2]- [55][56] and [Pt(CN)4]2- [16] are known .If the analogous CO complexes can be isolated, they should be isostructural with the CN-compounds, and their vibrational spectra should show similar patterns. Transition metalcyano complexes are usually neutral or anionic, and are often made using basic solvents,e.g. NH3. Carbonyl complexes are mostly neutral or cationic, and it seems reasonable touse acidic solvents, e.g. H2SO4. In both cases the metal is in a low oxidation state (videsupra). The cyanide ligand is not as good a 7r-electron acceptor as carbon monoxide [57]21due to its negative charge, but it is still capable of undergoing synergic bonding. It shouldbe noted that transition metal cyano complexes, with the negatively charged ligand and thepostively charged metal, do not need synergic bonding to explain their stability [57].22References1. R.J. Puddephatt, "The Chemistry of Gold", Elsevier: Amsterdam, Netherlands (1978).R.J. Puddephatt, in "Comprehensive Coordination Chemistry", Vol. 5, G.Wilkinson, Ed., Pergamon: Oxford, UK (1987) p 861.2. Handbook of Chemistry  and Physics, 57th ed.3. H. Schmidbaur and K.C. Dash, Adv. Inorg. Chem. Radiochem. (1982) 25, 239.4. J.E. Huheey, "Inorganic Chemistry: Principles of Structure and Reactivity", 3rd ed.,Harper & Row: New York, NY (1983).5. F.A. Cotton and G. Wilkinson, "Advanced Inorganic Chemistry", 4th ed. John Wiley& Sons: New York, NY (1980), and references therein.6. M. Melnik and R.V. Parish, Coord. Chem. Rev. (1986) 70, 157.7. R.J. Puddephatt, in "Comprehensive Coordination Chemistry", Vol. 5, G. Wilkinson,Ed., Pergamon: Oxford, UK (1987) p 861.8. F.R. Hartley, "The Chemistry of Platinum and Palladium", John Wiley & Sons: NewYork, NY (1973).9. A. Landsberg and J.L. Schaller, J. Less Common Metals (1971) 23, 195.10. L.J. Guggenberger, Chem. Comm. (1968) 512.11. A.D. Westland, J. Chem. Soc. (1965) 3060.12. D.M. Roundhill, in "Comprehensive Coordination Chemistry", G. Wilkinson, Ed.,Vol. 5, Pergamon: Oxford, UK (1987) p 351.13. B. Weinstock. H.H. Claasen and J.G. Maim, J. Chem. Phys. (1960) 32, 181.14. K. Nalcamoto, "Infrared Spectra of Inorganic and Coordination Compounds", 2nd ed.,John Wiley & Sons: New York, NY (1970).15. F.A. Cotton and C.S. Kraihanzel, J. Am. Chem. Soc. (1962) 84, 4432; C.S.Kraihanzel and F.A. Cotton, Inorg. Chem. (1963) 2, 533.16. L.H. Jones, "Inorganic Vibrational Spectroscopy", Vol. 1. Marcel Dekker: NewYork, NY (1971).17. B.E. Mann, in "Advances in Organometallic Chemistry", Vol. 12, F.G.A. Stone andR. West, Eds., Academic: New York, NY (1974) p 133.18. F. Basolo and R.C. Johnson, "Coordination Chemistry", 2nd ed., Science Reviews:Northwood, Middlesex, UK (1986).2319. F. Calderazzo, Pure. Appl. Chem. (1978) 50, 49.20. E.P. Kiindig, D. McIntosh, M. Moskovits and G.A. Ozin, J. Am. Chem. Soc. (1973)95, 7234.21. D. McIntosh and G.A. Ozin, Inorg. Chem. (1977) 16, 51.22. P. Schiitzenberger, Compt. Rend. (1870) 70, 1134.23. W. Manchot and H. Gall, Chem. Ber. (1925) 58B, 2175.24. M.S. Kharasch and H.S. Isbell, J. Am. Chem. Soc. (1930) 52, 2919.25. D. Zhang, personal communication.26. D. Mootz and K. Bartmann,Argi ew. Chem. Int. Ed. Engl. (1988) 27, 391.27. M.D. Lind and K.O. Christe, Inorg. Chem. (1972) 11, 608.28. R.J. Gillespie and B. Landa, kag. Chem. (1973) 12, 1383.29. E.A.V. Ebsworth, D.W.H. Rankin and S. Cradock, "Structural Methods in InorganicChemistry", Blackwell Scientific: Oxford, UK (1987).30. B.N. Figgis, "Introduction to Ligand Fields", John Wiley & Sons: New York, NY(1966).31. C.D. Wagner, W.M. Riggs, L.E. Davis and J.F. Moulder, "Handbook of X-RayPhotoelectron Spectroscopy", G.E. Muilenberg, Ed., Perkin Elmer: Eden Prairie,MN (1978).32. G.A. Olah, G.K.S. Prakash, and J. Sommer, "Superacids", John Wiley & Sons:New York, NY (1985), and references therein.33. N.F. Hall and J.B. Conant, J. Am. Chem. Soc. (1927) 49, 3047.34. R.J. Gillespie and T.E. Peel, Adv. Phys. Org . Chem. (1972) 9, 1. R.J. Gillespie andT.E. Peel, J. Am. Chem. Soc. (1973) 95, 5173.35. L.P. Hammett and A.J. Deyrup, J. Am. Chem. Soc. (1932) 54, 2721.36. T.E. Thorpe and W. Kirman, J. Chem. Soc. (1892) 921.37. R.J. Gillespie, Acc. Chem. Res. (1968) 1, 202.38. R. Savoie and P.A. Giguere, Can. J. Chem. (1964) 42, 277.39. A. Neppel, J.P. Hickey and I.S. Butler, J. Raman Spectroscopy, (1979) 8, 57.40. R.C. Thompson, in "Inorganic Sulfur Chemistry", G. Nickless, Ed., Elsevier:Amsterdam, Netherlands (1968) p 587.41. K.C. Lee, Ph.D. Thesis, The University of British Columbia (1980).2442. K.C. Lee and F. Aubke, IrKKg. Chem. (1979) 18, 389.43. K.C. Lee and F. Aubke, Inorg. Chem. (1984) 23, 2124.44. M.S.R. Cader and F. Aubke, Can. J. Chem. (1989) 67, 1700.45. G.H. Cady and J.M. Schreeve, Inorg. Synth. (1963) 7, 124.46. A. Engelbrecht, A_ngew. Chem. Int. Ed. Engl, (1964) 4, 641.47. F. Aubke, M.S.R. Cader and F. Mistry, in "Synthetic Fluorine Chemistry", G.A.Olah, R.D. Chambers and G.K.S. Prakash, Eds., John Wiley & Sons: New York,NY (1992) p 43.48. F.B. Dudley and G.H. Cady, J. Am. Chem. Soc. (1963) 85, 3375.49. W.V. Cicha, F.G. Herring and F. Aubke, Can. J. Chem. (1990) 68, 102.50. W.M. Johnson, R. Dev and G.H. Cady, Inorg. Chem. (1972) 11, 2260.51. K.C. Lee and F. Aubke, Inorg. Chem. (1980)j.9, 119.52. R.C. Woods, T.A. Dixon, R.J. Saylcally and P.G. Szanto, Phys.  Rev. Lett. (1975)35, 1269.53. H. Willner and F. Aubke, Inorg. Chem. (1990) 29, 2195.54. S.P. Mallela, S. Yap, J.R. Sams, and F. Aubke, Inorg. Chem. (1986) 25, 4327.55. B.M. Chadwick and S.G. Franlciss, J. Mol. Struct. (1976) 84, 578.56. L.H. Jones, Chem. Phys. (1957) 27, 468.57. B.M. Chadwick and A.G. Sharpe, Adv. Inorg. Chem. Radiochem. (1988) 8, 117.25CHAPTER 2. EXPERIMENTAL2.1 ChemicalsGold powder (-20 mesh, 99.95% purity) and platinum powder (0.5-1.2 Am) wereobtained from the Ventron Corporation (Alfa Inorganics). Fluorosulfuric acid, HSO3F(technical grade), was obtained from Orange County Chemicals and purified by doubledistillation under N2 [1]. Bis(fluorosulfuryl)peroxide, S206F2, was prepared byfluorination of SO3 using AgF2 as a catalyst [2]. Antimony pentafluoride, SbF5, wasobtained from Ozark-Mahoning and purified first by distillation under N2 and then bypumping in vacuo at 0°C. Carbon monoxide (C.P. grade, 99.5% purity) was obtainedfrom Linde Gases and dried by passing it through a trap at -196°C. Sulfur dioxide, SO2,(99.5% purity) was obtained from Matheson Gases and dried by storing over P4010.Acetonitrile was obtained from MCB (spectroquality) and also dried by storing overP4010. Gold tris(fluorosulfate), Au(SO3F)3, platinum tetralcis(fluorosulfate), Pt(SO3F)4,cesium fluorosulfate, CsSO3F, cesium tetralcis(fluorosulfato)aurate(III), Cs[Au(SO3F)4],cesium pentalcis(fluorosulfato)platinate(IV), Cs[Pt(SO3F)5], and cesiumhexalcis(fluorosulfato)platinate(IV), Cs[Pt(SO3F)6], were prepared as described by Leeand Aubke [3][4].2.2 ApparatusVolatile materials and gases were measured in a vacuum line of known volume. ASetra 280E pressure transducer with digital output was used to measure the pressure.Standard vacuum line techniques were used to manipulate air and moisture sensitivesamples. Synthetic reactions were carried out inside Pyrex round-bottom flasks(50 or 100 mL) fitted with 4 mm Kontes stopcocks and B10 ground glass cones(Figure 2-1).26Figure 2-1. Reactor Used for SynthesisFiltrations were carried out using an apparatus similar to that described by Shriver[5] (Figure 2-2).Figure 2-2. Filtration Apparatus27Teflon-coated stir bars were used for mixing the reactants. Since all products werehygroscopic, they were manipulated and stored inside a Vacuum Atmosphere Corp.Dri-Lab, model DL-001-S-G, filled with dry nitrogen and equipped with an HE 493Dri-Train.2.3 Instrumentation2.3.1 Vibrational SpectraInfrared spectra were recorded on three instruments: a Perkin-Elmer 598 gratingspectrometer, a Bomem MB 102 Fourier-Transform infrared spectrometer (FTIR), and aBomem DA3 Series FTIR. Solid samples were finely ground and pressed as thin filmsbetween AgBr or AgC1 windows (Harshaw Chemicals). Liquid samples were pipettedonto silicon windows and pressed to form a thin film. Gaseous samples were contained ina 10 cm cell fitted with AgBr windows and a 4 mm Kontes Teflon stopcock. The reportedfrequencies are accurate to + 1 cm -I for spectra of solid samples. The accuracy of thewavenumbers for [Au(C0)2]+(solv) are estimated at approximately + 0.5 cm-1, and allvalues are reproducible. Fourier Transform (FT) Raman spectra were obtained courtesyof Dr. H. Homborg and Prof. W. Preetz, University of Kiel, Germany. NMR, Ramanand additional FTIR spectra were obtained courtesy of Prof. H. Willner, J. Schaebs, andM. Bodenbinder, University of Hannover, Germany.2.3.2 Electron Spin Resonance SpectraESR spectra were obtained by Drs. F.G. Herring and P.S. Phillips, and F. Mistryall from this department. The samples were cooled to 103 K and kept at that temperatureusing a Varian E-257 temperature controller. The ESR spectra were run on an X-bandhomodyne spectrometer with a Varian 12-inch magnet equipped with a MkII field-dialcontrol. An Ithaco Dynatrac 391A lock-in amplifier was used to obtain phase-sensitivedetection at 100 kHz. Data were acquired using a Qua-Tech 12-bit data-acquisition board28(ADM 12-10), together with a Qua-Tech parallel expansion board (PXB-721) incorporatedinto an IBM XT computer. The relevant data-processing software was as describedpreviously [6][7][8]. The microwave frequency was measured with a HP5246L frequencycounter equipped with a HP5255A plug-in. Field calibration was accomplished using aVarian Gaussmeter, the output of which was also collected by the IBM computer. Theabsolute field was corrected for the placement of the gaussmeter probe by calibratingagainst peroxylamine sulfate in aqueous solution and was in error by about 0.01 G. Theprecision of the data is typically about 0.02 G for 2 K points over a 100-G sweep which,together with the ca. 10-kHz error in the microwave frequency, corresponds to an error ofca. 0.00002 in the g values quoted. Liquid samples were contained, under vacuum, in5 mm ESR tubes fitted with rotationally symmetric Young valves (Young, London).Solid samples were loaded into 2 mm o.d. glass capillary tubes and sealed under dry N2.2.3.2a SimulationsThe spin Hamiltonian parameters for the observed centers were determined using aprogram called QPOW, which was obtained from the Illinois ESR Research Center (NIHresources Grant No. RR01811) and used on a 386 PC. The goodness of the fit wasestablished by computer subtraction of the observed and simulated spectra in digital formto obtain a linear residual to within 2% of the total spectrum.2.3.3 X-ray Crystallographic DataX-ray data were collected and analyzed by Drs. J. Trotter and R. Jones. Intensitymeasurements were made on a Rigaku AFC6S diffractometer using graphitemonochromatized Mo Ka radiation. Samples were mounted in 0.5 mm o.d. quartzcapillaries and sealed under N2.292.3.4 UV-Visible SpectraTwo types of uv-visible spectrophotometers were used. One was theVarian-Cary 5 UV-VIS-NIR double beam spectrophotometer with a mercury sulfidedetector. The second was the HP Vectra System UV/VIS spectrophotometer, asingle-beam instrument with an 8452A diode array detector. Spectra were acquired andmanipulated on these machines using the associated software. Samples were contained ineither a standard 1 x 1 x 2 cm quartz cuvette with a ground glass joint and cap or a 1 mmpath length quartz cuvette attached to a tube with a B14 cone and a 4 mm Kontes stopcock(Figure 2-3).Figure 2-3. Cuvettes Used for UV-Visible Spectrophotometer Measurements.2.3.5 X-ray Photoelectron SpectraX-ray photoelectron spectra were acquired using a Leybold MAX 200 spectrometeroperating at ultra high vacuum. Unmonochromatized Mg Ka radiation at 10 kV and20 mA was used as the excitation source. The Cis core level was measured at a passenergy of 96 eV. The Au 4f712 binding energy at 83.8 eV was used as the reference. Thepeaks were identified by comparison to published data [9] and analyzed by Dr. P. Wongof this department. Samples were mounted on a 1 cm2 x 4 mm-thick piece of aluminum,then attached to the holder under an atmosphere of N2.302.4 MicroanalysisMicroanalyses were done by Mr. P. Borda of this department and BellerLaboratories, GOttingen, Germany. Samples for melting point measurements were sealedin 2 mm o.d. glass capillaries under N2. A typical sample size was about 1 mg. Meltingpoints were obtained on a Gallenkamp #889339.31References1. J. Barr, R.J. Gillespie and R.C. Thompson, Inorg. Chem. (1964) 3, 1149.2. G.H. Cady and J.M. Shreeve, Incisix-,Synth. (1963) 7, 124.3. K.C. Lee and F. Aubke, Inca-g. Chem. (1979) 18, 389.4. K.C. Lee and F. Aubke, Inorg  Chem. (1984) 21 2124.5. D.R. Shriver, "The Manipulation of Air-Sensitive Compounds," McGraw-Hill: NewYork, NY (1969).6. F.G. Herring and P.S. Phillips, J. Magn. Reson. (1984) 57, 43.7. F.G. Herring and P.S. Phillips, J. Magn. Reson. (1985) 62, 19.8. R.E.D. McLung, Can. J. Phys. (1968) 46, 2271.9. C.D. Wagner, W.M. Riggs, L.E. Davis and J.F. Moulder, "Handbook ofPhotoelectron Spectroscopy", G.E. Muilenberg, Ed. Perkin-Elmer: Eden Prairie,MN (1978).32CHAPTER 3. SYNTHESIS AND CHARACTERIZATION OF Au2+ IN THE SOLIDSTATE AND IN SOLUTION3.1 Introduction Gold tris(fluorosulfate), Au(SO3F)3, was first reported in 1972 [1], and is used asthe starting material for all the gold compounds described in this thesis. It was prepared bythe reaction of gold metal with an excess of bromine(I) fluorosulfate, and after removal ofall volatiles and excess BrSO3F, an intermediate was isolated and determined to beAu(SO3F)3.2BrSO3F by weight. Heating the intermediate to 100°C produced Au(SO3F)3as an orange-yellow solid. Later work by Lee showed that the intermediate was in factBr3[Au(SO3F)4] [2], and that Au(SO3F)3 prepared using this method was wealclyparamagnetic, with geff295 = 0.54 BM [3]. The spin-only value of Aeff295 for a goldcenter with one unpaired electron was calculated to be 1.73 BM. A more efficient anddirect route to Au(SO3F)3 was also introduced by Lee—the direct oxidation of gold metalby bis(fluorosulfuryl) peroxide, S206F2, in fluorosulfuric acid at ambient temperatures.The product was isolated by removing the volatile substances and solvent in vacuo [4].Gold tris(fluorosulfate) produced by this method was diamagnetic, withxm = -146 x 10-6cm3morl [4]. This was consistent with a square planar anddiagmagnetic gold(III) center having the electron configuration [Xe]4f145d8 [5].Therefore, it seemed worthwhile to investigate the source of the weak paramagnetismfound in samples of Au(SO3F)3 produced via the intermediate.One explanation for the observed paramagnetism initially considered wastemperature-independent paramagnetism due to 2nd order Zeeman splitting, but a magneticstudy by Lee using the Gouy method to determine the magnetic behaviour of Au(SO3F)3[3] showed that a sample of Au(SO3F)3 prepared using BrSO3F followed the Curie-WeissLaw from 295 K to 100 K. Temperature independent paramagnetism which appears in one33sample of Au(SO3F)3 and not in another would indicate the existence of two differentforms of Au(SO3F)3. This was unlikely, since the appearance, melting point,microanalysis, and vibrational spectra of samples prepared using the two methods wereidentical.Another explanation was the presence of Br2+, which has a 2I13/2g ground state,possibly produced by the pyrolysis of Br3+ in the diamagnetic intermediateBr3[Au(SO3F)4], but the Au(SO3F)3 made via this intermediate contained no detectablebromine [1]. The Br2+ cation gives a well resolved resonance Raman spectrum with acharacteristic band at 360 cm-1. Lee did not observe this peak in samples of weaklyparamagnetic Au(SO3F)3 [3], thus precluding the presence of Br2+ .The last remaining explanation for the paramagnetism is the possibility of Au2+,generated by the reductive elimination of SO3F radicals from Au(SO3F)3 during thepyrolysis step. Loss of SO3F radicals due to heating is rather uncommon; so far, onlythree binary fluorosulfates are known to do this. Silver bis(fluorosulfate), Ag(SO3F)2,reductively eliminates SO3F. at 215°C [6], as does the mixed-valency palladiumcompound Pdiipdiv(s03—)6,r which decomposes at 160°C to yield PdII(S03F)2 andS206F2 [7]. Xenon bis(fluorosulfate), Xe(SO3F)2, is also reported to reductively eliminateSO3F radicals, which combine to form S206F2 [8]. The two principal modes of thermaldecomposition of binary fluorosulfates are:(i) SO3 elimination to give MF. or MF„(SO3F)„, (M = Ta, Nb) [9], e.g.T02(93393 TaF3(S0392 ± SO3(ii) S205F2 elimination [10], e.g.MOO(SO3F)4 M002(SO3F)2 S205F2.In both of these cases the oxidation state of the metal is unchanged.It should be noted that unusual magnetic behaviour is also observed during thesynthesis of gold(III) fluoride, AuF3. There are two methods of producing AuF3: directfluorination of gold metal, giving a diamagnetic product [11], and fluorination of gold34metal by BrF3 and pyrolysis (at 180°C) of an intermediate with the compositionBrF2[AuF4] [12], which yields a wealdy paramagnetic product (pLeff295 = 0.5 BM) [13].There are very few examples of true, mononuclear Au(II) complexes [5][14]. Thefirst was reported in 1954 by Rich and Taube, who used kinetic data to suggest that[AuC14]2" was formed in aqueous solution as a very short-lived intermediate during thereduction of [AuC14]- by [Fe(H20)6]2+ [15]. There are reports of the possibility of Au(II)intermediates in free radical oxidations of Au(I) to Au(III), but there are no definite data tosupport the postulated mechanisms. It was not until 1959 that a true paramagnetic Au(II)complex, Au(S2CNEt2)2, was found to be stable enough for detection by ESR [16].However, the species thought to give rise to the spectrum was not isolated. It was in 1965that the first Au(II) complex, (Bu4N)2[Au{S2C2(CN)2}2], was isolated [17].There have been a number of mono and polynuclear compounds reported in whichgold has the formal oxidation state of +2, and they can be separated into three categories:(i) mixed valency, or "pseudo gold(II)" compounds, with linearly coordinatedAu(I) (d8) and square planar Au(III) (d10) [5]. These compounds are diamagnetic. Anexample is that of AuC12, whose crystal structure determination showed it to be Au4C18(Figure 3-1)[181;Figure 3-1. Crystal Structure of Au4C1835(ii) dimeric compounds with a gold-gold bond that renders the compounddiamagnetic, e.g. Au2I21/2-(CH2)2PMe212 (Figure 3-2) [14]; andPMe2/\CH2 CH2I^II — Au — Au—II^ICH2 CH2\/PMe2Figure 3-2. Structure of Au2I2{A-(CH2)2PMe2}2(iii) monomeric Au(II) compounds with unsaturated thiolate anion ligands, e.g.[Au(mnt)2]2- (mnt=maleonitrile dithiolate) [17]. ESR data about [Au(mnt)2]2- have beenreported, and the g values indicate that the unpaired electron is in a ligand-based orbitaldespite the observation of hyperfine splitting due to 197Au (1=3/2) [19]. There is also acarborane compound, [(C2114)4N]2{Au(B9C2H11)2}, which was found to be paramagnetic,with Aeff=1.79BM, consistent with a d9 configuration [20]. However, no ESR data areavailable to indicate whether the unpaired electron is delocalized around the gold center orthe carbollide anion. A phthalocyanine complex containing Au(II) has also been reported[21].From the brief review, it appears that a true Au2+ center having the electronconfiguration [Xe]4f145d9, comparable to Cu2+ or Ag2+, has not been unambiguouslyidentified. In cases where monomeric complexes of gold(II) are encountered, the ligandschosen in the past such as unsaturated dithiolates, the 1,2-dicarbollide anion, andphthalocyanine, appear to possess low lying unoccupied molecular orbitals, which allowelectron delocalisation according to36.3-2-+ e■■■110.anion[:)(:1 R)rSR ISradical anionand hence a complex of the type[RS zSRAuR^S^S"..-'-^Rj2may either be viewed as a gold(II) complex or a gold(III) radical anion due to theambiguity introduced by the vague oxidation state of the ligand.The difficulty in obtaining Au(II) complexes can be rationalized by considering theionization potentials of the metals in group 10: copper, silver, and gold. From the table ofionization potentials shown below (Table 3-1), it can be seen that less energy is requiredfor gold to reach the +3 oxidation state than for copper or silver, but the most energy isrequired for gold to reach the +2 oxidation state.Table 3-1. Ionization Potentials (1d.mol-1) for Group 11 Metals [22]2^3^Known Positive1st^2nd^3rd^E N^E N^OxidationN=1 N=1^StatesCu 745 1958 3824 2703 6527 1, 2, 3Ag 731 2074 3361 2805 6166 1, 2, 3Au 890 1980 2943 2870 5813 1, (2), 3, 5*most common oxidation state(s) is underscored37In square planar or distorted octahedral d9 complexes, the unpaired electron is inthe dx2-y2 orbital, which is at the highest energy level, and it should be easy to remove anelectron from this orbital. Hence the +2 oxidation state for gold should be unstable, andAu(II) should disproportionate to Au(I) and Au(III).It appears that in both instances where unusual magnetic behaviour of a supposedgold(III) compound Au(SO3F)3 and AuF3 [11] was observed, their syntheses has involveda pyrolysis step. It was thought that in the preparation of Au(SO3F)3, a paramagneticspecies was produced during this step, since the intermediate Br3[Au(SO3F)4] isdiamagnetic. It was decided to study the controlled pyrolysis of a diamagnetic sample ofAu(SO3F)3 in order to obtain evidence in favour of this assumption and to detect Au2+ byESR.3.2 Syntheses3.2.1 Pyrolysis of Au(SO3D3Au(SO3F)3 was prepared by the direct oxidation of the metal by S206F2 inHSO3F [4]. A 100 mL round bottom flask was charged with 265 mg (0.536 mmol) ofAu(SO3F)3, evacuated, and heated at 60°C in an oil bath for one week. There was noobservable change in colour from the initial bright orange, and no sublimate was visible.There was also no measureable pressure at -196°C. At room temperature, 4.9 mbar(9.8 /mop of volatile materials were measured and removed. The temperature of the oilbath was increased to 100°C and the reactor heated for four days. An orange crystallinesolid sublimed on the upper sides of the reactor. With the reactor at room temperature,3.5 mbar (7 /mop of volatile materials were measured and removed. The oil bathtemperature was increased to 125°C and the Au(SO3F)3 heated for another two days.After cooling the reactor to room temperature, 2.9 mbar (5.8 /mop of volatile materialswere removed. The sublimate was scraped from the walls of the reactor and mixed withthe residue, which was now slightly darker in colour. Since the pressures of the volatile38materials were low, the sublimate and residue were mixed together so that the totalpressure of any volatile materials produced by further pyrolysis would be easier tomeasure. The mixture was heated at 125°C for another week. No more volatiles wereobserved at room temperature. The pyrolyzed Au(SO3F)3 had an overall weight loss of17.8 mg, and microanalysis indicated that the sulfur content had decreased to 18.9% froma calculated value of 19.5%. The residue had a melting point of 138-139°C (lit. 140°C[4]). The volatile materials in the initial slow pyrolysis were at too low a pressure to beidentified (at least 5 mbar pressure is needed), so two other experiments were done wherethe Au(SO3F)3 was pyrolyzed at 115°C and 145°C. The two samples were found to beESR silent before the pyrolyses was carried out. All volatile materials (5 mbar,0.045 mmol) were collected at room temperature; there was no measureable pressure at-196°C or -78°C. The volatile materials were identified as S02F2 and SiF4 by infraredspectroscopy [23].3.2.2 Reduction of Au(III) to Au(II) Using  Gold Metal Approximately 3 mL HSO3F was added to a 50 mL round bottom flask containing255 mg Au(SO3F)3 (0.516 mmol) and 42 mg gold powder (0.213 mmol); the mole ratio ofAu(SO3F)3 to gold metal was 2.42:1. The mixture was stirred at room temperature; as theAu(SO3F)3 dissolved, an opaque orange solution formed. Over a period of four hours thesolution gradually cleared, and the colour changed to orange-red. It was then heatedovernight at 65°C (ca. 10 hours). All the gold metal had dissolved, and the solution wasnow dark orange-brown. An orange solid precipitated after 3-4 days and was removed byvacuum filtration. The solution was pipetted into an ESR tube and spectra of the frozenliquid were taken. The solution colour was unchanged after removal of the precipitate, butthe solution gradually became lighter in colour as more solid kept forming over a period ofa few weeks. The filtered, dried solid was identified by microanalysis as Au(SO3F)2 andfound to be ESR silent. It did not melt or decompose below 290°C.39Au^S^Anal. calc. for 06F2S2Au^49.85^16.23found^49.50^15.133.2.3 Reaction of Cs[Au(SO3F)4] with Gold MetalA 50 ml round bottom flask containing 16 mg (0.0812 mmol) gold metal wascharged with 172 mg (0.237 mmol) of Cs[Au(SO3F)4]. The mole ratio of Cs[Au(SO3F)4]to gold metal was 2.9:1. Approximately 3 mL HSO3F was added by distillation in vacuo.The Cs[Au(SO3F)4] dissolved to give a clear yellow solution, while the gold remainedundissolved. The mixture was placed in a 60°C oil bath and heated for 5 days. No changein the mixture was observed. The temperature of the oil bath was increased to 100°C andthe mixture heated for 3 days. An orange solid slowly precipitated. Unreacted gold wasstill visible at the bottom of the reactor, but a small amount appeared to have beenconsumed. The oil bath temperature was increased first to 130°C, then to 160°C, andheated for 3-4 days at each temperature. The amount of orange precipitate slowlyincreased. Gold metal was still present in the mixture. The reaction was repeated using a10:1 mole ratio of Cs[Au(SO3F)4] to gold metal, with the same results. Neither addingmore HSO3F nor elevated temperatures could dissolve all of the metal. A suspension ofthe precipitate and solution was removed from the mixture using a pipette. The orangeprecipitate was separated from the solution by vacuum filtration, and neither solid norsolution gave rise to an ESR spectrum. The solid did not melt or decompose below290°C. The filtered precipitate was investigated using infrared spectroscopy and thespectra were found to be consistent with Au(SO3F)2. Microanalysis of the precipitate gavepoor results, possibly due to traces of gold metal.403.3 Results and Discussion Pyrolysis of a sample of diamagnetic Au(SO3F)3 allows us to see if anyparamagnetic centers are generated, and if SO3F radicals or S206F2 are produced. SinceAu(II) (d9) has an unpaired electron, ESR spectroscopy is the best method for detectinglow concentrations of this moiety. The pyrolysis was carried out slowly to avoid thepossibility of disproportionation of the gold(II) center to gold(I) and gold(III). In addition,if any paramagnetic centers were generated, the slow pyrolysis would ensure that they werepresent in low concentrations. High concentrations of paramagnetic centers lead to linebroadening in ESR spectroscropy, and any hyperfine structure that may be present wouldbe obscured. The pyrolysis is followed by weight. Measurement and identification of anyvolatiles by infrared spectroscopy was undertaken.The magnetic moment of the Au(SO3F)3 made via BrSO3F is about 0.54 BM [3],well below the value of 1.73 BM (spin-only value) expected for a single unpaired electron.Thus, it appears that there is a very small concentration of paramagnetic species in thesample (calculated to be ca. 7%).The amounts of volatile materials obtained during the initial pyrolysis were toosmall for identification by IR spectroscopy. Subsequently, two shorter pyrolysisexperiments with larger amounts of Au(SO3F)3 were carried out. To ensure that thevolatile materials produced at different temperatures were the same, one sample was heatedat 115°C and another at 145°C. The melting point of Au(SO3F)3 is reported to be 140°C[1], so heating a sample of Au(SO3F)3 at 145°C allowed us to determine whether thevolatile fraction produced by decomposition of Au(SO3F)3 was the same as the fractionproduced by pyrolysis of Au(SO3F)3 at 115°C. The volatile byproducts in both cases werefound to be S02F2 and SiF4 [23], with possible traces of S205F2 and S206F2. In spite ofour efforts, we could not detect any evidence for dioxygen, 02, which is a possibledecomposition product.41Since evidence of SO3F radicals wwas found in the ESR spectra of the pyrolyzedsolid (vide infra), it seemed likely that S02F2 and SiF4 were formed by the reactionbetween SO3F radicals and the glass reactor. It has been reported that SO3F. attacks glassat temperatures above 120°C [24]. To confirm that a net loss of SO3F. or its dimerS206F2 had occurred during the pyrolysis, the solid residue from the sample that had beenheated at 115°C was dissolved in HSO3F and S206F2 was added. After removal of theacid, excess peroxide, and all volatile materials in vacuo, the the re-oxidized residue wasfound to have increased in weight by ca. 5.7%. Microanalysis of the residue showed it tobe Au(SO3F)3, and it was ESR silent. The overall weight loss after the pyrolysis was6.3%; re-oxidation of the residue resulted in a weight gain of 5.7%. The "missing" 0.6%is probably due to glass attack, since SiF4 was found in the infrared spectrum of thevolatiles during the pyrolysis.Gold tris(fluorosulfate) is also easily reduced by gold metal in HSO3F. When amole ratio of 2.4:1 of Au(SO3F)3 to Au(s) is used, with enough HSO3F to dissolve theAu(SO3F)3, the gold powder was completely consumed within 24 h, and the colour of thesolution changed from clear orange to opaque dark brown. The frozen brown solutiongave rise to an ESR signal. Precipitation of Au(SO3F)2 from a sample of the brown liquidoccurred slowly, and the colour of the solution became lighter as more solid formed.3.3.1 Vibrational Spectra3.3.1a Pyrolyzed Au(S03E)3The pyrolysis did not lead to well-defined compounds, e.g. Au(SO3F)2 or AuS03F,unlike the silver and palladium bis(fluorosulfates) mentioned earlier. A differential thermalgravimetry experiment was done by Prof. Meyer, Hannover, Germany, to observe thethermal decomposition of Au(SO3F)3. It was found that heating a sample of Au(SO3F)3resulted in a gradual, rather than a stepwise loss of mass and ultimately led to the cruciblebeing coated with a thin layer of gold metal.42While there was little evidence of S206F2 in the infrared spectra of the volatilematerials produced by the pyrolysis, and the observation of the SO3F radical in the ESRspectra was sporadic at best, the re-oxidation and ESR experiments strongly suggest thatthe following occurs during the pyrolysis:AAu(SO3F)3 -> Au(SO3F)3_x + x S03F.^(3)The non-stoichiometric loss of SO3F may account for our inability to detectS206F2, unlike the silver and palladium analogues, which lose half a mole of S206F2each [6][7]:Ag(SO3F)2 —> Ag(SO3F) + 1/2 S206F2^(4)Pd(S 03F) 3 -9° " Pd(S 03 F)2 " -I- 1/2 S206F2^(5)The temperature at which the Au(SO3F)3 is pyrolyzed (115°C) is also near thetemperature at which S206F2 starts to react with the walls of the glass reactor [24]. Thepotential difficulty in detecting S206F2 may also be due to its reoxidizing of sublimedAu(SO3F)3_x in the cooler parts of the reactor. Another possible decomposition product,dioxygen, was not detected; attempts to find evidence of 02 using mass spectrometry wereunsuccessful. If we assume that all weight loss is due to SO3F (which is not entirelycorrect, since the presence of SiF4 indicates some glass was etched away, possiblyresulting in an inflated value for the weight loss), it is possible to calculate the approximatevalue of x in Au(SO3F)3_x (x = 0.33) to give Au(SO3F)2.67. This formulation has acalculated sulfur value of 18.5%, which compares very well to the value of 18.9%obtained from microanalysis.It is interesting to note that sublimation of Au(SO3F)3 in a static vacuum does notproduce a paramagnetic species, but the same sublimation carried out under dynamicvacuum gives an ESR signal similar to that produced by the pyrolysis.43The molecular structure of Au(SO3F)3 provides a possible insight into thedecomposition mechanism. Au(SO3F)3 is dimeric [25] in the solid state, and possibly alsoin solution [26]. The structure of the solid shows both bridging and terminal SO3F groups(Figure 3). The environment around the Au(III) center is best described as almost squareplanar, with long, weak Au.. .0 contacts to adjacent groups above and below the squareplane formed by gold(III) and four oxygen atoms. The four oxygen atoms bound to thegold can be separated into two pairs that are cis to each other. One pair has an Au...0bond length of 2.02 A, the other an Au...0 bond length of 1.959 A.Figure 3-3. Structure of Au(SO3F)344This difference in Au-0 bond lengths produces local C2v symmetry (Figure 3-4).Figure 3-4. Enlarged Diagram of the Au(III) EnvironmentIt seems reasonable that with the reductive elimination of SO3F. (detected by ESRspectroscopy and discussed later), one of the terminal SO3F groups on an adjacent dimericunit bridges to the reduced center (Au2+) to form oligomers, thus restoring the squareplanar environment. The Au2+ center could then be considered as a lattice defect inAu(SO3F)3.The loss of a sulfur containing species, e.g. S03F., should cause changes in thevibrational spectra, particularly in the fluorosulfate stretching regions. A comparison ofthe infrared data of pyrolyzed, sublimed, and diamagnetic Au(SO3F)3 is provided inTable 3-2.45Table 3-2. Infrared Spectra of Pyrolyzed, Sublimed [4], and Diamagnetic [4]Au(SO3F)3pyrolyzedAu(Sp3F)3(cm-1), int.sublimedAu(S1103F)3(cm-'), int.diamagneticAu(Sp3F)3(cm- ), int.TentativeAssignment1434w 1435w,sh 1442m PS03, t1432m1407m,sh1427m,sh 1425m }vS03, br1381m,b1240vs^t1220w,sh 1220s,sh f vS03, t1112m,b1055w,sh1135ms t1055s^IPS03, br1037m 1030m960w,sh 960w,sh 960s,b t PS-O...Au924m,b 918m,b 920s,sh f891m,b 887m,b 895s,b t pS-F827m 820s^f682s^t Mu-0 + def664w 667w,sh 670s,sh I610w586m 590s582s SSO2541m 545m 550s OS02462w 461w 460m Mu-0 + defThe vibrational bands attributed to bridging fluorosulfate groups in pyrolyzedAu(SO3F)3 are split compared to the same bands arising from diamagnetic Au(SO3F)3.This band proliferation may be due to vibrational coupling or to factor group splittings forthe fluorosulfate group. The remaining bands appear unchanged .3.3.1b AL(.1 5123D2The characterization of the orange precipitate, Au(SO3F)2, was initially puzzling.It was found to be diamagnetic, not paramagnetic as expected for a d9 gold(II) center. Itsvibrational spectra are considerably more complex than those of other metal(II)46bis(fluorosulfates) [27]. The vibrational spectra of Au(SO3F)3 appear to more suitable forcomparison to those of Au(SO3F)2. The vibrational data for Au(SO3F)2 and Au(SO3F)3are listed in Table 3-3.Table 3-3. Vibrational Spectra of Au(SO3F)2 and Au(SO3F)3Infrared Infrared Raman Raman TentativeAu(sp3F)3 Au(sp3F)2 Au(SOF)3 Au(SOF)2 Assignment(cm^),int. (cm^),int. Av(cm'),Int. Ap(cm-A),mt.1442vs 1418s,sh 1449m PS03, t1425s,sh 1400vs 1423m,sh 1423m1369s 1409m PSO3, br1393w1375w1240s 1232s 1226s^k PS03, t1220s,sh 1200vs 1227vs 1199w,sh f1135ms 1085s,b 1102w 1114w PS-0, br1055s 1065m,sh 1053m 1044w t PS02, br1035ms 1025w 11012ms 1010w PS-0..Au993w960s,b 962ms 955m,sh 955w920s,sh 931s 936s895s,b 899s870ms 873m,sh 867vw836s 845w PS-F820s 822s,sh 822w 823w812s,sh682s 680ms Muni-04+def670s,sh 671m 668w648m 650vs MuI-02+def640m 642s610w 610w 600ms590s 595s OasymS03582s 585s 583w 577w552s 548ms 546m 541m460m 462m 465m444w456m450mMuni-04pS03F418w 415m47The diamagnetism of the sample presented the possibility that Au(SO3F)2 could bedescribed as a mixed valency Au(I)-Au(III) complex of the form AuiAuiii(s03—‘4.r) This isanalogous to the formulation of AuC12 as Au4C18 [5]. Au(SO3F)2 may even have astructure akin to Au4C18, i.e. a linearly coordinated Au(I) and a square planar Au(III)center.Examination of the vibrational data for AuiAor,,-.03ka F)4 shows that the peakpositions have shifted to slightly lower frequencies relative to Au(SO3F)3. There is alsoextensive band splitting, particulary in the bridging fluorosulfate and S-F stretchingregions.The band splitting may be caused by asymmetric fluorosulfate bridging betweenAu(I) and Au(III). The two metal centers are expected to exhibit different acceptorabilities towards the oxygen atoms of the fluorosulfate group. It is also possible thatAu(SO3F)2 is polymeric, and vibrational coupling among neighbouring fluorosulfategroups may cause band splittings.Additional support for the formulation of Au(SO3F)2 as Au1Aui11(s03F) 4 is thetendency for Au(II) to disproportionate to Au(I) and Au(III), and the observation thatdiamagnetic AuIAuiii (SO3F)4 precipitates from an ESR active (i.e. paramagnetic) speciesin solution.3.3.2 Electron Spin Resonance Spectra3.3.2a Au(S03E12.67The slow pyrolysis produced an ESR-active species. The pyrolyzed sample,Au(SO3F)2.67, gave an axial spectrum (Figure 3-5) with no hyperfine coupling. This isunexpected, since the nuclear spin of 195Au is 3/2.gzz = 2.882 gyy = 2.093250G SO3F•g ^2.103giso = 2.359Simulation48Figure 3-5. ESR Spectrum of Au(SO3F)2.67The g values used to simulate the spectrum are: gxx = 2.103, gyy = 2.093,g ^2.882, giso = 2.359. The "spike" seen to the right of the major feature (A) has a gvalue of 2.0033 and was attributed to the SO3F radical [28]. This "spike" only appears inthe spectra occasionally. So far, we have been unable to determine why there is nohyperfine coupling.3.3.2b Au(S03a3  Reduced by  Gold Metal The reduction of Au(SO3F)3 by gold metal resulted in a brown liquid andAu1AuIII(S03F)4. The frozen solution was ESR-active, giving an axial ESR spectrum witha four-line hyperfine splitting pattern (Figure 3-6). A nuclear quadrupole couplingconstant was necessary in the simulation, thus precluding the possibility that the splittingwas due to the presence of fluorine atoms (1=1/2). Including the nuclear quadrupolecoupling constant in the simulations gave the correct relative line intensities (Figure 3-7).gzz = 2.890 gyy = 2.093gxx = 2.103Simulation j-----\250GBgiso = 2.36249Figure 3-6. ESR Spectrum of Frozen Au2+(solv)(a) r1 2200 1 2400 2600 2600 ' 3000 3200 3400Figure 3-7. Au2+ Simulations With a Nuclear Coupling Constant (a) and Without (b).50It appears that the hyperfine coupling is consistent with an I=3/2 nucleus, ie.197Au. The g values used in the simulation are: gxx = 2.096, gyy = 2.103, gzz = 2.890,giso = 2.363, Axx = 145 Mhz, Ayy = 145 Mhz, Azz = 120 Mhz, Aiso = 136.7 Mhz.The axial form of the g values (g, g, gzz) for Au2+ both in solution and the solidsuggests the paramagnetic Au2+ center is in an environment very much like the Au(III),i.e. approximately square planar. Further evidence of similar environments for the twometal centers is also provided by the giso values of both the solid and solution, which areidentical within experimental error (2.359 vs. 2.363). A comparison of the g values withother known gold(II) species in the table below shows that we have obtained the highestvalues so far. A large g value indicates that the electron may be partly localized on anatom with a large spin-orbit coupling constant.Table 3-4. g Values of Known Gold(II) SpeciesComplex^T(K) gxx^gYY^gzz^giso^ref.Au(SO3F)3_x^103^2.093 2.103^2.882^2.359^this workAu2+(soiv)^103^2.093 2.103^2.890^2.362^this workAuiAuM(SO3F)4(solv)^77^2.065 2.234^2.656^2.318^this work[Au(mnt)2]2'^133^1.9769 2.0051 2.0023 1.9947^[19][Au(mnt)2]2-b 2.009^[17]Au(phthalocyanine)^77^ 2.065^[21]Ag(SO3F)2c^77^2.072 2.096^2.407^2.192^[6]a[Au(mnt)212- doped into [Ni(mnt)2]2-; bTemperature not given; Chi BrSO3F the giso value differsslightly from the one initially reported.Although we have not yet arrived at a definite explanation for the absence ofhyperfine coupling in the solid sample and the presence of hyperfine coupling in thesolution, it is possible that the difference between the two Au2+ ESR spectra is due to a51concentration effect. In Au2+(solv), the concentration of the paramagnetic species isaffected by the disproportion equilibrium to produce Au(SO3F)2. If the concentration ofAu2+(so1v) is much smaller than Au2+(solid), then it may be possible to see hyperfinecoupling in the former. It should be noted that a similar observation was made during thestudy of Ag(SO3F)2 [29]. The ESR spectrum of a solid sample of Ag(SO3F)2 showed nohyperfine structure, yet a solution of Ag(SO3F)2 in BrSO3F gave an ESR spectrum withsome hyperfine structure (Figure 3-8).Figure 3-8. ESR Spectra of Ag(SO3F)2 in (a) the solid state, and (b) in BrSO3F523.3.2c AuIMIII(S03E)4A sample of diamagnetic Au1Au111(S03F)4, when redissolved in HSO3F, formed adark red-brown solution that gave rise to an asymmetric ESR spectrum (Figure 3-9). Theg values used to simulate the spectrum are gxx = 2.656, gyy = 2.234, and gzz = 2.065(giso = 2.318). There is evidence of hyperfine splitting due to four fluorine atoms andformulation as [Au(SO3F)4]2- is suggested. If small amounts of Au(SO3F)3 are added, thespectrum gradually becomes more and more symmetric, and the value of giso changes from2.318 for the asymmetric species to 2.36 (Figure 3-10). In addition, if a sample of thedark brown liquid is sealed under vacuum in a 6 mm glass tube, over two to three weeksthe solution becomes lighter in colour, and the same orange solid slowly precipitated (thiswas confirmed by infrared spectroscopy).Figure 3-9. ESR Spectrum of AuTAu111(SO3F)4 in HSO3Fgxx = gyy = 2.1088gzz = 2.8569Figure 3-10. ESR Spectrum of Au2+(solv) with Added Au(SO3F)33.3.3 Reaction of Cs[Au(SO3F)1] and Gold Metal Reacting Cs[Au(SO3F)4] with gold metal produces an orange precipitate as well,but some metal is always present. Neither the solution nor the solid were ESR active,indicating that no Au2+ appears to be formed. Analysis of the orange solid by vibrationalspectroscopy, and comparison of its melting point to the solid isolated from the FSR-activesolution, showed it to be Au[Au(SO3F)4]. Au(SO3F)3 is acidic in HSO3F, whileCs[Au(SO3F)4] is basic (vide supra) [2][41 The proposed reaction for the formation ofAu[Au(SO3F)4] from Au2+(solv) may be written as follows:538 HSO3F + 2 Au2+(solv)^AurAuIII(S03F)4(S) + 4 H2S03F+ (6)54From the above equation, it seems that a high acidium ion concentration wouldstabilize Au2+(solv), while a high fluorosulfate anion concentration would favourformation of Au1Au111(so3F)4.Similar behaviour is observed in diamagnetic silver(II) oxide, Ag0 [30]. The solidis formulated as Agi-AgIII, and dissolving it in strong, aqueous mineral acids forms thebright blue Ag2+(solv), which is detectable by ESR.3.4 Conclusion Distinct evidence for the formation of Au2+ in both the liquid and solid states hasbeen obtained via ESR. The g values are the highest reported so far, indicating electrondelocalization around the Au2+ center, and not the ligands. Pyrolysis of Au(SO3F)3resulted in reductive elimination of SO3F radicals and formation of Au2+ as lattice defects.The ESR spectrum is axial, indicating that the paramagnetic center is in a site of highsymmetry. In solution, Au2+(solv) was produced by reduction of Au(SO3F)3 by goldpowder, and stabilized by the acidium ion, H2S03F+. The Au2+ was unstable anddisproportionated to form a mixed valency solid with the empirical formula Au(SO3F)2 andformulated to be Au1Auffi(SO3F)4 by infrared and Raman spectroscopy. The attemptedreduction of Cs[Au(SO3F)4] by gold powder resulted in the formation of AuIiku111(so3F)4.Attempts to isolate pure Au(II) have been unsuccessful to date.References1. W.M. Johnson, R. Dev and G.H. Cady, Inorg. Chem. (1972) 11, 2260.2. K.C. Lee and F. Aubke, Inorg. Chem. (1980) 19, 119.3. K.C. Lee, B.Sc. Thesis, The University of British Columbia (1976).4. K.C. Lee and F. Aubke, Inorg. Chem. (1979) 18, 389.5. R.J. Puddephatt, "Comprehensive Coordination Chemistry", G. Wilkinson, Ed.,Vol. 5, Pergamon Press: Oxford, (1987) p 861.6. P.C. Leung and F. Aubke, Inorg. Chem. (1978) 17, 1765.7. K.C. Lee and F. Aubke, Can. J. Chem. (1977) 55, 2473.8. M. Wechsberd, P.A. Bulliner, F.O. Sladkey, R. Mews and N. Bartlett, Inorg. Chem(1972) 11, 3063.9. D. Zhang, personal communication.10. F. Mistry and F. Aubke, presented at the Ninth International Fluorine Symposium,Leicester, England (1989).11. F.W.B. Einstein, P.R. Rao, J. Trotter and N. Bartlett, J. Chem. Soc. (A) (1967) 478.12. A.G. Sharpe, J. Chem. Soc. (1949) 2901.13. R.S. Nyholm and A.G. Sharpe, J. Chem. Soc. (1952) 3579.14. H. Schmidbaur and K.C. Dash, Adv. Inorg. Chem. Radiochem. (1982) 25, 39.15. R.L. Rich and H. Taube, J. Phys. Chem. (1954) 58, 6.16. T. Vanngard and S. AkerstrOm, Nature (London) (1959) 184, 183.17. J.H. Waters and H.B. Gray, J. Am. Chem. Soc. (1965) 87, 3534.18. D. Belli Dell'Amico, F. Calderazzo, F. Marchetti and S. Merlino, J. Chem. Soc. Dalton Trans. (1982) 2257.19. R. L. Schlupp and A. H. Maki, Inorg. Chem. (1974), 13, 44.20. L.F. Warren and M.F. Hawthorne, J. Am. Chem. Soc. (1968) 9Q, 4823.21. A. MacCragh and W. S. Koski, J. Am. Chem. Soc. (1965), 87, 2496.555622. J.E. Huheey, "Inorganic Chemistry: Principles of Structure and Reactivity", 3rd ed.,Harper & Row: New York, NY (1983).23. K. Nalcamoto, "Infrared Spectroscopy of Inorganic and Coordination Compounds",2nd ed., John Wiley & Sons: New York, NY (1963).24. F.B. Dudley and G.H. Cady, J. Am. Chem. Soc. (1963) $5 , 3375.25. H. Willner, S.J. Rettig, J. Trotter, and F. Aubke, Can. J. Chem. (1991) 69, 391.26. W.V. Cicha, K.C. Lee and F. Aubke, J. Solution Chem. (1990) 19, 609.27. C.S. Alleyne, K. O'Sullivan Mailer and R.C. Thompson, Can. J. Chem. (1974) 52,336.28. W.V. Cicha, F.G. Herring and F. Aubke, Can. J. Chem. (1990) 68, 102, andreferences therein.29. P.C.S. Leung, Ph.D. Thesis, The University of British Columbia (1979).30. J.A. McMillan, Chem. Rev. (1962) 62, 65, and references therein.57CHAPTER 4. SYNTHESIS AND CHARACTERIZATION OF [Au(C0)2][Sb2F11]4.1 Introduction There are few reports of stable carbonyl complexes of the group 11 elements. Nothermally stable, neutral binary carbonyl compounds of copper, silver, or gold have beenisolated, although matrix isolation experiments with gold have provided evidence forAu(C0). (n = 1, 2) [1]. Copper carbonyl cations of the type Cu(CO)n+ (n = 1-4) havebeen generated from either copper(I) oxide or copper(I) sulfate and CO in concentratedH2SO4 [2], and are used as carbonylation catalysts in reactions with olefins, alcohols, andhydrocarbons [3]-[5].Souma et al. have also reported the formation of [Ag(C0)2]+, which exhibitedcatalytic abilities similar to the Cu(I) carbonyl cations [6], and have obtained bothvibrational and 13C NMR data from the copper and silver carbonyl cations [6]. However,they were unable to isolate any of these cations. Recently, Ag(C0)[B(OTeF5)4] and[Ag(C0)2][B(OTeF5)4] have been isolated by Strauss and co-workers [7][8]. Although thesilver salts were characterized by X-ray crystallography, they are thermally unstable anddecompose with loss of CO.Copper and gold are the only group 11 elements known to form thermally stablecarbonyl chlorides [9]. The crystal structures of both Au(CO)C1 [10] and Cu(CO)C1 [11]are known, and differ from each other in that the gold compound consists of linearmonomers, whereas the copper congener is a polymeric sheet with bridging chlorideatoms. A [Cu(C0)][AsF6] species [12], and other copper carbonyl derivatives [9] havebeen reported in addition to some silver bis(carbonyl) complexes with the formula[Ag(C0)2][M(OTeF5)4] (M = Ti, Zn) [8].The first gold carbonyl complex, Au(CO)C1, was prepared in 1925 by Manchot andGall [13], and independently reported by Kharasch and Isbell [14]. Both groups passed58carbon monoxide over gold(III) chloride at temperatures varying from 50°C to 120°C. Noother gold carbonyl complexes were reported until recently. Then, three were prepared inrapid succession: Au(CO)S03F, made by reductive carbonylation of Au(SO3F)3 inHSO3F [15], [Au(C0)2][UF6], prepared in HF by oxidizing gold metal with UF6 in a COatmosphere [16], and Au(CO)Br, made by reacting Au2Br2 or AuBr and CO indibromomethane. However, Au(CO)Br could not be isolated from solution [17]. Neitherthe fluoride nor iodide analogues are known, and attempts to prepare Au(CO)I have beenreportedly unsuccessful [17].4.2 Synthesis of [Au(C0)2J[Sb2E1 llAu(CO)S03F (0.325 mg, 1.0 mmol) was prepared as described previously [15].Antimony pentafluoride (10 g, 46.1 mmol) and 2 mmol CO were condensed onto theAu(CO)S03F. The mixture was warmed to 50°C and stirred. Two liquid phases wereobserved, but upon warming to 75°C for one hour, one phase formed. Cooling to roomtemperature caused two phases to separate out again. Excess SbF5 and the byproductSb2F9S03F were removed in vacuo. Pumping the residue at 80°C to constant weightproduced [Au(C0)2][Sb2F1 i] (730 mg, 1.03 mmol). The white, crystalline solid could beheated to 130°C without obvious evolution of CO and was found to melt at 156°C.Au C^SbAnal. calc. for C202F11Sb2Au 27.9 3.40 34.5found 29.5 3.57 33.9Satisfactory elemental analysis for Au and Sb could not be obtained because ofinterference between the two metals.4.3 Results and Discussion The solvolysis of Au(CO)S03F in SbF5 under a pressure of carbon monoxideresulted in the quantitative formation of [Au(C0)2][Sb2F1i]. The byproduct, Sb2F9S03F,was identified by infrared spectroscopy [18]. Since the volume of both the vacuum line59and the reactor were known, the amount of carbon monoxide taken up was easilycalculated and the stoichiometry of the reaction can be written asA u(CO)S03F + 4 SbF5 + CO -* [Au(C0)2]{Sb2F11] + Sb2F9S03F (1)Bis(carbonyl)gold(I) undecafluorodiantimonate, [Au(C0)21[Sb2F11], is the fifthgold carbonyl species to be reported. The cation, [Au(C0)2]+(solv), was first observed insitu during a vibrational study of the reductive carbonylation of Au(SO3F)3 in HSO3F[15], but solvent removal resulted in partial substitution of CO by S03F-, andAu(CO)S03F was isolated. The use of a less basic anion allows us to isolate[Au(C0)2][Sb2F11]. The [Au(CO)2J ± cation is also reportedly present in [Au(C0)2][UF6][16], but due to its thermal instability, incomplete vibrational and microanalysis data, anunambiguous identification is still forthcoming.4.3.1 Vibrational SpectraGold in a +1 oxidation state has been shown to exhibit linear coordination, and thisis borne out by published crystal structure data of various gold(I) complexes and theoreticalbonding calculations [19][20]. Even though no molecular structure of [Au(C0)2][Sb2F11]is available yet, we can assume that [Au(CO)2] + will also be linear. In that case, thecation has Dcoh symmetry, and the irreducible representation is found to bervib = 2 Eg (Ra) + 2E (IR) + IIg(Ra) + 2IIu(IR)^(2)Of the seven fundamental vibrations of [Au(C0)2]+, four are observed in theinfrared spectrum and three in the Raman spectrum. Isotopic substitution using 13C and180 were used to ensure assignment of the bands with minimal ambiguity. The results aresummarized in Table 4-1.60Table 4-1. Infrared and Raman Data (cm-1) for [Au(CO)2] + and Its Isotopomers[Au(C0)2]+IR^Raman[Au(13C0)2]+IR^Raman[Au(C180)2]+IR^Raman Assignment2605vw 2547 2545 Eu+ P2+ P32239vw 2187 2188 Eu+2254vs 2199 }2203 E +g vi2217s 2165 2165 Eu+ v32176w 2125 2125 Eu+ P3 t , 13c406m 392 403 ilu P6400vw N/0* N/O E +g P2354w 348 344 Eu+ P4312sh 303 308 rig P5105 105 100 nu v7not observedThe average C-0 stretching frequency of [Au(CO)2] + in HSO3F was found to be2231 cm-1, which was unexpectedly high [15]. Solid [Au(C0)2][Sb2F11] has an evenhigher CO stretching frequency (ay. 2235.5 cm-1). The value of vC0 (v3) for[Au(C0)2][UF6] is reported at 2200 cm-1 [16]. The carbonyl gold(I) fluorosulfate,Au(CO)S03F, has C-0 stretching frequencies at 2196 cm-1 in the infrared and 2195 cm-1in the Raman [15]. Monocarbonyl gold(I) chloride, Au(CO)C1, exhibits solvent dependentinfrared active C-0 stretches between 2153 cm-1 and 2170 cm-1 [21] in solution, andRaman active C-0 vibrations at 2183 cm-1 in the solid [22]. The bromine analogue,Au(CO)Br, has infrared C-0 stretching frequencies between 2151 cm-1 and 2159 cm-1 thatare also dependent on the solvent used [17]. No Raman data are available for Au(CO)Br.A comparison of the stretching frequencies of the above compounds indicates that vC0increases with decreasing basicity of the anion, i.e. Br- < Cl- < S03F- < UF6-< [Sb2F11]-.The C-0 stretching frequency of [Au(C0)2][Sb2F11] decreases to 2199 cm-1 from2254 cm-1 in the Raman spectrum upon substitution of 13C for 12C, as expected. The61linear cation has a centre of inversion and the mutual exclusion principle holds: none ofthe bands observed in the infrared are coincident with those in the Raman. Comparison ofthe observed bands to the isoelectronic and isostructural [Au(CN)23- [23][24] was used inthe assignment of [Au(C0)21+ bands (Table 4-2).Table 4-2. Comparison of [Au(C0)2]+ and [Au(CN)21 Stretching Vibrations.[Au(C0)21+ [Au(C)2]-a Assignment^2254^2162^pi400 440 P2^2217^2142^P3354 426 P4^ 12^302^P5406 390 P6105^120^P7'Averaged values from references [23][24]Since the metals and counteranions are different, useful comparison of the C-0stretching frequencies as reported is of limited utility. A comparison of C-0 forceconstants among different metal carbonyl species may be more useful, since the magnitudeof the force constants are a quantitative measure of C-0 bond strengths. As can be seenfrom Table 4-3, the C-0 force constant for [Au(C0)2][Sb2F1i] is the highest, with theexception of HCO+. T-Backbonding is impossible in the formyl cation, HCO+ , so theforce constant of this molecule represents an upper limit and can be used as an example ofa pure a bond. The large force constant for [Au(C0)2][Sb2F1 i] implies that T-backbonding is greatly reduced.62Table 4-3. Stretching Frequencies and Force Constants of CO in Some TransitionMetal CarbonylsCompound' vC0(cm-1)b fr(102Nm-1) Ref.CO 2143 18.6 [25]CO+ 2184 19.3 [25]HCO+ 2184 21.3 [26]W(CO)6 2126 17.2 [27]Cr(C0)6 2119 17.2 [27][Re(C0)6] + e(solv) 2197 18.1 [27]Cu(CO)Cld 2157 18.3 e[Cu(C0)]+[AsF6r 2180 19.2 [27][Ag(C0)][B(OTeF5)4] 2204 19.6 [7]Au(CO)Brf 2153 N/Ag [17][28]Au(CO)C1 2170 19.0 [21][22][29]Au(CO)S03F 2196 19.5 [15][Au(C0)2][UF6] 2200 N/A [16][Au(C0)2][Sb2F11] 2235.5 20.1 this workaSpectra taken of solids unless otherwise indicated. bThe average vi frequencz is given for M(C0)6 speciesand the average C-0 stretch is given for [Au(CO3)21+ species. eIn CH3CN. In argon matrix. eH.S. Plitt,Ph.D. thesis, U. of Munich, Germany (1991). 'In CH2C12. gnot available.The force constant for CO(g) gives the bond strength of the uncomplexed molecule,and serves as the baseline value. The order of C-0 bond strength in decreasing order isHCO±, [Au(C0)23[Sb2F1 ir, [Ag(C0)][B(OTeF5)4], [Au(C0)2][UF6], Au(CO)S03F,COP, [Cu(C0)][AsF6], and Au(CO)C1. The large value of the force constant for the C-0bond in [Au(C0)2][Sb2F11] indicates that CO behaves more like a a donor than a 7acceptor. This is consistent with the discussion in the general introduction regarding Au(I)63compounds, and their tendency for linear coordination using bonds with more a characterthan ir character.The order of anion basicity, based on the available C-0 force constants, is the sameas the order established from examining the C-0 stretching frequencies in the infrared,i.e. C1 < SO3F- < [Sb2F11].The gold carbonyl complexes differ from the copper and silver carbonyl derivativesin that the last two lose CO readily [6]-[8], while the gold carbonyl compounds are allthermally stable and easily isolated. Table 4-4 gives the melting points of various goldcarbonyl compounds.Table 4-4. Melting Points of Gold Carbonyl Derivatives.Compound^Melting Point (°C)^Ref.[Au(C0)2][UF6]^80°C^[16]Au(CO)C1^110°C-114°C^[13]Au(CO)S03F^49-50°Ca^[15][Au(C0)2][Sb2F1i]^130°C^this work'decomposes at 190°CWith the exception of Au(CO)C1, the melting points of the carbonyl derivativesincrease as the counterions become more weakly nucleophilic.Previously reported single crystal X-ray diffraction studies of the [Sb2F1i] ion in[H3F2][S132F1l] [30] and [BrF4][Sb2F1 i] [31] indicate that the anion has D 4h symmetry. Ifwe assume that the anion in [Au(C0)2][8b2F11] also has DA symmetry, the irreduciblerepresentation of the normal vibrations for [Sb2F11] isrya) = 4Aig(Ra) + Ai u + 4A2(IR) + 2131g(Ra) + Biu + Big(Ra) +2B2u + 4Eg(Ra) + 5Eu(IR).^(3)The data for [Sb2F1 ir are listed in Table 4-5.64Table 4-5. Vibrational Assignments of [Sb2F11] in [Au(C0)2}[Sb2F11) and itsIsotopomers[Au(C0)2][Sb2F1i]IR.^Raman[Au(13C0)2][Sb2F1 I]IR^Raman[Au(C180)2][Sb2F1i]IR^Raman Assignment713 714 713 Pas Sb-Fax A2u697 697 697 Ps Sb-Fax A ig689 689 689 Eu662 663 663 li Sb-F4eq A2u653 653 653 A ig598 599 598 Eg,Big503 503 502 v A2u307 307 308 13 Sb-Fax Eu293 293 293 A ig279 279 279 6 Sb-F4 Big267 266 266 A2u230 229 230 229 230 229 B2g,Eu131 131 131 E gThe vibrational band positions of [Sb2F111- in [Au(C0)2}[Sb2F1ii are consistentwith the mutual exclusion principle in that none of the infrared and Raman bands overlap.Some difficulty was encountered in the assignment of the bands, since inconsistencies werefound in the previously reported vibrational spectra of [XeF][Sb2F11] [32], Cs[Sb2F11}[33], and [C3F3][Sb2F11] [34], particularly regarding the assignment of vSb-F andvSb-F-Sb.4.3.2 13C NMR SpectraThe isotopic substitutions and acquisition of the 13C NMR data were carried out byProf. H. Willner, J. Schaebs, and M. Bodenbinder at the University of Hannover,Germany. Hence, only a quick summary of the results will be given.65The existence of [Au(C0)2]+(solv) was first postulated from vibrational dataobtained during the formation of Au(CO)S03F, and the following sequence of reactionswas proposed [15]:(i) reduction of Au(SO3F)3Au(SO3F)3 + CO —> Au+(solv) + CO2(g) + SO3F-(solv) + S205F2(1) (4)(ii) formation of [Au(C0)2]+(solv)Au+(solv) + 2C0 —> [Au(C0)2]+(solv)^(5)(iii) dissociation with CO loss[Au(C0)2]+(solv) —> [Au(C0)]+(solv) + CO(g)^(6)(iv) reaction with SO3F-(solv)[Au(C0)] + (solv) + S03F-(solv) —> Au(CO)S03F(s)^(7)The reduction of Au(SO3F)3 by CO in HSO3F was followed by 13C NMRspectroscopy in an attempt to identify intermediate species and to observe any exchangeprocesses that could occur. All chemical shift values quoted are relative to TMS.The 13C NMR spectra obtained of the solutions were very simple, with singletsbeing the only resonances observed at all times. Initially, 13C0 alone was bubbled througha sample of HSO3F and a 13C NMR spectrum recorded. A singlet at 184 ppm wasobserved, and attributed to small amounts of dissolved 13C0. It should be noted that thesolubility of CO in HSO3F is very low [15]. Next, a 13C NMR spectrum of a mixture of13C0 and S206F2 to in HSO3F gave a single resonance at 125 ppm which was attributed to13CO2. Both of the chemical shift values are consistent with previous reports of 4513C0and 613CO2 in aprotic solvents [17][28][35][36], and were unchanged even though amonoprotic solvent was used in these experiments.In the reduction of gold(III) chloride by carbon monoxide in thionyl chloride,phosgene was reported as one of the byproducts [37]. The expected analogue in thereduction of Au(SO3F)3 by 13C0 in HSO3F, 13C0(SO3F)2, is not observed in the 13CNMR spectrum. It seems that this molecule is unstable, and decomposes to give 13CO266and S205F2 [38]. The presence of both of these byproducts were confirmed by infraredspectroscopy in our study, and the amounts of these two gases was determined by PVmeasurements.During the reduction of Au(SO3F)3 by 13CO3 three singlets are initially observed:a large peak at 174 ppm, and two smaller peaks at 162 ppm and 125 ppm. At no time wasany coupling of the 13C nucleus to the 195Au nucleus observed. This is also in keepingwith previous reports for Au(CO)C1 [22][35]. No 13C0 was detected. 13CO2 isresponsible for the peak at 125 ppm. Reducing the volume of solution present in thereaction vessel by pumping in vacuo removed the 13CO2, which resulted in the gradualdisappearance of the resonance at 125 ppm. Continued pumping resulted in the 162 ppmpeak increasing in size and the 174 ppm peak decreasing. When all the solvent wasremoved, the white solid Au(13C0)S03F was obtained. Therefore the resonance at174 ppm, which was initially dominant, is attributed to [Au(C0)2]±, while the resonanceat 162 ppm, which becomes dominant at high solute concentration, can be attributed to[Au(13C0)]+. This is consistent with the proposed reaction scheme for the formation ofAu(CO)S03F (vide supra) [15].The preparation of [Au(C0)2][Sb2F1i] involved adding SbF5 to Au(CO)S03Funder a pressure of CO. The 13C NMR spectrum of the solution showed a peak at174 ppm. This was attributed to [Au(13C0)2]± earlier, and appears unchanged in thesample containing SbF5. Solid state magic angle spinning NMR spectroscopy of a sampleof [Au(13C0)2][Sb2F11](s) also exhibited a peak at 174 ppm, providing further evidencethat the resonance is due to [Au(13C0)2]+.Evidence for exchange processes taking place between [Au(13C0)]+ and[Au(13C0)2]+ was also found (Figure 4-1). Heating a sample of the solution containingboth the 174 ppm and 162 ppm signals to 52°C from the initial temperature of 17°Ccaused the peaks to broaden, followed by coalescence at 37°C to a single broad peak.67Continued warming to 52°C resulted in narrowing of the signal to a sharp peak at167 ppm.Figure 4-1. Variable Temperature 13C NMR Spectra of a Mixture of [Au(13C0)]+and [Au(13C0)2]+ in HSO3FA kinetic study of the CO exchange between the two complexes is currentlyunderway, which should provide some insight into the exchange mechanism.4.4 Conclusion [Au(C0)2][Sb2F1i] has been characterized by vibrational arid NMR spectroscopy.All of the fundamental vibrational frequencies of the cation were observed and assigned.68The conditions required to isolate unusual cations such as [Au(C0)]+ and[Au(CO)2] + have been determined: a very strong protonic acid (HSO3F) is used toproduce the cations and very weakly nucleophilic anions ([932F1i], [UF6]) are used tostabilize them. The solid [Au(C0)2][Sb2F11] is thermally stable to 130°C, and the highCO stretching frequency (ave. 2235.5 cm-1) indicates very little 7-back bonding. Itappears that the behaviour of this new gold carbonyl compound is best described as acoordination compound where the CO molecule acts as a ligand, and not as a 7-acceptor asis found in the classical transition metal carbonyls.References1. D. McIntosh and G.A. Ozin, k_lorg. Chem. (1977) 16, 51.2. Y. Souma and H. Sano, Nippon Kagalcu Zasshi (1970) 91, 625 (Chem. Abs. (1970)73, 94192w p 469).3. Y. Souma, H. Sano and J. Iyoda, J. Org . Chem. (1973) a, 2016.4. Y. Souma and H. Sano, Bull Chem. Soc. Jpn. (1973) 46, 3237.5. Y. Souma and H. Sano, J. Org . Chem. (1973) 20, 3633.6. Y. Souma, J. Iyoda and H. Sano, Inorg. Chem. (1976) 15, 968.7. P.K. Hurlburt, O.P. Anderson and S.H. Strauss, J. Am. Chem. Soc. (1991) 113,6277.8. P.K. Hurlburt, J.J. Rack, S.F. Dec, O.P. Anderson, and S.H. Strauss, Inorg. Chem. (1993) 32, 373.9. M.I. Bruce, J. Organomet. Chem. (1972) 44, 209.10. P.G. Jones, Z. Naturforsch. (1982) 37B, 823.11. M. Halcansson and S. Jagner,k_Pag- . Chem. (1990) 29, 5241.12. C.D. Desjardins, D.B. Edwards and J. Passmore, Can. J. Chem. (1979) 17, 2714.13. W. Manchot and H. Gall, Chem. Ber. (1925) 58B, 2175.14. M.S. Kharasch and H.S. Isbell, J. Am. Chem. Soc. (1930) 52, 2919.15. H. Willner and F. Aubke, Lorg. Chem. (1990) 29, 2195.16. E. Adelhelm, W. Bacher, E.G. HOhn and E. Jacob, Chem. Ber. (1991) 124, 1559.17. D. Belli Dell'Amico, F. Calderazzo, P. Robino and A. Serge, J. Chem. Soc. DaltonTrans. (1991) 3017.18. W.W. Wilson and F. Aubke, J. Fluorine Chem. (1979) 13, 431.19. R.J. Puddephatt, "The Chemistry of Gold", Elsevier: Amsterdam, Netherlands(1978).20. R.J. Puddephatt, in "Comprehensive Coordination Chemistry", G. Wilkinson, Ed.,Pergamon Press: Oxford, UK. (1987) Vol. 5, p 861, and references therein.21. F. Calderazzo, Pure Appl. Chem. (1978) 50, 49.697022. J. Browning, P.L. Goggin, R.J. Goodfellow, M.J. Norton, A.J.M. Rattray,B.F. Taylor, and J. Mink, J. Chem. Soc.. Dalton Trans. (1977) 2061.23. B.M. Chadwick and S.G. Franlciss, J. Mol. Struct. (1976) a, 1.24. L.H. Jones, Chem. Phys. (1957) 27, 468.25. G. Herzberg, "Spectra of Diatomic Molecules", 2nd. ed.; D. Van Nostrand: NewYork, NY (1950).26. E. Hirota and J. Endo J. Mol. Spectrosc. (1988) J27, 524.27. L.H. Jones, "Inorganic Vibrational Spectroscopy", Vol. 1, Marcel Dekker: NewYork, NY (1971).28. D. Belli Dell'Amico, F. Calderazzo, P. Robino and A. Serge, Gazz. Chim. Ital. (1991) 121, 51.29. D. Belli Dell'Amico, F. Calderazzo and G. Dell'Amico, Gazz. Chim. Ital. (1977)107, 101.30. D. Mootz and K. Bartmann, Angew. Chem. Mt. Ed. Engl. (1988) 27, 391.31. M.D. Lind and K.O. Christe, Inorg. Chem. (1972) 11, 608.32. R.J. Gillespie and B. Landa, Inorg. Chem. (1973) 12, 1383.33. B. Bonnet and G. Mascherpa, .ILL•ag. . Chem. (1980) 19, 785.34. N.C. Craig, G.F. Fleming and J. Pranata, J. Am. Chem. Soc. (1985) 107, 7324.35. H.O. Kalinowski, S. Berger and S. Braun, "13C NMR Spectroscopy",Wiley-Interscience: New York, NY (1988).36. R. Ettinger, P. Blume, A. Patterson, and P.C. Lauterbur, J. Chem. Phys. (1960) 33,1597.37. D. Belli Dell'Amico, F. Calderazzo and F. Marchetti, J. Chem. Soc.. Dalton Trans. (1976) 1829.38. M. Lustig, Dim. Chem. (1965) 4, 1828.71CHAPTER 5. CRYSTAL AND MOLECULAR STRUCTURE OF [Au(NCCH3)2][SbF6]Introduction There are a number of crystal structures reported for gold(I) complexes in reviewarticles [1][2]. All of these compounds have linear or nearly linear geometry around thegold center, as expected.The gold-carbon bond in [Au(C0)2][Sb2F1i] was postulated to be weak due togreatly reduced w-backbonding (vide supra). This suggests that a donor molecule shouldbe able to replace the CO ligands. The substitution reaction described here occurredaccidentally during an attempt to recrystallize [Au(C0)2][Sb2F1i] from acetonitrile.SynthesisUpon the addition of an excess dry CH3CN to -40-50 mg [Au(C0)21[Sb2F1i],immediate evolution of gas was observed; the gas was identified by infrared spectroscopyas carbon monoxide. White crystals suitable for single crystal X-ray diffraction wereproduced by slow solvent evaporation and were mounted into 0.5 mm o.d. quartz tubesand analyzed by Drs. R. Jones and J. Trotter of this Department. The composition of thewhite solid was confirmed by microanalysis.C H NAnal. calc. for C4H6N2F6SbAu 9.33 1.17 5.43found 9.40 1.19 5.37The crystal data are summarized in Table 5-1.72Table 5-1. Selected Crystallographic Data For [Au(NCCH3)21[SbF6]FormulaFormula wtCrystal SystemSpace GroupC4H6N2F6AuSb514.81cubicPO (No. 205)a (A) 10.250(2)V (A) 1076.9(3)Z 4T (K) 294Pc(gem-3) 3.17X (A) 0.71069it(Mo Ka)cm1 1614Transmission Factors 0.40-1.00R 0.023Rw 0.024Number of independentmeasured reflections 527Reflections with I _.^3a(I) 147No. of parameters refined 25735.3 Results and Discussion Single crystals of [Au(NCCH3)2][SbF6] were obtained from the reaction of[Au(C0)2][Sb2F1l] with acetonitrile. Sulfur dioxide was initially used as the donorsolvent, but bis(carbonyl)gold(I) undecafluorodiantimonate was too soluble. A mixture ofSO2 and SO2FC1 appeared to be a suitable mixed solvent system, but single crystals of[Au(C0)2][Sb2F1i] have not yet been obtained.The use of a donor solvent such as acetonitrile successfully displaced the carbonmonoxide groups according to[Au(C0)2][Sb2F1 1] + 2 CH3CN --> [Au(NCCH3)2][SbF6] + 2 CO + SbF5^(1)Antimony pentafluoride has been reported to form SbF5.NCCH3 with acetonitrile,but in the presence of excess solvent the adduct is soluble [3] and was not isolated by us.The ease with which CO is displaced by CH3CN suggests further use of[Au(C0)2][Sb2F1l] in the synthesis of other cationic gold(I) complexes. The[Au(NCCH3)2]+ cation has been reported previously [4] as the SbC16- salt and has beencharacterized by infrared spectroscopy of [Au(NCCH3)2][SbC16] [5]. The solvated[Au(NCCH3)2]+ cation is also easily obtained by anodic oxidation of gold inacetonitrile [6][7], and its standard reduction potential is known [8].[Au(NCCH3)2][SbF6] forms clear and colourless cubic crystals that belong to thespace group PO (205). An ORTEP diagram, along with the packing, are shown inFigures 5-1 and 5-2.••^. •alb* • aaa^fibFigure 5-1. An ORTEP Diagram Showing the Atom Positions in [Au(NCCH3)2][SbF6].74Figure 5-2. Stereoview and Packing in fAu(NCCH3)2][SbF6]75In a cubic crystal, the sides of the unit cell are equal in length, and the cell axes areorthogonal. The gold and antimony atoms were found to be pseudo-body-centered withrespect to each other. The cation [Au(NCCH3)2]+ lies along the space diagonal of thecube that forms the unit cell; a three-fold symmetry axis is present along this line. Thetwo methyl groups are in a staggered conformation, and the overall symmetry of the cationis D3d. The N-Au-N bond angles are exactly 180.00. Since the carbon atom of thecyanide group is sp hybridized, the C-C EN moiety must also be linear. The terminalcarbon is sp3 hybridized and the hydrogens surrounding it form a tetrahedron. The bondangles, intramolecular distances, and interionic distances are given in Table 5-2.Table 5-2. Bond Lengths (A), Angles(°), and Interionic Distances (A) with EstimatedStandard Deviations for [Au(NCCH3)2][SbF6]Bond Lengths Bond Angles Interionic DistancesaAu N 1.97(1) N Au N'^180.0 Au F 3.455(5)Sb F 1.841(5) Au N C(1)180.0 Au H 3.51N C(1) 1.08(1) N C(1) C(2)180.0 F H 2.42C(1) C(2) 1.47(2) F Sb F'^180.0 F H 3.04F Sb F"^89.2(2) F C(1) 3.179(7)F Sb F" 90.8(2) F C(2) 3.122(7)F N 3.181(6)F H 3.46F C(1) 3.52(1)F H 3.56N H 3.53'Contacts out to 3.60 angstroms. Estimated standard deviations in the least significantfigure are given in parentheses.76The perfect linearity of the N::--- C-C bond angle is unusual in that while it isexpected theoretically, the same moiety in other transition metal complexes, e.g. cis- andtrans-OsBr2(NCCH3)(C0)(PPh3)2, have N:=-C-C bond angles of 178(2)° and 179(3)°respectively [9].Of the complexes containing nitrogen atoms bound to gold atoms, the Au-N bondlengths vary from 2.018(22) to 2.097(38) A [2][10]. These bond lengths are somewhatlonger than the 1.97(1) A found for [Au(NCCH3)2]+. An exception is the sodiumbis(N-methylhydantoinato)gold(I) tetrahydrate, [(MeN.CO.N.CO.CH2)2Au]Na+.4H20,where a bond length of 1.94 ii(ave) is found for Au-N [11]. Unfortunately, the light atompositions are usually of limited accuracy, so the Au-N bond lengths reported often havelarge estimated standard deviations (esd's) [2].Another feature that has been reported in linear Au-N containing complexes is shortAu.. .Au contacts, i.e. an intramolecular Au-Au distance of less than ca. 3.5 A [2]. Theshortest distance between two gold atoms in [Au(NCCH3)2][SbF6] is 7.247 A (aNi2).The C-N bond length in uncoordinated acetonitrile is 1.1571 A [12]; this is slightlylonger than the value of 1.08(1) A found for [Au(NCCH3)2]+. There appears to be little7-back donation, since this would cause lengthening of the C-N bond distance to greaterthan 1.1571 A.The hexafluoroantimonate(V) anion, SbF6-, is a regular octahedron with bondangles of 90° within experimental error. Alkali metal hexafluoroantimonates are allreported to contain octahedral SbF6- [13][14][15], although the space group may not becubic (e.g. LiSbF6 is rhombohedral [13]). The Sb-F bond distance in LiSbF6 is, at1.877(6) A, slightly longer than the 1.841(5) A reported here. The SbF6- anion may befound in a site of lower than Oh symmetry when it is paired with transition metal complexcations in compounds such as [Ni(CH3CN)6](SbF6)2 [16] and [Ni(CD3CN)6](SbF6)2 [17].In the latter case, the anion has C3 symmetry and Sb-F bond distances of 1.80(1) and771.83(1) A. In the former, the anion has bond lengths of 1.825(4) and 1.827(4) A and C3symmetry as well. It is postulated that the distortion is due to site symmetry effects.ConclusionThe weak gold-carbon bond, indicated in the high CO stretching frequency, and theproposed reduction in w-backbonding, allows the CO ligand to be easily replaced byacetonitrile, a stronger nucleophile. It can be seen from the molecular structure, withN-Au-N bonds that are exactly 180.00, that the gold(I) center prefers linear coordination.The short C-N distances suggest reduced w-backbonding. In addition, the a donor orbitalon the nitrogen atom of acetonitrile appears to be slightly antibonding, resulting in astronger C-N bond upon coordination of the N atom to the gold center; this phenomenon iscommonly observed in the vibrational spectra of acetonitrile complexes [11]. The SbF6-anion has regular octahedral geometry.References1. M. Melnik, Coord. Chem. Rev. (1986) 70, 157.2. P.G. Jones, Gold. Bull. (1981) 14, 102; P.G. Jones, ibid. , (1981) 14, 159; P.G.Jones, ibid. , (1983) 16, 114; P.G. Jones, ibid. , (1986) 19, 46.3. L. Kolditz and W.Z. Rehalc, Z. Anorg. Allg. Chem. (1966) 342, 32.4. A.P Zuur and W.P Groeneveld, Reel. Tray. Chim. Pays-Bas (1967) M., 1089.5. J. Reedijk, A.P. Zuur and W.L. Groeneveld, Reel. Tray. Chim. Pays-Bas (1967) 86,1127.6. R.J. Puddephatt, "The Chemistry of Gold", Elsevier:Amsterdam, Netherlands (1978).7. R.J. Puddephatt, in "Comprehensive Coordination Chemistry", Vol. 5, G. Wilkinson,Ed., Pergamon : Oxford, UK (1987) p 861.8. P.R. Johnson, J.M. Prattand and R.J. Tilley, J. Chem. Soc., Chem. Comm. (1978)606.9. P.D. Robinson, I.A. Ali and C.C. Hinckley, Acta Cryst. (1991) C47, 1397.10. J.J. Guy, P.G. Jones, M.J. Mays and G.M. Sheldrick, J. Chem. Soc., Dalton Trans. (1977), 8.11. N.A. Malik, P.J. Sadler, S. Neidle and G.L. Taylor, J. Chem. Soc., Chem. Comm. (1978) 711.12. C.C. Costain, J. Chem. Phys. (1958) 29, 864.13. J.H. Burns, Acta Cryst. (1962) 15, 1098.14. N. Schrewelius, Z. Anorg. Chem. (1938) 238, 241.15. H. Bode and E. Voss, Z. Anorg. Chem. (1951), 264, 144.16. I. Legan, D. Gantar, B. Frlec, D.R. Russell and J.H. Holloway, Acta Cryst. (1987),C43, 1888.17. R. Bougon, P. Charpin, K.O. Christe, J. Isabey, M. Lance, M. Nierlich, J. Vignerand W.W. Wilson, Inorg. Chem. (1988) 27, 1389.7879CHAPTER 6. SYNTHESES AND CHARACTERIZATIONS OF [Pt(C0)4][Pt(SO3F)6],Pt(C0)2(SO3F)2, AND [Pt(C0)4][Sb2F11126.1 Introduction Nickel tetracarbonyl was first prepared in 1890 from nickel metal and carbonmonoxide, and is the first binary carbonyl reported [1]. Its formation and thermolysis is animportant part of the Mond process, which is used to purify nickel. The thermally unstableplatinum and palladium congeners were not prepared until much later, and could only bestudied by co-condensation of the metal atoms with CO in an inert matrix between 4 and10K [2][3]. A study of the neutral binary carbonyls of the group 10 elements using matrixisolation techniques was reported by Kiindig et al. [4], and the physical and chemicalproperties of M(CO)n (M = Pd, Ni, Pt; n = 1-4) were compared. The thermal instabilityof Pt(C0)4, the reported tetrahedral geometry, and the observed C-0 stretchingfrequencies (co 2078 cm-1(IR); A pc0=2049 cm-1(Ra,dp)) [4], differ substantiallyfrom the data obtained for the platinum carbonyl compounds reported in this thesis.The continued interest in platinum and palladium carbonyl complexes is due to theirpotential use as carbonylation catalysts in the formation of acid chlorides and esters [6].Platinum carbonyl complexes are many and varied [5][6]. Our interest lies with theplatinum carbonyl halides. The first metal carbonyl complexes ever made were a series ofplatinum carbonyl chlorides, obtained by Schiitzenberger in 1870 [7]. He isolated threeinterconvertible products by sublimation: two yellow, flaky compounds analyzed asPt(CO)C12 (mp 192°C), Pt2(C0)3C14 (mp 130°C), and white needles, found to bePt(C0)2C12 (mp 142°C). Schiitzenberger also reported the facile reactions of the platinumcarbonyl chlorides with ammonia, ethylene, and phosphorus chlorides [8][9].The bromo and iodo carbonyl halides, Pt(CO)Br2 and Pt(CO)I2, were reported byMylius and Foerster some twenty years later [10][11]. The analogues were prepared by80dissolving Pt(CO)C12 in HX (X =Br, I), followed by re-crystallisation from benzene. Asimilar approach has been used by Calderazzo [12] to synthesize Pt(C0)2X2 (X=Br, I).These methods of preparing platinum carbonyl halides require forcing conditions, i.e.carbon monoxide pressures up to 210 atmospheres and temperatures exceeding100°C [6][12]. However, under these conditions the monomeric carbonyl halides lose COand form dinuclear complexes with halide bridges [13]. It has been reported thatcis-Pt(C0)2C12 will not undergo this conversion if thionyl chloride is used as solvent. Thefluoride analogues, Pt(CO)F2, have yet to be discovered.Most platinum carbonyl complexes have the metal in the +2 oxidation state [13].These complexes are usually neutral, e.g. Pt(CO)X2 (X=C1, Br, I), or anionic, e.g.[Pt(CO)X3]- (X =C1, Br, I) [5][13]. There are no reports of binary, square planar, cationicplatinum carbonyls. Platinum carbonyl derivatives are also known where the metal is inthe +1 (eg. (Prn4N)2[Pt2(C0)2C14]) [14] or +4 (eg. [Pt(CO)C15]-) oxidation state, butthese are quite rare [5][13].The majority of the C-0 stretching frequencies of these platinum carbonyl halideslie above the value of free gaseous carbon monoxide (2143 cm-1), with the exception of[Pt(CO)12]2 (see Table 6-1).Table 6-1. Average C-0 Stretching Frequencies of Some Platinum Carbonyl Halides.Compound^PCO (cm-1)^Ref.Pt(C0)2C12^2168-2180 cm-1 a^[15]Pt(C0)2Br2^2164 cm-1 (benzene)^[16][Pt(CO)I2]2^2112 cm4^[17]asolvent dependent81The high C-0 stretching frequencies are reportedly caused by reduced 7-backbonding andthe slightly antibonding nature of the 5cr orbital used in a donation to platinum [15].Since Au(503F)3 in HSO3F was so easily reduced by CO, it was decided to extendthis approach to the Pt(SO3F)4/HSO3F system to see if analogous platinum carbonylcomplexes could be synthesized. If the analogy holds true, the new platinum carbonylcomplexes should be easily prepared under mild conditions. The [Pt(C0)4]2+ cation,analogous to [Au(CO)21 +, should be obtainable and isolable, either in solution or as thefluoroantimonate(V) salt. The C-0 stretching frequency of any platinum carbonyl complexobtained in this manner should be well above 2143 cm-1.6.2 Syntheses6.2.1 Pt(CO)2Q33Platinum tetrakis(fluorosulfate), Pt(SO3F)4 (0.612 mg, 1.04 mmol), was made bythe oxidation of platinum metal by S206F2 in HSO3F as described by Lee and Aubke [18].A known amount of carbon monoxide (0.508 atm., 4.60 mmol) was introduced into the100 mL round-bottom flask containing red-brown Pt(SO3F)4 , and the mixture wasmagnetically stirred at room temperature. After 48 hours a bright yellow solid hadformed, and the solution was lighter in colour (pale orange). The volatiles at -196°C,-78°C, and room temperature were measured, removed and identified by infraredspectroscopy as CO (excess), CO2, and S205F2, respectively. More CO was added to themixture, and stirring of the mixture continued at room temperature. The addition wasrepeated until no more CO was taken up, the mixture consisted of a bright yellow solid in aclear yellow solution, and no more solid appeared to be formed. In each case all volatileswere measured and removed before any more CO was added. Total CO uptake was2.75 mmol, and the mole ratio of Pt:CO was calculated to be 1:2.64 (or approximately2:5). The product was isolated by vacuum filtration in approximately 80% yield, and was82identified by microanalysis as Pt(C0)2(SO3F)3. It is slightly soluble in HSO3F, and meltsat 140°C with decomposition and evolution of gas.PtAnal. calc. for C2011F3S3Pt 4.38 17.48 10.39 35.58found 4.60 18.00 9.7 35.166.2.2 Pt(C0)2(SO3F12Pt(C0)2(SO3F)2 was prepared by reacting 0.516 atm CO with Pt(S0394(0.621 mg, 1.05 mmol) in HSO3F in a 50 mL round-bottom flask. The mixture wasstirred and heated at 80°C overnight. The colour of the solution was initially red-brown.A mixture consisting of a yellow solid and an orange solution was observed. Withcontinued heating, the yellow solid gradually disappeared and the solution became clearand colourless. Excess HSO3F was removed by slow pumping in vacuo, leaving a waxy,ivory, hygroscopic solid. Cooling to 0°C was necessary to prevent bumping. The COuptake and all volatiles were measured and identified as before. The total CO uptake was3.32 mmol. The Pt:CO ratio from gas volumetric measurements was 1:3.16.Microanalysis gave the empirical formula of the white solid as Pt(CO)2(S0392-^C^SAnal. calc. for C208F2S2Pt^5.34^14.27found^5.41^14.17Pt(C0)2(SO3F)2 melts at 100°C to a translucent, creamy liquid.6.2.3 [Pt(C0)4)ISb2E1112A sample of solid Pt(C0)2(SO3F)2 (0.690 mg, 1.54 mmol) was weighed into around bottom flask. Excess SbF5 was added by vacuum distillation. Warming to 80°C wasnecessary to facilitate stirring the SbF5. Only one liquid phase was observed at all times.Pt(C0)2(SO3F)2 slowly dissolved in SbF5. Carbon monoxide was admitted into the83reactor and a white solid formed immediately at the surface of the liquid. Rapid COuptake was observed at room temperature; once the uptake slowed, the reactor waspressurized with a known amount of CO, then sealed and the mixture left stirring overnightat 80°C to ensure a complete reaction. The reaction was considered complete when nomore CO was taken up; this was established by pressure measurements. Total CO uptakewas 3.46 mmol, or 2.24 moles of CO per mole of Pt(C0)2(SO3F)2.Alternatively, the SbF5 addition can be carried outwhile the Pt(C0)2(SO3F)2 is stillin HSO3F solution. In this case, excess SbF5 was added by condensation in vacuo,followed by CO. Two phases were initially visible; the viscous SbF5 at the bottom, andthe HSO3F on top. Stirring at room temperature combined the two layers. A white solidformed immediately upon contact with the gas. A known pressure of CO was left in thereactor overnight to ensure complete reaction. The reaction was assumed complete whenthere was no more CO uptake at room temperature. There were no measureable volatilesat any temperature (-196°C, -78°C, room temperature), apart from unreacted CO.If the reaction was carried out solely in SbF5, the excess solvent can be removed bypumping at room temperature. If the reaction was carried out in HSO3F/SbF5, the reactormust be cooled to -0°C before pumping, or the mixture will bump. Conversion ofPt(C0)2(SO3F)2 to [Pt(C0)4][Sb2F11}2 was quantitative (calculated mw: 1227.4 g.mol1vs. expected mw: 1212.09 g.mo1-1). [Pt(C0)4][Sb2F11J2 melts with decomposition to abrown liquid at 200°C.C^FAnal. calc. for C404F22Sb4Pt^3.96^34.48found^4.33, 4.05^31.91, 35.63.72 (Beller)N.B.: The carbon analyses were carried out by Mr. P. Borda of this department. Fluorineanalyses (and one C analysis) were carried out by Beller Laboratories, Gottingen,84Germany. Here, as in the case of [Au(C0)2][Sb2F11], satisfactory elemental analysis foreither Pt or Sb could not be obtained due to interference between the two metals.6.3 Results and Discussion6.3.1 Pt(C0)2(S03E13Reduction of Pt(SO3F)4 in HSO3F by CO is achieved under the same conditions asthose used in the preparation of Au(CO)S03F [19] (room temperature, ca. 2 atm CO, 8 h).However, the yellow product obtained was not analogous to Au(CO)S03F. Monitoring theCO uptake indicated that ca. five moles of CO were required for two moles of Pt(SO3F)4.Following the reaction by weight was not possible due to the method of isolation (byfiltration) and the slight solubility of the yellow solid in HSO3F. The empirical formula ofthe precipitate was found to be Pt(C0)2(SO3F)3 from microanalysis, and the reaction maybe formulated as2 Pt(SO3F)4 + 5 CO —> 2 Pt(C0)2(SO3F)3 + CO2 + S205F2 (1)even though a product of the type Pt(C0)2X3 (X = anionic ligand) isunprecedented [5][6][13].The formation of phosgene, COC12, is one of the by-products in the reduction ofAu(III) or Pt(IV) halides by carbon monoxide [20], and the fluorosulfate analogue,CO(SO3F)2, is expected to be produced. However, only CO2 and S205F2 are observed,and it has been postulated that CO(SO3F)2 is unstable and decomposes [21] according toCO(SO3F)2 -+ CO2 ± S205F2^(2)These byproducts were also found for the preparation of Pt(C0)2(SO3F)2 and identified byinfrared spectroscopy.85It is noted that the mole ratio of Pt:CO is slightly higher than expected. This mayarise from the presence of residual S206F2 in the HSO3F solution from the preparation ofPt(SO3F)4, which will oxidize CO to CO2 according toS206F2 + CO --> CO2 + S205F2^(3)Another reason for the discrepancy between the expected and observed mole ratios may beslight inaccuracies in the determination of the vacuum line volume.The yellow solid behaves differently from Au(CO)S03F. Pt(C0)2(SO3F)3 cannotbe sublimed and is moderately soluble in HSO3F, while Au(CO)S03F is purified bysublimation and is completely soluble in HSO3F. Unlike Pt(C0)2X2 (X =C1, Br, I) [12],CO is not released upon heating Pt(C0)2(SO3F)3; the solid merely decomposes. Thedecomposition products are identified by infrared spectroscopy as SiF4 and S02F2.Pt(C0)2(SO3F)3 appears to be an intermediate in the reductive carbonylation ofPt(SO3F)4 to Pt(C0)2(SO3F)2, which is analogous to Au(CO)S03F. In the gold system,Au(SO3F)3 is completely reduced to [Au(CO)2] + (which was detected in situ and laterisolated), and solvent removal effected the loss of one mole of CO out of the three molesthat were initially taken up [19]. The platinum system appears less easily reduced, andslightly more forcing conditions are needed for a complete reduction (vide infra). Fromthese qualitative observations, it seems that gold is more readily oxidized by S206F2 thanplatinum, and gold(III) is more readily reduced than platinum(IV). Table 6-2 lists theredox potentials [22] of the four metals that are implicated in the formation of non-classicalmetal carbonyl complexes.86Table 6-2. Redox Potentials of Selected Metals in Aqueous Acid*Metal E0 (Volts)Ag(II)/Ag(I) 1.98Pd(IV)/Pd(II) 1.60Au(III)/Au(I) 1.40Pt(IV)/Pt(II) 1.10*Standard aqueous acid, aH+ = 1.0It can be seen that the oxidizing ability of the metals decreases in the orderAg(II) > Pd(IV) > Au(III) > Pt(IV). This is consistent with the relative reaction rates ofthe reductive carbonylation of palladium [23], gold [19], and platinum in HSO3F, all ofwhich produce thermally stable products. The reaction of palladium(IV) fluorosulfate withCO is complete within one hour at room temperature [23]. The same reaction withgold(III) fluorosulfate takes ca. ten hours at room temperature [19], and the platinum(IV)fluorosulfate reaction with CO requires forcing conditions in order to effect a completereduction of Pt(IV) to Pt(II).Pt(C0)2(SO3F)3 is diamagnetic and does not give rise to an ESR signal. This wasunusual, since Pt(III) should be paramagnetic (d7). This leads us to the possibility of amixed valency Pt(II)-Pt(IV) complex, of the form [Pt(C0)4][Pt(SO3F)6]. The formationof [Pt(C0)4][Pt(SO3F)6] in the reductive carbonylation of Pt(SO3F)4 may be viewed in thefollowing stepwise fashion in analogy to the reduction of Au(SO3F)3 by CO (videsupra) [19]:(i) reduction of Pt(SO3F)4Pt(SO3F)4(solv) + CO —> Pt2+(solv) + 2 S03F- + CO2 + S205F2^(4)(ii) stabilization of transient Pt2+(solv) by complex formationPt2+(solv) + 4 CO —> [Pt(C0)4]2+^(5)87(iii) complex anion formation with unreacted Pt(SO3F)4 [18]Pt(SO3F)4 + 2 SO3F- —0 [Pt(SO3F)612-^(6)(iv) salt formation[Pt(C0)4]21- + [Pt(SO3F)6]2- —0 [Pt(C0)4][Pt(SO3F)6] (7).The above equations only rationalize a possible pathway to the formation of[Pt(C0)4][Pt(SO3F)6], and detailed 13C NMR studies are needed in order tounambiguously identify any intermediates.The colour of [Pt(C0)4][Pt(SO3F)6] (yellow) and its partial solubility in HSO3Fallows uv-visible and two conductivity measurements. The uv-visible spectrum of anextremely dilute solution shows broad peaks at Xmax =256 nm and 300 nm. Electronicspectra of Pt(SO3F)4 and Cs2[Pt(SO3F)6] in HSO3F both have peaks at Xmax =245 nm[18]. The peak at 256 nm can be attributed to the [Pt(SO3F)6]2- anion. The shift of thispeak from 245 cm-1 may be due to the presence of the [Pt(C0)4]2+ cation. The 300 nmpeak may be tentatively attributed to [Pt(C0)4]2+. A uv-visible spectrum of HSO3Fshows a band below 200 cm*The observed change in conductivity of [Pt(C0)4][Pt(SO3F)6] in HSO3F was verysmall (ca. 1.6x10-3 111em-1). It is inconclusive from conductivity measurements alonewhether the compound produces ions upon dissociation.The anion, [Pt(SO3F)6]2-, is an extremely weak nucleophile (the weakest after[SbF6]- and [Sb2F1d-) based on 119Sn M8ssbauer spectra of various (CH3)2Sn2-1- salts[24], and it is not entirely surprising, after the discussion of gold carbonyl cations, that theanion can stabilize the very electrophilic [Pt(C0)4]2+ cation. Formation of[Pt(C0)4][Pt(SO3F)61 as a slightly soluble salt in HSO3F is also favoured by the highlattice energy generated by two doubly charged ions. The cation was identified byvibrational and 13C NMR spectroscopy. The anion was also identified by vibrationalspectroscopy and by 19F NMR spectroscopy.886.3.1a Vibrational SpectraThe assignment of bands due to the cation in the vibrational spectra of[Pt(C0)4][Pt(SO3F)6] was based upon the assignments for [Pt(CN)4]2- [25][26], and anionassignments were based on those for the Ba2+ and C102+ salts of [Pt(SO3F)6]2- [18]. Thevibrational data are shown in Table 6-3.Identification of the cation was somewhat problematic. [Pt(C0)4]2+ is the firstdoubly charged carbonyl cation reported. The only known carbonyl cations to date areoctahedral [M(C0)6]+ (M = Mn, Tc, Re) [27] and linear [M(C0)2]-/- (M = Ag [28], Au)(vide supra). Since there are no known square planar binary carbonyl cations, no data wasavailable for comparison. However, the isoelectronic, square planar [Pt(CN)4]2- anion isknown and has been studied by infrared spectroscopy [29].Infrared and Raman bands do not coincide, suggesting that the [Pt(C0)4] 2+ cation has acenter of symmetry. As expected, the C-0 stretching frequencies of [Pt(C0)4][Pt(SO3F)6]are quite high, and are easily identified at 2235 cm-I and 2231 cm-I in the infrared, and2281 cm-1 and 2257 cm-I in the Raman. The degenerate Eu mode in the infrared spectrumis slightly split into 2235 cm-1 and 2231 cm-1 peaks, observable only at high resolution(ca. 1 cm-1). The average C-0 stretching frequency of [Pt(C0)4][Pt(SO3F)6] is2251 cm-I, and is higher than PCO for the gold species [Au(C0)2][Sb2F11], which hasvav.CO at 2235.5 cm-1.89Table 6-3. Vibrational Data for [Pt(C0)4][Pt(SO3F)6], Ba[PtS03F)6], and(C102)2[Pt(SO3F)6][Pt(C0)4][Pt(SO3F)6]^Ba[Pt(S0396]^(C102)2[Pt(SO3F)61') Approx.Infrared^Raman Raman^InfraredAP(cm - I),int.^Av(cm4),int.^v(cm-1),int.Assignment2281 vs 1 v CO(Aid2257 s f v CO(Big)2235 ms 12231 m,sh f^ v 12C0(Eu)2190 vw, b V13 CO(E)1395 vs^1402s^1397 vw^1415 vs 1^vas SO21385 s,sh^1391 s,sh 1386 m 1378 s, sh f1230 m,sh^1252 vs^1258 vs^1245 m,sh 11200 vs^1216s 1218m 1215 vs, f^vsym SO21190 s,sh 1192 s,sh966 vs^-1050 w^1033 mv^v SO...Pt928 s,sh^1006,1025w^1012w^ss835 ms^854 m^857 w815 s,sh^812 w 838 vwv S-F805 vs 801 m E5 v5 s,ssh }660 m m t-0 +650 m,sh^633 vs^629 vs^22  }^P P6 SO3F595 ms^580 wv^583 vw^587 s 1560 m -555 vw 549 vw 546 s f^6 SO3530m v Pt-C (?)489 m468 w,sh^460 vw,sh^460 m^452 m,sh^viLyt-O+def446 s420 vw^422 vw411w^ pS03F277 vs^283 vs vPt-0 +269 vs '6S03F188 m131 s^ opt-COa)Ref. 18; b)Ref. 18; C102+ bands at 1298, 1285, 1045 and 517 cm-1 are omitted.90Other bands that may arise from the cation (eg. Pt-C stretches) cannot beunambiguously identified, although the two bands at 530 cm-1 and 489 cm"1 have beententatively assigned as Pt-C stretches in comparison to [Pt(CN)4] 2-, where vPt-C isobserved at 505 cm-1 and calculated to appear at 519 cm-1 [29].Identification of the anion was carried out via vibrational spectroscopy. There is athree-peak pattern characteristic of the [Pt(SO3F)6]2- anion in the Raman spectrum. Amoderately strong peak at ca. 630 cm-1, a weak peak at 450 cm"1 and another moderatelystrong peak at 280 cm-1 can be seen from Table 6-3. These bands correspond in part to thesymmetrical Pt-06 stretch, the asymmetrical Pt-06 stretch, and the symmetric Pt-06deformation mode, respectively. These vibrations are shown in Figure 6-1.00, IPt0400 I 0 -Pt- A,-I 00Figure 6-1. Selected Normal Vibrations of [Pt(S0396]2-The S-F stretch for [Pt(SO3F)6}2- appears at ca. 800 cm-1 and is slightly split, butstill in good agreement with the value found for ionic Ba[Pt(SO3F)6] and(C102)2[Pt(SO3F)6] [18], suggesting that [Pt(C0)4][Pt(S03F)6] may have some ioniccharacter.6.3.1b 19F and 13C NMR SpectraThe 19F NMR spectrum of [Pt(C0)4][Pt(SO3F)6] in HSO3F exhibited a resonanceat 47.4 ppm, which compares very well to the 19F NMR spectrum of Cs2[Pt(SO3F)6],which had a peak at 47.75 ppm [18]. A second, very intense peak found in the spectrumof [Pt(C0)4][Pt(SO3F)6] at 40.3 ppm was attributed to HSO3F. Lee reported the HSO3F91resonance at 40.77 ppm for a sample of Cs2[Pt(SO3F)6] in HSO3F [18]. In the 13C NMRspectrum, the isotopically labelled [Pt(13C0)4][P4S03F)6] gives a peak at 140.5 ppm.Two satellite bands are also observed, and are attributed to 13C-195Pt coupling. The13C-195R coupling constant was found to be 1576+2 Hz. Table 6-4 gives the NMRparameters for [Pt(C0)4liPt(SO3F)6] and some similar compounds.Table 6-4. NMR Parameters for Some Platinum Carbonyl ComplexesCompound a(13C)(ppm) J(13c-195p0(Hz) Solvent Ref.[Pt(C0)4](POS 03F)6] 140.5 1576+2 HSO3F This workPt(C0)2C12 151.6 1576 C6D6 [16]Pt(C0)2Br2 152.0 1566 C6D6 [16]The coupling constant for [Pt(C0)4]iPt(SO3F)6] compares very well to those for thechloride and bromide compounds, but the chemical shift is further upfield by 10-11 ppm.This may be due to the different solvents in which the compounds were dissolved.Shortening of the C-0 bond due to reduced w-backbonding may also cause the chemicalshift to move further upfield.6.3.2 Pt(C0)2(S03E12The partial reduction of Pt(SO3F)4 in HSO3F by CO was carried out at roomtemperature and -2 atmospheres of pressure. If the reaction temperature is increased to80°C, the initial red-brown mixture first forms a yellow solid and an orange liquid.Further heating results in a clear, colourless solution. Removal of the solvent in vacuoleaves a waxy white solid. The empirical formula of this solid was determined bymicroanalysis to be Pt(C0)2(SO3F)2. It melted at 100°C, with no evidence of CO loss (nogas evolution was observed). The CO uptake was monitored by pressure measurements,and the equation for the reaction can be written as92Pt(SO3F)4 + 3 CO --). Pt(C0)2(SO3F)2 + CO2 + S205F2^(8)The mole ratio of Pt:CO for this reaction is calculated to be 1:3.16. Again, themole ratio of Pt:CO is slightly higher than expected, and the presence of residual S206F2in Pt(SO3F)4 described earlier may account for this discrepancy (vide supra).Pt(C0)2(SO3F)2 was characterized by vibrational spectroscopy. The byproducts CO2 andS205F2 were obtained, as expected, and also identified by vibrational spectroscopy.6.3.2a Vibrational SpectraThe infrared and Raman data for Pt(C0)2(SO3F)2 and Pd(C0)2(SO3F)2 [23] arelisted in Table 6-5.The CO stretches are easily identified. From their positions, the ligands appear tobe terminally bound. Like [Pt(CO)4][Pt(SO3F)6], the Pt-C stretches and CO deformationmodes are obscured by SO3F vibrations. Two intense C-0 vibrations in the infraredspectrum and one in the Raman spectrum of solid Pt(C0)2(SO3F)2 suggest that thecomplex has the cis configuration. Overlapping infrared and Raman bands also indicate anon centrosymmetric molecule, which is consistent with cis-Pt(C0)2(SO3F)2. Furthersupport for our assignment of the vibrational spectra as being due to cis-Pt(C0)2(SO3F)2comes from the nearly superimposable vibrational spectra obtained forcis-Pd(C0)2(SO3F)2, which was recently made in our research group. The structure ofcis-Pd(C0)2(SO3F)2 was subsequently confirmed by X-ray crystallography(Figure 6-2) [23].The absence of vibrational bands in the 1100-1200 cm-1 region indicates that thereare no bridging bidentate fluorosulfate groups. The fluorosulfate bands in the terminalregion (1400-1250 cm-1) are complex, possibly due to vibrational coupling. The S-Fstretching bands, found around 800 cm-I are consistent with ionic SO3F, and imply that theOSO2F groups in cis-Pt(C0)2(SO3F)2 may be polar. A solution infrared spectrum ofcis-Pt(C0)2(SO3F)2 in HSO3F shows PCO shifting to higher frequency. The C-093stretching frequncies are now found at 2224 and 2219 cm-1. This shift may be due topartial ionization of Pt(C0)2(SO3F)2 in HSO3F.Table 6-5. Vibrational Data for Pt(C0)2(SO3F)2 and Pd(C0)2(SO3F)2Pt(C0)2(SO3F)2IR, in ^Raman, inPd(C0)2(SO3F)2IR, int.^Raman, int.2219s 2219vs 2228ms 2228vs^t2191w 2212w,sh f2185vs 2181mw 2208s 2207ms2145vw 2166w,sh1397s 1395s1389s,sh 1380s 1382s^t1378vs 1376m 1360s 1358ms 11362w,sh1230m,sh 1229s,sh1209vs 1212s 1206vs 1208s)1034m,sh 1038s 1031vs t1026s 1019s 1019vs 1003s^j1009vs 993m 935vw799s 815w792w794vsr8tniw }657ms 656s 648s 649vs648m,sh 638m,sh589s,sh 588mw 586vs 586m584s 580m 579m557ms 565w 559m551s 554w 554s 552mw476ms 475w,sh 514ms472ms436w 462ms 440ms 455mw411vw 412w 417vw 405wTentative Assignmentvsy. 12a)vI) 13C0vas SO2vsym SO2v S-0...Ptv SFv Pt-0, 6 SO26S03OPt-CO (?)vPt-0, 6 SO3pS03FFigure 6-2. Molecular Structure of Pd(C0)2(SO3P)2 [23]95The average CO stretching frequency of cis-Pt(C0)2(SO3F)2 is, at 2201 cm-1,somewhat lower than that of [Pt(C0)4][Pt(SO3F)6] (Pam CO = 2251 cm-1). The satellitebands at 2191 cm-1 (Ra) and 2145 cm-1 (IR) are attributed to 13C0 naturally occurring inthe sample. It was initially thought that these bands were due to traces oftrans-Pt(C0)2(SO3F)2, since a report by Calderazzo showed that differences in COstretching frequencies between the cis and trans forms of Pt(C0)2X2 (X = Cl, Br, I) wereabout 30 cm-1, with the trans isomer absorbing at lower frequency [12]. The differencesbetween peaks in our sample were about 27 cm-1 and 40 cm-1 in the Raman and infrared,respectively.Similar splittings for the CO moieties are found for cis-Pd(C0)2(SO3F)2. Sincethe infrared spectrum of the palladium carbonyl complex is obtained from single crystalfragments, it is unlikely that our interpretation of trans-M(C0)2(SO3F)2 is correct. It ismore likely that factor group effects and p13C-0 satellite bands are responsible for thesmall, low intensity bands.cis-Pt(CO)2C12 was prepared by reductive carbonylation of PtC14 in thionylchloride [30]. The bromo and iodo analogues were prepared by halogen exchange ofcis-Pt(C0)2C12 with HX (X =Br, I) [31]. Andreini et al. prepared the trans isomers byheating the cis isomers, causing CO loss to give a dinuclear species, and then formingtrans-Pt(C0)2C12 by cleaving the halogen bridges using an excess of CO [31] according to-2 CO CI\ zCl\ /CO +2 CO2 cis-Pt(C0)2C12^pt'^Pt^2 trans-Pt(CO)2C12^(9)/ "c( \OC"^CI^ClFormation of trans-Pt(C0)2C12 is consistent with the trans-directing influence ofCO. However, the trans isomer is unstable, and can be easily converted to the cisform [31]. This synthetic approach does not appear to be available to us because reversible96CO dissociation-association does not seem to occur for the fluorosulfate and thecorresponding dinuclear complex, Pt2(C0)2(SO3F)4, is not yet known.In the preparation of Pt(C0)2(SO3F)2, we postulate a different pathway for theformation of the complex. The reduction of Pt(SO3F)4(solv) initially forms[Pt(C0)4]2+(so1v) according to 13C NMR. The cation is stabilized by the highly acidicconditions and excess CO. The excess CO is easily removed by pumping in vacuo, sinceCO is not very soluble in HSO3F [19]. Like the gold system, CO may be displaced bySO3F- at the metal center. The formation of Pt(C0)2(SO3F)2 can then be written asfollows:[Pt(C0)4]2+(solv) + 2 S03F- --> cis-Pt(C0)2(SO3F)2 + 2 CO (10)Substitution reactions on square planar Pt(II) complexes usually follows anassociative pathway [32]. Since CO is an excellent trans-directing ligand, it is highlyprobable that cis-Pt(C0)2(SO3F)2 is the sole product.6.3.3 iPt(C0)11[Sb2F1112The first evidence of [Pt(C0)4]2+ is obtained by the isolation and vibrationalcharacterization of [Pt(C0)4][Pt(SO3F)6] as an intermediate in the partial reduction ofPt(SO3F)4(solv) by CO. However, only the C-0 stretching frequencies could be clearlyidentified; other vibrations appeared to overlap with SO3F vibrations and deformationmodes. With the successful preparation of [Pt(C0)4][Sb2F11]2, we hope to be able toconfirm the identity of [Pt(C0)4]2+•[Pt(C0)4][Sb2F1112 was prepared by dissolving Pt(C0)2(SO3F)2 in excess SbF5 inthe presence of CO. The product is isolated by pumping in vacuo to constant weight;cooling of the reactor was necessary to prevent bumping. Conversion of Pt(C0)2(SO3F)2to [Pt(C0)4][Sb2F1112 is quantitative. The byproduct, Sb2F9S03F, was identified byinfrared spectroscopy. From the amount of CO taken up, the reaction can be written as:97Pt(C0)2(SO3F)2 + 2 CO + 8 SbF5 -• [Pt(C0)4][Sb2F11]2 + 2 Sb2F9S03F^(11)[Pt(CO)4][Sb2F11)2 melts with decomposition at 200°C to a brown liquid. Vibrational andX-ray photoelectron spectroscopy are used to characterize [Pt(C0)4][Sb2F102.6.3.3a Vibrational SpectraThe vibrational data obtained from a sample of solid [Pt(C0)4][Sb2F1112 are listedin Table 6-6.Table 6-6. Vibrational Data for [Pt(CO)4][Sb2F102Infrared, int.^Raman, int.^Tentative Assignment2289vs t vC0 (A g)2267s f^vC0 (Big)2244m^ vasymC0 (En)2204w Pasym i3co (Eu)707vs vasym Sb-Fax688vs^686w^Pasym Sb-F,ieq675s 669m666m^657m vsym Sb-F4eq604w,sh 649m,sh596w^594w^Pasym Sb-F4eq517m503w,sh t v Pt-CO473m i305w^613t-CO231w140wThe CO stretching frequency of [Pt(C0)41[Sb2F1112 is found at 2244 cm-1 in theinfrared, and 2278 cm-1 (average) in the Raman. These are the highest values recorded sofar for any metal carbonyl complex.98The observation of two CO stretching vibrations in the Raman and one in theinfrared spectrum are consistent with a centrosymmetric [Pt(C0)4]2+ cation with DAsymmetry. The non-coincidence of the infrared and Raman CO vibrations, as expectedfrom the mutual exclusion rule, provide further support for DA symmetry. The infraredbands at 517, 503, and 473 cm-1 are tentatively attributed to vPt-00 by analogy to theassignments for [Pt(CN)02- [26]. An attempt at a complete vibrational analysis ispostponed pending the results of 13C and 180 isotopic substitution studies and force fieldcalculations similar to those carried out for [Au(C0)2][8b2Fii] (vide supra). Acomparison of the CO stretching frequencies of [Pt(C0)4][Pt(S03F)6] and[Pt(C0)4][Sb2F11]2 shows that the C-0 stretching frequency increases with decreasingnucleophilicity of the anion. The C-0 stretching frequencies are unprecedentedly high,supporting the postulation made earlier that 7-backbonding is minimal, more so in[Pt(C0)4][Sb2F1112 for either of Pt(C0)2(SO3F)2 or [Pt(C0)4][Pt(SO3F)6]•Preliminary force constant calculations have been carried out for the [Pt(C0)4]2+cation [33] according to the method of Cotton and Kraihanzel [34], and the force constantis found to be 20.64 x 102 Nm-1.The [Sb2F1i] vibrational bands appear in almost the same positions here as in[Au(C0)2][8b2F11], and assignments are based on D4h symmetry for the anion, analogousto the gold compound. Shifts in vibrational frequencies are probably due to the[Pt(C0)4]2+ cation.6.3.3b X-ray Photoelectron Spectra[Pt(C0)4][8b2F11]2 was analyzed by XPS. During the experiment, traces of thesample were left in the vacuum chamber and affected the instrument's ability to reattainultra-high vacuum (UHV) conditions (pressure= i0 to 10-8 bar). Consequently, no othersamples were analyzed.99All samples sent for XPS analysis contain some adventitious carbon in the form ofhydrocarbons, and this is impossible to remove, no matter how carefully the sample isprepared [35]. This air-borne carbon is used as an internal reference, and the Cis peakappears at 284.6 eV [35]. Cis reference peak shifts can happen, and may be caused by thespectrometer. These shifts can be neglected because we usually measure the energydifference between two peaks. A C-0 a bond increases the binding energy by 1.5 eV, andeach additional 7 bond increases the energy by approximately another 1.5 eV [36]. Thus,for a carbon atom triply bonded to oxygen the Cis peak should have a binding energy of289.1 eV, or 4.5 eV greater than 284.6 eV. Figure 6-3 shows the X-ray photoelectronspectrum of [Pt(C0)4][Sb2F102 in the Cis region.Figure 6-3. Cls binding energy of [Pt(C0)4][Sb2F102.The Cis reference peak appears at 285 eV. The appearance of the peak at 290.5eV is 5.5 eV greater than the energy of the reference peak and suggests that the carbonatom in [Pt(C0)4][Sb2F1112 is triply bonded to the oxygen atom. The anion may beresponsible for the slightly greater than expected energy shift.6.3.4 Reaction of Cs[Pt(S03E151 and Cs2[Pt(S03E)61 with CO in HSO3FNeither Cs[Pt(SO3F)5] nor Cs2[Pt(SO3F)6] in HSO3F reacted with CO, even withextended reaction times, and elevated temperatures. An infrared spectrum of the solidproduced in these reactions showed no CO stretch, and the melting points were identical tothe literature values (as reported by Lee and Aubke) [18].Redissolving Pt(SO3F)4 in HSO3F and adding CO at room temperature yielded onlya clear, colourless liquid, possibly Pt(C0)2(SO3F)2. It was not isolable due to difficultieswith removing all the acid. Warming the reactor caused a black film to form on thesurface of the solution. If Pt(SO3F)4 was redissolved in HSO3F and the mixture washeated immediately after adding carbon monoxide, the reaction proceeded through theyellow intermediate [Pt(C0)4][Pt(SO3F)6], and Pt(C0)2(SO3F)2 was eventually isolated asbefore.6.4 Conclusion Three new platinum carbonyl complexes have been prepared under mild reactionconditions. A highly acidic environment is suitable for stabilizing the hitherto unknown[Pt(C0)4]2+ cation in solution, and the use of weakly nucleophilic anions such as[Pt(SO3F)6]2" and [Sb2F1ir allow isolation of these cations as the corresponding salts. Itis possible to displace two carbon monoxide molecules by slow removal of HSO3F from[Pt(C0)4]2+(solv), and replace them with SO3F molecules. Pt(C0)2(SO3F)2 differs fromthe platinum carbonyl halides in that it does not appear to lose CO and form dinuclearcomplexes upon heating. All of the C-0 stretching frequencies are very high, and this isattributed to CO behaving as a a donor, with minimal 7r-backbonding.100References1. L. Mond, C. Langer and F. Quincke, Trans. Chem. Soc. (1890) 57, 749.2. H. Huber, P. Kiindig, M. Moskovits and G.A. Ozin, Nature (London). Phys. Sci. (1972) 235, 98.3. J. H. Darling and J.S. Ogden, Inorg. Chem. (1972) 11, 666.4. E.P. Kandig, D. McIntosh, M. Moskovits and G.A. Ozin, J. Am. Chem. Soc. (1973)95, 7234.5. S.C. Tripathi, S.C. Scrivastava, R.P. Mani and A.K. Shrimal, Inorg. Chim. Acta(1976) 17, 257.6. F.R. Hartley, "The Chemistry of Platinum and Palladium", John Wiley & Sons: NewYork, NY (1973).7. P. Schiitzenberger, Compt. Rend. (1870) 70, 1134.8. P. Schiitzenberger, Compt. Rend. (1870) 21. 1287.9. P. Schiitzenberger, Bull. Chim. France (1870) 14, 97.10. F. Mylius and F. Foerster, Ber. (1891) 24, 2424.11. F. Foerster, Ber. (1891) 2.4, 3751.12. F. Calderazzo, J. Organomet. Chem. (1990) 400, 303.13. D.M. Roundhill, in" Comprehensive Coordination Chemistry", G. Wilkinson, Ed.,Vol. 5, Pergamon: Oxford, UK (1987) p 351.14. P.L. Goggin and R.J. Goodfellow, J. Chem. Soc., Dalton Trans. (1973) 2355.15. F. Calderazzo, Pure and Appl. Chem. (1978) 50, 49.16. J. Browning, P.L. Goggin, R.J. Goodfellow, M.G. Norton, A.J.M. Rattray, B.F.Taylor and J. Mink, J. Chem. Soc., Dalton Trans. (1977) 2061.17. R.J. Irving annd E.A. Magnusson, J. Chem. Soc. (1956), 1860.18. K.C. Lee and F. Aubke, Inorg. Chem. (1984), 23, 2124.19. H. Willner and F. Aubke, .L.LcIrg. Chem. (1990) 29, 2195.20. F. Calderazzo and D.Belli Dell'Amico, Inorg. Chem. (1982) 21, 3639.21. M. Lustig, "nag. Chem. (1965) 4, 1828.10110222. C.S.G. Phillips and R.J.P. WLilliams, "Inorganic Chemistry", Vol. 2 (Metals),Oxford University: New York, NY (1966) pp 319, 654.23. C. Wang, unpublished results.24. S.P. Mallela, S. Yap, J.R. Sams and F. Aubke, Inorg. Chem. (1986) 25, 4327.25. L.H. Jones, "Inorganic Vibrational Spectroscopy", Vol. 1, Marcel Dekker: NewYork, NY. (1971).26. G.J. Kubas and L.H. Jones, Inag. Chem. (1974) 13, 2816.27. E.W. Abel and S.P. Tyfield, in "Advances in Organometallic Chemistry", Vol. 8,F.G.A. Stone and R. West, Eds., Academic: New York, NY (1970) p 117.28. P.K. Hurlburt, J.J. Rack, S.F. Dec, O.P. Anderson and S.H. Strauss, Inorg Chem(1993) 32, 373.29. D.M. Sweeny, I Nakagawa, SA. Mizushima and J.V. Quagliano, J. Am. Chem. Soc. (1956) 78, 889.30. D. Belli Dell'Amico and F. Calderazzo, Gazz. Chim. Ital. (1979) 109, 99.31. B.P. Andreini, D. Belli, Dell'Amico, F. Calderazzo, M.G. Venturi, B. Pelizzi andA. Segre, J. Organomet. Chem. (1988) 354, 357.32. K.F. Purcell and J.C. Kotz, "Inorganic Chemistry", W.B. Saunder Company:Philadelphia, PA (1977) p 697.33. M. Bodenbinder, personal communication.34. F.A. Cotton and C.S. Kraihanzel, J. Am. Chem. Soc. (1962) 84, 181.35. C.D. Wagner, W.M. Riggs, L.E. Davis and J.F. Moulder, "Handbook of X-RayPhotoelectron Spectroscopy", G.E. Muilenberg, Ed., Perkin Elmer: Eden Prairie,MN (1978).36. Dr. P. Wong, personal communication.CHAPTER 7. CONCLUSIONS AND SUGGESTIONS FOR FURTHER WORKThe investigation of the unusual magnetic behaviour of gold tris(fluorosulfate),Au(SO3F)3, using electron spin resonance spectroscopy led to the identification of a trueAu2+ center both in the solid state and in solution for the first time. Pyrolysis of solidAu(SO3F)3 reductively eliminated SO3F radicals and generated Au2+ centers as latticedefects. The pyrolysis of the diamagnetic intermediate, Br3[Au(SO3F)4], in thepreparation of Au(SO3F)3 via oxidation of gold metal by BrSO3F may produce the Au2+defects, which would explain the observed weak paramagnetism in these samples. This isconsistent with earlier observations that like Ag2+, wealdy paramagnetic samples ofAu(SO3F)3 followed the Curie-Weiss Law. In HSO3F solution, Au2+(solv) was producedas an unstable intermediate in the reduction of solvated Au(SO3F)3 by gold metal. TheAu2+ species in solution disproportionated to give a mixed valency complex of thecomposition Au'Au M(s0394.A new gold carbonyl compound, [Au(C0)2][Sb2F1d, was prepared. Earliersolution studies of the reductive carbonylation of Au(SO3F)3 in HSO3F had suggested thepresence of [Au(C0)2]+(so1v), but Au(CO)S03F was isolated instead. Solvolysis ofAu(CO)S03F in SbF5 in the presence of CO yields [Au(C0)2][Sb2F11]. This is the firstthermally stable complex with a binary, linear carbonyl cation, and it has beencharacterized by vibrational analysis and NMR studies. The average C-0 stretchingfrequency is 2235.5 cm-1, and indicates that carbon monoxide behaves primarily as aa-donor ligand, with minimal ir-backbonding. The Au-C bond is weak, and replacementof CO by donor ligands such as acetonitrile is facile, and gives [Au(NCCH3)2][SbF6].Crystals of [Au(NCCH3)21[SbF6] are isolated by slow solvent evaporation, and the X-raydiffraction study shows the Au(I) center in a perfectly linear arrangement with the N-C-Cmoieties of the acetonitrile ligands. The SbF6- anion is octahedral.103104The reductive carbonylation procedure was applied to the Pt(SO3F)4/HSO3Fsystem, and three new platinum carbonyls are isolated: [Pt(CO)4][Pt(S03F)6),cis-Pt(C0)2(SO3F)2, and [Pt(C0)4][Sb2F1112. The reaction conditions are mild, in starkcontrast to the preparation of Pt(C0)2X2 (X = Cl, Br, I), where elevated temperatures andhigh CO pressures are required.[Pt(C0)41[Pt(SO3F)6] is an intermediate isolated in the ambient temperaturereductive carbonylation of Pt(SO3F)4 in HSO3F, and provided the first evidence for the[Pt(C0)4]2+ cation. However, only C-0 vibrations were successfully assigned due tooverlap of most of the remaining vibrations with those of SO3F. cis-Pt(C0)2(SO3F)2 isanalogous to Au(CO)S03F, and unlike the corresponding Pt(C0)2X2 (X =C1, Br, I)compounds, does not appear to lose CO upon heating. The complete vibrational spectra ofPt(C0)2(SO3F)2 have been reported and assigned by analogy to cis-Pd(C0)2(SO3F)2,where a molecular structure has been obtained very recently in our laboratory.[Pt(C0)41[Sb2F102 is the group 10 analogue of [Au(C0)2liSb2F11), and was prepared bysolvolysis of Pt(C0)2(SO3F)2 in SbF5 in the presence of CO. All of the platinum carbonylcomplexes exhibited extremely high average C-0 stretching frequencies at 2251 cm-1,2201 cm4, and 2261 cull for [Pt(C0)4][Pt(SO3F)6], cis-Pt(C0)2(SO3F)2, and[Pt(C0)4)[Sb2F11]2 respectively, and like the gold carbonyl, carbon monoxide acts as aa donating ligand with minimal r-backdonation, which is drastically different from itsbehaviour in classical transition metal carbonyls.Our knowledge of thermally stable, cationic carbonyl derivatives of the noblemetals has recently been extended by Mr. C. Wang in our group to palladium. While[Pd(C0)4][Sb2F1112 and cis-Pd(C0)2(SO3F)2 (the latter has been characterized by singlecrystal X-ray diffraction) are apparently isostructural to the corresponding Pt(II) compounddescribed here, a third compound, cyclotPd2(2-00)2](S03F)2, which has also beenstructurally characterized, is unique and is found to contain the square planar cation[Pd2(it-00)2]2+ with symmetrically bridging CO ligands.105This recent work provides a stark contrast to the thermally highly unstable silvercarbonyl complexes of the type Ag(CO)nB(OTeF5)4 (n = 1, 2) which decompose at roomtemperature. This would suggest that the search for other non-classical carbonylderivatives should perhaps extend towards the left of group 10, with rhodium and iridiumpromising candidates, rather than to the right towards the post-transition metals.In all work described here, as well as in the studies of the palladium systems,fluorosulfuric acid, with its wide liquid range (-88.98 to 162.7°C), has been found to be avery useful medium for stabilizing solvated cations like [M(C0)4]2+ (M = Pt, Pd) and[Au(C0)2]+. It should be possible to stabilize other carbonyl cations in HSO3F byemploying synthetic strategies described in this thesis. There is no reason why othermetals, including non-transition metals or lanthanides, should not form carbonyl cationswith unusual spectroscopic properties and bonding characteristics similar to the onesobserved.A number of additional suggestions for futher work concern the following:(i) a more complete characterization of the metal carbonyl cations by 13C orheteronuclear NMR should be undertaken. The use of X-ray photoelectron spectroscopystarted here should also be continued.(ii) Synthetic use of the carbonyl cations should be extended. Substitution of COby CH3CN described here and the structural characterization of [Au(NCCH3)2][SbF6] is apromising start. All indications are that CO remains a very weak Lewis base andnumerous potential ligands like phosphines, amines or organic sulfides appear to bepromising candidates due to their better a donating ability.(iii) By analogy to the identification of Au2+ described in this thesis, the search forother metal cations in unusual oxidation states should be continued. Like Au(SO3F)3 andAuF3, weak paramagnetism has been reported in samples of PtF4 and Pt(SO3F)4, the causeof which is still unexplained.106(iv) A puzzling aspect of the metal carbonyl complexes still needs to be explained:why is the metal-carbon bond so stable in the derivatives of gold, platinum, and palladium,where all indications suggest only insignificant 7-backbonding? The recently obtainedstructure of cis-Pd(C0)2(SO3F)2 provides evidence for significant intermolecular 0-.0contacts involving oxygens from the fluorosulfate groups. In a Mn+*--CO segment,a donation is expected to generate a positive charge on carbon. To clarify this point moredetailed molecular structure determinations need to be undertaken.

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