William A. G. Graham

Carbonyl-η-hexamethylbenzene complexes of osmium. Carbon-hydrogen activation by (η-C6Me6)Os(CO)(H)2

Abstract Reduction of (η-C6Me6)Os(CO)Cl2 (1) with zinc/acetic acid/methanol gives (η-C6Me6)Os(CO)(Cl)H (2), which can be further reduced with Na[H2Al(OCH2- CH2OCH3)2] to (η-C6Me6)Os(CO)H2 (3). Photolysis of 3 in hydrocarbons (benzene, cyclohexane, neopentane) results in formation of the carbon-hydrogen bond activation products (η-C6Me6Os(CO)(R)(H) (6a–6c, R = C6H5, C6H11 and CH2C(CH3)3, respectively) and free hexamethylbenzene. Independent syntheses of the hydrides 6a–6c are described as well as syntheses of the complexes (η-C6Me6)Os(CO)(R)2 (4a–4c) and (η-C6Me6)Os(CO)(R)Cl (5a–5c). The structure of (η-C6Me6)Os(CO)(cyclohexyl)2 (4b) determined by single crystal X-ray diffraction is reported.

Preparation and properties of some pentafluorophenyl group IV compounds

Abstract The preparation of the compounds C6F5Si(CH3)2X [where X = H, CH3, C6F5, OCH13, N(CH3)2 or NHC6H5] and R3MYC6F5 (where R = CH3 or C6H5, M = Si, Ge, Sn or Pb and Y = O, S or NH) is described and their NMR and IR spectra are discussed.

Studies of organotin chemistry: I. Preparation and properties of new, soluble forms of trimethyltin formate and acetate

Abstract The previously known insoluble trimethyltin formate has been converted to a new, soluble form by heating in a sealed tube with cyclohexane at 100°. Trimethyltin acetate undergoes a similar transformation. The effects of concentration, temperature, and added complexing agents on the infrared and NMR spectra are reported. The results imply an equilibrium in solution between monomeric and associated forms. It is suggested that the associated forms may have a cyclic structure, in contrast to the linear polymeric structure usually attributed to the insoluble form.

Photochemistry of (η-C5Me5)Re(CO)3: preparation and X-ray crystal structure of (η-C5Me5)2Re2(µ-CO)3

Ultraviolet irradiation of (η-C5Me5)Re(CO)3 forms the stable complexes (η-C5Me5)Re2(µ-CO)(Co)4 and (η-C5Me5)2Re2(µ-CO)3; the length of the formal Re–Re triple bond in the latter is determined by X-ray diffraction to be 2·411 (1)A.

Stereochemically nonrigid six-coordinate metal carbonyl complexes : IV. A 13C NMR investigation of cis-M(CO)4X2 and M′(CO)5X derivatives (M = Fe, Ru, Os; M′ = Mn, Re; X = H, I)☆

Abstract The 13 C NMR spectra of cis -M(CO) 4 X 2 and M′(CO) 5 X (M = Fe, Ru, Os; M′ = Mn, Re; X = H, I) and cis ·Os(CO) 4 Me 2 are reported. Variable temperature spectra demonstrated the stereochemical nonrigidity of cis -Fe(CO) 4 H 2 and the stereochemical rigidity of the rest. The carbonyl averaging process in cis -Fe(CO) 4 H 2 occurs without ligand dissociation. Improved syntheses of some of these derivatives are also given.

Synthesis and Spectra of Cationic Bis(tertiary phosphine) derivatives of cycloheptatrienyliummolybdenum and cyclopentadienyliron complexes

Reaction of [(η-C7H7)Mo(CO)3][PF6] and [(η-C5H5)Fe(CO)2CH3CN][PF6] with ditertiary phosphine ligands afforded products of three types; the monosubstituted complexes [(Ring)M(CO)2Ph2P(CH2)nPPh2][PF6] (Ring = η-C7H7, M = Mo, n = 1; Ring = η-C5H5, M = Fe, n = 1 and 2), the chelated complexes [(Ring)M(CO)Ph2P(CH2)nPPh2][PF6] (Ring = η-C7H7, M = Mo, n = 1 and 2; Ring = η-C5H5, M = Fe, n = 1 and 2), and the dinuclear complex [{(η-C7H7)Mo(CO)2}2 -μ- Ph2PCH2CH2PPh2][(PF6)2]. Spectroscopic properties, including 31P NMR, are reported.

A carbon-13 NMR study of some pentacarbonylrhenium complexes

Abstract Carbon-13 NMR data are reported for derivatives XRe(CO) 5 (X = CH 3 , CH 3 CO, C 6 H 5 , C 6 H 5 CO, Br, Cl 3 Si, Me 3 Si, Me 3 Ge, Me 3 Sn, Me 3 Pb). Spectra of good quality were obtained at ambient temperature except for X = Me 3 Pb. In the XRe(CO) 5 series, the carbonyl carbon trans to X is more shielded (resonance at higher field) than carbonyl carbons cis to X. However, in the cationic complex [CH 3 CHRe(CO) 5 ][PF 6 ], the carbonyl carbon trans to CH 3 CN is less shielded than those in cis positions. Although there is a linear relation between the 13 C chemical shift and the stretching force constant for cis carbonyls in the XRe(CO) 5 series, there is no apparent correlation of force constants with other features of the 13 C NMR spectra.

Silicontransition metal chemistry : VIII. Synthesis of trimethylsilyliron compounds using bis(trimethylsilyl)mercury☆

Abstract The synthesis of cis -(OC) 4 Fe(SiMe 3 ) 2 and Hg[Fe(CO) 4 SiMe 3 ] 2 by the photochemical reaction of Hg(SiMe 3 ) 2 with Fe(CO) 5 is described. The spectroscopic properties of the new compounds are discussed.

Group V complexes of the tricarbonyl(η-cycloheptatrienylium)molybdenum cation and their reduction to monosubstituted derivatives of tricarbonyl(1-6-η-cycloheptatriene)molybdenum

Abstract Reaction of [(η-C 7 H 7 )Mo(CO) 3 ][PF 6 ] with certain Group V donor ligands afforded monosubstituted complexes [(η-C 7 H 7 )Mo(CO) 2 L][PF 6 ] (L = P(OPh) 3 , PPh 3 , PPh 2 Me, PPhMe 2 , AsPh 3 , SbPh 3 ). These were reduced by NaBH 4 to the corresponding cycloheptatriene complexes (1-6-η-C 7 H 8 )Mo(CO) 2 L. In addition, the preparation of alkylcycloheptatriene complexes (1-6-η-C 7 H 7 R)Mo(CO) 2 L (R = Me, L = P(OPh) 3 , PPh 3 , PPh 2 Me; R = t-Bu, L = PPh 3 ) is described. Spectroscopic properties, including 13 C NMR, are reported.

Photoactivation of methane by η5-cyclopentadienyl and substituted η5-cyclopentadienyl Group 8 metal dicarbonyl complexes, [M(η5-C5R5)(CO)2](M = Rh or Ir, R = H or Me), and dicarbonyl(η5-indenyl)iridium: a matrix isolation study

Infrared spectroscopic evidence, including deuterium labelling, is presented to show that photolysis of [M(η5-C5R5)(CO)2](M = Rh or Ir, R = H or Me) complexes in CH4 matrices at ca. 12 K leads primarily to [M(η5-C5R5)(CO)(Me)(H)] complexes. Comparative photolysis experiments in CH4, Ar, and 13CO-doped (5%) matrices provided evidence that the initial step is the loss of CO to form the ‘naked’ 16-electron species, [M(η5-C5R5)(CO)]. Additional photoproducts in CH4 matrices are tentatively assigned as the CH4 complexes [M(η5-C5R5)(CO)⋯ CH4]. Cobalt analogues failed to activate CH4 but did afford very weak bands which could possibly be assigned to the CH4 complexes [Co(η5-C5R5)(CO)⋯ CH4](R = H or Me). The indenyl complex, [Ir(η5-C9H7)(CO)2], behaves similarly to the cyclopentadienyl complexes. The mechanism of CH4 activation in matrices in discussed and related to the activation of CH4 in solution at ambient temperatures. The lack of CH4 activation by Co analogues seems to be best rationalised on thermodynamic grounds.