Thomas E. Bitterwolf

Bis(cyclopentadienylthallium)methane: A versatile intermediate for the synthesis of dinuclear cyclopentadienylmetal carbonyl complexes

Abstract Bis(cyclopentadienylthallium)methane has been prepared from dicyclopentadienyl-methane and was shown to be a versatile starting material for the synthesis of a series of new dinuclear carbonylmetal complexes. Reactions of CH 2 (Cp-Tl) 2 with carbonylhalometal complexes yielded CH 2 [CpMn(CO) 3 ] 2 , CH 2 [CpFe(CO)Br] 2 , CH 2 [CpRu(CO) 2 Cl] 2 , CH 2 [CpRu(CO) 2 ] 2 , CH 2 [CpRh(CO) 2 ] 2 , CH 2 [CpRh(CO)] 2 -μ-CO, and CH 2 [CpIr(CO) 2 ] 2 . Reduction of the iron and ruthenium halide derivatives was found to give the metalue5f8metal bonded complexes, or the corresponding dianions depending on the time of reaction and the stoichiometry. The reaction of these dianions with methyl iodide to give the methyl derivatives is described. The facile decarbonylation of CH 2 [CpRh(CO) 2 ] 2 and carbonylation of CH 2 [CpRh(CO)] 2 -μ-CO appears to be a consequence of the proximity of the two metal atoms. In contrast, CH 2 [CpIr(CO) 2 ] 2 does not appear to form an analogous bridging compound under the reaction conditions. Complete spectral and physical data for the compounds are presented.

Formation and synthetic utility of benzyl- and phenyl-cyclopentadienylthallium

Abstract Benzyl- and phenyl-cyclopentadiene have been shown to react with thallium ethoxide in ethanol to give the corresponding benzyl- and phenyl-cyclopentadienylthallium compounds in excellent yields. These reagents are air stable for brief periods, have extended shelf-lives, and have been shown to be superior starting materials for the synthesis of a variety of cyclopentadienylmetal complexes.

Synthesis and structure of tricarbonylchromium mono-, bis- and tris-complexes of 10-methyltribenzotriquinacene

Complexation of 10-methyltribenzotriquinacene (MTBT) a bent triarene of C3v symmetry afforded six mono-, bis- and tris-Cr(CO)3complexed isomers which have been isolated and identified. The results of various synthetic experiments indicate that complexation at the convex side of a free benzene ring is favoured, probably for steric reasons. As compared with the isomer complexed at the convex face (anti), that complexed at the concave one (syn) is less stable. The 1H and 13C NMR spectral data together with the X-ray structures of the two bis- and one tris-complexes account for the lower stability of the syn isomers.

Metallocene basicity. IV. Conformational and electronic behaviour of some protonated ferrocenes

Abstract The PMR spectra of several substituted ferrocenes in HBF3OH have been recorded and the metal protonated species are discussed. 1,3-di-t-butylferrocenonium compounds were found to exist as two noninterconverting rotamers in acid solution. Hammett substituent constants for ferrocene and ferrocenonium have been determined.

The addition of halogenocarbons to alkenes in the presence of [Fe2(CO)4(η-C5H5)2] and related complexes

Abstract A kinetic study has been made of the addition of halogenocarbons to alkenes in the presence of [Fe2(CO)4(η-C5H5)2] (I). The results, together with the results of cross-over addition reactions of a halogenocarbon mixture and cross-over studies on catalyst mixtures of I and [Fe2(CO)4(η-C5Me5)2] (II) have been interpreted in terms of a mechanism which involves catalysis by an intact dinuclear species, probably [Fe2(CO)3(η-C5R5)2], but which also involves free radical intermediates.

Synthesis, oxidation and acid reactions of dinuclear cyclopentadienylrhodium carbonyl phosphine compounds

Abstract The dinuclear rhodium compounds (η 5 : η 5 -C 10 H 8 )[Rh(CO) 2 ] 2 , CH 2 [η 5 -C 5 H 4 Rh(CO) 2 ] 2 and CH 2 [η 5 -C 5 H 4 Rh(CO)] 2 -μ-CO react with triphenylphosphine to give rhodium carbonyl phosphine derivatives. Reactions of (η 5 : η 5 -C 10 H 8 )[Rh-(CO) 2 ] 2 , with bis(diphenylphosphino)methane and either CH 2 [η 5 -C 5 H 4 Rh(CO) 2 ] 2 or CH 2 [η 5 -C 5 H 4 Rh(CO)] 2 -μ-CO with tetramethyldiphosphine give products in which the diphosphine ligand links the two metal atoms. CH 2 {η 5 -C 5 H 4 Rh(CO)[(C 6 H 5 ) 3 -P]} 2 reacts with acids to form a stable, doubly protonated dication and does not give an identifiable product upon oxidation with ferrocinium hexafluorophosphate. In contrast, (η 5 : η 5 -C 10 H 8 )[Rh(CO)] 2 -μ-[(C 6 H 5 ) 2 P] 2 CH 2 and CH 2 [η 5 -C 5 H 4 Rh (CO)] 2 -μ-(CH 3 ) 4 P 2 react both with acids and ferrocinium hexafluoroborate to give stable, diamagnetic dications which must possess Rhue5fbRh bonds. Reactions with acids are accompanied by dihydrogen evolution. Similarly, oxidations of (η 5 : η 5 -C 10 H 8 )[Rh(CO) 2 ] 2 and CH 2 [η 5 -C 5 H 4 Rh(CO) 2 ] 2 with ferrocinium hexafluoroborate yield diamagnetic, dicationic products. Analogous results have been previously reported for interactions of (η 5 : η 5 -C 10 H 8 ){(Rh(CO)[(C 6 H 5 ) 3 p])} 2 with acids and with ferrocinium hexafluoroborate.

Reductive elimination of dihydrogen from arenechromium dimers

Abstract Biphenylbis(chromium dicarbonyl)-μ-bis(diphenylphosphido)methane and its arsenic analog have been prepared in good yield by UV irradiation of biphenylbis(chromium tricarbonyl) and bis(diphenylphosphido)methane or bis(diphenylarsino)methane in benzene. Addition of strong acid to these dinuclear compounds results in rapid dihydrogen evolution and subsequent decomposition of the oxidized chromium species. A scheme for the dihydrogen elimination reaction is proposed in which both metal centers are protonated in an oxidative addition step, followed by reductive elimination of dihydrogen from the two metal centers.

Synthesis and conformations of chromium tricarbonyl substituted diarenes

Abstract The metallation of a series of seven planar and bent diarenes has been examined to determine the conformations of the mono- and dimetallated products. It has been found that bent diarenes can be metallated on either the convex ( syn ) or concave ( anti ) faces of the arene. In the absence of other directing groups, metallation at the concave face is favored. Dimetallation of planar diarenes results in exclusive trans metallation. Dimetallation of bent diarenes yields the trans isomer as the major species, but cis dimetallation of the convex face is also observed. Conformational assignments have been made using 1 H and 13 C NMR spectral evidence.

Correlation of 31P chemical shifts and carbonyl stretching force constants with substituent constants for a series of ring-substituted arene chromium dicarbonyl triphenylphosphine complexes

Abstract Fourteen mono-substituted arene chromium tricarbonyl and arene chromium dicarbonyl triphenylphosphine complexes have been prepared and characterized by IR and NMR spectroscopy. Carbonyl stretching force constants for all compounds have been calculated. Correlations of stretching forces constants of arene chromium tricarbonyl complexes with a series of substituent constants agree well with those reported in earlier studies. Similarly, both the stretching force constants and 31 P chemical shifts of arene chromium dicarbonyl triphenylphosphine complexes have been compared with the same series of substituent constants and were found to exhibit trends similar to those previously observed.

The addition of halogenocarbons to alkenes in the presence of [Mo2(CO)4(η-C5R5)2] (R = H, Me), [Mo2(CO)6(η-C5H5)2] and [{Mo(CO)3(η-C5H4)}2CH2]

Abstract The addition of halogenocarbons to alkenes in the presence of [Mo2(CO)4(η-C5Me5)2] (I) has been the subject of a detailed kinetic study. These results, together with the results of cross-over addition reactions of a halogenocarbon mixture and cross-over studies on catalyst mixtures of (I) and [Mo2(CO)4(η-C5H5)2] (IV) are interpreted in favour of a mechanism involving catalysis by an intact binuclear complex, but which also involves free radical intermediates. Studies on catalysis by [Mo2(CO)6(η-C5H5)2] (II) additional to those we reported earlier, suggest an analogous mechanism in this case, but also involving CO dissociation from the hexacarbonyl yielding IV as the active catalyst. A preliminary study of catalysis by [{Mo(CO)3(η-C5H4)}2CH2] (III) suggests this complex also follows a similar mechanism.