On the reactions of molybdenum and tungsten carbonyls with trimethyl‐ and triethyl‐aluminium

Abstract

Reactions of hexacarbonylmolybdenum, hexacarbonyltungsten and arene complexes of tricarbonylmolybdenum and tricarbonyltungsten with trimethyl-and triethyl-aluminium have been studied. It has been found, based on IR and NMR spectra, that trialkylaluminium does not form complexes with hexacarbonyls of molybdenum and tungsten. Arene (mesitylene, toluene and benzene) complexes of tricarbonylmolybdenum form 1 : 1 complexes with triethylaluminium, and arene complexes of tricarbonyltungsten form complexes with trimethyland triethyl-aluminium. Regardless of the molar ratios of reactants (arene)M(CO),/AIEt,, only one of the three CO groups bonded to molybdenum or tungsten forms a complex with AIEt,.Fast exchange between free and complexed trialkylaluminium and an exchange of trialkylaluminium between all three carbonyl groups have been observed in benzene, toluene and decalin solutions. In the 'H NMR spectra of the products of the reactions of (mesitylene)Mo(CO), with AIEt, and AIMe,, signals at -9 to -14 ppm (characteristic for molybdenum hydrides) were present. It confirmed an alkylation of molybdenum followed by 0-or a-hydrogen elimination with the formation of the corresponding molybdenum hydrides, the actual catalyst of aromatic hydrocarbon hydrogenation.

New insights into the reaction of nickelocene with methyllithium: the isolation and crystal structure of (NiCp)3(μ3-CH)

“…This material was characterised by mass spectra that were consistent with the molecular formula of (NiCp) 6 C. 1 Cluster (NiCp) 6 C was previously detected by mass spectroscopy in mixtures obtained from reaction of nickelocene with methyllithium [2,13,21]. Pathways leading to the formation of this cluster from transient {CpNiCH 3 } species were discussed by Pasynkiewicz [13,21]. Because cluster 2 is stable to purification on alumina and has been isolated in a number of cases without any traces of 1 [5,10], we assume that cluster (NiCp) 6 C is the most likely precursor to 1 (Eq.…”

“…However, extraction of sparingly soluble thermolysis residues produced deep-brown solutions which yielded a brown powder after crystallisation. This material was characterised by mass spectra that were consistent with the molecular formula of (NiCp) 6 C. 1 Cluster (NiCp) 6 C was previously detected by mass spectroscopy in mixtures obtained from reaction of nickelocene with methyllithium [2,13,21]. Pathways leading to the formation of this cluster from transient {CpNiCH 3 } species were discussed by Pasynkiewicz [13,21].…”

A 95Mo and 13C solid-state NMR and relativistic DFT investigation of mesitylenetricarbonylmolybdenum(0) – a typical transition metal piano-stool complex

“…This compound is of interest for several reasons. Arene molybdenum tricarbonyls have been investigated as co-catalysts in aromatic hydrocarbon hydrogenation 21 and phenylacetylene polymerization, 22 and the related piano-stool complex methylcyclopentadienyl manganese tricarbonyl has found use as an anti-knock gasoline additive. 23 Point-charge models indicate that the EFG at the central nucleus of piano-stool complexes of this type should be zero, or small, as is the case for perfectly tetrahedral and octahedral DOI: 10.1039/b202025b…”

Photochemical reactions of [W(CO)4(η4-nbd)] with hydrosilanes: Generation of new hydrido complexes of tungsten and their reactivity

“…209 ppm. Proton and carbon signals of other tungsten complexes containing g 6 -arene and carbonyl ligands have been observed before in a similar range of NMR spectra [26][27][28].…”

“…40%. (CO) 5 In photochemical reaction of the norbornadiene complex 1 with Ph 2 SiH 2 monitored by IR spectroscopy in n-heptane solution, a very fast decay of the m (C"O) frequency at 2044 (m), 1957 (vs) 1909 (s) cm À1 , characteristic for 1, and the appearance of bands at 1982 and 1911 cm À1 , characteristic for the three carbonyl moieties of the g 6 -arene complexes [W(CO) 3 (g 6 -arene)], were observed [26][27][28]. In the 1 H NMR spectrum of this sample in CDCl 3 solution, the proton signals characteristic for nbaSiHPh 2 and nba(SiHPh 2 ) 2 were detected at d 2.46, 2.37 and 2.29.…”