Functionalising transition metal carbynes with main group elements

Abstract

A lithiocarbyne complex Tp*(CO){u2082}Mo{u2261}CLi (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) can be generated in situ from treatment of a THF solution of the bromocarbyne complex Tp*(CO){u2082}Mo{u2261}CBr with one equivalent of nBuLi at - 78 {u00B0} Celsius. It shows versatile reactivities towards a wide range of electrophiles and serves as an excellent starting material for many heteroatom substituted carbyne complexes, many of which were previously inaccessible from conventional carbyne synthetic protocols.

The reactions of Tp*(CO)2Mo{u2261}CLi with catecholboron chloride, dimethoxyboron chloride, bis(dimethyl)aminoboron bromide led to formation of the corresponding borylcarbyne complexTp*(CO){u2082}Mo{u2261}C-BCat, Tp*(CO){u2082}Mo{u2261}C-B(OMe){u2082}, and Tp*(CO){u2082}Mo{u2261}C-B(NMe{u2082}){u2082}. From the reaction with the dimethoxyboron chloride, a boron-bridged biscarbyne complex [Tp*(CO){u2082}Mo{u2261}C]{u2082}-BOMe was also isolated. The reaction of Tp*(CO){u2082}Mo{u2261}CLi with trimethoxyborane led to formation of a boratocarbyne complex [Tp*(CO){u2082}Mo{u2261}C-B(OMe){u2083}][Li]. The analogous reaction with the triisopropoxyborane yielded the boratocarbyne complex [Tp*(CO){u2082}Mo{u2261}C-B(OiPr){u2083}][Li], which eliminated Li(OiPr) readily in solution to form the corresponding boryl carbyne complex Tp*(CO){u2082}Mo{u2261}C-B(OiPr){u2082}. A treatment of the dimethoxyborane carbyne complex Tp*(CO){u2082}Mo{u2261}C-B(OMe){u2082} with excess of potassium hydrogendifluoride and one equivalent of 18-crown-6 let to formation of complex [Tp*(CO){u2082}Mo{u2261}C-BF{u2082}(OMe)][K] .18-crown-6.

The reactions of Tp*(CO){u2082}Mo{u2261}CLi with trimethyltin chloride and dimethyltin dichloride led to formation of complexes Tp*(CO){u2082}Mo{u2261}C-SnMe{u2083} and [Tp*(CO){u2082}Mo{u2261}C]{u2082}-SnMe{u2082} respectively. Treatment of the complex Tp*(CO){u2082}Mo{u2261}C-SnMe{u2083} with an excess of tetrachlorotin led to formation of Tp*(CO){u2082}Mo{u2261}C-SnCl{u2083}. The complex Tp*(CO){u2082}Mo{u2261}C-SnMe{u2083} also reacted with AuCl . PPh{u2083} to form the first gold-substituted carbyne complex Tp*(CO){u2082}Mo{u2261}C-AuPPh{u2083}. Furthermore, a reaction of Tp*(CO){u2082}Mo{u2261}C-SnMe{u2083} with Pt(PPh{u2083}){u2082}({u03B7}{u00B2}-C{u2082}H{u2084}) led to isolation of a platinum-substituted carbyne complex Tp*(CO){u2082}MoC-Pt(cis-Me)(PPh{u2083}){u2082}.

Complexes [Tp*(CO){u2082}Mo{u2261}C-B(OMe){u2083}][Li], [Tp*(CO){u2082}Mo{u2261}C-BF{u2082}(OMe)][K] .18-crown-6 and Tp*(CO){u2082}Mo{u2261}C-SnMe{u2083} were investigated for palladium catalysed coupling reactions. All three complexes of exhibited reacitivites towards arylhalides (iodobenzene or diiodobenzene) to produce the corresponding coupling products. Spectroscopic data of the coupling product(s) were obtained by alternative syntheses for comparison.

The reaction of Tp*(CO){u2082}Mo{u2261}CLi with stoichiometric amount of dichlorophenylphosphine resulted in formation of the complex Tp*(CO){u2082}Mo{u2261}C-P(Cl)Ph. The addition of a second equivalent of nBuLi to the reaction mixture led to formation of a butylphenylcarbido-phosphine complex Tp*(CO){u2082}Mo{u2261}C-P(nBu)Ph. A small amount of the phosphorus-bridged biscarbyne complexes were also isolated from this reaction. The reaction of Tp*(CO){u2082}Mo{u2261}CLi with [ClP({u03BC}-NtBu)]{u2082} resulted in formation of a dimeric system [Tp*(CO){u2082}Mo=[CP({u03BC}-NtBu)]{u2082}. The attempted synthesis of Tp*(CO){u2082}Mo{u2261}C-P=N^{tBu}Mes (^{tBu}Mes = 2,4,6-tri-tert-butyl mesityl) from Tp*(CO){u2082}Mo{u2261}CLi and Cl-P=N^{tBu}Mes was unsuccessful due to the highly reactive nature of the target molecule. Instead, complex Tp*(CO){u2082}Mo{u2261}C-P(nBu)-N(H)^{tBu}Mes was isolated after extensive chromatography. The reaction of the tungsten bormocarbyne Tp*(CO){u2082}W{u2261}CBr with two equivalents of nBuLi and ClP=N^{tBu}Mes led to formation of the complex Tp*(CO){u2082}W{u2261}C-P(nBu){u2082}=N^{tBu}Mes. When two equivalents of tBuLi were used instead, a phosphorous-bridged biscarbyne complex [Tp*(CO){u2082}W{u2261}C-]{u2082}P-N^{tBu}Mes was structurally characterised. These complexes provided a great deal of information on the reactivity of the targeted molecule. -- provided by Candidate. Show more