H. Hashimoto, T. Fukuda, H. Tobita
Mar 19, 2012
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Influential Citations
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Journal
Angewandte Chemie
Abstract
The heavier analogues of transition-metal carbyne complexes are attractive synthetic targets for research in fundamental organometallic and main-group chemistry. Over the last 15 years, the syntheses of a series of complexes with M E bonds (E = Si, Ge, Sn, Pb) have been achieved, but examples are few. These complexes were synthesized by employing a base-stabilized halosilylene and stable divalent Group 14 element halides for E = Ge, Sn, or Pb as precursors. For example, Power and Simons reported the first example of this type of complex, [Cp(CO)2Mo Ge(C6H3-2,6-Mes2)] (Mes = mesityl = 2,4,6-trimethylphenyl), which was obtained by salt elimination from a germanium(II) chloride GeCl(C6H3-2,6Mes2) and an anionic complex Na[MoCp(CO)3]. [2a] Recently, we have synthesized a neutral hydrido (hydrogermylene) complex [Cp*(CO)2(H)W=Ge(H){C(SiMe3)3}] (1) and found that 1 reacted with mesitylisocyanate MesNCO upon heating to produce a germylyne complex [Cp*(CO)2W Ge{C(SiMe3)3}] (2) with release of MesNHCHO. In this reaction, 1 is formally dehydrogenated with MesNCO to give 2. This type of synthesis of a germylyne complex from a germylene complex has not been previously reported. We also succeeded in the isolation of an intermediate [Cp*(CO)2W(GeH(OCH=NMes){C(SiMe3)3})] (3). Herein, we report the details of this novel transformation and our mechanistic investigations, including kinetic studies with 3 and DFT calculations. We previously reported that 1 underwent hydrogermylation of PhNCO at the C=O bond at room temperature in 24 h to give a five-membered ring complex [Cp*(CO)2W(GeH(OCH=NPh){C(SiMe3)3})] (4) in 61% yield (85% NMR yield). A similar reaction of 1 with sterically hindered MesNCO (3 equiv) proceeded very slowly at room temperature to give the analogous complex 3 in 76 % yield after 10 days, together with germylyne complex 2 (24%) as determined from the H NMR spectrum (Scheme 1). Complex 3 was isolated in 61 % yield from a similar reaction using one