Synthesis of dimethylmanganese(II) complexes bearing N-heterocyclic carbenes and nucleophilic substitution reaction of tetraalkoxysilanes by diorganomanganese(II) complexes

Reactions of manganese(II) dichlorides bearing a N-heterocyclic carbene ligand (L), [MnCl(μ-Cl)(L)]2 (1a, L = 1,3-diisopropyl-4,5-dimethylimidazole-2-ylidene (IiPr); 1b, L = 1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene (IMes); 1c, L = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene (IPr)) with MeLi afford the dinuclear dimethylmanganese(II) complexes, [MnMe(μ-Me)(L)]2 (2a, L = IiPr; 2b, L = IMes; 2c, L = IPr). Complexes 2a-c achieve nucleophilic substitution of Si(OEt)4 to selectively form MeSi(OEt)3. Related arylmanganese(II) complexes analogously react with Si(OEt)4 to afford ArSi(OEt)3 and Ar2Si(OEt)2 (Ar = Ph, 2,6-Me2(C6H3)). Kinetic studies support an associative mechanism for the observed transformation of Si(OEt)4, in which both the manganese species and Si(OEt)4 are involved in the rate-limiting step.

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