Activation of Ge-H and Sn-H Bonds with N-Heterocyclic Carbenes and a Cyclic (Alkyl)(amino)carbene.

A study of the reactivity of several N-heterocyclic carbenes (NHCs) and the cyclic (alkyl)(amino)carbene 1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene (cAAC ) with the group 14 hydrides GeH Mes and SnH Me (Me=CH , Mes=1,3,5-(CH ) C H ) is presented. The reaction of GeH Mes with cAAC led to the insertion of cAAC into one Ge-H bond to give cAAC H-GeHMes (1). If 1,3,4,5-tetramethyl-imidazolin-2-ylidene (Me Im ) was used as the carbene, NHC-mediated dehydrogenative coupling occurred, which led to the NHC-stabilized germylene Me Im ⋅GeMes (2). The reaction of SnH Me with cAAC also afforded the insertion product cAAC H-SnHMe (3), and reaction of two equivalents Me Im with SnH Me gave the NHC-stabilized stannylene Me Im ⋅SnMe (4). If the sterically more demanding NHCs Me Im , 1,3-di-isopropyl-4,5-dimethyl-imidazolin-2-ylidene (iPr Im ) and 1,3-bis-(2,6-di-isopropylphenyl)-imidazolin-2-ylidene (Dipp Im) were employed, selective formation of cyclic oligomers (SnMe ) (5; n=5-8) in high yield was observed. These cyclic oligomers were also obtained from the controlled decomposition of cAAC H-SnHMe (3).