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 (cAACMe ) with the group 14 hydrides GeH2 Mes2 and SnH2 Me2 (Me=CH3 , Mes=1,3,5-(CH3 )3 C6 H2 ) is presented. The reaction of GeH2 Mes2 with cAACMe led to the insertion of cAACMe into one Ge-H bond to give cAACMe H-GeHMes2 (1). If 1,3,4,5-tetramethyl-imidazolin-2-ylidene (Me2 ImMe ) was used as the carbene, NHC-mediated dehydrogenative coupling occurred, which led to the NHC-stabilized germylene Me2 ImMe ⋅GeMes2 (2). The reaction of SnH2 Me2 with cAACMe also afforded the insertion product cAACMe H-SnHMe2 (3), and reaction of two equivalents Me2 ImMe with SnH2 Me2 gave the NHC-stabilized stannylene Me2 ImMe ⋅SnMe2 (4). If the sterically more demanding NHCs Me2 ImMe , 1,3-di-isopropyl-4,5-dimethyl-imidazolin-2-ylidene (iPr2 ImMe ) and 1,3-bis-(2,6-di-isopropylphenyl)-imidazolin-2-ylidene (Dipp2 Im) were employed, selective formation of cyclic oligomers (SnMe2 )n (5; n=5-8) in high yield was observed. These cyclic oligomers were also obtained from the controlled decomposition of cAACMe H-SnHMe2 (3).

N-heterocyclic carbene and cyclic (alkyl)(amino)carbene adducts of plumbanes and plumbylenes.

Lewis-acid/base adducts of N-heterocyclic carbenes (NHCs) and the cyclic (alkyl)(amino)carbene cAACMe (1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene) with selected lead(II) and lead(IV) compounds are presented. The reaction of the NHCs Me2ImMe (1,3,4,5-tetramethyl-imidazolin-2-ylidene), iPr2ImMe (1,3-di-isopropyl-4,5-dimethyl-imidazolin-2-ylidene), Dipp2Im (1,3-bis-(2,6-di-isopropylphenyl)-imidazolin-2-ylidene) and cAACMe (1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene) with PbI2 yielded the NHC-containing plumbylenes NHC·PbI2 (NHC = Me2ImMe (1), iPr2ImMe (2), Dipp2Im (3) and cAACMe·PbI2 (4)). Using the Pb(IV) compound PbCl2Ph2, the plumbane adducts NHC·PbCl2Ph2 (NHC = Me2ImMe (5), iPr2ImMe (6), Dipp2Im (7)) and cAACMe·PbCl2Ph2 (8)) were isolated in high yields. Reduction of the lead(IV) adducts 5 and 6 with excess KC8 afforded the diaryl substituted plumbylenes Me2ImMe·PbPh2 (9) and iPr2ImMe·PbPh2 (10), which are stable in the solid state but decompose in solution.