Reversible addition of tin(II) amides to nitriles.

Lappert's stannylene (Sn[N(SiMe 3 ) 2 ] 2 ) has been reacted with various nitriles, dinitriles and trinitriles with the formation of heteroleptic amidotin(II) amidinates of the general formulae [RC(NSiMe 3 ) 2 ]SnN(SiMe 3 ) 2 , R'{[C(NSiMe 3 ) 2 ]SnN(SiMe 3 ) 2 } 2 and R''{[C(NSiMe 3 ) 2 ]SnN(SiMe 3 ) 2 } 3 , where R = Ph (1), 2-(CN)-C 6 H 4 (2), 3-(CN)-C 6 H 4 (3); R' = 1,3-C 6 H 4 (4), 1,4-C 6 H 4 (5) and R'' = 1,3,5-C 6 H 3 (6). The reactions of amidotin(II) benzamidinate 1 with an excess of benzonitrile proceed to homoleptic tin(II) bis(benzamidinate) [PhC(NSiMe 3 ) 2 ] 2 Sn, which reversibly eliminates benzonitrile and 1 when warmed. The premise of reversibility has been supported by a multinuclear time-dependent NMR study and a theoretical (DFT) description. On the other hand, magnesium(II) bis(benzamidinate) [PhC(NSiMe 3 ) 2 ] 2 Mg (8) and lanthanum(II) tris(benzamidinate) [PhC(NSiMe 3 ) 2 ] 3 La (7) have been synthesised from appropriate metal hexamethyldisilazides and benzonitrile.