Ambiphilic Nature of Dipyrrolylpyridine-Supported Divalent Germanium and Tin Compounds

We describe the synthesis and characterization of a series of divalent Ge and Sn compounds of the dianionic ligand L (2,6-bis(3,5-diphenylpyrrolyl)pyridine). Forcing base-stabilized divalent group 14 elements (E) into a planar geometry with a sterically constrained pincer-type L ligand is expected to produce LE species possessing ambiphilic properties, as suggested by theoretical calculations. The reactions of LH 2 (the acid form of L ) with 1 equiv of M(HMDS) 2 (HMDS = N(SiMe 3 ) 2 ) yield the dimeric compounds ( LE ) 2 (E = Sn ( 1 ) and E = Ge ( 3 )) in benzene or toluene. The dimeric species 1 and 3 react with Lewis bases to yield monomeric LSn(THF) 2 ( 2 ) and LE(dmap) 2 (E = Sn ( 4 ), Ge ( 5 ); dmap = dimethylaminopyridine) and with the Lewis acidic W(CO) 5 THF to form LSnW(CO) 5 ( 6 ). Finally, compounds 1 and 3 undergo insertion reactions with a Sn(I) distannyne to give the triple-decker products 7 and 8 .