Low-Valent Group 14 Species Supported by BICAAC: Isolation of a Germylone and a Digermanium Compound.

Herein, we have disclosed the successful isolation and spectroscopic characterization of a series of bicyclic (alkyl)(amino) carbene (Me/iPrBICAAC) complexes of GeCl2 and SnX2; [MeBICAAC-GeCl2 (1); iPrBICAAC-GeCl2 (2); MeBICAAC-SnX2 (X = Cl (3); X = Br, (4))]. The in-situ KC8 reduction of GeCl2·dioxane in the presence of MeBICAAC led to the isolation of a zero-valent di-coordinated germylone [(MeBICAAC)2Ge] (5), whereas the reduction of adduct 2 afforded a trans-bent digermanium complex, [iPrBICAAC→Ge═Ge←iPrBICAAC] (6), having a Ge═Ge (2.3652(5) Å) double bond. Additionally, complexes 3 and 4 were reacted with diironnonacarbonyl Fe2(CO)9 to produce the corresponding Sn→Fe adducts 7 and 8, respectively. Further, attempts were made to convert the MeBICAAC-Sn adducts 3 and 4 to the corresponding tin-hydride complex, by treatment with LiBH4, however, in both the attempts, uncontrolled hydrogenation occurred to give the dihydrogented MeBICAAC complex, MeBICAAC(H2) (9). The solid-state structures of compounds 1-8 have also been elucidated using single-crystal X-ray diffraction technique. Further, computational investigations were performed to explain the bonding situation in 3-8 that establishes the ylidone character of 5, and supports the formation of 7-8 via donation of the lone pair at Sn to the Fe center.