Disproportionation and Ligand Lability in Low Oxidation State Boryl‐Tin Chemistry**
Xiongfei Zheng, Agamemnon E. Crumpton, Andrey V. Protchenko, Andreas Heilmann, Mathias A. Ellwanger, Simon Aldridge
Abstract
Abstract Boryltin compounds featuring the metal in the+1 or 0 oxidation states can be synthesized from the carbene‐stabilized tin(II) bromide (boryl)Sn(NHC)Br (boryl={B(NDippCH) 2 }; NHC=C{(N i PrCMe) 2 }) by the use of strong reducing agents. The formation of the mono‐carbene stabilized distannyne and donor‐free distannide systems (boryl)SnSn(IPrMe)(boryl) ( 2 ) and K 2 [Sn 2 (boryl) 2 ] ( 3 ), using Mg(I) and K reducing agents mirrors related germanium chemistry. In contrast to their lighter congeners, however, systems of the type [Sn(boryl)] n are unstable with respect to disproportionation. Carbene abstraction from 2 using BPh 3 , and two‐electron oxidation of 3 both result in the formation of a 2 : 1 mixture of the Sn(II) compound Sn(boryl) 2 , and the hexatin cluster, Sn 6 (boryl) 4 ( 4 ). A viable mechanism for this rearrangement is shown by quantum chemical studies to involve a vinylidene intermediate (analogous to the isolable germanium compound, (boryl) 2 Ge=Ge), which undergoes facile atom transfer to generate Sn(boryl) 2 and trinuclear [Sn 3 (boryl) 2 ]. The latter then dimerizes to give the observed hexametallic product 4 , with independent studies showing that similar trigermanium species aggregate in analogous fashion.