SYNTHESIS of INTRAMOLECULAR N-COORDINATED MAIN GROUP ORGANOSILYL METALLICS

Hydrosilanes (R₃Si-H) are powerful silylating agents in cooperation with transition metal complexes. In particular, hydrosilylation is effective with intramolecular coordinated silanes of type 1, easily activated through oxidative addition with low-valent transition metal centers affording complexes in which Si-M bond formation is accompanied by internal coordination that involves one or more donors.¹ In contrast, activation of intramolecular coordinated silanes 1 by main group elements (R₂M) are yet unknown.

Recently, it was shown by our group that silanes can be activated by main group organometallic reagents, R₂M (R=alkyl, M= Zn, Hg, Mg), via a radical mechanism.² In contrast, Si-H bond activation by RLi (R=alkyl) reagents are very rare.³

We now report that silanes 1 do not react with RLi reagents or R₂M separately (scheme, path a). However, upon addition of unsolvated tBuMe₂SiLi to 1 followed by addition of tBu₂Hg (scheme, path b) product 2 is obtained. 2 is a new type of intramolecular coordinated lithium-mercury “ate” complex. The X-ray structure and the NMR spectrum of 2 and its analogues will be discussed. The formation of 2 demonstrates, for the first time, the possibility to activate a Si-H bond by intramolecular coordination with main group organometallics.

¹ J. Takaya, S. Ito, H. Nomoto, N. Saito, N. Kirai and N. Iwasawa, Chem. Commun., 2015, 51, 17662—17665.

² T. Iwamoto, J. Okita, C. Kabuto, M. Kira, J.A.C.S, 2002, 124, 11604-11605.

³ R.Dobrovetsky, Y.Kratish, B.Tumanskii, M.Botoshansky, D.Bravo-Zhivotovskii, Y.Apeloig Angew. Chemie, 2012, 51, 4671-4675