Synthesis and reactivity of the yttrium-alkyl-carbene complex [Y(BIPM)(CH2C6H5)(THF)] (BIPM = {C(PPh2NSiMe3)2})

Abstract

Reaction of [YI(3)(THF)(3.5)] with three equivalents of [KBz] (Bz = CH(2)C(6)H(5)) affords the tri-benzyl complex [Y(Bz)(3)(THF)(3)] () in excellent yield. Complex reacts with H(2)C(PPh(2)NSiMe(3))(2) (H(2)BIPM) to afford the yttrium-alkyl-carbene complex [Y(BIPM)(Bz)(THF)] (, BIPM = {C(PPh(2)NSiMe(3))(2)}). Compound reacts with one equivalent of benzophenone to give the alkoxy 1,2-migratory insertion product [Y(BIPM)(OCPh(2)Bz)(THF)] () rather than the alkene Wittig-product Ph(2)C[double bond, length as m-dash]C(PPh(2)NSiMe(3))(2). Reaction of with one or more equivalents of benzophenone does not afford any detectable alkene products, rather it apparently catalyses rearrangement of monomeric to afford dimeric [{Y(micro-BIPM)(OCPh(2)Bz)}(2)] (). Investigations reveal that formation of is proportional to the amount of benzophenone added, but the benzophenone is recovered at the end of the reaction. Reaction of with diphenyldiazene affords the 1,2-migratory insertion product [Y(BIPM){N(Ph)N(Ph)(Bz)}(THF)] () Compounds , , , , and have been variously characterised by X-ray crystallography, multi-nuclear NMR spectroscopy, FTIR spectroscopy, and CHN micro-analyses. Density functional theory calculations on reveal the HOMO to be localised at the Y-C(alkyl) bond which is commensurate with the observed reactivity.