New Class of Fischer-Type Carbene Complexes Containing an <i>o</i>-Carboranyl Substituent. Synthesis and Crystal Structure of (CO)₅W[C(OMe)(PhC₂B₁₀H₁₀)] and (CO)₄(PhC₂B₁₀H₁₀)Mn[C(OCH₃)(CH₃)]

Abstract

Treating lithio-o-carborane RC2B10H10Li (3a,b R = CH3, C6H5) with metal carbonyl complexes M(CO)6 (M = Cr, W) followed by quenching the reaction with the electrophilic reagent [Me3O]+[BF4]- afforded the [(o-carboranyl)methoxycarbene]metal complexes (CO)5M[C(OMe)(RC2B10H10)] (1a−d) in yields ranging from 37 to 43%. Complexes 1a−d were also formed on reaction of alkynylcarbene complexes (CO)5M[C(OCH3)(C⋮CR)] (4a−d: M = Cr, W; R = CH3, C6H5) with B10H12L2 (5; L = CH3CN) in benzene in 47−63% isolated yield. The X-ray structure of complex 1d indicates that the tungsten atom is octahedrally coordinated by (o-carboranyl)methoxycarbene and by five carbonyl groups. Also, the synthesis of carbene complexes of manganese, bearing an o-carboranyl ligand, has been studied. Complexes (CO)5Mn(RC2B10H10) (6a,b: R = CH3, C6H5) easily react with CH3Li to give, after methylation of the acyl anion, new (o-carboranyl)metal carbene complexes (CO)4(RC2B10H10)Mn[C(OCH3)(CH3)] (2a,b: R = CH3, C6H5) in which the two functions are cis. X-ray analysis of this complex 2b provides support for the assignment of the metal carbene structure to the o-carborane derivatives.