Synthesis and characterization of isomeric 4- and 8-(σ-CH=CHPh)- closo-ruthenacarboranes with η~3:η~2- phosphacarbocyclic ligand

摘要

Reactions of [3,3-(PPh_3)_2-3-Cl-3-H-3,1,2-closo- RuC_2B_9H_(11)] (1) and its exo-nido isomer [exo-5,6,10-{Ru(Ph_3P)_2Cl}-5,6,10-(μ-H)_3-10-H-7,8-nido-C_2B_9H_8] (2) with NH_4PF_6 in methanol or ethanol solution followed by heating in the presence of an excess of phenylacetylene (3) affords a mixture of two isomeric closo species [3,3-{(1′-3′-η3):(5′, 6′-η~2)-ortho-C_6H_4PPh_2CHC(Ph)CHCHPh}-8-(σ-CHCHPh)-3,1,2-closo-RuC_2B_9H_(10)] (4) and [3,3-{(1′-3′-η~3): (5′,6′-η~2)-ortho-C_6H_4PPh_2CHC(Ph)CHCHPh}-4-(σ-CHCHPh)-3,1,2-closo-RuC_2B_9H_(10)] (5) in which boron vertexes in β- and α-sites with respect to the cage carbons bear the (E)-CHCHPh group. The X-ray diffraction study of 4 together with the multinuclear NMR data for 4 and 5 revealed that such an unusual η~3:η~2- phosphacarbocyclic ligand in both isomeric complexes is formed by specific insertion of the initially metal-bound PPh~3 group into the chain of two alkyne molecules coupled in a "head-to-tail" fashion around the metal vertex.