Reactions of Ru-alkynyl Complexes with Electrophilic Boranes

The species CpRu(PPh3)2(CCPh) (1) reacts with HB(C6F5)2 to effect the hydroboration of the metal-bound alkyne, giving the orange species CpRu(PPh3)2CHC(Ph)(B(C6F5)2) (2) in 95% isolated yield. Subsequent photolysis of this species results in the rearrangement of the vinyl group to give the species CpRu(PPh3)[PhCC(B(H)(C6F5)2)] (3) in 87% yield. The species exhibits a side-on alkyne donation to Ru as well as a bridging BH fragment. Intermediates in this conversion are discussed in relation to known species, and support for a transient zwitterionic intermediate is offered by the isolation of CpRu(PPh3)2(CCPh(C6F4)BF(C6F5)2) (4) from the reaction of CpRu(PPh3)2(CCPh) with B(C6F5)3. The compounds 2–4 are crystallographically characterized.