Reactivity of gold and copper acetylide with a secondary borane.

Gold(I) triphenylphosphine phenylacetylide reacts with bis(1-methyl-ortho-carboranyl)borane to give a hydroboration product that is best described as an η2-1-borataallene gold complex. Contrarily, the analogous reaction with the copper acetylide undergoes transmetalation to furnish an alkynylborate with the CuPPh3+ moiety bound to the alkyne and a hydride bridging boron to copper. The compounds were analyzed by single crystal X-ray diffraction and DFT computations that rationalize the unusual bonding arrangements.