The formation of sigma-phenylethynyl and sigma-diphenylbutenynyl complexesin the reaction of a-alkenyl ruthenium(II) complexes with phenylacetylene.The X-fay structure of a ruthenium(II) complex containing a sigma-phenylethynyl ligand

Ruthenium(II) complexes containing both sigma-alkenyl and n(2)-carboxylate ligands Ru(O2CR2)(CNCHR1)(CO)(PPh3)(2) (R-1=Bu-t, Ph; R-2=CH=CHCH=CHCH3) re act with phenylacetylene in two stages. Their reaction with an equivalent a mount of the alkyne led to the formation of sigma-alkynyl-containing ruthen ium(II) complex Ru(O2CR2) (C=CPh)(CO)(PPh3)(2)(R-2=CH=CHCH=CHCH3), the mole cular structure of which was established by X-ray diffraction. This sigma-a lkynyl complex then reacts with phenylacetylene to form a sigma-butenynyl-c ontaining compound Ru(O2CR2)(C(C equivalent to CPh)=CPhH)(CO)(PPh3)(2) (R-2 =CH=CHCH=CHCH3). Both reactions support the key role of alkynyl ligands in the dimerization of alkynes. (C) 1999 Elsevier Science S.A. All rights rese rved.