No abstract

The lightly ligated complex [Ru 3 (CO) 8 (MeCN)(µ-H)(µ-C 2 Bu t )] (4), derived from [Ru 3 (CO) 9 -(µ-H)(µ-C 2 Bu t )](1), reacts with terminal alkynes and alkynols under very mild conditions to give high yields of products derived from addition of three molecules of alkyne/alkynol. More interestingly, complex 4 also reacts with diphenylacetylene to form the novel butadienylic species [Ru 3 (CO) 8 {µ 3 -η 8 -C(Bu t )dCC(Ph)dC(H)Ph}] (6), stabilized by an uncommon interaction between a phenyl substituent and a cluster metal atom. Its formation represents a key step in understanding the reaction mechanism leading to tri-and tetra-alkyne-substituted derivatives. The acetonitrile derivative of 6 reacts further with diphenylacetylene to afford the complex [Ru 3 (CO) 7 {µ 3 -η 8 -C(Bu t )dCC(Ph)dC(H)Ph}{µ 3 -η 4 -C(Ph)dC(Ph)}] (7), which, upon heating, isomerizes to give [Ru 3 (CO) 7 {µ 3 -η 8 -C(Bu t )dCC(Ph)dC(Ph)H}{µ 3 -η 4 -C(Ph)dC(Ph)}]-(2) in high yield. The analogous complex [Ru 3 (CO) 7 {µ 3 -η 8 -C(Bu t )dCC(Ph)dC(CPh 2 OH)H}-{µ 3 -η 4 -C(CPh 2 OH)dC (Ph)}] (8) is formed directly from 4 through reaction with 1,1,3triphenyl-2-propyn-1-ol. Finally, the tetra-alkyne-substituted metallacyclic complex [Ru 3 (CO) 6 -{µ 3 -η 6 -C(Bu t )CC(CPh 2 OH)CH 2 }{µ 3 -η 6 -CHC(CPh 2 OH)COC(CPh 2 OH)CH}] (5a), obtained from reaction of 1,1-diphenyl-2-propyn-1-ol with 4, undergoes facile dehydration in the presence of silica gel to yield the cluster complex [Ru 3 (CO) 5 (µ-CO){µ 3 -η 5 -CC(Bu t )OC(Ph) 2 CCH}{µ 3η 6 -CHC(CPh 2 OH)COC(CPh 2 )CH}] (9), a process that involves formation of an unusual heterocycle. In addition, complex 9 contains a terminal carbene unit, one of the first examples of such a ligand in a cluster complex. The structures of complexes 6, 8, and 9 have been determined crystallographically and are discussed in association with possible reaction mechanisms.