Studies on nucleophilic additions at bridging vinyl ligands in triosmium clusters

Abstract The bridging vinyl clusters [HOs 3 (CHCHR)(CO) 10 ] (R = H, Ph, or n-Bu) react with PMe 2 Ph to give the zwitterionic adducts [HOs 3 (CHCHRPMe 2 Ph)(CO) 10 ] which contain μ 2 -alkylidene ligands. The adducts are not formed so readily when R = Ph or n-Bu but most readily when polar solvents are used. All three CHCHR complexes add cyanide ion irreversibly to give the anionic clusters which were isolated as [N(PPh 3 ) 2 ][HOs 3 (CHCHRCN)(CO) 10 ]. There is infrared evidence for the addition of various other anions. Acid reverses the addition of methoxide but HCl reacts with the cyanide adduct [HOs 3 (CHCH 2 CN)(CO) 10 ] − to give [HOs 3 Cl(CO) 10 ] and EtCN. No evidence for nucleophilic addition at [HOs 3 (PhCCHPh)(CO) 10 ] was obtained.