The synthesis and structural characterization of Os3(CO)8[Si(OMe)3][?-PMe2(C6H4](?-H)2: An unusual unsaturated triosmium cluster complex

Abstract

The reaction of Os3(CO)10(NCMe)[Si(OMe)3](μ-H),1, with PMe2Ph yielded the new complex Os3(CO)10(PMe2Ph)[Si(OMe)3](μ-H),2 by substitution of the MeCn ligand with the phosphine ligand. When heated to 125°C compound2 was decarbonylated and transformed into the new unsaturated cluster complex Os3(CO)8[μ-PMe2(C6H4)][Si(OMe)3](μ-H)2,3 in 54% yield. Compound3 was characterized by a single crystal X-ray diffraction analysis, osmium bonds. The phenyl ring of the phosphine ligand has undergoneortho-metallation by a neighboring metal atom. A terminally coordinated Si(OMe)3 ligand is coordinated to the third osmium atom. The cluster is unsaturated by the amount of 2 electrons, and there is an open coordination site on the siloxyl substituted osmium atom that is partially filled by a weak interaction with one of the π-bonds of theortho-metalled phenyl ring. Complex3 reacts with CO at 1 atm to reform compound2 in 85% yield in 5 h at 40°C. Crystal Data: for3: space group = P21/n,a = 9.911(2) A,b = 18.451(6) A,c = 14.872(2) A,β = 95.64(2)°,Z = 4, 1994 reflections,R = 0.028.