SYNTHESIS AND STRUCTURES OF PHOSPHINE, PHOSPHIDO AND PHOSPHINIDENE DERIVATIVES OF TRIOSMIUM FROM REACTIONS OF (TERT-BU)2PH, (CYCLOHEXYL)2PH WITH OS3(CO)12

Photolysis of Os3(CO)12 and t-Bu2PH in toluene yields the trisubstituted phosphine cluster Os3(CO)9(t-Bu2PH)3 (1) (63%). Reaction of t-Bu2PH with Os3(CO)12 by heating in toluene (12 h) yields the disubstituted phosphine complex Os3(CO)10(t-Bu2PH)2 (2) (24%) and the bis-phosphido complex Os3(CO)8(μ-H)2(μ-t-Bu2P)2 (3) (50%). Compound 3 may be converted into the 46-electron complex Os3(CO)6(t-Bu2PH)(μ-H)2(μ-t-Bu2P)2 (4) by further heating in refluxing toluene with t-Bu2PH. Refluxing 1, 2, 3 or 4 in di-n-butylether (143°C) affords the phosphinidene complex Os3(CO)7(t-Bu2PH)2(μ3-t-BuP) (5) (68%). The reaction of dicyclohexylphosphine (Cy2PH) with Os3(CO)12 in refluxing toluene yields the tris-phosphido-bridged complex Os3(CO)7(μ-H)(Cy2P)3 (6) (60%). The structures of 1-6 have been determined via single-crystal X-ray diffraction studies. The molecular structure of 1 is based on that of Os3(CO)12 with the three t-Bu2PH ligands occupying equatorial sites on each osmium in order to minimize steric interactions. The structure of 2 has two t-Bu2PH ligands in equatorial positions arranged trans to each other across an OsOs bond. Complex 3 contains two bridging t-Bu2P- groups which lie above and below the Os3 plane. Two bridging hydrides occupy positions trans to these groups. The coordination geometry of each metal is roughly octahedral if one ignores the OsOs bonds. The structure of 4 is similar to that of 3 except that one CO groups has been replaced by an OS(CO)3 unit and the adjacent Os(CO)3 group now bears only two CO units. Complex 5 contains a μ3-capping phosphinidene group (t-BuP2-) in addition to two terminal phosphines (t-Bu2PH) on adjacent metal atoms. The structure of 6 features three bridging Cy2P- groups which lie above, in and below the Os3 plane. © 1990.