SYNTHESIS OF PHOSPHIDO-BRIDGED MULTINUCLEAR COMPLEXES VIA A MONONUCLEAR RHODIUM(I) COMPOUND - X-RAY STRUCTURES OF RH3H(COD)2(MU-CO)2(MU-P(TERT-BU)2)2 AND [FE(CO3)](MU-CO)(MU-P(TERT-BU)2)[RH(CO)(HP(TERT-BU)2)] (COD=1,5-CYCLOOCTADIENE)

The mononuclear rhodium(I) complex trans-RhCl(CO){HP(t-Bu)2}2 (1) was used to form multinuclear complexes with P(t-Bu)2 bridges. Reaction of 1 with n-BuLi in THF yields yellow-orange crystalline [Rh(CO){HP(t-Bu)2}]2(mu-H){mu-P(t-Bu)2} (2) (74%). Reaction of a mixture of 1 and [Rh(COD)Cl]2 (COD = 1,5-cyclooctadiene) with n-BuLi in THF produces orange [Rh(COD)](mu-H){mu-P(t-Bu)2}[Rh(CO){HP(t-Bu)2}] (3) (46%) and dark red Rh3H(COD)2(mu-CO)2{mu-P(t-Bu)2}2 (4) (25%). Reaction of 1 with Fe(CO)5 in refluxing toluene yields orange crystalline [Fe(CO)3](mu-CO){mu-P(t-Bu)2}[Rh(CO){HP(t-Bu)2}] (5) (85%). The structures of 4 and 5 have been determined by X-ray crystallography. Complex 2 has been described elsewhere. The proposed structure of 3 has a planar core with a P(t-Bu)2 unit and a hydride bridging a metal-metal bond. One rhodium atom is further coordinated by a COD (1,5-cyclooctadiene) ligand, while the other rhodium atom bears a CO group and an HP(t-Bu)2 ligand. The molecular structure of 4 consists of a linear arrangement of three rhodium atoms with single metal-metal bonds bridged by P(t-Bu)2 and CO groups. The terminal rhodium atoms are coordinated by COD ligands. The molecular structure of 5 consists of a mixed metal dinuclear complex with a single Fe-Rh bond bridged by a P(t-Bu)2 unit and a CO group in a butterfly configuration. The rhodium atom is further coordinated by a CO and an HP(t-Bu)2 ligand. The iron atom bears three terminal CO groups.