Synthesis of phosphido-bridged multinuclear complexes via a mononuclear rhodium(I) compound: X-ray structures of Rh 3H(COD) 2(μ-CO) 2{μ-P(t-Bu) 2} 2 and [Fe(CO 3)](μ-CO){μ-P(t-Bu) 2}[Rh(CO){HP(t-Bu) 2}] (COD = 1,5-Cyclooctadiene)

Abstract

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(μ-H){μ-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)](μ-H){μ-P(t-Bu) 2}[Rh(CO){HP(t-Bu) 2}] ( 3) (46%) and dark red Rh 3H(COD) 2(μ-CO) 2{μ-P(t-Bu) 2} 2 ( 4) (25%). Reaction of 1 with Fe(CO) 5 in refluxing toluene yields orange crystalline [Fe(CO) 3](μ-CO){μ-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.