Synthesis and hydroformylation reaction of dinuclear rhodium( I ) complexes with mixed bridging ligands. X-Ray structure of [Rh 2 (µ-pz)(µ-SBu t )(CO) 2 {P(OMe) 3 } 2 ]

The preparation and properties of dinuclear complexes containing one azolate (az) and one t-butylthio group as bridging ligands are described. Bubbling of carbon monoxide through dichloromethane solutions of [Rh2(µ-az)(µ-SBut)(η4-cod)2](cod = cyclo-octa-1,5-diene), followed by addition of phosphorus donor ligands (L) affords the complexes [Rh2(µ-az)(µ-SBut)(CO)2L2]. The crystal and molecular structure of cis-[Rh2(µ-pz)(µ-SBut)(CO)2{P(OMe)3}2](pz = pyrazolate) was determined from a single crystal by X-ray diffraction. Crystals are monoclinic, space group P21, with a= 10.789(2), b= 12.226 0(3), c= 10.431 4(2)Å, β= 110.515(1)°, and Z= 2. The final agreement factors were R= 0.036 and R′= 0.044. In the dinuclear complex each rhodium atom is in a distorted square arrangement. The dihedral angle of 63.1(2)° between the two co-ordination planes leads to a bent geometry with a rhodium–rhodium distance of 3.477 0(9)Å. The [Rh2(µ-az)(µ-SBut)(CO)2L2] complexes are good precursors for the hydroformylation reaction of olefins under mild conditions.