Comparisons of solid-state and solution structures of rhodium carbonyl (R3P)2Rh(CO)Cl complexes with monodentate phosphole and phosphine ligands

Abstract

(R[sub 3]P)[sub 2]Rh(CO)Cl complexes have attacted considerable attention. They are catalysts for hydroformylation of alkenes and the nature of the phosphine strongly influences the linear to branched ratio of the aldehyde products. More recently, they have been found to be good catalysts for photolytically promoted C-H bond activation, and their catalytic activity decreases with increasing steric bulk of the phosphine. trans-[(Bu[sup t])[sub 2]PR][sub 2]Rh-(CO)X complexes exhibit hindered rotation about the Rh-P bond in solution as shown by dynamic [sup 31]P NMR studies. [(t-Bu)[sub 3]P][sub 2]-Rh(CO)Cl crystallizes as a distinctly non-planar molecule with considerable tetrahedral distortion. (Ph[sub 3]P)[sub 2]Rh(CO)Cl crystallizes in both monoclinic and triclinic forms, and, also as an orthorhombic CH[sub 2]Cl[sub 2] solvate. Phospholes such as 1-phenyl-3,4-dimethylphosphole (DMPP) and 1-phenyldibenzophosphole (DBP) are phosphorus donors with unusual donor properties. Their (DMPP)[sub 2]Rh(CO)Cl and (DBP)Rh(CO)[sub 2]Cl complexes have been previously described. The analogs (1-phenylphosphole)[sub 2]-Rh(CO)Cl and (3-methyl-1-phenylphosphole)[sub 2]Rh(CO)Cl are among the few examples of such complexes that have been reported to exhibit cis-trans isomerism. As part of continuing programs of investigation of the structure and properties of transition metal phosphole complexes and the utility of CP/MAS [sup 31]P([sup 1]H) NMR spectroscopy for solid-state structural determination, the authors now report on themore » solution and solid-state characterization of four trans-R[sub 3]P[sub 2]Rh(CO)Cl complexes. Wu and Wasylishen only recently reported the CP/MAS [sup 31]P NMR spectrum of (Ph[sub 3]P)[sub 2]Rh(CO)Cl at the same time as this study was nearing completion.« less