Phosphinidene transition metal complexes: A combined ab initio MO-DFT study of Cr(CO)(5)-PR

Ab initio MO and DFT calculations have been performed on phosphinidene comp lexes of the type Cr(CO)(5)-PR, with R = H-r CH3, SiH3, NH2, PH2, OH, and S H. The formation of the Cr-P bond essentially arises from a ligand-to-metal charge transfer. While a significant pi backdonation is also observed for the Cr(CO)S-PH, Cr(CO)(5)-PCH3, and Cr(CO)(5)-PSiH3 complexes, this is less the case for Cr(CO)(5)-POH, Cr(CO)(5)-PSHr and Cr(CO)(5)-PNH2, and the bac kbonding almost disappears for Cr(CO)(5)-PPH2. In both the lowest lying sin glet and triplet states. all complexes exhibit a staggered conformation. CA SSCF/CASPT2 calculations performed with the ANO basis sets indicate a close d-shell singlet ground state along the whole series. The binding energy bet ween Cr(CO)(5) and PR ranges from 216 kJ/mol for Cr(CO)(5)-PNH2 to 127 kJ/m ol for Cr(CO)(5)-PSiH3 (B3LYP values). In general, the B3LYP-DFT scheme yie lds reasonable qualitative and quantitative results when compared with CASP T2(12/12).