Synthesis and Structures of Low Valent Rhodium Complexes Bearing Diphosphinidenecyclobutene Ligands (DPCB)

摘要

There has been considerable recent interest in the coordination chemistry of low-coordinated phosphorus compounds. MO calculations on phosphaethene and related compounds suggested unique characteristics as ancillary ligands. The π* orbital level of the C=P double bond is much lower than those of C≡O and C=N bonds, while the nonbonding orbital including lone pair of electrons on the phosphorus is located at a high energy level, close to that of phosphine. Thus, phosphaalkenes are expected to stabilize low valent transition-metal complexes through the σ-donation and π-back donation interactions. We herein describe the synthesis and structures of low valent dirhodium complexes coordinated with 1,2-diphenyl-3,4-bis[(2,4,6-tri-t-butylphenyl)-phosphinidene]cyclobutene (DPCB) bearing two sp~2-hybridized phosphorus coordination sites.