STUDY OF THE BONDING PROPERTIES OF THE NEW LIGANDS C5H3N(2-R')(6-CH2PPHR) TOWARD RHODIUM(I) - EVIDENCE FOR A DYNAMIC COMPETITION FOR BONDING BETWEEN O-DONOR AND N-DONOR CENTERS WHEN R=O-ANISYL, R'=ME

The bonding properties of the optically active chiral-at-P polydentate ligands C5H3N(2-R')(6-CH2PPhR) (R = Me, R' = H, Me; R o-anisyl, R' = H, Me) and the achiral ligand C5H3N(2-Me)(6-CH2PPh2) toward (COD)Rh+ a re reported. The results show that steric hindrance of the 2-position of the pyridyl ring induces a labile character of the Rh-N bond. Moreo ver, for R = o-anisyl and R' = Me, a dynamic competition for bonding b etween the N-and O-donating centers is observed. Comparison of the sol id state structures of complexes [Rh(COD)(C5H4N(2-CH2PPhMe)][BF4] and [Rh(COD)(C5H3N(2-Me)(6-CH2PPh2)][BF4] shows a significant bond lengthe ning of the Rh-N bond in the latter complex, consistent with its fluxi onal behavior observed in solution.