Synthesis, Reactivity, and Coordination of Semihomologous dppf Congeners Bearing Primary Phosphine and Primary Phosphine Oxide Groups
Abstract
This contribution reports the synthesis of two phosphino-ferrocene ligands desymmetrized by an inserted methylene spacer, viz., a bis-phosphine combining primary and tertiary phosphine moieties in its structure, Ph(2)PfcCH(2)PH(2) [2], and a structurally unique, stable phosphine-primary phosphine oxide Ph(2)PfcCH(2)P(O)H(2) [7] (fc = ferrocene-1,1'-diyl). Compounds [2] and [7], together with 1,1'-bis(diphenylphosphino)ferrocene (dppf), the bis-tertiary phosphine Ph(2)PfcCH(2)PPh(2), and the adduct Ph(2)P(BH3)fcCH(2)PH(2) [6], were studied as ligands in Ru(II) complexes bearing auxiliary η(6)-arene ligands and both free ligands and the isolated complexes were structurally authenticated, using spectroscopic methods and X-ray crystallography, and further investigated by cyclic voltammetry.
The results suggest that distinct donor moieties in the unsymmetric ligands differentiate the otherwise identical coordinated metal centers and that the phosphine moiety in phosphine-phosphine oxide ligand [7] is preferably coordinated to Ru(II), before the phosphine oxide group, which must tautomerize into the hydroxyphosphine form prior to coordination.