Synthesis of the Tetradentate Phosphine α,α,α‘,α‘-Tetrakis(diphenylphosphino)-p-xylene (dppx) and Crystal and Molecular Structure of (CO)3Fe(dppx)Fe(CO)3

The tetradentate phosphine α,α,α‘,α‘-tetrakis(diphenylphosphino)- p -xylene ( 3, dppx) was prepared in two steps from α,α‘-bis(diphenylphosphino)- p -xylene ( 1 ) via the intermediate trisubstituted phosphine α,α,α‘-tris(diphenylphosphino)- p -xylene ( 2 ). The ligand, dppx, reacts with Fe 2 (CO) 9 to afford a bridging bischelated complex Fe(CO) 3 (dppx)Fe(CO) 3 ( 4 ), which was characterized by X-ray diffraction. Complex 4 crystallized in the monoclinic space group P 2 1 / n, a = 11.903(1) Å, b = 15.295(2) Å, c = 15.415(1) Å, β = 96.306(9)°, V = 2789.5(8)Å 3, Z = 2, R = 0.072, and R w = 0.079.