Group 6 metal carbonyl complexes of tridentate olefinic tertiary diphosphines. Crystal and molecular structure of {(E)-1,3-Bis[2-(diphenylphosphino)phenyl]-propene}tricarbonyltungsten(0),W(CO)₃ {(E)-o-Ph₂PC₆H₄CH=CHC₆H₄PPh2-o}

Abstract

The ligands (L) (E)-2,2'-bis(diphenylphosphino)stilbene, (E)-o-Ph₂PC₆H₄CH=CHC₆H₄PPh2-o (bdps), (E)-1,3-bis[2-(diphenylphosphino)phenyl]propene, (E)-o-Ph₂PC₆H₄CH=CHCH₂C₆H₄PPh₂-o (bdpp), and (E)-1,3-bis[2-(diphenylphosphino)phenyl]but-1-ene,( E)-o-Ph₂PC₆H₄CH=CHCHMeC₆- H₄PPh₂-o (bdpb), form complexes of general formula M(CO)₃L (M = Cr, Mo, W). N.m.r. (¹H, ¹³C and ³¹P) and i.r. data indicate that the metal atoms are octahedrally coordinated by mutually trans phosphorus atoms and the double bond of the olefinic tertiary diphosphines and by meridionally disposed carbonyl groups. Conformational isomers of the complexes of bdpb can be detected by n.m.r, spectroscopy, but there is no evidence for similar conformers in the corresponding complexes of bdps and bdpp. The crystal and molecular structure of W(CO)₃(bdpp),0.5CH₂C₁₂ has been determined by single-crystal X-ray diffraction analysis. The crystals are triclinic, space group PI, with a 10.1 13(Z), b 13.820(2), c 14.512(3) A, α 76.24(1), β 88.08(1), γ 76.31(1)°. The structure, solved by the heavy-atom method and refined to a conventional R of 0.049 for 8418 diffractometer data, confirms the conclusions drawn from spectroscopic studies. The olefinic double bond of bdpp is attached symmetrically to the metal atom [W-C(olefin) 2.403(8), 2.387(9) Ǻ] and is roughly parallel to the P-W-P axis. The C=C bond length of 1.359(11) Ǻ is only slightly longer than that expected for the free ligand and is indicative of relatively weak metal-olefin back-bonding. Other important bond lengths are: W-P 2.450(2), 2.462(2) Ǻ and W-C(C0) 2.020(7), 2.024(7) Ǻ (CO trans to CO) and 1.971(7) Ǻ (CO trans to olefin).