Addition reactions and rearrangements of 2,3-bis(diphenylphosphino)propene and its complexes with Group 6 metal carbonyls: routes to complexes of 1,2,3-tris(diphenylphosphino)propane

Abstract

The preparation of 2,3-bis(diphenylphosphino)propene (1) and its Group 6 metal tetracarbonyl complexes are described. The attempted base-catalysed addition of PR2H to (1) results in rearrangement to trans-1,2-bis(diphenylphosphino)propene (2) instead of the expected triphosphine. Under the same conditions the Group 6 metal carbonyl complexes of (1) can rearrange to complexes of the cis isomer of (2), but may also undergo the addition reaction to yield M(CO)4 complexes of the new ligand 1,2,3-tris(diphenylphosphino)propane by adjustment of the reaction conditions. These on heating yield the corresponding M(CO)3 complexes. Proton, 13C, and 31P n.m.r. spectral parameters of the new compounds are presented and are discussed in terms of metal- and backbone-mediated contributions and co-ordination chemical shifts.