The nature of the co-ordinate link. Part 11. Synthesis and phosphorus-31 nuclear magnetic resonance spectroscopy of platinum and palladium complexes containing side-bonded (E)-diphenyldiphosphene. X-Ray crystal and molecular structures of [Pd{(E)-PhPPPh}(Ph2PCH2CH2PPh2)] and [Pd{[(E)-PhPPPh][W(CO)5]2}(Ph2PCH2CH2PPh2)]
Abstract
The complexes cis-[MCl2L2] react with Li2(PhPPPh) to give [M(PhPPPh)L2][M = Pd, L2= 1,2-bis(diphenylphosphanyl)ethane (dppe), (1); M = Pt, L2= dppe or (PPh3)2]. Complex (1) reacts with [W(CO)5(thf)](thf = tetrahydrofuran) to give [Pd{(PhPPPh)[W(CO)5]2}(dppe)](2). Complexes were characterized by 31P-{1H} n.m.r. spectroscopy. X-Ray crystal-structure determinations of complexes (1) and (2) reveal nearly identical and planar PdP4 moieties comprising the donor atoms of L2 and η2-[(E)-diphenyldiphosphene] ligands. In (2) the two diphosphene lone pairs co-ordinate to W(CO)5 groups and the W–P bonds are bent 32° away from the Pd atom. The diphosphene P–P bond in (2)[2.186(6)Å] is 0.06 Å longer than that in (1)[2.121 (4)Å], which is similar to that in other diphosphene complexes and is approximately mid-way between the P–P single and double bond lengths. Small values of the coupling constants 1J(PtP) and 2J(PP) involving the diphosphene ligand indicate that the diphosphene uses electrons of low s character in η2-co-ordination.