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.