Abstract
Two new 2-[bis(diphenylphosphino)methyl]pyridine (PNP) complexes of rhenium have been synthesized. Re2(η2,η2-PNP)(CO)8 was synthesized from Re2(CO)8(μ-H)(μ-CH=CHC4H9) and an excess of PNP in CH2Cl2 solution. Re2(η2,η2-PNP)(CO)8 was characterized by IR, mass, and 1H, 31P, and 13C NMR spectroscopies. The structure of Re2(η2,η2-PNP)(CO)8 is based on Re2(CO)10 in which one eq-CO on each Re has been replaced with phosphino groups from the bridging PNP ligand. The pyridyl group is not coordinated. Re2(η2,η2-PNP)(CO)8 thermally decarbonylates in toluene solution to afford Re2(μ-PPh2)(μ-η1,η 4-CHPPh2C6H4N)(CO)7 in high yield. Re2(μ-PPh2)(μ-η1,η 4-CHPPh2C5H4N)(CO)7 was characterized spectroscopically and by a single-crystal X-ray diffraction [P, a = 10.906 (10) Å, b = 18.164 (9) Å, c = 10.973 (6) Å, α = 98.56 (5)°, β = 119.12 (6)°, γ = 94.14 (8)°, Z = 2, D = 1.951 g cm-3, R = 0.045]. The molecular structure was found to consist of two octahedral rhenium centers joined by a μ-PPh2 ligand and a μ-C5H4NCHPPh2 (PN) moiety. These two bridges are the fragments that result when the coordinated PNP in Re2(η2,η2-PNP)(CO)8 undergoes P-C bond activation. The PN group chelates in a bidentate manner to one Re and is σ-bonded via the methine C to the other Re. No Re-Re bond exists (4.189 Å).