Binuclear diphosphine-bridged complexes with the tridentate ligand 2-(bis(diphenylphosphino)methyl)pyridine, (Ph2P)2CHC5NH4 = PNP, have been prepared for rhodium and iridium. Two of the complexes, [Rh2(CO)2(PNP)2](P-F6) 2·C3H6O (1) and [Ir2(μ-CO)(CO)2(PNP)2](BF4) 2 (2), have been characterized by single-crystal X-ray diffraction. Complex 1 crystallizes in the orthorhombic space group Pbcn with Z = 4, a = 19.658 (7) Å, b = 18.528 (7) Å, c = 17.993 (6) Å, V = 6554 (7) Å3, and d = 1.553 g/cm3 while 2 crystallizes in the triclinic space group P1 with Z = 4, a = 16.387 (4) Å, b = 16.710 (6) Å, c = 24.710 (6) Å, α = 76.03 (2)°, β = 84.16 (2)°, γ = 75.37 (2)°, V = 6347 (4) Å3, and d = 1.638 g/cm3. Both complexes are of the diphosphine-bridged binuclear type with trans phosphorus atoms and with both pyridyl nitrogen atoms bonded to the metal atoms, giving five-membered PN chelate rings. The pyridyl nitrogen atoms are bonded to the metals on the same side of the binuclear complex. Complex 1 is of the face-to-face variety with a Rh⋯Rh separation of 3.054 (1) Å while 2 has a bridging CO ligand and approximate trigonal-bipyramidal geometry around each iridium atom. The Ir-Ir separation in 2 is 2.815 (1) Å and is consistent with the presence of an Ir-Ir bond. Complex 2 easily loses one CO ligand in solution, affording the iridium analogue of 1. Reactions of these complexes with nucleophiles such as halide and sulfide ions are described. Thus, 1 reacts with Cl- in acetone solution, giving the four-coordinate PN-bonded monomeric compound [Rh(Cl)(CO)(PNP)], which has a dangling phosphorus atom, whereas the analogous reaction with 2 gives the binuclear complex [Ir2(Cl)(CO)2(PNP)2]+, which has one bonded and one free pyridyl nitrogen atom. The reaction of 1 with S2- gives the binuclear sulfide-bridged A-frame complex [Rh2(μ-S)(CO)2(PNP)2], which has both pyridyl nitrogen atoms dangling. All of these complexes have been characterized by IR and 31P NMR spectroscopy, and their syntheses and properties are described.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry