L. Vaska

Carbon Dioxide Reduction via Homogeneous Catalytic Synthesis and Hydrogenation of N,N-Dimethylformamide.

Abstract : The previously reported catalytic reaction between CO2, H2, and (CH3)2NH to yield N,N-dimethylformamide (DMF) has been found to produce also trimethylamine (TMA) in the presence of several Ru, Os, Rh, Ir and Pt complexes. In separate experiments, the hydrogenation of DMF, catalyzed by the same or other complexes, also gave TMA. Thus, evidence is presented for the overall catalytic reduction of CO2 the the methyl group (-CH3, incorporated in TMA). Keywords: Carbon dioxide, Hydrogenation, Homogeneous catalysis, N, N Dimethylformamide, Ethyl radicals.

Reversible addition of carbon dioxide to rhodium and iridium complexes

Crystalline trans-[M(OH)(CO)(Ph3P)2](M = Rh, Ir) reacts with CO2 under normal conditions to form addition compounds, [(CO2)M(OH)(CO)(Ph3P)2], which, on pumping, release carbon dioxide and revert to the starting hydroxo complexes; the vibrational spectra of the bound CO2 indicate a substantial lowering of symmetry and bond order from those of the free molecule.

Luminescence of d8 complexes of iridium and rhodium, and its quenching by molecular oxygen and other gases

Certain cationic square-planar IrI and RhI complexes with chelating tertiary diphosphine ligands, [M(L–L)2]+, exhibit photoluminescence in the solid state at 25°, while their adducts with O2, CO, and H2 do not; emission and absorption spectra for a number of emitting compounds are compared, and some practical uses of the phenomena are suggested.

Reversible homogeneous catalysis of carbon dioxide hydrogenation/reduction at room temperature and low pressures

Abstract : A platinum complex, ?Pt2(u-PCP)3 (PCP = (C6H5)2PCH2P(C6H6)2, catalyzes the synthesis of N, N-dimehtylformamide (DMF) from CO2, H2 and (CH3)2NH in toluene solution at 25-100C and total pressures of 0.96-114 atm of the three reactant gases. The turnover numbers, DMF/complex/day, range from 9 at 25C and 0.96 atm to 1375 at 100 C and 114 atm. The homogeneous synthesis of DMF is readily reversible by either increasing the temperature, lowering the pressure of the reactants, or both, during the catalytic reaction. The formation of DMF appears to be dependent on the partial pressures of the individual reactants. Separate reactions of the three reactants with (Pt2(u-PCP)3) at ambient conditions (25C, 700 torr) give adducts with (CH3)2NH, but not with CO2 or H2. Keywords: Carbon Dioxide, Hydrogenation, Homogeneous Catalysis, N, N dimethylformamide, Platinum, Phosphine Complex.

Cyanotrihydroborato- and tetrahydroborato-complexes of rhodium and iridium

The synthesis and properties of air-stable hydroborato-complexes, trans-[MA(CO)(R3P)2][M = Ir, Rh; A = BH3(CN), BH4; R3P = tertiary phosphine] are reported; the co-ordination of BH3(CN)–, probably through the –NC group, is the first example of this anion acting as a ligand.

Reversible oxygenation of metal complexes: electronic and steric factors

The rates of oxygen addition to trans-[IrCl(CO)-(R3P)2](R3P = tertiary phosphine) and the stability of the resulting dioxygen adducts, [O2IrCl(CO)(R3P)2], increase with increasing basicity of the substituent R, provided the substituents have comparable structures; the geometry of R exerts a profound effect on the dynamics of these reactions.