Binding of CO and NH3 at a five-coordinate Ru(II) centre in the solid state and in solution.

The known five-coordinate, square-pyramidal, green trans-RuCl2(P-N)(PR3) complexes (P-N = o-diphenylphosphino-N,N'-dimethylaniline; R = Ph (1a), p-tolyl), in the solid state at ambient conditions, or in CDCl3 solution at low temperatures, coordinate CO (at 1 atm) to form beige-coloured trans-monocarbonyl derivatives. In the solution reactions at room temperature, the PR3 ligand dissociates and the yellow dicarbonyl complex RuCl2(CO)2(P-N) is formed as a mixture of trans,cis- and cis,cis-isomers. With use of (13)CO, the carbonyls complexes are characterized by variable temperature NMR and IR data, and (for the monocarbonyls) elemental analyses. Similarly, 1a and the dibromo analogue (1b) in the solid state bind NH3 to form the beige trans-monoammine species RuX2(P-N)(PPh3)(NH3), trans-4a (X = Cl) and trans-4b (X = Br), with cis P-atoms. The solution NH3 reactions, however, generate a species, speculatively thought to be the unusual, tight ion-pair, bisammine species [RuX(P-N)(PPh3)(NH3)2···X], 5a (X = Cl) and 5b (X = Br), in which a halide is considered strongly H-bonded to the cis-ammine ligands, although an alternative RuX(P-N)(PPh3)(NH3)2 formulation with a monodentate P-N ligand cannot be ruled out; dissolution in CDCl3 of isolated 5a and 5b, which are characterized by NMR, elemental analysis, and conductivity data, results in a partial, reversible loss of NH3 to form some cis- and trans-4a or -4b, respectively. Treatment of 5a with one mole equivalent of NH4PF6 in acetone solution removes the H-bonded chloride to give [RuCl(P-N)(PPh3)(NH3)2]PF6 (6), and this is converted by thermal loss of NH3 to generate the extremely air-sensitive, five-coordinate, ionic species [RuCl(P-N)(PPh3)(NH3)]PF6 (7). NMR evidence is presented for formation of the tris(ammine) species [Ru(P-N)(PPh3)(NH3)3](PF6)2 (8) via treatment of trans-RuCl2(P-N)(PPh3) with an atmosphere of NH3 in the presence of 2 mole equivalents of NH4PF6.

Comparative properties of coordinated H2 and H2S at a ruthenium(II) centre.

Thermodynamic data for the reversible formation of cis-RuCl2(P-N)(PPh3)(η(2)-H2) () from trans-RuCl2(P-N)(PPh3) in C6D6 are determined by variable temperature (31)P{(1)H} and (1)H NMR spectroscopy; P-N = o-diphenylphosphino-N,N'-dimethylaniline. Values of ΔH° = -26 ± 4 kJ mol(-1), ΔS° = -40 ± 15 J mol(-1) K(-1), and ΔG° (at 25 °C) = -13.8 ± 0.2 kJ mol(-1) are compared with recently reported data for the corresponding H2S adduct (4a), where the exothermicity is greater by ~20 kJ mol(-1), but this is counteracted by a more unfavourable entropy change, and overall the K and ΔG° values at 25 °C are close. For loss of H2 from 2a in the solid state, whose X-ray structure is presented, ΔH° is 50 ± 3 kJ mol(-1) as measured by Differential Scanning Calorimetry. The pKa values of the coordinated H2 (~11) and H2S (~14) are estimated by reactions of 2a and 4a with proton sponge (1,8-bis(dimethylamino)naphthalene) in CD2Cl2 at 20 °C; the mono-hydrido and -mercapto products are identified in situ. A corresponding H2O adduct is not deprotonated under the same conditions. Related dihydrido, mercapto and hydroxy species are formed by in situ reactions of 1a with NaH, NaSH, and NaOH, respectively.