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The water-soluble phosphine complex of ruthenium(II), cri-RuC^PTAL (3), has been prepared by the reduction of RuCls in ethanol in the presence of the air-stable phosphine l,3,5-triaza-7-phosphaadamantane (2). Complex 3 is an effective catalyst for the regioselective conversion of unsaturated aldehydes to unsaturated alcohols using a biphasic aqueous/organic medium with sodium formate as the source of hydrogen, thus affording facile catalyst recovery and recycle. Both aromatic and aliphatic aldehydes were reduced to the corresponding alcohols. The formate ion was shown to directly be the hydrogen source by deuterium labeling experiments. The rate of hydrogenation of benzaldehyde was found to be first order in catalyst concentration, first order in substrate concentration (in the low-concentration regime), and independent of formate concentration at concentrations > 2.5 M. The reduction process was greatly retarded by the presence of excess phosphine ligand. The apparent activation energy determined was 23.9 kcal mol"1. A catalytic cycle was proposed which involves the rapid formation of a ruthenium hydride formate complex followed by phosphine dissociation and aldehyde addition in a slower step. Subsequent formation

The syntheses of a variety of group 10 metal complexes of the water-soluble phosphine triazaphosphaadamantane (PTA) are described. Treatment of Ni(NO3)2 with NaNO2 and PTA provides the nitrosyl complex [Ni(NO)(PTA)3]NO3 (1). Complex 1 is soluble in water, DMSO, and CH3CN but insoluble in THF, acetone, or hydrocarbons. X-ray crystallography shows the nitrosyl ligand to be coordinated in a near linear mode (∠Ni−N−O = 171.5(4)°) with a Ni−N bond length of 1.653(4) Å. Concordantly, the υ(NO) vibration in H2O occurs at 1830 cm-1. The series of zerovalent M(PTA)4 (M = Ni, Pd, Pt) complexes, 2, 3, and 6 have been prepared in good yields by several procedures:  (i) the ligand exchange reaction of Ni(cod)2 with PTA; (ii) the reduction of PdCl2 or PtCl2 with hydrazine in the presence of PTA; and (iii) the ligand exchange reaction of Pt(PPh3)4 with PTA. All three derivatives are very water soluble (0.30 M) and resistant to PTA dissociation in solution at ambient temperature. Complexes 2, 3, and 6 can be crystallized from 0.10 M HCl to afford the nitrogen-protonated derivatives, [M(PTAH)4]Cl4. These salts were characterized by X-ray crystallography and shown to exist as slightly distorted tetrahedra with one nitrogen atom of each PTA ligand protonated. The M−P bond lengths are shorter than those found in related derivatives containing poorer electron-donating and/or sterically more encumbering phosphine ligands. The cis-MCl2(PTA)2 (M = Pd and Pt) derivatives, 4 and 7, were obtained by the metathesis reaction of (NH4)2PdCl4 or K2PtCl4 with PTA in refluxing ethanol. When the palladium reaction was carried out in a large excess of PTA, formation of the zerovalent Pd(PTA)4 complex occurred via the intermediacy of the [Pd(PTA)3Cl]+ cation as indicated by 31P NMR and mass spectrometry. The X-ray structures of the Pd(II) and Pt(II) derivatives, cis-PdCl2(PTA)2 and [cis-PtCl2(PTAH)2]Cl2, revealed these to exist as slightly distorted square planar complexes where the P−M−P angles are expanded to 94.4°. The platinum derivative, which contains the nitrogen protonated PTA ligands, displays an extensive array of hydrogen bonding and electrostatic interactions involving water, PTA, and HCl.

Molecular hydrogen, obtained by water electrolysis or photocatalytic water splitting, can be used to store energy obtained from intermittent sources such as wind and solar power. The storage and safe transportation of H2 , however, is an open and central question in such a hydrogen economy. Easy-to-synthesize, water-soluble iridium-N-heterocyclic carbene-phosphine (Ir(I) -NHC-phosphine) catalysts show unprecedented high catalytic activity in dehydrogenation of aqueous sodium formate. Fast reversible generation and storage of hydrogen can be achieved with these catalysts by a simple decrease or increase in the hydrogen pressure, respectively.

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The new water-soluble cis-mer-[IrH2Cl(mtppms)3] (mtppms = monosulfonated triphenylphosphine) was employed as a catalyst for selective decomposition of formic acid to H2 + CO2 in aqueous solution at T = 30-100 °C. The easily synthesized compound showed high catalytic activity (TOF up to 298 000 h(-1)) and could be reused several times with no loss of activity (total TON = 67 650). A sharp maximum in the reaction rate was observed at pH = 3.75; its coincidence with the pKa of formic acid shows that both H(+) or HCOOH and HCOO(-) play important roles in the reaction mechanism.

have equal configuration at the metal centre, were the only diastereomers detected. In solution, a diastereomerisation process between both isomers occurs, where the equilibrium constant depends on the solvent, amino acidate, and metal. The different localisation of the polar groups (NH or NH 2 moieties) on the molecular surface of the two diastereomers (1 and s) provides a qualitative explanation for the different diastereomer stability observed in solution. The new chiral trimers catalyse the reduction of unsaturated aldehydes to unsaturated alcohols by hydrogen transfer from aqueous sodium formate and the reduction of acetophenone by hydrogen transfer from 2-propanol with up to 75 % ee.