Reactivity of a binuclear Ru(II) N2-bridged complex towards phosphines: facile access to novel mono and binuclear phosphorous derivatives. X-ray structural characterization of two unusual binuclear complexes containing ‘pincer’ ligands: [{RuCl2(η3-NN′N)}2(μ-η2-P2)] (NN′N=2,6-bis[(dimethylamino)methyl]pyridine; P2=1,3-bis[(diphenylphosphino)methyl]benzene or 1,3-bis(diphenylphosphino)propane)

A diazene-bridged diruthenium complex with structural restraint defined by single meta-diphosphinobenzene

Creation of confined coordination spaces with controlled flexibility is of importance in mimicking enzymatic reactions. We found that a simple, non-chelating 1,3-bis(diphenylphosphino)benzene (DPPBz) assembled two Cp*Ru units to give a dinuclear complex, wherein only one DPPBz supports an open framework without metal-metal bonding. Subsequent treatment with an excess of hydrazine resulted in formal 2e^-/2H⁺ transfer from hydrazine to afford a diazene-bridged complex featuring intramolecular NHCl hydrogen bonds. In constrast, a monophosphine failed to stabilize the diazene-bridged dinuclear structure due to the lack of the enforcement of the conformation.

Synthesis and characterization of two new "pincer" complexes of zinc(II). The X-ray crystal structures of the five coordinate complexes [ZnCl2{η3-NN'N-2,6-(R2NCH2)2C5H3N}] (R = n-Bu or Me)

The potentially terdentate NN'N donor ligand 2,6-bis[di-(n-butyl)aminomethyl]pyridine (1) does not form a stable, isolable Ru complex using any standard Ru starting materials. This is in contrast to the dimethylamino derivative 2. In the presence of Zn metal as a reducing agent, the treatment of hydrated ruthenium trichloride with 2 leads instead to the isolation of a diamagnetic Zn(II) complex (3) of general formula [ZnCl2(1)]. Analysis of 3 (NMR, X-ray) reveals the complex to be a mononuclear Zn halide compound containing ligand 1 in an η3-NN'N bonding motif. The Zn atom is found to be five-coordinate and in a geometry best described as midway between trigonal bipyramidal and square pyramidal in structure. Similar experiments using 2 produce an analogous Zn species (4) which has likewise been fully characterized (NMR, X-ray) and found to be similar to 3 although the metal is in a distinctly square pyramidal environment. These compounds are viewed as relatives of the class of Zn "pybox" catalysts.Key words: pincer complexes, zinc(II) compounds, X-ray crystal structure.