Reactions of the dichloroboryl complex of osmium, Os(BCl2)Cl(CO)(PPh3)2, with water, alcohols, and amines -: Crystal structures of Os[B(OH)2]Cl(CO)(PPh3)2, Os[B(OEt)2]Cl(CO)(PPh3)2, and Os[BN(CH3)C6H4N(CH3)]Cl(CO)(PPh3)2

Reaction between the dichloroboryl complex, Os(BCl2)Cl(CO)(PPh3)(2), and water replaces both chloride substituents on the boryl ligand, without cleavage of the Os-B bond, giving yellow Os[B(OH)(2)]Cl(CO)(PPh3). (1). Compound I can be regarded as an example of a 'metalla-boronic acid' (LnM-B(OH)(2)) and in the solid state, X-ray crystal structure determination reveals that molecules of I are tetragonal pyramidal in geometry (Os-B, 2.056(3) Angstrom) and are arranged in pairs, as hydrogen-bonded dimers. This same arrangement is found in the crystalline state for simple boronic acids. Reaction between the dichloroboryl complex, Os(BCl2)Cl(CO)(PPh3)(2), and methanol and ethanol produces yellow Os[B(OMe)(2)]Cl(CO)(PPh3)(2) (2a) and yellow Os[B(OEt)(2)]Cl(CO)(PPh3)(2) (2b), respectively. The crystal structure of 2b reveals a tetragonal pyramidal geometry with the diethoxyboryl ligand in the apical site and with an Os-B bond distance of 2.081(5) Angstrom. Reaction between Os(BCl2)Cl(CO)(PPh3)(2), and N,N-dimethyl-o-phenylenediamine and N,N'-dimethyl-ethylenediamine produces yellow Os[BN(CH3)C6H4N(CH3)])Cl(CO)(PPh3)(2) (5) and yellow Os[BN(CH3)C2H4N(CH3)]Cl(CO)(PPh3)(2) (6), respectively. Compounds 1, 2a, 2b, 5, and 6 all react with carbon monoxide to give the colourless, six-coordinate complexes Os[B(OH)(2)]Cl(CO)(2)(PPh3)(2) (3), Os[B(OMe)(2)]Cl(CO)(2)(PPh3)(2) (4a), Os[B(OEt)(2)]Cl(CO)(2)(PPh3)(2) (4b), Os[BN(CH3)C6H4N(CH3)]Cl(CO)(2)(PPh3)(2) (7), and Os[BN(CH3)C2H4N(CH3)] Cl(CO)(2)(PPh3)(2) (8), respectively, but in the case of 6 only, this CO uptake is easily reversible. The crystal structure of 5 is also reported. (C) 2003 Elsevier Science B.V. All rights reserved.