Exchange of boryl ligand substituents in Os[B(OEt)2]Cl(CO)(PPh3)2

Reaction between Os[B(OEt)(2)]Cl(CO)(PPh3)(2) and 1,2-ethanediol in the presence of Me3SiCl (1 equivalent) leads to the tethered boryl complex, [B(OEt)(OC2H4OH)] Cl(CO)(PPh3)(2) (1), in which one ethoxy substituent on the boryl ligand is exchanged with one hydroxy group of the 1,2-ethanediol leaving the other OH group available to coordinate to osmium, so giving a six coordinate complex. This formulation is confirmed by crystal structure determination. The same reactants, but with 2 equivalents of Me3SiCl, lead to the yellow, coordinatively unsaturated complex, Os(BOC2H4O)Cl(CO)(PPh3)(2) (2). Complex (2) adds CO to give Os (BOC2H4O) Cl(CO)(2) (PPh3)(2) (3). Crystal structure determinations of 2 and 3 reveal a very marked difference in the Os-B distances found in the five coordinate complex 2 (2.043(4) Angstrom) and the six coordinate complex 3 (2.179(7) Angstrom). In a reaction similar to that used for forming 2 but with 1,3-propanediol replacing 1,2-ethanediol, the product is OS(BOC3H6O)Cl(CO)(PPh3)(2) (4). The crystal structure for 4 is also reported. (C) 2004 Elsevier B.V. All rights reserved.