Coordination chemistry of stibine and bismuthine ligands

The Organometallic Chemistry of Halocarbonyl Complexes of Molybdenum(II) and Tungsten(II)

The complexes [MI2(CO)3(NCMe)2] (M=Mo or W) react with one molar equivalent of L in CH2Cl2 at room temperature initially to afford the mononuclear sevencoordinate complexes [MI2(CO)3(NCMe)L] which have been isolated for L-PPh3, AsPh3, SbPh3, PPh2Cy or P(OPh3)3. Many of these complexes dimerise to give the iodide bridged compounds [{M(μ−I)I(CO)3L}2]via displacement of acetonitrile. When L=PPhCy2, PCy3, PEt3 or P(OMe)3 only the dimeric complexes have been isolated. The ease of dimerisation of the mononuclear complexes [MI2(CO)3(NCMe)L] is discussed in terms of the electronic and steric effects of the ligands, L. Low temperature13C n.m.r. spectroscopy of the mononuclear [Wl2(CO)3(NCMe)(EPh3)](E=P or As) complexes are interpreted as suggesting the likely stereochemistry of these seven-coordinate complexes.

The reactions of [MI2(CO)3(NCMe)2] (M=Mo or W) with one equivalent of L(L-phosphorus, arsenic and antimony donor ligands) to afford [MI2(CO)3(NCMe)L] and [M(μ-I)I(CO)3L]2

Synthesis of some mixed seven-coordinate complexes of the type [MI2(CO)3LL′] (M = Mo or W;L = pyridine or substituted pyridines; L′ = PPh3, AsPh3 or SbPh3)

The reactions of [MI2(CO)3(NCMe)2] (M = Mo or W) with one equivalent of L (L = pyridine or substituted pyridines) to give [WI2(CO)3(NCMe)L] and [M(μ-I)I(CO)3L]2

Halogen oxidation of several LMo(CO)s andcis-L2Mo(CO)4 (L = Ph3P1Ph3As and Ph3Sb) derivatives has been studied. The LMo(CO)5 complexes react with halogens to give hexacoordinate LMo(CO)3 X2 (X = Cl, Br or I) derivatives which are of very rare occurrence. Similar reactions withcis-L2Mo(CO)4 give heptacoordinate L2Mo(CO)3X2 derivatives. The complexes have been characterised by elemental analysis, i.r. and conductivity measurements.

Devi P. Pandey

Papers

Halogen derivatives of triphenylphosphine, triphenylarsine and triphenylstibine substituted molybdenum carbonyls