TRICYCLOHEXYLPHOSPHINECARBONDISULPHIDE 7-COORDINATE COMPLEXES OF MOLYBDENUM(II) AND TUNGSTEN(II)

The complexes [MI2(CO)3(NCMe)2] (M = Mo or W) react with one equivalent of S2CPCy3 in CH2Cl2 to afford the new seven-coordinate complexes [MI2(CO)3(S2CPCy3)]. Reaction of [MI2(CO)3(NCMe)2] (M = Mo or W), with two equivalents of S2CPCy3 afford the new dicatonic complexes [M(CO)3(S2CPCy3)2]2I in good yield. The dicationic nature of [W(CO)3(S2CPCy3)2]2I was confirmed by the formation of the complex [W(CO)3(S2CPCy3)2][BPh4]2 by iodide exchange with Na[BPh4]. Further reaction in situ of [M(CO)3(S2CPCy3)2]2I with one equivalent of S2CPCy3 afforded the tris ligand complex [W(CO)3(S2CPCy3)3]2I. The reaction of [W(CO)3(S2CPCy3)3]2I with Na[BPh4] in acetonitrile gave [W(CO)3(S2CPCy3)3][BPh4]2, which confirmed the dicationic nature of [W(CO)3(S2CPCy3)3]2I. The mixed ligand complexes [MI(CO)3(PPh3)(S2CPCy3)]I (M = Mo or W) and [WI(CO)3L(S2CPCy3)]I (L = P(OPh)3, AsPh3 or SbPh3) were synthesised by reaction of [MI2(CO)3(NCMe)2] with an equimolar quantity of L in CH2Cl2 followed by an in situ reaction with one equivalent of S2CPCy3. The cationic nature of [MI(CO)3(PPh3)(S2CPCy3)]I was confirmed by iodide exchange with Na[BF4] to afford the complexes [MI(CO)3(PPh3)(S2CPCy3)][BF4]. The reaction of two equivalents of [WI2(CO)3(NCMe)PPh3)] with S2CPCy3 afforded the ligand-bridged complex [W2I4(CO)6(PPh3)2(mu-S2CPCy3)]. Treatment of [WI2(CO)3(NCMe)2] with two equivalents of PPh3 followed by an in situ reaction with one equivalent of S2CPCy3 afforded the dicationic complex [W(CO)3(PPh3)2(S2CPCy3)]2I. The ionic nature of the complex was confirmed by iodide exchange with Na[BPh4] to give [W(CO)3(PPh3)2(S2CPCy3)][BPh4]2. Treatment of [W(CO)3(PPh3)2(S2CPCy3)]2I with one further equivalent of S2CPCy3 afforded the complex [W(CO)3(PPh3)2(S2CPCy3)2]2I. The low temperature C-13 NMR spectra (carbonyl region) of several seven-coordinate complexes are interpreted to suggest likely structures for these compounds.