7-COORDINATE COMPLEXES OF MOLYBDENUM(II) AND TUNGSTEN(II) CONTAINING PYRAZOLE AS A LIGAND

Equimolar quantities of [MI2(CO)3(NCMe)2] (M = Mo or W) and C3H4N2 (py razole) react in CH2Cl2 at room temperature to give the iodo-bridged d imers [M(mu-I)(CO)3(C3H4N2)]2 (1) and (2). Two equivalents of C3H4N2 r eact with [MI2(CO)3(NCMe)2] (M = Mo or W) to give the bis(pyrazole) co mplexes [MI2(CO)3(C3H4N2)2] (3) and (4) in good yield. Three and four equivalents of pyrazole react with [MoI2(CO)3(NCMe)2] to give the cati onic complexes [MoI(CO)3(C3H4N2)3]I (5) and [MoI(CO)2(C3H4N2)4]I (6), respectively. The mixed ligand complexes [MI2(CO)3(C3H4N2)L] (M = Mo o r W; L = PPh3, AsPh3 or SbPh3) (7)-(12) are prepared by reacting equim olar amounts Of [MI2(CO)3(NCMe)2] and L in CH2Cl2 at room temperature, followed by an in situ reaction with one equivalent Of C3H4N2. The Mo SnCl3 complex [MoCl(SnCl3)(CO)3(C3H4N2)2] (13) is prepared in an analo gous manner using acetone as the solvent, whilst the mixed ligand comp ound [MoCl(SnCl3)(CO)3(C3H4N2)(PPh3)] (14) was prepared by treating th e dimeric complex [Mo(mu-Cl)(SnCl3)(CO)3(PPh3)]2 with two equivalents of C3H4N2. All the new complexes were characterised by elemental analy sis (carbon, hydrogen and nitrogen), i.r. and H-1 n.m.r. spectroscopy.