3,5-Dimethylpyrazolylphosphine molybdenum(0) and tungsten(0) carbonyl complexes

Abstract

Complexes with the general formula [L_nM(CO)_m], where [Formula: see text] x = 0–2, n = 1 or 2, M = Mo(0) or W(0), m = 3 or 4, were prepared by thermal or photolytic methods by the reaction of the appropriate 3,5-dimethylpyrazolyl phosphine ligand with M(CO)₆, norbornadienemetaltetracarbonyl [C₇H₈M(CO)₄], cycloheptatrienylmetaltricarbonyl [C₇H₈M(CO)₃], [(Me₂N(CH₂)₃NMe₂)M(CO)₄], [(CH₃CN)₂M(CO)₄], or [(CH₃CN)₃M(CO)₃]. Structural evidence indicates octahedral geometry about the metal atom centre, and several modes of coordination for the ligands in those complexes isolated and characterized. For x = 2, the ligand [Formula: see text] was monodentate, via phosphorus in [Formula: see text] and bidentate in [Formula: see text] where coordination by P and the 2N site of the pyrazolyl ring yielded four-membered [Formula: see text] metallocycles. For x = 1, the [Formula: see text] ligand was bidentate, via the phosphorus atom and one of the 2N sites of one of the pyrazolyl substituents, thus giving the four-membered [Formula: see text] metallocycle in [Formula: see text] and tridentate in [Formula: see text] where three facial CO's, two 2N atoms of the pyrazolyl rings, and a part of the phenyl ring occupy the six coordination sites. For x = 0, the P(Me₂pz)₃ ligand was tridentate via the 2N atoms of all three pyrazolyl rings, thus giving tricyclic systems [P(Me₂pz)₃M(CO)₃] (VIII, IX).