Electrophilic addition of CCl 4 to a cyclopentadienyl ligand in the tungstenocene carbonyl [W( η5-C 5H 5) 2(CO)] to give [W( η5-C 5H 5)( η4-C 5H 5-exo-CCl 3)(CO) Cl

Abstract

Reaction of the tungstenocene monocarbonyl complex [W( η 5-C 5H 5) 2(CO)] with an excess of CCL 4 at room temperature gives a 50% yield of an adduct which crystallizes in the monoclinic space group P 2 1/ n with a = 12.938(2) A ̊ , b = 6.724 (1) A ̊ , c = 16.226(3) A ̊ , β = 93.29(1)° . A single crystal X-ray diffraction study ( R F = 3.36%, R w = 3.32%) has established that the adduct is [W( η 5-C 5H 5)( η 4-C 5H 5-exo-CCl 3)(CO)Cl], with a trichloromethyl group bonded exo to the saturated carbon of an η 4-cyclopentadiene ligand and a dihedral angle between the plane containing this carbon and the mean plane of the butadiene residue of 35.3°. The 1 J C-H coupling constants of the four carbon atoms of the butadiene residue indicate an average hybridization of sp 1.9. The first step in the addition is proposed to involve electron transfer from the metal to fragment the CCl 4 into the trichloromethyl radical and the chloride anion. Exo addition of the trichloromethyl radical to an η 5-C 5H 5 ligand would then be followed by trapping of the 16-electron cationic intermediate by the Cl − anion.