Bend lengths ethylene

The first isolable alkenetitanium complex, the bis(pentamethylcyclopentadienyl)-titanium—ethylene complex 5, was prepared by Bercaw et al. by reduction of bis(penta-methylcyclopentadienyl)titanium dichloride in toluene with sodium amalgam under an atmosphere of ethylene (ca. 700 Torr) or from ( (n-C5Mc5)2Ti 2(fJ-N2)2 by treatment with ethylene [42], X-ray crystal structure analyses of 5 and of the ethylenebis(aryloxy)trimethyl-phosphanyltitanium complex 6 [53] revealed that the coordination of ethylene causes a substantial increase in the carbon—carbon double bond length from 1.337(2) A in free ethylene to 1.438(5) A and 1.425(3) A, respectively. Considerable bending of the hydrogen atoms out of the plane of the ethylene molecule is also observed. By comparison with structural data for other ethylene complexes and three-membered heterocyclic compounds, the structures of 5 and 6 would appear to be intermediate along the continuum between a Ti(11)-ethylene (4A) and a Ti(IV)-metallacyclopropane (4B) (Scheme 11.1) as... 

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