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Photo-degradation studies on Di-η5-Cyclopentadienyldimethylvanadium, Di-η5-Cyclopentadienylmethylvanadium, Di-η5-Cyclopentadienyldimethylniobium, and some deuterated analogs

1980; Elsevier BV; Volume: 193; Issue: 2 Linguagem: Inglês

10.1016/s0022-328x(00)85618-1

1872-8561

Donald F. Foust, Marvin D. Rausch, E. Samuel,

Fluorine in Organic Chemistry

Abstract The photolysis of alkyl metallocene derivatives of vanadium and niobium in hydrocarbon solvents results in cleavage of the carbon—metal σ-bond. In the cases of (η 5 -C 5 H 5 ) 2 VCH 3 and (η 5 -C 5 H 5 ) 2 Nb(CH 3 ) 2 , only methane (>99%) is produced photochemically. (η 5 -C 5 H 5 ) 2 V(CH 3 ) 2 , prepared on a convenient new synthesis from (η 5 -C 5 H 5 ) 2 VCl 2 and methyllithium in toluene, degrades under photochemical conditions to yield both methane and ethane in a 2 : 1 ratio. The ethane arises from intra- and intermolecular methyl dimerization. Deuterium labeling studies have shown that the methyl group, the cyclopentadienyl ring, and the solvent are all sources of hydrogen in the formation of methane in these photolyses. The extent to which each source participates in the hydrogen abstraction process cannot be quantitatively determined because of the influence of an isotope effect. Chemical reactions with carbon monoxide during the photolyses give low yields of (η 5 -C 5 H 5 )V(CO) 4 from (η 5 -C 5 H 5 ) 2 VCH 3 or (η 5 -C 5 H 5 ) 2 V(CH 3 ) 2 , and of (η 5 -C 5 H 5 ) 2 Nb(CO)CH 3 from (η 5 -C 5 H 5 ) 2 Nb(CH 3 ) 2 .