Catalytic Dimerization of Terminal Alkynes by a Hafnium Carboranyl Complex. A “Self-Correcting” Catalyst
Organometallics1997Vol. 16(21), pp. 4508–4510
Citations Over TimeTop 10% of 1997 papers
Abstract
The dinuclear hafnium dicarbollide methyl complex (Cp*)(η5-C2B9H11)Hf(μ-η2:η3-C2B9H11)Hf(Cp*)Me2 (1; Cp* = C5Me5) catalyzes the regioselective dimerization of terminal alkynes RC⋮CH (R = Me, nPr, tBu) to 2,4-disubstituted 1-buten-3-ynes CH2C(R)C⋮CR. The selectivity for dimer rather than trimer or higher oligomers results from a “self-correcting” mechanism in which intermediate 8, which could potentially produce trimers or higher oligomers, undergoes an intramolecular cyclization reaction which ultimately yields the B-alkylated complex 6, which is too crowded to produce trimer in subsequent cycles.
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