143063-47-2Relevant articles and documents
Alkoxy-substituted group 6 allenylidene complexes - Synthesis and properties
Szesni, Normen,Weibert, Bernhard,Fischer, Helmut
, p. 617 - 632 (2006)
Bis(alkoxy)allenylidene complexes, [(CO)5MCCC(OR′)OR], as well as mono(alkoxy)allenylidene complexes, [(CO)5MCCC(OR′)Ph], of chromium and tungsten are accessible from propynones [HCCC(O)Ph] or propynoic acid esters [HCCC(O)OR; R = Et, (-)-menthyl, endo-bornyl] by the following reaction sequence: (a) deprotonation of the alkynes, (b) reaction with [(CO)5M-THF] (M = Cr, W), and (c) alkylation of the resulting alkynyl metallate, [(CO)5MCCC(O)R], with Meerwein salts. Vinylidene complexes, [(CO)5MCC(R′)C(O)OR], are formed as a by-product by Cβ-alkylation of the alkynyl metallate. Dimethylamine displaces one alkoxy substituent of the bis(alkoxy)allenylidene complexes to give dimethylamino(alkoxy)allenylidene complexes, [(CO)5MCCC(OR)NMe 2]. The analogous reaction of dimethylamine with a mono(alkoxy)-substituted allenylidene complex affords the aminoallenylidene complex [(CO)5CrCCC(NMe2)Ph]. When the amine is used in large excess, the α,β-unsaturated aminocarbene complex [(CO) 5CrC(NMe2)C(H)C(NMe2)Ph] is additionally formed by addition of the amine across the CαCβ-bond of the allenylidene ligand. The reaction of [(CO)5MCCC(OEt) 2] with dimethyl ethylenediamine offers access to bis(amino)allenylidene complexes, in which Cγ is part of a five-membered heterocycle. Photolysis of bis(alkoxy)allenylidene complexes in the presence of triphenylphosphine yields tetracarbonyl- and tricarbonyl{bis(phosphine)}allenylidene complexes. Diethylaminopropyne inserts into the CβCγ bond of [(CO) 5MCCC(OEt)OMethyl] to give alkenylallenylidene complexes. Subsequent acid-catalyzed intramolecular cyclization affords a pyranylidene complex.
