Reactions of co-ordinated ligands. Part 18. Ring-expansion reactions of tricarbonyl(η4-tetramethylcyclobutadiene)iron; molecular and crystal structures of [Fe{η4-C6Me4(CF3) 2}(CO)3] and [Fe{C8Me4(CF3)2O 2}(CO)3]

Alan Bond, Martin Bottrill, Michael Green, Alan J. Welch

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Abstract

Irradiation (u.v.) of a solution of [Fe(η4-C4Me4)(CO)3] and hexafluorobut-2-yne affords the arene tricarbonyl iron complex [Fe{η4-C6Me4(CF3) 2}(CO)3] identified by X-ray crystallography. The crystals are monoclinic, space group P21/n, Z = 4, in a unit cell of dimensions a = 13.377(5), b = 8.959(5), c = 13.544(6) Å, and β 100.54(3)°. A second product in the reaction is a bicyclic diketone [Fe{C8Me4(CF3)2O 2}(CO)3], which has also been structurally characterized by X-ray crystallography. The crystals are monoclinic, space group P21/n, Z = 4, in a unit cell of dimensions a = 9.031 (7), b = 17.865(16), c = 11.519(10) Å, and β 105.49(6)°. A similar irradiatron reaction between trifluoroethylene and [Fe(η4-C4Me4)(CO)3] afforded two isomeric η-cyclobutenyl complexes, one of which arises by a formal fluorine migration reaction and contains the arrangement FeCH(CF3)C. Thermolysis of this latter species results in a ring-enlargement reaction and the formatron of [Fe2(CO)44-C5Me 4(CF3)}]. A minor product in this reactrin is obtained in higher yield by carbonylation, and is formulated as a ring-expanded η3-C5Me4CO complex. The mechanism of formation of these products is discussed.

Original languageEnglish
Pages (from-to)2372-2381
Number of pages10
JournalJournal of the Chemical Society, Dalton Transactions
Issue number23
DOIs
Publication statusPublished - 1 Dec 1977
Externally publishedYes

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