Synthesis and properties of mono- and dimetal Fischer multicarbene complexes derived from thiophene and thieno[2,3-b]thiophene
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Date
Authors
Lamprecht, Zandria
Van Jaarsveld, Nina Alletta
Bezuidenhout, Daniela Ina
Liles, David C.
Lotz, Simon
Journal Title
Journal ISSN
Volume Title
Publisher
Royal Society of Chemistry
Abstract
Access to multicarbene complexes of a fused thienothiophene substrate was obtained by the use of the
tetrabrominated thieno[2,3-b]thiophene precursor in a lithium–bromide exchange reaction, followed by
nucleophilic attack on metal hexacarbonyls (M = Cr, W). Subsequent alkylation afforded unique triscarbene
complexes [M(CO)4{{C(OEt)}2C6H1S2C(OEt)}M(CO)5] (M = Cr 12, W 13) featuring three non-equivalent
carbene ligands on a single thiophene linker, as well as the bischelated tetracarbene complexes
[M(CO)4{{C(OEt)}2C6S2{C(OEt)}2}M(CO)4] (M = Cr 14, W 15). The triscarbene complexes 12 and 13 are the
first examples of multi-alkoxycarbene complexes featuring three non-equivalent carbene ligands. The
reaction also afforded the chelated mononuclear biscarbene complexes [M(CO)4{C(OEt)}2C6H2S2] (M =
Cr 10, W 11) in low yields. Similarly, employing tetrabromothiophene as precursor yielded the mononuclear
chelate biscarbene complexes [M(CO)4{C(OEt)}2C4H2S] (M = Cr 6, W 7) and the dinuclear tetracarbene
complexes [M(CO)4{{C(OEt)}2C4S{C(OEt)}2}M(CO)4] (M = Cr 8, W 9). Modification of the classic
Fischer carbene synthetic methodology to a process of stepwise additions of lithiating agent and metal
carbonyls to thieno[2,3-b]thiophene, facilitates the formation of the mixed metal biscarbene complex
[W(CO)5C(OEt){C6H2S2}C(OEt)Cr(CO)5] 5, as analogue of the homonuclear biscarbene complexes
[M(CO)5C(OEt){C6H2S2}C(OEt)M(CO)5], (M = Cr 3, W 4). The monocarbene complexes [M(CO)5{C(OEt)-
C6H3S2}], (M = Cr 1, W 2) were also obtained in high yields, and the molecular structures of the tungsten
complexes, with the exception of 9 and 11, were confirmed by single crystal X-ray diffraction studies.
Description
Keywords
Nucleophilic attack, Multicarbene complexes, Fischer, Monocarbene complexes
Sustainable Development Goals
Citation
Lamprecht, Z, Van Jaarsveld, NA, Bezuidenhout, DI, Liles, DC & Lotz, S 2015, 'Synthesis and properties of mono- and dimetal Fischer multicarbene complexes derived from thiophene and thieno[2,3-b]thiophene', Dalton Transactions, vol. 44, pp. 19218-19231.