Synthesis and properties of mono- and dimetal Fischer multicarbene complexes derived from thiophene and thieno[2, 3-b]thiophene. Issue 44 (21st October 2015)

• Record Type: Journal Article
• Authors: Lamprecht, Zandria; van Jaarsveld, Nina A.; Bezuidenhout, Daniela I.; Liles, David C.; Lotz, Simon
• Is Part Of: Dalton transactions. Volume 44:Issue 44(2015)
• Page Start: 19218
• Page End: 19231
• Publication Date: 2015-10-21
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c5dt03555d
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The syntheses, spectroscopic and structural properties of new mono- to tetracarbene mono- and dinuclear Fischer carbene complexes of (condensed) thiophene. 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)}2 C6 H1 S2 C(OEt)}M(CO)5 ] (M = Cr12, W13 ) featuring three non-equivalent carbene ligands on a single thiophene linker, as well as the bischelated tetracarbene complexes [M(CO)4 {{C(OEt)}2 C6 S2 {C(OEt)}2 }M(CO)4 ] (M = Cr14, W15 ). The triscarbene complexes12 and13 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)}2 C6 H2 S2 ] (M = Cr10, W11 ) in low yields. Similarly, employing tetrabromothiophene as precursor yielded the mononuclear chelate biscarbene complexes [M(CO)4 {C(OEt)}2 C4 H2 S] (M = Cr6, W7 ) and the dinuclear tetracarbene complexes [M(CO)4 {{C(OEt)}2 C4 S{C(OEt)}2 }M(CO)4 ] (M = Cr8, W9 ). 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)5 C(OEt){C6 H2 S2 }C(OEt)Cr(CO)5 ]5, as analogue of the homonuclear biscarbene complexes [M(CO)5 C(OEt){C6 H2 S2 }C(OEt)M(CO)5 ], (M = Cr3, W4 ). The monocarbene complexes [M(CO)5 {C(OEt)C6 H3 S2 }], (M = Cr1, W2 ) were also obtained in high yields, and the molecular structures of the tungsten complexes, with the exception of9 and11, were confirmed by single crystal X-ray diffraction studies.