Electronic communication in dinuclear C4-bridged tungsten complexes

Sergey N. Semenov, Olivier Blacque, Thomas Fox, Koushik Venkatesan, Heinz Berke*

*Corresponding author for this work

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

The dinuclear tungsten carbyne [X(CO)2(dppe)WC 4W(dppe)(CO)2X] (dppe = 1,2-bis(diphenylphosphino)ethane; X = I (3), Cl (7)) complexes were prepared from the bisacetylide precursor Li2[(CO)3(dppe)WC4W(CO)3(dppe)] (2) via oxidative replacement of one CO group at each tungsten center with a halide substituent. The iodide ligand In 3 could be substituted with Isothiocyanate or triflate resulting In [X(CO)2(dppe)WC4W(dppe)(CO) 2X] complexes (X = NCS (8), OTf (9)). Substitution of two and all four CO ligands In 3 was achieved via subsequent photolytic or thermal activation with dppe. The "half-substituted" complex [I(CO) 2(dppe)WC4W(dppe)2I] (11) allows reversible one-electron oxidation which results In the monocatlonlc species [I(CO) 2(dppe)WC4W(dppe)2I][PF6] (11[PFe]). The "all-dppe substituted" complex [I(dppe)2WC 4W(dppe)2I] (10) possesses two reversible redox states leading to the stable monocationic [I(dppe)2WC4W(dppe) 2I][PF6] (10[PF6]) and the dicationic [I(dppe)2WC4W(dppe)2I][PF6] 2 (10[PF6]2) compounds. The complexes 2, 3, [W(CO)3(dppe)(C=CPh)(I)] (4), [X(CO)2(dppe)W=C-C(Me)=C(Me)C=W(dppe) (CO)2X] (X = I (5), Cl (6)), 7, 8, 10, 11 and 11[PF6] were characterized by single crystal X-ray diffraction. The electronic properties of complexes 10,10[PF6], 10[PF6]2, as well as of compounds 11 and 11[PF6], were Investigated using cyclic voltammetry (CV), EPR, IR, near-IR spectroscopy, and magnetization measurements. These studies showed that the [W]≡C-C≡C-C≡[W] canonical form of the bridged system with strong tungsten-carbon Interaction contributes significantly to the electronic coupling In the mixedvalent species 10[PF6] (comproportionation constant Kc = 7.5 × 104) and to the strong antiferromagnetic coupling In the dicationic complex 10[PF 6]2 (exchange Integral J = -167 cm-1). In addition, the rate for electron transfer between the tungsten centers In 10[PF6] was evaluated by near-IR and IR studies.

Original languageEnglish
Pages (from-to)3115-3127
Number of pages13
JournalJournal of the American Chemical Society
Volume132
Issue number9
DOIs
Publication statusPublished - 10 Mar 2010
Externally publishedYes

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