Mono and Dinuclear Tungsten Alkenyl-Carbyne Complexes Bridged by Cyanide and Diisocyanide Ligands: Synthesis, Electrochemical- and 183W-NMR Studies
✍ Scribed by Lei Zhang; M. Pilar Gamasa; José Gimeno; Rodrigo J. Carbajo; Fernando López-Ortiz; M. Fátima C. Guedes da Silva; Armando J. L. Pombeiro
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 339 KB
- Volume
- 2000
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Neutral trans-cyanide alkenylcarbyne complexes 2a and 2b cyanide-bridged dinuclear complexes 3a-d with respect to the mononuclear ones, 2a and 2b, was observed. The δ 183 W have been prepared by reaction of the complex 1a and 1b with NaCN or [Bu 4 N]CN. The reaction of complexes 2a and of isocyanide bridging dinuclear complexes 4a and 4b appear at higher field than those of the corresponding 2b with an equimolar amount of the acetonitrile complexes 1a and 1b in CH 2 Cl 2 leads to the cationic cyanide-bridged mononuclear cyanide 2a and 2b in accordance with the higher π-acceptor electron properties of the isocyanide bis(alkenylcarbyne) di-tungsten complexes 3a-d. Diisocyanide-bridged bis(alkenylcarbyne) di-tungsten complexes ligand. The electrochemical behaviour of all the complexes has been investigated by cyclic voltammetry and controlled 4a and 4b have been synthesized by the reaction of complexes 1a and 1b with 0.5 equivalents of the diisocyanide potential electrolysis in aprotic media and at a Pt (or vitreous C) electrode. Complexes 1, 2, or 3 undergo multi-electron 1,4-(CN) 2 C 6 H 4 . IR as well as 1 H-, 31 P{ 1 H}-, 13 C{ 1 H}-, and 183 W-NMR data are reported. The spectroscopic data show irreversible oxidation processes involving anodically induced proton dissociation from the alkenylcarbyne ligands, and that in the dinuclear complexes 3a-d, the bridging CN group and the alkenylcarbyne units are located in trans positions, irreversible cathodic processes are also observed for all the complexes. The order of the redox potentials reflects that of while in the dinuclear complexes 4a and b, the isocyanide groups of the bridging ligand 1,4-(CN) 2 C 6 H 4 and the two the net electron π-acceptor/σ-donor character of the ligands and the ligating alkenylcarbynes are shown to behave as alkenylcarbyne moieties are cis. The 183 W chemical shifts of complexes 2a, 2b, 3a-d, 4a, and 4b were obtained through remarkably strong π-electron acceptors (even stronger than CO). two-dimensional indirect 31 P, 183 W NMR recording techniques. A downfield shifting of 183 W resonances of the sponding Fischer-type carbene derivatives have proven to [a] Instituto Universitario de Quı ´mica Organometa ´lica "Enrique clear complexes C (Scheme 1). Complexes of type A and B Moles" (Unidad Asociada al CSIC), Departamento de Quı ´mica Orga ´nica e Inorga ´nica, Facultad de belong to a new type of α,β-unsaturated carbyne dimetallic Quı ´mica, Universidad de Oviedo, derivatives in which the metal atoms are linked by a cyanide