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Mono and Dinuclear Tungsten Alkenyl‐Carbyne Complexes Bridged by Cyanide and Diisocyanide Ligands: Synthesis, Electrochemical‐ and 183 W‐NMR Studies
Author(s) -
Zhang Lei,
Gamasa M. Pilar,
Gimeno José,
Carbajo Rodrigo J.,
LópezOrtiz Fernando,
Guedes da Silva M. Fátima C.,
Pombeiro Armando J. L.
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(200002)2000:2<341::aid-ejic341>3.0.co;2-u
Subject(s) - chemistry , cyanide , isocyanide , acetonitrile , cyclic voltammetry , proton nmr , ligand (biochemistry) , electrochemistry , cationic polymerization , bridging ligand , stereochemistry , crystallography , carbon 13 nmr , polymer chemistry , inorganic chemistry , crystal structure , organic chemistry , electrode , biochemistry , receptor
Neutral trans ‐cyanide alkenylcarbyne complexes 2a and 2b have been prepared by reaction of the complex 1a and 1b with NaCN or [Bu 4 N]CN. The reaction of complexes 2a and 2b with an equimolar amount of the acetonitrile complexes 1a and 1b in CH 2 Cl 2 leads to the cationic cyanide‐bridged bis(alkenylcarbyne) di‐tungsten complexes 3a–d . Diisocyanide‐bridged bis(alkenylcarbyne) di‐tungsten complexes 4a and 4b have been synthesized by the reaction of complexes 1a and 1b with 0.5 equivalents of the diisocyanide 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 that in the dinuclear complexes 3a – d , the bridging CN group and the alkenylcarbyne units are located in trans positions, 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 alkenylcarbyne moieties are cis . The 183 W chemical shifts of complexes 2a , 2b , 3a – d , 4a , and 4b were obtained through two‐dimensional indirect 31 P, 183 W NMR recording techniques. A downfield shifting of 183 W resonances of the cyanide‐bridged dinuclear complexes 3a–d with respect to the mononuclear ones, 2a and 2b , was observed. The δ 183 W of isocyanide bridging dinuclear complexes 4a and 4b appear at higher field than those of the corresponding mononuclear cyanide 2a and 2b in accordance with the higher π‐acceptor electron properties of the isocyanide ligand. The electrochemical behaviour of all the complexes has been investigated by cyclic voltammetry and controlled potential electrolysis in aprotic media and at a Pt (or vitreous C) electrode. Complexes 1 , 2 , or 3 undergo multi‐electron irreversible oxidation processes involving anodically induced proton dissociation from the alkenylcarbyne ligands, and irreversible cathodic processes are also observed for all the complexes. The order of the redox potentials reflects that of the net electron π‐acceptor/σ‐donor character of the ligands and the ligating alkenylcarbynes are shown to behave as remarkably strong π‐electron acceptors (even stronger than CO).