18078-18-7Relevant articles and documents
Tungsten-183 NMR study of cis-[W(CO)4(PPh3)(4-RC 5H4N)]; Effect of varying the σ donor strength of the pyridine
Carlton, Laurence,Mokoena, Lebohang V.,Fernandes, Manuel A.
, p. 199 - 202 (2013/05/09)
Tungsten-183 NMR data are reported for the complexes cis-[W(CO) 4(PPh3)(4-RC5H4N)] (R = H, Me, Ph, COMe, COPh, OMe, NMe2, Cl, NO2). The 183W chemical shift (obtained by indirect detection using 31P) is found to correlate with the Hammett σ function for the group R, with 183W shielding increasing approximately linearly with the donor strength of the pyridine over a range of 93 ppm. The X-ray structures of cis-[W(CO)4(PPh3)(4-MeOC5H4N)] and cis-[W(CO)4(PPh3)(4-PhCOC5H4N)] are also reported. Copyright
The oxidative addition of SnCl4 to [W(CO)4(NCMe)(PPh3)]. The X-ray crystal structure of [WH(CO)3(NCMe)(PPh3)2]- [SnCl5·MeOH]
Szymańska-Buzar, Teresa,G?owiak, Tadeusz,Czelu?niak, Izabela
, p. 1817 - 1823 (2008/10/08)
The oxidative addition reaction of SnCl4 with [W(CO)4(NCMe)(PPh3)] in acetonitrile gives a mixture of seven-]coordinate tungsten(II) compounds: [WCl(SnCl3)(CO)3(NCMe)(PPh3)] (1), [WCl2(CO)3(NCMe)(PPh3)] (2), [WCl(SnCl3)(CO)2(NC-Me)2(PPh3)] (3), and [WCl2(CO)2(NCMe)2(PPh3)] (4) identified by IR and NMR (1H, 13C{1H}, and 31P{1H}) studies. Treatment of [W(CO)4(NCMe)(PPh3)] with 1 equiv. of SnCl4 in CH2Cl2 solution besides compounds 1 and 2 also gives ionic species such as [HPPh3]+ and [SnCl6]2- and cationic tungsten(II) complexes. The crystal structure of one of these, [WH(CO)3(NCMe)(PPh3)2][SnCl5 ·MeOH] (5), has been established by single-crystal X-ray diffraction. The IR, 1H, 13C{1H} and 31P{1H} spectra of 5 are also described and can be correlated with the crystallographically observed geometry. A notable feature of 5 is the presence of an agostic interaction of the hydride ligand with one of the carbonyl ligands.
Electron-Transfer Catalysis. Radical Chain Mechanism for the Ligand Substitution of Metal Carbonyls
Hershberger, J.W.,Klingler, R.J.,Kochi, J.K.
, p. 3034 - 3043 (2007/10/02)
A novel chain process for the ligand substitution of metal complexes is revealed by bulk and transient electrochemical methods.The large turnover numbers that are obtained for the ligand substitution of the tris(acetonitrile) complexes of molybdenum and tungsten carbonyls with phosphines and isocyanides underscore the electrocatalytic phenomenon.The efficient chain process derives from the substitution lability of the cation radicals, which are formed by the one-electron oxidation of metal carbonyls and subsequently undergo rapid electron transfer, as in Scheme II.Th e driving force for ligand substitution is related to the relative stabilities of the cation radicals.Electron-transfer equilibria between these cation radicals can be evaluated from the standart reduction potentials E0 or the cyclic voltammetric peak potentials Ep.The initiation of the chain process is finely tuned to the value of E0 and Ep for the various metal carbonyls.The effectiveness of metal carbonyls as catalysts in the enhanced oxidation of nucleophiles such as triphenylphosphine is also described.
