104049-88-9Relevant articles and documents
Halide ligands - More than just σ-donors? A structural and spectroscopic study of homologous organonickel complexes
Klein, Axel,Kaiser, Andre,Wielandt, Wolfram,Belaj, Ferdinand,Wendel, Eric,Bertagnolli, Helmut,Zalis, Stanislav
, p. 11324 - 11333 (2009/05/15)
The isoleptic organonickel complexes [(bpy)Ni(Mes)X) (bpy = 2,2′-bipyridine; Mes = 2,4,6-trimethylphenyl; X = F, Cl, Br, or I, and for comparison X = OMe and SCN) have been investigated by multiple spectroscopic means. Their structures have been determined in part by single-crystal X-ray diffraction, the full series by extended X-ray absorption fine structure. The long-wavelength charge transfer absorptions (mainly metal-to-ligand charge transfer) obtain contributions from the mesityl coligand but are almost invariable upon variation of X. UV-vis spectroscopy allowed investigation of the solvolysis reaction [(bpy)Ni(Mes)X) + Solv ? [(bpy)Ni(Mes)(Solv)] + + X-, which occurs very fast for X = I (k = 0.176(4) M-1 s-1) or Br but very slow for X = Cl (k = 5.18(5) × 10-5 M-1 cm-1) or F. Quantum chemical (density functional theory) calculations on the geometry, electronic states, and electronic transitions (time-dependent density functional theory) are very helpful for detailed insight into the role the X coligands play in these complexes. The combination of methods reveals rather strong, highly covalent Ni-X bonds for all halide coligands but marginal π-donation.
Investigation of the reductive coupling of aryl halides and/or ethylchloroacetate electrocatalyzed by the precursor NiX2(bpy) with X-=Cl-, Br- or MeSO3- and bpy=2,2′-dipyridyl
Durandetti,Devaud,Perichon
, p. 659 - 667 (2008/10/08)
The mechanism of the coupling of aryl halides and/or ethylchloroacetate electrocatalyzed by the complex Ni(bpy) in DMF solutions has been reexamined using cyclic voltammetry, chronocoulometry and exhaustive electrolysis. The oxidative addition of aryl halides to Ni(bpy) yields two arylnickel(II) complexes which were characterized by the splitting of the reduction wave of the ArNiX(bpy) group. The second oxidative addition of aryl halides to the ArNi(bpy) complex involves an electron transfer. Biaryl results from a reductive elimination on the diarylnickel(III) complex. Metathesis of arylnickel(II) or direct reaction between ArNiX(bpy) and ethylchloroacetate may also occur. Values of some kinetic constants have been obtained and a discussion of the whole system is presented. CNRS-Gauthier-Villars.
Reactivity of Compounds and the Crystal Structure of
Coronas, Juan Maria,Muller, Guillermo,Rocamora, Merce,Miravitlles, Carles,Solans, Xavier
, p. 2333 - 2342 (2007/10/02)
A series of compounds of the type trans- (L=PMe2Ph, R=C2Cl3, R'=Ph, C6H4OMe-4, C6H4Me-2, or -4, C6H2Me3-2,4,6; R=C6H4Cl-2, R'=C6H4Me-2 or C6H2Me3-2,4,6; R=C6H2Me3-2,4,6, R'=C6H4Me-2 or Ph; L=PEt3, R=C2Cl3, R'=C6H4Me-2, Ph, C6H4OMe-4, C6H4Cl-4, or C6H4Me-4; R=C6H4Cl-2, R'=Ph, C6H4Me-2 or-4; R=C6H4Me-2, R'=Ph, or C6H4Me-4; R=C6H2Me3-2,4,6, R'=C6H4Me-2) and cis- (bipy=2,2'-bipyridine) have been prepared.The proton n.m.r. signals of the ortho methyls of the mesityl ligand in the most hindered compound of the series appear overlapped despite the asymmetry of C2Cl3.The crystal structure of this compound indicates that this may be due to the phosphine aromatic rings.Ligand-exchange reactions of PMe2Ph by PEt3 in benzene,/ ->/, are complete in 0.5 h at room temperature, no intermediates being observed.The reverse process requires reflux for 10 h and in this case the intermediates can be obtained.If the groups R and R' contain ortho substituents the reaction does not take place.In refluxing benzene under nitrogen the stability of the organometallics containing PMe2Ph is greater than those with PEt3.Decomposition takes place via reductive elimination to give R-R' or via homolytic cleavage to give R-H and R'-H, the most favoured pathway depending on the size and electronegativity of the groups R and R'.The reductive-elimination process involves a previous step in which a phosphine group is lost.The addition of CO to solutions of (when R and R' possess ortho substituents) results in decomposition of the organometallics giving RCOR'.The compound is also decomposed but gives R-R'.When one ligands (R) contains an ortho substituent the corresponding two isomers (syn and anti) of the acyl derivative can be detected.The compounds cis- show a favourable associative decomposition pathway when R and R' are strong donor ligands.
