Synthesis, Molecular Structure, and EPR Analysis of the Three-Coordinate Ni(I) Complex [Ni(PPh₃)₃][BF₄]

Abstract

The compound [Ni(PPh(3))(3)][BF(4)] x BF(3) x OEt(2) was isolated in crystalline form from the olefin oligomerization catalyst system Ni(PPh(3))(4)/BF(3) x OEt(2) and structurally characterized by X-ray diffraction. The influence of vibronic coupling on the EPR parameters of three-coordinate metal complexes with a 3d(9) electronic configuration was investigated within the framework of ligand field theory. Analytical expressions for g-tensor components and isotropic hyperfine coupling constants with ligand nuclei were obtained using first-order perturbation theory. It has been shown that the account of the vibronic interaction in the excited state predicts the existence of three-axial anisotropy of the g-tensor even at the level of first-order perturbation theory; two axes of the g-tensor located in a plane of three-coordinate structure can rotate about the main z axis when a compound is distorted by motion of ligands. It has been shown that in three points of the potential energy surface minimum, for which linear and quadric constants of the vibronic interactions have an identical signs, the HFS isotropic constant from one ligand is larger than HFS constants from the other two; for different vibronic constant signs the ratio between HFS constants varies on opposite. This theoretical researches are in the quality consent with experimental data for a three-coordinate Ni(I) and Cu(II) flat complexes.

The Role of Low Valent Transition Metal Complexes in Homogeneous Catalysis: An EPR Investigation

“…1) all displayed the opposite and less common trend of g 3 -g 2 \ g 2 -g 1 . The ligand influence on the g tensor, specifically the NHC, must override the effects of the vibronic interactions, similar to that described previously for [Ni(N^N) Me (CO)] [25]. Therefore the different NHC ring sizes (6-, 7-and 8-membered), the different substituents (mesityl or tolyl) and the different halide (Cl or Br) all affect the spin Hamiltonian parameters as seen from the observed changes in the EPR spectra (Fig.…”

“…Whilst the theoretical parameters of 4-, 5-and 6-coordinate Ni(I) centres are well accounted for [23,24], by comparison a strict theoretical description of 3-coordinate Ni(I) centres incorporating vibronic interactions are less straightforward to treat [25]. The spin Hamiltonian parameters for a limited number of 3-coordinate Ni(I) complexes, such as [Ni(PPh 3 ) 3 ] [BF 4 ], [Ni(PPh 3 ) 2 X] (X = Cl, Br), and [Ni(N^N)(L)] (where N^N = a bulky b-diketiminate and L = PCy 3 or dppm), have previously been reported and these typically display rhombic g profiles with the trend g 3 -g 2 [ g 2 -g 1 ( Table 1) [26][27][28].…”

Synthesis, Characterisation and Reactions of Truly Cationic NiI–Phosphine Complexes

“…Coordination environments with four phosphines were observed in [Ni(PMe 3 ) 4 ][B(C 6 H 5 ) 4 ] and [Ni(dppf) 2 ][PF 6 ] (dppf=1,1′‐Bis(diphenyl‐phosphino)ferrocene) . Examples for lower coordination numbers of phosphine ligands ( n <4) around the cationic nickel atom were realized in a reaction of Ni(PPh 3 ) 4 with BF 3 ⋅Et 2 O, yielding the trigonal‐planar homoleptic complex [Ni(PPh 3 ) 3 ][BF 4 ] . Even a linear coordination geometry was just achieved by Poulten et al.…”

Tris(tri-o-tolyl phosphite-κP)nickel: a coordinatively unsaturated nickel(0) complex

“…1. Table 2 (Dick et al, 1990) and monovalent [Ni(PPh 3 ) 3 ]BF 4 ÁBF 3 ÁOEt 2 (Saraev et al, 2008), which are the closest analogues available for comparison.…”