Single crystal electronic spectra and ligand field parameters of some nickel(II) amine-isothiocyanato and amine-nitrito complexes

Abstract

The single crystal linearly polarized electronic spectra of tetragonal Ni(en)2(NCS)z and Ni(en)2(N02)z over the 8000-30000 cm™1 range have been reported and assigned. Ligand field parameters, Dq, Ds, and Dt, and angular overlap parameters, ea' and er' were derived from the assigned d-d spectra. These parameters have been compared with those of the respective tetragonal amine nickel complexes with known structure whose spectra were reliably assigned. The strong dependence of Dq on the metal-donor distance has been found for en and amine nickel complexes. The possibility of transferring the ea and tV parameters of the donor atoms, corrected for the appropriate distance, is also discussed.

The crystal structure and single crystal polarized spectra of trans-bis(trichloroacetato)bis(N,N-dimethylethylenediamine)cobalt(II)

“…We were thus able to extend the work of Bertini et 01. (5), thereby demonstrating a clear inverse correlation between metal ligand bond length and AOM u bonding parameters.…”

Mutual Influences of Ligands as Revealed by 2H NMR Shifts and the Angular Overlap Model Parameters: trans‐ and cis‐[CrX2(N)4]‐Type Complexes with Aliphatic Amine Ligands

“…[15] Another mutual influence or compensation due to the π donor-acceptor interaction of X-M-Y systems in a trans disposition has been theoretically claimed by Burdett, [16] although no such example has been reported so far. Such a mutual influence is expected to be found by examining the solvent-dependent 2 As shown in Figure 1, two well-separated 2 H NMR signals are observed due to paramagnetic isotropic contact shifts for inequivalent (axial and equatorial) deuterons in the ethylene backbone of trans-[CrF 2 (3,2,3-tet)] + (inset of Figure 1 2 θ relation for the paramagnetic contact shifts of Cr III complexes according to the following equation: [7] ∆δ = -(3 1/2 /2)(C·A) sin2φ, where C is a constant that varies reciprocally with absolute temperature, A is the hyperfine constant for the spin density of deuterons, and φ is the torsion angle of the Cr-N-C-C chain of the ethylene backbone in 3,2,3-tet. Since a plot of ∆δ vs. inverse temperature (1/T) gives a constant value, ∆δ is proportional to the spin density of the deuterons concerned, although, in view of the temperature-independent nature of sin2φ, there is no conformational change in 3,2,3-tet.…”

“…[1] General regularities in mutual influences for SP-4 platinum(II) complexes have been established, such as the trans influence, but for OC-6 mixed-ligand complexes they are limited to some trans-[MX 2 N 4 ]-type complexes where negative correlations have been found between the axial M-X and the basal M-N bond lengths both theoretically and experimentally by X-ray analysis and UV/Vis spectroscopy. [1][2][3][4][5] For example, Bertini et al [2] and Lever et al [3] have established negative linear correlations between Ni-N bond lengths and 10 Dq(N) or angular overlap model (AOM) parameter e σ (N) values, which represent the σ antibonding energy parameter, for some trans- [25] [a] Toyama National College [10 Dq xy (N)] increases, which they termed the "electronic cis effect". [4] Ito et al have studied this phenomenon extensively using the X-ray structural parameters of a series of Co III , Ni II , and Zn II macrocyclic tetraamine complexes [5] and a theoretical examination of the relationship between the softness of metal ions in terms of ab initio MO calculations.…”

“…This σ bond pathway gives more definite and clearer physical meaning to the negative correlation between the axial-basal bond length than the ligand-field parameter 10 Dq (∆) 4 ]-type complexes. [2][3][4][5][6] The change of e σ (N) associated with the variation of e σ (X) indicates the invalidity of transferring the AOM parameters from one complex to another.…”

“…The e σ value for the acac complex [e σ (acac)], for example, was estimated from its ∆δ value to be 6770 cm -1 which is smaller than that (7400-7700 cm -1 ) obtained spectroscopically and by AOM calculations for [Cr(acac) 3 ]. [28a] This may be due to the different number of acac ligands in the tris-(acac) and mono(acac) complexes as the spin-forbidden transition energy of [Cr(acac)(en) 2 ] 2+ [29] is larger than that of [Cr(acac) 2 …”