Complexes Derived from Strong Field Ligands. XVII. Electronic Spectra of Octahedral Nickel(II) Complexes with Ligands of the α-Diimine and Closely Related Classes

Homoleptic Nickel(II) Complexes of Redox-Tunable Pincer-type Ligands

“…As exemplified by the overlay of spectra for 1 , 6 , and 9 in the left of Figure 5 and as collected in Table 5, the second common set of bands in the spectra of 1 – 12 are lower-energy bands that are of similar shape and occur in the normal range (500 nm < λ max < 1000 nm) for d–d transitions of many other nickel(II) complexes with NiN 6 coordination. 31 The relatively high intensity ( ε ≈ 100–400 M −1 cm −1 ) of these lower energy bands as compared to typical d–d bands ( ε ≈ 1–100 M −1 cm −1 ) is suggestive of partial charge transfer character. TD-DFT calculations of 1 (right of Figure 5 and Supporting Information Table S5) support the assertion of partial charge transfer character in these bands.…”

“…Finally, as with most other nickel(II) complexes with distorted NiN 6 kernels, it is possible to evaluate the ligand field strength from the energy of the d–d bands with the aid of Tanabe–Sugano diagrams because the electronic effects arising from distortion from octahedral symmetry are generally small or negligible in room-temperature solution, especially for weaker-field ligands. 31 Notably the 12 current Ni(X,Y) 2 complexes have a nearly constant 10Dq value of 11 480(60) cm −1 , which is comparable to that found for nickel(II) complexes of other pyrazolyl-based ligands such as the tris(pyrazolyl)borates: Ni(Tp) 2 (10Dq = 11 900 cm −1 ), Ni(Tp*= tris(3,5-dimethylpyrazolyl)borate) 2 (10Dq = 11 400 cm −1 ), or [Ni(Tpm* = tris(3,5-dimethylpyrazolyl)-methane) 2 ] 2+ (10Dq = 11 700 cm −1 ). 32 Importantly, the constant value of 10Dq regardless of ligand substitution in these complexes reflects the weakness of any d π –p π interactions, in accord with the theoretical calculations.…”

Structure and Electronic Properties of an Expanded Terpyridine Complex of Nickel(II) [Ni(ddpd)2](BF4)2

“…Closely related pseudooctahedral nickel(II) complexes are [Ni(tpy) 2 ] 2+ ( 2 2+ ), [Ni(bipy) 3 ] 2+ ( 3 2+ ), and [Ni(phen) 3 ] 2+ ( 4 2+ ), (bipy = 2,2′‐bipyridine; phen = 1,10‐phenanthroline) (Scheme ).…”

Infrared and Electronic Spectral Studies of Cobalt(II) and Nickel(II) Complexes of N-Allyl Urea and N-Allyl Thiourea

“…These assignmen.ts are well supported by the excellent agreement between the calculated and experimental values of the v, band, obtained for the transition 3A2g + 3T1g(F) and also by the constancy of the ratio (3.0) of the values of V, and v,. In all our nickel(I1) complexes, the band assigned to v, around 14 000 cm-' has a double peak, characteristic of weak field complexes (21)(22)(23)(24)(25).…”