Nickel complexes tetragonal

A crystal structure determination of [Pd(dtb)2] showed a distorted tetragonal arrangement of sulfur atoms about the palladium atom. The Pd—S distances in the square plane are 2.32-2.34 A, while the Pd—S (apical) distance is 3.46 A, suggesting some interaction. 47 The nickel complex [Ni(dtb)2] can be readily oxidized to [Ni dtbhSj], which was postulated to be a NiIV complex,136 but it is more likely that the complex contains Ni11 with the structure (42).146... 

Tetraaza macrocycles nickel complexes, S Tetragonality copper(II) complexes, 603 Theophylline cadmium complexes, 957 Thermolysin zinc, 1006 Thiabendazole metal complexes, 951 Tollen s reagent, 780 Transcription DNA polymerases, 1007 Trans effect... 

A crystal-structure determination on [Ni(PhCH2CS2)2] showed evidence of a Ni-Ni bond (Ni—Ni distance, 256 pm) in a bridging, acetate-cage, binuclear complex (363). Each nickel atom is 5-coordinate and is in a tetragonally distorted, square-pyramid spectroscopic evidence for a Ni-Ni bond has been obtained (364). The polarized crystal spectra showed more bands than predicted for a mononuclear, diamagnetic, square-planar nickel(Il), and the spectra are indicative of substantial overlap of the d-orbitals between the two nickel atoms. The bis(dithiobenzation)nickeKII) complex was found to exhibit unusual spectrochemical behavior (365). 

A quantitative consideration on the origin of the EFG should be based on reliable results from molecular orbital or DPT calculations, as pointed out in detail in Chap. 5. For a qualitative discussion, however, it will suffice to use the easy-to-handle one-electron approximation of the crystal field model. In this framework, it is easy to realize that in nickel(II) complexes of Oh and symmetry and in tetragonally distorted octahedral nickel(II) complexes, no valence electron contribution to the EFG should be expected (cf. Fig. 7.7 and Table 4.2). A temperature-dependent valence electron contribution is to be expected in distorted tetrahedral nickel(n) complexes for tetragonal distortion, e.g., Fzz = (4/7)e(r )3 for com-... 

Scheme 1 Electronic states involved in the absorbtion bands in the region of the first singlet—triplet intersection for octahedral, tetragonal and trigonal complexes of nickel(II).336 Solid arrows denote spin-allowed absorbtion transitions, dotted arrows connect pairs of interacting levels. (reprinted with permission from ref. 336 1998, American Chemical Society).

Nickel(III) peptide complexes have a tetragonally-distorted octahedral geometry as shown by electron spin resonance studies (19) and by reaction entropies for the Ni(III,II) redox couple (17). Axial substitutions for Ni(III)-peptide complexes are very fast with formation rate constants for imidazole greater... 

Nickel(n).—Complexes. A detailed examination of the cr stal field description of tetragonal nickel(ii) complexes revealed the possible existence of and... 

Platinum(II) compounds are to be found only towards the bottom of this scheme, palladium(II) reaches further up, its fluoride belonging to the tetragonal, paramagnetic class. Nickel(II) complexes cover the whole range of behavior, and may in addition be tetrahedral. 

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