Nickel spectroscopic properties

Biomimetic chemistry of nickel was extensively reviewed.1847,1848 Elaborate complexes have been developed in order to model structural and spectroscopic properties as well as the catalytic function of the biological sites. Biomimetic systems for urease are described in Section 6.3.4.12.7, and model systems for [Ni,Fe]-hydrogenases are collected in Section 6.3.4.12.5. 

Many new Ni(II) complexes of aza-type macrocycles have been synthesized, and their redox chemistries have been explored. In particular, complexes of macropolycyclic ligands and bismacrocyclic ligands have been prepared. Complexes with uncommon oxidation states of nickel (Nim and Ni1 complexes) have also been synthesized by employing a specially designed macrocycle, and their characteristic spectroscopic properties and X-ray structures reported. These nickel(II) complexes... 

In Table 29 spectroscopic properties of selected six-coordinate nickel(II) complexes are shown. 

In general, all of the hexasolvates decompose rapidly when in contact with moisture. The formula and some spectroscopic properties of a number of representative complexes are reported in Table 77. All the complexes have been assigned a six-coordinate structure on the basis of electronic and IR spectra. The coordination of nickel(II) to the carbonyl oxygen is invariably indicated by the lowering of the CO stretching frequency compared with the frequency of the free ligand. 

Nickel has also been substituted into the active site of the enzyme.1390 Although the activity achieved was only about 12%, the spectroscopic properties are consistent with the nickel ions having entered the active site only, with the near tetrahedral geometry maintained. Attempted insertion of Nin into the non-catalytic sites was not successful. 

Redox reactions involving the nickel(IV) complex are also subject to divalent metal ion catalysis (170, 171). Oxidations of the two-electron reductant ascorbate (40) and the one-electron reductant [Fe(CN)6]4-(172) have been examined in some detail. Both reactions have as the rate-determining step the transfer of one electron from the reductant to nickel(IV) in an outer-sphere process to give an undetected nickel(III) transient. Spectroscopic properties of the nickel(III) species have been determined by pulse radiolysis (41). 

The structure and magnetic and spectroscopic properties of nickel(n) squarate dihydrate have been examined. The nickel is approximately octahedrally co-ordinated to four squarate oxygens and two water oxygens, the nickel lying on the edges of a cube with the squarate ligands on the cube faces.522... 

On treatment with aqueous silver nitrate it forms a stable crystalline complex (78), from which 75 can be recovered almost quantitatively by addition of ammonia ". Anhydrous nickel(ii) bromide converts cyclooctyne into the trimer (79) with a quantitative yield . However, when the reaction was carried out in the presence of a trace of water, the dimeric cyclobutadiene-nickel bromide complex (80) was obtained in 9-4% yield, together with 79 (85%) . The spectroscopic properties of 80 showed close similarity with those of the tetramethylcyclobutadiene-nickel chloride complex . 

The checkers observed a dark green solution after heating, and the green CH2C12 solution yielded blue crystals in a yield of 40%. These crystals had spectroscopic properties identical to those described above. The reaction failed with some sources of nickel(II) chloride. ... 

At variance with the easy accessibility of Ni(CO)4, the corresponding tetracarbonyls of palladium (0) and platinum (0), Pd(CO)4 and Pt(CO)4, have been identified only spectroscopically (IR) at low temperature, both being prepared by vaporization of the metal followed by reaction with CO in a solid matrix at about 20 K. These compounds decompose at higher temperature. Table 2 shows the IR spectroscopic properties of the tetracarbonyls of nickel, palladium, and platinum, as obtained by vaporization of the corresponding metal, measured under the same experimental conditions. The compounds show one carbonyl stretching vibration, as expected for the tetrahedral geometry. The values of v>co and the C-0 force constant of Pd(CO)4 are higher than those of both Ni(CO)4 and Pt(CO)4 (see Section Attempts have... 

Zhou ZH, Lin YJ, Zhang HB, Lin GD Tsai KR (1997) Syntheses, structures and spectroscopic properties of nickel(II) citrate complexes (NH,j)2[Ni(HcitXH20)j2-2H20 and (NH ) [Ni(Hcit)J-2H20. J Coord Chem 42 131-141... 

Owing to the advances in the synthesis of organoplatinum(ii) alkynyl compounds as well as the intriguing physical and photophysical properties exhibited by these materials, the evaluation of their structure-property relationship is therefore attractive and feasible. The spectroscopic properties of mononuclear nickel(ii), palladium(ii) and platinum(ii) alkynyl complexes of the type trans-[M(C=CR)2L2] (R = alkyl, aryl L = phosphine, stibine) have been widely investigated [111-114]. The electronic absorption spectra of this class of complexes have been reported by Masai et al. [115], while the emission properties of a series of closely related platinum(ii) complexes were reported by Demas and coworkers [116]. The lowest... 

Nickel(ll) is the only common d ion and its spectroscopic and magnetic properties have accordingly been extensively studied. 

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