Nitrogen nickel adducts

Reduction of both nickel porphyrins and thiaporphyrins to Ni1 species has been studied by EPR and 2H NMR spectroscopy.179, 2 58 The Ni1 complex of 5,10,15,20-tetraphenyl-21-thiaporphyrin has been isolated and characterized. Reaction of this complex with sulfur dioxide produced a paramagnetic five-coordinated Ni1 S02 adduct, while reaction with nitrogenous base ligands (amines, pyridines, imidazoles) yielded five- and six-coordinate complexes. In addition, the crystal structure of Ni1 diphenyldi-p-tolyl-21-thiaporphyrin has been determined. The coordination geometry about the nickel center is essentially square planar with extremely short Ni—N and Ni—S bonds (Ni—N = 2.015(2) A, 2.014(12) A, and 1.910(14) A and Ni—S = 2.143(6) A).2359... 

A novel approach to purine synthesis involves the use of ADC compounds as a source of one nitrogen atom in the five-membered ring.148 150 Treatment of 6-amino-l,3-dimethyluracil (94, R = H) with DEAZD gives the 5-substitution product (95, R = H). The N—N bond is cleaved by Raney nickel or formic acid, and ring closure to 1,3-dimethyluric acid is simply effected by heating.148 Whether the initial adduct is formed by a substitution... 

The addition of a-lithiomethoxyallene 144 [55] to benzaldehyde dimethylhydra-zone 145 (Eq. 13.48) leads to a mixture of pyrroline 146 and dihydroazete 147 [56]. The cydization in this case, which takes place in the same operation as the addition to the hydrazone, follows two distinct pathways, with attack of the nitrogen atom taking place at the inner, in addition to the terminal, carbon atom of the allene. A similar reaction of 144 with SAMP-hydrazone 148 (Eq. 13.49) leads to 3-pyrroline 149 in 88% yield and excellent diastereoselectivity [57]. Cleavage of the chiral auxiliary group from 149 takes place in two steps (1, methyl chloroformate 2, Raney nickel, 50 bar, 50 °C) in 74% overall yield. When the addition of 144 to 148 is conducted in diethyl ether, cydization of the adduct does not take place. Surprisingly, the hydrazones of aliphatic aldehydes react with 144 in poor yield in THF, but react quantitatively and diastereoselectively in diethyl ether to give the (uncyclized) allenyl hydrazone products. 

The S—Ni—S angle in Ni(ethyl-dtp)2 is decreased from 88 to 81.7° in Ni (ethyl-dtp). 2 pyridine and the S-P-S angle is increased from 103° in Ni(ethyl-dtp)2 to 110.4° in the pyridine adduct The nickel-nitrogen bond distance, 2.11 A, in Ni(ethyl-dtp)2 2 pyridine is normal for a neutral nitrogen ligand. However, adduct formation results in the increase of the Ni—S distance. The Ni—S bond distance is 2.21 A in Ni(ethyl-dtp)2 while it is 2.49A in the 6/s-pyridine adduct. 

Marshall, T., Fernando, Q. Thermodynamic constants of the adducts formed with heterocyclic nitrogen bases and nickel(II) dithiophosphates. Anal. Chem. 44, 1346 (1972). 

Cyclic silylphosphanes, see Silylphosphanes, phosphorus-rich, cyclic Cyclic sulfur-nitrogen compounds, see Sulfur-nitrogen compounds, cyclic Cyclic trithiolate ligand, 38 8-9 Cyclic voltammetry A. chroococcum Fd 1, 38 130-131 fullerene adducts, 44 19 nickel(ll) macrocyclic complexes, 44 112 Rieske proteins, 47 138, 139 Cyclidenes, as cobalt complex ligands, 44 282-284... 

Another arylation method, in the case of nitrogen heterocycles, does not need a halogenated derivative but a heterocycle activated by triflic anhydride260,261 (reaction 22). Simple aryl halides usually do not react with phosphines and special methods therefore have to be used for their arylation. The most widely used is the complex salt method , in which an aryl halide is heated with a phosphine in the presence of a transition metal such as nickel (II)2e (reaction 23). The catalytic cycle probably takes place by means of a reduced nickel(I) complex, generated in situ from the starting nickel(II) salt this nickel(I) species could undergo an oxidative addition of the aryl halide to yield a transient nickel(III) adduct, which after the reductive elimination of the aryphosphonium affords the recovery of the first active-nickel(I) complex (reaction 24). 

All of the organonitrile adducts of nickel(II) contain nickel(II) coordinated to six nitrogen atoms of the RCN molecules, as exemplified by the structure of [Ni(MeCN)s]2+ cation where the MeCN donor is coordinated in a nearly linear array (Ni—N—C angles average 172°) with Ni—N distances in the range 203-212 pm.1109... 

Adduct formation between nitrogen bases (py, substituted py, o-phen) and bis(mono-thio- 3-diketonato)nickel(ii) (137) in solution has been examined and equilibrium constants were determined. Electronic spectra point to a planar four-co-ordinate structure for the (137) complexes and a six-co-ordinate one for the adducts.585... 

The complexes with nickel(II), palladium(II), platinum(II), zinc(Il), cad-mium(II), mercury(II), and lead(II) and their adducts with nitrogen heterocycles have been described. The magnetic moment of the iron(III) complex is temperature-dependent owing to a spin-paired spin-free equilibrium. ... 

Bicyclo[2.1.0]pentane (7 equation 3) readily undergoes a cycloaddition across carbon-carbon double bonds in the presence of nickel(O) complexes. The mode is formally analyzed as a thermally forbidden [2 + 2] process and is in striking contrast to that of the lower homolog, bicyclo[1.1.0]butane, which suffers cleavage of two o -bonds and affords formal allylcarbene addition products. When a solution of bi-cyclo[2.1.0]pentane (7) and [Ni(AN)2] in excess methyl acrylate is heated at 40 C for 36 h under a nitrogen atmosphere, the stereoisomeric cycloadducts exo- and c/ product methyl 3-(cyclopent-2-enyl)propionate (10a 22%). Reaction of (7) with acrylonitrile affords the corresponding adducts (8b), (9b) and (10b). 

Some very interesting structural features exist for neutral jS-keto-enolate complexes (18) of the type M(AA)nLm. Adducts with nitrogenous bases or water have yielded a 5-coordinate irregular Zn(AA)2 H20 complex and trans 6-coordinate cobalt(II) and nickel (II) complexes M(AA)2 2B, with B = H2O or pyridine. The vanadyl complex, VO(AA)2, contains a square pyramid of oxygens about the metal, while U02(AA)2-H2O shows a pentagonal bipyramidal structure. The anhydrous material is dimeric. 

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