Nickel-phenyl group

A transition-state structure was proposed on the basis of the solid-state structure of [Ni((R,R)-DBF0X)(H20)3](C104)2 (Fig. 1.8). The catalyst-dienophUe complex is thought to be a square-bipyramidal structure containing an octahedral nickel ion. The dienophile adopts an s-cis conformation with the si face shielded by a phenyl group. 

Simple alkyl and aryl derivatives of nickel(II) with monodentate phosphines are, in general, too unstable to be isolated in the solid state as pure compounds. However, it has been found that a considerable stabilization occurs when the carbon cr-bonded to nickel(II) is part of either an alkynic group, a fluorinated or chlorinated group, or an orf/io-substituted phenyl group. 

On the basis of complexes which were found to contain sulfur donors one can draw the conclusion that the coordination of SR-, S2- and S2 species to nickel(II) in complexes with triphos, pp3 and np2 is possible only in coordination sites unoccupied by phosphine donors which are able to form strong covalent bonds as sulfur does. Moreover, the phenyl groups on the phosphorus atoms surround the sulfur atoms, preventing their non-bonded electron pairs from forming bonds with nickel atoms and forming polynuclear sulfides. 

Although the phenyl group does not appear to provide sufficient activation when the nickel complex is used, it does activate the disilane in a system involving a palladium complex, as reported by Tsuji and co-workers in 1992.50 Under carbon monoxide pressure, which is required to maintain... 

The reduction equivalents required for conversion of N2 to NH3 are obtained from the carbanionic phenyl groups bonded to nickel in 14 (biphenyl formation). The Ni atoms, which are still present as Ni(0), i.e., in the form of metallic nickel after hydrolysis, only function as agents for the transfer of electrons from C6H5 to N2. In this respect, the hydrolysis of... 

Structure (75). Lithiuni(l) seems to have a tetrahedral environment, being surrounded by two nickel atoms, one nitrogen of the Nj moiety, and an ether oxygen. Lithium(2) is in the center of a trigonal-planar grouping composed of a nickel atom, a phenyl group [bridging Li(S) of the other... 

With a view to preparing polymerizable complexes, thiophene-substituted nickel-dithiolene complexes [Ni(L)(L )] have been synthesized and used to prepare films by electrochemical polymerization. The features of the complexes and of the polymers depend on the number of thiophene substituents. In particular, the complex with four thiophene substituents (L = L = thpdt, 12) shows a narrower HOMO-LUMO gap as compared to complexes with two thiophene and two phenyl groups or four phenyl groups [Xmax, nm (e, M- cm- ) 976 (38800) L = L = 12 931 (37700) L = 12, L = 9, R = Ph 866 (30900) L = L = 9, R = Ph] and gave a polymer whose electrochemical features are similar to those of poly[l,2-di(2,5-thienylene)ethane], suggesting that similar extended chains are formed"". 

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