Metal nitrosyl compounds

Selected Reactions of Metal Nitrosyl Compounds with Nucleophiles... 

The syntheses, structures and properties of wide varieties of metal nitrosyl complexes have been well documented [4, 5, 20-23]. However, the bulk of the complexes reviewed previously are of academic interest and only a few of these metal nitrosyl complexes have been considered as biologically effective NO donors. It was observed that the metal nitrosyls with significant NO+ character are subject to attack from a variety of nucleophiles and have hypertensive properties. This could be due to the strong trans- labilizing effect of NO. In contrast, the metal nitrosyl compounds with the general formula [M(CN)5NO]n, where the NO ligand was either neutral (for M = Co) or anionic (for M = Cr) showed no vasodilatory effect [24]. 

The results are consistent with the predictions of the ligand field theory and with the observed photochemical reactions. Bond bending distortions are observed in metal-nitrosyl compounds. The photochemical reactions of CotCCO NO and the photohydrogenation catalyzed by RhCPPhjJ NO provide indirect support for the bending. 

Periodic Table to justify the leaving of such slighted elements for a more advanced course taken by students with special interests in inorganic chemistry. Similarly, I have passed over many interesting but somewhat exotic compounds of the more usual elements (for example, the nitrides of sulfur, metallic nitrosyl compounds, heteropoly acids, and interstitial carbides and nitrides). 

In recent years transition metal nitrosyl compounds have attracted considerable interest, and several review articles have been published 1-11). This interest has been directed towards three main areas. 

Although a large number of transition metal nitrosyl compounds have been prepared 208), Mn3(77--Cp)3(NO)4 described in Section II, D is the only characterized nitrosyl cluster 130). King has isolated a compound for which he postulated the formula Fe2(NO)2[S2C2(CF3)2]2, but the mass spectra indicated the formulation Fe3(NO)4S[S2C2(CF3)2]2 240). 

A review of metal-nitrosyl compounds has been published. ... 

Coppens P, Novozhilova I, Kovalevsky A (2002) Photoinduced linkage israners of transition-metal nitrosyl compounds and related complexes. Chem Rev 102 861-884... 

ITie reaction of some dicyclopentadienyl lanthanide chlorides and some bis(meth-ylcyclopentadienyl) lanthanide chlorides with Na[WCp(CO)3] results in some complexes, stable up to 220°C, which are soluble in tetrahydrofuran and dimethylsulfo-xide. Other anionic metal carbonyl or metal nitrosyl compounds gave no satisfying results, mainly because of side reactions. Infrared spectra indicate polymeric structures containing isocarbonyl bridges (Crease and Legzdins, 1973b) ... 

Nitrosyls.—A product characterization and N-tracer study of the reaction of rra/u-[RuCl(NO)(diars)2] with nitrogen bases, for example hydrazine, indicates nucleophilic attack at the nitrosyl-N. Similarly, the reaction of azide ion with [RuCl(NO)(bipy)2] is thought to involve attack at the nitrosyl-N. The rate law for this reaction is first order in each reactant. Varying degrees of nitrosyl-protonation are involved in the following reactions of metal nitrosyl compounds with hydrogen chloride ... 

Structural studies of large molecules may be illustrated by cyclopentadienyl chromium dicarbonyl nitrosyl ( ) —C5 H5)Cr(CO)2NO, a simple piano-stool-type configuration. Interest in these metal-nitrosyl compounds arises since NO is a neurotransmitter. A study of various iso-tomers gives the overall molecular configuration and structure of Fig. 15. 

In the binding of NO to metal ions to afford metal-nitrosyl compounds (as they are referred to in a general manner), electrons are formally transferred from the NO ligand to empty d orbitals, while electron density from the metal ion d electrons can back-donate to NO 71 orbitals, providing for multiple me-tal-N-atom bonding character, just as in classical metal-carbonyl compounds [56]. Enemark and Feltham [46] developed an incredibly useful and widely used... 

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