Metal/metallic nitrosyls properties

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]. 

An alternative approach to describing the bonding in MY2 complexes is to consider the triatomic MY2 unit as a covalent inorganic functional group. Enemark and Feltham have shown that the diverse properties of metal nitrosyl complexes can be conveniently interpreted by describing the complexes as derivatives of the [MNO] group, where n is the total number of electrons in the rf-orbitals of the metal and the 7i -orbitals of the nitrosyl ligand. 

The first accurately documented example of a distinctly bent M-N-0 linkage in a metal nitrosyl complex was presented in 1968. Ibers showed that the cation [IrCl(CO)NO(PPh3)2] (Figure 2) possessed a square pyramidal structure with a metal-nitrosyl bond angle of 124°. Subsequently other species exhibiting similar structural properties have been reported. It has now become clear that there are essentially two distinct orientations in which nitric oxide may be complexed. In one case the ligand is coordinated linearly and in the other it is bent (angle approximately 120°) for structural data available on linear and bent nitrosyls see Tables 1 and 2 respectively. 

Madhani M, Patra AK et al (2006) Biological activity of designed photolabile metal nitrosyls light-dependent activatirai of soluble guanylate cyclase and vasorelaxant properties in rat aorta. J Med Chem 49 7325-7330... 

The MB spectroscopy is apphcable in investigating the stmctures of metal nitrosyls, as MNO electronic stmcmre is extremely sensitive to its coordination environment. It is particularly effective when the spectroscopic measurements are combined with the results of DFT calculations. The application of the MB parameters in the isomer shift calibration allows one to precisely estimate the Fe and NO spin populations (see, e.g., [121]). Recently DFT has become an increasingly popular tool to calculate structures and Mossbauer properties [118, 138]. MB... 

ABSTRACT. An approach is described to the design of potential molecular wires and switches by exploitation of results obtained in the study of non-linear optical properties of hetero- and homo-bimetallic based on combinations of femocenyl and metal nitrosyl fragments linked by polarisable bridges. 

Properties of Metal Nitrosyl Carbonyls 5-2.7 Substitution Reactions... 

In analogy to its complexes with nitrosyl cation (as described above), benzene can form donor-acceptor adducts with a variety of metallic and non-metallic Lewis acids. These lead to materials with novel optical and electrical properties that can be tuned through substituents on the aromatic ring. 

The thermal stability, structures and physical properties of various non-metal perchlorates (nitrosyl, nitronium, hydrazinium, ammonium, etc.) have been reviewed [1], Many organic perchlorates were examined for sensitivity to impact. The salts of cations containing only C, H and S exploded quite consistently, while those with C, H, and N, or C, H, N, and S did not explode, except 1,2-bis(ethylammonio)ethane diperchlorate [2],... 

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