Nitric oxide, ligand effects

The compound Tr-CsHsNiNO is regarded as formed by a three-electron donation from the nitric oxide ligand. Most NO complexes are best considered as being formed by an initial one-electron transfer to the metal prior to donation from the nitrosonium ion (NO ). The nitric oxide ligand, a so-called odd molecule, is then effectively a three-electron donor. Such a bonding mode is supported by considerable infrared, ESR, and other structural data. It should be noted, however, that recent interpretation of ESR data in terms of MOT indicates that the nitric oxide ligand also can be described by the formal structures NO- and NO , in some complexes. 

Fe2(SR)2(CO)6], which are readily available from the reactions of R2S2 with [Fe3(CO)12] (33) and of RSH with [Fe2(CO)9] (34), can be nitrosylated in reactions which replace three carbonyl ligands by two nitrosyl ligands. Nitrosylation can be effected either by use of nitric oxide gas (27,29) or by use of sodium nitrite in aqueous ethanol (27) or, better, in dimethylformamide (DMF) (25). It is usually more convenient to employ nitric oxide if complexes of normal isotopic composition are required, but for 15N labeling the use of sodium nitrite in DMF is the more convenient and economical route. 

Martin E, Berka V, Bogatenkova E, Mnrad E, Tsai AL. Ligand selectivity of solnble guanylyl cyclase - Effect of the hydrogen-bonding tyrosine in the distal heme pocket on binding of oxygen, nitric oxide, and carbon monoxide. J. Biol. Chem. 2006 281 27836-27845. 

Nitrous oxide, N2O, is commonly used as a mild dental anesthetic and propellant for aerosols on atmospheric decomposition, it yields its innocuous parent gases and is therefore an environmentally acceptable substitute for chlorofluorocarbons. On the other hand, N2O contributes to the greenhouse effect and is increasing in the atmosphere. Nitric oxide, NO, is an effective coordinating ligand its function in this context is discussed in Chapter 13. It also has many biological functions, discussed in Chapter 16. 

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