Nitrosyl effect

NO induces a strong hydridic polarization of the Re-H bond in nitrosyl hydrides, the nitrosyl effect . The conjugation of these properties enables them to perform the heterolytic cleavage of H2 and RsSi-H bonds as depicted in Scheme 35 as well as the insertion of Re-H bonds into polar unsaturated organic substrates. ... 

Rose Ml, Mascharak PK (2008) Photoactive ruthenium nitrosyls effects of light and potential application as NO donors. Coord Chem Rev 252 2093-2114... 

Jiang Y, Schirmer B, Blacque O, Fox T, Grimme S, Berke H (2013) The Catalytic Nitrosyl Effect NO bending boosting the efficiency of rhenium based alkene hydrogenations. J Am Chem Soc 135(10) 4088-4102... 

Equations 1-10 illustrate some mild methods that can be used to cleave amides. Equations 1 and 2 indicate the conditions that were used by Woodward and Eschenmoser, respectively, in their synthesis of vitamin B12. Butyl nitrite, nitrosyl chloride, and nitrosonium tetrafluoroborate (NO BF4 ) have also been used to cleave amides. Since only tertiary amides are cleaved by potassium -butoxide (eq. 3), this method can be used to effect selective cleavage of tertiary amides in the presence of primary or secondary amides.(Esters, however, are cleaved by similar conditions.) Photolytic cleavage of nitro amides (eq. 4) is discussed in a review. 

The current example illustrates PVDOS formulation as an effective basis for comparison of experimental and theoretical NIS data for ferrous nitrosyl tetraphe-nylporph3Tin Fe(TPP)(NO), which was done [101] along with other ferrous nitrosyl porphyrins. Such compounds are designed to model heme protein active sites. In particular, the elucidation of the vibrational dynamics of the Fe atom provides a unique opportunity to specifically probe the contribution of Fe to the reaction dynamics. The geometrical structure of Fe(TPP)(NO) is shown in Fig. 5.16. 

The effect of metal basicity on the mode of reactivity of the metal-carbon bond in carbene complexes toward electrophilic and nucleophilic reagents was emphasized in Section II above. Reactivity studies of alkylidene ligands in d8 and d6 Ru, Os, and Ir complexes reinforce the notion that electrophilic additions to electron-rich compounds and nucleophilic additions to electron-deficient compounds are the expected patterns. Notable exceptions include addition of CO and CNR to the osmium methylene complex 47. These latter reactions can be interpreted in terms of non-innocent participation of the nitrosyl ligand. 

Schrader T J, Cherry W, Soper K, Langlois I and Vijay H M (2001), Examination of Altemaria altemata mutagenicity and effects of nitrosylation using the Ames Salmonella Test , Teratogenesis, Carcinogenesis, and Mutagenesis, 21, 261-274. 

Water soluble iron porphyrins [Fem(TPPS)(H20) ]3-330 and [Fem(TMPy)(H20)2]5+ 331 332 (TPPS = maso-tetrakis(/ -sulfonatophenyl)porphyrin, TMPyP = / /e.vo-tetrakis(7V-methyl-4-pyridi-nium)porphyrin331 or maso-tetrakis (A -methyl-2-pyridinium)porphyrin332 dications) act as effective electrocatalysts for the reduction of nitrite to ammonia in aqueous electrolytes (Equation (64) Ei/2= 0.103 V vs. SCE at pH 7), with NH2OH or N20 also appearing as products depending on the reaction conditions. Nitric oxide then ligates to the iron(III) porphyrin to form a nitrosyl complex [Fen(P)(NO+)] (P = porphyrin) as intermediate. 

At higher NO concentrations, MPO activity is inhibited through formation of an inactive ferric nitrosyl complex MPO(NO) the rate constant kori is 1.07xlO6 M-1s-1 and the dissociation rate constant, kQff, is 10.8 s-1 (pH 7.0 phosphate buffer at 10 °C) (Scheme 9, pathway A). However, the inhibitory effects of NO are reduced in the presence of plasma levels of Cl- (100 mM) where on and kQ rate constants were determined to be 1.5 x 105 M-1s-1 and 22.8 s-1, respectively. The modulating effects of NO on MPO activity parallel that of O2 which accelerates activity by serving as a substrate for compound II and inhibits activity by acting as a ligand for MPO (Scheme 9, pathway B) (29). 

It is interesting to note that the nitrosyl moieties of S N P and Roussin s salts exhibit significant N0+ character and they are also excellent NO donors. In particular, S N P is used widely to induce hypotension during surgery [14,15]. It significantly reduces the cerebral infarct size [16,17] and also inhibits platelet aggregation [18]. Transurethral administration of SNP can also induce an erectile response in cats without much side effects [19]. 

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]. 

Sodium nitroprusside (SNP), which is also known as Nipruss or Nipride to medical practitioners, was the first iron nitrosyl complex, prepared as far back as 1850 by Playfair [40]. The hypotensive property of SNP was first demonstrated by Johnson [41] in 1929. It was shown that application of a moderate dose of SNP reduces the blood pressure of a severely hypertensive patient without any side effect [42]. Since that time considerable research has been carried out to understand the mode of action of nitroprusside and its metabolic fate. SNP is now regarded as a potent vasodilator that causes muscle relaxation by releasing NO which activates the cytosolic isozyme of guanylyl cyclase [43-46]. 

Local administration of NO to the lungs has been shown to reverse pulmonary hypertension in animal models [103], importantly with no systemic side effects. This is likely to be as a result of surplus NO being removed as nitrosyl-hemoglobin [104]. Such advantages of gaseous NO were first reported in 1991 [105, 106]. In 1999 and 2001 NO gas was approved as a drug in the USA and European Union, for treating hypoxemic respiratory failure in infants [107]. 

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