Nitrosyl complexes preparation

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]. 

The preparation is carried out in the general apparatus for nitrosyl complex preparation (Fig. 6). 

The coordination chemistry of NO is often compared to that of CO but, whereas carbonyls are frequently prepared by reactions involving CO at high pressures and temperatures, this route is less viable for nitrosyls because of the thermodynamic instability of NO and its propensity to disproportionate or decompose under such conditions (p. 446). Nitrosyl complexes can sometimes be made by transformations involving pre-existing NO complexes, e.g. by ligand replacement, oxidative addition, reductive elimination or condensation reactions (reductive, thermal or photolytic). Typical examples are ... 

Six-coordinate organoiron porphyrin nitrosyl complexes, Fe(Por)(R)(NO), were prepared from Fe(Por)R (Por = OEP or TPP R = Me, n-Bu, aryl) with NO gas. The NMR chemical shifts were typical of diamagnetic complexes, and the oxidation state of iron was assigned as iron(ll). ... 

Al-Nitrosodiethanolamine, 2 449, 450 Nitroso dyes, 9 263-264 Nitro soluble dyes, 7 373t Nitroso soluble dyes, 7 373t Nitrosomonas, use in recirculating aquaculture biofiltration, 3 196 P-Nitrostyrenes, preparation by nitration of styrenes, 16 581 Nitrosyl chloride, 20 634 Nitrosyl complexes, osmium, 19 642 Nitrosyl perchlorate, 18 279 Nitrosyl tetrafluoroborate, 4 144t n-Nitrotoluene, 17 263... 

Group V Donors. Nitrosyl complexes. The new dark-brown complex [Rh(NO)-Cl(AsPh3)2] has been prepared ... 

Compared with the large number of nitrosyl complexes, only a few examples of thionitrosyl complexes have been studied. Although NS does not exist, a number of synthetic approaches to thionitrosyl complexes have been reported the reaction of nitrido complexes with S2CI2 or TMSNCS, treatment of chloro or 0x0 complexes with trithiazyl chloride or S(NTMS)2, or the use of heterocyclic nitrogen-sulfur rings. Pre-formed thionitrosyl cations in [NS][SbF6] or [NS)[AsFg] have been used to prepare the cationic complex [Re(NS)(CO)5] " in liquid S02. ... 

The complex [Ru(NO)(NH3)(S4)2] has been prepared and crystallographically characterized. It contains two 84 chelating ligands, and the NO and NH3 ligands are mutually trans. This complex was the first polysulfido nitrosyl complex of ruthenium. ... 

Reductive nitrosylation, transition metal nitrosyl complexes, 34 296-297 ReFejSj cluster, 38 41-43 self-assembly system, 38 41-42 Refining, of actinide metals, see Actinide, metals, purification Refractory compounds heat treatment of solids, 17 105-110 crystal growth, 17 105, 106 decomposition, 17 107,-110 spheroidization, 17 106, 107 preparation of, using radio-frequency plasma, 17 99-102... 

Several nitrosyl complexes have been prepared by the reaction of nitrosyl chloride with anionic carbonyls. Thus, [W(CO)5Cl]- reacts with NOC1395 to give [W(CO)4(NO)Cl] while [W(NO)Cl2L] and [W(NO)2ClL] (L = RB(Pz)3) were prepared from [LW(CO)3]- with variable amounts of NOC1. [W2(CO)8CL,] also reacts with NOQ to give in addition to [W(NO)2Cl2] the mononitrosyl [W(NO)Cl3]393 which exhibits only one v(NO) bond at 1590 cm-1. 

Cationic nitrosyl complexes have also been prepared. The reaction of [W(CO)3(MeCN)3] with NOPF6 in acetonitrile affords c -[W(NO)2(CO)(MeCN)3] (PF6)2 which exhibit two v(NO) IR bands at 1867 and 1775 cm-1. The proton NMR spectra consists of two bands of relative intensities of 2 1 consistent with both mer and fac arrangement of the MeCN ligands.24 ciy-[W(NO)2(CO)(MeCN)3]2+ reacts with NaS2CNEt2 to give the known cis-[W(NO)2(S2CNEt2)2] and with acac in the presence of base to give cis -[W(N0)2(acac)2].394... 

This is the largest class of nitrosyl complex and the members are shown in Table 2, together with notable physical properties. They are prepared by the following routes. 

A parallel situation appears to obtain for the mixed allyl nitrosyl complex Ru(NO)(C3H5)L2 prepared by Schoonover and Eisenberg (231). This complex which is coordinatively saturated (NO+ and rf -allyl), forms a CO adduct which is assigned a bent nitrosyl structure (231). Further reaction under CO leads to the formation of Ru(CO)3L2 with the possible elimination of acrolein oxime. The coupling of the allyl and nitrosyl ligands can be viewed in this case as nucleophilic attack of NO- on an f/3-allyl species. Unlike in reaction (110), both of the moieties to be coupled lie within the same coordination sphere. The significance of these results is that it lends viability to the notion embodied in (109) in which a migratory insertion of nitrosyl occurs as NO-. 

A series of comprehensive reviews7,9-11 documents the historical growth of nitrosyl chemistry and also shows the recent expansion that has taken place both in the more traditional areas and in the comparatively new organometallic branch12 of this subject. In this section it is our intention to discuss the structural aspects of nitrosyl coordination, to provide an account of the methods available for the preparation of nitrosyl complexes and to survey the reactions that occur at the nitrosyl group. 

It has been known for a long time that nitrosyl complexes can be prepared using nitric acid the nitroprusside ion [Fe(CN)5NO]2 was first obtained by its action on [Fe(CN)6]3-.85 In many cases the production of such species was accidental and the reactions are often quite complex. Several nitrosyls of the platinum metals have been obtained in this way and recently the polymeric species Pt4(MeC02)6(N0)2 was isolated, together with other products, from the reduction of PtIV in a mixture of nitric and acetic acids.57... 

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