Nitrosyl complexes bridging

Figure 11.13 Structures of polynuclear nitrosyl complexes (a) ((Cr( j -C5H5)(NO))2(M2-NH2)(M2-NO) showing linear-terminal and doubly bridging NO and (b) (Mn3( j -C5H5)3( 3-NO)3( 3-NO)] showing double-and triply-bridging NO the molecule has virtual symmetry and the average Mn-Mn distance is 250 pm (range 247-257 pm).

Osterloh, F., Saak, W, Haase, D. and Pohl, S. (1997) Synthesis, X-ray structure and electrochemical characterization of a binuclear thiolate bridged Ni-Fe-nitrosyl complex, related to the active site of NiFe hydrogenase. Chem. Commun. (Cambridge), 1997, 979-80. 

Nitric oxide can bind to metals in both terminal and bridging modes to give metal nitrosyl complexes. Depending upon the stereochemistry of the complexes, NO may exhibit within one given complex either NO+ or NO-character, as illustrated in Table 15.2.2. 

Bis[7i-cyclopentadienyl]bis[benzenetellurolato]titanium(IV) reacted with bis[tricarbonyl-(nitrosyl)iron] mercury to produce a Ti — Te dinuclear complex bridged by benzenetelluro-lato groups2. 

This chapter focuses on the chemistry ofbiomimetic copper nitrosyl complexes relevant to the NO-copper interactions in proteins that are central players in dissimilatory nitrogen oxide reduction (denitrification). The current state of knowledge of NO-copper interactions in nitrite reductase, a key denitrifying enzyme, is briefly surveyed the syntheses, structures, and reactivity of copper nitrosyl model complexes prepared to date are presented and the insight these model studies provide into the mechanisms of denitrification and the structures of other copper protein nitrosyl intermediates are discussed. Emphasis is placed on analysis of the geometric features, electronic structures, and biomimetic reactivity with NO or NOf of the only structurally characterized copper nitrosyls, a dicopper(II) complex bridged by NO and a mononuclear tris(pyrazolyl)hydroborate complex having a Cu(I)-NO formulation. 

A thiolato-nitrosyl complex [Re2 (NO)2 (SPh)7] has been made in low yield by reacting [Re(NO)Cl2(PPh3)2] (later reformulated as [Re(NO)Cl2(OMe)(PPh3)2])560,561 with thiophenol in refluxing methanol in the presence of triethylamine. The crystal structure performed on the [Pl P] salt of the p-tolylthiol derivative shows the complex to consist of two pseudooctahedral rhenium units linked by three bridging thiolato ligands. The Re—Re distance of 2.783(1) A indicates significant metal-metal interaction.562... 

There are a few thionitrosyl complexes of rhodium, many of which contain thionitrosyl bridges. They have been prepared by allowing [NSC1]3 to react with sundry rhodium nitrosyl complexes (equations 327 and 328). 

Several iridium( —I) nitrosyl complexes are known. Those with the general formula [Ir(NO)2X(PPh3)2] (X = Cl, Br, I) are produced upon reduction of [Ir(NO)2(PPh3)2] with the appropriate lithium halide. IR spectral data for these complexes indicate bridging NO groups, as shown by the low N—O frequencies [v(N—O) 1540-1490 cm-1].7 Reaction of [Ir(NO)2X(PPh3)2] with NO results in the oxidation of NO according to reaction (l).8... 

Binary Nitric Oxide Complexes. A binary iron nitrosyl complex is not known, although described in early reports as [Fe(NO)4], the compound having that stoichiometry is a dimer with an N2O2 bridging ligand (10). 

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