Transition metal complexes nitrosyl

In polynuclear complexes, nitric oxide can also act as a bridging ligand between two or three metal centers, as illustrated in (3). 

The only structurally characterized example of a M-O-N interaction, where M is a transition metal fragment, is in the polynuclear rhenium compound (4) 58). 

A variety of spectroscopic and structural techniques are available for characterising transition metal compounds, and in the following sections those that have been used to determine which of the nitrosyl geometries is adopted are critically discussed. 

Haymore and Ibers (62) have developed a series of corrections to the observed i no stretching frequencies that take into account the position of the metal in the periodic table, the charge on the complex, the metal s coordination number, and the other ligands present. The resulting corrected i no are more successful in predicting the nitrosyl geometry in transition metal complexes. 

Infrared Data for Some Mononuclear Nitrosyl Complexes 

PF3-containing transition metal nitrosyl complexes such as [Co(NO)(PF3)3] and [Fe(NO)2(PF3)2] were first prepared by Kruck and Lang (206, 207) by reduction of dimeric nitrosyl halide complexes with copper in the presence of PF3 (method A). 

More recently these volatile complexes have also been made by metal vapor syntheses (method B) in which vapors of the metals were cocondensed with NO, PF3, and boron trifluoride at liquid nitrogen temperature. The method also afforded [Mn(NO)3(PF3)], however, it is important to point out that in the absence of BF3 the condensate exploded violently on warming a little above — 196°C (257). 

Other useful methods involve displacement of CO by PF3 from mixed-metal carbonyl nitrosyl complexes (method C), passing C02 through a 

Transition Metal Nitrosyl Complexes Containing Trifluorophosphine 

Since the P—F bonds are labile in these complexes some mixed trifluorophosphine-fluorophosphite nitrosyl complexes have been prepared by reactions with either diisopropyl-water mixtures or barium hydroxide (method F) to give the (PF20) compounds which can be alkylated. 

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Nuclear quadrupole resonance spectroscopy, see also specific compounds cyclophosphazenes, 21 93 of subvalent compounds, 29 298, 308-309 transition metal nitrosyl complexes, 34 313-314... 

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... 

Transition Metal Nitrosyl Complexes D. Michael, P. Mingos, and Darren J. Sherman... 

Transition metal nitrosyl complexes have been the subject of several reviews.273"277... 

Transition Metal Nitrosyl Complexes Containing Trifluorophosphine... 

Transition-metal nitrosyl complexes 403 Dinitrogen trioxide 405 Dinitrogen tetroxide 406... 

Until recently most of the mechanistic studies on nitrosation have been concerned with N-nitrosation reactions of amines, including the diazotisation reactions of primary amines. Now, work has been extended to include both O- and S-nitrosation, so that comparisons can be made. Mechanistic studies have also been extended in recent years to include reactions of nitrogen oxides, nitrosamines, alkyl nitrites, thionitrites and transition metal nitrosyl complexes. Many of these reactions have been used preparatively for a long time, but little has been known about their detailed reaction mechanisms. 

Coppens, P, Fomitchev, D. V., Carducci, M. D. and Culp, K. (1998). Crystallography of molecular excited states. Transition-metal nitrosyl complexes and the smdy of transient species. J. Chem. Soc., Dalton Trans., 865-72. [30, 234]... 

This chapter describes the synthesis of transition metal nitrosyl complexes with particular reference to routes that involve common reagents (e.g., NO and NOBF4). Methods for their characterization by spectroscopic and structural techniques are critically reviewed. The application of NMR for distinguishing among linear, bent, and bridging nitrosyls are emphasized. The bonding in metal nitrosyl complexes is reviewed from a molecular orbital and valence-bond point of view. Finally, the reactions of transition metal nitrosyl complexes are discussed. 

A number of transition metal nitrosyl complexes are capable of transferring a nitrosyl group to another metal center. For example... 

No N nuclear quadrupole resonance (NQR) studies have been reported for transition metal nitrosyl complexes. This technique is expected to show interesting differences between linear and bent nitro-syls since the values of the quadrupole coupling constant and the asymmetry parameter depend on the relative populations of the nitrogen s,p, py, andpz orbitals. NQR spectroscopy has been used to study organic and inorganic nitroso compounds, and it is found that both... 

A large number of paramagnetic transition metal nitrosyl complexes have been studied using electron spin resonance (ESR) spectroscopy. Information on the electronic ground state can be derived from the g-value and the hyperfine coupling constants, and many [MLslNO)]" (see Table IV) and nitrosyl porphyrin complexes (99) have been studied in this way with a view to understanding their electronic structures. 

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