Transition metal nitrosyl complexes characterization

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. 

NO is a fascinating diatomic radical in the context of coordination chemistry due to its notorious non-innocent behavior in transition metal complexes. For example, NO adducts of ferrous iron complexes could have electronic structures that vary all the way from a Fe(I)—NO to a Fe(III)—NO extreme with the Fe(II)—NO (radical) case being intermediate. This distinction is significant, as it can be expected that NO, NO (radical), and NO will show very different reactivities. However, characterizing the exact electronic structures of transition metal nitrosyls is difficult, which led to the establishment of the famous Enemark-Feltham [Fe—NO]"" notation (the superscript x... 

Organolanthanide complexes are coordinately unsaturated and as a result take part in forming mixed complexes with transition metal complexes containing nitrosyl or carbonyl groups. As a result, mixed complexes containing metal-metal bonds or lanthanide-isocarbonyl or isonitrosyl interactions have been characterized. Some typical complexes are given below. 

NO can be employed eifiier as a probe to identify Lewis acid sites and characterize their density and strength [52], or as a reducing agent. However, NO may disproportionate into N2O and oxygen and is also very likely to form nitrosyl complexes in the presence of transition-metal ions. From a different... 

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