Isonitrosyl

NIS measurements (at 77 K) were also performed on a GNP single crystal (c-cut) (a) after the sample was illuminated with blue light (450 nm) at 50 K to populate metastable molecular states and (b) after warming up the illuminated crystal to 250 K at which the metastable states decay to the groundstate [94]. Comparison of measured and simulated (DFT) NIS spectra provided evidence for the isonitrosyl structure of the metastable state MSi [95] which was proposed earlier by Carducci et al. in their pioneering X-ray study [96]. 

Our latest results in this field stem from a matrix-spectroscopic study of the isomerization of nitrosyl halides (152) and isonitrosyl halides (153).201 Irradiation of nitrosyl bromide (152 X = Br) and nitrosyl chloride (152 X = Cl) leads to the corresponding isomers isonitrosyl bromide (153 X = Br) and isonitrosyl chloride (153 X = Cl). Both compounds, NOBr and NOC1,202 have again been identified by comparison of the experimental and calculated (BLYP/6-311+G ) IR spectra. The back-reactions 153 - 152 can be initiated by UV, visible or IR light. Astonishingly, this retransformation also occurs spontaneously even in the matrix at 10 K under exclusion of any UV/VIS or IR radiation. 

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. 

Isocarbonyl and isonitrosyl linkages to lanthanides are evident in the complexes noted above [256], confirmed by IR spectroscopy. In the Yb complex, an isocarbonyl bridge Yb-OC-Co has been confirmed while in the Iutetium complex Lu-Ru metal-metal bond is present [257]. 

Figure 26 Ortep diagrams of the nitroprusside anion (a), and its isonitrosyl (b), and side-on, jj -NO, (c) Imkage isomers...

Bonding of NO to transition metals usually occurs via the nitrogen atom. Other types of bonding occur in some rare cases and include twofold and threefold nitrosyl bridges o/jr-dihaptonitrosyls (so-called side-on nitrosyls) and isonitrosyls (M-O-N bound), as reviewed in [6]. 

Maier G, Reisenauer HP, De Marco M (2000) Isomerizations between nitrosyl halides X-N=0 and isonitrosyl halides X-O-N a matrix-spectroscopic study. Chem Eur J 6 800-808... 

Coppens and coworkers observed that laser irradiation of crystal samples of [Ru(bpy)2(N0)(N02)](PF6)2, at 90 K produces a double isonitrosyl-nitrito linkage isomer (Figure 15) and structurally identified the photogenerated hnkage isomers by a combination of X-ray crystallography and infrared spectroscopy (112). 

Giiida and coworkers have provided infrared spectral data to show two photogenerated metastable-excited states (MSI and MSII) for the related CpNi(NO) complex (131). They irradiated the parent CpNi(NO) with 488.0 and 514.5 nm light (Ar laser line) at 77 K to generate the metastable species [Ni( / -ON)(// -Cp)] and [Ni( / -NO)(// -Cp)]. The IR spectra of the photogenerated species showed downward shifts of the i/no by 260 and 460 cm , consistent with the generation of the isonitrosyl (MSI) and side-on (MSII) species, respectively. 

Schaniel et al. studied the photolysis products of some [(NH3)4Pt(NO)X] (X = C1, S04 , NO3 complexes) (F ure 21) (132,133). They reported the first photogeneration of nitrosyl linkage isomers in such Pt nitrosyl complexes, from irradiation of a powdered sample of the [(NH3)4Pt(NO)Cl] complex with h t in the spectral range 550—800 nm. IR spectral data revealed a surprising shift in the 1/440 band from 1673 to 1793 cm that they attributed to a nitrosyl-to-isonitrosyl linkage isomerization to a geometry between / -ON and // -ON (132). 

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