Vibrational spectra nitrosyl complexes

A direct, quantitative, and convenient method for the preparation of [Cr(H20)5N0] has been achieved by the slow, dropwise addition of an aqueous solution of Cr° (10 ml, 0.5 mol 1" ) to a stirred solution of HCIO4 (200 ml, 0.1 mol 1" ) which was continuously saturated with NO. This reaction is rapid and produces only [Cr(H20)5N0] , provided that NO is in excess. This study also confirmedthe previously reported d-d spectrum of this ion. Several e.s.r. studies of chromium nitrosyl complexes containing a variety of other ligands have been reported. The i.r.-polarized spectra of K3[Cr(CN)5N0],2H20 have been determined and the results strongly support the suggestion that the orientation of the anions is disordered. The salts K4[M(CN)5N0] (M = Cr or Mo) appear to be isomorphous and the assignment of the vibrational modes in these ° and related compounds has been discussed. ... 

Fig. 17 Measured Fe excitation probabilities for a series of iron porphyrins. All nitrosyl complexes have an Fe-NO stretch/bend mode in the 520-540 cm region. Comparison among the nitrosyl complexes (c-g) reveals that peripheral groups strongly influence the vibrational frequencies and amplitudes of the central Fe. Sample temperatures were 34 K for Fe(OEP), 30 K for Fe(OEP)(NO), 80 K for Fe(TPP)(NO), 35 K for Fe(DPIXDME)(NO), 34 K forFe(PPIXDME)(NO), and 64 K for Fe(MPIXDME) (NO). The Fe(OEP)(Cl) spectrum is an average over multiple scans with an estimated average temperature of 87 K. Reprinted from reference [192], with the permission of the American Chemical Society, copyright 2004...

Fig. 149) (534). Attempts to make the analogous chloride complexes upon addition of chlorine to [Fe(NO)(S2CNR2)2], however, failed (1261). The v(NO) vibration in the IR spectrum lies between 1804 and 1829 cm being shifted some 100-120 cm to higher wavenumbers than in the iron(II) nitrosyls (see below). 

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