Carbonyl compounds Mossbauer spectroscopy

Two other publications on Ir (73 keV) Mossbauer spectroscopy of complex compounds of iridium have been reported by Williams et al. [291,292]. In their first article [291], they have shown that the additive model suggested by Bancroft [293] does not account satisfactorily for the partial isomer shift and partial quadrupole splitting in Ir(lll) complexes. Their second article [292] deals with four-coordinate formally lr(l) complexes. They observed, like other authors on similar low-valent iridium compounds [284], only small differences in the isomer shifts, which they attributed to the interaction between the metal-ligand bonds leading to compensation effects. Their interpretation is supported by changes in the NMR data of the phosphine ligands and in the frequency of the carbonyl stretching vibration. 

Reactions of carbonyl compounds such as pyridine 2-carboxaldehyde, glyoxal, biacetyl, or benzil with 2-aminothiophenol on an Fe + template give benzothiazolinate (198) complexes. The complex from pyridine 2-carboxaldehyde, for example, was formulated, on the basis of NMR and Mossbauer spectroscopy and of analysis (C, H, N, and Fe) as the bis-(A,iS)-ligand-bis-aqua complexes of (199), an isomeric form in equilibrium with (198). However as they are diamagnetic it seems more likely that they are [Fe(199)2] 2H20, containing terdentate (N,N,S) (199), than the proposed [Fe(199)2(H20)2]. 

A98. N. N. Greenwood and T. C. Gibb, Mossbauer Spectroscopy. Chapman Hall, London, 1971. Chapter 9, pp. 221-238 Covalent iron compounds (41), treats binary carbonyls, carbonyl anions, hydride anions, substituted iron carbonyls, ferrocene and other 7r-cyclopentadienyl iron derivatives. 

Molecular rotation in the cavity has been discussed for many compounds using nmr(8,9), esr(lO) and Mossbauer spectroscopy(4,5). A complete description of the Mossbauer spectrum for such a case has been given by Gibb(4) for that of the 3 1 clathrate of thiocarbonyl diamide and bis( -cyclopentadienyl)iron(II). Evidence for conformational isomerism has been presented recently based on the ir spectra of y-cyclopentadienylmetal carbonyl complexes such as CpFe(CO) SiCl Me(ll), ip -MeC H Mn(CO) (P(OMe) )(12) and others(13), and on the Mossbauer... 

Mossbauer spectroscopy has been a particularly valuable technique for the study of the structural properties of organometallic compounds and useful data has been obtained from compounds containing a variety of Mossbauer atoms. The Mossbauer results have been especially informative when the compounds under examination have contained the Mossbauer atom in more than one site. Several examples of this are provided by studies of iron carbonyls and their derivatives. 

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