INS studies of metal carbonyls

Metal carbonyls Mx(CO)y (M = transition metal, x = 1 – 6, y>=4) and their derivatives are ubiquitous in inorganic and organometallic chemistry. The spectroscopy of the three iron carbonyls, Fe(CO)5, Fe2(CO)9 and Fe3(CO)12 and their ruthenium counterparts, Ru(CO)5 and Ru3(CO)12 has been investigated since the 1950’s but for all of them, there are modes that have not been observed. In some cases this is because they are not allowed in the infrared or Raman spectrum; in others it is that the modes are allowed but are intrinsically weak. We have recently shown that INS spectroscopy enables observation and assignment of all the modes in the region below 800 cm-1 for the series M(CO)6 (M = Cr, Mo, W). It is proposed to simultaneously measure the INS and Raman spectra of the compounds: Fe(CO)5, Fe2(CO)9, Fe3(CO)12, Ru(CO)5 and Ru3(CO)12. Note that for Ru(CO)5 only two (of 18) modes are known.