Infra-red spectra of some metal acetylacetonates

Infra-red spectra of a series of acetylacetonates XX′Sn(acac)₂ (X, X′ = alkyl, aryl and/or halogen), (CH₃)₂Pb(acac)₂, Cl₂Ti(acac)₂, Cl₂Ge(acac)₂ and Cl₄Sb(acac) have been measured in the region of 4000-400 cm⁻¹. The absorption bands in XX′Sn(acac)₂ are classified into three groups. The bands in the first group decrease in frequency with increasing electron attracting power of substituents X and/or X′ and those in the second group show an opposite behaviour. The bands in the third group are almost independent of the substituents. From the substituent dependence of the frequency, the upper strong band in the region of 1600-1500 cm⁻¹ is assigned to a perturbed CO stretching band and the lower band to a perturbed CC stretching band. The separation of these two bands becomes small as the electron attracting power of substituents increases and in Cl₄Sb(acac), which may be an extreme case, only a single sharp band is observed. The substituent sensitive bands in XX′Sn(acac)₂ in the region of 700-400 cm⁻¹ have been found to correspond to metal sensitive bands of usual metal acetylacetonates M(acac)_n (n = 1, 2, 3 and 4).