THE ELECTRONIC-STRUCTURE OF ORGANOMETALLIC COMPLEXES OF THE F-ELEMENT.41. CRYSTAL-FIELD STRENGTH OF ETA(8)-CYCLOOCTATETRAENYL LIGAND ESTIMATED ON THE BASIS OF THE PRELIMINARY CRYSTAL-FIELD PARAMETERS OF (COT)ND-III[HB(3,5-ME(2)PZ)(3)]

The absorption spectrum of (eta(8)-COT)Nd[HB(3,5-Me(2)pz)(3)] (COT=cyc looctatetraenyl, pz=pyrazol-1-yl) has been measured at room temperatur e, at approximately 90 K and in parts at ca. 30 K. The bands were assi gned by applying the selection rules for C-8v symmetry and by performi ng crystal field (CF) calculations assuming the CF parameters of the N d complex were the same as for the previously analyzed (COT)Pr[HB(3,5- Me(2)pz)(3)]. The parameters of an empirical Hamiltonian were fitted t o the energies of 27 levels to give an r.m.s. deviation of 25.5 cm(-1) . Neglecting the influence of [HB(3,5-Me(2)pz)(3)](-) ligand, the CF s trength of the [COT](--) ligand could be estimated from the CF paramet ers obtained.