Electronic structures of highly symmetrical compounds of f elements. 41 [1] synthesis, crystal, molecular and electronic structure of a bis(cyclohexylisonitrile) adduct derived from the Tris(bis(trimethylsilyl)amido)erbium(III) moiety and electronic structures of selected mono adducts

The reaction of tris(bis(trimethylsilyl)amido)erbium(III) (Er(btmsa)3) with two equivalents of cyclohexylisonitrile yields the corresponding bis adduct [Er(btmsa)(3)(CNC6H11)2] (1).Complex I crystallizes in the monoclinic space group C2/c with a 2542.9(11) pin, b = 1208.4(4) pm, c = 1783.0(2) pm, beta 122.39(3)degrees, V = 4.638(5)center dot 10(9) pm(3), Z=4 and R=0.0380. The structure of compound I features the five coordinate Er3+ central ion in a nearly exact trigonal bipyramidal environment, with three btmsa ligands in the equatorial and the two cyclohexylisonitrile molecules in the axial positions. On the basis of the absorption spectra of bis adduct 1 and the mono(tetrahydrofuran) as well as the mono(triphenylphosphine oxide) adducts [Er(btmsa)(3)(THF)] (2) and [Er(btmsa)(3)(OPPh3)] (3), respectively, the underlying truncated crystal field (CF) splitting patterns of these compounds could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian. Reduced r.m.s. deviations of 13.0 cm(-1) (42 assignments), 16.0 cm(-1) (63 assignments) and 17.5 cm(-1) (55 assignments) could be achieved for compounds 1, 2 and 3, respectively. Making use of the phenomenological CF parameters of the fits, the experimentally based non-relativistic molecular orbital schemes of complexes 1, 2 and 3 were set up, and compared with that of base-free Er(btmsa)(3).