Octacoordinate metal carbonyls of scandium and yttrium: theoretical calculations and experimental observation

The Scandium(II) Carbonyl Complex (C5H2tBu3)2Sc(CO) and Its Isocyanide Analog (C5H2tBu3)2Sc(CNC6H3Me2-2,6)

Treatment of the scandium(II) metallocene Cpttt2Sc (Cpttt = C5H2tBu3) with CO or the isocyanide CNXyl (Xyl = C6H3Me2-2,6) yields the carbonyl complex Cpttt2Sc(CO), 1, or the isocyanide complex Cpttt2Sc(CNXyl), 2, which were identified by X-ray crystallography. Isotopic labeling with 13CO shows the CO stretch of 1 at 1875 cm-1 shifts to 1838 cm-1 in 1-13CO. The CN stretch in 2 is shifted to 1939 cm-1 compared to 2118 cm-1 for the free isocyanide. The 80.1 MHz (28.7 G) 45Sc hyperfine coupling in 1 and 74.7 MHz (26.8 G) in 2 are similar to the 82.6 MHz (29.6 G) coupling constant in Cpttt2Sc and indicate that 1 and 2 are Sc(II) complexes. A comprehensive analysis of the electronic structures of 1 and 2 using DFT calculations is reported.

Applying the Jellium model to octacarbonyl metal complexes

The recently reported octacarbonyl metal complexes M(CO)₈ (M = Ca, Sr, Ba) feature interesting bonding structures. In these compounds, the bond order is 7, while accommodating 8 lone pairs of ligands in forming octa-coordinated complexes or ions. Here, by comparing [Ba(CO)₈]^2- and metal clusters of [BaBe₈]^2- analogically, we demonstrate that the Jellium model can not only be applied on metal clusters, but is also a useful tool to understand the electronic structures of [M(CO)₈]^q (M, q = Ca, 2-; Sc, 1-; Ti, 0; V, 1+; Cr, 2+; Ba, 2-). By applying the Jellium model, we find that a 20-e model with the configuration |1S²|1P⁶|1D¹⁰|1F²| is an appropriate description of the valence bonding structures of M(CO)₈ species, where each coordinative bond contains 7/8ths of the bonding orbitals and 1/8th non-bonding orbitals.

Electronic and structural features of octa-coordinated yttrium–ammonia complexes: the first neutral solvated electron precursor with eight ligands and three outer electrons

The neutral and charged yttrium metal–ammonia complexes, [Y(NH₃)₈]^0,±, are investigated quantum mechanically. It is shown that all of them bear a [Y(NH₃)₈]³⁺ core with two, three or four peripheral electrons.

Infrared photodissociation spectroscopy of M(N2)n(+) (M = Y, La, Ce; n = 7-8) in the gas phase

M(N2)n(+) (M = Y, La, Ce; n = 7-8) complexes have been studied by infrared photodissociation (IRPD) spectroscopy and density functional theory (DFT) calculations. The experimental results indicate that the N-N stretching vibrational frequencies are red-shifted from the gas-phase N2 value. The π back-donation is found to be a main contributor in these systems. IRPD spectra and DFT calculations reveal the coexistence of two isomers in the seven-coordinate M(N2)7(+) and eight-coordinate M(N2)8(+) complexes, respectively. The present studies on these metal-nitrogen complexes shed light on the interactions and coordinations toward N2 with transition and lanthanide metals.