Equiatomic transition metal (<i>T</i>) silicides <i>TT</i>′Si: systematics of ²⁹Si NMR Knight shifts

Abstract A series of 64 ternary equiatomic tetrelides TT ′ Tt ( T = electron-poor transition metal; T ′ = electron-rich transition metal; Tt = Si, Ge) was synthesized by arc-melting and subsequent annealing. The samples were characterized by powder X-ray diffraction and 20 structures were refined from single-crystal X-ray diffractometer data. These tetrelides (mostly silicides) crystallize with TiNiSi-related structures, orthorhombic space groups Pnma . They are ternary ordered, orthorhombically distorted superstructure variants of the aristotype AlB 2 . The precise single-crystal data show distinct differences in the bond lengths and angles within the three-dimensional [ T ′Si] networks as a consequence of different electron densities driven by the electronegativity differences. Systematic solid-state NMR-spectroscopic investigations allow observing the effect of the two transition metal atoms upon the 29 Si isotropic resonance shifts. For the silicides featuring T ′ elements from groups IX and X this value can be predicted from element-specific increments.