Multinuclear solid state NMR spectroscopy of ternary rare-earth silicides RET 2Si2 and germanides LaT 2Ge2 (RE = Sc, Y, La, Lu; T = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au)

A series of ternary rare earth - transition metal - tetrelides RET(2)Tt(2) (RE = Sc, Y, La, Lu; T = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au; Tt = Si, Ge) was synthesized by arc melting of the elements and subsequent annealing. The samples were characterized by powder X-ray diffraction and in addition, the structures of REOs2Si2 (RE = Y, La, Lu), LaAu2Si2, LaAg2Ge2 and LaAu2Ge2 were refined from single crystal X-ray diffractometer data. The tetrelides crystallize with the ThCr2Si2 type (I4/mmm) except the platinum compounds which adopt the klassengleiche superstructure of the CaBe2Ge2 type (P4/nmm). The transition metal atoms have tetrahedral tetrel coordination and the tetrahedra condense to layers via common edges. The stacking of these layers leads to Tt-Tt bonds in the ThCr2Si2 type phases and heteroatomic T-Tt bonds in the CaBe2Ge2 type phases. The rare earth atoms fill larger cages within these three-dimensional networks (coordination number 16 with RE@T(8)Tt(8)) with site symmetries 4/mmm (ThCr2Si2 type) and 4mm (CaBe2Ge2 type). Systematic multinuclear solid state NMR spectroscopic investigations allowed observing the effect of the involved rare-earth metal, transition metal and tetrel group element, respectively. In particular, Si-29 isotropic resonance shifts can be predicted from element-specific increments and interatomic Si-Si bonding interactions manifest themselves in axially symmetric magnetic shielding anisotropies.