Triclinic LaZnP with P, P, and P units: a combined study by P solid-state NMR spectroscopy and single crystal X-ray diffraction.

The ternary polyphosphide LaZnP was synthesized from the elements by using a salt flux or a ceramic method in sealed quartz ampoules. The obtained samples were investigated by X-ray powder and single crystal diffraction: own type, 1̄, = 775.33(13), = 827.45(13), = 1502.8(3) pm, = 82.111(3), = 77.034(3), = 89.996(3)°, w = 0.1553, 5852 values and 183 variables. This peculiar structure is characterized by the simultaneous presence of three distinct anionic phosphide species, namely P, P, and P units. LaZnP is an electron precise Zintl phase: (7La)(2Zn)(4P)(2P)(P). The P-P single bond distances range from 219.2 to 223.0 pm. The zinc sites show tetrahedral phosphorus coordination by three P and one P species. The tetrahedra are condensed to chains common corners. The P units with P-P-P angles of 113.7° have exclusively lanthanum coordination. P solid-state NMR was used to probe the phosphorus local environments, connectivities and spatial proximities. The eleven crystallographically distinct phosphorus atoms were assigned with the help of two-dimensional homonuclear dipolar correlation experiments. Even though the application of 2D measurements on such phosphorus-based polyanionic compounds is exceedingly challenging because of the wide dispersion of chemical shifts, the fast irreversible decay of the transverse magnetization, and slow spin-lattice relaxation, a complete assignment is possible using radiofrequency-driven dipolar recoupling (RFDR), -RESOLVED and total-through-bond correlation with R-sequence (R-TOBSY) techniques.