SCHEDULED MAINTENANCE
Triclinic La7Zn2P11 with P3−, P24−, and P35− units: a combined study by 31P solid-state NMR spectroscopy and single crystal X-ray diffraction
a
Christopher
Benndorf,
ac
Tobias
Uesbeck,
b
Thomas
Wiegand,
de
Hellmut
Eckert,
*bf
Hannes
Lincke
a
and
Rainer
Pöttgen
*a
Abstract
The ternary polyphosphide La7Zn2P11 was synthesized from the elements by using a salt flux or via a ceramic method in sealed quartz ampoules. The obtained samples were investigated by X-ray powder and single crystal diffraction: own type, P![[1 with combining macron]](https://www.rsc.org/images/entities/char_0031_0304.gif)
, a = 775.33(13), b = 827.45(13), c = 1502.8(3) pm, α = 82.111(3), β = 77.034(3), γ = 89.996(3)°, wR2 = 0.1553, 5852 F2 values and 183 variables. This peculiar structure is characterized by the simultaneous presence of three distinct anionic phosphide species, namely P3−, P24−, and P35− units. La7Zn2P11 is an electron precise Zintl phase: (7La3+)21+(2Zn2+)4+(4P3−)12−(2P24−)8−(P35−). The P–P single bond distances range from 219.2 to 223.0 pm. The zinc sites show tetrahedral phosphorus coordination by three P3− and one P24− species. The tetrahedra are condensed to chains via common corners. The P35− units with P–P–P angles of 113.7° have exclusively lanthanum coordination. 31P 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), J-RESOLVED and total-through-bond correlation with R-sequence (R-TOBSY) techniques.
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