A solid-state NMR investigation of single-source precursors for group 12 metal selenides; M[N(iPr2PSe)2]2 (M = Zn, Cd, Hg)

Abstract

The first solid-state NMR investigation of dichalcogenoimidodiphosphinato complexes, M[N(R₂PE)₂]_n, is presented. The single-source precursors for metal-selenide materials, M[N(ⁱPr₂PSe)₂]₂ (M = Zn, Cd, Hg), were studied by solid-state ³¹P, ⁷⁷Se, ¹¹³Cd, and ¹⁹⁹Hg NMR at 4.7, 7.0, and 11.7 T, representing the only ⁷⁷Se NMR measurements, and in the case of Cd[N(ⁱPr₂PSe)₂]₂¹¹³Cd NMR measurements, to have been performed on these complexes. Residual dipolar coupling between ¹⁴N and ³¹P was observed in solid-state ³¹P NMR spectra at 4.7 and 7.0 T yielding average values of R(³¹P,¹⁴N)_eff = 880 Hz, C_Q(¹⁴N) = 3.0 MHz, ¹J(³¹P,¹⁴N)_iso = 15 Hz, α = 90°, β = 26°. The solid-state NMR spectra obtained were used to determine the respective phosphorus, selenium, cadmium, and mercury chemical shift tensors along with the indirect spin–spin coupling constants: ¹J(⁷⁷Se,³¹P)_iso, ¹J(^111/113Cd,⁷⁷Se)_iso, ¹J(¹⁹⁹Hg,⁷⁷Se)_iso, and ²J(¹⁹⁹Hg,³¹P)_iso. Density functional theory magnetic shielding tensor calculations were performed yielding the orientations of the corresponding chemical shift tensors. For this series of complexes the phosphorus magnetic shielding tensors are essentially identical, the selenium magnetic shielding tensors are also very similar with respect to each other, and the magnetic shielding tensors of the central metals, cadmium and mercury, display near axial symmetry demonstrating an expected deviation from local S₄ symmetry.