Nuclear Magnetic Resonance in PtSb2and PtAs2

The nuclear magnetic resonances of ${\mathrm{Sb}}^{121}$, ${\mathrm{Sb}}^{123}$, and ${\mathrm{Pt}}^{195}$ in Pt${\mathrm{Sb}}_2$ and Pt${\mathrm{As}}_2$ are reported. The quadrupole coupling constants $\frac{e^2\mathrm{qQ}}{h}$ of Sb are unusually low for compounds of this element, being 98 mHz for ${\mathrm{Sb}}^{121}$ and 124.6 mHz for ${\mathrm{Sb}}^{123}$; similarly low results have been reported previously for the arsenide. The Pt resonance is anisotropic, with a center of gravity displaced - 0.40±0.02% relative to chloroplatinic acid; the shift is probably paramagnetic relative to the bare platinum nucleus. The mean shift and anisotropy are identical in the antimonide and in the arsenide. Analyses of the Sb and As resonances by the method of Townes and Dailey, and also of the anisotropy in the Pt resonance according to Ramsey's theory, all lead to the conclusion that Pt is in the formal valence state (-2) and that all bonds in these compounds are primarily covalent.