Chlorine-35 Solid-State Nuclear Magnetic Resonance Spectroscopy as an Indirect Probe of the Oxidation Number of Tin in Tin Chlorides.

Ultrawideline 35 Cl solid-state nuclear magnetic resonance (SSNMR) spectra of a series of 12 tin chlorides were recorded. The magnitude of the 35 Cl quadrupolar coupling constant ( C Q ) was shown to consistently indicate the chemical state (oxidation number) of the bound Sn center. The chemical state of the Sn center was independently verified by tin Mössbauer spectroscopy. C Q (35 Cl) values of >30 MHz correspond to Sn(IV), while C Q (35 Cl) readings of <30 MHz indicate that Sn(II) is present. Tin-119 SSNMR experiments would seem to be the most direct and effective route to interrogating tin in these systems, yet we show that ambiguous results can emerge from this method, which may lead to an incorrect interpretation of the Sn oxidation number. The accumulated 35 Cl NMR data are used as a guide to assign the Sn oxidation number in the mixed-valent metal complex Ph3 PPdIm SnCl2 . The synthesis and crystal structure of the related Ph3 PPtIm SnCl2 are reported, and 195 Pt and 35 Cl SSNMR experiments were also used to investigate its Pt-Sn bonding. Plane-wave DFT calculations of 35 Cl, 119 Sn, and 195 Pt NMR parameters are used to model and interpret experimental data, supported by computed 119 Sn and 195 Pt chemical shift tensor orientations. Given the ubiquity of directly bound Cl centers in organometallic and inorganic systems, there is tremendous potential for widespread usage of 35 Cl SSNMR parameters to provide a reliable indication of the chemical state in metal chlorides.