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Intermolecular 119Sn,31P Through-Space Spin–Spin Coupling in a Solid Bivalent Tin Phosphido Complex

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posted on 12.04.2016, 14:04 by Janet Arras, Klaus Eichele, Boris Maryasin, Hartmut Schubert, Christian Ochsenfeld, Lars Wesemann
A bivalent tin complex [Sn­(NP)2] (NP = [(2-Me2NC6H4)­P­(C6H5)]) was prepared and characterized by X-ray diffraction and solution and solid-state nuclear magnetic resonance (NMR) spectroscopy. In agreement with the X-ray structures of two polymorphs of the molecule, 31P and 119Sn CP/MAS NMR spectra revealed one crystallographic phosphorus and tin site with through-bond 1J(117/119Sn,31P) and through-space TSJ(117/119Sn,31P) spin–spin couplings. Density functional theory (DFT) calculations of the NMR parameters confirm the experimental data. The observation of through-space TSJ(117/119Sn,31P) couplings was unexpected, as the distances of the phosphorus atoms of one molecule and the tin atom of the neighboring molecule (>4.6 Å) are outside the sum of the van der Waals radii of the atoms P and Sn (4.32 Å). The intermolecular Sn···P separations are clearly too large for bonding interactions, as supported by a natural bond orbital (NBO) analysis.