N‐Heterocyclic Phosphenium Dihalido‐Aurates: On the Borderline between Classical Coordination Compounds and Ion Pairs Article Swipe
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· 2017
· Open Access
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· DOI: https://doi.org/10.1002/zaac.201700209
· OA: W2749985662
2‐Bromo‐ and 2‐chloro‐1,3,2‐diazaphospholenes react with (tht)AuCl to afford isolable N‐heterocyclic phosphenium (NHP) dihalido‐aurates, which were characterized by analytical and spectroscopic data and in one case by a single‐crystal X‐ray diffraction study. The T‐shaped metal coordination sphere found in the crystal consists of a pseudo‐linear Au X 2 unit that is perturbed by a weakly bound NHP unit. DFT studies indicate that the subunits interact mainly through electrostatic and dispersion forces, with negligible covalent contributions, and that the phosphenium dibromido‐aurate is slightly more stable than an isomeric complex with an intact bromophosphane ligand. NMR studies reveal that the NHP‐Au X 2 pairs persist in solution but are kinetically labile and readily undergo halide scrambling. The hydride/fluoride exchange reaction between a secondary phosphane‐AuCl complex and [Ph 3 C][BF 4 ] implies that a gold complex with an intact 2‐halogeno‐1,3,2‐diazaphospholene ligand may be more stable than its phosphenium dihalido‐aurate isomer when covalent P– X bonding contributions are strengthened.
