Formation, structural characterization, and reactions of a unique cyclotrimeric vicinal Lewis pair containing (C6F5)2P-Lewis base and (C6F5)BH-Lewis acid componentsElectronic supplementary information (ESI) available: Experimental, analytical details and crystallographic data. CCDC 1001587-1001589. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4dt02081b

The synthesis of the new vicinal frustrated Lewis pair 5 containing (C 6 F 5 ) 2 P-Lewis base and (C 6 F 5 )BH-Lewis acid functionality is described. It forms a unique cyclotrimer ( 5 ) 3 which was structurally characterized by X-ray crystallography and high-resolution solid-state NMR spectroscopy. The relevant NMR Hamiltonian parameters ( 11 B and 31 P chemical shielding tensors, 11 B quadrupolar coupling tensors, and 31 P- 11 B spin-spin coupling constants) indicate significant intramolecular covalent B P interactions, consistent with results from density functional theory (DFT) calculations. In addition, the 11 B/ 31 P and 31 P/ 31 P three-spin geometries are accurately reproduced by suitable high-resolution hetero- and homonuclear dipolar NMR experiments. As predicted from the bonding character portrayed by the solid-state NMR results, the cyclotrimer ( 5 ) 3 possesses only moderate catalytic activity. However, it undergoes an addition reaction with pyridine and hydroboration reactions with benzaldehyde and tert -butylacetylene. The products of the hydroboration reactions form stable adducts with pyridine. A unique vicinal Lewis pair cyclotrimer has been synthesized and characterized with respect to its structure and reactivity.