NUCLEAR QUADRUPOLAR COUPLING-CONSTANTS IN THE CYANOBOROHYDRIDE ION - T-1 MEASUREMENTS AND AB-INITIO MOLECULAR-ORBITAL CALCULATIONS

The B-11 and H-2 spin-lattice relaxation times, T-1, were measured for sodium cyanoborohydride (BH3CN-) and sodium cyanoborodeuteride (BD3CN -) in methanol-ethylene glycol solution as a function of temperature. Both B-11 and H-2 T-1 minima were observed, yielding B-11 and H-2 nucl ear quadrupolar coupling constants, chi, of 766 and 104 kHz, respectiv ely. Measurement of the N-14 T-1 at 300 K gave a chi(N-14) value of 2. 8 MHz. Electric field gradients were calculated using ab initio molecu lar orbital theory, in order to obtain theoretical B-11, N-14 and H-2 chi values. The values of 847 kHz, -3.25 MHz and 141 kHz for B-11, N-1 4 and H-2, respectively, are larger than those found in solution.