Substituent effects on 61Ni NMR chemical shifts.

(61)Ni chemical shifts of Ni(all-trans-cdt)L (cdt = cyclododecatriene, L = none, CO, PMe(3)), Ni(CO)(4), Ni(C(2)H(4))(2)(PMe(3)), Ni(cod)(2) (cod = cyclooctadiene) and Ni(PX(3))(4) (X = Me, F, Cl) are computed at the GIAO (gauge-including atomic orbitals), BPW91, B3LYP and BHandHLYP levels, using BP86-optimised geometries and an indirect referencing scheme. For this set of compounds, substituent effects on delta((61)Ni) are better described with hybrid functionals than with the pure BPW91 functional. On going from Ni(all-trans-cdt) to Ni(all-cis-cdt) the computations predict substantial shielding of the (61)Ni nucleus by nearly 700 ppm, as well as a sharp increase of the electric field gradient at this position. The latter result is predicted to afford an undetectably broad (61)Ni NMR line for the all-cis-cdt complex, rationalizing the apparent failure to record the NMR spectrum experimentally.