Hulley, EB; Williams, VA; Hirsekorn, KF; Wolczanski, PT; Lancaster, KM; Lobkovsky, EB
Nb-93 NMR chemical shifts and linewidths are reported for the following 4-coordinate series of (silox)(3)Nb (X-n/L-m) species: X-n/L-m = NNCH(SiMe3), 1=NNT; 0, 1=O; Cl-2, 2-Cl-2; C-13=(CO)-C-13, 1=(CCO)-C-13-C-13; CHCH3, 1=CHMe; CH2, 1=CH2; CH(trans-CH=CHCH3), 1-t-C4H6; CH(trans-CH=CH(CH2)(2)Ph), 1-t-C5H6Ph; CH (cis-CH=CHCH3), 1-c-C4H6; CH(cis-CH=CH(CH2)(2)Ph), 1-c-C5H6Ph; (mu-C2H4), 3-C2H4; (kappa(2)-C,C-CH2CHCHCH2), 2-C4H6; (eta(2)-CD2=CH(trans-2-Ph-Pr-c)), 3-VyPh(c)Pr; P-[Li(THE)(x)](+), 1-PLi; PH, 1=PH; PMe, 1=PMe; [(silox)(3)Nb](2)(mu:eta(1),eta(1)-N-2), 1(2)-N-2. Small scale syntheses of 1=NNT and 2-C4H6 are given, and the preparation of 1(2)-N-2, is reported, along with its X-ray crystal structure, and electronic structure. Calculated (DFT) Nb-93 NMR chemical shifts correlate with the experimental values, and delta is found to be generally proportional to 1/X (X is Pauling electronegativity). This trend is derived from the paramagnetic contribution, which is governed by the second-order Zeeman effect, and estimated using the Average Excitation Energy (AEE) model. (C) 2015 Elsevier Ltd. All rights reserved.