LAUSR

Abstract NMR chemical shifts of d 0 transition metal compounds show the following trends: (1) For single-bonded ligands such as M- H , M- C R 3 , M← N R 3 , M- Si R 3 and M← P R 3 , 1 H, 13 C, 15 N, 29 Si and 31 P shifts of these α atoms in the complexes of both first- and third-row transition metals are typically downfield from (or at higher frequencies than) those of second-row analogs with a “V-shape” (Trend 1). (2) For multiple-bonded ligands including those with d-p π bonds, such as M= C HR, M≡ C R, M= N R, M= O and M F , 13 C, 15 N, 17 O and 19 F shifts of the α atoms in the complexes of first-, second- and third-row transition metals move consecutively upfield (or to lower frequencies ) (Trend 2). NMR shifts of lanthanum(III) complexes help interpret Trend 1 in Group 3 congeners. Scandide (d-block) and lanthanide (f-block) contractions and relativistic effects are believed to contribute to the NMR shifts, leading to the observed trends. Comparisons are made with NMR chemical shifts of d n complexes and organic compounds. Since many chemical properties of the second- and third-row congeners such as Zr and Hf are similar, as a result of lanthanide contraction, the NMR chemical shifts are a rare property to distinguish compounds of the otherwise nearly identical congeners. The current paper points out the trends with our narrative interpretations of the trends.