Metal Valence Structures and Magnetic Interactions in Halogen-Bridged 1-D Ni–Pd Mixed-Metal Complexes Studied by 13C and 1H Solid State NMR

13C NMR spectra at room temperature and the temperature dependences of 1 H T 1 in the solid state were measured in [Ni 1 - x Pd x X(chxn) 2 ]X 2 (X: Cl, Br; chxn: 1R,2R-cyclohexanediamine; 0.0 ≤ x ≤ 1.0), where antiferromagnetically coupled paramagnetic -X-Ni 3 + -X-Ni 3 + -X- chains were formed at x = 0.00, while the mixed-valence -X-Pd 2 + -X-Pd 4 + -X- state was made at x = 1.00. 1 3 C signals at α-carbons in chxn coordinating to Pd atoms showed a doublet assignable to Pd 2 + and Pd 4 + in x = 1.00, while, with a slight decrease of x from 1.00, a clear broadening and a shift to low-field of signals, indicating conversion into the averaged Pd 3 + state, were observed. This can be explained by the fluctuation of the Pd valency caused by neighboring paramagnetic Ni 3 + sites introduced in small amounts in the 1-D chain. The x dependences of the chemical shifts of β- and γ-carbons are also attributable to the effect from a partial mixing of the paramagnetic Pd 3 + sites. The values of 1 H T 1 and its temperature dependence observed in the ranges of 100-300 K and x ≤ 0.13 for [Ni 1 - x Pd x Br(chxn) 2 ]Br 2 could be explained by a model of strong exchange interactions between Ni 3 + and Pd 3 + as well as Ni 3 + sites. Gradual changes in the T 1 value and slope with increasing x from 0.00 to 0.93 are attributable to the variation of the exchange interaction value, which depends upon the number of Ni-Ni pairs.