Metal Valence Structures and Magnetic Interactions in Halogen-Bridged 1-D Ni–Pd Mixed-Metal Complexes Studied by 13 C and 1 H Solid State NMR Noriyoshi Kimura,  Aki Josako, Masataka Kano, 1 Kenji Kisoda, 2 Toshio Manabe, 3 Masahiro Yamashita, 3 and Ryuichi Ikeda 1 Department of Chemistry, Faculty of Education, Wakayama University, Wakayama 640-8510 1 Department of Chemistry, University of Tsukuba, Tsukuba 305-8571 2 Department of Physics, Faculty of Education, Wakayama University, Wakayama 640-8510 3 Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 Received April 2, 2004; E-mail: nkimura@center.wakayama-u.ac.jp 13 C 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 3þ –X–Ni 3þ –X– chains were formed at x ¼ 0:00, while the mixed-valence –X–Pd 2þ –X– Pd 4þ –X– state was made at x ¼ 1:00. 13 C signals at -carbons in chxn coordinating to Pd atoms showed a doublet as- signable to Pd 2þ and Pd 4þ in x ¼ 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 3þ state, were observed. This can be explained by the fluc- tuation of the Pd valency caused by neighboring paramagnetic Ni 3þ sites introduced in small amounts in the 1-D chain. The x dependences of the chemical shifts of - and  -carbons are also attributable to the effect from a partial mixing of the paramagnetic Pd 3þ 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 3þ and Pd 3þ as well as Ni 3þ sites. Gradual changes in the T 1 value and slope with increasing x from 0.00 to 0.93 are at- tributable to the variation of the exchange interaction value, which depends upon the number of Ni–Ni pairs. Halogen-bridged quasi-one-dimensional (1-D) complexes 1–3 consisting of alternate arrangements of metals (M) (M: Cu, Ni, Pd, Pt) and halogens (X) (X: Cl, Br, I), expressed as –X–M–X– M–X–, have been of interest because of their almost isolated 1- D structure in which various metal valencies, such as M 2þ , M 3þ , and M 4þ , can be formed. Among those, [MX(chxn) 2 ]X 2 (chxn: 1R,2R-cyclohexanediamine, C 6 H 10 (NH 2 ) 2 ; X: Cl, Br) have been reported to form a mixed-valence diamagnetic structure of –X–M 2þ –X–M 4þ –X– for M = Pd, 1 whereas they have shown an averaged paramagnetic structure of –X–M 3þ – X–M 3þ –X– for M = Ni. 2 Recently, crystals of Ni–Pd mixed-metal complexes, [Ni 1x Pd x X(chxn) 2 ]X 2 (0:0  x  1:0), 4,5 consisting of homo- geneously mixed crystalline lattices of the two kinds of metal complexes with the isomorphous structure (I 222) were pre- pared by applying the electrochemical oxidation technique. 4,5 Concerning these series of complexes, the x dependence of the ESR spectra 6 was measured, and a continuous change of the spectrum-width with x was obtained. A remarkable result was that the evaluated spin susceptibility 6 showed no linear re- lation with x, but was almost constant up to x  0:6 with in- creasing x. This suggests that the majority of diamagnetic Pd 2þ and Pd 4þ metal sites behave like paramagnetic Pd 3þ at concentrations lower than x ¼ 0:6. A change in the Pd valence was also observed in the IR spectra 4,5 of the N–H stretching bands in both the Pd 2þ and Pd 4þ units, which showed a grad- ual shift to that in the Ni 3þ unit. We measured the 13 C spectra and the 1 H NMR relaxation of [Ni 1x Pd x X(chxn) 2 ]X 2 , and the preliminary result was report- ed, 7 where the presence of Pd 3þ sites at x  0:7 and a strongly coupled antiferromagnetic 1-D structure at x  0:13 were shown. In the present study, we performed 13 C NMR spectrum and 1 H NMR relaxation measurements over the whole range of 0:0  x  1:0 in more detail, and analyzed the obtained NMR data to determine the local spin structure in the 1-D chain. Experimental A series of crystals of Ni–Pd mixed-metal complexes, [Ni 1x Pd x X(chxn) 2 ]X 2 (X: Cl, Br; 0:0  x  1:0), were obtained by the electrochemical oxidation 4,5 of methanol solutions of [Ni(chxn) 2 ]X 2 and [Pd(chxn) 2 ]X 2 with various mixing ratios at 300–320 K with a dc current of 10–20 mA. 4,5 As electrolytes, tet- ramethylammonium chloride 5 and tetra-n-butylammonium bro- mide 4 were used. The mixing ratios of Pd to Ni in crystals were determined by ICP emission spectrometry. To identify the obtained crystals, the powder X-ray diffraction and IR spectra were measured using a Phillips X’pert PW3050/00 diffractometer and a Nicolet NEXUS 670 FT-IR spectrometer, re- spectively. A Bruker MSL-300 spectrometer was used for measur- ing the 13 C CP/MAS NMR spectra at a Larmor frequency of 75.468 MHz and with a sample spinning rate of ca. 4 kHz at room temperature. TMS and solid adamantane were used as external Ó 2004 The Chemical Society of Japan Bull. Chem. Soc. Jpn., 77, 1815–1819 (2004) 1815 Published on the web October 9, 2004; DOI 10.1246/bcsj.77.1815