Magnetostructural Studies on Zigzag One-Dimensional Coordination Polymers Formed by Tetraamidatodiruthenium(II,III) Paddlewheel Units Bridged by SCN Ligands

We report herein on three zigzag one-dimensional coordination polymers of {[Ru-2 (mu-NHOCR)(4)](mu-SCN)}(n) (R = o-Me-C6H4 (2), m-Me-C6H4 (3), p-Me-C6H4 (4)) formula. These new compounds have been obtained by reaction of the corresponding [Ru-2(mu-NHOR)(4)(THF)(2)](BF4) complex with (NBu4)(SCN) under different synthetic conditions. The crystal structure of [Ru-2 (mu-NHOCC6H4-o-Me)(4)(THF)(2)](BF4) (1), 2 and 3 are presented. A cis-(2,2) arrangement of the amidate ligands of the [Ru-2(mu-NHOCR)(4)](+) units is observed in all cases. Interestingly, the structures of 2 and 3 show linkage isomerism in alternated tetraamidatodiruthenium units whose axial positions are occupied by the same type of donor atom of the SCN ligands. This results in zigzag chains with a Ru-S-C angle of 98.97 degrees and Ru-N-C angle of 169.36 degrees in the case of 2 and 97.99 degrees and 159.26 degrees, respectively, in the case of 3. The magnetic data obtained for 2-4 are indicative of a sigma(2)pi(4)delta(2)(pi*delta*)(3) ground state (S = 3/2) and a large zero-field splitting (ZFS) in all cases (D = 54.57, 62.72 and 43.00 cm(-1) for 2-4, respectively). Similar small antiferromagnetic interactions between diruthenium units (zJ =-0.93, -0.79 and -1.11 cm(-1) for 2-4, respectively) are estimated for all the polymers, suggesting an analogous zigzag arrangement of the chains for 4.