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The crystal structures of the title compounds [C4H8SO (TMSO), C2H6SO (DMSO)] have been determined. The TMSO salt is orthorhombic [space group Pbca, a =13.844(10), b =6.418(12), and c =17.480(16) A] while the DMSO salt is monoclinic [space group P2]/c, a =7.774(1), b =13.557(3), c =6.475(1) A, and P ='103. 83(1) ']. Each contain linear chains of Cu ions withthree bridging ligands (2 C1, 1 0) between each pair of Cu ions. The bridging Cu-L-Cu angles are -87 for the symmetrical bridges and -80' for the asymmetrical bridges. In each salt, the copper coordination geometry is severely distorted from octahedral with four short Cu-ligand bonds (three chlorine and one oxygen) and two long Cu-. ligand bonds (one chlorine and one oxygen). Adjacent chains are well isolated from each other by the sulfoxide groups in one direction, but short sulfur-sulfur contacts occur between adjacent chains in the other direction.The susceptibility of the salts has been measured between 2.0 and 300 K on a PAR vibratingsample magnetometer and on a Faraday balance. The high-temperature data show positive deviation from Curie behavior, indicative of ferromagnetic coupling. However, considerable magnetic interactions between chains exist and the XT vs T plots show maxima at low temperature. The data have been analyzed with several one-dimensional models. The best fit is obtained with an Heisenberg linear chain with ferromagnetic interaction (J/k =39'K, TMSO; J/k =45'K, DMSO) with a mean-field correction for the antiferromagnetic interchain interactions (ZJ'/k = -1.6'K, TMSO; ZJ'/k = -4.0'K, DMSO). Thus, the relevant ratio defining the ideality of the system, J/J', is -50 for the TMSO salt and -25 for the DMSO salt.

The magnetic susceptibilities of powdered samples of Me4NCuCl3 (TMCuC) and [(CH3)3NH]3Cu2Cl7 (TTMCuC) have been measured. Both compounds behave like one-dimensional 5 = 4 Heisenberg ferromagnets which are weakly coupled antiferromagnetically to adjacent chains. For TMCuC, we obtained J/k^ 30 K with \J'\^0.003 K; the ratio |«/V«/| is the lowest yet found for a ferromagnetic 5 = J chain. For TTMCuC, we obtained Jj^yi/k^^O K, with \J' /J^y^\%l(i'^, and ^/AFMA^^-1^ K for the antiferromagnetic chains also present.The magnetic properties of low-dimensional materials continue to be of much interest to physicists and chemists.^ Of the many possible combinations of space dimensionality, spin dimensionality, and spin quantum number, one combination which has been conspicuous by the lack of suitable realizations is the one-dimensional (ID) spin-i Heisenberg ferromagneto The majority of studies on one-dimensional magnetic systems have been on antiferromagnets, with emphasis on S = | Heisenberg (Mn^^-), S^i Ising (Co^"'), and S=i Heisenberg (Cu^^) systems. The general lack of one-dimensional ferromagnets, particularly for S=i where quantum effects are expected to be most pronounced, has been unfortunate. Recently we reported two pseudo-one-dimen-sional ferromagnets ,2 CuClg'DMSO [DMSO = (CH3)2SO] and CuClg» TMSO [TMSO= C4H8SO] with a strong intrachain coupling, 2J/k, of '^ 80-90°K but the extent of interchain coupling (UV^l ^ 10"^) was large enough to preclude their study as ideal systemSo The structural insight gained in these studies prompted us to investigate two additional compounds where the interchain coupling, J', could be expected to be minimized.The results presented in this paper indicate that (CH3)4NCuCl3 (TMCuC) is the most one-dimensional S = i Heisenberg linear chain ferromagnet yet reported. The other compound discussed here, [(CH3)3NH]3Cu2Cl7 (TTMCuC), contains a similar set of linear (CuClg)^ chains with ferromagnetic interactions and very small inter-

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