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Coordination compounds having the general formula ML2Ox are described, with Ox = oxalato dianion; M = Ni, Co and Zn; 1. = water and imidazoles. The compounds are * ,-\uth~r to x~hom all correspondence should be addressed. characterised by chemical analyses, i.r., far-i.r., Raman, ligand field and e.s.r, spectra. Magnetic susceptibility measurements at low temperatures indicate a polymeric structure of anti-ferromagnetically coupled M 2. ions.All physical measurements agree with a polymeric structure built up by oxalate ions as tetradentate bridging ligands forming one-dimensional linear chains. F.ach metal ion is Transition Met. Chem. 3, 90-98 (1978) Polymeric Coordination Compounds of Nickel (IlL Cobalt(ll) and Zinc(ll) 91 coordinated by four oxalate oxygens and two donor atoms (N or O) in distorted octahedron. For M = Ni, the magnetic susceptibility measurements can be best described with the Heisenberg model including a zero-field splitting; for M = Co, the lsing model gives the best results. The exchange coupling constants, l J I, vary from 9-13 cm -t .

Magnetic susceptibility data have been measured in the temperature range 1.75 to 60 K for the following structurally characterized, single chloride-bridged copper(l1) chain compounds : dichlorobis(dimethy1 sulphoxide)copper( II), dichlorobis(imidazole)copper(ll), aquo(caffeine)dichlorocopper(ll), and dichloro[2-(2'-methylaminoethyl)pyridine]copper(ii). The first two compounds exhibit antiferromagnetic intrachain interactions with exchange coupling constants of -6.1 and -2.1 cm--l, respectively, while the second two compounds exhibit ferromagnetic interactions with J values of 0.48 and 1.58 cm-respectively. Except for dichlorobis(imidazole)copper(ii), which undergoes long-range magnetic ordering below 7.7 K, the exchange coupling constants become more negative as the angle a t the chloride bridge increases from 1 13.6" in dichloro[2-(2'-methylaminoethyl)pyridine]copper(l1) to 144.6' in dichlorobis(dimethy1 sulphoxide)copper(ll).

Communications t o the Editor 5569 +: and t,b; gives the predominant contribution to the total (5) Belyaev, L. M.; Nabatov. V. V.; Martyshev, Y. N. Soviet Phys. Crysta//ogr., 1963, 7, 464. (6) A relationship with the well-known phenomenon of triboluminescence7 was initially supposed. However, we were unable to detect any luminescence during or after the cracking.