The reaction of the divalent metal halides ZnCl(2), ZnBr(2), MnCl(2).4CH(3)CN, MnBr(2), FeCl(2).4CH(3)CN, CoCl(2).4CH(3)CN, CoBr(2), NiCl(2).6H(2)O, and NiBr(2), respectively, with the macrocycle 1,4,7-trimethyl-1,4,7-triazacyclononane (L) (1:1) in anhydrous acetonitrile, acetone, chloroform, or ethanol affords upon additon of NaBPh(4) the isomorphous series of complexes [LM(II)(&mgr;-X)(3)M(II)L]BPh(4): 1, M = Zn, X = Cl; 2, Zn, Br; 3, Mn, Cl; 4, Mn, Br; 5, Fe, Cl; 6, Co, Cl; 7, Co, Br; 8, Ni, Cl; 9, Ni, Br. Six of these complexes have been structurally characterized by single-crystal X-ray crystallography; they crystallize in the triclinic space group P&onemacr; (No. 2) with Z = 4. Crystal data are as follows 1, a = 16.654(1), b = 17.042(1), c = 17.684(1) Å, alpha = 97.30(1), beta = 93.58(1), gamma = 117.46(1) degrees; 3, a = 16.632(8), b = 17.012(8), c = 17.855(5) Å, alpha = 97.16(3), beta = 93.37(3), gamma = 117.24(3) degrees; 5, a = 16.658(3), b = 17.064(3), c = 17.741(4) Å, alpha = 97.32(3), beta = 93.47(3), gamma = 117.36(3) degrees; 6, a = 16.640(3), b = 17.040(3), c = 17.686(4) Å, alpha = 97.39(3), beta = 93.58(3), gamma = 117.39(3) degrees; 8, a = 16.608(3), b = 16.995(3), c = 17.555(3) Å, alpha = 97.36(1), beta = 93.52(1), gamma = 117.52(1) degrees; 9, a = 16.680(3), b = 17.016(2), c = 17.715(3)Å, alpha = 96.99(1), beta = 93.70(1), gamma = 117.42(1) degrees. All complexes consist of a dinuclear, face-sharing bioctahedral monocation with three &mgr;(2)-Cl or &mgr;(2)-Br bridging ligands and two LM fragments and well-separated tetraphenylborate anions (1:1). The cations cocrystallize in two different forms: an enantiomeric form with (lambdalambdalambda) (or (deltadeltadelta)) conformation at both LM fragments and a meso form with an (lambdalambdalambda) conformation at one LM fragment and (deltadeltadelta) at the other (ratio 1:1). From temperature-dependent magnetic susceptibility measurements (2-293 K) it was established that the spins of the unpaired electrons in 3 (d(5)d(5) high spin), 4 (d(5)d(5)), 6 (d(7)d(7) high spin), 7 (d(7)d(7)), 8 (d(8)d(8)), and 9 (d(8)d(8)) are intramolecularly, weakly antiferromagnetically coupled in each case. Surprisingly, the spins order ferromagnetically in 5 (d(6)d(6) high spin). This is in contrast to the previously reported complex [(thf)(3)Fe(II)(&mgr;-Cl)(3)Fe(II)(thf)(3)][SnCl(5)(thf)] (thf = tetrahydrofuran)(5) for which a new analysis of the temperature-dependence of the magnetic susceptibility and of field-dependent Mössbauer spectra establish a weak intramolecular antiferromagnetic coupling. The origin of this difference is analyzed.

A series of heterodinuclear complexes CunM, where M = Cr(III) (1), Mn(III) (2), Mn(II) (3), Fe(III) (4), Co(II) (5), Co(IlI) (6), Ni(II) (7), Cu(II) (8), and Zn(II) (9), containing the oximato dianion (Dopn* 12~) as bridging ligand and 1,4,7-trimethyl-1,4,7-triazacyclononane (L) as one of the two capping ligands have been synthesized by using the [Cu(DopnH)]+ cation (H2Dopn = 3,9-dimethyl-4,8-diazaundeca-3,8-diene-2,10-dione dioxime) as a ligand for the different ML"+ centers. The compounds have been characterized on the basis of IR, electronic, and EPR spectroscopy and variable-temperature (2-295 K) magnetic susceptibility measurements. The dinuclear complexes are quasi-isostructural with the copper(H) ion in a distorted square pyramidal environment, CuN40, and the M ion, except for that in 8, is six-coordinate with the MN3O3 or MN3O2CI coordination sphere. For M = Cu (8), the coordination geometry of M with the CuN302 chromophore is also square pyramidal. The crystal and molecular structures of the compounds [(Dopn)CuI1(OH2)CrIII(OCH3)L](C104)2,H20 (1) and [(Dopn)Cuu(u-CH3COO)-MnnIL] (C104)r2H20 (2) have been established by X-ray diffraction. 1 crystallizes in the monoclinic system space group P2i/n, with cell constants a = 13.096(3) A, b= 17.933(4) A, c= 15.994(3) A, /3= 113.49(3)°, V= 3444.9(13) A3 4, and Z = 4. The structure consists of oximato-bridged CunCrIn dications and noncoordinated perchlorate anions, with a Cu-• -Cr distance of 3.86 A. The crystal data for 2 are as follows: orthorhombic, space group Z>212121, a = 12.275(4) A,b = 14.171(9) A, c = 19.780(3) A, V -3441(2) A3, Z = 4. The structure consists of a six-coordinate Mn(III) center, MnN3C>3, and the copper(II) center has an N40 donor set. An acetate group bridges the manganese and copper ions with a Cu-• -Mn separation of 3.54 A. A low-quality X-ray structure determination for the CunFein complex is also reported. Analysis of the susceptibility data yields a strong antiferromagnetic interaction (27 = -596 cm-1) between adjacent Cu(II) ions in 8, showing once again that bridging oximes are good mediators for exchange interactions. The strength of the effective antiferromagnetic interaction decreases with increasing number of unpaired electrons in this series, 8>7>5>4~3.Moderately strong ferromagnetic interactions have been observed for CunMnIU (2) (27 = +109 cm-1) and CunCrin (1) (27 = +37 cm-1). A qualitative rationale has been provided for the difference in magnetic behaviors. The X-band EPR spectra (3-77 K) have been measured to establish the ground states of the dinuclear complexes. Well-resolved S = 2 EPR spectra for different heterometal systems have been observed.

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Very strong antiferromagnetic coupling exists between the Fe centers in the N‐bridged complexes 1 and 2. In 1 (shown on the right), which contains a symmetrical [FeIV = N = FeIV] unit, this results in an S = 0 ground state, while in 2, which has an unsymmetrical FeIII–N = FeIV bridge, it leads to an S = 3/2 ground state. Compound 2 forms in the photolysis of [FeIII(cat)N3] and can be oxidized with Br2 to give 1. L = trimethyltriazacyclononane, cat = tetrachlorocatecholate(2−).