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Die Umsetzung von Chlorodiphenylphosphan und 2, 6‐Diaminopyridin ergibt N, N′‐Bis(diphenylphosphino)‐2, 6‐diaminopyridin (PNP). Die Koordinationsverbindungen der beiden Typen mer‐[M(PNP)(CO)3] · 2 THF (M = Cr, Mo, W) und [M(PNP)Cl]Cl · L (M = Ni, L = H2O; M = Pd, L = C2H5OH; M = Pt) werden mit dem dreizähnigen Liganden PNP synthetisiert. Ihre Charakterisierung erfolgt durch IR‐, UV‐ und NMR‐Meßergebnisse. Die Resultate der Einkristall‐Röntgenstrukturbestimmungen von den triklinen Festkörpern mer‐[Mo(PNP)(CO)3] · 2 THF und [Ni(PNP)Cl]Cl · H2O zeigen sowohl bei der oktaedrischen Mo(d6) als auch bei der quadratisch planaren Nickel(d8)‐Komplexverbindung ein nahezu planares dreizähniges PNP‐Chelatring‐system: Zwei verbundene Fünfringe vom Typ , in dem die beobachteten Bindungsabstände auf π‐Elektronendelokalisation hinweisen. Die beobachtete Grammsuszeptibilität des diamagnetischen Nickel (d8)‐Festkörpers bleibt im Temperaturbereich von 293 bis 410 K unverändert. Das relative Aktivierungsvermögen für eine homogenkatalytische Standard‐Hydrierungsreaktion des Substrates Styrol zu Ethylenbenzol nimmt für die Katalysatorverbindungen vom Typ [M(PNP)Cl]Cl · nL gemäß der Reihenfolge MII = Ni > Pd > Pt ab.

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The reaction of Cu(MeC02)2.H20 with 1,4,7-trimethyl-I ,4,7-triazacyclononane (L) and imidazole (ImH) in methanol affords, in the presence of a small amount of triethylamine and NaC104, the blue trinuclear complex [L3C~3(lm)3](C104)3 which has been characterized by X-ray crystallography, EPR and magnetic susceptibility measurements to be a spin-frustrated triangular imidazolate-bridged copper(ii) complex without any p3-X ligand.

Two series of linear homo- and heterotrinuclear complexes, MnIIIMIIMnIII and MnIVMIIMnIV, where MII represents MnII (1 and 5), NiII (2 and 6), CuII (3 and 7), or ZnII (4 and 8), containing three dimethylglyoximato dianions (dmg2-) as bridging ligands and 1,4,7-trimethyl-1,4,7-triazacyclononane (L) as the capping ligand for the terminal MnIII or MnIV ions, have been synthesized. Compounds 1−8 have been characterized on the basis of elemental analyses, IR, UV−vis, and EPR spectroscopy, and variable-temperature (2−295 K) magnetic susceptibility measurements. The trinuclear complexes are quasi-isostructural with the terminal manganese ions in a distorted octahedral environment, MnIII/IVN3O3, and the divalent metal ions M are six-coordinate with the MIIN6 chromophore. The molecular structures of the compounds [LMnIII{(μ-dmg)3MnII}MnIIIL](ClO4)2 (1) and [LMnIII{(μ-dmg)3CuII}MnIIIL](ClO4)2 (3) have been established by X-ray diffraction. 1 crystallizes in the monoclinic system, space group C2/c, with cell constants a = 32.472(6) Å, b = 9.058(2) Å, c = 16.729(3) Å, β = 107.60(3)°, V = 4690.2(16) Å3, and Z = 4. The crystal data for 3 are as follows:  monoclinic, space group C2/c, a = 32.686(5) Å, b = 8.870(1) Å, c = 16.867(2) Å, β = 108.65(1), V = 4633(1) Å3, and Z = 4. Analyses of the susceptibility data indicate the presence of weak to moderate exchange interactions, both ferro- and antiferromagnetic, between the paramagnetic centers. It has been conclusively demonstrated that there are indeed two different coupling constants, J = J 12 = J 23 and J 13, operative in these linear trinuclear complexes. J 13 represents the exchange interaction between two terminal paramagnetic centers separated by a distance of ∼7 Å. The effect of J 13 on the energy-splitting pattern has been demonstrated by the variability of the ground states. A qualitative rationale has been provided for the difference in magnetic behaviors. The cyclic voltammograms of complexes 1−8 reveal two reversible and two quasireversible one-electron redox processes. The central divalent metal ion in these complexes is redox-inactive.