The reaction of Zn(NO3)2.6H2O or Cu(NO3)2.3H2O with the star-shaped ligand 2,4,6-tris(di-2-picolylamino)[1,3,5]triazine (dipicatriz) in acetonitrile results in the formation of the mono- or trinuclear coordination compounds [Zn(dipicatriz)(NO3)2] (1), [Zn3(dipicatriz)(NO3)6](CH3CN)3 (2), and [Cu3(dipicatriz)(NO3)2(H2O)6](NO3)4 (3), depending on the metal-to-ligand ratios used during the crystallization process. Their crystal structures exhibit unique supramolecular interactions. Compounds 1 and 2 show anion-pi interactions between coordinated nitrate ions and the s-triazine ring. Compound 3 exhibits remarkable interactions between two noncoordinated nitrate anions and the two faces of the electron-deficient heteroaromatic ring, corroborating earlier theoretical investigations in this area. New theoretical investigations have been carried out on nitrate-pi interactions, taking into account the particular position of the anion toward the aromatic ring observed in the crystal structures.

A series of EDA complexes of N-iodosaccharin (NISac) and N-bromosaccharin (NBSac) with nitrogen and oxygen electron-pair donors, NISacÁH 2 O, NISacÁTHF, NISacÁPy, NISac 2 ÁPyz and NBSac 2 ÁPyz, was prepared and examined by X-ray diffraction and NMR. The complexes are relatively stable, crystalline compounds with the ligand bound to the halogen atom in a nearly linear arrangement N-halogen-ligand. The halogen-ligand distances are inversely proportional to the donor ability of the ligand. The interactions between ligand and halogen are stronger for iodine than bromine. The X-ray structure analysis has shown that for some compounds the N-X bond in the halosaccharin moiety is not coplanar with the isothiazole ring, and the quantum-chemical calculations demonstrate a high flexibility of the corresponding angle. Complexes were modelled also by DFT calculations using B3LYP and MPW1K functionals. A better fit of the computed geometry was obtained by the geometry optimization in a polar solvent continuum than in vacuum.

Piperidine and pyrrolidine, both belonging to a group of secondary cyclic amines, reacted with acetonitrile in the presence of zinc(ii) to give the corresponding amidines that coordinated to the metal through their imine nitrogen.

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(PyH)5[Mo(V)OCl4(H2O)]3Cl2 and (PyH)n[Mo(V)OBr4]n reacted with glycolic acid (H2glyc) or its half-neutralized ion (Hglyc(-)) to afford a series of novel glycolato complexes based on the {Mo(V)2O4}2+ structural core: (PyH)3[Mo2O4Cl4(Hglyc)]. (1)/ 2CH 3CN (1), (PyH) 3[Mo 2O 4Br 4(Hglyc)].Pr(i)OH(2), (PyH)2[Mo2O4(glyc) 2Py 2] (3), (PyH) 4[Mo 4O 8Cl 4(glyc) 2].2EtOH (4), and [Mo 4O 8(glyc) 2Py 4] (5) (Py = pyridine, C 5H 5N; PyH(+) = pyridinium cation, C 5H 5NH (+) and glyc (2-) = a doubly ionized glycolate, (-)OCH 2COO (-)). The compounds were fully characterized by X-ray crystallography and infrared spectroscopy. The Hglyc (-) ion binds to the {Mo 2O 4} (2+) core through a carboxylate end in a bidentate bridging manner, whereas the glyc (2-) ion adopts a chelating bidentate coordination through a deprotonated hydroxyl group and a monodentate carboxylate. The orientations of glyc (2-) ions in 3- 5 are such that the alkoxyl oxygen atoms occupy the sites opposite the multiply bonded oxides. {(C6H5) 4P}[Mo(VI)O 2(glyc)(Hglyc)] ( 6), an oxidized complex, features a reversed orientation of the glyc(2-) ion. The theoretical DFT calculations on the [Mo(V)2O4(glyc) 2Py 2](2-) and [Mo(VI)O2(glyc)2](2-) ions confirm that binding of glycolate with the alkoxyl oxygen to the site opposite the MoO bond is energetically more favorable in {Mo(V)2O4}(2+) species, whereas a reversed orientation of the ligand is preferred in Mo(VI) complexes. An explanation based on the orbital analysis is put forward.

A series of oxomolybdate(V) complexes with methanol was prepared by the reaction of (PyH) 5 (3) or as an orthorhombic polymorph (4). After prolonged reaction times further assembly of dinuclear fragments takes place and tetranuclear

6− revealed the isomer with the staggered conformation of the µ 4 -oxalate ion to be of the lowest energy.

Reactions of mononuclear oxohalomolybdates() with squaric acid (3,4-dihydroxycyclobut-3-ene-1,2-dione) afforded two types of {Mo 2 O 4 } 2ϩ containing species with the squarato ligand engaged in a µ 2 -1,2-bis(monodentate) binding mode. In the presence of pyridine (Py) or 3,5-lutidine (3, 5-Lut) 1c were obtained. A pair of nitrogen donor ligands and a squarate oxygen occupy the three coordination sites of each metal in the {Mo 2 O 4 } 2ϩ unit in 1a, 1b and 1c. The squarate functions as a third, auxiliary bridge between a pair of molybdenum atoms at an average distance of 2.55 Å. Using 2,4,6-collidine (Col) afforded (ColMe) 4 [Mo 4 O 8 (C 4 O 4 ) 4 ]ؒ2MeOHؒ2Col 2a (ColMe ϩ = N-methylcollidinium cation, NC 9 H 14 ϩ ) and (ColH) 4 (PyEt)[Mo 4 O 8 (C 4 O 4 ) 4 ]Br 2b (ColH ϩ = protonated 2,4,6-collidine, NC 8 H 12 ϩ ; PyEt ϩ = N-ethylpyridinium cation, NC 7 H 10 ϩ ). The tetranuclear anions of 2a and 2b consist of a rare, cube-like {Mo 4 O 4 (µ 3 -O) 4 } 4ϩ core with four squarato ligands attached to its periphery. The squarato ligands in the [Mo 4 O 8 (C 4 O 4 ) 4 ] 4Ϫ anions bridge pairs of molybdenum atoms from neighbouring {Mo 2 O 4 } 2ϩ units, spanning an average distance of 3.43 Å. The compounds were fully characterized by infrared vibrational spectroscopy, NMR spectroscopy, elemental analyses and X-ray diffraction studies.