Vol 42, No 9 (2016)

The reactions of 2,2'-pyridyl, (2-Py)C(O)C(O)(2-Py), with the Cd(II) compounds under various conditions are studied. The medium and nature of the anions exert a decisive effect on the compositions and structures of the formed cadmium complexes. The reaction of cadmium diacetate with 2,2'-pyridyl in an aqueous-alcohol medium in air affords coordination compound [Cd(Рic)₂(H₂O)₂] · H₂O (I) (Pic⁻ is picolinate ion, CO₂C₅H₄N), and its crystal structure is determined. The crystals are monoclinic: space group P2₁/c, a = 7.499(1), b = 15.676(1), с = 12.719(1) Å, β = 94.79(1)°, V = 1490.0(2) Å3, Z = 4, ρ_calcd = 1.502 g/cm³. The molecular packing of compound I is a supramolecular 3D framework consisting of discrete complexes [Cd(Pic)₂(H₂O)₂] linked by hydrogen bonds O–H…O. The coordination sphere of Cd²⁺ contains two O atoms and two N atoms of the ligand and two water molecules. The coordination polyhedron of Cd²⁺ is a distorted octahedron.

The formation of transition metal complexes with pivalate and cymantrenecarboxylate ligands in the presence of axial cyclopentadienyl and α-substituted pyridine ligands is discussed. The latter present steric hindrances due to repulsion from the O atoms of the carboxylate bridges. Particular emphasis is placed on the role of outer-sphere ammonium cations: their hydrogen bonding to fluoride bridges limits the growth of cyclic chromium(III) complexes with the pivalate and fluoride ligands that possess the properties of molecular magnets.

The properties of the cymantrenecarboxylate (containing (CO)₃ Mn(η⁵-C₅H₄CO₂^- group) complexes of lanthanides obtained and studied by the authors in the years 2009–2015 are reviewed. The complexes represent a new type of heterometallic 3d–4f compounds. Both binuclear and polymer complexes of various types are synthesized. The variation of the synthesis conditions and the use of additional ligands make it possible to successively change the Mn: Ln ratio in a molecule of the compounds and to obtain the ratio equal to 3: 1, 2: 1, and 1: 1. The polymeric heteroleptic derivatives, acetate and acetyacetonate cymantrenecarboxylates, are synthesized. Using the photolabile cymantrene fragment as a source of Mn²⁺ ions, polynuclear Mn–Ln heterometallic cymantrenecarboxylates are obtained under the oxidative photolysis conditions. The influence of binuclear neodymium cymantrenecarboxylate on the polymerization of dienes is studied. The structures of the complexes, their physicochemical properties, and possibilities of practical application are considered.

Reactions of (α-Pic)₂Pd(OOCCMe₃)₂ (I) with dinuclear copper pivalate dihydrate and polymeric nickel bispivalate afforded the complexes (α-Pic)₂Pd(μ-OOCCMe₃)₂Cu₂(μ-OOCCMe₃)₄ (II) and Pd(μ- OOCCMe₃)₄Ni(α-Pic) (III), respectively, which were structurally characterized. The lantern dimers in complex II show no Cu···Cu bonds (Cu···Cu, 2.671(3) Å) and are united to form chains through the axial bridging pivalate groups inherited from palladium monomer I. In contrast, complex III features heterometallic palladium- nickel lanterns in which the Ni atom has an axial α-picoline ligand, while the Pd atom has no axial ligand; instead, a short Pd–Ni bond is formed (2.4976(3) Å). For triplet-state complex III and its zinc analog Pd(μ-OOCCMe₃)₄Zn(α-Pic) (IV), quantum chemical calculations and topological analysis of the electron density were performed.