No abstract

No abstract

A series of [OsII(NN)(CO)2Cl2] complexes where NN is a 2,2′‐bipyridine ligand substituted in the 4,4′ positions by H (C1), CH3 (C2), C(CH3)3 (C3), or C(O)OCH(CH3)2 (C4) has been studied as catalysts for the reduction of CO2. Electrocatalysis shows that the selectivity of the reaction can be switched toward the production of CO or HCOO− with an electron‐donating (C2, C3) or ‐withdrawing (C4) substituent, respectively. The electrocatalytic process is a result of the formation of an Os0‐bonded polymer, which was characterized by electrochemistry, UV/Visible and EPR spectroscopies. Photolysis of the complexes under CO2 in DMF+TEOA produces CO as a major product with a remarkably stable turnover frequency during 14 h of irradiation. Our results suggest that electrocatalysis and photocatalysis occur through two distinct processes, starting mainly from an OsI dimer precatalyst if the reduction is performed by an electrode and an OsI mononuclear species in case of a photoreduction process.

Noncovalent metal-metal interactions in the solid state were studied by investigating the stacking of the cationic mononuclear [Rh(H 2 bim)(CO) 2 ] þ (H 2 bim = 2,2 0 -biimidazole) and neutral dinuclear [Rh 2 (R 2 bim)Cl 2 (CO) 4 ] (R = Me, methyl or Bn, benzyl) complexes. In both cases, the d 8 rhodium atoms possessed square planar coordination geometries. The cationic [Rh(H 2 bim)(CO) 2 ] þ complexes with a chelating H 2 bim ligand all formed polymeric stacks with variable Rh 3 3 3 Rh distances (3.2743(3)-3.430(6) A ˚), depending on the counter-anions. In the solid state, the neutral dinuclear complexes with bridging Bn 2 bim formed isolated complexes with no metal-metal interactions between the dinuclear [Rh 2 (Bn 2 bim)Cl 2 (CO) 4 ] motifs. The use of the Me 2 bim ligand led to a tetranuclear complex [Rh 2 (Me 2 bim)Cl 2 (CO) 4 ] 2 with an intermolecular Rh 3 3 3 Rh distance of 3.4104(7) A ˚. A neutral polymeric stack of [Rh 2 (Me 2 bim)Cl 2 (CO) 4 ] n was obtained only in crystals with ethanol of crystallization. The effect of the intermolecular metal-metal interactions on the absorption properties of the compounds was studied using time-dependent density functional theory (TD-DFT) methods. A bathochromic shift was observed in the λ max metal-to-ligand charge transfer (MLCT) absorption with decreasing Rh 3 3 3 Rh distance. The shift was also observed spectroscopically. In the case of [Rh(H 2 bim)(CO) 2 ][BF 4 ], a clear dependence of color on temperature was also observed in the solid state due to the changes in Rh 3 3 3 Rh distance. Furthermore, the formation of an infinite linear metal chain generated metallic luster on the crystals.

Four new zinc and cadmium bisphosphonates [{NaZn(Cl2CP2O6H)(H2O)5}]n (1), [{Cd2(Cl2CP2O6)(H2O)4}.H2O]n (2), [{Zn(Cl2CP2O6Pri2)(H2O)3}.H2O]n (3), and [{Cd2(Cl2CP2O6Pri2)2(MeOH)2(H2O)2}.H2O]2 (4) have been prepared and their crystal structures determined by single-crystal X-ray diffractometry. Two bisphosphonate ligands were used: clodronate, (dichloromethylene)bis(phosphonate) and its symmetrical P,P'-diisopropyl ester derivative. The structure of the Zn complex 1 is three-dimensional, consisting of one-dimensional Zn-clodronate chains connected to the three-dimensional network by Na+ ions. The structure of Cd complex 2 consists of double layers, and a unique bond was found between the Cd2+ cation and a Cl atom of clodronate. Zn complex 3 consists of one-dimensional chains, but the binding of the bisphosphonate ligands is unique: in 3 the bisphosphonate ligand is only bidentate. Compound 4 is a tetramer, and hydrogen bonds hold the tetramers together, forming a layered structure.

This amino acid derived (red&blue) π-stacked (green) hydrogen bonded (striped) dimer forms a pcu-net with water molecules in the narrow channels. Four related molecules are also presented and all were subjected to graph set and Hirshfeld surface analyses.

Four new cobalt, manganese, and copper bis(phosphonates), [Co2{Cl2C(PO3)2}(H2O)7·4H2O] (1), [Co{Cl2C(PO2O(C(O)C6H5))2(H2O)5}·2H2O{Cl2C(PO2O(C(O)C6H5))2}{Co(H2O)6}] (2), [Mn{[Cl2C(PO2O(C(O)C6H5))2](H2O)3}] (3), and [Cu{(CH2C5H5N)C(OH)(PO3H)2}2·4H2O] (4), were prepared by gel, liquid, and evaporation crystallisation methods. Compounds 1–4 were characterised by X‐ray single‐crystal diffraction, elemental analysis, infrared spectroscopy, and thermogravimetric analysis. The effects of metal and various substituted groups in bis(phosphonate) ligands on the structure formation of bis(phosphonates) were studied. In the structure of 1, the clodronic acid ligand (L1) is in bischelating bonding mode, and the dinuclear units of 1 are surrounded by two‐dimensional water cluster patterns. The hydrogen bond network of compound 1 is extended to a three‐dimensional framework when the phosphonate oxygen atoms serve as hydrogen‐bond acceptors. In complex 2, the CoO6 octahedron shares a corner of one PCO3 tetrahedron of the dibenzoyl derivative of clodronic acid ligand (L2), and forms a two‐dimensional hydrogen bonding network, which consists of [Co(H2O)6}]2+ cations, lattice water molecules and L2 ligand molecules. Compound 3, in turn, consists of dimeric building blocks built up of PCO3 tetrahedra of the ligand L2, which connect the corner‐sharing MnO6 octahedra and form an overall 2D structure through hydrogen bonds of coordinated and crystal water molecules and phosphonate oxygen atoms. Complex 4 is among the first metal complexes of risedronic acid (L3). In compound 4, two L3 ligand molecules chelate tridentately the CuII atom at the center of symmetry, and the monomeric units of 4 are connected to a 3D structure through hydrogen bonding of coordinated and lattice water molecules to both protonated and deprotonated phosphonate oxygen atoms and protonated nitrogen atoms in the pyridine ring.

The metallophilic interactions were investigated within chains of oppositely charged rhodium carbonyl complexes. The cationic [Rh(CO)(2)(L)](+) (L = 2,2'-bipyridine and 1,10-phenanthroline) and anionic [RhCl(2)(CO)(2)](-) units were self-assembled into one dimensional rhodium chains supported by electrostatic interactions. The array of Rh centers in {[Rh(CO)(2)(2,2'-bpy)][RhCl(2)(CO)(2)]}(n) was found to be nearly linear with a Rh···Rh···Rh angle of 170.927(11)° and Rh···Rh distances of 3.3174(5) Å and 3.4116(5) Å. The crystal structure of {[Rh(CO)(2)(1,10-phen)][RhCl(2)(CO)(2)]} consisted of two sets of crystallographically independent chains with slightly different Rh···Rh···Rh angles (170.275(9)° and 159.573(9)°). The higher linearity allowed closer packing of the rhodium complexes. The Rh···Rh distances were 3.2734(3) Å and 3.3155(3) Å for the more linear and 3.3498(3) Å and 3.3211(3) Å for the less linear system. The existence of metallophilic interactions was confirmed computationally by TD-DFT and QTAIM analysis. The computational results also indicated that the intermolecular charge transfer from the cation to the anion had a significant contribution to the absorption properties of the chain compounds.