A family of cyano-bridged copper(II)-copper(I) mixed-valence polymers containing diamine ligands of formula [Cu(pn)(2)][Cu(2)(CN)(4)] (1, pn = 1,2-propanediamine), [Cu(2)(CN)(3)(dmen)] (2, dmen = N,N-dimethylethylenediamine), and [Cu(3)(CN)(4)(tmen)] (3, tmen = N,N,N',N'-tetramethylethylenediamine) have been prepared with the aim of analyzing how their architecture may be affected by steric constraints imposed by the diamine ligands. In the absence of diamine and with use of the voluminous NEt(4)(+) cation, the copper(I) polymer [NEt(4)][Cu(2)(CN)(3)] (4) forms. The structure of 1 consists of a three-dimensional diamond-related anionic framework host, [Cu(2)(CN)(4)](2-), and enclathrated [Cu(pn)(2)](2+) cations. The structure of 2 is made of neutral corrugated sheets constructed from fused 18-member nonplanar rings, which contain three equivalent copper(I) and three equivalent copper(II) centers bridged by cyanide groups in an alternative form. The 3D structure of 3 consists of interconnected stair-like double chains built from fused 18-member rings, which adopt a chairlike conformation. Each ring is constructed from two distorted trigonal planar Cu(I) centers, two bent seemingly two-coordinated Cu(I) centers, and two pentacoordinated Cu(II) atoms. The structure 4 is made of planar anionic layers [Cu(2)(CN)(3)](n)(n-) lying on mirror planes and NEt(4)(+) cations intercalated between the anionic layers. From the X-ray structural results and calculations based upon DFT theory some conclusions are drawn on the structure-steric factors correlation in these compounds. Compound 1 exhibits very weak luminescence at 77 K with a maximum in the emission spectrum at 520 nm, whereas compound 4 shows an intense luminescence at room temperature with a maximum in the emission spectrum at 371 nm. Polymers 2 and 3 exhibit weak antiferromagnetic magnetic exchange interactions with J = -0.065(3) and -2.739(5) cm(-1), respectively. This behavior have been justified on the basis of the sum of two contributions: one arising from the pure ground-state configuration and the other one from the charge-transfer configuration Cu(I)-CN-Cu(II)-CN-Cu(II) that mixes with the ground-state configuration.

Cyanide-bridged bimetallic systems, prepared from assembling cyanometallates and transition metal complexes building blocks, have been shown to exhibit fascinating structures with interesting magnetic, electrochemical, magneto-optical and zeolitic properties. 1 Linear cyanometallates, [M(CN) 2 ] 2 (M = Ag(I) and Au(I)), however, have been infrequently used as building blocks, probably as a consequence of their diamagnetic nature. Interestingly, gold(I) atoms of dicyanoaurate groups may be involved in intermolecular interactions comparable to hydrogen bonds. This closed-shell intermolecular interaction between gold(I) atoms, sometimes called aurophilicity, is known to be an useful tool for the design of intriguing and interesting polymeric structures in solid state. 2 Therefore, the interplay between covalent and aurophilic interactions involving dicyanoaurate groups might produce novel structural topologies. Moreover, according to precise theoretical calculations, the Au-Au interaction is effective over a wide range of distances. 3 In a earlier statistical study 4 based on 693 goldcontaining structures, it was found that there exists a strong correlation between the Au-Au distance (in the range 3-4 Å) and the dihedral angle between the donor atoms attached to the two adjacent gold atoms: the shorter the Au-Au distance is, the higher will be the probability of the staggered conformation. This has been also observed for dicyanoaurate containing compounds. 5 An interesting cation used in synthetic work with dicyanoaurate(I) anions is the cobalt(II) cation with its ability to display either octahedral or tetrahedral coordination. 6 For both chromophores the resulting structure in the solid state is a threedimensional network, where both ends of the dicyanoaurate(I) anions are coordinated to a cobalt(II) cation. Interestingly, the shortest Au-Au distances are significantly different: 3.11 Å in the tetrahedral and 3.33 Å in the octahedral analogue. If some of the coordination sites of a cation are blocked by an additional ligand, the dimensionality can be varied and then it might be possible to analyse the influence of the aurophilic interactions on the final structure. For instance, in a formally 1D structure of (tmeda)Cu[Au(CN) 2 ] 2 (tmeda = N,N,NA,NA-tetramethylethylenediamine) 7 the aurophilicity enhances the dimensionality to 3D, with Au-Au distances of 3.345 and 3.538 Å, less than the sum of the van der Waals radii of Au (3.60 Å).Here we applied the same strategy in synthetic work. Each cobalt assumes a slightly distorted octahedral CoN 4 O 2 coordination polyhedron, which is made up of four nitrogen atoms from the bridging cyanide groups in plane and two oxygen atoms of the DMF molecules in trans-positions. The Co-N bond distances are in the range 2.086(11) to 2.116(12) Å whereas Co-O bond distances are 2.088(10) and 2.093(10) Å. As expected, the two crystallographically non-equivalent [Au(CN) 2 ] 2 anions are almost linear with C-Au-C bond angles of 177.9(6) and 175.5(6)°. The CN-Co and NC-Au bond angles do n...

Two polymorphic cyano-bridged Au(I)-Ni(II) bimetallic complexes of formulas [Ni(en)2Au(CN)2][Au(CN)2] (1) and [Ni(en)2[Au(CN)2]2] (2) have been prepared from the 1:2 reaction between [Au(CN)2]- and either [Ni(en)2Cl2]Cl or [Ni(en)3]Cl2.2H2O, respectively. The structure of 1 consists of polymeric cationic chains of alternating [Au(CN)2]- and [Ni(en)2]2+ units running along the a axis and [Au(CN)2]- anions lying between the chains. The noncoordinated dicyanoaurate anions are aligned perpendicular to the ac plane and involved in aurophilic interactions with the bridging dicyanoaurate groups, ultimately leading to a 2D bimetallic grid. The structure of 2 consists of trinuclear molecules made of two [Au(CN)2]- anions linked to [Ni(en)2]2+ unit in trans configuration. Trinuclear units are joined by aurophilic interactions to form 1D zigzag chains. The magnetic properties of these compounds are strongly dominated by the local anisotropy of the octahedral Ni(II) ions, thus indicating that the magnetic exchange interaction mediated by dicyanoaurate bridging groups, if it exists, is very weak. To get insight into the electronic properties of the inter- and intramolecular interactions of the [Au(CN)2]- building blocks, the structures of different aggregates of dicyanogold units were optimized and then analyzed by making use of atoms-in-molecules (AIM) theory. Moreover, bond indices were calculated by methods based upon nonlinear population analysis.

Abstract:The crystal structure of bright-red crystals of the bidimensional polynuclear diamagnetic (kchloro)(k-pyrazine)copper(I) complex has been analyzed from X-ray diffraction data. The structure was solved by the heavy-atom method. Full-matrix least-squares refinement based on 673 reflections with F > 4u(F) converged to a final R = 0.043 and R,, = 0.048. Crystals of this complex are monoclinic, space group P2/c, a = 3.814(1), b = 6.356(1) and c = 11.497(5) A; P = 96.04(2)", Z = 2. The structure consists of planes of copper(1) atoms linked by pyrazine and C1-bridges, each Cu(1) being in a distorted tetrahedral environment formed by two chloride ions and two nitrogen atoms belonging to two pyrazine molecules, with bond distances of Cu-CI = 2.349(1) and Cu-N = 2.038(4) A. Vibrational and electronic spectroscopy of the title compound is also reported.Key words: two-dimensional copper(1)-pyrazine complexes.RCsumC : Utilisant les donnCes de la diffraction des rayons X, on a dCterminC la structure cristalline des cristaux rouge brillant du complexe diamagnktique polynuclCaire bidimensionnel (p-chloro)(k-pyrazine)cuivre(I). On a rCsolu la structure par la mkthode des atomes lourds et on l'a affinCe par la mCthode des moindres carrts

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The reaction of cis-[PdCl2(PPh3)2] with 8-(methylthio)theophylline (HL) leads to the formation of trans-[PdCl(L)(PPh3)2], an N(7)−Pd-bonded complex, which under mild conditions converts into the mixed-ligand complex trans-[Pd(L‘)(L)(PPh3)2] (HL‘ is theophylline). Noteworthy, the latter represents the first example of a C(8)−Pd-bonded complex.

Seven new polynuclear copper(II) complexes of formula [Cu(mu-pymca)2] (1) (pymca(-) = pyrimidine-2-carboxylato), [Cu(mu-pymca)Br] (2), [Cu(mu-pymca)Cl] (3), [Cu(mu-pymca)(SCN)(H2O)] x 4 H2O (4), [Cu(mu-pymca)N3] (5), [Cu2(mu1,5-dca)2(pymca)2] (6) (dca = dicyanamide), and K{[mu-Au(CN)2]2[(Cu(NH3)2)2(mu-pymca)]}[Au(CN)2]2 (7) have been synthesized by reactions of K-pymca with copper(II) ions in the presence of different counteranions. Compound 1 is a linear neutral chain with a carboxylato bridging ligand in a syn-anti coordination mode, whereas complexes 2 and 3 consist of cationic linear chains with cis and trans bis(chelating) pymca bridging ligands. Complex 4 adopts a helical pymca-bridged chain structure. In complex 5, zigzag pymca-bridged chains are connected by double end-on azide bridging ligands to afford a unique honeycomb layer structure. Complex 6 is a centrosymmetric dinuclear system with double mu 1,5-dicyanamide bridging ligands and pymca end-cap ligands. Complex 7 is made of pymca-bridged dinuclear [Cu(NH3)2(mu-pymca)Cu(NH3)2](3+) units connected by [Au(CN)2](-) anions to four other dinuclear units, giving rise to cationic (4,4) rectangular nets, which are linked by aurophilic interactions to afford a singular 3D network. Variable-temperature magnetic susceptibility measurements show that complex 1 exhibits a very weak antiferromagnetic coupling through the syn-anti (equatorial-axial) carboxylate bridge (J = -0.57 cm(-1)), whereas complexes 2-4 and 7 exhibit weak to strong antiferromagnetic couplings through the bis(chelating) pymca bridging ligand J = -17.5-276.1 cm(-1)). Quantum Monte Carlo methods have been used to analyze the experimental magnetic data for 5, leading to an antiferromagnetic coupling (J = -34 cm(-1)) through the pymca ligand and to a ferromagnetic coupling (J = 71 cm(-1)) through the azide bridging ligands. Complex 6 exhibits a very weak antiferromagnetic coupling through the dicyanamide bridging ligands (J = -5.1 cm(-1)). The magnitudes of the magnetic couplings in complexes 2-5 have been explained on the basis of the overlapping between magnetic orbitals and DFT theoretical calculations.