A luminescent heterometallic dirhodium-silver chain

Transition Metal Chain Complexes Supported by Soft Donor Assembling Ligands

The chemistry of discrete molecular chains constituted by metals in low oxidation states, displaying metal-metal proximity and stabilized by suitable metal-bridging, assembling ligands comprising at least one soft donor atom is comprehensively reviewed; complexes with a single (hard or soft) bridging atom (e.g., μ-halide, μ-sulfide, or μ-PR₂ etc.) as well as "closed" metal arrays (that fall in the realm of cluster chemistry) are excluded. The focus is on transition metal-based systems, with few excursions to cases combining transition and post-transition elements. Most relevant supporting ligands have neutral C, P, O, or S donor (mainly, N-heterocyclic carbene, phosphine, ether, thioether) or anionic donor (mainly phenyl, ylide, silyl, phosphide, thiolate) groups. A supporting-ligand-based classification of the metal chains is introduced, using as the classifying parameter the number of "bites" (i.e., ligand bridges) subtending each intermetallic separation. The ligands are further grouped according to the number of donor atoms interacting with the metal chain (called denticity in the following) and the column of the Periodic Table to which the set of donor atoms belongs (in ascending order). A complementary metal-based compilation of the complexes discussed is also provided in a concise tabular form.

Heteronuclear Dirhodium-Gold Anionic Complexes: Polymeric Chains and Discrete Units

In this article, we report on the synthesis and characterization of the tetracarboxylatodirhodium(II) complexes [Rh2(μ-O2CCH2OMe)4(THF)2] (1) and [Rh2(μ-O2CC6H4-p-CMe3)4(OH2)2] (2) by metathesis reaction of [Rh2(μ-O2CMe)4] with the corresponding ligand acting also as the reaction solvent. The reaction of the corresponding tetracarboxylato precursor, [Rh2(μ-O2CR)4], with PPh4[Au(CN)2] at room temperature, yielded the one-dimensional polymers (PPh4)n[Rh2(μ-O2CR)4Au(CN)2]n (R = Me (3), CH2OMe (4), CH2OEt (5)) and the non-polymeric compounds (PPh4)2{Rh2(μ-O2CR)4[Au(CN)2]2} (R = CMe3 (6), C6H4-p-CMe3 (7)). The structural characterization of 1, 3·2CH2Cl2, 4·3CH2Cl2, 5, 6, and 7·2OCMe2 is also provided with a detailed description of their crystal structures and intermolecular interactions. The polymeric compounds 3·2CH2Cl2, 4·3CH2Cl2, and 5 show wavy chains with Rh-Au-Rh and Rh-N-C angles in the ranges 177.18°-178.69° and 163.0°-170.4°, respectively. A comparative study with related rhodium-silver complexes previously reported indicates no significant influence of the gold or silver atoms in the solid-state arrangement of these kinds of complexes.

Linear One-Dimensional Coordination Polymers Constructed by Dirhodium Paddlewheel and Tetracyanido-Metallate Building Blocks

In this article, we describe the preparation of anionic heteronuclear one-dimensional coordination polymers made by dirhodium paddlewheels and tetracyanido-metallatate building blocks. A series of complexes of (PPh4)2n[{Rh2(µ-O2CCH3)4}{M(CN)4}]n (M = Ni (1), Pd (2), Pt (3)) formulae were obtained by reaction of [Rh2(μ-O2CCH3)4] with (PPh4)2[M(CN)4] in a 1:1 or 2:1 ratio. Crystals of 1−3 suitable for single crystal X-ray diffraction were grown by slow diffusion of a dichloromethane solution of the dirhodium complex into a chloroform solution of the corresponding tetracyanido–metallatate salt. Compounds 1 and 2 are isostructural and crystallize in the triclinic P-1 space group, while compound 3 crystallizes in the monoclinic P21/n space group. A detailed description of the structures is presented, including the analysis of the packing of anionic chains and PPh4+ cations.

Synthesis and Structural Characterization of a Series of One-Dimensional Heteronuclear Dirhodium-Silver Coordination Polymers

Herein, we describe the preparation of heteronuclear dirhodium-silver complexes by reaction between molecular Rh(II)-Rh(II) compounds [Rh₂(μ-O₂CR)₄L₂] (R = Me, Ph (1), CH₂OEt (2); L = solvent molecules) with paddlewheel structure and PPh₄[Ag(CN)₂]. One-dimensional coordination polymers of (PPh₄)_n[Rh₂(μ-O₂CR)₄Ag(CN)₂]_n (R = Me (3), Ph (4), CH₂OEt (5)) formula have been obtained by replacement of the two labile molecules in the axial positions of the paddlewheel structures by a [Ag(CN)₂]⁻ bridging unit. The crystal structures of 3–5 display a similar arrangement, having anionic chains with a wavy structure and bulky (PPh₄)⁺ cations placed between the chains. The presence of the (PPh₄)⁺ cations hinders the existence of intermolecular Ag-Ag interactions although several C-H····π interactions have been observed. A similar reaction between [Rh₂(μ-O₂CCMe₃)₄(HO₂CCMe₃)₂] and PPh₄[Ag(CN)₂] led to the molecular compound (PPh₄)₂{Rh₂(μ-O₂CCMe₃)₄[Ag(CN)₂]₂} (6) by replacement of the axial HO₂CCMe₃ ligands by two [Ag(CN)₂]⁻ units. The trimethylacetate ligand increases the solubility of the complex during the crystallization favouring the formation of discrete heteronuclear species.

Weak aurophilic interactions in a series of Au(iii) double salts

In this work, several new examples of rare Au^III⋯Au^IIIaurophilic contacts are reported.

Metal-metal interactions in linear tri-, penta-, hepta-, and nona-nuclear ruthenium string complexes

Density functional theory (DFT) methodology was used to examine the structural properties of linear metal string complexes: [Ru(3)(dpa)(4)X(2)] (X = Cl(-), CN(-), NCS(-), dpa = dipyridylamine(-)), [Ru(5)(tpda)(4)Cl(2)], and hypothetical, not yet synthesized complexes [Ru(7)(tpta)(4)Cl(2)] and [Ru(9)(ppta)(4)Cl(2)] (tpda = tri-α-pyridyldiamine(2-), tpta = tetra-α-pyridyltriamine(3-), ppta = penta-α-pyridyltetraamine(4-)). Our specific focus was on the two longest structures and on comparison of the string complexes and unsupported ruthenium backboned chain complexes, which have weaker ruthenium-ruthenium interactions. The electronic structures were studied with the aid of visualized frontier molecular orbitals, and Bader's quantum theory of atoms in molecules (QTAIM) was used to study the interactions between ruthenium atoms. The electron density was found to be highest and distributed most evenly between the ruthenium atoms in the hypothetical [Ru(7)(tpta)(4)Cl(2)] and [Ru(9)(ppta)(4)Cl(2)] string complexes.

Theoretical studies on metal-metal interaction, excited states, and spectroscopic properties of binuclear Au-Au, Au-Rh, and Rh-Rh complexes with diphosphine ligands: buildup of complexity from monomers to dimers

To understand their photocatalytic activity and application in luminescent materials, a series of gold and rhodium phosphine complexes (mononuclear [Au(I)(PH(3))(2)](+) (1) and [Rh(I)(CNH)(2)(PH(3))(2)](+) (2); homobinuclear [Au(I)(2)(PH(2)CH(2)PH(2))(2)](2+) (3) and [Rh(I)(2)(CNH)(4)(PH(2)CH(2)PH(2))(2)](2+) (4); heterobinuclear [Au(I)Rh(I)(CNH)(2)(PH(2)CH(2)PH(2))(2)](2+) (5), [Au(I)Rh(I)(CNH)(2)(PH(2)NHPH(2))(2)Cl(2)] (6), and [Au(I)Rh(I)(CNH)(2)(PH(2)NHPH(2))(2)](2+) (7); and oxidized derivatives [Au(II)Rh(II)(CNH)(2)(PH(2)CH(2)PH(2))(2)](4+) (8), [Au(II)Rh(II)(CNH)(2)(PH(2)NHPH(2))(2)Cl(3)](+) (9), and [Au(II)Rh(II)(CNH)(2)(PH(2)NHPH(2))(2)](4+) (10)) were investigated using ab initio methods and density functional theory. With the use of the MP2 method, the M-M' distances in 3-7 were estimated to be in the range of 2.76-3.02 A, implying the existence of weak metal-metal interaction. This is further evident in the stretching frequencies and bond orders of M-M'. The two-electron oxidation from 5-7 to their respective partners 8-10 was shown to mainly occur in the gold-rhodium centers. Experimental absorption spectra were well reproduced by our time-dependent density functional theory calculations. The metal-metal interaction results in a large shift of d(z(2)) --> p(z) transition absorptions in binuclear complexes relative to mononuclear analogues and concomitantly produces a low-lying excited state that is responsible for increasing visible-light photocatalytic activities. Upon excitation, the metal-centered transition and the metal-to-metal charge transfer strengthen the metal-metal interaction in triplet excited states for 3-6, while the promotion of electrons into the sigma*(d(z(2))) orbital weakens the interaction in 9.

Helices versus Zigzag Chains: One-Dimensional Coordination Polymers of AgI and Bis(4-pyridyl)amine

Five one-dimensional coordination polymers were prepared by the reaction of a bent bridging ligand, bis(4-pyridyl)amine (bpa), with an extensive series of AgX salts (X = CF3SO3, PF6, ClO4, NO3). The 1D polymer networks formed with AgCF3SO3 (1), AgPF6 (2.MeCN), and AgClO4 (3.2MeCN) all incorporated MeCN and were found to adopt a zigzag arrangement. The networks formed with AgClO4 (4) and AgNO3 (5) did not contain any solvent and adopted a single-stranded helical arrangement. Two-dimensional H-bonding networks were formed for 1 and 3.2MeCN, with network topologies 4.8(2) and (4, 4), respectively, whereas three-dimensional H-bonded networks of helices were formed for 4, showing an (8, 3)-a network topology, and 5, showing the topology of the alpha-polonium net. The three-dimensional networks both exhibited 4-fold interpenetration. The NO3- anion in 5 appeared to be acting as a template for the 3D structure.

Novel Luminescent Mixed-Metal PtTl-Alkynyl-Based Complexes: The Role of the Alkynyl Substituent in Metallophilic and η2(π⋅⋅⋅Tl)-Bonding Interactions

A novel series of [PtTl(2)(C[triple chemical bond]CR)(4)](n) (n = 2, R = 4-CH(3)C(6)H(4) (Tol) 1, 1-naphthyl (Np) 2; n = infinity, R = 4-CF(3)C(6)H(4) (Tol(F)) 3) complexes has been synthesized by neutralization reactions between the previously reported [Pt(C[triple chemical bond]CR)(4)](2-) (R = Tol, Tol(F)) or novel (NBu(4))(2)[Pt(C[triple chemical bond]CNp)(4)] platinum precursors and Tl(I) (TlNO(3) or TlPF(6)). The crystal structures of [Pt(2)Tl(4)(C[triple chemical bond]CTol)(8)]4 acetone, 14 acetone, [Pt(2)Tl(4)(C[triple chemical bond]CNp)(8)]3 acetone1/3 H(2)O, 23 acetone 1/3 H(2)O and [[PtTl(2)(C[triple chemical bond]CTol(F))(4)](acetone)S](infinity) (S = acetone 3 a; dioxane 3 b) have been solved by X-ray diffraction studies. Interestingly, whereas in the tolyl (1) and naphthyl (2) derivatives, the thallium centers exhibit a bonding preference for the electron-rich alkyne entities to yield crystal lattices based on sandwich hexanuclear [Pt(2)Tl(4)(C[triple chemical bond]CR)(8)] clusters (with additional Tlacetone (1) or Tlnaphthyl (2) secondary interactions), in the C(6)H(4)CF(3) (Tol(F)) derivatives 3 a and 3 b the basic Pt(II) center forms two unsupported Pt-Tl bonds. As a consequence 3 a and 3 b form an extended columnar structure based on trimetallic slipped PtTl(2)(C[triple chemical bond]CTol(F))(4) units that are connected through secondary Tl(eta(2)-acetylenic) interactions. The luminescent properties of these complexes, which in solution (blue; CH(2)Cl(2) 1,2; acetone 3) are very different to those in solid state (orange), have been studied. Curiously, solid-state emission from 1 is dependent on the presence of acetone (green) and its crystallinity. On the other hand, while a powder sample of 3 is pale yellow and displays blue (457 nm) and orange (611 nm) emissions, the corresponding pellets (KBr, solid) of 3, or the fine powder obtained by grinding, are orange and only exhibit a very intense orange emission (590 nm).

Synthesis and structural characterization of one- and two-dimensional coordination polymers based on platinum–silver metallic backbones

Seven Pt-Ag coordination polymers [Pt(NH3)2(NHCO(t)Bu)2Ag(H2O)](ClO4) (1), [Pt2(dap)2(NHCO(t)Bu)4Ag2(NO3)(ClO4)] (dap = 1,2-diaminopropane, 2), [Pt2(en)2(NHCO(t)Bu)4Ag2(m-C6H4(CO2)2)].3H2O (en = ethylenediamine, 3), [Pt2(NH3)2(NHCO(t)Bu)2Ag2(p-C6H4(CO2)2)].2H2O (4), [Pt3(en)3(NHCO(t)Bu)6Ag2(p-C6H4(CO2)2)(1.5)].6H2O (5), [Pt(NH3)2(NHCO(t)Bu)4Ag(4-C5H4NCO2)2].10H2O (6), and [Pt2(en)2(NHCO(t)Bu)4Ag2(4-C5H4NCO2)](ClO4) (7) were synthesized from the corresponding [Pt(RNH2)2(NHCO(t)Bu)2] and Ag salts, respectively, and their structures were determined by X-ray crystallography. The Pt and Ag units aggregate into one-dimensional chains based on Pt-Ag backbones. Compounds 1, 2, and 6 possess an extended zigzag Pt-Ag chain motif, and the metallic chains arrange in a parallel fashion into layered structures. Compounds 3-5, and 7 form 2-D brick wall sheets due to the coordination of the bifunctional anions to the Ag+ ions of the neighboring chains. These polymers are constructed based on the Pt-Ag interactions and the coordination of amidate oxygen atoms to Ag ions. There are three kinds of short Pt-Ag bonds observed in the structures of these compounds. The Pt-Ag metallic backbone is formed by the stacking unsupported Pt-Ag bonds, the amidate doubly bridged Pt-Ag bonds, and the amidate singly bridged Pt-Ag bonds. In the chains, the Pt-Ag bond distances are quite short, and appear in the range of 2.78-2.97 A, which are comparable to known Pt-Ag dative bonds.

Molecular Chemistry of Consequence to Renewable Energy

Energy conversion cycles are aimed at driving unfavorable, small-molecule activation reactions with a photon harnessed directly by a transition-metal catalyst or indirectly by a transition-metal catalyst at the surface of a photovoltaic cell. The construction of such cycles confronts daunting challenges because they rely on chemical transformations not understood at the most basic levels. These transformations include multielectron transfer, proton-coupled electron transfer, and bond-breaking and -making reactions of energy-poor substrates. We have begun to explore these poorly understood areas of molecular science with transition-metal complexes that promote hydrogen production and oxygen bond-breaking and -making chemistry of consequence to water splitting.