Series Of Homoleptic Research Articles

Coinage Metal Complexes of a Sterically Encumbered Anionic Pyridylborate.

Sterically loaded, anionic pyridine has been synthesized and utilized successfully in the stabilization of a isoleptic series of coinage metal complexes. The treatment of [4-(Ph3B)-2,6-Trip2Py]K (Trip=2,4,6-iPr3C6H2) with CuBr(PPh3), AgCl(PPh3) or AuCl(PPh3) (Py=pyridine) afforded the corresponding [4-(Ph3B)-2,6-Trip2Py]M(PPh3) (M=Au, Ag, Cu) complexes, via salt metathesis, as isolable, crystalline solids. Notably, these reactions avoid the facile single electron transfer chemistry reported with the less bulky ligand systems. The X-ray structures revealed that they are two-coordinate metal adducts. The M-N and M-P bond distances are longest in the silver and shortest in the copper adduct among the three group 11 family members. Computational analysis revealed an interesting stability dependence on steric bulk of the anionic pyridine (i. e., pyridyl borate) ligand. A comparison of structures and bonding of [4-(Ph3B)-2,6-Trip2Py]Au(PPh3) to pyridine and m-terphenyl complexes, {[2,6-Trip2Py]Au(PPh3)}[SbF6] and [2,6-Trip2Ph]Au(PPh3) are also provided. The Au(I) isocyanide complex, [4-(Ph3B)-2,6-Trip2Py]Au(CNBut) has been stabilized using the same anionic pyridylborate illustrating that it can support other gold-ligand moieties as well.

Palladium(II)-Based Self-Assembled Heteroleptic Coordination Architectures: A Growing Family.

Metal-driven self-assembly is one of the most effective approaches to lucidly design a large range of discrete 2D and 3D coordination architectures/complexes. Palladium(II)-based self-assembled coordination architectures are usually prepared by using suitable metal components, in either a partially protected form (PdL') or typical form (Pd; charges are not shown), and designed ligand components. The self-assembled molecules prepared by using a metal component and only one type of bi- or polydentate ligand (L) can be classified in the homoleptic series of complexes. On the other hand, the less explored heteroleptic series of complexes are obtained by using a metal component and at least two different types of non-chelating bi- or polydentate ligands (such as La and Lb ). Methods that allow the controlled generation of single, discrete heteroleptic complexes are less understood. A survey of palladium(II)-based self-assembled coordination cages that are heteroleptic has been made. This review article illustrates a systematic collection of such architectures and credible justification of their formation, along with reported functional aspects of the complexes. The collected heteroleptic assemblies are classified here into three sections: 1) [(PdL')m (La )x (Lb )y ]-type complexes, in which the denticity of La and Lb is equal; 2) [(PdL')m (La )x (Lb )y ]-type complexes, in which the denticity of La and Lb is different; and 3) [Pdm (La )x (Lb )y ]-type complexes, in which the denticity of La and Lb is equal. Representative examples of some important homoleptic architectures are also provided, wherever possible, to set a background for a better understanding of the related heteroleptic versions. The purpose of this review is to pave the way for the construction of several unique heteroleptic coordination assemblies that might exhibit emergent supramolecular functions.

Steric and Electronic Factors Affecting the Conformation of Bimetallic CuI Complexes: Effect of the Aliphatic Spacer of Tetracoordinating Schiff-Base Ligands.

A family of six homoleptic [CuI (Ln )]2 (ClO4 )2 and six heteroleptic [CuI (Ln )(PPh3 )2 ]2 (ClO4 )2 bimetallic complexes, in which Ln are bis-Schiff base ligands with alkyl spacers of variable length (n=2-7 -CH2 -), were prepared to evaluate the role of the spacer on the formation of helicates or mesocates. In the homoleptic series, spectroscopic and theoretical studies indicate that preferences for a conformation are based on energetic parameters, mainly, the establishment of noncovalent interactions. The odd-even nature of the spacers preconditions the superposition of the aromatic rings to allow the juxtaposition necessary for noncovalent interactions, whereas the increase of the length reduces the strength of such interactions. Consequently, complexes with even-spacers of short length were identified as helicates in solution, [CuI (Ln )]22+ (n=2, 4). Complexes [CuI (Ln )]22+ (n=3-7) dissociate in solution to produce the monometallic complexes in equilibrium, [CuI (Ln )]+ . The stability of the bimetallic species is discussed in terms of their conformations. The set of heteroleptic complexes was prepared to evaluate the reach of the "odd-even rule" in the solid, which is based on the "zig-zag" arrangements of the spacers. Based on crystallographic information, "S-" and "C"-type conformations of Ln are related to even and odd spacers, respectively. This trend is considered in addition to other factors to explain preferences for either a mesocate or helicate conformation in the homoleptic series.

Trans-Heteroleptic carboxylate-bridged paddlewheel diruthenium(ii, ii) complexes with 2,6-bis(trifluoromethyl)benzoate ligands.

Carboxylate-ligand substitution reactions of paddlewheel-type diruthenium(ii, iii) complexes ([Ru(RCO2)4](+)) with 2,6-bis(trifluoromethyl)benzoate (2,6-(CF3)2PhCO2(-)) involving a selective reduction to [Ru] provide a series of trans-substituted paddlewheel-type diruthenium(ii, ii) complexes, [Ru(2,6-(CF3)2PhCO2)2(RCO2)2(THF)2] (R = CH3, ; C2H5, ; C3H7, ; C4H9, ; C(CH3)3, ; 2,3,5,6-F4Ph, ). Crystal structures of were determined, and their electronic states were investigated by cyclic voltammetry, density functional theory (DFT) and magnetic measurements. This is the first example of trans-heteroleptic carboxylate-bridged [Ru] complexes.

Simple Tuning of the Optoelectronic Properties of IrIII and PtII Electrophosphors Based on Linkage Isomer Formation with a Naphthylthiazolyl Moiety

AbstractBy tuning the substitution position of a thiazolyl group on the naphthalene system (α or β site), the distinctive electronic structures associated with these functional ligands have a substantial influence on both the photophysical behavior and electroluminescent (EL) performance of the resulting linkage isomers for two series of IrIII and PtII phosphorescent emitters. The photoluminescence wavelength can be redshifted by ca. 23 nm for the linkage isomers upon replacing the β‐substituted thiazolyl‐based ligand with its α‐substituted counterpart in the homoleptic series of IrIII phosphors. Furthermore, the bathochromic effect can be as much as ca. 42 nm for the heteroleptic IrIII phosphors and ca. 59 nm for the PtII compounds. Similarly, metallophosphors that bear β‐substituted ligands exhibit a different EL performance with respect to that of their linkage isomers with α‐substituted ligands. The best EL results associated with the triplet emitters chelated with β‐substituted ligands show a maximum brightness (Lmax) of 22563 cd m–2, an external quantum efficiency (ηext) of 12.88 %, a luminance efficiency (ηL) of 30.84 cd A–1, and a power efficiency (ηp) of 26.17 lm W–1, whereas the EL performance of their α‐counterparts was characterized by a peak Lmax of 8653 cd m–2, ηext of 6.18 %, ηL of 8.55 cd A–1, and ηp of 6.54 lm W–1. Owing to its unique electronic structure, the thiazolyl group is a good alternative to the pyridyl moiety to improve the EL performance of the metallophosphor. We have also demonstrated a simple and useful route to tune the functional properties of cyclometalated triplet emitters for EL applications.

Synthesis and Structures of Group 11 Metal Triazenide Complexes: Ligand Supported Metallophilic Interactions

A homologous and homoleptic series of stable Group 11 metal triazenide complexes with the general formula [M(L')](n) (M = Cu or Au, n = 2; M = Ag, n = 3) featuring the bulky triazenide ligand N,N'-bis(2,6-di-isopropylphenyl)triazene, L'H, have been prepared by the reaction of Li[L'] with the metal chlorides, CuCl, AgCl, and [(THT)AuCl], respectively, in a 1:1 stoichiometric ratio. The compounds [Cu(2)(L')(2)] and [Au(2)(L')(2)] crystallized as dimers with M...M separations of 2.4458(4) A and 2.6762(4) A, respectively. In comparison, the reaction of AgCl with Li[L'] results in the formation of the tri-silver complex [Ag(3)(L')(3)] with Ag...Ag separations of 3.01184(17) A, 2.95329(17) A, and 2.92745(16) A. Attempts to react the parent triazene system L'H with [Cu(Mes)] resulted in the formation of the novel tri-copper system [Cu(3)(L')(2)(Mes)]. In all cases the molecular structures of the resultant complexes have been unambiguously determined by single crystal X-ray diffraction experiments.

A critical evaluation of homo- and hetero-leptic cadmium complexes using bond valence sums

The effect of the donor atoms in Cd complexes on the determination of R0 values for the bond valence sum (BVS) is reported. A total of 1321 CdXmYn fragments with X and Y = O, N, S, Cl, Br, and I were used to calculate the R0 values for Cd—X bonds from both homoleptic and heteroleptic fragments. The R0 values determined from mixed CdXmYn fragments agree with those determined from the homoleptic species, with no significant differences in the values as a function of either electronegativity or hard–soft character of the atoms. The new R0 values derived from the homoleptic series recommended for use in calculating the BVS are as follows: Cd(II)—O of 1.875(13) Å, Cd(II)—N of 1.951(15) Å, Cd(II)—S of 2.279(7) Å, Cd(II)—Cl of 2.216(17) Å, Cd(II)—Br of 2.334(7) Å, and Cd(II)—I of 2.525(7) Å. These R0 values can be used to calculate the oxidation state of Cd in complexes where Cd is bonded to any combination of O, N, S, Cl, Br, and I donor atoms. Cases where the BVS does not agree with the expected oxidation state are discussed. In particular, the planarity of Cd porphyrins is discussed in terms of the BVS.Key words: bond valence sums, cadmium complexes, cadmium porphyrins, cadmium distances.

A new series of homoleptic, paramagnetic organochromium derivatives: synthesis, characterization, and study of the magnetic properties.

The synthesis and characterization of the triad of organochromium derivatives [Cr(C(6)Cl(5))(4)](n-) (n=0, 1, 2) are described. By treating [CrCl(3)(thf)(3)] with LiC(6)Cl(5) in 1:5 molar ratio, the salt [Li(thf)(4)][Cr(III)(C(6)Cl(5))(4)] (1) was obtained as a violet solid in 57 % yield. Oxidation of 1 with [N(4-BrC(6)H(4))(3)][SbCl(6)] yielded the neutral complex [Cr(IV)(C(6)Cl(5))(4)] (2) as a brown solid in 71 % yield. The arylation of [CrCl(2)(thf)] with LiC(6)Cl(5) under similar conditions as above gave [[Li(thf)(3)](2)(mu-Cl)](2)[Cr(II)(C(6)Cl(5))(4)] (3) as an extremely air- and water-sensitive red solid in 47 % yield. The crystal and molecular structures of 1 and 3 have been established by X-ray diffraction methods. Complex 3 contains the unusual cation [[Li(thf)(3)](2)(mu-Cl)](+) with an almost linear Li-Cl-Li unit (174.2(6)degrees). All four C(6)Cl(5) groups are sigma-bonded to the Cr(II) center, which is located in a square-planar environment. The local geometry around the Cr(III) center in 1 is, in turn, pseudo-octahedral, since two of the C(6)Cl(5) groups act as standard sigma-bonded monodentate ligands, while the other two act as small-bite didentate ligands coordinated through both the ipso-C and one of the ortho-Cl atoms. Compounds 1-3 are paramagnetic with maximum spin multiplicity each (EPR and magnetization measurements).

ChemInform Abstract: Metal Alkoxides: Models for Metal Oxides. Part 16. Synthesis and Characterization of a New Class of Homoleptic 12‐Electron Molybdenum and Tungsten Alkoxide Clusters of Formula M4(OR)12: Structural Characterization of Mo4(OCH2‐c‐Bu)12·(HOCH2‐c‐Bu).

AbstractAddition of prim. alcohols (II) to hydrocarbon solutions of the hexaalkoxides (I) leads to the isolation of the first homoleptic series of the cluster alkoxides (III).

Metal alkoxides: models for metal oxides. 16. Synthesis and characterization of a new class of homoleptic 12-electron molybdenum and tungsten alkoxide clusters of formula M4(OR)12: structural characterization of Mo4(OCH2-c-Bu)12.cntdot.(HOCH2-c-Bu)

Addition of primary alcohols, RCH{sub 2}OH (> 6 equiv), to hydrocarbon solutions of M{sub 2}(O-t-Bu){sub 6} compounds has led to the isolation of the first homoleptic series of cluster alkoxides M{sub 4}(OCH{sub 2}R){sub 12} for both M = Mo and W where R = i-Pr, Cy (Cy = cyclohexyl), Cp (Cp = cyclopentyl), and c-Bu (c-Bu = cyclobutyl). The NMR data ({sup 1}H and {sup 13}C) indicate a common structural unit for this class of compounds containing a molecular mirror plane. For each M{sub 4}(OCH{sub 2}R){sub 12} compound there are eight types of alkoxide ligands in the integral intensity 2:2:2:2:1:1:1:1. Those having integral intensity two possess diastereotopic methylene protons, indicating that they do not lie on the mirror plane, whereas the other four alkoxides (1:1:1:1) are contained within the mirror plane. Though these compounds yield crystals from 1,2-dimethoxyethane, they failed to diffract beyond 10{degree} indicating a molecular disorder within hexagonal packing of M{sub 4} units. However, the cyclobutylmethoxide derivatives crystallize with an additional molecule of alcohol, M{sub 4}(CH{sub 2}-c-Bu){sub 12}(HOCH{sub 2}-c-Bu), and the molecular structure of the molybdenum compound was determined by an X-ray study. Crystal data for Mo{sub 4}(OCH{sub 2}-c-Bu){sub 12}(HOCH{sub 2}-c-Bu) at {minus}156{degree}C: a = b = 19.952more » (7) {angstrom}, c = 34.755 (16) {angstrom}, Z = 8, d{sub calcd} = 1.43 g cm{sup {minus}3}, and space group Pr{sub 1}. The unit cell contains two crystallographically independent molecules that are essentially equivalent with respect to M-M and M-O distances and angles. In each there is a central Mo{sub 4} butterfly with a dihedral angle between the Mo{sub 3} triangles of 132.5{degree}.« less