Synthesis, Structures, and Luminescence Behavior of Mixed Metal Alkynyl Platinum−Cadmium Complexes

A new supramolecular bonding motif involving NH bonds of ammonium salts and macrocycles derived from platinum corners and butadiynediyl linkers

The title Pt4C16 species can give roughly planar geometries in crystals, but afford folded forms with ammonium cations, which are captured like unsuspecting prey and potentially fossilized as with the ancient creatures who once roamed the galaxy.

High-nuclearity Pt-Tl-Fe complexes: structural, electrochemistry, and spectroelectrochemistry studies

A series of heteropolynuclear Pt-Tl-Fe complexes have been synthesized and structurally characterized. The final structures strongly depend on the geometry of the precursor and the Pt/Tl ratio used. Thus, the anionic heteroleptic cis-configured [cis-Pt(C(6)F(5))(2)(C≡CFc)(2)](2-) and [Pt(bzq)(C≡CFc)(2)](-) (Fc = ferrocenyl) complexes react with Tl(+) to form discrete octanuclear (PPh(3)Me)(2)[{trans,cis,cis-PtTl(C(6)F(5))(2)(C≡CFc)(2)}(2)] (1), [PtTl(bzq)(C≡CFc)(2)](2) (5; bzq = benzoquinolate), and decanuclear [trans,cis,cis-PtTl(2)(C(6)F(5))(2)(C≡CFc)(2)](2) (3) derivatives, stabilized by both Pt(II)···Tl(I) and Tl(I)···η(2)(alkynyl) bonds. By contrast, Q(2)[trans-Pt(C(6)F(5))(2)(C≡CFc)(2)] (Q = NBu(4)) reacts with Tl(+) to give the one-dimensional (1-D) anionic [(NBu(4)){trans,trans,trans-PtTl(C(6)F(5))(2)(C≡CFc)(2)}](n) (2) and neutral [trans,trans,trans-PtTl(2)(C(6)F(5))(2)(C≡CFc)(2)](n) (4) polymeric chains based on [PtFc(2)](2-) platinate fragments and Tl(+) (2) or [Tl···Tl](2+) (4) units, respectively, connected by Pt(II)···Tl(I) and secondary weak κ-η(1) (2) or η(2) (4) alkynyl···Tl(I) bonding. The formation of 1-4 is reversible, and thus treatment of neutral 3 and 4 with PPh(3)MeBr causes the precipitation of TlBr, returning toward the formation of the anionic 1 and 2' (Q = PPh(3)Me). Two slightly different pseudopolymorphs were found for 2', depending on the crystallization solvent. Finally, the reaction of the homoleptic [Pt(C≡CFc)(4)](2-) with 2 equiv of Tl(+) affords the tetradecanuclear sandwich type complex [Pt(2)Tl(4)(C≡CFc)(8)] (6). Electrochemical, spectroelectrochemical, and theoretical studies have been carried out to elucidate the effect produced by the interaction of the Tl(+) with the Pt-C≡CFc fragments. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) of 1-5 reveal that, in general, neutralization of the anionic fragments increases the stability of the fully oxidized species and gives higher E(1/2) (Fc) values than those observed in their precursors, increasing with the number of Pt-Tl bonding interactions. However, the electronic communication between Fc groups is reduced or even lost upon Tl(+) coordination, as confirmed by electrochemical (CVs and DPVs voltammograms, 1-5) and spectroelectrochemical (UV-vis-NIR, 2-4) studies. Complexes 2 and 4 still display some electronic interaction between the Fc groups, supported by the presence of an IVCT band in their UV-vis-NIR spectra of oxidized species and additional comparative DFT calculations with the precursor [trans-Pt(C(6)F(5))(2)(C≡CFc)(2)](2-) and complex 3.

Robust and efficient molecular catalysts with a M–O–M′ framework

Heterodimetallic systems are the most interesting among the heteropolynuclear compounds. The importance of these molecules is mainly due to their catalytic properties. Although various types of heterodimetallic systems are known the framework with a M-O-M' arrangement is of particular importance. This stems from its ability to catalyze various transformations. The improved catalytic ability is due to the oxygen bridge that makes the metal centres more electrophilic which is an essential criteria for a system to function as a catalyst. Therefore, the present article focuses on the synthesis of the M-O-M' system and explores the application of such materials as catalysts in olefin polymerization, ring opening polymerization of caprolactone, olefin epoxidation, and olefin hydroformylation reactions.

Luminescent Hepta- and Tetradecanuclear Complexes of 5,5‘-Diethynyl-2,2‘-bipyridine Capped with Triangular Trinuclear Cu3/Ag3 Cluster Units

Heteroheptanuclear ReM6 (M = Cu 2, Ag 3) complexes of 5,5-diethynyl-2,2'-bipyridine were prepared by the reaction of [M2(mu-dppm)2(MeCN)2]2+ (dppm = bis(diphenylphosphino)methane) with the precursor compound Re(Me3SiC[triple bond]CbpyC[triple bond]CSiMe3)(CO)3Cl in the presence of potassium fluoride by fluoride-catalyzed desilylation. When [Cu2(mu-dppm)2(MeCN)2]2+ reacts directly with Me3SiC[triple bond]CbpyC[triple bond]CSiMe3, a binuclear CuI complex [Cu2(mu-dppm)2(SiMe3C[triple bond]CbpyC[triple bond]CSiMe3)2]2+ (4) was isolated. Further addition of [Cu2(mu-dppm)2(MeCN)2]2+ into a THF-MeOH (3:1, v/v) solution of 4 in the presence of potassium fluoride induced isolation of a tetradecanuclear CuI14 complex [Cu14(mu-dppm)14(C[triple bond]CbpyC[triple bond]C)2]10+, which is composed of a binuclear Cu2(mu-dppm)2 and four triangular trinuclear Cu3 units. Both heteroheptanuclear ReIMI6 and tetradecanuclear CuI14 complexes display luminescence in both solid states and dichloromethane solutions at room temperature with emissive lifetimes in the range of microseconds. The dual emissive feature for the ReM6 and CuI14 complexes is ascribed tentatively to originate from both MLCT [d(Re/Cu) -->pi* (bpy)] and LMCT (acetylide --> M3) transitions. .

Influence of Solvent and Weak C−H···O Contacts in the Self-Assembled [Pt2M4{C⋮C(3-OMe)C6H4}8] (M = Cu, Ag) Clusters and Their Role in the Luminescence Behavior

New alkynyl complexes [Pt2M4{CC(3-OMe)C6H4}8] (M = Ag 1, Cu 2) have been synthesized and their structures and properties compared to those of related [Pt2M4(CCPh)8] compounds. For the Pt-Ag derivatives, the X-ray structures of the discrete yellow solvate monomer, [Pt2Ag4{CC(3-OMe)C6H4}8].2THF ([1.2THF]), and the dark garnet unsolvated polymeric form, [Pt2Ag4{CC(3-OMe)C6H4}8](infinity) ([1](infinity)), are presented. The yellow form ([1.2THF]) exhibits a distorted octahedral geometry of the metal centers with the platinum atoms mutually trans and the four silver atoms in the equatorial plane. Pairs of Ag atoms are weakly bridged by THF molecules [mu-Ag2...O(THF)]. The garnet form ([1](infinity)) has an unprecedented infinite stacked chain of octahedral clusters linked by short Pt...Pt bonds (3.1458(8) A). In both forms, different types of weak C-H...O (OMe) hydrogen bonds are observed. For comparative purposes, we have also provided the crystal structures of the yellow monomer form, [Pt2Ag4-(CCPh)8].CHCl3, and the red dimer form, [Pt2Ag4(CCPh)8]2 (Pt-Pt 3.221(2) A). These clusters display intense photoluminescence in both solution and the solid state, at room temperature and 77 K. The emission observed for the yellow form [1.2THF] in the solid state is assigned to a 3MLM'CT [Pt(d)/pi(CCR) --> Pt(p(z))/Ag(sp)/pi(CCR)] state modified by Pt...Ag, Ag...Ag, and Ag...(THF) contacts. However, in the garnet form [1](infinity) and in 2, the emissions are related to the axial Pt-Pt bonds and are assigned as phosphorescence from a metal-metal-to-ligand charge-transfer (3MMLCT) excited state ([1](infinity)), or an admixture of a metal-metal (Pt-Pt) centered 3(dsigmap(z)sigma) and 3MMLCT excited state (2). For 1, a remarkable quenching and a shift to higher energies in the emission is observed on changing from CH2Cl2 to THF, and for both 1 and 2, the emission spectra at 77 K varies with the concentration, showing their tendency to stack even in glass.