Preparation of platinum(II) sulfide complexes immobilized on silica

We report on preparation of silica-immobilized platinum(II) complexes of the [{SiO₂}O₂Si(CH₃)· (CH₂)₃SR]₂PtCl₂ type (R = Bu, Hex, or Bn; {SiO₂} = silica surface).     

Structural and mechanistic investigations of the oxidation of dimethylplatinum(II) complexes by dioxygen

The oxidation of (tmeda)Pt(II)(CH(3))(2) (1, tmeda = N,N,N',N'-tetramethylethylenediamine) to (tmeda)Pt(IV)(OH)(OCH(3))(CH(3))(2) (3) by dioxygen in methanol proceeds via a two-step mechanism. The initial reaction between (tmeda)Pt(CH(3))(2) and dioxygen yields a hydroperoxoplatinum(IV) intermediate, (tmeda)Pt(OOH)(OCH(3))(CH(3))(2) (2), which reacts with a second equivalent of (tmeda)Pt(CH(3))(2) to afford the final product 3. Both 2 and 3 have been fully characterized, including X-ray crystallographic structure determinations. The effect of ligand variation on the oxidation of several dimethylplatinum(II) complexes by 2 as well as by dioxygen has been examined.     

Structural investigations of palladium(II) and platinum(II) complexes of salicylhydroxamic acid

Complexes of salicylhydroxamic acid (shaH) with palladium(II) and platinum(II) were investigated. The synthesis of [Pt(sha)(2)] was attempted via a number of methods, and ultimately (1)H NMR investigations revealed that salicylhydroxamate would not coordinate to chloro complexes of platinum(II). However, [Pt(sha-H)(PPh(3))(2)] was successfully synthesized and the crystal structure determined (orthorhombic, space group Pca2(1) a = 17.9325(19) A, b = 11.3102(12) A, c = 18.2829(19) A, Z = 4, R = 0.0224). The sha binds via an [O,O] binding mode, in its hydroximate form. In contrast the palladium complex [Pd(sha)(2)] was readily synthesized and crystallized as [Pd(sha)(2)](DMF)(4) in the triclinic space group P(-)1,a = 7.066(1) A, b = 9.842(2) A, c = 12.385(2) A, alpha = 99.213(3)(o), beta = 90.669(3), gamma = 109.767(3)(o), Z = 1, R = 0.037. The unexpected [N,O'] binding mode of the salicylhydroxamate ligand in [Pd(sha)(2)] prompted investigation of the stability of a number of binding modes of salicylhydroxamic acid in [M(sha)(2)] (M = Pd, Pt) by density functional theory, using the B3LYP hybrid functional at the 6-311G* level of theory. Geometry optimizations were carried out for various binding modes of the ligands and their relative energies established. It was found that the [N,O'] mode gave the more stable complex, in accord with experimental observations. Stabilization of hydroxamate binding to platinum is evidently afforded by soft ligands lying trans to them.     

Hydrosilylation of low-molecular siloxanes in the presence of photactivated alkene and sulfoxide platinum(II) complexes

Hydrosilylation of tetramethyldivinyldisiloxane with pentamethyl-and tetramethyldisiloxane in the presence of photoactivated alkene and sulfoxide platinum(II) complexes was studied. The most active photoactivated catalysts are bis-sulfoxide platinum complexes; an additional photosensitive center, the oxalate ligand, enhances the effect of photoirradiation.     

New biimidazole and bibenzimidazole derivatives: mono and binuclear palladium(II) or platinum(II) complexes and heterobinuclear palladium(II)-rhodium(I) or platinum(II)-rhodium(I) complexes

Novel neutral biimidazolate or bibenzimidazolate palladium(II) and platinum(II) complexes of the type M(NN)₂(dpe) [M = Pd, Pt; (NN)₂^2? = BiIm^2?, BiBzIm^2?. dpe = 1,2-bis(diphenylphosphino) ethane] have been obtained by reacting MCl₂(dpe) with TI₂(NN)₂. Complexes M(NN)₂(dpe) which are Lewis bases react with HClO₄ or [M(dpe)(Me₂CO)₂](ClO₄)₂ to yield, respectively, mononuclear cationic complexes of general formula [M{H₂(NN)₂](dpe) (M = Pd, Pt; H₂(NN)₂ = H₂BiIm, H₂BiBzIm) and homobinuclear palladium(II) or platinum(II) cationic complexes of the type [M₂{μ - (NN)₂}(dpe)₂](ClO₄)₂. Reactions of M(BiBzIm)(dpe) with [Rh(COD) (Me₂CO)_X](ClO₄) render similar heterobinuclear palladium(II)-rhodium(I) and platinum(II)-rhodium(I) cationic complexes, of general formula [(dpe)M(μ-BiBzIm)Rh(COD)](ClO₄) (M = Pd, Pt; COD = 1,5-cyclooctadiene). Di- and mono-carbonyl derivatives [(dpe)M(μ-BiBzIm)Rh(CO)L](ClO₄) (M = Pd, Pt; L = CO, PPh₃) have also been prepared. The structures of the resulting complexes have been elucidated by conductance studies and IR spectroscopy.     

Mixed unsymmetric oxadiazoline and/or imine platinum(II) complexes

Iminoacylation of acetone oxime Me(2)C[double bond, length as m-dash]NOH upon reaction with trans-[PtCl(2)(NCCH(2)CO(2)Me)(2)] and [2 + 3] cycloaddition of acyclic nitrone (-)O(+)N(Me) = C(H)(C(6)H(4)Me-4) to a nitrile ligand in lead to the formation of mono-imine trans-[PtCl(2)(imine-a)(NCCH(2)CO(2)Me)] [imine-a = NH[double bond, length as m-dash]C(CH(2)CO(2)Me)ON = CMe(2)] and mono-oxadiazoline trans-[PtCl(2)(oxadiazoline-a)(NCCH(2)CO(2)Me)] [oxadiazoline-a = [upper bond 1 start]N[double bond, length as m-dash]C(CH(2)CO(2)Me)ON(Me)C[upper bond 1 end](H)(C(6)H(4)Me-4)] unsymmetric mixed ligand complexes, respectively, as the main products. Reactions of or with acetone oxime , cyclic nitrone (-)O(+)N = CHCH(2)CH(2)C[upper bond 1 end]Me(2) or N,N-diethylhydroxylamine give access, in moderate to good yields, to the unsymmetric mixed ligand oxadiazoline and/or imine complexes trans-[PtCl(2)(oxadiazoline-a)(imine-a)] , trans-[PtCl(2)(oxadiazoline-a)(oxadiazoline-b)] [oxadiazoline-b = [upper bond 1 start]N[double bond, length as m-dash]C(CH(2)CO(2)Me)O[lower bond 1 start]NC[upper bond 1 end](H)CH(2)CH(2)C[lower bond 1 end]Me(2)], trans-[PtCl(2)(imine-a)(imine-b)] [imine-b = NH = C(CH(2)CO(2)Me)ONEt(2)] or trans-[PtCl(2)(imine-a)(oxadiazoline-b)] . The cis mono-imine mixed ligand complex cis-[PtCl(2)(imine-a)(NCCH(2)CO(2)Me)] is the major product from the reaction of cis-[PtCl(2)(NCCH(2)CO(2)Me)(2)] with the oxime , while the di-imine compound cis-[PtCl(2)(imine-a)(2)] is a minor product. Reaction of cis-[PtCl(2)(imine-a)(NCCH(2)CO(2)Me)] with N,N-diethylhydroxylamine or the cyclic nitrone affords, in good yields, the unsymmetric mixed ligand complexes cis-[PtCl(2)(imine-a)(imine-b)] or cis-[PtCl(2)(imine-a)(oxadiazoline-b)] , respectively. All these complexes were characterized by elemental analyses, IR and (1)H, (13)C and (195)Pt NMR spectroscopies, and FAB(+)-MS. The X-ray structural analysis of trans-[PtCl(2){NH=C(CH(2)CO(2)Me)ON=CMe(2)}(NCCH(2)CO(2)Me)] is also reported.     

Preparation and electronic spectra of some alkyl- and aryl(2,2′-bipyridine)platinum(II) complexes

A series of alkyl- and aryl-(2,2′-bipyridine)-platinum (II) complexes has been prepared by displacement of the diene ligand in the corresponding cyclooctadiene complexes with 2,2′-bipyridine. Dimethyl(1,10-phenanthroline)platinum(II) was prepared in an analogous way. The electronic spectra of the complexes contain metal to ligand charge transfer bands whose energy is dependent on the nature of the substituents on platinum and on the solvent. It is suggested that π-bonding is important in the phenyl—platinum bond.     

Organoplumbio complexes of platinum(II)

The complex [Pt(C₂H₄)(PPh₃)₂] reacts with Pb₂Ph₆ to give cis-[PtPh(Pb₂Ph₅)(PPh₃)₂]; this decomposes in solution to cis-[PtPh(PbPh₃)(PPh₃)₂], which may also be obtained from the ethylene complex and PbPh₄. Lead compounds PbPhMe₃ and PbPh₃Br also give products of insertion into PbPh bonds, but PbMe₃Cl gives cis- and trans-[PtCl(PbMe₃)(PPh₃)₂]. The complex trans-[Pt(PbPh₃)₂(PEt₃)₂] reacts with 1,2-bis(diphenylphosphino)ethane (DPPE) to give [Pt(PbPh₃)₂(DPPE)] which readily decomposes in dichloromethane in presence of PEt₃ to give [Pt(PbPh₃)(PEt₃)(DPPE)]Cl and [PtPh(PEt₃)(DPPE)]Cl. The complex trans-[PtCl(PbPh₃)(PEt₃)₂] was detected in the products of reactions between trans-[PtCl₂(PEt₃)₂] and trans-[Pt(PbPh₃)₂(PEt₃)₂] or less than 2 moles of LiPbPh₃; it was not detected in the mixture after treatment of trans -[Pt(PbPh₃)₂(PEt₃)₂] with HCl. In contrast to an earlier report, we were unable to detect lead-containing complexes in the products of the reaction between trans-[PtHCl(PPh₃)₂] and Ph₃PbNO₃. The complexes and their decomposition products were identified by ^pre31P-{¹H} NMR spectroscopy.     

Organometallic formate complexes of platinum(II)

The compounds trans-[Pt(OCHO)R(PPh₃)₂] (R = C₆Cl₅; 2,3,4,6-C₆HCl₄; 2,3,4,5-C₆HCl₄; 2,5-C₆H₃Cl₂) have been prepared by treatment of [PtIR(PPh₃)₂] with AgClO₄ followed by reaction with NaOCHO in methanol. The cis isomers have been obtained by the direct reaction of HCO₂H with compounds containing PtHg bonds. For these and the analogous compounds containing C₆F₅ ligands, the dependence of J(³¹P¹⁹⁵Pt) on R has been studied, and the effects of cis-R shown to be in the opposite direction from those of trans-R ligands.     

Cationic pentafluorophenyl complexes of platinum(II)

The complex [O₃ClOPt(C₆F₅)(PEt₃)₂] which we have prepared for the first time, is used as a precursor of a series of cationic complexes [LPt(C₆F₅)(PEt₃)₂]ClO₄ (L = PEt₃, AsPh₃, H₂O, CO, OPPh₃, SPPh₃, HNPr₂, py), which are easily obtained by adding L to the perchlorato complex.     

Luminescence of ortho-metallated platinum(II) complexes

The absorption spectra, emission spectra, and emission lifetimes of Pt(Phpy)₂, Pt(Thpy)₂, and Pt(Bhq)₂ complexes (Phpy⁻, Thpy⁻, and Bhq⁻ are the ortho C-deprotonated forms of 2-phenylpyridine, 2-(2-thienyl)-pyridine, and benzo(h)quinoline) have been studied and compared with those of the C-protonated neutral ligands. For all complexes examined the low-energy absorption bands in the near UV and visible region are assigned to metal-to-ligand charge-transfer transitions. The strong and structured luminescence emissions observed in the 500–600 nm region (lifetime in the microsecond range at 77 K) are assigned to metal-to-ligand charge-transfer excited states.     

Carbamoyl and alkoxycarbonyl complexes of palladium(II) and platinum(II)

Carbamoyl and alkoxycarbonyl complexes of palladium(II) and platinum(II) of the type M(pnp)(CONHR)Cl (pnp = 2,6-bis(diphenylphosphinomethyl)pyridine; M Pd, R  C₆H₅, p-CH₃C₆H₄, p-CH₃OC₆H₄, C₆H₁₁, t-Bu; M  Pt, R  C₆H₅), Pd(pnp)[CON(Pr)₂]Cl (Pr = propyl), M(pnp)(COOR)Cl (M  Pd, R  C₆H₅, CH₃; M  Pt, R  CH₃), Pd(pnp)(COOCH₃)₂ result from reaction of M(pnp)Cl₂ with carbon monoxide and amines or alkoxides at room temperature and atmospheric pressure.The carbamoyl complexes react with bases to give urethane or diphenylurea depending upon the experimental conditions.     

The solid state chemistry of dichlorobis(pyridine)manganese(II) and dichlorobis(pyridine)nickel(II)

Summary The thermal decompositions of [MnCl₂(py)₂] and [NiCl₂(py)₂] were investigated and the following dissociation reactions were observed: [MnCl₂(py)₂](s)MnCl₂(py)(s)+(py)(g) [MnCl₂(py)₂](s)MnCl₂(s)+2(py)(g) and [NiCl₂(py)₂](s)NiCl₂(py)(s)+(py)(g) [NiCl₂(py)₂](s)NiCl₂(s)+2(py)(g). Quantitative thermodynamic as well as kinetic data were obtained by performing dynamic and isothermal studies on the complexes. The DSC studies provided evidence for the existence of the additional intermediates [Ni₃Cl₆(py)₂] and [Mn₃Cl₆(py)₂], which could not be obtained from the dynamic and isothermal studies.