Maria Michela Dell'Anna

Aerobic oxidation of sulfides catalysed by cobalt(II) complexes under homogeneous and heterogeneous conditions

Abstract The Co(II)-catalysed oxidation of alkyl- and aryl-sulfides was achieved under homogeneous and heterogeneous conditions using oxygen or air as the oxidant in the presence of excess aldehyde. The reactions in the homogeneous phase were carried out using the soluble Co(acac) 2 or Co(AAEMA) 2 complexes (AAEMA − = deprotonated form of 2-(acetoacetoxy)ethyl methacrylate) whereas the heterogeneous catalytic tests were carried out using the copolymers obtained by reaction of Co(AAEMA) 2 with acrylamides. Under suitable conditions excellent conversions and very good selectivities were achieved both in homogeneous and in heterogeneous phase. The supported complexes were recyclable with negligible loss of efficiency and did not suffer from metal leaching.

Hydrogenation reactions catalysed by a supported palladium complex

Abstract The catalytic activity of the cross-linked polymer obtained by reaction of Pd(AAEMA) 2 [HAAEMA=2-(acetoacetoxy)ethyl methacrylate] and suitable acrylates as comonomers and cross-linkers was investigated in the hydrogenation reactions of substrates such as olefins, aromatic and unsaturated aldehydes, unsaturated ketones and nitrocompounds. The polymer-supported palladium was found to be active and recyclable without loss of metal.

A Polymer-Supported β-Ketoesterate Complex of Palladium as an Efficient, Phosphane-Free, Air-Stable, Recyclable Catalyst for the Heck Reaction

The coupling between aryl iodides and bromides with olefins (Heck reaction) has been studied with a polymer-supported palladium catalyst in the presence of sodium or potassium acetate. The reactions can be performed in air without any activating phosphorus ligands and with non dried solvents. Under suitable conditions the catalyst, which exhibits high activity and selectivity, is recyclable several times with negligible leaching of metal. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Aerobic oxidation of α-hydroxyketones catalysed by cobalt(II) and iron(III) complexes under homogeneous and heterogeneous conditions

Abstract Aromatic α-hydroxyketones were easily oxidized by dioxygen in the presence of excess aldehyde or aldoacetal with catalytic amount of Co(II) or Fe(III) complexes, under homogeneous and heterogeneous conditions. Co(acac) 2 or Fe(acac) 3 were the catalysts used in homogeneous phase reactions whereas Co(II) or Fe(III) supported complexes, obtained by copolymerization of Co(AAEMA) 2 or Fe(AAEMA) 3 (AAEMA − = deprotonated form of 2-(acetoacetoxy)ethyl methacrylate) with acrylamides, were the heterogeneous catalysts. The supported metal complexes were recyclable and did not suffer from metal leaching.

Hydrido Phosphanido Bridged Polynuclear Complexes Obtained by Protonation of a Phosphinito Bridged Pt(I) Complex with HBF4 and HF

The protonation of the phosphinito-bridged Pt(I) complex [(PHCy(2))Pt(μ-PCy(2)){κ(2)P,O-μ-P(O)Cy(2)}Pt(PHCy(2))](Pt-Pt) (1) by aqueous HBF(4) or hydrofluoric acid leads selectively to the hydrido-bridged solvento species syn-[(PHCy(2))(H(2)O)Pt(μ-PCy(2))(μ-H)Pt(PHCy(2)){κP-P(OH)Cy(2)}](Y)(2)(Pt-Pt) ([2-H(2)O]Y(2)) {Y = BF(4), F(HF)(n)} when an excess of acid was used. On standing in halogenated solvents, complex [2-H(2)O](BF(4))(2) undergoes a slow but complete isomerization to [(PHCy(2))(2)Pt(μ-PCy(2))(μ-H)Pt{κP-P(OH)Cy(2)}(H(2)O)](BF(4))(2)(Pt-Pt) ([4-H(2)O][BF(4)](2)) having the P(OH)Cy(2) ligand trans to the hydride. The water molecule coordinated to platinum in [2-H(2)O][BF(4)](2) is readily replaced by halides, nitriles, and triphenylphosphane, and the acetonitrile complex [2-CH(3)CN][BF(4)](2) was characterized by XRD analysis. Solvento species other than aqua complexes, such as [2-acetone-d(6)](2+) or [2-CD(2)Cl(2)](2+) were obtained in solution by the reaction of excess etherate HBF(4) with 1 in the relevant solvent. The complex [2-H(2)O](Y)(2) [Y = F(HF)(n)] spontaneously isomerizes into the terminal hydrido complexes [(PHCy(2))Pt(μ-PCy(2)){κ(2)P,O-μ-P(O)Cy(2)}Pt(H)(PHCy(2))](Y)(Pt-Pt) ([6](Y)). In the presence of HF, complex [6](Y) transforms into the bis-phosphanido-bridged Pt(II) dinuclear complex [(PHCy(2))(H)Pt(μ-PCy(2))(2)Pt{κP-P(OH)Cy(2)}](Y)(Pt-Pt) ([7](Y)). When the reaction of 1 with HF was carried out with diluted hydrofluoric acid by allowing the HF to slowly diffuse into the dichloromethane solution, the main product was the linear 60e tetranuclear complex [(PHCy(2)){κP-P(O)Cy(2)}Pt(1)(μ-PCy(2))(μ-H)Pt(2)(μ-PCy(2))](2)(Pt(1)-Pt(2)) (8). Insoluble compound 8 is readily protonated by HBF(4) in dichloromethane, forming the more soluble species [(PHCy(2)){κP-P(OH)Cy(2)}Pt(1)(μ-PCy(2))(μ-H)Pt(2)(μ-PCy(2))](2)(BF(4))(2)(Pt(1)-Pt(2)) {[9][BF(4)](2)}. XRD analysis of [9][BF(4)](2)·2CH(2)Cl(2) shows that [9](2+) is comprised of four coplanar Pt atoms held together by four phosphanido and two hydrido bridges. Both XRD and NMR analyses indicate alternate intermetal distances with peripheral Pt-Pt bonds and a longer central Pt···Pt separation. DFT calculations allow tracing of the mechanistic pathways for the protonation of 1 by HBF(4) and HF and evaluation of their energetic aspects. Our results indicate that in both cases the protonation occurs through an initial proton transfer from the acid to the phosphinito oxygen, which then shuttles the incoming proton to the Pt-Pt bond. The different evolution of the reaction with HF, leading also to [6](Y) or 8, has been explained in terms of the peculiar behavior of the F(HF)(n)(-) anions and their strong basicity for n = 0 or 1.

Reactivity of mononuclear Pd(II) and Pt(II) complexes containing the primary phosphane (ferrocenylmethyl)phosphane towards metal chlorides and PPh3

The reaction of the primary phosphane (ferrocenylmethyl)phosphane [PH(2)CH(2)Fc, ] with an equimolar amount of [M(cod)Cl(2)] (cod = 1,5-cyclooctadiene, M = Pd, Pt) gave the unusual monobridged M(ii) dinuclear complexes of formula [(cod)ClM(micro-PHCH(2)Fc)M(PH(2)CH(2)Fc)Cl(2)] [M = Pt, ; M = Pd, ]. The mechanism leading to and involves the preliminary formation of cis-[M(PH(2)CH(2)Fc)(2)Cl(2)] which further reacts with free [M(cod)Cl(2)] before undergoing dehydrochlorination. The reaction of with PPh(3) led to the unexpected formation of the cyclic trinuclear complex [Pd(3)(micro-PHCH(2)Fc)(3)(PPh(3))(2)(PH(2)CH(2)Fc)Cl(3)] (). Further reaction of with PPh(3) led to the substitution of the tertiary phosphane for the primary one with formation of two geometric isomers and of formula [Pd(micro-PHCH(2)Fc)(PPh(3))Cl](3) differing only for the position of the PPh(3) group replacing the PH(2)CH(2)Fc ligand. In complex each micro-PHCH(2)Fc group bridging two palladium atoms has a terminal PPh(3) ligand in trans position with respect to the first Pd (the cis position being occupied by a chlorine) and a chlorine ligand trans to the other Pd (the cis position being occupied by a terminal PPh(3) ligand) thus rendering chemically equivalent the three PPh(3) (and the three phosphides). In complex the three terminal PPh(3) as well as the three bridging phosphido ligands are chemically inequivalent. Complexes and coexist in equilibrium in solution, but only precipitates from CH(2)Cl(2)-n-hexane yielding crystals suitable for X-ray analyses. These crystals are water/n-hexane solvates and belong to the monoclinic space P2(1)/c with a = 25.063(6) A, b = 15.564(4) A, c = 26.089(5) A, beta = 120.017(16) degrees . They contain two identical couples of enantiomers of . The peculiar arrangement of three metals and three phosphorus atoms of the bridging ligands ascertained for trimers , and has no precedent in the rich class of palladium and platinum phosphido chemistry.

Epoxidation of olefins catalysed by polymer-supported metal β-ketoesterato complexes of iron(III), nickel(II) and cobalt(II)

The epoxidation of linear and cyclic olefins was catalysed by iron(III), nickel(II) and cobalt(II) centres immobilized on insoluble polymers. The latter were obtained by reaction of the polymerizable complexes of Fe(III), Ni(II) and Co(II) with 2-(acetoacetoxy)ethyl methacrylate with acrylamides.

Coupling reactions between acyl chlorides and Grignard reagents in the presence of a supported Fe(III) -complex

Abstract The polymer-supported Fe(III) complex obtained by copolymerization of Fe(AAEMA)3 [AAEMA−=deprotonated form of 2-(acetoacetoxy) ethyl methacrylate] with suitable acrylamides facilitates the coupling reaction between acyl chlorides and Grignard reagents, affording ketones with yields up to 96%.

Regioselective aerobic oxidation of bis-sulfides into monosulfoxides

Abstract The cobalt(II) acetylacetonate/aldehyde-promoted aerobic oxidation of three bis-sulfides of general formula R 1 -SCH 2 CH 2 S-R 2 , where R 1 is a heterocycle and R 2 is p -tolyl, provides a method to functionalise selectively the sulfur atom bonded to the p -tolyl moiety leading to the corresponding monosulfoxides. The same chemoselectivity and little diastereoisomeric excess (10%) was achieved by submitting to oxidative conditions the chiral bis-sulfide ( S )-R 3 -SCH 2 CH(CH 3 )CH 2 -SR 4 (R 3 =benzothiazolyl, R 4 = p -tolyl).

Oxyfunctionalization of hydrocarbons by in situ formed peracid or by metal assisted aerobic oxidation

Abstract The oxidation of hydrocarbons such as adamantane, cyclohexane, tetraline and indane has been investigated using the oxygen/3-methylbutanal system in the presence and in the absence of metal catalyst. The reactivity order reflects the facility of hydrogen abstraction from the substrate.