Francesco Ruffo

Cationic platinum(II) - or palladium(II)-carbyl complexes and unsaturated substrates: a facile way to C-C bond formation

Abstract Alkenes, alkynes, 1,2- and 1,3-dienes react with [MR(N-N)(MeCN)] + (M = Pt or Pd; R = hydrocarbyl group; NN = bidentate nitrogen ligand) to give R-substituted derivatives. The organic fragment is generally retained within the metal environment in η 1 or η 3 coordination, except in the reaction of alkenes with Pd (II) complexes. In this case, a free R-substituted alkene is produced via a relatively fast β-elimination process from a Pd-alkyl intermediate. Different regiochemistries are detected in the reaction between monosubstituted olefins (propene or styrene) and homologous Pt and Pd complexes. The Pt-C bond is always formed with the terminal unsubstituted alkene carbon, while a preference toward the internal carbon, particularly if phenyl-substituted, is observed with Pd species. Neutral [MClR(N-N)] are markedly less reactive. In this case, when M = Pt, the unsaturated organic substrate generally adds to the metal affording fairly stable tbp five-coordinate complexes.

Stable five-coordinate [Pt(N Nt')(olefin)(R)X] complexes formed by oxidative addition to [Pt(N N′)(olefin)] precursors

Abstract The oxidative addition of an electrophilic reagent such as a halogen or an alkyl halide to a suitable three-coordinate species of the type [Pr( N N ′)(olefin)]( N N ′ = chelating N,N-ligand) affords a five-coordinate product. The reaction provides a new versatile route to the synthesis of trigonal bipyramidal complexes of general formula [Pt(X)(Y) N N ′)(olefin)] (X = halide; Y = hydrocarbyl or halide). This is apparently the first widely applicable oxidative addition process to three-coordinate M(0) organometallic derivatives of group 10 elements to give isolable five-coordinate M(II) products. Some general features of the addition and preliminary observations on the reaction mechanism are described.

Novel chiral diimines and diamines derived from sugars in copper-catalysed asymmetric cyclopropanation

Abstract New chiral diimino and diamino ligands derived from α- d -mannose and α- d -glucose are described. The ligands are obtained by introducing the appropriate nitrogen functions at C(2) and C(3) of the sugar rings. The ability of the new chelates to promote the asymmetric copper(I)-catalysed cyclopropanation of styrene has been investigated. The nature of both the sugars and the chelates is crucial in determining the enantioselectivity of the reaction.

Lipid based nanovectors containing ruthenium complexes: a potential route in cancer therapy.

Ruthenium complexes offer new perspectives in cancer therapy; towards this aim we have synthesized a new amphiphilic unimer able to coordinate ruthenium complexes and to form liposomes.

Synthesis and characterization of five-coordinate platinum(II) complexes [Pt(2,9-dimethyl-1,10-phenanthroline) (SnRnX3-n)X(olefin)] (X

Abstract Five-coordinate olefin complexes of platinum(II) of the general formula [Pt(2,9-Me2-1,10-phen)(SnRnX3-n)X(olefin)] have been synthesized through oxidative addition of organotin halides RnSnX4-n to three-coordinate platinum(O) complexes [Pt(2,9-Me2-1,10-phen)(olefin)]. The X-ray crystal structure of the title complex has been determined. This crystallizes in the monoclinic system, space group P21/n with a = 13.858(8), b = 13.730(6), c = 16.820(8) A, β = 102.44(5)°, and Z = 4. Refinement converged at R = 0.04 (Rw = 0.044). The geometry of the five-coordinate platinum complex is bipyramidal, with anionic ligands inapical positions and the olefinic double bond in the equatorial plane. Some general features of the addition process, and the structural and NMR properties of the complexes, are also discussed.

Preparation and catalytic properties of palladium(0) and rhodium(I) complexes containing new chiral P,N-ligands derived from carbohydrates

Abstract New chiral P,N-chelates o-Ph2PC6H4CHNR (R=carbohydrate residue) derived from d -glucose and d -mannose were described. The synthesis of palladium(0) and rhodium(I) complexes of respective formula [Pd(P,N-chelate)(fumarodinitrile)] and [Rh(1,5-cyclooctadiene)(P,N-chelate)]BF4 was performed. It was found that the ligands effectively discriminate between the enantioface of fumarodinitrile in the Pd(0) species, prompting up to 100% diastereomeric excess when R is a 2,3,4-tri-O-acetylated glucoside moiety linked to N through C6. The catalytic activity of the complexes towards allylic alkylation and olefin hydroboration was also examined.

Molecular rearrangements in the formation of five-coordinate platinum(II) olefin complexes. Structural and mechanistic aspects

Abstract The olefin addition reaction to square-planar complexes of the type [PtXMe(N-N)] (X = Cl, CH(CO2Me)2, N-N=bidentate nitrogen ligand), to form trigonal bipyramidal complexes has been shown to occur in two successive steps. First, a five-coordinate species (A) is formed in which the axial positions are occupied by the methyl group and by one nitrogen atom. In most cases this subsequently rearranges to the more stable isomer (B), in which both axial positions are occupied by the anionic ligands. The structure of the type A complex [PtMe{CH}CO2Me)2) (E-NCCH-CHCN) (dmphen)] has been determined by an X-ray diffraction study (triclinic, space group P1− (No. 2), a = 9.497(3), b = 10.884(4), c = 15.671(4) A, α = 75.62(3), β = 78.47(2), γ = 66.52(3)°, Z = 2). For the first time the equatorial-axial coordination of the dmphen ligand has been unequivocally ascertained. The molecule reveals a significant tension due to the short contacts between the methyl groups. The electronic and steric factors affecting the relative stability of type A and B species are discussed, and a mechanisms for the overall process is proposed.

Three-coordinate Pt(O) η2-complexes: electrophilic hydrogen attack through oxidative-addition of protic acids

Abstract Different types of products can be obtained by addition of protic acids HX (X=Cl, BF 4 ) to Pt(O) species of general formula [Pt(ol)(N-N)] (ol=olefin; N-N=N,N-chelate) according to the features of the two coordinated ligands. The typical attainment of four-coordinate hydrocarbyl derivatives by insertion of the alkene into the Pt-H bond is compared with the recently reported isolation of stable five-coordinate hydrides. The nature of the final product is also related to the coordinating ability of the X group. A general mechanism for the addition process is proposed.

Coordination modes of cis-P, P'-diphenyl-1,4-diphospha-cyclohexane to metal ions of Groups 9 and 10

Abstract Complexes of a tertiary diphosphine with cyclic core, cis - P , P ′-diphenyl-1,4-diphospha-cyclohexane (dpdpc), with metal ions of Groups 9 and 10 have been prepared and characterised. In neutral M(0) or M(II) (M=Pt, Pd) complexes the diphosphine acts as a bridge affording polynuclear products. Instead, in cationic mononuclear Pt(II) and Pd(II) species a clear preference for chelation of dpdpc is observed. Also the cation [Ni(dpdpc) 2 Cl] + contains the two dpdpc moieties as chelates. The molecular and crystal structure of [Ni(dpdpc) 2 Cl] 2 (NiCl 4 ) discloses a significantly small bite angle of the chelate and interaction of near phenyl rings pertaining to opposite dpdpc moieties. Coordination of dpdpc to cobalt prompts its oxidation to the corresponding P , P ′-dioxide.

Electrophilic Attack of [I(py)2]+(NO3−) on Three‐Coordinate Pt0 Precursors: Synthesis and In Vitro Antitumor Activity of Water‐Soluble, Five‐Coordinate PtII Complexes

[I(py)2]+(NO3−) oxidatively adds to the three-coordinate platinum(0) precursors [Pt(N,N-chelate)(olefin)] affording the cationic five-coordinate products [Pt(N,N-chelate)I(py)(olefin)]+(NO3−) (1) {N,N-chelate = 2,9-Me2-1,10-phenanthroline (dmphen), 2-methyl-6-[(phenylimino)methyl]pyridine (pimpy) and 2-methyl-6-[(4-methoxyphenylimino)methyl]pyridine (mpimpy)}. The crystal structure of [Pt(pimpy)I(py)(dimethyl fumarate)]+(NO3−) is reported. The crystals are triclinic, space group P1(bar), with a = 13.511(2), b = 13.754(2), c = 8.678(1) A, α = 95.2(1)°, β = 92.5(2)°, γ = 64.7(1)°, Z = 2. Type I complexes, which are soluble both in chlorinated solvents and in water, were tested for cytotoxicity against a panel of tumour cell lines of various histotypes including NSCLC H460, leukaemic HL-60, ovarian A 2780, IGROV-1, SKOV-3, and an ovarian carcinoma A 2780/CP selected for resistance to cis-platin [DDP = cis-diamminedichloroplatinum(II)]. [Pt(dmphen)I(py)(methyl acrylate)]+(NO3−) was the most active in all cell lines tested, its antitumoural activity in vitro being comparable to that of DDP.