Vincenzo De Felice

On the stabilization of five-coordinate trigonal-bipyramidal palladium(II) species. Crystal structure of (2,9-dimethyl-1,10-phenanthroline)methylchloropalladium(II)

Abstract The role of the steric requirements of the NN′ chelate ligand in the stabilization of trigonal-bipyramidal [Pd(NN′)(olefin)RX] complexes is discussed. The crystal structure of the precursor (2,9-dimethyl-1,10,phenanthroline)methylchloropalladium(II) (1a) has been determined. The molecule adopts a significantly distorted square-planar coordination geometry in order to accomodate the crowding in the coordination plane. The most significant distortions involves the coordinated methyl group and the dimethylphenanthroline molecule, whose mean plane lies out of the coordination plane by 39.3°. There is ready CO insertion into the PdMe bond of 1a to give an acyl derivative. The formation of a five-coordinate acyl derivative by subsequent uptake of an olefin also illustrates the importance of the steric effects of NN′ ligands.

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.

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.

Cis-(hydrido)hydrocarbylplatinum(IV) complexes as intermediates in the PtIIC bond breaking☆

Abstract Platinum(IV) complexes containing a cis -hydridohydrocarbyl arrangement have been obtained selectively on reaction of halotrimethylsilanes with bis(hydrocarbyl)( N , N -chelate)platinum(II) complexes. Hydrocarbon reductive elimination can be observed subsequently in solution.

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.

New cationic five-coordinate monoolefin hydrocarbyl complexes of platinum(II)

Abstract Cationic trigonal bipyramidal complexes of the type [PtRL(NN′)(olefin)]BF 4 with various hydrocarbyl (R), neutral monodentate (L), and bidentate nitrogen (NN′) ligands have been prepared and characterized by elemental analysis, conductivity measurements, and 1 H NMR spectroscopy. The coordination around Pt II is trigonal bipyramidal, with the olefin and the NN′ ligand in equatorial positions. The reversible loss of the olefin is markedly affected by the nature of the apical ligand L, which also influences stereochemical aspects, and by the steric requirements of NN′.

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.

Five-coordinate platinum(II) complexes containing substituted olefins : synthesis and cytostatic activity

Abstract The synthesis and characterization of five-coordinate platinum(II) complexes of general formula [PtClX(NN)(uns)] (X=Cl, Me; NN=bidentate nitrogen ligands; uns=substituted alkene containing carboxy or amino groups) are described. In some cases, the hindered rotation of the prochiral unsaturated ligand around the Pt-alkene bond, alone or in conjunction with a ligand environment affording a stereogenic metal centre, gives rise to a mixture of different stereoisomers. Some of the obtained complexes were tested on the neuroblastoma cell line SK-N-MC and a considerable inhibition of cellular proliferation was detected.

Pt(IV) derivatives formed by oxidative addition of organic halides to [Pt(CH3)2(N,N-chelate)] substrates: geometric isomers at equilibrium

Abstract The geometrical isomerism at equilibrium of Pt(IV) derivatives of general formula [Pt(CH 3 ) 2 (R)X(NN)] (NN=2,9-dimethyl-1,10-phenanthroline or 1,10-phenanthroline; R=σ C-bonded ligand; X=halide) has been investigated by variation of R, X, and NN. The complexes have been obtained mainly through oxidative addition of RX to [Pt(CH 3 ) 2 (NN)]. Some general trends can be traced in the relative stability of the geometrical isomers of the complexes, and attempts to discriminate sterical and electronic factors have been presented. The first attainment of a compound of the general formula [Pt(CH 3 ) 2 (R)R′(NN)] containing three different types of σ C-bonded groups is also reported.

Stabilization of unstable unsaturated molecules in five-coordinate TBP complexes of Pt(II): enol, diol and dialdehyde derivatives

Abstract Protection and stabilization of some unstable olefins has been effectively achieved by coordination in five-coordinate [PtClMe(2,9-Me2-1,10-phenanthroline)(olefin)] complexes. These have been characterized by 1H-NMR spectroscopy and in the case of [PtClMe(2,9-Me2-1,10-phenanthroline)(Z-EtCHCHOH)] by X-ray diffractometry. Chemoselective reactions have been accomplished on the complexes, some of them involving alcoholic or aldehydic functions of the unsaturated ligand.