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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.

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.

The addition−elimination equilibrium involving a platinum(0) nucleophile [Pt(N,N‘-chelate)(olefin)] (1), an organometal electrophile RmMXn (M = Hg, Sn; X = Cl, Br, I; R = hydrocarbyl group), and th...

New binucleating ligands based on 4,5-disubstituted xanthenes have been prepared. The ligands, which display either mono- (acyl, nitrile) or bi-dentate (diimino, dithioamide) functionalities, can be prepared through simple procedures from commercial sources. The molecules have been used to synthesise dinuclear platinum(II) complexes with coordination numbers 4 or 5. Relevant aspects of their spectroscopic characterisation and reactivity are discussed along with the molecular structure of a representative compound.

The oxidative addition of diselenides to novel platinum(II) precursors affording octahedral platinum-(IV) products was investigated. The properties of the substituents on Pt were finely tailored in order to prompt easy reversibility of the reaction. This allowed the achievement of the first example of equilibrium of oxidative addition of an E-E bond (E - chalcogen) to a Pt(II) precursor. The equilibrium constants could be evaluated by NMR spectroscopy, and the results were preliminarily rationalized in terms of steric and electronic factors.

A strategy for the synthesis of new chiral salen type ligands derived from α- d -glucose and α- d -mannose is described. The compounds were obtained by introducing appropriate functions at the C2 and C3 positions of the sugar ring. The efficiency of the complexes in the epoxidation of styrenes was also examined and shown to give good results, for example, cis -β-methylstyrene was functionalised with ee’s of up to 86%.

The oxidative addition of RE−ER molecules (E = O, R = H, C(O)Ph, C(O)Me; E = S, Se, Te, R = Me, Ph) to Pt(0) precursors [Pt(N,N-chelate)(olefin)] (1: N,N-chelate = e.g. 2,9-dimethyl-1,10-phenanthroline; olefin = maleic or fumaric ester) has been studied. Symmetrical cleavage of the E−E bonds affords unprecedented trigonal-bipyramidal Pt(II) complexes of the formula [Pt(ER)2(N,N-chelate)(olefin)] (2). Products of type 2, which have been characterized through 1H and 13C NMR spectroscopy, contain chalcogenide ligands in the axial positions. The reactivity of the new compounds has also been investigated. Thus, Pt−OH fragments generated by the addition of H2O2 are acetylated by acetic anhydride. Furthermore, S, Se, and Te coordinated to Pt are readily methylated by trimethyloxonium tetrafluoroborate, affording the first examples of dipositive coordinatively saturated platinum(II) cations (3). The structures of the related neutral [Pt(SMe)2(2,9-dimethyl-1,10-phenanthroline)(diphenyl fumarate)] and cationic [Pt...

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.

New nitrogen chelates of formula 6-R-C5H3NCHNR′-2 and R′NCHCHNR′ (R = H or Me; R′ = 2,3,4,6-tetra-O-acetyl-β-D-glucopyranose residue) were prepared. The nitrogen donor atom is directly linked to a chiral carbon, i.e. the C1 atom of the sugar ring. The ability of the ligands to induce enantioselective co-ordination of prochiral olefins was assessed by preparing palladium(0) complexes of formula [Pd(N,N-chelate)(olefin)]. Hydrophilic complexes obtained by deprotection of the hydroxy groups of the sugar residue were used for hydrogenating alkenes in water. The course of the reaction is strongly influenced by pH, and homogeneous hydrogenation of the double bond takes place only under basic conditions.

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.

New bidentate nitrogen ligands based on α-D-mannose were prepared and investigated by preparing a family of platinum(0) complexes of formula [Pt(N,N-chelate)(η2-olefin)]. The ability of one N,N-chelate to induce a stereoselective reaction in water was assessed.

The oxidative addition of PhSe–X molecules (X=Cl or Br) to Pt(II) complexes of formula [PtR(R ′ )( N , N -chelate)] [R, R ′ =Me, CH(CO 2 Me) 2 , CH(CO 2 Me)(CN); N , N -chelate=4,4 ′ -( tert -butyl) 2 -2,2 ′ -bipyridine] is described. The reaction quantitatively affords octahedral products [PtR(R ′ )(SePh)(X)( N , N -chelate)], and is highly selective, since only the isomers with -X and -SePh in trans position are obtained. When R=R ′ =CH(CO 2 Me) 2 or R=R ′ =CH(CO 2 Me) 2 (CN) an irreversible reductive elimination takes place in solution, giving rise to Pt(II) compounds [PtR(X)( N , N -chelate)] and organoselenium molecules PhSeR ′ .

Relevant stereochemical and coordination features of 1,3,5,7-tetramethyl-2,6,9-trioxo-bicyclo[3,3,1]nona-3,7-diene (TOND), a chiral molecule of C 2 symmetry are described. The X-ray crystal structure of [RhCl{(S)-CHPhMeNH 2 }{(+)-TOND}] has ascertained that the absolute configuration of (+)-TOND is R , R . Furthermore, the synthesis of stable cationic Pd(II) π-allyl complexes of general formula [Pd(η 3 -allyl)(TOND)][BF 4 ] has allowed to probe the ability of this ligand to afford stereoselective coordination of prochiral fragments. The X-ray molecular structure of the representative compound [Pd(η 3 -crotyl)(TOND)][BF 4 ] has been determined. Finally, the influence of TOND on the stereochemistry of prochiral nitrogen donors of diamine and phosphamine chelates has been explored in rhodium complexes of general formula [Rh(chelate)(TOND)][BF 4 ]. The configurations of the nitrogen donors have resulted as stereospecifically selected by the presence of TOND.

Carbon monoxide adds to [PtCl(R)(N-N)] (R=hydrocarbyl group; N-N = chelating N,N-ligand) to afford neutral five-coordinate [PtCl(R)(CO)(N-N)] or cationic four-coordinate [Pt(R)(CO)(N-N)]+ complexes, depending on the the sterical crowding of the N,N-ligand. For R-aryl, a migratory insertion process follows under mild conditions and the corresponding acyl species are obtained. Some reactions of the five-coordinate adducts with nucleophiles are reported, and a substitution at the metal or an addition to the coordinated carbon monoxide are described.

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.

Five-coordinate olefin complexes of palladium(II) of general formula PdClMe(N-N')(η 2 -olefin) have been prepared by reaction of the dimeric complex [PdClMe(Me 2 S)] 2 with planar sterically crowded nitrogenous bidentate ligands and the appropriate olefin. The X-ray crystal structure of the complex having N-N'=2,9-dimethyl-1,10-phenanthroline and olefin=maleic anhydride has been determined

An effective method for the synthesis of square-planar cationic Pt(II) complexes containing a methyl and an olefin in cis position is described. The addition of Me3OBF4 to [Pt(phen)(η3-E-MeO2CCHCHCO2Me)] affords the cationic olefin complex [PtMe(phen)(η2-E-MeO2CCHCHCO2Me)]+(BF4−). Dimethylfumarate is easily displaced by electron-rich olefins RCHCH2 (R  H, Ph, Me) and the products [PtMe(phen)(η2-RCHCH2)]+(BF4−) can be isolated in good yield.

A strategy for the preparation of a supported ‘salen-type’ Mn(III) catalyst derived from d -glucose is described. The compound has been prepared by introducing the ligand functions at positions 2 and 3 of the sugar, which has been subsequently anchored to a CHO-modified Wang resin through formation of a 4,6-O-benzylidene ring. The activity of the catalyst in the asymmetric epoxidation of styrenes has been investigated by using four different oxidants.

The title compounds were obtained by oxidative addition of hydrogen halides to suitable [Pt( N,N -chelate) (olefin)] species. The properties of the ligands and of the electrophile which allow the isolation of stable products must meet very strict requirements. The crystal structure of [PtCl(H)(2,9-Me 2 -1,1O-phenanthroline) (dimethyl maleate)] was determined by single-crystal X-ray diffraction. Substitution, insertion, and elimination reactions were performed on one hydride complex.

Stable five-coordinate hydrido / olefin complexes of general formula [Pt(2,9-Me 2 -1,10-phenanthroline)H(Cl)(olefin)] have been synthesized in high yield through oxidative addition of HCl to [Pt(2,9-Me 2 -1,10-phenanthroline)(olefin)] precursors. Relevant spectroscopic features and some preliminary results concerning the reactivity of the new compounds are also reported.

Cationic trigonal bipyramidal complexes of the type [PtRL(NN′)(olefin)]BF4 with various hydrocarbyl (R), neutral monodentate (L), and bidentate nitrogen (NN′) ligands have been prepared and characterized by elemental analysis, conductivity measurements, and 1H NMR spectroscopy. The coordination around PtII 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′.

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.

Amination of PtII-allene complexes of the type cis[PtCl2(Me2CCCHR)(PPh3)] gives the new four-membered C, N chelate aminoalkenyl complexes [ PtC(CMe 2 )CHRN Me2(PPh3)Cl]. These undergo ready insertion of carbon monoxide into the CPt σ-bond; the resulting acyl complexes are oxidized by hydrogen peroxide to aminoacidato complexes, and the free unsaturated β-aminoacids can be recovered in good yield by ligand displacement.

Resolution of endo-dicyclopentadine has been accomplished through fractional crystallization of choloro (3a,4,7,7a,tetrahydro-exo-6-methoxy-endo-4,7-methanoindene-endo-5σ,2π) (S-α-methylbenzylamine) platinum (II). and -palladium (II) complexes react with an excess of dl-sec-butyl alcohol to give the corresponding dicyclopentadiene sec-butoxy choloride complexes. The unreacted alcohol was recovered and was found to be optically active. This indicates the existance of asymmetric induction in the butoxylation reaction. In the most favorable run, the degree of stereoselectivity, calculated from experimental data, was about 18%.

An attempt has been made to resolve (diallylether) platinum(II) chloride. The complex was transformed by methoxide addition to a binuclear product containing carbon-platinum σ bonds. After bridge splitting of the binuclear alkyl derivative with (S)-α-methylbenzylamine, fractional crystallization gave two diastereoisomer complexes. Treatment of these with HCl gave optically inactive (diallylether)platinum(II) ch1oride. The molecular structure of one diastereoisomeric product was established by X-ray analysis.

Coordinatively saturated carbene complexes of platinum(II) have been obtained by oxidative addition of [ClCHNMe2]Cl to Pt(0) precursors. The cationic products of general formula [PtCl(CHNMe2)(N,N-chelate)(olefin)]Cl have been characterized through NMR spectroscopy and for [PtCl(CHNMe2)(2,9-Me2-1,10-phen)(Z-MeO2CCHCHCO2Me)]Cl by X-ray diffractometry. The latter species reacts with nucleophiles affording dimethylformamide and the corresponding Pt(0) precursor [Pt(2,9-Me2-1,10-phen)(Z-MeO2CCHCHCO2Me)]. Attempts to obtain related complexes containing carbene groups PtCHY without a heteroatom in α-position (Y = CO2Et, CO2NMe2, CN) have led to the isolation of complexes of formula [PtR(dmphen){η1,η2-CH(Y)O2CCHCHCO2Me}] (R = Me, Ph), formally derived from an intramolecular nucleophilic addition to a carbene intermediate. The X-ray structure of a representative product, [PtMe(dmphen){η1,η2-CH(CO2Et)O2CCHCHCO2Me}], is reported.

Anilines, 3-substituted with an ortho-para activating group, undergo, after protection of the amino group by acetylation, electrophilic addition with platinum(II)-co-ordinated 1,1-dimethylallene. This alkenylation is regiospecific, affording o-isopentenyl derivatives. A similar reaction is also observed with diphenylamine. A catalytic process is described.

The new complex [Pt(MeCN)4] [(BF4)2] catalyses the dimerisation of branched olefinic monomers in nitromethane solution.

1,1-Dimethylallene reacts with phenolic substrates in the presence of catalytic amounts of platinum(II) complexes. A regiospecific C-alkenylation takes place, affording o-isopentenylphenols and 2,2-dimethylchromans. Possible reaction mechanisms are also discussed.