Diego Tesauro

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.

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.

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.

Synthesis and characterization of five-co-ordinate alkyne complexes of platinum(II). Crystal and molecular structure of [(dmphen) MePt(µ-Cl)(µ-MeC≡CMe)Pt(Cl)Me]·CH2 Cl2(dmphen = 2,9-dimethyl-1,10-phenanthroline)

Alkynes with electron-withdrawing substituents add to square-planar platinum(II) complexes of general formula [Pt(Cl)R(N–N)](R = Me or C6H4OMe-4. N–N = bidentate nitrogen ligand) affording the corresponding five-co-ordinate trigonal-bipyramidal (TBPY) compounds [Pt(Cl)R(alkyne)(N–N)]. The related five-co-ordinate cationic species [PtMe(alkyne)(N–N)(MeCN)]+ have also been characterized in the presence of excess MeCN. Methyl insertion and formation of a β-methylvinyl dervative is instead observed by treating [PtMe(N–N)(MeCN)]+ with MeO2CC ≡ CCO2Me in the absence of free MeCN. Using a 1:2 alkyne:[Pt(Cl)Me(dmphen)] ratio (dmphen = 2,9-dimethyl-1,10-phenanthroline). binuclear species [Pt2Cl2Me2(alkyne)(dmphen)] are isolated. An X-ray crystallographic study was carried out on the but-2-yne derivative. Crystals are monoclinic, space group P21/c, Z= 4, in a unit cell of dimensions a= 15.719(4), b= 12.307(3), c= 25.048(7)A, β= 148.50(1)°. The structure has been refined to R 0.054 (R′ 0.064) for 3718 intensity data [I 3σ(I)]. The two platinum atoms display different co-ordination numbers [a five-(TBPY) and a four-co-ordinate square-planar arrangement of the ligands] and are held together by the but-2-yne and one chlorine bridge. The MeC≡CMe ligand transversely bridges the Pt ⋯ Pt vector (3.079 A) and the dihedral angle between the two planes formed by the two Pt-µ-C2 units is 102.2(5)°.