Rino A. Michelin

Reactions of transition metal-coordinated nitriles

Abstract The reaction chemistry of nitriles, RCN, where R is usually an organyl group, with transition metal complexes is reviewed. The review surveys data published during the period 1977-early 1994 on new reaction processes such as insertion into metal-hydrogen and -carbon bonds, coupling between one nitrile and an unsaturated metal fragment or between two nitriles, reduction to amines, attack by protic and aprotic nucleophiles and electrophilic attack as well as some catalytic transformations, which result from the ability of nitriles to coordinate to transition metal centres with a consequent change in the electrophilicity or nucleophilicity of the coordinated ligand.

Aminocarbene complexes derived from nucleophilic addition to isocyanide ligands

Abstract Isocyanides ligating medium to high-valent electron-poor metal centers can undergo activation toward α-nucleophilic addition to afford a variety of aminocarbene complexes with either heterocyclic or acyclic aminocarbene ligands. These reactions as well as the structural and electronic properties of such products are reviewed.

Aminocarbyne complexes derived from isocyanides activated towards electrophilic addition

Abstract When binding a low-valent electron-rich metal centre, isocyanides can be activated towards β-electrophilic attack at the N atom to give aminocarbyne complexes. The syntheses, structural and electronic properties of these compounds are reviewed, as well as their reactions, in particular, proton-induced CC coupling to form diaminoacetylene complexes, deprotonation, dehydrogenation and addition of electrophiles across the metal–carbon triple bond. The kinetic and mechanistic studies performed on these systems are also described.

Platinum—alkynyl and —alkyne complexes: old systems with new chemical and physical perspectives

Abstract The chemistry of alkynyl and alkyne ligands in platinum complexes of different oxidation states is described. The review focuses on the synthetic aspects of mono- and polynuclear compounds and on the reactivity of σ-alkynyl and π-alkyne species in different stoichiometric reactions such as insertion, addition of nucleophiles and electrophiles, rearrangements and isomerization processes and also some catalytic additions of heteroatoms (B, Si, S) across the CC triple bond. The relevant features of polynuclear complexes bearing the CC group in dendrimers and organometallic polymers are briefly reported.

Alkoxo and hydroxo complexes of platinum(II). Novel insertion reactions into platinumoxygen bonds and condensations with compound containing active hydrogen atoms

Abstract Hydroxo and alkoxo alkyl complexes of the general formula cis - and trans Pt(OR)(R x )L 2 (R = H, CH 3 ; R x = CH 2 CN, CF 3 , CH 2 CF 3 ; L 2 = 2 PPh 3 , diphosphine) were prepared by metathesis of PtCl(R x )L 2 or [Pt(R x )L 2 ]BF 4 with NaOR. The platinumoxygen bonds undergo facile insertion of CO, COS, CS 2 and SO 2 . The hydroxo complexes react with a variety of acids, including fairly weak carbon or nitrogen acids, such as phenylacetylene, acetamide and methylaniline, to give the corresponding condensation complexes.

Synthesis and spectroscopic investigation of cis and trans isomers of bis(nitrile)dichloroplatinum(II) complexes

Abstract A series of bis(nitrile) complexes cis- and trans-Cl2Pt(NCR)2(R=C6H5,p-CH3C6H4, p-CF3C6H4, o-CH3C6H4,CH3, CH3CH2, CH3CH2CH2, (CH3)2CH, (CH3)3C) has been prepared by either one of the two methods, K2PtCl4/H2O/ RCN(excess) or PtCl2/RCN(neat), both of which usually yield the nitrile complexes as a mixture of cis and trans isomers in different ratios depending on the experimental conditions such as the reaction temperature and the reaction time. The separation of the stereoisomers of each bis(nitrile) compound could be achieved by fractional crystallization by taking advantage of the generally higher solubility of the trans species in non-polar solvents. The complexes were characterized by IR, 1H and 13C NMR spectroscopies. Some general trends of v(CN) and v(PtCl) stretching frequencies as well as of the 2J(PtC) values have been found to be useful in determining the stereogeometry of the cis and trans isomers of the Cl2Pt(NCR)2 complexes.

Functionalized ylides: new trends in organometallic chemistry

The coordination and organometallic chemistry of P- and As-carbonyl stabilized ylides is reviewed. As a general feature, the coordination chemistry of R3ECHCOR′-type (E=P, As) ligands appears to be dominated by C(ylide) metal coordination, although a few examples of O(ylide)-bound complexes are known. The factors addressing C(ylide)-vs. O(ylide)-coordination in Pt(II) and Pd(II) systems are examined. The Ni(II) complexes containing P,O-chelate ylide ligands are also discussed, with a special emphasis on their catalytic activity. The synthesis and reactivity of phosphonium functionalized isocyanides and their corresponding ylides, which provide a new route to metal coordinated indole systems, are described. Finally, the reactivity of Ph3PCCO towards metal substrates is summarized including the formation of ketenyl complexes.

Synthesis, chemical and electrochemical deprotonation reactions of aminocarbene complexes of palladium(II) and platinum(II). X-ray structure of {(PPh3)ClPt[μC,N]}2

Abstract The diaminocarbene complexes cis-Cl2(PPh3)Pt[ CN(Bu t )CH 2 CH 2 N H] (1) and cis-Cl2Pt[ CN(C 6 H 4 -p-OMe)CH 2 CH 2 N H]2 (2) have been prepared by reaction of the corresponding isocyanide derivatives with aziridine/ClCH2CH2NH3+Cl− and aziridine alone, respectively. The aminooxycarbene complex cis-Cl2Pt[ CN(C 6 H 4 -p-OMe)CH 2 CH 2 O ]2 (3) has been prepared by reaction of the bis-isocyanide derivative with 2-chloroethanol/n-BuLi. The dimeric complexes {(PPh3)BrPd[μ- CN(Me)CH 2 CH 2 N C,N]}2 (4), {(PPh3)ClPd[μ- CN (C6H4-p-OMe)CH2CH2NC,N]}2 (5), {(PPh3)ClPt[μ- CN(C 6 H 4 -p-OMe)CH 2 CH 2 N C,N]}2 (6) have been prepared by deprotonation reaction of the NH group of the corresponding mononuclear derivatives with n-BuLi. The X-ray structure of {(PPh3)ClPt[μ- COCH 2 CH 2 N C,N]}2 (7) is reported. The structural model was refined to R=0.055 (Rw=0.061) for 7442 independent reflections. Crystal data: triclinic, space group P , a=19.564(3), b=16.497(3), c=13.243(2) A, α=88.93(3), β=97.88(3), γ=91.97(3)° Z=4. The crystal contains two crystallographically independent dimer units and a disordered dichloroethane molecule. Each dimer is formed by two bridging carbene ligands which are coordinated to one platinum on one side via a PtN bond and to the second platinum via a PtC bond. The coordination geometry around each platinum atom is an irregular square with deviations in the tetrahedral direction of the bonded atoms. The anodic behaviour of these and related monocarbene, dicarbene or dinuclear dicarbene complexes has been studied by cyclic voltammetry and controlled potential electrolysis in aprotic media and shown to present irreversible oxidation waves commonly with a multi-electron character (up to four electrons) and involving liberation of protons (in a number similar to that of the transfered electrons) conceivably resulting from anodically induced NH or CH bond cleavage, the former at an amino group and the latter occurring at methylene groups activated by adjacent amino- or oxy-carbene moieties.

Functionalized isocyanides as ligands. Synthesis of 2-(chloromethyl)- and 2-(iodomethyl)phenyl isocyanides and their transition-metal complexes

Preparation de 2-(XCH 2 ) C 6 H 4 NC (X=Cl ou I) par reaction en 4 etapes. Synthese des complexes de Pd, Pt, Cr, W et Do

Chemistry and biological activity of platinum amidine complexes.

Platinum amidine complexes represent a new class of potential antitumor drugs that contain the imino moiety HNC(sp2) bonded to the platinum center. They can be related to the iminoether derivatives, which were recently shown to be the first PtII compounds with a trans configuration endowed with anticancer activity. The chemical and biological properties of platinum amidine complexes, and more generally of platinum imino derivatives, can be rationally modified through suitable synthetic procedures with the aim of improving their cytotoxicity and antitumor activity. The addition of protic nucleophiles to nitriles coordinated to platinum in various oxidation states can offer a wide variety of complexes with chemical, structural, and physical properties specifically tuned for a more efficacious biological response.