Renzo Ros

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.

Preparation and reactivity of some new azido-bridged complexes of Pd(II) and Pt(II)

Abstract Azido-bridged complexes of Pt(II) and Pt(II) of the type [(dieneOCH 3 )MN 3 ] 2 (M = Pd, Pt) and[(π-allyl)PdN 3 ] 2 have been prepared by methathetical reaction from their chloro-bridged congeners. The bridging azido group in these new complexes reacts with carbon monoxide to give the corresponding cyanato-bridged complexes, whereas with CS 2 , CF 3 CN and SCNC 6 H 5 undergoes 1,3-cycloaddition to form thiatriazolate or tetrazolate groups bridging in dimeric complexes of the type [(diene)CH) 3 )M(N 3 CS 2 ) (M = Pd, Pt), [(π-allyl)Pd(N 3 CS 2 ] 2 ,[(π-allyl)Pd(N 3 CF 3 CN)] 2 and [(π-allyl)Pd(N 3 SCNC 6 H 5 )] 2 . Preliminary results on the termal decomposition of the CS 2 adducts and on the reaction with COS are reported and discussed.

Chemistry of tetrairidium carbonyl clusters. Part 1. Synthesis, chemical characterization, and nuclear magnetic resonance study of mono- and di-substituted phosphine derivatives. X-Ray crystal structure determination of the diaxial isomer of [Ir4(CO)7(µ-CO)3(Me2PCH2CH2PMe2)]

The reactions of the anionic cluster [NEt4][Ir4(CO)11Br] with uni- and bi-dentate phosphines and arsines have been investigated. The bromide ligand is quantitatively displaced by 1 mol equivalent of phosphine or arsine at low temperature, the only complexes being formed under these mild conditions being the monosubstituted products [Ir4(CO)11L](L = PPh3, PPh2Me, PPhMe2, or AsPh3), [Ir4(CO)11(L–L)](L–L =trans-Ph2PCHCHPPh2), and [(OC)11Ir4(L–L)Ir4(CO)11][L–L =trans-Ph2PCHCHPPh2 or Ph2P(CH2)nPPh2(n= 3 or 4)]. Similar reactions with higher than stoicheiometric amounts of phosphine (L = PPh3, PPh2Me, or PPhMe2) or diphosphine [L–L = Ph2P(CH2)nPPh2(n= 1–4), Me2P(CH2)2PMe2, cis-Ph2PCHCHPPh2, or o-Ph2PCH2C6H4CH2PPh2] give in good yields the disubstituted compounds [Ir4(CO)10(L–L)] respectively. The stereochemical arrangements of the phosphine ligands and the dynamic processes occurring in solutions of these complexes are discussed on the basis of i.r. and n.m.r, data. The structure of the diaxial isomer of [Ir4(CO)7(µ-CO)3(Me2PCH2CH2PMe2)] has been determined by X-ray diffraction. The complex crystallizes in the monoclinic space group P21/c, with cell constants a= 15.694(2), b= 10.403(2), c= 15.706(2)A, β= 92.63(2)°, and Z= 4. The structure has been solved from 2 289 diffraction intensities collected by counter methods, and refined by least-squares calculations to R= 0.087 (R′= 0.091). The four iridium atoms define a tetrahedron with three bridging CO ligands around a triangular face. All remaining carbonyls are terminally bonded and the two P atoms of the Me2PCH2CH2PMe2 ligand are found in axial positions, generating a six-membered ring.

Additions to the coordinated ethylene ligand in the [C5H5Fe(CO)2(C2H4)]+ complex

Abstract Reaction of [C5H5Fe(CO)2C2H4]+ with methylamine or methoxide ion (L) yields the stable σ-bonded carboniron complexes [C5H5Fe(CO)2(C2H4L)], which regenerate the original iron cationic complex when treated with hydrogen chloride. Reactions with other nucleophiles, such as N−3, NCO−, CN− have also been examined. With N−3 the nucleophilic attack occurs at the CO group to give the cyanato complex [C5H5Fe(CO)(C2H4)(NCO)], while with NCO− and CN− (X) ethylene is replaced to give [C5H5Fe(CO)2X] complexes.

Reactions of platnum(O) and palladium(0) complexes involving insertions into carbon—carbon bonds of electro-negatively-substituted cyclopropanes

Abstract 1,1,2,2-Tetracyanocyclopropane and its 3-alkyl derivatives react with Pt 0 and Pd 0 complexes of the type Pt(PPh 3 ) 2 (C 2 H 4 ) or ML n ( n = 3,4; M = Pd or Pt; L = phosphines or triphenylarsines) to give metallocyclobutane derivatives, which undergo exchange reactions of the neutral ligand L. The structures of these products have been assigned on the basis of the IR and NMR spectra.

Cyanoalkyl complexes of platinum(II). III. Alcoholysis and hydrolysis of the CN group

Abstract Nucleophilic additions of alcohols, thiols and water to the σ-coordinated CN group of cis-[Pt(o-CH2C6H4CN)(PPh3)2]2(BF4)2 give quantitative yields of stable N-bonded iminoether, iminothioether and amide complexes. The proposed mechanism involves a fast replacement of the σ-coordinated CN by the nucleophile HY followed by the intramolecular attack of HY on the ligand in the cis position. π-Coordination of CN to PtII has not been observed. The addition of methanol to other cyanoalkyls did not lead to stable iminoether complexes. The amide complex cis-[Pt(CH2C6H4CONH2)(PPh3)2]2(BF4)2 is converted into the nonionic imide cis-[Pt(CH2C6H4CONH)(PPh3)2]2 in methanolic KOH but it catalyzes for a few cycles the conversion of benzonitrile to benzamide by water under neutral conditions. The imino and isonitrile have a higher trans effect than alkyl groups whereas their trans influence as indicated by 1J(PtP) coupling constants is smaller.

Cyanoalkyl complexes of platinum(II) : II. Uncharged and cationic o-cyanobenzyl complexes

The oxidative addition of o-XCH2C6H4CN to PtL4 yields trans-PtX-(CH2C6H4CN)L2 (L = PPh3, AsPh3a X = Cl, Br). The trans complex is the thermodynamically stable isoer, but cistrans isomerization occurs readily in dichloromethane and is catalyzed by free L. Displacement of L by bidentate phosphorous ligands and insertion of CO in the σ PtC bond occurs readily. Abstraction of X gives a cis cationic complex in which the CN group is coordinated and is prone to nucleophilic attack by alcohols to give stable cis imino ether complexes.

Cationic cyanobenzylpalladium(II) complexes. Synthesis and reactivity of the cyano group towards nucleophiles

Abstract The addition of alcohols, thiols, water and amines to the σ-coordinated CN group of cis -[Pd( o -CH 2 C 6 H 4 CN)L 2 ] 2 (BF 4 ) 2 (L 2 = 2PPh 3 , 1,2-bis(diphenylphosphino)ethene or -ethane) yields stable N-bonded iminoether, iminothioether, amide and amidine complexes,respectively. Thiophenols, ArSH (Ar = p -C 6 H 4 CH 3 , p -C 6 H 4 Br) break the σ-PdC bond, forming o -cyano toluene and complexes of the type [Pd(SAr)L 2 ] 2 (BF 4 ) 2 . The azido complex PdN 3 ( o -CH 2 C 6 H 4 CN)(Ph 2 PCH 2 CH 2 PPh 2 ) is stable in the solid state but in solution it undergoes an intramolecular 1,3-cycloaddition yielding the corresponding tetrazolate complex.

Cyanobenzylpalladium(II) complexes. Synthesis and spectroscopic properties

Abstract The oxidative addition of benzyl, o- , m- and p- cyanobenzyl chlorides to Pd(PPh 3 ) 4 yields trans- PdCl(CH 2 C 6 H 4 Y)(PPh 3 ) 2 (Y= H or CN) (1a-d). In solution, these complexes are in equilibrium with the dimers [PdCl(CH 2 C 6 H 4 Y)PPh 3 ] 2 (2a--d) which are obtained in quantitative yields upon shifting the equilibria by oxidation of the free PPh 3 with H 2 0 2 . PPh 3 in both the monomers and the dimers is readily displaced by bidentate ligands yielding PdCI(CH 2 C 6 -H 4 Y)(L-L) (3). Chloride abstraction from 3 gives dimeric cationic complexes [Pd(o-CH 2 C 6 H 4 CN)(L-L)] 2 (BF 4 ) 2 having a σ-coordinated CN group. Insertion of carbon monoxide in the PdC bonds is quantitative.

Hydridocyanomethyl complexes of platinum(II)

Abstract The preparation and spectroscopic properties are described of some novel platinum(II) complexes having a hydride ligand cis or trans to an sp3 carbon, vis. PtH(CH2CN)(PPh3)2 and PtH(CH2CN)(LL) with LL = bis(diphenylphosphino)-ethene, -ethane, -propane and bis(diphenylarsino)ethane.