Hydroxopalladium(IV) complexes prepared using oxygen or hydrogen peroxide as oxidants.

The cycloneophylpalladium(II) complexes [Pd(CHCMeCH)(κ-'-L)], 1 or 2, with L = RO(CH)N(CH-2-CHN), with R = H or Me, respectively, react with either dioxygen or hydrogen peroxide in the presence of NH[PF] to give rare examples of the corresponding hydroxopalladium(IV) complexes [Pd(OH)(CHCMeCH)(κ-'''-L)][PF], 3 or 4. The complexes 3 and 4 are stable at room temperature and have been structurally characterized. On heating a solution of 3 or 4 in moist dimethylsulphoxide, selective reductive elimination with C(sp)-O bond formation is observed, followed by hydrolysis, to give the corresponding pincer complex [Pd(OH)(κ-'''-L)][PF] and 2--butylphenol as major products.

Self-assembly of the smallest and tightest molecular trefoil knot.

Molecular knots, whose synthesis presents many challenges, can play important roles in protein structure and function as well as in useful molecular materials, whose properties depend on the size of the knotted structure. Here we report the synthesis by self-assembly of molecular trefoil metallaknot with formula [Au{1,2-CH(OCHCC)}{PhP(CH)PPh}], Au, from three units of each of the components 1,2-CH(OCHCCAu) and PhP(CH)PPh. Structure determination by X-ray diffraction revealed that the chiral trefoil knot contains only 54 atoms in the backbone, so that Au is the smallest and tightest molecular trefoil knot known to date.

Chemistry of Gold(III) with a Pyridine-Oxaziridine Ligand: Competition between C-O and N-O bond Activation.

The oxaziridine derivative 2-t-butyl-3-(2-pyridinyl)oxaziridine reacted with Na[AuCl ].2H O to give, after recrystallization from a solvent mixture containing methanol, a mixture of gold(III) complexes which were characterized crystallographically as the amide complex [AuCl {κ -N,N'-2-C H NC(=O)N(t-Bu)] and the aldolate complex [AuCl {κ -N,O-2-C H NCH(OMe)O)]. It is suggested that these products arise after initial O-N or C-N bond cleavage respectively of the strained oxaziridine ring, after coordination to the gold(III) center.

Supramolecular organometallic chemistry: the platinum(IV) paradigm.

Supramolecular chemistry and the chemistry of alkyl derivatives of the transition metals are both topics of considerable current interest, but the combination of the two fields is still underdeveloped. The challenges are, in large part, experimental in nature. For example, the self-assembly of molecules in supramolecular chemistry often relies on intermolecular hydrogen bonding, but most alkyl-transition metal bonds are cleaved by the protic groups used in hydrogen bond formation.

DFT studies of two-electron oxidation, photochemistry, and radical transfer between metal centres in the formation of platinum(IV) and palladium(IV) selenolates from diphenyldiselenide and metal(II) reactants.

The oxidant diphenyldiselenide reacts with MIIMe2(bipy) (bipy = 2,2'-bipyridine) to form a pre-equilibrium involving weak adducts, from which [MMe2(bipy)]2·Ph2Se2 undergoes rate-limiting dissociation of phenylselenide preceded by the oxidative addition step to obtain [Me2(bipy)M-MMe2(bipy)(SePh)]+. Coordination of PhSe- gives the neutral MIII-MIII bonded dimers [MMe2(bipy)(SePh)]2. The dimers fragment in the presence of light to give radicals [MIIIMe2(bipy)(SePh)]˙.

Models for Cooperative Catalysis: Oxidative Addition Reactions of Dimethylplatinum(II) Complexes with Ligands Having Both NH and OH Functionality.

The role of NH and OH groups in the oxidative addition reactions of the complexes [PtMe(κ-,'-)], = 2-CHNCHNH--CHOH [, = 2, = ; , = 3, = ; , = 4, = ], has been investigated. Complex is the most reactive. It reacts with CHCl to give a mixture of isomers of [PtMe(CHCl)(κ-,',-(-H)], , and decomposes in acetone to give [PtMe(κ-,',-(-H)], , both of which contain the fac tridentate deprotonated ligand.

Supramolecular Polymer and Sheet and a Double Cubane Structure in Platinum(IV) Iodide Chemistry: Solution of a Longstanding Puzzle.

The complexes [PtMe()], = 2-CHNCHNH--CHOH ( = 2, 3, or 4), react with iodine to form [PtIMe()], by trans oxidative addition, when = 3 or 4, and they are shown to have polymeric or sheet structures formed through NH···I hydrogen bonding. However, ligand dissociation occurs when = 2 to give [(PtIMe) ] and, with methyl group transfer, the complex [(PtIMe·PtIMe)]. This tetraplatinum cluster complex is shown to have a double cubane structure, thus solving a longstanding puzzle.

Supramolecular Organoplatinum(IV) Chemistry: Dimers and Polymers Formed by Intermolecular Hydrogen Bonding.

The reaction of [PtMe(6-dppd)], , where 6-dppd is a 1,4-bis(2-pyridyl)pyridazine derivative, with bromoalkanes BrCHR, having a hydrogen-bond donor group R, gave the corresponding chiral products of trans oxidative addition [PtBrMe(CHR)(6-dppd)], , R = COH; , R = 4-CHCOH; , R = 4-CHCHCOH; , R = 2-CHCHOH; , R = 4-CHB(OH); , R = 3-CHB(OH); and , R = 2-CHB(OH). Complex was formed in equilibrium with two isomers formed by cis oxidative addition, while the reaction of with BrCHCHCOH gave mostly [PtBrMe(6-dppd)], . The supramolecular chemistry was studied by structure determination of six of the platinum(IV) complexes, with emphasis on the preference of the hydrogen bond acceptor (O, pyridyl N, or Br atom), formation of monomer, dimer, or polymer, and self-recognition or self-discrimination in self-assembly.

A Bridging Peroxide Complex of Platinum(IV).

The photolysis of the allylplatinum(IV) complex [PtBr(CH)(4-MeCH)(bipy)], 1, bipy = 2,2'-bipyridine, in air yielded [{PtBr(4-MeCH)(bipy)}(μ-O)], 2, the first diplatinum(IV) complex containing a single bridging peroxide ligand. The PtO-OPt bond distance in 2 is 1.481(3) Å.

Mild and selective Pd-Ar protonolysis and C-H activation promoted by a ligand aryloxide group.

A bidentate nitrogen-donor ligand with an appended phenol group, CHNCH[double bond, length as m-dash]N-2-CHOH, H(L1) was treated with a palladium cycloneophyl complex [Pd(CHCMeCH)(COD)], with both Pd-aryl and Pd-alkyl bonds, to give a Pd-alkyl complex, [Pd(CHCMeCH)(κ-N,N',O-OCHN[double bond, length as m-dash]CH(2-CHN))], 1. The cleavage of the Pd-aryl bond and the deprotonation of the ligand phenol to afford a bound aryloxide, indicates facile Pd-aryl bond protonolysis. Deuterium labelling experiments confirmed that the ligand phenol promotes protonolysis and that the reverse, aryl C-H activation, occurs under very mild reaction conditions (within 10 min at room temperature).

Photoswitchable and pH responsive organoplatinum(ii) complexes with azopyridine ligands.

Several platinum(ii) complexes with ligands containing azo groups have been prepared and structurally characterised, and their photoswitching between trans and cis azo group isomers has been studied. The azo groups in the cationic complexes [PtMe(bipy)(4-NCH-N[double bond, length as m-dash]N-4-CHX)][PF], X = H, OH or NMe, and in the dicationic complex [Pt(bipy)(4-HNCH-N[double bond, length as m-dash]N-CH)][OTf] undergo trans to cis photoswitching on irradiation at 365 nm. The complex [PtMe(bipy)(4-NCH-N[double bond, length as m-dash]N-4-CHNMe)][PF] also exhibits a reversible halochromic effect on protonation to give the dicationic complex [PtMe(bipy)(4-NCH-NH[double bond, length as m-dash]N-4-CHNMe].

Coordination chemistry of mercury(ii) with 2-pyridylnitrones: monomers to polymers.

The coordination chemistry of mercury(ii) halides, HgX, X = Cl, Br, I, with N-methyl-α-(2-pyridyl)nitrone, L1, and N-t-butyl-α-(2-pyridyl)nitrone, L2, is reported. The structures of 1 : 1 complexes [HgXL], X = Cl, L = L1; X = Br, L = L2, 2 : 1 complexes [(HgX)L], X = Br or I, L = L1; X = Cl or I, L = L2, and a unique compound [(HgBr)(L2)] have been determined. In the 1 : 1 and 1 : 2 complexes, the ligand L1 adopts the anti conformation, and is either monodentate or bridging, while the ligand L2 adopts the syn conformation and acts as a chelate ligand.

Pincer-plus-one ligands in self-assembly with palladium(ii): a molecular square and a molecular tetrahedron.

The combination of a palladium(ii) precursor with a diimine-phenol ligand and an oxidant (HO or O) under different conditions has, serendipitously, given both a molecular square and a molecular tetrahedron by self-assembly of building blocks comprising palladium(ii) centres coordinated to the oxidised forms of the ligand.

A biomimetic phenol substituent effect on the reaction of a dimethylplatinum(ii) complex with oxygen: proton coupled electron transfer and multiple proton relay.

The complex [PtMe2({κ(2)-N,N-RN[double bond, length as m-dash]CH-2-C5H4N})] reacts with oxygen in acetone solution to give the platinum(iv) complex [Pt(OH)Me2{κ(3)-N,N,O-RNH-CH(2-C5H4N)(CH[double bond, length as m-dash]CMeO)}], when R = 2-C6H4OH, but not when R = Ph. It has been suggested that the phenol substituent plays two key biomimetic roles; firstly, in proton coupled electron transfer reactions in the activation of oxygen and hydroperoxide groups and, secondly, in proton relay from a methyl group of the coordinated acetone.

Binuclear platinum-iridium complexes: synthesis, reactivity and luminescence.

The chemistry of the heterobinuclear platinum-iridium complex [PtIr(CO)3(μ-dppm)2][PF6], 1, dppm = Ph2PCH2PPh2, is described. The reaction of a hydride with 1 gave [HPtIr(CO)2(μ-dppm)2], by displacement of the carbonyl ligand from platinum, while reaction of 1 with dihydrogen, hydrogen chloride or Ph2MeSiH gave the fluxional complex [PtIrH4(CO)(μ-dppm)2][PF6], [PtIrH2Cl2(CO)(μ-dppm)2][PF6], or [PtIrH(SiMePh2)(CO)2(μ-dppm)2][PF6], respectively, by oxidative addition at iridium. Complex 1 reacted, often regioselectively, with several alkynes to give the μ-η(1),η(1) bridging alkyne complexes [PtIr(μ-RCCR')(CO)2(μ-dppm)2][PF6], R = H, R' = Ph, 4-C6H4Me, CO2Me; R = Ph, R' = CO2Me; R = R' = CO2Me.

3-Bromo-N-(3,5-di-tert-butyl-phen-yl)propanamide.

The title compound, C17H26BrNO, exhibits a small twist between the amide residue and the benzene ring [C-N-C-C torsion angle = 29.4 (5)°]. In the crystal, the amido NH group is involved in N-H⋯O hydrogen bonding, which connects mol-ecules into chains parallel to the c axis.

Easy activation of the aryl-sulfur bond by platinum(II).

The reagents 1,2-C6H4(CH=NR)(SMe), R = CH2CH2NMe2 or Ph, react with [Pt2Me4(μ-SMe2)2] by oxidative addition of the aryl-sulfur bond to give the corresponding crystalline binuclear platinum(IV) compounds [Pt2Me4(μ-SMe)2(κ(2)-C,N-C6H4-2-CH=NR)2], as the isomers with Ci (R = CH2CH2NMe2 or Ph) or C1 (R = Ph) symmetry. These first examples of C-S bond activation at platinum(II) occur easily at room temperature, and the reactions give complex equilibria of isomeric products, from which the isolated compounds crystallise.

Oxidation of dimethylplatinum(II) complexes with a peroxyacid.

The complexes [PtMe2(NN)], NN = 2,2′-bipyridine = bipy, 1a; NN = di-2-pyridylamine = dpa, 1b; NN = di-2-pyridyl ketone = dpk, 1c, NN = 4,4′-bis(ethoxycarbonyl)-2,2′-bipyridine, bebipy, react with m-chloroperoxybenzoic acid to give the platinum(IV) complexes [Pt(OH)(O2C-3-C6H4Cl)Me2(NN)], NN = bipy, 2, or [Pt(OH)(OH2···O2C-3-C6H4Cl)Me2(NN)], NN = bipy, 3a; dpa, 3b; bebipy, 3d, or [Pt(OH)2Me2(dpkOH)]3[Pt(OH)(OH2)Me2(dpkOH)][H(O2C-3-C6H4Cl)2]·2MeOH, 43·5·2MeOH. The reactions are proposed to occur by a polar oxidative addition mechanism, followed in most cases by the coordination of water. Complex 3a crystallises as a supramolecular polymer, the compound 43·5·2MeOH crystallises as a supramolecular sheet structure, and 3d easily forms a gel, all through strong intermolecular hydrogen bonding.

A versatile diphosphine ligand: cis and trans chelation or bridging, with self association through hydrogen bonding.

The diphosphine ligand, N,N'-bis(2-diphenylphosphinoethyl)isophthalamide, dpipa, contains two amide groups and can form cis or trans chelate complexes or cis,cis or trans,trans bridged complexes. The amide groups are likely to be involved in intramolecular or intermolecular hydrogen bonding. This combination of properties of the ligand dpipa leads to very unusual structural properties of its complexes, which often exist as mixtures of monomers and dimers in solution.

Self-assembly of isomeric clamshell dimers of platinum(II).

The controlled synthesis of isomeric organoplatinum clamshell dimers [Pt(2)Me(2)(μ(2)-κ(3)-6-dppd)(2)](2+), 6-dppd = 1,4-di-2-pyridyl-5,6,7,8,9,10-hexahydrocycloocta[d]pyridazine, is reported. The new complexes are formed selectively by self-assembly from mononuclear precursors, taking advantage of the slow cis-trans isomerization at platinum(II). Thus reaction of endo-[PtClMe(κ(2)-6-dppd)] with AgOTf gave endo,endo-[Pt(2)Me(2)(μ(2)-κ(3)-6-dppd)(2)](2+), while the reaction of [PtMe(2)(κ(2)-6-dppd)] with HOTf in solvent S = Me(2)C=O or MeCN gave first a mixture of exo- and endo-[PtMe(S)(κ(2)-6-dppd)](+) and then, by loss of solvent, a mixture of exo,exo- and endo,endo-[Pt(2)Me(2)(μ(2)-κ(3)-6-dppd)(2)](2+).

(OC-6-35)-(2,2'-Bipyridine-κN,N')dimeth-yl(3-sulfido-propionato-κS,O)platinum(IV).

The title complex, [Pt(CH(3))(2)(SCH(2)CH(2)CO(2))(C(10)H(8)N(2))], is formed by the unusual oxidative addition of the disulfide, R(2)S(2) (R = CH(2)CH(2)CO(2)H), to (2,2'-bipyridine)-dimethyl-platin-um(II) with elimination of RSH. The product contains an unusual six-membered thiol-ate-carboxyl-ate chelate ring. This slightly distorted octa-hedral complex exhibits cis angles ranging from 77.

Self-assembled polymers of silver(I) with a chiral diphosphine ligand.

Silver(I) salts, AgX, form self-assembled polymers with the chiral diphosphine ligand R,R-trans-C(6)H(10)(NHCO-2-C(6)H(4)PPh(2))(2), 1, of formula {Ag(2)X(2)(μ-1)}(n) and ring-opening polymerization of the trans chelate complex [Ag(1)]X has given the helical polymer [{Ag(μ-1)}(n)]X(n), when X = CF(3)SO(3).

Cyclometalated organoplatinum(II) complexes: first example of a monodentate benzo[h]quinolyl ligand and a complex with bridging bis(diphenylphosphino)ethane.

The cyclometalated complexes [Pt(ppy)R(SMe(2))] or [Pt(bhq)R(SMe(2))], where ppyH = 2-phenylpyridine, bhqH = benzo[h]quinoline and R = methyl or p-tolyl, react with bis(diphenylphosphino)ethane, dppe, in a 1:1 ratio to give the corresponding complexes [Pt(κ(1)-C-ppy)R(dppe)] or [Pt(κ(1)-C-bhq)R(dppe)], in which the ppy or bhq ligands are monodentate and dppe is chelating. The similar reaction in a 2:1 ratio gives the binuclear complexes [{Pt(ppy)R}(2)(μ-dppe)] or [{Pt(bhq)R}(2)(μ-dppe)], in which the dppe ligands are in the unusual bridging bidentate bonding mode.

Associative and dissociative mechanisms in the formation of phthalazine bridged organodiplatinum(II) complexes.

The reaction of phthalazine with the binuclear organoplatinum complexes [Me(2)Pt(μ-SMe(2))(μ-dppm)PtR(2)], R = Me, Ph, 4-tolyl or R(2) = (CH(2))(4), dppm = bis(diphenylphosphino)methane, gives the corresponding complexes [Me(2)Pt(μ-phthalazine)(μ-dppm)PtR(2)] by displacement of the bridging dimethylsulfide ligand. The structures of [Me(2)Pt(μ-SMe(2))(μ-dppm)PtMe(2)] and [Me(2)Pt(μ-phthalazine)(μ-dppm)PtMe(2)] have been determined. Kinetic studies show that the reactions occur mostly by a second order reaction when R = Me or R(2) = (CH(2))(4) but entirely by a first order reaction when R = Ph or 4-tolyl.

Easy oxidatively induced silicon-carbon bond activation in organoplatinum chemistry.

The oxidation of the complex [PtMe(2)(bps)], bps = bis(2-pyridyl)dimethylsilane, by oxygen, hydrogen peroxide or dibenzoyl peroxide in the presence of water or alcohol gives the complex cation, [PtMe(3)(kappa(3)-N,N,O-HOSiMe(2-C(5)H(4)N)(2))](+), in a reaction involving easy cleavage of a methylsilicon bond.