(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 77.55 (11) to 97.30 (8)° due to the presence of the thiol-ate-carboxyl-ate chelate ring and the constrained bipyridine group. The crystal packing appears to be controlled by a combination of π-stacking [centroid-centroid distance = 3.611 (2) Å] and C-H⋯O inter-actions.

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

The reaction of [PtMe2(6-dppd)], 1, where 6-dppd is a 1,4-bis(2-pyridyl)pyridazine derivative, with bromoalkanes BrCH2R, having a hydrogen-bond donor group R, gave the corresponding chiral products of trans oxidative addition [PtBrMe2(CH2R)(6-dppd)], 2a, R = CO2H; 3, R = 4-C6H4CO2H; 4, R = 4-C6H4CH2CO2H; 7, R = 2-C6H4CH2OH; 8, R = 4-C6H4B(OH)2; 9, R = 3-C6H4B(OH)2; and 10, R = 2-C6H4B(OH)2. Complex 2a was formed in equilibrium with two isomers formed by cis oxidative addition, while the reaction of 1 with BrCH2CH2CO2H gave mostly [PtBrMe(6-dppd)], 6. 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. Complex 7 formed a monomer with the OH···N hydrogen bond, and complexes 2a and 10 formed racemic dimers by complementary hydrogen bonding with self-discrimination between CO2H or B(OH)2 groups, respectively. Complexes 3, 4, and 9 formed polymers by intermolecular hydrogen bonding with self-recognition, with 4 containing OH···N and 3 and 9 containing OH···Br hydrogen bonds. It is concluded that there is no clear preference for the hydrogen bond acceptor group, and that the observed product depends also on the orientation of the hydrogen bond donor group.

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-NC5H4-N[double bond, length as m-dash]N-4-C6H4X)][PF6], X = H, OH or NMe2, and in the dicationic complex [Pt(bipy)(4-H2NC6H4-N[double bond, length as m-dash]N-C6H5)2][OTf]2 undergo trans to cis photoswitching on irradiation at 365 nm. The complex [PtMe(bipy)(4-NC5H4-N[double bond, length as m-dash]N-4-C6H4NMe)2][PF6] also exhibits a reversible halochromic effect on protonation to give the dicationic complex [PtMe(bipy)(4-NC5H4-NH[double bond, length as m-dash]N-4-C6H4NMe2]2+. The nature of the frontier orbitals in the platinum(ii) complexes depends on the charge on the complex and on the degree of metal-ligand π-bonding.

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.

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.

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+). The endo,endo isomer slowly isomerized to the more stable exo,exo isomer in solution. Reaction of PPh(3) with endo-[PtClMe(κ(2)-6-dppd)] gave a mixture of endo- and exo-[PtMe(PPh(3))(κ(2)-6-dppd)](+) but reaction with exo,exo-[Pt(2)Me(2)(µ(2)-κ(3)-6-dppd)(2)](2+) gave exo-[PtMe(PPh(3))(κ(2)-6-dppd)](+) selectively, with retention of stereochemistry. The structures of the clamshell dimers and of key precursors are reported and equilibria are studied both experimentally and by DFT calculations.