A dimeric tethered pi-coordinated-phenoxy ruthenium precatalyst has been used for the base-free hydrogenation of CO2 in DMSO. The same precatalyst was also efficient in the reverse dehydrogenation of formic acid yet under base-free conditions. An unprecedented base-free cycle consisting in hydrogen storage and release was successfully implemented with the same precatalyst. The latent property of the catalyst has been introduced in the concept of hydrogen storage/transportation/release.

Diverse synthetic routes of tethered eta(5)-oxocyclo-hexadienyl ruthenium complexes, which are the extended version of the eta(4)-cyclopentadienone Shvo-type active catalyst, are described and their reactivity studies are reported. An original dimeric eta(5)-oxocyclohexadienyl compound has been isolated and its solid-state structure was established by X-ray analysis. DFT computational data suggested that this dimeric compound is prone to generate a coordinatively unsaturated mononuclear Lewis acid metal complex bearing a Lewis basic pi-coordinated eta(5)-oxocyclohexadienyl Iigand. Preliminary studies in (transfer)-hydrogenation of acetophenone confirmed that the dimeric eta(5)-oxocyclohexadienyl complex behaves as a bifunctional catalyst with metal-ligand cooperativity. Promising results were obtained under base-free conditions using dihydrogen, iPrOH, and formic acid as hydrogen highlighting the robustness and stability of the catalyst and opening perspectives donors, the latter being active in water, hence toward sustainable catalytic transformations.

Optically active halogenated arenes containing stereogenic benzylic alcohol reacts with [CpRu(CH3CN)3][PF6] to give the major diastereomer with 90% de, in which the metal center is preferentially placed on one face of the arene ring. Thus starting with (S)-1-(2-chlorophenyl)ethanol the metal complex (pS, S)-[CpRu(HO(CH3)CH-C6H4-Cl)][PF6] (pS, S)-1 was obtained in good yield, while the (R)-alcohol provided (pR, R)-[CpRu(HO(CH3)CH-C6H4-Cl)][PF6] (pR, R)-1 metal complex. These compounds display planar and central chiralities. For comparison purposes the analogous racemic compound (rac)-[CpRu(HO(CH3)CH-C6H4-Cl)][PF6] (rac)-1 was also prepared in good yield as well. Subsequent treatment of enantiopure and racemic complexes 1 with NaSH in THF allows halogen displacement to occur at room temperature and generates the related enantiopure neutral metallothioligands of the type (pS, S)-[CpRu(HO(CH3)CH-C6H4-S)], (pS, S)-2, (pR, R)-[CpRu(HO(CH3)CH-C6H4-S)] (pR, R)-2, and (rac)-[CpRu(HO(CH3)CH-C6H4-S)] (rac)-2 (S = sulfur). These metallothioligands react rapidly with [(MeCN)Pt(terpy)][OTf]2 building blocks to give the chiral coordination assemblies [Pt(terpy)-(pS,S)-2][OTf]2 (pS,S)-3, [Pt(terpy)-(pR,R)-3][OTf]2 (pR,R)-3 and the related racemic complex (rac)-3 in which the metal-chromophore is now placed in a chiral environment. The molecular structures of (rac)-3 and the enantiopure heterobimetallic complex (pR,R)-3 were determined and show different arrangements at the supramolecular level depending on whether a homochiral or heterochiral assembly is obtained. The induced circular dichroism curves for the right-handed (pR,R)-3 and left-handed (pS,S)-3 bimetallic complexes displayed mirror image Cotton bands, confirming the enantiomeric relationship between both compounds. Our method provides an entry to the preparation of a wide range of optically pure coordination compounds with potentially important properties.

A novel synthetic procedure was set up to gain access to platinum coordination cages Pt2L4, which are less investigated compared to their palladium counterparts. This Pt2L4 nanocage exhibits an adequate cavity for guest encapsulation. Indeed, the Au(III) metal complex [Au(bdt)2]- (bdt = benzene-1,2-dithiolate) was successfully captured inside the cavity, in contrast to the analogous palladium cage which failed to host the gold complex. This result represents a rare example where a metal complex with thio-ligands can be encapsulated in a coordination cage. Moreover, it highlights the role of the metal center and the robustness of the platinum cage for host-guest chemistry. This discovery will inspire researchers in this area to pay more attention to Pt-cages. The host-guest system was fully characterized by NMR techniques and X-ray crystallographic analysis. Moreover, the nature of the host-guest interaction in this unique example was investigated and rationalized by DFT computational studies.

Two known and two new ortho-phenyl phosphonium-sulfonate compounds have been synthesized and analyzed in solution and in the solid state. When the phosphonium moiety bears alkyl substituents, two rotamers are in equilibrium in solution. These two rotamers have been entirely characterized and are shown to differ by the spatial arrangement of the phosphonium proton relative to the sulfonate moiety. The phosphonium proton chemical shift and the 1JPH coupling constant are characteristic values for each rotamer. The kinetic and thermodynamic constants have been determined by means of NMR and DFT studies.

Ces travaux de recherche présentés ici traitent de la synthèse d’une nouvelle classe d’assemblages de coordination de platine luminescents. En raison du savoir-faire du groupe, deux stratégies ont été suivies: (i) La première approche consiste en l’auto-assemblage d’une nouvelle famille de métallocages de platine de formule [Pt2L4][OTf]4 contenant divers ligands bidentés rigides. Les structures moléculaires de plusieurs complexes ont été déterminées. Les propriétés d'absorption et d'émission de ces assemblages ont été étudiées. De plus, la cage Pt2L4 (L=5-methoxy-1,3-bis(pyridin-3-ylethynyl)benzène) a montré des propriétés intéressantes en tant que molécule hôte envers une série de complexes métalliques plan-carrés agissant comme invités. Remarquablement on a déterminé la structure moléculaire d’un rare exemple dans lequel l’anion complexe dithiobenzène or(III) [Au(bdt)2]-1 a été encapsulé. Le comportement en solution a également été déterminé. De plus (ii) dans une seconde approche, on a décrit la synthèse d’un unique type d’assemblages de platine luminescents contenant un nouvel organométalloligand comportant une fonction chirale. L’organométalloligand permet un contrôle précis de la chiralité de l’assemblage au niveau supramoléculaire aussi bien que la modulation des interactions intermoléculaires Pt···Pt et π-π. En effet, plusieurs structures moléculaires analysées par diffraction des rayons X, ont été obtenues et confirment ce comportement. Les propriétés de luminescence de ces composés ont été étudiées en solution et à l’état solide. Elles ont montré que ces composés agissent en tant qu’intenses émetteurs rouges avec de bons rendements quantiques. De plus les propriétés chiroptiques de ces complexes de platine énantiopurs ont été étudiées aussi bien que leurs propriétés de luminescence par lumière polarisée.

A novel class of chiral luminescent square-planar platinum complexes with a π-bonded chiral thioquinonoid ligand is described. Remarkably the presence of this chiral organometallic ligand controls the aggregation of this square planar luminophor and imposes a homo- or hetero-chiral arrangement at the supramolecular level, displaying non-covalent Pt-Pt and π-π interactions. Interestingly these complexes are highly luminescent in the crystalline state and their photophysical properties can be traced to their aggregation in the solid state. A TD-DFT calculation is obtained to rationalize this unique behavior.

The enantiomeric relationship of chiral luminescent square-planar platinum complexes is confirmed by circular dichroism traces, as shown for the functionalized Pt(t-Bu3terpy) chromophore. The chiral organometallic ligand controls the homochiral or heterochiral solid-state aggregation through π–π and Pt–Pt interactions. These complexes are highly luminescent in the crystalline state; their photophysical properties arise from solid-state aggregation. More information can be found in the Communication by V. W. W. Yam, H. Amouri et al. on page 8032 ff.