The availability of glycerol is rapidly increasing due to the expanding biodiesel industry, which produces this polyol as the main waste material. Several value-added chemicals have been synthesized using glycerol as a feedstock; however, the conversion of glycerol to lactic acid has been investigated to a lesser extent despite the numerous and novel uses of lactic acid. We report a family of iridium complexes as the first homogeneous catalysts for the conversion of glycerol to lactic acid. These have higher activity and selectivity than the previously reported heterogeneous systems. In addition, hydrogen gas is generated as a useful byproduct. Unlike prior systems, the reactions can be performed in air, under mild conditions and without solvent. Our method has even been applied to samples of crude glycerol waste derived from the biodiesel industry without prior purification, albeit with somewhat lower activity while maintaining the same high selectivity.

Cationic Pd(II) catalysts incorporating bulky (8-p-tolylnaphthyl) substituted diimine ligands have been synthesized and investigated for ethylene polymerization and ethylene/methyl acrylate copolymerization. Homopolymerization of ethylene at room temperature resulted in branched polyethylene with narrow M w /M n values (ca. 1.1), indicative of a living polymerization. A mechanistic study revealed that the catalyst resting state was an alkyl olefin complex and that the turnover-limiting step was migratory insertion, thus the turnover frequency is independent of ethylene concentration. Copolymerization of ethylene and methyl acrylate (MA) was also achieved. MA incorporation was found to increase linearly with MA concentration and copolymers with up to 14 mol% MA were prepared. Mechanistic studies revealed that acrylate insertion into a Pd-CH 3 bond occurs at -70 °C to yield a four-membered chelate which isomerizes first to a fivemembered chelate then to six-membered chelate. Barriers to migratory insertion of both the (diimine)PdCH 3 (C 2 H 4 ) + (17.2 kcal/mol) and (diimine)PdCH 3 ( 2 -C 2 H 3 CO 2 Me) + (15.2 kcal/mol) were measured by low temperature NMR kinetics.

Organometallic iridium complexes bearing oxidatively stable chelate ligands are precursors for efficient homogeneous water-oxidation catalysts (WOCs), but their activity in oxygen evolution has so far been studied almost exclusively with sacrificial chemical oxidants. In this report, we study the electrochemical activation of Cp*Ir complexes and demonstrate true electrode-driven water oxidation catalyzed by a homogeneous iridium species in solution. Whereas the Cp* precursors exhibit no measurable O2-evolution activity, the molecular species formed after their oxidative activation are highly active homogeneous WOCs, capable of electrode-driven O2 evolution with high Faradaic efficiency. We have ruled out the formation of heterogeneous iridium oxides, either as colloids in solution or as deposits on the surface of the electrode, and found indication that the conversion of the precursor to the active molecular species occurs by a similar process whether carried out by chemical or electrochemical methods. This work makes these WOCs more practical for application in photoelectrochemical dyads for light-driven water splitting.

Vinylidene (HC=C) is a member of the family of compounds of composition CH (and isomeric with ethyne, HC≡CH), but it has been observed only transiently-with a lifetime in the region of 0.1 ns. Indeed, no simple (non-base-stabilized) compounds of the type RE=E have been characterized structurally for any of the group 14 elements. Here we show that by employing the bulky and strongly electron-donating boryl ligand (HCDippN)B (Dipp, 2,6-PrCH), a simple monomeric digermavinylidene compound, (boryl)GeGe, can be synthesized and is stable at room temperature. Both its formation via the two-electron chemical oxidation of the symmetrical Ge compound K[(boryl)GeGe(boryl)] and its subsequent reaction chemistry (for example, with H), are consistent with a high substituent lability and the accessibility of both 1,1- and 1,2-substitution patterns. Structural and computational studies of [(HCDippN)B]GeGe reveal a weak Ge-Ge double bond-the π component of which contributes to the highest occupied molecular orbital (HOMO)-with a Ge-centred lone pair as the HOMO-1.

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