Unravelling strong temperature-dependence of in transition metal hydrides: solvation and non-covalent interactions temperature-elastic H-H bonds.

A number of transition metal hydrides reveal intriguing temperature-dependent in their deuterated derivatives and possibly the temperature dependent hydrogen-hydrogen distance ((H-H)) as well. Previously, theoretical studies rationalized and (H-H) changes in such compounds through a "temperature-elastic" structure model with a significant population of vibrational states in an anharmonic potential. Based on the first variable temperature neutron diffraction study of a relevant complex, (-H-POCOP)IrH, observation of its elusive counterpart with longer (H-H), crystallized as an adduct with CFI, and thorough spectroscopic and computational study, we argue that the model involving isomeric species in solution at least in some cases is more relevant.

Oxidation-induced C-H bond activation in iridium pincer complexes.

Dehydrogenation reactions that produce molecular hydrogen are thermodynamically unfavourable. Desired is to couple them with a green driving force, such as oxidation with oxygen or an electric current. This, in turn, requires understanding of the catalyst's redox properties.

Iridium-Catalyzed Dehydrogenation in a Continuous Flow Reactor for Practical On-Board Hydrogen Generation From Liquid Organic Hydrogen Carriers.

To enable the large-scale use of hydrogen fuel cells for mobility applications, convenient methods for on-board hydrogen storage and release are required. A promising approach is liquid organic hydrogen carriers (LOHCs), since these are safe, available on a large scale, and compatible with existing refueling infrastructure. Usually, LOHC dehydrogenation is carried out in batch-type reactors by transition metals and their complexes and suffers from slow H release kinetics and/or inability to reach high energy density by weight, owing to low conversion or the need to dilute the reaction mixture.

Csp -H Activation without Chelation Assistance in an Iridium Pincer Complex Forming Cyclometallated Products.

Cyclometallation of 8-methylquinoline and 2-(dimethylamino)-pyridine in an iridium-based pincer complex is described. The C-H activation of 2-(dimethylamino)pyridine is not chelation assisted, which has not been described before for Csp -H bonds in cyclometallation reactions. The mechanism of the cyclometallation of 2-(dimethylamino)pyridine was studied by DFT calculations and kinetic measurements.

Solvent-Dependent Structure of Iridium Dihydride Complexes: Different Geometries at Low and High Dielectricity of the Medium.

The hydride iridium pincer complex [(PCyP)IrH2] (PCyP=cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane, 1) reveals remarkably solvent-dependent hydride chemical shifts, isotope chemical shifts, JHD and T1(min), with rHH increasing upon moving to more polar medium. The only known example of such behaviour (complex [(POCOP)IrH2], POCOP=2,6-(tBu2PO)2C6H3) was explained by the coordination of a polar solvent molecule to the iridium (J. Am.

Reversible α-Hydrogen and α-Alkyl Elimination in PC(sp(3))P Pincer Complexes of Iridium.

Despite significant progress in recent years, the cleavage of unstrained C(sp(3))-C(sp(3)) bonds remains challenging. A C-C coupling and cleavage reaction in a PC(sp(3))P iridium pincer complex is mechanistically studied; the reaction proceeds via the formation of a carbene intermediate and can be described as a competition between α-hydrogen and α-alkyl elimination; the latter process was observed experimentally and is an unusual way of C(sp(3))-C(sp(3)) bond scission, which has previously not been studied in detail. Mechanistic details that are based upon kinetic studies, activation parameters, and DFT calculations are also discussed.

Formation of a C-C double bond from two aliphatic carbons. Multiple C-H activations in an iridium pincer complex.

The search for novel, atom-economic methods for the formation of C-C bonds is of crucial importance in synthetic chemistry. Especially attractive are reactions where C-C bonds are formed through C-H activation, but the coupling of unactivated, alkane-type C -H bonds remains an unsolved challenge. Here, we report iridium-mediated intramolecular coupling reactions involving up to four unactivated C -H bonds to give carbon-carbon double bonds under the extrusion of dihydrogen.

Cyclometallated gold(III) aryl-pyridine complexes as efficient catalysts for three-component synthesis of substituted oxazoles.

Cyclometallated aryl-pyridine gold(iii) complexes are shown to be efficient catalysts for the multicomponent reaction between N-benzyl imines, alkynes, and acyl chlorides to form trisubstituted oxazoles. The reaction typically proceeds in good yields (up to over 80%) and short reaction times (∼15 minutes). The high stability of the investigated cyclometallated catalysts enables a retained efficiency for this reaction in terms of rate and yield using as little as 0.

Synthesis and characterization of fluorophenylpalladium pincer complexes: electronic properties of some pincer ligands evaluated by multinuclear NMR spectroscopy and electrochemical studies.

Palladium fluorophenyl complexes with different pincer ligands Pd(Ar)[2,6-(tBu(2)PCH(2))(2)C(6)H(3)] (13), Pd(Ar)[2,6-(tBu(2)PO)(2)C(6)H(3)] (14), Pd(Ar)[{2,5-(tBu(2)PCH(2))(2)C(5)H(2)}Fe(C(5)H(5))] (15), and Pd(Ar)[{2,5-(tBu(2)PCH(2))(2)C(5)H(2)}Ru(C(5)H(5))] (16) were synthesized by the reaction of LiAr (Ar = C(6)H(4)F-4) with the respective trifluoroacetate palladium pincer complexes 9-12. The molecular structures of 14 and 16 were determined by an X-ray crystallographic method. Complexes 13-16 and {Pd(Ar)[{2,5-(tBu(2)PCH(2))(2)C(5)H(2)}Fe(C(5)H(5))]}PF(6) (17) were studied by multinuclear NMR spectroscopy and cyclic voltammetry.