Electrocatalytic Transfer Hydrogenation of 1-Octene with [(PCP)Ir(H)(Cl)] and Water.

Electrocatalytic hydrogenation of 1-octene as non-activated model substrate with neutral water as H-donor is reported, using [(PCP)Ir(H)(Cl)] (1) as the catalyst, to form octane with high faradaic efficiency (FE) of 96 % and a k of 87 s. Cyclic voltammetry with 1 revealed that two subsequent reductions trigger the elimination of Cl and afford the highly reactive anionic Ir(I) hydride complex [(PCP)Ir(H)] (2), a previously merely proposed intermediate for which we now report first experimental data by mass spectrometry. In absence of alkene, the stoichiometric electrolysis of 1 in THF with water selectively affords the Ir(III) dihydride complex [(PCP)Ir(H)] (3) in 88 % FE from the reaction of 2 with HO.

Introducing Benzene-1,3,5-tri(dithiocarboxylate) as a Multidentate Linker in Coordination Chemistry.

Benzene-1,3,5-tri(dithiocarboxylate) (BTDTC), the sulfur-donor analogue of trimesate (BTC, benzene-1,3,5-tricarboxylate), is introduced, and its potential as a multidentate, electronically bridging ligand in coordination chemistry is evaluated. For this, the sodium salt NaBTDTC has been synthesized, characterized, and compared with the sodium salt of the related ditopic benzene-1,4-di(dithiocarboxylate) (NaBDDTC). Single-crystal X-ray diffraction of the respective tetrahydrofuran (THF) solvates reveals that such multitopic aromatic dithiocarboxylate linkers can form both discrete metal complexes (NaBTDTC·9THF) and (two-dimensional) coordination polymers (NaBDDTC·4THF).

Thermal Defect Engineering of Precious Group Metal-Organic Frameworks: A Case Study on Ru/Rh-HKUST-1 Analogues.

A methodology is introduced for controlled postsynthetic thermal defect engineering (TDE) of precious group metal-organic frameworks (PGM-MOFs). The case study is based on the Ru/Rh analogues of the archetypical structure [Cu(BTC)] (HKUST-1; BTC = 1,3,5-benzenetricarboxylate). Quantitative monitoring of the TDE process and extensive characterization of the samples employing a complementary set of analytical and spectroscopic techniques reveal that the compositionally very complex TDE-MOF materials result from the elimination and/or fragmentation of ancillary ligands and/or linkers.

Mixed precious-group metal-organic frameworks: a case study of the HKUST-1 analogue [RuRh(BTC)].

This work presents the first full series of mixed precious-group metal-organic frameworks (MPG-MOFs) using ruthenium and rhodium. The obtained crystalline, highly porous and thermally robust materials were characterized by means of powder X-ray diffraction, N/CO sorption isotherms, thermogravimetry, spectroscopy methods (IR, Raman, UV/VIS-, NMR and XPS) and as well by high resolution transmission electron microscopy (HR-TEM) with elemental mapping (HAADF-EDS). Additionally, the assignment of spectroscopic data is supported by computational (time dependent)-density functional theory methods.

Single-Site, Organometallic Aluminum Catalysts for the Precise Group Transfer Polymerization of Michael-Type Monomers.

Unlike different types of Lewis pairs as polymerization catalysts for acrylic monomers, organometallic aluminum(III) compounds are reported that show a surprisingly high polymerization activity even without an additional Lewis base. DFT calculations, end group analysis and kinetic investigations clearly suggest a main group element (MGE) group transfer polymerization (GTP) mechanism analogous to the known metal-mediated GTP mechanism. The novel catalysts perform a precision polymerization of a broad variety of monomers, ranging from 2-isopropenyl-2-oxazoline to tert-butylmethacrylate and N,N-dimethylacrylamide.

Acylation of Homoatomic Ge Cages and Subsequent Decarbonylation.

The direct acylation of Ge Zintl clusters by the reaction of K[Ge {Si(SiMe ) } ] with acyl chlorides in hexane or toluene solutions is presented, leading to the neutral, carbonyl-derivatized products [{Si(SiMe ) } Ge (CO)R'] (R'=Me, iPr, tBu, Ph, Bz, cyclopropylmethyl, phenethyl, 4-vinylphenyl). This reaction is applicable to a wide range of acyl chlorides and allows for diverse functionalization of Ge Zintl clusters. [{Si(SiMe ) } Ge (CO)tBu] readily releases CO at ambient conditions under formation of [{Si(SiMe ) } Ge tBu].

NXS, Morpholine, and HFIP: The Ideal Combination for Biomimetic Haliranium-Induced Polyene Cyclizations.

In contrast to Nature that accomplishes polyene cyclizations seemingly with ease, such transformations are difficult to conduct in the lab. In our program dealing with the development of selective halogenations of alkenes, we now asserted that standard X reagents are perfectly suited for the biomimetic cation-π cyclization of both electron rich and poor linear polyenes in the presence of the Lewis base morpholine and the Lewis acid HFIP. The method stands out due to its broad substrate scope and practicability together with high chemical yields and excellent selectivities, even for highly challenging chloriranium-induced polyene cyclizations.

Sphenoid sinus barotrauma in diving: case series and review of the literature.

About 50% of scuba divers have suffered from barotrauma of the ears and about one-third from barotrauma of paranasal sinuses. The sphenoid sinuses are rarely involved. Vital structures, as internal carotid artery and optic nerve, adjoin the sphenoid sinus.

Synthesis of Lactones via C-H Functionalization of Nonactivated C(sp)-H Bonds.

An electron-deficient amide is utilized as a directing group to functionalize nonactivated C(sp)-H bonds through radical 1,5-hydrogen abstraction. The γ-bromoamides formed are subsequently converted to γ-lactones under mild conditions. The method described is not limited to tertiary and secondary positions but also allows functionalization of primary nonactivated sp-hybridized positions in a one-pot sequence.

Hydrogen Production and Storage on a Formic Acid/Bicarbonate Platform using Water-Soluble N-Heterocyclic Carbene Complexes of Late Transition Metals.

The synthesis and characterization of two water-soluble bis-N-heterocyclic carbene (NHC) complexes of rhodium and iridium is presented. Both compounds are active in H generation from formic acid and in hydrogenation of bicarbonate to formate. The rhodium derivative is most active in both reactions, reaching a TOF of 39 000 h and a TON of 449 000 for H production.

Supramolecular exo-functionalized palladium cages: fluorescent properties and biological activity.

Metallosupramolecular systems are promising new tools for pharmaceutical applications. Thus, novel self-assembled Pd(ii) coordination cages were synthesized which were exo-functionalized with naphthalene or anthracene groups with the aim to image their fate in cells. The cages were also investigated for their anticancer properties in human lung and ovarian cancer cell lines in vitro.

Dynamics of the NbCl5-catalyzed cycloaddition of propylene oxide and CO2 : assessing the dual role of the nucleophilic Co-catalysts.

A mechanistic study on the synthesis of propylene carbonate (PC) from CO2 and propylene oxide (PO) catalyzed by NbCl5 and organic nucleophiles such as 4-dimethylaminopyridine (DMAP) or tetra-n-butylammonium bromide (NBu4 Br) is reported. A combination of in situ spectroscopic techniques and kinetic studies has been used to provide detailed insight into the reaction mechanism, the formation of intermediates, and interactions between the reaction partners. The results of DFT calculations support the experimental observations and allow us to propose a mechanism for this reaction.

Fluoridonitrosyl complexes of technetium(I) and technetium(II). Synthesis, characterization, reactions, and DFT calculations.

A mixture of [Tc(NO)F5](2-) and [Tc(NO)(NH3)4F](+) is formed during the reaction of pertechnetate with acetohydroxamic acid (Haha) in aqueous HF. The blue pentafluoridonitrosyltechnetate(II) has been isolated in crystalline form as potassium and rubidium salts, while the orange-red ammine complex crystallizes as bifluoride or PF6(-) salts. Reactions of [Tc(NO)F5](2-) salts with HCl give the corresponding [Tc(NO)Cl4/5](-/2-) complexes, while reflux in neat pyridine (py) results in the formation of the technetium(I) cation [Tc(NO)(py)4F](+), which can be crystallized as hexafluoridophosphate.

Cleavage of C-O bonds in lignin model compounds catalyzed by methyldioxorhenium in homogeneous phase.

Methyldioxorhenium (MDO)-catalyzed C-O bond cleavage of a variety of lignin β-O-4-model compounds yields phenolic and aldehydic compounds in homogeneous phase under mild reaction conditions. MDO is in situ generated by reduction of methyltrioxorhenium (MTO) and is remarkably stable under the applied reaction conditions allowing its reuse for least five times without significant activity loss. Based on the observed and isolated intermediates, 17 O- and 2 H-isotope labeling experiments, DFT calculations, and several spectroscopic studies, a reaction mechanism is proposed.

Synthesis and characterisation of chelated cationic ReI(CO)3bis(NHC)(WCA) complexes.

Twelve novel Re(I) acetonitrile complexes of the type [Re(CO)3(L)(MeCN)][WCA], with L being a chelating bis(NHC) ligand with alkylene-bridged and N-substituted bis(imidazolineylidene) moieties, and WCA (WCA = weakly coordinating anion) representing PF6(-) and [Al(OC(CF3)3)4](-), have been synthesized. 1D and 2D NMR spectroscopy as well as IR spectroscopy, elemental analysis and X-ray crystallography have been applied in characterization. The propylene-bridged complex, displaying mesitylene groups R, is discussed in depth revealing interesting chemical behaviour both in solid state and in solution.

The mechanism of borane-amine dehydrocoupling with bifunctional ruthenium catalysts.

Borane-amine adducts have received considerable attention, both as vectors for chemical hydrogen storage and as precursors for the synthesis of inorganic materials. Transition metal-catalyzed ammonia-borane (H3N-BH3, AB) dehydrocoupling offers, in principle, the possibility of large gravimetric hydrogen release at high rates and the formation of B-N polymers with well-defined microstructure. Several different homogeneous catalysts were reported in the literature.

Synthesis and comparison of transition metal complexes of abnormal and normal tetrazolylidenes: a neglected ligand species.

To date, only few examples of tetrazolylidene carbenes coordinated to transition metal complexes have been described. A direct comparison of "normal" tetrazolylidenes (1,4-substitution pattern) and "abnormal" tetrazolylidenes (also referred to as "mesoionic carbenes"; 1,3-substitution pattern) has not been performed at all. In this work, we describe coordination of both ligand types to a row of transition metals.

N-Heterocyclic carbenes via abstraction of ammonia: 'normal' carbenes with 'abnormal' character.

A new ammonia adduct of a N-heterocyclic carbene (NHC) has been isolated, which can be used as a reagent for the synthesis of transition metal carbene complexes. It represents the first example of a 1,2,3-triazolylidene with a 1,2,4-substitution pattern, thus opening a new subclass ('normal' 1,2,3-triazolylidenes) of sterically and electronically tunable NHCs.

The Étard reaction: a DFT study.

The mechanism of the Étard reaction of chromylchloride in toluene, discovered more than a century ago, has been investigated by DFT calculations (B3LYP/6-31G(d)). The formation of the experimentally observed product can be rationalized by multiple CH-abstraction reactions.

Ruthenium complexes with cooperative PNP-pincer amine, amido, imine, and enamido ligands: facile ligand backbone functionalization processes.

The quantitative formation of enamido complex [Ru(H)PMe(3)(PNP')] (3; PNP' = N(CHCHP(i)Pr(2))(CH(2)CH(2)P(i)Pr(2))) from the reaction of [RuCl(2)PMe(3)(HPNP)] (5; HPNP = HN(CH(2)CH(2)P(i)Pr(2))(2)) with an excess of base (KOtBu) can be explained by beta-hydride migration from an intermediate amido complex [RuClPMe(3)(PNP)] (6; PNP = N(CH(2)CH(2)P(i)Pr(2))(2)). Resulting imine complex [RuCl(H)PMe(3)(PNP*)] (7; PNP* = N(CHCH(2)P(i)Pr(2))(CH(2)CH(2)P(i)Pr(2))) could be independently synthesized and gives 3 with KOtBu. A computational examination of the reversible double H(2) addition and elimination equilibria of enamide 3, amido complex [Ru(H)PMe(3)(PNP)] (1), and amine complex [Ru(H)(2)PMe(3)(HPNP)] (2) explains why [Ru(H)(2)PMe(3)(PNP*)] (8) is not observed experimentally.

Highly stereoselective proton/hydride exchange: assistance of hydrogen bonding for the heterolytic splitting of H2.

The dihydrido amine complex [Ru(H)(2)PMe(3){HN(CH(2)CH(2)P(i)Pr(2))(2)}] and H(2)O exhibit highly unusual, stereoselective H(+)/H(-) exchange, as derived using (1)H 2D EXSY NMR spectroscopy. While H(RuA) rapidly exchanges with H(2)O [k = 337(20) L mol(-1) s(-1)], no direct H(RuB)/H(2)O proton exchange was detected. Methylation of the pincer amine nitrogen results in unselective slow exchange of both hydrides with H(2)O.

Studies on bis(halogeno) dioxomolybdenum(VI)-bipyridine complexes: synthesis and catalytic activity.

Dioxomolybdenum(VI) complexes with the general formula [MoO2Cl2L2] (L2=3,3'-dimethyl-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, 6,6'-dimethyl-2,2'-bipyridine, 4,4'-dibromo-2,2'-bipyridine, 5,5'-dibromo-2,2'-bipyridine, 5,5'-diamino-2,2'-bipyridine; 5,5'-dinitro-2,2'-bipyridine; 5,5'-di-ethoxycarbonyl-2,2'-bipyridine; 6-phenyl-2,2'-bipyridine; 2,2':6',2''-terpyridine) have been prepared and characterised. [MoO2Cl2(5,5'-di-ethoxycarbonyl-2,2'-bipyridine)] has been examined by single crystal X-ray analysis. The complexes were applied as homogenous catalysts for the epoxidation of cyclooctene with tert-butyl hydroperoxide (TBHP) as oxidising agent.

Mono- and bis- methyltrioxorhenium(VII) complexes with salen ligands: synthesis, properties, applications.

Methyltrioxorhenium(VII) (MTO) forms 1:1 (mono-) or/and 2:1 (bis-) complexes with salen ligands, undergoing a hydrogen transfer from a ligand-bound OH-group to a ligand nitrogen atom. Some complexes show good stability both in the solid state and in solution, while others must be kept at low temperatures under an argon atmosphere. X-ray crystallography shows distorted trigonal bipyramidal structures of all examined complexes in the solid state, this structure being due to the steric demands of the ligands, with the methyl group of MTO residing in the apical sites in the cis position.