Ethanol processable inorganic-organic hybrid hole transporting layers enabled 20.12% efficiency organic solar cells.

In this study, a high-performance inorganic-organic hybrid hole transporting layer (HTL) was developed using ethanol-soluble alkoxide precursors and a self-assembled monolayer (SAM). Three metal oxides-vanadium oxide (VOx), niobium oxide (Nb2O5), and tantalum oxide (Ta2O5)-were synthesized through successive low-temperature (100 °C) thermal annealing (TA) and UV-ozone (UVO) treatments of their respective precursors: vanadium oxytriethoxide (EtO-V), niobium ethoxide (EtO-Nb), and tantalum ethoxide (EtO-Ta). Among these, the Nb2O5 film exhibited excellent transmittance, a high work function, and good conductivity, along with a more compact and uniform structure featuring fewer interfacial defects, which facilitated efficient charge extraction and transport. Furthermore, the deposition of a SAM of (2-(9H-carbazol-9-yl)ethyl)phosphonic acid (2PACz) on top of Nb2O5 further passivated defects, enhancing interfacial contact with the photoactive layer. The resulting inorganic-organic hybrid HTL of Nb2O5/2PACz demonstrated excellent compatibility with various photoactive blends, achieving impressive power conversion efficiencies of 19.44%, 19.18%, and 20.12% for the PM6:L8-BO, PM6:BTP-eC9, and D18:BTP-eC9 based organic solar cells, respectively. 20.12% is the best performance for bulk heterojunction organic solar cells with binary components as the photoactive layer.

Group I Alkoxides and Amylates as Highly Efficient Silicon-Nitrogen Heterodehydrocoupling Precatalysts for the Synthesis of Aminosilanes.

Group I alkoxides are highly active precatalysts in the heterodehydrocoupling of silanes and amines to afford aminosilane products. The broadly soluble and commercially available KOt Amyl was utilized as the benchmark precatalyst for this transformation. Challenging substrates such as anilines were found to readily couple primary, secondary, and tertiary silanes in high conversions (>90 %) after only 2 h at 40 °C. Traditionally challenging silanes such as Ph3 SiH were also easily coupled to simple primary and secondary amines under mild conditions, with reactivity that rivals many rare earth and transition-metal catalysts for this transformation. Preliminary evidence suggests the formation of hypercoordinated intermediates, but radicals were detected under catalytic conditions, indicating a mechanism that is rare for Si-N bond formation.

Alkali-Metal-Alkoxide Powered Zincation of Fluoroarenes Employing Zinc Bis-Amide Zn(TMP)2.

Reminiscent of Lochmann-Schlosser superbase recipes, the addition of two molar equivalents of KOtBu to Zn(TMP)2 (TMP=2,2,6,6-tetramethylpiperidide) transforms this mild zinc bis-amide base to a powerful metalating agent able to perform facile regioselective zincation of a wide range of sensitive fluoroarenes. Structural authentication of the intermediates post Zn-H exchange demonstrates activation of both TMP groups to form a range of higher order bis-aryl potassium zincates, isolable as solids and further functionalized in electrophilic interception reactions. Studies assessing the role of KOtBu reveal that the first equivalent undergoes co-complexation with Zn(TMP)2 , enabling kinetic activation of the amide groups; whereas the second equivalent stabilizes the metalated intermediate preventing ligand redistribution. Showcasing its metalating power, this bimetallic KOtBu/Zn(TMP)2 partnership, can effect zincation of toluene and benzene at room temperature.

Reactivity of Diphenylberyllium as a Brønsted Base and Its Synthetic Application.

Diphenylberyllium [Be3 Ph6 ] is shown here to react cleanly as a Brønsted base with a vast variety of protic compounds. Through the addition of the simple molecules tBuOH, HNPh2 and HPPh2 , as well as the more complex 1,3-bis-(2,6-diisopropylphenyl)imidazolinium chloride, one or two phenyl groups in diphenylberyllium were protonated. As a result, the long-postulated structures of [Be3 (OtBu)6 ] and [Be(µ-NPh2 )Ph]2 have finally been verified and shown to be static in solution. Additionally [Be(µ-PPh2 )(HPPh2 )Ph]2 was generated, which is only the second beryllium-phospanide to be prepared; the stark differences between its behaviour and that of the analogous amide were also examined. The first crystalline example of a beryllium Grignard reagent with a non-bulky aryl group has also been prepared; it is stabilised with an N-heterocyclic carbene.

Olefin Metathesis Catalysts Generated In Situ from Molybdenum(VI)-Oxo Complexes by Tuning Pendant Ligands.

Tailored molybdenum(VI)-oxo complexes of the form MoOCl2 (OR)2 (OEt2 ) catalyse olefin metathesis upon reaction with an organosilicon reducing agent at 70 °C, in the presence of olefins. While this reactivity parallels what has recently been observed for the corresponding classical heterogeneous catalysts based on supported metal oxide under similar conditions, the well-defined nature of our starting molecular systems allows us to understand the influence of structural, spectroscopic and electronic characteristics of the catalytic precursor on the initiation and catalytic proficiency of the final species. The catalytic performances of the pre-catalysts are determined by the highly electron withdrawing (σ-donation) character of alkoxide ligands, Ot BuF9 being the best. This activity correlates with both the 95 Mo chemical shift and the reduction potential that follows the same trend: Ot BuF9 >Ot BuF6 >Ot BuF3 .

Aziridination Reactivity of a Manganese(II) Complex with a Bulky Chelating Bis(Alkoxide) Ligand.

Treatment of Mn(N(SiMe3)2)2(THF)2 with bulky chelating bis(alkoxide) ligand [1,1':4',1''-terphenyl]-2,2''-diylbis(diphenylmethanol) (H2[O-terphenyl-O]Ph) formed a seesaw manganese(II) complex Mn[O-terphenyl-O]Ph(THF)2, characterized by structural, spectroscopic, magnetic, and analytical methods. The reactivity of Mn[O-terphenyl-O]Ph(THF)2 with various nitrene precursors was investigated. No reaction was observed between Mn[O-terphenyl-O]Ph(THF)2 and aryl azides. In contrast, the treatment of Mn[O-terphenyl-O]Ph(THF)2 with iminoiodinane PhINTs (Ts = p-toluenesulfonyl) was consistent with the formation of a metal-nitrene complex. In the presence of styrene, the reaction led to the formation of aziridine. Combining varying ratios of styrene and PhINTs in different solvents with 10 mol% of Mn[O-terphenyl-O]Ph(THF)2 at room temperature produced 2-phenylaziridine in up to a 79% yield. Exploration of the reactivity of Mn[O-terphenyl-O]Ph(THF)2 with various olefins revealed (1) moderate aziridination yields for p-substituted styrenes, irrespective of the electronic nature of the substituent; (2) moderate yield for 1,1'-disubstituted α-methylstyrene; (3) no aziridination for aliphatic α-olefins; (4) complex product mixtures for the ß-substituted styrenes. DFT calculations suggest that iminoiodinane is oxidatively added upon binding to Mn, and the resulting formal imido intermediate has a high-spin Mn(III) center antiferromagnetically coupled to an imidyl radical. This imidyl radical reacts with styrene to form a sextet intermediate that readily reductively eliminates the formation of a sextet Mn(II) aziridine complex.

Inhibition of Alkali Metal Reduction of 1-Adamantanol by London Dispersion Effects.

A series of alkali metal 1-adamantoxide (OAd1 ) complexes of formula [M(OAd1 )(HOAd1 )2 ], where M=Li, Na or K, were synthesised by reduction of 1-adamantanol with excess of the alkali metal. The syntheses indicated that only one out of every three HOAd1 molecules was reduced. An X-ray diffraction study of the sodium derivative shows that the complex features two unreduced HOAd1 donors as well as the reduced alkoxide (OAd1 ), with the Ad1 fragments clustered together on the same side of the NaO3 plane, contrary to steric considerations. This is the first example of an alkali metal reduction of an alcohol that is inhibited from completion due to the formation of the [M(OAd1 )(HOAd1 )2 ] complexes, stabilized by London dispersion effects. NMR spectroscopic studies revealed similar structures for the lithium and potassium derivatives. Computational analyses indicate that decisive London dispersion effects in the molecular structure are a consequence of the many C-H⋅⋅⋅H-C interactions between the OAd1 groups.

Pincer-Supported Gallium Complexes for the Catalytic Hydroboration of Aldehydes, Ketones and Carbon Dioxide.

Gallium hydrides stabilised by primary and secondary amines are scarce due to their propensity to eliminate dihydrogen. Consequently, their reactivity has received limited attention. The synthesis of two novel gallium hydride complexes HGa(THF)[ON(H)O] and H2 Ga[µ2 -ON(H)O]Ga[ON(H)O] ([ON(H)O]2- =N,N-bis(3,5-di-tert-butyl-2-phenoxy)amine) is described and their reactivity towards aldehydes and ketones is explored. These reactions afford alkoxide-bridged dimers through 1,2-hydrogallation reactions. The gallium hydrides can be regenerated through Ga-O/B-H metathesis from the reaction of such dimers with pinacol borane (HBpin) or 9-borabicyclo[3.3.1]nonane (9-BBN). These observations allowed us to target the catalytic reduction of carbonyl substrates (aldehydes, ketones and carbon dioxide) with low catalyst loadings at room temperature.

Mononuclear Dysprosium Alkoxide and Aryloxide Single-Molecule Magnets.

Recent studies have shown that mononuclear lanthanide (Ln) complexes can be high-performing single-molecule magnets (SMMs). Recently, there has been an influx of mononuclear Ln alkoxide and aryloxide SMMs, which have provided the necessary geometrical control to improve SMM properties and to allow the intricate relaxation dynamics of Ln SMMs to be studied in detail. Here non-aqueous Ln alkoxide and aryloxide chemistry applied to the synthesis of low-coordinate mononuclear Ln SMMs are reviewed. The focus is on mononuclear DyIII alkoxide and aryloxide SMMs with coordination numbers up to eight, covering synthesis, solid-state structures and magnetic attributes. Brief overviews are also provided of mononuclear TbIII , HoIII , ErIII and YbIII alkoxide and aryloxide SMMs.

Reactions of Zirconium (IV) n-Propoxide with SiH-Functional Polysiloxanes as a Route to Siloxane-Zirconium Hybrid Materials with Enhanced Refractive Index.

The reaction of poly(hydromethylsiloxane-co-methylphenylsiloxane) with zirconium (IV) n-propoxide in dry toluene leads to extensive scission of the siloxane chain and conversion of Si-H groups. These processes produce oligomeric siloxanes and organosilanes containing moisture sensitive propoxy and siloxy-zirconate groups. The obtained post-reaction solution of zirconium containing heterosiloxane oligomers is stable under anhydrous conditions for several weeks. However, its exposure to moisture initiates the hydrolytic condensation of the reactive groups leading to cross-linking and the formation of a siloxane-zirconium composite. Spin coating of the siloxane-zirconium prepolymer followed by exposure to moisture produces thin films with excellent light transparency and increased refractive index. The final coatings are characterized by ellipsometry, UV-Vis, IR, and 29 Si MAS NMR spectroscopies.

Untangling the Complexity of Mixed Lithium/Magnesium Alkyl/Alkoxy Combinations Utilised in Bromine/Magnesium Exchange Reactions.

While it is known that the addition of Group 1 alkoxides to s-block organometallics can have an activating effect on reactivity, the exact nature of this effect is not that well understood. Here we describe the activation of sBu2 Mg towards substituted bromoarenes by adding one equivalent of LiOR (R=2-ethylhexyl), where unusually both sBu groups can undergo efficient Br/Mg exchange. Depending on the substitution pattern on the bromoarene two different types of organometallic intermediates have been isolated, either a mixed aryl/alkoxide [{LiMg(2-FG-C6 H4 )2 (OR)}2 ] (FG=OMe; NMe2 ) or a homoaryl [(THF)4 Li2 Mg(4-FG-C6 H4 )4 ] (FG=OMe, F). Detailed NMR spectroscopic studies have revealed that these exchange reactions and the formation of their intermediates are controlled by a new type of bimetallic Schlenk-type equilibrium between heteroleptic [LiMgsBu2 (OR)], alkyl rich [Li2 MgsBu4 ] and Mg(OR)2 , with [Li2 MgsBu4 ] being the active species performing the Br/Mg exchange process.

Regioselective Bromine/Magnesium Exchange for the Selective Functionalization of Polyhalogenated Arenes and Heterocycles.

Using the bimetallic combination sBu2 Mg⋅2 LiOR (R=2-ethylhexyl) in toluene enables efficient and regioselective Br/Mg exchanges with various dibromo-arenes and -heteroarenes under mild reaction conditions and provides bromo-substituted magnesium reagents. Assessing the role of Lewis donor additives in these reactions revealed that N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDTA) finely tunes the regioselectivity of the Br/Mg exchange on dibromo-pyridines and quinolines. Combining spectroscopic with X-ray crystallographic studies, light has been shed on the mixed Li/Mg constitution of the organometallic intermediates accomplishing these transformations. These systems reacted effectively with a broad range of electrophiles, including allyl bromides, ketones, aldehydes, and Weinreb amides in good yields.

Recent Advances of the Halogen-Zinc Exchange Reaction.

For the preparation of zinc organometallics bearing highly sensitive functional groups such as ketones, aldehydes or nitro groups, especially mild halogen-zinc exchange reagents have proven to be of great potential. In this Minireview, the latest research in the area of the halogen-zinc exchange reaction is reported, with a special focus lying on novel dialkylzinc reagents complexed with lithium alkoxides. Additionally, the preparation and application of organofluorine zinc reagents and transition-metal-catalyzed halogen-zinc exchange reactions are reviewed.

Molecular Engineering of Metal Alkoxides for Solution Phase Synthesis of High-Tech Metal Oxide Nanomaterials.

The 'bottom-up' synthesis of inorganic nanomaterials with precision at the atomic/molecular level offers many opportunities for the design and improvement of the nanomaterials for various applications. Molecular engineering during soft chemical processing for the synthesis of functional nanomaterials enables the desired chemical and physical properties of the precursors, such as solubility or volatility, clean decomposition, control of stoichiometry for multimetallic species to name a few, and leads to easy control of uniform particle size distribution, stoichiometry…. This Minireview illustrates some important aspects of the molecular engineering in light of some recent developments from the molecular synthesis of nanomaterials involving non-silicon metal alkoxide systems for high-tech applications.

Synthesis of Chromium(II) Complexes with Chelating Bis(alkoxide) Ligand and Their Reactions with Organoazides and Diazoalkanes.

Synthesis of new chromium(II) complexes with chelating bis(alkoxide) ligand [OO]Ph (H2[OO]Ph = [1,1':4',1''-terphenyl]-2,2''-diylbis(diphenylmethanol)) and their subsequent reactivity in the context of catalytic production of carbodiimides from azides and isocyanides are described. Two different Cr(II) complexes are obtained, as a function of the crystallization solvent: mononuclear Cr[OO]Ph(THF)2 (in toluene/THF, THF = tetrahydrofuran) and dinuclear Cr2([OO]Ph)2 (in CH2Cl2/THF). The electronic structure and bonding in Cr[OO]Ph(THF)2 were probed by density functional theory calculations. Isolated Cr2([OO]Ph)2 undergoes facile reaction with 4-MeC6H4N3, 4-MeOC6H4N3, or 3,5-Me2C6H3N3 to yield diamagnetic Cr(VI) bis(imido) complexes; a structure of Cr[OO]Ph(N(4-MeC6H4))2 was confirmed by X-ray crystallography. The reaction of Cr2([OO]Ph)2 with bulkier azides N3R (MesN3, AdN3) forms paramagnetic products, formulated as Cr[OO]Ph(NR). The attempted formation of a Cr-alkylidene complex (using N2CPh2) instead forms chromium(VI) bis(diphenylmethylenehydrazido) complex Cr[OO]Ph(NNCPh2)2. Catalytic formation of carbodiimides was investigated for the azide/isocyanide mixtures containing various aryl azides and isocyanides. The formation of carbodiimides was found to depend on the nature of organoazide: whereas bulky mesitylazide led to the formation of carbodiimides with all isocyanides, no carbodiimide formation was observed for 3,5-dimethylphenylazide or 4-methylphenylazide. Treatment of Cr2([OO]Ph)2 or H2[OO]Ph with NO+ leads to the formation of [1,2-b]-dihydroindenofluorene, likely obtained via carbocation-mediated cyclization of the ligand.

Mass spectrometry in the characterization of reactive metal alkoxides.

Metal alkoxides are metal-organic compounds characterized by the presence of MOC bonds (M = metal). Their chemistry seems to be, in principle, relatively simple but the number of possible reactant species arising as a consequence of their behavior is very remarkable. The physico-chemical properties of metal alkoxides are determined by many different parameters, the most important ones being the electronegativity of the metal, the ramification of the ligand, and the acidity of the corresponding alcohol. Their reactivity makes them suitable and versatile candidates for many applications, including homogeneous catalysis, synthesis of new ceramic materials through the sol-gel process and, recently, also for Cultural Heritage. Metal alkoxides are characterized by a strong tendency to give clusters and/or oligomers through oxo-bridges. Mass spectrometry has been successfully employed for the characterization of metal alkoxides in the gas-phase. Electron ionization (EI) allowed the assessment of the molecular weight and of the most relevant decomposition pathways giving information on the relative bond strength of differently substituted molecules. On the other hand, information on the reactivity in solution of these molecules have been obtained by electrospray ionization (ESI)-matrix assisted laser desorption ionization (MALDI) experiments performed on their reaction products. These data were relevant to investigate the sol-gel process. In this review, these aspects are described and the results obtained are critically evaluated. © 2016 Wiley Periodicals, Inc. Mass Spec Rev.

Preparation of Polyfunctional Arylzinc Organometallics in Toluene by Halogen/Zinc Exchange Reactions.

A wide range of polyfunctional diaryl- and diheteroarylzinc species were prepared in toluene within 10 min to 5 h through an I/Zn or Br/Zn exchange reaction using bimetallic reagents of the general formula R'2 Zn⋅2 LiOR (R'=sBu, tBu, pTol). Highly sensitive functional groups, such as a triazine, a ketone, an aldehyde, or a nitro group, were tolerated in these exchange reactions, enabling the synthesis of a plethora of functionalized (hetero)arenes after quenching with various electrophiles. Insight into the constitution and reactivity of these bimetallic mixtures revealed the formation of highly active lithium diorganodialkoxyzincates of type [R'2 Zn(OR)2 Li2 ].

Bonding Insights from Structural and Spectroscopic Comparisons of {SnW5 } and {TiW5 } Alkoxido- and Aryloxido-Substituted Lindqvist Polyoxometalates.

Incorporation of {MX}n+ groups into polyoxometalates (POMs) provides the means not only to introduce reactivity and functionality but also to tune the electronic properties of the oxide framework by varying M, X and n. In order to elucidate the factors responsible for differences in reactivity between {TiW5 } and {SnW5 } Lindqvist-type hexametalates, a series of alkoxido- and aryloxido-tin substituted POMs (nBu4 N)3 [(RO)SnW5 O18 ] (R=Me, Et, iPr and tBu) and (nBu4 N)3 [(ArO)SnW5 O18 ] (Ar=C6 H5 , 4-MeC6 H5 , 4-tBuC6 H5 , 4-HOC6 H4 , 3-HOC6 H4 and 2-CHOC6 H4 ) has been structurally characterised and studied by multinuclear NMR (1 H, 13 C, 17 O, 119 Sn and 183 W) and FTIR spectroscopy. Spectroscopic and structural parameters were compared with those of titanium-substituted homologues and, when coupled with theoretical studies, indicated that Sn-OR and Sn-OAr bonds are ionic with little π-contribution, whereas Ti-OR and Ti-OAr bonds are more covalent with π-bonding that is more prevalent for Ti-OR than Ti-OAr. This experimental and theoretical analysis of bonding in a homologous series of reactive POMs is the most extensive and detailed to date, and reveals factors which account for significant differences in reactivity between tin and titanium congeners.

Postfunctionalization of Tris(pyridyl) Aluminate Ligands: Chirality, Coordination, and Supramolecular Chemistry.

Postfunctionalization of the aluminate anion [EtAl(6-Me-2-py)3 ]- (1) (2-py=2-pyridyl) with alkoxide ligands can be achieved by the selective reactions of the lithium salt 1 Li with alcohols in the appropriate stoichiometry. This method can be used to introduce 3- and 4-py functionality in the form of 3- and 4-alkoxymethylpyridyl groups, while maintaining the integrity of the aluminate framework, thereby giving entry to new supramolecular chemistry. Chirality can be introduced either by using a chiral alcohol as a reactant or by the stepwise reaction of 1 Li with two different nonchiral alcohols. The latter route has allowed the synthesis of a rare example of a chiral-at-aluminium aluminate.

Cobalt Oxide Materials for Oxygen Evolution Catalysis via Single-Source Precursor Chemistry.

The utilization of metal alkoxides as single-source precursors for (mixed-)oxide materials offers remarkable benefits, such as the possibility to precisely control the metal ratio in the resulting material, highly homogeneous distribution of the elements in the film, and the low temperatures required for film processing. Herein we report on the isolation and characterization of the bimetallic Co-Mo alkoxide [Co3 Mo4 O10 (OCH3 )10 (dmf)4 ] (Co3 Mo4 ; dmf=N,N-dimethylformamide), which was prepared by the anion metathesis reaction of the corresponding metal chlorides. The Co-Mo alkoxide was explored as a well-defined precursor of cobalt oxide catalysts for the oxygen evolution reaction (OER) in alkaline electrolyte MOH. The catalysts demonstrated excellent activity in the OER, manifested in low onset potentials and Tafel slopes and superb stability under the operating conditions both in alkaline and nearly neutral media. It was observed that the nature of the metal cation of the alkaline electrolyte MOH (M+ =Li+ , Na+ , K+ , Cs+ ) greatly affected the catalytic performance of the material. We propose that the positive effect of larger metal cations on the film activity in the OER could be explained by the higher hydration enthalpies of larger ions and enhanced mass transport within a larger interlayer space between the [CoO2 ]δ-∞ sheets of the in situ formed binary oxides. It may be deduced that this trend is universal and may be extended to other types of metal oxides forming layered structures during the OER.