Chemical doping is a key process for investigating charge transport in organic semiconductors and improving certain (opto)electronic devices 1-9 . N-(electron)doping is fundamentally more challenging than p-(hole)doping and typically achieves very low doping efficiency (η) <10% 1,10 . An efficient molecular n-dopant should simultaneously exhibit a high reducing power and air stability for broad applicability 1,5,6,9,11 , which is very challenging. Here we show a general concept of catalysed n-doping of organic semiconductors using air-stable precursor-type molecular dopants. Incorporation of a transition metal as vapor-deposited nanoparticles (e.g. Pt, Au, Pd) or solution-processable 2 organometallic complexes (e.g. Pd 2 (dba) 3 ) catalyses the reaction, as assessed by experimental and theoretical evidence, enabling drastically increased η in a much shorter doping time and high electrical conductivities >100 S cm −1 12 . This methodology has technological implications for realizing improved semiconductor devices and offers a broad exploration space of ternary systems comprising catalysts, molecular dopants, and semiconductors, thus opening new opportunities in n-doping research and applications.N-doping of organic semiconductors is important for developing light-emitting diodes 1,6-9 , solar cells 7,8 , thin-film transistors 10 , and thermoelectric devices 12,13 . Although solution-based ndoping is widely investigated, only few air-stable n-dopants have been developed (Fig. S1), with the most prominent being organic hydrides 5,9,14-18 such as benzoimidazole derivatives, dimers of organic radicals 11,19,20 such as nineteen-electron organometallic sandwich compounds, and mono-/multi-valent anions 8,21,22 such as OH − , F − and Ox 2− . These air-stable dopants have a deep ionization potential (IP) in their initial forms, thus, cannot directly transfer electrons to n-dope organic semiconductors with a low electron affinity (EA). For anions, it was shown that dispersion into small anhydrous clusters enables sufficiently high donor levels for n-doping organic semiconductors with EAs up to 2.4 eV 8 . Hydride and dimer dopant precursors (or referred as precursor-type dopants) most undergo a C-H and C-C bond cleavage reaction, respectively, to generate active-doping-species in situ before electron transfer can occur [23][24][25][26] . Thus, their reducing strength and reaction kinetics are strongly affected by the thermodynamics and the activation energies of the doping reaction [23][24][25][26] . If the activation energy to the product is reduced, it is expected that the reaction rate, and extent of doping, will greatly increase (Fig. 1a). 3Transition metal (TM) catalysed C-H and C-C bond cleavage reactions are widely used in organic synthesis, with the most common TMs belonging to group 8-11 elements and the catalysts in the form of nanoparticles (NPs) and organometallic complexes 27,28 . Nanoparticle size, supporting material, and chemical structure of the complex can greatly affect catalytic activities. Thus, an i...

Developing earth-abundant, non-platinum metal catalysts for high-value chemical transformations is a critical challenge to contemporary chemical synthesis. Dearomatization of pyridine derivatives is an important transformation to access a wide range of valuable nitrogenous natural products, pharmaceuticals and materials. Here, we report an efficient 1,2-regioselective organolanthanide-catalysed pyridine dearomatization process using pinacolborane, which is compatible with a broad range of pyridines and functional groups and employs equimolar reagent stoichiometry. Regarding the mechanism, derivation of the rate law from NMR spectroscopic and kinetic measurements suggests first order in catalyst concentration, fractional order in pyridine concentration and inverse first order in pinacolborane concentration, with C=N insertion into the La-H bond as turnover-determining. An energetic span analysis affords a more detailed understanding of experimental activity trends and the unusual kinetic behaviour, and proposes the catalyst 'resting' state and potential deactivation pathways.

Organozirconium complexes are chemisorbed on Brønsted acidic sulfated ZrO2 (ZrS), sulfated Al2O3 (AlS), and ZrO2-WO3 (ZrW). Under mild conditions (25 °C, 1 atm H2), the supported Cp*ZrMe3, Cp*ZrBz3, and Cp*ZrPh3 catalysts are very active for benzene hydrogenation with activities declining with decreasing acidity, ZrS ≫ AlS ≈ ZrW, arguing that more Brønsted acidic oxides (those having weaker corresponding conjugate bases) yield stronger surface organometallic electrophiles and for this reason have higher benzene hydrogenation activity. Benzene selective hydrogenation, a potential approach for carcinogenic benzene removal from gasoline, is probed using benzene/toluene mixtures, and selectivities for benzene hydrogenation vary with catalyst as ZrBz3(+)/ZrS(-), 83% > Cp*ZrMe2(+)/ZrS(-), 80% > Cp*ZrBz2(+)/ZrS(-), 67% > Cp*ZrPh2(+)/ZrS(-), 57%. For Cp*ZrBz2(+)/ZrS(-), which displays the highest benzene hydrogenation activity with moderate selectivity in benzene/toluene mixtures. Other benzene/arene mixtures are examined, and benzene selectivities vary with arene as mesitylene, 99%, > ethylbenzene, 86% > toluene, 67%. Structural and computational studies by solid-state NMR spectroscopy, XAS, and periodic DFT methods applied to supported Cp*ZrMe3 and Cp*ZrBz3 indicate that larger Zr···surface distances are present in more sterically encumbered Cp*ZrBz2(+)/AlS(-) vs Cp*ZrMe2(+)/AlS(-). The combined XAS, solid state NMR, and DFT data argue that the bulky catalyst benzyl groups expand the "cationic" metal center-anionic sulfated oxide surface distances, and this separation/weakened ion-pairing enables the activation/insertion of more sterically encumbered arenes and influences hydrogenation rates and selectivity patterns.

Structural characterization of the catalytically significant sites on solid catalyst surfaces is frequently tenuous because their fraction, among all sites, typically is quite low. Here we report the combined application of solid-state 13 C-cross-polarization magic angle spinning nuclear magnetic resonance ( 13 C-CPMAS-NMR) spectroscopy, density functional theory (DFT), and Zr X-ray absorption spectroscopy (XAS) to characterize the adsorption products and surface chemistry of the precatalysts (η 5 O rganometallic molecule-derived heterogeneous catalysts are of increasing interest owing to their enhanced thermal stability and activity vs. their homogeneous analogs, and their atomically precise tailorable metal-ligand structures vs. other heterogeneous catalysts (1, 2). Furthermore, it is becoming increasingly evident that the inorganic support in many systems is noninnocent and can function as both a ligand and an activator, with the chemically important but poorly understood nature of the catalyst-support interaction strongly modulating catalytic activity and selectivity (3, 4). When adsorbed on Lewis acidic, dehydroxylated alumina surfaces, group 4 complexes such as Cp 2 ZrR 2 (Cp = η 5 -C 5 H 5 ; A, R = H; B, R = CH 3 ) and Cp*Zr (CH 3 ) 3 [C, Cp* = η 5 -C 5 (CH 3 ) 5 ] were argued on the basis of highresolution solid-state NMR spectroscopy to transfer an alkyl anion to unsaturated, Lewis acidic surface sites as in Fig. 1 (complexes B, C → qualitative model D) (5, 6). The resulting catalysts are extremely active for olefin hydrogenation and polymerization, and analogous ion-paired species form the basis for large-scale industrial polymerization processes (7,8). However, kinetic poisoning experiments in which the catalytic sites are titrated in situ with H 2 O or t BuCH 2 OH indicate that ≤5% of D-type sites are catalytically significant, likely reflecting, among other factors, the established heterogeneity of alumina surfaces (5, 6, 9), hence rendering active site structural and chemical descriptions necessarily imprecise. In contrast to these results, chemisorption of such organozirconium precursors on SiO 2 , Al 2 O 3 , and SiO 2 -Al 2 O 3 surfaces having appreciable coverage by weakly acidic OH groups predominantly yields covalently bound, poorly electrophilic Etype species via Zr-CH 3 protonolysis with CH 4 evolution (5, 6, 10, 11). Although the E-type sites may be characterized in some detail by high-resolution solid-state NMR and extended X-ray adsorption fine structure spectroscopy (EXAFS), they display minimal catalytic turnover in the absence of added, complicating activators [e.g., methylalumoxane or B(C 6 F 5 ) 3 ], and the fraction of catalytically significant sites is unknown (12, 13). In such situations, it is experimentally impossible to unambiguously distinguish catalytically significant sites from inactive "spectator" sites, hence to fully understand the catalytic chemistry.-In marked contrast to the above results, chemisorption of these same organozirconium molecules on highly Brønsted "super...