Roll-over cyclometalation: A versatile tool to enhance the catalytic activity of transition metal complexes

Roll-over cyclometalation is a special case of cyclometalation. While in classical cyclometalation, C,H-activation (deprotonation or oxidative addition) has to occur at the ligand to result in a metallacycle, in roll-over cyclometalation the ligand in principle has the chance to undergo chelating coordination without cleavage of a C-H bond (e.g. ?2-N,N?- vs. ?2-C,N-coordination at 2,2?-bipyridines). Nature thus can decide for which route shall be followed. In this review, the basic parameters for bringing a system into roll-over cyclometalation are discussed, followed by an overview on compounds that have been published in this field during the last years. The major emphasis of this review however is on applications of roll-over cyclometalation in catalysis, a rather new field in coordination and organometallic chemistry. 2018 Elsevier B.V.Our studies on roll-over cyclometalation are supported by the German research foundation DFG within the transregional collaborative research center SFB/TRR 88 Cooperative effects in homo and heterometallic complexes (3MET) and by the state research center OPTIMAS. We furthermore gratefully acknowledge the research college MAGNENZ and the state research unit NanoKat for financial support. M. L. thanks the Konrad-Adenauer-Stiftung and A.F. thanks the Cusanuswerk for a PhD grant. Dr. Kifah S. M. Salih studied chemistry at the Al-Mustansiriyah University (Baghdad, Iraq, B.Sc. 1998) and at the University of Jordan (Amman, Jordan, M.Sc. 2004), where he finished with a master thesis on Synthesis of Some New Coumarin Derivatives. After two years working as a researcher in the group of Prof. Dr. Mohammad S. Mubarak (Univ. of Jordan), he in 2006 joined the group of Prof. Dr. Lukas J. Goo?en at the Technische Universit?t Kaiserslautern for a PhD thesis supported by a DAAD scholarship. Kifah S. M. Salih finished his PhD in 2010 with a thesis on Environmentally Benign Synthesis of Enamides via Waste-Free Catalytic Addition of Amides to Terminal Alkynes. During this time, he received the award of the Karl-Ziegler-Stiftung. He then took the opportunity to work for three years as a postdoc in the group of Prof. Dr. Werner R. Thiel (TU Kaiserslautern), where he mainly focused on the synthesis of mangetic nanoparticles an their application in catalysis. From 2014 Kifah S. M. Salih was visiting lecturer at the Sultan Qaboos University (Muscat, Oman) and in 2015 he became lecturer at the Department of Chemistry and Earth Sciences of Qatar University (Doha, Qatar). Prof. Dr. Werner R. Thiel studied chemistry at the Technische Universitt Mnchen (Germany), where he received his diploma in 1987 with a thesis on Synthesis and Characterization of High Valent (? 5 -Pentamethylcyclopentadienyl)chromium Complexes carried out in the group of Prof. Dr. Wolfgang A. Herrmann. In 1990, he received his PhD with a thesis on Synthesis, Derivatization and Characterization of Chelate Complexes of 2,2?-Bipyridine: Reactivity and Structural Aspects (TU M nchen, W. A. Herrmann). Supported by a Feodor Lynen-Grant of the Alexander von Humboldt-Stiftung , Werner R. Thiel worked for one year in the group of Prof. Dr. Didier Astruc at the Universit de Bordeaux I (Bordeaux, France). After coming back to TU Mnchen in 1991 he started with own projects which were summarized in a habilitation in 1997. In 2000 he became associate professor for inorganic chemistry at the Technische Universit?t Chemnitz (Germany) and in 2004 full professor at the Technische Universit?t Kaiserslautern (Germany). Werner R. Thiel is author of about 180 publications with a focus on transition metal catalyzed reactions and their mechanisms and on the use of porous inorganic supports in catalysis

Indacenodithiazole-Ladder-Type Bridged Di(thiophene)-Difluoro-Benzothiadiazole-Conjugated Copolymers as Ambipolar Organic Field-Effect Transistors

A series of four donor-acceptor conjugated copolymers P1-P4 with linear and branched side chains based on a ladder-type indacenodithiazole (IDTz) moiety containing an electron-deficient thiazole unit are copolymerized with di-2-thienyl-2,1,3-benzothiadiazole (DTBT) and 4,7-di(thien-2-yl)-5,6-difluoro-2,1,3-benzothiadiazole (DTBTff) as building blocks. Their optical, electrochemical, and thermal properties and charge transport behavior in organic field-effect transistors (OFETs) are studied. All copolymers exhibit nearly identical features in solution with good solubility. In the solid state, P1 does not exhibit a significant shift, while P3 shows a 27 nm red shift, thus illustrating the influence of the side chain. In the case of copolymers P1 and P2 having linear side chains, there is a clear effect of fluorination on the film morphology, while it is less pronounced in the case of polymers P3 and P4 having branched side chains. All copolymers P1-P4 have similar highest occupied molecular orbitals regardless of fluorination, while fluorinated polymers P2 and P4 result in an increase in the lowest unoccupied molecular orbital. In addition, density functional theory calculations reveal that the energy levels of IDTz are down-shifted in comparison to its IDT counterpart containing an electron-rich thiophene unit. OFETs based on all copolymers exhibit ambipolar behavior; among the four copolymers, P2 having a linear dodecyl side chain exhibits remarkable transport properties with saturated hole mobility as high as 0.87 cm2 V-1 s-1, while P3 exhibits the highest electron mobility of up to 0.50 cm2 V-1 s-1. Our results set an interesting path to further utilize the electron-deficient thiazole block in semiconducting materials. Copyright - 2019 American Chemical Society.This work was supported by the Qatar National Research Fund (QNRF) and the National Priorities Research Program, project number NPRP 8-245-1-059.Scopu