Carbon–Fluorine Reductive Elimination from a High–Valent Palladium Fluoride

We have observed two high-valent arylpalladiumfluoride complexes that afford carbon−fluorine bond formation upon thermolysis.Chemistry and Chemical Biolog

Bimetallic Redox Synergy in Oxidative Palladium Catalysis

Polynuclear transition metal complexes, which are embedded in the active sites of many metalloenzymes, are responsible for effecting a diverse array of oxidation reactions in nature. The range of chemical transformations remains unparalleled in the laboratory. With few noteworthy exceptions, chemists have primarily focused on mononuclear transition metal complexes in developing homogeneous catalysis. Our group is interested in the development of carbon–heteroatom bond-forming reactions, with a particular focus on identifying reactions that can be applied to the synthesis of complex molecules. In this context, we have hypothesized that bimetallic redox chemistry, in which two metals participate synergistically, may lower the activation barriers to redox transformations relevant to catalysis. In this Account, we discuss redox chemistry of binuclear Pd complexes and examine the role of binuclear intermediates in Pd-catalyzed oxidation reactions. Stoichiometric organometallic studies of the oxidation of binuclear $Pd^{II}$ complexes to binuclear $Pd^{III}$ complexes and subsequent C–X reductive elimination from the resulting binuclear $Pd^{III}$ complexes have confirmed the viability of C–X bond-forming reactions mediated by binuclear $Pd^{III}$ complexes. Metal–metal bond formation, which proceeds concurrently with oxidation of binuclear $Pd^{II}$ complexes, can lower the activation barrier for oxidation. We also discuss experimental and theoretical work that suggests that C–X reductive elimination is also facilitated by redox cooperation of both metals during reductive elimination. The effect of ligand modification on the structure and reactivity of binuclear $Pd^{III}$ complexes will be presented in light of the impact that ligand structure can exert on the structure and reactivity of binuclear $Pd^{III}$ complexes. Historically, oxidation reactions similar to those discussed here have been proposed to proceed via mononuclear $Pd^{IV}$ intermediates, and the hypothesis of mononuclear $Pd^{II/IV}$ catalysis has guided the successful development of many reactions. Herein we discuss differences between monometallic $Pd^{IV}$ and bimetallic $Pd^{III}$ redox catalysis. We address whether appreciation of the relevance of bimetallic $Pd^{III}$ redox catalysis is of academic interest exclusively, serving to provide a more nuanced description of catalysis, or if the new insight regarding bimetallic $Pd^{III}$ chemistry can be a platform to enable future reaction development. To this end, we describe an example in which the hypothesis of bimetallic redox chemistry guided reaction development, leading to the discovery of reactivity distinct from monometallic catalysts.Chemistry and Chemical Biolog

A Transition State Analogue for the Oxidation of Binuclear Palladium(II) to Binuclear Palladium(III) Complexes

Cooperative metal–metal (M–M) redox chemistry has the potential to lower activation barriers for redox transformations relevant to catalysis. Pd2(III,III) complexes, generated by oxidation of Pd2(II,II) complexes, have recently been implicated as intermediates in a variety of Pd-catalyzed C–H oxidation reactions. M–M redox synergy, mediated by Pd–Pd bond formation and cleavage, has been proposed to facilitate both oxidation and reductive elimination steps during various Pd-catalyzed directed C–H oxidation reactions. Herein, we report a transition state mimic for the oxidation of Pd2(II,II) complexes which suggests that M–M redox synergy is involved in the oxidation of Pd2(II,II) complexes to Pd2(III,III) complexes.Chemistry and Chemical Biolog

Adaptive Observation Strategy for Dispersion Process Estimation Using Cooperating Mobile Sensors ⋆

Abstract: Efficient online state estimation of dynamic dispersion processes plays an important role in a variety of safety-critical applications. The use of mobile sensor platforms is increasingly considered in this context, but implies the generation of situation-dependent vehicle trajectories providing high information gain in real-time. In this paper, a new adaptive observation strategy is presented combining state estimation based on partial differential equation models of the dispersion process with a model-predictive control approach for multiple cooperating mobile sensors. In a repeating sequential procedure, based on the Ensemble Transform Kalman Filter, the uncertainty of the current estimate is determined and used to find valuable measurement locations. Those serve as target points for the controller providing optimal trajectories subject to the vehicles ’ motion dynamics and cooperation constraints. First promising results regarding accuracy and efficiency were obtained

Deoxyfluorination of Phenols

An operationally simple ipso fluorination of phenols with a new deoxyfluorination reagent is presented.Chemistry and Chemical Biolog

Benchmarking Image Sensors Under Adverse Weather Conditions for Autonomous Driving

Adverse weather conditions are very challenging for autonomous driving because most of the state-of-the-art sensors stop working reliably under these conditions. In order to develop robust sensors and algorithms, tests with current sensors in defined weather conditions are crucial for determining the impact of bad weather for each sensor. This work describes a testing and evaluation methodology that helps to benchmark novel sensor technologies and compare them to state-of-the-art sensors. As an example, gated imaging is compared to standard imaging under foggy conditions. It is shown that gated imaging outperforms state-of-the-art standard passive imaging due to time-synchronized active illumination

A Benchmark for Lidar Sensors in Fog: Is Detection Breaking Down?

Autonomous driving at level five does not only means self-driving in the sunshine. Adverse weather is especially critical because fog, rain, and snow degrade the perception of the environment. In this work, current state of the art light detection and ranging (lidar) sensors are tested in controlled conditions in a fog chamber. We present current problems and disturbance patterns for four different state of the art lidar systems. Moreover, we investigate how tuning internal parameters can improve their performance in bad weather situations. This is of great importance because most state of the art detection algorithms are based on undisturbed lidar data

Palladium-Mediated Fluorination of Arylboronic Acids

Saving the best for last: Novel palladium complexes allow mild, two-step fluorination of aryl boronic acids (see scheme). The reaction is regiospecific, functional-group tolerant, has a broad substrate scope, and is ideally suited for the introduction of fluorine substituents at a late stage for aryl fluoride synthesis.Chemistry and Chemical Biolog

Iron-Catalyzed Polymerization of Isoprene and Other 1,3-Dienes

Chemistry and Chemical Biolog