Carbon-Based Weakly Coordinating Anions: Molecular Design, Synthesis and Applications.

Although carbanions, which are usually regarded as reactive species and powerful metalation reagents, can be stabilized through choice of the substitution pattern, they have rarely been considered for the design of weakly coordinating anions (WCA).  Here, we report on an evaluation of the potential of a series of differently substituted carbanions to serve as WCA by computational methods. This led us to the synthesize the water- and air-stable allyl anion 1 with triflyl and 3,5-bis(trifluoromethyl)phenyl (ArF) moieties, which can be isolated in high yields even on a gram-scale. Single crystal X-ray crystallography and NMR studies confirmed the weak coordination ability of the anion by showing negligible or only weak interactions with different cations. This property enabled the application of 1 in the stabilization of reactive group 14 and 15 cations. In addition to the crystallization of a phosphenium cation, the first all-carbon salt with a non-aromatic carbanion is reported, which revealed to be a convenient reagent for hydride abstraction such as from silanes. Overall, this work demonstrates the so far untapped potential of carbanions as WCA, that are accessible with a variety of different cations for various applications.

P,N-Coordinating Ylide-Functionalized Phosphines (NYPhos): A Ligand Platform for the Selective Monoarylation of Small Nucleophiles.

Palladium-catalyzed coupling reactions of small nucleophiles are of great interest, but challenging due to difficulties in selectivity control. Herein, we report the development of a new platform of P,N-ligands consisting of ylide-functionalized phosphines with aminophosphonium groups (NYPhos) to address this challenge. These phosphine ligands are easily accessible in a wide structural diversity with highly modular electronic and steric properties. Based on a family of 14 ligands the selective monoarylation of acetone as well as other challenging ketones and amides was accomplished with record-setting activities even for aryl chlorides at room temperature including late-stage functionalizations of drug molecules. Moreover, ammonia and other small primary amines could be coupled at mild conditions. Isolation and structure analyses of palladium complexes within the catalytic cycle confirmed the P,N-coordination mode necessary to reach the observed selectivities and proved the facile adjustability of the N-donor strength, which is beneficial for the targeted design of tailored P,N-ligands for future applications.

From a mercury(II) bis(yldiide) complex to actinide yldiides.

The bis(yldiide) mercury complex, (L-Hg-L) [L = C(PPh3)P(S)Ph2], is prepared from the corresponding potassium yldiide and used to access the first substituted yldiide actinide complexes [(C5Me5)2An(L)(Cl)] (An = U, Th) via salt metathesis. Compared to previously reported phosphinocarbene complexes, the complexes exhibit long actinide-carbon distances, which can be explained by the strong polarization of the π-electron density toward carbon.