Pnictogen-mediated Lewis acidity is an emerging research subject in organic chemistry, supramolecular chemistry, etc. In contrast to the extensive studies on phosphorus and antimony, the diversity of arsenic-Lewis acids was...

Arsenic‐bridged silafluorene and germafluorene were synthesized as a novel class of mixed‐heteroatom‐bridged heterofluorenes. Their structures, photophysical properties, and electronic natures were studied by experimental and computational means. The doubly‐bridged biphenyl moieties were distorted from the reported singly‐bridged ones. The intersystem crossing from the singlet excitation states to the triplet ones was enhanced by the arsenic‐bridging structures, implying that bridging through an arsenic atom is favorable for phosphorescence.

Phosphorus and arsenic have different coordination ability to Lewis acids, though they belong to 15 group. Utilizing the difference, we designed a novel ligand, (p‐(diphenylarsino)phenyl)diphenylphosphine, in which diphenylphosphine and diphenylarsine units are combined through a p‐phenylene linker, as a template to arrange Lewis acids. The phosphorus atom exhibited superior coordination ability to the arsenic one. NMR studies revealed that BH3, AuCl, and PtCl2 were preferentially coordinated by the phosphorus atom. Sequential addition of these Lewis acids realized precise arrangement on the template ligand.

The Front Cover shows characteristic features of (p‐(diphenylarsino)phenyl)diphenylphosphine, in which the phosphorus atom preferentially coordinates to Lewis acids such as borane and metals (Au and Pt). The tilted balances represent about its asymmetric coordination behavior. This kind of molecule can be utilized as a template ligand to precisely arrange various Lewis acids, particularly transition metals. More information can be found in the Full Paper by Hiroaki Imoto, Kensuke Naka et al.