Transition‐Metal Complexes of Boron—New Insights and Novel Coordination Modes

Abstract

Since the publication of the last review in 1998, the transition-metal chemistry of boron has continued to raise unceasing interest. Boryl complexes, representing the most extensive subclass, have remained a focus of intense research, particularly for their implication in the metal-mediated functionalization of organic substrates. Absolute novelties such as borane complexes and terminal borylene complexes have been structurally authenticated. Upon further elaboration of these compounds, the known coordination modes of boron-based ligands have grown considerably. Combined structural and theoretical investigations have contributed to elucidate the fundamental electronic characteristics of the transition-metal-boron bond and are leading to applications of these compounds. The most useful synthetic strategies for the generation of transition-metal-boron bonds are highlighted here, and the most recent and intriguing compounds that have been reported are outlined and discussed.

Crystal field arguments to explain the trans labilisation within transition metal–borane complexes

“…Despite the classification of this mode of coordination for some time, they had received little attention. There were few examples of Z-type ligands claimed prior to the discovery of the metallaboratrane compounds and many of these examples were also later disproved [32][33][34][35][36][37][38][39][40][41][42]. This can be ascribed to the instability of the resulting compounds.…”

“…Furthermore, in similarity to boryl ligation [42,[47][48][49][50][51][52], borane coordination appears to exhibit a very large trans influence within specific geometries such as octahedral. In contrast, the trans influence observed in trigonal bipyramidal complexes, although moderately high, is much less pronounced than observed in octahedral systems.…”

Comparative Analysis of Electron‐Density and Electron‐Localization Function for Dinuclear Manganese Complexes with Bridging Boron‐ and Carbon‐Centered Ligands

“…II and III may additionally be subdivided into terminal and bridged ligands. [1][2][3][4][5] Here we concentrate on the first complex [6,7] with a bridging borylene ligand, 1 (see below), which has recently been investigated in an experimental electron-density (ED) study. [8,9] Analysis of the electron density of 1 by Baders "quantum theory of atoms in molecules" [10] (QTAIM) suggested not only the absence of the direct Mn À Mn bond expected from the 18-valence-electron rule.…”

Coordination Chemistry of Neutral (Ln)–Z Amphoteric and Ambiphilic Ligands

“…However, we would like to acknowledge and cite some leading references on topics that have been put aside deliberately. These include principally, but not exclusively, the work on:·ferrocenylboranes (and other related compounds) and the study of the M-B interaction in these complexes; [12] group IV metallocenylboranes and the study of zwitterionic complexes in ZieglerNatta polymerization; [13] the hydroboration of olefin-containing metallocenes; [14] the electrophilic attack of dienes and alkyl groups by Lewis acids; [15] boryls, borylenes and other metal-bonded boron species; [16] some bidentate Lewis acids; [17] multimetallic species containing bridging boronates. [18] Coordination of Base-Free Amphoteric Ligands…”