Recent Advances in the Chemistry of Iminoborane Derivatives

Abstract

Iminoboranes are important unsaturated organoboron compounds with the formula RB≡NR’. They are isoelectronic with alkynes, yet normally exhibit higher reactivity due to their polarity, thus enabling versatile applications in coordination, synthetic and materials chemistry. This review briefly describes the most recent progress in iminoborane derivatives with the focus on new persistent species and their diverse reactivity, which greatly enrich the iminoborane chemistry. In addition, the promising research directions are also provided.

A Crystalline Monomeric Phosphaborene

“…Compound 2 also features a short BN bond of 1.365(3), slightly contracted from that of 1, consistent with a change in hybridization from sp 2 to sp at boron, and in line with TMP−B lengths in structurally characterized iminoboranes. 26,56 Furthermore, the central CPBN core adopts a planar geometry with trans orientation of the C and N substituents, with a CPB angle of 115.5(1)°and a PBN angle of 161.5(2)°, in stark contrast to iminoboranes, which feature a linear core, 57,58 but in line with computational predictions. 49 The nature of the bonding in 2 was further investigated by computational means.…”

“…1.79–1.81 Å), ,,, AlBr 3 -stabilized (1.787 Å), and the concurrently reported “push-pull” phosphaborene (1.7788 Å), marginally shorter than that of the Cr­(CO) 5 -stabilized species (1.742(5) Å), and considerably longer than the sum of the Pyykkö triple bond radii (1.67 Å), though shorter than the double bond radii (1.80 Å), suggesting a lack of triple bond character. Compound 2 also features a short BN bond of 1.365(3), slightly contracted from that of 1 , consistent with a change in hybridization from sp 2 to sp at boron, and in line with TMP–B lengths in structurally characterized imino­boranes. , Furthermore, the central CPBN core adopts a planar geometry with trans orientation of the C and N substituents, with a CPB angle of 115.5(1)° and a PBN angle of 161.5(2)°, in stark contrast to iminoboranes, which feature a linear core, , but in line with computational predictions …”

A Free Phosphaborene Stable at Room Temperature

“…These bond angles suggest the high nonbonded character of the in-plane electron pairs at P(1) and N(1), in line with the electron localization function (ELF) calculations (Figure S4-4). Notably, the structural features of 5 are distinctly different from those found for iminoboranes that contain a polarized BN triple bond and the linear geometry at both B and N atoms …”

“…The rich and vast work on CC/NB isosterism has been extremely fruitful for the development of organic/inorganic hybrid architectures with unique physical or chemical properties . Iminoboranes (R–N + B – –R) that are isoelectronic with alkynes have exhibited diverse reactivity and have been utilized as potent synthons for various organoborane derivatives . However, the analogous chemistry based on CC/PB exchange has largely lagged behind due to the considerable lability of PB π bonds towards spontaneous oligomerization (Figure a)a consequence of the high ionic character of group 13/group 15 multiple bonds .…”

Synthesis, Structural Characterization and Coordination Chemistry of a NHC‐stabilized Iminoborane

“…A variety of Lewis base-coordinated iminoboranes have been synthesized and structurally characterized in the past decade. [1][2][3][4][5][6][7][8][9][10][11] Given the wide utilization of imine-incorporated ligands, such as α-diimine, [12][13][14][15][16] β-diketiminato, [17][18][19] and bis(imino)pyridine [20][21][22][23] ligands in coordination chemistry and catalysis, Lewis base-coordinated iminoboranes appear to be another promising novel type of ligand system. However, the research on the coordination chemistry of Lewis base-coordinated iminoboranes is extremely rare, [5][6][7] probably due to the lack of available starting materials.…”