We introduce a new type of strongly donating Nheterocyclic boryloxy (NHBO) ligand, [(HCDippN)2BO] − , which is isoelectronic with the well-known N-heterocyclic iminato (NHI) donor class. This 1,3,2-diazaborole functionalized oxy ligand can be employed to stabilize the first acyclic two-coordinate dioxysilylene and its Ge, Sn and Pb congeners, thereby presenting the first complete series of heavier group 14 dioxycarbene analogues. All four compounds have been characterized by X-ray crystallography and Density Functional Theory (DFT), enabling analysis of periodic trends: the potential for the [(HCDippN)2BO] − ligand to subtly vary its electronic donor capabilities is revealed via snapshots revealing gradual evolution of arene π-coordination on going from Si to Pb.

We disclose the synthesis and structural characterization of the first acid-free anionic oxoborane, [K(2.2.2-crypt)][(HCDippN) 2 BO] (1), which is isoelectronic with classical carbonyl compounds. 1 can readily be accessed from its borinic acid by a simple deprotonation/sequestration sequence. Crystallographic and DFT analyses support the presence of a polarized terminal B=O double bond. Subsequent π bond metathesis converts the B=O bond to a heavier B=S containing system, affording the first anionic thioxoborane [K(2.2.2-crypt)] [(HCDippN) 2 BS] (2), isoelectronic with thiocarbonyls. Facile B=O bond cleavage can also be achieved to access B−H and B−Cl bonds, and via a remarkable oxide (O 2− ) ion abstraction to generate a borenium cation [(HCDippN) 2 B(NC 5 H 5 )][OTf] (4). By extension, 1 can act as an oxide transfer agent to organic substrates, a synthetic role traditionally associated with transition metal compounds. Hence we show that B−O linkages, which are often considered to be thermodynamic sinks, can be activated under mild conditions towards bond cleavage and transfer, by exploiting the higher reactivity inherent in the B=O double bond.

Introduced here is a new type of strongly donating N‐heterocyclic boryloxy (NHBO) ligand, [(HCDippN)2BO]− (Dipp=2,6‐diisopropylphenyl), which is isoelectronic with the well‐known N‐heterocyclic iminato (NHI) donor class. This 1,3,2‐diazaborole functionalized oxy ligand has been used to stabilize the first acyclic two‐coordinate dioxysilylene and its Ge, Sn, and Pb congeners, thereby presenting the first complete series of heavier group 14 dioxycarbene analogues. All four compounds have been characterized by X‐ray crystallography and density‐functional theory, enabling analysis of periodic trends: the potential for the [(HCDippN)2BO]− ligand to subtly vary its electronic‐donor capabilities is revealed by snapshots showing the gradual evolution of arene π coordination on going from Si to Pb.

The synthetic viability of several N-heterocyclic carbene-stabilized dichloroborenium cations [NHCBCl 2 ] + (NHC = (RC) 2 (NR') 2 C;

A newly developed annulated 5-chlorinated 1,3,2,5-diazadiborinine derivative (4) selectively activates a C−H bond of benzene (C 6 H 6 ) and 1,3-di-(trifluoromethyl)benzene, as well as a C−F bond in partially fluorinated arenes, to furnish borylation products under catalyst-, metal-, and irradiation-free conditions. Moreover, 4 readily undergoes a reversible dearomative coupling reaction with polycyclic aromatic hydrocarbons to afford diboration products. The latter represents the first reversible intermolecular dearomative diboration of arenes.