A Base-Free Two-Coordinate Oxoborane.

Oxoboranes (R-BO) are transient species that rapidly trimerise to form boroxines. To date, the only method used to stabilise oxoboranes is to add a Lewis base, but this forms a three-coordinate at boron oxoborane that has a different bonding/reactivity profile. Herein we report a base-free, two-coordinate oxoborane that is isolated as a Lewis adduct with AlCl.

Amides as modifiable directing groups in electrophilic borylation.

Amide directed C-H borylation using ≥two equiv. of BBr forms borenium cations containing a RN(R')C[double bond, length as m-dash]O→B(Ar)Br unit which has significant Lewis acidity at the carbonyl carbon. This enables reduction of the amide unit to an amine using hydrosilanes.

Two Directing Groups Used for Metal Catalysed -C-H Functionalisation Only Effect Electrophilic C-H Borylation.

Two templates used in -directed C-H functionalisation under metal catalysis do not direct -C-H borylation under electrophilic borylation conditions. Using BCl only Lewis adduct formation with Lewis basic sites in the template is observed. While combining BBr and the template containing an amide linker only led to amide directed C-H borylation, with no pyridyl directed borylation.

Synthesis of Electrophiles Derived from Dimeric Aminoboranes and Assessing Their Utility in the Borylation of π Nucleophiles.

Dimeric aminoboranes, [HBNR] (R = Me or CHCH) containing BN cores, can be activated by I, HNTf (NTf = [N(SOCF)]), or [PhC][B(CF)] to form isolable HB(μ-NR)BHX (for X = I or NTf). For X = [B(CF)] further reactivity, presumably between [HB(μ-NMe)BH][B(CF)] and aminoborane, forms a BN-based monocation containing a three-center two electron B-(μ-H)-B moiety. The structures of HB(μ-NMe)BH(I) and [(μ-NMe)BH(NTf)] indicated a sterically crowded environment around boron, and this leads to the less common O-bound mode of NTf binding.

Preparation and Characterization of P BCh Ring Systems (Ch=S, Se) and Their Reactivity with N-Heterocyclic Carbenes.

Four-membered rings with a P BCh core (Ch=S, Se) have been synthesized by the reaction of phosphinidene chalcogenide (Ar*P=Ch) and phosphaborene (Mes*P=BNR ). The mechanistic pathways towards these rings are explained by detailed computational work that confirmed the preference for the formation of P-P, not P-B, bonded systems, which seems counterintuitive given that both phosphorus atoms contain bulky ligands. The reactivity of the newly synthesized heterocycles, as well as that of the known (RPCh) rings (n=2, 3), was probed by the addition of N-heterocyclic carbenes, which revealed that all investigated compounds can act as sources of low-coordinate phosphorus species.