A lithio-diazaborole reacted with diamino-chlorophosphines via metathesis to yield previously unavailable phosphinoboranes bearing amino substituents at both the phosphorus and boron atoms, and with Ph2PCl and Mes*PCl2via chloride transfer and reductive PP coupling to give a chloro-diazaborole and the corresponding diphosphine or diphosphene, respectively. Diazaboroles with phenylphosphino- and PH2-substituents were nonetheless accessible via inverse metathesis upon treatment of a bromoborane precursor with phosphides PhnPH2-nM (n = 0-2, M = Li, K). The products were characterised by spectroscopic data and in most cases by single-crystal X-ray diffraction studies which show the molecules to exhibit strongly pyramidal coordination at the phosphorus atom and long BP bonds of 1.93-1.95 Å. The insensitivity of the BP distance towards substituent effects and the tolerance of large sterically induced torsional twists along the BP bond axis suggest the presence of pure single bonds without any contribution from P→B dative π-interactions. This view was confirmed by DFT studies which indicate further that the molecules lack a significant electrophilic character at boron but may act as potential σ-donor/π-acceptor ligands through the phosphorus atom.

Reactions of selected diazadienes with PBr 3 and BBr 3 in the presence of a tertiary amine yielding N-heterocyclic phosphanes (NHPs) and N-heterocyclic boranes (NHBs) were studied. It is demonstrated that heterocycle formation occurs even without an amine or another auxiliary reagent, and the amine acts mainly as scavenger of Br 2 formed as by-product, but also that the additive speeds up reactions and has an influence on the product selectivity. In extension of the results of earlier studies it is shown that the reactions can follow two different pathways to give either 2-bromo-or 2,4-dibromo-substituted heterocycles. Computational studies enabled to propose a reaction mechanism, which relates the

Condensation of N,N′‐disubstituted ethylenediamines with BF3·OEt2, in the presence or absence of an auxiliary base, gives mixtures of 2‐fluoro‐1,3,2‐diazaborolidines and ammonium tetrafluoroborates, respectively. Using BF3·NEt3 as the reactant allows the introduction of the boron source and the auxiliary in a single component, but suffers from the inhibition of the cyclisation by an excess of free amine formed as a by‐product. In contrast, rapid and quantitative consumption of the starting materials is observed when the reaction is carried out with a 2:1 mixture of BF3·NEt3 and BF3·OEt2 per mol of ethylenediamine at elevated temperature. Extremely short reaction times are achieved by conducting the reaction in a superheated solution in a microwave reactor. The 2‐fluoro‐1,3,2‐diazaborolidines formed under these conditions are readily isolated in high yields, and their synthetic usability is demonstrated by reactions with lithium phosphanides to give 2‐phosphanyl‐1,3,2‐diazaborolidines. Both the F‐ and R2P‐substituted N‐heterocyclic boranes are fully characterised. In addition, the structural characterisation of an unprecedented BF3 complex of Hünig's base (iPr2EtN) and of a 1,3,2‐diazaborolidine–BF3 complex is reported.

Boryl-substituted phosphines NHB-P(R)Ph (R = H, Ph, NHB = N-heterocyclic boryl substituent) react with Fe 2 (CO) 9 to give isolable Fe(CO) 4 complexes, two of which were characterized by single-crystal XRD studies. The electronic and steric properties for a series of the boryl phosphines were further assessed by evaluation of TEPs for in-situ formed complexes [RhCl(NHB-PR 1 R 2 )(CO) 2 ] (R 1 , R 2 = H, Ph, Me, NMe 2 ), and calculations of buried volumes for Fe(CO) 4 complexes. The results imply that the NHB-phosphines exhibit due to their conforma- [a]

Reaction of an imidazolio-phosphide with a N-heterocyclic bromo-borane and NaH afforded a neutral analogue of a phosphamethine cyanine cation. DFT studies were used to analyse the dative bonding across P–C/B...