Contributions to the Chemistry of Boron, 214. Synthesis and Reaction Chemistry of Aminophosphanylboranes

Abstract

The formation of phosphanylboranes, R2P -BX2, from hydrogen or hydrogen halide elimination reactions between appropriate phosphane and borane reagents was examined intently for a number of These studies led to the isolation and partial characterization of several molecular ring compounds (RzPBX2), (n = 2, 3) as well as oligomeric species. Some of this chemistry has recently been revisited and extended in order to obtain monomeric boraphosphene species that contain a -P = B -double bond and to define new classes of boron-phosphorus ring and cage compounds["-5o1. These results make it clear that there is considerable potential for the development of additional chemistry from phosphanylborane reagents. In that regard, we report here the use of several phosphanylboranes as reagents for the formation of more complex compounds as well as some aspects of their derivative chemistry. ReactionsIn the past, the majority of phosphanylborane chemistry has been developed with phosphide fragments that contain strongly bonded alkyl or aryl substituents. Relatively few compounds have been reported that possess potentially labile substituents, such as organosilyl groups or hydrogen. We have previously noted that the silylphosphanylboranes 1 a -c, when combined with a second equivalent of LiP(SiMe3)2 in hexane or benzene, produce in good yield the corresponding diphosphadiboretane~ [~~], [R2NBP-(SiMe3)12 (6a-c), and an equivalent of P(SiMe3)3, as illustrated in eq. (5). It was assumed that (diorgany1amino)bis-[(trimethylsilyl)phosphanyl]boranes, R2NB[P(SiMe3)2]2 (5a-c), were formed as intermediates in each case, but none were isolated due to the facile elimination of P(SiMe3)3. In the present study, one bis(phosphanyl)borane, 5b, was prepared and isolated as outlined in eq. (5). However, the corresponding analogs 5a, 5c, and 5d were not detected in NMR spectra recorded from 1 : 1 reaction mixtures prepared from 1 a, 1 c, and 1 d with LiP(SiMe&. It is therefore assumed

Assembly of a Triple-Cage Species Containing B, P, and Si Atoms

“…Compound 7 was not isolated and purified; however, the 31 P NMR spectrum of the system prior to the addition of t BuLi shows a resonance for the known compound 5, δ 164, 10 and a resonance at δ -1.0, which is in the region expected for a bicyclic cage fragment. The proposed process is outlined in Scheme 1.…”

From polygons to polyhedra through intermediate structures. A shape measures study of six-atom inorganic rings and clusters

“…Two of the most puckered members of this family, [HP-B(NR 2 )] 3 , appear in two different conformations, a 38% trigonal prismatic boat for R = i Pr, 71 and a 29% octahedral chair for R = SiMe 3 . 72 The resulting loss of aromaticity in the former has provided an explanation for the long B-P bond lengths compared to those in similar rings. An isoelectronic compound intimately related to this family, a diazatetraborinin with a para-B 4 N 2 core, is a nearly perfectly planar hexagonal six π electron aromatic molecule 2.…”

Monomeric Triphosphinoboranes: Intramolecular Lewis Acid–Base Interactions between Boron and Phosphorus Atoms

“…The chemistry of diphosphinoboranes has been explored to a lesser extent than that of other P–B systems ( Chart 1 B). Most synthesis attempts have been made by Nöth et al 19 − 21 Recently, we vastly expanded the chemistry of these compounds, not only by the synthesis and isolation of several new diphosphinoboranes 22 but also by revealing their potential in the activation of small molecules. 23 Our preliminary research on the reactivity of selected diphosphinoboranes revealed that these species react with isocyanates, CO 2 , and H 2 .…”