Reaktionen des Diphenylphosphanoxids mit Organodiboranen(6) – Struktur einer zwitterionischen –POB– ‐Verbindung¹⁾

Abstract

'~ -4~ U d (C&&PH (7) bzw. (C6HSkPH -H B C B H~~ (7-4~).In der zuvor veroffentlichten Arbeit dieser Reihe4) berichteten wir, dal3 die Reduktion der Diphenylphosphinsaure (C6H5)2P(0)OH rnit den Alkyldiboranen (6) Diphenylphosphanoxid (1) und OrganoborReagenzienZunCchst wurden die Reaktionen von 1 niit verschiedenen Organobor-Reagenzien analytisch untersucht. Die gefundenen Kennzahlen EZ5"', HZSa1 und HZBBNSa) von 1 sind in Tab. 1 zusammengestellt.Reaktionen von 1 rnit Triethylboran 1 reagiert rnit iiberschiissigem, durch PivalinsCure aktiviertem Triethylboran (2a*)6) oberhalb ca. 20°C unter Abspaltung von 1 rnol Ethan: EZ5") = 1. WChrend 1 in siedendem 2 a ohne Zusatz von Pivalinslure praktisch nicht reagiert, fiihrt die katalysierte Reaktion nach G1. (a) quantitativ zu (Dipheny1phosphinooxy)diethylboran (3'a)k) mit 3fach koordiniertem Phosphor-Atom (3'P-NMR, vgl. Tab. 2).

Carbon dioxide reduction by an Al–O–P frustrated Lewis pair

“…However, they did not explicitly investigate adduct formations in the sense of FLP chemistry but only reported adducts with an additional hydridodialkylborane being coordinated to the phosphorus atom. 18 Only very recently were a few examples of neutral oxygen-bridged P–O–B systems presented, which show typical reactivity towards CO 2 and molecular hydrogen. However, these reactions require untypically harsh conditions or only reversibly form adducts despite the strongly electronegative substituents at boron.…”

Chemoselective Reduction of the P=O Bond in the Presence of P–O and P–N Bonds in Phosphonate and Phosphinate Derivatives

“…Nevertheless, these methods are generally useless for the reduction of strong P=O bonds in phosphonic and phosphinic acid derivatives that contain much weaker and more reactive P–O or P–N bonds is to be accomplished. The reaction of various reducing agents (metal hydrides, organoboron hydride, PHMS, Ph 2 SiH 2 , Ph 2 SiH 2 /Lewis acid or PhSiH 3 /Lewis acid) with phosphinates or phosphonates typically leads to the reduction of all phosphorus‐oxygen bonds in what constitutes a valuable preparation of secondary and primary phosphines, respectively. Similarly, phosphinic acid amides typically undergo P–N bond cleavage in the presence of reducing agents although two early and one recent exceptions have been reported.…”

Direct Conversion ofsec-Phosphine Oxides into Phosphinous Acid-Boranes

“…5,6 So far, they include only three phosphinous acid-boranes 3,5,6 and boranemodified nucleic acids 4 and, with the possible exception of the borane-modified nucleic acids, their properties and chemistry have not been systematically studied. Development of general methods for easy preparation of such compounds would undoubtedly spur on more detailed studies of their chemistry and synthetic utility.…”

“…As a consequence, the known examples of borane complexes of phosphorus acids are very few in number and they were all obtained via indirect routes 3,4 or were isolated in the course of other studies. 5,6 So far, they include only three phosphinous acid-boranes 3,5,6 and boranemodified nucleic acids 4 and, with the possible exception of the borane-modified nucleic acids, their properties and chemistry have not been systematically studied. Development of general methods for easy preparation of such compounds would undoubtedly spur on more detailed studies of their chemistry and synthetic utility.…”