Rhodium and Iridium Aminoborane Complexes: Coordination Chemistry of BN Alkene Analogues

Abstract

Side‐on or end‐on? Rhodium and iridium complexes featuring aminoboranes (R2NBH2) as ligands have been synthesized and structurally characterized. Crystallographic measurements show that the ligands—in contrast to isoelectronic alkene donors—bind in an end‐on fashion through a bis(σ‐borane) binding motif (see structure).

Ein Weg zu gemischten Pnictogenylboranen

“…[5] Die thermische Behandlung von tBuPHBH 2 -NMe 3 führt zur Abspaltung von NMe 3 und zur Kopf-Schwanz-Polymerisierung des reaktiven Intermediates [tBuPHBH 2 ]zu[ tBuPHBH 2 ] n . [8] Eine andere Mçglichkeit, diese Verbindungen bei Normalbedingungen zu untersuchen, besteht darin, sie entweder durch sterisch anspruchsvolle Gruppen am Boratom [9] oder durch Donor-Akzeptor-Stabilisierung zu schützen. [6] Unter Normalbedingungen ist jedoch eine Stabilisierung notwendig, beispielsweise mittels Abfangen durch Übergangsmetallkomplexe in ([RuH 2 (h 2 :h 2 -H 2 BNH 2 )(PCy 3 ) 2 ]).…”

“…[7] Eine ähnliche h 2 :h 2 -Koordination von [R 2 N=BH 2 ]w urde an einem Ir-Komplex beobachtet. [8] Eine andere Mçglichkeit, diese Verbindungen bei Normalbedingungen zu untersuchen, besteht darin, sie entweder durch sterisch anspruchsvolle Gruppen am Boratom [9] oder durch Donor-Akzeptor-Stabilisierung zu schützen. In letzerem Fall wird das freie p-Orbital am Boratom durch eine Lewis-Base (LB) blockiert, während das freie Elektronenpaar des Pnictogenatoms an eine Lewis-Säure (LS) koordiniert.…”

Access to FeII Bis(σ‐B−H) Aminoborane Complexes through Protonation of a Borohydride Complex and Dehydrogenation of Amine‐Boranes

“…[4] Over the past decade,avariety of Ru, Rh, and Ir based complexes have been reported in which H 3 BÀNR 3 ,H 2 B=NR 2 ,o r[ H 2 BÀNR 2 ] 2 fragments are bound to the metal. [5][6][7][8][9] In contrast, only few examples are known for first row transition metals which are restricted to tertiary amine-boranes and ar ecently published iron amidoborane complex. [10][11][12] In continuation of our work on the synthesis and catalytic application of iron polyhydride and s-complexes, [13] we considered the use amine-and aminoboranes as effective yet still labile ligands for the stabilization of the cationic 14 valence electron fragment [Fe(PNP)(H)] + .Herein, we report on the first synthesis and structural characterization of Fe II aminoborane complexes initiated by protonation of the borohydride complex [Fe(PNP)(H)(h 2 -BH 4 In contrast, if 1 is treated with [NH 2 Me 2 ] + only 2 is formed which could be isolated in 92 %y ield as PF 6 À salt.…”

A Convenient Route to Mixed Pnictogenylboranes

“…Recently,w er eported ac atalyst-free pathway as well as the synthesis of the first high-molecular-weight poly(alkylphosphinoborane). [8] Another way to investigate these compounds under ambient conditions is either their protection with sterically demanding groups on the boron atom [9] or donoracceptor stabilization. Similar highly reactive compounds such as [H 2 N=BH 2 ] have been isolated under cryogenic conditions.…”

“…[7] Thesame h 2 :h 2 coordination of [R 2 N=BH 2 ]w as observed within an Ir complex. [8] Another way to investigate these compounds under ambient conditions is either their protection with sterically demanding groups on the boron atom [9] or donoracceptor stabilization. In the latter case,t he vacant porbital on the boron atom is blocked by aLewis base (LB) while the lone pair of the pnictogen atom coordinates to aL ewis acid (LA).…”