Catalytic dehydrocoupling of amine-boranes and amines into diaminoboranes: isolation of a Pt(ii), Shimoi-type, η¹-BH complex

Abstract

The platinum complex [Pt(I(t)Bu')(I(t)Bu)][BAr(F)] is a very efficient catalyst in the synthesis of diaminoboranes through dehydrocoupling of amine-boranes and amines. Shimoi-type, η(1)-BH complexes are key intermediates in the process.

Synthesis and Characterization of Platinum and Palladium Complexes Featuring a Rare Secondary Borane Pincer Motif

“…Furthermore, these signals also exhibited platinum satellites with JPtH coupling constants ranging between 99 -118 Hz. These values are lower than have been reported for direct Pt-H-B interactions in which the hydrogen bridges the boron and platinum centers 37 and are more similar to a 2 JPtH coupling 38,39 thereby suggesting a Pt-B(H) connectivity with no direct platinum-hydrogen interactions in any of the complexes 1 -6.…”

The role of neutral Rh(PONOP)H, free NMe2H, boronium and ammonium salts in the dehydrocoupling of dimethylamine-borane using the cationic pincer [Rh(PONOP)(η2-H2)]+ catalyst

“…The hydrogen atoms associated with the boron were located and refined. The structure demonstrates an η 1 -bound H 3 B•NMe 3 ligand, rather than bidentate η 2 :η 2 51 (I t Bu = 1,3-di-tertbutylimidazolylidene). Solution NMR spectroscopic data are in agreement with the η 1 -binding of the amine-borane being retained in CD 2 Cl 2 .…”

Enhancing the catalytic properties of well-defined electrophilic platinum complexes

“…Although these species were observed by NMR at low temperatures, X-ray diffraction studies on the homologue complex bearing a pyridine borane C 5 H 5 NÁBH 3 (that cannot undergo a dehydrocoupling reaction) confirmed the postulated structure. 93 This coordination mode enhanced the electrophilic character of the boron atom so that it can undergo a nucleophilic addition of an external nucleophile leading to a net transfer of a hydride from the borane to the metal centre. As a result, a neutral platinum hydride complex and a boronium cation are formed.…”

“…Complex 49 proved to be an excellent catalyst in this reaction, with full conversion using as low as 0.5% of the catalyst leading to TOF numbers up to 3692 h À1 , outperforming previously described catalytic systems. 93 With these precedents in mind, we have also explored the catalytic activity of complex 49 in the dehydrocoupling of silanes and amines. In this particular reaction it's challenging to achieve good activities and good selectivities with the same catalytic system when primary silanes are used.…”