Reactions of Osmium–Pinacolboryl Complexes: Preparation of the First Vinylideneboronate Esters

Abstract

The reactions of OsHCl(CO)(PR 3 ) 2 (PR 3 = P i Pr 3 (1a), PCy 3 (1b)) with pinacolborane (HBpin) afford the boryl−dihydrogen derivatives Os(Bpin)Cl(η 2 -H 2 )(CO)(PR 3 ) 2 (PR 3 = P i Pr 3 (2a), PCy 3 (2b)), which lose the H 2 ligand to give the five-coordinate boryl complexes Os(Bpin)Cl(CO)(PR 3 ) 2 (PR 3 = P i Pr 3 (3a), PCy 3 (3b)). Treatment of 3a,b with LiCCPh leads to the five-coordinate alkynyl−boryl derivatives Os(Bpin)(CCPh)(CO)(PR 3 ) 2 (PR 3 = P i Pr 3 (4a), PCy 3 (4b)), which under a carbon monoxide atmosphere evolve into the vinylideneboronate esters Os{CC(Bpin)Ph}(CO) 2 (PR 3 ) 2 (PR 3 = P i Pr 3 (5a), PCy 3 (5b)). Complex 5a is also prepared by stirring of a toluene solution of 3a under CO and subsequent reaction of the resulting cis-dicarbonyl compound Os(Bpin)Cl(CO) 2 (P i Pr 3 ) 2 (6) with LiCCPh. The X-ray structures of 3a, 4a, and 5b are also reported.

Ligand survey results in identification of PNP pincer complexes of iridium as long-lived and chemoselective catalysts for dehydrogenative borylation of terminal alkynes

“…Esteruelas and López 69 were able to monitor the conversion of osmium boryl alkynyl complexes to vinylideneboronate esters, and we envisaged that other isomers of 10-Ir-v-tol might be obtained if a suitable ( Me PNP iPr )Ir precursor was reacted with A1-Bpin under milder conditions. We first attempted to mix 10-Ir-H 2 with A1-Bpin with subsequent rapid removal of volatiles.…”

Amide-Directed Formation of Five-Coordinate Osmium Alkylidenes from Alkynes

“… 29 We have described the preparation of osmium borylvinylidene derivatives through a 1,3-boryl shift in alkynyl boryl intermediates. 30 Dicarbon-disubstituted vinylidenes are generally salts, which have been prepared by electrophilic addition to the C β atom of an alkynyl ligand. 31 Under appropriate conditions, it is also possible to form dicarbon-disubstituted vinylidenes starting from unfunctionalized internal alkynes.…”

Silylosmium Anions for the Synthesis of Borylosmium(II) Complexes by Salt Elimination

“…Other oxidative addition strategies have yielded notable osmium boryl complexes . In this communication, however, we disclose the preparation of osmium anions for the synthesis of osmium boryl complexes through a salt elimination reaction …”