Bhattacharjee Jayeeta, Bockfeld Dirk, Tamm Matthias
Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany.
J Org Chem. 2022 Jan 21;87(2):1098-1109. doi: 10.1021/acs.joc.1c02377. Epub 2022 Jan 10.
The reactions of the N-heterocyclic carbene-phosphinidene adducts (NHC)PSiMe and (NHC)PH with the dinuclear ruthenium and osmium complexes [(η--cymene)MCl] (M = Ru, Os) afforded the half-sandwich complexes [(η--cymene){(NHC)P}MCl] and [(η--cymene){(NHC)PH}MCl] with two- and three-legged piano-stool geometries, respectively (NHC = IDipp, IMes; IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene). The complexes were initially tested as precatalysts for the hydroboration of benzonitrile, and the most active species, the ruthenium complex [(η--cymene){(IMes)P}RuCl], was further used for the efficient hydroboration of a wide range (ca. 50 substrates) of nitriles, carboxylic esters, and carboxamides in neat pinacolborane (HBpin) under comparatively mild reaction conditions (60-80 °C, 3-5 mol % catalyst loading). Preliminary mechanistic and kinetic studies are reported, and stoichiometric reactions with HBpin indicate the initial formation of the monohydride complex [(η--cymene){(IMes)P}RuH] as the putative catalytically active species.
氮杂环卡宾-磷烯加合物（NHC）PSiMe和（NHC）PH与双核钌和锇配合物[(η⁶-cymene)MCl]（M = Ru，Os）反应，分别得到具有两腿和三腿钢琴凳几何构型的半三明治配合物[(η⁶-cymene){(NHC)P}MCl]和[(η⁶-cymene){(NHC)PH}MCl]（NHC = IDipp，IMes；IDipp = 1,3-双(2,6-二异丙基苯基)咪唑啉-2-亚基；IMes = 1,3-双(2,4,6-三甲基苯基)咪唑啉-2-亚基）。这些配合物最初被测试作为苯甲腈硼氢化反应的预催化剂，其中活性最高的物种，即钌配合物[(η⁶-cymene){(IMes)P}RuCl]，进一步用于在相对温和的反应条件（60 - 80 °C, 3 - 5 mol%催化剂负载量）下，对大量（约50种底物）腈、羧酸酯和羧酰胺在纯频哪醇硼烷（HBpin）中的高效硼氢化反应。报道了初步的机理和动力学研究，与HBpin的化学计量反应表明，最初形成的单氢化物配合物[(η⁶-cymene){(IMes)P}RuH]是假定的催化活性物种。
