title: Synthesis and reactivity of BINEPINE-based chiral Fe(II) PNP pincer complexes.
abstract: A new asymmetric chiral PNP ligand based on the 2,6-diaminopyridine scaffold featuring aR-BINEPINE moiety was prepared. Treatment of anhydrous FeX2(X = Cl, Br) with 1 equiv of PNP-iPr,BIN at room temperature afforded the coordinatively unsaturated paramagnetic complexes [Fe(PNP-iPr,BIN)X2]. The structure of [Fe(PNP-iPr,BIN)Cl2] is described. Both complexes react readily with the strong π-acceptor ligand CO in solution to afford selectively the diamagnetic complexestrans-[Fe(PNP-iPr,BIN)(CO)X2] in quantitative yield. Due the lability of the CO ligand, these complexes are only stable under a CO atmosphere and isolation in pure form was not possible. The preparation of the carbonyl hydride complex [Fe(PNP-iPr,BIN)(H)(CO)Br] was achieved albeit in low yields via a one pot procedure by treatment of [Fe(PNP-iPr,BINEP)Br2] with CO and subsequent reaction with Na[HBEt3]. This complex was obtained as an inseparable mixture of two diastereomers in a ca. 1:1 ratio and was tested as catalyst for the hydrogenation of ketones. The catalyst showed acceptable activity under mild conditions (5 bar H2, room temperature) with yields up to >99 % within 18 h.
authors.affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163-OC, 1060 Vienna, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Schröder-Holzhacker
authors.affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163-OC, 1060 Vienna, Austria.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Gorgas
authors.affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, 1060 Vienna, Austria.
authors.forename: Berthold
authors.initials: B
authors.lastname: Stöger
authors.affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163-OC, 1060 Vienna, Austria.
authors.forename: Karl
authors.initials: K
authors.lastname: Kirchner
keywords: Carbon monoxide; Chiral phosphines; Iron; Pincer ligands