Steric effects enforce double stereoselective N-coordination in twelve-membered binuclear palladium(II)-complexes containing chiral bridging aminoalkyl-phosphine ligands

Publication date: Available online 28 November 2017 Source:Journal of Organometallic Chemistry Author(s): Zsófia Császár, Kristóf Stágel, Szabolcs Balogh, Attila Bényei, György Lendvay, Gergely Farkas, József Bakos The configuration of the ligand's N-substituent was found to determine the stoichiometry and strict stereoselectivity of N-coordination in twelve-membered palladium dimers 2a-b. The novel palladium(II)-complexes 2a-b have been synthesized in the reaction of [Pd(COD)Cl2] and optically pure (S,S)-pentane-2,4-diyl based aminoalkyl-phosphine ligands Ph2PCH(CH3)CH2CH(CH3)NHR 1a-b (R = (R)-α-phenylethyl 1a, R = (R)-α-(1-naphthyl)ethyl 1b) with stereogenic nitrogen atom, and studied by various 1D and 2D NMR techniques in solution and in the case of 2a by single-crystal X-ray diffraction. As an unprecedented case, ligands 1a-b were found to yield exclusively 12-membered cyclic dinuclear Pd(II)-complexes with stereospecific coordination of both of the donor nitrogen atoms. Formation of the 12-membered ring is shown to reduce the steric hindrance of the bulky substituents with respect to the six-membered ring. Graphical abstract

Source: Journal of Organometallic Chemistry - November 30, 2017 Category: Chemistry Source Type: research