Chiral amino-phosphine and amido-phosphine complexes of Ir and Mg. Catalytic applications in olefin hydroamination

• Published in: Dalton transactions : an international journal of inorganic chemistry 2016-08, Vol.45 (3), p.1228-124
• Main Authors: Schmid, Bernhard, Frieß, Sibylle, Herrera, Alberto, Linden, Anthony, Heinemann, Frank W, Locke, Harald, Harder, Sjoerd, Dorta, Romano
• Format: Article
• Language: English
• Subjects: Backbone; Crystal structure; Deformation; Iridium; Iridium compounds; Low energy; Olefins; Solvents
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c6dt01146b

The reactions of rac - and ( S , S )- trans -9,10-dihydro-9,10-ethanoanthracene-11,12-diamine (ANDEN) with PClPh 2 in the presence of NEt 3 yield the chiral amino-phosphine ligands rac - 6 and ( S , S )- 6 , respectively, on multi-gram scales. Both forms of 6 react quantitatively with MgPh 2 to afford the C 2 -symmetric, N-bound Mg amidophosphine complexes rac - 7 and ( S , S )- 7 . The former crystallizes as a racemic conglomerate, which is a rare occurrence. Mixing ( S , S )- or rac - 6 with [IrCl(COE) 2 ] 2 leads in both cases to the homochiral dinuclear chloro-bridged P-ligated aminophosphine iridium complexes ( S , S , S , S )- 9 and rac - 9 in excellent yields. X-ray quality single crystals only grow as the racemic compound (or 'true racemate') rac - 9 thanks to its lowered solubility. In the coordinating solvent CH 3 CN, rac - 9 transforms in high yield into mononuclear Ir-complex rac - 10 . The crystal structures of compounds rac - 6 , ( S , S )- 7 , rac - 9 , and rac - 10 reveal the ambidentate nature of the P-N function: amide-coordination in the Mg-complex ( S , S )- 7 and P-chelation of the softer Ir( i ) centres in complexes rac - 9 and rac - 10 . Furthermore, the crystal structures show flexible, symmetry lowering seven-membered P-chelate rings in the Ir complexes and a surprising amount of deformation within the ANDEN backbone. The simulation of this deformation by DFT and SCF calculations indicates low energy barriers. ( S , S )- 7 and ( S , S , S , S )- 9 catalyze the intra- and intermolecular hydroamination of alkenes, respectively: 5 mol% of ( S , S )- 7 affords 2-methyl-4,4′-diphenylcyclopentyl amine quantitatively (7% ee), and 2.5 mol% of ( S , S , S , S )- 9 in the presence of 5.0 mol% co-catalyst (LDA, PhLi, or MgPh 2 ) gives exo -(2-arylamino)bornanes in up to 68% yield and up to 16% ee. Chiral amido-phosphine magnesium and amino-phosphine iridium complexes catalyze intra- and intermolecular olefin hydroamination reactions, respectively.