Synthesis of a Tris(phosphaalkene)phosphine Ligand and Fundamental Organometallic Reactions on Its Sterically Shielded Metal Complexes

• Published in: Organometallics 2016-07, Vol.35 (13), p.2224-2231
• Main Authors: Miura-Akagi, Preston M, Nakashige, Mika L, Maile, Caitlin K, Oshiro, Shelly M, Gurr, Joshua R, Yoshida, Wesley Y, Royappa, A. Timothy, Krause, Colleen E, Rheingold, Arnold L, Hughes, Russell P, Cain, Matthew F
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.6b00250

A new tris­(phosphaalkene)­phosphine ligand (1) was synthesized via phospha-Wittig methodology. Metalation of 1 with [RhCl­(C2H4)2]2 and [IrCl­(COE)2]2 (COE = cyclooctene) produced trigonal bipyramidal metal chlorides 2a (M = Rh) and 2b (M = Ir) in which the ligand coordinates in a tetradentate fashion. X-ray crystallographic studies on 1·1.5THF, 2a·5CHCl3, and 2b·2.5CHCl3 combined with DFT calculations revealed a pronounced change in hybridization of the phosphaalkene phosphorus atoms upon coordination to the Rh/Ir centers, resulting in highly sterically congested metal complexes. Nucleophilic substitution on 2a with NaN3 afforded Rh–N3 complex 3; computational analysis, IR spectroscopy, and 15N­{1H} NMR spectroscopy on isotopologue 15 N-3 provided additional structural insights. Halide abstraction of the chloride in 2b with AgOTf in the presence of acetonitrile afforded cationic Ir–NCMe complex 4. Evidence of the bound acetonitrile unit was obtained by 2D NMR spectroscopy and deuterium labeling studies.