Hypervalent, low-coordinate phosphorus(III) centers in complexes of the phosphadiazonium cation with chelate ligands

Neil Burford; Andrew D Phillips; Heather A Spinney; Michael Lumsden; Ulrike Werner-Zwanziger; Michael J Ferguson; Robert McDonald

doi:10.1021/ja043691y

Hypervalent, low-coordinate phosphorus(III) centers in complexes of the phosphadiazonium cation with chelate ligands

J Am Chem Soc. 2005 Mar 23;127(11):3921-7. doi: 10.1021/ja043691y.

Authors

Neil Burford¹, Andrew D Phillips, Heather A Spinney, Michael Lumsden, Ulrike Werner-Zwanziger, Michael J Ferguson, Robert McDonald

Affiliation

¹ Department of Chemistry and Atlantic Region Magnetic Resonance Centre, Dalhousie University, Halifax, Nova Scotia B3H 4J3, Canada. neil.burford@dal.ca

PMID: 15771528
DOI: 10.1021/ja043691y

Abstract

Trifluoromethylsulfonyloxy-(2,4,6-tri-tert-butylphenylimino)phosphine, Mes*NPOTf (Mes = 2,4,6-tri-tert-butylphenyl, OTf = trifluoromethanesulfonate, triflate) reacts quantitatively with the multifunctional ligands 2,2'-bipyridine (2,2'-BIPY), N,N,N',N'-tetramethylethylenediamine (TMEDA), 1,2-bis(diethylphosphino)ethane (DEPE), 1,2-bis(diphenylphosphino)ethane (DIPHOS), and N,N,N',N' ',N' '-pentamethyldiethylenetriamine (PMDETA) to give the Lewis acid-base complexes [Mes*NP(2,2'-BIPY)][OTf], [Mes*NP(TMEDA)][OTf], [Mes*NP(DIPHOS)][OTf], [Mes*NP(DEPE)][OTf], and [Mes*NP(PMDETA)][OTf], respectively. Single-crystal X-ray diffraction studies indicate that the closest contact of the ligand donor atoms occurs at phosphorus in all cases, affecting significant displacement of the OTf anion. The resulting cations [Mes*NP(L)]+ are best described as complexes of a neutral chelating ligand on a phosphadiazonium Lewis acceptor, and highlight the potential for electron-rich centers to behave as Lewis acids despite the presence of a lone pair of electrons at the acceptor site. More importantly, the new complexes represent rare examples of systems containing hypervalent, low-coordinate phosphorus(III) centers.