Hypervalent, low-coordinate phosphorus(III) centers in complexes of the phosphadiazonium cation with chelate ligands.
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.
Burford
Neil
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Department of Chemistry and Atlantic Region Magnetic Resonance Centre, Dalhousie University, Halifax, Nova Scotia B3H 4J3, Canada. neil.burford@dal.ca
Phillips
Andrew D
AD
Spinney
Heather A
HA
Lumsden
Michael
M
Werner-Zwanziger
Ulrike
U
Ferguson
Michael J
MJ
McDonald
Robert
R