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Coordination Chemistry of a Bicyclic 3-Aza-7-phosphabicyclo[3.3.1]nonan-9-one Ligand

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posted on 09.04.2012, 00:00 by Almas I. Zayya, John L. Spencer
The coordination chemistry of the PN bicyclic ligand 7-tert-butyl-1,5-bis­(carbomethoxy)-6,8-bis­(p-dimethylaminophenyl)-3-methyl-3-aza-7-phosphabicyclo­[3.3.1]­nonan-9-one (1) was explored with rhodium, palladium and platinum, and a wide range of complexes were synthesized, including [ML2(1)] (M = Pd, Pt; L = Cl, Me), [ML­(1)] (M = Rh, Pd, Pt; L = C2H4, cycloocta-1,5-diene (cod), norborn-2-ene (nb)) and [PtL­(1)]­CH­(SO2CF3)2 (L = 1-σ,4–5-η-C8H13, 1–3-η-C8H13). Cycloplatination at the ortho positions of the 6,8-bis­(dimethylaminophenyl) substituents led to the formation of [Pt­(C2H4)­(1-2H)] and [Pt­(1–3-η-C8H13)­(1-H)]. Further reaction of [Pt­(C2H4)­(1-2H)] yielded the trans- and cis-hydroxo-bridged dimers [Pt2(μ-OH)2(1-H)2]. The nitrogen donor atom is not coordinated to the platinum metal center in the cyclometalated PN complexes. Protonation of [Pt­(nb)­(1)] with CH2(SO2CF3)2 produced [PtH­{CH­(SO2CF3)2}­(1)]. Similarly, protonation of [Pt­(nb)­(1)] with CHPh­(SO2CF3)2 gave the norbornyl agostic complex [Pt­(η2-C7H11)­(1)]­CPh­(SO2CF3)2, as confirmed by X-ray crystallography. PN metal complexes in which the central carbonyl group was hydrated to a geminal diol were also observed. 15N NMR data, obtained from 1H–15N HMBC experiments, showed no explicit relationship between the coordination mode of the nitrogen group in 1 and the 15N chemical shift.