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

The coordination chemistry of the PN bicyclic ligand 7-<i>tert</i>-butyl-1,5-bis­(carbomethoxy)-6,8-bis­(<i>p</i>-dimethylaminophenyl)-3-methyl-3-aza-7-phosphabicyclo­[3.3.1]­nonan-9-one (<b>1</b>) was explored with rhodium, palladium and platinum, and a wide range of complexes were synthesized, including [ML₂(<b>1</b>)] (M = Pd, Pt; L = Cl, Me), [ML­(<b>1</b>)] (M = Rh, Pd, Pt; L = C₂H₄, cycloocta-1,5-diene (cod), norborn-2-ene (nb)) and [PtL­(<b>1</b>)]­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)­(<b>1</b>-2H)] and [Pt­(1–3-η-C₈H₁₃)­(<b>1</b>-H)]. Further reaction of [Pt­(C₂H₄)­(<b>1</b>-2H)] yielded the trans- and cis-hydroxo-bridged dimers [Pt₂(μ-OH)₂(<b>1</b>-H)₂]. The nitrogen donor atom is not coordinated to the platinum metal center in the cyclometalated PN complexes. Protonation of [Pt­(nb)­(<b>1</b>)] with CH₂(SO₂CF₃)₂ produced [PtH­{CH­(SO₂CF₃)₂}­(<b>1</b>)]. Similarly, protonation of [Pt­(nb)­(<b>1</b>)] with CHPh­(SO₂CF₃)₂ gave the norbornyl agostic complex [Pt­(η²-C₇H₁₁)­(<b>1</b>)]­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 <b>1</b> and the ¹⁵N chemical shift