Platinum(II) and Palladium(II) Dibenzo[a,e]cyclooctatetraene (DBCOT) Oxo and Halide Complexes: Comparison to 1,5-COD Analogues

Abstract

The dialkene complexes L2MCl2 (M = Pt, Pd, L2 = dibenzo[a,e]cyclooctatetraene (DBCOT)) were prepared by treatment of MCl42- salts with L2. Comparison of the solid-state structures with those of the analogous 1,5-cyclooctadiene (COD) complexes shows strong congruence of the structures. Competition experiments between DBCOT and COD show that COD bonds more strongly to the Pt(II) center. In contrast, Ir(I) bonds slightly better to DBCOT. Reaction of PtCl2(DBCOT) with NaI gives PtI2(DBCOT), which reacts with PhMgBr to give PtPh2(DBCOT). 195Pt NMR data indicate a less electron-rich Pt center in the DBCOT complexes as compared to the analogous COD complexes. Treatment of PtCl2(DBCOT) with [(Ph3PAu)3(μ3-O)](BF4) yields trimeric [Pt(μ3-O)(DBCOT)(AuPPh3)]3(BF4)3, which contains a six-membered Pt3O3 ring in a twist-boat configuration. Au−Au and Au−Pt interactions may help stabilize the solid-state structure, but NMR and mass spectral data indicate a dynamic structure in solution and the likely presence of other oli...