A new cyclometalation motif: Synthesis, characterization, structures, and reactivity of pallada-and platinacycles with a bidentate {C(sp2, cyrhetrene), N} - Ligand

Abstract

The synthesis, characterization, X-ray crystal structure, and study of the reactivity of the novel cyretrenyl ligand [{(μ5-C 5H4-2-C5H4N) }Re(CO) 3 (1) with Pd(OAc) 2 or [MCl2(DMSO) 2] (M = Pd, Pt) are reported. These studies have allowed us to obtain the bis-μ-ligand cyclopalladated complexes [Pd{[k2-C, N-(μ5-C 5H3) -2(C5H4N)]Re(CO) 3) }(μ-X)]2 (X = OAc (2a), Cl (4a)) and monomeric pallada-and platinacycles of the general formula [M{[k2-C, N-(μ5- C5H3) -2(C5H4N)]Re-(CO) 3}(X) (L)] (M = Pd, L = PPh3, X = OAc (3a), Cl (5a) ; M = Pd, L = DMSO, X = Cl (6a) ; M = Pt, X = Cl, L = PPh3 (5b), DMSO (6b)), where compound 1 acts as a {C(sp2, cyrhetrene), N} - bidentate ligand. All complexes were characterized by elemental analyses, infrared spectroscopy, and one-and twodimensional NMR. The X-ray crystal structures of 5a 3 1/2CH2Cl2, 5b, 6a 3CH2Cl 2, and 6b confirm (a) the existence of the five-membered metallacycle, (b) the {C(sp2, cyrhetrene), N} - mode of binding of the metallo ligand 1, and (c) the cis arrangement between the metalated carbon and the neutral L ligand s (PPh3 or DMSO) in these products. A comparative study of the structures, spectroscopic properties, and reactivities of the new cyclometalated compounds and those of their analogues with a bidentate {C(sp2, ferrocene), N} - ligand is also reported. © 2011 American Chemical Society.