Complexes of Bis-ortho-cyclometalated Bisphosphinoaryl Ruthenium(II) Cations with Neutral Meta-bisphosphinoarene Ligands Containing and Agostic C-H...Ru Interaction

摘要

The synthesis, characterization, and reactivity of various ruthenium{II) complexes [Ru- (R- PCP)(R' -PCHP)] [OTfJ are presented. These complexes are highly dissymmetric and show fluxional behavior in solution. They contain one monoanionic, 773_P, C,P' -tridentate-bonded bisphosphinoarylligand (R-PCP = [C6H2(CH2PPh2)2-2,6-R-4]-; R = H or Br) and one neutral, trans-P,P'-bidentate-bonded bisphosphinoarene ligand (R'-PCHP = C6H3(CH2PPh2)2-3,5); R'-l). The C-H bond that is ortho to both CH2PPh2 substituents of the bidentate-bonded {' ligand is interacting with the metal center (i.e., has an agostic contact with the cationic ~;- ruthenium center). The location of the agostic proton in the lH NMR spectrum as well as f: the three-dimensional structure of these complexes in solution was obtained by means of ".' several two-dimensional NMR techniques rH-lH COSY, 3lp_lH COSY, l3C_lH COSY, lH NOESY, lH ROESY, and 3lp EXSY). The lJHC of the agostic contact amounted to 112 Hz, f which represents a reduction of 46 Hz in relation with the same coupling for this C- H bond .' in the free ligand. Furthermore, the molecular geometry of [Ru(H -PCP)(PCHP)] [OTfJ in , the solid state was established by single-crystal X-ray diffraction techniques, and the ~ structural features corroborate with the observations in solution. In the complex [Ru(H - ., PCP)(Br-PCHP)][OTf], interconversion of the cyclometalated and neutral bisphosphine [", ligands via exchange of the agostic hydrogen atom from the neutral to the cyclometalated ~ carbon to yield [Ru(Br-PCP)(H-PCHP)][OTf] was observed; A mechanistic proposal based t, on an aromatic electrophilic substitution is discussed. Moreover, the reaction of [RU(OSO2- :} CF3)(NCN)(PPh3)] (NCN = [C6H3(CH2NMe2)2-2,6]-) with the neutral bisphosphinoarene resulted in the quantitative formation of the new cyclometalated species [Ru(R-PCP)(R- PCHP)][OTf] with the net loss of the neutral bisaminoarene ligand NCHN and PPh3.