Ortho-CH activation of aromatic ketones, partially fluorinated aromatic ketones, and aromatic imines by a trihydride-stannyl-osmium(IV) complex

Complex OsH3(SnPh2Cl){eta(2)-CH2=C(CH3)(PPr2)-Pr-i}((PPr3)-Pr-i) (1) reacts with acetophenone and benzophenone to give OsH2(SnPh2Cl){C6H4C(O)R}((PPr3)-Pr-i)(2) (R = CH3 (2), Ph (3)). In the solid state, the structure of 2 determined by X-ray diffraction analysis can be described as a pentagonal bipyramid with the phosphorus atoms of the phosphines occupying axial positions. In solution the hydride ligands of 2 and 3 undergo a thermally activated site exchange process. The activation parameters for the exchange are DeltaH(not equal) = 11.9 +/- 0.5 kcal(.)mol(-1) and DeltaS(not equal) = -0.7 +/- 1.2 cal(.)mol(-1.)K(-1) for 2 and DeltaH(not equal) = 11.8 +/- 0.2 kcal(.)mol(-1) and DeltaS(not equal) = -2.6 +/- 1.9 cal(.)mol(-1.)K(-1) for 3. The reaction of 1 with perdeuterated benzophenone affords the hydridedeuteride Os(H)(D)(SnPh2Cl){C6D4C(O)C6D5}((PPr3)-Pr-i)(2) (3-d(10)), suggesting that the activation takes place on the monohydride intermediate OsH(SnPh2Cl)((PPr3)-Pr-i)(2). The reaction pathway for the formation of this intermediate is evaluated by DFT calculations. Complex 1 also reacts with 2,3,4,5,6-pentafluorobenzophenone, 2-fluoroacetophenone, and benzophenone imine. The reactions with the partially fluorinated ketones give OsH2(SnPh2Cl){C6H4C(O)-C6F5}((PPr3)-Pr-i)(2) (4) and OsH2(SnPh2Cl){C6H3FC(O)CH3}((PPr3)-Pr-i)(2) (5). In solution, the hydride ligands of 4 and 5 also exchange their positions. In this case, the activation parameters are DeltaH(not equal) = 12.6 +/- 0.5 kcal(.)mol(-1) and DeltaS(not equal) = -2.9 +/- 1 cal(.)mol(-1.)K(-1) for 4 and DeltaH(not equal) = 11.2 +/- 0.4 kcal(.)mol(-1) and DeltaS(not equal) = -2.8 +/- 1.1 cal(.)mol(-1.)K(-1) for 3. The reaction of 1 with benzophenone imine leads to OsH2(SnPh2Cl){C6H4C(NH)C6H5}((PPr3)-Pr-i)(2) (6), which has been characterized by X-ray diffraction analysis. The structure reveals an intramolecular Cl...H-N hydrogen bond between the chlorine bonded to the tin atom and the hydrogen of the imine. Treatment of 6 with KOH affords OsH2(SnPh2OH){C6H4C(NH)C6H5}((PPr3)-Pr-i)(2) (7). The X-ray diffraction analysis of 7 shows a intramolecular O...H-N hydrogen bond and intermolecular HO...H interactions between the oxygen and the O-H hydrogen atom of two adjacent molecules in the crystal. DFT calculations on the model compounds OsH2{Sn(CH=CH2)(2)Cl}{C6H4C(O)-CH3}(PH3)(2) (2t) and OsH2{Sn(CH=CH2)(2)X}{C6H4C(NH)CH3}(PH3)(2) (X = Cl (6t), OH (7t)) have allowed the complete determination of the hydride positions in 2, 6, and 7 and the full characterization of the hydrogen bonds in 6 and 7.