New Acylhydrido‐ and Diacylrhodium(III) Organocomplexes Derived from 8‐Quinolinecarbaldehyde and/or o‐(Diphenylphosphanyl)benzaldehyde

The acylhydridorhodium(III) complex [RhHCl{PPh2(o-C6H4CO)}(py)2] (1) reacts with 8-quinolinecarbaldehyde (C9H6NCHO) to afford mixed diacyl [RhCl(C9H6NCO){PPh2(o-C6H4CO)}(py)] (2) with acyl groups trans to chlorine and to pyridine. Complex 1 undergoes displacement of pyridine by 2-(aminomethyl)pyridine (ampy) or diphosphanes to give hydridoacyl neutral [RhHCl{PPh2(o-C6H4CO)}(LL)] [LL = ampy (3), bis(diphenylphosphanyl)methane (dppm, 5), 1,3-bis(diphenylphosphanyl)propane (dppp, 6), 1,2-bis(diphenylphosphanyl)ethane (dppe, 7)] with hydride trans to chloride. Complex 3 exchanges hydride with chloride to give [Rh(Cl)2{PPh2(o-C6H4CO)}(ampy)] (4). The reaction of 2 with bidentate N-donor ligands yields cationic mixed diacyl [Rh(C9H6NCO){PPh2(o-C6H4CO)}(NN)]+ species [NN = 2,2'-bipyridine (bipy, 8), ampy (9)]. Neutral or cationic diacyl complexes that contain two acylquinoline fragments can be obtained by the reaction of dimer [Rh(mu-Cl)(C9H6NCO)2]2 (10) with pyridine to give [Rh(Cl)(C9H6NCO)2(py)] (11) or with bidentate N- or P-donor ligands (LL) to afford [Rh(C9H6NCO)2(LL)]+ [LL = dppm (12), dppe (13), dppp (14), 1,4-bis(diphenylphosphanyl)butane (15), ampy (16), 8-aminoquinoline (17), biacetyldihydrazone (18), bipy (19)] with the acyl groups trans to LL. Complex 11 is highly fluxional in solution. At low temperatures, the acylquinoline chelate opens to allow an intramolecular exchange between 11a and 11b (Delta H-+(+) = 10.1 +/- 0.2 kcal?mol1 and Delta S-+(+) = 1.0 +/- 0.1 cal K1 mol1), and pyridine dissociation occurs at room temperature. All the complexes were characterized spectroscopically. Single crystal X-ray diffraction analysis was performed on 2.