Hydrogenation of esters to alcohols in the presence of an mn-pnn complex

A method for hydrogenating an ester of the general formula (III)

• in which the radicals Ra and Rb are each independently a carbon-containing organic, linear or branched, non-cyclic or cyclic, saturated or unsaturated, aliphatic, aromatic or araliphatic radical which is unsubstituted or interrupted or substituted by heteroatoms or functional groups and has a molar mass of 15 to 10 000 g/mol, wherein the two radicals Ra and Rb may also be bonded to each other,
• with molecular hydrogen to give the alcohols
• at a temperature of 50 to 200° C. and a pressure of 0.1 to 20 MPa abs in the presence of a manganese(I) complex, in which the manganese complex comprises a tridentate ligand L of the general formula (II)
• and comprises at least two carbonyl ligands, wherein
• R1, R2 are each independently an aliphatic hydrocarbon radical having 1 to 8 carbon atoms, an aromatic hydrocarbon radical having 6 or 10 carbon atoms or an araliphatic hydrocarbon radical having 7 to 12 carbon atoms, where the hydrocarbon radicals specified are unsubstituted or substituted by 1 to 3 methoxy, thiomethoxy or dimethylamino groups, and the two radicals R1 and R2 may be bonded to each other to form a 5- to 10-membered ring including the phosphorus atom,
• R3, R4, R5, R6, R10, R11 are each independently hydrogen, linear C1 to C4-alkyl, branched C3 to C4-alkyl, methoxy, hydroxyl, trifluoromethyl, nitrile or dialkylamino each independently having 1 to 4 carbon atoms per alkyl group,
• R7, R8, R9 are each independently hydrogen, linear C1 to C4-alkyl or branched C3 to C4-alkyl, n, m are each independently 0 or 1, and the solid-dashed double lines are a single or double bond, with the proviso that
• in the case of n=1, both solid-dashed double lines are a single bond and m is 1, and
• in the case of n=0, one solid-dashed double line is a single bond and the other solid-dashed double line is a double bond,
• wherein, in the case of a double bond on the side facing the phenyl ring m=1, in the case of a double bond on the side
• facing the pyridyl ring m=0, or both solid-dashed double lines are a single bond and m
• equals 1.