Use of a transition metal catalyst comprising a tetradentate ligand for hydrogenation of esters and/or formation of esters, a process for hydrogenation of esters, a process for formation of esters and a transition metal complex comprising said tetradentate ligand

A transition metal complex of formula II:

• wherein M is ruthenium,
• wherein R1 are each independently selected from the group consisting of a C1 to C40 alkyl radical, a C3 to C40 cycloalkyl radical, a C2 to C40 heterocycloalkyl radical, a C6 to C40 aryl radical, and a C2 to C40 heteroaromatic radical, and
• wherein R2 are each independently selected from the group consisting of a C1 to C40 alkyl radical, a C3 to C40 cycloalkyl radical, a C2 to C40 heterocycloalkyl radical, a C6 to C40 aryl radical, and a C2 to C40 heteroaromatic radical, and
• wherein R3 is selected from the group consisting of a C1 to C40 alkyl radical, a C3 to C40 cycloalkyl radical, a C2 to C40 heterocycloalkyl radical, a C6 to C40 aryl radical, a C7 to C40 arylalkyl radical, and a C2 to C40 heteroaromatic radical, or
• wherein R3 is C(═O)R4, wherein R4 is selected from the group consisting of a hydrogen, a C1 to C40 alkyl radical, a C3 to C40 cycloalkyl radical, a C2 to C40 heterocycloalkyl radical, a C6 to C40 aryl radical, a C7 to C40 arylalkyl radical, and a C2 to C40 heteroaromatic radical, wherein R3 in each case is bound via a carbon atom to the oxygen atom.

A transition metal catalyst comprising:

• a transition metal complex of formula II:
• wherein M is ruthenium,
• wherein R1 are each independently selected from the group consisting of a C1 to C40 alkyl radical, a C3 to C40 cycloalkyl radical, a C2 to C40 heterocycloalkyl radical, a C6 to C40 aryl radical, and a C2 to C40 heteroaromatic radical, and
• wherein R2 are each independently selected from the group consisting of a C1 to C40 alkyl radical, a C3 to C40 cycloalkyl radical, a C2 to C40 heterocycloalkyl radical, a C6 to C40 aryl radical, and a C2 to C40 heteroaromatic radical, and
• wherein R3 is selected from the group consisting of a C1 to C40 alkyl radical, a C3 to C40 cycloalkyl radical, a C2 to C40 heterocy-cloalkyl radical, a C6 to C40 aryl radical, a C7 to C40 arylalkyl radical, and a C2 to C40 heteroaromatic radical, or
• wherein R3 is C(═O)R4, wherein R4 is selected from the group consisting of a hydrogen, a C1 to C40 alkyl radical, a C3 to C40 cycloalkyl radical, a C2 to C40 heterocycloalkyl radical, a C6 to C40 aryl radical, a C7 to C40 arylalkyl radical, and a C2 to C40 heteroaromatic radical, wherein R3 in each case is bound via a carbon atom to the oxygen atom;
• and
• one or more ligand comprising an anion selected from the group consisting of hydrides, alkoxides, aryloxides, carboxylates and acyls, or a neutral ligand selected from the group consisting of carbon monoxide, triaryl phosphines, amines, N-heterocyclic carbenes and isonitriles.