Phenalenyl-based ligand for transition metal chemistry: Application in Henry reaction

ARUP MUKHERJEE^a, TAMAL K SEN^a, SWADHIN K MANDAL^a,*, DANIEL KRATZERT^b, DIETMAR STALKE^b, ALEXANDER DÖRING^b and CAROLA SCHULZKE^c

^aDepartment of Chemical Sciences, Indian Institute of Science Education and Research (IISER)-Kolkata, Mohanpur 741252, India

^bGeorg-August-Universität Göttingen, Tammannstr. 4, 37077 Göttingen, Germany

^cSchool of Chemistry, Trinity College Dublin, Dublin 2, Ireland

e-mail: swadhin.mandal@iiserkol.ac.in

Abstract. We report the synthesis and characterization of the first transition metal complex of a phenalenyl-based ligand. The reaction of Cu(OAc)₂.H₂O with 9-N-methylamino-1-N′ -methylimino-phenalene (LH) in 1:1 stoichiometric ratio results in the formation of a mononuclear copper complex [LCu(OAc)] (1). The molecular structure of 1 was established by X-ray crystallography. The electrochemistry of 1 indicates the formation of an anionic radical by one electron reduction into the non-bonding molecular orbital of the phenalenyl system. The complex 1 efficiently catalyses the C–C bond forming Henry reaction.

Graphical Abstract. We report the synthesis and characterization of the first transition metal complex of a phenalenyl-based ligand. The electrochemistry of the copper phenalenyl complex reveals the formation of an anionic radical by one electron reduction. The copper phenalenyl complex efficiently catalyses Henry reaction with very high isolated yield at mild reaction conditions.

Keywords. Cu-complex; phenalenyl; radical; X-ray crystallography; Henry reaction.