Substituent Controlled Synthesis of Dioxidomolybdenum(VI) Complexes of N,N,N’,N’‐Tetrakis(2‐Hydroxyl‐3,5‐Disubstitutedbenzyl)‐1,2‐Diaminoethane, Their Trans‐Metalation to Oxidovanadium(V) Complexes and Biocatalytic Applications

Abstract

AbstractThe reaction of [MoVIO2(acac)2] (acac=acetylacetonate anion) with N,N,N’,N’‐tetrakis(2‐hydroxy‐3,5‐disubstitutedbenzyl)‐1,2‐diaminoethane having different 3,5‐disubstituents on the phenyl ring in 1 : 1 molar ratio in MeOH results in the formation of two different types of substituent controlled mononuclear complexes. Ligands having 3,5‐di‐t‐butyl substituents [H4en(3,5‐dtbb)4, I] and 3‐t‐butyl‐5‐methyl substituents [H4en(3‐tb,5‐mb)4, II], result in the formation of complexes, [{MoVIO2(MeOH)}H2en(3,5‐dtbb)4] (1) and [{MoVIO2(MeOH)}H2en(3‐tb,5‐mb)4] (2), respectively. In these complexes ligands behave as a bis(dibasic ONO) donor and coordinate to only one side of the ONO functionalities. On the contrary, ligands having 3,5‐dimethyl substituents [H4en(3,5‐dmb)4, III] and 3,5‐dichloro substituents [H4en(3,5‐dcb)4, IV] facilitate mononuclear α‐cis, symmetric complexes, [{MoVIO2}H2en(3,5‐dmb)4] (3) and [{MoVIO2}H2en(3,5‐dcb)4] (4), respectively. Here ligands behave as a dibasic ONNO tetradentate. Further reaction of complexes 1 and 2 with equimolar amount of [MoVIO2(acac)2] in DMF‐MeOH gives homo‐binuclear complexes, [{MoVIO2(DMF)}2en(3,5‐dtbb)4] (5) and [{MoVIO2(DMF)}2en(3‐tb,5‐mb)4] (6), respectively. Reaction of VVO(OEt)3 with complexes 1–4 in refluxing EtOH caused the displacement of cis‐[MoVIO2] group by [VVO] along with the breaking of one of the arms of ligand and the formation of oxidovanadium(V) complexes, [{VVO}en(3,5‐dtbb)3] (7), [{VVO}en(3‐tb,5‐mb)3] (8), [{VVO}en(3,5‐dmb)3] (9), and [{VVO}en(3,5‐dcb)3] (10). This is an example of trans‐metalation. Complexes [{VVO}Hen(3,5‐dmb)4] (11) and [{VVO}Hen(3,5‐dcb)4] (12) upholding all four arms have also been obtained by direct reaction of ligands III and IV, respectively, with VVO(OEt)3. Biomimetic catalytic activity similar to enzymes haloperoxidases was performed with thymol and other phenol derivatives and all these complexes serve as excellent functional models.