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

The reaction of [(MoO2)-O-VI(acac)(2)] (acac=acetylacetonate anion) with N,N,N',N'-tetrakis(2-hydroxy-3,5-disubstitutedbenzyl)-1,2-di-aminoethane 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 [H(4)en(3,5-dtbb)(4), I] and 3-t-butyl-5-methyl substituents [H(4)en(3-tb,5-mb)(4), II], result in the formation of complexes, [{(MoO2)-O-VI(MeOH)}H(2)en-(3,5-dtbb)(4)] (1) and [{(MoO2)-O-VI(MeOH)}H(2)en-(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 [H(4)en(3,5-dmb)(4), III] and 3,5-dichloro substituents [H(4)en(3,5-dcb)(4), IV] facilitate mononuclear alpha-cis, symmetric complexes, [{(MoO2)-O-VI}H(2)en(3,5-dmb)(4)] (3) and [{(MoO2)-O-VI}H(2)en(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 [(MoO2)-O-VI(acac)(2)] in DMF-MeOH gives homo-binuclear complexes, [{(MoO2)-O-VI(DMF)}(2)en(3,5-dtbb)(4)] (5) and [{(MoO2)-O-VI(DMF)}(2)en(3-tb,5-mb)(4)] (6), respectively. Reaction of (VO)-O-V(OEt)(3) with complexes 1-4 in refluxing EtOH caused the displacement of cis-[(MoO2)-O-VI] group by [(VO)-O-V] along with the breaking of one of the arms of ligand and the formation of oxidovanadium(V) complexes, [{(VO)-O-V}en(3,5-dtbb)(3)] (7), [{(VO)-O-V} en(3-tb,5-mb)(3)] (8), [{(VO)-O-V}en(3,5-dmb)(3)] (9), and [{(VO)-O-V}en(3,5-dcb)(3)] (10). This is an example of trans-metalation. Complexes [{(VO)-O-V}Hen(3,5-dmb)(4)] (11) and [{(VO)-O-V}Hen(3,5-dcb)(4)] (12) upholding all four arms have also been obtained by direct reaction of ligands III and IV, respectively, with (VO)-O-V(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.

Automated summary

The reaction between [(MoO2)-O-VI(acac)(2)] and N,N,N',N'-tetrakis(2-hydroxy-3,5-disubstitutedbenzyl)-1,2-di-aminoethane with different substituents on the phenyl ring results in the formation of various mononuclear complexes, shedding light on the influence of ligand substituents on complex structures.