| Abstract |
The novel hexanuclear complexes [Cu4Fe2(OH)(Piv)(4)(tBuDea)(4)Cl]0.5CH(3)CN (1) and [Cu4Mn2(OH)(Piv)(4)(tBuDea)(4)Cl] (2) were prepared through one-pot self-assembly reactions of copper powder and iron(ii) or manganese(ii) chloride with N-tert-butyldiethanolamine (H(2)tBuDea) and pivalic acid (HPiv) in acetonitrile. Crystallographic studies revealed the uncommon molecular core type M-6(-X)(7)((3)-X)(2) in 1 and 2, which can be viewed as a combination of two trimetallic M-3(-X)(2)((3)-X) fragments joined by three bridging atoms. The analysis and classification of the hexanuclear complexes having a M-3(-X)(2)((3)-X) moiety as a core forming fragment using data from the Cambridge Structural Database (CSD) were performed. Variable-temperature (1.8-300 K) magnetic susceptibility measurements of 1 showed a decrease of the effective magnetic moment value at low temperature, indicative of antiferromagnetic coupling between the magnetic centres (J(Fe-Cu)/hc = -6.9 cm(-1), J(Cu-Cu)/hc = -4.1 cm(-1), J(Fe-Fe)/hc = -24.2 cm(-1)). Complex 1 acts as a catalyst in the reaction of mild oxidation of cyclohexane with H2O2, showing the yields of products, cyclohexanol and cyclohexanone, up to 17\% using pyrazinecarboxylic acid as a promoter. In the oxidation of cis-1,2-dimethylcyclohexane with m-chloroperoxybenzoic acid (m-CPBA), 70\% of retention of stereoconfiguration was observed for tertiary alcohols. Compound 1 also catalyses the amidation of cyclohexane with benzamide. In all three catalytic reactions the by-products were investigated in detail and discussed. |
