Dinuclear complexes of MnII, CoII and ZnII triply bridged by carboxylate groups: structures, properties and catalase-like function ‡

Abstract

1,3-Bis[(2-dimethylaminoethyl)iminomethyl]benzene (baib), having two isolated metal-binding sites separated by a m-xylenylene group, formed dinuclear metal() complexes [Mn 2 (baib)(O 2 CPh) 3 ]BPh 4 ؒMeCN 1, [Mn 2 (baib)-(O 2 CPh) 3 (NCS)] 2, [Co 2 (baib)(O 2 CMe) 3 ]BPh 4 3, [Co 2 (baib)(O 2 CPh) 3 ]BPh 4 4 and [Zn 2 (baib)(O 2 CMe) 3 ]BPh 4 5. The structure of a dimethylformamide adduct of 2, [Mn 2 (baib)(O 2 CPh) 3 (NCS)]ؒdmf 2Ј, was determined. It has a dinuclear core bridged by two benzoate groups in the symmetric η 1 :η 1 mode and one benzoate group in the asymmetric η 1 :η 2 mode, with a Mn ؒ ؒ ؒ Mn separation of 3.501(4) Å. A thiocyanate ion co-ordinates to one Mn through its nitrogen; both manganese ions are six-co-ordinated. Complex 3 was also characterized crystallographically. The pair of cobalt ions are bridged by three acetate groups in the η 1 :η 1 mode with a Co ؒ ؒ ؒ Co intermetallic separation of 3.449(2) Å. The geometry about each Co is a trigonal bipyramid. The complexes 4ؒMeCN (4Ј) and 5 have dinuclear cores essentially similar to that of 3: Co ؒ ؒ ؒ Co 3.482(2) and Zn ؒ ؒ ؒ Zn 3.4648(7) Å. The physicochemical properties of the complexes are reported together with the catalase-like function of 1-3.

Mono-and polynuclear CoII complexes with 2-hydroxy-6-methylpyridine

“…According to X ray diffraction data, the metal carb oxylate core of cluster 9 is structurally similar to that of the known hexanuclear complex Co 6 (µ 3 OH) 2 (µ 3 OOCCMe 3 ) 2 (µ 2 OOCCMe 3 ) 8 (HOOCCMe 3 ) 4 (10), which we have synthesized earlier 17 by the reaction of a stoichiometric amount of pivalic acid with polymeric co balt pivalate.…”

“…HOOCCMe 3 )4 •C 6 H 6 (9•C 6 H 6 ). A. Benzene (30 mL) was added to a mixture of the poly mer [Co(OH) n (µ OOCCMe 3 ) 2-n ] x (x = 0.05-0.1) (0.19 g, 0.73 mmol) (per formula unit Co(OOCCMe 3 ) 2 ) and 2 hydroxy 6 methylpyridine (0.08 g, 0.73 mmol), and the reaction mixture was stirred under argon at 80 °C for 30 min until the reagents were completely dissolved.…”

Designer ligands. Part 9.1 Catalytic activity of biomimetic cobalt(II) and copper(II) complexes of multidentate ligands

“…In computer models of the Co(II) complexes 3 and 7b, the octahedral Co ions are separated by 3.1 Å and 3.4 Å, respectively. Interestingly, Yamami et al 12 have reported Co-Co separations of 3.4-3.5 Å in the crystal structures of Co (II) complexes which catalyse the disproportionation of hydrogen peroxide. ).…”

“…1 Simple Co(II) complexes have also been shown to form metal complexoxygen adducts, 2 and Co(II) complexes have been used to model biological processes. 12 In this communication, we report the preparation and catalytic activity of Co(II) and Cu(II) complexes of selected multidentate ligands. …”

Designer ligands: The search for metal ion selectivity

“…10 Interestingly, Co(II) complexes have been observed to form metal-oxygen adducts, 16 and have been used to model biological processes. 17 With the exception of complex 9c, the Cu(II) complexes appeared to be polymeric, and their catalytic activity suggests that, in these cases at least, the copper ions are sufficiently close to permit dioxygen bridging and subsequent substrate binding.…”