Copper Complexes of Mono- and Ditopic [(Methylthio)methyl]borates: Missing Links and Linked Systems En Route to Copper Enzyme Models
✍ Scribed by Kai Ruth; Sandor Tüllmann; Hannes Vitze; Michael Bolte; Hans-Wolfram Lerner; Max C. Holthausen; Matthias Wagner
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 539 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
TMEDA‐free (TMEDA: tetramethylethylenediamine) LiCH~2~SMe is a suitable reagent for the selective introduction of (methylthio)methyl groups into PhBBr~2~ and its p‐silylated derivative Me~3~SiC~6~H~4~BBr~2~. The resulting compounds, R*C~6~H~4~B(Br)(CH~2~SMe) (R*=H: 2; R*=SiMe~3~: 7) and PhB(CH~2~SMe)~2~ (3), form cyclic dimers through BS adduct bonds in solution and in the solid state. Compounds 2 and 3 have successfully been used for preparing the (N~2~S) scorpionate [PhBpz~2~(CH~2~SMe)]^−^ ([5]^−^) (pz: pyrazol‐1‐yl) and the (NS~2~) scorpionate [PhBpz(CH~2~SMe)~2~]^−^, respectively. Compound 7 proved to be an excellent building block for the heteroditopic poly(pyrazol‐1‐yl)borate p‐[pz~3~BC~6~H~4~Bpz~2~(CH~2~SMe)]^2−^ ([10]^2−^) that mimics the two ligation sites of the copper enzymes peptidylglycine α‐hydroxylating monooxygenase and dopamine β‐monooxygenase. Treatment of the monotopic tripod [5]^−^ with CuCl and CuBr~2~ results in the formation of complexes K[Cu(5)~2~] and [Cu(5)~2~]. An X‐ray crystallography study of K[Cu(5)~2~] revealed a tetrahedral (N~2~S~2~) coordination environment for the Cu^I^ ion, whereas the Cu^II^ ion of [Cu(5)~2~] possesses a square‐pyramidal (N~4~S) ligand sphere (S‐atom in the axial position). The remarkable redox properties of K[Cu(5)~2~] and [Cu(5)~2~] have been assessed by cyclic voltammetry and quantum chemical calculations. The reaction of K[Cu(5)~2~] with dry air leads to the Cu^II^ species [Cu(5)~2~] and to a tetranuclear Cu^II^ complex featuring [PhB(O)pz~2~]^2−^ ligands. Addition of CuCl to K~2~[10] gives the complex K~3~[Cu(10)~2~] containing two ligand molecules per Cu^I^ center. The Cu^I^ ion binds to both heteroscorpionate moieties and thereby establishes a coordination environment similar to that of the Cu^I^ ion in K[Cu(5)~2~].