Copper Complexes of Mono‐ and Ditopic [(Methylthio)methyl]borates: Missing Links and Linked Systems En Route to Copper Enzyme Models

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 ].