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

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)Si--C(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 B--S 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)B--C(6)H(4)--Bpz(2)(CH(2)SMe)](2-) ([10](2-)) that mimics the two ligation sites of the copper enzymes peptidylglycine alpha-hydroxylating monooxygenase and dopamine beta-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)].

Synthesis, Molecular Structure, and Physical Properties of the Complexes [{PhB(pz)2(CH2SMe)}2M] (M = MnII, FeII; pz = pyrazol‐1‐yl) Containing a Novel [N,N,S]‐Heteroscorpionate Ligand

“…[21] A clean and high-yielding synthesis protocol requires the use of donorfree Li[CH 2 SMe], [22] Figure S1 in the Supporting Information}.…”

“…Compound 1 was synthesized according to a literature procedure. [21] Synthesis of 2: Compound 1 (0.071 g, 0.22 mmol) and FeCl 2 (0.015 g, 0.12 mmol) were suspended in toluene (25 mL). The reaction mixture was stirred for 6 d at room temp.…”

Synthesis and Applications of Group 14-metalated Arylboranes

“…The Sn B transmetalation was used in the synthesis of a sterically hindered silylated pentaarylborole 87 from an appropriate tin precursor 86 (Scheme 35) [44]. The treatment of a dimeric silylated phenylbromoborane 88 with BBr 3 gave a diboronated species 89, which was subsequently used for the construction of a ditopic scorpionate pyrazolylborate ligand 90 (Scheme 36) [45].…”

RhI-complexes of ditopic bis(pyrazol-1-yl)borate ligands: Assessment of their catalytic activity towards phenylacetylene polymerization

“…Our group has a long-standing interest in the development of oligotopic poly(pyrazol-1-yl)borate (''scorpionate" [12,13]) ligands [14][15][16][17][18][19][20] that are able to bring two metal ions into sufficiently close proximity so that they can act simultaneously on the same substrate molecule [21][22][23][24][25]. To identify promising applications of ditopic scorpionates of the general formula ½1; 4-ðBðR 0 Þpz R 2 Þ-C 6 H 4 -ðBðR 0 Þpz R 2 Þ 2À (pz R : 3-substituted pyrazolide) in homogeneous catalysis we chose to investigate the Rh-mediated polymerization of phenylacetylene, because (i) mononuclear complexes ½ðHBðR 0 Þpz R;R 2 ÞRhðcodÞ (cod: cyclooctadiene) reveal a high activity in this reaction [26], (ii) some benefit of two cooperating metal centers has already been confirmed for homogeneous olefin polymerization [27][28][29][30][31], and (iii) stereoregular poly(phenylacetylene) derivatives possess interesting and useful optoelectronic properties [32][33][34][35][36][37][38].…”