Pentacoordinate copper complexes of nitrogen-sulfur donors: structural chemistry of two complexes of bis(2-(2-benzimidazolyl)ethyl) sulfide with the sulfur alternatively in equatorial and axial coordination modes

Abstract

Simple and mixed-ligand copper(II) complexes were synthesized and characterized by crystallographic and spectroscopic techniques. The N,S-and O-donor chelating agents used include the following: l,5-bis(benzimidazol-2-yl)-3-thiapentane, BBES; l,5-bis(iV-methylbenzimidazol-2-yl)-3-oxopentane, Me2BBEO; 2,5,8-trimethyl-2,5,8-triazanonane, pmeta; pentane-2,4-dionate anion, acac"; 2,2'-bipyridyl, bpy; 2,2'-biimidazole, biim. The perchlorate of Cu(BBES) crystallizes from methanol as the salt [Cu(BBES)(Me0H)(0H2)](C104)2, with the symmetry of the space group Pi, Z = 2, a = 9.306(3) k,b= 10.072 (5) A, c = 14.194 (5) A, a = 92.23 (2)°, ß = 96.63 (4)°, 7 = 108.56 (3)°, and Pcalcd = 1.66 g-cm"3 456.The structure was solved with the Patterson method, incorporating 3088 of the 3884 independent reflections, to final R values of 5.6% and 6.1% (J?w). The complex cation has a distorted tetragonal pentacoordinate structure ( = 0.27) with the BBES occupying three equatorial positions, with a Cu-S linkage of 2.297 A, and the methanol bound axially. This contrasts with the perchlorate salt of a similar ligand's complex, obtained from ethanol, which has a perchlorate coordinated at this axial position. [Cu(BBES)(acac)]PF6-H20-Et0H was recrystallized from ethyl acetate to give the ester solvate, [Cu(BBES)(acac)]PF6*C4H802. This complex also crystallizes with symmetry Pi, and Z = 2, a = 13.961 (3) A, b = 12.892(3) A,c = 10.154 (3) A, a = 101.57 (4)°, ß = 104.99 (4)°, 7 = 104.34 (4)°, and Pcalcd = 1.160 g-cm"3. The structure was solved by the Patterson method, using 2939 of the 3243 independent reflections, to final R values of 6.3% and 6.1% CRyi). The complex cation is of regularly tetragonal pyramidal geometry ( = 0.02) with an equatorial N202-donor set and the thioether bound axially at 2.696 A, in contrast to the Cu(BBES) perchlorates. There are hydrogen-bonding interactions with benzimidazole and water protons in the lattices of the complexes. ESR spectroscopy shows that the Cu(BBES)2"1" and Cu(Me2BBEO)2+ complexes retain their distorted structures in solution; both give single-line ESR spectra in solution at ambient temperatures. The [Cu(BBES)(acac)]+ salts exhibit pairwise dipolar coupling in their crystalline states. Substitution of ether by thioether as donor causes absorptivity enhancement throughout the visible-near-UV spectrum, and difference spectroscopy has been used to assign sulfur-to-copper charge-transfer transitions. Unlike [Cu(bpy)(acac)]+ and [Cu-(BBES)(acac)]+, the complex cations [Cu(Me2BBEO)(acac)]+ and [Cu(biim)(acac)]+ are unstable toward coordinative disproportionation in the solvents used. The Cu(BBES)2"1" cation in solution is in equilibrium between the/ac-BBES and rwer-BBES isomers, the latter being dominant.

Pentadentate thioether-oxime macrocyclic and quasi-macrocyclic complexes of copper(II) and nickel(II)

“…This shift is consistent with a lower ligand field induced by oxygen donors compared to sulfur donors, within a pentacoordinate Cu(II) complex with strongly interacting in-plane donors [40]. The bands between 329 and 429 nm are due to S Cu(II) charge transfer [42,43].…”

Assembly of Dinuclear CuII Rigid Blocks by Bridging Azido or Poly(thiocyanato)chromates: Synthesis, Structures and Magnetic Properties of Coordination Polymers and Polynuclear Complexes

“…[22] Magnetic measurements were performed by using a Quantum Design MPMS SQUID magnetometer operating in the temperature range 2-300 K with a DC magnetic field of up to 5 T. Samples were measured in Teflon capsules, diamagnetic corrections were calculated by using Pascal's constants. [19] Crystallographic Data Collection and Structure Determination: Single crystals of the title compounds were mounted on a Nonius fourcircle diffractometer equipped with a CCD camera and a graphite monochromated Mo-K α radiation source (λ = 0.71073 Å) at the Centre de Diffractométrie (CDFIX), Université de Rennes 1, France. Data were collected at 293 K. An effective absorption correction was performed (SCALEPACK).…”

“…To avoid overparametrisation, g Cu was fixed at the level of 2.1, a value typical for copper complexes with S donors. [15,19] Notably, a decrease in g Cu results in an increase in g Cr at a comparable final R 2 value. The value of D Cr is consistent with D Cr calculated for other Cr III complexes from magnetochemical measurements.…”

Synthesis of some benzimidazole‐, benzothiazole‐ and pyridine‐derived chelating agents

“…The resulting grey precipitate was isolated by filtration and recrystallized from methanol (charcoal), giving 2.9 g (13.5 mmol, 60%) of pale yellow flakes. 1 To o-aminothiophenol (8.8 g, 70 mmol) in 30 ml of polyphosphoric acid at 130 °C was added 7.0 g (35 mmol) of (1R,3S)-(+)-camphoric acid. The reaction mixture was stirred at 110-140 °C for 5 hours and allowed to cool to ca.…”

“…We have been interested in the synthesis and properties of mulitidentate ligands containing benzimidazole, benzothiazole and pyridine groups for some time [1][2][3][4]. As an extension of our earlier work [5][6][7], we report the syntheses of new heterocycles which are potential ligands for transition metals, Figure 1.…”