Chromium(III) Complexes with Quadridentate Amines. Crystal Structure of [cis-β-Cr(trien)(C2O4)] Cl·2H2O (I) and [Cr2(μ-OH)2(μ-tren)2] Br4·2H2O (II)

Abstract

[cis-g-Cr(trien) C2O4)] Cl·2H2O (I) (CrC8H22N4O6Cl) crystallizes at 22°C, from deionized water solution as a racemate in space group Pn (No. 7). Lattice constants are: a = 7.193(2), b = 9.1545(12), c = 11.469(2) Å; g = 100.994(13)°; V = 741.3(3) Å3 and Dcalc = 1.603 gcm-3 (MW = 357.75, Z = 2). A total of 2251 data were collected, using MoK f radiation ( u = 0.71703 Å), over the range 4 h 2 è h 60°; of these, 1441 (independent and with I S 2 σ (I)) were used in the structural analysis. Data were corrected for absorption ( w = 9.81 cm-1) and the transmission coefficients ranged from 0.8676 to 0.9942. The final R (F) and Rw(F) residuals were 0.0338 and 0.0764, respectively. The cations of (II) exist in the lattice as enantiomeric pairs. [Cr2( w -OH)2( w -tren)2]Br4 ·2H2O (II) (Cr2C12H42N8O4Br4) crystallizes in the monoclinic space group P21/n (No. 14) with a = 10.835(2) Å, b= 7.859(3) Å, c = 16.397(2) Å, g = 105.45(2)°, V = 1345.7(5) Å33 and Dcalc = 1.940 g cm-1 (MW = 786.18, Z = 4). A total of 2467 data were collected, using MoK f radiation ( u = 0.71703 Å), over the range 4 h 2 è h 50°; of these, 1450 (independent and with I S 2 σ ( I )) were used in the structural analysis. Data were corrected for absorption ( w =67.79 cm-1) and the transmission coefficients ranged from 0.5589 to 0.9949. The final R(F) and Rw(F) residuals were 0.0481 and 0.1408, respectively for 2385 observed reflections with ( I S 2 σ ( I )). In the complex cation, the two Cr(III) centers are in a distorted octahedral environment and are bridged by two hydroxide groups and two ethylamine arms, one from each tren ligand, which spans over the binuclear core. Within the bridging moiety, the Cr···Cr separation is 3.005(2) Å, the ° Cr-OH-Cr = 101.3(2)° and ° O-Cr-O = 78.7(2)°, while the average Cr-N bond distance trans to the hydroxo groups (2.085(6) Å) is shorter than the corresponding cis Cr-N distance (2.104(5) Å).