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)

[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) ų and D_calc = 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 R_w(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) ų3 and D_calc = 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 R_w(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).

Keywords:

• Chromium Complexes
• Amines
• Oxalato
• Hydroxo
• Dinuclear Complexes
• Crystallization
• Racemates
• Conglomerates