Synthesis and magnetic and structural characterization of the binuclear complex di-μ-hydroxobis{[tris(2-pyridylmethyl)amine]chromium(III)} perchlorate tetrahydrate, [(tpa)CrOH] 2(ClO 4) 4·4H 2O

Abstract

The binuclear complex di-μ-hydroxobis{[tris(2-pyridylmethyl)amine]chromium(III)} perchlorate tetrahydrate, [Cr(C 18H 18N 4)OH] 2(ClO 4) 4·4H 2O or [Cr(tpa)OH] 2(ClO 4) 4·4H 2O, has been synthesized and characterized. The complex crystallizes in space group P2 1/ n of the monoclinic system with two binuclear units in a cell of dimensions a = 11.381(5), b = 17.856(4), c = 13.050(7) Å, β = 111.83(4)°. The structure has been refined to a final value of the conventional R factor of 0.056 on the basis of 3546 independent intensities. The geometry at the chromium is roughly octahedral, and the bridging unit has a CrOCr angle (φ) of 100.53(8)°. The CrCr separation is 3.003(1) Å, and the hydrogen atom on the bridging OH group sits 0.30 Å from the Cr 2O 2 plane, leading to a dihedral angle θ of 26.6°. The magnetic susceptibility of the complex indicates antiferromagnetic coupling, with the ground state singlet lying 30.58(6) cm −1 below the lowest lying triplet state.