Mixed Ground‐State in the Trinuclear Complex: [Mn 3 O(O 2 CCCl 3 ) 6 (H 2 O) 3 ]

The reaction of [Mn 12 O 12 (OAc) 16 (H 2 O) 4 ]·4H 2 O·2HOAc with Cl 3 CCO 2 H in dichloromethane leads to formation of mixed‐valence trinuclear oxo‐centered [Mn 3 O(O 2 CCCl 3 ) 6 (H 2 O) 3 ]·2H 2 O ( 1 ). Complex 1 crystallizes in two forms; the monoclinic and hexagonal systems. [Mn 3 O(O 2 CCCl 3 ) 6 (H 2 O) 3 ]·3H 2 O ( 1a ) crystallizes in hexagonal, space group P6 3 /m (295 K) with a = 10.0741(1) Å, c = 22.8668(4) Å, and z = 2. [Mn 3 O(O 2 CCCl 3 ) 6 (H 2 O) 3 ]·0.5C 6 H 14 ( 1b ) crystallizes in monoclinic, space group P2 1 /n (150 K) with a = 11.8258(2) Å, b = 41.9370(5) Å, c = 25.9619(4) Å, β = 95.297(1)°, and z = 12. Complex 1 possesses an oxo‐centered Mn 3 O unit with peripheral ligands provided by bridging trichloroacetate and terminal H 2 O groups. Each manganese ion is distorted octahedral, and consideration of overall charge of the trinuclear unit necessitates a mixed‐valence Mn II Mn III 2 description. Magnetization measurement at 2.0 K up to 70 kG indicates the mixed ground state S = 3/2 and S = 1/2 for complex 1 . X‐band EPR spectra measured at 4.0–100.0 K on polycrystalline sample of complex 1 . There is a transition centered at g ≈ 4, which decreases in intensity with increasing temperature. Also, there is a transition centered at g ≈ 2, which does not disappear with increasing temperature.