Covalent Bonding in Octahedral (MnCl6)4− and Tetrahedral (MnCl4)2− Complexes

Chlorine ligand hyperfine structure has been observed in the EPR spectrum of the octahedral complex ion (MnCl6)4−1, in dilute solution in a single crystal of K4CdCl6 at room temperature. From the isotropic and anisotropic components of the spectrum, it is estimated that fs = 0.40%, and (fσ − fπ) = 3.9%, respectively. No chlorine ligand hyperfine structure is observed in the tetrahedral complex ion (MnCl4)2− introduced as an impurity in either [N(CH3)4]2ZnCl4 or [(C6H5)3CH3As]2ZnCl4. A substantial reduction in the manganese nuclear hyperfine coupling constant As(Mn) is observed in both cases, however, As(Mn) having the value − 79.50 ± 0.50 G for [N(CH3)4]2ZnCl4, and − 79.30 ± 0.50 G for [(C6H5)3CH3AS]2ZnCl4 compared to − 86.40 ± 0.40 G found for MnCl64− in K4CdCl6. The failure to observe ligand hyperfine interactions in the tetrahedral ion is discussed in terms of the shorter bond distance in the four coordinated compound and the increased importance of π bonding.