Rhenium(IV) cyanate complexes: Synthesis, crystal structures and magnetic properties of NBu 4[ReBr 4(OCN)(DMF)] and (NBu 4) 2[ReBr(OCN) 2(NCO) 3

Abstract

Two new rhenium(IV) mononuclear compounds of formula NBu 4[ReBr 4(OCN)(DMF)] ( 1) and (NBu 4) 2[ReBr(OCN) 2(NCO) 3] ( 2) (NBu 4 = tetrabutylammonium cation, OCN = O-bonded cyanate anion, NCO = N-bonded cyanate anion and DMF = N, N-dimethylformamide) have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. 1 crystallizes in the monoclinic system with the space group P2 1/ n, whereas 2 crystallizes in the triclinic one with P 1 ¯ as space group. In both complexes the rhenium atom is six-coordinated, in 1 by four Br atoms in the equatorial plane, and two trans-oxygen atoms, one of a DMF molecule and another one from a cyanato group, while in 2 by one bromide anion and five cyanate ligands, two of which are O-bonded and three N-bonded, forming a somewhat distorted octahedral surrounding. Magnetic susceptibility measurements on polycrystalline samples of 1 and 2 in the temperature range 1.9–300 K are interpreted in terms of magnetically isolated spin quartets with large values of the zero-field splitting (|2 D| is ca. 41.6 and 39.2 cm −1 for 1 and 2, respectively).