Rhenium(IV) cyanate complexes: Synthesis, crystal structures and magnetic properties of NBu4[ReBr4(OCN)(DMF)] and (NBu4)2[ReBr(OCN)2(NCO)3]

Two new rhenium(IV) mononuclear compounds of formula NBu4[ReBr4(OCN)(DMF)] (1) and (NBu4)2[ReBr(OCN)2(NCO)3] (2) (NBu4 = 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 P21/n, whereas 2 crystallizes in the triclinic one with P1¯ 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 (|2D| is ca. 41.6 and 39.2 cm−1 for 1 and 2, respectively).

Graphical abstractTwo new anionic Re(IV) cyanate complexes, namely NBu4[ReBr4(OCN)(DMF)] (1) and (NBu4)2[ReBr(OCN)2(NCO)3] (2) were obtained by reaction of K2[ReBr6] with NaOCN in DMF and structurally characterized by X-ray diffraction. These crystal structures show for the first time the presence of O-bonded cyanato ligands in a mononuclear metal complex. Their magnetic properties correspond to magnetically isolated spin quartets with large values of the zero-field splitting.Figure optionsDownload full-size imageDownload as PowerPoint slide