Synthesis, structure and EPR spectra of (NBu4)2[(OH2)Br4ReNReBr4NReBr4(OH2)]

The reaction of (NBu4) [ReNBr4] with BBr3 in CH2Cl2 gives purple crystals of (NBu4)2[(OH2)Br4ReNReBr4NReBr 4(OH2)]. The centrosymmetric complex anion is formed by three ReBr4 units which are linked by two asymmetric nitrido bridges with ReN distances of 1.69(2) and 2.00(2) A. The coordination spheres of the terminal Re atoms are completed by water ligands. The EPR spectra of the trimer suggest a d2-d1-d2 sequence for the Re atoms. The g, AReand ABr tensor components deviate from those of [ReNBr4] − and indicate an increase in the ReBr covalency.