Synthesis, crystal structure and magnetic properties of H2tppz[ReCl6] and [Cu(bpzm)2(μ-Cl)ReCl3(μ-ox)Cu(bpzm)2(μ-ox)ReCl3(μ-Cl)]n†
Two new Re(IV) compounds of formulae H2tppz[ReCl6] (1) and [Cu(bpzm)2(μ-Cl)ReCl3(μ-ox)Cu(bpzm)2(μ-ox)ReCl3(μ-Cl)]n (2) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and bpzm = bis(pyrazolyl-1-yl)methane] have been prepared and their crystal structures determined by X-ray diffraction on single crystals. Compound 1 is a mononuclear species whose structure consists of octahedral hexachlororhenate(IV) anions and diprotonated H2tppz2+ cations which are arranged in the unit cell as alternating anionic and cationic layers, held together by electrostatic forces. The structure of 2 is made up of alternating [Cu(1)(bpzm)2]2+ and [(ox)ReCl3(μ-Cl)Cu(2)(bpzm)2(μ-Cl)ReCl3(ox)]2− entities interlinked by oxalate bridges to afford a neutral heterobimetallic chain. The oxalate group adopts the didentate (at Re)/monodentate (at Cu) bridging mode. The magnetic behavior of 1 and 2 has been investigated over the temperature range 1.9–295 K. 1 is a magnetically diluted Re(IV) complex, the relatively large value of the zero-field splitting of the ground level [D = −15.8(2) cm−1] accounting for the variation of χMT in the low temperature range. Weak intrachain ferromagnetic interactions between Re(IV) and Cu(II) through oxalate (J1 = +0.15 cm−1) and single chloro (J2 = +4.9 cm−1) bridges occur in 2 which are obscured by the large zero-field splitting of the Re(IV) ion (DRe = 42 cm−1). In addition, interchain antiferromagnetic interactions are also involved in 2 which are responsible for the metamagnetic behavior observed, the value of the critical dc magnetic field (Hc) being 20 kOe.