Hexahalorhenate(iv) salts of metal oxazolidine nitroxides. Issue 16 (4th April 2017)

• Record Type: Journal Article
• Authors: Pedersen, Anders H.; Geoghegan, Blaise L.; Nichol, Gary S.; Lupton, David W.; Murray, Keith. S.; Martínez-Lillo, José; Gass, Ian A.; Brechin, Euan K.
• Is Part Of: Dalton transactions. Volume 46:Issue 16(2017)
• Page Start: 5250
• Page End: 5259
• Publication Date: 2017-04-04
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt00752c
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Coordination compounds of the type [M II (L˙)2 ][Re IV X6 ] display a variety of different intra- and inter-molecular magnetic interactions. Abstract : Eight coordination compounds of formulae [Fe II (L˙)2 ][Re IV Cl6 ] (1a ), [Fe II (L˙)2 ][Re IV Br6 ] (1b ), [Co II (L˙)2 ][Re IV Cl6 ]·CH3 CN (2a ), [Co II (L˙)2 ][Re IV Br6 ] (2b ), [Ni II (L˙)(CH3 CN)3 ][Re IV Cl6 ]·CH3 CN (3a ), [Ni II (L˙)(CH3 CN)3 ][Re IV Br6 ]·3CH3 CN (3b ), [Cu II (L˙)2 ][Re IV Cl6 ] (4a ) and [Cu II (L˙)2 ][Re IV Br6 ] (4b ), where L˙ is the aminoxyl radical chelating ligand, 4, 4′-dimethyl-2, 2′-di(2-pyridyl)oxazolidine- N -oxide, have been synthesised. Structural and magnetic studies reveal metal–radical intramolecular antiferromagnetic interactions in the [M II (L˙)2 ] 2+ cations in the iron, cobalt and copper based compounds (1a, 1b, 2a, 2b, 4a and4b ) with the central metal ion low-spin in the case of iron (1a and1b ) and a gradual, cobalt based, spin-crossover transition present in2a and2b . The nickel based compounds, 3a and3b, were analysed in the dried form (3a (dried) and3b (dried) ) and directly in acetonitrile (3a (solvated) and3b (solvated) ). Microanalysis and IR spectroscopy on3a (dried) and3b (dried) suggest that the dried samples are best formulated as [Ni II (L˙)(H2 O)3 ][Re IV X6 ], where X = Cl (3a (dried) ) and Br (3b (dried) ). All forms of3a and3b exhibit cationic metal–radical ferromagnetic interactions resulting in S = 3/2 ground states. In addition, 3a (dried) exhibits spin-canting behaviour with an ordering temperature of 2.7 K, an open hysteresis loop with a coercive field H c = 580 Oe, and a remanent magnetisation M r = 0.21 μ B, resulting in a canting angle of ∼1.8°. In contrast, 3b (dried) shows no spin-canting behaviour; a maximum in χ M vs . T at T = 3 K suggesting long-range antiferromagnetic ordering.3a (solvated) and3b (solvated) show no indication of long-range magnetic ordering, unlike4a and4b where anomalies are evident in the low-temperature magnetic susceptibility measurements.