Homoleptic 1-D Iron Selenolate Complexes — Synthesis, Structure, Magnetic and Thermal Behaviour of 1•[Fe(SeR)2] (R = Ph, Mes)

The first examples of polymeric homoleptic iron chalcogenolato complexes 1 [Fe(SePh)2] and [Fe(SeMes)2] (Ph = phenyl = C6H5, Mes = mesityl = C6H2-2,4,6-(CH3)3) have been both prepared by reaction of [Fe(N(SiMe3)2)2] with two equivalents of HSeR (R = Ph, Mes) while 1 1[Fe(SePh)2] was found to be also easily accessible through reactions of either FeCl2, Fe(OOCCH3)2 or FeCl3 with PhSeSiMe3 in THF. In the crystal, the two compounds form one-dimensional chains with bridging selenolate ligands comprising distinctly different Fe–Se–Fe bridging angles, namely 71.15–72.57◦ in 1 [Fe(SePh)2] and 91.80◦ in 1 [Fe(SeMes)2]. Magnetic measurements supported by DFT calculations reveal that this geometrical change has a pronounced influence on the antiferromagnetic exchange interactions of the unpaired electrons along the chains in the two different compounds with a calculated magnetic exchange coupling constant of J = -137 cm-1 in 1 [Fe(SePh)2] and J = -20 cm-1 in 1 [Fe(SeMes)2]. In addition we were able to show that the ring molecule [Fe(SePh)2]12 which is a structural isomer of [Fe(SePh)2] behaves magnetically similar to the latter one. Investigations by powder XRD reveal that the ring molecule is only a metastable intermediate which converts in THF completely to form [Fe(SePh)2]. Thermal gravimetric analysis of 1 [Fe(SePh)2] under vacuum conditions shows that the compound is thermally labile and already starts to decompose above 30 ◦C in a two step process under cleavage of SePh2 to finally form at 250 ◦C tetragonal PbO-type FeSe. The reaction of [Fe(SePh)2] with the Lewis base 1,10-phenanthroline yielded, depending on the conditions, the octahedral monomeric complexes [Fe(SePh)2(1,10-phen)2] and [Fe(1,10-phen)3][Fe(SePh)4].

EICHHÖFER Andreas;  BUTH Gernot;  DOLCI Francesco;  FINK Karin;  MOLE Richard A.;  WOOD Paul T.; 

2011-08-04

ROYAL SOC CHEMISTRY

JRC61519

1477-9226,   

www.rsc.org/dalton,    https://publications.jrc.ec.europa.eu/repository/handle/JRC61519,   

10.1039/c1dt10089k,