Bakker, Jacinta M., Deacon, Glen B., Forsyth, Craig M., Junk, Peter C., and Wiecko, Michal (2010) A structural investigation of trivalent and divalent rare earth thiocyanate complexes synthesised by redox transmetallation. European Journal of Inorganic Chemistry, 2010 (18). pp. 2813-2825.

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Abstract

A wide range of reactive trivalent and divalent rare earth thiocyanate complexes with 1,2-dimethoxyethane (dme), tetrahydrofuran (thf) and acetonitrile namely [RE(NCS)3(dme)3] [RE = La (1a), Nd (1b)], [RE(NCS)3(dme)2(µ-dme)0.5]2 [RE = Dy (1d), Er (1e)], [RE(NCS)3(thf)4]2 [RE = Y (3a), La (3b), Nd (3c), Sm (3d), Dy (3e), Ho (3f)], [Ca(NCS)2(dme)3] [rac-(4a)], [RE(NCS)2(dme)3] (RE = Sm (rac-4b), Eu (rac-4c), [Ca(Yb)(NCS)2(NCMe)5]⋅NCMe [Ca (6a), Yb (6b)], and [Eu(NCS)2(thf)4]2 (7) have been prepared in good to high yield by redox transmetallation between rare earth metals and the commercially available Hg(SCN)2. In addition [Eu(NCS)3(dme)2(µ-dme)0.5]2 (1c) and [Yb(NCS)3(dme)2] (1f) have been prepared by oxidation of rac-4c and [Yb(NCS)2(thf)2], respectively, with Hg(SCN)2 in dme. Crystallisation of 1e from dme/diglyme (diglyme = bis(2-methoxyethyl) ether) and thf yields [Er(NCS)3(diglyme)(dme)] (2) and [Er(NCS)3(thf)4]2 (3g), respectively, and prolonged storage of rac-4a in cold dme gave [Ca(NCS)2(dme)2(H2O)] (5). All undergo rapid hydrolysis on exposure to air. Two structural breaks are observed for [RE(NCS)3(dme)n] complexes, all of which have solely RE–NCS binding. Compounds 1a,b are nine-coordinate monomers that differ in the arrangement (T or Y) of the RE(NCS)3 moiety, 1c–e are eight coordinate dinuclear complexes being bridged by a single η1:η1-(O,O')-dme and 1f is a seven coordinate monomer. 2 is an eight coordinate monomer with, unusually for the present complexes, a facial RE(NCS)3 array. By contrast 3a–g are all dimeric, eight coordinate complexes with two unusual RE–NCS–RE bridges. The RE–S bonds are very weak and show little variation with RE3+ radius, and Er–S of 3g increases by 0.18 Å between 123 K and room temperature), foreshadowing a change to a seven coordinate monomer with [Yb(NCS)3(thf)4]. Monomeric eight coordination with transoid (N–RE–N ≈ 149°) SCN–RE–NCS bonding is observed in rac-4a–c and Λ-4c, whilst 5 is a seven-coordinate monomer with a cis-Ca(NCS)2 array. Single crystals of 6,a,b contain seven-coordinate, pentagonal bipyramidal monomers with trans-NCS ligands, whereas 7 is dimeric with two Eu–NCS–Eu bridging ligands and seven coordination for Eu.

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