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Title: Rhenium calix[4]arenes: precursors to novel imaging and cancer therapy agents
Authors: Redshaw, Carl
Liu, Xiaoming
Zhan, Shuzong
Hughes, David L.
Baillie-Johnson, Hugo
Elsegood, Mark R.J.
Dale, Sophie H.
Keywords: Rhenium
Oxo groups
Organoimido groups
Issue Date: 2008
Publisher: © Wiley-VCH Verlag GmbH 72 & Co.
Citation: REDSHAW, C. ... et al., 2008. Rhenium calix[4]arenes: precursors to novel imaging and cancer therapy agents. European Journal of Inorganic Chemistry, 2008(17), pp.2698-2712.
Abstract: Interaction of [ReOCl3(PPh3)2] with tert-butylcalix[4]areneH4, Cax(OH)4, in the presence of MOtBu (M = Na, K), or MH, under anaerobic conditions affords the isostructural rhenium(V) oxo complexes [Re(O)(PPh3)Cax(O)4M(NCMe)2] · 4MeCN [M = Na, (1); K, (2)] containing an alkali-metal cation within an elliptical ligand conformation. In the presence of air, the same reaction affords dioxo rhenium(VII) complexes of the form [Re(O)2Cax(O)4M(NCMe)2] [M = Na, · ca. 2.8MeCN (3); K, · 3MeCN (4)]. Prolonged heating also led to the isolation of the first examples of rhenium–rhenium bonding supported by calixarene ligands, viz. [ReCax(O)4M(NCMe)2(μ-O)]2 · 4MeCN [M = Na, (5); K, (6)], and in one case to {ReCax(O)4K(NCMe)2[μ-OK(NCMe)2]}2Cax(O)2(OH)2 · 7MeCN (7). The use of 2 as starting material led to the isolation of the complex {[Re(O)Cax(O)4K(NCMe)2]2(μ-O)} · 2MeCN (8). Given the diversity and complexity of the products arising from these “oxo” reactions, attention was switched to the isoelectronic organoimido [NR] group, and given its synthetic utility, the tert-butylimido group [NtBu] was chosen as our entry point. Reaction of [Re(NtBu)2Cl3] with Cax(OH)4 in a 1:1 ratio afforded the orange [Re(NtBu)2ClCax(O)2(OH)2]· MeCN (9), containing both a linear and a bent imido group. Increasing the amount of Cax(OH)4 (2:3 ratio) afforded both 9 together with the dark red complex [Re(NtBu)Cax(O)4Cax(O)(OH)3]· 6MeCN (10), which contains both mono- and tetra-dentate calixarene ligands. In the presence of adventitious oxygen, the complex {[Re(NtBu)Cax(O)4]2(μ-O)} · 3MeCN (11) was formed. To favour monomeric complex formation, the lithium salt of the monomethoxycalix[4]arene, namely Cax(OLi)3(OMe), was treated with [Re(NtBu)2Cl3] affording the mono- and bisacetonitrile-ligated species [Re(NtBu)2Cax(O)4Li(NCMe)2][Re(NtBu)2Cax(O)4Li(NCMe)] · MeCN (12). To avoid the lithium incorporation of 12, Cax(OH)3(OMe) was treated with [Re(NtBu)3(OSiMe3)] affording [Re(NtBu)2Cax(O)3(OMe)] (13), for which the methoxy ether group protudes into the calixarene cavity. The compounds 1–13 have been structurally characterised by single-crystal X-ray diffraction (synchrotron radiation was used for 4, 6, 7, 9, 11–13).
Description: This item is Closed Access.
Sponsor: This work was supported by the Bryan Gunn Leukaemia Trust (Norwich, U. K.). The Engineering and Physical Sciences Research Council (EPSRC) is thanked for the award of beam-time at Daresbury Laboratory and a studentship (S. H. D.).
Version: Closed access
DOI: 10.1002/ejic.200800275
URI: https://dspace.lboro.ac.uk/2134/15564
Publisher Link: http://dx.doi.org/10.1002/ejic.200800275
ISSN: 1434-1948
Appears in Collections:Closed Access (Chemistry)

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