Bulky ytterbium formamidinates stabilise complexes with radical ligands, and related samarium "tetracyclone" chemistry

Werner, Daniel, Zhao, Xuefei, Best, Stephen P., Maron, Laurent, Junk, Peter C., and Deacon, Glen B. (2017) Bulky ytterbium formamidinates stabilise complexes with radical ligands, and related samarium "tetracyclone" chemistry. Chemistry: A European Journal, 23 (9). pp. 2084-2102.

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Abstract

Divalent [Yb(DippForm)(2)(thf)(n)] (n= 2 (1a), or 1 (1b), DippForm= N, N'-bis(2,6-diisopropylphenyl) formamidinate) complexes were treated with the ketones: 9-fluorenone (fn), or 2,3,4,5-tetraphenylcyclopentadienone (tpc, tetracyclone), giving ketyl complexes: [Yb(DippForm)(2)(fn(center dot)-CO)( thf)] (2), and [Yb(DippForm)(2)(tpc(center dot)-O)] (3), respectively (ketyl= a radical anion containing a C-center dot-O(-) group. By contrast, when perfluorobenzophenone (pfb) was treated with either 1a or 1b, transitory ketyl formation was followed by rapid decomposition through a C-F activation pathway, giving [YbF(DippForm)(2)(thf)] (4a) and a highly unusual fluoride/oxide-bridged species: [Yb5F6O2(DippForm)(5)] (4b). The reduction of diketones: 3,5-di-tert-butyl-1,2-benzoquinone (tbbq), 9,10-phenanthrenequinone (phen), or 1,2-acenaphthenequinone (acen), was also examined giving ketyl complexes: [Yb(DippForm)(2)(tbbq(center dot)-O-2)] (5), [Yb(DippForm)(2)(phenCO(2))] (6), and [Yb(DippForm)(2)(acen(center dot)-O-2)(thf)] (7). An unsolvated derivative of 7, namely [Yb(DippForm)(2)(acen(center dot)-O-2)] (8), was obtained from PhMe. All ketyl complexes had suitably elon gated C-center dot-O bonds, were stable in both polar and non-polar solvents-an uncommon trait for rare-earth ketyl complexes-and, with the exception of 3, showed radical signals in ESR spectra. To investigate the reactivity of the tpc(center dot)-O ketyl complex, 3 was treated with oxidants (CS2, Se) and reducing agents (Mg-0, KH, or [SmI2(thf)(2)]). Thus 3 was oxidised to tpc by Se. Treatment of 3 with KH led to a ligand exchange process giving an unusual diketyl species [Yb(DippForm)(tpc(center dot)-O)(2)(thf)(2)] (10), which has two cisoid tpc(center dot)-O- ligands in very close proximity. When treated with [SmI2(thf)(2)], the tpc(center dot)-O ketyl was further reduced to a dianion (1-oxido-2,3,4,5- tetraphenylcyclopentadianide(2 -)), ({C5Ph4}-O)(2-) by [SmI2(thf)(2)], giving dimeric [{SmI({C5Ph4}-O)(thf)(2)}(2)] (Sm11) and monomeric complexes [YbI(DippForm)(2)(thf)] (11b) and [YbI2(DippForm)(thf)(2)] (11 c). Activated Sm metal reduced neutral tetracyclone to the dianion, ({C5Ph4}-O)(2-), in THF, giving tetranuclear [{Sm-2(II)({C5Ph4}-O)(2)(thf)(3)}(2)] (Sm13). Treatment of Sm13 with iodine in situ provided access to [{SmI({C5Ph4}-O)(thf)(2)}(2)] (Sm11), in good yield.

Item ID: 50733
Item Type: Article (Refereed Research - C1)
Keywords: ketyl complexes, lanthanides, rare earths, reactivity, synthesis
ISSN: 0947-6539
Funders: Australian Research Council (ARC)
Projects and Grants: ARC #DP130100152
Date Deposited: 20 Sep 2017 11:25
FoR Codes: 03 CHEMICAL SCIENCES > 0302 Inorganic Chemistry > 030202 f-Block Chemistry @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 100%
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