Thorium and uranium porphyrins. Synthesis and crystal structure of bis(acetylacetonato)(2,3,7,8,12,13,17,18-octaethylporphyrinato)thorium(IV)

Abstract

The action of thorium tetrachloride or uranium tetrachloride with porphyrins affords the dichloro complexes (Por)MC12 (M = Th or U). The latter derivatives react with sodium acetylacetonate giving rise to bis(acety1acetonato) complexes (Por)M(acac)l. The two series of complexes are characterized on the basis of mass spectral, IR, UV-visible, and NMR data. The crystal structure of the title compound has been determined by X-ra diffraction methods: (OEP)Th(acac),, C46Hs8N404Th; M, = 963; triclinic, Pi; a = 9.493 (7), b = 21.185 (5), c = 24.331 (7) i; (Y = 104.18 (2), B = 96.11 (4), y = 92.35 (4)O; V = 4705 A'; d,,, = 1.359 g Z = 4; T = 298 K. A total of 9019 intensities were measured on a CAD 4 Enraf-Nonius diffractometer in the w-20 scan mode with monochromatized Mo Ka radiation (1.5 < 8 < 20'). The crystal structure was refined to a conventional R(F) = 0.047 for 5323 reflections having a(Z)/Z < 0.33. The thorium atom is octacoordinated by the four porphyrin nitrogen atoms and by the four oxygen atoms of the two acetylacetonato groups.

In-Plane Thorium(IV), Uranium(IV), and Neptunium(IV) Expanded Porphyrin Complexes

“…Notable features included changes to the phenyl and pyridine C H proton resonances and an absence of signals ascribable to the N H protons. In contrast with what is found in the case of various out-of-plane uranium­(IV)–porphyrin complexes, ,,, no discernible proton resonances for the dipyriamethyrin ligand were seen in the 1 H NMR spectrum of the uranium­(IV) complex 4 recorded in THF- d 8 at room temperature.…”

“…The low-valent actinide chemistry of porphyrin and its analogues is relatively unexplored. Initial efforts by the groups of Horrocks, Jr., Guilard, − and Girolami and Suslick − to prepare porphyrin actinide complexes yielded a series of thorium­(IV) and uranium­(IV) out-of-plane and sandwich structures .…”

Actinide Coordination Chemistry on Surfaces: Synthesis, Manipulation, and Properties of Thorium Bis(porphyrinato) Complexes

“…The binding energies (see Figure b) match the ones reported for oxidized Th (ThO 2 , E b = 344.2 and 334.9 eV) rather than the ones of the pure metal species ( E b = 342.4 and 333.1 eV) . This finding shows that the Th is incorporated into the porphyrin macrocycle and is consistent with a Th oxidation state +IV, as expected for Th­(TPP) 2 complexes …”

“…Comparing compounds with corresponding lanthanide and actinide atoms, bonds with actinide partners are generally considered to show increased covalent versus ionic character, whereas for the early group members Ce and Th, reversed results have been reported. , These properties, and the actinides’ larger ionic radii that affect bond character and geometry, open prospects for novel functional materials, including single-molecule magnets − and coordination architectures, covering metal–organic coordination frameworks. − The latter structures are expected to play a relevant role in nuclear waste management . Uranium- and thorium-based complexes and molecular materials have received the main attention, e.g., because of their interesting catalytic chemistry − and intriguing coordination structures reported. ,,,− Specifically, thorium tetrapyrrole complexes (including porphyrins, phthalocyanines, and corroles) were achieved, ,− affording double-decker bis­(porphyrinato)­thorium complexes, where a single thorium center is sandwiched between two macrocyclic ligands. − In addition, the large half-lives of 232 Th (1.4 × 10 10 years) and 238 U (4.47 × 10 9 years) minimize radiation hazards compared to other, more short-lived actinides.…”

Synthesis and Characterization of Thorium(IV) and Uranium(IV) Corrole Complexes

“…This is in contrast to the recently reported lanthanide corroles, as well as the actinide porphyrins, which are all monomeric. 23,24,34 The coordination geometry about the metal center is approximately dodecahedral, and both the metal−chloride 38,42−45 The average Th−N distance (2.39(1) Å) is longer than is typical for a Th−amido bond, but comparable to that of the thorium(IV) porphyrin (2.40 Å). 23 Likewise, the average U−N distance of 2.33(1) Å is slightly shorter than the analogous uranium(IV) porphyrin U− N distance at 2.41 Å.…”