The proposal that paramagnetic transition metal complexes could be used as qubits for quantum information processing (QIP) requires that the molecules retain the spin information for a sufficient length of time to allow computation and error correction. Therefore, understanding how the electron spin-lattice relaxation time ( T 1 ) and phase memory time ( T m ) relate to structure is important. Previous studies have focused on the ligand shell surrounding the paramagnetic centre, seeking to increase rigidity or remove elements with nuclear spins or both. Here we have studied a family of early 3d or 4f metals in the +2 oxidation states where the ground state is effectively a 2 S state. This leads to a highly isotropic spin and hence makes the putative qubit insensitive to its environment. We have studied how this influences T 1 and T m and show unusually long relaxation times given that the ligand shell is rich in nuclear spins and non-rigid.

Reduction of Th­(OC6H2 tBu2-2,6-Me-4)4 using either KC8 or Li in THF forms a new example of a crystallographically characterizable Th­(III) complex in the salts [K­(THF)5(Et2O)]­[Th­(OC6H2 tBu2-2,6-Me-4)4] and [Li­(THF)4]­[Th­(OC6H2 tBu2-2,6-Me-4)4]. Surprisingly, in each structure the four aryloxide ligands are arranged in a square-planar geometry, the first example of this coordination mode for an f element complex. The Th­(III) ion and four oxygen donor atoms are coplanar to within 0.05 Å with O–Th–O angles of 89.27(8) to 92.02(8)° between cis ligands. The ligands have Th–O–C­(ipso) angles of 173.9(2) to 178.6(4)°, and the aryl rings make angles of 58.5 to 65.1° with the ThO4 plane. The effect of the eight tert-butyl substituents in generating the unusual structure through packing and/or dispersion forces is discussed. EPR spectroscopy reveals an axial signal consistent with a metal-based radical in a planar complex. DFT calculations yield a C 4-symmetric structure that accommodates a low-lying SOMO of 6d z 2 character with 7s Rydberg admixture.

An approach to obtaining substantial amounts of data from a hazardous starting material that can only be obtained and handled in small quantities is demonstrated by the investigation of a single small-scale reaction of cyclooctatetraene, C8H8, with a solution obtained from the reduction of Cp′3Pu (Cp′ = C5H4SiMe3) with potassium graphite. This one reaction coupled with oxidation of a product has provided single-crystal X-ray structural data on three organoplutonium compounds as well as information on redox chemistry thereby demonstrating an efficient route to new reactivity and structural information on this highly radioactive element. The crystal structures were obtained from the reduction of C8H8 by a putative Pu­(II) complex, (Cp′3PuII)1−, generated in situ, to form the Pu­(III) cyclooctatetraenide complex, [K­(crypt)]­[(C8H8)2PuIII], 1-Pu, and the tetra­(cyclopentadienyl) Pu­(III) complex, [K­(crypt)]­[Cp′4PuIII], 2-Pu. Oxidation of the sample of 1-Pu with Ag­(I) afforded a third organoplutonium complex that has been structurally characterized for the first time, (C8H8)2PuIV, 3-Pu. Complexes 1-Pu and 3-Pu contain Pu sandwiched between parallel (C8H8)2– rings. The (Cp′4PuIII)− anion in 2-Pu features three η5-Cp′ rings and one η1-Cp′ ring, which is a rare example of a formal Pu–C η1-bond. In addition, this study addresses the challenge of small-scale synthesis imparted by radiological and material availability of transuranium isotopes, in particular that of pure metal samples. A route to an anhydrous Pu­(III) starting material from the more readily available PuIVO2 was developed to facilitate reproducible syntheses and allow complete spectroscopic analysis of 1-Pu and 2-Pu. PuIVO2 was converted to PuIIIBr3(DME)2 (DME = CH3OCH2CH2OCH3) and subsequently PuIIIBr3(THF) x , which was used to independently synthesize 1-Pu, 2-Pu, and 3-Pu.

To expand the range of synthetic options for generating complexes of the actinide metals in the +2 oxidation state, reduction of Cp″U (Cp″ = CH(SiMe)) and the lanthanide analogs, Cp″La and Cp″Ce with lithium in the absence of crown ether and cryptand chelates was explored. In each case, crystallographically characterizable [Li(THF)][Cp″M] complexes were obtainable in yields of 70-75% for M = La and Ce and 45-50% for M = U, that is, chelating agents are not necessary to sequester the lithium countercation to form isolable crystalline M(II) products. Reductions using Cs were also explored and X-ray crystallography revealed the formation of an oligomeric structure, [Cp″U(μ-Cp")Cs(THF)] , involving Cp″ ligands that bridge "(Cp″U)" moieties to "[Cp″Cs(THF)]" units.

Reduction of Cp Me 3 Ln(THF), 1-Ln (Ln = La and Gd; Cp Me = C 5 H 4 Me), with KC 8 in the presence of 2.2.2-cryptand (crypt) generates dark solutions, 2-Ln, with EPR spectra consistent with Ln(II) complexes: an eight-line hyperfine pattern for La at g = 1.971 and a broad single line for Gd at g = 1.988. The solutions decompose within minutes, and in the La system, a decomposition product was isolated in which a molecule of THF had been reduced by two electrons and ring-opened to generate an alkoxyalkyl-bridged bimetallic La(III) complex, [K(crypt)] 2 -[(Cp Me 3 La) 2 (μ-OCH 2 CH 2 CH 2 CH 2 )], 3-La. An analogous Pr complex, 3-Pr, was also crystallographically characterized. Since decomposition products were not readily isolated from the analogous yttrium Cp Me 3 Y(THF)/KC 8 /crypt reaction, the composition of the solution of 2-Y was probed by addition of the hydrogen delivery reagent, PhSiH 3 , which had previously been reported to form U(III) hydrides from tris(cyclopentadienyl) U(II) complexes. This generated an Y(III) silyl complex, [K(crypt)][Cp Me 3 Y(SiH 2 Ph)], 4, in addition to a hydride product, [K(crypt)][(Cp Me 3 Y) 2 (μ-H)], 5. The retention of three Cp Me ligands per metal in 3-Ln, 4, and 5 is consistent with the presence of a (Cp Me 3 Ln) 1− species in 2-Ln.