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Treatment of LnI 3 (Ln = La, Ce) or [UI 3 (py) 4 ] with 3 equivalents of terpy in acetonitrile gave the tris(terpy) complexes [M(terpy) 3 ]I 3 . Addition of 3 equivalents of Rbtp (2,2,pyridine) to MX 3 (X = I or OSO 2 CF 3 ) in pyridine or acetonitrile afforded the tris(Rbtp) compounds [M(Rbtp) 3 ]X 3 . By comparison with terpy, the Rbtp ligand has a better affinity for the 4f and 5f ions and is more selective for U() than for Ce() or La(). This trend has been revealed by 1 H NMR competition experiments and X-ray crystallographic studies which show that in the [M(terpy) 3 ] 3ϩ and [M(Rbtp) 3 ] 3ϩ cations, the M-N(Rbtp) bond lengths are shorter than the M-N(terpy) bond lengths, and the U-N bond lengths are shorter than the corresponding Ce-N or La-N bond distances. DALTON

Reaction of UO2(OTf)2 with 5 molar equivalents of NEt4CN in acetonitrile led to the formation of the pentacyano uranyl complex [NEt4]3[UO2(CN)5] which is monomeric in the solid state with the five C-coordinated cyanide ions lying in the equatorial plane perpendicular to the linear {UO2} axis.

The occurrence of the actinyl(v) species [AnO 2 ]+ (An = U, Np, Pu, Am) in the nuclear industry and in the natural environment is a particular reason for the current studies of their physicochemical properties.[ (n = 4, 5), [8] [UO 2 (H 2 O) 5 ] n+ (n = 1, 2) [9] and bare [UO 2 ] n+ ions (n = 1, 2) [8] were predicted from theoretical calculations using a variety of methods. In this context, the isolation of a pentavalent uranyl derivative, and the comparison of its crystal structure with that of its [UO 2 ] 2+ parent compound are highly desirable.In the course of our studies on the synthesis and structure of anhydrous uranyl triflate compounds, [10] Figure 1. The geometrical parameters are classical of hexavalent uranyl complexes; the linear {UO 2 } fragment is perpendicular to the equatorial plane defined by the uranium center and the four oxygen atoms of the OPPh 3 ligands. The mean U¼O bond length of 1.76(1) and the average equatorial UÀO bond length of 2.29(1) are identical to those found in [UO 2 {OP(NMe 2 ) 3 } 4 ](I 3 ) 2 . [12] In one attempt to crystallize complex 1, small red-orange, cube-shaped crystals were deposited in a small quantity along with the yellow crystals of the [UO 2 ] 2+ compound. X-ray diffraction analysis revealed that these crystals were of a new complex, the pentavalent uranyl derivative [UO 2 -(OPPh 3 ) 4 ](OTf) (2).[11] The unexpected formation of 2 requires elucidation; all attempts to produce it by reduction of 1 with UV light or various reducing agents are inconclusive at this time, and further work is in progress for controlling the synthesis of 2. Nevertheless, complex 2 was found to be kinetically stable under an inert atmosphere, which demonstrates that such [UO 2 ] + complexes can be isolated in the crystalline form, without suffering disproportionation.Crystals of 2 are composed of discrete cation-anion pairs; a view of one of the two independent [UO 2 (OPPh 3 ) 4 ]+ ions is represented in Figure 2. The cations of 1 and 2 adopt the same perfectly square bipyramidal configuration; in 2, the uranium center is located at a center of symmetry. The U ¼ O bond lengths of 1.817(6) and 1.821(6) are slightly longer than the Np¼O bond (1.797(2) ) in the isostructural [NpO 2 (OPPh 3 ) 4 ] + ion, [2] in agreement with the variation in

Plastic waste management is a major concern. While the societal demand for sustainability is growing, landfilling and incineration of waste plastics remain the norm and methods able to efficiently recycle these materials are desirable. Herein, we report the depolymerization, under mild conditions, of oxygenated plastics in the presence of hydrosilanes with the cationic pincer complex [Ir(PCP)H(THF)][B(C6F5)4] (PCP = 1,3-(tBu2P)2C6H3)) as catalyst. The iridium catalyst, with a low loading (0.3-1 mol%), proves selective toward the formation of silyl ethers or the corresponding alkanes depending only on the reaction temperature. It is noteworthy that the depolymerization of real household waste plastics such as PET (from plastic bottles) and polylactic acid (PLA) from 3D printer filaments is not altered by the presence of dye or other plastic's additives.

Uranyl organometallic complexes featuring uranium(VI)-carbon single and double bonds have been obtained from uranyl UO(2)X(2) precursors by avoiding reduction of the metal center. X-ray diffraction and density functional theory analyses of these complexes showed that the U-C and U=C bonds are polarized toward the nucleophilic carbon.

Treatment of [Ce(Cp*)(2)I] or [U(Cp*)(2)I(py)] with 1 mol equivalent of bipy (Cp*=C(5)Me(5); bipy=2,2'-bipyridine) in THF gave the adducts [M(Cp*)(2)I(bipy)] (M=Ce (1 a), M=U (1 b)), which were transformed into [M(Cp*)(2)(bipy)] (M=Ce (2 a), M=U (2 b)) by Na(Hg) reduction. The crystal structures of 1 a and 1 b show, by comparing the U-N and Ce-N distances and the variations in the C-C and C-N bond lengths within the bidentate ligand, that the extent of donation of electron density into the LUMO of bipy is more important in the actinide than in the lanthanide compound. Reaction of [Ce(Cp*)(2)I] or [U(Cp*)(2)I(py)] with 1 mol equivalent of terpy (terpy=2,2':6',2''-terpyridine) in THF afforded the adducts [M(Cp*)(2)(terpy)]I (M=Ce (3 a), M=U (3 b)), which were reduced to the neutral complexes [M(Cp*)(2)(terpy)] (M=Ce (4 a), M=U (4 b)) by sodium amalgam. The complexes [M(Cp*)(2)(terpy)][M(Cp*)(2)I(2)] (M=Ce (5 a), M=U (5 b)) were prepared from a 2:1 mixture of [M(Cp*)(2)I] and terpy. The rapid and reversible electron-transfer reactions between 3 and 4 in solution were revealed by (1)H NMR spectroscopy. The spectrum of 5 b is identical to that of the 1:1 mixture of [U(Cp*)(2)I(py)] and 3 b, or [U(Cp*)(2)I(2)] and 4 b. The magnetic data for 3 and 4 are consistent with trivalent cerium and uranium species, with the formulation [M(III)(Cp*)(2)(terpy(*-))] for 4 a and 4 b, in which spins on the individual units are uncoupled at 300 K and antiferromagnetically coupled at low temperature. Comparison of the crystal structures of 3 b, 4 b, and 5 b with those of 3 a and the previously reported ytterbium complex [Yb(Cp*)(2)(terpy)] shows that the U-N distances are much shorter, by 0.2 A, than those expected from a purely ionic bonding model. This difference should reflect the presence of stronger electron transfer between the metal and the terpy ligand in the actinide compounds. This feature is also supported by the small but systematic structural variations within the terdentate ligands, which strongly suggest that the LUMO of terpy is more filled in the actinide than in the lanthanide complexes and that the canonical forms [U(IV)(Cp*)(2)(terpy(*-))]I and [U(IV)(Cp*)(2)(terpy(2-))] contribute significantly to the true structures of 3 b and 4 b, respectively. This assumption was confirmed by the reactions of complexes 3 and 4 with the H(.) and H(+) donor reagents Ph(3)SnH and NEt(3)HBPh(4), which led to clear differentiation of the cerium and uranium complexes. No reaction was observed between 3 a and Ph(3)SnH, while the uranium counterpart 3 b was transformed in pyridine into the uranium(IV) compound [U(Cp*)(2){NC(5)H(4)(py)(2)}]I (6), where NC(5)H(4)(py)(2) is the 2,6-dipyridyl(hydro-4-pyridyl) ligand. Complex 6 was further hydrogenated to [U(Cp*)(2){NC(5)H(8)(py)(2)}]I (7) by an excess of Ph(3)SnH in refluxing pyridine. Treatment of 4 a with NEt(3)HBPh(4) led to oxidation of the terpy(*-) ligand and formation of [Ce(Cp*)(2)(terpy)]BPh(4), whereas similar reaction with 4 b afforded [U(Cp*)(2){NC(5)H(4)(py)(2)}]BPh(4) (6'). Th...

A series of base-stabilized silylium species were synthesized and their reactivity toward CO 2 explored, yielding the characterization of a novel N/ Si + FLP-CO 2 adduct. These silicon species are active catalysts in the hydroboration of CO 2 to the methoxide level with 9-BBN, catecholborane (catBH), and pinacolborane (pinBH). Both experiments and DFT calculations highlight the role of the FLP-CO 2 adduct in the catalysis. Depending on the nature of the hydroborane reductant, two distinct mechanisms have been unveiled. While 9-BBN and catBH are able to reduce an intermediate FLP-CO 2 adduct, the hydroboration of CO 2 with pinBH follows a different and novel path where the B−H bond is activated by the silicon-based Lewis acid catalyst. In these mechanisms, the formation of a highly stabilized FLP-CO 2 adduct is found detrimental to the kinetics of the reaction.