Electronic Structure and Magneto-Structural Correlations Study of Cu2UL Trinuclear Schiff Base Complexes: A 3d-5f-3d Case.

The magnetic properties of trinuclear Schiff base complexes M2AnLi (MII = Zn, Cu; AnIV = Th, U; Li = Schiff base; i = 1-4, 6, 7, 9), exhibiting the [M(µ-O)2]2U core structure with adjacent M1···U and M2···U and next-adjacent M1···M2 interactions, featuring 3d-5f-3d subsystems, have been investigated theoretically using relativistic ZORA/B3LYP computations combined with the broken symmetry (BS) approach. Bond order and natural population analyses reveal that the covalent contribution to the bonding within the Cu-O-U coordination is important thus favoring superexchange coupling between the transition metal and the uranium magnetic centers. The calculated coupling constants JCuU between the Cu and U atoms, agree with the observed shift from the antiferromagnetic (AF) character of the L1,2,3,4 complexes to the ferromagnetic (ferro) of the L6,7,9 ones. The structural parameters, i.e., the Cu···U distances and the Cu-O-U angles, as well as the electronic factors driving the magnetic couplings are discussed. The analyses are supported by the study of the mixed ZnCuULi and Cu2ThLi systems, where in the first complex the CuII (3d9) ion is replaced by the diamagnetic ZnII (3d10) one, whereas in the second complex the UIV (5f2) paramagnetic center is replaced by the diamagnetic ThIV (5f0) one.

Advances in f-element cyanide chemistry.

This Dalton perspective gives an overview of the development of cyanide chemistry of 4f- and 5f-elements, a field which was poorly explored in contrast to the attention paid to the cyanide complexes of the d transition metals. The use of the cyanide ligand led to the discovery of mono- and polycyanide complexes which exhibit unprecedented and unexpected coordination geometries. A new type of linear metallocenes including [U(Cp*)2(CN)5](3-) (Cp* = C5Me5) and the first bent actinocenes [An(Cot)2(CN)](-) (An = Th, U; Cot = C8H8) were isolated. Thorocene was found to be much more reactive than uranocene since a series of sterically crowded cyanide complexes have been obtained only from [Th(Cot)2]. A series of cyanido-bridged dinuclear compounds and mononuclear mono-, bis- and tris(cyanide) complexes were prepared by addition of cyanide salts to [MN*3] (M = Ce, U) and [UN*3](+) [N* = N(SiMe3)2]. The Ce(III), U(III) and U(IV) ions were clearly differentiated in these reactions by cyanide linkage isomerism, as shown for example by the structures of the cyanide complex [U(III)N*3(CN)2](2-) and of the isocyanide derivatives [Ce(III)N*3(NC)2](2-) and [U(IV)N*3(NC)](-). While the U-CN/NC coordination preference towards the U(III)/U(IV) pair is related to the subtle balance between steric, covalent and ionic factors, DFT computations and in particular the calculated total bonding energies between the metal and the cyanide ligand allowed the observed coordination mode to be predicted. The ability of the cyanide ligand to stabilize the high oxidation states was assessed with the synthesis of U(V) and U(VI) complexes in the inorganic and organometallic series.

U(III)-CN versus U(IV)-NC coordination in tris(silylamide) complexes.

Treatment of the metallacycle [UN*2(N,C)] [N* = N(SiMe3)2; N,C = CH2SiMe2N(SiMe3)] with [HNEt3][BPh4], [HNEt3]Cl, and [pyH][OTf] (OTf = OSO2CF3) gave the cationic compound [UN*3][BPh4] (1) and the neutral complexes [UN*3X] [X = Cl (3), OTf (4)], respectively. The dinuclear complex [{UN*(µ-N,C)(µ-OTf)}2] (5) and its tetrahydrofuran (THF) adduct [{UN*(N,C)(THF)(µ-OTf)}2] (6) were obtained by thermal decomposition of 4. The successive addition of NEt4CN or KCN to 1 led to the formation of the cyanido-bridged dinuclear compound [(UN*3)2(µ-CN)][BPh4] (7) and the mononuclear mono- and bis(cyanide) complexes [UN*3(CN)] (2) and [M][UN*3(CN)2] [M = NEt4 (8), K(THF)4 (9)], while crystals of [K(18-crown-6)][UN*3(CN)2] (10) were obtained by the oxidation of [K(18-crown-6)][UN*3(CN)] with pyridine N-oxide. The THF adduct of 1, [UN*3(THF)][BPh4], and complexes 2-7, 9 and 10 were characterized by their X-ray crystal structure. In contrast to their U(III) analogues [NMe4][UN*3(CN)] and [K(18-crown-6)]2[UN*3(CN)2] in which the CN anions are coordinated to the metal center via the C atom, complexes 2 and 9 exhibit the isocyanide U-NC coordination mode of the cyanide ligand. This U(III)/U(IV) differentiation has been analyzed using density functional theory calculations. The observed preferential coordinations are well explained considering the electronic structures of the different species and metal-ligand bonding energies. A comparison of the different quantum descriptors, i.e., bond orders, NPA/QTAIM data, and energy decomposition analysis, has allowed highlighting of the subtle balance between covalent, ionic, and steric factors that govern the U-CN/NC bonding.

U-CN versus Ce-NC coordination in trivalent complexes derived from M[N(SiMe3)2]3 (M = Ce, U).

Reactions of [MN*3] (M = Ce, U; N* = N(SiMe3)2) and NR4CN (R = Me, Et, or (n)Bu) or KCN in the presence of 18-crown-6 afforded the series of cyanido-bridged dinuclear compounds [NEt4][(MN*3)2(µ-CN)] (M = Ce, 2a, and U, 2b), [K(18-crown-6)(THF)2][(CeN*3)2(µ-CN)] (2'a), and [K(18-crown-6)][(UN*3)2(µ-CN)] (2'b), and the mononuclear mono-, bis-, and tris(cyanide) complexes [NEt4][MN*3(CN)] (M = Ce, 1a(Et), and U, 1b(Et)), [NMe4][MN*3(CN)] (M = Ce, 1a(Me), and U, 1b(Me)), [K(18-crown-6)][MN*3(CN)] (M = Ce, 1'a, and U, 1'b), [N(n)Bu4]2[MN*3(CN)2] (M = Ce, 3a, and U, 3b), [K(18-crown-6)]2[MN*3(CN)2] (M = Ce, 3'a, and U, 3'b), and [N(n)Bu4]2[MN*2(CN)3] (M = Ce, 4a, and U, 4b). The mono- and bis(cyanide) complexes were found to be in equilibrium. The formation constant of 3'b (K3'b) from 1'b at 10 °C in THF is equal to 5(1) × 10(-3), and -ΔH3'b = 104(2) kJ mol(-1) and -ΔS3'b = 330(5) J mol(-1) K(-1). The bis(cyanide) compound 3a or 3b was slowly transformed in solution into an equimolar mixture of the mono- and tris(cyanide) derivatives with elimination of N(n)Bu4N*. The crystal structures of 1a(Me), 1b(Me), 1'a·toluene, 1'b·toluene, 2'a, 2'b, 3a, 3'a, 3'b, 3'a·2benzene, 3'b·2benzene, 4a·0.5THF, and 4b·Et2O were determined. Crystals of the bis(cyanide) uranium complexes 3'b and 3'b·2benzene are isomorphous with those of the cerium counterparts 3'a and 3'a·2benzene, but they are not isostructural since the data revealed distinct coordination modes of the CN group, through the C or N atom to the U or Ce metal center, respectively. This differentiation has been analyzed using density functional theory calculations. The observed preferential coordination of the cyanide and isocyanide ions toward uranium or cerium in the bis(cyanide) complexes is corroborated by the consideration of the binding energies of these groups to the metals and by the comparison of DFT optimized geometries with the crystal structures. The better affinity of the cyanide ligand toward U(III) over Ce(III) metal center is related to the better energy matching between the 6d/5f uranium orbitals and the cyanide ligand ones, leading to a non-negligible covalent character of the bonding.

Selectivity of azine ligands toward lanthanide(III)/actinide(III) differentiation: a relativistic DFT based rationalization.

Polyazines emerge as highly selective ligands toward actinide versus lanthanide separation. Electronic structures of several mono- and polyazine f-complexes of general formula MX3L (M(+3) = Ce, Nd, Eu, U, Am, and Cm; X = RCp(-) or NO3(-); L = N-donor ligand) related to Ln(III)/An(III) differentiation have been investigated using scalar relativistic ZORA/DFT calculations. In all cases, DFT calculations predict shorter An-N bonds than Ln-N ones whatever the azine used, in good agreement with available experimental data. The An-N bonds are also characterized by higher stretching frequencies than Ln-N bonds. The electronic structures of all species have been studied using different population analyses, among them natural population (NPA) and the quantum theory of atoms in molecule approach (QTAIM), as well as using different bond indices. The ability for Ln(III)/An(III) differentiation of the terdentate bipyrazolate BPPR ligand in the M(BPPR)(NO3)3 complexes (M(3+) = Ce, Eu, U and Am ; R = H, 2,2-dimethylpropyl) where BPP = 2,6-bis(dialkyl-1H-pyrazol-3-yl)pyridine has been studied, with a special emphasis on the total metal-ligand bonding energy (TBE). The ZORA/DFT approach was found to properly reproduce the higher selectivity of the polyazine BPP ligand compared to monoazines, especially for the Eu(III)/Am(III) pair operating in spent nuclear fuel, using computed TBEs as criterion. Moreover, the orbital part of the total bonding energy appears also to rationalize well the observed selectivity.

Bent thorocene complexes with the cyanide, azide and hydride ligands.

Reaction of the linear thorocene with NC(-), N3(-) and H(-) led to the bent derivatives [(Cot)2Th(X)](-) (X = CN, N3) and the bimetallic [{(Cot)2Th}2(µ-H)](-), whereas only [(Cot)2U(CN)](-) could be formed from (Cot)2U.

Revisiting the chemistry of the actinocenes [(η8-C8H8)2An] (An = U, Th) with neutral Lewis bases. Access to the bent sandwich complexes [(η8-C8H8)2An(L)] with thorium (L = py, 4,4'-bipy, tBuNC, R4phen).

In stark contrast to uranocene, (Cot)2Th reacts with neutral mono- or bidentate Lewis bases to give the bent sandwich complexes (Cot)2Th(L) (L = py, 4,4'-bipy, tBuNC, phen, Me4phen). DFT calculations in the gas phase show that, for both U and Th, formation of the bent compound (Cot)2An(L) should be facile, the linear and bent forms being close in energy.

Nitrite complexes of uranium and thorium.

The first examples of inorganic nitrite complexes of the natural actinides are described, including the structures of the homoleptic thorium(IV) [PPh(4)](2)[Th(NO(2))(6)] and the uranyl(VI) [PPh(4)](2)[UO(2)(NO(2))(4)] complexes; the nitrite ligand can adopt two different coordination modes in the coordination sphere of the uranyl ion and is unstable towards reduction.

A N-aryloxy-ß-diketiminate ligand in 4d, 4f and 5f-metals complexes.

A new class of functionalized ß-diketiminate ligands has been prepared from commercially available reagents. The novel N-aryloxy-ß-diketiminate ligand proves to be an excellent ligand to support 4d, 4f and 5f metal ions.

Density functional theory investigation of the redox properties of tricyclopentadienyl- and phospholyluranium(IV) chloride complexes.

The redox behavior of tricyclopentadienyl- and phospholyluranium(IV) chloride complexes L(3)UCl with L = C(5)H(5) (Cp), C(5)H(4)Me (MeCp), C(5)H(4)SiMe(3) (TMSCp), C(5)H(4)(t)Bu ((t)BuCp), C(5)Me(5) (Cp*), and C(4)Me(4)P (tmp), has been investigated using relativistic density functional theory calculations, with the solvent being taken into account using the conductor-like screening model. A very good linear correlation (r(2) = 0.99) has been obtained between the computed electron affinities of the L(3)UCl complexes and the experimental half-wave reduction potentials E(1/2) related to the U(IV)/U(III) redox systems. From a computational point of view, our study confirms the crucial importance of spin-orbit coupling and solvent corrections and the use of an extended basis set in order to achieve the best experiment-theory agreement. Considering oxidation of the uranium(IV) complexes, the instability of the uranium(V) derivatives [L(3)UCl](+) is revealed, in agreement with experimental electrochemical findings. The driving roles of both the electron-donating ability of the L ligand and the U 5f orbitals on the redox properties of the complexes are brought to light. Interestingly, we found and explained the excellent correlation between variations of the uranium Hirschfeld charges following U(IV)/U(III) electron capture and E(1/2). In addition, this work allowed one to estimate theoretically the half-wave reduction potential of [Cp*(3)UCl].

Recycling of carbon and silicon wastes: room temperature formylation of N-H bonds using carbon dioxide and polymethylhydrosiloxane.

A highly active organocatalytic system based on N-heterocyclic carbenes has been designed for the formylation of N-H bonds in a large variety of nitrogen molecules and heterocycles, using two chemical wastes: CO(2) and polymethylhydrosiloxane (PMHS).

Iodide, azide, and cyanide complexes of (N,C), (N,N), and (N,O) metallacycles of tetra- and pentavalent uranium.

In contrast to the neutral macrocycle [UN*(2)(N,C)] (1) [N* = N(SiMe(3))(3); N,C = CH(2)SiMe(2)N(SiMe(3))] which was quite inert toward I(2), the anionic bismetallacycle [NaUN*(N,C)(2)] (2) was readily transformed into the enlarged monometallacycle [UN*(N,N)I] (4) [N,N = (Me(3)Si)NSiMe(2)CH(2)CH(2)SiMe(2)N(SiMe(3))] resulting from C-C coupling of the two CH(2) groups, and [NaUN*(N,O)(2)] (3) [N,O = OC(═CH(2))SiMe(2)N(SiMe(3))], which is devoid of any U-C bond, was oxidized into the U(V) bismetallacycle [Na{UN*(N,O)(2)}(2)(µ-I)] (5). Sodium amalgam reduction of 4 gave the U(III) compound [UN*(N,N)] (6). Addition of MN(3) or MCN to the (N,C), (N,N), and (N,O) metallacycles 1, 4, and 5 led to the formation of the anionic azide or cyanide derivatives M[UN*(2)(N,C)(N(3))] [M = Na, 7a or Na(15-crown-5), 7b], M[UN*(2)(N,C)(CN)] [M = NEt(4), 8a or Na(15-crown-5), 8b or K(18-crown-6), 8c], M[UN*(N,N)(N(3))(2)] [M = Na, 9a or Na(THF)(4), 9b], [NEt(4)][UN*(N,N)(CN)(2)] (10), M[UN*(N,O)(2)(N(3))] [M = Na, 11a or Na(15-crown-5), 11b], M[UN*(N,O)(2)(CN)] [M = NEt(4), 12a or Na(15-crown-5), 12b]. In the presence of excess iodine in THF, the cyanide 12a was converted back into the iodide 5, while the azide 11a was transformed into the neutral U(V) complex [U(N{SiMe(3)}SiMe(2)C{CHI}O)(2)I(THF)] (13). The X-ray crystal structures of 4, 7b, 8a-c, 9b, 10, 12b, and 13 were determined.

Towards high-valent uranium compounds from metallacyclic uranium(IV) precursors.

Treatment of [NaUN*(C,N)(2)] [N* = N(SiMe(3))(2); C,N = CH(2)SiMe(2)N(SiMe(3))] with I(2) led to the formation of the larger metallacycle [UN*(N{SiMe(3)}SiMe(2)CH(2)CH(2)SiMe(2)N{SiMe(3)})I] resulting from U-C cleavage and C-C coupling. Reaction of [NaUN*(O,N)(2)] [O,N = OC(=CH(2))SiMe(2)N(SiMe(3))] with I(2) afforded the U(V) complex [Na{UN*(O,N)(2)}(2)(µ-I)] which was converted into the mononuclear azido derivative [NaUN*(O,N)(2)(N(3))]. This latter was not transformed into the neutral U(VI) derivative in the presence of I(2) but afforded [U(V)(N{SiMe(3)}SiMe(2)C{CHI}O)(2)I(THF)], resulting from a cascade of addition, substitution and protonolysis reactions.

Solution, solid state, and film properties of a structurally characterized highly luminescent molecular europium plastic material excitable with visible light.

The synthesis and X-ray crystal structure of the ligand L (4,7-dicarbazol-9-yl-[1,10]-phenanthroline) are reported, as well as those of the molecular complex, [Eu(tta)(3)(L)] (1), (tta = 2-thenoyl trifluoroacetylacetonate). Their photophysical properties have been investigated both in solution and in the solid state. It was shown that the ligands used for designing 1 are well-suited for sensitizing the Eu(III) ion emission, thanks to a favorable position of the triplet state as investigated in the Gd(III) complex [Gd(tta)(3)(L)], (2). The low local symmetry of the Eu(III) ion shown by the X-ray crystal structure of 1 is also revealed by luminescence spectroscopy. Because of interesting volatility and solubility properties, 1 is shown to behave as a real molecular material that can be processed both by thermal evaporation and from solution. When doped in poly(methylmethacrylate) (PMMA), 1 forms air-stable and highly red-emitting plastic materials that can be excited in a wide range of wavelengths from the UV to the visible part of the electromagnetic spectrum (250-560 nm). Absolute quantum yields of 80% have been obtained for films comprising 1-3% of 1. Ellipsometry measurements have been introduced to gain information on physical data of 1. They have been performed on thin films of 1 deposited by thermal evaporation and gave access to the refractive index, n, and the absorption coefficient, k, as a function of the wavelength. A value of 1.70 has been found for n at 633 nm. These thin films also show interesting air-stability.

Exploring the uranyl organometallic chemistry: from single to double uranium-carbon bonds.

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.

Europium(II) compounds: simple synthesis of a molecular complex in water and coordination polymers with 2,2'-bipyrimidine-mediated ferromagnetic interactions.

Reaction between EuCl(2) and 2,2'-bipyrimidine (bpm) in de-oxygenated water afforded a cationic molecular complex [EuCl(bpm)(2)(H(2)O)(4)][Cl]·H(2)O (1). When performed in an organic solvent such as THF or methanol, the same reaction yielded a 3-dimensional coordination polymer of formula [EuCl(2)(bpm)(MeOH)(0.5)](∞) (2) in which both bpm and the chloride ions act as linkers between the Eu(II) ions. Upon replacing Cl(-) by I(-), two coordination polymers of formula {[Eu(bpm)(2)(H(2)O)(3)][I](2)·0.5bpm}(∞) (3) and {[Eu(I)(bpm)(MeOH)][I]}(∞) (4) were obtained from reaction in water and methanol, respectively. All these compounds were characterized by X-ray crystallography. Investigations of the magnetic properties revealed a weak antiferromagnetic coupling in 2, while 3 and 4 showed a weak ferromagnetic coupling at low temperature.

The bis metallacyclic anion [U(N{SiMe3}2)(CH2SiMe2N{SiMe3})2]-.

A series of bis metallacyclic compounds [M(THF)(x)UN*(CH(2)SiMe(2)N{SiMe(3)})(2)](n) [M = Na (2), Li (3), or K (4), N* = N(SiMe(3))(2)] were isolated from reactions of UCl(4) or [UN*(3)Cl] with MN* or by treatment of [UN*(2)(CH(2)SiMe(2)N{SiMe(3)})] (1) or [UN*(3)] with MN*, MH, or LiCH(2)SiMe(3) in tetrahydrofuran (THF). Crystals of 2a x 1/6n-pentane (x = 0), 2b (x = 1), 2c (x = 2), and 4b (x = 1) were obtained by crystallization of 2 and 4 from pentane, and [Na(18-crown-6)(THF)][UN*(CH(2)SiMe(2)N{SiMe(3)})(2)] (2d) and [Na(15-crown-5)][UN*(CH(2)SiMe(2)N{SiMe(3)})(2)] (2e) were formed upon addition of the crown ether. The crystal structures of 2a-2e and 4b exhibit the same [UN*(CH(2)SiMe(2)N{SiMe(3)})(2)] units which are linked to Na or K atoms via methylene or methyl groups, giving either tight cation-anion pairs (2d and 2e) or one-dimensional (1D) or two-dimensional (2D) polymeric compounds with Na or K atoms in bridging position between methylene groups of adjacent units. Reaction of 2 with CO gave the double insertion derivative [Na(2)(THF)U(2)N*(2)(OC{=CH(2)}SiMe(2)N{SiMe(3)})(4)] (5b) and [Na(15-crown-5)UN*(OC{=CH(2)}SiMe(2)N{SiMe(3)})(2)] (5c) in the presence of the crown ether. Thermal decomposition of 5b gave [Na(2)(THF)U(OC{=CH(2)}SiMe(2)N{SiMe(3)})(3)](2) (6), the product of CO insertion into the putative tris metallacycle [Na(2)(THF)(x)U(CH(2)SiMe(2)N{SiMe(3)})(3)]. The crystal structures of 5b, 5c, and 6 show the interaction of the Na atoms with the exocyclic C=CH(2) bonds. Diffusion of CO(2) into a THF solution of 2 led to the formation of [Na(THF)(x)UN*(OC{O}CH(2)SiMe(2)N{SiMe(3)})(2)] (7) which crystallized from pyridine/pentane to give [Na(THF)(2)(py)(2)UN*(OC{O}CH(2)SiMe(2)N{SiMe(3)})(2)] x 0.5 py (8 x 0.5 py), the first crystallographically characterized complex resulting from CO(2) insertion into a M(CH(2)SiMe(2)N{SiMe(3)}) metallacycle. Compound 2 reacted with I(2) to give [UN*(CH(2)SiMe(2)N{SiMe(3)})(N{SiMe(3)}SiMe(2)CH(2)I)] (9) which would represent a new type of so-called "pendulum" systems resulting from a degenerate sigma bond metathesis reaction of U-C and C-I bonds.

Formation of uranium(IV) oxide clusters from uranocene [U(eta(8)-C8H8)2] and uranyl [UO2X2] compounds.

Uranocene [U(eta(8)-C(8)H(8))(2)] reacted in refluxing pyridine with 2 equiv of the uranyl(VI) compound [UO(2)(OTf)(2)] or [UO(2)I(2)(THF)(3)] (OTf = O(3)SCF(3); THF = tetrahydrofuran) or 1 equiv of the uranyl(V) complex [UO(2)(py)(2.3)K(OTf)(2)] to afford the hexanuclear uranium(IV) oxide cluster [U(6)O(8)(OTf)(8)(py)(8)] (1) or [U(6)O(8)I(8)(py)(10)] (3). Complexes 1 and 3 were easily isolated in good yield because they were deposited as microcrystalline powders with the release of free cyclooctatetraene as a unique byproduct. A similar reaction in THF gave [U(6)O(8)(OTf)(8)(THF)(8)] (2), whose isolation was impeded by polymerization of the solvent. With complexes [U(eta(8)-C(8)H(8))(2)] and [UO(2)(OTf)(2)] in a molar ratio of 4:3 or in the presence of excess uranocene, only crystals of the mono(eta(8)-C(8)H(8)) aggregate [U(6)O(8)(eta(8)-C(8)H(8))(OTf)(6)(py)(8)] (4) were obtained. The crystal structures of 1 x 2 py, 2 x 2 THF, 3 x py, and 4 x py were determined. Whereas uranocene and uranyl(VI) compounds are generally viewed as the most robust uranium compounds, they were found to fuse together into hexanuclear assemblages. These studies revealed the unusual four-electron reductive capacity of a uranium(IV) complex, in particular uranocene, which, through the loss of its two C(8)H(8) ligands, induces the activation and reduction of the strong U=O bonds of the uranyl moiety.

Linear uranium metallocenes with polydentate aromatic nitrogen ligands.

Treatment of [Cp*(2)U(NCMe)(5)]X(2) [Cp* = C(5)Me(5), X = BPh(4) (1) or I (1')] or Cp*(2)UI(2) in acetonitrile with the polydentate aromatic nitrogen bases phen, terpy and R(4)btbp led to the formation of the linear uranium metallocenes [Cp*(2)U(NCMe)(3)(phen)]X(2) [X = BPh(4) (2), I (2')], [Cp*(2)U(NCMe)(2)(terpy)][BPh(4)](2) (4), [Cp*(2)U(NCMe)(Me(4)btbp)][BPh(4)](2) (5) and [Cp*(2)U(NCMe)(CyMe(4)btbp)][X](2), [X = BPh(4) (6), I (6')], [phen = 1,10-phenanthroline, terpy = 2,2':6,2''-terpyridine, Me(4)btbp = 6,6'-bis-(3,3,6,6-tetramethyl-1,2,4-triazin-3-yl)-2,2'-bipyridine, CyMe(4)btbp = 6,6'-bis-(3,3,6,6-tetramethyl-cyclohexane-1,2,4-triazin-3-yl)-2,2'-bipyridine]. The bent metallocene [Cp*(2)U(phen)(2)][BPh(4)](2) (3) was isolated from the reaction of 1 and two molar equivalents of phen in THF. The X-ray crystal structures of 2.2MeCN, 3.2THF, and 6'.2MeCN were determined.