Constructing cerium supramolecular wheels and encapsulating uranium with a Schiff-base calixpyrrole ligand.

Trinuclear, supramolecular wheel structures are formed spontaneously from the metallation of a Schiff-base-pyrrole macrocycle by Ce(3+) cations, while the related actinide U(3+) cation is instead oxidised to U(4+) and encapsulated by the macrocyclic framework.

Functionalised saturated-backbone carbene ligands: yttrium and uranyl alkoxy-carbene complexes and bicyclic carbene-alcohol adducts.

A new and modular route to bidentate ligands that combines an alkoxide with a saturated backbone N-heterocyclic carbene (NHC) is presented. The bi(heterocyclic) compounds are formally the addition product of a saturated NHC and the alcohol group of the N-functionalised arm. Using these compounds, the synthesis and structural characterisation of the first electropositive metal complexes of saturated N-heterocyclic carbenes has been achieved, and examples structurally characterised for the yttrium(III) and the uranyl [UO(2)](2+) cations.

Low-valent uranium iodides: straightforward solution syntheses of UI3 and UI4 etherates.

Uranium turnings react with elemental iodine in diethyl ether at room temperature, with sonication and/or stirring, over a period of days to afford UI 3, UI 4(OEt 2) 2, or UI 4(OBu (n) 2) depending on the stoichiometry or ether solvent. This is the first room temperature, and thus safe and convenient, synthesis of UI 3.

Comparisons between yttrium and titanium N-heterocyclic carbene complexes in the search for early transition metal NHC backbonding interactions.

The d (0) yttrium N-heterocyclic carbene compound YL 3 (L = OCMe 2CH 2[C{N(CHCH)NPr ( i )}]) has been made and structurally characterized. It adopts a mer configuration of the three bidentate ligands. A comparison of this with the isostructural d (1) titanium complex TiL 3 is made in order to seek experimental evidence of a pi-bonding contribution to the M-C bond. This has been augmented by DFT calculations. Experimentally, the metal radius-corrected Ti-C distance is shorter than the Y-C distance, suggesting a pi-bonding contribution in the d (1) complex, but the computational data suggest that a shorter sigma bond might simply be formed by the more strongly polarizing titanium cation. From the potassium reduction of TiL(OPr ( i )) 3, only a byproduct arising from silicone grease activation was isolable, identified as a mixed-valent, multinuclear, d (0)/d (1) cluster [Ti (III)L 2{Pr ( i )OSiMe 2O}K 2OTi (IV)(OPr ( i )) 4] 2 in which the carbene ligands are bound to the Ti (III) centers in preference to Ti (IV), with longer Ti-C distances than those found in TiL 3.

Magnesium amido N-heterocyclic carbene complexes.

Magnesium dications bind strongly to a tridentate anionic dicarbene ligand L = [N{CH(2)CH(2)(CNCHCHNMes)}(2)] forming dinuclear and trinuclear Mg complexes with some particularly short Mg-C bonds. Treatment of the proligand H(4)LCl(3) with three equivalents of methyl magnesium chloride or benzyl magnesium chloride affords Mg(3)(HL)Cl(6) in high yield. A suspension of in thf was heated to 80 degrees C for 2 h to afford Mg(2)(L)Cl(3), consistent with the loss of one equivalent of MgCl(2), and the deprotonation of the remaining acidic NH, lost as HCl gas. Treatment of Mg(3)(HL)Cl(6) with one equivalent of KC(8) results in deprotonation of the ligand amine NH to afford Mg(3)(L)Cl(5); treatment with a second equivalent forms the radical anion of the complex, K[Mg(3)(L)Cl(5)], which decomposes upon storage, precluding its structural characterisation. The acidic NH proton of the ligand in Mg(3)(HL)Cl(6) can also be removed by deprotonation with Li{N(SiMe(3))(2)}; additional equivalents of which also exchange the magnesium-bound chlorides for silylamido ligands, affording Mg(2)(L)Cl(2)N'' and Mg(2)(L)Cl(N'')(2), which have both been characterised by single-crystal X-ray diffraction studies.

Cubane and step-form structures of dilithium bis(aryloxy)phosphines.

The lithium complexes RP(3,5-tBu2C6H2OLi)2(THF)4, where R = Ph or i Pr, (R[OPO]Li2)2(THF)4, synthesized by reaction of the 2-bromo-4,6-di-tert-butylphenol with BuLi and the appropriate dichlorophosphine, possess solid state structures composed of lithium oxide tetragons arranged in a step-form or face sharing half-cubane arrangements. Incorporation of excess lithium aryloxide results in the formation of complexes that display an extended step-form structure, [Ph[OPO]Li2(ArOLi)]2, or a distorted cubane arrangement of tetragons, [iPr[OPO]Li3Cl(ArOLi)](THF)3.

Formation of phosphorus-nitrogen bonds by reduction of a titanium phosphine complex under molecular nitrogen.

The reduction of high oxidation state metal complexes in the presence of molecular nitrogen is one of the most common methods to synthesize a dinitrogen complex. However, the presence of strong reducing agents combined with the poor binding ability of N2 can lead to unanticipated outcomes. For example, the reduction of [NPN]ZrCl2(THF) (where NPN = PhP(CH2SiMe2NPh)2) with KC8 under N2 leads to the formation of the side-on bridged dinuclear dinitrogen complex ([NPN]Zr(THF))2(mu-eta2:eta2-N2) with an N-N bond distance of 1.503(3) A; however, reduction of the corresponding titanium precursor, [NPN]TiCl2, under N2 does not generate a dinitrogen complex, rather the bis(phosphinimide) derivative, ([N(PN)N]Ti)2, is isolated in which the added N2 is incorporated between the titanium and phosphine centers. Performing the reaction under 15N2 results in the 15N label being incorporated in the phosphinimide unit. A suggested mechanism for this process involves an initially formed dinitrogen complex being over reduced to generate a species with bridging nitrides that undergoes nucleophilic attack by the coordinated phosphine ligands and formation of the P=N bond of the phosphinimide.

Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors.

The preparation and characterization of the macrocyclic diamido-diarsine ligand [As2N2]Li2(1,4-dioxane) (1) (where As2N2 = PhAs(CH2SiMe2NSiMe2CH2)2AsPh) and a series of early transition metal complexes are presented. The complexes [As2N2]MCl2 (M = Zr, 2; Ti, 4) and the complex ([As2N2]Y)2(mu-Cl)2 (5) can be prepared by reaction of 1 with the corresponding THF adduct of the metal halide. The iodide derivative of 2, [As2N2]ZrI2 (3) can be prepared by reaction with iodotrimethylsilane. The lithium complex 1 displays a very long lithium-arsenic bond distance of 3.162(10) A, and the yttrium complex 5 is the first known complex containing a yttrium-arsenic bond. Reduction of 2, 3 or 4 using C8K or activated magnesium decomposed the complexes in such a manner that the ligand was separated from the metal centre. Indirect evidence suggests this may be due to reduction of arsenic in the ligand in preference to the metal.