Robert P. Tooze

Carbon monoxide coupling and functionalisation at a simple uranium coordination complex

A simple coordination complex of uranium(III), a uranium tris(amide), can selectively couple gaseous CO to the linear ynediolate [OCCO]2− dianion, at room temperature and pressure, regardless of the reagent stoichiometry. This product exhibits further reactivity upon warming in the form of the addition of a C–H bond of a methyl group across the CC triple bond, this second carbon–carbon bond forming reaction generating a functionalised enediolate dianion.

Covalency in CeIV and UIV Halide and N‐Heterocyclic Carbene Bonds

Oxidative halogenation with trityl chloride provides convenient access to Ce(IV) and U(IV) chloroamides [M(N{SiMe(3)}(2))(3)Cl] and their N-heterocyclic carbene derivatives, [M(L)(N{SiMe(3)}(2))(2)Cl] (L = OCMe(2)CH(2)(CNCH(2)CH(2)NDipp) Dipp = 2,6-iPr(2)C(6)H(3)). Computational analysis of the bonding in these and a fluoro analogue, [U(L)(N{SiMe(3)}(2))(2)F], provides new information on the covalency in this relative rare oxidation state for molecular cerium complexes. Computational studies reveal increased Mayer bond orders in the actinide carbene bond compared with the lanthanide carbene bond, and natural and atoms-in-molecules analyses suggest greater overall ionicity in the cerium complexes than in the uranium analogues.

Platinum catalysed 3,4- and 1,4-diboration of α,β-unsaturated carbonyl compounds using bis-pinacolatodiboron

Bis-pinacolatodiboron reacts with α,β-unsaturated carbonyl compounds to give 1,4- and unprecedented 3,4-additions in the presence of a second generation Pt(0) catalyst at ambient temperature.

Addition-Elimination Reactions across the M−C Bond of Metal N-Heterocyclic Carbenes

Silyl, phosphinyl, stannyl, and boryl reagents can be added across the neutral metal-carbon dative bond in d(0) f-block metal N-heterocyclic carbene complexes in a reversible manner, allowing additional functional groups to be incorporated into redox-inactive organo-f-block compounds.

Palladium(II) complexes of new bulky bidentate phosphanes: active and highly regioselective catalysts for the hydroxycarbonylation of styrene.

The synthesis of four new bulky bidentate phosphines that possess both tert-butyl and trifluoromethylphenyl substituents is described. Symmetric ligands were readily obtained by alkylation of phosphidoboranes of the type Li[P(BH(3))(tBu)(Ar)] with dihaloalkanes. Non-symmetric ligands were prepared from a new stable precursor, tBu(2)P(BH(3))(CH(2))(3)Br, that should prove useful for other ligand syntheses. Palladium(II) complexes of the four new ligands were prepared and were characterised by spectroscopic methods, microanalysis and X-ray crystallography. The new [PdCl(2)(L)] complexes were evaluated as catalysts for the hydroxycarbonylation of styrene and found to give unprecedented regioselectivity and yields for a diphosphine-based catalyst. A study on promoter effects reveals that the presence of acid and chloride is necessary to achieve such selectivities. It has been proposed in the literature that such conditions result in a new pathway in which styrene is converted into 2-phenethyl chloride, with the latter being the real substrate in the reaction. However, a deuterium labelling study seems to rule out this mechanism, at least under the conditions used herein.

A 1,1′-ferrocenyl phosphine-borane: synthesis, structure and evaluation in Rh-catalyzed hydroformylation

The new ambiphilic ligand Ph2P–(1,1′-ferrocenyl)–BMes2, prepared by sequential lithiation/electrophilic trapping of 1,1′-dibromoferrocene, adopts a monomeric structure free of dative P → B and Fe → B interactions. This flexible phosphine-borane and the related o-phenylene bridged system have been evaluated in Rh-catalyzed hydroformylation.

Highly active and selective catalysts for the production of methyl propanoate via the methoxycarbonylation of ethene

A highly active and selective catalyst for the production of methyl propanoate via the methoxycarbonylation of ethene is described, based on the new zero valent palladium complex L2Pd(dba) [where L2 = 1,2-bis(di-tert-butylphosphinomethyl)benzene and dba = trans,trans-dibenzylideneacetone].

Alkyl compounds of ruthenium-(III) and -(V) and osmium(III). X-Ray crystal structures of hexakis(trimethylsilylmethyl)- and hexakis(neopentyl)diruthenium(III), dioxohexakis(trimethylsilylmethyl)diruthenium(V), and bis(η3-allyl)tetrakis(neopentyl)diosmium(III)

The interaction of MgRCl or MgR2, R = CH2SiMe3 or CH2CMe3, with Ru2(µ-O2CMe)4Cl or Os2(µO2CMe)4Cl2 leads to the compounds M2R6 and M2R4(µ-O2CMe)2; diruthenium(II) tetra-acetate, Ru2(µ-O2CMe)4, is formed in some of these alkylations. Interaction of Ru2R4(µ-O2CMe)2 with MgMe2 or MgEt2 gives the corresponding mixed hexa-alkyls. Interaction of Ru2R6 with oxygen gives the unique ruthenium(V) oxoalkyls R3Ru(O)Ru(O)R3, while interaction of Os2(µ-O2CMe)2(CH2CMe3)4 with allylmagnesium halide gives Os(η3-C3H5)2(CH2CMe3)4. X-Ray crystal structures of the two diruthenium hexa-alkyls, the ruthenium oxoalkyl, and the diosmium tetra-alkylbis(allyl) have been determined. The ruthenium(V) oxo trimethylsilylmethyl has been shown to react stoicheiometrically with propene to give the epoxide. It also reacts with PhNCO and Me3SiNPMe3 to give the respective ruthenium(V) imido complexes, Ru2(NR)2(CH2SiMe3)6.

Probing the effects of ligand structure on activity and selectivity of Cr(III) complexes for ethylene oligomerisation and polymerisation.

A series of distorted octahedral Cr(III) complexes containing tridentate S-, S/O- or N-donor ligands comprised of three distinct architectures: facultative {S(CH(2)CH(2)SC(10)H(21))(2) (L(1)) and O(CH(2)CH(2)SC(10)H(21))(2) (L(2))}, tripodal {MeC(CH(2)S(n)C(4)H(9))(3) (L(3)), MeC(CH(2)SC(10)H(21))(3) (L(4))} and macrocyclic {(C(10)H(21))[9]aneN(3) (L(5)), (C(10)H(21))(3)[9]aneN(3) (L(6)), with [9]aneN(3)=1,4,7-triazacyclononane} are reported and characterised spectroscopically. Activation of [CrCl(3)(L)] with MMAO produces very active ethylene trimerisation, oligomerisation and polymerisation catalysts, with significant dependence of the product distribution upon the ligand type present. The properties of the parent [CrCl(3)(L)] complexes are probed by cyclic voltammetry, UV-visible, EPR, EXAFS and XANES measurements, and the effects upon activation with Me(3)Al investigated similarly. Treatment with excess Me(3)Al leads to substitution of Cl ligands by Me groups, generation of an EPR silent Cr species (consistent with a change in the oxidation state of the Cr to either Cr(II) or Cr(IV)) and substantial dissociation of the neutral S and S/O-donor ligands.

Precise structure activity relationships in asymmetric catalysis using carbohydrate scaffolds to allow ready fine tuning: dialkylzinc-aldehyde additions.

The ready construction of 24 stereochemically and functionally diverse carbohydrate ligand structures from a core D-glucosamine scaffold has allowed the evaluation of broad ranging structure activity relationships in ligand accelerated zincate additions to aldehydes, with variations in deltadeltaG+/+(R-S) of up to 5650 J mol(-1) that create opposing senses of asymmetric induction and that are consistent with models based on several ligand X-ray structures and molecular mechanics analysis. Factorial analysis of enantioselectivity using key dihedral angles and steric volume on N-2 also highlight the potential for the use of factorial design in ligand construction.