Structural basis for regioisomerization in the alkali-metal-mediated zincation (AMMZn) of trifluoromethyl benzene by isolation of kinetic and thermodynamic intermediates.

Performed with a desire to advance knowledge of the structures and mechanisms governing alkali-metal-mediated zincation, this study monitors the reaction between the TMP-dialkylzincate reagent [(TMEDA)Na(TMP)((t)Bu)Zn((t)Bu)] 1 and trifluoromethyl benzene C(6)H(5)CF(3) 2. A complicated mixture of products is observed at room temperature. X-ray crystallography has identified two of these products as ortho- and meta-regioisomers of heterotrianionic [(TMEDA)Na(TMP)(C(6)H(4)-CF(3))Zn((t)Bu)], 3-ortho and 3-meta, respectively. Multinuclear NMR data of the bulk crystalline product confirm the presence of these two regioisomers as well as a third isomer, 3-para, in a respective ratio of 20:11:1, and an additional product 4, which also exhibits ortho-zincation of the aryl substrate. Repeating the reaction at 0 degrees C gave exclusively 4, which was crystallographically characterized as [{(TMEDA)(2)Na}(+){Zn(C(6)H(4)-CF(3))((t)Bu)(2)}(-)]. Mimicking the original room-temperature reaction, this kinetic product was subsequently reacted with TMP(H) to afford a complicated mixture of products, including significantly the three regioisomers of 3. Surprisingly, 4 adopts a solvent-separated ion pair arrangement in contrast to the contacted ion variants of 3-ortho and 3-meta. Aided by DFT calculations on model systems, discussion focuses on the different basicities, amido or alkyl, and steps, exhibited in these reactions, and how the structures and bonding within these isolated key metallic intermediates (prior to any electrophilic interception step), specifically the interactions involving the alkali metal, influence the regioselectivity of the Zn-H exchange process.

(Acetato-kappaO)[tris(3,5-dimethylpyrazol-1-yl-kappaN2)hydroborato]zinc(II).

The title complex, [Zn(C15H22BN6)(C2H3O2)] or (Tp(Me,Me))Zn(OAc), contains a tripodal tris(pyrazolyl)hydroborate ligand, a monodentate acetate ligand and a Zn(II) centre in a distorted tetrahedral coordination environment capped on one triangular face by a secondary Zn...O interaction with the second O atom of the acetate ligand. The four-coordination of Zn(II) and the essentially monodentate character of the acetate ligand are due to the high steric demands of the ligand set, which prevent chelate formation and five-coordination and lead to relatively long Zn-O and Zn-N bonds compared with related complexes of Zn(II) and other metals.

Bis(tetraphenylphosphonium) (hexasulfido-2kappa2S1,S6)di-mu-sulfido-disulfido-1kappa2S-tungsten(VI)zinc(II) acetone solvate.

The title complex, (C(24)H(20)P)(2)[WZnS(4)(S(6))].C(3)H(6)O or (Ph(4)P)(2)[WS(2)(mu-S)(2){Zn(S(6))}].Me(2)CO, was unexpectedly obtained on attempted recrystallization of a mixed tungten-zinc complex of a tris(pyrazolato)borate ligand. The two metal centres of the anion have distorted tetrahedral coordination and the two tetrahedra share one S...S edge; tungsten is additionally coordinated by two terminal sulfide ligands and zinc by a chelating S(6)(2-) ligand, which has one central S-S bond significantly longer than the other four, a pattern found to be consistent for this ligand. This is the first reported example of a tetrahedral zinc centre bridging an edge of a single tetrathiotungstate(VI) or tetrathiomolybdate(VI) anion, although there are many previous examples with other metals.

Transamination chemistry of sodium TMP-zincate: synthesis and crystal structure of a chiral amidozincate.

In a new type of reactivity for sodium TMP-zincate [(TMEDA)NaZn((t)Bu)(2)(TMP)] (1), transamination reactions with the amines diisopropylamine, DA(H), hexamethyldisilazane, HMDS(H) and chiral (R)-N-benzyl-alpha-methylbenzylamine have produced new sodium amido-di-tert-butyl zincates (all structurally characterised) with concomitant loss of TMP(H).

Structural variations in bimetallic sodium-magnesium and sodium-zinc ketimides, and a sodium-zinc alkide-alkoxide-amide: connections to ring-stacking, ring-laddering, and inverse crown concepts.

The first sodium-magnesium and sodium-zinc ketimido complexes display contrasting inverse crown ring and pseudo-cubane structures respectively, while a sodium-zinc heterotrianionic alkide-alkoxide-amide adopts a third type of structure with a stepped ladder motif.

Dizincation and dimagnesiation of benzene using alkali-metal-mediated metallation.

Benzene can be easily 1,4-dideprotonated stoichiometrically on reaction with two equivalents of a synergic mixture of tBu2Zn, NaTMP and TMEDA to give a unique 1,4-dizincated benzene product which has been characterised by X-ray crystallography and NMR spectroscopy as well as modelled theoretically by DFT computational studies; a related synergic dimagnesiation of benzene is also reported.

Vanadyl C and N-capped tris(phenolate) complexes: influence of pro-catalyst geometry on catalytic activity.

Vanadyl complexes of C or N-capped tripodal ligands, possessing distorted tetrahedral geometry at vanadium, serve as extremely active, thermally robust pro-catalysts for ethylene homo- and ethylene/propylene copolymerisation, whereas pseudo-octahedral pro-catalysts produce far lower activities.

Vanadyl complexes bearing bi- and triphenolate chelate ligands: highly active ethylene polymerisation procatalysts.

Vanadyl procatalysts bearing chelating aryloxide ligands are found to polymerise ethylene, in the presence of dimethylaluminium chloride, with (for this metal) exceptionally high activities.

Bis(benzimidazole)amine vanadium catalysts for olefin polymerisation and co-polymerisation: thermally robust, single-site catalysts activated by simple alkylaluminium reagents.

Vanadium complexes containing bis(benzimidazole)amine ligands, upon activation by simple alkylaluminium reagents, give unusually robust, single-site, catalysts for olefin polymerisation/co-polymerisation.

Synthesis, structure and ethylene polymerisation behaviour of vanadium(IV and V) complexes bearing chelating aryloxides.

The reaction of [V(Np-tolyl)Cl3] with the sulfur-bridged diphenol ligand 2,2'-thiobis(4,6-di-tert-butylphenol), {2,2'-S[4,6-(t-Bu)2C6H2OH]2} (LSH2) afforded the complexes [V(LS)2] (1) and [VOCl3(MeCN)2][H3Np-tolyl] (2). Complex 2 could also be prepared directly from [V(Np-tolyl)Cl3] and 'wet' acetonitrile. Reaction of [V(Np-tolyl)(Ot-Bu)3] with LSH2 afforded [VO(mu2-OH)(LS)]2 x 6(MeCN) (3), whilst reaction of [VO(On-Pr)3] with 2,2'-sulfinylbis(4,6-di-tert-butylphenol), {2,2'-SO2[4,6-(t-Bu)2C6H2OH]2} (LSO2H2), afforded [V(LSO2)2] x MeCN (4). The reaction of [VO(Oi-Pr)3] with the ethylidene-bridged diphenol 2,2'-ethylidenebis(4,6-di-tert-butylphenol), {2,2'-CH3CH[4,6-(t-Bu)2C6H2OH]2} (LH2) afforded the hydroxyl bridged complexes [(VOL)2(mu2-OH)(mu2-Oi-Pr)] (5) (major product) and [VO(mu2-OH)(L)]2 x 4(MeCN) (6) (minor product). In general, we find that controlled hydrolysis of [V(NAr)(On-Pr)3] (Ar = p-ClC6H4, p-OCNC6H4 or p-tolyl) in the presence of LH2 reproducibly led to the vanadyl complex [VO(mu-On-Pr)L]2 x 2(MeCN) (7), in which the n-propoxide bridges both unexpectedly lie above the V2O2 plane. Reaction of the linear triphenol 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-tert-butylphenol, [ArCH2Ar(1)CH2Ar] (Ar = 4,6-di-tert-butylphenol; Ar()1 = 4-tert-butylphenol) (L(1)H3), and [VO(On-Pr)3] afforded the complex [VOL(1)]2 x 3(MeCN) (8), whilst reaction of [V(Np-tolyl)(Oi-Pr)3] with the related methylene-bridged linear triphenol 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-methylphenol, [ArCH2Ar(2)CH2Ar] (L(2)H3) (Ar(2) = 4-methylphenol), gave {[V(mu2-O)(Np-tolyl)][VO(Oi-Pr)]L(2)}2 x 1.5(MeCN) (9). The crystal structures of 1 to 9 are reported. Complexes 1-4 and 7-9 were screened as pro-catalysts for the polymerisation of ethylene in the presence of the co-catalyst dimethylaluminium chloride (DMAC) and the re-activator ethyltrichloroacetate (ETA). All are highly active ethylene polymerisation catalysts with activities covering the range 2000 to 90,000 g mmol(-1) h(-1) bar(-1), and these results are discussed in terms of the ligands present at vanadium in the pro-catalyst. Complex 3 has also been screened for ethylene/propylene copolymerisation.

Two square-planar palladium(II) complexes with P,O-bidentate hybrid ligands.

In the two square-planar palladium(II) complexes chloro[(diphenylphosphinoamino)diphenylphosphine oxide]methylpalladium(II) dimethyl sulfoxide solvate, [Pd(CH3)Cl(C24H21NOP2)].C2H6OS, (I), and chloro{[2-(diphenylphosphino)phenyl]diethoxymethane}methylpalladium(II), [Pd(CH3)Cl(C23H25O2P)], (II), a trans disposition of the diphenylphosphino and chloro groups is observed. The Pd atom in both complexes displays a distorted square-planar configuration formed by the four unique donor atoms (P, Cl, C and O). In compound (I), the five-membered Pd-P-N-P-O metallacycle is best described as having an envelope conformation, whereas in (II) the six-membered Pd-P-C-C-C-O metallacycle adopts a skewed boat conformation. Furthermore, within the P-N-P-O backbone in (I), the P-N distances are consistent with single-bond character [1.659 (3) and 1.692 (3) A], whilst the P=O bond shows appreciable double-bond character [1.509 (2) A].

Synthesis and characterization of mixed-metal complexes of Ag/Cu and W/Mo and a complex of Ag with heterocyclic thione ligands.

Reactions of AgI with salts of [WS(4)](2-) or [MoS(4)](2-) and with either imidazolidine-2-thione (Imt) or [1,3]diazepane-2-thione (Diap) give the complexes [WS(4)Ag(2)(Imt)(2)](n) and [MS(4)Ag(2)(Diap)(4)] [M = W or Mo]; in the case of Diap, corresponding Cu complexes can be obtained with CuCl instead of AgI. Decomposition of the Ag-Diap complexes during attempted recrystallization leads to the polymeric complex [AgI(Diap)](n). The monomeric mixed-metal Diap complexes contain edge-sharing WS(4) and AgS(4) tetrahedra, the Diap ligands being terminally bonded to Ag through sulfur. The mixed-metal W-Ag-Imt complex is a chain polymer with two different environments for the WS(4) unit and three different coordination environments for Ag, one of which is an unprecedented AgS(5) square-based pyramid; Imt ligands are terminally coordinated to Ag. [AgI(Diap)](n) has a complex polymeric chain structure with three different distorted tetrahedral environments for Ag, direct Ag-Ag bonding, both bridging and terminal I, and all Diap ligands bridging pairs of Ag atoms. All the crystal structures feature N-H[...]S or N-H[...]I hydrogen bonding. The complexes have also been characterised by infrared, UV-Vis and (1)H and (13)C NMR spectroscopy.