Chemoselective cycloadditions to epoxide derivatives of erucic acid with CO2 and CS2: controlled access to value-added bio-derived compounds

The potential for application of bio-derived molecules in our everyday lives is attracting vast interest as attention moves towards development of a truly circular and sustainable economy. Whilst a large number of molecules are naturally available and contain a variety of functional groups, few of these compounds are able to be immediately transferred to applications where they can directly replace established oil-derived species. This issue presents both a challenge and an opportunity for the synthetic chemistry community. This study demonstrates how erucic acid, a molecule containing an olefin and a carboxylic acid, which is readily available from commonly cultivated rapeseed oils, can be used as a platform to be chemoselectively converted into a range of value-added compounds using established and high yielding synthetic procedures. In particular, the work showcases approaches towards the chemoselective (and in cases regioselective) oxidation with m-CPBA and incorporation of cyclic carbonate and cyclic dithiocarbonate functionalities which have potential to be employed in a range of applications. Expedient routes to unusual derivatives containing both cyclic carbonate and cyclic dithiocarbonates are also presented taking advantage of the distinct reactivities of the two different epoxides in the intermediate compounds. This work also provides a rare example of the synthesis of internal cyclic dithiocarbonates. These new products have potential to be applied as monomers in the growing field of bio-based non-isocyanate polyurethane synthesis.Comunidad de MadridMinisterio de Ciencia, Innovación y UniversidadesUniversidad de Alcal

Group 4 metallocene complexes with non-bridged and tetramethyldisiloxane-bridged methyl-phenyl-cyclopentadienyl ligands: synthesis, characterization and olefin polymerization studies

The non-vicinal methyl-phenyl-substituted zirconocene dichlorides meso-and rac-[Zr{η5-(1-Ph-3-Me-C5H3)}2Cl2] and [Zr(η5-C5H5){η5-(1-Ph-3-Me-C5H3)}Cl2] have been isolated by transmetallation of the lithium salt Li(1-Ph-3-Me-C5H3) to ZrCl4(THF)2 and [Zr(η5-C5H5)Cl3 · DME] (DME = dimethoxyethane), respectively. Similar transmetallation of the lithium salt Li2[(Me-Ph-C5H2SiMe2)2O] to MCl4 gave the ansa-metallocenes [M{η5-(Me-Ph-C5H2SiMe2)2O}Cl2] (M = Zr, Hf) for which the meso- and rac-diastereomers were separated. The dimethyl and dibenzyl derivatives of these metallocenes were also prepared and the structure of all of these compounds determined by NMR spectroscopy. The molecular structure of rac-[Zr{η5-(2-Me-4-Ph-C5H2SiMe2)2O}Cl2] was determined by single crystal X-ray diffraction methods. The activity of the dichlorometallocenes/MAO catalysts for ethene and propene polymerization was evaluated.Ministerio de Educación, Cultura y DeporteRepsol-YP

Evidence of fluoride transfer from the anion of\ud [Zr{C5H3[SiMe2(η1-NtBu)]2}]+[RB(C6F5)3]_\ud complexes to the zirconocenium cation

In summary, we have found experimental evidence to support a reaction pathway involving direct fluoride migration\ud to the zirconium cation without previous transfer of C6F5.\ud It is noteworthy that the opening of the silyl–amido bridge was not observed in the course of these activations. Experiments with other donor ligands are in progress to investigate the conditions under which the ion pairs 1 and 2 may follow different decomposition routes and the possible mechanisms of these reactions.Financial support by the Spanish MEC (project MAT2004-02614)\ud and DGUI/CM (program S/0505/PPQ-0328) is acknowleged

Dinuclear dialkoxo-bridged cyclopentadienylsiloxo titanium complexes

The dinuclear dialkoxo-bridged complexes [(TiCl)2(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (O2L = 1,2-O2C2H41a, 1,2-O2C6H41b, 1,2-(OCH2)2C6H41c, O2SiPh21d) were obtained by reaction of [(TiCl2)2(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (A) with the corresponding dilithium salt (1a) or diol (1b, 1c, 1d). Alkylation of 1a and 1b with ClRMg afforded [(TiR)2(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (O2L = 1,2-O2C2H4, R = Me 2a, Bz 3a; O2L = 1,2-O2C6H4, R = Me 2b, Bz 3b). Addition of four equiv. of LiOiPr to A afforded [{Ti(OiPr)2}2(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (4). Reaction of 1a with Al(C6F5)3 produced the elimination of the dialkoxo ligand to give [{TiCl(C6F5)}2(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (5), whereas the same reaction of 1b with Al(C6F5)3 produced the oxo-alane adduct [(TiCl)2(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O·Al{C6F5}3)})] (O2L = 1,2-O2C6H46) which was further transformed to give a mixture of 5 and [(TiCl){Ti(C6F5)}(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O)})] (O2L = 1,2-O2C6H47). One benzyl group of complexes 3 was abstracted with E(C6F5)3 (E = B, Al) to give the monoionic compounds [Ti(TiBz)(μ-O2L)(μ-{(η5-C5Me4SiMeO)2(μ-O)})][BzE(C6F5)3] (O2L = 1,2-O2C2H4, E = B 8B, Al 8Al; O2L = 1,2-O2C6H4, E = B 9B), although 8Al was unstable in CD2Cl2 evolving to a mixture of compounds where [(TiBz)2(μ-Cl)(μ-{(η5-C5Me4SiMeO)2(μ-O)})][BzAl(C6F5)3] (10) was identified, and compound 9B was also unstable at ambient temperature. Polymerization of ε-caprolactone was only achieved with the tetraalkoxo compound 4. All of these complexes were characterized by NMR spectroscopy and 1a, 1b and 7 by X-ray diffraction studies

Aryl-imido niobium complexes with chloro-silyl and aryl-η-amidosilyl cyclopentadienyl ligands: X-ray structure of the constrained-geometry compound [Nb(η5-C5H4SiMe2-η1-NAr)(NAr)Cl](Ar=2,6-Me2C6H3)

Reactions of the magnesium imides [Mg(NAr)(THF)]6 (Ar = 2,6-Me2C6H3, 1a; Ph, 1b) with [NbCpClCl4] (CpCl = η5-C5H4(SiMe2Cl)) afforded the imido complexes [NbCpClCl2(NAr)] (Ar = 2,6-Me2C6H3, 2a; Ph, 2b) in good yield. Compound 2a reacted with excess LiNH(2,6-Me2C6H3) to give the silyl-η-amido complex [Nb(η5-C5H4SiMe2-η1-NAr)Cl(NAr)] (Ar = 2,6-Me2C6H3, 3a). Hydrolysis of the Si–Cl bond of compounds 2a and 2b yielded the dinuclear complexes [{NbCl2(NAr)}2{(η5-C5H4SiMe2)2(μ-O)}] (Ar = 2,6-Me2C6H3, 4a; Ph, 4b), respectively. All of the new compounds reported were characterized by NMR spectroscopy and the molecular structure of 3a was determined by X-ray diffraction methods.We gratefully acknowledge the Ministerio de Educación y Ciencia (Project MAT2004-02614) and\ud DGUI-Comunidad de Madrid (Project GR/MAT/0622/2004) (Spain) for financial support. R.A.-M. acknowledges MCyT for a fellowshi

Synthesis and reactivity of oxametallacyclic niobium compounds by using α,ß-unsaturated carbonyl ligands

Reduction of mono(cyclopentadienyl)niobium complexes\ud [NbCpRCl4] [CpR = C5Me4H (1), C5H4SiMe2Cl (2),\ud C5H4SiMe3 (3)] with Na/Hg in the presence of methyl methacrylate\ud [MMA, CH2=C(Me)C(O)OMe (a)], methyl acrylate\ud [MA, CH2=CHC(O)OMe (b)] and mesityl oxide [MO,\ud CMe2=CHC(O)Me (c)] afforded the corresponding derivatives\ud [NbCpRCl2(LL)] [CpR = C5Me4H, LL = MMA (1a); CpR\ud = C5H4SiMe2Cl, LL = MMA (2a), MA (2b), MO (2c); CpR =\ud C5H4SiMe3, LL = MMA (3a), MA (3b)] in variable yields depending\ud on both the cyclopentadienyl and the ¿,ß-unsaturated\ud carbonyl compounds. The reactivity of these complexes\ud was studied toward protic and Lewis acids. Addition of triflic\ud acid TfOH (Tf = CF3SO2) to 3b gave the triflate complex\ud [NbCpRCl2{(CH2)2C(O)OMe}(OTf)] [CpR = C5H4SiMe3 (4)].\ud The Lewis acids E(C6F5)3 (E = B, Al) reacted with complexes\ud Introduction\ud The bonding interaction of a butadiene ligand with a\ud metal center is clearly dependent on the metal atom and\ud may be formulated as a system containing a dianionic ligand\ud for early high-valent transition metals or as a neutral\ud ligand for low-valent late transition metals. However, the\ud stability of the formal oxidation state of the metal atom and\ud the nature of the ancillary substituents of both the complex\ud and the diene ligand could play an important role in defining\ud this interaction. Hence, complexes with this type of ligand\ud are better represented with contributions from two\ud main canonical forms, ¿2,¿-metallacyclic or ¿2-butadiene\ud (Figure 1).[1¿5]\ud [a] Departamento de Química Inorgánica, Universidad de Alcalá,\ud Campus Universitario,\ud 28871 Alcalá de Henares (Madrid), Spain\ud Fax: 34-91-885-4683\ud E-mail: [email protected]\ud [¿] X-ray diffraction studies\ud Supporting information for this article is available on the\ud WWW under http://www.eurjic.org/ or from the author.\ud Eur. J. Inorg. Chem. 2008, 2313¿2320 © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2313\ud 2b and 3b to give the three-membered metallacyclic (or ¿2-\ud enone) compounds [NbCpRCl2{¿2-CH2=CHC(OMe){O·\ud E(C6F5)3}}] [CpR = C5H4SiMe2Cl, E = B (5), Al (6); CpR =\ud C5H4SiMe3, E = B (7), Al (8)], which decomposed to the corresponding\ud adducts MA·E(C6F5)3. The same reaction with the\ud 2a and 3a derivatives only allowed the observation of the\ud corresponding adducts MMA·E(C6F5)3. Complexes 2a,b and\ud 3a,b reacted with CO with elimination of the acrylate compounds,\ud MA and MMA, respectively, to give the carbonylniobium(\ud III) compounds [NbCpRCl2(CO)2]2 [CpR = C5H4Si-\ud Me2Cl (9), C5H4SiMe3 (10)]. Analogous reactions with CNAr\ud showed the elimination of the free MA and MMA compounds.We gratefully acknowledge the Ministerio de Educación y Ciencia\ud (MEC) (project MAT2007-60997) and the Dirección General de\ud Universidades e Investigación (DGUI) – Comunidad de Madrid\ud (programme S-0505/PPQ-0328 COMAL-CM) (Spain) for financial\ud support. R. A. A.-M. acknowledges MEC for a fellowship

Cyclopentadienyl and Alkynyl Copper(I) Derivatives with the [{Ti(η5-C5Me5)(μ-NH)}3(μ3-N)] Metalloligand

The treatment of [ClCu{(mu(3) NH)(3)Ti-3(eta(5) C5Me5)(3)(mu(3) N)}] (2) with lithium cyclopentadienide in toluene at room temperature affords [(C5H5)Cu{(mu(3) NH)(3)Ti-3(eta(5) C5Me5)(3)(mu(3) N)}] (4) where the cyclopentadienyl ligand is bound to copper(l) in an eta(2) fashion The analogous reaction of 2 with lithium acetylides [Li(C equivalent to CR)] gives complexes [(RC equivalent to C)Cu{(mu(3) NH)(3) (eta(5) C5Me5)(3)(mu(3) N)}] (R = SiMe3 (5) Ph (6)) with terminal alkynyl ligands bound to copper Compound 6 is prepared in higher yield by the treatment of [{Ti(eta(5) C5Me5)(mu NH)}(3)(mu(3) N)] (1) with [Cu(C equivalent to CPh)] in toluene at room temperature The cyclopentadienyl derivative 4 decomposes in solution to generate the edge linked double cube nitrido complex [{Cu(mu(4) N)(mu(3) NH)(2)Ti-3(eta(5) C5Me5)(3)(mu(3) N)}(2)] (3) via C5H6 elimination However solutions of the alkynyl derivatives 5 and 6 lead to copper(I) acetylide bridged double cube complexes [{Cu(mu 1 kappa C-1 2 kappa C-1 C equivalent to CR)Cu(mu(4) N)(mu(3) NH)(2)Ti-3(eta(5) C5Me5)(3)(mu(3) N)}(2)] (R = SiMe3 (7) Ph (8)) along with 1 and RC equivalent to CH The X ray crystal structures of 4 5 7 and 8 have been determinedMinisterio de Educación y Ciencia de Españ

Carbon dioxide activation assisted by a bis(chlorodimethylsilyl)cyclopentadienyl titanium compound

A great deal of interest has focused on the role of metal ions\ud as the active centers in the fixation of CO2 and its transformation. Activation of CO2 by hydroxo and oxo metal complexes to afford metal hydrogencarbonato and carbonato\ud species, respectively, is related to the function of the carbonic\ud anhydrase metalloenzyme, which catalyzes the physiologically\ud important hydration of CO2 to hydrogencarbonate

Mercury or Silver Atoms Bridging Trinuclear Titanium Imido-Nitrido Systems

The imido - nitrido complex [{Ti(eta(5)-C5Me5)(mu-NH)}(3)(mu(3)-N)] entraps mercury(II) or silver(I) halides MXn to give cube-type adducts [XnM{(mu(3)-NH)(3)Ti-3(eta(5)-C5Me5)(3)(mu(3)-N)}] which react with alkali metal bis(trimethylsilyl) amide reagents to afford [M-2{(mu(3)-N)(n)(mu(3)-NH)(2-n)Ti-3(eta(5)-C5Me5)(3)(mu-NH)(mu(3)-N)}(2)] (M = Hg, n = 2; M = Ag, n = 1) where two [Ti3N4] cores are linked by two mercury or silver atoms in a linear geometry.Ministerio de Educación y Ciencia de España, Comunidad de Madrid, Universidad de Alcal

Lewis Base Behavior of Bridging Nitrido Ligands of Titanium Polynuclear Complexes

The Lewis base behavior of mu(3)-nitrido ligands of the polynuclear titanium complexes [{Ti(eta(5)-C(5)Me(5))(mu-NH)}(3)(mu(3)-N)] (1) and [{Ti(eta(5)-C(5)Me(5))}(4)-(mu(3)-N)(4)] (2) to MX Lewis acids has been observed for the first time. Complex 1 entraps one equivalent of copper(I) halide or copper(I) trifluorornethanesulfonate through the basal NH imido groups to give cube-type adducts [XCu{(mu(3)-NH)(3)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)}] (X=Cl (3), Br (4), I (5), OSO(2)CF(3) (6)). However, the treatment of 1 with an excess (>= 2 equiv) of copper reagents afforded complexes [XCu{(mu(3)-NH)(3)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(4)-N)(CuX)}] (X=Cl (7), Br (8), I (9) OSO(2)CF(3) (10)) by incorporation of an additional CuX fragment Lit the mu(3)-N nitrido apical group. Similarly, the tetranuclear cube-type nitrido derivative 2 is capable of incorporating one, two, or up to three CuX units at the mu(3)-N ligands to give complexes [{Ti(eta(5)-C(5)Me(5))}(4)(mu(3)-N)(4-n)-{(mu(4)-N)CuX}(n)] (X=Br (11), n=1; X=Cl (12) n=2; X=OSO(2)CF(3) (13), n=3). Compound 2 also reacts with silver(I) trifluoromethanesulfortate (>= 1 equiv) to give the adduct [{Ti(eta(5)-C(5)Me(5))}(4)(mu(3)-N)(3){(mu(4)-N)AgOSO(2)CF(3)}] (14). X-ray crystal structure determinations have been performed for complexes 8-13. Density functional theory calculations have been carried out to understand the nature and strength of the interactions of [{Ti(eta(5)-C(5)H(5))(mu-NH)}(3)(mu(3)-N)] (1') and [{Ti(eta(5)-C(5)H(5))}(4)-(mu(3)-N)(4)] (2') model complexes with copper and silver MX fragments. Although coordination through the three basal NH imido groups is thermodynamically preferred in the case of V, in both complexes the mu(3)-nitrido groups act as two-electron donor Lewis bases to the appropriate Lewis acids.MINISTERIO DE EDUCACIÓN Y CIENCIA, COMUNIDAD DE MADRID, UNIVERSIDAD DE ALCALÁ, GENERALITAT DE CATALUNY