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1.
Adv Mater ; 35(43): e2300429, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36897816

RESUMO

Chloride oxidation is a key industrial electrochemical process in chlorine-based chemical production and water treatment. Over the past few decades, dimensionally stable anodes (DSAs) consisting of RuO2 - and IrO2 -based mixed-metal oxides have been successfully commercialized in the electrochemical chloride oxidation industry. For a sustainable supply of anode materials, considerable efforts both from the scientific and industrial aspects for developing earth-abundant-metal-based electrocatalysts have been made. This review first describes the history of commercial DSA fabrication and strategies to improve their efficiency and stability. Important features related to the electrocatalytic performance for chloride oxidation and reaction mechanism are then summarized. From the perspective of sustainability, recent progress in the design and fabrication of noble-metal-free anode materials, as well as methods for evaluating the industrialization of novel electrocatalysts, are highlighted. Finally, future directions for developing highly efficient and stable electrocatalysts for industrial chloride oxidation are proposed.

2.
Dalton Trans ; 48(13): 4124-4138, 2019 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-30638242

RESUMO

A new family of sterically demanding N2N' heteroscorpionate pro-ligands (HC(tBu2pz)2SiMe2N(H)R (R = iPr, tBu, Ph, Xyl)) has been prepared via a straightforward modular synthetic route. An extensive study into the synthesis and characterisation of lithium, magnesium, calcium and zinc complexes supported by both 3,5-tBu and 3,5-Me substituted N2N' ligand families has been conducted. Attempted deprotonation of the pro-ligands with nBuLi afforded the corresponding lithium salts Li{HC(tBu2pz)2SiMe2NR} (R = iPr (1), tBu (2), Ph (3) and Xyl (4)) but air- and thermal-sensitivity limited the yields of these potentially useful precursors; only the sterically encumbered ligand system allowed clean reactivity. Magnesium methyl complexes Mg{HC(tBu2pz)2SiMe2NR}Me (R = iPr (5) and R = Ph (6)) were prepared using an excess of the Grignard reagent MeMgCl. Magnesium butyl complexes were synthesised in good yields using the dialkyl precursor MgnBu2 to afford Mg{HC(R'2pz)2SiMe2NR}nBu (R' = Me; R = iPr (7), tBu (8), Ad (9), Ph (10). R' = tBu; R = iPr (11), Ph (12)). Protonolylsis reactions were used to synthesise magnesium and calcium amide complexes Mg{HC(R'2pz)2SiMe2NR}{N(SiHMe2)2} (R' = Me; R = iPr (13), tBu (14), Ph (15). R' = tBu; R = Ph (16)) or Mg{HC(R'2pz)2SiMe2NR}{N(SiMe3)2} (R' = Me; R = iPr (17), tBu (18), Ph (19). R' = tBu; R = Ph (20)), and Ca{HC(R'2pz)2SiMe2NR}{N(SiMe2)2} (L) (R' = Me; L = thf; R = iPr (21), tBu (22), Ph (23). R' = tBu; L = none; R = Ph (24). Zinc methyl complexes Zn{HC(R'2pz)2SiMe2NR}Me (R' = Me; R = iPr (25), tBu (26), Ph (27). R' = tBu; R = Ph (28)) were prepared by reaction of the N2N' heteroscorpionate pro-ligands with ZnMe2. In preliminary studies, magnesium amide complexes 16 and 20 were evaluated as initiators for the ring-opening polymerisation (ROP) of ε-caprolactone (ε-CL) and rac-lactide (rac-LA). Although the overall polymerisation control was poor, 16 and 20 were found to be active initiators.

3.
Angew Chem Int Ed Engl ; 56(47): 15098-15102, 2017 11 20.
Artigo em Inglês | MEDLINE | ID: mdl-28940979

RESUMO

Reduction of indium boryl precursors to give two- and three-dimensional M-M bonded networks is influenced by the choice of supporting ligand. While the unprecedented nanoscale cluster [In68 (boryl)12 ]- (with an In12 @In44 @In12 (boryl)12 concentric structure), can be isolated from the potassium reduction of a bis(boryl)indium(III) chloride precursor, analogous reduction of the corresponding (benzamidinate)InIII Br(boryl) system gives a near-planar (and weakly aromatic) tetranuclear [In4 (boryl)4 ]2- system.

4.
J Am Chem Soc ; 138(13): 4555-64, 2016 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-26981766

RESUMO

By employing strongly σ-donating boryl ancillary ligands, the oxidative addition of H2 to a single site Sn(II) system has been achieved for the first time, generating (boryl)2SnH2. Similar chemistry can also be achieved for protic and hydridic E-H bonds (N-H/O-H, Si-H/B-H, respectively). In the case of ammonia (and water, albeit more slowly), E-H oxidative addition can be shown to be followed by reductive elimination to give an N- (or O-)borylated product. Thus, in stoichiometric fashion, redox-based bond cleavage/formation is demonstrated for a single main group metal center at room temperature. From a mechanistic viewpoint, a two-step coordination/proton transfer process for N-H activation is shown to be viable through the isolation of species of the types Sn(boryl)2·NH3 and [Sn(boryl)2(NH2)](-) and their onward conversion to the formal oxidative addition product Sn(boryl)2(H)(NH2).

5.
J Am Chem Soc ; 136(31): 10902-5, 2014 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-25036798

RESUMO

Monomeric five-valence-electron bis(boryl) complexes of gallium, indium, and thallium undergo oxidative M-C bond formation with 2,3-dimethylbutadiene, in a manner consistent with both the redox properties expected for M(II) species and with metal-centered radical character. The weaker nature of the M-C bond for the heavier two elements leads to the observation of reversibility in M-C bond formation (for indium) and to the isolation of products resulting from subsequent B-C reductive elimination (for both indium and thallium).

6.
Chem Commun (Camb) ; 50(29): 3841-4, 2014 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-24589585

RESUMO

Synthetic routes to the first boryl complexes of cadmium and mercury are reported via transmetallation from boryllithium; the syntheses of related group 14 systems highlight the additional factors associated with extension to more redox-active post-transition elements.

7.
Nat Chem ; 6(4): 315-9, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24651198

RESUMO

The chemistry of the Group 13 metals is dominated by the +1 and +3 oxidation states, and simple monomeric M(II) species are typically short-lived, highly reactive species. Here we report the first thermally robust monomeric MX2 radicals of gallium, indium and thallium. By making use of sterically demanding boryl substituents, compounds of the type M(II)(boryl)2 (M = Ga, In, Tl) can be synthesized. These decompose above 130 °C and are amenable to structural characterization in the solid state by X-ray crystallography. Electron paramagnetic resonance and computational studies reveal a dominant metal-centred character for all three radicals (>70% spin density at the metal). M(II) species have been invoked as key short-lived intermediates in well-known electron-transfer processes; consistently, the chemical behaviour of these novel isolated species reveals facile one-electron shuttling processes at the metal centre.

8.
Dalton Trans ; 42(25): 9313-24, 2013 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-23435514

RESUMO

Reaction of the OOO-coordinating tridentate bis(phenolate) protio-ligand 2,2'-{oxybis(methylene)}bis{4,6-di(1-methyl-1-phenylethyl)phenol} (L(O3)-H2), with 1 equiv. of KN(SiMe3)2 in toluene or THF yielded [K(L(O3)-H)] (1) or [K(L(O3)-H)(THF)] (2), respectively. Single-crystal X-ray diffraction studies of 1 and 2 revealed mononuclear structures with the phenyl rings of the bulky ligand displaying stabilising π-interactions to the potassium centre. L(O3)-H2 also reacts with 1 equiv. of ZnEt2 or Mg(n)Bu2 to give [M2(L(O3))2] (M = Zn (3) or Mg (4)) in good yield. The molecular structures of complex 3 and 4 reveal dinuclear species in which the metal centres are tetra-coordinated to the three oxygen atoms of one L(O3) ligand, and to the bridging oxygen atom of one phenolate group of another. Complexes 1-4 are catalysts for ring-opening polymerisation of ε-caprolactone and L- and rac-lactide in the presence of benzyl alcohol (BnOH) and also other initiators to give the corresponding polyesters. Kinetic studies for the ROP of ε-caprolactone using 3 and BnOH gives an unusual rate expression R(p) = -d[CL]/dt = k(p)[BnOH]0[3]0(0.5) for which a tentative kinetic model is proposed.


Assuntos
Ésteres/química , Magnésio/química , Compostos Organometálicos/química , Fenóis/química , Potássio/química , Zinco/química , Caproatos/química , Catálise , Dioxanos/química , Lactonas/química , Ligantes , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/síntese química , Polimerização
9.
Angew Chem Int Ed Engl ; 52(2): 568-71, 2013 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-23165894

RESUMO

Si in sight: a one-pot, single-step synthesis of an acyclic silylsilylene, Si{Si(SiMe(3))(3)}{N(SiMe(3))Dipp} (Dipp=2,6-iPr(2)C(6)H(3)), from a silicon(IV) starting material is reported, together with evidence for a mechanism involving alkali metal silylenoid intermediates.

11.
J Am Chem Soc ; 134(15): 6500-3, 2012 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-22443679

RESUMO

Simple two-coordinate acyclic silylenes, SiR(2), have hitherto been identified only as transient intermediates or thermally labile species. By making use of the strong σ-donor properties and high steric loading of the B(NDippCH)(2) substituent (Dipp = 2,6-(i)Pr(2)C(6)H(3)), an isolable monomeric species, Si{B(NDippCH)(2)}{N(SiMe(3))Dipp}, can be synthesized which is stable in the solid state up to 130 °C. This silylene species undergoes facile oxidative addition reactions with dihydrogen (at sub-ambient temperatures) and with alkyl C-H bonds, consistent with a low singlet-triplet gap (103.9 kJ mol(-1)), thus demonstrating fundamental modes of reactivity more characteristic of transition metal systems.

12.
Dalton Trans ; 41(8): 2277-88, 2012 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-22223159

RESUMO

We report a combined experimental and computational comparative study of the reactions of the homologous titanium dialkyl- and diphenylhydrazido and imido compounds Cp*Ti{MeC(N(i)Pr)(2)}(NNR(2)) (R = Me (1) or Ph (2)) and Cp*Ti{MeC(N(i)Pr)(2)}(NTol) (3) with silanes, halosilanes, alkyl halides and [Et(3)NH][BPh(4)]. Compound 1 underwent reversible Si-H 1,2-addition to Ti=N(α) with RSiH(3) (experimental ΔH ca. -17 kcal mol(-1)), and irreversible addition with PhSiH(2)X (X = Cl, Br). DFT found that the reaction products and certain intermediates were stabilised by ß-NMe(2) coordination to titanium. The Ti-D bond in Cp*Ti{MeC(N(i)Pr)(2)}(D){N(NMe(2))SiD(2)Ph} underwent σ-bond metathesis with BuSiH(3) and H(2). Compound 1 reacted with RR'SiCl(2) at N(α) to transfer both Cl atoms to Ti; 2 underwent a similar reaction. Compound 3 did not react with RSiH(3) or alkyl halides but formed unstable Ti=N(α) 1,2-addition or N(α) protonation products with PhSiH(2)X or [Et(3)NH][BPh(4)]. Compound 1 underwent exclusive alkylation at N(ß) with RCH(2)X (R = H, Me or Ph; X = Br or I) whereas protonation using [Et(3)NH][BPh(4)] occurred at N(α). DFT studies found that in all cases electrophile addition to N(α) (with or without NMe(2) chelation) was thermodynamically favoured compared to addition to N(ß).


Assuntos
Nitrogênio/química , Prótons , Silanos/química , Silício/química , Titânio/química , Alquilação , Sítios de Ligação , Indicadores e Reagentes/química , Ligantes , Teoria Quântica , Especificidade por Substrato
13.
Inorg Chem ; 50(23): 12155-71, 2011 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-22043927

RESUMO

The synthesis and molecular and electronic structures of the first tert-butoxyimido complexes of titanium (TiNO(t)Bu functional group) are reported, featuring a variety of mono- or poly-dentate, neutral or anionic N-donor ligands. Reaction of Ti(NMe(2))(2)Cl(2) with (t)BuONH(2) gave good yields of Ti(NO(t)Bu)Cl(2)(NHMe(2))(2) (1). Compound 1 serves as an excellent entry point into new tert-butoxyimido complexes by reaction with a variety of fac-N(3) donor ligands, namely, Me(3)[9]aneN(3) (trimethyl-1,4,7-triazacyclononane), HC(Me(2)pz)(3) (tris(3,5-dimethylpyrazolyl)methane), or Me(3)[6]aneN(3) (trimethyl-1,3,5-triazacyclohexane) to give Ti(NO(t)Bu)(Me(3)[9]aneN(3))Cl(2) (2), Ti(NO(t)Bu){HC(Me(2)pz)(3)}Cl(2) (3), or Ti(NO(t)Bu)(Me(3)[6]aneN(3))Cl(2) (4) in good yield. It was found that 4 could be converted into Ti(NO(t)Bu)Cl(2)(py)(3) (5) in very good yield by reaction with an excess of pyridine. Compound 5 is effective in a range of salt metathesis reactions with lithiated amide or pyrrolide ligands, and reacts with Li(2)N(2)N(py), Li(2)N(2)N(Me), LiN(pyr)N(Me(2)), or Li(2)N(2)(pyr)N(Me) to give Ti(N(2)N(py))(NO(t)Bu)(py) (6), Ti(N(2)N(Me))(NO(t)Bu)(py) (7), Ti(N(pyr)N(Me(2)))(NO(t)Bu)Cl(py)(2) (9), or Ti(N(2)(pyr)N(Me))(NO(t)Bu)(py)(2) (10) in moderate to good yields (N(2)N(py) = (2-NC(5)H(4))C(Me)(CH(2)NSiMe(3))(2); N(2)N(Me) = MeN(CH(2)CH(2)NSiMe(3))(2); N(pyr)N(Me(2)) = Me(2)NCH(2)(2-NC(4)H(3)); N(2)(pyr)N(Me) = MeN{CH(2)(2-NC(4)H(3))}(2)). Compounds 7, 9, and 10 reacted with 2,2'-bipyridyl by pyridine exchange reactions forming Ti(N(2)N(Me))(NO(t)Bu)(bipy) (8), Ti(N(pyr)N(Me(2)))(NO(t)Bu)Cl(bipy) (11), and Ti(N(2)(pyr)N(Me))(NO(t)Bu)(bipy) (12). Ten tert-butoxyimido compounds, namely, 1-6, 11, and 12, have been structurally characterized revealing approximately linear Ti-N-O(t)Bu linkages with Ti-N distances [range 1.686(2)-1.734(2) Å] that are generally intermediate between those in the homologous alkylimido and phenylimido analogues, and shorter than in the diphenylhydrazido counterparts. Density functional theory (DFT) studies on the model compounds Ti(NR)Cl(2)(NHMe(2))(2) (1_R; R = OMe, Me, Ph, NMe(2)) confirmed this trend and found that the destabilizing effect of the -OMe oxygen 2p(π) lone pair on one of the Ti-N π-bonds in 1_OMe is comparable to that of the occupied phenyl ring π orbitals in the phenylimido homologue 1_Ph but much less than for the -NMe(2) nitrogen lone pair in 1_NMe(2).

14.
Chem Commun (Camb) ; 47(17): 4926-8, 2011 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-21445387

RESUMO

The first Group 4 alkoxyimido compounds are reported. The Ti=N-O(t)Bu group in Ti(N(2)N(Me))(NO(t)Bu)(py) undergoes facile 2-electron N-O bond cleavage with PhCCMe as the reductant to form a 1,2-diamidoalkene group via two highly selective N-C bond forming events.

15.
J Am Chem Soc ; 133(11): 3836-9, 2011 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-21344905

RESUMO

Reaction of [Ln(CH(2)SiMe(3))(2)(THF)(n)][BPh(4)] (Ln = Sc, Y, Lu ; n = 3, 4) with Li{B(NArCH)(2)}(THF)(2) (Ar = 2,6-C(6)H(3)(i)Pr(2)) formed the first group 3 and lanthanide boryl compounds, Sc{B(NArCH)(2)}(CH(2)SiMe(3))(2)(THF) and Ln{B(NArCH)(2)}(CH(2)SiMe(3))(2)(THF)(2) (Ln = Y, Lu), which contain two-center, two-electron Ln-B σ bonds. All of these systems were crystallographically characterized. Density functional theory analysis of the Ln-B bonding found it to be predominantly ionic, with covalent character in the σ-bonding Ln-B HOMO.

16.
Chemistry ; 17(1): 265-85, 2011 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-21207623

RESUMO

We report a range of new transformations of the diamide-amine supported Ti=NNPh(2) functional group with a variety of unsaturated substrates, along with DFT studies of the key mechanisms. Reaction of [Ti(N(2) N(py) )(NNPh(2) )(py)] (4, N(2) N(py) =(2-NC(5) H(4) )CMe(CH(2) NSiMe(3) )(2) ; py=pyridine) with MeCN gave the dimeric species [Ti(2) (N(2) N(py) )(2) {µ-NC(Me)(NNPh(2) )}(2) ] through a [2+2] cycloaddition process. Reaction of 4 or [Ti(N(2) N(Me) )(NNPh(2) )(py)] (5, N(2) N(Me) =MeN(CH(2) CH(2) NSiMe(3) )(2) ) with fluorinated benzonitriles gave the terminal hydrazonamide complexes [Ti(N(2) N(R) ){NC(Ar F x)NNPh(2) }(py)] (R=py or Me; Ar F x=2,6-C(6) H(3) F(2) or C(6) F(5) ). DFT studies showed that this proceeds through an overall [2+2] cycloaddition-reverse cycloaddition, resulting in net insertion of Ar F xCN into the Ti=N(α) bonds of the respective hydrazides. Reaction of 4 with a mixture of MeCN and PhCCMe gave the metallacycle [Ti(N(2) N(py) ){NC(Me)C(Ph)C(Me)NNPh(2) }] by sequential coupling of Ti=NNPh(2) with PhCCMe and then MeCN. A related product, [Ti(N(2) N(py) ){NC(Me)C(Ar(F) )C(H)NNPh(2) }], was formed by insertion of MeCN into the Ti-C bond of the isolated azatitanacyclobutene [Ti(N(2) N(py) ){N(NPh(2) )C(H)C(Ar(F) )}] (Ar(F) =3-C(6) H(4) F). Reaction of 4 with two equivalents of B(Ar F 5)(3) (Ar F 5=C(6) F(5) ) formed the zwitterionic borate [Ti(N(2) N(py) ){η(2) -N(NPh(2) )B(Ar F 5)(3) }] by electrophilic attack at N(α) . Compounds 4 and 5 reacted with tBuNC and/or XylNC (Xyl=2,6-C(6) H(3) Me(2) ) to give the N(α)-N(ß) bond cleavage products, [Ti(N(2) N(R) )(NCNR')(NPh(2) )] (R=py or Me; R'=tBu or Xyl), containing metallated carbodiimide ligands. DFT studies of these reactions found an initial addition of RNC across Ti=N(α) followed by N(ß) coordination, and finally complete N(α) transfer from the NNPh(2) to the RNC fragment. Reaction of 5 with Ar'NCE (E=O, S, Se; Ar'=2,6-C(6) H(3) iPr(2) ) gave the [2+2] cycloaddition products [Ti(N(2) N(Me) ){N(NPh(2) )C(NAr')O}(py)] and [Ti(N(2) N(Me) ){N(NPh(2) )C(NAr')E}] (E=S or Se), which did not undergo further transformation of the Ti-N-NPh(2) moiety.

17.
J Am Chem Soc ; 132(30): 10484-97, 2010 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-20617837

RESUMO

A combined experimental and DFT study of the reactions of diamide-amine supported titanium hydrazides with alkynes is presented. Reaction of Ti(N2N(py))(NNPh2)(py) (1, N2N(py) = (2-NC5H4)CMe(CH2NSiMe3)2) with terminal and internal aryl alkynes ArCCR (Ar = Ph or substituted phenyl, R = Me or H) at room temperature gave the fully authenticated azatitanacyclobutenes Ti(N2N(py)){N(NPh2)C(R)CAr} via ArCCR [2 + 2] cycloaddition to the Ti=N(alpha) bond of the hydrazide ligand. In contrast, reaction of 1 with PhCCMe at 60 degrees C, or of Ti(N2NMe)(NNPh2)(py) (11, N2NMe = MeN(CH2CH2NSiMe3)2) with RCCMe (R = Me, Ph or substituted phenyl) at room temperature or below, gave vinyl imido compounds of the type Ti(N2N(R')){NC(R)C(Me)NPh2}(py), in which RCCMe had undergone net insertion into the N(alpha)-N(beta) bond. These are the first examples of this type of reaction for any metal hydrazide. The reaction of 11 with PhCCMe had the activation parameters DeltaH(double dagger) = 18.8(4) kcal mol(-1), DeltaS(double dagger) = 1(1) cal mol(-1) K(-1) and DeltaG(298)(double dagger) = 18.5(7) kcal mol(-1). Mechanistic and DFT studies for 1 and 11 found that the N(alpha)-N(beta) insertion event is preceded by alkyne cycloaddition to Ti=N(alpha), and that N(alpha)-N(beta) bond "insertion" is really an intramolecular N(alpha) atom migration process within the azatitanacyclobutenes following intramolecular chelation of NPh2 of the hydrazide ligand. Electron-withdrawing aryl groups on ArCCMe stabilize the azatitanacyclobutenes and also promote a specific regiochemistry (ArC carbon bound to Ti). This in turn defines the regiochemistry of the overall N(alpha)-N(beta) insertion reaction (ArC carbon bound to N(alpha)). In contrast, electron-releasing aryl groups promote the final N(alpha) migration stage of the mechanism, and a Hammett analysis of the rates of insertion of (4-C6H4X)CCMe into the N(alpha)-N(beta) bond of 11 found a reaction constant, rho, of -0.74(5), consistent with NPA charge changes of ArC along the DFT reaction coordinate.

18.
Chem Commun (Camb) ; 46(2): 273-5, 2010 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-20024349

RESUMO

Dicationic, zwitterionic and "conventional" yttrium compounds act as catalysts for the primary or secondary amine-initiated immortal ROP of rac-lactide; amine-terminated, highly heterotactic poly(rac-lactides) with narrow polydispersities and well-controlled molecular weights are prepared in this manner.


Assuntos
Aminas/química , Cátions/química , Dioxanos/química , Poliésteres/síntese química , Catálise , Conformação Molecular , Poliésteres/química , Ítrio/química
19.
Inorg Chem ; 48(21): 10442-54, 2009 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-19780610

RESUMO

Reaction of RCH(2)N(CH(2)CH(2)NHSO(2)Tol)(2) (R = 2-NC(5)H(4) (8, H(2)L(py)) or MeOCH(2) (9, H(2)L(OMe))) with Ti(NMe(2))(4) at room temperature afforded Ti(L(py))(NMe(2))(2) (10) or Ti(L(OMe))(NMe(2))(2) (11), respectively, which contain tetradentate bis(sulfonamide)amine ligands. The corresponding reactions with Ti(O(i)Pr)(4) or Zr(O(i)Pr)(4) x HO(i)Pr required more forcing conditions to form the homologous bis(isopropoxide) analogues, M(L(R))(O(i)Pr)(2) (M = Ti, R = py (12) or OMe (14); M = Zr, R = py (13) or OMe (15)). Reaction of Ti(NMe(2))(2)(O(i)Pr)(2) with H(2)L(R) formed 12 or 14 under milder conditions. The X-ray structures of 10-15 have been determined revealing C(s) symmetric, 6-coordinate complexes except for 13 which is 7-coordinate with one kappa(2)(N,O) bound sulfonamide donor. Compounds 10-15 are all catalysts for the ring-opening polymerization (ROP) of epsilon-caprolactone, with the isopropoxide compounds being the fastest and best controlled, especially in the case of zirconium. In addition, Zr(L(OMe))(O(i)Pr) (2) (15) was an efficient catalyst for the well-controlled ROP of rac-lactide both in toluene at 100 degrees C and in the melt at 130 degrees C, giving atactic poly(rac-lactide). The polymerization rates and control achieved for 13 and 15 are comparable to those of the well-established bis(phenolate)amine-supported Group 4 systems reported recently.


Assuntos
Caproatos/química , Lactonas/química , Sulfonamidas/química , Catálise , Cristalografia por Raios X , Estrutura Molecular , Compostos Organometálicos/síntese química , Compostos Organometálicos/química , Polímeros/química , Titânio/química , Zircônio/química
20.
Dalton Trans ; (1): 85-96, 2009 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-19081975

RESUMO

The reaction of bis(3,5-dimethylpyrazolyl)methylphenol N(2)O(Ar)H (1) with NaH in THF formed dimeric [Na(kappa(2)-N(2)O(Ar))(THF)](2) (2), which contains a kappa(2)(N,O)-bound bidentate N(2)O(Ar) ligand. The reaction of 1 with Mg(n)Bu(2) gave the four-coordinate monomeric butyl compound Mg(N(2)O(Ar))(n)Bu (3), whereas with (n)BuMgCl, a mixture of products was formed, including the six-coordinate homoleptic species Mg(N(2)O(Ar))(2) (4). The reaction of [Na(kappa(2)-N(2)O(Ar))(THF)](2) with (n)BuMgCl also gave 3, as did the redistribution reaction of Mg(n)Bu(2) with 4. The reaction of 1 with Mg{N(SiRMe(2))(2)}(2) afforded the four-coordinate amide derivatives Mg(N(2)O(Ar)){N(SiRMe(2))(2)} (R = Me (6) or H (7)), together with 4. The reactions of 1 with ZnMe(2) or Zn{N(SiMe(3))(2)}(2) gave the monomeric compounds Zn(N(2)O(Ar))Me (8) and Zn(N(2)O(Ar)){N(SiMe(3))(2)} (9), respectively. The reaction 9 of with HCl formed Zn(N(2)O(Ar))Cl (11), and subsequent addition of LiN(SiHMe(2))(2) to 11 led to Zn(N(2)O(Ar)){N(SiHMe(2))(2)} (12). The reaction of 1 with either Zn{N(SiMe(3))(2)}(2) or 9 gave Zn(N(2)O(Ar))(2). The compounds 2, 3, 4, 6, 8, 9 and 11 were crystallographically characterized. Compound was very active for the ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) but the process was very poorly controlled as judged by the M(n) and polydispersity index of the polymer. Compounds 3, 8, 9 and 12 gave poor conversions to poly(epsilon-CL) over extended periods. N(2)O(Ar)H = 2,4-di-tert-butyl-6-(bis(3,5-dimethylpyrazolyl)methyl)phenol.

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