N-Heterocyclic Carbene Based Tri-organyl-Zn-Alkyl Cations: Synthesis, Structures, and Use in CO2 Functionalization.

Tri-organyl and tricoordinate N-heterocyclic carbene (NHC) Zn-NHC alkyl cations [(nNHC)2 Zn-Me]+ (nNHC=C2-bonded-IMes/-IDipp; 3+ and 4+ ; IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene, IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were first synthesized and structurally characterized by ionization of the corresponding neutral precursors [(nNHC)ZnMe2 ] with [Ph3 C][B(C6 F5 )4 ] in the presence of one equivalent of free NHC. Whereas cation [(nIMes)2 Zn-Me]+ (3+ ) is stable, its sterically congested analogue [(nIDipp)2 Zn-Me]+ (4+ ) readily undergoes an nNHC-to-aNHC isomerization in the presence of THF or IDipp to afford the more thermodynamically stable [(aIDipp)(nIDipp)Zn-Me]+ (aIDipp=C4-bonded IDipp, 5+ ), reflecting the adaptable-to-sterics coordination chemistry of these cations for improved stability. Cations 3+ -5+ are the first Zn cations of the type Zn(C)(C')(C'')+ (C, C', C''=σ-donor carbyl ligand). Kinetic studies combined with DFT calculations agree with an nNHC-to-aNHC process proceeding through the initial deprotonation of 4+ (at a Zn-bonded C4-IDipp moiety) by IDipp. Unlike 3+ and 4+ , the rearranged cation 5+ reacts with CO2 through insertion into the Zn-Me bond yielding the corresponding Zn(κ2 -OAc)+ cation 6+ . Both cations 5+ and 6+ were successfully used in CO2 hydrosilylation catalysis for silylformate formation.

P,O-Phosphinophenolate zinc(II) species: synthesis, structure and use in the ring-opening polymerization (ROP) of lactide, ε-caprolactone and trimethylene carbonate.

The P,O-type phosphinophenol proligands (1·H, 2-PPh2-4-Me-6-Me-C6H2OH; 2·H, 2-PPh2-4-Me-6-(t)Bu-C6H2OH) readily react with one equiv. of ZnEt2 to afford in high yields the corresponding Zn(II)-ethyl dimers of the type [(κ(2)-P,O)Zn-Et]2 (3 and 4) with two µ-OPh bridging oxygens connecting the two Zn(II) centers, as determined by X-ray diffraction (XRD) studies in the case of 3. Based on diffusion-ordered NMR spectroscopy (DOSY), both species 3 and 4 retain their dimeric structures in solution. The alcoholysis reaction of Zn(II) alkyls 3 and 4 with BnOH led to the high yield formation of the corresponding Zn(II) benzyloxide species [(κ(2)-P,O)Zn-OBn]2 (5 and 6), isolated in a pure form as colorless solids. The centrosymmetric and dimeric nature of Zn(II) alkoxides 5 and 6 in solution was deduced from DOSY NMR experiments and multinuclear NMR data. Though the heteroleptic species 5 is stable in solution, its analogue 6 is instable in CH2Cl2 solution at room temperature to slowly decompose to the corresponding homoleptic species 8via the transient formation of (κ(2)-P,O)2Zn2(µ-OBn)(µ­κ(1):κ(1)-P,O) (6'). Crystallization of compound 6 led to crystals of 6', as established by XRD analysis. The reaction of ZnEt2 with two equiv. of 1·H and 2·H allowed access to the corresponding homoleptic species of the type [Zn(P,O)2] (7 and 8). All gathered data are consistent with compound 7 being a dinuclear species in the solid state and in solution. Data for species 8, which bears a sterically demanding P,O-ligand, are consistent with a mononuclear species in solution. The Zn(II) alkoxide species 5 and the [Zn(P,O)2]-type compounds 7 and 8 were evaluated as initiators of the ring-opening polymerization (ROP) of lactide (LA), ε-caprolactone (ε-CL) and trimethylene carbonate (TMC). Species 5 is a well-behaved ROP initiator for the homo-, co- and ter-polymerization of all three monomers with the production of narrow disperse materials under living and immortal conditions. Though species 7 and 8 are ROP inactive on their own, they readily polymerize LA in the presence of a nucleophile such as BnOH to produce narrow disperse PLA, presumably via an activated-monomer ROP mechanism.

Reactivity of TCNE and TCNQ derivatives of quinonoid zwitterions with Cu(I).

The reactions of TCNE- and TCNQ-functionalized (TCNE: tetracyanoethylene and TCNQ: 7,7',8,8'-tetracyanoquinodimethane) zwitterionic benzoquinonemonoimines with a Cu(I)-BIAN complex (BIAN = bis(o,o'-bisisopropylphenyl)acenaphthenequinonediimine) have been investigated and found to follow a diversity of interesting patterns. The complexes [Cu(BIAN)(NCMe)(L2)]BF4 (2) and [Cu(BIAN)(L2)2]BF4 (4) were obtained by reacting [Cu(BIAN)(NCMe)2]BF4 (1) with one and two equivalents of L2, respectively. Following similar procedures, the complexes [Cu(BIAN)(NCMe)(L3)]BF4 (6) and [Cu(BIAN)(L3)2]BF4 (7) were obtained by reaction of 1 with L3. The reaction of 2 with 0.5 equiv. of 4,4'-bipyridine afforded [{Cu(BIAN)(L2)}2(µ-4,4'-bipyridine)](BF4)2 (3). The complexes were characterized by multinuclear NMR, IR and UV-Vis spectroscopic techniques, mass spectrometry, cyclic voltammetry and elemental analysis. The molecular structures of complexes 3 ·4CH2Cl2 and 4 ·CH2Cl2 were determined by single crystal X-ray diffraction. An unexpected coordination polymer [Cu((L2-))2]∞ (5) was also structurally characterized, which contains Cu(II) centres chelated by two N,O-bound ligands resulting from the monodeprotonation of L2.

One electron reduced square planar bis(benzene-1,2-dithiolato) copper dianionic complex and redox switch by O2/HO(-).

The complex [Ph4P]2[Cu(bdt)2] (1(red)) was synthesized by the reaction of [Ph4P]2[S2MoS2CuCl] with H2bdt (bdt = benzene-1,2-dithiolate) in basic medium. 1(red) is highly susceptible toward dioxygen, affording the one electron oxidized diamagnetic compound [Ph4P][Cu(bdt)2] (1(ox)). The interconversion between these two oxidation states can be switched by addition of O2 or base (Et4NOH = tetraethylammonium hydroxide), as demonstrated by cyclic voltammetry and UV-visible and EPR spectroscopies. Thiomolybdates, in free or complex forms with copper ions, play an important role in the stability of 1(red) during its synthesis, since in its absence, 1(ox) is isolated. Both 1(red) and 1(ox) were structurally characterized by X-ray crystallography. EPR experiments showed that 1(red) is a Cu(II)-sulfur complex and revealed strong covalency on the copper-sulfur bonds. DFT calculations confirmed the spin density delocalization over the four sulfur atoms (76%) and copper (24%) atom, suggesting that 1(red) has a "thiyl radical character". Time dependent DFT calculations identified such ligand to ligand charge transfer transitions. Accordingly, 1(red) is better described by the two isoelectronic structures [Cu(I)(bdt2, 4S(3-,)*)](2-) ↔ [Cu(II)(bdt2, 4S(4-))](2-). On thermodynamic grounds, oxidation of 1(red) (doublet state) leads to 1(ox) singlet state, [Cu(III)(bdt2, 4S(4-))](1-).

Copper(II) complexes of bis(aryl-imino)acenaphthene ligands: synthesis, structure, DFT studies and evaluation in reverse ATRP of styrene.

Two new Ar-BIAN Cu(II) complexes (where Ar-BIAN = bis(aryl-imino)acenaphthene) of formulations [CuCl2(Mes-BIAN)] (1) (Mes = 2,4,6-Me3C6H2) and [CuCl2(Dipp-BIAN)] (2) (Dipp = 2,6-iPr2C6H3) were synthesised by direct reaction of CuCl2 suspended in dichloromethane with the respective ligands Mes-BIAN (L1) and Dipp-BIAN (L2), dissolved in dichloromethane, under an argon atmosphere. Attempts to obtain these compounds by solubilising CuCl2 in methanol and adding a dichloromethane solution of the corresponding ligand, under aerobic conditions, gave also compound 1, but, in the case of L2, the Cu(I) dimer [CuCl(Dipp-BIAN)]2 (3) was obtained instead of compound 2. The compounds were fully characterised by elemental analyses, MALDI-TOF mass spectrometry, FT-IR, (1)H NMR and EPR spectroscopic techniques. The solid-state molecular structures of compounds 1-3 were determined by single crystal X-ray diffraction, showing the expected chelation of the Ar-BIAN ligands and two chloride ligands completing the coordination sphere of the Cu(II) centre. In the case of the complex 1, an intermediate coordination geometry around the Cu(II) centre, between square planar and tetrahedral, was revealed, while the complex 2 showed an almost square planar geometry. The structural differences and evaluation of energetic changes were rationalised by DFT calculations. Analysis of the electrochemical behaviour of complexes 1-3 was performed by cyclic voltammetry and the experimental redox potentials for Cu(II)/Cu(I) pairs have been compared with theoretical values calculated by DFT in the gas phase and in dichloromethane and methanol solutions. The complex 1 exhibited good activity in the reverse atom transfer radical polymerisation (ATRP) of styrene.

Influence of a thioether function in short-bite diphosphine ligands on the nature of their silver complexes: structure of a trinuclear complex and of a coordination polymer.

New cationic Ag(I) complexes were prepared by reaction of AgBF4 with two thioether-functionalized bis(diphenylphosphino)amine ligands, Ph2PN(p-ArSMe)PPh2 (L1) and Ph2PN(n-PrSMe)PPh2 (L2), and compared with those obtained from the unfunctionalized ligands Ph2PN(Ph)PPh2 (L3) and Ph2PN(n-Bu)PPh2 (L4), respectively. The complex [Ag3(µ3-Cl)2(µ2-L1-P,P)3](BF4) (1·BF4) contains a triangular array of Ag centres supported by three bridging L1 ligands and two triply-bridging chlorides. In contrast, ligand L2 led to the coordination polymer [{Ag2(µ3-L2,-P,P,S)2(MeCN)2}{Ag2(µ2-L2-P,P)2(MeCN)2}(BF4)4]n (2) in which the tethered thioether group connects intermolecularly a Ag2 unit to the diphosphine bridging the other Ag2 unit. With L3 and L4, two similar complexes were obtained, [Ag2(µ2-L3)(BF4)2] (3) and [Ag2(µ2-L4)(BF4)2] (4), respectively, with bridging diphosphine ligands and a BF4 anion completing the coordination sphere of the metal. Complexes 1·BF4·CH2Cl2, 2·THF, 3·3CH2Cl2 and 4 have been fully characterized, including by single crystal X-ray diffraction.

Synthesis and structural characterisation of (aryl-BIAN)copper(I) complexes and their application as catalysts for the cycloaddition of azides and alkynes.

A series of Ar-BIAN-based copper(I) complexes (where Ar-BIAN = bis(aryl)acenaphthenequinonediimine) were synthesised and characterised by (1)H and (13)C NMR spectroscopies, FT-IR spectroscopy, MALDI-TOF-MS spectrometry, cyclic voltammetry and single crystal X-ray diffraction. The bis-chelated complexes of general formula [Cu(Ar-BIAN)(2)]BF(4) (where Ar = C(6)H(5) (1), 4-iPrC(6)H(4) (3), 2-iPrC(6)H(4) (4)) were prepared by reaction of [Cu(NCMe)(4)]BF(4) with two equivalents of the corresponding Ar-BIAN ligands, in dichloromethane, while the mono-chelated complexes of the type [Cu(Ar-BIAN)L(2)]BF(4) (where Ar = 2,6-iPr(2)C(6)H(3), L = PhCN (6); Ar = 4-iPrC(6)H(4), L = PPh(3) (7)) were readily accessible by treatment of [Cu(NCR)(4)]BF(4) (R = Me, Ph) with one equivalent of the corresponding Ar-BIAN ligands in the absence or presence of two equivalents of PPh(3), in the same solvent. The structures of complexes 3, 4, 6 and 7 were obtained by single crystal X-ray diffraction, showing distorted tetrahedral geometries around the copper centres in all cases. The electrochemical studies of these complexes and of the already reported [Cu(2,4,6-Me(3)C(6)H(2)-BIAN)(2)]BF(4) (2) and [Cu(2,6-iPr(2)C(6)H(3)-BIAN)(NCMe)(2)] (5), demonstrated that the bis-chelated complexes 1-4 undergo a reversible one-electron reduction or oxidation processes on copper, while the mono-chelated complexes 5-7 show a partially reversible oxidation and an irreversible reduction feature. Both kinds of (Ar-BIAN)copper(I) complexes are active catalysts for the copper(I)-catalysed azide-alkyne cycloaddition reaction (CuAAC). Complex 7, bearing PPh(3) ligands, exhibits the highest catalytic activity, which is comparable with that of the typical CuSO(4)-sodium ascorbate catalyst system.

Highly active zinc alkyl cations for the controlled and immortal ring-opening polymerization of ε-caprolactone.

Zinc alkyl cations supported by N,N-BIAN-type bidentate ligands were found to be highly active in the immortal ROP of ε-caprolactone to yield narrowly disperse and chain length-controlled poly(ε-caprolactone), whether in solution or bulk polymerization conditions.

Comparison of the structure and stability of new α-diimine complexes of copper(I) and silver(I): density functional theory versus experimental.

New compounds of the general formulas [M(Ar-BIAN)(2)]BF(4) and [M(Ar-BIAN)(NCMe)(2)]BF(4), where M = Cu(I) or Ag(I) and Ar-BIAN = bis(aryl)acenaphthenequinonediimine, were synthesized by the direct reaction of [Cu(NCMe)(4)]BF(4) or [Ag(NCMe)(4)]BF(4) with the corresponding Ar-BIAN ligand in dried CH(2)Cl(2). The synthesized compounds are [M(o,o',p-Me(3)C(6)H(2)-BIAN)(2)]BF(4) where M = Cu(I) (1) and Ag(I) (2), [M(o,o'-iPr(2)C(6)H(3)-BIAN)(NCMe)(2)]BF(4) where M = Cu(I) (3) and Ag(I) (4), and [Ag(o,o'-iPr(2)C(6)H(3)-BIAN)(2)]BF(4) (5). The crystal structures of compounds 1-3 and 5 were solved by single-crystal X-ray diffraction. In all cases copper(I) or silver(I) are in a distorted tetrahedron that is constructed from the four nitrogen atoms of the two α-diimine ligands or, in 3, from one α-diimine ligand and two acetonitrile molecules. All compounds were characterized by elemental analyses, matrix-assisted laser desorption-ionization time-of-flight mass spectrometry, and IR, UV-vis, and (1)H NMR spectroscopy. The analysis of the molecular geometry and the energetic changes for the formation reactions of the complexes, in a CH(2)Cl(2) solution, were evaluated by density functional theory calculations and compared with the experimental results.

Synthesis and characterization of Co and Ni complexes stabilized by keto- and acetamide-derived P,O-type phosphine ligands.

The coordination properties of the beta-keto phosphine ligands R(2)PCH(2)C(O)Ph (, R = i-Pr; , R = Ph), of the new acetamide-derived phosphine ligand (i-Pr)(2)PNHC(O)Me () and of Ph(2)PNHC(O)Me () have been examined towards Ni(ii) complexes. Comparisons are made between systems in which the PCH(2) function of the ketophosphine has been replaced with an isoelectronic PNH group in amide-derived ligands, or the PCH functionality of phosphinoenolates with a PN group in phosphinoiminolate complexes. Furthermore, ligands and reacted with [(eta(5)-C(5)H(5))CoI(2)(CO)] to afford the phosphine mono-adducts [(eta(5)-C(5)H(5))CoI(2){Ph(2)PCH(2)C(O)Ph}] () and [(eta(5)-C(5)H(5))CoI(2){Ph(2)PNHC(O)Me}] (), respectively, which upon reaction with excess NEt(3) yielded the phosphinoenolate complex [(eta(5)-C(5)H(5))[upper bond 1 start]CoI{Ph(2)PCH[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Ph}] () and the phosphinoiminolate complex [(eta(5)-C(5)H(5))[upper bond 1 start]CoI{Ph(2)PN[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Me}] (), respectively. The complexes cis-[[upper bond 1 start]Ni{(i-Pr)(2)PN[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Me}(2)] () and cis-[[upper bond 1 start]Ni{Ph(2)PN[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Me}(2)] () were obtained similarly from NiCl(2) and (3) and (4), respectively, in the presence of a base. The phosphinoenolate complex [[upper bond 1 start]Ni{(i-Pr)(2)PCH[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Ph}(2)] () exists in ethanol as a mixture of the cis and trans isomers, in contrast to cis-[[upper bond 1 start]Ni{(Ph(2)PCH[horiz bar, triple dot above]C([horiz bar, triple dot above]O[upper bond 1 end])Ph}(2)], and the solid-state structure of the trans isomer of was established by X-ray diffraction. The structures of the ligand (3) and of the complexes , in .3/2CH(2)Cl(2), , and have also been determined by X-ray diffraction and are compared with those of related complexes. Complexes , and contain a five-membered heteroatomic metallocyclic moiety, which is constituted by five different chemical elements. The structural consequences of the steric bulk of the P substituents and of the electronic characteristics of the P,O chelates are discussed.

A new bis(1-naphthylimino)acenaphthene compound and its Pd(II) and Zn(II) complexes: synthesis, characterization, solid-state structures and density functional theory studies on the syn and anti isomers.

A new rigid bidentate ligand, bis(1-naphthylimino)acenaphthene, L1, and its Zn(II) and Pd(II) complexes [ZnCl 2( L1)], 1, and [PdCl 2( L1)], 2, were synthesized. L1 was prepared by the "template method", reacting 1-naphthyl amine and acenaphthenequinone in the presence of ZnCl 2, giving 1, which was further demetallated. Reaction of 1-naphthyl amine with acenaphthenequinone and PdCl 2 afforded dichloride bis(1-naphthyl)acenaphthenequinonediimine palladium, 2. L1, 1, and 2 were obtained as a mixture of syn and anti isomers. Compound 2 was also obtained by the reaction of PdCl 2 activated by refluxing it in acetonitrile followed by the addition of L1; by this route also a mixture of syn and anti isomers was obtained, but at a different rate. The solid-state structures of L1 and the anti isomer of compound 2 have been determined by single-crystal X-ray diffraction. All compounds have been characterized by elemental analyses; matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry; IR; UV-vis; (1)H, (13)C, and (1)H- (1)H correlation spectroscopy; (1)H- (13)C heteronuclear single quantum coherence; (1)H- (13)C heteronuclear single quantum coherence-total correlation spectroscopy; and (1)H- (1)H nuclear Overhauser effect spectrometry NMR spectroscopies when applied. Density functional theory studies showed that both conformers for [PdCl 2(BIAN)] are isoenergetic, and they can both be obtained experimentally. However, we can predict that the isomerization process is not available in a square-planar complex, but it is possible for the free ligand. The molecular geometry is very similar in both isomers, and only different orientations for naphthyl groups can be expected.

Effect of trimethylsilyl substitution on the chemical properties of triarylphosphines and their corresponding metal-complexes: solubilising effect in supercritical carbon dioxide.

The donor strengths of the following triarylphosphine ligands P(Ar)(2)(Ar')(Ar = Ar'= 4-Me(3)SiC(6)H(4), 1b; 4-Me(3)CC(6)H(4), 1d; 4-F(3)CC(6)H(4), 1e; Ar = C(6)H(5), Ar'= 4-Me(3)SiC(6)H(4), 1c) have been evaluated experimentally and theoretically. The measurements of the J(P-Se) coupling constants of the corresponding synthesised selenides Se=P(Ar)(2)(Ar'), 2b,c and the DFT calculation of the energies of the phosphine lone-pair (HOMO) reveal insignificant influence on the electronic properties of the substituted phosphines when the trimethylsilyl group is attached to the aryl ring, in marked contrast to the strong electronic effect of the trifluoromethyl group. These triarylphosphine ligands P(Ar)(2)(Ar') reacted with (eta5-C(5)H(5))Co(CO)(2), (eta5-C(5)H(5))Co(CO)I(2) or PdCl(2) to yield the new compounds (eta5-C(5)H(5))Co(CO)[P(Ar)(2)(Ar')], 3b,d; (eta5-C(5)H(5))CoI(2)[P(Ar)(2)(Ar')], 4b-e; and PdCl(2)[P(Ar)(2)(Ar')](2), 5b,c respectively. These complexes have been characterized and their spectroscopic properties compared with those reported for the known triphenylphosphine complexes. Again, the contrast of the (31)P NMR and (13)C NMR chemical shifts or C-O or M-Cl stretching frequencies, when applied, does not show an important electronic effect on the metal complex of the trimethylsilyl substituted phosphines with respect to P(C(6)H(5))(3) derivatives. Solubility measurements of complexes 3a and 3b in scCO(2) were performed. We conclude that Me(3)Si groups on the triarylphosphine improve the solubility of the corresponding metal complex in scCO(2).

Congenital diaphragmatic hernia

Un infante varón había estado bien hasta los 5 meses de edad cuando desarrolló tos, taquipnea y aparentemente broncospasmo que no respondió a los broncodilatadores orales. A la exploración física tenía disminución de los ruidos respiratorios y peristaltismo intestinal en el hemitorax izquierdo. La radiografía de torax comprobó el diagnóstico de hernia diafragmática izquierda. La corrección quirúrgica fue curativa y el infante seguía asintomático 6 meses más tarde. La hernia difragmática que se manifiesta después del período neonatal es rara. La afección debe sospecharse en todo neonato con dificultad respiratoria y además en el infante con síntomas y signos pulmonares anormales persistentes