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The reaction of μ-nitrido[((tetraphenylporphyrinato)manganese)(phthalocyaninatoiron)], [(TPP)Mn−N−FePc], with I2 in THF develops with the formation of two different species, i.e., [(THF)(TPP)Mn−N−FePc(H2O)](I5)·2THF (I) and [(TPP)MnIV−N−FeIIIPc](I3) (II). On the basis of single-crystal X-ray work and Mossbauer, EPR, Raman, and magnetic susceptibility data, I, found to be isostructural with the corresponding Fe−Fe complex, is shown to contain a low-spin triatomic MnIVNFeIV system (metal-centered oxidation). Data at hand for II (Mossbauer, EPR, Raman) show, instead, that oxidation takes place at one of the two macrocycles, very likely TPP (ligand-centered oxidation). The same cationic fragment present in I, and containing the MnIVNFeIV bond system, is also obtained when (TPP)Mn−N−FePc is allowed to react in THF with (phen)SbCl6 (molar ratio 1:1). There are indications that the use of (phen)SbCl6 in excess (2:1 molar ratio), in benzene, probably determines further oxidation with the formation of a species sh...

The present report deals with the one electron oxidation and the one- and two-electron reduction of [Mn(tmtaa)L], [L = THF, 1a; L = none, 1b; tmtaa = dibenzotetramethyltetraaza[14]annulene]. The former class of reactions led to the formation of a variety of functionalised Mn(III) species, [(tmtaa)Mn–X] [X = I, 2; X = Cl, 3; X = NCS, 5], including the cationic derivatives [Mn(tmtaa)(L)(L′)]BPh4 [L = L′ = THF, 4a; L = L′ = DME, 4b; L = Py, L′ = none, 4c]. The magnetic properties of the Mn(III) derivatives are strongly dependent on the axial ligand. Reaction of 1a with NO gave [(tmtaa)Mn(NO)], 6, which takes up an axial pyridine leading to the diamagnetic [(tmtaa)Mn(NO)(Py)], 7. Complex 6 displays a peculiar magnetic behavior, which has been interpreted as a S = 0 S = 2 spin equilibrium with a ΔHeff = 4.0 kJ mol−1 and a ΔSeff = 11.3 J mol−1 K−1 associated to the spin transition process. Reaction of 1 with sodium metal in DME leads to [Mn2(μ2-tmtaa)2{Na·(DME)2}2], 8, while in THF [Mn2(*tmtaa2*)Na4·(THF)6], 9, is formed. Extended Huckel calculations have been performed for a better understanding of the magnetic and electronic properties of 6 and 9. The proposed structures have been supported by X-ray analyses of 3, 4b, 6, 8, and 9.

The metallation of [p-Butcalix[4](ONa)2(OMe)2] 1 was performed using [CrCl3(THF)3] and the resulting complex [Cr{p-Butcalix[4](O)2(OMe)2}(Cl)(THF)] 2 allowed entry into low valent and organometallic chemistry of chromium. In the presence of strong bases or nucleophiles the ligand underwent demethylation exemplified by the reaction of 2 with pyridine, which led to [C5H4NMe][Cr{p-Butcalix[4](O)3(OMe)}Cr(py)(Cl)] 3. The alkylation of 2 was successful only when the concurrent reduction to CrII was irrelevant, in which case the two well characterized organometallic derivatives [Cr{p-Butcalix[4](O)2(OMe)2}(Mes)] 4 [Mes = 2,4,6-Me3C6H2] and [Cr{p-Butcalix[4](O)2(OMe)2}(η5-C5H5)] 5 were obtained. None of them showed, even under photochemical or thermal forced conditions, any sign of reactivity, due to the kinetic inertness of the d3 configuration. Complex 2 was easily reduced to the chromium(II) derivative [Cr{p-Butcalix[4](O)2(OMe)2}(THF)] 6, which underwent facile oxidative functionalization. The reaction with O2 led to an unprecedented di-µ-oxo chromium(IV) derivative, [Cr2{p-Butcalix[4](O)2(OMe)2}2(µ-O2)] 7, which displays a ferromagnetic coupling between the two d2 centres. The proposed structures are supported by X-ray analyses of complexes 24, 6 and 7.

A new class of porphyrazine macrocycles carrying peripheral diazepine rings, i.e. tetrakis-2,3-(5,7-diphenyl-6H-1,4-diazepino)porphyrazine [Ph2DzPzH2](H2O)4, and its metal derivatives of formula [Ph2DzPzM](H2O)x=2–7 [M = MgII(H2O), CuII, ZnII] have been prepared and characterized. Single crystal X-ray work on the monomeric precursor 5,7-diphenyl-2,3-dicyano-6H-1,4-diazepine, Ph2(CN)2Dz, and NMR spectra (CDCl3, (CD3)2SO) and UV/Vis spectra in solution of different media (basic, neutral, acid) of the monomer and its macrocyclic derivatives have provided information on the conformational flexibility of the diazepine ring as well as on the structural and electronic features of the entire porphyrazine skeleton.

This report deals with the stepwise reduction of the parent compound [cis-Cl2W{p-But-calix[4]-(O)4}], 2, leading to metal−metal-bonded metalla-calix[4]arene dimers containing the WW, W⋮W, and WW fu...

This report deals with the olefin rearrangements achieved on a W-calix[4]arene oxo fragment that mimicks a heterogeneous metal−oxo surface both in the results and the chemical pathways. The olefin complexation by the W(IV)-calix[4]arene fragment has been achieved, generating the [{p-But-calix[4]-(O)4}W]-d2 from the reduction of [cis-(Cl)2W{p-But-calix[4]-(O)4}], 1, in the presence of the appropriate olefin. With this method, [{p-But-calix[4]-(O)4}W(η2-C2H4)], 2, [{p-But-calix[4]-(O)4}W(η2-MeC2H3)], 3, and [{p-But-calix[4]-(O)4}W(C6H10)], 4, have been obtained. In the latter complex the very labile cyclohexene can be replaced by another olefin, such as trans-stilbene in [{p-But-calix[4]-(O)4}W(η2-Ph2C2H2)], 5. The ethylene complex, 2, undergoes deprotonation with LiBu, leading to the corresponding anionic alkylidyne [{p-But-calix[4]-(O)4}W⋮CMe]Li, 6, which can be protonated, not back to the starting olefin complex, but rather to the corresponding alkylidene [{p-But-calix[4]-(O)4}WC(H)Me], 7. Complexes 6 an...

This report deals with the chemistry of anionic W-alkylidynes generated over the oxo surface defined by a calix[4]arene tetraanion. The exhaustive alkylation of [cis-(Cl)2W{p-But-calix[4]−(O)4}] (1...

This report deals with the different transition metal- and alkali cation-assisted oxidation pathways of the meso-octaethylporphyrinogen tetraanion [Et8N4]4-. The two-electron oxidation of [Et8N4Mn{Na(thf)2}2], 4, with Cp2FeBPh4 led to the corresponding monocyclopropane derivative [Et8N4(Δ)Mn], 6, [Δ ≡ cyclopropane], while the one-electron oxidation with CuCl2 or O2 led to the Mn(III)−porphyrinogen [Et8N4Mn][Li(thf)4], 5, which can be further oxidized by an excess of CuCl2 to [Et8N4(Δ)2Mn−Cl]+[Cu9Cl11]0.5, 7. The formation of 7 does not follow the expected sequence Mn(II) → Mn(III) → Mn(II)−monocyclopropane → Mn(II)−biscyclopropane−porphyrinogen. In the case of iron(II)−porphyrinogen, [Et8N4Fe{Li(thf)2}2], 9, the oxidation led in a preliminary stage to the iron(III) derivative [Et8N4Fe][Li(thf)4], 10, then to the metalated form of the biscyclopropane−porphyrinogen [Et8N4(Δ)2Fe−Cl]{μ-Cu4Cl5}], 11. The supposed stabilization of the biscyclopropane by the copper(I) cluster was ruled out by carrying the oxidat...

Tantalum–carbon functionalities bonded over an oxo matrix (here calix[4]arene anions) undergo a variety of multiple migratory insertion reactions which lead to the metal-assisted formation of C–C and CC bonds.

A novel mode of storing and releasing electrons, based on the reversible formation and cleavage of C−C bonds, has been created. The C−C bonds formed by the reductive coupling of imino groups across two [M(salophen)] complexes (see structure) function as shuttle for two electrons, permitting long-range electron transfer to a variety of substrates (e.g. quinone, dioxygen, and azides). This electron transfer is mediated by the metal, which becomes the reactive site, while the C–C functionality is never directly involved.

The organometallic chemistry of titanium− and vanadium−macrocycle was investigated using meso-octaethyl mono(pyridine)−tris(pyrrole), [Et8(C5H3N)(C4H2NH)3], 1, and meso-octaethyl cis-bis(pyridine)−bis(pyrrole), [Et8cis-(m-MeC5H2N)(C5H3N)(C4H2NH)2], 7, as ligands for titanium(IV) and vanadium(III), respectively. The metalation of 1 with LiBu followed by the reaction with TiCl4·thf2 led to [Et8(C5H3N)(C4H2N)3Ti−Cl], 3, which was alkylated to [Et8(C5H3N)(C4H2N)3Ti−Me], 4. The Ti−C bond in 4 underwent a migratory insertion reaction with ButNC and carbon monoxide. In the former case the corresponding η2-iminoacyl was isolated and structurally characterized as [Et8(C5H3N)(C4H2N)3Ti(η2-C(Me)NBut)], 6, while the reaction of 4 with carbon monoxide led to the homologation of one pyrrolyl anion, thus converting the mono(pyridine)−tris(pyrrole) into a cis-bis(pyridine)−bis(pyrrole) macrocycle and the oxotitanium(IV) functionality in [Et8(m-MeC5H2N)(C5H3N)(C4H2N)2TiO], 5. The homologation occurs via a carbenium ion η2...

The structural characterization by X-ray diffraction analysis of the title compound is reported. Crystallographic details are: C42H70O35°C15H12N3O4 SNa·8D2O, triclinic, space group P1, a = 14.767(3), b = 12.237(2), c = 11.537(2)A, α = 79.49(1), β = 110.91-(1), c = 104.61(1)°, d calc = 1.460 g/cm3, Z = 1, R = 0.045 for 6635 observed reflections. The crystal structure consists of head-to-tail β-cyclodextrin molecules (β-CD) linked together by piroxicam anions in infinite polymeric chains running along the c axis. In a chain each β-CD molecule takes up simultaneously two guest molecules including on the secondary hydroxyl end the benzene ring and on the primary hydroxyl end the pyridine ring of two adjacent piroxicam anions. The piroxicam anion is located with its central hydrophilic moiety at the interface between two adjacent β-CD molecules, forming with them hydrogen bonds through the enolate and amide oxygen atoms. Conformation of piroxicam is different from those observed for its neutral and zw...

Complexation of metal ion and counterion by the same compound is possible with zirconium meso-octaalkylporphyrinogens (structure of a dimeric complex with four encapsulated equivalents of LiH is depicted): they carry salts in the molecular ion-pair form in hydrocarbons, and function as acid-base bifunctional compounds.

This report deals with the chemistry of V−C functionalities anchored to a quasi-planar O4 matrix represented here by the [p-But-calix[4]-(OMe)2(O)2]2- macrocycle. The starting material [p-But-calix[4]-(OMe)2(O)2V−Cl], 2, has been converted into the corresponding alkyl and aryl derivatives [p-But-calix[4]-(OMe)2(O)2V−R] (R = Me, 3; R = CH2Ph, 4; R = p-MeC6H4, 5) by conventional procedures. The structure of 5 reveals the self-assembling of the monomeric unit into a columnar arrangement with the p-tolyl substituent functioning as a guest moiety in a neighboring unit. Complexes 3−5 undergo migratory insertion reactions with CO and ButNC to the corresponding η2-acyls [p-But-calix[4]-(OMe)2(O)2V(η2-COR)] (R = Me, 6; R = CH2Ph, 7) and η2-iminoacyls [p-But-calix[4]-(OMe)2(O)2V{η2-C(NBut)R}] (R = Me, 8; R = CH2Ph, 9; R = p-MeC6H4, 10), the reaction with CO being strongly dependent on the R substituent. The structural model for the hexacoordinate intermediate leading to the inserted product is exemplified by the d2...

Lithiation of [ p -Bu t -calix[4]-(OMe) 2 (OH) 2 ] ( 1 ), followed by reaction with TiCl 3 (thf) 3 or TiCl 4 (thf) 2 , led to the corresponding titanium-calix[4]arene complexes [ p -Bu t -calix[4]-(OMe) 2 (O) 2 ]TiCl] ( 2 ) and [ p -Bu t -calix[4]-(OMe) 2 (O) 2 ]TiCl 2 ] ( 3 ), respectively. Reaction of 1 with TiCl 4 (thf) 2 results in demethylation of the calix[4]arene and the obtention of [ p -Bu t -calix[4]-(OMe) 2 (O) 3 ]TiCl] ( 4 ), whose hydrolysis led to [ p -Bu t -calix[4]-(OMe)(OH) 3 ] ( 6 ). The preparation of 6 can be carried out as a one-pot synthesis. Both 2 and 4 undergo alkylation reactions using conventional procedures, thus forming surprisingly stable organometallic species, namely [ p -Bu t -calix[4]-(OMe) 2 (O) 2 Ti(R)] (R = Me ( 7 ); CH 2 Ph ( 8 ), p -MeC 6 H 4 ( 9 ) and [ p -Bu t -calix[4]-(OMe)(O) 3 Ti(R)] (R = Me ( 10 ); CH 2 Ph ( 11 ); p -MeC 6 H 4 ( 12 )). Complexes 7 and 9 undergo a thermal oxidative conversion into 10 and 12 , occurring with the demethylation of one of the methoxy groups. A solid state structural property of 9 and 12 has been revealed by X-ray analysis showing a self-assembly of the monomeric units into a columnar polymer, where the p -tolyl substituent at the metal functions as a guest group for an adjacent titanium-calixarene. Reductive alkylation of 3 with Mg(CH 2 Ph) 2 gave 8 instead of forming the corresponding dialkyl derivative. Two synthetic routes have been devised for the synthesis of the Ti(III)-Ti(III) dimer [ p -Bu t -calix[4]-(OMe)(O) 3 Ti] 2 ] ( 13 ): the reduction of 4 and the reaction of TiCl 3 (thf) 3 with the lithiated form of 6 . A very strong antiferromagnetic coupling is responsible for the peculiar magnetic behavior of 13 . The proposed structures have been supported by the X-ray analyses of 4, 9, 12 and 13 .

Bis(phthalocyaninato)niobium(IV) has been prepared and isolated as a monosolvate, [Pc2Nb]·ClNP (ClNP = 1-chloronaphthalene). It is a light-brown, stable-to-air Nb(IV) (d1) paramagnetic sandwich-like species, which, upon oxidation by I2 under mild conditions, undergoes a metal-centered monoelectronic oxidation to give the diamagnetic Nb(V) (d0) [Pc2Nb]+ fragment, with formation of saltlike species of formula [Pc2Nb](I3)(I2)0.5(ClNP)3.5 (I). The structure of I has been elucidated by single-crystal X-ray work. Crystals are triclinic: formula C64H32N16Nb·I3·0.5I2·3.5C10H7Cl, M = 2194.8, a = 17.702(3) A, b = 18.708(3) A, c = 13.504(2) A, V = 4267.5(13) A3, α = 106.00(2)°, β = 93.39(2)°, γ = 83.26(1)°, Z = 2, space group P1. The structure of the [Pc2Nb]+ fragment, “stapled” by two inter-ligand C−C σ bonds (C11A−C11B and C31A−C31B = 1.574(15) A), together with its color and UV−visible spectral behavior, allows a straightforward assignment of the same “stapled” structure to the unoxidized [Pc2Nb]. The present n...

Dichloro(phthalocyaninato)niobium(IV), PcNbCl2, has been isolated as a new polymorph and its X-ray crystal structure solved. Crystals are triclinic: formula C32H16Cl2N8Nb , space group P1, cell parameters a = 8.707(2) Å, b = 12.288(3) Å, c = 12.801(3) Å, α = 80.72(2) °, β = 85.43(2) °, γ = 76.62(2) °, V = 1313.7(6) Å3, Z = 2. The molecular structure closely resembles that already found for the monoclinic polymorph. Thus, Nb ( IV ) is six-coordinated in a cis arrangement, being displaced out of the inner N4square planar system of the phthalocyanine ring by 0.898(1) Å, towards the two chlorine atoms (average Nb - N (Pc) bond distance: 2.130(15) Å; Nb-Cl bond distances: 2.408(1) and 2.396(1) Å; angle Cl1-Nb-Cl2: 80.7 °). The main difference between the two polymorphs is the different stacking of the molecules in the crystal lattice. PcNbCl3is also triclinic: formula C32H16Cl3N8Nb , space group P1, cell parameters a = 12.086(2) Å, b = 13.710(2) Å, c = 8.345(1) Å, α = 93.49(2) °, β = 100.95(2) °, γ = 79.79(2) °, V = 1335.6(4)Å3, Z = 2. In the molecular structure the Pc chromophore and the three chlorine atoms are at opposite sites with respect to the Nb atom, which is seven coordinate (average Nb-N (Pc) bond distance: 2.178(5) Å; Nb-Cl bond distances: 2.482(1), 2.426(1) and 2.380(1) Å; angles Cl-Nb-Cl : 85.3(0), 80.3(0), and 76.5(0) °). The stability of PcNbCl2and PcNbCl3towards water has been examined. The reactivity of PcNbCl2with pyrocathecol, oxalic acid, H2SO4and iodine has also been examined and has led to the isolation and characterization of the following Nb ( IV ) and Nb ( V ) species: PcNbIV(cat), PcNbIV(oxal), PcNbIVSO4, PcNbVCl2I , PcNbV(cat)I.

This report deals with the first examples of butadienes bonded to a Zr−O matrix provided by a calix[4]arene skeleton and their reactivity. The reaction of [{p-But-calix[4]-(OMe)2(O)2}ZrCl2], 2, with Mg(C4H6)(thf)2 and Mg(Ph2C4H4)(thf)3 led to [{p-But-calix[4]-(OMe)2(O)2}Zr(η4-C4H6)], 3, and [{p-But-calix[4]-(OMe)2(O)2}Zr(η4-Ph2C4H4)], 4. The butadiene fragment exhibits a π2,η4 bonding mode, as shown by an X-ray analysis on both compounds. Extended Huckel calculations confirmed the energetically preferred s-cis conformation and the π2,η4 bonding mode vs the σ2,π,η4 one. The parent compound 3 of this series behaves, however, both as a source of zirconium(II) in displacement reactions or as a dialkyl derivative of zirconium(IV) in insertion reactions. In the former class of transformations, the reaction of 3 with Ph2CO and PhCOCOPh led to the dioxo metallacycles [{p-But-calix[4]-(OMe)2(O)2}Zr{−OC(Ph)2−C(Ph)2O−}], 5, and [{p-But-calix[4]-(OMe)2(O)2}Zr{−OC(Ph)C(Ph)O−})], 6, respectively. Butadiene was also dis...

Four copper(I) complexes have been designed as photosensitizers for assisting the norbornadiene (NBD) → quadricyclene (Q) isomerization with the purpose of carrying out the reaction using visible light and achieving a high NBD/photocatalyst turnover. All complexes contain π-delocalized bidentate N⌒O monoanionic ligands. Their syntheses have been performed either by the metathesis reaction from CuCl or by reaction of the monoprotic ligands with Cu5Mes5 (Mes ≡ 2,4,6-Me3C6H2) in the presence of norbornadiene. The dinuclear complexes [Cu2L2(μ-NBD)], 3, [Cu2L‘2(μ-NBD)], 4, [Cu2L‘‘2(μ-NBD)], 5, and [Cu2L‘‘‘2(μ-NBD)], 6 [where L = 2-methyl-8-oxoquinolinato, L‘ = 2-methyl-5,7-dichloro-8-oxoquinolinato, L‘‘ = 4-oxoacridinato, and L‘‘‘ = 2-(2-oxo-3,5-di-tert-butyl phenyl)benzotriazole], have been isolated and characterized in the solid state, including the X-ray analysis on 3 and 6. All compounds show absorption in the visible spectrum, due to the presence of metal-to-ligand charge-transfer (MLCT) bands. Most were ...

The multistep synthesis of the novel diphosphine reference ligand L(2), 6, Ph(2)P(o-C(6)H(4)CH(2)C(6)H(4)-o)PPh(2), has been streamlined and can be prepared on a ca. 20 g scale. It forms metallacycles with a variety of metal fragments. The resulting, and very rigid, boat-boat conformation forces a proton (H(endo)()) of the bridging methylene in close proximity to the metal, which in turn renders these protons (H(endo)(), H(exo)()) diastereotopic. The NMR spectra of [L(2)MCl(2)] [M = Pd, 9; M = Pt, 10] and of the organometallic derived compounds [L(2)Pd(PPh(3))], 11, and [L(2)Pd(Cl)(eta(2)-CH(2)Ph)], 12, consist of a pair of doublets, with the H(endo)() coupled to the P of the metallacycle. The CH(2)-metal close proximity drives the electrophilic metalation of the bridging methylene by RhCl(3) to form [L(2)Rh(Cl)(2)(MeCN)], 13, [L(2) = Ph(2)P(o-C(6)H(4)CHC(6)H(4)-o)PPh(2)]. A significant example, which shows how the coordination number of the metal can affect the H(exo)()-H(endo)() resonance separation, is provided by the couple [L(2)Ni(C(2)H(4))], 14, and [L(2)Ni(CO)(2)], 15. In order to show that the metallacycle size is crucial for the bridging methylene to function as a spectroscopic probe, we complexed the same [Fe(CO)(3)] fragment to L(2), 6, and L'(2), 17, [L'(2) = Ph(2)PO(o-C(6)H(2)(4,6Bu(t)(2))CH(2)(4,6Bu(t)(2))C(6)H(2)-o)OPPh(2)], to give [L(2)Fe(CO)(3)], 19, and [L'(2)Fe(CO)(3)], 18, respectively. In complex 17 the diastereotopic nature of these protons and hence the spectroscopic information was lost because of the presence of a 10-membered metallacycle. Crystal data: 9 is triclinic, space group Ponemacr;, a = 11.987(1) Å, b = 15.990(2) Å, c = 10.872(1) Å, alpha = 91.42(1) degrees, beta = 111.01(2) degrees, gamma = 99.86(2) degrees, V = 1908.2(5) Å(3), Z = 2, and R = 0.053; 11 is monoclinic, space group C2/c, a = 39.071(5) Å, b = 13.657(4) Å, c = 19.848(5) Å, beta = 92.45(2) degrees, V = 10581(5) Å(3), Z = 8, and R = 0.047; 12 is triclinic, space group Ponemacr;, a = 11.289(1) Å, b = 18.769(2) Å, c = 11.077(1) Å, alpha = 91.20(1) degrees, beta = 111.27(1) degrees, gamma = 105.26(1) degrees, V = 2107.7(4) Å(3), Z = 2, and R = 0.039; 13 is orthorhombic, space group P2(1)2(1)2(1), a = 15.346(2) Å, b = 18.188(3) Å, c = 12.072(2) Å, V = 3369.5(9) Å(3), Z = 4, and R = 0.042.

The reduction of [Mn(II)-salophen] derivatives [salophen = N,N ‘-ethylenebis(salicylideneaminato) dianion] led to the formation of C−C bridged dimers. Such C−C bonds function as two electron shuttles in electron-transfer reactions. The reduction of [Mn(salophen)(THF)]2 (1) and [Mn(3,5-But4salophen)(THF)]2 (3) with 2 equiv of sodium metal led to the corresponding single C−C bond bridged dimers, [Mn2(salophen2)Na2(DME)4] (5) [salophen2 = C−C bonded salophen dimer] and [Mn2(3,5-But4salophen2)Na2(DME)6] (7), respectively. Complexes 5 and 7 undergo a further two electron reduction to [Mn2(*salophen2*)Na4(DME)6] (6) [*salophen2* = C−C doubly bonded salophen dimer] and [Mn2(*3,5-But4salophen2*)Na4(DME)4] (8), respectively, both containing a double C−C bridge. The obtention of [Mn2{salophen(Me)CH2)}2Na4(DME)4] (9) from [Mn(salophen-Me2)(THF)]2 (2) strongly supports the existence of free radical precursors in the formation of C−C bonds. Complex 6 has been used as a source of four electrons in a number of reactions...

The pathway of the metal-assisted electrophilic cleavage of the porphyrinogen skeleton has been synthetically elucidated in the reaction of meso-octaethylporphyrinogen−titanium and −zirconium with benzaldehyde. This reaction led to modified porphyrinogen and doubly functionalized hemiporphyrinogen derivatives.

p-tert-Butylcalix[4]arene tetrakis(diphenylphosphinite), calix[4]-(PPh(2))(4) (1), and tetrakis(dimethylphosphinite), calix[4]-(PMe(2))(4) (2), provide a phosphorus surface consisting of four coplanar trivalent phosphorus atoms for binding two metal ions into a close geometrical proximity. Homodimetallic complexes have been obtained in the reaction of 1 with [(COD)MCl(2)] [COD = cycloocta-1,5-diene], namely, [{calix[4]-(PPh(2))(4)}(MCl(2))(2)] [M = Pd (3), Pt (4)]. Characterizations by (1)H and (31)P NMR were particularly informative and showed how the bridging methylene of the calix[4]arene skeleton may function as a spectroscopic probe. A dimeric complex was obtained by reacting 1 with [Rh(CO)(2)Cl](2) to give [{calix[4]-(PPh(2))(4)}{Rh(CO)Cl}(2)] (5). Reaction of 1 with excess NiCl(2) gave exclusively the monometallic complex, [{calix[4]-(PPh(2))(4)}NiCl(2)] (6), regardless of the stoichiometry used. The analogous Pd monometallic complex (7) undergoes a ligand disproportionation reaction, while the corresponding Pt analogue does not exist under the same conditions. Complex 6 represents a good entry to dinuclear heterodimetallic complexes. In fact, its reaction with [(NBD)Mo(CO)(4)] [NBD = norbornadiene] led to [{calix[4]-(PPh(2))(4)}NiCl(2){Mo(CO)(4)}] (8). The use of the more basic and less sterically demanding ligand 2 led to the synthesis of homonuclear bimetallic complexes [{calix[4]-(PMe(2))(4)}(MCl(2))(2)] [M = Ni (9), Pd (10), Pt (11)].

Two model compounds have been used for exploring the ligand-based redox chemistry of zirconium–Schiff base complexes, namely [Zr(salophen)Cl 2 (thf)] 1 and [Zr(salophen) 2 ] 2 [salophen = N,N′-bis (salicylidene)-o-phenylenediamine dianion, thf = tetrahydrofuran]. The latter occurs in two thermally non-interconvertible isomeric forms, 2A and 2B. Both contain eight-co-ordinate zirconium in a dodecahedral, 2A, and in a square-antiprismatic environment, 2B. The reduction of 1 with either Na or Mg led to the isolation of [Zr 2 LL′ 2 ] (L′ = thf 3 or pyridine 4). The centrosymmetric dinucleating octaanionic ligand L, which contains two-fold coupled salophen units joined by two C–C bonds, arises from the intermolecular reductive coupling of four imino groups belonging to two Zr(salophen) units. In an attempt to perform intramolecularly the same transformation, complexes 2A and 2B were reduced with sodium. Both isomers gave complex [ZrL″Na 4 (dme) 4 ] 5 (dme = 1,2-dimethoxyethane) containing a novel form of an hydrogenated coupled salophen ligand, L″, where the two salophen units are joined by a single C–C bond. The C–C bonds in the ligand L have been exploited as two-electron reservoirs in the reaction of 3 with PhICl 2 and 9,10-phenanthrenequinone. In this reaction the original salophen moiety is restored in its original form and the Zr(salophen) moiety present in 3 behaves as a source of masked zirconium(II).

The function of the solvent in the self-assembling mode of [CuCl] with tetrahydrothiophene is reported. Copper(l) chloride has been used in the form of [CuCOCl] n , which is slightly soluble in the most common solvents, and to allow an homogeneous phase reaction. The reaction of [CuCOCl] n with THT gave [(CuCl)2(THT)3] x ,1, in CH3OH, [(CuCl)(THT)2] x ,2 in THF [(CuCl)(THT)] x ,3, in CH2Cl2, and [(CuCl)3(THT)2] x ,4, in DME. Compound1 consists of polymeric chains of centrosymmetric Cu2Cl2 dinuclear units bridged by THIT molecules running parallel to the [101] axis. In the structure of2 we found polymeric layers generated from the [(CuCl)(THT)] asymmetric unit by the center of symmetry and by the twofold axis. In compound3 the structure consists of layers generated through the center of symmetry by the [(Cu2Cl2)(THT)2] asymmetric unit, while4 consists of layers generated through the center of symmetry by the [(Cu3Cl3)(THT)2] asymmetric unit. Crystallographic details are as [ollows:2 is monoclinic, space group P21/c.a=9.657(3) A,b=6.441(2) A,c=11.459(3) A,\=111.96(2)°,V=661.0(4) A3. andR=0.075;3 is monoclinic, space group P21/n,a=19.327(7) A,b=6.703(2) A,c=10.116(3) A,s=103.04(3)°,V=1276.7(7) A3 andR=0.043:4 is triclinic, space group Pl,a=12.513(2) A,b=6.698(1) A,c=9.651(1) A,α=91.98(1)°,\=107.86(1)°,γ=74.59(1)°,V=741.2(2) A3, andR=0.044.

The controlled ionization of the linear [Cl–Ti–O–Ti–Cl] skeleton allowed the generation of the [Cl–Ti–O–Ti]+ dimer, which is nonsymmetrical as a consequence of extended Cl–Ti–O π interactions. The [TiO] unit thus formed is a building block for a variety of titanoxane structures. This chemistry has been investigated from a theoretical point of view by ab initio MO analysis of the [Cl–Ti–O–Ti–Cl] and [Cl–Ti–OTi]+ fragments. These calculations lead to the conclusion that single ionization generates the [TiO] unit, whereas double ionization does not affect the μ-oxo bonding mode in [Ti–O–Ti]2+ or [S–Ti–O–Ti–S]2+ (where S is a pure σ-donor ligand or solvent). This observation has been confirmed experimentally by ionizing the following model complexes: [(Cl)(acacen)-Ti–O–Ti(acacen)(Cl)] (3) (acacen = N,N'-ethylenebisacetylacetoneiminato dianion) and [(Cl)(salen)Ti–O–Ti(salen)-(Cl)] (4) (salen = N,N'-ethylenebissalicylideneiminato dianion), where the linear Cl–Ti–O–Ti–Cl unit is assured by the square-planar bonding mode of the tetradentate Schiff base ligand. The double ionization of 3 with AgNO3 gave the conventional μ-oxo derivative [(acacen)(η1-ONO2)Ti–O–Ti(acacen)(η1-ONO2)] (5). In contrast, the stepwise ionization of 3 and 4 with NaBPh4 in THF led to the nonsymmetrical [Cl–Ti–OTi]+ intermediates, which are the parent compounds for a variety of linear titanoxanes. The following species containing a TiO unit have been isolated from the NaBPh4-assisted ionization of 3: [(acacen)TiO–BPh3] (6) and [(L)(acacen)TiO–Ti(acacen)–O–(acacen)Ti–OTi(acacen)(L)]2+2 BPh-4 (L = THF, 7; L = none, 8). The same reaction carried out on 4 led to [(THF)-(salen)TiO – Ti (salen) – O – (salen)Ti-(THF)]2+2 BPh-4 (9) and [(L)(salen)-TiO–Ti(salen) – O – (salen)Ti–OTi-(salen)(L)]2+ 2BPh-4 (L = THF, 10; L = Py, 11; L = none, 12, polymeric form). A scheme is proposed to explain the formation of the species derived from the single ionization of 3 and 4, where the origin and the binding properties of the [TiO] unit play a major role.

Mesityl aldehyde binds TiCl4 leading to the first structurally characterized TiCl4-aldehyde adduct, cis-[(MesCHO)2TiCl4] (Mes = 2,4,6-Me3C6H2) (1), which contains a pseudooctahedral titanium and two aldehyde carbonyl groups in a cis arrangement. However, in the case of 1:1 TiCl4–acetone adduct [(Me2CO)TiCl3)2(μ-Cl)2] (3) the solid-state structure of this acid-base complex is that of a chloro-bridged dimer. Both kinds of structures were suggested for the products [{(PhCOMe)TiCl3}2(μ-Cl)2] (4) and [cis-(PhCOMe)2TiCl4] (5) formed by the reaction of TiCl4 with acetophenone in 1:1 and 1:2 molar ratio. Thioesters behave like acetone in that they give adducts 8 and 9 with TiCl4, where 9, [{(PhSC(Me)O)TiCl3}2(μ-Cl)2], exhibits a solid-state dimeric structure like 3. The bidentate bonding mode of the chiral propionyloxazolidone 12 with TiCl4 was revealed by an X-ray analysis of 13.

The UV-stabilizer 2-(2′-hydroxy-5′-methylphenyl)benzotriazole (Tinuvin P, LH) has been used as a monoanionic bidentate ligand for complexing oxocations. Displacement of acacH from [VO(acac) 2 ] and [MoO 2 (acac) 2 ] gave [∗VO(acac) 2 ∗(μ-L)] ( 2 ) and [ cis - O 2 Mo(acac)L] ( 3 ) respectively, as crystalline compounds. Their structure has been determined by an X-ray analysis showing the structural changes occurring upon coordination. The UV spectrum of Tinuvin P is significantly affected by complexation.

Vanadyl cation complexed by 2-hydroxyisonaphthalic acid under basic conditions gave an extended layer-type structure where planar, dimeric units are held together by the K + countercations, as revealed by an X-ray analysis.

This report concerns the organometallic chemistry of niobium based on a macrocyclic ligand. To this purpose, the (meso-octaalkylporphyrinogen)niobium(V) complex [(η5:η1:η5:η1-Et8N4)NbCl], 2, has be...

The reduction of cobalt−Schiff base complexes has been explored as a function of the nature of the ligand. In the case of substituted salen complexes, reduction occurred at the metal with the formation of bifunctional Co(I)−Na complexes, while for salophen derivatives the reductive coupling of imino groups was observed. Such C−C bonds function as electron shuttles in chemical reductions. Reduction of [Co(MeOsalen)] (1) with Na metal in THF led to a monomeric [Co(MeOsalen)Na(THF)2] (2A) and a dimeric [{Co(MeOsalen)Na(THF)}2] (2B) compound. Compounds 2A and 2B exemplify a bifunctional acid−base system with both centers in close proximity. The analogous reduction of [Co(salophen)] (3) and [Co(MeOsalophen)] (5) led to dimeric cobalt(II) derivatives containing a bridging C−C bond across two units in [Co2(salophen)2Na2(THF)6] (4) and [Co2(MeOsalophen)2Na2(THF)4] (6), respectively. However, such cobalt(II) centers behave as cobalt(I), since the C−C bond provides a pair of electrons to the metal couple during the...

Reference LPI-ARTICLE-1995-002doi:10.1021/om00009a013View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

Reference LPI-ARTICLE-1995-001View record in Web of Science Record created on 2006-02-21, modified on 2016-08-08

The Zr-C bond chem. and, particularly, its migration properties were studied where the metal is bonded to the dibenzotetramethyltetraaza[14]annulene (tmtaa) dianion in the model complexes cis-[Zr(tmtaa)R2]. In this respect the [Zr(tmtaa)] fragment was analyzed in comparison with the known [Cp2Zr] moiety, with the support of an extended Hueckel anal. The synthesis of [Zr(tmtaa)R2] (R = Me, 2; R = CH2Ph, 3) (shown as structure I) from [Zr(tmtaa)Cl2] (1) was achieved under highly controlled reaction conditions. Complexes 2 and 3 are thermally labile, and one of the alkyl groups undergoes a thermally-induced migration to one of the imino groups, leading to a trianionic ligand [Zr(R-tmtaa)R] (R = Me, 4; R = CH2Ph, 5). The nature of such complexes was elucidated by an x-ray anal. on the THF-solvated form of 4, [Zr(Me-tmtaa)(Me)(THF)] (6). Nucleophiles are even more effective in inducing the alkyl migration to the ligand. In the presence of THF or pyridine 5 may be easily converted to [Zr(R2-tmtaa)] (R = CH2Ph, 7), in which both alkyl groups have migrated to the imino groups of the ligand. The use of an excess of LiMe during the alkylation of 1 gave [Zr(Me2-tmtaa)¬?¬?¬?Li(THF)2] (8) via the intermediacy of 4. Complex 8 is a bifunctional carrier of LiMe. The general consequences of two electrophilic sites on the ligand, eventually, in competition with the electrophilic metal were analyzed. The net charge and electrophilic index are significantly higher for the metal in [Cp2Zr]2+ than in [Zr(tmtaa)]2+. The relatively higher thermal inertness of 3 allowed the authors to study the migration of the alkyl group toward the unsatd. incoming nucleophiles, ButNC and CO. The reaction of 3 with ButNC gave the bis(??2-iminoacyl) compd. [Zr(tmtaa)(??2-C(Me):NBut)2]. The four low-lying d orbitals can accommodate the two ??2-iminoacyl groups. The reaction of 3 with Bu'NC led to the formation of the bis(y2-iminoacyl) compound [Zr(tmtaa)(v2-C(Me)=NBut)2T]h.e four low-lying d orbitals can accommodate the two y2-iminoacyl groups. The reaction of 3 with CO gave [Zr(tmtaa)(yz-OC(CH2Ph)~)(]1 1) via the intermediacy of a very reactive oxycarbene $-acyl compound and ultimately gave 12 and 13, illustrating the reactivity of both zirconium and the iminato carbons in the [Zr(tmtaa)] fragment. The crystallographic details are as follows: 3 is orthorhombic, space group Pnma, a = 16.028(3) A, b = 20.666(4) A, c = 9.018(2) A, a = p = y = 90°, Z = 4, and R = 0.063. 6 is monoclinic, space group P2l/n, a = 19.859(5) A, b = 14.771(5) A, c = 9.072(4) A, a = y = 90°, /3 = 93.85(3)", Z = 4, and R = 0.044. 7 is monoclinic, space group C2/c, a = 23.608(6) A, b = 9.529(3) A, c = 19.050(4) A, a = y = 90", p = 99.30(2)", Z = 4, and R = 0.046. 10 is triclinic, space group P i , a = 12.800(4) A, b = 15.795(5) A, c = 11.758(1) A, a = 91.8(2)", p = 93.56(1)", y = 97.81(2)", Z = 2, and R = 0.042.

Thirty-four @2-R1C2R2)Co2(C0)6 complexes (14 new) were prepared and characterized by their IR v(C0) and lH- and 13C-NMR spectra. The 13C-NMR chemical shifts of the coordinated sp carbon atoms were correlated with those of the corresponding free acetylenes. This indicated that the interaction between the R1 and R2 groups and the c2co2(co)6 moiety is very sensitive not only to the donor/acceptor character of R1 and R2 but also to the orbital symmetry of the atoms attached directly to the C(sp) atoms. The changes of the W3C) values of the C(sp) atoms upon coordination were also analyzed in these terms. It is concluded that although the dinuclear p2-coordination of the acetylene results in a high degree of excitation the stability of the c2co2(co)6 moiety diminished the reactivity of the organic ligand. Differences in the reactivity of the @2-R1C2R2)Co2(CO)6 complexes in carbonylation are also discussed. The crystal and molecular structure of (PhC2SiPhs)Coz(CO)a was determined by single crystal X-ray diffraction. This compound crystallizes in the orthorhombic Pbca space group with a = 28.790(2) A, b = 11.577(1) A, c = 17.833(2) A, 2 = 8. The structure was determined with R = 0.039, R, = 0.036.

The arylation of FeCl 2 (THF) 1.5 in THF with MesMgBr (Mes=1,3,5-Me 3 C 6 H 2 ) in the presence of 9,10-phenanthroline (phen) led to the crystalline [Fe(phen)(Mes) 2 ], 1, which contains a tetrahedral iron(II) σ-bonded to two aryl groups. They can be removed by a variety of protic ligands under aprotic conditions. The reaction of 1 with amino acids AH led to the isolation of monomeric iron(II)-amino acid complexes [Fe(phen)(A) 2 ]