Montserrat Ferrer

Anionic trimetallic compounds containing FeEM skeletons (E = Zn, Cd, Hg; M = Fe, Mo, W). Crystal structure of [N(PPh3)2]2[(OC)4FeHgFe(CO)4]

Dichlorides of group 12 elements react with (NEt4)[HFe(CO)4] in tetrahydrofuran to give the di-hydrides [(OC)4HFeEFeH(CO)4] (E = Zn, Cd, Hg) in good yields. These compounds undergo proton abstraction by nBuLi to give di-anions [(OC)4FeEFe(CO)4]2-, stabilized as their bis(triphenylphosphine)nitrogen(+) (PPN+) salts. (PPN)2[(OC)4FeHgFe(CO)4] crystallizes in the triclinic system, space group P1 with a 20.382(3), b 15.328(2), and c 13.420(2) A; α 115.96(3), β 108.89(2), and γ 87.09(2)o, and Z = 2. The anion consists of an almost linear spine (FeHgFe angle 178.7(1)o), with an average FeHg bond distance of 2.546(2) A. The Fe atoms display a trigonal bipyramidal geometry, and the equatorial CO groups linked to the iron atoms are in an eclipsed conformation, resulting in an idealized D3h symmetry. The existence of two conformers for this anion and the presence of Hg · · · CO backbonding are discussed on the basis of qualitative molecular orbital theory. The [(OC)4FeHgFe(CO)4]2- anion undergoes redistribution reactions with [M(CO)3(η-C5H5)]2 Hg (M = Mo, W) to give the new unsymmetrical anions [(OC)4FeHgM(CO)3(η-C5H5)]-.

Anionic iron clusters as building blocks for the synthesis of higher nuclearity compounds containing 11- and 12-group elements

Abstract Anionic iron clusters have been widely used as building blocks for the formation of mixed metal clusters with 11- and 12- group elements. This review summarizes the results reported in this area, paying special attention to the structural features of the metal core of the species reported.

Kinetics of the anation of aquopentaamminecobalt(III) by phosphoric acid dihydrogenphosphate

The kinetics of the anation reaction of [Co(NH3)5H2O]3+ by H2PO-4/H3PO4 in aqueous solution has been studied at 50, 60 and 70 °C and I = 1.0 (LiClo4). The results indicate a rate law of the form kobs = kf[H2PO−4], with no (or small) contribution from H3PO4. No kinetic evidence of ion-pair formation has been observed in contrast to the analogous chromium(III) study. Values of kf × 105 (M−1s−1) are: 4.50 ± 0.07, 15.4 ± 0.2, and 53.9 ± 0.8 at 50, 60 and 70 °C respectively; the corresponding activation parameters are ΔH± = 26.9 ± 0.8 Kcal mol−1 and ΔS± = 4.2 ± 2.4 cal K−1 mol−1.

Study of the self-assembly reactions between the organic linker 1,4-bis(4-pyridyl)butadiyne and the metal-containing corners (diphosphine)M(II) (M=Pd, Pt; diphosphine=dppp, dppf, depe, dppbz)

Abstract The diaza ligand 1,4-bis(4-pyridyl)butadiyne ( L ) has been used as a linker in self-assembly reactions with different diphosphine Pd(II) and Pt(II) triflates to build metallosupramolecular squares and triangles. Equilibria between triangular and square entities have been detected in most of the cases and their composition studied by multinuclear NMR spectroscopy and mass spectrometry. The self-assembly process has been shown to be strongly dependent on the conditions of the medium and the nature of the transition metal. The ability of some of these compounds to recognise inorganic anions has been investigated.

Electrospray mass spectrometric studies of some heterometal anionic carbonyl clusters

Electrospray mass spectra (ESMS) are reported for a series of anionic transition-metal clusters of the type (PPh4)[Fe3(CO)10(μ-CO){μ-Hg(m)}] (m = Mo(CO)3Cp; Co(CO)4; Fe(CO)2Cp; W(CO)3Cp; Mn(CO)5) and also for the species of higher nuclearity (NEt4)[Fe6C(CO)16AuPPh3] in methanol solution. The results were compared with those obtained by FAB-MS, and they indicate that ESMS is the most appropriate technique by which to obtain control fragmentation. Information about the strength of the different metal-metal bonds present in the cluster can be deduced from the species generated.

Antisymbiotic Self-Assembly and Dynamic Behavior of Metallamacrocycles with Allylic Corners

The design and synthesis of discrete supramolecular architectures by metal–ligand self-assembly is an area of current interest. The application of the directional bonding approach has proved to be very versatile, allowing the synthesis of many molecular triangles, squares, rectangles, pentagons, hexagons, and cages. Among them, homometallic molecular squares, formed by the reaction of cis-protected square planar complexes with linear symmetric ditopic ligands, have been the most widely studied. The assembly of metallamacrocycles containing different metal corners and/or nonsymmetric ligands using this method presents additional difficulties due to the possible generation of a mixture of isomers that are difficult to separate. To overcome this, they are generally obtained through modular self-assembly methodology. This strategy requires the initial synthesis of mononuclear complexes with strong covalently bound ligands that have additional donor sites available for coordination to further acceptor building blocks. Nevertheless, several molecular triangles and squares have been recently assembled following the directional bonding approach by using nonsymmetric linkers and identical metal corners. Interestingly, in some cases, unexpected self-selection of a single linkage isomer was observed. To analyze the large quantity of metallamacrocycles reported to date, the following classification is proposed, according to the nature of the assembled units: 1) species containing identical metal corners and symmetric linkers; 2) species containing identical metal corners and nonsymmetric linkers; and 3) species containing different metal corners and nonsymmetric linkers. Herein, we report the use for the first time of the directional bonding approach for the synthesis of metallamacrocycles displaying two different metal corners connected by a nonsymmetric ditopic linker. By the correct choice of the different units, that is, metal corners and ambidentate ligand, we have been able to promote its self-assembly producing molecular square architectures and, more interestingly, achieving the self-selection of a single linkage isomer. Evidently, the correct choice of a heteroditopic ligand in which the different (stereo)electronic characteristics of the donor groups could control the reactivity at the metal site is decisive. Thus, we focused our attention on the 4-PPh2py ligand (py=pyridine), given its hard-soft character. Furthermore, the electronic nature of the ancillary ligands in the metal corners on the proposed assembly is also crucial for the self-selection process. As a result, complex [Pd(h-2Me-C3H4) ACHTUNGTRENNUNG(cod)] ACHTUNGTRENNUNG(CF3SO3) was chosen as the source of {Pd(h-2-Me-C3H4)} + , a potential metal corner that could provide a varied reactivity to the system, as expected for the allyl palladium species. On the other hand, the complex [PdACHTUNGTRENNUNG(H2O)2 ACHTUNGTRENNUNG(dppp)] ACHTUNGTRENNUNG(CF3SO3)2 was chosen as the second metal corner supplier, {Pd ACHTUNGTRENNUNG(dppp)}2+ (dppp=bis(diphenylphosphino)propane). The selected metal fragments were expected to coordinate selectively to each of the donor atoms of the heteroditopic 4-PPh2py ligand. Following Pearson s antisymbiotic effect, the greatest stability is expected when the softest ligands are bonded trans to the hardest ones. With these three components in our hands, that is, [Pd(h2-Me-C3H4) ACHTUNGTRENNUNG(cod)] ACHTUNGTRENNUNG(CF3SO3), [Pd ACHTUNGTRENNUNG(H2O)2ACHTUNGTRENNUNG(dppp)] ACHTUNGTRENNUNG(CF3SO3)2, and 4-PPh2py, the self-assembly was explored in solution in dichloromethane at room temperature (Scheme 1). After several minutes, the color of the solution faded away and the P NMR spectrum (Supporting Information, Figure S1) showed two signals associated with the P atoms of the dppp ligand and those bonded to the allylpalladium fragment, respectively, indicating the presence of only one species in solution. This species, the targeted macrocycle 1, was obtained [a] Dr. I. Angurell, Dr. M. Ferrer, Dr. A. Guti rrez, Prof. M. Mart nez, Dr. L. Rodr guez, Prof. O. Rossell Departament de Quimica Inorg nica, Universitat de Barcelona Mart i Franqu s 1-11, 08028 Barcelona (Spain) Fax: (+34)934907725 E-mail : montse.ferrer@qi.ub.es [b] Dr. M. Engeser Kekul -Institut f r Organische Chemie und Biochemie der Universit t, Gerhard-Domagk-Str.1, 53121 Bonn (Germany) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201002605.

Oxidative-addition reactions of [W2(η-C5H4R)2X4](R = Pri or Me; X = Cl or Br): reversible addition of dihydrogen to a tungsten–tungsten triple bond and X-ray crystal structures of [W2(η-C5H4Pri)2Cl4(µ-H)(µ-PPh2)] and [W2(η-C5H4Pri)2Cl3(µ-Cl)(µ-H)(µ-PPh2)(PMe3)]

The unsupported WW bond of [W2(η-C5H4R)2X4](X = Cl, R = Pri1a or Me 1b; X = Br, R = Pri2) readily undergoes oxidative-addition reactions with HY [Y = H, Cl, SR′(R′= Me, Et, Pri, Ph or But), or PPhR′(R′= H or Ph)] to afford the corresponding derivatives [W2(η-C5H4R)2X4(µ-H)(µ-Y)] in good yields. For 1a the addition of H2 is reversible with reductive elimination occurring readily at ca. 50 °C under reduced pressure. The µ-phosphido complex [W2(η-C5H4Pri)2Cl4(µ-H)(µ-PPh2)] has been crystallographically characterised and possesses a WW double bond [2.6558(3)A]. The µ-thiolato complexes [W2(η-C5H4R)2Cl4(µ-H)(µ-SR′)] are fluxional and undergo inversion at the µ-S atom; ΔG‡ values for this process have been determined and increase in the order R′= But < Pri < Ph < Et < Me. The µ-chloro complexes [W2(η-C5H4R)2Cl4(µ-Cl)(µ-H)] undergo a different fluxional process which effectively involves rotation of the (µ-Cl)(µ-H) fragment about the W–W vector. The complexes [W2(η-C5H4Pri)2Cl4(µ-H)(µ-Y)](Y = H or PPh2) react with PMe3 to give the corresponding adducts [W2(η-C5H4Pri)2Cl3(µ-Cl)(µ-H)(µ-Y)(PMe3)], the X-ray crystal structure of the µ-phosphido complex (Y = PPh2) having been determined. In contrast, treatment of [W2(η-C5H4Pri)2Cl4(µ-H)(µ-Y)](Y = Cl or SR′) with an excess of PMe3 affords the mononuclear complex [W(η-C5H4Pri)Cl(PMe3)3].

Anions [Fe2(CO)8]2– and [Fe2(CO)6(µ-CO)(µ-PPh2)]– as building blocks for the synthesis of mixed-metal clusters. Crystal structure of [Fe2(CO)6(µ-CO)(µ-PPh2){µ-Cu(PPh3)}]

Treatment of the salt [NEt4]2[Fe2(CO)8] with a tetrahydrofuran solution of the complex [Cul(PPh3)] gives an anionic orange-red cluster [NEt4][Fe2(CO)6(µ-CO)2{µ-Cu(PPh3)}]1 which is air- and thermally unstable. When [NEt4][Fe2(CO)6(µ-CO)(µ-PPh2] and [MX(PPh3)](M = Cu, Ag or Au) are allowed to react in the presence of TIBF4, the new neutral clusters [Fe2(CO)6(µ-CO)(µ-PPh2)-{µ-M(PPh3)}](M = Cu, 2; Ag, 3; or Au, 4) are obtained in ca. 80% yield. These relatively air-stable clusters have been characterized by IR and 31P NMR spectroscopy and the structure of 2 has been established by single-crystal X-ray diffraction studies: triclinic, space group P, with a= 11.081(3), b= 12.190(3), c= 15.808(4)A, α= 76.41(2), β= 87.03(2), γ= 80.48(2)°, Z= 2 and R= 0.05. The basic skeleton consists of the first example of a Fe2Cu triangle. In this, the iŕon–iron bond is bridged by a phosphido and a carbonyl group.

Kinetico-mechanistic insights on the assembling dynamics of allyl-cornered metallacycles: the Pt-Npy bond is the keystone.

The square-like homo- and heterometallamacrocycles [{Pd(η(3) -2-Me-C3 H4 )(L(n) )2 }2 {M(dppp)}2 ](CF3 SO3 )6 (dppp=1,3-bis(diphenylphosphino)propane) and [{Pd(η(3) -2-Me-C3 H4 )(L(1) )2 }2 {M(PPh3 )2 }2 ](CF3 SO3 )6 [py=pyridine, M=Pd, Pt, L(n=) 4-PPh2 py (L(1) ), 4-C6 F4 PPh2 py (L(2) )] containing allyl corners were synthesised by antisymbiotic self-assembly of the different palladium and platinum metallic corners and the ambidentate N,P ligands. All the synthesised assemblies displayed a complex dynamic behaviour in solution, the rate of which is found to be dependent on the electronic and/or steric nature of the different building blocks. A kinetico-mechanistic study by NMR line shape analysis of the dynamics of some of these assemblies was undertaken in order to determine the corresponding thermal activation parameters. Both an enhanced thermodynamic stability and slower dynamics were observed for platinum-pyridine-containing species when compared with their palladium analogues. Time-dependent NMR spectroscopy in combination with ESI mass spectrometry was used to study the exchange between the assemblies and their building blocks, as well as that occurring between different metallamacrocycles. Preliminary studies were carried out on the activity of some of the metallamacrocyclic compounds as catalytic precursors in the allylic substitution reaction, and the results compared with that of the monometallic allylic corner [Pd(η(3) -2-Me-C3 H4 )(L(1) )2 ](+) .

Synthesis and structure of a perpendicular bridging alkylidyneamine ligand in [W2(η-C5H4Pri)2Cl4(µ-Cl)(µ-EtCNH)]

Treatment of the WW triply-bonded dimers [W2(η-C5H4R)2Cl4](R = Pri or Me) with R′CN (R′= Me, Et, or Ph) followed by HCl gas affords the complexes [W2(η-C5H4R)2Cl4(µ-Cl)(µ-R′CNH)] in quantitative yield; the X-ray crystal structure for R = Pri, R′= Et reveals a perpendicular bridging EtCNH ligand.