María J. Fernández-Trujillo

Synthesis, Reactivity, and Kinetics of Substitution in W3PdSe4 Cuboidal Clusters. A Reexamination of the Kinetics of Substitution of the Related W3S4 Cluster with Thiocyanate

The reaction of Pd(dba)(2) (dba = dibenzylideneacetone) with [W(3)Se(4)(H(2)O)(9)](4+) in 2 M HCl gives the cuboidal cluster [W(3)(PdCl)Se(4)(H(2)O)(9)](3+), which undergoes edge-to-edge condensation and crystallizes from Hpts solutions as edge-linked double-cubane cluster [{W(3)PdSe(4)(H(2)O)(9)}(2)](pts)(8) x 18 H(2)O (pts(-) = p-toluenesulfonate). The substitution of Cl(-) by different ligands, including phenylsulfinate PhSO(2)(-), was explored. The phenylsulfinate complex was crystallized as a 2:1 adduct with cucurbit[6]uril (C(36)H(36)N(24)O(12)), [W(3)(Pd(PhSO(2))Se(4)(H(2)O)(8.58)Cl(0.42)](2)(C(36)H(36)N(24)O(12))Cl(5.16) x 16.83 H(2)O, and its structure was determined by X-ray diffraction. Solution studies indicate that the Pd atom is able to stabilize the pyramidal tautomer of hypophosphorous and phosphorous acid: HP(OH)(2) and P(OH)(3). Kinetic studies were carried out on the reactions with H(3)PO(2) and thiocyanate, which were found to proceed in two and three kinetically resolvable steps, respectively. The kinetic results are discussed in terms of the mechanistic proposals put forward in the literature for related complexes. To gain insight into the details of the substitution kinetics in these kinds of clusters, the reaction of the related [W(3)S(4)(H(2)O)(9)](4+) complex with NCS(-) has been reexamined, and the results obtained provide for the first time information about the rates of substitution of the whole set of nine-coordinated water molecules.

Sol–gel materials with trapped trinuclear class-II mixed-valence macrocyclic complexes that mimic their solution redox behaviour

The redox chemistry of mixed-valence CoIII/FeII/CoIII complexes in solution and trapped in sol–gel matrices has been compared. Whereas the redox S2O82−/OH− reactivity cycling of the complexes [{LnCoIII(µ-NC)}2FeII(CN)4]2+ physically immobilized into the pore network of TEOS-derived xerogels, where Ln represents a polyaza macrocycle, mimic perfectly the reactivity shown in solution without leaching of the complex to the reaction medium, all attempts to immobilize smaller and negatively charged dinuclear [{LnCoIII(µ-NC)}FeII(CN)5]− related complexes have been found unsuccessful. A fine tuning of the pore size of the matrix, the electrostatic interactions between the matrix’s surface and the complexes, as well as possible chemical adduct formation between the OR groups of the matrix and the cyanide ligands, seem to be responsible for the effects observed. The chemical preparation of the mixed-valence complexes inside the sol–gel matrix has also been tried by using a silylated modified Ln ligand with four hydrolysable-Si(OEt)3 groups. Following the anchoring of the ligand to a TEOS-derived matrix, the initial formation of the LnCoIII building block has been achieved, but diffusion of the negatively charged [Fe(CN)6]4− species to the {LnCoIII}3+ centre is severely hindered unless high acidity is used. Nevertheless, under such acidic conditions the mixed-valence [{LnCoIII(µ-NC)}FeII(CN)5]− compounds have been successfully formed inside the matrix and have been characterized by IR and UV-Vis spectroscopy. Despite this fact, the redox S2O82−/OH− reactivity cycling carried out on the latter materials has proved to be much more slow than for xerogels containing the trinuclear [{LnCoIII(µ-NC)}2FeII(CN)4]2+ species physically trapped.

Displacement of tetrahydrofuran ligands by tripodal phosphines. Crystal structure of [MoCl3{N(CH2CH2PPh2)3}]·C4H8O

The complexes [MoCl3{P(CH2CH2PPh2)3}]·thf and [MoCl3{N(CH2CH2PPh2)3}]·thf (thf = tetrahydrofuran) have been prepared from [MoCl3(thf)3] by ligand replacement reaction of thf. An X-ray crystal structure investigation of [MoCl3{N(CH2CH2PPh2)3}]·thf shows a distorted-octahedral structure with a meridional arrangement of the three chlorine ligands. The amine acts as tridentate ligand with a pendant PPh2 group.

Dinitrogen and related compounds of molybdenum with the tripodal phosphines N(CH2CH2PPh2)3 or P(CH2CH2PPh2)3 as coligands

The reduction of [MoCl3{N(CH2CH2PPh2)3}] with a sodium dispersion in tetrahydrofuran (thf) under a dinitrogen atmosphere yields the unstable complex cis-[Mo(N2)2{N(CH2CH2PPh2)3}], which decomposes in a few days even in solution under dinitrogen. Studies of the chemical reactivity of this compound towards carbon monoxide, PMe3, Mel and CF3CO2H have been carried out and the complexes [Mo(CO)3L], [Mo(PMe3)3L], [Mol2L] and [Mo(CF3CO2)2L][L = N(CH2CH2PPh2)3] have been isolated and identified. The reduction of the analogous complex [MoCl3{P(CH2CH2PPh2)3}] gives unstable trans-[Mo(N2)2{P(CH2CH2PPh2)3}]. The ligand-substitution reaction of cis-[Mo(N2)2(PMe3)4] with N(CH2CH2PPh2)3 yields the complex cis-[Mo(N2)(PMe3){N(CH2CH2PPh2)3}].

Synthesis and reactivity of [MCl2(CNBut)3(PMe3)2] (M = Mo or W): preparation of [MCl(CNBut)4(PMe3)2]Cl and [M(SnCl3)(CNBut)3(PMe3)3](SnCl3) derivatives. The crystal structure of [MoCl(CNBut)4(PMe3)2]Cl·2Me2CO

Abstract The reaction of the sixteen-electron paramagnetic complex [MCl 2 (PMe 3 ) 4 ](M = Mo or W) with CNBu t gives the eighteen-electron diamagnetic seven-coordinate complex [MoCl 2 (CNBu t ) 3 (PMe 3 ) 2 ] ( 1 ) or [WCl 2 (CNBu t ) 3 (PMe 3 ) 2 ] ( 2 ). These complexes react with additional CNBu t to give the complexes [MCl(CNBu t ) 4 -(PMe 3 ) 2 ]Cl (M = Mo ( 3 ) or W ( 4 )). An X-ray diffraction study of 3 shows it to have a capped trigonal prismatic structure in the solid state. The reaction of [MCl 2 -(CNBu t ) 3 (PMe 3 ) 2 ] with anhydrous SnCl 2 yields the complexes [M(SnCl 3 )-(CNBu t ) 3 (PMe 3 ) 3 ](SnCl 3 ) (M = Mo ( 5 ) or W ( 6 )), which have been studied by 119 Sn NMR spectroscopy. A new route to the complex trans -[MoCl 2 (PMe 3 ) 4 ] from MoCl 5 has also been developed.

Dihydrogen complexes: striking effect of ion pairing to BF4− on the rotation of coordinated dihydrogen and the 19F relaxation time

Unexpected changes in the T(1) values for the (19)F NMR signal of the BF(4)(-) anion in the presence of dihydrogen complexes reveal that ion pairing with BF(4)(-)...H(2) interactions of different strengths can lead to significant changes in the rotation barrier for coordinated dihydrogen.

Ag(I) complexes with alkylidene-bis(2-aminopyrimidines) as building units for discrete metallomacrocyclic frames. A structural and solution study

Alkylidene-bis(2-aminopyrimidines) (pyr2Cx, x = 2-5) are useful ligands to interact with Ag(I) yielding discrete metallocycles. Crystal structures of the [(pyr2C2)Ag(NO3)]2 and [(H-pyr2C4)Ag(NO3)2]2 have been isolated where each macrocyclic moiety interacts with their surroundings through weak interactions, yielding 3D discrete structures, On the other hand, the solution study shows that the equilibrium constants for the formation of Ag(pyr2Cx)+ complexes are higher than the literature values for Ag(I) complexes with single pyrimidines, although the differences could be explained by invoking the solid-state structures of the Ag(I)-pyr2Cx complexes.

Reactivity of seven-coordinate molybdenum(II) and tungsten(II) isocyanide complexes: The crystal structure of [MoCl(CNBut4(PMe3)2]Cl

Abstract The seven-coordinate isocyanide complexes [MCl2(CNBut)3(PMe3)2] (M = Mo or W), react with additional CNBut yielding the derivatives [MCl(CNBut)4(PMe3)2]Cl. The crystal structure of the [MoCl(CNBut)4(PMe3)2]Cl complex shows an almost perfect two- fold symmetry for the cation [MoCl(CNBut)4(PMe3)2+ along the MoCl bond and two different possible orientations for the t-butyl groups. The reaction of [MCl2(CNBut)3 (PMe3)2 (M = Mo or W) with anhydrous SnCl2 yields complexes containing the SnCl3− ligand, derived from the insertion of SnCl2 into the metal-halide bond.