Building C(sp(3)) Molecular Complexity on 2,2 '-Bipyridine and 1,10-Phenanthroline in Rhenium Tricarbonyl Complexes

The reactions of [Re(N-N)(CO)(3)(PMe3)]OTf (N-N=2,2 '-bipyridine, bipy; 1,10-phenanthroline, phen) compounds with tBuLi and with LiHBEt3 have been explored. Addition to the N-N chelate took place with different site-selectivity depending on both chelate and nucleophile. Thus, with tBuLi, an unprecedented addition to C5 of bipy, a regiochemistry not accessible for free bipy, was obtained, whereas coordinated phen underwent tBuLi addition to C2 and C4. Remarkably, when LiHBEt3 reacted with [Re(bipy)(CO)(3)(PMe3)]OTf, hydride addition to the 4 and 6 positions of bipy triggered an intermolecular cyclodimerization of two dearomatized pyridyl rings. In contrast, hydride addition to the phen analog resulted in partial reduction of one pyridine ring. The resulting neutral Re-I products showed a varied reactivity with HOTf and with MeOTf to yield cationic complexes. These strategies rendered access to Re-I complexes containing bipy- and phen-derived chelates with several C(sp(3)) centers

Two Jahn–Teller systems involved in different kinds of crystal-to-crystal transformations

Two molecular-crystal solids with Jahn-Teller active Cu(II) centers undergo crystal-to-crystal transformations by different routes. The first example is a coordination copolymer with alternating Co and Cu centers along the polymer chain, and with a charge of (+1) for each link in the chain. Charge is balanced by an anion whose composition is identical to the Cocentered link of the copolymer. The overall composition can be described as {[Co(orot)2(bpy)][μCu(bpy)(H2O)]}n[Co(orot)2(bpy)]n‧5nH2O, 1, in which H2orot is orotic acid, C5H4N2O4. With gentle heating in dry nitrogen gas, crystals of this compound undergo a chemical reaction in which the anion is incorporated into the polymer as a metalloligand with one oxygen atom of the original anion substituting an aqua ligand on the Cu center of the polymer. Structure analysis at intermediate stages of the process indicate that substitution occurs by an associative mechanism. The second example involves a Jahn-Teller intermediate, formed in solution and isolable as a crystalline precipitate, which when left in contact with the reaction mixture undergoes a solvent mediated crystal-to-crystal transformation in which the two axial ligands involved in Jahn-Teller elongation are lost. The intermediate Cs2[transCu(orot)2(H2O)2]∙4H2O, 2, proceeds to the simple square-planar final product, Cs2[trans-Cu(orot)2]∙3H2O, 3. It is noted that the nickel-centered analogue of compound 2 does not undergo further transformation to a square-planar product

Field induced slow magnetic relaxation in a zig-zag chain-like Dy(iii) complex with the ligando-phenylenedioxydiacetato

The new complex [Dy(PDOA)(NO3)(H2O)(2)](n)center dot nH(2)O (1) (H(2)PDOA iso-phenylenedioxydiacetic acid) was isolated from the reaction of dysprosium(iii) nitrate and H(2)PDOA in a 1 : 1 molar ratio. Its crystal structure is formed of neutral zig-zag chains in which the nona-coordinated Dy(iii) atoms (O(9)donor set) are linked by PDOA ligands with a chelating-bridging coordination mode. DC and AC magnetic studies revealed that1behaves as a field-induced SMM with three relaxation channels. The derived values, considering the Orbach relaxation process, of the barrier to spin reversal and the extrapolated relaxation time areU/k(B)= 59.5 K and tau(0)= 6.3 x 10(-10)s, respectively.Ab initiocalculations support the experimental results

Syntheses, crystal structures and magnetic properties of complexes based on [Ni(L-L)3]2+ complex cations with dimethylderivatives of 2, 2'-bipyridine and TCNQ

From the aqueous-methanolic systems Ni(NO3)2 – LiTCNQ – 5, 5'-dmbpy and Ni(NO3)2 – LiTCNQ – 4, 4'-dmbpy three novel complexes [Ni(5, 5'-dmbpy)3](TCNQ)2 (1), [Ni(4, 4'-dmbpy)3](TCNQ)2 (2) and [Ni(4, 4'-dmbpy)3]2(TCNQ-TCNQ)(TCNQ)2·0.60H2O (3), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5, 5'-dmbpy)]2+ (1) or [Ni(4, 4'-dmbpy)]2+ (2 and 3). The anionic parts of the respective crystal structures 1–3 are formed by TCNQ·- anion-radicals and in 3 also by a s-dimerized dianion (TCNQ-TCNQ)2- with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2–300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S = 1 and TCNQ·- anion-radicals with S = 1/2 while the (TCNQ-TCNQ)2- dianion is magnetically silent. The magnetic behavior was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQ·- anion-radicals

Pairwise assembly of organopalladium(II) units with cyanurato(3-) and trithiocyanurato(3-) ligands: formation of chiral Pd12, Pd10 and Pd9 cage-molecules

The o-palladated, chloro-bridged dimers [Pd{2-phenylpyridine(-H)}-μ-Cl]2 and [Pd{N,N-dimethylbenzylamine(-H)}-μ-Cl]2 react with cyanuric acid in the presence of base to afford closed, chiral cage-molecules in which twelve organo-Pd(II) centers, located in pairs at the vertices of an octahedron, are linked by four tetrahedrally-arranged cyanurato(3-) ligands. Incomplete (Pd10) cages, having structures derived from the corresponding Pd12 cages by replacing one pair of organopalladium centers with two protons, have also been isolated. Reaction of [Pd{2-phenylpyridine(-H)}-μ-Cl]2 with trithiocyanuric acid gives an entirely different and more open type of cage-complex, comprising only nine organopalladium centers and three thiocyanurato(3-) ligands: cage-closure in this latter system appears to be inhibited by steric crowding of the thiocarbonyl groups

In Search of Optically Active γ-Keto Acetylenes via Regioselective Coupling of Allenylidene Groups and Cyclic Enolates

11 páginas, 2 figuras, 1 tabla, esquemas.(Indenyl)ruthenium(II) allenylidene complexes [Ru{ C C C(R)Ph}(η5-C9H7)(PPh3)2][PF6] (R = Ph (1), H (2)) regioselectively react with enolates derived from cyclopentanone and cyclohexanone at the Cγ atom to yield the σ-alkynyl derivatives (R = Ph, n = 1 (3a), 2 (3b); R = H, n = 1 (4a), 2 (4b)). Protonation of these species at Cβ of the alkynyl chain with HBF4 affords vinylidene complexes 5a,b and 6a,b, which can easily be demetalated with acetonitrile to yield the γ-keto acetylenes (7a,b and 8a,b). Compounds 4a,b, 6a,b and 8a,b, derived from the monosubstituted allenylidene complex 2, have been obtained as nonseparable mixtures of two diastereoisomers. The optically active allenylidene [Ru{ C C C(C9H16)}(η5-C9H7)(PPh3)2][PF6] (10) (C(C9H16) = (1R)-1,3,3-trimethylbicyclo[2.2.1]hept-2-ylidene) undergoes a selective exo addition of the cyclopentanone enolate to afford the σ-alkynyl diastereoisomers (11a,b). Demetalation of 11a and 11b, via their corresponding vinylidenes, allows the preparation of optically pure terminal alkynes (13a,b, respectively). The oxacycloalkenyl derivative (14) has been obtained by treatment of 11a or 11b with a catalytic amount of AlCl3. Protonation of 14 affords the corresponding cyclic carbene 15. The reactivity of allenylidene complexes 1, 2, and 10 toward lithium enolates derived from the optically active ketones (R)-(−)-carvone and (R)-(+)-pulegone has been also explored. For diphenylallenylidene 1 diastereoselective additions are observed, yielding the optically pure σ-alkynyl complexes 16 and 19, respectively. While attempts to demetalate 19 failed, demetalation of 16 yields the optically pure γ-keto alkyne HC CCPh2(C10H13O) (18) in excellent yield. The crystal structures of compounds 11b and 14 have been determined by X-ray diffraction.This work was supported by the Ministerio de Ciencia y Tecnología (MCyT) and the Dirección General de Investigación Científica y Técnica (DGICyT) of Spain (Projects BQU2000-0227 and PB98-1593).Peer reviewe