Synthesis, Structure, and Supramolecular Architecture of Benzonitrile and Pyridine Adducts of Bis(pentafluorophenyl)zinc: Pentafluorophenyl–Aryl Interactions versus Homoaromatic Pairing

Insights into the mechanism for ring-opening polymerization of lactide catalyzed by Zn(C6F5)2/organic superbase Lewis pairs

A plausible mechanism for ring-opening polymerization of lactide catalyzed by Zn(C₆F₅)₂-based Lewis pairs was proposed based on in situ NMR and MALDI-TOF MS analyses. Several experimental results show very good consistency with the proposed mechanism.

Gold(I) complexes with alkylated PTA (1,3,5-triaza-7-phosphaadamantane) phosphanes as anticancer metallodrugs

New stable thiolate gold(I) derivatives containing the alkylated phosphanes [PTA-CH2Ph]Br and [PTA-CH2COOMe]Br derived from 1,3,5-triaza-7-phosphaadamantane (PTA) have been prepared by different routes of synthesis. By the use of basic media to deprotonate the corresponding thiol in the former and by transmetallation reactions from tin (IV) complexes, in the later, thus avoiding side reactions on the phosphane. Strong antiproliferative effects are observed for most of the compounds, including the chloro- and bromo precursors with the series of phosphanes derived from PTA, in human colon cancer cell lines (Caco-2, PD7 and TC7 clones). Apoptosis-induced cell death is found for all compounds, being the thiolate derivatives with [PTA-CH2Ph]Br the most effective, as shown by an annexin-V/propidium iodide double-staining assay.

Synthesis and structure of amido- and imido(pentafluorophenyl)borane zirconocene and hafnocene complexes: N-H and B-H activation

Treatment of Me(2)S·B(C(6)F(5))(n) H(3-n) (n=1 or 2) with ammonia yields the corresponding adducts. H(3)N·B(C(6)F(5))H(2) dimerises in the solid state through N-H···H-B dihydrogen interactions. The adducts can be deprotonated to give lithium amidoboranes Li[NH(2)B(C(6)F(5))(n)H(3-n)]. Reaction of the n=2 reagent with [Cp(2)ZrCl(2)] leads to disubstitution, but [Cp(2)Zr{NH(2)B(C(6)F(5))(2)H}(2)] is in equilibrium with the product of β-hydride elimination [Cp(2)Zr(H){NH(2)B(C(6)F(5))(2)H}], which proves to be the major isolated solid. The analogous reaction with [Cp(2)HfCl(2)] gives a mixture of [Cp(2)Hf{NH(2)B(C(6)F(5))(2)H}(2)] and the N-H activation product [Cp(2)Hf{NHB(C(6)F(5 )(2)H}]. [Cp(2)Zr{NH(2)B(C(6)F(5))(2)H}(2)]·PhMe and [Cp(2)Hf{NH(2)B(C(6)F(5))(2)H}(2)]·4(thf) exhibit β-B-agostic chelate bonding of one of the two amidoborane ligands in the solid state. The agostic hydride is invariably coordinated to the outside of the metallocene wedge. Exceptionally, [Cp(2)Hf{NH(2)B(C(6)F(5))(2)H}(2)]⋅PhMe has a structure in which the two amidoborane ligands adopt an intermediate coordination mode, in which neither is definitively agostic. [Cp(2)Hf{NHB(C(6)F(5))(2)H}] has a formally dianionic imidoborane ligand chelating through an agostic interaction, but the bond-length distribution suggests a contribution from a zwitterionic amidoborane resonance structure. Treatment of the zwitterions [Cp(2)MMe(μ-Me)B(C(6)F(5))(3)] (M=Zr, Hf) with Li[NH(2)B(C(6)F(5))(n)H(3-n)] (n=2) results in [Cp(2) MMe{NH(2)B(C(6)F(5))(2)H}] complexes, for which the spectroscopic data, particularly (1)J(B,H), again suggest β-B-agostic interactions. The reactions proceed similarly for the structurally encumbered [Cp''(2)ZrMe(μ-Me)B(C(6)F(5))(3)] precursor (Cp''=1,3-C(5)H(3)(SiMe(3))(2) , n=1 or 2) to give [Cp''(2)ZrMe{NH(2)B(C(6)F(5))(n)H(3-n)}], both of which have been structurally characterised and show chelating, agostic amidoborane coordination. In contrast, the analogous hafnium chemistry leads to the recovery of [Cp''(2)HfMe(2)] and the formation of Li[HB(C(6)F(5))(3)] through hydride abstraction.