One-pot synthesis of Mo(0) dinitrogen complexes possessing monodentate and multidentate phosphine ligands.

Mo(0) dinitrogen complexes bearing electron-rich mono- and bidentate phosphines can be synthesized in good yields from inexpensive and readily accessible MoCl(5) via a one-step mild reduction with Mg metal. trans-[(N(2))(2)Mo(PMePh(2))(PPh(CH(2)CH(2)PPh(2))(2))] can also be obtained via this strategy. However, in the presence of tri- and tetradentate ligands that are sterically restrictive, the analogous reduction leads to either (η(6)-arene) formation or [Mo(multidentate phosphine)(m)](n) oligomer complexes that have no dinitrogen ligands.

Catalyst-site-controlled coordination polymerization of polar vinyl monomers to highly syndiotactic polymers.

This contribution reports a combined synthetic, kinetic, mechanistic, and theoretical/computational study of the recently discovered catalyst-site-controlled coordination polymerization of polar vinyl monomers [such as methyl methacrylate (MMA) and N,N-dimethylacrylamide (DMAA)] into highly syndiotactic polymers. Among the 12 C(s)-ligated ansa-cyclopentadienyl (Cp)-R(2)E(C,Si)-fluorenyl (Flu) group 4 metallocene catalyst systems examined-which varied in metal center, anion structure, bridging atom and substituents, and ligand substitution pattern-cationic ansa-metallocene ester enolate catalyst 6(+)[B(C(6)F(5))(4)](-), derived from the activation of the precatalyst [Ph(2)C(Cp)(2,7-(t)Bu(2)-Flu)]Zr[OC(O(i)Pr)=CMe(2)](2) with [Ph(3)C][B(C(6)F(5))(4)], stood out as the best catalyst in all aspects of the MMA polymerization at room temperature, including the highest activity (1554 h(-1) TOF), efficiency (98% I*), syndiotacticity (94% rr), and control (predicted number-average molecular weight and 1.14 molecular weight distribution).

[Electronic spectral study on salicylaldehyde-amino acid Schiff bases in water].

Seven salicylaldehyde-amino acid Schiff bases in water were investigated by means of electronic spectra, which is helpful to investigate the label of radionuclides with the seven ligands in water for radiopharmaceutical study. Except 10(-5) mol x L(-1) for Sal-tyr, the minimum concentration of formation is 10(-4) mol x L(-1) for all other Sal-aas. Only Sal-his is generated at pH 9-10, while the minimum pH conditions for formation are 8 for Sal-gly and Sal-tyr, and 9 for other four.