No abstract

An overview over the binding situation in transition metal and lanthanide aminopyridinato complexes is given. True aminopyridinato complexes in which we observe a significant longer N‐amido than N‐pyridine bond length are rare and for instance observed for ruthenium. Additional examples of ruthenium aminopyridinato complexes were synthesized and characterized by X‐ray crystal structure analysis.

(4-Methyl-pyridin-2-yl)(trimethylsilanyl)amine (ApSi-H) and tert-butyl(4-methyl-pyridin-2-yl)amine (AptBu-H) were synthesized via salt metathesis and aryl amination reactions, respectively. Lithiation of these two aminopyridines using n-BuLi and the reactions with [(dme)NiCl2] (dme = dimethoxyethane) or [(cod)PdCl2] (cod = cyclooctadiene) in THF at low temperature gave rise--after workup in hexane--to group 10 amido compounds, [(ApSi)4Ni2], [(AptBu)2Pd], [(AptBu-H)(AptBu)2Ni], [(AptBu)3(C2H5O)3Ni3OLi(thf)], and [(AptBu)2Ni(tBupy)2] (tBupy = 4-tert-butylpyridine). The aminopyridinato complexes were characterized by X-ray crystal structure analysis. The highly strained binding situation of the aminopyridinato ligands suggested that these compounds might be efficiently converted into catalytically active species. The applications of some of the synthesized complexes as Suzuki cross-coupling catalysts (activation of aryl chlorides) are described and [(ApSi)4Ni2] is a rare example of a "phosphine-free" catalyst system. A number of late transition metal complexes were found to successfully catalyze polymerization of MeH2SiSiH2Me toward soluble, linear poly(methylsilane). Remarkable activity was observed for [(ApSi)2Pd].

Silsesquioxanes are formed in situ during mixing and curing of a phenolic resin and a molecular silane precursor (3-(triethoxysilyl)-1-propaneamine) yielding a nanocomposite. As indicated by a higher onset temperature, a higher characteristic decomposition temperature, and a lower maximum heat flow, the thermal stability of the nanocomposite is significantly improved over the pristine resin. Moreover, the bending strength and the strain at break could also be enhanced by 36% and 51%, respectively. The nanocomposite was characterized by 29 Si solidstate NMR, STEM/EDS, TGA, DSC, and three point bending tests. The STEM/EDS measurements showed a homogenous distribution of silsesquioxanes in the phenolic resin.

Stoichiometric-deficient lithiation of (2,6-diisopropylphenyl)(4-methylpyridin-2-yl)amine and reaction with [(cod)PdCl2] (cod = 1,5-cyclooctadiene) yield a dimeric Pd complex. X-ray structural analysis of this complex reveals a very short Pd-Pd distance (2.429 A). Topological analysis of the electron density and the electron localization function from scalar relativistic density functional theory calculations clearly indicate a Pd(I)-Pd(I) sigma-bonding interaction, for which the corresponding occupied localized orbital can be identified.