Pyrimidine-hydrazone and phosphole architectures have been combined to create a new heteroditopic ligand capable of forming heterobimetallic Zn/Pd, Pb/Pd and Cu/Pd complexes in high yielding stepwise or one pot reactions. The catalytic activity of these complexes in Heck coupling and Miyaura borylation reactions was investigated.
1. Of the carcinogenic aromatic nitrogenous compounds investigated, 10 out of 11 were found to be biotransformed in rabbit liver microsomal preparations to nitroxide radicals, as detected by ESR spectroscopy; with non-carcinogenic nitrogenous compounds only 2 out of 8 formed nitroxide radicals. 2. The radicals are stable mixed nitroxides formed by covalent binding of the aromatic nitroxide to endogenous constituents of the microsomal membrane with preservation of the nitroxide radical group (spin-trapping). 3. From the high chemical stability and the observed ESR spectra, spin-label-like structures can be deduced. 4. From this and the known one-electron redox properties of spin-labels, a redox cycle catalysing the production of reactive oxygen species and involved in tumour initiation and/or promotion by aromatic nitrogenous compounds is proposed.
A facile two-step synthesis of bis(1-methylhydrazinyl)pyrimidine from pyridine-2-carbaldehyde and 2diphenylphosphanylbenzaldehyde gave access to the new asymmetric ligand 1. The phosphane selectively guides Pd II into the softer tridentate N,N,P pocket, yielding monometallic complex 2. A second reaction with a 3d transition metal complex precursor (groups 7 to 12) fills the vacant N,N,N pocket and thus provides a variety of heterobimetallic complexes of the type Pd II /M II (M = Mn (3), Fe (4), Co (5), Ni (6), Cu (7), Zn ( 8)). Single-crystal X-ray diffraction studies were performed for all complexes. The assembly of μ 2 -chlorido-bridged dimers was observed for complexes 5−7 in the solid state, while DOSY NMR experiments have shown that 5−7 are unbridged monomers in solution. As an exception, Fe II prefers to form the homoleptic meridional complex [Fe{PdCl(1)} 2 ](OTf) 4 (4). The electrochemical behavior and the effective magnetic moment in solution were investigated for all complexes by cyclic voltammetry and Evans method, respectively. Experimental UV/vis results were interpreted by performing TD-DFT calculations on 1, 2, and 3.
A series of heterobimetallic PdII/MII complexes (MII = Mn, Co) were synthesised and tested as precatalysts for sequential Sonogashira coupling–alkyne semi-hydrogenation reactions to form Z-aryl alkenes. The carbometalated heterobimetallic PdII/CoII...
The syntheses of the first B9-connected carboranylphosphines (B9-Phos) featuring two carboranyl moieties as well as access to B9-Phos ligands with bulky electron-donating substituents, previously deemed unattainable, is reported. The electrochemical properties of the B9-Phos ligands were investigated, revealing the ability of the mesityl derivatives to form stabilized phosphoniumyl radical cations. The B9-Phos ligands display an extremely electron-releasing character surpassing that of alkyl phosphines and commonly used Nheterocyclic carbenes. This is demonstrated by their very small Tolman electronic parameters (TEPs) as well as extremely low PÀ Se coupling constants. Cone angles and buried volumes attest to the high steric demand exerted by the (di)carboranyl phosphines. The dicarboranyl phosphine Au I complexes show superior catalytic performance in the hydroamination of alkynes compared to the monocarboranyl phosphine analogs.
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