Greek Bureaucracy and Public Administration

Requirements for Lewis Acid-Mediated Capture and N–N Bond Cleavage of Hydrazine at Iron

“…To probe the requirement of N 2 H 4 capture by boron Lewis acids independent of the metal center, we sought to design a system that was coordinatively saturated at iron with substitutionally inert ligands. The 2,6-bis(carbene)pyridine system [34][35][36][37][38][39] presents a robust ligand template with a similar bite-angle and steric profile to the previously studied pyridine(dipyrazole) species. Installment of 9-borabicyclo [3.3.1]nonyl (9-BBN) and 4,4,5,5tetramethyl-1,2,2-dioxoboryl (BPin) Lewis acids on the 2,6-bis(imidazol-1-yl)pyridine (CNC) framework was achieved by two methods: 1) hydroboration of the previously reported 2,6-bis(N-allyl-imidazolium)pyridine, 40 Figure 2).…”

“…The carbonyl ligands of complexes 2 are more activated than those in other dicarbonyl Fe(0) pincer compounds including ( iPr PDI)Fe(CO) 2 (1974, 1914 cm −1 ) ( iPr PDI = 2,6-((DIPP)N=CMe) 2 -C 5 H 3 N; DIPP = 2,6-diisopropylphenyl), 46 ( Ph PDP OSiMe3 )Fe(CO) 2 (1935, 1868 cm −1 ), 31 and, notably, ( DIPP CNC)Fe(CO) 2 (1928, 1865 cm −1 ). 38 Single crystal X-ray diffraction studies on 2-allyl confirmed a five-coordinate (τ 5 = 0.52) iron dicarbonyl complex with the allylic substituents intact ( Figure 2). Following reduction, the Fe-C carbene distances contract to 1.9194(15) Å and the Fe-C carbonyl distances (1.7457(15) Å) are identical to ( DIPP CNC)Fe(CO) 2 (1.746 3and 1.767(4) Å).…”

“…Whereas examples of redox chemistry with the pyridine(dipyrazole) framework are rare, 31 pyridine(dicarbene) ligands are capable of stabilizing metal centers in multiple oxidation states. 32,33 Herein, we describe the development of a highly modular pyridine(dicarbene) ligand platform with appended boron Lewis acids, the requirements of N 2 H 4 capture, and consequence of a substitutionally inert primary coordination sphere on N-N bond cleavage.…”

Enabling Two-Electron Pathways with Iron and Cobalt: From Ligand Design to Catalytic Applications

“…54 Contemporary with our report of the synthesis of ( iPr PDI)Fe(N 2 ) n (n = 1,2), 35a Danopoulos and coworkers described the synthesis and structural characterization of a related complex, ( iPr CNC)Fe(N 2 ) 2 ( iPr CNC = 2,6-bis[(2,6-diisopropylphenyl)imidazol-2-ylidene]pyridine) where the imine donors were replaced by N-heterocyclic carbenes. 55 Subsequent experimental and computational studies 56,57 established that the iPr CNC ligand was acting as a classic π-acceptor, with no evidence for ligand-centered radicals and, therefore, the iron was best described as a hybrid between low-spin Fe(0) and Fe(II). Such an electronic structure description is expected from an 18-electron, coordinatively saturated bis-dinitrogen compound as ligand-redox activity and, hence, radical character, are more common with four-coordinate compounds.…”

Design and synthesis of cyclometallated sulphur-n-heterocyclic carbene complexes and their application in catalysis

“…22 The ease in preparation of functionalized NHC ligands by combining NHC moieties with wide range of classical donors such as P, N, O & S provides a gate way for construction of new chiral/achiral polydentate ligand with novel coordination chemistry. The NHC ligands functionalized with phosphine, 23 pyridine, 24 oxazoline, 25 amido, 26 ether 27 and their application in metal catalyzed reaction are reported in the literature. NHC functionalized with phosphines, pyridine, oxazoline and sulphur followed by its major applications in homogenous catalysis will be discussed briefly.…”