A 2,2′-bipyridyl calcium complex: synthesis, structure and reactivity studies

Abstract

2,2’-bipyridyl calcium complex based on a tridentate ligand [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]Ca(bipy)(THF) (1) was prepared by reduction of {[CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]CaI(THF)}2 with potassium graphite in the presence of 2,2’-bipyridine (bipy). Complex 1 is a good...

Reduction of Ketones and Coupling of Ketyls by a Zn–Zn-Bonded Compound

“…Since the first isolation and structural characterization of a metal ketyl complex, i.e., the samarium complex [Sm­(biphenyl-2,2′-diylketyl)­(OAr) 2 (THF) 2 ] (Ar = 2,6- t Bu 2 -4-MeC 6 H 2 ), in 1995, a couple of lanthanide ketyls have been synthesized by the reaction of ketones (benzophenone, fluorenone, etc.) with lanthanide-reducing agents. − Moreover, some ketyl complexes of group 1 and 2 metals have also been reported. − Generally, the ketyl fragments of these complexes are either in the radical state or in the coupled pinacolate form, whereas complex 2 represents a unique example that contains both pinacolate units and ketyl radicals.…”

“…Thus, we speculate that the ketyl radical might also exist in the reaction mixture as either a zinc or potassium complex; unfortunately, no such species could be identified. Most of the previous examples of metal-promoted 9-fluorenone ketyl generation or pinacol coupling have focused on main group metals (Mg, Ca, , and Al) and lanthanides. , For example, the reaction of magnesium­(I) dimer [{( Mes Nacnac)­Mg} 2 ] ( Mes Nacnac = [HC­(MeCNMes) 2 ] − , Mes = mesityl) with 9-fluorenone produced magnesium fluorenone ketyl [{( Mes Nacnac)­Mg­(μ-9-fluorenone • )} 2 ]. In this complex, two ketyl groups bridge two Mg centers, and no C–C coupling occurred .…”

“…16 Thus, we speculate that the ketyl radical might also exist in the reaction mixture as either a zinc or potassium complex; unfortunately, no such species could be identified. Most of the previous examples of metal-promoted 9-fluorenone ketyl generation or pinacol coupling have focused on main group metals (Mg, 18 Ca, 6,9 and Al 22 ) and lanthanides. 14,15 .…”

“…In order to better understand their structure and reactivity, scientists have devoted great efforts to stabilize ketyl radicals, e.g., by metal coordination, during the past decades. A number of complexes of ketyl and its dimerized pinacolato ligand with either alkali − or alkaline earth − metals, transition metals, − and f-block elements − have been isolated and structurally characterized. These compounds are generally prepared by the one-electron reduction of ketones (or aldehydes) by reductants such as alkali metals and other active metals or low-valent metal complexes (e.g., lanthanides).…”