Electron paramagnetic resonance of tetrakis(1-norbonyl) vanadium and cobalt

Effect of Electron Donors on the Radical Polymerization of Vinyl Acetate Mediated by [Co(acac)2]: Degenerative Transfer versus Reversible Homolytic Cleavage of an Organocobalt(III) Complex

“…It should be mentioned that at least one sufficiently stable alkylcobalt(IV) complex for isolation and characterization, [Co(norbornyl) 4 ], is known, though its stability may be attributed to the severe steric encumbrance of the ligand coordination sphere. [51,52] For the present system, an aliquot of the reaction mixture did not reveal any EPR signal after quenching to liquid nitrogen temperature. Thus, it seems that the diA C H T U N G T R E N N U N G alkyl Co IV species is either a transition state or an intermediate with too short a lifetime for measurement by this techA C H T U N G T R E N N U N G nique.…”

Some highlights from the development and use of bulky monodentate ligands

“…Other ligands of a similar type, lacking b-hydrogens such as -CH 2 Bu t (neopentyl), -CH 2 CMe 2 Ph (neophyl), -CH 2 Ph (benzyl) were also explored [18,120]. In addition, ''bridgehead'' ligands such as 1-norbornyl [125] or 1-adamantyl [126], which contain b-hydrogens, but do not readily undergo elimination (mainly for reasons of geometrical strain at an unsaturated bridgehead carbon of the decomposition product), also afforded generally very stable four coordinate complexes [127]. These involved an expanded variety of transition metals in both common and unusual oxidation states.…”

“…These involved an expanded variety of transition metals in both common and unusual oxidation states. Thus, in addition to TiR 4 , VR 4 and CrR 4 complexes (R = 1-norbornyl), MnR 4 , FeR 4 , CoR 4 species could also be stabilized [127].…”

The synthesis and X-ray crystal structures of homoleptic tetrahedral aryls of osmium(IV) and of cyclohexyls of ruthenium(IV), osmium(IV), and chromium(IV)

“…C(13') 3.47(3) A. The methyl carbons are also in close contact with the metal atom CC (7,14) 0 s 3.35(1), 3.36( 1) 813, but since the hydrogen atoms seem to be disordered (see Experimental section); there are no indications of any 0 s ... H bonding interactions.…”

“…The 'tetrahedral' geometry for the OsC, unit is somewhat flattened and this may be ascribed to the steric repulsions between the three methyl groups and the methylated ring carbons on the phenyl rings across the two-fold axes, i.e. C (7) C(6') 3.45 (2) and C (14) .…”