ansa-Chromocenes: An alternative route to Me2Si(C5Me4)2Cr

Tuning steric and electronic effects in transition-metal β-diketiminate complexes

“…and neutral ligands (CO, PPh 3 , etc.) can be coordinated to a metal center with less sterically hindered β-diketiminate in LScCl 2 (THF) n (L tBu,iPr , 16 n=0; L Me,iPr , 47 n = 1) LSc(CH 3 ) 2 (THF) n (L tBu,iPr , 16 n=0; L Me,iPr , 16 n = 1), LSc(Cl)(NHAr)(THF) n L tBu,iPr , 48 n=0; L Me,iPr , 49 n = 1), [LSc(CH 3 )(arene) n ] + (L tBu,iPr , 50 n=0; L Me,iPr , 50 n = 1), LTiCl 2 (THF) n (L tBu,iPr , 51 L tBu,Me3 , 52 L Me,Tbt/Me3 , 53 n=0; L Me,iPr , 54 n=1; L Me,H , 55 n=2), LVCl 2 (THF) n (L Me,iPr , 52, 56 L Me,Et , 34 L Me,Me3 , 34 L Ph,iPr , 34 n=0; L Me, H , 55 n=2), [LCr(μ-Cl)(Solvent) n ] 2 (L tBu,iPr , 35 n=0; L Me,iPr , 36 L Me,Me , 37 n = 1; Solvent = THF, benzene), LFe(NHdipp)(THF) n (L tBu,iPr , 19 n=0; L Me,iPr , 28 n = 1), and LCu(PPh 3 ) n ( Ph L H,iPr , 57 L Me,Me , 58 L Me,iPr , 59 L Me,Me3 , 60 n=1; Ph L H,Me , 57 L CF3, m -CF3 , 61 n=2). Steric conflict between N -aryl substituents and metal can also push the metal center out of the β-diketiminate ligand plane in some metal complexes, especially for early transition metals (Table 3.1.2).…”

Direct Synthesis of Ligand-Based Radicals by the Addition of Bipyridine to Chromium(II) Compounds

“…The direct addition of bpy to chromocene at room temperature generates Cp 2 Cr(bpy) ( 3 ). Unlike its highly reactive heavier group 6 congeners, chromocene typically only forms weak bonds with neutral donor ligands because of the relative stability of the S = 1 state for Cp 2 Cr . The stability of 3 can be attributed to single electron transfer from Cr II to bpy to generate an inert chromium(III) complex antiferromagnetically coupled to a bpy radical anion while retaining the S = 1 state with μ eff = 2.92 μ B in solution (Evans, C 6 D 6 ).…”