Details

Autor(en) / Beteiligte

• Boynton, Jessica N
• Merrill, W. Alexander
• Reiff, William M
• Fettinger, James C
• Power, Philip P

Titel

Two-Coordinate, Quasi-Two-Coordinate, and Distorted Three Coordinate, T-Shaped Chromium(II) Amido Complexes: Unusual Effects of Coordination Geometry on the Lowering of Ground State Magnetic Moments

Ist Teil von

• Inorganic chemistry, 2012-03, Vol.51 (5), p.3212-3219

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2012

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The synthesis and characterization of the mononuclear chromium­(II) terphenyl substituted primary amido-complexes Cr­{N­(H)­ArPri 6 }2 (ArPri 6 = C6H3-2,6-(C6H2-2,4,6- i Pr3)2 (1), Cr­{N­(H)­ArPri 4 }2 (ArPri 4 = C6H3-2,6-(C6H3-2,6- i Pr2)2 (2), Cr­{N­(H)­ArMe6 }2 (ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2 (4), and the Lewis base adduct Cr­{N­(H)­ArMe6 }2(THF) (3) are described. Reaction of the terphenyl primary amido lithium derivatives Li­{N­(H)­ArPri 6 } and Li­{N­(H)­ArPri 4 } with CrCl2(THF)2 in a 2:1 ratio afforded complexes 1 and 2, which are extremely rare examples of two coordinate chromium and the first stable chromium amides to have linear coordinated high-spin Cr2+. The reaction of the less crowded terphenyl primary amido lithium salt Li­{N­(H)­ArMe6 } with CrCl2(THF)2 gave the tetrahydrofuran (THF) complex 3, which has a distorted T-shaped metal coordination. Desolvation of 3 at about 70 °C gave 4 which has a formally two-coordinate chromous ion with a very strongly bent core geometry (N–Cr–N= 121.49(13)°) with secondary Cr--C­(aryl ring) interactions of 2.338(4) Å to the ligand. Magnetometry studies showed that the two linear chromium species 1 and 2 have ambient temperature magnetic moments of about 4.20 μB and 4.33 μB which are lower than the spin-only value of 4.90 μB typically observed for six coordinate Cr2+. The bent complex 4 has a similar room temperature magnetic moment of about 4.36 μB. These studies suggest that the two-coordinate chromium complexes have significant spin–orbit coupling effects which lead to moments lower than the spin only value of 4.90 μB because λ (the spin orbit coupling parameter) is positive. The three-coordinated complex 3 had a magnetic moment of 3.79 μB.