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
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- 作者：Jessica N. Boynton ; W. Alexander Merrill ; William M. Reiff ; James C. Fettinger ; Philip P. Power
- 刊名：Inorganic Chemistry
- 出版年：2012
- 出版时间：March 5, 2012
- 年：2012
- 卷：51
- 期：5
- 页码：3212-3219
- 全文大小：327K
- 年卷期：v.51,no.5(March 5, 2012)
- ISSN：1520-510X
文摘
The synthesis and characterization of the mononuclear chromium(II) terphenyl substituted primary amido-complexes Cr{N(H)ArPri6}2 (ArPri6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2 (1), Cr{N(H)ArPri4}2 (ArPri4 = C6H3-2,6-(C6H3-2,6-iPr2)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)ArPri6} and Li{N(H)ArPri4} 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 掳C gave 4 which has a formally two-coordinate chromous ion with a very strongly bent core geometry (N鈥揅r鈥揘= 121.49(13)掳) with secondary Cr--C(aryl ring) interactions of 2.338(4) 脜 to the ligand. Magnetometry studies showed that the two linear chromium species 1 and 2 have ambient temperature magnetic moments of about 4.20 渭B and 4.33 渭B which are lower than the spin-only value of 4.90 渭B typically observed for six coordinate Cr2+. The bent complex 4 has a similar room temperature magnetic moment of about 4.36 渭B. These studies suggest that the two-coordinate chromium complexes have significant spin鈥搊rbit coupling effects which lead to moments lower than the spin only value of 4.90 渭B because 位 (the spin orbit coupling parameter) is positive. The three-coordinated complex 3 had a magnetic moment of 3.79 渭B.