Transmetalation of Chromocene by Lithium-Amide, -Phosphide, and -Arsenide Nucleophiles
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- 作者：Sabine Scheuermayer ; Floriana Tuna ; Eufemio Moreno Pineda ; Michael Bodensteiner ; Manfred Scheer ; Richard A. Layfield
- 刊名：Inorganic Chemistry
- 出版年：2013
- 出版时间：April 1, 2013
- 年：2013
- 卷：52
- 期：7
- 页码：3878-3883
- 全文大小：264K
- 年卷期：v.52,no.7(April 1, 2013)
- ISSN：1520-510X
文摘
The pnictogen-centered nucleophiles LiE(SiMe3)2 (E = N, P, or As) substitute a cyclopentadienide ligand of chromocene (Cp2Cr), with elimination of lithium cyclopentadienide, to give the series of pnictogen-bridged compounds [(渭:畏2:畏5-Cp)Cr{渭-N(SiMe3)2}2Li] (1) and [(畏5-Cp)Cr{渭-E(SiMe3)2}]2, with E = P (2) or E = As (3). Whereas 1 is a heterobimetallic coordination polymer, 2 and 3 are homometallic dimers, with the differences being due to a structure-directing influence of the hard or soft character of the bridging group 15 atoms. For compound 1, the experimental magnetic susceptibility data were accurately reproduced by a single-ion model based on high-spin chromium(II) (S = 2), which gave a g-value of 1.93 and an axial zero-field splitting parameter of D = 鈭?.83 cm鈥?. Determinations of phosphorus- and arsenic-mediated magnetic exchange coupling constants, J, are rare: in the dimers 2 and 3, variable-temperature magnetic susceptibility measurements identified strong antiferromagnetic exchange between the chromium(II) centers, which was modeled using the spin Hamiltonian H = 鈭?J(SCrA路SCrB), and produced large coupling constants of J = 鈭?66 cm鈥? for 2 and 鈭?7.5 cm鈥? for 3.