Citation: Wenke ZHENG, Ce LIU, Wei CHEN, Hongshan KE, Fanlong ZENG, Yibo LEI, Anyang LI, Wenyuan WANG. Synthesis and bonding analysis of low-coordinate Fe and Cr complexes with ultra-bulky silylamino groups[J]. Chinese Journal of Inorganic Chemistry, ;2025, 41(7): 1285-1293. doi: 10.11862/CJIC.20250095 shu

Synthesis and bonding analysis of low-coordinate Fe and Cr complexes with ultra-bulky silylamino groups

College of Chemistry and Materials Science, Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Northwest University, Xi′an 710127, China

Corresponding author: Anyang LI, liay@nwu.edu.cn Wenyuan WANG, wangwy@nwu.edu.cn
Received Date: 19 March 2025
Revised Date: 7 May 2025

Figures(7)

The ultra-bulky and stable monodentate amino groups can provide effective kinetic protection during the preparation of low-coordinate transition metal complexes, thereby preventing oligomerization. In this work, the ultra-bulky sodium hexa-isopropyl disilylamide (2) was synthesized for the first time by the reaction of silylamine and sodium amide, and the crystal structures of 2-THF and 2-Tol, which are complexes of 2 coordinated by tetrahydrofuran (THF) or toluene (Tol), respectively, were characterized. Then, the diamino iron [Fe(Ⅱ)(N(Si^ⅰPr₃)₂)₂] (3) and diamino dichloro-bis-chromium [Cr(Ⅱ)(N(SiⁱPr₃)₂)Cl]₂ (4) were synthesized through the salt metathesis reaction of 2 with the corresponding transition metal halides FeCl₂ and CrCl₂. Due to the steric hindrance of the ultra-bulky amino groups, complex 3 presents a nearly linear geometry, with the N—Fe—N bond angle of 178.10°. Complex 4 is a dimer of monoamino chromium(Ⅱ) chloride; the three-coordinate Cr(Ⅱ) ions form a {Cr₂Cl₂} rhombic core via two Cl-bridges. The improved iCAS method (imposed automatic selection and localization of complete active spaces) was used to calculate the molecular orbitals of 3 and 4 to logically describe the strongly correlated systems of electrons of the low-coordinate sphere of transition metals. The calculation shows that the bonding contribution of 3 mainly consists of the two Fe—N σ bonds, and the charge of Fe (+1.03) and N (-1.21) confirms a strong ionic coordination environment. The Fe—N π-bonding is not evident. The quintuplet high-spin Fe has one doubly occupied orbital and four singly occupied orbitals, originating from the 3d orbitals of Fe. The six fully occupied molecular orbitals of 4 correspond to two Cr—N σ bonds, two p-type lone pairs on Cl atoms, and two p-type lone pairs on N atoms. Two Cr atoms have eight high-energy d electrons, each in a singly occupied active orbital, and one of them exhibits Cr…Cr interaction.
- iron,
- chromium,
- ultra-bulky silylamino group,
- low-coordination
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