Abstract

Crystal structure, thermal stability, and the process of scandium tris-methylcyclopentadienyl Sc(MeCp)₃ evaporation are studied. It is shown by XRD that crystals of this compound with the C2/c space group and the following parameters at 150 K are formed from the gas phase and from the solution: a = 7.9568(4) Å, b = 13.7620(6) Å, c = 28.239(2) Å, β = 107.4860(10)°, V = 2949.3(3) Å³, Z = 8, D_calc = 1.217 g/cm³. The violation of the crystal packing order is manifested as diffuse scattering accompanied by single-crystal Bragg diffraction. The obtained data suggest that the complex has the Sc(η⁵-MeCp)₂(η¹-MeCp) structure with Sc–Z distances equal to 2.26-2.37 Å, where Z is the center of the η⁵-MeCp species or the C atom (for η¹-MeCp). The NMR data obtained for the Sc(MeCp)₃ samples, which were kept for 7 days at 423 K, 453 K, and 483 K, indicate that the substance undergoes noticeable decomposition only at the highest temperature. Temperature dependences of the saturated vapor pressure of the complex are measured independently by the flow method (transpiration) (392-469 K) and by the static method (441-514 K). As a result of joint processing of the tensimetry data, the following thermodynamic parameters of Sc(MeCp)₃ evaporation are determined: Δ_evH⁰(458.5) = 82.5±1.1 kJ/mol, Δ_evS⁰(458.5) = 135±2 J/(mol·K).

中文翻译：

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三(甲基环戊二烯基)钪的结构和热性能

摘要

研究了三甲基环戊二烯基钪Sc (MeCp) ₃的晶体结构、热稳定性和蒸发过程。XRD 表明，该化合物具有C 2/ c空间群，在 150 K 下由气相和溶液形成具有以下参数的晶体：a  = 7.9568(4) Å, b  = 13.7620(6) Å，c  = 28.239(2) Å，β = 107.4860(10)°，V  = 2949.3(3) Å ³，Z  = 8，D_计算值= 1.217 g/cm ³。晶体堆积顺序的破坏表现为伴随单晶布拉格衍射的漫散射。获得的数据表明该配合物具有 Sc(η ⁵ -MeCp) ₂ (η ¹ -MeCp) 结构，Sc- Z距离等于 2.26-2.37 Å，其中Z是 η ⁵ -MeCp 物质 的中心或C 原子（对于 η ¹ -MeCp）。在 423 K、453 K 和 483 K 下保存 7 天的Sc(MeCp) _{3样品获得的 NMR 数据表明，该物质仅在最高温度下才会发生明显的分解。}通过流动法（蒸腾作用）（392-469 K）和静态法（441-514 K）独立测量复合物饱和蒸气压的温度依赖性。通过对张力测量数据的联合处理，确定了以下Sc(MeCp) _{3蒸发的热力学参数： Δ ev} H ⁰ (458.5) = 82.5±1.1 kJ/mol， Δ _ev S ⁰ (458.5) = 135± 2J/(摩尔·K)。