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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Displacement of ethene from the decamethyltitanocene-ethene complex with internal alkynes, substituent-dependent alkyne-to- allene rearrangement, and the electronic transition relevant to the back-bonding interaction
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Displacement of ethene from the decamethyltitanocene-ethene complex with internal alkynes, substituent-dependent alkyne-to- allene rearrangement, and the electronic transition relevant to the back-bonding interaction

机译：十甲基噻吨-乙烯配合物中带有内部炔烃的乙烯置换，依赖于取代基的炔烃至丙二烯的重排以及与背键相互作用相关的电子跃迁

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The titanocene-ethene complex [Ti((II))(eta(2)-C2H4)(eta(5)-C5Me5)(2)] (1) with simple internal alkynes (RC)-C-1 equivalent to CR2 gives complexes [Ti(II)(eta(2)-(RC)-C-1 equivalent to CR2)(eta(5)-C5Me5)(2)] {R-1, R-2: Ph, Ph (3), Ph, Me (4), Me, SiMe3 (5), Ph, SiMe3 (6), t-Bu, SiMe3 (7), and SiMe3, SiMe3 (8). In contrast, alkynes with R-1 = Me and R-2 = t-Bu or i-Pr afford allene complexes [Ti(II)(eta(2)-CH2=C=CHR2)(eta(5)-C5Me5)(2)] (11) and (12), whereas for R-2 = Et a mixture of alkyne complex (13A) and minor allene (13) is obtained. Crystal structures of 4, 6, 7 and 11 have been determined; the latter structure proved the back-bonding interaction of the allene terminal double bond. Only the synthesis of 8 from 1 was inefficient because the equilibrium constant for the reaction [1] + [Me3SiC equivalent to CSiMe3] reversible arrow [8] + [C2H4] approached 1. Compound 9 (R-1, R-2: Me), not obtainable from 1, together with compounds 3-6 and 10 (R1, R2: Et) were also prepared by alkyne exchange with 8, however this reaction did not take place in attempts to obtain 7. Compounds 1 and 3-9 display the longest-wavelength electronic absorption band in the range 670-940 nm due to the HOMO -> LUMO transition. The assignment of the first excitation to be of predominantly a b(2) double right arrow a(1) transition was confirmed by DFT calculations. The calculated first excitation energies for 3-9 followed the order of hypsochromic shifts of the absorption band relative to 8 that were induced by acetylene substituents: Me > Ph SiMe3. Computational results have also affirmed the back-bonding nature in the alkyne-to-metal coordination.
机译：钛碳烯-乙烯络合物[Ti（（II））（eta（2）-C2H4）（eta（5）-C5Me5）（2）]（1）具有与CR2等效的简单内部炔烃（RC）-C-1络合物[Ti（II）（eta（2）-（RC）-C-1等同于CR2）（eta（5）-C5Me5）（2）] {R-1，R-2：Ph，Ph（3） ，Ph，Me（4），Me，SiMe3（5），Ph，SiMe3（6），t-Bu，SiMe3（7）和SiMe3，SiMe3（8）。相反，具有R-1 = Me和R-2 = t-Bu或i-Pr的炔烃提供丙二烯配合物[Ti（II）（eta（2）-CH2 = C = CHR2）（eta（5）-C5Me5） （2）]（11）和（12），而对于R-2 ＝ Et，获得炔配合物（13A）和次要丙二烯（13）的混合物。已经确定了4、6、7和11的晶体结构。后一种结构证明了丙二烯末端双键的后键相互作用。仅从1合成8是无效的，因为反应[1] + [相当于CSiMe3的Me3SiC]可逆箭头[8] + [C2H4]的平衡常数接近1。化合物9（R-1，R-2：Me ），也无法通过与炔烃8进行炔交换制得1与化合物3-6和10（R1，R2：Et）一起制得，但是该反应并未试图获得7。化合物1和3-9由于HOMO-> LUMO跃迁，显示670-940 nm范围内的最长波长电子吸收带。通过DFT计算确认了第一激励主要为b（2）双向右箭头a（1）过渡的分配。计算出的3-9的第一激发能遵循由乙炔取代基引起的吸收带相对于8的变色移的顺序：Me> Ph SiMe3。计算结果也证实了炔烃与金属配位中的背键性质。

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