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首页> 外文期刊>Thermochimica Acta: An International Journal Concerned with the Broader Aspects of Thermochemistry and Its Applications to Chemical Problems >THERMODYNAMIC STABILITY AND OPTIMIZED STRUCTURES OF HYPERVALENT MOLECULES M2CN (M = LI, NA, K)
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THERMODYNAMIC STABILITY AND OPTIMIZED STRUCTURES OF HYPERVALENT MOLECULES M2CN (M = LI, NA, K)

机译：超价分子M2CN（M = LI，NA，K）的热力学稳定性和优化结构

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The hypervalent M2CN (M = Li, Na, K) molecules have been detected in the vapor at elevated temperatures over mixtures of alkali metals and sodium cyanide by means of Knudsen-effusion mass spectrometry. The experimentally obtained ionization energies were IP (Li2CN+) = 5.4 +/- 0.2 eV, IP(Na2CN+) = 4.9 +/- 0.2 eV and IP (K2CN+) = 4.0 +/- 0.2 eV, agreeing well with the theoretical values 5.13, 4.66 and 3.7 eV, respectively, calculated for the vertical ionization. The energies of dissociation into MCN and M were D-0 degrees(LiNC-Li) = 137 +/- 14 kJ/mol, D-0 degrees(NaCN-Na) = 104 +/- 14 kJ/mol, and D-0 degrees(KCN-K) = 81 +/- 8 kJ/mol. Although the theoretically calculated values were slightly lower (103.8 kJ/mol for Li2CN, 72.8 kJ/mol for Na2CN, and 74.5 kJ/mol for K2CN), the dissociation energies indicate moderately strong bonding of alkali metals to the alkali cyanides (MCN) of octet molecules. The agreement between experiment and theory confirms the existence of the M2CN species, which are the hypervalent molecules with more than one electronegative atom. The theoretically optimized structures of M2CN are quite similar to each other, with four isomers (two planar structures with C-s symmetry and two linear structure with C-infinity v symmetry), although there are differences in bond length. The favored structure of M2CN has C-s symmetry and is best described as a complex of the CN- anion with the M-2(+) cation. [References: 48]
机译：利用克努德森-扩散质谱法，在碱金属和氰化钠的混合物中，在升高的温度下在蒸气中检测到了高价的M2CN（M = Li，Na，K）分子。实验获得的电离能为IP（Li2CN +）= 5.4 +/- 0.2 eV，IP（Na2CN +）= 4.9 +/- 0.2 eV和IP（K2CN +）= 4.0 +/- 0.2 eV，与理论值5.13吻合得很好，垂直电离分别计算为4.66和3.7 eV。分解成MCN和M的能量为D-0度（LiNC-Li）= 137 +/- 14 kJ / mol，D-0度（NaCN-Na）= 104 +/- 14 kJ / mol和D- 0度（KCN-K）= 81 +/- 8 kJ / mol。尽管理论计算值略低（Li2CN为103.8 kJ / mol，Na2CN为72.8 kJ / mol，K2CN为74.5 kJ / mol），但解离能表明碱金属与碱金属氰化物（MCN）具有中等强度的键合八位字节分子。实验和理论之间的一致性证实了M2CN物种的存在，M2CN物种是具有多个负电性原子的超价分子。 M2CN的理论优化结构彼此非常相似，具有四个异构体（两个具有C-s对称性的平面结构和两个具有C-无穷大v对称性的线性结构），尽管键长有所不同。 M2CN的偏爱结构具有C-s对称性，最好被描述为CN-阴离子与M-2（+）阳离子的络合物。 [参考：48]

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