CEQUINOR (UNLP-CONICET), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 esq. 115, 1900 La Plata, República Argentina.
Inorg Chem. 2010 Dec 6;49(23):11142-57. doi: 10.1021/ic101741e. Epub 2010 Nov 8.
Fluorocarbonyl thio- and isothiocyanate, FC(O)SCN and FC(O)NCS, were fully characterized by IR (gas, Ar and N(2) matrixes), Raman (liquid and solid), UV (gas), and (13)C NMR (liquid) spectroscopy, as well as single-crystal X-ray diffraction. Their vibrational and conformational properties were analyzed using matrix isolation techniques guided by quantum chemical calculation at the ab initio [MP2 and CCSD(T)], density functional theory B3LYP, and CBS-QB3 levels of theory. A complete assignment of the fundamental modes of FC(O)SCN was performed. In both the gas and liquid states, FC(O)SCN and FC(O)NCS were found to exist as two conformers (C(s) symmetry), in which the carbonyl double bond (C═O) adopts a synperiplanar (syn) and an antiperiplanar (anti) orientation with respect to either the SCN or NCS group. For FC(O)SCN, the conformational enthalpy difference, ΔH° = H°(anti) - H°(syn), was determined by matrix IR experiments to be 0.9 ± 0.2 kcal mol(-1). The conformational equilibria were evaluated by fast-cooling gaseous samples highly diluted in argon at different temperatures as cryogenic matrixes. The conformational properties of both molecules were analyzed in terms of the hyperconjugative electronic effect applying the natural bond orbital method. The kinetics of the thermal conversion of the high-energy anti into the syn FC(O)NCS conformer was studied in Ar and N(2) matrixes at cryogenic temperatures. The reversed syn → anti photoisomerization was observed using UV-vis light. Rearrangement of FC(O)SCN into FC(O)NCS was observed in the neat liquid and in solution. Under 193 nm (ArF excimer laser) irradiation, FC(O)NCS isolated in cryogenic Ar matrixes forms FC(O)SCN. At low temperature, single crystals of the two constitutional isomers were obtained using a miniature zone melting procedure. According to X-ray diffraction, they exclusively crystallize in their syn forms (C(s) symmetry) in the orthorhombic crystal system.
氟羰基硫代和异硫氰酸酯，FC(O)SCN 和 FC(O)NCS，通过红外（气体、Ar 和 N2 基质）、拉曼（液体和固体）、紫外（气体）和（13）C NMR（液体）光谱以及单晶 X 射线衍射进行了全面表征。使用基质隔离技术，结合从头算[MP2 和 CCSD(T)]、密度泛函理论 B3LYP 和 CBS-QB3 理论的量子化学计算，分析了它们的振动和构象特性。对 FC(O)SCN 的基本模式进行了完整的分配。在气体和液体状态下，FC(O)SCN 和 FC(O)NCS 被发现存在两种构象（C(s)对称性），其中羰基双键（C=O）相对于 SCN 或 NCS 基团呈顺式（syn）和反式（anti）取向。对于 FC(O)SCN，通过基质红外实验确定构象焓差 ΔH°= H°(anti) - H°(syn) 为 0.9 ± 0.2 kcal mol(-1)。通过快速冷却在不同温度下以氩气高度稀释的气态样品作为低温基质，评估了构象平衡。通过自然键轨道方法应用超共轭电子效应分析了两种分子的构象性质。在低温下的 Ar 和 N2 基质中研究了高能反式向顺式 FC(O)NCS 构象的热转换动力学。用紫外-可见光观察到顺式→反式光致异构化。在纯液体和溶液中观察到 FC(O)SCN 向 FC(O)NCS 的重排。在 193nm（ArF 准分子激光）照射下，低温下在 Ar 基质中分离的 FC(O)NCS 形成 FC(O)SCN。在低温下，使用微型区域熔化程序获得了两种结构异构体的单晶。根据 X 射线衍射，它们仅在正交晶系的 C(s)对称中结晶为顺式形式。
