三元配合物RE(Et_2dtc)_3(phen)热化学性质的规律性

Regularity of Thermochemical Properties of Ternary Complexes RE(Et_2dtc)_3(phen)

在无水乙醇中,用铜试剂(NaEt2dtc?3H2O)和邻菲咯啉(o-phen?H2O)分别与13种低水合氯化稀土合成了三元固态配合物(其中5种尚未见文献报道),确定它们的组成可用通式RE(Et2dtc)3(phen)表示.IR光谱表明配合物中RE3+与3个NaEt2dtc中的6个硫原子双齿配位,同时与o-phen中的2个氮原子双齿配位.用RD496-Ⅲ微量热计测定了298.15K下13种水合氯化稀土盐及两个配体在无水乙醇中的溶解焓,两个配体醇溶液的混合焓及13种化合物液相生成反应的焓变,并通过合理的热化学循环,求得了标题配合物的固相生成反应焓变;测定了标题配合物298.15K的比热容.用RBC-II精密转动弹热量计测定了标题配合物的恒容燃烧热,计算了它们的标准摩尔燃烧焓和标准摩尔生成焓.发现系列配合物RE(Et2dtc)3(phen)(RE=La,Pr,Nd,Sm～Lu)的多项热化学性质,如低水合氯化稀土盐在无水乙醇中的溶解焓以及配合物的液相生成反应焓变和固相生成反应焓变、常温比热容、标准摩尔燃烧焓和标准摩尔生成焓都与稀土原子序数作图呈现“三分组现象”.较集中地反映出配合物中RE3+与配体间的化学键有一定程度的共价性,这是由于稀土离子5s25p6轨道对4f电子的不完全屏蔽引起的.

Treatment of chloride rare earth （RE=La, Pr, Nd, Sm-Lu） hydrate with sodium diethyldithiocarbamate （NaEt2dtc） and 1,10-phenanthroline （phen） gave rise to thirteen complexes with an empirical formula RE（Et2dtc）3（phen）. IR spectra of the resulting complexes showed that two sulfur atoms in NaEt2dtc and two nitrogen atoms in phen coordinate to RE in bidentate fashion, respectively. The enthalpies of solution of rare-earth chloride hydrate, NaEt2dtc and phen in ethanol were measured by an RD-496 ELI microcalorimeter at 298.15 K, together with the mixing enthalpy of ethanol solution of NaEt2dtc and phen and the enthalpies of reaction of formation of the title complexes in ethanol. The enthalpies of reaction of formation of the title complexes in solid were available through a rationally thermochemical cycle. Using the same microcalorimeter, a model was developed for calculating the special heat capacity and the corresponding special heat capacities of the complexes at 298.15 K were determined. The constant-volume energies of combustion of the complexes were measured by an RBC-Ⅱ rotating-bomb calorimeter, and the standard molar enthalpies of combustion and the standard molar enthalpies of formation were calculated. The thermochemical properties, including the enthalpies of solution of chloride rare earth hydrate in ethanol, the enthalpies of reaction of formation of the title complexes in ethanol or in solid, the special heat capacities at room temperature, the standard molar enthalpies of combustion and the standard molar enthalpies of formation for this series of complexes versus the atomic numbers of rare earth, presented triplet effect, which is representative of certain covalent bond between RE and the ligands and the result of 4f electron to be not shielded fully by 5s5p.