Theoretical Aspects of the Heterobimetallic Dimers with the T over Square Structural Motif. Synthesis and Structure of a Heteronuclear Platinum and Palladium Complex with 1-Methylcytosinato Bridging Ligands
Theoretical Aspects of the Heterobimetallic Dimers with the T over Square Structural Motif. Synthesis and Structure of a Heteronuclear Platinum and Palladium Complex with 1-Methylcytosinato Bridging Ligands
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具有 T over Square 结构基序的异双金属二聚体的理论方面。
DOI：
10.1021/ic00117a008
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发表时间：
1995
影响因子：
4.6
通讯作者：
B. Lippert
中科院分区：
文献类型：
--
作者：
C. Mealli;F. Pichierri;L. Randaccio;E. Zangrando;M. Krumm;Dagmar Holtenrich;B. Lippert
反式-[(NH&Pt@1-MeC-)2Pd(NH3)][Pd(NH3)4]0.5(N03)3-3H2O(1)的分子结构已通过X射线晶体学测定。该化合物结晶为三斜空间群P i (No. 2)，a = 7.476(2) A, b = 11.373(3) A, c = 16.397(4) A, a = 87.27(2)",,8 = 85.32(2)", y = 88.74(2)", Z = 2。结构精修为R = 0.034 且 R = 0.038 5045 个独立反射。该复合体最好通过 Pd 的方形平面配位和 Pt 的方形金字塔配位来描述，其中 Pd 位于顶端位置（T 超过方形几何形状，TSQ）。 Pt 和 Pd 原子由两个几乎共面的 1-甲基胞嘧啶阴离子桥接，Pt-Pd 距离为 2.511(1) A。基于 EHMO 计算的理论分析， 强调了这种类型的 d8-d8 二聚体 (4:3) 中单个 M-M' 键的性质，并指出了与以两个平行方形平面配位几何为特征的更广为人知的 ds-ds 二聚体 (4:4) 的相关性。后者的 M-M' 键序接近于零，但不为零。最后，向上述 TSQ 物质添加一个或两个电子的 M-M' 连接的命运正式为 分析了。与具有 ds-d9 和 ds-dIo 电子计数的二聚体可用的结构数据建立相关性 [例如具有桥接核碱基的 Pt(I1)-Cu(1I) 和 Pt(I1)-Hg(I1) 物种]。虽然一个额外的电子削弱了 M-M' 连接而不破坏主要的 TSQ 几何结构，但两个额外的电子迫使以前的配体被驱逐 与金属同轴（4:2 加合物）。 4:2 加合物中的 M-M' 相互作用与 4:4 物质中的 M-M' 相互作用相当。
The molecular structure of trans-[(NH&Pt@l-MeC-)2Pd(NH3)] [Pd(NH3)4]0.5(N03)3-3H20 (1) has been determined by X-ray crystallography. The compound crystallizes in the triclinic space group P i (No. 2), with a = 7.476(2) A, b = 11.373(3) A, c = 16.397(4) A, a = 87.27(2)", ,8 = 85.32(2)", y = 88.74(2)", and Z = 2. The structure was refined to R = 0.034 and R, = 0.038 for 5045 independent reflections. The complex is best described by a square planar coordination of Pd and a square pyramidal one of Pt with the Pd in the apical position (T over square geometry, TSQ). The Pt and Pd atoms are bridged by two nearly coplanar 1-methylcytosinate anions with a Pt-Pd distance of 2.511(1) A. A theoretical analysis, based on EHMO calculations, highlights the nature of the single M-M' bond in d8-d8 dimers of this type (4:3) and points out the correlations with the better known ds-ds dimers (4:4) characterized by two parallel square planar coordination geometries. The M-M' bond order in the latter is close to zero, but not null. Finally, the fate of the M-M' linkage for adding one or two electrons to the above TSQ species is formally analyzed. A correlation is made with the structural data available for dimers with ds-d9 and ds-dIo electron counts [e.g. Pt(I1)-Cu(1I) and Pt(I1)-Hg(I1) species with bridging nucleobases]. While one additional electron weakens the M-M' linkage without destroying the primary TSQ geometry, two extra electrons force the expulsion of the ligand formerly coaxial with the metals (4:2 adducts). The M-M' interaction in the 4:2 adducts is comparable with that proposed for the 4:4 species.