International Research Center for Elements Science (IRCELS), Institute for Chemical Research & IRCCS, Kyoto University, Uji, Kyoto 611-0011, Japan.
Present Address: Interdisciplinary Research Center for Catalytic Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, 305-8565, Japan.
Chemistry. 2018 Nov 16;24(64):17055-17061. doi: 10.1002/chem.201803097. Epub 2018 Oct 23.
The four-coordinate Pt complex [Pt(PPh )(Eind -BPEP)] (Eind=1,1,3,3,5,5,7,7-octaethyl-1,2,3,5,6,7-hexahydro-s-indacen-4-yl; BPEP=2,6-bis(1-phenyl-2-phosphaethenyl)pyridine), which bears a PNP-pincer-type phosphaalkene ligand (Eind -BPEP; PNP=N,N-bis(diphenylphosphine)-2,6-diaminopyridine), were found to adopt a square-planar configuration around the Pt center (τ =0.11). This coordination geometry is very uncommon for formal d complexes. In this study, a series of ligands with different electronic properties (i.e., DMAP, 2,6-lutidine, PMe , tBuNC, and CO) were introduced in place of PPh , and their effects on the coordination geometry were examined. X-ray diffraction analysis revealed that all complexes adopted a square-planar configuration (τ =0.20-0.27). In contrast, DFT calculations indicated that the geometrical stability towards distortion around Pt varied with the ligand. The complexes with pyridine-based ligands had rigid planar structures, whereas those with π-accepting ligands, such as CO, were relatively flexible towards distortion. The electronic effects of the ligands were reflected in the spectroscopic properties of the complexes, which showed a large color change in the near-infrared region.
四配位 Pt 配合物 [Pt(PPh )(Eind -BPEP)]（Eind=1,1,3,3,5,5,7,7-辛基-1,2,3,5,6,7-六氢-s-茚并-4-基；BPEP=2,6-双（1-苯基-2-膦烯基）吡啶），其带有 PNP 型膦烯配体（Eind -BPEP；PNP=N，N-双（二苯基膦基）-2,6-二氨基吡啶），被发现采用 Pt 中心周围的正方形平面构型（τ=0.11）。这种配位几何结构对于形式 d 配合物非常罕见。在这项研究中，一系列具有不同电子性质的配体（即 DMAP、2,6-联吡啶、PMe 、tBuNC 和 CO）被引入取代 PPh ，并研究了它们对配位几何的影响。X 射线衍射分析表明，所有配合物均采用正方形平面构型（τ=0.20-0.27）。相比之下，DFT 计算表明，Pt 周围扭曲的几何稳定性随配体而变化。基于吡啶的配体的配合物具有刚性的平面结构，而具有 π-接受配体（如 CO）的配合物则相对较灵活。配体的电子效应反映在配合物的光谱性质上，其在近红外区域表现出较大的颜色变化。
