title: Theoretical Study of Pd11 Si6 Nanosheet Compounds Including Seven-Coordinated Si Species and Its Ge Analogues.
abstract: Nanosheet compounds Pd11 (SiiPr)2 (SiiPr2 )4 (CNtBu)10 (1) and Pd11 (SiiPr)2 (SiiPr2 )4 (CNMes)10 (2), containing two Pd7 (SiiPr)(SiiPr2 )2 (CNR)4 plates (R=tBu or Mes) connected with three common Pd atoms, were investigated with DFT method. All Pd atoms are somewhat positively charged and the electron density is accumulated between the Pd and Si atoms, indicating that a charge transfer (CT) occurs from the Pd to the Si atoms of the SiMe2 and SiMe groups. Negative regions of the Laplacian of the electron density were found between the Pd and Si atoms. A model of a seven-coordinated Si species, that is, Pd5 (Pd-SiMe), is predicted to be a stable pentagonal bipyramidal molecule. Five Pd atoms in the equatorial plane form bonding overlaps with two 3p orbitals of the Si atom. This is a new type of hypervalency. The Ge analogues have geometry and an electronic structure similar to those of the Si compounds. But their formation energies are smaller than those of the Si analogues. The use of the element Si is crucial to synthesize these nanoplate compounds.
authors.affiliation: Fukui Institute for Fundamental Chemistry, Takano-Nishihiraki-cho 34-4, Sakyo-ku, Kyoto, 606-8103, Japan.
authors.forename: Yue
authors.identifier: http://orcid.org/0000-0003-4323-0001
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University and CREST (Japan) Science and Technology Agency (JST), Fukuoka, 816-8580, Japan.|Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka, 816-8580, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Sunada
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University and CREST (Japan) Science and Technology Agency (JST), Fukuoka, 816-8580, Japan.|Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka, 816-8580, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Nagashima
authors.affiliation: Fukui Institute for Fundamental Chemistry, Takano-Nishihiraki-cho 34-4, Sakyo-ku, Kyoto, 606-8103, Japan. sakaki.shigeyoshi.47e@st.kyoto-u.ac.jp.|CREST (Japan) Science and Technology Agency (JST), Kyoto University, Takano-Nishihiraki-cho 34-4, Sakyo-ku, Kyoto, 606-8103, Japan. sakaki.shigeyoshi.47e@st.kyoto-u.ac.jp.
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Sakaki
keywords: bonding nature; cluster compounds; density functional calculations; hypervalency; palladium; silicon