Multinuclear palladium compounds containing palladium centers ligated by five silicon atoms

doi:10.1073/pnas.0700450104

Multinuclear palladium compounds containing palladium centers ligated by five silicon atoms

^†Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan;
^§Research Institute for Computational Sciences, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan; and
^¶Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan

Edited by Jack Halpern, University of Chicago, Chicago, IL, and approved March 12, 2007 (received for review January 17, 2007)

Abstract

Palladium (Pd) generally prefers low oxidation states. So far, no stable Pd compound with a +5 oxidation state is known. Here, we report two multinuclear Pd compounds containing Pd centers ligated by five silicon (Si) atoms. A thermal condensation reaction of [{1,2-C₆H₄(SiMe₂)(SiH₂)}Pd^II(Me₂PCH₂CH₂PMe₂)] (Me = methyl) afforded two stereoisomers of dinuclear Pd^II compounds and a trinuclear Pd compound as major products and a tetranuclear Pd compound as a minor product. The structures of the four Pd compounds were confirmed by single-crystal x-ray structure analysis. The dinuclear Pd compounds have a dimeric structure of [{1,2-C₆H₄(SiMe₂)(SiH)}Pd^II(Me₂PCH₂CH₂PMe₂)] connected through a Si–Si single bond formed by dehydrogenation of two molecules of the starting compound. The trinuclear and tetranuclear Pd compounds proved to have Pd centers bonded to five Si atoms with normal Pd–Si single-bond distances. Theoretical calculations of the trinuclear and tetranuclear Pd compounds accurately reproduced their x-ray structures and suggested that all of the Pd–Si bonds of the central Pd atoms have a relatively high single-bond character.

Footnotes

^‡To whom correspondence should be addressed. E-mail: s-shimada{at}aist.go.jp
Author contributions: S.S. and M.T. designed research; S.S., Y.-H.L., Y.-K.C., M.B., and T.U. performed research; S.S. analyzed data; and S.S. and Y.-K.C. wrote the paper.
↵ ^‖Present address: State Key Laboratory of Fine Chemicals, Dalian University of Technology, 158 Zhongshan Road, Dalian 116012, China.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Data deposition: The atomic coordinates have been deposited in the Cambridge Structural Database, Cambridge Crystallographic Data Centre, Cambridge CB2 1EZ, United Kingdom (CSD reference nos. 626200–626203).
This article contains supporting information online at www.pnas.org/cgi/content/full/0700450104/DC1.
Abbreviations:

AIM,

atoms in molecule;

DME,

1,2-dimethoxyethane;

dmpe,

1,2-bis(dimethylphosphino)ethane.