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Platinum−Silicon Four-Membered Rings of Two Different Structural Types

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journal contribution
posted on 23.12.1999, 00:00 by Lee M. Sanow, Minghui Chai, David B. McConnville, Kevin J. Galat, Richard S. Simons, Peter L. Rinaldi, Wiley J. Youngs, Claire A. Tessier
The synthesis and characterization of platinum−silicon four-membered rings of two different structural types is reported. The reaction of Pt(PR3)3 (R = Et or Pr) and Si(Hex)H3 (Hex = n-hexyl) gives [Pt(PR3)2SiH(Hex)]2 (R = Et, 1a; R = Pr, 1b) and [(R3P)Pt(μ-Si(μ-H)(Hex)(Pt(PR3)2)H)]2 (R = Et, 2a; R = Pr, 2b). The ratio of 1a to 2a is highly dependent on the reaction conditions, whereas 1b is always the major product in the PPr3 substituted case. Evidence that suggests that 1a and 1b are precursors to 2a and 2b, respectively, is presented. X-ray crystallography of the rings 1b and 2a shows they contain short Si−Si and Pt−Pt contacts, respectively. The 29Si NMR chemical shifts for the two types of rings differ by over 250 ppm. A 2D-NMR study of these rings has provided detailed coupling information, including information on the agostic Pt−H−Si hydride in 2a.