Isocyanide and Diisocyanide Complexes of a Triplatinum Cluster: Fluxionality, Isomerism, Structure, and Bonding

Arleen M. Bradford, Eva Kristof, Mehdi Rashidi, Dong Sheng Yang, Nicholas C. Payne, Richard J. Puddephatt

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56 Scopus citations


The reaction [Pt33-CO)(μ-dppm)3]2+, 1, with RNC (R = t-Bu, cyclohexyl or o-xylyl) gives an intermediate characterized as [Pt3(μ-CO)(CNR)(μ-dppm)3]2+, 2, which then isomerizes to the stable complex [Pt33-CO)-(CNR)(μ-dppm)3]2+, 3. When R = o-xylyl, reaction of 3 with more RNC gives an intermediate [Pt3(μ-CO)-(CNR)2(μ-dppm)3]2+, 4, which then loses CO to give [Pt3(CNR)2(μ-dppm)3]2+, 5, the first example of a Pt3 cluster complex having no bridging atom. The cluster 5 has been characterized by an X-ray structure determination. [The solvated salt crystallizes in the monoclinic space group P21, cell dimensions a = 17.639(2) Å, b = 19.704(3) Å, c = 14.5444(12) Å, and β = 101.99(2)° with Z = 2. Full matrix least-squares refinement on F2 of 558 variables converged at a conventional R factor of 0.0393 for 6334 data with I > 2σ(I).] The two xylyl isocyanide ligands are trans-bonded to Pt(l), and as a result the Pt(2)-Pt(3) distance of 2.548(1) Å is significantly shorter than the mean of the two distances to Pt(1), 2.649(1) Å. Complexes 3 and 5 are fluxional; the RNC ligands can migrate easily around the face of the Pt3 triangle. The diisocyanides 1,4-C≡NC6R4N≡C, R = H or Me, react with 1 to give polymeric complexes {[Pt3(μ-1,4-C≡NC6R4N≡C)(μ-dppm)3][PF6]2}n, 7, in which the diisocyanide bridges between Pt3 cluster units. The local stereochemistry at platinum is similar to that in 5, and the fluxionality appears even easier in 7 than in 5. Evidence is presented for diisocyanide complexes analogous to 2 and 3, namely [Pt3(μ-CO)(CNC6H4NC)(μ-dppm)3]2+ and [{Pt33-CO)(μ-dppm)3}2(μ-CNC6H4NC)]4+, 8. Calculations of the EHMO type on model complexes give insight into the factors which influence the preferred binding mode (terminal or triply bridging) of the isocyanide at the Pt3 triangle.

Original languageEnglish
Pages (from-to)2355-2363
Number of pages9
JournalInorganic Chemistry
Issue number11
StatePublished - May 1 1994

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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