Insertion of a platinum(0) fragment into the strained silicon-carbon bond of a silicon-bridged [1]ferrocenophane: synthesis, alkyne insertion chemistry, and catalytic reactivity of the [2]platinasilaferrocenophane Fe(eta(5)-C5H4)(2)Pt(PEt3)(2)SiMe2

摘要

The reaction of Pt(PEt3)(3) with the silicon-bridged [1]ferrocenophane Fe(eta(5)-C5H4)(2)SiMe2 1 at 60 degrees C resulted in the insertion of a platinum(0) Pt(PEt3)(2) fragment into the strained Si-C bond to yield the first [2] platinasilaferrocenophane Fe(eta(5)-C5H4)(2)Pt(PEt3)(2)SiMe2 4. Complex 4 serves as a model for the proposed intermediate during the transition metal-catalyzed ring-opening polymerization (ROP) of 1. The reactivity of 4 was illustrated by the insertion of diphenylacetylene into the Pt-Si bond at elevated temperatures to yield a [4]ferrocenophane Fe(eta(5)-C5H4)(2)Pt(PEt3)(2)C(Ph)C(Ph)SiMe2 5 with a cis Pt-C=C-Si bridge. Both 4 and 5 were fully characterized spectroscopically and by single crystal X-ray diffraction. Despite the reactivity of the Pt-Si bond, the [2]platinasilaferrocenophane 4 was inactive as a ROP catalyst for 1 even at 95 degrees C. However, addition of BH3.THF co-catalyst rendered 4 active towards the ROP of 1 at 25 degrees C, presumably via abstraction of one or more PEt3 ligands, affording low molecular weight [M-n (number average molecular weight) = ca. 1720-4695; PDI (polydispersity index)= 1.51-1.73], cyclic poly(ferrocenylsilanes) 6. [References: 82]