Selective Carbon–Carbon Bond Activation of Epoxides by a Bisphosphine Pt(0) Complex

Contrasting established bond activation
chemistry of oxiranes (epoxides),
the unprecedented insertion of a Pt(0) complex into the carbon–carbon
bonds of ethylene oxide and other epoxides, generating 3-oxaplatinacyclobutanes
under remarkably mild conditions, has been found. Pt­(II) neopentyl
hydride complex (dtbpm-κ2P)­Pt­(Np)­H
(1) undergoes first-order reductive elimination of neopentane
at ambient temperature in solution, forming a highly reactive species
of an overall composition [(dtbpm)­Pt(0)] (C). This intermediate
inserts into epoxide C–C bonds or, in the absence of substrates,
dimerizes to d10–d10 Pt(0) species D. The epoxide activation products have been fully characterized
including X-ray structure determinations. Various experiments have
been conducted in order to decipher mechanistic details of this unusual
chemistry. Theoretical studies on various levels do not allow a reliable
conclusion as to the actual nature of the reactive intermediate C. Both conceivable structures C1 (ring-opened
[(dtbpm-κ1P)­Pt­(0), d10-ML, 12 VE]) and C2 (chelate, [(dtbpm-κ2P)­Pt­(0)], d10-ML2, 14 VE)
are minimum-energy structures with a very small (method-dependent)
energy difference.