Synthesis of a Novel Volatile Platinum Complex for Use in CVD and a Study of the Mechanism of Its Thermal Decomposition in Solution

The synthesis, characterization, chemical vapor deposition, and
mechanistic investigation of the thermal
decomposition in aromatic solvents of
cis-bis(η2,η1-pent-4-en-1-yl)platinum
(1) are described. Complex 1 has
a
unique chelated structure, giving rise to enhanced volatility, and has
proved useful for the chemical vapor deposition
of thin platinum films under mild conditions. Films deposited on a
glass slide in a hot walled glass tube at 175 °C
have an elemental composition of 82% Pt and 18% C. Kinetic,
deuterium labeling, and chemical trapping experiments
indicate that the decomposition of 1 in aromatic solvents
proceeds by reversible β-hydride elimination followed by
reversible dissociation of 1,4-pentadiene to give a 3-coordinate
platinum hydride intermediate (9).
Reductive
elimination of 1-pentene from 9 deposits metallic platinum.
The rate of decomposition exhibits a significant
β-deuterium isotope effect of
kH/kD = 3.8 ± 0.3.
Added olefins are rapidly isomerized during the decomposition
of
1; trapping experiments with diphenylacetylene indicate that
intermediate 9 is the highly active catalyst that
is
responsible for the alkene isomerization.