The reactivity (e.g., toward hydrolysis, alcoholysis, reduction by CO or H2) of various [Os3(CO)10(μ-H)(μ-OSiPh2R‘)] (R‘ = Ph, OH, OSiPh2OH) clusters and the thermal behavior of
[Os3(CO)10(μ-H)(μ-OSiEt3)] have been studied with the aim of clarifying by a molecular
approach some aspects of the surface chemistry of silica-anchored [Os3(CO)10(μ-H)(μ-OSi⋮)].
Their easy and selective reduction to [Os3(CO)12] (under CO) and to [H4Os4(CO)12] (under
H2) suggests that [Os3(CO)10(μ-H)(μ-OSi⋮)] does not require, as a reactive intermediate, a
previous hydrolysis to the more reactive molecular species [Os3(CO)10(μ-H)(μ-OH)] in order
to generate different osmium carbonyl clusters in their silica-mediated synthesis starting
from OsCl3 or [Os(CO)3Cl2]2. The thermal behavior of [Os3(CO)10(μ-H)(μ-OSiEt3)] dissolved
in triethylsilanol (to mimic a silica surface with many available surface silanols) or triglyme
(to mimic a highly dehydroxylated silica surface) gives an answer to the controversy on the
nature of the products formed by thermal degradation on the silica surface of [Os3(CO)10(μ-H)(μ-OSi⋮)]. In triethylsilanol, oxidation occurs to give a Os(II) hydrido carbonyl species
which, on the basis of chemical and spectroscopic evidence, we suggest to be [Os(CO)3(μ-OSiEt3)2(OSiEt3)(H)Os(CO)2]
n
(n = probably 2), whereas in triglyme an aggregation to high-nuclearity clusters such as [H4Os10(CO)24]2- and [H5Os10(CO)24]- occurs. Therefore, it is shown
for the first time that molecular models not only are a tool to define structural aspects but
also may be a springboard to understand and clarify by a molecular approach aspects of the
reactivity of organometallic species on the silica surface.