The cluster [Ru3(CO)12] normally
reacts readily with tertiary phosphines and diphosphines
in the presence of Me3NO to give simple
phosphine-substituted derivatives by a reaction
involving nucleophilic attack of the amine oxide at CO leading to
CO2 formation. However,
the corresponding reaction of
[Ru3(CO)12] with (R)-BINAP
[2,2‘-bis(diphenylphosphino)-1,1‘-binaphthyl] in the presence of Me3NO does not give
[Ru3(CO)10(BINAP)], as expected,
but
instead an 80% yield of the dihydroxy complex
[Ru3(μ-OH)2(CO)8{μ-(R)-BINAP}]
(1) as the
first example of a μ-BINAP complex. NMR coalescence effects are
observed in the 1H NMR
spectra, but by using a 13CO-enriched sample, we were
able to show that the fluxionality is
not cluster-centered since the 13C{1H}
NMR spectrum for the CO ligands is invariant over
a wide temperature range. COSY spectra were used to show that
there is restricted rotation
about two of the four P−Ph bonds while the other two are rotating
freely. From a single-crystal XRD study it can be seen that two Ph groups are unimpeded while
the other two are
closely aligned to the naphthyl rings in a graphitic manner and it is
this that leads to the
restricted rotation. This bridging ligand adopts quite a different
conformation about the
C−PPh2 bonds to that in free BINAP, the structure of
which was also determined for
comparison, and somewhat different from that in known chelating BINAP
complexes. In
contrast, the direct thermal reaction of (R)-BINAP with
[Ru3(CO)12] in octane gives,
in
addition to traces of two uncharacterized species, a 38% yield of the
cluster [Ru3(μ-H){μ-(R)-BINAP-H}(CO)9] (2), in
which we believe that ortho metalation has occurred at one
of
the four Ph rings to form the first example of a cyclometalated BINAP
ligand. We have
been unable to obtain simple derivatives such as
[Ru3(CO)11(BINAP)] or
[Ru3(CO)10(BINAP)],
although we have shown that the osmium analogues may be synthesized.
Iodobenzene and 4-iodotoluene react with
[Ru3(CO)12] to give the oxidative
addition products [Ru3(μ-I)(μ,η1:η6-C6H4R)(CO)8]
(R = H, 4-Me), whereas 1-iodonaphthalene and 9-iodophenanthrene give the aryne
clusters
[Ru4(μ4,η2-L)(CO)12]
(L = 1,2-naphthyne, 9,10-phenanthryne).
The 46-electron heteronuclear clusters
[Pt2M(μ3-η1:η1:η2-PhC⋮CC⋮CPh)(CO)5(PPh3)2]
(M = Fe or Ru)
are formed in moderate yield by treating
[Pt(η2-PhC⋮CC⋮CPh)(PPh3)2] with
[Fe(CO)5] or [Ru3(CO)12]
in refluxing toluene. The Pt2Fe and
Pt2Ru clusters are
isostructural, being composed of two Pt(CO)(PPh3)
units
and a M(CO)3 group linked by two Pt−Fe or
Pt−Ru
bonds with the μ3-diyne coordinated through only
one
C⋮C bond.
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