(
)
J.C. Jeffery et al.rJournal of Organometallic Chemistry 551 1998 27–36
33
Ž13 Ä1
4 .
C H spectrum , with the cage carbon
Ž
.
and 28.5
nuclei showing the usual broad resonance at d 76.8 in
TLC , material in one of the yellow fractions was
2
5
w
Ž
. Ž
characterised as Ru CO h ,h -7,8-Me2-10-
C H 5C H SiMe3-7,8-C2 B9 H8 5a .
2
11
Ä1
4
Ž .
Ž .
.
x
Ž
.
the latter NMR spectrum. The B H NMR spectrum
1
Ž
.
was as expected Table 3 .
The H NMR spectrum of compound 5a showed two
The addition of PPh3, But NC, and pyridine to
w
Ž
.
sets of doublet signals at d 3.76 and 4.94 J HH s15
x
Ž .
Ž .
CH2Cl2 solutions of reagent 4b generates the stable
Hz corresponding to the trans C H 5C H protons.
As a result of the asymmetry of the system, two singlets
are observed in the 1H NMR spectrum for the cage
5
w
Ž .Ž . Ž
.x Ž
complexes Ru L CO h -7,8-Me2-7,8-C2 B9 H9 4d,
2
t
.
LsPPh3; 4e, LsCNBu ; 4f, LsNC5H5 , respec-
Ž
.
tively, all isolated in good yield after column chro-
methyl groups d 2.37 and 2.43 and four signals are
observed in the C H NMR spectrum at d 67.5
and 82.7 CMe and at 31.4 and 32.3 C Me . Also
in this spectrum, a broad resonance was observed at
d 98.5, and this may be assigned to the vinyl carbon
bound to one of the boron atoms in the metal-coordina-
13
Ä1
4
matography. All molecules possess Cs symmetry as
evidenced by their B H NMR spectra Table 3 .
Furthermore, the H and C H NMR spectra of the
complexes revealed single resonances for the cage car-
bon and cage methyl nuclei in addition to single peaks
for the CO carbon nuclei Table 3 . The P H NMR
spectrum of 4d showed the expected singlet for the
ligated phosphine at d 45.7. The spectra of compound
11
Ä1
4
Ž
.
Ž
.
Ž
.
1
13
Ä1
4
31
Ž
.
Ä1
4
ting
face of the cage. The other vinyl carbon,
to which the SiMe3 group is bound, displayed a signal
at d 75.8. The B H NMR spectrum showed a
resonance at d 19.2, which is attributable to the cage
11
Ä1
4
Ž
.
4e were as expected with a nmax NC band in the IR
spectrum at 2186 cmy1 and the CNBut nucleus giving
2
Ž .
Ž .
b-boron carrying the h -C H 5C H SiMe3 group, with
rise to a triplet resonance in the 13C H NMR spectrum
1
Ä1
4
this signal showing as expected no H–11 B coupling in
the fully coupled 11 B NMR spectrum. The chemical
shift is similar in magnitude to that for the correspond-
ing b-B nucleus in the related complex
w
Ž
.
x
at d 137.2 J NC s20 Hz .
The treatment of compound 4a with alkenes, alkynes
and transition metal alkylidynes has proven extremely
2
5
w
x
w
Ž
. Ž .x
Ž .
Ž .
fruitful 2,3 . Some reactions of complex 4b with transi-
Ru CO h ,h -10-C H 5C H SiMe3-7,8-C2 B9 H10
2
5b d 20.0 2 . The 11 B NMR spectra allow us to
w x
Ž
. Ž
. w x
tion metal alkylidynes have also been documented 3 ,
but to date we have not reported reactions of 4b with
simple alkenes and alkynes. A CH2Cl2 solution of
complex 4b, when treated with C7 H12 norbornene , did
not yield a stable ruthenium–alkene adduct. IR and
distinguish which boron atom in the coordinating face
of the cage may be involved in the non-innocent be-
haviour. Thus the corresponding signal for the com-
pound Ru CO h ,h -9-C H 5C H SiMe3-7,8-
C 2 B 9 H 1 0
Ž
.
2
5
w
Ž
x
. Ž
Ž
.
Ž .
2
.
Ž
.
mass spectral analysis revealed that the fragment
5c , w here an a-boron is
5
w
Ž
. Ž
.x
Ru CO h -7,8-Me2-7,8-C2 B9 H9 had been formed,
utilised in the
coordinating ring, occurs at d
2
w x
along with unidentified dark solid, which may be the
10.2 2 . Compound 5c is formed in the same reaction
as 5b, and is readily separated by column chromatogra-
phy. The employment of the b-boron in compound 5a
is further supported by previous observations that the
presence of methyl groups on the cage carbons in-
creases the propensity of the b-B–H bonds to become
5
w
Ž
. Ž
.x
polymeric Ru CO h -7,8-Me2-7,8-C2 B9 H9 n. To
2
our surprise, a similar result was obtained when CH2Cl2
solutions of 4b were treated with one or two equivalents
of MeC[CMe, PhC[CPh, or ButC[CH, respectively.
This is in stark contrast with the reactivity of complex
4a, which forms stable adducts with alkenes and alkynes.
w x
activated over the a-B–H bonds 9 . However, we
In the corresponding reactions of 4b, some
cannot rule out the formation of an a-isomer of com-
pound 5a, which may be present in the remainder of the
intractable mixture.
5
w
Ž
. Ž
.x
Ru CO h -7,8-Me2-7,8-C2 B9 H9 was detected in all
2
11
Ä1
4
cases. The B H NMR spectra of the residues from
the reactions were complex and indicated that nido-cage
systems were also present with peaks appearing at -d
y30, and other resonances in these spectra did not
3. Conclusion
show H–11 B coupling in fully coupled 11 B NMR
1
w
The formation of the salt 2a from Tl closo-1,2-Me2-
3
x
w
Ž
. Ž
.x
spectra. The treatment of complex 4b with a very large
excess of the alkenes or alkynes still produced in-
tractable mixtures and we have not been able to harness
these reactions. Thus, uncontrolled multiple hydrobora-
tions of the unsaturated hydrocarbon molecules may
have occurred, leading eventually to partial decomposi-
tion of the closo-3,1,2-RuC2 B9 cluster. It is, however,
possible to report a positive result with one particular
alkyne: reaction of a CH2Cl2 solution of 4b with
Me3SiC[CH gave a very complicated mixture. Never-
theless, after preparative thin layer chromatography
3,1,2-TlC2 B9 H9 and RuBr CO h -C3H5 was en-
3
tirely unexpected, and provides a novel example of a
bridging thallium centre. Despite the formation of 1b
and 2a as a mixture, this preparation was optimised to
produce a useful one-pot synthesis of complex 4b. The
Ž
reactions of 4b with simple donor molecules L Ls
PPh3, But NC, NC5H5 gave the expected products, but
.
the inability of compound 4b to react with alkynes and
alkenes to yield stable adducts is curious, particularly in
the light of successful reactions with tungsten– and
w x
molybdenum–alkylidyne complexes 3 . The latter reac-
Jeffery, John C.
