of the intermediate 8 was at its highest, the solution was cooled
to 253 K to allow 8 to be characterised by NMR spectroscopy.
The solution was then warmed up to room temperature, with
analogue 15 (see below). Warming the other solution resulted in
disproportionation of 14 to 6, H3Bؒ4MePy and 14, although
some decomposition also occurred. Addition of more 4-MePy
then converted 6 to 14 and H3Bؒ4MePy.
1
complete conversion to 1, identified by comparison of its H
and 31P NMR spectra with those of an authentic sample of the
complex.14
Conversion of 14 to 15
The reaction between 6 and 4-MePy (molar ratio 1 : 2) was
carried out at 293 K using C6H6 (1 cm3) plus a little C6D6 as
the solvent. NMR spectra recorded immediately after addi-
tion confirmed that conversion to 14 was complete, and CCl4
(20 mm3) was added straight away to the solution. The reson-
ances for 14 disappeared immediately. All volatile materials
were removed under reduced pressure, and the residue was
recrystallised from a 50 : 50 mixture of ethanol and light petrol-
eum (bp 313–333 K). NMR spectra recorded on this material
revealed the presence of an impurity, which was separated from
the main product 15 by chromatography on a 20 × 1 cm alu-
mina column, eluted with a 1 : 1 mixture of Et2O and CHCl3.
Complex 15 was in the second band to be eluted, and was
obtained as pale yellow crystals on removal of the solvent
(Found: C, 48.65; H, 5.11; N, 2.72. Calc. for C23H29Cl2NOP2Ru:
C, 48.51; H, 5.13; N, 2.46%. IR in CHCl3 solution: 1966 cmϪ1).
Preparation of complex 10
Nitrogen was bubbled through a stirred solution of ttt-[Ru(CO)2-
Cl2(PMe2Ph)2] (100 mg, 0.20 mmol) in refluxing methanol
(50 cm3) for 2 h. After cooling to room temperature, the solvent
was removed under reduced pressure, and the residue was
recrystallised from a mixture of propanone and light petroleum
(bp 353–373 K) (Found: C, 43.10; H, 4.83. Calc. for C34H44-
Cl4O2P4Ru2: C, 42.87; H, 4.66%. IR in CHCl3 solution: 1955
cmϪ1.).
Preparation of complex 6
An ethanol (5 cm3) suspension of 10 (100 mg, 0.10 mmol) was
stirred with NaBH4 (100 mg, 2.6 mmol) at 273 K for 30 min.
The solvent was then removed from the resulting solution under
reduced pressure, still at 273 K. The residual oil was extracted
into benzene (4 × 5 cm3) at a temperature just above its freezing
point. The extract was filtered and the benzene removed under
reduced pressure, still at the same temperature, leaving 6 as a
yellow oil. Crystals of 6 could be obtained by dissolving the
oil in the minimum quantity of hexane at 273 K and cooling
the solution to 253 K (Found: C, 48.11; H, 6.29. Calc. for
C17H27BO2P2Ru: C, 48.47; H, 6.46%. IR in hexane solution:
2435, 2413, 1952, 1172 cmϪ1.).
Reaction of 6 with ethene
Ethene was bubbled through a solution of 6 (45 mg, 0.1 mmol)
in either CD3C6D5 or CD3COCD3 (0.7 cm3) in an NMR tube
for 5 min at 195 K, and the solution was transferred to the pre-
cooled probe of the NMR spectrometer. Spectra recorded at
193 K and 213 K established the existence of an equilibrium
between 6, ethene and a species 16, which was only stable at low
temperatures and was characterised by NMR spectra recorded
at 193 K. Meanwhile slow conversion to 17 was also occurring,
and on raising the temperature to 273 K (or simply by carrying
out the whole reaction at 273 K) the conversion was completed.
Slow evaporation of the solvent under a stream of nitrogen at
273 K left 17 as a light brown oil, which appeared on the basis
of NMR spectra recorded at 273 K to be free of impurity, but
that would not crystallise. The stability of 17 was limited, and it
was stored under ethene at 253 K (IR in hexane solution: 2425,
2405, 1938, 1725, 1703, 1172 cmϪ1).
Reaction of 6 with PMe2Ph
A CD3C6D5 (1 cm3) solution of 6 (18 mg, 0.04 mmol) in an
NMR tube was treated at 213 K with the desired amount of
PMe2Ph (6 mm3 for an approximately 1 : 1 molar ratio of the
reactants, 12 mm3 for a 2 : 1 ratio). In both cases 11 was quickly
formed: it was only stable at low temperatures and was charac-
terised by NMR spectroscopy at 213 K. Warming the solution
containing a 2 : 1 molar ratio of the reactants to 300 K resulted
in conversion of 11 to H3BؒPMe2Ph and 5, identified by
spectroscopic comparison with an authentic sample.17 The
same treatment of the solution containing a 1 : 1 molar ratio of
the reactants caused a disproportionation of 11 to equimolar
quantities of 6, 5 and H3BؒPMe2Ph, but addition of more
PMe2Ph completed the conversion of 6 to 5 and H3BؒPMe2Ph.
Acknowledgements
We thank Johnson Matthey PLC (“JM”) for a generous loan of
ruthenium trichloride, and Rachael Dumbill, Andrea Thoma
and Nicholas Wood for experimental assistance.
Reaction of 6 with CO
Carbon monoxide was bubbled through a CD3C6D5 (1 cm3)
solution of 6 (36 mg, 0.08 mmol) in an NMR tube for 10 min at
210 K. The CO flow was then stopped and the NMR tube was
transferred to the probe of the spectrometer (also at 210 K).
The product of the reaction, 12, which was only stable at low
temperatures, was characterised by NMR spectroscopy. Warm-
ing the solution to 300 K caused complete conversion of 12 to
H3BؒCO and 4, identified by comparison of its spectra with
those of an authentic sample.16
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Reaction of 6 with 4-methylpyridine (4-MePy)
A CD3C6D5 (1 cm3) solution of 6 (36 mg, 0.08 mmol) in an
NMR tube was treated at 220 K with 4-MePy (either a roughly
equimolar quantity, 8 mm3, or an excess, 38 mm3). Immediate
conversion to 13 occurred: this complex, only stable at low tem-
peratures, was characterised by NMR spectroscopy at 220 K.
Warming the solution containing an excess of 4-MePy to 273 K
yielded H3Bؒ4-MePy and 14. 14, which was insufficiently stable
at room temperature to be isolated, was characterised by NMR
spectroscopy at 250 K and by conversion to its dichloro-
D a l t o n T r a n s . , 2 0 0 3 , 2 6 0 3 – 2 6 1 4
2613
Chamberlain, Barbara
