333
It is interesting that the principal phosphine substitution products of the pentao
methylcydopentadienyl cluster 4 have structures with two bridging hydrogen atoms
around the Ru3 basal plane, as found for the normal cydopentadienyl derivatives,
and not as found in the main form of the parent cluster. However, contrary to the
cyclopentadienyl system, the most stable isomer of the mono-phosphine duster 7
does not involve phosphorus coordination at Ru(1) and a more geometrically rigid
isomer is produced.
Experimental
All reactions were carried out using Schlenk techniques under an atmosphere of
dry, gaseous nitrogen using freshly distilled, predried solvents, as previously de-
scribed [5]. Starting dusters [RhRu3(#-H)2(/x-CO)(CO)9CP] (1) and [RhRu3(#-
H)2(#-CO)(CO)gCp*] (4) were prepared as reported [3]. Ligands PPh3 (BDH) and
P(OMe)3 (Aldrich) were obtained commercially and used as supplied. Silica gel used
for column chromatography was 70-230 mesh (Merck) and petroleum ether had a
boiling range 60-80 oC, unless otherwise specified. NMR spectra were recorded on
a Bruker WP 200 SY spectrometer at 200 MHz for 1H, using SiMe4 as reference,
and at 81.0 MHz for 31p, with 85% H3PO4 as reference, at ca. 25°C, unless
otherwise stated. IR spectra were obtained on a Perkin Elmer 580 spectrometer and
FAB mass spectra on a Kratos MS 50 TC instrument from matrices in m-nitro-
benzylalcohol at the University of Edinburgh. Elemental analyses were determined
at UMIST, Manchester and/or at the University of Edinburgh.
Reaction of cluster I with triphenylphosphine
This reaction was carried out in THF as previously reported [5]. After chro-
matography with petroleum ether/dichloromethane in 5/1 and 1/1 mixtures,
respectively, [RhRu3(p-H)2(p-CO)(CO)s(PPha)Cp] (2) and [RhRu3(p-H)2(/L-
CO)(CO)7(PPh3)2Cp] (3), were obtained and identified from reported spectroscopic
data [5]. Continued chromatography with dichloromethane/acetone eluted at least
two different bands: the major product was an orange solid; IR (CH2C12) ~,(CO):
2
060 s, 2025 vs, 1998 s, 1958 s, cm-1; 1H NMR (CDCla) 7.4 ppm (br, mult.).
Reaction of cluster 1 with trimethylphosphite
Cluster 1 (80 mg, 0.106 mmol) and P(OMe)3 (0.11 mmol) in THF (10 cm -1) were
stirred for 5 h at room temperature. The solution was evaporated to dryness in the
presence of a little silica gel and the resulting solid residue was chromatographed on
a column of silica gel. Petroleum ether eluted [Rh(CO)2Cp] and petroleum ether/
dichloromethane, 10/1, gave some unreacted 1.
Petroleum ether/dichloromethane, 3/1, eluted an orange-brown band which
gave an oily brown product after evaporation of solvent (ca. 5 mg). Recrystallisation
from petroleum ether gave brown crystals (still somewhat oily) of slightly impure
[
2
(
RhRu3(p-H)2(p-CO(CO)s{P(OMe)3}Cp] (5). IR (petroleum ether) p(CO): 2070 m,
049 sh, 2040 vs, 2005 m, 1991 m, 1823 m, 1789 vw, cm-l; lH NMR (CO2C12) 5.74
s, 5H, C5H5), 3.62 (d, J(P-H) = 12 Hz, 9H, CH3), - 17.13 (d, (br), J(P-H) --- 8.6
Hz, 2H, R u - H ) ppm; FAB-MS: M+ and (M - n C O )+, n -- 1-9, {but also small
ion peaks at (M + mCO)+, m = 1-3}.
Grand, Jean-Luc Le
