4500 Organometallics, Vol. 19, No. 22, 2000
Hall et al.
(H2Os3(CO)10), yellow, and yellow, in order of decreasing Rf.
Extraction of the plate above the top yellow band yielded
colorless H3Os3(CO)9(SiEt3)3 (IR (hexanes) 2078 w, 2032 vs,
2026 vw sh, 2008 m cm-1; 1H NMR (CDCl3, 20 °C) 1.179 (t, 27
H, J ) 7 Hz), 1.070 (q, 18 H), -16.31 (s, 3 H) ppm).
most of these the isolated product is the oxidative
addition product H3Os3(CO)10(ER3) (eq 1). We report
here a study of the kinetics and mechanism of of this
reaction.
Rea ction of 1 Equ iv of HGeBu 3 w ith H2Os3(CO)10. In
an NMR tube was placed 10.5 mg (0.0123 mmol) of H2Os3-
(CO)10 and 3.6 mg (0.0147 mmol) of HGeBu3 in approximately
1 mL of deuteriochloroform. 1H NMR (20 °C): -9.2 (br, 1H),
-9.5 (br, 1H), -11.5 (s, 3H), -15.5 (br, 1H), -16.8 (s, 1H),
H2Os3(CO)10 + HER3 f H3Os3(CO)10(ER3) (1)
Exp er im en ta l Section
Ch em ica ls. H2Os3(CO)10 was prepared as described in the
literature.9 Triphenyl- and triethylsilane, triphenyl- and tri-
butylstannane, tributyltin deuteride, and tributylgermane
were purchased from Aldrich and used as received. Heptane
and octane were obtained from Fisher. Purification by distil-
lation from CaH2 under nitrogen had no effect on the kinetics;
therefore, solvents were used as received.
1
-18.3 (s, 1H), -18.4 (s, 1H) ppm. H NMR (-70 °C): H3Os3-
(CO)10(GeBu3) (92% of total hydride integral); isomer 1t (17%),
-9.52 (d, 1H, J HH ) 12 Hz), -17.06 (d, 1H, J HH ) 12 Hz),
-18.35 (s, 1H) ppm; isomer 2t (6.1%), -9.51 (d, 1H, J HH ) 13
Hz), -17.38 (d, 1H, J HH ) 13 Hz), -17.76 (s, 1H) ppm; isomer
1c (75%), -10.04 (d, 1H, J HH ) 3 Hz), -17.03 (s, 1H), -19.49
(d, 1H) ppm. IR (heptane): 2124 w, 2100 vw, 2092 w, 2073 m,
Gen er a l Con sid er a tion s. The IR spectra were obtained
on a Nicolet 550 Magna FT-IR spectrometer. The 1H NMR
spectra were obtained on a Varian 400 MHz spectrometer.
Ch a r a cter iza tion of P r od u cts fr om HSiEt3. To obtain
a sample of H3Os3(CO)10(SiEt3), H2Os3(CO)10 was dissolved in
neat triethylsilane. After the solution turned yellow, the
triethylsilane was removed by vacuum transfer. The yellow
residue was then used for spectroscopic characterization. IR
(heptane): 2126 w, 2100 w, 2094 w, 2079 w, 2074 m, 2043 vs,
2038 sh, 2025 s, 2008 w, 1990 w, 1975 vw, 1965 vw cm-1. The
1H NMR spectrum of the product mixture was obtained as
follows. A solution of 17.1 mg of H2Os3(CO)10 and 11.5 mg of
HSiEt3 in 0.64 mL of dichloromethane-d2 was allowed to stand
at room temperature for 1.5 h. Then the spectra were recorded
at temperature intervals down to -70 °C. In the hydride region
at this temperature 88% of the total integrated resonances
could be assigned to the following: H3Os3(CO)10(SiEt3) (79%,
three isomers), H2Os3(CO)10 (4.5%), and H3Os3(CO)9(SiEt3)
(4.5%). In addition, a number of very small resonances were
observed, perhaps due to other isomers of the addition product.
At this time no signals due to H2Os3(CO)10(SiEt3)2 or H3Os3-
(CO)9(SiEt3)3 were present; after 2 days the room-temperature
spectrum contained resonances assignable to H2Os3(CO)10-
(SiEt3)2 (-16.830 (d), -17.568 (d) ppm, J ) 1.6 Hz) and
H3Os3(CO)9(SiEt3)3 (-16.185 ppm), in addition to signals from
H3Os3(CO)10(SiEt3), H2Os3(CO)10, and H3Os3(CO)9(SiEt3) and
other, new unassigned peaks.
2064 vw, 2043 vs, 2024 s, 2010 m, 2006 m, 1990 w cm-1
.
Kin etics of HSiR3 Ad d ition to H2Os3(CO)10. In a 25 mL
Erlenmeyer flask was weighed out H2Os3(CO)10 (ca. 8 mg) and
heptane (ca. 5 mL) to give a known concentration of ca. 1.5
mM. The solution was placed in a 50 mL Schlenk flask under
a nitrogen atmosphere, and the flask was immersed in a Haake
temperature bath ((0.1 °C) and allowed to come to thermal
equilibrium. A weighed amount of silane (10-40-fold excess)
was then mixed with the solution, and aliquots were taken at
intervals. The kinetics for the disappearance of H2Os3(CO)10
was followed periodically for over 3 half-lives using the 2062
cm-1 absorption (R ) Et) or the 2074 cm-1 absorption (R )
Ph) in the IR spectrum.
Kin etics of HGeBu 3 Ad d ition to H2Os3(CO)10. To 2 mL
of distilled heptane was added 6.0 mg (0.0070 mmol) of
H2Os3(CO)10. The cluster was dissolved at room temperature,
and the solution was then placed in a vial in the circulating
bath for 10 min. Another vial containing the pure excess of
HGeBu3 was also allowed to come to temperature in the
circulating bath for 10 min. At this point, both solutions were
quickly mixed and placed in a thermostated cuvette. The
cuvette was then flushed with argon gas, and the kinetics of
addition of HGeBu3 was followed by monitoring the absorbance
at 560 nm for H2Os3(CO)10.
Kin etics for Ad d ition of HSn R3 to H2Os3(CO)10. A 4.9
mM solution of H2Os3(CO)10 was placed in one syringe and a
solution of HSnR3 in the other syringe of an Applied Photo-
physics SX-18MV stopped-flow kinetics instrument. For each
concentration of tin hydride, 10 injections were done. The
temperature of the kinetic runs was maintained by a Haake
temperature bath. The reactions were followed for 3 half-lives.
Tr ea tm en t of Da ta . For triethylsilane the corrected ab-
sorbance at 2062 cm-1 was fit to eq 2 by a nonlinear least-
squares procedure, using Psi-Plot for Windows, Version 4.01
(Poly Software International); At is the absorbance at time t,
Aeq is the absorbance at equilibrium, and kobs is the rate
constant for relaxation to equilibrium. The values of the
The residues from kinetic runs were combined and sepa-
rated by thin-layer chromatography on silica gel, with hexanes
as eluent. Four bands were eluted, colored yellow, purple
(17) (a) Suss-Fink, G.; Ott, J .; Schmidkonz, B.; Guldner, K. Chem.
Ber. 1982, 115, 2487. (b) Suss-Fink, G. Angew. Chem., Int. Ed. Engl.
1982, 21, 73. (c) Suss-Fink, G.; Reiner, J . J . Organomet. Chem. 1981,
221, C36.
(18) (a) Duggan, T. P.; Golden, M. J .; Keister, J . B. Organometallics
1990, 9, 1656. (b) Churchill, M. R.; J anik, T. S.; Duggan, T. P.
Organometallics 1987, 6, 799. (c) Churchill, M. R.; Ziller, J . W.; Dalton,
D. M.; Keister, J . B. Organometallics 1987, 6, 806. (d) Ziller, J . W.;
Bower, D. K.; Dalton, D. M.; Keister, J . B.; Churchill, M. R. Organo-
metallics 1989, 8, 492. (e) Strickland, D. A.; Shapley, J . R. J .
Organomet. Chem. 1991, 401, 187. (f) Bower, D. K.; Keister, J . B.
Organometallics 1990, 9, 2321. (g) Safarowic, F. J .; Keister, J . B.
Organometallics 1996, 15, 3310.
(19) (a) Calvert, R. B.; Shapley, J . R. J . Am. Chem. Soc. 1978, 100,
6544; 1977, 99, 5225. (b) Koike, M.; VanderVelde, D. G.; Shapley, J .
R. Organometallics 1994, 13, 1404. (c) Cree-Uchiyama, M.; Shapley,
J . R.; St. George, G. M. J . Am. Chem. Soc. 1986, 108, 1316.
(20) (a) Hudson, R. H. E.; Poe, A. J . Organometallics 1995, 14, 3238.
(b) Neubrand, A.; Poe, A. J .; van Eldik, R. Organometallics 1995, 14,
3249.
(21) (a) Keister, J . B.; Shapley, J . R. Inorg. Chem. 1982, 21, 3304.
(b) Churchill, M. R.; DeBoer, B. G. Inorg. Chem. 1977, 16, 2397. (c)
Churchill, M. R.; DeBoer, B. G. Inorg. Chem. 1977, 16, 878. (d) Adams,
R. D.; Golembeski, N. M. Inorg. Chem. 1979, 18, 1909. (e) Deeming,
A. J .; Hasso, S. J . Organomet. Chem. 1976, 114, 313.
(22) Aime, S.; Gobetto, R.; Valls, E. Inorg. Chim. Acta 1998, 275-
276, 521.
At ) (At - Aeq) exp(-kobst) + Aeq
kobs ) k1[HSiEt3] + k2
Keq ) k1/k2
(2)
(3)
(4)
adjustable parameters Aeq and kobs thus determined by the best
fit, combined with the initial absorbance before mixing, were
used to determine Keq, k1, and k2. The values from a range of
concentrations were averaged, with the error expressed as the
standard deviation.
For all other reactions plots of ln(absorbance) vs time were
analyzed by least-squares fit.
Resu lts
(23) Hudson, R. H. E.; Poe¨, A. J . Inorg. Chim. Acta 1997, 259, 257.
(24) Einstein, F. W. B.; Pomeroy, R. K.; Willis, A. C. J . Organomet.
Chem. 1986, 311, 257.
Ad d ition of HER3 to H2Os3(CO)10 (E ) Si, Ge, Sn ;
R ) Alk yl, P h en yl). Pomeroy and co-workers previ-