Dihydrogen Thiolate vs Hydride Thiol
Organometallics, Vol. 15, No. 21, 1996 4435
using SHELXTL-PC on a 486-66 personal computer.39 Elec-
trochemical measurements were made on a Princeton Applied
Research Model 273 potentiostat/galvanostat (without iR
package. The Os-H distance was set to the standard bond
length of 1.6 Å34 and the bond positioned at an angle of 90° to
the carbonyl ligand in the plane defined by the metal and the
chelate.
compensation) interfaced with
a Macintosh SE running
[Os(η2-H2)(CO)(p yS)(P P h 3)2]BF 4 (6a ,b). (a ) Obser va -
tion of th e Isom er ic Mixtu r e in Solu tion . In a 5 mm NMR
tube 2a ,b (30 mg, 0.035 mmol) was dissolved in 1 mL of CDCl3
and 10 µL of HBF4‚Et2O (excess, 85% in Et2O) was added,
resulting in an immediate color change from yellow to almost
colorless. Under 1 atm of argon this solution was stable for
several days at room temperature (298 K). The spectrum
showed an isomeric mixture of 6a (major isomer, H trans to
N) and 6b (minor isomer, H trans to S), reflecting the isomer
distribution of the parent monohydride complex 2a ,b (2:1). 1H
NMR (CDCl3, 400 MHz): δ -5.70 (br, 2H, Os(η2-H2), 6a ), -6.84
(br, 2H, Os(η2-H2), 6b), 5.85, 6.29, 6.72, 7.16 (br, 4H, 2-pyridi-
nethiolate protons), 7.20-8.00 (30 H, phenyl region, 6a ). The
corresponding peaks for 6b are obscured by resonances of 6a .
31P NMR (300 MHz, CH2Cl2): δ 9.07 (s, 6a ), 11.77 (s, 6b). IR
(CH2Cl2): ν(CO) 1993 cm-1. The ν(CO) peaks of the isomers
are not resolved in the IR spectrum.
(b) Isola tion of 6a . 2 (230 mg, 0.27 mmol) was dissolved
in 15 mL of CH2Cl2, and 70 µL of HBF4‚Et2O (excess, 85% in
Et2O) was added, causing an immediate color change from
yellow to colorless. A 60 mL portion of hexanes was added
with stirring and the solution stored at -20 °C for several
days. A light yellow precipitate formed, from which slow gas
evolution was observed. Filtering and drying in vacuo yields
a light yellow solid (230 mg, 0.24 mmol, 90%).11 1H and 31P
NMR spectra show only the presence of 6a .
Interactive Cyclic Voltammogram Acquisition Program (ICY-
VAP).40 All cyclic voltammograms were obtained using an
electrochemical cell consisting of a platinum working electrode,
tungsten secondary electrode, and silver-wire reference elec-
trode in a Luggin-Haber probe capillary. All measurements
were made under Ar gas using 0.2 M NBu4PF6 in freshly
distilled CH2Cl2 as the electrolyte solution. The cyclic volta-
mmograms were collected as two cycles of negative to positive
to negative potential sweeps. The applied potential was varied
over a 2 V range from -0.6 to +1.4 V.
Ru H(CO)(qu S)(P P h 3)2 (3a ,b). Quinoline-8-thiol hydro-
chloride (300 mg, 1.5 mmol) was dissolved in a mixture of 5
mL of water and 10 mL of ethanol to give a clear, cherry red
solution. This was combined with a solution of RuH2(CO)-
(PPh3)3 (450 mg, 0.5 mmol) in 100 mL of toluene. To the
biphasic mixture was added NaHCO3 (500 mg, excess) with
stirring, causing the organic phase to turn red immediately
due to dissolution of quinoline-8-thiol in the organic phase.
The mixture was heated to reflux for 2 h. The solvents were
removed completely in vacuo. The red residue was redissolved
in CH2Cl2 and the solution passed through a short column of
basic alumina (2.5 × 10 cm) to remove excess ligand. The
column was eluted with two 30 mL portions of CH2Cl2, and
the combined eluates were concentrated in vacuo to a total
volume of about 20 mL. Then, 100 mL of hexanes was layered
on top of the deep red solution. After 3 days at -20 °C a bright
red, air-stable, microcrystalline solid formed. Filtering, wash-
ing with hexanes, and drying in vacuo gave 300 mg of product
(0.37 mmol, 74%). The solid was a 1:3 mixture of the isomers
3a (minor isomer, H trans to N) and 3b (major isomer, H trans
to S). See Table 2 for NMR and IR spectroscopic data. 1H
NMR (300 MHz, CDCl3): δ 6.2-7.6 (m, 30H + 5H, overlapping
PPh3 and quinoline-8-thiolate resonances). Anal. Calcd for
[Os(η2-HD)(CO)(p yS)(P P h 3)2]BF 4 (6c). Under 1 atm of
Ar, 2a ,b (10 mg) was dissolved in 1 mL of CDCl3 and DBF4 in
Et2O (excess, obtained from the reaction of EtOD with
Et3O+BF4-) was added, resulting in an immediate color change
from yellow to almost colorless. 1H NMR (400 MHz): δ -5.7
(J (HD) ) 21 Hz). The corresponding HD complex of the minor
isomer could not be observed.
P r oton a tion of MH(CO)(L)(P P h 3)2 (M ) Ru , L ) p yS-;
M ) Ru , Os, L ) qu S-) w ith HBF 4 a t Low Tem p er a tu r e.
VT NMR Stu d ies. In a typical experiment 30 mg (0.035
C
46H37NOP2SRu: C, 67.79; H, 4.58; N, 1.72. Found: C, 67.47;
H, 4.59; N, 1.75.
OsH(CO)(qu S)(P P h 3)2 (4a ,b). OsH2(CO)(PPh3)3 (400 mg,
0.3 mmol) was dissolved in 10 mL of toluene. To this solution
was added quinoline-8-thiol (90 mg, 0.46 mmol) in 20 mL of
toluene. The solution was heated to reflux for 24 h, during
which time the color changed from red to a deep purple. The
reaction mixture was filtered through Celite and pumped down
to dryness. The residue was redisolved in 5 mL of CH2Cl2,
layered with 25 mL of hexanes, and stored at -20 °C. After
2 days the product (160 mg, 0.18 mmol, 59%) was isolated as
a deep red, microcrystalline solid. Concentrating the mother
liquor gives a second yield, usually contaminated with free
ligand. The solid is a 1:3 mixture of the isomers 4a (minor
isomer, H trans to N) and 4b (major isomer, H trans to S).
See Table 2 for NMR and IR spectroscopic data. 1H NMR (300
MHz, CDCl3): δ 6.2-7.6 (m, 30H + 5H, overlapping PPh3 and
mmol) of complex was dissolved in 0.6 mL of CD
2Cl2 under 1
atm of hydrogen gas and transferred to a 5 mm NMR tube
fitted with a septum. The sample was cooled to 195 K, and 6
µL of HBF4‚Et2O (85% in Et2O; 1 mmol ) 173 µL) was added
using a microliter syringe. The cold sample was briefly shaken
to homogenize the viscous solution and inserted into the NMR
spectrometer precooled to 193 K. Spectra were recorded
immediately in temperature intervals of 10-20 K up to room
temperature or the temperature of complete decomposition,
as indicated by the lack of signals in the hydride region in the
spectrum and formation of a precipitate.
[Ru (η2-H2)(CO)(p yS)(P P h 3)2]BF 4 a n d [Ru H(CO)(p ySH)-
(P P h 3)2]BF 4 (5). The complexes can only be observed at
temperatures below 233 K. Above that temperature irrevers-
ible loss of H2 gas and rapid decomposition occurs. 1H NMR
(CD2Cl2, 300 MHz, 193 K): δ -6.05 (br, 2H, Ru(η2-H2), 5a ),
-7.30 (br, 2H, Ru(η2-H2), 5b), -13.41 (pseudo t (dd), J (HPx)
) J (HPy) ) 18.6 Hz, 1H, RuH(pySH), 5c), 5.5-8 (m, 34 H,
overlapping signals of pyridine-2-thiolate and PPh3 protons).
31P NMR (300 MHz, CD2Cl2, 193 K): δ 36.24 (s, 5a ), 40.24 (s,
5b), 40.79 and 49.63 (br, 5c).
[Ru (η2-H2)(CO)(qu S)(P P h 3)2]BF4 an d [Ru H(CO)(qu SH)-
(P P h 3)2]BF 4 (7). The η2-H2 complex of the major isomer 7a
can only be observed for a short period of time at temperatures
below 213 K. Even at that temperature irreversible loss of
H2 gas and decomposition occurs. The complexes 7b-d can
be observed up to 273 K. Above that temperature decomposi-
tion takes place. The peak assignments are based on a 1H-
{31P} heteronuclear decoupling experiment. 1H NMR (300
MHz, CD2Cl2, 193 K): δ -5.4 (br, 2H, Ru(η2-H2), 7b), -7.5
(br, 2H, Ru(η2-H2), 7a ), -8.81 (t, J HP ) 17.8 Hz, 1H,
RuH(quSH), 7d ), 4.51 (dd, J HP ) 21.8, 8.5 Hz, 1H, RuH(quSH),
quinoline-8-thiolate resonances). Anal. Calcd for C46H37
NOOsP2S: C, 61.11; H, 4.13; N, 1.55. Found: C, 59.94; H,
4.13; N, 1.61.
-
EHMO Ca lcu la tion s on p yS-, qu S-, a n d OsH(CO)-
(p yS)(P H3)2 (2a *). The geometries of the chelates were
obtained from CHEM3D minimized models using the standard
parameter file supplied with the program.41 The geometry of
2a * was based on the X-ray data for 6a . It was assumed that
the Os-N, Os-S, and Os-C bond distances change little on
protonation of the hydride ligand in 2a . The PPh3 ligands in
2 were replaced with PH3 to allow use of the CACAO program
(39) Sheldrick, G. M. SHELXTL/PC V5.0, PC program; Siemens
Analytical X-ray Instruments, Karlsruhe, West Germany, 1990.
(40) Burrow, T. Interactive Cyclic Voltammogram Acquisition Pro-
gram (ICYVAP); Apple Macintosh program, unpublished, Toronto,
1994.
(41) CSC CHEM3D, Apple Macintosh Program, Cambridge Scien-
tific Computing, Inc., Cambridge, MA, 1993.
Schlaf, Marcel
