Synthesis, Characterization, and Reactivity of Dicationic Dihydrogen Complexes of Osmium and Ruthenium

Article abstract of DOI:10.1021/ic970975t

The dicationic complexes [Os(H₂)(PR₃)²⁺ (bpy)(CO)]²⁺ [PR₃ = PPh₃, PMePh₂ (2a.b)], [Os(H₂) (PPh₃)₂(phen)(CO)]²⁺ (2c), and [Ru(H₂)(PPh₃)2(bpy)(CO)]²⁺ (4) (bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline) have been prepared by the protonation of the corresponding monocationic hydrides using an excess of trifluoromethanesulfonic acid. The presence of a bound dihydrogen ligand is indicated by short T₁ minimum values consistent with H-H distances of 0.92-1.04 ?. For the partially deuterated derivatives, J_HD values of 25.1-31.0 Hz were observed. The dicationic complexes are strong acids, indicating that the bound H₂ is substantially activated toward heterolytic cleavage. The H₂ ligand is tightly bound to the metal center and does not undergo exchange with D₂ over the course of several weeks. The complex [Os(H₂)(PPh₃)₂(bpy)(CO)]²⁺ (2a) has been shown to be very stable in solution at room temperature. In contrast, the ruthenium analogue, [Ru(H₂)(PPh₃)₂(bpy)(CO)]²⁺ (4), decomposes in solution at room temperature but is relatively stable at temperatures less than 245 K.

Full text of DOI:10.1021/ic970975t

Inorg. Chem. 1998, 37, 127-132
127
Synthesis, Characterization, and Reactivity of Dicationic Dihydrogen Complexes of Osmium
and Ruthenium
Thomas A. Luther and D. Michael Heinekey*
Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195
ReceiVed August 1, 1997X
The dicationic complexes [Os(H2)(PR3)2(bpy)(CO)]2+ [PR3 ) PPh3, PMePh2 (2a,b)], [Os(H2)(PPh3)2(phen)(CO)]2+
(2c), and [Ru(H2)(PPh3)2(bpy)(CO)]2+ (4) (bpy ) 2,2′-bipyridine; phen ) 1,10-phenanthroline) have been prepared
by the protonation of the corresponding monocationic hydrides using an excess of trifluoromethanesulfonic acid.
The presence of a bound dihydrogen ligand is indicated by short T1 minimum values consistent with H-H distances
of 0.92-1.04 Å. For the partially deuterated derivatives, JHD values of 25.1-31.0 Hz were observed. The dicationic
complexes are strong acids, indicating that the bound H2 is substantially activated toward heterolytic cleavage.
The H2 ligand is tightly bound to the metal center and does not undergo exchange with D2 over the course of
several weeks. The complex [Os(H2)(PPh3)2(bpy)(CO)]2+ (2a) has been shown to be very stable in solution at
room temperature. In contrast, the ruthenium analogue, [Ru(H2)(PPh3)2(bpy)(CO)]2+ (4), decomposes in solution
at room temperature but is relatively stable at temperatures less than 245 K.
Introduction
complexes are surprisingly nonacidic in spite of the 2+ charge,
and the monohydride analogues are unknown. The complexes
exhibit very strong M-H2 interactions and quite long H-H
bond lengths in the H2 ligand (1.09-1.34 Å).
The preparation of dicationic dihydrogen complexes by the
protonation of monocationic hydrides was only recently re-
ported: [Os(H2)(PiPr3)2(NCMe)3]2+ by Caulton, Tilset, and
co-workers,9 [Os(H2)(dppe)2(NCMe)]2+ (dppe ) 1,2-bis(di-
phenylphosphino)ethane) by Morris and co-workers,10 [M(H2)-
(dppp)2(CO)]2+ (M ) Ru, Os; dppp ) 1,3-bis(diphenylphos-
phino)propane) by Mezzetti and co-workers,11 and, most
recently, [Fe(H2)(L)(dppe)2]2+ (L ) CO, CNH) by Morris and
co-workers.12
We recently reported the initial results of the protonation of
[OsH(PPh3)2(bpy)(CO)]+ (1a) to generate [Os(H2)(PPh3)2(bpy)-
(CO)]2+ (2a).13 We now report the results of further investiga-
tions of 2a and its analogues [Os(H2)(PMePh2)2(bpy)(CO)]2+
(2b), [Os(H2)(PPh3)2(phen)(CO)]2+ (2c), and [Ru(H2)(PPh3)2-
(bpy)(CO)]2+ (4) (bpy ) 2,2′-bipyridine, phen ) 1,10-phenan-
throline).
Since the initial discovery by Kubas and co-workers of the
transition metal dihydrogen complex W(H2)(PiPr3)2(CO)3,1 a
large number of isolable H2 complexes have been prepared, the
majority of which have been found to be singly charged cationic
species.2 While the plethora of monocationic complexes may
be due to the common synthetic route of protonating a neutral
metal hydride, an underlying aspect may be that the positive
charge confers additional stability on the H2 complexes.3 An
assessment of the effect of charge on the binding of H2 requires
the preparation of charged complexes of the form [M(H2)(L)5]n+
with ligands L comparable to those employed in the tungsten
complexes. Recently, the preparation of cationic rhenium
analogues, [Re(H2)(PR3)2(CO)3]+ and [Re(H2)(PR3)2(CNtBu)3]+,
and comparative studies with the neutral tungsten complexes
were reported.3-5
At the outset of this study the only well-characterized
dicationic complexes belonged to the osmium series [Os(H2)-
(NH3)4(L)]2+ and [Os(H2)(en)2(L)]2+ (en ) ethylenediamine).6-8
The preparation and properties of these osmium dihydrogen
dications (and monocations when L is anionic) differ greatly
from those of other known dihydrogen complexes. The
complexes are prepared by the reduction of osmium(III) and
osmium(VI) dications under acidic conditions. The dihydrogen
Results
Synthesis and Characterization of the Monocationic
Hydrides: [MH(PR3)2(N-N)(CO)]+ [M ) Os, PR3 ) PPh3,
PMePh2, N-N ) bpy (1a,b); M ) Os, PR3 ) PPh3, N-N )
phen (1c); M ) Ru, PR3 ) PPh3, N-N ) bpy (3)]. The
X Abstract published in AdVance ACS Abstracts, December 15, 1997.
(1) Kubas, G. J.; Ryan, R. R.; Swanson, B. I.; Vergamini, P. J.;
Wasserman, H. J. J. Am. Chem. Soc. 1984, 106, 451-452.
(2) Review articles: (a) Heinekey, D. M.; Oldham, W. J., Jr. Chem. ReV.
1993, 93, 913-926. (b) Morris, R. H.; Jessop, P. G. Coord. Chem.
ReV. 1992, 121, 155-289. (c) Crabtree, R. H. Acc. Chem. Res. 1990,
23, 95-101. (d) Kubas, G. J. Acc. Chem. Res. 1988, 21, 120-128.
(3) Heinekey, D. M.; Radzewich, C. E.; Voges, M. H.; Schomber, B. M.
J. Am. Chem. Soc. 1997, 119, 4172-4181.
monocationic hydrides [OsH(PR3)2(bpy)(CO)](OTf) (PR3
PPh3, PMePh2 (1a,b)), [OsH(PPh3)2(phen)(CO)](OTf) (1c), and
)
(9) Smith, K.-T.; Tilset, M.; Kuhlman, R.; Caulton, K. G. J. Am. Chem.
Soc. 1995, 117, 9473-9480.
(10) Schlaf, M.; Lough, A. J.; Maltby, P. A.; Morris, R. H. Organometallics
1996, 15, 2270-2278.
(4) Heinekey, D. M.; Voges, M. H.; Barnhart, D. M. J. Am. Chem. Soc.
1996, 118, 10792-10802.
(11) Rocchini, E.; Mezzetti, A.; Ru¨egger, H.; Burckhardt, U.; Gramlich,
V.; Del Zotto, A.; Martinuzzi, P.; Rigo, P. Inorg. Chem. 1997, 36,
711-720.
(5) Heinekey, D. M.; Schomber, B. M.; Radzewich, C. E. J. Am. Chem.
Soc. 1994, 116, 4515-4516.
(6) Li, Z.-W.; Taube, H. J. Am. Chem. Soc. 1994, 116, 9506-9513.
(7) Harman, W. D.; Taube, H. J. Am. Chem. Soc. 1990, 112, 2261-2263.
(8) Li, Z.-W.; Taube, H. J. Am. Chem. Soc. 1991, 113, 8946-8947.
(12) Forde, C. E.; Landau, S. E.; Morris, R. H. J. Chem. Soc., Dalton Trans.
1997, 1663-1664.
(13) Heinekey, D. M.; Luther, T. A. Inorg. Chem. 1996, 35, 4396-4399.
S0020-1669(97)00975-0 CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/12/1998

128 Inorganic Chemistry, Vol. 37, No. 1, 1998
Luther and Heinekey
Table 2. Selected NMR Properties of the Dicationic Dihydrogen
Complexes
Scheme 1
c
1H δa
JHD
31P δf
(∆ν1/2
b
e
complex
(∆ν1/2
)
(∆δ)d
T1
)
[Os(H2)(PPh3)2(bpy)(CO)]2+ (2a) -5.78 25.3
15.2g +8.54
(6.5)
(170)
(+18)
[Os(H2)(PMePh2)2(bpy)(CO)]2+
-6.23 25.5
16.5h -6.02
(8.4)
(2b)
(41)
(+20)
[Os(H2)(PPh3)2(phen)(CO)]2+ (2c) -5.63 25.5
6.3i +8.60
(7.0)
(39)
(< +20)
[Ru(H2)(PPh3)2(bpy)(CO)]2+ (4) -6.70j 31.0j
3.9k +32.81j
(12.6)
(110)
(< +20)
a
1H NMR chemical shift of the H2 resonance (ppm). b Half-height
c
line width (Hz). JHD value of the HD analogue measured at 500 MHz
(Hz). 1H NMR chemical shift difference between the H2 and HD
d
Table 1. Selected NMR Data for the Monocationic Hydride
resonances, δH - δHD (ppb). e T1 minimum of the H2 resonance (ms).
2
Complexesa
1P NMR chemical shift of the H2 complex (ppm). g 263 K at 500
f
MHz. h 260 K at 500 MHz. i 200 K at 200 MHz. j Recorded at 253 K.
k 240 K at 200 MHz.
1H δH
(ppm)
JHP
(Hz)
31P
δ (ppm)
complex
[OsH(PPh3)2(bpy)(CO)]+ (1a)
[OsH(PMePh2)2(bpy)(CO)]+ (1b)
[OsH(PPh3)2(phen)(CO)]+ (1c)
[RuH(PPh3)2(bpy)(CO)]+ (3)
-12.19
-12.22
-11.98
-11.31
18.4
17.6
18.1
19.6
+18.76
+0.08
+19.25
+46.53
deuterated triflic acid (DOTf) to a solution of the monocationic
hydride in CD2Cl2. The hydride region of the 1H NMR spectra
exhibit a sharp “triplet” resonance, as opposed to the broad
singlet in the H2 complexes. The intensity ratio of the three
resonances is approximately 1:1.2:1 for these complexes. The
increased intensity of the center peak of the triplet of the HD
resonances is due to the presence of a small amount of the H2
species resulting from the incomplete deuteration of the triflic
a In CD2Cl2.
[RuH(PPh3)2(bpy)(CO)](OTf) (3) were prepared as the triflate
salts as outlined in Scheme 1.
1
The H NMR spectra for 1a-c and 3 exhibit the expected
1
acid.13 The 31P{selective H} NMR spectra exhibit a singlet
phosphine proton resonances and separate resonances for each
proton in the bipyridyl or phenanthroline ligand in the aromatic
region. A triplet resonance is observed in the hydride region.
The 31P{selective 1H} NMR spectra of these complexes consist
of a single doublet resonance due to coupling to the hydride (a
selective decoupling procedure was used to decouple the proton
nuclei of the phosphine ligands). The NMR spectra are
consistent with two equivalent trans phosphines and a bipyridyl
or phenanthroline ligand with inequivalent protons as depicted
in Scheme 1 (Table 1).
resonance for the HD complex with no observable coupling.
1
We find that the H NMR spectra of the H2 complexes and
their corresponding HD analogues are essentially independent
of temperature (including JHD values) down to 165 K.
A sealed NMR tube containing 2a in CD2Cl2 and 1 atm of
D2 was monitored for a period of 2 weeks. A similar sample
was prepared containing 4 in CD2Cl2 with 1 atm of D2, stored
at 245 K, and monitored by NMR for a period of 2 months. No
1
evidence of deuterium incorporation was observed by H and
31P NMR spectroscopy in either sample.
Synthesis of [M(H2)(PR3)2(N-N)(CO)]2+ [M ) Os, N-N )
bpy, PR3 ) PPh3, PMePh2 (2a,b); M ) Os, N-N ) phen,
PR3 ) PPh3 (2c); M ) Ru, N-N ) bpy, PR3 ) PPh3 (4)].
We find that protonation can be conveniently carried out using
the triflate salt of the monocationic hydrides and excess triflic
acid (HOTf) in nitromethane or in methylene chloride (Scheme
1). The dicationic products, [Os(H2)(PR3)2(bpy)(CO)]2+ (PR3
) PPh3, PMePh2 (2a,b)) and [Os(H2)(PPh3)2(phen)(CO)]2+ (2c)
are soluble in these solvents and thermally robust, showing no
loss of H2 with only minor (estimated to be <10% as determined
by 31P NMR) decomposition occurring over a period of 18
months in CD2Cl2 at room temperature for 2a. The presence
of bases such as diethyl ether or water will immediately
deprotonate the dicationic complexes and regenerate the mono-
cationic hydrides without any loss to decomposition.
The 1H and 31P{selective 1H} NMR spectra for the ruthenium
analogue, 4, are similar to those of the other dihydrogen
dications (Table 2). However, 4 is much less robust than the
osmium dications. In fact, 4 decomposes at room temperature
but appears to be relatively stable when stored at 245 K. The
31P{selective 1H} NMR spectrum (in CD2Cl2) indicates that the
decomposition of 4 leads initially to the formation of the chloride
cation, [RuCl(PPh3)2(bpy)(CO)]OTf.
Basicity of [MH(PPh3)2(bpy)(CO)]+ [M ) Os, Ru (1a, 3)].
Approximately 4 equiv of HOTf is required to completely
generate the dication species. When a large excess (10 equiv)
of [H(Et2O)x]BAr′4 (Ar′ ) 3,5-(CF3)2C6H3) is reacted with 1a,
the formation of 2a does not occur. When [H(Et2O)]BF4 is
used for protonation, the hydride monocations are only partially
protonated. A direct basicity comparison was performed in an
NMR tube with equimolar amounts of 1a and 3. Incremental
amounts of HOTf were added, and the percentages of the mono-
and dicationic species were determined by 31P NMR spectros-
copy. The data indicate that the ruthenium complex 4 is slightly
more acidic than the osmium analogue 2a.
Attempts to isolate the dication 2a were unsuccessful.
Addition of pentane to a methylene chloride solution of 2a
resulted in precipitation of a gummy residue. The NMR spectra
of this residue are consistent with the presence of 2a and HOTf.
When a methylene chloride solution of 2a is placed under
dynamic vacuum, an oily film is observed upon the removal of
1
solvent. The H and 31P NMR spectra indicate that only 2a,
1a, and HOTf are present. There is no evidence of any product
that involves the loss of H2.
Synthesis of [MX(PPh3)2(bpy)(CO)]+ [M ) Os, Ru; X )
Cl, Br]. When N-chlorosuccinimide (NCS) is added to solutions
of 1a and 3, succinimide is generated along with a single new
complex that is formed cleanly and quantitatively by NMR. The
Preparation of [M(HD)(PR3)2(N-N)(CO)]2+ [M ) Os, N-N
) bpy, PR3 ) PPh3, PMePh2 (2a-d1,b-d1); M ) Os, N-N )
phen, PR3 ) PPh3 (2c-d1); M ) Ru, N-N ) bpy, PR3 ) PPh3
(4-d1)]. The HD complexes were prepared by addition of excess
1
aromatic region in the H NMR spectra for these complexes

Dihydrogen Complexes of Osmium and Ruthenium
Inorganic Chemistry, Vol. 37, No. 1, 1998 129
Scheme 2
dihydrogen complexes15 and smaller than what is observed in
H2/HD gas (∆δ ) +36 ppb).16 This small chemical shift
difference and the magnitude of the H-D coupling are
essentially independent of temperature, suggesting that there is
only one structure for these dicationic complexes. A rapid
equilibrium between a dihydride and a dihydrogen structure
would likely lead to temperature-dependent isotope effects
resulting from isotopic perturbation of equilibrium.17
In reported dihydrogen complexes which have been structur-
ally characterized by neutron diffraction or solid state NMR
methods, an inverse correlation between the H-H distance and
JHD of the HD analogue is observed.13 The equation corre-
sponding to the inverse relationship between rHH and JHD from
corrected neutron diffraction and solid state NMR data18 is
rHH ) 1.44 - 0.0168(JHD
)
(1)
exhibit the expected eight resonances for the inequivalent
bipyridyl protons and a narrow band for the triphenylphosphine
protons and are now lacking observable resonances in the
hydride region. The 31P{selective 1H} NMR spectra reveal only
a singlet resonance (δ -1.17 for the osmium complex and δ
+27.39 for the ruthenium analogue). The NMR spectra are
consistent with the formulation of these complexes as [OsCl-
(PPh3)2(bpy)(CO)]+ and [RuCl(PPh3)2(bpy)(CO)]+ (Scheme 2).
Complex 1a was also reacted with N-bromosuccinimide (NBS)
with similar results, the generation of succinimide and a single
new complex characterized as [OsBr(PPh3)2(bpy)(CO)]+. The
1H and 31P{selective 1H} NMR spectra for this species are very
similar to the others with a singlet resonance at δ -1.97 in the
Morris and co-workers have used a larger set of distances and
JHD values to develop a similar equation for the H-H bond
length. They have also included the uncorrected neutron data
and distances determined from X-ray diffraction data along with
the more reliable distances from solid state NMR and corrected
neutron data. However, with this larger data set, the equation
is surprisingly similar to eq 1:18a
rHH ) 1.42 - 0.0167(JHD
)
(2)
The rapid T1 relaxation of the H2 resonance of the dicationic
complexes provides another method for the determination of
the H-H distance. Quantitative analysis by the method of
Halpern and co-workers19 leads to two possible values for the
H-H distance in the dihydrogen complexes, depending upon
the relative rate of the H2 ligand rotation.20 Gusev and co-
workers21 have analyzed the T1 minimum and JHD data of
reported dihydrogen complexes that have JHD values g25 Hz.
In only a few cases, namely those with the general formula
trans-M(H2)H(P-P)2+ (M ) Fe, Ru; P-P ) chelating phosphine),
is it necessary to invoke the fast rotation model to produce a
reasonable H-H distance in the H2 ligand. In general, the
determination of the H-H distance in the H2 ligand using T1
1
31P{selective H} NMR spectrum. [RuCl(PPh3)2(bpy)(CO)]+
was also formed when a CD2Cl2 solution of 3 was allowed to
stand at room temperature for an extended period (Scheme 2).
After 6 months, the concentration of the chloride cation is
approximately the same as the concentration of 3, as determined
by the intensity of the resonances in the 31P{selective 1H} NMR
spectrum.
A solution of the ruthenium chloride cation [RuCl(PPh3)2-
(bpy)(CO)]+ was reacted with silver triflate (AgOTf) under an
atmosphere of hydrogen. The 31P{selective 1H} NMR spectrum
exhibits a new resonance at δ +15.7. After 24 h, this resonance
decreased in intensity and several new unidentified resonances
emerged. No reactions were observed between AgOTf and the
corresponding osmium monocationic chloride and bromide
complexes.
(15) Reported isotope shifts in dihydrogen complexes are generally <50
ppb. Reported exceptions: (a) ∆δ ) +90 ppb for Ru(H2)(OEP)(THF)
(OEP ) octaethylporphyrin), +130 ppb for Os(H2)(OEP)(*Im) (*Im
) 3-tert-butyl-4-phenylimidazole), and -200 ppb for Ru2(H2)(DPB)-
(*Im)2 (DPB ) 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethyl)-
porphyrinyl]biphenylene) [Collman, J. P.; Wagenknecht, P. S.; Hutch-
ison, J. E.; Lewis, N. S.; Lopez, M. A.; Guilard, R.; L’Her, M.;
Bothner-By, A. A.; Mishra, P. K. J. Am. Chem. Soc. 1992, 114, 5654-
5664]. (b) ∆δ ) +200 ppb for [Cp2Ta(CO)(H2)]+ [Moreno, B.; Sabo-
Etienne, S.; Chaudret, B.; Rodriguez, A.; Jalo´n, F.; Trofimenko, S. J.
Am. Chem. Soc. 1994, 116, 2635-2636]. (c) ∆δ ) +80 ppb for [Os-
(H2)(en)2OAc]+ (en ) ethylenediamine; OAc ) acetate) [Hasegawa,
T.; Li, Z.-W.; Parkin, S.; Hope, H.; McMullan, R. K.; Koetzle, T. F.;
Taube, H. J. Am. Chem. Soc. 1994, 116, 4352-5356].
Discussion
The 31P{selective 1H} NMR spectra of the dications display
a single sharp resonance for the equivalent phosphines as
expected for a trans structure. A bound dihydrogen ligand often
lacks observable coupling to adjacent bound phosphines.14 The
(16) Evans, D. F. Chem. Ind. 1961, 1960.
(17) Heinekey, D. M.; Oldham, W. J., Jr. J. Am. Chem. Soc. 1994, 116,
3137-3138.
1
narrowness of the line widths (∆ν1/2) in the 31P{selective H}
(18) Includes structural and solution data reported in ref 13 and recently
published data from: (a) Maltby, P. A.; Schlaf, M.; Steinbeck, M.;
Lough, A. J.; Morris, R. H.; Klooster, W. T.; Koetzle, T. F.; Srivastava,
R. C. J. Am. Chem. Soc. 1996, 118, 5396-5407. (b) King, W. A.;
Luo, X-L.; Scott, B. L.; Kubas, G. J.; Zilm, K. W. J. Am. Chem. Soc.
1996, 118, 6782-6783.
NMR spectra for the dications (6.5-12.6 Hz) imply that any
H-P coupling must be less than 3 Hz. More definitive NMR
evidence of a bound dihydrogen ligand is the observation of a
large H-D coupling in the partially deuterated analogue. The
preparation of the HD analogues of 2a-c and 4 is accomplished
by reacting the monocationic hydrides with excess DOTf. The
small upfield shift of the HD resonance from the H2 signal (∆δ
< +20 ppb) for these complexes is typical of reported
(19) Desrosiers, P. J.; Cai, L.; Lin, Z.; Richards, R.; Halpern, J. J. Am.
Chem. Soc. 1991, 113, 4173-4184.
(20) Bautista, M. T.; Earl, K. A.; Maltby, P. A.; Morris, R. H.; Schweitzer,
C. T.; Sella, A. J. Am. Chem. Soc. 1988, 110, 7031-7036.
(21) Gusev, D. G.; Kuhlman, R. L.; Renkema, K. B.; Eisenstein, O.;
Caulton, K. G. Inorg. Chem. 1996, 35, 6775-6783.
(22) Luther, T. A.; Heinekey, D. M. J. Am. Chem. Soc. 1997, 119, 6688-
6689.
(14) Heinekey, D. M.; Liegeois, A.; van Roon, M. J. Am. Chem. Soc. 1994,
116, 8388-8389.

130 Inorganic Chemistry, Vol. 37, No. 1, 1998
Luther and Heinekey
Table 3. Determination of the H-H Distance in the H2 Ligand of
the Dicationic Dihydrogen Complexes from T1 Minimum
(Fast-Rotation and Static Models) and JHD Values of the HD
Analogues
with 1a due to the larger amount of diethyl ether associated
with the acid and the water that is inevitably present.25 It is
important to note that the protonation reactions of the mono-
hydride cations were performed in CD2Cl2 and quantitation of
pKa values is difficult.26 The dicationic complexes 2a-c and
4 are extremely acidic since they will protonate diethyl ether
([H(Et2O)]+ pKa ) -2.6)27 and are similar in acid strength to
HOTf (estimated aqueous pKa ) -4.9).28,29
rHH (Å)
complex
[Os(H2)(PPh3)2(bpy)(CO)]2+ (2a)
[Os(H2)(PMePh2)2(bpy)(CO)]2+ (2b)
[Os(H2)(PPh3)2(phen)(CO)]2+ (2c)
[Ru(H2)(PPh3)2(bpy)(CO)]2+ (4)
0.82/1.03a
0.83/1.04
0.82/1.03
0.76/0.95
1.02b,c
1.01
1.02c
0.92
The instability of [Ru(H2)(PPh3)2(bpy)(CO)]2+ (4) at room
temperature in comparison with the osmium analogues is
consistent with the observed trend in the iron triad as noted by
Morris and co-workers30 and also in the complexes [M(H2)-
(dppp)2(CO)]2+ (M ) Ru, Os) as noted by Mezzetti and co-
workers.11 The H-H distance in the H2 ligand of 4, as
determined by T1 minimum and JHD data, is shorter than the
distance in the osmium analogues, consistent with a weaker
M-H2 interaction. The loss of H2 from 4 would generate the
a H-H distance calculated from the T1 minimum values for fast-
rotation/static regimes of the H2 ligand. b H-H distance calculated from
the JHD value of the HD complex and eq 1. c Distance calculated from
the corrected JHD value of 25.1 Hz.22
highly reactive 16-electron Lewis acid [Ru(PPh3)2(bpy)(CO)]2+
,
which can presumably abstract chloride from the solvent (CD2-
Cl2), forming the chloride cation [RuCl(PPh3)2(bpy)(CO)]+. The
chloride cation can also be generated from the monohydride
cation [RuH(PPh3)2(bpy)(CO)]+ (3) by the immediate and
quantitative reaction with N-chlorosuccinimide. The chloride
cation has also been observed to form via a slow reaction of 3
with the CD2Cl2 solvent over a 6 month period (Scheme 2).
The generation of a similar chloride cation was observed by
Mezzetti and co-workers11 in the decomposition of [Ru(H2)-
(dppp)2(CO)]2+
.
Figure 1. Plot of H-H distance versus JHD. The line represents the
inverse linear relationship between rHH and JHD values using eq 1. H-H
distances for the dicationic species [Os(H2)(PR3)2(bpy)(CO)]2+ (PR3
) PPh3, PMePh2) (2a,b), [Os(H2)(PPh3)2(phen)(CO)]2+ (2c), and [Ru-
(H2)(PPh3)2(bpy)(CO)]2+ (4) are calculated from the T1 minimum values
using static and fast-rotation models for the H2 ligand. The JHD values
The preparation of the chloride analogues of 1a and 3, [OsCl-
(PPh3)2(bpy)(CO)]+ and [RuCl(PPh3)2(bpy)(CO)]+, was of
interest as a possible alternative route for the preparation of the
dihydrogen dicationic complexes [Os(H2)(PPh3)2(bpy)(CO)]2+
(2a) and [Ru(H2)(PPh3)2(bpy)(CO)]2+ (4). It was recently
reported that AgOTf can be used to abstract chloride from Cp*-
Ir(PMe3)Cl2 under an atmosphere of hydrogen to cleanly
generate [Cp*Ir(PMe3)H3]+.17 However, we found the reaction
of [RuCl(PPh3)2(bpy)(CO)]+ with AgOTf under H2 at room
temperature leads to a new species which was not the expected
dihydrogen dication (no reaction occurred at lower tempera-
tures). The 31P{selective 1H} NMR spectrum exhibits a singlet
at +15.7, which is consistent with the formulation [Ru(OTf)-
(PPh3)2(bpy)(CO)]+. In contrast to the reaction of the ruthenium
chloride complex with AgOTf, there is no reaction with the
osmium chloride or bromide analogues.
for 2a-d1 and 2c-d1 have been corrected for the field-dependent residual
22
DHD
.
minimum data should consider the rotation around the M-H2
axis as static.
The determination of the H-H bond lengths in the H2 ligand
of the dications 2a-c and 4 by the T1 minimum method using
a static rotation model is in general agreement with the distances
calculated from the JHD values (Table 3 and Figure 1). The
slight overestimation of the bond length by the T1 minimum
method using the static model (<4% in these complexes) was
also reported for W(H2)(PiPr3)2(CO)3.23
The complexes [Os(H2)(PR3)2(bpy)(CO)]2+ (PR3 ) PPh3,
PMePh2) (2a,b), [Os(H2)(PPh3)2(phen)(CO)]2+ (2c), and [Ru-
(H2)(PPh3)2(bpy)(CO)]2+ (4) are extremely strong acids, as
demonstrated by their immediate deprotonation by diethyl ether.
Thus 2a-c and 4 along with the complexes recently reported
by Mezzetti and co-workers,11 [M(H2)(dppp)2(CO)]2+ (M ) Ru,
Os), and [Fe(H2)(R)(dppe)2]2+ (R ) CO, CNH) reported by
Morris and co-workers12 represent an interesting combination
of high reactivity toward heterolysis and very tight binding of
H2. In contrast to the properties of this group of dihydrogen
A relatively long H-H distance is consistent with the tight
binding of H2 to the metal center. A common route for partial
incorporation of deuterium into the H2 ligand of dihydrogen
complexes is to expose the complex to deuterium gas. The
incorporation is proposed to occur by isotopic scrambling due
to the combination of the lability and the acidity of the H2
ligand.24 An example of deuterium incorporation by this route
is the reaction of [Re(H2)(PCy3)2(CNtBu)3]+ with D2.4 We have
found no observable deuterium incorporation when samples of
2a and 4 (maintaining temperatures of <245 K for 4) were
exposed to D2 for extended periods.
It has been found that an excess of triflic acid is required to
protonate the monocationic hydrides. A large excess of
[H(Et2O)]BF4 will only partially generate the dications, presum-
ably due to the presence of diethyl ether. The dication 2a was
not observed when 10 equiv of [H(Et2O)x]BAr′4 was reacted
(25) Radzewich, C. E. Ph.D. Thesis, University of Washington, 1997.
(26) Kristja´nsdo´ttir, S. S.; Norton, J. R. In Transition Metal Hydrides;
Dedieu, A., Ed.; VCH: New York, 1992; Chapter 9, pp 324-334.
(27) The pKa of protonated diethyl ether in aqueous sulfuric acid:
Perdoncin, G.; Scorrano, G. J. Am. Chem. Soc. 1977, 99, 6983-6986.
(28) Fujinaga, T.; Sakamoto, I J. Electroanal. Chem. 1977, 85, 185-201.
(29) The aqueous pKa of HOTf has also been estimated to be <-10: Cox,
R. A.; Krull, U. J.; Thompson, M.; Yates, K. Anal. Chim. Acta 1979,
106, 51-57.
(23) Kubas, G. J.; Unkefer, C. J.; Swanson, B. I.; Fukushima, E. J. Am.
Chem. Soc. 1986, 108, 7000-7009.
(24) Albeniz, A. C.; Heinekey, D. M.; Crabtree, R. H. Inorg. Chem. 1991,
30, 3632-3632.
(30) Cappellani, E. P.; Drouin, S. D.; Jia, G.; Maltby, P. A.; Morris, R.
H.; Schweitzer, C. T. J. Am. Chem. Soc. 1994, 116, 3375-3388.

Dihydrogen Complexes of Osmium and Ruthenium
Inorganic Chemistry, Vol. 37, No. 1, 1998 131
Experimental Section
Table 4. Properties of the Acidic Dicationic Dihydrogen
Complexes
General Procedures. Manipulations of air-sensitive complexes were
performed under argon using standard vacuum-line, Schlenk, or syringe
techniques. Argon was deoxygenated and dried by passage through
R3-11 CuO catalyst (BASF) followed by Mallinckrodt Aquasorb
containing P2O5. CD2Cl2 and CD3NO2 (Cambridge Isotope Labora-
tories) were vacuum-distilled from CaH2. OsO4 was purchased from
Stevens Metallurgical Inc. RuCl3‚3H2O was purchased from Alfa
Products. All other solvents and reagents were used without further
purification, except for CH2Cl2, which was vacuum-distilled from CaH2.
Elemental analyses were performed by Canadian Microanalytical
Services, Delta, British Columbia, Canada. Infrared spectra were
recorded on a Perkin-Elmer model 1600 Fourier transform spectro-
photometer (2.0 cm-1 resolution). Samples were examined on NaCl
cells as Nujol mulls.
a
b
c
complex
E1/2
JHD
rHH stabilityd
[Os(H2)(PiPr3)2(NCMe)3]2+ e
[Os(H2)(dppe)2(NCMe)]2+ g
[Fe(H2)(CNH)(dppe)2]2+ i
[Os(H2)(bpy)2(CO)]2+ j
1.9 25.5 1.01
f
h
2.1 21.4 1.08 H2/D2
2.3 32.5 0.89 stable
2.4 29.0 0.95 24 hk
2.6 25.1l 1.02 stable
[Os(H2)(PPh3)2(bpy)(CO)]2+ (2a)
[Os(H2)(PMePh2)2(bpy)(CO)]2+ (2b) 2.6 25.5 1.01 stable
[Os(H2)(PPh3)2(phen)(CO)]2+ (2c)
[Os(H2)(dppp)2(CO)]2+m
2.6 25.1l 1.02 stable
2.7 32.0 0.90 stable
[Ru(H2)(PPh3)2(bpy)(CO)]2+ (4)
[Fe(H2)(CO)(dppe)2]2+ i
2.9 31.0n 0.92 unstable
3.0 33.1 0.88 stable
3.0 34.2o 0.87 unstable
[Ru(H2)(dppp)2(CO)]2+ m
a Calculated E1/2 of the N2 analogue (V).32 JHD of the HD analogue
(Hz). c Calculated from the JHD value of the HD analogue using eq 1
(Å). d Stability with respect to loss of H2 at room temperature.
e Reference 9. f Not reported. g Reference 10. h Exchanges slowly with
D2. i Reference 12. j Reference 13. k Loss of H2 occurs after 24 h.
l Corrected JHD value.22 m Reference 11. n Measured at 253 K. o Mea-
sured at 193 K.
b
1H NMR spectra were recorded on Bruker AC200, DPX200, AF300,
and AM500 spectrometers and referenced internally to the residual
proton resonance of the deuterated solvent with respect to TMS. 31P-
1
{selective H} NMR spectra were recorded on Bruker AC200 (31P:
81.02 MHz) and AM500 (31P: 202.46 MHz) spectrometers and
referenced externally to 85% H3PO4. 13C{1H} NMR spectra were
recorded on Bruker AF300 (13C: 75.47 MHz) and AM500 (13C: 125.76
MHz) spectrometers and referenced internally to the carbon resonance
of the solvent relative to TMS. Variable-temperature 1H NMR
experiments were conducted using a AM500 spectrometer equipped
with a Bruker B-VT 1000 temperature control module with a copper-
constantan thermocouple. Proton T1 studies were performed using the
standard inversion recovery 180°-τ-90° pulse sequence method.34
Temperature calibration was accomplished by following the Van Geet
methanol calibration method.35 Deuterated trifluoromethanesulfonic
acid (DOTf) was prepared by reacting equimolar quantities of trifluo-
romethanesulfonic anhydride and D2O which was deoxygenated by three
freeze-pump-thaw cycles and stored under Ar. 1H NMR chemical
dications, highly acidic dihydrogen complexes such as [Ru(H2)-
Cp*(CO)2]+ are very labile with respect to loss of H2,31 while
the dicationic H2 complexes such as [Os(H2)(NH3)4(L)]2+ and
[Os(H2)(en)2(L)]2+ reported by Taube and co-workers, which
tightly bind H2, are not acidic.6-8 The two other dicationic
complexes [Os(H2)(PiPr3)2(NCMe)3]2+ reported by Tilset, Caul-
ton, and co-workers,9 and [Os(H2)(dppe)2(NCMe)]2+, reported
by Morris and co-workers,10 represent an intermediate level of
reactivity toward heterolysis and binding of the H2 ligand. The
lability of the H2 ligand has been demonstrated in the generation
of the HD complex [Os(HD)(dppe)2(NCMe)]2+ by slow, revers-
ible H2/D2 ligand exchange. On the basis of the similarity in
the calculated E1/2 values for the corresponding N2 analogues32
of the two complexes, [Os(H2)(PiPr3)2(NCMe)3]2+ may also
show reversible H2 loss comparable with that of [Os(H2)(dppe)2-
(NCMe)]2+ (Table 4).
shift differences between the H2 and HD resonances (∆δ ) δH - δHD
)
2
were determined using 180°-τ-90° pulse sequences with delays
designed to separately nullify the H2 and HD resonances in the
deuterated sample. OsH(Cl)(PPh3)3(CO),36 RuH(Cl)(PPh3)3(CO),36
[OsH(PPh3)2(bpy)(CO)](OSO2CF3) (1a),13 [Os(H2)(PPh3)2(bpy)(CO)]-
(OSO2CF3)2 (2a),13 and [H(Et2O)x](BAr′4)37 were prepared by published
procedures.
[OsH(PPh3)2(bpy)(CO)](OSO2CF3) (1a). Additional data are as
follows. 1H NMR (CD2Cl2): δ 8.62 (1 H, d, JHH ) 5.3 Hz), 7.54 (1
H, d, JHH ) 5.3 Hz) 6,6′-bipyridyl, 8.13 (2 H, d, JHH ) 8.1 Hz) 3,3′-
bipyridyl, 7.79 (1 H, t, JHH ) 7.9 Hz), 7.72 (1 H, t, JHH ) 7.9 Hz)
4,4′-bipyridyl, 7.05 (1 H, t, JHH ) 6.5 Hz), 6.38 (1 H, t, JHH ) 6.5 Hz)
The stability of the dicationic dihydrogen complexes is
surprising in light of the calculated oxidation potential33 of the
corresponding dinitrogen complexes. It was predicted that if
the oxidation potential of the N2 complex was greater than 2
V, the π back-donation from the metal center to the dihydrogen
ligand would not be sufficient for a stable M-H2 complex.32
The formal charge of the metal center in these dicationic
complexes apparently increases the M-H2 σ interaction,
strengthening the binding of the H2 ligand.
5,5′-bipyridyl, 7.33-7.23 (m, 30 H, P(C6H5)3), -12.19 (t, 1 H, JHP
)
18.4 Hz, OsH, T1 min ) 500 ms (247 K, 500 MHz)). 31P{selective
1H} NMR (CD2Cl2): δ 18.76 (d, JPH ) 17 Hz). 13C{1H} NMR (CD2-
Cl2): δ 186.56 (t, JCP ) 10.8 Hz, CO), 155.6, 154.9 (2,2′-bipyridyl),
155.2, 153.7 (6,6′-bipyridyl), 138.1, 137.3 (4,4′-bipyridyl), 127.6, 127.2
(5,5′-bipyridyl), 124.2, 123.8 (3,3′-bipyridyl), 133.4 (t, JCP ) 5.4 Hz,
o-C6H5), 131.2 (t, JCP ) 25.4 Hz, ipso-C6H5), 130.7 (s, p-C6H5), 128.9
(t, JCP ) 4.5 Hz, m-C6H5). Anal. Calcd for C48H39N2F3O4P2SOs: C,
54.96; H, 3.75; N, 2.67. Found: C, 54.52; H, 3.80; N, 2.66. IR
(Nujol): ν(OsH) ) 2081 cm-1, ν(CO) ) 1923 cm-1 (s).
Conclusions
The complexes [Os(H2)(PR3)2(bpy)(CO)]2+ (PR3 ) PPh3,
PMePh2) (2a,b), [Os(H2)(PPh3)2(phen)(CO)]2+ (2c), and [Ru-
(H2)(PPh3)2(bpy)(CO)]2+ (4) are formulated as dihydrogen
complexes with H-H distances of 0.92-1.02 Å. The osmium
complexes are extremely acidic and exhibit very strong M-H2
interactions as evidenced by long H-H distances and the
nonlability of the H2 ligand. The ruthenium complex 4 is
relatively stable at temperatures less than 245 K but decomposes
at room temperature and is also slightly more acidic than the
osmium analogues.
OsH(Cl)(PMePh2)3(CO). This was prepared using conditions
similar to those reported for OsH(Cl)(PPh3)3(CO) with the substitution
of PMePh2 for PPh3. 1H NMR (C6D6): δ 7.82-6.63 (m, 30 H, PCH3-
(C6H5)2), 2.30 (s, 6 H, PCH3(C6H5)2), 1.90 (s, 3 H, PCH3(C6H5)2), -6.45
(dt, 1 H, JHP ) 85.3 Hz, JHP ) 22.2 Hz, OsH). 31P{1H} NMR
trans
cis
(C6D6): δ -20.1 (t, JPP ) 13 Hz), -23.3 (d, JPP ) 13 Hz).
[OsH(PMePh2)2(bpy)(CO)](OSO2CF3) (1b). This was prepared
under conditions similar to those for 1a using OsH(Cl)(PMePh2)3(CO).
(34) Hamilton, D. G.; Crabtree, R. H. J. Am. Chem. Soc. 1988, 110, 4126-
4133.
(35) Van Geet, A. L. Anal. Chem. 1970, 42, 679-680.
(36) Ahmad, N.; Levinson, J. J.; Robinson, S. D.; Uttley, M. F. Inorg.
Synth. 1974, 15, 45-64.
(37) Brookhart, M.; Grant, B.; Volpe, A. F., Jr. Organometallics 1992, 11
3920-3922.
(31) Chinn, M. S.; Heinekey, D. M.; Payne, N. G.; Sofield, C. D.
Organometallics 1989, 8, 1824-1826.
(32) Morris, R. H. Inorg. Chem. 1992, 31, 1471-1478.
(33) Lever, A. B. P. Inorg. Chem. 1990, 29, 1271-1285.

132 Inorganic Chemistry, Vol. 37, No. 1, 1998
Luther and Heinekey
1H NMR (CD2Cl2): δ 8.61-6.92 (m, 28 H, bipyridyl and PCH3(C6H5)2),
1.75 (t, 6 H, JHP ) 3.2 Hz, PCH3(C6H5)2), -12.22 (t, 1 H, JHP ) 17.6
Table 5. Protonation Comparison of [OsH(PPh3)2(bpy)(CO)]+ (1a)
and [RuH(PPh3)2(bpy)(CO)]+ (3) with Triflic Acida
1
Hz, OsH). 31P {selective H} NMR (CD2Cl2): δ 0.08 (d, JPH ) 14
no. of equiv of HOTf
% 1a
% 2a
% 3
% 4
Hz).
1
2
3
4
100
58
16
0
0
42
84
100
79
40
0
0
21
60
[OsH(PPh3)2(phen)(CO)](OSO2CF3) (1c). This was prepared under
conditions similar to those for 1a substituting phenanthroline for
bipyridine. 1H NMR (CD2Cl2): δ 9.02 (1 H, d, JHH ) 4.9 Hz), 7.95
(1 H, d, JHH ) 5.2 Hz) 2,9-phenanthroline, 8.28 (1 H, d, JHH ) 8.1
Hz), 8.21(1 H, d, JHH ) 8.1 Hz) 4,7-phenanthroline, 7.91 (2 H, s) 5,6-
phenanthroline, 6.84 (1 H, d, JHH ) 5.3 Hz), 6.83 (1 H, d, JHH ) 5.3
Hz) 3,8-phenanthroline, 7.29-7.10 (m, 30 H, P(C6H5)3), -11.98 (t, 1
100
100
a Samples were prepared and maintained at temperatures of 195-
265 K, and relative concentrations were determined by integration of
1
the resonances in the 31P{selective H} NMR spectra recorded at 222
1
H, JHP ) 18.1 Hz, OsH). 31P{selective H} NMR (CD2Cl2): δ 19.25
K.
(d, JPH ) 17 Hz). IR (Nujol): ν(OsH) ) 2063 cm-1, ν(CO) ) 1929
cm-1 (s).
amounts of HOTf (4-12 µL) or [H(Et2O)]BF4 (8-33 µL) were added
via a gastight microsyringe under a flow of Ar, and the tube was sealed.
The basicity study with [H(Et2O)x]BAr′4 (Ar′ ) 3,5-(CF3)2C6H3) (174
mg) and 1a (21 mg, 0.020 mmol) was performed by adding both solids
to a sealable NMR tube and vacuum-transferring CD2Cl2 (0.5 mL) to
the solids. The tube was evacuated and flame-sealed.
The comparative basicity study was carried out by adding 1a (30
mg, 0.029 mmol) and 3 (28 mg, 0.029 mmol) to an NMR tube equipped
with a J. Young Teflon valve. CD2Cl2 (0.5 mL) was vacuum-transferred
to the solids and dissolved. Incremental amounts of HOTf (5-20 µL)
were added via a gastight microsyringe under a flow of Ar, and the
tube was sealed. The concentrations were obtained from integration
of the 31P{selective 1H} NMR spectra. Due to decomposition at room
temperature, the basicity measurements involving 3 were performed
at 222 K (Table 5).
[RuH(PPh3)2(bpy)(CO)](OSO2CF3) (3). This was prepared under
conditions similar to those for 1a using RuH(Cl)(PPh3)3(CO). 1H NMR
(CD2Cl2): δ 8.64 (1 H, d, JHH ) 4.8 Hz), 7.59 (1 H, d, JHH ) 5.0 Hz)
6,6′-bipyridyl, 8.05 (1 H, d, JHH ) 9.1 Hz), 8.03 (1 H, d, JHH ) 9.7
Hz) 3,3′-bipyridyl, 7.81 (1 H, t, JHH ) 7.7 Hz), 7.69 (1 H, t, JHH ) 7.7
Hz) 4,4′-bipyridyl, 7.15 (1 H, t, JHH ) 6.2 Hz), 6.44 (1 H, t, JHH ) 6.4
Hz) 5,5′-bipyridyl, 7.35-7.25 (m, 30 H, P(C6H5)3), -11.31 (t, 1 H,
JHP ) 19.6 Hz, RuH, T1 min ) 193 ms (205 K, 200 MHz), T1 min )
475 ms (252 K, 500 MHz)). 31P{selective 1H} NMR (CD2Cl2): δ 46.5
(d, JPH ) 18 Hz, T1 min ) 616 ms (202 K, 202 MHz)). 13C{1H} NMR
(CD2Cl2): δ 204.9 (t, JCP ) 14.9 Hz, CO), 155.0, 153.7 (6,6′-bipyridyl),
154.3, 153.9 (2,2′-bipyridyl), 138.1, 137.9 (4,4′-bipyridyl), 126.8, 126.6
(5,5′-bipyridyl), 123.5, 123.4 (3,3′-bipyridyl), 133.4 (t, JCP ) 5.7 Hz,
o-C6H5), 131.7 (t, JCP ) 22.1 Hz, ipso-C6H5), 130.6 (s, p-C6H5), 128.9
(t, JCP ) 4.4 Hz, m-C6H5). Anal. Calcd for C48H39N2F3O4P2SRu‚-
CH2Cl2: C, 56.33; H, 3.96; N, 2.68. Found: C, 56.64; H, 3.93; N,
2.75.
[RuCl(PPh3)2(bpy)(CO)](OSO2CF3). [RuH(PPh3)2(bpy)(CO)](OSO2-
CF3) (3) (8 mg, 0.01 mmol) and N-chlorosuccinimide (2 mg, 0.02
mmol) were added to a sealable NMR tube. CD2Cl2 (0.5 mL) was
vacuum-transferred to the solids. Diethyl ether (2 mL) was added to
the solution via syringe under a flow of Ar. The resulting precipitate
was washed with diethyl ether (2 × 2 mL) and the excess solvent
removed with a pipet. The solids were dried in vacuo overnight. CD2-
Cl2 (0.5 mL) was added via vacuum transfer, and the tube was flame-
sealed. 1H NMR (CD2Cl2): δ 8.47-6.43 (bipyridyl and P(C6H5)3).
[Os(H2)(PMePh2)2(bpy)(CO)](OSO2CF3)2 (2b). This was prepared
using conditions similar to those reported for 2a and 2a-d1. 1H NMR
(CD2Cl2): δ 8.46-7.03 (m, 28 H, bipyridyl and PCH3(C6H5)2), 1.81
(t, 6 H, JHP ) 3.8 Hz, PCH3(C6H5)2), -6.23 (s, 2 H, Os(H2), ∆ν1/2
)
41 Hz, T1 min ) 16.5 ms (260 K, 500MHz)). 31P{1H} NMR (CD2-
Cl2): δ -6.02 (s, ∆ν1/2 ) 8.4 Hz). For 2b-d1: JHD ) 25.5 Hz, ∆δ )
+20 ppb.
1
31P{selective H} NMR (CD2Cl2): δ 27.38 (s).
[Os(H2)(PPh3)2(phen)(CO)](OSO2CF3)2 (2c). This was prepared
using conditions similar to those reported for 2a and 2a-d1. 1H NMR
(CD2Cl2): δ 8.58 (d, 1 H, JHH ) 8.2 Hz), 8.49 (d, 1 H, JHH ) 8.2 Hz),
8.44 (d, 1 H, JHH ) 4.7 Hz), 8.28 (d, 1 H, JHH ) 4.8 Hz), 8.09 (m, 2
H), 7.37 (dd, 2H, JHH ) 5.4 Hz, JHH ) 5.5 Hz), 7.45 (t, 6 H, JHH ) 7.5
Hz, p-P(C6H5)3), 7.26 (t, 12 H, JHH ) 7.3 Hz, o-P(C6H5)3), 6.94 (dt, 12
H, JHH ) 6.0 Hz JHH ) 6.1 Hz, m-P(C6H5)3), -5.63 (s, 2 H, Os(H2),
∆ν1/2 ) 39 Hz, T1 min ) 6.3 ms (200 K, 200MHz)). 31P{selective
[OsCl(PPh3)2(bpy)(CO)](OSO2CF3). This was prepared as above
using [OsH(PPh3)2(bpy)(CO)](OSO2CF3) (1a). 1H NMR (CD2Cl2): δ
8.40 (1 H, d, JHH ) 8.0 Hz), 8.25 (1 H, d, JHH ) 8.0 Hz) 3,3′-bipyridyl,
8.32 (1 H, d, JHH ) 5.2 Hz), 7.62 (1 H, d, JHH ) 5.7 Hz) 6,6′-bipyridyl,
7.96 (1 H, t, JHH ) 7.5 Hz), 7.65 (1 H, t, JHH ) 7.7 Hz) 4,4′-bipyridyl,
6.97 (1 H, t, JHH ) 6.3 Hz), 6.48 (1 H, t, JHH ) 6.5 Hz) 5,5′-bipyridyl,
7.35-7.23 (m, 30 H, P(C6H5)3). 31P{selective 1H} NMR (CD2Cl2): δ
-0.33 (s).
1H} NMR (CD2Cl2): δ 8.60 (s, ∆ν1/2 ) 7.0 Hz). For 2c-d1: JHD
25.5 Hz, ∆δ < +20 ppb.
)
[OsBr(PPh3)2(bpy)(CO)](OSO2CF3). This was prepared as above
using N-bromosuccinimide. 1H NMR (CD2Cl2): δ 8.50 (1 H, d, JHH
) 8.0 Hz), 8.34 (1 H, d, JHH ) 7.9 Hz) 3,3′-bipyridyl, 8.42 (1 H, d,
JHH ) 5.1 Hz), 7.65 (1 H, d, JHH ) 6.6 Hz) 6,6′-bipyridyl, 7.96 (1 H,
t, JHH ) 7.6 Hz), 7.66 (1 H, t, JHH ) 8.0 Hz) 4,4′-bipyridyl, 6.89 (1 H,
t, JHH ) 6.4 Hz), 6.46 (1 H, t, JHH ) 6.4 Hz) 5,5′-bipyridyl, 7.34-7.21
(m, 30 H, P(C6H5)3). 31P{selective 1H} NMR (CD2Cl2): δ -1.97 (s).
Reaction of [RuCl(PPh3)2(bpy)(CO)](OSO2CF3) with AgOSO2CF3
and H2. [RuCl(PPh3)2(bpy)(CO)](OSO2CF3) (8 mg, 0.01 mmol) and
silver triflate (2 mg, 1 mmol) were added to an NMR tube equipped
with a J. Young Teflon valve. The NMR tube was evacuated, CD3-
NO2 (0.5 mL) was vacuum-transferred to the sample, and H2 (800 Torr)
was added. 1H NMR (CD3NO2): δ 8.74-7.09 (bipyridyl and
[Ru(H2)(PPh3)2(bpy)(CO)](OSO2CF3)2 (4). This was prepared
using conditions similar to those reported for 2a and 2a-d1 with the
added precautions that the sample was kept at 195 K until inserted
into the precooled NMR probe and spectra were recorded at temper-
atures less than 273 K. 1H NMR (CD2Cl2, 253 K): δ 8.02-7.01 (m,
8 H, bipyridyl), 7.50 (t, 6 H, JHH ) 7.4 Hz, p-P(C6H5)3), 7.33 (t, 12 H,
JHH ) 7.7 Hz, o-P(C6H5)3), 7.08 (dt, 12 H, JHH ) 6.5 Hz, JHH ) 6.7
Hz, m-P(C6H5)3), -6.70 (s, 2 H, Ru(H2), ∆ν1/2 ) 110 Hz, T1 min )
3.9 ms (240 K, 200 MHz)). 31P{selective 1H} NMR (CD2Cl2, 253 K):
δ 32.81 (s, ∆ν1/2 ) 12.6 Hz). For 4-d1: JHD ) 31.0 Hz, ∆δ < +20
ppb.
Basicity Measurements of [OsH(PPh3)2(bpy)(CO)](OSO2CF3)
(1a) and [RuH(PPh3)2(bpy)(CO)](OSO2CF3) (3). The individual
basicity studies were performed by adding either 1a (20-22 mg, 0.019-
0.021 mmol) or 3 (20-22 mg, 0.021-0.023 mmol) to an NMR tube
equipped with a J. Young Teflon valve. CD2Cl2 (0.5 mL) was vacuum-
transferred to the tube, and the solids were dissolved. Incremental
1
P(C6H5)3). 31P{selective H} NMR (CD3NO2): δ 15.7 (s).
Acknowledgment. This research was supported by the
National Science Foundation.
IC970975T