Synthesis, characterization, and acidity properties of [MCl(H2)(L)(PMP)]BF4 (M = Ru, L = PPh3, CO; M = Os, L = PPh3; PMP = 2,6-(Ph2PCH2)2C5H3N)

Article abstract of DOI:10.1021/om970207+

Treatment of RuCl₂(PPh₃)₃ with PMP (PMP = 2,6-(Ph₂PCH₂)₂C₅H₃N) in acetone produced RuCl₂(PPh₃)(PMP), which has been characterized by X-ray diffra

Full text of DOI:10.1021/om970207+

Organometallics 1997, 16, 3941-3949
3941
Syn th esis, Ch a r a cter iza tion , a n d Acid ity P r op er ties of
[MCl(H2)(L)(P MP )]BF 4 (M ) Ru , L ) P P h 3, CO; M ) Os, L
) P P h 3; P MP ) 2,6-(P h 2P CH2)2C5H3N)
Guochen J ia,* Hon Man Lee, and Ian D. Williams
Department of Chemistry, The Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong
Chak Po Lau* and Yuzhong Chen
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic
University, Hung Hom, Kowloon, Hong Kong
Received March 13, 1997X
Treatment of RuCl2(PPh3)3 with PMP (PMP ) 2,6-(Ph2PCH2)2C5H3N) in acetone produced
RuCl2(PPh3)(PMP), which has been characterized by X-ray diffraction. Treatment of RuCl2-
(PPh3)(PMP) with NaBH4 in methanol gave RuHCl(PPh3)(PMP), acidification of which with
HBF4‚Et2O produced the molecular dihydrogen complex [RuCl(H2)(PPh3)(PMP)]BF4. Treat-
ment of RuHCl(CO)(PPh3)3 with PMP in benzene produced RuHCl(CO)(PMP), which reacted
with HBF4‚Et2O to give the molecular dihydrogen complex [RuCl(H2)(CO)(PMP)]BF4. The
osmium molecular dihydrogen complex [OsCl(H2)(PPh3)(PMP)]BF4 was prepared by proton-
ation of OsHCl(PPh3)(PMP) with HBF4‚Et2O. Relative acidities of the dihydrogen complexes
were investigated by NMR spectroscopy of equilibrium reactions conducted in CD2Cl2. [RuCl-
(H2)(CO)(PMP)]BF4 is more acidic than [RuCl(H2)(PPh3)(PMP)]BF4, which is in turn more
acidic than its osmium analog [OsCl(H2)(PPh3)(PMP)]BF4.
In tr od u ction
have been reported.8-11 However, a generalization in
the trend in the acidity of isostructural dihydrogen
complexes is complicated by the fact that H-H interac-
tions could have a significant effect on the acidity. The
presence of a strong H-H interaction may make dihy-
drogen complexes less acidic than may be suggested by
the general trend in the acidity of classic hydride
The acid-base properties of transition metal hydride
complexes have attracted considerable attention.1 It is
now well-established that the acidity of hydride com-
plexes is strongly influenced by the metal as well as the
auxiliary ligands. With a few exceptions,1c,2 the acidity
of isostructural classic hydride complexes decreases as
ligands become more electron donating and as the metal
is replaced successively by heavier metals in the same
group.3-6
(7) (a) Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 789.
(b) Heinekey, D. M.; Oldham, W. J ., J r. Chem. Rev. 1993, 93, 913. (c)
J essop, P. G.; Morris, R. H. Coord. Chem. Rev. 1992, 121, 155. (d)
Crabtree, R. H.; Hamilton, D. G. Adv. Organomet. Chem. 1988, 28,
289.
Dihydrogen complexes are an interesting class of
(8) (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. (b) Schlaf, M.; Lough, A. J .; Maltby, P. A.; Morris,
R. H. Organometallics 1996, 15, 2270. (c) Chin, B.; Lough, A. J .; Morris,
R. H.; Schweitzer, C. T.; D’Agostino, C. Inorg. Chem. 1994, 33, 6278.
(d) Cappellani, E. P.; Drouin, S. D.; J ia, G.; Maltby, P. A.; Morris, R.
H.; Schweitzer, C. T. J . Am. Chem. Soc. 1994, 116, 3375. (e) Lough, A.
J .; Park, S.; Ramachandran, R.; Morris, R. H. J . Am. Chem. Soc. 1994,
116, 8356. (f) Schlaf, M.; Lough, A. J .; Morris, R. H. Organometallics
1993, 12, 3808. (g) J ia, G.; Morris, R. H. J . Am. Chem. Soc. 1991, 113,
875. (h) J ia, G.; Morris, R. H. Inorg. Chem. 1990, 29, 581.
(9) (a) Chinn, M. S.; Heinekey, D. M. J . Am. Chem. Soc. 1990, 112,
5166. (b) Chinn, M. S.; Heinekey, D. M.; Payne, N. G.; Sofield, C. D.
Organometallics 1989, 8, 1824. (c) Chinn, M. S.; Heinekey, D. M. J .
Am. Chem. Soc. 1987, 109, 5865.
hydride complexes7 for which a wide range of pKa values
X Abstract published in Advance ACS Abstracts, August 1, 1997.
(1) (a) Angelici, R. J . Acc. Chem. Res. 1995, 28, 51. (b) Kristja´ns-
do´ttir, S. S.; Norton, J . R. Recent Advances in Theory and Experiment.
In Transition Metal Hydrides; Dedieu, A., Ed.; VCH: New York, 1992.
(c) Pearson, R. G. Chem. Rev. 1985, 85, 41.
(2) (a) Sowa, J . R., J r.; Bonanno, J . B.; Zanotti, V.; Angelici, R. J .
Inorg. Chem. 1992, 31, 1370. (b) Sowa, J . R., J r.; Zanotti, V.; Facchin,
G.; Angelici, R. J . J . Am. Chem. Soc. 1992, 114, 160. (c) Vidal, J . L.;
Walker, W. E. Inorg. Chem. 1981, 20, 249. (d) Kruck, T.; Lang, W.;
Derner, N.; Stadler, M. Chem. Ber. 1968, 101, 3816.
(3) (a) Kristja´nsdo´ttir, S. S.; Loendorf, A. J .; Norton, J . R. Inorg.
Chem. 1991, 30, 4470. (b) Kristja´nsdo´ttir, S. S.; Moody, A. E.; Weberg,
R. T.; Norton, J . R. Organometallics 1988, 7, 1983. (c) Edidin, R. T.;
Sullivan, J . M.; Norton, J . R. J . Am. Chem. Soc. 1987, 109, 3945. (d)
Moore, E. J .; Sullivan, J . M.; Norton, J . R. J . Am. Chem. Soc. 1986,
108, 2257. (e) J ordan, R. F.; Norton, J . R. J . Am. Chem. Soc. 1982,
104, 1255.
(4) (a) Skagestad, V.; Tilset, M. J . Am. Chem. Soc. 1993, 115, 5077.
(b) Smith, K. T.; Rømming, C.; Tilset, M. J . Am. Chem. Soc. 1993, 115,
8681 and references therein. (c) Parker, V. D.; Handoo, K. L.; Roness,
F.; Tilset, M. J . Am. Chem. Soc. 1991, 113, 7493.
(5) (a) Wang, D.; Angelici, R. J . Inorg. Chem. 1996, 35, 1321. (b)
Rottink, M. K.; Angelici, R. J . J . Am. Chem. Soc. 1993, 115, 7267. (c)
Rottink, M. K.; Angelici, R. J . Inorg. Chem. 1993, 32, 3282. (d) Sowa,
J . R., J r.; Zanotti, V.; Angelici, R. J . Inorg. Chem. 1993, 32, 848 and
references therein.
(6) (a) Lemke, F. R.; Brammer, L. Organometallics 1995, 14, 3980.
(b) Protasiewicz, J . D.; Theopold, K. H. J . Am. Chem. Soc. 1993, 115,
5559. (c) J ia, G.; Lough, A. J .; Morris, R. H. Organometallics 1992,
11, 161.
(10) Rocchini, E.; Mezzetti, A.; Ru¨egger, H.; Burckhardt, U.; Gram-
lich, V.; Del Zotto, A.; Martinuzzi, P.; Rigo, P. Inorg. Chem. 1997, 36,
711.
(11) For additional reports on the deprotonation reactions of dihy-
drogen complexes, see for example: (a) Crabtree, R. H.; Lavin, M. J .
Chem. Soc., Chem. Commun. 1985, 794. (b) Crabtree, R. H.; Lavin,
M.; Bonneviot, L. J . Am. Chem. Soc. 1986, 108, 4032. (c) Baker, M. V.;
Field, L. D.; Young, D. J . J . Chem. Soc., Chem. Commun. 1988, 546.
(d) Van Der Sluys, L. S.; Miller, M. M.; Kubas, G. J .; Caulton, K. G. J .
Am. Chem. Soc. 1991, 113, 2513. (e) Bianchini, C.; Perez, P. J .;
Peruzzini, M.; Zanobini, F.; Vacca, A. Inorg. Chem. 1991, 30, 279. (f)
Sellmann, D.; Ka¨ppler, J .; Moll, M. J . Am. Chem. Soc. 1993, 115, 1830.
(g) Mudalige, D. C.; Rettig, S. J .; J ames, B. R.; Cullen, W. R. J . Chem.
Soc., Chem. Commun. 1993, 830. (h) Bianchini, C.; Linn, K.; Masi, D.;
Peruzzini, M.; Polo, A.; Vacca, A.; Zanobini, F. Inorg. Chem. 1993, 32,
2366. (i) Heinekey, D. M.; Voges, M. H.; Barnhart, D. M. J . Am. Chem.
Soc. 1996, 118, 10792. (j) Heinekey, D. M.; Luther, T. A. Inorg. Chem.
1996, 35, 4396.
S0276-7333(97)00207-0 CCC: $14.00 © 1997 American Chemical Society

3942 Organometallics, Vol. 16, No. 18, 1997
J ia et al.
Sch em e 1
complexes. A good example of the effect of H-H
interactions on the acidity is provided by the observation
that the more electron-rich trihydide complex
[RuH3(dppf)2]+ (dppf ) (Ph2PC5H4)2Fe)8c is more acidic
than the less electron-rich dihydrogen complex [RuH-
(H2)(dppe)2]+.8d It has been noted that the relative acid
strengths of a series of isostructural dihydrogen com-
plexes may depart from the trend observed for classic
hydride complexes. For example, [CpRu(H2)(dppm)]+ 8h
is more acidic than [CpRu(H2)(dmpe)]+,9a as expected
from the relative electron-richness of the metal centers;
the ruthenium dihydrogen complex [RuCl(H2)(dppe)2]+ 8a,c
is more acidic than the corresponding osmium complex,
as expected from the general trend in M-H bond
strength and from the pKa values of MH2(CO)4 (M )
Fe, Ru, Os).3d In contrast, the effect of H-H interaction
in [MH(H2)(dppe)2]+ on the acidity is so important that
the pKa values of the dihydrogen complexes [MH(H2)-
(dppe)2]+ are now in the order of Fe < Os < Ru,8d due
to the presence of strong H-H bonding in the ruthenium
complex. Due to the limited pKa data available for
dihydrogen complexes, a distinctive trend in the acidity
of isostructural dihydrogen complexes is not apparent.
In this regard Morris et al. have recently proposed that
H-H interactions will have a negligible effect on the
acidity of dihydrogen complexes when d(HH) is longer
than 1.0 Å.8a
In order to further study the acidity properties of
dihydrogen complexes and to delineate trends in relative
acidities, we have prepared the molecular dihydrogen
complexes [MCl(H2)(L)(PMP)]BF4 (M ) Ru, L ) PPh3,
CO; M ) Os, L ) PPh3; PMP ) 2,6-(Ph2PCH2)2C5H3N)
and have measured their pKa values. Reported dihy-
drogen complexes closely related to the [MCl(H2)(L)-
(PMP)]BF4 complexes are the bis(diphosphine) com-
plexes [MCl(H2)(PP)2]+ (M ) Ru, Os; PP ) diphos-
phines).8a,c,10,12 Our system differs from the bis(diphos-
phine) system in that it contains a tridentate ligand
with one nitrogen and two phosphorus donor atoms and
a monodentate ligand L. This system enables us to
evaluate how the acidity of dihydrogen complexes
changes when L is changed from PPh3 to CO and when
the metal is changed from Ru to Os.
F igu r e 1. Molecular structure for RuCl2(PPh3)(PMP)‚
CH2Cl2. Hydrogen atoms and the solvent molecule are
omitted for clarity.
in Scheme 1. Treatment of RuCl2(PPh3)3 (2) with PMP
(1) in acetone produced RuCl2(PPh3)(PMP) (3). The
related complex RuCl2(PPh3)(EtN(CH2CH2PPh2)2) has
been reported.13 It is of interest to note that reactions
of RuCl2(PPh3)3 with the related triphosphine ligands
such as PhP(CH2CH2PPh2)2 (etp)14 and PhP(CH2CH2-
CH2PCy2)2 (Cyttp)15 lead to [Ru2Cl3(etp)2]Cl and
RuCl2(Cyttp), respectively. These observations may
indicate that PMP and EtN(CH2CH2PPh2)2 ligands are
sterically less demanding than the triphosphine ligands
etp and Cyttp. The structure of complex 3 can be
readily assigned based on the 31P and 1H NMR data.
The 1H NMR spectrum in CDCl3 showed only one
virtual triplet at 4.52 ppm for the methylene protons,
indicating that the geometry of the PMP ligand is
meridional16 and that the complex has a symmetric
structure. Consistent with the structure, the 31P NMR
spectrum in CDCl3 showed a doublet at 29.6 ppm (d,
J (PP) ) 27.7 Hz) for the PPh2 groups and a triplet at
35.9 ppm for the PPh3 ligand.
The structure of compound 3 has been confirmed by
X-ray diffraction (see Figure 1). Selected bond lengths
and angles are given in Table 2. The geometry around
ruthenium can be described as a distorted octahedron
with a meridional PMP ligand, two mutually trans Cl
atoms, and a PPh3 ligand trans to the nitrogen atom.
The distortion from an idealized octahedral geometry
can be attributed to the bending of the two PPh2 groups
toward nitrogen (P(1)-Ru-N(1) ) 79.6(1)°, P(2)-Ru-
N(1) ) 78.6(1)°), probably due to the size of the chelating
bite angle. Overall the structure is very similar to that
of RuCl2(PPh3)(EtN(CH2CH2PPh2)2).13a The Ru-PPh3
bond (2.346(1) Å) is slightly shorter than the mutually
trans Ru-P(1) (2.360(1) Å) and Ru-P(2) (2.369(1) Å)
bonds, which may be related to the smaller trans
(13) (a) Bianchini, C.; Masi, D.; Peruzzini, M.; Romerosa, A.;
Zanobini, F. Acta Crystallogr., Sect. C 1995, 51, 2514. (b) Bianchini,
C.; Peruzzini, M.; Romerosa, A.; Zanobini, F. Organometallics 1995,
14, 3152. (c) Bianchini, C.; Glendenning, L.; Peruzzini, M.; Romerosa,
A.; Zanobini, F. J . Chem. Soc., Chem. Commun. 1994, 2219.
(14) Albinati, A.; J iang, Q.; Ru¨egger, H.; Venanzi, L. M. Inorg. Chem.
1993, 32, 4940.
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of [Ru Cl(H2)-
(P P h 3)(P MP )]BF 4 a n d Rela ted Com p lexes. The
molecular dihydrogen complex [RuCl(H2)(PPh3)(PMP)]-
BF4 (5) was prepared according to the sequence shown
(15) J ia, G.; Lee, I. M.; Meek, D. W.; Galluci, J . C. Inorg. Chim. Acta
1990, 177, 81.
(16) Crabtree, R. H. The Organometallic Chemistry of the Transition
Metals, 2nd ed.; J ohn Wiley & Sons: New York, 1990; Chapter 10, p
236.
(12) Mezzetti, A.; Del Zotto, A.; Rigo, P.; Farnetti, E. J . Chem. Soc.,
Dalton Trans. 1991, 1525.

Properties of [MCl(H2)(L)(PMP)]BF4
Organometallics, Vol. 16, No. 18, 1997 3943
Ta ble 1. Cr ysta l Da ta a n d Refin em en t Deta ils for
Treatment of complex 4 with HBF4‚Et2O in dichloro-
methane produced the molecular dihydrogen complex
[RuCl(H2)(PPh3)(PMP)]BF4 (5), which is stable in both
the solid state and in solution under a dihydrogen or
argon atmosphere. Although the dihydrogen complex
can be pumped briefly without decomposition, upon
overnight evacuation it partially loses the dihydrogen
ligand to give uncharacterized products. The existence
of the η2-H2 moiety in 5 was confirmed by variable-
temperature T1 measurements and the observation of
Ru Cl2(P P h 3)(P MP )‚CH2Cl2
formula
fw
C50H44Cl4NP3Ru
994.6
color and habit
cryst dimens, mm
cryst syst
space group
a, Å
pale orange trapezoid
0.50 × 0.45 × 0.15
triclinic
P1h
10.831(2)
b, Å
13.729(2)
c, Å
17.483(2)
R, deg
71.98(2)
88.65(2)
67.97(2)
2279.1(6)
1
a large J (HD) for the corresponding isotopomer.7 The
â, deg
γ, deg
1H NMR spectrum of 5 in CD2Cl2 showed a broad
hydride signal at δ -10.49 ppm. A minimum T1 value
of 21 ms (400 MHz) was obtained for this hydride signal
at 236 K. Acidification of RuHCl(PPh3)(PMP) with
DBF4 gave the η2-HD isotopomer, [RuCl(HD)(PPh3)-
(PMP)]BF4, which showed a 1:1:1 triplet (1J (HD) ) 28.0
Hz) of quartets (2J (HP) ) 8.0 Hz) centered at -10.56
V, Å3
Z
d
2
calc, g cm-3
1.449
0.720
1016
abs coeff, mm-1
F(000)
radiation
T, K
Mo KR (λ ) 0.071 073 Å)
213
2θ range, deg
scan type
3.0-50.0
2θ-θ
1
ppm in the H NMR spectrum.
The stereochemistry of complex 5 shown in Scheme
1 is supported by the NMR spectroscopic data and its
deprotonation reaction with CpRuH(PPh3)2 at low tem-
perature. The meridional geometry of the PMP ligand
in 5 is indicated by the AM2 pattern for the signals in
scan range (ω)
standard reflections
index range
0.80° plus KR-separation
3 measured every 150 reflns
-1 e h e 14, -16 e k e 17,
-23 e l e 23
no. of reflns collected
no. of independent reflns
no. of obsd reflns
abs corr
system used
no. of params refined
hydrogen atoms
final R indices (obsd data)
R indices (all data)
goodness of fit
data to parameter ratio
largest difference peak
largest difference hole
12 664
11 282 (Rint ) 1.72%)
9198 (F > 4.0σ(F))
semi-empirical
Siemens SHELXTL IRIS
534
riding model, fixed isotropic U
R ) 3.36%, Rw ) 4.11%
R ) 4.44%, Rw ) 4.40%
1.27
1
the 31P NMR spectrum and its H NMR spectrum which
showed two doublet of triplet signals for the methylene
protons. The position of the dihydrogen ligand in
complex 5 is inferred from the structure of its precursor
4 and the fact that deprotonation of complex 5 at 200 K
with CpRuH(PPh3)2 gave complex 4 (in which the
hydride is trans to chloride and cis to PPh3) as the only
deprotonation product. The position of the dihydrogen
ligand in a dihydrogen complex is expected to be the
same as that of the hydride ligand in the kinetic
deprotonation product. For example, the kinetic depro-
tonation product of trans-[RuH(H2)(dppe)2]+ is trans-
RuH2(dppe)2 which isomerizes to the thermodynami-
cally stable mixture of cis- and trans-RuH2(dppe)2.8d The
structure of complex 5 has been confirmed by a NOE
experiment. In this experiment, a positive NOE effect
was observed for one of the signals of the methylene
protons when the dihydrogen signal was irradiated.
The H-H distance in complex 5 can be estimated
from the T1(min) value20 and J (HD) data.8a On the
basis of the T1(min) value of 21 ms (at 400 MHz), d(HH)
was estimated to be 1.13 Å for complex 5 with a slow
spinning dihydrogen ligand or 0.89 Å for a fast spinning
dihydrogen ligand. It should be mentioned that the
calculated d(HH) values are the minimum H-H dis-
tances, as contributions to T1(min) from other groups
are not corrected for here. A d(HH) value of 0.95 Å can
be obtained by use of the relationship d(HH) )
-0.0167J (HD) + 1.42 and J (HD) ) 28.0 Hz.8a
17.2:1
0.45 e Å-3
-0.51 e Å-3
influence of the pyridine ligand. The Ru-N(1) bond
distance (2.161(2) Å) is comparable to those in the
pyridine complex [Ru(CtCC6H11)(CO)(py)2(PPh3)2]ClO4
(2.16(2), 2.21(2) Å)17 and shorter than that (2.337(4) Å)
in RuCl2(PPh3)(EtN(CH2CH2PPh2)2).13a The Ru-Cl bond
distances (2.430(1) and 2.411(1) Å) agree well with the
reported values for trans-dichlororuthenium complexes
such as RuCl2(PPh3)(EtN(CH2CH2PPh2)2),13a RuCl2(CO)-
(PMePh2)3,18 and RuCl2(PhAs(CH2PPh2)2)2.19
Compound 3 reacted with NaBH4 in refluxing metha-
nol to give RuHCl(PPh3)(PMP) (4). The 1H NMR
spectrum in C6D6 showed a hydride signal at -16.55
ppm as an apparent quartet with J (PH) ) 22.2 Hz; this
indicates that the hydride is cis to the three phosphorus
atoms, the PMP ligand is meridionally coordinated to
ruthenium, and the PPh3 is cis to the two PPh2 groups.
Consistent with this structural assignment, the 31P
NMR spectrum in C6D6 contained a doublet at 47.2 ppm
(d, J (PP) ) 27.8 Hz) for the PPh2 groups and a triplet
at 57.9 ppm for the PPh3 ligand. On the basis of the
1H and 31P NMR data, two possible structures can be
proposed for 4, with the hydride trans to the pyridine
ring or trans to the chloride. The latter structure was
confirmed by a NOE experiment in which irradiation
of the hydride signal induced enhancement of one of the
signals for the methylene protons.
Related dihydrogen complexes [RuCl(H2)(PP)2]+ (PP
) dppe, depe, dcpe, dppp) have been reported.8c,10,12 It
is of interest to note that the J (HD) values for the
isotopomers of [RuCl(HD)(PP)2]+ (16-26 Hz) are smaller
than that of [RuCl(HD)(PPh3)(PMP)]+ (28.0 Hz). The
J (HD) data may indicate that [RuCl(HD)(PPh3)(PMP)]+
is less electron-rich than [RuCl(HD)(PP)2]+ and that the
H-H bond in complex 5 is stronger than those in
(17) Echavarren, A. M.; Lo´pez, J .; Santos, A.; Romero, A.; Hermoso,
J . A.; Vagas, A. Organometallics 1991, 10, 2371.
(18) Krassowski, D. W.; Nelson, J . H.; Brower, K. R.; Hauenstein,
D.; J acobson, R. A. Inorg. Chem. 1988, 27, 4294.
(19) Balch, A. L.; Olmstead, M. M.; Reedy, P. E., J r.; Rowley, S. P.
Inorg. Chem. 1988, 27, 4289.
(20) (a) Hamilton, D. G.; Crabtree, R. H. J . Am. Chem. Soc. 1988,
110, 4126. (b) Bautista, M. T.; Earl, K. A.; Maltby, P. A.; Morris, R.
H.; Schweitzer, C. T.; Sella, A. J . Am. Chem. Soc. 1988, 110, 7031. (c)
Desrosiers, P. J .; Cai, L.; Lin, Z.; Richards, R.; Halpern, J . J . Am. Chem.
Soc. 1991, 113, 4173.

3944 Organometallics, Vol. 16, No. 18, 1997
J ia et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles (d eg) for Ru Cl2(P P h 3)(P MP )‚CH2Cl2
Interatomic Distances
Ru-P(1)
Ru-Cl(1)
2.360(1)
2.430(1)
Ru-P(2)
Ru-Cl(2)
2.369(1)
2.411(1)
Ru-P(3)
Ru-N(1)
2.346(1)
2.161(2)
Intermolecular Angles
P(1)-Ru-P(2)
P(1)-Ru-Cl(2)
P(2)-Ru-Cl(1)
P(3)-Ru-Cl(1)
Cl(1)-Ru-Cl(2)
158.1(1)
90.9(1)
95.1(1)
96.5(1)
170.9(1)
P(1)-Ru-P(3)
P(1)-Ru-N(1)
P(2)-Ru-Cl(2)
P(3)-Ru-Cl(2)
Cl(1)-Ru-N(1)
102.4(1)
79.6(1)
89.1(1)
90.8(1)
86.4(1)
P(1)-Ru-Cl(1)
P(2)-Ru-P(3)
P(2)-Ru-N(1)
P(3)-Ru-N(1)
Cl(2)-Ru-N(1)
82.3(1)
99.5(1)
78.6(1)
176.7(1)
86.5(1)
Sch em e 2
CD2Cl2 showed a triplet hydride signal at -13.65 ppm
with J (PH) ) 19.9 Hz and two doublets of triplets for
the methylene protons at 4.13 and 4.64 ppm. The NMR
data are consistent with a structure in which the PMP
ligand is meridionally coordinated to ruthenium. The
chemical shift (-13.65 ppm) of the hydride signal
indicates that the hydride is trans to Cl or pyridine
rather than to CO. In comparison, the signal for the
hydride trans to CO is at -5.15 ppm for RuHCl(CO)2-
24
(P(i-Pr)3)2 and at -3.68 to -7.25 ppm for [RuH(CO)-
(PP)2]+ (PP ) dppm, dppe, dppe);25 the signal for the
hydride trans to pyridine is at -11.3 ppm for [RuH(CO)-
(bpy)2]+ 26 and at -12.10 ppm for [RuH(CO)(py)2(PPh3)2]-
ClO4;27 the signal for the hydride trans to Cl is at -13.5
to -15.4 ppm for RuHCl(CO)(PPh3)(PP) (PP ) dppm,
dppp).25 In the present case, the trans disposition of
the hydride and the chloride was established by a NOE
experiment in which a positive enhancement was ob-
served for one of the signals of the methylene protons
upon irradiation of the hydride signal.
[RuCl(H2)(PP)2]+. The difference may be attributed to
the presence of the pyridine ligand which is a poorer
σ-electron-pair donor. In this regard, it is noted that
the J (HD) for Tp*RuH(HD)(PCy3) (21.0 Hz) is also
reported to be smaller than that of Tp*RuH(HD)(py)
(26.7 Hz) (Tp* ) hydrotris(3,5-dimethylpyrazolyl)-
borate).21 Related to this is the report that the CO
stretching frequencies of [CpFe(CO)2(py)]PF6 are higher
than those of [CpFe(CO)2(PPh3)]PF6 and [Cp(CO)2Fe-
(µ-dppe)Fe(CO)2Cp](PF6)2.22
Due to its low stability, complex 10 was primarily
1
characterized by H and 31P NMR spectroscopy. Con-
sistent with the meridional geometry of the PMP ligand,
the 31P NMR spectrum displayed a singlet at 40.6 ppm.
A signal assignable to Ru(H2) was observed at -8.50
ppm (in CD2Cl2). Formulation of complex 10 as a
dihydrogen complex is supported by the observation of
a short T1(min) of the hydride signal (11 ms, 400 MHz
Syn th esis a n d Ch a r a cter iza tion of [Ru Cl(H2)-
(CO)(P MP )]BF 4. The molecular dihydrogen complex
[RuCl(H2)(CO)(PMP)]BF4 (10) was prepared by proton-
ation of RuHCl(CO)(PMP) (7) with HBF4‚Et2O in di-
chloromethane. Complex 7 was in turn prepared by the
substitution reaction of RuHCl(CO)(PPh3)3 with PMP
in benzene (see Scheme 2). The dihydrogen complex 10
is stable at room temperature in dichloromethane
solution under a hydrogen atmosphere. However, at-
tempts to isolate pure samples of 10 using diethyl ether
as the precipitating solvent failed; the predominant
phosphorus-containing species of the solid eventually
isolated was in fact the monohydride complex 7. Thus,
the dihydrogen complex 10 is deprotonated by excess
diethyl ether. There are several reported examples of
dihydrogen complexes or intermediates that can be
deprotonated by diethyl ether, for example, [Os(H2)(CH3-
1
at 232 K) and a large J (HD) (30.1 Hz) for the corre-
sponding isotopomer [RuCl(HD)(CO)(PMP)]BF4. The
H-H distance in 10 was estimated to be 0.92 Å by use
of the relationship d(HH) ) -0.0167J (HD) + 1.42 and
J (HD) ) 30.1 Hz.
The J (HD) coupling constant for [RuCl(HD)(CO)-
(PMP)]BF4 (30.1 Hz) is surprisingly close to that of
[RuCl(HD)(PPh3)(PMP)]BF4 (28.0 Hz). Replacement of
PR3 in [MH2(PR3)Ln]x+ with CO are known to have
drastic effect on the structure. For example, the dihy-
drogen form is stable for complexes such as [CpRu(H2)-
(CO)(PR3)]+,9a,c Os(H2)H2(CO)(PR3)2,28 [Re(H2)H2(CO)-
(PR3)3]+ (PR3 ) PMe3, PMe2Ph),29,30 and [Re(H2)-
(CO)2(PR3)3]+,30-32 but the classic hydride form is adopted
CN)(dppe)2]2+ 8b
(NO)]+,9b [CpRu(H2)(dfepe)]+ (dfepe ) (C2F5)2PCH2-
CH2P(C2F5)2),23 and [Os(H2)(CO)(bpy)(PPh3)2]2+ 11j
,
[Cp*Ru(H2)(CO)2]+,9b [Cp*Re(H2)(CO)-
(24) Esteruelas, M. A.; Werner, H. J . Organomet. Chem. 1986, 303,
221.
(25) Santos, A.; Lo´pez, J .; Montoya, J .; Noheda, P.; Romero, A.;
Echavarren, A. M. Organometallics 1994, 13, 3605.
(26) Sullivan, B. P.; Caspar, J . V.; J ohnson, S. R.; Meyer, T. J .
Organometallics 1984, 3, 1241.
(27) Romero, A.; Vegas, A.; Santos, A.; Martinez-Ripoll, M. J .
Organomet. Chem. 1987, 319, 103.
(28) Gusev, D. G.; Kuhlman, R. L.; Renkema, K. B.; Eisenstein, O.;
Caulton, K. G. Inorg. Chem. 1996, 35, 6775.
(29) (a) Luo, X. L.; Crabtree, R. H. J . Chem. Soc., Chem. Commun.
1990, 189. (b) Luo, X. L.; Crabtree, R. H. J . Am. Chem. Soc. 1990,
112, 6912.
.
The monohydride complex 7 was characterized by 1H
and 31P NMR spectroscopy and elemental analysis. The
31P NMR spectrum in CD2Cl2 showed a singlet at 50.4
ppm for the PPh2 groups. The 1H NMR spectrum in
(21) Moreno, B.; Sabo-Etienne, S.; Chaudret, B.; Rodriguez, A.;
J alon, F.; Trofimenko, S. J . Am. Chem. Soc. 1995, 117, 7441.
(22) Treichel, P. M.; Shubkin, R. L.; Barnett, K. W.; Reichard, D.
Inorg. Chem. 1966, 5, 1177.
(30) Gusev, D. G.; Nietlispach, D.; Eremenko, I. L.; Berke, H. Inorg.
Chem. 1993, 32, 3628.
(23) Keady, M. S.; Koola, J . D.; Ontko, A. C.; Merwin, R. K.; Roddick.
D. M. Organometallics 1992, 11, 3417.
(31) Luo, X. L.; Michos, D.; Crabtree, R. H. Organometallics 1992,
11, 237.

Properties of [MCl(H2)(L)(PMP)]BF4
Organometallics, Vol. 16, No. 18, 1997 3945
by [CpRuH2(PR3)2]+,33,34 OsH4(PR3)4,20a,35 [ReH4(PR3)4]+,36
and [ReH2(CO)(PR3)4]+ (PR3 ) PMe3, PMe2Ph).30,31 In
the cases where both [M(H2)(CO)Ln]x+ and [M(H2)(PR3)-
Ln]x+ are stable, the H-H interaction in [M(H2)(CO)-
Ln]x+ is so strong that the J (HD) coupling constants for
the HD isotopomers [M(HD)(CO)Ln]x+ are usually larger
than (or equal to) 32 Hz.30,37
Sch em e 3
A small change in J (HD) coupling constants for η2-
HD complexes upon variation of the electron-donating
ability of the ligands is known for complexes lying at
the early stage of the oxidative addition of dihydrogen
at metal centers. For example, the J (HD) values for
[RuH(HD)(PP)2]+ (PP ) dtfpe, dppe, depe, dcpe)8d,12 and
[RuH(HD)(PR3)(PhP(CH2CH2PPh2)2)]+ (PR3 ) PMe2Ph,
P(OCH2)3CEt)38 are in the range of 31-33 Hz. The
same argument can be used to explain the similarity in
the J (HD) values observed for [RuCl(HD)(CO)(PMP)]-
BF4 (30.1 Hz) and [RuCl(HD)(PPh3)(PMP)]BF4 (28.0
Hz). Alternatively, the similarity may be related to the
fact that the dihydrogen ligand is trans to chloride.
Morris et al. have noted that the H-H distances in
trans-[OsH(H2)(PP)2]+ change significantly when PP is
changed from dppe to depe and dcpe, but the H-H
distances in trans-[OsCl(H2)(PP)2]+ only change slightly
when the ligand is varied.8a The insensitivity of the
H-H bond distance to the change in the ligands in
trans-[OsCl(H2)(PP)2]+ has been attributed to the buffer
effect of the trans chloride.
(14), a white compound which showed a hydride signal
at -9.04 ppm with J (PH) ) 11.8 Hz (in CD2Cl2).
Variable-temperature T1 measurements gave a T1(min)
of 39 ms for the hydride signal at 300 MHz and 220 K.
Protonation of 13 with DBF4 produced [OsCl(HD)-
(PPh3)(PMP)]BF4, which exhibited a hydride signal at
-9.10 ppm with J (HD) ) 17.7 Hz. The J (HD) value of
17.7 Hz is larger than those observed for [OsCl(HD)-
(PP)2]+ (PP ) dppe, depe, dcpe).8a The T1(min) and
J (HD) data imply that complex 14 contains an elongated
dihydrogen ligand. On the basis of the T1(min) value,
the minimum H-H distance in 14 was estimated to be
1.26 Å for 14 with a slow spinning dihydrogen ligand
and 1.00 Å for 14 with a fast spinning dihydrogen
ligand. The H-H distance was estimated to be 1.12 Å
based on the J (HD) value of 17.7 Hz. As expected, the
H-H distance in 14 is longer than that in 5. The
stereochemistry of complex 14 is similar to that of
complex 5, as inferred by its spectroscopic data and
results of a NOE experiment. In contrast to the case
with complex 5, the dihydrogen ligand in complex 14
cannot be removed under vacuum.
Ot h er R ea ct ion s of P MP w it h R u H Cl(CO)-
(P P h 3)3. During the attempts to prepare RuHCl(CO)-
(PMP) from the reaction of RuHCl(CO)(PPh3)3 and PMP,
it was found that other compounds can also be isolated
from the reaction (see Scheme 2). Thus, the cationic
complex [RuH(CO)(PPh3)(PMP)]Cl (8) was formed when
the reaction was carried out in refluxing acetone. The
isomeric cationic complex [RuH(CO)(PPh3)(PMP)]Cl (9)
was formed when the reaction was carried out in
refluxing benzene, followed by treatment with methanol.
The stereochemistry of complexes 8 and 9 was readily
Acid ity P r op er ties of Com p lex 5. The pKa value
of 5 was estimated by studying the equilibrium shown
1
in eq 1 by using H and 31P NMR spectroscopy. Due to
1
assigned on the basis of the H and 31P NMR data.
RuHCl(PPh3)(PMP) + HP(p-tolyl)3+ h
[RuCl(H2)(PPh3)(PMP)]+ + P(p-tolyl)3 (1)
Syn th esis a n d Ch a r a cter iza tion of [OsCl(H2)-
(P P h 3)(P MP )]BF 4 a n d Rela ted Com p lexes. The
molecular dihydrogen complex [OsCl(H2)(PPh3)(PMP)]-
BF4 (14) was prepared according to the sequence shown
in Scheme 3.
Treatment of OsCl2(PPh3)3 (11) with PMP (1) in
acetone produced the orange complex OsCl2(PPh3)(PMP)
(12). Compound 12 was converted by NaBH4 in reflux-
ing THF into the yellow monohydride complex OsHCl-
(PPh3)(PMP) (13). These compounds were characterized
by their NMR and analytical data.
the tendency of complex 5 to lose H2, the equilibrium
measurements were conducted under 1 atm of H2.
Equilibrium mixtures were obtained by mixing RuHCl-
(PPh3)(PMP) with HP(p-tolyl)3BF4 or by protonation
with a limited amount of HBF4‚Et2O of a mixture of
RuHCl(PPh3)(PMP) and P(p-tolyl)3 in CD2Cl2. As in-
dicated by both the 1H and 31P NMR spectroscopy, minor
side products, one of which was identified as RuCl2-
(PPh3)(PMP), were also present in the mixture. Owing
to proton exchange, the signals of P(p-tolyl)3 and HP(p-
Acidification of OsHCl(PPh3)(PMP) (13) with HBF4‚
Et2O in CH2Cl2 produced [OsCl(H2)(PPh3)(PMP)]BF4
+
tolyl)3 merged at room temperature to give a broad
(32) Bianchini, C.; Marchi, A.; Marvelli, L.; Peruzzini, M.; Romerosa,
A.; Rossi, R.; Vacco, A. Organometallics 1995, 14, 3203.
(33) Brammer, L.; Klooster, W. T.; Lemke, F. R. Organometallics
1996, 15, 1721 and references therein.
(34) Wilczewski, T. J . Organomet. Chem. 1989, 361, 219.
(35) (a) Hart, D. W.; Bau, R.; Koetzle, T. F. J . Am. Chem. Soc. 1977,
99, 7557. (b) Douglas, P. G.; Shaw, B. L. J . Chem. Soc. A 1970, 334.
(36) (a) Lunder, D. M.; Green, M. A.; Streib, W. E.; Caulton, K. G.
Inorg. Chem. 1989, 28, 4527. (b) Costello, M. T.; Fanwick, P. E.; Green,
M. A.; Walton, R. A. Inorg. Chem. 1992, 31, 2359. (c) J ia, G.; Lough,
A. J .; Morris, R. H. J . Organomet. Chem. 1993, 461, 147.
(37) Heinekey, D. M.; Schomber, B. M.; Radzewich, C. E. J . Am.
Chem. Soc. 1994, 116, 4515.
peak but separated into two peaks below 270 K. Thus,
the equilibrium constant cannot be obtained at room
temperature but can be estimated at lower tempera-
tures. The relative concentrations of P(p-tolyl)3 and
HP(p-tolyl)3+ can be estimated from integrations of the
31P signals in the 31P NMR spectrum, and those of the
hydride species can be obtained from both the 31P and
1H NMR spectroscopy. At 253 K, the equilibrium
constant was determined to be 16 from the mixture
obtained by mixing RuHCl(PPh3)(PMP) with HP(p-
tolyl)3+ and 18 from the mixture obtained by protonation
(38) Michos, D.; Luo, X. L.; Crabtree, R. H. Inorg. Chem. 1992, 31,
4245.

3946 Organometallics, Vol. 16, No. 18, 1997
J ia et al.
of a mixture of RuHCl(PPh3)(PMP) and P(p-tolyl)3 with
a limited amount of HBF4‚OEt2. The pKa value of HP(p-
acid and diethyl ether signals, it was estimated that the
relative amounts of HBF4‚Et2O and Et2O were in a
molar ratio of 1:0.93. The relative molar concentrations
of HBF4‚Et2O, Et2O, RuHCl(CO)(PMP), and RuCl(H2)-
+
tolyl)3 (on the aqueous scale) has been reported to be
3.84.39 Thus, a pKa value of 5.1 was calculated based
on an equilibrium constant of 17 for eq 1. For compari-
son, the pKa value of the closely related dihydrogen
complex [RuCl(H2)(dppe)2]+ is 6.08c and that of [RuCl-
(H2)(dppp)2]+ is 4.4.10
To verify the equilibrium study, we also studied
reactions of [RuCl(H2)(PPh3)(PMP)]+ (or RuHCl(PPh3)-
(PMP)) with other bases (or acids) (see eq 2). The
1
(CO)(PMP)]BF4 were 3.0, 2.8, 1.0, and 0.33 based on H
NMR integrations. Thus, an equilibrium constant of 0.3
for eq 3 can be estimated. The pKa values of protonated
RuHCl(CO)(PMP) + HBF4‚Et2O h
[RuCl(H2)(CO)(PMP)]BF4 + Et2O (3)
ether are in the range from -2.39 (at 25 °C) to -2.48
(at 90 °C) in aqueous sulfuric acid.40 Thus, the pKa
value of [RuCl(H2)(CO)(PMP)]BF4 was calculated to be
-2.8 at 203 K if that of HBF4‚OEt2 is taken as -2.4.
Although the uncertainty in the estimated pKa value
may be significant, the pKa value is consistent with the
fact that the dihydrogen complex 10 was formed from
the reaction of RuHCl(CO)(PMP) in dichloromethane
with excess HBF4‚Et2O but was deprotonated by excess
ether to give the monohydride complex 7. Interestingly,
it was reported recently that the CO-containing complex
[Ru(H2)(CO)(dppp)2]2+ has a pKa value close to -6.10
Attempts to study the acid properties of complex 10
with phosphines (or protonated phosphines) were un-
successful, due to the formation of [RuH(CO)(PR3)-
(PMP)]+. For example, reaction of RuHCl(CO)(PMP)
with HPPh3BF4 did not lead to the dihydrogen complex
10 but rather to the phosphine adduct [RuH(CO)(PPh3)-
(PMP)]BF4 (9).
RuHCl(PPh3)(PMP) + HPPh3+ f
[RuCl(H2)(PPh3)(PMP)]+ + PPh3 (2)
equilibrium for eq 2 must lie to the far right as reaction
of RuHCl(PPh3)(PMP) with a slight excess of HPPh3-
BF4 leads to complete consumption of RuHCl(PPh3)-
(PMP) to give the dihydrogen complex 5. No deproton-
ation was observed when the dihydrogen complex 5 was
treated with PPh3. These observations are consistent
+
with the fact the HPPh3 (pKa ) 2.73 on aqueous
scale)39 is much more acidic than the dihydrogen
complex 5 (pKa ) 5.1 on aqueous scale).
[CpRuH2(PPh3)2]+ is reported to have an aqueous pKa
value of 8.3 in CD2Cl2.8h As expected, the more acidic
dihydrogen complex [RuCl(H2)(PPh3)(PMP)]BF4 in
CD2Cl2 was completely deprotonated with a slight
excess of CpRuH(PPh3)2 to give the monohydride com-
plex RuHCl(PPh3)(PMP) and the dihydride complex
[CpRuH2(PPh3)2]BF4. It should be mentioned that
CpRuCl(PPh3)2 was also observed if the reaction mix-
ture was set at room temperature for over 30 min.
Acid ity P r op er ties of Com p lex 10. We mentioned
in the previous section that the dihydrogen complex 10
is so acidic that it was deprotonated to give the mono-
hydride complex 7 during the attempted isolation using
diethyl ether as the precipitating solvent. Deprotona-
tion of complex 10 by diethyl ether to give 7 can also be
demonstrated by an NMR experiment. These observa-
tions prompted us to estimate the equilibrium constant
by NMR for the protonation reaction of complex 7 with
Acid ity P r op er ties of Com p lex 14. The pKa value
of 14 was estimated by studying the equilibrium shown
1
in eqs 4 and 5, using H and 31P NMR spectroscopy. In
CpRuH(PPh3)2 + [OsCl(H2)(PPh3)(PMP)]+ h
[CpRuH2(PPh3)2]+ + OsHCl(PPh3)(PMP) (4)
CpRuH(dppm) + [OsCl(H2)(PPh3)(PMP)]+ h
[CpRu(H2)(dppm)]+ + OsHCl(PPh3)(PMP) (5)
these experiments, all the relevant species can be
readily detected by 1H and 31P NMR spectroscopy,
although very small amounts of unidentified species
were also present in the reaction mixture. The relative
concentrations of the relevant species can be readily
obtained by integration of the hydride signals. An
equilibrium constant of 6.8 for eq 4 was obtained from
the mixture obtained by protonation with HBF4‚Et2O
of a mixture of CpRuH(PPh3)2 and OsHCl(PPh3)(PMP).
An equilibrium constant of 2.2 for eq 5 was obtained
for the mixture obtained by protonation with HBF4‚
Et2O of a mixture of CpRuH(dppm) and OsHCl(PPh3)-
(PMP). The pKa values (aqueous scale) of [CpRuH2-
(PPh3)2]BF4 and [CpRu(H2)(dppm)]+ have been reported
to be 8.3 and 7.1, respectively.8h Thus, the pKa value
for complex 14 was estimated to be 7.5 from eq 4 and
6.8 from eq 5. It could be concluded that the pKa value
of complex 14 is close to 7.2 on an aqueous scale.
To further verify the acidity of complex 14, we have
directly compared the acidity of [RuCl(H2)(PPh3)-
(PMP)]+ with [OsCl(H2)(PPh3)(PMP)]+. When RuHCl-
(PPh3)(PMP) was mixed with [OsCl(H2)(PPh3)(PMP)]+
in CD2Cl2, no signals of OsHCl(PPh3)(PMP) could be
HBF4‚Et2O.
A
1H NMR spectrum (in CD2Cl2) of a
commercially available sample of HBF4‚Et2O at 203 K
indicated that the sample contained both HBF4‚Et2O
and Et2O in an approximate molar ratio of 1:0.7 (cor-
responding to ca. 76% HBF4‚Et2O). No appreciable
reaction was observed when 1 µL of this commercially
available acid (containing ca. 0.0056 mmol HBF4‚Et2O)
was added to a solution of RuHCl(CO)(PMP) (ca. 10 mg,
0.016 mmol) at 243 K. Further addition of another 2
µL of the acid caused the hydride signal at -13.65 ppm
of RuHCl(CO)(PMP) to become broad (at 243 K). This
signal remained broad at 203 K. A small hydride signal
due to [RuCl(H2)(CO)(PMP)]BF4 became observable (at
203 K) after the addition of another 2 µL of the acid to
the reaction mixture. A mixture containing both [RuCl-
(H2)(CO)(PMP)]BF4 and RuHCl(CO)(PMP) (in a molar
ratio of 0.3:1) formed after adding a total of 7 µL of the
acid (ca 0.039 mmol HBF4‚Et2O), as indicated by both
the 31P and 1H NMR spectroscopy at 203 K. The 1H
NMR spectrum also showed a broad signal at 11.5 ppm
assignable to HBF4‚Et2O. From the integration of the
(39) Allman, T.; Goel, R. G. Can. J . Chem. 1982, 60, 716.
(40) Perdoncin, G.; Scorrano, G. J . Am. Chem. Soc. 1977, 99, 6983.

Properties of [MCl(H2)(L)(PMP)]BF4
Organometallics, Vol. 16, No. 18, 1997 3947
Ta ble 3. Sp ectr oscop ic P r op er ties a n d Acid ities of
Selected Hyd r id e Com p lexes
in the H-H interaction has less importance than the
inductive effect of the ligands in determining the acidity
of [RuCl(H2)(L)(PMP)]+.
T1(min),
msa
d(HH),
Åb
c
complexes
J (HD)
pKa
refs
The observation that [RuCl(H2)(PPh3)(PMP)]BF4 (pKa
) 5.1) is more acidic than the osmium analog [OsCl-
(H2)(PPh3)(PMP)]BF4 (pKa ) 7.2) is consistent with the
trend reported for [MCl(H2)(dppe)2]+ (pKa ) 6.0, M )
Ru;8c pKa ) 7.4, M ) Os8a) and [MCl(H2)(dppp)2]+ (pKa
) 4.4, M ) Ru; pKa ) 12.5, M ) Os).10 The trend is
also similar to those observed for classic hydride com-
plexes such as [CpMH2(PPh3)2]+ (M ) Ru, Os)8d and
H2M(CO)4 (pKa(CH3CN) ) 18.7, M ) Ru; pKa ) 20.8,
M ) Os).3d Such a trend is expected as the Os-H bond
is usually stronger than the Ru-H bond. In contrast,
the pKa values of [MH(H2)(PP)2]+ (PP ) dppe, dtfpe,
depe) are in the order of Os < Ru.8d The distinctive
order in the acidity of complexes [MH(H2)(PP)2]+ has
been attributed to the stronger H-H interactions
present in [RuH(H2)(PP)2]+ complexes. Indeed, the
strong H-H interactions in [RuH(H2)(PP)2]+ complexes
are reflected in the J (HD) (g32 Hz) for their corre-
sponding isotopomers. To explain the distinctive trend
in the acidity of [MH(H2)(PP)2]+, it was suggested that
as the d(HH) bond stretches above 1.0 Å, the M-H bond
energy drops to that of dihydride and the acidity
becomes the same as the classic complexes.8a Although
the H-H interactions in [RuCl(H2)(PP)2]+ and [RuCl-
(H2)(PPh3)(PMP)]+ (H-H distance is likely shorter than
1.0 Å) are also substantially stronger than that in the
osmium analogs, as reflected in the J (HD) coupling
constants (see Table 3), the H-H interactions in the
ruthenium complexes are not strong enough to give a
distinctive trend in the acidity of [MCl(H2)(PP)2]+ and
[MCl(H2)(PPh3)(PMP)]+. For comparison, J (HD) is 28.0
Hz for [RuCl(HD)(PPh3)(PMP)]+ and 32 Hz for [RuH-
(H2)(dppe)2]+.
[RuCl(H2)(PPh3)(PMP)]+
[OsCl(H2)(PPh3)(PMP)]+
[RuCl(H2)(dppe)2]+
[OsCl(H2)(dppe)2]+
[RuCl(H2)(dppp)2]+
[OsCl(H2)(dppp)2]+
[RuH(H2)(dtfpe)2]+
[OsH(H2)(dtfpe)2]+
[RuH(H2)(dppe)2]+
[OsH(H2)(dppe)2]+
[RuH(H2)(depe)2]+
[OsH(H2)(depe)2]+
[RuH(H2)(dppp)2]+
[OsH3(dppp)2]+
21
28.0
17.7
25.9
13.9
24
11
33
28
32
25.5
32.3
11
32
0
30.1
34
32
0.95 5.1d
1.12 7.2
0.99 6.0
1.19 7.4
this work
this work
8c
8a
10
10
39e
25
53
8.2f
23.7f
10
1.0
1.2
4.4
12.5
0.87 10.0g 8d
15
20
40
16
0.95 9.2g
8d
0.89 15.0g 8a,d
0.99 13.6g 8a,d
0.88 17.5g 8a,d
1.23 17.3g 8a,d
80
5.5f
72f
11
0.89 10.2
10
10.3h 10
[RuCl(H2)(CO)(PMP)]+
[Ru(H2)(CO)(dppp)2]2+
[Os(H2)(CO)(dppp)2]2+
0.92 -2.8i this work
0.85 ca. -6 10
5.0f
5.5f
0.89 -5.7 10
1.06 -2
[Os(H2)(CH3CN)(dppe)2]2+ 28
21.4
8b
a
b
At 400 MHz, unless otherwise stated. Calculated based on
J (HD) values. c pKa values were determined in CD2Cl2, but
reported on pseudo aqueous scale. Determined at 253 K. e At 300
d
MHz. f At 200 MHz. g Conjugated bases are trans-MH2(PP)2. The
h
i
conjugated base is cis-OsH2(dppp)2. Determined at 203 K.
observed by 1H and 31P NMR spectroscopy, although
small signals due to [RuCl(H2)(PPh3)(PMP)]+ could be
observed. The latter compound could be produced from
traces of acid present in the sample of [OsCl(H2)(PPh3)-
(PMP)]BF4. When a mixture of OsHCl(PPh3)(PMP) and
RuHCl(PPh3)(PMP) was protonated with a limited
amount of HBF4‚Et2O, only OsHCl(PPh3)(PMP) was
protonated to give the molecular dihydrogen complex
14. These experiments clearly indicate that [RuCl(H2)-
(PPh3)(PMP)]BF4 is more acidic than [OsCl(H2)(PPh3)-
(PMP)]BF4.
Com m en ts on th e Acid ities of Com p lexes 5, 10,
a n d 14. It should be stressed that the pseudo aqueous
pKa values of complexes 5, 10, and 14 are obtained
based on the assumption that the differences in the pKas
of the dihydrogen complexes and the reference acids are
the same in water and CD2Cl2. Because the assumption
has not been confirmed yet, the pseudo aqueous pKa
values of the complexes may be different from the true
aqueous pKa values. However, the pseudo aqueous pKa
values can still provide valuable information on the
trend in the acidities of the complexes. For comparison,
the pseudo aqueous pKa values of complexes 5, 10, 14,
and related dihydrogen complexes are listed in Table
3.
Con clu sion . We have successfully synthesized and
characterized the dihydrogen complexes [MCl(H2)(L)-
(PMP)]BF4 (5, M ) Ru, L ) PPh3; 10, M ) Ru, CO; 14,
M ) Os, L ) PPh3). Complex 10 is so acidic that it is
deprotonated by diethyl ether. Equilibrium studies
show that the acidity decreases in the order of 10 > 5
> 14. The trend is the same as that expected for classic
hydride complexes.
Exp er im en ta l Section
All manipulations were carried out under a nitrogen atmo-
sphere using standard Schlenk techniques, unless otherwise
stated. Solvents were distilled under dinitrogen from sodium-
benzophenone (hexane, diethyl ether, THF, benzene) and
calcium hydride (CH2Cl2). The starting materials RuCl2-
(PPh3)3,41 RuHCl(CO)(PPh3)3,42 CpRuH(PPh3)2,43 [CpRuH2-
Substitution of PPh3 for CO is known to change the
acidity of related classic hydride complexes by 5-8 pKa
3d
units. For example, MnH(CO)5 has a pKa(CH3CN) of
45
(PPh3)2]BF4,34 PMP,44 and OsCl2(PPh3)3 were prepared ac-
3e
15.1 vs 20.4 for MnH(CO)4(PPh3);3b CpCrH(CO)3 has
cording to literature methods. All other reagents were used
as purchased from Aldrich.
Microanalysis were performed by M-H-W Laboratories
(Phoenix, AZ). 1H and 31P{1H} NMR spectra were collected
on a J EOL EX-400 or Bruker ARX-300 or 400 spectrometer.
a pKa(CH3CN) of 13.3 vs 21.8 for CpCrH(CO)2(PPh3),4c
3d
and HCo(CO)4 has a pKa(CH3CN) of 8.3 vs 15.4 for
HCo(CO)3(PPh3).3d The pKa values of closely related
molecular dihydrogen complexes LnM(H2)(CO) and
LnM(H2)(PPh3) have not been reported previously. Due
to the presence of the stronger H-H bond in LnM(H2)-
(CO) as compared to LnM(H2)(PPh3), the difference in
the acidity of LnM(H2)(CO) and LnM(H2)(PPh3) may be
reduced. This study shows that complex 10 is more
acidic than complex 5 by ca. 7.9 pKa (pseudo aqueous)
units. The difference is quite similar to that of classic
hydride complexes. Thus, it appears that the difference
(41) Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth.
1970, 12, 237.
(42) Ahmad, N.; Levison, J . J .; Robinson, S. D.; Uttley, M. F.;
Wonchoba, E. R.; Parshall, G. W. Inorg. Synth. 1974, 15, 45.
(43) Bruce, M. I.; Humphrey, M. G.; Swincer, A. G.; Wallis, R. C.
Aust. J . Chem. 1984, 37, 1747.
(44) Dahlhoff, W. V.; Nelson, S. M. J . Chem. Soc. A 1971, 2184.
(45) Hoffman, P. R.; Caulton, K. G. J . Am. Chem. Soc. 1975, 97,
4221.

3948 Organometallics, Vol. 16, No. 18, 1997
J ia et al.
1H chemical shifts are relative to TMS, and 31P NMR chemical
shifts are relative to 85% H3PO4. IR spectra were collected
on a Perkin-Elmer 1600 spectrometer.
was recrystallized using dichloromethane/diethyl ether to give
a pale yellow solid. The solid was collected on a filter frit and
dried under vacuum overnight. Yield: 0.29 g, 85%. Anal.
Calcd for
C32H28ClNOP2Ru: C, 59.96; H, 4.40; N, 2.19.
Ru Cl2(P P h 3)(P MP ) (3). A mixture of 2.00 g of RuCl2-
(PPh3)3 (2.09 mmol) and 1.00 g of PMP (2.10 mmol) in acetone
(30 mL) was refluxed for 1 h to give a yellow precipitate. The
yellow solid was collected by filtration. A second crop of yellow
solid was obtained from the filtrate by reducing the volume of
the filtrate and cooling with an ice bath. The yellow solid was
dried under vacuum overnight. Yield: 1.81 g, 87%. The solid
was recrystallized from dichloromethane/methanol. Anal.
Calcd for C49H42Cl2NP3Ru‚CH2Cl2: C, 60.38; H, 4.46; N, 1.41.
Found: C, 60.88; H, 4.49; N, 1.41. 1H NMR (400 MHz,
CDCl3): δ 4.52 (t, J (PH) ) 4.9 Hz, 4 H, 2 CH2), 6.83-7.52 (m,
38 H, PPh3, 2 PPh2, py-3,4,5-H). 31P{1H} NMR (161.70 MHz,
CDCl3): δ 29.6 (d, J (PP) ) 27.7 Hz), 35.9 (t, J (PP) ) 27.7 Hz).
Ru HCl(P P h 3)(P MP ) (4). A mixture of 0.20 g of RuCl2-
(PPh3)(PMP) (0.22 mmol) and 0.10 g of NaBH4 (0.24 mmol) in
methanol (25 mL) was refluxed for 30 min to give an orange-
brown solution. The reaction mixture was allowed to cool to
room temperature to give a bright yellow precipitate. The solid
was collected on a filter frit, washed with hexane, and dried
under vacuum overnight. Yield: 0.18 g, 91%. Anal. Calcd
for C49H43ClNP3Ru: C, 67.24; H, 4.95; N, 1.60. Found: C,
67.10; H, 5.19; N, 1.51. 1H NMR (400 MHz, C6D6): δ -16.55
(q, J (PH) ) 22.2 Hz, 1 H, RuH), 3.73 (dt, J (HH) ) 15.7 Hz,
J (PH) ) 3.9 Hz, 2 H, CHH(C5H3N)CHH), 4.69 (br d, J (HH) )
15.7 Hz, 2 H, CHH(C5H3N)CHH), 6.41 (d, J (HH) ) 7.8 Hz, 2
H, py-3,5-H), 6.59 (t, J (HH) ) 7.8 Hz, 1 H, py-4-H), 6.84-8.14
(m, 35 H, PPh3, 2 PPh2). 31P{1H} NMR (161.70 MHz, C6D6): δ
47.2 (d, J (PP) ) 27.8 Hz), 57.9 (t, J (PP) ) 27.8 Hz).
Found: C, 59.73; H, 4.66; N, 1.92. IR (KBr, cm-1): ν(CO) 1916
(s). 1H NMR (300 MHz, CD2Cl2): δ -13.65 (t, J (PH) ) 19.9,
1H, RuH), 4.13 (dt, J (HH) ) 16.6 Hz, J (PH) ) 4.8 Hz, 2 H,
CHH(C5H3N)CHH), 4.64 (dt, J (HH) ) 16.6 Hz, J (PH) ) 4.5
Hz, 2 H, CHH(C5H3N)CHH), 6.82-7.85 (m, 23 H, 2 PPh2, py-
3,4,5-H). 31P{1H} NMR (121.51 MHz, CD2Cl2): δ 50.4 (s).
[Ru H(CO)(P P h 3)(P MP )]Cl (8). A mixture of 0.80 g of
RuHCl(CO)(PPh3)3 (0.84 mmol) and 0.57 g of PMP (1.2 mmol)
in 30 mL of acetone was refluxed for 45 min to give a greenish
solution. The hot solution was filtered through a filter frit.
The solvent was reduced to ca. 1 mL under vacuum, and 40
mL of diethyl ether was added to give a white solid. The solid
was recrystallized with CH2Cl2/benzene, washed with diethyl
ether and hexane, and dried under vacuum overnight. Yield:
0.52 g, 68%. Anal. Calcd for C50H43ClNOP3Ru: C, 66.48; H,
4.80; N, 1.55. Found: C, 66.31; H, 5.01; N, 1.50. IR (KBr,
cm-1): ν(CO) 1978 (s), ν(Ru-H) 1885 (w). 1H NMR (300 MHz,
CDCl3): δ -4.08 (q, J (PH) ) 20.4 Hz, 1 H, RuH), 4.08 (dt,
J (HH) ) 16.3 Hz, J (PH) ) 4.2 Hz, 2 H, CHH(C5H3N)CHH),
4.50 (br d, J (HH) ) 16.3 Hz, 2 H, CHH(C5H3N)CHH), 6.94-
7.56 (m, 38 H, PPh3, 2 PPh2, py-3,4,5-H). 31P{1H} NMR
(121.51 MHz, CDCl3): δ 51.3 (d, J (PP) ) 26.0 Hz), 54.0 (t, J (PP)
) 26.0 Hz).
[Ru H(CO)(P P h 3)(P MP )]Cl (9). A mixture of 0.54 g of
RuHCl(CO)(PPh3)3 (0.57 mmol) and 0.30 g of PMP (0.63 mmol)
in benzene (25 mL) was refluxed overnight to give a clear
yellow solution. The solution was allowed to cool to room
temperature. The solvent was removed completely under
vacuum. Then 30 mL of methanol was added, and the mixture
was stirred for 1 min to give a clear yellow solution. The
solvent was removed again under vacuum, and 30 mL of
diethyl ether was added to give a yellow solid. The yellow solid
was collected on a filter frit, washed with diethyl ether and
hexane, and dried under vacuum overnight. Yield: 0.41 g,
82%. Anal. Calcd for C50H43ClNOP3Ru: C, 66.48; H, 4.80;
N, 1.55. Found: C, 66.23; H, 4.72; N, 1.46. IR (KBr, cm-1):
ν(CO) 1938 (s). 1H NMR (300 MHz, CD2Cl2): δ -6.79 (dt,
J (PH) ) 88.3, 21.5 Hz, 1 H, RuH), 3.72 (dt, J (HH) ) 16.9 Hz,
J (PH) ) 3.8 Hz, 2 H, CHH(C5H3N)CHH), 4.45 (dt, J (HH) )
16.9 Hz, J (PH) ) 5.0 Hz, 2 H, CHH(C5H3N)CHH), 6.72-7.70
(m, 38 H, PPh3, 2 PPh2, py-3,4,5-H). 31P{1H} NMR (121.51
MHz, CD2Cl2): δ 22.9 (t, J (PP) ) 14.9 Hz), 40.6 (d, J (PP) )
14.9 Hz).
[Ru Cl(H2)(CO)(P MP )]BF 4 (10). Due to its low stability,
this compound was not isolated but was characterized in situ.
To a dichloromethane-d2 solution (0.5 mL) of 10 mg of RuHCl-
(CO)(PMP) (0.016 mmol) in an NMR tube was added HBF4‚
Et2O until all the hydride signal of complex 7 disappeared.
1H and 31P NMR spectra were obtained immediately. 1H NMR
(300 MHz, CD2Cl2): δ -8.50 (br, Ru(H2)), 4.40-4.79 (m, CH2),
7.01-7.74 (m, PPh2, py-3,4,5-H). 31P{1H} NMR (121.51 MHz,
CD2Cl2): δ 40.6 (s). T1(400 MHz, CD2Cl2): ms (temperature)
22 (293 K), 15 (273 K), 12 (253 K), 11 (243 K), 11 (233 K), 11
(223 K), 12 (213 K), 15 (202 K). A plot of ln T1 vs 1000/T
showed the familiar “V” shape, and T1(min) was found to be
11 ms at 232 K.
[Ru Cl(H2)(P P h 3)(P MP )]BF 4 (5). Meth od A. To a CD2Cl2
solution (0.5 mL) of 10 mg of RuHCl(PPh3)(PMP) (0.01 mmol)
in an NMR tube was added 3 µL of tetrafluoroboric acid-
diethyl ether complex. 1H and 31P NMR were obtained
immediately.
Meth od B. A dichloromethane solution (4 mL) of 0.17 g
RuHCl(PPh3)(PMP) (0.65 mmol) was treated with tetra-
fluoroboric acid-diethyl ether complex (ca. 0.16 mL). The color
changed from bright yellow to yellow. The solution was
allowed to stir for 15 min and then transferred to a solution
of diethyl ether (30 mL) via a cannula. The white solid formed
was collected on a filter frit, washed with diethyl ether, and
dried under vacuum. Anal. Calcd for C49H44BClF4NP3Ru‚
CH2Cl2: C, 57.30; H, 4.42; N, 1.33. Found: C, 57.41; H, 4.68;
N, 4.68. 1H NMR (300 MHz, CD2Cl2): δ -10.49 (br, 2 H,
Ru(H2)), 4.19 (dt, J (HH) ) 16.7 Hz, J (PH) ) 4.3 Hz, 2 H, CHH-
(C5H3N)CHH), 4.81 (dt, J (HH) ) 16.7 Hz, J (PH) ) 4.4 Hz, 2
H, CHH(C5H3N)CHH), 7.02-7.55 (m, 38 H, PPh3, 2 PPh2, py-
3,4,5-H). 31P{1H} NMR (121.51 MHz, CD2Cl2): δ 33.4 (d, J (PP)
) 25.2 Hz), 38.5 (t, J (PP) ) 25.2 Hz). T1(400 MHz, CD2Cl2):
ms (temperature) 32 (293 K), 25 (273 K), 22 (253 K), 21 (243
K), 21 (233 K), 22 (223 K), 24 (213 K), 28 (202 K). A plot of ln
T1 vs 1000/T showed the familiar “V” shape, and T1(min) was
found to be 21 ms at 236 K.
[Ru Cl(HD)(P P h 3)(P MP )]BF 4. This complex was not iso-
lated but was prepared in an NMR tube and characterized by
NMR spectroscopy in situ. To a sample of 10 mg of RuHCl-
(PMP)(PPh3) dissolved in CD2Cl2 (0.5 mL) was added DBF4.
The DBF4 was prepared by adding 0.1 mL of D2O into 0.4 mL
of HBF4‚Et2O. The tube was then placed in an NMR probe,
and a 1H NMR spectrum of the solution was taken. The η2-
HD signal was observed after nulling the η2-H2 peak at δ
-10.49 by the inversion-recovery method. 1H NMR (400
MHz, CD2Cl2): δ -10.56 (tq, J (HD) ) 28.0, J (PH) ) 8.0 Hz,
Ru(HD)).
[Ru Cl(HD)(CO)(P MP )]BF 4. The compound was prepared
similarly, except that DBF4 was used instead of HBF4‚Et2O.
The η2-HD signal was observed after nulling the η2-H2 peak
at δ -8.50 ppm by the inversion-recovery method. 1H NMR
(400 MHz, CD2Cl2): δ -8.55 (br t, J (HD) ) 30.1 Hz, Ru(HD)).
OsCl2(P P h 3)(P MP ) (12). A mixture of 0.21 g of PMP (0.44
mmol) and 0.35 g of OsCl2(PPh3)3 (0.33 mmol) in 20 mL of
acetone was stirred at room temperature for 2 min. The color
changed immediately from green to orange. The solvent was
reduced to 1 mL under vacuum, and 40 mL of diethyl ether
was added to give an orange solid. The solid was collected on
a filter frit, washed with diethyl ether, and dried under
Ru HCl(CO)(P MP ) (7). A mixture of 0.51 g of RuHCl(CO)-
(PPh3)3 (0.54 mmol) and 0.30 g of PMP (0.63 mmol) in benzene
(25 mL) was refluxed overnight to give a clear yellow solution.
The solution was allowed to cool to room temperature. The
solvent was removed completely under vacuum, and 30 mL of
diethyl ether was added to give a yellow solid. The yellow solid

Properties of [MCl(H2)(L)(PMP)]BF4
Organometallics, Vol. 16, No. 18, 1997 3949
vacuum overnight. Yield: 0.29 g, 87%. Anal. Calcd for
of an acid and a base were loaded into an NMR tube, then
CD2Cl2 was added. After a suitable period of time, 1H and
31P NMR spectra were collected. The equilibrium is confirmed
by monitoring the reactions with NMR spectroscopy. In some
cases, the NMR spectra were recorded below room temperature
as mentioned previously. By measuring the intensity of the
1H and/or 31P resonances, one can estimate the relative
concentration of the species in equilibrium and therefore the
equilibrium constants.
Alternatively, an appropriate mixture of monohydrido com-
plexes were dissolved in CD2Cl2 in an NMR tube and then a
limited amount HBF4‚Et2O was added. After a suitable period
of time, NMR spectra were then recorded.
C
49H42Cl2NP3Os: C, 58.92; H, 4.24; N, 1.40. Found: C, 58.99;
H, 4.48; N, 1.50. 1H NMR (300 MHz, CDCl3): δ 4.50 (t, J (PH)
) 4.7 Hz, 4 H, 2 CH2), 6.88-7.57 (m, 38 H, PPh3, 2 PPh2, py-
3,4,5-H). 31P{1H} NMR (121.51 MHz, CDCl3): δ -17.0 (t,
J (PP) ) 15.6 Hz), -0.1 (d, J (PP) ) 15.6 Hz).
OsHCl(P P h 3)(P MP ) (13). A mixture of 0.21 g of OsCl2-
(PPh3)(PMP) (0.21 mmol) and 0.20 g of NaBH4 (5.3 mmol) was
refluxed in 20 mL of THF overnight. Then the reaction
mixture was cooled down to room temperature. The solvent
was then removed completely under vacuum, and the residue
was extracted with 30 mL of benzene, which was removed
subsequently under vacuum. After the addition of 30 mL of
ethanol, a yellow solid was formed, which was collected on a
filter frit, washed with ethanol, and dried under vacuum. The
solid was recrystallized from CH2Cl2/ethanol and dried under
Cr yst a llogr a p h ic An a lysis for R u Cl2(P P h 3)(P MP )‚
CH2Cl2. Suitable crystals for X-ray diffraction study were
obtained by slow diffusion of Et2O to a saturated CH2Cl2
solution of RuCl2(PPh3)(PMP) at room temperature. A speci-
men of dimensions 0.50 × 45 × 0.15 mm was mounted on a
glass fiber and used for the X-ray structure determination. The
diffraction data was collected on a Siemens P4-RA diffractom-
eter at 213 K. The crystal system was triclinic and in the space
group P1h. A total of 12 664 intensity measurements were
made using the 2θ-θ scan technique in the range 3.0 e 2θ e
vacuum. Yield: 0.14 g, 69%. Anal. Calcd for
C49H43-
ClNP3Os‚CH2Cl2: C, 57.23; H, 4.32; N, 1.34. Found: C, 57.33;
H, 4.53; N, 1.34. 1H NMR (300 MHz, CD2Cl2): δ -18.53 (q,
J (PH) ) 17.5 Hz, 1 H, Os-H), 4.09 (dt, J (HH) ) 15.8 Hz,
J (HH) ) 4.7 Hz, 2 H, CHH(C5H3N)CHH), 4.72 (dt, J (HH) )
15.8 Hz, J (PH) ) 3.7 Hz, 2 H, CHH(C5H3N)CHH), 6.78-7.80
(m, 38 H, PPh3, 2 PPh2, py-3,4,5-H). 31P{1H} NMR (121.51
MHz, THF-d8): δ 7.6 (t, J (PP) ) 15.7 Hz), 16.7 (d, J (PP) )
15.7 Hz).
50° (Mo KR radiation). Of these, 11 282 were unique (Rint
)
1.72%) and 9198 observed F g 4σ(F), which were used for
structure solution and refinement using the SHELXTL PLUS
program package. Solution by direct methods yielded the
positions of all non-hydrogen atoms. Refinement by full-
matrix least squares resulted in final discrepancy indices R
) 3.36%, Rw ) 4.11% with GOF ) 1.27. All non-hydrogen
atoms were refined with anisotropic thermal parameters. All
hydrogens were revealed in difference Fourier maps but then
placed in geometrically determined positions with dC-H ) 0.96
Å and refined isotropically with riding constraints and group
thermal parameters. The data/parameter ratio was 17.2/1 and
residual electron density/hole ratio +0.45/-0.51 e Å-3. Further
crystallographic details and selected bond distances and angles
for RuCl2(PPh3)(PMP)‚CH2Cl2 are given in Tables 1 and 2,
respectively.
[OsCl(H 2)(P P h 3)(P MP ]BF 4 (14). A few drops of HBF4‚
Et2O was added to a solution of 0.10 g of OsHCl(PPh3)(PMP)
(0.10 mmol) in 5 mL of dichloromethane, and the reaction
mixture was allowed to stir at room temperature for 10 min.
After the addition of 30 mL of diethyl ether, a white solid was
formed. The solid was collected on a filter frit, washed with
water and diethyl ether, and dried under vacuum overnight.
Yield: 80 mg, 73%. Anal. Calcd for C49H44BClF4NP3Os: C,
1
55.93; H, 4.21; N, 1.33. Found: C, 55.98; H, 4.27; N, 1.25. H
NMR (300 MHz, CD2Cl2): δ -9.04 (br q, J (PH) ) 11.8 Hz,
Os-H), 4.26 (dt, J (HH) ) 16.9 Hz, J (PH) ) 4.7 Hz, 2 H, CHH-
(C5H3N)CHH), 5.00 (dt, J (HH) ) 16.9 Hz, J (PH) ) 4.8 Hz, 2
H, CHH(C5H3N)CHH), 6.78-7.80 (m, 38 H, PPh3, 2 PPh2, py-
3,4,5-H). 31P{1H} NMR (121.51 MHz, CD2Cl2): δ -5.9 (t, J (PP)
) 14.1 Hz), 6.3 (d, J (PP) ) 14.1 Hz). T1 (300 MHz, CD2Cl2):
ms (temperature) 87 (298 K), 58 (273 K), 51 (263 K), 45 (253
K), 41 (243 K), 40 (233 K), 39 (223 K), 42 (213 K), 42 (203 K),
52 (193 K), 57 (183 K). A plot of ln T1 vs 1000/T showed the
familiar “V” shape, and T1(min) was found to be 39 ms at 220
K.
[OsCl(HD)(P P h 3)(P MP )]BF 4. The compound was pre-
pared similarly, except that DBF4 was used instead of HBF4‚
Et2O. The DBF4 was prepared by mixing HBF4‚Et2O and D2O
in a 3:1 volume ratio. The η2-HD signal was observed after
nulling the η2-H2 peak at δ -9.04 ppm by the inversion-
recovery method. 1H NMR (400 MHz, CD2Cl2): δ -9.10 (tq,
J (HD) ) 17.7 Hz, J (PH) ) 11.8 Hz, Ru(HD)).
Ack n ow led gm en t. We acknowledge the financial
support from the Hong Kong Research Grant Council
(Grant No. HKP 91/94P). We thank Professor Richard
Haynes for helpful discussion and proofreading the
manuscript.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and equivalent isotropic displacement coefficients,
complete bond lengths and bond angles, anisotropic displace-
ment coefficients, H-atom coordinates, and isotropic displace-
ment coefficients for RuCl2(PPh3)(PMP)‚CH2Cl2 (7 pages).
Ordering information is given on any current masthead page.
Acid ity Stu d y. The experiments were conducted under a
H2 atmosphere. In a typical experiment, appropriate amounts
OM970207+