Oxidative Addition of HX (X = H, SiR3, GeR3, SnR3, Cl) Molecules to the Complex Os(η5-C5H5)Cl(PiPr 3)2

Article abstract of DOI:10.1021/om990235n

The cyclopentadienyl complex Os(η⁵-C₅H₅)Cl(PⁱPr ₃)₂ (1) reacts with molecular hydrogen to give a mixture of the isomers transoid-dihydride OsH₂(η⁵-C₅H₅)Cl(P ⁱPr₃) (2a) and cisoid-dihydride OsH₂(η⁵-C₅H₅)Cl(P ⁱPr₃) (2b). Isomer 2a has a rigid structure in solution. However, the hydride ligands of 2b undergo a thermally activated site exchange process and show quantum exchange coupling. The reaction of the isomeric mixture of 2a and 2b with NaBH₄ and methanol leads to the trihydride OsH₃(η⁵-C₅H₅)(P ⁱPr₃) (3). In solution, the cisoid hydride ligands of this complex also undergo a thermally activated site exchange process. The activation parameters are ΔH? = 15.1 ± 0.3 kcal?mol^-1 and ΔS? = 0.5 ± 0.7 cal?mol^-1?K^-1. Complex 1 also reacts with group 14 element hydride compounds to afford OsH(η⁵-C₅H₅)Cl(ER₃)(P ⁱPr₃) [ER₃ = SiEt₃ (4), Si(CH₂-CH=CH₂)Me₂ (5), SiPh₃ (6), SiHPh₂ (7), SiH₂-Ph (8), GeEt₃ (9), GePh₃ (10), GeHPh₂ (11), SnⁿBu₃ (12), SnPh₃ (13)]. The structure of 7 has been determined by an X-ray investigation. The distribution of ligands around the metallic center can be described as a piano stool geometry with the triisopropylphosphine and diphenylsilyl ligands disposed mutually transoid. Complex 12 reacts with HSnⁿBu₃ to give the dihydride-stannyl derivative OsH₂(η⁵-C₅H₅)(Sn ⁿBu₃)(PⁱPr₃) (14). The reaction of 1 with HCl leads to a mixture of the monohydrides OsH(η⁵-C₅H₅)Cl₂(P ⁱPr₃) (15) and [OsH(η⁵-C₅H₅)Cl(PⁱPr ₃)₂]⁺ (16). Complexes 15 and 16 can also be obtained by reaction of 6 with HCl and by protonation of 1 with HBF₄, respectively.

Full text of DOI:10.1021/om990235n

5034
Organometallics 1999, 18, 5034-5043
Oxid a tive Ad d ition of HX (X ) H, SiR3, GeR3, Sn R3, Cl)
Molecu les to th e Com p lex Os(η5-C5H5)Cl(P iP r 3)2
Miguel Baya,† Pascale Crochet,† Miguel A. Esteruelas,*,†
Enrique Gutie´rrez-Puebla,‡ and Natividad Ruiz†
Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain, and Instituto de Ciencia de
Materiales de Madrid, CSIC, Campus de Cantoblanco, 28049 Madrid, Spain
Received April 5, 1999
The cyclopentadienyl complex Os(η5-C5H5)Cl(PiPr3)2 (1) reacts with molecular hydrogen
to give a mixture of the isomers transoid-dihydride OsH2(η5-C5H5)Cl(PiPr3) (2a ) and cisoid-
dihydride OsH2(η5-C5H5)Cl(PiPr3) (2b). Isomer 2a has a rigid structure in solution. However,
the hydride ligands of 2b undergo a thermally activated site exchange process and show
quantum exchange coupling. The reaction of the isomeric mixture of 2a and 2b with NaBH4
and methanol leads to the trihydride OsH3(η5-C5H5)(PiPr3) (3). In solution, the cisoid hydride
ligands of this complex also undergo a thermally activated site exchange process. The
activation parameters are ∆Hq ) 15.1 ( 0.3 kcal‚mol-1 and ∆Sq ) 0.5 ( 0.7 cal‚mol-1‚K-1
.
Complex 1 also reacts with group 14 element hydride compounds to afford OsH(η5-
C5H5)Cl(ER3)(PiPr3) [ER3 ) SiEt3 (4), Si(CH2-CHdCH2)Me2 (5), SiPh3 (6), SiHPh2 (7), SiH2-
Ph (8), GeEt3 (9), GePh3 (10), GeHPh2 (11), SnnBu3 (12), SnPh3 (13)]. The structure of 7 has
been determined by an X-ray investigation. The distribution of ligands around the metallic
center can be described as a piano stool geometry with the triisopropylphosphine and
diphenylsilyl ligands disposed mutually transoid. Complex 12 reacts with HSnnBu3 to give
the dihydride-stannyl derivative OsH2(η5-C5H5)(SnnBu3)(PiPr3) (14). The reaction of 1 with
HCl leads to a mixture of the monohydrides OsH(η5-C5H5)Cl2(PiPr3) (15) and [OsH(η5-
C5H5)Cl(PiPr3)2]+ (16). Complexes 15 and 16 can also be obtained by reaction of 6 with HCl
and by protonation of 1 with HBF4, respectively.
In tr od u ction
ligand occurs, and the resulting fragment is capable of
activating a methyl C-H bond of a triisopropylphos-
In recent years, we have shown that in the iron triad
not only iron and ruthenium but also osmium form
complexes that behave as good catalysts for the reduc-
tion of unsaturated organic substrates1 and for the
addition of group 14 element hydride compounds to
terminal alkynes.2 In connection with these reactions,
the oxidative additions of molecular hydrogen, silanes,
germanes, and stannanes to osmium precursors are
elementary processes of considerable interest.3
phine to give [OsH(η5-C5H5){CH2CH(CH3)PiPr2}(PiPr3)]+.
On the other hand, in pentane and toluene, the dis-
sociation of a phosphine ligand is favored, and the
reactions of 1 with olefins and alkynes afford chloro
π-olefin and π-alkyne derivatives.4 The π-alkyne com-
plexes evolve into vinylidene or alternatively alle-
nylidene derivatives, depending upon the nature of the
alkyne.6c
As a part of our study on the chemical properties of
the six-coordinate osmium(IV) complex OsH2Cl2(PiPr3)2,
we have recently reported the synthesis of the half-
sandwich compound Os(η5-C5H5)Cl(PiPr3)2 (1).4 Al-
though, in comparison with the related iron and ruthe-
nium complexes, the Os(η5-C5H5)L3 derivatives show a
higher kinetic stability,5 complex 1 is a useful starting
material for the development of new cyclopentadienyl-
osmium chemistry.4,6 Thus, in polar solvents such as
methanol and acetone, the dissociation of the chlorine
(3) (a) Clark, G. R.; Flower, K. R.; Rickard, C. E. F.; Roper, W. R.;
Salter, D. M.; Wright, L. J . J . Organomet. Chem. 1993, 462, 331. (b)
Buil, M. L.; Espinet, P.; Esteruelas, M. A.; Lahoz, F. J .; Lledo´s, A.;
Mart´ınez-Ilarduya, J . M.; Maseras, F.; Modrego, J .; On˜ate, E.; Oro, L.
A.; Sola, E.; Valero, C. Inorg. Chem. 1996, 35, 1250. (c) Clark, A. M.;
Rickard, C. E. F.; Roper, W. R.; Wright, L. J . J . Organomet. Chem.
1997, 543, 111. (d) Wanandi, P. W.; Tilley, T. D. Organometallics 1997,
16, 4299. (e) Hu¨bler, K.; Hu¨bler, U.; Roper, W. R.; Schwerdtfeger, P.;
Wright, L. J . Chem. Eur. J . 1997, 3, 1608. (f) Hu¨bler, K.; Roper, W.
R.; Wright, L. J . Organometallics 1997, 16, 2730. (g) Hu¨bler, K.; Hunt,
P. A.; Maddock, S. M.; Rickard, C. E. F.; Roper, W. R.; Salter, D. M.;
Schwerdtfeger, P.; Wright, L. J . Organometallics 1997, 16, 5076. (h)
Attar-Bashi, M. T.; Rickard, C. E. F.; Roper, W. R.; Wright, L. J .;
Woodgate, S. D. Organometallics 1998, 17, 504. (i) Corey, J . Y.;
Braddock-Wilking, J . Chem. Rev. 1999, 99, 175.
† Universidad de Zaragoza-CSIC.
‡ Instituto de Ciencia de Materiales de Madrid, CSIC.
(1) (a) Chaloner, P. A.; Esteruelas, M. A.; J oo´, F.; Oro, L. A.
Homogeneous Hydrogenation; Kluwer Academic Publishers: Dor-
drecht, 1994; Chapter 2. (b) Sa´nchez-Delgado, R. A.; Rosales, M.;
Esteruelas, M. A.; Oro, L. A. J . Mol. Catal. A: Chem. 1995, 96, 231.
(c) Esteruelas, M. A.; Oro, L. A. Chem. Rev. 1998, 98, 577.
(2) (a) Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics 1991,
10, 462. (b) Esteruelas, M. A.; Lo´pez, A. M.; Oro, L. A.; Tolosa, J . I. J .
Mol. Catal. A: Chem. 1995, 96, 21.
(4) Esteruelas, M. A.; Lo´pez, A. M.; Ruiz, N.; Tolosa, J . I. Organo-
metallics 1997, 16, 4657.
(5) Atwood, J . D. Inorganic and Organometallic Reaction Mecha-
nisms; VCH Publishers: New York, 1997; Chapter 3.
(6) (a) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Oro, L. A.
Organometallics 1996, 15, 878. (b) Crochet, P.; Esteruelas, M. A.;
Gutie´rrez-Puebla, E. Organometallics 1998, 17, 3141. (c) Crochet, P.;
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1998, 17, 3479.
10.1021/om990235n CCC: $18.00 © 1999 American Chemical Society
Publication on Web 10/24/1999

Oxidative Addition to Os Complexes
Organometallics, Vol. 18, No. 24, 1999 5035
In the search for new osmium complexes that could
be catalytically active in the reduction of unsaturated
organic substrates and in the addition of group 14
element hydride compounds to terminal alkynes, we
have now studied the reactivity of 1 toward molecular
hydrogen, group 14 element hydride compounds, and
HCl.
In this paper, we report the resulting products of the
reactions of 1 with these molecules. Although the half-
sandwich Ru(η5-C5R5) (R) Me, H) and Os(η5-C5Me5)
complexes exhibit a particularly rich and interesting
chemistry,7 which has formed one of the cornerstones
in the development of organometallic chemistry, the
chemistry of the corresponding Os(η5-C5H5) unit is a
little-known field.8
(29 Hz)9 and in the dihydride cations [RuH2(η5-C5Me5)-
(PMe3)2]+ (33 Hz),10 [RuH2(η5-C5H5)(PMe3)2]+ (29 Hz),11
[OsH2(η5-C5H5)(PiPr3)2]+ (32.2 Hz),4 and [OsH2(η5-C5H5)-
(PPh3)2]+ (29.0 Hz),12 where hydride and phosphine
ligands mutually cisoid have been also proposed. Fur-
thermore, in agreement with the presence in the mol-
ecule of a mirror plane of symmetry containing the
i
Os-P bond, the spectrum shows only one Pr-methyl
chemical shift, in the low-field region.
The 31P{1H} NMR spectrum contains at 43.1 ppm a
singlet, which is split into a triplet under off-resonance
conditions as a result of the P-H coupling with two
equivalent hydride ligands.
In contrast to the 1H NMR spectrum of 2a , the 1H
NMR spectrum of 2b is temperature dependent and
consistent with the operation of a thermally activated
site exchange process involving the hydride ligands. In
toluene-d8, at room temperature, it exhibits in the
hydride region a single doublet resonance at -11.05
ppm with a H-P coupling constant of 15.6 Hz, which is
between that found in 2a and the expected one for a
hydride ligand disposed transoid to the phosphine
(about 8 Hz).13 Lowering the sample temperature leads
to broadening of the resonance until becoming lost in
the baseline of the spectrum, which happens between
223 and 193 K. At temperatures lower than 193 K, the
spectra show two broad complex resonances centered
at -7.50 and -15.04 ppm. With 31P decoupling, these
resonances are simplified to the expected doublets. The
values of the chemical shifts show no significant tem-
perature dependence. However, the magnitude of the
observed H-H coupling constant is sensitive to tem-
perature, decreasing in the sequence 63 Hz (178 K), 52
Hz (173 K), 40 Hz (168 K), and 30 Hz (163 K).
Resu lts a n d Discu ssion
1. Rea ction of Os(η5-C5H5)Cl(P iP r 3)2 w ith Molec-
u la r Hyd r ogen . Bubbling molecular hydrogen through
a pentane solution of the complex Os(η5-C5H5)Cl(PiPr3)2
(1) produces the displacement of a coordinated triiso-
propylphosphine ligand and the formation of the os-
mium(IV) dihydride OsH2(η5-C5H5)Cl(PiPr3) (2), which
was isolated as a white solid in 67% yield. The solid is
a mixture of the isomers 2a and 2b (eq 1), as is proved
by the IR spectrum of the solid in Nujol, which shows
two ν(Os-H) bands at 2059 (2a ) and 2121 (2b) cm-1
.
At room temperature, in solution, the 2a :2b molar ratio
depends on the used solvent. In dichloromethane-d2 this
value is 20:1, while in toluene-d8 it decreases to 9:2.
We note that Caulton et al. have previously reported
the reaction of Ru(η5-C5Me5)(ORf)(PiPr2Ph) (ORf )
OSiPh3, NHPh, OCH2CF3) with 2 equiv of HSi(OMe)3
to afford RuH2(η5-C5Me5){Si(OMe)3}(PiPr2Ph), which
has also a four-legged piano stool structure with the
hydrides mutually cisoid. For this complex, the value
2
of the J HH constant is 10 Hz.13 In agreement with this
magnitude, Graham has reported a value of 9 Hz for
the H-H coupling constant between the inequivalent
hydride ligands of OsH3(η5-C5Me5)(CO).14 For 2b, the
large value of the 2J HH constant and its dependence with
the temperature can be rationalized in terms of quan-
tum exchange coupling between the hydrides. This
phenomenon, which is presently attracting considerable
interest,15 is usually observed on trihydride complexes.
For osmium, three types of compounds have been shown
to display quantum exchange coupling: the cationic
arene osmium(IV) derivatives [OsH3(η6-C6H6)(PR3)]+
(PR3 ) PCy3, PPh3, MPTB),16 the six-coordinate os-
1
The H NMR spectrum of 2a in dichloromethane-d2,
which is temperature invariant between 293 and 163
K, is consistent with a four-legged piano stool structure
with the hydrides transoid. Thus, it shows at -10.09
ppm a doublet with a H-P coupling constant of 33.6
Hz, which agrees well with those found in the dihy-
dride-silyl derivative RuH2(η5-C5Me5)(SiMePh2)(PiPr3)
(7) (a) Albers, M. O.; Robinson, D. J .; Singleton, E. Coord. Chem.
Rev. 1987, 79, 1. (b) Davies, S. G.; McNally, J . P.; Smallridge, A. J .
Adv. Organomet. Chem. 1990, 30, 1.
(9) (a) Campion, B. K.; Heyn, R. H.; Tilley, T. D. Chem. Commun.
1992, 1201. (b) Campion, B. K.; Heyn, R. H.; Tilley, T. D.; Rheingold,
A. L. J . Am. Chem. Soc. 1993, 115, 5527.
(10) Grumbine, S. K.; Mitchell, G. P.; Strauss, D. A.; Tilley, T. D.;
Rheingold, A. L. Organometallics 1998, 17, 5607.
(11) Lemke, F. R.; Brammer, L. Organometallics 1995, 14, 3980.
(12) Rottink, M. K.; Angelici, R. J . J . Am. Chem. Soc. 1993, 115,
7267.
(13) J ohnson, T. J .; Loan, P. S.; Caulton, K. G. Inorg. Chem. 1993,
32, 4594.
(14) Hoyano, J . K.; Graham, W. A. G. J . Am. Chem. Soc. 1982, 104,
3722.
(8) (a) Bruce, M. I.; Wong, F. S. J . Organomet. Chem. 1981, 210,
C5. (b) Hoyano, J . K.; May, C. J .; Graham, W. A. G. Inorg. Chem. 1982,
21, 3095. (c) Bruce, M. I.; Tomkins, I. B.; Wong, F. S.; Shelton, B. W.;
White, A. H. J . Chem. Soc., Dalton Trans. 1982, 687. (d) Wilczewski,
T. J . Organomet. Chem. 1986, 317, 307. (e) Bruce, M. I.; Humphrey,
M. G.; Koutsantonis, G. E.; Liddell, M. J . J . Organomet. Chem. 1987,
236, 247. (f) Bruce, M. I.; Koutsantonis, G. A.; Liddell, M. J .; Nicholson,
B. K. J . Organomet. Chem. 1987, 320, 217. (g) Kawano, Y.; Tobita, H.;
Ogino, H. Organometallics 1994, 13, 3849. (h) J ia, G.; Ng, W. S.; Yao,
J .; Lau, C.; Chen, Y. Organometallics 1996, 15, 5039. (i) Shapley, P.
A.; Shusta, J . M.; Hunt, J . L. Organometallics 1996, 15, 1622. (j)
Freedman, D. A.; Gill, T. P.; Blough, A. M.; Koefod, R. S.; Mann, K. R.
Inorg. Chem. 1997, 36, 95. (k) Koch, J . L.; Shapley, P. A. Organome-
tallics 1999, 18, 814.
(15) Sabo-Etienne, S.; Chaudret, B. Chem. Rev. 1998, 98, 2077.
(16) Heinekey, D. M.; Harper, T. G. P. Organometallics 1991, 10,
2891.

5036 Organometallics, Vol. 18, No. 24, 1999
Baya et al.
mium(IV) complexes OsH3X(PiPr3)2 (X ) Cl, Br, I),17 and
the seven-coordinate osmium(IV) compounds OsH3-
(Hbiim)(PiPr3)2 (H2biim ) 2,2-biimadazole), (PiPr3)2H3-
Os(µ-biim)M(COD) (M ) Rh, Ir),18 [OsH3(diolefin)-
(PiPr3)2]+ (diolefin ) TFB, NBD),19 OsH3{κ-N,κ-S-(2-
Spy)}(PiPr3)2, and [(PiPr3)2H3Os(µ-biim)M(TFB)]2 (TFB
) tetrafluorobenzobarrelene, M ) Rh, Ir).20 With the
notable exception of the tantalum complexes [TaH2(η5-
C5H5)2(PR3)]+ (PR3 ) P(OMe)3, PMe2Ph),21 the phenom-
enon has not been previously observed on dihydride
derivatives.
In contrast to the 1H NMR spectrum, the 31P{1H}
NMR spectrum of 2b is temperature invariant. At 293
K, it shows a singlet at 32.1 ppm, which is split into a
broad triplet under off-resonance conditions as a result
of the P-H coupling with two inequivalent hydrides
undergoing a rapid fluxional process.
Treatment at room temperature of a toluene solution
of the isomeric mixture of 2 with NaBH4 and some drops
of methanol leads to the trihydride derivative OsH3(η5-
C5H5)(PiPr3) (3), which was isolated as a colorless oil,
according to eq 2.
1
F igu r e 1. Variable-temperature 300 MHz H{31P} NMR
spectra in the high-field region of complex OsH3(η5-C5H5)-
(PiPr3) (3) in toluene-d8: (a) experimental, (b) simulated.
The IR spectrum of the oil between polyethylene
sheets shows a strong ν(Os-H) band at 2091 cm-1. At
room temperature, the 31P{1H} NMR spectrum in
dichloromethane-d2 as solvent contains at 53.9 ppm a
singlet. This spectrum is temperature invariant down
1
to 243 K. However, the H NMR spectrum is tempera-
ture dependent. At 363 K, the spectrum exhibits in the
hydride region a single broad doublet resonance at
-14.97 ppm with a H-P coupling constant of about 16
Hz. This observation is consistent with the operation
of the thermally activate site exchange process shown
in eq 3, which proceeds at a sufficient rate to lead to a
single hydride resonance.
F igu r e 2. Eyring plot of the rate constants for thermally
activated site exchange process of complex OsH3(η5-C5H5)-
(PiPr3) (3).
Consistent with this, lowering the sample tempera-
ture leads to broadening of the resonance. At 313 K,
decoalescence occurs and a pattern corresponding to an
AB2X spin system (X ) 31P) is observed, which becomes
well-resolved at 243 K. The AB2X spin system is defined
by the parameters δA ) -13.9 ppm, δB ) -15.0 ppm,
J AB ) 3.4 Hz, J AX ) 3 Hz, and J BX ) 33.0 Hz, which
are temperature invariant. This indicates that, in
contrast to 2b, quantum exchange coupling between Ha
and Hb does not take place.
(17) (a) Gusev, D. G.; Kuhlman, R.; Sini, G.; Eisenstein, O.; Caulton,
K. G. J . Am. Chem. Soc. 1994, 116, 2685. (b) Clot, E.; Leforestier, C.;
Eisenstein, O.; Pe´lissier, M. J . Am. Chem. Soc. 1995, 117, 1797. (c)
Kuhlman, R.; Clot, E.; Leforestier, C.; Streib, W. E.; Eisenstein, O.;
Caulton, K. G. J . Am. Chem. Soc. 1997, 119, 10153.
(18) Esteruelas, M. A.; Lahoz, F. J .; Lo´pez, A. M.; On˜ate, E.; Oro,
L. A.; Ruiz, N.; Sola, E.; Tolosa, J . I. Inorg. Chem. 1996, 35, 7811.
(19) Castillo, A.; Esteruelas, M. A.; On˜ate, E.; Ruiz, N. J . Am. Chem
Soc. 1997, 119, 9691.
(20) Castillo, A.; Barea, G.; Esteruelas, M. A.; Lahoz, F. J .; Lledo´s,
A.; Maseras, F.; Modrego, J .; On˜ate, E.; Oro, L. A.; Ruiz, N.; Sola, E.
Inorg. Chem. 1999, 38, 1814.
(21) (a) Leboeuf, J . F.; Lavastre, O.; Leblanc, J . C.; Moise, C. J .
Organomet. Chem. 1991, 418, 359. (b) Chaudret, B.; Limbach, H. H.;
Moise, C. C. R. Acad. Sci., Ser. II 1992, 315, 533. (c) Sabo-Etienne, S.;
Chaudret, B.; Abou El Makarim, H.; Barthelat, J . C.; Daudey, J . P.;
Ulrich, S.; Limbach, H. H.; Moise, C. J . Am. Chem. Soc. 1995, 117,
11602.
With 31P decoupling (Figure 1a), the spectra are
simplified to the expected AB2 spin system. Line shape
analysis of the spectra of Figure 1 allows the calculation
of the rate constants for the thermal exchange process
at different temperatures. The activation parameters
obtained from the Eyring analysis (Figure 2) are ∆Hq
) 15.1 ( 0.3 kcal‚mol-1 and ∆Sq ) 0.5 ( 0.7 cal‚mol-1
‚
K-1. The value for the entropy of activation, close to
zero, is in agreement with an intramolecular process,

Oxidative Addition to Os Complexes
Organometallics, Vol. 18, No. 24, 1999 5037
while the value for the enthalpy of activation lies in the
range reported for thermal exchange processes in other
trihydride and hydride-dihydrogen derivatives.18-20,22
Theoretical studies on the hydride exchange processes
in trihydride species suggest that the thermally acti-
vated site exchange takes place through dihydrogen
transition states, which are reached by a shortening of
the H-H distance and a lengthening of the M-H
distance. Thus, the barrier for the exchange is the
addition of the necessary energy for the dihydrogen
formation and the rotation energy of the dihydrogen.23
Comparison of the 1H NMR spectra of 3 and 2b
indicates that the barrier for the thermally activate site
exchange between the hydrides Ha and Hb of 3 is higher
than the barrier for the related process on 2b. A similar
relationship has been previously observed between the
barriers for the exchanges of the related hydrogens of
2. Rea ction s of Os(η5-C5H5)Cl(P iP r 3)2 w ith Si-
la n es. Addition of an excess of HSiEt3 to a benzene-d6
solution of 1 leads to a mixture of 1 and the hydride-
silyl complex OsH(η5-C5H5)Cl(SiEt3)(PiPr3) (4), accord-
ing to the equilibrium shown in eq 4. After 30 min the
equilibrium is reached, and at 293 K the value of the
equilibrium constant is 0.4. In diethyl ether as solvent
and in the presence of 1 equiv of HBF4, the equilibrium
is displaced to the right due to the formation of [HPiPr3]-
[BF4], which precipitates as a white solid. In this way,
complex 4 can be isolated from the diethyl ether solution
as a yellow solid.
Similarly to HSiEt3, addition of HSi(CH2-CHdCH2)-
Me2 to a benzene-d6 solution of 1 produces a mixture of
1 and the hydride-silyl compound OsH(η5-C5H5)Cl{Si-
(CH2-CHdCH2)Me2}(PiPr3) (5). In this case, at 293 K
the value of the equilibrium constant is 45.2. Under the
same conditions, addition of 1 equiv of HSiPh3, H2SiPh2,
or H3SiPh to benzene-d6 solutions of 1 leads to the
derivatives OsH(η5-C5H5)Cl(SiR3)(PiPr3) [SiR3 ) SiPh3
(6), SiHPh2 (7), SiH2Ph (8)] in quantitative yield,
according to the 1H and 31P{1H} NMR spectra of the
reaction mixtures. These compounds were also isolated
as yellow solids.
the trihydride OsH3{NHdC(Ph)C6H4}(PiPr3)2 and the
elongated dihydrogen OsCl{NHdC(Ph)C6H4}(η2-H2)-
(PiPr3)2. Although in both cases the hydrogen atoms
form dihydrogen ligands in the transition state, the
energy barrier for the exchange in the trihydride is
significantly higher than the barrier for the exchange
in the elongated dihydrogen. The explanation for this
fact can be found in the different cost for the dihydrogen
formation. The approach of the dihydrogen atoms in the
elongated dihydrogen complex costs only 4.0 kcal‚mol-1
,
while 10.5 kcal‚mol-1 is necessary in the trihydride. The
presence of a cis-chloride ligand instead of a hydride
facilitates the approach between the hydrogen atoms.
Once the dihydrogen ligands are formed, the rotational
barriers are similar.24
We note that the trihydride OsH3(η5-C5Me5)(PPh3)
has been previously prepared by reaction of Os(η5-C5-
Me5)Br2(PPh3) with NaBH4.25 In contrast to 3, it is
nonfluxional. As it has been previously mentioned, the
thermally activated site exchange processes in trihy-
drido species take place through dihydrogen transition
states. Since the dihydrogen character of the H2 unit is
favored by decreasing the basicity of the coligand, and
the basicity of triisopropylphosphine is higher than that
of triphenylphosphine, the different behavior of the H3
unit of 3 and OsH3(η5-C5Me5)(PPh3) can be related with
the different electron donor power of the cyclopentadi-
enyl and pentamethylcyclopentadienyl ligands. The
lower basicity of the first favors the dihydrogen transi-
tion state, giving rise to a lower energy barrier to the
hydrogen exchange. The relation between the basicity
of these ligands and the energy barriers for the ex-
change between the hydride ligands of the complexes
RuH3(η5-C5R5)(PR′3) (R ) H, Me) has been elegantly
ilustrated by Chaudret et al.15
The above-mentioned observations indicate that the
constant of the equilibrium shown in eq 4 increases in
the sequence HSiEt3<HSi(CH2-CHdCH2)Me2<H4-x
-
SiPhx (x ) 1-3). Previously, it has been recognized that
the strength of the metal-silyl bond depends on the
substituent effects and also on the coordination number
and the oxidation state of the metal.26 For basic metallic
fragments, the more electronegative substituents appear
to give rise to stronger metal-silicon bonds.27 Recently,
Hu¨bler, Roper, and co-workers3g have studied from
structural and theoretical points of view osmium-silyl
complexes of the type OsCl(SiR3)(CO)(PPh3)2, with the
silyl group changing from SiF3 to SiCl3, Si(OH)3, and
SiMe3. The results reveal that, in addition to the Os-
Si σ-bond, there is an increasing importance of π-bond-
ing when going from the methyl to the hydroxy, the
chloro, and the fluoro derivative. However, no higher
d-orbital population on silicon was found in any complex
when compared with the corresponding free silanes. The
osmium d-orbitals mostly donate into a linear combina-
tion of Si-R σ*-orbitals to form the π-bond. The d-
orbitals on silicon serve to polarize the Si-R σ*-orbitals.
(22) (a) Earl, K. A.; J ia, G.; Maltby, P. A.; Morris, R. H. J . Am. Chem.
Soc. 1991, 113, 3027. (b) Bautista, M. T.; Cappellani, E. P.; Drouin, S.
D.; Morris, R. H.; Schweitzer, C. T.; Sella, A.; Zubkowski, J . J . Am.
Chem. Soc. 1991, 113, 4876. (c) J ia, G.; Drouin, S. D.; J essop, P. G.;
Lough, A. J .; Morris, R. H. Organometallics 1993, 12, 906.
(23) (a) J arid, A.; Moreno, M.; Lledo´s, A.; Lluch, J . M.; Beltra´n, J .
J . Am. Chem. Soc. 1995, 117, 1069. (b) Demachy, I.; Esteruelas, M.
A.; J ean, Y.; Lledo´s, A.; Maseras, F.; Oro, L. A.; Valero, C.; Volatro´n,
F. J . Am. Chem. Soc. 1996, 118, 8388. (c) Camanyes, S.; Maseras, F.;
Moreno, M.; Lledo´s, A.; Lluch, J . M.; Beltra´n, J . J . Am. Chem. Soc.
1996, 118, 4617.
(24) Barea, G.; Esteruelas, M. A.; Lledo´s, A.; Lo´pez, A. M.; On˜ate,
E.; Tolosa, J . I. Organometallics 1998, 17, 4065.
(25) Gross, C. L.; Wilson, S. R.; Girolami, G. S. J . Am. Chem. Soc.
1994, 116, 10294.
(26) Cundy, C. S.; Kingston, B. M.; Lappert, M. F. Adv. Organomet.
Chem. 1973, 11, 253.
(27) Lichtenberger, D. L.; Rai-Chaudhuri, A. J . Am. Chem. Soc.
1991, 113, 2923.

5038 Organometallics, Vol. 18, No. 24, 1999
Baya et al.
Sch em e 1
F igu r e 3. Molecular diagram of complex OsH(η5-C5-
H5)Cl(SiHPh2)(PiPr3) (7). Thermal ellipsoids are shown at
50% probability.
(E ) Si, Ge, Sn) bond to the osmium atom of the
fragment Os(η5-C5H5)Cl(PiPr3) parallel to the Cl-P
vector, with the E atom on the chloride (Scheme 1). The
basis of this preference is probably steric and involves
minimizing nonbonded interactions between the ER3
ligands and the isopropyl groups of the phosphine.
The Os-Si bond length [2.406(2) Å] is about 0.05 Å
shorter than the Os-Si distance found in the trihydride
OsH3(SiHPh2)(CO)(PiPr3)2 [2.448(2) Å],3b and about 0.1
Å longer than that reported for OsH3{Si(N-pirrolyl)3}-
(PPh3)2 [2.293(3) Å].3e The environment of the silicon
atom is tetrahedral, with angles between 97(3)° and
118.2(2)°.
The hydride ligand H(01) was located in the difference
Fourier maps and refined as an isotropic atom together
with the rest of non-hydrogen atoms of the structure,
giving an Os-H(01) distance of 1.69(8) Å. The separa-
tion between this ligand and the silyl group (about 2.24
Å) precludes any hydride-silyl interaction and indicates
that one of the two H-Si bonds of H2SiPh2 has been
fully oxidatively added to the metal.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) of th e Com p lex
OsH(η5-C5H5)Cl(P iP r 3)(SiHP h 2) (7)
Os-Cl
Os-P
2.426(2)
2.354(2)
2.406(2)
1.69(8)
Si-C(15)
Si-C(21)
Si-H(02)
1.887(8)
1.903(8)
1.32(8)
Os-Si
Os-H(01)
Ga-Os-Cl
Ga-Os-P
113.2(3)
131.2(3)
124.2(3)
108(2)
80.76(7)
101.96(8)
64(2)
P-Os-H(01)
Cl-Os-H(01)
Os-Si-C(15)
Os-Si-C(21)
Os-Si-H(02)
C(15)-Si-C(21)
C(15)-Si-H(02)
C(21)-Si-H(02)
77(2)
136(2)
110.3(2)
118.2(2)
116(3)
107.4(3)
107(3)
97(3)
Ga-Os-Si
Ga-Os-H(01)
Si-Os-Cl
Si-Os-P
Si-Os-H(01)
P-Os-Cl
87.08(8)
a
G is the midpoint of the C(1)-C(5) Cp ligand.
As a result, the π-bonding between osmium and silicon
is enhanced and the antibonding between the silicon and
the substituents diminishes.
The stability of the Os-Si bond of the complexes OsH-
(η5-C5H5)Cl(SiR3)(PiPr3) is determined not only by the
electronic nature of the substituents but also by the cone
angle of the silane. Thus, we have also observed that,
at room temperature, addition of 1 equiv of H2SiPh2 to
a benzene-d6 solution of 6 instantly produces quantita-
tive formation of 7 and HSiPh3. The reaction most
probably involves the reductive elimination of HSiPh3
and the subsequent oxidative addition of H2SiPh2 to the
unsaturated fragment Os(η5-C5H5)Cl(PiPr3).
In agreement with the presence of a hydride ligand
in the molecules of these compounds, the IR spectra in
Nujol show ν(Os-H) bands between 2096 and 2196
1
cm-1, and the H NMR spectra contain the correspond-
ing hydride resonances in the high-field region. The
hydride ligands of 4-6 give rise, at about -13.5 ppm,
to doublets with H-P coupling constants of about 32
Hz, while the hydride ligand of 7 displays a double
doublet at -14.43 ppm by spin coupling with the
phosphorus atom of the phosphine ligand (J HP ) 32.4
Hz) and the hydrogen atom of the diphenyl silyl group
(J HH ) 1.2 Hz). The resonance corresponding to the
hydride ligand of 8 appears at -14.82 ppm as a double
doublet of doublets, by spin coupling with the phospho-
rus atom of the phosphine (J HP ) 32.4 Hz) and the two
inequivalent hydrogen atoms of the phenylsilyl group
(J HH ) 3.3 and 2.1 Hz). The 31P{1H} NMR spectra show
singlets between 15.0 and 22.4 ppm.
For complexes 4-8, the structure proposed in eq 4 is
1
supported by the H and 31P{1H} NMR spectra of these
compounds. Furthermore, it was confirmed by an X-ray
diffraction analysis on a monocrystal of complex 7.
A view of the molecular geometry of 7 is shown in
Figure 3. Selected bond distances and angles are listed
in Table 1. The distribution of ligands around the
osmium atom can be described as a piano stool geom-
etry, with the cyclopentadienyl ligand occupying the
three-membered face, while the four monodentate ligands
lie in the four-membered face.
The most noticeable feature of the structure is the
transoid positions of the bulky ligands, triisopropyl-
phosphine and diphenylsilane. The angle Si-Os-P is
101.96(8)°. This stereochemistry, which is general for
the addition of group 14 element hydride compounds to
1 (vide infra), seems to be thermodynamically and
kineticly favored and involves the approach of the H-E
3. Rea ction s of Os(η5-C5H5)Cl(P iP r 3)2 w ith Ger -
m a n es. The addition of 1 equiv of HGeEt3 to a benzene-
d6 solution of 1 produces in quantitative yield the
hydride-germyl complex OsH(η5-C5H5)Cl(GeEt3)(PiPr3)
(9), according to the 1H and 31P{1H} NMR spectra of
the reaction mixture. Similarly, treatment of 1 with
HGePh3 and H2GePh2 affords OsH(η5-C5H5)Cl(GePh3)-
(PiPr3) (10) and OsH(η5-C5H5)Cl(GeHPh2)(PiPr3) (11),
respectively, according to eq 5.

Oxidative Addition to Os Complexes
Organometallics, Vol. 18, No. 24, 1999 5039
1
2 and Et3Ge-GeEt3 (eq 7), which was identified by H
NMR spectroscopy.
The comparison of the yields of the reactions of 1 with
HSiEt3 and HGeEt3 suggests that the oxidative addition
of H-Ge bonds to 1 is more favored than the oxidative
addition of H-Si bonds. In agreement with this, we
have observed that the addition of 1 equiv of HGePh3
to a benzene-d6 solution of 6 instantly leads to 10 in
quantitative yield (eq 6).
In contrast to 9, the respective treatments of 10 with
HGePh3 and 11 with H2GePh2 do not give rise to
reaction. However, addition of 1 equiv of H2GePh2 to a
benzene-d6 solution of 10 affords 11 and HGePh3 in
quantitative yield (eq 8). This reaction agrees well with
that shown in eq 6 and indicates that the cone angle of
the ER3 groups determines not only the stability of the
Os-Si bonds but also the stability of the Os-Ge bonds.
Since the bond dissociation enthalpy for the H-Si
bond is only 1.1 times that for the H-Ge bond,28 the
above-mentioned observations suggest that, for our
system, the Os-Ge bonds are significantly stronger
than the Os-Si bonds. Although thermochemical data
for the series of transition metal silyl and germyl
complexes are quite limited, for basic metal systems,
the bond strengths appear to follow the order M-Ge >
M-Si.29 For these systems, bond dissociation energies
may be significantly influenced by π-interactions be-
tween the transition metal and the group 14 atom, in
agreement with the results of Hu¨bler, Roper, and co-
workers.
In contrast to the above-mentioned order, Otero and
co-workers have found similar bond dissociation enthal-
pies for the Nb-Si and Nb-Ge bonds in complexes of
the type NbH2(η5-C5H4SiMe3)2(ER3)2 (E ) Si, Ge),30 and
Levy and Puddephatt have estimated that the Pt-EMe3
bond dissociation energies for [PtX(Me)2(EMe3)(bpy-
tBu2)]+ are 233 and 182 kJ ‚mol-1 for E ) Si and Ge,
respectively.31
Complexes 9-11 were isolated as yellow solids and
1
characterized by MS, elemental analysis, IR, H, and
31P{1H} NMR spectroscopies. The most noticeable ab-
sorptions in the IR spectra in Nujol are the ν(Os-H)
bands, which appear between 2084 and 2189 cm-1. The
1H NMR spectra show the hydride resonance between
-13.9 and -15.0 ppm as doublets with H-P coupling
constants of about 34 Hz. The 31P{1H} NMR spectra
contain singlets between 16 and 22 ppm. Under off-reso-
nance conditions, these singlets are split into doublets,
as a result of the P-H coupling with one hydride ligand.
4. Rea ction s of Os(η5-C5H5)Cl(P iP r 3)2 w ith Sta n -
n a n es. Similarly to the reactions of 1 with germanes,
addition of 1 equiv of HSnnBu3 or HSnPh3 to benzene-
d6 solutions of 1 leads to the hydride-stannyl deriva-
tives OsH(η5-C5H5)Cl(SnR3)(PiPr3) [SnR3 ) SnnBu3 (12),
SnPh3 (13)] in quantitative yield, according to eq 9.
There is another significant difference between the
behavior of HSiEt3 and HGeEt3. While complex 4 does
not react with a second molecule of HSiEt3, addition of
1 equiv of HGeEt3 to a benzene-d6 solution of 9 affords
(28) J ackson, R. A. J . Organomet. Chem. 1979, 166, 17.
(29) (a) Cardin, D. J .; Keppie, S. A.; Lappert, M. F.; Litzow, M. R.;
Spalding, T. R. J . Chem. Soc. A 1971, 2262. (b) Burnham, R. A.;
Stobart, S. R. J . Chem. Soc., Dalton Trans. 1977, 1489. (c) Spalding,
T. R. J . Organomet. Chem. 1978, 149, 371.
(30) Antin˜olo, A.; Carrillo-Hermosilla, F.; Castel, A.; Fajardo, M.;
Ferna´ndez-Baeza, J .; Lanfranchi, M.; Otero, A.; Pellinghelli, M. A.;
Rima, G.; Satge´, J .; Villasen˜or, E. Organometallics 1998, 17, 1523.
(31) Levy, C.; Puddephatt, R. J . J . Am. Chem. Soc. 1997, 119, 10127.

5040 Organometallics, Vol. 18, No. 24, 1999
Baya et al.
Complex 12 was isolated as a yellow oil, while
complex 13 was isolated as a yellow solid. In the IR
spectrum of 13 in Nujol, the most noticeable absorption
10, according to the equilibrium shown in eq 12. At 293
K, the equilibrium is rapidly reached, and the value of
the equilibrium constant is 0.3.
is the ν(Os-H) vibration, which appears at 2138 cm-1
.
The 1H NMR spectra of both compounds are similar,
showing in the high-field region doublets at -13.29 (12)
and -14.34 (13) ppm, with H-P coupling constants of
34.5 (12) and 33.0 (13) Hz. Satellites due to the NMR-
active Sn isotopes are also observed near the hydride
resonance of 12. The values of the H-Sn coupling
constants are 37.2 and 35.0 Hz. The 31P{1H} NMR
spectra contain singlets at 23.0 (12) and 21.2 (13) ppm
along with the satellites due to the 117Sn and 119Sn
isotopes. The values of the P-119Sn coupling constants
are 133 (12) and 144 (13) Hz, while the values of the
P-117Sn coupling constants are 127 (12) and 137 (13)
Hz. Under off-resonance conditions the singlets are split
into doublets.
As 9 reacts with HGeEt3, 12 reacts with HSnnBu3.
However, different reaction products are obtained. The
reaction of 12 with HSnnBu3 leads to the dihydride-
stannyl derivative OsH2(η5-C5H5)(SnnBu3)(PiPr3) (14)
and ClSnnBu3 (eq 10) instead of 2. A similar reaction
between 13 and HSnPh3 is not observed.
It has been previously estimated that the H-Ge bond
is 1.1 times stronger than the H-Sn bond.28 So, at 293
K, and on the basis of the value of the constant
measured for the equilibrium shown in eq 12, one can
estimate that, in these systems, the Os-Ge bond is
between 3 and 4 times stronger than the Os-Sn bond.
M-Ge bonds stronger than the corresponding M-Sn
bonds are also found in the previously mentioned
systems of Otero and co-workers30 and Levy and Pud-
dephatt.31
Complex 14 was isolated as a colorless oil and
characterized by MS and 1H and 31P{1H} NMR spec-
troscopy. In agreement with the transoid disposition of
the hydride ligands, the 1H NMR spectrum, which is
temperature invariant, shows only one hydride reso-
nance at -15.53 ppm, as a doublet with a H-P coupling
constant of 28.2 Hz. Satellites due to the NMR-active
Sn isotopes are also observed near this resonance. The
values of the H-Sn coupling constants are 53.4 (H-
119Sn) and 51.0 Hz (H-117Sn). As the spectrum of 2a ,
5. Rea ction s of Os(η5-C5H5)Cl(P iP r 3)2 w ith HCl.
Treatment of a toluene solution of 1 with a saturated
solution of HCl in toluene in an 1:3 molar ratio leads to
a red suspension, from which a red solid was separated.
The 1H and 31P{1H} NMR spectra of the solid in
dichloromethane-d2 indicate that it is a mixture of the
monohydrides OsH(η5-C5H5)Cl2(PiPr3) (15) and [OsH-
(η5-C5H5)Cl(PiPr3)2]+ (16). The first of them is the result
of the oxidative addition of HCl to the unsaturated
metallic fragment Os(η5-C5H5)Cl(PiPr3), while the sec-
ond one is the consequence of the protonation of 1. In
agreement with this, we have also observed that com-
plex 6 reacts with HCl in toluene to afford 15 and
HSiPh3 (eq 13) and that the addition of the stoichio-
metric amount of a diethyl ether solution of HBF4 to a
dichloromethane-d2 solution of 1 leads to 16 (eq 14).
Complex 15 was isolated in 84% yield and character-
i
the spectrum of 14 also shows only one Pr-methyl
chemical shift in the low-field region. The 31P{1H} NMR
spectrum of 14 contains at 46.3 ppm a singlet, along
with the satellites due to the 117Sn and 119Sn isotopes.
In this case, the value of the P-119Sn coupling constant
is 111 Hz, while the value of the P-117Sn coupling
constant is 106 Hz. Under off-resonance conditions, the
singlet is split into a triplet due to the P-H coupling
with two equivalent hydride ligands. Traces of an isomer
of 14 containing hydride ligands in cisoid disposition
are not detected.
For these systems, the Os-Sn bond appears to be
significantly stronger than the Os-Si bond and slightly
weaker than the Os-Ge bond. Thus, we have observed
that the addition of 1 equiv of HSnPh3 to a benzene-d6
solution of 6 leads to 13 and HSiPh3 (eq 11), while under
the same conditions, addition of 1 equiv of HSnPh3 to a
benzene-d6 solution of 10 produces a mixture of 13 and
1
ized by MS, elemental analysis, IR, and H and 31P{1H}
NMR spectroscopies. In the IR spectrum in Nujol, the
most noticeable absorption is the ν(Os-H) vibration,
which appears at 2190 cm-1. In the high-field region,
1
the H NMR spectrum shows at -12.83 ppm a doublet
with a H-P coupling constant of 33.6 Hz, which sup-
ports the cisoid disposition of the hydride and the
triisopropylphosphine ligands. The 31P{1H} NMR spec-
trum contains at 22.3 ppm a singlet, which under off-
resonance conditions is split into a doublet as a result
of the P-H coupling with the hydride.

Oxidative Addition to Os Complexes
Organometallics, Vol. 18, No. 24, 1999 5041
The oxidative addition of HCl gives rise to a mixture
of the monohydrides OsH(η5-C5H5)Cl2(PiPr3) and [OsH-
(η5-C5H5)Cl(PiPr3)2]+. The first one is the result of the
addition of HCl to the unsaturated fragment Os(η5-
C5H5)Cl(PiPr3), while the second one is the consequence
of the protonation of the precursor Os(η5-C5H5)Cl-
(PiPr3)2.
In conclusion, despite the high kinetic stability of the
CpOsL3 compounds, the complex Os(η5-C5H5)Cl(PiPr3)2
is a useful starting material to prepare not only π-olefin,
π-alkyne, vinylidene, allenylidene, and carbyne com-
pounds but also dihydride, trihydride, hydride-silyl,
hydride-germyl, hydride-stannyl, and dihydride-
stannyl derivatives of osmium(IV). In particular, it
should be pointed out that the cisoid-dihydride OsH2-
(η5-C5H5)Cl(PiPr3) is a rare case of a dihydride com-
pound showing quantum exchange coupling.
Exp er im en ta l Section
All reactions were carried out with rigorous exclusion of air
using Schlenk-tube techniques. Solvents were dried by the
usual procedures and distilled under argon prior to use. The
starting material Os(η5-C5H5)Cl(PiPr3)2 (1) was prepared by
the published method.4
1
Cation 16 was characterized in solution by H and
In the NMR spectra, chemical shifts are expressed in ppm
upfield from Me4Si (1H) and 85% H3PO4 (31P). Coupling
constants, J , are given in hertz.
31P{1H} NMR spectroscopies. In the H NMR spectrum
1
in dichloromethane-d2, the most characteristic reso-
nance is the corresponding to the hydride ligand, which
appears at -14.36 ppm as a triplet with a H-P coupling
constant of 33.6 Hz. In agreement with the transoid
disposition of the phosphine ligands, the 31P{1H} NMR
spectrum contains at 4.5 ppm a singlet. Under off-
resonance conditions, this signal is split into a doublet.
1
Kin etic An a lysis. Complete line-shape analysis of the H-
{31P} NMR spectra was achieved using the program gNMR
v3.6 for Macintosh (Cherwell Scientific Publishing Limited).
The rate constants (k) for various temperatures were obtained
by visually matching observed and calculated spectra. The
transverse relaxation time T2 used was common for the two
signals for all temperatures recorded and was obtained from
the line width of the exchange-averaged resonance above the
fast-exchange limit. The activation parameters ∆Hq and ∆Sq
were calculated by least-squares fit of ln(k/T) vs 1/T (Eyring
equation). Error analysis assumed a 10% error in the rate
constant and 1 K in the temperature. Errors were computed
by published methods.32
Con clu d in g Rem a r k s
This study has revealed that the metallic fragment
Os(η5-C5H5)Cl(PiPr3) is capable of activating by oxida-
tive addition molecules such as H2, HSiR3, HGeR3,
HSnR3, and HCl to afford osmium(IV) hydride deriva-
tives of the type OsH(η5-C5H5)ClX(PiPr3) (X ) H, SiR3,
GeR3, SnR3, Cl), with a distribution of ligands around
the metallic center that can be described as a four-
legged piano stool geometry.
Addition of molecular hydrogen leads to a mixture of
the transoid-dihydride OsH2(η5-C5H5)Cl(PiPr3) (2a ) and
cisoid-dihydride OsH2(η5-C5H5)Cl(PiPr3) (2b) isomers.
Isomer 2a has a rigid structure in solution. However,
the hydride ligands of 2b undergo a thermally activated
site exchange process. Furthermore, they show quantum
exchange coupling. The isomeric mixture reacts with
NaBH4 to give the trihydride OsH3(η5-C5H5)(PiPr3). The
mutually cisoid hydrides of this compound also undergo
a thermally activated site exchange process. However,
they do not show quantum exchange coupling.
The trend to the oxidative addition of silanes in-
creases in the sequence HSiEt3 < HSi(CH2-CHdCH2)-
Me2 < H4-xSiPhx (x ) 1-3). The addition of these
molecules, as well as germanes and stannanes, is
selective and leads to only one isomer, containing the
added fragments in cisoid position, and the ER3 group
(E ) Si, Ge, Sn) transoid to the phosphine. The
thermodynamic stability of the Os-ER3 bonds depend
on the cone angle of the ER3 group (Os-EHR2 > Os-
ER3) and increases in the sequence Os-Si , Os-Sn <
Os-Ge.
P r ep a r a tion of OsH2(η5-C5H5)Cl(P iP r 3) (2). Molecular
hydrogen was bubbled through a pentane solution (40 mL)
saturated with 1 (120.8 mg, 0.20 mmol) during 45 min. The
resulting grayish solution was concentrated to ca. 5 mL, and
the solvent was decantated, leading to a white solid, which
was washed twice with pentane (3 mL). Yield: 60 mg (67%).
Anal. Calcd for C14H28ClOsP: C, 37.12; H, 6.24. Found: C,
37.49; H, 6.60. Spectroscopic data for 2a : IR (Nujol): ν(Os-
1
H): 2059 cm-1 (m). H NMR (300 MHz, C6D6, 293 K): δ 4.79
2
2
(s, 5H, Cp); 1.94 (m, 3H, PCH); 0.97 (dd, J HP ) 13.8 Hz, J HH
) 6.9 Hz, 18H, PCHCH3); -10.09 (d, 2J HP ) 33.6 Hz, 2H, Os-
H). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ 43.1 (s, t in
off-resonance). Spectroscopic data for 2b: IR (Nujol): ν(Os-
1
H): 2121 cm-1 (w). H NMR (300 MHz, C6D6, 293 K): δ 4.89
(s, 5H, Cp); 2.19 (m, 3H, PCH); 1.05-0.90 (m, 18H, PCHCH3);
2
-11.05 (d, J HP ) 15.6 Hz, 2H, Os-H). 31P{1H} NMR (121.4
MHz, C6D6, 293 K): δ 32.1 (s, br t in off-resonance). MS
(FAB+): m/e 452 (M+ - HCl).
P r ep a r a tion of OsH3(η5-C5H5)(P iP r 3) (3). An excess of
NaBH4 (89 mg, 2.35 mmol) was added to a toluene solution
(10 mL) of 2 (153 mg, 0.34 mmol). Methanol (1 mL) was added
dropwise, and the mixture was allowed to react for 15 min.
The solution was vacuum-dried, and the resulting residue was
extracted with pentane (20 mL). The solvent was again
vacuum dried, and an ivory oil was obtained. Yield: 66 mg
(32) Morse, P. M.; Spencer, M. O.; Wilson, S. R.; Girolami, G. S.
Organometallics 1994, 13, 1646, and references therein.

5042 Organometallics, Vol. 18, No. 24, 1999
Baya et al.
1
(47%). Anal. Calcd for C14H29OsP: C, 40.16; H, 7.00. Found:
(vs). H NMR (300 MHz, C6D6, 293 K): δ 8.1-7.2 (5H, -Ph);
2 3
1
C, 40.42; H, 7.04. IR (Nujol): ν(Os-H): 2091 cm-1 (br, s). H
6.06 (dd, J HH ) 6.9 Hz, J HH ) 3.3 Hz, 1H, Si-H); 5.47 (dd,
3
NMR (300 MHz, C6D6, 293 K): δ 4.88 (s, 5H, Cp); 1.64 (m,
2J HH ) 6.9 Hz, J HH ) 2.1 Hz, 1H, Si-H); 4.73 (s, 5H, Cp);
3
3
3
3
3H, PCH); 0.93 (dd, J PH ) 13.2 Hz, J HH ) 6.9 Hz, 18H,
2.29 (m, 3H, PCH); 0.96 (dd, J PH ) 14.4 Hz, J HH ) 7.2 Hz,
3 3
2
PCHCH3); -14.14 (s br, 1H, Os-Ha); -15.21 (d, J HP ) 31.2
9H, PCHCH3); 0.91 (dd, J PH ) 14.4 Hz, J HH ) 7.2 Hz, 9H,
2 3 3
Hz, 2H, Os-Hb). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ
53.9 (s). MS (FAB+): m/e 415 (M+ - 3H).
PCHCH3); -14.82 (ddd, J HP ) 32.4 Hz, J HH ) 3.3 Hz, J HH
) 2.1 Hz, 1H, Os-H). 31P{1H} NMR (121.4 MHz, C6D6, 293
K): δ 22.4 (s, d in off-resonance). MS (FAB+): m/e 559 (M+
H), 523 (M+ - Cl).
-
P r ep a r a tion of OsH(η5-C5H5)Cl(SiEt3)(P iP r 3) (4). To a
diethyl ether solution (10 mL) of 1 (159.1 mg, 0.26 mmol) was
added HSiEt3 (430 µL, 2.63 mmol) and then HBF4 in ether
(35 µL, 0.26 mmol). After 30 min, the suspension was filtered,
and the resulting solution was vacuum-dried and then washed
twice with cold methanol (2 mL), leading to a yellow solid.
Yield: 76 mg (51%). Anal. Calcd for C20H42ClOsPSi: C, 42.34;
H, 7.48. Found: C, 42.40; H, 7.68. IR (Nujol): ν(Os-H): 2096
P r ep a r a tion of OsH(η5-C5H5)Cl(GeEt3)(P iP r 3) (9). To a
solution of 1 (200.5 mg, 0.33 mmol) in toluene (10 mL) was
added HGeEt3 (75 µL, 0.46 mmol). The mixture was stirred
for 10 min and then vacuum-dried. The residue was washed
twice with cold methanol (3 mL), resulting in a yellow solid.
Yield: 83.6 mg (42%). Anal. Calcd for C20H42ClGeOsP: C,
39.26; H, 6.93. Found: C, 39.41; H, 7.20. IR (Nujol): ν(Os-
cm-1 (m). 1H NMR (300 MHz, C6D6, 293 K): δ 4.78 (s, 5H,
3
1
Cp); 2.28 (m, 3H, PCH); 1.4-1.1 (15H, -Et); 0.97 (dd, J HP
)
H): 2084 cm-1 (m). H NMR (300 MHz, C6D6, 293 K): δ 4.84
12.9 Hz, 3J HH ) 7.2 Hz, 18H, PCHCH3); -13.45 (d, 2J HP ) 32.1
Hz, 1H, Os-H). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ
18.0 (s, d in off-resonance). MS (FAB+): m/e 568 (M+), 452 (M+
- HSiEt3).
(s, 5H, Cp); 2.29 (m, 3H, PCH); 1.35 (m, 15H, GeEt3); 0.97 (dd,
3J PH ) 13.2 Hz, 3J HH ) 7.2 Hz, 9H, PCHCH3); 0.96 (dd, 3J PH
)
3
2
13.2 Hz, J HH ) 7.2 Hz, 9H, PCHCH3); -14.01 (d, J HP ) 34.1
Hz, 1H, Os-H). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ
19.0 (s, d in off-resonance). MS (FAB+): m/e 612 (M+), 579 (M+
- Cl), 517 (M+ - 2H - 2Et - Cl), 452 (M+ - H - GeEt3), 418
(M+ - H - Cl - GeEt3).
P r epar ation of OsH(η5-C5H5)Cl{Si(CH2-CHdCH2)Me2}-
(P iP r 3) (5). To a solution of 1 (23 mg, 0.038 mmol) in benzene-
d6 (0.5 mL) was added HSi(CH2-CHdCH2)Me2 (5.4 µL, 0.038
mmol). After 1 h, a yellow solution was obtained, in which
P r ep a r a tion of OsH(η5-C5H5)Cl(GeP h 3)(P iP r 3) (10). To
a solution of 1 (166 mg, 0.27 mmol) in toluene (10 mL) was
added HGePh3 (176.2 mg, 0.58 mmol). The mixture was left
to react for 2 h and then vacuum-dried. The yellow residue
was washed twice with pentane (3 mL) and twice with
methanol (3 mL). Yield: 117.6 mg (57.3%). Anal. Calcd for
1
complex 5 was detected. H NMR (300 MHz, C6D6, 293 K): δ
6.17 (m, 1H, Si-CH2-CH); 5.1-5.0 (2H, dCH2); 4.78 (s, 5H,
3
Cp); 2.21 (m, 3H, PCH); 2.2-2.0 (2H, Si-CH2); 0.95 (dd, J HP
) 13.2 Hz, 3J HH ) 6.9 Hz, 9H, PCHCH3); 0.93 (dd, 3J HP ) 13.2
3
Hz, J HH ) 6.9 Hz, 9H, PCHCH3); 0.80 (s, 3H, Si-CH3); 0.75
2
(s, 3H, Si-CH3); -13.76 (dd, J HP ) 32.1 Hz, 1H, Os-H). 31P-
C32H42ClGeOsP: C, 50.84; H, 5.61. Found: C, 50.49; H, 5.45.
{1H} NMR (121.4 MHz, C6D6, 293 K): δ 19.4 (s, d in off-
resonance). MS (FAB+): m/e 508 (M+ - H - (CH2-CHdCH2)),
477 (M+ - Cl- (CH2-CHdCH2)).
IR (Nujol): ν(Os-H): 2170 cm-1 (m). 1H NMR (300 MHz, C6D6,
293 K): δ 8.1-7.1 (15H, -Ph); 4.80 (s, 5H, Cp); 2.18 (m, 3H,
PCH); 0.79 (dd, 3J PH ) 13.5 Hz, 3J HH ) 6.9 Hz, 9H, PCHCH3);
0.75 (dd, 3J PH ) 13.5 Hz, 3J HH ) 6.9 Hz, 9H, PCHCH3); -14.29
P r ep a r a tion of OsH(η5-C5H5)Cl(SiP h 3)(P iP r 3) (6). To a
solution of 1 (153 mg, 0.25 mmol) in toluene (10 mL) was added
HSiPh3 (130 mg, 0.50 mmol). The mixture was allowed to react
for 2 h and then vacuum-dried. The yellow sticky residue was
then washed twice with pentane (3 mL) and later with
(d, J HP ) 33.9 Hz, 1H, Os-H). 31P{1H} NMR (121.4 MHz,
2
C6D6, 293 K): δ 16.9 (s, d in off-resonance). MS (FAB+): m/e
756 (M+), 721 (M+ - Cl), 677 (M+ - Ph), 643 (M+ - H - Cl -
Ph), 452 (M+ - HGePh3), 418 (M+ - Cl - GePh3).
methanol (3 mL). Yield: 156 mg (88%). Anal. Calcd for C32H42
-
P r ep a r a tion of OsH(η5-C5H5)Cl(GeHP h 2)(P iP r 3) (11). To
a solution of 1 (180.3 mg, 0.29 mmol) in toluene (10 mL) was
added H2GePh2 (110 µL, 0.59 mmol). The mixture was stirred
for 2 h and then vacuum-dried. The yellow residue was washed
twice with pentane (3 mL) and twice with methanol (3 mL).
Yield: 106.7 mg (53%). Anal. Calcd for C26H38ClOsPGe: C,
45.93; H, 5.65. Found: C, 45.85; H, 5.78. IR (Nujol): ν(Os-
H): 2189 cm-1 (m); ν(Ge-H): 1992 cm-1 (s). 1H NMR (300
MHz, C6D6, 293 K): δ 8.0-7.1 (10H, -Ph); 6.70 (s, 1H, Ge-
ClOsPSi: C, 54.02; H, 5.96. Found: C, 53.81; H, 5.90. IR
1
(Nujol): ν(Os-H): 2157 cm-1 (m). H NMR (300 MHz, C6D6,
293 K): δ 8.1-7.1 (15H, -Ph); 4.76 (s, 5H, Cp); 2.13 (m, 3H,
PCH); 0.81 (dd, 3J PH ) 13.5 Hz, 3J HH ) 6.9 Hz, 9H, PCHCH3);
0.75 (dd, 3J PH ) 13.5 Hz, 3J HH ) 6.9 Hz, 9H, PCHCH3); -13.56
2
(d, J HP ) 32.7 Hz, 1H, Os-H). 31P{1H} NMR (121.4 MHz,
C6D6, 293 K): δ 15.0 (s, d in off-resonance). MS (FAB+): m/e
452 (M+ - HSiPh3).
3
P r ep a r a tion of OsH(η5-C5H5)Cl(SiHP h 2)(P iP r 3) (7). H2-
SiPh2 (108 µL, 0.58 mmol) was added to a toluene solution
(10 mL) of 1 (171.6 mg, 0.28 mmol). The mixture was stirred
for 2 h and then vacuum-dried. The resulting residue was
washed twice with pentane (3 mL) and then twice with
methanol (3 mL), leading to a yellow solid. Yield: 118.9 mg
(67%). Anal. Calcd for C26H38ClOsPSi: C, 49.15; H, 6.04.
Found: C, 49.20; H, 6.00. IR (Nujol): ν(Os-H): 2196 cm-1
(m); ν(Si-H): 2117 cm-1 (s). 1H NMR (300 MHz, C6D6, 293
H); 4.77 (s, 5H, Cp); 2.28 (m, 3H, PCH); 0.93 (dd, J HP ) 13.8
3
3
Hz, J HH ) 7.2 Hz, 9H, PCHCH3); 0.81 (dd, J HP ) 13.8 Hz,
3J HH ) 7.2 Hz, 9H, PCHCH3); -14.89 (d, J HP ) 33.3 Hz, 1H,
2
Os-H). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ 21.4 (s, d
in off-resonance). MS (FAB+): m/e 680 (M+), 643 (M+ - Cl),
603 (M+ - Ph), 452 (M+ - H2GePh2), 418 (M+ - Cl - HGePh2).
P r ep a r a t ion of OsH (η5-C5H 5)Cl(Sn n Bu 3)(P iP r 3) (12).
HSnnBu3 (10 µL, 0.037 mmol) was added to a benzene-d6
solution (0.5 mL) of 1 (18.2 mg, 0.030 mmol). The mixture was
left to react for 15 min, leading to a yellow solution, in which
the compound 12 was detected. 1H NMR (300 MHz, C6D6, 293
K): δ 4.78 (s, 5H, Cp); 2.28 (m, 3H, PCH); 2.0-0.6 (45H, -Bu/
3
K): δ 8.1-7.1 (10H, -Ph); 6.77 (d, J HH ) 1.2 Hz, 1H, Si-H);
3
4.76 (s, 5H, Cp); 2.26 (m, 3H, PCH); 0.93 (dd, J HP ) 13.8 Hz,
3
3
3J HH ) 7.2 Hz, 9H, PCHCH3); 0.81 (dd, J HP ) 13.8 Hz, J HH
2
3
2
) 7.2 Hz, 9H, PCHCH3); -14.43 (dd, J HP ) 32.4 Hz, J HH
)
PCHCH3); -13.29 (d, J HP ) 34.5 Hz, 1H, Os-H). 31P{1H}
1.2 Hz, 1H, Os-H). 31P{1H} NMR (121.4 MHz, C6D6, 293 K):
δ 21.4 (s, d in off-resonance). MS (FAB+): m/e 636 (M+), 601
(M+ - Cl), 452 (M+ - H2SiPh2), 418 (M+ - Cl - HSiPh2).
P r ep a r a tion of OsH(η5-C5H5)Cl(SiH2P h )(P iP r 3) (8). H3-
SiPh (50 µL, 0.40 mmol) was added to a toluene solution (10
mL) of 1 (128.3 mg, 0.21 mmol). The mixture was stirred for
30 min and then vacuum-dried. The residue was then washed
twice with methanol (3 mL), resulting in a yellow solid. Yield:
71.2 mg (61%). Anal. Calcd for C20H34ClOsPSi: C, 42.95; H,
6.14. Found: C, 42.84; H, 6.10. IR (Nujol): ν(Si-H): 2104 cm-1
NMR (121.4 MHz, C6D6, 293 K): δ 23.0 (s, d in off-resonance).
MS (FAB+): m/e 741 (M+ - H), 649 (M+ - H - Cl - nBu), 627
n
n
(M+ - H - Bu - Bu).
P r epar ation of OsH(η5-C5H5)Cl(Sn P h 3)(P iP r 3) (13). HSn-
Ph3 (186.0 mg, 0.53 mmol) was added to a toluene solution
(10 mL) of 1 (132.6 mg, 0.22 mmol). The mixture was stirred
for 2 h and then vacuum-dried. The sticky residue was washed
twice with methanol (3 mL), leading to a yellow solid. Yield:
123.2 mg (71%). Anal. Calcd for C32H42ClOsPSn: C, 47.92; H,
5.29. Found: C, 48.00; H, 5.78. IR (Nujol): ν(Os-H): 2138

Oxidative Addition to Os Complexes
Organometallics, Vol. 18, No. 24, 1999 5043
1
cm-1 (m). H NMR (300 MHz, C6D6, 293 K): δ 8.1-7.0 (15H,
Ta ble 2. Cr ysta l Da ta a n d Da ta Collection a n d
Refin em en t for OsH(η5-C5H5)Cl(SiHP h 2)(P iP r 3) (7)
3
-Ph); 4.81 (s, 5H, Cp); 2.17 (m, 3H, PCH); 0.84 (dd, J PH
)
3
3
12.9 Hz, J HH ) 6.9 Hz, 9H, PCHCH3); 0.77 (dd, J PH ) 12.9
Crystal Data
3
2
Hz, J HH ) 6.9 Hz, 9H, PCHCH3); -14.34 (d, J HP ) 33.0 Hz,
formula
molecular wt
color and habit
size, mm
symmetry
space group
a, Å
C26H38ClOsPSi
635.27
1H, Os-H). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ 21.2
(s, d in off-resonance). MS (FAB+): m/e 802 (M+), 724 (M+
-
yellow, prismatic block
0.36 × 0.36 × 0.20
monoclinic
P21
9.9859(9)
9.9172(9)
13.4605(12)
97.462(2)
1321.7(2)
2
H - Ph), 689 (M+ - H - H - Ph), 647 (M+ - H - Ph - Ph),
418 (M+ - Cl - SnPh3).
P r ep a r a tion of OsH2(η5-C5H5)(Sn n Bu 3)(P iP r 3) (14). To
a solution of 1 (22.2 mg, 0.036 mmol) in benzene-d6 was added
HSnnBu3 (20 µL, 0.074 mmol). The mixture was allowed to
react for 7 days, leading to an ivory solution in which the
complex 14 was detected. 1H NMR (300 MHz, C6D6, 293 K): δ
4.69 (s, 5H, Cp); 2.0-0.6 (30H, PCH/-Bu); 0.94 (dd, 3J PH ) 13.5
Hz, 3J HH ) 7.5 Hz, 18H, PCHCH3); -15.53 (d, 2J HP ) 28.2 Hz,
2H, Os-H). 31P{1H} NMR (121.4 MHz, C6D6, 293 K): δ 46.3
(s, t in off-resonance). MS (FAB+): m/e 709 (M+ - H), 651 (M+
b, Å
c, Å
â, deg
V, Å3
Z
D
calc, g cm-3
1.596
Data Collection and Refinement
Siemens-CCD
0.71073
diffractometer
λ(Mo KR), Å
- Bu), 593 (M+ - H - Bu - Bu), 535 (M+ - H - H - Bu
n
n
n
n
- Bu - Bu), 491 (M+ - PiPr3 - Bu).
n
n
n
monochromator
graphite oriented
5.042
P r ep a r a tion of OsH(η5-C5H5)Cl2(P iP r 3) (15). To a solu-
tion of 6 (423.5 mg, 0.60 mmol) in toluene (3 mL) was added
a saturated solution of HCl in toluene (7 mL). The mixture
was stirred for 6 h, leading to a red suspension. The suspension
was concentrated to ca. 3 mL and then decantated, and the
solvent was put away. The red solid was finally washed twice
with toluene (3 mL) and twice with diethyl ether (3 mL).
Yield: 242.3 mg (84%). Anal. Calcd for C14H27Cl2OsP: C, 34.49;
H, 5.59. Found: C, 34.84; H, 5.05. IR (Nujol): ν(Os-H): 2190
µ, mm-1
scan type
θ range, deg
temp, K
0.3° ω scans at different æ values
1.7 e θ e 23.3°
190.0(2)
no.of data collect
no. of unique data
no. of params refined
3350 (h, -11, 2; k, -10, 11; l, -9, 14)
2556 (merging R factor 0.0276)
286
a
R1 [F2 > 2σ(F2)]
0.0207
0.0508
1.065
b
wR2 [all data]
Sc [all data]
1
cm-1 (m). H NMR (300 MHz, CCl2D2, 293 K): δ 5.63 (s, 5H,
R1(F) ) ∑||Fo| - |Fc||/∑|Fo|. wR2(F2) ) {∑[w(Fo - Fc2)2]/
a
b
2
3
3
Cp); 2.80 (m, 3H, PCH); 1.26 (dd, J PH ) 13.8 Hz, J HH ) 6.9
∑[w(Fo2)2]}1/2
.
c Goof ) S ) {∑[w(Fo - Fc2)2]/(n - p)}1/2, where n
2
3
3
Hz, 9H, PCHCH3); 1.24 (dd, J PH ) 13.8 Hz, J HH ) 6.9 Hz,
is the number of reflections and p is the number of refined
9H, PCHCH3); -12.83 (d, J HP ) 33.6 Hz, 1H, Os-H). 31P-
2
parameters.
{1H} NMR (121.4 MHz, CCl2D2, 293 K): δ 22.3 (s, d in off-
resonance). MS (FAB +): m/e 452 (M+ - H - Cl).
parameters were used in the last cycles of refinement for all
non-hydrogen atoms. Hydrogen atoms were included in cal-
culated positions and refined riding on their respective carbon
atoms with a fixed common thermal parameter. H(01) and
H(02) were refined as free isotropic atoms. Atomic scattering
factors, corrected for anomalous dispersion, were implemented
by the program. The refinement converged to R1 ) 0.0207 [F2
> 2σ(F2)] and wR2 ) 0.0508 [all data], with weighting
parameters x ) 0.0201 and y ) 1.5777.
P r ep a r a tion of [OsH(η5-C5H5)Cl(P iP r 3)2]+ (16). To a
solution of 1 (26.5 mg, 0.043 mmol) in dichloromethane-d2 was
added HBF4‚Et2O (6 µL, 0.043 mmol). The mixture was left to
react for 10 min, leading to a reddish solution in which the
cationic complex 16 was detected. 1H NMR (300 MHz, CD2-
Cl2, 293 K): δ 5.90 (s, 5H, Cp); 2.66 (m, 6H, PCH); 1.5-1.2
(36H, PCHCH3); -14.36 (t, J HP ) 33.6 Hz, 1H, Os-H). 31P-
2
{1H} NMR (121.4 MHz, CD2Cl2, 293 K): δ 4.5 (s, d in
off-resonance). MS (FAB +): m/e 613 (M+), 577 (M+ - H - Cl).
X-r a y Str u ctu r e An a lysis of Com p lex OsH(η5-C5H5)Cl-
(SiHP h 2)(P iP r 3) (7). Crystals suitable for the X-ray diffraction
study were obtained by cooling a saturated solution of the
complex 7 in pentane. A summary of crystal data and refine-
ment parameters is reported in Table 2. The yellow, prismatic
crystal of approximate dimensions 0.36 × 0.36 × 0.20 mm was
glued on a glass fiber and mounted on a Siemens-CCD
diffractometer (sealed tube 2.4 kW, λ ) 0.71073). Two quad-
rants of data (3350 reflections) were collected via two runs of
0.3° ω scans at different æ values, over a θ range of 1.7-23.3°.
All data were corrected for absorption using a semiempirical
method.33 The structure was solved by Patterson (Os atom,
SHELXL9734) and conventional Fourier techniques and refined
by full-matrix least-squares on F2 (SHELXL9734). Anisotropic
Ack n ow led gm en t. We thank the DGES (Project
PB95-0806, Programa de Promocio´n General del Cono-
cimiento) for financial support. M.B. thanks the DGA
(Diputacio´n General de Arago´n) for a grant.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and equivalent isotropic displacement coefficients,
anisotropic thermal parameters, experimental details of the
X-ray studies, and bond distances and angles for 7. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM990235N
(34) Sheldrick, G. SHELX-97. Programs for Crystal Structure
Solution and Refinement; Institu¨t fu¨r Anorganische Chemie der
Universita¨t: Go¨ttingen, Germany, 1997.
(33) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351.