Synthesis and characterization of osmium(II) trispyrazolylborate complexes

Article abstract of DOI:10.1021/ic0602291

Treatment of H₂OsBr₆ with excess 1,5-cyclooctadiene (cod) in boiling tert-butyl alcohol affords the polymer [OsBr ₂(cod)]_x (1), which reacts with acetonitrile to form the mononuclear adduct OsBr₂(cod)

Full text of DOI:10.1021/ic0602291

Inorg. Chem. 2006, 45, 5215−5224
Synthesis and Characterization of Osmium(II) Trispyrazolylborate
Complexes
Paul W. Dickinson and Gregory S. Girolami*
School of Chemical Sciences, The UniVersity of Illinois at Urbana-Champaign,
600 South Mathews AVenue, Urbana, Illinois 61801
Received February 9, 2006
Treatment of H2OsBr6 with excess 1,5-cyclooctadiene (cod) in boiling tert-butyl alcohol affords the polymer
[OsBr2(cod)]x (1), which reacts with acetonitrile to form the mononuclear adduct OsBr2(cod)(CH3CN)2 (2). Polymer
1 reacts with potassium trispyrazolylborate (KTp) in ethanol to afford the hydride TpOs(cod)H (3) and the bromide
complex TpOs(cod)Br (4). Bromide complex 4 reacts with sodium methoxide in methanol to afford TpOs(cod)OMe
(5), which has been structurally characterized. Treatment of hydride 3 with methyl trifluoromethanesulfonate (MeOTf)
in diethyl ether results in loss of methane and formation of the triflate complex TpOs(cod)OTf (6), which reacts with
MgMe2 to give the methyl complex TpOs(cod)Me (7). The addition of bis(dimethylphosphino)methane (dmpm) to
the known compound TpOs(PPh3)2Cl yields a mixture of the substitution products TpOs(
TpOs(
2-dmpm)Cl (9); the latter reacts with methyllithium to generate the methyl compound TpOs(dmpm)Me (10).
NMR and IR data for these new compounds are reported. Crystal data for 5
monoclinic, P21/n, a 10.728(1) Å, b 14.004(2) Å, c 13.906(2) Å, â ) 102.42(6)
4, RF 0.0247 for I (I), and RwF2 0.0539 for all data.
η
1-dmpm)(PPh3)Cl (8) and
η
‚
MeOH at
−
80
)
°
C are as follows:
)
)
)
°
, V
2040.3(5) Å3, Z
)
)
g
2σ
)
Introduction
the Os-Os bond and afforded the mononuclear complexes
TpOs(CO)2Br or (pzTp)Os(CO)2Br, respectively. Potassium
polypyrazolylborate reagents have also been used to prepare
the mixed sandwich complexes TpOs(C5H5) and (pzTp)Os-
(C5H5) from [(C5H5)Os(CH3CN)3+][PF6-].7 Similarly, Schrock
has used potassium trispyrazolylborate (KTp) to prepare the
alkylidyne TpOs(C-tBu)(CH2-tBu)2 from Os(C-tBu)(CH2-
tBu)2(py)2(OTf), where OTf ) trifluoromethanesulfonate,8
and Shapley prepared the analogous nitride complex
Since the first preparation of polypyrazolylborates by
Trofimenko in 1966,1 a substantial body of literature (over
2000 publications) has appeared describing the syntheses and
applications of polypyrazolylborate ligands in various areas
of chemistry.2 This diverse class of ligands has been used
in applications ranging from modeling metalloenzymes to
catalyzing a wide variety of organic reactions.3 Complexes
bearing polypyrazolylborate ligands are known for every
d-block element and most of the lanthanides and actinides.4,5
Polypyrazolylborate osmium complexes remain less ex-
plored than those of most other d-block elements. In 1990,
the first such complexes, [TpOs(CO)2]2 and [(pzTp)Os-
(CO)2]2, were prepared by reaction of [Os(O2CMe)(CO)3]2
with the appropriate potassium polypyrazolylborate, where
Tp ) tris(pyrazolyl)borate and pzTp ) tetrakis(pyrazoyl)-
borate.6 Treatment of these dinuclear species with Br2 cleaved
+
-
Tp′Os(N)Ph2 from the reaction of [Os(N)Ph2(py)2 ][BF4 ]
with KTp′, where Tp′ ) tris(3,5-dimethylpyrazolyl)borate.9
Potassium polypyrazolylborate reagents have also been
used to prepare several osmium complexes bearing phosphine
ligands; occasionally, these reactions generate products with
bidentate Tp ligands. For example, the complex (η2-Tp)Os-
(CO)(PPh3)2Ph was prepared by treatment of Os(CO)(PPh3)2-
(Ph)Cl with KTp;10 heating a solution of the isolated product
* To whom correspondence should be addressed. E-mail: girolami@
scs.uiuc.edu.
(6) Steyn, M. M. d. V.; Singleton, E.; Hietkamp, S.; Liles, D. C. J. Chem.
Soc., Dalton Trans. 1990, 2991-2997.
(1) Trofimenko, S. J. Am. Chem. Soc. 1966, 88, 1842-1844.
(2) Trofimenko, S. Polyhedron 2004, 23, 197-203.
(3) Trofimenko, S. Scorpionates: The Coordination Chemistry of Poly-
pyrazolylborate Ligands; Imperial College Press: London, 1999.
(4) Paulo, A.; Correia, J.; Campello, M.; Santos, S. Polyhedron 2004,
23, 331-360.
(7) Freedman, D. A.; Gill, T. P.; Blough, A. M.; Koefod, R. S.; Mann,
K. R. Inorg. Chem. 1997, 36, 95-102.
(8) LaPointe, A. M.; Schrock, R. R. Organometallics 1993, 12, 3379-
3381.
(9) Hunt, J. L.; Shapley, P. A. Organometallics 1997, 16, 4071-4076.
(10) Burns, I. D.; Hill, A. F.; White, A. J. P.; Williams, D. J.; Wilton-Ely,
J. D. E. T. Organometallics 1998, 17, 1552-1557.
(5) Santos, S.; Marques, N. New J. Chem. 1995, 19, 551-571.
10.1021/ic0602291 CCC: $33.50
Published on Web 05/27/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 13, 2006 5215

Dickinson and Girolami
-
in toluene resulted in loss of one phosphine ligand and
coordination of the third pyrazolyl group to give (η3-Tp)-
Os(CO)(PPh3)Ph. Similarly, treatment of Os(CO)(PiPr3)2HCl
with NaTp afforded (η2-Tp)Os(CO)(PiPr3)2H, which loses a
phosphine ligand when heated to reflux in toluene, generating
(η3-Tp)Os(CO)(PiPr3)H.11 Protonation of TpOs(CO)(PiPr3)H
with HBF4 yielded the dihydrogen complex, [TpOs(CO)-
(PiPr3)(H2)][BF4]. Jia12 and Hill13 independently reported the
synthesis of TpOs(PPh3)2Cl by treatment of OsCl2(PPh3)3
with KTp, and the conversion of this compound to the
monohydride TpOs(PPh3)2H by the addition of either NaOMe
or KOH. Protonation of TpOs(PPh3)2H yielded the dihydro-
gen complex [TpOs(PPh3)2(H2)+].12
The reduced analogue [PPN+][TpOsCl3 ], where PPN+ is
the bis(triphenylphosphine)iminium cation, has been de-
scribed by Meyer.22 The triflate complex TpOs(OTf)Cl2 is
surprisingly resistant to substitution,23 but reacts with nitriles
and ammonia to afford the nitride TpOsNCl2.24 Interestingly,
reduction of TpOs(OTf)Cl2 with (C5Me5)2Fe gives the
-
osmium(III) salt [(C5Me5)2Fe+][TpOs(OTf)Cl2 ], which re-
acts with a variety of Lewis bases to afford the osmium(III)
complexes TpOs(L)Cl2 (L ) MeCN, PhCN, PPh3, py,
imidazole, and NH3). Oxidation of the neutral osmium(III)
complexes with [NO]BF4 affords the corresponding os-
+
-
mium(IV) salts of the formula [TpOs(L)Cl2 ][BF4 ].21
An unusual reaction is the addition of BPh2R (R ) Ph,
OBPh2) to TpOs(N)Cl2, which afforded the insertion product
TpOs[N(Ph)(BPhR)]Cl2. In this product, one Cl atom is coor-
dinated to boron, forming a four-membered Os-N-B-Cl
ring.15 The nitride complex TpOs(N)Cl2 has also served as
a starting material for several polynuclear species. Reduc-
tion of TpOs(N)Cl2 with Cp2Co gives a salt containing a
mixed-valence anion [Cp2Co+][TpOsIICl2(NtN)Cl2OsIIITp-].25
The reaction of TpOs(N)Cl2 with CpCo[η4-Cp(C6F5)] affords
the complex [TpOsCl2(N)]2CoCp, in which the nitride atoms
serve as donors to the cobalt center.26 TpOs(N)Cl2 reacts
slowly with PtCl2(SMe2)2 to give the similar donor complex
TpOsCl2(N)-PtCl2(Me2S).26 The surprising thermal stabili-
ties of the latter two compounds are attributed to the π-acid
character of the TpOs(N)Cl2 fragment, which in turn arises
from the electrophilic nature of the nitride ligand.
Apart from the compounds above, most osmium Tp
complexes are made from other osmuim Tp species, as
shown particularly by the work of Mayer. The osmium(VI)
nitride TpOs(N)Cl2, which can be prepared by the reaction
of K[Os(N)O3] with KTp in ethanolic HCl, is a particularly
good starting material for other complexes containing the
TpOs fragment.14,15 For example, the chloride ligands can
be replaced to give complexes of the type TpOs(N)X2 (X )
1
acetate, trihaloacetate, bromide, nitrate, and /2 oxalate).16
Because the nitride ligand in TpOs(N)Cl2 is electrophilic,
Grignard reagents and phosphines add directly to the nitrogen
atom. For example, treatment of TpOs(N)Cl2 with PhMgCl
-
yielded [TpOs(NPh)Cl2 ], which can be protonated to afford
the structurally characterized amide TpOs(NHPh)Cl2.15 The
amido ligand in TpOs(NHPh)Cl2 is inert to further pro-
tonation and electrophilic attack at nitrogen.17 In contrast,
To date, the vast majority of TpOs complexes in the +2
oxidation state also bear carbonyl or triphenylphosphine
ligands. As part of an effort to expand the synthetic versatility
of TpOs species, we now present the synthesis and charac-
terization of new tris(pyrazolyl)borate osmium(II) com-
pounds of the types TpOs(cod)X (where X ) H, Br, OTf,
Me, OMe and cod ) 1,5-cyclooctadiene) and TpOs(PR3)2Cl.
Some of these reactions are summarized in Scheme 1. We
also describe a useful starting material for a wide array of
osmium chemistry, the dibromo(1,5-cyclooctadiene)osmium(II)
polymer [OsBr2(cod)]x.
-
the reduced form of this complex, [TpOs(NHPh)Cl2 ], can
be protonated to give the aniline complex TpOs(NH2Ph)-
Cl2.18 The hydrogen atom self-exchange rates between TpOs-
(NHPh)Cl2 and TpOs(NH2Ph)Cl2 have been investigated.19
A surprising reaction is the addition of piperidine to TpOs-
(NHPh)Cl2, which yields the aromatic substitution product,
TpOs[NHC6H4-p-(NC5H10)]Cl2.15 Reduction of TpOs(N)Cl2
with PPh3 affords the phosphiniminato complex TpOs-
(NPPh3)Cl2, which reacts with triflic acid in acetonitrile to
produce the salt [TpOs(NHPPh3)Cl2]OTf.20 The addition of
excess HOTf to the same phosphiniminato complex in
CH2Cl2 gives products of a different kind, TpOs(OTf)Cl2
and TpOsCl3, in which the nitride-derived ligands are lost.21
This work was undertaken in part to complement our
previous studies of the chemistry of C5Me5 osmium com-
plexes, particularly in relation to dihydrogen and alkane
activation processes.27-30 We became interested in expanding
(11) Bohanna, C.; Esteruelas, M. A.; Gomez, A. V.; Lopez, A. M.; Martinez,
M.-P. Organometallics 1997, 16, 4464-4468.
(12) Ng, W. S.; Jia, G.; Hung, M. Y.; Lau, C. P.; Wong, K. Y.; Wen, L.
Organometallics 1998, 17, 4556-4561.
(21) Bennett, B. K.; Pitteri, S. J.; Pilobello, L.; Lovell, S.; Kaminsky, W.;
Mayer, J. M. J. Chem. Soc., Dalton Trans. 2001, 3489-3497.
(22) Demadis, K. D.; El-Samanody, E.-S.; Meyer, T. J.; White, P. S.
Polyhedron 1999, 18, 1587-1594.
(23) Castro-Rodrigues, I.; Nakai, H.; Gantzel, P.; Zakharov, L. N.;
Rheingold, A. L.; Meyer, K. J. Am. Chem. Soc. 2004, 125, 15734-
15735.
(13) Buriez, B.; Burns, I. D.; Hill, A. F.; White, A. J. P.; Williams, D. J.;
Wilton-Ely, J. D. E. T. Organometallics 1999, 18, 1504-1516.
(14) Crevier, T. J.; Lovell, S.; Mayer, J. M. J. Chem. Soc., Chem. Commun.
1998, 2371-2372.
(15) Crevier, T. J.; Bennett, B. K.; Soper, J. D.; Bowman, J. A.; Dehestani,
A.; Hrovat, D. A.; Lovell, S.; Kaminsky, W.; Mayer, J. M. J. Am.
Chem. Soc. 2001, 123, 1059-1071.
(24) Bennett, B. K.; Lovell, S.; Mayer, J. M. J. Am. Chem. Soc. 2001,
123, 4336-4337.
(16) Dehestani, A.; Kaminsky, W.; Mayer, J. M. Inorg. Chem. 2003, 42,
605-611.
(25) Demadis, K. D.; El-Samanody, E.-S.; Coia, G. M.; Meyer, T. J. J.
Am. Chem. Soc. 1999, 121, 535-544.
(17) Soper, J. D.; Bennett, B. K.; Lovell, S.; Mayer, J. M. Inorg. Chem.
2001, 40, 1888-1893.
(26) Crevier, T. J.; Lovell, S.; Mayer, J. M.; Rheingold, A. L.; Guzei, I.
A. J. Am. Chem. Soc. 1998, 120, 6607-6608.
(18) Soper, J. D.; Rhile, I. J.; DiPasquale, A. G.; Mayer, J. M. Polyhedron
2004, 23, 323-329.
(27) Brumaghim, J. L.; Priepot, J. G.; Girolami, G. S. Organometallics
1999, 18, 2139-2144.
(19) Soper, J. D.; Mayer, J. M. J. Am. Chem. Soc. 2003, 125, 12217-
(28) Gross, C.; Girolami, G. S. J. Am. Chem. Soc. 1998, 120, 6605-6606.
(29) Webster, C. E.; Gross, C. L.; Young, D. M.; Girolami, G. S.; Schultz,
A. J.; Hall, M. B.; Eckert, J. J. Am. Chem. Soc. 2005, 127, 15091-
15101.
12229.
(20) Bennett, B. K.; Saganic, E.; Lovell, S.; Kaminsky, W.; Samuel, A.;
Mayer, J. M. Inorg. Chem. 2003, 42, 4127-4134.
5216 Inorganic Chemistry, Vol. 45, No. 13, 2006

Osmium(II) Trispyrazolylborate Complexes
Scheme 1. Syntheses of Tp Osmium Complexesa
we obtained yields of 15-20% using this procedure. Our
difficulty in obtaining high yields of [OsCl2(cod)]x prompted
us to explore the bromo analogue, [OsBr2(cod)]x.
Addition of HBr to OsO4 generates H2OsBr6,43,44 which
reacts with excess cod in boiling tert-butyl alcohol to afford
a yellow-brown precipitate of [OsBr2(cod)]x (1) in 90%
yield.45 In the latter reaction, the osmium center is reduced
from OsIV to OsII. Because the yield of 1 is so high,
disproportionation processes involving soluble OsV or OsVI
byproducts can be ruled out. It is also unlikely that the
reductant is the tert-butyl alcohol solvent because this alcohol
cannot be oxidized to an aldehyde. Therefore, the reductant
is probably cod, which has the potential to act as a
dehalogenating or dehydrohalogenating agent. Compound 1
can also be obtained by refluxing H2OsBr6 in neat cod but
in lower yield (30-40%).
a
cod ) 1,5-cyclooctadiene, OTf ) trifluoromethanesulfonate.
this investigation to related osmium complexes in which the
C5Me5 ligand was replaced by other ancillary groups such
as Tp. One especially important question is whether the
strongly directional frontier orbitals of the TpM fragment
(see below) would change the chemistry relative to their
(C5Me5)Os analogues.
[OsBr (cod)]
H2OsBr6 + cod f
x + Br2 + 2HBr
2
1
The IR spectrum of 1 is similar to that of the known
polymers [RuCl2(cod)]x46 and [OsCl2(cod)]x.41 Compound 1
is probably polymeric: it has a high melting point (>280
°C) and is insoluble in pentane, diethyl ether, benzene,
toluene, tetrahydrofuran, and dichloromethane.
Results and Discussion
Synthesis of [OsBr2(cod)]x (1) and OsBr2(cod)(MeCN)2
(2). The ruthenium polymer [RuCl2(cod)]x, cod ) 1,5-
cyclooctadiene, first described by Bennett and Wilkinson in
1959, has proven to be a useful precursor to a wide variety
of monomeric ruthenium compounds.13,31-37 It is readily
prepared in 30-40% yield from RuCl3 and cod in boiling
ethanol.38-40 The analogous osmium polymer, [OsCl2(cod)]x,
is known, but its utility as a starting material has remained
relatively unexplored. This compound was first prepared by
Winkhaus et al. in 35% yield by the reaction of H2OsCl6
and cod in boiling isoamyl alcohol.41 Lewis and Schrock
claimed that a higher yield (90%) could be obtained by
heating OsO4 in a mixture of concentrated HCl and isoamyl
alcohol, adding cod, and distilling off the solvent to afford
the product as a yellow-brown precipitate.42 In our hands,
Compound 1 dissolves in refluxing acetonitrile to afford
the adduct OsBr2(cod)(MeCN)2 (2). The chlororuthenium
analogue RuCl2(cod)(MeCN)2 has been reported by Lewis.47
The 1H NMR spectrum of 2 shows a multiplet at δ 4.15 and
two multiplets at δ 2.31 and 1.87, corresponding to the vinyl
and two chemically inequivalent methylene protons of the
cod ligand, respectively. The acetonitrile resonance occurs
at δ 2.70. The NMR data indicate that 2 adopts an octahedral
structure with C2V symmetry.
OsBr (cod)(MeCN)
[OsBr2(cod)]x + 2 MeCN f
2
2
2
(30) Mui, H. D.; Brumaghim, J. L.; Gross, C. L.; Girolami, G. S.
Organometallics 1999, 18, 3264-3272.
Synthesis of TpOs(cod)H (3) and TpOs(cod)Br (4).
Treatment of the polymer 1 with 1.5-2 equiv of tris-
(pyrazolyl)borate, KTp, in boiling ethanol for 24 h affords
the osmium(II) hydride TpOs(cod)H (3) in 96% yield. At
shorter reflux times, a mixture of TpOs(cod)H (3) and TpOs-
(cod)Br (4) is formed (see below). The presence of the
bromide complex 4 at shorter reflux times suggests that it is
formed first and subsequently converts to the hydride 3 under
the reaction conditions. A possible source of the hydride
(31) Belderrain, T. R.; Grubbs, R. H. Organometallics 1997, 16, 4001-
4003.
(32) Wilhelm, T. E.; Belderrain, T. R.; Brown, S. N.; Grubbs, R. H.
Organometallics 1997, 16, 3867-3869.
(33) Cucullu, M. E.; Nolan, S. P.; Belderrain, T. R.; Grubbs, R. H.
Organometallics 1999, 18, 1299-1304.
(34) Coalter, J. N. I.; Caulton, K. G. New. J. Chem. 2001, 25, 679-684.
(35) Schroder, M.; Stephenson, T. A. In ComprehensiVe Coordination
Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.;
Pergamon: New York, 1987; Vol. 5, pp 363-364.
(36) Bennett, M. A. In ComprehensiVe Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: New York,
1995; Vol. 7, p 748.
(37) Alvarez, P.; Gimeno, J.; Lastra, E.; Garcia-Granda, S.; van der Maelen,
J. F.; Bassetti, M. Organometallics 2001, 20, 3762-3771.
(38) Bennett, M. A.; Wilkinson, G. Chem. Ind. (London, U.K.) 1959,
1516.
(43) Dwyer, F. P.; Hogarth, J. W. Inorg. Synth. 1957, 5, 204-207.
(44) Bruce, M. I.; Windsor, N. J. Aust. J. Chem. 1977, 30, 1601-
1604.
(45) To obtain the best yields of 1, the hexabromoosmic acid must be dried
thoroughly at temperatures not exceeding 50 °C. Failure to do so results
in a greenish reaction mixture and little precipitate (<20% yield). The
tert-butyl alcohol solvent must also be very dry; if it is not, the reaction
could take up to 6 days to reach completion.
(39) Albers, M. O.; Singleton, E.; Yates, J. E. Inorg. Synth. 1989, 26, 249-
258.
(40) Albers, M. O.; Ashworth, T. V.; Oosthuizen, H. E.; Singleton, E. Inorg.
Synth. 1989, 26, 68-77.
(41) Winkhaus, G.; Singer, H.; Kricke, M. Z. Naturforsch., B: Chem. Sci.
1966, 21, 1109-1110.
(46) Abel, E. W.; Bennett, M. A.; Wilkinson, G. J. Chem. Soc. 1959, 3178-
3182.
(42) Schrock, R. R.; Johnson, B. F. G.; Lewis, J. J. Chem. Soc., Dalton
Trans. 1974, 951-959.
(47) Johnson, B. F. G.; Lewis, J.; Ryder, I. E. J. Chem. Soc., Dalton Trans.
1977, 719-724.
Inorganic Chemistry, Vol. 45, No. 13, 2006 5217

Dickinson and Girolami
Figure 1. 1H NMR spectrum (C6D6, 22 °C) of TpOs(cod)H (3).
ligand in 3 is the ethanol solvent:
of peaks at 514.3 and 580.4 m/z, typically in a 95:5 ratio,
respectively. The former envelope corresponds to 3, and the
latter is assigned to the pyrazolyl complex TpOs(cod)-
(pyrazolyl)+ or alternatively to the tetrakis(pyrazolyl)borate
hydride (pzTp)Os(cod)H+, which may be formed in the
ionization process.
[OsBr2(cod)]x + KTp + CH3CH2OH f
TpOs(cod)H + CH3CHO + KBr + HBr
3
Interestingly, however, if pure samples of the bromo complex
4 are heated in ethanol for 24 h, the bromo complex is
recovered unchanged and no hydride 3 is formed. It is
possible that cod or the KTp reagent promotes the conversion
of 4 to 3 (note that the KTp is added to the polymer 1 in a
slight excess).
The initial product of the reaction of [OsBr2(cod)]x (1) with
KTp in boiling ethanol is the bromo complex TpOs(cod)Br
(4), but even at short reaction times a substantial amount of
the hydride TpOs(cod)H (3) is also present; the ratio is
roughly 1:1 after 2 h. Pure samples of 4 are best prepared
by heating a mixture of [OsBr2(cod)]x (1) and KTp in ethanol
for 2 h, followed by the addition of bromoform, CHBr3. The
bromoform efficiently converts the hydride to the bromo
complex.
The IR spectrum of 3 shows a B-H stretch at 2460 cm-1
and an Os-H stretch at 2085 cm-1. The 1H NMR spectrum
of 3 (Figure 1) indicates that the molecule is octahedral with
Cs symmetry. Two doublets at δ 8.22 (1H) and 7.42 (1H)
are assigned to the protons at the 3- and 5-positions of the
pyrazolyl ring that lies in the molecular mirror plane, and a
triplet at δ 6.01 (1H) is assigned to the proton at the
4-position of this same ring. Two doublets at δ 7.42 (2H)
and 7.30 (2H) and a triplet at δ 5.74 (2H) are due to the
3,5- and 4-protons of the two pyrazole rings that are related
to one another across the molecular mirror plane. Two
multiplets at δ 3.89 (2H) and 2.86 (2H) and three multiplets
at δ 2.46 (2H), 2.17 (4H), and 2.87 (2H) are assigned to the
cod vinyl and methylene protons, respectively. The hydride
resonance appears at δ -8.52.
TpOs(cod)H + CHBr3 f TpOs(cod)Br + CH2Br2
4
In this way, the bromo compound 4 is isolated in 48% yield.
The IR spectrum of 4 shows a B-H stretch at 2466 cm-1.
Synthesis and X-ray Crystal Structure of TpOs(cod)-
OMe (5). Treatment of bromide 4 with NaOMe in methanol
at reflux for 20 h affords the methoxide compound, TpOs-
(cod)OMe‚MeOH (5), in 32% yield. At this point, the
reaction mixture contains the starting material 4, the hydride
complex 3, and the methoxy compound 5 in a 1:2:17 ratio,
respectively. At longer reaction times, starting material 4
disappears, but increasing amounts of hydride 3 are formed;
after 2 weeks, the ratio of 3 to 5 is 2:9.
All compounds of the formula TpOs(cod)X described
subsequently in this paper also have Cs symmetry, and the
NMR signals from the Tp and cod ligands closely resemble
those seen for 3 and will not be discussed further. All
compounds of stoichiometry TpOsL2X in the present paper
are air stable, both in solution and in the solid state.
Small amounts of pyrazole, a byproduct of the reaction,
cocrystallize with 3 from pentane, diethyl ether, and toluene.
For example, recrystallization from diethyl ether affords
samples of 3 that contain approximately 0.5-2% of pyrazole,
Solutions of sodium alkoxides in alcohols are commonly
used in transition metal chemistry to convert halide com-
(48) Williams, J. K. J. Org. Chem. 1964, 29, 1377-1379.
(49) The acidic proton of pyrazole rapidly exchanges between the two
nitrogen atoms at room temperature, giving a broad resonance at δ
13.3. A doublet at δ 7.32 and a triplet at δ 6.07 correspond to the
other ring protons. (We speculated whether this compound could be
the protonated pyrazolium cation, PzH+, which would exhibit a similar
NMR spectrum. We prepared the salt [PzH+][OTf-] separately and
found that this was not the case.)
1
which is evident in the H NMR spectrum.48,49 The field
desorption mass spectra of such samples exhibit envelopes
5218 Inorganic Chemistry, Vol. 45, No. 13, 2006

Osmium(II) Trispyrazolylborate Complexes
Table 1. Crystallographic Data for TpOs(cod)OMe‚MeOH (7)
workup, affords the osmium(II) methyl compound TpOs-
(cod)Me (7) in 10% yield and other unidentified products.
The 1H NMR spectrum of 7 displays a singlet at δ 1.44 for
the Os-Me group. The IR spectrum of 7 shows a B-H
stretch at 2471 cm-1.
formula
fw
C19H29BN6O2Os
574.49
space group
a, Å
b, Å
P21/n
10.728(1)
14.004(2)
13.906(2)
102.42(2)
2040.3(5)
4
c, Å
â, deg
V, Å3
Z
TpOs(cod)OTf + MgMe2 f
TpOs(cod)Me + “Mg(Me)OTf”
7
T, °C
λ, Å
-80
0.71073
1.870
6.279
0.0247
D
calcd, Mg m-3
The slow rate of methylation suggests that the triflate ligand
in 6 is not particularly labile.
µ, mm-1
RFa (I g 2σ(I))
RwF2b (all data)
0.0539
Synthesis of TpOs(PR3)2X Complexes. We investigated
the reactivity of the bromo complex TpOs(cod)Br, 4, with
phosphines in an effort to replace the cod ligand. Interest-
ingly, 4 is remarkably inert toward phosphine substitution.
For example, when solutions (toluene, dmf, heptane, octane,
dodecane) of TpOs(cod)Br and bis(dimethylphosphino)-
methane, dmpm, are heated to reflux for several days, no
reaction occurs. Similar results were obtained with PMe3.
Kirchner and co-workers observed similarly slow cod
substitution rates in the ruthenium analogue TpRu(cod)Cl.57
In that system, the cod ligand could be exchanged with
phosphines (and other Lewis bases) in refluxing dimethyl-
formamide (dmf) (bp ) 153 °C). Unfortunately, the osmium
analogue does not undergo substitution even under these
forcing conditions; the starting material 4 is recoverable in
near-quantitative yield.
a RF ) ∑||Fo| - |Fc||/∑|Fo|. RwF2 ) {∑[w(Fo2 - Fc )2]/∑[w(Fo )2]}1/2
.
b
2
2
plexes into their corresponding hydride analogues.50 The
mechanism of this conversion is thought to proceed via
displacement of the halide by the alkoxide, followed by
â-hydride elimination and dissociation of the aldehyde (or
ketone).51-55 The slow rate at which the methoxy complex
5 undergoes â-hydrogen elimination suggests that the pyr-
azole and cod ligands in TpOs(cod)X compounds are slow
to dissociate from the osmium center.
The 1H NMR spectrum of 5 shows a resonance at δ 2.86
for the methoxy group. For comparison, the methoxy group
1
in (C6H3Me3)OsH(OMe)(iPr2PCHdCH2) has a H NMR
chemical shift of δ 4.05.56 The IR spectrum of 5 shows a
B-H stretch at 2484 cm-1.
The sluggish nature of the cod substitution reactions in 4
is surprising in light of the relatively facile replacement of
cod in similar cyclopentadienyl systems: (C5Me5)Os(cod)-
Br readily reacts with dmpm in refluxing heptane to give
high yields of the corresponding phosphine complex.58 One
explanation for the low lability of the cod ligand in 4 is
stronger back-bonding to the cod CdC double bonds caused
by the pyrazolyl groups, which are more strongly donating
than cyclopentadienyl groups.
Single crystals of the methanol solvate TpOs(cod)OMe‚
MeOH crystallize in the P21/n space group. Crystal data are
presented in Table 1, and selected bond distances and angles
are given in Table 2. The Os-O bond length is 2.127(2) Å,
and the Os-O-C angle is 125.1(2)°. There is a hydrogen
bonding interaction between the oxygen atom of the Os-
OMe group and the hydroxyl proton of the methanol solvate
molecule (Figure 2); the O‚‚‚O contact distance is 2.655(2)
Å. The hydroxyl proton of the methanol could not be not
located in the difference Fourier map. The average Os-N
and Os-C bond distances are 2.146(3) and 2.172(3) Å,
respectively.
Synthesis of TpOs(cod)OTf (6) and TpOs(cod)Me (7).
Treatment of the hydride 3 with excess methyl trifluoro-
methanesulfonate (MeOTf) in diethyl ether at -78 °C affords
the triflate complex TpOs(cod)OTf (6) in 54% yield. The
IR spectrum of 6 shows a B-H stretch at 2506 cm-1. The
19F NMR spectrum consists of a singlet at δ -79.4.
Although we were not able to prepare TpOs(dmpm)Br by
treatment of TpOs(cod)Br with dmpm, we have developed
an alternative route to the chloro analogue, TpOs(dmpm)-
Cl. Treatment of TpOs(PPh3)2Cl with dmpm for 1 week at
room temperature affords two primary products, TpOs(η1-
dmpm)(PPh3)Cl (8) and TpOs(η2-dmpm)Cl (9) in a 17:1
ratio, respectively. The 31P{1H} NMR spectrum of the
reaction mixture at this point (Figure 3) shows three
resonances for 8: a doublet at δ 2.4 corresponds to the
coordinated PPh3 ligand, and a doublet of doublets at δ -35.7
and a doublet at δ -58.0 are assigned to the bound and
unbound phosphorus atoms, respectively, of the unidentate
dmpm ligand. In addition, the spectrum features a singlet at
TpOs(cod)H + MeOTf f TpOs(cod)OTf + MeH
6
Treatment of 6 with 1.1 equiv of dimethylmagnesium
(MgMe2) in diethyl ether for 1 week, followed by an aqueous
(53) Bernard, K. A.; Rees, W. M.; Atwood, J. D. Organometallics 1986,
5, 390-391.
(50) Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles
and Applications of Organotransition Metal Chemistry; University
Science Books: Mill Valley, CA, 1987; p 90.
(51) Blum, O.; Milstein, D. J. Am. Chem. Soc. 1995, 117, 4582-4592.
(52) Bryndza, H. E.; Calabrese, J. C.; Marsi, M.; Roe, D. C.; Tam, W.;
Bercaw, J. E. J. Am. Chem. Soc. 1986, 108, 4805-4813.
(54) Hartwig, J. F.; Andersen, R. A.; Bergman, R. G. Organometallics 1991,
10, 1710-1719.
(55) Hoffman, D. M.; Lappas, D.; Wierda, D. A. J. Am. Chem. Soc. 1989,
111, 1531-1533.
(56) Werner, H.; Henig, G.; Windmuller, B.; Gevert, O.; Lehmann, C.;
Herbst-Irmer, R. Organometallics 1999, 18, 1185-1195.
Inorganic Chemistry, Vol. 45, No. 13, 2006 5219

Dickinson and Girolami
Table 2. Selected Bond Distances and Angles for TpOs(cod)OMe‚MeOH (7)
Distances (Å)
Os(1)-O(1)
Os(1)-N(1)
Os(1)-N(3)
Os(1)-N(5)
Os(1)-C(10)
Os(1)-C(11)
Os(1)-C(14)
Os(1)-C(15)
O(1)-C(18)
N(1)-N(2)
2.127(2)
2.159(3)
2.133(3)
2.147(3)
2.198(3)
2.181(3)
2.141(3)
2.166(3)
1.312(5)
1.376(4)
N(1)-C(1)
C(1)-C(2)
C(2)-C(3)
N(2)-C(3)
B(1)-N(2)
N(3)-N(4)
N(3)-C(4)
C(4)-C(5)
C(5)-C(6)
1.350(4)
1.379(5)
1.365(5)
1.349(4)
1.552(5)
1.369(4)
1.347(4)
1.390(5)
1.366(5)
N(4)-C(6)
1.348(4)
1.535(5)
1.370(4)
1.340(4)
1.390(5)
1.367(5)
1.352(4)
1.531(5)
1.399(5)
C(11)-C(12)
1.523(5)
1.540(5)
1.524(5)
1.396(5)
1.517(5)
1.537(5)
1.531(5)
1.415(5)
1.816(5)
B(1)-N(4)
N(5)-N(6)
N(5)-C(7)
C(7)-C(8)
C(8)-C(9)
N(6)-C(9)
B(1)-N(6)
C(10)-C(11)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(15)-C(16)
C(16)-C(17)
C(10)-C(17)
C(100)-O(100)
O(1)‚‚‚H(10A)
Angles (deg)
113.7(1)
O(1)-Os(1)-N(1)
O(1)-Os(1)-N(3)
O(1)-Os(1)-N(5)
O(1)-Os(1)-C(10)
O(1)-Os(1)-C(11)
O(1)-Os(1)-C(14)
O(1)-Os(1)-C(15)
N(1)-Os(1)-C(10)
157.7(1)
87.5(1)
78.9(1)
113.4(1)
76.2(1)
79.2(1)
116.7(1)
78.5(1)
N(1)-Os(1)-C(11)
N(1)-Os(1)-C(15)
N(3)-Os(1)-N(1)
N(3)-Os(1)-N(5)
N(3)-Os(1)-C(10)
N(3)-Os(1)-C(11)
N(3)-Os(1)-C(14)
N(3)-Os(1)-C(15)
N(5)-Os(1)-N(1)
N(5)-Os(1)-C(10)
N(5)-Os(1)-C(11)
N(5)-Os(1)-C(15)
C(10)-Os(1)-C(11)
C(14)-Os(1)-N(1)
88.6(1)
C(14)-Os(1)-N(5)
C(14)-Os(1)-C(10)
C(14)-Os(1)-C(11)
C(14)-Os(1)-C(15)
C(15)-Os(1)-C(10)
C(15)-Os(1)-C(11)
C(18)-O(1)-Os(1)
158.1(1)
88.5(1)
81.1(1)
37.8(1)
78.7(1)
95.0(1)
125.1(2)
83.3(1)
83.1(1)
88.9(1)
158.7(1)
163.1(1)
91.8(1)
80.7(1)
98.6(1)
92.0(1)
164.0(1)
37.3(1)
121.1(1)
δ -69.2 corresponding to the bidentate dmpm ligand in 9.
The 1H NMR spectrum of 9 (Figure 4) indicates that, like
compounds of stoichiometry TpOs(cod)X, the molecule is
pseudo-octahedral with Cs symmetry. The methyl protons
of the dmpm ligand appear as a pair of virtually coupled
triplets at δ 1.62 and 0.91; two PMe2 peaks are seen because
the methyl groups are either promixal or distal to the Tp
ligand. The backbone methylene protons of the dmpm ligand
also can be either proximal or distal with respect to the Tp
ligand, and they appear as two separate doublets of triplets
at δ 3.72 and 3.55. The IR spectrum shows a B-H stretch
at 2457 cm-1.
1
TpOs(PPh ) Cl + dmpm f
+ PPh
3
TpOs(η -dmpm)(PPh3)Cl
3 2
8
2
TpOs(PPh ) Cl + dmpm f
+ 2PPh
3
TpOs(η -dmpm)Cl
3 2
9
Transition metal complexes containing unidentate dmpm
ligands are rare, but a few examples are known.54,59-66 As is
often the case for unidentate diphosphine complexes, the η1-
dmpm compound 8 is a kinetic product. It is best prepared
by stirring TpOs(PPh3)2Cl with dmpm for several days at
room temperature. At this point, the solution still contains
unreacted starting material as well as detectable amounts of
the bidentate complex 9; at room temperature, about 3 weeks
are required for complete disappearance of the starting
material. Loss of the remaining PPh3 ligand in 8 is also
sluggish: the conversion to 9 is not even half complete after
6 weeks of stirring at room temperature.
We obtained our highest yields of 9 by heating the mixture
of TpOs(PPh3)2Cl and dmpm in toluene for 2 days. (Heating
the reaction mixture for longer than 2 days produces other
unidentified products and diminishes the yield of 9.) The
reaction supernatant is filtered, concentrated, and cooled,
affording 9 as a white, microcrystalline precipitate in 23%
yield. Subsequent crops obtained by cooling the supernatant
consist of a mixture of compounds 8 and 9.
(57) Gemel, C.; Trimmel, G.; Slugovc, C.; Kremel, S.; Mereiter, K.;
Schmid, R.; Kirchner, K. Organometallics 1996, 15, 3998-4004.
(58) Gross, C. L.; Girolami, G. S. Organometallics 1996, 15, 5359-5367.
(59) Chisholm, M. H.; Folting, K.; Huffman, J. C.; Kramer, K. S.; Tatz,
R. J. Organometallics 1992, 11, 4029-4036.
(60) Cotton, F. A.; Dikarev, E. V.; Herrero, S. Inorg. Chem. 1999, 38,
490-495.
(61) Lin, W.; Wilson, S. R.; Girolami, G. S. Organometallics 1997, 16,
2987-2994.
(62) Mague, J. T. Inorg. Chem. 1994, 33, 4261-4270.
(63) Mague, J. T.; Balakrishna, M. S. Polyhedron 1996, 15, 4259-4268.
(64) Palma-Ramirez, P.; Cole-Hamilton, D. J.; Pogorzelec, P.; Campora,
J. Polyhedron 1990, 9, 1107-1112.
Figure 2. ORTEP diagrams of TpOs(cod)OMe‚MeOH (7): (a) side view
and (b) view down the B-Os bond axis showing the hydrogen bonding
interaction with the MeOH solvent molecule. The 35% probability density
surfaces are shown. The hydrogen atoms have been omitted for clarity.
(65) Wong, W. K.; Chiu, K. W.; Wilkinson, G.; Motevalli, M.; Hursthouse,
M. B. Polyhedron 1985, 4, 1231-1237.
(66) Wong, W. K.; Chiu, K. W.; Wilkinson, G.; Howes, A. J.; Motevalli,
M.; Hursthouse, M. B. Polyhedron 1985, 4, 603-614.
5220 Inorganic Chemistry, Vol. 45, No. 13, 2006

Osmium(II) Trispyrazolylborate Complexes
Figure 3. 31P{1H} NMR spectrum (C7D8, 22 °C) of TpOs(PPh3)(η1-dmpm)Cl (8) and TpOs(η2-dmpm)Cl (9).
Figure 4. 1H NMR spectrum (C7D8, 22 °C) of TpOs(dmpm)Cl (9).
Treatment of 9 with methyllithium produces the methyl
compound TpOs(dmpm)Me (10), which was prepared in situ.
The methyl resonance of TpOs(dmpm)Me appears as a triplet
TpOs(cod)(OTf) reacts sluggishly with alkylating agents,
such as dimethylmagnesium (reaction times of several days),
whereas the tetramethylcyclopentadienyl complex (C5Me4H)-
Os(cod)Br can be alkylated to (C5Me4H)Os(cod)Me in less
than 8 h.67 Thus, both neutral π-acceptors (cod) and anions
(OTf) are slow to dissociate from TpOsII centers.
Although the strong σ-donor character of Tp versus C5Me5
could explain why acceptor ligands such as cod are more
strongly bound, the slow dissociation kinetics cannot be so
explained. Instead, as has been pointed out by other
authors,68-72 these phenomena are most likely a consequence
1
at δ 0.45 in the H NMR spectrum.
Comparison of TpOs and (C5Me5)Os Chemistry. A
trend resulting from this work is that ligand substitution rates
appear to be significantly slower for TpOsII complexes than
for their (C5Me5)OsII counterparts. Whereas (C5Me5)Os(cod)-
Br reacts with phosphines in refluxing heptane (98 °C) in
less than an hour to afford products in which the cod ligand
has been replaced,58 the corresponding TpOs(cod)Br is
unreactive even at much higher temperatures (>150 °C).
Similarly, treatment of TpOs(cod)Br with sodium methoxide
affords the methoxy complex TpOs(cod)OMe, which is quite
stable toward â-elimination, but the corresponding C5Me5
reaction affords (C5Me5)Os(cod)H in high yield after similar
reaction times, and the methoxy complex was never observed
among the reaction products.58 Further evidence of the lower
lability of the TpOs compounds is that the triflate complex
(67) Dickinson, P. W. Tris(pyrazolyl)borate and Tetramethylcyclopenta-
dienyl Chemistry of Osmium: Towards Methane Coordination
Complexes. Ph.D. Dissertation, University of Illinois, Urbana-Cham-
paign, IL, 2006.
(68) Bengali, A. A.; Mezick, B. K.; Hart, M. N.; Fereshteh, S. Organo-
metallics 2003, 22, 5436-5440.
(69) Ruba, E.; Simanko, W.; Mereiter, K.; Schmid, R.; Kirchner, K. Inorg.
Chem. 2000, 39, 382-384.
(70) Tellers, D. M.; Bergman, R. G. Organometallics 2001, 20, 4819-
4832.
Inorganic Chemistry, Vol. 45, No. 13, 2006 5221

Dickinson and Girolami
Dibromo(1,5-cyclooctadiene)bis(acetonitrile)osmium(II), OsBr2-
(cod)(MeCN)2 (2). A brown suspension of [OsBr2(cod)]x (0.50 g,
1.09 mmol) in acetonitrile (150 mL) was heated to reflux for 3
days. The yellow supernatant was filtered while the reaction mixture
was still hot. The remaining brown solid was extracted into
additional acetonitrile (3 × 20 mL), and the extracts were filtered
and combined with the supernatant. The resulting solution was
concentrated to ca. 6 mL and cooled to -20 °C for 8 h to afford
yellow plates. Yield: 0.20 g (34%). Additional crops can be
obtained by further concentrating and cooling the filtrate. Mp: 104
°C. Anal. Calcd for C12H18N2Br2Os: C, 26.7; H, 3.4; N, 5.2.
Found: C, 27.1; H, 3.4; N, 5.4. MS (FD): 456.0 m/z [OsBr2(cod)+].
1H NMR (CD3CN): δ 4.15 (m, 4H, cod), 2.70 (s, 6H, CH3CN),
2.31 (m, 4H, cod), 1.87 (m, 4H cod). 13C{1H} NMR (CD3CN): δ
124.5 (s, CH3CN), 77.0 (s, cod), 32.1 (s, cod), 4.8 (s, CH3CN). IR
(cm-1): 2723 (m), 2670 (m), 2363 (w), 2285 (w), 2246 (m), 2037
(w), 1410 (m), 1333 (m), 1305 (m), 1215 (m), 1192 (m), 1179
(m), 1168 (m), 1088 (m), 1013 (m), 1002 (m), 969 (m), 951 (m),
918 (m), 870 (m), 846 (m), 835 (m), 818 (m), 785 (m), 668 (w),
606 (w), 537 (w), 503 (w), 491 (w), 447 (w), 433 (w).
of the strongly directional character of the frontier orbitals
of the TpM fragment, which overlap strongly with ligands
that complete a pseudo-octahedral coordination sphere about
the metal center. These differences between Tp complexes
and their cyclopentadienyl analogues are likely to find
increasing utility in synthetic transition-metal chemistry.
Experimental Section
All operations were carried out under argon or vacuum using
standard Schlenk techniques unless otherwise specified. All solvents
were distilled under nitrogen from magnesium (ethanol), calcium
hydride (acetonitrile, dichloromethane), or sodium benzophenone
(pentane, ether, toluene). tert-Butyl alcohol was dried over MgSO4
and distilled from magnesium under argon. Osmium tetroxide
(Colonial Metals), hydrobromic acid (Aldrich), 1,5-cyclooctadiene
(Aldrich), Celite (Fisher), methyl trifluoromethanesulfonate (Ald-
rich), NaOMe (Aldrich), triphenylphosphine (Aldrich), and pyrazole
(Aldrich) were used as received. Trifluoromethanesulfonic acid and
bromoform were distilled under argon before use. Potassium tris-
pyrazolylborate,73 dimethylmagnesium,74 and ammonium hexa-
chloroosmate43 were prepared according to literature procedures.
Bis(dimethylphosphino)methane was either used as received (Strem)
or prepared by a literature route.75
Elemental analyses were performed by the University of Illinois
Microanalytical Laboratory. Field-desorption (FD) mass spectra
were performed on a 70-VSE-A mass spectrometer. The samples
were loaded as CH2Cl2 solutions, and the spectrometer source
temperature was 25 °C. All peak envelopes matched the calculated
isotope distribution patterns for the respective ions. The IR spectra
were obtained on a Nicolet Impact 410 spectrometer as Nujol mulls
between KBr plates. The 1H, 13C, and 19F NMR data were recorded
on a Varian Unity-400 spectrometer at 9.4 T. Chemical shifts are
reported in δ units (positive shifts to higher frequency) relative to
TMS or CFCl3. Melting points were measured on a Thomas-Hoover
Unimelt apparatus in sealed capillaries under argon.
Dibromo(1,5-cyclooctadiene)osmium(II), [OsBr2(cod)]x (1). A
solution of OsO4 (3.0 g, 11.8 mmol) in concentrated hydrobromic
acid (80 mL) was heated to reflux for 2 h. The resulting dark red
solution was taken to complete dryness on a rotary evaporator, and
care was taken to ensure that the bath temperature during this step
did not exceed 50 °C. The dark solid, H2OsBr6, was dissolved in
freshly distilled tert-butyl alcohol (200 mL) and treated with 1,5-
cyclooctadiene (6.0 mL, 63 mmol). The dark red solution was
heated to reflux for 2 days, during which time a brown solid
precipitated. (The supernatant should be pale yellow to colorless.
If it is dark yellow-orange, the reaction mixture should be heated
to reflux for 1-4 more days until the supernatant is pale yellow to
colorless.) The solid was collected by filtration, washed with acetone
(3 × 30 mL) and diethyl ether (3 × 30 mL), and dried under
vacuum. Yield: 4.88 g (90%). Mp: >280 °C. Anal. Calcd for
C8H12Br2Os: C, 21.0; H, 2.6; Br, 34.9. Found: C, 20.9; H, 2.7;
Br, 34.4. IR (cm-1): 2721 (m), 2663 (m), 2024 (m), 1699 (m),
1327 (s), 1296 (m), 1262 (w), 1243 (w), 1207 (vw), 1181 (sh),
1165 (m), 1092 (w), 1073 (w), 1024 (w), 1009 (s), 969 (vw), 920
(w), 894 (vw), 872 (vw), 843 (vw), 816 (w), 789 (w).
[Tris(pyrazolyl)borato]hydrido(1,5-cyclooctadiene)osmi-
um(II), TpOs(cod)H (3). A mixture of [OsBr2(cod)]x (0.50 g, 1.09
mmol) and KTp (0.41 g, 1.64 mmol) in ethanol (150 mL) was
heated to reflux for 24 h. Over this time, the initially brown slurry
produced a yellow supernatant and white solid. The solvent was
removed on a rotary evaporator, and the resulting yellow residue
was extracted with Et2O (2 × 20 mL). The extracts were filtered
through Celite on a sintered glass frit, combined, concentrated to
ca. 3 mL, and cooled to -20 °C for 24 h to afford yellow plates.
Yield 0.54 g (96%). Anal. Calcd for C17H23N6BOs: C, 39.9; H,
4.5; N, 16.4. Found: C, 40.1; H, 4.8; N, 15.9. MS (FD): 514.3
m/z [TpOs(cod)H+], 580.4 m/z [TpOs(cod)(pyrazolyl)+]. 1H NMR
(C6D6): δ 8.22 (d, 1H, JHH ) 1.5 Hz, Tp), 7.42 (d, 3H, JHH ) 2.0
Hz, Tp), 7.30 (d, 2H, JHH ) 2.0 Hz, Tp), 6.01 (t, 1H, JHH ) 2.3
Hz, Tp), 5.74 (t, 2H, JHH ) 2.3 Hz, Tp), 3.89 (m, 2H, cod), 2.86
(m, 2H, cod), 2.46 (m, 4H, cod), 2.17 (m, 2H, cod), 2.87 (m, 2H,
cod), -8.52 (s, 1H, Os-H). 13C{1H} NMR (C6D6): δ 142.9 (s,
Tp), 140.9 (s, Tp), 134.9 (s, Tp), 106.1 (s, Tp), 105.5 (s, Tp), 58.0
(s, cod), 54.5 (s, cod), 35.7 (s, cod), 31.3 (s, cod). IR (cm-1): 2460
(m), 2085 (m), 1506 (sh), 1496 (w), 1428 (w), 1412 (m), 1397
(m), 1377 (m), 1366 (sh), 1352 (w), 1321 (w), 1306 (m), 1288
(m), 1262 (w), 1236 (w), 1213 (m), 1182 (w), 1156 (w), 1117 (m),
1076 (w), 1070 (w), 1047 (m), 1040 (m), 1003 (w), 981 (w), 977
(w), 929 (w), 920 (w), 897 (w), 878 (w), 850 (vw), 836 (vw), 826
(vw), 816 (w), 791 (w), 749 (m), 731 (m), 663 (vw), 619 (w), 531
(vw), 508 (vw), 499 (w).
[Tris(pyrazolyl)borato]bromo(1,5-cyclooctadiene)osmi-
um(II), TpOs(cod)Br (4). A mixture of [OsBr2(cod)]x (2.80 g, 6.11
mmol) and KTp (3.08 g, 12.22 mmol) in ethanol (70 mL) was
heated to reflux for 2 h. Over this time, the initially brown slurry
produced a light yellow supernatant and white solid. (In different
reaction runs, the supernatant sometimes turned dark orange. A
darker color had no effect on the final yield.) The reaction mixture
was treated with freshly distilled CHBr3 (ca. 1 mL). After the
mixture had stirred for 5 min, the solvent was evaporated on a rotary
evaporator. The product was extracted into Et2O (3 × 30 mL), and
the extracts were filtered through Celite on a sintered glass frit and
combined. The resulting solution was concentrated to 7 mL and
cooled to -20 °C for 8 h to afford a yellow microcrystalline solid.
Yield 1.72 g (48%). A small amount of pyrazole may cocrystallize
with 6. The pyrazole can be removed by stirring the solid product
in pentane (200 mL) for 12 h, followed by filtration. Mp: 215-
218 °C. Anal. Calcd for C17H22N6BrBOs: C, 34.5; H, 3.8; N, 13.8.
(71) Bergman, R. G.; Cundar, T. R.; Gillespie, A. M.; Gunnoe, T. B.;
Harman, W. D.; Klinckman, T. R.; Temple, M. D.; White, D. P.
Organometallics 2003, 22, 2331-2337.
(72) Beach, N. J.; Williamson, A. E.; Spirak, G. T. J. Organomet. Chem.
2005, 690, 4640-4647.
(73) Trofimenko, S. J. Am. Chem. Soc. 1967, 89, 3170-3177.
(74) Andersen, R. A.; Wilkinson, G. Inorg. Synth. 1979, 19, 262-264.
(75) Mainz, V. V. Compounds Containing Multiple Metal-Metal Bonds:
Synthesis and Reactions. Ph.D. Dissertation, University of California,
Berkeley, CA, 1981.
5222 Inorganic Chemistry, Vol. 45, No. 13, 2006

Osmium(II) Trispyrazolylborate Complexes
Found: C, 35.1; H, 3.7; N, 13.8. MS (FD): 592.1 m/z [TpOs(cod)-
Br+]. 1H NMR (C6D6): δ 7.74 (d, 1H, JHH ) 2.4 Hz, Tp), 7.62 (d,
2H, JHH ) 2.4 Hz, Tp), 7.26 (d, 2H, JHH ) 2.4 Hz, Tp), 7.19 (d,
1H, JHH ) 2.8 Hz, Tp), 5.83 (t, 2H, JHH ) 2.2 Hz, Tp), 5.75 (t,
1H, JHH ) 2.4 Hz, Tp), 5.09 (m, 2H, cod), 3.75 (m, 2H, cod), 3.14
(m, 2H, cod), 2.40 (m, 2H, cod), 2.21 (m, 2H, cod), 2.03 (m, 2H,
cod). 13C{1H} NMR (C6D6): δ 144.1 (s, Tp), 142.1 (s, Tp), 136.3
(s, Tp), 134.7 (s, Tp), 106.2 (s, Tp), 106.2 (s, Tp), 76.9 (s, cod),
71.1 (s, cod), 33.5 (s, cod), 32.3 (s, cod). IR (cm-1): 3187 (w),
3123 (w), 3111 (w), 2722 (w), 2671 (w), 2617 (w), 2515 (vw),
2464 (m), 2433 (w), 2389 (w), 2354 (w), 2006 (w), 1915 (w), 1506
(w), 1495 (w), 1415 (sh), 1406 (m), 1397 (s), 1327 (m), 1311 (s),
1300 (s), 1229 (s), 1219 (s), 1211 (s), 1195 (m), 1183 (m), 1175
(m), 1164 (m), 1122 (s), 1075 (m), 1054 (s), 1046 (s), 1011 (m),
1005 (m), 989 (m), 980 (m), 925 (w), 917 (w), 900 (w), 889 (m),
880 (m), 868 (w), 841 (w), 818 (w), 793 (m), 767 (s), 754 (s), 731
(m), 663 (w), 654 (w), 619 (m), 534 (w), 505 (w), 484 (w), 465
(vw), 457 (vw), 447 (vw), 430 (vw), 418 (w), 415 (w), 407 (vw).
3024 (m), 2723 (w), 2623 (w), 2506 (m), 2386 (w), 2353 (w), 1504
(m), 1416 (s), 1401 (s), 1319 (s), 1280 (sh), 1260 (s), 1229 (s),
1216 (s), 1203 (s), 1180 (s), 1125 (s), 1082 (s), 1075 (s), 1048 (s),
1014 (s), 1001 (s), 984 (s), 938 (m), 926 (m), 918 (m), 891 (m),
882 (m), 867 (m), 834 (m), 819 (m), 795 (m), 770 (sh), 760 (s),
731 (m), 676 (w), 662 (w), 652 (w), 631 (s), 618 (s), 583 (m), 567
(w), 518 (w), 507 (w), 478 (w), 413 (sh), 403 (vw).
[Tris(pyrazolyl)borato]methyl(1,5-cyclooctadiene)osmi-
um(II), TpOs(cod)Me (7). To a solution of TpOs(cod)OTf‚0.5Et2O
(0.15 g, 0.22 mmol) in diethyl ether (30 mL) was added di-
methylmagnesium (0.31 mL of a 0.80 M solution in Et2O, 0.25
mmol). The solution was stirred at room temperature for 24 h,
during which time the solution color changed from yellow to
colorless. Distilled water (30 mL) was added to the reaction solution.
The Et2O layer was separated in air in a separatory funnel. The
organic layer was washed with distilled water (3 × 30 mL) and
brine solution (30 mL) and then dried over MgSO4. The colorless
Et2O solution was filtered, concentrated to 8 mL, and cooled to
-20 °C for 48 h to afford white plates. Yield: 0.011 g (10%).
Anal. Calcd for C18H25N6BOs: C, 41.1; H 4.8. Found: C, 40.5;
[Tris(pyrazolyl)borato]methoxy(1,5-cyclooctadiene)osmi-
um(II), TpOs(cod)(OMe)‚MeOH (5). To a mixture of TpOs(cod)-
Br (0.26 g, 0.44 mmol) and NaOMe (0.10 g, 1.8 mmol) was added
methanol (50 mL), and the yellow suspension was refluxed for 20
h. The solvent was evaporated, and the yellow residue was extracted
into Et2O (2 × 20 mL). The Et2O extracts were filtered through a
sintered glass frit, combined, concentrated to ca. 2 mL, and cooled
to -20 °C for 8 h to afford yellow plates. Yield: 0.08 g (32%).
Mp: 198 °C. Anal. Calcd for C19H29N6BO2Os [TpOs(cod)OMe‚
MeOH]: C, 39.7; H, 5.1; N, 14.6. Found: C, 39.6; H, 4.9; N, 14.4.
1H NMR (C6D6): δ 7.67 (d, 1H, JHH ) 2.0 Hz, Tp), 7.64 (d, 2H,
JHH ) 1.6 Hz, Tp), 7.33 (d, 2H, JHH ) 2.0 Hz, Tp), 7.25 (d, 1H,
JHH ) 2.4 Hz, Tp), 5.85 (t, 2H, JHH ) 2.4 Hz, Tp), 5.77 (t, 1H, JHH
) 2.4 Hz, Tp), 4.54 (m, 2H, cod), 3.85 (m, 2H, cod), 3.48 (s,
MeOH), 2.86 (s, 3H, Os-OMe), 2.83 (m, 2H, cod), 2.29 (m, 2H,
cod), 2.16 (m, 4H, cod). 13C{1H} NMR (C6D6): δ 144.2 (s, Tp),
140.3 (s, Tp), 136.1 (s, Tp), 134.5 (s, Tp), 106.0 (s, Tp), 105.8 (s,
Tp), 79.1 (s, cod), 73.6 (s, cod), 56.2 (s, OMe), 50.3 (s, CH3OH),
33.3 (s, cod), 30.9 (s, cod). IR (cm-1): 2484 (m), 1410 (m), 1396
(m), 1309 (m), 1228 (m), 1214 (m), 1208 (m), 1196 (w), 1159
(vw), 1124 (m), 1119 (m), 1076 (m), 1047 (s), 1020 (sh), 922 (m),
977 (m), 917 (w), 890 (w), 874 (w), 849 (w), 814 (m), 801 (m),
792 (m), 781 (m), 767 (m), 753 (m), 681 (w), 668 (w), 652 (w),
625 (w), 617 (w), 605 (vw), 534 (vw), 527 (vw), 487 (w), 462
(m), 450 (m), 438 (m), 427 (m), 419 (m), 411 (m).
1
H, 5.1. MS (FD): 528.3 m/z [TpOs(cod)Me+]. H NMR (C6D6):
δ 8.13 (d, 1H, JHH ) 2.0 Hz, Tp), 7.36 (d, 1H, JHH ) 2.0 Hz, Tp),
7.30 (d, 2H, JHH ) 2.4 Hz, Tp), 7.20 (d, 2H, JHH ) 2.0 Hz, Tp),
5.93 (t, 1H, JHH ) 2.2 Hz, Tp), 5.78 (t, 2H, JHH ) 2.2 Hz, Tp),
3.55 (m, 2H, cod), 3.11 (m, 2H, cod), 2.58 (m, 2H, cod), 2.45 (m,
2H, cod), 1.97 (m, 2H, cod), 1.84 (m, 2H, cod), 1.44 (s, 3H, Os-
Me). 13C{1H} NMR (C6D6): δ 143.3 (s, Tp), 138.4 (s, Tp), 135.4
(s, Tp), 134.5 (s, Tp), 106.1 (s, Tp), 106.0 (s, Tp), 68.8 (s, cod),
61.1 (s, cod), 32.3 (s, cod), 32.1 (s, cod), -3.1 (s, Os-Me). IR
(cm-1): 2471 (w), 1498 (w), 1408 (m), 1398 (m), 1304 (m), 1262
(m), 1217 (m), 1212 (m), 1155 (w), 1122 (m), 1114 (m), 1083
(m), 1075 (m), 1051 (sh), 1044 (s), 985 (w), 976 (w), 903 (vw),
877 (w), 819 (m), 803 (m), 794 (m), 753 (s), 737 (w), 667 (vw),
660 (vw), 621 (w), 497 (w).
Dichlorotris(triphenylphosphine)osmium(II), OsCl2(PPh3)3.
This procedure is a modification of that in ref 76. A solution of
tert-butyl alcohol (300 mL) and deionized water (120 mL) was
frozen at -78 °C and evacuated in three successive freeze-pump-
thaw cycles. The solution was then sparged with argon for 20 min
(complete exclusion of air throughout the procedure is crucial to
obtain a high yield of product). Ammonium hexachloroosmate(IV)
(3.80 g, 8.65 mmol) and triphenylphosphine (15.96 g, 60.84 mmol)
were added to the solution, and the mixture was heated to reflux
for 3 h, during which time the red-white suspension turned deep
green. The mixture was filtered hot on a sintered glass frit, and the
filtrate was washed with ethanol (6 × 30 mL) and ether (6 × 30
mL) and dried in a vacuum. (If the reaction mixture is not filtered
hot, a substantial amount of PPh3 will cocrystallize with the
product.) The green solid was extracted into dichloromethane (30
mL); the extract was filtered, and the filtrate was diluted with
heptane (10 mL). The green solution was concentrated to 15 mL
and cooled to -20 °C for 8 h to afford green plates. The product
was isolated by filtration and dried in a vacuum. Yield: 4.10 g
(45%). Additional crops could be obtained by further concentrating
the filtrate.
[Tris(pyrazolyl)borato]trifluoromethanesulfonato(1,5-
cyclooctadiene)osmium(II), TpOs(cod)OTf (6). To a solution
of TpOs(cod)H (0.30 g, 0.59 mmol) in diethyl ether (60 mL) at 0
°C was added methyl trifluoromethanesulfonate (0.13 mL, 1.2
mmol). The solution was stirred for 5 h at 0 °C, after which time
a small amount of yellow precipitate had formed. The yellow
supernatant was filtered, concentrated to 8 mL, and cooled to -20
°C for 24 h to afford orange crystals. Yield: 0.21 g (52%). Anal.
Calcd for C20H27N6O3.5BF3SOs [TpOs(cod)OTf‚0.5Et2O]: C, 34.4;
H, 3.9; N, 12.0. Found: C, 34.0; H, 3.9; N, 11.7. 1H NMR (C6D6):
δ 7.68 (d, 2H, JHH ) 2.0 Hz, Tp), 7.29 (d, 2H, JHH ) 2.0 Hz), 7.22
(d, 1H, JHH ) 2.0 Hz,Tp), 7.07 (d, 1H, JHH ) 2.0 Hz, Tp), 5.91 (t,
2H, JHH ) 2.0, Tp), 5.60 (t, 1H, JHH ) 2.0 Hz, Tp), 5.22 (m, 2H,
cod), 4.12 (m, 2H, cod), 3.25 (q, JHH ) 7.0 Hz, Et2O), 2.76 (m,
2H, cod), 2.16 (m, 2H, cod), 2.05 (m, 2H, cod), 1.99 (m, H cod),
1.11 (t, JHH ) 7.0 Hz, Et2O). 13C{1H} NMR (C6D6): δ 145.0 (s,
Tp), 142.6 (s, Tp), 137.2 (s, Tp), 135.6 (s, Tp), 106.8 (s, Tp), 106.6
(s, Tp), 84.0 (s, cod), 79.7 (s, cod), 66.1 (s, Et2O), 33.1 (s, cod),
30.6 (s, cod), 15.8 (s, Et2O). 19F NMR (C6D6): δ -79.4 (s, SO2CF3).
IR (cm-1): 3180 (w), 3146 (w), 3134 (w), 3113 (w), 3037 (m),
[Tris(pyrazolyl)borato]chloro[bis(triphenylphosphine)]os-
mium(II), TpOs(PPh3)2Cl. This procedure is a modification of
that in ref 13. To a mixture of OsCl2(PPh3)2 (3.80 g, 6.49 mmol)
and KTp (3.27 g, 12.98 mmol) was added dichloromethane (70
mL). The mixture was stirred for 4 h, during which time the reaction
(76) Elliott, G. P.; Mcauley, N. M.; Roper, W. R. Inorg. Synth. 1989, 26,
184-189.
Inorganic Chemistry, Vol. 45, No. 13, 2006 5223

Dickinson and Girolami
mixture turned dark green/yellow. The solvent was evaporated, the
residue was extracted with toluene (2 × 10 mL), and the extracts
were filtered and combined. The green solution was diluted with
heptane (20 mL), concentrated to ca. 25 mL, and cooled to -20
°C for 48 h to afford a yellow microcrystalline solid. Yield: 1.40
g (23%). Additional crops can be obtained by further concentration.
Anal. Calcd for C45H40N6BP2ClOs: C, 56.1; H, 4.2; N, 8.7.
Found: C, 56.4; H, 4.5; N, 8.3.
[Tris(pyrazolyl)borato]chloro[η1-bis(dimethylphosphino)-
methane]triphenylphosphineosmium(II), TpOs(PPh3)(η1-dmpm)-
Cl (8). To a solution of TpOs(PPh3)2Cl (15 mg, 0.016 mmol) in
C7D8 (1 mL) was added Me2PCH2PMe2 (0.012 mL, 0.078 mmol).
The green solution was stirred for 4 days to yield TpOs(PPh3)(η1-
dmpm)Cl, TpOs(dmpm)Cl (characterization given below), free
PPh3, and starting materials, as observed by NMR spectroscopy
and mass spectrometry. MS(FD): 838.2 m/z [TpOs(PPh3)(η1-
dmpm)Cl+]. 31P{1H} NMR (C7D8): δ 2.4 (d, 1P, JPP ) 33 Hz,
Os-PPh3), -35.7 (dd, 1P, JPP ) 33, 45 Hz, Os-PMe2CH2PMe2),
-58.0 (d, 1P, JPP ) 45 Hz, Os-PMe2CH2PMe2).
C, 22.0; H, 2.3; N, 12.8. Found: C, 22.0; H, 2.3; N, 12.4. 1H NMR
(C4D8O): δ 14.82 (s, 2H, NH), 8.36 (d, 2H, JHH ) 2.8 Hz, 3,5-
CH), 6.83 (t, 1H, JHH ) 2.8 Hz, 4-CH). 13C{1H} NMR (C4D10O):
δ 135.5 (s, 3,5-C), 108.6 (s, 4-C). 19F NMR (C4D8O): δ -79.9 (s,
SO3CF3). IR (cm-1): 3193 (br), 2725 (s), 2677 (sh), 2520 (m),
2475 (m), 2382 (m), 2366 (sh), 2311 (w), 2251 (w), 2212 (w),
2176 (w), 2113 (w), 1986 (w), 1933 (w), 1839 (m), 1563 (s), 1522
(s), 1422 (s), 1162 (s), 1111 (s), 1046 (s), 927 (sh), 915 (s), 907
(s), 793 (s), 765 (s), 650 (s), 613 (s), 578 (s), 520 (s).
Crystallographic Studies.77 Single crystals of TpOs(cod)OMe‚
MeOH, 7‚MeOH, grown by layering a methanol solution with
diethyl ether, were mounted on glass fibers with Paratone-N oil
(Exxon) and immediately cooled to -75 °C in a cold nitrogen gas
stream on the diffractometer. Standard peak search and indexing
procedures gave rough cell dimensions, and least-squares refinement
using 19 322 reflections yielded the cell dimensions given in Table
1.
Data were collected with an area detector. Systematic absences
for 0k0 (k * 2n) and h0l (h + l * 2n) were only consistent with
space group P21/n. The measured intensities were reduced to
structure factor amplitudes, and their estimated standard deviations
(esd’s) were reduced by correction for background, scan speed,
Lorentz, and polarization effects. Although corrections for crystal
decay were unnecessary, a face-indexed absorption correction was
applied, the maximum and minimum transmission factors being
0.855 and 0.109, respectively. Systematically absent reflections were
deleted, and symmetry equivalent reflections were averaged to yield
the set of unique data. All 5004 data were used in the least-squares
refinement.
[Tris(pyrazolyl)borato]chloro[bis(dimethylphosphino)methane]-
osmium(II), TpOs(dmpm)Cl (9). A solution of TpOs(PPh3)2Cl
(0.60 g, 0.62 mmol) and Me2PCH2PMe2 (0.19 mL, 1.24 mmol) in
toluene (150 mL) was heated to reflux for 2 days. During this time,
the solution turned from yellow to green, and a small amount of
white precipitate formed. The supernatant was filtered, concentrated,
and cooled to -20 °C for 8 h to afford a green microcrystalline
solid. Yield: 0.12 g (23%). Anal. Calcd for C15.75H26N6ClBP2Os
[TpOs(dmpm)Cl‚0.25C7H8]: C, 31.7; H, 4.4; N 14.1; Cl, 5.9.
Found: C, 31.0; H, 4.5; N, 13.6; Cl, 6.1. 1H NMR (C7D8): δ 7.83
(d, 2H, JHH ) 1.6 Hz, Tp), 7.44 (d, 1H, JHH ) 2.4 Hz, Tp), 7.41
(d, 2H, JHH ) 2.4 Hz, Tp), 7.21 (d, 1H, JHH ) 1.6 Hz, Tp), 5.95
(t, 2H, JHH ) 2.0 Hz, Tp), 5.89 (t, 1H, JHH ) 2.2 Hz, Tp), 3.72 (dt,
1H, JHH ) 14.4 Hz, JPH ) 10.4, PCH2P), 3.55 (dt, 1H, JHH ) 14.4
Hz, JHP ) 9.6 Hz, PCH2P), 1.62 (t, 6H, JHP ) 5.0 Hz, PMe), 0.91
(t, 6H, JHP ) 4.6 Hz, PMe). 13C{1H} NMR (C7D8): δ 145.9 (s,
Tp), 143.5 (s, Tp), 135.3 (s, Tp), 133.6 (s, Tp), 105.7 (s, Tp), 105.3
(s, Tp), 57.1 (s, PCH2P), 14.4 (t, JPC ) 12.9 Hz, PMe), 13.5 (t, JPC
) 15.0 Hz, PMe). 31P{1H} NMR (C7D8): δ -69.2 (s). IR (cm-1):
2457 (m), 1417 (m), 1399 (m), 1335 (vw), 1308 (m), 1298 (m),
1278 (m), 1240 (vw), 1212 (m), 1197 (m), 1157 (w), 1136 (w),
1111 (m), 1043 (w), 1037 (w), 1027 (w), 980 (vw), 942 (w), 929
(w), 891 (w), 864 (vw), 842 (vw), 816 (vw), 792 (w), 763 (w),
757 (w), 742 (w), 715 (w), 695 (m), 665 (w), 644 (vw), 621 (m).
[Tris(pyrazolyl)borato]methyl[bis(dimethylphosphino)methane]-
osmium(II), TpOs(dmpm)Me (10). A solution of TpOs(dmpm)-
Cl‚0.25C7H8 (0.40 g, 0.67 mmol) in tetrahydrofuran (60 mL) was
treated with methyllithium (1.49 mL of a 1.80 M solution in diethyl
ether, 2.68 mmol). The resulting yellow solution was stirred for
The structure was solved by direct methods using SHELXTL,
and the correct positions for the Os and non-hydrogen atoms were
deduced from an E-map. Subsequent least-squares refinement and
difference Fourier calculations revealed the positions of the
remaining non-hydrogen atoms. The quantity minimized by the
2
2
least-squares program was ∑w(Fo - Fc2)2, where w ) {[σ(Fo )]2
+ (0.0272P)2}-1 and P ) (Fo + 2Fc2)/3. The analytical ap-
2
proximations to the scattering factors were used, and all structure
factors were corrected for both real and imaginary components of
anomalous dispersion. In the final cycle of least squares, indepen-
dent anisotropic displacement factors were refined for the non-
hydrogen atoms. All hydrogen atoms except the methanol hydroxyl
hydrogen were located in the difference Fourier map, and their
locations were independently refined with each being given an
individual isotropic displacement factor. The hydroxyl hydrogen
on the methanol was fixed in an “idealized” position with the O-H
bond equal to 0.84 Å and its displacement parameter set equal to
1.5 times that of O(100). Successful convergence was indicated
by the maximum shift/error of 0.000 for the last cycle. The largest
peak in the final Fourier difference map (0.89 e Å-3) was located
0.06 Å from Os1. A final analysis of variance between observed
and calculated structure factors showed no apparent errors.
1
24 h, and then the solvent was evaporated. H NMR (C4D8O): δ
7.84 (s, 1H, Tp), 7.62 (d, 1H, JHH ) 2.4 Hz, Tp), 7.56 (d, 2H, JHH
) 2.4 Hz, Tp), 7.45 (d, 2H, JHH ) 2.4 Hz, Tp), 6.09 (t, 1H, JHH
2.4 Hz, Tp), 6.04 (t, 2H, JHH ) 2.4 Hz, Tp), 4.17 (dt, 1H, JHH
14.0 Hz, JPH ) 12.0, PCH2P), 3.66 (dt, 1H, JHH ) 14.0 Hz, JHP
)
)
)
Acknowledgment. We thank the American Chemical
12.0 Hz, PCH2P), 1.50 (t, 6H, JHP ) 4.7 Hz, PMe), 1.43 (t, 6H,
JHP ) 4.7 Hz, PMe), 0.45 (t, 3H, JHP ) 5.9 Hz, Os-Me). 31P{1H}
NMR (C4D8O): -69.6 (s).
Pyrazolium Trifluoromethansulfonate, [C3H5N2][OTf]. To a
solution of pyrazole (0.30 g, 4.4 mmol) in Et2O (60 mL) at 0 °C,
was added trifluoromethanesulfonic acid (0.39 mL, 4.4 mmol). A
white, flocculent precipitate formed immediately. The reaction
mixture was warmed to room temperature and stirred for 30 min.
The solid was isolated by filtration and dried in a vacuum. Yield:
0.35 g (36%). Mp: 139-140 °C. Anal. Calcd for C4H5N2O3F3S:
Society Petroleum Research Fund for support.
Supporting Information Available: X-ray crystallographic file
in CIF format for TpOs(cod)OMe‚MeOH (7). This material is
available free of charge via the Internet at http://pubs.acs.org.
IC0602291
(77) For details of the crystallographic methods used, see Brumaghim, J.
L.; Priepot, J. G.; Girolami, G. S. Organometallics 1999, 18, 3139-
2144.
5224 Inorganic Chemistry, Vol. 45, No. 13, 2006