187Os NMR study of (η6-arene)osmium(II) complexes: Separation of electronic and steric ligand effects

Article abstract of DOI:10.1021/om960053i

Osmium-187 NMR data have been collected for 37 Os(arene)X₂L type complexes, using inverse two-dimensional (³¹P, ¹⁸⁷Os){¹H} and (¹H, ¹⁸⁷Os) NMR spectroscopy. In the series Os(p-cymene)X₂PMe₃, shielding increases in the order Cl < Br < I < Me < H. Systematic variation of the phosphite ligand of Os(p-cymene)Cl₂P(OR)₃ (R = Me, Et, ⁿBu, Ph, ⁱPr) reveals a linear dependence on Tolman's electronic parameter χ with metal shielding increasing as the acceptor character of the P(OR)₃ ligand increases. Conversely, the structurally related Os(p-cymene)X₂PR₃ types (X = Cl, I; PR₃ = PMe₃, PMe₂Ph, PⁿBu₃, PPh₂Me, P(CH₂Ph)₃ PPh₃, P(m-tolyl)₃, PⁱPr₃, PCy₃) exhibit a linear dependence on Tolman's cone angle θ, with shielding decreasing as larger phosphine ligands are introduced. Variation of the arene ligand of Os(C₆H₅X)Cl₂PMe₃ (X = H, Me, Et, ⁱPr, ^tBu) shows a linear dependence of chemical shift on Taft's steric parameter E_s for group X. In only one case, for the monohydride complexes Os(p-cymene)HClPR₃ (PR₃ = PMe₃, PMe₂Ph, PⁿBu₃, PPh₃, PⁱPr₃, PCy₃), has it been possible to separate both steric and electronic effects of the phosphorus ligand on the observed Os chemical shifts. There are some correlations between ¹(¹⁸⁷Os, ³¹P) and the acceptor character of the phosphorus ligand, and a relationship between Os-P bond lengths and coupling constants was found. Osmium relaxation rates T₁^-1 and their B₀ field dependence are reported for selected complexes. The crystal structures of four Os(p-cymene)Cl₂L complexes (L = PMe₃ (1), P(OMe)₃ (6), PBz₃ (13), and PPh₃ (15)) have been determined.

Full text of DOI:10.1021/om960053i

3124
Organometallics 1996, 15, 3124-3135
187Os NMR Stu d y of (η6-Ar en e)osm iu m (II) Com p lexes:
Sep a r a tion of Electr on ic a n d Ster ic Liga n d Effects†
Andrew G. Bell, Wiktor Koz´min´ski, Anthony Linden, and
Wolfgang von Philipsborn*,‡
Organisch-chemisches Institut, Universita¨t Zu¨rich-Irchel, Winterthurerstrasse 190,
CH-8057 Zu¨rich, Switzerland
Received J anuary 26, 1996X
Osmium-187 NMR data have been collected for 37 Os(arene)X2L type complexes, using
inverse two-dimensional (31P, 187Os){1H} and (1H, 187Os) NMR spectroscopy. In the series
Os(p-cymene)X2PMe3, shielding increases in the order Cl < Br < I < Me < H. Systematic
variation of the phosphite ligand of Os(p-cymene)Cl2P(OR)3 (R ) Me, Et, nBu, Ph, iPr) reveals
a linear dependence on Tolman’s electronic parameter ø with metal shielding increasing as
the acceptor character of the P(OR)3 ligand increases. Conversely, the structurally related
Os(p-cymene)X2PR3 types (X ) Cl, I; PR3 ) PMe3, PMe2Ph, PnBu3, PPh2Me, P(CH2Ph)3, PPh3,
P(m-tolyl)3, PiPr3, PCy3) exhibit a linear dependence on Tolman’s cone angle θ, with shielding
decreasing as larger phosphine ligands are introduced. Variation of the arene ligand of
Os(C6H5X)Cl2PMe3 (X ) H, Me, Et, iPr, tBu) shows a linear dependence of chemical shift on
Taft’s steric parameter Es for group X. In only one case, for the monohydride complexes
Os(p-cymene)HClPR3 (PR3 ) PMe3, PMe2Ph, PnBu3, PPh3, PiPr3, PCy3), has it been possible
to separate both steric and electronic effects of the phosphorus ligand on the observed 187Os
1
chemical shifts. There are some correlations between J (187Os,31P) and the acceptor character
of the phosphorus ligand, and a relationship between Os-P bond lengths and coupling
-1
constants was found. Osmium relaxation rates T1 and their B0 field dependence are
reported for selected complexes. The crystal structures of four Os(p-cymene)Cl2L complexes
(L ) PMe3 (1), P(OMe)3 (6), PBz3 (13), and PPh3 (15)) have been determined.
In tr od u ction
as part of our research on the application of transition-
metal NMR spectroscopy.
Transition-metal NMR spectroscopy can be used to
explore both electronic2 and steric3 effects in organo-
metallic systems. In addition, its use as a probe to
screen the activity of catalysts,4 correlate rate data,5 and
provide insight into mechanistic pathways6 is an on-
going area of research in our group, although these
attempts have not always been successful.7 Given the
current interest in osmium for catalytic transforma-
tions,8 we decided to examine this nucleus in more detail
Osmium has two magnetically receptive nuclei, al-
though the 189Os isotope is not useful because it has a
5
spin of /2 and contains a severe quadrupole moment
(Q ) 0.91). The 187Os isotope has spin 1/2 but has a
natural abundance of only 1.64% and is the most
insensitive nucleus in the periodic table, making its
observation by conventional NMR techniques extremely
difficult.9 For many years, the only known chemical
shift was of the reference compound OsO4.10 However,
the advent of polarization transfer techniques, which
require a nonzero scalar J (M,X) coupling, has improved
the detection of low-γ spin 1/2 nuclei, with sensitivity
gains over direct metal detection proportional to (γX/
γM). Further enhancements are possible by employing
indirect 2D spectroscopy, which involves detection of the
† Transition Metal NMR Spectroscopy. 32. Part 31: Reference 1.
‡ E-mail: egysi@oci.unizh.ch.
X Abstract published in Advance ACS Abstracts, J une 1, 1996.
(1) Meier, E. J . M.; Koz´min´ski, W.; Lustenberger, P.; Linden, A.;
von Philipsborn, W. Organometallics 1996, 15, 2469.
(2) Graham, P. B.; Rausch, M. D.; Ta¨schler, K.; von Philipsborn, W.
Organometallics 1991, 10, 3049.
metal resonance at the frequency of a more receptive
(3) (a) Asaro, F.; Costa, G.; Dreos, R.; Pellizer, G.; von Philipsborn,
W. J . Organomet. Chem. 1996, 513, 193. (b) Ludwig, L.; O¨ hrstro¨m, L;
Steinborn, D. Magn. Reson. Chem. 1995, 33, 984. (c) Elsevier, C. J .;
Kowall, B.; Kragten, H. Inorg. Chem. 1995, 34, 4836. (d) Tavagnacco,
C; Balducci, G; Costa, G.; Ta¨schler, K; von Philipsborn, W. Helv. Chim.
Acta 1990, 73, 1469.
(4) (a) Bo¨nnemann, H.; Brijoux, W.; Brinkmann, R.; Meurers, W.;
Mynott, R.; von Philipsborn, W.; Egolf, T. J . Organomet. Chem. 1984,
272, 231. (b) Bender, B. R.; Koller, M.; Nanz, D.; von Philipsborn, W.
J . Am. Chem. Soc. 1993, 115, 5889.
(5) (a) Koller, M.; von Philipsborn, W. Organometallics 1992, 11,
467. (b) DeShong, P.; Sidler, D. R.; Rybczynski, J .; Ogilvie, A. A.; von
Philipsborn, W. J . Org. Chem. 1989, 54, 5432. (c) DeShong, P.; Slough,
G. A.; Sidler, D. R.; Rybczynski, J .; von Philipsborn, W.; Kunz, R. W.;
Bursten, B. E.; Clayton, T. W. Organometallics 1989, 8, 1381.
(6) Tedesco, V.; von Philipsborn, W. Organometallics 1995, 14, 3600.
(7) Dowler, M. E.; Le, T.-X.; DeShong, P.; von Philipsborn, W.;
Vo¨hler, M.; Rentsch, D. Tetrahedron 1993, 49, 5673.
1
spin
/
nucleus. This gives a factor of (γX/γM)5/2
2
increase in sensitivity over direct detection, which for
187Os NMR spectroscopy corresponds to gains of 1300
and 12 000 for 31P and 1H-detected spectra. These
techniques have been applied to other transition-metal
nuclei such as 183W, 103Rh, and 57Fe.11
Mann and Maitlis have successfully applied a double
INEPT 2D NMR technique to study some µ-hydrido
(9) Mason, J ., Ed. Multinuclear NMR; Plenum Press: New York,
1987.
(10) Kaufmann, J .; Schwenk, A. Phys. Lett. 1967, 24A, 115.
(11) (a) Pregosin, P. S., Ed. Transition Metal Nuclear Magnetic
Resonance; Elsevier: Amsterdam, 1991. (b) Mann, B. E. In Annual
Report on NMR Spectroscopy; Webb, G. A., Ed.; Academic Press:
London, 1991; Vol. 23, p 141. (c) von Philipsborn, W. Pure Appl. Chem.
1986, 58, 513.
(8) For
a recent review of homogeneous catalysis by osmium
complexes, see: Sa´nchez-Delgado, R. A.; Rosales, M.; Esteruelas, M.
A.; Oro, A. J . Mol. Catal. A 1995, 96, 231.
S0276-7333(96)00053-2 CCC: $12.00 © 1996 American Chemical Society
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(η6-Arene)osmium(II) Complexes
Organometallics, Vol. 15, No. 14, 1996 3125
Ch a r t 1. Typ es of Os(a r en e)X2L Com p lexes
In vestiga ted
staggered conformation, with the Os-P bond bisecting
the C(2)-C(3) bond of the arene at approximately its
i
midpoint. It is noticeable with 13 that the Pr group
bound to the ring points away from the phosphine
ligand, as evidenced by the increase in the C(2)-C(1)-
C(7)-C(9) torsion angle. However, 15 adopts a confor-
mation in which the Os-P bond bisects the C(4)-C(5)
i
bond distant to the bulky Pr group, presumably for
steric reasons, resulting in a restoration of the C(2)-
C(1)-C(7)-C(9) torsion angle. The p-cymene ligand is
tilted toward the OsCl2L moiety, placing the C-C bond
that bisects the Os-P bond closer to the metal than the
parallel C-C bond [C(5)-C(6) or C(1)-C(2)], but this
becomes less marked as larger ligands are introduced.
The p-cymene ring is puckered in a manner dictated
by the size of the phosphorus ligand. Thus, the ø2
distributions17 for deviations of the η6-arene atoms C(1)
to C(6) from planarity are 30.3 for 1b, increasing to
289.5 for 15. For complexes 1 and 13, atoms C(1) and
C(4) lie above the average plane of the η6-arene ring,
with the others below. However, for the P(OMe)3-
substituted case 6, the reverse is true. Complex 15
behaves like 6, except that, due to the change in
conformation of the PPh3 ligand, it is now the C(3)-
C(6) axis which lies beneath the plane of the arene
ligand. Finally, the crystal structures suggest that as
the phosphorus ligand becomes more sterically demand-
ing, the Os-P bond distance increases in length.
However, the effect of the ligand on the Os-Cl bond
lengths and Cl-Os-Cl bond angles varies, especially
for 1.
binuclear osmium complexes.12 However, the first
systematic approach to gaining some δ(187Os), J (Os,X),
and T1(187Os) parameters was made more recently by
Benn and co-workers for a range of Os(Cp)L2R com-
plexes (Cp ) η5-C5H5), using the HMQC technique.13
The success of this type of spectroscopy has made it the
method of choice for determining δ(187Os) and J (Os,X)
scalar couplings (X ) H, F, P) in later work.14,15
Ch em ical Sh ifts. Ramsey18 described nuclear shield-
ing (σ) as arising from a diamagnetic (σd) and paramag-
netic (σp) contribution, of which the former remains
fairly constant for a given nucleus. Later work by
Griffith and Orgel19 has elaborated upon the Ramsey
model to give a better description for transition metal
nuclei, for which the σp contribution to the nuclear
shielding term is shown in eq 1, where ∆E is the average
Resu lts a n d Discu ssion
An 187Os NMR study has been made of the six classes
of structurally related η6-arene-substituted osmium(II)
complexes shown in Chart 1.16 Classes I and VI are
PMe3 substituted but contain various η1- and η6- ligands,
respectively. Classes II and III are dichlorides bearing
phosphite and phosphine ligands, class IV compounds
are diiodides, and class V compounds are monohydrides.
All these types have the advantage of being both soluble,
ca. 0.5 M, and stable in CD2Cl2 and THF-d8 solvents,
allowing for easier detection of the osmium resonance.
X-r a y Cr ysta l Str u ctu r es. Some selected bond
angles and lengths for complexes 1, 6, 13, and 15 are
given in Table 1, and the crystal structures of 1
(molecule A) and 13 are shown in Figure 1. The
structure of 1 has two molecules in the asymmetric unit
(A and B); however, there are no major differences in
their conformation other than a small rotation of the
PMe3 group. The complexes exhibit a number of
structural similarities, as well as some noticeable dif-
ferences. The PR3 ligands of 1, 6, and 13 adopt a
-3
σP ) -constant (∆E)-1 rd
Q
(1)
∑
N
d-d excitation energy and rd is the effective radius of
the d-orbital electron. The ∑QN term describes the
distribution of charge in the valence p and d orbitals,
which can be assumed to remain fairly constant for
structurally related molecules.
Initially, the concentration and temperature de-
pendence of δ(187Os) was investigated. At 300 K, the
shifts of 6 in CD2Cl2 exhibit a linear concentration
dependence (six points, concentration coefficient 18.3
ppm‚L‚mol-1), with the osmium resonance at 7.7 × 10-2
M (20 mg in 0.5 mL of solvent) being more highly
shielded by 7 ppm than in a 4.6 × 10-1 M solution (120
mg in 0.5 mL). Similarly, a linear temperature coef-
ficient of +0.7 ppm K-1 was observed for a 4.6 × 10-1
M solution of 6 between 233 and 303 K (six points) in
polar CD3CN and nonpolar CD2Cl2 solvents. This effect
(12) (a) Cabeza, J . A.; Mann, B. E.; Maitlis, P. M.; Brevard, C. J .
Chem. Soc., Dalton Trans. 1988, 629. (b) Cabeza, J . A.; Nutton, A.;
Mann, B. E.; Brevard, C.; Maitlis, P. M. Inorg. Chim. Acta 1986, 115,
L47. (c) Cabeza, J . A.; Mann, B. E.; Brevard, C.; Maitlis, P. M. J . Chem.
Soc., Chem. Commun. 1985, 65.
(13) (a) Benn, R.; Brenneke, H.; J oussen, E.; Lehmkuhl, H.; Ortiz,
F. L. Organometallics 1990, 9, 756. (b) Benn, R.; J oussen, E.; Lehm-
kuhl, H.; Ortiz, F. L.; Rufinska, A. J . Am. Chem. Soc. 1989, 111, 8754.
(14) Christe, K. O.; Dixon, D. A.; Mack, H. G.; Oberhammer, H.;
Pagelot, A.; Sanders, J . C. P.; Schrobilgen, G. J . J . Am. Chem. Soc.
1993, 115, 11279.
20
is in the same order as that observed for Fe(CO)5 but
is substantially less than the value of 2.48 ppm K-1
(17) Stout, G. H.; J ensen, L. H. X-Ray Structure Determination-A
Practical Guide, 2nd ed.; J ohn Wiley & Sons: New York, 1989; p 409.
(18) Ramsey, N. F. Phys. Rev. 1950, 77, 567; 78, 699; 1951, 83, 540;
1952, 86, 243.
(19) Griffith, J . S.; Orgel, L. E. Trans. Faraday Soc. 1957, 53, 601.
(20) Schwenk, A. Phys. Lett. 1970, 31A, 513.
(15) Michelman, R. I.; Ball, G. E.; Bergman, R. G.; Andersen, R. A.
Organometallics 1994, 13, 869.
(16) For a review of the organometallic chemistry of (η6-arene)Os
complexes, see: LeBozec, H.; Touchard, D.; Dixneuf, P. H. Adv.
Organomet. Chem. 1989, 29, 163.
+
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3126 Organometallics, Vol. 15, No. 14, 1996
Bell et al.
Ta ble 1. Selected Bon d Len gth s (Å), An gles (d eg), a n d Tor sion An gles (d eg) for Com p lexes 1, 6, 13, a n d 15
1
molecule A
molecule B
6
13
15
Os-Cl(1)
Os-Cl(2)
2.424(2)
2.426(6)
2.428(2)
2.416(1)
2.422(2)
2.425(2)
2.4251(7)
2.4220(7)
2.427(1)
2.414(1)
Os-P
2.341(2)
2.340(2)
2.281(1)
2.3608(7)
2.355(1)
Os-C(1)
Os-C(2)
Os-C(3)
Os-C(4)
Os-C(5)
Os-C(6)
ø2 a
2.201(6)
2.181(6)
2.158(6)
2.184(6)
2.235(5)
2.248(5)
100.5
2.215(6)
2.194(5)
2.186(5)
2.201(5)
2.189(5)
2.236(5)
30.3
2.204(6)
2.180(5)
2.199(6)
2.229(5)
2.270(5)
2.276(5)
145.4
2.212(3)
2.171(3)
2.210(3)
2.225(3)
2.248(3)
2.237(3)
154.7
2.258(4)
2.231(4)
2.187(4)
2.236(4)
2.203(4)
2.169(4)
289.5
Cl(1)-Os-Cl(2)
85.73(6)
88.00(6)
86.27(6)
87.78(3)
87.18(4)
Cl(1)-Os-P
Cl(2)-Os-P
83.22(6)
87.94(6)
82.71(5)
85.33(6)
86.37(5)
90.48(6)
85.06(3)
79.69(2)
85.54(3)
87.55(4)
C(2)-C(1)-C(7)-C(8)
C(2)-C(1)-C(7)-C(9)
105.1(9)
-17.5(9)
110.8(7)
-14.5(8)
93.7(7)
-31.6(9)
-168.6(3)
68.0(3)
95.1(4)
-29.3(5)
a
Deviation of C(1)-C(2)-C(3)-C(4)-C(5)-C(6) from planarity.17
control of our samples, we predict that our chemical
shifts are accurate to within (1 ppm.
The 187Os shifts of compounds 1-37 span a range of
approximately 3500 ppm in total but show considerable
variations according to class (Tables 2-4). The greatest
variation (approximately 3000 ppm) occurs in class I as
the electronegativity of X is varied. Changing alkyl
substituents on the η6-ligand of VI still has a consider-
able influence on chemical shift (approximately 600
ppm). The phosphine-substituted examples III and IV
exhibit a similar chemical shift range (approximately
550 ppm) while the phosphites II and monohydrides V
contain less variation (approximately 150 ppm). By
systematically varying the stereoelectronic properties
of the ligands in the coordination sphere of the metal,
we have been able to establish a number of structural
correlations as a function of the osmium chemical shift
and have been able to separate electronic and steric
effects.
I. Electr on ic Effects. Complexes I exhibit a “nor-
mal” halogen dependence, with deshielding in the order
Cl > Br > I > sp3 C > H. Thus, replacement of both
chlorine ligands of 1 with bromine results in a 270 ppm
shielding of the osmium nucleus (moves to lower fre-
quency). Further displacement of bromine by iodine
causes an additional 760 ppm shielding, while the
dihydride 5 resonates a further 2000 ppm to lower
frequency of the diiodide 4 and is the most shielded
example in this study. This indicates that the observed
-3
shielding effects are largely determined by the rd
term in eq 1.22 These ligand effects largely parallel
those reported by Benn et al.13a for Os(C5H5)(PR3)2X
complexes.
The shifts of complexes II (Figure 2) exhibit a good
linear relationship (r ) 0.96) with Tolman’s electronic
parameter ø for the P(OR)3 ligand,23 with the metal
nucleus becoming progressively more shielded with
increasing π-acidity (larger ø values). However, with
the exception of the P(OMe)3 complex 6, type II phos-
phite complexes are more shielded relative to their
phosphine counterparts of series III. This “inverse”
F igu r e 1. ORTEP50 plot of Os(p-cymene)Cl2PMe3 (1,
molecule A) and Os(p-cymene)Cl2P(CH2Ph)3 (13) (50%
probability ellipsoids; H atoms given arbitrary thermal
parameters for clarity).
(21) Meier, E. J . M.; von Philipsborn, W. Unpublished results.
(22) Mason, J . Chem. Rev. 1987, 87, 1299.
(23) Bartik, T.; Himmler, T.; Schulte, H. G.; Seevogel, K. J . Organo-
met. Chem. 1984, 272, 29.
observed for the complex Fe(Cp)(PPh3)(CO)(COMe).21
Therefore, with careful temperature and concentration
+
+

(η6-Arene)osmium(II) Complexes
Organometallics, Vol. 15, No. 14, 1996 3127
Ta ble 2. 187Os a n d 31P NMR Da ta (CD2Cl2, 300 K) for Typ e I a n d II Com p lexes
no.
compd
δ(187Os)/ppm
Type I
δ(31P)/ppm
1J (Os,P)/Hz
nJ (Os,H)/Hz
a
1
2
3
4
5
Os(p-cymene)Cl2PMe3
-2226
-2495
-3260
-3330
-5265a
-39.2
-48.3
-61.6
-41.8
-44.5a
272
269
266
280
264
Os(p-cymene)Br2PMe3
Os(p-cymene)I2PMe3
Os(p-cymene)ClMePMe3
5 (2J )
79 (1J )
b
Os(p-cymene)H2PMe3
Type II
6
7
8
9
10
Os(p-cymene)Cl2P(OMe)3
Os(p-cymene)Cl2P(OEt)3
Os(p-cymene)Cl2P(OnBu)3
Os(p-cymene)Cl2P(OPh)3
Os(p-cymene)Cl2P(OiPr)3
-2168
-2142
-2153
-2257
-2076
73.6
69.2
68.0
58.4
63.6
453
448
447
477
442
a
b
p-cymene ) p-MeC6H4CHMe2. Measured in THF-d8.
Ta ble 3. 187Os a n d 31P NMR Da ta (CD2Cl2, 300 K) of Typ e III-V Com p lexes
no.
compd
δ(187Os)/ppm
δ(31P)/ppm
1J (Os,P)/Hz
1J (Os,H)/Hz
Type III
1
11
12
13
14
15
16
17
18
Os(p-cymene)Cl2PMe3
Os(p-cymene)Cl2PMe2Ph
Os(p-cymeneCl2PPh2Me
Os(p-cymene)Cl2P(CH2Ph)3
Os(p-cymene)Cl2PnBu3
Os(p-cymene)Cl2PPh3
Os(p-cymene)Cl2P(m-tolyl)3
Os(p-cymene)Cl2PiPr3
Os(p-cymene)Cl2PCy3
-2226
-2162
-2097
-2028
-2081
-1906
-1892
-1735
-1697
-39.2
-33.9
-20.3
-22.0
-26.6
-13.1
-14.3
-8.5
272
271
275
278
270
282
281
269
266
-18.7
Type IV
19
20
21
22
23
24
Os(p-cymene)I2PMe2Ph
Os(p-cymene)I2PnBu3
Os(p-cymene)I2PPh2Me
Os(p-cymene)I2PPh3
Os(p-cymene)I2PiPr3
Os(p-cymene)I2PCy3
-3201
-3119
-3173
-3036
-2738
-2688
-54.6
-46.1
-37.6
-23.7
-21.7
-31.2
268
268
275
285
270
268
Type Va
25
26
27
28
29
30
31
Os(p-cymene)ClHPMe3
Os(p-cymene)ClHPMe2Ph
Os(p-cymene)ClHPnBu3
Os(p-cymene)ClHPPh2Me
Os(p-cymene)ClHPPh3
Os(p-cymene)ClHPiPr3
Os(p-cymene)ClHPCy3
-3758
-3723
-3814
-3740
-3680
-3764
-3738
-40.3
-27.8
-9.1
-7.8
-8.2
22.5
260
264
263
270
277
265
264
73
72.5
72
71
70
69
68.5
14.5
a
Measured in THF-d8.
Ta ble 4. 187Os a n d 31P NMR Da ta (CD2Cl2, 300 K)
for Typ e VI Com p lexes
duced (Figure 3). Similarly, the iodides IV, which are
on average 1050 ppm more shielded than III, give a
linear correlation between δ(187Os) and θ (r ) 0.97).
There appears to be a mild ligand effect, as the correla-
tion is less significant than for the analogous dichloride
complexes III. This effect has been observed for some
(Cp*)RhX2PR3 complexes (X ) Cl, Br, I, Cp* ) η5-
C5Me5).25 However, a plot of the osmium shifts of III
against IV is linear (r ) 0.98), suggesting that the
introduction of progressively larger PR3 ligands in both
cases has the same and co-operative effect of decreasing
both the ∆E and rd parameters because of their size.26
Similar observations have been made by Elsevier for
some (η4-COD)Rh(PR3)Cl complexes.3c
The osmium shifts of complexes VI reveal a deshield-
ing influence as more sterically demanding arene groups
are introduced. Thus, the hexamethylbenzene-substi-
tuted complex 37 resonates 600 ppm to higher frequency
relative to the parent complex 32. Unfortunately,
relatively little is known about the steric or electronic
properties of arene ligands. In steric terms, Maitlis has
calculated cone angles of 162 and 192° for the Ru-C6H6
δ(187Os)/
ppm
δ(31P)/
ppm
1J (Os,P)/
no.
compd
Hz
32
33
34
35
36
1
Os(C6H6)Cl2PMe3
-2431
-2364
-2352
-2348
-2268
-2226
-1829
-37.5
-37.7
-38.0
-38.2
-38.0
-39.2
-42.3
266
269
270
270
267
272
290
Os(C6H5-Me)Cl2PMe3
Os(C6H5-Et)Cl2PMe3
Os(C6H5-iPr)Cl2PMe3
Os(C6H5-tBu)Cl2PMe3
Os(p-cymene)Cl2PMe3
Os(C6Me6)Cl2PMe3
37
ligand behavior is probably due to an increase in the
spectrochemical ∆E parameter caused by a larger
metal-ligand orbital interaction of more strongly π-
accepting P(OR)3 ligands. This offsets the deshielding
effect expected by way of the associated decrease in the
nephelauxetic rd parameter. An analogous effect was
reported for the osmium bis(phosphine) and bis(phos-
phite) complexes.13a
II. Ster ic Effects. The shifts of the phosphine-
substituted compounds III are linearly dependent on
Tolman’s steric parameter θ for the PR3 ligand24 (r )
0.98) with the osmium nucleus becoming progressively
more deshielded as larger phosphine ligands are intro-
(25) Tedesco, V., von Philipsborn W. Magn. Reson. Chem. 1996, 34,
373.
(24) Tolman, C. A. Chem. Rev. 1977, 77, 313.
(26) Rehder, D. Chimia 1986, 40, 186.
+
+

3128 Organometallics, Vol. 15, No. 14, 1996
Bell et al.
F igu r e 2. Plot of δ(187Os) vs Tolman’s electronic parameter
ø for complexes II (r ) 0.96).
F igu r e 4. Plot of δ(187Os) vs Taft’s steric parameter Es
for complexes VI (r ) 0.99).
F igu r e 5. Plot of δ(187Os) vs Tolman’s electronic parameter
ø for complexes V.
F igu r e 3. Plot of δ(187Os) vs Tolman’s steric parameter θ
for complexes III (r ) 0.98): (a) cone angles taken from
ref 24; (b) cone angle taken from ref 34; (c) cone angle
determined from crystal structure of 13.
steric parameter Es (r ) 0.99).30 This clearly demon-
strates the steric origin of the deshielding effects and
complements previous observations for 59Co,3d 103Rh,3a,b
and 57Fe.1 The poor correlations obtained using the field
and resonance constants, F and R, further suggest that
the steric influence of the arene substituent X operates
by a combination of field and resonance effects.
III. Mixed Effects. In one case, it has been possible
to observe both the electronic and steric effects of similar
ligands within the same system. The monohydrides V
are easily accessible from III but give no linear correla-
tion between δ(187Os) and other structural parameters.
A plot of δ(187Os) against ø (Figure 5) does reveal a near-
linear correlation with the ligands PnBu3 to PPh3, but
unlike II the metal shifts exhibit a “normal” ligand
dependence and are shielded by less π-acidic ligands.
This behavior changes when larger and less electroni-
and Ru-C6Me6 moieties.27 Their electronic properties
have been more thoroughly investigated by determining
core binding energies in the (Cp)Fe(η6-arene)+ system,
using X-ray photoelectron spectroscopy.28 This study
has shown that the introduction of a methyl substituent
onto the arene slightly enhances its donor properties,
although the effect is not great.
We have studied chemical shift correlations with
Hammett and Taft-type substituent constants for the
five Os(η6-C6H5X)Cl2PMe3 complexes 32-36 (X ) H, Me,
i
Et, Pr, tBu). Statistically insignificant correlations
were obtained for Hammett σm, σp, σp+, and σp- and
Swain-Lupton F and R values,29 whereas an excellent
linear correlation (Figure 4) was obtained using Taft’s
(27) Maitlis, P. M. Chem. Soc. Rev. 1981, 10, 1.
(28) Gassman, P. G.; Deck, P. A. Organometallics 1994, 13, 2890.
(29) Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165.
(30) March, J . Advanced Organic Chemistry, 4th ed.; J ohn Wiley &
Sons: New York, 1992; p 285.
+
+

(η6-Arene)osmium(II) Complexes
Organometallics, Vol. 15, No. 14, 1996 3129
cally demanding phosphines (PiPr3 and PCy3) are
introduced. These ligands possess virtually no π-
acceptor ability and presumably deshield the metal
nucleus because of their size, as with III and IV. Thus,
it appears that as the metal becomes more electron rich,
the acceptor character of the phosphorus ligand becomes
the principal factor determining the chemical shift of
the osmium nucleus, with better donor ligands shielding
the metal, until a threshold of ø is attained (ø < 5.25, θ
> 145°) where steric factors become dominant.
For comparison, we have attempted similar correla-
tions using more conventional 31P NMR methods. For
complexes II and III, ø or θ do not correlate with their
absolute 31P shifts but do show modest (r ) 0.93) and
good (r ) 0.98) correlations, respectively, with their
coordination chemical shifts ∆ (δfree ligand - δcomplex). In
contrast, for types IV-VI ø or θ do not correlate with
either δ or ∆(31P), thus reflecting a greater sensitivity
of the metal nucleus to subtle stereoelectronic changes.
We have been able to use the correlation shown in
Figure 3 to determine qualitatively the cone angles of
various phosphine ligands by 187Os NMR. For example,
24,31
32
literature values for P(CH2Ph)3
and P(m-tolyl)3
suggest equivalent cone angles of 165°, which do not
correspond with the observed shifts of complexes 13 and
16. However, these values were measured using simple
CPK molecular models with rotation of the R groups to
achieve C3v symmetry.33 Coville has calculated a cone
angle of 148° for P(m-tolyl)3 on the basis of a nonsym-
metrical arrangement of the three phenyl rings.34
Evidence for this geometry is now provided by a vari-
F igu r e 6. Variable-temperature 1H-NMR spectra (1.9-
2.7 ppm region) of Os(p-cymene)Cl2P(m-tolyl)3 (16) in
CD2Cl2 at 400 MHz showing two methyl resonances for the
P(m-tolyl)3 ligand at 203 K.
1
able-temperature H NMR investigation of the m-tolyl
region of 16 (Figure 6). At room temperature, all three
methyl substituents are equivalent, giving a single
resonance. However, at -50 °C the signal broadens and
is resolved at -70 °C into two separate resonances with
a 2:1 ratio, indicating nonequivalence of the m-tolyl
rings. Similarly, the crystal structure of complex 13
(Figure 1) reveals a different orientation of the three
benzyl groups. One phenyl ring is directed toward the
p-cymene group with the other two pointing away,
probably to reduce steric interactions about the con-
gested metal center. This arrangement gives a cone
angle 5-6° smaller than that measured for the PPh3
complex 15.35 These corrected cone angles agree with
the observed 187Os shifts obtained for complexes 13 and
16.
Values of 1J (M,P) scalar coupling constants are known
to depend on a number of contributing factors, such as
the electronegativity of substituents on phosphorus,
metal oxidation state, and structural effects.9,36 How-
1
ever, on the basis of the assumption that J (187Os,31P)
coupling constants are a reflection of the σ-bond order
of the M-P bond, we have attempted to correlate these
with the spectral properties of the ligands in the metal
coordination sphere. The magnitude of 1J (187Os,31P) in
series I increases in the order H < I < Br < Cl < Me,
but we do not believe that this trend necessarily reflects
the Os-P bond strength. It is generally accepted that
M-C bonds are weaker than M-H bonds by 15-25 kcal
mol-1, which may genuinely account for the large
187Os,31P coupling obtained for 4. However, thermo-
chemical studies of Ru(Cp*)(PMe3)2X (X ) Cl, Br, I, H)
show that the Ru-PMe3 bond dissociation energy
increases in the order Cl < Br ≈ I < H.37 A more
convincing case is provided by compounds 32-37,
Cou p lin g Con sta n ts. A simplified expression to
describe one-bond metal-phosphorus coupling con-
2
2
stants is given in eq 2,36 where |ΨM(0)| and |ΨP(0)|
J M,P KRM2RP |ΨM(0)| |ΨP(0)| / ∆E
(2)
2
2
2 3
are s-electron densities at the nucleus of each atom, R2
represents the localized hybrid bond s-character in a
valence bond description, and K is the reduced coupling
constant.
t
which, with the exception of the Bu-substituted com-
plex, show a clear trend of increasing 1J (187Os,31P) with
the introduction of larger η6-arene ligands. This obser-
vation complements the trend observed with δ(187Os)
and clearly suggests a weakening of the osmium-arene
bond by larger arene groups, which is also evident from
the concomitant strengthening of the Os-P bond.
For types II and III, 187Os,31P coupling constants are
linearly dependent on the electronic character of the
phosphorus ligand ø, giving a very modest correlation
(r ) 0.86) for the phosphine series III, which improves
(31) Manzer, L. E.; Tolman, C. A. J . Am. Chem. Soc. 1975, 97, 1955.
(32) (a) Liu, H. Y.; Eriks, K.; Prock, A.; Giering, W. P. Organo-
metallics 1990, 9, 1758. (b) Rahman, M. M.; Liu, H. Y.; Prock, A.;
Giering, W. P. Organometallics 1987, 6, 650.
(33) Tolman, C. A. J . Am. Chem. Soc. 1970, 92, 2956.
(34) (a) White, D.; Coville, N. J . Adv. Organomet. Chem. 1994, 36,
95. (b) White, D.; Carlton, L.; Coville, N. J . J . Organomet. Chem. 1992,
440, 15.
(35) Cone angles were measured using the equation given in ref 24
with the Os-P bond set to 2.28 Å.
(36) Pregosin, P. S.; Kunz, R. W. 31P and 13C NMR of Transition
Metal Phosphine Complexes; Springer-Verlag: Berlin, 1979.
(37) Bryndza, H. E.; Domaille, P. J .; Paciello, R. A.; Bercaw, J . E.
Organometallics 1989, 8, 379.
+
+

3130 Organometallics, Vol. 15, No. 14, 1996
Ta ble 5. 187Os Sp in -La ttice Rela xa tion Ra tes T1 (CD2Cl2, 300 K) of Selected Com p lexesa
Bell et al.
-1
T1-1/s-1
T1-1(csa) (%)
-1
T1 (other)
no.
compd
9.4 T
14.1 T
9.4 T
14.1 T
9.1 T
1
2
3
6
7
Os(p-cymene)Cl2PMe3
Os(p-cymene)Br2PMe3
Os(p-cymene)I2PMe3
0.60
0.46
0.39
0.51
0.67
0.89
0.94
0.71
0.88
1.3
1.3
0.98
0.78
1.1
1.6
2.0
2.2
1.7
2.0
3.1
2.7
2.0
3.3
0.56 (93)
0.42 (91)
0.31 (79)
0.47 (92)
0.74 (100)*
0.89 (100)
1.0 (100)*
0.79 (100)*
0.9 (100)*
1.4 (100)*
1.2 (100)
0.9 (100)*
1.4 (100)
1.4 (100)*
0.94 (96)
0.7 (90)
0.04
0.04
0.08
0.04
0.0*
0.03
0.0*
0.0*
0.0*
0.0*
0.0
Os(p-cymene)Cl2P(OMe)3
Os(p-cymene)Cl2P(OEt)3
Os(p-cymene)Cl2P(OnBu)3
Os(p-cymene)Cl2P(OPh)3
Os(p-cymene)Cl2P(OiPr)3
Os(p-cymene)Cl2PPh2Me
Os(p-cymene)Cl2PnBu3
Os(p-cymene)Cl2PPh3
Os(p-cymene)Cl2PiPr3
Os(p-cymene)Cl2PCy3
1.1 (100)
1.7 (100)*
2.0 (100)
2.3 (100)*
1.8 (100)*
2.0 (100)*
3.2 (100)*
2.7 (100)
2.0 (100)
3.2 (100)
8
9
10
12
14
15
17
18
1.2
0.87
1.5
0.0*
0.1
a
Asterisk indicates result of calculation of the CSA relaxation rate greater than 100%, but within limit of experimental error.
greatly (r ) 0.99) for the phosphites II. The magnitude
of 1J (187Os,31P) increases with increasing π-acidity of the
ligand, which also reflects an increase in the electro-
negativity of group R. The trialkyl-containing examples
introduced, we believe that the correlation is not related
to the strength of the Os-H bond. It possibly reflects
changes of the H-Os-Cl bond angle to accommodate
the ligands across the series PMe3 (θ ) 118°) to PCy3
(θ ) 170°). In conclusion, at least two independent
effects (bond distances and angles) can influence the
value of one-bond 187Os,31P couplings. Therefore, care
has to be taken in any interpretation of this parameter
in terms of bond strength.
i
of III (R ) Me, nBu, Pr, Cy, CH2Ph) exhibit a better
correlation against ø with 1J (187Os,31P) generally de-
creasing with increasing ligand size. However, this
behavior deviates considerably when aryl groups are
included, as with PPh2Me, possibly indicating variations
in π-bonding interactions for these complexes that are
not adequately represented by literature values of ø.
Opening of the R-P-R bond angle should increase the
phosphorus s character in the P-R bond and decrease
it in the Os-P bond. Thus, larger phosphorus ligands
should possess smaller 187Os,31P couplings, but this is
not generally observed within a particular series. These
results complement the observation made by Nolan for
the cleavage of the dimer [Ru(p-cymene)Cl2]2 using
various phosphorus ligands. Here, the enthalpy of the
Rela xa tion Tim es. We have been able to measure
accurate 187Os T1 relaxation times for representative
examples of types I-III (Table 5).41 Measurements
taken of II and III at 9.4 and 14.1 T show that the rate
of relaxation varies from 0.39 to 3.3 s-1 and is propor-
tional to the square of the ratio of the two magnetic field
strengths (2.25). Hence, the mechanism is chemical
shift anisotropy (CSA) dominated. We have compared
these T1 rates with other NMR and structural param-
eters, but only rough correlations with the molecular
weight of the attached phosphorus ligand are apparent,
with heavier ligands relaxing the metal nucleus more
efficiently than smaller ones within their respective
groups. This reflects the molecular tumbling or cor-
relation time, τc, of the molecule. However, the phos-
phites II relax at a rate 15-30% slower than their
lighter counterparts of III, which suggests that other
factors are involved. This is also evident in the halogen
series Os(p-cymene)X2PMe3 (X ) Cl, Br, I), which shows
a trend of slower T1 rates as the weight of the halogen
increases from chlorine to iodine. This is opposed to an
effect of τc and may be related to the polarization of the
Os-X bond, which for more electronegative substituents
is greater, thus increasing the anisotropy of the ligand
field and of the shielding tensor. Further evidence is
provided by the fact that the CSA contribution to T1 is
substantially reduced at the lower field strength. We
are currently trying to extend these measurements to
more varied types of complexes to determine whether
we can extract additional structural information from
this NMR parameter.
reaction was found to increase in the order PCy3
<
P(OPh)3 < PiPr3 < PPh3 < P(CH2Ph)3 < PPh2Me <
P(OMe)3 < PMe2Ph < PMe3 but with a combination of
both electronic and steric factors playing an important
role in dictating the magnitude of -∆H for the reac-
tion.38
Assuming that the R2 term in eq 2 makes the
dominant contribution to 1J (187Os,31P), the correlations
observed against ø for II and III suggests that larger
coupling constants may be a consequence of shorter
M-P bond lengths, as has been shown for some plati-
num complexes.39 We have compared these couplings
with our crystallographic data for the phosphines 1, 13,
and 15 and phosphite 6. Although the data are not
extensive, it does suggest a relationship in our case (r
) 0.96), although the Os-PMe3 bond of 1 is slightly
shorter than the 187Os,31P coupling would predict. The
diiodides IV exhibit no similar correlations against ø
or θ. This may be an effect of the soft iodine ligand,
which can be polarized more easily by the metal to
compensate for variations in the bonding requirements
of the phosphine.
The monohydrides V exhibit no linear correlations
1
between J (187Os,31P) and other structural parameters.
1
However, values of J (187Os,1H) were found to give a
(38) Serron, S. A.; Nolan, S. P. Organometallics 1995, 14, 4611.
(39) Mather, G. G; Pidcock, A.; Rapsey, G. J . N. J . Chem. Soc.,
Dalton Trans. 1973, 2095.
(40) Bennett, M. A.; Weerasuria, M. M. J . Organomet. Chem. 1990,
394, 481.
(41) Koz´min´ski, W.; von Philipsborn, W. J . Magn. Reson. A 1995,
116, 262.
good correlation with Tolman’s steric parameter θ (r )
0.99), with coupling constants decreasing with increas-
ing phosphine size. Because infrared measurements of
these and related complexes40 indicate that the Os-H
bond strength increases as larger PR3 ligands are
+
+

(η6-Arene)osmium(II) Complexes
Con clu sion s
Organometallics, Vol. 15, No. 14, 1996 3131
and distilled prior to use. The monomeric complexes 1, 3-5,
9, 15, and 29 and dimers [Os(p-cymene)Cl2]2, [Os(C6Me6)Cl2]2,
and [Os(C6H6)Cl2]2 were prepared by literature procedures.45-48
Complexes 13, 16, and 18 and osmium trichloride were
generously donated by Dr. A. Hafner (Ciba-Geigy, Marly,
Switzerland).
Osmium-187 chemical shifts appear to be very sensi-
tive to subtle changes in the coordination sphere of the
metal, making this technique useful in gauging both the
electronic and steric effects of various ligands. Some
of the electronic ligand effects are similar to those
observed in bis(phosphine) complexes of the type OsCp-
(PR3)2X which, however, are characterized by much
higher osmium shielding. In addition, osmium-phos-
phorus and osmium-hydride coupling constants can
provide useful structural information in the Os(arene)-
X2L series, in particular on Os-P bond lengths. It is
now possible to run 187Os NMR spectra on a routine
basis, and we are currently applying the technique to
screen the activity of some homogeneous catalysts.
Os(p -cym en e)Br 2P Me3 (2). The dichloride 1 (140 mg, 0.3
mmol) and NaBr (300 mg, 3.0 mmol) were stirred in MeOH
(10 mL) overnight at room temperature. The solution was
evaporated, redissolved in CH2Cl2 (10 mL), and filtered
(Celite), and the volume of solvent was reduced to 2-3 mL.
Pentane (15 mL) was added to precipitate an orange powder,
which was filtered out and washed with cold ether (5 mL).
Yield: 150 mg (90%). Mp: 197-209 °C. 1H NMR (CDCl3):
p-cymene, δ 1.25 (d, J ) 6.9 Hz, 6H, CHMe2), 2.26 (s, 3H, Me),
2.87 (sept, J ) 6.9 Hz, 1H, CHMe2), 5.45 (m, 4H, MeC6H4-
CHMe2); PR3, δ 1.72 (d, J ) 10.4 Hz, 9H, P-Me). 13C{1H}
NMR (CDCl3): p-cymene, δ 22.3 (s, C7), 18.9 (s, C1), 30.8 (s,
C6), 99.1 and 87.9 (s, C2 and C5), 86.1 and 80.6 (s, C3 and
C4); PR3, δ 16.8 (d, J ) 39.1 Hz, P-Me). Anal. Calcd for
Exp er im en ta l Section
Inverse-detected 187Os NMR spectra were obtained in CD2Cl2
at 300 K using the HMQC technique, with 31P detection at
9.4 T for types I-IV and (VI) and 1H detection at 14.1 T for
V. Approximately 120 mg of sample in 0.5 mL of solvent in a
5-mm NMR tube was required to obtain a phosphorus-detected
spectrum using a Bruker AM-400-WB spectrometer equipped
with a TBI 1H, 31P, BB (9-41 MHz) probe head (ν0(187Os) )
9.2 MHz). A second PTS160 synthesizer together with a BSV3
decoupling unit was used for pulsing the osmium frequency.
Typically 128 increments, each of 24 scans, were accumulated
over 3 h to obtain an overview spectrum: spectral width in
F1 30 000 Hz, spectral width in F2 800-1000 Hz, 90° pulse
length for osmium 60 µs, 90° phosphorus pulse 14.5 µs,
relaxation delay 2 s. Final spectra of 256 increments, each of
40 scans, with a spectral window of 2000 Hz in F1 were
measured overnight to ensure that the osmium signals were
not folded. Proton-detected spectra were acquired on a Bruker
AMX-600 spectrometer, which required only 40 mg of sample,
using a TBI-LR 1H, 31P, BB (7-21.5 MHz) probe head (ν0(187Os)
) 13.8 MHz). Typically 128 increments, each of 8 or 16 scans,
were accumulated in 1 to 2 h: spectral width in F1 800 Hz,
spectral width in F2 300 Hz, 90° pulse length for osmium 70-
80 µs, 90° for proton 11 µs, relaxation delay 2 s. Pulse
sequences reported by Benn et al.42 and by Bax et al.43 were
used. Osmium-187 spectra of IV were obtained using ap-
proximately 20 mg of sample by applying a binomial suppres-
sion of the central phosphorus resonance.44 Prior to Fourier
transformation, the data were zero filled and multiplied by
sine functions in both dimensions. Chemical shifts are re-
ported relative to OsO4 in a field where the protons of TMS
resonate at precisely 100 MHz (¥ ) 2.282 343 MHz).9,10
Osmium relaxation times T1 were measured at the frequency
of the 31P nucleus by employing inverse detection methods
recently developed in our group.41
C
13H23Br2OsP: C, 27.9; H, 4.11. Found: C, 28.3; H, 4.00.
Complexes 6-18 were similarly prepared by cleavage of
[Os(p-cymene)Cl2]2 using 2.2 equiv of PR3, of which a repre-
sentative example is given for the P(OMe)3-substituted com-
plex 6.
Os(p -cym en eCl2P (OMe)3 (6). [Os(p-cymene)Cl2]2 (150 mg,
0.2 mmol) and P(OMe)3 (0.5 mL, 0.45 mmol) were stirred in
CH2Cl2 (10 mL) for 1 h at 40 °C. The cooled solution was
filtered (Celite) and the volume of solvent reduced to 2-3 mL.
The product was purified by column chromatography using
neutral grade (IV) alumina and diethyl ether as eluant. The
solvent was evaporated, and the product was redissolved in
CH2Cl2 (2 mL). Pentane (15 mL) was added to precipitate a
yellow powder, which was filtered out and washed with of cold
ether (5 mL). Yield: 130 mg (70%). Mp: 149-151 °C. 1H
NMR (CDCl3): p-cymene, δ 1.27 (d, J ) 7.0 Hz, 6H, CHMe2),
2.28 (s, 3H, Me), 2.87 (sept, J ) 7.0 Hz, 1H, CHMe2), 5.66 (d,
J ) 5.8 Hz, 2H, MeC6H4CHMe2), 5.12 (d, J ) 5.8 Hz, 2H,
MeC6H4CHMe2); P(OR)3, δ 3.80 (d, J ) 11.2 Hz, 9H, OMe).
13C{1H} NMR (CDCl3), p-cymene, δ 22.1 (s, C7), 18.1 (s, C1),
30.1 (s, C6), 101.8 (d, J ) 3.2 Hz, C2 or C5), 95.1 (d, J ) 2.2
Hz, C2 or C5), 81.2 (d, J ) 4.8 Hz, C3 or C4) 80.4 (d, J ) 5.7
Hz, C3 or C4); P(OR)3, δ 53.6 (d, J ) 5.7 Hz, P-OMe). Anal.
Calcd for C13H23Cl2O3OsP: C, 30.1; H, 4.43. Found: C, 30.0;
H, 4.31.
Os(p -cym en e)Cl2P (OEt)3 (7): Yellow powder, yield 140
mg (66%). Mp: 89-91 °C. 1H NMR (CDCl3): p-cymene, δ 1.27
(d, J ) 6.8 Hz, 6H, CHMe2), 2.27 (s, 3H, Me), 2.88 (sept, J )
6.8 Hz, 1H, CHMe2), 5.63 (d, J ) 5.2 Hz, 2H, MeC6H4CHMe2),
5.48 (d, J ) 5.2 Hz, 2H, MeC6H4CHMe2); P(OR)3, δ 1.28 (t, J
) 6.8 Hz, 9H, CH3), 4.17 (m, J ) 6.8 Hz, 6H, OCH2). 13C{1H}
NMR (CDCl3): p-cymene, δ 22.2 (s, C7), 18.0 (s, C1), 30.1 (s,
C6), 101.1 and 94.5 (s, C2 and C5), 81.0 (d, J ) 5.3 Hz, C3 or
C4), 80.3 (d, J ) 5.2 Hz, C3 or C4); P(OR)3, δ 16.1 (d, J ) 6.0
Hz, CH3), 62.4 (d, J ) 6.0 Hz, OCH2). Anal. Calcd for
Routine 1H and 13C NMR spectra were recorded at 300 K
on a Bruker ARX-300 spectrometer and are referenced relative
to TMS. 31P NMR spectra were recorded on a Bruker AM-
400 spectrometer and are referenced relative to 85% H3PO4.
For 13C {1H} shift assignments, the p-cymene carbon atoms
have been labeled:
C
16H29Cl2O3OsP: C, 34.2; H, 5.17. Found: C, 34.5; H, 5.19.
Os(p -cym en e)Cl2P (On Bu )3 (8): Orange powder, yield 145
mg (63%). Mp: 50-56 °C. 1H NMR (CDCl3): p-cymene, δ 1.25
(d, J ) 6.9 Hz, 6H, CHMe2), 2.24 (s, 3H, Me), 2.85 (sept, J )
6.9 Hz, 1H, CHMe2), 5.48 (d, J ) 5.7 Hz, 2H, MeC6H4CHMe2),
5.62 (d, J ) 5.7 Hz, 2H, MeC6H4CHMe2); P(OR)3, δ 0.94 (t, J
) 7.2 Hz, 9H, CH3), 4.08 (m, 6H, OCH2), 1.41 (m, 6H, CH2),
1.62 (m, 6H, CH2).13C{1H} NMR (CDCl3): p-cymene, δ 22.2
(s, C7), 17.9 (s, C1), 30.1 (s, C6), 100.5 and 93.8 (s, C2 and
C5), 80.9 (d, J ) 5.6 Hz, C3 or C4) 80.6 (d, J ) 5.9 Hz, C3 or
All reactions were performed in dry glassware under an
inert atmosphere of nitrogen. Solvents were chemically dried
(45) Cabeza, J . A.; Maitlis, P. M. J . Chem. Soc., Dalton Trans. 1985,
573
(42) Benn, R.; Brevard, C. J . Am. Chem. Soc. 1986, 108, 5622.
(43) Bax, A; Griffey, R. H.; Hawkins, B. L. J . Magn. Reson. 1983,
55, 301.
(46) Werner, H.; Zenkert, K. J . Organomet. Chem. 1988, 345, 151.
(47) Kiel, W. A.; Ball, R. G.; Graham, W. A. G. J . Organomet. Chem.
1990, 383, 481.
(44) Meier, E. J . M.; Koz´min´ski, W.; von Philipsborn, W. Magn.
Reson. Chem. 1996, 34, 89.
(48) Arthur, T.; Stephenson, T. A. J Organomet. Chem. 1981, 208,
369.
+
+

3132 Organometallics, Vol. 15, No. 14, 1996
Bell et al.
C4); P(OR)3, δ 13.7 (s, CH3), 66.1 (d, J ) 6.6 Hz, OCH2), 32.4
and 18.9 (s, CH2). Anal. Calcd for C22H41Cl2O3OsP: C, 40.9;
H, 6.36. Found: C, 40.7; H, 6.14.
44 mg (65%). Mp: 158-170 °C. 1H NMR (CDCl3): p-cymene,
δ 1.11 (d, J ) 6.9 Hz, 6H, CHMe2), 2.10 (s, 3H, Me), 2.88 (sept,
J ) 6.9 Hz, 1H, CHMe2), 5.27 (d, J ) 5.7 Hz, 2H, MeC6H4-
CHMe2), 5.21 (d, J ) 5.7 Hz, 2H, MeC6H4CHMe2); PR3, δ 2.24
(d, J ) 10.4 Hz, 6H, P-Me), 7.40-7.28 (m, 5H, Ph). 13C{1H}
NMR (CDCl3): p-cymene, δ 22.3 (s, C7), 19.4 (s, C1), 31.2 (s,
C6), 102.4 and 87.7 (s, C2 and C5), 81.5 (d, 2.9 Hz, C3 or C4),
77.1 (d, 4.6 Hz, C3 or C4); PR3, δ 18.7 (d, J ) 42.7 Hz, P-Me),
139.1 (d, J ) 45.5 Hz, ipso C6H5), 130.0 (s, Ph), 129.7 (d, J )
7.9 Hz, Ph), 128.3 (d, J ) 9.3 Hz, Ph). Anal. Calcd for
Os(p -cym en e)Cl2P (OiP r )3 (10): Orange powder, yield 190
mg (85%). Mp: 113-121 °C. 1H NMR (CDCl3): p-cymene, δ
1.26 (d, J ) 6.9 Hz, 6H, CHMe2), 2.23 (s, 3H, Me), 2.87 (sept,
J ) 6.9 Hz, 1H, CHMe2), 5.61 (d, J ) 5.7 Hz, 2H, MeC6H4-
CHMe2), 5.46 (d, J ) 5.7 Hz, 2H, MeC6H4CHMe2); P(OR)3, δ
1.30 (d, J ) 6.4 Hz, 18H, CH3), 4.94 (m, J ) 6.4 Hz, 3H, OCH).
13C{1H} NMR (CDCl3): p-cymene, δ 22.3 (s, C7), 17.7 (s, C1),
30.2 (s, C6), 100.0 and 95.3 (s, C2 and C5), 80.6 (d, J ) 4.5
Hz, C3 or C4), 79.7 (d, J ) 6.3 Hz, C3 or C4); P(OR)3, δ 23.9
(d, J ) 3.8 Hz, CH3), 70.8 (d, J ) 7.0 Hz, OCH). Anal. Calcd
for C19H35Cl2O3OsP: C, 37.8; H, 5.80. Found: C, 37.9; H, 5.53.
Os(p -cym en e)Cl2P Me2P h (11): Orange powder, yield 180
mg (89%). Mp: 163-177 °C. 1H NMR (CDCl3): p-cymene, δ
1.12 (d, J ) 7.0 Hz, 6H, CHMe2), 1.96 (s, 3H, Me), 2.49 (sept,
J ) 7.0 Hz, 1H, CHMe2), 5.34 (d, J ) 5.1 Hz, 2H, MeC6H4-
CHMe2), 5.24 (d, J ) 5.1 Hz, 2H, MeC6H4CHMe2); PR3, δ 1.85
(d, J ) 10.7 Hz, 6H, P-Me), 7.45 (m, 3H, Ph), 7.07 (t, J ) 8.5
Hz, 2H, Ph). 13C{1H} NMR (CDCl3), p-cymene, δ 21.8 (s, C7),
17.2 (s, C1), 29.7 (s, C6), 98.2 and 86.6 (s, C2 and C5), 80.2 (d,
J ) 3.8 Hz, C3 or C4), 80.1 (d, J ) 4.5 Hz, C3 or C4); PR3, δ
11.4 (d, J ) 39.2 Hz, P-Me), 137.4 (d, J ) 49.0 Hz, ipso C6H5),
129.7, 129.1, and 128.1 (s, Ph). Anal. Calcd for C18H25Cl2-
OsP: C, 40.3; H, 4.69. Found: C, 40.6; H, 4.82.
C
18H25I2OsP: C, 30.2; H, 3.49. Found: C, 30.2; H, 3.58. MS:
m/z 718 [M+] (192Os).
Os(p -cym en e)I2P n Bu 3 (20): Red powder, yield 42 mg
(60%). Mp: 156-164 °C. 1H NMR (CDCl3): p-cymene, δ 1.28
(d, J ) 6.8 Hz, 6H, CHMe2), 2.38 (s, 3H, Me), 3.13 (sept, J )
6.8 Hz, 1H, CHMe2), 5.12 (m, 4H, MeC6H4CHMe2); PR3, δ 0.95
(t, J ) 7.0 Hz, 9H, Me), 1.30-1.50 (m, 12H, CH2), 2.23 (m,
6H, P-CH2). 13C{1H} NMR (CDCl3): p-cymene, δ 22.5 (s, C7),
19.6 (s, C1), 31.5 (s, C6), 102.4 and 86.9 (s, C2 and C5), 80.9
and 76.2 (s, C3 or C4); PR3, δ 13.7 (s, CH3), 29.1 (d, J ) 33.6
Hz, P-CH2), 26.7 and 24.3 (s, CH2). Anal. Calcd for C22H41I2-
OsP: C, 33.9; H, 5.26. Found: C, 33.6; H, 5.20. MS: m/z 782
[M+] (192Os).
Os(p -cym en e)I2P P h 2Me (21): Red powder, yield 45 mg
(64%). Mp: 183-193 °C. 1H NMR (CDCl3): p-cymene, δ 0.91
(d, J ) 6.8 Hz, 6H, CHMe2), 2.18 (s, 3H, Me), 2.81 (sept, J )
6.8 Hz, 1H, CHMe2), 5.50 (d, J ) 5.4 Hz, 2H, MeC6H4CHMe2),
5.37 (d, J ) 5.4 Hz, 2H, MeC6H4CHMe2); PR3, δ 2.57 (t, J )
10.0 Hz, 3H, P-Me), 7.41-7.37 (m, 10H, Ph). 13C{1H} NMR
(CDCl3): p-cymene, δ 21.9 (s, C7), 18.6 (s, C1), 31.0 (s, C6),
102.7 and 88.7 (s, C2 and C5), 81.7 (s, C3 or C4), 78.3 (d, 4.7
Hz, C3 or C4); PR3, δ 19.9 (d, J ) 44.4 Hz, P-Me), 136.8 (d, J
) 52.3 Hz, ipso C6H5), 133.3 (d, J ) 9.0 Hz, Ph), 130.2 (s, Ph),
127.9 (d, J ) 10.0 Hz, Ph). Anal. Calcd for C23H27I2OsP: C,
35.5; H, 3.47. Found: C, 35.8 H, 3.53. MS: m/z 780 [M+]
Os(p -cym en e)Cl2P P h 2Me (12): Orange-yellow powder,
yield 200 mg (89%). Mp: 169-170 °C. 1H NMR (CDCl3):
p-cymene, δ 0.92 (d, J ) 7.0 Hz, 6H, CHMe2), 1.98 (s, 3H, Me),
2.32 (sept, J ) 7.0 Hz, 1H, CHMe2), 5.45 (d, J ) 5.7 Hz, 2H,
MeC6H4CHMe2), 5.39 (d, J ) 5.7 Hz, 2H, MeC6H4CHMe2); PR3,
δ 1.96 (d, J ) 11.4 Hz, 3H, P-Me), 7.4-7.7 (m, 10H, Ph).
13C{1H} NMR (CDCl3): p-cymene, δ 21.7 (s, C7), 17.1 (s, C1),
29.6 (s, C6), 99.0 and 87.7 (s, C2 and C5), 80.7 and 77.9 (s, C3
and C4); PR3, δ 11.1 (d, J ) 39.6 Hz, P-Me), 134.7 (d, J )
52.0 Hz, ipso C6H5), 132.7, 130.3 and 128.0 (s, Ph). Anal.
Calcd for C23H27Cl2OsP: C, 46.4; H, 4.54. Found: C, 46.4; H,
4.46.
Os(p -cym en e)Cl2P P n Bu 3 (14): Orange powder, yield 196
mg (87%). Mp: 176-179 °C. 1H NMR (CDCl3): p-cymene, δ
1.29 (d, J ) 6.9 Hz, 6H, CHMe2), 2.22 (s, 3H, Me), 2.77 (sept,
J ) 6.9 Hz, 1H, CHMe2), 5.61 (d, J ) 5.6 Hz, 2H, MeC6H4-
CHMe2), 5.40 (d, J ) 5.6 Hz, 2H, MeC6H4CHMe2); PR3, δ 0.95
(t, J ) 6.9 Hz, 9H, CH3), 2.00 (m, 6H, P-CH2), 1.40 (m, 12H,
CH2). 13C{1H} NMR (CDCl3): p-cymene, δ 22.3 (s, C7), 17.8
(s, C1), 30.3 (s, C6), 97.6 and 86.2 (s, C2 and C5), 80.1 (d, 3.1
Hz, C3 or C4), 76.6 (d, 6.5 Hz, C3 or C4); PR3, δ 13.6 (s, CH3),
23.7 (d, J ) 32.9 Hz, P-CH2), 25.1 (d, J ) 12.7 Hz, CH2), 24.2
(d, J ) 3.1, CH2). Anal. Calcd for C22H41Cl2OsP: C, 44.2; H,
6.87. Found: C, 44.3; H, 6.67.
(
192Os).
Os(p -cym en e)I2P P h 3 (22): Red powder, yield 47 mg (62%).
Mp: 220-223 °C. 1H NMR (CDCl3): p-cymene, δ 1.25 (d, J )
6.9 Hz, 6H, CHMe2), 2.01 (s, 3H, Me), 3.33 (sept, J ) 6.9 Hz,
1H, CHMe2), 5.61 (d, J ) 5.8 Hz, 2H, MeC6H4CHMe2), 5.10
(d, J ) 5.6 Hz, 2H, MeC6H4CHMe2); PR3, δ 7.40-7.75 (m, 15H,
Ph). 13C{1H} NMR (CDCl3): p-cymene, δ 22.8 (s, C7), 18.6 (s,
C1), 31.7 (s, C6), 105.2 and 91.4 (s, C2 and C5), 81.9 and 80.3
(s, C3 and C4); PR3, δ 135.3 (d, J ) 53.8 Hz, ipso C6H5), 135.8
(d, J ) 9.0 Hz, Ph), 130.5 (s, Ph), 127.5 (d, J ) 10.1 Hz, Ph).
Anal. Calcd for C28H29I2OsP: C, 40.0; H, 3.45. Found: C, 40.6;
H, 3.52. MS: m/z 715 [M+ - I] (192Os).
Os(p -cym en e)I2P iP r 3 (23): Red powder, yield 35 mg (53%).
Mp: 151-163 °C. 1H NMR (CDCl3): p-cymene, δ 1.33 (d, J )
7.3 Hz, 6H, CHMe2), 2.41 (s, 3H, Me), 3.17 (sept, J ) 7.3 Hz,
1H, CHMe2), 5.83 (m , 4H, MeC6H4CHMe2); PR3, δ 1.35 (dd,
J (PH) ) 13.1 Hz, J (H,H) ) 7.4 Hz, 18H, CH3), 3.01 (m, 3H,
P-CH). 13C{1H} NMR (CDCl3): p-cymene, δ 23.1 (s, C7), 19.4
(s, C1), 31.6 (s, C6), 102.2 and 87.2 (s, C2 and C5), 81.6 and
76.1 (s, C3 and C4); PR3, δ 21.1 (s, Me), 28.9 (d, J ) 26.0 Hz,
P-CH). Anal. Calcd for C19H35I2OsP: C, 30.9; H, 4.74.
Found: C, 30.9; H, 4.00. MS: m/z 613 [M+ - I] (192Os).
Os(p -cym en e)I2P Cy3 (24): Red powder, yield 48 mg (62%).
Mp: 143-151 °C. 1H NMR (CDCl3): p-cymene, δ 1.33 (d, J )
6.9 Hz, 6H, CHMe2), 2.38 (s, 3H, Me), 3.19 (sept, J ) 6.9 Hz,
1H, CHMe2), 5.81 (m, 4H, J ) 5.9 Hz, MeC6H4CHMe2); PR3, δ
2.26 (m, 3H, P-CH), 2.20 (m, 6H, CH2), 1.81 (m, 12H, CH2),
1.40 (m, 12H, CH2). 13C{1H} NMR (CDCl3): p-cymene, δ 22.9
(s, C7), 19.3 (s, C1), 31.6 (s, C6), 102.4 and 87.0 (s, C2 and
C5), 81.7 and 75.9 (s, C3 and C4); PR3, δ 38.9 (d, J ) 24 Hz,
P-CH), 30.6 (s, CH2), 27.3 (d, J ) 9.6 Hz, CH2), 26.5 (s, CH2).
No satisfactory microanalysis was obtained.
Os(p -cym en e)Cl2P P iP r 3 (17): Orange powder, yield 150
mg (71%). Mp: 142-146 °C. 1H NMR (CDCl3): p-cymene, δ
1.34 (d, J ) 7.5 Hz, 6H, CHMe2), 2.21 (s, 3H, Me), 2.83 (sept,
J ) 7.5 Hz, 1H, CHMe2), 5.87 (d, J ) 5.5 Hz, 2H, MeC6H4-
CHMe2), 5.78 (d, J ) 5.5 Hz, 2H, MeC6H4CHMe2); PR3, δ 1.34
(dd, J (P,H) ) 12.9 Hz, J (H,H) ) 6.9 Hz, 18H, CH3), 2.83 (m,
3H, P-CH). 13C{1H} NMR (CDCl3): p-cymene, δ 23.0 (s, C7),
17.9 (s, C1), 30.7 (s, C6), 97.5 and 87.2 (s, C2 and C5), 79.9 (d,
3.0 Hz, C3 or C4), 76.7 (d, 3.0 Hz, C3 or C4); PR3, δ 20.1 (s,
CH3), 25.3 (d, J ) 25.0 Hz, P-CH). Anal. Calcd for C19H35
Cl2OsP: C, 41.1; H, 6.31. Found: C, 41.4; H, 6.17.
-
Complexes 19-24 were similarly prepared by halogen
exchange of the corresponding dichloride complex of III using
NaI, for which a representative example is given for the
PMe2Ph-substituted complex 19.
Os(p -cym en e)I2P Me2P h (19). The dichloride 11 (50 mg,
0.09 mmol) and NaI (300 mg, 2.0 mmol) were stirred in MeOH
(10 mL) overnight at room temperature. The solution was
evaporated, redissolved in CH2Cl2 (10 mL), and filtered
(Celite), and the volume of solvent was reduced to 2-3 mL.
Pentane (15 mL) was added to precipitate a red powder, which
was filtered out and washed with cold ether (5 mL). Yield:
Os(p -cym en e)HClP Me3 (25). Complex 1 (90 mg, 0.19
mmol) and Et3N (0.5 mL, 0.5 mmol) were stirred at 80 °C in
ethanol (20 mL) for 5 h. The cooled solution was filtered
(Celite) and the volume of solvent reduced to 2-3 mL. The
product was purified by column chromatography using neutral
+
+

(η6-Arene)osmium(II) Complexes
Organometallics, Vol. 15, No. 14, 1996 3133
solvent resonance. MS: m/z 562 [M+] (192Os, 35Cl), C23H28
grade (IV) alumina and diethyl ether as eluant, giving a yellow
powder. Yield: 50 mg (60%). Mp: 121-123 °C. 1H NMR
(C6D6): p-cymene, δ 1.08 (d, J ) 6.7 Hz, 3H, CHMe2), 1.11 (d,
J ) 6.7 Hz, 3H, CHMe2), 2.02 (s, 3H, Me), 2.13 (sept, J ) 6.7
Hz, 1H, CHMe2), 5.23 (d, 1H, J ) 5.2 Hz, MeC6H4CHMe2),
4.98 (d, 1H, J ) 5.2 Hz, MeC6H4CHMe2), 4.46 (d, 1H, J ) 5.6
Hz, MeC6H4CHMe2), 4.25 (d, 1H, J ) 5.6 Hz, MeC6H4CHMe2);
PR3, δ 1.34 (d, J ) 10.0 Hz, 9H, P-Me); -8.63 (d, J ) 45.4
Hz, 1H, Os-H). 13C{1H} NMR (C6D6): p-cymene, δ 25.1 and
23.2 (s, C7), 19.6 (s, C1), 32.4 (s, C6), 96.4 and 93.5 (s, C2 and
C5), 78.8, 78.5, 78.6, 72.0 (s, C3 and C4); PR3, δ 20.8 (d, J )
-
ClOsP. ν(Os-H) (CH2Cl2): 2059 cm-1
.
Os(p -cym en eHClP iP r 3 (30). Complex 17 (100 mg, 0.18
mmol) and Et3N (0.5 mL, 0.5 mmol) were stirred at 80 °C in
ethanol (20 mL) for 10 min. The cooled solution was filtered
(Celite) and the volume of solvent reduced to 2-3 mL. The
product was purified by column chromatography using neutral
grade (IV) alumina and diethyl ether as eluant, giving a yellow
oil. Yield: 84 mg (90%). 1H NMR (C6D6): p-cymene, δ 1.99
(s, 3H, Me), 2.13 (sept, J ) 7.0 Hz, 1H, CHMe2), 5.61 (d, 1H,
J ) 5.8 Hz, MeC6H4CHMe2); 5.50 (d, 1H, J ) 5.3 Hz, MeC6H4-
CHMe2), 4.41 (d, 1H, J ) 5.8 Hz, MeC6H4CHMe2), 4.19 (d, 1H,
J ) 5.8 Hz, MeC6H4CHMe2), CHMe2 under PiPr3 resonance;
PR3, δ 1.04-1.23 (m, 24H, CHMe2 and P-CHMe2), 2.25 (m,
3H, P-CH); -8.61 (d, J ) 41.5 Hz, 1H, Os-H). 13C{1H} NMR
(C6D6): p-cymene, δ 21.6 and 22.1 (s, C7), 18.9 (s, C1), 30.2 (s,
C6), 95.8 and 91.0 (s, C2 and C5), 82.5, 81.0, 78.3 and 70.2 (s,
C3 and C4); PR3, δ 19.9 (d, J ) 12.4 Hz, Me), 27.0 (d, J ) 51.9
Hz, P-CH). MS: m/z 522 [ M+] (192Os, 35Cl), C19H36ClOsP.
37.6 Hz, P-Me). MS: m/z 437 [M+ - H] (192Os, 35Cl), C13H24
-
ClOsP. ν(Os-H) (CH2Cl2): 2056 cm-1
.
Os(p -cym en e)HClP Me2P h (26). Complex 11 (90 mg, 0.17
mmol) and Et3N (0.5 mL, 5.0 mmol) were stirred at 80 °C in
ethanol (20 mL) for 5 h. The cooled solution was filtered
(Celite) and the volume of solvent reduced to 2-3 mL. The
product was purified by column chromatography using neutral
grade (IV) alumina and diethyl ether as eluant, giving a yellow
oil. Yield: 52 mg (62%). 1H NMR (C6D6): p-cymene, δ 1.02
(d, J ) 6.8 Hz, 3H, CHMe2), 1.08 (d, J ) 6.8 Hz, 3H, CHMe2),
1.87 (s, 3H, Me), 2.00 (sept, J ) 6.8 Hz, 1H, CHMe2), 5.17 (d,
1H, J ) 5.6 Hz, MeC6H4CHMe2); 4.81 (d, 1H, J ) 5.3 Hz,
MeC6H4CHMe2), 4.42 (d, 1H, J ) 5.6 Hz, MeC6H4CHMe2), 4.19
(d, 1H, J ) 5.3 Hz, MeC6H4CHMe2); PR3, δ 1.84 (d, J ) 10.3
Hz, 3H, P-Me), 1.64 (d, J ) 10.0 Hz, 3H, P-Me); 7.05-7.50
(m, 5H, Ph); -8.59 (d, J ) 45.2 Hz, 1H, Os-H). 13C{1H} NMR
(C6D6): p-cymene, δ 24.9 and 23.1 (s, C7), 19.2 (s, C1), 31.9 (s,
C6), 98.3 and 93.5 (s, C2 and C5), 80.2, 79.8, 79.0, 72.5 (s, C3
and C4); PR3, δ 21.2 (d, J ) 41.8 Hz, P-Me), 17.6 (d, J ) 37.1
Hz, P-Me), 141.4 (d, J ) 46.9 Hz, ipso C6H5), 130.4 and 129.6
(s, Ph), remainder under solvent resonance. MS: m/z 500 [M+]
ν(Os-H) (CH2Cl2): 2084 cm-1
.
Os(p -cym en e)HClP Cy3 (31). Complex 18 (100 mg, 0.15
mmol) and Et3N (0.5 mL, 5.0 mmol) were stirred at room
temperature in ethanol (20 mL) for 10 min. The cooled
solution was filtered (Celite) and the volume of solvent reduced
to 2-3 mL. The product was purified by column chromatog-
raphy using neutral grade (IV) alumina and diethyl ether as
eluant, giving a yellow powder. Yield: 50 mg (53%). Mp:
153-159 °C. 1H NMR (C6D6): p-cymene, δ 1.16 (d, J ) 6.9
Hz, 3H, CHMe2), 1.25 (d, J ) 6.9 Hz, 3H, CHMe2), 2.02 (s, 3H,
Me), CHMe2 under PCy3 resonance, 5.68 (d, 1H, J ) 5.4 Hz,
MeC6H4CHMe2); 5.61 (d, 1H, J ) 5.0 Hz, MeC6H4CHMe2), 4.40
(d, 1H, J ) 5.4 Hz, MeC6H4CHMe2), 4.26 (d, 1H, J ) 5.0 Hz,
MeC6H4CHMe2); PR3, δ 2.21 (m, 3H, P-CH), 2.14 (m, 6H,
CH2); 1.95 (m, 4H, CH2); 1.76 (m, 6H, CH2); 1.54 (m, 12H, CH2);
-8.45 (d, J ) 41.8 Hz, 1H, Os-H). 13C{1H} NMR (C6D6):
p-cymene, δ 25.6 and 21.4 (s, C7), 18.9 (s, C1), 31.7 (s, C6),
96.0 and 89.4 (s, C2 and C5), 82.7, 79.1, 78.3, 70.1 (s, C3 and
C4); PR3, δ 37.0 (d, J ) 26.8 Hz, P-CH), 30.1, 28.2, and 27.4
(CH2). MS: m/z 641 [M+ - H] (192Os, 35Cl), C28H48ClOsP.
(
192Os, 35Cl), C18H26ClOsP. ν(Os-H) (CH2Cl2): 2022 cm-1
Os(p -cym en e)HClP n Bu 3 (27). Complex 14 (90 mg, 0.15
.
mmol) and Et3N (0.5 mL, 5.0 mmol) were stirred at 80 °C in
ethanol (20 mL) for 5 h. The cooled solution was filtered
(Celite) and the volume of solvent reduced to 2-3 mL. The
product was purified by column chromatography using neutral
grade (IV) alumina and diethyl ether as eluant, giving a yellow
oil. Yield: 55 mg (65%). 1H NMR (C6D6): p-cymene, δ 1.21
(d, J ) 7.3 Hz, 3H, CHMe2), 1.13 (d, J ) 6.7 Hz, 3H, CHMe2),
2.06 (s, 3H, Me), 2.14 (m, 1H, CHMe2), 5.45 (d, 1H, J ) 5.7
Hz, MeC6H4CHMe2); 5.22 (d , 1H, J ) 5.1 Hz, MeC6H4CHMe2),
4.52 (d, 1H, J ) 5.7 Hz, MeC6H4CHMe2), 4.17 (d, 1H, J ) 5.1
Hz, MeC6H4CHMe2); PR3, δ 0.9 (t, J ) 7.1 Hz, 9H, CH3), 1.73
(m, 6H, P-CH2); 1.32 (m, 12H, CH2); -8.61 (d, J ) 43.2 Hz,
1H, Os-H). 13C{1H} NMR (C6D6): p-cymene, δ 24.9 and 22.0
(s, C7), 19.1 (s, C1), 32.5 (s, C6), 94.8 and 93.0 (s, C2 and C5),
81.1 , 81.2, 78.6, 69.7 (s, C3 and C4); PR3, δ 14.5 (s, CH3), 28.4
(d, J ) 33.2 Hz, P-CH2), 26.7 and 25.1 (s, CH2). MS: m/z
564 [M+] (192Os, 35Cl), C22H42ClOsP. ν(Os-H) (CH2Cl2): 2060
ν(Os-H) (CH2Cl2): 2088 cm-1
.
Os(C6H6)Cl2P Me3 (32). [Os(C6H6)Cl2]2 (300 mg, 0.44 mmol)
was stirred at 60 °C with PMe3 (0.3 mL, 4 mmol) in toluene
for 2 h. Additional PMe3 (0.3 mL) was added and stirring
continued for a further 2 h. The cooled solution was filtered
(Celite) and washed with CD2Cl2 until the filtrate was clear.
The solution was evaporated and redissolved in CH2Cl2 (5 mL),
and pentane (20 mL) was added to obtain an orange precipi-
tate, which was filtered off and washed with cold ether (5 mL).
Yield: 210 mg (57%). Mp: decomposes at 220-230 °C. 1H
NMR (CDCl3): δ 1.67 (d, 9H, J ) 11.1 Hz, P-Me), 5.73 (s,
6H, C6H6). 13C{1H} NMR (CDCl3): δ 15.0 (d, J ) 38.3 Hz,
P-Me), 78.6 (d, J ) 2.8 Hz, C6H6). Anal. Calcd for C9H15Cl2-
OsP: C, 26.0; H, 3.61. Found: C, 26.0; H, 3.95. MS: m/z 416
[M+] (192Os, 35Cl).
cm-1
.
Os(p -cym en e)HClP P h 2Me (28). Complex 12 (90 mg, 0.15
mmol) and Et3N (0.5 mL, 5.0 mmol) were stirred at 80 °C in
ethanol (20 mL) for 5 h. The cooled solution was filtered
(Celite) and the volume of solvent reduced to 2-3 mL. The
product was purified by column chromatography using neutral
grade (IV) alumina and diethyl ether as eluant, giving a yellow
oil. Yield: 55 mg (65%). 1H NMR (C6D6): p-cymene, δ 0.96
(d, J ) 6.8 Hz, 3H, CHMe2), 1.05 (d, J ) 7.2 Hz, 3H, CHMe2),
1.87 (s, 3H, Me), 1.81 (m, 1H, CHMe2), 5.27 (d, 1H, J ) 5.6
Hz, MeC6H4CHMe2); 4.96 (d , 1H, J ) 5.2 Hz, MeC6H4CHMe2),
4.49 (d, 1H, J ) 5.6 Hz, MeC6H4CHMe2), 4.09 (d, 1H, J ) 5.2
Hz, MeC6H4CHMe2); PR3, δ 2.18 (d, J ) 9.8 Hz, 3H, P-Me)
6.90-7.71 (m, 10H, Ph); -8.40 (d, J ) 44.6 Hz, 1H, Os-H).
13C{1H} NMR (C6D6): p-cymene, δ 24.9 and 22.9 (s, C7), 18.7
(s, C1), 31.5 (s, C6), 98.4 and 94.5 (s, C2 and C5), 81.4 (s, C3
or C4), 81.1 (d, J ) 5.3 Hz, C3 or C4), 79.2 (s, J ) 6.0 Hz, C3
or C4), 72.5 (s, C3 or C4); PR3, δ 20.3 (d, J ) 41.5 Hz, P-Me),
140.7 (d, J ) 53.6 Hz, ipso C6H5), 137.9 (d, J ) 47.2 Hz, ipso
C6H5), 133.1, 132.5, 130.1 and 129.6 (s, C6H5), remainder under
49
[Os(C6H5Me)Cl2]2. 2-Methylcyclohexa-1,4-diene (1.0 g,
100 mmol) and OsCl3 (500 mg, 17 mmol) were stirred in
ethanol (15 mL) for 3 days at 80 °C. The cooled solution was
filtered (Celite) and washed with hot CDCl3, and the volume
was reduced to 2-3 mL. Pentane (20 mL) was added to
precipitate a yellow powder, which was filtered off and washed
with cold ether (5 mL). Yield: 520 mg (87%). Mp: slowly
decomposes above 170 °C. 1H NMR (CDCl3): δ 2.24 (s, 6H,
Me), 6.05 (d, J ) 5.0 Hz, 4H, CH), 6.21 (t, 2H, J ) 4.8 Hz,
CH), 6.28 (m, 4H, CH). 13C DEPT NMR (CDCl3): δ 19.7 (s,
Me), 78.8, 72.2 and 70.8 (s, CH) (quaternary C not visible).
Anal. Calcd for C14H16Cl4Os2: C, 23.8; H, 2.27. Found: C,
24.8; H, 2.93. MS: m/z 354 [M+/2] (192Os, 35Cl).
(49) Krapcho, A. P.; Bothner-By, A. A. J . Am. Chem. Soc. 1959, 81,
3658.
(50) J ohnson, C. K. ORTEPII; Report ORNL-5138; Oak Ridge
National Laboratory: Oak Ridge, TN, 1976.
+
+

3134 Organometallics, Vol. 15, No. 14, 1996
Bell et al.
Os(C6H5Me)Cl2P Me3 (33). [Os(C6H5Me)Cl2]2 (150 mg, 0.2
mmol) and P(Me)3 (0.2 mL, 2.6 mmol) were stirred in CH2Cl2
(15 mL) for 1 h at 40 °C. The cooled solution was filtered
(Celite) and the volume reduced to 2-3 mL. Pentane (15 mL)
was added to precipitate a yellow powder, which was filtered
off and washed with of cold ether (5 mL). Yield: 133 mg (73%).
Mp: 209-215 °C. 1H NMR (CDCl3): δ 2.28 (s, Me), 5.67 (m,
2H, CH), 5.47 (m, 2H, CH), 5.42 (t, 1H, CH), 1.68 (d, J ) 10.5
Hz, 9H, PMe3). 13C{1H} NMR (CDCl3): δ 18.5 (s, 3H, Me),
15.4 (d, J ) 38.2 Hz, PMe3), 99.9 (s, quaternary), 78.7, 77.9,
and 69.6 (s, CH). Anal. Calcd for C10H17Cl2OsP: C, 28.0; H,
3.96. Found: C, 28.3; H, 3.57.
[Os(C6H5Et)Cl2]2. 2-Ethylcyclohexa-1,4-diene49 (1.0 g, 100
mmol) and OsCl3 (500 mg, 17 mmol) were stirred in ethanol
(15 mL) for 3 days at 80 °C. The cooled solvent was filtered
(Celite) and washed with hot CDCl3, and the volume of solvent
was reduced to 2-3 mL. Pentane (20 mL) was added to
precipitate a yellow powder which was filtered off and washed
with cold ether (5 mL). Yield: 560 mg (90%). Mp: decomposes
200-225 °C. 1H NMR (CDCl3): δ 1.29 (t, J ) 7.4 Hz, 6H, CH3),
2.55 (q, J ) 7.4 Hz, 4H, CH2), 6.08 (d, J ) 4.4 Hz, 4H, CH),
6.20 (t, J ) 3.9 Hz), 2H, CH), 6.28 (m, 4H, CH). 13C{1H} NMR
(CDCl3): δ 14.0 (s, CH3), 27.0 (s, CH2), 94.2 (s, quaternary),
76.5, 71.7, and 71.4 (s, CH). Anal. Calcd for C16H20Cl4Os2:
C, 26.2; H, 2.72. Found: C, 26.4; H, 3.13. MS: m/z 368 [M+/
2] (192Os, 35Cl).
with cold ether (5 mL). Yield: 600 mg (90%). Mp: slowly
decomposes above 180 °C. 1H NMR (CDCl3): δ 1.40 (s, 18H,
CMe3), 6.57 (d, J ) 5.3 Hz, 4H, CH), 5.57 (m, 6H, CH). 13C{1H}
NMR (CDCl3): δ 30.6 (s, CMe3), 35.3 (s, CMe3), 95.3 (s,
quaternary), 77.6, 74.4, and 70.9 (s, CH). Anal. Calcd for
C
20H28Cl4Os2: C, 30.4; H, 3.54. Found: C, 30.5; H, 4.09. MS:
m/z 396 [M+/2] (192Os, 35Cl).
t
Os(C6H5tBu )Cl2P Me3 (36). [Os(C6H5 Bu)Cl2]2 (200 mg,
0.27 mmol) and P(Me)3 (0.2 mL, 2.6 mmol) were stirred in
CH2Cl2 (15 mL) for 1 h at 40 °C. The cooled solution was
filtered (Celite) and the volume reduced to 2-3 mL. Pentane
(15 mL) was added to precipitate a yellow powder, which was
filtered out and washed with cold ether (5 mL). Yield: 210
mg (83%). Mp: decomposes at 180-200 °C. 1H NMR
(CDCl3): δ 1.45 (s, 9H, CMe3), 5.95 (d, J ) 5.8 Hz, 2H, CH),
5.65 (m, 2H, CH), 5.46 (t, J ) 5.2 Hz, 1H, CH), 1.63 (d, J )
10.6 Hz, 9H, P-Me). 13C{1H} NMR (CDCl3): δ 30.8 (s, CMe3),
35.2 (s, CMe3), 108.4 (d, J ) 38.4 Hz, quaternary), 80.6 (d, J
) 4.5 Hz, CH), 71.9 and 71.8 (s, CH). Anal. Calcd for
C12H23Cl2OsP: C, 33.1; H, 4.88. Found: C, 33.0; H, 4.68.
Os(C6Me6)Cl2P Me3 (37). [Os(C6Me6)Cl2]2 (200 mg, 0.24
mmol) and P(Me)3 (0.2 mL, 2.6 mmol) were stirred in CH2Cl2
(15 mL) for 1 h at 40 °C. The cooled solution was filtered
(Celite) and the volume reduced to 2-3 mL. Pentane (15 mL)
was added to precipitate a yellow powder, which was filtered
out and washed with cold ether (5 mL). Yield: 132 mg (62%).
Mp: decomposes at 209-219 °C. 1H NMR (CDCl3): δ 2.08 (s,
18H, Me), 1.53 (d, J ) 10.3 Hz, 9H, P-Me). 13C{1H} NMR
(CDCl3): δ 16.0 (s, CMe), 87.3 (d, J ) 3.7 Hz, CMe), 14.7 (d, J
) 37.0, P-Me). Anal. Calcd for C15H27Cl2OsP: C, 36.1; H,
5.41. Found: C, 35.6; H, 4.82. MS: m/z 500 [M+] (192Os, 35Cl).
Os(C6H5Et)Cl2P Me3 (34). [Os(C6H5Et)Cl2]2 (200 mg, 0.27
mmol) and P(Me)3 (0.2 mL, 2.6 mmol) were stirred in CH2Cl2
(15 mL) for 1 h at 40 °C. The cooled solution was filtered
(Celite) and the volume reduced to 2-3 mL. Pentane (15 mL)
was added to precipitate a yellow powder, which was filtered
out and washed with cold ether (5 mL). Yield: 205 mg (84%).
Mp: 176-179 °C. 1H NMR (CDCl3): δ 1.31 (t, J ) 7.4 Hz,
3H, CH3), 2.57 (q, J ) 7.4 Hz, 2H, CH2), 5.67 (m, 2H, CH),
5.52 (m, 2H, CH), 5.31 (t, J ) 5.3 Hz, 1H, CH), 1.66 (d, J )
10.7 Hz, 9H, PMe3). 13C{1H} NMR (CDCl3): δ 13.9 (s, CH3),
25.7 (s, CH2), 15.4 (d, J ) 38.4 Hz, PMe3), 103.6 (s, quaternary),
78.5, 77.5, and 70.3 (s, CH). Anal. Calcd for C11H19Cl2OsP:
C, 29.8; H, 4.29. Found: C, 29.8; H, 3.99.
X-r a y Str u ctu r e Deter m in a tion s. The structures of 1,
6, 13, and 15 were determined at 173 K. All measurements
were made on a Rigaku AFC5R diffractometer using graphite-
monochromated Mo KR radiation (λ ) 0.710 69 Å) and a 12
kW rotating anode generator. For each compound, the inten-
sities of three standard reflections were measured after every
150 reflections and remained stable throughout the data
collection. The intensities were corrected for Lorentz and
polarization effects. Semi-empirical absorption corrections,
based on ψ-scans of several reflections, were applied to 1 and
13.51 An analytical absorption correction was used for 6,52 and
an empirical absorption correction using the program DI-
FABS53 was used for 15 because other absorption correction
methods produced unsatisfactory results. Equivalent reflec-
tions were merged. Data collection and refinement parameters
are given in Table 6.
i
[Os(C6H5 P r )Cl2]2. 2-Isopropylcyclohexa-1,4-diene49 (1.2 g,
100 mmol) and OsCl3 (500 mg, 17 mmol) were stirred in
ethanol (15 mL) for 3 days at 80 °C. The cooled solvent was
filtered (Celite) and washed with hot CDCl3, and the volume
of solvent was reduced to 2-3 mL. Pentane (20 mL) was
added to precipitate a yellow powder which was filtered off
and washed with cold ether (5 mL). Yield: 460 mg (72%).
Mp: slowly decomposes above 170 °C. 1H NMR (CDCl3): δ
1.31 (s, J ) 6.2, 12H, CHMe2), 2.82 (sept, J ) 6.2, 2H, CHMe2),
6.19 (m, 6H, CH), 5.46 (m, 4H, CH). 13C{1H} NMR (CDCl3):
δ 22.2 (s, CH3), 31.5 (s, CH), 69.3 (s, quaternary), 75.0, 73.0,
and 71.8 (s, CH). Anal. Calcd for C18H24Cl4Os2: C, 28.4; H,
3.15. Found: C, 28.8; H, 2.85. MS: m/z 382 [M+/2] (192Os,
35Cl).
The structures were solved by Patterson methods using
SHELXS8654 and DIRDIF92,55 which revealed the positions
of the heavy atoms. All remaining non-hydrogen atoms were
located in Fourier expansions of the Patterson solutions. The
non-hydrogen atoms were refined anisotropically. The H
atoms were fixed in geometrically calculated positions [d(C-
H) ) 0.95 Å], and they were assigned fixed isotropic temper-
ature factors with a value of 1.2Ueq of the parent C atom. The
orientations of the methyl group H atoms were based on peaks
located in difference electron density maps. Refinement of
each structure was carried out on F using full-matrix least-
squares procedures, which minimized the function ∑w(|Fo| -
|Fc|)2. The weighting scheme was based on counting statistics
and included a factor to downweight the intense reflections.
Plots of ∑w(|Fo| - |Fc|)2 versus |Fo|, reflection order in data
i
i
Os(C6H5 P r )Cl2P Me3 (35). [Os(C6H5 Pr)Cl2]2 (200 mg, 0.26
mmol) and PMe3 (0.2 mL, 2.6 mmol) were stirred in CH2Cl2
(15 mL) for 1 h at 40 °C. The cooled solution was filtered
(Celite) and the volume reduced to 2-3 mL. Pentane (15 mL)
was added to precipitate a yellow powder, which was filtered
out and washed with cold ether (5 mL). Yield: 220 mg (92%).
Mp: decomposes 180-195 °C. 1H NMR (CDCl3): δ 1.32 (s, J
) 6.8, 6H, CHMe2), 2.90 (sept, J ) 6.8, 1H CHMe2), 5.59 (m,
4H, CH), 5.46 (t, J ) 5.3 Hz, 1H, CH), 1.66 (d, J ) 10.6 Hz,
9H, PMe3). 13C{1H} NMR (CDCl3): δ 22.0 (s, CH3), 30.6 (s,
CH), 15.2 (d, J ) 38.0 Hz, PMe3), 107.7 (s, quaternary), 77.3,
77.0, and 70.3 (s, CH). Anal. Calcd for C12H21Cl2OsP: C, 31.5;
H, 4.60. Found: C, 31.4; H, 4.31.
(51) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351.
(52) De Meulenaer, J .; Tompa, H. Acta Crystallogr. 1965, 19, 1014.
(53) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.
(54) Sheldrick, G. M. SHELXS-86. Acta Crystallogr. 1990, A46, 467.
(55) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garc´ıa-Granda, S.; Smits, J . M. M.; Smykalla, C. DIRDIF-92. The
DIRDIF program system; Technical Report of the Crystallography
Laboratory; University of Nijmegen: Nijmegen, The Netherlands,
1992.
[Os(C6H5tBu )Cl2]2. 2-tert-Butylcyclohexa-1,4-diene49 (1.3
g, 100 mmol) and OsCl3 (500 mg, 17 mmol) were stirred in
ethanol (15 mL) for 3 days at 80 °C. The cooled solvent was
filtered (Celite) and washed with hot CDCl3, and the volume
was reduced to 2-3 mL. Pentane (20 mL) was added to
precipitate a yellow powder, which was filtered off and washed
+
+

(η6-Arene)osmium(II) Complexes
Organometallics, Vol. 15, No. 14, 1996 3135
Ta ble 6. Cr ysta llogr a p h ic Da ta for 1, 6, 13, a n d 15
1
6
13
15
crystallized from
empirical formula
fw
methanol
C13H23Cl2OsP
471.40
hexane/ethyl acetate
C13H23Cl2O3OsP
519.40
ethanol
C31H35Cl2OsP
699.70
CH2Cl2
C28H29Cl2OsP.CH2Cl2
742.55
cryst color, habit
cryst dimens, mm
temp, K
orange, thin prism
0.08 × 0.25 × 0.43
173(1)
orange, needle
0.10 × 0.21 × 0.39
173(1)
orange, prism
0.15 × 0.25 × 0.30
173(1)
orange, irregular prism
0.38 × 0.38 × 0.43
173(1)
cryst system
space group
Z
monoclinic
P21/n
8
monoclinic
P21/c
4
triclinic
P1h
2
triclinic
P1h
2
reflcns for cell determ
25
25
25
25
2θ range for cell determ, deg
39-40
39-40
39-40
39-40
a, Å
10.269(6)
27.168(7)
13.002(4)
90
13.329(2)
7.286(2)
17.480(2)
90
10.381(1)
14.610(1)
9.277(1)
96.860(9)
97.01(1)
88.631(8)
1386.4(3)
692
12.625(2)
13.509(2)
9.361(2)
109.38(1)
102.27(2)
99.67(1)
1421.4(5)
728
b, Å
c , Å
R, deg
â, deg
112.37(3)
90
3354(2)
1808
1.867
7.991
91.48(1)
90
1697.1(5)
1000
2.033
7.921
ω /2θ
60
0.096, 0.378
5515 (+h,+k,(l)
4949
γ, deg
V, Å3
F(000)
Dx, g cm-3
1.676
4.865
ω /2θ
60
0.479, 1.000
8494 (+h,(k,(l)
8088
1.735
4.932
ω /2θ
60
0.818, 1.098
8592 (+h,(k,(l))
8249
µ(Mo KR), mm-1
scan type
ω
55
2θ(max), deg
min and max transm factors
tot. reflcns measd
sym indepdt reflcns
Rmerge
0.449, 1.000
8276 (+h,+k,(l)
7679
0.020
0.054
0.017
0.021
reflcns used [I > 2σ(I)]
params refined
R
6097
307
0.0296
3665
181
0.0335
7341
316
0.0233
7327
316
0.0285
Rw
0.0260
0.005
1.364
0.0007
0.0288
0.005
1.330
0.0008
0.0228
0.005
1.367
0.002
0.0325
0.01
1.549
0.001
weights: p in w ) [σ2(Fo) + (pFo)2]-1
goodness of fit
final ∆max/σ
max and min ∆F, e Å-3
1.48, -0.89
1.26, -1.03
1.72, -1.13
1.29, -1.25
collection, (sin θ)/λ, and various classes of indices showed no
unusual trends. Corrections for secondary extinction were not
applied.
Neutral atom scattering factors for non-hydrogen atoms
were taken from Maslen, Fox, and O’Keefe,56a and the scat-
tering factors for H atoms were taken from Stewart, Davidson,
and Simpson.57 Anomalous dispersion effects were included
in Fc;58 the values for f ′ and f ′′ were those of Creagh and
McAuley.56b All calculations were performed using the TEX-
SAN crystallographic software package.59
bond) or are slightly disordered. However, no attempt was
made to resolve any potential disorder. As a result, the C(7)-
C(8) and C(7)-C(9) bond lengths appear to be shorter than
they probably are. The crystals of 15 contain molecules of
CH2Cl2 in a ratio of 1:1 with the osmium complex. The
residual electron density of between 1.2 and 1.7 e Å-3 in each
structure was located near the Os atoms and near the Cl atoms
of the solvent molecule in 15. The latter peaks might be due
to slight disorder of the solvent molecule.
Ack n ow led gm en t . We thank the Swiss National
Science Foundation and Dr. Helmut Legerlotz-Stiftung
for financial support and Dr. A. Hafner (Ciba-Geigy,
Marly, Switzerland) for providing stimulating discus-
sions.
The structure of 1 has two molecules in the asymmetric unit;
however, there are no major differences in their conformation
other than a small rotation of the PMe3 group. Some of the
terminal methyl groups, especially in molecule A, are under-
going strong thermal motion (rotation about the C(1)-C(7)
Su p p or tin g In for m a tion Ava ila ble: Listings of frac-
tional atomic coordinates and equivalent isotropic temperature
factors, interatomic distances, bond angles, torsion angles,
anisotropic temperature factors, and hydrogen atom coordi-
nates for compounds 1, 6, 13, and 15 (24 pages). Ordering
information is given on any current masthead page.
(56) International Tables for Crystallography; Wilson, A. J . C., Ed.;
Kluwer Academic Publishers: Dordrecht, The Netherlands, 1992; Vol.
C: (a) Maslen, E. N.; Fox, A. G.; O’Keefe, M. A. Table 6.1.1.1, pp 477-
486; (b) Creagh, D. C.; McAuley, W. J . Table 4.2.6.8, pp 219-222.
(57) Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J . Chem. Phys.
1965, 42, 3175.
(58) Ibers, J . A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(59) TEXSAN. Single Crystal Structure Analysis Software, Version
5.0; Molecular Structure Corp.: The Woodlands, TX, 1989.
OM960053I
+
+