N- versus S-Metalation of Nitridobis(3,4-toluenedithiolato)osmium(VI)

Full text of DOI:10.1021/ic980136m

6382
Inorg. Chem. 1998, 37, 6382-6384
Notes
complexes.6 As our continuous effort to explore the reactivity
N- versus S-Metalation of
of nitridometal complexes, we herein describe the reaction of
nitridobis(3,4-toluenedithiolato)osmium(VI) with organometallic
electrophiles and the isolation of the corresponding bimetallic
complexes.
Nitridobis(3,4-toluenedithiolato)osmium(VI)
Wa-Hung Leung,*,† Joyce L. C. Chim,† and
Wing-Tak Wong‡,§
Experimental Section
Departments of Chemistry, The Hong Kong
University of Science and Technology, Clear Water Bay,
Kowloon, Hong Kong, and The University of Hong Kong,
Pokfulam Road, Hong Kong
Solvents were purified and distilled prior to use. NMR spectra were
recorded on a Bruker ALX 300 spectrometer operating at 300 and 121.5
MHz for 1H and 31P, respectively. Chemical shifts (δ, ppm) were
reported with reference to SiMe4 (1H) and H3PO4 (31P). Infrared spectra
(Nujol) were recorded on a Perkin-Elmer 16 PC FT-IR spectropho-
tometer. Mass spectra were obtained on a Finnigan TSQ-7000
spectrometer. Cyclic voltammetry was performed with a Princeton
Applied Research (PAR) model 273A potentiostat. The working and
reference electrodes are glassy carbon and Ag/AgNO3 (0.1 M in
acetonitrile), respectively. Potentials were reported with reference to
Cp2Fe+/0. Elemental analyses were performed by Medac Ltd, Surrey,
U.K.
ReceiVed February 5, 1998
Introduction
Nitridometal complexes have attracted attention because these
complexes are believed to be involved in biological nitrogen
fixation process1,2 and have been employed as reagents for
nitrogen atom transfer.3 One important reaction for nitridometal
complexes is electrophilic attack on the nitride ligand resulting
in the formation of nitrogen bridges between the metal ion with
a metal or nonmetal ion. Of particular interest is the electropilic
attack on nitridometal complexes with thiolate ligands, which
contain two potential nucleophilic sites. Shapley and co-workers
reported that alkylation of [n-Bu4N][OsN(CH2SiMe3)2(SCH2-
CH2S)] occurs at the more basic sulfur site.4 More recently,
Sellmann and co-workers reported that the position of alkylation
for [n-Bu4N][OsN(C6H4S2)2] is dependent on the entering
electrophiles. While methyl triflate alkylates the sulfur atom
of the benzendithiolate ligand, trityl cation preferentially attacks
on the less hindered nitride ligand.5 It would be of interest to
see if this kind of N- versus S-selectivity for nitridoosmium
thiolates will also hold for other types of electrophiles such as
organometallic fragments. Recently we found that cationic
organometallic fragments including [Au(PPh3)]+ and [Ir(CO)-
(PPh3)2]+ react with [OsO3N]- to give nitrido-bridged bimetallic
Materials. H2L (L ) 3,4-toluenedithiol) was purchased from Strem
Ltd. and used as received. [Bu4N][OsNCl4],7 Au(PPh3)Cl,8 and trans-
9
Ir(CO)Cl(PPh3)2 were prepared according to the literature methods.
Preparations. [n-Bu4N][OsNL2] (1). This was prepared by a
modification of the literature method. To a solution of [n-Bu4N]-
[OsNCl4] (0.07 g, 0.12 mmol) in MeOH (20 mL) was added H2L (0.05
g, 0.32 mL) and Et3N (0.05 mL). The solution was stirred at room
temperature in air for 1 h, during which a yellow solid precipitated.
The solid was collected and washed with ether and the filtrate
evaporated to dryness and recrystallization from CH2Cl2/Et2O to give
a yellow solid. Recrystallization from CH2Cl2/Et2O afforded yellow
crystals (yield 80%). 1H NMR (CDCl3): δ 0.79 (s, 12 H, CH3 of n-Bu),
2.27 (m, 16H, CH2 of n-Bu), 2.27 (s, 6H, CH3 of L), 2.60 (t, 8H, NCH2),
6.64-7.45 (m, 6 H, phenyl protons). 31P{1H} (CDCl3): δ 36.22. IR
(cm-1): 1112 ν(OstN). MS(CI), m/z: 514 (M - n-Bu4N)+. Anal.
Calcd for OsC30H48N2S4: C, 47.7; H, 6.4; N, 3.7. Found: C, 47.4; H,
6.3; N, 3.6.
OsNL[SC7H6S(AuPPh3)] (2). To a solution of 1 (0.1 g, 0.13 mmol)
in CH2Cl2 (10 mL) was added 1 equiv of Au(PPh3)(OTf), which was
prepared from Au(PPh3)Cl (0.066 g, 0.13 mmol) and AgOTf (0.034 g,
0.13 mmol) in THF (10 mL), and the mixture was stirred overnight
and filtered. Evaporation of the filtrate to dryness and recrystallization
from CH2Cl2/hexane afforded orange crystals (yield 25%). 1H NMR
(CDCl3): δ 2.35 (s, 6H, CH3), 6.81-7.61 (m, 21 H, phenyl protons).
31P{1H} NMR (CDCl3): δ 36.23 (s). IR (cm-1): 1102 ν(OstN).
MS(CI), m/z: 1256 (M)+. Anal. Calcd for OsC30H48N2S4: C, 39.6;
H, 2.8; N, 1.4. Found: C, 39.6; H, 3.0; N, 1.4.
L2OsNIr(CO)(PPh3)2 (3). To a solution of 1 (0.08 g, 0.1 mmol) in
CH2Cl2 (10 mL) was added 1 equiv of Ir(CO)(PPh3)2(OTf), prepared
from trans-Ir(CO)Cl(PPh3)2 (0.03 g, 0.1 mmol) with AgOTf (0.03 g,
0.1 mmol) in CH2Cl2 (10 mL). The mixture was stirred at room-
temperature overnight, during which the color changed from yellow to
green, and filtered. Evaporation of the solvent and recrystallization
from CH2Cl2/hexane afforded green crystals (yield 75%). 1H NMR
(CDCl3): δ 2.21 (s, 3H, CH3), 2.31 (s, 3H, CH3), 6.64-7.45 (m, 36H,
phenyl protons). 31P{1H} NMR (CDCl3): δ 20.82 (s). IR (cm-1): 1984
ν(CtO), 1100 ν(OstN). Anal. Calcd for OsC30H48N2S4: C, 47.7;
H, 6.4; N, 3.7. Found: C, 47.4; H, 6.3; N, 3.6.
* To whom correspondence should be addressed.
† The Hong Kong University of Science and Technology.
‡ The University of Hong Kong.
§ To whom crystallographic inquires should be addressed.
(1) Dehnicke, K.; Stra¨hle, J. Angew. Chem., Int. Ed. Engl. 1992, 31, 955.
(2) (a) Chatt, J.; Dilworth, J. R.; Richards, R. L. Chem. ReV. 1978, 78,
589. (b) Che, C. M.; Lam, H.-W.; Tong, W.-F.; Lai, T. F.; Lau, T. C.
J. Chem. Soc., Chem. Commun. 1989, 1883. (c) Ware, D. C.; Taube,
H. Inorg. Chem. 1991, 30, 4605. (d) Coia, G. M.; White, P. S.; Meyer,
T. J.; Wink, D. A.; Keefer, L. K.; Davis, W. M. J. Am. Chem. Soc.
1994, 116, 3649. (e) Laplaza, C. E.; Cummins, C. C. Science 1995,
268, 861. (f) Ishitani, O.; White, P.; Meyer, T. J. Inorg. Chem. 1996,
35, 2167.
(3) (a) Groves, J. T.; Takahashi, T. J. Am. Chem. Soc. 1983, 105, 2073.
(b) Groves, J. T.; Takahashi, T. Butler, W. Inorg. Chem. 1983, 22,
884. (c) Mahy, J.-P.; Bedi, G.; Battioni, P.; Mansuy, D. J. Chem. Soc.,
Perkin Trans. 2 1988, 1517. (d) Evans, D A.; Faul, M.; Bilodeau, M.
T. J. Am. Chem. Soc. 1994, 116, 2742 and references therein. (e) Du
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1997, 30, 364 and references therein.
(4) Zhang, N.; Wilson, S. R. Shapley, P. A. Organometallics 1988, 7,
1126.
(5) Sellmann, D.; Wemple, M. W.; Donaubauer, W.; Heinemann, F. W.
Inorg. Chem. 1997, 36, 1397.
(6) (a) Leung, W.-H.; Chim, J. L. C.; Wong, W.-T. J. Chem. Soc., Dalton
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Chem. Soc., Dalton Trans. 1997, 3277.
(7) Griffith, W. P.; Pawson, D. J. Chem. Soc., Dalton Trans. 1973, 1315.
(8) Braunstein, P. B.; Lehner, H.; Matt, D.; Burgess, K.; Ohlmeyer, M. J.
Inorg. Synth. 1990, 27, 218.
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10.1021/ic980136m CCC: $15.00 © 1998 American Chemical Society
Published on Web 10/31/1998

Notes
Inorganic Chemistry, Vol. 37, No. 24, 1998 6383
Table 1. Crystal Data and Experimental Details for
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
OsN(L)[SC7H6S(AuPPh3)] (2) and L2OsNIr(CO)(PPh3)2 (3)
L2OsNIr(CO)(PPh3)2
2
3
Ir(1)-P(1)
Ir(1)-N(1)
Os(1)-S(1)
Os(1)-S(3)
Os(1)-N(1)
2.318(2)
2.002(5)
2.310(2)
2.294(2)
1.676(5)
Ir(1)-P(2)
Ir(1)-C(1)
Os(1)-S(2)
Os(1)-S(4)
2.322(2)
1.814(9)
2.300(2)
2.301(2)
formula
fw
cryst syst
space group
a, Å
b, Å
c, Å
AuOsC32H27NPS4
971.95
IrOsC51H42NOPS4
1257.51
monoclinic
P21/c (No. 14)
16.811(1)
13.911(1)
21.341(1)
108.850(2)
4723.1(4)
4
monoclinic
P21/n (No. 14)
15.128(4)
11.961(5)
11.196(4)
90.40(3)
3211(1)
P(1)-Ir(1)-P(2)
P(1)-Ir(1)-C(1)
P(2)-Ir(1)-C(1)
S(1)-Os(1)-S(2)
S(1)-Os(1)-S(4)
S(2)-Os(1)-S(3)
S(2)-O(1)-N(1)
S(3)-Os(1)-N(1)
Ir(1)-N(1)-Os(1)
177.05(6)
91.5(2)
91.3(2)
85.61(7)
147.43(8)
142.75(7)
109.5(2)
107.8(2)
176.1(3)
P(1)-Ir(1)-N(1)
P(2)-Ir(1)-N(1)
N(1)-Ir(1)-C(1)
S(1)-Os(1)-S(3)
S(1)-Os(1)-N(1)
S(2)-Os(1)-S(4)
S(3)-Os(1)-S(4)
S(4)-Os(1)-N(1)
Ir(1)-C(1)-O(1)
887.9(2)
89.3(2)
179.2(2)
84.42(7)
106.5(2)
83.59(7)
85.84(8)
106.1(2)
179.2(7)
â, deg
V, Å3
Z
4
F
calcd (g cm-3
)
2.010
1.768
color, habit
λ, Å
brown, prism
0.710 73
25
yellow, rod
0.710 73
25
T, °C
µ, cm-1
88.63
57.92
8434
4638
total no. of reflcns 4551
no. of obsd reflcns 2197
(I > 3.00σ(I))
weighting scheme 1/[σ2(F) + 0.002F2/4] 1/[σ2(F) + 0.025F2/4]
Ra
Rw
0.040
0.034
1.82
0.027
0.027
1.11
b
goodness of fitc
2
a R ) ∑|Fo| - |Fc|/|Fo|. b Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| )]1/2
.
c [∑w(|Fc| - |Fo|)2/(Nobs - Nparam)]1/2
.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
OsN(L)[SC7H7S(AuPPh3)]
Au(1)-S(2)
Os(1)-S(1)
Os(1)-S(3)
Os(1)-N(1)
2.379(5)
2.324(6)
2.297(6)
1.65(2)
Au(1)-P(1)
Os(1)-S(2)
Os(1)-S(4)
2.266(5)
2.366(5)
2.315(5)
Figure 1. Perspective view of OsN(L)[SC7H6S(Au(PPh3)], 2.
S(2)-Au(1)-P(1)
S(1)-Os(1)-S(3)
S(1)-Os(1)-N(1)
S(2)-Os(1)-S(4)
S(3)-Os(1)-S(4)
S(4)-Os(1)-N(1)
171.8(2)
83.8(2)
106.5(6)
84.6(2)
86.7(2)
105.9(6)
S(1)-Os(1)-S(2)
S(1)-Os(1)-S(4)
S(2)-Os(1)-S(3)
S(2)-Os(1)-N(1)
S(3)-Os(1)-N(1)
86.0(2)
147.6(2)
145.8(2)
108.4(6)
108.4(6)
X-ray Crystallography. A summary of crystal and data processing
parameters for 2 and 3 is given in Table 1. Single crystals of 2 and 3
were grown from CH2Cl2/hexane at room temperature. Data for 2 and
3 were collected on a Rigaku AFC7R and an MAR-Research Image
Plate diffractometer, respectively. Intensity data were corrected for
Lorentz and polarization effects. The space groups of all crystals were
determined from a Laue symmetry check and their systematic absences
were confirmed by successful refinement of the structures. For 2,
although the â angle is close to 90°, the Laue symmetry is 2/m instead
of mmm. Therefore a monoclinic system is used. There were some
positional disorder problems associated with the 3,4-toluenedithiolate
(L) ligands in 2 and 3. In 2, the L exhibits a 2-fold disorder and was
modeled by two sites each with occupancy factors 0.6 and 0.4 while a
similar problem in 3 was modeled by two sites with occupancy factors
0.7 and 0.3. Both structures were solved by Direct methods (SHELXS
8610 and SIR 8811 for 2 and 3, respectively) and refined by a full-
matrix least-squares analysis. Some non-hydrogen atoms were refined
anistropically, while the rest were refined isotropically. Hydrogen
atoms were included and fixed in their idealized positions (C-H )
0.95 Å). Selected bond lengths and angles for 2 and 3 are given in
Tables 2 and 3, respectively.
Figure 2. Perspective view of L2OsNIr(CO)(PPh3)2, 3.
according to Sellmann’s method, isolated as an air-stable yellow
solid. Treatment of 1 with Au(PPh3)(OTf) afforded the AuI-
OsVI complex OsN(L)[SC7H6S(AuPPh3)], 2, which has been
characterized by X-ray crystallography. Figure 1 shows a
diagram of the molecule; selected bond lengths and angles are
given in Table 2. As would be anticipated, the Au(PPh3)
fragment binds to one sulfur atom of L with the S-Au-P angle
of 171.8(2)°. Unexpectedly, only one signal for the methyl
Results and Discussion
The nitridoosmium(VI) complex [n-Bu4N][OsNL2] 1 was
prepared from [n-Bu4N][OsNCl4] and H2L (3,4-toluenedithiol)
(10) SHELX86: Sheldrick, G. M. In Crystallographic Computing 3;
Sheldrick, G. M., Kruger, C., Goddard, R., Eds.; Oxford University
Press: 1985; p 175.
(11) SIR88: Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, D.;
Polidori, G.; Spagna, R.; Viterbo, D. J. App. Crystallogr. 1989, 22,
389.
1
protons of L was observed in the H NMR spectrum possibly
because the two methyl signals are very close and accidentally
coincide with each other. Although there is no significant
difference in Os-N bond length between 2 (1.65(2) Å) and

6384 Inorganic Chemistry, Vol. 37, No. 24, 1998
Notes
[n-Bu4N][OsN(C6H4S2)2] (1.64(1) Å),5 the ν(ÃstΝ) decreases
slightly to 1112 cm-1 (cf. 1102 cm-1 for 1) on binding to
AuPPh3. The formation of Au-S(2) bond also results in
lengthening of the Os-S(2) (2.366(5) Å) and shortening of the
Os-S(3) (2.297(6) Å).
reduction at -1.72 V vs ferrocene-ferrocenium. The oxidation
wave is assigned to the osmium-centered oxidation while the
reduction wave is attributed to the Ir(I/0) reduction. For
comparison, under the same conditions, 1 exhibits a reversible
Os(VII/VI) couple at 0.39 V. The Ir(I/0) potential reduction
as well as ν(CtO) (1984 cm-1) for 3 are similar to those for
Ir(CO)(PPh3)2(NOsO3) (-1.67 V and 1986 cm-1, respectively),6b
suggesting that the donor strength of [OsVINL2]- is comparable
to that for [OsVIIIO3N]-.
On the other hand, treatment of 1 with Ir(CO)(PPh3)2(OTf)
afforded the nitrido-bridged bimetallic complex L2OsNIr(CO)-
(PPh3)2, 3. Figure 2 shows the molecular structure of 3; selected
bond lengths and angles are given in Table 3. Apparently the
bulky Ir(CO)(PPh3)2 fragment binds to nitride instead of the
more basic sulfur site in 1 in order to minimize the nonbonding
repulsion between the PPh3 and L. Because of the steric
congestion around 3, the Os-to-basal plane distance for 3 (ca.
0.69 Å) is longer than that for [Os(N)(C6H4S2)2]- (0.63 Å).5
The Ir-N distance of 2.002(5) Å is similar to that in trans-Ir-
(CO)(PPh3)2(NOsO3) (1.998(7) Å).6b The long Ir-N bond and
short Os-N bond and linear Os-N-Ir linkage for 3 is indicative
of the asymmetric bridging mode of the nitride, i.e., Ir-Nt
Os. The Os-N distance in 3 (1.676(5) Å) is longer than that
for [Os(N)(C6H4S2)2]- (1.64(1) Å)5 and the ν(OstN) (1100
cm-1) for 3 is lower than that for 1 (1112 cm-1), suggesting
that the Os-N triple bond is weakened upon coordination to
Ir(CO)(PPh3)2. The cyclic voltammogram of 3 in CH2Cl2 shows
an irreversible oxidation wave at ca. 0.36 V and an irreversible
In summary, we have demonstrated that [OsNL2]- reacts with
organometallic electrophiles to give heterobimetallic complexes
in a way similar to its alkylation reactions. Small electrophiles
such as [Au(PPh3)]+ and methyl attack the more basic sulfur
while bulky electrophiles such as [Ir(CO)(PPh3)2]+ and trityl
add to the less-hindered nitride ligand of [OsNL2]-.
Acknowledgment. The financial support from the Hong
Kong University of Science and Technology and the Hong Kong
Research Grants Council is gratefully acknowledged.
Supporting Information Available: Listings of crystal data,
complete bond lengths and angles, and atomic coordinates with isotropic
parameters (6 pages). Ordering information is given on any current
masthead page.
IC980136M