Molybdenum and tungsten complexes of sulfene (thioformaldehyde S,S-dioxide)

Article abstract of DOI:10.1021/ic010963e

Propionitrile complexes fac-[M(CO)₃(P-P)(NCEt)] (M = Mo (3), W (4); P-P = Ph₂PCH₂PPh₂ (a), Ph₂PC₂H₄PPh₂ (b), Ph₂PC₃H₆PPh₂ (c), (S,S)-Ph₂PCHMeCHMePPh₂ (d), Fe(C₅H₄PPh₂)₂ (e)) were synthesized from [M(CO)₃(NCEt)₃] and the corresponding diphosphine. Reactions of 3 and 4 with sulfur dioxide initially gave complexes fac-[M(CO)₃-(P-P)(η₂-SO₂)] (M = Mo (5), W (6)), which slowly isomerized to mer-[M(CO)₃(P-P)(η¹-SO₂)] (M = Mo (7), W (8)). The structures of 7b and 8b were determined by X-ray crystallography. Both compounds are isostructural (monoclinic, space group P2₁/n (No. 14)) with almost identical unit cell dimensions (7b, a = 14.511(5) A, b = 12.797(2) A, c = 16.476(6) A, β = 115.92(2)°; 8b, a = 14.478(8) A, b = 12.794(3) A, c = 16.442(9) A, β = 116.01(2)°) and molecular geometries. Treatment of either fac-[M(CO)₃(P-P)(η²-SO₂)] or mer-[M(CO)₃(P-P)(η¹-SO₂)] with diazomethane yielded the sulfene complexes mer-[M(CO)₃(P-P)(η²-CH₂SO₂)] (M = Mo (9), W (10)). The structure of 10a was determined crystallographically: monoclinic, space group P2₁/n (No. 14), a = 11.719(2) A, b = 17.392(4) A, c = 13.441(3) A, β = 95.58(2)°. The tungsten atom resides in the center of a distorted pentagonal bipyramid. The sulfene ligand occupies two adjacent equatorial sites with the bond distances W-C, 2.322(13) A, W-S, 2.353(3) A, and S-C, 1.721(12) A. The latter equals the S-C single bond distance in thiirane S,S-dioxide, indicating a high degree of charge density transfer into the LUMO of the sulfene ligand.

Full text of DOI:10.1021/ic010963e

Inorg. Chem. 2002, 41, 1079−1085
Molybdenum and Tungsten Complexes of Sulfene (Thioformaldehyde
S,S-Dioxide)1
Wolfdieter A. Schenk,* Katja Nielsen, Nicolai I. Burzlaff,† and Michael Hagel
Institut fu¨r Anorganische Chemie, UniVersita¨t Wu¨rzburg, Am Hubland,
D-97074 Wu¨rzburg, Germany
Received September 10, 2001
Propionitrile complexes fac-[M(CO)3(P-P)(NCEt)] (M ) Mo (3), W (4); P-P ) Ph2PCH PPh2 (a), Ph2PC H PPh2
2
2 4
(b), Ph2PC H PPh2 (c), (S,S)-Ph2PCHMeCHMePPh (d), Fe(C H PPh2)2 (e)) were synthesized from [M(CO)3(NCEt)3]
3
6
2
5 4
and the corresponding diphosphine. Reactions of 3 and 4 with sulfur dioxide initially gave complexes fac-[M(CO)3-
(P-P)(η2-SO )] (M ) Mo (5), W(6)), which slowly isomerized to mer-[M(CO)3(P-P)(η1-SO )] (M ) Mo (7), W(8)).
2
2
The structures of 7b and 8b were determined by X-ray crystallography. Both compounds are isostructural (monoclinic,
space group P21/n (No. 14)) with almost identical unit cell dimensions (7b, a ) 14.511(5) Å, b ) 12.797(2) Å, c
) 16.476(6) Å, â ) 115.92(2)°; 8b, a ) 14.478(8) Å, b ) 12.794(3) Å, c ) 16.442(9) Å, â ) 116.01(2)°) and
molecular geometries. Treatment of either fac-[M(CO)3(P-P)(η2-SO )] or mer-[M(CO)3(P-P)(η1-SO )] with diazomethane
2
2
yielded the sulfene complexes mer-[M(CO)3(P-P)(η2-CH SO )] (M ) Mo (9), W (10)). The structure of 10a was
2
2
determined crystallographically: monoclinic, space group P21/n (No. 14), a ) 11.719(2) Å, b ) 17.392(4) Å, c )
13.441(3) Å, â ) 95.58(2)°. The tungsten atom resides in the center of a distorted pentagonal bipyramid. The
sulfene ligand occupies two adjacent equatorial sites with the bond distances W−C, 2.322(13) Å, W−S, 2.353(3)
Å, and S−C, 1.721(12) Å. The latter equals the S−C single bond distance in thiirane S,S-dioxide, indicating a high
degree of charge density transfer into the LUMO of the sulfene ligand.
Scheme 1. Elimination-Addition Reactions of Sulfonic Acid
Derivatives
Introduction
Short-lived and highly reactive molecules can often be
stabilized by coordination to a transition metal complex.2
This provides an opportunity to gain structural and spectro-
scopic information not accessible by other means. In an ideal
case the species under consideration is not only stabilized
but sufficiently modified that it can undergo novel stoichio-
metric and perhaps even catalytic reactions. Transition metal
complexes of carbenes are certainly the most prominent
examples of this principle.3 Sulfenes R1R2CdSO2 are reactive
intermediates that may be generated by 1,2-elimination or
by cycloreversion reactions.4 They are involved in numerous
transformations of derivatives of alkanesulfonic acids4
(Scheme 1) as well as in the SO2-catalyzed decomposition
of diazo compounds4,5 (Scheme 2).
A limited number of sulfenes bearing highly electrone-
gative substituents have been isolated as base adducts.6 The
(3) (a) Doyle, M. P. In ComprehensiVe Organometallic Chemistry II;
Hegedus, L. S., Ed.; Pergamon: Oxford, 1995; Vol. 12, pp 387-420.
(b) Wulff, W. D. In ComprehensiVe Organometallic Chemistry II;
Hegedus, L. S., Ed.; Pergamon: Oxford, 1995; Vol. 12, pp 469-547.
(c) Hegedus, L. S. In ComprehensiVe Organometallic Chemistry II;
Hegedus, L. S., Ed.; Pergamon: Oxford, 1995; Vol. 12, pp 549-576.
(d) Stille, J. R. In ComprehensiVe Organometallic Chemistry II;
Hegedus, L. S., Ed.; Pergamon: Oxford, 1995; Vol. 12, pp 577-594.
(4) King, J. F.; Rathore, R. In The Chemistry of Sulfonic Acids, Esters,
and Their DeriVatiVes; Patai, S., Rappoport, Z., Eds.; Wiley: New
York, 1991; pp 583-669.
* To whom correspondence should be addressed. E-mail:
wolfdieter.schenk@mail.uni-wuerzburg.de. FAX (+49) (0)931-888-4605.
† Current address: Fachbereich Chemie, Universita¨t Konstanz, Univer-
sita¨tsstrasse 10, D-78457 Konstanz, Germany.
(1) Sulfur(IV) Compounds as Ligands. 26. Part 25: El-khateeb, M.;
Wolfsberger, B.; Schenk, W. A. J. Organomet. Chem. 2000, 612, 14-
17.
(2) Collman, C. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles
and Applications of Organotransition Metal Chemistry; University
Science Books: Mill Valley, 1987; pp 1-18.
(5) Staudinger, H.; Pfenninger, F. Ber. Dtsch. Chem. Ges. 1916, 49, 1941-
1951.
(6) (a) Hartwig, U.; Pritzkow, H.; Rall, K.; Sundermeyer, W. Angew.
Chem. 1989, 101, 224-225; Angew. Chem., Int. Ed. Engl. 1989, 28,
221-222. (b) Sundermeyer, W. Synthesis 1988, 5, 349-359. (c) Opitz,
G.; Ehlis, T.; Rieth, K. Chem. Ber. 1990, 123, 1989-1998.
10.1021/ic010963e CCC: $22.00 © 2002 American Chemical Society
Published on Web 02/08/2002
Inorganic Chemistry, Vol. 41, No. 5, 2002 1079

Schenk et al.
Scheme 2. SO2-Catalyzed Decomposition of Diazo Compounds
Scheme 5. Synthesis of Sulfinic Acid Esters via Cationic
Ruthenium-Sulfene Complexes
Scheme 3. Mono- and Binuclear Complexes of Sulfene
(Thioformaldehyde S,S-Dioxide)
The work reported here was undertaken with the aim to
investigate the reactivity of the neutral uncharged sulfur
dioxide complexes [M(CO)3(P-P)(SO2)] (M ) Mo, W, (P-
P) ) chelating diphosphine)12 toward the nucleophile diazo-
methane and to assess the structure and stability of the
resulting sulfene complexes.
Scheme 4. Cationic Ruthenium Complexes of Sulfene
Experimental Section
Analytical Measurements. C, H, and S analyses were carried
out by the Analytical Laboratory of the Institute of Inorganic
Chemistry, University of Wu¨rzburg (due to carbide formation
tungsten complexes occasionally analyze low for carbon). Melting
points were determined by differential scanning calorimetry (DSC).
Infrared spectra were run on a Bruker IFS 25 instrument. 1H, 13C-
{1H}, and 31P{1H} NMR spectra were recorded using a Bruker
AMX 400 instrument. Chemical shifts were referenced to the
internal solvent signals and are reported relative to TMS (1H, 13C)
or 85% H3PO4 (31P).
parent thioformaldehyde S,S-dioxide has been stabilized as
a η2(S,O) ligand in two complexes of osmium and iridium7
and in some binuclear complexes of cobalt and rhodium8
(Scheme 3).
Materials. The propionitrile complexes [M(CO)3(NCEt)3] (M
) Mo, W) were obtained by refluxing the metal hexacarbonyls in
propionitrile.13 The diphosphines were obtained from Strem Chemi-
cals and were used as received. The phosphine-nitrile complexes
3a,b and 4a,b12,14 and the sulfur dioxide complexes 7b and 8b12
were obtained by published procedures or slight adaptations thereof.
Sulfur dioxide was dried by passing it through concentrated sulfuric
acid. Diazomethane was prepared from N-methyl-N-nitroso-4-
toluenesulfonamide and employed as a dilute solution in ether.
Propionitrile Complexes 3c-e and 4c-e. General Procedure.
[M(CO)3(NCEt)3] (2.00 mmol) and diphosphine (2.00 mmol) were
suspended in propionitrile (40 mL). The flask was immersed for 5
min into an ultrasonic cleaning bath in order to disperse the starting
complex, and stirred at 20 °C for 1 h (M ) Mo) or 8 h (M ) W),
respectively. Ether (40 mL) was added to precipitate the products,
which were then filtered off, washed with ether (40 mL), and dried
under vacuum.
Cationic ruthenium complexes of the type [(C5H5)(R3P)2-
Ru{η2(S,C)-H2CdSO2}]+ are readily accessible by methylene
transfer to the corresponding sulfur dioxide complexes9
(Scheme 4).
This reaction exploits the pronounced electrophilicity of
cationic complexes of sulfur dioxide.10 The products also
turned out to be higly reactive electrophiles which readily
add a variety of bases (amines, phosphines, halides).9
Furthermore, they undergo C-C coupling reactions with
enamines and enolates leading ultimately to a transition metal
mediated synthesis of esters of functionalized sulfinic acids11
(Scheme 5).
(7) Roper, W. R.; Waters, J. M.; Wright, A. H. J. Organomet. Chem.
1984, 276, C13-C15.
(8) (a) Herrmann, W. A.; Bauer, C. Organometallics 1982, 1, 1101-1102.
(b) Herrmann, W. A.; Bauer, C.; Weichmann, J. Chem. Ber. 1984,
117, 1271-1268.
(12) (a) Schenk, W. A.; Baumann, F.-E. Chem. Ber. 1982, 115, 2615-
2625. (b) Schenk, W. A.; Baumann, F.-E. J. Organomet. Chem. 1983,
256, 261-267. (c) Kubas, G. J.; Jarvinen, G. D.; Ryan, R. R. J. Am.
Chem. Soc. 1983, 105, 1883-1891.
(13) Kubas, G. J.; van der Sluys, L. S. Inorg. Synth. 1990, 28, 29-33.
(14) (a) Darensbourg, D. J.; Zalewski, D. J.; Plepys, C.; Campana, C. Inorg.
Chem. 1987, 26, 3727-3732. (b) Hsu, S. C. N.; Yeh, W. Y.; Chiang,
M. Y. J. Organomet. Chem. 1995, 492, 121-127. (c) Song, L.-C.;
Liu, J.-T.; Hu, Q.-M.; Wang, G.-F.; Zanello, P.; Fontani, M. Orga-
nometallics 2000, 19, 5342-5351.
(9) (a) Schenk, W. A.; Urban, P. J. Organomet. Chem. 1991, 411, C27-
C31. (b) Schenk, W. A.; Urban, P.; Dombrowski, E. Chem. Ber. 1993,
126, 679-684.
(10) (a) Schenk, W. A.; Karl, U. Z. Naturforsch., B 1989, 44, 993-995.
(b) Schenk, W. A.; Urban, P.; Sta¨hrfeldt, T.; Dombrowski, E. Z.
Naturforsch., B 1992, 47, 1493-1500.
(11) (a) Schenk, W. A.; Bezler, J. Eur. J. Inorg. Chem. 1998, 605-611.
(b) Schenk, W. A.; Bezler, J.; Burzlaff, N.; Hagel, M.; Steinmetz, B.
Eur. J. Inorg. Chem. 2000, 287-297.
1080 Inorganic Chemistry, Vol. 41, No. 5, 2002

Molybdenum and Tungsten Complexes of Sulfene
(a) [Mo(CO)3(dppp)(NCEt)], 3c: yield 93%, yellow crystalline
powder, mp 71 °C (dec). Anal. Calcd for C33H31MoNO3P2: C,
61.21; H, 4.83; N, 2.16. Found: C, 60.82; H, 4.69; N, 2.23. IR
(e) mer-[W(CO)3(dppm)(SO2)], 8a: yield 54%, bright red
crystalline powder, mp 146 °C (dec). Anal. Calcd for C28H22O5P2-
SW: C, 46.95; H, 3.10; S, 4.48. Found: C, 46.22; H, 3.05; S, 4.21.
IR (CH2Cl2): ν(CO) 2021 (w), 1950 (m), 1922 (vs) cm-1. IR
(CH2Cl2): ν(CO) 1934 (vs), 1842 (s), 1811 (s) cm-1
.
31P NMR
(Nujol): ν(SO) 1211 (w), 1059 (s) cm-1 31P NMR (CD2Cl2): δ
.
(CD2Cl2): δ 22.0 (s).
-28.6 (d, J(P,P) ) 6 Hz, J(W,P) ) 213 Hz), -27.6 (d, J(P,P) )
6 Hz, J(W,P) ) 208 Hz).
(b) [Mo(CO)3(chir)(NCEt)], 3d: yield 95%, yellow crystalline
powder, mp 140 °C (dec). Anal. Calcd for C34H33MoNO3P2: C,
61.73; H, 5.03; N, 2.12. Found: C, 61.59; H, 5.02; N, 2.22. IR
(f) mer-[W(CO)3(dppp)(SO2)], 8c: yield 82%, bright red
crystalline powder, mp 126 °C (dec). Anal. Calcd for C30H26O5P2-
SW: C, 48.41; H, 3.52; S, 4.31. Found: C, 48.80; H, 3.64; S, 3.99.
IR (CH2Cl2): ν(CO) 2018 (w), 1951 (m), 1919 (vs) cm-1. IR
(CH2Cl2): ν(CO) 1934 (vs), 1843 (s), 1811 (s) cm-1 31P NMR
.
(CD2Cl2): δ 59.7 (d, J(P,P) ) 7 Hz), 63.4 (d, J(P,P) ) 7 Hz).
(c) [Mo(CO)3(dppf)(NCEt)], 3e: yield 87%, dark yellow
crystalline powder, mp 98 °C (dec). Anal. Calcd for C40H33-
FeMoNO3P2: C, 60.86; H, 4.21; N, 1.77. Found: C, 60.39; H, 4.34;
(Nujol): ν(SO) 1229 (w), 1068 (s) cm-1 31P NMR (CD2Cl2): δ
.
-4.7 (d, J(P,P) ) 30 Hz, J(W,P) ) 224 Hz), 2.1 (d, J(P,P) ) 30
Hz, J(W,P) ) 244 Hz).
N, 1.63. IR (CH2Cl2): ν(CO) 1932 (vs), 1837 (s), 1809 (s) cm-1
31P NMR (CD2Cl2): δ 30.5 (s).
.
(g) mer-[W(CO)3(chir)(SO2)], 8d: yield 87%, bright red crystal-
line powder, mp 90 °C (dec). Anal. Calcd for C31H28O5P2SW: C,
49.09; H, 3.72; S, 4.23. Found: C, 48.81; H, 3.85; S, 3.81. IR (CH2-
Cl2): ν(CO) 2015 (w), 1949 (m), 1916 (vs) cm-1. IR (Nujol): ν-
(d) [W(CO)3(dppp)(NCEt)], 4c: yield 59%, yellow crystalline
powder, mp 78 °C (dec). Anal. Calcd for C33H31NO3P2W: C, 53.90;
H, 4.25; N, 1.90. Found: C, 53.52; H, 4.09; N, 1.99. IR (CH2Cl2):
.
ν(CO) 1911 (vs), 1831 (s), 1809 (s) cm-1 31P NMR (CD2Cl2): δ
(SO) 1237 (w), 1070 (s) cm-1 31P NMR (CD2Cl2): δ 45.9 (d, J(P,P)
.
7.6 (s, J(W,P) ) 220 Hz).
) 12 Hz, J(W,P) ) 250 Hz), 46.6 (d, J(P,P) ) 12 Hz, J(W,P) )
(e) [W(CO)3(chir)(NCEt)], 4d: yield 84%, yellow crystalline
powder, mp 151 °C (dec). Anal. Calcd for C34H33NO3P2W: C,
54.49; H, 4.44; N, 1.87. Found: C, 54.05; H, 4.31; N, 1.92. IR
231 Hz).
The fac isomers 5d and 6d,e were obtained as purple crystalline
compounds when the reaction was worked up after 2 h at 0 °C.
They were contaminated with 10-25% of the corresponding mer
isomers, but further purification was not attempted.
(CH2Cl2): ν(CO) 1924 (vs), 1831 (s), 1816 (s) cm-1 31P NMR
.
(CD2Cl2): δ 49.0 (d, J(P,P) ) 3 Hz, J(W,P) ) 225 Hz), 53.3 (d,
J(P,P) ) 3 Hz, J(W,P) ) 225 Hz).
(h) fac-[Mo(CO)3(chir)(SO2)], 5d. IR (CH2Cl2): ν(CO) 1996
(f) [W(CO)3(dppf)(NCEt)], 4e: yield 64%, dark yellow crystal-
line powder, mp 68 °C (dec). Anal. Calcd for C40H33FeNO3P2W:
C, 54.76; H, 3.79; N, 1.60. Found: C, 54.17; H, 3.98; N, 1.76. IR
(vs), 1924 (s), cm-1. IR (Nujol): ν(SO) 1158 (m), 997 (w) cm-1
.
31P NMR (CD2Cl2): δ 46.2 (d, J(P,P) ) 19 Hz), 58.1 (d, J(P,P) )
19 Hz).
(CH2Cl2): ν(CO) 1927 (vs), 1831 (s), 1809 (s) cm-1
.
31P NMR
(i) fac-[W(CO)3(dppp)(SO2)], 6c. IR (CH2Cl2): ν(CO) 1993
(CD2Cl2): δ 21.5 (s, J(W,P) ) 233 Hz).
(m), 1909 (s) cm-1. IR (Nujol): ν(SO) 1152 (m), 968 (w) cm-1
.
Sulfur Dioxide Complexes. General Procedure. [M(CO)3(P-
P)(NCEt)] (0.50 mmol) was suspended in dichloromethane (20 mL)
and the solution saturated at 0 °C with SO2. The mixture turned
red immediately and was stirred for 2 h at 0 °C and then for 24 h
at 20 °C. Excess SO2 and solvent were removed by partial
evaporation, and the product was precipitated by addition of hexane
(40 mL).
31P NMR (CD2Cl2): δ -0.9 (d, J(P,P) ) 28 Hz), -0.4 (d, J(P,P)
) 28 Hz).
(j) fac-[W(CO)3(chir)(SO2)], 6d. IR (CH2Cl2): ν(CO) 1991 (m),
1909 (s) cm-1. IR (Nujol): ν(SO) 1155 (m), 989 (w) cm-1 31P
.
NMR (CD2Cl2): δ 32.7 (d, J(P,P) ) 9 Hz), 48.1 (d, J(P,P) ) 9
Hz).
Sulfene Complexes. General Procedure. [M(CO)3(P-P)(SO2)]
(0.20 mmol) was suspended in dichloromethane (10 mL), and a
solution of diazomethane (1.0 mmol) in ether was added at 0 °C.
The reactions were accompanied by gas evolution and a quick color
change to yellow. Excess diazomethane and solvent were removed
by evaporation to a volume of 2 mL. The products were precipitated
by slow addition of ether (10 mL) and hexane (20 mL).
(a) fac-[W(CO)3(dppf)(SO2)], 6e: yield 71%, purple crystalline
powder, mp 54 °C (dec). Anal. Calcd for C37H28FeO5P2SW: C,
50.14; H, 3.18; S, 3.62. Found: C, 49.51; H, 3.53; S, 3.30. IR (CH2-
Cl2): ν(CO) 1985 (vs), 1894 (s) cm-1. IR (Nujol): ν(SO) 1145
(s), 997 (w) cm-1 31P NMR (CD2Cl2): δ 8.0 (d, J(P,P) ) 29 Hz,
.
J(W,P) ) 220 Hz), 16.0 (d, J(P,P) ) 29 Hz, J(W,P) ) 217 Hz).
(b) mer-[Mo(CO)3(dppm)(SO2)], 7a: yield 52%, bright red
crystalline powder, mp 141 °C (dec). Anal. Calcd for C28H22-
MoO5P2S: C, 53.52; H, 3.53; S, 5.10. Found: C, 52.94; H, 3.59;
(a) mer-[Mo(CO)3(dppm)(CH2SO2)], 9a: yield 71%, beige
crystalline powder, mp 74 °C (dec). Anal. Calcd for C29H24-
MoO5P2S: C, 54.22; H, 3.77; S, 4.99. Found: C, 54.24; H, 3.93;
S, 4.93. IR (CH2Cl2): ν(CO) 2012 (w), 1960 (sh), 1935 (vs) cm-1
.
S, 4.91. IR (CH2Cl2): ν(CO) 2037 (m), 1987 (m), 1939 (vs) cm-1
.
IR (Nujol): ν(SO) 1220 (w), 1061 (s) cm-1
.
31P NMR (CD2Cl2):
IR (Nujol): ν(SO) 1207 (w), 1097 (s) cm-1. 1H NMR (CDCl3): δ
1.23 (broad s, SCH2), 4.38 (t, J(P,H) ) 9.2 Hz, PCH2), 7.4-8.0
(m, Ph). 13C NMR (CD2Cl2): δ -7.1 (m, SCH2), 42.1 (t, J(P,C) )
21 Hz, PCH2), 131.6-134.5 (m, Ph), 208.9-209.7 (m, CO). 31P
NMR (CD2Cl2): δ -11.6 (d, J(P,P) ) 32 Hz), -5.6 (d, J(P,P) )
32 Hz).
δ -3.1 (s), 0.8 (s).
(c) mer-[Mo(CO)3(dppp)(SO2)], 7c: yield 45%, bright red
crystalline powder, mp 67 °C (dec). Anal. Calcd for C30H26-
MoO5P2S: C, 54.89; H, 3.99; S, 4.88. Found: C, 55.17; H, 3.98;
S, 4.33. IR (CH2Cl2): ν(CO) 2014 (w), 1954 (sh), 1918 (vs) cm-1
.
IR (Nujol): ν(SO) 1234 (w), 1069 (s) cm-1
.
31P NMR (CD2Cl2):
δ 13.9 (d, J(P,P) ) 38 Hz), 24.3 (d, J(P,P) ) 38 Hz).
(b) mer-[Mo(CO)3(dppe)(CH2SO2)], 9b: yield 72%, beige
crystalline powder, mp 68 °C (dec). Anal. Calcd for C30H26-
MoO5P2S: C, 54.89; H, 3.99; S, 4.88. Found: C, 54.62; H, 3.80;
(d) mer-[Mo(CO)3(chir)(SO2)], 7d: yield 60%, bright red
crystalline powder, mp 61 °C (dec). Anal. Calcd for C31H28-
MoO5P2S: C, 55.53; H, 4.21; S, 4.78. Found: C, 55.31; H, 4.57;
S, 4.93. IR (CH2Cl2): ν(CO) 2035 (m), 1979 (m), 1938 (vs) cm-1
.
1
IR (Nujol): ν(SO) 1227 (w), 1092 (s) cm-1. H NMR (CDCl3):
δ 1.14 (d, J(P,H) ) 2.0 Hz, SCH2), 2.65-2.77 (m, PCH2),
7.4-7.7 (m, Ph). 13C NMR (CD2Cl2): δ -10.9 (m, SCH2), 28.6-
S, 4.50. IR (CH2Cl2): ν(CO) 2018 (w), 1955 (sh), 1928 (vs) cm-1
.
.
IR (Nujol): ν(SO) 1238 (w), 1065 (s) cm-1 31P NMR (CD2Cl2):
δ 61.7 (d, J(P,P) ) 23 Hz), 65.1 (d, J(P,P) ) 23 Hz).
Inorganic Chemistry, Vol. 41, No. 5, 2002 1081

Schenk et al.
29.3 (m, PCH2), 129.2-135.4 (m, Ph), 207.0-207.2 (m, CO). 31
NMR (CDCl3): δ 56.0 (d, J(P,P) ) 27 Hz), 60.1 (d, J(P,P) ) 27
Hz).
P
Table 1. Crystallographic Data for 7b, 8b, and 10a
7b 8b
10a
empirical formula C29H24MoO5P2S C29H24O5P2SW C29H24O5P2SW
(c) mer-[Mo(CO)3(chir)(CH2SO2)], 9d: yield 29%, beige crys-
talline powder, mp 54 °C (dec). This compound was not obtained
in analytically pure form. IR (CH2Cl2): ν(CO) 2037 (w), 1973 (m),
1927 (vs) cm-1. IR (Nujol): ν(SO) 1212 (vw), 1091 (m) cm-1. 1H
NMR (CD2Cl2): δ 0.98 (m, CH3), 2.35-2.52 (m, PCH), 7.2-7.7
(m, Ph). 13C NMR (CD2Cl2): δ -8.3 (m, SCH2), 15.1 (dd, J(P,C)
) 22 Hz, J(P,C) ) 5 Hz, CH3), 15.5 (dd, J(P,C) ) 21 Hz, J(P,C)
) 5 Hz, CH3), 37.0-37.6 (m, PCH), 127.0-135.4 (m, Ph).31P NMR
(CD2Cl2): δ 63.0 (d, J(P,P) ) 38 Hz), 64.6 (d, J(P,P) ) 38 Hz).
(d) mer-[W(CO)3(dppm)(CH2SO2)], 10a: yield 96%, off-white
crystalline powder, mp 118 °C (dec). Anal. Calcd for C29H24O5P2-
SW: C, 47.69; H, 3.31; S, 4.39. Found: C, 47.53; H, 3.30; S, 4.38.
IR (CH2Cl2): ν(CO) 2036 (m), 1978 (m), 1930 (vs) cm-1. IR
fw
642.46
293
730.37
293
730.37
193
temp, K
space group
a, Å
b, Å
c, Å
â, deg
V, Å3
Z
P21/n (No. 14)
14.511(5)
12.797(2)
16.476(6)
115.92(2)
2752(1)
4
0.71073
1.551
2.66
P21/n (No. 14) P21/n (No. 14)
14.478(8)
12.794(3)
16.442(9)
116.01(2)
2737(2)
4
0.70930
1.772
2.87
11.719(2)
17.392(4)
13.441(3)
95.58(3)
2726.6(9)
4
0.71073
1.779
2.78
λ, Å
F
calcd, g cm-3
µ, cm-1
R1 [I > 2σ(I)]
0.044
0.0289
0.0502
0.0749
0.137
wR2 [I > 2σ(I)]a 0.0648
a wR2 ) {[∑w(Fc - Fo )2]/[∑w(Fo )2]}1/2
.
2
2
2
1
(Nujol): ν(SO) 1191 (w), 1097 (m) cm-1. H NMR (CDCl3): δ
Table 2. Relevant Bond Distances (Å) and Angles (deg) for 7b, 8b,
and 10a
1.48 (broad s, SCH2), 4.58 (t, J(P,H) ) 10.0 Hz, PCH2), 7.3-7.9
(m, Ph). 13C NMR (CD2Cl2): δ -12.7 (m, SCH2), 40.8 (t, J(P,C)
) 27 Hz, PCH2), 129.3-133.8 (m, Ph), 199.8-199.9 (m, CO). 31
P
7b (M ) Mo)
8b (M ) W)
10a (M ) W)
NMR (CDCl3): δ -34.8 (d, J(P,P) ) 26 Hz, J(W,P) ) 199 Hz),
-30.8 (d, J(P,P) ) 26 Hz, J(W,P) ) 171 Hz).
M-S
2.254(1)
2.509(1)
2.531(1)
2.030(4)
2.024(4)
2.045(4)
2.258(1)
2.500(1)
2.525(1)
2.021(4)
2.017(4)
2.024(4)
2.353(3)
2.490(3)
2.498(3)
2.008(12)
2.017(14)
2.010(13)
2.322(13)
1.721(12)
1.438(10)
1.499(9)
M-P(1)
M-P(2)
M-C(1)
M-C(2)
M-C(3)
M-C(5)
S-C(5)
S-O(4)
S-O(5)
(e) mer-[W(CO)3(dppe)(CH2SO2)], 10b: yield 72%, off-white
crystalline powder, mp 157 °C (dec). Anal. Calcd for C30H26O5P2-
SW: C, 48.41; H, 3.52; S, 4.31. Found: C, 47.85; H, 3.59; S, 4.22.
IR (CH2Cl2): ν(CO) 2031 (m), 1972 (m), 1921 (vs) cm-1. IR
1
(Nujol): ν(SO) 1201 (w), 1096 (m) cm-1. H NMR (CDCl3): δ
1.442(3)
1.430(4)
1.443(3)
1.434(4)
1.36 (d, J(P,H) ) 2.0 Hz, SCH2), 2.72-2.83 (m, PCH2), 7.4-7.7
(m, Ph). 13C NMR (CDCl3): δ -16.0 (m, SCH2), 20.5 (dd, J(P,C)
) 29 Hz, J(P,C) ) 15 Hz, PCH2), 29.4 (dd, J(P,C) ) 29 Hz, J(P,C)
S-M-P(1)
177.89(4)
100.96(4)
90.12(11)
178.03(4)
100.90(4)
90.56(12)
160.28(10)
92.38(10)
116.3(4)
43.2(3)
68.10(10)
83.3(4)
156.2(3)
151.1(4)
135.6(3)
173.1(5)
113.1(6)
S-M-P(2)
) 15 Hz, PCH2), 129.3-133.4 (m, Ph), 199.4-199.6 (m, CO). 31
P
S-M-C(2)
NMR (CDCl3): δ 40.4 (d, J(P,P) ) 18 Hz, J(W,P) ) 199 Hz),
42.0 (d, J(P,P) ) 18 Hz, J(W,P) ) 198 Hz).
S-M-C(5)
P(1)-M-P(2)
P(1)-M-C(2)
P(1)-M-C(5)
P(2)-M-C(2)
P(2)-M-C(5)
C(1)-M-C(3)
O(4)-S-O(5)
80.63(3)
88.31(11)
80.58(4)
87.98(12)
(f) mer-[W(CO)3(dppp)(CH2SO2)], 10c: yield 62%, off-white
crystalline powder, mp 96 °C (dec). Anal. Calcd for C31H28O5P2-
SW: C, 49.09; H, 3.72; S, 4.23. Found: C, 48.94; H, 3.86; S, 3.62.
IR (CH2Cl2): ν(CO) 2021 (m), 1971 (m), 1908 (vs) cm-1. IR
168.90(11)
168.51(11)
176.5(2)
112.4(2)
176.1(2)
112.3(2)
1
(Nujol): ν(SO) 1205 (w), 1081 (m) cm-1. H NMR (CDCl3): δ
0.98 (d, J(P,H) ) 5.2 Hz, SCH2), 2.05 (m, CH2), 2.69-2.84 (m,
PCH2), 7.4-7.5 (m, Ph). 13C NMR (CD2Cl2): δ -9.0 (m, SCH2),
18.1 (s, CH2), 27.5 (dd, J(P,C) ) 26 Hz, J(P,C) ) 10 Hz, PCH2),
29.2 (dd, J(P,C) ) 27 Hz, J(P,C) ) 9 Hz, PCH2), 129.1-134.8
(m, Ph), 202.1-202.2 (m, CO), 207.7 (m, CO). 31P NMR (CD2-
Cl2): δ -5.5 (d, J(P,P) ) 40 Hz, J(W,P) ) 173 Hz), -4.4 (d,
J(P,P) ) 40 Hz, J(W,P) ) 192 Hz).
|J(P,C) + J(P′,C)| ) 5 Hz, CH), 74.0 (d, J(P,C) ) 6 Hz, CH),
74.3 (d, J(P,C) ) 6 Hz, CH), 75.7 (d, J(P,C) ) 5 Hz, CH), 75.9
(d, J(P,C) ) 4 Hz, CH), 129.0-135.0 (m, Ph). 31P NMR (CD2-
Cl2): δ 14.8 (d, J(P,P) ) 36 Hz), 16.0 (d, J(P,P) ) 36 Hz).
Crystallographic Studies of 7b, 8b, and 10a. Crystals were
grown by diffusion of hexane into a dichloromethane solution of
the complex. The data sets were collected on an Enraf-Nonius
CAD4 using Mo KR radiation. Empirical absorption corrections
were applied.15 The structures were solved by Patterson methods
with SHELXS-86.16a The structures were refined by full-matrix
least-squares procedures on F2 using SHELXL-93.16b All
non-hydrogen atoms were refined anisotropically, and a riding
model was employed in the refinement of the hydrogen atoms.
Relevant crystallographic data can be found in Table 1, and selected
bond distances and angles are given in Table 2. Further details on
the structure investigations may be obtained from the Cambridge
Crystallographic Data Centre on quoting the deposition
numbers CCDC 165311 (7b), CCDC 165312 (8b), and CCDC
165313 (10a).
(g) mer-[W(CO)3(chir)(CH2SO2)], 10d: yield 69%, off-white
crystalline powder, mp 107 °C (dec). Anal. Calcd for C32H30O5P2-
SW: C, 49.76; H, 3.91; S, 4.15. Found: C, 48.46; H, 4.02; S, 3.90.
IR (CH2Cl2): ν(CO) 2033 (m), 1969 (m), 1916 (vs) cm-1. IR
1
(Nujol): ν(SO) 1211 (w), 1092 (m) cm-1. H NMR (CD2Cl2): δ
0.8-1.01 (m, SCH2, CH3), 2.38-2.51 (m, PCH), 7.4-7.7 (m, Ph).
13C NMR (CD2Cl2): δ 15.0 (vt, N ) |J(P,C) + J(P′,C)| ) 23 Hz,
CH3), 30.1 (vt, N ) |J(P,C) + J(P′,C)| ) 9 Hz, CH3), 37.4-38.4
(m, PCH), 129.0-135.5 (m, Ph), 200.5-200.6 (m, CO). 31P NMR
(-30 °C, CD2Cl2): δ 45.8 (d, J(P,P) ) 28 Hz, J(W,P) ) 186 Hz),
46.9 (d, J(P,P) ) 28 Hz, J(W,P) ) 180 Hz).
(h) mer-[W(CO)3(dppf)(CH2SO2)], 10e: yield 95%, yellow
crystalline powder, mp 108 °C (dec). Anal. Calcd for C38H30FeO5P2-
SW: C, 50.69; H, 3.36; S, 3.56. Found: C, 50.38; H, 3.51; S, 3.50.
IR (CH2Cl2): ν(CO) 2028 (m), 1964 (m), 1910 (vs) cm-1. IR
(15) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351-358.
(16) (a) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473. (b)
Sheldrick, G. M. Program for crystal structure refinement. University
of Go¨ttingen, 1993.
1
(Nujol): ν(SO) 1217 (w), 1084 (m) cm-1. H NMR (CD2Cl2): δ
1.02 (d, J(P,H) ) 6.4 Hz, SCH2), 4.24-4.43 (m, C5H4), 7.4-7.7
(m, Ph). 13C NMR (CD2Cl2): δ -6.6 (m, SCH2), 72.8 (vt, N )
1082 Inorganic Chemistry, Vol. 41, No. 5, 2002

Molybdenum and Tungsten Complexes of Sulfene
Results
The tris(propionitrile) complexes 1 and 2 react smoothly
with chelating diphosphines to produce the mixed-donor
complexes 3a-e and 4a-e (eq 1).
Figure 1. ORTEP plot of mer-[Mo(CO)3(dppe)(SO2)] (7b).
Initially we had carried out this reaction in dichloro-
methane, which had led to products contaminated with
varying amounts of the ligand-bridged dinuclear complexes
[{M(CO)3(P-P)}2(µ-P-P)]. The use of propionitrile as a
solvent slows the reaction down but makes it highly selective
for the desired mononitrile complexes. Products 3a-e and
4a-e are yellow crystalline, slightly air-sensitive compounds.
Their facial geometry as shown in eq 1 is easily inferred
from the ν(CO) pattern in the IR spectra and, with the
exception of the chiral complexes 3d and 4d, the equivalence
of the two phosphorus nuclei in the 31P NMR spectra. It
should be mentioned here that closely analogous but
somewhat less reactive acetonitrile complexes had been
obtained in much the same way.12,14
Figure 2. ORTEP plot of mer-[W(CO)3(dppe)(SO2)] (8b).
As had been noted earlier, phosphine-nitrile complexes
of this type react instantaneously with sulfur dioxide.12 IR
monitoring indicated that initially the facial complexes 5a-e
and 6a-e were formed which, with the exception of 5e and
6e, rearranged slowly to the meridional isomers (eq 2).
of the ν(CO) absorptions, while the coordination mode of
the sulfur dioxide ligand, η2(S,O) in the facial and η1(S) in
the meridional complexes, reveals itself through the readily
identifiable SO stretching vibrations.17 The η2-(MSO2) moiety
is chiral, and as a result the two phosphorus nuclei in
complexes 5 and 6 are diastereotopic. For 5d and 6d there
is the possibility of the formation of diastereoisomers.
However, only a single set of signals was observed in the
31P NMR spectra, indicating the highly preferential formation
of one diastereoisomer.
The structures of 7b and 8b were determined by X-ray
crystallography; ORTEP diagrams are shown in Figures 1
and 2.
Both compounds are isostructural with almost identical
unit cell data, and even the molecular dimensions of the two
complexes are identical within 2σ. The structures are best
described as slightly distorted octahedral. The largest devia-
tion from the idealized geometry originates from the restraints
imposed by the five-membered chelate ring which enforces
a P-M-P angle of 80°. As a consequence, the corresponding
P-M-S angle is opened up to 100°. The two M-P distances
are, as expected, unequal due to the large structural trans
influence of the strongly binding CO ligand.18 The M-S
distances at 2.254 Å (M ) Mo) and 2.258 Å (M ) W) are
The formation of 5e was only detected by IR spectroscopy;
its low stability precluded isolation of a pure sample. Workup
after short reaction times produced the facial isomers 5b,d
and 6b-e in a sufficiently pure state for unambiguous
spectroscopic identification. Since 5b and 6b had been
isolated previously,12 and since for the next step both isomers
are equally suitable, we did not attempt a complete separa-
tion.
The facial isomers of the SO2 complexes are deep
burgundy-red or purple microcrystalline compounds while
the meridional isomers are brick-red in color. They are
soluble only in polar organic media such as dichloromethane,
chloroform, or THF. The geometry around the central metal
atom is unambiguously deduced from the relative intensity
(17) (a) Kubas, G. J. Inorg. Chem. 1979, 18, 182-188. (b) Ryan, R. R.;
Kubas, G. J.; Moody, D. C.; Eller, P. G. Struct. Bonding 1981, 46,
47-100.
Inorganic Chemistry, Vol. 41, No. 5, 2002 1083

Schenk et al.
between that in [Mo(CO)3(P-i-Pr3)2(SO2)] (2.285 Å), where
the SO2 ligand is situated trans to a CO,12c and that in the
more electron-rich [Mo(CO)2(dmpe)(PPh3)(SO2)] (2.244 Å),
where the SO2 is trans to one arm of the dmpe ligand.19
Thus it is clear that also the metal-sulfur distance depends
on both the trans influence and the extent of π-bonding.
Treatment of the SO2 complexes with diazomethane at 0
°C in each case gave a smooth reaction accompanied by gas
evolution and a conspicuous color change to yellow. The
resulting sulfene complexes were isolated as beige micro-
crystalline solids (eq 3).
Figure 3. ORTEP plot of mer-[W(CO)3(dppm)(CH2SO2)] (10a).
Discussion
The synthesis of the sulfur dioxide complexes 5-8 as
outlined in eqs 1 and 2 exploits the well-known reactivity
of nitrile derivatives of the chromium group carbonyls.24 The
facial intermediates 5 and 6 are thermodynamically less stable
than their meridional isomers 7 and 8. In the latter, the
LUMO of the strongly π-accepting ligand SO2 can interact
with a high and largely metal-centered HOMO (dxy if the
trans-M(CO)2 unit is taken as defining the z axis) which is
stabilized by π bonding to only one carbonyl ligand. The
isomerization is expected to proceed via some form of
intramolecular twist mechanism25 which on the way to the
transition state requires a considerable compression of some
of the bond angles around the central metal atom. This would
offer a ready explanation why the bis(diphenylphosphino)-
ferrocene complexes 5e and 6e with their relatively large
and unflexible P-M-P angles14c,26 are reluctant to isomerize.
The reaction of the SO2 complexes with diazomethane is
smooth and selective. Analogy with the formation of the
cationic ruthenium sulfene complexes9 (Scheme 4) suggests
that also in the present case the methylene transfer is initiated
by nucleophilic attack at sulfur. Nucleophilic additions to
cationic SO2 complexes are well-documented.10,27,28 Un-
charged complexes of sulfur dioxide, however, and notably
those of the chromium group, react with nucleophiles with
substitution of either SO2 or other labile ligands.12,17,19 There
appear to be only two reported cases of nucleophilic addition
to neutral SO2 complexes, one involving the formation of a
platinum-sulfine complex from [Pt(PPh3)3(SO2)],29 and the
The tungsten complexes are thermally more robust than
their molybdenum congeners, which decompose rapidly in
solution and even as solids have to be stored at -70 °C.
The presence of the sulfene ligand was diagnosed by a
doublet or broad singlet at 1.0-1.5 ppm, and in particular
by its typical high-field 13C NMR signal in the region around
-6 to -16 ppm, slightly downfield from those of the cationic
sulfene complexes [(C5H5)Ru(P-P)(CH2SO2)]+ (-16 to -22
ppm).9,11 Spin-spin coupling with the two nonequivalent
phosphorus nuclei is only small and was not resolved. Other
characteristic features are the ν(SO) absorptions in the
infrared spectra and, for the tungsten complexes, surprisingly
small 183W-31P couplings. The latter is a clear indication of
the presence of a strongly π-bonding η2 ligand.20 Indeed, as
judged from the high frequency of the CO stretching
vibrations, the sulfene ligand surpasses typical π-acceptor
ligands such as maleic anhydride,21 CS, CS2,22 or even SO2
in its ability to take up electron density from the metal.
The structure of 10a was determined by X-ray crystal-
lography; Figure 3 shows an ORTEP diagram.
The tungsten atom resides in the center of a distorted
pentagonal bipyramid with the sulfene ligand occupying two
adjacent sites. The largest angle deviations within the
pentagonal base are associated with the three-membered
W-S-C ring and the vicinity of the bulky phosphine ligand.
The two W-P bonds are almost equal in length and
marginally shorter than in the SO2 complex 8b, but the W-S
bond is 0.1 Å longer than that in 8b. The W-C(5) distance
compares well with the length of metal-carbon bonds in
tungsten-alkene complexes.23
(23) (a) Grevels, F. W.; Lindemann, M.; Benn, R.; Goddard, R.; Kru¨ger,
C. Z. Naturforsch., B 1980, 35, 1298-1309. (b) Berke, H.; Huttner,
G.; Sontag, C.; Zsolnai, L. Z. Naturforsch., B 1985, 40, 799-807. (c)
Grevels, F. W.; Jacke, J.; Betz, P.; Kru¨ger, C.; Tsay, Y. H.
Organometallics 1989, 8, 293-298.
(24) (a) Tate, D. P.; Knipple, W. R.; Augl, J. M. Inorg. Chem. 1962, 1,
433-434. (b) Kubas, G. J. Inorg. Chem. 1983, 22, 692-694.
(25) (a) Rodger, A.; Johnson, B. F. G. Inorg. Chem. 1988, 27, 3061-
3062. (b) Wilkins, R. G. Kinetics and Mechanism of Reactions of
Transition Metal Complexes, 2nd ed; VCH: Weinheim, 1991; p 343-
354.
(26) Bandoli, G.; Dolmella, A. Coord. Chem. ReV. 2000, 209, 161-196.
(27) Schenk, W. A. Angew. Chem. 1987, 99, 101-112; Angew. Chem.,
Int. Ed. Engl. 1987, 26, 98-109.
(28) Kubas, G. J. Acc. Chem. Res. 1994, 27, 183-190.
(29) Go¨tzfried, F.; Beck, W. J. Organomet. Chem. 1980, 191, 329-338.
(18) (a) Appleton, D. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. ReV.
1973, 10, 335-422. (b) Shustorovich, E. M.; Porai-Koshits, M. A.;
Buslaev, Y. A. Coord. Chem. ReV. 1975, 17, 1-98.
(19) Shen, J.-K.; Kubas, G. J.; Rheingold, A. L. Inorg. Chim. Acta 1995,
240, 99-104.
(20) Schenk, W. A.; Buchner, W. Inorg. Chim. Acta 1983, 70, 189-196.
(21) Schenk, W. A.; Mu¨ller, H. Chem. Ber. 1982, 115, 3618-3630.
(22) Schenk, W. A.; Schwietzke, T.; Mu¨ller, H. J. Organomet. Chem. 1982,
232, C41-C47.
1084 Inorganic Chemistry, Vol. 41, No. 5, 2002

Molybdenum and Tungsten Complexes of Sulfene
other one describing the addition of methoxide ion to the
cluster [Ir4(CO)11(µ-SO2)].30
The stability of the sulfene complexes depends largely on
the electron density at the metal and the ability of the metal
complex fragment to engage in π-back-bonding. For ex-
ample, in the ruthenium series the complexes [(C5H5)Ru(P-
P)(CH2SO2)]PF6 are quite labile and have to be handled at
low temperature, while [(C5Me5)Ru(PMe3)2(CH2SO2)]PF6 is
a perfectly stable compound.9 Indeed, all attempts to convert
the less electron-rich complexes [W(CO)4(PR3)(SO2)]12a into
analogous sulfene complexes have failed and lead only to
intractable mixtures of decomposition products. The higher
stability of the tungsten complexes 10a-e compared to their
molybdenum analogues 9a-d is in line with previous
experience with tungsten carbonyl-alkene complexes, which
undergo dissociative ligand exchange reactions much slower
than the corresponding molybdenum compounds.21,31
A comparison of the bond lengths of the sulfene complexes
with those in uncoordinated sulfene and in thiirane S,S-
dioxide reveals some interesting aspects (Figure 4).
The CdS double bond in sulfene (as calculated by ab
initio-SCF methods)32 is very short. This is undoubtedly due
to the contraction of the valence orbitals at sulfur caused by
the two electronegative oxygen substituents. Upon coordina-
tion to the cation [(C5Me5)Ru(PMe3)2]+ the C-S distance
increases by more than 0.1 Å9b as a result of electron
donation into the LUMO of the CH2SO2 ligand. Apparently
the degree of back-donation is even larger in the neutral
complex 10a where the C-S bond length has increased to
Figure 4. Comparison of bond lengths (Å) of mer-[W(CO)3(dppm)(CH2-
SO2)] (10a), [(C5Me5)Ru(PMe3)2(CH2SO2)]PF6,9b sulfene,32 and thiirane
S,S-dioxide.33
1.72 Å, comparable to the single bond in thiirane S,S-
dioxide.33 The net result is a remarkable stability of the
sulfene complexes mer-[M(CO)3(P-P)(CH2SO2)], particularly
for M ) W. The molybdenum complexes nevertheless tend
to release the sulfene ligand under mild conditions and may
thus provide a ready source of sulfene. Work along these
lines is in progress in our laboratory.
Acknowledgment. This work was generously supported
by the Deutsche Forschungsgemeinschaft (SFB 347) and the
Fonds der Chemischen Industrie.
Supporting Information Available: Three X-ray crystal-
lographic files, in CIF format. This material is available free of
charge via the Internet at http://pubs.acs.org.
(30) Braga, D.; Ros, R.; Roulet, R. J. Organomet. Chem. 1985, 286, C8-
IC010963E
C12.
(31) Schenk, W. A.; Mu¨ller, H. Inorg. Chem. 1981, 20, 6-8.
(32) Block, E.; Schwan, A.; Dixon, D. A. J. Am. Chem. Soc. 1992, 114,
3492-3499.
(33) Nakano, Y.; Saito, S.; Morino, Y. Bull. Chem. Soc. Jpn. 1970, 43,
368-371.
Inorganic Chemistry, Vol. 41, No. 5, 2002 1085