Synthetic and structural study of cyclopentadienylchromium dithiocarbamate complexes and their thermolytic derivatives

Article abstract of DOI:10.1021/om0202930

The reaction of [CpCr(CO)₃]₂ (1) with the tetraalkylthiuram disulfides [R₂NC(S)S]₂ (R = Me, Et, i-Pr) has been investigated. At ambient temperature, CpCr(CO)₂(η²-S₂CNR₂) (3) was obtained as air-stable dark red crystals in 81-87% yields from reactions in solution and in quantitative yield from a reaction in the solid state (3a, R = Me); the precursor complex CpCr(CO)₃(η¹-S₂CNMe₂) (2a) crystallized out in a 1:1 admixture with 3a from a product solution after 3 days at -29 °C. At 90 °C for 2 h, the same reaction or the thermal degradation of 3 led to the isolation of the thiocarbenoid complex CpCr(CO)₂(η²-SCNR₂) (4) as dark red crystals (ca. 10%), double cubanes Cp₆Cr₈S₈(η²:⁴-SCNR ₂)₂ (5a, R = Me; 5b, R = Et) as dark brown crystals (3-7%), Cp₆Cr₆S₈(η¹:η?²-S ₂CNR) (6) as dark crystals (7-14%), Cr(η²-S₂CNR₂)₃ (7) as dark blue crystals (16-21%), Cp₂Cr₂(CO)₄S as dark green crystals (1-3%), and Cp₄Cr₄S₄ (12-22%) as dark green solids. The crystal structures of 2-6 were reported. Unprecedented bridging modes were found in the double cubanes: in 5, two Cr₄S₄ cubane clusters were linked by a μ-η²:η⁴-dithiooxamide ligand as well as a Cr - Cr bridge with bond distances of 3.101 and 3.118 A? in the two independent molecules of the compound, and in 6, the cubanes were linked by two μ-η¹:η²-dithiocarbamate ligands.

Full text of DOI:10.1021/om0202930

4398
Organometallics 2002, 21, 4398-4407
Syn th etic a n d Str u ctu r a l Stu d y of
Cyclop en ta d ien ylch r om iu m Dith ioca r ba m a te Com p lexes
a n d Th eir Th er m olytic Der iva tives
Lai Yoong Goh,*,† Zhiqiang Weng, Weng Kee Leong,* and Pak Hing Leung
Department of Chemistry, National University of Singapore, Kent Ridge, Singapore 119260
Received April 16, 2002
The reaction of [CpCr(CO)3]2 (1) with the tetraalkylthiuram disulfides [R2NC(S)S]2 (R )
Me, Et, i-Pr) has been investigated. At ambient temperature, CpCr(CO)2(η2-S2CNR2) (3) was
obtained as air-stable dark red crystals in 81-87% yields from reactions in solution and in
quantitative yield from a reaction in the solid state (3a , R ) Me); the precursor complex
CpCr(CO)3(η1-S2CNMe2) (2a ) crystallized out in a 1:1 admixture with 3a from a product
solution after 3 days at -29 °C. At 90 °C for 2 h, the same reaction or the thermal degradation
of 3 led to the isolation of the thiocarbenoid complex CpCr(CO)2(η2-SCNR2) (4) as dark red
crystals (ca. 10%), double cubanes Cp6Cr8S8(η2:η4-SCNR2)2 (5a , R ) Me; 5b, R ) Et) as dark
brown crystals (3-7%), Cp6Cr8S8(η1:η2-S2CNR2)2 (6) as dark crystals (7-14%), Cr(η2-S2CNR2)3
(7) as dark blue crystals (16-21%), Cp2Cr2(CO)4S as dark green crystals (1-3%), and Cp4-
Cr4S4 (12-22%) as dark green solids. The crystal structures of 2-6 were reported.
Unprecedented bridging modes were found in the double cubanes: in 5, two Cr4S4 cubane
clusters were linked by a µ-η2:η4-dithiooxamide ligand as well as a Cr-Cr bridge with bond
distances of 3.101 and 3.118 Å in the two independent molecules of the compound, and in 6,
the cubanes were linked by two µ-η1:η2-dithiocarbamate ligands.
1. In tr od u ction
contrast to the plethora of coordination compounds
known.5 In fact, only a few cyclopentadienyl dithiocar-
bamate complexes have been reported, viz. the much-
investigated Fe complex CpFe(CO)2(S2CNR2) (R ) Me,
Et),6 the analogous complexes of Mo and W,6a,7 and some
recently reported Ru complexes.8 Considering that there
exists much current interest in dithiocarbamate com-
plexes as precursors to metal sulfides,9 this investiga-
tion is timely. In the course of this study, a preliminary
communication has been published;10 this paper de-
scribes the comprehensive results, which include nu-
merous new cyclopentadienylchromium complexes.
We have been interested in the cleavage of S-S bonds
in inorganic1 and organic substrates2 by [CpCr(CO)3]2
(Cp ) η5-C5H5). Recently we encountered very facile
reactions with the thiophosphorus compounds bis-
3a
(diphenylthiophosphinyl)disulfane Ph2P(S)SSP(S)Ph2
and the analogous bis(thiophosphoryl)disulfane (RO)2P-
(S)SSP(S)(OR)2 (R ) i-Pr).3b At the same time, we have
initiated a study with the tetraalkylthiuram disulfides
R2NC(S)SSC(S)NR2 (R ) Me, Et, i-Pr). It is anticipated
that the reaction will lead to metal dithiocarbamates4
and contribute to the organometallic chemistry of this
class of compounds, in particular of cyclopentadienyl-
metal complexes, which to date remain scarce, in
2. Exp er im en ta l Section
2.1. Gen er a l P r oced u r es. All reactions were carried out
using conventional Schlenk techniques under an inert atmo-
sphere of nitrogen or under argon in an M. Braun Labmaster
130 inert gas system. NMR spectra were measured on a
† E-mail: chmgohly@nus.edu.sg. Fax: (65) 6779 1691.
(1) Goh, L. Y. Coord. Chem. Rev. 1999, 185-186, 257 and references
therein.
(2) (a) Goh, L. Y.; Tay, M. S.; Mak, T. C. W.; Wang, R.-J . Organo-
metallics 1992, 11, 1711. (b) Goh, L. Y.; Tay, M. S.; Lim, Y. Y.; Mak,
T. C. W.; Zhou, Z.-Y. J . Chem. Soc., Dalton Trans. 1992, 1239. (c) Goh,
L. Y.; Tay, M. S.; Chen, W. Organometallics 1994, 13, 1813.
(3) (a) Goh, L. Y.; Leong, W. K.; Leung, P. H.; Weng, Z.; Haiduc, I.
J . Organomet. Chem. 2000, 607, 64. (b) Goh, L. Y.; Weng, Z.; Leong,
W. K.; Haiduc, I.; Lo, K. M.; Wong, R. C. S. J . Organomet. Chem. 2001,
631, 67.
(6) (a) Cotton, F. A.; McCleverty, J . A. Inorg. Chem. 1964, 3, 1398.
(b) O’Connor, C.; Gilbert, J . D.; Wilkinson, G. J . Chem. Soc. (A) 1969,
84. (c) Roma´n, E.; Catheline, D.; Astruc, D. J . Organomet. Chem. 1982,
236, 229. (d) Catheline, D.; Roma´n, E.; Astruc, D. Inorg. Chem. 1984,
23, 4508.
(7) (a) Alper, H.; Einstein, F. W. B.; J ones, R. H.; Hartstock, F. W.
Organometallics 1987, 6, 829. (b) Shi, Y.; Cheng, G.; Lu, S.; Guo, H.;
Wu, Q.; Huang, X.; Hu, N. J . Organomet. Chem. 1993, 455, 115. (c)
Abrahamson, H. B.; Freeman, M. L.; Hossain, M. B.; van der Helm,
D. Inorg. Chem. 1984, 23, 2286.
(8) (a) Harlow, K. J .; Hill, A. F.; Welton, T.; White A. J . P.; Williams,
D. J . Organometallics 1998, 17, 1916. (b) Buriez, B.; Cook, D. J .;
Harlow, K. J .; Hill, A. F.; Welton, T.; White, A. J . P.; Williams, D. J .;
Wilton-Ely, J . D. E. T. J . Organomet. Chem. 1999, 578, 264.
(9) (a) Cheon, J .; Kang, H.-K.; Zink, J . I. Coord. Chem. Rev. 2000,
200-202, 1009. (b) Cheon J .; Zink, J . I. J . Am. Chem. Soc. 1997, 119,
3838.
(4) Victoriano, L. I. Coord. Chem. Rev. 2000, 196, 383 and references
cited therein.
(5) (a) Thorn, G. D.; Ludwig, R. A. The Dithiocarbamates and
Related Compounds; Elsevier: Amsterdam, 1962. (b) Livingstone, S.
E. Q. Rev. Chem. Soc. 1965, 19, 416. (c) Brinkhoff, H. C.; Cras, J . A.;
Steggarda, J . J .; Willemse, J . Recl. Trav. Chim. Pays-Bas 1969, 88,
633. (d) Brinkhoff, H. C.; Matthijssen, A. G.; Oomes, C. G. Inorg. Nucl.
Chem. Lett. 1971, 7, 87. (e) Coucouvanis, D. Prog. Inorg. Chem. 1970,
11, 233; 1979, 26, 301. (f) Eisenberg, R. Prog. Inorg. Chem. 1970, 12,
295. (g) Willemse, J .; Cras, J . A.; Steggerda, J . J .; Keijzers, C. P. Struct.
Bonding (Berlin) 1976, 28, 83. (h) Fackler, J . P. Adv. Chem. Ser. 1976,
No. 150, 394. (i) Bond, A. M.; Martin, R. L. Coord. Chem. Rev. 1984,
54, 23.
(10) Goh, L. Y.; Weng, Z.; Leong, W. K.; Leung, P. H. Angew. Chem.,
Int. Ed. 2001, 40, 3236.
10.1021/om0202930 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 09/14/2002

Cyclopentadienylchromium Dithiocarbamate Complexes
Organometallics, Vol. 21, No. 21, 2002 4399
Bruker 300 MHz FT NMR spectrometer (1H at 300.14 MHz
and 13C at 75.43 MHz); 1H chemical shifts were referenced to
residual C6H6 in C6D6 and 13C chemical shifts to the triplet of
C6D6. IR spectra in Nujol mulls or KBr pellets were measured
in the range 4000-400 cm-1 on a BioRad FTS-165 FTIR
instrument. Mass spectra were obtained on a Finnigan Mat
95XL-T spectrometer. Elemental analyses were performed by
the microanalytical laboratory in house. [CpCr(CO)3]2 (1) was
synthesized as described by Manning11 from chromium hexac-
arbonyl (98% purity from Fluka). The tetraalkylthiuram
disulfides [R2NC(S)S]2 (98% purity) were obtained commer-
cially and used as supplied (for R ) Me, Et, from Fluka; for R
) i-Pr, from Aldrich). All solvents were dried over sodium/
benzophenone and distilled before use. Silica gel (Merck
Kieselgel 60, 230-400 mesh) was dried at 140 °C overnight
before chromatographic use.
solid (18 mg). Similarly for R ) Et and i-Pr were isolated
analogous complexes, the yields of which are indicated in
Scheme 1.
(c) At -29 °C. A deep green solution of 1 (40 mg, 0.10 mmol)
in 2 mL of toluene was added to a solution of [Me2NC(S)S]2
(24 mg, 0.10 mmol) in 1 mL of toluene in a test tube, and the
dark green mixture was immediately kept at -29 °C. After 3
days, a mixture of red needle-shaped crystals of CpCr(CO)3-
(η1-S2CNMe2) (2a ) and fine dark red crystals of CpCr(CO)2-
(η2-S2CNMe2) (3a ) was collected. Crystals of 2a (28 mg, 0.087
mmol, 44% yield) were physically separated from 3a under
the microscope.
The analogous 2b and 2c complexes were detected in proton
NMR spectra of product solutions, in an admixture with 3b
and 3c, respectively, and considering the difficulty of isolating
2a , no attempt has been made to isolate them.
(d ) Solid Sta te Rea ction . A deep green mixture of 1 (20
mg, 0.05 mmol) and [Me2NC(S)S]2 (12 mg, 0.05 mmol) was
ground in a mortar at ambient temperature for ca. 20 min;
the mixture slowly turned red. After 16 h, IR and NMR
spectral examination showed total conversion to CpCr(CO)2-
(η2-S2CNMe2) (3a ).
2.2. Rea ction s of [Cp Cr (CO)3]2 (1) w ith Tetr a a lk ylth i-
u r a m Disu lfid es, [R2NC(S)S]2. (a ) At Am bien t Tem p er a -
tu r e. A deep green mixture of [CpCr(CO)3]2 (1) (121 mg, 0.30
mmol) and [R2NC(S)S]2 (0.30 mmol; 72, 89, and 106 mg for R
) Me, Et, i-Pr, respectively) in toluene (8 mL) was stirred at
ambient temperature for 1 h. The resultant dark red product
solution was filtered, although there was no visible residue.
Concentration of the filtrate to 3 mL followed by addition of
n-hexane (ca. 2 mL) and subsequent overnight cooling at -29
°C gave air-stable dark red crystals of CpCr(CO)2(η2-S2CNR2)
(R ) Me (3a ), 151 mg, 0.52 mmol, 86% yield; R ) Et (3b), 167
mg, 0.52 mmol, 87% yield; R ) i-Pr (3c), 171 mg, 0.49 mmol,
82% yield).
(e) Da ta . Com p ou n d 2a . IR (KBr, cm-1): ν(CO) 2028 m,
1
1994 sh, 1969 s; ν(CN) 1531 m; ν(CS) 970 m. H NMR (C6D6):
δ 4.21 (s, 5H, C5H5), 3.26 (6H, CH3). 13C NMR (C6D6): δ 91.7
(C5H5), 47.3 (CH3), 194.1 (CS2), 251.1 (CO), 237.8 (CO). Anal.
Calcd for C11H11CrNO3S2: C, 41.1; H, 3.5. Found: C, 40.4; H,
3.8. MS FAB+ (m/z): 322 [M + H]+, 293 [M - CO]+, 265 [M -
2CO]+, 237 [M - 3CO]+.
Com p ou n d s 2b,c. These were detected in the proton NMR
(b) At 90 °C. A deep green mixture of 1 (201 mg, 0.50 mmol)
and [R2NC(S)S]2 (0.50 mmol; 120, 148, and 176 mg for R )
Me, Et, i-Pr, respectively) in toluene (10 mL) was stirred at
90 °C for 2 h. The resultant dark brown reaction mixture was
filtered, to remove deep blue solids of Cr(η2-S2CNR2)3 (R ) Me
(7a ), 15 mg, 0.036 mmol, 4% yield; R ) Et (7b), 21 mg, 0.042
mmol, 4% yield) or dark red solids of CpCr(CO)2(η2-S2CNR2)
(R ) i-Pr (3c), 31 mg, 0.089 mmol, 9% yield). The filtrate was
then concentrated to ca. 4 mL and loaded onto a silica gel
column (2.5 × 16 cm) prepared in n-hexane. A typical
chromatographic workup is described for R ) Me as follows.
Elution gave seven fractions (i) A yellow eluate in n-hexane/
toluene (2:1, 5 mL) was obtained, which on concentration gave
deep green crystalline solids of Cp2Cr2(CO)4S (3 mg, 0.008
mmol, 2% yield), identified by its color characteristics and its
Cp proton resonance in benzene-d6 at δ 4.36.1 (ii) A dark red
eluate in n-hexane/toluene (3:1, 10 mL) was then obtained,
which on concentration gave dark red crystalline solids of
CpCr(CO)2(η2-S2CNMe2) (3a ) (44 mg, 0.15 mmol, 15% yield).
(iii) A brown eluate in toluene (10 mL) was obtained, from
which was isolated dark brown solids (54 mg), the 1H NMR
spectra of which indicated the presence of a 1:2 molar mixture
of Cp4Cr4S4 and 4a . The mixture was extracted with n-hexane/
toluene (1:1, 3 × 3 mL), leaving behind on the walls of the
flask a dark green solid of Cp4Cr4S4 (ca. 19 mg, 13% yield).
The combined extracts were concentrated to dryness, yielding
dark red crystalline solids of CpCr(CO)2(η2-SCNMe2) (4a ) (29
mg, 0.11 mmol, 11% yield). (iv) A red brown eluate in toluene
(5 mL) was obtained, from which was isolated brown solids of
Cp6Cr8S8(µ-η2:η4-SCNMe2)2 (5a ) (4 mg, 0.003 mmol, 3% yield).
(v) A brown eluate in toluene (10 mL) was obtained, from
which was isolated a brown solid of Cp6Cr8S8(µ-η1:η2-S2-
CNMe2)2 (6a ) (12 mg, 0.01 mmol, 7% yield). (vi) A blue eluate
in THF (20 mL) was obtained, which on concentration yielded
dark blue crystalline solids of Cr(η2-S2CNMe2)3 (7a ) (85 mg,
0.21 mmol, 21% yield). FAB+ mass spectrum: m/z 412 [M+],
292 [Cr(S2CNMe2)2]. (vii) A dark brown eluate in THF (10 mL)
was obtained, from which was isolated a dark unidentified
1
spectra and were not isolated. H NMR for 2b (C6D6): δ 4.19
(s, 5H, C5H5), 3.91 (q, J ) 7 Hz, 4H, CH2), 1.13 (t, J ) 7 Hz,
1
6H, CH3). H NMR for 2c (C6D6): δ 4.19 (s, C5H5).
Com p ou n d 3a . IR (KBr, cm-1): ν(CO) 1934 vs, 1864 vs;
ν(CN) 1532 m; ν(CS) 821 s; ν(NC2) 1152 m. 1H NMR (C6D6):
δ 4.58 (s, 5H, C5H5), 2.40 (s, 6H, CH3). 13C NMR (C6D6): δ
93.0 (C5H5), 37.2 (CH3), 204.1 (CS2), 267.3 (CO). Anal. Calcd
for C10H11CrNO2S2: C, 41.0; H, 3.8; N, 4.8. Found: C, 41.0;
H, 3.7; N, 4.6. MS FAB+ (m/z): 293 [M]+, 265 [M - CO]+, 237
[M - 2CO]+.
Com p ou n d 3b. IR (KBr, cm-1): ν(CO) 1935 vs, 1874 s, sh,
1858 vs; ν(CN) 1503 s; ν(CS) 828 s; ν(NC2) 1150 m. IR(toluene,
1
cm-1): ν(CO) 1952 s, 1884 s. H NMR (C6D6): δ 4.60 (s, 5H,
C5H5), 3.16 and 3.13 (each q (unres), J ) 7 Hz, CH2), 0.73 (t,
J ) 7 Hz, 6H, CH3). 13C NMR (C6D6): δ 93.1 (C5H5), 43.1 (CH2),
13.0 (CH3), 203.5 (CS2), 267.4 (CO). Anal. Calcd for C12H15
-
CrNO2S2: C, 44.9; H, 4.7; N, 4.4. Found: C, 44.5; H, 4.7; N,
4.4. MS FAB+ (m/z): 321 [M]+, 265 [M - 2CO]+.
Com p ou n d 3c. IR (KBr, cm-1): ν(CO) 1936 vs, 1864 vs;
1
ν(CN) 1487 s; ν(CS) 822 s; ν(NC2) 1048 m. H NMR (C6D6): δ
4.61 (s, 5H, C5H5), 4.22 (br, ν1/2 ) 84 Hz, 2H, CH), 1.03 (s,
12H, CH3). 13C NMR (C6D6): δ 93.0 (C5H5), 49.9 (CH), 20.4
(CH3), 204.6 (CS2), 267.2 (CO). Anal. Calcd for C14H19
-
CrNO2S2: C, 48.1; H, 5.5; N, 4.0. Found: C, 48.3; H, 5.5; N,
4.0. MS FAB+ (m/z): 349 [M]+, 293 [M - 2CO]+.
Com p ou n d 4a . IR (KBr, cm-1): ν(CO) 1928 vs, 1858 s, sh,
1839 vs; ν(CN) 1570 m; ν(CS) 821 m; ν(NC2) 1170 m. IR
(toluene, cm-1): ν(CO) 1954 s, 1868 s. 1H NMR (C6D6): δ 4.42
(s, 5H, C5H5), 3.10 (s, 3H, CH3), 2.71 (s, 3H, CH3). 13C NMR
(C6D6): δ 91.1 (C5H5), 49.1 (CH3), 45.5 (CH3), 255.8 (CdCr),
254.0 (CO), 251.4 (CO). Anal. Calcd for C10H11CrNO2S: C, 46.0;
H, 4.2; N, 5.4. Found: C, 46.3; H, 4.3; N, 5.0. MS FAB+ (m/z):
261 [M]+, 205 [M - 2CO]+.
Com p ou n d 4b. IR (KBr, cm-1): ν(CO) 1943 vs, 1855 vs;
1
ν(CN) 1537 m; ν(CS) 819 m; ν(NC2) 1197 m. H NMR (C6D6):
δ 4.45 (s, 5H, C5H5), 3.89 (br, ν1/2 ) 30 Hz, 1H, CH2), 3.72 (br,
ν1/2 ) 30 Hz, 1H, CH2), 3.25 (q, br, J ) 7 Hz, 2H, CH2), 0.99 (t,
J ) 7 Hz, 3H, CH3), 0.82 (t, J ) 7 Hz, 3H, CH3). 13C NMR
(C6D6): δ 91.2 (C5H5), 54.6 (CH2), 52.2 (CH2), 14.4, (CH3), 13.1
(CH3), 254.5 (CdCr), 253.5 (CO), 251.7 (CO). MS FAB+ (m/z):
(11) Manning, A. R.; Hackett, P.; Birdwhistell, R.; Soye, P. Inorg.
Synth. 1990, 28, 148.
289 [M]+, 233 [M - 2CO]+. HR-MS FAB+ (m/z): for [C12H15
-

4400 Organometallics, Vol. 21, No. 21, 2002
Goh et al.
Sch em e 1a
a
Legend: (#) detected in solution; (*) the six Cr-Cr bonds in each of the cubanes are omitted for clarity.
CrNO2S] 289.0222 (found), 289.0229 (calcd). This compound
was an oil (mp -29 °C). No satisfactory elemental analysis
was obtained. The proton NMR spectrum of a pure sample is
given as Supporting Information.
J ) 7 Hz, 4H, CH2), 3.21 (q, J ) 7 Hz, 4H, CH2), 1.21 (t, J )
7 Hz, 12H, CH3). 13C NMR (C6D6): δ 92.2 (C5H5), 91.9 (C5H5),
91.5 (C5H5), 91.4 (C5H5), 48.6 (CH2), 14.0 (CH3). Anal. Calcd
for C40H50Cr8N2S10‚C4H8O: C, 38.7; H, 4.3; N, 2.1. Found: C,
39.0; H, 4.3; N, 2.2. MS FAB+ (m/z): 1295 [M]+, 1063 [Cp6-
Cr8S8]+, 531 [Cp3Cr4S4]+.
Com p ou n d 4c. IR (KBr, cm-1): ν(CO) 1944 vs, sh, 1932
vs, 1866 vs, 1838 vs; ν(CN) 1537 s; ν(CS) 820 m; ν(NC2) 1147
1
m. IR (toluene, cm-1): ν(CO) 1948 s, 1861 s. H NMR (C6D6):
5c was not detected in the proton NMR spectrum of the
product solution.
δ 4.46 (s, 5H, C5H5), 5.37 (septuplet, J ) 7 Hz, 1H, CH), 3.35
(septuplet, J ) 7 Hz, 1H, CH), 1.14 (d, J ) 7 Hz, 6H, CH3),
0.89 (d, J ) 7 Hz, 6H, CH3). 13C NMR (C6D6): δ 91.2 (C5H5),
63.8 (CH), 52.3 (CH), 20.8 (CH3), 20.5 (CH3), 254.8 (CdCr),
252.0 (CO), 245.5 (CO). Anal. Calcd for C14H19CrNO2S: C, 53.0;
H, 6.0; N, 4.4. Found: C, 53.5; H, 6.4; N, 4.5. MS FAB+ (m/z):
317 [M]+, 261 [M - 2CO]+, 117 [CrCp]+, 52 [Cr]+.
Com p ou n d 6a . IR (Nujol, cm-1): ν(CN) 1572 m; ν(CS) 801
1
s; ν(NC2) 1151 m. H NMR (C6D6): δ 5.24 (s, 30H, C5H5), 2.95
(s, 12H, CH3). 13C NMR (C6D6): δ 92.0 (C5H5), 40.8 (CH3). Anal.
Calcd for C36H42Cr8N2S12‚3/4C7H8: C, 36.1; H, 3.5; N, 2.1.
Found: C, 35.9; H, 3.6, N, 2.6. MS FAB+ (m/z): 651 1/2[M]+,
586 [Cp2Cr4S4(S2CNMe2)]+, 531 [Cp3Cr4S4]+.
1
Com p ou n d 5a . H NMR (C6D6): δ 5.19 (s, 5H, C5H5), 5.15
Com p ou n d 6b. IR (KBr, cm-1): ν(CN) 1495 s; ν(CS) 801 s;
ν(NC2) 1145 m. 1H NMR (C6D6): δ 5.09 (br, ν1/2 ) 22 Hz, 30H,
C5H5), 3.55 (d, J ) 7 Hz, 8H, CH2), 0.95 (t, J ) 7 Hz, 12H,
CH3). VT 1H NMR (C6D5CD3, 223 K): δ 5.40 (s, 10H, C5H5),
5.28 (s, 10H, C5H5), 5.06 (s, 10H, C5H5). 13C NMR (C6D6): δ
(s, 10H, C5H5), 5.07 (s, 10H, C5H5), 5.03 (s, 5H, C5H5), 2.88 (s,
12H, CH3). The 1H NMR spectrum of a sample is given in
Supporting Information.
Com p ou n d 5b. IR (KBr, cm-1): ν(CN) 1434 m; ν(CS) 802
1
s; ν(NC2) 1115 w. H NMR (C6D6): δ 5.20 (s, 5H, C5H5), 5.14
91.7 (C5H5), 45.5 (CH2), 13.5 (CH3). Anal. Calcd for C40H50
-
(s, 10H, C5H5), 5.08 (s, 10H, C5H5), 5.06 (s, 5H, C5H5), 3.44 (q,
Cr8N2S12‚1/2C6H14: C, 36.8; H, 4.1; N, 2.0. Found: C, 37.1; H,

Cyclopentadienylchromium Dithiocarbamate Complexes
Organometallics, Vol. 21, No. 21, 2002 4401
4.2; N, 1.2. MS FAB+ (m/z): 679 1/2[M]+, 614 [Cp2Cr4S4(S2-
CNEt2)]+, 563 [Cp2Cr3S4(S2CNEt2)]+, 531 [Cp2Cr3S3(S2CNEt2)]+.
Com p ou n d 6c. IR (KBr, cm-1): ν(CN) 1483 s; ν(CS) 802 s;
ν(NC2) 1149 m. 1H NMR (C6D6): δ 5.39 (br, ν1/2 ) 55 Hz, 30H,
C5H5), 1.24 (br, ν1/2 ) 52 Hz, 24H, CH3). VT 1H NMR (C6D5-
CD3, 223 K): δ 5.39 (s, 10H, C5H5), 5.27 (s, 10H, C5H5), 5.11
(s, 10H, C5H5). 13C NMR (C6D6): δ 91.6 (C5H5), 52.3 (CH), 20.9
(CH3). Anal. Calcd for C44H58Cr8N2S12‚1/2C7H8: C, 39.0; H, 4.3;
N, 1.9. Found: C, 39.2; H, 4.6; N, 1.9. MS FAB+ (m/z): 707
1/2[M]+, 642 [Cp2Cr4S4(S2CN-i-Pr2)]+.
2.3. Th er m olysis of Cp Cr (CO)2(η2-S2CNR2) (3) a t 90 °C.
Red solutions of CpCr(CO)2(η2-S2CNR2) (R ) Me (3a ), 117 mg,
0.40 mmol; R ) Et (3b), 289 mg, 0.90 mmol; R ) i-Pr (3c), 87
mg, 0.25 mmol) in toluene (8 mL) was stirred at 90 °C for 2 h.
The workup of this product solution, as described in section
2.2, gave the same complexes in similar yields, in addition to
some recovered starting material (3a , 27%; 3b, 19%; 3c, 18%).
2.4. NMR Tu be Rea ction s. The following reactions were
monitored in septum-capped 5 mm tubes under argon via 1H
NMR spectral analysis for purposes of detection of intermedi-
ates and/or products.
carried out with the SHELXTL suite of programs.14 The
structure was solved by direct methods to locate the heavy
atoms, followed by difference maps for the light, non-hydrogen
atoms. The Cp and alkyl hydrogens were placed in calculated
positions. Data collection and processing parameters are given
in Table 1.
3. Resu lts a n d Discu ssion
3.1. Rea ction of [Cp Cr (CO)3]2 (1) w ith [R2NC-
(S)S]2 (R ) Me, Et, i-P r ). At ambient temperature, a
deep green suspension of [CpCr(CO)3]2 (1) in toluene
reacted with 1 mol equiv of tetraalkylthiuram disulfide
[R2NC(S)S]2 (R ) Me, Et, i-Pr) within 1 h, giving dark
red solutions, from which were obtained in high yields
air-stable dark red crystals of CpCr(CO)2(η2-S2CNR2)
(3), as shown in Scheme 1. This reaction also proceeded
between the reactants in the solid state. When the
progress of the reaction was monitored via time-depend-
ent proton NMR spectral scans, it was observed that 3
was formed either concurrently with or via the inter-
mediate compound CpCr(CO)3(η1-S2CNR2) (2), which
converted to 3 within 2-3 h at ambient temperature.
This slower rate of conversion in a sealed NMR tube is
in agreement with suppression of the reaction by the
released carbon monoxide. Indeed, red needle-shaped
crystals of 2a in an approximately 1:1 admixture with
fine crystals of 3a were obtained after mixing the
reactants and keeping the solution at -29 °C for 3 days.
At 90 °C for 2 h, the reaction led to the isolation of 3
together with CpCr(CO)2(η2-SCNR2) (4) as dark red
crystals (R ) Me, i-Pr) or a dark red oil (R ) Et), Cp6-
Cr8S8(η2:η4-SCNR2)2 (5) as dark brown crystals, Cp6-
Cr8S8(η1:η2-S2CNR2)2 (6) as dark brown crystals, Cr(η2-
S2CNR2)3 (7) as dark blue crystals, Cp2Cr2(CO)4S as
dark green crystals, and Cp4Cr4S4 as deep green solids,
with yields as presented in Scheme 1. A similar product
composition was obtained from a thermolytic degrada-
tion of 3 at 90 °C for 2 h.
(a ) Rea ction of [Cp Cr (CO)3]2 (1) w ith [R2NC(S)S]2. A
deep green mixture of [CpCr(CO)3]2 (1) (8 mg, 0.02 mmol) and
[R2NC(S)S]2 (R ) Me, 5 mg; R ) Et, 6 mg; R ) i-Pr, 7 mg) in
1
benzene-d6 (0.5 mL) was shaken up for 2 min and then its H
NMR spectrum scanned at intervals, to monitor the time-
dependent change in the relative concentration of complexes
2 and 3. This was found to be as follows (time in min (relative
concentration)): R ) Me, 5 (2:1), 10 (3:2), 40 (5:6), 60 (1:3),
and 180 (1:50); R ) Et, 5 (2:1), 10 (1:1), 15 (3:4), 30 (1:4), 60
(1:9), and 120 (1:100); R ) i-Pr, 5 (1:1), 10 (1:4), 20 (1:6), 30
(1:7), 60 (1:8), and 120 (1:50).
(b) Rea ction of [Cp Cr (CO)2]2(Cr tCr ) w ith [Et2NC-
(S)S]2. A deep green mixture of [CpCr(CO)2]2(CrtCr) (7 mg,
0.02 mmol) and [Et2NC(S)S]2 (6 mg, 0.02 mmol) in benzene-
d6 (0.5 mL) was shaken up for 10 min and then its 1H NMR
spectrum scanned at intervals (10 min, 120 min, 100 h).
(c) Rea ction of Cp 4Cr 4S4 w ith [i-P r 2NC(S)S]2 a t 80 °C.
A dark green mixture of Cp4Cr4S4 (12 mg, 0.02 mmol) and
[i-Pr2NC(S)S]2 (3.5 mg, 0.01 mmol) in benzene-d6 (0.5 mL) was
maintained at ca. 80 °C for 1 h, and its 1H NMR spectrum
was scanned.
3.2. Rea ction P a th w a ys. The reaction pathways are
illustrated in Scheme 1. In view of the facile dissociation
of the Cr dimer (1) into the monomeric 17-electron
radical species,15 and the known susceptibility of the
S-S bond in organic disulfides to cleavage by nucleo-
philic, electrophilic, and radical processes,16 it is con-
ceivable that the reaction is initiated by the attack of
CpCr(CO)3 on the S-S bond of thiuram disulfide, as
shown in eq i, forming the complex 2, which contains a
(d ) Th er m olysis of Cp Cr (CO)2(SCNEt2) (4b). A red
solution of CpCr(CO)2(SCNEt2) (4b) (9 mg, 0.03 mmol) in
toluene-d8 (0.5 mL) in a septum-capped 5 mm NMR tube under
argon was maintained at ca. 110 °C, and its proton NMR
spectrum was scanned at intervals of 2 h.
(e) Th er m olysis of Cp 6Cr 8S8(S2CNEt2)2 (6b). A red-brown
solution of Cp6Cr8S8(S2CNEt2)2 (6b) (4 mg, 0.003 mmol) in
benzene-d6 (0.5 mL) was maintained at ca. 80 °C, and its 1H
NMR spectrum was monitored at intervals (30, 60, and 120
min).
2.5. Cr ystal Str u ctu r e An alyses. Diffraction-quality single
crystals were obtained from solutions in toluene layered with
hexane at -29 °C as follows: 2a as red needles as described
in section 2.2, 3a as a dark red rhombus after 3 days, 3b as
dark red prisms after 2 days, 3c as dark red needles after 2
days, 4a ,c as dark red rhombuses after 7 and 5 days,
respectively, 6b,c as dark blue rhombuses after 5 and 8 days,
respectively, and 5b as a dark blue rhombus by diffusion of
n-hexane into a THF solution after 7 days.
The crystals were mounted on quartz fibers. X-ray data were
collected on a Siemens SMART diffractometer, equipped with
a CCD detector, using Mo KR radiation (λ ) 0.710 73 Å).
The data were corrected for Lorentz and polarization effcts
with the SMART suite of programs12 and for absorption effects
with SADABS.13 Structure solution and refinement were
monodentate dithiocarbamate ligand. A terminating
(14) SHELXTL, version 5.03; Siemens Energy & Automation Inc.,
Madison, WI.
(15) (a) Review: Baird, M. C. Chem. Rev. 1988, 88, 1217 and
references therein. (b) McLain, S. J . J . Am. Chem. Soc. 1988, 110, 643.
(c) Goh, L. Y.; Lim, Y. Y. J . Organomet. Chem. 1991, 402, 209. (d) Goh,
L. Y.; Khoo, S. K.; Lim, Y. Y. J . Organomet. Chem. 1990, 399, 115.
(16) Kice, J . L. In Sulfur in Organic and Inorganic Chemistry;
Senning, A., Ed.; Marcel Dekker: New York, 1971; Vol. 1, p 153.
(12) SMART, version 4.05; Siemens Energy & Automation Inc.,
Madison, WI.
(13) Sheldrick, G. M. SADABS, 1996.

4402 Organometallics, Vol. 21, No. 21, 2002
Goh et al.

Cyclopentadienylchromium Dithiocarbamate Complexes
Organometallics, Vol. 21, No. 21, 2002 4403
(eq iii). A few examples of this occurrence have been
F igu r e 1. Intermediate A.
step involving direct coupling of the CpCr and the
dithio-organic radicals will also generate 2 (eq ii). The
reported, viz. at Re,19 Ru,20 Rh,21 Mo,22 and W,23 though
thiocarbamoyl complexes are commonly synthesized by
oxidative addition of R2NC(S)X (eq iv), a method em-
radical initiation step had been postulated before for the
reaction of 1 with Ph2E2 (E ) S, Se, Te), which gave
rise to complexes containing η1-EPh and η2-EPh ligands,2
and for the scission of the S-S bonds in bis(thiophos-
phinyl) and bis(thiophosphoryl) disulfanes.3 A similar
mechanism had been demonstrated by Abrahamson and
Helm for the reaction of [CpW(CO)3]2 with tetrameth-
ylthiuram disulfide, in which case the W monomeric
species was generated by visible irradiation of the
dimer.7c A subsequent facile dissociation of a CO ligand
from 2 is accompanied by chelation of the ligand to
produce 3, without violation of the 18-electron rule,
considering the monodentate and bidentate ligands as
one- and three- electron donors, respectively. While this
process was found to occur readily at ambient temper-
ature, the same transformation in the W analogue7c and
in CpFe(CO)2(η1-S2CNR2)17 required higher energy ac-
tivation, e.g. thermolysis, photolysis, or electron-transfer
catalysis. The Mo analogue of 3 had been obtained from
the reaction of thiuram disulfide with [CpMo(CO)3]2 in
refluxing methylcyclohexane (101 °C) after 18 h6a or
with the triply bonded Mo dimer [CpMo(CO)2]2 at
ambient temperature after 16 h.7a Alper proposed for
both of these reactions an initial coordination of the Mo
atoms in the MotMo species to the sulfur atoms of the
ligand, generating the intermediate A (Figure 1), prior
to S-S and Mo-Mo bond cleavages. In our case,
however, we found [CpCr(CO)2]2(CrtCr) to be rather
sluggish toward thiuram disulfide, with a half-life on
the order of 60 h at ambient temperature; also, we saw
no evidence of a species of the nature of A in the time-
dependent proton NMR spectral scans of the reaction
mixture.
ployed by Kreissl for Mo and W complexes,24 by Weiss
for an Fe complex,22 and by Dean for Mo, Mn, and Fe
complexes.25 The thermal conversion of 3 to the double-
cubanes 5 and 6 is an unprecedented reactivity feature,
not observed before for the Mo or W analogues,7 even
though the synthesis of the latter complexes had also
involved thermolytic conditions. In fact, thermolytic
degradation of the cyclopentadienylchromium complex
3 gives rise to two classes of products, viz. complexes
containing the intact dithiocarbamate ligand, as in 6
and 7, and complexes in which the ligand has undergone
one C-S bond cleavage, as in 4 and 5. The structural
features of 5 show that its formation from 3 has involved
a single C-S bond cleavage cum C-C coupling, result-
ing in a metallacyclopropane moiety, i.e., Cr(5)C(1)C-
(2) in complex 5b. There exists a striking similarity
between the bridging component in 5 and the dithiolene
complexes B obtained by Lindner from the manganese-
induced reductive dimerization of the thioaroyl chlorides
RC(S)Cl, for which an unstable carbenoid intermediate
was proposed (eq v).26 However, in this study an NMR
The thermolytic degradation of 3 gave a multicom-
ponent mixture from which complexes 4-7 could be
isolated, together with the well-known cubane Cp4Cr4S4
and [CpCr(CO)2]2S1,18a in trace amounts. The formation
of the carbenoid complexes 4 from 3 involves the
cleavage of a S atom, resulting in the conversion of a
dithiocarbamate ligand to a thiocarboxamido ligand
(17) (a) Desbois, M. H.; Nunn, C. M.; Cowley, A. H.; Astruc, D.
Organometallics 1990, 9, 640. (b) Amatore, C.; Verpeaux, J .-N.;
Madonik, A.; Desbois, M. H.; Astruc, D. J . Chem. Soc., Chem. Commun.
1988, 200. (c) Verpeaux, J .-N.; Desbois, M.-H.; Madonik, A.; Amatore,
C.; Astruc, D. Organometallics 1990, 9, 630. (d) Desbois, M. H.; Astruc,
D. J . Chem. Soc., Chem. Commun. 1990, 943.
(18) (a) Goh, L. Y.; Hambley, T. W.; Robertson, G. B. Organometal-
lics 1987, 6, 1051. (b) Goh, L. Y.; Chen, W.; Wong, R. C. S.;
Karaghiosoff, K. Organometallics 1995, 14, 3886.
tube experiment showed that the carbenoid complex 4
was thermally stable in solution. Neither was 5 derived

4404 Organometallics, Vol. 21, No. 21, 2002
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles (d eg) for Com p lexes 2-4
Goh et al.
2a
3a
3b
3c
4a
4c
Bond Lengths
2.4240(6)
Cr(1)-S(1)
Cr(1)-S(2)
C(1)-S(1)
C(1)-S(2)
C(1)-N(1)
C(1)-Cr(1)
2.4406(5)
2.4209(6)
2.4266(6)
1.703(2)
1.709(2)
1.325(3)
2.4108(4)
2.4209(5)
1.7201(16)
1.7171(16)
1.3353(19)
2.4495(6)
1.675(2)
2.4188(9)
1.666(3)
2.4172(5)
1.7568(18)
1.6822(19)
1.340(2)
1.7058(19)
1.7116(19)
1.326(2)
1.301(3)
1.953(2)
1.306(3)
1.978(3)
Bond Angles
70.608(17)
89.70(6)
S(1)-Cr(1)-S(2)
C(1)-S(1)-Cr(1)
C(1)-S(2)-Cr(1)
S(1)-Cr(1)-C(1)
S(1)-C(1)-Cr(1)
S(1)-C(1)-S(2)
S(1)-C(1)-N(1)
S(2)-C(1)-N(1)
Cr(1)-C(1)-N(1)
C(1)-N(1)-C(2)
C(1)-N(1)-C(3)
C(2)-N(1)-C(3)
70.693(19)
89.54(7)
89.22(7)
70.333(14)
90.90(5)
90.63(5)
114.00(6)
52.53(7)
54.20(9)
89.79(7)
42.91(6)
84.56(9)
43.09(8)
82.72(13)
123.67(11)
113.70(13)
122.63(14)
-
123.31(17)
121.95(18)
114.71(18)
110.54(11)
124.25(16)
125.20(16)
-
120.55(19)
122.14(19)
117.2(2)
109.91(10)
125.47(15)
124.61(15)
-
121.39(18)
121.08(17)
117.47(17)
108.12(8)
124.29(12)
127.58(12)
-
118.48(13)
123.73(13)
117.60(12)
129.29(17)
-
146.04(16)
123.4(2)
121.24(19)
115.3(2)
132.9(2)
-
144.3(2)
123.7(2)
119.8(2)
116.4(2)
from thermolysis of the dithiocarbamate-bridged double
cubane 6 or thermal treatment of Cp4Cr4S4 with the
ligand. The following paper in this issue describes the
role of CpCr(CO)3 and/or CpCr(CO)2 in the formation
of 5 from 3 or Cr(η2-S2CNR2)3 (7), a known coordination
compound previously synthesized from the direct reac-
tion of Cr(III) salts with Na(S2CNR2)27 and one of the
thermolytic products of 3 in this study. The dissociation
of η5-Cp ligands from the metal atom, as evident in the
formation of 7 and also of 5, is not common but appears
to be facilitated in this system, as well as the related
complexes containing the bis(diphenylthiophosphinyl)-
disulfane and bis(thiophosphoryl)disulfane ligands.3 In
comparison, the Cp rings remain intact in the cubane
molecules Cp4Cr4X2Y2 (X ) S, Se; Y ) S, O, CO), often
encountered from the thermolysis of CpCr chalcogen
complexes.1
3.3. P r op er ties a n d Sp ectr a l Ch a r a cter istics. The
complexes 3-6, with the exception of 2b,c, 4b, and 5a ,c,
were fully characterized by microanalytical and spectral
data (see the Experimental Section). The compounds
2b,c were not isolated as solids and were characterized
by their proton NMR spectra. Microanalytical data were
lacking for 4b, which was an oil even at -29 °C. It was
not possible to purify the low-yield compound 5a , and
its presence was based on the resemblance of its Cp
proton NMR spectral characteristics to those of its
analogue 5b. The presence of 5c was not detected in
the proton NMR spectrum of the product solution. The
Cp proton resonances of the 18-electron mononuclear
complexes 2-4, all containing chromium in oxidation
state +2, are found in the range δ 4.19-4.61, within
the normal range observed for other CpCr moieties;1-3
likewise, the corresponding 13C{1H} resonances at δ
91.1-93.1 are in the normal range for diamagnetic
compounds. Other 13C resonances are observed for CO
at δ 237.8-267.4, for CS2 at δ 194.1-204.6, and for Cd
Cr at δ 254.5-255.8. The proton Cp resonances of the
60-electron double cubanes 5 and 6, containing chro-
mium in the +3 oxidation state, are observed at lower
field than the mononuclear complexes, viz. δ 5.06-5.20
for 5b and δ 5.06-5.40 for complexes 6a -c, but the
corresponding 13C peaks are found in the same region
as for the mononuclear compounds. The observation of
four Cp signals (relative intensity 1:2:2:1) in the mol-
ecule 5b is consistent with the structure of the mol-
ecule.10 The spectrum confirms the presence of two
cubane cores in different magnetic environments, each
possessing two equivalent Cp ligands different from a
third. Likewise in the carbon spectrum, four signals are
observed. In the dithiocarbamate-bridged double cubane
6, the Cp rings resonate as a single very broad peak at
room temperature, indicative of fluxionality, which is
often encountered with dithiocarbamate ligands.28 In
this case the fluxionality can be totally arrested at
temperatures of -55 °C and below, at which tempera-
tures three sharp signals can be observed for the three
Cp rings of each cubane, thus also providing evidence
for the equivalence of the two cubane cores. The IR
stretching frequencies for the CO ligands in the mono-
nuclear complexes are found in the normal carbonyl
region. The stretching frequencies of the dithiocarbam-
ate ligand in all the complexes fall in the range as
follows: ν(CN) between 1487 and 1570 cm-1, ν(CS)
between 819 and 828 cm-1 for the bidentate ligands,
and ν(NC2) between 1048 and 1197 cm-1
.
3.4. X-r a y Diffr a ction An a lyses. The molecular
structures of 2a , 3a -c, 4a ,c, 5b, and 6b,c have been
determined. The ORTEP diagrams are shown in Figures
2-6. Selected bond parameters are given in Table 2 for
the mononuclear complexes and Table 3 for the doube-
cubane complexes.
The structure of 2a (Figure 2) contains a CpCr moiety
bonded to a η1-dithiocarbamate and three CO ligands,
(19) Ichimura, A.; Yamamoto, Y.; Kajino, T.; Kitagawa, T.; Kuma,
H.; Kushi, Y. J . Chem. Soc., Chem. Commun. 1988, 1130.
(20) Miessler, G. L.; Pignolet, L. H. Inorg. Chem. 1979, 18, 210.
(21) Gal, A. W.; Van Der Ploeg, A. F. J . M.; Vollenbroek, F. A.;
Bosman, W. J . Organomet. Chem. 1975, 96, 123.
(22) Ricard, L.; Estienne, J .; Weiss, R. Inorg. Chem. 1973, 12, 2182.
(23) Brower, D. C.; Tonker, T. L.; Morrow, J . R.; Rivers, D. S.;
Templeton, J . L. Organometallics 1986, 5, 1093.
(24) Ogric, C.; Lehotkay, Th.; Wurst, K.; J aitner, P.; Kreissl, F. R.
J . Organomet. Chem. 1997, 541, 71.
(25) (a) Dean, W. K.; Treichel, P. M. J . Organomet. Chem. 1974,
66, 87. (b) Dean, W. K.; Wetherington, J . B.; Moncrief, J . W. Inorg.
Chem. 1976, 15, 1566. (c) Dean, W. K. J . Organomet. Chem. 1977, 135,
195.
(26) Lindner, E.; Butz, I. P.; Hoehne, S.; Hiller, W.; Fawzi, R. J .
Organomet. Chem. 1983, 259, 99.
(27) Sinn, E. Inorg. Chem. 1976, 15, 369; Raston, C. L.; White, A.
H. Aust. J . Chem. 1977, 30, 2091.
(28) Golding, R. M.; Healy, P. C.; Newman, P. W. G.; Sinn, E.; White,
A. H. Inorg. Chem. 1972, 11, 2435. Lindmark, A. F.; Fay, R. C. Inorg.
Chem. 1983, 22, 2000.

Cyclopentadienylchromium Dithiocarbamate Complexes
Organometallics, Vol. 21, No. 21, 2002 4405
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p lexes 5 a n d 6
5b
6b
6c
Bond Distances for the Bridging Ligand
3.101(6)
Cr(1)-Cr(5)
Cr(1)-S(9)
Cr(1)-S(10)
Cr(1)-S(11)
Cr(5)-S(9)
Cr(5)-S(11)
Cr(5)-S(12)
Cr(5)-C(1)
Cr(5)-C(2)
C(1)-S(9)
C(1)-S(10)
C(2)-S(11)
C(2)-S(12)
C(1)-C(2)
C(1)-N(1)
C(2)-N(2)
2.331(7)
2.495(9)
2.443(10)
2.552(10)
2.581(10)
2.505(9)
2.441(9)
2.4870(12)
2.4131(12)
2.5486(13)
2.5501(13)
2.4835(12)
2.4209(13)
2.340(8)
2.364(7)
2.469(7)
2.32(3)
2.45(2)
1.72(3)
1.77(3)
1.71(3)
1.78(3)
1.62(3)
1.769(4)
1.696(4)
1.775(4)
1.698(4)
1.81(2)
1.41(3)
1.44(3)
1.38(3)
1.37(3)
1.40(3)
1.322(5)
1.314(5)
F igu r e 2. Molecular structure of 2a . Thermal ellipsoids
are drawn at the 50% probability level.
Bond Angles for the Bridging Ligand
S(9)-Cr(1)-S(10)
S(9)-Cr(1)-S(11)
S(9)-Cr(5)-S(11)
S(11)-Cr(5)-S(12)
S(9)-Cr(5)-C(1)
S(11)-Cr(5)-C(2)
C(1)-Cr(5)-C(2)
Cr(1)-S(11)-Cr(5)
Cr(1)-S(9)-Cr(5)
C(1)-S(9)-Cr(1)
C(1)-S(10)-Cr(1)
S(9)-C(1)-Cr(5)
C(1)-S(9)-Cr(5)
C(2)-S(11)-Cr(1)
C(2)-S(12)-Cr(5)
S(9)-C(1)-S(10)
C(2)-C(1)-Cr(5)
S(10)-C(1)-N(1)
S(11)-C(2)-S(12)
C(1)-C(2)-Cr(5)
C(2)-S(11)-Cr(5)
S(11)-C(2)-Cr(5)
N(1)-C(1)-S(9)
N(2)-C(2)-Cr(5)
C(1)-C(2)-S(11)
N(2)-C(2)-S(11)
S(12)-C(2)-N(2)
C(2)-C(1)-S(9)
N(1)-C(1)-C(2)
N(2)-C(2)-C(1
71.5(3)
71.41(4)
71.44(4)
81.4(3)
78.1(2)
71.1(3)
43.1(6)
43.2(6)
34.4(8)
80.3(2)
82.7(2)
86.7(9)
99.2(3)
98.7(3)
86.7(9)
89.8(9)
98.34(4)
98.21(4)
86.47(15)
90.50(15)
69.8(9)
67.1(9)
109.1(8)
109.2(10)
112.0(10)
89.3(10)
112.12(14)
113.68(15)
90.36(15)
111.2(2)
112.1(15)
77.8(15)
127(2)
115.7(15)
125.8(3)
111.1(2)
F igu r e 3. Molecular structure of 3a . Thermal ellipsoids
are drawn at the 50% probability level.
67.8(14)
67.8(8)
69.0(8)
122.8(19)
135.0(17)
114.2(18)
115.5(17)
83.8(9)
121(2)
86.59(14)
122.9(3)
pounds, viz. in Pt(S2CN(tBu)2)2(PMe2Ph), Pt(S2CNEt2)-
(PPh3), Ru(S2CNEt2)3(NO), and Au(S2CNEt2)3.30 The
gross features of the structure of the molecules of 3a -c
are similar and are illustrated in Figure 3 for 3a . There
is present a CpCr unit bonded to a η2-dithiocarbamate
and two CO ligands, isostructural with CpMo(CO)2(η2-
S2CN(i-Pr)2).7a This bidentate bonding is the common
coordination mode in mononuclear thiocarbamate com-
plexes. The bond parameters of 3a -c are presented in
Table 2, together with those of the other mononuclear
complexes for comparison. The M-S bond distances,
ranging from 2.4108(4) to 2.4266(6) Å, are similar to
those reported for CpMo(CO)2(S2CN(i-Pr)2)2 (average
2.4965(1) Å)7a and CpMo(CO)2(S2CNMe2) (average 2.503-
(1) Å),7b allowing for the difference in atomic size
between Cr and Mo. The range of Cr-S distances for
the series of compounds 2-4 (2.4108(4)-2.4495(6) Å)
lie within the range observed for other CpCr com-
119(2)
125(2)
121.8(3)
126.9(3)
120.9(19)
114(2)
130(2)
113(3)
115(3)
C(1)-N(1)-C(111)
C(1)-N(1)-C(113)
124(3)
120(2)
115(3)
118(2)
127(3)
114(3)
121.8(4)
123.8(4)
114.4(4)
123.7(4)
121.3(4)
114.9(4)
C(111)-N(1)-C(113) 107(3)
C(2)-N(2)-C(121)
C(2)-N(2)-C(123)
119(2)
123(2)
C(121)-N(2)-C(123) 115(2)
Bond Distances for the Cr4S4 Cubes
Cr-S
2.208(7)-
2.264(7)
2.764(6)-
2.887(6)
2.218(11)- 2.2392(13)-
2.290(11)
2.783(8)-
2.926(7)
2.2776(13)
2.7955(10)-
2.9067(10)
Cr-Cr
Bond Angles for the Cr4S4 Cubes
98.6(2)- 97.5(4)-
104.1(3) 103.2(4)
S-Cr-S
97.94(5)-
102.67(5)
76.44(4)-
80.20(4)
Cr-S-Cr
Cr-Cr-Cr
75.4(2)-
79.2(3)
75.8(3)-
80.4(3)
(29) (a) Delville-Desbois, M.-H.; Mross, S.; Astruc, D.; Linares, J .;
Varret, F.; Rabaaˆ, H.; Le Beuze, A. ; Saillard, J .-Y.; Culp, R. D.; Atwood,
D. A.; Cowley, A. H. J . Am. Chem. Soc. 1996, 118, 4133. (b) Desbois,
M. H.; Astruc, D. Angew. Chem., Int. Ed. Engl. 1989, 28, 460. (c)
Roma´n, E.; Catheline, D.; Astruc, D.; Batail, P.; Ouahab, L.; Varret,
F. J . Chem. Soc., Chem. Commun. 1982, 129.
(30) (a) Lin, I. J . B.; Chen, H. W.; Fackler, J . P. J r. Inorg. Chem.
1978, 17, 394. (b) Fackler, J . P., J r.; Thompson, L. D.; Lin, I. J . B.;
Stephenson, T. A.; Gould, R. O.; Alison, J . M. C.; Fraser, A. J . Inorg.
Chem. 1982, 21, 2397. (c) Domenicano, A.; Vaciago, A.; Zambonelli,
L.; Loader, P. L.; Venanzi, L. M. J . Chem. Soc., Chem. Commun. 1966,
476. (d) Noordik, J . H. Cryst. Struct. Commun. 1973, 2, 81.
57.70(13)- 57.34(18)- 58.04(2)-
61.95(15) 61.88(18) 61.66(2)
similar to the W analogue discussed above.7c There is
only one other case known of η1-bonding in dithiocar-
bamate organometallic compounds, i.e., CpFe(CO)2(η1-
S2CNR2) and its Cp* analogues, which have been
extensively investigated by Astruc,17,29 though a few
examples have been reported for coordination com-

4406 Organometallics, Vol. 21, No. 21, 2002
Goh et al.
Ta ble 4. Bon d P a r a m eter s of th e Th ioca r boxa m id e Ca r ben oid MCS Un it in Rela ted Com p lexes (L )
(S)CNR2)
CpCr(CO)2L
(this work)
4a
42.91(6)
1.953(2)
1.675(2)
2.4495(6)
1.817(2), 1.849(2)
4c
CpW(CO)2L24
41.3(3)
2.098(10)
1.694(1)
2.552(3)
1.964(12), 1.929(11)
(HBPz3)Mo(CO)2L24
(Ph3P)Mn(CO)3L25b
C-M-S (deg)
M-C (Å)
43.09(8)
1.978(3)
1.666(3)
2.4188(9)
41.2(5)
2.09(2)
1.68(2)
2.531(5)
1.91(2), 1.81(3)
44.0(2)
1.924(6)
1.68(2)
2.404(3)
C-S (Å)
M-S (Å)
M-C(CO) (Å)
1.806(4), 1.816(4)
1.815(7), 1.784(0)
F igu r e 4. Molecular structure of 4a . Thermal ellipsoids
are drawn at the 50% probability level.
F igu r e 5. Molecular structure of 5b. Thermal ellipsoids
are drawn at the 50% probability level.
plexes that we have studied, i.e. 2.348-2.466 Å for
complexes containing bare S ligands,18a 2.486-2.517 Å
for complexes containing bare P/S ligands,18b 2.365(1)-
2.471(3) Å for complexes containing bridging SPh
ligands,2a and 2.3711(8)-2.517(8) Å for complexes con-
taining S2PR2 or S2P(OR)2 ligands.3 The C-S distances
in 3a -c (1.703(2)-1.7201(16) Å), comparable to previ-
ously reported values for dithiocarbamate ligands (1.700-
(7)-1.79(2) Å)31a-c and the C-N distances (1.325(3)-
1.3353(19) Å), slightly longer than previous values
(1.288(8)-1.52(9) Å) for dithiocarbamate complexes,31a,b
are indicative of partial double-bond character (C-S,
1.81 Å; CdS, 1.61 Å; C-N, 1.47 Å; CdN, 1.27 Å).32 In
complex 2a , the distance of C(1) to S(2), the uncoordi-
nated S atom (1.6822(19) Å), approaches the value for
a CdS double bond, in agreement with the monoden-
ticity of the ligand.
The structures of 4a ,c are similar, each containing a
carbenoid Cr-C bond; a representative ORTEP diagram
is illustrated in Figure 4 for 4a . These compounds
complete the family of such complexes of group 6, the
Mo and W members of which have recently been
synthesized by Kreissl and his group, alongside analo-
gous complexes containing pyrazolylborate ligands, HB-
(pz)3 or HB(pzMe2)3, instead of Cp.24 The bond param-
eters defining the cyclo-MCS unit in these carbenoid
complexes are compared with those of 4 in Table 4,
which also includes a Mn complex.25b It is seen that the
bond lengths and bond angles subtended at the metal
atoms all fall within a narrow range. Notable is the
significantly shorter C-S bond (1.666(3)-1.675(2) Å; cf.
1.61 Å for CdS32) when compared with the same bonds
(1.703-1.7201 Å) in the dithiocarbamate ligand in
complex 3, reflecting the stronger π-acidity of the
chelating thiocarboxamido ligand. The CrdC bond
(1.953(2) and 1.978(3) Å in 4a ,c, respectively) is com-
parable to similar bonds within the range observed for
Fischer-type carbene complexes.33 We also note that it
is longer than the Cr-C(carbonyl) distances 1.849(2)
and 1.817(2) Å in 4a and 1.806(4)-1.837(4) Å for the
analogous distances in the two independent molecules
of 4c, indicative of its weaker interaction. In the
complexes 2-4, N assumes a planar configuration, in
agreement with its sp2 character.
The structures of 5b and 6b, illustrated in Figures 5
and 6, respectively, have been described.10 The molecule
of 6c is isostructural with 6b. Some selected bond
parameters of these complexes are listed in Table 3. The
salient feature in 6 is a double cubane doubly bridged
by two dithiocarbamate ligands, each bonding in a η1-
(S):η2(S,S′) coordination mode. The significant feature
in 5b is the presence of a dithiooxamide ligand (DTO )
Et2NC(S)C(S)NEt2), which links the two cubanes with
a η2:η4 bonding mode, in addition to a weak M-M bond
between the two cubanes.
Con clu d in g Rem a r k s
Thermally induced C-S bond cleavage(s) of a S,S′-
bidentate dithiocarbamate ligated to cyclopentadienyl-
chromium led to the formation of thiocarbenoid and
(31) (a) Pignolet, L. H.; Wheeler, S. H. Inorg. Chem. 1980, 19, 935.
(b) Elduque, A.; Finestra, C.; Lo´pez, J . A.; Lahoz, F. J .; Mercha´n, F.;
Oro, L. A.; Pinillos, M. T. Inorg. Chem. 1998, 37, 824. (c) Heard, P. J .;
Kite, K.; Nielsen, J . S.; Tocher, D. A. J . Chem. Soc., Dalton Trans.
2000, 1349.
(32) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; pp 224-229.
(33) Fischer, H.; Kreissl, F. R.; Schubert, U.; Hofmann, P.; Do¨tz, K.
H.; Weiss, K. Transition Metal Carbene Complexes; VCH: Weinheim,
Germany, 1984; pp 94-96.

Cyclopentadienylchromium Dithiocarbamate Complexes
Organometallics, Vol. 21, No. 21, 2002 4407
F igu r e 6. Molecular structure of 6b. Thermal ellipsoids are drawn at the 50% probability level.
Su p p or tin g In for m a tion Ava ila ble: ORTEP diagrams
double-cubane complexes, doubly bridged by dithiocar-
bamate ligands in one case and by a dithiooxamide
ligand in another.
and tables of atomic coordinates and equivalent isotropic
displacement parameters, anisotropic displacement param-
eters, hydrogen coordinates and isotropic displacement pa-
rameters, and all bond lengths and angles for the structures
of 2a , 3a -c, 4a ,c, 5b, and 6b,c and figures giving proton NMR
spectra of 4b and 5a . This material is available free of charge
via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. We thank the National Univer-
sity of Singapore for support under the Academic
Research Fund (Grant No. R143-000-046-112) and a
research scholarship to Z.W.
OM0202930