Organometallic radical-initiated carbon-sulfur bond cleavage and carbon-carbon coupling in dithiocarbamate and thiocarbenoid cyclopentadienylchromium complexes

Article abstract of DOI:10.1021/om020294s

Cothermolysis of the dithiocarbamate complex CpCr(CO)₂(S₂CNEt₂) (2b) with [CpCr(CO)₃]₂ (1) in toluene at 110 °C for 2 h led to the isolation of a yellowish red low-melting solid of CpCr(CO)₂(CNEt₂) (3b; 6%), a dark red viscous liquid of CpCr(CO)₂(SCNEt₂) (4b; 19%), dark red crystalline solids of CpCr(CO)₂(η²(C,O)-C(O)C(NEt₂)CH(NEt₂ )) (5b; 4%), dark green solids of Cp₄Cr₄S₄ (30%), dark brown solids of the double cubane Cp₆Cr₈S₈(C(S)NEt₂)₂ (6b; 13%), and blue solids of Cr(S₂CNEt₂)₃ (8b; 9% yield). Except for 5b, the same product composition (3b, 11%; 4b, 14%; 6b, 37%; Cp₄Cr₄S₄, 20%) was obtained from a similar thermal treatment of 8b with 1. A similar reaction of the thiocarbenoid complex CpCr(CO)₂(SCNMe₂) (4a) yielded yellow crystalline solids of CpCr(CO)₂(CNMe₂) (3a, 16%), a dark brown solid of Cp₄Cr₄S₂-(CO)(CNMe₂) (7a, 36%), Cp₄Cr₄C₄ (10% yield), and Cp₂Cr₂(CO)₄ (17%). Complexes 3a, 5b, and 7a have been characterized by single-crystal X-ray diffraction analysis. The structures of 3a and 5b possess a metal - carbyne and a metal-alkenylacyl moiety, respectively. Complex 7a is a μ₃-aminocarbyne cubane complex.

Full text of DOI:10.1021/om020294s

4408
Organometallics 2002, 21, 4408-4414
Or ga n om eta llic Ra d ica l-In itia ted Ca r bon -Su lfu r Bon d
Clea va ge a n d Ca r bon -Ca r bon Cou p lin g in
Dith ioca r ba m a te a n d Th ioca r ben oid
Cyclop en ta d ien ylch r om iu m Com p lexes
Lai Yoong Goh,* Zhiqiang Weng, Andy T. S. Hor, and Weng Kee Leong
Department of Chemistry, National University of Singapore, Kent Ridge, Singapore 119260
Received April 16, 2002
Cothermolysis of the dithiocarbamate complex CpCr(CO)2(S2CNEt2) (2b) with [CpCr(CO)3]2
(1) in toluene at 110 °C for 2 h led to the isolation of a yellowish red low-melting solid of
CpCr(CO)2(CNEt2) (3b; 6%), a dark red viscous liquid of CpCr(CO)2(SCNEt2) (4b; 19%), dark
red crystalline solids of CpCr(CO)2(η2(C,O)-C(O)C(NEt2)CH(NEt2)) (5b; 4%), dark green solids
of Cp4Cr4S4 (30%), dark brown solids of the double cubane Cp6Cr8S8(C(S)NEt2)2 (6b; 13%),
and blue solids of Cr(S2CNEt2)3 (8b; 9% yield). Except for 5b, the same product composition
(3b, 11%; 4b, 14%; 6b, 37%; Cp4Cr4S4, 20%) was obtained from a similar thermal treatment
of 8b with 1. A similar reaction of the thiocarbenoid complex CpCr(CO)2(SCNMe2) (4a ) yielded
yellow crystalline solids of CpCr(CO)2(CNMe2) (3a , 16%), a dark brown solid of Cp4Cr4S2-
(CO)(CNMe2) (7a , 36%), Cp4Cr4S4 (10% yield), and Cp2Cr2(CO)4 (17%). Complexes 3a , 5b,
and 7a have been characterized by single-crystal X-ray diffraction analysis. The structures
of 3a and 5b possess a metal-carbyne and a metal-alkenylacyl moiety, respectively. Complex
7a is a µ3-aminocarbyne cubane complex.
In tr od u ction
where double C-S bond cleavage could be effected
merely by thermal activation.3c,h,i Recently we have also
encountered such an occurrence in the complex CpCr-
(CO)2(S2CNEt2) (2b), which resulted in the formation
of the thiocarbenoid complex CpCr(CO)2(SCNEt2) (4b)
and a dithiooxamide-bridged double cubane additionally
linked by a Cr-Cr bond.4 We report here a hitherto
unknown organometallic radical initiated C-S cleavage
and C-C coupling leading to the isolation of a variety
of cyclopentadienylchromium complexes, which include
a new η2(C,O)-bis(amino)alkenylacyl compound and an
aminocarbyne cubane.
Carbon-carbon and carbon-sulfur bond-making and
-breaking reactions bear relevance to many significant
biological and industrial processes.1,2 They are becoming
an increasingly common feature in the reactivity of
dithiocarbamates, since the first observation of carbon-
sulfur bond cleavage in a Mo complex in 1972.3 In some
of these cases, a single C-S cleavage in the reaction of
the dithiocarbamate anion with the metal substrate
results in a complex in which the cleaved S atom
assumes a distinctly different coordination mode, e.g.,
in bridged species of µ-S M2,3a-c µ3-S M3, and µ-η1(C):
η2(S) M23d types or in an MdS bond.3e In other instances,
C-S bond cleavage is initiated by reaction with external
reagents, e.g. with Co2(CO)8,3f with thiophilic PEt3 to
abstract the sulfur atom,3c,g with Ru3(CO)12,3h and with
an organic isocyanate.3c Some examples are known
Exp er im en ta l Section
Gen er a l P r oced u r es. All reactions were carried out using
conventional Schlenk techniques under an inert atmosphere
of nitrogen or under argon in an M. Braun Labmaster 130 inert
gas system. NMR spectra were measured on a Bruker 300
MHz FT NMR spectrometer (1H at 300.14 MHz and 13C at
75.43 MHz); 1H and 13C chemical shifts were referenced to
residual C6H6 in C6D6. IR spectra in Nujol mulls or KBr disks
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 Manning9 from
chromium hexacarbonyl (98% purity from Fluka). CpCr(CO)2-
(η2-S2CNEt2) (2b), CpCr(CO)2(η2-SCNMe2) (4a ), and Cr(S2-
CNEt2)3 (8b) were obtained as described in the preceding paper
* To whom correspondence should be addressed. E-mail: chmgohly@
nus.edu.sg.
(1) SulfursIts Significance for Chemistry; for the Geo-, Bio-, and
Cosmosphere and Technology; Mu`ller, A., Krebs, B., Eds.; Elsevier:
Amsterdam, 1984.
(2) Transition Metal Sulfur Chemistry: Biological and Industrial
Significance; Stiefel, E. I., Matsumoto, K., Eds.; ACS Symposium Series
653; American Chemical Society: Washington, DC, 1996.
(3) (a) Ricard, L.; Estienne, J .; Weiss, R. J . Chem. Soc., Chem.
Commun. 1972, 906; Inorg. Chem. 1973, 9, 2182. (b) Herrick, R. S.;
Neiter-Burgmayer, S.; Templeton, J . L. J . Am. Chem. Soc. 1983, 105,
2599. (c) Coffey, T. A.; Forster, G. D.; Hogarth, G. J . Chem. Soc., Dalton
Trans. 1996, 183. (d) Fan, X.; Cao. R.; Hong, M.; Su, W.; Sun. D. J .
Chem. Soc., Dalton Trans. 2001, 2961. (e) Gilletti, P. F.; Femec, D. A.;
Keen, F. I.; Brown, T. M. Inorg. Chem. 1992, 31, 4008. (f) J effery, J .
C.; Went, M. J . J . Chem. Soc., Chem. Commun. 1987, 1766; J . Chem.
Soc., Dalton Trans. 1990, 567. (g) Brower, D. C.; Tonker, T. L.; Morrow,
J . R.; Rivers, D. S.; Templeton, J . L. Organometallics 1986, 5, 1093.
(h) Deeming, A. J .; Vaish, R. J . Organomet. Chem. 1993, 460, C8. (i)
Hitchcock, P. B.; Lappert, M. F.; McGeary, M. J . Organometallics 1990,
9, 2645.
(4) Goh, L. Y.; Weng, Z.; Leong, W. K.; Leung, P. H. Angew. Chem.,
Int. Ed. 2001, 40, 3236.
(5) Goh, L. Y.; Weng, Z.; Leong, W. K.; Leung, P. H. Organometallics
2002, 21, 4398.
(6) (a) Chen, W.; Goh, L. Y.; Mak, T. C. W. Organometallics 1986,
5, 1997. (b) Chen, W.; Goh, L. Y.; Bryan, R. F.; Sinn, E. Acta
Crystallogr. 1986, C42, 796.
10.1021/om020294s CCC: $22.00 © 2002 American Chemical Society
Publication on Web 09/14/2002

Dithiocarbamate and Thiocarbenoid Cr Complexes
Organometallics, Vol. 21, No. 21, 2002 4409
in this issue.5 All solvents were dried over sodium/benzophe-
none and distilled before use. Silica gel (Merck Kieselgel 60,
230-400 mesh) was dried at 140 °C overnight before chro-
matographic use.
n-hexane. Elution gave four fractions. (i) A yellow eluate in
n-hexane/toluene (1:2, 5 mL) was obtained, which on concen-
tration gave CpCr(CO)2(CNEt2) (3b) (6 mg, 0.02 mmol, 12%
yield). (ii) A dark red eluate in toluene (6 mL) was collected,
which on concentration gave CpCr(CO)2(SCNEt2) (4b) (8 mg,
0.03 mmol, 14% yield). (iii) A dark brown eluate in toluene
(15 mL) was isolated, from which was obtained a brown solid;
extraction of this with n-hexane/toluene (1:2, 2 × 3 mL)
separated insoluble dark green solids of Cp4Cr4S4 (6 mg, 0.01
mmol, 20% yield) from a solution which on concentration
yielded Cp6Cr8S8(µ-η2,η2-SCNEt2)2 (6b)4,5 (12 mg, 0.01 mmol,
37% yield). (iv) A brown eluate in THF (10 mL) gave a dark
brown unidentified solid (5 mg).
Da ta for th e Com p ou n d s Obta in ed . Com p ou n d 3a . 1H
NMR (C6D6): δ 4.75 (s, 5H, Cp), 2.31 (6H, CH3). 13C NMR
(C6D6): δ 88.6 (Cp); 41.1 (CH3); 282.0 (CtCr); 245.3 (CO). IR
(KBr, cm-1): ν(CO) 1940 (s), 1863 (s); ν(CN) 1588 (m); ν(NC2)
1170 (m). MS FAB+ (m/z): 229 [M]+, 201 [M - CO]+, 173 [M
- 2CO]+, 117 [CpCr]+, 52 [Cr]+. Anal. Calcd for C10H11NO2-
Cr: C, 52.40; H, 4.84; N, 6.11. Found: C, 52.07; H, 4.74; N,
6.18.
Coth er m olysis of Cp Cr (CO)2(η2-S2CNEt2) (2b) w ith
[Cp Cr (CO)3]2 a t 110 °C. A dark brown mixture of [CpCr-
(CO)3]2 (1) (100 mg, 0.25 mmol) and CpCr(CO)2(η2-S2CNEt2)
(2b) (144 mg, 0.45 mmol) in toluene (8 mL) was stirred at 110
°C for 2 h. The resultant dark brown reaction mixture was
concentrated to ca. 3 mL and loaded onto a silica gel column
(2.5 × 15 cm) prepared in n-hexane. Elution gave five fractions.
(i) A yellow eluate in n-hexane/toluene (1:2, 5 mL) was
obtained, which on concentration gave a reddish yellow liquid
of CpCr(CO)2(CNEt2) (3b) (8 mg, 0.03 mmol, 6% yield). (ii) A
dark red eluate in toluene (10 mL) was isolated, which on
concentration gave dark red “oily” solids of CpCr(CO)2(η2-
SCNEt2) (4b) (28 mg, 0.10 mmol, 19% yield). (iii) A dark brown
eluate in toluene (15 mL) was collected, from which was
obtained a brown solid; extraction of this with n-hexane/
toluene (1:2, 3 × 3 mL) separated the less soluble Cp4Cr4S4 as
dark green solids (22 mg, 0.04 mmol, 30% yield), giving a
solution which after concentration to 2 mL was chromato-
graphed on a silica gel column (2 × 8 cm). A red eluate in
toluene (5 mL) led to the isolation of red crystalline solids of
CpCr(CO)2(η2(C,O)-C(O)C(NEt2)CH(NEt2)) (5b) (8 mg, 0.02
mmol, 4% yield); a reddish brown eluate in toluene (8 mL) was
also collected, from which was isolated Cp6Cr8S8(µ-η2:η2-
SCNEt2)2 (6b) (10 mg, 0.01 mmol, 12% yield).4,5 (iv) A blue
eluate in toluene (8 mL) was obtained, from which was isolated
a blue solid of Cr(S2CNEt2)3 (8b) (21 mg, 0.04 mmol, 9% yield).
(v) A brown eluate in THF (10 mL) was obtained, which gave
a dark brown solid (12 mg), consisting of a mixture of Cp4-
Cr4S2(CO)2 and an unidentified compound.
Coth er m olysis of Cp Cr (CO)2(η2-SCNMe2) (4a ) w ith
[Cp Cr (CO)3]2 a t 110 °C. A dark brown mixture of [CpCr-
(CO)3]2 (1) (80 mg, 0.20 mmol) and CpCr(CO)2(η2-SCNMe2) (4a )
(52 mg, 0.20 mmol) in toluene (10 mL) was stirred at 110 °C
for 3 h. The resultant dark brown reaction mixture was
concentrated to ca. 3 mL and loaded onto a silica gel column
(3 × 16 cm) prepared in n-hexane. Elution gave four fractions.
(i) A dark green eluate in n-hexane/toluene (1:1, 8 mL) was
collected, which on concentration gave dark green solids of Cp2-
Cr2(CO)4(CrtCr) (12 mg, 0.03 mmol, 17% yield). (ii) A yellow
eluate in n-hexane/toluene (1:4, 8 mL) was obtained, which
on concentration gave reddish yellow crystalline solids of CpCr-
(CO)2(CNMe2) (3a ) (15 mg, 0.07 mmol, 16% yield). (iii) A dark
green eluate in toluene (10 mL) was obtained, which on
concentration gave dark green solids of Cp4Cr4S4 (6 mg, 0.01
mmol, 10% yield). (iv) A brown eluate in toluene/THF (4:1, 10
mL) was obtained, from which was isolated a highly air-
sensitive dark brown solid of Cp4Cr4S2(CO)(CNMe2) (7a ) (22
mg, 0.04 mmol, 36%).
Com p ou n d 3b. 1H NMR (C6D6): δ 4.74 (s, 5H, Cp), 2.66
(q, J ) 7 Hz, 4H, CH2), 0.89 (t, J ) 7 Hz, 6H, CH3). 13C NMR
(C6D6): δ 88.5 (Cp); 48.0 (CH2); 14.8 (CH3); 282.1 (CtCr); 245.6
(CO). IR (KBr, cm-1): ν(CO) 1947 (s), 1864 (s); ν(CN) 1562 (m);
ν(NC2) 1163 (m). MS FAB+ (m/z): 257 [M]+, 229 [M - CO]+,
201 [M - 2CO]+, 117 [CpCr]+, 52 [Cr]+. HR-MS FAB+ (m/z):
for [M]+ 257.0506 (found), 257.0508 (calcd). This compound is
an oil (mp <-5 °C). No satisfactory elemental analysis was
obtained. The proton NMR spectrum of a pure sample is given
as Supporting Information.
1
Com p ou n d 5b. H NMR (C6D6): δ 8.45 (s, 1 H, CH), 4.70
(s, 5 H, Cp), 3.84 (unres q, J ) 7 Hz, 2 H, CH2), 2.83 (q, J )
7 Hz, 2 H, CH2), 2.75 and 2.71 (overlapping q, J ) 7 Hz, 4 H,
CH2), 0.93 (t, J ) 7 Hz, 3 H, CH3), 0.86 (t, J ) 7 Hz, 6 H,
CH3), 0.81 (t, J ) 7 Hz, 3 H, CH3). 13C NMR (CD2Cl2): δ 90.6
(Cp); 51.2, 48.1, 42.5 (CH2); 14.9, 13.6, 13.3 (CH3); 162.2 (d
CH); 119.0 (dC); 389.5 (very weak, C(O)); 227.2, 258.0 (CO).
IR (toluene, cm-1): ν(CO) 1936 (s), 1844 (s); ν(CdC), ν(η2-C(O)),
or ν(CN) 1633 (m), 1534 (m), 1470 (w), 1425 (w); ν(NC2) 1151
(m). MS FAB+ (m/z): 370 [M]+, 314 [M - 2CO]+, 286 [M -
3CO]+, 169 [C(NEt2)CH(NEt2)]+. HR-MS ESI+ (m/z): for [M
+ H]+ 371.1435 (found), 371.1426 (calcd); for [M + Na]+
393.1238 (found), 393.1246 (calcd). It was not possible to
completely remove the trace amounts of Cp4Cr4S4 contaminant.
The proton NMR spectrum of a sample is given as Supporting
Information.
Com p ou n d 7a . 1H NMR (C6D6): δ 16.2 (s, ν1/2 ) 22 Hz,
Cp), 15.0 (s, ν1/2 ) 33 Hz, Cp), 11.6 (s, ν1/2 ) 138 Hz, Cp). IR
(Nujol, cm-1): ν(CO) 1600 (s), ν(CN) 1567 (m), ν(NC2) 1103
(m). MS EI+: m/z 588 [M - CO]+, 471 [Cp3Cr3S2(CNMe2)]+,
117 [CpCr]+, 52 [Cr]+. This compound was highly air-sensitive,
resulting in unsatisfactory elemental analysis data. The proton
NMR spectrum of a pure sample is given as Supporting
Information.
Coth er m olysis of Cr (S2CNEt2)3 (8b) w ith [Cp Cr (CO)3]2
a t 110 °C. A blue-green mixture of [CpCr(CO)3]2 (1) (40 mg,
0.10 mmol) and Cr(S2CNEt2)3 (8b) (34 mg, 0.07 mmol) in
toluene (5 mL) was stirred at 110 °C for 2 h. The resultant
dark brown reaction mixture was concentrated to ca. 2 mL
and loaded onto a silica gel column (2 × 10 cm) prepared in
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 to 2 h.
(7) (a) Goh, L. Y. Coord. Chem. Rev. 1999, 185-186, 257 and
references therein. (b) Goh, L. Y.; Hambley, T. W.; Robertson, G. B.
Organometallics 1987, 6. 1051. (c) Goh, L. Y.; Chen, W.; Wong, R. C.
S. Angew. Chem., Int. Ed. Engl. 1993, 32, 1728. (d) Goh, L. Y.; Chen,
W.; Wong, R. C. S.; Karaghiosoff, K. Organometallics 1995, 14, 3886.
(e) Goh, L. Y.; Chen, W.; Wong, R. C. S. J . Chem. Soc., Chem. Commun.
1999, 1481.
(8) (a) Filippou, A. C.; Wanniger, K.; Mehnert, C. J . Organomet.
Chem. 1993, 461, 99. (b) Filippou, A. C.; Lungwitz, B.; Wanniger, K.
M. A.; Herdtweck, E. Angew. Chem., Int. Ed. Engl. 1995, 34, 924. (c)
Filippou, A. C.; Wo¨ssner, D.; Kociok-Ko¨hn, G.; Hinz, I. J . Organomet.
Chem. 1997, 541, 333.
Cr ysta l Str u ctu r e An a lyses. Diffraction-quality single
crystals were obtained at -29 °C as follows: 3a as reddish
yellow needles and 5b as red needles after 5 and 32 days,
respectively, from solutions in toluene layered with hexane;
7a as dark brown rhombuses from solutions in THF layered
with hexane after 3 days.
The crystals were mounted on quartz fibers. The air-
sensitive crystal of 7a was coated with grease. 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
(9) Manning, A. R.; Hackett, P.; Birdwhistell, R.; Soye, P. Inorg.
Synth. 1990, 28, 148.

4410 Organometallics, Vol. 21, No. 21, 2002
Ta ble 1. Da ta Collection a n d P r ocessin g P a r a m eter s
Goh et al.
3a
5b
7a
formula
Mr
temp, K
C
10H11CrNO2
C18H26CrN2O3
370.41
223(2)
C24H26Cr4NOS2‚THF
688.68
153(2)
229.20
223(2)
cryst color, habit
cryst size, mm
cryst syst
space group
red-yellow, needle
0.10 × 0.24 × 0.32
monoclinic
P21/m
red, needle
0.06 × 0.22 × 0.34
orthorhombic
Pbca
dark brown, rhombus
0.39 × 0.20 × 0.19
orthorhombic
Pnma
a, Å
b, Å
c, Å
5.9268(2)
10.7263(4)
8.3862(3)
90
97.171(2)
90
528.96(3)
2
1.439
12.7127(4)
16.0862(5)
18.3629(6)
90
90
90
3755.2(2)
8
1.310
0.626
1568
17.3950(15)
10.6646(9)
14.7196(13)
90
90
90
2730.6(4)
4
1.675
1.730
1412
R, deg
â, deg
γ, deg
V, Å3
Z
density, g cm-3
abs coeff, mm-1
F(000)
1.054
236
θ range for data collecn, deg
2.45-30.74
-8 e h e 8, 0 e k e 14,
0 e l e 11
4520
2.22-26.37
0 e h e 15, 0 e k e 20,
0 e l e 22
29 008
2.34-25.03
0 e h e 20, 0 e k e 12,
0 e l e 17
19 114
index ranges
no. of rflns collected
no. of indep rflns
1604
3836
2555
max, min transmissn
no. of data/restraints/
params
0.928, 0.715
1604/0/93
0.928, 0.567
3836/0/217
0.801, 0.602
2555/2/171
final R indices (I > 2σ(I))a,b
R indices (all data)
goodness of fit on F2 c
large diff peak, hole, e Å-3
R1 ) 0.0369, wR2 ) 0.0964
R1 ) 0.0401, wR2 ) 0.0981
1.061
R1 ) 0.0537, wR2 ) 0.1182
R1 ) 0.0855, wR2 ) 0.1312
0.964
R1 ) 0.0850, wR2 ) 0.2066
R1 ) 0.1036, wR2 ) 0.2170
1.145
0.578, -0.263
0.531, -0.295
1.356, -0.809
a
b
2
R1 ) (∑|Fo| - |Fc|)∑|Fo|. wR2 ) [(∑w|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
c GOF ) [(∑w|Fo| - |Fc|)2/(Nobservns - Nparams)]1/2
.
the SMART suite of programs10 and for absorption effects with
SADABS.11 Structure solution and refinement were carried out
with the SHELXTL suite of programs.12 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. The
data collection and processing parameters are given in Table
1.
study was found to react with 1 at 90 °C within 1 h,
transforming to noncharacterizable paramagnetic spe-
cies. A comparison of the products and their yields from
these three reactions and the analogous reaction of 4a
is given in Table 2. This shows that while the cleavage
of one sulfur atom from 2 is a thermally achievable
process, double desulfurization requires assistance from
1a , the incumbent monomer of 1 arising from its facile
dissociation.13 The detection of Cp4Cr4S2(CO)2 (1H
NMR: δ(Cp) 9.74 and 5.66) and the isolation of the
previously characterized cubane Cp4Cr4S4 in substantial
amounts in all these thermolytic reactions provide
evidence for the initial formation of the precursor
complex [CpCr(CO)2]2S,6 a finding congruent with the
observed thiophilicity of the CpCr(CO)3• species 1a .7 In
the reaction between 8b and 1, a transfer of dithiocar-
bamate ligands from the tris(dithiocarbamate) coordina-
tion compound to 1a has been effected, undoubtedly
initiated by cleavage of the chelate rings in 8b. The
thermolytic desulfurization of the thiocarbenoid complex
4a with 1 was found to yield the carbyne complex CpCr-
(CO)2(CNMe2) (3a ) as yellow crystalline solids in 16%
yield and dark brown solids of the aminocarbyne cubane
Cp4Cr4S2(CO)(CNMe2) (7a ) as the major product (36%),
together with dark green solids of Cp4Cr4S4 (10%) and
Cp2Cr2(CO)4 (17%), as shown in Scheme 3. It was
demonstrated that complexes 3a /3b and 7a /7b did not
originate from thermal degradation of the thiocarbene
complex 4a /4b, which remained unchanged after 2 h in
refluxing toluene-d8. The intermediate formation of the
carbenoid species R2NC: is indicated by the presence
of alkene and alkenyl moieties in the structural com-
Resu lts a n d Discu ssion
P r od u cts a n d Rea ction P a th w a ys. The cother-
molysis of CpCr(CO)2(S2CNEt2) (2b) with [CpCr(CO)3]2
(1) in refluxing toluene for 2 h led to the isolation of
the chromium carbyne complex CpCr(CO)2(CNEt2) (3b)
as reddish yellow low-melting solids (6% yield), the
thiocarbenoid complex CpCr(CO)2(SCNEt2) (4b) as dark
red “oily solids” (19%), the aminoacyl complex CpCr-
(CO)2(η2(C,O)-C(O)C(NEt2)CH(NEt2)) (5b) as dark red
crystalline solids (4%), the double cubane Cp6Cr8S8-
(C(S)NEt2)2 (6b) as dark brown solids (13%), the coor-
dination compound Cr(S2CNEt2)3 (8b) as blue solids
(9%), and the cubane Cp4Cr4S4 as dark green solids
(30%), as presented in Scheme 1. It was truly unex-
pected that except for the low-yield complex 5b, the
same product composition (3b, 11%; 4b, 14%; 6b, 37%;
Cp4Cr4S4, 20%) was obtained from a similar cother-
molysis of 8b with 1 (Scheme 2). Among these products,
4b, 6b, 8b, and Cp4Cr4S4 were obtained also by thermal
degradation of 2b alone, which also produced the
thermally unstable bis(dithiocarbamate) doubly bridged
dicubane Cp6Cr8S8(S2CNEt2)2 (9),4,5 which in this present
(10) SMART version 4.05; Siemens Energy & Automation Inc.,
Madison, WI.
(11) Sheldrick, G. M. SADABS; 1996.
(12) SHELXTL version 5.03; Siemens Energy & Automation Inc.,
Madison, WI.
(13) (a) Baird, M. C. Chem. Rev. 1988, 88, 1217. (b) McLain, S. J . J .
Am. Chem. Soc. 1988, 110, 643. (c) Goh, L. Y.; Lim, Y. Y. J . Organomet.
Chem. 1991, 402, 209.

Dithiocarbamate and Thiocarbenoid Cr Complexes
Organometallics, Vol. 21, No. 21, 2002 4411
Sch em e 1a
a
R ) Et. The six Cr-Cr bonds in each of the cubanes 6b are omitted for clarity.
Sch em e 2a
under an atmosphere of CO. The product complexes
show that, with respect to sulfur cleavage, the reaction
pathways fall into three categories in which (i) the
dithiocarbamate (DTC) ligand remains intact, as in
compounds 8 and 9, (ii) the DTC ligand has undergone
mono sulfur cleavage, producing species of types I and
II, as found in the thiocarbenoid complex 4 and the
dithiooxamide dicubane 6, and (iii) the DTC ligand has
suffered double sulfur cleavage, generating species of
types III-V, as found in the Cr-aminocarbyne complex
3, the alkenylacyl compound 5, and the aminocarbyne
cubane 7, respectively (Scheme 4).
1
Sp ectr a l F ea tu r es. The H and 13C NMR spectra of
the mononuclear complex 3 show the Cp resonances (δ
4.75 and 88.6 for 3a ; δ 4.74 and 88.5 for 3b) in the range
observed for other CpCr moieties;7 the CtCr resonances
in the 13C NMR spectrum (δ 282.0 for 3a ; δ 282.1 for
3b) are comparable to that of the analogous complex
CpCr(CO)2(CNi-Pr2) (δ 281.7).8a The two equivalent cis-
oriented carbonyl ligands in complex 3 show only one
resonance in the 13C NMR spectrum (δ 245.3 for 3a ; δ
245.6 for 3b). This is consistent with the observation in
CpCr(CO)2(CN-i-Pr2) (δ 245.7).8a The Cp resonance of
the acyl complex 5b is observed in the 1H NMR
spectrum at δ 4.70 and at δ 90.6 in the 13C NMR
spectrum, which also shows the two carbonyl ligands
at δ 227.2 and 258.0, respectively. The acyl resonance
in 13C NMR is barely visible at δ 389.5 (range observed
for metal-acyl complexes δ 136.5-391.6),15 and the
alkenyl carbon atoms appear at δ 162.2 and 119.0,
respectively. Four nonequivalent CH2 protons were
observed at δ 3.84, 2.83, 2.75, and 2.71. Three sets of
CH3 protons were found at δ 0.93 (3 H), 0.86 (6 H), and
0.81 (3 H). The proton Cp resonances of 7a were seen
a
R ) Et.
positions of 6b and 5b, respectively, suggestive of
carbene dimerization, which is a well-established pro-
cess.14 The carbyne moiety R2NCt is evident in the
structures of 3a and 7a . The thermal instability of 5b
in solution (t1/2 ) ca. 1.5 h at 110 °C) explains its
extremely low isolated yield and frustrates our efforts
to detect its immediate precursor. However, it is likely
that the insertion of CO into the Cr-C bond involved
in its formation originated from ligated CO, since these
thermal degradations were found to be suppressed
(14) (a) Fischer, H.; Kreissl, F. R.; Schubert, U.; Hofmann, P.; Do¨tz,
K. H.; Weiss, K. Transition Metal Carbene Complexes; VCH: Wein-
heim, Germany, 1984; pp 94-96. (b) Casey, C. P. In Transition Metal
Organometallics in Organic Synthesis; Alper, H., Ed.; Academic
Press: New York, 1976; Vol. I, p 190. (c) Do¨tz, K. H. Angew. Chem.,
Int. Ed. Engl. 1984, 23, 587.
(15) Durfee, L. D.; Rothwell, I. P. Chem. Rev. 1988, 88, 1059 and
references therein.

4412 Organometallics, Vol. 21, No. 21, 2002
Ta ble 2. Yield (%) of P r od u ctsa
Goh et al.
products
3
4
5
6
7
8
reacn
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
8a
8b
9
Cp4Cr4S4
2b + 1 at 110 °C/2 h
6 (7)
12 (33)
19 (22)
14 (40)
4 (5)
0
13
37
b
0
9 (10)
0
0
0
30
20
10
22
8b + 1 at 110 °C/2 h
4a + 1 at 110 °C/2 h
16 (33)
0
0
36
0
thermolysis of 2b at 90 °C/2 h5
0
11
b
7
0
19
11
a
b
Yields are based on 1 (values in parentheses are based on the respective substrates). A trace observed in the 1H NMR spectrum of
the product mixture but lost in the chromatographic separation.
Sch em e 3a
F igu r e 1. Molecular structure of 3a . Thermal ellipsoids
are drawn at the 50% probability level.
a
R ) Me. The six Cr-Cr bonds in the cubane core of 7a
are omitted for clarity.
Str u ctu r es. The molecular structures of 3a , 5b, and
7a have been determined. The ORTEP diagrams are
shown in Figures 1-3, and selected bond parameters
are given in Tables 3-5 for these complexes.
Sch em e 4
The complex 3a (Figure 1) belongs to the rare group
of aminocarbyne chromium complexes, the first example
of which was isolated fairly recently by Filippou and
co-workers from a multiple-step synthesis from Cr-
(CO)6.8 The structure shows a CpCr moiety bonded to
an aminocarbyne and two CO ligands, similar to the
case for the W analogue. The Cr-Ccarbyne (1.740(2) Å)
bond is longer than that of CpCr(CO)2(tCPh)8c (1.705-
(2) Å) but is shorter than the Cr-Ccarbonyl bond (1.8313-
(18) Å). The C-N bond (1.461(2) Å) is longer than that
of CpCr(CO)2(S2CNMe2) (1.325(3) Å).5 The Cr-C-N
linkage (angle Cr(1)-C(1)-N(1) 177.7(2)°) is almost
linear.
The structure of 5b, illustrated in Figure 2, contains
a metal-acyl unit, the bond parameters of which are
given in Table 4; Table 6 shows a similarity of this
structure to those of analogous Mo and W complexes.
Noting that ∆((M-O) - (M-C)) is inversely proportional
to the strength of the metal-acyl group interaction,17
the data indicate that the Cr-acyl bond is stronger than
those reported for similar Mo and W complexes. The
short C(1)-C(2) distance (1.378(4) Å) is in close agree-
ment with that of a double bond (1.335(3) Å), while that
of C(1)-C(33) (1.415(4) Å) tends more toward the C-C
at δ 16.2, 15.0, and 11.6, as broad peaks, in accord with
paramagnetism arising from an odd valence electron
count (57 electrons) in the cubane molecule. In fact, such
low-field resonances for Cp rings have been observed
previously for other paramagnetic cyclopentadienyl-
chromium complexes.13c,16 Unfortunately, accurate in-
tegrals for the broad peaks could not be obtained. The
N-methyl signals could not be observed.
(17) (a) Curtis, M. D.; Shiu, K. B.; Butler, W. M. J . Am. Chem. Soc.
1986, 108, 1550. (b) Carmona, E.; Sa´nchez, L.; Mar´ın, J . M.; Poveda,
M. L.; Atwood, J . L.; Priester, R. D.; Rogers, R. D. J . Am. Chem. Soc.
1984, 106, 3214. (c) Skagestad, V.; Rømming, C.; Tilset, M. Inorg.
Chem. 1995, 34, 3194. (d) Adams, H.; Cubbon, R. J .; Sarsfield, M. J .;
Winter, M. J . Chem. Commun. 1999, 491. (e) Debad, J . D.; Legzdins,
P. Organometallics 1993, 12, 2094.
(16) Goh, L. Y.; Leong, W. K.; Leung, P. H.; Weng, Z.; Haiduc, I. J .
Organomet. Chem. 2000, 607, 64.

Dithiocarbamate and Thiocarbenoid Cr Complexes
Organometallics, Vol. 21, No. 21, 2002 4413
Ta ble 4. Selected Bon d Dista n ces a n d An gles
for 5b
Bond Distances (Å)
Cr(1)-C(33)
C(1)-C(2)
1.977(3)
1.378(4)
1.439(3)
1.242(3)
1.480(4)
1.472(4)
1.154(4)
Cr(1)-O(33)
C(1)-C(33)
C(2)-N(2)
N(1)-C(111)
N(2)-C(121)
C(31)-O(31)
2.104(2)
1.415(4)
1.320(3)
1.473(4)
1.486(4)
1.154(3)
C(1)-N(1)
C(33)-O(33)
N(1)-C(113)
N(2)-C(123)
C(32)-O(32)
Bond Angles (deg)
Cr(1)-C(33)-O(33)
O(33)-Cr(1)-C(33)
O(33)-C(33)-C(1)
C(33)-C(1)-N(1)
C(2)-C(1)-N(1)
77.92(17) Cr(1)-O(33)-C(33)
66.80(16)
151.8(2)
125.2(3)
113.9(2)
133.3(3)
112.6(2)
35.27(9) Cr(1)-C(33)-C(1)
130.1(3)
120.8(2)
125.2(3)
133.3(3)
112.8(2)
124.9(3)
N(1)-C(1)-C(2)
C(33)-C(1)-C(2)
C(1)-C(2)-N(2)
C(1)-N(1)-C(113)
C(111)-N(1)-C(113) 111.2(2)
C(2)-N(2)-C(123) 120.9(3)
N(2)-C(2)-C(1)
C(1)-N(1)-C(111)
C(2)-N(2)-C(121)
C(121)-N(2)-C(123) 114.0(3)
Ta ble 5. Selected Bon d Dista n ces a n d An gles
for 7a
Bond Distances (Å)
Cr(1)-Cr(2)
Cr(2)-Cr(3)
Cr(2)-S(4)
Cr(1)-C(3)
C(3)-O(3)
Cr(3)-C(1)
2.752(2)
2.746(2)
2.249(2)
2.020(13)
1.010(13)
1.962(7)
Cr(1)-Cr(3)
Cr(1)-S(4)
Cr(3)-S(4)
Cr(3)-C(3)
Cr(2)-C(1)
C(1)-N(1)
2.7817(19)
2.268(2)
2.253(3)
2.209(9)
2.212(11)
1.365(14)
Bond Angles (deg)
Cr(2)-Cr(1)-Cr(3)
Cr(1)-Cr(3)-Cr(2)
59.51(5) Cr(1)-Cr(2)-Cr(3) 60.79(5)
59.70(5) C(3)-Cr(1)-S(4)
101.6(2)
99.8(3)
S(4)-Cr(1)-S(4A) 103.18(13) C(3)-Cr(1)-Cr(2)
S(4)-Cr(1)-Cr(2)
S(4)-Cr(1)-Cr(3)
S(4)-Cr(2)-S(4A) 104.37(13) C(1)-Cr(2)-Cr(3)
52.17(6) C(3)-Cr(1)-Cr(3)
51.78(7) C(1)-Cr(2)-S(4)
51.9(3)
F igu r e 2. Two views of the molecular structure of 5b.
Thermal ellipsoids are drawn at the 50% probability level.
96.89(18)
45.04(19)
91.9(3)
99.0(3)
96.5(3)
S(4)-Cr(2)-Cr(3)
S(4)-Cr(2)-Cr(1)
C(1)-Cr(3)-S(4)
C(1)-Cr(3)-Cr(2)
S(4)-Cr(3)-Cr(2)
C(3)-Cr(3)-Cr(1)
Cr(2)-S(4)-Cr(3)
Cr(3)-S(4)-Cr(1)
C(2)-N(1)-C(2A)
O(3)-C(3)-Cr(3)
52.48(7) C(1)-Cr(2)-Cr(1)
52.78(6) C(1)-Cr(3)-C(3)
104.6(3)
52.9(3)
52.36(7) C(1)-Cr(3)-Cr(1)
46.0(3)
C(3)-Cr(3)-S(4)
C(3)-Cr(3)-Cr(2)
95.3(3)
96.7(3)
S(4)-Cr(3)-Cr(1)
52.27(7)
75.05(8)
123.6(5)
139.9(11)
82.1(4)
75.17(9) Cr(2)-S(4)-Cr(1)
75.95(9) C(1)-N(1)-C(2)
112.6(10) O(3)-C(3)-Cr(1)
127.5(7)
Cr(1)-C(3)-Cr(3)
N(1)-C(1)-Cr(3)
Cr(3)-C(1)-Cr(2)
Cr(3)-C(3)-Cr(3A) 74.8(4)
N(1)-C(1)-Cr(2) 115.0(8)
Cr(3)-C(1)-Cr(3A) 86.3(4)
135.0(3)
82.0(4)
(3) Å) is indicative of double-bond character (C-N )
1.47 Å and CdN ) 1.27 Å),18 in agreement with an sp2
N center possessing a planar conformation. The second
such distance, C(1)-N(1) (1.439(3) Å), is closer to the
C-N single-bond distances in the amino side chains
(1.472(4)-1.486(4) Å), in keeping with a pyramidal
geometry at N(1), which is 0.418 Å above the C(1)-
C(111)-C(113) plane. The C(33)-O(33) distance (1.242-
(3) Å) is slightly longer than the corresponding distance
(1.154(4) Å) in the terminal CO ligands. The atoms
O(33), C(33), C(1), C(2), N(2), C(121), and C(123) are
coplanar, with Cr(1) and N(1) located on opposite sides
of the plane, while the atoms N(1), C(111), and C(113)
of the other tetraalkylamino “branch” are in a perpen-
dicular plane.
F igu r e 3. Molecular structure of 7a . Thermal ellipsoids
are drawn at the 50% probability level.
Ta ble 3. Selected Bon d Dista n ces a n d An gles
for 3a
Bond Distances (Å)
Cr(1)-C(1)
C(1)-N(1)
C(2)-O(2)
1.740(2)
1.297(3)
1.151(2)
Cr(1)-C(2)
N(1)-C(11)
1.8313(18)
1.461(2)
Bond Angles (deg)
177.7(2) C(1)-N(1)-C(11) 121.89(11)
The ORTEP plot of the cubane complex 7a is il-
lustrated in Figure 3. The structure contains a unique
combination of three varieties of triply bridging ligands,
viz., one µ3-CO, one µ3-CNR2, and two µ3-S ligands. As
Cr(1)-C(1)-N(1)
C(11)-N(1)-C(11A) 116.2(2)
single-bond value of 1.532(2) Å. The unsymmetrical
nature of substituents on the C(1)-C(2) alkenyl moiety
has resulted in very different values of the C-NEt2
distances. Of the two such distances, C(2)-N(2) (1.320-
(18) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; pp 224-229.

4414 Organometallics, Vol. 21, No. 21, 2002
Goh et al.
Ta ble 6. Bon d Dista n ces (Å) a n d An gles (d eg) of th e Tr icyclo Acyl Un it in 5b a n d Rela ted Com p lexes
∆((M-O) -
(M-C))
complexes
M-C
M-O
C-O
M-C-O
M-O-C
O-M-C
CpCr(CO)2(η2(C,O)-C(O)(CNEt2)(CHNEt2)) (5b) 1.977(3)
2.104(2)
2.222(5)
2.189(3)
2.200(4)
2.246(5)
2.324(4)
1.242(3)
1.23(1)
1.224(6)
1.896(7)
1.898(8)
1.234(6)
0.127
0.204
0.168
0.197
0.244
0.30
0.62
0.197
0.156
77.92(17) 66.80(16)
35.27(9)
33.2(3)
33.5(2)
33.4(2)
33.23
32.0(2)
35.7(6)
34.0(4)
33.6(1)
TpMo(CO)2(η2-COMe)17a
2.018(8)
2.021(5)
2.003(6)
2.002(8)
2.024(6)
82.6(5)
80.8(3)
82.2(4)
84.2(5)
87.5(4)
80.6(9)
64.2(4)
65.7(3)
64.4(4)
62.5(4)
60.5(3)
63.6(9)
TpMo(CO)2(η2-COPh)17a
TpMo(CO)(P(OMe)3)(η2-COMe)17a
TpMo(CO)(PEt3)(η2-COMe)17a
Mo(η2-COCH2SiMe3)Cl(CO)(PMe3)3)17b
- 17c
CpW(NCMe2)(Br)(η2-COMe)+BF4
1.960(17) 2.158(10) 1.278(19)
2.02(2)
TpW(CO)2(η2-C(O)(c-C3H5)17d
2.217(10) 1.25(2)
2.202(3) 1.236(5)
Cp*W(NO)(η2-C(O)CH2CMe3)(Ph) 17e
2.046(4)
80.2(2)
far as we are aware, this is the first case of a cubane
containing a µ3-aminocarbyne ligand; the closest ex-
amples of bridging aminocarbyne ligands are found in
µ2-CNR2 complexes of tungsten3g and ruthenium.3f,19
The cubane core of 7a possesses a plane of symmetry
which passes through Cr(1), Cr(2), C(3)O(3), and C(1)N-
(1). The aminocarbyne ligand is planar at its N atom,
indicative of sp2 character and consistent with the
double-bond character of the C-N bond, as reflected in
its short distance of 1.365(14) Å. The Cr-C(3)-Cr
angles (74.8(4), 82.1(4)°) at the µ3-CO group are smaller
than those at the µ3-CNR2 group (Cr-C(1)-Cr )
82.0(4), 86.3(4)°). Other bond parameters are compa-
rable to those in the allied mixed µ3-CO/µ3-S cubane
complex Cp4Cr4S2(CO)2, the structure of which has been
previously determined.6a The C-O distance of µ3-CO in
7a (1.010(13) Å) is much shorter than the corresponding
distance in terminal CO ligands in 5b but very close to
those in Cp4Cr4S2(CO)2 (1.041(10) and 1.006(11) Å). It
is seen that the replacement of a µ3-CO by a µ3-CNR2
ligand in the cubane core does not have any significant
effect on the corresponding bond parameters of the two
cubes.
Con clu d in g Rem a r k s
This study demonstrates the effectiveness of the
•
organometallic radical CpCr(CO)3 in mono- and disulfur
cleavage of η2-dithiocarbamate ligands in cyclopentadi-
enylchromium and chromium(III) complexes, leading to
the formation of various types of cyclopentadienylchro-
mium compounds belonging to the thiocarbene, carbyne,
(amino)alkenylacyl, triply bridging aminocarbyne cu-
bane, and doubly bridged dithiooxamido double-cubane
varieties.
Ack n ow led gm en t. Support from the National Uni-
versity of Singapore for Academic Research Fund (Grant
No. R143-000-046-112) and a research scholarship to
Z.W. is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: ORTEP diagrams
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 3a , 5b, and 7a and figures giving proton NMR spectra of
3b, 5b, and 7a in C6D6. This material is available free of charge
via the Internet at http://pubs.acs.org.
(19) Bodensieck, U.; Stoeckli-Evans, H.; Rheinwald, G.; Su¨ss-Fink,
G. J . Organomet. Chem. 1992, 433, 167.
OM020294S