Addition reactions of the novel mononuclear dithio-o-carboranylcobalt(III) complex (η5-C5H5)Co(η2-S 2C2B10H10)

Article abstract of DOI:10.1021/om990269v

The mononuclear 16-electron dithio-o-carboranylcobalt(III) complex CpCo(S₂C₂B₁₀H₁₀) (2) was obtained by the reaction of CpCo(CO)I₂ with dilithium dithio-o-carborane, Li₂[S₂C₂B₁₀H₁₀] (1). Complex 2 reacts with a variety of substrates such as CpCo(C₂H₂)₂, alkynes, and a diazoalkane, generating a new class of dithio-o-carboranylcobalt(III) compounds incorporating a CpCo unit and alkene and alkylidene ligands.

Full text of DOI:10.1021/om990269v

2738
Organometallics 1999, 18, 2738-2740
Ad d ition Rea ction s of th e Novel Mon on u clea r
Dith io-o-ca r bor a n ylcoba lt(III) Com p lex
(η5-C5H5)Co(η2-S2C2B10H10)
Dae-Hyun Kim,† J aejung Ko,*,† Kwonil Park,‡ Sungil Cho,‡ and
Sang Ook Kang*,†
Department of Chemistry, Korea University, 208 Seochang, Chochiwon,
Chung-nam 339-700, Korea, and Department of Chemical Engineering, J unnong-dong 90,
Seoul City University, Seoul 130-743, Korea
Received April 16, 1999
Summary: The mononuclear 16-electron dithio-o-carbo-
ranylcobalt(III) complex CpCo(S2C2B10H10) (2) was ob-
tained by the reaction of CpCo(CO)I2 with dilithium
dithio-o-carborane, Li2[S2C2B10H10] (1). Complex 2 reacts
with a variety of substrates such as CpCo(C2H2)2,
alkynes, and a diazoalkane, generating a new class of
dithio-o-carboranylcobalt(III) compounds incorporating
a CpCo unit and alkene and alkylidene ligands.
(THF) afforded an 83% yield of 2 as an air-stable green
solid (eq 1).
The synthesis and study of organometallic complexes
possessing an ancillary dithio-o-carboranyl ligand have
continued to receive attention.1 To further develop the
chemistry of dithio-o-carborane and assess its ability to
form reactive transition-metal complexes, we examined
its reactions with a selection of cyclopentadienyl transi-
tion-metal complexes. In particular, we have been
interested in obtaining coordinatively unsaturated low-
valent cobalt compounds, capable of binding biologically
interesting substrates such as acetylene, CO, diazenes,
or dinitrogen. It was, therefore, of interest to investigate
the possibility of synthesizing such coordinatively un-
saturated low-valent cobalt compounds bearing both
bulky o-carborane2 and cyclopentadienyl units that
might potentially stabilize the 16-electron metal center.3
Here we report the synthesis of the mononuclear 16-
electron dithio-o-carboranylcobalt(III) complex CpCo-
(S2C2B10H10) (2), as well as its reactivity. Included are
the addition of organic and organometallic compounds
into the Co-S bond of 2.
Analytical and spectroscopic data4 support the for-
mulation of 2 as a mononuclear 16-electron dithio-o-
carboranylcobalt(III) complex, and this formulation has
been confirmed by an X-ray structural study5 which
showed coordinative unsaturation in the steric sense
around the cobalt center in the two-legged piano-stool
geometry (Figure 1). Such a monomeric 16-electron
thiolatocobalt(III) structure has been reported for the
benzenedithiolate complex CpCo(µ-S2C6H4).6 A revers-
ible mononuclear-dinuclear interconversion in the ben-
zenedithiolate complexes was also reported by Miller et
al. for CpCo(µ-S2C6H4).7 We have isolated the mono-
nuclear cobalt(III) analogue 2 and have found that it
exists only in the monomeric form. Formation of a
dinuclear species in solution was not observed. It is
recognized that π donation by a lone pair of electrons
on the coordinated sulfur atom alleviates such electron
deficiency and thus the coordinative unsaturation around
the transition-metal center.8 Consequently, this geom-
etry suggests that some of multiple-bond character is
present in the Co-S bonds of complex 2. To verify the
nature of the Co-S bonds, the addition reactions of
several organic and organometallic compounds to 2 have
been investigated.
The reaction of CpCo(CO)I2 (3 mmol) with the lithium
salt Li2[S2C2B10H10] (1) (3.2 equiv) in tetrahydrofuran
† Korea University.
‡ Seoul City University.
(1) (a) Base, K.; Grinstaff, M. W. Inorg. Chem. 1998, 37, 1432. (b)
Crespo, O.; Gimeno, M. C.; J ones, P. G.; Laguna, A. J . Chem. Soc.,
Dalton Trans. 1997, 1099. (c) Crespo, O.; Gimeno, M. C.; J ones, P. G.;
Laguna, A. J . Chem. Soc., Chem. Commun. 1993, 1696. (d) Contreras,
J . G.; Silva-trivino, L. M.; Solis, M. E. J . Coord. Chem. 1986, 14, 309.
(e) Smith, H. D., J r.; Robinson, M. A.; Papetti, S. Inorg. Chem. 1967,
6, 1014. (f) Smith, H. D., J r.; Obenland, C. O.; Papetti, S. Inorg. Chem.
1966, 5 1013. (g) Smith, H. D., J r. J . Am. Chem. Soc. 1965, 87, 1817.
(2) Beall, H. In Boron Hydride Chemistry; Muetterties, E., Ed.;
Academic Press: New York, 1975; Chapter 9.
(4) Data for 2. Anal. Calcd for C7H15B10S2Co: C, 25.45; H, 4.58.
Found: C, 25.51; H, 4.63. IR (KBr, cm-1): ν(BH), 2554. 1H NMR
(200.13 MHz, ppm, CDCl3): 5.26 (s, 5H, C5H5). 13C{1H} NMR (50.3
MHz, ppm, CDCl3): 81.81 (s, C5H5).
(3) (a) Mashima, K.; Kaneyoshi, H.; Kaneko, S.; Mikami, A.; Tani,
K.; Nakamura, A. Organometallics 1997, 16, 1016. (b) Michelman, R.
I.; Ball, G. E.; Bergman, R. G.; Anderson, R. A. Organometallics 1994,
13, 869. (c) Garcia, J . J .; Torrens, H.; Adams, H.; Bailey, N. A.;
Scacklady, A.; Maitlis, P. M. J . Chem. Soc., Dalton Trans. 1993, 1529.
(d) Michelman, R. I.; Anderson, R. A.; Bergman, R. G. J . Am. Chem.
Soc. 1991, 113, 5100. (e) Garcia, J . J .; Torrens, H.; Adams, H.; Bailey,
N. A.; Maitlis, P. M. J . Chem. Soc., Chem. Commun. 1991, 74. (f) Klein,
D. P.; Kloster, G. M.; Bergman, R. G. J . Am. Chem. Soc. 1990, 112,
2022.
(5) Crystallographic data for 2: a ) 11.2866(12) Å, b ) 12.677(6)
Å, c ) 13.2760(19) Å, R ) 114.12(3)°, â ) 104.985(10)°, and γ ) 107.18-
(3)° with Z ) 2 in space group P1h (No. 2). R1 (wR2) ) 0.1751 (0.5016)
for 5070 data with I > 2.0σ(I) and anisotropic refinements of the model
with idealized hydrogen atoms.
(6) Heck, R. F. Inorg. Chem. 1968, 7, 1513.
(7) Miller, E. J .; Brill, T. B.; Rheingold, A. L.; Fultz, W. C. J . Am.
Chem. Soc. 1983, 105, 7580.
(8) Sellmann, D.; Geck, M.; Knoch, F.; Ritter, G.; Dengler, J . J . Am.
Chem. Soc. 1991, 113, 3819.
10.1021/om990269v CCC: $18.00 © 1999 American Chemical Society
Publication on Web 06/25/1999

Communications
Organometallics, Vol. 18, No. 15, 1999 2739
F igu r e 3. ORTEP drawing of adduct 4a . Selected bond
lengths (Å) and angles (deg): Co(1)-S(1) 2.247(2), Co(1)-
S(2) 2.246(1), Co(1)-C(11) 1.912(5), C(10)-C(11) 1.340(7),
S(2)-C(10) 1.777(5), S(1)-C(1) 1.778(5), S(2)-C(2) 1.794-
(5), C(1)-C(2) 1.659(6); S(1)-Co(1)-S(2) 93.51(5), S(2)-
Co(1)-C(11) 72.4(2), S(1)-Co(1)-C(11) 92.8(1). The centers
of the five atoms of the CoS2C2 moiety [Co(1), S(1), S(2),
C(1), C(2)] are within 0.15 Å of a plane. The angle between
planes [Co(1), S(2), C(10), C(11)] and CoS2C2 is 81.0(1)°.
F igu r e 1. ORTEP drawing of 2 with the numbering
scheme.
Compound 2 was found to be a good precursor for
other addition reactions. Thus, treatment of 2 with 1-2
equiv of an alkyne in refluxing benzene for 2 h gave
novel alkyne adduct complexes, CpCo(R1CdCR2)(S2C2-
B10H10), 4, in moderate yield (Scheme 1).11 Adducts
4a -c were isolated as air-stable, microcrystalline solids
and were spectroscopically characterized.12 Each of the
adducts shows the expected 1H and 13C NMR signals
and is a 1:1 adduct of the cobaltadithia-o-carborane and
alkene groups by elemental analyses. The 1H NMR
spectrum of adduct 4a showed two nonequivalent 1H
signals of the OCH3 groups of the ester and two
nonequivalent 13C signals of the ester CO groups, in
agreement with molecular structure of this adduct as
determined by single-crystal X-ray analysis (Figure 3).13
F igu r e 2. ORTEP drawing of 3 with the numbering
scheme.
The reaction of 2 with 1 equiv of CpCo(C2H4)2 in
toluene at -78 °C proceeded smoothly, as monitored by
the change of the green solution to blue. The blue
complex 3 was isolated in 90% yield as a crystalline solid
after precipitation from toluene/hexanes. Exact mass
measurements on the parent ion of 3 support the
(11) In a typical run, 2 (0.33 g, 1.0 mmol) and dimethyl acetylene-
dicarboxylate (0.25 mL, 2.0 mmol) were dissolved in benzene (10 mL)
under N2, and the solution was heated ar reflux for 2 h. Addition of
hexane to the resulting dark red solution afforded 4a as dark red
crystals (0.43 g, 0.91 mmol, 91%). Complexes 4b and 4c were obtained
with essentially the same procedure in 87% and 23% yields, respec-
tively.
formulation of the compound as [(C5H5)Co]2S2C2B10H10
,
(12) Data for 4a . Anal. Calcd for C13H21B10O4S2Co: C, 35.05; H, 4.48.
Found: C, 35.10; H, 4.52. IR (KBr, cm-1): ν(BH) 2580; ν(CdO), 1710;
ν(CdC), 1579. 1H NMR (200.13 MHz, ppm, CDCl3): 5.23 (s, 5H, C5H5),
3.94 (s, 3H, OCH3), 3.77 (s, 3H, OCH3). 13C{1H} NMR (50.3 MHz, ppm,
CDCl3): 171.07 (s, CH3OCO), 155.25 (s, CH3OCO), 118.84 (CH3-
OCOCd), 98.40 (CH3OCOCd), 86.70 (s, C5H5), 52.85 (s, OCH3), 52.71
(s, OCH3). Data for 4b. Anal. Calcd for C15H21B10S2Co: C, 41.66; H,
4.89. Found: C, 41.73; H, 4.95. IR (KBr, cm-1): ν(BH), 2600; ν(CdC),
1488; ν(CdC), 1442. 1H NMR (200.13 MHz, ppm, CDCl3): 7.30 (s, 5H,
C6H5), 4.51 (s, 5H, C5H5), 2.36 (s, 1H, CdCH). 13C{1H} NMR (50.3 MHz,
ppm, CDCl3): 192.05 (s, HCdC-C6H5), 176.64 (s, HCdC-C6H5),
127.58 (m, C6H5), 84.96 (s, C5H5). Data for 4c. Anal. Calcd for
indicating that a CpCo unit has been incorporated into
the Co-S bond of the cobaltadithia-o-carborane ring.9
Indeed, an X-ray study10 of 3 showed it to be the
product of the addition of a CpCo unit into the Co-S
bond in 2. As shown in Figure 2, the structure of 3
consists of binuclear (CpCo)2 fragments in which each
CpCo unit is attached to both sulfur atoms of a 1,2-
dithio-o-carboranyl ligand 1.
11
12
1
(9) Data for 3. Exact mass calcd. for
B
C
59Co2 H2032S2 456.0601,
C12H25B10S2SiCo: C, 33.63; H, 5.88. Found: C, 33.68; H, 5.93. IR (KBr,
10
12
found 456.0607. Anal. Calcd for C12H20B10S2Co2: C, 31.72; H, 4.44.
Found: C, 31.69; H, 4.49. IR (KBr, cm-1): ν(BH), 2586. 1H NMR
(200.13 MHz, ppm, CDCl3): 5.00 (s, 5H, C5H5). 13C{1H} NMR (50.3
MHz, ppm, CDCl3): 77.79 (s, C5H5).
cm-1): ν(BH), 2586; ν(CdC), 1401. 1H NMR (200.13 MHz, ppm,
CDCl3): 5.00 (s, 5H, C5H5), 1.91 (s, 1H, CdCH), 0.29 (s, 9H, Si(CH3)3).
13C{1H} NMR (50.3 MHz, ppm, CDCl3): 146.51 (s, HCdC-Si(CH3)3),
77.92 (s, C5H5), 1.78 (s, Si(CH3)3).
(10) Crystallographic data for 3: a ) 15.981(4) Å, b ) 55.478(17)
Å, c ) 12.0562(17) Å, and â ) 115.063(16)° with Z ) 4 in space group
Cc (No. 9). R1 (wR2) ) 0.0630 (0.1685) for 9948 data with I > 2.0σ(I)
and anisotropic refinements of the model with idealized hydrogen
atoms.
(13) Crystallographic data for 4a : a ) 10.0447(7) Å, b ) 11.5109(6)
Å, c ) 12.0399(5) Å, R ) 115.980(3)°, â ) 106.281(5)°, and γ ) 102.960-
(5)° with Z ) 2 in space group P1h (No. 2). R1 (wR2) ) 0.0480 (0.1205)
for 4325 data with I > 2.0σ(I) and anisotropic refinements of the model
with idealized hydrogen atoms.

2740 Organometallics, Vol. 18, No. 15, 1999
Communications
Sch em e 1
F igu r e 4. ORTEP drawing of adduct 5. Selected bond
lengths (Å) and angles (deg): Co(1)-S(1) 2.264(1), Co(1)-
S(2) 2.1567(9), Co(1)-C(8) 1.994(4), S(2)-C(8) 1.760(3),
S(1)-C(1) 1.776(3), S(2)-C(2) 1.808(8), C(1)-C(2) 1.647-
(4); S(1)-Co(1)-S(2) 94.78(3), S(2)-Co(1)-C(8) 50.0(1),
S(1)-Co(1)-C(8) 91.9(1), Co(1)-C(8)-S(2) 69.8(1), Co(1)-
S(2)-C(8) 60.2(1). The centers of the five atoms of the
CoS2C2 moiety [Co(1), S(1), S(2), C(1), C(2)] are within 0.16
Å of a plane. The angle between planes [Co(1), S(2), C(8)]
and CoS2C2 is 83.0(1)°.
lecular structure of 5 is shown in Figure 4, together with
important bond parameters. The plane of the C-Co-S
three-membered ring is almost perpendicular to the
plane of the cobaltadithia-o-carborane ring. In 5, the
trimethylsilyl group is located in the anti-position with
respect to the cobaltadithia-o-carborane ring. The for-
mation of a methylene bridge between a metal and a
chalcogen in a reaction with a diazoalkane compound
is a typical result due to unsaturation.17 These cycload-
dition reactions suggest that a certain degree of multiple-
bond character is present in the Co-S bond of complex
2.
This structure results from the addition of R1CtCR2
into the Co-S bond of CpCo(S2C2B10H10), 2. In adduct
4a , the alkene moiety thus formed bridges between Co
and S of the metalladithia-o-carborane ring without
breaking the Co-S bond [Co(1)-S(1) ) 2.247(2) Å, Co-
(1)-S(2) ) 2.246(1) Å]. This adduct has a piano-stool
structure consisting of a four-membered and a five-
membered ring. The central metal is coordinatively
saturated, in contrast to the pentacoordinate structure
of complex 2. In this adduct, the plane of the C(11)-
Co(1)-S(2)-C(10) four-membered ring is almost per-
pendicular to the plane of the almost planar dithia-o-
carborane ring. Such an addition of an alkyne into an
M-S bond has been observed in Sugimori’s work on the
chemoselective addition of dimethyl acetylenedicar-
boxylate to the Rh-S bond in a rhodium-catalyzed
reaction.14
Ack n ow led gm en t . We gratefully acknowlege the
financial support from the Korean Ministry of Education
through the Basic Science Research Institute Program
(BSRI-98-3407).
Similar to the reactions between 2 and alkynes, the
cobaltadithia-o-carborane ring in 2 undergoes the ad-
dition of a methylene group between Co and S in its
reaction with a diazoalkane. The reaction of 2 with
trimethylsilyldiazomethane in dichloromethane solution
at room temperature for 1 h gave the trimethylsilyl-
methylene adduct 515 in 84% yield. To establish the
exact conformation of the adduct, the structure of 5 was
determined by single-crystal X-ray analysis.16 The mo-
Su p p or tin g In for m a tion Ava ila ble: Tables describing
the X-ray analysis (data collection and analysis), crystal data,
atomic coordinates, anisotropic thermal parameters, bond
lengths and angles, and least-squares planes for 4a and 5. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM990269V
(16) Crystallographic data for 5: a ) 7.8599(4) Å, b ) 9.7306(8) Å,
c ) 14.7510(7) Å, R ) 102.517(5)°, â ) 104.820(4)°, and γ ) 96.329(5)°
with Z ) 2 in space group P1h (No. 2). R1 (wR2) ) 0.0374 (0.1028) for
4107 data with I > 2.0σ(I) and anisotropic refinements of the model
with idealized hydrogen atoms.
(17) (a) Takayama, C.; Takeuchi, K.; Kajitani, M.; Sugiyama, T.;
Sugimori, A. Chem. Lett. 1998, 241. (b) Sakurada, M.; Kajitani, M.;
Dohki, K.; Akiyama, T.; Sugimori, A. J . Organomet. Chem. 1992, 423,
141. (c) Sakurada, M.; Okubo, J .; Kajitani, M.; Akiyama, T.; Sugimori,
A. Phosphorus, Sulfur, Silicon, Relat. Elements 1992, 67, 145. (d)
Kajitani, M.; Sakurada, M.; Dohki, K.; Suetsugu, T.; Akiyama, T.;
Sugimori, A. J . Chem. Soc., Chem. Commun. 1990, 19. (e) Sakurada,
M.; Okubo, J .; Kajitani, M.; Akiyama, T.; Sugimori, A. Chem. Lett.
1990, 1837.
(14) (a) Kajitani, M.; Suetsugu, T.; Takagi, T.; Akiyama, T.; Sugi-
mori, A.; Aoki, K.; Yamazaki, H. J . Organomet. Chem. 1995, 487, C8.
(b) Sakurada, M.; Kajitani, M.; Dohki, K.; Akiyama, T.; Sugimori, A.
J . Organomet. Chem. 1992, 423, 141. (c) Kajitani, M.; Suetsugu, T.;
Wakabayashi, R.; Igarashi, A.; Akiyama, T.; Sugimori, A. J . Orga-
nomet. Chem. 1985, 293, C15.
(15) Data for 5. Anal. Calcd for C11H25B10S2SiCo: C, 31.72; H, 6.05.
Found: C, 31.77; H, 6.09. IR (KBr, cm-1): ν(BH), 2596; ν(BH), 2568.
1H NMR (200.13 MHz, ppm, CDCl3): 4.99 (s, 5H, C5H5), 3.49 (s, 1H,
(CH3)3SiCH), 0.24 (s, 9H, Si(CH3)3). 13C{1H} NMR (50.3 MHz, ppm,
CDCl3): 83.10 (s, C5H5), 43.93 (s, (CH3)3SiCH), 0.00 (s, Si(CH3)3).