Reactions of Doubly Bridged Biscyclopentadienes with Molybdenum (Tungsten) Carbonyl

Article abstract of DOI:10.1021/om034039z

Dimolybdenum complexes (X)(Y)[(η⁵-C₅H ₃)Mo(CO)₃]₂ [Y = Me₂Si, X = Me ₂C, (CH₂)₅C, CH₂; Y = Ph ₂Si, X = Me₂C] and desilylation products (X)[(η ⁵-C₅H₄)Mo(CO)₃]₂ were obtained from the reactions of carbon and silicon doubly bridged biscyclopentadiene ligands (X)(Y)(C₅H₄)₂ with Mo(CO)₆ in refluxing xylene. When these ligands reacted with W(CO)₆, under similar conditions, in addition to ditungsten complexes (X)(Y)[(η⁵-C₅H₃)W(CO) ₃]₂ [X = Me₂C; Y = Me₂Si, Ph ₂Si] and desilylation products (X)[(η?⁵-C ₅H₄)W(CO)₃]₂, a class of structurally novel complexes (X)(η⁵-C₅H ₃)(η⁵,η¹-C₅H ₃)[(Y)W(CO)₃][W(CO)₃] [for X = Me₂C, (CH₂)₅C; Y = Me₂Si] with a W-Si bond were also isolated. The reactions of carbon and germanium doubly bridged biscyclopentadiene ligands (X)(Me₂Ge)(C₅H ₄)₂ [X = Me₂C, (CH₂)₅C] with Mo(CO)₆ or W(CO)₆ gave similar novel complexes (X)(η⁵-C₅H₃)(η⁵,η ¹-C₅H₃)[(Me₂Ge)M(CO) ₃][M(CO)₃] [X = Me₂C, (CH₂) ₅C; M = Mo, W] with a M-Ge bond. The reactions also produced degermylation products. However, the corresponding dimolybdenum or ditungsten complexes were not isolated in these cases. The molecular structures of 2, 6, 8, 10, 11, 13, 14, 15, 19, 21, 22, 25t, and 26t have been determined by X-ray diffraction. The M-M distances in complexes 2 [3.4328(12) A], 8 [3.453(2) A], and 11 [3.403(2) A] are conspicuously elongated and are in fact the longest ever reported among the biscyclopentadienyl dimolybdenum or ditungsten complexes. The factors affecting the structures of dimolybdenum or ditungsten complexes are discussed.

Full text of DOI:10.1021/om034039z

4842
Organometallics 2003, 22, 4842-4852
Articles
Rea ction s of Dou bly Br id ged Biscyclop en ta d ien es w ith
Molybd en u m (Tu n gsten ) Ca r bon yl
Baiquan Wang,* Bolin Zhu, Shansheng Xu, and Xiuzhong Zhou
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry,
Nankai University, Tianjin 300071, People’s Republic of China
Received J uly 15, 2003
Dimolybdenum complexes (X)(Y)[(η5-C5H3)Mo(CO)3]2 [Y ) Me2Si, X ) Me2C, (CH2)5C, CH2;
Y ) Ph2Si, X) Me2C] and desilylation products (X)[(η5-C5H4)Mo(CO)3]2 were obtained from
the reactions of carbon and silicon doubly bridged biscyclopentadiene ligands (X)(Y)(C5H4)2
with Mo(CO)6 in refluxing xylene. When these ligands reacted with W(CO)6, under similar
conditions, in addition to ditungsten complexes (X)(Y)[(η5-C5H3)W(CO)3]2 [X ) Me2C; Y )
Me2Si, Ph2Si] and desilylation products (X)[(η5-C5H4)W(CO)3]2, a class of structurally novel
complexes (X)(η5-C5H3)(η5,η1-C5H3)[(Y)W(CO)3][W(CO)3] [for X ) Me2C, (CH2)5C; Y ) Me2-
Si] with a W-Si bond were also isolated. The reactions of carbon and germanium doubly
bridged biscyclopentadiene ligands (X)(Me2Ge)(C5H4)2 [X ) Me2C, (CH2)5C] with Mo(CO)6
or W(CO)6 gave similar novel complexes (X)(η5-C5H3)(η5,η1-C5H3)[(Me2Ge)M(CO)3][M(CO)3]
[X ) Me2C, (CH2)5C; M ) Mo, W] with a M-Ge bond. The reactions also produced
degermylation products. However, the corresponding dimolybdenum or ditungsten complexes
were not isolated in these cases. The molecular structures of 2, 6, 8, 10, 11, 13, 14, 15, 19,
21, 22, 25t, and 26t have been determined by X-ray diffraction. The M-M distances in
complexes 2 [3.4328(12) Å], 8 [3.453(2) Å], and 11 [3.403(2) Å] are conspicuously elongated
and are in fact the longest ever reported among the biscyclopentadienyl dimolybdenum or
ditungsten complexes. The factors affecting the structures of dimolybdenum or ditungsten
complexes are discussed.
In tr od u ction
complexes with superlong Fe-Fe bond distances and
novel complexes with Fe-Si or Fe-Ge bonds.4 This
paper will further report the reaction of the doubly
bridged biscyclopentadiene ligands with molybdenum
and tungsten carbonyl.
Considerable attention has been focused on the
synthesis and chemical behavior of a variety of doubly
bridged biscyclopentadienyl carbonyl dimetallic com-
plexes (M ) Ti, V, Cr, Fe, Ru, Co, Ni).1 Compared to
their nonbridged and single-bridged analogues, these
complexes exhibit unique characteristics in both their
structures and reactivity. Reactions of doubly bridged
biscyclopentadiene (C5H4)2(SiMe2)2 with metal carbonyl
compounds have been extensively studied in the past
decade.2,3 We have recently investigated the reaction of
a certain type of doubly bridged biscyclopentadiene
ligands with Fe(CO)5 and obtained a series of diiron
Exp er im en ta l Section
Gen er a l Con sid er a tion s. Schlenk and vacuum line tech-
niques were employed for all manipulations. All solvents were
distilled from appropriate drying agents under argon prior to
use. 1H NMR spectra were recorded on a Bruker AC-P200,
while IR spectra were recorded as KBr disks on a Nicolet 560
E.S.P. FTIR spectrometer. Mass spectra were obtained from
a VG ZAB-HS. EPR spectra were recorded on a Bruker EMX
instrument. Elemental analyses were performed on a Perkin-
* Corresponding
bqwang@nankai.edu.cn.
author.
Fax:
86-22-23502458.
E-mail:
(1) Corey, J . Y.; Huhmann, J . L.; Rath, N. P. Inorg. Chem. 1995,
34, 3203, and references therein.
(3) (a) McKinley S. G.; Angelici, R. J . Organometallics 2002, 21,
1235. (b) Ovchinnikov, M. V.; Angelici, R. J . J . Am. Chem. Soc. 2000,
122, 6130. (c) Ovchinnikov, M. V.; Guzei, I. A.; Angelici, R. J .
Organometallics 2001, 20, 691. (d) Ovchinnikov, M. V.; Wang, X.;
Schultz, A. J .; Guzei, I. A.; Angelici, R. J . Organometallics 2002, 21,
3292. (e) Ovchinnikov, M. V.; Ellern, A. M.; Guzei, I. A.; Angelici, R.
J . Inorg. Chem. 2001, 40, 7014. (f) Ovchinnikov, M. V.; LeBlanc, E.;
Guzei, I. A.; Angelici, R. J . J . Am. Chem. Soc. 2001, 123, 11494. (g)
Ovchinnikov, M. V.; Klein, D. P.; Guzei, I. A.; Choi, M. G.; Angelici, R.
J . Organometallics 2002, 21, 617.
(2) (a) Amor, F.; Gomez-Sal, P.; J esus, E.; Royo, P.; Vazquez de
Miguel, A. Organometallics 1994, 13, 4322. (b) Amor, F.; J esus, E.;
Perez, A. I.; Royo, P.; Vazquez de Miguel, A. Organometallics 1996,
15, 365. (c) Amor, F.; Gomez-Sal, P.; J esus, E.; Martin, A.; Perez, A.
I.; Royo, P.; Vazquez de Miguel, A. Organometallics 1996, 15, 2103.
(d) Galakhov, M. V.; Gil, A.; J esus, E.; Royo, P. Organometallics 1995,
14, 3746. (e) Calvo, M.; Galakhov, M. V.; Gomez-Garcia, R.; Gomez-
Sal, P.; Martin, A.; Royo, P.; Vazquez de Miguel, A. J . Organomet.
Chem. 1997, 548, 157. (f) Amor, F.; de J ustes, F.; Royo, P.; de Miguel,
A. V. Inorg. Chem. 1996, 35, 3440. (g) Calvo, M.; Gomes-Sal, P.;
Manzanero, A.; Royo, P. Polyhedron 1998, 17, 1081. (h) Gomez-Gacia,
R.; Royo, P. J . Organomet. Chem. 1999, 583, 86.
(4) (a) Xu, S.; Zhang, J .; Zhu, B.; Wang, B.; Zhou, X.; Weng, L. J .
Organomet. Chem. 2001, 626, 186. (b) Wang, B.; Zhu, B.; Zhang, J .;
Xu, S.; Zhou, X.; Weng, L. Organometallics 2003, submitted.
10.1021/om034039z CCC: $25.00 © 2003 American Chemical Society
Publication on Web 10/11/2003

Doubly Bridged Biscyclopentadienes
Organometallics, Vol. 22, No. 24, 2003 4843
Elmer 240C analyzer. (Me2C)(Me2Si)(C5H4)2 (1),5 [CH2)5C](Me2-
Si)(C5H4)2 (4),4 (Me2C)(Ph2Si)(C5H4)2 (7),4 (CH2)(Me2Si)(C5H4)2
(9),4 (Me2C)(Me2Ge)(C5H4)2 (18),5 [CH2)5C](Me2Ge)(C5H4)2 (20),4
and (Me2C)(Me2Si)(t-BuC5H3)2 (24)4 were prepared according
to literature methods.
Rea ction of (Me2C)(Me2Si)(C5H4)2 (1) w ith Mo(CO)6. A
solution of 0.40 g (1.75 mmol) of (Me2C)(Me2Si)(C5H4)2 (1) and
0.80 g (3.03 mmol) of Mo(CO)6 in 40 mL of xylene was refluxed
for 6.5 h. After removal of solvent the residue was chromato-
graphed on an alumina column using petroleum ether/CH2-
Cl2 as eluent. The first band (red) afforded 0.03 g (3%) of 3 as
deep red crystals. The second band (green) gave 0.19 g (18%)
of 2 as black crystals. 2: mp 220 °C (dec). Anal. Calcd for
Rea ction of (Me2C)(Me2Si)(C5H4)2 (1) w ith W(CO)6. A
solution of 0.40 g (1.75 mmol) of (Me2C)(Me2Si)(C5H4)2 (1) and
1.00 g (2.84 mmol) of W(CO)6 in 40 mL of xylene was refluxed
for 24 h. After removal of solvent the residue was chromato-
graphed on an alumina column using petroleum ether/CH2-
Cl2 as eluent. The first band (yellow) afforded 0.08 g (6%) of
13 as orange crystals. The second band (red) gave 0.05 g (4%)
of 12 as deep red crystals. The third band (gray) gave 0.03 g
(2%) of 11 as black crystals. 11: mp 210 °C (dec). Anal. Calcd
for C21H18O6SiW2: C, 33.09; H, 2.38. Found: C, 33.05; H, 2.46.
1H NMR (CDCl3) δ: 5.31 (m, 2H, C5H3), 5.27 (m, 4H, C5H3),
1.54 (s, 3H, C-Me), 1.36 (s, 3H, C-Me), 0.56 (s, 3H, Si-Me), 0.49
(s, 3H, Si-Me). IR (νCO, cm-1): 2015(s), 1937(s), 1910(s), 1887-
(s). 12:6 mp 281-282 °C. 1H NMR (CDCl3) δ: 5.26 (m, 8H,
C5H4), 1.55 (s, 6H, C-Me). IR (νCO, cm-1): 1997(s), 1958(s),
1910(s), 1885(s), 1870(s), 1858(s). 13: mp 260 °C (dec). Anal.
Calcd for C21H18O6SiW2: C, 33.09; H, 2.38. Found: C, 33.24;
C
21H18Mo2O6Si: C, 43.02; H, 3.09. Found: C, 42.67; H, 3.18.
1H NMR (CDCl3) δ: 5.36 (m, 2H, C5H3), 5.21 (m, 2H, C5H3),
5.07 (m, 2H, C5H3), 1.50 (s, 3H, C-Me), 1.35 (s, 3H, C-Me), 0.55
(s, 3H, Si-Me), 0.46 (s, 3H, Si-Me). IR (νCO, cm-1): 2026(s),
1938(s), 1920(s), 1896(s), 1870(s). MS (EI): m/ Z 586 (M+, 8.5),
558 (M+ - CO, 22.5), 530 (M+ - 2CO, 8.9), 502 (M+ - 3CO,
38.7), 474 (M+ - 4CO, 84.6), 472 (M+ - 2CO - SiMe2, 90.6),
446 (M+ - 5CO, 63.4), 444 (M+ - 3CO - SiMe2, 70.5), 418
(M+ - 6CO, 52.3), 412 (100), 317 (M+ - 6CO-Mo, 6.4), 224
(M+ - 6CO - 2Mo, 16.2). 3:6 mp 200 °C (dec). 1H NMR (CDCl3)
δ: 5.34 (m, 4H, C5H4), 5.22 (m, 4H, C5H4), 1.51 (s, 6H, C-Me).
IR (νCO, cm-1): 2002(s), 1960(s), 1946(s), 1914(s), 1894(s), 1878-
(s), 1864(s).
1
H, 2.42. H NMR (CDCl3) δ: 6.20 (m, 1H, C5H3), 5.84 (m, 1H,
C5H3), 5.30 (m, 1H, C5H3), 5.19 (m, 1H, C5H3), 5.10 (m, 1H,
C5H3), 4.96 (m, 1H, C5H3), 1.60 (s, 3H, C-Me), 1.58 (s, 3H,
C-Me), 0.74 (s, 3H, Si-Me), 0.73 (s, 3H, Si-Me). IR (νCO, cm-1):
2026(s), 1989(s), 1940(s), 1914(s), 1890(s).
Rea ction of [(CH2)5C](Me2Si)(C5H4)2 (4) w ith W(CO)6.
A solution of 1.00 g (3.72 mmol) of 4 and 1.50 g (4.26 mmol) of
W(CO)6 in 40 mL of xylene was refluxed for 24 h. After removal
of the solvent the residue was chromatographed on an alumina
column using petroleum ether/CH2Cl2 as eluent. The first band
(orange) afforded 0.08 g (3%) of 15 as orange crystals. The
second band (red) gave 0.03 g (1%) of 14 as dark red crystals.
14: mp 222 °C (dec). Anal. Calcd for C22H18O6W2: C, 35.42;
H, 2.43. Found: C, 35.41; H, 2.44. 1H NMR (CDCl3) δ: 5.65
(m, 2H, C5H4), 5.43 (m, 2H, C5H4), 5.16 (m, 2H, C5H4), 5.09
(m, 2H, C5H4), 1.90-1.20 (m, 10H, CH2). IR (νCO, cm-1): 2002-
(s), 1946(s), 1914(s), 1886(s), 1868(s), 1850(s). 15: mp 260 °C
Rea ction of [(CH2)5C](Me2Si)(C5H4)2 (4) w ith Mo(CO)6.
A solution of 0.30 g (1.12 mmol) of 4 and 0.70 g (2.65 mmol) of
Mo(CO)6 in 40 mL of xylene was refluxed for 6.5 h. After
removal of solvent the residue was chromatographed on an
alumina column using petroleum ether/CH2Cl2 as eluent. The
first band (red) afforded 0.05 g (9%) of 6 as deep red crystals.
The second band (green) gave 0.10 g (15%) of 5 as black
crystals. 5: mp 190 °C (dec). Anal. Calcd for C24H22Mo2O6Si:
1
C, 46.02; H, 3.54. Found: C, 45.92; H, 4.18. H NMR (CDCl3)
(dec). Anal. Calcd for
C24H22O6SiW2: C, 35.93; H, 2.76.
Found: C, 35.91; H, 2.67. 1H NMR (CDCl3) δ: 6.31 (m, 1H,
C5H3), 5.85 (m, 1H, C5H3), 5.27 (m, 2H, C5H3), 5.10 (m, 1H,
C5H3), 4.95 (m, 1H, C5H3), 2.10-1.30 (m, 10H, CH2), 0.71 (s,
6H, Si-Me). IR (νCO, cm-1): 2026(s), 1989(s), 1954(m), 1910-
(s), 1880(s).
δ: 5.36 (m, 2H, C5H3), 5.20 (m, 4H, C5H3), 1.90-1.20 (m, 10H,
CH2), 0.53 (s, 3H, Si-Me), 0.45 (s, 3H, Si-Me). IR (νCO, cm-1):
2010(s), 1954(s), 1906(s), 1863(m). 6: mp 230 °C (dec). Anal.
Calcd for C22H18Mo2O6: C, 46.34; H, 3.18. Found: C, 46.28;
H, 3.17. 1H NMR (CDCl3) δ: 5.25 (m, 8H, C5H4), 1.90-1.35
(m, 10H, CH2). IR (νCO, cm-1): 2010(s), 1950(s), 1918(s), 1894-
(s), 1878(s), 1863(s).
Rea ction of (Me2C)(P h 2Si)(C5H4)2 (7) w ith Mo(CO)6. A
solution of 0.50 g (1.42 mmol) of 7 and 0.70 g (2.65 mmol) of
Mo(CO)6 in 40 mL of xylene was refluxed for 6.5 h. After
removal of solvent the residue was chromatographed on an
alumina column using petroleum ether/CH2Cl2 as eluent. The
first band (red) gave 0.05 g (7%) of 3. The second band (green)
afforded 0.08 g (8%) of 8 as black crystals. 8: mp 200 °C (dec).
Anal. Calcd for C31H22Mo2O6Si: C, 52.41; H, 3.12. Found: C,
52.36; H, 3.10. 1H NMR (CDCl3) δ: 7.60-7.30 (m, 10H, C6H5),
5.60 (m, 2H, C5H3), 5.50 (m, 2H, C5H3), 5.15 (m, 2H, C5H3),
1.35 (s, 3H, C-Me), 1.13 (s, 3H, C-Me). IR (νCO, cm-1): 2015-
(s), 1956(s), 1945(s), 1890(m), 1874(m).
Rea ction of (H2C)(Me2Si)(C5H4)2 (9) w ith Mo(CO)6. A
solution of 0.40 g (2.00 mmol) of 9 and 0.70 g (2.65 mmol) of
Mo(CO)6 in 40 mL of xylene was refluxed for 6.5 h. After
removal of solvent the residue was chromatographed on an
alumina column using petroleum ether/CH2Cl2 as eluent. The
red band afforded 0.10 g (9%) of 10 as dark red crystals. 10:
mp 210 °C. Anal. Calcd for C19H14Mo2O6Si: C, 40.88; H, 2.63.
Found: C, 40.40; H, 2.39. 1H NMR (CDCl3) δ: 5.32 (m, 2H,
C5H3), 5.27 (m, 4H, C5H3), 3.92 (d, J ) 16.0 Hz, 1H, CH2), 3.24
(d, J ) 16.0 Hz, 1H, CH2), 0.57 (s, 3H, Si-Me), 0.33 (s, 3H,
Si-Me). IR (νCO, cm-1): 2010(s), 1958(s), 1934(m), 1918(m),
1890(s), 1866(s).
Rea ction of (Me2C)(P h 2Si)(C5H4)2 (7) w ith W(CO)6. A
solution of 1.00 g (2.84 mmol) of 7 and 1.50 g (4.26 mmol) of
W(CO)6 in 40 mL of xylene was refluxed for 24 h. After removal
of the solvent the residue was chromatographed on an alumina
column using petroleum ether/CH2Cl2 as eluent. The first band
(red) gave 0.11 g (6%) of 12. The second band (gray) afforded
0.03 g (1%) of 16 as black crystals. 16: mp 230 °C (dec). Anal.
Calcd for C31H22W2O6SiW2: C, 42.01; H, 2.50. Found: C, 41.68;
1
H, 2.44. H NMR (CDCl3) δ: 7.60-7.45 (m, 4H, C6H5), 7.40-
7.25 (m, 6H, C6H5), 5.72 (m, 2H, C5H3), 5.40 (m, 2H, C5H3),
5.36 (m, 2H, C5H3), 1.37 (s, 3H, C-Me), 1.16 (s, 3H, C-Me). IR
(νCO, cm-1): 2010(s), 1962(s), 1946(s), 1922(s), 1898(s), 1859-
(m).
Rea ction of (H2C)(Me2Si)(C5H4)2 (9) w ith W(CO)6. A
solution of 0.40 g (2.00 mmol) of 9 and 1.00 g (2.84 mmol) of
W(CO)6 in 40 mL of xylene was refluxed for 24 h. After removal
of the solvent the residue was chromatographed on an alumina
column using petroleum ether/CH2Cl2 as eluent. The red band
afforded 0.18 g (18%) of 17 as dark red crystals. 17:7 mp 220
1
°C (dec) (lit. 226-228 °C dec7). H NMR (CDCl3) δ: 5.28 (m,
8H, C5H4), 3.88 (s, 2H, CH2). IR (νCO, cm-1): 1997(s), 1946(s),
1878(s), 1859(s).
Rea ction of (Me2C)(Me2Ge)(C5H4)2 (18) w ith Mo(CO)6.
A solution of 0.60 g (2.20 mmol) of 18 and 0.80 g (3.03 mmol)
of Mo(CO)6 in 40 mL of xylene was refluxed for 7 h. After
removal of solvent the residue was chromatographed on an
alumina column using petroleum ether/CH2Cl2 as eluent. The
first band (yellow) afforded 0.10 g (7%) of 19 as orange-red
(5) Nifant’ev, I. E.; Yarnykh, V. L.; Borzov, M. V.; Mazurchik, B.
A.; Mstyslasky, V. I.; Roznyatovsky, V. A.; Ustynyuk, Y. A. Organo-
metallics 1991, 10, 3739.
(6) Fierro, R.; Bitterwolf, T. E.; Rheingold, A. L.; Yap, G. P. A.;
Liable-Sands, L. M. J . Organomet. Chem. 1996, 524, 19.
(7) Bitterwolf, T. E.; Rheingold, A. L. Organometallics 1991, 10,
3856.

4844 Organometallics, Vol. 22, No. 24, 2003
Wang et al.
crystals. The second band (red) afforded 0.25 g (22%) of 3. 19:
mp 250 °C (dec). Anal. Calcd for C21H18GeMo2O6: C, 39.98;
H, 2.88. Found: C, 39.51; H, 2.74. 1H NMR (CDCl3) δ: 5.98
(m, 1H, C5H3), 5.69 (m, 1H, C5H3), 5.37 (m, 1H, C5H3), 5.18
(m, 1H, C5H3), 5.00 (m, 1H, C5H3), 4.90 (m, 1H, C5H3), 1.55 (s,
Calcd for C27H30Mo2O6: C, 39.63; H, 3.70. Found: C, 39.56;
1
H, 3.65. H NMR (CDCl3) δ: 5.28 (m, 6H, C5H3), 1.54 (s, 3H,
C-Me), 1.49 (s, 3H, C-Me), 1.24 (s, 18H, CMe3). IR (νCO, cm-1):
2002(s), 1942(s), 1890(s), 1876(s).
Cr ysta llogr a p h ic Stu d ies. Single crystals of complexes 2,
6, 8, 10, 11, 13, 14, 15, 19, 21, 22, 25t, and 26t suitable for
X-ray diffraction were obtained from hexane/CH2Cl2 solution.
Data collection was performed on a Bruker SMART 1000,
using graphite-monochromated Mo KR radiation (ω-2θ scans,
λ ) 0.71073 Å). Semiempirical absorption corrections were
applied for all complexes. The structures were solved by direct
methods and refined by full-matrix least-squares. All calcula-
tions were using the SHELXL-97 program system. The crystal
data and summary of X-ray data collection are presented in
Tables 1 and 2.
3H, C-Me), 1.53 (s, 3H, C-Me), 0.82 (s, 6H, Ge-Me). IR (νCO
,
cm-1): 2034(s), 1993(s), 1954(s), 1934(s), 1918(s), 1902(s).
Rea ction of [(CH2)5C](Me2Ge)(C5H4)2 (20) w ith Mo-
(CO)6. A solution of 0.50 g (1.60 mmol) of 20 and 1.00 g (3.79
mmol) of Mo(CO)6 in 40 mL of xylene was refluxed for 6.5 h.
After removal of solvent the residue was chromatographed on
an alumina column using petroleum ether/CH2Cl2 as eluent.
The first band (red) afforded 0.15 g (16%) of 6. The second
band (green) gave 0.10 g (10%) of 21 as black crystals. 21: mp
210 °C (dec). Anal. Calcd for C24H22GeMo2O6: C, 42.97; H, 3.31.
Found: C, 42.89; H, 3.32. 1H NMR (CDCl3) δ: 6.08 (m, 1H,
C5H3), 5.69 (m, 1H, C5H3), 5.36 (m, 1H, C5H3), 5.27 (m, 1H,
C5H3), 4.97 (m, 1H, C5H3), 4.90 (m, 1H, C5H3), 2.10-1.30 (m,
Resu lts a n d Discu ssion
10H, CH2), 0.81 (s, 3H, Ge-Me), 0.79 (s, 3H, Ge-Me). IR (νCO
,
Rea ction of th e Ca r bon a n d Silicon Dou bly
Br id ged Biscyclop en ta d ien e Liga n d s w ith Mo-
(CO)6. When the carbon and silicon doubly bridged
biscyclopentadiene ligands (X)(Y)(C5H4)2 [Y ) Me2Si, X
) Me2C (1), (CH2)5C (4), CH2 (9); Y ) Ph2Si, X) Me2C
(7)] reacted with Mo(CO)6 in refluxing xylene, the
corresponding intramolecular dimolybdenum complexes
(X)(Y)[(η5-C5H3)Mo(CO)3]2 [Y ) Me2Si, X ) Me2C (2),
(CH2)5C (5), CH2 (10); Y ) Ph2Si, X ) Me2C (8)] and
the desilylation products (X)[(η5-C5H4)Mo(CO)3]2 [X )
Me2C (3), (CH2)5C (6)] were obtained (Scheme 1). The
expected complex of type C was not isolated in all cases,
although the steric effect at the bridging carbon atom
or silicon atom was changed with different substituents.
This is different from the reactions of the carbon and
silicon doubly bridged biscyclopentadiene ligands with
Fe(CO)5, which afforded novel complexes with Fe-Si
bonds.4b When the reaction was performed in toluene,
similar products were obtained but in lower yields. In
DME or diglyme, only the desilylation products were
obtained. All these complexes are air stable in the solid
state. The doubly bridged biscyclopentadienyl dimolyb-
denum complexes 2, 5, and 8 are slightly air sensitive
in solution, which is in agreement with the superlong
Mo-Mo bond distances within their molecular struc-
tures. All these complexes show two or three Cp-H
cm-1): 2026(s), 1989(s), 1962(s), 1922(s), 1886(s).
Rea ction of (Me2C)(Me2Ge)(C5H4)2 (18) w ith W(CO)6.
A solution of 0.80 g (3.03 mmol) of 13 and 1.50 g (4.26 mmol)
of W(CO)6 in 40 mL of xylene was refluxed for 24 h. After
removal of the solvent the residue was chromatographed on
an alumina column using petroleum ether/CH2Cl2 as eluent.
The first band (yellow) afforded 0.08 g (3%) of 22 as orange-
red crystals. The second band (red) afforded 0.12 g (6%) of 12.
22: mp 285 °C (dec). Anal. Calcd for C21H18GeO6W2: C, 31.27;
H, 2.38. Found: C, 31.20; H, 2.24. 1H NMR (CDCl3) δ: 6.20
(m, 1H, C5H3), 5.86 (m, 1H, C5H3), 5.25 (m, 1H, C5H3), 5.21
(m, 1H, C5H3), 5.13 (m, 1H, C5H3), 4.94 (m, 1H, C5H3), 1.58 (s,
6H, C-Me), 0.82 (s, 6H, Ge-Me). IR (νCO, cm-1): 2034(s), 1988-
(s), 1941(s), 1924(s), 1910(s), 1894(s).
Rea ction of [(CH2)5C](Me2Ge)(C5H4)2 (20) w ith W(CO)6.
A solution of 1.00 g (3.20 mmol) of 20 and 1.50 g (4.26 mmol)
of W(CO)6 in 40 mL of xylene was refluxed for 24 h. After
removal of the solvent the residue was chromatographed on
an alumina column using petroleum ether/CH2Cl2 as eluent.
The first band (orange) afforded 0.10 g (4%) of 23 as orange
crystals. The second band (red) gave 0.03 g (1%) of 14. 23: mp
230 °C (dec). Anal. Calcd for C24H22GeMo2O6: C, 34.04; H, 2.62.
Found: C, 34.08; H, 2.66. 1H NMR (CDCl3) δ: 6.29 (m, 1H,
C5H3), 5.85 (m, 1H, C5H3), 5.28 (m, 1H, C5H3), 5.23 (m, 1H,
C5H3), 5.13 (m, 1H, C5H3), 4.94 (m, 1H, C5H3), 2.10-1.20 (m,
10H, CH2), 0.81 (s, 3H, Ge-Me), 0.78 (s, 3H, Ge-Me). IR (νCO
,
cm-1): 2026(s), 1989(s), 1954(m), 1910(s), 1880(s).
Rea ction of (Me2C)(Me2Si)(t-Bu C5H3)2 (24) w ith Mo-
(CO)6. A solution of 0.30 g (0.88 mmol) of 24 and 0.60 g (2.27
mmol) of Mo(CO)6 in 30 mL of xylene was refluxed for 6.5 h.
After removal of solvent the residue was chromatographed on
an alumina column using petroleum ether/CH2Cl2 as eluent.
The red band gave 0.07 g (12%) of 25t as deep red crystals.
25t: mp 190 °C (dec). Anal. Calcd for C27H30Mo2O6: C, 50.48;
H, 4.71. Found: C, 50.50; H, 4.79. 1H NMR (CDCl3) δ: 5.45
(m, 2H, C5H3), 5.10 (m, 2H, C5H3), 4.86 (m, 2H, C5H3), 1.46 (s,
6H, C-Me), 1.20 (s, 18H, CMe3). IR (νCO, cm-1): 2002(s), 1950-
(s), 1918(w), 1890(s), 1870(s).
Reaction of (Me2C)(Me2Si)(t-Bu C5H3)2 (24) with W(CO)6.
A solution of 1.00 g (2.94 mmol) of 24 and 1.50 g (4.26 mmol)
of W(CO)6 in 40 mL of xylene was refluxed for 24 h. After
removal of the solvent the residue was chromatographed on
an alumina column using petroleum ether/CH2Cl2 as eluent.
The red band gave 0.20 g (8%) of the mixture of 26t and 26c
as black-red crystals. According to the different crystal shape,
a small amount of pure cis isomer 26c and trans isomer 26t
were separated mechanically. 26t: mp 190 °C (dec). Anal.
Calcd for C27H30W2O6: C, 39.63; H, 3.70. Found: C, 39.51; H,
3.63. 1H NMR (CDCl3) δ: 5.52 (m, 2H, C5H3), 5.03 (m, 2H,
C5H3), 4.97 (m, 2H, C5H3), 1.50 (s, 3H, C-Me), 1.47 (s, 3H,
C-Me), 1.22 (s, 18H, CMe3). IR (νCO, cm-1): 2002(s), 1954(s),
1944(s), 1910(s), 1878(s), 1862(s). 26c: mp 210 °C (dec). Anal.
1
proton peaks at 5.60-5.07 ppm in the H NMR spectra
and four to six strong terminal carbonyl bands at 2026-
1
1860 cm-1 in the IR spectra. In the H NMR spectrum
of 10 the bridging methylene protons were split as two
double peaks at 3.92, 3.24 (∆δ ) 0.68 ppm) with J )
16.0 Hz, which is much greater than that of ligand 9
(∆δ: 0.10 ppm),4b and the Si-Me protons were split as
two single peaks at 0.57, 0.33 ppm (∆δ ) 24 ppm), which
is much smaller than that of ligand 9 (∆δ: 1.64 ppm).
Rea ction of th e Ca r bon a n d Silicon Dou bly
Br id ged Biscyclop en ta d ien e Liga n d s w ith W(CO)6.
When the carbon and silicon doubly bridged biscyclo-
pentadiene ligands (X)(Y)(C5H4)2 [Y ) Me2Si, X ) Me2C
(1), (CH2)5C (4), CH2 (9); Y ) Ph2Si, X ) Me2C (7)]
reacted with W(CO)6 in refluxing xylene, novel com-
plexes (X)(η5-C5H3)(η5,η1-C5H3)[(Y)W(CO)3][W(CO)3] [Y
) Me2Si; X ) Me2C (13), (CH2)5C (15)] (type C) were
isolated in addition to the ditungsten complexes (X)(Y)-
[(η5-C5H3)W(CO)3]2 [X ) Me2C; Y ) Me2Si (11), Ph2Si
(16)] and the desilylation products (X)[(η5-C5H4)W-
(CO)3]2 [X ) Me2C (13), (CH2)5C (15)] (Scheme 1). All
these complexes are air stable except the ditungsten

Doubly Bridged Biscyclopentadienes
Organometallics, Vol. 22, No. 24, 2003 4845
Ta ble 1. Cr ysta l Da ta a n d Su m m a r y of X-r a y Da ta Collection of 2, 6, 8, 10, 11, 13-15, 19, a n d 21
2
6
8
10
11
formula
fw
C
21H18Mo2O6 Si
C22H18Mo2O6
570.24
C
31H22Mo2O6Si
C19H14Mo2O6Si
558.27
C21H18O6SiW2
762.14
586.32
710.46
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/m
9.098(3)
14.337(5)
9.710(3)
90
117.384(5)
90
1124.5(6)
2
monoclinic
P21/c
13.982(10)
10.557(8)
15.492(11)
90
114.687(11)
90
2078(3)
4
monoclinic
P21/c
11.352(5)
15.051(6)
16.731(7)
90
101.09(3)
90
2805(2)
4
monoclinic
P21/n
10.000(3)
13.870(5)
14.489(5)
90
96.700(6)
90
1996.0(12)
4
monoclinic
P21/n
9.030(5)
14.267(9)
9.649(6)
90
117.500(9)
90
1102.7(11)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
D
calc (g‚cm-3
)
1.732
1.202
580
1.823
1.244
1128
1.682
0.980
1416
1.858
1.349
1096
2.295
10.512
708
µ (mm-1
F(000)
)
cryst size (mm)
max. 2θ (deg)
0.25 × 0.20 × 0.20
0.26 × 0.24 × 0.20
0.20 × 0.16 × 0.12
0.20 × 0.18 × 0.10
0.24 × 0.22 × 0.20
50.04
52.96
50.10
52.82
52.08
no. of reflns collected
no. of indep reflns/Rint
no. of params
4696
2077/0.0231
166
1.010
0.0226, 0.0541
0.0309, 0.0577
11545
4260/0.0334
271
1.009
0.0276, 0.0565
0.0463, 0.0616
8847
4888/0.0447
361
1.002
0.0411, 0.0974
0.0830, 0.1137
9165
4058/0.0373
253
0.999
0.0349, 0.0624
0.0659, 0.0695
5980
2268/0.0501
146
1.040
0.0332, 0.0610
0.0581, 0.0679
goodness-of-fit on F2
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
13
14
15
19
21
formula
fw
C
21H18O6SiW2
C
22H18O6W2
C
24H22O6SiW2
C
21H18GeMo2O6
C24H22GeMo2O6
670.89
762.14
746.06
802.21
630.82
cryst syst
space group
a (Å)
b (Å)
c (Å)
triclinic
P1h
monoclinic
P2(1)/c
13.915(9)
10.500(6)
15.413(9)
90
114.273(9)
90
2053(2)
4
triclinic
P1h
triclinic
P1h
triclinic
P1h
9.540(4)
10.366(5)
11.167(5)
101.693(7)
93.921(7)
92.578(8)
1077.0(8)
2
9.776(3)
9.764(3)
13.718(4)
76.427(5)
74.818(5)
69.489(5)
1168.7(6)
2
9.614(3)
10.472(4)
11.189(4)
101.361(6)
94.495(6)
92.575(6)
1099.0(7)
2
9.770(3)
9.847(3)
13.793(5)
76.617(6)
75.152(6)
69.777(5)
1188.6(7)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
D
calc (g‚cm-3
)
2.350
10.763
708
2.414
11.235
1384
2.280
9.925
752
1.906
2.517
616
1.875
2.333
660
µ (mm-1
F(000)
)
cryst size (mm)
max. 2θ (deg)
0.20 × 0.16 × 0.12
0.22 × 0.20 × 0.18
0.24 × 0.22 × 0.16
0.24 × 0.22 × 0.18
0.20 × 0.16 × 0.08
50.00
53.00
52.84
52.84
52.84
no. of reflns collected
no. of indep reflns/Rint
no. of params
5641
3787/0.0405
276
0.972
0.0391, 0.0686
0.0714, 0.0776
11554
4164/0.0800
271
0.940
0.0404, 0.0658
0.0838, 0.0757
6762
4745/0.0605
301
0.975
0.0568, 0.1243
0.0920, 0.1397
6275
4423/0.0295
272
0.998
0.0376, 0.0762
0.0689, 0.0858
6917
4803/0.0285
301
1.002
0.0325, 0.0627
0.0576, 0.0723
goodness-of-fit on F2
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
complexes 11 and 16, which are slightly air sensitive
especially in solution. The IR spectra of 13 and 15
exhibited five terminal carbonyl bands at 2026, 1989,
1940, 1914, 1890 cm-1 and 2026, 1989, 1940, 1914, 1890
to the reaction with Fe(CO)5, that the bulky substituents
at the bridging carbon atom may promote the formation
of the complex of type C, whereas the two phenyl groups
at the bridging silicon atom may prevent the formation
of the complex of type C. It was noteworthy that the
reaction of ligand 9 with W(CO)6 gave the desilylation
product 17 as the only isolable product.
Rea ction of th e Ca r bon a n d Ger m a n iu m Dou bly
Br id ged Biscyclop en ta d ien e Liga n d s w ith M(CO)6
(M ) Mo, W). When the carbon and germanium doubly
bridged biscyclopentadiene ligands (X)(Me2Ge)(C5H4)2
[X ) Me2C (18), (CH2)5C (20)] reacted with Mo(CO)6 or
Mo(CO)6, similar novel complexes of type C, (X)(η5-
C5H3)(η5,η1-C5H3)[(Me2Ge)M(CO)3][M(CO)3] [M ) Mo, X
) Me2C (19), (CH2)5C (21); M ) W, X ) Me2C (22),
(CH2)5C (23)], were obtained along with the degermy-
lation products (Scheme 1). However in this case, the
corresponding dimolybdenum or ditungsten complexes
were not isolated, probably due to the weakness of the
C-Ge bond. All the isolated complexes are air stable.
The 1H NMR spectra of 19, 21, 22, and 23 each
displayed six Cp-H proton peaks at 6.30-4.90 ppm,
1
cm-1, respectively. Their H NMR spectra displayed six
or five Cp-H proton peaks at 6.20, 5.84, 5.30, 5.19, 5.10,
4.96 and 6.31, 5.85, 5.27 (2H), 5.10, 4.95 ppm, respec-
tively, indicating the unsymmetrical structures. X-ray
diffraction analysis shows that complexes 13 and 15
contain a W-Si bond, suggesting that the formation of
13 and 15 should be accompanied by the cleavage of a
C-Si bond in the ligands. The structures of 13 and 15
are very similar to the complexes (X)(η5-C5H3)(η5,η1-
C5H3)[(Me2Si)Fe(CO)2][Fe(CO)2] [X ) Me2C, (CH2)5C],4b
which were obtained from the reactions of the corre-
sponding ligands with Fe(CO)5 in refluxing xylene.
The reaction of ligand 4 with W(CO)6 only gave type
C complex 15 and the desilylation product 14. The
corresponding ditungsten complex was not isolated. On
the other hand, the reaction of ligand 7 gave only
ditungsten complex 16 and the desilylation product 12.
No type C complex was obtained. This indicates, similar

4846 Organometallics, Vol. 22, No. 24, 2003
Wang et al.
Ta ble 2. Cr ysta l Da ta a n d Su m m a r y of X-r a y Da ta
Collection for 22, 25t, a n d 26t
22
25t
26t
formula
fw
cryst syst
space group
a (Å)
C
21H18GeO6W2
C
27H30Mo2O6
C
27H30O6W2
806.64
triclinic
P1h
642.39
monoclinic
P21/c
16.530(7)
9.453(4)
19.501(8)
90
114.838(6)
90
2765(2)
4
818.21
monoclinic
P21/c
16.498(19)
9.435(11)
19.45(2)
90
114.672(16)
90
2751(5)
4
9.546(3)
10.398(4)
11.104(4)
101.448(5)
94.525(6)
92.555(5)
1074.8(6)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
D
calc (g‚cm-3
)
2.493
12.101
744
1.543
0.944
1296
1.976
8.393
1552
µ (mm-1
F(000)
)
cryst size (mm)
0.32 × 0.24 × 0.34 × 0.26 × 0.26 × 0.22 ×
0.20 0.22 0.20
50.00 52.80 52.86
12633 15114
max. 2θ (deg)
no. of reflns
collected
5383
no. of indep
reflns/Rint
3686/0.0325
5584/0.0447 5590/0.0501
no. of params
goodness-of-fit
on F2
276
0.997
317
1.026
324
1.040
R1, wR2 [I > 2σ(I)] 0.0414,
0.0402,
0.0693
0.0822,
0.0788
0.0389,
0.0847
0.0685,
0.0947
0.1012
R1, wR2 (all data) 0.0565,
0.1097
Sch em e 1
F igu r e 1. ORTEP diagram of 2. Thermal ellipsoids are
shown at the 30% level. The top drawing shows the view
perpendicular to the Mo-Mo bond and the labeling scheme.
The bottom drawing depicts the view down the Mo-Mo
axis. Selected bond lengths [Å] and angles [deg]: Mo(1)-
Mo(1a) 3.4328(12), Mo(1)-C(4) 2.341(3), Mo(1)-C(8) 2.347-
(3), Si(1)-C(4) 1.858(3), C(8)-C(9) 1.515(3), C(4a)-Si(1)-
C(4) 96.33(17), O(1)-C(1)-Mo(1) 169.8(3), O(2)-C(2)-
Mo(1) 179.2(3), O(3)-C(3)-Mo(1) 170.0(3), C(8)-C(9)-
C(8a) 109.4(3).
Sch em e 2
xylene, only the desilylation products 25 and 26 were
obtained (Scheme 2).
Neither the normal intramolecular dinuclear complex
(type A) nor the type C complex was obtained.The bulky
tert-butyl groups might either prevent the formation of
the type C complex and/or promote the desilylation
reaction. Both the cis (two tert-butyl groups on the same
side) and trans (two tert-butyl groups on opposite sides)
isomers of 26 were obtained, but only one isomer of 25
was isolated and assigned to the trans isomer 25t based
on the X-ray diffraction analysis.
suggesting again the unsymmetrical structures. More-
over, we already noted that the reactions of 1 and 4,
silyl analogues of 18 and 20, failed to give any type C
complexes. The formation of type C molybdenum com-
plexes 19 and 21 here indicates that the weaker C-Ge
bond favors the formation of type C structure through
the cleavage of the C-Ge bond.
Rea ction of (Me2C)(Me2Si)(t-Bu C5H3)2 (24) w ith
M(CO)6 (M ) Mo, W). To study the steric effect of this
reaction, a tert-butyl group was introduced to the
cyclopentadienyl rings and the ligand (Me2C)(Me2Si)(t-
BuC5H3)2 (24) was used in the reaction. However, when
24 reacted with Mo(CO)6 or W(CO)6 under refluxing
Molecu la r Str u ctu r es. The molecular structures of
2, 6, 8, 10, 11, 13, 14, 15, 19, 21, 22, 25t, and 26t are
shown in Figures 1-13, respectively.
Complexes 2, 8, 10, and 11 are intramolecular doubly
bridged biscyclopentadienyl dimolybdenum or ditung-
sten complexes. The M-M distances in complexes 2

Doubly Bridged Biscyclopentadienes
Organometallics, Vol. 22, No. 24, 2003 4847
F igu r e 2. ORTEP diagram of 6. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths [Å] and
angles [deg]: Mo(1)-Mo(2) 3.1708(18), Mo(1)-C(11) 2.415-
(3), Mo(2)-C(18) 2.367(3), C(11)-C(12) 1.531(4), C(12)-
C(18) 1.525(4), C(11)-Mo(1)-Mo(2) 80.20(7), C(18)-Mo-
(2)-Mo(1) 81.68(7), C(12)-C(11)-Mo(1) 129.89(18), C(18)-
C(12)-C(11) 111.8(2), C(12)-C(18)-Mo(2) 126.93(19).
[3.4328(12) Å], 8 [3.453(2) Å], and 11 [3.403(2) Å] are
conspicuously elongated and are in fact the longest ever
reported among the biscyclopentadienyl dimolybdenum
or ditungsten complexes (Table 3). The covalent radius
of the molybdenum atom has been estimated from
structural data of Mo(dien)(CO)3 to be 1.62 Å.8,9 So the
distances of the Mo-Mo bond in complexes 2 [3.4328-
(12) Å] and 8 [3.453(2) Å] are on average 0.2 Å greater
than the sum of the covalent radius of two molybdenum
(3.24 Å). This is very different from the singly bridged
biscyclopentadienyl dimolybdenum or ditungsten com-
plexes, in which cases the bridging caused a small
decrease in the M-M distances. This can be attributed
to three factors. First, the inflexibility of the doubly
bridged biscyclopentadienyl dinuclear metal complexes
forces the CO groups on the different metal atoms to
repel each other and thereby increases the M-M
distance. In singly bridged biscyclopentadienyl dimo-
lybdenum or ditungsten complexes, the flexibility of the
singly bridged biscyclopentadienyl ligands could reduce
the above-mentioned repulsion by increasing the CNT-
M-M-CNT′ (CNT ) centroid of cyclopentadienyl ring)
torsion angles. The structures of complexes 2, 8, and
11 are conformationally much more rigid and con-
strained as a result of the double bridges. The CNT-
M-M-CNT′ torsion angles for the doubly bridged
complexes (0° for 2, 1.7° for 8, 0° for 11) are much
smaller than those in the singly bridged complexes (44-
48°). As a result of such constrained structures, the
repulsion between the CO groups on the different metal
atoms will be much greater than that in the singly
bridged complexes if the M-M bond remains the same
length. In these bridged complexes, a relationship
appears to exist between the degree of twist in a
molecule and its M-M distance (Table 3). In general,
F igu r e 3. ORTEP diagram of 8. Thermal ellipsoids are
shown at the 30% level. The top drawing shows the view
perpendicular to the Mo-Mo bond and the labeling scheme.
The bottom drawing depicts the view down the Mo-Mo
axis. Selected bond lengths [Å] and angles [deg]: Mo(1)-
Mo(2) 3.453(2), Mo(1)-C(7) 2.335(6), Mo(1)-C(11) 2.346-
(6), Mo(2)-C(15) 2.365(6), Mo(2)-C(19) 2.323(5), Si(1)-C(7)
1.855(6), Si(1)-C(19) 1.853(6), C(11)-C(12) 1.515(8), C(12)-
C(15) 1.533(8), C(19)-Si(1)-C(7) 98.8(3), C(20)-Si(1)-
C(26) 107.4(3), C(11)-C(12)-C(15) 109.7(5), O(1)-C(1)-
Mo(1) 177.8(6), O(2)-C(2)-Mo(1) 168.3(6), O(3)-C(3)-
Mo(1) 170.0(6), O(4)-C(4)-Mo(2) 172.0(6), O(5)-C(5)-
Mo(2) 170.6(6), O(6)-C(6)-Mo(2) 177.9(6).
the M-M distances increase with decreasing CNT-M-
M-CNT′ torsion angles (except 10). Second, all these
complexes contain single carbon and single silicon atom
double bridges, which are the shortest bridges for the
doubly bridged biscyclopentadienyl metal complexes up
to now. Such short bridges increase the steric repulsions
between the substituents at two bridge atoms and the
substituents with Mo(CO)3 groups, which make the
Cp-Cp fold angle (149.3° for 2, 149.5° for 8, 149.2°
for 11) much larger than those with two longer bridges
(for example, (Me2Si)2[C5H3W(CO)3]212 135.6°) or singly
(10) Adams, R. D.; Collins, D. M.; Cotton, F. A. Inorg. Chem. 1974,
13, 1086.
(8) Cotton, F. A. And Wing, R. M. Inorg. Chem. 1965, 4, 314.
(9) Adams, R. D.; Collins, D. M.; Cotton, F. A. J . Am. Chem. Soc.
1974, 96, 749.
(11) Drage, J . S.; Vollhardt, K. P. Organometallics 1986, 5, 280.
(12) McKinley, S. G.; Angelici, R. J .; Choi, M.-G. Organometallics
2002, 21, 1235.

4848 Organometallics, Vol. 22, No. 24, 2003
Wang et al.
F igu r e 5. ORTEP diagram of 11. Thermal ellipsoids are
shown at the 30% level. The top drawing shows the view
perpendicular to the Mo-Mo bond and the labeling scheme.
The bottom drawing depicts the view down the Mo-Mo
axis. Selected bond lengths [Å] and angles [deg]: W(1)-
W(1a) 3.403(2), W(1)-C(4) 2.328(6), W(1)-C(8) 2.331(7),
Si(1)-C(4) 1.838(8), C(8)-C(9) 1.515(10), C(4a)1-Si(1)-
C(4) 95.9(5), O(1)-C(1)-W(1) 171.0(7), O(2)-C(2)-W(1)
179.3(8), O(3)-C(3)-W(1) 169.3(7), C(8)-C(9)-C(8a) 110.1-
(8).
F igu r e 4. ORTEP diagram of 10. Thermal ellipsoids are
shown at the 30% level. The top drawing shows the view
perpendicular to the Mo-Mo bond and the labeling scheme.
The bottom drawing depicts the view down the Mo-Mo
axis. Selected bond lengths [Å] and angles [deg]: Mo(1)-
Mo(2) 3.1669(9), Mo(1)-C(1) 2.426(4), Mo(1)-C(5) 2.353-
(4), Mo(2)-C(7) 2.303(4), Mo(2)-C(11) 2.409(4), Si(1)-C(5)
1.876(4), Si(1)-C(11) 1.889(4), C(1)-C(6) 1.513(5), C(6)-
C(7) 1.513(5), C(5)-Si(1)-C(11) 97.32(18), C(7)-C(6)-C(1)
111.6(3).
complexes are being continued in our laboratories. The
molecule of complex 10 has no substituent at the
bridging carbon atom. In this case the intramolecular
nonbonding interaction was remarkably reduced, as
reflected by a decreased Cp-Cp fold angle (133.7°) and
shortened Mo-Mo bond distance. It is interesting that
complex 10 has a slightly shorter Mo-Mo distance
[3.1669(9) Å] even than some singly bridged biscyclo-
pentadienyl dinuclear metal complexes [3.1708(18) Å for
6, 3.1723(11) Å for 25t], although its Cp-Cp fold angle
and the CNT-Mo-Mo-CNT′ torsion angle (34.0°) are
between those of the doubly bridged and singly bridged
biscyclopentadienyl dimolybdenum complexes. This may
be attributed to the considerably reduced steric effect
of the CH2 bridge as noted previously in the singly CH2
bridged complex CH2[C5H4Mo(CO)3]2 (Mo-Mo 3.1406
Å).6
bridged biscyclopentadienyl dimolybdenum (or ditung-
sten) complexes (∼120°) (Table 3), and thus lead to
increased M-M distances. Third, the bridging carbon
and silicon atom each is substituted with two methyl
or phenyl groups. The steric repulsions between the
substituents at the two bridge atoms and the M(CO)3
moiety again make the Cp-Cp fold angle (149.3° in
2, 149.5° in 8, 149.2° in 11) much larger than the
unsubstituted analogues (for example, (CH2)(Me2Si)[(η5-
C5H3)Mo(CO)3]2 (10), 133.7°) and therefore favor form-
ing structures with longer M-M distances. It is inter-
esting that the Cp-Cp fold angles in 2, 8, and 11 are
comparable with that in (Me2Si)2[C5H3W(CO)3]2H+
[149.7(2)°],12 which has long a W‚‚‚W distance [3.657-
(6) Å] without bonding. Further studies on the effects
of the long M-M distances on the reactivity of these

Doubly Bridged Biscyclopentadienes
Organometallics, Vol. 22, No. 24, 2003 4849
F igu r e 8. ORTEP diagram of 15. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths [Å] and
angles [deg]: W(1)-Si(1) 2.617(3), W(1)-C(9) 2.378(11),
W(1)-C(10) 2.326(13), W(2)-C(9) 2.221(12), W(2)-C(14)
2.306(11), W(2)-C(15) 2.336(12), Si(1)-C(14) 1.911(14),
C(10)-C(19) 1.522(17), C(15)-C(19) 1.540(17), C(9)-W(1)-
Si(1) 84.1(3), C(10)-W(1)-Si(1) 86.3(3), C(9)-W(2)-C(14)
81.2(4), C(9)-W(2)-C(15) 74.2(5), C(14)-Si(1)-W(1) 103.8-
(4), W(2)-C(9)-W(1) 127.5(5), C(10)-C(19)-C(15) 105.4-
(10).
F igu r e 6. ORTEP diagram of 13. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths [Å] and
angles [deg]: W(1)-Si(1) 2.620(3), W(1)-C(7) 2.315(10),
W(1)-C(8) 2.368(10), W(2)-C(8) 2.225(9), W(2)-C(13)
2.306(9), W(2)-C(14) 2.286(11), Si(1)-C(14) 1.922(11),
C(7)-C(12) 1.544(13), C(12)-C(13) 1.527(13), C(7)-W(1)-
Si(1) 85.9(2), C(8)-W(1)-Si(1) 83.4(2), C(8)-W(2)-C(13)
73.3(3), C(8)-W(2)-C(14) 80.7(3), C(14)-Si(1)-W(1) 104.1-
(3), W(2)-C(8)-W(1) 128.7(4), C(13)-C(12)-C(7) 104.9(7).
F igu r e 9. ORTEP diagram of 19. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths [Å] and
angles [deg]: Mo(1)-Ge(1) 2.6671(10), Mo(1)-C(7) 2.391-
(5), Mo(1)-C(8) 2.336(5), Mo(2)-C(7) 2.229(5), Mo(2)-C(13)
2.316(5), Mo(2)-C(14) 2.312(5), Ge(1)-C(14) 1.970(5), C(8)-
C(12) 1.522(7), C(12)-C(13) 1.530(7), C(7)-Mo(1)-Ge(1)
83.47(11), C(8)-Mo(1)-Ge(1) 85.35(11), C(7)-Mo(2)-C(13)
73.67(16), C(7)-Mo(2)-C(14) 81.04(17), C(14)-Ge(1)-Mo-
(1) 103.18(13), Mo(2)-C(7)-Mo(1) 129.4(2), C(8)-C(12)-
C(13) 105.1(4).
F igu r e 7. ORTEP diagram of 14. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths [Å] and
angles [deg]: W(1)-W(2) 3.1582(16), W(1)-C(7) 2.350(8),
W(2)-C(13) 2.404(9), C(7)-C(12) 1.506(11), C(12)-C(13)
1.528(12), C(7)-W(1)-W(2) 81.6(2), C(13)-W(2)-W(1) 80.2-
(2), C(12)-C(7)-W(1) 127.9(6), C(7)-C(12)-C(13) 111.9-
(7), C(12)-C(13)-W(2) 129.6(5).
Complexes 6 and 25t are singly bridged biscyclopen-
tadienyl dimolybdenum complexes. As shown in Figure
12, 25t is a trans isomer. The Mo-Mo distances are
3.1708(18) Å in 6 and 3.1723(11) Å in 25t, both shorter
than that in trans-[CpMo(CO)3]2 [3.235(1) Å],10 showing
a moderate compression on the Mo-Mo bond imposed
by the single carbon bridged ligand, similar to that in
(CH2)[(η5-C5H4)Mo(CO)3]2 [3.1406 Å].6 This may be
attributed to the flexibility of the singly bridged biscy-
clopentadienyl ligands which allows the CO groups to
reduce steric repulsions that force the metal atoms away
from each other (CNT-Mo-Mo-CNT torsion angle:
46.4° for 6, 44.8 for 25t). For the singly carbon bridged
complexes 6 and 25t, the crowdedness around the Mo-
Mo bond is partially relaxed by the assumption of larger
CNT-Mo-Mo-CNT torsion angles, which is not pos-
sible for the fulvalene complex FvMo2(CO)6 and the
doubly bridged biscyclopentadienyl complexes 2 and 8
(whose CNT-Mo-Mo-CNT torsion angles were 0° and
1.7°, respectively). Similarly, complexes 14 and 26t are

4850 Organometallics, Vol. 22, No. 24, 2003
Wang et al.
F igu r e 12. ORTEP diagram of 25t. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths [Å] and
angles [deg]: Mo(1)-Mo(2) 3.1723(11), Mo(1)-C(7) 2.401-
(4), Mo(2)-C(19) 2.328(4), C(7)-C(16) 1.517(5), C(16)-
C(19) 1.516(5), C(7)-Mo(1)-Mo(2) 79.43(10), C(19)-Mo-
(2)-Mo(1) 82.03(10), C(16)-C(7)-Mo(1) 129.6(3), C(19)-
C(16)-C(7) 112.8(3), C(16)-C(19)-Mo(2) 125.7(2).
F igu r e 10. ORTEP diagram of 21. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths [Å] and
angles [deg]: Mo(1)-Ge(1) 2.6569(9), Mo(1)-C(9) 2.395-
(4), Mo(1)-C(10) 2.342(4), Mo(2)-C(9) 2.237(4), Mo(2)-
C(14) 2.321(4), Mo(2)-C(15) 2.322(4), Ge(1)-C(14) 1.967(4),
C(15)-C(19) 1.518(6), C(10)-C(19) 1.521(5), C(9)-Mo(1)-
Ge(1) 84.15(10), C(10)-Mo(1)-Ge(1) 86.13(10), C(9)-Mo-
(2)-C(14) 81.41(14), C(9)-Mo(2)-C(15) 73.27(14), C(14)-
Ge(1)-Mo(1) 103.15(11), Mo(2)-C(9)-Mo(1) 127.72(17),
C(15)-C(19)-C(10) 105.6(3).
F igu r e 13. ORTEP diagram of 26t. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths [Å] and
angles [deg]: W(1)-W(2) 3.165(3), W(1)-C(15) 2.392(8),
W(2)-C(10) 2.321(8), C(10)-C(12) 1.532(10), C(12)-C(15)
1.513(12), C(15)-W(1)-W(2) 79.5(2), C(10)-W(2)-W(1)
82.2(2), C(12)-C(10)-W(2) 125.2(5), C(15)-C(12)-C(10)
112.9(6), C(12)-C(15)-W(1) 129.8(5).
F igu r e 11. ORTEP diagram of 22. Thermal ellipsoids are
shown at the 30% level. Selected bond lengths [Å] and
angles [deg]: W(1)-C(7) 2.370(11), W(1)-C(8) 2.315(9),
W(1)-Ge(1) 2.6522(13), W(2)-C(7) 2.213(10), W(2)-C(15)
2.308(10), W(2)-C(16) 2.289(10), Ge(1)-C(16) 1.982(11),
C(8)-C(12) 1.502(13), C(12)-C(15) 1.493(14), C(7)-W(1)-
Ge(1) 83.5(2), C(8)-W(1)-Ge(1) 85.3(2), C(7)-W(2)-C(15)
73.1(3), C(7)-W(2)-C(16) 81.4(4), C(16)-Ge(1)-W(1) 103.3-
(3), W(2)-C(7)-W(1) 129.5(4), C(15)-C(12)-C(8) 106.1(8).
and 47.0° for 26t, reflecting the flexibility of the singly
bridged biscyclopentadienyl ligands.
Complex 13, 15, 19, 21, and 22 have similar novel
structures. These complexes all contain a M-Si or
M-Ge bond, and one metal atom is coordinated with a
cyclopentadienyl ligand in η5 manner, while the other
metal atom coordinated with both cyclopentadienyl
ligands in a η1 and η5 manner, respectively. Similar
ruthenium complexes [Ru(CO)2]2(µ-η5:η1-C5H4)[µ-Me2Si-
(η5-C5H4)]15 and [Ru(CO)2]2(µ-η5:η1-C5Me4)[µ-Me2Si-(η5-
C5H4)]16 have been reported from the photolysis of silyl-
bridged complexes Me2Si[η5-C5H4Ru(CO)2]2 and Me2Si[η5-
C5Me4Ru(CO)2]2, respectively. In our recent work, iron
complexes (R2C)(η5-C5H3)(η5,η1-C5H3)[(Me2E)Fe(CO)2]-
[Fe(CO)2] (R2C ) Me2C, (CH2)5C, E ) Si, Ge) with
singly bridged biscyclopentadienyl ditungsten com-
plexes. 26t is a trans isomer, as shown in Figure 13.
Similar to (CH2)[(η5-C5H4)W(CO)3]2 [3.166(1) Å],7 the
W-W distances in 14 [3.1582(16) Å] and 26t [3.165(3)
Å], as compared to those in nonbridged complex trans-
(η5-C5H5)2W2(CO)6 [3.222(1) Å]10 and singly silyl bridged
complex (Me2Si)[(η5-C5H4)W(CO)3]2 [3.196(1) Å],13 were
compressed by the short single carbon bridged ligands.
The CNT-W-W-CNT torsion angles are 45.3° for 14
(14) Abrahamson, H. B.; Heeg, M. J . Inorg. Chem. 1984, 23, 2281.
(15) (a) Bitterwolf, T. E.; Shade, J . E.; Hansen, J . A.; Rheingold, A.
L. J . Organomet. Chem. 1996, 514, 13. (b) Bitterwolf, T. E.; Leonard,
M. B.; Horine, P. A.; Shade, J . E.; Hansen, J . A.; Rheingold, A. L.;
Staley, D. J .; Yap, G. P. A. J . Organomet. Chem. 1996, 512, 11.
(16) Fox, T.; Burger, P. Eur. J . Inorg. Chem. 2001, 795.
(13) Abriel, W.; Heck, J . J . Organomet. Chem. 1986, 302, 363.

Doubly Bridged Biscyclopentadienes
Organometallics, Vol. 22, No. 24, 2003 4851
F igu r e 14. EPR spectrum of 2 in crystal powder.
Ta ble 3. Str u ctu r a l P a r a m eter Com p a r ison for Biscyclop en ta d ien yl Dim olybd en u m (Ditu n gsten )
Com p lexesa
Cp-Cp
fold angle (deg)
CEN-M-M-CEN
torsion angles
complex
M-M (Å)
ref
trans-[CpMo(CO)3]2
FvMo2(CO)6
CH2[C5H4Mo(CO)3]2
3.235(1)
3.371(1)
3.1406
10
11
6
164.7
(CH2)5C[C5H4Mo(CO)3]2 (6)
Me2C[t-BuC5H3Mo(CO)3]2 (25t)
(Me2C)(Me2Si)[C5H3Mo(CO)3]2 (2)
(Me2C)(Ph2Si)[C5H3Mo(CO)3]2 (8)
(CH2)(Me2Si)[C5H3Mo(CO)3]2 (10)
trans-[CpW(CO)3]2
FvW2(CO)6
CH2[C5H4W(CO)3]2
Me2Si[C5H4W(CO)3]2
(CH2)5C[C5H4W(CO)3]2 (14)
Me2C[t-BuC5H3W(CO)3]2 (26t)
(Me2C)(Me2Si)[C5H3W(CO)3]2 (11)
(Me2Si)2[C5H3W(CO)3]2
(Me2Si)2[C5H3W(CO)3]2H+
3.1708(18)
3.1723(11)
3.4328(12)
3.453(2)
3.1669(9)
3.222(1)
3.347(1)
3.166(1)
3.196(1)
3.1582(16)
3.165(3)
3.403(2)
3.260(5)
3.657(6)
120.5
121.9
149.3
149.5
133.7
46.4
44.8
0
1.7
34.0
this work
this work
this work
this work
this work
10
14
7
13
this work
this work
this work
12
163.9
5.0(2)
47.8(6)
∼47.8
45.3
47.0
0
120.4
121.9
149.2
135.6(7)
149.7(2)
28.7(4)
12
a
Cp-Cp fold angle ) the dihedral angle between the planes of the cyclopentadienyl ring; CEN ) the centroid of the cyclopentadienyl
ring.
Sch em e 3
similar structures were obtained from thermal reactions
of the corresponding doubly bridged ligands with Fe-
(CO)5.4b The results presented here further indicated
that the formation of type C complexes presents a
common feature for the reactions of the carbon and
silicon (or germanium) doubly bridged biscyclopentadi-
ene ligands with metal carbonyl (M ) Fe, Mo, W)
compounds. Compared to the corresponding dinulear
metal complexes, the Cp-Cp fold angles of the type
C complexes were much smaller, suggesting that the
intramolecular nonbonding interactions were highly
relaxed, which is consistent with the thermal stability
of these complexes.
EP R Sp ectr a . Although the distances of the Mo-
Mo bond in complexes 2 [3.4328(12) Å] and 8 [3.453(2)
Å] are the longest of all the analogues known, there is
no evidence for metal-metal bond homolysis in their
1H NMR spectra. This is similar to the fulvalene
complexes FvM2(CO)6 (M ) Cr, Mo, W),11,14,17 another
class of biscyclopentadienyl dinuclear metal complexes
with long metal-metal bonds, but very different from
the chromium-chromium complex [CpCr(CO)3]2, which
shows a very broad resonance.9 To further study the
superlong metal-metal bond, EPR experiments were
performed. There was no signal in benzene solution,
indicating that the long metal-metal bond is still stable
in solution. Surprisingly, a distinct EPR signal (Figure
14, g ) 2.160) was recorded for the crystal state of
complex 2, suggesting the presence of radicals in the
solid state (Scheme 3). Similar observations were re-
ported in the crystalline [CpCr(CO)3]2 obtained by
sublimation, and the authors claimed the presence of
approximately 50% of the substance as radicals accord-
ing to the intense signal.18
(17) McGovern, P. A.; Vollhardt, K. P. C. Chem. Commun. 1996,
1593.
(18) Keller, H. J . Z. Naturforsch. B 1968, 23, 133.

4852 Organometallics, Vol. 22, No. 24, 2003
Wang et al.
Mech a n ism Discu ssion . Our experiments on the
reactions of carbon and silicon or germanium doubly
bridged biscyclopentadiene ligands with different metal
carbonyl compounds, namely, Fe(CO)5,4b Mo(CO)6, or
W(CO)6, gave similar and consistent results. In most
cases the reactions gave a series of dinuclear metal
complexes with superlong M-M bonds and the corre-
sponding desilylation or degermylation products, whereas
the formation of the novel type C complexes depends
on the ligand and metal. There is no relationship
between the three types of products, meaning they
cannot be converted to one another under the conditions
used in the reactions. This suggests that the three types
of products were formed at the same time. However, it
was experimentally difficult to follow the reaction under
such conditions for more detailed mechanistic studies.
The exact course of the reactions still remains unclear
after all the efforts. There are some reports about the
cleavage of the C-Si or C-Ge bond and the migration
of the silyl or germyl group.19-21 When C5H5EMe3 (E )
Si, Ge, Sn) reacted with (MeCN)3M(CO)3 (M ) Cr, Mo,
W), it was found that GeMe3 and SnMe3 could easily
migrate to the metal atom to give C5H5(CO)3M-EMe3
(M ) Cr, Mo, W; E ) Ge, Sn), while SiMe3 was more
difficult to transfer.19-21 This made us propose that the
type C complexes with a W-Si or M-Ge (M ) Mo, W)
bond in this work could be the silyl or germyl single-
migration products. For the reaction with Fe(CO)5 and
W(CO)6, both ligands with carbon/silicon double bridges
and carbon/germanium double bridges gave the novel
type C complexes. However, for the reaction with Mo-
(CO)6, only the carbon and germanium doubly bridged
ligands gave the type C complexes. Since the type C
complexes contain a M-Si or M-Ge bond, their forma-
tion was apparently accompanied by the cleavage of a
C-Si or C-Ge bond in the ligands. Due to the weakness
of the C-Ge bond, one can predict that type C complexes
with M-Ge bonds will form more readily than those
with M-Si bonds. The results from our experiments
were in agreement with this prediction. The bulky
substituents at the bridging carbon atom (ligands 1, 4,
18, and 20) may increase the intramolecular nonbonding
interactions and thus promote the silyl or germyl
transfer and promote the formation of the complexes of
type C (13, 15, 19, 21, 22, and 23). Also supporting this
is the fact that the reaction of the doubly bridged ligands
with a methylene bridge (no sbstitutent at the bridging
carbon) with metal carbonyl failed to give any type C
complexes. The reaction of the doubly bridged ligands
with a methylene bridge with metal carbonyl cannot
give the complex of type C, indicating that the repulsion
between the substituents at the two bridging atoms
might be the driving force of silyl or germyl transfer.
On the other hand, the bulky substituents at the
bridging silicon atom or on the cyclopentadienyl rings
turn to prevent silyl or germyl transfer and the forma-
tion of the type C complexes.
Con clu sion s
Reactions of carbon and silicon or germanium doubly
bridged biscyclopentadiene ligands (X)(Y)(C5H4)2 with
molybdenum (tungsten) carbonyl were studied. A series
of doubly bridged biscyclopentadienyl dinuclear metal
complexes with unusually long M-M bonds and a novel
type C complexes with a M-Si or M-Ge bond were
obtained. The factors affecting the structures of dimo-
lybdenum or ditungsten complexes were discussed.
Ack n ow led gm en t. We thank the National Natural
Science Foundation of China (No. 20202004), the Re-
search Fund for the Doctoral Program of Higher Educa-
tion (2000005504), and the Scientific Research Foun-
dation for the Returned Overseas Chinese Scholars,
State Education Ministry (2001-345), for financial sup-
port.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data collection information, final positional and
thermal parameters of the non-hydrogen atoms, general
temperature factors, and bond distances and angles for 2, 6,
8, 10, 11, 13, 14, 15, 19, 21, 22, 25t, and 26t. This material is
available free of charge via the Internet at http://pubs.acs.org.
(19) (a) Heck, J .; Kriebisch, K.-A.; Mellinghoff, H. Chem. Ber. 1988,
121, 1753. (b) Xu, S.; Xie, W.; Zhou, X.; Wang, J .; Chen, H.; Guo, H.;
Miao, F. Chem. J . Chin. Univ. 1996, 17, 1065.
(20) Keppie, S. A.; Lappert, M. F. J . Organomet. Chem. 1969, 19,
P5.
(21) Abel, E. W.; Moorhouse S. J . Organomet. Chem. 1971, 28, 211.
OM034039Z