Syntheses of functionalized ferratricarbadecaboranyl complexes

Article abstract of DOI:10.1021/ic049827a

The reactions of nitriles (RCN) with arachno-4,6-C₂B ₇H₁₂^- provide a general route to functionalized tricarbadecaboranyl anions, 6-R-nido-5,6,9-C₃B ₇H₉^-, R = C₆H₅ (2 ^-), NC(CH₂)₄ (4^-), (p-BrC ₆H₄)(Me₃SiO)CH (6^-), C ₁₄H₁₁ (8^-), and H₃BNMe ₂(CH₂)₂ (10^-). Further reaction of these anions with (η⁵-C₅H₅)Fe(CO) ₂I yields the functionalized ferratricarbadecaboranyl complexes 1-(η⁵-C₅H₅)-2-C₆H ₅-closo-1,2,3,4-FeC₃B₇H₉ (3), 1-(η⁵-C₅H₅)-2-NC(CH₂) ₄-closo-1,2,3,4-FeC₃B₇H₉ (5), 1-(η⁵-C₅H₅)-2-[(p-BrC₆H ₄)(Me₃SiO)CH]-closo-1,2,3,4-FeC₃B ₇H₉ (7), 1-(η⁵-C₅H ₅)-2-C₁₄H₅-closo-1,2,3,4-FeC₃B ₇H₉ (9), and 1-(η₅-C₅H ₅)-2-H₃BNMe₂(CH₂) ₂-closo-1,2,3,4-FeC₃B₇H₉ (11). Reaction of 11 with DABCO (triethylenediamine) resulted in removal of the BH₃ group coordinated to the nitrogen of the side chain, giving 1-(η⁵-C₅H₅)-2-NMe₂(CH ₂)₂-closo-1,2,3,4-FeC₃B₇H ₉ (12). Crystallographic studies of complexes 3, 5, 7, 9, and 11 confirmed that these complexes are ferrocene analogues in which a formal Fe ²⁺ ion is sandwiched between the cyclopentadienyl and tricarbadecaboranyl monoanionic ligands. The metals are η ⁶-coordinated to the puckered six-membered face of the tricarbadecaboranyl cage, with the exopolyhedral substituents bonded to the low-coordinate carbon adjacent to the iron.

Full text of DOI:10.1021/ic049827a

Inorg. Chem. 2004, 43, 3467−3474
Syntheses of Functionalized Ferratricarbadecaboranyl Complexes
Bhaskar M. Ramachandran, Patrick J. Carroll, and Larry G. Sneddon*
Department of Chemistry, UniVersity of PennsylVania, Philadelphia, PennsylVania 19104-6323
Received February 11, 2004
The reactions of nitriles (RCN) with arachno-4,6-C B H - provide a general route to functionalized tricarbadecaboranyl
2
7 12
anions, 6-R-nido-5,6,9-C B H -, R ) C H (2-), NC(CH ) (4-), (p-BrC H )(Me3SiO)CH (6-), C H (8-), and
3
7
9
6
5
2 4
6
4
14 11
H BNMe2(CH ) (10-). Further reaction of these anions with (η5-C H )Fe(CO)2I yields the functionalized
3
2 2
5 5
ferratricarbadecaboranyl complexes 1-(η5-C H )-2-C H -closo-1,2,3,4-FeC B H (3), 1-(η5-C H )-2-NC(CH ) -closo-
5
5
6
5
3
7
9
5
5
2 4
1,2,3,4-FeC B H (5), 1-(η5-C H )-2-[(p-BrC H )(Me3SiO)CH]-closo-1,2,3,4-FeC B H (7), 1-(η5-C H )-2-C H -closo-
3
7
9
5
5
6
4
3
7
9
5
5
14 11
1,2,3,4-FeC B H (9), and 1-(η5-C H )-2-H BNMe2(CH ) -closo-1,2,3,4-FeC B H (11). Reaction of 11 with DABCO
3
7
9
5
5
3
2 2
3 7 9
(triethylenediamine) resulted in removal of the BH group coordinated to the nitrogen of the side chain, giving
3
1-(η5-C H )-2-NMe2(CH ) -closo-1,2,3,4-FeC B H (12). Crystallographic studies of complexes 3, 5, 7, 9, and 11
5
5
2 2
3 7 9
confirmed that these complexes are ferrocene analogues in which a formal Fe2+ ion is sandwiched between the
cyclopentadienyl and tricarbadecaboranyl monoanionic ligands. The metals are η6-coordinated to the puckered
six-membered face of the tricarbadecaboranyl cage, with the exopolyhedral substituents bonded to the low-coordinate
carbon adjacent to the iron.
Introduction
cationic ferratricarbadecaboranyl [1-CpFe-2-CH3-2,3,4-
C3B7H9]+X- salts, like their ferrocenium counterparts, have
now been shown to be effective cytotoxic agents, blocking
growth in a number of culture lines.4 More recently, we have
designed and tested5 a variety of new early metal tricarba-
decaboranyl halide complexes that exhibit properties comple-
mentary to those of early-metal metallocene halide anticancer
complexes.3
Because of their equivalent charges and formal electron
donating abilities, the tricarbadecaboranyl (6-CH3-nido-5,6,9-
- 1
C3B7H9 ) (1-) and cyclopentadienyl monoanions have been
found to exhibit many similar transition metal coordination
properties.2 However, the resulting metallatricarbadecabo-
ranyl complexes have significantly greater oxidative, chemi-
cal, thermal, and hydrolytic stabilities than their metallocene
counterparts. Such differences have been exploited in the
design of new active metallatricarbadecaboranyl analogues
of established metallocene antitumor agents.3 For example,
Previous studies of metallatricarbadecaboranyl complexes
have generally employed only the 6-CH3-nido-5,6,9-C3B7-
H9- anion, but in order to achieve increased water solubility
and/or specific binding properties, efficient routes are needed
to generate functionalized complexes. The work described
in this paper demonstrates that the reactions of a variety of
* Author to whom correspondence should be addressed. E-mail: lsned-
don@sas.upenn.edu.
(1) Kang, S. O.; Furst, G. T.; Sneddon, L. G. Inorg. Chem. 1989, 28,
2339-2347.
-
nitriles with the arachno-4,6-C2B7H12 monoanion provide
a general route to tricarbadecaboranyl anions and complexes
with chemically active substituents.
(2) (a) Plumb, C. A.; Carroll, P. J.; Sneddon, L. G. Organometallics 1992,
11, 1665-1671. (b) Plumb, C. A.; Carroll, P. J.; Sneddon, L. G.
Organometallics 1992, 11, 1672-1680. (c) Barnum, B. A.; Carroll,
P. J.; Sneddon, L. G. Organometallics 1996, 15, 645-654. (d)
Weinmann, W.; Wolf, A.; Pritzkow, H.; Siebert, W.; Barnum, B. A.;
Carroll, P. J.; Sneddon, L. G. Organometallics 1995, 14, 1911-1919.
(e) Barnum, B. A.; Carroll, P. J.; Sneddon, L. G. Inorg. Chem. 1997,
36, 1327-1337. (f) Mu¨ller, T.; Kadlecek, D. E.; Carroll, P. J.; Sneddon,
L. G.; Siebert, W. J. Organomet. Chem. 2000, 614-615, 125-130.
(g) Ramachandran, B. M.; Carroll, P. J.; Sneddon, L. G. J. Am. Chem.
Soc. 2000, 122, 11033-11034. (h) Wasczcak, M. D.; Wang, Y.; Garg,
A.; Geiger, W. E.; Kang, S. O.; Carroll, P. J.; Sneddon, L. G. J. Am.
Chem. Soc. 2001, 123, 2783-2790. (i) Ramachandran, B. M.; Trupia,
S. M.; Geiger, W. E.; Carroll, P. J.; Sneddon, L. G. Organometallics
2002, 21, 5078-5090.
(3) (a) Ko¨pf-Maier, P.; Ko¨pf, H. Chem. ReV. 1987, 87, 1137-1152. (b)
Dombrowski, K. E.; Baldwin, W.; Sheats, J. E. J. Org. Chem. 1986,
302, 281-306. (c) Ko¨pf-Maier, P.; Ko¨pf, H. Drugs Future 1986, 11,
297-319. (d) Ko¨pf-Maier, P.; Ko¨pf, H. Structure and Bonding;
Springer: Berlin, 1988; Vol. 70, pp 104-185.
(4) (a) Hall, I. H.; Warren, A. E.; Lee, C. C.; Wasczak, M. D.; Sneddon,
L. G. Anticancer Res. 1998, 18, 951-962. (b) Wasczcak, M. D.; Hall,
I. H.; Carroll, P. J.; Sneddon, L. G. Angew. Chem., Int. Ed. Eng. 1997,
36, 2227-2228.
(5) Hall, I. H.; Durham, R.; Tran, M.; Mueller, S.; Ramachandran, B.
M.; Sneddon, L. G. J. Inorg. Biochem. 2003, 93, 125-131.
10.1021/ic049827a CCC: $27.50 © 2004 American Chemical Society
Published on Web 04/29/2004
Inorganic Chemistry, Vol. 43, No. 11, 2004 3467

Ramachandran et al.
Table 1. NMR Data
compd
nucleus
11Ba,b
δ [multiplicity, assignment, J (Hz)]
2-
8.1 (d, 1B, JBH 144), 5.8 (d, 1B, JBH 140), -4.0 (d, 1B, JBH 148), -9.2 (d, 1B, JBH 142), -12.4 (d, 1B, JBH 144), -22.0 (d, 1B, JBH 162),
-28.0 (d, 1B, JBH 145)
26.9 (d, 1B, JBH 167), 4.9 (d, 1B, JBH 150), 2.8 (d, 1B, JBH 161), -0.2 (d, 1B, JBH 155), -3.9 (d, 1B, JBH 176), -6.9 (d, 1B, JBH 146),
2
11Bc,d
-30.1 (d, 1B, JBH 164)
1H{11Bd,e
13Cd,g
}
}
7.44 (m, Ph), 7.24 (m, Ph), 6.97 (m, Ph), 3.94 (s, C9H, exo), 1.97 (s, C5H), -1.21 (s, C9H, endo)
157.56 (br, s, C6H), 130.84 (s, Ph), 128.81 (s, Ph), 128.52 (s, Ph), 57.24 (s, C4H), 30.16 (br, s, C9H2)
7.2 (d, 1B, JBH 139), 4.9 (d, 1B, JBH 136), -4.8 (d, 1B, JBH 131), -10.0 (d, 1B, JBH 145), -12.4 (d, 1B, JBH 137), -23.8 (d, 1B, JBH 158),
-30.9 (d, 1B, JBH 142)
4-
4
11Ba,b
11Bc,d
26.5 (d, 1B, JBH 157), 5.3 (d, 1B, JBH 149), 3.2 (d, 1B, JBH 151), 0.1 (d, 1B, JBH 156), -6.0 (d, 1B, JBH 139), -6.6 (d, 1B, JBH 122),
-31.4 (d, 1B, JBH 164)
1H{11Bd,e
13Cd,g
3.25 (s, C9H, exo), 1.85 (s, C5H), 1.30 (m, CH2), 0.92 (m, CH2), -1.52 (s, C9H, endo)
162.07 (br, s, C6H), 118.86 (s, CN), 61.16 (s, C4H), 32.30 (br, s, C9H2), 28.60 (s, CH2), 27.47 (s, CH2), 26.29 (s, CH2)
2.2 (d, 1B, JBH 158), -0.5 (d, 1B, JBH 161), -8.9 (d, 1B, JBH 141), -11.4 (d, 1B, JBH 146), -25.4 (d, 1B, JBH 151), -28.3 (d, 1B, JBH 152),
-32.5 (d, 1B, JBH 157)
6.60 (s, C3H), 3.92 (s, Cp), 2.81 (m, CH2), 2.43 (m, CH2), 1.54 (m, CH2), 1.22 (m, CH2), 0.81 (s, C4H)
4.6 (d, 1B, JBH 153), -1.2 (d, 1Bi), -8.0 (d, 1Bh), -11.0 (d, 1Bh), -23.8 (d, 1B, JBH 138), -27.6 (d, 1B, JBH 149), -32.1 (d, 1Bh)
7.34 (m, Ph), 6.41 (s, C3H), 4.18 (s, Cp), 1.83 (s, C4H), 0.0 (s, Me3)
5
11Bc,d
1H{11Bd,e
11Bc,d
}
}
7
9
1H{11Bd,e
11Bc,d
7.5 (d, 1B, JBH 150), 0.8 (d, 1B, JBH 144), -3.9 (d, 1B, JBH 147), -7.5 (d, 1B, JBH 152), -19.8 (d, 1B, JBH 143), -23.9 (d, 1B, JBH 155),
-28.8 (d, 1B, JBH 148)
1H{11Bd,e
}
}
7.85 (m, Ant), 7.33 (m, Ant), 7.18 (m, Ant), 7.04 (m, Ant), 6.57 (s, Ant, CH), 6.04 (s, C3H), 4.40 (d, Ant, CH2), 4.16 (s, Cp), 3.63
(d, Ant, CH2), 1.23 (s, C4H)
3.4 (d, 1B, JBH 145), -0.4 (d, 1B, JBH 164), -9.3 (d, 1B, JBH 136), -9.8 (m, 1B, JBH 128), -10.9 (d, 1B, JBH 130), -24.5 (d, 1B, JBH 143),
11
12
11Bc,d
-27.6 (d, 1B, JBH 158), -32.2 (d, 1B, JBH 161)
1H{11Bd,e
6.61 (s, C3H), 4.14 (s, Cp), 3.77 (m, CH2), 3.61 (m, CH2), 3.01 (m, CH2), 2.79 (m, CH2), 2.22 (s, Me), 2.08 (s, Me), 0.79 (s, C4H)
2.3 (d, 1B, JBH 156), -0.3 (d, 1B, JBH 164), -8.8 (d, 1B, JBH 144), -11.3 (d, 1B, JBH 146), -25.3 (d, 1B, JBH 146), -28.1 (d, 1B, JBH 157),
-32.2 (d, 1B, JBH 155)
11Bc,f
1H{11Be,f}
6.80 (s, C3H), 4.75 (s, Cp), 3.78 (m, CH2), 3.61 (m, CH2), 3.28 (m, CH2), 3.12 (m, CH2), 1.99 (s, Me), 1.27 (s, Me), 0.88 (s, C4H)
a
Glyme. b 64.2 MHz. c 160.5 MHz. d C6D6. e 500.1 MHz. f CD2Cl2. g 125.8 MHz. h The resonance was too broad to accurately measure the coupling
constant.
croanalysis facility. Melting points were determined using a standard
melting point apparatus and are uncorrected.
Experimental Section
General Synthetic Procedures and Materials. Unless otherwise
noted, all reactions and manipulations were performed in dry
glassware under a nitrogen or argon atmosphere using the high-
vacuum or inert-atmosphere techniques described by Shriver.6
Syntheses of Li+6-Ph-nido-5,6,9-C3B7H9- (2-) and 6-Ph-nido-
5,6,9-C3B7H10 (2). In a glovebag under nitrogen, 0.090 g (11.3
mmol, 0.95 equiv) of LiH and 1.34 g (11.9 mmol, 1.0 equiv) of
arachno-4,6-C2B7H13 were added to a two-neck, round-bottomed
flask fitted with a stirbar, septum, and vacuum-connector/nitrogen-
inlet. The flask was then connected to a vacuum line, and ∼20 mL
of dry glyme was condensed into the flask at -196 °C. After stirring
at room temperature for 45 min, the reaction mixture was filtered
in a glovebag under nitrogen to remove any unreacted LiH. To the
filtrate was added 10.0 mL (97.9 mmol) of PhCN, and the solution
then was heated at reflux for 2 days under N2. When 11B NMR
analysis indicated that the reaction was complete, the solution was
filtered under N2 and the solvent vacuum evaporated from the
filtrate to give a yellow oily residue. Mass spectrometric analysis
The LiH, PhCN, NC(CH2)4CN, (p-BrC6H4)CHO, Me3SiCN,
ZnI2, Me2NCH2CH2CN, C14H9CN, 1.0 M HCl in Et2O, (η5-C5H5)-
Fe(CO)2I, and DABCO (triethylenediamine) were purchased from
Strem or Aldrich and used as received. Spectrochemical grade
glyme, Et2O, toluene, CH3CN, CH2Cl2, and hexanes were purchased
from Fisher or EM Science. Glyme was freshly distilled from
sodium-benzophenone ketyl prior to use. Acetonitrile was dried
over P2O5, transferred onto activated 4 Å molecular sieves, and
stored under vacuum. All other solvents were used as received
unless noted otherwise.
-
confirmed the presence of the 6-Ph-nido-5,6,9-C3B7H9 (2-)
Preparative thin-layer chromatography was conducted on 0.5 mm
(20 × 20) silica gel F-254 plates (Merck-5744). The yields of all
metallatricarbaborane products are calculated on the basis of starting
metal reagents.
1
-
anion: HRMS (ES-) calcd for 12C9 H1411B7 198.1797, found
198.1787. The residue was dissolved in toluene to make a ∼0.5 M
solution, which was then employed for the synthesis of the
ferratricarbadecaboranyl complex 1-(η5-C5H5)-2-C6H5-closo-1,2,3,4-
FeC3B7H9 (3), as described elsewhere.2i The exact concentration
of the stock solution and the yield (74%) of 2- were determined
by integrating the resonances in the 11B NMR spectrum of a B10H14
sample of known concentration, and comparing that value with the
integrated value of the resonances of the stock solution.
Physical Methods. The 11B NMR at 64.2 MHz was obtained
on a Bruker AC 200 Fourier transform spectrometer equipped with
appropriate decoupling accessories. 11B NMR at 160.5 MHz and
1H NMR at 500.1 MHz were obtained on a Bruker AM-500
spectrometer equipped with the appropriate decoupling accessories.
All 11B chemical shifts are referenced to BF3-O(C2H5)2 (0.0 ppm),
with a negative sign indicating an upfield shift. All proton chemical
shifts were measured relative to internal residual protons from lock
solvents (99.5% C6D6 and 99.9% CD2Cl2) and then referenced to
(CH3)4Si (0.0 ppm). NMR data are given in Table 1.
To generate 6-Ph-nido-5,6,9-C3B7H10 (2), a stirred solution of
2-, which was obtained by dissolving the crude product from above
in 20 mL of methylene chloride, was reacted for 20 min at 0 °C
with 12 mL of a 1 M solution of HCl in diethyl ether (12 mmol)
(added slowly by syringe). With the reaction solution still main-
tained at 0 °C, the solvent was vacuum evaporated, leaving behind
neutral 6-Ph-nido-5,6,9-C3B7H10 (2). For 2: crude yield (0.89 g,
High- and low-resolution mass spectra were obtained on a VG-
ZAB-E high-resolution mass spectrometer. IR spectra were obtained
on a Perkin-Elmer system 2000 FTIR spectrometer. Elemental
analyses were obtained at the University of Pennsylvania mi-
1
4.4 mmol, 37%); HRMS calcd for 12C9 H1511B7 200.1825, found
200.1835; mp ∼0 to -5 °C.
-
Syntheses of Li+6-NC(CH2)4-nido-5,6,9-C3B7H9 (4-) and
(6) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-SensitiVe
Compounds, 2nd ed.; Wiley: New York, 1986.
6-NC(CH2)4-nido-5,6,9-C3B7H10 (4). Using the concentrations and
3468 Inorganic Chemistry, Vol. 43, No. 11, 2004

Syntheses of Ferratricarbadecaboranyl Complexes
-
procedures described above, the arachno-4,6-C2B7H12- anion was
refluxed with 10.0 mL (88 mmol) of NC(CH2)4CN to give an ∼80%
yield (again determined by NMR integration) of Li+6-NC(CH2)4-
nido-5,6,9-C3B7H9-. Mass spectrometric analysis confirmed the
presence of the 6-NC(CH2)4-nido-5,6,9-C3B7H9- (4-) anion: HRMS
confirmed the presence of the 6-C14H11-nido-5,6,9-C3B7H9 (8-)
1H2011B7 301.2216, found
12
-
anion: HRMS (ES-) calcd for
301.2201.
C
17
The reaction of a toluene solution of 8- (2.4 mL of 0.5 M, 1.2
mmol) with (η5-C5H5)Fe(CO)2I (0.365 g, 1.2 mmol) in THF (35
mL) gave, following workup as described above for 5 and TLC
separation (CH3CN), a dark blue band (Rf 0.6) of 1-(η5-C5H5)-2-
C14H11-closo-1,2,3,4-FeC3B7H9 (9) in 8.5% yield (0.043 g, 0.10
1
(ES-) calcd for 12C8 H1711B714N- 204.2012, found 204.2009.
Acidification of 4- using a procedure identical to that described
for 2 gave the neutral 6-NC(CH2)4-nido-5,6,9-C3B7H10 (4) in 31%
1
yield (0.75 g, 3.7 mmol): HRMS calcd for 12C8 H1811B714N
mmol). For 9: mp 184 °C. Anal. Calcd: C, 62.77; H, 5.99.
12
Found: C, 62.90; H, 5.99. HRMS: calcd for
C
1H2511B756Fe
205.2091, found 205.2088; mp ∼0 to -5 °C.
22
422.1957, found 422.1987. IR (KBr, cm-1): 3110 (s), 3048 (m),
3027 (s), 2929 (s), 2872 (s), 2821 (s), 2800 (m), 2361 (w), 2262
(w), 1987 (m), 1812 (w), 1607 (m), 1575 (m), 1487 (s), 1448 (s),
1421 (s), 1363 (s), 1351 (m), 1325 (w), 1282 (m), 1257 (m), 1237
(w), 1204 (w), 1173 (m), 1154 (m), 1118 (s), 1043 (w), 1013 (w),
1004 (w), 974 (m), 936 (m), 922 (m), 900 (w), 865 (m).
Synthesis of 1-(η5-C5H5)-2-NC(CH2)4-closo-1,2,3,4-FeC3B7H9
(5). A toluene solution of 4- (3.45 mL of 0.5 M, 1.7 mmol) was
added dropwise to a stirring solution of (η5-C5H5)Fe(CO)2I (0.523
g, 1.7 mmol) in THF (35 mL), resulting in a blue-green solution.
After 12 h at room temperature, the mixture was opened to air and
filtered and the dark filtrate evaporated to dryness. The residue was
chromatographed on TLC plates (7:3 hexanes-CH2Cl2) to give a
dark blue band (Rf 0.3) of 1-(η5-C5H5)-2-NC(CH2)4-closo-1,2,3,4-
FeC3B7H9 (5) in 29% yield, (0.16 g, 0.49 mmol). For 5: mp 111
Syntheses of Li+6-H3BNMe2(CH2)2-nido-5,6,9-C3B7H9- (10-)
and 1-(η5-C5H5)-2-H3BNMe2(CH2)2-closo-1,2,3,4-FeC3B7H9 (11).
Following the procedures described earlier, the arachno-4,6-
C2B7H12- anion was refluxed with 5.0 mL (44 mmol) of Me2NCH2-
CH2CN for 4-5 days under N2. After 11B NMR analysis indicated
consumption of the arachno-4,6-C2B7H12-, the solution was filtered
under N2 and the solvent vacuum evaporated from the filtrate to
give a ∼17% (0.3 g, 1.5 mmol) crude yield of an oily product.
Mass spectrometric analysis confirmed the presence of the 6-H3-
BNMe2(CH2)2-nido-5,6,9-C3B7H9- (10-) anion: LRMS (ES-) calcd
°C. Anal. Calcd: C, 48.22; H, 6.85; N, 4.33. Found: C, 48.43; H,
12
7.03; N, 4.24. HRMS: calcd for
C
1H2211B714N56Fe 325.1753,
13
found 325.1770. IR (KBr, cm-1): 3111 (m), 2945 (s), 2865 (s),
2245 (m), 1706 (s), 1464 (s), 1421 (s), 1263 (s), 1210 (w), 1147
(w), 1116 (m), 1060 (w), 1012 (m), 967 (m), 935 (m), 837 (s), 817
(m).
Syntheses of Li+6-[(p-BrC6H4)(Me3SiO)CH]-nido-5,6,9-C3B7H9-
(6-) and 1-(η5-C5H5)-2-[(p-BrC6H4)(Me3SiO)CH]-closo-1,2,3,4-
FeC3B7H9 (7). Using the concentrations and procedures described
earlier, the arachno-4,6-C2B7H12- anion was refluxed with 36.4 g
(96 mmol) of [(p-BrC6H4)(Me3SiO)CH]CN [prepared by room-
temperature reaction of Me3SiCN (5.0 g, 50.4 mmol) and (p-
BrC6H4)CHO (9.32 g, 50.4 mmol) in the presence of catalytic
amounts of ZnI2 (2 mg)]7 for 4-5 days under N2. After 11B NMR
analysis indicated consumption of the arachno-4,6-C2B7H12-, the
solution was filtered under N2 and the solvent vacuum evaporated
from the filtrate to give a ∼35% (1.2 g, 3.1 mmol) crude yield of
the oily product. Mass spectrometric analysis confirmed the
1
for 12C7 H2211B814N- 208, found 208.
The reaction of a toluene solution of 10- (2.2 mL of 0.5 M, 1.1
mmol) with (η5-C5H5)Fe(CO)2I (0.314 g, 1.1 mmol) in THF (35
mL) gave, following workup as described above for 5 and TLC
separation (CH3CN), a dark blue band (Rf 0.4) of 1-(η5-C5H5)-2-
H3BNMe2(CH2)2-closo-1,2,3,4-FeC3B7H9 (11) in 7% yield (0.022
g, 0.70 mmol). For 11: mp 143 °C. Anal. Calcd: C, 43.99; H,
8.30; N, 4.27. Found: C, 43.25; H, 8.29; N, 4.28. HRMS: calcd
12
for
C
1H2711B814N56Fe 329.2237, found 329.2234. IR (KBr,
12
cm-1): 3306 (s), 3113 (m), 3035 (m), 2956 (s), 2854 (m), 2360
(w), 2118 (m), 1608 (w), 1458 (w), 1418 (w), 1364 (m), 1275 (m),
1217 (w), 1150 (w), 1113 (m), 1050 (m), 1015 (w), 976 (w), 865
(m), 846 (m).
-
presence of the 6-[(p-BrC6H4)(Me3SiO)CH]-nido-5,6,9-C3B7H9
(6-) anion: HRMS (ES-) calcd for
C
1H2311B780Br16O28Si-
12
13
Reaction of 11 with Triethylenediamine (DABCO): Synthesis
of 1-(η5-C5H5)-2-NMe2(CH2)2-closo-1,2,3,4-FeC3B7H9 (12). A 0.03
mmol (0.010 g) sample of 11 dissolved in 10 mL of glyme was
refluxed with 0.6 mmol (0.672 g) of DABCO for 12 h. The solvent
was vacuum evaporated and the residue separated by TLC (CH3-
CN) to give a single blue band (Rf 0.1) of the oily blue product,
1-(η5-C5H5)-2-NMe2(CH2)2-closo-1,2,3,4-FeC3B7H9 (12), in 97%
379.1353, found 379.1333.
The reaction of a toluene solution of 6- (1.2 mL of 0.5 M, 0.6
mmol) with (η5-C5H5)Fe(CO)2I (0.179 g, 0.6 mmol) in THF (35
mL) gave, following workup as described above for 5 and TLC
separation (7:3 hexanes-CH2Cl2), a dark blue band (Rf 0.65) of
1-(η5-C5H5)-2-[(p-BrC6H4)(Me3SiO)CH]-closo-1,2,3,4-FeC3B7H9 (7)
in 22% yield (0.064 g, 0.13 mmol). For 7: mp 161 °C. Anal.
1
11
yield (0.009 g, 0.029 mmol). For 12: HRMS calcd for 12C12 H24
-
Calcd: C, 43.25; H, 5.65. Found: C, 43.35; H, 5.56. HRMS: calcd
B714N56Fe 315.1909, found 315.1919; IR (KBr, cm-1) 3364 (s),
2962 (s), 2928 (s), 2549 (s), 2366 (w), 2354 (w), 1731 (w), 1652
(m), 1567 (m), 1462 (m), 1415 (m), 1360 (w), 1260 (s), 1093 (s),
801 (s), 687 (m).
12
for
C
1H2811B780Br56Fe16O28Si 500.1094, found 500.1115. IR
18
(KBr, cm-1): 3106 (s), 3053 (m), 2963 (s), 2925 (s), 2854 (s),
2363 (w), 2270 (w), 2050 (w), 1944 (w), 1907 (m), 1783 (m), 1701
(w), 1589 (s), 1485 (s), 1447 (m), 1403 (w), 1376 (w), 1261 (s),
1191 (w), 1096 (s), 931 (w), 801 (s).
Crystallographic Data for Compounds 5, 7, 9, and 11. Single
crystals of 1-(η5-C5H5)-2-NC(CH2)4-closo-1,2,3,4-FeC3B7H9, (5)
(UPenn No. 3159), 1-(η5-C5H5)-2-[(p-BrC6H4)(Me3SiO)CH]-closo-
1,2,3,4-FeC3B7H9, (7) (UPenn No. 3162), 1-(η5-C5H5)-2-C14H11-
closo-1,2,3,4-FeC3B7H9 (9) (UPenn No. 3185), and 1-(η5-C5H5)-
2-H3BNMe2(CH2)2-closo-1,2,3,4-FeC3B7H9 (11) (UPenn No. 3177)
were grown via slow evaporation from CH2Cl2 or 50:50 hexanes:
CH2Cl2 in air.
Collection and Reduction of the Data. X-ray intensity data for
5, 7, 9, and 11 were collected on a Rigaku R-AXIS IIc area detector
employing graphite-monochromated Mo KR radiation. Indexing was
performed from a series of oscillation angles. A hemisphere of data
Syntheses of Li+6-C14H11-nido-5,6,9-C3B7H9- (8-) and 1-(η5-
C5H5)-2-C14H11-closo-1,2,3,4-FeC3B7H9 (9). Following the pro-
cedures described earlier, the arachno-4,6-C2B7H12 anion was
refluxed with 11.0 g (54 mmol) of C14H9CN for 4-5 days under
N2. After 11B NMR analysis indicated consumption of the arachno-
4,6-C2B7H12-, the solution was filtered under N2 and the solvent
vacuum evaporated from the filtrate to give a ∼15% (0.4 g, 1.3
mmol) crude yield of the oily product. Mass spectrometric analysis
-
(7) Evans, D. A.; Truesdale, L. K.; Carroll, G. L. J. Chem. Soc., Chem.
Commun. 1973, 55-56.
Inorganic Chemistry, Vol. 43, No. 11, 2004 3469

Ramachandran et al.
Table 2. Crystallographic Data Collection and Structure Refinement Information
5
7
9
11
empirical formula
fw
FeC13B7H22N
323.84
FeC18B7H28SiOBr
499.92
FeC22B7H25
420.94
FeC12B8H27N
327.68
crystal class
space group
Z
monoclinic
P21/c
4
monoclinic
P21/c
4
triclinic
P1
2
monoclinic
P21/c
4
a, Å
b, Å
c, Å
8.0275(1)
9.5860(1)
21.2344(4)
13.0327(3)
7.7587(1)
22.6750(6)
11.304(2)
13.901(3)
7.5662(14)
105.688(8)
109.808(13)
100.35(2)
1027.5(3)
7.41
12.8071(1)
6.5162(1)
21.0254(2)
R, deg
â, deg
95.635(1)
100.783(1)
95.785(1)
γ, deg
V, Å3
1626.13(4)
9.15
2252.34(8)
25.05
1745.71(3)
8.52
µ, cm-1
crystal size, mm
0.32 × 0.18 × 0.02
0.40 × 0.08 × 0.06
0.24 × 0.20 × 0.003
0.38 × 0.18 × 0.06
D
calc, g/cm3
1.323
1.474
1.361
1.247
F(000)
672
1016
436
688
radiation
2θ angle, deg
temp, K
Mo KR
Mo KR
5.28-50.7
210
Mo KR
5.8-50.76
200
Mo KR
5.28-50.7
200
5.1-50.7
210
hkl collected
-9 e h e 9,
-11 e k e 11,
-25 e l e 25
13047
-15 e h e 15,
-8 e k e 9,
-27 e l e 27
16434
-13 e h e 13,
-16 e k e 16,
-9 e l e 9
8252
-15 e h e 15,
-7 e k e 7,
-25 e l e 24
13517
no. of reflns measd
no. of unique reflns
2958 (Rint ) 0.0370)
4074 (Rint ) 0.0424)
5746 (Rint ) 0.0519)
3145 (Rint ) 0.0348)
no. of observed reflns (F > 4σ)
no. of reflns used in refinement
no. of parameters
2758
3712
5292
2975
2958
267
4074
374
5746
542
3145
307
Ra indices (F > 4σ)
R1 ) 0.0390
wR2 ) 0.0844
R1 ) 0.0437
wR2 ) 0.0867
1.104
R1 ) 0.0481
wR2 ) 0.0843
R1 ) 0.0563
wR2 ) 0.0877
1.168
R1 ) 0.0607
wR2 ) 0.1547
R1 ) 0.0666
wR2 ) 0.1616
1.081
R1 ) 0.0417
wR2 ) 0.0944
R1 ) 0.0451
wR2 ) 0.0965
1.130
Ra indices (all data)
GOFb
final difference peaks, e/Å3
+0.203, -0.456
+0.276, -0.460
+0.507, -0.534
+0.208, -0.509
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) {∑w(Fo - Fc )2/∑w(Fo )2}1/2
.
b GOF ) {∑w(Fo - Fc )2/(n - p)}1/2 where n ) no. of reflections; p ) no. of
2
2
2
2
2
parameters refined.
was collected using 8° oscillation angles for 5, 5° oscillation angles
for 7, 6° oscillation angles for 9 and 11, and a crystal-to-detector
distance of 82 mm. Exposure times of 200 s (5), 300 s (7), 1000 s
(9), and 300 s (11) were employed. Oscillation images were
processed using bioteX,8 producing a listing of unaveraged F2 and
σ(F2) values which were then passed to the teXsan program9
package for further processing and structure solution on a Silicon
Graphics Indigo R4000 computer. The intensity data were corrected
for Lorentz and polarization effects, but not for absorption.
Solution and Refinement of the Structures. The structure was
solved by direct methods (SIR9210). Refinement was by full-matrix
least squares based on F2 using SHELXL-93.11 All reflections were
used during refinement (F2 values that were experimentally negative
were replaced by F2 ) 0). Data collection and structure refinement
information is given in Table 2.
Results and Discussions
Figure 1. Previously proposed reaction sequence for the synthesis of
6-CH3-nido-5,6,9-C3B7H9- from the reaction of arachno-4,6-C2B7H12- with
CH3CN.
We have previously shown1 that the 6-CH3-nido-5,6,9-
-
C3B7H9 (1-) monoanion can be synthesized in excellent
yields (eq 1) by a process (Figure 1) involving the initial
nucleophilic attack of the arachno-4,6-C2B7H12- anion at the
nitrile carbon of acetonitrile, followed by nitrile reduction,
deamination, and monocarbon insertion.
(8) bioteX: A suite of Programs for the Collection, Reduction and
Interpretation of Imaging Plate Data; Molecular Structure Corpora-
tion: 1995.
(9) teXsan: Crystal Structure Analysis Package; Molecular Structure
Corporation: 1985 and 1992.
Li+arachno-4,6-C2B7H12- + CH3CN f
Li+(6-CH3-nido-5,6,9-C3B7H9 ) + NH3 (1)
-
(10) SIR92: Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.;
Giacovazzo, C.; Guagliardi, A.; Polidoro, G. J. Appl. Crystallogr. 1994,
27, 435.
(11) Sheldrick, G. M. SHELXL-93: Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1993.
We have now found that similar reactions with a variety
of nitriles lead to the formation of substituted 6-R-nido-5,6,9-
-
C3B7H9 anions. The reactions with PhCN, NC(CH2)4CN,
3470 Inorganic Chemistry, Vol. 43, No. 11, 2004

Syntheses of Ferratricarbadecaboranyl Complexes
-
C3B7H9 (1-) with (η5-C5H5)Fe(CO)2I.2a
(η5-C5H5)Fe(CO)2I +
-LiI, -2CO8
Li+(6-CH3-nido-5,6,9-C3B7H9 )
-
1-
1-(η5-C5H5)-2-CH3-closo-1,2,3,4-FeC3B7H9 +
Figure 2. Protonation reactions of 2- and 4-.
1-(η5-C5H5)-4-CH3-closo-1,2,3,4-FeC3B7H9 +
commo-Fe-(5-CH3-closo-1,2,3,5-FeC3B7H9)
(4-CH3-closo-1,2,3,4-FeC3B7H9) (2)
and [(p-BrC6H4)(Me3SiO)CH]CN proceeded in a straight-
-
forward manner to give the Li+(6-Ph-nido-5,6,9-C3B7H9 )
-
(2-), Li+(6-NC(CH2)4-nido-5,6,9-C3B7H9 ) (4-), and Li+-
-
(6-[(p-BrC6H4)(Me3SiO)CH]-nido-5,6,9-C3B7H9 ) (6-) tri-
Similar reactions (eq 3) have now been used to prepare
functionalized metallatricarbadecaborane complexes.
carbadecaboranyl anions. Typical isolated yields for Li+2-
and Li+4- products were in the 74-80% range, but, most
likely due to its larger steric demands, lower yields (35%)
were found for Li+6-. As can be seen in Table 1 for 2- and
4-, the 11B NMR spectra for each of the substituted
tricarbadecaboranyl anions have a seven-line pattern es-
sentially identical to that reported for 6-CH3-nido-5,6,9-
(η5-C5H5)Fe(CO)2I +
-LiI, -2CO8
Li+(6-R-nido-5,6,9-C3B7H9 )
-
2-, 4-, 6-
1-(η5-C5H5)-2-R-closo-1,2,3,4-FeC3B7H9
3, 5, 7
(3)
- 1
C3B7H9 . The peak positions in 2- are shifted slightly
downfield, which is consistent with the electron withdrawing
nature of a Ph group compared to the Me group in 1-.
As shown in Figure 2, the neutral compounds 6-Ph-nido-
5,6,9-C3B7H10 (2) and 6-NC(CH2)4-nido-5,6,9-C3B7H10 (4)
were prepared by reacting 2- and 4- with HCl. The 11B NMR
spectra of both 2 and 4 show seven different doublets at
chemical shifts nearly identical to that observed for 6-CH3-
-
Reactions employing 6-CH3-nido-5,6,9-C3B7H9 usually
result in a skeletal rearrangement to produce isomeric side
products, such as the 1-(η5-C5H5)-4-CH3-closo-1,2,3,4-
FeC3B7H9 complex in eq 2, where the methyl is attached at
the 4-position carbon.13 Likewise, bis-cage, (CH3-C3B7H9)2M,
side products are usually produced. On the other hand, in
the reactions with 2-, 4-, and 6- (as well as the reactions of
8- and 10- discussed below) neither isomerization nor bis-
cage (R-C3B7H9)2Fe products were observed. In fact, as
previously2i noted, even reactions intentionally designed to
produce bis-cage complexes from the 6-Ph-nido-5,6,9-
1
nido-5,6,9-C3B7H10 (1).1 Their H NMR spectra show, in
addition to the resonances of their respective phenyl and
methylene substituents, three cage CH resonances. As in
6-CH3-nido-5,6,9-C3B7H10, one of the CH resonances in the
spectra of both 2 and 4 appears at a high-field shift
characteristic of an endo-CH hydrogen (2, -1.21 ppm; 4,
-1.52 ppm).12 This is consistent with the protonations of
2- and 4- occurring, as was observed for 6-CH3-nido-5,6,9-
-
C3B7H9 (2-) anion have been unsuccessful. The inability
to form bis-cage complexes containing the functionalized
monoanions is most probably a result of the unfavorable
steric interactions that would occur between the bulky
substituents on the two cages of such a complex. Thus,
because other products are not produced, reactions with the
new functionalized anions provide a more efficient route to
mixed ligand metallatricarbadecaboranyl complexes than
-
C3B7H9 , at the endo-positions of their C9 carbons. The two
remaining cage CH resonances in both compounds appear
at lower field (exo-C9H, 3.94 (2) and 3.25 (4) ppm; and C5H,
1.97 (2) and 1.85 (4) ppm). The room-temperature proton-
decoupled 13C NMR spectra of both compounds show, in
addition to their substituent resonances, three broad reso-
nances corresponding to three cage carbons.
As illustrated in eq 2, ferratricarbadecaboranyl analogues
of ferrocene, including both bis-cage, (CH3-C3B7H9)2Fe, and
mixed-ligand, (η5-C5H5)Fe(CH3-C3B7H9), complexes, have
been shown to result from the reactions of 6-CH3-nido-5,6,9-
-
those reactions employing the 6-CH3-nido-5,6,9-C3B7H9
anion.
All ferratricarbadecaboranyl complexes were isolated as
air-stable solids and were purified by TLC. Their composi-
tions were established by mass spectrometry and elemental
analyses.
The 11B NMR spectra of 5 and 7 (and of 9 and 11
discussed below) are each consistent with C1 cage sym-
metries and are similar to that previously reported for 32g,i
and 1-(η5-C5H5)-2-CH3-closo-1,2,3,4-FeC3B7H9.2a The H
NMR spectra of these compounds are likewise similar to
that of 1-(η5-C5H5)-2-CH3-closo-1,2,3,4-FeC3B7H9, each
showing, in addition to the resonances arising from their C2
substituents, two CH resonances with one occurring at a low
field shift (∼6.61 to 6.04 ppm) characteristic of the proton
attached to the low-coordinate C3 carbon, and the other at a
high field shift (>1.83 ppm) characteristic of the C4H proton.
(12) (a) Plesek, J.; Herma´nek, S.; Janousek, Z. Collect. Czech. Chem.
Commun. 1977, 42, 785-792. (b) Tebbe, F. N.; Garrett, P. M.;
Hawthorne, M. F. J. Am. Chem. Soc. 1966, 88, 607-608. (c) Tebbe,
F. N.; Garrett, P. M.; Hawthorne, M. F. J. Am. Chem. Soc. 1968, 90,
869-879. (d) Stibr, B.; Plesek, J.; Herma´nek, S. Chem. Ind. 1972,
19, 649. (e) Stibr, B.; Base, K.; Herma´nek, S.; Plesek, J. J. Chem.
Soc., Chem. Commun. 1976, 150-151. (f) Base, K.; Herma´nek, S.;
Stibr, B. Chem. Ind. 1976, 18, 1068-1069. (g) Base, K.; Herma´nek,
S.; Hanousek, F. J. Chem. Soc., Chem. Commun. 1984, 299. (h)
Janousek, Z.; Plesek, J.; Herma´nek, S.; Stibr, B. Polyhedron 1985, 4,
1797-1798. (i) Stibr, B.; Janousek, Z.; Plesek, J.; Jelinek, T.;
Herma´nek, S. J. Chem. Soc., Chem. Commun. 1985, 1365-1366. (j)
Jelinek, T.; Herma´nek, S.; Stibr, B.; Plesek, J. Polyhedron 1986, 5,
1303-1305. (k) Stibr, B.; Plesek, J.; Jelinek, T.; Herma´nek, S.;
Solntsev, K. A.; Kuznetsov, N. T. Collect. Czech. Chem. Commun.
1987, 52, 957-959.
1
(13) Plumb, C. A.; Sneddon, L. G. Organometallics 1992, 11, 1681-1685.
Inorganic Chemistry, Vol. 43, No. 11, 2004 3471

Ramachandran et al.
Table 3. Selected Intramolecular Distances (Å) in 3, 5, 7, 9, and 11
bond
3a
5
7
9b
11
Fe-C2
Fe-C3
Fe-C4
Fe-B5
Fe-B6
Fe-B7
Fe-Cp
C2-C4
C4-B7
B7-C3
C3-B6
B6-B5
B5-C2
1.982(2)
1.955(3)
2.258(3)
2.239(3)
2.253(3)
2.275(3)
1.695(3)
1.502(4)
1.750(4)
1.576(4)
1.578(4)
1.841(5)
1.593(4)
1.980(2)
1.956(3)
2.244(2)
2.245(3)
2.239(3)
2.265(3)
1.686(3)
1.500(3)
1.747(4)
1.574(4)
1.580(4)
1.843(4)
1.586(3)
1.991(4)
1.954(4)
2.282(4)
2.224(4)
2.227(4)
2.292(4)
1.694(5)
1.500(4)
1.746(5)
1.558(5)
1.588(5)
1.846(6)
1.584(5)
1.970(8)
1.957(8)
2.244(8)
2.238(7)
2.253(8)
2.287(9)
1.692(7)
1.509(11)
1.749(13)
1.579(13)
1.576(11)
1.846(12)
1.589(9)
1.980(2)
1.959(3)
2.250(2)
2.241(3)
2.241(3)
2.283(3)
1.688(2)
1.497(3)
1.746(4)
1.568(4)
1.578(4)
1.854(4)
1.594(4)
a Taken from ref 2i. b Since there were no significant differences, bond
distances for only one of the two independent molecules found in the
asymmetric unit of 9 are given.
Figure 3. ORTEP drawing of the structure of 1-(η5-C5H5)-2-NC(CH2)4-
closo-1,2,3,4-FeC3B7H9 (5). Important intracage distances are given in Table
3. Other selected distances (Å) and angles (deg): C2-C12, 1.524(3); C16-
N17, 1.139(4); C12-C2-B8, 115.7(2); C15-C16-N17, 178.3(3); Fe1-
C2-C12, 126.4(2); C2-Fe1-C3, 111.17(10).
1 skeletal electron) and it, therefore, adopts the octadeca-
hedral structure normally observed for such systems.
Selected intracage distances for 3, 5, and 7 (and 9 and
11) are compared in Table 3. In each case, the metal is
approximately centered over the puckered six-membered
open face, with the closest metal-cage interactions being
with the two carbons, C2 and C3, which are puckered out
of the ring. Longer and approximately equivalent bond
lengths are observed between the metals and the remaining
four atoms (C4, B5, B6, and B7) on the tricarbadecaboranyl
bonding face. The M-C2 and M-C3 bond lengths in these
complexes are significantly shorter than the M-C bond
lengths found to the ring carbons in their cyclopentadienyl
(∼2.05 to 2.07 Å) ligands. As previously noted,15 the orbitals
on the open face of even a planar polyhedral cluster are
orientated more directly toward the metal than in a cyclo-
pentadienyl ring. This enhances the overlap of the metal and
ligand orbitals and strengthens the bonding. In the case of
the tricarbadecaboranyl cages, the puckered ring structure
allows even stronger interactions of the metal with the C2
and C3 carbons.
Figure 4. ORTEP drawing of the structure of 1-(η5-C5H5)-2-[(p-
BrC6H4)(Me3SiO)CH]-closo-1,2,3,4-FeC3B7H9 (7). Important intracage
distances are given in Table 3. Other selected distances (Å) and angles
(deg): C2-C12, 1.544(5); C12-O1, 1.413(4); Si-O1, 1.657(3); C12-
C2-B8, 115.6(3); Fe1-C2-C12, 126.4(3); C2-Fe1-C3, 110.4(2); C2-
C12-O1, 108.0(3); C2-C12-C13, 112.1(3); Si-O1-C12, 128.4(2).
Regardless of the substituent at the C2 carbon, the Fe-
C2 distances (3, 1.982(2) Å; 5, (1.980(2) Å; 7, 1.991(4) Å)
were found to be considerably longer than their correspond-
ing Fe-C3 distances (3, 1.955(3) Å; 5, 1.956(3) Å; 7,1.954-
(4) Å, respectively). In complexes 3 and 5, the plane of the
η5-C5H5 ring is reasonably parallel to the C4-B5-B6-B7
plane, but, consistent with the longer Fe-C2 distance in 7
relative to those in 3 and 5, in 7 these planes have a dihedral
angle of 8.3(9)° such that the η5-C5H5 group is tilted away
from the bulky (p-BrC6H4)(Me3SiO)CH- substituent.
In agreement with both the spectroscopic data and the
previous structural determinations of 1-(η5-C5H5)-2-CH3-
closo-1,2,3,4-FeC3B7H92a and 1-(η5-C5H5)-2-Ph-closo-1,2,3,4-
2g,i
FeC3B7H9 (3), crystallographic determinations of 1-(η5-
C5H5)-2-NC(CH2)4-closo-1,2,3,4-FeC3B7H9 (5) (Figure 3)
and 1-(η5-C5H5)-2-[(p-BrC6H4)(Me3SiO)CH]-closo-1,2,3,4-
FeC3B7H9 (7) (Figure 4) confirm that the metal atoms in these
complexes are η6-coordinated to the puckered six-membered
face of the tricarbadecaboranyl cage with the functional
groups bonded to the C2 cage carbon adjacent to the metal.
Thus, these complexes can be considered as mixed ligand
analogues of ferrocene in which a formal Fe2+ ion is
sandwiched between tricarbadecaboranyl and cyclopentadi-
enyl monoanions. From a cluster point of view,14 the 11-
vertex FeC3B7H9 fragment has a closo skeletal electron count
(24 skeletal electrons, with the (η5-C5H5)Fe group donating
-
The reaction (Figure 5) of arachno-4,6-C2B7H12 with
cyanoanthracene was expected to provide a route to an
anthracene-substituted ferratricarbadecaboranyl complex.
However, a structural characterization of the final product
revealed that, during the course of the reaction, anthracene
reduction occurred to produce the dihydroanthracene (DHA)
(15) (a) Hawthorne, M. F.; Young, D. C.; Andrews, T. D.; Howe, D. V.;
Pilling, R. L.; Pitts, A. D.; Reintjes, M.; Warren, L. F., Jr.; Wegner,
P. A. J. Am. Chem. Soc. 1968, 90, 879-896. (b) Calhorda, M. J.;
Mingos, D. M. P.; Welch, A. J. Organomet. Chem. 1982, 228, 309-
320. (c) Mingos, D. M. P. J. Chem. Soc., Chem. Commun. 1977, 602-
610.
(14) (a) Wade, K. AdV. Inorg. Chem. Radiochem. 1976, 18, 1-66. (b)
Williams, R. E. AdV. Inorg. Chem. Radiochem. 1976, 18, 67-142.
(c) Williams, R. E. Chem. ReV. 1992, 92, 117-201. (d) Williams, R.
E. In Electron Deficient Boron and Carbon Clusters; Olah, G. A.,
Wade, K., Williams, R. E., Eds.; Wiley: New York, 1991.
3472 Inorganic Chemistry, Vol. 43, No. 11, 2004

Syntheses of Ferratricarbadecaboranyl Complexes
Figure 7. Reaction of 10- with (η5-C5H5)Fe(CO)2I.
Figure 5. Reaction of 8- with (η5-C5H5)Fe(CO)2I.
Figure 8. ORTEP drawing of the structure of 1-(η5-C5H5)-2-H3BNMe2-
(CH2)2-closo-1,2,3,4-FeC3B7H9 (11). Important intracage distances are given
in Table 3. Other selected distances (Å) and angles (deg): C2-C12,
1.525(3); B17-N14, 1.620(4); C13-N14, 1.506(3); C15-N14, 1.484(4);
C16-N14, 1.492(4); C12-C2-B8, 115.1(2); C12-C2-Fe1, 126.8(2); C2-
Fe1-C3, 110.74(10); B17-N14-C13, 112.4(2); B17-N14-C15, 111.2-
(3); B17-N14-C16, 108.4(2); C15-N14-C16, 108.4(2).
Figure 6. ORTEP drawing of the structure of one of the two independent
molecules in the unit cell of 1-(η5-C5H5)-2-C14H11-closo-1,2,3,4-FeC3B7H9
(9). Important intracage distances are given in Table 3. Other selected
distances (Å) and angles (deg): C2-C12, 1.578(9); C12-C25, 1.515(9);
C25-C20, 1.377(11); C18-C19, 1.500(10); C18-C13, 1.388(11); C13-
C12, 1.518(9); C19-C20, 1.509(10); C20-C21, 1.420(10); C21-C22,
1.389(12); C22-C23, 1.354(13); C23-C24, 1.396(11); C24-C25, 1.423(10);
C13-C14, 1.432(10); C14-C15, 1.411(12); C15-C16, 1.372(14); C16-
C17, 1.372(11); C17-C18, 1.399(10); C12-C2-B8, 114.9(6); C12-C2-
Fe1, 127.5(5); C2-Fe1-C3, 111.5(3); C2-C12-C13, 112.1(6); C2-C12-
C25, 111.2(5); C13-C12-C25, 112.6(6); C18-C19-C20, 114.2(7); C19-
C20-C25, 122.4(7); C20-C25-C12, 121.5(6); C18-C13-C12, 122.1(6);
C19-C18-C13, 121.4(6).
value (and 77.4° in the other independent molecule) found
for the C12-C13-C18-C19-C20-C25 ring in 9 is similar
to that found in 9-Me3Si-10-Me-DHA (85.4°), but much
smaller than those found for the more distorted 9-Me-DHA
(136.4°) and 9-Me3Si-DHA (121.5°) derivatives.17a The
intracage distances (Table 3) and angles are consistent with
those observed for the other ferratricarbaboranes.
As can be seen in Figure 7, the reaction of arachno-4,6-
C2B7H12 and Me2NCH2CH2CN was expected to provide a
substituted product 1-(η5-C5H5)-2-C14H11-closo-1,2,3,4-
FeC3B7H9 (9). As can be seen in the ORTEP drawing in
Figure 6, hydrogenation of the central ring occurred and, as
a result, the tetrahedral C12 and C19 carbons are puckered
out of the C13-C18-C20-C25 plane, such that the central
ring adopts a boat conformation with the ferratricarbaboranyl
fragment bound at the axial position of the C12 ring carbon.
Accordingly, the planes of the C13-C14-C15-C16-C17-
C18 and C20-C21-C22-C23-C24-C25 rings no longer
lie in the C13-C18-C20-C25 plane, forming 8(1)° and
7(1)° dihedral angles with that plane. These dihedral angles,
as well as the distances and angles observed for the central
ring, are consistent with those that have been observed in
dihydroanthracene16 and its derivatives.17 The degree of
nonplanarity of the central ring can be expressed by the sum
of the six torsional angles of the six carbons within the central
ring (for a planar ring this sum would be 0°).17a The 81.5°
-
route to the complex 1-(η5-C5H5)-2-NMe2(CH2)2-closo-
1,2,3,4-FeC3B7H9 (12), which would have a dimethylamine
group tethered to the cage. Surprisingly, as shown in the
ORTEP drawing in Figure 8, a crystallographic determination
established that the final product was instead the complex
1-(η5-C5H5)-2-BH3NMe2(CH2)2-closo-1,2,3,4-FeC3B7H9 (11)
containing a BH3-coordinated amine. Given the low yields
observed for the formation of 11 (7% from arachno-4,6-
C2B7H12-), the BH3 group was undoubtedly generated by
(16) Herbstein, F. H.; Kapon, M.; Reisner, G. M. Acta Crystallog., Sect B
1986, 42, 181-187.
(17) (a) Dhar, R. J.; Sygula, A.; Fronczek, F. R.; Rabideau, P. W.
Tetrahedron 1992, 48, 9417-9426. (b) Brennan, T.; Putkey, E. F.;
Sundaralingam, J. Chem. Soc., Chem. Commun. 1971, 1490-1491.
(c) Bordner, J.; Stanford, R. H., Jr.; Ziegler, H. E. Acta Crystallog.,
Sect B 1973, 29, 313-318. (d) Leory, F.; Courseille, C.; Daney, M.;
Bouas-Laurent, H. Acta Crystallog., Sect B 1976, 32, 2792-2796.
Inorganic Chemistry, Vol. 43, No. 11, 2004 3473

Ramachandran et al.
cage decomposition reactions during the course of the
reaction. The B-N distance of 1.620(4) Å in 11 is similar
to the values that have been found in other amine-boranes,18
and the intracage distances (Table 3) and angles are likewise
consistent with those of the other ferratricarbadecaboranyl
complexes reported above. In agreement with the structural
determination, the 11B NMR of 11 contains, in addition to
the seven cage-boron resonances observed for complexes 3,
5, 7, and 9, an eighth resonance at -9.8 ppm that can be
assigned to the amine-coordinated BH3.
As shown in Figure 7, removal of the BH3 group from 11
to produce the 1-(η5-C5H5)-2-NMe2(CH2)2-closo-1,2,3,4-
FeC3B7H9 (12) complex containing the free amine group was
achieved by reaction of 11 with DABCO (triethylenedi-
amine). Although 12 was not crystallographically character-
ized, the removal of the borane was confirmed by both mass
spectrometry and 11B NMR. Thus, instead of the eight
resonances observed for 11, the 11B NMR spectrum of 12
exhibited only the seven cage-boron resonances.
To summarize, this paper demonstrates both a general
route to 6-R-nido-5,6,9-C3B7H9- anions via the reactions of
arachno-4,6-C2B7H12- with nitriles and that the new tricar-
badecaboranyl anions can then be used to generate func-
tionalized metallatricarbadecaboranyl complexes containing
a wide range of organic substituents. These pathways now
provide great flexibility for the systematic tuning of the
chemical and bioactivity properties of metallatricarbade-
caborane complexes.
Acknowledgment. We thank the National Science Foun-
dation for the support of this research.
Supporting Information Available: X-ray crystallographic data
for structure determinations of compounds 5, 7, 9, and 11 (CIF).
This material is available free of charge via the Internet at
http://pubs.acs.org.
(18) Buhl, M.; Steinke, T.; Schleyer, P. v. R.; Boese, R. Angew. Chem.,
Int. Ed. Engl. 1991, 30, 1160-1161.
IC049827A
3474 Inorganic Chemistry, Vol. 43, No. 11, 2004