Dioxygen-ActiWating Centers in Non-Heme Diiron Enzymes
4. Colorless blocks of 5 (187 mg, 0.126 mmol, 69%) precipitated
upon vapor diffusion of pentanes into the reaction mixture and were
analyzed by X-ray crystallography. FT-IR (KBr, cm-1): 3119, 3055,
3021, 2919, 2863, 1608, 1541, 1516, 1454, 1409, 1378, 1306, 1287,
1241, 1188, 1147, 1111, 1095, 1071, 1020, 945, 847, 819, 800,
783, 765, 736, 713, 701, 656, 615, 543, 520, 453. Anal. Calcd for
C92H80N4O8Fe2: C, 74.59; H, 5.44; N, 3.78. Found: C, 74.26; H,
5.49; N, 3.48.
[Fe2(µ-O2CArTol)3(O2CArTol)(2,6-lutidine)] (6). A rapidly stirred
CH2Cl2 (4 mL) solution of 2 (130 mg, 89.0 µmol) was treated with
neat 2,6-lutidine (250 µL, 2.15 mmol). A flash of intense yellow
color appeared, which gradually faded during the addition. Vapor
diffusion of Et2O into the reaction mixture afforded 6 as an off-
white solid (81 mg, 57 µmol, 64%). Colorless blocks of 6 suitable
for X-ray crystallography were obtained by vapor diffusion of Et2O
into a concentrated CH2Cl2 solution of this material at -30 °C.
FT-IR (KBr, cm-1): 3054, 3024, 2971, 2920, 2864, 1601, 1580,
1541, 1515, 1454, 1407, 1382, 1305, 1184, 1150, 1111, 1072, 1021,
860, 844, 834, 819, 799, 784, 709, 585, 531, 470. Anal. Calcd for
C91H77NO8Fe2: C, 76.74; H, 5.45; N, 0.98. Found: C, 76.55; H,
5.95; N, 0.96.
[Fe2(µ-O2CArTol)4(4-tBuC5H4N)2] (7). Method 1. To a rapidly
stirred pale yellow CH2Cl2 solution (5 mL) of 2 (144 mg, 99 µmol)
was added dropwise neat 4-tert-butylpyridine (32 µL, 0.22 mmol).
The solution was intense greenish yellow following the addition.
Greenish yellow blocks of 7 (100 mg, 63 µmol, 64%) were obtained
by vapor diffusion of Et2O into the reaction mixture. Layering of
benzene over a CH2Cl2 solution of this material provided crystals
suitable for X-ray crystallography.
Method 2. To a rapidly stirred THF (20 mL) suspension of
NaO2CArTol (570 mg, 1.76 mmol) was added Fe(OTf)2‚2MeCN
(385 mg, 0.883 mmol) in a single portion. The heterogeneous
mixture was stirred overnight, and volatile fractions were removed
under reduced pressure. The residual ivory solid was extracted into
CH2Cl2 (10 mL) and filtered. A portion of 4-tert-butylpyridine (130
µL, 0.880 mmol) was added to the filtrate, and the greenish yellow
solution was concentrated to ca. 3 mL. Vapor diffusion of Et2O
into the solution afforded 7 (373 mg, 0.235 mmol, 53%) as greenish
yellow blocks. FT-IR (KBr, cm-1): 3051, 3020, 2965, 2919, 2866,
1614, 1585, 1514, 1502, 1438, 1422, 1404, 1384, 1304, 1273, 1185,
1150, 1109, 1072, 2029, 1021, 842, 830, 812, 786, 763, 726, 712,
706, 584, 568, 525, 458. UV-vis (CH2Cl2, λmax, nm (ꢀ, M-1 cm-1)):
370 (1400). Anal. Calcd for C102H94N2O8Fe2: C, 77.17; H, 5.97;
N, 1.76. Found: C, 77.31; H, 6.06; N, 1.64.
[Fe2(µ-O2CAr4-FPh)2(O2CAr4-FPh)2(THF)2] (8). This compound
was prepared from Fe(OTf)2‚2MeCN (221 mg, 0.507 mmol) and
NaO2CAr4-FPh (375 mg, 1.13 mmol) by a procedure analogous to
that used to prepare 2. Colorless blocks of 8 (192 mg, 0.129 mmol,
51%) were obtained by recrystallization from CH2Cl2/pentanes/
hexanes and analyzed by X-ray crystallography. FT-IR (KBr, cm-1):
3063, 2975, 2886, 1608, 1514, 1458, 1413, 1384, 1300, 1219, 1186,
1160, 1094, 1071, 1035, 1014, 938, 882, 836, 809, 792, 773, 739,
712, 700, 602, 582, 555, 531, 462. Anal. Calcd for C84H60O10F8-
Fe2‚0.25CH2Cl2: C, 66.82; H, 4.03. Found: C, 66.65; H, 4.05.
[Fe2(µ-O2CAr4-FPh)4(THF)2] (9). To a rapidly stirred pale
yellow CH2Cl2 (5 mL) solution of 8 (57 mg, 38 µmol) was added
dropwise [Cp2Fe](PF6) (28 mg, 84 µmol) suspended in CH2Cl2 (3
mL). The dark blue-green reaction mixture was stirred at room
temperature for 1.5 h. Volatile fractions were removed under
reduced pressure, and the residual dark green solid was washed
repeatedly with pentanes. The remaining solid material was
extracted into CH2Cl2 (4 mL) and filtered. Vapor diffusion of
pentanes into the filtrate afforded 9 as pale green blocks suitable
for X-ray crystallography. No further attempts were made to purify
this material, which was obtained together with purple powders.
[Fe2(µ-O2CAr4-FPh)4(C5H5N)2] (10). This compound was pre-
pared from 8 (95 mg, 64 µmol) and pyridine (10 µL, 0.12 mmol)
by a procedure analogous to that used to obtain 4. Vapor diffusion
of pentanes into the reaction mixture afforded 10 (61 mg, 40 µmol,
67%) as a yellow microcrystalline solid. Single crystals suitable
for X-ray crystallography were obtained by vapor diffusion of
pentanes into a saturated CH2Cl2 solution of this material at -30
°C. FT-IR (KBr, cm-1): 3057, 1605, 1551, 1510, 1488, 1449, 1404,
1381, 1300, 1225, 1160, 1096, 1071, 1042, 1011, 843, 809, 792,
771, 704, 582, 555, 530, 464. UV-vis (CH2Cl2, λmax, nm (ꢀ, M-1
-
cm-1)): 366 (930). Anal. Calcd for C86H54N2O8F8Fe2: C, 68.54;
H, 3.61; N, 1.86. Found: C, 68.49; H, 3.70; N, 1.92.
[Fe2(µ-O2CAr4-FPh)4(1-MeIm)2] (11). This compound was
prepared in a manner similar to that described for 10, except that
1-methylimidazole was used instead of pyridine. Pale yellow blocks
of 11 (44%) suitable for X-ray crystallography were obtained by
vapor diffusion of pentanes/hexanes (1:1) into the reaction mixture.
FT-IR (KBr, cm-1): 3136, 3059, 2962, 2928, 1605, 1535, 1511,
1454, 1404, 1381, 1222, 1160, 1094, 1015, 948, 842, 809, 792,
771, 714, 705, 655, 555, 531, 466. Anal. Calcd for C84H56N4O8F8-
Fe2: C, 66.68; H, 3.73; N, 3.70. Found: C, 66.71; H, 4.03; N,
3.67.
[Fe2(µ-O2CAr4-FPh)4(4-tBuC5H4N)2] (12). This compound was
prepared in a manner similar to that described for 10, except that
4-tert-butylpyridine was used instead of pyridine. Greenish yellow
blocks of 12 (62%) were obtained by vapor diffusion of pentanes
into the reaction mixture and analyzed by X-ray crystallography.
FT-IR (KBr, cm-1): 3057, 2966, 2905, 2870, 1614, 1580, 1554,
1510, 1452, 1403, 1382, 1222, 1159, 1095, 1074, 844, 831, 818,
793, 772, 727, 706, 555, 530, 468. UV-vis (CH2Cl2, λmax, nm (ꢀ,
M-1cm-1)): 365 (1200). Anal. Calcd for C94H70N2O8F8Fe2: C,
69.72; H, 4.36; N, 1.73. Found: C, 69.97; H, 4.45; N, 1.64.
X-ray Crystallographic Studies. Intensity data were collected
on a Bruker (formerly Siemens) CCD diffractometer with graphite-
monochromated Mo KR radiation (λ ) 0.71073 Å), controlled by
a Pentium-based PC running the SMART software package.40 Single
crystals were mounted at room temperature on the tips of quartz
fibers, coated with Paratone-N oil, and cooled to 188 K under a
stream of cold nitrogen maintained by a Bruker LT-2A nitrogen
cryostat. Data collection and reduction protocols are described
elsewhere.41 The structures were solved by direct methods and
refined on F2 by using the SHELXTL software package.42 Empirical
absorption corrections were applied with SADABS,43 part of the
SHELXTL program package, and the structures were checked for
higher symmetry by the PLATON program.44 All non-hydrogen
atoms were refined anisotropically unless otherwise noted. Hydro-
gen atoms were assigned idealized positions and given thermal
parameters equivalent to either 1.5 (methyl hydrogen atoms) or 1.2
(all other hydrogen atoms) times the thermal parameter of the carbon
atom to which they were attached. The hydrogen atoms associated
with the disordered solvent molecules were not included in the
(40) SMART V5.05: Software for the CCD Detector System; Bruker AXS:
Madison, WI, 1998.
(41) Feig, A. L.; Bautista, M. T.; Lippard, S. J. Inorg. Chem. 1996, 35,
6892-6898.
(42) Sheldrick, G. M. SHELXTL97-2: Program for the Refinement of
Crystal Structures; University of Go¨ttingen: Go¨ttingen, Germany,
1997.
(43) Sheldrick, G. M. SADABS: Area-Detector Absorption Correction;
University of Go¨ttingen: Go¨ttingen, Germany, 1996.
(44) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht
University: Utrecht, The Netherlands, 1998.
Inorganic Chemistry, Vol. 41, No. 10, 2002 2707