Foley et al.
(30 mL). nBuLi (1.31 mL, 2.5M) was added to the solution
dropwise. The solution was stirred for 15 min, followed by addition
of 0.5 equiv of FeBr2 (0.353 g, 1.64 mmol). The brown solution
was stirred for 16 h at room temperature followed by removal of
the solvent in vacuo. The product was extracted with pentane. Pale
green crystals were obtained from 5 mL of pentane at -30 °C (0.80
g, 73% yield). IR (Nujol): 3458(m), 3420(w), 1652(m), 1534(vs),
1341(s), 1298(m), 1255(m), 1179(m), 1146(m), 1065(m), 1049(m),
978(w), 887(m) cm-1. Anal. Calcd for C38H68FeN6: C, 68.65; H,
10.31; N, 12.64. Found: C, 68.25; H, 10.01; N, 12.28. µeff ) 7.28
µB.
[FeBr{µ-(CyN)2C(HNCy)}]2 (4). Tricyclohexylguanidine (0.500
g, 1.64 mmol) was dissolved in diethyl ether (30 mL). nBuLi (0.68
mL, 2.5 M) was added to the solution dropwise. The solution was
stirred for 15 min, followed by addition of 1 equiv of FeBr2 (0.353
g, 1.64 mmol). The brown/green solution was stirred for 16 h at
room temperature. Pale crystals were obtained from 5 mL of diethyl
ether at -30 °C (0.47 g, 82% yield). IR (Nujol): 3261(s), 3200(m),
1611(vs), 1248(m), 1151(m), 1099(m), 978(w), 890(m), 797(w),
713(w) cm-1. Anal. Calcd for C19H34BrFeN3: C, 51.84; H, 7.78;
N, 9.54. Found: C, 52.16; H, 8.10; N, 9.32. µeff ) 8.63 µB.
Li2[Fe{µ-(iPrN)2CdNiPr}{(iPrN)2C(HNiPr)}]2 (5). Dropwise
addition of MeLi (0.97 mL, 1.4 M) to a solution of 0.570 g (0.671
mmol) of 5 dissolved in THF (20 mL) led to formation of a green
solution. The reaction mixture was stirred for 16 h at room
temperature and the solvent was removed in vacuo. The resultant
solid was extracted with pentane. Pale yellow crystals were obtained
from 3 mL of pentane at -30 °C (0.39 g, 68% yield). IR (Nujol):
3429(m), 1614(m), 1560(vs), 1538(vs), 1364(s), 1357(s), 1330(m),
1305(s), 1173(m), 1117(m), 1064(w), 1051(w), 988(m), 951(w),
932(w), 894(m), 850(m), 753(w) cm-1. Anal. Calcd for C20H43-
FeLiN3: C, 61.85; H, 11.16; N, 10.82. Found: C, 62.02; H, 10.88;
N, 11.19. µeff ) 7.51 µB.
preference of this oxidation state with the current ligand
system. Structural examination of the Fe(II) guanidinate
complexes 2-7 indicates a tendency for this ligand system
to support four-coordinate distorted pseudotetrahedral ge-
ometries which in turn leads to dominance of dinuclear
species generated through previously unobserved bridging
interaction of the guanidinate ligand.
Metal-bound guanidinate ligands can be transformed into
dianionic species or prompted to undergo coupling reactions
to generate biguanidinate ligands by deprotonation with
strong bases. This report continues to demonstrate the
structural and electronic flexibility of the guanidinate ligand
frame. We are currently exploring related chemistry with
tetrasubstituted guanidinate and alkyl amidinate ligands.
Experimental Section
General Procedure. All reactions were carried out in a nitrogen-
filled drybox. Diethyl ether, THF, hexane, toluene, and pentane
were distilled under nitrogen from Na/K alloy. FeBr2, FeCl3, tBuLi
(1.7 M in hexane), MeLi (1.4 M in hexane), LiCH2SiMe3, BzMgCl,
Et2Zn, diisopropylcarbodiimide, and dicyclohexylcarbodiimide were
purchased from Aldrich and used without further purification.
Infrared spectra were recorded with a Mattson Galaxy 3020 FTIR
instrument as Nujol mulls. Magnetic susceptibilities were measured
at room temperature in a Gouy balance (Johnson-Matthey) on
samples prepared in sealed tubes in a drybox. Values were corrected
for diamagnetism. Elemental analyses were run on a Perkin-Elmer
PE CHN 4000 system.
FeCl{(iPrN)2C(HNiPr)}2 (1). Triisopropylguanidine (1.212 g,
6.55 mmol) was dissolved in THF (50 mL). MeLi (4.68 mL, 1.4
M) was added to the solution dropwise. The solution was stirred
for 15 min, followed by addition of 0.5 equiv of FeCl3 (0.531 g,
3.27 mmol). The purple solution was stirred for 24 h at room
temperature followed by removal of the solvent in vacuo. The
product was extracted with pentane. Purple crystals were obtained
from 15 mL of pentane at -30 °C (0.63 g, 42% yield). IR (Nujol):
3419(m), 3376(s), 1612(w), 1527(vs), 1484(vs), 1328(s), 1303(s),
1214(s), 1180(m), 1125(m), 994(m), 736(m), 689(m) cm-1. Anal.
Calcd for C20H44N6ClFe: C, 52.23; H, 9.64; N, 18.27. Found: C,
52.03; H, 9.35; N, 18.06. µeff ) 5.67 µB.
Fe2{µ-(iPrNCNiPr)2(NiPr)}{(iPrN)2C(HNiPr)}2 (6). Addition
of 2 equiv of LiCH2SiMe3 (2.70 mL, 2.70 mmol, 1.0 M) to a
solution of 1 (0.620 g, 1.35 mmol) in THF (50 mL) yielded a brown
solution. The reaction mixture was stirred for 24 h at room
temperature and filtered, and the solvent was removed in vacuo.
Pale crystals were obtained from pentane at -30 °C (0.10 g, 19%
yield). Anal. Calcd for C35H79Fe2N11: C, 54.90; H, 10.40; N, 20.12.
Found: C, 55.00; H, 10.18; N, 19.93.
Li4(THF)2[Fe{(iPrN)2CNiPr}(CH2SiMe3)2]2 (7). Addition of 4.2
equiv of LiCH2SiMe3 (5.68 mL, 5.68 mmol, 1.0 M) to a solution
of 1 (0.620 g, 1.35 mmol) dissolved in THF (50 mL) led to
formation of a dark red solution. After being stirred for 48 h at
room temperature, the reaction mixture was filtered and the solvent
was removed in vacuo. Pale crystals were obtained from pentane
at -30 °C (0.182 g, 27% yield). Anal. Calcd for C22H51N3OSi2-
FeLi2: C, 52.89; H, 10.29; N, 8.41. Found: C, 52.58; H, 10.00; N,
8.08.
Structural Determination of 3‚1.5(THF), 4, 5, and 7. Suitable
crystals were selected, mounted on thin glass fibers with viscous
oil, and cooled to the data collection temperature. Data were
collected on a Bruker AX SMART 1k CCD diffractometer, using
0.3° ω-scans at 0, 90, and 180° in φ. Unit-cell parameters were
determined from 60 data frames collected at different sections of
the Ewald sphere. Semiempirical absorption corrections based on
equivalent reflections were applied.18
[Fe{µ-(iPrN)2C(HNiPr)}{(iPrN)2C(HNiPr)}]2 (2). Triisopro-
pylguanidine (0.500 g, 2.70 mmol) was dissolved in THF (40 mL).
MeLi (1.93 mL, 1.4 M) was added to the solution dropwise. The
solution was stirred for 15 min, followed by addition of 0.5 equiv
of FeBr2 (0.291 g, 1.35 mmol). The blue/green solution was stirred
for 16 h at room temperature followed by removal of the solvent
in vacuo. The product was extracted with pentane. Pale green
crystals were obtained from 5 mL of pentane at -30 °C (0.47 g,
82% yield). IR (Nujol): 3426(m), 3397(w), 1650(m), 1532(vs),
1436(vs), 1311(s), 1176(m), 1133(m), 1075(w), 986(m), 838(w),
732(m) cm-1. Anal. Calcd for C20H44N6Fe: C, 56.59; H, 10.45;
N, 19.80. Found: C, 56.95; H, 10.54; N, 20.10. µeff ) 7.50 µB.
Reduction of FeCl{(iPrN)2C(HNiPr)}2 (1) to [Fe{µ-(iPrN)2C-
(HNiPr)}{(iPrN)2C(HNiPr)}]2 (2). To a solution of 4 in THF was
added an alkylating reagent (1 equiv of BzMgCl, 0.5 equiv of Et2-
Zn, 1 equiv of LiCH2SiMe3, or LiMe). The purple solutions were
stirred overnight and filtered, and the solvent was removed in vacuo.
Crystals of 5 were obtained from pentane as the sole isolable
product in yields from 40 to 80%. Confirmation of 5 was done
through comparison of unit cell parameters.
No symmetry higher than triclinic was evident from the diffrac-
tion data of 3‚1.5(THF) and 5. Solution in the centric option yielded
chemically reasonable and computationally stable results of refine-
[Fe{µ-(CyN)2C(HNCy)}{(CyN)2C(HNCy)}]2 (3). Tricyclo-
hexylguanidine (1.00 g, 3.28 mmol) was dissolved in diethyl ether
(18) Blessing, R. Acta Crystallogr. 1995, A51, 33-38.
4156 Inorganic Chemistry, Vol. 41, No. 16, 2002
Foley, Stephen R.
