8038 Inorganic Chemistry, Vol. 48, No. 16, 2009
Bunge et al.
Chart 1. Structures of Monoanionic Guanidinate Ligandsa
The solution was heated to reflux for 10 min and then allowed to
evaporate yielding colorless crystals within 12 h. Yield 78%
(0.44 g, 2.3 mmol). 1H NMR (toluene-d8): δ 3.14 (m, 8 H,
NdC(N(CH2CH3)2)2), 1.10 (m, 12 H, NdC(N(CH2CH3)2)2).
13C NMR (toluene-d8): δ 154.6(NdC(N(CH2CH3)2)2), 42.7
(NdC(N(CH2CH3)2)2),14.4 (NdC(N(CH2CH3)2)2). FT-IR
(KBr, cm-1) 2966 (s), 2895 (s), 1545 (s), 1459 (m), 1405 (m),
1380 (m), 1245 (m), 1119 (w), 1077 (w), 1006 (m), 938 (w), 879
(m), 842 (m), 749 (w), 669 (w), 633 (w), 612 (w), 561 (w), 482 (w).
General Synthesis of 2-5. Lithium diethylamide (0.237 g,
3 mmol) was dissolved in ether (10 mL). To this solution,
diethylcyanamide (0.294 g, 3 mmol), dissolved in ether (5 mL),
was added dropwise and allowed to stir for approximately
15 min. LiN(SiMe3)2 (0.501 g, 3 mmol) was subsequently
dissolved in the solution. MBr2 (M = Mn, Fe, Co) or ZnCl2
(3 mmol) was then added, and the reaction stirred for 24 h. The
volatiles were then removed under vacuum, and the remaining
solid was dissolved in hexanes. The solution was then centri-
fuged, the liquid was decanted off, concentrated, and placed in a
-35 °C freezer. Crystals {pink (2), yellow (3), blue (4), colorless
(5)} formed within 24 h.
a R, R0 and R00 = silyl, alkyl or aryl.
Because of the versatility of the TAG framework, our
research group has initiated an effort to further detail the
coordination chemistry and reactivity.11-13 We envisioned
that utilizing bulky TAG ligands in conjunction with
[N(SiMe3)2] would facilitate the isolation of well-defined
low-coordinate complexes. The resulting coordinatively
unsaturated systems could then be readily reacted with protic
reagents such as alcohols, thiols, and primary amines to
generate reagents for areas such as nanocrystal synthesis and
chemical vapor deposition.14 Toward this goal, the synthesis
of lithium 1,1,3,3-tetraethylguanidinate [Li(μ-TEG)]6 (1) is
described herein, and its use for the isolation of a family of
d-block metal complexes with the general formula [M(μ-
TEG){N(SiMe3)2}]2 {M = Mn (2), Fe (3), Co (4), and Zn
(5)} reported. The reactivity of 2 was further investigated
through reaction with HOC6H3(CMe3)2-2,6 (H-DBP) and
ethanol (H-OEt) in a 1:2 ratio to form the resultant [Mn(μ-
OEt)(DBP)(H-TEG)]2 (6). The six novel compounds were
characterized by single-crystal X-ray diffraction. The bulk
powders for all complexes were found to bein agreement with
the crystal structures based on elemental analyses, FT-IR
spectroscopy, 1H and 13C NMR studies.
[Mn(μ-TEG){N(SiMe3)2}]2 (2). Yield 25% (0.30 g, 0.38
mmol). Anal. Calcd for C30H76Mn2N8Si4: C 46.72, H 9.93, N
14.53. Found: C 47.19, H 10.17, N 14.12. FT-IR (KBr, cm-1
)
2972 (s), 2945 (s), 2894 (m), 2875 (m), 1528 (s), 1509 (s), 1463 (s),
1377 (m), 1250 (s), 1211 (w), 1191 (w), 1121 (m), 1072 (m), 1012
(s), 937 (m), 874 (s), 827 (s), 778 (m), 666 (m), 612 (m). UV-vis
absorption spectra λmax (nm) and ε (mL mol-1 cm-1) values in
parentheses: 328 (36700). Magnetic moment (μB): 4.30.
[Fe(μ-TEG){N(SiMe3)2}]2 (3). Yield 45% (0.52 g, 0.68
mmol). Anal. Calcd for C30H76Fe2N8Si4: C 46.61, H 9.91, N
14.50. Found: C 45.88, H 9.54, N 15.42. FT-IR (KBr, cm-1
)
2948 (m), 2895 (w), 1514 (s), 1455 (s), 1438 (s), 1409 (w), 1378
(m), 1345 (s), 1261 (s), 1240 (s), 1126 (w), 1056 (w), 978 (s), 944
(m), 868 (s), 847 (s), 788 (m), 750 (w), 669 (m), 612 (w), 573 (w).
UV-vis absorption spectra (nm) and ε (mL mol-1 cm-1) values
in parentheses: 301 (128000), 388 (14800), 456 (6710). Magnetic
moment (μB) 2.77.
Experimental Section
All syntheses were handled with rigorous exclusion of air
and water using standard glovebox techniques. All anhy-
drous solvents were stored under argon and used as received
in sure seal bottles. The following chemicals were used as
receivedfromcommercialsuppliers:LiN(CH2CH3)2, diethyl-
cyanamide, LiN(SiMe3)2, ZnCl2, MnBr2, FeBr2, and CoBr2.
FT-IR data were obtained on a Bruker Tensor 27 Instrument
using a KBr window under an atmosphere of flowing nitro-
gen. Electronic absorption spectra were obtained on a Cary
5000 UV-vis spectrophotometer. Elemental analysis was
performed on a Perkin-Elmer 2400 Series 2 CHN-S/O Ele-
mental Analyzer. Magnetic susceptibility measurements for
2-4and6weremeasuredat298Kanddeterminedinsolution
by the method of Evans.15 The calculated magnetic moments
were corrected for underlying diamagnetism. All NMR sam-
ples were prepared from dried crystalline materials that were
handled and stored under an argon atmosphere and redis-
solved in toluene-d8. All solution spectra were obtained on a
Bruker DRX 400 spectrometer at 400.1 and 100.6 MHz for
1H and 13C experiments.
[Co(μ-TEG){N(SiMe3)2}]2 (4). Yield 66% (0.77 g, 1.0 mmol).
Anal. Calcd for C30H76Co2N8Si4: C 46.24, H 9.83, N 14.38.
Found: C 45.90, H 9.14, N 14.72. FT-IR (KBr, cm-1) 2966 (s),
2896 (m), 1535 (s), 1460 (s), 1399 (m), 1377 (m), 1355 (m), 1255
(s), 1243 (s), 1214 (w), 1198 (w), 1123 (m), 1073 (m), 1051 (m),
998 (s), 938 (m), 867 (s), 843 (s), 827 (s), 785 (m), 749 (m), 668
(m). UV-vis absorption spectra λmax (nm) and ε (mL mol-1
cm-1) values in parentheses: 279 (289000), 504 (28500), 688
(13900). Magnetic moment (μB): 3.35.
[Zn(μ-TEG){N(SiMe3)2}]2 (5). Yield62%(0.73g, 0.93 mmol).
Anal. Calcd for C30H76N8Si4Zn2: C 45.49, H 9.67, N 14.15.
Found: C 45.54, H 9.68, N 14.64. 1H NMR (400.1 MHz,
C6D6): δ 3.185 (q, J = 7.25 Hz, 16 H, NdC(N(CH2CH3)2)2),
1.026 (t, J = 7.02 Hz, 24 H, NdC(N(CH2CH3)2)2), 0.300 (s, 36 H
N(Si(CH3)3)2). 13C NMR (100.6 MHz,C6D6):δ 164.7 (NdC(N-
(CH2CH3)2)2), 44.2 (NdC(N(CH2CH3)2)2), 14.3(NdC(N(CH2-
CH3)2)2), 6.1 (N(Si(CH3)3)2). FT-IR (KBr, cm-1) 2966 (s), 2894
(s), 1540 (s), 1516 (s), 1463 (s), 1378 (m), 1354 (m), 1254 (s), 1126
(m), 1073 (w), 1000 (s), 937 (w), 880 (s), 828 (s), 749 (w), 668 (m),
631 (w), 611 (w), 567 (w).
Synthesis of [Li(μ-TEG)]6 (1). A hexanes solution of diethyl-
cyanamide (0.31 g, 3.0 mmol) (5 mL) was added dropwise to a
hexanes solution (10 mL) of LiN(CH2CH3)2 (0.25 g, 3.0 mmol).
Synthesis of [Mn(μ-OEt)(DBP)(H-TEG)]2 (6). Compound 2
(0.63 g, 0.8 mmol) was dissolved in tetrahydrofuran (THF). In a
separate vial ethanol 0.075 g (1.6 mmol) and H-DBP 0.34 g
(1.6 mmol) were dissolved in THF. The solutions were mixed
and left to stir for several hours. The solution was then con-
centrated via slow evaporation. Colorless crystals formed
from solution at -35 °C in 24 h. Yield 39% (0.31 g, 0.3 mmol).
Anal. Calcd for C46H84Mn2N6O4:C63.00, H9.94, N8.82. Found:
C 62.51, H 9.75, 8.72. FT-IR (KBr, cm-1) 3345 (w), 3051 (w), 2957
(s), 2859 (s), 1560 (s), 1500 (s), 1445 (s), 1410 (s), 1380 (s), 1363 (s),
1290 (s), 1260 (m), 1240 (s), 1200 (m), 1149 (w), 1126 (s), 1102 (s),
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I. P. Chem. Vap. Deposition 1995, 1, 49. Dumestre, F.; Chaudret, B.; Amiens, C.;
Renaud, P.; Fejes, P. Science 2004, 303, 821.
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