Bis(imino)pyridine Iron Di- and Monoalkyl Complexes
Organometallics, Vol. 27, No. 1, 2008 117
(308 Hz, 2H, CH2CH3), -192.59 (62 Hz, 6H, C(CH3)); the
FeCH2C(CH3)3 resonance was not located.
purple crystals identified as 2-(CH2SiMe3)2. Anal. Calcd for
C37H57FeN3Si2: C, 67.76; H, 8.76; N, 6.41. Found: C, 67.89; H,
8.49; N: 6.37. Magnetic susceptibility (benzene-d6, 293 K): µeff 5.3
Preparation of (iPrPDI)FeC6H5 (1-Ph). A 20 mL scintillation
vial was charged with 0.400 g (0.57 mmol) of 1-Br2, and a slurry
formed with diethyl ether. The mixture was chilled in a -35 °C
freezer for approximately 30 min, after which time a solution of
phenyllithium (0.64 mL, 1.8 M in di-n-dibutyl ether) was added
dropwise. The blue slurry immediately became a dark-green
solution. The resulting reaction mixture was stirred for 30 min,
and the volatiles were removed in vacuo. The solid residue was
dissolved in approximately 5 mL of pentane, filtered through Celite,
and cooled at -35 °C overnight to afford 0.136 g (39%) of 1-Ph
as a green crystalline solid. Anal. Calcd for C39H48FeN3: C, 76.21;
H, 7.87; N, 6.84. Found: C, 75.97; H, 7.49; N, 6.94. Magnetic
susceptibility (benzene-d6, 293 K): µeff 4.2 µB. 1H NMR (benzene-
d6, 293 K): δ 216.59 (130 Hz, 1H, p-pyr), 64.37 (464 Hz, 2H,
m-pyr), 50.80 (56 Hz, 4H, m-Ph), 50.11 (61 Hz, 4H, o-Ph), 11.21
(70 Hz, 1H, p-Ph), -3.40 (19 Hz, 4H, m-aryl), -12.01 (21 Hz,
12H, CHCH32), -18.63 (68 Hz, 12H, CH(CH3)2), -79.87 (477 Hz,
4H, CH(CH3)2), -153.70 (73 Hz, 6H, C(CH3).
1
µB. H NMR (benzene-d6, 298 K): δ 285.58 (405 Hz, 1H, p-pyr),
59.81 (173 Hz, 2H, m-pyr), 26.16 (326 Hz, 4H, CH2CH3), 21.83
(2960 Hz, 4H, CH2CH3), 11.98 (434 Hz, 18H, Si(CH3)3), 0.15 (218
Hz, 12H, CH2CH3), -16.72 (69 Hz, 4H, m-aryl), -150.31 (563
Hz, 6H, C(CH3)); two peaks were not located.
Preparation of (iPrPDI)Fe(CH2Si(CH3)3) (1-CH2SiMe3). A 20
mL scintillation vial was charged with 0.100 g (0.162 mmol) of
1-Br (or 0.093 g of 1-Cl) and diethyl ether, forming a slurry. The
solution was cooled at -35 °C for approximately 30 min, after
which time a diethyl ether solution of LiCH2SiMe3 (0.015 g, 0.16
mmol) was added dropwise. The blue slurry immediately turned
to a soluble dark-green solution. The resulting reaction mixture was
stirred for 30 min, and the volatiles were removed in vacuo. The
resulting solid was dissolved in approximately 2–3 mL of pentane,
filtered through Celite, and cooled at -35 °C overnight to yield
0.079 g (78%) of compound 1-CH2SiMe3 as a green crystalline
solid. Anal. Calcd for C37H54FeN3Si: C, 71.13; H, 8.71; N, 6.73.
Found: C, 70.81; H, 8.47; N, 6.44. Magnetic susceptibility (benzene-
d6, 293 K): µeff 3.8 µB. 1H NMR (benzene-d6, 298 K): δ 66.93 (96
Hz, 2H, m-pyr), 48.80 (169 Hz, 9H, C(CH3)3), -11.22 (31 Hz,
1H, m-aryl), -17.87 (23 Hz, 2H, p-aryl), -18.90 (40 Hz, 12H,
CH(CH3)2), -32.46 (107 Hz, 12H, CH(CH3)2), -109.04 (531 Hz,
4H, CH(CH3)2), -206.76 (150 Hz, 6H, C(CH3)); p-pyr and
FeCH2C(CH3)3 resonances were not located.
Preparation of [(iPrPDI)Fe(C6H4-p-CH3)N2]Li(Et2O)3 ([(1-Tol)-
N2]Li(Et2O)3). A 20 mL scintillation vial was charged with 0.100
g (0.17 mmol) of 1-(N2)2, and approximately 10 mL of diethyl ether
was added to form a green solution. The solution was cooled at
-35 °C for approximately 30 min, after which time a diethyl ether
solution of p-tolyllithium (0.033 g, 0.34 mmol) was added dropwise.
The green solution immediately turned to a dark-red solution. The
resulting reaction mixture was stirred for 30 min, and the volatiles
were removed in vacuo. The resulting solid was dissolved in
approximately 1–2 mL of diethyl ether, filtered through Celite, and
cooled at -35 °C overnight, yielding 0.065 g (43%) of red crystals
identified as [1-(Tol)N2]Li(Et2O)3. Anal. Calcd for
C52H80FeLiN5O3: C, 70.49; H, 9.10; N, 7.90. Found: C, 69.99; H,
9.16; N, 7.84. Magnetic susceptibility (benzene-d6, 293 K): µeff 2.7
Preparation of (py)2Fe(CH2SiMe3)Cl. A 20 mL scintillation
vial was charged with 0.200 g (0.45 mmol) of (py)4FeCl2 and
pentane, forming a slurry. The mixture was cooled at -35 °C for
approximately 30 min, after which time a pentane solution of
LiCH2SiMe3 (0.042 g, 0.45 mmo1) was added dropwise. The yellow
slurry turned dark red and was stirred for 1–2 h at room temperature.
The resulting reaction mixture was filtered through Celite, and the
volatiles were removed in vacuo to afford 0.131 g (86%) of a red
oil identified as (py)2Fe(CH2SiMe3)Cl. 1H NMR (benzene-d6, 298
K): δ 136.17 (2226 Hz, 4H, o-pyr), 37.69 (215 Hz, 4H, m-pyr),
17.82. (230 Hz, 2H, p-pyr), 11.32 (223 Hz, 9H, Si(CH3)3); the
FeCH2Si(CH3)3 resonance was not located.
Preparation of (py)2Fe(CH2CMe3)Cl. This compound was
prepared in a manner similar to that of (py)2Fe(CH2SiMe3)Cl with
0.200 g (0.45 mmol) of (py)4FeCl2 and 0.035 g (0.45 mmo1) of
LiCH2CMe3, yielding 0.102 g (71%) of an orange crystalline solid
identified as (py)2Fe(CH2CMe3)Cl. 1H NMR (benzene-d6, 298 K):
δ 132.63 (2055 Hz, 4H, o-pyr), 41.76 (938 Hz, 9H, C(CH3)3), 37.63
(456 Hz, 4H, m-pyr), 16.38 (364 Hz, 2H, p-pyr); the FeCH2C(CH3)3
resonance was not located.
Preparation of (py)2Fe(CH2CMe3)2. A 20 mL scintillation vial
was charged with 0.200 g (0.45 mmol) of (py)4FeCl2 and ap-
proximately 2 mL of pentane, forming a slurry. The solution was
cooled at -35 °C for approximately 30 min, after which time a
pentane solution of LiCH2CMe3 (0.071 mg, 0.91 mmol) was added
dropwise. The yellow slurry turned dark purple and was stirred for
1–2 h at ambient temperature. The resulting reaction mixture was
filtered through Celite, and the volatiles were removed in vacuo.
The residue was dissolved in approximately 1–2 mL of pentane
and cooled at -35 °C overnight to afford 0.095 g (59%) of
(py)2Fe(CH2CMe3)2 as a purple crystalline solid. 1H NMR (benzene-
d6, 298 K): δ 124.56 (1735 Hz, 4H, o-pyr), 36.50 (166 Hz, 4H,
m-pyr), 24.53 (428 Hz, 18H, C(CH3)3), 15.03 (118 Hz, 2H, p-pyr);
the FeCH2C(CH3)3 resonance was not located.
Preparation of (py)2Fe(CH2CMe3)(CH2SiMe3). A 20 mL
scintillation vial was charged with 0.200 g (0.62 mmol) of
(py)2Fe(CH2CMe3)Cl and approximately 5 mL of diethyl ether. The
solution was cooled at -35 °C for approximately 30 min, after
which time a diethyl ether solution of LiCH2SiMe3 (0.058 g, 0.62
mmo1) was added dropwise. The orange solution turned dark red
µB. IR (pentane): νN 2068 cm-1
.
2
Preparation of [(iPrPDI)Fe(C6H5)N2]Li(Et2O)3 ([1-(Ph)N2]Li-
(Et2O)3). This molecule was prepared in a manner similar to that
of [1-(Tol)N2]Li(Et2O)3 (vide infra) with 0.400 g (0.57 mmol) of
1-Br2 and 0.98 mL of 1.8 M phenyllithium in di-n-butyl ether,
yielding 0.235 g (47%) of [1-(Ph)N2]Li(Et2O)3 as a red crystalline
solid. Anal. Calcd for C51H78FeLiN5O3: C, 70.25; H, 9.02; N, 8.03.
Found: C, 70.55; H, 8.99; N, 7.70. Magnetic susceptibility (benzene-
d6, 293 K): µeff 2.9 µB. IR (pentane): νN 2069 cm-1
.
2
Alternative Procedure for the Preparation of (iPrPDI)Fe-
(CH2SiMe3)2 (1-(CH2SiMe3)2). A 20 mL scintillation vial was
charged with 0.200 g (0.45 mmol) of (py)4FeCl2 and 2 mL of
pentane, forming a slurry. The mixture was cooled at -35 °C for
approximately 30 min, after which time a pentane solution of
LiCH2SiMe3 (0.084 g, 0.90 mmol) was added dropwise. The yellow
slurry turned dark purple and was stirred for 1–2 h at ambient
temperature. After this time, the reaction mixture was filtered
through Celite and the filtrate transferred to a new vial. This solution
was then chilled at -35 °C for approximately 30 min, after which
time a pentane solution of the iPrPDI ligand (0.217 g, 0.45 mmo1)
was added dropwise. The purple solution turned immediately dark
violet and was stirred for 1–2 h at ambient temperature. After this
time, the reaction mixture was filtered through Celite and the
volatiles from the filtrate were removed in vacuo. The resulting
solid was dissolved in approximately 2–4 mL of pentane and cooled
at -35 °C overnight to afford 0.217 g (68%) of 1-(CH2SiMe3)2 as
a light-violet crystalline solid. The product has spectroscopic
properties identical with those of authentic 1-(CH2SiMe3)2 prepared
by previously reported procedures.12
Improved Procedure for the Preparation of (EtPDI)Fe-
(CH2SiMe3)2 (2-(CH2SiMe3)2). A procedure similar to that for
1-(CH2SiMe3)2 was used with 0.200 g (0.45 mmol) of py4FeCl2
and 0.192 g (0.45 mmol) of EtPDI, yielding 0.233 g (79%) of deep-