Unusual reactions of {μ-(phthalazine-N2:N3)} Fe2(μ-CO)(CO)6 with organolithium reagents. A novel coordination mode of 1,2-diazane diiron carbonyl compounds

Article abstract of DOI:10.1039/b510676c

{μ-(Phthalazine-N²:N³)}Fe₂(μ-CO)( CO) ₆ (1) reacts with organolithium reagents, RLi (R = CH₃, C₆H₅, p-CH₃C₆H₄, p-CH₃OC₆H₄, p-CF₃C₆H ₄, p-C₆H₅C₆H₄), followed by treatment with Me₃SiCl to give the novel diiron carbonyl complexes with a saturated N-N six-membered diazane ring ligand, {C₆H ₄CH(R)NNCH₂}Fe₂(CO)(CO)₆ (2, R = CH₃; 3, R = C₆H₅; 4, R = p-CH₃C ₆H₄; 5, R = p-CH₃OC₆H₄; 6, R = p-CF₃C₆H₄; 7, R = p-C₆H ₅C₆H₄). Compounds 4 and 5 were treated with (NH₄)₂Ce(NO₃)₆ to afford the aryl-substituted phthalazine-coordinated diiron carbonyl compounds (μ-{1-(p-CH₃C₆H₄)-phthalazine-N ²:N³})Fe₂(μ-CO)(CO)₆ (8) and (μ-{1-(p-CH₃OC₆H₄)-phthalazine-N ²:N³})Fe₂(μ-CO)(CO)₆ (9), respectively. The structures of complexes 4 and 9 have been established by X-ray diffraction studies. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b510676c

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www.rsc.org/dalton | Dalton Transactions
Unusual reactions of [{l-(phthalazine-N2:N3)}Fe2(l-CO)(CO)6] with
organolithium reagents. A novel coordination mode of 1,2-diazane
diiron carbonyl compounds
Nu Xiao,a Qiang Xu,*b Jie Suna and Jiabi Chen*a
Received 26th July 2005, Accepted 30th September 2005
First published as an Advance Article on the web 28th October 2005
DOI: 10.1039/b510676c
[{l-(Phthalazine-N2:N3)}Fe2(l-CO)(CO)6] (1) reacts with organolithium reagents, RLi (R = CH3,
C6H5, p-CH3C6H4, p-CH3OC6H4, p-CF3C6H4, p-C6H5C6H4), followed by treatment with Me3SiCl to
give the novel diiron carbonyl complexes with a saturated N–N six-membered diazane ring ligand,
=
[{C6H4CH(R)NNCH2}Fe2(C O)(CO)6] (2, R = CH3; 3, R = C6H5; 4, R = p-CH3C6H4; 5, R =
p-CH3OC6H4; 6, R = p-CF3C6H4; 7, R = p-C6H5C6H4). Compounds 4 and 5 were treated with
[(NH4)2Ce(NO3)6] to afford the aryl-substituted phthalazine-coordinated diiron carbonyl compounds
[(l-{1-(p-CH3C6H4)-phthalazine-N2:N3})Fe2(l-CO)(CO)6] (8) and [(l-{1-(p-CH3OC6H4)-phthalazine-
N2:N3})Fe2(l-CO)(CO)6] (9), respectively. The structures of complexes 4 and 9 have been established by
X-ray diffraction studies.
Introduction
=
The organometallic chemistry of 1,2-diazenes (–N N–) is a field
of increasing importance and there has been much research on
this area1 given probable intermediates of diazene complexes in
biological nitrogen fixation and the nonenzymatic conversion of
coordinated dinitrogen into diazene derivatives. Cyclic diazenes
have been used as model compounds for cis-diimines in the
studies on biological nitrogen fixation.2 In recent years, olefin-
coordinated transition-metal carbene and carbyne complexes
and/or their isomerized products have been examined extensively,
and a series of olefin-coordinated dimetal bridging carbene and
carbyne complexes were synthesized in our laboratory.3 One of
new synthetic methods for dimetal bridging carbene and carbyne
complexes is to conduct reactions4 of olefin-ligated dimetal car-
bonyl compounds with nucleophilic aryllithium reagents followed
by alkylation with alkylating reagents. However, only a few
examples of aza-alkene-coordinated metal carbene complexes are
known5 and no examples of diazene-coordinated metal carbene
complexes have been reported up to now. Most recently, we have
obtained a new type of diazene-coordinated dimetal bridging
siloxycarbene complexes [(C4H4N2)Fe2{l-C(OSiMe3)Ar}(CO)6]
(Ar = C6H5, m-CH3C6H4)6 by the reactions of the pyridazine-
ligated diiron carbonyl compound, [{l-(pyridazine-N1:N2)}Fe2(l-
CO)(CO)6], with aryllithium reagents at low temperature followed
by treatment with Me3SiCl (eqn (1)).
(1)
carbonyl compound [{l-(phthalazine-N2:N3)}Fe2(l-CO)(CO)6]
(1) as the starting material for the reactions with organolithium
reagents. These reactions led to nucleophilic addition to the
aromatic diazene ring to afford a series of the novel diiron
carbonyl complexes with a saturated N–N six-membered diazane
ring ligand. Herein we describe these unusual reactions and the
structures of the resulting products.
Experimental
All procedures were performed under a dry, oxygen-free N2
atmosphere by using standard Schlenk techniques. All solvents
employed were reagent grade and dried by refluxing over appro-
˚
priate drying agents and stored over 4 A molecular sieves under N2
atmosphere. Tetrahydrofuran and diethyl ether were distilled from
sodium benzophenone ketyl, while petroleum ether (bp 30–60 ◦C)
and CH2Cl2 were distilled from CaH2. The neutral alumina (Al2O3,
100–200 mesh) used for chromatography was deoxygenated at
room temperature under high vacuum for 16 h, deactivated with
5% w/w N2-saturated water, and stored under N2 atmosphere.
Compounds Me3SiCl, CH3Li, n-C4H9Li and [(NH4)2Ce(NO3)6]
were purchased from Aldrich Chemical Co. or Acros, a Fisher
Scientific Worldwide Company. [{l-(Phthalazine-N2:N3)}Fe2(l-
CO)(CO)6] (1)7 and aryllithium reagents8–12 were prepared by
literature methods.
In order to further investigate the reactivity of aromatic diazene-
coordinated dimetal carbonyl compounds towards nucleophiles
and to examine the effect of the different diazene ligands on
the reaction products, we chose the phthalazine-ligated diiron
aState Key Laboratory of Organometallic Chemistry, Shanghai Institute of
Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai,
200032, China
bNational Institute of Advanced Industrial Science and Technology (AIST),
1-8-31 Midorigaoka, Ikeda, Osaka, 563-8577, Japan
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The IR spectra were measured on a Nicolet AV-360 spectropho-
tometer using NaCl cells with 0.1 mm spacers. All 1H NMR
and 13C NMR spectra were recorded at ambient temperature
in acetone-d6 solution or deuterated solvents with TMS as the
internal reference using a Varian Mercury 300 spectrometer
running at 300 MHz. The 13C NMR data were not obtained
due to their sensitivity to temperature (complexes 2–7) and poor
solubility (complex 8). Electron ionization mass spectra (EIMS)
were run on a Hewlett Packard 5989A spectrometer. Melting
points obtained on samples in sealed nitrogen-filled capillaries
are uncorrected.
Reaction of 1 with p-CH3C6H4Li to give
=
[{C6H4CH(C6H4CH3-p)NNCH2}Fe2(C O)(CO)6] (4)
Similar to the reaction of 1 with CH3Li, the reaction of 0.250 g
(0.57 mmol) of 1 with 1.10 mmol of p-CH3C6H4Li9 at −50 to
−15 ◦C for 5 h and further treatment afforded 0.136 g (45%, based
on 1) of orange–red crystals of 4: mp 70 ◦C decomp.; IR (CH2Cl2)
−1
=
m(CO) 2077 (s), 2034 (vs), 2006 (vs), 1988 (vs) cm ; m(C O) 1699
(m) cm−1; 1H NMR (CD3COCD3) d 7.49–7.39 (m, 8H, aromatics),
5.83 (s, 1H, CH(C6H4CH3-p)), 4.89, 4.45 (AB, 2H, J = 15 Hz,
CH2), 2.41 (s, 3H, p-CH3C6H4); MS m/z 530 (M+), 502 (M+ − CO),
474 (M+ − 2CO), 446 (M+ − 3CO), 418 (M+ − 4CO), 390 (M+ −
5CO), 362 (M+ − Fe(CO)3 − CO), 334 [M+ − Fe(CO)3 − 2CO],
306 [M+ − Fe(CO)3 − 3CO], 250 [M+ − Fe2(CO)6], 222 [M+
−
Reaction of [{l-(phthalazine-N2:N3)}(l-CO)Fe2(CO)6] (1) with
Fe2(CO)6 − CO], 207 [M+ − Fe2(CO)6 − CO − CH3], 179 [M+ −
Fe2(CO)6 − CO − CH3 − N2]. Anal. Calc. for C22H14O7N2Fe2: C,
49.85; H, 2.66; N, 5.28. Found: C, 49.46; H, 2.86; N, 5.62%.
=
CH3Li to give [{C6H4CH(CH3)NNCH2}Fe2(C O)(CO)6] (2)
To a solution of 0.250 g (0.57 mmol) of 1 dissolved in 40 mL of
THF at −55 ◦C was added 1.20 mmol of CH3Li with stirring. The
solution turned immediately from deep violet to deep brown. After
stirring at −55 to −30 ◦C for 4 h, the resulting solution was cooled
to −40 ◦C, to which 0.50 ml of Me3SiCl in 5 mL of THF was added
dropwise. The reaction mixture was stirred at −40 to −15 ◦C for
2–3 h. The solvent was removed under high vacuum below −20 ◦C,
and the brown–red residue was chromatographed on an alumina
column (1.6 × 15–20 cm) at −20 to −25 ◦C with petroleum ether–
CH2Cl2 (1 : 1) as the eluent. A green–brown brand was eluted and
collected. After vacuum removal of the solvent, the residue was
recrystallized from petroleum ether–CH2Cl2 solution at −80 ◦C to
give 0.155 g (46%, based on 1) of brown–red crystalline 2: mp 57–
59 ◦C decomp.; IR (CH2Cl2) m(CO) 2076 (s), 2034 (vs), 2003 (vs),
Reaction of 1 with p-CH3OC6H4Li to give
=
[{C6H4CH(C6H4OCH3-p)NNCH2}Fe2(C O)(CO)6] (5)
A solution of 0.220 g (1.18 mmol) of p-CH3OC6H4Br in 20 mL of
ether was mixed with 1.18 of n-C4H9Li. After 1–2 h stirring at room
temperature, the resulting ether solution of p-CH3OC6H4Li10 was
reacted, as described in the synthesis of 2, with 0.250 g (0.57 mmol)
of 1 at −50 to −15 ◦C for 4–5 h. Further treatment of the resulting
brown–yellow mixture as in the preparation of 2 yielded 0.170 g
(55%, based on 1) of brown–yellow crystalline 5: mp 90–92 ◦C
decomp.; IR (CH2Cl2) m(CO) 2076 (s), 2034 (vs), 2005 (vs), 1990
−1
−1
1
=
(vs) cm ; m(C O) 1703 (m) cm ; H NMR (CD3COCD3) d 7.49–
7.13 (m, 8H, aromatics), 5.83 (s, 1H, CH(C6H4OCH3-p)), 4.88,
4.44 (AB, 2H, J = 15 Hz, CH2), 3.86 (s, 3H, p-CH3OC6H4); MS
m/z 490 (M+ − 2CO), 462 (M+ − 3CO), 434 (M+ − 4CO), 406
(M+ − 5CO), 378 [M+ − Fe(CO)3 − CO], 350 [M+ − Fe(CO)3−
2CO], 322 [M+ − Fe(CO)3 − 3CO], 294 [M+ − Fe(CO)3 − 4CO],
−1
−1
1
=
1993 (vs) cm ; m(C O) 1700 (m) cm ; H NMR (CD3COCD3)
d 7.58–7.38 (m, 4H, aromatics), 5.16 (m, 1H, CHCH3), 4.76, 4.36
(AB, 2H, J = 15 Hz, CH2), 1.64 (d, 3H, J = 6.3 Hz, CH3); MS m/z
398 (M+ − 2CO), 370 (M+ − 3CO), 314 [M+ − Fe(CO)3], 286 [M+ −
Fe(CO)3 − CO], 230 [M+ − Fe(CO)3 − 3CO], 174 [M+ − Fe2(CO)6],
146 [M+ − Fe2(CO)6 − CO], 131 [M+ − Fe2(CO)6 − CO − CH3],
118 [M+ − Fe2(CO)6 − CO − N2], 103 [M+ − Fe2(CO)6 − CO −
CH3 − N2]. Anal. Calc. for C16H10O7N2Fe2: C, 42.34; H, 2.22; N,
6.17. Found: C, 41.86; H, 2.23; N, 6.63%.
266 [M+ − Fe2(CO)6], 238 [M+ − Fe2(CO)6 − CO], 223 [M+
−
Fe2(CO)6 − CO − CH3], 207 [M+ − Fe2(CO)6 − CO − OCH3],
179 [M+ − Fe2(CO)6 − CO − OCH3 − N2]. Anal. Calc. for
C22H14O8N2Fe2: C, 48.39; H, 2.58; N, 5.13. Found: C, 48.07; H,
2.74; N, 5.25%.
Reaction of 1 with C6H5Li to give
Reaction of 1 with p-CF3C6H4Li to give
=
=
[{C6H4CH(C6H5)NNCH2}Fe2(C O)(CO)6] (3)
[{C6H4CH(C6H4CF3-p)NNCH2}Fe2(C O)(CO)6] (6)
To a solution◦of 0.250 g (0.57 mmol) of 1 dissolved in 40 mL of
THF at −55 C was added 1.10 mmol of C6H5Li8 with stirring.
Immediately, the solution turned from deep violet to deep brown–
yellow. The reaction mixture was stirred at −55 to −15 ◦C for
5 h. Further treatment of the resulting mixture as described in
the synthesis of 2 gave 0.118 g (40%, based on 1) of 3 as brown
crystals: mp 63–64 ◦C decomp.; IR (CH2Cl2) m(CO) 2077 (s),
A solution of 0.260 g (1.15 mmol) of p-CF3C6H4Br in 20 mL of
ether was mixed with 1.14 of n-C4H9Li. After 40 min stirring at
room temperature, the resulting ether solution of p-CF3C6H4Li11
was treated, in a manner similar to that in the synthesis of 2, with
0.250 g (0.57 mmol) of 1 at −55 to −15 ◦C for 5 h. Further
treatment of the resulting brown mixture as described for the
preparation of 2 yielded 0.140 g (42%, based on 1) of 6 as orange–
red crystals: mp 70–71 ◦C decomp.; IR (CH2Cl2) m(CO) 2078 (s),
−1
−1
1
=
2034 (vs), 2006 (vs), 1991 (vs) cm ; m(C O) 1703 (m) cm ; H
NMR (CD3COCD3) d 7.57–7.39 (m, 9H, aromatics), 5.62 (s, 1H,
CH(C6H5)), 4.90, 4.46 (AB, 2H, J = 15 Hz, CH2); MS m/z 460
(M+ − 2CO), 404 (M+ − 4CO), 348 (M+ − Fe − 4CO), 320
[M+ − Fe(CO)3 − 2CO], 292 [M+ − Fe(CO)3 − 3CO], 236 [M+ −
Fe2(CO)6], 208 [M+ − Fe2(CO)6 − CO], 131 [M+ − Fe2(CO)6 −
CO − C6H5]. Anal. Calc. for C21H12O7N2Fe2: C, 48.88; H, 2.34; N,
5.43. Found: C, 49.09; H, 2.55; N, 5.69%.
−1
−1
1
=
2035 (vs), 2006 (vs), 1993 (vs) cm ; m(C O) 1703 (m) cm ; H
NMR (CD3COCD3) d 7.99–7.45 (m, 8H, aromatics), 5.63 (s, 1H,
CH(C6H4CF3-p)), 4.92, 4.50 (AB, 2H, J = 15 Hz, CH2); MS m/z
528 (M+ − 2CO), 472 (M+ − 4CO), 416 [M+ − Fe(CO)3 − CO],
388 [M+ − Fe(CO)3 − 2CO], 360 [M+ − Fe(CO)3 − 3CO]. Anal.
Calc. for C22H11O7F3N2Fe2: C, 45.25; H, 1.90; N, 4.80. Found: C,
45.16; H, 2.12; N, 4.92%.
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Reaction of 1 with p-C6H5C6H4Li to give
135.56, 131.91, 127.93, 127.73, 127.48, 115.21, 55.99 (OCH3);
[{C6H4CH(C6H4C6H5-p)NNCH2}Fe2(C O)(CO)6] (7)
MS m/z 236 (M+ − Fe2(CO)7), 221 (M+ − Fe2(CO)7 − CH3),
=
205 (M+ − Fe2(CO)7 − OCH3), 84 (CH2Cl2 ). Anal. Calc. for
+
A solution of 0.270 g (1.16 mmol) of p-C6H5C6H4Br in 20 mL
of ether was mixed with 1.14 of n-C4H9Li. After 2 h stirring at
room temperature, the resulting ether solution of p-C6H5C6H4Li12
was reacted, as described for the reaction of 1 with CH3Li, with
0.250 g (0.57 mmol) of 1 at −50 to −30 ◦C for 4 h. Further
treatment of the resulting brown mixture as described for the
preparation of 2 yielded 0.165 g (49%, based on 1) of brown–yellow
crystals of 7: mp 42–43 ◦C decomp.; IR (CH2Cl2) m(CO) 2077 (s),
C23H14Cl2Fe2N2O8·CH2Cl2: C, 43.92; H, 2.24; N, 4.45. Found: C,
43.13; H, 2.43; N, 5.09%.
X-Ray crystal structure determinations of complexes 4 and 9
The single crystals of 4 and 9 suitable for X-ray diffraction studies
were obtained by recrystallization from petroleum ether–CH2Cl2
solution at −80 ◦C. Single crystals of approximate dimensions
0.278 × 0.209 × 0.187 mm for 4 and 0.364 × 0.336 × 0.051 mm
for 9 were mounted on a glass fibre and sealed with epoxy glue.
The X-ray diffraction intensity data for 4 and 9 were collected with
−1
−1
1
=
2034 (vs), 2006 (vs), 1992 (vs) cm ; m(C O) 1706 (m) cm ; H
NMR (CD3COCD3) d 7.90–7.38 (m, 13H, aromatics), 5.95 (s, 1H,
CH(C6H5C6H4-p)), 4.93, 4.48 (AB, 2H, J = 15 Hz, CH2); MS m/z
536 (M+ − 2CO), 480 (M+ − 4CO), 396 [M+ − Fe(CO)3 − 2CO],
◦
a Bruker Smart diffractometer at 20 C using Mo-Ka radiation
368 [M+ − Fe(CO)3 − 3CO], 312 [M+ − Fe2(CO)6], 284 [M+
−
˚
(k = 0.71073 A) with an x–2h scan mode.
Fe2(CO)6 − CO], 256 (M+ − Fe2(CO)6 − CO − N2), 179 (M+ −
Fe2(CO)6 − CO − N2 − C6H5). Anal. Calc. for C27H16O7N2Fe2: C,
54.77; H, 2.72; N, 4.73. Found: C, 54.37; H, 3.21; N, 5.14%.
The structures of 4 and 9 were solved by the direct methods and
expanded using Fourier techniques. For both complexes, the non-
hydrogen atoms were refined anisotropically, and the hydrogen
atoms were included but not refined. The final cycle of full-matrix
least-squares refinement gave the agreement factors of R and Rw
listed in Table 1.
Reaction of 4 with [(NH4)2Ce(NO3)6] to give
[(l-{1-(p-CH3C6H4)-phthalazine-N2:N3})Fe2(l-CO)(CO)6] (8)
The details of the crystallographic data and the procedures
used for data collection and reduction information for complexes
4 and 9 are given in Table 1. The selected bond lengths and
angles are listed in Table 2. The atomic coordinates and Biso/Beq,
anisotropic displacement parameters, complete bond lengths and
angles, and least-squares planes for 4 and 9 are given in the CIF
file. The molecular structures of 4 and 9 are given in Fig. 1 and 2,
respectively.
A solution of 0.400 g (0.80 mmol) of [(NH4)2Ce(NO3)6] dissolved
in 10 mL of ethanol was added to the solution of 0.200 g
(0.38 mmol) of 4 in 20 mL of THF at −35 C. The mixture was
◦
stirred at −35 to 20 ◦C for 1–2 h, during which time the color of the
solution turned gradually from green–brown to red–brown. After
stirring at 20 ◦C for an additional 8–10 h, the solvent was removed
under high vacuum and the brown residue was chromatographed
on an alumina column (1.6 × 15–20 cm) with petroleum ether–
CH2Cl2 (1 : 1) as the eluent. A purple–brown band was eluted and
collected. After vacuum removal of the solvent, the residue was
recrystallized from petroleum ether–CH2Cl2 solution at −80 ◦C to
give ◦0.076 g (38%, based on 4) of deep brown crystals of 8: mp 180–
181 C decomp.; IR (CH2Cl2) m (CO) 2047 (vs), 1998 (vs), 1975
(vs), 1955 (vs), 1762 (m) cm−1; 1H NMR (CD3COCD3) d 9.66 (s,
1H, C6H4C2HN2), 8.31–8.29 (m, 4H, C6H4C2HN2), 7.57–7.48 (m,
4H, CH3C6H4), 5.64 (m, 0.5H, CH2Cl2), 2.55 (s, 3H, CH3C6H4);
MS m/z 220 (M+ − Fe2(CO)7), 205 (M+ − Fe2(CO)7 − CH3), 84
Table 1 Crystal data and experimental details for complexes 4 and 9
4
9·CH2Cl2
Formula
Mr
C22H14O7N2Fe2
530.05
C23H14O8N2Cl2Fe2
628.96
P1 (no. 2)
¯
Space group
P21/c (no. 14)
13.786(3)
9.7314(18)
17.518(3)
90
109.790(4)
90
2211.4(7)
4
1.592
1072
13.58
1714
4.861–38.72
3.14–56.60
5192
2689
343
0.7690–1.0000
0.0486
0.0684
˚
a/A
10.1738(10)
10.2354(10)
12.7042(13)
85.943(2)
86.833(2)
79.760(2)
1297.4(2)
2
1.610
632
13.73
1709
5.015–45.202
3.22–56.58
5727
3297
335
0.76847–1.00000
0.0687
0.1763
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
+
(CH2Cl2 ). Anal. Calc. for C22H12O7N2Fe2·1/4CH2Cl2: C, 48.65;
H, 2.29; N, 5.10. Found: C, 48.49; H, 2.96; N, 4.99%.
3
˚
V/A
Z
Reaction of 5 with [(NH4)2Ce(NO3)6] to give
Dc/g cm−3
[(l-{1-(p-CH3OC6H4)-phthalazine-N2:N3})Fe2(l-CO)(CO)6] (9)
F(000)
l(Mo-Ka)/cm−1
No. orientation reflections
Orientation range, 2h/◦
Data coll. range, 2h/◦
No. unique data, total
with I > 2.00r(I)
No. params refined
Correct. factors, max. min.
Ra
A solution of 0.460 g (0.84 mmol) of [(NH4)2Ce(NO3)6] dissolved
in 10 mL of ethanol was added to a solution of 0.250 g (0.46 mmol)
of 5 in 20 mL of THF at −35 ◦C. The mixture was stirred at −35
to 20 ◦C for 1–2 h, during this time the color of the reaction
solution turned gradually from green–brown to red–brown. After
◦
stirring at 20 C for additional 10 h, the solvent was removed in
vacuo. Further treatment of the brown residue as described in the
reaction of 4 with [(NH4)2CeNO3] produced 0.077 g (31%) of 9
as deep brown crystals: mp 209–210 ◦C decomp.; IR (CH2Cl2)
m (CO) 2047 (s), 1998 (vs), 1976 (s), 1955 (s), 1763 (m) cm−1;
1H NMR (CD3COCD3) d 9.63 (s, 1H, C6H4C2HN2), 8.30–8.15
(m, 4H, C6H4C2HN2), 7.51–7.29 (m, 4H, CH3OC6H4), 5.63 (m,
2H, CH2Cl2), 3.99 (s, 3H, CH3OC6H4); 13C NMR (CD3COCD3)
d 223.38 (CO), 211.81 (l-CO), 160.67, 160.22, 135.93, 135.69,
b
Rw
Quality of fit indicatorc
0.766
0.910
Max shift/esd final cycle
0.111
0.417
0.041
0.914
−3
Largest peak/e−
A
˚
−3
Minimum peak/e−
−0.345
−0.846
˚
A
ꢀ
ꢀ
ꢀ
ꢀ
a R = ꢀFo| − |Fcꢀ|/ |Fo|. b Rw = [ w(|Fo| − |Fc|)2/ w|Fo| ]1/2; w =
2
ꢀ
1/r2(|Fo|). c Quality-of-fit = [ w(|Fo| − |Fc|)2/(Nobs − Nparameters)]1/2
.
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◦
a
a
˚
Table 2 Selected bond lengths (A) and angles ( ) for complexes 4 and 9
4
9
4
9
Fe(1)–Fe(2)
Fe(1)–C(4)
Fe(2)–C(4)
Fe(1)–N(1)
Fe(2)–N(1)
Fe(2)–N(2)
N(1)–N(2)
C(4)–N(2)
C(4)–O(4)
2.5633(7)
1.935(4)
2.5498(10)
1.975(5)
1.984(6)
2.008(4)
N(1)–C(12)
N(2)–C(5)
C(5)–C(6)
C(11)–C(12)
C(6)–C(11)
C(12)–C(13)
Fe(1)–C(CO) (av)
Fe(2)–C(CO) (av)
1.498(4)
1.476(4)
1.478(5)
1.513(4)
1.404(4)
1.501(4)
1.788
1.329(6)
1.304(6)
1.400(7)
1.422(7)
1.412(7)
1.472(7)
1.799
1.941(2)
1.881(2)
1.976(3)
1.437(3)
1.452(4)
1.206(3)
1.978(4)
1.380(5)
1.784
1.798
1.165(6)
Fe(1)–Fe(2)–N(1)
Fe(1)–Fe(2)–N(2)
Fe(2)–Fe(1)–N(1)
Fe(1)–N(1)–Fe(2)
Fe(1)–N(1)–N(2)
Fe(2)–N(1)–N(2)
Fe(2)–N(2)–N(1)
N(1)–Fe(2)–N(2)
Fe(1)–C(4)–N(2)
Fe(1)–C(4)–Fe(2)
Fe(1)–C(4)–O(4)
Fe(2)–C(4)–O(4)
N(1)–Fe(1)–C(4)
48.89(8)
64.94(8)
46.88(7)
84.22(10)
93.62(17)
71.72(14)
64.63(14)
43.65(9)
93.4(2)
N(2)–Fe(2)–C(4)
Fe(1)–N(1)–C(12)
Fe(2)–N(2)–C(5)
O(4)–C(4)–N(2)
N(2)–N(1)–C(12)
N(1)–N(2)–C(5)
N(1)–C(12)–C(11)
N(2)–C(5)–C(6)
C(5)–C(6)–C(11)
C(6)–C(11)–C(12)
N(1)–C(12)–C(13)
C(11)–C(12)–C(13)
84.17(19)
134.3(3)
131.1(4)
72.61(11)
73.18(12)
136.47(19)
129.9(2)
120.4(3)
114.3(2)
119.4(3)
109.9(2)
110.8(3)
117.9(3)
117.2(3)
106.0(3)
118.6(3)
105.3(3)
108.7(3)
120.4(4)
120.1(4)
121.2(5)
123.7(5)
116.7(4)
117.9(5)
117.8(4)
121.0(5)
80.2(2)
140.1(4)
139.5(4)
83.02(18)
146.2(3)
70.21(12)
a Estimated standard deviations in the least significant figure are given in parentheses.
Fig. 2 Molecular structure of 9, showing the atom-numbering scheme
with 45% thermal ellipsoids.
Fig. 1 Molecular structure of 4, showing the atom-numbering scheme
with 45% thermal ellipsoids.
CH2Cl2 solution at −80 ◦C to afford the novel diiron carbonyl
CCDC reference numbers 225626 (4) and 278404 (9).
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b510676c
complexes with a saturated N–N six-membered diazane ring
=
ligand [{C6H4CH(R)NNCH2}Fe2(C O)(CO)6] (2–7) (eqn (2)) in
40–55% yields.
Complexes 2–7 are soluble in polar organic solvents but slightly
soluble in nonpolar solvents. They are very sensitive to air and
temperature both in solution and solid states. Elemental analyses
and spectroscopic data are consistent with their compositions and
Results and discussion
[{l-(phthalazine-N2:N3)}Fe2(l-CO)(CO)6] (1) reacts with about
2 molar equiv. of the organolithium reagents, RLi (R = CH3,
C6H5, p-CH3C6H4, p-CH3OC6H4, p-CF3C6H4, p-C6H5C6H4) in
THF at low temperature (−55 to −15 ◦C) for 4–5 h, followed
by treatment with an excess of Me3SiCl. After removal of the
solvent under high vacuum at low temperature, the residue was
chromatographed on an alumina column at low temperature,
and the crude product was recrystallized from petroleum ether–
assigned structures. The IR spectra of complexes 2–7 show a CO
−1
=
absorption band at ca. 1699–1706 cm , as evidence for a C O
group in these complexes, indicating the conversion of the l-CO
group in 1 into a C O group. The H NMR spectra of 2–7 show
a singlet proton signal at ca. 5.80 ppm and two AB proton signals
at ca. 4.90 and 4.50 ppm, which suggest the formation of the
saturated N–N six-membered diazane ring in these complexes.
1
=
606 | Dalton Trans., 2006, 603–608
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to form a novel diiron carbonyl compounds with a saturated
N–N six-membered diazane ring ligand, a novel coordination
mode of 1,2-diazane carbonyl complexes. It can be excluded that
products 2–7 were formed on the neutral alumina containing
water during the column chromatography since the isolation
of the resulting mixture obtained from the reaction of 1 with
organolithium reagents, such as CH3Li and C6H5Li, has also
been attempted by extraction with petroleum ether–CH2Cl2 and
repeated recrystallization from petroleum ether–CH2Cl2 at low
temperature, instead of the column chromatograph on alumina,
so that the products (2 and 3) were obtained. This indicated that
the protonation has occurred in the original reaction mixture.
It is certain that products 2–7 were not formed directly by the
reaction of compound 1 with organolithium reagents without
further treatment with Me3SiCl. This type of nucleophilic addition
of R− (alkyl or aryl) anion to the phthalazine ligand to form
the alkyl or aryl-substituted diazane-coordinated diiron carbonyl
complexes is very unusual.
It is well-known that the ammonium ceric nitrate,
[(NH4)2Ce(NO3)6], is an excellent oxidizing agent in the oxidation
of the olefin-coordinated carbonyliron compound to organic
compounds.15–17 It is interesting to understand how complexes 2–7
react with [(NH4)2Ce(NO3)6]. and what product is formed. Thus,
complexes 4 and 5 were treated respectively with [(NH4)2Ce(NO3)6]
in THF–EtOH solution at −35 to 20 ◦C. After workup as described
in the Experimental section, the unexpected aryl-substituted
phthalazine-coordinated diiron carbonyl compounds [(l-
{1-(p-CH3C6H4)-phthalazine-N2:N3})Fe2(l-CO)(CO)6] (8) and
[(l-{1-(p-CH3OC6H4)-phthalazine-N2:N3})Fe2(l-CO)(CO)6] (9)
(eqn (3)) were obtained in 31 and 38% yields, respectively.
(2)
A single-crystal X-ray diffraction study of 4 confirmed the
structures of complexes 2–7 shown in eqn (2). The molecular
structure (Fig. 1) of 4 shows a novel Fe(1)Fe(2)C(4)N(1)N(2)
core arrangement, which constructs an incomplete tetrahedron
structure with the Fe–Fe distance of 2.5633(7) A. The Fe(1)–
N(1), Fe(2)–N(1), Fe(2)–N(2) and N(1)–N(2) bond distances are
1.941(2), 1.881(2), 1.976(3) and 1.437(3) A, respectively. Of the two
nitrogen atoms, one (N(1)) is coordinated to the two Fe atoms; the
other (N(2)) is only coordinated with the Fe(2) atom and linked
˚
˚
=
mediately to the Fe(1) atom through the C O group, thus giving
each of the two Fe atoms an 18-electron configuration. Compound
4 appears tobe thefirst example ofaspecies withsuchFe–Fe, l-Fe–
N and N–N bonds studied by X-ray crystallography, and hence,
comparison of these bond distances with others involving these
elements is not possible. The Fe(1), N(1), N(2) and C(4) atoms
lie approximately in a plane (torsion angles of C(4)–Fe(1)–N(1)–
◦
=
N(2) −8.86(17) ). The C O group, which could be converted
from the l-CO of starting 1, is bridging by the Fe(1) and N(2)
atoms with the bond lengths of Fe(1)–C(4) = 1.935(4) A, C(4)–
˚
˚
˚
N(2) = 1.452(4) A, and C(4)–O(4) = 1.206(3) A. The saturated
N–N six-membered ring is a twisted boat-configuration, which
may be caused by the steric hindrance of the p-CH3C6H4 group
and the rigidity of the N(1)–N(2) and C(6)–C(11) bonds (the
torsion angles of N(1)–N(2)–C(5)–C(6), N(2)–C(5)–C(6)–C(11)
and C(5)–C(6)–C(11)–C(12) are 36.4(4), −42.4(4) and 3.2(4)◦,
respectively). The dihedral angles between the Fe(1)N(1)Fe(2) and
Fe(2)N(1)N(2) planes is 84.25◦, indicating that the Fe(1)N(1)Fe(2)
plane is almost perpendicular to the Fe(2)N(1)N(2) plane. The
angle between the Fe(2)N(1)N(2) plane and the benzene ring
C(6)C(7)C(8)C(9)C(10)C(11) plane is 81.278◦, which indicates
that the Fe(2)N(1)N(2) plane is nearly perpendicular to the
C(6)C(7)C(8)C(9)C(10)C(11) plane. The benzene ring plane com-
prised of C(13) though C(18) is oriented at an angle of 55.26◦ with
respect to the benzene ring C(6)C(7)C(8)C(9)C(10)C(11) plane;
(3)
In complexes 8 and 9, the disappearance of the absorption
band at 1699 cm−1 and the appearance of the absorption band
at 1762 cm−1 in their IR spectra indicate the resurrection of the
=
l-CO ligand from the C O group of complexes 4 and 5; and the
disappearances of the singlet proton signal at ca. 5.83 ppm and two
AB proton signals at ca. 4.89 and 4.45 ppm and the appearances
of a singlet signal at ca. 9.66–9.63 ppm and a multiplet signal at
1
ca. 8.31–8.15 ppm in their H NMR suggest the reformation of
the phthalazine ligand.
=
and the p-CH3C6H4 group is in the trans position of the C O
group bonded to the Fe(1) and N(2) atoms.
The structures of complexes 8 and 9 shown in eqn (3) were
also confirmed by the X-ray crystallography of complex 9.
The results of the X-ray structure determination of 9 show
that in the oxidation with [(NH4)2Ce(NO3)6], complex 5 lost
one molecule of hydrogen (H2) to form an aryl-substituted
phthalazine ring, and, at the same time, the C(4)–N(2) bond
cleaved to reform a l-CO ligand bridged by the two Fe atoms, as
anticipated from its IR spectrum. The molecular structure (Fig. 2)
of complex 9 is very similar to that of the pyridazine-ligated
The formation of complexes 2–7 is unexpected, and it is not
yet clear how they are formed. Presumably, it seems possible via
an attack of the R− anion on one a-carbon of the nitrogen atoms
of the phthalazine ring of 1, then the l-CO group redistributed
=
to form a C O group with the formation of the new C–N
bond (C(4)–N(2)) aided by Me3SiCl. The other a-carbon could
abstract a hydrogen from the solvent THF13,14 or water, which
is the trace contaminant in solvent THF or from glassware,
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diiron carbonyl compound [{l-(pyridazine-N1:N2)}Fe2(l-
CO)(CO)6],18 except that the diazene ligand bridged by the two
Fe atoms is an aryl-substituted phthalazine in the former but a
pyridazine in the latter. The distances of the Fe–Fe bond bridged
References
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˚
by the l-CO in 9 is 2.5498(10) A, which is somewhat shorter than
1
2
18
˚
that in [{l-(pyridazine-N :N )}Fe2(l-CO)(CO)6] (2.573(1) A).
˚
The average Fe-l-C(O) distance of 1.980 A is approximately equal
1
2
18
˚
to that in [{l-(pyridazine-N :N )}Fe2(l-CO)(CO)6] (1.978 A),
˚
while the average Fe–N distance (1.993 A) in 9 is significantly
longer than that in [{l-(pyridazine-N1:N2)}Fe2(l-CO)(CO)6]
(1.955 A).18 The two Fe atoms lie approximately in the same plane
˚
with the phthalazine ring plane. The dihedral angles between
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Fe(1)Fe(2)N(1)N(2) and phthalazine ring planes are 83.91 and
4.28◦, respectively, indicating that the Fe(1)C(4)Fe(2) plane is
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Fe(1)Fe(2)N(1)N(2) plane is nearly parallel to the phthalazine
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In summary, we have found the novel reactions of phthalazine-
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reagents, which produce a series of six-membered diazane-
coordinated diiron carbonyl complexes with a novel coordination
mode (2–7), of which complexes 4 and 5 have been converted
into the aryl-substituted phthalazine-coordinated diiron carbonyl
compounds by treating with [(NH4)2Ce(NO3)6]. Further studies
on the scope of the reaction and the application in organic
and organometallic synthesis are now being carried out in our
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Acknowledgements
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We thank the National Natural Science Foundation of China, the
Science Foundation of the Chinese Academy of Sciences, and the
JSPS of Japan for financial support of this research.
608 | Dalton Trans., 2006, 603–608
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The Royal Society of Chemistry 2006
©