Synthesis and structures of iron(II) alkyl and thiolate compounds containing sterically hindered N-functionalized alkyl ligands

Article abstract of DOI:10.1021/om950806l

Iron(II) dialkyl compounds [FeR₂] (R = C(SiMe₃)₂C₅H₄N-2 (1), C(Ph)(SiMe₃)C₅H₄N-2 (2), CH(SiMe₃)C₉H₆N-8 (4)) and [{Fe(CHSi^tBuMe₂C₅H₄N-2) ₂}₂] (3) have been prepared from the reaction of FeCl₂ with the appropriate N-functionalized alkyllithium reagent in a 1:2 molar ratio. The monoalkylated iron(II) complex [Fe{CPhSiMe₃C₅H₄N-2}(Cl)(TMEDA)] (5) has been prepared by treating FeCl₂ with a stoichiometric amount of the organolithium reagent. X-ray analysis revealed that the alkyl ligands are bonded to the metal centers in a chelating manner in the mononuclear compounds 1 and 5, whereas in 3 one of the alkyl ligands forms an interligand bridge betwen the two iron centers. Compounds 1, 2, 4, and 5 have magnetic moments in the range 4.24-4.96 μ_B that are characteristic of a high-spin d⁶ electronic configuration with four unpaired electrons. The magnetic moment of the binuclear compound 3 is 2.92 μ_B per iron atom, apparently a consequence of antiferromagnetic coupling between the two metal centers. Subsequent reaction of 1 with Ar^MeOH (Ar^Me = 2,6-^t Bu₂-4-MeC₆H₂) and ArSH (Ar = 2,4,6-^tBu₃C₆H₂) gave the neutral monomeric iron(II) bis(aryloxide) [Fe-(OAr^Me)₂{CH(SiMe₃)₂C ₅H₄N-2}] (6) and dithiolate [Fe(SAr)₂{CH(SiMe₃)₂C₅H ₄N-2}] (7), respectively. Both of the latter compounds have a rare coordination number of 3 at the iron(II) center. The magnetic moment of 5.11 μ_B for 7 indicates a high-spin configuration with four unpaired electrons on the iron(II) center. Electrochemical studies on the compoounds are also reported.

Full text of DOI:10.1021/om950806l

Organometallics 1996, 15, 1785-1792
1785
Syn th esis a n d Str u ctu r es of Ir on (II) Alk yl a n d Th iola te
Com p ou n d s Con ta in in g Ster ica lly Hin d er ed
N-F u n ction a lized Alk yl Liga n d s
Wing-Por Leung,* Hung Kay Lee, Lin-Hong Weng, Bao-Sheng Luo,
Zhong-Yuan Zhou,† and Thomas C. W. Mak
Department of Chemistry, The Chinese University of Hong Kong,
Shatin, New Territories, Hong Kong
Received October 12, 1995X
Iron(II) dialkyl compounds [FeR2] (R ) C(SiMe3)2C5H4N-2 (1), C(Ph)(SiMe3)C5H4N-2 (2),
CH(SiMe3)C9H6N-8 (4)) and [{Fe(CHSitBuMe2C5H4N-2)2}2] (3) have been prepared from the
reaction of FeCl2 with the appropriate N-functionalized alkyllithium reagent in a 1:2 molar
ratio. The monoalkylated iron(II) complex [Fe{CPhSiMe3C5H4N-2}(Cl)(TMEDA)] (5) has
been prepared by treating FeCl2 with a stoichiometric amount of the organolithium reagent.
X-ray analysis revealed that the alkyl ligands are bonded to the metal centers in a chelating
manner in the mononuclear compounds 1 and 5, whereas in 3 one of the alkyl ligands forms
an interligand bridge betwen the two iron centers. Compounds 1, 2, 4, and 5 have magnetic
moments in the range 4.24-4.96 µB that are characteristic of a high-spin d6 electronic
configuration with four unpaired electrons. The magnetic moment of the binuclear compound
3 is 2.92 µB per iron atom, apparently a consequence of antiferromagnetic coupling between
the two metal centers. Subsequent reaction of 1 with ArMeOH (ArMe ) 2,6-tBu2-4-MeC6H2)
and ArSH (Ar ) 2,4,6-tBu3C6H2) gave the neutral monomeric iron(II) bis(aryloxide) [Fe-
(OArMe)2{CH(SiMe3)2C5H4N-2}] (6) and dithiolate [Fe(SAr)2{CH(SiMe3)2C5H4N-2}] (7), re-
spectively. Both of the latter compounds have a rare coordination number of 3 at the iron(II)
center. The magnetic moment of 5.11 µB for 7 indicates a high-spin configuration with four
unpaired electrons on the iron(II) center. Electrochemical studies on the compoounds are
also reported.
In tr od u ction
series of iron(II) diaryl complexes [FeR2(dippe)] (dippe
) 1,2-bis(diisopropylphosphino)ethane) have been re-
ported by Girolami et al.5 These complexes possess a
very low electron count of 14, which usually occurs in
organotransition-metal complexes. The complex [Fe-
(CH2Ph)2(TMEDA)] (TMEDA ) Me2NCH2CH2NMe2)
was recently reported and characterized by NMR stud-
ies.6 To date, only a few examples of simple homoleptic
iron dialkyl or diaryl compounds have been synthesized.
The well-characterized homoleptic diaryl complexes
have the formula [{FeR2}2] (R ) 2,4,6-Me3C6H2 or 2,4,6-
iPr3C6H2),7-9 and their dimeric nature was established
by X-ray structural analysis recently.8 A monomeric
form of the iron dimesityl compound [FeMes2(py)2] can
be obtained from the reaction of [{FeMes2}2] with
pyridine in toluene.9 To date, the only known mono-
meric homoleptic diaryl complex with a two-coordinate
iron(II) center is [FeAr2] (Ar ) 2,4,6-tBu3C6H2).10
In a recent communication, we reported the prepara-
tion and structural characterization of the iron(II)
The vast majority of organoiron(II) complexes that
have been isolated so far exist either in the form of
[FeRXLn] or [FeR2Ln], where R may be an alkyl or aryl
group, X is generally η5-C5H5, and L is a strong-field
ligand such as CO, PR3, or bipyridine.1 These complexes
are diamagnetic and obey the 18-electron rule. In
contrast, paramagnetic and coordinatively unsaturated
organoiron(II) compounds are less abundant, and stud-
ies on the reactivities of these compounds are rare.
Earlier work by Chatt and Shaw showed that iron-
(II) diaryls of the type [FeR2(PEt2Ph)2] (R ) C6Cl5) could
be obtained by treating [FeCl2(PEt2Ph)2] with the ap-
propriate Grignard reagents.2 Yamamoto et al. have
reported the synthesis of [FeEt2(bpy)2] by treating
Fe(acac)3 with Et2Al(OEt) in the presence of bipyridine.3
By a similar approach, Kochi et al. have also prepared
the methyl and n-propyl analogues.4 Recently, the
† On leave from Chengdu Institute of Organic Chemistry, Chinese
Academy of Science, Chengdu, Sizhuan, China.
(4) Lau, W.; Huffman, J . C.; Kochi, J . K. Organometallics 1982, 1,
155.
(5) Hermes, A. R.; Girolami, G. S. Organometallics 1987, 6, 763.
(6) Hill, D. H.; Parvez, M. A.; Sen, A. J . Am. Chem. Soc. 1994, 116,
2889.
(7) Machelett, B. Z. Chem. 1976, 16, 116.
(8) Mu¨ller, H.; Seidel, W.; Go¨rls, H. J . Organomet. Chem. 1993, 445,
133.
X Abstract published in Advance ACS Abstracts, March 1, 1996.
(1) (a) The Organic Chemistry of Iron; Koerner von Gustorf, E. A.,
Grevels, F. W., Fischer, I., Eds.; Academic: London, 1978; Vol. I. (b)
Pearson, A. J . In Comprehensive Organometallic Chemistry; Wilkinson,
G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, U.K., 1982;
Vol. 8, Chapter 58.
(2) Chatt, J .; Shaw, B. L. J . Chem. Soc. 1961, 185.
(3) (a) Yamamoto, A.; Morifuji, K.; Ikeda, S.; Saito, T.; Uchida, Y.;
Misono, A. J . Am. Chem. Soc. 1965, 87, 4652. (b) Yamamoto, A.;
Morifuji, K.; Ikeda, S.; Saito, T.; Uchida, Y.; Misono, A. J . Am. Chem.
Soc. 1968, 90, 1878.
(9) (a) Klose, A.; Solari, E.; Ferguson, R.; Floriani, C.; Chiesi-Villa,
A.; Rizzoli, C. Organometallics 1993, 12, 2414. (b) Klose, A.; Solari,
E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.; Re, N. J . Am. Chem. Soc.
1994, 116, 9123.
0276-7333/96/2315-1785$12.00/0 © 1996 American Chemical Society

1786 Organometallics, Vol. 15, No. 7, 1996
Leung et al.
Sch em e 1
dialkyl [Fe(R1)2]11 and cobalt(II) dialkyl [Co(R1)2],12 in
which R1 is the sterically hindered N-functionalized
alkyl ligand [C(SiMe3)2C5H4N-2]-. Early work involving
R1 has shown that it stabilizes several novel main-group
metal alkyl complexes which exhibit unusual coordina-
tion behavior.13 We have focused our attention on the
use of similar alkyl ligands in the preparation of
kinetically labile homoleptic transition-metal alkyl com-
plexes with a low electron count (e14). Accordingly, the
series of N-functionalized alkyl ligands [(CPhSiMe3)-
C5H4N-2]- (R2),14 [CH(SitBuMe2)C5H4N-2]- (R3),14 and
[CH(SiMe3)2C9H6N-8]- (R4) have been developed.14 We
now report the synthesis and structural characterization
of a series of iron(II) dialkyl complexes of stoichiometry
[Fe(Ri)2] where Ri is a bulky pyridine- or quinoline-
functionalized alkyl ligand. In addition, the reactivity
of the coordinatively unsaturated organoiron compound
1 toward the bulky phenol 2,6-tBu2-4-MeC2H2OH and
thiophenol 2,4,6-tBu3C6H2SH has also been investigated.
(10) The compound was prepared and structurally characterized by
two independent groups: Mu¨ller, H.; Seidel, W.; Go¨rls, H. Angew.
Chem., Int. Ed. Engl. 1995, 34, 325. Wehmschulte, R. J .; Power, P. P.
Organometallics 1995, 14, 3264.
(11) Leung, W.-P.; Lee, H. K.; Zhou, Z.-Y.; Mak, T. C. W. J .
Organomet. Chem. 1993, 443, C39.
Resu lts
(12) Lee, H. K.; Luo, B.-S.; Mak, T. C. W.; Leung, W.-P. J .
Organomet. Chem. 1995, 489, C71.
Syn th esis of Ir on (II) Dia lk yl Com p lexes. Treat-
ment of 2 molar equiv of organolithium reagents with
ferrous chloride in ether leads to the formation of the
corresponding lipophilic homoleptic iron(II) dialkyl com-
plexes 1-4 (Scheme 1). The physical properties of the
compounds prepared are listed in Table 1. Compounds
1, 2, and 4 were isolated as extremely air-sensitive
yellow, brown, and dark brown crystals, respectively,
while 3 was obtained as a dark red powder. These
compounds are thermally stable with melting points
ranging from 110 to 159 °C. Compound 1 can be
sublimed at 116 °C under high vacuum (10-2 mmHg).11
The thermal stability contrasts remarkably with the
(13) (a) Papasergio, R. I.; Raston, C. L.; White, A. H. J . Chem. Soc.,
Chem. Commun. 1983, 1419. (b) Colgan, D.; Papasergio, R. I.; Raston,
C. L.; White, A. H. J . Chem. Soc., Chem. Commun. 1984, 1708. (c)
Bailey, S. I.; Colgan, D.; Engelhardt, L. M.; Leung, W.-P.; Papasergio,
R. I.; Raston, C. L.; White, A. H. J . Chem. Soc., Dalton Trans. 1986,
603. (d) Henderson, M. J .; Papasergio, R. I.; Raston, C. L.; White, A.
H.; Lappert, M. F. J . Chem. Soc., Chem. Commun. 1986, 672. (e)
Engelhardt, L. M.; J olly, B. S.; Lappert, M. F.; Raston, C. L.; White,
A.H. J . Chem. Soc., Chem. Commun. 1988, 336. (f) van den Ancker,
T.; J olly, B. S.; Lappert, M. F.; Raston, C. L.; Skelton, B. W.; White, A.
H. J . Chem. Soc., Chem. Commun. 1990, 1006. (g) Papasergio, R. I.;
Raston, C. L.; White, A. H. J . Chem. Soc., Chem. Commun. 1984, 612.
(h) Engelhardt, L. M.; Kynast, U.; Raston, C. L.; White, A. H. Angew.
Chem., Int. Ed. Engl. 1987, 26, 7. (i) Papasergio, R. I.; Raston, C. L.;
White, A. H. J . Chem. Soc., Dalton Trans. 1987, 3085. (j) Kynast, U.;
Skelton, B. W.; White, A. H.; Henderson, M. J .; Raston, C. L. J .
Organomet. Chem. 1990, 384, C1. (k) Cameron, J .; Engelhardt, L. M.;
J unk, P. C.; Hutchings, D. S.; Patalinghug, W. C.; Raston, C. L.; White,
A. H. J . Chem. Soc., Chem. Commun. 1991, 1560. (l) J olly, B. S.;
Lappert, M. F.; Engelhardt, L. M.; White, A. H.; Raston, C. L. J . Chem.
Soc., Dalton Trans. 1993, 2653.
(14) (a) Leung, W.-P.; Weng, L.-H.; Zhou, Z.-Y.; Mak, T. C. W.
Organometallics 1995, 14, 4832. (b) Quinoline ligand: Lawrance, T.
C. M.Phil. Thesis, The Chinese University of Hong Kong, 1994.

Fe(II) N-Functionalized-Alkyl Complexes
Organometallics, Vol. 15, No. 7, 1996 1787
Ta ble 1. P h ysica l P r op er ties of Com p ou n d s 1-7
compd
yield (%)
color
yellow
mp (°C)
110-112b
118-120 dec
155-159
µ
eff (µB)a
4.24
80
52
58
[Fe{C(SiMe3)2C5H4N-2}2] (1)
[Fe{(CPhSiMe3)C5H4N-2}2] (2)
[{Fe(CH(SitBuMe2)C5H4N-2)2}2] (3)
[Fe{(CHSiMe3)C9H6N-8}2] (4)
red
4.92
brown
dark brown
red
2.92c
65
71
161-163 dec
124-126 dec
4.96
4.45
[Fe{(CPhSiMe3)C5H4N-2}(Cl) (TMEDA)] (5)
[Fe(OC6H3-4-Me-2,6-tBu2)2{CH(SiMe3)2C5H4N-2}] (6)
[Fe(SC6H2tBu3-2,4,6)2{CH(SiMe3)2C5H4N-2}] (7)
41
65
colorless
yellow
129-131
182-185 dec
5.11
a
b
Evans NMR method in C6D6 solution at 298 K. Sublimed at 116 °C/10-2 mmHg. c Per iron atom.
Sch em e 2
case for the iron(II) dialkyls, which readily decompose
to coupled products at ambient temperature.
F igu r e 1. Molecular structure of [Fe{C(SiMe3)2C5H4N-2}2]
(1) with the atomic labeling scheme. Hydrogen atoms have
been omitted, and the thermal ellipsoids are drawn at the
35% probability level.
Syn th esis of th e Mon oa lk ylir on (II) Com p lex [F e-
(R 2)Cl(TME DA)]. Monoalkyliron(II) species may be
considered as intermediates during the course of reac-
tion to form the corresponding dialkyl complex. Their
preparation normally requires a strict and proper
control of stoichiometry. Alkylation of ferrous chloride
with 1 molar equiv of the organolithium reagent [R2Li-
(TMEDA)] in ether gave the monoalkyliron(II) complex
4, which was isolated as reddish brown crystals. The
coordinated TMEDA is presumably a requirement for
coordination saturation which contributes to the stabil-
ity and solubility of the adduct formed.
Rea ctivities of [F e(R1)2] (1). Reactivities of dialkyl
complex 1 toward protic reagents such as the phenol
ArMeOH (ArMe ) 2,6-tBu2-4-MeC6H2OH) and thiophenol
ArSH (Ar ) 2,4,6-tBu3C6H2SH), which bear bulky ortho
substituents, have been investigated. Reaction of 1 with
2 equiv of ArMeOH or ArSH in hexane yielded, respec-
tively, the monomeric iron(II) bis(aryloxide) or dithiolate
complexes with a coordination number of 3 for the metal
and an electron count of only 12 (Scheme 2).
Attempted reaction of 1 with benzonitrile was unsuc-
cessful, and only the dialkyl 1 was recovered. The
inertness of compound 1 toward benzonitrile via an
insertion reaction may be ascribed to steric hindrance
from the two bulky alkyl ligands.
F igu r e 2. Molecular structure of [Fe{CH(SitMe2)C5H4N-
2}2]2 (3) with the atomic labeling scheme. Hydrogen atoms
have been omitted, and the thermal ellipsoids are drawn
at the 35% probability level.
X-r a y Str u ctu r a l Stu d ies. [F e(R 1)2] (1). The mo-
lecular structure of 1 along with the atom-numbering
scheme is shown in Figure 1. The selected bond
distances and angles are shown in Table 2. The iron-
(II) center has a highly distorted tetrahedral coordina-
tion environment with each of the two alkyl ligands
acting in a C,N-chelating manner. Coordination from
the pyridyl nitrogens is believed to impose a stabilizing
effect on the metal complex. The observed Fe-CR bond
distances are 2.129(7) and 2.154(8) Å, and the Fe-N
distances are 2.11(8) and 2.135(5) Å. The bite angles
C-Fe-N are 66.8(2) and 67.2(3)°, and the interligand
angle C(1)-Fe-C(13) is large, viz. 160.4(3)°.
[{F e(R3)2}2] (3). The dimeric molecular structure of
3 is depicted in Figure 2, and selected bond distances
and angles are shown in Table 2. The long Fe‚‚‚Fe
distance of 3.828 Å excludes any possibility of an iron-
iron bond. The Fe-CR distance of 2.163(2) Å, involving
the bridging C(13) ligand, is only 0.03 Å longer than
that of the terminal C(1) ligand. However, the Fe-N(2)
distance of 2.189(2) Å is substantially longer than the
Fe-N(1) distance of 2.097(2) Å. A weak interaction

1788 Organometallics, Vol. 15, No. 7, 1996
Leung et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d
An gles (d eg)
[Fe{C(SiMe3)2C5H4N-2}2] (1)
Fe(1)-C(1)
Fe(1)C(13)
Fe(1)-N(1)
Fe(1)-N(2)
C(1)-C(2)
C(2)-N(1)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(13)-C(14)
C(6)-N(1)
C(1)-Si(1)
2.154(8)
2.139(7)
2.135(5)
2.111(8)
1.489(9)
1.347(10)
1.391(10)
1.348(12)
1.362(14)
1.389(11)
1.469(12)
1.321(9)
1.861(8)
C(1)-Fe-C(13)
160.4(3)
116.3(2)
124.1(3)
125.4(3)
66.8(2)
67.2(3)
109.4(3)
87.7(5)
92.3(4)
87.2(5)
91.7(6)
111.3(4)
144.5(9)
N(1)-Fe-N(2)
C(1)-Fe-N(2)
N(1)-Fe-C(13)
C(1)-Fe-N(1)
C(13)-Fe-N(2)
Fe(1)-C(1)-Si(1)
Fe(1)-C(1)-C(2)
Fe(1)-N(1)-C(2)
Fe(1)-C(13)-C(14)
Fe(1)-N(2)-C(14)
Fe(1)-C(13)-Si(3)
Fe(1)-N(2)-C(18)
[Fe{CH(SitBuMe2)C5H4N-2}2]2 (3)
F igu r e 3. Molecular structure of [Fe{CH(SitMe2)C5H4N-
2}(Cl)(TMEDA)] (5) with the atomic labeling scheme.
Hydrogen atoms have been omitted, and the thermal
ellipsoids are drawn at the 35% probability level.
Fe(1)-C(1)
Fe(1)-C(13a)
Fe(1)-N(1)
Fe(1)-N(2)
N(1)-C(6)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
N(1)-C(2)
2.133(2)
2.163(2)
2.189(2)
2.097(2)
1.347(4)
1.473(4)
1.395(4)
1.368(5)
1.363(5)
1.362(5)
1.352(3)
N(1)-Fe(1)-C(1)
C(1)-Fe(1)-N(2)
C(1)-Fe(1)-C(13a)
N(1)-Fe(1)-N(2)
N(1)-Fe(1)-C(13a)
N(2)-Fe(1)-C(13a)
Fe(1)-N(1)-C(2)
Fe(1)-C(1)-C(2)
Fe(1)-N(2)-C(14)
Si(2)-C(13)-Fe(1a)
Fe(1)-N(1)-C(6)
C(14)-C(13)-Fe(1a)
66.1(1)
103.6(1)
148.0(1)
103.2(1)
121.0(1)
104.4(1)
87.6(1)
86.9(1)
119.2(2)
108.4(1)
145.9(2)
107.6(1)
[Fe(CPhSiMe3C5H4N-2)(Cl)(TMEDA)] (5)
Fe(1)-Cl(1)
Fe(1)-N(2)
Fe(1)-C(6)
Fe(1)-N(1)
Fe(1)-N(3)
N(1)-C(1)
N(1)-C(5)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(6)-C(7)
C(6)-Si(1)
2.310(2)
2.284(6)
2.212(6)
2.218(6)
2.206(6)
1.333(10)
1.345(8)
1.367(11)
1.371(12)
1.369(11)
1.384(9)
1.471(10)
1.492(10)
1.880(8)
Cl(1)-Fe(1)-N(1)
N(1)-Fe(1)-N(2)
N(1)-Fe(1)-N(3)
Cl(1)-Fe(1)-C(6)
N(2)-Fe(1)-C(6)
Cl(1)-Fe(1)-N(2)
Cl(1)-Fe(1)-N(3)
N(2)-Fe(1)-N(3)
N(1)-Fe(1)-C(6)
N(3)-Fe(1)-C(6)
Fe(1)-N(1)-C(5)
Fe(1)-C(6)-C(5)
Fe(1)-C(6)-C(7)
C(5)-C(6)-C(7)
98.0(2)
167.6(2)
92.6(2)
128.8(2)
111.8(2)
93.5(2)
106.0(2)
79.8(2)
63.8(2)
121.3(2)
92.6(4)
89.5(4)
121.1(4)
121.1(4)
t
F igu r e 4. Molecular structure of [Fe(SC6H2 Bu3-2,4,6)2-
{CH(SiMe3)2C5H4N-2}] (7) with the atomic labeling scheme.
Hydrogen atoms have been omitted, and the thermal
ellipsoids are drawn at the 35% probability level.
[Fe(SC6H2tBu3-2,4,6)2{CH(SiMe3)2C5H4N-2}] (7)
Fe(1)-S(1)
Fe(1)-S(2)
S(2)-C(31)
Fe(1)-N(1)
S(1)-C(13)
2.259(4)
2.261(3)
1.80(1)
2.086(9)
1.80(1)
S(1)-Fe(1)-S(2)
S(1)-Fe(1)-N(1)
S(2)-Fe(1)-N(1)
Fe(1)-S(1)-C(13)
Fe(1)-S(2)-C(31)
117.8(1)
118.7(2)
123.4(2)
113.1(4)
101.0(3)
The three interligand angles around the iron center are
different, namely 117.8(1), 118.7(2), and 123.4(2)°.
Discu ssion
between Fe(1) and C(2) (2.525 Å) is consistent with a
slight distortion from planarity for the pyridyl ring on
the terminal ligand.
Although a large number of organoiron(II) compounds
which contain stabilizing ligands (e.g., CO, C5H5, PR3,
bipyridines) have been reported, examples of simple
homoleptic iron dialkyl or diaryl species of the type
[FeR2] are rare.1 Recently, a few homoleptic iron(II)
diaryl complexes, which contain bulky hydrocarbon
substituents, have been prepared and structurally
characterized.7-10 In contrast, homoleptic dialkyl com-
plexes of iron(II) remain virtually unknown. Indeed,
an interesting exception of a homoleptic organoiron
compound which contains Fe-C(sp3) bonds is probably
Fe(1-norbornyl)4,15 which decomposes slowly at room
temperature with a half-life of ca. 30 h.15
[F e(R2)(Cl)(TMEDA)] (5). Figure 3 shows the mo-
lecular structure of 5. The structural data are shown
in Table 2. The five-coordinate iron atom is surrounded
by a C,N-chelating R2 ligand, a chloride ligand, and two
N-donors from TMEDA. The Fe-CR distance is 2.212
Å, and the Fe-N(pyridine) distance is 2.218(6) Å.
Coordination of the TMEDA molecule is unsymmetrical
and the two unexceptional Fe-N distances differ by
about 0.08 Å.
[F e(SAr )2(HR1)] (7). The molecular structure of 7
is shown in Figure 4, with selected bond distances and
angles listed in Table 2. The dithiolate complex pos-
sesses a trigonal-planar coordination geometry around
the central Fe(II) atom (sum of bond angles 359.9°).
Owing to their bulkiness, the three ligands are oriented
in such a way that the complex adopts a propeller-like
structure. The Fe-S bond distances are 2.259(4) and
2.261(3) Å, and the Fe-N distance in 7 is 2.086(9) Å.
Compounds 1-4 were prepared by the reaction of the
appropriate organolithium reagents with ferrous chlo-
ride, while the monoalkyl species 5 was prepared with
proper control of the stoichiometries of starting materi-
als.
(15) Bower, B. K.; Tennent, H. G. J . Am. Chem. Soc. 1972, 94, 2512.

Fe(II) N-Functionalized-Alkyl Complexes
Organometallics, Vol. 15, No. 7, 1996 1789
Ta ble 3. Selected X-r a y Da ta Collection a n d Str u ctu r e An a lysis P a r a m eter s for Com p ou n d s 1, 3, 5, a n d 7
1
3
5
7
mol formula
mol wt
C24H44N2Si4Fe
528.8
C48H80N4Si4Fe2
937.2
C21H34N3ClSiFe
447.9
C48H81NSi2S2Fe
848.29
color and habit
cryst size, mm
cryst syst
space group
a, Å
dark brown plates
0.36 × 0.40 × 0.60
monoclinic
P21/c (No. 14)
23.882(5)
16.820(6)
16.406(4)
107.32(1)
6291(3)
brown prism
0.24 × 0.28 × 0.38
triclinic
P1h (No. 2)
10.850(2)
11.254(2)
11.580(2)
84.32(2)
1350.6(4)
1
1.152
0.66
0.686-0.872
ω-scan
red needle
0.30 × 0.16 × 0.44
monoclinic
P21/n (No. 14)
10.598(2)
14.205(6)
16.334(4)
96.290(0)
2444(1)
4
yellow prism
0.30 × 0.30 × 1.00
monoclinic
P21/c (No. 14)
14.585(5)
19.894(6)
19.266(5)
111.16(1)
5213(3)
b, Å
c, Å
â, deg
V, Å3
Z
8
4
density, g cm-3
abs coeff, mm-1
transmissn factor
scan type
1.117
0.645
0.691-0.819
ω-scan
3.08-29.3
50
10957
4418
559
1.217
0.79
1.081
0.44
0.921-0.965
ω-2θ scan
4.19-29.3
45
6826
3656
487
0.085
0.664-0.912
ω-scan
scan rate, deg min-1
2θmax, deg
no. of unique data measd
no. of obsd rflns
no. of variable
R
3-29.3
50
4762
4049
451
3-29.3
45
4281
2137
407
0.060
0.041
0.035
Rw
0.062
0.046
0.060
0.125
Protonolysis of 1 by ArMeOH and ArSH yielded the
iron(II) bis(aryloxide) 6 and dithiolate 7, respectively.
The three bulky ligands, namely the two thiolato groups
and a free ligand molecule of R1H, are believed to play
a vital role in preventing association of the neighboring
[Fe(EAr)2] (E ) O, S) moieties, thus leading to the
formation of the neutral, mononuclear, three-coordinate
iron(II) bis(aryloxide) and dithiolate complexes.
of the presence of the byproduct NH(SiMe3)2. Reaction
of 1 with ArMeOH and ArSH, giving 6 and 7, provides
an alternative route for the preparation of monomeric
metal aryloxide and thiolate compounds via metal alkyls
in which a free R1H molecule remains coordinated to
the Fe(II) center through N-coordination. To our knowl-
edge, apart from the mononuclear two-coordinate spe-
cies 8,21b a structurally characterized neutral mononu-
clear iron(II) dithiolate with a coordination number of
3 around the Fe(II) center has not been reported.
Transition-metal aryloxides and thiolates tend to form
aggregrates that show very poor solubility in hydrocar-
bon solvents.16-19 This makes structural characteriza-
tion of these compounds difficult to carry out. With the
introduction of aryloxy and thiolato ligands which bear
bulky hydrocarbyl substituents, the degree of associa-
tion of these compounds can be greatly reduced. Fur-
thermore, the structural geometry of these compounds
also depends on the steric requirements of the substit-
uents. Recently it has been reported that reaction of
the iron(II) amide [Fe{N(SiMe3}2}2] with phenols and
thiophenols bearing bulky ortho substituents provides
a convenient route to the corresponding metal aryloxide
and thiolate complexes with two- or three-coordinate
metal centers.20,21 Known examples of these include
[Fe(SAr1)2] (8),21b [Fe(SAr1){N(SiMe3)2}] (9),21b [{Fe-
(EAr)2}2] (E ) O,20b S (10)21a), [{Fe(OAr){N(SiMe2)2}}2],20b
Str u ctu r a l Com p a r ison . X-ray diffraction studies
of complexes 1 and 3 have revealed different structural
features, with 1 being mononuclear and 3 being di-
nuclear. Nevertheless, the iron centers are four-
coordinate in both compounds. In 3, the anionic ligand
bridges the two metallacycle units through C(13) and
N, forming an eight-membered Fe2(CN)2 core which
adopts a stairlike conformation. Hence, two different
bonding modes are observed for the ligand R3 in each
molecule of 3, namely C,N-bridging and terminal C,N-
chelating. Steplike eight-membered-ring structures
have been reported for dimeric lithium,13a copper,13a
silver,13d and gold13i complexes which contain analogous
pyridine-functionalized alkyl ligands,13 although the
iron centers in 3 have additional terminal C,N-chelating
ligands. Despite the increased steric bulk of the R1
ligand in 1, shorter Fe-CR distances are observed than
in 3. The Fe-C(terminal) and Fe-C(bridging) distances
in 3 are 2.160(2)-2.163(2) Å, while the Fe-CR distances
in 1 are 2.129(7)-2.154(8) Å. This may be attributted
to an electronic effect in which the two trimethylsilyl
substituents greatly stabilize the negative charge on CR
of the alkyl ligand R1 through polarization. The Fe-
CR bond lengths in 1 and 3 are longer than those
observed in [FeEt2(bpy)2] (2.065 Å)3,4 and [Fe(CH2C6H4-
Me)2(dippe)] (2.120(6) Å).5 They are also longer than
the Fe-C(terminal) distances in the dinuclear aryl
complex [{FeMes2}2] (2.024 Å) and [{FeArip2}2] (2.083-
(9)-2.104(9) Å).8,9 However, they are similar to those
of 2.141(5) and 2.156(5) Å in the monomeric dimesityl
complex [FeMes2(py)2].9b The relatively long Fe-C(sp2)
σ bonds in the latter complex may be due to the steric
hindrance of the mesityl groups, which contain ortho-
and [{Fe(SAr2)2}2] (11;21c Ar1 ) 2,6-Mes2C6H3, Ar2
)
2,4,6-Ph3C6H2). Among these complexes, only 8 and 9
are mononuclear species with a two-coordinate iron(II)
center and the rest are binuclear species with a three-
coordinate iron(II) center. The Lewis acid centers of
these complexes are free from base coordination in spite
(16) Bradley, D. C.; Mehrotra, R. C.; Gaur, D. P. Metal Alkoxides;
Academic: New York, 1978.
(17) Dance, I. G. Polyhedron 1986, 5, 1037.
(18) Blower, P. J .; Dilworth, J . R. Coord. Chem. Rev. 1987, 76, 121.
(19) Krebs, B.; Henkel, G. In Rings, Cluster and Polymers of Main
Group Transition Elements; Roesky, H. W., Ed.; Elsevier: Amsterdam,
1989.
(20) (a) Murray, B. D.; Power, P. P. J . Am. Chem. Soc. 1984, 106,
7011. (b) Olmstead, M. M.; Power, P. P.; Sigel, G. Inorg. Chem. 1986,
25, 1027. (c) Sigel, G.; Barlett, R. A.; Decker, D.; Olmstead, M. M.;
Power, P. P. Inorg. Chem. 1987, 26, 1773. (d) Barlett, R. A.; Ellison, J .
J .; Power, P. P.; Shoner, S. C. Inorg. Chem. 1991, 30, 2888.
(21) (a) Shoner, S. C.; Power, P. P. Angew. Chem., Int. Ed. Engl.
1991, 30, 330. (b) Ellison, J . J .; Ruhlandt-Senge, K.; Power, P. P.
Angew. Chem., Int. Ed. Engl. 1994, 33, 1178. (c) Ruhlandt-Senge, K.;
Power, P. P. Bull. Soc. Chim. Fr. 1992, 129, 594.

1790 Organometallics, Vol. 15, No. 7, 1996
Leung et al.
Ta ble 4. Electr och em ica l Da ta for Com p ou n d s
1, 2, 4, 5 a n d 7a
substituted methyl groups. The Fe-CR distances in 1
and 3 are also longer than the corresponding distance
of 2.051(5) Å in the two-coordinate iron diaryl complex
[FeAr2].10 The Fe-N distances of 2.111(8) and 2.135-
(5) Å in 1 are significantly longer than those of 1.937-
(2) and 1.943(2) Å in [FeEt2(bpy)2].3,4 However, they are
only slightly shorter than those of 2.169(8) and 2.179-
(7) Å in the dimesityl complex [FeMes2(py)2].9b The
Fe-C and Fe-N(aromatic) bond lengths in the mono-
alkyl species 5 are longer than the corresponding bond
lengths in 1 and 3, probably related to the increased
coordination number of the metal in 5.
a
c
Ep
Ep
(V)
E1/2
(V)
∆Ep
compd
[Fe(R1)2] (1)
(V)
(mV)b
W1
0.85
W2 -2.11 -2.32 -2.21
110
190
W3 -2.54 -2.73 -2.72
[Fe(R2)2] (2)
[Fe(R4)2] (4)
W1
0.64
W2 -1.82 -2.03 -1.93
210
W3
W1
W2
-2.31
0.61
-2.23
W3 -2.52 -2.72 -2.62
200
[FeR2(Cl)(TMEDA)] (5) W1
0.71
The C-Fe-N bite angles in the three complexes 1,
3, and 5 are similar and fall in the range 63.8(2)-66.8-
(2)°.
W2
-2.90
[Fe(SAr)2(R1H)] (7)
W1
W2
W3
0.15
0.58
-2.00
The dithiolate 7 exhibits a trigonal-planar geometry
in which the three ligands are bound to the iron center
in a propeller-like manner. The Fe-S distances in 7
are similar to the terminal Fe-S distances of 2.256(3)
Å observed in the binuclear complexes 10; these dis-
tances are shorter than the bridging Fe-S distances of
2.365(3) and 2.366(3) Å in 10. They are similar to the
range of Fe-S distances of 2.267(1)-2.285(1) Å in
[Fe(SAr)3]-, where the Fe(II) atom in the latter complex
exhibits a slightly distorted trigonal planar geometry.22
With reference to the monomeric thiolate complexes 8
and 9,21b the Fe-S distances in 7 are comparable to
those of 2.277(2) and 2.275(2) Å in 8 but are shorter
than those of 2.308(2) and 2.314(2) Å in 9. However,
Fe-S(thiolate) bonds are observed to increase in the
order 2.259(4)-2.261(3) Å for 7,21a 2.315(1) Å for [Fe-
a
Conditions: solvent, THF; supporting electrolyte, 0.4
M
b
c
a
Bu4NBF4 solution; room temperature. ∆Ep ) Ep - Ep
.
4 at room temperature in benzene solution are in the
range of 4.24-4.96 µB, which are close to the spin-only
value of 4.90 µB for four unpaired electrons. This
suggests a high-spin d6 electronic configuration with
four unpaired electrons for the iron(II) center in these
complexes. Since X-ray analysis has established that
compound 1 has a highly distorted tetrahedral geom-
etry, and the small crystal field splitting resulting from
tetrahedral geometry favors a high-spin electronic con-
figuration, it is conceivable that, at least from the
standpoint of their effective magnetic moments, the
iron(II) centers in 2 exist in a tetrahedral environment.
Nevertheless, attempts to obtain single crystals of 2 and
4 suitable for X-ray diffraction studies have not been
successful.
(SArip)2(SC(NMe2)2)2],23 and 2.338(2) Å for [Fe(SPh)4]2- 24
,
although the steric bulk of the thiolato ligands increases
in the reverse order -SPh > -SArip > -SAr. Obvi-
ously, this effect is not related to the steric bulk of the
hydrocarbon substituents on the thiolato ligands but
may be attributed both to the increased coordination
number around the central metal, which renders a
closer approach of thiolato ligands to the metal centers
difficult, and to the presence of electronic repulsion in
the anionic tetrathiolate complex.
The trigonal-planar arrangement of the three ligands
in 7 around the central metal is actually unsymmetrical.
The S-Fe-S angle in 7 is less than the corresponding
angles in the neutral dithiolate complexes 8 (121.8°) and
[Fe(SArip)2(SC(NMe2)2)2] (125.7(1)°).23 The large N(1)-
Fe-S(2) angle of 123.4(2)° in 7 over the remaining two
angles, viz. 118.7(2) and 117.8(1)° in the FeS2N plane,
may be attributed to the steric bulk of the C(SiMe3)2
group at the ortho position of the pyridine ring.
It has been reported that there is a weak agostic
interaction in 10, as indicated by a small M‚‚‚H distance
of ca. 1.8 Å.21a A relatively close M‚‚‚C distance of ca.
2.5 Å involving adajcent phenyl groups has also been
observed in the two-coordinate compounds 8 and 9 and
the dimeric three-coordinate compound 11.21b,c In this
work, no such agostic interaction is detected in com-
pound 7.
Likewise, the magnetic moment of 4.45 µB of the
pentacoordinated monoalkyl compound 5 implies a high-
spin d6 configuration with four unpaired electrons for
the iron(II) center.
The magnetic moment of 2.92 µB per iron atom for
the binuclear compound 3, being much lower than the
spin-only value for tetrahedral iron(II) with four un-
paired electrons, is apparently a consequence of anti-
ferromagnetic coupling between the two iron(II) centers.
The magnetic moment of the dithiolate compound 7
at room temperature was determined to be 5.11 µB. This
value indicates that the trigonal-planar iron(II) center
most likely adopts a high-spin d6 configuration with four
unpaired electrons.
The redox behavior of compounds 1-5 and 7 has been
studied by cyclic voltammetry with THF as solvent and
tetrabutylammonium tetrafluoroborate as the support-
ing electrolyte at a scan rate of 100 mV/s. Table 4
summarizes the electrochemical data for these com-
pounds. The dialkyl compounds 1 and 2 display similar
CVs consisting of an irreversible oxidation (0.85 V for
1 and 0.64 V for 2), a quasi-reversible reduction (-2.21
V for 1 and -1.93 V for 2), and an irreversible reduction
(-2.72 V for 1 and -2.31 V for 2). The dialkyl 4 shows
analogous anodic behavior, but its cathodic behavior is
slightly different from those of 1 and 2. Its CV consists
of an irreversible oxidation at 0.61 V, an irreversible
reduction at -2.23 V, and a quasi-reversible wave at
-2.62 V.
Ma gn etic P r op er ties a n d Electr och em istr y. The
magnetic moments of the dialkyl compounds 1, 2, and
(22) MacDonnell, F. M.; Ruhlandt-Senge, K.; Ellison, J . J .; Holm.
R. H.; Power, P. P. Inorg. Chem. 1995, 34, 1815.
(23) Bierbach, U.; Saak, W.; Haase, D.; Pohl, S. Z. Naturforsch. B
1991, 46, 1629.
(24) Coucouvanis, D.; Swenson, D.; Baenziger, N. C.; Murphy, C.;
Holah, D. G.; Sfarnas, N.; Simopoulos, A.; Kostikas, A. J . Am. Chem.
Soc. 1981, 103, 3350.
The dinuclear compound 3 did not show any redox
behavior within the limits of solvent decomposition. The
monoalkyl complex 5 shows an irreversible oxidation at

Fe(II) N-Functionalized-Alkyl Complexes
Organometallics, Vol. 15, No. 7, 1996 1791
at room temperature for 20 h. The grayish brown precipitate
was separated by filtration, and the filtrate was concentrated
to ca. 20 mL in vacuo followed by cooling to -30 °C for 1 day,
affording 1 as yellow crystals. Yield: 1.35 g (80%). Mp: 110-
112 °C. MS: m/ z (%) 529 (3%) [M]+, 456 (26%) [M - SiMe3]+,
293 (6%) [M - R1]+. Anal. Found: C, 55.82; H, 9.05; N, 5.43.
Calcd for C24H44N2Si4Fe: C, 54.51; H, 8.39; N, 5.30.
0.71 V and an irreversible reduction at -2.90 V. The
latter peak was superimposed on the fringe of THF
reduction.
Dithiolate complex 7 exhibits two irreversible peaks
at 0.15 and 0.58 V and an irreversible cathodic peak at
-2.00 V.
[F e{(CP h SiMe3)C5H4N-2}2], (2). To a suspension of FeCl2
(0.13 g, 1.06 mmol) in ether (20 mL) at room temperature was
added a solution of [{LiR2(TMEDA)}2] (0.71 g, 0.98 mmol) in
ether (30 mL). After the mixture was stirred for 6 h, all
volatile materials were removed in vacuo and the residue was
extracted with pentane (30 mL). After filtration, the resultant
red solution was concentrated under reduced pressure to ca.10
mL. When the temperature was lowered to -18 °C, dark red
crystals of 2 were obtained. Yield: 0.27 g (52%). Mp: 118-
120 °C dec. MS: m/ z 536 [M]+, 480 [(R2)2]+, 240 [R2]+, 225
[R2 - Me]+, 167 [R2 - SiMe3]+. Anal. Found: C, 65.72; H,
6.69; N, 5.03. Calcd for C30H36N2Si2Fe: C, 67.14; H, 6.76; N,
5.22.
Su m m a r y
Iron(II) dialkyl complexes [Fe{C(SiMe3)2C5H4N-2}2]
(1), [Fe{(CPhSiMe3)C5H4N-2}2] (2), [{Fe(CHSitBuMe2-
C5H4N-2)2}2] (3), and [Fe{CH(SiMe3)C9H6N-8}2] (4) are
readily prepared by the metathesis of chloride from
ferrous chloride with 2 molar equiv of the appropriate
sterically demanding N-functionalized alkyl ligands.
The monoalkyl iron(II) species 5 is obtained by treating
iron(II) chloride with the corresponding organolithium
reagent with strict and proper control of stoichiometry.
Single-crystal X-ray analysis revealed that 1 possesses
a highly distorted tetrahedral geometry, 3 is dimeric in
nature with the [Fe(CN)2] core adopting an eight-
membered chair conformation, and 5 is a five-coordinate
species. Magnetic moment measurements indicate that
compounds 1-5 are high-spin with four unpaired elec-
trons per iron center.
Compound 1 reacts readily with the bulky phenol 2,6-
tBu2-4-MeC6H2OH and the bulky thiophenol 2,4,6-tBu3-
C6H2SH to give the corresponding bis(aryloxide) 7 and
dithiolate 8, respectively. Both 7 and 8 are neutral,
monomeric, three-coordinate species with each bearing
an electron count of only 12.
[F e{CH(SitBu Me2)C5H4N-2}2]2, (3). To a suspension of
FeCl2 (0.12 g, 0.91 mmol) in ether (10 mL) was added a solution
of [{LiR3(TMEDA)}2] (0.60 g, 0.91 mmol) in the same solvent
(30 mL). After the mixture was stirred for 10 min, the deep
brown mixture was filtered immediately and allowed to stand
at ambient temperature for a few days to give 3 as brown
prismatic crystals. The crystals were washed with hexane and
dried in vacuo. Yield: 0.25 g (58%). Mp: 155-159 °C. Anal.
Found: C, 60.96; H, 8.53; N, 5.76. Calcd for C48H80N4Si4Fe2:
C, 61.12; H, 8.60; N, 5.94.
[F e{CH(SiMe3)C9H6N-8}2], (4). To a stirred suspension
of FeCl2 (0.38 g, 3.0 mmol) in ether (20 mL) at 0 °C was added
a solution of [LiR4(TMEDA)] (2.02 g, 6.0 mmol) in ether (40
mL). The resulting dark brown suspension was further stirred
at room temperature for 8 h. The gray precipitate was filtered
off, and the resultant solution was concentrated to ca. 20 mL
in vacuo followed by cooling to -30 °C to give 4 as dark brown
needle-shaped crystals. Yield: 0.94 g (65%). Mp: 161-163
°C dec. MS: m/ z (%) 484 (4.8) [M]+, 214 (25) [R3]+, 199 (100)
[R3 - CH3]+. Anal. Found: C, 62.73; H, 6.52; N, 5.59. Calcd
for C26H32N2Si2Fe: C, 64.45; H, 6.66; N, 5.78.
Exp er im en ta l Section
Gen er a l P r oced u r es. All manipulations were carried out
under an argon or dinitrogen atmosphere using standard
Schlenk techniques or in a drybox. Solvents were dried over
and distilled from CaH2 (hexane) and sodium benzophenone
(THF, ether, toluene) and degassed twice prior to use. Anhy-
drous FeCl2 was used as purchased from Fluka. 2,6-tBu2-4-
MeC6H2OH was purchased from Aldrich and recrystallized
from pentane before use. The organolithium reagents [{Li-
R1}2],13a [{LiR2(TMEDA)}2],14 [{LiR3(TMEDA)}2],14 and [LiR4-
(TMEDA)] were prepared according to literature procedures.14
2,4,6-tBu3C6H2SH was prepared by the published method.25
P h ysica l Mea su r em en ts. Mass spectra (EI, 70 eV) were
obtained on a VG7070F mass spectrometer. Melting points
were recorded on an Electrothermal melting point apparatus
and were uncorrected. Elemental (C, H, N) analyses were
performed by MEDAC Ltd., Brunel University, U.K. Magnetic
moments were measured in benzene solution by the Evans
method using a J EOL 60 MHz NMR spectrometer. Cyclic
voltammetric measurements were performed by using a BAS
CV-50W voltammetric analyzer. The electrochemical cell
consisted of a platinum-wire working electrode, a silver-wire
reference electrode, and a tungsten-wire counter electrode. All
samples were manipulated under an argon atmosphere. All
sample solutions (THF) were prepared to be 0.4 M in nBu4-
NBF4 (supporting electrolyte) and ca. 4 × 10-3 M in sample
complexes. Chemical potentials were internally referenced to
the FeCp2+/FeCp2 reference redox system.
[F e(CP h SiMe3C5H4N-2)(Cl)(TMEDA)], (5). A solution of
[{LiR2(TMEDA)}2] (0.48 g, 0.65 mmol) in ether (20 mL) was
added slowly to a suspension of anhydrous FeCl2 (0.17g, 1.30
mmol) in ether (10 mL). The resultant mixture was stirred
at room temperature for 10 h, whereupon a reddish brown
mixture was obtained. The mixture was filtered through
Celite, and the red filtrate was concentrated to ca. 10 mL.
When the temperature was lowered to -30 °C, red needle-
shaped crystals of 5 were obtained, which were washed with
cold pentane and dried in vacuo. Yield: 0.41 g (71%). Mp:
124-126 °C dec. Anal. Found: C, 55.73; H, 7.47; N, 8.89.
Calcd for C21H34N3ClSiFe: C, 56.31; H, 7.65; N, 9.38.
[F e(OC6H2-4-Me-2,6-tBu 2)2{CH(SiMe3)2C5H4N-2}], (6). A
solution of 4-Me-2,6-tBu2C6H2OH (0.46 g, 2.08 mmol) in hexane
(30 mL) was added dropwise to a stirred solution of 1 (0.55 g,
1.04 mmol) in hexane (20 mL) at 0 °C. The resultant clear
yellowish brown solution was further stirred at ambient
temperature for 8 h. The solution was filtered and then
concentrated to ca. 20 mL in vacuo, followed by cooling to -30
°C for 1 day to give 6 as colorless crystals. Yield: 0.32 g (41%).
Mp: 129-131 °C. Anal. Found: C, 69.75; H, 9.96; N, 2.81.
Calcd for C42H69NO2Si2Fe: C, 68.91; H, 9.50; N, 1.91.
[F e(SC6H2tBu 3-2,4,6)2{CH(SiMe3)2C5H4N-2}], (7). A hex-
ane solution (40 mL) of 2,4,6-tBu3C6H2SH (0.41 g, 1.47 mmol)
was added dropwise to a stirred solution of 1 (0.38 g, 0.73
mmol) in the same solvent (20 mL) at 0 °C. After addition
had been completed, the resultant pale brown solution was
further stirred for 8 h at ambient temperature. It was filtered
and the filtrate concentrated to ca. 20 mL in vacuo. When
Syn th esis. [F e{C(SiMe3)2C5H4N-2}2], (1). An ether solu-
tion (30 mL) of [{LiR1}2] (1.57 g, 3.2 mmol) was added dropwise
to a stirred suspension of FeCl2 (0.41 g, 3.2 mmol) in the same
solvent (50 mL) at 0 °C. The suspension was further stirred
(25) Rundel, W. Chem. Ber. 1968, 101, 2956.

1792 Organometallics, Vol. 15, No. 7, 1996
Leung et al.
the temperature was lowered to -30 °C for 1 day, yellow
crystals of 7 were obtained. Yield: 0.40 g (65%). Mp: 182-
185 °C dec. Anal. Found: C, 67.88; H, 9.70; N, 1.60. Calcd
for C48H81NS2Si2Fe: C, 67.96; H, 9.62; N, 1.65.
are summarized in Table 3. Atomic coordinates of 1, 3, 5, and
7 are given in the Supporting Information.
Ack n ow led gm en t. This research work was sup-
ported by Hong Kong Research Grants Council Earmark
Grants CUHK 22/91 and 306/94P.
X-r a y Str u ctu r e Deter m in a tion of Com p ou n d s 1, 3, 5,
a n d 7. Single crystals were sealed in 0.5 mm Lindemann glass
capillaries under argon. X-ray data were collected on a Nicolet
P4/PC diffractometer using graphite-monochromatized Mo KR
radiation (λ ) 0.710 73 Å) in the ω/2θ scan mode. N unique
reflections were measured, and N0 “observed” reflections with
|Fo| g 3σ(|Fo|) were used in the structure solution and refine-
Su p p or tin g In for m a tion Ava ila ble: Tables giving struc-
ture determination summaries, atomic and thermal param-
eters, and bond distances and angles for 1, 3, 5, and 7,
additional drawings of the structures of 3 and 7, and figures
giving cyclic voltammetry traces for 1, 2, 4, 5, and 7 (43 pages).
Ordering information is given on any current masthead page.
2
ment. The weighting scheme w ) [σ2|Fo| + 0.0008|Fo| ]-1 was
2
used for 1, w ) [σ2|Fo| + 0.0002|Fo| ]-1 for 3, w ) [σ2|Fo| +
2
2
0.0005|Fo| ]-1 for 5, and w ) [σ2|Fo| + 0.0035|Fo| ]-1 for 7. The
structures were solved by direct phase determination using
the computer program SHELXTL-PC on a PC 486 and refined
by full-matrix least squares with anisotropic thermal param-
eters for the non-hydrogen atoms.26 Hydrogen atoms were
introduced in their idealized positions and included in struc-
ture factor calculations with assigned isotropic temperature
factors.27 The crystal data and structure analysis parameters
OM950806L
(26) Sheldrick G. M. In Crystallographic Computing 3: Data Col-
lection, Structure Determination, Proteins, and Databases; eds. Shel-
drick, G. M., Kruger, C., Goddard, R., Eds.; Oxford University Press:
New York, 1985; p 175.
(27) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1974.