Iron(II)-nitrile complexes: Synthesis, structure and property of trans-[FeH(NCR)(dppe)2]+X- (dppe=Ph2PCH2CH2PPh2: R=CH3, CH2CH2OCH3, CH2CH2CH2Cl, C6H5: X=Cl, BPh4, BF4)

Article abstract of DOI:10.1016/S0022-328X(99)00392-7

Dissolution of trans-FeHCl(dppe)₂, 1, in various nitriles under argon led to the formation of complexes of the type trans-[FeH(NCR)(dppe)₂]Cl (2a (R=CH₃), 3a (R=CH₂CH₂OMe), 4a (R=CH₂CH₂CH₂Cl), 5a (R=Ph)) in several hours. Complexes 2a-4a could be further converted to trans-[FeH(NCR)(dppe)₂][BPh₄] (2b-4b) and trans-[FeH(NCR)(dppe)₂][BF₄] (2c-4c) when they were treated with NaBPh₄ and NaBF₄, respectively. The stability and electrochemical properties of these complexes appeared to depend mainly on their counteranions (Cl^-, BPh₄^-, BF₄^-). Compounds 2b, 2c, 3b, 3c, 4b and 4c reacted with KCN or NaCN to give [FeH(CN)(dppe)₂] (6). Compound 6 underwent electrophilic addition at the cyano nitrogen by RSO₃CF₃ (R=Me, H) to give [FeH(CNR)(dppe)₂][SO₃CF₃] (7a for R=Me, 7b for R=H). Crystallographic data for 2b: monoclinic space group P2₁/c, a=22.508(1) A, b=16.120(1) A, c=19.257(1) A, β=113.86(1)°, Z=4, R(wR₂)=0.0361(0.0882). Crystallographic data for 3b: triclinic space group P1, a=13.240(1) A, b=14.732(2) A, c=19.807(1) A, α=75.276(6)°, β=72.466(6)°, γ=82.033(6)°, Z=2, R(wR₂)=0.0368(0.0835). Crystallographic data for 7a: monoclinic space group P2₁/c, a=12.456(1) A, b=21.880(3) A, c=19.924(3) A, β=108.08(1)°, Z=4, R(wR₂)=0.0663 (0.1647).

Full text of DOI:10.1016/S0022-328X(99)00392-7

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 589 (1999) 138–149
Iron(II)–nitrile complexes: synthesis, structure and property of
trans-[FeH(NCR)(dppe)2]+X− (dppe=Ph2PCH2CH2PPh2:
R=CH3, CH2CH2OCH3, CH2CH2CH2Cl, C6H5: X=Cl, BPh4,
BF4)
Jae-Gyung Lee a, Beom-Sang Yoo a, Nam-Sun Choi a, Keun Il Park b, Sung Il Cho b,
Chongmok Lee c, Soon W. Lee a,*
a Department of Chemistry, Sungkyunkwan Uni6ersity, Natural Science Campus, Suwon 440-746, South Korea
b Department of Chemical Engineering, Uni6ersity of Seoul, Seoul 130-143, South Korea
c Department of Chemistry, Ewha Women’s Uni6ersity, Seoul 120-750, South Korea
Received 27 April 1999; received in revised form 3 July 1999
Abstract
Dissolution of trans-FeHCl(dppe)2, 1, in various nitriles under argon led to the formation of complexes of the type
trans-[FeH(NCR)(dppe)2]Cl (2a (R=CH3), 3a (R=CH2CH2OMe), 4a (R=CH2CH2CH2Cl), 5a (R=Ph)) in several hours.
Complexes 2a–4a could be further converted to trans-[FeH(NCR)(dppe)2][BPh4] (2b–4b) and trans-[FeH(NCR)(dppe)2][BF4]
(2c–4c) when they were treated with NaBPh4 and NaBF4, respectively. The stability and electrochemical properties of these
complexes appeared to depend mainly on their counteranions (Cl−, BPh4−, BF4−). Compounds 2b, 2c, 3b, 3c, 4b and 4c reacted
with KCN or NaCN to give [FeH(CN)(dppe)2] (6). Compound 6 underwent electrophilic addition at the cyano nitrogen by
RSO3CF3 (R=Me, H) to give [FeH(CNR)(dppe)2][SO3CF3] (7a for R=Me, 7b for R=H). Crystallographic data for 2b:
,
,
,
monoclinic space group P21/c, a=22.508(1) A, b=16.120(1) A, c=19.257(1) A, i=113.86(1)°, Z=4, R(wR2)=0.0361(0.0882).
(
,
,
,
Crystallographic data for 3b: triclinic space group P1, a=13.240(1) A, b=14.732(2) A, c=19.807(1) A, h=75.276(6)°,
i=72.466(6)°, k=82.033(6)°, Z=2, R(wR2)=0.0368(0.0835). Crystallographic data for 7a: monoclinic space group P21/c,
,
,
,
a=12.456(1) A, b=21.880(3) A, c=19.924(3) A, i=108.08(1)°, Z=4, R(wR2)=0.0663 (0.1647). © 1999 Elsevier Science S.A.
All rights reserved.
Keywords: Iron nitrile; Crystallographic data; Counteranions; Electrophilic addition
some related complexes possessing XꢀCꢁN ligands in
which X is other than an alkyl or aryl substituent [3].
1. Introduction
Nitriles (RꢀCꢁN) are isoelectronic with dinitrogen
(N2) and their transition-metal complexes can serve as
convenient precursors for a wide variety of interesting
metal complexes. Nitriles have two potential coordina-
tion sites, the nitrile nitrogen lone pair (an end-on
fashion, A) and the carbon–nitrogen triple bond (a
side-on fashion, B) [1,2]. In addition, a combined mode
(C) of these two fundamental modes has often been
observed in several polynuclear complexes as well as in
Nitrile complexes are usually prepared by dissolving
a metal halide in the nitrile or replacing CO from
carbonyl complexes. They can even be prepared from
other nitrile complexes by nitrile exchange reaction [3].
Nitrile complexes provide an example of activation
because the electrophilicity of the nitrile a-carbon is
enhanced on coordination. For example, coordinated
nitriles were reduced to amines in a stepwise manner by
* Corresponding author. Tel.: +82-331-290-7066; fax: +82-331-
290-7075.
E-mail address: swlee@chem.skku.ac.kr (S.W. Lee)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00392-7

J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
139
addition of H− (a nucleophile) at the a-carbon fol-
lowed by addition of H+ (an electrophile) at the nitrile
nitrogen [4,5]. In addition, addition of primary amines
(RNH2) to nitrile complexes led to NHR-substituted
imine complexes [6].
Recently, Pombeiro’s group prepared a series of
iron(II)–isocyanide complexes, trans-[FeH(CNR)-
(dppe)2][A] (R=alkyl or aryl, A=BF4 or PF6), by
treating trans-[FeHCl(dppe)2] (1), with appropriate
cyanides in the presence of Tl[A] [7]. This group ex-
tended this type of chemistry to alkynes and carbon
disulfide [8]. In addition, 1 is well known as a precursor
for the dinitrogen complex [FeH(N2)(dppe)2]+, from
Cyclic voltammetric studies were carried out by using
BAS 100 electrochemical analyzer. Solutions
a
(CH2Cl2) were ca. 1 mM in the metal complex and
contained 0.1 M tetrabutylammonium tetrafluorobo-
rate ([nBu4N][BF4]) supporting electrolyte. For these
measurements, a conventional three-electrode cell (Pt-
wire working electrode, Pt-plate auxiliary electrode,
Ag/AgCl reference electrode) was employed. The E°
value for the [Cp2Fe]/[Cp2Fe]+ couple was 0.632 V at
300 mV s−1 in this cell. All the experiments were
carried out under nitrogen.
1H- and 13C{1H}-NMR spectra were recorded with a
Bruker AMX 500 MHz spectrometer with reference to
internal solvent resonances and reported relative to
tetramethylsilane. 31P-NMR spectra were also recorded
with a Bruker AMX 500 MHz spectrometer with refer-
ence to external 85% H3PO4. IR spectra were recorded
with a Nicolet 205 FTIR spectrophotometer. Melting
points were measured with a Thomas Hoover capillary
melting point apparatus without calibration. Elemental
analyses were performed by the Korea Basic Science
Center.
which
[FeH(NCCH3)(dppe)2][ClO4]
and
[FeH(-
NCPh)(dppe)2][BPh4] were prepared by replacement of
N2 with the corresponding nitriles [9].When 1 dissolved
in nitriles under argon, 1 exhibited an immediate color
change from red to orange or yellow. This interesting
phenomenon prompted us to investigate as to what the
products were and what their structures were. Herein
we report the synthesis, structure and properties of
iron(II)–nitrile complexes of the type trans-[FeH(-
NCR)(dppe)2]+X− (R=CH3, CH2CH2OCH3, CH2-
CH2CH2Cl, C6H5: X=Cl, BPh4, BF4).
2.1. Preparation of [FeH(NCCH3)(dppe)2]Cl (2a)
CH3CN (15 ml) was added to 0.178 g (0.20 mmol) of
1 at room temperature (r.t.) and the red slurry was
stirred for 1 h. The resultant yellow solution was
filtered and the solvent was removed under vacuum to
give yellow–brown solids. These solids were washed
with diethyl ether (2×30 ml) and recrystallized from
acetonitrile–diethyl ether to give yellow crystals of 2a
(0.132 g, 0.14 mmol, 71%). 1H-NMR (CD2Cl2): l
7.370–6.710 (40H, m, phenyl, Ph2PCH2CH2PPh2),
2.483 (4H, broad m, Ph2PCH2CH2PPh2), 1.969 (4H,
broad m, Ph2PCH2CH2PPh2), 1.340 (3H, s, CH3CN),
−20.762 (1H, quintet, 2JPꢀH=46.5 Hz, HꢀFe). 31P-
2. Experimental
Unless otherwise stated, all the reactions were per-
formed with standard Schlenk line and cannula tech-
niques under an argon atmosphere. Air-sensitive solids
were manipulated in a glove box filled with argon.
Glassware was soaked in KOH-saturated 2-propanol
for ca. 24 h and washed with distilled water and
acetone before use. Glassware was either flame-dried or
oven-dried. Hydrocarbon solvents were stirred over
concentrated H2SO4 for ca. 48 h, neutralized with
K2CO3, stirred over sodium metal and distilled by
vacuum transfer. Benzene, diethyl ether and tetrahydro-
furan (THF) were stirred over sodium metal and dis-
tilled by vacuum transfer. Dichloromethane and
acetonitrile (CH3CN) were stirred over CaH2 and dis-
tilled by vacuum transfer. NMR solvents (C6D6,
CDCl3, CD2Cl2 and CD3CN) were degassed by freeze–
pump–thaw cycles before use and stored over molecu-
lar sieves under argon. FeCl2·4H2O, bis(diphenylphos-
phino)ethane (dppe=Ph2PCH2CH2PPh2), 4-chlorobu-
tyronitrile (ClCH2CH2CH2CN), 3-methoxypropionitrile
(CH3OCH2CH2CN) and benzonitrile (C6H5CN) were
purchased from Fluka Chemical. Sodium tetraphenyl-
borate (NaBPh4), sodium tetrafluoroborate (NaBF4),
methyl trifluoromethanesulfonate (MeSO3CF3, MeOTf)
and trifluoromethanesulfonic acid (CF3SO3H, HOTf)
were purchased from Aldrich Chemical. FeHCl(dppe)2,
(1), was prepared by the literature method [10].
2
NMR (CD2Cl2): l 86.555 (d, JPꢀH=46.5 Hz). Anal.
Calc. for C54H52NP4ClFe: C, 69.73; H, 5.63; N, 1.51.
Found: C, 69.22; H, 5.79; N, 1.78. M.p. (dec.): 118–
120°C. IR (KBr): 2250 (CN) cm−1
.
2.2. Preparation of [FeH(NCCH3)(dppe)2][BPh4] (2b)
On addition of NaBPh4 (0.411 g, 1.2 mmol) to 30 ml
of CH3CN containing 2a (0.930 g, 1 mmol), a white
powder immediately formed. The resulting slurry was
allowed to stir for 1 h and then filtered. The solvent was
removed under vacuum to give yellow solids. These
solids were extracted with CH2Cl2 (2×30 ml) and
the solvent was removed under vacuum to give yellow
solids that were recrystallized from CH2Cl2–hexane
o give orange crystals of 2b (1.190 g, 0.98 mmol, 98%).
1H-NMR (CDCl3): l 7.438–6.661 (60H, m, phenyl,
Ph2PCH2CH2PPh2, BPh4), 2.407 (4H, broad m, Ph2PC-
H2CH2PPh2), 1.943 (4H, broad m, Ph2PCH2CH2-

140
J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
PPh2), 0.970 (3H, s, CH3CN), −20.793 (1H, quintet,
2JPꢀH=47 Hz, HꢀFe). 13C{1H}-NMR (CDCl3):
solvent was removed under vacuum to give yellow
solids. These solids were extracted with 20 ml of
CH2Cl2 and the solvent was removed. The resulting
bright yellow solids were washed with THF (2×20 ml)
and recrystallized from CH2Cl2–hexane to give orange
crystals of 3b (0.21 g, 0.17 mmol, 85%). 1H-NMR
(CD2Cl2): l 7.392–6.698 (40H, m, phenyl), 3.314 (3H,
s, MeOCH2CH2CN), 3.203 (2H, t, J=5.6 Hz,
MeOCH2CH2CN), 2.601 (4H, broad m, Ph2PCH2CH2-
PPh2), 2.087 (4H, broad m, Ph2PCH2CH2PPh2), 2.052
(2H, t, J=5.6 Hz, MeOCH2CH2CN), −20.355 (1H,
quintet, 2JPꢀH=47.0 Hz, HꢀFe). 13C{1H}-NMR
l
138.280–121.804
(Ph),
34.782
(Ph2PCH2-
CH2PPh2), 0.735 (CH3CN). 31P-NMR (CDCl3): l
85.468 (d, 2JPꢀH=47 Hz). Anal. Calc. for C78H72-
BNP4Fe: C, 77.17; H, 5.98; N, 1.15. Found: C, 77.51;
H, 5.72; N, 1.67. M.p. (dec.): 138–140°C. IR (KBr):
2244 (CN), 1843 (FeꢀH) cm−1
.
2.3. Preparation of [FeH(NCCH3)(dppe)2][BF4] (2c)
This compound was prepared in the same method
employed to prepare 2b. NaBF4 (0.165 g, 1.50 mmol)
was added to 80 ml of CH3CN containing 2a (0.931 g,
1.01 mmol) and the resulting solution was allowed to
stir for 14 h. Compound 2c was recrystallized from
CH2Cl2–hexane to give orange crystals (0.915 g, 0.93
(CD2Cl2):
l
136.610, 135.872, 135.174, 133.842,
133.021, 130.685, 130.351, 128.691, 128.449, 126.254,
122.366 (Ph), 67.070 (MeOCH2CH2CN), 59.511
(MeOCH2CH2CN), 33.133 (Ph2PCH2CH2PPh2), 22.488
(MeOCH2CH2CN). 31P-NMR (CD2Cl2): l 84.985 (d,
2JPꢀH=47.0 Hz). Anal. Calc. for C80H76BNOP4Fe: C,
76.38; H, 6.09; N, 1.11. Found: C, 76.54; H, 6.43; N,
1.25. M.p. (dec.): 150–152°C. IR (KBr): 2236 (CN),
1
mmol 92%). H-NMR (CDCl3): l 7.468–6.683 (40H,
m, phenyl, Ph2PCH2CH2PPh2), 2.674 (4H, broad m,
Ph2PCH2CH2PPh2), 2.056 (4H, broad m, Ph2PCH2-
CH2PPh2), 1.795 (3H, s, CH3CN), −20.974 (1H, quin-
1842 (FeꢀH) cm−1
.
2
tet, JPꢀH=46.7 Hz, HꢀFe). 13C{1H}-NMR (CDCl3): l
136.698, 135.139, 133.872, 133.105, 130.489, 130.319,
2.6. Preparation of [FeH(NCCH2CH2OMe)(dppe)2]-
[BF4] (3c)
129.189, 128.335, 33.825 (Ph2PCH2CH2PPh2), 0.694
2
(CH3CN). 31P-NMR (CDCl3): l 86.142 (d, JPꢀH=46.7
Hz). Anal. Calc. for C54H52BNF4P4Fe: C, 66.08; H,
5.34; N, 1.43. Found: C, 66.43; H, 4.99; N, 1.53. M.p.
This compound was prepared by the same method
employed to prepare 3b. NaBF4 (0.22 g, 0.2 mmol) was
added to 15 ml of MeOCH2CH2CN containing 3a
(0.097 g, 0.1 mmol) and the resulting solution was
stirred for 2 h. 3c was recrystallized from CH2Cl2–hex-
ane to give orange crystals (0.065 g, 0.063 mmol,
63.4%). 1H-NMR (CDCl3): l 7.460–6.719 (40H, m,
phenyl), 3.339 (3H, s, MeOCH2CH2CN), 2.616 (4H,
broad m, Ph2PCH2CH2PPh2), 2.423 (2H, broad m,
MeOCH2CH2CN), 2.051 (4H, broad m, Ph2PCH2CH2-
PPh2), 1.759 (2H, broad m, MeOCH2CH2CN), −
(dec.): 189–191°C. IR (KBr): 2245 (CN) cm−1
.
2.4. Preparation of [FeH(NCCH2CH2OMe)(dppe)2]Cl
(3a)
MeOCH2CH2CN (20 ml) was added to 0.267 g (0.3
mmol) of 1 at r.t. and the resulting solution was stirred
for 2 h. The solvent was removed under vacuum and
washed with diethyl ether (2×30 ml) to give yellow
solids of 3a (0.252 g, 0.26 mmol, 86.2%). 1H-NMR
2
20.774 (1H, quintet, JPꢀH=36.6 Hz, HꢀFe). 13C{1H}-
(CDCl3):
l
7.436–6.702
(40H,
m,
phenyl,
NMR (CDCl3): l 136.517, 136.447, 135.196, 135.139,
133.913, 133.133, 130.571, 129.309, 128.409 (Ph), 67.786
(MeOCH2CH2CN), 59.588 (MeOCH2CH2CN), 33.487
(Ph2PCH2CH2PPh2), 23.209 (MeOCH2CH2CN). 31P-
{1H}-NMR (CDCl3): l 85.558 (d, 2JPꢀH=36.6 Hz).
Anal. Calc. for C56H56BNOF4P4Fe: C, 65.58; H, 5.50;
N, 1.37. Found: C, 65.53; H, 4.91; N, 1.15. M.p. (dec.):
Ph2PCH2CH2PPh2), 3.341 (3H, s, MeOCH2CH2CN),
2.613 (4H, broad m, Ph2PCH2CH2PPh2), 2.373 (2H,
broad m, MeOCH2CH2CN), 2.042 (4H, broad m,
Ph2PCH2CH2PPh2), 1.876 (2H, broad m, MeOCH2-
CH2CN), −20.762 (1H, quintet, 2JPꢀH=46.8 Hz,
HꢀFe). 31P-NMR (CDCl3): l 85.347 (d, 2JPꢀH=46.8
Hz). Anal. Calc. for C56H56NOP4ClFe: C, 69.04; H,
5.79; N, 1.44. Found: C, 69.24; H, 5.26; N, 1.11. M.p.
(dec.): 139–141°C. IR (KBr): 2236 (CN), 1886 (FeꢀH)
165–167°C. IR (KBr): 2239 (CN), 1875 (FeꢀH) cm−1
.
2.7. Preparation of [FeH(NCCH2CH2CH2Cl)(dppe)2]Cl
(4a)
cm−1
.
2.5. Preparation of
[FeH(NCCH2CH2OMe)(dppe)2][BPh4] (3b)
ClCH2CH2CH2CN (10 ml) was added to 0.178 g
(0.20 mmol) of 1 at r.t. and the solution was stirred
for 1 h. The resultant solution was filtered and the
solvent was removed under vacuum and washed with
diethyl ether (2×30 ml) to give yellow solids of 4a
(0.191 g, 0.19.mmol, 95%). 1H-NMR (CDCl3): l 7.421–
6.789 (40H, m, phenyl), 3.212 (2H, broad m,
MeOCH2CH2CN (10 ml) containing 1 (0.178 g, 0.20
mmol) was stirred for 4 h and then NaBPh4 (0.075 g,
0.22 mmol) was added. The resulting solution was
allowed to stir for an additional 1 h and filtered and the

J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
141
ClCH2CH2CH2CN), 2.734 (4H, broad m, Ph2PCH2-
CH2Ph2), 2.081 (4H, broad m, Ph2PCH2CH2PPh2),
1.667 (2H, broad m, ClCH2CH2CH2CN), 1.602 (2H, t,
J=7 Hz, ClCH2CH2CH2CN), −21.022 (1H, quintet,
2JPꢀH=36.6 Hz, HꢀFe). 31P-NMR (CD2Cl2): l 85.317
(phenyl), 43.824 (ClCH2CH2CH2CN), 33.269 (Ph2P-
CH2CH2PPh2), 28.508 (ClCH2CH2CH2CN), 18.432
(ClCH2CH2CH2CN). 31P-NMR (CD2Cl2): l 84.654 (d,
2JPꢀH=36.6 Hz). Anal. Calc. for C56H55BNF4P4ClFe:
C, 64.42; H, 5.31; N, 1.34. Found: C, 64.77; H, 5.12; N,
1.54. M.p. (dec.): 172–174°C. IR (KBr): 2232 (CN).
2
(d, JPꢀH=36.6 Hz). Anal. Calc. for C56H55NP4Cl2Fe:
C, 67.76; H, 5.58; N, 1.41. Found: C, 67.39; H, 4.77; N,
1.47. M.p. (dec.): 130–132°C. IR (KBr): 2232 (CN),
2.10. Preparation of [FeH(NCPh)(dppe)2]Cl (5a)
1860 (FeꢀH) cm−1
.
PhCN (10 ml) was added to 0.178 g (0.20 mmol) of
1 at r.t. and the solution was stirred for 1 h. The color
of the solution changed from red–violet to yellow. The
resultant solution was filtered and the solvent was
removed under vacuum and washed with benzene (2×
30 ml) to give yellow solids of 5a (0.181 g, 0.18 mmol,
91%). 1H-NMR (CDCl3): l 7.805–6.769 (45H, m,
phenyl), 2.550 (4H, broad m, Ph2PCH2CH2PPh2), 2.095
(4H, broad m, Ph2PCH2CH2PPh2), −19.224 (1H,
2.8. Preparation of [FeH(NCCH2CH2CH2Cl)(dppe)2]-
[BPh4] (4b)
NaBPh4 (0.034 g, 0.1 mmol) was added to 10 ml of
THF containing 4a (0.05 g, 0.05 mmol) and then the
resulting solution was stirred for 2 h. The solvent was
removed under vacuum to give yellow solids, which
were extracted with 20 ml of CH2Cl2. The solvent was
again removed and the resulting yellow solids were
washed with diethyl ether (2×10 ml) and recrystallized
from CH2Cl2–hexane to give orange crystals of 4b
(0.043 g, 0.034 mmol, 67.4%). 1H-NMR (CDCl3): l
7.465–6.651 (60H, m, phenyl), 2.830 (2H, broad t,
J=5.5 Hz, ClCH2CH2CH2CN), 2.470 (4H, broad m,
Ph2PCH2CH2PPh2), 2.024 (4H, broad m, Ph2PCH2-
CH2PPh2), 1.739 (2H, broad m, ClCH2CH2CH2CN),
1.177(2H, m, ClCH2CH2CH2CN), −20.701 (1H, quin-
2
quintet, JPꢀH=49.8 Hz, HꢀFe). 31P-NMR (CDCl3): l
83.779 (d, 2JPꢀH=49.8 Hz). Anal. Calc. for
C59H54NP4ClFe: C, 71.42; H, 5.49; N, 1.41. Found: C,
71.28; H, 5.12; N, 1.43. M.p. (dec.): 118–120°C. IR
(KBr): 2050 (CN) cm−1
.
2.11. Preparation of [FeH(CN)(dppe)2] (6)
2
tet, JPꢀH=47 Hz, HꢀFe). 13C{1H}-NMR (CD2Cl2): l
2.11.1. Reaction of 2b with NaCN
To a mixed solvent (20 ml) THF–MeOH (1:1) were
added 2b (0.121 g, 0.1 mmol) and NaCN (0.007 g, 0.15
mmol) and the resulting solution was stirred for 8 h.
The solvent was removed under vacuum and the re-
maining solids were extracted with 20 ml of
dichloromethane and washed with hexane (2×20 ml)
to give a yellow powder of 6 (0.081 g, 0.09 mmol, 88%).
1H-NMR (CDCl3): l 7.516–6.990 (40H, m, phenyl,
Ph2PCH2CH2PPh2), 2.467 (4H, broad m, Ph2PCH2-
CH2PPh2), 1.983 (4H, broad m, Ph2PCH2CH2PPh2),
136.614, 135.628, 134.781, 133.660, 130.706, 129.129,
128.544, 126.312, 122.404 (Ph), 43.498 (ClCH2-
CH2CH2CN), 32.910 (Ph2PCH2CH2PPh2), 28.322
(ClCH2CH2CH2CN), 18.303 (ClCH2CH2CH2CN). 31P-
NMR (CD2Cl2): l 84.080 (d, 2JPꢀH=47 Hz). Anal.
Calc. for C80H75BNP4ClFe: C, 75.28; H, 5.92; N, 1.10.
Found: C, 75.08; H, 5.43; N, 1.13. M.p. (dec.): 151–
153°C. IR (KBr): 2248 (CN), 1841.2 (FeꢀH) cm−1
.
2.9. Preparation of
[FeH(NCCH2CH2CH2Cl)(dppe)2][BF4] (4c)
2
−14.748 (1H, quintet, JPꢀH=46 Hz, HꢀFe). 13C{1H}-
NMR (CDCl3): l 164.421 (CN), 139.591, 138.536,
134.685, 134.206, 129.259, 129.098, 127.671 (phenyl),
34.143 (t, JPꢀC=13.1 Hz, Ph2PCH2CH2PPh2). 31P-
NMR (CDCl3): l 90.175 (d, 2JPꢀH=46 Hz). Anal. Calc.
for C53H49NP4Fe: C, 72.36; H, 5.61; N, 1.59. Found: C,
72.54; H, 5.25; N, 1.72. M.p. (dec.): 188–190°C. IR
NaBF4 (0.022 g, 0.2 mmol) was added to 10 ml of
ClCH2CH2CH2CN containing 4a (0.095 g, 0.1 mmol)
and then the resulting solution was stirred for 2 h. The
solvent was removed under vacuum to give yellow
solids, which were extracted with 15 ml of CH2Cl2. The
solvent was removed again and the resulting yellow
solids were recrystallized from CH2Cl2–hexane to give
yellow crystals of 4c (0.037 g, 0.034 mmol, 67.4%).
1H-NMR (CD2Cl2): l 7.458–7.140 (40H, m, phenyl,
Ph2PCH2CH2PPh2), 3.272 (2H, t, J=6 Hz, ClCH2CH2-
CH2CN), 2.599 (4H, broad m, Ph2PCH2CH2PPh2),
2.258 (2H, t, J=7 Hz, ClCH2CH2CH2CN), 2.059 (4H,
(KBr): 2050 (CN) cm−1
.
2.11.2. Reaction of 2b, 2c, 3b, 3c, 4b or 4c with KCN
To a mixed solvent (20 ml) THF–MeOH (1:1) were
added 2b (0.150 g, 0.12 mmol) and KCN (0.012 g, 0.18
mmol) and the solution was stirred for 6 h. The color of
the solution changed from orange to yellow–green. The
solvent was removed under vacuum and the remaining
solids were extracted with 30 ml of dichloromethane
and washed with hexane (2×20 ml) to give yellow
powder of 6 (0.085 g, 0.09 mmol, 77%).
broad m, Ph2PCH2CH2PPh2), 1.526 (2H, broad m,
2
ClCH2CH2CH2CN), −20.599 (1H, quintet, JPꢀH
=
36.6 Hz, HꢀFe). 13C{1H}-NMR (CD2Cl2): l 136.062,
135.005, 133.714, 133.066, 130.586, 129.208, 128.445

142
J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
2
To a mixed solvent (20 ml) CH2Cl2–MeOH (1:1)
(s, NCH3). 31P-NMR (CDCl3): l 88.544 (d, JPꢀH=46
Hz). Anal. Calc. for C55H52NO3F3P4SFe: C, 63.29;
H, 5.02; N, 1.34. Found: C, 63.65; H, 5.37; N, 1.27.
M.p. (dec.): 96–98°C. IR (KBr): 2118 (CN)
were added 2c (0.098 g, 0.1 mmol) and KCN (0.10 g,
0.15 mmol) and the solution was stirred for 7 h. The
solvent was removed under vacuum and the remaining
solids were extracted with 20 ml of dichloromethane
and washed with hexane (2×20 ml) to give yellow
powder of 6 (0.066 g, 0.08 mmol, 75%).
To a mixed solvent (20 ml) THF–MeOH (1:1) were
added 3b (0.126 g, 0.1 mmol) and KCN (0.010 g, 0.15
mmol) and the solution was stirred for 8 h. The sol-
vent was removed under vacuum and the remaining
solids were extracted with 30 ml of dichloromethane
and washed with hexane (2×20 ml) to give yellow
powder of 6 (0.076 g, 0.086 mmol, 86%).
To a mixed solvent (20 ml) THF–MeOH (1:1) were
added 3c (0.103 g, 0.1 mmol) and KCN (0.010 g, 0.15
mmol) and the solution was stirred for 12 h. The
solvent was removed under vacuum and the remaining
solids were extracted with 30 ml of dichloromethane
and washed with hexane (2×20 ml) to give yellow
powder of 6 (0.080 g, 0.09 mmol, 90%).
To a mixed solvent (20 ml) THF–MeOH (1:1) were
added 4b (0.128 g, 0.1 mmol) and KCN (0.010 g, 0.15
mmol) and the solution was stirred for 12 h. The
solvent was removed under vacuum and the remaining
solids were extracted with 30 ml of dichloromethane
and washed with hexane (2×20 ml) to give yellow
powder of 6 (0.066 g, 0.075 mmol, 75%).
cm−1
.
2.12.2. [FeH(CNH)(dppe)2][SO3CF3] (7b)
Trifluoromethanesulfonic acid (CF3SO3H,
4 ml,
0.045 mmol) was added to 10 ml of CH2Cl2 containing
6 (0.04 g, 0.045 mmol) and then the resulting solution
was allowed to stir for 3 h. The color of the solution
turned from yellow to yellow–green. The solvent was
removed under vacuum to give yellow–green solids,
which were washed with diethyl ether (2×10 ml) and
pentane (2×10 ml) and then dried under vacuum to
give 7b (0.042 g, 0.041 mmol, 91%). 1H-NMR
(CDCl3): l 7.429–7.034 (40H, m, phenyl, Ph2PCH2-
CH2PPh2), 2.456 (4H, broad m, Ph2PCH2CH2PPh2),
2.000 (4H, broad m, Ph2PCH2CH2PPh2), 1.858 (1H, s,
2
NꢀH), −11.115 (1H, quintet, JPꢀH=47 Hz, HꢀFe).
13C{1H}-NMR (CDCl3): l 136.876, 135.906, 133.996,
133.426, 130.489, 130.348, 128.847, 128.203 (phenyl),
34.052 (Ph2PCH2CH2PPh2). 31P-NMR (CDCl3):
l
88.061 (d, 2JPꢀH=47 Hz). Anal. Calc. for C54H50-
NO3F3P4SFe: C, 62.98; H, 4.89; N, 1.36. Found: C,
62.67; H, 4.34; N, 1.57. M.p. (dec.): 132–134°C. IR
(KBr): 3140 (NH), 1978 (CN) cm−1
.
To a mixed solvent (10 ml) CH2Cl2–MeOH (1:1)
were added 4c (0.052 g, 0.05 mmol) and KCN (0.005
g, 0.08 mmol) and the solution was stirred for 12 h.
The solvent was removed under vacuum and the re-
maining solids were extracted with 30 ml of
dichloromethane and washed with hexane (2×20 ml)
to give 6 as a yellow powder (0.020 g, 0.023 mmol,
46%).
2.13. X-ray structure determination
All X-ray data were collected with use of either a
Siemens P4 (2b and 7a) or an Enraf–Nonius CAD4
(3b) diffractometer equipped with a Mo X-ray tube
and a graphite crystal monochromator. The orienta-
tion matrix and unit cell parameters were determined
by least-squares analyses of the setting angles of
25–40 reflections in the range 10.0°B2qB30.0°.
Three check reflections were measured every 100
reflections throughout data collection and showed no
significant variations in intensity. Intensity data were
corrected for Lorenz and polarization effects. Decay
corrections were also made. The intensity data were
empirically corrected with „-scan data. All calcula-
tions were carried out with use of the SHELX-97 pro-
grams [11].
A yellow crystal of 2b, shaped as a block, of
approximate dimensions 0.35×0.68×0.75 mm3, was
used for crystal and intensity data collection. The unit
cell parameters and systematic absences, h0l (l=2n+
1) and 0k0 (k=2n+1), unambiguously indicated P21/
c as a space group. The structure was solved by
the direct method and refined by full-matrix least-
squares calculations of F2s, initially with isotropic and
finally anisotropic temperature factors for all non-
hydrogen atoms. The hydride ligand was located
2.12. Preparation of [FeH(CNR)(dppe)2][SO3CF3]
2.12.1. [FeH(CNMe)(dppe)2][SO3CF3] (7a)
Methyl trifluoromethanesulfonate (MeSO3CF3, 10
ml, 0.088 mmol) was added to 30 ml of CH2Cl2
containing 6 (0.072 g, 0.082 mmol) and then the re-
sulting solution was allowed to stir for 14 h. The color
of the solution turned from yellow to yellow–green.
The solvent was removed under vacuum to give
yellow–green solids, which were recrystallized from
CH2Cl2–hexane to give 7a (0.05 g, 0.048 mmol, 61%).
1H-NMR (CDCl3): l 7.446–6.836 (40H, m, phenyl,
Ph2PCH2CH2PPh2), 3.092 (3H, s, NꢀCH3), 2.519
(4H, broad m, Ph2PCH2CH2PPh2), 2.029 (4H, broad
m, Ph2PCH2CH2PPh2), −11.265 (1H, quintet,
2JPꢀH=46 Hz, HꢀFe). 13C{1H}-NMR (CDCl3): l
164.892 (q, CNMe), 136.480, 136.034, 133.781,
133.051, 130.670, 130.637, 129.036, 128.422 (phenyl),
34.279 (t, JPꢀC=12.5 Hz, Ph2PCH2CH2PPh2) 30.372

J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
143
trans-FeHCl(dppe)2, 1, in various nitriles under argon
leads to the formation of complexes of the type trans-
[FeH(NCR)(dppe)2]Cl (2a (R=CH3), 3a (R=CH2-
CH2OMe), 4a (R=CH2CH2CH2Cl) and 5a (R=
Ph)) in several hours. Complexes 2a–4a can be further
converted to trans-[FeH(NCR)(dppe)2][BPh4] (2b–4b)
and trans-[FeH(NCR)(dppe)2][BF4] (2c–4c) when they
are treated with NaBPh4 and NaBF4, respectively.
However, the iron(II)–benzonitrile complex 5a will not
proceed further when it is treated with NaBPh4 or
NaBF4. In these reactions nitriles behave both as
reagents and as solvents. As expected, complexes of
2b–4b and 2c–4c can also be prepared directly (in one
step) from 1 with NaX (X=BPh4, BF4) in the corre-
sponding nitriles. In all of the reactions, there is a color
change from red to orange or yellow. In addition, a
down-field shift (Dl 7.6–5.8) of the chemical shift of
in the difference Fourier map and refined isotropically.
All the other hydrogen atoms were generated in ideal-
ized positions and refined in a riding model.
A yellow crystal of, 3b·C6H14, shaped as a block, of
approximate dimensions 0.5×0.4×0.5 mm3, was used
for crystal and intensity data collection. The unit cell
parameters indicated a triclinic lattice. A statistical
analysis of intensities suggested a centrosymmetric
space group and the structural analysis converged only
(
in the space group P1. The structure was solved by the
heavy atom method and refined by full-matrix least-
squares calculations of F2, with anisotropic tempera-
ture factors for all non-hydrogen atoms, except for the
carbon atoms in the cocrystallized hexane (C81–C86)
that exhibited an extreme structural disorder. The best
fit for the disordered hexane was obtained by consider-
ing the five out of six hexane carbons to be distributed
over two positions with the site occupation factors of
0.54:0.46 (C82–C86: C82A–C86A). The hydride ligand
was located in the difference Fourier map and refined
isotropically. Locating the hydrogen atoms in the dis-
ordered hexane was not tried. All the other hydrogen
atoms were generated in idealized positions and refined
in a riding model.
1
the hydride in H-NMR spectra is consistent with the
formation of a salt, in which the hydride resides in the
cationic part of the product.
It has been reported that the reaction of trans-FeH-
Cl(depe)2 (depe=Et2PCH2CH2PEt2) with NaBPh4 in
acetone under nitrogen leads to the formation of a
relatively stable dinitrogen complex, trans-[FeH(N2)(-
depe)2][BPh4] (Eq. (1)) [12]. This methodology has also
been employed to prepare a series of cationic iron–hy-
dride complexes of the type trans-[MH(L)(depe)2]-
[BPh4] (M=Fe, L=CO, p-MeOC6H4NC, Me3CNC,
P(OPh)3, P(OMe)3, N2, PhCN, or CH3CN; M=Ru or
Os, L=CO, p-MeOC6H4NC, Me3CNC, P(OPh)3, N2,
or PhCN) [13].
A yellow crystal of 7a, shaped as a block, of approxi-
mate dimensions 0.60×0.42×0.40 mm3, was used for
crystal and intensity data collection. The unit cell
parameters and systematic absences, h0l (l=2n+1)
and 0k0 (k=2n+1), unambiguously indicated P21/c
as a space group. The structure was solved by the
direct method and refined by full-matrix least-squares
calculations of F2, with anisotropic temperature factors
for all non-hydrogen atoms except for the counteranion
(CF3SO3) that exhibited an extreme structural disorder.
The atoms in the counteranion were refined isotropi-
cally because anisotropic refinements including these
atoms were unstable. The best fit was obtained by
considering these atoms to be distributed over two
positions with site occupation factors (S1:S1A=
0.65:0.35, O1:O1A=0.42:0.58, O3:O3A=0.42:0.58
and F3:F3A=0.36:0.64). The hydride ligand was lo-
cated in the difference Fourier map and refined isotrop-
ically. All the other hydrogen atoms were generated in
idealized positions and refined in a riding model.
trans-FeHCl(depe)2+N2+NaBPh4
“trans-[FeH(N2)(depe)2][BPh4]+NaCl
(1)
The closely related complex [FeH(L)(dppe)2]X (X=
BPh4 or ClO4; L=Me2CO, N2, CO, NH3, py, MeCN
or PhCN) has been prepared by reactions of 1
with NaX under nitrogen in the presence of L [9]. In
addition, [FeH(L)(dppe)2][BF4] has been prepared
by the reaction of cis-FeH2(dppe)2 with HBF4·Et2O in
the presence of the strongly coordinating ligand L
(L=CH3CN, CO) through H2 evolution at 26°C
[9].
Complexes (2b–4b and 2c–4c) containing larger
counterions (BPh−4 or BF4−) are stable both in solution
and in the solid state. On the other hand, complexes
(2a–5a) containing a smaller counterion (Cl−) are sta-
ble in the solid state but unstable in solution. For
Details on crystal data and intensity data are given
in Table 1. The selected bond distances and bond
angles for 2b, 3b and 7a are given in Tables 2–4.
1
example, H- and 31P-NMR spectra of 2a–5a could be
obtained, but their 13C{1H}-NMR spectra, which re-
quire a longer time, could not be obtained due to the
equilibrium shown in Eq. (2). This observation is con-
sistent with the well-known fact that a large counterion
can stabilize an ionic lattice of a large organometallic
ion [14].
3. Results and discussion
3.1. Preparation
Reactions to prepare iron(II)–nitrile complexes in
this study are summarized in Scheme 1. Dissolution of

144
J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
Table 1
X-ray data collection and structure refinement for 2b, 3b and 6
2b
3b · C6H14
7a
Formula
C78H72BNP4Fe
C86H90BNOP4Fe
C55H52NO3F3P4SFe
FW
1213.91
293
Monoclinic
P21/c
22.508(1)
16.120(1)
19.257(1)
1344.13
293
Triclinic
1043.77
294
Monoclinic
P21/c
12.456(1)
21.880(3)
19.924(3)
Temperature (K)
Crystal system
Space group
(
P1
,
a (A)
13.240(1)
14.732(2)
19.807(1)
75.276(6)
72.466(6)
82.033(6)
3554.8(6)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
113.86(1)
108.08(1)
3
,
V (A)
6389.9(6)
4
5162(1)
4
Z
Dcalc (g cm−3
)
1.262
0.382
0.3966
0.4263
2552
1.256
0.350
0.8629
1.0000
1424
1.343
0.511
0.3374
0.3649
2168
v (mm−1
Tmin
)
Tmax
F(000)
2q range (°)
Scan type
Scan speed
No. of reflections measured
No. of reflections unique
No. of reflections with I\2|(I)
3.5–50
ꢀ
3–52
3.5–50
ꢀ
ꢀ−2u
Variable
14300
13687
8671
849
0.464
−0.284
0.844
0.0368
0.0835
Variable
13099
11119
11119
772
0.306
−0.317
1.065
0.0361
0.0882
Variable
9429
9003
6287
622
0.896
−1.026
1.031
0.0663
0.1647
No. of parameters refined
−3
,
Max. in Dz (e A
)
−3
,
Min. in Dz (e A
)
GOF on F2
R
wR2
a
a wR2=S[w(Fo2−Fc2)2]/S[w(Fo2)2]1/2
.
reaction (Eq. (3)) also shows a possibility of the nitrile
exchange reaction, through which many nitrile
complexes have been prepared [3].
Table 2
,
Selected bond distances (A) and bond angles (°) in 2b
,
Bond lengths (A)
(2)
FeꢀN1
FeꢀP4
FeꢀP1
FeꢀP3
FeꢀP2
FeꢀH1
P1ꢀC1
P2ꢀC2
P3ꢀC3
1.933(2)
2.2318(6)
2.2739(6)
2.2547(6)
2.2453(5)
1.50(2)
1.861(2)
1.837(2)
1.854(2)
P4ꢀC4
1.838(2)
1.141(3)
1.514(3)
1.519(3)
1.454(3)
1.643(3)
1.651(3)
1.642(4)
1.642(4)
All of the ionic products exhibit a quintet (l
−19.224 to −21.022) for the hydride ligand in their
1H-NMR spectra and a doublet (l 83.779–86.555) for
the four phosphine ligands in their 31P-NMR spectra.
These observations indicate that the hydride ligand
couples with the four equivalent phosphorus nuclei in
the phosphines occupying the equatorial plane and that
the trans orientation between the hydride and the nitrile
remains intact. The trans orientation has been
confirmed further by the crystal structure determination
(see below) and the substitution reaction (Eq. (3)).
When 2b is treated with excess deuterated acetonitrile
(CD3CN), [FeH(NCCD3)(dppe)2][BPh4] (2b–CD3CN)
N1ꢀC53
C1ꢀC2
C3ꢀC4
C53ꢀC54
B1ꢀC55
B1ꢀC61
B1ꢀC67
B1ꢀC73
Bond angles (°)
N1ꢀFeꢀP2
P4ꢀFeꢀP2
N1ꢀFeꢀP3
P4ꢀFeꢀP3
P2ꢀFeꢀP3
N1ꢀFeꢀP1
P4ꢀFeꢀP1
P2ꢀFeꢀP1
C53ꢀN1ꢀFe
91.35(5)
171.09(2)
91.09(5)
84.32(2)
95.14(2)
89.92(5)
96.62(2)
83.75(2)
174.9(2)
N1ꢀC53ꢀC54
N1ꢀFeꢀH1
176.3(3)
175.4(9)
91.9(9)
104.8(2)
112.5(2)
113.9(2)
110.1(2)
111.7(2)
104.0(2)
P1ꢀFeꢀH1
C73ꢀB1ꢀC67
C73ꢀB1ꢀC55
C67ꢀB1ꢀC55
C73ꢀB1ꢀC61
C67ꢀB1ꢀC61
C55ꢀB1ꢀC61
1
is formed. In the H-NMR spectra of 2b–CD3CN, a
singlet at l 0.97 for CH3CN in 2b disappears, but a
quintet (l −20.61 for FeꢀH) remains intact. This

J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
145
Table 3
Selected bond distances (A) and bond angles (°) in 3b
3.2. Structure
,
The structure of the cationic part of 2b,
[FeH(NCCH3)(dppe)2]+, with the atomic numbering
scheme is shown in Fig. 1. The structure of the cationic
part of 3b, [FeH(NCCH2CH2OCH3)(dppe)2]+, is shown
in Fig. 2, in which the extremely disordered cocrystal-
lized hexane molecule is omitted for clarity. The struc-
ture of the cationic part of 7a, [FeH(CNMe)(dppe)2]+,
is shown in Fig. 3, in which the disordered counteran-
ion (O3SCF3) is omitted for clarity. The coordination
sphere of each Fe metal can be described as an octahe-
dron, with two bidentate dppe ligands at the equatorial
,
Bond lengths (A)
FeꢀN1
FeꢀP4
FeꢀP1
FeꢀP3
FeꢀP2
FeꢀH1
P1ꢀC1
P2ꢀC2
P3ꢀC3
P4ꢀC4
O1ꢀC55
1.930(2)
2.2500(6)
2.2569(6)
2.2573(6)
2.2594(6)
1.44(2)
1.847(2)
1.861(2)
1.864(2)
1.842(2)
1.399(3)
O1ꢀC56
N1ꢀC53
C1ꢀC2
1.430(3)
1.149(2)
1.524(3)
1.518(3)
1.458(3)
1.518(3)
1.632(3)
1.640(3)
1.651(3)
1.653(3)
C3ꢀC4
C53ꢀC54
C54ꢀC55
B1ꢀC57
B1ꢀC75
B1ꢀC63
B1ꢀC69
Bond angles (°)
N1ꢀFeꢀP4
98.07(5)
175.15(2)
83.68(2)
93.23(5)
83.32(2)
178.1(8)
174.3(2)
109.5(1)
177.6(2)
108.7(2)
111.3(2)
104.7(2)
111.7(2)
N1ꢀFeꢀP1
N1ꢀFeꢀP3
P1ꢀFeꢀP3
P4ꢀFeꢀP2
P3ꢀFeꢀP2
C55ꢀO1ꢀC56
C1ꢀC2ꢀP2
C3ꢀC4ꢀP4
C53ꢀC54ꢀC55
C57ꢀB1ꢀC75
C75ꢀB1ꢀC63
C75ꢀB1ꢀC69
86.76(5)
91.12(5)
95.85(2)
96.77(2)
175.51(2)
112.4(2)
110.2(1)
108.3(1)
112.2(2)
112.9(2)
105.6(2)
110.8(2)
P4ꢀFeꢀP1
P4ꢀFeꢀP3
N1ꢀFeꢀP2
P1ꢀFeꢀP2
N1ꢀFeꢀH1
C53ꢀN1ꢀFe
C4ꢀC3ꢀP3
N1ꢀC53ꢀC54
O1ꢀC55ꢀC54
C57ꢀB1ꢀC63
C57ꢀB1ꢀC69
C63ꢀB1ꢀC69
Table 4
,
Selected bond distances (A) and bond angles (°) in 7a
,
Bond lengths (A)
FeꢀC53
FeꢀP1
FeꢀP4
FeꢀP3
FeꢀP2
FeꢀHfe
P1ꢀC49
1.851(5)
2.232(1)
2.240(1)
2.257(1)
2.262(1)
1.52(5)
P2ꢀC50
P3ꢀC51
P4ꢀC52
N1ꢀC53
N1ꢀC54
C49ꢀC50
C51ꢀC52
1.849(5)
1.853(5)
1.828(5)
1.154(6)
1.432(7)
1.507(7)
1.505(8)
Scheme 1.
1.831(5)
Bond angles (°)
C53ꢀFeꢀP1
P1ꢀFeꢀP4
P1ꢀFeꢀP3
C53ꢀFeꢀP2
P4ꢀFeꢀP2
104.0(1)
94.38(5)
162.03(5)
92.0(2)
178.81(5)
175(2)
C53ꢀFeꢀP4
C53ꢀFeꢀP3
P4ꢀFeꢀP3
P1ꢀFeꢀP2
P3ꢀFeꢀP2
P4ꢀFeꢀHfe
N1ꢀC53ꢀFe
89.2(2)
93.7(2)
82.85(5)
85.16(5)
97.25(5)
96 (2)
C53ꢀFeꢀHfe
C53ꢀN1ꢀC54
173.0(6)
177.4(4)
Fig. 1. ORTEP drawing [24] of the cationic part of 2b,
[FeH(NCCH3)(dppe)2]+, showing the atom-labeling scheme and 50%
probability thermal ellipsoids.
(3)

146
J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
,
in 3b lies 0.095 A above the equatorial plane. The
ꢀCH2CH2OCH3 moiety of the nitrile in 3b is directed
toward the open space between the two phenyl rings
(C29–C34 and C47–C52), probably due to steric conges-
tion. In addition, the equatorial plane in 7a, defined by
the four dppe phosphorus atoms (P1–P4) and iron atom
(Fe), is roughly planar with an average atomic displace-
,
ment of 0.1627 A.
The hydride ligands (H1 for 2b and 3b and Hfe for 7a)
for these three compounds could be located and reason-
ably refined with an isotropic thermal parameter and the
,
,
distances of FeꢀH (1.50(2) A for 2b, 1.44(2) A for 3b and
,
1.52(5) A for 7a) appear to be fairly reliable. In the closely
related complex, trans-[FeH(h2-H2)(dppe)2][BF4], which
has been prepared by protonation of FeH2(dppe)2 with
HBF4·Et2O and structurally characterized by X-ray dif-
fraction, the bond distance of FeꢀH (terminal) is 1.28(8)
Fig. 2. ORTEP drawing [24] of the cationic part of 3b,
2
[FeH(NCCH2CH2OCH3)(dppe)2]+
,
showing the atom-labeling
,
A [15]. In another related complex, trans-[FeH(h -
scheme and 50% probability thermal ellipsoids.
H2)(dppe)2][BPh4], which was prepared by counterion
exchange of trans-[FeH(h2-H2)(dppe)2][BF4] with NaB-
Ph4 and structurally characterized both by X-ray diffrac-
tion and by neutron diffraction, the bond distances of
,
FeꢀH (terminal) are 1.30(3) A (X-ray diffraction) and
,
1.535(12) A (neutron diffraction), respectively [16]. The
mean values of transition metal–hydride (MꢀH) bond
distances determined by neutron diffraction have been
summarized by Bau and Drabnis and the average distance
,
of a terminal FeꢀH bond is 1.575(17) A and that of a
,
bridging FeꢀHꢀFe bond is 1.664(11) A [17].
,
The FeꢀN1 bond distances (1.933(2) A for 2b and
,
1.930(2) A for 3b) indicate an FeꢀN single bond, because
a metal–nitrogen single bond is expected to lie within
,
1.95–2.15 A [18]. The C53ꢀN1ꢀFe bond angle of
174.9(2)° in 2b and the C53ꢀN1ꢀFe bond angle of
174.3(2)° in 3b are fairly typical of nitrile ligands (168–
178°) and indicate an ‘end-on’ coordination of these
,
ligands [2]. The bond distances of N1ꢀC53 (1.141(3) A
,
for 2b and 1.149(2) A for 3b) parallel the known fact that
Fig. 3. ORTEP drawing [24] of the cationic part of 7a, [FeH(C-
NMe)(dppe)2] +, showing the atom-labeling scheme and 50% proba-
bility thermal ellipsoids.
the NꢁC bond distances in nitrile ligands usually shorten
on coordination. The NꢁC bond distances (in nitrile
,
ligands) of 1.11–1.15 A are most frequently found,
,
compared to 1.16 A in the free CH3CN [3].
sites and the hydride and nitrile (NCCH3 for 2b and
NCCH2CH2OCH3 for 3b) or methyl isocyanide (for 7a)
ligands at the axial sites. The anions [BPh4]− in 2b and
3b and [SO3CF3]− in 7a are not bonded to the Fe metal
and act as counteranions to retain electroneutrality. The
bond distances and angles around the B atom in 2b and
3b indicate that the boron atom in [BPh4]− in both
compounds is sp3-hybridized (Tables 2 and 3).
,
In 7a, the FeꢀC53 bond distance of 1.851(5) A belongs
to the lower limit of the range (1.923–1.850 A) of the
,
FeꢀC bond distance found for FeꢀCN (terminal) com-
,
plexes [19]. The C53ꢀN1 bond distance of 1.154(6) A
indicates a CꢁN triple bond and the N1ꢀC54 bond
,
distance of 1.432(7) A indicates an NꢀC single bond. In
addition, the FeꢀC53ꢀN1 and C53ꢀN1ꢀC54 bonds are
almost linear with the angles of 177.4(4) and 173.0(6)°.
These bonding parameters suggest that resonance form
I is a major contribution in which Fe“C p-back bonding
does not play an important role.
The equatorial plane in 2b, defined by the four dppe
phosphorus atoms (P1–P4) and Fe, is nearly planar with
,
an average atomic displacement of 0.0786 A. On the other
hand, the equatorial plane in 3b, defined by the four dppe
phosphorus atoms (P1–P4), is essentially planar with an
,
average atomic displacement of 0.0001 A. The Fe metal

J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
147
All the structurally characterized compounds in this
study have a pseudo four-fold rotation axis that passes
through the Fe, N1 and H1 atoms (for 2b and 3b) or Fe,
C53 and Hfe atoms (for 7a) and is perpendicular to the
equatorial plane, implying that the four phosphorus
nuclei are equivalent. These crystal structures explain the
NMR spectra of the compounds that show a quintet for
the H ligand (l −20.793 for 2b, l −20.355 for 3b and
l −11.265 ppm for 7a) in their 1H-NMR and a doublet
for the four P atoms (l 85.468 for 2b, l 84.985 for 3b
and l 88.544 for 7a) in their 31P-NMR spectra. The
results of the X-ray crystal structures and NMR spectral
data indicate that these molecules have the same struc-
ture both in solution and in the solid state.
L (L=PPh3, CNtBu, or HCꢁCPh) [20]. The geometry of
6 can be readily deduced from NMR data (a quintet for
1
hydride in H-NMR and a doublet for phosphorus in
31P-NMR) and elemental analysis data. The IR spectra
of 6 show the CꢁN band at 2050 cm−1, whereas the
starting materials show that band at 2232–2248 cm−1
In addition, the H-NMR spectra of 6 do not show any
.
1
peak assignable to nitrile ligand protons.
3.3. Properties
As mentioned in Section 1, nitrile complexes are
known to provide an example of activation because the
electrophilicity of the nitrile a-carbon is enhanced upon
coordination. On the contrary to this expectation, com-
pounds 2b, 2c, 3b, 3c, 4b and 4c react with KCN or
NaCN to give [FeH(CN)(dppe)2] (6), which is a substitu-
tion product, not a nucleophilic addition product
([FeH(NC(CN)R)(dppe)2]) (Eq. (4)). In other words, the
nucleophile CN− attacked directly at the Fe metal, not
at the nitrile a-carbon. This pattern of substitution for
metal–nitrile complexes has often been observed. For
(4)
There are no signs of reactions of compounds 2b, 2c,
3b, 3c, 4b and 4c with phosphines (PMe3, PEt3, or PPh3),
amines (tBuNH2, NEt2H, or 4-tert-butylpyridine), or
unsaturated organic molecules (H2CꢂCH2 or HCꢁCPh).
These compounds, however, react with NaN3 to give
several products that cannot be identified.
Electrophilic attack at the cyanide nitrogen in 6 with
MeOTf or HOTf (OTf=O3SCF3) generates a methyl
isocyanide (7a) or a hydrogen isocyanide (7b) complex
(Eq. (5)). In 13C{1H}-NMR spectra of 7b, the peak
corresponding to the hydrogen isocyanide carbon
(ꢀCNH) does not appear. The IR spectra of 7b, how-
ever, show a band assingable to the NꢀH bond in the
hydrogen isocyanide ligand at 3140 cm−1. A 68 cm−1
increase in n(CꢁN) accompanies methylation but a 72
cm−1 decrease accompanies protonation. This type of
reactivity, electrophilic addition to the cyanide ligand,
has often been observed [21]. The structure of 7a has
been confirmed further by X-ray diffraction study (see
Section 3.2).
example,
a
cationic rhenocene–nitrile adduct
[Cp2Re(NCCH3)][BF4] (Cp=C5H5) has a labile acetoni-
trile ligand that can be readily replaced by other ligands
(5)
As shown in Fig. 4 and in Table 5, complexes 2b, 3b
and 4b, which possess a larger counteranion BPh−4 ,
display one reversible oxidation (0.649 V for 2b, 0.660 V
for 3b and 0.635 V for 4b) and one irreversible oxidation
(1.322 V for 2b, 1.164 V for 3b and 1.272 V for 4b) in
their cyclic voltammograms.
Fig. 4. Cyclic voltammograms (300 mV/s) in 0.1
[nBu4N][BF4]ꢀCH2Cl2 solutions of 3b (top) and 3c (bottom).
M

148
J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
Table 5
Electrochemical data from cyclic voltammetry studies at 300 mV s−1
Compound
Scan rate (mV s−1
)
E°
I
pc/Ipa
Epa (V)
Epc (V)
0.502
2b
3b
4b
2c
300
300
300
0.649
0.660
0.635
1.019
0.864
0.894
0.796
1.322
0.741
1.164
0.784
1.272
0.725
0.730
0.758
0.660
0.672
0.740
0.579
0.486
200
300
500
1000
300
300
0.660
0.654
0.648
0.592
0.593
0.677
0.999
1.005
0.915
0.989
0.935
0.895
0.594
0.578
0.538
0.523
0.514
0.614
3c
4c
Fig. 5. Linear sweep voltammogram (100 mV/s) in 0.1 M [nBu4N][BF4]ꢀCH2Cl2 solution of 3b.
The one-electron character of the oxidation waves
oxidation (0.654 V for 2c, 0.593 V for 3c and 0.677 V
for 4c). At various scan rates (Table 5), the oxidation of
2c remains constant, which suggests that the cation
has been confirmed by microelectrode linear sweep
voltammetry (LSV). When the limiting current flows,
the number of electrons transferred per molecule, n, can
be estimated from Eq. (6) [22]. Linear sweep
voltammtry has been carried out in a 3 ml solution of
compound 3b with a 100 mm microdisc electrode, where
two-step steady-state currents have been obtained (Fig.
5). A plot of E versus log[(il−i )/i ] for each step shows
a straight line with a slope of 59 and 61 mV, respec-
tively. These slopes mean one-electron transfer at each
step.
radical of 2c ([FeH(NCCH2CH2OMe)(dppe)2][BF4]+
)
’
is stable.
On the basis of the inductive effect (H for 2b and 2c,
CH2OMe for 3b and 3c and CH2CH2Cl for 4b and 4c),
the oxidation potential is expected to be in the order
3bB2bB4b and 3cB2cB4c. However, the ease of
oxidation has turned out to be 4bB2bB3b and 3cB
2cB4c, which suggests that the induction effect does
not play an important role in the redox property for
these complexes.
In related complexes of the type trans-[Fe-
H(CNR)(dppe)2][A] (R=Me, Et, tBu, C6H4Me-4,
C6H4NO2-4, C6H4OMe-4; A=BPh4, BF4), the alkyliso-
cyanide complexes show a first quasi-reversible anodic
(oxidation) wave and a second reversible anodic wave.
In contrast, the arylisocyanide complexes show a first
irreversible anodic wave and a second quasi-reversible
anodic wave [23].
E=E1/2+(59.1 mV/n) log[(il−i)/i] at 25°C
(6)
The electrochemical data suggest that the first cation
2b+–4b+ containing Fe(III) is stable on the cyclic
voltammetry time scale and the second cation 2b2+
–
4b2+ containing Fe(IV) is unstable, assuming that oxi-
dation occurs at the Fe metal center. On the contrary,
complexes 2c, 3c and 4c, which possess a smaller coun-
teranion BF−4 , display only one chemically reversible

J.-G. Lee et al. / Journal of Organometallic Chemistry 589 (1999) 138–149
149
[3] H.I.P. Endres, in: G. Wilkinson, R.D Gillard, J.A. McCleverty
(Eds.), Comprehensive Coordination Chemistry, vol. 2, Perga-
mon, Oxford, 1987, p. 261.
[4] S.G. Feng, J.L. Templeton, J. Am. Chem. Soc. 111 (1989) 6477.
[5] S.G. Feng, J.L. Templeton, Organometallics 11 (1992) 1295.
[6] S.G. Feng, P.S. White, J.L. Templeton, Organometallics 12
(1993) 1765.
[7] M.B. Baptista, M.A.N.D.A. Lemos, J.J.R. Frau´sto da Silva,
A.J.L. Pombeiro, J. Organomet. Chem. 424 (1992) 49.
[8] S.S.P. Almeidia, M.T. Duarte, L.M.D. Ribeiro, F. Gormley,
A.M. Galva˜o, J.J.R. Frau´sto da Silva, A.J.L. Pombeiro, J.
Organomet. Chem. 524 (1996) 63.
[9] P. Giannoccaro, M. Rossi, A. Sacco, Coord. Chem. Rev. 8
(1972) 77.
[10] P. Giannoccaro, A. Sacco, Inorg. Synth. 17 (1977) 69.
[11] G.M. Sheldrick, SHELX-97, University of Go¨ttingen, Go¨ttingen,
Germany, 1997.
In summary, we have prepared several Fe(II)–nitrile
complexes of the type [FeH(NCR)(dppe)2] +X− (R=
CH3, CH2CH2OCH3, CH2CH2CH2Cl, C6H5: X=Cl,
BPh4, BF4). The stability and electrochemical properties
of these complexes appear to depend mainly on their
counteranions. Compounds [FeH(NCR)(dppe)2]+X−
(R=CH3, CH2CH2OCH3, CH2CH2CH2Cl: X=BPh4,
BF4) react with KCN or NaCN to give [Fe-
H(CN)(dppe)2]. In these reactions, the nucleophile CN−
has attacked directly at the Fe metal, not at the nitrile
a-carbon. The compound [FeH(CN)(dppe)2] undergoes
electrophilic addition at the cyano nitrogen by RO3SCF3
(R=Me or H) to give [FeH(CNR)(dppe)2][SO3CF3].
[12] G.M. Bancroft, M.J. Mays, B.E. Prater, J. Chem. Soc. Chem.
Commun. (1969) 586.
4. Supplementary material
[13] G.M. Bancroft, M.J. Mays, B.E. Prater, F.P. Stefanini, J.
Chem. Soc. A (1970) 2146.
[14] J.E. Huhee, E.A. Keiter, R.L. Keiter, Inorganic Chemistry,
fourth edition, Harper Collins, New York, 1993, p. 511.
[15] R.H. Morris, J.F. Sawyer, M. Shiralian, J.D. Zubkowski, J.
Am. Chem. Soc. 107 (1985) 5581.
[16] J.S. Ricci, T.F. Koetzle, M.T. Bautista, T.M. Hofstede, R.H.
Morris, J.F. Sawyer, J. Am. Chem. Soc. 111 (1989) 8823.
[17] R. Bau, M.H. Drabnis, Inorg. Chim. Acta 259 (1997) 27.
[18] B.R. Davis, N.C. Payne, J.A. Ibers, Inorg. Chem. 8 (1969)
2719.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC no. 131473 for 2b, CCDC no.
131471 for 3b and CCDC no. 131472 for 7a. Copies of
this information may be obtained free of charge from:
The Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (Fax: +44-1223-336-033; email: deposit-
@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
[19] A.G. Orpen, L. Brammer, F.H. Allen, O. Kennard, D.G. Wat-
son, J. Chem. Soc. Dalton Trans. (1989) S10.
[20] H. Tobita, K. Hashidzume, K. Endo, H. Orgino, Organometal-
lics 17 (1998) 3405.
[21] D.S. Frohnapfel, S. Reinartz, P.S. White, J.L. Templeton,
Organometallics 17 (1998) 3759.
Acknowledgements
This work is based on research sponsored by the Korea
Ministry of Education under grant BSRI-98-3420.
[22] A.J. Bard, L.R. Faulkner, Electrochemical Methods: Funda-
mentals and Applications, Wiley, New York, 1980, p. 30.
[23] M.A.N.D.A. Lemos, A.J.L. Pombeiro, J. Organomet. Chem.
438 (1992) 159.
References
[24] L.J. Farrugia, ORTEP-3 for Windows, University of Glasgow,
Glasgow, 1997.
[1] R.A. Walton, Q. Rev. Chem. Soc. 19 (1965) 126.
[2] B.N. Storhoff, H.C. Lewis Jr., Coord. Chem. Rev. 23 (1977) 1.
.