Electrophilic attack of alkyl halide at the cyanide nitrogen in trans- [Fe(H)(CN)bis(dppe)]: Preparation, structure and properties of trans- [Fe(H)(CNR)bis(dppe)]X (dppe=1,2 bis(diphenylphosphine)ethane; R=Me, Et, Pr, I- Pr, n-Bu, 2 bromoethyl, 3 iodopropyl, 2 propenyl, 2 propynyl; X=Br, I)

Article abstract of DOI:10.1016/S0020-1693(00)00252-8

Compound trans-[FeH(CN)(dppe)₂] (1) reacted with alkyl iodides or alkyl bromides to give Fe(II)-organic isocyanide complexes of the type trans-[FeH(CNR)(dppe)₂]X [X = I: R = Me (2), Et (3), Pr (4), CH₂CH₂CH₂I (5), i-Pr (6), CH₂CH=CH₂ (7); X = Br: R = Et (8), Pr (9), n-Bu (10), CH₂CH₂Br (11), CH₂CH=CH₂ (12), CH₂C≡CH (13)]. Compound 1 reacted with BF₃ to give a Lewis acid-base adduct, trans-[FeH(CN→BF₃)(dppe)₂]. Compounds 5 and 13 were characterized structurally by X-ray diffraction, in which the hydride ligand appears to be involved in the dihydrogen bonding, M-H···H-C. (C) 2000 Elsevier Science B.V.

Full text of DOI:10.1016/S0020-1693(00)00252-8

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 309 (2000) 137–145
Electrophilic attack of alkyl halide at the cyanide nitrogen in
trans-[Fe(H)(CN)(dppe)2]: preparation, structure, and properties of
trans-[Fe(H)(CNR)(dppe)2]X (dppe=Ph2PCH2CH2PPh2; R=Me,
Et, Pr, i-Pr, n-Bu, CH2CH2Br, CH2CH2CH2I, CH2CHꢀCH2,
CH2CꢁCH; X=Br, I)
Beom-Sang Yoo, Nam-Sun Choi, Chang Yong Shim, Yongkeun Son, Soon W. Lee *
Department of Chemistry, Sungkyunkwan Uni6ersity, Natural Science Campus, Suwon 440-746, South Korea
Received 17 March 2000; accepted 12 July 2000
Abstract
Compound trans-[FeH(CN)(dppe)2] (1) reacted with alkyl iodides or alkyl bromides to give Fe(II)–organic isocyanide
complexes of the type trans-[FeH(CNR)(dppe)2]X [X=I: R=Me (2), Et (3), Pr (4), CH2CH2CH2I (5), i-Pr (6), CH2CHꢀCH2 (7);
X=Br: R=Et (8), Pr (9), n-Bu (10), CH2CH2Br (11), CH2CHꢀCH2 (12), CH2CꢁCH (13)]. Compound 1 reacted with BF3 to give
a Lewis acid–base adduct, trans-[FeH(CN“BF3)(dppe)2]. Compounds 5 and 13 were characterized structurally by X-ray
diffraction, in which the hydride ligand appears to be involved in the dihydrogen bonding, MꢂH···HꢂC. © 2000 Elsevier Science
B.V. All rights reserved.
Keywords: Electrophilic attack; Dihydrogen bonding; Crystallographic data
isocyanide
complexes,
trans-[FeH(CNR)(dppe)2]X
1. Introduction
(R=Me, Et, Pr, i-Pr, n-Bu, CH2CH2Br, CH2CH2-
CH2I, CH2CHꢀCH2, or CH2CꢁCH; X=Br or I), which
were prepared from 1 and mild electrophiles (RBr, RI).
Organic isocyanide complexes of transition metals
(MꢂCNR) are prepared generally by the ligand ex-
change with a free organic isocynide [1], electrophilic
addition of an electrophile (RX) at the cyano nitrogen
[2,3], radical alkylation of a cyanometalate with a dia-
zonium salt [4], or hydroisocynation of an olefine [5].
Recently, our group prepared a couple of iron(II)–
organic isocyanide complexes, trans-[FeH(CNR)-
(dppe)2] (R=CH3, H), by treating trans-[FeH(CN)-
(dppe)2] (1) with strong electrophiles (CH3O3SCF3,
HO3SCF3) (Eq. (1)) [6]. In order to prepare organic
isocyanide complexes under milder conditions, we in-
vestigated the nucleophilic properties of the cyano lig-
and in the neutral iron complex 1. Herein we reported
synthesis, structure, and properties of iron(II)–organic
(1)
2. Experimental
Unless otherwise stated, all reactions have been
performed with standard Schlenk line and cannula
techniques under argon. Air-sensitive solids were ma-
nipulated in a glove box filled with argon. Glassware
was soaked in KOH-saturated 2-propanol for about 24
* Corresponding author. Tel.: +82-331-2907066; fax: +82-331-
2907075.
E-mail address: swlee@chem.skku.ac.kr (S.W. Lee).
0020-1693/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(00)00252-8

138
B.-S. Yoo et al. / Inorganica Chimica Acta 309 (2000) 137–145
h and washed with distilled water and acetone before
use. Dichloromethane was stirred over CaH2 and dis-
tilled by vacuum transfer. Diethyl ether and tetrahydro-
furan (THF) were distilled over sodium metal under
argon. The NMR solvent (CDCl3) was degassed by
several freeze–pump–thaw cycles before use and stored
over molecular sieves under argon. Iodomethane
(CH3I), iodoethane (C2H5I), iodopropane (C3H7I),
NꢂCH3), 2.545 (4H, broad, Ph2PCH2CH2PPh2), 2.034
(4H, broad, Ph2PCH2CH2PPh2), −11.213 (1H, quintet,
2JPꢂH=46 Hz, HꢂFe). 13C{1H} NMR (CDCl3): l
136.438, 135.873, 133.748, 133.129, 130.720, 130.621,
129.078,
128.475
(phenyl),
34.316
(m,
Ph2PCH2CH2PPh2) 32.967 (s, NCH3). 31P NMR
2
(CDCl3): l 88.755 (d, JPꢂH=46 Hz). Anal. Calc. for
C54H52NP4FeI (Mr=1021.66): C, 63.49; H, 5.13; N,
1,3-diiodopropane
(ICH2CH2CH2I),
bromoethane
1.37. Found: C, 63.18; H, 5.19; N, 1.32%. M.p. (dec.):
(C2H5Br), bromopropane (C3H7Br), bromobutane
(C4H9Br), and 1,2-dibromoethane (BrCH2CH2Br) were
purchased from Aldrich Co. 2-Iodopropane (iso-
C3H7I), allyl bromide (C3H5Br), and propargyl bromide
(HCꢁCCH2Br) were purchased from Fluka Co. Com-
pound trans-FeH(CN)(dppe)2 (1) was prepared by the
literature method [6].
Electrochemical measurements were performed with
a model 263A EG&G potentiostat. A platinum disc of
2 mm in diameter was used as a working electrode, and
a platinum plate (1×1 cm) was used as a counter
electrode. A silver wire in a Luggin capillary was used
as a pseudo reference electrode. Measurements were
carried out in THF containing 0.2 M [n-Bu4N][BF4] as
a supporting electrolyte and approximately 1 mM metal
complex. Potential sweeps were performed at the rate
of 100–3000 mV s−1 between 0.7 and 1.5 V. All the
electrochemical experiments were carried out under
nitrogen.
210–212°C. IR (KBr): 2134 (CN), 1833 (FeꢂH) cm−1
.
The data for 3 are as follows. Yield: 0.077 g (0.074
1
mmol, 66%). Reaction time: 5 h. H NMR (CDCl3): l
7.442–6.755 (40H, m, Ph2PCH2CH2PPh2), 3.530 (2H,
q, NCH2CH3), 2.528 (4H, broad, Ph2PCH2CH2PPh2),
2.052 (4H, broad, Ph2PCH2CH2PPh2), 0.993 (2H, t,
NCH2CH3), −11.262 (1H, quintet, 2JPꢂH=46 Hz,
HꢂFe). 13C{1H} NMR (CDCl3): l 136.492, 135.968,
133.682, 133.212, 130.707, 129.020, 128.504 (phenyl),
41.838 (s, NCH2CH3), 34.292 (m, Ph2PCH2CH2PPh2)
15.378 (s, NCH2CH3). 31P NMR (CDCl3): l 88.332 (d,
2JPꢂH=46 Hz). Anal. Calc. for C55H54NP4FeI (Mr=
1035.69): C, 63.78; H, 5.26; N, 1.35. Found: C, 63.59;
H, 5.14; N, 1.27%. M.p. (dec.): 248–250°C. IR (KBr):
2104 (CN), 1846 (FeꢂH) cm−1
.
The data for 4 are as follows. Yield: 0.058 g (0.055
1
mmol, 49%). Reaction time: 5 h. H NMR (CDCl3): l
7.423–6.911 (40H, m, Ph2PCH2CH2PPh2), 3.431 (2H, t,
NCH2CH2CH3), 2.518 (4H, broad, Ph2PCH2CH2PPh2),
2.064 (4H, broad, Ph2PCH2CH2PPh2), 1.360 (2H, m,
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 and 11B{1H} NMR spectra were
also recorded with a Bruker AMX 500 MHz spectrom-
eter with reference to external 85% H3PO4 and
Et2O·BF3, respectively. IR spectra were recorded with a
Nicolet 205 FTIR spectrophotometer. Melting points
were measured with a Thomas Hoover capillary melt-
ing point apparatus without calibration. The elemental
analyses were performed by the Korea Basic Science
Center.
NCH2CH2CH3), 0.665 (3H, t, NCH2CH2CH3)
−
11.244 (1H, quintet, 2JPꢂH=47 Hz, HꢂFe). 13C{1H}
NMR (CDCl3): l 136.512, 135.906, 133.637, 133.212,
130.728, 129.032, 128.529 (phenyl), 48.316 (s,
NCH2CH2CH3), 34.267 (m, Ph2PCH2CH2PPh2),
23.094 (s, NCH2CH2CH3), 12.016(s, NCH2CH2CH3).
2
31P NMR (CDCl3): l 88.061 (d, JPꢂH=47 Hz). Anal.
Calc. for C56H56NP4FeI (Mr=1049.71): C, 64.08; H,
5.38; N, 1.35. Found: C, 63.65; H, 4.97; N, 1.35%. M.p.
(dec.): 220–222°C. IR (KBr): 2114 (CN), 1839 (FeꢂH)
cm−1
.
The data for 5 are as follows. Yield: 0.092 g (0.078
1
2.1. Preparation of trans-[FeH(CNR)(dppe)2]I (2–7)
mmol, 84%). Reaction time: 14 h. H NMR (CDCl3): l
7.440–6.904 (40H, m, Ph2PCH2CH2PPh2), 3.675 (2H, t,
NCH2CH2CH2I), 2.909 (2H, t, NCH2CH2CH2I) 2.585
(4H, broad, Ph2PCH2CH2PPh2), 2.068 (4H, broad,
Ph2PCH2CH2PPh2), 1.815 (2H, quintet, NCH2-
CH2CH2I) −11.121 (1H, quintet, 2JPꢂH=47 Hz,
HꢂFe). 13C{1H} NMR (CDCl3): l 136.496, 135.976,
133.678, 133.175, 130.827, 129.251, 128.512 (phenyl),
47.441 (s, NCH2CH2CH2I) 34.279 (m, Ph2PCH2-
CH2PPh2) 33.174 (s, NCH2CH2CH2I), 2.943 (s,
NCH2CH2CH2I). 31P NMR (CDCl3): l 88.061 (d,
2JPꢂH=47 Hz). Anal. Calc. for C56H55NP4FeI2 (Mr=
1175.84): C, 57.21; H, 4.72; N, 1.19. Found: C, 57.65;
H, 4.37; N, 1.27%. M.p. (dec.): 224–226°C. IR (KBr):
Compound 1 [0.082 g (0.093 mmol) for 2, 0.099 g
(0.113 mmol) for 3, 0.099 g (0.113 mmol) for 4, 0.082 g
(0.093 mmol) for 5, 0.101 g (0.114 mmol) for 6, and
0.097 g (0.110 mmol) for 7] was dissolved in 5–7 ml of
RI (R=Me for 2, Et for 3, Pr for 4, CH2CH2CH2I for
5, i-Pr for 6, and CH2CHꢀCH2 for 7), and the solution
was stirred. During stirring, an orange–yellow solution
turned to pale yellow slurry. The resulting solution was
filtered, and the remaining solid was washed with di-
ethyl ether (2×10 ml) and then dried under vacuum.
The data for 2 areas follows. Yield: 0.079 g (0.077
mmol, 83%). Reaction time: 1.5 h. 1H NMR (CDCl3): l
7.462–6.860 (40H, m, Ph2PCH2CH2PPh2), 3.190 (3H, s,
2102 (CN), 1845 (FeꢂH) cm−1
.

B.-S. Yoo et al. / Inorganica Chimica Acta 309 (2000) 137–145
139
The data for 6 are as follows. Yield: 0.097 g (0.092
mmol, 81%). Reaction time: 5 h. H NMR (CDCl3): l
988.68): C, 66.82; H, 5.50; N, 1.42. Found: C, 66.65; H,
5.37; N, 1.27%. M.p. (dec.): 232–234°C. IR (KBr):
1
2123 (CN), 1848 (FeꢂH) cm−1
.
7.395–6.941 (40H, m, Ph2PCH2CH2PPh2), 3.788 (1H,
septet, NꢂCH(CH3)2), 2.464 (4H, broad, Ph2PCH2-
CH2PPh2), 2.078 (4H, broad, Ph2PCH2CH2PPh2), 1.109
(6H, d, NCH(CH3)2), −11.333 (1H, quintet, 2JPꢂH=47
The data for 9 are as follows. Yield: 0.066 g (0.066
1
mmol, 72%). Reaction time: 14 h. H NMR (CDCl3): l
7.419–6.910 (40H, m, phenyl, Ph2PCH2CH2PPh2),
3.401 (2H, t, NCH2CH2CH3), 2.497 (4H, broad m,
Hz, HꢂFe). 13C{1H} NMR (CDCl3):
l 136.521,
135.894, 133.591, 133.290, 131.471, 130.881, 130.773,
129.040, 128.574, 127.683, (phenyl), 50.272 (s,
Ph2PCH2CH2PPh2),
2.059
(4H,
broad
m,
Ph2PCH2CH2PPh2), 1.382 (2H, m, NCH2CH2CH3),
0.687 (3H, t, NCH2CH2CH3), −11.234 (1H, quintet,
2JPꢂH=47 Hz, HꢂFe). 13C{1H} NMR (CDCl3): l
136.471, 135.857, 133.612, 133.195, 130.761, 129.024,
128.525 (phenyl), 48.134 (s, NCH2CH2CH3), 34.164 (m,
Ph2PCH2CH2PPh2), 23.098 (s, NCH2CH2CH3),
12.032(s, NCH2CH2CH3). 31P NMR (CDCl3): l 88.061
(d, 2JPꢂH=47 Hz). Anal. Calc. for C56H56NP4FeBr
(Mr=1002.71): C, 67.09; H, 5.63; N, 1.40. Found: C,
66.65; H, 5.37; N, 1.27%. M.p. (dec.): 246–248°C. IR
NCH(CH3)2), 34.081 (m, Ph2PCH2CH2PPh2) 23.717 (s,
2
NCH(CH3)2). 31P NMR (CDCl3): l 88.549 (d, JPꢂH
=
47 Hz). Anal. Calc. for C56H56NP4FeI (Mr=1049.71):
C, 64.08; H, 5.38; N, 1.33. Found: C, 63.65; H, 5.37; N,
1.27%. M.p. (dec.): 252–254°C. IR (KBr): 2095 (CN),
1847 (FeꢂH) cm−1
.
The data for 7 are as follows. Yield: 1.013 g (0.098
mmol, 89%). Reaction time: 0.5 h. 1H NMR (CDCl3): l
7.447–6.912 (40H, m, Ph2PCH2CH2PPh2), 5.421 (1H,
m, NCH2CHꢀCH2), 5.125 (2H, m, NCH2CHꢀCH2),
4.135 (2H, d, NCH2CHꢀCH2), 2.538 (4H, broad,
Ph2PCH2CH2PPh2), 2.059 (4H, broad, Ph2PCH2-
CH2PPh2), −11.045 (1H, quintet, 2JPꢂH=46 Hz,
HꢂFe). 13C{1H} NMR (CDCl3): l 136.400, 135.778,
133.657, 133.216, 130.786, 130.724, 129.069, 128.525
(phenyl), 129.981 (s, NCH2CHꢀCH2), 120.233 (s,
NCH2CHꢀCH2), 49.368 (s, NCH2CHꢀCH2), 34.139
(m, Ph2PCH2CH2PPh2). 31P NMR (CDCl3): l 88.182
(d, 2JPꢂH=46 Hz). Anal. Calc. for C56H54NP4FeI
(Mr=1000.70): C, 64.20; H, 5.19; N, 1.34. Found: C,
64.39; H, 4.97; N, 1.35%. M.p. (dec.): 220–222°C. IR
(KBr): 2111 (CN), 1847 (FeꢂH) cm−1
.
The data for 10 are as follows. This product was
washed with THF (2×10 ml) instead of diethyl ether.
Yield: 0.030 g (0.030 mmol, 32%). Reaction time: 2
days. 1H NMR (CDCl3): l 7.424–6.912 (40H, m,
phenyl, Ph2PCH2CH2PPh2), 3.425 (2H, t, NCH2CH2-
CH2CH3), 2.503 (4H, broad, Ph2PCH2CH2PPh2), 2.061
(4H, broad, Ph2PCH2CH2PPh2), 1.296 (2H, m,
NCH2CH2CH2CH3), 1.101 (2H, m, NCH2CH2CH2-
CH3), 0.826 (3H, t, NCH2CH2CH2CH3), −11.248 (1H,
quintet, 2JPꢂH=47 Hz, HꢂFe). 13C{1H} NMR (CDCl3):
l 136.521, 135.894, 133.645, 133.220, 130.757, 129.020,
128.521 (phenyl), 46.302 (s, NCH2CH2CH3), 34.672 (m,
Ph2PCH2CH2PPh2), 20.593 (s, NCH2CH2CH3), 14.277
(s, NCH2CH2CH3). 31P NMR (CDCl3): l 88.122 (d,
2JPꢂH=47 Hz). Anal. Calc. for C57H58NP4FeBr (Mr=
1016.74): C, 67.34; H, 5.75; N, 1.38. Found: C, 67.47;
H, 5.48; N, 1.35%. M.p. (dec.): 230–232°C. IR (KBr):
(KBr): 2114 (CN), 1839 (FeꢂH) cm−1
.
2.2. Preparation of trans-[FeH(CNR)(dppe)2]Br (8–13)
Compound 1 [0.088 g (0.10 mmol) for 8, 0.080 g
(0.091 mmol) for 9, 0.10 g (0.114 mmol) for 10, 0.10 g
(0.114 mmol) for 11, 0.097 g (0.11 mmol) for 12, and
0.10 g (0.114 mmol) for 13] was dissolved in 5–7 ml of
RBr (R=Et for 8, Pr for 9, n-Bu for 10, CH2CH2Br
for 11, CH2CHꢀCH2 for 12, and CH2CꢁCH for 13),
and the solution was stirred. During stirring, the or-
ange–yellow solution gradually turned to a yellow
slurry. The resulting solution was filtered, and the
remaining solid was washed with diethyl ether (3×10
ml) and then dried under vacuum.
2110 (CN), 1849 (FeꢂH) cm−1
.
The data for 11 are as follows. Yield: 0.11 g (0.103
1
mmol, 91%). Reaction time: 3 days. H NMR (CDCl3):
l 7.692–6.916 (40H, m, Ph2PCH2CH2PPh2), 3.979 (2H,
broad, NCH2CH2Br), 3.407 (2H, broad, NCH2CH2Br)
2.563 (4H, broad, Ph2PCH2CH2PPh2), 2.045 (4H,
broad, Ph2PCH2CH2PPh2), −10.786 (1H, quintet,
2JPꢂH=47 Hz, HꢂFe). 13C{1H} NMR (CDCl3): l
136.430, 135.782, 133.921, 133.303, 132.857, 131.075,
130.980, 129.540, 128.768 (phenyl), 50.635 (s,
NCH2CH2Br) 34.469 (m, Ph2PCH2CH2PPh2) 32.559 (s,
The data for 8 are as follows. Yield: 0.070 g (0.070
1
mmol, 62%). Reaction time: 14 h. H NMR (CDCl3): l
7.437–6.906 (40H, m, Ph2PCH2CH2PPh2), 3.511 (2H,
broad, NCH2CH3), 2.506 (4H, broad, Ph2PCH2-
CH2PPh2), 2.047 (4H, broad, Ph2PCH2CH2PPh2), 1.024
NCH2CH2Br). 31P NMR (CDCl3): l 88.303 (d, 2JPꢂH
=
2
47 Hz). Anal. Calc. for C55H53NP4FeBr2 (Mr=
1067.58): C, 61.88; H, 5.00; N, 1.31. Found: C, 61.47;
H, 5.25; N, 1.72%. M.p. (dec.): 220–222°C. IR (KBr):
(3H, t, NCH2CH3), −11.255 (1H, quintet, JPꢂH=47
Hz, HꢂFe). 13C{1H} NMR (CDCl3):
l 136.438,
133.653, 133.187, 130.744, 129.007, 128.512 (phenyl),
41.549 (s, NCH2CH3), 34.147 (m, Ph2PCH2CH2PPh2),
15.345 (s, NCH2CH3). 31P NMR (CDCl3): l 88.303 (d,
2JPꢂH=47 Hz). Anal. Calc. for C55H54NP4FeBr (Mr=
2082 (CN), 1850 (FeꢂH) cm−1
.
The data for 12 are as follows. Yield: 0.083 g (0.083
1
mmol, 75%). Reaction time: 4 h. H NMR (CDCl3): l

140
B.-S. Yoo et al. / Inorganica Chimica Acta 309 (2000) 137–145
7.437–6.907 (40H, m, Ph2PCH2CH2PPh2), 5.454 (1H, m,
NCH2CHꢀCH2), 5.154 (2H, m, NCH2CHꢀCH2), 4.098
(2H, d, NCH2CHꢀCH2), 2.513 (4H, broad,
Ph2PCH2CH2PPh2), 2.052 (4H, broad, Ph2PCH2-
CH2PPh2), −11.022 (1H, quintet, 2JPꢂH=47 Hz, HꢂFe).
13C{1H} NMR (CDCl3): l 136.400, 135.778, 133.657,
133.216, 130.786, 130.724, 129.069, 128.525 (phenyl),
trix and unit cell parameters were determined by least-
squares analyses of the setting angles of 39 reflections for
5 and 42 reflections for 13 in the range of 15.0B2qB
25.0°. 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 calculations
were carried out with use of the SHELXTL programs [7].
A yellow crystal of 5 of approximate dimensions
0.58×0.14×0.12 mm3, shaped as a block, was used for
crystal and intensity data collection. The unit cell
parameters and systematic absences, h0l (h+l=2n+1)
and 0k0 (k=2n+1), unambiguously indicated P21/n as
a space group. The structure was solved by the direct-
method. All non-hydrogen atoms were refined anisotrop-
ically. The counterion I− exhibited a structural disorder.
The best fit for the iodide anion was obtained by
considering the I− ion to be distributed over two
positions with the site occupation factors of 0.70:0.30. All
hydrogen atoms were generated in idealized positions
and refined in a riding model.
A yellow crystal of 13·2H2O of approximate dimen-
sions 0.10×0.28×0.78 mm3, shaped as a block, was
used. The unit cell parameters and systematic absences,
h0l (h+l=2n+1) and 0k0 (k=2n+1), unambiguously
indicated P21/n as a space group. The structure was
solved by the direct-method. All non-hydrogen atoms
were refined anisotropically. The hydrogen atoms of the
two cocrystallized water molecules were not located. The
other hydrogen atoms were generated in idealized posi-
tions and refined in a riding model.
129.948
(s,
NCH2CHꢀCH2),
120.256
(s,
NCH2CHꢀCH2), 49.133 (s, NCH2CHꢀCH2), 34.139 (m,
Ph2PCH2CH2PPh2). 31P NMR (CDCl3): l 88.152 (d,
2JP–H=47 Hz). Anal. Calc. for C56H54NP4FeBr (Mr=
1000.70): C, 67.21; H, 5.44; N, 1.40. Found: C, 67.10; H,
5.34; N, 1.35%. M.p. (dec.): 240–242°C. IR (KBr): 2107
(CN), 1848 (FeꢂH) cm−1
.
The data for 13 are as follows. Yield: 0.105 g (0.105
1
mmol, 93%). Reaction time: 1 day. H NMR (CDCl3):
l 7.472–6.892 (40H, m, Ph2PCH2CH2PPh2), 2.616 (1H,
s, NCH2CꢁCH), 2.543 (2H, broad, NꢂCH2CꢁCH), 2.530
(4H, broad, Ph2PCH2CH2PPh2), 2.055 (4H, broad,
2
Ph2PCH2CH2PPh2), −10.529 (1H, quintet, JPꢂH=47
Hz, HꢂFe). 13C{1H} NMR (CDCl3): l 136.228, 135.493,
133.756, 133.084, 130.901, 130.736, 129.172, 128.566
(phenyl), 75.015 (s, NCH2CꢁCH), 74.809 (s,
NCH2CꢁCH), 36.334 (s, NCH2CꢁCH), 34.222 (m,
Ph2PCH2CH2PPh2). 31P NMR (CDCl3): l 88.152 (d,
2JPꢂH=47 Hz). Anal. Calc. for C56H52NP4FeBr (Mr=
998.68): C, 67.35; H, 5.25; N, 1.40. Found: C, 67.56; H,
5.19; N, 1.64%. M.p. (dec.): 224–226°C. IR (KBr): 2103
(CN), 2001 (CꢁC), 1850 (FeꢂH) cm−1
.
2.3. Preparation of trans-[FeH(CN“BF3)(dppe)2] (14)
Et2O·BF3 (15 ml, 0.120 mmol) was added to 10 ml of
CH2Cl2 containing 1 (0.097 g, 0.110 mmol), and the
resulting solution was stirred for 10 min. The solvent was
removed under vacuum to give yellow solids, which were
washed with diethyl ether (2×10 ml) and then dried
under vacuum to give yellow–green solids of 14. Yield:
0.077 g (0.081 mmol, 74%). 1H NMR (CDCl3): l
7.394–7.037 (40H, m, Ph2PCH2CH2PPh2), 2.407 (4H,
broad, Ph2PCH2CH2PPh2), 1.981 (4H, broad,
Details on crystal data and intensity data are given in
Table 1. The selected bond distances and bond angles for
5 and 13 are shown in Tables 2 and 3.
3. Results and discussion
2
Ph2PCH2CH2PPh2), −12.155 (1H, quintet, JPꢂH=46
3.1. Preparation
Hz, HꢂFe). 13C{1H} NMR (CDCl3): l 137.697, 136.591,
134.103, 133.938, 129.989, 129.965, 128.582, 128. 025
(phenyl), 33.953 (m, Ph2PCH2CH2PPh2). 31P NMR
Organic isocyanide complexes of the type trans-[Fe-
H(CNR)(dppe)2]X (R=alkyl; X=Br, I) have been pre-
2
(CDCl3): l 89.267 (d, JPꢂH=46 Hz). 11B{1H} NMR
pared from
a
neutral Fe(II)–cyanide complex,
(CDCl3): l −4.130. Anal. Calc. for C53H49NBF3P4Fe
(Mr=947.52): C, 67.18; H, 5.21; N, 1.48. Found: C,
67.49; H, 5.10; N, 1.53%. M.p. (dec.): 202–204°C. IR
trans-[FeH(CN)(dppe)2] (1), and various alkyl halides
(Eq. (2)). The types of the alkyl are primary (R=Me,
Et, Pr, n-Bu, CH2CH2Br, and CH2CH2CH2I), secondary
(i-Pr), allyl (R=CH2CHꢀCH2), and propargyl
(CH2CꢁCH). Recently, Pombeiro’s group prepared a
related series of iron(II)–organic isocyanide complexes,
trans-[FeH(CNR)(dppe)2][A] (R=Me, Et, t-Bu,
C6H4OMe-4, C6H5, or C6H4NO2-4, A=BF4, or PF6), by
treating trans-[FeHCl(dppe)2] with the organic iso-
(KBr): 2094 (CN) cm−1, 1890 (FeꢂH) cm−1
.
2.4. X-ray structure determination
All X-ray data were collected with use of a Siemens
P4 diffractometer equipped with a Mo X-ray tube and
a graphite crystal monochromator. The orientation ma-

B.-S. Yoo et al. / Inorganica Chimica Acta 309 (2000) 137–145
141
Table 1
When 1 is treated with the alkyl halide in a stoichiomet-
ric fashion or even in two- to fivefold excess of the alkyl
halide, only a trace amount of the desired product is
formed, which has been monitored by NMR and IR
spectroscopy. In contrast, reactions of 1 with aryl
halides such as iodobenzene, 4-iodotolulene, and 1-
iodo-4-nitrobenzene, have not been successful.
X-ray data collection and structure refinement for 5 and 13·2H2O
5
13·2H2O
Formula
C56H55NP4FeI2 C56H56NP4FeBr
Formula weight
Temperature (K)
Crystal system
Space group
1175.84
297(2)
monoclinic
P21/n
1034.66
296(2)
monoclinic
P21/n
,
a (A)
13.579(2)
17.077(3)
21.778(3)
90.471(7)
5050(1)
4
13.422(2)
17.132(3)
21.454(3)
90.443(9)
4933(1)
4
,
b (A)
,
c (A)
i (°)
V (A )
3
,
Z
Dcalc (g cm−3
)
1.546
1.686
1.393
1.289
v (mm−1
Tmin
)
0.2788
0.3073
2360
0.0364
8959
8616
5888
592
3.5–51.0
ꢀ
0.2242
0.2709
2144
0.0578
8911
8532
5218
589
3.5–501.0
ꢀ
Tmax
F(000)
Rint
Reflections measured
Reflections unique
Reflections with I\2|(I)
Parameters refined
2q Range (°)
(2)
In these reactions, the initially orange–yellow solu-
tion gradually turns to a slightly yellow slurry, which is
filtered, washed, and dried under vacuum to give the
product. All the products are stable in the solid state,
but unstable in solution. As expected on the basis of
leaving group effects (RI\RBr), complexes 2–7 (reac-
tion time: 1.5–4 h) possessing the I− counterion are
formed much faster than complexes 8–13 (reaction
time: 14 h–3 days) possessing the Br− counterion.
Due to the coupling between a hydride and four
equivalent phosphorus nuclei in the dppe ligands occu-
pying the equatorial sites, complexes 2–13 show a
Scan type
Scan speed
variable
1.021
0.872, −2.168
0.0730
0.1828
variable
1.038
0.954, −1.386
0.0803
0.1959
Goodness-of-fit on F2
−3
,
Max., min. in Dz (e A
)
R
wR2
a
a wR2=ꢀ[w(Fo2−Fc2)2]/ꢀ[w(Fo2)2]1/2
.
1
quintet for the hydride ligand in their H NMR spectra
and a doublet for the dppe ligand in their 31P NMR
spectra with a coupling constant of JPꢂH=46–47 Hz.
On alkylation, whereas the chemical shift for the hy-
dride peak in the parent molecule 1 shifts to a lower
cyanides in the presence of Tl[A] or by replacing N2 in
trans-[FeH(N2)(dppe)2][A] with the appropriate iso-
cyanides [1].
Stirring the alkyl halide solution containing 1 at
room temperature gives the corresponding organic iso-
cyanide complex of Fe(II). In these reactions, the alkyl
halide behaves both as a reagent and as a solvent.
1
field in the H NMR spectra, that for the dppe peak
shifts to a higher field in the 31P NMR spectra. In IR
spectra, an increase in w(CꢁN) by 50–89 cm−1 is
observed on alkylation, which suggests that the lone
Table 2
,
Selected bond distances (A) and bond angles (°) in 5
Fe1ꢂC53
Fe1ꢂP1
I1ꢂC56
1.845(6)
2.257(2)
2.00(2)
1.50(1)
Fe1ꢂP4
Fe1ꢂP2
N1ꢂC53
C55ꢂC56
2.237(2)
2.259(2)
1.161(8)
1.48(2)
Fe1ꢂP3
Fe1ꢂHfe
N1ꢂC54
2.251(2)
1.59(6)
1.422(8)
C54ꢂC55
C53ꢂFe1ꢂP4
P4ꢂFe1ꢂP3
P4ꢂFe1ꢂP1
C53ꢂFe1ꢂP2
P3ꢂFe1ꢂP2
C53ꢂFe1ꢂHfe
C53ꢂN1ꢂC54
N1ꢂC54ꢂC55
C55ꢂC56ꢂI1
97.2(2)
83.78(6)
95.64(6)
87.5(2)
96.52(6)
175(2)
175.4(7)
111.7(6)
112.3(9)
C53ꢂFe1ꢂP3
C53ꢂFe1ꢂP1
P3ꢂFe1ꢂP1
P4ꢂFe1ꢂP2
P1ꢂFe1ꢂP2
P4ꢂFe1ꢂHfe
N1ꢂC53ꢂFe1
C56ꢂC55ꢂC54
91.6(2)
94.6(2)
173.86(7)
175.26(7)
83.55(6)
81(2)
175.6(6)
116.3(10)

142
B.-S. Yoo et al. / Inorganica Chimica Acta 309 (2000) 137–145
Table 3
,
Selected bond distances (A) and bond angles (°) in 13·2H2O
Fe1ꢂC53
Fe1ꢂP1
N1ꢂC53
C51ꢂC52
1.851(6)
2.256(2)
1.153(8)
1.506(9)
Fe1ꢂP3
Fe1ꢂP2
N1ꢂC54
C54ꢂC55
2.234(2)
2.255(2)
1.398(9)
1.319(12)
Fe1ꢂP4
2.251(2)
1.61(9)
1.528(9)
1.255(13)
Fe1ꢂHfe
C49ꢂC50
C55ꢂC56
C53ꢂFe1ꢂP3
P3ꢂFe1ꢂP4
P3ꢂFe1ꢂP1
C53ꢂFe1ꢂP2
P4ꢂFe1ꢂP2
C53ꢂFe1ꢂHfe
N1ꢂC53ꢂFe1
C56ꢂC55ꢂC54
98.2(2)
83.98(7)
95.51(6)
88.9(2)
96.58(7)
178(3)
C53ꢂFe1ꢂP4
C53ꢂFe1ꢂP1
P4ꢂFe1ꢂP1
P3ꢂFe1ꢂP2
P1ꢂFe1ꢂP2
C53ꢂN1ꢂC54
C55ꢂC54ꢂN1
92.5(2)
92.6(2)
174.93(7)
172.89(7)
83.29(6)
177.1(7)
120.9(7)
177.4(6)
176.8(10)
Fig. 1. ORTEP drawing of the cationic part of 5, showing the atom-labeling scheme and 50% probability thermal ellipsoids.
[RuCp(PPh3)2(CN)]+RX“[RuCp(PPh3)2(CNR)][X]
pair of electrons on the cyano nitrogen is slightly
antibonding in nature. In addition, FeꢂH bands in 2–13
that have variable intensities appear in the range of
1833–1850 cm−1. In UV–Vis spectra in CH2Cl2, all of
the products show two maximum peaks at 229–232 and
258–263 nm.
(R=alkyl; X=1 or Br)
(3)
[FeCp(dppe)(CN)]+[Me3O][BF4]
“[FeCp(dppe)(CNMe)][BF4]
(4)
3.2. Structure
Recently, Baird and Davies have prepared alkyl isocy-
anide complexes of Ru(II) by treating the electron-rich
Ru(II) cyanide complex with mild electrophiles (alkyl
halides) (Eq. (3)). However, they could prepare the
Fe(II) analogue by treating the Fe(II) cyanide complex
only with a strong electrophile such as trimethyloxonium
tetrafluoroborate (Eq. (4)) [8]. In our reactions, we have
prepared alkyl isocyanide complexes of Fe(II) by treat-
ing 1 with mild electrophiles such as alkyl iodides or
alkyl bromides, which act both as solvents and as
reagents.
The structure of the cationic part of 5,
[FeH(CNCH2CH2CH2I)(dppe)2]+, with the atomic
numbering scheme is shown in Fig. 1, and that of
13·2H2O, [FeH(CNCH2CCH)(dppe)2]+ in Fig. 2. The
coordination sphere of the Fe metal in both complexes
can be described as an octahedron, with two bidentate
dppe ligands at the equatorial sites and the hydride and
nitrile ligands at the axial sites. The anions I− for 5 and
Br− for 13 are not bonded to the Fe metal and act as
counterions.

B.-S. Yoo et al. / Inorganica Chimica Acta 309 (2000) 137–145
143
The equatorial plane in 5, defined by the four dppe
phosphorus atoms (P1ꢂP4), is nearly planar with the
bonding parameters suggest that the resonance form I
in both compounds is a major contribution in which
Fe“C p-back bonding does not play an important
role.
,
average atomic displacement of 0.0142 A. The Fe metal
,
lies 0.1064
A below the equatorial plane. The
ꢂCH2CH2CH2I fragment of the isocyanide is directed
toward the open space between the two phenyl rings
(C31ꢂC36 and C43ꢂC48), probably due to steric con-
gestion. The equatorial plane in 13, defined by the four
dppe phosphorus atoms (P1ꢂP4), is nearly planar with
Compound 5 and 13 appear to have to a pseudo-C2
axis that passes through the Fe, C53, and Hfe atoms
and is perpendicular to the equatorial plane. This sym-
metry might reflect the equivalency of the four phos-
phorus nuclei in the NMR spectra of 5. In other words,
the crystal structures explain the NMR spectra of both
compounds that show a quintet for the H ligand in
,
the average atomic displacement of 0.0192 A. The Fe
,
metal lies 0.1189 A below the equatorial plane. The
propargyl fragment ꢂCH2CꢁCH of the isocyanide is
also directed toward the open space between the two
phenyl rings (C31ꢂC36 and C37ꢂC42).
The hydride ligands (Hfe) could be located and rea-
sonably refined with an isotropic thermal parameter,
1
their H NMR and a doublet for the four P atoms their
,
,
and the distances of FeꢂH (1.59(6) A for 5, 1.61(9) A
for 13) appear to be somewhat reliable. The mean
values of transition metalꢂhydride (MꢂH) bond dis-
tances determined by neutron diffraction have been
summarized by Bau and Drabnis, and the average
31P NMR spectra. The results of the X-ray structures
and NMR spectral data indicate that these compounds
have the same structure both in solution and in the
solid state.
,
distance of a terminal FeꢂH bond is 1.575(17) A and
3.3. MꢂH···HꢂC dihydrogen bonding
,
that of a bridging FeꢂHꢂFe bond is 1.664(11) A [9].
The bond distances between the iron metal and the
alpha carbon of the isonitrile ligand (FeꢂC53), 1.845(6)
A for 5 and 1.851(6) A for 13, belong to the lowest
Recently, the hydrogen bond in organometallic com-
pounds has been the focus of research. It is now
accepted that most kinds of CꢂH groups can act as
hydrogen-bond donors [11–17]. Moreover, it has been
recognized for many years that the CꢂH bonds can act
as weak hydrogen-bond proton donors in the order:
C(sp)ꢂH\C(sp2)ꢂH\C(sp3)ꢂH [18].
Crabtree and co-workers proposed recently a new
type of the dihydrogen bonding (MꢂH···HꢂC) in aryl
phosphine (PAr3) hydride complexes [19]. According to
their own work and CSD survey, the H···H distances
,
,
,
limit of the range (1.923–1.850 A) of the FeꢂC bond
distance found for FeꢂCN (terminal) complexes [10].
,
The C53ꢂN1 bond distances (1.161(8), 1.153(8) A) indi-
cate a CꢁN triple bond, and the N1ꢂC54 bond dis-
,
tances (1.422(8), 1.398(9) A) indicate an NꢂC single
bond. In addition, the FeꢂC53ꢂN1 and C53ꢂN1ꢂC54
bonds are almost linear with the angles of (175.6(6)–
177.4(6)°) and (175.4(7)–177.1(7)°), respectively. These
Fig. 2. ORTEP drawing of the cationic part of 13·2H2O, showing the atom-labeling scheme and 50% probability thermal ellipsoids.

144
B.-S. Yoo et al. / Inorganica Chimica Acta 309 (2000) 137–145
Table 4
These spectral data are in good agreement with those
observed for CpFe(CO)2(CHꢀCꢀCH2) (J=6.5 Hz) [21],
Cp(CO)3W(CHꢀCꢀCH2) (J=6.7 Hz) [22], and
Cp(CO)2Ru(CHꢀCꢀCH2) (J=6.5 Hz) [23] complexes.
In fact, the allenyl–propargyl tautomerism is now com-
mon in organometallic compounds [24]. The 1H and
13C NMR spectroscopy are important tools in differen-
tiating these two isomers. For example, the long-range
coupling constants (4JHꢂH) have been recognized as
being diagnostic of the tautomeric bonding mode
adopted. The allenyl (ꢂCHꢀCꢀCH2) fragment displays a
,
Distances (A) and angles (°) in the MꢂH···HꢂC moiety
Compound 5
Compound 13
H···H
Hfe···H8: 2.21
Hfe···H30: 2.18
Fe1ꢂHfe···H8: 125
Fe1ꢂHfe···H30: 124
Hfe···H8ꢂC8: 138
Hfe···H30ꢂC30: 137
Hfe···H6: 2.12
Hfe···H20: 2.14
Fe1ꢂHfe···H6: 129
Fe1ꢂHfe···H20: 127
Hfe···H6ꢂC6: 138
Hfe···H20ꢂC20: 138
MꢂH···H
H···HꢂC
4
larger JHꢂH value (6–7 Hz) than the propargyl
,
,
range from 1.50 to 2.20 A (mean, 1.96 A), MꢂH···H
angles from 109 to 170° (mean, 130°) with a strong
preference for the range 122–142°, and H···HꢂC angles
from 118 to 164° (mean, 142°) with a strong preference
for the range 138–148°. For comparison, the der Waals
(ꢂCH2ꢂCꢁCH) counterpart (2–3 Hz). Unfortunately,
we cannot give a clear-cut explanation for 13l13a
tautomeric rearrangement in our study.
,
radius of H is 1.2 A.
Compounds 5 and 13 have the aryl phosphine (dppe)
ligand, and the distances and angles of the MꢂH···HꢂC
moiety (Table 4) are highly consistent with the pre-
ferred values suggested by the Crabtree’s study. On the
basis of the bonding parameters described above, the
hydride ligand (Hfe) in both compounds appears to be
involved in the dihydrogen bond of the type
MꢂH···HꢂC. Moreover, each hydride ligand seems to
be dihydrogen-bonded simultaneously to the two CꢂH
bonds, which might make possible the location of this
ligand in the X-ray diffraction studies.
(6)
In 13C{1H} NMR spectra, the central carbon of the
allenyl ligand (ꢀCꢀ) appears at l 211.539 ppm, and the
CH2 and CH carbon atoms appear at l 90.929 and l
86.873 ppm, respectively. The quaternary carbon atoms
of the h1-allenylic complexes are known to resonate at
extremely low field (l ꢀ200 ppm), far apart from those
of the propagylic tautomers that appear at much higher
filed (Dl=120 ppm) [24]. In our case, the difference in
chemical shifts of the central carbon atoms of the both
isomers (Dl) is 142 ppm. In IR spectra, we can see a
strong band (2071 cm−1) assigned to 6(CN), but we
cannot see the band assignable to the CꢀCꢀC bond.
Cyclic voltammograms for complexes 2 and 3 have
been recorded, and the observed anodic waves are in
accord with those for [FeH(CNR)(dppe)2]A (R=Me,
Et; A=BF4, PF6) reported by the Pombeiro’s group
[25].
In summary, we have readily prepared Fe(II)–or-
ganic isocyanide complexes of the type trans-[Fe-
H(CNR)(dppe)2]X by the attack of mild electrophiles
(alkyl halides, RX) under mild conditions. In these
reactions, alkyl halides behave both as reagents and
solvents. Molecular structures of compounds 5 and 13
show that the MꢂH hydrogen (or hydride) in both
compounds appears to be dihydrogen-bonded simulta-
neously to the two CꢂH bonds.
3.4. Properties
Compound 1 reacts with trifluoroborane (BF3) to
give a Lewis acid–base adduct, trans-[FeH(CNBF3)-
1
(dppe)2] (14), which has been characterized by IR, H
NMR, 31P NMR, and 11B{1H} NMR (Eq. (5)). The
11B{1H} NMR spectra of 14 in CDCl3 exhibit a singlet
at l −4.130 ppm, which belongs to the range (l−
2.9ꢀ −4.8 ppm) found for CpRu(PPh3)2(CNBF3),
CpFe(dppe)(CNBF3), trans-Pt(PEt3)2(CNBF3)2, trans-
Pt(PPh3)2(CNBF3)2, and CpFe(CO)(PPh3)(CNBF3)
complexes in CDCl3 [20]. Compound 1 does not react
with trimethylaluminum (AlMe3) that is a weaker Lewis
acid than BF3.
[FeH(dppe)(CN)]+BF3“[FeH(dppe)(CN“BF3)] (14)
(5)
When 13 is kept in dichloromethane, a mixture of an
iron propargyl isocyanide (13) and an iron allenyl
1
isocaynide (13a) is formed (Eq. (6)). On the basis of H
NMR peak intensities of these two tautomeric isomers,
1
the ratio of 13 to 13a is approximately 6:4. In H NMR
spectra of 13a, the CH2 protons appear at l 5.543 ppm
as a doublet and the CH proton at l 6.017 ppm as a
triplet. In addition, a relatively large coupling constant
of JHꢂH=6.0 Hz is observed for the four-bond cou-
pling between the terminal CH2 and the internal CH.
4. Supplementary material
4
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data

B.-S. Yoo et al. / Inorganica Chimica Acta 309 (2000) 137–145
145
[7] Bruker, SHELXTL, Structure Determination Software Programs,
Bruker Analytical X-ray Instruments Inc., Madison, WI, 1997.
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Center, CCDC no. 140834 for 5, CCDC no. 140833 for
13·2H2O. Copies of this information may be obtained
free of charge from: The director, CCDC, 12 Union
Road, Cambridge, CB2 1EZ, UK (fax: +44-1223-
336033; email: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
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The authors wish to acknowledge the sabbatical leave
in the Program Year 1998–1999 of Sungkyunkwan
University.
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