Synthesis and reactivity of [(R1R2N)2PH]Fe(CO)4 complexes. X-ray crystal structure of [(Ph2N)2PH]Fe(CO)4

Article abstract of DOI:10.1016/S0022-328X(98)00744-X

KHFe(CO)₄ reacts with tris(amino)phosphines by substitution at phosphorus leading to [bis(amino)phosphine]tetracarbonyliron complexes [(R¹R²N)₂PH]Fe(CO)₄. The X-ray structure has been determined for R¹=R²=Ph. Deprotonation of these complexes with KH affords stable potassium phosphidotetracarbonylferrates which can be alkylated or acylated at phosphorus.

Full text of DOI:10.1016/S0022-328X(98)00744-X

Journal of Organometallic Chemistry 570 (1998) 195–200
Synthesis and reactivity of [(R1R2N)2PH]Fe(CO)4 complexes. X-ray
crystal structure of [(Ph2N)2PH]Fe(CO)4
Jean-Jacques Brunet, Remi Chauvin, Ousmane Diallo, Bruno Donnadieu, Joe¨lle Jaffart,
Denis Neibecker *
Laboratoire de Chimie de Coordination du CNRS, Unite´ No 8241,
lie´e par con6entions a` l’Uni6ersite´ Paul Sabatier et a` l’Institut National Polytechnique, 205 route de Narbonne, 31077 Toulouse, Cedex 4, France
Received 13 March 1998; received in revised form 29 May 1998
Abstract
KHFe(CO)4 reacts with tris(amino)phosphines by substitution at phosphorus leading to [bis(amino)phosphine]tetracarbonyliron
complexes [(R1R2N)2PH]Fe(CO)4. The X-ray structure has been determined for R1=R2=Ph. Deprotonation of these complexes
with KH affords stable potassium phosphidotetracarbonylferrates which can be alkylated or acylated at phosphorus. © 1998
Elsevier Science S.A. All rights reserved.
Keywords: Aminophosphines; Iron carbonyl; Hydridotetracarbonylferrates; Phosphidotetracarbonylferrates
1. Introduction
We report here the synthesis of several of these
complexes and the X-ray crystal structure of
[(Ph2N)2PH]Fe(CO)4, which is the first X-ray crystal
structure of a bis(amino)phosphine coordinated to a
transition metal, along with preliminary results on both
the deprotonation of [(R2N)2PH]Fe(CO)4 derivatives
and the reactivity of the resulting phosphidotetracar-
bonylferrate complexes.
As part of our interest in the chemistry of hydridote-
tracarbonylferrates M+[HFe(CO)4]− [1], we have re-
ported the reaction of K+[HFe(CO)4]− with
phosphites and phosphines [2]. These reactions procee
by CO exchange processes [3], providing highly selective
routes to a large variety of ionic and neutral phos-
phane-substituted ironcarbonyl complexes [4–6].
In contrast, the reaction of K+[HFe(CO)4]− with
tris(dimethylamino)phosphine does not proceed by CO
substitution. Instead, substitution of an amino group at
phosphorus is observed, affording K2Fe(CO)4 and the
neutral irontetracarbonyl complex [(Me2N)2PH]
(Fe(CO)4 [7]. This reaction provides a very easy, labora-
tory scale preparation of the Collman type reagents
M2Fe(CO)4 (M=Na, K) for immediate use. It should
also be an easy way to prepare ironcarbonyl-stabilized
secondary bis(amino)phosphines.
2. Results and discussion
2.1. Synthesis of [(R1R2N)2PH]Fe(CO)4 complexes
The reaction of KHFe(CO)4 1 with tris(amino)
phosphines 2a–c is conducted at room temperature in
(r.t.) THF (Eq. (1)). For 2b, the reaction is instanta-
neous, as indicated by an immediate white precipitate
of K2Fe(CO)4, whereas for 2a and 2c, the reaction
occurs only on evaporation of the solvent under re-
duced pressure. Classical work-up allows isolation of
complexes 4a–c in a 70–90% yield.
* Corresponding author. Tel.: +33 561 333195; fax: +33 561
553003; e-mail: neibeker@lcctoul.lcc-toulouse.fr
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00744-X

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J.-J. Brunet et al. / Journal of Organometallic Chemistry 570 (1998) 195–200
3
˚
Complex 4c is reported for the first time. 4a and 4b have
atoms (1.66–1.68 A [10,11]) and sp -type nitrogen atoms
been previously prepared by reacting either (iPr2N)2PH
with Fe(CO)4(THF) (4b) [8] or [PPh4][HFe(CO)4] with the
corresponding bis(dialkylamino)chlorophosphine (4a,
4b) [9].
˚
(1.73–1.74 A [11]), respectively.
2.3. Reaction of [(R1R2N)2PH]Fe(CO)4 complexes 4
with KH
The synthesis of complexes 4 from tris(amino)phos-
phines (Eq. (1)) thus appears as an interesting alternative
to the above-mentioned procedures via a P–N bond
activation process instead of a P–Cl one. Nevertheless,
when tris(amino)phosphines are not readily accessible,
the reaction shown in Eq. (2) [9] involving such a P–Cl
bond activation is the best synthetic procedure and has
been used to obtain 4c and the previously unreported
[(Ph2N)2PH]Fe(CO)4, 4d.
Several mechanistic proposals involving terminal phos-
phinidene complexes as intermediates [12] encouraged us
to study the deprotonation of complexes 4 under non-re-
versible conditions.
Reaction of 4a,c,d with excess KH in Et2O or THF at
r.t. results in the quantitative formation (31P-NMR) of
the air-sensitive phosphido complexes 5a,c,d (Eq. (3)).
As verified for 5c, complexes 5a,c,d can alternatively
be obtained by allowing K2Fe(CO)4 to react with the
corresponding (R1R2N)2PCl in DMAC, according to the
route reported from Na2Fe(CO)4 and Ar2PCl [13].
In the case of 4b (R1=R2=iPr), the reaction with KH
regenerates [HFe(CO)4]− and (iPr2N)2PH, indicating
that H− acts as a competitive ligand for the [Fe(CO)4]
moiety.
The phosphidotetracarbonylferrates 5 can be repre-
sented by the resonance forms shown in Scheme 1 and
are characterized by a low-field 31P-NMR signal in the
range 220–230 ppm.
This deshielding suggests the participation of the
amido-stabilized phosphinidene resonance form in the
description of the complex. This proposal is supported
by analogy with literature data on base-stabilized ironsi-
lylene complexes, e.g. [Fe(CO)4{SiMe2–(NMe2H)}] [14],
and by the behaviour of complex 5a. Indeed, although
complexes 5c and 5d are stable in THF, complex 5a slowly
decomposes at r.t. Thus, stirring a solution of 4a in the
presence of excess KH in THF leads to the clean
formation of 5a (31P{1H}-NMR). After 2 days at r.t. the
2.2. X-ray crystal structure of 4d
The structure of 4d has been determined by X-ray
diffraction analysis (Table 1). A view of the molecular
structure with atom labelling scheme is shown in Fig. 1.
The Fe atom adopts an approximately trigonal-bipyrami-
dal geometry with a nearly perfect trigonal plane of three
CO ligands for which each C–Fe–C bond angle is 120°.
The phosphorus atom and the fourth CO ligand occupy
axial sites (P1–Fe–C2=176.6°). The Fe–P1 bond length
˚
(2.234(1) A) is close to that found for [(Me2N)3P]Fe(CO)4
˚
˚
(2.245 A) and for (Ph3P)Fe(CO)4 (2.244 A) [10]. The
geometry at phosphorus is approximately tetrahedral, the
average bond angle N1–P1–N2, Fe–P1–N1 and Fe–
P2–N2 being 115°. The sum of the angles about nitrogen
is equal to 360°. The most intriguing structural feature
is that, although the geometry at each nitrogen atom is
perfectly trigonal planar, the two P–N bond lengths are
unexpectedly very different (P1–N2=1.670(3); P1–
˚
N1=1.739(4) A) and in the range found for phospho-
rus–nitrogen compounds containing sp2-type nitrogen

J.-J. Brunet et al. / Journal of Organometallic Chemistry 570 (1998) 195–200
197
By contrast, the phosphido character (Scheme 1) of
complexes 5 is revealed by their reaction with CH3I or
CH3COCl to afford the expected alkyl- or acyl-
bis(amino)phosphinetetracarbonyliron complexes 9c
and 10c in good yield, as demonstrated for 5c (Eq. (5))
Scheme 3.
deaerated by distillation from P2O5 under argon. Sam-
ples of (Me2N)3P and KH as a dispersion in mineral oil
were purchased from Fluka and Aldrich, respectively.
Literature methods or methods adapted therefrom were
used to prepare (i-Pr2N)3P, (EtPhN)3P, (i-Pr2N)2PCl,
(EtPhN)2PCl,
(Ph2N)2PCl
[17],
solutions
of
These reactions are additional examples of the depro-
tonation-alkylation sequence of coordinated secondary
phosphines known for a long time [15] and of the
synthesis of coordinated acylphosphines [16].
KHFe(CO)4 in THF [2] and K2Fe(CO)4 [7]. NMR
spectra were recorded on Bruker AC-200 or Bruker
AMX-400 spectrometers. 31P{1H}-NMR-spectra were
1
referenced to external H3PO4. H-NMR spectra were
referenced to the residual proton resonance of the
deuterated solvents (SDS) (CDCl3, lH=7.27; C6D6,
lH=7.15; THF-d8, lH=3.60 ppm). 13C{1H}-NMR
spectra were referenced to the carbon resonance of the
solvents (CDCl3, lC=77.0; C6D6, lC=128.5; THF-
d8, lC=25.8 ppm). Satisfactory C, H, N analysis (9
0.6%) were obtained for complexes 4a–d, 9c and 10c
(Laboratory In-house Service, Perkin-Elmer 2400 ap-
paratus).
3. Experimental section
3.1. General procedure and reagent syntheses
All manipulations were performed under argon using
standard Schlenk tube and vacuum line techniques.
THF (SDS) and diethylether (SDS) were dried and
deaerated by distillation from sodium–benzophenone
ketyl under argon. n-Pentane (SDS) was dried and
3.2. Preparation of complexes 4
Table 1
Complexes 4a and 4b were prepared from
KHFe(CO)4 and the corresponding tris(dialky-
lamino)phosphine, as previously described for
(Me2N)3P [7]. 4b could also be prepared from
KHFe(CO)4 and (i-Pr2N)2PCl. 4a and 4b displayed
similar NMR spectra as those previously reported [7,9].
4c: (EtPhN)2PCl (4.9 mmol) was added to a solution
of KHFe(CO)4 (5.0 mmol) in THF (15 ml) at r.t. After
10 min stirring, the solvent was evaporated and pentane
(20 ml) was added. The liquid phase was cannulated
into another Schlenk flask and evaporated to give
[(EtPhN)2PH]Fe(CO)4 4c (oil, 72%). 31P{1H}-NMR
(162.0 MHz) (THF-d8) l (ppm)=136.3; 1H-NMR
(400.1 MHz) (THF-d8) l (ppm)=0.94 (t, 6H, CH3CH2,
3JH–H=7.0 Hz); 3.58 and 3.78 (ABC3Y system, 4H,
Crystal and collection data for complex 4d
Crystal parameters
Empirical formula
M (g)
Shape (color)
Size (mm)
C28H21FeN2O4P
536.31
Plate (orange)
0.5×0.5×0.07
Triclinic
Crystal system
Space group
(
P1
˚
a (A)
9.051(1)
11.111(2)
13.827(2)
100.66(1)
109.50(2)
104.53(2)
1212.6(4)
2
˚
b (A)
˚
c (A)
h (°)
i (°)
k (°)
3
˚
V (A )
Z
3
2
F(000)
4040
1.40
6.9
CH3CH2, JH–P=8.9 Hz, JH–H=14.0 Hz); 7.1–7.35
Dcalc. (g cm−3
)
1
(10H, aromatic H); 8.0 (d, 1H, HP, JH–P=454.3 Hz;
v (Mo–Ka) (cm−1
Data Collection
Diffractometer
Monochromator
Radiation
)
13C{1H}-NMR (50.3 MHz) (THF-d8) l (ppm)=15.0
3
2
(d, CH3CH2, JC–P=4 Hz); 47.5 (d, CH3CH2, JC–P
=
IPDS Stoe
Graphite
Mo–Kh (u=0.71073)
ƒ
2
8 Hz); 127.1, 128.8, 130.6, 146. (d, JC–P=3 Hz) (aro-
matic C); 214.6 (d, CO, JC–P=20 Hz).
2
Scan mode
4d: (Ph2N)2PCl (2.5 mmol) was added to a solution
of KHFe(CO)4 (4 mmol) in THF (15 ml) at r.t. After 5
h stirring, the solvent was evaporated and pentane (20
ml) was added. The liquid phase was cannulated into
another Schlenk flask in which [(Ph2N)2PH]Fe(CO)4 4d
slowly crystallised as orange plates (32%). 31P{1H}-
ƒ range (°)
ƒ incr. (°)
2q range (°)
No. of rflns collected
No. of unique rflns
No. rflns used (I\3|(I))
Refinement
R
Rw
Weighting scheme
Coeff. Ar
Goodness-of-fit
L.s parameters
0BƒB250
2
2.9BqB48.4
8963
3449
2337
1
NMR (81.0 MHz) (CDCl3) l (ppm)=120.4; H-NMR
0.053
0.059
Chebyshev
3.17; −0.408; 2.59
1.10
330
(200.1 MHz) (CDCl3) l (ppm)=7.00–7.30 (20H, aro-
1
matic H); 8.77 (d, 1H, HP, JH–P=444.0 Hz; 13C{1H}-
NMR (50.3 MHz) (CDCl3) l (ppm)=125.8, 127.3 (d,
J
C–P=3 Hz), 129.2, 145.9 (aromatic C); 212.6 (d, CO,
2JC–P=20 Hz).

198
J.-J. Brunet et al. / Journal of Organometallic Chemistry 570 (1998) 195–200
Fig. 1. Molecular structure of complex 4d showing the atom numbering scheme.
P=8 Hz); 117.3 (d, JC–P=2 Hz), 120.0 (d, JC–P=17
Hz), 128.7, 151.7 (d, 2JC–P=19 Hz) (aromatic C); 220.3
(CO).
3.3. Synthesis of complexes 5a,c,d
In a typical experiment, an excess of KH in mineral
oil was washed with THF (3×2 ml) and the solvent
was evaporated under vacuum until a mobile powder
was obtained. A solution of 4c (2 mmol) in diethyl
ether (10 ml) was then added and the reaction mixture
was stirred until gas evolution ceased. The supernatant
phase was then cannulated into another Schlenk flask
and the solvent removed under vacuum to afford 5c
(73%).
5d: 31P{1H}-NMR (81.0 MHz) (C6D6) l (ppm)=
208.3; 13C{1H}-NMR (50.3 MHz) (C6D6) l (ppm)=
118.5, 122.4, 126.7 (d, JC–P=7.5 Hz), 129.5, 130.6,
151.8 (d, 2JC–P=3 Hz) (aromatic C); 218.6 (d, CO,
JC–P=3 Hz).
3.4. Alternati6e generation of complex 5c
Complexes 5a and 5d were similarly prepared but
only 5d could be isolated (70% yield) (see text).
5a: 31P{1H}-NMR (162.0 MHz) (THF-d8) l (ppm)=
A solution of (PhEtN)2PCl (0.25 mmol) in DMAC
(1.2 ml) was dropped by means of a syringe into a
magnetically stirred solution of K2Fe(CO)4 (0.25 mmol)
in DMAC (4 ml) at r.t. After 15 min, the 31P{1H}-
NMR spectrum of the crude solution indicated the
quantitative formation of 5c.
1
231.2; H-NMR (400.1 MHz) (THF-d8) l (ppm)=2.47
3
(d, CH3, JH–P=9.0 Hz); 13C{1H}-NMR (50.3 MHz)
(THF-d8) l (ppm)=43.1 (d, CH3, 2JC–P=15 Hz);
2
222.1 (d, CO, JC–P=3 Hz).
5c: 31P{1H}-NMR (162.0 MHz) (THF-d8) l (ppm)=
3.5. Synthesis of complexes 9c and 10c
1
231.2; H-NMR (400.1 MHz) (THF-d8) l (ppm)=1.09
3
Methyl iodide (or acetyl chloride) (0.4 mmol) was
added to a solution of 5c (0.4 mmol) in diethyl ether (5
ml) at r.t. After a few min., the liquid phase was
cannulated into another Schlenk flask and the solvent
(t, 6H, CH3CH2, JH–H=6.8 Hz); 3.58 and 3.78 (ABC3
2
system, 4H, CH3CH2, JH–H=15.0 Hz); 6.85–7.15
(10H, aromatic H); 13C{1H}-NMR (100.6 MHz) (THF-
2
d8) l (ppm)=14.6 (CH3CH2); 45.0 (d, CH3CH2, JC–

J.-J. Brunet et al. / Journal of Organometallic Chemistry 570 (1998) 195–200
199
Scheme 1.
Scheme 2.
Scheme 3.
3.6. X-ray diffraction study of 4d
evaporated under vacuum to afford 9c or 10c as solids
in an 85 and 75% yield, respectively.
9c: 31P{1H}-NMR (162.0 MHz) (C6D6) l (ppm)=
X-ray quality crystals were obtained by slow evapo-
ration of a pentane solution. The data was collected on
a Stoe Imaging Plate Diffraction System (IPDS). The
crystal-to-detector distance was 80 mm. A total of 125
exposures (4 min per exposure) were obtained with
0BƒB250° and with the crystals rotated through 2° in
ƒ. Coverage of the unique set was over 95% complete
to at least 24.2°. Crystal decay was monitored by
measuring 200 reflexions per image. The final unit cell
parameters were obtained by the least-squares refine-
ment of 2000 reflections. Only statistical fluctuations
were observed in the intensity monitors over the course
of the data collection. Owing to the rather low vx
value, 0.35, no absorption correction was considered.
The structure was solved by direct methods (SIR92)
[18] and refined by least-squares procedures on Fo. H
atoms were located on difference Fourier maps, but
those attached to C atoms were introduced in calcula-
1
135.7; H-NMR (400.1 MHz) (C6D6) l (ppm)=0.85 (t,
6H, CH3CH2, 3JH–H=7.0 Hz); 1.34 (d, 3H, CH3P,
2JH–P=7.3 Hz); 3.36 and 3.62 (ABC3Y system, 4H,
3
2
CH3CH2, JH–P=7.0 Hz, JH–H=14.0 Hz); 6.70–7.15
(5H, aromatic H); 13C{1H}-NMR (100.6 MHz) (C6D6)
l (ppm)=14.6 (CH3CH2); 25.9 (d, CH3P, JC–P=49
1
Hz); 47.9 (CH3CH2); 127.4, 129.6, 131.3, 143.8 (d,
2
2JC–P=4 Hz) (aromatic C); 215.3 (d, CO, JC–P=20
Hz).
10c: 31P{1H}-NMR (162.0 MHz) (C6D6) l (ppm)=
1
149.5; H-NMR (200.1 MHz) (C6D6) l (ppm)=0.72 (t,
3
6H, CH3CH2, JH–H=7.0 Hz); 1.89 (d, 3H, CH3COP,
3JH–P=4.0 Hz); 3.44 and 3.53, ABC3Y system, 4H,
3
2
CH3CH2, JH–P ca. 7 Hz, JH–H=14.0 Hz); 7.00–7.30
(5H, aromatic H); 13C{1H}-NMR (100.6 MHz) (C6D6)
l (ppm)=14.3 (d, CH3CH2, 3JC–P=3 Hz); 28.3 (d,
CH3COP, JC–P=48 Hz); 48.7 (d, CH3CH2, JC–P=6
Hz); 127.3, 129.8, 130.2, 143.6 (aromatic C); 211.9 (d,
CH3COP, 1JC–P=25 Hz); 214.0 (d, CO, 2JC–P=17
Hz).
2
2
˚
tion in idealized positions ((d(CH)=0.96 A) and their
atomic coordinates were recalculated after each cycle.
They were given isotropic thermal parameters 20%
higher than those of the carbon to which they are
attached. The H atom attached to the phosphorus was
refined isotropically. Least-squares refinements were
carried out by minimizing the function ꢀw(ꢁFoꢁ–ꢁFcꢁ)2,
where Fo and Fc are the observed and calculated struc-
ture factors. The weighting scheme used in the last
refinement cycles was w=w%{1-[DF/6|(Fo)]2}2 where
n
w%=1/ꢀ1ArTr(x) with three coefficients Ar for the
Fig. 2. Unsymmetrical diphosphene bis(irontetracarbonyl) complexes.
Chebyshev polynomial ArTr(x) where x was Fc/Fc(max)

200
J.-J. Brunet et al. / Journal of Organometallic Chemistry 570 (1998) 195–200
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151.
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156.
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202.
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[19]. Models reached convergence with R=ꢀ(ꢂFoꢁ–
ꢁFcꢂ)/ꢀ(ꢁFoꢁ) and Rw=[ꢀw(ꢁFoꢁ–ꢁFcꢁ)2/Sw(Fo)2]21, having
values listed in Table 1. Criteria for a satisfactory
complete analysis were the ratios of rms shift to stan-
dard deviation less than 0.1 and no significant features
in final difference maps.
The calculations were carried out with the CRYS-
TALS package programs [20] running on a PC. The
drawing of the molecule was realized with the help of
CAMERON [21].
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Schmidbaur, J. Am. Chem. Soc. 118 (1996) 12673.
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Blenkiron, M.J. Morris, J. Organomet. Chem. 460 (1993) 73.
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Organomet. Chem. 533 (1997) 79. (b) H. Adams, N.A. Bailey, P.
Blenkiron, M.J. Morris, J. Chem. Soc. Dalton Trans. (1997)
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[18] A. Altomare, G. Cascarano, G. Giacovazzo, et al., SIR92–a
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methods, J. Appl. Cryst. 27 (1994) 435.
[19] E. Prince, Mathematical Techniques in Crystallography, Berlin,
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4. Supplementary material
Complete tables of interatomic distances, bond an-
gles, fractional atomic coordinates with the equivalent
thermal parameters for all atoms but H, anisotropic
thermal parameters for non hydrogen atoms and
atomic coordinates for H atoms have been deposited at
the Cambridge Crystallographic Data Centre.
Acknowledgements
This work was supported by the Centre National de
la Recherche Scientifique. Thanks are due to Dr J.-C.
Daran for helpful discussions.
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