Synthesis and characterization of some alkyl(diferrocenyl)phosphines and alkyl(diferrocenyl)phosphine oxides

Article abstract of DOI:10.1081/SIM-120013149

Reaction of ferrocene with alkyldichlorophosphines (RPCl₂, R=Me, Et, t-Bu) in the presence of aluminum chloride produces diferrocenyl(alkyl)phosphines (Fc₂PR, (1a)-(3a), R=Me, Et, t-Bu) and diferrocenyl(alkyl) phosphine oxides Fc

Full text of DOI:10.1081/SIM-120013149

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SYNTHESIS AND CHARACTERIZATION OF SOME
ALKYL(DIFERROCENYL)PHOSPHINES AND
ALKYL(DIFERROCENYL)PHOSPHINE OXIDES
Daniel A. Durfey a , Rein U. Kirss b , Melvyn Rowen Churchill c , Kim M. Keil c & William
Feighery d
a Department of Chemistry , Northeastern University , Boston, MA, 02115, U.S.A.
b Department of Chemistry , Northeastern University , Boston, MA, 02115, U.S.A.
c Department of Chemistry , State University of New York at Buffalo , Buffalo, NY, 14260,
U.S.A.
d Department of Chemistry , Indiana University-South Bend , South Bend, IN, 46634, U.S.A.
Published online: 15 Feb 2007.
To cite this article: Daniel A. Durfey , Rein U. Kirss , Melvyn Rowen Churchill , Kim M. Keil & William Feighery (2002)
SYNTHESIS AND CHARACTERIZATION OF SOME ALKYL(DIFERROCENYL)PHOSPHINES AND ALKYL(DIFERROCENYL)PHOSPHINE
OXIDES, Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry, 32:1, 97-115, DOI: 10.1081/SIM-120013149
To link to this article: http://dx.doi.org/10.1081/SIM-120013149
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SYNTH. REACT. INORG. MET.-ORG. CHEM., 32(1), 97–115 (2002)
SYNTHESIS AND CHARACTERIZATION
OF SOME ALKYL(DIFERROCENYL)-
PHOSPHINES AND ALKYL(DIFERRO-
CENYL)PHOSPHINE OXIDES
Daniel A. Durfey,1 Rein U. Kirss,1,* Melvyn Rowen
Churchill,2,* Kim M. Keil,2 and William Feighery3
1Department of Chemistry, Northeastern University,
Boston, MA 02115
2Department of Chemistry, State University of New
York at Buffalo, Buffalo, NY 14260
3Department of Chemistry, Indiana University-South
Bend, South Bend, IN 46634
ABSTRACT
Reaction of ferrocene with alkyldichlorophosphines (RPCl2,
R ¼ Me, Et, t-Bu) in the presence of aluminum chloride pro-
duces diferrocenyl(alkyl)phosphines (Fc2PR, (1a)7(3a), R ¼
Me, Et, t-Bu) and diferrocenyl(alkyl) phosphine oxides
Fc2P(O)R, (1b)7(3b) in low yields. Diferrocenyl(ethyl)phos-
phine oxide (2b) crystallizes in the P1 space group with one
equivalent of water in the crystal. Compounds (1a)7(3a) are
oxidized at lower potentials than the corresponding phenyl
derivative, Fc2PPh. Cyclic voltammetry of (1a)7(3a) indicates
*Corresponding authors. E-mail: rkirss@neu.edu
97
Copyright # 2002 by Marcel Dekker, Inc.
www.dekker.com

98
DURFEY ET AL.
that the first oxidation is irreversible. The corresponding di-
ferrocenyl(alkyl)phosphine oxides (1b)7(3b) are more difficult
to oxidize than (1a)7(3a) but show two reversible oxidations
separated by 1407160 mV.
INTRODUCTION
Ferrocenyl substituted phosphines are of interest in asymmetric
synthesis1 and in the preparation of high molecular phosphorus-bridged
polyferrocenes2. Much of the work in these areas has focused on the
readily available ferrocenyl(aryl)phosphines (e.g. 1,10-bis(diphenylphos-
phino)ferrocene). As part of our investigation of electron transfer
between iron centers in heteroatom-bridged, mixed valent biferrocenes3, we
were interested in the synthesis and characterization of alkyl(diferro-
cenyl)phosphines Fc2PR (1a) R ¼ Me, (2a) R ¼ Et, (3a) R ¼ t-Bu. Dia-
lkyl(ferrocenyl)phosphines, FcPR2 (where Fc ¼ Z5-C5H5FeC5H4, for R ¼
Me, i-Pr, and t-Bu) are prepared by Friedel Crafts reactions between fer-
rocene and the corresponding alkyl(chloro)phosphines476. Surprisingly, the
Friedel Crafts route has not been extensively applied to the synthesis of
alkyl(diferrocenyl)phosphines. Synthesis of Fc2PEt and FcP(Pr-i)2 by this
route is described in a footnote in a paper on their use as ligands in osmium
carbonyl clusters but details of their synthesis are missing6. The synthesis of
alkyl(diferrocenyl)phosphines, Fc2PR, by reduction of the corresponding
phosphine oxides with lithium aluminum hydride and aluminum chloride
has been reported7. Unfortunately, this method is hampered by low yield
syntheses of the starting diferrocenyl(alkyl)phosphine oxides7, Fc2P(O)R.
The present paper describes the synthesis of three alkyl(diferrocenyl)pho-
sphines, (1a)7(3a) and the corresponding alkyl(diferrocenyl)phosphine
oxides, Fc2P(O)R (1b) R ¼ Me, (2b) R ¼ Et, (3c) R ¼ t-Bu. Compounds
(1)7(3) were characterized by elemental analyses, cyclic voltammetry, IR,
1H and 31P NMR. The single crystal X-ray structure of
Fc2P(O)EtÁH2O(2bÁH2O) is also reported.
EXPERIMENTAL
Materials and Methods
All compounds described in this work were handled using Schlenk
techniques, an M. I. Braun glovebox under a purified argon atmosphere, or

ALKYL(DIFERROCENYL)PHOSPHINES
99
on a vacuum line equipped with oil diffusion and mechanical pumps (10À2
Torr)8. Ferrocene, alkyldichlorophosphines and AlCl3 were purchased from
Strem Chemical Co. and used as received. Hexane, benzene, and toluene
were purified by refluxing over Na=benzophenone and distilled prior to use.
Dichloromethane and acetonitrile were distilled from P2O5 and CaH2, re-
spectively. Deuterated solvents were purchased from Cambridge Isotope
Laboratories and dried as described above. Melting points were determined
on an Electrothermal 9100 apparatus in capillaries sealed with epoxy under
argon and are uncorrected. Elemental analyses (C, H) were performed by
Desert Analytics, Inc., Tucson, AZ.
1H and 31P{1H} spectra were recorded on a Varian 300XL spectro-
meter in 5 mm tubes equipped with a Teflon valve (J. Youngs). Proton
chemical shifts are listed relative to residual protons in the solvent (C6D5H
at d 7.15 ppm). Phosphorus chemical shifts (Table II) are referenced to
external 85% H3PO4 at d 0.00 ppm. Infrared spectra were obtained as KBr
pellets on a Mattson Satellite FTIR interfaced with a Digital PC3000
computer.
Oxidation potentials of (1)7(3) were determined on a BAS 100B
Electrochemical Analyzer in CH2Cl2 solution (2 mM) containing 0.1 M [n-
Bu4N][ClO4] (Fluka Chemical Co.) as the supporting electrolyte. A 1.2 mm
gold disk working electrode (BAS), platinum counter electrode and Ag=Agþ
reference electrodes (Ag wire in 10 mM AgNO3 and 0.1 M [NEt4][BF4] in
CH3CN)9 were used. All experiments were performed under a nitrogen or
argon atmosphere at a scan rate of 100 mV=s.
Synthesis of Diferrocenyl(methyl)phosphine (1a)
and Diferrocenyl(methyl)phosphine Oxide (1b)
A slurry of ferrocene, (3.72 g, 20 mmols) and AlCl3 (1.33 g, 10 mmols)
in hexane (35 mL) was stirred under nitrogen, warmed slightly, and allowed
to cool to room temperature. Methyldichlorophosphine, (1.17 g, 10 mmols)
in hexane (20 mL) was added dropwise to the stirring reaction mixture. A
dark brown precipitate formed rapidly. After addition was completed, the
mixture was refluxed for 24 hours. Upon cooling, the supernatant con-
taining unreacted ferrocene was decanted leaving a dark brown solid. The
solid was extracted with hot hexane and the ferrocene-containing washings
discarded. The remaining solid was washed with 10 mL portions of boiling,
de-ionized, de-gassed water until the solid turned yellow. The blue-green
aqueous washings were decanted and discarded. The resultant yellow solid
was extracted with hot benzene until the extracts were colorless. The com-
bined benzene extracts were dried over Na2SO4 and filtered under nitrogen.

100
DURFEY ET AL.
Solvent was removed in vacuo yielding a yellow oÀra2nge solid. Residual
ferrocene was removed via sublimation (100 ꢀC, 10 mmHg). The non-
volatile solid was taken up in a minimum amount of benzene and
chromatographed on a 2615 cm alumina column under nitrogen. Diferro-
cenyl(methyl)phosphine (1a) was eluted with benzene. Diferrocenyl(methyl)-
phosphine oxide (1b) was subsequently eluted with CHCl3. Evaporation of
the solvent under vacuum yielded 0.62 g (15% yield) of (1a) and 0.11 g
(2.6% yield) of (1b). The phosphine (1a) can be re-crystallized from ethanol
or toluene.
Synthesis of Diferrocenyl(ethyl)phosphine (2a)
and Diferrocenyl(ethyl)phosphine Oxide (2b)
Ferrocene (3.72 g, 20 mmols), AlCl3, (1.33 g, 10 mmols) and EtPCl2,
(1.33 g, 10 mmols) were reacted as described for (1). After work-up and
chromatography, 1.08 g (25%) of diferrocenyl(ethyl)phosphine (2a) and
0.278 g (6%) of diferrocenyl(ethyl)phosphine oxide (2b) were isolated.
Synthesis of Diferrocenyl(t-butyl)phosphine (3a)
and Diferrocenyl(t-butyl)phosphine Oxide (3b)
Ferrocene (8.07 g, 43.4 mmols), AlCl3, (2.89 g, 21.7 mmols) and
t-BuPCl2, (3.45 g, 21.7 mmols) were reacted for 48 h as described for (1).
After work-up and chromatography, 0.89 g (9%) of diferrocenyl(t-butyl)-
phosphine (3a) and 1.1 g (11%) of diferrocenyl(t-butyl)phosphine oxide (3b)
were isolated. Both (3a) and (3b) were re-crystallized from benzene or to-
luene.
.
Solid State Structure Determination of (2b H2O)
Single crystals suitable for X-ray diffraction were grown by slow
ꢀ
cooling of toluene solutions of (2b) to 0 C. The mother liquor was removed
by cannula and the crystals washed with cold toluene before drying in
vacuum. An orange plate (0.8460.4360.11 mm) was mounted in a sealed
capillary. Data were collected on a Siemens R3m=V diffractometer. Solution
and refinement were performed using Siemens SHELXTL PLUS Release
4.11 (VMS) software. The structure was solved using a Patterson map and
refined by full-matrix least squares for which the function minimized was
Sw(FoÀFc)2 where wÀ1 ¼ s2 (F) + 0.006 F2. Hydrogen atoms were located

ALKYL(DIFERROCENYL)PHOSPHINES
101
by optimization from the difference Fourier map with some refinement of
selected hydrogens. Positional parameters for the non-hydrogen atoms can
be found in the supplemental material.
Crystals of (3a) were obtained from toluene but crumbled upon drying
and were unsuitable for X-ray diffraction.
RESULTS AND DISCUSSION
Synthesis of Diferrocenyl(alkyl)phosphines
and Diferrocenyl(alkyl)phosphine Oxides
Diferrocenyl(alkyl)phosphines (1a)7(3a) can prepared in 5725% yield
microanalyses (Table I) by Friedel-Crafts reaction of ferrocene with alkyl-
dichlorophosphines using the published procedure for diferrocenyl(phe-
nyl)phosphine [Eq. (1)]10. Significant amounts of ferrocene are recovered
during the purification procedure. As mentioned, the synthesis of Fc2PEt
(2a) was reported in a footnote677 but yields and additional characterization
data are not reported6. Compared to Fc2PPh, the yields of (1a)7(3a) (Table I)
are quite low but reflect those reported for other ferrocenyl(alkyl)-

102
DURFEY ET AL.

ALKYL(DIFERROCENYL)PHOSPHINES
103
phosphines4,6. For example, ferrocenyldimethylphosphine was prepared in
23% yield from dichloroferrocenylphosphine. The starting material, how-
ever, was synthesized from ferrocene and (dimethylamino)dichloropho-
sphine with low and irreproducible yields ranging from 0 to 25%4b. The
overall yield for FcPMe2 ( ꢁ6%) is within the range of our yields for
(1a)7(3a). Better yields of (1a) and (2a) are realized by reduction of
the corresponding phosphine oxides (1b) and (1b) with lithium aluminum
hydride and aluminum chloride, but yields of the oxides themselves are
quite low7.
Compounds (1a)7(3a) are thermally stable, orange solids which are
slightly soluble in hexane and soluble in benzene, toluene and methylene
chloride. Exposure to air leads to rapid oxidation of (1a)7(3a) to the cor-
responding phosphine oxides. We have experienced considerable difficulty in
obtaining accurate microanalyses (Table I) for compounds (1a)7(3a).
Chromatography and repeated recrystallizations were required to obtain
pure compounds. A similar problem was encountered in the synthesis of
FcPMe2 where the phosphine proved to be an extremely strong s-donor
capable of extracting and complexing aluminum compounds during pur-
ification by chromatography on alumina4b. Separation of (1a)7(3a) from the
corresponding phosphine oxides (1b)7(3b) by fractional crystallization was
unsuccessful. Analyses of (1a) were consistent with the presence of an
ꢀ
equivalent of water. Melting points for (1a) and (2a) are within Æ 1 C of
the literature values7. Good microanalyses for solvent-free (2a) and (3a)
were achieved, possibly as the greater steric bulk of the larger alkyl group
renders coordination to the phosphine more difficult.
Low yields of diferrocenyl(alkyl)phosphine oxides (1b)7(3b) are ob-
tained as by-products of the synthesis of (1a)7(3a) and can be separated by
chromatography on alumina with benzene and chloroform eluents . No
attempt was made to optimize the yields of (1b)7(3b). The source of the
oxygen in (1b)7(3b) is unknown but formation of the phosphine oxides is
still detected even when working under rigorously air-free conditions. The
role of water used during the hydrolysis of the aluminate intermediates in
the Friedel-Crafts reaction on the formation of (1b)7(3b) is not known.
Addition of de-oxygenated water to solutions of (2a) does not produce (2b).
Surface reactions with alumina can not be ruled out based on the literature
pertaining to the purification of FcPMe24b. Elemental analyses of diferro-
cenyl(ethyl)phosphine oxide (2b) are consistent with retention of water even
after recrystallization from rigorously dried aromatic hydrocarbon solvents.
The presence of water in (2b) is confirmed by a single crystal X-ray
structure (vide infra). Based on microanalyses, diferrocenyl (t-butyl)pho-
sphine oxide (3b) retains benzene from either the chromatography or
crystallization steps.

104
DURFEY ET AL.

ALKYL(DIFERROCENYL)PHOSPHINES
NMR Spectroscopyof (1) 7(3)
105
1
The H NMR spectra (Table II) of (1a)7(3a) are similar to those re-
ported for diferrocenyl(phenyl)phosphine10. The unsubstituted ring appears
as a singlet in all three compounds. Four multiplets are observed for the
substituted ring protons in (1a)20. By analogy to dimethyl- and diphe-
nyl(ferrocenyl)phosphine, the upfield resonance are assigned to the protons
attached to the ring carbons adjacent to the phosphorus4b,10. Three multi-
plets are observed for the substituted ring protons in (2a). Integration of the
spectra of (2a) indicates that the resonance for the fourth proton on the
substituted ring lies under the resonance assigned to the unsubstituted Cp
ring. A similar spectrum is reported for Os3(CO)11(PEtFc2). The observa-
tion of three or four resonances of equal intensity (2H each) for the sub-
stituted ring protons of (1a) and (2a) is the result of chemical inequivalence
of the protons of the unsubstituted ring from slow inversion about the
1
phosphorus. The H NMR spectrum of (3a), however, consists of only two
signals for the substituted ring protons and a singlet for the unsubstituted
ring protons. 31P NMR spectra of all three diferrocenyl(alkyl)phosphines
were singlets.
1
The H NMR spectra of (1b)7(3b) (Table II) reveal four resonances
for the substituted ring protons in each case and a single resonance for the
unsubstituted cyclopentadienyl ring. Small differences in chemical shift are
observed between the spectra for (1a)7(3a) and the spectra of the phosphine
oxides (1b)7(3b). In general, there is a downfield shift of the protons in
(1b)7(3b) relative to (1a)7(3a). The magnitude of the chemical shift differ-
ence is sufficient to distinguish the phosphine oxide from the phosphine by
NMR. The furthest upfield resonances in (1b)7(3b) are again tentatively
assigned to protons attached to the ring carbons adjacent to the phos-
phorous by analogy to literature studies of ferrocenyl(phenyl)phosphines10.
A single resonance is observed in the 31P{H} NMR spectrum of all three
diferrocenyl(alkyl)phosphine oxides at chemical shifts downfield from the
corresponding phosphines (1a)7(3a). Large differences in 31P NMR che-
mical shifts are common between aryl or alkyl phosphines and their phos-
phine oxides11.
IR Spectra of (1)7(3)
Infrared spectra of (1)7(3) are summarized in Table III. The spectra of
all six compounds are similar with bands assigned to ferrocenes C-C stretch-
ing, CH stretching, C-H in plane and out-of-plane bending modes are ob-
served at similar energies as in diferrocenyl(phenyl)phosphine oxide12. Low

106
DURFEY ET AL.

ALKYL(DIFERROCENYL)PHOSPHINES
107
Table IV. Crystal Structure Data and Refinement for (2bÁH2O)
Crystal Data
Molecular Formula
Color, Habit
Crystal size (mm)
Crystal System
C22H23Fe2OPÁH2O
Orange plates
0:84 Â 0:43 Â 0:11
Triclinic
Space Group
Unit Cell Dimensions
P1 (No. 2)
a ¼ 9:115 ð5Þ A
b ¼ 9:195 ð4Þ A
c ¼ 12:024 ð6Þ A
a ¼ 95:51 ð4Þ ꢀ
b ¼ 97:04 ð4Þ ꢀ
g ¼ 90:69 ð4Þ A
995:2ð9Þ A3
2
Volume
Z
Formula Weight
Density (calc.)
Absorption Coefficient
F(000)
464.1
1:549 Mg=m3
1:551 mmÀ1
480
Data Collection
Diffractometer Used
Radiation
Temperature (K)
Monochromator
2y Range
Siemens R3m=V
Mo Ka ðl ¼ 0:71073 A)
296
Highly oriented graphite crystal
5.0 to 50.0 ꢀ
Scan Type
Scan Speed
Scan Range (o)
Background Measurement
2y-y
Constant; 2.00ꢀ=min in o
0.70 ꢀ plus Ka-separation
Stationary crystal and stationary
counter at beginning and end of scan, each
for 25.0% of total scan time
3 measured every 197 reflections
À10 ꢂ h ꢂ 10; À10 ꢂ k ꢂ 10; À14 ꢂ l ꢂ 14
6996
Standard Reflections
Index Ranges
Reflections Collected
Independent Reflections
Observed Reflections
Absorption Correction
Min.=Max. Transmission
3515 (Rint ¼ 0:98 %)
2817 (F > 6:0 sðFÞ)
Semi-empirical
0:5729=0:8992
Solution and Refinement
System Used
Siemens SHELXTL PLUS Release
4.11 (VMS)
(continued)

108
DURFEY ET AL.
Table IV. Continued
Solution
Refinement Method
Quantity Minimized
Extinction Correction
Hydrogen Atoms
Patterson map
Full-Matrix Least-Squares
P
2
wðFo À FcÞ
not necessary
optimized from diff. Fourier; some refined
Weighting Scheme
wÀ1 ¼ s2ðFÞ þ 0:008 F2
Number of Parameters refined
Final R Indices (obs. data)
R Indices (all data)
249
R ¼ 2:85% wR ¼ 4:05%
R ¼ 3:86 % wR ¼ 4:45%
1.19
Goodness-of-Fit
Largest and Mean D=s
Data-to-Parameter Ratio
Largest Difference Peak
Largest Difference Hole
0.002, 0.000
11.3:1
0:41 eAÀ3
À0:33 eAÀ3
energy absorptions between 400 and 525 cmÀ1are assigned to P-C vibrational
modes while the absorptions in the region 101571045 are typical of ferrocene-
phosphorous moieties12. The phosphine oxides (1b)7(3b) show n(P›O) at
1177 cmÀ1, within the range observed for alkyl- and arylphosphine oxides
(Ph3P›O, n(P›O) 1195 cmÀ1, Me3P›O, n(P›O) 1170 cmÀ1)11.
.
Crystal Structure of Diferrocenyl(ethyl)phosphine Oxide (2b H2O)
A single crystal of diferrocenyl(ethyl)phosphine oxide monohydrate
(2bÁH2O) suitable for single crystal X-ray diffraction was grown by slow
cooling of a toluene solution. Crystal data and specifics of the data
collection and refinement of (2bÁH2O) are summarized in Table IV.
Selected bond distances and bond angles are listed in Table V. The
geometry about the phosphorus atom (Fig. 1) is tetrahedral with C-P-O
angles (1127114ꢀ) slightly larger than the C-P-C angles (106ꢀ). These
angles are nearly identical to those reported for both Ph3P›O and
Me3P›O11. The phosphorus- oxygen bond distance (1.485 A) and the
three phosphorus-carbon distances (1.7871.80 A) are also the same as
those in both alkyl and aryl phosphine oxide structures. There is nothing
unusual about the ferrocenyl ligands as bond distances (average dFe-
¼ 2.038 A) and geometry are similar to those observed in ferrocene itself
C
(average dFe-C ¼ 2.045 A)13.
The most interesting feature of the solid state structure of (2bÁH2O) is
the inclusion of one equivalent of water in the structure (Fig. 2). The

ALKYL(DIFERROCENYL)PHOSPHINES
Table V. Selected Bond Lengths and Angles For (2bÁH2O)
109
Bond Lengths (A)
Fe(1)-C(11)
Fe(1)-C(13)
Fe(1)-C(15)
Fe(1)-C(22)
Fe(1)-C(24)
Fe(2)-C(31)
Fe(2)-C(33)
Fe(2)-C(35)
Fe(2)-C(42)
Fe(2)-C(44)
P(1)-O(1)
2.033 (3)
2.053 (3)
2.034 (3)
2.046 (4)
2.026 (3)
2.024 (3)
2.039 (3)
2.036 (3)
2.036 (3)
2.022 (4)
1.485 (2)
1.782 (3)
1.520 (5)
1.429 (4)
1.407 (5)
1.408 (5)
1.409 (5)
1.388 (5)
1.434 (4)
1.404 (6)
1.384 (5)
1.419 (6)
1.383 (7)
0.838 (48)
2.814
Fe(1)-C(12)
Fe(1)-C(14)
Fe(1)-C(21)
Fe(1)-C(23)
Fe(1)-C(25)
Fe(2)-C(32)
Fe(2)-C(34)
Fe(2)-C(41)
Fe(2)-C(43)
Fe(2)-C(45)
P(1)-C(1)
2.045 (3)
2.053 (3)
2.047 (3)
2.023 (4)
2.041 (3)
2.036 (3)
2.044 (4)
2.044 (4)
2.025 (4)
2.044 (4)
1.803 (3)
1.780 (3)
1.428 (4)
1.416 (4)
1.422 (4)
1.373 (5)
1.421 (6)
1.430 (4)
1.417 (5)
1.414 (5)
1.386 (5)
1.415 (6)
0.863 (55)
1.977
P(1)-C(11)
C(1)-C(2)
P(1)-C(31)
C(11)-C(15)
C(12)-C(13)
C(14)-C(15)
C(21)-C(25)
C(23)-C(24)
C(31)-C(35)
C(32)-C(33)
C(34)-C(35)
C(41)-C(45)
C(43)-C(44)
O(3W)-H(3A)
O(1) Á Á Á H(3A)
O(1) Á Á Á H(3B)
C(11)-C(12)
C(13)-C(14)
C(21)-C(22)
C(22)-C(23)
C(24)-C(25)
C(31)-C(32)
C(33)-C(34)
C(41)-C(42)
C(42)-C(43)
C(44)-C(45)
O(3W)-H(3B)
O(1) Á Á Á O(3W)
2.060
Bond Angles (ꢀ)
C(1)-P(1)-C(11)
O(1)-P(1)-C(1)
O(1)-P(1)-C(31)
Fe(1)-C(11)-P(1)
P(1)-C(1)-C(2)
105.8 (1)
112.0 (1)
114.8 (1)
127.2 (1)
112.7 (2)
163 (5)
C(1)-P(1)-C(31)
C(11)-P(1)-C(31)
O(1)-P(1)-C(11)
Fe(2)-C(31)-P(1)
H(3A)-O(3W)-H(3B)
O(3W)-H(3B) Á Á Á O(1)
105.9 (1)
105.8 (1)
111.8 (1)
125.5 (1)
121.8 (1)
147 (5)
O(3W)-H(3A) Á Á Á O(1)
compound is exposed to water only during the hydrolysis of the diferroce-
nyl(ethyl)phosphine aluminate salts in the synthesis of (2a) and (2b). Water
is retained by (2b) during chromatography, recrystallization from non-polar
solvents, drying under vacuum and storage in an inert atmosphere. The
orientation of the water molecules points the hydrogens toward the phos-
phorus-oxygen bonds of two molecules of (2b). The average P›O Á Á Á H

110
DURFEY ET AL.

ALKYL(DIFERROCENYL)PHOSPHINES
111

112
DURFEY ET AL.

ALKYL(DIFERROCENYL)PHOSPHINES
113
distance of 2.019 A is consistent with the presence of hydrogen bonds
between the phosphoryl oxygen and the included water14. Hydrogen
bonding in hydrates of triphenylphosphine has been reported but not
crystallographically demonstrated11. To our knowledge, the structure in Fig.
1 represents the first structurally characterized ferrocenyl(alkyl)phosphine
oxide. The structures of 1,10-diphenylphosphinoferrocene oxide and sulfide
were reported but details are missing11.
Electrochemistry of Diferrocenyl(alkyl)phosphines and Phosphine
Oxides
Electrochemical oxidation of (1a)7(3a) in CH2Cl2 reveals two
oxidations separated by ꢁ 300 to 330 mV (Table VI). As expected, the
electron-rich, diferrocenyl(alkyl)phosphines are easier to oxidize than
diferrocenyl(phenyl)phosphine but are still oxidized at potentials more po-
sitive than ferrocene itself3,15. The diferrocenyl(alkyl)phosphine oxides
(1b)7(3b) are more difficult to oxidize than the corresponding phosphines
(1a)7(3a) with much smaller separations between the first and second oxi-
dations ( ꢁ 1407160 mV, Table VI). The oxidations of (1b)7(3b), however,
appear to be more reversible (Ipc=Ipa › 0.70 to 1.83) than for the ferro-
cenylphosphines (1a)7(3a).
ACKNOWLEDGMENTS
The purchase of the X-ray diffractometer was made possible by Grant
89-13733 from the Chemical Instrumentation Program of the National
Science Foundation.
REFERENCES
1. a. Togni, A.; Hayashi, T., Ed. Ferrocenes, VCH Publishers, Inc.; New
York, 1995. b. Hayashi, T.; Kumada, M. Asymmetric Synthesis Cat-
alyzed by Transition-Metal Complexes with Functionalized Chiral
Ferrocenylphosphine Ligands. Acc. Chem. Res. 1982, 15, 3957401.
2. Foucher, D.A.; Honeyman, C.H.; Nelson, J.M.; Tang, B.Z.; Manners, I.
Organometallic Ferrocenyl Polymers Displaying Tunable Cooperative
Interactions Between Transition Metal Centers. Angew. Chem., Int.
Ed. Engl. 1993, 32, 170971711.

114
DURFEY ET AL.
3. Durfey, D.A.; Kirss, R.U.; Frommen, C.; Felghery, W. Synthesis and
Mossbauer Spectroscopic Studies of Chemically Oxidized Ferro-
cenyl(phenyl)phosphines. Inorg. Chem. 2000, 39, 350973514.
4. a. Kiso, Y.; Kumada, M.; Tamao, K.; Umero, M. Silicon Hydrides
and Nickel Complexes I. Phosphine-Nickel(II) Complexes as Hydro-
silylation Catalysts. J. Organometal. Chem. 1973, 50, 2977310.
b. Knox, G.R.; Pauson, P.L.; Willison, D. Ferrocene Derivatives. 27.
Ferrocenyldimethylphosphine. Organometallics 1992, 11, 2930.
5. Mann, G.; Incarvito, C.; Rheingold, A.L.; Hartwig, J.F. Palladium-
Catalyzed C-O Coupling Involving Unactivated Aryl Halides. Steri-
cally Induced Reductive Elimination to Form the C-O Bond in Diaryl
Ethers. J. Am. Chem. Soc. 1999, 121, 322473225.
6. Cullen, W.R.; Rettig, S.J.; Zheng, T.C. Double Metalation and Iron-
Osmium Bonding Involving Ferrocenyl Moieties on Clusters. Crystal
and Molecular Structures of H2Os3(CO)8[(Z-C5H4)Fe(Z-C5H3P0Pr2)]
and H2Os3(CO)8[(Z-C5H4)Fe(Z-C5H3PFcEt)]. Organometallics 1992,
11, 343473439.
7. a. Tolkunova, V.S.; Peregudov, A.S.; Gorelikow, Yu.Yu.; Krylova,
A.I.; Tsvetkov, E.N.; Vil’chevskaya, V.D.; Kravtsov, D. Synthesis of
Asymmetric Tertiary Ferrocenylphosphines. Organometallic Chem-
istry in the USSR. 1991, 4, 2167219. b. Tolkunova, V.S.; Tsvetkov,
E.N.; Peregudov, A.S.; Krylova, A.I.; Gorelikow, Yu.Yu.; Vil’chevs-
kaya, V.D.; Kravtsov, D. The Synthesis and the 1H, 13C, and 31P NMR
Spectra of the Oxides of Asymmetric Tertiary Ferrocenylphosphines.
Organometallic Chemistry in the USSR. 1989, 2, 3417344.
8. Shriver, D.F. Manipulation ofAir Sensitive Compounds ; McGraw Hill,
Inc.; New York, 1969.
9. Miller, T.M.; Ahmed, K.J.; Wrighton, M.S. Complexes of Rhenium
Carbonyl Containing Ferrocenyl-Derived Ligands: Tunable Electron
Density at Rhenium by Control of the Redox State of the Ferrocenyl
Ligand. Inorg. Chem. 1989, 28, 234772355.
10. a. Kotz, J.C.; Nivert, C.A. Organometallic Ligands. The Preparation
and Properties of Complexes of the Ferrocenylphosphines. J. Orga-
nometal. Chem. 1973, 52, 3877406. b. Kotz, J.C.; Nivert, C.A.; Lieber,
J.M.; Reed, R.C. Organometallic Ligands III. The Electrochemistry of
Ferrocenylphopshines and Their Complexes. J. Organometal. Chem.
1975, 91, 87795.
11. Gilheany, D.G. In The Chemistry ofOrganophosphorous Compounds ;
Hartley, F.R., Ed.; John Wiley, Inc.: New York, 1992, 2, 1752.
12. Sollott, G.P.; Mertwoy, H.E.; Portnoy, S.; Snead, J.L. Unsymmetrical
Tertiary Phosphines of Ferrocene by Friedel-Crafts Reactions.
I. Ferrocenylphenylphosphines. J. Org. Chem. 1963, 28, 109071092.

ALKYL(DIFERROCENYL)PHOSPHINES
115
13. Seiler, P.; Dunitz, J. A New Interpretation of the Disordered Crystal
Structure of Ferrocene. Acta Crystallogr. Sect. B 1979, 35, 106871074.
14. Wells, A.F. Structural Inorganic Chemistry, Third Edition; Oxford
University Press: Oxford, 1962.
15. Gref, A.; Diter, P.; Guillaneux, D.; Kagan, H.B. Electrochemical Be-
havior of Various Sulfur and Phosphorus Derivatives of Ferrocene.
New J. Chem. 1997, 21, 135371358.
Received August 16, 2001
Accepted October 23, 2001
Referee I: D. A. Rockcliffe
Referee II: J. P. Jasinski