Synthesis of 1,1′-ferrocenylene-bridged bisdiphosphenes

Article abstract of DOI:10.1021/om060073c

A simple synthetic access to the first ferrocenylene-bridged bisdiphosphenes Fe(C₅H₄-P=P-R)₂ is reported. The unsaturated P=P units require steric protection by adjacent substituents such as Dmp (2,6-dimesitylphenyl) and Tbt (2,4,6-tris[bis(trimethylsilyl)methyl] phenyl) and should be capable of conjugative interaction with the central metallocene unit. The electronic situation in these molecules has been assessed on the basis of DFT calculations. As a derivative of the Tbt-substituted bisdiphosphene with Tbt-PH₂, the resulting ferrocenylene-bridged bis-1,3-dihydrotriphosphane has been characterized by X-ray crystallography

Full text of DOI:10.1021/om060073c

Organometallics 2006, 25, 2667-2672
2667
Synthesis of 1,1′-Ferrocenylene-Bridged Bisdiphosphenes
Carmen Moser,† Martin Nieger,‡ and Rudolf Pietschnig*,†
Institut fu¨r Chemie, Bereich Anorganische Chemie, Karl-Franzens-UniVersita¨t Graz, Schubertstrasse 1,
A-8010 Graz, Austria, and Institut fu¨r Anorganische Chemie, Rheinische Friedrich-Wilhelms-UniVersita¨t
Bonn, Gerhard-Domagk-Strasse 1, D-53121 Bonn, Germany
ReceiVed January 24, 2006
A simple synthetic access to the first ferrocenylene-bridged bisdiphosphenes Fe(C5H4-PdP-R)2 is
reported. The unsaturated PdP units require steric protection by adjacent substituents such as Dmp (2,6-
dimesitylphenyl) and Tbt (2,4,6-tris[bis(trimethylsilyl)methyl]phenyl) and should be capable of conjugative
interaction with the central metallocene unit. The electronic situation in these molecules has been assessed
on the basis of DFT calculations. As a derivative of the Tbt-substituted bisdiphosphene with Tbt-PH2,
the resulting ferrocenylene-bridged bis-1,3-dihydrotriphosphane has been characterized by X-ray
crystallography
to date. We prepared the first examples of ferrocenyl-substituted
diphosphenes, iminophosphanes, and phosphaalkenes.15-17 In
our initial study we employed the Mes* substituent (Mes* )
2,4,6-tri-tert-butylphenyl) to protect the reactive PdP unit in
1.15 This concept was later extended by the work of Tokitoh et
al. employing the more bulky Tbt (Tbt ) 2,4,6-tris[bis-
(trimethylsilyl)methyl]phenyl) substituent (2).18,19 All these
compounds show substantial conjugative interaction of the
unsaturated PdE moiety with the ferrocenyl group. Nevertheless
the so far reported examples carry only one PdE unit at the
metallocene. For diphosphenes, the preparation of molecules
containing two or more PdP units has been accomplished with
strictly organic linking groups.8,20 In this contribution we report
on the preparation of ferrocenes carrying a diphosphene unit
on each of the ferrocene cyclopentadienyl rings (3). These
compounds are the first 1,1′-ferrocenylene-bridged bisdiphos-
phenes21,22 and should open the way to the preparation of more
extended analogues.
Introduction
Compounds containing phosphorus in low coordination
numbers have fascinated chemists for several decades.1-5
Initially the interest in these compounds was mainly focused
on the unusual bond situation present in these molecules.6 More
recently, the incorporation of unsaturated phosphane units such
as PdC and PdP connected by phenylene and arylene groups
into oligomers and polymers attracted considerable attention as
new types of electronic materials.7-10 Such materials can support
electronic communication across extended π-conjugated sys-
tems, and a recent review describes the first applications of
phosphorus-based materials in optoelectronics (nonlinear optics,
organic light-emitting diodes, etc.).11,12
Extending this concept by incorporation of low-coordinated
phosphorus centers into metallocene-based polymers should
provide unique electronic properties and, moreover, the redox
activity of the metal centers should allow some control of the
electronic and magnetic properties in this type of com-
pounds.13,14
Results and Discussion
However, the knowledge of compounds containing unsatur-
ated phosphane units adjacent to metallocenes is very limited
To generate 1,1′-ferrocenylene-bridged bisdiphosphenes, we
reacted 1,1′-ferrocenylene bisdihalophosphanes23,24 with the
bulky substituted lithium phosphanides Dmp-PHLi (Dmp ) 2,6-
dimesitylphenyl)25 and Tbt-PHLi26 in ether solution. Subsequent
* To whom correspondence should be addressed. E-mail:
rudolf.pietschnig@uni-graz.at.
† Karl-Franzens-Universita¨t Graz.
‡ Rheinische Friedrich-Wilhelms-Universita¨t Bonn.
(1) Dimroth, K.; Hoffmann, P. Angew. Chem., Int. Ed. Engl. 1964, 3,
384.
(15) Pietschnig, R.; Niecke, E. Organometallics 1996, 15, 891.
(16) Pietschnig, R.; Niecke, E.; Nieger, M.; Airola, K. J. Organomet.
Chem. 1997, 529, 127.
(2) Ma¨rkl, G. Angew. Chem., Int. Ed. Engl. 1966, 5, 846.
(3) Niecke, E.; Flick, W. Angew. Chem. 1973, 85, 586-7.
(4) Becker, G. Z. Anorg. Allg. Chem. 1976, 423, 242.
(5) Yoshifuji, M.; Shima, I.; Inamoto, N.; Hirotsu, K.; Higuchi, T. J.
Am. Chem. Soc. 1981, 103, 4587-4589.
(17) Pietschnig, R.; Nieger, M.; Niecke, E.; Airola, K. J. Organomet.
Chem. 1997, 541, 237.
(18) Nagahora, N.; Sasamori, T.; Takeda, N.; Tokitoh, N. Chem. Eur. J.
2004, 10, 6146-51.
(19) Nagahora, N.; Sasamori, T.; Takeda, N.; Tokitoh, N. Organome-
tallics 2005, 3074.
(20) Yoshifuji, M.; Shinohara, N.; Toyota, K. Tetrahedron Lett. 1996,
37, 7815-7818.
(21) Pietschnig, R.; Nieger, M.; Belaj, F.; Moser, C. 11th Austrian
Chemistry Days, Leoben, Austria, Sept 19-22, 2005; abstract # VO-39.
(22) Tokitoh, N.; Mieda, E.; Nagahora, N.; Sasamori, T.; Takeda, N.;
Takagi, N.; Nagase, S. Pacifichem Conference, Honolulu, Hawai, Dec 15-
20, 2005; abstract # 1270.
(6) Schoeller, W. W. In Multiple Bonds and Low Coordination in
Phosphorus Chemistry; Regitz, M., Scherer, O. J., Eds.; Thieme: Stuttgart,
1990.
(7) Wright, V. A.; Gates, D. P. Angew. Chem. 2002, 114, 2495-8.
(8) Smith, R. C.; Protasiewicz, J. D. J. Am. Chem. Soc. 2004, 126, 2268-
2269.
(9) Smith, R. C.; Protasiewicz, J. D. Eur. J. Inorg. Chem 2004, 5, 998-
1006.
(10) Dutan, C.; Shah, S.; Smith, R. C.; Choua, S.; Berclaz, T.; Geoffroy,
M.; Protasiewicz, J. D. Inorg. Chem. 2003, 42, 6241-6251.
(11) Hissler, M.; Dyer, P. W.; Reau, R. Top. Curr. Chem. 2005, 127-
163.
(12) Gates, D. P. Top. Curr. Chem. 2005, 250, 107-126.
(13) Manners, I. AdV. Organomet. Chem. 1995, 37, 131-68.
(14) Manners, I. Science 2001, 294, 1664-1666.
(23) Pietschnig, R. Diploma Thesis, University of Bonn, 1993.
(24) Moser, C.; Nieger, M.; Belaj, F.; Pietschnig, R. 2006, manuscript
submitted.
(25) Urnezius, E.; Klippenstein, S. J.; Protasiewicz, J. D. Inorg. Chim.
Acta 2000, 297, 181-190.
(26) Sasamori, T.; Takeda, N.; Tokitoh, N. J. Phys. Org. Chem. 2003,
16, 450-462.
10.1021/om060073c CCC: $33.50 © 2006 American Chemical Society
Publication on Web 04/14/2006

2668 Organometallics, Vol. 25, No. 10, 2006
Moser et al.
Figure 1. 31P NMR spectra of 3a (left) and 3b (right).
Table 1. Comparison of the 31P Data of Diphosphenes Adjacent to Ferrocene (Fc ) ferrocenyl; Fc′ ) 1,1′-ferrocenylene)
λmax
PA
[ppm]
PB
[ppm]
1JPP
[Hz]
(n(Fe)-π*)
λ (π-π*)
[nm]
[nm]
ref
Fc-PdP-Mes*
Fc-PdP-Tbt
Fc′(-PdP-Dmp)2
Fc′(-PdP-Tbt)2
471.2
501.7
470.3
500.0
442.6
479.5
444.9
492.5
532
546
537
555
515
542
542
545
357
371
351
380
15
18
this work
this work
Scheme 1. First Ferrocenyl Diphosphenes 115 and 218 and
Ferrocenylene Bisdiphosphenes 3a,b
1JPP coupling constants for diphosphenes, indicating conjugative
interaction of the PdP units with the ferrocene core. The
27
comparison of Fc-PdP-Tbt and Fc′(-PdP-Tbt)2 (Fc )
ferrocenyl, Fc′ ) 1,1′-ferrocenylene) reveals that the attachment
of a second identical diphosphene unit has a moderately
deshielding effect on the phosphorus atom showing a 31P
resonance at higher field. This indicates a slightly reduced
π-donation of the ferrocene system into the PdP units of Fc′-
(-PdP-Tbt)2 compared to Fc-PdP-Tbt.
For both diphosphenes 3a,b the λmax absorptions in the UV/
vis region at 542 nm (3a) and 545 nm (3b) indicate electronic
interaction of the PdP unit with the ferrocene system. On the
basis of quantum chemical calculations these absorptions have
been assigned to a metal-to-ligand charge transfer (MLCT) due
to the electronic transition from iron-centered d-orbitals to the
Scheme 2. Synthesis of Ferrocenylene Bisdiphosphenes 3a
(R ) Dmp) and 3b (R ) Tbt)
18
π*-orbital of the PdP moiety. As in related diphosphenes,
the π-π* transition is observed at lower wavelength. For 3a
the corresponding absorption band is observed at 371 nm and
for 3b at 380 nm. The characteristic spectroscopic data of the
ferrocenylene bisdiphosphenes correspond well with those of
ferrocenyl diphosphenes and are summarized in Table 1.
Both ferrocenylene diphosphenes 3a,b are very sensitive to
air and moisture, but remain unchanged under inert conditions
in solution as well as in the solid state. However, the Dmp-
substituted diphosphene 3a is significantly more sensitive toward
air than the Tbt-substituted 3b. The protection provided by the
Tbt substituent seems to be significantly more efficient than in
the case of Dmp. Preliminary experiments exploring the
reactivity of 3a,b show that addition of water leads to Dmp-
PH2 and Tbt-PH2, respectively along with 1,1-ferrocenebispho-
sphinic acid (and 1,1-ferrocenebisphosphonic acid in the
dehydrohalogenation with DBU furnished dark red solutions
of the envisaged diphosphenes 3a (R ) Dmp) and 3b (R )
Tbt) (Scheme 2). The presence of the PdP unit in 3a,b is evident
from their 31P NMR spectra, which show a AB spin system at
characteristically high chemical shift values with 1JPP coupling
constants of 537 Hz (3a) and 555 Hz (3b) typical for diphos-
phenes (Figure 1). The values observed for ferrocenylene
compounds 3a,b are quite close to those of the corresponding
ferrocenyl analogues reported before (Table 1). As in other
π-donor-substituted diphosphenes, the 31P NMR shifts of these
compounds appear at rather high field along with rather small
(27) Weber, L. Chem. ReV. 1992, 92, 1839-1906.

1,1′-Ferrocenylene-Bridged Bisdiphosphenes
Organometallics, Vol. 25, No. 10, 2006 2669
Figure 2. Contour plots of the HOMO (top) and the HOMO-3
(bottom) of 4.
presence of oxygen).28,29 These findings can be rationalized
assuming a polarized PdP double bond in which the π-donor
properties of the ferrocene unit, which have been found to be
comparable with that of an amino group, increase π-electron
density on the phosphorus atom adjacent to the bulky ligand.
Such a description is in good agreement with results from ab
initio calculations on the simplified model systems Fc-PdP-
Mes (4) and Fc′(-PdP-Mes)2 (5). On the DFT (B3LYP) level
employing a LAN2DZ basis set, the HOMO of 4 is mainly an
iron d-orbital showing little interaction with the PdP bond. The
π(PdP)-orbital (HOMO-3) is clearly polarized with the
π-electron density shifted away from the ferrocene system
(Figure 2). Attachment of a second diphosphenyl group as in 5
leads to a similar situation, where in addition to a conjugation
of the cyclopentadienyl rings with the -PdP- units also direct
interaction of Fe d-electrons with the diphosphene units occurs
(Figure 3). The LUMO in 4 and 5 is a π*-orbital located at the
PdP unit, which in the case of 5 is significantly augmented
with d-states at the Fe center (Figure 4).
Figure 3. Contour plots of the HOMO (top) and the HOMO-1
(bottom) of 5.
Scheme 3. Formation of 6
Table 2. Comparison of the NBO Charges Calculated for
Fc-PdP-Mes (4) and Fc′(-PdP-Mes)2 (5)
(B3LYP/LANL2DZ)
A comparison of the calculated NBO charges (Table 2) shows
that the net polarization of the PdP-π-system is only small (0.1
electron). Also the electron-donating capacity of the ferrocenyl
system is not significantly lowered by interacting with one
PdP system. Thus, interaction with a second PdP unit raises
the positive charge on Fe only marginally and shows even less
effect on the Cp carbon atoms (Table 2). This as well as the
net positive charge of the P atoms indicates that the PdP units
in 4 and 5 act as an acceptor on the π-level, but as a donor on
the σ-level toward the ferrocene system. Therefore, the electron-
releasing capacity of the ferrocene system is not exhausted by
a single diphosphene unit, and on attachment of a second such
unit the characteristic polarization of the PdP π-system is
retained.
Fc-PdP-Mes (4)
Fc′(-PdP-Mes)2 (5)
Cp-PdP-R +0.209 ∆q ) 0.109 +0.206 +0.218 ∆q ) 0.095
Cp-PdP-R +0.318 ∆q ) 0.109 +0.324 +0.313 ∆q ) 0.095
CR
Fe
Cipso
-0.428
+0.242
-0.341
-0.422 -0.423
+0.257
-0.340 -0.341
heating of neat 6 to approximately 100 °C leads to elimination
of Tbt-PH2 and liberation of the initial bisdiphosphene 3b
(Scheme 3), in analogy with what has been observed for the
related monodiphosphene. 19 Therefore, 6 can be considered as
a less sensitive storage form of 3b in the presence of Tbt-PH2.
In solution the resonances of the 16 possible stereoisomers of
6 are observed in a range between -18 and -85 ppm in the
31P NMR spectra, which is close to what has been reported for
the related compound with only one triphosphane unit at the
metallocene. As in the latter case the NMR signals of the
mixture of diastereomers are broadened due to hindered rotation
at the Tbt moieties at room temperature. In contrast to the
previously reported ferrocenyl 1,3-dihydrotriphosphane, heating
of a toluene solution of 6 to 95 °C does not lead to coalescence
On treatment with Tbt-PH2, bisdiphosphene 3b reacts under
formation of bistriphosphane 6. This reaction is reversible, and
(28) Knox, J. R.; Pauson, P. L.; Willison, D. Organometallics 1992, 11,
2930.
(29) Alley, S. R.; Henderson, W. J. Organomet. Chem. 2001, 636-639,
216-29.

2670 Organometallics, Vol. 25, No. 10, 2006
Moser et al.
Figure 4. Contour plots of the LUMOs of 4 (left) and 5 (right).
Figure 5. Molecular structure of 6 in the solid state. Hydrogen atom and solvent molecules are omitted for clarity.
of the signals in the 31P NMR spectra. We have been able to
determine the crystal structure of 6 (Table 3), and a drawing of
the molecule and selected structural parameters are shown in
Figure 5 and Table 4, respectively. Since the position of the
phosphorus-bonded hydrogen atoms could be localized by
electron density determination, the molecular structure of this
particular single crystal could be assigned to the isomer of 6
with 2S,3R,5R,6R configuration at the phosphorus atoms (space
group: P212121 (No. 19), Flack parameter x ) -0.01(2)). As
expected all six phosphorus atoms show a pyramidal coordina-
tion environment. The phosphorus atoms adjacent to the
ferrocenyl moiety show the strongest pyramidalization, with a
sum of angles of 295° (P1) and 294° (P4). These values are
close to the 293° found for the only other structurally character-
ized 1,3-dihydrotriphosphane in the literature.19 For the other
phosphorus atoms in 6, the sum of angles is somewhat higher
(302° (P5), 309° (P3), 311° (P6)), with the largest value found
for P2 (313°), which is also the phosphorus atom with a
configuration opposite of the other ones.
In summary, our results show that ferrocenylene-bridged
bisdiphosphenes are synthetically accessible. On the basis of
experimental spectroscopic results and ab initio calculations, it
is evident that the low-lying π*-states provided by the PdP
unit interact with the ferrocene system in which the latter serves
as electron donor. Interestingly, the capacity of this electron
reservoir is reduced yet not exceeded on attachment of a second
diphosphene unit, as spectroscopic data and ab initio calculations
for ferrocenyl diphosphenes and ferrocenylene bisdiphosphenes
suggest. In future work we will focus on preparing analogous
ferrocenylene-bridged bis-PdC and bis-PdN derivatives in
order to gain synthetic access to ferrocene-based oligomers and
polymers with such units in the backbone.

1,1′-Ferrocenylene-Bridged Bisdiphosphenes
Organometallics, Vol. 25, No. 10, 2006 2671
1
1
Table 3. Crystal Data and Structure Refinement for 6
537 Hz), 444.9 (d, JPP ) 537 Hz). H (C6D6): 2.17 (s, 24 H),
2.32 (s, 12 H), 3.85-4.55 (m, 8 H), 6.97 (s, 8 H), 7.10 (d, 3JHH
)
formula
fw
C118H248FeP6Si24‚C6H6
2661.1
7.6 Hz; d, JHP ) 1.3 Hz; 4 H), 7.36 (t, JHH ) 7.6 Hz; 2 H). 13C
(C6D6): 21.36 (o-CH3), 21.54 (p-CH3), 72.32-75.94 (m, brd, C5H4),
128.06 (s, m-C6H3), 128.86 (s, m-C6H2), 131.05 (s, p-C6H3), 136.08
(s, o-Cq-Mes), 136.74 (s, Cq-aryl), 139.81 (s, Cq-aryl), 142.30 (s,
Cq-aryl),146.26 (d, JCP ) 11 Hz, Cq-aryl). Anal. (%) Calcd for
C58H58FeP4 (934.82): C 74.52, H 6.25. Found: C 74.44, H 6.52.
UV-vis (benzene): 542 nm, 351 nm. MS (EI): 934,2 (3%, M+),
590.2 (63%, M+ - DmpP), 440.2 (17%, CpHPPDmp+), 331
(100%), 246.0 (19%, M+ - 2DmpP), 151.2 (32%, CpFeP+), 96.2
(17%, CpPH+), 56.2 (4%, Fe+).
4
3
temp, K
wavelength, Å
cryst syst
space group
unit cell dimens
a, Å
123
0.71073
orthorhombic
P212121 (No. 19)
19.6366(2)
24.3191(3)
34.6941(5)
90
90
90
16568.0(4)
4
1.067
0.362
0.849
b, Å
c, Å
R, deg
â, deg
γ, deg
volume, Å3
Z
Synthesis of 1,1′-Bis(2,4,6-tris[bis(trimethylsilyl)methyl]phenyl)-
diphosphenyl)ferrocene (3b). Tbt-PH2 (0.91 g, 1.55 mmol) was
dissolved in diethyl ether (10 mL) and cooled to -78 °C. To this
mixture was added a solution of n-butyllithium in n-hexane (1.6
M, 0.97 mL, 1.55 mmol) while stirring. The mixture was warmed
to room temperature for 0.5 h and subsequently cooled to -78 °C
again. A cooled (-78 °C) solution of Fc′(PCl2)2 (0.30 g, 0.78 mmol)
in diethyl ether (5 mL) was added to the reaction mixture. After
stirring at the same temperature for 1 h, the mixture was allowed
to warm to room temperature for 1 h, upon which it turned orange.
DBU (0.24 g, 1.58 mmol) was added to the solution at room
temperature, and the mixture immediately turned red-violet. After
continued stirring for 30 min the solvent is removed. The residue
is extracted with n-hexane and filtered. Evaporation of the filtrate
under reduced pressure afforded diphosphene 3b (1.00 g, 0.71
mmol, 91%) as a dark red solid (mp: 259.5 °C (dec)). 31P (C6D6):
density (calcd), Mg/m3
µ (mm-1
)
goodness-of-fit on F2
R1 (obsd data)
0.0558
0.1049
-0.01(2)
wR2 (all data)
Flack parameter x
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 6
P(1)-P(2)
2.219(2)
2.234(2)
2.244(2)
2.233(2)
1.836(5)
1.814(5)
1.852(5)
1.830(5)
1.847(5)
1.839(5)
P(2)-P(1)-P(3)
P(6)-P(4)-P(5)
C(1)-P(1)-P(2)
C(1)-P(1)-P(3)
C(6)-P(4)-P(5)
C(6)-P(4)-P(6)
C(11)-P(2)-P(1)
92.10(7)
97.13(7)
P(1)-P(3)
P(4)-P(5)
P(4)-P(6)
105.64(19)
97.10(16)
100.56(16)
96.28(17)
111.94(17)
C(1)-P(1)
C(6)-P(4)
C(11)-P(2)
C(38)-P(3)
C(65)-P(5)
C(92)-P(6)
C(92)-P(6)-P(4)
1
1
1
H(2p)-P(2)-C(11) 102.6(11)
500.0 (d, JPP ) 555 Hz), 492.5 (d, JPP ) 555 Hz). H (C6D6):
H(2p)-P(2)-P(1)
C(38)-P(3)-P(1)
98.9(11)
111.36(16)
0.11 (s, 36 H), 0.20 (s, 36 H), 0.26 (s, 36 H), 2.66 (s, 4 H), 2.83
(s, 2 H), 4.30-4.80 (brd m, 8 H), 6.53 (s, 2 H), 6.64 (s, 2 H). 13
C
108.58(16) H(3p)-P(3)-C(38) 101.2(11)
(C6D6): 0.72 (CH3), 0.80 (CH3), 1.66 (CH3), 29.23 (CH), 30.38
(CH), 30.59 (CH), 69.82-76.51 (m, brd, C5H4), 122.80 (s, m-C6H2),
124.88 (s, p-C6H2), 127.82 (d, 3JCP ) 33 Hz, m-C6H2), 144.13 (dd,
H(6p)-P(6)-C(92) 103.5(12)
H(6p)-P(6)-P(4) 98.6(11)
H(3p)-P(3)-P(1)
C(65)-P(5)-P(4)
96.8(10)
106.30(16)
H(5p)-P(5)-C(65) 99.5(11)
H(5p)-P(5)-P(4)
96.0(10)
2
1JPP ) 64 Hz, JPP ) 44 Hz, ipso-C6H2), 150.16-152.43 (m, brd,
o-C6H2). Anal. (%) Calcd for C64H126FeP4Si12 (1412.45): C 54.42,
H 8.99. Found: C 54.14, H 9.27. UV-vis (toluene): 545 nm, 380
nm. MS (FAB, m-NBA): 1412.3 (24%, M + H+), 1166.4 (10%,
Tbt2P2H2+), 828.2 (25%, M+ - TbtP), 583.3 (98%, TbtPH+), 552.3
(60%, TbtH+), 246 (2%, M+ - 2TbtP), 73.1 (100%, TMS+).
Experimental Section
All chemical experiments were performed in an argon atmosphere
using standard Schlenk techniques or a glovebox. Solvents were
dried over sodium/potassium alloy and stored under argon. 1H, 13C,
and 31P NMR spectra have been recorded on Bruker AMX 360
and Varian Unity 400 spectrometers at room temperature. Chemical
shift values are given in ppm and are referenced to external
standards. Mass spectra have been measured on Kratos MS-50 and
Masslab VG 12-250 spectrometers using the EI ionization technique
or FAB with an m-NBA matrix. Dmp-PH2, Tbt-PH2, and Fc′(PCl2)2
have been prepared according to published procedures.18,24,30
Synthesis of 1,1′-Bis(2,6-dimesitylphenyldiphosphenyl)ferrocene
(3a). Dmp-PH2 (0.34 g, 0.98 mmol) was dissolved in diethyl ether
(10 mL) and cooled to -78 °C. To this mixture was added a
solution of n-butyllithium in n-hexane (1.6 M, 0.6 mL, 0.95 mmol)
while stirring. The mixture was warmed to room temperature for
0.5 h and subsequently cooled to -78 °C again. The reaction
mixture was added to a solution of Fc′(PCl2)2 (0.19 g, 0.49 mmol)
in diethyl ether (5 mL) at -78 °C. After stirring at the same
temperature for 1 h, the mixture was allowed to warm to room
temperature for 1 h, upon which it turned orange. DBU (0.15 g,
0.98 mmol) was added to the solution at room temperature, and
the mixture immediately turned red-violet. After continued stirring
for 30 min the solvent is removed. The residue is extracted with
n-hexane and filtered. Evaporation of the filtrate under reduced
pressure afforded diphosphene 3a (0.36 g, 0.38 mmol, 77%) as a
Bis-1,3-dihydrotriphosphane (6). A solution of Tbt-PH2 (1.17
g, 2 mmol) in benzene was added to a solution of 3b (1.41 g, 1
mmol) in benzene at room temperature while stirring. The resulting
solution is stored at room temperature without stirring in the dark.
After several days platelike orange crystals of 6 formed, which were
separated from the supernatant mother liquor and dried in a vacuum
(1.16 g, 0.45 mmol, 45%). On heating, liquescent samples of neat
6 turned dark orange at 92 °C and intensive dark red at 98 °C. 31
P
(C6D6): -18 to -85 (broad multiplets of the various spin systems
of the isomeric mixture). Anal. (%) Calcd for C118H248FeP6Si24
(2582.97): C 54.87, H 9.68. Found: C 54.49, H 9.77.
Crystallographic Details for 6. A yellow plate-shaped crystal
of 6 with dimensions 0.25 × 0.10 × 0.05 mm was used. The
measurements were performed on a Nonius Kappa CCD diffrac-
tometer using graphite-monochromatized Mo KR radiation at 123
K. A total of 65 722 reflections were collected (θmax ) 25.02°),
from which 27 445 were unique (Rint ) 0.0640), with 13 425 having
I > 2σ(I). The structure was solved by direct methods and refined
by full-matrix least-squares techniques against F2 with SHELXL-
97. The non-hydrogen atoms were refined with anisotropic dis-
placement parameters. Also the H(P) were localized by electron
density determination, and the coordinates were refined free with
U(H) ) 1.2 Ueq(P). The absolute structure of 6 has been determined
by refinement of Flack’s x parameter (x ) -0.01(2)). For 1366
parameters (31 restraints) final R indices of R ) 0.0558 (for I >
2σ(I)) and wR2 ) 0.1049 (for all data) (GOF ) 0.849) were
obtained.
dark red solid (mp: 136.4 °C (dec)). 31P (C6D6): 470.3 (d, 1JPP
)
(30) Urnezius, E.; Protasiewicz, J. D. Main Group Chem. 1996, 1, 369-
372.

2672 Organometallics, Vol. 25, No. 10, 2006
Moser et al.
Computational Details. Ab initio quantum chemical calculations
were performed for compounds 4 and 5 using the program package
Gaussian 0331 at the Hartree-Fock and DFT(B3LYP) levels,
employing a Dunning/Huzinaga full double-ú basis set on first-
row elements32 and Los Alamos ECP plus DZ on Na-Bi.33-35
Harmonic vibrational frequencies and their infrared intensities for
all of the optimized structures have been evaluated by the B3LYP
method to determine if a structure is a genuine minimum.
Representations of the molecular orbitals are shown at a contour
value of 0.04.
Acknowledgment. Financial support by the Austrian Science
Fund (FWF) is gratefully acknowledged (Project: P18591-B03).
(31) http://www.gaussian.com/.
Supporting Information Available: Complete crystallographic
details of the X-ray structure of 6 (CIF). This material is available
free of charge via the Internet at http://pubs.acs.org.
(32) Modern Theoretical Chemistry; Dunning, T. H., Jr., Hay, P. J.,
Schaefer, H. F., III, Eds.; Plenum: New York, 1977; Vol. 3.
(33) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270-83.
(34) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284-98.
(35) Hay, P. J.; Wadt, W. R.J. Chem. Phys. 1985, 82, 299-310.
OM060073C