Cyclopentadienyl tantalum(V) complexes with primary and secondary ferrocenylphosphine ligands

Article abstract of DOI:10.1002/zaac.200700391

The reaction of [Cp*TaCl₄] (1a, Cp* = C ₅Me₅) or [Cp′TaCl₄(THF)] (1b, Cp′ = C₅MeH₄) with PH₂Fc [Fc = Fe(η⁵- C₅H₅)(η⁵-C₅H

Full text of DOI:10.1002/zaac.200700391

DOI: 10.1002/zaac.200700391
Cyclopentadienyl Tantalum(V) Complexes with Primary and Secondary
Ferrocenylphosphine Ligands
a
a
b
b
a,
´
Rene Kalio , Peter Lönnecke , Arnaldo Cinquantini , Piero Zanello , and Evamarie Hey-Hawkins *
a Leipzig/Germany, Institut für Anorganische Chemie der Universität
b
`
Siena/Italy Dipartimento di Chimica dell’Universita di Siena
Received July 14th, 2007.
Dedicated to Professor Dieter Fenske on the Occasion of his 65th Birthday
Abstract. The reaction of [Cp*TaCl4] (1a, Cp* ϭ C5Me5) or
[CpЈTaCl4(THF)] (1b, CpЈ ϭ C5MeH4) with PH2Fc [Fc ϭ Fe(η5-
C5H5)(η5-C5H4)] and PH2CH2Fc gives the primary ferrocenylphos-
phine complexes [CpRTaCl4(PH2Fc)] [CpR ϭ Cp* (2a), CpЈ (2b)]
and [CpRTaCl4(PH2CH2Fc)] [CpR ϭ Cp* (3a), CpЈ (3b)], respec-
tively. 1 reacts with (PH2)2fc [fc ϭ Fe(η5-C5H4)2] or with the new
secondary phosphine PH(CH2Fc)2 to give the ferrocenyl-bridged
complexes [{(CpRTaCl4)[PH2(η5-C5H4)]}2Fe] [CpR ϭ Cp* (4a), CpЈ
(4b)] or [CpRTaCl4{PH(CH2Fc)2}] [CpR ϭ Cp* (5a), CpЈ (5b)].
Complexes 1b and 2Ϫ5 were characterised spectroscopically (1H,
13C, 31P NMR, MS, IR) and 1b, 2a, 3a, 4a, and 5a also by X-ray
crystallography. The electrochemical behaviour of complexes 3a
and 5b exhibits complicated electron transfer processes, which are
due to the complex redox activity of the corresponding ferrocenyl-
phosphine ligands PH2CH2Fc and PH(CH2Fc)2.
Keywords: Tantalum; Ferrocenylphosphines; 31P NMR spec-
troscopy; Electrochemistry
Introduction
heating oil to reduce formation of soot, iron-containing fer-
tilisers, UV absorbers and protective coatings for rockets
and satellites [12].
Organometallic dialkyl- and diarylphosphanido complexes
of early transition metals have been studied intensively,
while complexes derived from functionalized phosphines
which have a reactive phosphorusϪligand bond have been
largely neglected [1] due to the toxicity and high reactivity
of the free phosphines (some are even pyrophoric). This
lack of attention has prompted the development of primary
and secondary phosphines that are more air-stable and
hence easier to use [2Ϫ8]. Interest in these phosphines has
arisen from the possibility of post-coordination modifi-
cation of the PϪH bond, which allows for chemical flexi-
bility in the synthesis of new and intriguing transition metal
phosphine complexes [9]. A recent development in the
stabilisation of primary [2Ϫ4] and secondary [10, 11] phos-
phines has been the use of the ferrocenylmethyl fragment.
Due to the redox properties of the ferrocenyl unit and the
possibility to obtain chiral compounds readily, ferrocenyl-
phosphines are an important class of ligands in transition
metal chemistry [12]. In addition, ferrocene derivatives usu-
ally show enhanced stability and are generally non-toxic.
Thus, their industrial applications range from additives for
To date, only a few phosphanido derivatives of or-
ganometallic [13Ϫ15] and inorganic [16, 17] niobium and
tantalum compounds, diphosphinediyl complexes [18], one
phosphinidene-bridged dimeric TaIV complex [14] and two
stable terminal phosphinidene complexes [17, 19] have been
described in the literature, although potential starting mate-
rials such as cyclopentadienyl-substituted metal halides,
alkyls, hydrides and carbonyls [20] are accessible, as are in-
organic metal halides [21]. We expect cyclopentadienyl tan-
talum chloride complexes with primary or secondary phos-
phines to be suitable precursors for tantalum phosphanido
or phosphinidene complexes, based on our work on the re-
actions of Zr and Mo complexes with primary phosphines
or alkali metal phosphanides [22, 23], where we could show
that a wide variety of products is obtained, depending on
the nature of the organic substituents on phosphorus and
the transition metal.
The Lewis acidity of tantalum(V) complexes has been
extensively studied, and a large number of adducts of
[CpRTaCl4] with ethers, amines, nitriles and isonitriles has
been reported [24]. Up to now, only a few phosphine com-
plexes of cyclopentadienyl tantalum tetrachloride are
known, all but one of which have tertiary phosphine
ligands [24d, 25Ϫ27]. We reported the synthesis of
[CpЈTaCl4(PH2Tipp)] (CpЈ ϭ C5MeH4, Tipp ϭ 2,4,6-
Pri3C6H2), which was the first cyclopentadienyl tantalum
tetrachloride complex with a primary phosphine [14a], and
a number of other tantalum and niobium complexes with
* Prof. Dr. E. Hey-Hawkins
Institut für Anorganische Chemie der Universität
Johannisallee 29
D-04103 Leipzig / Germany.
Fax: (0049)3419739319
Tel: (0049)3419736151
E-mail: hey@rz.uni-leipzig.de
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Z. Anorg. Allg. Chem. 2007, 633, 2470Ϫ2480

Cyclopentadienyl Tantalum(V) Complexes
primary phosphine ligands [28]. We have already shown
that the phosphines PH2Fc [Fc ϭ Fe(η5-C5H5)(η5-C5H4)]
[29], PH2CH2Fc [3, 4] and PH(CH2Fc)2 [10] (ϭ L) react
with transition metal complexes with reactive MϪX bonds
(X ϭ halide) without loss of HX but with clean formation
of the corresponding phosphine complexes, such as
Table
1
Selected bond lengths /pm and angles /° in
[CpЈTaCl4(THF)] (1b) (CEN ϭ C5 centroid of the cyclopenta-
dienyl ring)
Ta(1)-O(1)
Ta(1)-Cl(3)
Ta(1)-Cl(2)
Ta(1)-Cl(4)
Ta(1)-Cl(1)
Ta(1)-CEN
O(1)-Ta(1)-CEN
Cl(1)-Ta(1)-CEN
Cl(2)-Ta(1)-CEN
Cl(3)-Ta(1)-CEN
Cl(4)-Ta(1)-CEN
231.3(4)
239.9(2)
240.4(2)
240.6(2)
241.4(2)
212.1
178.5
101.9
103.3
103.8
[(p-cymene)RuCl2(L)] (p-cymene
ϭ
1-Me-4-PriC6H4)
[3, 30, 31], [MI2(CO)3L2], [MI2(CO)2L3] (M ϭ Mo, W)
[32, 33, 34], and [WI(CO)2L4]I (L ϭ PH2CH2Fc) [35].
We now report the synthesis of heterobimetallic di-
and trinuclear organometallic tantalum complexes with
primary or secondary ferrocenylphosphine ligands
[CpRTaCl4{PH2(CH2)nFc}] [n ϭ 0: CpR ϭ Cp* (2a),
102.0
CpЈ (2b);
n ϭ ϭ Cp* (3a), CpЈ (3b)],
1: CpR
[{(CpRTaCl4)[PH2(η5-C5H4)]}2Fe] [CpR ϭ Cp* (4a), CpЈ
(4b)] and [CpRTaCl4{PH(CH2Fc)2}] [CpR ϭ Cp* (5a), CpЈ
(5b)].
As can be seen by comparison between 1a and 1b, coordi-
nation of the THF molecule to the tetragonal-pyramidal
[CpRTaCl4] fragment to give a six-coordinate octahedral
complex results in a shortening of the distance between the
equatorial plane of the four chloro ligands and the tanta-
lum atom from 80.6 pm in 1a to only 53.1 pm in 1b.
Results and Discussion
Synthesis
Synthesis of tantalum ferrocenylphosphine complexes
Starting materials
When an equimolar amount of the primary phosphines
PH2Fc, PH2CH2Fc or the secondary phosphine
PH(CH2Fc)2 is added to complexes 1 in non-coordinating
solvents like toluene or CH2Cl2, complexes 2, 3 and 5 can
be isolated as orange or red crystals in high yields. The
products are soluble in toluene, chloroform and dichloro-
methane, but hardly soluble in n-pentane or n-hexane. On
addition of (PH2)2fc (fc ϭ Fe(η5-C5H4)2) to two equivalents
of 1 the trinuclear products can be isolated as red crystals
(4a) or a yellow powder (4b). The solubility of 4a is much
lower than that of the other complexes, and 4b is almost
insoluble in any common solvent. If the reaction between 1
and the ferrocenylphosphines is carried out in diethyl ether,
the products form in poor yields and low purity, whereas
use of THF often causes decomposition. In the solid state
complexes 2-5 are quite stable in dry air (except for 3b,
which rapidly loses solvent), but in solution they decom-
pose in a matter of hours if exposed to air.
Recently, we published the crystal structure of [Cp*TaCl4]
(1a) [28], one of our starting materials, whose monomeric
molecular structure is apparently due to the large Cp* li-
gand. We therefore invested some effort in crystallising the
related tantalum complex [CpЈTaCl4], whose CpЈ ring is
sterically less demanding, and which until today was only
known as a yellow powder. While we could not crystallise
the solvent-free complex [CpЈTaCl4], we obtained
[CpЈTaCl4(THF)] (1b) on recrystallisation of [CpЈTaCl4]
from a mixture of diethyl ether with a small amount of
THF. The crystal structure of 1b is shown in Figure 1, and
selected bond lengths and angles are listed in Table 1.
Spectroscopic studies
Complexes 1b and 2Ϫ5 were fully characterised by elemen-
tal analysis, infrared spectroscopy and NMR spectroscopy,
the last-named mostly at low temperature. FAB mass spec-
trometry gave no molecular ion peak, but the fragment
peaks could be unambiguously assigned, the heaviest
mostly being the respective complex with loss of one or two
chloro ligands or its adduct with the 3-nitrobenzyl alcohol
matrix.
NMR spectroscopic investigations
As we already observed in previous investigations on tanta-
lum phosphine complexes [28], the quadrupole momentum
Fig. 1 Molecular structure of [CpЈTaCl4(THF)] (1b).
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R. Kalio, P. Lönnecke, A. Cinquantini, P. Zanello, E. Hey-Hawkins
Scheme 1 Reactions of [Cp*TaCl4] and [CpЈTaCl4(THF)] with the ferrocenylphosphines FcPH2, FcCH2PH2, fc(PH2)2 and (FcCH2)2PH
to give the products 2؊5 (CpR ϭ Cp*, CpЈ).
Table 2 31P NMR spectroscopic data of the tantalum complexes
2؊5 recorded at 25 °C in CDCl3. ∆δ is the difference of the chemi-
cal shifts between the free ferrocenylphosphine and the respective
complex.
δ
∆δ
1JPH
♣
♣
♣
[Cp*TaCl4(PH2Fc)] (2a)
Ϫ3.1 ppm 141.4 ppm 367 Hz
ϩ1.2 ppm 130.3 ppm 359 Hz
Ϫ7.6 ppm 139.9 ppm 367 Hz
[Cp*TaCl4(PH2CH2Fc)] (3a)
[{(Cp*TaCl4)[PH2(η5-C5H4)]}2Fe] (4a)
[Cp*TaCl4{PH(CH2Fc)2}] (5a)
[CpЈTaCl4(PH2Fc)] (2b)
[CpЈTaCl4(PH2CH2Fc)] (3b)
[{(CpЈTaCl4)[PH2(η5-C5H4)]}2Fe] (4b)
[CpЈTaCl4{PH(CH2Fc)2}] (5b)
ϩ38.5 ppm
91.9 ppm 375 Hz
Ϫ0.2 ppm 144.3 ppm 366 Hz
Ϫ2.7 ppm 126.4 ppm 372 Hz
Ϫ3.3 ppm 144.2 ppm 375 Hz
♣
♣
ϩ43.5 ppm
96.9 ppm 377 Hz
♣ recorded at Ϫ60 °C
sition metal, the signal of the phosphine ligand is shifted to
low field compared to the free phosphine, by up to
147 ppm. This value is relatively high compared with pre-
viously described complexes of the type [Cp*TaCl4(PH2R)]
with R ϭ But, adamantyl, Cy, Ph and Mes (2,4,6-
Me3C6H2), where the low field shift on coordination
Fig. 2 31P NMR FIDs of [Cp*TaCl4(PH2Fc)] (2a) in CDCl3 re-
corded at ϩ25 °C (first 20 ms, upper diagram) and at Ϫ63 °C (first
200 ms, lower diagram).
1
amounts to ca. 100Ϫ120 ppm. The JPH coupling constant
of the Ta atom causes extreme line broadening in the 31P
NMR spectra of the tantalum ferrocenylphosphine com-
plexes at room temperature. The very short relaxation time
at room temperature can be followed in the FID of the
complexes (see Fig. 2). Nevertheless, it was possible to re-
cord 31P NMR spectra of suitable quality at low tempera-
ture, except in cases of low solubility.
increases by 160Ϫ180 Hz [28].
The differences in the chemical shift between the free
phosphine and the respective tantalum(V) complex are
larger for the primary ferrocenylphosphines than for the
secondary (FcCH2)2PH. This could be due to increased
shielding of the phosphorus atom when the primary phos-
phine ligand is coordinated to the [CpRTaCl4] fragment. On
the other hand, the difference between the complexes with
Cp* and CpЈ ligands is negligible (∆δ ca. 5 ppm).
The 31P NMR spectroscopic data of compounds 2Ϫ5 are
shown in Table 2. As expected on coordination to a tran-
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Cyclopentadienyl Tantalum(V) Complexes
Table 3 IR frequencies of the PϪH stretching vibrations (in
cmϪ1) of complexes 2؊5.
Complex
ν(P-H) (cmϪ1
)
[Cp*TaCl4(PH2Fc)] (2a)
2399, 2378
2371
2388 (sh), 2365
2386
2389, 2369
2391
2387, 2364
2391
[Cp*TaCl4(PH2CH2Fc)] (3a)
[{(Cp*TaCl4)[PH2(η5-C5H4)]}2Fe] (4a)
[Cp*TaCl4{PH(CH2Fc)2}] (5a)
[CpЈTaCl4(PH2Fc)] (2b)
[CpЈTaCl4(PH2CH2Fc)] (3b)
[{(CpЈTaCl4)[PH2(η5-C5H4)]}2Fe] (4b)
[CpЈTaCl4{PH(CH2Fc)2}] (5b)
IR spectroscopy
The PϪH stretching vibrations in the IR spectra of the tan-
talum complexes 2Ϫ5 have their absorption maxima be-
tween 2364 and 2399 cmϪ1 (see Table 3).
As expected, complexes 5a and 5b exhibit only one PH
stretching band, while complexes 2a, 2b, 4a and 4b show
two absorptions (νas and νs PH2). However, unexpectedly,
only one PH vibration is observed for 3a and 3b, as was
previously also observed for some related tungsten and mol-
ybdenum complexes [34]. As is observed for other ferrocen-
ylphosphine complexes [10, 30, 31, 33Ϫ35], the PϪH
stretching vibrations are shifted to higher wavenumbers
compared to the free phosphines (PH2Fc: 2225 cmϪ1 [29];
PH2CH2Fc: 2285 cmϪ1 [3]; PH(CH2Fc)2: 2285 cmϪ1 [10]).
Fig. 3 Molecular structure of [Cp*TaCl4(PH2Fc)] (2a)
X-ray structure determination
Molecular structures of [Cp*TaCl4(PH2Fc) (2a),
[Cp*TaCl4(PH2CH2Fc)] (3a), [{(Cp*TaCl4)[PH2(η5-
C5H4)]}2Fe] (4a) and [Cp*TaCl4{PH(CH2Fc)2}] (5a)
Complex 2a could be crystallised in two modifications un-
der identical conditions (Ϫ30 °C, from toluene). The sol-
vent-free compound crystallises as dark red rhombohedra,
whereas 2a·0.5 toluene crystallises as dark red multilayered
plates. Both modifications belong to the monoclinic space
group P21/c.
Fig. 4 Molecular structure of [Cp*TaCl4(PH2CH2Fc)] (3a). Mole-
cule from the 70 % domain shown.
Figure 3 illustrates the molecular structure of the solvent-
free complex 2a.
In the solvent-free complex the asymmetric unit com-
prises one molecule of the complex, while the asymmetric
unit in the toluene solvate consists of two independent mol-
ecules of 2a and one molecule of toluene. Although both
structures appear to be very similar, packing effects cause
large divergences in the bond lengths and angles of the two
modifications (Table 4).
Fig. 5 The fragments [TaCl4(PH2CH2Fc)] of the disordered mole-
cules (70 % (left) and the 30 % domain (right) of 3a) viewed from
the centre of the C5Me5 rings. The C5Me5 rings and all H atoms
have been left out for clarity.
[Cp*TaCl4(PH2CH2Fc)] (3a) was obtained as large, dark
red prisms. The examined crystal contained two types of the
molecule in a ratio of 70:30 %, apparently as enantiomers in
different domains of the crystal (approximately mirror im-
ages, as shown in Fig 5.) The molecular structures of both
types of molecule are shown in Figure 4; selected bond
lengths and angles are given in Table 4.
planar arrangement of the two substituted cyclopentadi-
enyl rings, as would be expected for bulky substituents in
1,1Ј-substituted ferrocenes (Fig. 6, Table 4) [12].
[Cp*TaCl4{PH(CH2Fc)2}] (5a) was isolated as dark red
crystals of the toluene solvate. 5a crystallises in the mono-
[{(Cp*TaCl4)PH2(η5-C5H4)}2Fe] (4a) is located on a
crystallographic inversion centre resulting in an antiperi-
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R. Kalio, P. Lönnecke, A. Cinquantini, P. Zanello, E. Hey-Hawkins
Table 4 Selected bond lengths (pm) and angles (°) of 2a, 2b, 3a,
4a, and 5a.
Compound
2a1)
2a·0.5
3a3)
4a
5a
toluene2)
Ta(1)-Cl(1)
Ta(1)-Cl(2)
Ta(1)-Cl(3)
Ta(1)-Cl(4)
Ta(1)-C(CpR)
239.0(1) 239.7(2), 241.2(7),
238.8(2) 241.8(3)
240.1(1) 238.5(2), 239.6(7),
241.2(2) 240.4(3)
241.4(1) 241.3(2), 243.4(7),
239.2(2) 243.2(3)
242.9(1) 241.0(2), 242.3(7),
240.6(2) 241.4(3)
240.9(1) 241.5(3)
238.1(1) 239.3(2)
241.3(1) 240.4(3)
242.3(1) 241.6(2)
244.6(3)- 241.3(2)- 248(2)-
251.4(3) 250.6(7), 267(3),
243.5(6)- 242.2(14)-
244.2(5)- 245.6(9)-
250.5(5) 251.3(9)
252.4(6)
251.7(10)
Ta-CEN(CpR)4)
216.8
216.1,
215.9
221.0,
216.5
216.6
61.3
217.4
59.5
Ta-(mean plane 4 Cl) 61.1
61.7,
60.9
58.6,
60.6
Ta(1)-P(1)
264.7(1) 265.5(2), 265.6(7),
264.8(2) 265.9(3)
179.6(3) 180.6(7), 190(3),
265.2(1) 267.7(2)
Fig. 7 Molecular structure of [Cp*TaCl4{PH(CH2Fc)2}]·toluene
(5a·toluene). All H atoms (except PH) and the solvent molecule
are omitted for clarity.
P(1)-C
179.4(5) 182.2(9),
184.5(9)
177.7(7)
183.0(11)
Cl(1)-Ta(1)-Cl(2)
Cl(1)-Ta(1)-Cl(3)
Cl(2)-Ta(1)-Cl(3)
Cl(1)-Ta(1)-Cl(4)
Cl(2)-Ta(1)-Cl(4)
Cl(3)-Ta(1)-Cl(4)
Cl(1)-Ta(1)-P(1)
Cl(2)-Ta(1)-P(1)
Cl(3)-Ta(1)-P(1)
Cl(4)-Ta(1)-P(1)
C-P(1)-Ta(1)
88.3(1)
89.84(9), 87.5(3),
87.77(6) 84.8(1)
150.37(5) 150.2(1)
86.01(6) 87.6(1)
86.37(6) 85.1(1)
150.62(5) 152.5(1)
85.02(7) 88.6(1)
72.60(5) 77.4(1)
75.93(5) 79.1(1)
77.79(5) 72.9(1)
74.85(5) 73.8(1)
87.43(9)
85.07(12)
150.7(1) 150.38(7), 151.2(2),
150.57(7) 150.58(11)
clinic space group P21/c. The molecular structure is illus-
trated in Figure 7, selected bond lengths and angles of com-
plex 5a are given in Table 4. In the crystal the ferrocenyl
groups exhibit considerable distortion, which apart from
packing effects seems to result from the steric influence of
these bulky groups on each other. Free rotation of these
voluminous groups is hindered even in solution, as indi-
88.1(1)
86.3(1),
86.08(8)
85.3(3),
86.84(12)
84.5(1)
85.47(7), 87.1(3),
86.9(1) 86.03(14)
150.5(1) 149.96(7), 152.6(2),
150.61(7) 151.26(11)
84.5(1) 83.40(8), 86.6(3),
84.81(9) 87.64(12)
78.1(1) 73.84(6), 77.6(2),
72.96(7) 77.13(11)
73.2(1) 73.64(6), 78.7(2),
73.35(7) 77.87(10)
72.2(1) 76.90(6), 73.7(2),
77.67(6) 73.52(12)
77.3(1) 76.55(6), 73.9(2),
77.42(7) 73.52(10)
120.4(1) 121.0(2), 118.2(8),
1
cated by two signals for the CH2 groups in the H NMR
spectrum (∆δ ϭ 0.51 ppm in 5a, 0.47 ppm in 5b).
General features
All complexes 2a, 3a, 4a, and 5a (Fig. 3Ϫ7, Table 4) show
a slightly distorted octahedral environment around the Ta
atom, the axial positions of which are occupied by the cen-
troid of the C5 ring and the phosphine ligand. The chloro
ligands arrange themselves in the equatorial plane, but are
tilted away from the Cp* ligand.
As expected the [Cp*TaCl4] fragments point away from
the iron atom of the ferrocenyl group in all complexes.
By comparing the bond lengths and angles we were
able to obtain a coherent picture of the steric influence
123.0(2) 117.7(3),
117.5(3)
121.9(2)
119.5(4)
C-P(1)-C
Ϫ
Ϫ
Ϫ
Ϫ
105.2(4)
1) solvent-free modification of 2a
2) two independent molecules are present in the asymmetric unit
3) 30 % and 70 % domain
4) CEN ϭ C5 centroid of the CpR ring
Fig. 6 ORTEP plot of [{(Cp*TaCl4)[PH2(η5-C5H4)]}2Fe] (4a). All H atoms (exept PH) are omitted for clarity.
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Cyclopentadienyl Tantalum(V) Complexes
of different phosphine ligands on the geometry of the com-
plex molecules. The TaϪP bond length is mainly influenced
by electronic effects of the phosphine, and the
TaϪPϪC bond angles are reduced considerably in
[Cp*TaCl4{PH(CH2Fc)2}] (5a, 117.5° and 117.7°) com-
pared with other known complexes of the type
[CpRTaCl4(PH2R)], which exhibit angles in the range be-
tween 119.5° and 131.0°.
Electrochemical studies on FcCH2PH2 and
(FcCH2)2PH and their complexes
[Cp*TaCl4(PH2CH2Fc)] (3a) and
[CpЈTaCl4{PH(CH2Fc)2}] (5b)
Figure 8 Cyclic voltammetric responses recorded in CH2Cl2 solu-
tion of [Cp*TaCl4(PH2CH2Fc)] (3a) (0.9x10Ϫ3 mol dmϪ3).
[NBu4][PF6] (0.2 mol dmϪ3) supporting electrolyte. (a) Platinum
The difficulties encountered in interpreting the electro-
chemical behaviour of mono- and diferrocenylphosphines
of the types FcCH2PR2 and (Fc)2PR are well established
[36, 37]. They usually afford responses complicated by elec-
trode adsorption phenomena and/or chemical compli-
cations. The present ferrocenylphosphines FcCH2PH2 and
(FcCH2)2PH give rise to even more complicated electro-
chemical responses, which are in turn reflected in the redox
behaviour of the complexes [Cp*TaCl4(PH2CH2Fc)] (3a)
and [CpЈTaCl4{PH(CH2Fc)2}] (5b). In fact, unexpectedly,
a CH2Cl2 solution of FcCH2PH2 displays a first, partially
chemically reversible, oxidation ([FcCH2PH2]0/ϩ: E°Ј ϭ
ϩ0.35 V, vs. SCE), followed by further closely spaced oxi-
dations arising from chemical complications following the
first step, the main of which is tentatively attributed to the
oxidation of the byproduct [FcCH2OH] (E°Ј ϭ ϩ0.42 V)
[38]. Since it is known that hydridic hydrogen atoms in me-
tal complexes undergo anodic oxidation [39], the generation
of the mentioned byproduct likely occurs from the partial
stability of [FcCH2PH2]ϩ, which triggers oxidative elimin-
ation of hydrides, breakage of the CϪP bond, and insertion
of an OH group from the nominally anhydrous solution.
We note that such behaviour is in sharp contrast with
that of FcCH2PPh2, which exhibits a chemically reversible
one-electron oxidation accompanied by slight adsorption
phenomena [40].
electrode; (b) glassy carbon electrode. Scan rate 0.2 VsϪ1
.
The use of the two electrode materials confirmed that the
overall oxidation process is accompanied by release of protons.
In fact, since the reduction of protons at the glassy carbon elec-
trode is shifted towards very negative potentials with respect
to the standard electrode potentials of the H2/Hϩ couple [41],
the presence of the backscan peak at Ep ϭ Ϫ0.26 V at the plati-
num electrode confirms the hypothesis.
It is hence concluded that also in this case the first step
(E°Ј ϭ ϩ0.50 V in Osteryoung square-wave voltammetry)
of the three ferrocenyl-centred oxidations triggers decoordi-
nation followed by the previously illustrated anodic path of
the released ferrocenyl ligand.
Figure 9 finally shows the cyclic voltammetric pattern
for the oxidation of the diferrocenyl complex
[CpЈTaCl4{PH(CH2Fc)2})] (5b), also in comparison with
that of the free ligand (FcCH2)2PH.
In confirmation of the complex oxidation pattern, coulo-
metric measurements corresponding to the overall oxi-
dation process (Ew ϭ ϩ0.7 V) showed the consumption of
three electrons per molecule. In fact, the original yellow
solution does not show any colour change after about one
electron per molecule, turns green after about two electrons
per molecule (as a consequence of the spectrally supported
generation of [FcCH2OH]ϩ) and blue after about three elec-
trons per molecule.
This being stated, let us consider the cyclic voltammetric
profile of the oxidation path of the monoferrocenyl complex
[Cp*TaCl4(PH2CH2Fc)] (3a) at a platinum and at a glassy
carbon electrode, respectively. As far as the cathodic region
is concerned, an irreversible tantalum(V)-centred reduction
(not shown in Figure 8) is also present (Ep ഠ Ϫ0.7 V),
which is ill defined probably because of electrode-poison-
ing phenomena.
Figure 9 Cyclic voltammetric responses recorded at a platinum
electrode in CH2Cl2 solution of: (a) (FcCH2)2PH (0.8x10Ϫ3 mol
dmϪ3); (b, c) [CpЈTaCl4{PH(CH2Fc)2}] (5b) (0.6x10Ϫ3 mol dmϪ3).
[NBu4][PF6] (0.2 mol dmϪ3) supporting electrolyte. Scan rates:
(a, b) 0.2 VsϪ1; (c) 2.0 VsϪ1
.
Z. Anorg. Allg. Chem. 2007, 2470Ϫ2480
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2475

R. Kalio, P. Lönnecke, A. Cinquantini, P. Zanello, E. Hey-Hawkins
The response of (FcCH2)2PH is qualitatively reminiscent
of that of (FcCH2)2PPh under the same experimental con-
ditions [37a], i.e. a relatively broad, two-electrons oxidation
with features of chemical reversibility (E°Ј ϭ ϩ0.51 V;
∆Ep ϭ 120 mV at 0.2 VsϪ1) which is preceded by a prewave
typical of strong adsorption of the electron-transfer product
(Ep ϭ ϩ0.33 V) [40]. At variance with the latter, exhaustive
electrolysis of (FcCH2)2PH consumes six electrons per mol-
ecule. As in the case of FcCH2PH2, the yellow colour of
the original solution remains unchanged in the first stages
of the oxidation process (up to about 1.5 electrons per mol-
ecule), then progressively turns green and blue. Concomi-
tantly, in confirmation of the cited adsorption phenomena,
a blue deposit appears on the electrode surface. The final
species remaining in solution exhibits a reversible reduction
at ϩ0.40 V.
cess, since after the consumption of about two electrons per
molecule the electrolysis current suddenly dies out. Since
the cyclic voltammetric profile remains substantially un-
changed with respect to the original one, we attribute the
current breaking to electrode-poisoning phenomena.
In conclusion, the ferrocenylphosphines FcCH2PH2 and
(FcCH2)2PH undergo complicated oxidation processes
which are substantially reflected in the anodic behaviour of
their tantalum(V) complexes [Cp*TaCl4(PH2CH2Fc)] (3a)
and [CpЈTaCl4{PH(CH2Fc)2}] (5b). This also holds for the
pertinent redox potentials, that is, the tantalum complex
fragment does not substantially affect the electronic situ-
ation of the ferrocenyl ligands.
Subsequent reactions of complexes 2؊5
In turn, the tantalum complex shows two closely spaced
oxidations, which are not resolved even in Osteryoung
square-wave voltammetry (peak A, Ep ഠ ϩ0.4 V; peak B,
E°Ј ϭ ϩ0.54 V) and are preceded by a very minor peak
(marked with *), which coincides with the adsorption pre-
wave of the free ligand. In the backscan profile (not shown
in Figure 9) a reduction around Ϫ0.2 V also appears which,
since it takes place only at the platinum electrode, is as-
signed to proton reduction. As illustrated in Figure 9c,
upon increasing the scan rate, the second anodic process
tends to decrease, thus indicating that it arises from chemi-
cal complications following the first anodic step. Finally,
the tantalum(V)-centred reduction is also detected at
Ϫ0.69 V upon direct scan towards negative potentials.
Unfortunately, we did not succeed in determining the
number of electrons involved in the overall oxidation pro-
Apart from attempting to prepare suitable starting materi-
als for the preparation of phosphanido and phosphinidene
complexes we observed spontaneous reactions between the
complexes and the solvent which emphasize the high reac-
tivity of the PϪH bond in the tantalum primary phos-
phine complexes.
On dissolving complexes of the type [CpRTaCl4(PH2R)]
in CDCl3 proton/deuterium exchange could be observed at
the PH2 groups of the phosphine ligand of complexes 2a,
2b, 3a and 5b. In the 31P NMR spectrum the PHD groups
gave the typical 1:1:1 triplet in which the 1J(31P2H) coupling
1
constant is ca. 15 % of the J(31P1H) coupling constant of
the PH2 group [42] (Fig. 10).
Scheme 2 shows the H/D exchange reaction with deuter-
ated protic solvents.
Fig. 10 31P NMR spectra of [Cp*TaCl4(PH2CH2Fc)]. Left: Proton-decoupled spectrum in CDCl3. Apart from the singlet of the educt a
1:1:1 triplet due to 1J(PD) coupling of the H-D exchange product [Cp*TaCl4{(PHD)CH2Fc}] can be seen. Centre: Proton-coupled spectrum
in CDCl3. 1J(PH) coupling gives a triplet for the unchanged complex which overlaps with a doublet of 1:1:1 triplets for the exchange
product. Right: Proton-coupled spectrum in CHCl3.
Scheme 2 H-D exchange reaction between [CpRTaCl4(PH2R)] and deuterated protic solvents (DR).
2476
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 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2007, 2470Ϫ2480

Cyclopentadienyl Tantalum(V) Complexes
X-ray diffraction data were collected on a Siemens SMART CCD
diffractometer (radiation: MoKα, λ ϭ 71.073 pm; method: ω scans
rotation). Absorption correction was performed using the program
SADABS [46]. The structures were solved by direct methods, and
all non-hydrogen atoms were refined anisotropically (SHELX97)
Experimental Section
General
All manipulations were carried out with standard high-vacuum and
dry-nitrogen techniques. Solvents were purified and dried accord-
ing to standard procedures. NMR spectra: Avance DRX 400
(Bruker), standards: 1H NMR (400 MHz): TMS, 13C NMR
(100.6 MHz): TMS, 31P NMR (162 MHz): external 85 % H3PO4.
31P NMR data of 2؊5 are given in Table 2. The IR spectra were
recorded as KBr disks on a Perkin-Elmer System 2000 FT-IR spec-
trometer in the range 350-4000 cmϪ1. Mass spectra were obtained
with a Varian MAT 711 Spectrometer (FAB, 70 eV, source tem-
perature 180 °C, 3-NBA matrix). The melting points were deter-
mined in sealed capillaries and are uncorrected. PH2Fc [29],
PH2CH2Fc [3, 4], PH(CH2Fc)2 [10], [{PH2(η5-C5H4)}2Fe] [43],
[CpЈTaCl4] [24b], and [Cp*TaCl4] [44] were prepared according to
the literature. Materials and apparatus for electrochemistry and
spectroelectrochemistry have been described elsewhere [45]. The po-
tential values are referred to the Saturated Calomel Electrode
(SCE). Under the present experimental conditions, the one-electron
oxidation of ferrocene occurs at E°Ј ϭ ϩ0.39 V.
[47].
H atoms were refined isotropically. The protons were
calculated on idealised positions. The thermal ellipsoids in Figs. 1
and 3Ϫ7 are shown with 50 % probability. Crystal data and struc-
ture refinement for compounds 1b, 2a, 3a, 4a, and 5a are given in
Table 5. CCDC 660554 1b, CCDC 660556 2a, CCDC 660555 2a·0.5
toluene, CCDC 660557 3a, CCDC 660553 4a, and 660558 5a con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(ϩ44)1223-336-033; or deposit@ccdc.cam.uk).
The atom labelling scheme for the NMR assignments is as follows
(R ϭ PH2, CH2PH2 or CH2P(H)CH2Fc):
X-Ray crystallography
In most cases it was possible to grow crystals suitable for X-ray
crystallography, either by cooling a concentrated solution to
Ϫ30 °C, or by evaporation of solvent under inert gas. Although
crystals of 3b could be grown at low temperature in CH2Cl2, they
disintegrated rapidly on exposure to room temperature or removal
from the solvent, to form a grey or black, microcrystalline, appar-
ently solvent-free modification, so that our attempts to structurally
characterise the complex were unsuccessful. Attempts to grow crys-
tals of 4b were thwarted by its low solubility.
Preparations
[CpЈTaCl4(THF)] (1b). [CpЈTaCl4] was recrystallised from diethyl
ether to which a stoichiometric amount of THF was added (ca.
0.2 g THF for 1 g [CpЈTaCl4]). The crystalline yellow product 1b
was obtained in almost quantitative yield. Mp: dec. 65 °C,
Table 5 Crystal data and structure refinement for 1b and 2Ϫ5.
Complex
1b
2a
2a·0.5 toluene
3a
4a
5a·toluene
Empirical formula
Formula weight
Temperature
C10H15Cl4OTa
473.97
217(2) K
C20H26Cl4FePTa
675.98
208(2) K
C23.5H30Cl4FePTa
772.04
208(2) K
C21H28Cl4FePTa
690.00
208(2) K
C32H46Cl12FeP2Ta2
1335.78
210(2) K
C39H46Cl4Fe2PTa
980.18
208(2) K
Crystal system
Space group
monoclinic
P21/n
monoclinic
P21/c
monoclinic
P21/c
monoclinic
P21/c
monoclinic
C2/c
monoclinic
Cc
Unit cell dimensions
a ϭ 694.66(11) pm
b ϭ 2103.2(3) pm
c ϭ 968.19(16) pm
β ϭ 105.487(3)°
1.3632(4) nm3
4
a ϭ 993.53(10) pm
b ϭ 1257.13(13) pm
c ϭ 1856.44(18) pm
β ϭ 95.019(2)°
2.3098(4) nm3
4
a ϭ 1716.8(3) pm
b ϭ 859.44(15) pm
c ϭ 3528.3(6) pm
β ϭ 91.946(3)°
5.2030(16) nm3
8
a ϭ 1316.7(3) pm
b ϭ 1113.7(2) pm
c ϭ 1696.8(3) pm
β ϭ 104.276(4)°
2.4112(8) nm3
4
a ϭ 1274.10(7) pm
b ϭ 1205.62(7) pm
c ϭ 2896.6(2) pm
β ϭ 98.947(1)°
4.3952(4) nm3
4
a ϭ 2027.53(10) pm
b ϭ 1719.70(10) pm
c ϭ 1221.13(6) pm
β ϭ 115.2380(10)°
3.8513(3) nm3
4
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
2.309 g/cm3
8.823 mmϪ1
896
1.944 g/cm3
5.898 mmϪ1
1312
1.844 g/cm3
5.243 mmϪ1
2824
1.901 g/cm3
5.652 mmϪ1
1344
2.019 g/cm3
6.120 mmϪ1
2576
1.690 g/cm3
3.924 mmϪ1
1952
Crystal size
θ range for data collection
Index ranges
0.20 x 0.12 x 0.10 mm
1.94Ϫ28.86°
Ϫ9ՅhՅ9
Ϫ27ՅkՅ28
Ϫ12ՅlՅ6
0.10 x 0.10 x 0.05 mm
1.96Ϫ28.98°
Ϫ13ՅhՅ13
Ϫ16ՅkՅ17
Ϫ24ՅlՅ9
0.20 x 0.15 x 0.05 mm
1.63Ϫ28.88°
Ϫ139ՅhՅ22
Ϫ9ՅkՅ11
Ϫ45ՅlՅ47
32918
0.20 x 0.10 x 0.05 mm
2.21Ϫ28.97°
Ϫ15ՅhՅ17
Ϫ14ՅkՅ15
Ϫ22ՅlՅ17
15615
0.40 x 0.30 x 0.20 mm
1.42Ϫ26.37
Ϫ14ՅhՅ15
Ϫ14ՅkՅ15
Ϫ34ՅlՅ24
9885
0.20 x 0.10 x 0.04 mm
1.62Ϫ29.00°
Ϫ18ՅhՅ27
Ϫ19ՅkՅ23
Ϫ16ՅlՅ13
12593
Reflections collected
Independent reflections
Completeness to θmax
8838
15043
3275 [R(int) ϭ 0.0826] 5610 [R(int) ϭ 0.0406] 12526 [R(int) ϭ 0.0816] 5824 [R(int) ϭ 0.1060] 3999 [R(int) ϭ 0.0246] 6588 [R(int) ϭ 0.0580]
to θ ϭ 28.86°: 91.6 %
to θ ϭ 28.98°: 91.5 %
0.7569 and 0.5900
5610 / 0 / 273
0.984
to θ ϭ 28.88°: 91.7 %
0.7795 and 0.4203
12526 / 22 / 577
0.965
to θ ϭ 28.97°: 91.2 %
0.7653 and 0.3977
5824 / 74 / 293
0.855
to θ ϭ 26.37°: 89.5 %
0.3741 and 0.1933
3999 / 0 / 270
1.247
to θ ϭ 29.00°: 91.2 %
0.8588 and 0.5075
6588 / 3 / 386
1.001
Max. and min. transmission 0.4724 and 0.2714
Data / restraints / parameters 3275 / 0 / 146
Goodness-of-fit on F2
1.043
Final R indices [I>2σ(I)]
R1 ϭ 0.0384,
wR2 ϭ 0.1004
R1 ϭ 0.0440,
wR2 ϭ 0.1047
Ϫ
R1 ϭ 0.0267,
wR2 ϭ 0.0548
R1 ϭ 0.0376,
wR2 ϭ 0.0574
Ϫ
R1 ϭ 0.0490,
wR2 ϭ 0.1008
R1 ϭ 0.0836,
wR2 ϭ 0.1127
Ϫ
R1 ϭ 0.0600,
wR2 ϭ 0.1217
R1 ϭ 0.1280,
wR2 ϭ 0.1364
Ϫ
R1 ϭ 0.0278,
wR2 ϭ 0.0633
R1 ϭ 0.0305,
wR2 ϭ 0.0702
Ϫ
R1 ϭ 0.0416,
wR2 ϭ 0.0912
R1 ϭ 0.0548,
wR2 ϭ 0.0995
0.545(10)
R indices (all data)
Absolute structure parameter
Largest diff. peak and hole
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
˚
˚
˚
˚
˚
˚
1.864 and Ϫ2.563 e A
1.073 and Ϫ0.867 e A
2.655 and Ϫ2.223 e A
2.002 and Ϫ1.169 e A
0.874 and Ϫ1.527 e A
1.312 and Ϫ1.311 e A
Z. Anorg. Allg. Chem. 2007, 2470Ϫ2480
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2477

R. Kalio, P. Lönnecke, A. Cinquantini, P. Zanello, E. Hey-Hawkins
1H NMR (25 °C, CDCl3): δ 2.08 (br s, 4H, THF), 2.97 (s, 3H, C5H4CH3),
4.73 (vbr s, 4H, THF, OCH2), 6.50 and 6.95 (2 m, C5H4); 1H NMR (Ϫ30 °C,
CDCl3): no change. 13C{1H} NMR (25 °C, CDCl3): δ 17.3 (s, C5H4CH3),
26.5 (s, THF), 71.4 (s, THF, OCH2), 122.8 and 123.9 (2 s, C5H4), 136.6 (s,
ipso-C in C5H4).
PH2CH2C5H4), 69.7 (s, C5H5), 70.6 (s, CC in PH2CH2C5H4), 19.7 (br,
PH2CH2), 133.7 (s, C5(CH3)5); 31P{1H} NMR (25 °C, CDCl3): δ Ϫ1.4
(vbr s, full width at half-maximum 3 ppm); 31P NMR (25 °C, CDCl3): no
signal; 31P{1H} NMR (Ϫ63 °C, CDCl3): δ 1.2 (s, PH2), 0.4 (PHD, 1:1:1
1
triplet, JPD ϭ 55 Hz), ratio 1:0.6; 31P NMR (Ϫ63 °C, CDCl3): δ 1.2 (t,
1
1
1JPH ϭ 359 Hz, PH2), 0.4 (d of 1:1:1 triplet, JPH ϭ 358 Hz (d), JPD
ϭ
56 Hz (1:1:1-t), PHD); 31P NMR (Ϫ62 °C, CHCl3, lock on C6D6): δ 3.5
1
[Cp*TaCl4(PH2Fc)] (2a). PH2Fc (0.12 g, 0.55 mmol) was added to
a stirred solution of [Cp*TaCl4] (0.25 g, 0.55 mmol) in toluene
(10 mL). A brown precipitate formed slowly. After 24 h the solvent
was evaporated in vacuum, and the residue washed with n-pentane
and dried. Yield 0.36 g (97 %), yellow powder. Dark red crystals of
solvent-free 2a and/or 2a·toluene can be obtained from a saturated
toluene solution at Ϫ30 °C (after 1 d) or by slow diffusion of n-
pentane into a toluene solution of 2a. Mp (powder): dec. >194 °C
(thermolysis to FcPH2 and [Cp*TaCl4] as shown by IR spectra of
the residue after thermolysis in vacuum). Anal. calc. for
C20H26Cl4FePTa (675.98): C, 35.54; H, 3.88; Cl, 20.60. Found: C,
35.89; H, 4.02; Cl, 20.60 %.
(t, JPH ϭ 358 Hz, PH2), no signals with P-D coupling are observed);
MS: m/z
ϭ
772.1 [Cp*TaCl2(PH2CH2Fc)·3-NBA]ϩ (9.1 %), 655.0
[Cp*TaCl3(PH2CH2Fc)]ϩ (62.3 %), 520.0 [TaCl3(PH2CH2Fc)]ϩ (31.3 %),
423.0 [Cp*TaCl3]ϩ (8.6 %), 289.1 [TaCl3]ϩ (50.5 %), 232.0 [PH2CH2Fc]ϩ
(17 %), 199.1 [CH2Fc]ϩ (79 %); IR (cmϪ1): 3079 w, 2994 w, 2964 w, 2909 m,
2371 w, 1644 m, 1491 m, 1455 m, 1437 m, 1411 m, 1374 s, 1261 m, 1149 w,
1104 s, 1070 m, 1044 m, 1025 m, 923 m, 867 s, 835 m, 813 m, 749 w, 703 w,
648 w, 599 w, 493 m, 422 w.
[CpЈTaCl4(PH2CH2Fc)] (3b). PH2CH2Fc (0.14 g, 0.60 mmol) was
added to a solution of [CpЈTaCl4(THF)] (0.28 g, 0.59 mmol) in
toluene (50 mL). After 12 h the solvent was evaporated in vacuum,
and the brown residue washed with pentane (10 mL) and dried to
give an orange powder. To obtain crystals, the latter was dissolved
in CH2Cl2 (5 ml), and the solution filtered and cooled to Ϫ30 °C.
After 1 d orange platelets had formed that rapidly decomposed to
a grey powder in air by loss of solvent. Yield: 0.31 g (83 %); mp
(orange powder): 166-167 °C (dec. >176 °C); Anal. calc. for
C17H20Cl4FePTa (633.93): C, 32.21; H, 3.18; Cl, 22.37. Found: C,
32.00; H, 2.27, Cl, 22.65 % [48].
1H NMR (25 °C, CDCl3): δ 2.47 (s, 15H, CH3), 4.23 (s, 5H, C5H5), 4.54 and
4.45 (2 s, each 2 H, PH2C5H4), 6.19 (br d, full width at half-maximum
1
0.05 ppm, JPH ϭ 352 Hz, 2H, PH2); at Ϫ63 °C, CDCl3, the PH2 signal
occurs as a doublet at 6.41 (2H, full width at half-maximum 0.01 ppm,
1JPH ϭ 367 Hz); 13C{1H} NMR (25 °C, CDCl3): δ 13.3 (s, C5(CH3)5), 66.1
(d, 1JPC ϭ 33.4 Hz, PC in PH2C5H4), 70.5 (s, C5H5), 71.8 (d, 3JPC ϭ 7.0 Hz,
2
CA in PH2C5H4), 74.3 (d, JPC ϭ 8.7 Hz, CB in PH2C5H4), 133.3 (s,
C5(CH3)5); 31P NMR (25 °C, C6D6 or CDCl3): no signal observed; 31P{1H}
NMR (25 °C, CDCl3): Ϫ7.3 (vbr s, full width at half-maximum 9 ppm); 31P
1H NMR (25 °C, C6D6): δ 2.40 (s, 3H, CH3C5H4), 3.32 (m, 2H, PH2CH2),
3.74 and 3.83 (2 s, each 2H, PH2CH2C5H4), 3.86 (s, 5H, C5H5), 5.51 (d,
1JPH ϭ 361 Hz, 2H, PH2), 5.79 (m (pseudotriplets), 3JHH/4JHH ϭ 5.2 Hz, 2H,
1
NMR (Ϫ63 °C, CDCl3): Ϫ3.1 (t, JPH ϭ 367 Hz) (see Table 2); MS:
m/z
ϭ
716.1 [Cp*TaCl2(PH2Fc)·3-NBA]ϩ (6.2 %), 420.8 [Cp*TaCl3]ϩ
(62.6 %), 384.9 [Cp*TaCl2]ϩ (38.6 %), 218.1 [PH2Fc]ϩ (79 %); IR (cmϪ1):
3106 w, 2994 w, 2964 w, 2910 m, 2399 w, 2378 w, 1645 w, 1491 m, 1455 w,
1436 m, 1419 w, 1375 s, 1260 w, 1180 m, 1105 m, 1072 w, 1049 m, 1026 m,
1002 w, 896 w, 868 s, 841 m, 819 m, 686 w, 639 w, 596 w, 510 m, 488 m,
450 m, 421 w.
3
CH3C5H4), 6.33 (m (pseudotriplets), JHH/4JHH ϭ 5.2 Hz, 2H, CH3C5H4);
1
13C{1H} NMR (25 °C, C6D6): δ 16.2 (s, CH3C5H4), 20.4 (d, JPC ϭ 17.3 Hz,
PH2CH2), 68.0 and 68.1 (2 s, CA and CB in PH2CH2C5H4), 69.9 (s, C5H5),
2
85.3 (d, JPC ϭ 11.1 Hz, CC in PH2CH2C5H4), 125.2 and 126.2 (2 s,
CH3CCHCH and CH3CCHCH in CH3C5H4), 135.7 (s, CH3CCHCH in
CH3C5H4); 31P{1H} NMR (25 °C, CDCl3): δ 4.2 (br s, full width at half-
1
maximum 0.3 ppm); 31P NMR (25 °C, C6D6): δ 4.1 (br t, JPH ϭ 366 Hz);
[CpЈTaCl4(PH2Fc)] (2b). Crystalline PH2Fc (0.15 g, 0.69 mmol)
was added to a stirred solution of [CpЈTaCl4(THF)] (0.31 g,
0.65 mmol) in toluene (10 mL). The solution changed colour from
orange to brown. After 24 h the solvent was evaporated in vacuum
and the beige residue washed with pentane and dried. Yield: 0.38 g
(94 %); mp: 191-192 °C (dec. >187 °C); Anal. calc. for
C16H18Cl4FePTa (619.90): C, 31.00; H, 2.93. Found: C, 31.13; H,
2.85 %.
31P{1H} NMR (Ϫ63 °C, CDCl3): δ 2.6 (s); 31P NMR (Ϫ63 °C, CDCl3):
1
δ Ϫ2.7 (br t, JPH ϭ 372 Hz); MS: m/z ϭ 716.1 [CpЈTaCl2(PH2CH2Fc)·3-
NBA]ϩ
(6.2 %),
599.1
[CpЈTaCl3(PH2CH2Fc)]ϩ
(6.6 %),
526.9
[CpЈTaCl(PH2CH2Fc)]ϩ (10.0 %), 295.0 [CpЈTaCl]ϩ (49 %), 232.1
[PH2CH2Fc]ϩ (100 %), 199.1 [CH2Fc]ϩ (73 %), 154.1 [3-NBA]ϩ (96 %); IR
(cmϪ1): 3107 m, 3092 m, 2952 w, 2920 w, 2391 w, 1633 w, 1496 m, 1463 m,
1453 m, 1400 m, 1375 m, 1308 s, 1242 s, 1184 s, 1129 s, 1105 s, 1078 m,
1060 m, 1047 w, 1036 m, 1022 m, 1000 s, 984 s, 946 m, 925 m, 884 s, 862 m,
844 m, 825 m, 803 m, 759 w, 599 w, 496 m, 482 m, 429 w, 416 w.
1H NMR (25 °C, CDCl3): δ 2.82 (s, 3H, CH3C5H4), 4.25 (s, 5H, C5H5), 4.43
1
and 4.55 (2 s, each 2H, PH2C5H4), 6.49 (d, JPH ϭ 378 Hz, 2H, PH2), 6.35
3
[{(Cp*TaCl4)PH2(η5-C5H4)}2Fe] (4a).
A solution of (PH2)2fc
(m (pseudotriplets), JHH/4JHH ϭ 2.4 Hz, 2H, CH3C5H4), 6.83 (m (pseudo-
3
triplets), JHH/4JHH
ϭ
2.6 Hz, 2H, CH3C5H4); 13C{1H} NMR (25 °C,
(0.065 g, 0.26 mmol) in toluene (10 mL) was added to a solution
of [Cp*TaCl4] (0.24 g, 0.52 mmol) in toluene (15 mL). An orange
precipitate formed slowly. After 24 h the solid was isolated by fil-
tration, washed twice with n-pentane (2 x 10 mL) and dried for 3 h
in vacuum. Yield: 0.24 g (79 %). The orange product is soluble in
THF and slightly soluble in chlorinated organic solvents. Recrystal-
lisation from CH2Cl2 gave red crystals of 4a·2 CH2Cl2. Mp
(powder): dec. >215 °C; Anal. calc. for C30H42Cl8FeP2Ta2
(1165.98)·toluene: C, 35.32; H, 4.01; Cl, 22.54. Found: C, 35.80;
H, 4.44, Cl, 21.89 %.
1
CDCl3): δ 16.5 (s, CH3C5H4), 65.7 (d, JPC ϭ 36.7 Hz, PϪCC), 70.5 (s, CD),
3
2
72.1 (d, JPC ϭ 7.0 Hz, CA), 74.2 (d, JPC ϭ 7.8 Hz, CB), 125.9 (s, CH3CC4
in CH3C5H4), 125.1 (s, CH3CC4 in CH3C5H4), 136.0 (s, CH3ϪC in
CH3C5H4); 31P NMR (25 °C, C6D6): δ Ϫ0.2 (t, vbr, JPH ϭ 366 Hz); MS:
1
m/z ϭ 734.9 [CpЈTaCl3(PFc)·3-NBA]ϩ (8 %), 584.9 [CpЈTaCl3H(PH2Fc)]ϩ
(5.3 %), 581.0 [CpЈTaCl3(PFc)]ϩ (5.3 %), 369.0 [CpЈTaCl3]ϩ (10.5 %), 218.1
[PH2Fc]ϩ (96.1 %); IR (cmϪ1): 3103 m, 2950 w, 2918 w, 2389 w, 2369 w,
1496 m, 1449 m, 1410 m, 1385 w, 1375 m, 1360 w, 1265 w, 1249 w, 1180 m,
1105 m, 1078 w, 1050 m, 1027 m, 1001 m, 937 w, 895 m, 869 s, 818 m, 636 w,
613 w, 595 w, 485 m, 451 s.
1H NMR (25 °C, CDCl3): δ 2.35 (s, 3H, CH3 in toluene), 2.48 (s, 30H,
C5(CH3)5), 4.47 and 4.57 (2 s, each 4H, PH2C5H4), ca. 6.0 (vbr d, full width
at half-maximum 0.1 ppm, 1JPH ഠ 340 Hz, PH2), 7.18 (m, 5H, C6H5 in tolu-
[Cp*TaCl4(PH2CH2Fc)] (3a). PH2CH2Fc (0.10 g, 0.43 mmol) was
added to a solution of [Cp*TaCl4] (0.19 g, 0.42 mmol) in toluene
(10 mL). After 3 h the solution was concentrated in vacuum to
2 mL. At Ϫ30 °C large prismatic dark red crystals were obtained
after 24 h. Yield: 0.20 g (69 %); mp: dec. >169 °C (thermolysis to
PH2CH2Fc and [Cp*TaCl4]); Anal. calc. for C21H28Cl4FePTa
(690.00): C, 36.55; H, 4.09. Found: C, 36.61; H, 4.41 %.
1
ene); 1H NMR (Ϫ60 °C, CDCl3): signal at δ 6.33 (d, JPH ϭ 367 Hz, 4 H,
PH2); 13C{1H} NMR (25 °C, CDCl3): δ 13.4 (s, C5(CH3)5), 22.2 (s, CH3 in
3
2
toluene), 73.8 (d, JPC ϭ 6.2 Hz, CA in PH2C5H4), 76.0 (d, JPC ϭ 7.8 Hz,
CB in PH2C5H4), 133.4 (s, C5(CH3)5), 126.0, 128.9, 129.7 and 138.6 (4 s, CH
in toluene), CC in PH2C5H4 not observed; 31P{1H} NMR (25 °C, CDCl3):
no signal; 31P NMR (Ϫ60 °C, CDCl3): δ Ϫ7.6 (t, 1JPH ϭ 367 Hz). MS (FAB,
700 < m/z < 1300): m/z ϭ 1057.6 [MϪ3Cl]ϩ (4 %), 923.7 [MϪCp*Ϫ3Cl)]ϩ
(14 %), 823.6 [MϪ2Cp*Ϫ2Cl)]ϩ (19 %), 757.8 [MϪ2Cp*Ϫ4Cl)]ϩ (13 %); IR
(cmϪ1): 3090 w, 2994 w, 2962 w, 2911 m, 2365 w, 1602 w, 1492 m, 1454 w,
1436 m, 1418 w, 1375 m, 1261 w, 1181 m, 1171 w, 1073 w, 1053 m, 1028 m,
1H NMR (25 °C, CDCl3): δ 2.46 (s, 15H, CH3), 3.20 (br s, 2H, PCH2Fc),
4.14 and 4.19 (2 br s, 9H, Fe(η5-C5H5)(η5-C5H4)), 5.21 (br d, full width at
1
half-maximum 0.01 ppm, JPH ϭ 367 Hz, 2H, PH2); 13C{1H} NMR (25 °C,
CDCl3):
δ
13.4 (s, C5(CH3)5), 68.7 and 69.0 (2 s, CA and CB in
2478
www.zaac.wiley-vch.de
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2007, 2470Ϫ2480

Cyclopentadienyl Tantalum(V) Complexes
889 m, 865 s, 830 m, 809 w, 740 m, 697 m, 598 w, 487 m, 468 w, 451 w, 427 m.
in toluene (20 mL). After 24 h the solution was filtered through
Celite, and the solvent was evaporated in vacuum. The remaining
ochre powder was washed with pentane (10 mL) and dried. The
residue was dissolved in CH2Cl2 (5 ml), and the solution filtered
and kept at r.t. After 1 month intergrown needles had formed.
Yield: 0.24 g (85 %); mp: dec. >174 °C; Anal. calc. for
C28H30Cl4Fe2P2Ta [831.94]: C, 40.42; H, 3.64; Cl, 17.05. Found: C,
41.20; H, 2.33, Cl, 16.06 % [48].
[{(CpЈTaCl4)PH2(η5-C5H4)}2Fe] (4b).
A solution of (PH2)2fc
(0.065 g, 0.26 mmol) in toluene (10 mL) was added to a solution of
[CpЈTaCl4(THF)] (0.25 g, 0.52 mmol) in toluene (40 mL). A colour
change from orange to brown occurred and a dark brown precipi-
tate formed. After 24 h the solid was isolated by filtration, washed
with toluene (2 ϫ 10 mL) and n-pentane (2 ϫ 10 mL). The solid
was dried for 3 h in vacuum. The product is slightly soluble in THF
and Et2O, but insoluble in most other organic solvents. The solid
was extracted with hot Et2O to yield the product as a yellow pow-
der. Yield: 0.26 g (95 %); mp: ca. 270 °C (dec. >177 °C); Anal. calc.
for C22H26Cl8FeP2Ta2 (1053.77)·0.85 toluene: C, 29.65; H, 2.92;
Cl, 25.05. Found: C, 29.70; H, 2.65; Cl, 24.75 %.
1H NMR (25 °C, CDCl3): δ 2.85 (s, 3H, C5H4CH3), 3.11 and 3.58 (2 m, each
2H, PCH2Fc), 4.07 (s, 10H, C5H5), 4.05 and 4.14 (2 s, each 4H, C5H4), 4.99
1
3
(d of quint, 1H, JPH ϭ 378 Hz, JHH ϭ 3.5 Hz, PH), 6.35 (m (pseudotrip-
lets), JHH/4JHH ϭ 5.2 Hz, 2H) and 6.83 (m (pseudotriplets), JHH/4JHH
ϭ
3
3
5.2 Hz, 2H) (both CH3C5H4); 13C{1H} NMR (25 °C, CDCl3): δ 16.5 (s,
CH3C5H4), 23.7 (br s, PH2CH2), 68.4 and 68.7 (2 s, CA and CB in
PH2CH2C5H4), 69.6 (s, C5H5), 70.1 (s, CC in PH2CH2C5H4), 125.1 and 125.8
(2 s, CH3CCHCH and CH3CCHCH in CH3C5H4), 128.9 (s, CH3CCHCH
in CH3C5H4); 31P{1H} NMR: see Table 2; MS (FAB, 400 < m/z < 1000):
1H NMR (25 °C, CDCl3): δ 2.30 (s, CH3 in toluene), 2.83 (s, 6H, CH3C5H4),
4.38 (s, 8H, Fe(C5H4)2), 6.43 and 6.86 (2 s, each 4H, CH3C5H4), 7.20-7.07
(2 m, C6H5 in toluene), PH2 not observed. 1H NMR (Ϫ50 °C, CDCl3): δ
2.30 (s, CH3 in toluene), 2.72 (s, 6H, CH3C5H4), 4.65-4.14 (m, 8H,
m/z
ϭ
946.7
[CpЈTaCl3{P(CH2Fc)2}·3-NBA]ϩ
(6.7 %),
832.8
[CpЈTaCl4{PH(CH2Fc)2}]ϩ or [TaCl2{P(CH2Fc)2}·3-NBA]ϩ (1.2 %), 796.8
[CpЈTaCl3{PH(CH2Fc)2}]ϩ (8.6 %), 752.7 [TaCl4{PH(CH2Fc)2}]ϩ (2.1 %),
716.0 [TaCl3{PH(CH2Fc)2}]ϩ (2.6 %); IR (cmϪ1): 3107 m, 3092 m, 2961 w,
2920 m, 2910 m, 2391 w, 1634 br w, 1496 m, 1463 m, 1453 m, 1400 m,
1375 m, 1261 m, 1247 m, 1234 m, 1213 w, 1105 s, 1078 m, 1047 m, 1038 m,
1023 s, 1002 m, 939 m, 925 m, 854 s, 862 m, 845 m, 825 s, 803 s, 760 w, 730 w,
694 w, 598 w, 497 s, 482 s, 428 w, 417 w, 404 w.
1
PH2C5H4), 6.54 (d, JPH ϭ 375 Hz) and 6.57 (d, 1JPH ϭ 376 Hz) (PH2, total
4H, ratio 1:2, different rotamers), 6.50 and 6.93 (2 s, each 4H, CH3C5H4),
7.21-7.11 (2 m, C6H5 in toluene); 13C{1H} NMR (25 °C, THF-d8): δ 21.4 (s,
CH3C5H4), 73.2 (PH2C5H4), 125.9, 128.8, 125.9, 125.1 (4 s, CH3CCHCH
and CH3CCHCH in CH3C5H4)), 138.3 (s, CH3CCHCH in CH3C5H4), the
intensity of the signals is rather low due to the low solubility, and some
signals of 4b (fc group) are obscured by the solvent (ca. 67 ppm); 31P{1H}
NMR (25 °C, THF/CDCl3): δ no signal; 31P{1H} NMR (Ϫ62 °C, THF/
CDCl3): δ Ϫ3.3 (s, 100 %), rotamers at Ϫ1.9 (s, 93 %), Ϫ1.0 (s, 23 %) and
Ϫ0.3 (s, 9 %); 31P{1H} NMR (Ϫ60.5 °C, THF-d8): δ Ϫ8.4 (s, 100 %), rota-
mers at Ϫ7.0 (s, 50 %), and Ϫ5.4 (s, 8 %); 31P NMR (Ϫ60.5 °C, THF/
Acknowledgment. We gratefully acknowledge financial support by
the Deutsche Forschungsgemeinschaft and a generous supply of
tetrakis(hydroxymethyl)phosphonium chloride by Cytec. P.Z.
acknowledges the financial support of the University of Siena
(PAR progetti, 2005).
1
1
CDCl3): δ Ϫ3.3 (t, JPH ϭ 375 Hz), rotamer at Ϫ1.9 (t, JPH ϭ 373 Hz);
31P{1H} NMR (Ϫ60.5 °C, THF-d8): δ Ϫ8.4 (t, JPH ϭ 376 Hz), rotamer at
1
Ϫ7.0 (t, JPH ϭ 374 Hz); the 31P NMR spectra show the signals of (PH2)2fc
1
as impurity. MS (FAB, 500 < m/z < 1500): m/z ϭ 946.5 [MϪ3Cl]ϩ (12.8 %),
867.8 [MϪCpЈϪ3Cl)]ϩ (5.4 %), 787.8 [MϪ2CpЈϪ3Cl)]ϩ (9.3 %), 752.6
[MϪ2CpЈϪ4Cl)]ϩ (3.0 %), 714.9 [MϪ2CpЈϪ5Cl)]ϩ (49.4 %); IR (cmϪ1):
3117 m, 3090 m, 3019 w, 2959 w, 2914 w, 2387 w, 2364 w, 1602 w, 1495 m,
1450 m, 1419 w, 1401 w, 1386 m, 1375 m, 1248 w, 1183 m, 1174 m, 1078 m,
1048 m, 1030 m, 936 w, 891 m, 864 s, 836 m, 737 m, 697 m, 636 w, 610 w,
594 w, 490 m, 459 m, 424 m.
References
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[Cp*TaCl4{PH(CH2Fc)2}] (5a). PH(CH2Fc)2 (0.15 g, 0.35 mmol)
was added to a solution of [Cp*TaCl4] (0.16 g, 0.35 mmol) in tolu-
ene (20 mL). After 24 h the solution was filtered through Celite,
and the solvent was evaporated in vacuum. A brown oily residue
was obtained, which was stirred in n-pentane until it solidified. The
ochre powder was washed with n-pentane (10 mL) and dried. Yield:
0.28 g (90 %). Recrystallisation from toluene gave dark red crystals
of 5a·toluene. Mp (crystals): dec. 117-119 °C; Anal. calc. for
C32H38Cl4Fe2PTa [888.09]·toluene: C, 47.79; H, 4.73; Cl, 14.47.
Found: C, 46.90; H, 3.09, Cl, 13.93 % [48].
1H NMR (25 °C, CDCl3): δ 2.50 (s, 15H, C5(CH3)5), 3.05 and 3.56 (2 br m,
each 2H, PCH2Fc), 4.07 (s, 10H, C5H5), 3.88 (s, 2H, C5H4), 4.14 (s, 2H,
1
C5H4), 4.03 (s, 4H, C5H4), 4.86 (br d, JPH ϭ 373 Hz, 1H, PH); 13C{1H}
1
NMR (25 °C, CDCl3): δ 13.4 (s, C5(CH3)5), 23.7 (d, JPC ϭ 15.0 Hz,
PH2CH2), 68.2 and 68.5 (2 s, CA and CB in PH2CH2C5H4), 69.5 (s, C5H5),
70.2 (2 s, ∆δ ϭ 0.058, CA and CB in PH2CH2C5H4), 85.6 (d, 2JPC ϭ 8 Hz, CC
in PH2CH2C5H4), 133.1 (s, C5(CH3)5); 13C{31P,1H} NMR (25 °C, CDCl3):
δ 13.4 (s, C5(CH3)5), 23.7 (s, PH2CH2), 68.2 and 68.5 (2 s, CA and CB in
PH2CH2C5H4), 69.5 (s, C5H5), 70.2 (2 s, ∆δ
ϭ 0.058, PCCC4 in
PH2CH2C5H4), 85.6 (s, CC in PH2CH2C5H4), 133.1 (s, C5(CH3)5); 31P{1H}
NMR: see Table 3; MS (FAB, 200
<
m/z
<
1000): m/z
ϭ
642.6
or
[TaCl{PH(CH2Fc)2}]ϩ
(2.8 %), 611.1
[Cp*TaCl4 ·3-NBA]ϩ
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2913 m, 2386 w, 1633 br w, 1494 m, 1460 m, 1437 m, 1403 m, 1372 s, 1261 m,
1235 m, 1201 w, 1178 w, 1104 s, 1040 m, 1023 m, 1000 m, 922 m, 872 m,
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Z. Anorg. Allg. Chem. 2007, 2470Ϫ2480
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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