Reactivity of a phosphido-niobocene derivative toward CS2 and alkyl halides to give phosphinodithioformato- and phosphino-niobocene complexes: X-ray crystal structures of [Nb(η5-C5H 4SiMe3)2(κ1-S-SC(S)(PPh 2))(CO)]

Article abstract of DOI:10.1021/om051013u

The reaction of the niobocene complex [Nb(η⁵-C ₅H₄SiMe₃)₂(PHPh₂)(CO)]Cl (1) with NaOH yielded the corresponding phosphidoniobocene derivative [Nb(η⁵-C₅H₄SiMe₃) ₂(PPh₂)(CO)] (2) by deprotonation of the P-H bond. The subsequent insertion reaction of carbon disulfide into the Nb-P bond yielded the first examples of a diphenylphosphinodithioformato ligand coordinated to the niobocene system by giving [Nb(η⁵-C₅H ₄SiMe₃)₂(κ¹-S-SC(S)(PPh ₂))(CO)] (3) and [Nb(η⁵-C₅H ₄SiMe₃)₂(κ²-S,S-SC(S)(PPh ₂))] (4); the latter compound can also be prepared by the corresponding CO elimination of 3. The cationic d² species [Nb(η⁵-C₅H₄SiMe₃) ₂(PRPh₂)(CO)]X (R = Me, X = I (5); CH₂Ph, X = Br (6); CH₂CH₂Ph, X = Br (7)) were prepared by the reaction of alkyl halides RX (R = Me, X = I; CH₂Ph, X = Br; CH ₂CH₂Ph, X = Br) with 2 by electrophilic attack on the phosphorus atom present in the phosphido terminal ligand. In the same way, the reaction of 2 with ICH₂CH₂I yielded the complex [Nb(η⁵-C₅H₄SiMe₃) ₂(P(I)Ph₂)(CO)]-I₃ (8). The molecular structures of 3 and 8 were determined by single-crystal X-ray diffraction studies.

Full text of DOI:10.1021/om051013u

1310
Organometallics 2006, 25, 1310-1316
Reactivity of a Phosphido-Niobocene Derivative toward CS2 and
Alkyl Halides to Give Phosphinodithioformato- and
Phosphino-Niobocene Complexes: X-ray Crystal Structures of
[Nb(η5-C5H4SiMe3)2(K1-S-SC(S)(PPh2))(CO)] and
[Nb(η5-C5H4SiMe3)2(P(I)Ph2)(CO)]I3
Antonio Antin˜olo,* Santiago Garc´ıa-Yuste, Antonio Otero,* Juan C. Pe´rez-Flores,
Rebeca Reguillo-Carmona, Ana M. Rodr´ıguez, and Elena Villasen˜or
Departamento de Qu´ımica Inorga´nica, Orga´nica y Bioqu´ımica, Facultad de Quimica, UniVersidad de
Castilla-La Mancha, 13071 Ciudad Real, Spain
ReceiVed NoVember 24, 2005
The reaction of the niobocene complex [Nb(η5-C5H4SiMe3)2(PHPh2)(CO)]Cl (1) with NaOH yielded
the corresponding phosphidoniobocene derivative [Nb(η5-C5H4SiMe3)2(PPh2)(CO)] (2) by deprotonation
of the P-H bond. The subsequent insertion reaction of carbon disulfide into the Nb-P bond yielded the
first examples of a diphenylphosphinodithioformato ligand coordinated to the niobocene system by giving
[Nb(η5-C5H4SiMe3)2(κ1-S-SC(S)(PPh2))(CO)] (3) and [Nb(η5-C5H4SiMe3)2(κ2-S,S-SC(S)(PPh2))] (4); the
latter compound can also be prepared by the corresponding CO elimination of 3. The cationic d2 species
[Nb(η5-C5H4SiMe3)2(PRPh2)(CO)]X (R ) Me, X ) I (5); CH2Ph, X ) Br (6); CH2CH2Ph, X ) Br (7))
were prepared by the reaction of alkyl halides RX (R ) Me, X ) I; CH2Ph, X ) Br; CH2CH2Ph, X )
Br) with 2 by electrophilic attack on the phosphorus atom present in the phosphido terminal ligand. In
the same way, the reaction of 2 with ICH2CH2I yielded the complex [Nb(η5-C5H4SiMe3)2(P(I)Ph2)(CO)]-
I3 (8). The molecular structures of 3 and 8 were determined by single-crystal X-ray diffraction studies.
reaction of ClPPh2 into the Nb-H bond of [Nb(η5-C5H4SiMe3)2-
Introduction
(H)L)]. Treatment of derivative 1 with aqueous NaOH yielded
Dithiocarbamato ligands, R2NCS2-, have attracted consider-
able attention in coordination chemistry,1 mainly due to their
ability to form stable chelate complexes. However, very little
effort has been directed toward investigating the analogous
dialkylphosphinodithioformato ligands, R2PCS2-. Indeed, only
a few well-characterized R2PCS2--containing complexes of
early-middle transition metals such as Zr,2 Mo,3 and W4,5 have
been reported to date, and in these complexes, the ligand
coordinates to metal centers through the two S atoms2 (a), the
P and S atoms by chelation5a (b), and either simple S- or
P-coordination5b (c and d) (see Figure 1).
the corresponding neutral phosphidoniobocene complex [Nb-
(η5-C5H4SiMe3)2(PPh2)(CO)] (2) by deprotonation of the P-H
bond.7 This complex represents an interesting starting material
to extend the phosphorus-containing niobocene chemistry. The
phosphorus atom from the phosphido terminal ligand has a lone
electron pair that is expected to give rise to interesting chemistry
that can be explored. We focused our attention on the synthesis
of new phosphorus-containing niobocene complexes from 2 by
exploring the possibilities for both the insertion reaction into
the Nb-P bond, using carbon disulfide as the reagent, and the
electrophilic attack on the P atom of the phosphido terminal
ligand in alkylation processes with several RX reagents. The
first type of reactivity has allowed the preparation of the new
niobocene containing the anionic diphenylphosphinodithiofor-
mato ligand, Ph2PCS2-, namely, [Nb(η5-C5H4SiMe3)2(κ1-S-SC-
(S)(PPh2))(CO)] (3) and [Nb(η5-C5H4SiMe3)2(κ2-S-SC(S)-
(PPh2))] (4), and the second one, the isolation of a new family
of cationic d2 18-electron complexes [Nb(η5-C5H4SiMe3)2-
(PRPh2)(CO)]X (R ) Me, X ) I (5); CH2Ph, X ) Br (6); CH2-
CH2Ph, X ) Br (7)). Finally, the reaction of 2 in the presence
of ICH2CH2I gave [Nb(η5-C5H4SiMe3)2(P(I)Ph2)(CO)]I3 (8).
A few years ago, we reported the synthesis of a new family
of complexes including [Nb(η5-C5H4SiMe3)2(PHPh2)L]Cl (1),
where L ) CO, CNR,6 and these were prepared by an insertion
* To whom correspondence should be addressed. E-mail:
antonio.antinolo@uclm.es; antonio.otero@uclm.es. Fax: +34926295318.
(1) (a) Coucouvanis, D. Progr. Inorg. Chem. 1979, 26, 301. (b)
Coucouvanis, D. Progr. Inorg. Chem. 1970, 11, 233. (c) Cras, J. A.;
Willemse, J. In ComprehensiVe Coordination Chemistry; Wilkinson, G.,
Gillard, R. D., McCleverty, J. A., Eds.; Pergamon Press: Oxford, 1987;
Vol. 2, p 579. (d) Stucher, D.; Patterson, D.; Mayne, C. L.; Orendt, A. M.;
Grant, D. M.; Parry, R. W. Inorg. Chem. 2001, 40, 1902, and references
therein.
(2) Hey-Hawkins, E.; Lappert, M. F.; Atwood, J. L.; Boot, S. G. J. Chem.
Soc., Chem. Commun. 1987, 421.
(3) Davies, J. E.; Feeder, N.; Mays, M. J.; Tompkin, P. K.; Woods, A.
D. Organometallics 2000, 19, 984.
(6) Antin˜olo, A.; Carrillo-Hermosilla, F.; Fernandez-Baeza, J.; Garc´ıa-
Yuste, S.; Otero, A.; Sa´nchez-Prada, J.; Villasen˜or, E. Eur. J. Inorg. Chem.
2000, 1437.
(4) Sanchez-Pelaez, A. E.; Perpin˜an, M. F.; Gutierrez-Puebla, E.; Monge,
A.; Ruiz-Valero, C. J. Organomet. Chem. 1990, 384, 79.
(5) (a) Yih, K.-H.; Lin, Y.-C.; Cheng, M.-C.; Wang, Y. J. Chem. Soc.,
Dalton Trans. 1995, 1305. (b) Yih, K.-H.; Lin, Y.-C.; Cheng, M.-C.; Wang,
J. Chem. Soc., Chem. Commun. 1993, 1380.
(7) (a) Bonnet, G.; Lavastre, O. J. C.; Moise, C. New J. Chem. 1988,
12, 551. (b) Oudet, P.; Kubicki, M. M.; Moise, C. Organometallics 1994,
13, 4278. (c) Oudet. P.; Perrey, D.; Bonnet, G.; Moise, C.; Kubicki, M. M.
Inorg. Chim. Acta 1995, 273, 79. (d) Challet, S.; Leblanc, J. C.; Moise, C.
New J. Chem. 1993, 17, 251.
10.1021/om051013u CCC: $33.50 © 2006 American Chemical Society
Publication on Web 02/02/2006

ReactiVity of a Phosphido-Niobocene DeriVatiVe
Organometallics, Vol. 25, No. 5, 2006 1311
Figure 1. Coordination modes of the Ph2P(S)CS- ligand.
Scheme 1
prepared by stirring a mixture of 2 with carbon disulfide for 4
h. This reaction, after the appropriate workup procedure, gave
complex 3 as a red solid. However, when the reaction was
carried out in thf over a longer period of time, the solution
became dark green and the complex [Nb(η5-C5H4SiMe3)2(κ2-
S,S-SC(S)(PPh2))] (4) was isolated after the appropriate workup
(see Scheme 1).
Results and Discussion
Synthesis and Characterization of Diphenylphosphino-
dithioformato-Containing Complexes. We previously reported
the synthesis of the complex [Nb(η5-C5H4SiMe3)2(PHPh2)(CO)]-
Cl (1), which was prepared by an insertion reaction of ClPPh2
into the Nb-H bond of [Nb(η5-C5H4SiMe3)2(H)(CO)].6 In the
study described here it was envisaged that [Nb(η5-C5H4SiMe3)2-
(PPh2)(CO)] (2) would be obtained by deprotonation7 of the
P-H bond of 1. In fact, the preparation of the phosphidonio-
biocene complex 2 was achieved by deprotonation of the PHPh2
ligand present in the complex [Nb(η5-C5H4SiMe3)2(PHPh2)-
(CO)]Cl (1) with aqueous NaOH (eq 1).
In accordance with the different coordination modes for the
phosphinodithioformato ligand depicted in Figure 1, situations
c and a are proposed for complexes 3 and 4, respectively
(Scheme 1).
The new derivatives 3 and 4 were isolated as air-sensitive
solids and were characterized by IR and NMR spectroscopy.
Furthermore, the molecular structure of complex 3 was deter-
mined by X-ray diffraction. The IR spectra of 3 and 4 each
display a characteristic band at ca. 1000 cm-1, which is due to
ν(CdS). However, only the IR spectrum of 3 contains the band
due to the ν(CO), and this is seen at 1927 cm-1. The 1H NMR
spectra contain four multiplets for 3 and two multiplets for 4,
and these correspond to the cyclopentadienyl ligands; these
signals are consistent with an asymmetrical and symmetrical
environment for the niobium center8 in these complexes,
respectively (see Scheme 1). Further evidence for this situation
is provided by the 13C{1H} NMR spectra of the complexes,
which contain five and three resonances corresponding to the
cyclopentadienyl ligands. In addition, a very low field resonance
is present in each 13C{1H} NMR spectrum, and this appears as
a doublet centered at δ 264.0 (1JCP ) 47.62 Hz) and 244.0 ppm
(1JCP ) 20.00 Hz), respectively, for 3 and 4. These signals
correspond to the carbon atom of the diphenylphosphinodithio-
formato ligand. Furthermore, the 13C{1H} NMR spectrum of 3
shows a signal at δ 254.6 ppm that is typical of a CO ligand.
Finally, the 31P NMR spectra each contain a broad signal, at δ
46.9 ppm as a multiplet for 3 and at δ 2.03 ppm as a quintuplet
(3JPH ) 7.30 Hz due to phosphorus coupling with the ortho
hydrogen atoms of the phenyl group) for 4. The crystal structure
of 3 was determined on crystals obtained by crystallization from
hexane and confirms the structural arrangement described above.
Complex 2 was isolated as a yellow-brown oil that was air-
sensitive and insoluble in most organic solvents. Complex 2
was characterized by IR and 1H, 13C{1H}, and 31P NMR
spectroscopy. The IR spectrum of 2 shows one band at 1918
cm-1, and this corresponds to ν(CtO) of the carbonyl ligand.
A band corresponding to ν(P-H) of the P-H bond was not
observed in the IR spectrum, which is consistent with the
conversion of the coordinated diphenylphosphine ligand to a
new phosphido ligand. Further evidence for this transformation
was provided by the 1H NMR spectrum, which did not contain
the doublet corresponding to the P-H bond at ca. 7 ppm that
is present in the parent complex 1.6 Evidence for the presence
of a new phosphido ligand was provided by the 31P NMR
spectrum, which contains a singlet at δ -10.8 ppm due to the
PPh2 ligand.7 This latter signal is at higher field than that in the
corresponding PHPh2 ligand in complex 1, which shows the
greater electron density on the P atom in the neutral phosphido
ligand. At low field the 13C{1H} NMR spectrum exhibits one
signal at δ 260.0 ppm for the carbonyl ligand. The spectroscopic
data are in agreement with an 18-electron d2 niobocene species
in which the phosphido terminal ligand is coordinated as a
monoanionic donor ligand. Thus, the phosphorus atom of the
phosphido ligand retains one electron pair, and this makes it
susceptible to further electrophilic attack. The niobium atom
must adopt a pseudo-tetrahedral structure with both cyclopen-
tadienyl rings bonded in a η5-coordination mode to give the
typical bent metallocene conformation.
X-ray Diffraction Study of [Nb(η5-C5H4SiMe3)2(K1-S-SC-
(S)(PPh2))(CO)] (3). The ORTEP diagram obtained by X-ray
diffraction of 3 is shown in Figure 2. To the best of our
knowledge, the molecular structure of complex 3 represents the
first example of an early transition metal where a diphenylphos-
The new diphenylphosphinodithioformato-containing niob-
(8) Antinolo, A.; Carrillo-Hermosilla, F.; Fajardo, M.; Garc´ıa-Yuste, S.;
Otero, A. J. Organomet. Chem. 1994, 482, 93.
ocene [Nb(η5-C5H4SiMe3)2(κ1-S-SC(S)(PPh2))(CO)] (3) was

1312 Organometallics, Vol. 25, No. 5, 2006
Antin˜olo et al.
It is worth noting the relative disposition of the Cp′ ligands
(Cp′ ) C5H4SiMe3) with respect to one another. These ligands
are eclipsed with the two SiMe3 groups in cis positions and
coordinated to the Nb atom in the conventional η5-fashion. The
metal atom, the S, and the carbonyl ligand are practically
coplanar and bisect the dihedral angle formed by the two Cp′
ligands. The angle between the CO ligand and the sulfur atom,
C(1)-Nb(1)-S(1), is 88.6(5)°.
The angle O(1)-C(1)-Nb(1) (173(1)°) is practically linear.
The C(1)-O(1) distance is shorter than that of a free CO, and
this indicates substantial back-donation from the metal to the
coordinated CO ligand. The PCS2 unit is planar. The P atom is
pyramidal (the sum of bond angles at the phosphorus atom is
307°). The noncoordinated S(2) atom is in an exo disposition
with respect to the aforementioned angle C(1)-Nb(1)-S(1).
The angles S(2)-C(2)-P(1) (114.1(8)°) and S(1)-C(2)-P(1)
(117.7(8)°) show that the phosphorus atom is closer to the S
exo atom. This is probably due to steric hindrance between the
SiMe3 groups situated in this area and the lone pair on the
phosphorus atom.
Mechanistic Proposal for Ph2P(S)CS- Ligand Formation.
The mechanistic proposal for Ph2P(S)CS- ligand formation in
complex 3 is represented in Scheme 2.
Figure 2. Molecular structure of 3 with 30% probability ellipsoids.
The formation of the Ph2P(S)CS- ligand in an insertion
reaction can be understood by the interaction between the Nb-
PPh2 moiety and the heterocumulene species CS2 (see Scheme
2). Two intermediate species are possible, and both of these
evolve to complex 3. The first possibility (a) involves initial
nucleophilic attack of the coordinated phosphido ligand, through
the lone electron pair on the phosphorus atom, onto the electron-
deficient carbon atom (electrophilic center) of the CS2 to give
a zwitterionic intermediate.5a This intermediate evolves to 3 by
attack of the noncoordinated sulfur atom on the niobium metal
center with the simultaneous cleavage of the Nb-P bond. The
second possibility (b) is consistent with a four-centered con-
certed transition state8 obtained by an intermolecular insertion
process involving the Nb-P bond and one of the CdS bonds.
The formation of complex 4 can be envisaged as being the
result of attack of the noncoordinated S atom of the k1-S-
diphenylphosphinodithioformato ligand on the Nb atom and
concurrent CO ligand elimination. The substitution of the CO
ligand in this class of niobocene, i.e., [Nb(η5-C5H4SiMe3)2(κ1-
S-SC(S)H)(CO)],8 is not a common reaction, but with a ligand
Hydrogen atoms have been omitted.
Table 1. Selected Bond Lengths [Å] and Angles [deg] for 3
and 8
[Nb(η5-C5H4SiMe3)2
[Nb(η5-C5H4SiMe3)2
(P(I)Ph2)(CO)]I3 (8)
(κ1-S-SC(S)(PPh2))(CO)] (3)
Nb(1)-C(1)
1.97(1)
2.542(5)
1.81(1)
1.81(1)
1.84(2)
1.69(1)
1.67(1)
1.19(1)
88.6(5)
121.1(4)
104.9(7)
101.9(6)
102.3(7)
112.6(5)
173(1)
Nb(1)-C(1)
2.069(6)
2.565(2)
2.472(1)
2.921(2)
2.924(1)
1.823(6)
1.817(6)
1.131(7)
87.3(2)
177.39(3)
101.6(2)
99.9(2)
118.6(2)
115.5(2)
114.55(6)
178.2(5)
Nb(1)-S(1)
Nb(1)-P(1)
P(1)-C(2)
I(1)-P(1)
P(1)-C(19)
I(2)-I(3)
P(1)-C(25)
I(3)-I(4)
S(1)-C(2)
P(1)-C(31)
S(2)-C(2)
P(1)-C(41)
O(1)-C(1)
O(1)-C(1)
C(1)-Nb(1)-S(1)
C(4)-Nb(1)-S(1)
C(19)-P(1)-C(2)
C(19)-P(1)-C(25)
C(2)-P(1)-C(25)
C(2)-S(1)-Nb(1)
O(1)-C(1)-Nb(1)
S(2)-C(2)-S(1)
S(2)-C(2)-P(1)
S(1)-C(2)-P(1)
C(1)-Nb(1)-P(1)
I(2)-I(3)-I(4)
C(41)-P(1)-I(1)
C(31)-P(1)-I(1)
C(41)-P(1)-Nb(1)
C(31)-P(1)-Nb(1)
I(1)-P(1)-Nb(1)
O(1)-C(1)-Nb(1)
128.2(9)
114.1(8)
117.7(8)
7
other than carbonyl (e.g., P(OR)38 or PHPh2 ) the reaction can
take place easily. In this particular case the high stability of
derivative 4 probably provides the driving force for the
formation of [Nb(κ2-S,S-SC(S)PPh2)].
Synthesis and Characterization of Cationic d2 Phosphino-
Containing Complexes. In the second part of this article we
describe the reactivity of complex 2 toward alkylation processes
with several RX reagents as electrophilic species. The reaction
of 2 with excess alkyl halide species such as methyl iodide
(MeI), benzyl bromide (BzBr), and 1-bromo-2-ethylbenzene
(PhCH2CH2Br) gives d2 18 e- cationic phosphinoniobocene
phinodithioformato ligand has a κ1-S coordination mode.
Selected bond distances and bond angles are listed in Table 1.
Complex 3 crystallizes in the monoclinic space group P21/c
with 4 molecules in the asymmetric unit cell. The local
coordination geometry around the Nb atom can be described
as pseudo-tetrahedral with two cyclopentadienyl rings bonded
to the metal in a η5 mode and sulfur and carbon atoms of the
dithioformato and carbonyl ligands, respectively, comprising the
immediate coordination sphere. The distances between the metal
atom and the centroids of the Cp rings are 2.042(5) and 2.039-
(5) Å, and the value of the angle Cent(1)-Nb(1)-Cent(2) is
140° (Cent(1) is the centroid of C(3)-C(7) and Cent(2) is the
centroid of C(11)-C(15)). These values are typical of bent
niobocene derivatives. The Nb(1)-S(1) bond distance is 2.542-
(5) Å, and this is very similar to those found in other niobocene
systems.9
(9) (a) Fu, P.-F.; Khan, M. A.; Nicholas, K. M. Organometallics 1993,
12, 3790. (b) Bach, H. J.; Brunner, H.; Wachter, J.; Kubicki, M. M.; Leblanc,
J. C.; Moise, C.; Volpato, F.; Nuber, B.; Zieglert, M. L. Organometallics
1992, 11, 1403. (c) Darensbourg, M. Y.; Silva, R.; Reibenspies, J.; Proutt,
C. K. Organometallics 1989, 8, 1315. (d) Darensbourg, M. Y.; Bischoff,
C. J.; Houliston, S. A.; Pala, M.; Reibenspies, J. J. Am. Chem. Soc. 1990,
112, 6905.
(10) (a) Lopez, E. M.; Miguel, D.; Perez, J.; Riera, V.; Bois, C.; Jeannin,
Y. Organometallics 1999, 18, 490. (b) Carmona, E.; Galindo, A.; Guille-
Photin, C.; Lai, R.; Monge, A.; Ruiz, C.; Sanchez, L. Inorg. Chem. 1988,
27, 488. (c) Carmona, E.; Gutierrez-Puebla, E.; Monge, A.; Perez, P. J.;
Sanchez, L. Inorg. Chem. 1989, 28, 2120.
Molecular structures of complexes containing the [M-(SC-
(S)PPh3)]+ moiety are well documented,10 although molecular
structures of related phosphinodithioformato-containing [M-(SC-
(S)PPh2)] complexes are very rare in the literature.2,5

ReactiVity of a Phosphido-Niobocene DeriVatiVe
Organometallics, Vol. 25, No. 5, 2006 1313
Scheme 2
Scheme 3
45.4, 55.7, and 48.4 for 5, 6, and 7, respectively. These chemical
shift values show the effect of alkylation of the phosphorus by
comparison with the 31P NMR chemical shift of the phosphido
terminal ligand in complex 2. This comparison shows the
differences in electron density on the P atom. In agreement with
the IR spectra, the 13C{1H} NMR spectra of 5-7 show low-
field resonances for the carbonyl ligand (ca. δ 250 ppm) as broad
signals due to the quadrupolar moment of the niobium atom.
The use of 1,2-diiodoethane (ICH2CH2I) as the alkylating
reagent with 2 gave the unexpected cationic iodophosphinoniob-
ocene triiodide complex [Nb(η5-C5H4SiMe3)2(P(I)Ph2)(CO)]I3
(8) rather than the expected dicationic derivative [{Nb(η5-C5H4-
SiMe3)2(CO)}2(Ph2P(CH2CH2)PPh2)]I2 (see eq 3).
complexes [Nb(η5-C5H4SiMe3)2(PRPh2)(CO)]X (R ) Me, X )
I (5); CH2Ph, X ) Br (6); CH2CH2Ph X ) Br (7)) in high yield
(see eq 2):
The reaction of complex 2 with I2/Et2O was successful as an
alternative method to obtain derivative 8. The new iododiphe-
nylphosphine complex was isolated as a deep red air-sensitive
solid. The ionic nature of complex 8 was confirmed by
measurement of the molar conductivity (ΛM ) 146.7 Ω-1 cm2
mol-1), which is consistent with a 1:1 electrolyte.11 The
structural characterization was carried out by both spectroscopic
and X-ray diffraction studies (see Experimental Section).
The IR spectrum shows one band at 1969 cm-1, and this
corresponds to ν(CO). In the NMR spectra (1H and 13C) the
absence of a resonance in the typical region for the Ph2P(CH2-
CH2)PPh2 ligand, corresponding to the ethylene bridge of the
P(CH2CH2)P moiety, confirms that this ligand is not present.
The 13C{1H} NMR spectrum shows the resonance of the CO
ligand at δ 210 ppm. The 31P NMR spectrum contains a signal
at δ 40.0 ppm due to the iodophosphine ligand. These chemical
shift values show the effect of the presence of the iodine atom
by comparison with the data for complex 2. This comparison
is consistent with the decreasing electronic density.
The formation of these complexes must be considered, in
terms of an alkylation process, as the result of electrophilic
attack of the alkyl halide on the nucleophilic P atom of the
phosphido terminal ligand7a (see Scheme 3).
Complexes 5, 6, and 7 were isolated as deep red air-sensitive
crystalline solids. The low solubility of the complexes in
hydrocarbons, ethers, and aromatic solvents enabled us to isolate
the products very easily in analytically pure form. Fortunately,
all of the complexes are sufficiently soluble in acetone to allow
their NMR spectra to be recorded. The ionic nature of complexes
5, 6, and 7 was confirmed by measurement of the molar
conductivity (ΛM ) 126.8, 166.6, and 134.7 Ω-1 cm2 mol-1
for 5, 6, and 7, respectively), and the values are consistent with
1:1 electrolytes.11
Compounds 5, 6, and 7 were characterized spectroscopically
(see Experimental Section). The most significant bands in the
IR spectra appear at 1968, 1947, and 1911 cm-1, which
correspond to ν(CO) for 5, 6, and 7, respectively. The 31P NMR
spectra each show a broad resonance, and these appear at δ
5
X-ray Diffraction Study of [Nb(η -C5H4SiMe3)2(P(I)Ph2)-
(CO)]I3 (8). A microcrystalline sample of 8 suitable for X-ray
diffraction was obtained by recrystallization from CH2Cl2/Et2O.
The ORTEP diagram of 8 is shown in Figure 3. Selected
bond distances and bond angles are listed in Table 1.
Complex 8 crystallizes in the triclinic space group P1h with
two molecules in the asymmetric unit cell. The local coordina-
(11) Geray, W. J. Coord. Chem. ReV. 1971, 7, 81.

1314 Organometallics, Vol. 25, No. 5, 2006
Antin˜olo et al.
8. Steps 3 and 4 were experimentally confirmed since the direct
reaction of 2 with I2 gave 8 and are consistent with the
mechanism reported by Cotton et al.15 for the formation of [Ph3-
PI]I3 on employing Ph3P and I2.
Conclusions
We have studied the reactivity of a phosphido-containing
niobocene complex 2 toward CS2, and an insertion process into
the Nb-P bond occurs to give complexes 3 and 4, where a
phosphinodithioformato ligand is present. The X-ray molecular
structure of 3 has been carried out, and it represents the first
example of an early transition metal where a phosphinodithio-
formato ligand has a κ1-S coordination mode. Additionally, the
electrophilic attack of alkyl halides on the phosphorus atom of
the phosphide ligand in 2 has allowed the isolation of a new
family of d2 cationic niobocene species 5-7. Finally, an
interesting reactivity was found in the reaction of 2 with ICH2-
CH2I, yielding the complex 8, whose X-ray crystal structure
has also been determined.
Figure 3. Molecular structure of 8 with 30% probability ellipsoids.
Hydrogen atoms have been omitted.
tion geometry around the Nb atom can be described as pseudo-
tetrahedral with two cyclopentadienyl rings bonded to the metal
in a η5-mode and phosphorus and carbon atoms of the
iodophosphine and carbonyl ligands, respectively, comprising
the immediate coordination sphere. The distances between the
metal atom and the centroids of the Cp rings are 2.062(6) and
2.054(5) Å, and the value of the angle Cent(1)-Nb(1)-Cent-
(2) is 141° (Cent(1) is the centroid of C(11)-C(15) and Cent-
(2) is the centroid of C(21)-C(25)). These values are typical
of bent niobocene derivatives. The Nb(1)-P(1) bond distance
is 2.542(5) Å, and this is in the usual range found for
phosphinoniobocene derivatives.12
The I(1)-P(1) bond length of 2.472(1) Å is close to the values
of 2.43(4) and 2.398(3) Å found in PI3 and [Ph3PI]I3, respec-
tively.13,14 The carbonyl ligand has a typical terminal CO
disposition in agreement with the bond distance and angle values
of Nb(1)-C(1), C(1)-O(1), and Nb(1)-C(1)-O(1), which are
2.067(6) Å, 1.132(8) Å, and 178.3(6)°, respectively. The P atom
is pseudo-tetrahedral. As far as the triiodide anion is concerned,
the bond distances between I(2)-I(3) and I(3)-I(4) are practi-
cally equivalent, with values of 2.921(2) and 2.924(1) Å, and
the value of I(2)-I(3)-I(4) is 177.39(3)°, in agreement with a
linear disposition.
Although there are numerous reports in the literature on the
structures of triiodide compounds,14 compound 8 appears to be
unique in two ways. First, it is the only complex to include an
iodophosphino-metallocene cation, and second, it is the only
example in which a PIR2 ligand is coordinated to an early
transition metal that has been characterized by X-ray diffraction.
The preparation of complex 8 could proceed according to
the four steps depicted in Scheme 4. Step 1 corresponds to the
electrophilic attack on the phosphorus atom followed by the
elimination of CH2dCH2 and iodine, step 2. The subsequent
attack by the iodine, steps 3 and 4, would give the final complex
Experimental Section
General Procedures. All reactions were carried out using
Schlenk techniques. Oxygen and water were excluded through the
use of vacuum lines supplied with purified N2. Toluene was distilled
from sodium. Hexane was distilled from sodium/potassium alloy.
Diethyl ether and THF were distilled from sodium benzophenone.
All solvents were deoxygenated prior to use. [Nb(η5-C5H4SiMe3)2-
(PHPh2)CO)]Cl (1)6 was prepared as described in the literature.
Deuterated solvents were dried over 4 Å molecular sieves and
degassed prior to use. ClPPh2, CS2, MeI, (C6H5)CH2Br, (C6H5)CH2-
1
CH2Br, and I2 were used as supplied by Aldrich. H, 13C, and 31P
NMR spectra were recorded on a Varian Innova 500 MHz
1
spectrometer at ambient temperature unless stated otherwise. H,
13C, and 31P NMR chemical shifts (δ values) are given in ppm
relative to the solvent signal (1H, 13C) or standard resonances (31P,
external 85% H3PO4). IR spectra were recorded on a Perkin-Elmer
883 spectrophotometer as Nujol mulls on CsI windows.
Synthesis of [Nb(η5-C5H4SiMe3)2(PPh2)(CO)] (2). A solution
of [Nb(η5-C5H4SiMe3)2(PHPh2(CO))]Cl (1) (0.56 g, 0.87 mmol)
in toluene (30 mL) was treated with 0.5 M aqueous NaOH (1.72
mL, 10% excess). The mixture was vigorously stirred. Within 4 h
the precipitate had dissolved and the organic phase had turned dark
brown. The toluene solution was filtered and evaporated to dryness.
The product 2 was obtained as a yellow-brown oil in 80% yield.
1
IR (Nujol): ν (cm-1) 1918 (CO). H NMR (500 MHz, C6D6): δ
0.22 (s, 18 H, SiMe3), 4.33, 4.74, 4.80, 5.30 (m, 2 H each a complex
signal, C5H4SiMe3); 7.15, 7.23, 7.26 (m, C6H5). 13C{1H} NMR (125
MHz, C6D6): δ 0.1 (SiMe3), 97.0 (C1, C5H4SiMe3), 93.9, 95.3, 98.9,
102.6 (C2-5, exact assignment not possible, C5H4SiMe3); 124.4
(C6H5), 133.0, 134.1 (d, 2JCP ) 17.00 Hz, C6H5), 150.9 (d, 1JCP
)
35.18 Hz, C6H5), 253.2 (CO). 31P{1H} NMR (202 MHz, C6D6): δ
-10.8 (PPh2). Anal. Calcd for C31H36NbOPSi2: C, 61.60; H, 6.00.
Found: C, 61.10; H, 5.90.
Synthesis of [Nb(η5-C5H4SiMe3)2(K1-SC(S)(PPh2))(CO)] (3).
Compound [Nb(η5-C5H4SiMe3)2(PPh2)(CO)] (2) (0.56 g, 0.93
mmol) was treated with a stoichiometric amount of CS2 (0.07 g,
0.06 mL, F ) 1.26 g/mL; 0.93 mmol), and the mixture was stirred
with dry THF (30 mL) at room temperature for 4 h. During this
time the solution changed color from yellow-brown to dark red.
The solvent was evaporated under vacuum to dryness. The dark
red oily residue was extracted with hexane (5 mL). The resulting
solution was filtered and evaporated to dryness. The deep red oil
was dissolved in hexane (5 mL) and kept at 5 °C for 10 h. A
(12) (a) Challet, S.; Kubicki, M. M.; Leblanc, J.-C.; Moise, C.; Nuber,
B. J. Organomet. Chem. 1994, 483, 47. (b) Thiygarajan, B.; Michalczyk,
L.; Bollinger, J. C.; Bruno, J. W, Organometallics 1996, 15, 2588. (c) Bailey,
N. J.; Green, M. L. H.; Leech, M. A.; Saunders, J. F.; Tidswell, H. M. J.
Organomet. Chem. 1997, 538, 111. (d) Humphries, M. J.; Douthwaite, R.
E.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 2000, 2952. (e) Nikonov,
G. I.; Crishin, Y. K.; Lemenovskii, D. A.; Kazennova, N. B.; Kumina, L.
G.; Howard, S. A. K. J. Organomet. Chem. 1997, 547, 183. (f) Nikonov,
G. I.; Lemenovskii, Yudorogar, K.; Churakov, A. V. Polyhedron 1999, 18,
1159.
(13) Allen, P. W.; Sutton, L. E. Acta Crystallogr. 1950, 3, 46.
(14) Cotton, F. A.; Wilkinson, G.; Murillo, C. A.; Bochmann, M.
AdVanced Inorganic Chemistry, 6th ed.; John Wiley and Sons: New York,
1999; Chapter 13.
(15) Cotton, F. A.; Kibala, P. A. J. Am. Chem. Soc. 1987, 109, 3308.

ReactiVity of a Phosphido-Niobocene DeriVatiVe
Organometallics, Vol. 25, No. 5, 2006 1315
Scheme 4
microcrystalline dark purple-red solid was obtained. The solid was
stirred at room temperature for 2 h. During this time the solution
changed to a deep red color. The solvent was evaporated under
vacuum to dryness. The resulting solid was recrystallized by
dissolving it in dichloromethane and placing a layer of diethyl ether
above it in a Schlenk tube. Deep red crystals began to grow within
a few days. The resulting solid was filtered off to give a deep red
solid in 80%, 85%, and 80% yield for 5, 6, and 7, respectively.
filtered off to give 80% yield of 3. IR (Nujol): ν (cm-1) 1927 (CO),
1
1046 (CdS), 634 (C-S). H NMR (500 MHz, C6D6): δ 0.01 (s,
18 H, SiMe3), 4.71 (4 H, a complex signal, C5H4SiMe3) 4.92, 5.33
(2 H, each a complex signal, C5H4SiMe3); 7.00-7.54 (10 H, C6H5).
13C{1H} NMR (125 MHz, C6D6): δ 0.1 (SiMe3), 97.0 (C1, C5H4-
SiMe3), 94.1, 95.6, 99.1 (C2-5, exact assignment not possible, C5H4-
2
SiMe3); 127.7, 127.8, 133.4 (C6H5) (d, JCP ) 16.70 Hz, C6H5),
1
Complex 5. IR (Nujol): ν (cm-1) 1968 (CO). H NMR (500
1
150.9, 151.0 (d, JCP ) 25.30 Hz, C6H5); 254.6 (CO). 264.0 (d,
2
MHz, C6D6): δ 0.05 (s, 18 H, SiMe3), 2.92 (d, JHP ) 14.8 Hz,
1JCP ) 47.62 Hz, CS2). 31P{1H} NMR (202 MHz, C6D6): δ 46.9
(PPh2). Anal. Calcd for C32H36NbOPS2Si2: C, 56.48; H, 5.33.
Found: C, 56.03; H, 5.21.
CH3), 5.06, 5.49, 5.73, 5.88 (2 H each a complex signal, C5H4-
SiMe3); 7.82 (m, 10 H, C6H5). 13C{1H} NMR (125 MHz, C6D6):
1
δ 0.8 (SiMe3); 20.5 (d, JCP ) 30.65 Hz, CH3), 95.5 (C1, C5H4-
Synthesis of [Nb(η5-C5H4SiMe3)2(K2-S,S-SC(S)(PPh2))] (4). A
mixture of [Nb(η5-C5H4SiMe3)2(κ1-S-SC(S)(PPh2))(CO)] (3) (0.56
g, 0.82 mmol) and dry THF (20 mL) was stirred at room
temperature for 8 h. During this time the solution changed color
from dark red to dark green. The solvent was evaporated under
vacuum to dryness. The dark green oily residue was extracted with
hexane (5 mL). The solid was filtered off to give 90% yield of 4.
IR (Nujol): ν (cm-1) 1000 (CdS). 1H NMR (500 MHz, C6D6): δ
0.23 (s, 18 H, SiMe3), 4.94, 5.09 (m, 4 H each a complex signal,
SiMe3), 96.9, 97.3, 101.5, 102.2 (C2-5, exact assignment not
3
possible, C5H4SiMe3); 130.2 (d, JCP ) 9.70 Hz, C6H5), 131.8
2
1
(C6H5), 132.9 (d, JCP ) 10.20 Hz, C6H5), 136.5 (d, JCP ) 39.79
Hz, C6H5); 250.0 (CO). 31P{1H} NMR (202 MHz, C6D6): δ 45.4
(s, PMePh2). Anal. Calcd for C32H39INbOPSi2: C, 51.49; H, 5.26.
Found: C, 51.18; H, 5.15.
1
Complex 6. IR (Nujol): ν (cm-1) 1947 (CO). H NMR (500
MHz, C6D6): δ 0.31 (s, 18 H, SiMe3); 4.01 (d, 2 H, 2JHP ) 4.4 Hz,
CH2(C6H5)); 5.14, 5.56, 5.85, 5.93 (2 H each a complex signal,
C5H4SiMe3); 7.21 (m, 15 H, C6H5). 13C{1H} NMR (125 MHz,
C6D6): δ -0.2 (SiMe3), 35.6 (d, 1JCP ) 15.30 Hz, CH2(C6H5); 94.4,
98.83, 99.1, 100.8 (C2-5, exact assignment not possible, C5H4-
SiMe3); 103.1 (C1 from C5H4), 125.5-133.3 (m, C6H5); 250.0 (CO).
31P{1H} NMR (125 MHz, C6D6): δ 55.8 (s, P(CH2(C6H5))(C6H5)2).
Anal. Calcd for C38H43BrNbOPSi2: C, 58.86; H, 5.59. Found: C,
58.99; H, 5.73.
3
3
C5H4SiMe3); 6.55 (t, JHH ) 7.2 Hz, 2 H, C6H5), 6.80 (d, JHH
)
7.1 Hz, 4 H, C6H5), 7.53 (t, JHH ) 7.1 Hz, 4 H, C6H5). 13C{1H}
NMR (125 MHz, C6D6): δ 0.4 (SiMe3), 105.9 (C1, C5H4SiMe3),
97.8, 105.3 (C2-3, exact assignment not possible, C5H4SiMe3);
124.3, 125.7, 129.7 (C6H5), 141.8 (d, 1JCP ) 23.00 Hz, C6H5), 244.0
3
(d, JCP ) 20.00 Hz, CS2). 31P{1H} NMR (C6D6): δ 2.03 (PPh2).
1
31P{1H} NMR (202 MHz, C6D6): δ 2.03 (q, 3JPH ) 7.30 Hz, PPh2).
Anal. Calcd for C31H36NbPS2Si2: C, 56.80; H, 5.54. Found: C,
56.00; H, 5.33.
1
Complex 7. IR (Nujol): ν (cm-1) 1911 (CO). H NMR (500
Syntheses of [Nb(η5-C5H4SiMe3)2(PRPh2)(CO)], R ) CH3 (5);
R ) CH2C6H5 (6); R ) CH2CH2C6H5 (7). To a solution of [Nb-
(η5-C5H4SiMe3)2(PPh2)(CO)] (2) (0.50 g, 0.83 mmol) in dry toluene
(30 mL) was added an excess of the appropriate alkyl halide (5,
methyl iodide (1:10) (1.17 g, 0.51 mL, F ) 2.28 g/mL, 8.30 mmol);
6, benzyl bromide (1:10) (1.42 g, 0.98 mL, F ) 1.44 g/mL, 8.30
mmol); and 7 1-bromo-2-ethylbenzene (1:10) (1.53 g, 1.14 mL, F
) 1.34 g/mL, 8.30 mmol)). In each case the reaction mixture was
MHz, C6D6): δ 0.24 (s, 18 H, SiMe3), 2.67 (m, 2 H, CH2CH2Ph),
2.90 (m, 2 H, CH2CH2Ph), 5.22, 5.56, 5.75, 5.83 (2 H each a
complex signal, C5H4SiMe3); 7.21 (m, 15 H, C6H5). 13C{1H} NMR
2
(125 MHz, C6D6): δ -0.6 (SiMe3), 31.2 (d, JCP ) 6.00 Hz,
1
CH2CH2Ph), 34.0 (d, JCP ) 20.00 Hz, CH2CH2Ph), 94.9, 96.9,
100.8, 102.0 (C2-5, exact assignment not possible, C5H4SiMe3);
104.0 (C1, C5H4SiMe3), 130.2, 131.8, 132.9 (C6H5), 136.5 (d, 1JCP
) 39.79 Hz, C6H5); 250.0 (CO). 31P{1H} NMR (202 MHz, C6D6):

1316 Organometallics, Vol. 25, No. 5, 2006
Antin˜olo et al.
Table 2. Crystal Data and Structure Refinement for 3 and 8
δ 48.2 (s, P(CH2CH2Ph)Ph2). Anal. Calcd for C39H45BrNbOPSi2:
C, 59.34; H, 5.75. Found: C, 59.55; H, 5.84.
3
8
Synthesis of [Nb(η5-C5H4SiMe3)2(P(I)Ph2)(CO)]I3 (8). Method
1. To a solution of [Nb(η5-C5H4SiMe3)2(PPh2)(CO)] (2) (0.45 g,
0.74 mmol) in dry toluene (30 mL) was added excess 1,2-
diiodoethane (ICH2CH2I (1:10) (2.23 g; 1.05 mL; F ) 2.13 g/mL;
7.40 mmol)). The reaction mixture was stirred at room temperature
for 2 h. During this time the solution changed to a deep red color.
The solvent was evaporated under vacuum to dryness. The
remaining solid was crystallized by dissolving it in dichloromethane
and placing a layer of diethyl ether above it in a Schlenk tube.
Deep red crystals began to grow within a few days. The resulting
solid was filtered off to give a deep red solid in 85% yield.
Method 2. To a solution of [Nb(η5-C5H4SiMe3)2(PPh2)(CO)] (2)-
(0.50 g, 0.83 mmol) in dry toluene (30 mL) was added excess I2 in
diethyl ether (1:2) (0.42 g; 1.66 mmol). The reaction mixture was
stirred at room temperature for 2 h. During this time the solution
changed to a deep red color. The solvent was evaporated under
vacuum to dryness. The resulting solid was crystallized by
dissolving it in dichloromethane and placing a layer of diethyl ether
above it in a Schlenk tube. Deep red crystals began to grow within
a few days. The resulting solid was filtered off to give a deep red
solid in 80% yield.
empirical formula
fw
C30H36NbOPS2Si2
656.77
250(2)
0.71073
monoclinic
P21/c
17.063(8)
10.834(8)
18.488(6)
C29H36I4NbOPSi2
1088.24
230(2)
0.71073
triclinic
temperature (K)
wavelength (Å)
cryst syst
space group
a (Å)
P1h
11.608(1)
12.194(5)
14.197(2)
81.77(2)
78.42(1)
72.22(1)
1867.4(8)
2
b (Å)
c (Å)
R (deg)
â (deg)
108.76(4)
γ (deg)
volume (Å3)
Z
3236(3)
4
1.348
6.46
0.689-1.000
1360
0.4 × 0.3 × 0.3
-19 e h e 18
0 e k e 12
0 e l e 20
density (calcd) (g/cm3)
1.935
37.56
0.591-1.000
1028
0.3 × 0.3 × 0.2
-15 e h e 15
-15 e k e 16
0 e l e 18
abs coeff (cm-1
)
range of transmn factor
F(000)
cryst size (mm3)
index ranges
no. of indep reflns
4874/4700 [R(int) ) 8989 [R(int) )
0.0914]
0.0218]
8989/0/343
1.027
R1 ) 0.0548,
wR2 ) 0.1484
4.118 and -4.117
no. of data/restraints/params 4700/0/334
1
Complex 8. IR (Nujol): ν (cm-1) 1969 (CO). H NMR (500
goodness-of-fit on F2
final R indices
0.958
R1 ) 0.0863,
wR2 ) 0.1398
0.747 and -0.671
MHz, C6D6): δ 0.34 (s, 18 H, SiMe3); 5.25, 5.31, 5.69, 6.08 (2 H
each a complex signal, C5H4SiMe3); 7.75 (m, 10 H, C6H5). 13C-
{1H} NMR (125 MHz, C6D6): δ -0.1 (SiMe3), 97.4, 100.9, 102.8,
103.8 (C2-5, exact assignment not possible, C5H4SiMe3); 107.1 (C1,
C5H4SiMe3); 129.9 133.1 134.1 (C6H5); 135.6 (d, 1JCP ) 25.30 Hz,
C6H5); 210.0 (CO). 31P{1H} NMR (202 MHz, C6D6): δ 40.0 (s,
PIPh2). Anal. Calcd for C31H36I4NbOPSi2: C, 33.48; H, 3.26.
Found: C, 33.35; H, 3.21.
[I > 2σ(I)]a
largest diff peak and
hole (e‚Å-3
)
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) [∑[w(Fo - Fc )2]/∑[w(Fo )2]]0.5
.
analysis.18 Anisotropic temperature parameters were considered for
all non-hydrogen atoms, while hydrogen atoms were included in
calculated positions but not refined.
X-ray Structure Determination of 3 and 8. Crystal data
collection and refinement parameters are collected in Table 2.
Suitable crystals were selected and mounted on a fine glass fiber
with epoxy cement, sealed, and used for data collection. The unit
cell parameters were determined from the angular setting of a least-
squares fit of 25 strong high-angle reflections. Reflections were
collected at 250 K (for 3) and 230 K (for 8) on a NONIUS-MACH3
diffractometer equipped with graphite-monochromated radiation (λ
) 0.71073 Å). The samples did not show significant intensity decay
during data collection.
Acknowledgment. We gratefully acknowledge financial
support from the Direccio´n General de Investigacio´n Cient´ıfica
Spain (MEC Grant. No. BQU2002-04638-CO2-02) and the
Junta de Comunidades de Castilla-La Mancha (Grant. Nos.
PAC-02-003, GC-02-010, PBI05-23, and PBI-05-029).
Supporting Information Available: Detailed X-ray crystal-
lographic data of atomic positional parameters, bond distances and
angles, and anisotropic thermal parameters for complexes 3 and 8.
Tables of X-ray crystallographic data for complexes 3 and 8. This
material is available free charge of charge via the Internet at
http://pubs.acs.org.
Data were corrected in the usual fashion for Lorentz and
polarization effects, and a semiempirical absorption correction16
was applied (µ ) 37.56 cm-1 (3) and 6.46 cm-1 (8)). The space
group was determined from the systematic absences in the diffrac-
tion data. The structures were solved by direct methods,17 and
refinement on F2 was carried out by full-matrix least-squares
OM051013U
(17) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla,
M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 435-436.
(18) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal
Structures from Diffraction Data; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(16) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351.