Lewis base character of the phosphorus atom in phosphanido-niobocene complexes. Synthesis of new early-early homo- and heterobimetallic entities

Article abstract of DOI:10.1039/c0dt00865f

The reaction of phosphanido complexes [Nb(η⁵-C ₅H₄SiMe₃)₂(L)(PPh₂)] [L = CO (1), CNXylyl (2)] with early transition metal halides in high oxidation states has been carried out. New bimetallic niobocene complexes [{Nb(η⁵-C₅H₄SiMe₃) ₂(L)}(μ-PPh₂)(MCl₅)] [M = Nb, L = CO (3), L = CNXylyl (4); M = Ta, L = CO (5), L = CNXylyl (6)] have been successfully synthesized by the reaction with [MCl₅]₂ (M = Nb or Ta). In a similar way [{Nb(η⁵-C₅H₄SiMe ₃)₂(L)}(μ-PPh₂)(MCl₄)] [M = Ti, L = CO (13), CNXylyl (14); M = Zr, L = CO (15), CNXylyl (16)] were synthesized using MCl₄ (M = Ti or Zr). Solutions of complexes 4-6 in chloroform produced new ionic derivatives [Nb(η⁵-C₅H ₄SiMe₃)₂(P(H)Ph₂)(L)] [MCl ₆] [M = Nb, L = CO (7), L = CNXylyl (8); M = Ta, L = CO (9), L = CNXylyl (10)]. Ionic complexes [Nb(η⁵-C₅H ₄SiMe₃)₂(P(Cl)Ph₂)(L)] [NbCl ₄O(thf)] [L = CO (11), CNXylyl (12)] were formed from solutions in thf - rapidly in the case of 3 but more slowly for 4. New heterometallic complexes [Nb(η⁵-C₅H₄SiMe₃) ₂(L)(μ-PPh₂){(Ti(η⁵-C₅R ₅)Cl₃}] [R = H, L = CO (17), CNXylyl (18); R = CH ₃, L = CO (19), CNXylyl (20)] were synthesized by the reaction of 1 or 2 with [Ti(η⁵-C₅R₅)Cl₃] (R = H or CH₃). All of these compounds were characterized by IR and multinuclear NMR spectroscopy, and the molecular structures of 9 and 12 were determined by single-crystal X-ray diffraction.

Full text of DOI:10.1039/c0dt00865f

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PAPER
Lewis base character of the phosphorus atom in phosphanido-niobocene
complexes. Synthesis of new early–early homo- and heterobimetallic entities†
R. Reguillo-Carmona, A. Antin˜olo,* S. Garc´ıa-Yuste, I. Lo´pez-Solera and A. Otero*
Received 19th July 2010, Accepted 9th December 2010
DOI: 10.1039/c0dt00865f
5
The reaction of phosphanido complexes [Nb(h -C5H4SiMe3)2(L)(PPh2)] [L = CO (1), CNXylyl (2)] with
early transition metal halides in high oxidation states has been carried out. New bimetallic niobocene
5
complexes [{Nb(h -C5H4SiMe3)2(L)}(m-PPh2)(MCl5)] [M = Nb, L = CO (3), L = CNXylyl (4); M =
Ta, L = CO (5), L = CNXylyl (6)] have been successfully synthesized by the reaction with [MCl5]2 (M =
5
Nb or Ta). In a similar way [{Nb(h -C5H4SiMe3)2(L)}(m-PPh2)(MCl4)] [M = Ti, L = CO (13), CNXylyl
(14); M = Zr, L = CO (15), CNXylyl (16)] were synthesized using MCl4 (M = Ti or Zr). Solutions of
5
complexes 4–6 in chloroform produced new ionic derivatives [Nb(h -C5H4SiMe3)2(P(H)Ph2)(L)] [MCl6]
[M = Nb, L = CO (7), L = CNXylyl (8); M = Ta, L = CO (9), L = CNXylyl (10)]. Ionic complexes
5
[Nb(h -C5H4SiMe3)2(P(Cl)Ph2)(L)] [NbCl4O(thf)] [L = CO (11), CNXylyl (12)] were formed from
solutions in thf – rapidly in the case of 3 but more slowly for 4. New heterometallic complexes
5
5
[Nb(h -C5H4SiMe3)2(L)(m-PPh2){(Ti(h -C5R5)Cl3}] [R = H, L = CO (17), CNXylyl (18); R = CH3, L =
5
CO (19), CNXylyl (20)] were synthesized by the reaction of 1 or 2 with [Ti(h -C5R5)Cl3] (R = H or
CH3). All of these compounds were characterized by IR and multinuclear NMR spectroscopy, and the
molecular structures of 9 and 12 were determined by single-crystal X-ray diffraction.
or related moieties. In the last decade we have developed a series
Introduction
of studies focused on the reactivity of phosphanido-containing
niobocene complexes; thus, the insertion reaction of carbon
disulfide into the Nb–P bond gave a series of new niobocene
complexes that contained the anionic phosphanylthioformato
In the last three decades the chemistry of early/late heterobimetal-
lic complexes (ELHBs) has been extensively developed,1 mainly
due to the synergistic effect produced in this type of system by
the simultaneous presence of a hard Lewis acid early-metal centre
and a soft Lewis base late-metal centre. In this field, phosphanido-
bridged heterobimetallic compounds are well documented and in a
good rational approach they have been prepared by the incorpora-
tion of an appropriate late metal moiety into a metallophosphide,
MPR2, unit of the early transition metal. The first examples of
this type of complex were described several years ago by Stelzer
et al.2 Although most of the complexes have been based on group
4 phosphanido-containing moieties,3 similar types of complexes
containing group 5 metal moieties have been prepared, particularly
in the pioneering work of Mo¨ıse et al. in the 1990s, by using
both niobocene(tantalocene)-phosphanido systems and M(CO)x
(M = Fe, Mo, W) as building blocks.4 More recently, Nikonov
et al.5 used an imido-phosphanido niobocene for the construction
of Nb/Rh heterobimetallic complexes that have proven to be
active precatalysts for the hydrosilylation of ketones and aldehydes.
In addition, Hey-Hawkins et al.6 have prepared a series of
dimeric phosphinidene-bridged TaVcomplexes, a rare example of
homobimetallic group 5 species containing bridged-phosphanido
ligand R2PCS2 .7 More recently, we described the preparation
-
of a series of niobacycles that involved the insertion reaction of
electron-deficient alkynes into the Nb–P bond.8 We became in-
terested in analyzing the behavior of our phosphanido-containing
niobocene complexes as metallophosphides towards group 4 and
5 metal moieties in order to prepare new types of hetero- and
homobimetallic early-early organometallic entities.
Herein we report the synthesis of several new dinuclear d2–
d0, homo- and heterobimetallic mono-bridged complexes [Nb(m-
PPh2)M] (M = Nb, Ta, Ti, Zr). This approach takes advantage
5
of the ability of the niobium(III) phosphanido complexes [Nb(h -
C5H4SiMe3)2(L)(PPh2)] (1 and 2) to act as Lewis bases toward a
series of halide group 4 and 5 transition metal species MClx that
can act as Lewis acids.
Results and discussion
The reaction of toluene solutions of 1 or 2 with the Lewis
acids (MCl5)2, where M = Nb or Ta, gave the new bimetallic
complexes 3–6 as red solids, in which the two metals on each
complex are in a different oxidation state, i.e. Nb(III) and M(V).
TiCl4 and ZrCl4 yielded the heterobimetallic complexes 13–16 and
with monocyclopentadienyl Ti(IV) trichloride the new complexes
Dpto. de Qu´ımica Inorga´nica, Org. y Bioq., Facultad de Qu´ımicas, Universi-
dad de Castilla La Mancha, 13071, Ciudad Real, Spain
† CCDC reference numbers 784737 and 784738. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/c0dt00865f
2622 | Dalton Trans., 2011, 40, 2622–2630
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Scheme 1
17–20 were isolated as orange-red solids in high yield after the
appropriate workup (see Scheme 1).
Complexes 4–6 and 13–20 were characterized by elemental
analysis, IR and multinuclear NMR spectroscopy in solution.
The low solubility of complex 3 in hydrocarbons, ethers or
aromatic solvents and its high reactivity toward chloroform or
dichloromethane precluded characterization by NMR techniques.
The IR spectra for 3, 5, 13, 15, 17 and 19 contain a characteristic
band due to the carbonyl ligand n(C O) at 1950 (1949–1956) cm-1
(a typical value for niobium(III) metallocenes7), and for 4, 6, 14,
16,18, and 20 there is a band corresponding to the isocyanide
n(C N) at 2060 (2073–2050) cm-1.
Scheme 2
conformational preferences have been described previously4a,9 and
can be distinguished by the 31P NMR chemical shift. In fact, in
all cases where the metal–metal bond exists the chemical shift
of the signal for the phosphorus is found between +300 and
50 ppm, whereas when a metal–metal bond does not exist this
signal appears between +50 and -300 ppm.
1
The 31P{ H} NMR spectra of these complexes in deuterated
chloroform show a single broad signal for each complex, at
27.4 ppm for 4, 29.9 ppm for 5 and 77.3 ppm for 6. These
resonances were shifted downfield with respect to those of the
phosphanido ligand in complexes 1 or 2. This change is consistent
with the expected decrease in electron density on the phosphorus
atom upon coordination to another metal centre. Furthermore, all
the resonances are in the expected region for a phosphanido bridge
with donation of the phosphanido lone pair to some of the empty
orbitals in MCl5 (M = Nb or Ta). Two conformational dispositions
are possible in the bimetallic complexes as a consequence of
this interaction (Scheme 2); the exo conformer in which the new
MCl5 entity is located away from the niobocene moiety, and the
endo conformer in which this moiety and the metallic halide are
closer and may interact to form a new metal–metal bond. These
The 31P NMR chemical shifts found for 4 and 5 are in the region
corresponding to the exo conformer. However, in the case of 6 the
observed value is in the boundary region for the two conformers,
and it is not possible to distinguish between the two possibilities.
However, the chemical shifts of the signals observed in the
31P{ H} NMR spectra of complexes 13, 14 and 16 (157.2, 166.1
1
and 165.8 ppm, respectively) are consistent4a,9 with an interaction
between the lone pair of the niobium(III) atom and the empty
orbital of the other metal centre, as shown in Scheme 3 II.
This additional metal–metal bonding interaction must provide
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Scheme 3
further stabilization for these complexes, in which the coordination
number of Ti or Zr can be increased to six. In the case of complex
15 the value of the chemical shift for phosphorus is 28.7 ppm,
which indicates that an interaction does not occur between the two
metal centres, as shown in the Scheme 2 I. This situation could
be because the lone pair of the d2 niobocene system is mainly
involved in p back-donation to the carbonyl ancillary ligand and
an additional Nb–Zr interaction is therefore probably not present
in complex 15. Assuming an exo conformation for this complex
(see Scheme 1), the zirconium centre increases its coordination
number to five (bpt), and two isomers are possible (I.a and I.b, see
Scheme 3).
Furthermore, the 1H NMR spectra of 17 and 20 each contain a
singlet signal at ca. 6.71 ppm corresponding to the C5H5 fragment
for 17 and 18 or a signal at ca. 2.19 ppm corresponding to the
methyl group of the C5Me5 unit for 18 and 20.
The spectroscopic data are all consistent with the structural
disposition depicted in Scheme 1, where the two metal centres
are connected by a phosphanido-bridging moiety bearing the
niobocene unit as a metallophosphide coordinated to the titanium
centre, which exhibits the well known four-legged piano-stool
structure.11
The low stability in solution of complexes 3–6 precludes their
1
characterization by 13C{ H} NMR; in fact, solutions of complex
5
There are few examples where the coordination number of five
appears for titanium(IV) or zirconium(IV) complexes, and in these
cases it displays a coordination environment intermediate between
square-pyramidal and trigonal-bipyramidal.10
3–6 in chloroform give rise to new ionic derivatives [Nb(h -
C5H4SiMe3)2(P(H)Ph2)(L)] [MCl6] [M = Nb; L = CO (7), CNXylyl
(8); M = Ta, L = CO (9), CNXylyl (10)], probably due to attack by
HCl arising from the solvent. In fact when complex 3–6 were solved
in deuterated chloroform, the deuterated phosphonium complexes
was identified by NMR; thus, the 31P NMR spectrum shows a
1 : 1 : 1 triplet resonance due to coupling with the deuterium atom
(1JPD ca. 34 Hz). This signal allowed us to confirm the existence of
the P–D bond as reported previously.7a
1
In the case of complexes 17–20 the 31P{ H} NMR are
particularly informative, since the chemical shifts observed
between 12.8 and 26.6 ppm (see Experimental section) are
consistent4a,9 with a structural disposition bearing a phosphanido
bridge between the two metal centres without any additional
interaction.
The ionic nature of complexes 7–10 was confirmed by conduc-
tivity measurements on solutions of the complexes in acetone. The
values obtained were between 116 and 121 X-1 cm2 mol-1 and these
are consistent with 1 : 1 electrolytes.12
1
The H NMR spectra of complexes 4–6 and 13–20 provide
evidence for the Cs symmetry of the niobocene moiety, and contain
a singlet for the methyl groups of the SiMe3 at ca. 0.20 ppm and
four multiplets corresponding to the cyclopentadienyl protons,
which adopt an ABCD spin system, in the range 4.58–5.80 ppm.
The 1H NMR spectra of 4–6 and 13–20 also contain signals
corresponding to the phenyl groups, and the spectra of 4, 6, 14, 16,
18 and 20 contain a singlet for the methyl groups of the CNXylyl
at ca. 2.3 ppm and a multiplet at ca. 7.3 ppm for the phenyl ring
of the same group.
1
The spectroscopic data for complexes 7–10 [IR, 31P{ H} NMR,
1
1H and 13C{ H} NMR spectra] are consistent with the formula
5
[Nb(h -C5H4SiMe3)2(P(H)Ph2)(L)]+ (L = CO, CNXylyl), as re-
ported previously.7a In fact, these cations can also be synthesized
5
by reaction of [Nb(h -C5H4SiMe3)2(P(H)Ph2)(L)]Cl (L = CO,
CNXylyl)7a with [MCl5]2 (M = Nb or Ta) in chloroform (Scheme 4).
Additionally, complex 9 was characterized by X-ray diffraction.
Scheme 4
2624 | Dalton Trans., 2011, 40, 2622–2630
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◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for complex 9
those found in other niobium–phosphane complexes previously
reported by our group.7
The positive charge of the metallocene is stabilized by the
hexachlorotantalate(V) anion, in which the tantalum atom has
an octahedral geometry.13
˚
Bond lengths (A)
Bond angles (◦)
Nb(1)–Cp(1)a
Nb(1)–Cp(2)a
Nb(1)–C(1)
Nb(1)–P(1)
C(1)–O(1)
P(1)–C(31)
P(1)–C(41)
Ta(1)–Cl(1)
Ta(1)–Cl(2)
Ta(1)–Cl(3)
Ta(1)–Cl(4)
Ta(1)–Cl(5)
Ta(1)–Cl(6)
2.07
2.06
Cent(1)–Nb–Cent(2)b
C(1)–Nb(1)–P(1)
Nb(1)–P(1)–C(31)
Nb(1)–P(1)–C(41)
C(31)–P(1)–C(41)
Cl(1)–Ta(1)–Cl(2)
Cl(1)–Ta(1)–Cl(3)
Cl(1)–Ta(1)–Cl(4)
Cl(1)–Ta(1)–Cl(5)
Cl(2)–Ta(1)–Cl(3)
Cl(2)–Ta(1)–Cl(4)
Cl(3)–Ta(1)–Cl(4)
Cl(4)–Ta(1)–Cl(5)
140.4
82.9(10)
117.6(8)
122.5(8)
104.2(12)
178.0(3)
88.8(4)
89.2(4)
91.4(4)
89.9(4)
89.3(3)
92.2(3)
176.9(5)
2.11(4)
2.56(1)
1.14(4)
1.81(3)
1.80(2)
2.33(1)
2.35(1)
2.32(1)
2.32(1)
2.30(1)
2.37(1)
The characterization of the niobiocene cation has already
been described by our group through different spectroscopic
techniques,7 but this structure represents the first example of a
diphenylphosphanyl–niobiocene species to be characterized by X-
ray diffraction.
The behavior of the Lewis acid [NbCl5]2 in thf solution has
recently been reported,14 and it was found that the niobium(V)
centre promoted activation of the thf. As a result, we assessed
the ability of complexes 3 and 4 to interact with this solvent.
Thus, dissolution of 3 and 4 in thf at room temperature led to the
formation of a precipitate after a reaction time of 30 min in each
case. The appropriate workup led to the isolation of red solids,
which were identified as complexes 11 and 12 (eqn (1)).
a Refers to the average bond distance between Nb(1) and the carbon atoms
of the C5 ring of the corresponding cyclopentadienyl moiety. b Cent(1) and
Cent(2) are the centroids of C(11)–C(15) and C(21)–C(25), respectively.
A microcrystalline sample of 9, which was suitable for X-
ray diffraction, was obtained by crystallization from chloroform.
Structure is depicted in Fig. 1. Selected bond distances and angles
are listed in Table 1.
thf
[{Nb(η5-C5H4SiMe3)2(L)(μ-PPh2 )}(MCl5)] ⎯⎯→
[Nb(η5-C5H4SiMe3)2(P(Cl)Ph2 )(L)][NbCl4O(thf)]
(1)
where L=CO (3),CNXylyl(4), CO (11), CNXylyl(12)
5
Furthermore, the ionic complexes [Nb(h -C5H4SiMe3)2-
(P(Cl)Ph2)(L)] [NbCl4O(thf)] [L = CO (11), CNXylyl (12)] were
also isolated quickly from 1 or more slowly from 2 when
solutions of these compounds in thf were treated with [NbCl5]2
at room temperature; in this reaction the probably formed 3 or
4 undergoes the halogenations of the phosphorous atom to give
the corresponding cationic chlorophosphane complexes, while the
[NbCl4O(thf)]- is formed15 by the interaction with thf. In fact, as
mentioned above, when 3 or 4 previously isolated were solved in
thf at room temperature led to the formation of 11 or 12.
Complexes 11 and 12 were fully characterized by elemental
analysis, IR and multinuclear NMR spectroscopy in solution.
Complex 12 was also characterized by X-ray diffraction.
The ionic nature of complexes 11 and 12 was confirmed by con-
ductivity measurements on solutions in acetone (see Experimental
section). The spectroscopic data for 11 and 12 also confirm their
1
ionic nature. For example, the 31P{ H} NMR spectra show a single
broad signal at 27.1 ppm for 11 and at 34.2 ppm for 12 for the
chlorophosphane ligand. These resonances were shifted downfield
with respect to those in the corresponding phosphanido ligand in
complexes 1 and 2, but at high field with respect to the signal at
80 ppm presented by free16 PClPh2. These findings are consistent
with the expected decrease in electron density on the phosphorus
atom with respect to 1 and 2, and the increase in electron density
with respect free PClPh2 by mean of the electron withdrawal from
the niobium(III) centre. This behavior are in agreement with the
31P chemical shift observed in other halophosphanes coordinated
to niobium.7c
Fig. 1 Structure of complex 9. Hydrogen atoms (except H1) have been
omitted for clarity.
The structure of 9 shows the typical bent metallocene con-
formation with both cyclopentadienyl rings bound to the metal
5
centre in a h fashion. The niobium atom is also coordinated to
the phosphane and the carbonyl ligands. The niobium–carbon
˚
bond length (carbonyl ligand), Nb(1)–C(1), is 2.11(4) A, which
The IR spectra of complexes 11 and 12 contain the characteristic
band due to the carbonyl ligand n(C O) at ca. 1950 cm-1 for 11
and the band corresponding to n(C N) at ca. 2067 cm-1 for 12.
Additionally, a strong band was also observed at ca. 957 cm-1 in
the expected region for n(Nb O).17
is in the range found for other metallocene complexes with
terminal carbonyl ligands.7 The carbonyl ligand is linear, with
an O(1)–C(1)–Nb(1) angle of 174(3)◦ and an O(1)–C(1) distance
˚
of 1.14(4) A, both values that are close to those found for the
terminal carbonyl ligand in other niobocene complexes.7
The 1H NMR spectra of complexes 11 and 12 evidence the lack
of symmetry of the niobocene moiety and contain two singlets for
the methyl groups of the two different SiMe3 groups at ca. 0.25 ppm
The phosphorus atom is in a distorted tetrahedral environment,
˚
and the Nb(1)–P(1) bond length of 2.56(1) A is similar to
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and eight multiplets in the range 5.23–5.31 ppm corresponding
to the two cyclopentadienyl protons, each of which adopts an
ABCD spin system. The different NMR behavior of the two
cyclopentadienyl ring might be due to hindered rotation about the
Nb–P bond or hindered rotation about the two Cp¢–Nb axes; the
rotation about the two Cp¢–Nb axes could be hindered by steric
reasons or some interaction between the terminal oxygen atom
present in the anion [NbCl4O(thf)] and one of the cyclopentadienyl
rings through one of the methyl of the SiMe3 groups. This
interaction has been also observed in the solid state in the X-
ray studies carried out for the complex 12. However, hindered
rotation about the Nb–P bond related to the bigger size of the
chloride atom in comparison with the hydrogen atom must be
taken into account.
Fig. 2 ORTEP view of complex 12. Hydrogen atoms have been omitted
Furthermore, the spectrum of 12 contains two signals for the
methyl groups of the CNXylyl ligand at 2.34 and 2.50 ppm and a
multiplet at ca. 7.3 ppm for the phenyl ring; finally, in the spectra
of 11 and 12 two resonances at 1.85 and 3.86 ppm are observed,
and these are due to the methylene protons of the thf coordinated
to the niobium center.
for clarity. Thermal ellipsoids are drawn at the 20% probability level.
The phosphorus atom is also in a distorted tetrahedral environ-
ment, as indicated by the values of the angles formed by the phenyl
rings and the chlorine atom; C(51)–P(1)–Cl(1) 99.0(4)◦, C(41)–
P(1)–Cl(1) 98.5(4)◦, C(41)–P(1)–C(51) 102.7(5)◦ and Nb(1)–P(1)–
Cl(1) 114.5(2)◦.
The positive charge of the metallocene is stabilized by the
tetrachloro-oxo-tetrahydrofuran-niobate(V) anion. The structure
of this anion has been described previously.17 The Nb(2)–O(1)
1
The 13C{ H} NMR spectra of complexes 11 and 12 also provide
evidence for the lack of symmetry of the niobocene moiety.
Two singlets are observed for the carbon atoms of the SiMe3
groups and ten signals for the cyclopentadienyl rings. Signals due
to the quaternary carbon atom of the ancillary ligand are not
observed.
˚
bond distance of 1.69(1) A is consistent with the presence of a
A red microcrystalline sample of 12, which was suitable for X-
ray diffraction, was obtained by crystallization from thf/hexane
by cooling the solution at -20 ◦C for three days.
double Nb O bond. The ion has four chlorine atoms arranged in
˚
the equatorial plane of the molecule at distances of ca. 2.39 A (see
˚
Table 1). The niobium atom is 0.29 A out of the equatorial plane
An ORTEP diagram of 12 is depicted in Fig. 2. Selected bond
distances and angles are listed in Table 2.
The niobium atom has a distorted tetrahedral environment with
two positions occupied by the cyclopentadienyl rings and the other
two by the phosphane and the isocyanide ligands.7
formed by the four chlorine atoms, which are oriented away from
the oxygen atom of the oxo ligand. The niobium atom completes
its coordination sphere with a molecule of thf, with a Nb(2)–O(2)
˚
bond length of 2.39(1) A.
The crystal is stabilized by an extensive weak hydrogen-
interaction network, the geometrical features of which are shown
in Table 3. A noticeable feature of this structure is the ob-
served hydrogen-bonding interaction18 between one methyl of
the (trimethylsilyl)cyclopentadienyl ring and the oxygen atom
of the tetrachloro-oxo-tetrahydrofuran-niobate(V) anion, which
correspond to the atoms represented as C5–H5 ◊ ◊ ◊ O1 in the
ORTEP diagram (Fig. 3).
The distance between the nitrogen and the carbon atoms of
˚
the isocyanide ligand, N(1)–C(1) 1.17(1) A, and the angle N(1)–
C(1)–Nb(1), 175.4(9)◦, indicate the presence of a triple C
N
bond and an almost linear coordination with the metal center.
The Nb(1)–P(1) bond length is in the range of values observed in
other phosphane–niobocene complexes described previously by
our group.7
◦
˚
Table 2 Selected bond lengths (A) and angles ( ) for complex 12
Bond angles (◦)
˚
Bond lengths (A)
Nb(1)–Cp(1)a
Nb(1)–Cp(2)a
Nb(1)–P(1)
Nb(1)–C(1)
P(1)–Cl(1)
2.05
2.06
Cent(1)–Nb(1)–Cent(2)b
P(1)–Nb(1)–C(1)
Nb(1)–P(1)–Cl(1)
Nb(1)–P(1)–C(41)
Nb(1)–P(1)–C(51)
Cl(1)–P(1)–C(41)
Cl(1)–P(1)–C(51)
C(41)–P(1)–C(51)
C(1)–N(1)–C(31)
Nb(1)–C(1)–N(1)
O(1)–Nb(2)–O(2)
140.3
85.0(3)
114.5(2)
116.0(3)
122.5(4)
98.5(4)
2.55(1)
2.13(1)
2.04(1)
1.17(1)
1.69(1)
2.39(1)
2.38(1)
2.39(1)
2.37(1)
2.41(1)
N(1)–C(1)
Nb(2)–O(1)
Nb(2)–O(2)
Nb(2)–Cl(2)
Nb(2)–Cl(3)
Nb(2)–Cl(4)
Nb(2)–Cl(5)
99.0(4)
102.7(5)
175.9(12)
175.4(9)
178.3(4)
a Refers to the average bond distance between Nb(1) and the carbon atoms
of the C5 ring of the corresponding cyclopentadienyl moiety. b Cent(1) and
Cent(2) are the centroids of C(11)–C(15) and C(21)–C(25), respectively.
Fig. 3 Selected hydrogen bonds of complex 12.
2626 | Dalton Trans., 2011, 40, 2622–2630
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Table 3 Hydrogen bonds for compound 12
∠DHA (◦)
d(D ◊ ◊ ◊ A) (A)
Symmetrya
˚
˚
˚
D–H
d(D–H) (A)
d(H ◊ ◊ ◊ A) (A)
C5–H5a ◊ ◊ ◊ O1
0.96
0.93
0.96
0.96
0.93
0.96
0.98
2.19
2.49
2.89
2.81
2.76
2.82
2.87
154.9
173.4
140.8
150.4
156.8
148.3
160.0
3.09(2)
3.42(2)
3.69(1)
3.68(1)
3.63(1)
3.67(1)
3.80(1)
x, y, z
C44–H44 ◊ ◊ ◊ O1
C37–H37a ◊ ◊ ◊ Cl1
C7–H7c ◊ ◊ ◊ Cl3
C34–H34 ◊ ◊ ◊ Cl3
C37–H37c ◊ ◊ ◊ Cl3
C23–H23 ◊ ◊ ◊ Cl5
1 - x, 1 - y, 1 - z
x, y, z
x, y - 1, z
2 - x, 1 - y, 1 - z
x, y - 1, z
1 - x, 1 - y, -z
a Symmetry operation for A.
Although some organometallic halophosphane complexes have
been described previously,7,19–21 to the best of our knowledge
complex 12 is the first chlorophosphanyl–metallocene complex
to be characterized by X-ray diffraction.
of 1 (0.50 g, 0.86 mmol) or 2 (0.58 g, 0.86 mmol) in anhydrous
toluene (30 mL) was added to a cooled (-78 ◦C) suspension
of a stoichiometric amount of niobium pentachloride (0.23 g,
0.86 mmol) or tantalum pentachloride (0.30 g, 0.86 mmol) (1 : 1
ratio) in the same solvent. The addition gave a deep green solution,
which was allowed to reach room temperature and stirred for 1 h. A
red solid was observed in the solution after this time. The red pre-
cipitate was filtered off and dried under vacuum, yielding the new
Concluding remarks
In conclusion, we have studied the reactivity of phosphanido
complexes 1 and 2 with early transition metal halides in
high oxidation states, and have successfully synthesized new
homo- and heterobimetallic d2–d0 early–early complexes with a
diphenylphosphanido-bridging moiety. Analysis of the possible
conformational preferences in these complexes based on spectro-
scopic data was also carried out. Additionally, the formation of
ionic complexes 7–10 based on cationic niobocene moieties and
hexahalometallates was achieved. The molecular structures of 9
and 12 were determined by single-crystal X-ray diffraction.
5
niobocene complexes [{Nb(h -C5H4SiMe3)2(L)}(m-PPh2)(MCl5)]
[M = Nb, L = CO (3), CNXylyl (4); M = Ta, L = CO (5), CNXylyl
(6)], which were isolated as red solids in ca. 70% yield.
3. (0.52, 65%) Found: C, 39.89; H, 4.31; Calc. for
C29H36Cl5Nb2POSi2: C, 40.94; H, 4.26%. IR (Nujol/polyethylene):
n (cm-1); 1958 (C O). The low solubility of complex 3 in hydro-
carbons, ethers or aromatic solvents and its high reactivity toward
chloroform or dichloromethane precluded characterization by
NMR techniques.
4. (0.59 g, 80%) Found: C, 46.32; H, 4.56; N, 1.39. Calc.
Experimental
for C37H45Cl5NNb2PSi2: C, 46.58; H, 4.75; N, 1.47%. IR (Nu-
1
jol/polyethylene): n (cm-1); 2062 (C N). H NMR (CDCl3): d
General
(ppm); 0.29 (s, 18H, SiMe3), 2.51 (s, 6H, CH3 of CNXylyl), 4.58,
1
5.29, 5.32, 5.80 (m, 2H, C5H4), 7.89 (m, 13H, Ph). 31P{ H} NMR
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. All solvents were deoxy-
(CDCl3): d (ppm); 27.4 (s). 31P NMR (CDCl3): d (ppm); 27.4 (m).
5. (0.52, 65%) Found: C, 36.89; H, 3.71; Calc.
for C29H36Cl5NbPOSi2Ta: C, 37.10; H, 3.86%. IR
(Nujol/polyethylene): n (cm-1); 1955 (C O). 1H NMR (CDCl3):
d (ppm); 0.19 (s, 18H, SiMe3), 4.58, 5.31, 5.57, 5.65 (m, 2H,
5
genated prior to use. Complexes [Nb(h -C5H4SiMe3)2(PPh2)L] [L =
CO (1), CNXylyl (2)] were prepared by literature procedures.7
Niobium pentachloride, tantalum pentachloride, titanium tetra-
chloride, zirconium tetrachloride and [Ti(h -C5R5)Cl3] (R = H,
CH3) were used as received from Aldrich and were manipulated
1
C5H4), 7.05 (m, 10H, Ph). 31P{ H} NMR (CDCl3): d (ppm); 29.9
5
(s). 31P NMR (CDCl3): d (ppm); 29.9 (m).
in a glovebox (model MBRAUN). Deuterated solvents were
6. (0.70 g, 79%). Found: C, 42.52; H, 4.26; N, 1.28; Calc.
for C37H45Cl5NNbPSi2Ta: C, 42.65; H, 4.35; N, 1.34%; IR
(Nujol/polyethylene): n (cm-1); 2050 (C N). 1H NMR (CDCl3):
d (ppm); 0.21 (s, 18H, SiMe3), 2.33 (6H, CH3 of CNXylyl), 4.89,
˚
supplied by SDS, dried over 4 A molecular sieves and degassed
prior to use. H, 13C and 31P NMR spectra were recorded on
1
a Varian Inova 500 MHz spectrometer at ambient temperature
1
unless stated otherwise. H, 13C and 31P NMR chemical shifts
1
5.09, 5.25, 5.67 (m, 2H, C5H4), 7.34 (m, 13H, Ph). 31P{ H} NMR
(CDCl3): d (ppm); 77.3 (s). 31P NMR (CDCl3): d (ppm); 77.3 (m).
(d values) are reported in parts per million (ppm) and trace
amounts of protonated solvents (1H, 13C) or standard resonances
(31P, external 85% H3PO4) were used as references. IR spectra in
the region 200–4000 cm-1 were recorded on a Perkin-Elmer 883
spectrophotometer. The samples were prepared as Nujol mulls
and the spectra were collected on Nujol/polyethylene.
[Nb(g5-C5H4SiMe3)2(P(H)Ph2)(L)][MCl6], M = Nb, L = CO (7),
CNXylyl (8); M = Ta, L = CO (9), CNXylyl (10). A saturated
solution of complexes 3–6 (ca. 1 mmol) in chloroform yielded red
crystals after three days at room temperature. The red crystals were
filtered off and dried under vacuum, yielding the new niobocene
5
complexes [Nb(h -C5H4SiMe3)2(P(H)Ph2)(L)][MCl6] [M = Nb, L =
Preparations
CO (7), CNXylyl (8); M = Ta, L = CO (9), CNXylyl (10)].
Complexes 7–10 can also be obtained by reaction of a solution
[{Nb(g5-C5H4SiMe3)2(L)}(l-PPh2)(MCl5)], M = Nb, L = CO
(3), CNXylyl (4); M = Ta, L = CO (5), CNXylyl (6). A solution
5
7a
of complex [Nb(h -C5H4SiMe3)2(P(H)Ph2)(L)]Cl
(L = CO,
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CNXylyl) in anhydrous chloroform (30 mL) with stoichiometric
amounts of MCl5 (M = Nb or Ta). The reaction mixture was stirred
for 1 h and the resulting red precipitate was filtered off and dried
under vacuum, yielding the new complexes 7–10 in ca. 90% yield.
7 and 9: 7: (0.80 g, 90%). Found: C, 39.55; H, 4.02; Calc. for
C29H37Cl6Nb2OPSi2: C, 39.26; H, 4.20%. 9: (0.87 g, Yield: 90%)
Found: C, 35.47; H, 3.65; Calc. for C29H37Cl6NbOPSi2Ta: C, 35.71;
H, 3.82%; IR (Nujol/polyethylene): n (cm-1); 1941 (CO), 2280
0.04, 0.08 (s, 9H, SiMe3), 1.85 (m, 4H, CH2 of thf), 2.34, 2.50 (3H,
CH3 of CNXylyl), 3.86 (m, 4H, CH2O of thf), 4.58, 4.86, 5.12,
5.25, 5.27, 5.33, 5.64, 5.79 (m, 1H, C5H4), 7.20 (s, 2H, Ph), 7.26
1
(s, 3H, Ph), 7.49 (m, 8H, Ph). 13C{ H} NMR (CDCl3): d (ppm);
0.2, 0.9 (SiMe3), 19.1 (CH3 of CNXylyl), 25.5 (CH2 of thf), 68.6
(CH2O of thf), 91.2, 93.0, 99.8, 100.1, 100.5, 101.1, 101.9, 102.3,
1
103.8 (C5H4), 128.9–132.3 (Ph). 31P{ H} NMR (CDCl3): d (ppm);
34.2 (s). 31P NMR (CDCl3): d (ppm); 34.2 (m).
1
(P–H). H NMR (CDCl3): d (ppm); 0.07 (s, 18H, SiMe3), 5.35
(m, 4H, C5H4), 5.66, 6.00 (m, 2H, C5H4), 7.25 (m, 10H, C6H5),
Synthesis of [{Nb(g5-C5H4SiMe3)2(L)}(l-PPh2)(MCl4)], M =
Ti, L = CO (13), CNXylyl (14). An appropriate volume of
titanium tetrachloride (r = 1.73 g mL; 0.12 g, 0.34 mmol for
1; 0.14 g; 0.75 mmol for 2) was added in 1 : 1 molar ratio to a
cooled (-78 ◦C) solution of 1 (0.21 g, 0.34 mmol) or 2 (0.55 g,
0.75 mmol) in anhydrous hexane (30 mL). The solution became
green. The reaction mixtures were kept at low temperature for 1 h
(until a red precipitate appeared) and were then allowed to reach
room temperature. The solid was filtered off and washed twice with
anhydrous hexane (10 mL) and dried under vacuum. Complexes
13 and 14 were isolated as orange-red and red solids, respectively,
in ca. 83% yield.
1
1
7.30 (d, JHP = 367.6 Hz, PHPh2). 13C{ H} NMR (CDCl3): d
(ppm); -0.1 (SiMe3), 97.0, 98.0, 99.1, 99.6 (C5H4), 101.3 (C1 of
3
C5H4), 129.3 (d, JCP = 9.90 Hz, C6H5), 130.9 (C6H5), 132.4 (d,
2JCP = 9.90 Hz, C6H5), 130.4 (d, JCP = 43.49 Hz, Cipso of C6H5),
1
250.0 (CO). 31P{ H} NMR (CDCl3): d (ppm); 27.6 (s). 31P NMR
1
(CDCl3): d (ppm); 27.7 (d, 1JPH = 367.6 Hz).
8 and 10: 8: (0.88 g, 90%) Found: C, 45.47; H, 4.65; Calc. for
C37H46Cl6Nb2PSi2: C, 45.51; H, 4.75%. 10: (0.96 g, Yield: 90%)
Found: C, 41.67; H, 4.23; Calc. for C37H46Cl6NbPSi2Ta: C, 41.75;
H, 4.36%; IR (Nujol/polyethylene): n (cm-1); 2280 (P–H), 2058
1
(C N). H NMR (CDCl3): d (ppm); 0.17 (s, 18H, SiMe3), 2.31
[CN(2,6-Me2C6H3)], 5.36 (m, 2H, C5H4), 5.55 (m, 2H, C5H4),
13. (0.24 g, 83%) Found: C, 45.42; H, 4.81%. Calc.
6.65 (m, 2H, C5H4), 6.11 (m, 2H, C5H4), 7.35 (m, 13H, C6H5 and
for C29H36Cl4NbOPSi2Ti: C, 45.22; H, 4.71%. IR (Nu-
1
1
C6H3), 8.70 (d, 1JHP = 387.0 Hz, PHPh2). 13C{ H} NMR (CDCl3):
jol/polyethylene): n (cm-1); 1956 (C O). H NMR (CDCl3): d
d (ppm); -0.1 (SiMe3), 19.4 (CH3 of CNXylyl), 92.3, 100.0, 100.8,
102.4 (C5H4), 100.2 (C1 of C5H4), 127.6 (d, 3JCP = 9.83 Hz, C6H5),
(ppm); 0.26 (s, 18H, SiMe3), 4.44, 5.39, 5.62, 5.91 (m, 2H, C5H4),
1
7.55 (m, 10H, Ph). 31P{ H} NMR (CDCl3): d (ppm); 157.2 (s). 31
P
2
1
129.0 (C6H5), 133.0 (d, JCP = 9.90 Hz, C6H5), 132.5 (d, JCP
=
NMR (CDCl3): d (ppm); 157.2 (m).
43.49 Hz, Cipso of C6H5), 248.0 (CNXylyl). 31P{ H} NMR (CDCl3):
1
14. (0.57 g, 84%) C, 50.99; H, 5.24; N 1.61%. Calc. for
d (ppm); 38.50 (s). 31P NMR (CDCl3): d (ppm); 38.50 (d, JPH
=
1
C37H45Cl4NNbPSi2Ti: C, 50.88; H, 5.19; N 1.60%. IR (Nu-
387.0 Hz).
1
jol/polyethylene): n (cm-1); 2073 (C N). H NMR (CDCl3): d
Synthesis of [Nb(g5-C5H4SiMe3)2(P(Cl)Ph2)(L)][NbCl4O(thf)],
L = CO (11), CNXylyl (12). A solution of 1 (0.31 g, 0.50 mmol)
or 2 (0.42 g, 0.58 mmol) in anhydrous thf (30 mL) was added
to a cooled (-78 ◦C) 1 : 1 stoichiometric suspension of niobium
pentachloride (0.14 g, 0.50 mmol for 1; 0.16 g, 0.58 mmol, for 2)
in the same solvent. The reaction mixture, which was deep green,
was allowed to reach room temperature and stirred for 1 h (until
a red solid appeared). The solid was filtered off and washed twice
with anhydrous hexane (10 mL). The red solids were dried under
vacuum, yielding the new complexes 11 and 12.
Complex 11 can also be obtained by stirring a solution of
complex 3 in anhydrous thf (30 mL) for 30 min. The resulting
red solid was filtered off and washed twice with anhydrous hexane
(10 mL). The product was isolated in 90% yield and corresponded
with complex 11.
(ppm); 0.27 (s, 18H, SiMe3), 2.50 (6H, CH3 CNXylyl), 4.63, 5.75
1
(m, 2H, C5H4), 5.30 (m, 4H, C5H4), 7.36 (m, 13H, Ph). 13C{ H}
NMR (CDCl3): d (ppm); 0.3 (SiMe3), 19.5 (CH3 CNXylyl), 92.3,
100.0, 100.2, 101.3 (C5H4), 128.8, 131.1, 132.5, 132.6 (Ph), 129.6
2
1
(d, JCP = 9.21 Hz, Ph), 195.7 (CN) 31P{ H} NMR (CDCl3): d
(ppm); 166.1 (s). 31P NMR (CDCl3): d (ppm); 166.1 (m).
Synthesis of [{Nb(g5-C5H4SiMe3)2(L)}(l-PPh2)(MCl4)], M =
Zr, L = CO (15), CNXylyl (16). A suspension of zirconium
tetrachloride (0.16 g, 0.70 mmol for 1, 0.15 g, 0.63 mmol for 2) in
◦
anhydrous hexane was added to a cooled (-78 C) solution of 1
(0.44 g, 0.70 mmol) or 2 (0.45 g, 0.63 mmol) in anhydrous hexane
(30 mL). After the appropriate workup (see complexes 13 and 14),
orange-red solids corresponding to 15 and 16 were isolated in ca.
80% yield.
15. (0.50 g, 81%). C, 42.81; H, 4.71%. Calc.
for C29H36Cl4NbOPSi2Zr: C, 42.93; H, 4.79%; IR
(Nujol/polyethylene): n (cm-1); 1949 (C O). 1H NMR (CDCl3):
d (ppm); 0.27 (s, 18H, SiMe3), 4.65, 5.25, 5.35, 5.63 (m, 2H,
11. (0.42 g, 90%) Found: C, 41.98; H, 4.67; Calc. for
C33H44Cl5Nb2O3PSi2: C, 42.21; H, 4.72%; Electric conductivity:
KM(X-1 cm2 mol-1); 116.4. IR (Nujol/polyethylene): n (cm-1); 1950
(C O), 955 (Nb O). 1H NMR (CDCl3): d (ppm); 0.25, 0.26 (s,
9H, SiMe3), 1.84 (m, 4H, CH2 of thf), 3.89 (m, 4H, CH2O of
thf), 4.58, 4.68, 5.30, 5.32, 5.48, 5.57 (m, 1H, C5H4), 5.67 (m, 2H,
1
C5H4), 6.95 (m, 10H, Ph). 31P{ H} NMR (CDCl3): d (ppm); 28.7
(s). 31P NMR (CDCl3): d (ppm); 28.7 (m).
16. (0.48 g, 81%). C, 48.82; H, 4.99; N 1.58%. Calc. for
1
C5H4), 7.39 (m, 10H, Ph). 31P{ H} NMR (CDCl3): d (ppm); 27.1
C37H45Cl4NNbPSi2Zr: C, 48.74; H, 4.95; N 1.53%. IR (Nu-
(s). 31P NMR (CDCl3): d (ppm); 27.1 (m).
1
jol/polyethylene): n (cm-1); 2058 (C N). H NMR (CDCl3): d
12. (0.54 g, 89%) Found: C, 47.02; H, 5.06; N, 1.31; Calc.
for C41H53Cl5NNb2O2PSi2: C, 47.26; H, 5.13; N, 1.34%; Electric
conductivity: KM(X-1 cm2 mol-1); 121.0. IR (Nujol/polyethylene):
n (cm-1); 2067 (C N), 957 (Nb O). 1H NMR (CDCl3): d (ppm);
(ppm); 0.27 (s, 18H, SiMe3), 2.50 (6H, CH3 CNXylyl), 4.70, 5.29,
5.31, 5.71 (m, 2H, C5H4), 7.24 (s, 3H, Ph), 7.48 (m, 6H, Ph), 7.54
1
(m, 4H, Ph). 13C{ H} NMR (CDCl3): d (ppm); 0.3 (SiMe3), 19.5
(CH3 CNXylyl), 91.6, 100.1, 100.3, 100.8 (C5H4), 128.7, 132.6,
2628 | Dalton Trans., 2011, 40, 2622–2630
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1
132.7, 134.1 (Ph), 129.5 (d, JCP = 9.49 Hz, Ph), 194.8 (CN). 31P{ H}
Synthesis
of
[Nb(g5-C5H4SiMe3)2(L)(l-PPh2){(Ti(g5-
NMR (CDCl3): d (ppm); 165.8 (s). 31P NMR (CDCl3): d (ppm);
C5R5)Cl3}], R = CH3, L = CO (19), CNXylyl (20). The
same procedure was performed as for the synthesis of
complexes 17 and 18, starting with solutions of 1 (0.38 g,
0.61 mmol) or 2 (0.34 g, 0.47 mmol) and solutions of
pentamethylcyclopentadienyltrichlorotitanium(IV)
0.61 mmol for 1, 0.13 g, 0.47 mmol for 2). Red solids
corresponding to 19 and 20 were isolated in ca. 87% yield.
165.8 (m).
Synthesis
of
[Nb(g5-C5H4SiMe3)2(L)(l-PPh2){(Ti(g5-
(0.18
g,
C5R5)Cl3}], R = H, L = CO (17), CNXylyl (18). A solution of
cyclopentadienyltrichlorotitanium(IV) (0.13 g, 0.59 mmol for 1,
0.15 g, 0.70 mmol for 2) in anhydrous hexane was added to a
cooled (-78 ◦C) solution of 1 (0.36 g, 0.59 mmol) or 2 (0.51 g,
0.70 mmol) in anhydrous hexane (30 mL). After the appropriate
workup (see complexes 13 and 14) red solids corresponding to 17
and 18 were isolated in ca. 86% yield.
19. (0.48 g, 88%) Found: C, 51.92; H, 5.72; Calc.
for C39H51Cl4NbOPSi2Ti: C, 51.73; H, 5.68%; IR (Nu-
jol/polyethylene): n (cm-1); 1944 (C O). 1H NMR (C6D6): d
(ppm); 0.14 (s, 18H, SiMe3), 2.19 (s, 15H, C5Me5), 4.48, 5.88,
5.97, 6.87 (m, 2H, C5H4), 6.95 (t, 4H, JHP = 6.59 Hz, Ph), 7.14 (m,
4H, Ph), 7.74 (t, 2H, JHP = 8.06 Hz, Ph). 31P{ H} NMR (C6D6): d
1
17. (0.42 g, 86%) Found: C, 49.12; H, 5.02; Calc.
for C34H41Cl4NbOPSi2Ti: C, 49.05; H, 4.95%. IR (Nu-
jol/polyethylene): n (cm-1); 1944 (C O). 1H NMR (C6D6): d
(ppm); 0.07 (s, 18H, SiMe3), 4.28, 5.31, 5.60, 5.94 (m, 2H, C5H4),
(ppm); 21.6 (s). 31P NMR (C6D6): d (ppm): 21.6 (m).
20. (0.41 g, 86%) Found C, 56.05; H, 6.03; N, 1.41; Calc.
for C47H60Cl4NNbPSi2Ti: C, 55.96; H, 6.00; N,1.39%; IR (Nu-
jol/polyethylene): n (cm-1); 2056 (C N). 1H NMR (C6D6): d
(ppm); 0.12 (s, 18H, SiMe3), 2.03 (s, 15H, C5Me5), 2.20 (s, 6H,
CH3 CNXylyl), 5.25, 5.90 (m, 2H, C5H4), 5.69 (m, 4H, C5H4),
1
6.75 (s, 5H, C5H5), 6.89 (s, 2H, Ph), 7.36 (s, 8H, Ph). 31P{ H}
NMR (C6D6): d (ppm); 26.6 (s). 31P NMR (C6D6): d (ppm); 26.6
(m).
6.78 (s, 3H, Ph), 7.03 (m, 6H, Ph), 7.84 (m, 4H, Ph). 31P{ H}
1
18. (0.57 g, 87%) Found: C, 53.63; H, 5.24; N, 1.42; Calc.
for C42H50Cl4NNbPSi2Ti: C, 53.75; H, 5.37; N 1.49%. IR (Nu-
jol/polyethylene): n (cm-1); 2061 (C N). 1H NMR (C6D6): d
(ppm); 0.01 (s, 18H, SiMe3), 2.14 (s, 6H, CH3 CNXylyl), 4.90,
5.31, 5.34, 5.71 (m, 2H, C5H4), 6.40 (s, 5H, C5H5), 6.76 (s, 4H,
Ph), 6.95 (s, 2H, Ph), 7.04 (t, 4H, JHP = 6.95 Hz, Ph), 7.65 (m,
NMR (C6D6): d (ppm); 12.8 (s). 31P NMR (C6D6): d (ppm); 12.8
(m).
Crystallographic data
Crystals of compound 9 were of poor quality. We have attempted
to repeat the crystallization many times and we have mounted
several crystals, but we were unable to obtain better data. However,
considering the importance of the structure, it was solved despite
the aforementioned problems. Data for complexes 9 and 12 were
5H, Ph). 13C{ H} NMR (C6D6): d (ppm); 0.3 (SiMe3), 19.7 (CH3
1
CNXylyl), 92.3, 100.0, 100.2, 101.3 (C5H4), 121.8 (C5H5), 127.0,
128.7, 130.6, 131.8, 132.0 (Ph), 196.0 (CN). 31P{ H} NMR (C6D6):
1
d (ppm): 20.1 (s). 31P NMR (C6D6): d (ppm); 20.1 (m).
Table 4 Crystal data and structure refinement for complexes 9 and 12
Complex
9
12
Empirical formula
MW
C29H37Cl6NbOPSi2Ta
975.30
C41H53Cl5NNb2O2PSi2
1042.06
T/K
250(2)
0.71073
180(2)
0.71073
˚
Wavelength/A
Crystal system
Monoclinic
P21
Triclinic
P1
¯
Space group
˚
a/A
10.515(3)
12.939(3)
13.888(4)
90
95.035(6)
90
1882.1(9)
2
1.721
12.025(2)
12.159(2)
15.964(2)
90.091(2)
93.465(2)
90.778(3)
2329.5(6)
2
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
Volume/A
Z
Density (calcd)/g cm-3
m/cm-1
1.486
0.899
1064
3.764
956
F(000)
Crystal size/mm
Index ranges
0.43 ¥ 0.17 ¥ 0.13
-9 £ h £ 9
-12 £ k £ 12
-12 £ l £ 13
6395
0.53 ¥ 0.25 ¥ 0.18
-12 £ h £ 12
-12 £ k £ 12
-16 £ l £ 16
10199
Reflections collected
Independent reflections
No. of data/restraints/params.
Goodness-of-fit on F2
3206 [R(int) 0.0973]
3206/61/266
1.044
R1 = 0.0723
wR2 = 0.1344
0.889 and -0.509
5041 [R(int) 0.0503]
5041/18/495
1.314
R1 = 0.0760
wR2 = 0.2046
0.973 and -1.297
Final R indices [I > 2s(I)]
-3
˚
Largest diff peak hole/e A
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 2622–2630 | 2629
©

View Article Online
collected on a Bruker X8 APPEX II CCD-based diffractometer,
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equipped with a graphite-monochromated Mo-Ka radiation
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˚
source (l = 0.71073 A). The crystal data, data collection, structural
solution, and refinement parameters are summarized in Table 4.
Data were integrated using SAINT22 and an absorption correction
was performed with the program SADABS.23 The structure was
solved by direct methods using SHELXTL24 and refined by full-
matrix least-squares methods based on F2. All non-hydrogen
atoms were refined with anisotropic thermal parameters (except
aromatic rings in complex 9, which were refined isotropically).
Hydrogen atoms were placed using a “riding model” and included
in the refinement at calculated positions.
Acknowledgements
The authors gratefully acknowledge financial support from
the Ministerio de Ciencia e Innovacio´n, Spain (Grant Nos.
Consolider-Ingenio 2010 ORFEO CSD 2007-00006, CTQ2008-
00318/BQU, CTQ2009-09214), UE action COST CM0802 and
the Junta de Comunidades de Castilla–La Mancha (Grant. Nos.
PCI08-0010, PCIO8-0032).
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2630 | Dalton Trans., 2011, 40, 2622–2630
This journal is
The Royal Society of Chemistry 2011
©