2-indenylidene pincer complexes of zirconium and palladium

Article abstract of DOI:10.1021/ja809892a

[IndH₂(Ph₂PdX) ₂] derivatives (1, X) NMes; 4, X) = react with [Zr(NMe₂)₄] and [PdCl₂ (cod)] to afford the complexes {[Ind(Ph₂PNMes) ₂] Zr(NMe₂)₂}

Full text of DOI:10.1021/ja809892a

Published on Web 02/20/2009
2-Indenylidene Pincer Complexes of Zirconium and Palladium
Pascal Oulie´,† Noel Nebra,† Nathalie Saffon,‡ Laurent Maron,*,§
Blanca Martin-Vaca,*,† and Didier Bourissou*,†
UniVersite´ de Toulouse, UPS, Laboratoire He´te´rochimie Fondamentale et Applique´e (LHFA),
118 route de Narbonne, F-31062 Toulouse, France, CNRS, LHFA UMR 5069,
F-31062 Toulouse, France, UniVersite´ de Toulouse, UPS, Structure Fe´de´ratiVe Toulousaine en
Chimie Mole´culaire, FR2599, 118 Route de Narbonne, F-31062 Toulouse, France, and
UniVersite´ de Toulouse, INSA, UPS, Laboratoire de Physique et Chimie des Nanoobjets
(LPCNO), 135 aVenue de Rangueil, F-31077 Toulouse, France, CNRS, LPCNO UMR 5215,
F-31077 Toulouse, France
Received May 30, 2008; E-mail: dbouriss@chimie.ups-tlse.fr
Abstract: [IndH2(Ph2PdX)2] derivatives (1, X ) NMes; 4, X ) S) react with [Zr(NMe2)4] and [PdCl2(cod)]
to afford the complexes {[Ind(Ph2PNMes)2]Zr(NMe2)2} (3), {[Ind(Ph2PS)2]Zr(NMe2)2} (5), and {[Ind(Ph2PS)2]-
Pd(HNc-Hex2)} (7). The ability of the phosphazene and thiophosphinoyl side arms to support the coordination
of the indenyl ring as 2-indenylidene was evidenced by NMR spectroscopy and X-ray diffraction studies.
Analysis of the bonding situation by density functional theory calculations revealed a strong σ interaction
but a negligible (if any) π interaction between C2 and the metal.
Chart 1
Introduction
Intrigued by the ability of cyclopentadienyl (Cp)-type rings
to adopt unusual coordination modes, we recently showed that
the introduction of a short and strongly donating phosphazene
moiety may enforce η1 coordination of fluorenyl and indenyl
(Ind) rings to transition metals (Zr and Rh complexes of type
A in Chart 1).1 Such a low hapticity is rare for Cp-type rings2
but opens interesting perspectives because of the increased
accessibility of the metal center.3 Ylidene coordination of Cp-
type rings is even less common. Although related cycloprope-
nylidene complexes have been known for 40 years,4,5 it was
not until 1997 that the related and to date unique Ta cyclopen-
tadienylidene complex I was structurally authenticated.6 In
addition, a few 1-indenylidene Ru complexes of type II have
been prepared by intramolecular cyclization of allenylidene
precursors and have proved to be very efficient catalysts for
olefin metathesis and atom-transfer radical polymerization.7
The spectacular achievements reported over the past two
decades in the synthesis and application of pincer complexes8
prompted us to investigate the preparation of complexes of type
B (Chart 1), in which two donor buttresses would support the
coordination of the 2-indenylidene fragment. In view of the
versatile coordination chemistry reported by Cavell, Le Floch,
and others for pincer methanediide complexes III,9 phosphazene
and thiophosphinoyl moieties were chosen as strongly donat-
ing and easily introduceable side arms for complexes B. Here
we report the synthesis and complete characterization of the
† Laboratoire He´te´rochimie Fondamentale et Applique´e.
‡ Structure Fe´de´rative Toulousaine en Chimie Mole´culaire.
§ Laboratoire de Physique et Chimie des Nanoobjets.
(1) (a) Oulie´, P.; Freund, C.; Saffon, N.; Martin-Vaca, B.; Maron, L.;
Bourissou, D. Organometallics 2007, 26, 6793. (b) Freund, C.; Barros,
N.; Gornitzka, H.; Martin-Vaca, B.; Maron, L.; Bourissou, D.
Organometallics 2006, 25, 4927.
(2) (a) Alt, H. G.; Samuel, E. Chem. Soc. ReV. 1998, 27, 323. (b) Stradiotto,
M.; McGlinchey, M. J. Coord. Chem. ReV. 2001, 219-221, 311. (c)
Kirillov, E.; Saillard, J.-Y.; Carpentier, J.-F. Coord. Chem. ReV. 2005,
249, 1221.
(3) (a) Irwin, L. J.; Reibenspies, J. H.; Miller, S. A. J. Am. Chem. Soc.
2004, 126, 16716. (b) Irwin, L. J.; Miller, S. A. J. Am. Chem. Soc.
2005, 127, 9972. (c) Schwerdtfeger, E. D.; Miller, S. A. Macromol-
ecules 2007, 40, 5662. (d) Schwerdtfeger, E. D.; Irwin, L. J.; Miller,
S. A. Macromolecules 2008, 41, 1080.
(7) (a) Dragutan, V.; Dragutan, I.; Verpoort, F. Platinum Metals ReV. 2005,
49, 33. (b) Boeda, F.; Clavier, H.; Nolan, S. P. Chem. Commun. 2008,
2726.
(8) (a) The Chemisty of Pincer Compounds; Morales-Morales, D., Jensen,
C., Eds.; Elsevier: Amsterdam, 2007. (b) Albrecht, M.; van Koten,
G. Angew. Chem., Int. Ed. 2001, 40, 3750. (c) van der Boom, M. E.;
Milstein, D. Chem. ReV. 2003, 103, 1759.
(4) For the first cyclopropenylidene complex, see: Ofe¨le, K. Angew. Chem.,
Int. Ed. Engl. 1968, 7, 950.
(5) For the first cyclopropenylidene isolated in the free state, see: Lavallo,
V.; Canac, Y.; Donnadieu, B.; Schoeller, W. W.; Bertrand, G. Science
2006, 312, 722.
(9) (a) Cavell, R. G.; Kamalesh Babu, R. P.; Aparna, K. J. Organomet.
Chem. 2001, 617-618, 158. (b) Jones, N. D.; Cavell, R. G. J.
Organomet. Chem. 2005, 690, 5485. (c) Cantat, T.; Me´zailles, N.;
Auffrant, A.; Le Floch, P. Dalton Trans. 2008, 1957.
(6) Briggs, P. M.; Young, V. G., Jr.; Wigley, D. E. Chem. Commun. 1997,
791.
9
10.1021/ja809892a CCC: $40.75
2009 American Chemical Society
J. AM. CHEM. SOC. 2009, 131, 3493–3498 3493

A R T I C L E S
Oulie´ et al.
Scheme 2
in the 13C NMR spectrum for C2 strongly suggested the
formation of a 2-indenylidene zirconium complex.12 Crystals
of 3 suitable for X-ray diffraction analysis were obtained by
slow diffusion of pentane into a saturated mesitylene solution
at 0 °C, and the obtained structure is shown in Figure 1. The
Zr atom is pentacoordinate and deviates slightly (0.495 Å) from
the (N1, C2, N2) coordination plane defined by the pincer ligand.
The C2-Zr bond deviates by 16° from the mean plane of the
indenyl ring, while C1 and C3 are in perfectly planar environ-
ments. The C2-Zr bond distance [2.221(5) Å] is significantly
longer than those observed in the few structurally characterized
Zr alkylidene complexes (2.01-2.02 Å)12a,b but lies in the same
range as those reported by Cavell and Le Floch for Zr complexes
of type III.13
Figure 1. Molecular structures of complexes 2 (left) and 3 (right). Thermal
ellipsoids are projected at the 50% probability level. Selected bond distances
(Å) and angles (deg) for 2: Zr1-N1, 2.224(3); N1-P1-C1, 103.41(15);
N2-P2-C3, 118.17(16). For 3: Zr1-C2, 2.22(5); Zr1-N1, 2.286(4);
Zr1-N2, 2.262(3); N1-Zr1-N2, 142.87(14).
Scheme 1
The phosphazene groups were then replaced by thiophosphi-
noyl moieties in order to further demonstrate the propensity of
donor side arms to support 2-indenylidene coordination to
zirconium. Thus, [IndH2(Ph2PdS)2] (4)14 was reacted with
[Zr(NMe2)4] in deuterated benzene at 100 °C (Scheme 2). After
5 h of reaction, 31P NMR spectroscopy showed complete
consumption of derivative 4 and the clean formation of a new
compound 5 exhibiting a single signal at 40.1 ppm, indicating
symmetrical coordination of the thiophosphinoyl side arms. The
poor stability of 5 prevented the formation of single crystals
suitable for X-ray diffraction analysis, but its structure was
unambiguously assessed by NMR spectroscopy: (i) the 1H NMR
spectrum indicated the retention of only two NMe2 groups at
Zr, and (ii) a triplet signal at 206.3 ppm (JCP ) 44.5 Hz) was
observed for C2 in the 13C NMR spectrum.
The formation of complexes 3 and 5 substantiates the ability
of donor buttresses to support the coordination of the indenyl
ring to zirconium as a 2-indenylidene. To demonstrate the
generality of this strategy, we then investigated the preparation
of 2-indenylidene complexes with a late transition metal. Only
complex mixtures were obtained from bisphosphazene 1 and
[PdCl2(cod)] (cod ) η4-cycloocta-1,5-diene), whereas a clean
reaction was observed with the related 1,3-bis(thiophosphinoyl)-
indene 414 (Scheme 3). After 10 days at room temperature, 4
was quantitatively converted into complex 6. According to the
two doublet signals observed at 55.9 and 52.2 ppm (JPP ) 3.1
Hz) in the 31P NMR spectrum, both thiophosphinoyl groups are
coordinated to the Pd atom [the 31P NMR spectrum of compound
first representatives of such pincer 2-indenylidene complexes
with Zr and Pd and discuss their bonding situation on the basis
of experimental as well as theoretical data.
Results and Discussion
Synthesis and Characterization of the 2-Indenylidene
Complexes. The Staudinger reaction of 1,3-bis(diphenylphos-
phino)indene10 with 2 equiv of mesityl azide readily afforded
[IndH2(Ph2PdNMes)2] (1) in 70% yield. The broad signal
centered at ∼5 ppm in the 31P NMR spectrum of 1 most likely
results from the coexistence of several tautomeric forms, as
previously observed with monophosphazene Cp and Ind
ligands.1a,11 Coordination to zirconium was then studied by
reacting 1 with [Zr(NMe2)4] (Scheme 1). Elimination of the first
molecule of Me2NH readily proceeded at room temperature to
afford complex 2 having a single phosphazene arm coordinated
to the Zr atom, as indicated by the two 31P NMR signals
observed at 40.2 and -14.8 ppm attributed to the coordinated
and noncoordinated phosphazene moieties, respectively. The
presence of a Cq doublet signal (JCP ) 67.3 Hz) at 74.3 ppm in
the 13C NMR spectrum suggested a low hapticity for the indenyl
fragment. This was unambiguously confirmed by X-ray dif-
fraction analysis (Figure 1). The zirconium atom is tetracoor-
dinate (three NMe2 groups and one of the phosphazene side
arms) and adopts a distorted tetrahedral geometry. The distance
between Zr and C1 (2.94 Å) is significantly longer than those
observed in complexes A (2.51-2.60 Å),1a suggesting a very
weak (if any) interaction.
The removal of a second Me2NH molecule from complex 2
required forcing conditions (heating for 12 h at 120 °C),
consistent with the weak acidity of the hydrogen atom at C2.
The unique sharp 31P NMR signal observed at 30.1 ppm for
the resulting complex 3 was consistent with symmetric coor-
dination of the two phosphazene moieties. In addition, the
diagnostic triplet signal observed at 209 ppm (JCP ) 32.7 Hz)
(12) This chemical shift is in the lower portion of the range of those reported
for alkylidene zirconium complexes (δ 210-230 ppm). See: (a)
Fryzuk, M. D.; Mao, S. S. S. H.; Zaworotko, M. J.; MacGillivray,
L. R. J. Am. Chem. Soc. 1993, 115, 5336. (b) Fryzuk, M. D.; Duval,
P. B.; Mao, S. S. S. H.; Zaworotko, M. J.; MacGillivray, L. R. J. Am.
Chem. Soc. 1999, 121, 2478. (c) Weng, W.; Yang, L.; Foxman, B. M.;
Ozerov, O. V. Organometallics 2004, 23, 4700.
(13) (a) Kamalesh Babu, R. P.; McDonald, R.; Decker, S. A.; Klobukowski,
M.; Cavell, R. G. Organometallics 1999, 18, 4226. (b) Aparna, K.;
Kamalesh Babu, R. P.; McDonald, R.; Cavell, R. G. Angew. Chem.,
Int. Ed. 2001, 40, 4400. (c) Cantat, T.; Ricard, L.; Me´zailles, N.; Le
Floch, P. Organometallics 2006, 25, 6030.
(10) Falls, K. A.; Anderson, G. K.; Rath, N. P. Organometallics 1992, 11,
885.
(11) Petrov, A. R.; Rufanov, K. A.; Ziemer, B.; Neubauer, P.; Kotov, V. V.;
Sundermeyer, J. Dalton Trans. 2008, 909.
(14) Stradiotto, M.; Kozak, C. M.; McGlinchey, M. J. J. Organomet. Chem.
1998, 564, 101.
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2-Indenylidene Pincer Complexes of Zr and Pd
A R T I C L E S
results from π delocalization between C2 and C1/C3, in
agreement with the short bond distances [1.418(7) and 1.425(7)
Å].
Theoretical Study of the 2-Indenylidene Complexes. To shed
some light on the bonding situation in complexes 3, 5, and 7,
density functional theory (DFT) calculations were carried out.19
The key geometric features determined experimentally for the
{[Ind(Ph2PdNMes)2]Zr(NMe2)2} complex 3 were very well
reproduced (with deviations of only 0.01 Å in the C2-Zr bond
distance and 0.05 Å in the N-Zr ones), indicating the ability
of the B3PW91/SDD(Zr, P),6-31G**(other atoms) method in
describing such systems (Table 1). The geometry of the related
{[Ind(Ph2PdS)2]Zr(NMe2)2} complex 5 was optimized at the
same level of theory (Figure 3). The zirconium center adopts a
quasi-ideal trigonal bipyramidal environment, with C2 and the
two NMe2 groups lying in the equatorial plane and the two sulfur
atoms occupying the axial positions. The C2-Zr bond does not
deviate from the indenyl plane, and the C2-Zr bond distance
(2.29 Å) is very similar to that predicted for 3 (2.23 Å). Thus,
the phosphazene and thiophosphinoyl donor side arms induce
rather similar geometries in the zirconium complexes 3 and 5,
with only minor distortions that presumably result from different
steric shielding. The geometry of the corresponding palladium
complex 7 was also very well reproduced at the B3PW91/
SDD(Pd, P),6-31G**(other atoms) level of theory. In particular,
the C2-Pd bond distance predicted theoretically (1.97 Å) is
very close to that determined experimentally [1.984(5) Å]. In
order to take into account the different sizes of the metals
involved, the C2-M bond distances [d(C2-M)] were compared
with the corresponding sums of covalent radii (Rcov).20 Accord-
ingly, the ratio r ) d(C2-M)/∑Rcov falls in the range 0.90-0.93
for all of the complexes, suggesting similar bonding situations.
The atomic charges derived from natural bonding orbital
(NBO) analyses21 of complexes 3, 5, and 7 (Table 2) provide
further insight into the influence of the donor side arm and the
metal. The atomic charges on the indenyl backbone are very
similar in the two zirconium complexes 3 and 5 (ca. -0.45 at
C2 and -0.61 at C1/C3). The atomic charge at zirconium is
positive in both complexes and higher with the phosphazene
than with the thiophosphinoyl side arms (2.21 in 3 vs 1.65 in
5), consistent with the higher electronegativity of nitrogen
relative to sulfur (3.0 for N vs 2.5 for S). In the corresponding
palladium complex, similar negative atomic charges were
predicted at C1/C3 (-0.66). A small negative charge at C2
(-0.09) and a positive charge of 0.44 at palladium were found.
Accordingly, the C2-Pd bond in 7 appears to be less polarized
than the C2-Zr bonds in 3 and 5, in agreement with the
carbon-metal electronegativity differences (∆ꢀC-Pd ) 0.3 vs
∆ꢀC-Zr ) 1.1).
Figure 2. Molecular structure of complex 7. Thermal ellipsoids are
projected at the 50% probability level. Only one of two disordered positions
of the Cy2NH ligand is shown. Selected bonds distances (Å) and angles
(deg): Pd1-C2, 1.984(5); Pd1-S1, 2.340(2); Pd1-S2, 2.336(2); Pd1-N1,
2.279(14); C2-Pd1-N1, 172.7(4); S1-Pd1-S2, 176.3(1).
Scheme 3
4 exhibits two doublets at 30.4 and 45.2 ppm (JPP ) 5.6 Hz)].
The Cq 13C NMR multiplet signal at 182.0 ppm and the CH
doublet of doublets signal at 72.8 ppm (JCP ) 53.9 and 18.1
1
Hz), which is associated with a doublet of doublets H NMR
signal at 5.46 ppm (JHP ) 24.9 and 2.7 Hz), indicate a Pd atom
bonded to the indenyl C2 atom. This fact denotes the preferential
2
3
activation of the Csp -H bond of 4 rather than the Csp -H bond.
Dehydrochlorination of 6 with 2 equiv of Cy2NH (Cy )
cyclohexyl)15 readily afforded the amine complex 7, which was
isolated in 84% yield as an orange powder. The symmetric
structure of 7 was substantiated by the single signal observed
at 41.7 ppm in the 31P NMR spectrum, and the 2-indenylidene
structure of 7 was supported by the low-field triplet at 164.5
ppm (JCP ) 27.5 Hz) observed for C2 in the 13C NMR spectrum.
The molecular structure of complex 7 was definitely confirmed
by X-ray crystallography (Figure 2). The Pd atom is surrounded
by the two sulfur atoms, the nitrogen atom of Cy2NH, and C2,
which are organized in a quasi-ideal square planar arrangement.
The C2-Pd bond length [1.984(5) Å] is very similar to those
observed in the few reported Pd carbene complexes free of
heteroatomic substituents at carbon (1.97-2.00 Å),16 and the
Pd-N bond distance [2.244(15) and 2.279(14) Å for the two
disordered positions] is slightly longer than those reported
recently in [LPd(Ar)X(H2NR)] complexes (2.12-2.14 Å).17 All
of the carbon atoms C1, C2, and C3 remain planar. The planar
environment around C2 in the 2-indenylidene complex 7
contrasts with the pyramidal geometry observed in the related
methanediide complex {(Ph3P)Pd[C(Ph2PS)2]}18 and presumably
The NBO analyses21 also provide a more precise description
of the nature of the C2-Zr and C2-Pd bonds. For the
{[Ind(Ph2PdNMes)2]Zr(NMe2)2} complex 3, a strong σ dona-
tion from C2 to Zr (∼140 kcal/mol) was found at the second-
order donor-acceptor perturbation level. The σ interaction
between C2 and Zr was found at the first-order level for the
related {[Ind(Ph2PdS)2]Zr(NMe2)2} complex 5 but remained
highly polarized (80% C2/20% Zr), in agreement with the
weaker but still significant atomic charge at Zr. For both
complexes, no significant π interaction between C2 and Zr was
(15) The corresponding ammonium salt was readily removed after pre-
cipitation with pentane, thereby facilitating the isolation of the Pd
complex 7.
(16) (a) Bro¨ring, M.; Brandt, C. D.; Stellwag, S. Chem. Commun. 2003,
2344. (b) Weng, W.; Chen, C.-H.; Foxman, B. M.; Ozerov, O. V.
Organometallics 2007, 26, 3315.
(17) (a) Biscoe, M. R.; Barder, T. E.; Buchwald, S. L. Angew. Chem., Int.
Ed. 2007, 46, 7232. (b) Biscoe, M. R.; Fors, B. P.; Buchwald, S. L.
J. Am. Chem. Soc. 2008, 130, 6686.
(19) See the Supporting Information for details.
(20) Cordero, B.; Go´mez, V.; Pletro-Prats, A. E.; Reve´s, M.; Echeverr´ıa,
J.; Cremades, E.; Barraga´n, F.; Alvarez, S. Dalton Trans. 2008, 2832.
(21) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. ReV. 1988, 88, 899.
(18) Cantat, T.; Me´zailles, N.; Ricard, L.; Jean, Y.; Le Floch, P. Angew.
Chem., Int. Ed. 2004, 43, 6382.
9
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A R T I C L E S
Oulie´ et al.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for Complexes 3, 5, and 7a
complex
method
X-M
C2-M
X-P
P-C
X-P-C
∑C1R
∑C3R
∑C2R
C1-C2
C2-C3
3
X-ray
2.262(3)
2.286(4)
2.31
2.31
2.68
2.221(5)
1.644(4)
1.634(4)
1.69
1.68
2.06
1.740(5)
1.734(5)
1.76
1.76
1.76
103.3(2)
104.7(2)
104
104
127
360
360
356
1.405(6)
1.417(6)
DFT
DFT
X-ray
DFT
2.23
360
360
359
360
360
360
360
360
357
360
360
360
1.41
1.41
5
7
2.29
1.42
1.42
2.68
2.06
1.76
127
2.3398(17)
2.3360(17)
2.36
1.984(5)
1.97
2.0297(19)
2.030(2)
2.07
1.719(6)
1.714(5)
1.75
105.13(19)
106.39(19)
106
1.418(7)
1.42
1.425(7)
1.42
2.36
2.07
1.75
106
a For 3, M ) Zr and X ) N; for 5, M ) Zr and X ) S; for 7, M ) Pd and X ) S. The DFT calculations were performed at the B3PW91/SDD(Zr,
Pd, P),6-31G**(other atoms) level of theory.
Figure 3. Structure of complex 5 optimized at the B3PW91/SDD(Zr, P),6-
31G**(other atoms) level of theory. Hydrogen atoms have been omitted.
Table 2. NBO Atomic Charges for Complexes 3, 5, and 7a
complex
M
C2
X
P
C1/C3
3
5
7
2.21
1.65
0.44
-0.47
-0.41
-0.09
-1.18
-0.54
-0.55
2.03
1.62
1.64
-0.61
-0.61
-0.66
a For 3, M ) Zr and X ) N; for 5, M ) Zr and X ) S; for 7, M )
Pd and X ) S.
Table 3. Wiberg Indices for Complexes 3, 5, and 7
complex
M-C2
C2-C1/C3
3
0.57
1.34
1.34
1.34
1.34
1.35
1.35
5
7
0.63
0.66
Figure 4. Kohn-Sham representations of selected molecular orbitals for
complexes 3, 5, and 7.
identified. As expected, a highly covalent σ bond was found
between C2 and Pd in the corresponding {[Ind(Ph2PdS)2]Pd-
(NHCy2)} complex 7 (53% C2/47% Pd), but in this case as
well, no π interaction between C2 and Pd was found. Overall,
the three complexes 3, 5, and 7 thus exhibit similar bonding
situations, with strong σ bonding but weak (if any) π interactions
between C2 and M. This is reminiscent of the bonding found
in pincer complexes of type III.22
This bonding situation was further confirmed by computing
Wiberg indices23 (Table 3). The values found for the C2-M
bonds in complexes 3, 5, and 7 (0.57-0.66) fall in the same
range as those computed for the methanediide complexes
{(Ph3P)2Ru[C(Ph2PdS)2]} (0.67)22b and {(Me3SiCH2)(THF)-
Y[C(Ph2PdNSiMe3)2]} (0.606)22d and are consistent with
essentially single bonds. In addition, bond orders of 1.34-1.35
were found between C2 and C1/C3, indicating some multiple-
bond character.
The molecular orbitals of the zirconium complexes 3 and 5
confirmed the π interactions of C2 with C1 and C3 and the
absence of π interactions between C2 and Zr. Indeed, the
HOMO-1 orbitals (Figure 4) display π interactions between
C2 and C1/C3, but no bonding molecular orbital displaying a
π interaction between C2 and Zr was found. For the palladium
complex 7, the HOMO-19 and HOMO-1 orbitals both display
π interactions between C2 and C1/C3, but they differ in the
bonding versus antibonding π overlap between C2 and Pd
(Figure 4). This is consistent with the essentially single-bond
character of the C2-Pd bond.24
Lastly, atoms in molecules (AIM)25 calculations show the
presence of a bond critical point between C2 and M in all of
(22) For theoretical studies of the bonding situation in pincer complexes
of type III, see: (a) Smurnyy, Y.; Bibal, C.; Pink, M.; Caulton, K. G.
Organometallics 2005, 24, 3849. (b) Cantat, T.; Demange, M.;
Me´zailles, N.; Ricard, L.; Jean, Y.; Le Floch, P. Organometallics 2005,
24, 4838. (c) Orzechowski, L.; Jansen, G.; Harder, S. J. Am. Chem.
Soc. 2006, 128, 14676. (d) Liddle, S. T.; McMaster, J.; Green, J. C.;
Arnold, P. L. Chem. Commun. 2008, 1747, and refs 13c and 18.
(23) Wiberg, K. B. Tetrahedron 1968, 24, 1083.
(24) Similarly, two occupied molecular orbitals involving π and π* C-Pd
interactions were found in the methanediide complex {(Ph3P)Pd-
[C(Ph2PdS)2]}.18
(25) Bader, R. F. W. Atoms in Molecules: A Quantum Theory; Oxford
University Press: Oxford, U.K., 1990.
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2-Indenylidene Pincer Complexes of Zr and Pd
A R T I C L E S
3.52 (broad s, 1H, NH), 2.15 (s, 6H, CH3paraMes), 2.02 (s, 12H,
CH3orthoMes). 13C{1H} NMR (75.5 MHz, C6D6, 300 K): δ 140.0
the complexes 3, 5, and 7, with bond ellipticities (0.11 for 3,
0.12 for 5, and 0.04 for 7) similar to that found by Caulton and
co-workers22a in the ruthenium methanediide complex {(p-
cymene)Ru[C(Ph2PdNPh)2]} (0.04) and consistent with es-
sentially σ bonding.26
2
2-3
(t, JCP ) 14.4 Hz, C2Ind), 138.2 (pseudo-t,
J
) 14.8 Hz,
CP
2
C4,9Ind), 135.3 (CipsoMes), 132.9 (d, JCP ) 10.0 Hz, CorthoPhP),
131.1 (CparaPhP), 129.1 (CmetaMes), 128.0 (d, JCP ) 12.6 Hz,
2
CmetaPhP), 119.9 (C5,8Ind), 119.2 (C6,7Ind), 20.6 (CH3paraMes), 20.5
(CH3orthoMes), C1,3 not observed. Mp: 119-220 °C. Anal. Calcd
for C51H48N2P2: C, 81.58; H, 6.44; N, 3.73. Found: C, 81.84; H,
6.69; N, 3.36.
Conclusion
The first 2-indenylidene complexes were obtained from
pincer-type ligands. Both phosphazene and thiophosphinoyl
groups were shown to support 2-indenylidene coordination to
zirconium. The two zirconium complexes 3 and 5 exhibit similar
structures, indicating only a small, essentially steric influence
of the donor side arms. In addition, the 1,3-bis(thiophosphi-
noyl)indene 4 provided access to the 2-indenylidene palladium
complex 7. DFT calculations, including NBO and AIM analyses,
revealed similar bonding situations in these three complexes,
with strong σ bonding but weak (if any) π interactions between
C2 and M. Accordingly, the 2-indenylidene coordination in the
zirconium and palladium complexes 5 and 7 differs only in the
polarization of the C2-M σ bond. Current efforts aim at (i)
further extending the variety of metal fragments and (ii)
extrapolating the strategy to the preparation of fluorenylidene
pincer complexes.27
Synthesis of Zr(NMe2)3[IndH(Ph2PdNMes)2] (2). A mixture
of 1 (746 mg, 0.99 mmol) and [Zr(NMe2)4] (267 mg, 1.00 mmol)
in toluene (4 mL) was stirred at room temperature for 5 min. 31P
NMR spectroscopy revealed quantitative conversion of 1 into
complex 2, which was obtained as a pale-green powder after
removal of the volatiles. Compound 2 was characterized by NMR
spectroscopy and employed in the next reaction without further
purification. 31P{1H} NMR (202.3 MHz, C6D6): δ 40.2 (s, coor-
1
dinated PdNMes), -14.8 (s, free PdNMes). H NMR (500.3
MHz, C6D6): δ 8.10 (m, 1H, H ), 7.95-7.90 (m, 4H, HorthoPhP),
2
3
7.89 (d, JHH ) 7.8 Hz, 1H, H8), 7.25-7.20 (m, 4H, HorthoPhP),
7.14-7.00 (m, 6H, HmetaPhP), 7.00-6.90 (m, 10H, HMes, HmetaPhP,
HparaPhP, H7), 6.87 (m, 1H, H6), 6.68 (s, 2H, HMes), 6.50 (d, 3JHH
) 8.1 Hz, 1H, H5), 2.67 (s, 18H, N Me2), 2.27 (d, 3 JHP ) 2.7 Hz,
3
3H, CH3paraMes), 2.19 (d, J ) 1.5 Hz, 6H, CH3orthoMes), 2.09
HP
3
(d, JHP ) 2.1 Hz, 3H, CH3paraMes), 1.94 (s br, 6H, CH3orthoMes).
13C{1H} NMR (125.8 MHz, C6D6): δ 146.0 (CipsoMes), 140.7 (m,
1
C3), 139.7 (CipsoMes), 139.0 (m, C2), 136.6 (C qMes), 135.8 (d, J
Experimental Section
CP ) 92.6 Hz, CipsoPhP), 134.0 (CqMes), 132.6 (d, 2JCP ) 10.0 Hz,
2
All of the reactions were performed using standard Schlenk
CorthoPhP), 132.3 (d, JCP ) 9.5 Hz, C orthoPhP), 132.0 (CparaPhP),
1
techniques under an argon atmosphere. 31P, H, and 13C spectra
130.0 (CparaPhP), 129.8 (d, 3JCP ) 3.0 Hz, CHMes), 128.6 (d, 3 JCP
3
were recorded on Bruker Avance 300 or 400 and AMX500
spectrometers. 31P, 1H, and 13C chemical shifts are expressed with
a positive sign in parts per million relative to external 85% H3PO4
and Me4Si. Unless otherwise stated, NMR was recorded at 293 K.
THF, mesitylene, and toluene were dried under sodium and distilled
prior to use. All of the organic reagents were obtained from
commercial sources and used as received, except for dicyclohexy-
lamine, which was distilled over KOH. [Pd(cod)Cl2] and
[Zr(NMe2)4] were purchased from Strem Chemicals, stocked in the
dark in a glovebox and used without further purification. Mesityl
azide,28 1,3-bis(diphenylphosphino)indene,10 and 1,3-bis(diphe-
nylthiophosphinoyl)indene 414 were prepared according to literature
procedures. The N values corresponding to 1/2(JAX + JAX′) are
provided when second-order AXX′ systems were observed in the
13C NMR spectra.29
) 3.0 Hz, CHMes), 128.4 (d, JCP ) 9.5 Hz, CmetaPhP), 127.8
(overlapped with C6D6, CmetaPhP), 122.7 (C8), 120.7 (br, C6, C7),
3
119.5 (C ), 74.3 (d, J ) 67.3 Hz, C1), 42.3 (NMe2), 21.1 (br,
CH3orthoMes), 21.0 (br, CH3paraMes), C4,9 not observed.
5
CP
Synthesis of Zr(NMe2)2[Ind(Ph2PdNMes)2] (3). A solution of
2 (880 mg, 0.9 mmol) in mesitylene (4 mL) was heated overnight
at 120 °C. 31P NMR spectroscopy revealed quantitative conversion
of complex 2 into complex 3, which was obtained as a pale-green
powder after removal of the volatiles. Slow diffusion of pentane
in a mesitylene solution of 3 at 0 °C afforded crystals of 3 suitable
for X-ray diffraction analysis (151 mg, 18% yield, as a result of
the high solubility of 3). 31P{1H} NMR (202.3 MHz, C6D6): δ 30.1.
1H{31P} NMR (500.3 MHz, C6D6): δ 7.90 (d, 3JHH ) 7.5 Hz, 3JHP
) 12.0 Hz, 8H, HorthoPhP), 7.62 (m, 2H, H5,8), 7.26 (m, 2H, H6,7),
6.96 (t, 3JHH ) 7.5 Hz, 4H, HparaPhP), 6.89 (t, 3JHH ) 7.5 Hz, 8H,
HmetaPhP), 6.77 (s, 4H, HmetaMes), 2.56 (s, 12H, NMe2), 2.26 (s,
6H, CH3paraMes), 2.07 (s, 12H, CH3orthoMes). 13C{1H} NMR (125.8
Synthesis of IndH2[Ph2PdNMes]2 (1). A degassed solution of
MesN3 (1.045 g, 6.48 mmol) in toluene (5 mL) was added dropwise
at 0 °C to a degassed suspension of [IndH2(PPh2)2] (1.57 g, 3.24
mmol) in toluene (20 mL). After the mixture was stirred for 1 h at
room temperature, 20 mL of pentane was added, and the reaction
medium was then cooled at -20 °C overnight to favor complete
precipitation of the product. The solvent was eliminated by filtration
to yield a pale-yellow solid, which was washed with cold pentane
(2 × 20 mL). Yield: 1.70 g (70%). 31P{1H} NMR (121.5 MHz,
MHz, C6D6): δ 209.0 (t, 2JCP ) 32.7 Hz, C2), 142.9 (d, 2JCP ) 6.3
3
Hz, CipsoMes), 139.0 (AXX′, N ) 18.9 Hz, C4,9), 136.9 (d, JCP
)
1
5.0 Hz, CorthoMes), 134.2 (d, JCP ) 86.8 Hz, CipsoPh), 133.2 (d,
2JCP ) 10.1 Hz, CorthoPh), 131.9 (d, 5JCP ) 3.8 Hz, CparaMes), 129.1
(CmetaMes), 128.2 (CparaPhP), 127.9 (CmetaPhP), 119.9 (C5,8), 119.6
(C6,7), 99.7 (AXX′, N ) 86.2 Hz, C1,3), 41.1 (NMe2), 20.7
(CH3paraMes), 20.1 (CH3orthoMes). Mp: 138-140 °C.
1
C6D6, 300 K): δ 5 (very broad s). H NMR (300.2 MHz, C6D6,
Synthesis of Zr(NMe2)2[Ind(Ph2PdS)2] (5). A solution of 4
(110 mg, 0.2 mmol) in toluene (10 mL) was added dropwise to a
solution of [Zr(NMe2)4] (54 mg, 0.2 mmol) in pentane (10 mL) at
-10 °C. The solution slowly became yellow, and a white precipitate
appeared. After 3 h, the supernatant was removed by filtration. The
yellow-white powder was washed three times with 10 mL of
pentane and then thermolyzed for 5 h at 100 °C in benzene-d6 (6
mL). The Schlenk line was continuously evacuated to remove the
free amine (Me2NH). The yellow solution was cooled to room
temperature and filtered. NMR analysis was carried out without
further purification. 31P{1H} NMR (121.5 MHz, C6D6): δ 40.0. 1H
NMR (300.1 MHz, C6D6): δ 7.98 (dd, 3JHH ) 7.0 Hz, 3JHP ) 13.4
Hz, 8H, HorthoPhP), 7.45 (m, 2H, H5,8), 7.08 (m, 2H, H6,7),
6.94-6.90 (m, 12H, HmetaPhP, HparaPhP), 3.02 (s, 12H, NMe2).
13C{1H} NMR (75.5 MHz, C6D6): δ 206.3 (t, 2JCP ) 44.5 Hz, C2),
3
3
300 K): δ 7.72 (broad dd, JHH ) 10.7 Hz, JHP ) 8.0 Hz, 9H,
HorthoPhP and H2Ind overlapped), 7.32 (m, 2H, H5,8Ind), 7.02-6.95
(m, 14H, HparaPhP, HmetaPhP, and H6,7Ind), 6.73 (s, 4H, HmetaMes),
(26) The cylindrical symmetry of σ bonds typically leads to ellipticities
near zero.
(27) An unsupported fluorenylidene ruthenium complex has recently been
prepared from the corresponding diazofluorene complex. See: Zhang,
J.; Gandelman, M.; Shimon, L. J. W.; Milstein, D. Organometallics
2008, 27, 3526.
(28) (a) Murata, S.; Abe, S.; Tomioka, H. J. Org. Chem. 1997, 62, 3055.
(b) Spencer, L. P.; Altwer, R.; Wei, P.; Gelmini, L.; Gauld, J.; Stephan,
D. W. Organometallics 2003, 22, 384.
(29) (a) Nuclear Magnetic Resonance Spectroscopy; Bovey, F. A., Ed.;
Academic Press: New York, 1969. (b) Abraham, R. J.; Berstein, H. J.
Can. J. Chem. 1961, 39, 216.
9
J. AM. CHEM. SOC. VOL. 131, NO. 10, 2009 3497

A R T I C L E S
Oulie´ et al.
139.3 (AXX′, N ) 18.3 Hz, C4,9), 134.3 (d, 1JCP ) 82.5 Hz, CipsoPh),
132.5 (d, 3JCP ) 11.6 Hz, CmetaPh), 131.4 (br s, CparaPh), 128.6 (d,
2JCP ) 12.7 Hz, CorthoPhP), 119.6 (s, C5,8), 119.3 (s, C6,7), 99.7
(AXX′, N ) 72.8 Hz, C1,3), 39.6 (s, NMe2).
Table 4. Crystallographic Data for Complexes 2, 3, and 7
2
3
7
empirical formula C59H69Cl4N5P2Zr C55H58N4P2Zr C47H51NO0.5P2PdS2
formula weight
crystal system
space group
a (Å)
b (Å)
c (Å)
1143.15
triclinic
P1
928.21
monoclinic
P21/n
12.8825(14) 11.3074(4)
23.109(2) 14.8453(5)
17.1419(18) 25.2573(7)
870.35
monoclinic
P21/n
Synthesis of PdCl[IndH(Ph2PdS)2] (6). A suspension of
[PdCl2(cod)] (210 mg, 0.73 mmol) and 4 (400 mg, 0.73 mg) in 40
mL of THF was stirred for 10 days at room temperature. Addition
of 40 mL of pentane induced the precipitation of a yellow solid.
After filtration, the solid was washed with 3 × 20 mL of pentane
and dried under vacuum to yield a pale-yellow solid. Yield: 480
mg (95%). 31P{1H} NMR (81 MHz, CD2Cl2): δ 55.9 (d, 3JPP ) 3.1
j
10.0482(10)
14.0223(14)
21.011(2)
94.687(2)
103.329(2)
91.388(2)
2868.2(5)
2
R (deg)
90
90
90.580(2)
90
4239.5(2)
4
1.364
0.647
42235
7158
ꢂ (deg)
110.034(2)
90
4794.3(9)
4
1.286
0.337
26697
6171
3
1
γ (deg)
Hz), 52.2 (d, JPP ) 3.1 Hz). H NMR (500.3 MHz, CD2Cl2): δ
7.95 (m, 2H, HorthoPhP), 7.85-7.75 (m, 3H, HorthoPhP, HparaPhP),
7.70 (m, 2H, HmetaPhP), 7.65 (m, 2H, HparaPhP), 7.60-7.50 (m,
6H, HPhP), 7.40 (m, 2H, HmetaPhP), 7.30 (m, 2H, HorthoPhP), 7.23
(m, 2H, HparaPhP, H5), 7.14 (m, 1H, H7), 7.09 (m, 1H, H6), 6.57
V (Å3)
Z
Dcalcd (Mg/m3)
abs coeff (mm-1
reflns collected
1.324
0.476
19734
)
3
2
3
(d, JHH ) 7.5 Hz, 1H, H8), 5.46 (dd, JPH ) 24.9 Hz, JPH ) 2.7
independent reflns 9549
Hz, 1H, H1). 13C{1H} NMR (75.5 MHz, CD2Cl2): δ 182.0 (m, C2),
R1 [I > 2σ(I)]
0.0465
0.1014
0.590/-0.424
0.0452
0.0710
0.0485
0.1069
2
3
2
145.6 (dd, JCP ) 18.2 Hz, JCP ) 3.9 Hz, C9), 139.8 (dd, JCP
)
wR2
3
4
(∆/r)max (e/Å3)
0.463/-0.310 0.508/-0.786
9.1 Hz, JCP ) 2.9 Hz, C4), 134.0 (d, JCP ) 3.1 Hz, CparaPhP),
4
4
133.3 (d, JCP ) 3.1 Hz, CparaPhP), 133.2 (d, JCP ) 3.1 Hz,
CparaPhP), 133.2 (d, 3JCP ) 9.6 Hz, CmetaPhP), 132.7 (d, 4JCP ) 3.1
3
3
tures were solved by direct methods (SHELXS-97)31 and refined
using the least-squares method on F 2.32
Hz, CparaPhP), 132.4 (d, JCP ) 11.5 Hz, CmetaPhP), 132.1 (d, JCP
3
) 10.8 Hz, CmetaPhP), 131.6 (d, JCP ) 11.5 Hz, CmetaPhP), 129.8
(d, 2JCP ) 12.5 Hz, CorthoPhP), 129.2 (d, 2JCP ) 13.0 Hz, CorthoPhP),
Computational Details. Zirconium, palladium, and phosphorus
atoms were treated with Stuttgart-Dresden pseudopotentials in
combination with their adapted basis sets.33,34 In all cases, the basis
set was augmented by a set of polarization functions (f for Zr and
Pd, d for P).35 Carbon, sulfur, nitrogen, and hydrogen atoms were
described with a 6-31G(d,p) double-ꢁ basis set.36 Calculations were
carried out using DFT with the hybrid functional B3PW91.37,38
Geometry optimizations were carried out without any symmetry
restrictions, and the nature of the extrema (minima) was verified
with analytical frequency calculations. All of these computations
were performed with the Gaussian 98 suite of programs.39 The
electronic density was analyzed using the NBO technique.21
129.2 (d, 2JCP ) 12.6 Hz, CorthoPhP), 128.6 (d, 3JCP ) 1.6 Hz, C7),
2
1
128.2 (d, JCP ) 12.8 Hz, CorthoPhP), 127.4 (d, JCP ) 80.5 Hz,
CipsoPhP), 126.4 (d, 1JCP ) 76.1 Hz, CipsoPhP), 124.3 (s, C6), 123.3
(s, C5), 121.7 (d, 1JCP ) 81.4 Hz, C3), 118.6 (s, C8), 72.8 (dd, 1JCP
) 53.9 Hz, JCP ) 18.1 Hz, C1). MS (EI 78 eV) m/z: 483 [M]+,
3
318 [M - Flu]+, 240 [M - Flu - Ph]+, 165 [Flu]+. Mp: 182 °C
(dec). Anal. Calcd for C33H25ClP2PdS2: C, 57.48; H, 3.65. Found:
C, 56.99; H, 3.52.
Synthesis of Complex Pd(NHCy2)[Ind(Ph2PdS)2] (7). Distilled
Cy2NH (55 µL, 0.143 mmol, 2 equiv) was added at room
temperature to a solution of 6 (52 mg, 0.071 mmol) in 25 mL of
THF. After the mixture was stirred for 2 h at room temperature,
40 mL of pentane was added in order to precipitate the ammonium
salts. After filtration, the solvent was removed under vacuum to
yield an orange solid. Yield: 50 mg (84%). Single crystals of 7
were grown from a THF solution at 20 °C. 31P{1H} NMR (81 MHz,
C6D6): δ 41.7 (s). 1H NMR (500.3 MHz, THF-d6): δ 7.90 (dd, 3JHH
) 13.0 Hz, 3JPH ) 8.0 Hz, 8H, HorthoPhP), 7.51 (dt, 3JHH ) 6.0 Hz,
5JPH ) 1.5 Hz, 4H, HparaPhP), 7.45 (dt, 3JHH ) 7.5 Hz, 4JPH ) 2.0
Acknowledgment. We are grateful to the CNRS, UPS, and
ANR program (Project BILI) for financial support of this work.
CalMip (CNRS, Toulouse, France) is acknowledged for calculation
facilities. L.M. thanks the Institut Universitaire de France. N.N.
thanks the MEC for a Ph.D. grant.
Supporting Information Available: Computational data for
complexes 3, 5, and 7; complete ref 39; and crystallographic
data for complexes 2, 3, and 7 (CIF). This material is available
free of charge via the Internet at http://pubs.acs.org.
3
Hz, 8H, HmetaPhP), 7.06-7.04 (m, 2H, H6,7), 6.62 (dd, JHH ) 6.0
Hz, 3JHH ) 3.0 Hz, 2H, H5,8), 2.95-2.91 (m, 2H, NCH), 2.3-2.60
3
(m, 3H, NH and CH2), 2.00 (d, JHH ) 12.0 Hz, 2H, CH2),
1.88-1.66 (m, 8H, 4CH2), 1.39-1.18 (m, 8H, 4CH2). 13C{1H}
3
NMR (75.5 MHz, C6D6): δ 164.5 (t, JCP ) 27.5 Hz, C2), 137.5
1
JA809892A
(AXX′, N ) 16.0 Hz, C4,9), 133.9 (d, JCP ) 82.3 Hz, CipsoPhP),
131.9 (CmetaPhP), 128.2 (CparaPhP), 128.1 (CortoPhP), 127.9
1
4
(CparaPhP), 129.2 (d, JCP ) 92.1 Hz, CipsoPhP), 128.7 (d, JCP
)
(31) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(32) Sheldrick, G. M. SHELXL-97: Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(33) Andrae, D.; Haeussermann, U.; Dolg, M.; Stoll, H.; Preuss, H. Theor.
Chim. Acta 1990, 77, 123.
2.3 Hz, CmetaPhP), 127.5 (d, 3JCP ) 10.6 Hz, CorthoPhP), 127.2 (C5,8),
115.7 (C6,7), 104.7 (AXX′, N ) 74.2 Hz, C1,3), 52.9 (CHN), 33.5
(CH2), 32.9 (CH2), 26.2 (CH2), 26.0 (CH2). Mp: 202 °C (dec). Anal.
Calcd for C45H47NP2PdS2: C, 64.78; H, 5.68. Found: C, 64.23; H,
5.34.
(34) Bergner, A.; Dolg, M.; Kuechle, W.; Stoll, H.; Preuss, H. Mol. Phys.
1993, 80, 1431.
Crystal Structure Determinations for Complexes 2, 3, and
7. Data for each structure (Table 4) were collected at 193(2) K
using an oil-coated shock-cooled crystal on a Bruker AXS CCD
1000 diffractometer with Mo KR radiation (λ ) 0.7103 Å).
Semiempirical absorption corrections were employed.30 The struc-
(35) Ehlers, A. W.; Bo¨hme, M.; Dapprich, S.; Gobbi, A.; Ho¨llwarth, A.;
Jonas, V.; Ko¨hler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G.
Chem. Phys. Lett. 1993, 208, 111.
(36) Hariharan, P. C.; Pople, J. A. Theor. Chim. Acta 1973, 28, 213.
(37) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
(38) Burke, K.; Perdew, J. P.; Yang, W. In Electronic Density Functional
Theory: Recent Progress and New Directions; Dobson, J. F., Vignale,
G., Das, M. P., Eds.; Springer; New York, 1998.
(30) SADABS: Program for Data Correction, version 2.10; Bruker AXS:
(39) Frisch, M. J.; et al. Gaussian 03, revision D-02; Gaussian, Inc.:
Pittsburgh, PA, 2003.
Madison, WI, 2003.
9
3498 J. AM. CHEM. SOC. VOL. 131, NO. 10, 2009