Enforced η1-fluorenyl and indenyl coordination to zirconium: Geometrically constrained and sterically expanded complexes derived from the bifunctional (FluPPh2NAr)- and (IndPPh2NAr) - ligands

Article abstract of DOI:10.1021/om700974g

The (FluPPh₂NAr) and (IndPPh₂NAr) ligands 2a-c and 4a-c (a, Ar = Ph; b, R = DIPP; c, = Mes) were readily prepared by Staudinger reactions between aryl azides and Flu/Ind diphenylphosphines, and they were coordinated to zirconium via toluene elimination. The propensity of the pendent phosphazene group to enforce low hapticity of the Flu and Ind rings in the ensuing complexes has been demonstrated experimentally and theoretically. Of particular interest, geometrically constrained and sterically expanded structures have been evidenced spectroscopically and structurally for both complexes [(FluPPh₂NPh)ZrBn₃] 5a and [(IndPPh ₂NPh)ZrBn₃] 7a. In addition, the ability of the aryl substituent at nitrogen to modulate the hapticity of the Ind ring (from η¹ to η², and η³) has been substantiated, and intramolecular CH-activation reactions leading to doubly cyclometalated complexes 6c and 8c have been observed when R = Mes.

Full text of DOI:10.1021/om700974g

Organometallics 2007, 26, 6793–6804
6793
Enforced η1-Fluorenyl and Indenyl Coordination to Zirconium:
Geometrically Constrained and Sterically Expanded Complexes
Derived from the Bifunctional (FluPPh2NAr)- and (IndPPh2NAr)-
Ligands
Pascal Oulié,† Christelle Freund,† Nathalie Saffon,‡ Blanca Martin-Vaca,*,†
Laurent Maron,*,§ and Didier Bourissou*,†
Laboratoire Hétérochimie Fondamentale et Appliquée du CNRS (UMR 5069), UniVersité Paul Sabatier,
118, route de Narbonne, F-31062 Toulouse Cedex 09, France, Structure FédératiVe Toulousaine en
Chimie Moléculaire (FR 2599) UniVersité Paul Sabatier, 118, route de Narbonne, F-31062 Toulouse
Cedex 09, France, and Laboratoire de Physique et Chimie des Nanoobjets (UMR 5215), INSA, UniVersité
Paul Sabatier, 135, aVenue de Rangueil, F-31077 Toulouse Cedex, France
ReceiVed October 1, 2007
The (FluPPh2NAr) and (IndPPh2NAr) ligands 2a–c and 4a–c (a, Ar ) Ph; b, R ) DIPP; c, ) Mes)
were readily prepared by Staudinger reactions between aryl azides and Flu/Ind diphenylphosphines, and
they were coordinated to zirconium via toluene elimination. The propensity of the pendent phosphazene
group to enforce low hapticity of the Flu and Ind rings in the ensuing complexes has been demonstrated
experimentally and theoretically. Of particular interest, geometrically constrained and sterically expanded
structures have been evidenced spectroscopically and structurally for both complexes [(FluPPh2NPh)ZrBn3]
5a and [(IndPPh2NPh)ZrBn3] 7a. In addition, the ability of the aryl substituent at nitrogen to modulate
the hapticity of the Ind ring (from η1, to η2, and η3) has been substantiated, and intramolecular CH-
activation reactions leading to doubly cyclometalated complexes 6c and 8c have been observed when R
) Mes.
Introduction
Cyclopentadienyl rings (Cp) and the related indenyl (Ind) and
fluorenyl (Flu) systems are among the most commonly used
ligands, with examples of their complexes across the periodic
table. In particular, they have found enormous use in the
preparation of Ziegler–Natta-type initiators for olefin polym-
erization.1 Variation of the Cp substitution pattern has been
extensively studied in order to tune the stereoelectronic proper-
ties around the metal, to control the orientation and rotation of
the Cp-type ring (such as in ansa-metallocenes2), and to
Figure 1. Structure of the archetypal CGCs A and of the
geometrically constrained and sterically expanded Flu complexes
B.
introduce functional groups that may interact with the metal
center.3,4 Constrained geometry complexes (CGCs) A (Figure
1) obtained by introduction of a short silylamido sidearm on a
Cp-type ring clearly represent one of the most spectacular
achievements in this area.5
* To whom correspondence should be addressed. E-mail: dbouriss@
chimie.ups-tlse.fr.
The modularity of the Ind and Flu ligands is further increased
by their ability to accommodate several easily interconvertible
† Laboratoire Hétérochimie Fondamentale et Appliquée du CNRS.
‡ Structure Fédérative Toulousaine en Chimie Moléculaire.
§ Laboratoire de Physique et Chimie des Nanoobjets.
(1) (a) Brintzinger, H. H.; Fischer, D.; Mülhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (b)
Bochmann, T. J. Chem. Soc., Dalton Trans. 1996, 255. (c) Alt, H. G.; Köppl,
A. Chem. ReV. 2000, 100, 1205. (d) Resconi, L.; Cavallo, L.; Fait, A.;
Piemontesi, F. Chem. ReV. 2000, 100, 1253. (e) Lin, S.; Waymouth, R. M.
Acc. Chem. Res. 2002, 35, 765.
(5) (a) McKnight, A. L.; Waymouth, R. M. Chem. ReV. 1998, 98, 2587.
(b) Gibson, V. C.; Spitmesser, S. K. Chem. ReV. 2003, 103, 283. (c)
Braunschweig, H.; Breitling, F. M. Coord. Chem. ReV. 2006, 250, 2691–
2720.
(6) (a) O’Connor, J. M.; Casey, C. P. Chem. ReV. 1987, 87, 307. (b)
Calhorda, M. J.; Veiros, L. F. Coord. Chem. ReV. 1999, 185–186, 37. (c)
Calhorda, M. J.; Veiros, L. F. Comments Inorg. Chem. 2001, 22, 375. (d)
Calhorda, M. J.; Romão, C. C.; Veiros, L. F. Chem. Eur. J. 2002, 8, 868.
(e) Zargarian, D. Coord. Chem. ReV. 2002, 233–234, 157.
(2) (a) Shapiro, P. J. Coord. Chem. ReV. 2002, 231, 67. (b) Prashar, S.;
Antiñolo, A.; Otero, A. Coord. Chem. ReV. 2006, 250, 133. (c) Wang, B.
Coord. Chem. ReV. 2006, 250, 242.
(3) Erker, G.; Kehr, G.; Fröhlich, R. Coord. Chem. ReV. 2006, 250, 36.
(4) For Cp metal complexes featuring pendant donor groups, see: (a)
Jutzi, P.; Redeker, T. Eur. J. Inorg. Chem. 1998, 663. (b) Siemeling, U.
Chem. ReV. 2000, 100, 1495. (c) Butenschön, H. Chem. ReV. 2000, 100,
1527. (d) Piers, W. E. Chem. Eur. J. 1998, 4, 13. (e) Hill, M.; Erker, G.;
Kehr, G.; Fröhlich, R.; Kataeva, O. J. Am. Chem. Soc. 2004, 126, 11046.
(7) For zirconium sandwich complexes featuring η9-indenyl ligands, see:
(a) Bradley, C. A.; Keresztes, I.; Lobkovsky, E.; Young, V. G.; Chirik,
P. J. J. Am. Chem. Soc. 2004, 126, 16937. (b) Veiros, L. F. Chem. Eur. J.
2005, 11, 2505. (c) Veiros, L. F. Organometallics 2006, 25, 2266. (d)
Bradley, C. A.; Veiros, L. F.; Pun, D.; Lobkovsky, E.; Keresztes, I.; Chirik,
P. J. J. Am. Chem. Soc. 2006, 128, 16600.
10.1021/om700974g CCC: $37.00
2007 American Chemical Society
Publication on Web 12/05/2007

6794 Organometallics, Vol. 26, No. 27, 2007
Oulié et al.
hapticities (so-called “ring slippage”).6–8 In particular, low Ind
and Flu hapticities, which increase accessibility for the incoming
substrates for both geometric and electronic reasons, have
attracted considerable interest.9 Very significantly, Miller et al.
recently reported for the η1-complex B, featuring the sterically
hindered (FluSiMe2N-t-Bu)2- ligand (M ) Zr, X ) Cl, and L
) Et2O), an inverted preference for R-olefin over ethylene
polymerization (with homopolymerization activity typically 6
times higher toward propylene versus ethylene at 25 °C) and
unprecedented stereoselectivity (resulting in syndiotactic polypro-
pylene with melting temperatures as high as 165 °C).10a,b This
peculiar behavior further reinforces the interest for group 4
complexes featuring low coordinated Ind or Flu ligands, whose
number and variety remain so far extremely limited. Indeed,
the fluorenyl complexes B10a,c are the very unique examples of
so-called geometrically constrained and sterically expanded11
systems combining bent Cipso-Si-N bond angles (∼96°, in the
typical range associated with CGCs A) and widened Si-Cipso
-
Cg bond angles (∼202°), resulting in outward pyramidalization
of the Cipso center (with the silicon atom and the metal being
located on opposite sides of the Flu ring, in marked contrast
with that observed with CGCs A). Only a few other η1-
complexes C-H12–16 of group 4 metals (Figure 2) have been
structurally characterized, the low Flu or Ind hapticity being
typically favored by the presence of strongly donating coligands
(η5-Cp, η5-Ind, η5-Flu, alkoxy, phosphinimide).17,18
Figure 2. Structurally characterized η1-fluorenyl and η1-indenyl/
group 4 metal complexes C-H.
1-aza-2-phospha(V)allyl ligands.20–24 The presence of the short
and strongly donating phosphazene sidearm25 was expected to
influence dramatically the bonding mode of the Cp-type ring,26
as evidenced in the κ2-N,C[(FluPPh2NPh)Rh(nbd)] complex.27
In addition, coordination to group 4 metals was expected to
In this context, we recently initiated a research program aimed
at exploring the coordination chemistry of bifunctional
(CpPR2NR′)- ligands,19 formally deriving from the well-known
(8) For η4- and η6-indenyl coordination through the benzo ring, see:
(a) Bradley, C. A.; Lobkovsky, E.; Chirik, P. J. J. Am. Chem. Soc. 2003,
125, 8110. (b) Wang, S.; Tang, X.; Vega, A.; Saillard, J. -Y.; Sheng, E.;
Yang, G.; Zhou, S.; Huang, Z Organometallics 2006, 25, 2399.
(9) For recent reviews on η1-fluorenyl and η1-indenyl complexes, see:
(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)
Carpentier, J.-F.; Saillard, J.-Y.; Kirillov, E. Coord. Chem. ReV. 2005, 249,
1221.
(20) (a) Izod, K. Coord. Chem. ReV. 2002, 227, 153. (b) Steiner, A.;
Zacchini, S.; Richards, P. I. Coord. Chem. ReV. 2002, 227, 193.
(21) For Li complexes, see: López-Ortiz, F. Curr. Org. Synth. 2006, 3,
187 and references therein.
(22) For Zr and Ti complexes, see: (a) Sarsfield, M. J.; Thornton-Pett,
M.; Bochmann, M. J. Chem. Soc., Dalton Trans. 1999, 3329. (b) Sarsfield,
M. J.; Said, M.; Thornton-Pett, M.; Gerrard, L. A.; Bochmann, M. J. Chem.
Soc., Dalton Trans. 2001, 822. (c) Said, M.; Thornton-Pett, M.; Bochmann,
M. J. Chem. Soc., Dalton Trans. 2001, 2844. (d) Said, M.; Thornton-Pett,
M.; Hughes, D. L.; Bochmann, M. Inorg. Chim. Acta 2007, 360, 1354.
(23) For late metal complexes, see: (a) Imhoff, P.; Nefkens, S. C. A.;
Elsevier, C. J.; Goubitz, K.; Stam, C. H. Organometallics 1991, 10, 1421.
(b) Imhoff, P.; van Asselt, R.; Ernsting, J. M.; Vrieze, K.; Elsevier, C. J.;
Smeets, W. J. J.; Spek, A. L.; Kentgens, A. P. M. Organometallics 1993,
12, 1523. (c) Avis, M. W.; Vrieze, K.; Kooijman, H.; Veldman, N.; Spek,
A. L.; Elsevier, C. J. Inorg. Chem. 1995, 34, 4092. (d) Avis, M. W.; Vrieze,
K.; Ernsting, J. M.; Elsevier, C. J.; Veldman, N.; Spek, A. L.; Katti, K. V.;
Barnes, C. L. Organometallics 1996, 15, 2376. (e) Masuda, J. D.; Wei, P.;
Stephan, D. W. Dalton Trans. 2003, 3500. (f) Smurnyy Bibal, C.; Pink,
M.; Caulton, K. G J. Am. Chem. Soc. 2005, 127, 8944. (g) Fang, M.; Jones,
N. D.; Lukowski, R.; Tjathas, J.; Ferguson, M. J.; Cavell, R. G. Angew.
Chem., Int. Ed. 2006, 45, 3097.
(10) (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) Irwin, L. J.; Reibenspies, J. H.; Miller, S. A. Polyhedron
2005, 24, 1314. (d) Schwerdtfeger, E. D.; Miller, S. A. Macromolecules
2007, 40, 5662.
(11) The term “sterically-expanded”, introduced for complexes featuring
mono- and bis(tetramethylbenzo)fluorenyl substituents (Miller, S. A.;
Bercaw, J. E. Organomeyallics 2004, 23, 1777), refers here to the open
structure that is induced by the low hapticity of the Cp-type ring and that
increases the accessibility of the metal center.
(12) Schmidt, M. A.; Alt, H. G.; Milius, W. J. Organomet. Chem. 1997,
541, 3.
(13) Schmidt, M. A.; Alt, H. G.; Milius, W. J. Organomet. Chem. 1997,
544, 139.
(14) Knjazhanski, S. Y.; Cadenas, G.; Garcia, M.; Pérez, C. M.;
Nifant’ev, I. E.; Kashulin, I. A.; Ivchenko, P. V.; Lyssenko, K. A.
Organometallics 2002, 21, 3094.
(24) For main group complexes, see: (a) Hitchcock, P. B.; Lappert, M. F.;
Wang, Z.-X. J. Organomet. Chem. 2006, 691, 2748. (b) Leung, W. P.;
Wong, K. W.; Wang, Z. X.; Mak, T. C. W. Organometallics 2006, 25,
2037. (c) Alhomaidan, O.; Hollink, E.; Stephan, D. W. Organometallics
2007, 26, 3041.
(15) Guérin, F.; Beddie, C. L.; Stephan, D. W.; Spence, R. E.; Wirz, R.
v. H. Organometallics 2001, 20, 3466.
(16) Brintzinger, H. H.; Gritzo, H.; Wieser, U. CCDC-230739, 2004.
(17) The introduction of a sterically demanding phenoxide sidearm was
reported to induce η1-indenyl coordination toward Ta(NMe2)3: (a) Thorn,
M. G.; Fanwick, P. E.; Chesnut, R. W.; Rothwell, I. P. Chem. Commun.
1999, 2543. (b) Thorn, M. G.; Parker, J. R.; Fanwick, P. E.; Rothwell, I. P.
Organometallics 2003, 22, 4658. But η5-coordination was retained in the
related Ti(NMe2)2 and Zr(NMe2)2 complexes. (c) Turner, L. E.; Thorn,
M. G.; Fanwick, P. E.; Rothwell, I. P. Organometallics 2004, 23, 4658.
(18) η1-Fluorenyl coordination has also been found in the geometrically-
constrained dimeric yttrium complex [(FluSiMe2N-t-Bu)YH(THF)2]2. Harder,
S. Organometallics 2005, 24, 373.
(25) For selected references, see: (a) Reetz, M. T.; Bohres, E.; Goddard,
R. Chem. Commun. 1998, 935. (b) Sauthier, M.; Forniés-Cámer, J.; Toupet,
L.; Réau, R. Organometallics 2000, 19, 553. (c) Spencer, L. P.; Altwer,
R.; Wie, P.; Gelmini, L.; Gauld, J.; Stephan, D. W. Organometallics 2003,
22, 3841. (d) Kocher, N.; Leusser, D.; Murso, A.; Stalke, D. Chem. Eur. J.
2004, 10, 3622. (e) Boubekeur, L.; Ricard, L.; Mézailles, N.; Le Floch, P.
Organometallics 2005, 24, 1065. (f) Co, T. T; Shim, S. C.; Cho, C. S.;
Kim, T.-J.; Kang, S. O.; Han, W.-S.; Ko, J.; Kim, C.-K. Organometallics
2005, 24, 4824.
(26) Introduction of a pendant phosphine sulfide has recently allowed
for the first structural characterization of an η1-indenyl rhodium complex. (a)
Wechsler, D.; McDonald, R.; Ferguson, M. J.; Stradiotto, M. Chem.
Commun. 2004, 2446. (b) Wechsler, D.; Myers, A.; McDonald, R.;
Ferguson, M. J.; Stradiotto, M. Inorg. Chem. 2006, 45, 4562.
(27) Freund, C.; Barros, N.; Gornitzka, H.; Martin-Vaca, B.; Maron,
L.; Bourissou, D. Organometallics 2006, 25, 4927.
(19) Related Cp-phosphazene zirconium and lutetium complexes were
reported to adopt η5-coordination with phosphazene f metal interaction. (a)
Truflandier, L.; Marsden, C. J.; Freund, C.; Martin-Vaca, B.; Bourissou,
D. Eur. J. Inorg. Chem. 2004, 1939. (b) Rufanov, K. A.; Petrov, A. R.;
Kotov, V. V.; Laquai, F.; Sundermeyer, J. Eur. J. Inorg. Chem. 2005, 3805.

Enforced η1-Fluorenyl and Indenyl Coordination to Zirconium
Organometallics, Vol. 26, No. 27, 2007 6795
Scheme 1. Synthesis of the Fluorenyl Ligands 2a–c
Scheme 2. Synthesis of the Indenyl Ligands 4a–c
give access to a new type of phosphorus-containing analogues
of CpSiN CGCs A.28 We report here a detailed investigation
of zirconium complexes deriving from (FluPPh2NAr)- and
(IndPPh2NAr)-, demonstrating that the pendent phosphazene
can also enforce and modulate low hapticity of Flu and even
Ind rings with group 4 metals. The geometrically constrained
and sterically expanded structure of the resulting complexes is
substantiated by X-ray analyses and DFT calculations. The
substituent at nitrogen is shown to strongly influence the
coordination mode, and CH-activation reactions leading to
doubly cyclometalated complexes are reported.
Following the same strategy, the related indenyl ligands 4a–c
were obtained from indenyldiphenylphosphine34 and aryl azides,
complete reactions only requiring 2 h at room temperature in
this case (Scheme 2). 31P NMR characterization of the crude
reaction mixtures revealed more complicate situations than those
encountered for the fluorenyl ligands 2a–c, three isomeric forms
4, 4′, and 4′′ being detected for each ligand. The preparation of
indenyldiphenylphosphine from indenyllithium and chlorodiphe-
nylphosphine is known to give first the allyl isomer 3′ that
slowly rearranges to the more stable vinyl isomer 3 at ambient
temperature.34 From a practical viewpoint, complete tautomer-
ization, which can be promoted by filtration through a short
pad of alumina34 or stirring with a catalytic amount of
triethylamine, proved to facilitate the workup and isolation of
3 (white solid, 59% yield). But whatever the isomeric ratio 3/3′
engaged, the Staudinger reaction led in all cases to the same
Results and Discussion
Synthesis and Characterization of Ligands 2a–c and
4a–c. The fluorenyl ligands 2b and 2c featuring, respectively,
the DIPP (2,6-diisopropylphenyl) and Mes (2,4,6-trimethylphe-
nyl) susbtituent at the nitrogen atom were prepared following
the same strategy than that previously reported for their
phenylated analogue 2a,27 that is the Staudinger reaction
between fluorenyldiphenylphosphine29 and the corresponding
aryl azides30 (Scheme 1). As for 2a, derivatives 2b and 2c adopt
the tautomeric phosphazene form (NdP-CH) rather than the
ylidic one (NH-PdC)31 both in solution and in the solid state,
as deduced from 13C NMR spectroscopy (for both compounds,
CH signals at ∼53 ppm were observed for the central C1 atom
of the fluorenyl ring)32 and from an X-ray diffraction analysis
carried out for 2c (the hydrogen atom at C1 could be located
and refined without any constraint).33
isomeric distribution of 4, 4′, and 4′′. According to 1H and 13
C
NMR spectroscopy, the three isomers could be authenticated
as the vinyl phosphazene 4, the allyl phosphazene 4′, and the
P-amino phosphorus ylide 4′′. The vinyl phosphazene form 4,
which has been structurally authenticated in the solid state for
4b,33 is generally predominant.35 It is characterized by a Cq
doublet signal at ∼139 ppm (1JCP ≈ 94 Hz) attributed to C1
1
and a broad signal at ∼3.00 ppm in the H NMR associated
(28) For related phosphorus-containing analogues of CpSiN CGCs A,
see: (a) Brown, S. J.; Gao, X.; Harrison, D. G.; Koch, L.; Spence, R. E. v.
H.; Yap, G. P. A. Organometallics 1998, 17, 5445. (b) Kunz, K.; Erker,
G.; Döring, S.; Fröhlich, R. J. Am. Chem. Soc. 2001, 123, 6181. (c) Kotov,
V. V.; Avtomonov, E. V.; Sundermeyer, J.; Harms, K.; Lemenovskii, D. A.
Eur. J. Inorg. Chem. 2002, 678. (d) Altenhoff, G.; Bredeau, S.; Erker, G.;
Kehr, G.; Kataeva, O.; Fröhlich, R. Organometallics 2002, 21, 4084. (e)
Bourissou, D.; Freund, C.; Martin-Vaca, B.; Bouhadir, G. C. R. Chimie
2006, 9, 1120.
with a doublet at ∼39.5 ppm (2JCP ≈ 12.5 Hz) in the 13C NMR
for the (C8H2) methylene of the indenyl.33 Comparatively, the
allyl phosphazene form 4′ exhibits a doublet at ∼4.85 ppm in
1
the H NMR (2JHP ≈ 27 Hz) associated in the 13C NMR with
a doublet at ∼56.5 ppm (1JCP ≈ 65 Hz) for C1 and a CH singlet
at ∼132.5 ppm in 13C NMR for C8. Finally, a broad signal at
∼4.5 ppm in the 1H NMR supports the assignment of the
P-amino phosphorus ylide form 4′′. Since all of these isomers
were supposed to yield the same product upon metalation, no
effort was devoted to their separation and they were used directly
as a mixture.
(29) Baiget, L.; Bouslikhane, M.; Escudié, J.; Cretiu Nemes, G.; Silaghi-
Dumitrescu, I.; Silaghi-Dumitrescu, L. Phosphorus, Sulfur, Silicon 2003,
178, 1949.
(30) (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.
Synthesis and Characterization of Zirconium-
Fluorenyl Complexes. Elimination of toluene between the
bifunctional ligands 2/4 and tetrabenzylzirconium36 proved to
(31) The opposite situation was encountered in the related Cp′PMe2NAd
ligand.18
(32) The following atom numbering has been used in NMR assignment
and in X-ray labeling of the (FluPPh2NAr)/(IndPPh2NAr) ligands and
ensuing zirconium complexes:
(34) Falls, K. A.; Anderson, G. K.; Rath, N. P. Organometallics 1992,
11, 885.
(35) The relative proportions of the three tautomeric structures were
estimated by 31P NMR as follows: 4a/4′′a/4′′a ) 45/14/41, 4b/4′b/4′′b )
82/12/6 and 4c/4′c/4′′c ) 57/11/32.
(36) Compared with the conventional salt elimination synthetic route,
the toluene elimination strategy greatly facilitates the workup and affords
direct access to (di)alkyl complexes: (a) van der Linden, A.; Schaverien,
C. J.; Meijboom, N.; Ganter, C.; Orpen, A. G. J. Am. Chem. Soc. 1995,
117, 3008. (b) Chen, Y.-X.; Marks, T. J. Organometallics 1997, 16, 3649.
.
(33) See the Supporting Information.

6796 Organometallics, Vol. 26, No. 27, 2007
Oulié et al.
Scheme 3. Synthesis of the Fluorenyl Zirconium Complexes
5a and 6c
zirconium center (with Zr-N and Zr-C1 bond lengths of 2.182
and 2.561 Å, respectively), in marked contrast with that found
for
the
corresponding
rhodium
complex
κ2-
N,C[(FluPPh2NPh)Rh(nbd)] (N-Rh 2.123 Å and Rh-C1 2.188
Å),27 but in a similar way to that observed for the 1-aza-2-
phospha(V)allyl complex [(ArCHPPh2NMes)Zr(NMe2)3] (Zr-N
2.262 and Zr-C 2.560 Å).22c As a result of this chelation, the
N-P-C bond angle is rather acute (98.8°) and falls in the
typical range of those reported for CGCs A. The η1-Flu
coordination is supported by the large distances observed
between the remaining Flu carbon atoms and the zirconium
center (>3 Å). Although the Zr-C1 bond (2.561 Å) is much
longer than that reported for the related complexes B10a,c
(2.28–2.33 Å) and C12 (2.384 Å), the outward pyramidalization
of C1 (ΣC1R ) 349.4°)37 suggests a significant C-Zr bonding
interaction. Notably, the η1 coordination of the fluorenyl ligand
results also in a very open P-C1-Cg angle (208°). This value
is slightly larger than those reported by Miller for the related
Si-C1-Cg angle (198–204°) of the sterically expanded η1
complexes B.10a,c Note finally that the electron deficiency
induced at the metal by the η1-Flu coordination is at least
partially compensated in 5a by η2-coordination of one of the
benzyl ligands (Zr-Cipso, 2.62 Å, and Zr-CH2-Cipso, 87.5°).
This behavior is also apparent in solution, the most diagnostic
parameters being the chemical shifts for Hortho (6.51 ppm) and
C
ipso (146.1 ppm) together with the 1JCH value (124 Hz) for the
be a convenient way to prepare the corresponding complexes.
Accordingly, the reaction of 2a with 1 equiv of ZrBn4 was
complete after 5 h at 90 °C, as indicated by 31P NMR monitoring
(Scheme 3). The coordination of a single (FluPPh2NPh)- ligand
per metal center was deduced from the retention of three benzyl
CH2 group.38,39 The structure adopted by 5a confirms further
the propensity of the pendent phosphazene moiety to enforce
η1-Flu coordination evidenced for the related rhodium com-
plex,27 thereby giving access to geometrically constrained and
sterically expanded complexes even with group 4 metals.
Aiming at probing the influence of the substituent at nitrogen,
the coordination of the related ligands 2b and 2c was then
investigated. No signal other than that of 2b was detected by
31P NMR spectroscopy after heating for 3 days at 90 °C with
1.7 equiv of ZrBn4, and only thermal decomposition36b of the
zirconium precursor was observed by 1H NMR. In contrast, the
reaction indeed took place with the less sterically demanding
ligand 2c, although significantly harsher conditions than those
used for 2a were necessary to achieve complete ligand conver-
1
groups in the H NMR spectrum of the resulting complex 5a.
Notably, all of the Flu quaternary carbon atoms appear at more
than 130 ppm in 13C NMR, except C1, which resonates at 56.0
ppm as a doublet (1JPC ) 96.6 Hz). This chemical shift is
significantly lower than those reported for fluorenyl Zr com-
plexes, even in the rare examples of η1-coordination (67–88
ppm),10a,c,12,14 and suggests a rather unusual structure for 5a.
Complex 5a proved to be very sensitive to air and moisture.
Single crystals, suitable for an X-ray diffraction study, were
obtained from a saturated toluene/pentane solution at room
temperature. The zirconium center adopts a distorted trigonal
bipyramidal geometry in the solid state (Figure 3). Two benzyl
groups and the nitrogen occupy the equatorial positions, while
the remaining benzyl group and the fluorenyl are located in the
pseudoaxial positions. The nitrogen and the C1 atoms of the
(FluPPh2NPh)- ligand are unsymmetrically bonded to the
sion (1.7 vs 1 equiv of ZrBn4 and 5 days vs 5 h at 90 °C). 31
P
NMR indicated a similar deshielding upon metalation of 2c (∆δ
) 16.8 ppm) than that observed for 2a (∆δ ) 13.5 ppm).
However, the 1H NMR spectrum revealed that only two benzyl
groups have been retained, ruling out the formation of the
expected complex 5c. Moreover, only two singlet signals,
integrating for three protons each, were observed for the methyl
groups at mesityl (2.30 and 2.08 ppm), with an additional singlet
signal integrating for only two protons and appearing at higher
field (1.80 ppm). These data suggested that another elimination
of toluene had occurred between a benzyl group at zirconium
and one of the o-methyl groups at mesityl. So far, the poor
stability of complex 6c did not allow us to obtain single crystals
(37) The ylidic carbon center is planar in fluorenylidenephosphoranes:
(a) Burford, N.; Clyburne, J. A. C.; Sereda, S. V.; Cameron, T. S.; Pincock,
J. A.; Lumsden, M. Organometallics 1995, 14, 3762. (b) Brady, E. D.;
Hanusa, T. P.; Pink, M.; Young , V. G., Jr. Inorg. Chem. 2000, 39, 6028.
(38) At room temperature, a single set of resonances is observed for
the three benzyl groups as a result of fast exchange between the η1 and
η2-coordination modes.
(39) The coordination mode of benzyl groups toward group 4 metals
can usually be distinguished by 1H and 13C NMR spectroscopy. Typically,
η1-coordination is associated with δ Hortho > 6.5 ppm, δ Cipso ∼ 150 ppm,
and 1JCH values ∼ 120 Hz, while η2-coordination is associated with δ Hortho
1
< 6.5 ppm, δ Cipso ∼ 140 ppm, and JCH values ∼ 135 Hz. See: Bei, X.;
Figure 3. Molecular view of 5a in the solid state, with hydrogen
atoms omitted.
Swenson, D. C.; Jordan, R. F. Organometallics 1997, 16, 3282 and
references therein.

Enforced η1-Fluorenyl and Indenyl Coordination to Zirconium
Organometallics, Vol. 26, No. 27, 2007 6797
deviations of only 0.06 Å in the N-Zr bond distance and 0.04
Å in the C-Zr one), indicating the ability of the B3PW91/
SDD(Zr,P),6-31G**(other atoms) method in describing such
systems (Figure 4, Table 1). An NBO analysis was also carried
out on 5a* to get a better understanding of the unsymmetrical
coordination of the NPC skeleton that markedly contrasts with
the almost symmetric coordination previously observed for the
related rhodium complex. Accordingly, the C-M bond is
significantly polarized in 5a* (90% C1-10% Zr) {vs 35%
C1-65% Rh in κ2-N,C[(FluPPh2NPh)Rh(nbd)]}. The combina-
tion of X-ray and NBO analyses thus suggests that the behavior
of the chelating (FluPPh2NPh)- ligand is best described as an
amido/phosphorus ylid in 5a (Lewis structure I) and as a
phosphazene/alkyl in κ2-N,C[(FluPPh2NPh)Rh(nbd)] (Lewis
structure II) (Figure 5).41
Figure 4. Optimized structures for complexes 5a,c* and 6c* at the
B3PW91/SDD(Zr,P),6-31G**(other atoms) level of theory, with
hydrogen atoms omitted.
In addition, a minimum could be located on the potential
energy surface (PES) for the putative intermediate 5c*. Ac-
cording to its optimized geometry, complex 5c* retains the η1-
coordination of the fluorenyl ring and an unsymmetrical bonding
of the NPC skeleton. In fact, the key geometric features
predicted for complex 5c* very much resemble those of 5a*,
except that none of the benzyl group at zirconium is η2-
coordinated. This subtle difference between 5a* and 5c* most
likely results from the increased steric crowding induced by
the mesityl substituent at nitrogen, a situation that also probably
favors the intramolecular CH-activation leading to 6c. The
optimized geometry of 6c* further supports the structure
deduced from the spectroscopic analysis, with retention of the
η1-Flu coordination and cyclometalation of one of the ortho
positions of the mesityl ring, resulting in a short CH2-Zr bond
(2.24 Å). Notably, the transformation of 5c* into 6c* is
accompanied by (i) the rotation of the aryl ring at nitrogen by
about 90°, (ii) a pseudorotation of the zirconium environment
(the pseudoaxial positions being now occupied by the nitrogen
atom and one of the remaining benzyl group at zirconium), (iii)
a shortened C1-Zr bond (2.54 f 2.46 Å), and (iv) a slight
decrease of the steric expansion as measured by the P-C1-Cg
bond angle (208 f 201°). The cyclometalation reaction (5c*
f 6c* + toluene) is predicted to be favored energetically, with
a ∆E value of –7.74 kcal/mol.42 Although the cyclometalation
of phosphazenes is all but unknown, the transformation of 5c
into 6c deserves some comments. Indeed, cyclometalation
reactions of phosphazenes occur usually at a P-substituent (as
typically illustrated by complexes of 1-aza-2-phospha(V)allyl
ligands22a–c,23b,c and ortho-metalated triphenylphosphazenes43),
but only scarcely at the N-substituent.44 In addition, the
formation of 6c provides a rare example of intramolecular CH-
activation within neutral group 4 complexes.45,46 From a
mechanistic viewpoint, the reaction may proceed either by
σ-bond metathesis or by R-elimination of toluene leading to a
zirconium-benzylidene complex followed by intramolecular
addition of a CH bond from an ortho-methyl group at Mes.45c,d
Figure 5. Limiting structures for κ2-N,C complexes deriving from
1-aza-2-phospha(V)allyl ligands.
Scheme 4. Postulated Assistance of the Phosphazene Sidearm
to the Metalation Reaction
to carry out an X-ray diffraction analysis, but its structure was
further assessed by in situ NMR spectroscopy. As far as the
hapticity of the fluorenyl ring is concerned, the 13C NMR signal
observed at 57.6 ppm (1JPC ) 100.6 Hz) for C1 supported η1
coordination, by analogy with that observed for 5a. In addition,
the low chemical shifts observed for Hortho (5.94 ppm) and Cipso
(142.3 ppm) together with the high 1JCH value (130 Hz) for the
CH2 group suggested an even greater contribution of η2-
coordination for the benzyl coligands than that found in 5a.
From a mechanistic viewpoint, complex 6c most probably results
from the transient formation of 5c followed by intramolecular
CH-activation. 31P NMR monitoring of the reaction between
2c and ZrBn4 did not allowed us to detect the intermediate
complex 5c, no reaction occurring below 40 °C and only the
direct formation of 6c being observed at higher temperatures.
In order to rationalize the pronounced influence of the steric
demand of the aryl group at nitrogen on the kinetics of the
metalation reaction, we propose that the formation of complexes
5 results from initial coordination of the phosphazene moiety
of 2 to the metal center,40 followed by intramolecular CH-
activation with toluene elimination, that would be favored by
increased basicity of the benzyl groups at zirconium as well as
higher acidity of the H atom at the fluorenyl induced by the
precoordination (Scheme 4).
(41) The contribution of forms I and II have also been discussed for
1-aza-2-phospha(V)allyl complexes.22a,23b
Theoretical Study of Zirconium-Fluorenyl Complexes.
In order to further support the structures proposed for 5c/6c
and to gain more insight into the bonding situations encountered
in these complexes, a theoretical investigation has been carried
out at the DFT level of theory. The full substitution pattern of
the NPC ligands was conserved in order to take reliably into
account electronic and steric factors. Accordingly, the key
features of complex 5a could be very well reproduced (with
(42) The Free Gibbs energy can hardly be computed for such a large
system, but the entropic term for the fragmentation reaction (5c* f 6c* +
toluene) can be roughly estimated to favor the cyclometalated complex by
8 ( 2 kcal/mol at 25 °C. Watson, L. A.; Eisenstein, O. J. Chem. Educ.
2002, 79, 1269.
(43) (a) Wei, P.; Chan, K. T. K.; Stephan, D. W. Dalton Trans. 2003,
3804. (b) Chan, K. T. K.; Spencer, L. P.; Masuda, J. D.; McCahill, J. S. J.;
Wei, P.; Stephan, D. W. Organometallics 2004, 23, 381.
(44) (a) Vicente, J.; Abad, J. A.; Clemente, R.; López-Serrano, J.;
Ramírez de Arellano, M. C.; Jones, P. G.; Bautista, D Organometallics
2003, 22, 4248. (b) Aguilar, D.; Aragüés, M. A.; Bielsa, R.; Serrano, E.;
Navarro, R.; Urriolabeitia, E. P. Organometallics 2007, 26, 3541.
(40) For representative examples of phosphazene complexes with group
4 metals, see refs 22b,c.

6798 Organometallics, Vol. 26, No. 27, 2007
Oulié et al.
Table 1. Selected Bond Lengths and Angles (in Å and deg, Respectively) for Complexes 5a, 5c, and 6c
N-Zr
C-Zr
N-Zr-C
N-P
P-C
N-P-C
ΣC1R
P-C1-Cg
5a (X-ray)
5aa
2.182(6)
2.24
2.28
2.561(8)
2.56
2.54
64.9(2)
65.9
66.5
1.655(6)
1.67
1.68
1.724(7)
1.79
1.79
98.8(3)
98.7
99.5
349.4
344.8
348.4
353.4
204.0
212.8
208.1
201. 1
5ca
6ca
2.28
2.46
66.7
1.68
1.79
98.5
a Predicted at the B3PW91/SDD(Zr,P),6-31G**(other atoms) level of theory.
Scheme 5. Synthesis of the Indenyl Zirconium Complexes
7a–c and 8c
Figure 6. Molecular view of 7a in the solid state, with hydrogen
atoms omitted.
7a proved to be highly unstable in solution at room
temperature (noticeable decomposition being typically ob-
served within a few hours)47 and was therefore characterized
by multinuclear NMR at 250 K. The 1H NMR spectrum
revealed the presence of three equivalent benzyl groups per
(IndPPh2NPh) ligand, the CH2 groups appearing as an AB
2
system (δ 1.89 and 2.02 ppm, JHH ) 10.5 Hz) as expected
because of the dissymmetry induced by the indenyl fragment.
The downfield chemical shifts of the remaining protons H8
(7.02 ppm) and H9 (6.57 ppm)32 of the five-membered ring
suggested a low hapticity for the indenyl fragment, a
hypothesis which is further supported by the doublet signal
observed at 67.8 ppm (1JPC ) 111.4 Hz) in 13C NMR for
C1.48
Single crystals of 7a, suitable for an X-ray diffraction study,
were obtained from a saturated toluene solution at -20 °C
(Figure 6, Table 2). In a similar way to that observed in 5a, the
zirconium center adopts a distorted trigonal bipyramidal geom-
etry (with one of the benzyl groups at zirconium and the nitrogen
atom occupying the pseudoaxial positions), and the NPC chelate
is unsymmetrically bonded to the metal. All of the benzyl groups
are η1-coordinated, and the distances between zirconium and
the carbon atoms of the indenyl C5-ring are all longer than 2.85
Å, excepted Zr-C1 (2.603 Å). Although the latter value
significantly exceeds those observed in complexes B-G and
even in 5a (2.561 Å), it clearly indicates some bonding
interaction. The η1 coordination of the indenyl ring is ac-
Synthesis and Characterization of Zirconium-Indenyl
Complexes. The geometrically constrained and sterically
expanded structures evidenced for complexes 5a,c demon-
strate the propensity of the phosphazene sidearm to enforce
low η1-fluorenyl coordination even with group 4 metals. This
prompted us to investigate the possible access to η1-indenyl
coordination from the corresponding (IndPPh2NAr)- ligands.
Such η1-coordination is less favored with indenyl than with
fluorenyl rings due to competitive η2- or η3-coordination, and
with group 4 metals, it has only been structurally authenti-
cated in complexes D,13 G,15 and H.16 Thanks to reduced
steric pressure, the phenylated ligand 4a (engaged as a
mixture of its three isomers 4, 4′, and 4′′) readily reacted
with ZrBn4 (1 equiv) in toluene at room temperature (Scheme
5). According to 31P NMR monitoring, the reaction was
complete in a few minutes (<10 min), and all isomers led to
a single product 7a exhibiting a signal at 17.6 ppm. Complex
companied by the outward pyramidalization of C1 (ΣC1R
352.0°), resulting in a widened P-C1-Cg bond angle (202.4°).
This result thus confirms the propensity of the pendent phos-
)
2
(45) For selected examples of intramolecular activation of Csp -H bonds,
see: (a) Bulls, A. R.; Schaefer, W. P.; Serfas, M.; Bercaw, J. E.
Organometallics 1987, 6, 1219. (b) Qian, B.; Scanlon, W. J., IV; Smith,
M. R., III; Morty, D. H.; Organometallics 1999, 18, 1693. (c) Shao, P.;
Gendron, R. A. L.; Berg, D. J.; Bushnell, G. W. Organometallics 2000,
19, 509. (d) Deckers, P. J. W.; Hessen, B. Organometallics 2002, 21, 5564.
(e) Planalp, R. P.; Andersen, R. A.; Zalkin, A. Organometallics 1983, 2,
16. (f) Jimenez Pindado, G.; Thornton-Pett, M.; Bochmann, M. Chem.
Commun. 1997, 609. (g) Pool, J. A.; Lobkovsky, E.; Chirik, P. J. J. Am.
Chem. Soc. 2003, 125, 2241–2251. (h) Otten, E.; Dijkstra, P.; Visser, C.;
Meetsma, A.; Hessen, B. Organometallics 2005, 24, 4374. (i) Waterman,
R. Organometallics 2007, 26, 2492.
(47) R-Eliminationoftolueneleadingtoextremelyreactivezirconium-carbene
complex seems the most probable decomposition route of 7a. For rare
examples of stable zirconium-benzylidene complexes, see: (a) Fryzuk,
M. D.; Duval, P. B.; Mao, S. S. S.; Zaworotko, M. J.; MacGillivray, L. R.
J. Am. Chem. Soc. 1999, 121, 2478. (b) Weng, W.; Yang, L.; Foxman,
B. M.; Ozerov, O. V. Organometallics 2004, 23, 4700.
(48) The high-field shift accompanying the ring slippage from η5- to
η1-indenyl coordination has been established for late transition metals,
especially palladium: (a) Sui-Seng, C.; Enright, G. D.; Zargarian, D.
Organometallics 2004, 23, 1236. (b) Sui-Seng, C.; Enright, G. D.; Zargarian,
D. J. Am. Chem. Soc. 2006, 128, 6508.
(46) A zirconocene imido complex was recently found to be capable of
3
intermolecularly activating the Csp -H bonds of mesitylene; see: Hoyt,
H. M.; Bergman, R. G. Angew. Chem., Int. Ed. 2007, 46, 5580.

Enforced η1-Fluorenyl and Indenyl Coordination to Zirconium
Organometallics, Vol. 26, No. 27, 2007 6799
Table 2. Selected Bond Lengths and Angles (in Å and deg, Respectively) for Complexes 7a–c and 8c
N-Zr
C1-Zr
C2-Zr
C9-Zr
C7-Zr
C8-Zr
N-Zr-C
N-P
P-C1
N-P-C ΣC1R P-C1-Cg
E
7a
2.153(6) 2.603(8) 2.875(8) 3.660(8) 3.865(9) 4.257(9)
63.9(2)
65.6
66.1
64.0(1)
66.5
64.1
64.7(2)
64.4
63.9
64.6
65.1
1.616(5) 1.743(8)
98.4(4) 352.0
202.4
207.1
163.5
165.8
199.9
158.3
201.5
209.8
158.6
202.7
160.9
170.5
a
a
7a1
7a2
7b
7b1
7b2
7c
7c1
7c2
7c3
8c1
8c2
2.22
2.38
2.66
2.47
2.95
2.75
3.66
2.50
3.92
2.85
4.27
2.66
1.67
1.66
1.77
1.79
100.2
99.8
353
357.4
0
7.7
2.327(2) 2.513(3) 2.692(3) 2.681(3) 2.953(3) 2.913(3)
1.616(2) 1.759(3)
99.1(2) 357.5
a
2.27
2.38
2.57
2.53
3.15
2.70
3.35
2.69
3.96
2.95
4.04
2.90
1.68
1.66
1.78
1.78
100.8
99.0
353.6
358.3
6.2
0
a
2.235(4) 2.535(7) 3.504(7) 2.815(7) 4.055(7) 3.707(7)
1.623(4) 1.742(6)
99.2(3) 353.6
a
2.22
2.37
2.26
2.31
2.30
2.64
2.55
2.61
2.55
2.51
3.15
2.79
3.61
2.88
2.68
3.61
2.69
2.81
2.55
2.78
4.11
3.05
4.17
2.97
3.03
4.33
2.95
3.74
2.78
3.05
1.68
1.66
1.67
1.65
1.65
1.78
1.78
1.77
1.79
1.78
101.5
98.6
99.2
99.5
99.5
350.6
358.4
353.1
357.3
358.5
5.5
3.1
0
0
0.1
a
a
a
a
65.8
a Predicted at the B3PW91/SDD(Zr,P),6-31G**(other atoms) level of theory. E, relative energy in kcal/mol.
result, the environment around C1 is slightly pyramidalized
inward rather than outward (ΣC1R ) 357.5°) and the P-C1-Cg
angle (165°) significantly closes, while remaining noticeably
larger than that of CGCs A (∼148°). This result reveals that
the steric demand of the substituent at nitrogen may dramatically
affect the hapticity of the indenyl ring and thereby the overall
geometry of the geometrically constrained complex. Notably,
η3-indenyl coordination has only been scarcely observed in
group 4 metallocenes, and in all of the previous examples, the
Ind/M bonding involved the three external carbon atoms (C1,
C8, and C9).50 The η3-coordination through C1, C2, and C9,
as observed in 7b, is rather unusual, and noticeably contrasts
with the η5-coordination systematically observed so far for the
related IndSiN CGCs, as revealed by a Cambridge Database
search.
Figure 7. Molecular view of 7b in the solid state, with hydrogen
atoms omitted.
With the less encumbered ligand 4c featuring a Mes group
at nitrogen, the reaction toward ZrBn4 is complete after 4 h at
room temperature in toluene. In marked contrast with that
observed in the fluorenyl series, the 1H NMR spectrum indicated
the retention of three benzyl groups per indenyl and the integrity
of the mesityl substituent. The 13C NMR chemical shift for C1
(δ 71.3 ppm with 1JPC ) 118.7 Hz) is at halfway between those
of 7a and 7b (67.4 and 73.5 ppm, respectively), suggesting low
indenyl coordination but not allowing to discriminate between
η1 and η3 hapticity. The downfield chemical shifts of the
remaining protons H8 and H9 of the five-membered ring (6.97
and 6.92 ppm) also suggest weak if any interactions of the
corresponding carbon atoms with the metal center. Cooling a
saturated solution of 7c in toluene at -20 °C yielded orange-
brown crystals suitable for X-ray diffraction study (Figure 7).
Accordingly, 7c also adopts a distorted trigonal bipyramidal
geometry and the key Zr-N and Zr-C1 bond lengths (2.235
and 2.535 Å, respectively) are in between those observed for
7a and 7b, as expected from the intermediate steric demand of
the mesityl group compared with the phenyl and DIPP substit-
uents. The distances between the other indenyl carbon atoms
and the zirconium center are quite large (>3 Å) except Zr-C9
(2.815 Å) which is at the upper limit to consider a bonding
interaction. In addition, complex 7c also exhibits outward
pyramidalization of C1 (ΣC1R ) 353.6°) associated with a
widened P-C1-Cg angle (201.5°). All these data indicate η1-
coordination of the indenyl ring (or a strongly unsymmetrical
η2-coordination,51 taking into account the additional weak
interaction between Zr and C9). The electron deficiency induced
at the metal center by this low hapticity is at least partially
compensated by η2-coordination of one of the benzyl ligands
phazene moiety to enforce not only η1-Flu but also η1-Ind
coordination to group 4 metals, and to the best of our knowledge,
complex 7a is the first geometrically constrained and sterically
expanded complex featuring an indenyl ring.
The much higher reactivity of the indenyl (vs fluorenyl) ligand
noticed with 4a (vs 2a) encouraged us to investigate then the
coordination of the more sterically demanding ligands 4b/c and
to determine thereby the influence of the substituent at nitrogen.
Accordingly, the reaction of 4b featuring the DIPP group with
1 equiv of ZrBn4 took place within 10 h at room temperature
(whereas no reaction was observed with its fluorenyl analogue
2b even at 90 °C) to give a new complex 7b exhibiting a 31P
1
NMR signal at δ 12.6 ppm. The H NMR spectrum indicated
the presence of three benzyl groups per (IndPPh2NDIPP) ligand,
and the broad 13C NMR signal observed for C1 at 73.5 ppm
supported low coordination of the indenyl ring. No additional
information could be gained from the NMR data, only broad
signals being observed even at low temperature (-50 °C). But
the precise structure of complex 7b could be assessed by
crystallization from a THF solution at -20 °C and X-ray
diffraction analysis (Figure 7). Accordingly, the distorted
trigonal bipyramidal geometry around zirconium was retained,
but the steric pressure induced by the DIPP vs phenyl group
induced a noticeable elongation of the Zr-N bond (2.327 Å,
compared to 2.153 Å in 7a) and, as a compensation, a shortening
of the Zr-C1 distance (2.513 Å, compared to 2.603 Å in 7a).
Notably, two other indenyl carbons (C2 and C9) are located at
distances <2.80 Å from the zirconium (2.692 Å and 2.681 Å,
respectively) suggesting η3 rather than η1 coordination.49 As a
(49) The weak contacts of Zr with C2 and C9 do not affect the C1-C2,
C1-C9, and C9-C8 bond lengths, with deviations of less than 0.03 Å
compared with 7a.
(50) For an ansa-hafnocene complex featuring an η3-indenyl ring, see:
Christopher, J. N.; Jordan, R. J.; Petersen, J. L.; Young, V. G., Jr.
Organometallics 1997, 16, 3044.

6800 Organometallics, Vol. 26, No. 27, 2007
Oulié et al.
Table 3. Crystallographic Data for Complexes 5a and 7a–c
5a
7a
7b
7c
empirical formula
formula weight
crystal system
space group
a, Å
C52H44NPZr
805.07
C
58.50H54 NPZr
C62H70NO2PZr
983.38
monoclinic
P2(1)/c
12.8193(7)
19.4797(11)
21.7493(12)
90
106.4130(10)
90
5209.8(5)
4
1.254
0.286
26086
C51H48NPZr
797.09
893.22
triclinic
P-1
monoclinic
P2(1)/c
9.9869(14)
18.293(3)
22.616(3)
90
101.602(3)
90
4047.3(10)
4
1.321
0.348
15744
4873
0.0687
0.0970
0.556 and -0.441
orthorhombic
P2(1)2(1)2(1)
10.7685(4)
16.9735(7)
22.2085(9)
90
90
90
4059.3(3)
4
1.304
0.346
37507
5763
0.0454
0.0758
0.257 and -0.333
12.8962(12)
12.9966(10)
15.1856(12)
82.994(5)
78.340(5)
68.739(5)
2319.7(3)
2
1.279
0.311
21119
6368
b, Å
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
densitycalcd, Mg/m3
absorp coeff, mm-1
reflections collected
independent reflections
R1 (I > 2σ(I))
wR2
8802
0.0429
0.0965
0.417 and -0.358
0.0532
0.1170
0.333 and -0.367
(∆/r)max (e Å-3
)
at zirconium, as supported by the short Cipso-Zr distance (2.71
Å) and the acute Zr-CH2-Cipso bond angle (90.5°).
estimate the propensity of a given ligand (IndPPh2NAr)- to
adopt different coordination modes, DFT calculations were
performed on the real complexes 7a–c* and 8c*. For each
complex, at least two minima, corresponding to different indenyl
hapticities, were located on the PES (see Figure 9, and Table 2
for key geometric data).
The milder conditions required for the metalation of 4c (4 h
at rt) compared to 2c (5 days at 90 °C) thus allowed the isolation
of the indenyl complex 7c, whose fluorenyl analogue 5c could
not be detected. We then explored the propensity of 7c to
similarly undergo another cyclometalation reaction. Accordingly,
a toluene solution of 7c was heated at 80 °C, and complete
conversion in a new complex 8c was achieved after 4 h,
according to 31P NMR spectroscopy. The elimination of a
second molecule of toluene was indicated by the 1H NMR
spectrum. As expected, two AB systems integrating for 2H each
were observed for the CH2 groups of the two remaining benzyl
groups. A third AB pattern (δ 2.53 and 2.43 ppm, 2JHH ) 13.8
Hz) was attributed to the metalated ortho position of the mesityl
substituent, the two remaining CH3 groups resonating as two
singlets integrating for 3H each (δ 2.27 and 1.60 ppm). The
13C NMR signal observed at 72.7 ppm (1JPC ) 127.1 Hz) for
C1 is very similar to those of 7a–c, in agreement with low
indenyl hapticity. In addition, the 1H chemical shifts of H9 (6.27
ppm) and H8 (6.93 ppm), suggests that C9, and eventually C8,
interact with the metal. No suitable crystals could be obtained
in this case to determine the precise coordination of 8c in the
solid state.
The most stable structure predicted for the N-phenylated
derivative is the η1-complex 7a1*, in agreement with experi-
mental observations. The DFT calculations reproduced very well
the unsymmetrical coordination of the chelating NPC ligand
(N-Zr ) 2.22 Å and C1-Zr ) 2.66 Å), as well as the outward
pyramidalization of C1, with a P-C1-Cg bond angle of 207.1°.
The second energy minimum located 7a2* exhibits a much
higher indenyl hapticity (with all distances between the metal
and the carbon atoms of the five-membered ring varying from
2.47 to 2.85 Å), together with a longer N-Zr bond (2.33 Å).
As a consequence, the overall geometry 7a2* resembles that of
CGCs A, with an inward pyramidalized around C1 associated
with a P-C1-Cg angle of 163.5°. The fairly large energy
difference predicted between 7a1* and 7a2* (7.7 kcal/mol)
substantiates the propensity of the phosphazene sidearm to
enforce η1-indenyl coordination.
By analogy with that found experimentally, the related
complex 7b* featuring the DIPP group at nitrogen was predicted
to preferentially adopt η3-indenyl coordination with inward
pyramidalization around C1. The optimized geometry for the
most stable form 7b2* fits perfectly well with that found in the
solid-state. In particular, the elongated N-Zr (2.38 Å) and
shortened C1-Zr (2.53 Å) bond distances are nicely reproduced,
as well as the additional bonding interactions with C2 (2.70 Å)
and C9 (2.69 Å). The related η1-indenyl structure 7b1* was
found 6.0 kcal/mol higher in energy, as the result of the
detrimental steric constrain associated with the shortened N-Zr
contact (2.27 Å). Accordingly, the sterically demanding DIPP
substituent at nitrogen prevents strong coordination of the
phosphazene sidearm and thus disfavors the sterically expanded
geometry.
Theoretical Study of Zirconium-Indenyl Complexes. The
X-ray diffraction analyses carried out on 7a–c revealed a rather
strong influence of the substituent at nitrogen on the coordination
mode of the indenyl ring. To further evidence this trend and to
The unsymmetrical η2-coordination mode and outward C1-
pyramidalization observed in the solid-state structure of 7c was
also very well reproduced theoretically. This form 7c3* corre-
(51) For rare examples of η2-indenyl coordination toward group 4 metals,
see: (a) Diamond, G. M.; Green, M. L. H.; Mountford, P.; Popham, N. A.;
Chernega, A. N. Chem. Commun. 1994, 103. (b) Diamond, G. M.; Green,
M. L. H.; Popham, N. A.; Chernega, A. N. Chem. Commun. 1994, 727. (c)
Chen, E. Y.-X; Jin, J. Organometallics 2002, 21, 13.
Figure 8. Molecular view of 7c in the solid state, with hydrogen
atoms omitted.

Enforced η1-Fluorenyl and Indenyl Coordination to Zirconium
Organometallics, Vol. 26, No. 27, 2007 6801
complexes. This emphasizes the prominent role of kinetic factors
in the isolation of the intermediate complex 7c in the indenyl
series.
Conclusion
Bifunctional ligands featuring a phosphazene group directly
bonded to a fluorenyl or indenyl ring have been prepared and
coordinated to the ZrBn3 fragment via toluene elimination.
Despite the associated geometry constraint, the nitrogen atom
was found to strongly interact with the metal center and to
enforce thereby low fluorenyl and indenyl hapticities. In
particular, the η1-fluorenyl and indenyl complexes 5a and 7a
were obtained from the (FluPPh2NPh) and (IndPPh2NPh)
ligands, respectively. These complexes exhibit outward pyra-
midalization of Cipso (associated with P-Cipso-Cg bond angles
of more than 200°), a situation that markedly contrasts with
that observed in classical CGCs. These results demonstrate that
geometrically constrained and sterically expanded arrangements
can be enforced electronically in group 4 metal complexes using
a short and strongly donating phosphazene sidearm. In addition,
the steric demand of the substituent at nitrogen was shown to
strongly influence the indenyl hapticity (from η1 with Ph, to
strongly unsymmetrical η2 with Mes, and η3 with DIPP).
Original intramolecular CH-activation reactions leading to
doubly cyclometalated complexes have also been evidenced
upon thermolysis of the NMes-substituted systems.
The development of an increasing variety of geometrically
constrained and sterically expanded complexes should greatly
help in rationalizing and improving further the peculiar activity
and selectivity evidenced by Miller et al. for the prototypical
complexes [(FluSiMe2N-t-Bu)MX2L] B toward homo- and
copolymerization of R-olefins.10 Future research will seek
particularly to increase the stability of such complexes by
varying the ligand framework as well as the metal fragment so
that their reactivity can be investigated and the precise role of
low Flu and Ind hapticities can be understood.
Figure 9. Optimized structures for complexes 7a–c* and 8c* at
the B3PW91/SDD(Zr,P),6–31G**(other atoms) level of theory, with
hydrogen atoms omitted.
sponds to the global mininum on the PES, and the related η1
and η3-complexes, 7c1* and 7c2*, were found only 5.5 and 3.1
kcal/mol higher in energy, respectively. Given the results
obtained for 7a* and 7b* featuring Ph and DIPP groups,
respectively, it is logical that the intermediate steric demand of
the Mes substituent induces only small energetic separations
between the different forms of 7c*.
Experimental Section
All reactions were performed using standard Schlenk techniques
under an argon atmosphere. 31P, 1H, and 13C spectra 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, diethyl ether,
and toluene were dried under sodium and distilled prior to use. All
organic reagents were obtained from commercial sources and used
as received. ZrBn4 was purchased from Strem Chemicals, stocked
out of light in a glovebox, and used without further purification.
The fluorenyldiphenylphosphine 1,29 ensuing phenylphosphazene
2a,27 indenyldiphenylphosphine 3,34 and azides30 were prepared
according to literature procedures. All of the zirconium complexes
proved to be too sensitive to get satisfactory elemental analysis or
HRMS data.
Synthesis of Ph2FluPdN(i-Pr2)2C6H3 (2b). A degassed solution
of 2,6-i-Pr2C6H3N3 (0.60 g, 3.10 mmol) in toluene (8 mL) was added
at room temperature to a degassed suspension of Ph2PFlu (1.00 g,
2.85 mmol) in toluene (20 mL). After the mixture was stirred for
20 h at 30 °C, the solvent was eliminated under vacuum to yield a
pale yellow solid which was washed with cold pentane (20 mL).
Yield: 1.20 g (80%). 31P{1H} NMR (81 MHz, C6D6): δppm -1.9
(s). 1H NMR (300 MHz, C6D6): δppm 7.64 (d, 3JH,H ) 7.8 Hz, 2H,
H3,3′), 7.46–7.38 (m, 6H, H13 and H6,6′), 7.18 (m, 2H, H10), 7.10
(m, 2H, H5,5′), 7.04 (m, 3H, H4,4′ and H11), 6.92–6.78 (m, 6H, H15
and H14), 5.20 (d, 2JH,P ) 24.6 Hz, 1H, H1), 3.58 (sept, 3JH,H ) 6.8
Calculations were also performed on the ensuing doubly
cyclometalated complex 8c in order to substantiate further the
structure suggested by the NMR data. Two energy minima 8c1*
and 8c2* of similar energy (∆E ) 0.1 kcal/mol) were located.
For both structures, the intramolecular CH-activation reaction
has induced the rotation of the aryl substituent at nitrogen by
about 90°, and the cyclometalated ortho position occupies the
pseudoaxial position trans to C1. The NPC skeleton is very
similarly bonded in the two forms, with a slight elongation of
N-Zr bond (2.30 and 2.31 Å) compared to that found in the
intermediate complex 7c3* (2.26 Å). Moreover, structure 8c1*
(8c2*, respectively) exhibits additional contacts with C9 (2.55
Å) and to a less extent C8 (2.78 Å) [C2 (2.68 Å) and C9 (2.78
Å), respectively]. Accordingly, both forms 8c1* and 8c2* present
inward pyramidalization around C1 and may be considered η2-
or η3-coordinated. This situation contrasts with the η1-coordina-
tion and outward pyramidalization predicted for the related
fluorenyl complex 6c* and further illustrates the lower propen-
sity of Ind vs Flu rings to adopt η1-coordination. Finally, the
cyclometalation reaction (7c3* f 8c1* + toluene) is predicted
to be favored energetically, with a ∆E value (-3.38 kcal/mol)
in the same range than that computed for the related fluorenyl

6802 Organometallics, Vol. 26, No. 27, 2007
Oulié et al.
3
Hz, 2H, CH(CH3)2), 1.17 (d, JH,H ) 6.8 Hz, 12H, CH(CH3)2).
orange powder (0.95 g, 91%). 31P{1H} NMR (121.4 MHz, C6D6):
13C{1H} NMR (75.5 MHz, C6D6): δppm 144.6 (C8), 142.4 (d, 2JC,P
isomer 4b δppm -16.5; isomer 4′b δppm -6.0; isomer 4′′b δppm 23.9.
3
3
) 7.4 Hz, C9), 142.2 (d, JC,P ) 4.8 Hz, C7,7′), 140.2 (d, JC,P
)
1H NMR (300 MHz, C6D6): isomer 4b δppm 7.82–7.75 (m, 4JH,P
)
3.9 Hz, C2,2′), 131.9 (d, 2JC,P ) 8.3 Hz, C13), 131.0 (d, 4JC,P ) 2.8
9.6 Hz, 4H, H16), 7.68 (m, 1H, H3), 7.21–7.17 (m, 3H, H12,13), 7.20
(overlapped, 1H, H6), 7.10–6.97 (m, 6H, H15,17), 7.05–6.97 (m, 2H,
1
3
Hz, C15), 128.0 (d, JC,P ) 91.6 Hz, C12), 127.7 (d, JC,P) 11.4
Hz, C13), 127.4 (d, 5JC,P ) 2.0 Hz, C5,5′), 126.5 (d, 3JC,P ) 1.9 Hz,
H
4,5), 6.29 (dt, 1H, 3JH,P ) 9.0 Hz, 3JH,H ) 2.0 Hz, H9), 3.66 (sept,
4
4
C3,3′), 126.3 (d, JC,P ) 2.3 Hz, 6 C4,4′), 122.9 (d, JC,P ) 1.8 Hz,
2H, 3JH,H ) 6.9 Hz, -CH(CH3)2), 2.94 (pseudo t, 2H, 4JH,P ) 2.0
Hz, 3JH,H ) 2.0 Hz, H8), 0.96 (d, 12H, 3JH,H ) 6.9 Hz, -CH(CH3)2);
isomer 4′b δppm 6.90 (overlaps, 1H, H8), 6.55 (br s, 1H, H9), 4.87
C10), 119.8 (d, 5JC,P ) 2.9 Hz, C11), 119.6 (d, 4JC,P ) 1.1 Hz, C6,6′),
1
53.4 (d, JC,P ) 68.7 Hz, C1), 28.8 (CH), 23.9 (CH3). MS (EI 78
eV) m/z: 483 (M)+, 318 (M - Flu)+, 240 (M - Flu - Ph)+, 165
(Flu)+. Mp: 186 °C. Anal. Calcd for C37H36NP: C, 84.54; H, 6.90;
N, 2.66. Found: C, 84.14; H, 7.04; N, 2.64.
(d, 1H, JH,P ) 27.1 Hz, H1), 3.66 (overlaps, 1H, -CH(CH3)2),
2
3
3.27 (m, 1H, -CH(CH3)2), 1.26 (d, 6H, JH,H ) 6.8 Hz,
3
-CH(CH3)2), 0.74 (d, 6H, JH,H ) 6.8 Hz, -CH(CH3)2); isomer
Synthesis of Ph2FluP)NMes (2c). A degassed solution of
MesN3 (1.00 g, 6.20 mmol) in toluene (5 mL) was added at room
temperature to a degassed suspension of Ph2PFlu (2.15 g, 6.15
mmol) in toluene (50 mL). After the mixture was stirred for 24 h
at room temperature, the solvent was eliminated under vacuum to
yield a pale yellow solid. Cooling a solution of 2c in toluene/pentane
to -25 °C yielded 2.50 g of pale yellow crystals (84%). 31P{1H}
NMR (81 MHz, C6D6): δppm -1.7 (s). 1H NMR (300 MHz, C6D6):
4′′b δppm 4.15 (br s, 1H, N-H), 3.80 (br m, 1H, -CH(CH3)2), 3.66
(overlaps, 1H, -CH(CH3)2), 1.06 (overlaps, 6H, -CH(CH3)2), 0.85
3
(d, 6H, JH,H ) 6.7 Hz, -CH(CH3)2). 13C{1H} NMR (75.5 MHz,
2
C6D6): isomer 4b δppm 145.8 (d, JC,P ) 8.8 Hz, C9), 144.3 (d,
2JC,P ) 2.7 Hz, C10), 143.8 (d, 3JC,P ) 9.5 Hz, C7), 143.3 (d, 2JC,P
3
1
) 11.6 Hz, C2), 142.8 (d, JC,P ) 7.0 Hz, C11), 140.7 (d, JC,P
)
95.1 Hz, C1), 132.1 (d, 1JC,P ) 106.0 Hz, C1), 132.0 (d, 3JC,P ) 9.6
Hz, C16), 131.1 (d, 4JC,P ) 2.7 Hz, C17), 128.3 (d, 2JC,P ) 12.1 Hz,
C15), 126.4 (C4 or 5), 125.5 (C4 or 5), 123.5 (d, 3JC,P ) 9.8 Hz, C3),
122.8 (d, 4JC,P ) 2.5 Hz, C12), 119.9 (d, 5JC,P ) 2.5 Hz, C13), 39.4
(d, 3JC,P ) 12.6 Hz, C8), 28.5 (CH(CH3)2), 23.6 (CH(CH3)2); isomer
δ
ppm 7.65 (d, 3JH,H ) 7.8 Hz, 2H, H3,3′), 7.44 (m, 4H, H13), 7.37 (d,
3JH,H ) 7.5 Hz, 2H, H6,6′), 7.14 (m, 2H, H5,5′), 7.03 (m, 2H, H4,4′),
6.95 (m, 2H, H15), 6.90 (m, 4H, H14), 6.85 (m, 2H, H10), 5.12 (d,
5
2
3
2JH,P ) 24.0 Hz, 1H, H1), 2.35 (d, JH,H ) 1.5 Hz, 6H, o-CH3),
4′b δppm 134.0 (d, JC,P ) 8.7 Hz, C9), 132.4 (d, JC,P ) 9.5 Hz,
C8), 56.8 (d, JC,P ) 67.9 Hz, C1), 28.9 (CH(CH3)2), 28.1
7
1
2.25 (d, JH,H ) 2.4 Hz, 3H, p-CH3). 13C{1H} NMR (75.5 MHz,
2
C6D6): δppm 145.4 (C8), 142.2 (d, JC,P ) 4.5 Hz, C7,7′), 140.2 (d,
(CH(CH3)2), 23.8 (CH(CH3)2), 23.7 (CH(CH3)2); isomer 4′′b δppm
28.9 (CH(CH3)2), 28.1 (CH(CH3)2), 23.8 (CH(CH3)2), 23.7
(CH(CH3)2). MS (EI, 70 eV) m/z: 475 [M]+ (74), 460 [M - CH3]+
(28), 432 [i-Pr]+ (40), 360 [M - Ind]+ (75), 300 [M - N((i-
Pr2)2C6H3)]+ (12), 185 [M - N((i-Pr2)2C6H3) - Ind]+ (72), 115
[Ind]+ (85); HRMS (ES+): calcd for C33H35NP 476.2507, found
476.2498. Mp: 175 °C dec.
3JC,P ) 3.8 Hz, C2,2′), 131.9 (d, 2JC,P ) 8.3 Hz, C13), 131.6 (d, 3JC,P
) 6.8 Hz, C9,9′), 130.8 (d, 4JC,P ) 3.0 Hz, C15), 129.9 (C11), 129.2
(d, 1JC,P ) 92.1 Hz, C12), 128.7 (d, 4JC,P ) 2.3 Hz, C10), 127.5 (d,
3JC,P)10.6 Hz, C14), 127.2 (d, 5JC,P ) 2.3 Hz, C5,5′), 126.8 (d, 3JC,P
4
4
) 3.0 Hz, C3,3′), 126.3 (d, JC,P ) 2.3 Hz, C4,4′), 119.5 (d, JC,P
)
1
4
1.5 Hz, C6,6′), 53.0 (d, JC,P ) 65.7 Hz, C1), 21.6 (d, JC,P ) 1.5
6
Hz, o-CH3), 20.5 (d, JC,P ) 0.8 Hz, p-CH3). MS (EI 70 eV) m/z:
Synthesis of Ph2IndPdNMes (4c). A degassed solution of
MesN3 (0.61 g, 3.80 mmol) in dichloromethane (5 mL) was added
at room temperature to a degassed solution of Ph2PInd (0.96 g,
3.20 mmol) in dichloromethane (10 mL). After being stirred for
2 h, the reaction mixture was concentrated (about 5 mL), and
pentane (60 mL) was added to induce the precipitation of a black-
orange solid. The orange solution was filtered and evaporated to
dryness. The orange residue was washed with pentane (3 × 10
mL), and 4c was obtained as a yellow powder (0.95 g, 68%).
31P{1H} NMR (121.4 MHz, C6D6): isomer 4c δppm -18.2; isomer
483 (M)+, 318 (M - Flu)+, 240 (M - Flu - Ph)+, 165 (Flu)+.
Anal. Calcd foror C34H30NP: C, 84.45; H, 6.25; N, 2.90. Found:
C, 84.21; H, 6.26; N, 2.82. Mp 182 °C.
Synthesis of Ph2IndPdNPh (4a). A degassed solution of PhN3
(0.800 g, 6.70 mmol) in dichloromethane (5 mL) was added at room
temperature to a degassed solution of Ph2PInd (2.00 g, 6.60 mmol)
in dichloromethane (10 mL). After being stirred for 2 h, the reaction
mixture was concentrated (about 10 mL), and pentane (40 mL) was
added. The yellow precipitate was filtered off and washed with three
portions of pentane (20 mL) to give 4a as a yellow powder (2.31
g, 90%). 31P{1H} NMR (121.4 MHz, C6D6): isomer 4a δppm -8.3;
isomer 4′a δppm -4.5; isomer 4′′a δppm 18.7. 1H NMR (300 MHz,
1
4′′c δppm 22.3; isomer 4′c δppm -5.4. H NMR (300 MHz, C6D6):
3
isomer 4c δppm 7.82–7.77 (m, 4H, H16), 7.68 (dd, 1H, JH,P ) 6.3
3
Hz, JH,H ) 2.0 Hz, H3), 7.17 (overlaps, 1H, H6), 7.06–6.96 (m,
4
C6D6): isomer 4a δppm 7.90 ppm (m, JH,P ) 9.8 Hz, 4H, H16),
6H, H15,17), 6.96–6.91 (m, 2H, H4,5), 6.91 (br s, 2H, H12), 6.41 (dt,
7.74 (m, 1H, H3), 7.32 (m, 2H, H11), 7.17 (m, 2H, H12), 7.15
(overlapped, 1H, H6), 7.05–6.95 (m, 6H, H15,17), 7.00 (overlapped,
1H, H4 or 5), 6.90 (overlapped, 1H, H4 or 5), 6.80 (m, 1H, H13), 6.71
1H, 3JH,P ) 9.2 Hz, 3JH,H ) 1.6 Hz, H9), 3.00 (br s, 2H, H8), 2.30
2
(s, 9H, CH3), isomer 4′c δppm 4.88 (d, 1H, JH,P ) 26.7 Hz, H1),
2.30 (s, 6H, o-CH3), 2.26 (overlaps, 3H, p-CH3); isomer 4′′c δppm
4.00 (br s, 1H, NH), 2.00 (s, 3H, p-CH3), 1.74 (s, 3H, o-CH3).
3
3
(dt, 1H, JH,P ) 9.5 Hz, JH,H ) 1.8 Hz, H9), 2.98 (pseudo t, 2H,
4JH,P < 2.0 Hz, JH,H < 1.8 Hz, H8); isomer 4′′a δppm 4.97 (br s,
13C{1H} NMR (75.5 MHz, C6D6): isomer 4c δppm 145.5 (d, JC,P
3
2
1H, NH). 13C{1H} NMR (75.5 MHz, C6D6): isomer 4a δppm 152.0
) 8.8 Hz, C9), 144.9 (d, 2JC,P ) 1.6 Hz, C10), 143.8 (d, 3JC,P ) 9.5
Hz, C7), 143.4 (d, 2JC,P ) 11.7 Hz, C2), 141.1 (d, 1JC,P ) 94.2 Hz,
C1), 138.0 (d, 3JC,P ) 2.6 Hz, C11), 131.9 (d, 3JC,P ) 9.7 Hz, C16),
130.9 (d, 4JC,P ) 2.7 Hz, C17), 128.8 (d, 4JC,P ) 2.6 Hz, C12), 128.2
(d, 2JC,P ) 12.1 Hz, C15), 126.4 (C4 or 5), 125.4 (C4 or 5), 123.6 (C3
and C6), 39.4 (d, 3JC,P ) 12.5 Hz, C8), 20.9 (o-CH3), 20.6 (p-CH3);
2
2
(d, JC,P ) 2.1 Hz, C10), 148.4 (d, JC,P ) 9.4 Hz, C9), 143.9 (d,
3JC,P ) 9.9 Hz, C7), 143.0 (d, 2JC,P ) 11.5 Hz, C2), 137.6 (d, 1JC,P
3
1
) 95.6 Hz, C1), 132.2 (d, JC,P ) 9.8 Hz, C16), 131.7 (d, JC,P
)
)
4
2
103.0 Hz, C14), 128.5 (d, JC,P ) 12.8 Hz, C17), 128.4 (d, JC,P
12.0 Hz, C15), 126.7 (C4 or 5), 125.6 (C4 or 5), 123.9 (d, 3JC,P ) 4.0
4
3
1
Hz, C3), 123.4 (d, JC,P ) 3.5 Hz, C6), 39.7 (d, JC,P ) 12.9 Hz,
C8). MS (EI, 70 eV) m/z: 391 [M]+ (55), 276 [M - Ind]+ (100),
115 [Ind]+ (38); HRMS (ES+): calcd for C27H22NP 392.1568, found
392.1545. Mp: 105 °C dec.
isomer 4′c δppm 56.3 (d, JC,P ) 63.2 Hz, C1), 21.3 (o-CH3), 20.4
1
(p-CH3); isomer 4′′c δppm 70.4 (d, JC,P ) 140.2 Hz, C1), 20.6 (p-
CH3), 19.6 (o-CH3). MS (EI, 70 eV) m/z: 433 [M]+ (87), 318 [M
- Ind]+ (100), 115 [Ind]+ (82). HRMS (ES+): calcd for C30H29NP
434.2038, found 434.2031. Mp: 165 °C dec.
Synthesis of Ph2IndPdN(i-Pr2)2C6H3 (4b). A degassed solution
of (i-Pr2)2C6H3N3 (0.40 g, 2.00 mmol) in dichloromethane (5 mL)
was added at room temperature to a degassed solution of Ph2PInd
(0.54 g, 1.80 mmol) in dichloromethane (10 mL). After being stirred
for 2 h, the orange solution was evaporated to dryness. The residue
was washed with four portions of pentane (5 mL) to yield 4b as an
Synthesis of Complex ZrBn3(Ph2FluPdNPh) (5a). A solution
of 2a (296 mg, 0.67 mmol) and ZrBn4 (307 mg, 0.67 mmol) in
toluene was heated at 90 °C in the absence of light for 5 h. The
toluene was evaporated under vacuum to yield an orange-brown
solid (512 mg, 95%). Orange-brown crystals of 5a suitable for X-ray

Enforced η1-Fluorenyl and Indenyl Coordination to Zirconium
Organometallics, Vol. 26, No. 27, 2007 6803
crystallography were obtained from a toluene/pentane solution at
mL)/pentane (0.5 mL) mixture at -25 °C. 31P{1H} NMR (202.5
MHz, CD2Cl2, 287 K): δppm 12.6. 1H{31P} NMR (500 MHz,
CD2Cl2, 287 K): δppm 7.70–7.59 (m, 2H, H17), 7.40–7.36 (m, 4H,
H16), 7.32–7.12 (m, 4H, H15), 7.23 (m, 1H, H13), 7.17 (m, 2H, H12),
room temperature. 31P{1H} NMR (121.4 MHz, C6D6): δppm 21.3
1
3
(s). H NMR (300.1 MHz, C6D6): δppm 8.04 (d, JH,H ) 7.5 Hz,
2H, H6,6′), 7.28–7.08 (m, 10H, H4,4′,6,6′,9,9′,13), 7.08–7.00 (m, 11H,
3
3
H
3,3′,10,11,19), 6.95–6.85 (m, 5H, H15,20), 6.80–6.70 (m, 4H, H14), 6.58
7.12 (pseudo t, 6H, JH,H ) 7.5 Hz, H21), 6.87 (t, 3H, JH,H ) 7.0
3
(d, JH,H ) 8.1 Hz, 6H, H18), 2.17 ppm (s, 6H, H16). 13C{1H}-
3
3
Hz, H22), 6.77 (d, 6H, JH,H ) 7.5 Hz, H20), 3.30 (sept, 2H, JH,H
) 6.6 Hz, -CH-(CH3)2), 2.40 (very br s, 3H, H18), 1.80 (very br s,
3H, H18′), 0.94 (br s, 6H, -CH(CH3)2), 0.79 (br s, 6H, -CH(CH3)2).
13C{1H} NMR (125.3 MHz, CD2Cl2, 287 K): δppm 150.5 (C19),
145.4 (d, 3JC,P ) 5.5 Hz, C11), 141.3 (d, 2JC,P ) 6.9 Hz, C10), 133.6
NMR (75.5 MHz, C6D6): δppm 146 (C17), 141.3 (d, 2JC,P ) 6.5 Hz,
3
2
C2,2′), 137.0 (d, JC,P ) 10.3 Hz, C7,7′), 132.8 (d, JC,P ) 10.3 Hz,
2
C13), 132.4 (C15), 129.2 (C3,3′), 129.1 (d, JC,P ) 81.0 Hz, C12),
2
128.8 (d, JC,P ) 11.8 Hz, C14), 128.2 (C19), 127.9 (C18), 126.3
2
4
(C10), 126.1 (C4,4′), 123.4 (C5,5′), 123.2 (C9,9′), 122.3 (C20), 120.8
(br d, JC,P ) 9.0 Hz, C15), 133.3 (d, JC,P ) 2.7 Hz, C17),
2
3
(C6,6′), 120.1 (C11), 79.7 (C16), 56.0 ppm (d, JC,P ) 96.6 Hz, C1),
C8 not observed. Mp: 146 °C dec.
128.9–129.1 (d, JC,P ) 13.1 Hz, C16), 127.9 (C21), 126.4 (C20),
125.4 (C13), 124.9 (C12), 120.9 (C22), 78.5 (C18), 73.5 (very br, C1),
28.6 (CH(CH3)2), 23.9–24.5 (CH(CH3)2). Mp: 129–130 °C dec.
Synthesis of ZrBn3(Ph2IndPdNMes) (7c). A solution of 4c
(200 mg, 0.46 mmol) and ZrBn4 (230 mg, 0.50 mmol) in toluene
(1.5 mL) was stirred at room temperature in the absence of light
for 4 h. The reaction can also be performed in diethyl ether (8
mL). Although a slightly longer reaction time (14 h) was required,
probably due to the poor solubility of 4c in this solvent, the resulting
complex 7c directly precipitated from the reaction mixture, which
facilitated the workup. The yellow precipitate was washed with
toluene (0.5 mL), and 7c was obtained as a yellow powder (0.26
g, 70%). Orange crystals of 7c suitable for X-ray crystallography
were obtained from a dichloromethane (0.5 mL)/pentane (1 mL)
mixture at -10 °C. 31P{1H} NMR (202.5 MHz, CD2Cl2): δppm 13.4.
1H{31P} NMR (500 MHz, CD2Cl2): δppm 7.70 (d, 1H, 3JH,H ) 8.0
Hz, H6), 7.78 and 7.67 (br s, 1H each, H17), 7.57 and 7.34 (br s,
Synthesis of Complex 6c. Reaction Performed in an NMR
Tube. A solution of 2c (36 mg, 0.08 mmol) and ZrBn4 (58 mg,
0.13 mmol, 1.7 equiv) in toluene-d8 (0.75 mL) was heated at 90
°C in the absence of light for 5 days. Complete consumption of
the ligand was observed. 31P{1H} NMR (81 MHz, toluene-d8): δppm
1
3
15.1 (s). H NMR (400 MHz, toluene-d8): δppm 7.98 (d, JH,H
)
7.8 Hz, 2H, H6,6′), 7.52 (m, 4H, H13), 7.18 (m, 2H, H5,5′), 7.03 (m,
2H, H15), 6.96 (m, 2H, H19), 6.94 (m, 2H, H4,4′), 6.90 (m, 5H, H10,14),
6.86 (m, H20), 6.69 (m, 1H, H10′), 6.68 (m, 2H, H3,3′), 5.94 (d, 3JH,H
) 8.0, 4H, H18), 2.30 (s, 3H, p-CH3), 2.08 (s, 3H, o-CH3), 1.80 (s,
2H, CH2Ar), 1.47 and 1.49 (2 s, 2H each, H16). 13C NMR (100
2
MHz, toluene-d8): δppm 145.9 (d, JC,P ) 6.5 Hz, C8), 144.8 (d,
3JC,P ) 15.6 Hz, C9′ Ar ipso-bridge), 142.3 (C17), 141.8 (d, 2JC,P
)
)
3
4
7.8 Hz, C2,2′), 136.8 (d, JC,P ) 10.0 Hz, C7,7′), 132.8 (d, JC,P
2
4
8.0 Hz, C11), 132.5 (d, JC,P ) 9.9 Hz, C13), 132.0 (d, JC,P ) 2.8
2H each, H16) 7.34 and 6.98 (br s, 2H each, H15), 7.27 (m, 1H,
Hz, C15), 130.5 (C19), 128.6 (C14), 128.3 (C10), 127.5 (C10′), 127.0
3
4
3
H5), 7.08 (m, 6H, H21), 7.02 (m, 1H, H4), 6.97 (dd, 1H, JH,H
)
)
(C18,18′), 125.3 (d, JC,P ) 1.2 Hz, C4,4′), 125.0 (d, JC,P ) 1.7 Hz,
4
3
3
C9), 122.8 (C20), 122.5 (C5,5′), 121.0 (d, 3JC,P ) 1.3 Hz, C3,3′), 120.5
4.2 Hz, JH,P ) 3.1 Hz, H8), 6.94 (d, 1H, JH,H ) 4.2 Hz, JH,P
3
1
2.6 Hz, H9), 6.87 (m, 5H, H22 and H12), 6.52 (d, 6H, JH,H ) 7.5
(C6,6′), 74.5 (C16), 68.7 (CH2 Ar), 57.6 (d, JC,P ) 100.6 Hz, C1),
3
23.2 (o-CH3), 20.8 (p-CH3).
Hz, H20), 6.33 (d, 1H, JH,H ) 8.5 Hz, H3), 2.32 (s, 3H, p-CH3),
3
2.19 (br d, 3H, JH,H ) 10.0 Hz, H18), 1.95 (m, 9H, overlapped
Synthesis of ZrBn3(Ph2IndPdNPh) (7a). Reaction
performed in an NMR Tube. Compound 4a (39 mg, 0.1 mmol)
and ZrBn4 (46 mg, 0.1 mmol, 1.0 equiv) were dissolved in
dichloromethane-d2 (0.6 mL) at room temperature and manually
shaken for a few minutes. Complete consumption of the ligand was
observed. Pale yellow-orange crystals of 7a suitable for X-ray
crystallography were obtained from a toluene (1 mL)/pentane (0.4
mL) mixture at 0 °C. 31P{1H} NMR (202.5 MHz, CD2Cl2, 250
o-CH3 and H18′). 13C{1H} NMR (125.3 MHz, CD2Cl2): δppm 148.1
2
3
(C19), 141.5 (d, JC,P ) 6.7 Hz, C10), 137.5 (d, JC,P ) 12.3 Hz,
C7), 134.9 (d, 3JC,P ) 4.9 Hz, C11), 134.5 (d, 2JC,P ) 13.0 Hz, C2),
134.3 (C13), 134.0 and 133.5 (br s, C17), 132.7 and 132.0 (br d,
2JC,P ≈ 7.0 Hz, C15), 129.0 and 128.5 (br d, JC,P ≈ 10.0 Hz C16),
3
3
128.2 (C21), 127.0 (C20), 124.3 (C4), 124.0 (d, JC,P ) 11.9 Hz,
2
C8), 123.4 and 123.3 (C4 or C5), 121.5 (C22), 121.0 (d, JC,P
)
1
1
K): δppm 17.6. H{31P} NMR (500 MHz, CD2Cl2, 250 K): δppm
11.0 Hz, C9), 120.9 (C4), 79.1 (C18), 71.3 (d, JC,P ) 118.7 Hz,
C1), 21.4 (o-CH3), 20.4 (p-CH3).
7.80 (d, 1H, 3JH,H ) 7.9 Hz, H6), 7.67 (m, 2H, H17), 7.44 (m, 4H,
H16), 7.40 (overlapped, 1H, H5), 7.39–7.34 (m, 4H, H15), 7.28
(overlapped, 1H, H6), 7.22 (m, 2H, H12), 7.15 (pseudo t, 6H, 3JH,H
) 8.0 Hz, H21), 7.02 (d, 1H, 3JH,H ) 4.6 Hz, H8), 6.98 (t, 3H, 3JH,H
Synthesis of Complex 8c. A solution of 7c (100 mg, 0.12 mmol)
in toluene (2.5 mL) was heated at 80 °C in the absence of light for
5 h and evaporated to dryness. The brown residue was dissolved
in dichloromethane-d2 (0.5 mL) and transferred to an NMR tube.
31P{1H} NMR (202.5 MHz, CD2Cl2,): δppm 7.4. 1H{31P} NMR
3
) 7.0 Hz, H22), 6.90 (d, 1H, JH,H ) 7.9 Hz, H3), 6.73 (d, 2H,
3
3JH,H ) 7.6 Hz, H11), 6.60 (t, 1H, JH,H ) 7.9 Hz, H13), 6.57 (d,
(500.3 MHz, CD2Cl2): δppm 7.98 (dd, 2H, 3JH,H ) 7.2 Hz, 3JH,P
)
3
3
1H, JH,H ) 4.6 Hz, H9), 6.48 (d, 6H, JH,H ) 8.0 Hz, H20), 2.02
(d, 3H, 2JH,H ) 10.5 Hz, H18), 1.89 (d, 3H, 2JH,H ) 10.5 Hz, H18′).
13C{1H} NMR (125.3 MHz, CD2Cl2, 250 K): δppm 146.3 (C19),
146.0 (d, 2JC,P ) 5.0 Hz, C10), 140.7 (d, 3JC,P ) 11.3 Hz, C7), 134.6
12.9 Hz, H15), 7.85 (t, 1H, 3JH,H ) 7.5 Hz, H17), 7.71 and 7.65 (dt,
3
3
3
2H, JH,H ≈ 8.0 Hz, JH,P ≈ 3.0 Hz, H16), 7.57 (br d, 1H, JH,H
)
8.5 Hz, H6), 7.55–7.49 (m, 3H, H15 17), 7.35 (m, 1H, H5),
and
2
4
7.12–7.00 (m, 4H, H21), 7.03 (overlapped, 1H, H4), 6.90–6.80 (m,
(d, JC,P ) 10.1 Hz, C2), 133.3 (d, JC,P ) 2.5 Hz, C17), 132.8 (d,
3
3
2JC,P ) 11.0 Hz, C15), 129.7 (d, JC,P ) 11.3 Hz, C9), 129.4 (d,
2
2H, H22), 6.93 (d, 1H, JH,H ) 3.8 Hz, H8), 6.74 (d, 2H, JH,H
)
3
3JC,P ) 10,5 Hz, C16), 129.3 (C12), 128.9 (C21), 128.2 (d, JC,P
)
1
7.5 Hz, H20), 6.73 (s, 1H, H12), 6.67 (d, 1H, JH,H ) 8.0 Hz, H20),
3
3
6.54 (d, 1H, JH,H ) 7.5 Hz, H20), 6.41 (s, 1H, H12′), 6.27 (d, 1H,
87.0 Hz, C14), 127.2 (C20), 125.8 (d, JC,P ) 10.0 Hz, C11), 124.1
(C4), 124.0 (C13), 123.5 (C5), 123.2 (C6), 122.1 (C22), 119.7 (d,
3JC,P ) 12.5 Hz, C8), 118.4 (C3), 78.4 (C18), 67.8 (d, 1JC,P ) 111.4
Hz, C1).
3JH,H ) 3.8 Hz, H9), 6.11 (d, 1H, 3JH,H ) 8.5 Hz, H3), 2.53 (d, 1H,
3JH,H ) 13.8 Hz, Zr-CH2-o-Mes), 2.43 (d, 1H, JH,H ) 13.8 Hz,
3
Zr-CH2-o-Mes), 2.27 (s, 3H, o-CH3), 2.07 (d, 1H, 3JH,H ) 9.9 Hz,
H18), 1.99 (d, 1H, 3JH,H ) 9.9 Hz, H18′), 1.60 (s, 3H, p-CH3), 1.19
Synthesis of ZrBn3(Ph2IndPdN(i-Pr2)C6H3) (7b). A solution
of 4b (144 mg, 0.30 mmol) and ZrBn4 (194 mg, 0.43 mmol) in
toluene (1.5 mL) was stirred at room temperature in the absence
of light for 10 h. The solution orange was filtered and placed at 0
°C for 15 h. The yellow precipitate formed was filtered and washed
with cold (-20 °C) toluene (2 mL). Compound 7b was obtained
as a pale yellow powder (0.16 g, 64%). Yellow crystals of 7b
suitable for X-ray crystallography were obtained from a THF (1
3
3
(d, 1H, JH,H ) 9.7 Hz, H18), –0.06 (d, 1H, JH,H ) 9.7 Hz, H18′).
13C{1H} NMR (125.3 MHz, CD2Cl2): δppm 150.6 (C19), 147.6 (d,
2JC,P ) 19.7 Hz, C10), 143.1 (C19′), 141.5 (d, 2JC,P ) 6.7 Hz, C10),
137.5 (d, 3JC,P ) 12.3 Hz, C7), 134.9 (d, 3JC,P ) 4.9 Hz, C11), 134.5
(d, 2JC,P ) 13.0 Hz, C2), 132.9 and 133.7 (d, 4JC,P ) 3.0 Hz, C17),
131.3 and 132.8 (d, 2JC,P ∼ 10–11 Hz, C15), 129.6 and 129.7 (br d,
3JC,P ≈ 12.6 Hz, C16), 128.3 and 128.1 (C20), 128.2 (C22), 127.9

6804 Organometallics, Vol. 26, No. 27, 2007
Oulié et al.
and 128.1 (C21), 126.5 and 126.7 (br s, C12), 125.9 (d, 2JC,P ) 12.9
Hz, C2), 125.3 (C4 or C5), 125.1 (C4 or C5), 124.1 (C6), 122.4 (C3),
119.5 (d, 2JC,P ) 14.3 Hz, C9), 114.6 (d, 2JC,P ) 11.9 Hz, C8), 89.6
(d, JC,P ) 2.8 Hz, Zr-CH2-Mes), 72.7 (d, JC,P ) 127.1 Hz, C1),
65.7 and 62.3 (C18), 22.6 (o-CH3), 20.3 (p-CH3).
optimizations were carried out without any symmetry restrictions,
and the nature of the extrema (minimum) was verified with analytical
frequency calculations. All of these computations have been
performed with the Gaussian 9859 suite of programs. The electronic
density has been analyzed using the natural bonding analysis (NBO)
technique.60
3
1
Crystal Structure Determination of Complexes 5a and 7a–
c. Data for all structures were collected at 193(2) K using a oil-
coated shock-cooled crystal on a Bruker-AXS CCD 1000 diffrac-
tometer with Mo KR radiation (λ ) 0.7103 Å). Semiempirical
absorption corrections were employed.52 The structures were solved
by direct methods (SHELXS-97)53 and refined using the least-
squares method on F2.54
Computational Details. Zirconium and phosphorus were treated
with a Stuttgart-Dresden pseudopotential in combination with their
adapted basis set.55 In all cases, the basis set has been augmented
by a set of polarization functions (f for Zr and d for P).56 Carbon,
nitrogen, and hydrogen atoms have been described with a 6-31G(d,p)
double-ꢁ basis set.57 Calculations were carried out at the DFT level
of theory using the hybrid functional B3PW91.58 Geometry
Acknowledgment. We are grateful to the CNRS, UPS,
and ANR program (project BILI) for financial support of
this work. CalMip (CNRS, Toulouse, France) is acknowl-
edged for calculation facilities. L.M. thanks the Institut
Universitaire de France. H.G. is acknowledged for his
assistance in the X-ray diffraction analysis of complex 5a.
Note Added after ASAP Publication. In the version of this
paper posted on the Web on December 5, 2007, due to a production
error, the artwork for Figure 3 was incorrect and a small error was
introduced into ref 46. The version of this paper that now appears
is correct.
(52) SADABS, Program for data correction, Bruker-AXS, version 2.10,
2003.
(53) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(54) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement, University of Göttingen, 1997.
(55) (a) Andrae, D.; Haeussermann, U.; Dolg, M.; Stoll, H.; Preuss, H.
Theor. Chim. Acta 1990, 77, 123. (b) Bergner, A.; Dolg, M.; Kuechle, W.;
Stoll, H.; Preuss, H. Mol. Phys. 1993, 80, 1431.
(56) Ehlers, A. W.; Böhme, M.; Dapprich, S.; Gobbi, A.; Höllwarth,
A.; Jonas, V.; Köhler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G.
Chem. Phys. Lett. 1993, 208, 111.
Supporting Information Available: Complete atom numbering
for the NMR assignments; complete ref 59 citation; Cartesian
coordinates for the optimized complexes 5a*/5c*/6c*/7a–c*/8c*
and crystallographic data for ligands 2c/4b and complexes 5a/7a–c
(CIF). This material is available free of charge via the Internet at
http://pubs.acs.org.
OM700974G
(57) Hariharan, P. C.; Pople, J. A. Theor. Chim. Acta 1973, 28, 213.
(58) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Burke, K.;
Perdew, J. P.; Yang, W. Electronic Density Functional Theory: Recent
Progress and New Directions; Dobson, J. F., Vignale, G., Das, M. P., Eds.;
Springer: Berlin, 1998.
(59) Frisch, M. J.; et al. Gaussian 98, ReVision A.11, Gaussian, Inc.,
Pittsburgh, PA, 1998.
(60) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. ReV. 1988, 88,
899.