Zirconium-butadiene bonded over a planar set of oxygens derived from calix[4]arene and its behavior as a source of zirconium (II)

Article abstract of DOI:10.1021/om970624m

This report deals with the first examples of butadienes bonded to a Zr-O matrix provided by a calix[4]arene skeleton and their reactivity. The reaction of [{p-Bu^t-calix[4]-OMe)₂-(O)₂)ZrCl₂], 2, with Mg(C₄H₆)(thf)₂ and Mg(Ph₂C₄H₄)(thf)₃ led to [{p-Bu_t-calix[4]-(OMe)₂(O)₂}-Zr(η ⁴-C₄H₆)], 3, and [{p-Bu^t-calix[4]-(OMe)₂(O)₂}Zr(η ⁴-Ph₂C₄H₄)], 4. The butadiene fragment exhibits a π²,η⁴ bonding mode, as shown by an X-ray analysis on both compounds. Extended Hu?ckel calculations confirmed the energetically preferred s-cis conformation and the π²,η⁴ bonding mode vs the σ²,π,η⁴ one. The parent compound 3 of this series behaves, however, both as a source of zirconium(II) in displacement reactions or as a dialkyl derivative of zirconium(IV) in insertion reactions. In the former class of transformations, the reaction of 3 with Ph₂CO and PhCOCOPh led to the dioxo metallacycles [{p-Bu^t-calix[4]-(OMe)₂(O)₂}-Zr{-OC(Ph) ₂-C(Ph)₂O-}], 5, and [{p-Bu^t-calixt[4](OMe)₂(O) ₂}Zr{-OC(Ph)=C(Ph)O-})], 6, respectively. Butadiene was also displaced by diphenylacetylene leading to [{p-Bu^t-calix-[4]-(OMe)₂(O)₂}Zr(η ²-Ph₂C₂)], 7, and by a phenylnitrene source [PhN₃] forming the dinuclear phenylimido-bridged complex [{p-Bu^t-calix[4]-(OMe)₂(O)₂}₂Zr ₂(μ-NPh)₂], 8. Unlike at room temperature, Ph₂CO reacted with 3 at low temperature without displacing the butadiene, but leading, instead, to the stepwise insertion of the ketone to form [{p-Bu^t-calix[4]-(OMe)₂(O)₂}Zr{CH ₂CH=CHCH₂C(Ph)₂O}], 10, and [{p-Bu^t-calix[4](OMe)₂(O)₂}Zr{-OC(Ph) ₂-CH₂CH=CHCH₂C(Ph)₂O-}], 11. Using 2 mol of acetone, [{p-Bu^t-calix[4]-(OMe)₂(O)₂}Zr{-OC(Me) ₂CH₂CH=CHCH₂C(Me)₂O-}], 12, was obtained. MeCN and EtCN inserted in a single Zr-C bond (of a formal σ²,π,η⁴ structure) yielding [{p-Bu^t-calix[4]-(OMe)₂(O)₂}Zr{-CH ₂CH=CHCH₂C(Me)=N-}], 13, and [{p-Bu^t-calix[4](OMe)₂(O)₂}Zri{-CH ₂CH=CHCH₂-C(Et)=N-}], 14. Bu^tNC engaged 3 in a multistep insertion reaction leading to [{p-Bu^t-calix[4]-(OMe)₂(O)₂}Zr{-(Bu ^t)NC(C₄H₆)C(C=NBu^t)N(Bu ^t)-}], 15, via a pathway which has been observed in the reaction of Bu^tNC with dialkylzirconium calix[4]arene derivatives. The σ² behavior of butadiene in 3 was further verified in the reaction with H₂O to give [{p-Bu^t-calix[4]-(OMe)₂(O)₂}₂Zr ₂(μ-O)₂], 9, and butenes.

Full text of DOI:10.1021/om970624m

Organometallics 1997, 16, 5457-5469
5457
Zir con iu m -Bu ta d ien e Bon d ed over a P la n a r Set of
Oxygen s Der ived fr om Ca lix[4]a r en e a n d Its Beh a vior a s
a Sou r ce of Zir con iu m (II)
Alessandro Caselli, Luca Giannini, Euro Solari, and Carlo Floriani*
Institut de Chimie Mine´rale et Analytique, BCH, Universite´ de Lausanne,
CH-1015 Lausanne, Switzerland
Nazzareno Re
Dipartimento di Chimica, Universita` di Perugia, I-06100 Perugia, Italy
Angiola Chiesi-Villa and Corrado Rizzoli
Dipartimento di Chimica, Universita` di Parma, I-43100 Parma, Italy
Received J uly 22, 1997X
This report deals with the first examples of butadienes bonded to a Zr-O matrix provided
by a calix[4]arene skeleton and their reactivity. The reaction of [{p-But-calix[4]-(OMe)2-
(O)2}ZrCl2], 2, with Mg(C4H6)(thf)2 and Mg(Ph2C4H4)(thf)3 led to [{p-But-calix[4]-(OMe)2(O)2}-
Zr(η4-C4H6)], 3, and [{p-But-calix[4]-(OMe)2(O)2}Zr(η4-Ph2C4H4)], 4. The butadiene fragment
exhibits a π2,η4 bonding mode, as shown by an X-ray analysis on both compounds. Extended
Hu¨ckel calculations confirmed the energetically preferred s-cis conformation and the π2,η4
bonding mode vs the σ2,π,η4 one. The parent compound 3 of this series behaves, however,
both as a source of zirconium(II) in displacement reactions or as a dialkyl derivative of
zirconium(IV) in insertion reactions. In the former class of transformations, the reaction of
3 with Ph2CO and PhCOCOPh led to the dioxo metallacycles [{p-But-calix[4]-(OMe)2(O)2}-
Zr{-OC(Ph)2-C(Ph)2O-}], 5, and [{p-But-calix[4]-(OMe)2(O)2}Zr{-OC(Ph)dC(Ph)O-})], 6,
respectively. Butadiene was also displaced by diphenylacetylene leading to [{p-But-calix-
[4]-(OMe)2(O)2}Zr(η2-Ph2C2)], 7, and by a phenylnitrene source [PhN3] forming the dinuclear
phenylimido-bridged complex [{p-But-calix[4]-(OMe)2(O)2}2Zr2(µ-NPh)2], 8. Unlike at room
temperature, Ph2CO reacted with 3 at low temperature without displacing the butadiene,
but leading, instead, to the stepwise insertion of the ketone to form [{p-But-calix[4]-
(OMe)2(O)2}Zr{CH2CHdCHCH2C(Ph)2O}], 10, and [{p-But-calix[4]-(OMe)2(O)2}Zr{-OC(Ph)2-
CH2CHdCHCH2C(Ph)2O-}], 11. Using 2 mol of acetone, [{p-But-calix[4]-(OMe)2(O)2}Zr{-
OC(Me)2CH2CHdCHCH2C(Me)2O-}], 12, was obtained. MeCN and EtCN inserted in a
single Zr-C bond (of a formal σ2,π,η4 structure) yielding [{p-But-calix[4]-(OMe)2(O)2}Zr{-
CH2CHdCHCH2C(Me)dN-}], 13, and [{p-But-calix[4]-(OMe)2(O)2}Zr{-CH2CHdCHCH2-
C(Et)dN-}], 14. ButNC engaged 3 in a multistep insertion reaction leading to [{p-But-
calix[4]-(OMe)2(O)2}Zr{-(But)NC(C4H6)C(CdNBut)N(But)-}], 15, via a pathway which has
been observed in the reaction of ButNC with dialkylzirconium calix[4]arene derivatives. The
σ2 behavior of butadiene in 3 was further verified in the reaction with H2O to give [{p-But-
calix[4]-(OMe)2(O)2}2Zr2(µ-O)2], 9, and butenes.
In tr od u ction
rocyclic ligands, which, by their conformation, allow the
metal to have two cis coordination sites. They are the
dibenzotetramethyltetraaza[14]annulene (A),3 [tmtaa]
and the calix[4]arene-dimethoxy dianion (B), [p-But-
calix[4]-(OMe)2(O)2],4 which provide a set of N4 and O4
atoms, respectively. In the latter case, we took advan-
tage of a preorganized set of oxygen donor atoms of
calix[4]arene5 in an almost planar arrangement. This
The zirconium-diene fragment became one of the
most widely used organometallic synthons, this work
origining from the earlier investigation by Erker and
Nakamura on [Cp2Zr(butadiene)].1 How much the
ancillary ligand determines the reactivity of such a
functionality still remains to be explored. Very few
investigations in this field have moved away from
cyclopentadienyl-type ligands.2 Our recent approach in
organometallic chemistry made use of dianionic mac-
(3) (a) Giannini, L.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli,
C. Angew. Chem., Int. Ed. Engl. 1994, 33, 2204. (b) Giannini, L.; Solari,
E.; De Angelis, S.; Ward, T. R.; Floriani, C.; Chiesi-Villa, A.; Rizzoli,
C. J . Am. Chem. Soc. 1995, 117, 5801. (c) Floriani, C.; Ciurli, S.; Chiesi-
Villa, A.; Guastini, C. Angew. Chem., Int. Ed. Engl. 1987, 26, 70.
(4) Giannini, L.; Solari, E.; Zanotti-Gerosa, A.; Floriani, C.; Chiesi-
Villa, A.; Rizzoli, C. Angew. Chem., Int. Ed. Engl. 1996, 35, 85.
(5) (a) Gutsche, C. D. Calixarenes; The Royal Society of Chemistry:
Cambridge, U.K., 1989. (b) Calixarenes, A Versatile Class of Macrocyclic
Compounds; Vicens, J ., Bo¨hmer, V., Eds.; Kluwer: Dordrecht, The
Netherlands, 1991.
X Abstract published in Advance ACS Abstracts, November 15, 1997.
(1) (a) Yasuda, H.; Tatsumi, K.; Nakamura, A. Acc. Chem. Res. 1985,
18, 120. (b) Erker, G.; Kru¨ger, C.; Mu¨ller, G. Adv. Organomet. Chem.
1985, 24, 1 and references therein.
(2) Fryzuk, M. D.; Haddad, T. S.; Rettig, S. J . Organometallics 1989,
8, 1723. Diamond, G. M.; Green, M. L. H.; Walker, N. M.; Howard, J .
A. K. J . Chem. Soc., Dalton Trans. 1992, 2641.
S0276-7333(97)00624-9 CCC: $14.00 © 1997 American Chemical Society

5458 Organometallics, Vol. 16, No. 25, 1997
Caselli et al.
was added [Mg(C4H6)(thf)2] (10.1 g, 45.0 mmol). The reaction
mixture was allowed to warm up to room temperature over-
night, resulting in a dark red suspension. Volatiles were then
removed in vacuo, and pentane (300 mL) was added to the
residue. Extraction over 72 h gave 3 as an orange powder,
which was then collected by filtration and finally dried in vacuo
(30.4 g, 86%). Anal. Calcd for 3, C50H64O4Zr: C, 73.21; H,
7.86. Found: C, 73.30; H, 8.26. 1H NMR (C6D6, 298 K): δ
7.27 (s, 4H, ArH), 6.80 (s, 4H, ArH), 5.97 (m, 2H, CH), 4.35
(br, 4H, endo-CH2) overlapping with 4.35 (br, 6H, MeO), 3.49
(m, 2H, CH2(3,4)), 3.21 (d, J ) 12.5 Hz, 4H, exo-CH2), 2.30 (m,
2H, CH2(1,2)), 1.47 (s, 18H, But), 0.74 (s, 18H, But). 1H NMR
(C7D8, 298 K): δ 7.21 (s, 4H, ArH), 6.81 (s, 4H, ArH), 5.90 (m,
2H, CH), 4.32 (br, 4H, endo-CH2) overlapping with 4.32 (br,
6H, MeO), 3.35 (m, 2H, CH2(3,4)), 3.19 (d, 4H, exo-CH2), 2.19
(m, 2H, CH2(1,2)), 1.45 (s, 18H, But), 0.74 (s, 18H, But). 1H
NMR (C7D8, 245 K): δ 7.26 (s, 4H, ArH), 6.83 (s, 4H, ArH),
5.95 (m, 2H, CH), 4.54 (d, J ) 12.4 Hz, 2H, endo-CH2), 4.26
(s, 3H, MeO), 4.18 (d, J ) 12.6 Hz, 2H, endo-CH2), 3.62 (s,
3H, MeO), 3.46 (m, 2H, CH2(3,4)), 3.23 (m, 4H, exo-CH2), 2.27
(m, 2H, CH2(1,2)), 1.51 (s, 18H, But), 0.71 (s, 18H, But). 1H
NMR (C7D8, 333 K): δ 7.17 (s, 4H, ArH), 6.77 (s, 4H, ArH),
5.85 (m, 2H, CH), 4.28 (d, J ) 12.5 Hz, 4H, endo-CH2), 4.13
(s, 6H, MeO), 3.26 (m, 2H, CH2(3,4)), 3.14 (d, J ) 12.5 Hz,
4H, exo-CH2), 2.16 (m, 2H, CH2(1,2)), 1.40 (s, 18H, But), 0.79
(s, 18H, But). Crystals suitable for X-ray analysis were
obtained at room temperature by slow evaporation of a
saturated solution of 3 in n-hexane.
phenoxo matrix, in the case of zirconium, has been
widely employed in exploring the chemistry of the Zr-C
functionalities.6 These studies, like the present one,
have particular relevance with regard to a modeling
approach to organometallic functionalities anchored to
heterogeneous, oxygen-rich surfaces.7
We report here the related chemistry of the Zr-
butadiene functionality supported by the calix[4]-
dimethoxy dianion B. Unlike in the cyclopentadienyl
series,1b butadiene displays, in the present case, exclu-
sively the s-cis π2,η4 bonding mode to the metal, though
its chemistry follows two general pathways. In the first
one, butadiene behaves like a σ2,π,η4 system and, thus,
functions in insertion reactions, while in the second
pathway we observed displacement of the butadiene
unit. Importantly, the [{p-But-calix[4]-(OMe)2(O)2}Zr-
(η4-C4H6)] functions as a source of zirconium(II). Pre-
liminary results on the synthesis of the parent com-
pound have been communicated.4
Syn th esis of 4. 2 (8.26 g, 8.66 mmol) and Mg(C16H14)(thf)3
(3.9 g, 8.7 mmol) were suspended in toluene (250 mL) at -30
°C. The mixture, which became deep red in seconds, was
allowed to warm to room temperature while stirring. Dioxane
(5 mL) was added, and the mixture was stirred for 1 h.
Volatiles were then removed in vacuo (heating at 50 °C). The
residue was extracted overnight with a mixture of hexane (230
mL) and benzene (30 mL). The red suspension was kept at
-25 °C for 24 h to give 4 as a deep red microcrystalline solid,
which was collected and dried in vacuo (5.79 g, 61.4%). Anal.
Calcd for 4‚(C6H6)1.5, C71H81O4Zr: C, 78.26; H, 7.49. Found:
C, 78.31; H, 7.73. 1H NMR (C6D6, 298 K): δ 7.36-6.63 (m,
27H, ArH, benzene), 6.07 (m, 2H, H(5,6)), 4.48 (s, 3H, MeO),
4.31 (d, J ) 12.5 Hz, 2H, endo-CH2), 4.00 (m, 2H, H(1,2)), 3.92
(d, 2H, endo-CH2) overlapping with 3.89 (s, 3H, MeO), 3.30
(d, J ) 12.5 Hz, 2H, exo-CH2), 2.94 (d, J ) 12.5 Hz, 2H, exo-
Exp er im en ta l Section
Gen er a l P r oced u r e. All reactions were carried out under
an atmosphere of purified nitrogen. Solvents were dried and
distilled before use by standard methods. 1H NMR and IR
spectra were recorded on AC-200, DPX-400 Bruker, and
Perkin-Elmer FT 1600 instruments. GC and GC-MS analyses
were carried out using a HP 5890 Series II system and a HP
5890A GC system, respectively. The syntheses of [p-But-calix-
[4]-(OMe)2(OH)2],8 [p-But-calix[4]-(OMe)2(O)2ZrCl2],4 PhN3,9
Mg(C4H6)(thf)2,10 and Mg(C4H6)(thf)211 have been performed as
reported.
Syn th esis of 3. 1 (29.2 g, 43.0 mmol) and ZrCl4(thf)2 (16.3
g, 43.0 mmol) were suspended in benzene (220 mL), and the
reaction mixture refluxed for 2 h. The solvent was removed
by distillation and then readded. After 10 min of refluxing,
the solvent was removed by distillation and the residue dried
in vacuo at 80 °C. The flask was then charged with fresh
toluene (300 mL) and cooled to -40 °C, and to this mixture
1
CH2), 1.37 (s,18H, But), 0.70 (s, 9H, But), 0.64 (s, 9H, But). H
NMR (CD2Cl2, 298 K): δ 7.37-6.50 (m, 27H, ArH, benzene),
6.09 (m, 2H, H(5,6)), 4.97 (s, 3H, MeO), 4.72 (s, 3H, MeO), 4.29
(d, J ) 12.5 Hz, 2H, endo-CH2), 3.80 (m, 2H, H(1,2)) overlap-
ping with 3.72 (d, 2H, endo-CH2), 3.32 (d, J ) 12.5 Hz, 2H,
exo-CH2), 2.86 (d, J ) 12.5 Hz, 2H, exo-CH2), 1.20 (s, 18H, But),
1.06 (s, 9H, But), 1.00 (s, 9H, But). Crystals suitable for X-ray
analysis were obtained at room temperature from a super-
saturated solution of 4 in hexane/benzene (10:1).
Syn th esis of 5. A solution of Ph2CO (1.13 g, 6.38 mmol)
in toluene (50 mL) was added dropwise to a solution of 3 (2.73
g, 3.33 mmol) in toluene (50 mL), and the resulting clear yellow
solution was stirred for 2 h. Volatiles were removed in vacuo,
and n-hexane (30 mL) was added to the residue. White
crystals of 5‚C7H8 were then collected and dried in vacuo (2.22
g, 55%). Anal. Calcd for 5‚C7H8, C79H86O6Zr: C, 77.60; H,
7.09. Found: C, 77.49; H, 7.37. 1H NMR (C6D6, 298 K): δ
7.96 (m, 8H, Ph), 7.26 (s, 4H, ArH), 7.13-6.98 (m, 17H, Ph,
toluene), 6.84 (s, 4H, ArH), 4.50 (d, J ) 12.4 Hz, 4H, endo-
CH2), 3.95 (s, 6H, MeO), 3.22 (d, J ) 12.4 Hz, 4H, exo-CH2),
2.10 (s, 3H, toluene), 1.45 (s, 18H, But), 0.80 (s, 18H, But).
(6) (a) Giannini, L.; Caselli, A.; Solari, E.; Floriani, C.; Chiesi-Villa,
A.; Rizzoli, C.; Re, N.; Sgamellotti, A. J . Am. Chem. Soc. 1997, 119,
9198. (b) Giannini, L.; Caselli, A.; Solari, E.; Floriani, C.; Chiesi-Villa,
A.; Rizzoli, C.; Re, N.; Sgamellotti, A. J . Am. Chem. Soc. 1997, 119,
9709.
(7) (a) Corker, J .; Lefebvre, F.; Lecuyer, C.; Dufaud, V.; Quignard,
F.; Choplin, A.; Evans, J .; Basset, J .-M. Science 1996, 271, 966. (b)
Niccolai, G. P.; Basset, J .-M. Appl. Catal., A 1996, 146, 145. (c) Vidal,
V.; Theolier, A.; Thivolle-Cazat, J .; Basset, J .-M.; Corker, J . J . Am.
Chem. Soc. 1996, 118, 4595.
(8) Arduini, A.; Casnati, A. In Macrocycle Synthesis; Parker, O., Ed.;
Oxford University Press: New York, 1996; Chapter 7.
(9) Lindsay, R. O.; Allen, C. F. H. Organic Syntheses; Wiley: New
York, 1955; Collect. Vol. III, p 710.
(10) Fujita, K.; Ohnuma, Y.; Yasuda, H.; Tani, H. J . Organomet.
Chem. 1976, 113, 201.
Syn th esis of 6. A solution of PhCOCOPh (0.71 g, 3.38
mmol) in toluene (50 mL) was added to a solution of 3 (2.73 g,
3.33 mmol) in toluene (50 mL), and the resulting green solution
was stirred for 2 h. Volatiles were removed in vacuo, n-hexane
(60 mL) was added to the residue, and the resulting solution
was kept at -24 °C for 1 day. 6‚C7H8 precipitated as a green
powder, which was then collected and dried in vacuo (2.56 g,
(11) Yasuda, H.; Kajihara, Y.; Mashima, K.; Nagasuna, K.; Lee, K.;
Nakamura, A. Organometallics 1982, 1, 388.

Zirconium-Butadiene Bonded over a Set of Oxygens
Organometallics, Vol. 16, No. 25, 1997 5459
65%). Anal. Calcd for 6‚C7H8, C71H82O6Zr: C, 75.96; H, 7.36.
Found: C, 75.29; H, 7.35. 1H NMR (C6D6, 298 K): δ 8.06 (m,
4H, Ph), 7.26-7.00 (m, 15H, ArH, Ph, toluene), 6.79 (s, 4H,
ArH), 4.40 (d, J ) 12.5 Hz, 4H, endo-CH2), 3.96 (s, 6H, MeO),
3.14 (d, J ) 12.5 Hz, 4H, exo-CH2), 2.10 (s, 3H, toluene), 1.46
(s, 18H, But), 0.72 (s, 18H, But).
with 3.59 (s, 6H, MeO), 3.28 (d, J ) 12.5 Hz, 4H, exo-CH2),
3.10 (d, J ) 10.6 Hz, 2H, butadiene), 2.14 (s, 3H, toluene),
1.48 (s, 18H, But), 1.27 (m, 4H, hexane), 0.89 (m, 3H, hexane),
0.83 (s, 18H, But).
Syn th esis of 11. A solution of Ph2CO (0.57 g, 3.15 mmol)
in toluene (40 mL) was added dropwise to a cooled (-90 °C)
stirred solution of 3 (2.57 g, 3.14 mmol) in toluene (150 mL).
The resulting dark yellow solution was allowed to warm to
room temperature overnight. The 1H NMR spectrum of the
crude solution showed clean 10. A solution of Ph2CO (0.57 g,
3.15 mmol) in toluene (40 mL) was then added dropwise to
the cooled (-90 °C), stirred reaction mixture. The resulting
colorless solution was allowed to warm to room temperature
and then filtered, the volatiles were removed in vacuo, and
finally n-hexane (50 mL) was added to the residue. White 11‚-
Syn th esis of 7. 3 (4.89 g, 5.96 mmol) and Ph2C2 (1.09 g,
6.11 mmol) were dissolved in toluene (175 mL). The reaction
mixture was refluxed for 12 h, the resulting yellow solution
was then filtered, and the volatiles were removed in vacuo.
n-Hexane (60 mL) was added to the residue, and 7 was
collected as a white solid (4.12 g, 73%). Anal. Calcd for 7,
C
60H68O4Zr: C, 76.31; H, 7.26. Found: C, 76.54; H, 7.28. 1H
NMR (C6D6, 298 K): δ 7.50 (m, 4H, ArH, Ph), 7.25 (s, 4H, ArH)
overlapping with 7.24 (m, 4H, Ph), 6.98 (m, 2H, Ph), 6.83 (s,
4H, ArH), 4.50 (d, J ) 12.4 Hz, 4H, endo-CH2), 4.25 (s, 6H,
MeO), 3.20 (d, J ) 12.4 Hz, 4H, exo-CH2), 1.45 (s, 18H, But),
0.80 (s, 18H, But). Crystals suitable for X-ray analysis were
obtained at room temperature from a supersaturated toluene
solution.
Syn th esis of 8. A solution of PhN3 (0.449 g, 3.77 mmol) in
toluene (10 mL) was added dropwise to a stirred toluene (80
mL) solution of 3 (3.20 g, 3.77 mmol) cooled at -70 °C. The
stirred reaction mixture was allowed to warm to room tem-
perature overnight to give a light brown suspension. Volatiles
were removed in vacuo, and n-hexane (40 mL) was added to
the residue. 8 was collected as a white solid (1.60 g, 50%).
Anal. Calcd for 8, C104H126N2O8Zr2: C, 72.85; H, 7.41; N, 1.63.
Found: C, 72.42; H, 7.81; N, 1.26. 1H NMR (CDCl3, 298 K):
δ 7.27 (m, 4H, Ph), 7.10 (m, 4H, ArH), 6.88 (m, 4H, ArH), 6.74
(m, 4H, ArH), 6.63 (m, 4H, ArH), 6.61 (m, 4H, Ph), 6.50 (m,
2H, Ph), 4.30 (s, 12H, OMe), 4.25 (d, J ) 12.4 Hz, 4H, endo-
CH2), 3.35 (d, J ) 12.4 Hz, 4H, endo-CH2), 3.15 (d, J ) 12.4
Hz, 4H, exo-CH2), 2.57 (d, J ) 12.4 Hz, 4H, exo-CH2), 1.35 (s,
36H, But), 0.90 (s, 36H, But). Crystals suitable for X-ray
analysis were obtained at room temperature from a super-
saturated pentane solution.
Syn th esis of 9. A solution of water (0.685 M in THF, 4.25
mmol) was added dropwise to a stirred THF (80 mL) solution
of 3 (3.57 g, 4.35 mmol) cooled at -80 °C. The reaction mixture
was allowed to warm to room temperature overnight. Volatiles
were removed in vacuo, n-hexane (30 mL) was added to the
residue, and 9‚thf‚C6H14 was collected as a white solid (1.53
g, 41%). Anal. Calcd for 9‚thf‚C6H14, C102H138O11Zr2: C, 71.12;
H, 8.07. Found: C, 71.09; H, 8.20. 1H NMR (C6D6, 298 K): δ
7.26 (s, 8H, ArH), 6.91 (s, 8H, ArH), 4.61 (d, J ) 12.4 Hz, 8H,
endo-CH2), 4.40 (s, 12H, MeO), 3.58 (m, 4H, thf), 3.26 (d, J )
12.4 Hz, 8H, exo-CH2), 1.49 (s, 36H, But), 1.40 (m, 4H, thf),
1.23 (m, 8H, hex), 0.88 (s, 36H, But) overlapping with 0.88 (m,
6H, hex). Crystals suitable for X-ray analysis were obtained
from a room-temperature saturated toluene/hexane solution.
Syn th esis of 10. A solution of Ph2CO (0.86 g, 4.74 mmol)
in toluene (50 mL) was added dropwise to a cooled (-90 °C)
stirred solution of 3 (3.88 g, 4.73 mmol) in toluene (150 mL).
The resulting dark yellow solution was allowed to warm to
room temperature overnight and then filtered, the volatiles
were removed in vacuo, and finally n-hexane (50 mL) was
(C6H14
)
was then collected and dried in vacuo (1.90 g, 49%).
0.5
Anal. Calcd for 11‚(C6H14)0.5, C79H91O6Zr: C, 77.28; H, 7.47.
Found: C, 77.27; H, 7.90. 1H NMR (C7D8, 298 K): δ 7.57-
6.84 (m, 28H, ArH, Ph), 5.49 (m, 2H, butadiene), 4.63 (br, 4H,
endo-CH2), 4.00 (br, 6H, MeO), 3.69-2.93 (br, 4H, butadiene)
overlapping with (br, 4H, exo-CH2), 1.42 (s, 18H, But), 1.26
(m, 4H, hexane), 0.88 (m, 3H, hexane), 0.74 (s, 18H, But). 1H
NMR (C7D8, 372 K): δ 7.48 (m, 8H, Ph), 7.15 (s, 4H, ArH),
7.10-6.99 (m, 12H, Ph), 6.84 (s, 4H, ArH), 5.56 (m, 2H,
butadiene), 4.17 (d, J ) 12.8 Hz, 4H, endo-CH2), 3.77 (s, 6H,
MeO), 3.46 (m, 4H, butadiene), 3.12 (d, J ) 12.8 Hz, 4H, exo-
CH2), 1.38 (s, 18H, But), 1.25 (m, 4H, hexane), 0.86 (m, 3H,
hexane), 0.74 (s, 18H, But). 1H NMR (C7D8, 263 K): δ 7.61
(m, 4H, Ph), 7.32 (m, 4H, Ph), 7.25 (s, 2H, ArH), 7.17-7.07
(m, 14H, ArH, Ph), 6.98 (s, 2H, ArH), 6.80 (s, 2H, ArH), 5.44
(m, 2H, butadiene), 4.67 (d, J ) 12.8 Hz, 2H, endo-CH2), 4.01
(s, 3H, MeO), 3.70 (m, 2H, butadiene), 3.56 (d, J ) 12.8 Hz,
2H, endo-CH2), 3.47 (d, J ) 12.8 Hz, 2H, exo-CH2), 3.39 (s,
3H, MeO), 3.09 (m, 2H, butadiene), 2.91 (d, J ) 12.8 Hz, 2H,
exo-CH2), 1.42 (s, 18H, But), 1.26 (m, 4H, hexane), 0.88 (m,
3H, hexane), 0.77 (s, 9H, But), 0.71 (s, 9H, But).
Syn th esis of 12. Acetone (1.00 mL, 13.6 mmol) was added
to a stirred benzene (100 mL) solution of 3 (3.96 g, 4.83 mmol).
1
The H NMR (C6D6) spectrum of a dried sample showed that
the reaction was complete, affording clean 12. Volatiles were
removed in vacuo from the colorless solution, and n-hexane
(30 mL) was added to the residue. The flask was kept for 1
day at -24 °C, then the white 12‚(C6H6)0.5 solid was collected
and dried in vacuo (1.15 g, 24%). Anal. Calcd for 12‚(C6H6)0.5
,
C59H79O6Zr: C, 72.64; H, 8.16. Found: C, 72.65; H, 8.35. 1H
NMR (C6D6, 298 K): δ 7.36 (s, 4H, ArH), 6.96 (s, 4H, ArH),
5.32 (m, 2H, butadiene), 4.44 (d, J ) 12.5 Hz, 4H, endo-CH2),
3.87 (s, 6H, MeO), 3.44 (d, J ) 12.5 Hz, 4H, exo-CH2), 2.36
(m, 4H, butadiene), 1.49 (s, 18H, But), 1.24 (s, 12H, CH3), 1.23
(m, 4H, hexane), 0.88 (m, 3H, hexane), 0.75 (s, 18H, But).
Crystals suitable for X-ray analysis were obtained at room
temperature from a saturated benzene solution.
Syn th esis of 13. CH3CN (0.156 g, 3.80 mmol) was added
to a stirred solution of 3 (3.10 g, 3.77 mmol) in benzene(100
1
mL), yielding a yellow solution. The H NMR (C6D6) spectrum
showed that the reaction was complete, affording clean 13.
Volatiles were removed in vacuo, and n-hexane (30 mL) was
added. The resulting suspension was stirred for 3 h, and
13‚C6H14 was collected as a yellow solid and dried in vacuo
(2.01 g, 56%). Anal. Calcd for 13‚C6H14, C58H81NO4Zr: C,
added to the residue. White 10‚C7H8‚(C6H14
)
0.5
was collected
and dried in vacuo (2.9 g, 54%). Anal. Calcd for
10‚C7H8‚(C6H14 0.5, C87H89O5Zr: C, 77.07; H, 7.89. Found: C,
)
76.73; H, 8.10. 1H NMR (C6D6, 298 K): δ 7.83 (m, 4H, Ph),
7.32 (s, 4H, ArH), 7.16-7.12 (m, 6H, Ph) overlapping with
7.14-6.98 (m, 5H, toluene), 6.85 (s, 4H, ArH), 6.56 (m, 1H,
butadiene), 5.59 (m, 1H, butadiene), 4.63 (br, 4H, endo-CH2),
3.62 (br, 6H, MeO) overlapping with 3.62 (br, 2H, butadiene),
3.28 (br, 4H, exo-CH2), 3.08 (d, J ) 10.7 Hz, 2H, butadiene),
2.10 (s, 3H, toluene), 1.49 (s, 18H, But), 1.23 (m, 4H, hexane),
0.88 (m, 3H, hexane), 0.76 (s, 18H, But). 1H NMR (C6D6, 338
K): δ 7.81 (m, 4H, Ph), 7.30 (s, 4H, ArH), 7.15 (m, 6H, Ph)
overlapping with 7.14-6.98 (m, 5H, toluene), 6.88 (s, 4H, ArH),
6.53 (m, 1H, butadiene), 5.56 (m, 1H, butadiene), 4.53 (d, J )
12.5 Hz, 4H, endo-CH2), 3.60 (m, 2H, butadiene) overlapping
1
73.52; H, 8.62; N, 1.48. Found: C, 73.30; H, 8.49; N, 1.34. H
NMR (C6D6, 298 K): δ 7.40-7.26 (m, 4H, ArH), 7.15 (m, 1H,
butadiene) overlapping with C6D6, 6.96 (m, 2H, ArH), 6.87 (m,
2H, ArH), 6.56 (m, 1H, butadiene), 6.15 (m, 1H, butadiene),
5.51 (m, 1H, butadiene), 4.72 (d, J ) 12.4 Hz, 1H, endo-CH2),
4.64 (d, J ) 12.0 Hz, 1H, endo-CH2), 4.59 (d, J ) 12.4 Hz, 1H,
endo-CH2), 4.51 (d, J ) 12.4 Hz, 1H, endo-CH2), 4.05 (s, 3H,
MeO), 4.03 (s, 3H, OMe), 3.58 (m, 1H, butadiene), 3.40-3.31
(m, 4H, exo-CH2), 2.11 (m, 1H, butadiene), 2.07 (s, 3H, CH3),
1.59 (s, 9H, But), 1.57 (s, 9H, But), 1.23 (m, 8H, hexane), 0.88
(m, 6H, hexane), 0.86 (s, 9H, But), 0.83 (s, 9H, But).

5460 Organometallics, Vol. 16, No. 25, 1997
Caselli et al.
Ta ble 1. Exp er im en ta l Da ta for th e X-r a y Diffr a ction Stu d ies on Cr ysta llin e Com p lexes 3, 4, 7, 8, a n d 9
complex
formula
a, Å
b, Å
3
4
7
8
9
C50H64O4Zr
10.411(2)
12.931(3)
34.344(7)
90
98.72(2)
90
4570.1(17)
4
C62H70O4Zr‚1.5C6H6 C60H68O4Zr‚4.5C7H8 C104H126N2O8Zr2‚4C7H8 C92H116O10Zr2‚C7H8‚2C6H14
14.684(2)
17.992(2)
13.033(2)
109.64(1)
103.51(1)
86.55(1)
3152.6(8)
2
28.846(5)
17.387(3)
30.241(5)
90
90.19(3)
90
13.580(2)
22.240(3)
37.707(5)
90
98.48(2)
90
12.375(2)
40.636(5)
21.083(3)
90
103.91(2)
90
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
15167(5)
8
11264(3)
4
10291(3)
4
fw
820.3
P21/c
-130
0.710 68
1.045
1087.6
P1h
1359.1
C2/c
-130
1.541 78
1.190
15.64
0.435-1.000
0.067
0.197
2083.2
C2/c
-130
1.541 78
1.228
19.64
0.805-1.000
0.088
0.248
1828.9
C2/c
-130
1.541 78
1.180
20.91
0.351-1.000
0.066
0.198
space group
T, °C
λ, Å
20
1.541 78
1.146
17.71
F
calc, g cm-3
µ, cm-1
2.74
transmission coeff 0.679-1.000 0.696-1.000
R1a
0.079
0.215
0.080
0.249
wR2b
a
b
2 2
R1 ) ∑|∆F |/∑|Fo| calculated on the unique observed data [I > 2σ(I)]. wR2 ) [∑w|∆F 2|2/∑w|Fo | ]1/2 calculated on the unique total
data with I > 0.
Syn th esis of 14. CH3CH2CN (0.310 g, 5.64 mmol) was
added to a stirred solution of 3 (4.63 g, 5.64 mmol) in toluene
(125 mL) to give a yellow solution. The 1H NMR (C6D6)
spectrum showed that the reaction was complete, affording
clean 14. The toluene was concentrated to 25 mL, and
n-hexane (75 mL) was added. The resulting solution was then
293 for 4. For the intensities and background, the individual
reflection profiles were analyzed.13 The structure amplitudes
were obtained after the usual Lorentz and polarization cor-
rections, and the absolute scale was established by the Wilson
method.14 The crystal quality was tested by ψ scans showing
that crystal absorption effects could not be neglected. The data
were corrected for absorption using a semiempirical method.15
The function minimized during the full-matrix least-square
refinements was ∑w(∆F 2)2. Weights were applied according
filtrated and kept at -26 °C for 24 h. 14‚C7H8‚(C6H14
)
0.5
was
collected as a yellow solid and dried in vacuo (2.05 g, 37%).
Anal. Calcd for 14‚C7H8‚(C6H14 0.5, C63H84NO4Zr: C, 74.88; H,
)
2
8.38; N, 1.39. Found: C, 74.57; H, 8.89; N, 1.21. 1H NMR
(C6D6, 298 K): δ 7.29-7.23 (m, 4H, ArH) overlapping with (m,
1H, butadiene), 7.14-6.95 (m, 5H, toluene), 6.85 (m, 2H, ArH),
6.76 (m, 2H, ArH), 6.46 (m, 1H, butadiene), 6.03 (m, 1H,
butadiene), 5.43 (m, 1H, butadiene), 4.63-4.40 (m, 4H, endo-
CH2), 3.96 (s, 3H, MeO), 3.94 (s, 3H, OMe), 3.47 (m, 1H,
butadiene), 3.28-3.21 (m, 4H, exo-CH2), 2.20 (m, 2H, CH2),
2.10 (s, 3H, toluene), 1.98 (m, 1H, butadiene), 1.48 (s, 9H, But),
1.46 (s, 9H, But), 1.23 (m, 4H, hexane), 1.18 (m, 3H, CH3), 0.88
(m, 3H, hexane), 0.75 (s, 9H, But), 0.72 (s, 9H, But). Crystals
suitable for X-ray analysis were obtained at -24 °C from a
room-temperature saturated solution in benzene/pentane.
Syn th esis of 15. A solution of ButNC (1.13 g, 13.55 mmol)
in toluene (49 mL) was added dropwise to a solution of 3 (3.71
g, 4.18 mmol) in toluene (100 mL). The resulting light orange
solution was stirred for 2 h, volatiles were removed in vacuo,
to the scheme w ) 1/[σ2(Fo2) + (aP)2] (with P ) (Fo + 2Fc2)/3
and a ) 0.1302, 0.1228, 0.1211, 0.2028, and 0.0989 for
complexes 3, 4, 7, 8, and 9, respectively. Anomalous scattering
corrections were included in all structure factor calculations.16b
Scattering factors for neutral atoms were taken from ref 16a
for non-hydrogen atoms and from ref 17 for H atoms. Among
the low-angle reflections, no correction for secondary extinction
was deemed necessary.
All calculations were carried out on a Quansan personal
computer equipped with an Intel Pentium processor. The
structures were solved starting from three-dimensional Patter-
son maps using the observed reflections [I > 2σ(I)].18 Structure
refinements were based on the unique data having I > 0 using
SHELX92.19 Refinement was first done isotropically and then
anisotropically for all non-H atoms, except for the disordered
atoms.
and n-hexane (50 mL) was added to the residue. 15‚(C6H14
)
0.5
In complex 3, a ∆F map calculated after the isotropic
refinement revealed a statistical distribution of the butadiene
ligand over two positions (A and B). The two orientations,
which do not share any atom, form a dihedral angle of 17.4-
(82)°. Refinement of the relative occupancies resulted in a
value of 0.65(2) and 0.35(2) for A and B, respectively.
In complex 4, a statistical distribution around the C47‚‚‚-
C50 line in the diphenylbutadiene ligand was evident from a
difference Fourier map calculated after the anisotropic refine-
ment. The two orientations (A and B) of the butadiene
framework share the C47, C50 terminal carbon atoms and
form a dihedral angle of 21.0(14)° such that only C48 and C49
appear to be disordered. Refinement of the relative occupan-
was collected as a pale yellow powder (3.22 g, 64%). Anal.
Calcd for 15‚(C6H14 0.5, C69H98N3O4Zr: C, 73.40; H, 8.88; N,
)
3.78. Found: C, 73.10; H, 8.95; N, 3.64. 1H NMR (C6D6, 298
K): δ 7.39-7.32 (m, 4H, ArH), 6.99-6.89 (m, 4H, ArH), 5.74
(m, 2H, butadiene), 5.26 (d, J ) 12.1 Hz, 1H, endo-CH2), 5.05
(d, J ) 12.0 Hz, 1H, endo-CH2), 4,83 (d, J ) 12.2 Hz, 1H, endo-
CH2), 4.70 (d, J ) 12.1 Hz, 1H, endo-CH2), 4.35 (s, 3H, MeO),
4.02 (s, 3H, MeO), 3.53 (m, 1H, butadiene), 3.47-3.27 (m, 4H,
exo-CH2), 2.85 (m, 1H, butadiene), 2.53 (m, 2H, butadiene),
1.60 (s, 9H, But), 1.53 (m, 9H, But), 1.48 (s, 9H, But), 1.43 (s,
9H, But), 1.25 (s, 9H, But) overlapping with 1.25 (m, 4H,
hexane), 0.88 (m, 3H, hexane), 0.78 (s, 18H, But). IR (Nujol,
ν
max/cm-1): 1965.0 (s).
X-r a y Cr ysta llogr a p h y for Com p lexes 3, 4, a n d 7-9.
(13) Lehmann, M .S.; Larsen, F. K. Acta Crystallogr., Sect. A: Cryst.
Phys., Diffr., Theor. Gen. Crystallogr. 1974, A30, 580-584.
(14) Wilson, A. J . C. Nature 1942, 150, 151.
(15) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.,
Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1968, A24, 351.
(16) (a) International Tables for X-ray Crystallography; Kynoch
Press: Birmingham, England, 1974; Vol. IV, p 99. (b) Ibid., p 149.
(17) Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J . Chem. Phys.
1965, 42, 3175.
Suitable crystals were mounted in glass capillaries and sealed
under nitrogen. The reduced cells were obtained with the use
of TRACER.12 Crystal data and details associated with data
collection are given in Table 1 and in the Supporting Informa-
tion (Table S1). Data were collected on a Rigaku AFC6S
single-crystal diffractometer at 143 K for 3, 7, 8, and 9 and
(18) Sheldrick, G. M. SHELX76. Program for crystal structure
determination; University of Cambridge: Cambridge, England, 1976.
(19) Sheldrick, G. M. SHELXL92. Program for Crystal Structure
Refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1992.
(12) Lawton, S. L.; J acobson, R. A. TRACER (a cell reduction
program); Ames Laboratory. Iowa State University of Science and
Technology: Ames, IA, 1965.

Zirconium-Butadiene Bonded over a Set of Oxygens
Organometallics, Vol. 16, No. 25, 1997 5461
Sch em e 1
Sch em e 2
metry. However, at temperatures above 40 °C, the
spectrum simplifies and resembles that of a compound
with C2v symmetry (one pair of doublets for the bridging
methylenes and a singlet for the methoxy groups). It
is important to note that the splitting patterns for the
butadiene protons of 3 are temperature independent
(though the chemical shifts depend slightly on the
temperature). The fact that the signals for the (3,4) and
(1,2) protons in the butadiene ligand never coalesce
proves that the dynamic process responsible for the
increase in the apparent symmetry of complex 3 at high
temperatures is not the flipping21 of the butadiene
fragment (involving a metallacyclopentene transition
state). This observation is most likely due to the
rotation2 of butadiene.
cies resulted in a value of 0.69(2) for C48A, C49A and 0.31(2)
for C48B, C49B.
In addition, the toluene molecules in complexes 7-9, some
tert-butyl groups in complexes 3, 4, 8, and 9, and the n-hexane
molecule in complex 9 were found to be affected by disorder.
This was solved by considering the carbon atoms with higher
thermal parameters as statistically distributed over two
positions (A and B) and isotropically refined with the site
occupation factors given in the Supporting Information (Table
S2-S6). During the refinement, the aromatic rings of the
disordered toluene molecules in complexes 7 and 8 were
constrained to have a D6h symmetry.
In the solid state, as shown by the X-ray analysis
performed on single crystals of 3 and 4, the bonding
mode of the butadiene ligands in both complexes can
be described as π2,η4. A variety of bonding modes of
butadiene to zirconium ranging from π,η4 to σ2,π,η4 can
be found in complexes having subunits other than Cp2-
Zr.2,3a,22 The structural and spectroscopic characteris-
tics of the Zr-diene fragment in 3 and 4 are more closely
related to the [(tmtaa)Zr]3a derivatives (tmtaa )
dibenzotetramethyltetraaza[14]annulene dianion) than
the corresponding [Cp2Zr]1,11,23,24 species. In particular,
we can say that the s-cis form is the only butadiene
conformer detected in the solid state; heating of 3 or 4
did not result in any cis-trans isomerization.24,25
The labeling scheme adopted for calixarene is given
in Scheme 2. Selected bond distances and angles are
quoted in Tables 2, 3, 4, 5, and 6 for complexes 3, 4, 7,
The hydrogen atoms, except those related to disordered
carbon atoms, which were ignored, were put in geometrically
calculated positions for 3 and 7-9 and located from a differ-
ence map for 4. They were introduced in the subsequent
refinement as fixed atom contribution with U’s fixed at 0.5 Å2
for for 3 and 7-9 and at 0.12 Å2 for 4.
The final difference maps showed no unusual features, with
no significant peaks above the general background except for
a residual peak of 2.71 e Å-3 in 8 located midway along the
Zr-N1 bond.
Final atomic coordinates are listed in the Supporting
Information (Tables S2-S6 for non-H atoms and in Tables S7-
S11 for hydrogens). Thermal parameters are also given in the
Supporting Information (Tables S12-S16) in addition to bond
distances and angles (Tables S17-S21).20 Ordering informa-
tion is given on any current masthead page.
Resu lts a n d Discu ssion
(21) Erker, G.; Engel, K.; Kru¨ger, C.; Chiang, A.-P. Chem. Ber. 1982,
115, 3311.
(22) Blenkers, J .; Hessen, B.; van Bolhuis, F.; Wagner, A. J .; Teuben,
J . H. Organometallics 1987, 6, 459. Yasuda, H.; Nakamura, A. Angew.
Chem., Int. Ed. Engl. 1987, 26, 723.
(23) Erker, G.; Dorf, U.; Benn, R.; Reinhardt, R.-D. J . Am. Chem.
Soc. 1984, 106, 7649. Erker, G.; Lecht, R.; Petersen, J . L.; Bo¨nnemann,
H. Organometallics 1987, 6, 1962. Akita, M.; Matsuoka, K.; Asami,
K.; Yasuda, H.; Nakamura, A. J . Organomet. Chem. 1987, 327, 193.
Bu¨rgi, H. B.; Dubler-Steude, K. C. J . Am. Chem. Soc. 1988, 110, 4953.
Erker, G.; Aul, R. Organometallics 1988, 7, 2070. Erker, G.; Sosna,
F.; Zwettler, R.; Kru¨ger, C. Organometallics 1989, 8, 450. Yasuda, H.;
Okamoto, T.; Matsuoka, Y.; Nakamura, A.; Kai, Y.; Kanehisa, N.;
Kasai, N. Organometallics 1989, 8, 1139. Erker, G.; Friedrich, S.; Ralf,
N. Chem. Ber. 1990, 123, 821. Erker, G.; Babil, M. Chem. Ber. 1990,
123, 1327. Beckhaus, R.; Wilbrandt, D.; Flatau, S.; Bo¨hmer, H. J .
Organomet. Chem. 1992, 423, 211.
Zr -Bu ta d ien e Der iva tives. The synthesis of the
parent compound used in this study, 3, is displayed,
along with the analogous diphenyl derivative, in Scheme
1. The reaction can be carried out either via the
preliminary isolation of 2 or it can be performed in situ
with the corresponding Mg-butadiene derivative. All
the analytical and spectroscopic data are in agreement
with the formulations reported for complexes 3 and 4.
In solution, complex 4 has Cs symmetry; the 1H NMR
spectrum consists of two pairs of doublets for the
bridging methylenes and two singlets for the methoxy
groups. Below -10 °C (in toluene-d8), complex 3 also
(24) Erker, G.; Engel, K.; Korek, U.; Czisch, P.; Berke, H.; Caube`re,
P.; Vanderesse, R. Organometallics 1985, 4, 1531.
1
exhibits a H NMR spectrum characteristic of Cs sym-
(25) Erker, G.; Wicker, J .; Engel, K.; Kru¨ger, C. Chem. Ber. 1982,
115, 3300.
(20) See paragraph at the end regarding Supporting Information.

5462 Organometallics, Vol. 16, No. 25, 1997
Caselli et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 3
Ta ble 5. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 8
Zr1-O1
1.990(6)
2.349(6)
1.988(6)
2.360(5)
2.394(18)
2.398(17)
2.44(2)
2.525(16)
2.51(3)
2.39(3)
O1-C1
1.331(9)
1.408(10)
1.464(11)
1.334(11)
1.407(12)
1.464(12)
1.44(2)
1.44(2)
1.41(2)
1.46(4)
1.45(4)
Zr1-O1
Zr1-O2
Zr1-O3
Zr1-O4
Zr1-N1
Zr1-N1′
O1-C1
2.001(4)
2.319(4)
1.981(4)
2.321(4)
2.105(7)
2.105(7)
1.325(8)
O2-C13
O2-C45
O3-C20
O4-C27
O4-C46
N1-C47
1.413(9)
1.454(8)
1.354(8)
1.400(8)
1.441(8)
1.431(8)
Zr1-O2
O2-C13
Zr1-O3
Zr1-O4
O2-C45
O3-C20
Zr1-C47A
Zr1-C48A
Zr1-C49A
Zr1-C50A
Zr1-C47B
Zr1-C48B
Zr1-C49B
Zr1-C50B
O4-C27
O4-C46
C47A-C48A
C48A-C49A
C49A-C50A
C47B-C48B
C48B-C49B
C49B-C50B
N1-Zr1-N1′
O4-Zr1-N1′
O4-Zr1-N1
O3-Zr1-N1′
O3-Zr1-N1
O3-Zr1-O4
O2-Zr1-N1′
O2-Zr1-N1
O2-Zr1-O4
O2-Zr1-O3
O1-Zr1-N1′
O1-Zr1-N1
O1-Zr1-O4
O1-Zr1-O3
76.9(2)
86.6(2)
120.6(2)
96.1(2)
154.1(2)
83.2(2)
116.8(2)
83.9(2)
150.6(1)
77.1(2)
157.3(2)
95.0(2)
79.4(2)
99.7(2)
O1-Zr1-O2
N1-Zr1′-N1′
Zr1-O1-C1
Zr1-O2-C45
Zr1-O2-C13
C13-O2-C45
Zr1-O3-C20
Zr1-O4-C46
Zr1-O4-C27
C27-O4-C46
Zr1-N1-Zr1′
Zr1′-N1-C47
Zr1-N1-C47
82.8(2)
76.9(3)
178.1(4)
127.5(4)
121.6(4)
110.9(5)
172.0(4)
127.3(4)
119.0(4)
113.7(5)
102.3(3)
131.9(5)
125.4(5)
2.38(3)
2.38(4)
1.41(4)
C49B-Zr1-C50B
C48B-Zr1-C49B
C47B-Zr1-C48B
C49A-Zr1-C50A
C48A-Zr1-C49A
C47A-Zr1-C48A
O3-Zr1-O4
34.5(11) Zr1-O2-C45
35.5(10) Zr1-O2-C13
34.5(10) C13-O2-C45
130.5(6)
115.6(4)
113.9(7)
172.8(6)
132.1(5)
115.5(4)
112.4(6)
32.9(6)
34.7(6)
35.1(6)
82.4(2)
83.1(2)
82.4(2)
83.4(2)
171.3(5)
Zr1-O3-C20
Zr1-O4-C46
Zr1-O4-C27
C27-O4-C46
C47A-C48A-C49A 114.9(15)
C48A-C49A-C50A 120.7(15)
C47B-C48B-C49B 114(2)
C48B-C49B-C50B 120(2)
O2-Zr1-O3
O1-Zr1-O4
O1-Zr1-O2
Ta ble 6. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 9a
Zr1-O1-C1
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 4
Zr1-O1
Zr1-O2
Zr1-O5
Zr2-O3
Zr2-O4
Zr2-O5
1.988(5)
2.445(6)
1.974(7)
1.985(6)
2.492(4)
1.987(7)
O1-C1
1.345(10)
1.417(9)
1.457(10)
1.337(10)
1.402(9)
1.453(9)
O2-C13
O2-C45
O3-C20
O4-C27
O4-C46
Zr1-O1
1.945(5)
2.309(8)
1.946(5)
2.348(8)
2.427(10)
2.450(16)
2.485(13)
2.58(3)
O2-C45
1.434(16)
1.348(10)
1.433(12)
1.463(15)
1.25(2)
Zr1-O2
O3-C20
Zr1-O3
O4-C27
Zr1-O4
O4-C46
Zr1-C47
Zr1-C48A
Zr1-C49A
Zr1-C48B
Zr1-C49B
Zr1-C50
O1-C1
C47-C48A
C47-C48B
C47-C57
C48A-C49A
C49A-C50
C48B-C49B
C49B-C50
C50-C51
O5-Zr1-O5′
O2-Zr1-O5′
O2-Zr1-O5
O1-Zr1-O5′
O1-Zr1-O5
O1-Zr1-O2
O5-Zr2-O5′
O4-Zr2-O5′
O4-Zr2-O5
O3-Zr2-O5′
O3-Zr2-O5
76.4(3)
72.5(2)
141.0(2)
128.0(2)
105.8(2)
76.8(2)
75.8(3)
144.7(2)
71.2(2)
O3-Zr2-O4
Zr1-O1-C1
Zr1-O2-C45
Zr1-O2-C13
C13-O2-C45
Zr2-O3-C20
Zr2-O4-C46
Zr2-O4-C27
C27-O4-C46
Zr1-O5-Zr2
78.7(2)
169.5(5)
127.1(4)
122.1(5)
110.8(6)
171.4(5)
130.6(4)
116.9(4)
112.5(6)
103.9(2)
1.17(4)
1.477(15)
1.437(18)
1.36(2)
1.38(4)
1.18(4)
2.60(4)
2.505(12)
1.353(10)
1.410(11)
O2-C13
1.498(14)
C49B-Zr1-C50
C48B-Zr1-C49B
C49A-Zr1-C50
C48A-Zr1-C49A
C47-Zr1-C48B
C47-Zr1-C48A
O3-Zr1-O4
26.7(8)
30.8(10) Zr1-O3-C20
C13-O2-C45
114.0(8)
171.4(6)
134.7(6)
112.6(6)
112.7(8)
128(2)
109.6(2)
121.8(2)
31.6(4)
33.8(5)
26.8(7)
29.8(5)
83.8(3)
84.0(2)
82.5(3)
82.2(3)
174.6(6)
131.2(6)
114.8(5)
Zr1-O4-C46
Zr1-O4-C27
C27-O4-C46
C48B-C47-C57
C48A-C47-C57
C47-C48A-C49A 123.3(16)
C48A-C49A-C50 118.8(14)
C47-C48B-C49B 132(3)
C48B-C49B-C50 122(3)
C49B-C50-C51
C49A-C50-C51
a
Prime denotes a transformation of -x, y, 0.5 - z.
123.6(16)
O3, and O4, respectively. The structure of 3 is shown
in Figure 1.
O2-Zr1-O3
O1-Zr1-O4
The overall geometry of the [p-But-calix[4]-(OMe)2Zr]
moiety, although similar to that observed in six-
coordinate metal complexes,6 is significantly different
from that found in 2. The four Zr-O bond distances
are significantly longer in 3 than in 2: 1.989(6) vs 1.914-
(3) Å and 2.355(6) vs 2.246(3) Å (average values for Zr-
O1, Zr-O3 and Zr-O2, Zr-O4 couples, respectively).
The O4 core shows remarkable tetrahedral distortions
ranging from -0.269(7) to 0.269(7) Å. Zirconium is
displaced by 0.811(1) Å from the O4 core toward buta-
diene.
The s-cis-butadiene is statistically distributed over
two positions (A and B) tilted with respect to each other
by 17.4(17)° and related by a pseudo mirror plane
running through zirconium and bisecting the A and C
aromatic rings. The Zr-C distances, which fall within
a rather narrow range (2.398(17)-2.525(16) and 2.38-
(3)-2.51(3) for A and B, respectively) and the close C-C
bond lengths within butadiene, averaging 1.43(2) and
1.44(4) Å for A and B, respectively, support the π2,η4
bonding mode. The planarity of the ligand as well as
the s-cis conformation could be indicated by the C48-
C49 internal torsion angle (0(2)° and 9(4)° for A and B,
respectively). The plane of the ligand is nearly parallel
O1-Zr1-O2
Zr1-O1-C1
Zr1-O2-C45
Zr1-O2-C13
126(2)
122.1(13)
Ta ble 4. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lex 7
Zr1-O1
Zr1-O2
Zr1-O3
Zr1-O4
Zr1-C47
Zr1-C48
O1-C1
1.957(3)
2.316(4)
1.957(3)
2.311(4)
2.172(6)
2.192(6)
1.346(7)
1.411(7)
O2-C45
O3-C20
O4-C27
O4-C46
C47-C48
C47-C55
C48-C49
1.454(6)
1.372(6)
1.417(7)
1.458(6)
1.318(8)
1.478(9)
1.477(8)
O2-C13
C47-Zr1-C48
O3-Zr1-O4
O2-Zr1-O3
O1-Zr1-O4
O1-Zr1-O2
Zr1-O1-C1
Zr1-O2-C45
Zr1-O2-C13
35.2(2)
86.8(1)
83.9(1)
81.4(1)
83.8(1)
172.0(3)
131.6(3)
116.9(3)
C13-O2-C45
Zr1-O3-C20
Zr1-O4-C46
Zr1-O4-C27
C27-O4-C46
C48-C47-C55
C47-C48-C49
111.4(4)
155.6(3)
131.4(3)
117.3(3)
111.2(4)
130.6(6)
131.9(6)
8, and 9, respectively. In Table 7, a comparison of the
relevant conformational parameters is reported. A, B,
C, and D refer to the aromatic rings related to O1, O2,

Zirconium-Butadiene Bonded over a Set of Oxygens
Organometallics, Vol. 16, No. 25, 1997 5463
Ta ble 7. Com p a r ison of Releva n t Con for m a tion a l
P a r a m eter s w ith in Ca lixa r en e for Com p lexes 3, 4,
7, 8, a n d 9
3
4
7
8
9
(a) Dihedral Angles (deg) between
Planar Moietiesa
EˆA
EˆB
EˆC
EˆD
AˆC
BˆD
AˆA′
BˆB′
CˆC′
DˆD′
135.0(2) 147.3(2) 143.6(1) 139.7(2) 134.5(2)
98.7(2) 101.1(2) 108.7(1) 113.2(2) 110.3(2)
135.6(2) 136.8(2) 131.1(2) 147.4(2) 139.6(2)
99.1(2)
90.6(2)
94.9(3)
108.4(1) 106.6(2) 95.5(2)
104.0(3) 94.7(2) 107.1(2)
162.2(3) 165.0(3) 142.7(2) 140.2(2)
90.9(2)
139.3(3)
99.2(2)
168.9(3)
(b) Contact Distances (Å) between
para Carbon Atoms of Opposite Aromatic Rings
9.378(13) 9.793(12) 9.486(9) 9.733(10)
F igu r e 2. SCHAKAL view of complex 4. Disorder has been
omitted for clarity.
C4‚‚‚C17
C10‚‚‚C24 6.043(12) 5.871(15) 6.989(8) 7.144(9)
C4‚‚‚C4′
9.189(13)
7.317(13)
9.661(14)
5.688(11)
C10‚‚‚C10′
C17‚‚‚C17′
C24‚‚‚C24′
diene. The torsion angles around the C48-C49 bond
are 2(2)° and -12(5)° for A and B, respectively. The
plane of the butadiene carbon atoms is nearly parallel
to the O4 mean plane, the dihedral angle being 9.1(7)°
and 12.3(11)° for position A and B, respectively. The
C51-C56 and C57-C62 phenyl rings are tilted with
respect to the butadiene plane downward by 15.3(7)°,
20.7(9)° and 14.1(9)°, 6.6(7)° for A and B, respectively.
The C51-C56 ring is oriented in such a way as to eclipse
the A aromatic ring, the dihedral angle between them
being 17.6(3)°. The C‚‚‚C separations between opposite
atoms range from 3.508(16) to 4.356(19) Å. The C57‚‚‚-
C62 ring is twisted with respect the C aromatic ring by
43.3(6)°.
a
E (reference plane) refers to the least-squares mean plane
defined by the C7, C14, C21, C28 bridging methylenic carbons. A
prime denotes a transformation of -x, y, 0.5 - z.
The calixarene ligand assumes an elliptical cone
section with a conformation (Table 7) similar to that
observed in complex 3 with the opposite A and C rings
almost perpendicular (dihedral angle 104.0(3)°) and the
B and D rings parallel (dihedral angle 164.0(3)°).
Accordingly, the dimension of the cavity, indicated by
the separations between opposite p-carbon atoms (C4‚‚‚-
C17, 9.793(12) Å; C10‚‚‚C24, 5.871(15) Å), is such to
prevent the inclusion of guest molecules.
Although the bonding mode of the butadiene fragment
in 3 and 4 is π2,η4, we should expect two general
reactivity trends from the Zr-butadiene functionality.
One forces the displacement of butadiene, thus making
available the [p-But-calix[4]-(OMe)2(O)2ZrII] fragment,
the other leads to the insertion products, which would
be expected for the σ2,π,η4 bonding mode.
F igu r e 1. SCHAKAL view of complex 3. Disorder has been
omitted for clarity.
to the O4 mean plane, the dihedral angle they form
being 9.7(8)° and 7.7(14)° for A and B, respectively.
The elliptical cone section (Table 7) is different from
that of 2, the A and C opposite rings being nearly
perpendicular (dihedral angle 90.6(2)° vs 108.2.(2)° in
2) and the opposite B and C rings nearly parallel each
other (dihedral angle 162.2(3)° vs 137.5(2)° in 2). The
contraction of the cavity is revealed by the narrow
separation between the opposite C10‚‚‚C24 para carbon
atoms being shortened (6.043(12) Å vs 7.309(8) Å in 2).
Crystals of 4 (Figure 2) contain benzene as a solvent
of crystallization in a 1/1.5 Zr/C6H6 ratio. The four
oxygen atoms of the O4 core show remarkable tetrahe-
dral distortion ranging from -0.308(6) to 0.303(6) Å, the
zirconium atom projecting above the O4 mean plane by
0.798(1) Å toward the butadiene unit. The trend of the
Zr-O distances is similar to 3. The butadiene fragment
was found to be disordered over two positions (A and
B) sharing the C47, C50 terminal carbon atoms, so only
the C48 and C49 atoms appeared to be affected by
disorder. The Zr-C distances, ranging from 2.427(10)
to 2.505(12) Å and the localization of the terminal
double bonds, support the π2,η4 bonding mode of buta-
Extended Hu¨ckel calculations26,27 were performed to
elucidate the nature of the bonding between the buta-
diene unit and the central metal in complex 3. The
ligand hereafter named p-But-calix[4]-(OMe)2(O)2 has
been simplified by two phenoxo anions and two anisole
molecules organized like in 3 according to a C2v geom-
etry. This simplified model retains the main features
of the whole ligand; in particular, the geometrical
constraints on the O4 set of donor atoms has been
maintained by fixing the geometry of the four phenoxo
groups to the experimental values.
The coordination geometry of the butadiene unit was
optimized with respect to the three parameters R, L,
and θ depicted in Scheme 3, while all the other geo-
metrical parameters were kept fixed to the experimental
(26) Hoffmann, R., Lipscomb, W. N. J . Chem. Phys. 1962, 36, 2179.
(27) Hoffmann, R. J . Chem. Phys. 1963, 39, 1397.

5464 Organometallics, Vol. 16, No. 25, 1997
Caselli et al.
Sch em e 3
bonds show the same bond strength and also that the
C1-C2 and C2-C3 bonds are equally strong.
The π2 coordination mode of butadiene in 3 is very
different from the σ2-π metallacyclopentene structure
observed in [Cp2Zr(butadiene)] (Scheme 4) and in other
butadiene complexes of early transition metals.1,29 This
seemingly surprising difference is easily explained on
the basis of the different frontier orbitals of the [p-But-
calix[4]-(OMe)2(O)2Zr] and [Cp2Zr] metal fragments. In
the [Cp2Zr] fragment, there is only one dπ orbital (1b2-
(dyz), interacting with π2), while back-donation is de-
scribed by the 1a1-π3* mixing, which involves (as shown
in Scheme 5) only the terminal carbons. Instead, in
[p-But-calix[4]-(OMe)2(O)2Zr], a second dπ orbital (1b1-
(dxz)) is available for the back-donation to π3*, all four
carbon atoms being involved in such an interaction.
Figure 3 illustrates that a low-lying orbital of a1
symmetry, almost degenerate with 1b1, is also available
for the [p-But-calix[4]-(OMe)2(O)2Zr] fragment so that
a 1a1-π3* interaction would be expected for 3 leading
to a quite stable σ2-π structure. To study this point,
we performed EH (extended Hu¨ckel) calculations on 3
in which the dihedral angle θ was progressively in-
creased from 10° (the optimal value for the π2 structure)
to 30°, which is a typical value for a σ2-π geometry. A
small energy increase is observed, and the σ2-π struc-
ture is calculated only to be ca. 6 kcal mol-1 higher than
the optimal π2 one. Moreover, an analysis of the
molecular orbitals shows that, on increasing θ, the
HOMO shifts continuously from a b1-π3* to an a1-π3*
character, reaching a mainly a1-π3* nature in the final
σ2-π geometry. In other words, the [p-But-calix[4]-
(OMe)2(O)2Zr] fragment has two low-lying almost de-
generate b1 and a1 orbitals available for back-donation
to the π3* orbital of butadiene, leading, respectively, to
a π2 and a σ2-π structure. The observed preference for
the former structure is probably determined by the
better b1-π3* overlap, but the σ2-π structure is easily
available and may play an important role in the peculiar
reactivity pattern of this butadiene complex.
values. R describes the distance of the butadiene from
zirconium, L defines its slide from the main symmetry
axis (z) of the metal fragment, while θ denotes the
dihedral angle between the butadiene plane and the
fragment reference plane. The geometrical parameters
taken for the metal fragment were Zr-O ) 1.99 (phe-
noxy), Zr-O ) 2.35 (Me-phenoxy), O-C(Ph) ) 1.33
(phenoxy), O-C(Ph) ) 1.41 (Me-phenoxy), O-C(Me)
) 1.43, O-Zr-O ) 114° (phenoxy), O-Zr-O ) 153°
(Me-phenoxy), Zr-O-C(Ph) ) 172° (phenoxy), Zr-O-
C(Ph) ) 116° (Me-phenoxy), and Zr-O-C(Me) ) 131°.
The butadiene moiety was taken as a planar unit with
C1-C2 ) 1.43 Å, C2-C3 ) 1.44 Å, C-H ) 1.09 Å, C1-
C2-C3 ) 120°, C-C-H ) 120°.
The minimum was calculated for R ) 1.9 Å, L ) 0.6
Å, and θ ) 12°, which corresponds to a π2,η4 structure
and are in qualitative agreement with the experimental
X-ray geometry. The electronic structure is analyzed
in terms of the interactions between the frontier orbitals
of the metal fragment and of the butadiene unit. The
orbitals of the [p-But-calix[4]-(OMe)2(O)2Zr] fragment
have already been discussed in detail,6 and the resulting
MO diagram is reported in the first column of Figure
3. We will recall only the main characteristics of this
MO pattern here, which is characterized by four low-
2
2
lying empty metal-based orbitals. The dx -y orbital,
pointing more closely towards the oxygen ligands, is
pushed high in energy, while the remaining four δ
orbitals are found within 1 eV. Due to the reduced
interaction with the methoxylated phenoxo ligands, the
1b1(dxz) orbital is almost 1 eV lower in energy than 1b2-
2
(dyz), with the 1a1(dz ) orbital only slightly higher. For
a ZrII fragment with a d2 electron count, the lowest 1b1
orbital is doubly occupied and constitutes the HOMO.
On the extreme right of Figure 3, we show the frontier
orbitals of butadiene, i.e., the four π and π* orbitals.
The interaction between the [p-But-calix[4]-(OMe)2(O)2-
Zr] fragment and the butadiene moiety is illustrated by
the molecular orbital diagram for 3 in the central
column of Figure 3.
It has to be mentioned that in the solid state structure
of 3 the orientation of the butadiene unit is such that
the plane bisecting the butadiene lies in the xz plane
containing the two methoxy groups of the calix[4]arene
ligand. This orientation is determined by the more
favorable interaction of the butadiene π2 and π3* orbitals
with the two dπ orbitals of the the [p-But-calix[4]-
(OMe)2(O)2Zr] fragment and also leads to a lower steric
repulsion between the butadiene and the methoxy
groups of the calix[4]arene ligand. An energy barrier
for the rotation of the butadiene unit around the C2v
pseudo axis, leading to a rearrangement between the
two possible configurations of the butadiene (Scheme
6), is then expected. To estimate this barrier, the
alternative orientation with the plane bisecting the
butadiene in the orthogonal yz plane has been calcu-
lated, reoptimizing R, L, and θ. An energy barrier of
∼20 kcal mol-1 has been found, which is compatible
The two most significant interactions can be seen in
Figure 3. The empty 1b2(dyz) orbital interacts with the
occupied π2 orbital, while the occupied 1b1(dxz) orbital
matches with the empty π3* and becomes the HOMO
of the complex. The former interaction is of the dona-
tion type, while the latter describes the back-donation
from the metal to butadiene. These interactions are
similar to those observed in the [Fe(CO)3(butadiene)]
complex28 and lead to an analogous π2,η4 bonding mode
with all four carbon atoms of butadiene almost equally
involved in the Zr-butadiene bond. This is confirmed
by the overlap populations calculated for the optimized
geometry of 3 and compared in Table 8 with literature
values for the [Fe(CO)3(butadiene)] and [Cp2Zr-
(butadiene)] complexes.28 We see that in 3 all four Zr-C
1
with the observed H NMR behavior.
Finally, we have also considered the s-trans butadiene
complex in an attempt to understand why such an
isomer is never observed in these zirconium-calixarene
(29) Yasuda, H.; Tatsumi, K.; Okamoto, T.; Mashima, K.; Lee, K.;
Nakamura, A.; Kai, Y.; Kanehisa, N.; Kasai, N. J . Am. Chem. Soc.
1985, 107, 2410.
(28) Tatsumi, K.; Yasuda, H.; Nakamura, A. Isr. J . Chem. 1983, 23,
145.

Zirconium-Butadiene Bonded over a Set of Oxygens
Organometallics, Vol. 16, No. 25, 1997 5465
F igu r e 3. Orbital interaction diagram for Zr(calix[4]arene) and butadiene.
Ta ble 8. Com p a r ison of th e Ca lcu la ted Over la p
P op u la tion s in 3 w ith Th ose for
Sch em e 6
[Cp 2Zr (bu ta d ien e)]28 a n d [F e(CO)3(bu ta d ien e)]28
3
[Fe(CO)3(butadiene)]
[Cp2Zr(butadiene)]
M-C1
M-C2
C1-C2
C2-C3
0.237
0.218
0.961
0.971
0.202
0.184
0.979
0.974
0.338
0.060
0.991
1.012
Sch em e 4
is much smaller than that with s-cis-π3*. This explains
why s-trans-butadiene complexes are so rare. In the
[p-But-calix[4]-(OMe)2(O)2Zr] fragment, the b1(dxz) or-
bital overlaps much better with s-cis-π3* than with the
s-trans-π3*, suggesting an instable s-trans isomer. How-
ever, a low-energy a1 orbital is also available so that
the s-trans isomer is not expected to be too high in
energy. Accordingly, our calculations give the s-trans
isomer to be ca. 15 kcal mol-1 higher in energy than
the s-cis isomer. This energy difference, although
seemingly small, is high enough to prevent the detection
of any s-trans isomer in equilibrium conditions. Note
that for the [Cp2Zr(butadiene)], which shows an equi-
librium between the s-cis and s-trans isomers, an energy
barrier of ca. 2 kcal mol-1 has been calculated at
extended Hu¨ckel level.28
Sch em e 5
systems. Our analysis followed the procedures of ref
28, according to which the stability of the [Cp2Zr(diene)]
s-trans complexes is attributed to the comparable
overlap of the s-trans-π3* and s-cis-π3* orbitals with the
1a1 orbital of the metal fragment. On the other hand,
for most of the familiar metal-diene complexes like [Fe-
(CO)3(butadiene)], the metal fragment only has a donor
orbital of dπ symmetry and its overlap with s-trans-π3*
In connection with the s-trans form, a π,η2 butadiene
coordination mode has often been proposed as an
intermediate in zirconocene-butadiene chemistry.
1b As
we never observed the s-trans isomer and all the
products obtained in insertion reactions can be rational-

5466 Organometallics, Vol. 16, No. 25, 1997
Caselli et al.
Sch em e 7
F igu r e 4. SCHAKAL view of complex 7. Disorder has been
omitted for clarity.
maintained also at low temperature (243 K). Complexes
5 and 6 form equally well from the corresponding [{p-
But-calix[4]-(OMe)2(O)2}Zr(R2C-X)] (X ) O, NR) zirco-
nium-imine/ketone derivatives.6b The formation of the
η2-monoacetylene complex, 7, is a rare event in the
general context of zirconium organometallic chemistry,
namely with alkoxo and cyclopentadienyl ancillary
ligands, which are the most widely used. A complex like
7 has been proposed as an intermediate in the formation
of zirconopentadiene, coming from the reductive cou-
pling of the diphenylacetylenes and isolated as the PMe3
adduct.31 Due to its unusual occurrence, 7 has been
structurally characterized by an X-ray analysis, while
the 1H NMR spectrum shows a typical C2v symmetry
for the calix[4]-Zr fragment.
Crystals of 7 (Figure 4) contain toluene as a solvent
of crystallization in a 1/4.5 Zr/C7H8 ratio. The O4 core
is tetrahedrically distorted, displacements ranging from
-0.206(3) to 0.213(3) Å. Zirconium protrudes from it
toward the alkene ligand by 0.720(1) Å, while the Zr-O
bond trend is similar to 3 and 4. The diphenylacetylene
displays a nearly symmetric bonding mode to the metal,
with very close bond distances (Zr-C47, 2.172(6) Å; Zr-
C48, 2.192(6) Å). The C47-C48 bond distance (1.318-
(8) Å) is consistent with a double-bond character. The
plane through the η2-bonded atoms (Zr, C47, C48) is
perpendicular to the O4 mean plane (dihedral angle
89.8(2)°) and forms dihedral angles of 42.9(3)° and 46.0-
(3)° with the C49-C54 and C55-C60 phenyl rings,
respectively. The calixarene macrocycle assumes an
elliptical cross-section conformation (Table 7). The B
and D rings form a dihedral angle of 142.7(2)° vs 162.2-
ized by the σ2,π,η4 model, the intermediacy of such a
high-energy η2 butadiene complex does not seem to play
any role here. Therefore, the latter form will not be
discussed in detail.
Disp la cem en t Rea ction s. Scheme 7 displays reac-
tions where 3 behaves as a source of a Zr(II) derivative.
They can be formally viewed as oxidative additions to
the [p-But-calix[4]-(OMe)2(O)2Zr] fragment.
The main driving force in the case of ketones is the
high oxophilicity of the metal, which induces the reduc-
tive coupling of benzophenone leading to 5 or the
addition of dibenzoyl causing the formation of the
dioxometallacycle in 6, which contains a C-C double
bond. It has to be mentioned that the reaction of 3 with
ketones at low temperature (vide infra) follows a very
different pathway and leads to the insertion of the
carbonylic group into a Zr-C σ bond. In the reaction
with 3, phenylazide functions as a source of phenylni-
trene,30 leading to the corresponding Zr(IV)-dimeric
phenylamido derivative.
Displacement of butadiene with diphenylacetylene1a
occurs under more drastic conditions. We should com-
ment on the nature of the complexes 5-8. All of these
complexes have been analytically and spectroscopically
characterized and the 1H NMR can be, in this sense,
particularly informative. Complexes 5 and 6 show two
pairs of doublets and a single methoxy group along with
two singlets for the But groups. This apparent C2v
symmetry is not only seen at room temperature, but is
(31) Negishi, E.-I.; Takahashi, T. Acc. Chem. Res. 1994, 27, 124. van
Wagenen, B. C.; Linghouse, T. Tetrahedron Lett. 1989, 30, 3495.
Takahashi, T.; Swanson, D. R.; Negishi, E.-I. Chem. Lett. 1987, 623.
Buchwald, S. L.; Watson, B. T. J . Am. Chem. Soc. 1987, 109, 2544.
Lefeber, C.; Baumann, W.; Tillack, A.; Kempe, R.; Go¨rls, H.; Rosenthal,
U. Organometallics 1996, 15, 3486. Rosenthal, U.; Ohff, A.; Baumann,
W.; Tillack, A. Z. Anorg. Allg. Chem. 1995, 621, 77. Rosenthal, U.; Ohff,
A.; Michalik, M.; Go¨rls, H.; Burlakov, V. V.; Shur, V. B. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 1193.
(30) Cenini, S.; La Monica, G. Inorg. Chim. Acta 1976, 18, 279.
Osborne, J . H.; Rheingold, A. L.; Trogler, W. C. J . Am. Chem. Soc.
1985, 107, 7945. Gambarotta, S.; Chiesi-Villa, A.; Guastini, C. J .
Organomet. Chem. 1984, 270, C49. Nugent, W. A.; Haymore, B. L.
Coord. Chem. Rev. 1980, 31, 123. Hubert-Pfalzgraf, L. G.; Aharonian,
G. Inorg. Chim. Acta 1985, 100, L21.

Zirconium-Butadiene Bonded over a Set of Oxygens
Organometallics, Vol. 16, No. 25, 1997 5467
-0.352(4) to 0.357(4) Å); zirconium being displaced by
0.935(1) Å toward the imido atoms. The Zr2N2 mean
plane is nearly perpendicular to the O4 core (dihedral
angle 81.9(2)°). Phenylimido bridges two Zr atoms at a
distance of 3.279(1) Å. The complex has a crystallo-
graphically imposed C2 symmetry with the 2-fold axis
perpendicular to the mean plane through the Zr2N2 core
center of gravity. The Zr-N bond distance (2.105(7) Å)
is a little longer than those found for [{(µ-NPh)ZrCl2-
(thf)2}2]33 and [{(µ-NBut)Zr(NMe2)2}2].32b
In ser tion Rea ction s. Although the bonding mode
of butadiene to zirconium is π2,η4, as revealed by the
X-ray analysis, in a number of reactions and under
certain conditions it behaves like a σ2,π,η4 butadiene,
thus the zirconium-butadiene functionality behaves as
though it contains two Zr-C σ bonds. This behavior is
illustrated in the reactions listed in Scheme 8.
These reactions include the hydrolysis to form the
µ-dioxo dimer 9 and the products derived from the
formal insertion of nitriles, ketones, and ButNC into the
Zr-C σ bonds. In the case of hydrolysis, butenes have
been identified. The occurrence of the zirconyl com-
pound in a monomeric form remains rather rare.34 The
1H NMR spectrum of 9 is in agreement with an
approximate D2 symmetry and, thus, shows a singlet
for the methoxy groups and a pair of doublets for the
bonding methylene. The structural peculiarities have
been disclosed by an X-ray analysis (Figure 6).
Crystals of 9 (Figure 6) contain toluene and n-hexane
as solvents of crystallization in a 1/1/2 dimer/toluene/
n-hexane ratio. The complex has a crystallographically
imposed C2 symmetry, the 2-fold axis running through
the two zirconium atoms. The O4 cores are tetrahedri-
cally distorted (displacements ranging from -0.191(4)
to 0.191(4) Å), Zr1 and Zr2 protruding by 0.931(1) and
0.933(1) Å from the corresponding O4 mean planes
toward the oxo bridges. The mean plane through the
zirconium atoms and the O5 oxygen atoms is strictly
perpendicular to the O4 mean planes from symmetry
requirements. The Zr1‚‚‚Zr2 and O5‚‚‚O5′ separation
within the Zr2O2 system are 3.120(1) and 2.440(7) Å,
respectively. Zirconium is in a very distorted six-
coordination geometry. The Zr-O5 bond distances
(mean value 1.981(7) Å) are close to those found in a
series of complexes containing the [Zr2(µ-O)2] moiety
(mean value 1.953(3) Å averaged over 29 entries). The
Zr1-O1 and Zr2-O3 bond distances are close to those
in 4 and 7, while the Zr1-O2 and Zr2-O4 bond
distances (mean value 2.469(6) Å) are significantly
longer as a consequence of some intraligand interac-
tions. The elliptical cone section conformation assumed
by the two calixarene ligands (Table 7) is significantly
different. The macrocycle related to the Zr1 atom shows
a conformation almost similar to that observed in 7 and
8 (C10‚‚‚C10′, 7.317(13) Å; prime denotes a transforma-
tion of -x, y, 0.5 - z) and the dimension of the cavity
allows a toluene molecule to be included as a guest. The
geometry of a macrocycle related to Zr2 compares better
with that observed in 3 and 4, from the C24‚‚‚C24′
(5.688(11) Å) separation.
F igu r e 5. SCHAKAL view of complex 8. Disorder has been
omitted for clarity. Prime denotes a transformation of -x,
y, 0.5 - z.
(3)° and 164.0(3)° in 3 and 4, respectively. Conse-
quently, a remarkable lengthening of the distance
between the opposite p-carbon atoms is observed (C10‚‚‚-
C24, 6.989(8)°). This separation, which is comparable
to that observed in 2, allows the inclusion of a toluene
molecule.
A particularly interesting synthetic approach to the
imido derivative 8 concerns the reaction of 3 with
phenylazide. The synthesis of zirconium imido com-
pounds in the bis(cyclopentadienyl) series has been
mainly achieved by amine or alkane elimination from
the corresponding diamido or dialkylamido deriva-
tives.32 The imido derivative occurs in the dimeric form
like 8, eventually in equilibrium with the corresponding
monomeric one to which it is associated.32a There is no
evidence in the present case of any relationship between
8 and the corresponding monomeric form, though the
steric conditions would be favorable to it. Further, this
is the first example of a zirconium-imido functionality
associated with alkoxo ancillary ligands. The structure
of 8 is given in Figure 5.
Crystals of 8 contain toluene as a solvent of crystal-
lization in a 1/4 Zr/C7H8 ratio. Coordination around
zirconium is distorted octahedral, the best equatorial
plane being defined by the O2, O3, O4, N1 atoms, the
O1 and N1′ atoms assuming a trans arrangement (O1-
Zr-N1′, 157.3(2)°; prime denotes a transformation of
-x, y, 0.5 - z). As is usually observed for six-coordinate
calixarene metal complexes, the O4 core shows remark-
able tetrahedral distortion (displacement ranging from
(33) Polamo, M.; Mutikainen, I.; Leskela¨, M. Acta Crystallogr. Sect.
C: Cryst. Struct. Commun. 1996, 52, 1082.
(34) Lee, S. Y.; Bergman, R. G. J . Am. Chem. Soc. 1996, 118, 6396.
J acoby, D.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J . Am. Chem. Soc.
1993, 115, 7025. Howard, W. A.; Waters, M.; Parkin, G. J . Am. Chem.
Soc. 1993, 115, 4917. Carney, M. J .; Walsh, P. J .; Hollander, F. J .;
Bergman, R. G. Organometallics 1992, 11, 761.
(32) (a) Walsh, P. J .; Hollander, F. J .; Bergman, R. G. J . Am. Chem.
Soc. 1992, 110, 8729. (b) Nugent, W. A.; Harlow, R. L. Inorg. Chem.
1979, 18, 2030 and references therein.

5468 Organometallics, Vol. 16, No. 25, 1997
Caselli et al.
Sch em e 8
leading to the seven-membered metallacyle in 10. The
reaction then proceeds further with a second mole of
Ph2CO to give 11.1b The proposed structures for 10 and
11 have been supported by the elemental and spectro-
scopic analyses. Above 40 °C, compound 10 exhibits a
1H NMR spectrum of C2v symmetry: one pair of doublets
for the bridging methylene groups and a singlet for the
methoxy groups. It should be noted that the pattern of
the protons of the organic fragment bound to the metal
remains unchanged in the range of temperatures from
25 to 70 °C. A dynamic process increases the apparent
symmetry of the compound in solution, but a clear low-
symmetry spectrum cannot be seen even at the low-
temperature limit. On the other hand, at low temper-
ature, compound 11 shows a spectrum of Cs symmetry,
with two pair of doublets for the bridging methylene
groups, three singlets for the But groups, and two
singlets for the methoxy groups; three multiplets for the
organic fragment protons bound to the metal are visible,
as is the case for the diene complex 3. Above 60 °C,
compound 11 exhibits a 1H NMR spectrum with C2v
symmetry: one pair of doublets for the bridging meth-
ylene groups and a singlet for the methoxy groups; two
of the three multiplets corresponding to the butadiene
fragment collapse to give a single broad signal.
A
F igu r e 6. SCHAKAL view of complex 9. Disorder has been
omitted for clarity. Prime denotes a transformation of -x,
y, 0.5 - z.
structural model for the nine-membered dioxo metal-
lacycle 11 has been supported by preliminary X-ray
results on 12, derived from the insertion of two mol-
ecules of acetone on 3, behaving as a dialkyl-zirconium
derivative. The structural data confirm, in particular,
the cis stereochemistry of the CdC bond, at variance
with what is often found in zirconocene chemistry.23
Unlike in the case of [Cp2Zr(butadiene)] complexes,35
complex 3 inserts a single molecule of nitrile, leading
to complexes 13 and 14. For both compounds, the H
The reaction of 3 with ketones has a particular
dependence on the temperature. When it was per-
formed at room temperature (see Scheme 7, compounds
5 and 6), we observed the displacement of butadiene by
the incoming substrate. On the contrary, when the
reaction was carried out at low temperature and with
a 1:1 molar ratio (Scheme 8), the insertion of the ketone
unit was observed in one of the two Zr-C σ bonds,
1

Zirconium-Butadiene Bonded over a Set of Oxygens
Organometallics, Vol. 16, No. 25, 1997 5469
NMR spectrum shows C1 symmetry at room tempera-
ture with the appearance of four pairs of doublets for
the bridging methylenes, two singlets for the methoxy
groups, and four singlets for the But substituents. A
preliminary X-ray analysis on 14 (see Supporting In-
formation) confirms the proposed structure, which
serves also as a structural model for 10.
supported by a tetraoxo dianionic matrix: (i) 1,1 inser-
tion reactions into the terminal Zr-C bonds, best
visualized in the σ2,η4 description of the complex; (ii)
reactions where the butadiene ligand is displaced,
making available the tetraoxo-zirconium(II) fragment
to a variety of coordinative and oxidative addition
reactions.
The reaction of 3 with ButNC emphasizes its behavior
as a σ2,π,η4 metal-bonded butadiene. The reaction
proceeds as in the case of the dialkyl derivatives [{p-
But-calix[4]-(OMe)2(O)2}Zr(R)2] and consumes 3 equiv
of the isocyanide.6b The pathway leading to 15 has been
clarified in the latter case, and it goes through the
preliminary formation of a η2-imine which further
inserts a molecule of isocyanide to give a carbenoid
structure, which couples with the third equivalent of
ButNC.36 Unlike the dialkyl derivative, we were not
able to isolate the intermediate η2-imino complex.
Complex 15 has C1 symmetry, and its 1H NMR spec-
trum shows four pairs of doublets for the bridging
methylene groups, two singlets for the MeO groups, and
three singlets for the But groups. This spectrum
resembles the analogous complex derived from the
reaction of [{p-But-calix[4]-(OMe)2(O)2}Zr(Me)2] with 3
equiv of ButNC, whose structure has been determined
by an X-ray analysis. The IR data are also very close
for the two compounds (ν(C-N), cm-1: 1968 vs 1964.6
for 15).
The main differences with the corresponding [Cp2Zr]-
based chemistry are: (i) the [p-But-calix[4]-(OMe)2(O)2-
Zr] fragment promotes multiple insertions, as exempli-
fied by the obtention of a spyro, cumulenic product 15
from the insertion of 3 equiv of isocyanide; (ii) the
butadiene ligand can be displaced under very mild
conditions, especially when reacted with polar ligands,
leading to thermodynamically favored species, the best
example being the formation of the phenylimido complex
8 from the reaction with phenylazide. The obtention of
the remarkably stable diphenylacetylene complex 7
illustrates the exceptional ability of the [p-But-calix[4]-
(OMe)2(O)2Zr] fragment to stabilize unsaturated frag-
ments without the need of added ligands, explained by
the peculiar facial arrangement of the three lowest-lying
metal orbitals.
Ack n ow led gm en t. We thank the “Fonds National
Suisse de la Recherche Scientifique” (Bern, Switzerland,
Grant No. 20-46′590.96), Ciba Specialty Chemicals
(Basle, Switzerland), and Fondation Herbette (Univer-
sity of Lausanne, N. Re) for financial support.
Con clu sion s
This work emphasizes the two reaction paths acces-
sible to s-cis π2,η4 butadiene bound to a formal Zr(II)
(35) Erker, G.; Pfaff, R. Organometallics 1993, 12, 1921. Erker, G.;
Pfaff, R.; Kowalski, D.; Wu¨rthwein, E.-U. J . Org. Chem. 1993, 58, 6771.
(36) The coupling of isocyanides with (transient) carbenoids to give
cumulenes is well-estabilished, see: Moloy, K. G.; Fagan, P. J .;
Manriquez, J . M.; Marks, T. J . J . Am. Chem. Soc. 1986, 108, 56. Valero,
C.; Grehl, M.; Wingbermu¨hle, D.; Kloppenburg, L.; Carpenetti, D.;
Erker, G.; Petersen, J . L. Organometallics 1994, 13, 415. Scott, M. J .;
Lippard, S. J . J . Am. Chem. Soc. 1997, 119, 3411.
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic files, in CIF format, for complexes 3, 4, 7-9, and 14
are available on the Internet only. Access information is given
on any current masthead page.
OM970624M