Cooperative reactivity of unsupported early-late heterobimetallics: Ring opening and subsequent decarbonylation of biaryllactones

Article abstract of DOI:10.1021/om980007d

Reaction of the heterodinuclear complex [HC-{SiMe₂N(2-FC₆H₃)}₃Zr-FeC _p(CO)₂] (1) with 1,3-di-methyl-6H-benzo[b]naphtho[1,2-d]pyranone (2) and 1,3-dimethoxy-6H-benzo[b]-naphtho-[1,2-d]pyrano

Full text of DOI:10.1021/om980007d

Organometallics 1998, 17, 1643-1645
1643
Coop er a tive Rea ctivity of Un su p p or ted Ea r ly-La te
Heter obim eta llics: Rin g Op en in g a n d Su bsequ en t
Deca r bon yla tion of Bia r ylla cton es
Andreas Schneider,† Lutz H. Gade,†,* Matthias Breuning,‡ Gerhard Bringmann,‡
Ian J . Scowen,§ and Mary McPartlin§
Institut fu¨r Anorganische Chemie and Institut fu¨r Organische Chemie der Universita¨t
Wu¨rzburg, Am Hubland, 97074 Wu¨rzburg, Germany, and School of Applied Chemistry,
University of North London, Holloway Road, London N7 8DB, U.K.
Received J anuary 6, 1998
Summary: Reaction of the heterodinuclear complex [HC-
{SiMe2N(2-FC6H3)}3Zr-FeCp(CO)2] (1) with 1,3-di-
methyl-6H-benzo[b]naphtho[1,2-d]pyranone (2) and 1,3-
dimethoxy-6H-benzo[b]-naphtho-[1,2-d]pyranone (3) led
to immediate ring opening of the lactones to yield
products which combine the biaryl fragment with aryl-
oxyzirconium and acyl-FeCp(CO)2 units. The latter
slowly decarbonylate to yield the corresponding hetero-
bimetallic complexes in which the {MCp(CO)2} fragment
is directly bonded to the naphthalene ring.
of Zr-Fe heterobimetallics toward two configuratively
unstable biaryl lactones, 1,3-dimethyl-6H-benzo[b]naph-
tho[1,2-d]pyranone (2) and 1,3-dimethoxy-6H-benzo[b]-
naphtho-[1,2-d]-pyranone (3),5a which constitute sub-
strates for asymmetric lactone cleavage reactions5b as,
e.g., employed in the synthesis of axially chiral biaryl
alkaloids.6,7
Reaction of 2 and 3 with the heterodinuclear complex
[HC{SiMe2N(2-FC6H3)}3Zr-FeCp(CO)2] (1)8 cleanly led
to the ring opening of the lactones with concomitant
cleavage of the metal-metal bond, yielding compounds
Heterobimetallic complexes containing one or more
metal-metal bonds between metals of the Ti-triad and
late transition metals have been studied with the aim
of utilizing the cooperative reactivity of the electrophilic
and nucleophilic metal centers in reactions with polar
organic substrates.1 The combination of complementary
metal complex fragments may, in principle, lead to
highly selective conversions, although direct experimen-
tal evidence is still rare.2 Stabilizing the early transi-
tion metal center by coordination of a tridentate amido
ligand provided unsupported heterobimetallics which
are kinetically sufficiently stable to allow the systematic
investigation of their reactivity.3,4 A characteristic
feature of all the conversions involving zirconium-iron
and -ruthenium complexes studied to date is the high
reactivity of the heterodinuclear compounds and, con-
sequently, the extremely mild reaction conditions which
may be chosen, as well as the selectivity of the chemical
transformations. In this paper, we report the reactivity
1
4 and 5 (Scheme 1).9 A characteristic feature of the H
and 13C NMR spectra of both compounds is the diaste-
reotopic splitting of the methyl resonances of the SiMe2
units in the tripod ligand and the chemical shift of the
signal assigned to the acyl carbon nuclei which is
observed at δ 296.0 and 297.6 for 4 and 5, respectively.
These chemical shifts at extremely low field are indica-
tive of the coordination of the acyl oxygen atoms to the
Lewis acidic zirconium centers, thus forming an eight-
membered metallacycle in which the biaryl unit is
(5) (a) Bringmann, G.; Hartung, T.; Go¨bel, L.; Schupp, O.; Ewers,
C. L. J .; Scho¨ner, B.; Zagst, R.; Peters, K.; von Schnering, H. G.;
Burschka, C. Liebigs Ann. Chem. 1992, 225. (b) Bringmann, G.;
Schupp, O. S. Afr. J . Chem. 1994, 47, 83.
(6) Bringmann, G.; Pokorny, F. in The Alkaloids; Cordell, G., Ed.;
Academic Press: New York, 1995; Vol. 46, p 127.
(7) Bringmann, G.; Holenz, J .; Weinrich, R.; Ru¨benacker, M.; Funke
C.; Boyd, M. R.; Gulakowski, R. J .; Franc¸ois, G. Tetrahedron 1998,
54, 497.
(8) Memmler, H.; Walsh, K.; Gade, L. H.; Lauher, J . W. Inorg. Chem.
1995, 34, 4062. See also ref 4a.
† Institut fu¨r Anorganische Chemie, Universita¨t Wu¨rzburg.
‡ Institut fu¨r Organische Chemie, Universita¨t Wu¨rzburg.
§ University of North London.
(1) (a) Casey, C. P.; J ordan, R. F.; Rheingold, A. L. J . Am. Chem.
Soc. 1983, 105, 665. (b) Casey, C. P.; J ordan, R. F.; Rheingold, A. L.
Organometallics 1984, 3, 504. (c) Sartain, W. S.; Selegue, J . P. J . Am.
Chem. Soc. 1985, 107, 5818. (d) Sartain, W. S.; Selegue, J . P.
Organometallics 1987, 6, 1812. (e) Sartain, W. S.; Selegue, J . P.
Organometallics 1989, 8, 2153. (f) Selent, D.; Beckhaus, R.; Pickardt,
J . Organometallics 1993, 12, 2857.
(2) (a) Casey, C. P. J . Organomet. Chem. 1990, 400, 205. (b)
Ferguson, G. S.; Wolczanski, P. T.; Parkanyi, L.; Zonnevylle, M.
Organometallics 1988, 7, 1967. (c) Baranger, A. M.; Bergman, R. G. J .
Am. Chem. Soc. 1994, 116, 3822. (c) Hanna, T. A.; Baranger, A. M.;
Bergman, R. G. J . Am. Chem. Soc. 1995, 117, 665.
(9) Data for 4 are as follows. Anal. Calcd for C51H50F3FeN3O4Si3Zr:
C, 57.99; H, 4.74; N, 3.98. Found: C, 57.69; H, 4.78; N, 3.52. 1H NMR
(C6D6, 295 K): δ -0.18 (s, HC(Si...)3), 0.42, 0.55 (s, (Si(CH3)2), 1.74
(6′-CH3), 2.09 (4′-CH3), 3.85 (s, C5H5), 5.62-7.57 (m, 2-FC6H4 and
lactone 2). 13C NMR (C6D6, 295 K): δ 3.9, 4.8 (Si(CH3)2), 7.7 (HC(Si...)3),
2
20.9 (ArCH3), 21.1 (ArCH3), 87.2 (C5H5), 115.2 (d, J FC ) 22.1 Hz, C3
of 2-FC6H4), 120.3 (C4 of 2-FC6H4), 124.2 (C5 of 2-FC6H4), 126.7 (C6 of
2
1
2-FC6H4), 141.8 (d, J FC ) 13.1 Hz, C1 of 2-FC6H4), 157.9 (d, J FC
)
235.4 Hz, C2 of 2-FC6H4), 211.2, 212.2 (CO), 296.2 (ZrO(...)COFe), 115.9,
117.0, 119.4, 121.8, 122.7, 126.1, 126.7, 127.5, 128.5, 132.7, 132.9, 155.2,
161.8 (lactone 2). 19F NMR (C6D6, 295 K): δ -122.0. 29Si NMR (C6D6,
295 K): δ 2.0. IR (benzene): ν(CO) 2028, 1985 cm-1. Data for 5 are as
follows. Anal. Calcd for C51H50F3FeN3O6Si3Zr: C, 56.28; H, 4.60; N,
3.86. Found: C, 56.36; H, 4.77; N, 3.58. 1H NMR (C6D6, 295 K):
δ
(3) (a) Friedrich, S.; Memmler, H.; Gade, L. H.; Li, W.-S.; McPartlin,
M. Angew. Chem., Int. Ed. Engl. 1994, 33, 676. (b) Friedrich, S.;
Memmler, H.; Gade, L. H.; Li, W.-S.; Scowen, I. J .; McPartlin, M.;
Housecroft, C. E. Inorg. Chem. 1996, 35, 2433. (c) Findeis, B.; Schubart,
M.; Platzek, C.; Gade, L. H.; Scowen, I. J .; McPartlin, M. Chem.
Commun. 1996, 219.
(4) (a) Memmler, H.; Kauper, U.; Gade, L. H.; Scowen, I. J .;
McPartlin, M. Chem. Commun. 1996, 1751. (b) Friedrich, S.; Gade, L.
H.; Scowen, I. J .; McPartlin, M. Angew. Chem., Int. Ed. Engl. 1996,
35, 1338.
-0.17 (s, HC(Si...)3), 0.43, 0.54 (s, (Si(CH3)2), 2.96 (6′-CH3), 3.41 (4′-
OCH3), 3.93 (s, C5H5), 5.60-7.50 (m, 2-FC6H4 and lactone 3). 13C NMR
(C6D6, 295 K): δ 4.0, 4.3 (Si(CH3)2), 7.8 (HC(Si...)3), 54.6 (OCH3), 55.4
2
(OCH3), 87.1 (C5H5), 115.2 (d, J FC ) 22.1 Hz, C3 of 2-FC6H4), 120.3
(C4 of 2-FC6H4), 124.2 (C5 of 2-FC6H4), 126.7 (C6 of 2-FC6H4), 141.7 (d,
1
2J FC ) 13.1 Hz, C1 of 2-FC6H4), 157.9 (d, J FC ) 235.4 Hz, C2 of
2-FC6H4), 210.6, 211.5 (CO), 297.6 (ZrO(...)COFe), 115.9, 117.8, 121.8,
123.1, 126.0, 129.5, 132.9, 133.5, 155.7, 158.7, 161.9, 163.7 (lactone
3). 19F NMR (C6D6, 295 K): δ -121.9. 29Si NMR (C6D6, 295 K): δ 2.1.
IR (benzene): ν(CO) 2030, 1991 cm-1
.
S0276-7333(98)00007-7 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 04/09/1998

1644 Organometallics, Vol. 17, No. 9, 1998
Communications
Sch em e 1
Sch em e 2
conformationally stable on the NMR time scale, as
reflected in the diastereotopicity of the SiMe2 signals
mentioned above. On the basis of the low-field 13C NMR
resonances, which should be compared with those
observed at ca. δ 254 in [Cp(CO)2Fe(COR)] (R ) Me,
Ph),10 the acyl-metal groups in 4 and 5 are thought to
be more adequately formulated as carbene metal units,
implying a formally zwitterionic nature of the dinuclear
complexes as depicted in Scheme 1.11
of a disordered toluene solvent, resulting in relatively
large esd’s on all parameters, the structure of the
compound is well established. The structural center
(12) Data for 6 are as follows. Anal. Calcd for C50H50F3FeN3O3Si3-
Zr: C, 58.35; H, 4.90; N, 4.08. Found: C, 57.98; H, 4.73; N, 3.94. 1H
NMR (C6D6, 295 K): δ -0.35 (s, HC(Si...)3), 0.22, 0.31 (s, (Si(CH3)2),
1.70 (6′-CH3), 2.10 (4′-CH3), 4.23 (s, C5H5), 6.33-7.64 (m, 2-FC6H4 and
lactone 2). 13C NMR (C6D6, 295 K): δ 3.1, 4.9 (Si(CH3)2), 8.8 (HC(Si...)3),
2
20.9 (ArCH3), 21.5 (ArCH3), 86.4 (C5H5), 115.0 (d, J FC ) 23.1 Hz, C3
of 2-FC6H4), 120.1 (C4 of 2-FC6H4), 122.2 (C5 of 2-FC6H4), 125.3 (C6 of
2
1
2-FC6H4), 139.9 (d, J FC ) 12.1 Hz, C1 of 2-FC6H4), 158.1 (d, J FC
)
Upon stirring 4 and 5 in pentane solution, slow
decarbonylation occurs, yielding the dinuclear com-
plexes 6 and 7 in which the {Cp(CO)2Fe} fragment is
directly bonded to the naphthalene ring (Scheme 2).12
The most characteristic spectroscopic changes accom-
panying this conversion is the shift of the (CO) infrared
bands by ca. 30 cm-1 to lower wavenumbers (4 2030,
1991 cm-1; 5 2028, 1985 cm-1 to 6 2000, 1956 cm-1; 7
1997, 1954 cm-1), the disappearance of the acyl/carbene
227.4 Hz, C2 of 2-FC6H4), 214.2, 217.2 (CO), 117.1, 119.0, 124.1, 124.6,
124.9, 125.6, 129.3, 132.1, 132.7, 144.8, 146.9, 148.4, 160.5 (lactone
2). 19F NMR (C6D6, 295 K): δ -123.0. 29Si NMR (C6D6, 295 K): δ 3.3.
IR (benzene): ν(CO) 2000, 1956 cm-1. Data for 7 are as follows. Anal.
Calcd for C50H50F3FeN3O5Si3Zr: C, 56.59; H, 4.75; N, 3.96. Found: C,
56.39; H, 4.49; N, 3.90. 1H NMR (C6D6, 295 K): δ -0.37 (s, HC(Si...)3),
0.24, 0.30 (s, (Si(CH3)2), 3.01 (6′-OCH3), 3.48 (4′-OCH3), 4.15 (s, C5H5),
6.30-7.68 (m, 2-FC6H4 and lactone 3). 13C NMR (C6D6, 295 K): δ 3.0,
5.1 (Si(CH3)2), 8.7 (HC(Si...)3), 54.2 (ArOCH3), 55.1 (ArOCH3), 86.8
(C5H5), 114.4 (d, 2J FC ) 22.8 Hz, C3 of 2-FC6H4), 120.0 (C4 of 2-FC6H4),
2
122.6 (C5 of 2-FC6H4), 125.4 (C6 of 2-FC6H4), 140.3 (d, J FC ) 12.0 Hz,
C1 of 2-FC6H4), 158.5 (d, 1J FC ) 228.6 Hz, C2 of 2-FC6H4), 214.1, 217.8
(CO), 117.2, 119.3, 124.1, 124.7, 124.7, 125.5, 129.9, 133.0, 132.8, 145.2,
146.7, 148.9, 161.3 (lactone 3). 19F NMR (C6D6, 295 K): δ -124.1. 29Si
1
resonance just below 300 cm-1, and the H NMR shift
of the Cp signal to higher field (4 δ 3.93; 5 δ 3.85 to 6 δ
4.23; 7 δ 4.15, recorded in C6D6). We note that the
thermally and photochemically induced decarbonylation
of acyliron complexes has been reported previously.13
To fully establish the structures of the decarbonyla-
tion products 6 and 7, a single-crystal X-ray structure
analysis of 7 was carried out (Figure 1).14 Although the
crystal diffracted weakly, a consequence of the presence
NMR (C6D6, 295 K): δ 3.4. IR (benzene): 1997, 1954 cm-1
.
(13) Representative examples: (a) King, R. B.; Bisnette, M. B. J .
Organomet. Chem. 1964, 2, 15. (b) Labinger, J . A.; Bonfiglio, J . N.;
Grimmet, D. L.; Masuo, S. T.; Shearin, E.; Miller, J . S. Organometallics
1983, 2, 733.
(14) Crystal data for 7‚1/2C7H8: C53.5H54F3FeN3O5Si3Zr, M ) 1107.34,
monoclinic, space group C2/c, a ) 40.373(7) Å, b ) 13.056(4) Å, c )
20.130(4) Å, â ) 96.067(10)°, V ) 10551(4) Å3, Z ) 8, F(000) ) 4568,
Dc ) 1.394 g cm-3, µ(Mo KR) 0.600 mm-1, λ(Mo KR) ) 0.710 73 Å. All
samples examined diffracted weakly. Of 6662 data collected from a
yellow block (0.34 × 0.36 × 0.44 mm) using a Siemens P4 four-circle
diffractometer, 5668 unique reflections corrected for absorption by
Ψ-scans (Rint ) 0.0867, Tmax 0.603, Tmin 0.547) in the limited θ-range
1.01-21.00° were used in subsequent analysis. The structure was
solved by direct methods and refined on F2 to convergence at R1 [I
>2σ(I)] ) 0.0852 and wR2 ) 0.1623 (wR2 (all data) ) 0.2310) for 581
parameters (GooF on F2 ) 0.998). SHELXTL-PC (version 5.03; Siemens
Analytical X-ray: Madison, WI, 1996) running on an AT486-66 PC was
used for all computations.
(10) (a) Kuhlmann, E. J .; Alexander, J . J . Inorg. Chem. Acta 1979,
34, L193. (b) Felkin, H.; Meunier, B.; Pascard, C.; Prange, T. J .
Organomet. Chem. 1977, 135, 361.
(11) 13C NMR data of related alkoxycarbeneiron complexes: (a)
Casey, C. P.; Miles, W. H.; Tukuda, H. J . Am. Chem. Soc. 1985, 107,
2924. (b) Akita, M.; Kawahara, T.; Moro-oka, Y. J . Chem. Soc., Chem.
Commun. 1987, 1356. (c) Brookhart, M.; Studabaker, G. R.; Husk, G.
R. Organometallics 1987, 6, 1141.

Communications
Organometallics, Vol. 17, No. 9, 1998 1645
groups, which is coplanar with the phenyl ring, is an
indication of π-interaction between the aromatic ring
and the substituents. Coordination of two of the
fluorine atoms of the tripodal ligand to the zirconium
center in the complex generates a hexacoordinate metal
center with a highly distorted ligand polyhedon that
may be best viewed as a bicapped tetrahedron with the
two fluorine donors capping the faces. We previously
observed the participation of potentially binding pe-
ripheral donor atoms in the coordination to an early
transition metal center in [HC{SiMe2N(2-FC6H3)}3-
ZrCl2Li(OEt2)2] and [HC{SiMe2N(2-FC6H3)}3Y(OEt2)] in
which, respectively, one and three F atoms coordinate
to the metal center.8 In this system, we envisage that
the coordinated fluorines play a role in shielding open
portions of the high-valent metal center.
This first study of the reactivity of unsupported Zr-
Fe heterobimetallics toward biaryl lactones has shown
that they not only achieve the ring opening to generate
the axially chiral substrates but, in addition, remove
the “auxiliary” carbonyl function of the lactone. This
is of importance for the synthesis of natural products
containing a biaryl axis but lacking such a C1 unit next
to the axis.6 In present and future studies, we inves-
tigate the potential of chiral early-late heterobimetal-
lics, containing a previously reported C3-chiral tripodal
amido ligand,15 in order to achieve stereoselectivity in
the ring-opening reactions of the lactones.
F igu r e 1. Molecular structure of 7. Principal bond lengths
(Å) and interbond angles (deg): Zr(1)-O(72) 1.965(9), Zr-
(1)-N(1) 2.061(11), Zr(1)-N(2) 2.075(11), Zr(1)-N(3) 2.099-
(10), Zr(1)-F(3) 2.548(8), Zr(1)-F(1) 2.591(9), Fe(2)-C(41)
2.12(2), Fe(2)-C(42) 2.15(2), Fe(2)-C(43) 2.11(2), Fe(2)-
C(44) 2.12(2), Fe(2)-C(45) 2.115(14), Fe(2)-C(51) 1.72(2),
Fe(2)-C(61) 1.75(2), Fe(2)-C(82) 1.993(14), O(72)-Zr(1)-
N(1) 131.3(4), O(72)-Zr(1)-N(2) 106.6(4), N(1)-Zr(1)-N(2)
100.8(4), O(72)-Zr(1)-N(3) 114.5(4), N(1)-Zr(1)-N(3) 100.3-
(4), N(2)-Zr(1)-N(3) 98.0(4), O(72)-Zr(1)-F(3) 74.7(3),
N(1)-Zr(1)-F(3) 88.8(3), N(2)-Zr(1)-F(3) 164.8(3), N(3)-
Zr(1)-F(3) 68.4(3), O(72)-Zr(1)-F(1) 73.8(3), N(1)-Zr(1)-
F(1) 67.1(4), N(2)-Zr(1)-F(1) 89.2(4), N(3)-Zr(1)-F(1)
166.6(4), F(3)-Zr(1)-F(1) 105.6(3), C(51)-Fe(2)-C(61)
89.9(8), C(51)-Fe(2)-C(82) 95.6(6), C(61)-Fe(2)-C(82)
90.8(7).
Ack n ow led gm en t. We thank the Deutsche Fors-
chungsgemeinschaft (SFB 347), the European Commis-
sion (TMR network MECATSYN), the Fonds der Che-
mischen Industrie, the Engineering and Physical Science
Research Council, the Deutscher Akademischer Aus-
tauschdienst, and the Britisch Council (ARC program)
for support.
Su p p or tin g In for m a tion Ava ila ble: Detailed prepara-
tive procedures as well as tables of atomic coordinates, thermal
parameters, and full bond lengths and angles (17 pages).
Ordering information is given on any current masthead page.
piece is the ring-opened and decarbonylated biaryl
lactone with the {Fe(CO)2Cp} unit bonded to the 2-posi-
tion of the naphthyl group (Fe-C(82) 1.993(14)). The
aromatic units of the biaryl lactone lie in a virtually
orthogonal disposition (dihedral angle 87.5°), which
appears to be fixed by the steric interplay of the {Fe-
(CO)2Cp} unit with the periphery of the tripodal trisi-
lylmethane ligand. The orientation of the two methoxy
OM980007D
(15) (a) Memmler, H.; Gade, L. H.; Lauher, J . W. Inorg. Chem. 1994,
33, 3064. (b) Memmler, H.; Kauper, U.; Gade, L. H.; Stalke, D.; Lauher,
J . W. Organometallics 1996, 15, 3637.