Transfer of ketyls from alkali metals to transition metals. Formation and diverse reactivities of D-block transition-metal ketyls

Article abstract of DOI:10.1021/om981013c

This paper reports our studies on the preparation of d-block transition-metal ketyls via metathesis reactions of alkali-metal ketyls with transition-metal chlorides as well as via deprotonation of pinacols with a transition-metal base. The metathesis reaction of sodium fluorenone ketyl with (C₅Me₅)₂ZrCl₂ in THF gave the corresponding zirconium fluorenone ketyl complex (C₅Me₅)₂Zr(OC₁₃H₈)Cl (1), which represents the first example of a structurally characterized d-block transition-metal ketyl complex. In the case of sodium benzophenone ketyl, further reaction between the ketyl radical and a C₅Me₅ ligand took place to give finally the zirconium bis(alkoxide) complex (η⁵-C₅Me₅)(η⁵:η ¹-C₅Me₄CH₂C(Ph) ₂O)Zr(OCHPh₂) (2). In contrast, the similar reaction of [(C₅Me₅)Ir(μ-Cl)Cl]₂ with sodium fluorenone ketyl yielded the iridium carbonyl complex (C₅Me₅)Ir(CO)(C₁₂H₈) (5), as a result of decarbonylation of fluorenone. When [(C₅Me₅)Ir(μ-H)Cl]₂ was used to react with sodium fluorenone or benzophenone ketyl, the dechlorination (reduction) product [(C₅Me₅)Ir(μ-H)]₂ (8), together with fluorenone or benzophenone, formed selectively. The ketone-free 8 could be obtained in high yields by reaction of [(C₅Me₅)Ir(μ-H)Cl]₂ with 2 equiv of K or Na in THF. The reaction of 1,2-bis(biphenyl-2,2′-diyl)ethane-1,2-diol (9) with the iridium imido complex (C₅Me₅)IrN^tBu in THF gave a mixture of 5 (30%) and 8·2(fluorenone) (30%). However, when the reaction was carried out in benzene, the pinacolate complex (C₅Me₅)Ir(O₂C₂₆H₁₆) (10) was formed as a major product (73%) together with a small amount of 5 (9%) and 8 (13%).

Full text of DOI:10.1021/om981013c

Organometallics 1999, 18, 1979-1985
1979
Tr a n sfer of Ketyls fr om Alk a li Meta ls to Tr a n sition
Meta ls. F or m a tion a n d Diver se Rea ctivities of d -Block
Tr a n sition -Meta l Ketyls
Zhaomin Hou,*,† Akira Fujita,‡ Take-aki Koizumi,† Hiroshi Yamazaki,‡ and
Yasuo Wakatsuki*,†
The Institute of Physical and Chemical Research (RIKEN), Hirosawa 2-1,
Wako, Saitama 351-0198, J apan, and Department of Applied Chemistry, Chuo University,
Kasuga 1-13-27, Bunkyo, Tokyo 112-0003, J apan
Received December 14, 1998
This paper reports our studies on the preparation of d-block transition-metal ketyls via
metathesis reactions of alkali-metal ketyls with transition-metal chlorides as well as via
deprotonation of pinacols with a transition-metal base. The metathesis reaction of sodium
fluorenone ketyl with (C5Me5)2ZrCl2 in THF gave the corresponding zirconium fluorenone
ketyl complex (C5Me5)2Zr(OC13H8)Cl (1), which represents the first example of a structurally
characterized d-block transition-metal ketyl complex. In the case of sodium benzophenone
ketyl, further reaction between the ketyl radical and a C5Me5 ligand took place to give finally
the zirconium bis(alkoxide) complex (η5-C5Me5)(η5:η1-C5Me4CH2C(Ph)2O)Zr(OCHPh2) (2). In
contrast, the similar reaction of [(C5Me5)Ir(µ-Cl)Cl]2 with sodium fluorenone ketyl yielded
the iridium carbonyl complex (C5Me5)Ir(CO)(C12H8) (5), as a result of decarbonylation of
fluorenone. When [(C5Me5)Ir(µ-H)Cl]2 was used to react with sodium fluorenone or ben-
zophenone ketyl, the dechlorination (reduction) product [(C5Me5)Ir(µ-H)]2 (8), together with
fluorenone or benzophenone, formed selectively. The ketone-free 8 could be obtained in high
yields by reaction of [(C5Me5)Ir(µ-H)Cl]2 with 2 equiv of K or Na in THF. The reaction of
1,2-bis(biphenyl-2,2′-diyl)ethane-1,2-diol (9) with the iridium imido complex (C5Me5)IrNtBu
in THF gave a mixture of 5 (30%) and 8‚2(fluorenone) (30%). However, when the reaction
was carried out in benzene, the pinacolate complex (C5Me5)Ir(O2C26H16) (10) was formed as
a major product (73%) together with a small amount of 5 (9%) and 8 (13%).
In tr od u ction
highlights in this area.3-11 However, the previously
reported metal ketyls have almost all been limited to
those of the metal ions which are good electron transfer
agents when in low oxidation states. Ketyl complexes
of nonreducing metals, particularly those of the d-block
transition metals, have remained unexplored.12,13
During our recent studies on structurally well-defined
reducing-metal ketyl complexes,3,4,6,8-10 we became
interested in the ketyl complexes of d-block transition
metals. In this paper, we report the first structurally
Metal ketyls, which are usually formed via one-
electron reduction of ketones or aldehydes by reducing
metals, represent one of the most important intermedi-
ates in organic chemistry.1 These highly reactive and
synthetically useful species have received continuous
attention from a broad range of chemists since their
discovery more than 100 years ago.1,2 The recent suc-
cessful isolation and structural characterization of a
series of alkali-metal, alkaline-earth-metal, and lan-
thanide-metal ketyl complexes represent one of the
(3) Hou, Z.; Wakatsuki, Y. Chem. Eur. J . 1997, 3, 1005.
(4) Hou, Z.; Fujita, A.; Zhang, Y.; Miyano, T.; Yamazaki, H.;
Wakatsuki, Y. J . Am. Chem. Soc. 1998, 120, 754.
(5) Takats, J . J . Alloys Compd. 1997, 249, 51.
† The Institute of Physical and Chemical Research (RIKEN).
‡ Chuo University.
(1) For reviews on metal ketyl-involved organic synthesis, see: (a)
Molander, G. A. Acc. Chem. Res. 1998, 31, 603. (b) Skrydstrup, T.
Angew. Chem., Int. Ed. Engl. 1997, 36, 345. (c) Molander, G. A.; Harris,
C. R. Chem. Rev. 1996, 96, 307. (d) Wirth, T. Angew. Chem., Int. Ed.
Engl. 1996, 35, 61. (e) Fu¨rstner, A.; Bogdanovic, B. Angew. Chem., Int.
Ed. Engl. 1996, 35, 2442. (f) Molander, G. A. Chem. Rev. 1992, 92, 29.
(g) Huffman, J . W. In Comprehensive Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon: New York, 1991; Vol. 8, Chapter 1.4. (h)
Robertson, G. M. In Comprehensive Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon: New York, 1991; Vol. 3, Chapter 2.6. (i)
McMurry, J . E. Chem. Rev. 1989, 89, 1513. (j) Kahn, B. E.; Riecke, R.
T. Chem. Rev. 1988, 88, 733. (k) Pradhan, S. K. Tetrahedron 1986, 42,
6351. (l) Huffman, J . W. Acc. Chem. Res. 1983, 16, 399. (m) McMurry,
J . E. Acc. Chem. Res. 1983, 16, 405; 1974, 7, 281. (n) House, H. O. In
Modern Synthetic Reactions, 2nd ed.; W. A. Benjamin: Menlo Park,
CA, 1972; Chapter 3.
(6) Hou, Z.; J ia, X.; Wakatsuki, Y. Angew. Chem., Int. Ed. Engl.
1997, 36, 1292.
(7) Clegg, W.; Eaborn, C.; Izod, K.; O’Shaughnessy, P.; Smith, J . D.
Angew. Chem., Int. Ed. Engl. 1997, 36, 2815.
(8) Hou, Z.; Fujita, A.; Yamazaki, H.; Wakatsuki, Y. J . Am. Chem.
Soc. 1996, 118, 7843.
(9) Hou, Z.; Fujita, A.; Yamazaki, H.; Wakatsuki, Y. J . Am. Chem.
Soc. 1996, 118, 2503.
(10) Hou, Z.; Miyano, T.; Yamazaki, H.; Wakatsuki, Y. J . Am. Chem.
Soc. 1995, 117, 4421.
(11) Bock, H.; Herrmann, H.-F.; Fenske, D.; Goesmann, H. Angew.
Chem., Int. Ed. Engl. 1988, 27, 1067.
(12) The formation of silicon ketyl species via C-C bond cleavage
of the corresponding pinacolates at high temperature has been
previously described. See: (a) Newmann, W. P.; Schroeder, B.; Zie-
barth, M. Liebigs Ann. Chem. 1975, 2279. (b) Ziebarth, M.; Newmann,
W. P. Liebigs Ann. Chem. 1978, 1765.
(13) For a spectroscopic study on titanium ketyls which are gener-
ated by using a Ti(III) reducing agent, see: Covert, K. J .; Wolczanski,
P. T.; Hill, S. A.; Krusic, P. J . Inorg. Chem. 1992, 31, 66.
(2) For early examples of the formation of ketyl species, see: (a)
Bechman, F.; Paul, T. J ustus Liebigs Ann. Chem. 1891, 266, 1. (b)
Schlenk, W.; Weichel, T. Ber. Dtsch. Chem. Ges. 1911, 44, 1182. (c)
Schlenk, W.; Thal, A. Ber. Dtsch. Chem. Ges. 1913, 46, 2480.
10.1021/om981013c CCC: $18.00 © 1999 American Chemical Society
Publication on Web 04/22/1999

1980 Organometallics, Vol. 18, No. 10, 1999
Hou et al.
Sch em e 1
characterized d-block transition-metal ketyl complex,
(C5Me5)2Zr(OC13H8)Cl, which is synthesized by the
metathesis reaction of sodium fluorenone ketyl with (C5-
Me5)2ZrCl2. Similar approaches to iridium ketyl, the
reactions of alkali metals with an iridium chloride/
hydride complex, and deprotonation of pinacols with an
iridium imido complex are also described. Dramatic
metal dependence of the reactivity of the ketyl species
has been observed.
F igu r e 1. UV-vis spectra in THF: (solid line) Zr ketyl
complex 1 (5.54 × 10-4 mmol/cm3): (dashed line) sodium
fluorenone ketyl (5.43 × 10-4 mmol/cm3).
Resu lts a n d Discu ssion
R ea ct ion of Sod iu m F lu or en on e Ket yl w it h
(C5Me5)2Zr Cl2. As a typical example of nonreducing
early-transition-metal compounds, the Zr(IV) complex
(C5Me5)2ZrCl2 was first chosen. Reaction of (C5Me5)2-
ZrCl2 with 1 equiv of sodium fluorenone ketyl in THF9
was carried out according to Scheme 1. From this
reaction the dark brown crystalline product 1 was
isolated in 73% yield. The ESR spectrum of 1 in THF
(g ) 2.0032) was very similar to that of sodium fluo-
renone ketyl and those of other metal fluorenone ketyl
species,4,8,9,11 suggesting that 1 contains a ketyl radical
species. The UV-vis spectrum of 1 showed a maximum
absorbance at 415 nm, which was greatly blue-shifted
from that of the starting sodium fluorenone ketyl (see
Figure 1). This result suggested that transfer of fluo-
renone ketyl from sodium to the zirconium metal center
had occurred.14
F igu r e 2. ORTEP drawing of 1 with 30% thermal el-
lipsoids. The lattice solvent is omitted for clarity.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) of 1
Zr(1)-Cl(1)
Zr(1)-C(14)
Zr(1)-C(16)
Zr(1)-C(18)
Zr(1)-C(25)
Zr(1)-C(27)
O(1)-C(1)
2.456(2)
2.562(7)
2.554(7)
2.539(7)
2.562(7)
2.564(6)
1.315(8)
Zr(1)-O(1)
Zr(1)-C(15)
Zr(1)-C(17)
Zr(1)-C(24)
Zr(1)-C(26)
Zr(1)-C(28)
2.002(5)
2.523(8)
2.561(7)
2.540(7)
2.544(7)
2.553(7)
Single crystals suitable for diffraction studies were
obtained by recrystallization of 1 from toluene/OEt2. An
X-ray analysis has revealed that 1 is a zirconium(IV)
fluorenone ketyl complex which is stabilized by two C5-
Me5 and one Cl ligands (Figure 2 and Table 1). The
length of the C-O bond in the fluorenone ketyl unit of
1 (1.315(8) Å) is in the 1.27-1.32 Å range reported for
other metal ketyl complexes.3-11 The distance is longer
than the C-O double bond of free fluorenone (1.220(4)
Å)15 but shorter than the C-O single bond found in the
fluorenoxide ligand of Sm(OC13H9)(OAr)2(HMPA)2 (1.404-
Cp*(centroid)-Zr(1)-Cp*(centroid)
O(1)-Zr(1)-Cp*C(14)-C(18)(centroid)
O(1)-Zr(1)-Cp*C(24)-C(28)(centroid)
Cl(1)-Zr(1)-Cp*C(14)-C(18)(centroid)
Cl(1)-Zr(1)-Cp*C(24)-C(28)(centroid)
137.4
104.9
105.2
103.7
101.8
Cl(1)-Zr(1)-O(1)
O(1)-C(1)-C(2)
C(2)-C(1)-C(13)
97.0(2)
124.9(6)
108.9(6)
Zr(1)-O(1)-C(1)
O(1)-C(1)-C(13)
170.4(4)
126.1(6)
t
in 1 (2.002(5) Å) can be compared with those of the Zr-
OH and Zr-OAr bonds found in (C5Me5)2Zr(OH)Cl
(1.950(2) Å),17 (C5Me5)2Zr(OH)2 (1.975(2), 1.982(7) Å),17
Zr(OAr)2(η2-tBuNCCH2Ph)2 (2.027(2) Å),18 and Zr(OAr)-
(8) Å; Ar ) C6H2 Bu2-2,6-Me-4, HMPA ) hexameth-
ylphosphoric triamide).16 The Zr-O(ketyl) bond distance
(14) Metal dependence of the λmax value of ketyls in UV-vis spectra
has been previously observed. See: (a) Mao, S. W.; Hirota, N. Chem.
Phys. Lett. 1973, 22, 26. (b) Mao, S. W.; Nakamura, K.; Hirota, N. J .
Am. Chem. Soc. 1974, 96, 5341. See also refs 4 and 10.
(15) Luss, H. R.; Smith, D. L. Acta Crystallogr., Sect. B 1972, 28,
884.
(17) Bortolin, R.; Patel, V.; Munday, I.; Taylor, N. J .; Carty, A. J . J .
Chem. Soc., Chem. Commun. 1985, 456.
(18) Chamberlain, L. R.; Durfee, L. D.; Fanwick, P. E.; Kobriger,
L.; Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Folting, K.;
Huffman, J . C.; Streib, W. E.; Wang, R. J . Am. Chem. Soc. 1987, 109,
390.
(16) Yoshimura, T.; Hou, Z.; Wakatsuki, Y. Organometallics 1995,
14, 5382.

d-Block Transition-Metal Ketyls
Organometallics, Vol. 18, No. 10, 1999 1981
Sch em e 2
F igu r e 3. ORTEP drawing of 2 with 30% thermal el-
lipsoids.
(η2-tBuNCCH2Ph)3 (2.058(2) Å) (Ar ) C6H3 Bu2-2,6).18,19
Similar to the case for other fluorenone ketyl com-
plexes,4,8-11 the whole fluorenone ketyl unit of 1 remains
planar, showing that the radical carbon atom in the
ketyl unit is still in an sp2 hybrid state.
t
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) of 2
Zr(1)-O(1)
Zr(1)-C(27)
Zr(1)-C(29)
Zr(1)-C(31)
Zr(1)-C(38)
Zr(1)-C(40)
O(1)-C(1)
2.015(7)
Zr(1)-O(2)
Zr(1)-C(28)
Zr(1)-C(30)
Zr(1)-C(37)
Zr(1)-C(39)
Zr(1)-C(41)
O(2)-C(14)
C(27)-C(32)
1.983(8)
2.501(10)
2.620(11)
2.545(12)
2.621(12)
2.588(11)
1.402(13)
1.573(15)
1.02(16)
2.563(10)
2.624(12)
2.653(13)
2.618(12)
2.580(13)
1.409(14)
1.506(16)
Further reaction of the mono(ketyl)zirconium chloride
complex with 1 equiv of sodium fluorenone ketyl to give
a bis(ketyl)zirconium species was not observed in THF
at room temperature, probably due to steric hindrance.
Similarly, the reaction of (C5Me5)2ZrCl2 with 2 equiv of
sodium fluorenone ketyl under the same conditions gave
1 as the only isolable zirconium species. As far as we
are aware, complex 1 represents the first example of a
structurally characterized d-block transition-metal ketyl
complex.
Rea ction of Sod iu m Ben zop h en on e Ketyl w ith
(C5Me5)2Zr Cl2. Next, the reaction of (C5Me5)2ZrCl2 with
2 equiv of sodium benzophenone ketyl was carried out.
A color change from blue to purple-red was observed
during the reaction. However, in contrast to what was
observed in the case of fluorenone ketyl, the color of the
reaction mixture faded gradually overnight, and an
ESR-silent pale yellow crystalline product (2) was finally
obtained (Scheme 2) in 54% yield.
C(1)-C(32)
C(14)-H(14)
Cp*(centroid)-Zr(1)-Cp′(centroid)
O(1)-Zr(1)-Cp*(centroid)
O(1)-Zr(1)-Cp′(centroid)
O(2)-Zr(1)-Cp*(centroid)
O(2)-Zr(1)-Cp′(centroid)
134.1
103.4
97.9
106.3
108.4
O(1)-Zr(1)-O(2)
101.7(4)
Zr(1)-O(2)-C(14) 158.4(8)
Zr(1)-O(1)-C(1)
135.4(7)
111.1(10)
107.7(9)
111.2(10)
113.1(11)
O(1)-C(1)-C(2)
O(1)-C(1)-C(32)
C(2)-C(1)-C(32)
O(2)-C(14)-C(15)
O(1)-C(1)-C(8)
C(2)-C(1)-C(8)
C(8)-C(1)-C(32)
O(2)-C(14)-C(21) 111.9(10) C(15)-C(14)-C(21) 111.0(10)
C(1)-C(32)-C(27) 110.9(9)
109.7(9)
107.1(9)
110.0(9)
with 2 equiv of sodium benzophenone ketyl could first
give the bis(ketyl) species 3. The initial color change of
the reaction mixture from blue (sodium benzophenone
ketyl) to purple-red is consistent with the formation of
a zirconium ketyl species at the early stages of the
reaction. Abstraction of a hydrogen atom (H•) from a C5-
Me5 group by one of the two benzophenone ketyls in 3
would afford 4, and then intramolecular coupling be-
tween the other benzophenone ketyl radical and the
An X-ray analysis has shown that 2 is a zirconium-
(IV) complex which contains a C5Me5 ligand and two
benzophenone-derived units, one of which is coupled
with a C5Me4CH2 unit through its carbonyl carbon atom,
while the other is hydrogenated at the carbonyl carbon
atom to form a normal diphenylmethoxide ligand (Fig-
•
1
resulting C5Me4CH2 radical could produce 2.
ure 3, Table 2). The H NMR spectrum of 2 in CD2Cl2
The isolation of 2 rather than a benzophenone ketyl
species in the present reaction again demonstrates that
benzophenone ketyl is more reactive than fluorenone
ketyl due to its less conjugated structure.6 In the case
of 1 or the previously reported C5Me5-ligated lanthanide
fluorenone ketyl complexes,4 hydrogen abstraction from
a C5Me5 group by fluorenone ketyl was not observed.
Rea ction s of Sod iu m Ketyls w ith [(C5Me5)Ir (µ-
Cl)Cl]2. To see how a ketyl radical species would
interact with a late-transition-metal center, the reaction
of the iridium(III) dichloride complex [(C5Me5)Ir(µ-Cl)-
Cl]2 with 4 equiv of sodium fluorenone ketyl in THF was
carried out (Scheme 3). Unexpectedly, the decarbony-
is consistent with its solid-state structure. The C5Me4-
CH2 unit shows four singlets for the Me groups at δ 2.09,
2.02, 1.36, and 1.28, respectively, and two doublets (J
) 14 Hz) for the CH2 group at δ 3.75 and 3.64,
respectively. Well-resolved signals for the phenyl groups
are observed in the range δ 7.61-6.65, while the OCH
part in the diphenylmethoxide unit appears as a singlet
at δ 6.22. The C5Me5 group gives a singlet at δ 1.94.
The formation of 2 could be explained by the reaction
paths shown in Scheme 2. The reaction of (C5Me5)2ZrCl2
(19) The similarity in bond distances between metal-ketyl bonds
and metal-aryloxide bonds has been previously observed.4

1982 Organometallics, Vol. 18, No. 10, 1999
Hou et al.
Sch em e 4
21
Me5)Ir(CH2CH2)2 and fluorenone at either room tem-
perature or 60 °C in THF. These results suggest that
the formation of 5 is mediated by an iridium fluorenone
ketyl or fluorenone dianion species. One possible mech-
anism for the formation of 5 is shown in Scheme 3.20
The formation of 5 under the present reaction condi-
tions constitutes a rare example of room-temperature
decarbonylation of a ketone moiety. Although the C-C
bond cleavage of cyclic ketones by low-valent transition
metals has been known for a long time,22,23 the decar-
bonylation of fluorenone is, to the best of our knowledge,
unprecedented.
F igu r e 4. ORTEP drawing of 5 with 30% thermal el-
lipsoids. Only one of the two independent molecules is
shown for clarity.
Sch em e 3
The similar reaction of [(C5Me5)Ir(µ-Cl)Cl]2 with
sodium benzophenone ketyl yielded a mixture of uni-
dentified iridium hydrides and benzophenone. Neither
an iridium benzophenone ketyl species nor the decar-
bonylation product was observed, which again demon-
strates that benzophenone ketyl behaves differently
from fluorenone ketyl.
R ea ct ion s of Sod iu m F lu or en on e Ket yl a n d
Alk a li Meta ls w ith [(C5Me5)Ir (µ-H)Cl]2. In an at-
tempt to obtain a better understanding of the decarbo-
nylation of fluorenone ketyl in its reaction with the
iridium(III) dichloride complex [(C5Me5)Ir(µ-Cl)Cl]2, the
similar reaction of the iridium(III) chloride/hydride
complex [(C5Me5)Ir(µ-H)Cl]2 with 2 equiv of sodium
fluorenone ketyl was carried out (Scheme 4). In this
reaction, formation of a fluorenone decarbonylation
product was not observed, but instead, the reduction
(dechlorination) of the iridium(III) chloride/hydride
complex took place to give the corresponding iridium-
(II) hydride complex [(C5Me5)Ir(µ-H)]2 (8) and fluorenone
almost quantitatively. The similar reaction of [(C5Me5)-
Ir(µ-H)Cl]2 with sodium benzophenone ketyl gave 8 and
benzophenone almost quantitatively. The ketone-free 8
was isolated as fine brown crystals in 95% yield from
the reaction of [(C5Me5)Ir(µ-H)Cl]2 with 2 equiv of K in
THF (Scheme 4). Similarly, the reaction of [(C5Me5)Ir-
(µ-H)Cl]2 with Na also produced 8, but a longer reaction
time (2 days) was required to complete the reaction.
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) of 5
Ir(1)-C(1)
Ir(1)-C(13)
Ir(1)-C(15)
Ir(1)-C(17)
O(1)-C(23)
2.07(2)
2.25(3)
2.27(3)
2.28(2)
1.14(3)
Ir(1)-C(12)
Ir(1)-C(14)
Ir(1)-C(16)
Ir(1)-C(23)
2.05(2)
2.27(3)
2.27(2)
1.83(1)
C(1)-Ir(1)-Cp*(centroid)
C(12)-Ir(1)-Cp*(centroid)
C(23)-Ir(1)-Cp*(centroid)
126.5
126.1
135.4
C(1)-Ir(1)-C(12)
C(12)-Ir(1)-C(23)
77.7(8)
86.0(9)
C(1)-Ir(1)-C(23)
Ir(1)-C(23)-O(1)
86.4(8)
179(2)
lation product 5 together with free fluorenone was
obtained in this reaction (Figure 4, Table 3).20 The
reaction of [(C5Me5)Ir(µ-Cl)Cl]2 with 2 equiv of sodium
fluorenone dianion also gave 5, but without the forma-
tion of fluorenone.20 To obtain 5, the prior preparation
of sodium fluorenone ketyl or fluorenone dianion is not
required. The one-pot reaction of [(C5Me5)Ir(µ-Cl)Cl]2
with 4 equiv of sodium and 2 equiv of fluorenone in THF
also afforded 5 in about 70% isolated yield. However, if
the reaction was carried out by first mixing [(C5Me5)-
Ir(µ-Cl)Cl]2 with sodium for a few hours and then adding
fluorenone, a mixture of unidentified iridium hydrides
was formed, while fluorenone remained unchanged. No
reaction was observed between the Ir(I) complex (C5-
(21) Moseley, K.; Kang, J . W.; Maitlis, P. M. J . Chem. Soc. A 1970,
2875.
(22) For examples of C-C bond cleavage and/or decarbonylation of
cyclic ketones, see: (a) Evans, J . A.; Everitt, G. F.; Kemmitt, D. W.;
Russell, D. R. J . Chem. Soc., Chem. Commun. 1973, 158. (b) Kaneda,
K.; Azuma, H.; Wayaku, M.; Teranishi, S. Chem. Lett. 1974, 215. (c)
Huffman, M. A.; Liebeskind, L. S. J . Am. Chem. Soc. 1991, 113, 2771.
(d) Huffman, M. A.; Liebeskind, L. S. Organometallics 1992, 11, 255.
(e) Murakami, M.; Amii, H.; Ito, Y. Nature 1994, 370, 540. (f)
Murakami, M.; Amii, H.; Shigeto, K.; Ito, Y. J . Am. Chem. Soc. 1996,
118, 8285. (g) Murakami, M.; Takahashi, K.; Amii, H.; Ito, Y. J . Am.
Chem. Soc. 1997, 119, 9307.
(23) The formation of the cobalt and rhodium analogues of 5 in the
reaction of (C5Me5)M(CO)2 (M ) Co, Rh) with biphenylene was recently
reported: Perthuisot, C.; Edelbach, B. L.; Zubris, D. L.; J ones, W. D.
Organometallics 1997, 16, 2016.
(20) The formation and structure of 5 have been previously com-
municated. See: Hou, Z.; Fujita, A.; Yamazaki, H.; Wakatsuki, Y.
Chem. Commun. 1998, 669.

d-Block Transition-Metal Ketyls
Organometallics, Vol. 18, No. 10, 1999 1983
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) of 10
Ir(1)-O(1)
Ir(1)-C(27)
Ir(1)-C(29)
Ir(1)-C(31)
O(2)-C(14)
1.963(6)
2.129(9)
2.130(11)
2.138(9)
1.419(11)
Ir(1)-O(2)
Ir(1)-C(28)
Ir(1)-C(30)
O(1)-C(1)
C(1)-C(14)
1.977(7)
2.154(9)
2.130(11)
1.428(10)
1.567(12)
O(1)-Ir(1)-Cp*(centroid)
O(2)-Ir(1)-Cp*(centroid)
O(1)-Ir(1)-O(2)
138.7
139.4
81.9(3)
113.8(5)
113.0(5)
Ir(1)-O(1)-C(1)
F igu r e 5. ORTEP drawing of 8 with 30% thermal el-
lipsoids. Fluorenone is omitted for clarity.
Ir(1)-O(2)-C(14)
above, an attempt to generate an iridium ketyl species
via deprotonation of a pinacol and subsequent C-C
bond cleavage of the resulting pinacolate was also
made.4,9 The reaction of 1,2-bis(biphenyl-2,2′-diyl)e-
thane-1,2-diol (9) with the iridium(III) imido complex
(C5Me5)IrNtBu in THF gave the iridium(III) carbonyl
complex 5 and the iridium(II) hydride complex 8‚
2(fluorenone) in 30% isolated yield, respectively, as
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) of 8
Ir(1)-Ir(1′)
Ir(1)-C(2)
Ir(1)-C(4)
Ir(1)-H(1)
2.4157(6)
2.215(14)
2.216(16)
1.61
Ir(1)-C(1)
Ir(1)-C(3)
Ir(1)-C(5)
Ir(1)-H(1′)
2.187(11)
2.18(3)
2.222(13)
1.80
Cp*(centroid)-Ir(1)-Ir(1′)
Cp*(centroid)-Ir(1)-H(1)
Cp*(centroid)-Ir(1)-H(1′)
H(1)-Ir(1)-H(1′)
Ir(1)-H(1)-Ir(1′)
1
179
133
137
90.2
89.8
1
confirmed by H NMR and X-ray analyses (Scheme 5).
However, when the reaction was carried out in benzene,
the pinacolate complex 10 was formed as a major
product (73%) together with a small amount of 5 (9%)
and 8 (13%). Purple-brown crystals of 10 suitable for
X-ray analyses were obtained from THF/OEt2/hexane.
An ORTEP drawing and selected bond lengths and
angles for 10 are given in Figure 6 and Table 5,
respectively. Complex 10 represents a rare example of
a structurally characterized iridium pinacolate complex.
The similar reaction of benzopinacol with (C5Me5)IrNt-
Bu in THF yielded benzophenone and several unidenti-
fied species.
The formation of 10 could be viewed as a simple
proton-exchange reaction between the pinacol 9 and the
iridium imido complex (C5Me5)IrNtBu, while the routes
to 5 and 8‚2(fluorenone) are not so straightforward.
Apparently, formation of 5 and 8‚2(fluorenone) requires
the cleavage of the central C-C bond of the pinacol 9.
As in the case of the metathesis reactions described
above, an iridium ketyl species might possibly be formed
as an intermediate,4,9 although details including the
solvent effects are not yet clear. Conversion of the
pinacolate 10 to either 5 or 8‚2(fluorenone) was not
observed in THF at either room or reflux temperature.
The H NMR spectrum of 8 in C6D6 showed a singlet
at δ 1.81 for the C5Me5 groups and a singlet at δ -13.42
for the hydrides.24 Crystals suitable for diffraction
studies were obtained in the form of 8‚2(fluorenone)
from benzene. An X-ray analysis has established that
8 is a dihydride-bridged binuclear iridium(II) complex
which possesses a crystallographic inversion center at
the center of the molecule (Figure 5, Table 4). The length
of the Ir(1)-Ir(1′) bond in 8 (2.4157(6) Å) is much
shorter than those previously reported for the formal
Ir-Ir triple bonds found in the cationic complexes
[(C5Me5)2Ir2(µ-H)3]+[BF4]- (2.458(6) Å),25 [Ir2(µ-H)3H2-
(PPh3)4]+[PF6]- (2.518 Å),26 and [Ir2H5(dppp)2]+[BF4]-
(2.514(1) Å) (dppp ) 1,3-bis(diphenylphosphino)pro-
pane)27 and those for the formal Ir-Ir double bonds
found in [(C5Me5)Ir(µ-CO)]2 (2.554(1) Å)28 and [Ir(µ-
PPh2)(CO)(PPh3)]2 (2.551(1) Å).29 To the best of our
knowledge, the Ir(1)-Ir(1′) bond distance in 8 is the
shortest ever reported for a bonding interaction between
iridium atoms. Although this unusually short Ir-Ir
bond distance and the 18-electron rule may suggest that
8 should possess an Ir-Ir triple bond, an examination
of the molecular orbitals has shown that only a single
metal-metal bond may be formed between the two Ir
atoms, which is similar to the situation of the isoelec-
tronic tetrahydride-bridged Ru complex (C5Me5)Ru(µ-
H)4Ru(C5Me5).30,31
Con clu d in g Rem a r k s
We have demonstrated that the metathesis reaction
of alkali-metal ketyls with d-block transition-metal
chlorides can be a convenient method for the prepara-
tion of the corresponding transition-metal ketyls. How-
ever, the isolability or reactivity of the resulting tran-
sition-metal ketyls depends significantly on both the
nature of the metal centers and the structure of the
ketyl species. The zirconium fluorenone ketyl complex
1 was successfully isolated from the reaction of (C5Me5)2-
ZrCl2 with sodium fluorenone ketyl, while in the case
of benzophenone ketyl further reaction between the
ketyl radical and the C5Me5 ligand took place to give
finally the zirconium bis(alkoxide) complex 2. In con-
trast, the similar reaction of [(C5Me5)Ir(µ-Cl)Cl]2 with
sodium fluorenone ketyl yielded the iridium carbonyl
complex 5, as a result of decarbonylation of fluorenone.
This demonstrates that late transition metals may
Rea ction s of (C5Me5)Ir NtBu w ith Ar om a tic P i-
n a cols. Parallel to the metathesis approaches described
(24) The 1H NMR signals for the starting iridium(III) chloride/
hydride complex [(C5Me5)Ir(µ-H)Cl]2 are at δ 1.51 for C5Me5 and δ
-13.48 for Ir-H, respectively.
(25) Bau, R.; Teller, R. G.; Kirtley, S. W.; Koetzle, T. F. Acc. Chem.
Res. 1979, 12, 176.
(26) (a) Crabtree, R. H. Acc. Chem. Res. 1979, 12, 331. (b) Crabtree,
R. H.; Felkin, H. Morris, G. E.; King, T. J .; Richards, J . A. J .
Organomet. Chem. 1976, 113, C7.
(27) Wang, H. H.; Pignolet, L. H. Inorg. Chem. 1980, 19, 1470.
(28) Ball, R. G.; Graham, W. A. G.; Heinekey, D. M.; Hoyano, J . K.;
McMaster, A. D.; Mattson, B. M.; Michel, S. T. Inorg. Chem. 1990, 29,
2023.
(29) Bellon, P. L.; Benedicenti, C.; Caglio, G.; Manassero, M. J .
Chem. Soc., Chem. Commun. 1973, 946.
(30) Suzuki, H.; Omori, H.; Lee, D. H.; Yoshida, Y.; Fukushima, M.;
Tanaka, M.; Moro-oka, Y. Organometallics 1994, 13, 1129.
(31) Koga, N.; Morokuma, K. J . Mol. Struct. 1993, 300, 181.

1984 Organometallics, Vol. 18, No. 10, 1999
Hou et al.
Sch em e 5
Ta ble 6. Su m m a r y of Cr ysta llogr a p h ic Da ta
1‚THF
2
[5]2
8‚2(fluorenone)
10‚0.5C6H14
formula
fw
cryst syst
space group
a (Å)
b (Å)
c (Å)
C37H46O2ClZr
649.45
C46H50O2Zr
726.13
triclinic
P1h (No. 2)
9.869(2)
11.435(4)
17.399(5)
104.72(3)
92.25(2)
100.04(2)
1862.7(9)
2
C46H46O2Ir2
1015.32
orthorhombic
Pcab (No. 61)
16.476(5)
31.468(8)
14.645(4)
C46H48O2Ir2
1017.33
triclinic
P1h (No. 2)
8.722(4)
10.571(2)
11.778(2)
104.01(2)
96.89(2)
66.67(2)
968.0(5)
1
C39H38O2Ir
730.96
triclinic
P1h (No. 2)
11.204(6)
11.618(9)
12.542(4)
104.57(5)
92.09(4)
83.23(6)
1569(2)
2
monoclinic
P21/c (No. 14)
19.012(7)
9.637(5)
18.277(7)
R (deg)
â (deg)
γ (deg)
V (Å3)
95.55(3)
3333(2)
4
1.29
Mo KR, 0.710 73
+h,+k,(l
6
7593(3)
8
1.78
Z
Dcalcd (g cm-3
)
1.29
1.75
1.55
radiation, λ (Å)
data collcd
Mo KR, 0.710 73
(h,+k,(l
6
Mo KR, 0.710 73
+h,+k,+l
6
3-55
70.131
9831
7404
4071
451
Mo KR, 0.710 73
-h,(k,(l
6
Mo KR, 0.710 73
(h,-k,(l
6
scan speed (deg/min)
2θ range (deg)
3-55
3.486
8612
6661
5165
370
3-50
3-55
3-55
µ (cm-1
)
3.245
68.766
5090
42.691
7802
no. of rflns collcd
no. of unique rflns
no. of rflns with Io > 3σ(Io)
no. of variables
Rint
7143
5648
4438
6671
3183
4010
5386
446
230
364
0.04
0.05
0.03
0.03
R (%)
Rw (%)
6.00
6.70
5.76
6.93
7.38
5.67
7.71
8.65
8.72
7.22
compounds, a very rich chemistry for transition-metal
ketyls can be expected.
Exp er im en ta l Section
Gen er a l Meth od s. All manipulations were carried out
under a dry and oxygen-free argon atmosphere by using
Schlenk techniques or under a nitrogen atmosphere in an
Mbraun glovebox. The argon was purified by passing through
a Dryclean column (4A molecular sieves, Nikka Seiko Co.) and
a Gasclean GC-XR column (Nikka Seiko Co.). The nitrogen in
the glovebox was constantly circulated through a copper/
molecular sieves (4A) catalyst unit. The oxygen and moisture
concentrations in the glovebox atmosphere were monitored by
an O2/H2O Combi-Analyzer (Mbraun) to ensure both were
always below 1 ppm. Samples for spectroscopic studies were
prepared in the glovebox. J . Young valve UV cells and NMR
tubes (Wilmad 528-J Y) were used for measurements. UV-vis
spectra were recorded on a Shimadzu UV-2400PC spectrom-
eter. ESR spectra were obtained on a J EOL J ES FE 3AX
X-band spectrometer, and the g value was calibrated with
F igu r e 6. ORTEP drawing of 10 with 30% thermal
ellipsoids. The lattice solvent is omitted for clarity.
behave very differently toward alkali-metal ketyls than
early transition metals. When [(C5Me5)Ir(µ-H)Cl]2 was
used, the dechlorination (reduction) product [(C5Me5)-
Ir(µ-H)]2 (8) formed selectively, showing that a subtle
change in the environment around the metal center can
greatly alter the behavior of a ketyl species. In view of
the dramatic metal dependence of the reactivity of the
ketyl species and the great variety of transition-metal
1
DPPH (2,2-diphenyl-1-picrylhydrazyl). H NMR spectra were
recorded on a J NM-EX 270 (FT, 270 MHz) spectrometer and
are reported in ppm downfield from tetramethylsilane. El-
emental analyses were performed by the chemical analysis
laboratory of The Institute of Physical and Chemical Research
(RIKEN). Solvents were distilled from sodium/benzophenone
ketyl, degassed by the freeze-thaw method (three times), and
dried over fresh Na chips in the glovebox. (C5Me5)2ZrCl2 and

d-Block Transition-Metal Ketyls
Organometallics, Vol. 18, No. 10, 1999 1985
[(C5Me5)Ir(µ-Cl)Cl]2 were purchased from Aldrich. (C5Me5)IrNt-
sure. Addition of hexane gave 8 as a brown powder (312 mg,
0.475 mmol, 95% yield). The similar reaction of [(C5Me5)Ir(µ-
H)Cl]2 with Na also yielded 8, but a longer reaction time (2
days) was required to complete the reaction. Reaction of [(C5-
Me5)Ir(µ-H)Cl]2 with 2 equiv of sodium fluorenone ketyl in THF
for 3 h yielded, after recrystallization from benzene, brown
crystals of 8‚2(fluorenone) (97% yield), which were suitable for
Bu32 and [(C5Me5)Ir(µ-H)Cl]2 were synthesized according to
33
the literature. Sodium ketyls were synthesized by the reactions
of sodium metal with 1 equiv of ketones in THF9 and were
used for subsequent reactions without isolation.
(C5Me5)2Zr (OC13H8)Cl (1). Addition of a brown THF solu-
tion (10 mL) of sodium fluorenone ketyl (0.44 mmol) to (C5-
Me5)2ZrCl2 (188 mg, 0.44 mmol) in THF (10 mL) gave gradually
a dark brown mixture, which was stirred at room temperature
for 20 h. After removal of NaCl by filtration, the THF solvent
was pumped off to give a dark brown crystalline product, which
after recrystallization from toluene/OEt2 yielded 1 as dark
brown blocks (185 mg, 0.32 mmol, 73% yield). The similar
reaction of (C5Me5)2ZrCl2 with 2 equiv of sodium fluorenone
ketyl also gave 1 as the only isolable zirconium species.
Formation of a bis(ketyl)zirconium species was not observed.
The UV-vis spectrum of 1 is shown in Figure 1. ESR (THF,
22 °C): g ) 2.0032. Anal. Calcd for C33H38OClZr: C, 68.65; H,
6.63. Found: C, 67.75; H, 6.50.
1
diffraction studies. H NMR for 8 (C6D6, 22 °C): δ 1.81 (s, 30
H, C5Me5), -13.42 (s, 2 H, Ir-H). 13C NMR (C6D6, 22 °C): δ
85.8, 11.7. Anal. Calcd for C20H32Ir2: C, 36.57; H, 4.91.
Found: C, 36.42; H, 5.03.
(C5Me5)Ir (O2C26H16) (10). Addition of a benzene solution
(5 mL) of 1,2-bis(biphenyl-2,2′-diyl)ethane-1,2-diol (9; 95 mg,
0.26 mmol) to (C5Me5)IrNtBu (104 mg, 0.26 mmol) in benzene
(5 mL) gave a brown solution, which was stirred at room
temperature for 18 h. Evaporation of the solvent under vacuum
1
gave a crude brown powder. The H NMR spectroscopic study
has shown that this crude product is a mixture of 5, 8, and
10, with the yields being 9%, 13%, and 73%, respectively, as
measured by using anisole as an internal standard. Purple-
brown crystals of 10 suitable for diffraction studies were
obtained by recrystallization of the crude brown product from
THF/OEt2/hexane. 1H NMR for 10 (CD2Cl2, 22 °C): δ 6.95-
7.30 (m, 16 H, O2C26H16), 1.91 (s, 15 H, C5Me5). 13C NMR (CD2-
Cl2, 22 °C): δ 139.6, 127.6, 125.8, 125.5, 118.6, 80.5, 9.7. Anal.
Calcd for C36H31O2Ir: C, 62.86; H, 4.54. Found: C, 63.12; H,
5.08.
X-r a y Cr ysta llogr a p h ic Stu dies. Crystals for X-ray analy-
ses were obtained as described in the preparations. The
crystals were manipulated in the glovebox under a microscope
mounted on the glovebox window and were sealed in thin-
walled glass capillaries. Data collections were performed at
20 °C on a Mac Science MXC3K diffractometer (Mo KR
radiation, λ ) 0.710 73 Å, graphite monochromator, ω-2θ
scan). Lattice constants and orientation matrixes were ob-
tained by least-squares refinement of 22 reflections with 30°
e 2θ e 35°. Three reflections were monitored periodically as
(η5-C5Me5)(η5:η1-C5Me4CH2C(P h )2O)Zr (OCHP h 2) (2). Ad-
dition of a blue THF solution (10 mL) of sodium benzophenone
ketyl (0.44 mmol) to (C5Me5)2ZrCl2 (94 mg, 0.22 mmol) in THF
(10 mL) gave gradually a purple-red mixture whose color
eventually faded when being stirred at room temperature for
16 h. After removal of NaCl by filtration, the THF solvent was
pumped off to give a yellow residue, which was then dissolved
in toluene and concentrated. Addition of OEt2 gave 2 as pale
1
yellow blocks (85 mg, 0.12 mmol, 54% yield). H NMR (CD2-
Cl2, 22 °C): δ 7.61 (d, J ) 8.41 Hz, 2 H, Ph), 7.21-7.47 (m, 14
H, Ph), 7.10 (t, J ) 7.26 Hz, 1 H, Ph), 6.85 (t, J ) 7.26 Hz, 1
H, Ph), 6.65 (t, J ) 7.59 Hz, 2 H, Ph), 6.22 (s, 1 H, OCHPh2),
3.75 (d, J ) 14 Hz, 1 H, C5Me4CH2), 3.64 (d, J ) 14 Hz, 1 H,
C5Me4CH2), 2.09 (s, 3 H, C5Me4CH2), 2.02 (s, 3 H, C5Me4CH2),
1.36 (s, 3 H, C5Me4CH2), 1.28 (s, 3 H, C5Me4CH2), 1.94 (s, 15
H, C5Me5). 13C NMR (CD2Cl2, 22 °C): δ 154.1, 154.0, 147.7,
147.3, 136.1, 128.0, 127.9, 127.8, 127.7, 127.6, 126.8, 126.7,
126.1, 125.9, 125.4, 125.2, 122.0, 120.6, 119.6, 117.1, 114.7,
106.6, 82.4, 39.4, 12.0, 11.7, 11.1, 10.9. Anal. Calcd for
C46H50O2Zr: C, 76.09; H, 6.94. Found: C, 75.81; H, 6.85.
(C5Me5)Ir (CO)(C12H8) (5). A brown THF solution (10 mL)
of sodium fluorenone ketyl (0.44 mmol) was added to [(C5Me5)-
Ir(µ-Cl)Cl]2 (87 mg, 0.11 mmol) in THF (10 mL). The resulting
brown mixture was stirred at room temperature for 3 h. After
removal of NaCl by filtration, the THF solvent was pumped
off to give a light brown residue, which was then dissolved in
toluene and concentrated. Addition of OEt2 gave 5 as colorless
blocks (77 mg, 0.15 mmol, 69% yield). Fluorenone was con-
a
check for crystal decomposition or movement, and no
significant decay was observed. All data were corrected for
X-ray absorption effects and polarization effects. The observed
systematic absences were consistent with the space groups
given in Table 6. Structures were solved by direct methods
using SIR92 in the Crystan-GM software package. Hydrogen
atoms were either located from the difference Fourier maps
or placed at the calculated positions. Refinements against |F|
were performed anisotropically for non-hydrogen atoms by the
block-diagonal least-squares method. Hydrogen atoms were
not refined. The function minimized in the least-squares
refinements was ∑(|Fo| - |Fc|)2. Neutral atomic scattering
factors were taken from ref 34. The residual electron densities
were of no chemical significance. Crystal data, data collection,
and processing parameters are given in Table 6.
1
firmed in the mother liquor by H NMR comparison with an
authentic sample. The similar reaction of [(C5Me5)Ir(µ-Cl)Cl]2
with 2 equiv of sodium fluorenone dianion gave 5 in 68%
isolated yield, without the formation of fluorenone being
observed.20 1H NMR (CD2Cl2, 22 °C): δ 7.47 (d of d, J 1 ) 7.26
Hz, J 2 ) 1.32 Hz, 2 H, C12H8), 7.46 (d of d, J 1 ) 7.26 Hz, J 2
)
1.32 Hz, 2 H, C12H8), 7.06 (d of t, J 1 ) 7.26 Hz, J 2 ) 1.32 Hz,
2 H, C12H8), 6.90 (d of t, J 1 ) 7.26 Hz, J 2 ) 1.32 Hz, 2 H, C12H8),
1.87 (s, 15 H, C5Me5). 13C NMR (CD2Cl2, 22 °C): δ 169.3, 154.5,
141.1, 137.2, 125.8, 123.6, 120.3, 99.1, 8.8. IR (in THF): ν-
(CO) 1996.9 cm-1. Anal. Calcd for C23H23OIr: C, 54.42; H, 4.57.
Found: C, 54.24, H, 4.49.
[(C5Me5)Ir (µ-H)]2 (8). A blue THF solution (10 mL) of [(C5-
Me5)Ir(µ-H)Cl]2 (364 mg, 0.5 mmol) was added to freshly cut
K chips (39 mg, 1.0 mmol). The mixture was stirred at room
temperature for 6 h, during which time the color changed
gradually from blue to brown. After removal of KCl by
filtration, the solution was concentrated under reduced pres-
Ack n ow led gm en t. This work was partially sup-
ported by a grant-in-aid from the Ministry of Education,
Science, Sports and Culture of J apan. T.K. is a Special
Postdoctoral Researcher under the Basic Science Pro-
gram of The Institute of Physical and Chemical Re-
search (RIKEN).
Su p p or tin g In for m a tion Ava ila ble: Listings of atomic
coordinates, thermal parameters, and bond distances and
angles for 1, 2, 5, 8, and 10. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM981013C
(32) Glueck, D. S.; Wu, J .; Hollander, F. J .; Bergman, R. G. J . Am.
Chem. Soc. 1991, 113, 2041.
(33) Gill, D. S.; Maitlis, P. M. J . Organomet. Chem. 1975, 87, 359.
(34) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Kynoch: Birmingham, England, 1974.