N/O- and C-bound (enolato)palladium complexes with hydrotris(pyrazoly)borato ligands (TpR: R = iPr2, Me2) obtained via dehydrative condensation between the hydroxo complexes TpRPd(Py)OH and active methylene compounds: Factors determining the isomer distribution and dimerization of cyano compounds

Article abstract of DOI:10.1021/om010448o

Reaction of a hydroxopalladium complex bearing the Tp^iPr₂ ligand, (Tp^iPri₂)(py)Pd-OH (1^iPr₂), with active methylene compounds, X-CH₂-Y 2 [dicyanomethane (2a), methyl cyanoacetate (2b), benzoylacetonitrile (2c)], resulted in dehydrative condensation to afford the N/O-bound enolates, (Tp^iPr₂)(py)Pd-X-CH-Y 3^iPr₂a-c. When the hydroxo complex 1^Mei₂ with the less bulky Tp^Me₂ ligand was allowed to react with 2 at 0°C, similar N/O-bound enolato complexes, (Tp^Me₂)(py)Pd-X-CH-Y (3^Mei₂a-c), were obtained as kinetic products, which were gradually converted to the more stable C-bound enolato complexes (Tp^Me₂)(py)Pd-CHXY (4^Me₂a-c) upon warming to 50°C. X-ray crystallography of the N/O- and C-bound enolates reveals that (1) the Pd center adopts the square-planar or square-pyramidal geometry, (2) the structure of the C-bound isomer is consistent with the canonical structure with the localized bonding scheme, and (3) in the N/O-bound isomers the negative charge is delocalized over the X-CH-Y linkage to form the zwitterionic structure. The N-bound enolato complexes 3a,b obtained from cyano compounds further reacted with the cyano compounds to give the 1:2 condensates: i.e., the 2-cyanoethenylamido complexes (Tp^R)(py)Pd-NH-C(CH₂Y)=CCN-(Y) (6), whereas the C-bound enolates 4^Me₂a,b showed no indication of the dimerization. Thus, the present study reveals that the reactivity of transition-metal enolates is dependent on their structures.

Full text of DOI:10.1021/om010448o

Organometallics 2001, 20, 4049-4060
4049
N/O- a n d C-Bou n d (En ola to)p a lla d iu m Com p lexes w ith
Hyd r otr is(p yr a zolyl)bor a to Liga n d s (Tp R: R ) iP r 2, Me2)
Obta in ed via Deh yd r a tive Con d en sa tion betw een th e
Hyd r oxo Com p lexes Tp RP d (P y)OH a n d Active Meth ylen e
Com p ou n d s: F a ctor s Deter m in in g th e Isom er
Distr ibu tion a n d Dim er iza tion of Cya n o Com p ou n d s
Masato Kujime, Shiro Hikichi, and Munetaka Akita*
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku,
Yokohama 226-8503, J apan
Received May 29, 2001
iPr2
iP r 2
Reaction of a hydroxopalladium complex bearing the TpiPr ligand, (Tp )(py)Pd-OH (1 ),
with active methylene compounds, X-CH2-Y 2 [dicyanomethane (2a ), methyl cyanoacetate
(2b), benzoylacetonitrile (2c)], resulted in dehydrative condensation to afford the N/O-bound
2
enolates, (TpiPr )(py)Pd-X-CH-Y 3 a -c. When the hydroxo complex 1
with the less
iP r 2
Me2
2
bulky TpMe ligand was allowed to react with 2 at 0 °C, similar N/O-bound enolato complexes,
2
(TpMe )(py)Pd-X-CH-Y (3 a -c), were obtained as kinetic products, which were gradually
Me2
2
converted to the more stable C-bound enolato complexes (TpMe )(py)Pd-CHXY (4 a -c)
Me2
2
upon warming to 50 °C. X-ray crystallography of the N/O- and C-bound enolates reveals
that (1) the Pd center adopts the square-planar or square-pyramidal geometry, (2) the
structure of the C-bound isomer is consistent with the canonical structure with the localized
bonding scheme, and (3) in the N/O-bound isomers the negative charge is delocalized over
the X-CH-Y linkage to form the zwitterionic structure. The N-bound enolato complexes
3a ,b obtained from cyano compounds further reacted with the cyano compounds to give the
1:2 condensates: i.e., the 2-cyanoethenylamido complexes (TpR)(py)Pd-NH-C(CH2Y)dCCN-
(Y) (6), whereas the C-bound enolates 4Me a ,b showed no indication of the dimerization.
2
Thus, the present study reveals that the reactivity of transition-metal enolates is dependent
on their structures.
In tr od u ction
drocarbons and aromatic halides have a chance to be
coupled with enolates. In particular, the recent reports
by Murahashi on Ru-catalyzed aldol and Michael reac-
tions have attracted much attention, because the dehy-
drative condensation was effected via C-H activation
under neutral reaction conditions.3,4 It was also dem-
onstrated that reactant selectivity is not dependent on
the acidity of the C-H moiety to be activated but on
the kind of the functional groups included in the
molecule.
Transition-metal enolates1 are expected to display
chemical reactivity which has not been realized by main-
group-metal enolates.2 For example, unsaturated hy-
(1) (a) Heathcock, C. H. In Comprehensive Organic Synthesis; Trost,
B. M., Ed.; Pergamon: Oxford, U.K., 1991; Vol. 2, Chapter 1.9. (b)
Burkhardt, E. R.; Doney, J . J .; Slough, G. A.; Stack, J . M.; Heathcock,
C. H.; Bergman, R. G. Pure Appl. Chem. 1988, 60, 1. (c) Davies, S. G.
Pure Appl. Chem. 1988, 60, 13. (d) Brunner, H. Angew. Chem., Int.
Ed. 1999, 38, 1194. (e) Slough, G. A.; Bergman, R. G.; Heathcock, C.
H. J . Am. Chem. Soc. 1989, 111, 938. (f) Burkhardt, E. R.; Bergman,
R. G.; Heathcock, C. H. Organometallics 1990, 9, 30. (g) Stack, J . G.;
Doney, J . J .; Bergman, R. G.; Heathcock, C. H. Organometallics 1990,
9, 453. (h) Hartwig, J . F.; Andersen, R. A.; Bergman, R. G. Organo-
metallics 1991, 10, 3326. (i) Hartwig, J . F.; Bergman, R. G.; Andersen,
R. A. Organometallics 1991, 10, 3344. (j) Balegroune, F.; Grand-jean,
D.; Lakkis, D.; Matt, D. J . Chem. Soc., Chem. Commun. 1992, 1084.
(k) Veya, P.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Organometallics
1993, 12, 4892. (l) Veya, P.; Floriani, C.; Chiesi-Villa, A.; Rizzori, C.
Organometallics 1993, 12, 4899. (m) Hamann, B. C.; Hartwig, J . F. J .
Am. Chem. Soc. 1997, 119, 12382. (n) Fujii, A.; Hagiwara, E.; Sodeoka,
M. J . Am. Chem. Soc. 1999, 121, 5450. (o) Ruiz, J .; Rodr´ıguez, V.;
Cutillas, N.; Pardo, M.; Pe´rez, J .; Lo´pez, G.; Chaloner, P.; Hitchcock,
P. B. Organometallics 2001, 20, 1973. (p) Vicente, J .; Arcas, A.;
Ferna´ndez-Herna´ndez, J . M.; Bautista, D. Organometallics 2001, 20,
2767. (q) Culkin, D. A.; Hartwig, J . F. J . Am. Chem. Soc. 2001, 123,
5816.
As an extension of the chemistry of TpRM complexes
(TpR ) hydrotris(pyrazolyl)borato ligands)5 to organo-
metallic systems6,7 (e.g. highly coordinatively unsatur-
(3) (a) Naota, T.; Taki, H.; Mizuno, M.; Murahashi, S.-I. J . Am.
Chem. Soc. 1989, 111, 5954. (b) Murahashi, S.-I.; Naota, T.; Taki, H.;
Mizuno, M.; Takaya, H.; Komiya, S.; Mizuho, Y.; Oyasato, N.; Hiraoka,
M.; Hirano, M.; Fukuoka, A. J . Am. Chem. Soc. 1995, 117, 12436. (c)
Takaya, H.; Naota, T.; Murahashi, S.-I. J . Am. Chem. Soc. 1998, 120,
4244. (d) Naota, T.; Tannna, A.; Murahashi, S.-I. J . Am. Chem. Soc.
2000, 122, 2960. (e) Murahashi, S.-I.; Take, K.; Naota, T.; Takaya, H.
Synlett 2000, 1016. (f) Murahashi, S.-I.; Naota, T. Bull. Chem. Soc.
J pn. 1996, 69, 1805. (g) Murahashi, S.; Takaya, H. Acc. Chem. Res.
2000, 33, 225.
(4) (a) Mizuho, Y.; Kasuga, N.; Komiya, S. Chem. Lett. 1991, 2127.
(b) Hirano, M.; Ito, Y.; Hirai, M.; Fukuoka, A.; Komiya, S. Chem. Lett.
1993, 2057. (c) Hirano, M.; Hirai, M.; Ito, Y.; Tsurumaki, T.; Baba, A.;
Fukuoka, A.; Komiya, S. J . Organomet. Chem. 1998, 569, 3. (d) Hirano,
M.; Takenaka, A.; Mizuho, Y.; Hiraoka, M.; Komiya, S. J . Chem. Soc.,
Dalton Trans. 1999, 3209.
(2) (a) Comprehensive Organic Synthesis; Fleming, I., Trost, B. M.,
Eds.; Pergamon: Oxford, U.K., 1991; Vols. 2 and 3. (b) Seebach, D.
Angew. Chem., Int. Ed. Engl. 1988, 27, 1624. (c) Smith, M. B.; March,
J . Advanced Organic Chemistry, 5th ed.; Wiley-Interscience: New
York, 2001.
10.1021/om010448o CCC: $20.00 © 2001 American Chemical Society
Publication on Web 08/16/2001

4050 Organometallics, Vol. 20, No. 19, 2001
Kujime et al.
ated hydrocarbyl complexes, TpRM-R′, M ) Fe (14e),
Co (15e)),6b,g,o we examined the synthesis and reactivity
of (enolato)palladium complexes as an example of func-
tionalized alkyl complexes. Transition-metal enolates
studied extensively for the last two decades1,3,4 have
been prepared mainly by three methods: (1) dehydra-
tive condensation between a transition-metal hydroxide
and carbonyl compounds, (2) a metathesis reaction
between a transition-metal halide and main-group-
metal enolates, and (3) oxidative addition of a â-oxoalkyl
halide to a low-valent metal species.8 Because our first
attempts to synthesize ketone enolates, (TpR)(py)Pd-
CH2(CdO)R′ or -OC(R′)dCH2, by reaction of (TpR)(py)-
Pd-Cl (or [(TpR)(py)2Pd]+) with various enolate anions
(method 2) were unsuccessful, the substrate was changed
to active methylene compounds. Although the metath-
esis reaction also has not met with success, dehydrative
condensation with the hydroxo complex (TpR)(py)Pd-
OH7a and active methylene compounds CH2XY (X, Y)
CN, COR) (method 1) successfully produced the expected
enolato complexes. Herein we disclose the synthesis,
characterization, isomer distribution, and reactivity of
N/O- and C-bound (enolato)palladium complexes bear-
ing TpR ligands, (TpR)(py)Pd-X-CH-Y and (TpR)(py)-
Pd-CHXY.
Sch em e 1
(5) Abbreviations used in this paper: TpR, hydrotris(pyrazolyl)borato
Me2
ligands; TpiPr , 3,5-diisopropylpyrazolyl derivative; Tp , 3,5-dimeth-
2
ylpyrazolyl derivative; pzR, pyrazolyl group in TpR; 4-pz-H, hydrogen
atom at the 4-position of pzR; 3-, 4-, and 5-pz, pz ring carbon atoms at
3-, 4-, and 5-positions, respectively. The superscript in the compound
number denotes the kind of TpR ligand.
(6) Our recent work based on the TpR ligand: (a) Akita, M.; Ohta,
K.; Takahashi, Y.; Hikichi, S.; Moro-oka, Y. Organometallics 1997, 16,
4121. (b) Akita, M.; Shirasawa, N.; Hikichi, S.; Moro-oka, Y. Chem.
Commun. 1998, 973. (c) Hikichi, S.; Komatsuzaki, H.; Akita, M.; Moro-
oka, Y. J . Am. Chem. Soc. 1998, 120, 4699. (d) Hikichi, S.; Yoshizawa,
M.; Sasakura, Y.; Akita, M.; Moro-oka, Y. J . Am. Chem. Soc. 1998,
120, 10567. (e) Akita, M.; Miyaji, T.; Hikichi, S.; Moro-oka, Y. Chem.
Commun. 1998, 1005. (f) Takahashi, Y.; Akita, M.; Hikichi, S.; Moro-
oka, Y. Organometallics 1998, 17, 4884. (g) Shirasawa, N.; Akita, M.;
Hikichi, S.; Moro-oka, Y. Chem. Commun. 1999, 417. (h) Takahashi,
Y.; Hikichi, S.; Akita, M.; Moro-oka, Y. Chem. Commun. 1999, 1491.
(i) Takahashi, Y.; Hikichi, S.; Akita, M.; Moro-oka, Y. Organometallics
1999, 18, 2571. (j) Ohta, K.; Hashimoto, M.; Takahashi, Y.; Hikichi,
S.; Akita, M.; Moro-oka, Y. Organometallics 1999, 18, 3234. (k)
Takahashi, Y.; Hashimoto, M.; Hikichi, S.; Akita, M.; Moro-oka, Y.
Angew. Chem., Int. Ed. 1999, 38, 3074. (l) Akita, M.; Miyaji, T.; Hikichi,
S.; Moro-oka, Y. Chem. Lett. 1999, 813. (m) Hikichi, S.; Yoshizawa,
M.; Sasakura, Y.; Komatsuzaki, H.; Akita, M.; Moro-oka, Y. Chem. Lett.
1999, 979. (n) Akita, M.; Hashimoto, M.; Hikichi, S.; Moro-oka, Y.
Organometallics 2000, 19, 3744. (o) Shirasawa, N.; Nguyet, T. T.;
Hikichi, S.; Moro-oka, Y.; Akita, M. Organometallics 2001, 20, 3582.
Reviews: (p) Akita, M.; Hikichi, S.; Moro-oka, Y. J . Synth. Org. Chem.
1999, 57, 619. (q) Hikichi, S.; Akita M., Moro-oka, Y. Coord. Chem.
Rev. 2000, 198, 61.
Resu lts
P r ep a r a tion of Tp iP r P d (p y)-En ola te Com p lexes
2
via Deh yd r a tive Con d en sa tion of Tp iP r P d (p y)-
2
OH (1iP r ) w ith Active Meth ylen e Com p ou n d s 2 To
2
Give N/O-Bou n d En ola to Com p lexes. When active
methylene compounds 2 were treated with the hydroxo-
palladium complex bearing the TpiPr ligand 1
in the
iP r 2
2
presence of Na2SO4, dehydrative condensation pro-
ceeded to give yellow to orange complexes 3iP r and 5
iP r 2
2
as the sole products (Scheme 1).9
The products 3iP r a -c obtained from cyano com-
2
pounds show the νCN and νCO vibrations, which are
shifted to lower energies compared to those of the
starting compounds (νCN, 3iP r a -c < 2200 cm < 2a -
-1
2
(7) For TpRM(L)-OH complexes, see the following references. M )
Pd: (a) Akita, M.; Miyaji, T.; Muroga, N.; Mock-Knoblauch, C.; Adam,
W.; Hikichi, S.; Moro-oka, Y. Inorg. Chem. 2000, 39, 2096. M ) V: (b)
Kosugi, M.; Hikichi, S.; Akita, M.; Moro-oka, Y. Inorg. Chem. 1999,
38, 2567. (c) Kosugi, M.; Hikichi, S.; Akita, M.; Moro-oka, Y. J . Chem.
Soc., Dalton Trans. 1999, 1369. M ) Mn: (d) Komatsuzaki, H.;
Ichikawa, S.; Hikichi, S.; Akita, M.; Moro-oka, Inorg. Chem. 1998, 37,
3652. (e) Komatsuzaki, H.; Sakamoto, N.; Satoh, M.; Hikichi, S.; Akita,
M.; Moro-oka, Y. Inorg. Chem. 1998, 37, 6554. (f) Kitajima, N.; Singh,
U. P.; Amagai, H.; Osawa, M.; Moro-oka, Y. J . Am. Chem. Soc. 1991,
113, 7757. M ) Fe: (g) Ogihara, T.; Hikichi, S.; Fujisawa, K.; Kitajima,
N.; Akita, M.; Moro-oka, Y. Inorg. Chem., 1997, 36, 4539. M ) Co, Ni:
(h) Hikichi, S.; Yoshizawa, M.; Sasakura, Y.; Akita, M.; Moro-oka, Y.
J . Am. Chem. Soc. 1998, 120, 10567. (i) Kitajima, N.; Hikichi, S.;
Tanaka, M.; Moro-oka, Y. J . Am. Chem. Soc. 1993, 115, 5496; Cu: (j)
Kitajima, N.; Koda, T.; Hashimoto, S.; Kitagawa, T.; Moro-oka, Y. J .
Am. Chem. Soc. 1991, 113, 5664. M ) Ru: (k) Takahashi, Y.; Akita,
M.; Hikichi, S.; Moro-oka, Y. Inorg. Chem. 1998, 37, 3186. (l) Akita,
M.; Takahashi, Y.; Hikichi, S.; Moro-oka, Y. Inorg. Chem. 2001, 40,
169. For other metal complexes see also: (m) Parkin, G. Adv. Inorg.
Chem. 1995, 42, 291.
-1
c; νCO, 3iP r b,c < 1700 cm < 2b,c) (Table 1). When
2
1
the following aspects ((1) the larger J CH values for the
CH-CN methine carbon atom (>170 Hz) indicative of
sp2 hybridization and (2) the presence of the pyridine
ligand) are taken into account,10 it is suggested that
square-planar N/O-bound enolates (rather than C-bound
enolates) are formed via the dehydrative reaction. It
should be noted that (1) one of the two δC(CN) signals
observed for 3iP r a (δC 143.5) is shifted to lower field
2
than the other signal (δC 125.2), which appears in the
normal range of CN signals, and (2) the δC(CN) signals
(9) When an acetone solution of 1iP r was refluxed for several hours,
2
a mixture of products containing (TpiPr )(py)Pd-CH2C(dO)CH3 was
2
obtained but a pure sample could not be isolated from it.
(10) Pretsch, P. D.; Seible, J .; Simon, W.; Clerc, T. Strukturaufkla¨-
lung organischer Verbindungen, 2nd ed.; Springer: Berlin, 1981.
(8) For Pd complexes, see refs 1l,o and references therein.

(Enolato)palladium Complexes with Borato Ligands
Organometallics, Vol. 20, No. 19, 2001 4051
Ta ble 1. Selected Sp ectr oscop ic Da ta for 3-5
b-d
IR/cm-1 a
1H NMR/δH
c-e
13C NMR/δC
compd
νBH
others
4-pz-H
CH
others
enolate
3iP r
3iP r
3iP r
3iP r
a
b
c
d
e
(2545)f
2485
2189g
2110g
1607h
2139g
1646k
1606h
2185g
1608h
5.72
5.83
5.96
5.72
5.84
5.97
5.74
5.85
5.95
5.72
5.82
6.02
5.75 (1H)
5.82 (2H)
5.69
5.81
5.85
1.96
6.3 (d, J ) 180, CH), 125.2 (s, CN), 143.5 (s, Pd-NC)
2
i,j
2
2
2
2
2533
2482
2.92
2.68
3.32
3.37
34.3, 34.4 (d × 2, J ) 173, CH), 49.5, 49.8 (q × 2, J ) 144, OMe),
139.9, 140.5 (s × 2, CN), 173.2. 173.9 (s × 2, CdO)
(2545)f
2486
4.29
4.85
51.0 (d, J ) 169, CH), 136.2 (s, CN), 188.7 (s, CdO)
2479
2545
1617k
0.62
0.65
27.9 (q, J ) 125, CMe2), 32.2 (s, CMe2),
47.5, 50.3 (d × 2, J ) 126, CH2), 104.0 (d, J ) 158, CH),
188.5, 197.4 (t × 2, J ) 5, CdO)
5iP r
3Me
1599k
4.79
2.02
1.83
3.56
25.0 (q, J ) 127, COMe), 52.2 (q, J ) 146, OMe),
84.7 (d, J ) 162, CH), 171.0, 186.6 (s × 2, CdO)
6.4 (d, J ) 182, CH), 124.2 (s, CH), 144.0 (s, Pd-NC)
i
2188g
2138g
2110g
1608h
2230g
2215g
1609h
2170g
1639k
1607h
2206g
1699k
1608h
2191g
1608h
2
a
2522
2484
4Me
3Me
4Me
3Me
4Me
3Me
a
b
b
c
c
d
2468
2516
2473
2512
2511
2474
5.65
5.86
5.93
5.69
5.79
5.84
5.67
5.87
5.89
5.69
5.81
5.86
5.11
5.58
5.97
5.72 (2H)
5.94 (1H)
2.72
-15.9 (d, J ) 151, Pd-CH), 118.6, 120.5 (d × 2, J ) 8, CN)
2
2
2
2
2
2
i,j
2.94
2.71
3.32
3.35
38.7, 39.3 (d × 2, J ) 171, CH), 54.0, 54.4 (q x 2, J ) 144, OMe),
145.4, 146.5 (s × 2, CN), 177.7, 178.3 (s × 2, CdO)
3.17
4.30
4.19
5.19
3.11
5.2 (d, J ) 147, Pd-CH), 51.5 (q, J ) 146, OMe),
123.9 (s, CN), 172.5 (d, J ) 7 Hz, CdO)
l
50.0 (d, J ) 169, CH), 140.3 (d, J ) 7, CN), 186.7 (s, CdO)
2205g
1676k
1609h
1611k
14.1 (d, J ) 143, Pd-CH), 124.6 (d, J ) 6, CN),
195.8 (d, J ) 4, CdO)
0.68
28.1, 28.3 (q, J ) 130, CMe2), 32.3 (s, CMe2),
47.6, 50.2 (t × 2, J ) 125, CH2), 103.8 (d, J ) 156, CH),
188.9, 197.6 (s × 2, CdO)
a
b
Observed as KBr pellets. Observed at 400 MHz in CDCl3 at room temperature unless otherwise stated. c Multiplicities and coupling
d
constants (in Hz) are shown in parentheses. Signals are singlets unless otherwise stated. Other signals are reported in the Experimental
Section. e Observed at 100 MHz in CDCl3 at room temperature unless otherwise stated. f The weak signals were occasionally observed,
g
h
i
j
depending on the conditions of the samples (see text.). νCN
stereoisomers (see text). νCO
.
νpy. NMR spectra were observed at -50 °C in CD2Cl2. A mixture of
k
l
.
NMR spectra were observed at -80 °C in CD2Cl2.
10
for 3iP r b,c appear in the former region. These obser-
vations, similar to those of the N-bound Ru-enolato
complexes reported by Murahashi3 and Komiya,4 lead
N-bound enolato complexes 3iP r a -c. In contrast to the
2
2
hitherto discussed reactions, methyl acetoacetate (2e)
produces the chelate product 5iP r e, resulting from
2
to the assignment of 3iP r a -c as the N-bound enolates.
2
elimination of the pyridine ligand, but no reaction is
observed with dimethyl malonate (2f). Formation of
similar chelated products was recently reported for the
(κ2-o-C6H4CH2NMe2)Pd system having two cis coordina-
tion sites.10
The N-coordination of 3iP r c derived from benzoylaceto-
2
nitrile 2c was confirmed by X-ray crystallography
(Figure 1 and Table 2), and the spectroscopic features
of 3iP r b are close to those of the N-bound Tp
Me2
2
derivative 3Me b, which was also characterized crystal-
2
Thus, the reaction of 1iP r with active methylene
2
lographically (see below). Structural features will be
discussed later. Thus, the enolato complexes derived
from cyano compounds turn out to be square-planar
N-bound species (3iP r a -c). Lo´pez and co-workers re-
ported the closely related dehydrative condensation
between the dianionic bis(µ-hydroxo)dipalladium com-
plex [(C6F5)4Pd2(µ-OH)2]2- and 2a to give the dinuclear
bis(µ-malononitrilate) complex [(C6F5)4Pd2[µ-CH(CN)-
compounds containing CN and CO functional groups
produces the N/O-bound enolato complexes 3iP r and no
2
indication for formation of the C-bound enolato complex
4iP r has been observed at all. The complex 3iP r
b
2
2
exhibits dynamic behavior which is frozen below -50
°C. Because the other complexes 3iP r a ,c,d are not
2
fluxional, the dynamic behavior should result from
stereochemical nonrigidity of the ester moiety, i.e.,
interconversion between the s-trans and s-cis isomers,
as shown in Scheme 2. Similar isomerization was noted
for the Ru enolates obtained from cyanoacetate esters
as reported by Murahashi.3e
CN]2]2- 11
1,3-Diketones also undergo dehydration with 1iP r
.
2
.
Dimedone (2d ) affords the O-bound enolato complex
3iP r e, which is characterized by its spectroscopic fea-
tures ((1) two kinds of δC(CO) signals and (2) the
presence of the sp2-hybridized methine carbon signal at
δC 104.0) similar to those of the above-mentioned
Effect of th e Su bstitu en ts on th e Tp R Liga n d :
Deh yd r a tive Con d en sa tion of Tp Me P d (p y)-OH
2
(1Me ) w ith Active Meth ylen e Com p ou n d s 2 To
2
Lea d to Sequ en tia l F or m a tion of N/O-Bou n d En o-
(11) Ruiz, J .; Rodriguez, V.; Lo´pez, G.; Casabo´, J .; Molins, E.;
Miravitlles, C. Organometallics 1999, 18, 1177.
la to Com p lexes 3Me a n d C-Bou n d En ola to Com -
2

4052 Organometallics, Vol. 20, No. 19, 2001
Kujime et al.
iP r 2
Me2
Me2
F igu r e 1. Molecular structures of the (enolato)palladium complexes 3Me b, 3 c, 3 d , and 4 c drawn (with displacement
2
ellipsoid amplitudes) at the 30% probability level.
Ta ble 2. Str u ctu r a l P a r a m eter s for th e Cor e P a r ts of th e Tp RP d Com p lexes 3, 4, a n d 6a
complex, X
3iP r c, N1
3Me b, N1
3Me d , O1
4Me c, C2
6iP r a , N3
6iP r b, N2
2
2
2
2
2
2
Pd1-N11
2.019(7)
1.987(8)
2.717(7)
2.051(7)
2.00(1)
85.7(3)
82.7(2)
176.7(3)
94.4(3)
89.2(3)
91.3(3)
179.6(3)
95.8(2)
90.4(3)
88.6(3)
2.006(2)
2.017(3)
2.794(2)
2.021(2)
2.016(3)
86.7(1)
86.46(7)
178.1(1)
93.1(1)
82.92(7)
91.7(1)
179.5(1)
92.31(8)
97.50(9)
88.5(1)
2.004(4)
2.007(5)
3.388(6)
2.021(5)
1.990(4)
88.1(2)
2.009(3)
2.068(3)
3.003(3)
2.039(3)
2.102(4)
86.3(1)
2.017(3)
2.012(4)
3.484(4)
2.038(3)
2.033(4)
85.5(1)
2.005(6)
2.023(7)
3.494(6)
2.046(7)
2.015(7)
86.9(2)
Pd1-N21
Pd1-N31
Pd1-N41
Pd1-X
N11-Pd1-N21
N11-Pd1-N31
N11-Pd1-N41
N11-Pd1-X
N21-Pd1-N31
N21-Pd1-N41
N21-Pd1-X
N31-Pd1-N41
N31-Pd1-X
N41-Pd1-X
176.3(2)
94.9(2)
177.6(1)
89.9(1)
175.1(1)
94.9(1)
176.8(3)
91.5(3)
93.6(2)
172.6(2)
92.3(1)
172.5(1)
90.4(1)
179.5(2)
90.4(3)
178.2(2)
83.9(2)
91.6(1)
89.2(1)
91.2(3)
a
Interatomic distances in Å and bond angles in deg.
p lexes 4Me . To examine the effect of the substituents
enolato complexes 3Me a -d , whereas the condensation
at ambient temperature followed by recrystallization
from warm solvents produced the C-bound enolato
2
2
attached to the pyrazolyl (pz) rings in the TpR ligand,
the TpMe derivative 1Me was subjected to dehydrative
2
2
complexes 4Me a -c, which were not observed for the
2
condensation. The reaction proceeded in a manner
similar to that for the TpiPr derivative 1iP r described
above, but two different types of products were obtained,
depending on the reaction conditions (Scheme 3). The
condensation carried out at 0 °C afforded the N/O-bound
TpiPr system. In addition, when CDCl3 solutions of
2
2
2
isolated samples of 3Me a -c were heated at 50 °C,
2
isomerization occurred over a period of 2 h to give the
C-bound enolate 4Me a -c. These observations reveal
2

(Enolato)palladium Complexes with Borato Ligands
Organometallics, Vol. 20, No. 19, 2001 4053
Ta ble 3. Selected Sp ectr oscop ic Da ta for 6
b-d
IR/cm-1 a
others
1H NMR/δH
c-e
compd BH
4-pz-H
others
13C NMR/δC
6iP r
a
2498 3268,i 2258,f
2201,f 2177,f
1609g
5.72 2.51, 2.64
47.9 (s, dC(CN)2), 53.4 (t. J ) 177, CH2),
112.9 (t, J ) 15, CH2CN), 117.4, 118.3 (s × 2, dC(CN)2),
170.3 (s, N-Cd)
42.9 (t. J ) 132, CH2), 50.2, 51.3 (q × 2, J ) 147 Hz, OMe),
68.4 (s, )CCN), 122.0 (s, CN), 168.3 (s, N-Cd),
171.1, 173.3 (s × 2, CdO)
2
5.91
6.01
(2H, AB q, J ) 16, CH2),
5.72 (1H, br, NH)
6iP r
b
2482 3221,i 2184,f
1743,h 1651,h
1609g
5.69 2.55, 2.72
2
5.82
5.98
(2H, AB q, J ) 17, CH2),
3.27, 3.65 (3H × 2, s × 2, OMe),
8.89 (1H, br, NH)
6Me
a
2485 3275,i 2257,f
2199,f 2173,f
1610g
5.70 2.89, 2.98
23.9 (t, J ) 137, CH2), 47.7 (s, dC(CN)2),
113.3 (t, J ) 11, CH2CN), 117.6, 118.5 (s × 2, dC(CN)2),
170.3 (s, N-Cd)
2
5.84
5.95
(2H, AB q, J ) 16, CH2),
5.76 (1H, br, NH)
a
b
Observed as KBr pellets. Observed at 400 MHz in CDCl3 at room temperature unless otherwise stated. c Multiplicities and coupling
d
constants (in Hz) are shown in parentheses. Signals are singlets unless otherwise stated. Other signals are reported in the Experimental
Section. e Observed at 100 MHz in CDCl3 at room temperature unless otherwise stated. νCN
.
νpy
.
νCO. νNH.
f
g
h
i
Sch em e 2
Sch em e 4
Sch em e 3
The N/O-bound enolates 3Me a -d are readily char-
2
acterized by comparison of their spectroscopic features
with those of the TpiPr derivatives 3iP r a -d discussed
2
2
above, and the molecular structures of 3Me b,d obtained
2
from methyl cyanoacetate 2b and dimedone 2d have
been determined by X-ray crystallography (Figure 1 and
Table 2; for discussion, see below). In contrast to the
iP r 2
TpiPr derivatives 3 , fluxional behavior was observed
2
for 3Me a -c. Although the dynamic behavior of 3
can be interpreted in terms of the mechanism shown in
b
Me2
2
Scheme 2, the mechanism for the other derivatives
Me2
3Me a ,c should involve pseudorotation of the Tp
2
ligand, as already discussed for the related square-
planar TpRRhI complexes.6a,j,n,12 The mechanism for
3Me b at higher temperature may be associated with a
2
similar pseudorotation of the TpMe ligand.
2
As for the C-bound enolates 4Me , the Pd-CH linkage
2
can be confirmed by (1) the upfield shift of the methine
carbon signals by 20-30 ppm compared to those of 3Me
,
2
1
(2) the change of the J CH value of the Pd-CH moiety
to ∼150 Hz, consistent with sp3 hybridization, and (3)
the upfield shift of the δC(CN) signals to the normal
uncoordinated CN region (∼120 ppm)). The molecular
structure of 4Me c has been verified by X-ray crystal-
2
lography (Figure 1 and Table 2; for a detailed discussion,
see below).
Dim er iza tion of Cya n o Com p ou n d s by 1 to Give
2-Cya n oeth en yla m id o Com p lexes 6. The condensa-
tion of 1 in the presence of an excess amount of
dicyanomethane (2a ) and methyl cyanoacetate (2b)
afforded the (2-cyanoethenyl)amido complexes 6a ,b
(Scheme 4), which showed the characteristic νNH ab-
that, in the present TpMe Pd system, the N/O-bound
2
enolates 3Me and C-bound enolates 4
and thermodynamic products, respectively, of the de-
hydrative condensation of the hydroxo complexes 1Me
with active methylene compounds 2. However, no
isomerization was observed for 3Me d obtained from
dimedone 2d , presumably due to the steric repulsion,
because the C-bound form contains the highly congested
secondary Pd-CHXY moiety.
are the kinetic
Me2
2
2
2
sorption in addition to a couple of νCN and/or νCO
iP r 2
vibrations (Table 3). The TpiPr derivatives 6 a ,b were
2
(12) See references cited in 6a,j,n.

4054 Organometallics, Vol. 20, No. 19, 2001
Kujime et al.
polarized, due to contribution of the zwitterionic forms
6A,A′ and 6B, as is indicated by (1) the N-C lengths
being shorter than the normal length (1.38 Å; values
shown with 6 (Chart 1) are normal lengths (in Å) for
each bond) by 0.07-0.08 Å and (2) the elongated CdC
lengths. In the case of 6iP r a the negative charge is
2
delocalized over the CN group cis to the NH group (6A),
as suggested by the shorter C1-C2 bond (cf. C2-C3)
and the longer C1-N1 bond (cf. C3-N2 and C6-N4).
No significant delocalization over the ester moiety is
evident for 6iP r b, judging from the similar C2-C3 and
2
C2-C1 lengths (6A′), although the ester oxygen atom
(O1) is hydrogen-bonded with the N-H proton. The
hydrogen bond causes elongation of the C3-O1 distance
(cf. C7-O3). The presence of the amino groups is also
indicated by the νNH vibrations and the δH(NH) signals,
and the fact that the absorption for 6iP r b is weaker and
2
lower in energy than that of 6iP r a should be a result of
2
the intramolecular hydrogen bonding.
Reaction of the obtained enolato complexes 3 and 4
with electrophiles, including benzaldehyde, was also
examined, but no reaction was observed.13
Discu ssion
Molecu la r Str u ctu r es of Tp RP d -En ola to Com -
p lexes 3 a n d 4. (i) St r u ct u r es of t h e E n ola t o
iP r 2
Moieties. Two N-bound complexes (3Me b and 3
c),
2
one O-bound species (3Me d ), and one C-bound enolato
2
complex (4Me c) have been characterized by X-ray
2
crystallography (Figure 1), and the structural param-
eters for the enolato parts are summarized in Chart 2
(The upper and lower values shown for N-bound eno-
Me2
lates are for 3iP r c and 3 b, respectively.). Other
2
parameters are listed in Table 2.
For the structure of the C-bound enolate 4Me c, no
F igu r e 2. Molecular structures of the ((2-cyanoethenyl)-
2
iP r 2
amido)palladium complexes 6iP r a and 6 b drawn (with
2
significant electron delocalization is evident and all the
displacement ellipsoid amplitudes) at the 30% probability
level.
bond lengths for 4Me c shown in Chart 2 are in good
2
agreement with the values reported for typical bond
lengths (Pd-C ) 2.071 Å ((TpiPr )(PPh3)Pd-Me);
15
2
characterized by X-ray crystallography (Figure 2 and
C(sp3)-C(sp) ) 1.47 Å, C(sp)tN(sp) ) 1.14 Å, C(sp3)-
C(sp2) ) 1.51 Å, C(sp2)-C(sp2) ) 1.48 Å, C(sp2)dO(sp2)
) 1.21 Å),2c and the structural parameters for the Pd-
CH(CN) moiety are comparable to those of [(C6F5)4Pd2-
[µ-CH(CN)-CN]2 reported by Lo´pez.11 The slight elon-
gation of the C1-C2 bond should be due to the
contribution of an η2-(C1dC2) form,14 although the
Pd1-C2-C1 angle is not acute, as would be anticipated
for such an η2 structure.
Table 2). However, reaction between 1Me and 2b gave
2
a mixture of products, and an analogous product was
not formed from benzoylacetonitrile 2c. The dimeric
condensates 6a ,b were also obtained by treatment of
the 1:1 condensates 3 with the corresponding cyano
compounds, but no catalytic formation of the dimerized
organic product (YCH2(H2N)CdC(CN)(Y); Y ) CN,
COOMe) was observed even when 1 or 3 was heated in
the presence of an excess amount of cyano compounds.
It is noteworthy that, of the two types of TpMe Pd-
Complex 4Me c contains two chiral centers (Pd1 and
2
2
enolato complexes, i.e., the N- (3Me a ) and C-bound
2
C2), but only one diastereomer has been detected by
spectroscopic and crystallographic analyses. The ob-
served structure should be a result of minimizing steric
repulsions in the molecule.
Me2
species (4Me a ), only the N-bound enolate 3 a afforded
2
the condensate 6Me a and no trace of the product was
2
formed from the C-bound species 4Me a even under
2
In contrast to the C-bound enolate 4Me c discussed
2
forced conditions. This result clearly indicates that the
N-bound species 3 is the intermediate of the dimeriza-
tion, giving 6, and the C-bound species 4 is inactive for
the dimerization.
above, significant deformation from the localized form
3A is observed for the N-bound enolates (3Me b and
2
3iP r c), in particular, for the latter derived from ben-
2
The highly functionalized alkenyl moieties in 6 are
characterized by spectroscopic as well as crystallo-
graphic analyses. The δC signals for the alkenyl carbon
atoms, one with the two electron-withdrawing groups
(CN and COOMe) and the other with the two electron-
donating groups (NH and alkyl groups), are much
separated (>100 ppm).3c,10 The CdC bond is highly
(13) Komiya reported that the Re-enolate [(PhMe2P)4{R′OC(dO)-
CHRCN}Re]+ did not react with aldehyde but reacted in the presence
of a proton donor, revealing the importance of proton.4d However, no
condensation was observed under similar reaction conditions.
(14) So-called â-effect: Ariyaratne, J . K.; Bierrum, A. M.; Green,
M. L. H.; Ishaq, M.; Prout, C. K.; Swanwick, M. G. J . Chem. Soc. A
1969, 1309.
(15) Tanaka, M.; Akita, M. Unpublished results.

(Enolato)palladium Complexes with Borato Ligands
Organometallics, Vol. 20, No. 19, 2001 4055
Ch a r t 1
Ch a r t 2
zoylacetonitrile 2c. It is notable for 3iP r c that the C1-
C2 and C2-C3 distances are substantially shorter than
the corresponding bond lengths of the C-bound enolate
N-bound enolate 3Me b, the extent of the deformation
2
2
is smaller than that of 3iP r c. In addition, because the
2
C3-O1 length is comparable to the localized C(sp2)d
O(sp2) length (1.21 Å), the delocalization may not be
effectively extended to the ester moiety, presumably due
to π-donation from the methoxy group (R). In both of
the N-bound enolates the Pd-N-C linkage is bent from
a linear structure by ca. 10°. The bending could be
4Me c, whereas the C3-O1 separation is longer than the
2
corresponding C3-O1 distance of 4Me c, indicating
2
delocalization of the negative charge over the N1-C1-
C2-C3-O1 linkage, as typically depicted for 3. Al-
though similar deformation is observed for the other

4056 Organometallics, Vol. 20, No. 19, 2001
Kujime et al.
Sch em e 5
attributed to the contribution of the azaallenyl structure
3B,16 because no severe steric repulsion between the
enolato ligand and the TpRPd(py) backbone is found.
Similar structural features were already pointed out
for the related Ru- and Re-enolato complexes derived
from cyanoacetate esters, LnM-NCCHC(dO)OR (LnM
) (Ph3P)3(H){ROC(dO)CH2CN}Ru,3b [(PhMe2P)4{R′OC-
(dO)CHRCN}Re]+,4b,c (dppe)(cod)(H)Ru,4d Cp(dppe)-
Ru).3d Although the authors proposed an oxo-π-allyl
structure such as 3C, the NC-C distances (1.30-1.40
Å), which are shorter than or comparable to the corre-
sponding distances of our complexes, reveal the double-
bond character for the NC-C moiety. We therefore
conclude that structure 3, in which the negative charge
is delocalized over the N-C-C-Y linkage, can best
describe the structural features of the N-bound enolates.
The M-N-C angles of 3 being slightly more acute than
those of the Ru and Re complexes (166-176°)3,4 indicate
the increased contribution of the azaallenyl structure
3B.16
of the Pd center and the steric effects of the TpR and
enolato ligands. In general, the Lewis acidity of the
metal center increases as the ligand system becomes
more electron withdrawing (electronegative). Therefore,
the Pd center in an N-bound enolato complex coordi-
nated by the more electronegative nitrogen atom should
be more Lewis acidic than that in a C-bound enolato
complex. As a result, the third pz ligand in the N-bound
enolates would be coordinated to the more Lewis acidic
Pd center to lead to a square-pyramidal structure with
the κ3-TpR ligand. Although the lone pair electrons of
Averaging of the bond lengths of the enolato moiety
is also observed for the O-bound enolate 3Me d , but the
2
C2-C3-O2 moiety is not as deformed as the Pd-O1-
C1-C2 moiety is. Although these structural features
suggest that delocalization of π-electrons may not be
extended to the C3-O2 part, the νCO absorption ap-
pearing at 1611 cm-1 clearly indicates that the C3dO2
bond order is substantially decreased due to the delo-
calization.
the third pz ring of the C-bound isomer 4Me c appear to
2
be projected toward the Pd center, this should result
from the π-π stacking between the pz and Ph rings of
the enolato moiety (distances between the two rings
ranging from 3.455(5) (C4-C31) to 4.282(7) Å (C7-C33);
dihedral angle between the rings 18.7(2)°), as can be
seen from the molecular structure, and bonding interac-
tion is negligible, judging from the Pd1-N31 separation
(3.003(3) Å) (Figure 1). These considerations, however,
are not consistent with the κ2 coordination of the TpMe
Thus it has been revealed that, in the N/O-bound
enolates 3 π-electrons are delocalized over the two
functional groups (X and Y) attached to the central
methine carbon atom, in contrast to the C-bound enolate
4, where the structure can be described by the localized
canonical form. Contribution of the azaallenyl form 3B
is also indicated by the bending of the Pd-N-C linkage.
(ii) Str u ctu r e of th e Tp RP d (p y) Ba ck bon e. The
Pd coordination planes (Pd1-N11-N21-N41-X; X )
the coordinating atom of the enolato ligands) are es-
sentially planar, judging from the interligand angles
close to the right angle, the linear N11-Pd1-N41 and
N21-Pd1-X linkages, and the sum of the interligand
angles (360.0-360.5°).
ligand in 3Me d , bearing a more electron-withdrawing
2
O-coordinated enolato ligand. This inconsistency could
be attributed to the steric repulsion between the TpMe
and enolato ligands. As can be seen from the molecular
structures, the N-bound enolato ligand of the cyano
derivatives with the linear N-C-C does not virtually
suffer from steric repulsion with the other parts of the
complex, whereas the O-enolate of dimedone, being
much bulkier than the N-bound enolates, may prevent
coordination of the third pz ring.
The enolato complexes can be divided into two groups
on the basis of the presence/absence of the coordination
of the third pz groups (N31), i.e., the N31-Pd1 distance
2
(Table 2). The TpR ligand in the N-bound enolates 3Me
b
and 3iP r c, where the Pd1-N31 separations are ∼2.8
Å, are κ3-coordinated to the Pd center. Although the
Pd1-N31 distances are considerably longer than the
other Pd1-N distances in the basal plane and the sum
of atomic radii of Pd and N (∼2.1 Å), the orientation of
the third pz ring indicates some bonding interaction
between them. The lone pair electrons of N31 are
projected toward the Pd center. In contrast to the
2
F a ct or s Det er m in in g t h e St r u ct u r es of t h e
Tp RP d -En ola to Com p lexes: N-Bou n d vs C-Bou n d .
Me2
Comparison of the results for the TpiPr Pd and Tp Pd
2
systems reveals that dehydrative condensation between
the hydroxopalladium complex 1 and active methylene
compounds containing the cyano group 2 affords the
N-bound enolates 3 as the kinetic products and the
C-bound enolates 4 as the thermodynamic products.
This result can be interpreted in terms of steric and
electronic effects (Scheme 5).
The linear cyano-enolato ligand in N-bound enolates
3 suffers from steric repulsion with the TpR and py
ligands to a much smaller extent than the secondary
alkyl enolate group in C-bound species 4 does. A similar
structural effect of the metal fragment has been already
noted for the Cp(R3P)2Ru-CH(CN)(SO2Ph) system by
Murahashi,3d where the distribution of N- and C-bound
N-bound enolates, the Pd1-N31 separation of the
Me2
O-bound (3Me d ) and C-bound enolates (4 c) are longer
2
than 3.0 Å, which exceeds the range for a bonding
interaction.
The coordination behavior of the third pz ring can be
interpreted in terms of a combination of Lewis acidity
(16) Badley, W. H.; Choudhury, P. J . Organomet. Chem. 1973, 60,
C64. Suzuki, K.; Nakamura, S. Inorg. Chim. Acta 1977, 25, L21.
Suzuki, K.; Sakurai, M. Inorg. Chim. Acta 1979, 32, L3.

(Enolato)palladium Complexes with Borato Ligands
Organometallics, Vol. 20, No. 19, 2001 4057
Sch em e 6
nucleophilic attack of the carbanion at the cyano carbon
atom of the external cyano compound C followed by
replacement of the coordinated cyano group by the
resultingimide anion (D). Because the obtained enolato
complexes 3 and 4 are not reactive enough to be coupled
with other electrophiles as mentioned above, the former
mechanism seems to be preferable to the latter one. The
low reactivity of the enolato complexes may be ascribed
to the small electron density at the enolate carbon atom
due to (1) delocalization of the anionic charge over the
enolate linkage and (2) the electrostatic attractive
interaction between the negative charge on the enolato
moiety and the virtually +2-charged Pd center (see
above). In addition, because the Pd-N bond in 6 is not
basic enough to be protonated by NC-CH2-Y (2),
catalytic production of the dimeric organic product
YCH2(H2N)CdC(CN)(Y) is not observed. Dimerization
of active methylene compounds containing a cyano
group has been successfully catalyzed by a hydridoiri-
dium complex as reported by Murahashi, who originally
proposed a C-bound enolate as the reaction intermediate3c
but, in their recent account, reported that an N-bound
enolato species was active for the dimerization.3g
Con clu sion s. The present study reveals the following
aspects of the enolatopalladium complexes bearing the
TpR and py ancillary ligands, as summarized in Scheme
7.
isomers is dependent on the bulkiness of the phosphine
ligand (PR3); i.e., a compact phosphine with a small cone
angle leads to the C-bound enolate, whereas a bulky
phosphine affords the N-bound enolate.
As for electronic effects, the enolato complexes should
be formed by coupling between the enolate anion and
the cationic [TpRPd(py)]+ species generated by dehydra-
tion. Because the negative charge of the TpR anion is
localized on the B atom, the Pd center is the virtually
+2-charged, hard center. When the two canonical forms
of the cyano-enolate, where the negative charge is
localized on the N and C atoms, respectively, are taken
into account, the hard Pd center should prefer coupling
with the hard N-enolate to that with the soft C-enolate.
The formation of the dinuclear µ-malononitrilate com-
plex [(C6F5)4Pd2[µ-CH(CN)CN]2] was interpreted in
terms of dimerization of the initially generated mono-
nuclear C-bound enolato complex [(H2O)(C6F5)Pd-CH-
(CN)2].11 The difference could be attributed to the soft
hydrocarbyl groups (C6F5) making the palladium center
soft.
Sch em e 7
In both aspects, formation of the N-bound enolate 3Me
2
rather than the C-bound enolate 4Me seems to be the
2
preferable reaction pathway, and therefore, the N-bound
species 3Me should be formed as the kinetic product.
2
The C-bound species 4Me containing the covalent Pd-C
2
bond, however, may be more stable than the zwitterionic
iPr2
N-bound form 3Me . In the case of Tp
complexes, the
2
bulky TpiPr ligand prohibits conversion into the C-bound
2
form, and the N-bound form 3iP r is the kinetic as well
2
as thermodynamic product.
(1) The enolato complexes (TpR)(py)Pd-enolato (3 and
4) are obtained by dehydrative condensation between
the hydroxopalladium complex (TpR)(py)Pd-OH (1) and
active methylene compounds CH2(X)(Y) (2).
Dim er iza tion of Cya n o Com p ou n d s. Reaction of
the hydroxo complex 1 with an excess amount of cyano
compounds 2a ,b or reaction of the 1:1 condensate 3 with
2a ,b resulted in stoichiometric dimerization of the cyano
compound 2 to produce the 1:2 condensate, i.e., the
2-cyanoethenylamido complex 6, in a specific manner.17
The most important reaction aspect is that the C-bound
(2) Of the two possible isomeric N- (3Me ) and C-bound
2
Me2
(TpMe )(py)Pd-enolato complexes (4 ) derived from
2
cyano compounds, the former is the kinetic product and
the latter is the thermodynamic product and the former
complex is gradually converted to the latter isomer.
enolate 4Me did not react with 2 any more and remained
2
unreacted.
However, enolato complexes with the bulky TpiPr ligand
2
On the basis of the results obtained, possible reaction
mechanisms are shown in Scheme 6. Coordination of
the cyano compound to the Pd center would form the
five-coordinate intermediate A, and the subsequent
electrocyclic reaction should afford the imino intermedi-
ate B, which is finally converted to the 1:2 condensate
6 via a H-shift. Another possible mechanism involves
forms only the N-bound isomer 3iP r , due to steric
2
repulsion between the TpiPr ligand and the C-bound,
2
secondary alkyl moiety.
(3) Both the N/O- and C-bound enolates are charac-
terized by a combination of spectroscopic and crystal-
lographic analyses, and the two isomers are readily
1
discriminated on the basis of the νCN, δC(CH), and J CH
-
(17) Attempted cross-condensation (3iP r a + 2b or MeCN; 3 b +
2a or MeCN) resulted in the formation of a mixture of products.
Formation of condensates was suggested by the appearance of the νNH
vibrations of the Pd-NH moiety.
iP r 2
2
(CH) values.
(4) The 2-cyanoethenylamido complex 6 is obtained
by reaction between the hydroxo complex 1 and cyano

4058 Organometallics, Vol. 20, No. 19, 2001
Kujime et al.
5, 3,5-pz), 152.4 (dd, J ) 187 and 4 Hz, o-py), 138.4 (dt, J )
165 and 6 Hz, p-py), 124.4 (dt, J ) 167 and 6 Hz, m-py), 99.1,
99.0, 98.7 (d × 3, J ) 173 Hz, 4-pz), 28.5-20.8 (CHMe2). Anal.
Calcd for C40H62BN7O2Pd: C, 60.80; H, 7.91; N, 12.41. Found:
compounds 2a ,b. The 1:2 condensate 6 is also obtained
from the N-bound isomer 3 but not from the C-bound
isomer 4.
C, 60.68; H, 7.95; N, 12.00. 5iP r e was obtained in 64% yield
2
Exp er im en ta l Section
as yellow crystals. 1H NMR (CDCl3; at room temperature): δH
3.5 (6H, br, CHMe2), 1.5-1.0 (36H, m, CHMe2). 13C NMR
(CDCl3; at room temperature): δC 157.0, 159.9 (s × 2, 3,5-pz),
98.1 (d, J ) 171 Hz, 4-pz), 27.7 - 22.9 (CHMe2). Anal. Calcd
for C32H53BN6O3Pd: C, 55.94; H, 7.78; N, 12.23. Found: C,
55.60; H, 7.64; N, 12.56.
Gen er a l Meth od s. All manipulations were carried out
under an Ar atmosphere using standard Schlenk tube tech-
niques. Hexane and CH2Cl2 were dried over Na-K/benzophe-
none and CaH2, respectively, under Ar and distilled just before
use. NMR spectra were recorded on a J EOL EX-400 spectrom-
eter (1H, 400 MHz; 13C, 100 MHz). CDCl3 and CD2Cl2 for NMR
measurements containing 0.5% TMS were dried over molec-
ular sieves and distilled under reduced pressure. IR spectra
P r ep a r a tion of 3Me . As a typical example the preparative
2
Me
procedure for 3Me a is described, and 3 b,c were prepared
2
2
in a manner similar to the synthesis of 3Me a . To a CH2Cl2
2
solution (15 mL) of 1Me (139 mg, 0.278 mmol) cooled to 0 °C
2
(KBr pellets) were obtained on a J ASCO FT/IR 5300 spec-
Me
trometer. The hydroxo complexes 1iP r and 1
were prepared
was added Na2SO4 (ca. 150 mg) and CH2(CN)2 (18 mg, 0.272
mmol), and the resultant mixture was stirred for 1 h at the
same temperature. Then the mixture was filtered through a
Celite pad, the filtrate was concentrated, and crystallization
2
2
by hydrolysis of the corresponding chloride complexes (TpR)-
(py)Pd-Cl with aqueous NaOH solution.7a
P r ep a r a tion of 3iP r . As a typical example, the preparative
2
from CH2Cl2-hexane at -20 °C gave 3Me a (110 mg, 0.207
procedure for 3iP r a is described and 3 b,c were prepared
iP r
2
2
2
mmol, 72% yield) as yellow crystals. 1H NMR (CD2Cl2; at -50
°C): δH 8.57 (2H, d, J ) 5 Hz, o-py), 7.85 (1H, t, J ) 7 Hz,
p-py), 7.36 (2H, t, J ) 7 Hz, m-py), 2.35, 2.33, 2.30, 2.09, 2.06,
1.41 (3H × 6, s × 6, J ) 7 Hz, Me). 13C NMR (CD2Cl2; at -50
°C): δC 152.4 (d, J ) 186 Hz, o-py), 150.3, 148.9, 148.2, 146.9,
146.5, 144.1 (s × 6, 3,5-pz), 139.4 (dt, J ) 173 and 6 Hz, p-py),
125.6 (d, J ) 169 Hz, m-py), 106.9, 106.5, 105.4 (d × 3, J )
170 Hz, 4-pz), 14.3, 13.3, 13.25, 13.16, 13.09, 11.9 (q × 6, J )
in a manner similar to the synthesis of 3iP r a . To 1
(264
iP r
2
2
mg, 0.395 mmol) dissolved in CH2Cl2 (5 mL) was added Na2-
SO4 (ca. 150 mg). A CH2Cl2 solution (15 mL) of CH2(CN)2 (26
mg, 0.394 mmol) was added dropwise to the mixture at
ambient temperature. The resultant mixture was stirred for
1 h and filtered through a Celite pad to remove solids. The
filtrate was concentrated under reduced pressure, and crystal-
lization from CH2Cl2-hexane gave 3iP r a as a yellow solid (156
2
129 Hz, Me). Anal. Calcd for C23.2H28.4BN9Cl0.4Pd (3Me a ‚
mg, 0.218 mmol, 55% yield). 1H NMR (CDCl3; at room
temperature): δH 8.61 (2H, d, 6 Hz, o-py), 7.83 (1H, t, J ) 8
Hz, p-py), 7.35 (2H, t, J ) 7 Hz, m-py), 3.50 (1H, sept, J ) 7
Hz, CHMe2), 3.43 (2H, sept, J ) 7 Hz, CHMe2), 2.92, 2.69,
2.05 (1H × 3, sept × 3, J ) 7 Hz, CHMe2), 0.55-1.42 (36H, m,
CHMe2). 13C NMR (CDCl3; at room temperature): δC 160.8,
159.3, 158.8, 157.8 155.3 (s × 5, 3,5-pz), 153.1 (d, J ) 186 Hz,
o-py), 139.0 (d, J ) 165 Hz, p-py), 125.2 (d, J ) 165 Hz, m-py),
99.2, 98.8, 98.1 (d × 3, J ) 173 Hz, 4-pz), 28.6-20.2 (CHMe2).
Anal. Calcd for C35H52BN9Pd: C, 58.71; H, 7.32; N, 17.60.
2
0.2CH2Cl2): C, 49.34; H, 5.07; N, 22.32. Found: C, 49.32; H,
5.13; N, 22.31. 3Me b was obtained in 59% yield as yellow
2
crystals. 1H NMR (CD2Cl2; at -50 °C; an isomeric mixture):
δH 8.60 (2H, d, J ) 5 Hz, o-py), 7.83 (1H, t, J ) 7 Hz, p-py),
7.33 (2H, t, J ) 7 Hz, m-py), 1.4-2.9 (18H, m, Me). 13C NMR
(CD2Cl2; at -50 °C; an isomeric mixture): δC 157.1 (d, J )
190 Hz, o-py), 155.1, 153.4, 152.8, 151.4, 150.9, 148.6 (s × 6,
3,5-pz), 143.8, 143.7 (d × 2, J ) 160 Hz, p-py), 130.0, 129.9 (d,
J ) 170 Hz, m-py), 111.3, 111.0, 109.9 (d × 3, J ) 167 Hz,
4-pz), 18.9, 18.7, 17.8, 17.7, 17.6, 16.4, 16.3 (q × 6, J ) 129
Hz, Me). Anal. Calcd for C24H31BN8O2Pd: C, 49.63; H, 5.38;
Found: C, 58.51; H, 7.22; N, 17.56. Complexes 3iP r b-d and
2
5iP r e were prepared in a manner similar to the synthesis of
2
N, 19.29. Found: C, 49.38; H, 5.49; N, 19.35. 3Me c was
iP r
1
2
3iP r a . 3 b was obtained in 64% yield as yellow crystals. H
NMR (CD2Cl2; at -50 °C; an isomeric mixture): δH 8.48 (2H,
d, J ) 6 Hz, o-py), 7.81 (1H, t, J ) 7 Hz, p-py), 7.31 (2H, t, J
) 7 Hz, m-py), 3.6-2.0 (6H, m, CHMe2), 1.36-0.38 (36H, m,
CHMe2). 13C NMR (CD2Cl2; at -50 °C; an isomeric mixture):
δC 160.5, 159.2, 158.9, 158.8, 157.7, 157.5, 157.3, 155.1 (s × 7,
3,5-pz), 152.9, 152.8 (d, J ) 191 Hz, o-py), 140.5, 139.9 (s × 2,
3,5-pz), 139.3, 139.1 (d × 2, J ) 166 Hz, p-py), 125.3, 125.1 (d
× 2, J ) 164 Hz, m-py), 99.2, 99.1, 99.0. 97.6 (d, J ) 169 Hz,
4-pz), 20.8-27.9 (CHMe2). Anal. Calcd for C36H55BN8Pd: C,
2
2
1
obtained in 69% yield as yellow crystals. H NMR (CD2Cl2; at
-80 °C): δH 8.74 (2H, br, o-py), 7.86 (1H, t, J ) 7 Hz, p-py),
7.60 (2H, d, J ) 7 Hz, o-Ph), 7.40 (2H, br, m-py), 7.26 (3H, m,
m,p-Ph), 2.50, 2.31, 2.28, 2.20, 2.03, 1.41 (3H × 6, s × 6, Me).
13C NMR (CD2Cl2; at -80 °C): δC 152.6 (d, J ) 185 Hz, o-py),
150.5, 148.8, 148.4, 147.0, 146.3, 144.1 (s × 6, 3,5-pz), 139.4
(dt, J ) 173 and 6 Hz, p-py), 125.7 (d, J ) 169 Hz, m-py),
106.8, 106.5, 105.0 (d × 3, J ) 170 Hz, 4-pz), 14.6, 13.3, 12.1
(q × 3, J ) 125 Hz, Me). Anal. Calcd for C29H33BN8OPd: C,
55.56; H, 5.31; N, 17.78. Found: C, 55.20; H, 5.60; N, 17.90.
57.72; H, 7.40; N, 14.96. Found: C, 57.99; H, 7.62; N, 14.72.
1
3Me d was obtained in 67% yield as yellow crystals. H NMR
3iP r c was obtained in 68% yield as yellow crystals. H NMR
1
2
2
(CDCl3; at room temperature): δH 8.91 (2H, d, J ) 5 Hz, o-py),
7.82 (1H, t, J ) 8 Hz, p-py), 7.34 (2H, t, J ) 7 Hz, m-py), 2.56
(3H, s, Me), 2.44 (6H, s, Me × 2), 2.21, 2.11, 1.87 (3H × 3, s ×
3, Me). 13C NMR (CDCl3; at room temperature): δC 152.2 (d,
J ) 186 Hz, o-py), 150.8 (s, 3,5-pz), 148.6, 147.6 (br × 2, 3,5-
pz), 146.4 (s, 3,5-pz), 143.5, (br, 3,5-pz), 138.6 (dt, J ) 165 and
6 Hz, p-py), 124.6 (dt, J ) 167 and 7 Hz, m-py), 107.2, 106.9,
103.8 (d × 3, J ) 170 Hz, 4-pz), 28.3, 28.1 (q × 3, J ) 125 Hz,
Me). Anal. Calcd for C28H38BN7O2Pd: C, 54.08; H, 6.16; N,
15.77. Found: C, 54.17; H, 6.15; N, 15.65.
(CDCl3; at room temperature): δH 8.81 (2H, d, J ) 6 Hz, o-py),
7.78 (1H, t, J ) 8 Hz, p-py), 7.74 (2H, dd, J ) 6 and 3 Hz,
m-Ph), 7.39 (2H, t, J ) 7 Hz, m-py), 7.30 (2H, d, J ) 2 Hz,
o-Ph), 7.29 (1H, m, p-Ph), 3.66, 3.50, 3.48, 2.87 2.69, 2.11 (1H
× 6, sept × 6, J ) 7 Hz, CHMe2), 1.38-0.59 (36H, m, CHMe2).
13C NMR (CDCl3; at room temperature): δC 161.4, 159.3, 158.8,
158.0, 157.9, 155.3 (s × 6, 3,5-pz), 153.6 (d, J ) 191 Hz, o-py),
141.7 (s, ipso-Ph), 138.9 (dt, J ) 162 and 7 Hz, p-py), 136.2 (s,
CN), 129.2 (dt, J ) 162 and 7 Hz, p-Ph), 127.6 (dd, J ) 161
and 4 Hz, o-Ph), 126.3 (dt, J ) 158 and 5 Hz, m-Ph), 125.2
(dt, J ) 167 and 6 Hz, m-py), 99.1, 98.9, 98.2 (d × 3, J ) 173
Hz, 4-pz). Anal. Calcd for C41H57BN8OPd: C, 61.93; H, 7.23;
P r ep a r a tion of 4Me . As a typical example, the preparative
2
Me
procedure for 4Me a is described and 4 b,c were prepared in
2
2
N, 14.09. Found: C, 62.25; H, 7.96; N, 13.77. 3iP r d was
a manner similar to the synthesis of 4Me a . To a CH2Cl2
2
2
1
2
obtained in 66% yield as yellow crystals. H NMR (CDCl3; at
solution (20 mL) of 1Me (162 mg, 0.324 mmol) was added Na2-
room temperature): δH 8.84 (2H, d, J ) 6 Hz, o-py), 7.76 (1H,
t, J ) 8 Hz, p-py), 7.29 (2H, t, J ) 7 Hz, m-py), 3.58 (2H, m,
CHMe2), 3.33, 3.00, 2.68, 2.09 (1H × 4, sept × 6, J ) 7 Hz,
CHMe2), 1.40-0.87 (36H, m, CHMe2). 13C NMR (CDCl3; at
room temperature): δC 161.5, 159.1, 157.8, 157.4, 154.7 (s ×
SO4 (ca. 150 mg) and CH2(CN)2 (21 mg, 0.318 mmol), and the
resultant mixture was stirred for 1 h at room temperature.
Then the mixture was filtered through a Celite pad, the filtrate
was concentrated, and crystallization from CH2Cl2-hexane at
-20 °C gave 4Me a (111 mg, 0.214 mmol, 66% yield) as yellow
2

(Enolato)palladium Complexes with Borato Ligands
Organometallics, Vol. 20, No. 19, 2001 4059
Ta ble 4. Cr ysta llogr a p h ic Da ta
3iP r c‚1.74CH2Cl2
3Me
b
3Me
d
4Me2
c
6iP r 2a ‚CH2Cl2
6iP r 2b‚0.5CH2Cl2
2
2
2
formula
fw
cryst syst
space group
a/Å
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
C42.74H62.48BN6Cl3.48Pd C24H31BN8O2Pd C28H38BN7O2Pd C29H33BN8OPd C39H56BN11Cl2Pd C40.5H62BN9O4ClPd
960.96
580.77
621.86
626.74
867.06
891.66
triclinic
P1h
monoclinic
P21/n
13.606(2)
16.630(1)
23.331(2)
monoclinic
P21/c
13.0558(6)
14.3339(8)
14.8052(8)
orthorhombic
Pbca
17.855(2)
19.375(4)
17.092(4)
monoclinic
P21/n
8.6448(3)
17.7105(9)
18.9942(9)
monoclinic
P21/n
16.5082(7)
14.0485(6)
21.2050(10)
10.378(3)
22.092(4)
10.381(3)
98.43(2)
97.843(4)
80.52(2)
2306(1)
2
102.653(2)
95.855(2)
92.759(3)
111.660(2)
5150.8(8)
4
2756.1(2)
4
5912(1)
8
2904.7(2)
4
4570.5(4)
4
Z
d
calcd/g cm-3
1.24
1.40
1.40
1.43
1.26
1.28
µ/cm-1
2θ/deg
5.81
7.09
6.65
6.77
5.62
5.08
<55
<55
<55
<55
<55
<55
transmissn factor
no. of data collected
0.41-0.94
26 179
0.73-0.93
21 378
6493
0.38-0.94
31 131
6411
0.74-0.93
19 940
6038
0.61-0.95
31 919
10345
7221
0.57-0.95
12 003
8142
no. of unique data collected 10 788
no. of unique data with
F > 4σ(F)
5617
544
5843
4084
4620
5121
no. of params refined
336
0.056
0.147
360
0.066
0.206
367
0.042
0.126
496
0.062
0.174
515
0.084
0.221
R1a for data with F > 4σ(F) 0.097
wR2b for all data
0.285
a
b
2
R1 ) [∑||Fo| - |Fc||]/∑|Fo| (for data with I > 4σ(F)). wR2 ) [∑{w(Fo - Fc2)}2/∑{w(Fo2)2}]0.5; w ) 1/[σ2(Fo2) + (0.1000P)2], where P )
[2Fc + Max(Fo2,0)]/3 (for all data).
2
crystals. 1H NMR (CDCl3; at room temperature): δH 9.23 (2H,
d, J ) 5 Hz, o-py), 7.86 (1H, t, J ) 8 Hz, p-py), 7.44 (2H, t, J
) 7 Hz, m-py), 2.45, 2.42, 2.36, 2.30, 2.08, 1.47 (3H × 6, s × 6,
Me). 13C NMR (CDCl3; at room temperature): δC 152.7 (d, J
) 185 Hz, o-py), 150.1, 148.8, 148.4, 147.3, 146.2, 143.3 (s ×
6, 3,5-pz), 138.8 (dt, J ) 167 and 6 Hz, p-py), 125.6 (dt, J )
169 and 6 Hz, m-py), 107.6, 106.6, 106.3 (d, J ) 173 Hz, 4-pz),
14.1, 13.8, 13.6, 13.3, 12.6 (q × 5, J ) 127 Hz, Me). Anal. Calcd.
for C23.1H28.2BN9Cl0.2Pd: C, 49.88; H, 5.11; N, 22.66. Found:
(dt, J ) 165 and 6 Hz, p-py), 125.7 (dt, J ) 167 and 6 Hz,
m-py), 100.0, 99.2 (d × 2, J ) 172 Hz, 4-pz), 20-28 (CHMe2).
Anal. Calcd for C38H54BN11Pd: C, 58.35; H, 6.96; N, 19.70.
Found: C, 58.10; H, 6.83; N, 19.64. 6iP r b was obtained in 50%
2
yield as yellow crystals. 1H NMR (CDCl3; at room tempera-
ture): δH 9.01 (2H, d, J ) 5 Hz, o-py), 7.82 (1H, t, J ) 8 Hz,
p-py), 7.36 (2H, t, J ) 7 Hz, m-py), 3.59, 3.29, 3.20, 3.03, 2.60,
1.89 (1H × 6, sept × 6, J ) 7 Hz, CHMe2), 1.52-0.57 (36H, m,
CHMe2). 13C NMR (CDCl3; at room temperature): δC 161.1,
159.0, 158.2, 158.1, 157.3, 155.2 (s × 6, 3,5-pz), 153.2 (d, J )
180 Hz, o-py), 138.6 (dt, J ) 165 and 6 Hz, p-py), 125.0 (dt, J
) 167 and 7 Hz, m-py), 99.3, 98.9, 98.6 (d × 3, J ) 171 Hz,
4-pz), 28.0-20.7 (CHMe2). Anal. Calcd for C40.6H61.4BN9O4Pd
C, 49.80; H, 5.19; N, 22.53. 4Me b was obtained in 54% yield
2
as yellow crystals. 1H NMR (CDCl3; at room temperature): δH
9.25 (2H, d, J ) 5 Hz, o-py), 7.79 (1H, t, J ) 4 Hz, p-py), 7.35
(2H, t, J ) 7 Hz, m-py), 2.47, 2.44, 2.32, 2.26, 1.97, 1.47 (3H
× 6, s × 6, Me). 13C NMR (CDCl3; at room temperature): δC
152.9 (d, J ) 185 Hz, o-py), 150.3, 148.2, 147.4, 147.3, 145.9,
144.2 (s × 6, 3,5-pz), 138.2 (dt, J ) 163 and 6 Hz, p-py), 124.8
(dt, J ) 165 and 5 Hz, m-py), 107.7, 106.6, 106.2 (d × 3, J )
170 Hz, 4-pz), 14.8, 14.1, 13.8, 13.2, 13.1, 12.3 (q × 6, J ) 125
Hz, Me). Anal. Calcd for C24H31BN8O2Pd: C, 49.63; H, 5.38;
(6iP r b‚0.1hexane): C, 55.91; H, 7.22; N, 14.71. Found: C,
2
56.06; H, 7.40; N, 14.81. 6Me a was obtained in 73% yield as
2
yellow crystals. 1H NMR (CDCl3; at room temperature): δH
9.13 (2H, d, J ) 6 Hz, o-py), 7.93 (1H, t, J ) 8 Hz, p-py), 7.47
(2H, t, J ) 7 Hz, m-py), 2.46, 2.34, 2.33, 2.31, 2.16, 1.50 (3H
× 6, s × 6, Me). 13C NMR (CDCl3; at room temperature): δC
152.9 (d, J ) 185 Hz, o-py), 150.6, 148.9, 148.4, 147.4, 146.9,
144.6 (s × 6, 3,5-pz), 139.4 (d, J ) 165 Hz, p-py), 125.8 (dt, J
) 167 and 6 Hz, m-py), 108.1, 107.0, 106.7 (d × 2, J ) 172
Hz, 4-pz), 14.1, 13.8, 13.6, 13.3, 12.6 (q × 5, J ) 127 Hz, Me).
N, 19.29. Found: C, 49.36; H, 5.59; N, 19.25. 4Me c (59% yield;
2
yellow crystals): 1H NMR (CDCl3; at room temperature): δH
9.70 (2H, d, J ) 8 Hz, o-py), 7.83 (1H, t, J ) 8 Hz, p-py), 7.38
(2H, t, J ) 6 Hz, m-py), 7.26 (1H, t, J ) 7 Hz, p-Ph), 7.07,
(2H, d, J ) 8 Hz, o-Ph), 6.97 (2H, t, J ) 8 Hz, m-Ph), 2.63,
2.54, 2.32, 2.22, 1.55, 1.45 (3H × 6, s × 6, J ) 7 Hz, Me). 13C
NMR (CDCl3; at room temperature): δC 153.3 (d, J ) 191 Hz,
o-py), 150.3, 148.3, 147.7, 145.5, 142.6 (s × 5, 3,5-pz), 138.2
(dt, J ) 165 and 6 Hz, p-py), 137.0 (s, 3,5-pz), 131.4 (dt, J )
165 and 7 Hz, Ph), 127.45, 127.49 (d × 2, J ) 160 Hz, Ph),
124.5 (d, J ) 167 Hz, m-py), 107.9, 106.1, 105.6 (d × 3, J )
170 Hz, 4-pz), 15.1, 13.9, 13.3, 13.1, 12.9 (q × 5, J ) 125 Hz,
Me). Anal. Calcd for C29H33BN8OPd: C, 55.56; H, 5.31; N,
17.78. Found: C, 55.20; H, 5.66; N, 17.79.
Anal. Calcd for C26.2H30.4BN11Cl0.4Pd (6Me a ‚0.2CH2Cl2): C,
2
49.89; H, 4.86; N, 24.42. Found: C, 49.70; H, 4.91; N, 24.26.
X-r a y Cr ysta llogr a p h y. Diffraction measurements were
made on a Rigaku RAXIS IV imaging plate area detector with
Mo KR radiation (λ ) 0.710 69 Å). All the data collections were
carried out at -60 °C. Indexing was performed from three
oscillation images, which were exposed for 4 min. The crystal-
to-detector distance was 110 mm. Data collection parameters
were as follows (detector swing angle(deg)/number of oscilla-
P r ep a r a tion of 6. As a typical example the preparative
iP r
Me
procedure for 6iP r a is described and 6 b and 6 a were
2
tion images/exposure time (min)): 4.0/45/30 (3iP r c‚1.74CH2-
2
2
2
prepared in a manner similar to the synthesis of 6iP r a . To a
Me
Me
2
Cl2), 3.0/60/15 (3Me b), 5.0/36/21 (4 b), 4.0/45/23.3 (3 d ),
2
2
2
CH2Cl2 solution (15 mL) of 1iP r (97 mg, 0.145 mmol) was added
2
5.0/36/20 (6iP r a ‚CH2Cl2), 5.0°/36/50 min (6 b‚0.5CH2Cl2).
iP r
2
2
Na2SO4 (ca. 150 mg) and CH2(CN)2 (20 mg, 0.30 mmol), and
the resultant mixture was stirred for 1 h at room temperature.
Then the mixture was filtered through a Celite pad, the filtrate
was concentrated, and crystallization from CH2Cl2-hexane at
Readout was performed with a pixel size of 100 µm × 100 µm.
(18) teXsan; Crystal Structure Analysis Package, version 1.11;
Rigaku Corp., Tokyo, J apan, 2000.
(19) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1975; Vol. 4.
(20) Higashi, T. Program for Absorption Correction; Rigaku Corp.,
Tokyo, J apan, 1995.
(21) (a) Sheldrick, G. M. SHELXS-86: Program for Crystal Structure
Determination; University of Go¨ttingen, Go¨ttingen, Germany, 1986.
(b) Sheldrick, G. M. SHELXL-97: Program for Crystal Structure
Refinement; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
-20 °C gave 6iP r a (76 mg, 0.097 mmol, 67% yield) as yellow
2
crystals. 1H NMR (CDCl3; at room temperature): δH 9.03 (2H,
d, J ) 5 Hz, o-py), 7.90 (1H, t, J ) 8 Hz, p-py), 7.45 (2H, t, J
) 7 Hz, m-py), 3.58, 3.27, 3.20, 3.12, 2.77, 1.83 (1H × 6, sept
× 6, J ) 7 Hz, CHMe2), 1.42-0.61 (36H, m CHMe2). 13C NMR
(CDCl3; at room temperature): δC 161.3, 159.3, 159.0, 158.9,
157.8, 155.9 (s × 6, 3,5-pz), 152.9 (d, J ) 184 Hz, o-py), 139.4

4060 Organometallics, Vol. 20, No. 19, 2001
Kujime et al.
Crystallographic data and the results of refinements are
summarized in Table 4. The structural analysis was performed
on an IRIS O2 computer using the teXsan structure solving
program system18 obtained from Rigaku Corp., Tokyo, J apan.
Neutral scattering factors were obtained from the standard
source.19 In the reduction of data, Lorentz and polarization
corrections were made. An absorption correction was also
made.20
The structures were solved by a combination of direct
methods (SHELXS-86,21 SAPI91, SIR92, or MITHRIL90)22 and
Fourier synthesis (DIRDIF94).23 Least-squares refinements
were carried out using SHELXL-9721 (refined on F2) linked to
teXsan. All the non-hydrogen atoms were refined anisotropi-
cally. Riding refinements were applied to the methyl hydrogen
atoms of the isopropyl groups (B(H) ) B(C)), and the other
hydrogen atoms were fixed at the calculated positions. Riding
refinements were applied to the methyl hydrogen atoms (B(H)
) B(C)). The CH2Cl2 solvates, except that associated with
Me
3iP r c, were refined isotropically. H2 (3 b) and H0,1,2 atoms
2
2
(6iP r a ) were refined isotropically.
2
Ack n ow led gm en t. We are grateful to the Ministry
of Education, Culture, Sports, Science, and Technology
of the J apanese Government for financial support of this
research (Grant-in-Aid for ScientificResearch: 11228201).
Su p p or tin g In for m a tion Ava ila ble: Tables giving crys-
tallographic results. This material is available free of charge
via the Internet at http://pubs.acs.org.
(22) (a) SAPI91: Fan, H.-F. Structure Analysis Programs with
Intelligent Control; Rigaku Corp., Tokyo, J apan, 1991. (b) SIR92:
Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.; Giacovazzo,
C.; Guagliardi, A.; Polidori, G. J . Appl. Crystallogr. 1994, 27, 435. (c)
MITHRIL90: Gilmore, C. J . MITHRIL-an Integrated Direct Methods
Computer Program; University of Glasgow, Glasgow, U.K., 1990.
OM010448O
(23) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF Program System; Technical Report of the Crystallography
Laboratory; University of Nijmegen, Nijmegen, The Netherlands, 1992.