Syntheses and chemistry of Tris(2-pyridyl)phosphine complexes of Group VI transition metals. X-ray structural studies of the molybdenum complexes

Article abstract of DOI:10.1016/S0022-328X(99)00387-3

Treatment of P(2-py)₃ with Mo(CO)₆ or M(CO)₃(CH₃CN)₃ (M=Cr, W) in CH₃CN affords compounds of the type P(2-py)₃M(CO)₃ (1a, M=Cr; 1b, M=Mo; 1c, M=W). Complex P(2-py)₃Mo(CO)₃·CH₂Cl₂ was structurally characterized, and its ORTEP drawing shows an almost perfect octahedral arrangement around the Mo center, and the P(2-py)₃ ligand occupying the facial position of the octahedron through the coordination of three pyridyl nitrogen atoms. Substitution of CO ligands can take place when treating compounds 1b and 1c with one or two equiv. of NOBF₄ in CH₃NO₂ solvent to afford [P(2-py)₃M(CO)_3-n(NO)_n](BF₄) _n (2a, M=Mo, n=1; 2b, M=W, n=1; 3a, M=Mo, n=2; 3b, M=W, n=2). These singly and doubly charged cationic species have been characterized by ¹H-, ¹³C-, ³¹P-, ¹⁹F-NMR and IR spectroscopy, as well as elemental analysis. The CO lability of 3a and 3b generated the 16-electron species, [P(2-py)₃M(NO)₂]²⁺, which binds to most Lewis basic donor ligands to give complexes of the type, [P(2-py)₃M(L)(NO)₂](BF₄)₂ (L=nitriles, aldehydes). A single crystal of [P(2-py)₃M(CH₃CH₂CN)(NO)₂](BF ₄)₂·CH₃NO₂ was also isolated and structurally characterized. The crystallographic analysis indicated an octahedral arrangement about the Mo metal center. The ¹H-NMR downfield shift of the metal-coordinated crotonaldehyde in compounds 4c and 5c is used as a qualitative measurement of relative Lewis acidity, and the acid strength of [P(2-py)₃M(NO)₂]²⁺ is comparable to that of TiCl₄ when M=Mo and to BF₃ and AlCl₃ when M=W. The Diels-Alder reactions between cyclohexadienes and methyl vinyl ketone were catalyzed by 0.3 mol% of [P(2-py)₃W(CO)(NO)₂](BF₄)₂ (3b) to afford an average 94% conversion and 83% isolated yield.

Full text of DOI:10.1016/S0022-328X(99)00387-3

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 588 (1999) 260–267
Syntheses and chemistry of Tris(2-pyridyl)phosphine complexes of
Group VI transition metals. X-ray structural studies of the
molybdenum complexes
a
a
a
a,
Cheng-Yi Kuo , Yaw-Shyan Fuh , Jay-Yun Shiue , S. Joyce Yu *,
b
b
Gene-Hsiang Lee , Shie-Ming Peng
a
Department of Chemistry, National Chung Cheng Uni6ersity, Ming Hsiung, Chia Yi 621, Taiwan, ROC
b
Department of Chemistry, National Taiwan Uni6ersity, Taipei 106, Taiwan, ROC
Received 11 May 1999; received in revised form 28 June 1999
Abstract
Treatment of P(2-py)3 with Mo(CO)6 or M(CO) (CH CN) (M=Cr, W) in CH CN affords compounds of the type,
3
3
3
3
P(2-py) M(CO) (1a, M=Cr; 1b, M=Mo; 1c, M=W). Complex P(2-py) Mo(CO) ·CH Cl was structurally characterized, and
3
3
3
3
2
2
its ORTEP drawing shows an almost perfect octahedral arrangement around the Mo center, and the P(2-py) ligand occupying the
3
facial position of the octahedron through the coordination of three pyridyl nitrogen atoms. Substitution of CO ligands can take
place when treating compounds 1b and 1c with one or two equiv. of NOBF in CH NO solvent to afford [P(2-py) M(CO)
4
3
2
3
3−
n(NO) ](BF ) (2a, M=Mo, n=1; 2b, M=W, n=1; 3a, M=Mo, n=2; 3b, M=W, n=2). These singly and doubly charged
n
4 n
1
13
31
19
cationic species have been characterized by H-, C-, P-, F-NMR and IR spectroscopy, as well as elemental analysis. The CO
lability of 3a and 3b generated the 16-electron species, [P(2-py) M(NO) ] , which binds to most Lewis basic donor ligands to
2
+
3
2
give complexes of the type [P(2-py) M(L)(NO) ](BF )
(L=nitriles, aldehydes).
A
single crystal of [P(2-
3
2
4 2
py) M(CH CH CN)(NO) ](BF ) ·CH NO was also isolated and structurally characterized. The crystallographic analysis indi-
3
3
2
2
4 2
3
2
1
cated an octahedral arrangement about the Mo metal center. The H-NMR downfield shift of the metal-coordinated
crotonaldehyde in compounds 4c and 5c is used as a qualitative measurement of relative Lewis acidity, and the acid strength of
2
+
[
P(2-py) M(NO) ]
is comparable to that of TiCl4 when M=Mo and to BF3 and AlCl3 when M=W. The Diels–Alder
3
2
reactions between cyclohexadienes and methyl vinyl ketone were catalyzed by 0.3 mol% of [P(2-py) W(CO)(NO) ](BF ) (3b) to
3
2
4 2
afford an average 94% conversion and 83% isolated yield. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Group VI transition metals; Molybdenum; X-ray
nation possibility. There are four coordination modes
1
. Introduction
found for complexes containing P(2-py) , namely, P-
3
2
monodentate [3,4], h -P,N-chelate [5,6a], m-P,N-bridge
The synthesis of Tris(2-pyridyl)phosphine (P(2-py)3,
-py=2-pyridyl) was first reported [1] in 1944 by
3
[
7] and h -N,N%,N¦-chelate [8]. Thus, application of
2
P(2-py) ligations affords numerous novel and useful
Davies and Mann as part of a study on the optical
resolution of tertiary phosphines. Yet the complexation
of P(2-py) with metal ions was not reported until 1970
3
complexes. Apart from its characteristics in coordina-
tion chemistry, the catalysis aspects of P(2-py) for the
3
3
reactions employing triphenylphosphine have been re-
[2]. There has been an increasing usage of P(2-py) in
3
cently explored [6]. We have focused our interest on the
inorganic and organometallic chemistry primarily be-
cause of its interesting structural feature retaining both
phosphorus and nitrogen atoms with versatile coordi-
3
h -N,N%,N¦-P(2-py) ligation, where the P(2-py) ligand
3
3
binds to group VI transition metals at facial position of
an octahedron via three pyridyl nitrogen atoms. The
3
h -N,N%,N¦-chelate has been mostly observed as a p-ac-
*
Corresponding author. Fax: +886-5-2721040.
ceptor ligand in sandwich complexes of first-row transi-
E-mail address: chejyy@ccunix.ccu.edu.tw (S. Joyce Yu)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00387-3

C.-Y. Kuo et al. / Journal of Organometallic Chemistry 588 (1999) 260–267
261
tion metals with low oxidation state. The electrochemi-
cal properties such as the s- and p-delocalization as
well as the p-accepting capability of a series of cobalt
All solvents were dried with use of standard proce-
dures. Crotonaldehyde and methyl vinyl ketone were
purified by vacuum-transferred from CaH . Cyclohexa-
2
3
complexes containing two h -N,N%,N¦-chelating ligands
diene was used as purchased. All other materials were
used as received without further purification. Tris(2-
pyridyl)phosphine was prepared by a modification of
the reported procedure [6a]. Cr(CO) (CH CN) and
have been discussed [9]. These sandwich complexes are
2
+
generally formulated as [M(P(2-py) ) ]
(M=Mn,
3
2
Co, Ni, Cu, Zn, Ru) [8a–c]. However, only two exam-
ples of half-sandwich complexes have been reported,
3
3
3
W(CO) (CH CN) were prepared by following the liter-
3
3
3
1
2
that is, ZnP(2-py) )(h -NO )(h -NO ) [8d] and
ature methods [13].
3
3
3
RuCl(PPh )P(2-py) [8e].
3
3
In this paper, we report our research on the synthe-
sis, characterization, and reactivity of Group VI transi-
2.1. Synthesis of P(2-py)
Cr(CO)
3
3
(1a)
tion-metal half-sandwich complexes supported by
A suspension of 0.28 g Cr(CO)
of CH CN was heated at reflux under N for 48 h,
3 2
6
(1.2 mmol) in 30 ml
3
h -N,N%,N¦-P(2-py) ligation. Substitution of the neu-
3
tral CO ligands in P(2-py) M(CO) (M=Cr: 1a, Mo:
tris-2-pyridylphosphine (0.28 g, 1.1 mmol) was then
added to the yellow solution. The reaction mixture was
heated at reflux for another 12 h. A purple-colored
precipitate formed during reflux. After cooling, the
resulting solution was concentrated, and the superna-
tant was decanted and the precipitate was washed with
3
3
+
1
b, W: 1c) by the isoelectronic NO groups affords
cationic species of the type [P(2-py) M(CO)
3
3−
n+
n(NO)n]
(n=1, 2). The dinitrosyl complexes, [P(2-
py) M(CO)(NO) ](BF ) (M=Mo: 3a, W: 3b), have
3
2
4 2
been proven to be strong Lewis acid precursors. In
solution, complexes 3a and 3b release their CO and
generate 16-electron species of the type [P(2-
CHCl
py) Cr(CO)
added). H-NMR (CDCl
and dried in vacuo overnight to afford P(2-
3
. Yield 0.27 g (64%, based on P(2-py)
3
3
3
2
+
1
py) M(NO) ] , which are capable of binding basic
3
, 27°C, 200 MHz): l 7.15 (t),
3
2
31
nitriles and aldehydes. Furthermore, 3b is also active in
promoting the Diels–Alder reaction of cyclohexadiene
and methyl vinyl ketone. The Diels–Alder reactions of
7.62 (t), 8.05 (t), 9.55 (d). P-NMR (CDCl
MHz): l −12.4 ppm. IR (CDCl
3
, 27°C, 80
,): wCO=1901 (s),
1777 (br) cm . Anal. Calc. for C18 PCr: C,
3
−
1
H N O
12 3 3
1
,3-butadiene and methyl vinyl ketone [10] as well as
53.29; H, 3.14; N, 10.21. Found: C, 53.88; H, 3.01; N,
10.47%.
the additions of silylated C-nucleophiles to carbonyl
compounds [11] have also been observed to be cata-
lyzed by the analogues Lewis acid precursor, [HC(2-
py) W(CO)(NO) ](SbF ) , where the HC(2-py) ligand
3
2
6 2
3
3
is an h -N,N%,N¦ ligand.
Though catalysis using complexes containing
pyridylphosphine ligands, PPh3−n(2-py) (n=1,2) has
n
developed noticeably in the past two decades [4,12], the
application of P(2-py) in homogeneous catalysis is still
3
limited [6]. We are therefore interested in exploring the
catalytic aspects of P(2-py) in homogeneous systems.
2.2. Synthesis of P(2-py) Mo(CO) (1b)
3
3
3
A mixture of Tris-2-pyridyl-phosphine (200 mg, 0.7
2. Experimental
mmol) and Mo(CO) (200 mg, 0.7 mmol) in 10 ml of
6
CH CN was heated at reflux under N for 8 h to afford
3
2
All manipulations were carried out either by use of
a red precipitate. The crude product was filtered and
washed with petroleum ether, and the solid was dried in
vacuo overnight to give red P(2-py) Mo(CO) . Yield
standard Schlenk techniques or in a Vacuum Atmo-
spheres glove-box unless specified otherwise. NMR
spectra were recorded on a Varian Gemini-200 QNP or
a Bruker AMX 400 QNP spectrometer, and chemical
3
3
1
288 mg (89%). H-NMR (CDCl , 27°C, 200 MHz): l
3
31
7.20 (t), 7.70 (t), 8.08 (t), 9.45 (d). P-NMR (CDCl3,
1
shifts were reported relatively to TMS for H- and
27°C, 80 MHz): l −3.2 ppm. IR (CDCl ): wCO=1908
3
1
3
31
−1
C-NMR spectra, 85% H PO for P-NMR spectra,
(s), 1797 (br) cm . Anal. Calc. for C H N O PMo:
3
4
18 12
3
3
1
9
and CFCl for F-NMR spectra in CDCl , CD NO ,
C, 48.35; H, 2.72; N, 9.41. Found: C, 48.56; H, 2.72; N,
9.44%.
3
3
3
2
CD CN and DMSO-d . Infrared spectra were obtained
3
6
with a Perkin–Elmer 682 spectrometer. Elemental
analyses were performed by the Microanalytical Labo-
ratory of South Taiwan National Science Council In-
strument Center. Mass spectra were obtained on a VG
TRIO-2000 spectrometer.
2.3. Synthesis of P(2-py) W(CO) (1c)
3
3
A suspension of W(CO) (220 mg, 0.56 mmol) in 10
6
ml of CH CN was heated at reflux under N for 24 h,
3
2

262
C.-Y. Kuo et al. / Journal of Organometallic Chemistry 588 (1999) 260–267
Tris-2-pyridylphosphine (136 mg, 0.51 mmol) was then
added to the yellow solution. The reaction mixture was
heated at reflux for another 12 h. A maroon-colored
precipitate formed during reflux. After cooling, the
resulting solution was concentrated, and the superna-
tant was decanted and the precipitate was washed with
petroleum ether and dried in vacuo overnight to afford
P(2-py) W(CO) . Yield 300 mg (61%, based on P(2-py)
give [P(2-py) W(CO) (NO)](BF ). Yield 89 mg (76%).
3 2 4
1
H-NMR (CD CN, 27°C, 200 MHz): l 7.55–7.65 (m),
3
8.02–8.20 (m), 8.32–8.46 (m), 9.05 (d, J=5.12 Hz),
1
3
9.28 (d, J=5.12 Hz). C-NMR (d -DMSO, 27°C, 100
6
31
MHz): l 222.1 (CO). P-NMR (CD CN, 27°C, 80
MHz): l −8.07. F-NMR (CD CN, 27°C, 376 MHz):
3
19
3
l −151.3 ppm. IR (KBr): wCO=2012 (s), 1912 (br);
−
1
wNO=1650 (s); wBF=1060 (br) cm . Anal. Calc. for
3
3
3
1
added). H-NMR (CDCl , 27°C, 200 MHz): l 7.15 (t),
C H BF N O PW: C, 38.81; H, 1.91; N, 9.01. Found:
3
17 12
4
4
3
3
1
7
.75 (t), 8.15 (t), 9.45 (d). P-NMR (CDCl , 27°C, 80
C, 32.83; H, 1.94; N, 9.01%.
3
MHz): l −4.5 ppm. IR (CDCl ): wCO=1899 (s), 1784
3
−
1
(
br) cm . Anal. Calc. for C H N O PW: C, 40.49;
2.6. Synthesis of [P(2-py) Mo(CO)(NO) ](BF ) (3a)
1
8
12
3
3
3
2
4 2
H, 2.33; N, 7.89. Found: C, 40.55; H, 2.27; N, 7.88%.
To a suspension of [P(2-py) Mo(CO) (100 mg, 0.225
3
3
2
.4. Synthesis of [P(2-py) Mo(CO) (NO)](BF ) (2a)
mmol) in 5 ml of CH
3
NO
2
was added 2 equiv. of
3
2
4
NOBF (53 mg, 0.454 mmol). An immediate vigorous
4
To a suspension of P(2-py) Mo(CO) (100 mg, 0.225
gas evolution was observed upon addition of NOBF .
4
3
3
mmol) in 10 ml of CH Cl2 was added 1 equiv. of
The reaction mixture was allowed to stir at ambient
temperature for 10 min. The suspended impurities were
filtered off from the dark green solution, and dried in
2
NOBF (26 mg, 0.222 mmol). An immediate vigorous
4
gas evolution was observed upon addition of NOBF4.
The reaction mixture was allowed to stir at ambient
vacuo overnight to give green solids of [P(2-
1
temperature for 1 h. The unreacted P(2-py) Mo(CO)3
py)
NMR (CD
8.58 (m), 9.08 (d), 9.18 (d). P-NMR (CD
80 MHz): l −5.8 ppm. IR (CD NO ): wCO=2037 (br);
NO=1839 (s), 1738 (s); wBF=1026 (br) cm
Mo(CO)(NO)
3
2
](BF )
4
2
. Yield 90 mg (90%). H-
3
was filtered off from the dark red solution, and the
solvent was removed from the filtrate to give an or-
ange–red solid. The solid was then dried in vacuo
overnight to give orange–red [P(2-py) Mo(CO) -
3
NO
2
, 27°C, 200 MHz): l 7.87 (m), 8.37 (m),
31
NO , 27°C,
2
3
3
2
−
1
w
.
3
2
1
(
NO)](BF ). Yield 95 mg (79%). H-NMR (CD CN,
4
3
2
8
7°C, 200 MHz): l 7.55–7.65 (m), 8.06–8.18 (m),
.28–8.41 (m), 8.97 (d, J=5.12 Hz), 9.20 (d, J=4.76
1
3
Hz). C-NMR (d -DMSO, 27°C, 100 MHz): l 222.0
6
3
1
(
CO). P-NMR (CD CN, 27°C, 80 MHz): l −4.75.
3
1
9
F-NMR (CD CN, 27°C, 376 MHz): l −151.3 ppm.
3
IR (KBr): wCO=2046 (s), 1940 (br); wNO=1668 (s);
−
1
wBF=1060
(br)
cm
.
Anal.
Calc.
for
C H BF N O PMo: C, 38.23; H, 2.30; N, 10.41.
Found: C, 38.24; H, 2.26; N, 10.49%.
1
7
12
4
4
3
2.7. Synthesis of [P(2-py)
W(CO)(NO) ](BF ) (3b)
3 2 4 2
To a suspension of P(2-py) W(CO) (100 mg, 0.188
3
3
mmol) in 5 ml of CH NO2 was added 2 equiv. of
3
NOBF (44 mg, 0.376 mmol). An immediate vigorous
4
gas evolution was observed upon addition of NOBF4.
The reaction mixture was allowed to stir at ambient
temperature for 30 min. The suspended impurities were
filtered off from the dark green solution. Recrystalliza-
tions of the crude product from CH NO –ether solu-
3
2
2
.5. Synthesis of [P(2-py) W(CO) (NO)](BF ) (2b)
tion at −18°C for 24 h gave green crystals of
3
2
4
1
[
P(2-py) W(CO)(NO) ](BF ) . Yield 75 mg (56%). H-
3 2 4 2
To a suspension of P(2-py) W(CO) (100 mg, 0.188
NMR (CD NO , 27°C, 200 MHz): l 7.89–7.96 (m),
3
3
3 2
1
3
mmol) in 10 ml of CH Cl2 was added 1 equiv. of
8.43–8.50 (m), 8.64–8.74 (m), 9.25–9.43 (m). C-
2
3
1
NOBF (22 mg, 0.188 mmol). An immediate vigorous
NMR (CD NO , 27°C, 50 MHz): l 192.2 (CO). P-
4
3 2
19
gas evolution was observed upon addition of NOBF4.
The reaction mixture was allowed to stir at ambient
temperature for 1 h. The suspended impurities were
filtered off from the dark purple solution, and the
solvent was removed from the filtrate to give a purple
solid. The solid was then dried in vacuo overnight to
NMR (CD NO , 27°C, 80 MHz): l −10.58. F-NMR
3 2
(CD NO , 27°C, 188 MHz): l −151.7 ppm. IR (KBr):
3
2
wCO=2148 (br); wNO=1844 (s), 1758 (s); wBF=1030
−
1
(br) cm . Anal. Calc. for C H B F N O PW: C,
16
12
2
8
5
3
26.74; H, 1.78; N, 9.70. Found: C, 27.04; H, 1.70; N,
9.85%.

C.-Y. Kuo et al. / Journal of Organometallic Chemistry 588 (1999) 260–267
263
1
3
2
.8. Synthesis of [P(2-py) M(L)(NO) ](BF ) , where
(s, CH CN). C-NMR (CD NO , 27°C, 50 MHz): l
3 3 2
3
2
4 2
31
M=Mo and W; L=CH CN and CH CH CN
138.1 (CH CN), 4.8 (CH CN). P-NMR (CD NO ,
3
3
2
3 3 3 2
19
2
7°C, 80 MHz): l −10.75. F-NMR (CD NO , 27°C,
3 2
A typical procedure for the synthesis of [P(2-
py) M(L)(NO) ](BF ) is described as follows. To a
188 MHz): l −151.3 ppm. IR (KBr): wCN=2296 (br);
wNO=1802 (s), 1716 (s) cm . Anal. Calc. for
−
1
3
2
4 2
suspension of P(2-py) Mo(CO) (50 mg, 0.112 mmol) in
C H B F N O PW: C, 28.20; H, 2.10; N, 11.52.
3
3
17 15
2
8
6
2
5
0
ml of CH CN was added 2 equiv. of NOBF (26 mg,
.222 mmol). An immediate vigorous gas evolution was
Found: C, 28.21; H, 2.09; N, 11.61%.
3
4
observed upon addition of NOBF . The reaction mix-
4
2
.8.4. [P(2-py) W(CH CH CN)(NO) ](BF ) (5b)
3
3
2
2
4 2
ture was allowed to stir at ambient temperature for 30
min. The suspended impurities were filtered off from
the dark green solution, and 5 ml of dry diethyl ether (5
ml) was added to the filtrate. The resulting solution was
allowed to sit at−18°C for 24 h to give green crys-
talline solids of [P(2-py) Mo(CH CN)(NO) ](BF ) .
1
H-NMR (CD NO , 27°C, 200 MHz): l 7.82–7.96
3
2
(
(
m), 8.34–8.46 (m), 8.52–8.72 (m), 9.16–9.22 (m), 3.00
q, J=7.52 Hz, CH CH CN), 1.37 (t, J=7.50 Hz,
3
2
13
CH CH CN). C-NMR (CD NO , 27°C, 50 MHz): l
3
2
3
2
1
41.0 (CH CH CN), 14.1 (CH CH CN), 9.2
3 2 3 2
31
3
3
2
4 2
(
CH CH CN). P-NMR (CD NO , 27°C, 80 MHz): l
3 2 3 2
19
Spectroscopic data are given below.
−
10.71. F-NMR (CD NO , 27°C, 188 MHz): l −
3 2
1
51.3 ppm. IR (KBr): wCN=2284 (br); wNO=1790 (s),
2
.8.1. [P(2-py) Mo(CH CN)(NO) ](BF ) (4a)
−1
3
3
2
4 2
1688 (s) cm . Anal. Calc. for C H B F N O PW: C,
18 17 2 8 6 2
1
H-NMR (CD NO , 27°C, 200 MHz): l 7.81–7.91
3
2
29.37; H, 2.29; N, 11.16. Found: C, 29.30; H, 2.32; N,
1.39%.
(
m), 8.30–8.40 (m), 8.56–8.72 (m), 9.08 (d, J=5.12
1
13
Hz), 9.28 (d, J=5.20 Hz), 2.62 (s, CH CN). C-NMR
3
(
(
6
CD NO , 27°C, 50 MHz): l 136.5 (CH CN), 4.3
3 2 3
3
1
2.9. Reactions of [P(2-py)
aldehydes, where M=Mo and W;
aldehyde=CH CHꢀCHCHO and C H CHO
3 2 4 2
M(CO)(NO) ](BF ) with
CH CN). P-NMR (CD NO , 27°C, 80 MHz): l −
3 3 2
1
9
.26. F-NMR (CD NO , 27°C, 188 MHz): l −151.5
3 2
3
6
5
ppm. IR (KBr): wCN=2294 (br); wNO=1834 (s), 1732
−
1
(
s) cm . Anal. Calc. for C H B F N O PMo: C,
17 15 2 8 6 2
A typical procedure for the synthesis of [P(2-
py) M(L)(NO) ](BF ) is described as follows. A solu-
2
1
8.20; H, 2.10; N, 11.52. Found: C, 28.21; H, 2.09; N,
1.61%.
3
2
4 2
tion of P(2-py) Mo(CO)3 (50 mg, 0.112 mmol) and
3
NOBF (9 mg, 0.084 mmol) in 0.5 ml of CD NO was
4
3
2
allowed to react for 20 min in a 5 mm Wilmad 528 pp
NMR tube equipped with an air-free J. Young Valve.
A slight excess of crotonaldehyde (50 ml) was then
added into the reaction tube. The solution was allowed
to react at room temperature for one day until no
starting metal material resonances were observed by the
1
H-NMR. Spectroscopic data is given below.
2
.9.1. [P(2-py) Mo(CH CHꢀCHCHO)(NO) ](BF )
3
3
2
4 2
(
4c)
1
2
.8.2. [P(2-py) Mo(CH CH CN)(NO) ](BF ) (4b)
H-NMR (CD NO , 27°C, 200 MHz): l 7.81–7.95
3
3
2
2
4 2
3 2
1
H-NMR (CD NO , 27°C, 200 MHz): l 7.81–7.92
(m), 8.30–8.45 (m), 8.54–8.69 (m), 8.90–9.05 (m), 9.91
3
2
(
m), 8.29–8.41 (m), 8.52–8.67 (m), 9.08 (d, J=5.22
(d, J=8.70 Hz, CH CHꢀCHCHO), 7.98–8.15 (m,
3
Hz), 9.17 (d, J=5.20 Hz), 2.98 (q, J=7.40 Hz,
CH CH CN), 1.36 (t, J=7.62 Hz, CH CH CN). C-
NMR (CD NO , 27°C, 50 MHz):
CH CHꢀCHCHO),
6.64–6.76
(m,
CH CH=
3
3
13
3
2
3
2
CHCHO), 2.34 (d, J=6.50 Hz, CH CHꢀCHCHO).
3
13
l
139.5
C-NMR (CD NO , 27°C, 50 MHz):
l
211.5
3
2
3
2
(
CH CH CN), 13.8 (CH CH CN), 9.4 (CH CH CN).
(CH CHꢀCHCHO), 177.6 (CH CHꢀCHCHO), 134.4
3
2
3
2
3
2
3
3
3
1
19
P-NMR (CD NO , 27°C, 80 MHz): l −5.91. F-
(CH CHꢀCHCHO), 21.7 ppm (CH CHꢀCHCHO).
3
2
3
3
NMR (CD NO , 27°C, 188 MHz): l −151.7 ppm. IR
3
2
−
1
(
KBr): wCN=2294 (br); wNO=1830 (s), 1728 (s) cm
.
2.9.2. [P(2-py) W(CH CHꢀCHCHO)(NO) ](BF ) (5c)
1
3
3
2
4 2
Anal. Calc. for C H B F N O PMo: C, 31.93; H,
H-NMR (CD NO 27°C, 200 MHz): l 7.75–8.00
1
9
20
2
8
7
4
3
2
2
2
.83; N, 13.57. Found: C, 32.07 H, 2.81; N, 13.78%.
(m), 8.30–8.45 (m), 8.55–8.72 (m), 8.87 (d, J=5.80
Hz), 9.10 (d, J=5.76 Hz), 9.16–9.22 (m), 9.96 (d,
.8.3. [P(2-py) W(CH CN)(NO) ](BF ) (5a)
J=8.90 Hz, CH CHꢀCHCHO), 8.11–8.29 (m,
3
3
2
4 2
3
1
H-NMR (CD NO , 27°C, 200 MHz): l 7.82–7.95
CH CHꢀCHCHO), 6.70–6.82 (m, CH CHꢀCHCHO),
3
2
3
3
13
(
m), 8.33–8.45 (m), 8.58–8.71 (m), 9.17–9.22 (m), 2.66
2.37 (d, J=6.88 Hz, CH CHꢀCHCHO). C-NMR
3

264
C.-Y. Kuo et al. / Journal of Organometallic Chemistry 588 (1999) 260–267
o
(
(
(
CD NO ,
27
C,
50
MHz):
l
211.1
the Patterson heavy-atom method [14] and refined by a
full-matrix least-square procedure using NRCVAX [15] to
reveal the positions of molybdenum atoms. Systematic
absences and subsequent least-squares refinement indi-
3
2
CH CHꢀCHCHO), 180.7 (CH CHꢀCHCHO), 134.8
CH CHꢀCHCHO), 22.2 ppm (CH CHꢀCHCHO).
3
3
3
3
2
.9.3. [P(2-py) W(C H CHO)(NO) ](BF ) (5d)
cated
py) Mo(CO)
group for
a
monoclinic C2/c space group for P(2-
·CH Cl and a monoclinic P2 /c space
[P(2-py) Mo(CH CH CN)(NO) ](BF
3
6
5
2
4 2
1
H-NMR (CD NO , 27°C, 200 MHz): l 10.60 (s,
3
3
2
2
1
3
2
C H CHO), 8.00–8.20 ppm (m, C H CHO).
3
3
2
2
) ·
4 2
6
5
6
5
CH NO . The remaining atoms were located in suc-
3
2
2.10. Catalytic Diels–Alder reactions of cyclohexadiene
and methyl 6inyl ketone
Table 1
Crystallographic data for P(2-py) Mo(CO) ·CH Cl and [P(2-
All Diels–Alder reactions were carried out in the
same manner. In a typical procedure, 10 mg (14.0
3
3
2
2
py) Mo(CH CH CN)(NO) ](BF ) ·CH NO
3
3
2
2
4 2
3
2
mmol) of [P(2-py) W(CO)(NO) ](BF ) (3b) in 10 ml of
3
2
4 2
Formula
FW
Diffractometer
Space group
C19H14N O MoPC1 C19H20N O MoB F
3 3 2 7 4 2 8
CH Cl was placed in a 25-ml flask. The flask was
530.15
710.93
2
2
cooled to 0°C before the addition of 0.4 ml of methyl
vinyl ketone (4.8 mmol). Cyclohexadiene (0.53 ml, 5.6
mmol) was then added dropwise to the reaction mixture
over 2–3 min. After 24 h, the solution was subjected to
a rotary evaporator to remove all volatiles. The crude
products were then purified by column chromatography
using 20:1 hexane–ethylacetate as eluent. Yield 0.61 g
Nonius
Nonius
Monoclinic, C2/c
26.304 (6)
10.8570 (20)
17.087 (6)
121.53 (3)
4159.6 (19)
8
Monoclinic, P21/c
a (A
,
)
)
)
17.754 (4)
b (A
,
11.204 (3)
16.025 (3)
115.292 (18)
2882.2 (12)
4
c (A
,
i (°)
V (A
3)
,
Z
Dcalc. (g cm−3)
1.693
1.638
(
85%). All Diels–Alder products were identified by
u (A
F(000)
,
)
0.7107
0.7107
NMR comparison to authentic material made as de-
scribed in the literature. The percentage conversion and
2101
1410
Unit cell detn: c
(2q range)
Scan type
25 (20.84–38.10°)
25 (14.74–29.36°)
1
isomer ratios were determined by H-NMR integration
q /2q
q/2q
of the enone aldehydic proton and methyl protons of
the cyclohexadiene adducts.
Scan width (°)
2 (0.65+
2 (0.60+
0.35 tan q)
2.06–8.24
50.0
0
.35 tan q)
Scan speed (° min−1)
2q (max)
h, k, l ranges
2.06–8.24
50.0
2.11. X-ray crystallographic analyses of
P(2-py) Mo(CO) ·CH Cl and
(−31; 26),
((21; 19), (0; 13),
(0; 18)
3
3
2
2
(
0; 12), (0; 20)
[
P(2-py) Mo(CH CH CN)(NO) ](BF ) ·CH NO
3 3 2 2 4 2 3 2
v (cm−1)
6.319
5.713
Crystal size (mm)
Transmission
Temperature (K)
Number of meas
reflections
0.40×0.50×0.55
0.881; 1.000
298
0.15×0.25×0.35
0.965; 1.000
298
General operation procedures have been reviewed.
Some selected crystallographic data and data collection
parameters are summarized in Tables 1 and 2. Suitable
single crystals of P(2-py) Mo(CO) ·CH Cl and [P(2-
3730
5064
3
3
2
2
Number of obsed
reflections (I\2.0|(I))
Number of unique
3105
2326
5064
py) Mo(CH CH CN)(NO) ](BF ) ·CH NO
were
grown at −18°C from CH Cl2 and CH CH CN–
3
3
2
2
4 2
3
2
2
3
2
3645
a
CH NO solutions, respectively, for X-ray single-crystal
reflections
3
2
b
structure
determination.
A
crystal
of
P(2-
R
f
; R
w
(I\2.0|(I))
0.029; 0.030
0.064; 0.063
0.147; 0.067
2.88
R ; R (all reflections) 0.037; 0.036
py) Mo(CO) ·CH Cl with dimensions of 0.40×0.50×
f
w
3
3
2
2
c
3
Goodness of-fit
1.47
NRCVAX
0
(
0
.55 mm and a crystal of [P(2-py) Mo(CH CH CN)-
3 3 2
Refinement program
Number of atoms
Number of refined
parameters
NRCVAX
NO) ](BF ) ·CH NO with dimensions of 0.15×
2 4 2 3 2
3
47
62
.25×0.35 mm were mounted in capillary tubes under
272 (3105 out of
380 (2326 out of
a nitrogen atmosphere. Data were recorded at ambient
temperature on an Enraf–Nonius CAD4 diffractometer
using graphite-monochromatized MoꢁKa radiation.
Unit-cell dimensions were determined from 25 well-cen-
tered reflections (20.8452q538.10°) for P(2-
py) Mo(CO) ·CH Cl , and from 25 well-centered
3645)
5064)
2
2
Minimize function
S(w ꢀ F −F ꢀ )
S(wꢀF −F ꢀ )
o
c
o
c
(
Z/|) max
0.0117
0.0372
(0.690; 0.810
Residual in final D-map −0.730; 0.770
3
max min (e A )
,
a
Three standard reflns monitored every 3600 s, intensity variation
B2%, solvent: CH Cl (disorder) for [P(2-py) Mo(CO) ]·CH Cl . An-
3
3
2
2
reflections (14.7452q529.36°) for [P(2-py) Mo-
2
2
3
3
2
2
3
−
ion: 2BF4 , Solvent: CH NO for [P(2-py) Mo(CH CH CN)(NO) ]-
3
2
3
3
2
2
(
CH CH CN)(NO) ](BF ) ·CH NO . Three intensity
3 2 2 4 2 3 2
(
BF ) ·CH NO .
4
2
3
2
standards were measured for every 1 h of exposure time
and declined systematically by 2% during the course of
the measurements. Both structures were solved using
b
R =S(F −F )/S(F ); R =[S(w(F −F ) )/S(wF )]1/2.
2
2
o
f
o
c
o
w
o
c
c
2
Goodness of-fit [S(w(F −F ) )/(number of reflections−number
o
c
1
/2
of parameters)]
.

C.-Y. Kuo et al. / Journal of Organometallic Chemistry 588 (1999) 260–267
265
Table 2
3
.2. Synthesis and characterization of
Selected bond distances (A
Py) Mo(CO )·CH Cl
,
)
and angles (°) for P(2-
[P(2-py) M(CO) (NO)](BF ), where M=Mo (2a) and
3
2
4
3
3
2
2
W (2b)
Bond distances
MoꢁN(1)
MoꢁN(3)
MoꢁC(2)
C(1)ꢁO(1)
C(3)ꢁO(3)
+
2.279(3)
2.266(3)
1.928(4)
1.158(4)
1.165(4)
MoꢁN(2)
MoꢁC(1)
MoꢁC(3)
2.282(3)
1.951(4)
1.938(4)
1.170(4)
The reaction of NO with low-valent transition-
metal complexes has been widely employed in the syn-
thesis of nitrosyl complexes of both molybdenum and
tungsten [16,17]. The treatment of 1a and 1b with 1
equiv. of NOBF in CH Cl resulted in immediate gas
C(2)ꢁO(2)
4
2
2
Bond angles
1
evolution to afford complexes 2a and 2b. The H-NMR
spectra of both 2a and 2b showing two sets of pyridyl
protons with a ratio of 2:1 indicated that the C36
symmetry was no longer present. The higher CO
stretching frequencies (2a: 2046, 1940 and 2b: 2012,
912 cm ) than those found for complexes 1a–c
suggested a weaker M–CO interaction. However, com-
plexes 2a and 2b still possessed rather high stability
against further CO ligand replacement in most coordi-
nating solvent systems. In addition to the CO stretching
bands, the strong NO stretching bands at 1668 and
N(1)ꢁMoꢁN(2)
N(2)ꢁMoꢁN(3)
N(1)ꢁMoꢁC(2)
N(2)ꢁMoꢁC(3)
N(3)ꢁMoꢁC(3)
N(2)ꢁMoꢁC(2)
C(1)ꢁMoꢁC(2)
C(2)ꢁMoꢁC(3)
84.56(10)
83.74(10)
92.84(12)
97.49(13)
92.51(12)
177.35(12)
86.32(15)
85.13(15)
N(1)ꢁMoꢁN(3)
N(1)ꢁMoꢁC(1)
N(2)ꢁMoꢁC(1)
N(3)ꢁMoꢁC(2)
N(1)ꢁMoꢁC(3)
N(3)ꢁMoꢁC(1)
C(1)ꢁMoꢁC(3)
84.12(10)
95.89(12)
93.39(13)
96.56(12)
175.85(12)
177.12(13)
87.60(14)
−1
1
ceeding difference Fourier syntheses. Hydrogen atoms
were located and added to the structures, but their
position were not refined.
−
1
1650 cm
for 2a and 2b respectively were typical for
linear MꢁNꢁO bonding mode [18].
3. Results and discussion
3.3. Synthesis and characterization of
[
P(2-py) M(CO)(NO) ](BF ) , where M=Mo (3a) and
3
2
4 2
3
.1. Synthesis and characterization of P(2-py) M(CO) ,
W (3b)
3
3
where M=Cr (1a), Mo (1b) and W (1c)
Subsequent substitution of the second CO ligand can
be achieved by treating complexes 2a and 2b with a
further 1 equiv. of NOBF in CH NO. Alternatively,
The reactions of P(2-py)3 and
1
equiv. of
M(CO) (CHCN) , where M=Cr and W, or Mo(CO)
3
3
6
4
3
in CH CN resulted in the formation of complexes
complexes 3a and 3b can also be synthesized by the
3
P(2-py) M(CO) (1a–c). The infrared spectra of 1a–c
direct reaction of 1a–b and 2 equiv. of NOBF in
3
3
4
1
showing two wCO bands (1a: 1901, 1777; 1b: 1908, 1797,
CH NO . The H-NMR spectra of both 3a and 3b
3
2
−
1
and 1c: 1899, 1784 cm ) suggested that complexes
a–c held a C36 symmetry. As compared with the CO
showing two sets of pyridyl protons with a ratio of 2:1
indicated that the C36 symmetry was no longer present.
1
−
1
stretching frequency for CO gas (2143 cm ), the wCO
found for 1a–c were lower in energy due to a certain
degree of metal-to-ligand p-back bonding. Only one set
of pyridyl protons (between l 7.15–9.55 ppm) with a
1
ratio of 1:1:1:1 in the H-NMR spectra of 1a–c indi-
3
cated a h -N,N%,N¦-P(2-py) coordination. Complexes
3
1
a–c gave only one phosphorus resonance in their
P-NMR spectra. The phosphorus chemical shift at l
3
1
−
4.5 ppm for 1c indicated no sign of P–W interaction.
Transparent purple crystals of P(2-
py) Mo(CO) ·CH Cl suitable for X-ray crystallo-
3
3
2
2
graphic
analysis
were
obtained
from
the
recrystallization of 1b in CH CN+CH Cl solution.
3
2
2
The ORTEP drawing of P(2-py) Mo(CO) ·CH Cl (Fig.
3
3
2
2
1) shows an almost perfect octahedral arrangement
around the Mo center, and the P(2-py) ligand is occu-
3
pying at the facial position of the octahedron through
the coordination of three pyridyl nitrogen atoms with
three NꢁMoꢁC angles of 175.85, 177.35, and 177.12°
Fig. 1. ORTEP drawing of P(2-py) Mo(CO) ·CH Cl showing the
3
3
2
2
and three MoꢁN bonds of 2.279, 2.282 and 2.266 A
,
in
atom-labeling scheme used. Note that the CH Cl molecule has been
2
2
length (Table 2).
omitted for clarity.

266
C.-Y. Kuo et al. / Journal of Organometallic Chemistry 588 (1999) 260–267
−
1
The only infrared wCO band at 2037 and 2148 cm
a and 3b, respectively, was very close to that of free
CO, and was higher in energy than those found for 1a,
b, 2a, and 2b. Apparently, these high CO stretching
for
3
1
frequencies were attributed to the coordination of two
+
NO ligands. Thus, an expected weak MꢁCO interac-
tion could facilitate the loss of CO in the presence of a
suitable coordinating ligand. In addition to the CO
stretching bands, two strong NO stretching bands at
−
1
−1
1839, 1738 cm
and 1844, 1785 cm
for 3a and 3b,
respectively, were typical for cis dinitrosyl complexes
with linear MꢁNꢁO bonding modes [17,18]. As implied
in the infrared spectral data, complexes 3a and 3b
possessed a characteristic feature of strong CO lability
when dissolving in donor solvents. Presumably, the loss
of CO generated
a
16-electron species, [P(2-
Fig.
2.
ORTEP
drawing
of
[P(2-py) Mo(CH CH CN)-
3 3 2
2
+
py) M(NO) ] ; the metal–anion interaction, there-
3
2
(NO) ](BF ) ·CH NO showing the atom-labeling scheme used. Note
that CH NO and BF4 have been omitted for clarity.
3 2
2
4 2
3
2
−
fore, became possible without the presence of
coordinating solvent. Many examples of organometallic
−
complexes of weakly coordinating anions, e.g. BF ,
4
−
6
−
6
−
6
PF , AsF and SbF , have been reported [19,20].
hydes, the [P(2-py) M(NO) ](BF ) –crotonaldehyde ad-
3
2
4 2
However, the infrared absorption bands of w at 1026
BF
ducts 4c (M=Mo) and 5c, (M=W) as well as [P(2-
py) W(NO) ](BF ) –benzaldehyde adduct 5d can be
−
1
and 1030 cm for 3a and 3b, respectively, indicated no
3
2
4 2
−
asymmetric broadening of the BF . Moreover, subse-
4
spectroscopically analyzed by NMR. Attempts to iso-
late these aldehyde adducts failed, probably because the
relative basicities of these aldehydes were not strong
enough, as can be seen in the isolated [P(2-
py) M(NO) ](BF ) –nitrile adducts 4a–b and 5a–b.
1
9
quent F-NMR studies for 3b showing two equivalent
BF4 anions (l −151.7 ppm) at room temperature
−
suggested no direct MꢁFꢁBF interaction [10]. Appar-
3
−
ently, the hard BF4 anions in 3a and 3b did not bind
3
2
4 2
to soft metal centers in the presence of coordinating
solvents.
3
.4. Lewis acidity and reacti6ity of [P(2-
The CO lability in complexes 3a and 3b enables the
isolation
py) W(CO)(NO) ](BF ) (3b)
3
2
4 2
of
a
series
of
complexes,
[P(2-
py) M(L)(NO) ](BF ) (L=nitriles, aldehydes). At am-
3
2
4 2
Organometallic Lewis acids are of great importance
in the catalysis of carbonꢁcarbon bond formation reac-
tions because the steric bulk of the supporting ligands
bient temperature, the facile CO loss of 3a and 3b in the
presence of nitriles resulted in the formation of com-
plexes [P(2-py) M(CH CN)(NO) ](BF ) (4a, M=Mo;
3
3
2
4 2
5
a, M=W) and [P(2-py) M(CH CH CN)(NO) ](BF )
3
3
2
2
4 2
(
4b, M=Mo; 5b, M=W). A total conversion of 4a
Table 3
and 5a to 4b and 5b can be accomplished within hours
in the presence of a stoichiometric amount of CH CN.
Selected bond distances (A
,
)
and angles (°) for [P(2-
py) Mo(CH CH CN)(NO) ](BF ) ·CH NO
3
3
2
2
4 2
3
2
3
Transparent green crystals of [P(2-py) Mo(CH -
3
3
Bond distances
MoꢁN(1)
MoꢁN(3)
CH CN)(NO) ](BF ) ·CH NO suitable for X-ray crys-
2
2
4 2
3
2
1.820(9)
2.149(8)
2.206(8)
1.155(12)
1.112(13)
1.59(3)
MoꢁN(2)
MoꢁN(4)
MoꢁN(6)
N(2)ꢁO(2)
C(1)ꢁC(2)
1.819(9)
2.202(9)
2.160(8)
1.147(13)
1.464(16)
tallographic analysis were obtained from the recrystal-
lization of 3a in CH CH CN/CH NO (1:1) solutions.
MoꢁN(5)
3
2
3
2
N(1)ꢁO(1)
N(3)ꢁC(1)
C(2)ꢁC(3)
The ORTEP drawing of [P(2-py) Mo(CH CH CN)-
3
3
2
(
NO) ](BF ) ·CH NO (Fig. 2) shows an almost perfect
2 4 2 3 2
octahedral arrangement around the Mo center, and the
P(2-py)3 ligand occupies the facial position of the
octahedron through the coordination of three pyridyl
nitrogen atoms. The almost linear MoꢁNꢁO arrange-
Bond angles
N(1)ꢁMoꢁN(2)
N(1)ꢁMoꢁN(4)
N(1)ꢁMoꢁN(6)
N(2)ꢁMoꢁN(4)
N(2)ꢁMoꢁN(6)
N(3)ꢁMoꢁN(5)
N(4)ꢁMoꢁN(5)
N(5)ꢁMoꢁN(6)
MoꢁN(2)ꢁO(2)
90.6(5)
89.1(4)
93.1(3)
178.1(3)
94.0(4)
85.8(3)
85.9(3)
86.2(3)
178.5(9)
N(1)ꢁMoꢁN(3)
N(1)ꢁMoꢁN(5)
N(2)ꢁMoꢁN(3)
N(2)ꢁMoꢁN(5)
N(3)ꢁMoꢁN(4)
N(3)ꢁMoꢁN(6)
N(4)ꢁMoꢁN(6)
MoꢁN(1)ꢁO(1)
MoꢁN(3)ꢁC(1)
94.3(4)
175.0(4)
92.9(4)
94.4(4)
85.2(3)
169.8(3)
87.9(3)
177.0(10)
178.5(9)
ment with the angles MꢁNꢁO of 175.0 and 177.0°
+
(
Table 3) indicates the two NO ligands are cis to each
other.
A similar chemistry has also been observed when 3a
and 3b were treated with Lewis basic organic carbonyl
compounds. In the presence of excess amounts of alde-

C.-Y. Kuo et al. / Journal of Organometallic Chemistry 588 (1999) 260–267
267
CH NO (23 pages). Ordering information is given on
3
2
any current masthead page.
Acknowledgements
Financial supports from the National Science Coun-
cil (NSC88-2113-M-194-018) and National Chung
Cheng University are gratefully acknowledged.
References
[
[
1] W.C. Davies, F.G. Mann, J. Chem. Soc. (1944) 276.
2] J.E. Parker, B.E. Wagner, R.H. Holm, J. Am. Chem. Soc. 92
Scheme 1.
(
1970) 3500.
and the electronic character of the metals can offer
influential effects on the rate and selectivity. The Lewis
acidities of complexes 3a and 3b are reflected in their
facile formation of nitrile (4a, 4b, 5a, 5b) and aldehyde
adducts (4c, 5c, 5d). The method developed by Childs et
al. [21a] and Hersh and co-workers [21b] took the
[3] C.J.L. Lock, M.A. Turner, Acta. Cryst. Sect. C 43 (1987) 2096.
[4] Y. Xie, B.R. James, J. Organomet. Chem. 417 (1991) 277.
5] (a) Y. Xie, C.-L. Lee, Y. Yang, S.J. Rettig, B.R. James, Can. J.
Chem. 70 (1992) 751. (b) R.P. Schutte. Ph.D. Dissertation,
University of British Columbia, 1995.
6] (a) K. Kurtev, D. Ribola, R.A. Jones, D.J. Cole-Hamulton and
G.J. Wilkinson, J. Chem. Soc. Dalton Trans. (1980) 55. (b) I.R.
baird, M.B. Smith, B.R. James, Inorg. Chim. Acta. 235 (1995)
[
[
1
H-NMR chemical shift differences of the 3-position
2
91, and references therein.
hydrogen of crotonaldehyde before and after coordi-
nated to a Lewis acid as a relative scale to determine
the acid strength. In our system, the complexation of
crotonaldehyde provided downfield shifts of Dl 1.01
ppm and Dl 1.18 ppm for 3a and 3b, respectively, and
the acidities of 3a and 3b were found to be comparable
to those of TiCl (Dl 1.03 ppm) and BF (Dl 1.17 ppm)
[
7] (a) A.J. Deeming, M.B. Smith, J. Chem. Soc. Chem. Commun.
(
(
1993) 844. (b) L.Y. Xie, B.R. James, Inorg. Chim. Acta. 217
1994) 209.
[8] (a) R.K. Boggess, D.A. Zatko, J. Coord. Chem. 4 (1975) 217. (b)
F.R. Keene, M.R. Snow, P.J. Stephenson, E.R.T. Tiekink, In-
org. Chem. 27 (1988) 2040. (c) P.S. Moritz, A.A. Diamantis,
F.R. Keene, M.R. Snow, E.R. T. Tiekink, Aust. J. Chem. 41
4
3
(
1988) 1353. (d) R. Gregorzik, J. Wirbser, H. Vahrenkamp,
and AlCl (Dl 1.23 ppm), respectively. Accordingly, we
3
Chem. Ber. 125 (1992) 1575. (e) R.P. Schutte, S.J. Rettig, B. R.
James, Can. J. Chem. 74 (1996) 2064.
looked into the study of Lewis acid reactivity of com-
plex 3b for the classical Diels–Alder catalysis. As indi-
cated in Scheme 1, complex 3b has shown potential
activity in promoting the cycloaddition reaction of cy-
clohexadiene and methyl vinyl ketone. With a loading
of 0.3 mol% of 3b, the cycloaddition reactions provided
an average of 94% conversion with a 99% endo-selectiv-
ity, while the corresponding thermal reaction only af-
forded a less than 5% conversion at 0°C. An average
[9] (a) R.K. Boggess, D.A. Zatko, Inorg. Nucl. Chem. Lett. 12
(
6
1976) 7. (b) R.K. Boggess, D.A. Zatko, Inorg. Chem. 15 (1976)
26. (c) R.A. Kenneth, P.A. Anderson, T. Astley, I.M. Atkinson,
J.M. Charnock, C.D. Garner, J.M. Gulbis, T.W. Hambley, M.A.
Hitchman, F.R. Keene, E.R.T. Tiekink, J. Chem. Soc. Dalton
Trans. (1997) 519.
[10] J.W. Faller, Y. Ma, J. Am. Chem. Soc. 113 (1991) 1579.
11] J.W. Faller, L.-L. Gundersen, Tetrahedron Lett. 34 (1993) 2275.
12] (a) E. Lindner, H. Rauleder, P. Wegner, Z. Naturforsch. Teil B
[
[
3
9 (1984) 1224. (b) G.R. Newkome, Chem. Rev. 93 (1993) 2067,
83% isolated yield of the Diels–Alder adduct was ob-
and references therein.
tained when the reaction mixtures were purified by
column chromatography.
[13] D.P. Tate, W.R. Knipple, J.M. Augl, Inorg. Chem. 1 (1962) 433.
[14] For detailed references, see supplementary material of crystallo-
graphic analyses.
The polydiene is often observed as a potential side-
product of Lewis acid-catalyzed Diels–Alder reactions.
However, at a reaction temperature of 0°C, no poly-
meric materials were observed in the NMR spectro-
scopic analysis nor insoluble precipitates formed during
the course of 3b-catalyzed Diels–Alder reactions of
cyclohexadiene and methyl vinyl ketone. The reactivi-
ties, kinetic and mechanistic insights of the catalysis will
be subjected to further investigation.
[
15] E.J. Gabe, Y. Le Page, J.-P. Charland, F.L. Lee, P.S. White, J.
Appl. Cryst. 22 (1989) 384.
[
16] (a) M. Green, S.H. Taylor, J. Chem. Soc. Dalton, Trans. (1972)
2629. (b) A. Sen, R. Thomas, Organometallics 1 (1982) 1251.
[17] R.P. Stewart Jr., G.T. Moore, Inorg. Chem. 14 (1975) 2699.
[
18] (a) J.H. enemark, R.D. Feltham, Coord. Chem. Rev., 13 (1974)
29. (b) T.W. Hawkins, M.B. Hall, Inorg. Chem. 19 (1980) 1735.
3
[
19] W. Beck, K. S u¨ nkel, Chem. Rev. 88 (1988) 1405, and references
therein.
[20] (a) W.H. Hersh, J. Am. Chem. Soc. 107 (1985) 4599. (b) R.V.
Honeychuck, P.V. Bonnesen, J. Farahi, W.H. Hersh, J. Org.
Chem. 52 (1987) 5293. (c) P.V. Bonnesen, C.L. Puckett, R.V.
Honeychuck, W.H. Hersh, J. Am. Chem. Soc. 111 (1989) 6070.
4. Supplementary information
(
5
d) S. Sato, I. Matsuda, Y. Izumi, Terahedron Lett. 27 (1986)
517.
Tables of crystal data, complete bond angles and
distances, atomic coordinates, and equivalent displace-
ment coefficients for P(2-py) Mo(CO) ·CH Cl (17
[
21] (a) R.F. Childs, D.L. Mulholland, A. Nixon, Can. J. Chem. 60
(1982) 801. (b) P.V. Bonnesen, C.L. Puckett, R.V. Honeychuck,
W.H. Hersh, J. Am. Chem. Soc. 111 (1989) 6070.
3
3
2
2
pages) and [P(2-py) Mo(CH CH CN)(NO) ](BF ) ·
3
3
2
2
4 2