1814 Organometallics, Vol. 17, No. 9, 1998
van Belzen et al.
Rea ction s of 1 w ith Or ga n ic Ha lid es: Syn th esis of
P a lla d iu m (4-Alk yl/a r yl-1,2,3,4-tetr a k is(ca r bom eth oxy)-
1,3-bu ta d ien yl) Ha lid es (3-5). Meth od A. To a solution
of 80 mg of 1a (0.11 mmol) in dichloromethane was added an
excess of methyl iodide (1 mL, 16 mmol). This solution was
stirred for 48 h at room temperature and then filtered through
Celite filter aid (to remove the metallic palladium). The
solvent was subsequently removed in vacuo, and the product
was washed with diethyl ether (2 × 20 mL). The yield of 3a
was 79 mg (0.9 mmol, 81%).
various nitrogen ligands and their reaction with organic
halides and small molecules such as dihydrogen, carbon
monoxide, and carbon dioxide. On the basis of the
results, we have designed a catalytic cycle for the
synthesis of conjugated dienes from acetylenes.
A
preliminary report has been published.4g
Exp er im en ta l Section
Gen er a l. All reactions were performed in an atmosphere
of dry nitrogen using standard Schlenk techniques. All
solvents were distilled prior to use. 1H and 13C{1H} NMR
spectra were recorded on a Bruker AMX 300 spectrometer
(300.13 and 75.48 MHz, respectively) at room temperature
unless stated otherwise. Chemical shift values are in ppm
relative to TMS with high-frequency shifts assigned positive.
19F NMR data were collected on a Bruker AC 100 spectrometer
(94.20 MHz) relative to CFCl3. Exact mass determinations
were obtained on a Varian MAT 711 double-focusing mass
spectrometer and were performed by the Institute for Mass
Spectroscopy, University of Amsterdam. GC-MS data were
obtained using a HP 510 with a 80 mesh column of 12 m. The
osmometric determinations were performed on a Hewlett-
Packard 320B osmometer. Elemental analyses were carried
out by Dornis und Kolbe, Mikroanalytisches Laboratorium,
Mu¨lheim a.d. Ruhr, Germany. The starting materials phenyl-
bip,5 (p-tolyl)-bian,6 3,3′-dicarbomethoxy-2,2′-bipyridine (dcm-
The reactions with benzyl bromide were carried out in
acetonitrile. For the synthesis of 4b, the benzyl bromide was
removed by extracting the solution with pentane, since the
product was soluble in diethyl ether. This procedure gave
similar yields for 3b,d and 4b,d of 80-91%. Anal. Found
(Calcd) for C39H31N2O8IPd (3d ): C, 52.55 (52.69); H, 3.46 (3.51);
N, 3.20 (3.15). Other data have been compiled in the Results.
Meth od B. A solution of 75 mg of 1a (0.1 mmol) and 140
µL of benzyl bromide (1 mmol) in toluene was heated at 80 °C
for 3 h. The solvent was then removed in vacuo, the organic
products were extracted with diethyl ether (3 × 30 mL) and,
after evaporation of the solvent, analyzed by GC-MS and NMR.
Tr im er iza tion of 1,4-Dich lor o-2-bu tyn e: Syn th esis of
1-(1′-Ch lor oet h en yl)-1,2,3,4,5-p en t a k is(ch lor om et h yl)-
2,4-cyclop en ta d ien e (6). A solution of 15 mg of 1a (0.02
mmol) and 250 µL of 1,4-dichloro-2-butyne (2 mmol) in 10 mL
of toluene was heated at 80 °C for 3 h. The solution was
evaporated to dryness, yielding 6, a white sticky solid, in 82%
yield. 1H NMR (293 K, CDCl3): 5.68, 5.59 (d, 2H, J ) 2.9 Hz,
CH2d), 4.56 (s, 4H, 3,4-CH2Cl), 4.40, 4.25 (d, 2 × 2H, J ) 12.7
Hz, 2,5-CH2Cl), 4.09 (s, 2H, 1-CH2Cl). 13C NMR (293 K,
CDCl3): 144.8, 143.4 (2 × 2C, 2/5- and 3/4-CdC), 137.9 (1C,
ClCdCH2), 118.0 (1C, ClCdCH2), 68.5 (1C, Cquat), 43.9 (1C,
1-CH2Cl), 35.7, 35.6 (2 × 2C, 2/5- and 3/4-CH2Cl). Exact
mass: found m/z ) 365.904 (calcd 365.907).
Syn th esis of [(µ-3,3′-Dica r bom eth oxy-2,2′-bip yr id in e)-
P d (tcn e)]2 (7). A mixture of 200 mg of Pd(dba)2 (0.35 mmol),
100 mg of 3,3′-dicarbomethoxy-2,2′-bipyridine (0.36 mmol), and
45 mg (0.35 mmol) of tcne in 30 mL toluene was stirred for 3
h at room temperature. The suspension was filtered, and the
solid product was washed subsequently with toluene (50 mL)
and diethyl ether (5 × 25 mL). The product was dissolved in
dichloromethane and filtered over Celite filter aid. The solvent
was again removed in vacuo, yielding 151 mg (0.30 mmol, 85%)
of yellow product. Crystals of 7 were obtained from dichloro-
methane/hexane. Anal. Found (Calcd) for C20H12N6O4Pd: C,
47.54 (47.43); H, 2.45(2.39); N, 16.48(16.58). 1H NMR (293
K, CDCl3): 9.01 (d, 2H, J ) 4.5 Hz, H(6)), 8.55 (d, 2H, J ) 7.9
Hz, H(4)), 7.80 (dd, 2H, H(5)), 3.83 (s, 6H, CH3O). 13C NMR
(293 K, DMSO-d6): 165.4 (1C, CdO), 155.7 (2C, C(2)), 154.9
(2C, C(6)), 141.5 (2C, C(4)), 132.2 (2C, C(3)), 127.9 (2C, C(5)),
114.4 (4C, CN), 54.0 (2C, CH3O), 15.9 (2C, CdC).
Rea ction s of 1 w ith H2, CO, a n d CO2. All reactions were
carried out using 10 mL of a 0.01 M solution of 1a , 1b, or 1c
in dichloromethane. Hydrogen gas was bubbled through the
solution at room temperature for 2-15 min, and carbon dioxide
was bubbled through the solution for 1.5 h. In the case of
carbon monoxide, the solution was pressurized up to 50 bar
in an autoclave and stirred for 16 h. The solvent was
evaporated, and the organic products were extracted with
diethyl ether, which was dried and evaporated. The remaining
solids were analyzed by NMR, and the organic products were
analyzed by NMR and GC-MS.
Ca ta lytic Syn th esis of Con ju ga ted Dien es. Dim eth yl-
(2Z,4Z)-3,4-bis(car bom eth oxy)-2,5-dim eth yl-2,4-h exadien -
1,6-d ioa te (8a ). A solution of 15 mg of 1b (0.02 mmol), 245
µL of dmbd (2 mmol), 180 mg of Me4Sn (1 mmol), and 0.6 mL
of methyl iodide (10 mmol) in 10 mL of DMF was stirred for
16 h at 65 °C. The reaction mixture was dissolved in 100 mL
dichloromethane, washed with water (3 × 150 mL), and dried.
The solvent was removed by evaporation, after which a sticky
17
bpy),16 and Pd(dba)2 were prepared according to literature
procedures. Dimethyl-2-butynedioate (dmbd), methyl iodide,
tetracyanoethylene (tcne), tert-butylisonitrile, bipyridine, bi-
pyrimidine, and 1,3-diphenylphosphinopropane (dppp) were
obtained commercially and used without further purification.
Syn th esis of P a lla d a -2,3,4,5-tetr a k is(ca r bom eth oxy)-
cyclop en ta d ien es (1a -f) a n d P a lla d a -2,3,4,5-tetr a k is-
(tr iflu or om eth yl)cyclop en ta dien es (2a , 2b). Typ ica l P r o-
ced u r e for 1a . Meth od A. To a suspension of 0.50 g of
Pd(dba)2 (0.9 mmol) and 0.35 g of phenyl-bip (0.95 mmol) in
20 mL of acetone was added 0.3 mL of dmbd (2.4 mmol) at
room temperature. After 1 h, the solvent was removed in
vacuo and the product was washed with diethyl ether (2 × 20
mL). The brown product was dissolved in dichloromethane
and filtered over Celite filter aid in order to remove the
metallic palladium. The solvent was again removed in vacuo,
yielding 0.57 mg (0.77 mmol, 85%) of light-brown product.
Crystals of 1a were obtained by slow diffusion of pentane into
a dichloromethane solution of 1a at 4 °C; crystals of 1d were
obtained by slow evaporation of the solvent of a solution of 1d
in dichloromethane. Anal. Found (Calcd) for C38H30N2O8Pd
(1a ): C, 86.53 (87.12); H, 5.30 (5.06); N, 7.45 (7.82). Other
data are presented in the Results.
In the case of 2a and 2b, the mixture of Pd(dba)2 and
phenyl-bip was stirred overnight in an atmosphere of per-
fluoro-2-butyne. The yields of the compounds 1b-f, 2a , and
2b were 80-90%. Anal. Found (Calcd) for C26H24N2O12Pd
(1f): C, 46.94 (47.11); H, 3.75 (3.65); N, 4.28 (4.23). Anal.
Found (Calcd) for C34H18N2F12Pd (2a ): C, 51.64 (51.76); H, 2.39
(2.30); N, 3.59 (3.55).
The platinum analogue of 1a (1′a ) was prepared similarly
to 1a , starting from Pt(dba)2, by extending the reaction time
to 2 weeks. Complex 1′a was obtained in 88% yield as a dark
brown solid.
Meth od B. To a solution of 0.5 mg of (CH3CN)2Pd(dmbd)2
(1.1 mmol, prepared by method A) in 25 mL of dichloromethane
was added 0.4 mg of phenyl-bip (1.1 mmol). After 5 min of
stirring, the solvent was evaporated and the product was
washed with diethyl ether (2 × 20 mL) and air-dried, yielding
0.8 mg of 1a (1.0 mmol, 97%).
(16) Rebek, J .; Trend, J . E.; Wattley, R. V.; Chakravorti, S. J . Am.
Chem. Soc. 1979, 101, 4336.
(17) Rettig, M. F.; Maitlis, P. M. Inorg. Synth. 1977, 17, 134.