Mixed P-N and As-N Bis-Ylide Pd Complexes
Organometallics, Vol. 25, No. 19, 2006 4663
exclusion of light and then filtered over Celite. The clear deep
yellow solution was evaporated to dryness, and the oily residue
was treated with Et2O (50 mL) and continuous stirring, giving 4 as
a yellow solid. This solid was filtered, washed with additional Et2O
(50 mL), and dried in vacuo. Yield: 1.102 g (99% yield). The
characterization of 4 by NMR showed the presence of a mixture
fragments show in these complexes the same conformational
preferences as those characterized in pure P or N bis-ylide
complexes. The mixed bis-ylides and their corresponding
complexes have been studied by means of DFT calculations
and by Bader analysis of electron density. As in pure P and N
bis-ylides, the 1,4-P‚‚‚O and 1,6-CH‚‚‚OdC intramolecular
interactions were characterized by localization of their corre-
sponding bond and ring critical points. In addition, we have
characterized a new 1,4-As‚‚‚O intramolecular interaction, which
is very similar in nature to the previously determined 1,4-P‚‚‚
O moderate electrostatic-type interaction. Both types of interac-
tions (1,4-E‚‚‚O and 1,6-CH‚‚‚OdC) take place simultaneously
in cisoid-cisoid isomers 2cc and 15cc, playing a key role in the
higher stabilization of these isomers. Moreover, the cisoid-cisoid
conformational preferences of the free mixed PN and AsN bis-
ylides are transferred to the complexes, as was the case for pure
P and N bis-ylides. Thus, it seems clear that the two types of
interactions operate in a cooperative way. The reactivity of the
complexes containing the [Pd{Ph3PC(H)C(O)C(H)NC5H5}] unit
shows striking differences from the analogous [Pd{Ph3PC(H)C-
(O)C(H)PPh3}] unit, probably because of a combination of steric
and electronic effects. For instance, the ortho-palladation of the
bis-ylide is only achieved by refluxing of the bis-ylide com-
plexes in the presence of bulky ligands. The ortho-platination
of the mixed bis-ylide is, however, easily achieved by direct
reaction of PtCl2 with the mixed salt [H5C5NCH2C(O)C(H)d
PPh3]Cl.
1
of two isomers in 2.25/1 molar ratio. H NMR (CD2Cl2, δ): 3.97
(s, br, C(H)P, both isomers), 5.78 (s, br, C(H)N, minor isomer),
5.99 (s, br, C(H)N, major isomer), 7.51-7.79 (m, PPh3 + H3(py),
both isomers), 8.26 (s, br, H4, py, both isomers), 8.86 (s, br, H2,
py, minor isomer), 8.95 (s, br, H2, py, major isomer). 31P{1H} NMR
(CD2Cl2, δ): 24.19 (minor isomer), 23.74 (major isomer).
Synthesis of [PdCl(PPh3){Ph3PC(H)C(O)C(H)NC5H5}]ClO4
(6). To a suspension of 3 (0.200 g, 0.157 mmol) in CH2Cl2 (20
mL) was added PPh3 (0.082 g, 0.314 mmol). The initial yellow
suspension dissolved in a few seconds, but the stirring was
maintanined for 30 min at room temperature. After the reaction
time, the resulting yellow solution was evaporated to dryness and
the residue was treated with Et2O, giving 6 as a yellow solid. This
solid was filtered, washed with Et2O (10 mL), and dried in vacuo.
Yield: 0.230 g (81%). 1H NMR (CD2Cl2, δ): 4.22, (ddd, 1H,
2
3
4
C(H)P, JPH ) 6.4, JPH ) 9.9, JHH ) 0.9 Hz), 5.99 (s, br, 1H,
3
C(H)N), 7.05 (t, 2H, H3, py, JHH ) 7.2 Hz), 7.19-7.23 (m, 6H,
Hm, PPh3), 7.28-7.32 (m, 3H, Hp, PPh3), 7.35-7.41 (m, 6H, Ho,
PPh3), 7.44-7.52 (m, 6H, Hm, PPh3), 7.54-7.61 (m, 3H, Hp, PPh3),
7.77 (t, 1H, H4, py, 3JHH ) 7.2 Hz), 7.80-7.87 (m, 6H, Ho, PPh3),
3
4
8.27 (dd, 2H, H2, py, JHH ) 5.9, JHH ) 1.2 Hz). 31P{1H} NMR
(CD2Cl2, δ): 23.68 (d, 1P, Pd-PPh3, 3JPP ) 4.7 Hz), 26.30 (d, 1P,
C(H)PPh3).
Synthesis of [Ph3AsdC(H)C(O)CH2Br] (14). To a solution of
Na2CO3 (0.233 g, 2.2 mmol) in H2O (15 mL) was added rapidly a
solution of 13 (2.300 g, 4.40 mmol) in MeOH (15 mL). A white
solid (14) precipitated almost instantaneously. The mixture was
diluted with additional water (30 mL) and further stirred at room
temperature for 15 min. After the reaction time, the ylide 14 was
filtered, washed with cold water (10 mL), and dried in vacuo.
Yield: 1.440 g (74%). 1H NMR (CDCl3, δ): 3.87 (s, 2H, CH2Br),
Experimental Section
Safety Note. Caution! Perchlorate salts of metal complexes with
organic ligands are potentially explosive. Only small amounts of
these materials should be prepared, and they should be handled
with great caution.34
Synthesis of [Ph3PdC(H)C(O)CH2NC5H5]Cl (2a). A clear
solution of [Ph3PdC(H)C(O)CH2Cl] (3.000 g, 8.5 mmol) and
pyridine (6.8 mL, 85 mmol) in THF (15 mL) was refluxed for 30
h. After the reaction time, the solid (2a) was filtered, washed with
cold THF (20 mL) and Et2O (50 mL), and dried by suction. Yield:
3
4.44 (s, 1H, AsdCH), 7.56 (t, 6H, Hm, AsPh3, JHH ) 7.6 Hz),
3
7.65 (t, 3H, Hp, AsPh3, JHH ) 7.2 Hz), 7.70 (d, 6H, Ho, AsPh3,
3JHH ) 7.6 Hz).
3.110 g (85%). 1H NMR (CD2Cl2, δ): 4.26 (d, 1H, C(H)P, 2JPH
)
Synthesis of [Ph3AsdC(H)C(O)CH2NC5H5]Br (15). Com-
pound 15 was prepared by following a synthetic procedure similar
to that reported for 2a. Yield: 0.566 g (60% yield). 1H NMR (CD2-
Cl2, δ): 5.56 (s, vbr, 1H, C(H)As), 6.08 (s, 2H, CH2N), 7.66 (t,
22.0 Hz), 5.66 (s, 2H, CH2N), 7.45-7.67 (m, 15H, PPh3), 7.92 (t,
3
3
2H, H3, py, JHH ) 6.8 Hz), 8.31 (t, 1H, H4, py, JHH ) 7.7 Hz),
3
9.18 (d, 2H, H2, py, JHH ) 6.0 Hz). 31P{1H} NMR (CD2Cl2, δ):
3
3
6H, Hm, AsPh3, JHH ) 7.0), 7.73 (t, 3H, Hp, AsPh3, JHH ) 7.2),
15.44.
3
3
7.84 (d, 6H, Ho, AsPh3, JHH ) 7.2), 7.89 (t, 2H, H3, py, JHH
6.8), 8.43 (t, 1H, H4, py, 3JHH ) 7.6), 9.61 (d, 2H, H2, py, 3JHH
6.0).
)
)
Synthesis of cis-[Cl2Pd{Ph3PC(H)C(O)C(H)NC5H5}] (3).
Method A. To a suspension of 1 (0.313 g, 0.67 mmol) in CH2Cl2
(20 mL) was added Pd(OAc)2 (0.150 g, 0.67 mmol). The resulting
red-orange solution was stirred at room temperature for 30 min.
During this time a deep yellow solid (3) precipitated, which was
filtered, washed with additional CH2Cl2 (10 mL) and Et2O (50 mL),
and dried by suction. Yield: 0.298 g (78%).
Synthesis of cis-[Cl2Pd{Ph3AsC(H)C(O)C(H)NC5H5}] (16). To
a solution of 15 (0.200 g, 0.38 mmol) in MeOH (20 mL) were
added NEt3 (54 µL, 0.39 mmol) and PdCl2(NCMe)2 (0.100 g, 0.38
mmol) at room temperature. A light brown solid (16) precipitated
almost instantaneously. This solid was filtered, washed with MeOH
(5 mL) and Et2O (25 mL), and dried in vacuo. Yield: 0.177 g
Method B. To a solution of 2a (0.300 g, 0.69 mmol) in MeOH
(15 mL) were added NEt3 (97 µL, 0.69 mmol) and PdCl2(NCMe)2
(0.180 g, 0.69 mmol) at room temperature. A deep yellow solid
(3) precipitated almost instantaneously. This solid was filtered,
washed with MeOH (10 mL) and Et2O (25 mL), and dried in vacuo.
1
(75%). H NMR (DMSO-d6, δ): 4.54 (s, br, 1H, CHAs), 5.89 (s,
br, 1H, CHN), 7.59-7.86 (m, 15H, PPh3), 7.99 (t, 2H, H3, py, 3JHH
3
) 6.9), 8.45 (t, 1H, H4, py, JHH ) 7.2), 9.07 (s, br, 2H, H2, py).
1
Yield: 0.381 g (96%). H NMR (DMSO-d6, δ): 4.22 (s, br, 1H,
Synthesis of [PdCl(C6H4-2-PPh2C(H)C(O)CH2NC5H5)(PPh3)]-
ClO4 (18). A suspension of 6 (0.200 g, 0.222 mmol) in dry NCMe
(20 mL) was refluxed for 24 h. At this point, some decomposition
(black Pd0) is evident. Once it was cooled, the orange-brown
suspension was filtered over Celite and the resulting solution was
evaporated to dryness. The residue was suspended in MeOH (15
mL), and the suspension was stirred at room temperature for 12 h.
A small fraction of an insoluble solid (mainly starting product 6)
was filtered and discarded. The alcoholic solution was evaporated
to dryness, and the residue was treated with Et2O (20 mL) and
C(H)P), 5.73 (s, br, 1H, C(H)N), 7.61-7.63 (m, 6H, Hm, PPh3),
7.71-7.76 (m, 3H, Hp, PPh3), 7.78-7.90 (m, br, 6H, Ho, PPh3),
7.98 (t, 2H, H3, py, 3JHH ) 7.0 Hz), 8.45 (t, 1H, H4, py, 3JHH ) 7.7
Hz), 9.01 (d, 2H, H2, py, 3JHH ) 6.0 Hz). 31P{1H} NMR (DMSO-
d6, δ): 23.82.
Synthesis of [Pd(µ-Cl){Ph3PC(H)C(O)C(H)NC5H5}]2(ClO4)2
(4). To a suspension of 3 (1.000 g, 1.746 mmol) in CH2Cl2 (40
mL) was added AgClO4 (0.362 g, 1.75 mmol). The resulting yellow
suspension was stirred at room temperature for 30 min with
Serrano, Elena
