Pd(II) Bis(pyrazolyl)methane Complexes
Organometallics, Vol. 18, No. 23, 1999 4763
Sch em e 1
thirds complete (4.00 g collected, 5.67 g expected), the volatiles
were distilled off under reduced pressure. The resulting solid
was purified by column chromatography on silica using ethyl
acetate as an eluent and then recrystallized from hexanes (10
Ph2C), 34.0 (s, Me3C), 31.2 (q, J CH ) 127, Me3C).25 Anal. Calcd
for C27H32N4Cl2Pd‚1.5CH2Cl2: C, 47.71; H, 4.93; N, 7.81.
Found: C, 47.77; H, 4.80; N, 7.82.
{P h 2C(p z)2}P d Cl2 (2). A solution of (CH3CN)2PdCl2 (0.52
g, 2.0 mmol) and Ph2C(pz)2 (0.61 g, 2.0 mmol) in CH2Cl2 (40
mL) was stirred for 3 h at 23 °C in air. The mixture was
filtered, and CH2Cl2 was removed from the filtrate under
vacuum. The resulting orange solid was recrystallized from
CH2Cl2/Et2O at -50 °C yielding orange crystals (0.50 g, 52%).
The presence of CH2Cl2 of crystallization was established by
1H NMR and X-ray crystallography. 1H NMR (CD2Cl2): δ 8.39
(dd, J ) 1.1, 2.5, 2H, 3-pz), 7.68 (br t, 2H, p-Ph), 7.57 (br m,
4H, m-Ph), 7.42 (dd, 1.3, 3.2, 2H, 5-pz), 6.48 (t, J ) 2.9, 2H,
4-pz).26 1H NMR (-50 °C, CD2Cl2): δ 8.28 (dd, J ) 0.4, 2.2,
2H, 3-pz), 7.71-7.63 (m, 4H; Ha, Hb, Hc, Hf), 7.55 (t, J ) 7,
2H, He), 7.43 (dd, J ) 0.7, 2.9, 2H, 5-pz), 7.4 (m, 1H, Hb′), 6.57
(d, 1H, Ha′), 6.48 (t, J ) 2.7, 2H, 4-pz), 6.18 (m, 2H, Hd). 1H
NMR (CDCl2CDCl2, 90 °C): δ 8.45 (br, 2H, 3-pz), 7.63 (t, J )
7, 2H, p-Ph), 7.52 (t, J ) 8, 4H, m-Ph), 7.34 (dd, J ) 0.7, 2.9;
2H, 5-pz), 6.66 (br d, 4H, o-Ph), 6.44 (t, J ) 2.6, 2H, 4-pz). 13C
1
mL) to yield pale orange crystals (9.1 g, 25%). H NMR (CD2-
Cl2): δ 7.39-7.29 (m, 6H, Ph), 7.12-7.09 (m, 6H, Ph and 5-pz),
t
6.12 (d, J ) 2.2, 2H, 4-pz), 1.28 (s, 18H, Bu). 13C NMR (CD2-
Cl2): δ 162.9 (s, 3-pz), 141.9 (s, ipso-Ph), 132.9 (d, J CH ) 189,
5-pz), 129.7 (d, J CH ) 156, m-Ph), 129.0 (d, J CH ) 162, p-Ph),
128.0 (d, J CH ) 156, o-Ph), 101.7 (d, J CH ) 174, 4-pz), 87.3 (s,
Ph2C), 32.5 (s, Me3C), 30.5 (q, J CH ) 124, Me3C). Anal. Calcd
for C27H32N4: C, 78.59; H, 7.83; N, 13.58. Found: C, 78.35; H,
8.06; N, 13.41.
P h 2C(p z)2. A mixture of Ph2C(OMe)2 (9.7 g, 44 mmol),
pyrazole (6.0 g, 88 mmol), and p-TsOH‚H2O (0.04 g, 0.2 mmol)
was heated so that the evolved MeOH distilled slowly. When
the MeOH evolution was half complete (1.4 g collected, 2.8
expected), the mixture was allowed to cool, affording a white
solid and clear liquid. The solid was separated, washed with
hexanes (10 mL), and recrystallized from toluene (10 mL),
1
yielding white needles (2.5 g, 19%). H NMR (CD2Cl2): δ 7.65
NMR (CD2Cl2): δ 146.0 (d, J CH ) 197, 3-pz), 136.6 (d, J CH
)
(d, J ) 1.7, 2H, 3-pz), 7.52 (d, J ) 2.7, 2H, 5-pz), 7.43-7.33
(m, 6H, Ph), 7.06-7.03 (m, 4H, Ph), 6.31 (dd, J ) 1.7, 2.7, 2H,
196, 5-pz), 132 (v br, Ph), 129.9 (br d, J CH ) 168, p-Ph), 127 (v
br, Ph), 106.9 (d, J CH ) 183, 4-pz).27 Anal. Calcd for C19H16N4-
Cl2Pd‚0.6CH2Cl2: C, 44.53; H, 3.29; N, 10.60. Found: C, 44.71;
H, 3.41; N, 10.61.
4-pz). 13C NMR (CD2Cl2): δ 140.9 (s, ipso-Ph), 140.4 (d, J CH
)
187, 3-pz), 132.9 (d, J CH ) 190, 5-pz), 129.6 (d, J CH ) 160,
m-Ph), 129.4 (d, J CH ) 161, p-Ph), 128.2 (d, J CH ) 161, o-Ph),
105.6 (d, J CH ) 175, 4-pz), 87.9 (s, Ph2C). Anal. Calcd for
{Me2C(p z)2}P d Me2 (3). Me2C(pz)2PdMe2 was prepared
using the procedure reported by Canty (white crystalline solid,
0.65 g, 65%).7 1H NMR (CD2Cl2): δ 7.71 (dd, J ) 0.7, 2.9, 2H,
5-pz), 7.70 (d, J ) 1.8, 2H, 3-pz), 6.33 (dd, J ) 2.0, 2.5, 2H,
4-pz), 2.64 (br s, 6H, Me2C), 0.11 (s, 6H, PdMe2). 13C NMR (CD2-
Cl2, -60 °C): δ 140.5 (d, J CH ) 190, 3-pz), 127.7 (d, J CH ) 190,
C
19H16N4: C, 75.96; H, 5.38; N, 18.66. Found: C, 75.69; H,
5.54; N, 18.40.
{P h 2C(3-tBu -p z)2}P d Cl2 (1). A solution of (CH3CN)2PdCl2
(2.08 g, 8.00 mmol) and Ph2C(3-tBu-pz)2 (3.37 g, 8.16 mmol)
in CH2Cl2 (160 mL) was stirred for 2 h at 23 °C in air. The
mixture was filtered, and the solvent was removed from the
filtrate under vacuum. The resulting orange solid was recrys-
tallized from CH2Cl2 at -30 °C, yielding orange crystals (2.54
g, 54%). The presence of 1.5 equiv of CH2Cl2 of crystallization
was established by 1H NMR and X-ray crystallography. 1H
NMR (CD2Cl2): δ 7.64 (t, J ) 7, 2H, p-Ph), 7.56 (t, J ) 7, 2H,
m-Ph), 7.5 (br, 2H, m-Ph), 7.34 (d, J ) 3, 2H, 5-pz), 6.98 (m,
5-pz), 105.5 (d, J CH ) 180, 4-pz), 75.3 (s, Me2C), 29.7 (q, J CH
)
132, Me2C), 25.4 (q, J CH ) 130, Me2C), -10.5 (q, J CH ) 126,
PdMe2).
Gen er a tion of [{Me2C(p z)2}P d Me(NMe2P h )][B(C6F 5)4]
(4a ). An NMR tube was charged with {Me2C(pz)2}PdMe2 (9.6
mg, 31 µmol) and [HNMe2Ph][B(C6F5)4] (24.7 mg, 30.8 µmol),
and CD2Cl2 was added by vacuum transfer at -78 °C. The
resulting solution was kept at -78 °C prior to NMR analysis.
4a was the only organometallic product observed. 1H NMR
(CD2Cl2, -60 °C): δ 7.81 (d, J ) 7.9, 2H, o-Ph), 7.74 (d, J )
2.9, 1H, 5-pz), 7.63 (d, J ) 2.9, 1H, 5′-pz), 7.61 (d, J ) 2.2, 1H,
3-pz), 7.47 (t, J ) 8.0, 2H, m-Ph), 7.35 (t, J ) 7.6, 1H, p-Ph),
6.39 (t, J ) 2.7, 1H, 4-pz), 6.01 (t, J ) 2.5, 1H, 4′-pz), 5.30 (d,
J ) 2.2, 1H, 3′-pz), 3.23 (s, 6H, NMe2), 2.85 (s, 3H, Meax), 2.41
(s, 3H, Meeq), 1.10 (s, 3H, PdMe). 13C NMR (CD2Cl2, -60 °C):
t
2H, o-Ph), 6.32 (d, J ) 3, 2H, 4-pz), 1.71 (s, 18H, Bu); the
other o-Ph resonance is broadened into the baseline. 1H NMR
(CD2Cl2, -50 °C): δ 7.64-7.52 (m, 5H; Hb, Hc, He, Hf), 7.44-
7.37 (m, 2H; Ha, Hb′), 7.35 (d, J ) 3.2, 2H, 5-pz), 6.95 (m, 2H;
Hd), 6.71 (br d, 1H, Ha′), 6.30 (d, J ) 3.2, 2H, 4-pz), 1.64 (s,
18H, tBu). 1H NMR (CDCl2CDCl2, 90 °C): δ 7.61-7.53 (m, 4H,
Ph), 7.48 (br t, 2H, m-Ph), 7.27 (d, J ) 3, 2H, 5-pz), 7.11 (br d,
2H, o-Ph), 6.97 (m, 2H, o-Ph), 6.27 (d, J ) 3, 2H, 4-pz), 1.73
t
(s, 18H, Bu). 13C NMR (CD2Cl2): δ 169.4 (s, 3-pz), 138.5 (s,
(25) The other o-Ph signals are broadened into the baseline.
(26) The pyrazolyl H3 and H5 1H NMR resonances were assigned
on the basis of a NOESY correlation between H5 and Ha. The o-Ph
signal is broadened into the baseline at 20 °C.
ipso-Ph), 136.3 (d, J CH ) 193, 5-pz), 136.0 (s, ipso-Ph), 132.6
(d, overlapping, m- or p-Ph), 132.5 (d, J CH ) 165, m- or p-Ph),
130.9 (d, J CH ) 163, m- or p-Ph), 129.7 (d, J CH ) 162, o-Ph),
129.3 (d, J CH ) 159, m-Ph), 105.9 (d, J CH ) 181, 4-pz), 91.9 (s,
(27) The ipso-Ph signals were not observed.