PCP-Type Pincer Complexes of Nickel
Organometallics, Vol. 27, No. 21, 2008 5731
of hexanes was left. Golden-brown crystals of 2 formed by keeping
25.90 (vt, vJPC ) 10.6 Hz, CH(CH3)2, 2C), 38.41 (vt, vJPC ) 10.6
Hz, CH2CH2P, 2C), 56.38 (t, 2JPC ) 10.1 Hz, CHNi, 1C), 98.44 (t,
2JPC ) 30.8 Hz, Ct CCH3, 1C) 115.74 (s, Ct CCH3, 1C). 31P{1H}
NMR (C6D6): 76.1. 31P{1H} NMR (CDCl3): 76.0. IR (KBr): 2100
cm-1 (µCt C). Anal. Calcd for C20H40NiP2: C, 59.88; H, 10.05.
Found: C, 60.12; H, 10.33.
1
the solution at -14 °C for 1 h (1.065 g, 37%). H NMR (C6D6):
3
v
0.97 (dvt, JHH ∼ JPH ) 5.8-6.6 Hz, CH(CH3)2, 6H), 1.13 (dvt,
v
v
3JHH ∼ JPH ) 6.6-6.8 Hz, CH(CH3)2, 6H), 1.46 (dvt, 3JHH ∼ JPH
) 7.5-7.7 Hz, CH(CH3)2, 12H), 1.00-1.70 (CH2CH2P, 8H), 1.78
(m, CHNi, 1H), 2.06-2.24 (CH(CH3)2, 4H). 1H{31P} NMR (C6D6):
3
3
0.97 (d, JHH ) 7.1 Hz, CH(CH3)2, 6H), 1.13 (d, JHH ) 7.0 Hz,
CH(CH3)2, 6H), 1.46 (d, 3JHH ) 7.1 Hz, CH(CH3)2, 12H). 13C{1H}
NMR (C6D6): 17.56 (s, CH(CH3)2, 2C), 18.61 (s, CH(CH3)2, 2C),
{(i-Pr2PCH2CH2)2CH}NiPh (6). PhMgBr (0.90 mL of a 1 M
solution in THF, 0.90 mmol) was added to a solution of 2 (0.400
g, 0.90 mmol) in toluene (5.0 mL), and the mixture was stirred
and refluxed for 1 h. The solvent was then evaporated, hexanes
(20 mL) were added, and the resultant suspension was filtered. The
filtrate was washed with degassed water (3 × 20 mL) and
evaporated to dryness to give complex 6 as a yellow-brown powder
(0.245 g, 62%). 1H NMR (C6D6): 0.87-1.05 (m, CH(CH3)2, 24H),
0.85-2.50 (CH(CH3)2, CH2CH2P, CHNi, 13H), 6.90-7.80 (Ph,
5H). 13C{1H} NMR (C6D6): 17.64 (s, CH(CH3)2, 2C), 17.79 (s,
CH(CH3)2, 2C), 18.53 (s, CH(CH3)2, 2C), 18.97 (s, CH(CH3)2, 2C),
22.84 (vt, vJPC ) 10.7 Hz, CH(CH3)2, 2C), 24.44 (vt, vJPC ) 10.1
v
v
19.36 (vt, JPC ) 2.8 Hz, CH(CH3)2, 2C), 19.94 (vt, JPC ) 1.7
v
Hz, CH(CH3)2, 2C), 22.12 (vt, JPC ) 10.3 Hz, CH2P, 2C), 23.38
v
v
(vt, JPC ) 10.7 Hz, CH(CH3)2, 2C), 25.46 (vt, JPC ) 9.7 Hz,
v
CH(CH3)2, 2C), 38.94 (vt, JPC ) 10.3 Hz, CH2CH2P, 2C), 52.30
(t, JPC ) 9.0 Hz, CHNi, 1C). 31P{1H} NMR (C6D6): 67.4. Anal.
2
Calcd for C17H37BrNiP2: C, 46.19; H, 8.44. Found: C, 45.97; H,
8.83.
{(i-Pr2PCH2)2C6H3}NiBr (3). The preparation of this complex
from Ni(cod)2 and the corresponding brominated ligand has already
been reported;6g we report here another synthetic pathway. i-Pr2PCH2-
C6H4CH2P(i-Pr)2 (0.500 g, 1.48 mmol) was added to a solution of
anhydrous NiBr2 (0.387 g, 1.77 mmol) and DMAP (0.180 g, 1.48
mmol) in ethanol (10 mL), and the reaction mixture was refluxed
for 1.5 h. The solvent was then evaporated to dryness, the Schlenk
was opened to air, and hexanes (40 mL) were added. The resultant
mixture was filtered in the air on a glass frit and the filtrate
v
Hz, CH(CH3)2, 2C), 25.84 (vt, JPC ) 10.7 Hz, CH2P, 2C), 37.98
(vt, vJPC ) 10.7 Hz, CH2CH2P, 2C), 56.81 (t, 2JPC ) 8.9 Hz, CHNi,
1C), 120.78 (s, Ph, 1C), 125.80 (s, Ph, 1C), 127.49 (s, Ph, 1C),
129.06 (s, Ph, 1C), 140.55 (s, Ph, 1C), 168.77 (t, 2JPC ) 24.0 Hz,
Ph (Cipso), 1C). 31P{1H} NMR (C6D6): 68.1. Anal. Calcd for
C23H42NiP2 · H2O: C, 60.42; H, 9.70. Found: C, 60.89; H, 9.73.
{(i-Pr2PCH2CH2)2CH}NiBu (7). Addition of n-BuLi (52 µL of
a 2.5 M solution in hexanes, 0.131 mmol) to a concentrated solution
of 2 (0.058 g, 0.131 mmol) in benzene-d6 (0.6 mL) resulted in the
instantaneous formation of the butyl species 7, as observed by NMR
spectroscopy. 1H NMR (C6D6): 0.50 (m, CH2(CH2)2CH3, 2H).
evaporated to give complex 3 as a yellow solid (0.281 g, 40%). 1H
3
NMR (CDCl3): 1.17 (dvt, JHH
∼
vJPH ) 6.7 -7.0 Hz,
CH(CH3)2,12H), 1.45 (dvt, 3JHH ∼ JPH ) 7.4-8.4 Hz, CH(CH3)2,
v
v
12H), 2.38 (m, CH(CH3)2, 4H), 3.08 (vt, JPH ) 3.7 Hz, PCH2,
4H), 6.91 (s, ArH, 3H). 13C{1H} NMR (CDCl3): 18.31 (s,
PCH(CH3)2, 4C), 19.12 (s, PCH(CH3)2, 4C), 24.01 (vt, vJPC ) 11.0
Hz, PCH(CH3)2, 4C), 32.83 (vt, vJPC ) 12.8 Hz, PCH2, 2C), 122.26
13C{1H} NMR (C6D6): 0.51 (t, JPC ) 19.0 Hz, CH2(CH2)2CH3,
2
1C), 14.46 (s, CH2(CH2)2CH3, 1C), 17.91 (s, CH(CH3)2, 2C), 18.74
(s, CH(CH3)2, 2C), 19.52 (vt, vJPC ) 3.4 Hz, CH(CH3)2, 2C), 20.00
v
v
v
(vt, JPC ) 9.0 Hz, ArH, 2C), 125.35 (s, ArH, 1C), 152.46 (t, JPC
(vt, JPC ) 2.7 Hz, CH(CH3)2, 2C), 23.74 (vt, JPC ) 9.5 Hz,
2
v
) 13.1 Hz, ArCH2, 2C), 159.13 (t, JPC )15.9 Hz, Aripso, 1C).
CH(CH3)2, 2C), 25.90 (vt, JPC ) 11.4 Hz, CH2P, 2C), 25.94 (vt,
31P{1H} NMR (CDCl3): 61.8 (s). Anal. Calcd for C20H35BrNiP2:
C, 50.46; H, 7.41. Found: C, 49.94; H, 7.53.
vJPC ) 8.3 Hz, CH(CH3)2, 2C), 31.02 (s, CH2(CH2)2CH3, 1C), 36.41
(t, 3JPC ) 2.3 Hz, CH2(CH2)2CH3, 1C), 37.45 (vt, vJPC ) 10.2 Hz,
CH2CH2P, 2C), 57.50 (t, 2JPC ) 9.5 Hz, CHNi, 1C). 31P{1H} NMR
(C6D6): 68.1.
{(i-Pr2PCH2CH2)2CH}NiMe (4). MeMgCl (0.15 mL of a 3 M
solution in THF, 0.45 mmol) was added to a solution of 2 (0.200
g, 0.45 mmol) in toluene (2.5 mL). After 5 min, the solvents were
evaporated, hexanes (20 mL) were added, and the resultant
suspension was filtered. The filtrate was washed with degassed water
(3 × 20 mL) and evaporated to dryness to give complex 4 as a
{(i-Pr2PCH2CH2)2CH}NiCt CPh (8). Method A. Reaction of
complex 4 (0.021 g, 0.06 mmol) with HCt CPh (6 µL, 0.06 mmol)
in DMSO-d6 (0.8 mL) for 15 h led to full conversion of the starting
material into complex 8, as observed by NMR spectroscopy.
Method B. Refluxing a mixture of complex 5 (0.020 g, 0.05 mmol)
and excess HCt CPh (100 µL, 0.91 mmol) in toluene (0.8 mL) for
2 h led to the full conversion of the starting material into the
phenylacetylide complex 8, as observed by 31P{1H} NMR spec-
troscopy. Method C. Reacting LiCt CPh (0.110 g, 1.02 mmol)
with complex 2 (0.300 g, 0.679 mmol) in toluene (3 mL) at room
temperature for 1 h gave complex 8, as observed by 31P{1H} NMR
spectroscopy. 13C{1H} NMR (CDCl3): 17.87 (s, CH(CH3)2, 2C),
18.72 (s, CH(CH3)2, 2C), 19.36 (s, CH(CH3)2, 2C), 19.67 (s,
CH(CH3)2, 2C), 23.84 (vt, vJPC ) 11.4 Hz, CH(CH3)2, 2C), 24.31
(vt, vJPC ) 9.9 Hz, CH2P, 2C), 25.79 (vt, vJPC ) 10.4 Hz, CH(CH3)2,
yellow powder (0.121 g, 71%). 1H NMR (C6D6): -0.50 (t, 3JPH
)
3
7.7 Hz, NiCH3, 3H), 0.96 (dvt, JHH
∼
vJPH ) 5.5-6.3 Hz,
v
CH(CH3)2, 6H), 1.12 (dvt, 3JHH ∼ JPH ) 6.2-6.5 Hz, CH(CH3)2,
6H), 1.21 (m, CH(CH3)2, 12H), 0.80-2.20 (CH(CH3)2, CH2CH2P,
2
CHNi, 13H). 13C{1H} NMR (C6D6): -18.64 (t, JPC ) 19.9 Hz,
NiCH3, 1C), 17.55 (s, CH(CH3)2, 2C), 19.01 (s, CH(CH3)2, 2C),
v
v
19.46 (vt, JPC ) 3.3 Hz, CH(CH3)2, 2C), 19.63 (vt, JPC ) 2.4
Hz, CH(CH3)2, 2C), 22.68 (vt, vJPC ) 9.5 Hz, CH(CH3)2, 2C), 25.81
(vt, vJPC ) 10.4 Hz, CH2P, 2C), 25.85 (vt, vJPC ) 9.0 Hz, CH(CH3)2,
v
2
2C), 37.70 (vt, JPC ) 10.9 Hz, CH2CH2P, 2C), 58.56 (t, JPC
)
9.5 Hz, CHNi, 1C). 31P{1H} NMR (C6D6): 71.4. Anal. Calcd for
C18H40NiP2 · H2O: C, 54.71; H, 10.71. Found: C, 54.39; H, 10.48.
{(i-Pr2PCH2CH2)2CH}NiCt CMe (5). To complex 2 (1.000 g,
2.26 mmol) was added MeCt CMgBr (4.52 mL of a 0.5 M solution
in THF, 2.26 mmol) and the mixture stirred. After 5 min, the solvent
was evaporated, hexanes (40 mL) were added, and the resultant
suspension was filtered. The filtrate was washed with degassed water
(3 × 20 mL) and the solvent evaporated to dryness to give complex
v
2
2C), 37.89 (vt, JPC ) 10.3 Hz, CH2CH2P, 2C), 57.35 (t, JPC
)
9.4 Hz, CHNi, 1C), 120.12 (t, 2JPC ) 29.0 Hz, Ct CPh, 1C), 122.29
(s, 1C), 123.71 (s, Ph, 1C), 127.79 (s, Ph, 2C), 130.06 (s, 1C),
130.34 (s, Ph, 2C). 31P{1H} NMR (CDCl3): 77.9.
{(i-Pr2PCH2CH2)2CH}NiX2 (9). To a solution of 2 (0.100 g,
0.23 mmol) in CH2Cl2 (10 mL) was added FeCl3 (0.037 g, 0.23
mmol) or FeBr3 (0.067 g, 0.23 mmol). The mixture was stirred 5
min and filtered through a glass frit. Complex 9a was obtained
quantitatively as a red powder after evaporation of the filtrate to
dryness. 1H NMR (C6D6): 0.5-3.0 (broad resonances). The
combustion data are consistent with either Ni(PCsp3Pi-Pr)ClBr or
1
5 as a yellow powder (0.716 g, 79%). H NMR (C6D6): 1.02 (m,
CH(CH3)2, 6H), 1.14 (m, CH(CH3)2, 6H), 1.25-1.50 (m, CH(CH3)2,
12H), 0.80-2.20 (CH(CH3)2, CH2CH2P, CHNi, 13H), 2.13 (s,
Ct CCH3, 3H). 13C{1H} NMR (C6D6): 7.61 (s, Ct CCH3, 1C),
17.81 (s, CH(CH3)2, 2C), 18.74 (s, CH(CH3)2, 2C), 19.40 (vt, vJPC
) 2.5 Hz, CH(CH3)2, 2C), 19.68 (s, CH(CH3)2, 2C), 23.93 (vt, vJPC
an equimolar mixture of Ni(PCsp3Pi-Pr)Br2 and Ni(PCsp3 i-Pr)Cl2.
P
Anal. Calcd for C17H37BrNiClP2: C, 42.76; H, 7.81. Found: C,
42.96; H, 7.21. Complex 9b could not be purified due to similar
v
) 11.1 Hz, CH(CH3)2, 2C), 24.76 (vt, JPC ) 9.6 Hz, CH2P, 2C),