A R T I C L E S
Keen et al.
for Catalysis and Materials Research, Windsor, Ontario, Canada. The
compounds (Et3P)2NiBr(2-Br-4,5-F2-C6H2),11 Ni(PEt3)4,31 and 1-F-2,3-
I2C-6H317 were prepared by literature procedures. The complex Br2Ni-
(PEt3)2 was prepared by the addition of PEt3 to commercially available
(DME)NiBr2 followed by recrystallization from pentane. The com-
pounds PEt3, B(C6F5)3, Na, and Hg were purchased from Aldrich. The
compound B(C6F5)3 was sublimed prior to use.
6.7 Hz, aromatic 6-H), 7.18 (ddd, 1H, JHF ) 3.3 Hz, JHH ) 6.7 Hz,
JHH ) 7.4 Hz, aromatic-5-H), 7.41 (dd, 1H, JHF ) 6.3 Hz, JHH ) 7.4
Hz, aromatic-4-H). 31P{1H} NMR (C6D6, 298 K, 202.47 MHz): δ 29.7
(br s), 27.1 (br s). 19F NMR (C6D6, 298 K, 282.48 MHz): δ -28.4
(ddd, JHF ) 6.3 Hz, JHF ) 3.3 Hz, JHF ) 3.3 Hz). 13C{1H} NMR (C6D6,
298 K, 125.27 MHz): δ 9.0 and 9.3 (br, PCH2Me), 20.0 and 20.7 (br,
PCH2), 113.0 (d, J ) 32.5 Hz), 118.0 (s), 129.4 (d, J ) 97 Hz), 130.2
1
Synthesis of (PEt3)4Ni2(µ-η1:η1-3,3′,4,4′-F4-C12H4) (2a). To a stirred
solution of NiBr(2-Br-4,5-F2C6H2)(PEt3)2 (0.5 g, 0.88 mmol) in 20 mL
of pentane over excess 1% Na/Hg amalgam (40 g) was added a solution
of Br2Ni(PEt3)2 (0.1 g, 0.22 mmol) in 15 mL of pentane. The solution
was then stirred slowly for 20 h. The solution was then filtered through
Celite, and the volume was reduced to ca. 20 mL. The solution was
cooled to -40 °C, upon which dark brown crystals of (PEt3)4Ni2-
(s), 153.9 (br d, J ) 10 Hz), 163.1 (d, JCF ) 254.8 Hz).
Synthesis of (PEt3)3Ni3(µ3-4,5-F2C6H2)(µ3-4,5-F2C6H2-4′,5′-F2C6H2)
(6). To a stirred solution of Ni(η2-C6H2F2)(PEt3)2 (0.65 g, 0.0016 mol)
in 25 mL of pentane was added dropwise a solution of tris-
(pentafluorophenyl)borane (B(C6F5)3) (0.82 g, 0.0016 mol) in 15 mL
of pentane. The resulting brown solution was stirred for 15 min and
then filtered to remove the white precipitate. The solvent was then
reduced to half volume, and the product was recrystallized at -40 °C
to yield (PEt3)3Ni3(η2-C6H2F2)(η2-C6H2F2-C6H2F2) as dark brown
crystals in a 31% yield. 1H NMR (C6D6, 298 K, 500 MHz): δ 0.66 (br
m, 27 H, CH3), 1.00(br m, 18 H, CH2), 6.97(dd, 2 H, JHF ) 12.3 Hz,
JHF ) 7.2 Hz), 7.34 (vt, 2 H, JHF ) 9.5 Hz), 7.79(dd, 2 H, JHF ) 10.6
Hz, JHF ) 8.8 Hz). 31P{1H} NMR (C6D6, 298 K, 202.47 MHz): δ
13.2 (br, 2P), 5.1 (br, 1P). 13C{1H} NMR (C6D6, 298 K, 75.50 MHz):
1
(C6H2F2)2 were obtained (0.22 g, 60% yield). H NMR (C6D6, 20 °C,
500 MHz): δ 1.05 (br, 36H, CH3), 1.90 (br, 24H, CH2), 6.55 (m, 4H).
1H NMR (C6D6, -60 °C, 500 MHz, aromatic region): δ 6.44 (ddd,
2H, 3JHH ) 8.0, 4JHF ) 4.0, 5JHF ) 0.7 Hz), 6.64 (ddd, 3JHH ) 8.0 Hz,
4
4JH(a)F(b) ) 7.3 Hz, JH(a)F(a) ) 10.2 Hz). 31P{1H} NMR (C6D6, 20 °C,
202.47 MHz): δ 8.8 (br s), -3.8 (br s). 31P{1H} NMR (C6D6, -60 °C,
202.47 MHz): δ -3.8 (vt, JPP ) 5.4 Hz), 8.8 (vtdd, JPP ) 5.4 Hz, JFP
) 7.1, 11.3 Hz). 19F NMR (C6D6, 20 °C, 282.48 MHz): δ -34.3 (dddd,
4JH(a)F(a) ) 10.2 Hz, 4JH(b)F(a) ) 4.0 Hz, 3JFF ) 35.6 Hz, JFP ) 6.0 Hz),
δ 108.25 (d, 2JCF ) 12.6), 111.8 (d, 2JCF ) 18.9 Hz), 131.0 (d, 2JCF
12.6 Hz), 135.8 (s, ipso C), 146.1 (dd, JCF ) 251.5 Hz, JCF ) 18.9
)
1
2
3
1
2
1
-71.1 (ddd, JFP ) 11.5 Hz, JH(a)F(b) ) 7.3 Hz, JFF ) 35.6 Hz). 13C-
Hz), 148.4 (dd, JCF ) 213.8, JCF ) 12.6), 149.1 (dd, JCF ) 232.6,
{1H} NMR (C6D6, 298 K, 75.50 MHz): δ 8.2 and 9.5 (br, CH3), 17.1
and 21.5 (br, CH2), 109.9 (d, 2JCF ) 19.8 Hz), 114.23 (s, ipso-C), 150.5
2JCF ) 12.6), 151.4 (s, ipso C), 168.1 (s, ipso C). 19F NMR (C6D6, 298
3
K, 282.48 MHz): δ -69.1 (ddd, JFF ) 19.9 Hz, JHF ) 12.3 Hz, JHF
1
2
2
(dd, JCF ) 244.3 Hz, JCF ) 22.0 Hz), 151.5 (d, JCF ) 17.6 Hz),
155.7 (dd, 1JCF ) 226.1 Hz, 2JCF ) 14.7 Hz), 155.9 (s, ipso-C). Anal.
Calcd: C, 53.11; H, 7.92. Found: C, 52.67; H, 7.81. UV/vis: ꢀ )
72 000 L mol-1 cm-1. λmax ) 428 nm.
) 8.8 Hz), -66.5 (vt, JHF ) 9.5 Hz), -61.6 (ddd, 3JFF ) 19.9 Hz, JHF
) 10.6 Hz, JHF ) 7.2 Hz). Anal. Calcd for C39H77F6Ni3P3: C, 49.88;
H, 5.93. Found: C, 49.56; H, 5.91.
Synthesis of [(PEt3)2Ni]2(µ-η2:η2-4,5-F2C6H2-4′,5′-F2C6H2) (7a).
To a solution of 6 (0.12 g, 0.154 mmol) in 20 mL of pentane was
added PEt3 (0.06 mL, 0.406 mmol, 2.6 equiv) and stirred for 5 min.
The mixture was then reduced to ca. 10 mL and placed in the freezer
Synthesis of [(PEt3)2Ni]2(µ-η2:η2-C6H2F2) (3). To a stirred solution
of Ni(η2-C6H2F2)(PEt3)2 (80 mg, 0.197 mmol) in 15 mL of pentane
over excess 1% Na/Hg amalgam (50 g) was added dropwise, over 1 h,
a dilute solution of Br2Ni(PEt3)2 (89 mg, 0.197 mmol) in 25 mL of
pentane. The solution was then stirred for 20 min before being filtered
through Celite, and the solvent was reduced to ca. 20 mL. The solution
was then cooled to -40 °C, and pale orange crystals of Ni2(µ-η2:η2-
1
at -40 °C. The products separated as a dark oily product. H, 31P-
{1H}, and 19F NMR data were used to identify (PEt3)4Ni2(η2-C6H2-
3,4-F2)2 (1a) and a second product assigned as [(PEt3)2Ni]2(4,5-F2C6H2-
1
4′,5′-F2C6H2) (7a). H NMR (C6D6, 298 K, 300 MHz): δ 1.09 (br,
1
C6H2F2)(PEt3)2 were obtained (60 mg, 43% yield). H NMR (C6D6,
36H, CH3), 1.86 (br, 24H, CH2), 6.58 (dd, JHF ) 7.6, 11.9 Hz, aromatic),
6.77 (dd, JHF ) 9.4, 11.2 Hz, aromatic). 31P{1H} NMR (C6D6, 20 °C,
202.47 MHz): δ 8.1 (br), -6.6 (br). 19F NMR (C6D6, 298 K, 282.48
20 °C, 300 MHz): δ 0.91 (m, 18H, CH3), 1.42 (m, 12H, CH2), 7.33 (t,
3
2H, JHF ) 7.3 Hz). 31P{1H} NMR (C6D6, 20 °C, 121.54 MHz): δ
14.8 (s). 19F NMR (C6D6, 20 °C, 282.46 MHz): δ -74.0 (m). Anal.
Calcd: C, 51.32; H, 8.90. Found: C, 51.68; H, 8.70.
MHz): δ -72.7 (m, JHF ) 11.9, 9.4 Hz, JFF ) 20.0 Hz), -73.0 JHF
11.2, 7.6 Hz, JFF ) 20.0 Hz).
)
Synthesis of [(PEt3)(PMe3)Ni]2(µ-η1:η1-4,5-F2C6H2-4′,5′-F2C6H2)
(7b). To a solution of 6 (0.111 g, 0.142 mmol) in 15 mL of pentane
was added PMe3 (0.044 mL, 0.43 mmol). The solution was stirred for
5 min and then cooled to -40 °C. The first compound to precipitate
out of solution was Ni(η2-C6H2F2)(PMe3)(PEt3), 1b, as an orange solid.
This was filtered off, and the remaining solution was concentrated and
cooled to -40 °C. Brown crystals of (PEt3)2(PMe3)2Ni2(η2-C6H2-3,4-
Synthesis of NiI(3-F-2-I-C6H3)(PEt3)2 (4). A suspension of Ni-
(COD)2 (0.55 g, 0.002 mol) in 25 mL of pentane was cooled to 0 °C.
A solution of PEt3 (0.59 g, 0.005 mol) was added dropwise to the
solution and stirred for 5 min. A solution of 2,3-diiodofluorobenzene
(1.02 g, 0.003 mol) in 25 mL of pentane was then added. The mixture
was stirred for 10 min at 0 °C and then for 4 h at room temperature.
The solvent was then removed under vacuum, and the residue was
extracted with pentane and filtered through Celite. The solution was
then placed in the freezer at -40 °C. Dark yellow crystals of NiI(2-
1
F2)2 were isolated (0.03 g, 32% yield). H NMR (C6D6, 298 K, 300
MHz): δ 1.03 (m, 18H, CH3, PEt3), 1.15 (d, 18H, CH3 of PMe3), 1.38
(m, 12H, PCH2), 6.57 (dd, J ) 7.1 Hz, J ) 11.6 Hz, 2H, aromatic),
6.70 (dd, 2H). 31P{1H} NMR (C6D6, 298 K, 202.47 MHz): δ -0.3
(vt, J ) 10.3 Hz, Ni-PEt3), -21.2 (vt, J ) 10.3 Hz, Ni-PMe3). 19F
NMR (C6D6, 298 K, 282.48 MHz): δ -73.0 (m), -73.6 (m). Anal.
Calcd for C30H52F4Ni2P4: C, 49.36; H, 7.18. Found: C, 49.56; H, 7.32.
Complex 9a. To a solution of 6 (0.14 g, 0.179 mmol) in 15 mL of
pentane was added PEt3 (0.20 mL g, 1.35 mmol) and stirred. The
mixture was then reduced to ca. 10 mL and placed in the freezer at
-40 °C. The products separated as a pale brown oil. 1H, 31P{1H}, and
19F NMR data were used to identify excess PEt3, Ni(PEt3)4, (PEt3)4-
Ni2(η2-C6H2-3,4-F2)2 (1), and a product assigned tentatively as [(PEt3)2-
Ni](4,5-F2C6H2-4′,5′-F2C6H2) (9a); complex 9a is thermally unstable
in the absence of Pet3 and could not be isolated pure. 1H NMR (C6D6,
298 K, 300 MHz): δ 6.79 (dd, 2H, JHF ) 8.6 Hz, JHF ) 10.7 Hz,
aromatic H), 6.81 (dd, 2H, JHF ) 7.5 Hz, JHF ) 11.8 Hz, aromatic H).
1
I-3-FC6H3)(PEt3)2 were isolated (0.27 g, 30% yield). H NMR (C6D6,
298 K, 300 MHz): δ 0.96 (m, 18H), 1.52 (m, 12H), 6.44 (dd, 1H, JHF
) 8.8 Hz, JHH ) 7.6 Hz), 6.65 (m, 2H). 31P{1H} NMR (C6D6, 298 K,
202.47 MHz): δ 9.9 (s). 19F NMR (C6D6, 298 K, 282.48 MHz): δ
-13.2 (d, JHF ) 8.8 Hz). Anal. Calcd for C18H33I2FP2Ni: C, 33.63; H,
5.17. Found: C, 33.78; H, 5.24.
Synthesis of Ni(η2-3-F-C6H3)(PEt3)2 (5). A solution of NiI(2-I-3-
FC6H3)(PEt3)2 (0.10 g, 0.26 mmol) in 25 mL of pentane was stirred
over excess 1% Na/Hg (40 g) for 1 h. The solution was then filtered
through Celite. The solvent was then removed under vacuum, leaving
1
a dark yellow oil that freezes below 0 °C (0.037 g, 62% yield). H
NMR (C6D6, 298 K, 300 MHz): δ 0.97 (overlapping br m, 18H, CH3),
1.46 and 1.56 (br m, 12H, CH2), 6.93 (dd, 1H, JHF ) 3.3 Hz, JHH
)
(31) Cundy, C. S. J. Organomet. Chem. 1974, 69, 305-310.
9
818 J. AM. CHEM. SOC. VOL. 129, NO. 4, 2007