Synthesis, structures, and reactivity of nickel complexes incorporating sulfonamido-imine ligands

Article abstract of DOI:10.1021/om800001w

Nickel complexes incorporating sulfonamido-imine ligands [o-C(H)NDipp-C₆H₄NSO₂(Ar)]^- (Dipp = 2,6-iPr₂C₆H₃; L¹ where Ar = 2,4,6-Me₃C₆H₂, L² where Ar = 4-MeC₆H₄, L³ where Ar = 4-O₂NC ₆H₄) were synthesized and characterized. Reaction of L¹Li with irans-[Ni(Cl)(Ph)(PPh₃)₂], NiBr ₂(THF)_1.5, and NiCl₂(Py)₄ resulted in the formation of the nickel(I) complex L¹Ni(PPh₃) (1) and the four-coordinate nickel halides L¹Ni(Br)(THF) (2) and L ¹Ni(Cl)(Py) (3), respectively. In contrast, reactions of less hindered L²Li and L³Li with NiBr₂(DME) yielded the bis(sulfonamido-imine)nickel complexes (L²)₂Ni (4) and (L³)₂Ni (5). Alkylation of 2 with LiCH ₂SiMe₃ afforded the neutral nickel alkyl L ¹Ni(CH₂SiMe₃) (6). The molecular structures of 1-5 have been determined by X-ray single-crystal analysis. DFT calculations revealed that 6 adopts a distorted square-planar geometry with one of the oxygen atoms of the sulfonyl group being bound to the nickel center.

Full text of DOI:10.1021/om800001w

Organometallics 2008, 27, 1605–1611
1605
Synthesis, Structures, and Reactivity of Nickel Complexes
Incorporating Sulfonamido-Imine Ligands
Jianfeng Li, Dawei Tian, Haibin Song, Chunhua Wang, Xiaoqing Zhu, Chunming Cui,* and
Jin-Pei Cheng*
State Key Laboratory of Elemento-Organic Chemistry, Nankai UniVersity,
Tianjin 300071, People’s Republic of China
ReceiVed January 1, 2008
Nickel complexes incorporating sulfonamido-imine ligands [o-C(H)NDipp-C6H4NSO2(Ar)]- (Dipp )
2,6-iPr2C6H3; L1 where Ar ) 2,4,6-Me3C6H2, L2 where Ar ) 4-MeC6H4, L3 where Ar ) 4-O2NC6H4)
were synthesized and characterized. Reaction of L1Li with trans-[Ni(Cl)(Ph)(PPh3)2], NiBr2(THF)1.5, and
NiCl2(Py)4 resulted in the formation of the nickel(I) complex L1Ni(PPh3) (1) and the four-coordinate
nickel halides L1Ni(Br)(THF) (2) and L1Ni(Cl)(Py) (3), respectively. In contrast, reactions of less hindered
L2Li and L3Li with NiBr2(DME) yielded the bis(sulfonamido-imine)nickel complexes (L2)2Ni (4) and
(L3)2Ni (5). Alkylation of 2 with LiCH2SiMe3 afforded the neutral nickel alkyl L1Ni(CH2SiMe3) (6).
The molecular structures of 1–5 have been determined by X-ray single-crystal analysis. DFT calculations
revealed that 6 adopts a distorted square-planar geometry with one of the oxygen atoms of the sulfonyl
group being bound to the nickel center.
Chart 1
Introduction
In recent years, there has been great interest in the synthesis
and characterization of single-site polymerization catalysts based
on nickel, palladium, and other late transition metals.1 These
metal complexes are less electrophilic and, therefore, tolerant
to a wide range of organic functional groups. Pioneer work by
Brookhart and Grubbs has shown that cationic nickel and
palladium alkyls incorporating R-diimine ligands2 and neutral
salicylaldimine nickel complexes3 are viable for the copoly-
merization of ethylene and polar monomers. Since then, a
number of different types of monoanionic bidentate ligands with
N, P, and O donors have been employed for this purpose.4 These
studies indicate that suitable ligand frameworks could result in
highly efficient copolymerization catalysts. In this vein, we are
interested in developing alternative ligand systems to support
nickel alkyls and explore their structures and reactivity.
We have previously reported the coordination chemistry of
monoanionic sulfonamido aluminum complexes.5 We now
extend this ligand family to mimic well-known salicyladimine
ligand sets considering that the acidity of sulfonamines is similar
to that of phenols as a result of the electron-withdrawing nature
of the sulfonyl group (Chart 1). In addition, one of the oxygen
atoms on a sulfonyl group may have, to some extend, interaction
with the central metal atom, resulting in a unique coordination
environment and modification of reactivity of the corresponding
metal complexes. It is anticipated that the oxygen atoms of a
sulfonyl group may act as a potential hamilabile arm due to the
relatively weak coordination ability of the oxygen atom to late
transition metals. It has been shown that the low-coordinate and
electronically unsaturated active metal center can be stabilized
by hemilabile arms, which are capable of reversible dissociation
from the metal center to provide a vacant coordination site for
bonding of incoming substrates.6 Herein we report on the
synthesis and structures of novel nickel complexes bearing
sulfonamido-imine ligands.
* Corresponding author. E-mail: cmcui@nankai.edu.cn.
(1) Reviews: (a) Boffa, L. S.; Novak, B. M. Chem. ReV. 2000, 100,
1479. (b) Mecking, S. Coord. Chem. ReV. 2000, 203, 325. (c) Ittel, S. D.;
Johnson, L. K.; Brookhart, M. Chem. ReV. 2000, 100, 1169. (d) Gibson,
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J. Am. Chem. Soc. 1998, 120, 888.
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Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460.
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R.; Saillard, B.; Spitz, R.; Claverie, J.; Llaurro, M. F.; Monnet, C.
Macromolecules 2002, 35, 1513. (c) Drent, E.; Dijk, R. V.; Ginkel, R. V.;
Oort, B. V.; Pugh, R. I. Chem. Commun. 2002, 744. (d) Britovsek, G. J. P.;
Gibson, V. C.; Spitzmesser, S. K.; Tellman, K. P.; White, A. J. P.; Williams,
D. J. J. Chem. Soc., Dalton Trans. 2002, 1159. (e) Li, X.-F.; Li, Y.-G.; Li,
Y.-S.; Chen, Y.-X.; Hu, N.-H. Organometallics 2005, 24, 2502. (f) Groux,
L. F.; Weiss, T.; Reddy, D. N.; Chase, P. A.; Piers, W. E. J. Am. Chem.
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J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 1134. (i) Carone, C. L. P.;
Bisatto, R.; Galland, G. B.; Rojas, R.; Bazan, G. J. Polym. Sci., Part A:
Polym. Chem. 2008, 46, 54.
Experimental Section
All manipulations involving air- and moisture-sensitive com-
pounds were carried out under an atmosphere of dry argon by using
modified Schlenk line and glovebox techniques. Elemental analyses
(5) Zhao, J.; Song, H.; Cui, C. Organometallics 2007, 26, 1947.
(6) For examples, see:(a) Dove, A. P.; Gibson, V. C.; Marshall, E. L.;
White, A. J. P.; Williams, D. J. Dalton Trans. 2004, 570. (b) Wang, X.;
Liu, S.; Jin, G.-X. Organometallics 2004, 23, 6002.
10.1021/om800001w CCC: $40.75
2008 American Chemical Society
Publication on Web 03/08/2008

1606 Organometallics, Vol. 27, No. 7, 2008
Li et al.
1
were carried out on an Elemental Vario EL analyzer. The H and
13C NMR spectroscopic data were recorded on a Varian Mercury
Plus 400 spectrometer. Infrared spectra were recorded on a Bio-
Rad FTS 6000 spectrophotometer. The solvents (THF, toluene,
n-hexane, and diethyl ether) were freshly distilled from sodium and
degassed prior to use. Methylene chloride was dried over CaH2
and freshly distilled and degassed prior to use. The free ligand
precursors o-CHO-C6H4NHSO2(Ar) (Ar ) 2,4,6-Me3C6H2, 4-MeC6H4,
4-O2NC6H4)7 and the nickel halides NiBr2(THF)1.5,8 NiBr2(DME),9
132.93, 134.80, 138.32, 139.13, 146.03, 146.73, 150.39 (Ar C),
166.19 (CHdN). IR (cm-1): ν(CdN) 1623, νas(SO2) 1348, νs(SO2)
1167.
Preparation of L1Li, L2Li, and L3Li. n-BuLi (1.1 equiv, 1.6
M in n-hexane) was slowly added to a solution of L1H, L2H, or
L3H in toluene at -78 °C. The color of the solution turned from
pale yellow to yellow upon addition. The mixture was warmed to
room temperature and stirred for additional 2 h. All volatile
materials were removed under vacuum. The remaining powder was
washed with n-hexane and dried under vacuum. These lithium salts
are insoluble in organic solvents and were used directly.
12
NiCl2(Py)4,10 trans-[Ni(Cl)(Ph)(PPh3)2],11 and LiCH2SiMe3 were
synthesized according to the published procedures.
Synthesis of L1Ni(PPh3) (1). A solution of L1Li (468 mg, 1
mmol) in toluene was slowly added to a solution of trans-
[Ni(Cl)(Ph)(PPh3)2] (696 mg, 1 mmol) in toluene at room temper-
ature and stirred overnight. After filtration through Celite, the dark
red filtrate was concentrated (ca. 5 mL) and n-hexane (30 mL) was
added. The resulting red powder was recrystallized from THF/n-
hexane (1:2) at -35 °C to give red brown crystals (407 mg, 52.1%).
Mp: 217-218 °C. Anal. Calcd for C46H48N2NiO2PS (782.62): C,
70.60; H, 6.18; N, 3.58. Found: C, 70.13; H, 6.23; N, 3.65. IR
(cm-1): ν(CdN) 1610, νas(SO2) 1334, νs(SO2) 1119.
Synthesis of L1H. A solution of o-CHO-C6H4NHSO2(Ar) (Ar
) 2,4,6-Me3C6H2) (9.10 g, 30 mmol), 2,6-diisopropylaniline (5.66
mL, 30 mmol), and p-toluenesulfonic acid (0.10 g) was refluxed
in toluene (160 mL) for 4 h while the resulting water was removed
as an azeotrope with a Dean and Stark apparatus. After evaporation,
the resulting residue was taken up in CH2Cl2 and the extract was
washed with saturated aqueous Na2CO3. The organic phase was
separated, dried over Na2SO4, and filtered. L1H was crystallized
from CH2Cl2/EtOH (1:5) to give white crystals (12.67 g, 91.4%).
Mp: 160 °C. Anal. Calcd for C28H34N2O2S (462.23): C, 72.69; H,
7.41; N, 6.06. Found: C, 72.83; H, 7.43; N, 6.39. 1H NMR (CDCl3):
δ 1.19 (d, J ) 6.86 Hz, 12H, CHMe2), 2.28 (s, 3H, p-ArMe), 2.73
(s, 6H, o-ArMe), 3.03 (sept, J ) 6.86 Hz, 2H, CHMe2), 6.95 (s,
2H, Ar H), 7.01-7.20 (m, 7H, Ar H), 8.25 (s, 1H, CH ) N), 12.77
(s, 1H, NH). 13C NMR (CDCl3): δ 20.94 (p-ArMe), 22.76 (o-ArMe),
23.74 (CHMe2), 28.11 (CHMe2), 109.75, 115.72, 119.17, 121.43,
123.27, 125.3, 132.11, 132.28, 134.37, 138.40, 139.32, 139.88,
142.56, 147.10 (Ar C), 165.83 (CHdN). IR (cm-1): ν(CdN) 1623,
νas(SO2) 1336, νs(SO2) 1156.
Synthesis of L1Ni(Br)(THF) (2). A solution of NiBr2 (240 mg,
1.1 mmol) in THF (50 mL) was refluxed for about 24 h, and then
a solution of L1Li (468 mg, 1 mmol) in THF was added. After the
mixture was refluxed 48 h, the volatiles were removed in vacuum.
The yellow brown residue was extracted with CH2Cl2. After
filtration, all volatiles were removed in vacuum. The remaining solid
was recrystallized from THF/n-hexane (1:2) at -35 °C to yield
yellow brown crystals of 2 (301 mg, 45.0%). Mp: 201 °C dec. Anal.
Calcd for C32H41BrN2NiO3S (670.14): C, 57.16; H, 6.15; N, 4.17.
1
Synthesis of L2H. This compound was prepared from o-CHO-
C6H4NHSO2(Ar) (Ar ) 4-MeC6H4) (8.26 g, 30 mmol), 2,6-diiso-
propylaniline (5.66 mL, 30 mmol), and p-toluenesulfonic acid (0.10
g) as described for L1H. The product was obtained as pale yellow
crystals (7.59 g, 58.3%). Mp: 162-163 °C. Anal. Calcd for
C26H30N2O2S (434.2): C, 71.86; H, 6.96; N, 6.45. Found: C, 71.99;
H, 7.09; N, 6.42. 1H NMR (CDCl3): δ 1.12 (d, J ) 6.87 Hz, 12H,
CHMe2), 2.31 (s, 3H, p-ArMe), 2.85 (sept, J ) 6.87 Hz, 2H,
CHMe2), 7.00-7.74 (m, 11H, Ar H), 8.15 (s, 1H, CHdN), 12.62
(s, 1H, NH). 13C NMR (CDCl3): δ 21.29 (p-ArMe), 23.43 (CHMe2),
28.03 (CHMe2), 116.99, 119.87, 122.30, 123.14, 125.26, 126.95,
129.45, 132.28, 134.22, 137.06, 137.97, 139.56, 143.60, 146.91(Ar
C), 165.76 (CHdN). IR (cm-1): ν(CdN) 1626, νas(SO2) 1345,
νs(SO2) 1167.
Found: C, 56.62; H, 6.33; N, 3.65. H NMR (CDCl3): δ -8.59,
0.88, 1.21, 1.27, 1.29, 3.00, 3.21, 5.31, 6.96, 8.27, 10.09, 11.05,
12.79, 16.38, 22.94. IR (cm-1): ν(CdN) 1612, νas(SO2) 1334,
νs(SO2) 1117.
Synthesis of L1Ni(Cl)(Py) (3). A mixture of NiCl2(Py)4 (245
mg, 0.55 mmol) and L1Li (234 mg, 0.5 mmol) in THF (40 mL)
was refluxed for 24 h, and then the volatiles were removed in
vacuum. The yellow residue was extracted with toluene, and the
orange filtrate was concentrated. Storage overnight at -35 °C gave
orange crystals of 3 (168 mg, 53.0%). Mp: 210 °C dec. Anal. Calcd
for C33H38ClN3NiO2S (633.17): C, 62.43; H, 6.03; N, 6.62. Found:
C, 62.89; H, 6.17; N, 6.59. 1H NMR (C6D6): δ -7.22, -4.70, 1.42,
1.97, 2.57, 4.64, 9.02, 10.50, 13.52, 17.20, 19.50, 24.01, 48.43. IR
(cm-1): ν(CdN) 1606, νas(SO2) 1305, νs(SO2) 1116.
Synthesis of (L2)2Ni (4). A mixture of NiBr2(DME) (155 mg,
0.5 mmol) and L2Li (440 mg, 1 mmol) in THF (40 mL) was
refluxed for 24 h, and then the volatiles were removed in vacuum.
The yellow residue was extracted with CH2Cl2, and the yellow
solution was filtered. All volatile materials were removed in
vacuum. Crystallization from THF at -35 °C yielded orange
crystals of 4 (373 mg, 80.9%). Mp: >300 °C. Anal. Calcd for
C52H58N4NiO4S2 (924.33): C, 67.46; H, 6.31; N, 6.05. Found: C,
66.95; H, 6.14; N, 6.05. 1H NMR (C6D6): δ -3.77, -2.38, -1.97,
0.82, 1.41, 1.66, 3.58, 5.64, 7.92, 10.38, 16.69, 17.30, 26.70. IR
(cm-1): ν(CdN) 1603, νas(SO2) 1308, νs(SO2) 1129.
Synthesis of L3H. L3H was prepared from o-CHO-C6H4NH-
SO2(Ar) (Ar ) 4-O2NC6H4) (9.18 g, 30 mmol), 2,6-diisopropyl-
aniline (5.66 mL, 30 mmol), and p-toluenesulfonic acid (0.10 g)
as described for L1H. The product was obtained as pale yellow
crystals (12.71 g, 91.1%). Mp: 140-141 °C. Anal. Calcd for
C25H27N3O4S (465.17): C, 64.50; H, 5.85; N, 9.03. Found: C, 64.56;
H, 5.93; N, 9.08. 1H NMR (CDCl3): δ 1.20 (d, J ) 6.86 Hz, 12H,
CHMe2), 2.87 (sept, J ) 6.86 Hz, 2H, CHMe2), 7.14-7.47 (m,
6H, Ar H), 7.81 (d, J ) 8.35 Hz, 1H, Ar H), 8.10 (d, J ) 8.79 Hz,
2H, Ar H), 8.23 (s, 1H, CHdN), 8.30 (d, J ) 8.79 Hz, 2H, Ar H),
13.21 (s, 1H, NH). 13C NMR (CDCl3): δ 23.83 (CHMe2), 28.50
(CHMe2), 117.36, 120.42, 123.52, 123.66, 124.51, 125.95, 128.56,
Synthesis of (L3)2Ni (5). A mixture of NiBr2(DME) (155 mg,
0.5 mmol) and L3Li (471 mg, 1 mmol) in THF (40 mL) was
refluxed for 24 h, and then the volatiles were removed in vacuum.
The yellow residue was extracted with CH2Cl2, and the mixture
was filtered. All volatiles were removed in vacuum. Crystallization
from THF at -35 °C gave yellow crystals of 5 (353 mg, 71.6%).
Mp: >300 °C. Anal. Calcd for C50H52N6NiO8S2 (986.26): C, 60.79;
H, 5.31; N, 8.51. Found: C, 60.31; H, 5.34; N, 7.71. 1H NMR
(C6D6): δ -4.00, -2.61, -2.44, -0.70, 0.29, 0.51, 1.10, 1.57, 8.76,
10.38, 16.78, 17.66, 25.75. IR (cm-1): ν(CdN) 1606, νas(SO2) 1348,
νs(SO2) 1140.
(7) Fonseca, M. H.; Eibler, E.; Zabel, M.; König, B. Tetrahedron:
Asymmetry 2003, 14, 1989.
(8) Eckert, N. A.; Bones, E. M.; Lachicotte, R. J.; Holland, P. L. Inorg.
Chem. 2003, 42, 1720.
(9) Huang, S. B. Masteral Dissertation, University of Zhejiang, 2006.
(10) Kenessey, G.; Liptay, G. J. Therm. Anal. 1993, 39, 333.
(11) Zeller, A.; Herdtweck, E.; Strassner, T. Eur. J. Inorg. Chem. 2003,
1802.
(12) Vaughn, G. D.; Krein, K. A.; Gladysz, J. A. Organometallics 1986,
5, 936.

Ni Complexes with Sulfonamido-Imine Ligands
Organometallics, Vol. 27, No. 7, 2008 1607
Table 1. Crystallographic Detail for 1–5
1
2
3 · 3/2C7H8
4 · 6C4H8O
5 · 4C4H8O
formula
fw
T (K)
space group
a (Å)
b (Å)
C46H48N2NiO2PS
782.60
C32H41BrN2NiO3S
672.35
C
43.5H50ClN3NiO2S
C76H106N4NiO10S2
1358.48
113(2)
C66H84N6NiO12S2
1276.22
113(2)
773.09
113(2)
C2/c
51.72(2)
14.234(6)
11.046(5)
90
101.719(5)
90
294(2)
113(2)
j
j
P1
P1
P21/n
P2/c
9.381(6)
10.605(7)
19.553(12)
76.759(11)
88.739(10)
83.266(10)
1881(2)
8.277(4)
9.648(5)
20.574(11)
77.699(11)
81.838(18)
77.803(15)
1560.9(14)
2
12.7320(7)
15.4904(6)
36.9865(18)
90
98.778(2)
90
7209.2(6)
4
1.252
14.6947(19)
10.0558(13)
22.450(2)
90
104.286(6)
90
3214.8(7)
2
1.318
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
7962(6)
8
1.290
Z
2
dcalcd (Mg/m3)
F(000)
1.382
826
1.431
700
3272
2920
1356
GOF
1.028
0.873
1.136
1.063
1.111
R1, wR2 (I > 2σ(I))
R1, wR2 (all data)
0.0864, 0.2186
0.1271, 0.2597
0.0458, 0.0994
0.0680, 0.1089
0.0650, 0.1367
0.0759, 0.1426
0.0877, 0.2368
0.1015, 0.2487
0.0593, 0.1295
0.0680, 0.1345
Scheme 1. General Synthesis of Sulfonamido-Imine Ligands
Synthesis of L1Ni(CH2SiMe3) (6). LiCH2SiMe3 (50 mg, 0.53
mmol) in Et2O was added to 2 (370 mg, 0.55 mmol) in Et2O at
-78 °C. The mixture was warmed to room temperature and stirred
continuously for 2 h. All volatile materials were removed under
vacuum. The yellow residue was extracted with 10 mL of n-hexane,
and the red filtrate was concentrated. Storage at -35 °C overnight
afforded red brown crystals of 6 (111 mg, 34.7%). Mp: 174-176
°C. Anal. Calcd for C32H44N2NiO2SSi (606.22): C, 63.26; H, 7.30;
monochromated Mo KR radiation (λ ) 0.71073 Å). The structures
were resolved by direct methods and refined by full-matrix least-
squares on F2. Hydrogen atoms were considered in calculated
positions. All non-hydrogen atoms were refined anisotropically.
Crystal data and data collection details are collected in Table 1.
Crystals of 1, 2, and 5 suitable for X-ray analysis were obtained
from THF/n-hexane at room temperature, 3 was obtained from
toluene at room temperature, and 4 was obtained from THF at -
35 °C.
1
N, 4.61. Found: C, 62.97; H, 7.57; N, 4.32. H NMR (C6D6): δ
-0.91 (d, 2JHH ) 12.02 Hz, 1H, NiCHH), -0.63 (d, 2JHH ) 12.03
Hz, 1H, NiCHH), 0.44 (s, 9H, Si(CH3)3), 0.86 (d, J ) 6.73 Hz,
3H, CHMe2), 1.08 (d, J ) 6.85 Hz, 3H, CHMe2), 1.33 (d, J ) 6.78
Hz, 3H, CHMe2), 1.62 (d, J ) 6.83 Hz, 3H, CHMe2), 1.83 (s, 3H,
p-ArMe), 3.30 (s, 6H, o-ArMe), 3.50 (sept, J ) 6.66 Hz, 1H,
CHMe2), 4.70 (sept, J ) 6.93 Hz, 1H, CHMe2), 6.37-7.02 (m,
9H, Ar H), 7.14 (s, 1H, CHdN). 13C NMR (C6D6): δ -8.25
(NiCH2), 2.38 (Si(CH3)3), 20.72, 23.02, 23.18, 23.97, 24.70, 24.99,
28.20, 28.82 (CHMe2, CHMe2, p-ArMe, o-ArMe), 117.37, 119.91,
121.87, 123.45, 123.85, 127.27, 132.58, 134.29, 135.40, 135.95,
139.25, 139.44, 140.19, 142.54, 149.91 (Ar C), 167.58 (CHdN).
IR (cm-1): ν(CdN) 1603, νas(SO2) 1290, νs(SO2) 1105.
Ethylene Polymerization. Ethylene polymerization was per-
formed in a 100 mL autoclave. After evacuation and flushing with
nitrogen three times, then with ethylene two times, the autoclave
was charged with 30 mL of toluene and stirred under ambient
ethylene atmosphere. When the ethylene pressure was raised to 10
atm and temperature was kept at 40 °C, 7 µmol Ni complex and
1.2 mL of MAO (10% in toluene, Al:Ni 260:1) were injected into
the reactor. After 30 min it was quickly cooled down to 20 °C,
and then quenched by adding ethanol/HCl (10%) to give polyethylene.
Computational Methods. The DFT calculations were carried
out with Gaussian 03.13 The density functional hybrid model
B3LYP was used together with the basis set 6-31g for C, S, O, Br,
Si, N, H and Lanl2dz for Ni.
Results and Discussion
Synthesis of Ligands. The ligands were synthesized by
standard condensation reactions of the corresponding aldehydes7
and anilines (Scheme 1). By selection of easily available
arylsulfonyl chlorides and anilines, the steric and electronic
properties of the ligands can be tuned. Thus, they are potential
spectator ligands for metal complexes. All of these ligands have
been characterized by elemental analyses and H NMR, 13C
1
NMR, and IR spectroscopy. Deprotonation of these free ligands
was accomplished with n-BuLi in toluene to afford pale yellow
powders (L1Li, L2Li, and L3Li). These lithium salts can be used
directly without further purification.
(13) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K.
N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.;
Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03,
revision C.01; Gaussian, Inc.: Wallingford, CT, 2004.
X-ray Structural Determination. All intensity data were collected
with a Bruker SMART CCD diffractometer, using graphite-

1608 Organometallics, Vol. 27, No. 7, 2008
Li et al.
Scheme 2. Synthesis of Nickel Complexes
Synthesis of Nickel Complexes 1–5. The nickel complexes
1–5 shown in Scheme 2 were synthesized by reactions of
appropriate nickel halides with the lithium salts L1Li, L2Li, and
L3Li. Reaction of the bulky L1Li with trans-[Ni(Cl)(Ph)(PPh3)2]
in toluene yielded the three-coordinate nickel(I) complex L1-
Ni(PPh3) (1) as red brown crystals. Similar Ni(I) complexes
have been generated by the reaction of trans-[Ni(Cl)(Ph)(PPh3)2]
with an anilido-imine and bulky ꢀ-diketiminato lithium salts.14,15
However, reactions of L2Li and L3Li with trans-[Ni(Cl)(Ph)(P-
Ph3)2] yielded a complicated mixture, which cannot be either
separated or identified definitely. For the synthesis of divalent
nickel alkyls, nickel halides might be good precursors. Thus,
reaction of L1Li with NiBr2(THF)1.5 or NiCl2(Py)4 in refluxing
THF afforded the four-coordinate nickel halides 2 as yellow
brown crystals and 3 as orange crystals, respectively. However,
reactions of the less hindered lithium salts L2Li and L3Li with
NiBr2(DME) in refluxing THF yielded the bis(sulfonamido-
imine) nickel complexes 4 (orange crystals) and 5 (yellow
crystals), irrespective of the molar ratio of the lithium salts and
NiBr2(DME) employed. The formation of 4 and 5 apparently
resulted from the less hindered aryl groups on the sulfonyl group.
It is surprising that L2Li and L3Li do not react with NiCl2(Py)4
under the same conditions as for the synthesis of 3–5, probably
due to the lower reactivity of NiCl2(Py)4 than NiBr2(DME). All
these paramagnetic complexes 1–5 have been characterized by
nonbonding interaction between the two atoms, resulting in the
lengthening of the S1-O1 bond (S1-O1 ) 1.412(5) Å com-
pared to S1-O2 ) 1.391(5) Å). Consequently, the N2-Ni-P1
angle of 148.27(17)° is much more open in comparison to the
N1-Ni1-P1 of 119.15(18)°. The Ni-N and Ni-P bond lengths
are only slightly shorter than those observed in the previously
reported three-coordinate nickel(I) complexes shown in Table
2. The short C-N bond length of 1.262(8) Å reveals an
essentially double bond character, indicating little electron
delocalization through the imine system.
The molecular structures of 2 and 3 are shown in Figures 2
and 3, respectively. The two nickel halides feature a distorted
tetrahedral geometry with almost orthogonal N1-Ni1-N2
angles (90.83(12)° in 2 and 89.55(12)° in 3). The Ni-N bond
lengths of 1.971(3) and 2.029(3) Å in 2 and 1.975(3) and
1
elemental analyses and H NMR and IR spectroscopy. The IR
spectra of these complexes show stretching vibration bands of
CdN at 1603-1612 cm-1, which are red-shifted compared to
those of the corresponding free ligands (1623-1626 cm-1). The
molecular structures of 1–5 were determined by X-ray single-
crystal analysis. The X-ray crystallographic data for 1–5 are
summarized in Table 1. The structures are shown in Figures
1-5 with the relevant bond parameters.
Crystal Structures of Nickel Complexes 1–5. The structure
of 1 in Figure 1 shows that the nickel atom is three-coordinate,
being bound to the sulfonamido-imine ligand in an η2 fashion
and one triphenyphosphine ligand. The geometry of the nickel
atom can be best described as distorted trigonal-planar (the sum
of the three angles around the nickel center ) 360°). The very
close Ni1-O1 (2.495 Å) distance indicates the existence of a
Figure 1. ORTEP representation of the X-ray structure of 1.
Hydrogen atoms have been omitted for clarity. Thermal ellipsoids
are drawn at 30% probability. Selected bond lengths (Å) and angles
(deg): Ni1-N1 1.906(5), Ni1-N2 1.878(6), Ni1-P1 2.167(2),
Ni1-O1 2.495, N1-C13 1.262(8), S1-O1 1.412(5), S1-O2
1.391(5), S1-N2 1.566(5), N1-Ni1-N2 92.3(2), N1-Ni1-P1
119.15(18), N2-Ni1-P1 148.27(17).
(14) Wang, H.-Y.; Meng, X.; Jin, G.-X. Dalton Trans. 2006, 2579.
(15) Zhang, D.; Jin, G.-X.; Weng, L.-H.; Wang, F.-S. Organometallics
2004, 23, 3270.

Ni Complexes with Sulfonamido-Imine Ligands
Organometallics, Vol. 27, No. 7, 2008 1609
Table 2. Comparison of the Relevant Bond Lengths (Å) and Angles
(deg) in the Related Three-Coordinate Nickel(I) Complexesa
Ni-N
Ni-P
N-Ni-N
[o-C(H)NDipp-
C6H4NDipp]Ni(PPh3)
1.908(4)-1.970(4) 2.233(2)
94.56(8)
[o-C(H)NAr-C6H4NDipp]- 1.899(2)-1.933(2) 2.2096(9) 95.27(8)
Ni(PPh3)b
{HC[C(Me)NDipp]2}-
Ni(PPh3)
1.899(3)-1.911(3) 2.2044(12) 96.77(14)
1.943(2)-1.957(2) 2.2786(8) 96.70(9)
1.878(6)-1.906(5) 2.1167(2) 92.3(2)
{HC[C(Me)NDipp]2}-
Ni(PCy3)
L1Ni(PPh3)
a All data taken from refs 14-16 except those in L1Ni(PPh3), Dipp )
2,6-iPr2C6H3. b Ar ) 2,6-Me2C6H3.
Figure 4. ORTEP representation of the X-ray structure of 4.
Hydrogen atoms and iPr groups have been omitted for clarity.
Thermal ellipsoids are drawn at 30% probability. Selected bond
lengths (Å) and angles (deg): Ni1-N1 1.995(4), Ni1-N2 2.036(4),
Ni1-N3 1.990(4), Ni1-N4 2.049(4), Ni1-O2 2.510, Ni1-O3
2.447, N1-Ni1-N2 88.59(15), N3-Ni1-N4 87.38(15), N1-Ni1-
N3 162.50(15), N2-Ni1-N4 115.88(17).
the four-coordinate nickel bromides {[o-C(H)NAr-C6H4NAr]-
Ni(Br)}2 (Ar ) 2,6-Me2C6H3, 2,6-iPr2C6H3)17 and {HC[C(Me)-
NAr]2}Ni(Br)(PPh3) (Ar ) 2,6-Me2C6H3).18 The Ni1-Cl1 bond
length of 2.246(5) Å in 3 is slightly shorter those observed in
four-coordinate nickel chlorides [{HC[C(Me)NDipp]2}Ni(Cl)]2
(2.324(1)-2.349(1) Å).8 The Ni-O(sulfonyl) distances of 2.348
Å in 2 and 2.377 Å in 3 are shorter by ca. 0.15 and 0.12 Å,
respectively, than that observed in 1, but still longer than the
sum of the covalent radius of Ni and O (2.18 Å). Consistent
with the close Ni-O interaction, the S-O double bond was
elongated by 0.028 Å in 2 and 0.025 Å in 3 compared to a
normal S-O double bond, and the halide ligands in 2 and 3
are pushed from the bisector of the N1-Ni1-N2 to the imine
group.
Figure 2. ORTEP representation of the X-ray structure of 2.
Hydrogen atoms have been omitted for clarity. Thermal ellipsoids
are drawn at 30% probability. Selected bond lengths (Å) and angles
(deg): Ni1-N1 2.029(3), Ni1-N2 1.971(3), Ni1-O1 2.348,
Ni1-O3 2.026(2), Ni1-Br1 2.363(1), S1-N2 1.617(3), S1-O1
1.471(2), S1-O2 1.443(2), N1-C13 1.285(4), N2-C19 1.377(4),
C13-C14 1.463(5), C14-C19 1.431(5), N1-Ni1-O3 102.50(10),
N1-Ni1-Br1 102.16(8), N1-Ni1-N2 90.83(12).
The molecular structures of 4 and 5 are shown in Figures 4
and 5 with selected bond parameters. In the solid state, 4 is
essentially C2 symmetric and 5 has a crystallographically
required C2 symmetry. Both compounds adopt a distorted
tetrahedral geometry. The most striking feature for the bis-
ligated complexes is the unusual wide N1-Ni1-N3 (162.50(15)°)
angle observed in 4 and N2-Ni1-N2* (163.86(15)°) in 5. Con-
sequently, the Ni-N(sulfonyl) bond lengths (1.990(4)-2.001(2)
Å) in 4 and 5 are slightly longer than those found in 2 and 3
(1.971(3) and 1.975(3) Å). The wide N-Ni-N angle might
result from the close contact of the nickel atom with one of the
oxygen atoms on the sulfonyl group (2.447-2.647 Å). The
Ni-N(imine) bond lengths in 4 and 5 (2.032(3)-2.049(4) Å)
are comparable to those in complexes 2 and 3. The overall
geometry of 4 and 5 is quite distinct from that of the bis(anilio-
imine) nickel complex [o-C(H)N(C6H6)-C6H4N(C6H6)]2Ni,14
indicating that the close Ni-O interaction has a significant
influence on the structure and geometry of metal complexes.
Figure 3. ORTEP representation of the X-ray structure of 3.
Hydrogen atoms have been omitted for clarity. Thermal ellipsoids
are drawn at 30% probability. Selected bond lengths (Å) and angles
(deg): Ni1-N1 1.975(3), Ni1-N2 2.028(3), Ni1-N3 2.018(3),
Ni1-Cl1 2.246(5), Ni1-O2 2.377, N1-S3 1.621(3), N1–10
1.378(4), N2-C16 1.294(5), S3-O1 1.438(3), S3-O2 1.463(3),
C10-C15 1.415(5), C15-C16 1.448(5), N1-Ni1-N3 101.73(12),
N1-Ni1-N2 89.55(12), N2-Ni1-N3 105.87(12), N2-Ni1-Cl1
101.38(9).
(16) Bai, G.; Wei, P.; Stephan, D. W. Organometallics 2005, 24, 5901.
(17) Gao, H.; Gao, W.; Bao, F.; Gui, G.; Zhang, J.; Zhu, F.; Wu, Q.
Organometallics 2004, 23, 6273.
2.028(3) Å in 3 are longer than those in 1 because of the high
coordination number of 2 and 3. The Ni1-Br1 bond length of
2.363(1) Å for 2 falls in the range of 2.352(1) to 2.376(1) Å for
(18) Zhang, L.; Ke, Z.; Bao, F.; Long, J.; Gao, H.; Zhu, F.; Wu, Q. J.
Mol. Catal. A 2006, 249, 31.

1610 Organometallics, Vol. 27, No. 7, 2008
Li et al.
Figure 5. ORTEP representation of the X-ray structure of 5.
Hydrogen atoms and iPr groups have been omitted for clarity.
Thermal ellipsoids are drawn at 30% probability. Selected bond
lengths (Å) and angles (deg): Ni1-N1 2.032(3), Ni1-N2 2.001(2),
Ni1-O1 2.647, N1-Ni1-N2 88.74(10), N1-Ni1-N1* 118.40(14),
N2-Ni1-N2* 163.86(15).
Figure 7. Optimized structure of 6 (DFT; only hydrogen atoms on
C1 are shown). Selected bond lengths (Å) and angles (deg): Ni1-C1
1.937, Ni1-N1 1.930, Ni1-N2 1.950, Ni1-O1 2.018, N1-Ni1-N2
91.4, N1-Ni1-C1 99.54.
Table 3. Ethylene Polymerization Results by 1, 2, and 6 Combined
with MAOa
c
entry
complex
yield/g
activityb
10-3Mw
PDIc
1
2
3
1
2
6
0.271
0.088
0.204
77
25
58
97
152
169
2.4
2.0
2.1
a Conditions: 7 µmol of complexes 1, 2, and 6, ethylene pressure )
10 atm, 40 °C, 30 min, 30 mL of toluene, Al/Ni ) 260. b kg/mol-Ni · h.
c Mw and PDI (Mw/Mn) were determined by GPC vs polystyrene standards.
from the VT NMR studies. To understand the coordination
properties of 6, DFT calculations with the B3LYP approach
were performed (Supporting Information). The optimized
structure of 6 (Figure 7) revealed that one of the oxygen atoms
on the sulfonyl group is coordinated to the nickel center
(Ni-O(sulfonyl) ) 2.018 Å). The nickel atom is four-coordinate
and adopts a distorted square-planar configuration (the sum of
the internal angles ) 360°). This geometry is well-correlated
with the experimental NMR data in solution. It is noted that
four-coordinate nickel alkyl with symmetric pincer-type ligands
are known.19
1
Figure 6. H NMR spectrum of 6 in C6D6 at 22 °C.
Alkylation of Nickel Complexes 2 and 3. Attempts to
prepare well-defined nickel alkyls by the reactions of halides 2
and 3 with several kinds of lithium alkyls and Grignard reagents
have been, so far, unsuccessful. However, reaction of LiCH2-
SiMe3 with 2 afforded the desired air- and moisture-sensitive
complex 6 as red brown crystals in modest yield (Scheme 2).
Compound 6 has been characterized by elemental analysis and
1H NMR, 13C NMR, and IR spectroscopy. The 1H NMR
spectrum (Figure 6) disclosed that 6 is a solvent-free species.
Ethylene Polymerization. Compounds 1, 2, and 6 have been
investigated as catalysts for ethylene polymerization reactions.
They are active for ethylene polymerization when combined
with methyaluminoxane (MAO).20 The polymerization results
are summarized in Table 3. All of them showed modest activity.
The Ni(II) complexes 2 and 6 gave high molecular weight
polyethylene (PE; Mw ≈ 1.5 × 105 – 1.7 × 105) with narrow
polydispersity indices (PDI ) 2.0–2.1). In contrast, the Ni(I)
complex 1 yielded lower molecular weight PE (Mw ) 9.7 ×
104) with relatively broad molecular weight distribution (PDI
) 2.4). Complex 6 was found to be inactive for ethylene
polymerization in the absence of any activator in C6D6 at
temperatures ranging from 22 to 45 °C. This behavior may be
attributed to the strong bonding of the oxygen atom to the nickel
center and ethylene coordination is prohibited. Further explora-
1
Both the H and 13C NMR spectra of 6 showed a singlet (δ
0.44 and 2.38 ppm, respectively) for the methyl protons and
carbons of the CH2SiMe3 group, suggesting a small rotation
barrier for the SiMe3 group. The 1H NMR spectrum shows two
2
doublets (δ -0.91 and -0.63 ppm, JHH ) 12.0 Hz) for the
diastereotopic protons of the methylene group in CH2SiMe3,
indicating C1 symmetry of the molecule. Unfortunately, we were
unable to obtain single crystals of 6 suitable for X-ray diffraction
studies under various conditions.
1
The H NMR spectra of 6 in toluene-d8 from -80 to 50 °C
showed similar patterns at these temperatures except that the
chemical shift differences of the two doublets for the methylene
resonances become smaller with the increase of the temperature
(Supporting Information), indicating that the molecular geometry
is maintained throughout the temperatures. As compound 6 is
decomposed above 50 °C in toluene-d8, further information on
the structure of 6 at high temperatures could not be obtained
(19) Liang, L.-C.; Chien, P.-S.; Lin, J.-M.; Huang, M.-H.; Huang, Y.-
L.; Liao, J.-H. Organometallics 2006, 25, 1399.
(20) (a) Feldman, J.; McLain, S. J.; Parthasarathy, A.; Marshall, W. J.;
Calabrese, J. C.; Arthur, S. D. Organometallics 1994, 16, 1514. (b) Zhou,
M.-S.; Huang, S.-P.; Weng, L.-H.; Sun, W.-H.; Liu, D.-S. J. Organomet.
Chem. 2003, 665, 237.

Ni Complexes with Sulfonamido-Imine Ligands
Organometallics, Vol. 27, No. 7, 2008 1611
tion of the reactivity, especially polymerization reactions with
other activators, of these novel complexes is currently in pro-
gress.
renders the formation of the solvent-free nickel alkyl 6, in which
the bonding interaction of the Ni-O has been proposed by DFT
calculations.
Acknowledgment. This work was supported by the
National Natural Science Foundation of China (NSFC), the
Key Project of Chinese Ministry of Education, and the 111
Plan.
Conclusion
Sulfonamide-imine ligands have been employed for the
synthesis of novel mono- and bis(sulfonamido-imine) nickel
complexes. The X-ray structural analyses indicate that there
exists a nonbonding interaction between one of the oxygen
atoms on the sulfonyl group and nickel center for complexes
1–5 as evidenced by the long S-O distances and short Ni-O
contacts. The interaction not only effects the changes in the
structural parameters but also favors the formation of the
mononuclear halides 2 and 3. The bulky alkyl ligand CH2SiMe3
Supporting Information Available: Computational details for
compounds 2 and 6, VT NMR studies for compound 6, and CIF
files for compounds 1–5. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM800001W