Cationic methallylnickel(II) complexes with α-diimine ligands: Synthesis and X-ray structure

Article abstract of DOI:10.1016/S0022-328X(03)00345-0

The α-diimine ligands Ar-N=C(R)C(R)=N-Ar react with Ni(COD)₂ (2) in the presence of methallyloxyphosphonium hexafluorophosphate [CH₂=C(Me)CH₂-O-P (NMe₂)₃]⁺·PF₆ ^- (3) to give new cationic methallyl complexes of nickel(II) with α-diimine ligands 4a and 4b. The same complexes 4a-d can also be generated in high yields by reacting [α-diimine] NiBr₂ with zinc and methallyloxyphosphonium salt 3. Molecular structure of 4a was determined by a single-crystal X-ray diffraction.

Full text of DOI:10.1016/S0022-328X(03)00345-0

Journal of Organometallic Chemistry 677 (2003) 53ꢂ56
/
www.elsevier.com/locate/jorganchem
Cationic methallylnickel(II) complexes with a-diimine ligands:
synthesis and X-ray structure
Ali Mechria a, Claude Bavoux b, Faouzi Bouachir a,*
a Laboratoire de Chimie de Coordination, Faculte´ des Sciences de Monastir, 5000 Monastir, Tunisia
b Universite´ Claude Bernard Lyon 1, CNRS UMR 5078, Laboratoire de Crystallographie, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne
Cedex, France
Received 9 October 2002; received in revised form 8 April 2003; accepted 22 April 2003
Abstract
The a-diimine ligands ArÃ
hexafluorophosphate [CH2ÄC(Me)CH2Ã
diimine ligands 4a and 4b. The same complexes 4aꢂ
/
NÄ
/
C(R)C(R)Ä
OÃ
P(NMe2)3]ꢀ
d can also be generated in high yields by reacting [a-diimine] NiBr2 with zinc and
/
NÃ
/
Ar react with Ni(COD)2 (2) in the presence of methallyloxyphosphonium
/
/
/
×
/
PF6ꢁ (3) to give new cationic methallyl complexes of nickel(II) with a-
/
methallyloxyphosphonium salt 3. Molecular structure of 4a was determined by a single-crystal X-ray diffraction.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Nickel; Chemical reduction; Cationic methallyl complexes; a-Diimine; Methallyloxyphosphonium salt
Cationic allylnickel complexes with non-chelating
ligands are known to catalyze the oligomerisation of
ethylene [1,2]. A few examples of cationic h3-allylnickel
compounds with chelating ligands have been reported
[3]. However, the synthesis of cationic h3-allylnickel(II)
complexes with a-diimine ligands is almost unknown
and their catalytic properties have not been reported.
In this note, we report the synthesis of new cationic
h3-methallylnickel(II) complexes with bulky aryl-sub-
stituted a-diimine ligands.
pound Ni(COD)2 [6] in the presence of bulky aryl-
substituted a-diimine ligands led to an exclusive forma-
tion, in high yields, of cationic h3-methallylnickel(II)
complexes with bidentate nitrogen ligands [(h3-
C4H7)Ni(NfflN)]ꢀ PF6ꢁ (Scheme 2).
×
/
One thing to be noticed is that the preparation of the
Ni(COD)2 complex involves significant synthetic effort
and that it is an air-sensitive product. This reagent must,
therefore, be stored and handled under strictly con-
trolled conditions. In order to use more simple and
stable reagents, we have investigated the possibility of in
situ generation of low-coordinated Ni0(a-diimine) spe-
cies. A convenient method for the in situ generation of
these complexes results from the chemical reduction of
divalent nickel(II) complexes containing aryl-substituted
a-diimine ligands with zinc. Indeed, the reduction of the
According to the literature, [4] cationic h3-methallyl-
nickel complexes with chelating ligands 1a and 1b have
been prepared by the reaction of bis[m-bromo(h3-
methallyl)nickel] (1) with these ligands followed by the
bromo ligand abstraction via metathetical exchange
with tetrafluoroborate by adding TlBF4 (Scheme 1).
Recently, we have described the development of a new
class of cationic methallylpalladium complexes with
aryl-substituted a-diimines [5]. This method has been
successfully applied in the case of Ni(II) complexes. In
fact, the oxidative addition of methallyloxyphospho-
nium hexafluorophosphate 3 to the zerovalent com-
(a-diimine) NiBr2 [7ꢂ/9] complexes with zinc in the
presence of the salt 3 in dichloromethane generates the
cationic h3-methallylnickel complexes with a-diimine
ligands [(h3-C4H7)Ni(NfflN)]ꢀ
×
/
PF6ꢁ (Scheme 3):
The new complexes exhibit spectroscopic data in
accord with the proposed structures. The formation of
the allyl complexes 4aꢂd is clear from the observed syn-
/
1
and anti-proton signals in the H-NMR spectra. The
complex 4a presents equivalent signals of the syn- and
anti-protons on one end of the allyl moiety as indicated
* Corresponding author. Fax: ꢀ
/
216-73-500-278.
E-mail address: faouzi.bouachir@fsm.rnu.tn (F. Bouachir).
0022-328X/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00345-0

54
A. Mechria et al. / Journal of Organometallic Chemistry 677 (2003) 53ꢂ56
/
Scheme 1.
by analysis of the HMQC spectral data in which cross-
peak was observed between dH 2.28 (Hsyn,anti) and dC
which are very close to those reported for other nickelꢂ
iminoꢂnitrogen bonds [11].
The N(1)ÃNiÃN(2) angle of 82.1(3)8 reflects a slightly
distorted square-planar coordination sphere. The metal-
chelate ring (NiÃN1ÃC5ÃC6ÃN2) in complex 4a is
almost flat as indicated by the torsion angles of
2.9(3), 1.2(6) and 3.1(8)8 for N(1)ÃC(5)ÃC(6)ÃN(2),
NiÃN(2)ÃC(6)ÃC(5), and NiÃN(1)ÃC(5)ÃC(6), respec-
/
/
1
61.9 (C1,3). The H-NMR spectra of complexes 4b and
/
/
4c are characterized by the syn- and anti-allylic protons;
thus, the two resonances are at 2.34 ppm (Hanti); 2.45
ppm (Hsyn) for 4b and at 2.61 ppm (Hanti); 2.76 ppm
(Hsyn) for 4c. In the 13C-NMR spectra, the allylic
carbons C1 and C3 appear at 61.9, 62.5, 61.8 and 60.9
/
/
/
/
ꢁ
/
/
/
/
/
/
/
/
/
/
tively. The methyl on the allyl group is slightly tilted out
for 4a, 4b, 4c and 4d, respectively. The CÄ
/N carbon
of the allyl plane by approximately 158 as indicated by
appears at 178.7, 178.4, 173.5 ppm for 4a, 4b, 4c and at
185.0, 185.3 for 4d. The IR spectra are also instructive.
the torsion angle of 165.4(8) for C(4)Ã
/
C(2)Ã
/
C(3)Ã/C(1).
The allyl plane makes an angle of 107.7(3)8 with the
nickel coordinative plane which is normal for h3-2-
methylallyl complexes of nickel [4]. The o,o?-dimethyl-
phenyl groups make an angle of approximately 908 to
The complexes 4aꢂ
stretching frequency in the region 1590ꢂ
/
d show in IR spectroscopy a CÄ
/
N
/
1690 cmꢁ1
,
which is in agreement with those reported for other a-
diimine complexes coordinated as an s-cis conformation
[9,10]. The n(PF6ꢁ) value is evident (843 cmꢁ1).
The single-crystal X-ray diffraction study of complex
4a reveals a structure consisting of loosely associated
[(h3-C4H7)Ni(NfflN)]ꢀ cations and octahedral PF6ꢁ
counteranions without direct interactions as appears
the plane of the CÄ
o-methyl substituents, as appears from the torsion
angles of ꢁ87.8(6), 90.4(8), 92.3(7), and ꢁ91.1(4)8 for
C(5)ÃN(1)ÃC(9)ÃC(10), C(5)ÃN(1)ÃC(9)ÃC(14), C(6)Ã
N(2)ÃC(17)ÃC(18) and C(6)ÃN(2)ÃC(17)ÃC(22), re-
spectively.
/N bonds, due to the presence of the
/
/
/
/
/
/
/
/
/
/
/
/
/
/
from the large distance between the metal and the
˚
F2ꢃ4.755(3) A). The ORTEP
In conclusion, a novel synthetic procedure for cationic
methallylnickel(II) complexes with a-diimine ligands
was described. This procedure offers the possibility to
exchange the PF6ꢁ counteranion against more bulky and
nearest fluorine atom (NiÃ
/
/
diagram of 4a is shown in Fig. 1. The ligand a was
coordinated with an s-cis conformation as seen in Fig. 1,
2
N(sp ) bond lengths of 1.922(7) and 1.923(7) A
˚
with NiÃ
/
Scheme 2.

A. Mechria et al. / Journal of Organometallic Chemistry 677 (2003) 53ꢂ
/
56
55
Scheme 3.
very weakly coordinating anions. Our ongoing efforts in
this way will be reported.
1.1. Preparation of 4a
1.1.1. Method A
To 20 ml of CH2Cl2 solution of Ni(COD)2 (140 mg,
0.5 mmol) was added 193 mg of salt 3 (0.5 mmol) and
DAB a (150 mg, 0.5 mmol) at ambient temperature.
After 24 h of stirring, the red solution was filtered
through a celite filter and the residue was washed with
1. Experimental
All manipulations were performed under an argon
atmosphere using standard Schlenk tube techniques.
Dichloromethane and diethylether were distilled under
argon from P2O5 and sodium benzophenone ketyl,
respectively, and stored under argon. The complexes
CH2Cl2 (2ꢄ
rated to dryness and the product was washed with
diethylether (3ꢄ10 ml) and dried in vacuo yielding 240
/5 ml). The combined filtrates were evapo-
/
Ni(COD)2 [6] and (a-diimine) NiBr2 [7ꢂ/9] were synthe-
mg of 4a as a red solid (87%).
sized following established procedures. NMR spectra
were recorded on a Bruker AMX 300 spectrometer and
infrared spectra on a BioRad FTS-6000 spectrophot-
ometer.
1.1.2. Method B
To a mixture of [diacetyl-bis(2,6-dimethylphenylimi-
ne)]NiBr2 (340 mg, 0.66 mmol) in dichloromethane (20
ml) was added 252 mg of salt 3 (0.66 mmol) and Zn
powder (65 mg, 1 mmol). After 48 h of stirring at
ambient temperature, the mixture was filtered through a
celite filter to remove zinc bromide formed and the
residue was washed with dichloromethane (2ꢄ
The combined filtrates were evaporated to dryness and
the product was washed with diethyl ether (3ꢄ15 ml) to
/
5 ml).
/
remove HMPT and dried in vacuo yielding 280 mg of 4a
as a red solid (78%).
Decomposition: 210 8C. IR [n cmꢁ1] (KBr): 841
(PF6ꢁ); 1591; 1629 (CÄ
CD2Cl2): d 2.03 (s, 3H, H4); 2.06 (s, 6H, o-CH3); 2.13
/
N). 1H-NMR (300 MHz,
(s, 6H, o-CH3); 2.28 (s, 4H, Hanti,syn); 2.31 (s, 6H, CH3);
Fig. 1. ORTEP diagram of 4a×CH2Cl2. Thermal ellipsoids are at 40%
/
7.08ꢂ
CD2Cl2): d 18.4, 18.5 (o-CH3); 19.0 (CH3); 24.2 (C4);
61.9 (C1,3); 127.8ꢂ135.7 (CarꢀC2); 146.5 (Cipso); 178.7
(Cimin). Anal. Calc. for 4a×CH2Cl2(C24H31N2NiPF6×
/
7.20 (m, 6H, Harom). 13C-NMR (75.47 MHz,
probability. Methylene chloride of crystallization and PF6ꢁ anion are
˚
omitted for clarity. Selected bond lengths (A) and angles (8): NiÃ
/
N1ꢃ
1.977(10),
1.450(10), N2Ã
1.388(14), C2ÃC3ꢃ
103.6(4), N2ÃNiÃC3ꢃ
C6ꢃ115.3(5).
/
1.922(7), NiÃ
NiÃC3ꢃ2.003(10), N1Ã
C6ꢃ1.290(11), N2ÃC17ꢃ
1.38(2); N1ÃNiÃN2ꢃ82.1(3), N1Ã
102.7(4), NiÃN1ÃC5ꢃ115.7(6), NiÃ
/
N2ꢃ
/
1.923(7), NiÃ
C5ꢃ1.268(10), N1Ã
1.447(10), C1ÃC2ꢃ
NiÃC1ꢃ
N2Ã
/
C1ꢃ
/
2.010(10), NiÃ
/
C2ꢃ
/
/
/
/
/
/
/
/
C9ꢃ
/
/
/
/
/
/
/
/
/
/
/
CH2Cl2): C, 47.20; H, 5.22; N, 4.40%. Found: C,
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
46.82, H, 5.11; N, 4.45%.

56
A. Mechria et al. / Journal of Organometallic Chemistry 677 (2003) 53ꢂ56
/
1
1.2. Preparation of 4b
(PF6ꢁ); 1595; 1650; 1689 (CÄ
CDCl3): d 0.59 (s, 3H, H12); 0.95 (s, 3H, H14); 1.05 (s,
3H, H13); 1.74ꢂ2.12 (m, 4H, H8,9); 2.19 (s, 3H, H4);
2.55ꢂ2.70 (m, 5H, 2Hanti 2Hsyn H10); 7.18 (d, JHH
7.29 Hz, 4H, Ho,o?); 7.40ꢂ
7.51 (m, 6H, Hm,m?,p). 13C-
/
N). H-NMR (300 MHz,
The complex 4b was obtained from Ni(COD)2 (170
mg; 0.62 mmol), 250 mg of b (0.62 mmol) and 235 mg of
salt 3 (0.62 mmol) in 88% yield by the same procedure
/
/
ꢀ
/
ꢀ
/
ꢃ
/
/
(method A) as an orangeꢂ
/
red solid.
NMR (75.47 MHz): d 11.4, 17.5, 22.1 (C12,13,14);
24.6 (C4); 24.0, 33.1 (C8,9); 50.8 (C7); 51.4(C10); 57.9
(C11); 60.9 (C1,3); 121.4, 122.3 (Co,o?); 128.4, 129.0
(Cp); 130.0, 130.4 (Cm,m?); 133.5 (Callyl); 147.4, 147.5
1.2.1. Method B
The complex 4b was synthesized in 79% yield follow-
ing the procedure for 4a (method B) from [diacetyl-
bis(2,6-diisopropylphenylimine)]NiBr2.
Decomposition: 203 8C. IR [n cmꢁ1] (KBr): 844
(Cipso); 185.0, 185.3 (C5,6). Anal. Calc. for 4d×
/
CH2Cl2(C26H31N2NiPF6×
/
CH2Cl2): C, 49.12; H, 5.03;
N, 4.24%. Found: C, 49.05, H, 5.44; N, 4.10%.
(PF6ꢁ); 1590; 1625 (CÄ
/
N). 1H-NMR (300 MHz,
CDCl3): d 1.10 (d, JHH
(d, 6H, JHH
7.43Hz, CH3Ã
Hz, 12H, CH3Ã
iPr); 2.03 (s, 3H, H4); 2.18 (s, 6H, CH3);
2.34 (s, 2H, H1anti, H3anti); 2.45 (s, 2H, Hs1yn, H3syn); 2.90
(m, 2H, CHÃ
iPr); 3.17 (m, 2H, CHÃiPr); 7.26 (m, 6H,
Har). 13C-NMR (75.47 MHz): d 20.5 (CH3); 23.4 (C4);
23.7, 24.2, 24.4 (CH3Ã
iPr); 29.9, 30.1 (CHÃiPr); 62.5
(C1,3); 125.2ꢂ137.4 (CarꢀC2); 143.9 (Cipso); 178.4 (Ci-
min).
ꢃ
/
7.13 Hz, 6H, CH3Ã
/
iPr); 1.23
6.98
iPr); 1.32 (d, JHH
ꢃ
/
1.5. Crystallographic data for 4a
ꢃ
/
/
/
C24H31N2PF6Ni×
P2(1); Zꢃ2; aꢃ10.952(2) A; bꢃ
110.41(3)8; Vꢃ1456.7(5) A ; Dcalc
1.453 g cmꢁ3; Rꢃ
0.0703; Rwꢃ0.1730; ꢁ145h 514;
135k 512; ꢁ175l517; Mo (Rwꢃ0.7107 A); Tꢃ
223 (2) K.
/
CH2Cl2; f.w.ꢃ
/
636.12; monoclinic;
˚
˚
/
/
/
10.759(2) A; cꢃ
/
/
/
3
˚
˚
13.191(3) A; bꢃ
/
/
ꢃ
/
/
/
/
/
/
/
/
˚
ꢁ
/
/
/
/
/
/
/
/
/
/
Atomic coordinates and anisotropic temperature
factors have been deposited at the Cambridge Crystal-
lographic Data Center, University Chemical Labora-
tory, 12 Union Road, Cambridge CB2 1EZ (CCDC
176884).
1.3. Preparation of 4c
The complex 4c was synthesized from [2,6-iPr2C6H3-
BIAN]NiBr2 following the procedure for 4a (method B),
in 72% yield as an orangeꢂ
Decomposition: 237 8C. IR [n cmꢁ1] (KBr): 844
(PF6ꢁ); 1600; 1635 (CÄN). 1H-NMR (300 MHz,
CDCl3): d 0.91 (d, JHH
6.23 Hz, 6H, CH3Ã
iPr); 1.05
(d, JHH 6.73
6.47 Hz, 6H, CH3Ã
iPr); 1.40 (d, JHH
Hz, 12H, CH3Ã
iPr); 2.19 (s, 3H, CH3-allyl); 2.61 (s, 2H,
H1anti, H3anti); 2.76 (s, 2H, H1syn, H3syn); 3.15 (m, 2H,
CHÃ 7.29
iPr); 3.43 (m, 2H, CHÃiPr); 6.63 (d, JHH
Hz, 2H, H3); 7.36 (m, 4H, H10,12); 7.43 (m, 2H, H11);
7.53 (pst, 2H, H4); 8.23 (d, Jꢃ
8.35 Hz, 2H, H5). 13C-
NMR (75.47 MHz): d 23.3, 23.5 (CH3Ã
iPr); 24.1 (C4);
24.4 (CH3Ã
iPr); 30.0 (CHÃiPr); 61.8 (C1,3); 124.4 (C7);
/
red solid.
/
References
ꢃ
/
/
ꢃ
/
/
ꢃ
/
[1] R.B.A. Pardy, I. Tkatchenko, J. Chem. Soc. Chem. Comm. (1981)
49.
/
[2] R. Ceder, G. Muller, J. Sales, J. Vidal, D. Neibecker, I.
Tkatchenko, J. Mol. Catal. 68 (1991) 23.
/
/
ꢃ
/
[3] A. Ecke, W. Keim, F. Dahan, M.C. Bonnet, I. Tkatchenko,
Organometallics 14 (1995) 5302.
/
[4] M.C. Bonnet, F. Dahan, A. Ecke, W. Keim, R.P. Schultz, I.
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[5] A. Mechria, M. Rzaigui, F. Bouachir, Tetrahedron Lett. 41 (2000)
7199.
/
/
/
125.2, 125.4 (Cm,m?); 126.2 (Cp); 129.6 (C8); 129.9 (C6);
132.1 (C9); 134.3 (C10); 135.6 (Co,o?); 138.5 (C11); 143.0
(C2); 147.8 (C12); 173.5 (C5).
[6] B. Bogdanovic, M. Kroner, G. Wilke, Annalen 1 (1966) 699.
[7] R. van Asselt, E. Rijnberg, C. Elsevier, J. Organometallics 13
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[8] R. van Asselt, E.E.C.G. Gielens, R.E. Rulke, K. Vrieze, C.J.
¨
Elsevier, J. Am. Chem. Soc. 116 (1994) 977.
1.4. Preparation of 4d
[9] R. van Asselt, C.J. Elsevier, W.J.J. Smeets, A.L. Spek, R.
Benedix, Recl. Trav. Chim. Pays-Bas 113 (1994) 88.
The complex 4d was obtained from [PhÃ
following the procedure for 4c, in 83% yield as a red
solid. Decomposition: 220 8C. IR [n cmꢁ1] (KBr): 843
/BIC]NiBr2
[10] M. Svoboda, H. tom Dieck, J. Organomet. Chem. 191 (1980) 321.
[11] J. Feldman, S.J. McLain, A. Parthasarathy, W.J. Marshall, J.C.
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