Synthesis and characterization of (η5-cyclopentadienyl) (η5-(1-(η5-cyclopentadienyl))-2-phenyl-3-ethyl-1- nickelaindenyl)nickel, a new nickelacyclic analogue of nickelocene

Article abstract of DOI:10.1016/j.inoche.2006.01.006

A new nickelacyclic compound (η⁵-cyclopentadienyl) (η⁵-(1-(η⁵-cyclopentadienyl))-2-phenyl-3-ethyl-1- nickelaindenyl)nickel was synthesised in the reaction of (E)-1-lithio-1-phenyl- 2-(2′-lithiophenyl)ethane with nickelocene. The compound was characterised by high resolution mass spectrometry, magnetic moment determination and X-ray single crystal analysis. It crystallises from hexane/THF mixture in the monoclinic crystal system and the P2₁/n space group.

Full text of DOI:10.1016/j.inoche.2006.01.006

Inorganic Chemistry Communications 9 (2006) 375–378
www.elsevier.com/locate/inoche
Synthesis and characterization of
(g5-cyclopentadienyl)(g5-(1-(g5-cyclopentadienyl))-2-phenyl-3-ethyl-1-
nickelaindenyl)nickel, a new nickelacyclic analogue of nickelocene
a,
a
a
Piotr Buchalski *, Stanisław Pasynkiewicz , Antoni Pietrzykowski ,
a
b
´
Artur Piłka , Kinga Suwinska
a
Warsaw University of Technology, Faculty of Chemistry, Koszykowa 75, 00-662 Warsaw, Poland
Institute of Physical Chemistry of the Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
b
Received 16 November 2005; accepted 11 January 2006
Available online 9 March 2006
Abstract
A new nickelacyclic compound (g5-cyclopentadienyl)(g5-(1-(g5-cyclopentadienyl))-2-phenyl-3-ethyl-1-nickelaindenyl)nickel was syn-
thesised in the reaction of (E)-1-lithio-1-phenyl-2-(20-lithiophenyl)ethane with nickelocene. The compound was characterised by high res-
olution mass spectrometry, magnetic moment determination and X-ray single crystal analysis. It crystallises from hexane/THF mixture
in the monoclinic crystal system and the P21/n space group.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Nickel; Alkali metals; Clusters; Cyclopentadienyl; Metallacyclic compounds
We have recently reported that a new metallacyclic com-
pound, (g5-cyclopentadienyl)(g5-(1-(g5-cyclopentadienyl))-
2-phenyl-3-methyl-1-nickelaindenyl)nickel, which could be
regarded as a nickelacyclic analogue of nickelocene, was
formed, among other products, in the reaction of nickelo-
cene with sodium in the presence of trans-methylstilbene
[1]. The compound was formed in low yield (about 2%),
therefore the above reaction could not be regarded as a syn-
thetic method of preparation of this compound.
To achieve that goal, we have carried out the reaction
of (E)-1-lithio-1-phenyl-2-(20-lithiophenyl)ethene complex
with TMEDA, 1 with nickelocene in diethyl ether.
Et
+ 2 NiCp2
2 TMEDA
·
Ph
Li Li
1
Cyclopentadienylnickel compounds have been recently
thoroughly investigated due to their ability of polymerising
alkenes and alkynes and the possibility of application in
organic syntheses [2–4]. Finding a suitable preparative
method of synthesis of such nickelocene analogues would
give a chance to check their catalytic properties.
ð1Þ
NiCp
Et
Et2O
+ LiCp
Ph
Ni
Cp
2
Nickelocene (1.825 g, 9.7 mmol), TMEDA complex of
(E)-1-lithio-1-phenyl-2-(20-lithiophenyl)ethene [5] (2.368 g,
5.2 mmol) and 50 cm3 of diethyl ether were placed in Schlenk
flask and stirred at ꢀ15 °C for 2 h and then overnight
*
Corresponding author. Tel.: +48 22 660 7859; fax: +48 22 660 5462.
E-mail address: pjb@ch.pw.edu.pl (P. Buchalski).
1387-7003/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2006.01.006

376
P. Buchalski et al. / Inorganic Chemistry Communications 9 (2006) 375–378
at room temperature. After the reaction was completed, the
solvent was removed and the residue was extracted with
80 cm3 toluene. The extract was filtered through the alu-
mina layer and the solvent was evaporated. The residue
was dissolved (6 cm3 of hexane + 5 cm3 of toluene) and
chromatographed on alumina (deactivated with 5% of
water). One brown band was collected (hexane/toluene
4:1). The solvent was removed and compound 2 was
obtained (1.255 g, 2.8 mmol, 58%) as a brown solid. Crys-
tals appropriate for X-ray measurements were grown from
hexane/THF solution.
Compound 2 is a dark-brown crystalline solid soluble in
common organic solvents. It can be regarded as an ana-
logue of nickelocene in which one of the cyclopentadienyl
rings is replaced with nickelacyclopentadienyl ring. Similar
to nickelocene, it does not react with water but slowly oxi-
dises in air.
The compound was characterized by mass spectrometry
and magnetic moment measurements. EI HR MS:
observed 452.05921, calcd. for C26H2458Ni2 452.05850.
EIMS spectrum of 2 showed the parent ion at m/e 452
(58Ni calc.) with an isotopic pattern characteristic for two
Fig. 1. ORTEP view of the molecular structure of 2 showing the atom
numbering scheme. Thermal ellipsoids drawn at 30% probability level.
1
nickel atoms in a molecule1. In H NMR spectrum of 2,
there were no signals in the range between 0 and 10 ppm.
There were no signals in X-band EPR spectrum at room
temperature and at 77 K.
Table 1
a
˚
Selected bond lengths (A) and angles (degree) in 2
Ni(1)–Ni(2)
Ni(1)–C(12)
Ni(1)–C(11)
Ni(1)–C(17)
Ni(1)–C(18)
Ni(2)–C(12)
2.4176(4)
2.211(2)
2.245(2)
2.179(2)
2.119(2)
1.895(3)
Ni(2)–C(18)
Ni(1)–Cg1
Ni(2)–Cg2
C(11)–C(12)
C(11)–C(17)
C(17)–C(18)
1.908(2)
1.805(1)
1.757(1)
1.430(3)
1.464(3)
1.372(3)
Magnetic susceptibility was determined by NMR mea-
surements at 298 K by Evans method [6–8] from differ-
ences in chemical shifts of methyl group protons of
toluene used as solvent and as external standard. The
magnetic moment calculated from these measurements
was 2.53 lB, which indicated that compound 2 is para-
magnetic and corresponded to 2 unpaired electrons per
molecule.
The compound crystallises in a monoclinic crystal sys-
tem (space group P21/n)2. The molecular structure of 2 is
presented in Fig. 1. Selected bond lengths and angles are
shown in Table 1. Crystallographic data for the structural
analysis of 2 have been deposited with the Cambridge Crys-
tallographic Data Centre, CCDC No. 289549. Copies of
this information may be obtained free of charge from
The Director, CCDC, 12, Union Road, Cambridge CB2
C(12)–Ni(2)–C(18)
Ni(2)–C(18)–C(17)
C(18)–C(17)–C(11)
C(17)–C(11)–C(12)
a
83.81(10)
116.08(17)
113.2(2)
C(11)–C(12)–Ni(2)
Ni(1)–Ni(2)–Cg2
Ni(2)–Ni(1)–Cg1
114.77(17)
141.19(2)
139.96(2)
111.9(2)
Estimated standard deviations in parentheses.
1EZ (fax +44 223 36033 or e-mail: deposit@ccdc.cam.a-
c.uk or http://www.ccdc.cam.ac.uk).
Both cyclopentadienyl and nickelacyclopentadienyl
rings are almost parallel forming a typical sandwich com-
pound. To define a bonding mode of the central nickel
atom (Ni1) to the nickelacyclopentadienyl ring, we have
determined the degree of slip-fold distortion, using param-
eters as described in [13]. The slip parameter defined as
1
EIMS (70 eV) m/e (calcd. for 58Ni; rel. int.): 452 (M+, 16%), 424
(C24H20Niþ2 , 46%), 246 (C10H10Ni2þ, 100%), 208 (C16H1þ6, 48%), 188
(C10H10Ni+, 69%), 123 (C5H5Ni+, 21%), 105 (C8Hþ9 , 58%), 91 (C7Hþ7 ,
29%).
DM–C = avg d(M–C11, C12) ꢀ avg d(M–C17, C18) is
˚
0.079(4) A. The hinge angle, HA defined as the angle
between the planes [Ni2, C17, C18] and [Ni2, C11, C12,
C17] is 3.60°. The fold angle, FA, defined as the angle
between the planes [Ni2, C17, C18] and [C11, C12, C13,
C14, C15, C16] is 5.00°. All these values correspond to
nearly undistorted g5-coordination of the ring [13]. It is
interesting to compare the structural parameters of 2 with
the structurally characterized indenyl complexes of other
metals [14]. The striking feature of indenyl complexes with
g5 bonded indenyl ligands is a more localized bonding
2
Crystal structure determination. The crystal was sealed in a glass
capillary under nitrogen stream. Unit cell from 3783 reflections
2.91 < h < 26.37°. X-ray data were collected on a Nonius Kappa CCD
diffractometer. Data were collected with subsequent u and x scans (300
frames, rotation per frame 1°, exposure per frame 10 s) 12,483 reflections
collected, 4174 unique, 3182 above threshold [I > 2 (I)]. Diffractometer
control program Collect [9], unit cell parameters and data reduction with
Denzo and Scalepak [10], structure solved by direct methods SHELXS-97
[11] and refined on F2 by full-matrix least-squares with SHELXL-97 [12].
All the hydrogen atoms were placed in calculated positions and refined
using a riding model. Final R indices R1 = 0.0370, R1 (all data) = 0.0582.

P. Buchalski et al. / Inorganic Chemistry Communications 9 (2006) 375–378
377
Fig. 2. Selected interatomic distances in 2. Cyclopentadienyl rings were omitted for clarity.
within the 6-membered ring [13,15]. We did not observe
this phenomenon in 2. This is probably due to the replace-
ment of one carbon atom in 5-membered ring by the nickel
atom, prevents a typical aromatisation of this ring. At pres-
ent, there are too few examples of the structurally charac-
terised metallaindenyl complexes to discuss this
phenomenon further.
bond is formed and the species 4 stabilises by the formation
of nickelacyclopentadienyl ring 5.
Et
Ni
+
Ph
(TMEDA)Li Li(TMEDA)
3
The position of Ni1 atom over the nickelaindenyl ring is
shown in Fig. 2. The Ni2 atom together with four carbon
atoms forms an almost flat nickelacyclopentadienyl ring
(the maximum deviation from the mean plane defined by
Et
Et
Ph
Ni
Cp
Ph
˚
C11, C12, C17, C18 and Ni2 atoms is 0.0407 A for C12).
(TMEDA)Li
(TMEDA)Li Ni
Cp
The central nickel atom (Ni1) possesses 20 VE, like the
nickel atom of nickelocene, and is placed between this ring
and the cyclopentadienyl ring. Both rings lay almost paral-
lel to each other. The dihedral angle between the planes
defined by both rings is 4.7°. A comparison of bond lengths
between compound 2 and the analogous compound
described by us previously [1] showed that the correspond-
ing values are almost identical. Both compounds can then
be regarded as the first examples of nickelacyclic analogues
of nickelocene.
5
4
ð3Þ
The second lithium atom reacts then with another nickelo-
cene molecule to form the final product 2.
Et
Ph
Ni
Cp
(TMEDA)Li
The formation of 2 can be explained by the following
scheme: It can be assumed that one of the cyclopentadienyl
rings of nickelocene can undergo g5 ! g1 bonding mode
transformation to species 3 in which nickel atom possesses
16 VE [16].
5
ð4Þ
NiCp
Et
NiCp2
+ CpLi
Ph
Ni
Cp
Ni
2
Ni
ð2Þ
Appendix A. Supplementary data
3
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.inoche.
2006.01.006.
The nickel atom in 3 is exposed to the nucleophilic attack
of carbon atom bonded to lithium in 1. The nickel carbon

378
P. Buchalski et al. / Inorganic Chemistry Communications 9 (2006) 375–378
[9] B.V. Nonius, ‘‘Collect’’ Data Collection Software, 1998.
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