Phosphine nickel(0) π-complexes with vinylcyclosilazane - Synthesis and structure

Article abstract of DOI:10.1016/S0277-5387(02)01001-X

Synthesis, spectroscopic (¹H, ¹³C, ³¹p, ²⁹Si NMR) characterisation and X-ray structure of the first nickel(O) π-complex with vinylcyclosilazane [{Ni(PPh₃)}₂{μ-(η-CH₂=CH(Me) Si(μ-NH))₄}] (1a) have been presented. This is the first report on the structure of a TM complex with a vinylsilazane ligand. Complex 1a is synthesised by the reaction of [Ni(cod)₂] with cyclotetra (vinylmethylsilazane). The complex occupies a special position of the space group P2_1/c on the centre of symmetry that lies in the middle of the cyclotetrasilazane ring. The coordination of nickel is close to triangular one.

Full text of DOI:10.1016/S0277-5387(02)01001-X

Polyhedron 21 (2002) 1261Á1265
/
www.elsevier.com/locate/poly
Phosphine nickel(0) p-complexes with vinylcyclosilazane
synthesis and structure
*
/
Hieronim Maciejewski *, Maciej Kubicki, Bogdan Marciniec, Agnieszka Sydor
Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan´, Poland
Received 8 January 2002; accepted 13 March 2002
Abstract
Synthesis, spectroscopic (1H, 13C, 31P, 29Si NMR) characterisation and X-ray structure of the first nickel(0) p-complex with
vinylcyclosilazane [{Ni(PPh3)}2{m-(h-CH2ÄCH(Me)Si(m-NH))4}] (1a) have been presented. This is the first report on the structure
/
of a TM complex with a vinylsilazane ligand. Complex 1a is synthesised by the reaction of [Ni(cod)2] with cyclotetra
(vinylmethylsilazane). The complex occupies a special position of the space group P21/c on the centre of symmetry that lies in
the middle of the cyclotetrasilazane ring. The coordination of nickel is close to triangular one. # 2002 Elsevier Science Ltd. All
rights reserved.
Keywords: Nickel(0); Vinylcyclosilazane complexes; Crystal structure
1. Introduction
methyldisiloxane gave [{Pt(h-CH2Ä
CHC(O)OC(O)CH}] [4], [{Pt(h-CH2Ä
(h2-CH2Ä
CHPh)] [4] and [{Pt(h-CH2Ä
{h2-(CH2Ä
CHSiMe2)2O}] [5].
Due to the fact that tertiary phosphine ligands play a
crucial role in many industrially important metals*
catalysed organic reactions, phosphine metal*vinylsi-
/
CHSiMe2)2O}{h2-
/
CHSiMe2)2O}-
CHSiMe2)2O}-
The recent interest in the chemistry of transition metal
olefin complexes containing vinyl derivatives of orga-
nosilicon compounds as p-ligands is fully justified not
only by the particular nature of the bond between
vinylsilicon derivatives and transition metals, but mainly
by the possible application of this kind of complex as
catalysts in hydrosilylation of olefins [1]. Hydrosilyla-
tion is also used to a much greater extent in industry to
produce crosslinked products [2]. Such processes gen-
/
/
/
/
/
licon complexes were also synthesised [6,7]. The reaction
between Karstedt’s catalyst [{Pt(LL)}2(m-LL)] (where
LLꢀ
/
{CH2Ä
/
CHSiMe2}2O) and mono-, bis- or tris(ter-
tiary phosphine) led to complexes of the type
[Pt(LL)(PR3)] [6], [{Pt(LL)}2(DIPHOS)] or
erally require the use of highly active platinum*
/
[{Pt(LL)}3(TRIPHOS)] [7], respectively. Moreover there
is arousing interest in complexes with cyclic p-vinylsili-
con ligands. Cyclotetrakis[vinyl(methyl)siloxane] has
been used to generate the platinum complex
containing catalysts. One class of platinum compounds
used as hydrosilylation catalysts includes Pt(0) com-
plexes containing vinyl-siloxane ligands. An example is
the Karstedt’s catalyst, which contains both bridging
[{Pt(PPh3)}2{m-(h-CH2ÄCH(Me)Si(m-O))4}] acting as a
/
and chelating divinyl ligands [{Pt(h-CH2Ä
Me2)2O}2{m-(h-CH2ÄCHSiMe2)2O}] [3,4]. Besides
showing a high catalytic activity, this complex is also a
good starting compound for synthesis of other plati-
num(0) p-complexes. The treatment of the Karstedt’s
catalyst with maleic anhydride, styrene or divinyltetra-
/
CHSi-
hydrosilylation catalyst equivalent to Karstedt’s catalyst
[2,5,9].
/
The cost of platinum compounds has stimulated much
research to check other transition metal compounds as
potential hydrosilylation catalysts. By analogy to Kar-
stedt’s catalyst, the nickel complex [{Ni(h-CH2Ä
/
CHSi-
Me2)2O}2{m-(h-CH2ÄCHSiMe2)2O}] was obtained and
/
showed high catalytic activity in the hydrosilylation and
related reactions (dehydrogenative coupling especially
of vinyl derivatives) [10]. In analogy to platinum
* Corresponding author. Tel.: ꢁ
91508.
E-mail address: maciejm@main.amu.edu.pl (H. Maciejewski).
/
48-61-82-91366; fax: ꢁ48-61-82-
/
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 0 0 1 - X

1262
H. Maciejewski et al. / Polyhedron 21 (2002) 1261Á1265
/
complexes, those of the type [Ni(LL)(PR3)] were also
prepared [6,7]. Very recently, nickel complexes with
3J(1H1Ã
3J(1H3Ã
/
31P)ꢀ
31P)ꢀ
/
4.6
6.0 Hz.
Hz,
3J(1H2Ã
/
31P)ꢀ
/
7.7
Hz,
/
/
cyclotetrasiloxane [{Ni(PR3)}2{m-(h-CH2Ä/CH(Me)Si-
13C NMR (C6D6, 298 K, 125.8 MHz); d 2.66 (s, CH3),
(m-O))4}] were synthesised and the X-ray structure of
one of them was determined [11]. There are also well
known platinum or nickel complexes with vinylsilanes
(i.e. vinyltrimethylsilane [12,13] or divinyldimethylsilane
[7]) used as ligands, however, the application of vinyl
derivatives of silazane as ligands in organometallic
chemistry has been rather rare. Hitherto only two
examples of the synthesis of nickel complexes with
60.66 (d, Ä
/
CHÃ
Ph), J(13C1Ã31P)ꢀ
29Si NMR (C6D6, 298 K, 99.4 MHz); d ꢃ
3J(29SiÃ31P)ꢀ
3.8 Hz.
31P NMR (C6D6, 298 K, 101.2 MHz); d 38.59.
/
), 62.93 (s, Ä
/
CH2), 129.00Á134.00 (m,
/
2
/
/
6.7 Hz.
/
12.07(d),
/
/
2.2.2. [{NiP(C6H4Me-4)3}2{m-(h-CH2Ä
NH))4}] (1b)
/CH(Me)Si(m-
linear divinyltetramethyldisiloxane, i.e. [{Ni(h-CH2Ä
CHSiMe2)2NH}2 {m-(h-CH2ÄCHSiMe2)2NH}] and
[Ni(PR3)(h-CH2ÄCHSiMe2)2NH}], have been reported
in Ph.D. Theses [8,14], however, they have not been fully
characterised and their crystallographic structures have
not been resolved.
/
Compound 1b (0.76 g, 0.74 mmol, 82%) was prepared
in a similar manner to 1a, except that P(C6H4Me-4)3 was
used in the place of PPh3. Yellow crystals of 1b were
obtained by recrystalisation from benzene, at ambient
temperature.
/
/
1H NMR (C6D6, 298 K, 300 MHz); d 0.15 (s, 12H),
In this paper, we present a synthetic procedure,
spectroscopic characterisation and X-ray structure of
2.10 (s, 9H), 2.72 (td, 4H), 3.12 (dd, 8H), 6.90Á
24H).
13C NMR (C6D6, 298 K, 125.8 MHz); d 2.39 (s, CH3),
21.58 (s, CH3), 58.28 (s, ÄCHÃ), 61.86 (s, ÄCH2),
127.90Á139.22 (m, tol).
29Si NMR (C6D6, 298 K, 99.4 MHz); d ꢃ
31P NMR (C6D6, 298 K, 101.2 MHz); d 39.24.
/
7.34 (m,
phosphineÁnickel complexes with vinylcyclosilazane
/
ligands. To the best of our knowledge this is the first
example of a fully characterised TM complex with a
vinylsilazane ligand.
/
/
/
/
/
12.57 (d).
2.2.3. [{NiP(C6H11-c)3}2{m-(h-CH2Ä
/CH(Me)Si(m-
2. Experimental
NH))4}] (1c)
Compound 1c (0.65 g, 0.66 mmol, 72%) was prepared
in a similar manner to 1a, except that P(C6H11-c)3 was
used in the place of PPh3. Yellow crystals of 1c were
obtained by recrystalisation from benzene at ambient
temperature.
2.1. General procedures
All reagents were dried and purified before use by the
usual procedures. [Ni(cod)2] was prepared as described
in literature [15]. Other chemicals were purchased from
Fluka. The NMR spectra (1H, 13C, 31P, 29Si) were
recorded on a Varian XL 300 spectrometer. In all cases
C6D6 was used as a solvent.
1H NMR (C6D6, 298 K, 300 MHz); d 0.17 (s, 12H),
1.21Á
13C NMR (C6D6, 298 K, 125.8 MHz); d 2.54 (s, CH3),
26.23Á35.54 (m, C6H11-c), 59.76 (s, ÄCHÃ), 61.34 (s, Ä
CH2).
/1.82 (m, 33H), 2.63 (td, 4H), 3.08 (dd, 8H).
/
/
/
/
29Si NMR (C6D6, 298 K, 99.4 MHz); d ꢃ
12.94(d).
/
2.2. Synthesis of complexes
31P NMR (C6D6, 298 K, 101.2 MHz); d 38.27.
2.2.1. [{Ni(PPh3)}2{m-(h-CH2Ä
/CH(Me)Si(m-
NH))4}] (1a)
2.3. Crystal structure determination of 1a
Cyclotetrakis [vinyl(methyl)silazane] (2 ml) was added
slowly to a stirred red suspension of [Ni(cod)2] (0.5 g, 1.8
mmol) and PPh3 (0.47 g, 1.8 mmol) in diethyl ether (10
ml) at ambient temperature, yielding a yellow solution.
The reaction mixture was allowed to stir overnight. The
volatiles were removed in vacuo to give a yellow oil,
Diffraction data from a yellow, prism-shaped crystal
with dimensions 0.2ꢂ0.2ꢂ0.15 mm, sealed in a glass
capillary, were collected on a KUMA KM4CCD
/
/
diffractometer [16] at room temperature (r.t.), using
graphite-monochromated Mo Ka radiation (lꢀ
/
˚
0.71073 A). The data collection was performed in six
which was extracted into pentane (2ꢂ
was filtered through Celite. The filtrate was concen-
trated, then set aside at ꢃ30 8C to yield a yellow solid
/2 ml). The extract
separate runs in order to cover the symmetry-indepen-
dent part of the reciprocal space. The v-scan was used
with a step of 0.758, two reference frames were measured
after every 50 frames, they did not show any systema-
tical changes either in the peaks positions or in their
intensities. A total of 782 frames was collected, giving
/
compound (0.66 g, 0.72 mmol, 79%). Yellow crystals of
1a suitable for X-ray diffraction, were grown from
benzene at ambient temperature over a period of 24 h.
1H NMR (C6D6, 298 K, 300 MHz,) d 0.09 (s, 12H),
2.68 (td, 4H), 3.04 (dd, 8H), 7.08Á
/
7.76 (m, 30H);
16.0 Hz,
22 024 reflections up to 2uꢀ
meters were determined by the least-squares treatment
/
608. The unit-cell para-
3J(1H1Ã1H2)ꢀ12.0 Hz, 3J(1H1Ã1H3)ꢀ
/
/
/
/

H. Maciejewski et al. / Polyhedron 21 (2002) 1261Á
/
1265
1263
of the setting angles of 2400 highest-intensity reflections,
chosen from the whole experiment. The Lorentz and
polarisation corrections were applied [17], and then the
reflexes were merged and corrected for absorption
3. Results and discussion
The reaction of [Ni(cod)2] with cyclotetra(vinyl-
methylsilazane) in the presence of tertiary phosphine
was effective for the preparation of the corresponding
(Amin
ꢀ
/
0.747, Amax
ꢀ0.767) with Sortav [18]. The
/
phosphine nickelÁvinylcyclosilazane complexes accord-
ing to the following equation.
/
merging procedure produced 6003 unique data with
Rint of 0.13. The structure was solved by direct methods
with SHELXS-97 program [19], and refined with full-
matrix least-squares by SHELXL-97 [20]. Non-hydrogen
atoms were refined anisotropically, hydrogen atoms
were generated geometrically and were refined as a
‘riding model’ with their Uiso parameters set at 1.2 times
Ueq of the appropriate carrier atom. Selected geometric
parameters are listed in Table 1.
Crystallographic data for [Ni2(PPh3)2(Si4N4C12H28)]:
empirical formula Ni2P2Si2N4C48H58, monoclinic, space
The above reaction seems to be a very simple and
convenient route to synthesise various phosphine com-
plexes with vinylsilicon ligands. As mentioned earlier,
the nickel phosphine complexes with cyclotetra(vinyl-
˚
˚
group P21/c, aꢀ
/
13.5628(17) A, bꢀ
90.349(10)8, Vꢀ
1.332 g cmꢃ3, m(Mo Ka)ꢀ
1032, R(F) [Foꢀ4(Fo)]ꢀ
0.057, wR(F2)ꢀ
ꢃ1ꢀ[s2(Fo)2ꢁ(0.01P)2ꢁ5P]ꢃ1 (Max(Fo 2,0)ꢁ
Pꢀ
2Fc 2/3), Sꢀ
1.29, (D/s)max
/
9.7290(12) A, cꢀ
/
3
˚
˚
18.605(2) A, bꢀ
/
/
2454.9(5) A , Zꢀ
/2,
dxꢀ
/
/
0.97 mmꢃ1, F(000)ꢀ
0.127, where
/
/
/
/
methylsiloxane) [{Ni(PR3)}2{m-(h-CH2Ä
O))4}] (2) (where RꢀC6H5 (a), C6H4ÃMe (b) and c-
C6H11 (c)) were synthesised previously [11].
/
CH(Me)Si(m-
w
/
/
/
,
/
/
/
/
/
ꢀ
/
0.001 in the last cycle of
0.42 e Aꢃ3, Drmin
ꢃ3
˚
˚
refinement, Drmax
ꢀ
/
ꢀ
/
ꢃ
/
0.35 e A
.
Table 1
˚
Selected bond lengths (A), bond angles (8) and torsion angles (8) with e.s.d.’s in parentheses
Bond lengths
Ni(1)ÃX(1)
Ni(1)ÃP(1)
P(1)ÃC(31)
Si(1)ÃN(2)
Si(1)ÃC(1A)
C(1A)ÃC(1B)
C(2A)ÃSi(2)
Si(2)ÃN(1)
1.890(10)
2.175(3)
1.850(12)
1.710(9)
1.840(10)
1.364(14)
1.841(11)
1.722(7)
Ni(1)ÃX(2)
P(1)ÃC(21)
P(1)ÃC(11)
Si(1)ÃN(1)
Si(1)ÃC(1)
C(2A)ÃC(2B)
N(2)ÃSi(2)
Si(2)ÃC(2)
1.920(10)
1.836(10)
1.859(12)
1.722(8)
a
1.873(10)
1.417(15)
1.724(9)
1.872(11)
Bond angles
X(1)ÃNi(1)ÃX(2)
X(2)ÃNi(1)ÃP(1)
C(31)ÃP(1)ÃNi(1)
127.5(4)
117.1(4)
116.8(4)
111.0(4)
111.3(5)
105.4(5)
121.6(8)
129.7(5)
111.1(5)
105.8(4)
108.9(5)
X(1)ÃNi(1)ÃP(1)
C(21)ÃP(1)ÃNi(1)
C(11)ÃP(1)ÃNi(1)
N(2)ÃSi(1)ÃC(1A)
N(2)ÃSi(1)ÃC(1)
C(1A)ÃSi(1)ÃC(1)
C(2B)ÃC(2A)ÃSi(2)
N(1)ÃSi(2)ÃN(2)
N(2)ÃSi(2)ÃC(2A)
N(2)ÃSi(2)ÃC(2)
Si(1) aÃN(1)ÃSi(2)
113.6(3)
123.1(4)
108.1(4)
108.9(5)
112.1(5)
108.1(4)
121.2(8)
111.3(4)
109.1(4)
110.7(5)
132.7(5)
a
N(2)ÃSi(1)ÃN(1)
N(1)iÃSi(1)ÃC(1A)
N(1)iÃSi(1)ÃC(1)
C(1B)ÃC(1A)ÃSi(1)
Si(1)ÃN(2)ÃSi(2)
N(1)ÃSi(2)ÃC(2A)
N(1)ÃSi(2)ÃC(2)
C(2A)ÃSi(2)ÃC(2)
Torsion angles
N(2)ÃSi(1)ÃC(1A)ÃC(1B)
C(1)ÃSi(1)ÃC(1A)ÃC(1B)
C(1A)ÃSi(1)ÃN(2)ÃSi(2)
Si(1)ÃN(2)ÃSi(2)ÃN(1)
Si(1)ÃN(2)ÃSi(2)ÃC(2)
C(2B)ÃC(2A)ÃSi(2)ÃN(2)
ꢃ134.2(8)
103.8(9)
23.1(8)
N(1) aÃSi(1)ÃC(1A)ÃC(1B)
N(1) aÃSi(1)ÃN(2)ÃSi(2)
C(1)ÃSi(1)ÃN(2)ÃSi(2)
ꢃ11.5(10)
ꢃ99.9(7)
142.6(6)
101.8(7)
ꢃ140.8(6)
130.4(9)
Si(1)ÃN(2)ÃSi(2)ÃC(2A)
C(2B)ÃC(2A)ÃSi(2)ÃN(1)
C(2B)ÃC(2A)ÃSi(2)ÃC(2)
ꢃ21.1(8)
7.4(10)
ꢃ108.8(9)
92.6(8)
a
a
N(2)ÃSi(2)ÃN(1)ÃSi(1)
C(2)ÃSi(2)ÃN(1)ÃSi(1)
ꢃ29.2(9)
ꢃ149.4(8)
C(2A)ÃSi(2)ÃN(1)-Si(1)
a
X1 and X2 denote the middlepoints of the C1AÃC1B and C2AÃC2B bonds, respectively.
a
Symmetry transformations used to generate equivalent atoms: ꢃxꢁ1, ꢃy, ꢃzꢁ1.

1264
H. Maciejewski et al. / Polyhedron 21 (2002) 1261Á
/
1265
All kinds of analyses of the crystalline yellow com-
plexes 1aÁc have brought satisfactory results. The NMR
spectra taken for complexes 1aÁc, were very similar to
those for complexes 2aÁc. The NH signal was not
/
/
/
1
observed in the spectra which is consistent with the H
spectrum obtained for hexamethyldisilazane [21].
The 1H NMR spectra of 1aÁ
c reveals one signal from
/
the methyl group and two signals from the vinyl group
in the region appropriate for vinylsilicon complexes of
this type. The 13C NMR spectra also confirm the
structure of complexes 1aÁc. These spectra showed
/
one signal assigned to the methyl carbons and the
signals corresponding to the vinyl carbons at frequencies
lower than those observed for the free ligand. The 31P
NMR spectra of each of the complexes obtained
revealed a single signal. The signals in these spectra
showed some differences in positions, depending on the
type of phosphine used, however, they always appeared
in the region typical of a coordinated phosphine. The
Fig. 2. The conformation of the tetrasilazane ring. The thermal
ellipsoids are drawn at 50% probability level, only symmetry-indepen-
dent atoms are labelled.
double bonds, respectively). The NiÃ
/
P bond length of
2.175(3) A is within the range for short NiÃP bonds (the
NiÃP lengths distribution is bimodal [22]).
˚
/
/
1
values of spectroscopic chemical shifts in H, 13C and
The eight-membered silazane ring adopts the chair
conformation; six atoms N1, Si2, Si1, N1?, Si2? and Si1?
are almost perfectly coplanar (the prime denotes the
atoms created by the centre of symmetry), with the
largest deviation from the least-square plane of 0.012(5)
31P NMR spectra for complexes 1aÁ
/c are quite similar
to those for complexes 2aÁ
/
c, but some differences are
observed in the 29Si NMR spectra. For the complexes
with vinylsiloxane ligands, the 29Si NMR spectrum
showed signals at ꢃ
complexes with vinylsilazane these signals were observed
at ꢃ12 ppm. The difference depends on the nature of
/
24 ppm but in the spectra of
˚
A, while the N2 and N2? atoms are tilted out of this
˚
0.729(9) A, respectively, (Figs. 1 and
plane by ꢁ
/
and ꢃ
/
/
2). This different character of N1 and N2 nitrogen
atoms is reflected in differences of the SiÃNÃSi angles:
132.7(5)8 for N1 and 129.7(5)8 for N2, while the SiÃ
bond lengths are almost equal with the mean value of
the vinylsilicon compounds used.
The crystal structure of 2b is very similar to that one
established for 1a.
/
/
/N
The complex 1a lies in a special position of the space
group P21/c, on the centre of symmetry that lies in the
middle of the cyclotetrasilazane ring. The coordination
of nickel is close to a triangular (regarding the mid-
dlepoints of the double bonds as coordination centres),
however, some degree of pyramidalization can be
noticed. The sum of the angles around nickel is
˚
1.720(2) A. The methyl substituents are in quasi-
equatorial positions, and the vinyl ones in quasi-axial
ones (cf. Table 1).
The phenyl rings are planar within experimental error,
˚
Car bond length is 1.380(7) A,
the mean value of the CarÃ
/
and agrees well with the typical value. The mutual
disposition of these rings can be described by the
dihedral angles between their least-squares planes A/B
85.1(4)8, B/C 72.6(4)8, A/C 82.8(3)8, where A, B, and C
denote the rings with C11, C21, and C31 atoms,
respectively. The crystal packing is determined mainly
by van der Waals interactions.
˚
358.2(3)8 and the Ni1 atom is displaced by 0.156(5) A
from the plane defined by P1, X1 and X2 (X1 and X2
denote the middlepoints of C1AÃ
/
C1B and C2AÃ
/
C2B
4. Conclusions
1) Nickel complexes of the type [{Ni(PR3)}2{m-(h-
CH2ÄCH(Me)Si(m-NH))4}] are the first examples
/
of TM complexes with vinylsilazane whose crystal
structure has been determined.
2) The NMR and crystal structure data obtained have
proved that the compounds 1aÁ
/
c and 2aÁc are
/
similar. They both are binuclear nickel(0) complexes
with a inversion centre at the mid-point of the chair-
shaped (SiO)4 or (SiNH)4 ring.
Fig. 1. The thermal ellipsoid view of the complex 1a (at 50%
probability level) with the numbering scheme [23]. The hydrogen
atoms are omitted for clarity.

H. Maciejewski et al. / Polyhedron 21 (2002) 1261Á
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1265
1265
[3] B.D. Karstedt, US Patent 3775452, 1973.
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Int. Ed. Engl. 30 (1991) 438.
3) Phosphine nickel(0) p-complexes with vinylcyclosi-
lazane ligands seem to be promising potential
catalysts for hydrosilylation and related reactions;
the catalytic aspects will be considered in a separate
paper.
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5. Supplementary data
Supplementary data are available from the CCDC, 12
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336033; e-mail: deposit@ccdc.cam.ac.uk; or www:
http://www.ccdc.cam.ac.uk) on request, quoting the
deposition number CCDC 168038.
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