Reactions of M[CH(SiMe3)2] (M = Na or K) with PhCN, and related chemistry

Article abstract of DOI:10.1039/b601881e

A number of metal complexes containing one of the following ligands: the 1-azaallyl [N(R)C(Ph)C(H)R]^- (L^-), the 1,3-diazaallyl(≡ LL′^-) and the isomeric β-diketiminate [{N(R)C(Ph)]}₂CH]^- (≡ LL ^-

Full text of DOI:10.1039/b601881e

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PAPER
www.rsc.org/dalton | Dalton Transactions
Reactions of M[CH(SiMe3)2] (M = Na or K) with PhCN, and related
chemistry
Peter B. Hitchcock, Michael F. Lappert* and Rafae¨l Sablong
Received 8th February 2006, Accepted 7th June 2006
First published as an Advance Article on the web 20th June 2006
DOI: 10.1039/b601881e
A number of metal complexes containing one of the following ligands: the 1-azaallyl
|
[N(R)C(Ph)C(H)R]− (≡L−), the 1,3-diazaallyl[N(R)C(Ph)NC(Ph) = C(H)R]− (≡ LLꢀ−) and the
isomeric b-diketiminate [{N(R)C(Ph)]}2CH]− (≡ LL−) have been prepared (R = SiMe3). These are the
crystalline compounds H(LL) (2), Na(LL) (3), [Na(LL)(thf)2] (4), Na(L) (6), [Na(l-LLꢀ)]8 (7),
6
[K(l-L)(g -C6H6)]2 (8), [K(l-LLꢀ)(thf)]2 (9), [K(thf)2(l-LL)]∞ (10) and [Ni(LLꢀ)2] (11). A new synthesis
of Na[C(H)R2] (1) involved Hg[C(H)R2]2 and Na/Hg as reagents. The b-diketimine 2 was obtained
from Li(LL) and cyclopentadiene. Under different conditions compounds 3, 6 and 7 were isolated from
1 and benzonitrile, and compounds 8, 9 and 10 from K[C(H)R2] and PhCN. Complex 11 was derived
from [Li(LLꢀ)]2 and [NiBr2(dme)]. The solution obtained from 1 + 2 PhCN in Et2O at ambient
temperature was a mixture (5) of 3 (predominantly) and 7. The 1-azaallyl complex 8 has the ligand
bound to the metal as the enamide, and this is also probably (NMR) the case for 6. The molecular
structures of the crystalline complexes 7, 8 and 11 are presented; that of 10 was published earlier.
Compound 7, a cyclooctamer, is particularly interesting, in that each LLꢀ− ligand is bridging via one of
ꢀ
2
=
its N atoms to two neighbouring sodium ions and is not only N,N - but also (g -C C)-chelating to one
of them.
Introduction
We have previously shown that from LiCH(SiMe3)2 and PhCN
a diversity of products is obtained: a lithium 1-azaallyl (I),
1,3-diazaallyl (II) or the isomeric b-diketiminate (III) and each
coordinated ligand may be terminal or bridging. The outcome
of such reactions depends on stoichiometry, reaction conditions
and the presence or absence of a strong neutral coligand D.1
The principal focus of the present study was to investigate
the corresponding system using the heavier alkali metal alkyl
MC(H)R2 (M = Na or K, R = SiMe3).
The various reactions between LiC(H)R2 and PhCN are sum-
marised in Scheme 1 and typical structures of crystalline I–III are
shown schematically in Iꢀ, IIꢀ and IIIꢀ, respectively.1
Scheme 1 (R = SiMe3).
The reaction pathway from LiC(H)R2 and PhCN to I, II
and III was proposed to implicate successive intermediates: the
donor–acceptor adduct Li{C(H)R2}(NCPh) and the Li imide
from LiC(H)R2 + PhCN → Li{N(R)C(Ph)C(H)C(Ph)N(R)} is
also reproduced in ref. 2 as is that of a related Zr(IV) 1,3-diazaallyl
to the isomeric Zr(IV) b-diketiminate. In the light of the above
proposals, it is unsurprising that in a further paper by Eisen et al.,3
it was shown (by NMR observations in the −25 to 20 ◦C range)
that the Li b-diketiminate Li{N(R)C(Ph)C(H)C(Ph)N(R)} did
not rearrange to the 1,3-diazaallyllithium isomer.
=
LiN C(Ph)C(H)R2, which by a Brook 1,3-Me3Si migration (C →
N) gave the Li 1-azaallyl I. The latter, in the presence of a
strong donor (including thf), behaved as an N-centred nucleophile
=
=
towards PhCN, affording (via Li{N C(Ph)N(R)C(Ph) C(H)R}
and a 1,3-Me3Si (N → N) shift) the Li 1,3-diazaallyl II. In
the absence of such a strong donor (as in an Et2O solution),
I behaved as a C-centered nucleophile yielding (via the imide
=
Li{N C(Ph)C(H)(R)C(Ph)N(R)} and a final 1,3-Me3Si (C →
N) shift) the Li b-diketiminate III.1 In order to account for the
thermal isomerisation of IIꢀ to the thermodynamically preferred
IIIꢀ, it was suggested that each of the final two steps from Iꢀ → IIꢀ
and Iꢀ → III was reversible. The above proposal1 for the pathway
Department of Chemistry, University of Sussex, Brighton, UK BN1 9QJ.
E-mail: m.f.lappert@sussex.ac.uk; Tel: 44 1273 678316
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Scheme 2). A good yield of the yellow hexane-insoluble solid 3
was obtained (iv in Scheme 2) from the sodium alkyl 1 and two
equivalents of PhCN in Et2O.
Results and discussion
A new synthesis of bis(trimethylsilyl)methylsodium (1)
The sodium b-diketiminate 3 was used in previous studies, as
a precursor to some lanthanoid,9a actinoid,9b and thallium(I)7 b-
diketiminates. The earlier route to 3 was from the reaction of
the lithium compound III and NaOBut in hexane, and 3 was
characterised by elemental analysis, NMR solution spectra in
pyridine-d5 and by an X-ray structure of its bis(thf) adduct 37
(see also v of Scheme 2).
Compound 1 was originally prepared, in 1993, from LiC(H)R2
by a metathetical exchange reaction in hexane with LiOBut,4a and
1 was used in situ to prepare the ytterbium(II) 1-azaallyl [Yb{j2-
N(R)C(But)C(H)R}2] from YbI2(OEt2)2, 2(1) and ButCN.5 A full
report on this synthesis of 1 revealed that a significant problem
was the separation of the products, both 1 and LiOBut being
hexane soluble (1 < LiOBut).4b The X-ray structure showed pure 1
to crystallise as a chain polymer having singly-bridging −C(H)R2
ligands, [Na{l-C(H)R2}]∞.4a
Routes to a sodium 1-azaallyl, 1,3-diazaallyl and their
characterisation
An alternative strategy to 1 was modelled on a procedure which
had been used to prepare Li(CH2)3Li from ButHg(CH2)3HgBut
and 2 LiBut.6 Thus, Hg[C(H)R2]2 was treated with 2 NaBun; this
method proved to be unsatisfactory due to the difficulty of
Whereas addition of two equivalents of benzonitrile to the sodium
alkyl 1 in Et2O yielded (iv in Scheme 2) the sodium b-diketiminate
3, use of one equivalent of PhCN at low temperature afforded
(i in Scheme 3) the orange crystalline sodium 1-azaallyl 6 in
good yield. This situation differs from that in the corresponding
Li[C(H)R2]2/PhCN system, in which even use of equivalent
portions of the two reagents led to the b-diketiminatolithium
product; and the lithium 1-azaallyl (I) was obtained only in
the presence of a stronger neutral donor such as tmeda (see
III).1 It is clearly the case that [N(R)C(Ph)C(H)R]− is a more
powerful nucleophile than [C(H)R2]− for Li+, but not Na+, as
counter cation, i.e., nucleophilicity decreases for Li(1-azaallyl) >
LiC(H)R2, but NaC(H)R2 > Na(1-azaallyl). The main factor may
be the greater covalent character of the Li rather than the Na
bis(trimethylsilyl)methyl.
separating 1 from HgBun .4b
2
We now report that this dialkylmercury was a convenient
substrate, when reacted with sodium amalgam in hexane, eqn (1).
The separation of 1 in 78% yield from the coproduct mercury
was straightforward. A similar procedure had been used for
NaCH2R.4c
C
H
14
6
Hg[C(H)R2] + 2Na/Hg −−−→ NaC(H)R21
(1)
−Hg
Routes to a sodium b-diketiminate and its characterisation
Three alternative pathways to the sodium analogue of the lithium
b-diketiminate III were explored, Scheme 2, using as precursor
Na[C(H)R2] 1 or the b-diketimine 2, which had previously been
obtained from K[{N(R)C(Ph)}2CH]8 and 1,2-dibromoethane or,
for a close analogue H[{N(R)C(C6H4Me-4)}2CH], by the carefully
controlled hydrolysis of the lithium b-diketiminate.1 This is not
straightforward because of the hydrolytic sensitivity of the N–Si
bonds. It is now shown that the pentane soluble 2 is conveniently
accessible (i in Scheme 1) from the latter and cyclopentadiene in
pentane, the precipitated coproduct LiCp being readily separated.
Treatment of 2 with Na[N(SiMe3)2] in toluene gave (ii in Scheme 2)
the sodium b-diketiminate 3 almost quantitatively, while use of
NaNH2 in Et2O as the base was rather less satisfactory (iii in
Scheme 3 (R = SiMe3). Reagents and conditions: i, PhCN, Et2O, −78 ◦C,
and crystallisation from C6H14; ii, 2 PhCN, Et2O, 23 ◦C, removal of
volatiles, and washing C6H14; iii, crystallisation from C5H12.
Addition of two equivalents of benzonitrile to 1 in Et2O
at ambient temperature, followed by removal of volatiles and
crystallisation from pentane gave (ii followed by iii in Scheme 3)
yellow crystals of the 1,3-diazaallylsodium compound 7 in modest
yield. In another experiment (ii of Scheme 3), the ether-free residue
was dissolved in C6D6 and was shown by 1H NMR spectroscopy to
correspond to an 81% conversion of 1 and 2 PhCN into a mixture
of the two isomers: the sodium b-diketiminate 3 and the diazaallyl
7, in a ratio of 89 : 11, respectively.
Compound 6 has been used extensively as a 1-azaallyl ligand
transfer reagent; its characterisation herein rests solely on its
NMR solution and EI-mass spectra. As for the latter, this simply
1
revealed signals of the metal-free ligand. The H NMR spectra
in C6D6 showed the appropriate signals and relative intensities
of the 1-azaallyl ligand [N(R)C(Ph)C(H)R]−. From the chemical
shifts characteristic of the C(H)R group it is likely that in 6 the
Scheme 2 (R = SiMe3). Reagents and conditions at ca. 25 ◦C: i, C5H6,
C5H12, 12 h; ii, Na[N(SiMe3)2], PhMe, 20 h; iii, 2, Et2O, 12 h; iv, 2 PhCN,
Et2O, 0 ◦C; v, crystallisation from thf.
1
−
=
ligand is present in the enamido (j ) form [N(R)C(Ph) C(H)R] ,
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3
rather than the delocalised (g ) form. This is based on data on
various lithium compounds of the same ligand, in which the j1-
1
was identified from d(1H) at 3.5–4.0 ppm and d[13C{ H}] at 83–
1
85 ppm, compared with d(1H) at 4.8 and d13[C{ H}] at 95–97 ppm.1
The crystalline sodium 1,3-diazaallyl 7, a benzamidinate, was
characterised by satisfactory microanalytical data (C, H, N), its
1
1H and 13C{ H} solution NMR and EI-mass spectra and finally
by a single-crystal X-ray diffraction| study. The latter reveals the
molecule to have theNa[N(R)C(Ph)NC(Ph) = C(H)R]monomers
associated into a cyclo-octamer lying across the four-fold rotation
axis, in which successive sodium ions are joined by an N,Nꢀ-
bridging ligand. Thus, the structure of 7 is that of a 32-membered
macrocycle containing eight NaNCN repeating units, as shown in
the ball-and-stick model of Fig. 1. An ORTEP representation is in
Fig. 2, geometrical parameters are in Table 1, while the space-filling
model of Fig. 3 shows that the sodium ions are well protected and
the internal cavity is very small. Selected geometrical parameters
are conveniently described in the context of the dimeric fragment
of Fig. 4.
Fig. 2 ORTEP representation of crystalline 7 with selected labelling of a
dimeric fragment.
◦
˚
Table 1 Selected bond lengths (A) and angles ( ) of 7
Na(1)–N(4)
Na(1) · · · C(2)
Na(2)–N(2)a
Na(2) · · · C(23)
Si(1)–N(1)
Si(3)–N(3)
N(1)–C(1)
N(2)–C(2)
N(4)–C(22)
C(1)–C(4)
C(2)–C(10)
C(22)–C(25)
C(23)–C(31)
2.417(8)
2.722(9)
2.376(7)
2.813(9)
1.714(7)
1.718(7)
1.333(11)
1.418(11)
1.299(10)
1.501(12)
1.506(13)
1.507(12)
1.489(12)
Na(1)–N(1)
Na(1) · · · C(3)
Na(2)–N(3)
Na(2) · · · C(24)
Si(2)–C(3)
Si(4)–C(24)
N(2)–C(1)
N(3)–C(22)
N(4)–C(23)
C(2)–C(3)
2.431(8)
2.728(9)
2.420(8)
2.748(9)
1.847(10)
1.863(10)
1.328(11)
1.335(10)
1.425(11)
1.352(12)
1.383(12)
1.348(12)
1.374(12)
C(4)–C(9)
C(23)–C(24)
C(25)–C(26)
N(4)–Na(1)–N(1)
C(1)–N(1)–Si(1)
Si(1)–N(1)–Na(1)
C(1)–N(2)–Na(2)b
C(22)–N(3)–Si(3)
Si(3)–N(3)–Na(2)
C(22)–N(4)–Na(1)
N(2)–C(1)–N(1)
N(1)–C(1)–C(4)
C(3)–C(2)–C(10)
C(2)–C(3)–Si(2)
C(9)–C(4)–C(1)
C(11)–C(10)–C(2)
N(4)–C(22)–N(3)
N(3)–C(22)–C(25)
C(24)–C(23)–C(31)
C(23)–C(24)–Si(4)
C(36)–C(31)–C(23)
174.7(3)
125.9(6)
115.7(4)
127.2(6)
129.2(6)
107.9(4)
120.4(6)
127.3(8)
121.1(8)
123.9(9)
127.3(8)
122.4(9)
121.4(9)
127.5(8)
120.5(8)
123.5(9)
125.6(7)
122.6(9)
N(2)a–Na(2)–N(3)
C(1)–N(1)–Na(1)
C(1)–N(2)–C(2)
173.5(3)
117.9(5)
117.8(7)
115.0(5)
120.2(6)
117.0(7)
122.6(5)
111.5(8)
120.4(9)
115.5(8)
119.7(9)
117.8(10)
120.7(9)
111.9(8)
121.0(8)
115.4(8)
119.8(8)
120.7(8)
C(2)–N(2)–Na(2)b
C(22)–N(3)–Na(2)
C(22)–N(4)–C(23)
C(23)–N(4)–Na(1)
N(2)–C(1)–C(4)
Fig. 1 Ball-and-stick model of crystalline 7.
Whereas one sodium ion, say Na1, has adjacent N(R) moieties
belonging to neighbouring 1,3-diazaallyl ligands, the next sodium
ion, say Na(2)ꢀꢀ, is attached to two N{C(Ph)} moieties one of
which is the partner of one of the ligands joined to Na(1). Each
sodium ion is only just outside the N–Nꢀ vector, the N(1)–Na(1)–
N(4) and N(2)–Na(2)ꢀꢀ–N(3)ꢀꢀ bond angles being almost identical,
174.1 0.6◦. A 1,3-diazaallyl ligand, say of skeletal arrangement
N(1)C(1)N(2)C(2)C(3), not only acts as a bridge between Na(1)
C(3)–C(2)–N(2)
N(2)–C(2)–C(10)
C(5)–C(4)–C(1)
C(11)–C(10)–C(15)
C(15)–C(10)–C(2)
N(4)–C(22)–C(25)
C(24)–C(23)–N(4)
N(4)–C(23)–C(31)
C(26)–C(25)–C(22)
C(32)–C(31)–C(23)
and Na(2)ꢀꢀ, but is also chelating to Na(1) via an g -alkene-
2
Symmetry transformations to generate equivalent atoms: a −y + 1/2, x +
1, z. b y − 1, x + 1/2, z.
contact. The coordination environment around Na(1) is shown
2
schematically in Fig. 5. In support of this unusual (g -alkene)–Na+
contact, it is noted that the Na(1)–C(2), Na(1)–C(3), Na(2)ꢀ–C(23)
ꢀꢀ
˚
and Na(2) –C(24) distances of 2.75 A (mean) are only slightly
are closely similar not only to one another but also to the Na–
N bond distances of 2.358(6) A of the b-diketiminate 4. Each
of the three-coordinate N(1), C(1), N(2) and C(2) atoms is in a
distorted trigonal planar environment, with the endocyclic bond
7
˚
˚
longer than the 2.56 0.02 A for the Na–C distance in [Na{l-
C(H)R2}]∞,4a and are close to the 2.72 A cited for side-on Na –(p-
+
˚
olefin) systems.10 The Na–N(R) and Na–N{C(H)Ph} bond lengths
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Scheme 4 (R = SiMe3). Reagents and conditions: i, PhCN, Et2O, −78 ◦C,
1 h, crystallisation from C6H6; ii, PhCN, Et2O, −78 ◦C, removal of volatiles,
reflux thf, then PhCN, 2 min; iii, 2 PhCN, thf–C5H12.
Fig. 3 Space-filling model of crystalline 7.
of hexane, and crystallisation of the hexane-insoluble solid from
thf furnished (ii in Scheme 4) the yellow–brown, crystalline 1,3-
diazaallylpotasium–thf adduct 9 in modest yield. The isomeric,
crystalline, polymeric b-diketiminatopotassium–bis(thf) adduct 10
was obtained (iii in Scheme 4) as shown earlier.8
In a preliminary communication it was reported that the
b-diketiminate K[{N(R)C(Ph)}2CH] (IV) was accessible in
good yield from either K[C(H)R2] + 2 PhCN in Et2O, or
Li[{N(R)C(Ph)}2CH] + KOBut in hexane. For example, reac-
tion between K[C(H)R2] + 2 PhCN in Et2O at −78 ◦C af-
|
forded a mixture of IV,K[N(R)C(Ph)NC(Ph)=C(H)R] , and
H[{N(R)C(Ph)}2CH] in a ratio of 87 : 7 : 6 (from 1H NMR). Later
it was shown that IV was convertible into the X-ray-characterised
derivative 10.8
Each of the crystalline potassium salts 8–10 gave satisfactory
microanalyses (C, H, N), NMR solution and EI-mass spectra.
Single-crystal X-ray diffraction data were obtained for 8, but for
crystalline 9 these were adequate solely to confirm its structure to
be as shown in Scheme 4; the structure of crystalline 10 has been
published.8
Fig. 4 ORTEP representation of a dimeric fragment of 7 (50% ellipsoids).
The molecular structure of the crystalline dimeric 1-
azaallylpotassium–benzene adduct 8 is illustrated in Fig. 6; the
molecules are connected into chains along the 21 screw axis by
weak intermolecular K(2) · · · C(10)ꢀ interactions giving rise to a
polymeric array, Fig. 7; geometrical parameters are in Table 2. The
coordination environment of the two potassium atoms K(1) and
Fig. 5 The environment of Na in 7: angles (◦): a = 28.74(25), b =
65.62(26), c = 96.78(28), d = 174.7(3), e = 75.84(51), eꢀ = 75.42(51).
angles of 117.9(6), 127.3(8), 117.8(7) and 120.4(9)◦ at these atoms,
respectively.
3
K(2) are different. That of K(1) approximates to that of a bis(g -
6
1-azaallyl)(g -benzene)potassiate, while that of K(2) resembles a
6
(g -benzene)potassium cation with close K(2)–N(1) and K(2)–
N(2) contacts but more remote (agostic) K(2) distances to C(12)
and C(27) [from Si(2)Me3 and Si(4)Me3, respectively] and C(10)ꢀ
[from Si(1)ꢀMe3] carbon atoms. The centre of the molecule is the
The bis(trimethylsilyl)methylpotassium–benzonitrile system:
synthesis and structures of the derived potassium 1-azaallyl,
1,3-diazaallyl and the isomeric b-diketiminate
K(1)N(1)K(2)N(2) rhombus, having K–N bond lengths of 2.783
8
˚
˚
0.008 A (cf. 2.830 0.003 A in 10) and endocyclic bond angles of
96.3 0.2◦ at the potassium and 86.7 0.2◦ at the nitrogen atoms.
The K–C(Ph) and K–C(H)SiMe3 distances are almost equal and
The yellow, crystalline, dimeric 1-azaallylpotassium compound 8
was obtained (i in Scheme 4) in good yield from K[C(H)R2]4b
and an equimolar portion of benzonitrile in diethyl ether and
recrystallisation from benzene. In another experiment, removal of
Et2O followed successively by heating a thf solution under reflux,
addition of a second equivalent of PhCN, removal of thf, addition
closely similar to those in [K{l-C(H)R2}{O(Me)But}]∞ of 3.000
4b
˚
0.012 A. The distance from each K atom to the centroid of the
6
˚
attached g -benzene is slightly shorter for K(1) at 2.921(4) A, but
both are unexceptional.11
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◦
˚
Table 2 Selected bond lengths (A) and angles ( ) of 8
K(1)–N(1)
K(1)–C(1)
K(1)–C(15)
K(1)–M(1)
K(2)–N(2)
K(2)–C(27)
2.775(3)
3.077(4)
3.002(3)
2.921(4)
2.776(3)
3.303(5)
K(1)–N(2)
K(1)–C(2)
K(1)–C(16)
K(2)–N(1)
K(2)–C(12)
K(2)–C(10)a
2.783(3)
3.087(3)
3.000(3)
2.767(3)
3.391(4)
3.496(4)
K(2)–M(2)
Si(2)–N(1)
Si(4)–N(2)
N(1)–C(2)
C(1)–C(2)
C(15)–C(16)
3.039(4)
1.697(3)
1.704(3)
1.354(4)
1.374(5)
1.377(4)
Si(1)–C(1)
Si(3)–C(15)
Si(4)–C(27)
N(2)–C(16)
C(2)–C(3)
1.835(4)
1.831(3)
1.874(4)
1.357(4)
1.512(4)
1.504(4)
C(16)–C(17)
N(1)–K(1)–N(2)
N(2)–K(1)–M(1)
N(2)–K(1)–C(16)
N(1)–K(1)–C(15)
M(1)–K(1)–C(15)
N(1)–K(1)–C(1)
M(1)–K(1)–C(1)
C(15)–K(1)–C(1)
N(2)–K(1)–C(2)
C(16)–K(1)–C(2)
C(1)–K(1)–C(2)
N(1)–K(2)–M(2)
N(1)–K(2)–C(27)
M(2)–K(2)–C(27)
N(2)–K(2)–C(12)
C(27)–K(2)–C(12)
N(2)–K(2)–C(10)a
C(27)–K(2)–C(10)a
N(1)–K(2)–C(2)
M(2)–K(2)–C(2)
96.12(8)
131.27(9)
26.80(8)
94.05(9)
124.85(7)
48.71(8)
105.93(7)
129.05(10)
105.39(8)
124.44(9)
25.77(9)
142.02(10)
119.00(10)
97.90(9)
113.55(10)
168.16(11)
158.07(10)
106.09(11)
21.08(7)
N(1)–K(1)–M(1)
N(1)–K(1)–C(16)
M(1)–K(1)–C(16)
N(2)–K(1)–C(15)
C(16)–K(1)–C(15)
N(2)–K(1)–C(1)
C(16)–K(1)–C(1)
N(1)–K(1)–C(2)
M(1)–K(1)–C(2)
C(15)–K(1)–C(2)
N(1)–K(2)–N(2)
N(2)–K(2)–M(2)
N(2)–K(2)–C(27)
N(1)–K(2)–C(12)
M(2)–K(2)–C(12)
N(1)–K(2)–C(10)a
M(2)–K(2)–C(10)a
C(12)–K(2)–C(10)a
N(2)–K(2)–C(2)
C(27)–K(2)–C(2)
130.83(9)
106.27(9)
121.98(7)
49.14(9)
26.52(9)
95.40(9)
120.93(9)
26.01(8)
112.80(7)
118.68(9)
96.47(8)
97.53(10)
55.42(9)
54.60(9)
87.47(7)
82.16(10)
96.77(8)
83.60(11)
95.54(8)
101.19(10)
C(12)–K(2)–C(2)
C(1)–Si(1)–C(10)
C(13)–Si(2)–C(14)
C(24)–Si(3)–C(25)
C(2)–N(1)–Si(2)
Si(2)–N(1)–K(2)
Si(2)–N(1)–K(1)
C(16)–N(2)–Si(4)
Si(4)–N(2)–K(2)
Si(4)–N(2)–K(1)
C(2)–C(1)–Si(1)
Si(1)–C(1)–K(1)
N(1)–C(2)–C(3)
N(1)–C(2)–K(1)
C(3)–C(2)–K(1)
Si(2)–C(12)–K(2)
C(16)–C(15)–K(1)
N(2)–C(16)–C(15)
C(15)–C(16)–C(17)
Si(4)–C(27)–K(2)
74.29(9)
116.1(2)
107.2(2)
108.3(2)
130.3(2)
112.04(13)
117.29(13)
130.3(2)
110.54(13)
119.51(13)
131.2(3)
135.1(2)
117.8(3)
64.0(2)
135.9(2)
85.8(2)
76.7(2)
124.0(3)
118.0(3)
87.7(2)
C(10)a–K(2)–C(2)
N(1)–Si(2)–C(12)
C(15)–Si(3)–C(25)
C(26)–Si(4)–C(27)
C(2)–N(1)–K(2)
C(2)–N(1)–K(1)
K(2)–N(1)–K(1)
C(16)–N(2)–K(2)
C(16)–N(2)–K(1)
K(2)–N(2)–K(1)
C(2)–C(1)–K(1)
N(1)–C(2)–C(1)
C(1)–C(2)–C(3)
C(1)–C(2)–K(1)
Si(1)–C(10)–K(2)b
C(16)–C(15)–Si(3)
Si(3)–C(15)–K(1)
N(2)–C(16)–C(17)
N(2)–C(16)–K(1)
C(17)–C(16)–K(1)
75.34(10)
107.5(2)
106.0(2)
105.6(2)
111.6(2)
89.9(2)
83.85(7)
114.7(2)
85.5(2)
83.53(7)
77.5(2)
125.8(3)
116.3(3)
76.7(2)
150.2(2)
132.0(3)
123.8(2)
117.9(3)
67.7(2)
160.71(6)
129.2(2)
M(1) and (M2) are the centroids of the C(35) to C(40), and C(29) to C(34) rings, respectively. Symmetry transformations to generate equivalent atoms: a −x
+ 3/2, y + 1/2, −z − 1/2. b −x + 3/2, y − 1/2, −z − 1/2.
Fig. 7 A section of the polymeric chain, formed by aggregation of units
Fig. 6 The X-ray structure of 8 (50% ellipsoids).
of 8.
Preparation and structure of the bis(1,3-diazaallyl)nickel(II)
complex 11
(Fig. 8) was established by a single-crystal X-ray diffraction study;
selected geometrical parameters are in Table 3.
The lithium 1,3-diazaallyllithium compound IIIꢀ proved to be an
|
[Li{l − N(R)C(Ph) C(PH)=C(H)R}] + [NiBr (dme)]
N
2
2
effective ligand transfer reagent in its reaction with a nickel(II)
bromide complex. Thus, the crystalline, deep purple, diamagnetic,
monomeric purple nickel(II) complex 11 was obtained in 63%
yield, eqn (2). It was characterised by microanalysis (C, H, N), 1H
thf
→[Ni{l-N(R)C(Ph)C(Ph)=C(H)R}]211 + 2LiBr
(2)
The nickel atom of the molecule 11 is at the spiro junction of
1
3
and 13C{ H} NMR spectra in solution, and its EI-mass spectrum
two g -1,3-diazaallyl ligands and is in a distorted square planar
which showed its parent molecular ion. The molecular structure
environment. The dihedral angle between the NiN(1)C(1)N(2) and
4150 | Dalton Trans., 2006, 4146–4154
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narrower at each (Me3Si)N than the Nꢀ atom, while that at C(1) or
C(22) is 109.7 0.3◦.
◦
˚
Table 3 Selected bond lengths (A) and angles ( ) of 11
Ni–N(1)
Ni–N(3)
1.949(7)
1.934(7)
1.741(8)
1.737(8)
1.337(11)
1.415(11)
1.321(10)
1.472(12)
1.492(13)
1.473(12)
1.364(12)
Ni–N(2)
Ni–N(4)
1.885(7)
1.898(7)
1.848(10)
1.779(9)
1.312(11)
1.335(10)
1.437(11)
1.349(13)
1.395(12)
1.492(13)
A
number
of
mononuclear
1,3-diazaallylnickel(II)
complexes have been previously published. The[N(R)C(Ph)-
|
Si(1)–N(1)
Si(3)–N(3)
N(1)–C(1)
N(2)–C(2)
N(4)–C(22)
C(1)–C(10)
C(2)–C(3)
C(22)–C(31)
C(23)–C(30)
Si(2)–C(9)
Si(4)–C(30)
N(2)–C(1)
N(3)–C(22)
N(4)–C(23)
C(2)–C(9)
C(10)–C(15)
C(23)–C(24)
NC(Ph) = C(H)R]− (LLꢀ−) has featured in the six-coordinate
Ni(II) complex [Ni(LLꢀ)(acac)(tmeda)].3 Two other C1-symmetric
3
ligands [g -N(SiMe3)C(Ph)NR*]− (LL*−) (R*
=
myrtanyl)
and [g -N(SiMe3)C(Ph)N(C6H3Pri2-2,6)]− (LLꢀꢀ−) were present
in the diamagnetic [Ni(LL*)2], [Ni(LL*)Me(py)] and trans-
[Ni(LL*)2(py)2]12 and [Ni(LLꢀꢀ)2].13 Homoleptic mononuclear
nickel(II) C2-symmetric 1,3-diazaallyls characterised earlier
3
3
include the tetrahedral, paramagnetic (leff = 3.1 lB) [Ni{g -N(R)-
N(2)–Ni–N(4)
N(4)–Ni–N(3)
111.4(3)
68.9(3)
N(2)–Ni–N(3)
N(2)–Ni–N(1)
N(3)–Ni–N(1)
C(1)–N(1)–Ni
C(1)–N(2)–C(2)
C(2)–N(2)–Ni
C(22)–N(3)–Ni
C(22)–N(4)–C(23)
C(23)–N(4)–Ni
N(2)–C(1)–C(10)
C(9)–C(2)–N(2)
N(2)–C(2)–C(3)
C(8)–C(3)–C(2)
C(2)–C(9)–Si(2)
C(11)–C(10)–C(1)
N(4)–C(22)–C(31)
C(30)–C(23)–N(4)
N(4)–C(23)–C(24)
C(29)–C(24)–C(23)
C(27)–C(28)–C(29)
C(32)–C(31)–C(22)
174.1(3)
68.9(3)
111.4(3)
88.8(5)
127.9(7)
139.7(6)
89.7(5)
127.8(7)
137.5(6)
126.7(8)
122.6(9)
112.1(9)
120.3(9)
129.4(7)
119.4(8)
125.8(8)
125.1(8)
112.5(8)
121.3(8)
120.4(12)
119.5(8)
C(Ph)NR}2],14 and the square planar, diamagnetic [Ni{g -N(Pri)-
3
C(Me)NPri}2]15 and [Ni{g -N(C6H3Pri2-2,6)C(Ph)NC6H3Pri-
3
N(4)–Ni–N(1)
C(1)–N(1)–Si(1)
Si(1)–N(1)–Ni
174.0(3)
126.7(6)
127.6(4))
92.4(6)
2,6}2].16 It has long been established that steric effects in an N,Nꢀ-
chelating anionic ligand can control the geometry of homoleptic
late transition metal(II) complexes.17 Thus, in the b-diketiminates
[M{N(R1)C(R2)C(H)C(R2)N(R1)}2] those with M = Ni and
R2 = Me were diamagnetic for R1 = Ph but paramagnetic for
R1 = C6H4Me-2,18 and the cobalt complex with R2 = Ph was
tetrahedral for R1 = SiMe3 but square planar for R1 = H.19
C(1)–N(2)–Ni
C(22)–N(3)–Si(3)
Si(3)–N(3)–Ni
129.7(6)
130.8(4)
91.7(5)
C(22)–N(4)–Ni
N(2)–C(1)–N(1)
N(1)–C(1)–C(10)
C(9)–C(2)–C(3)
C(4)–C(3)–C(2)
C(3)–C(4)–C(5)
C(15)–C(10)–C(1)
N(4)–C(22)–N(3)
N(3)–C(22)–C(31)
C(30)–C(23)–C(24)
C(25)–C(24)–C(23)
C(27)–C(26)–C(25)
C(23)–C(30)–Si(4)
C(36)–C(31)–C(22)
109.9(7)
123.3(8)
125.3(9)
123.1(11)
120.9(14)
122.7(8)
109.5(7)
124.7(8)
122.4(8)
120.8(9)
118.9(11)
135.2(8)
122.4(8)
Conclusions
We have prepared
a number of sodium or potassium
1-azaallyls [M{N|(R)C(Ph)C(H)R}]− [≡ M(L)], 1,3-diazaal-
lylsM[N(R)C(Ph)NC(Ph) = C(H)R] [≡ M(LLꢀ)], and the iso-
meric b-diketiminates M[{N(R)C(Ph)]}2CH] [≡ M(LL)] from
the appropriate metal alkyl M[C(H)R2] (M = Na or K, R =
SiMe3) and PhCN in Et2O. It is noteworthy that the metal 1-
6
azaallyl Na(L) (6) and [K(l-L)(g -C6H6)]2 (8) were accessible
from Na[C(H)R2] or the K analogue and an equivalent por-
tion of PhCN; this is a contrast with the Li[C(H)R2]–PhCN
system which in Et2O gave Li(LL). The formation of M(L)
from M[C(H)R2] is believed to implicate as an intermediate the
−
+
donor–acceptor adductR (H)C
−
CPh, which by a Brook 1,3-
N
M
2
SiMe3 migration from C → N yields in solution an equilibrium
=
mixture of the enamide and ketimide: M–N(R)C(Ph) C(H)R
=
ꢀ M–C(R)(H)C(Ph) NR; crystallisation from the appropriate
solvent yielded 6 or 8. The isolation of the crystalline metal 1,3-
diazaallyl or b-diketiminate is further proposed to implicate the
solution reaction between the metal enamide or ketimide M(L),
respectively, involving a further 1,3-SiMe3 migration for M(LL).
A particular structural feature of an unprecedented nature is the
ability of the 1,3-diazaallyl ligand LLꢀ− to function in [Na(l-
LLꢀ)]8 (7) not only as an N,Nꢀ-centered moiety but also as a
chelating species in which it binds to a sodium ion both through
Fig. 8 The X-ray structure of 11 (50% ellipsoids).
2
=
a nitrogen-centre but also via an g -C C close contact. Such
binding participation of an alkene moiety is not found in other 1,3-
the NiN(3)N(4) planes is 10.8(4)◦. The ipso-carbon C(31) attached
diazaallyl metal complexes of the LLꢀ− ligand: [K(thf)2(l-LL)]∞
3
to C(22) of the [g -N(3)(SiMe3)C(22)(Ph)N(4)] fragment is ca.
(10),8 [Ni(LLꢀ)2] (11), [Ni(LLꢀ)(acac)(tmeda)],3 [Li(LLꢀ)(thf)],1 or
˚
0.12 A out of the NiN(3)N(4) plane, whereas the corresponding
ipso-carbon C(10) of the other ligand is more nearly (0.06 A)
ꢀ
[{UCl(LL)( NR)}2][UCl2(LL)(LL )]2.19 The preparation of the b-
=
˚
diketimine H(L) (2) from Li(L) and CpH in C5H12 is noteworthy.
within its NiN(1)C(1)N(2) plane. The Me3Si substituents at the
terminal nitrogen atoms of each ligand are arranged in a gauche
fashion. The Ni–N(SiMe3) bonds are slightly longer than the Ni–
N{C(Ph)}, as are the (Me3Si)N–C(Ph) bonds compared with the
{Ph(C)}N–C(Ph). The endocyclic bond angles in each NiNCNꢀ
moiety are close to 90◦ at the nitrogen atoms, and somewhat
Experimental
All manipulations were carried out under argon, using standard
Schlenk techniques. Solvents were pre-dried over sodium wire,
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˚
Na[N(R)C(Ph)C(H)R] (6). A solution of benzonitrile (0.8 mL,
7.84 mmol) in Et2O (30 mL) was added dropwise to a solution of
Na[C(H)R2] (1.46 g, 8 mmol) in Et2O (30 mL) at ca. −78 ◦C. The
initially colourless solution immediately became yellow. After
stirring for 2 h the volatiles were removed in vacuo at ambient
temperature. Recrystallisation from hexane at ca. −30 ◦C afforded
orange crystals of compound 6 (1.89 g, 83%), mp 111–112 ◦C
(change in colour at 56–57 ◦C). MS: m/z (%, assignment, L =
ligand): 263 (32, [LH]+), 248 (7, [LH − Me]+), 190 (3, [LH −
SiMe3]+), 186 (11, [LH − Ph]+), 176 (42, [LH − NSiMe3 − Me]+),
146 (100). 1H NMR (C6D6): d (s, SiMe3, 9 H), 0.05 (s, NSiMe3, 9
distilled from drying agents and stored over molecular sieves (4 A).
Deuteriated solvents were likewise stored over such molecular
sieves and degassed prior to use. The NMR spectra were recorded
in C6D6, C6D5CD3 or C5D5N at 298 K using a DPX 300 (1H,
300.1; 13C 75.5 MHz) Bruker instrument and referenced to residual
solvent resonances (data in d). All 13C NMR spectra were proton-
decoupled. Electron impact mass spectra were taken from solid
samples using a Kratos MS 80 RF instrument. Melting points
were taken in sealed capillaries. Elemental analyses (calculated
data are for empirical formulae) were determined by Medac Ltd.,
Brunel University. The compounds Hg[C(H)R2]2,20 Li[C(H)R2],21
1
H), 3.63 (s br, CH, 1 H), 7.12–7.30 (m, Ph, 10 H). 13C{ H} NMR
K[C(H)R2],4a [NiBr2(dme)],22 [Li{N(R)C(Ph)}2CH],1 and[Li −
|
3
(C6D6): d 2.4 (s, SiMe3), 4.0 (s, NSiMe3), 87.5 (s, CH), 125.6.,
126.9–128.3 (s, aromatic carbons), 148.6 (s, ipso-C) and 177.1 (s,
CN).
{l-N(R)C(Ph)NC(Ph)=C(H)R}(thf)]2 were synthesised accord-
ing to published procedures (R = SiMe3).
|
Preparations
[Na{N(R)C(Ph) C(Ph)=C(H)R}] (7). Benzonitrile (2.3 mL,
N
8
◦
22.4 mmol) was added at ca. 23 C to a solution of Na[C(H)R2]
[NaC(H)R2]∞ (1).
A solution of Hg[C(H)R2]2 (4.5 g,
(2.3 g, 10.9 mmol) in Et2O (30 mL). The volatiles were removed
in vacuo at 50 ◦C and the orange/brown residue was treated with
pentane (30 mL). Filtration and concentration of the pale brown
filtrate gave upon cooling yellow crystals of 7 (1.1 g, 26%) (Found:
C, 64.3; H, 7.50; N, 7.12. C21H29NaN2Si2 requires C, 64.9; H, 7.52;
8.66 mmol) in hexane (20 mL) was added to a 40/60 Na/Hg
amalgam (6.8 g) already covered with hexane (50 mL) at ca.
23 ◦C. The reaction mixture was stirred for ca. 12 h. The pale
yellow mother-liquor was filtered from a Na/Hg black residue
and the volatiles were removed from the filtrate in vacuo, affording
the pale brown solid 1 (2.5 g, 78%), which was used without further
◦
N, 7.21%), mp 84–86 C. MS: m/z (%, assignment, L = ligand):
365 (37, [L]+), 351 (7, [LH − Me]+), 293 (46, [LH − SiMe3]+), 277
(22, [L − SiMe3 − Me]+), 263 (10, [L − NSiMe3 − Me]+), 220 (88,
[LH − 2SiMe3]+), 176 (52, [N(SiMe3)C(Ph)]+), 147 (78), 103 (100)
and 73 (76, [SiMe3]+). 1H NMR (C6D5N): d −0.15 (s, SiMe3, 9 H),
0.01 (s, NSiMe3, 9 H), 4.56 (s br, CH, 1 H), 7.15–7.63 (m, Ph,
1
purification. H NMR (C6D6): d −2.19 (s, CH, 1 H) and 0.19 (s,
SiMe3, 18 H); this was identical to that published.4b
H[N(R)C(Ph)C(H)C(Ph)NR] (2). Cyclopentadiene (2.2 mL,
32.6 mmol) was added to a suspension of [Li{N(R)C(Ph)}2CH]
(9.14 g, 24.53 mmol) in pentane (75 mL) at ambient temperature.
The mixture was stirred for ca. 12 h, then filtered. The yellow
filtrate was dried in vacuo affording the yellow solid 2 (8.52 g, 95%)
which was used without further purification. 1H NMR (C6D5CD3):
d 0.11 (s, SiMe3, 18 H), 5.51 (s, CH, 1 H), 7.02 (m, Ph, 6 H), 7.30
(m, Ph, 4 H) and 12.52 (s, NH, 1 H); this was identical to the
published spectrum.1
1
10 H). 13C{ H} NMR (C6D5N): d 1.6 (s, SiMe3), 3.7 (s, NSiMe3),
107.1 (s, CH), 125.6, 126.6, 127.2, 127.8, 129.2 and 129.5 (s, Ph o-,
m- and p-CH), 132.4 and 133.9 (s, Ph ipso-C), 166.8 and 172.4 (s,
CN).
6
=
[K{l-N(R)C(Ph) C(H)R}(g -C6H6)]2 (8). Addition of ben-
zonitrile (0.21 mL, 2.06 mmol) to a solution of K[C(H)R2] (0.40 g,
2.02 mmol) in Et2O (30 mL) at −78 ◦C immediately gave a yellow
solution. After stirring for 1 h, the volatiles were removed in vacuo
and stripped off with hexane (5 mL); the resulting yellow solid was
washed with hexane yielding 8 (0.48 g, 79%) (Found: C, 55.35; H,
7.95; N, 4.62. C14H24KNSi2 requires C, 55.75; H, 8.02; N, 4.64%).
Crystals suitable for X-ray analysis were obtained from benzene;
mp 131–133 ◦C (change in colour at 56–57 ◦C). MS: m/z (%,
assignment): 263 (69, [LH]+), 248 (18, [LH − Me]+), 190 (9, [LH −
SiMe3]+), 186 (22, [LH − Ph]+), 176 (74, [LH − NSiMe3 − Me]+),
146 (100). 1H NMR (C6D5CD3): d −0.11 (s, SiMe3, 9 H), 0.23 (s,
Na[{N(R)C(Ph)}2CH] (3) and [Na{N(R)C(Ph))2CH}(thf)2] (4).
Method 1. Addition of Na[N(SiMe3)2] (4.05 g, 22.09 mmol) to a
solution of 2 (6.85 g, 18.68 mmol) in toluene (100 mL) at ca. 25 ◦C
rapidly gave a yellow precipitate. After stirring for 20 h, the solid 3
(6.84 g, 94%) was separated by decantation, filtration and washing
with toluene (20 mL); it was used without further purification.
Method 2. NaNH2 (0.10 g, 2.56 mmol) was added to a solution
of 2 (0.47 g, 1.28 mmol) in Et2O (50 mL) at ca. 25 ◦C. The
mixture was vigorously stirred for 12 h. Unreacted NaNH2 was
then separated by filtration and the volatiles were removed from
the filtrate in vacuo. The yellow residue was washed with hexane
(2 × 20 mL) and 3 (0.23 g, 46%) was recovered as a yellow solid
after drying.
1
NSiMe3, 9 H), 3.18 (s, CH, 1 H), 7.05–7.15 (m, Ph, 10 H). 13C{ H}
NMR (C6D5CD3): d 2.9 (s, SiMe3), 3.6 (s, NSiMe3), 84.7 (s, CH),
126.4, 127.8, 128.2 (s, aromatic carbons), 149.6 (s, ipso-C) and
176.3 (s, CN).
|
Method 3. Benzonitrile (2.4 mL, 23.52 mmol) was added slowly
to a solution of 1 (2.11 g, 11.57 mmol) in Et2O (30 mL) at
0 ◦C. After 4 h, the yellow mixture was allowed to warm to room
temperature. The volatiles were removed in vacuo and stripped off
twice with hexane. The residue was then washed with hexane to
give the yellow solid 3 (3.37 g, 75%). 1H NMR (C5D5N): d −0.04
(s, SiMe3, 18 H), 5.23 (s, CH, 1 H), 7.18–7.24 (m, Ph, 6 H), 7.44–
7.47 (m, Ph, 4 H). Crystals of [Na{(N(R)C(Ph))2CH}(thf)2] (4),
suitable for X-ray analysis,3 were obtained from thf.
[K{N(R)C(Ph) C(Ph)=C(H)R}(thf) ](9). Benzonitrile (0.38 mL,
N
2
3.73 mmol) was added to a solution of K[C(H)R2] (0.74 g,
3.73 mmol) in Et2O at −78 ◦C. The mixture was stirred for
45 min and the solvent was removed in vacuo. The resulting yellow
sticky solid was dissolved and refluxed in thf (20 mL). Benzonitrile
(0.40 mL, 3.92 mmol) was added dropwise and the yellow–brown
solution was stirred for 2 min. The solvent was removed in vacuo.
Addition of hexane (30 mL) afforded the yellow–brown solid
of thf-free 9 (0.61 g, 40%) (Found: C, 61.57; H, 6.97; N, 7.04.
4152 | Dalton Trans., 2006, 4146–4154
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Table 4 Crystal and refinement details for 7, 8 and 11
Compound
7
8
11
Formula
M
C168H232N16Na8Si16·4C5H12
C40H60K2N2Si4
759.5
Monoclinic
P21/n (14)
18.754(3)
13.053(2)
18.970(4)
105.88(2)
4,467(1)
4
C42H58N4NiSi4
790.0
3397.64
Crystal system
Space group (no.)
Tetragonal
P4/n (85)
32.690(7)
32.690(7)
9.819(2)
90
10,493(4)
2
Monoclinic
P21/c (14)
11.439(6)
12.9546)
30.37(3)
97.85(6)
4,458(6)
4
˚
a/A
˚
b/A
˚
c/A
b/◦
3
˚
U/A
Z
l/mm−1
0.16
0.347
0.58
Unique reflections, Rint
Reflection with I > 2r(I)
Final R indices [I > 2r(I)]
R Indices (all data)
6,404, 0.112
3063
5,447, 0.027
3972
6,217, 0.065
3732
R1 = 0.092, wR2 = 0.209
R1 = 0.042, wR2 = 0.086
R1 = 0.080, wR2 = 0.168
R1 = 0.198, wR2 = 0.273
R1 = 0.069, wR2 = 0.096
R1 = 0.149, wR2 = 0.227
C21H29KN2Si2 requires C, 62.32; H, 7.22; N, 6.92%), which was
separated by filtration and dried in vacuo. Crystals suitable for
X-ray analysis were obtained from thf, mp > 220 ◦C. MS: m/z
(%, assignment, L = ligand): 500 (23, [M − 3SiMe3 − CHSiMe3 −
2thf]+), 404 (4, [1/2M − thf]+), 365 (29, [L]+), 351 (7, [LH − Me]+),
293 (48, [LH − SiMe3]+), 278 (43, [L − NSiMe3]+), 263 (21, [L −
NSiMe3 − Me]+), 220 (88, [LH − 2SiMe3]+), 147 (100), 128 (28),
104 (42) and 73 (53, [SiMe3]+). 1H NMR (C6D6): d −0.04 (s, SiMe3,
9 H), 0.01 (s, NSiMe3, 9 H), 1.39 (m, CH2, 4 H), 3.55 (m, OCH2,
CH), 126.7, 127.7, 128.3, 129.2 and 130.6 (s, Ph o-, m- and p-CH),
142.2 (s, Ph ipso-C), 154.4 and 168.6 (s, CN).
Crystal data and refinement details for 7, 8 and 11
Diffraction data for each of 7, 8 and 11 were collected on an
Enraf-Nonius CAD-4 diffractometer using monochromated Mo-
˚
Ka radiation, k = 0.71073 A at 173(2) K. Crystals were coated in
oil and then mounted directly on the diffractometer under a stream
of cold nitrogen gas. The structures were solved on all F2 using
SHELXL-97.23 Non-hydrogen atoms were refined anisotropically;
hydrogen atoms were included in the riding mode for 7 and 11 for
10, those H atoms which might have been affected by interactions
with K atoms had their positions freely refined (no distortions
from normal were found); other H atoms were included in the
riding mode. The diffraction data for 7 were very weak at high
theta values; the poorly defined pentane solvate was included with
isotropic C atoms, N atoms omitted, and 1,2 and 1,3 distance
constraints. Further details are in Table 4.
1
4 H), 4.40 (s br, CH, 1 H), 7.07–7.41 (m, Ph, 10 H). 13C{ H}
NMR (C6D6): d 1.1 (s, SiMe3), 3.4, (s, NSiMe3), 25.8 (s, CH2), 67.9
(s, OCH2), 109.8 (s, CH), 126.8., 127.1, 127.4, 127.8, 127.9 and
128.5 (s, Ph o-, m- and p-CH), 132.4, 133.0, 144.7 and 146.5 (s, Ph
ipso-C), 166.3 and 171.3 (s, CN).
|
[Ni{N(R)C(Ph) C(Ph)=C(H)R} ](11). [Li{l-N(R)C(Ph)N–
N
2
=
C(Ph) C(H)R}(thf)]2 (0.8 g, 0.90 mmol) in thf (20 mL) was
added dropwise to a solution of [NiBr2(dme)] (0.26 g, 0.84 mmol)
in thf (20 mL) at ca. 23 ◦C. The resulting deep-yellow/brown
mixture was stirred for ca. 5 min. The solvent was removed in
vacuo, the residue “stripped” (this procedure refers to adding the
solvent and then removing it in vacuo) with pentane (3 × 10 mL)
and then dissolved in pentane (10 mL). Filtration from a white
precipitate followed by concentration of the filtrate to ca. 3–4 mL
and cooling to −30 ◦C yielded deep purple crystals (0.41 g, 63%)
(Found: C, 62.9; H, 7.48; N, 7.09; C42H58N4NiSi4 requires C, 63.9;
H, 7.40; N, 7.09%), which were dried in vacuo. Three compounds
CCDC reference numbers 297453–297455.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b601881e
Acknowledgements
We are grateful to European Commission for the award to R. S. of
a Marie Curie Fellowship and for EPSRC for other support and
to Dr A. V. Protchenko for useful discussions.
1
of relative intensities 94, 3 and 3 were observed from H NMR,
=
the CH region at d 4.99, 5.18 and 5.48 ppm; one of the latter
References
two may be due to a geometric isomer of 11 and the other to
Ni(1,3-diazaallyl)Br]. The compound 11 had mp: 62–64 ◦C. MS:
m/z (%, assignment, L = ligand): 788 (24, [M]+), 716 (2, [M −
SiMe3]+), 612 (4, [M − 2SiMe3 − 2Me]+, 424 (3, [M − L]+), 365
(75, [L]+), 351 (39, [LH − Me]+), 293 (75, [LH − SiMe3]+), 278 (68,
[L − NSiMe3]+), 263 (29, [L − NSiMe3 − Me]+), 220 (14, [LH −
2SiMe3]+), 176 (90, [N(SiMe3)C(Ph)]+), 147 (82), 104 (42) and 73
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(100, [SiMe3]+). H NMR (C6D5CD3): d major) 0.21 (s, SiMe3, 9
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4154 | Dalton Trans., 2006, 4146–4154
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