Highly Electron-Rich β-Diketiminato Systems: Synthesis and Coordination Chemistry of Amino-Functionalized “N-nacnac” Ligands

Article abstract of DOI:10.1002/chem.201700757

The synthesis of a class of electron-rich amino-functionalized β-diketiminato (N-nacnac) ligands is reported, with two synthetic methodologies having been developed for systems bearing backbone NMe₂ or NEt₂ groups and a range of N-bound aryl substituents. In contrast to their (Nacnac)H counterparts, the structures of the protio-ligands feature the bis(imine) tautomer and a backbone CH₂ group. Direct metalation with lithium, magnesium, or aluminium alkyls allows access to the respective metal complexes through deprotonation of the methylene function; in each case X-ray structures are consistent with a delocalized imino-amide ligand description. Transmetalation using lithium N-nacnac complexes is then exploited to access p- and f-block metal complexes, which allow for like-for-like benchmarking of the N-nacnac ligand family against their more familiar Nacnac counterparts. In the case of Sn^II, the degree of electronic perturbation effected by introduction of the backbone NR₂ groups appears to be constrained by the inability of the amino group to achieve effective conjugation with the N₂C₃ heterocycle. More obvious divergence from established structural norms is observed for complexes of the harder Yb^II ion, with azaallyl/imino and even azaallyl/NMe₂ coordination modes being demonstrated by X-ray crystallography.

Full text of DOI:10.1002/chem.201700757

A Journal of
Accepted Article
Title: Highly electron rich β-diketiminato systems: Synthesis and
coordination chemistry of amino functionalized 'N-nacnac' ligands
Authors: Dinh Cao Huan Do, Ailsa Keyser, Andrey Protchenko, Brant
Maitland, Indrek Pernik, Haoyu Niu, Eugene Kolychev, Arnab
Rit, Dragoslav Vidovic, Andreas Stasch, Cameron Jones, and
Simon Aldridge
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To be cited as: Chem. Eur. J. 10.1002/chem.201700757
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10.1002/chem.201700757
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Highly electron rich β-diketiminato systems: Synthesis and
coordination chemistry of amino functionalized ‘N-nacnac’
ligands
Dinh Cao Huan Do,[a] Ailsa Keyser,[a] Andrey V. Protchenko,[a] Brant Maitland,[b] Indrek Pernik,[b] Haoyu
Niu,[a] Eugene L. Kolychev,[a] Arnab Rit,[a] Dragoslav Vidovic,[c] Andreas Stasch,*[b,d] Cameron Jones,*[b]
and Simon Aldridge*[a]
Abstract: The synthesis of
a
class of electron-rich amino-
stable complexes through chelation, and the ready tuning of
their steric properties through the N-alkyl/aryl substituents. As
such, a number of recent landmark compounds from the s-, p-, d
and f-blocks have drawn on Nacnac supporting frameworks.[3,4]
functionalized β-diketiminato (N-nacnac) ligands is reported, with
two synthetic methodologies having been developed for systems
bearing backbone NMe2 or NEt2 groups and a range of N-bound aryl
substituents. In contrast to their (Nacnac)H counterparts, the
structures of the protio-ligands feature the bis(imine) tautomer and a
backbone CH2 group. Direct metallation with lithium, magnesium or
aluminium alkyls allows access to the respective metal complexes
via deprotonation of the methylene function; in each case X-ray
structures are consistent with a delocalized imino-amide ligand
description. Trans-metallation using lithium N-nacnac complexes has
then been exploited to access p and f-block metal complexes which
allow for like-for-like benchmarking of the N-nacnac ligand family
against their more familiar Nacnac counterparts. In the case of SnII
the degree of electronic perturbation effected by introduction of the
backbone NR2 groups appears to be constrained by the inability of
the amino group to achieve effective conjugation with the N2C3
heterocycle. More obvious divergence from established structural
norms are observed for complexes of the larger, harder YbII ion, with
azaallyl/imino and even azaallyl/NMe2 coordination modes being
demonstrated by X-ray crystallography.
While tuning the steric demands of the N-substituents to
modulate access to the metal centre is relatively easily
accomplished, variation in ligand electronic properties has been
examined to
a
lesser extent.[4c] The incorporation of
electronically modifying substituents within the N-aryl groups, for
example, has been examined, although the extent of
communication with the N-donor itself is presumably dependent
on the torsional alignment of the aryl ring.; another option is to
modify the nature of the backbone C-bound groups, with
examples including trifluoromethyl, and electron-withdrawing aryl
substituents having been reported.[5] Bearing in mind the
differences in the donor capabilities of amidinato and
guanidinato ligands derived from the inclusion of a pendant NR2
group,[6] we hypothesized that the incorporation of a similar
backbone π-donor into a Nacnac ligand framework might lead to
enhanced donor properties (Scheme 1). In Valence Bond terms
the electronic perturbation brought about by the inclusion of
peripheral NR2 substituents can be viewed as resulting from
additional ‘double amido’ resonance structures incorporating a
pendant =NR2+ function.
Introduction
The mono-anionic β-diketiminate (or ‘Nacnac’) ligand class,
[R''C(R'CRN)2]-, has been widely employed in the stabilization of
metal complexes from across the Periodic Table.[1,2] In part, this
reflects the strongly electron-donating properties of these
systems, allied to their potential for forming thermodynamically
NR2
NR2
NR2
Ar
Ar
Ar
Ar
Ar
Ar
N
N
N
N
N
N
R2N
Ar
NR2
R2N
Ar
NR2
Ar
[a]
Mr D Do, Dr A Protchenko, Ms A Keyser, Mr H Niu, Dr E Kolychev,
Dr A Rit, Prof S Aldridge
N
N
N
N
Ar
Department of Chemistry, University of Oxford, Inorganic Chemistry
Laboratory, South Parks Road, Oxford, UK. OX1 3QR
E-mail: Simon.Aldridge@chem.ox.ac.uk
Dr B Maitland, Dr I Pernik, Dr A Stasch, Prof C Jones
School of Chemistry, Monash University, PO Box 23, Melbourne,
Victoria 3800, Australia
R2N
Ar
NR2
Ar
R2N
Ar
NR2
[b]
N
N
N
N
Ar
E-mail: Cameron.Jones@monash.edu
[c]
[d]
Dr D Vidovic
Scheme 1. Potential resonance forms for (upper) guanidinato and (lower)
SPMS-CBC, Nanyang Technological University, 21 Nanyang Link,
Singapore, 637371.
Present address: EaStCHEM School of Chemistry, University of St
Andrews, North Haugh, St Andrews, KY16 9ST, United Kingdom. E-
mail: as411@st-andrews.ac.uk
amino-functionalized Nacnac ligands.
While unpublished theoretical studies appear to corroborate
this viewpoint,[7] and synthetic studies giving access to protio-
ligands employing an –NMe2 substituent date back to 1971,[7,8]
Supporting information for this article is given via a link at the end of
the document.
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10.1002/chem.201700757
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little attempt has been made to systematically appraise the
chemistry of amino-functionalized Nacnac (or N-nacnac)
ligands.[9] With this in mind, we set out to explore the synthetic,
coordination and structural chemistry of this ligand family, and to
compare their properties with those of the corresponding
(backbone Me) Nacnac systems.
iPr2C6H3)], were designed to probe the scope for variation in
steric bulk compatible with this synthetic approach.
The resulting protio-ligands [1Ph]H and [1Dipp]H can be obtained
as analytically pure materials (in yields of 50-60 and 30-40%,
respectively) either directly without further purification (in the
case of [1Ph]H) or following recrystallization from acetone/hexane
(for [1Dipp]H). Both NMR studies in hydrocarbon solution and
crystallographic studies in the solid state reveal differences in
the structures of [1Ph]H/[1Dipp]H compared to the corresponding
(Nacnac)H protio-ligands. In the (Nacnac)H systems hydrogen-
bonding between the N-H proton and the imine N atom helps to
Results and Discussion
Protio-ligand synthesis and structural characterization. Two
different approaches have been investigated for the synthesis of
the target (N-nacnac)H protio-ligands, involving either (i) the
condensation of RNH2 (R = aryl, alkyl) with a pre-formed
bifunctional backbone or (ii) the coupling of two amino-imine
units though the C2 backbone position (Scheme 2).
stabilize
a
planar conjugated amino-imine tautomer.[10] By
contrast, in the (N-nacnac)H systems [1Ph]H and [1Dipp]H,
intramolecular hydrogen bonding is absent and the diimine
structure pertains, allowing for much longer distances between
the two imine N atoms and relief of steric congestion caused by
the pendant aryl groups (Figure 1).
The lack of conjugation about the NCCCN unit in
[1Ph]H/[1Dipp]H is consistent with C1-C2 and C2-C3 distances
determined crystallographically which are in the C-C single bond
R'2N
NR'2
R'2N
NR'2
2 RNH2
Base
(i)
N
N
Cl
Cl
R
R
range (e.g. 1.527(2)
Å and 1.524(1) Å, respectively, for
[1Ph]H).[11] Consistently, the imine C-N distances (e.g. 1.292(1) Å
and 1.288(1) Å for [1Ph]H), are typical of isolated C-N double
bonds [11] On the other hand, the corresponding exocyclic C1-N3
and C3-N4 distances (e.g. 1.360(2) Å and 1.374(1) Å for [1Ph]H)
are found to lie between C-N single and double bond ranges,
indicating a degree of conjugation of the lone pairs of the NMe2
units into the imine functions.
R''
R''
R'2N
NR'2
R'2N
Cl
NR'2
(ii)
-LiCl
N
N
N
Li
N
R
R
R
R
Scheme 2. The two different synthetic routes to (N-nacnac)H protio-ligands
1H NMR spectroscopy provides evidence that the diimine form
of [1Ph]H/[1Dipp]H is also retained in solution, showing in each
case a signal integrating to two protons for the saturated
methylene linker (at δH = 3.37 and 3.27 ppm for [1Ph]H/[1Dipp]H,
investigated in the current study.
Route (i) was optimized based on a procedure originally
reported by Viehe et al. in 1971, and subsequently explored by
Clyburne.[7,8] This approach involves initial reaction between
Viehe’s Salt (dichloromethylene-dimethyliminium chloride) and
N,N-dimethyl-acetamide, followed by in situ addition of the
aniline of choice to yield the protio-ligands, [1R]H (Scheme 3).
The two aryl groups initially chosen [R = Ph and Dipp (2,6-
O
Me
Cl
Me
Me2N
NMe2
Cl-
NMe2
N
Cl-
(0.5 equiv.)
CH2Cl2, reflux
Cl
Cl
Cl
RNH2 (2 equiv.)
CHCl3, reflux
basic work-up
Figure 1. Molecular structures (upper) of [1Ph]H, [1Xyl]H and [1Dipp]H, and
(lower) of [4Mes]H, 2 and 3 in the solid state as determined by X–ray
crystallography. Colour scheme: hydrogen, white; carbon, grey; nitrogen, pale
blue; chlorine, green. Displacement ellipsoids drawn at 50 % probability level;
most H-atoms and solvate molecules omitted, and N-substituents drawn in
wireframe format for clarity. Key bond lengths (Å) and angles (o): (for 2): C16-
C20 1.351(4), C15-C16 1.454(3), C13-C15 1.336(3), C12-C13 1.529(3), C12-
C18 1.520(3), C17-C18 1.334(3), C16-C17 1.459(3); (for 3): C8-C14 1.411(2),
C14-C15 1.407(2), C8-N7 1.348(2), C8-N9 1.353(2), C15-N16 1.366(2), C15-
N19 1.348(2). Key metrical data for [1Ph]H, [1Xyl]H, [1Dipp]H and [4Mes]H are
given in Table 1.
Me2N
NMe2
R = Ph, o-Xyl, Dipp, tBu
N
N
R
R
[1R]H
Scheme 3. Condensation based synthetic route to (N-nacnac)H protio-ligands
of the type [1R]H.
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Table 1. Crystallographically determined bond lengths (Å) for
(N-nacnac)H protio-ligands.
Protio-ligand
d(C1-N1),a
d(C3-N2)
d(C1-N3),
d(C3-N4)
d(C1-C2),
d(C2-C3)
[1Ph]H
1.292(1)
1.288(1)
1.360(2)
1.374(1)
1.527(2)
1.524(2)
[1Xyl]H
1.283(3)
1.369(3)
1.526(3)
[1Dipp]H
1.287(2)
1.286(2)
1.365(2)
1.367(2)
1.512(2)
1.529(2)
Figure 3. Potential diimine and amino-imine tautomers for (N-nacnac)H and
(Nacnac)H protio-ligands.
[4Mes]H
1.292(2)
1.371(2)
1.529(2)
conjugation associated with linking two isolated imine units over
the corresponding process for two amidine functions.
a See Figure 2 for atom numbering scheme. b Metric parameters
given for one of the molecules in the asymmetric unit.
Interestingly, the one-pot synthetic methodology outlined in
Scheme 2 is found to be more problematic for anilines bearing a
C5
N3
C7
N4
para-methyl substituent, such as MesNH2 (Mes
= 2,4,6-
C2
C4
C1
N1
C3
N2
C6
Me3C6H2). Thus, the spirocyclic system 2 was unexpectedly
isolated (rather than pro-ligand [1Mes]H) when MesNH2 was
employed as the aniline reagent (Figures 1 and 4). The identity
of 2 was unambiguously established by X-ray crystallography
and is consistent with the assimilation of a single equivalent of
MesNH2, followed by ring closure to generate a quaternary
carbon centre. Particularly remarkable is the activation of the
para-methyl group of the mesityl ring, chemistry which is
consistent with the appearance of alkenic CH2 and CH reson-
ances in the 1H NMR spectrum of 2, and with the disappearance
of the para-CH3 signal. Consistently, the C-C bond distances
determined crystallographically for the six-membered ring are no
longer equivalent, with the C2-C3, C4-C5, C5-C6 and C2-C7
separations ranging from 1.454(3) to 1.529(3) Å (consistent with
descriptions as carbon-carbon single bonds),[11] and the C1-C2,
C3-C4 and C6-C7 distances [1.351(4), 1.336(3) and 1.334(3) Å,
respectively] are indicative of double bond character. Mechanist-
ically, the formation of 2 necessitates initial uptake of a single
equivalent of MesNH2, followed by deprotonation at the mesityl
para-CH3 group thereby generating a C-based nucleophile,
which (by virtue of resonance) attacks the second chloro-imine
function through the ipso-carbon. While such a proposal has
little literature precedent, it is entirely consistent with the notion
that the related ortho-xylyl amine, 2,6-Me2C6H3NH2, does not
undergo analogous spirocyclic ring closure, but instead
generates the desired protio-ligand [1Xyl]H in good yield (Scheme
3 and Figure 1).
Ar
Ar
Figure 2. Atom numbering scheme used in Table 1 for compounds [1Ph]H,
[1Xyl]H, [1Dipp]H and [4Mes]H.
respectively) and no resonances in the regions expected for an
N-H proton or for the γ-CH unit of an amino-imino system (cf. δH
= 12.12 ppm and 4.84 ppm, respectively, for {HC(MeCDippN)2}H
in CDCl3).[12]
DFT calculations carried out for [1Ph]H and [1Dipp]H at the
BP86-D3(TZP) level reveal that the energetic difference
between the diimine and amino-imine forms is small (⏐ΔE⏐ < 10
kJ mol-1) both in the gas phase and in simulated benzene or
chloroform solution (Table
2 and Figure 3). While these
calculations indicate that the diimine tautomer is marginally
favored for [1Ph]H, and that the energy difference is essentially
zero for [1Dipp]H, the analogous calculations for the related
(Nacnac)H compounds (with backbone methyl substituents)
indicate a slightly larger energetic preference (ΔE > 25 kJ mol-1)
in the opposite sense, i.e. favoring the amino-imine form.
Presumably such differences reflect, at least in part, a greater
increase in delocalization achieved for X = Me on adoption of the
amino-imine tautomeric form (Figure 3), i.e. a greater gain in
Table 2. DFT calculated energies of diimine and amino-imine tautomers for
(N-nacnac)H and (Nacnac)H protio-ligands .
tBu
NH
ΔE (kJ mol-1)a
Cl-
H
Me2N
Ligand
X
R
N
NMe2
Gas-phase
-6.5
Benzene
-8.3
Chloroform
-9.0
Cl-
NMe2
NH
NMe2
NMe2
Me
Ph
tBu
H
Me2N
(N-nacnac)H
3
2
Dipp
Ph
+0.6
+0.8
+0.8
+35.3
+60.0
+28.7
+36.1
+25.6
Figure 4. Spiro-cyclic compound 2 obtained from condensation chemistry
utilising MesNH2; rearranged product 3 obtained with tBuNH2 under aqueous
conditions.
(Nacnac)H
Me
Dipp
+35.6
a
ΔE = E(dimine form) – E(amino-imine form). A negative figure therefore
The one-pot protocol can be extended to alkyl amines, such as
tBuNH2, although in this case the isolation of the desired pro-
ligand [1tBu]H necessitates an anhydrous work-up, followed by
indicates that the diimine tautomer possesses a lower overall energy.
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sublimation, and suffers from a very poor yield (ca. 5%). [1tBu]H
isolated in this fashion has been characterized by multinuclear
NMR spectroscopy and by mass spectrometry (including
accurate mass measurement), with its existence as the diimine
tautomer in solution being suggested by a methylene resonance
integrating to two hydrogens at δH = 3.86 ppm (cf. 3.37 and 3.27
ppm for [1Ph]H/[1Dipp]H, respectively). However, the use of a
more convenient aqueous work-up procedure similar to that
employed for N-aryl substituted diimines [1Ph]H, [1Xyl]H and
[1Dipp]H, leads instead to the formation of the re-arranged
amidinium chloride salt 3, the identity of which was confirmed by
standard spectroscopic/analytical methods and X-ray crystal-
ography (Figures 1 and 4). The solid state structure is consistent
with rearrangement of the amino-functions across the C3
backbone, presumably mediated by reversible imine/iminium
formation under aqueous conditions. Geometrically, 3 reveals a
highly conjugated heavy atom skeleton, with the C-C [1.407(2)
and 1.411(2) Å] and C-N bond distances [1.348(2) - 1.366(2) Å]
falling in each case between the respective carbon-carbon and
carbon-nitrogen single and double bond lengths.
ultimately with a view to comparing donor properties with more
well established Nacnac analogues. With this in mind, we
targeted (i) the use of metal alkyl reagents (M = Li, Mg, Al) to
generate a range of metal N-nacnac complexes via deproton-
ation of the protio-ligands; and (ii) the use of such reagents in
trans-metallation chemistry, targeting complexes of SnII (as an
exemplar from the p-block) and YbII as examples of f-element
complexes. The existence of the corresponding metal complex-
es featuring (backbone-Me) Nacnac ligands made these two
platforms attractive from the perspective of like-for-like
comparison.[13,14]
Accordingly, the reactions of (N-nacnac)H protio-ligands with
nBuLi, for example, lead to deprotonation of the backbone
methylene group and to the formation of the corresponding
lithium complex of the conjugate base [N-nacnac]-. Such
chemistry can be carried out either in the presence or absence
of a coordinating solvent, leading to the generation of either
monomeric donor-stabilized complexes such as [1Dipp]Li(OEt2),
or donor-free oligomeric systems such as {[4Mes]Li}2 (Scheme 5).
In each case, the formation of an essentially planar six member-
ed LiN2C3 chelate ring could be established definitively by X-ray
crystallography, with the nearly identical C-N and C-C distances
Access to N-mesityl ligand systems requires the use of an
alternative synthetic approach, in which the (N-nacnac)H protio-
ligand is assembled via C-C bond formation from two pre-formed
amidine components. Deprotonation of an N-aryl-N',N'-dialkyl
substituted amidine at the β-CH2 position, followed by
electrophilic quenching with ClC(NR)NR’2 allows for the modular
synthesis of a range of (N-nacnac)H systems (Scheme 4). Thus,
[1Dipp]H can be synthesized in this fashion, with the yield of the
final step (ca. 35%) being comparable to that achieved in the
condensation procedure outlined above. While the methodology
outlined in Scheme 4 does require additional synthetic steps for
the formation of the amidine precursors, it is of note that both
components can be prepared from a common urea starting
material of the type R(H)NC(O)NR'2 (see SI). Moreover, the
scope of this approach is such that systems bearing N-mesityl
substituents, such as [4Mes]H and backbone phenyl groups (e.g.
[5Mes]H) can be prepared in this way. Each of these systems has
been characterized by conventional spectroscopic and analytical
techniques, with crystallographic data obtained for [4Mes]H in the
solid state also confirming the presence of the diimine tautomer
implied in solution by NMR measurements (Figure 1).
H
H
Me2N
Dipp
NMe2
Dipp
Me2N
Dipp
NMe2
Dipp
nBuLi, Et2O
N
N
Li
N
N
OEt2
[1Dipp]Li(OEt2)
Et2N
NEt2
H
H
N
N
Mes
Et2N
Mes
NEt2
Mes
Li
nBuLi, hexane
Li
Mes
N
N
N
N
Et2N
NEt2
{[4Mes]Li}2
Scheme 5. Lithiation of (N-nacnac)H protio-ligands with nBuLi.
Figure 5. (left to right) Molecular structures of [1Dipp]Li(OEt2), and one of the
molecules in the asymmetric unit of {[4Mes]Li}2, in the solid state as determined
by X–ray crystallography. Displacement ellipsoids drawn at 50 % probability
level; most H-atoms, minor disorder components and solvate molecules
omitted and N-substituents drawn in wireframe format for clarity. Key metrical
parameters are given in Table 3.
Scheme 4. C-C bond formation as a synthetic route to (N-nacnac)H protio-
ligands.
Complexation studies. Having established routes to the target
(N-nacnac)H protio-ligands, we then sought to establish viable
synthetic approaches for a range of coordination complexes,
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Table 3. Crystallographically determined bond lengths (Å) and angles (o) for
N-nacnac and (N-nacnac)H complexes of lithium, magnesium and
aluminium.
Complex
d(M1-N1),a
d(M1-N2)
d(N1-C1),
d(N2-C3)
d(C1-C2),
d(C2-C3)
∠(N1-M1-N2)
[1Dipp]Li(OEt2)
1.908(4)
1.914(3)
1.321(3)
1.336(3)
1.409(2)
1.420(2)
101.4(2)
b
{[4Mes]Li}2
1.927(5)
1.918(5)
2.062(5)c
2.063(5)c
2.075(5)c
2.065(5)c
1.346(3)
1.346(3)
1.357(3)
1.344(3)
1.408(3)
1.420(4)
1.410(3)
1.412(4)
101.5(2)
102.5(2)
[1Dipp]MgI(OEt2)b
[4Mes]MgI(OEt2)
{[4Mes]H}MgI2
[1Ph]AlMe2
2.036(2)
2.035(2)
1.358(3)
1.330(3)
1.396(2)
1.441(3)
98.7(1)
95.3(1)
91.6(1)
95.3(3)
99.5(1)
2.035(2)
2.026(2)
1.345(3)
1.352(3)
1.414(3)
1.409(3)
2.082(3)
2.092(2)
1.319(5)
1.312(5)
1.533(4)
1.527(4)
1.917(5)
1.906(8)
1.36(1)
1.36(1)
1.42(1)
1.42(1)
Scheme 6. Metallation of (N-nacnac)H protio-ligands with methyl-magnesium
and -aluminium reagents.
[1Dipp]AlMe2
1.923(2)
1.923(2)
1.355(3)
1.344(3)
1.404(3)
1.422(3)
b
a See Fig. 6 for atom numbering scheme. Metric parameters given for one
of the molecules in the asymmetric unit. c Associated with a bridging N atom.
C5
N3
C7
N4
C2
M1
C4
C1
N1
C3
N2
C6
Ar
Ar
Figure 6. Atom numbering scheme used in Table 2.
within the ring [e.g. 1.321(3)/1.336(3) and 1.409(2)/1.420(2) Å
for [1Dipp]Li(OEt2)] being consistent with a delocalized imino-
amide formulation (Figure 5 and Table 3).[15]
Figure 7. Molecular structures of (upper) [1Dipp]MgI(OEt2) (one of two
molecules in the asymmetric unit) and [4Mes]MgI(OEt2), and (lower) [1Ph]AlMe2
and [1Dipp]AlMe2 in the solid state as determined by X–ray crystallography.
Displacement ellipsoids drawn at 50 % probability level; most H-atoms, minor
disorder components and solvate molecules omitted and N-substituents drawn
in wireframe format for clarity. Key metrical parameters are given in Table 3.
Similar chemistry can also be effected using magnesium or
aluminium alkyls (Scheme 6 and Figure 7); the reactions with
either methyl Grignard reagents in diethyl ether or trimethyl-
aluminium in toluene generate methane and [N-nacnac]-
complexes featuring the respective metals in four-coordinate
environments. As with the lithium complexes outlined above,
metrical parameters for [1Dipp]MgI(OEt2), [4Mes]MgI(OEt2),
[1Ph]AlMe2 and [1Dipp]AlMe2 are consistent with backbone
Lithiated N-nacnac derivatives, either as isolated materials, or
generated in situ from the corresponding protio-ligand and nBuLi,
prove to be convenient reagents for trans-metallation chemistry,
e.g., for the synthesis of SnII chloride and hydride complexes.
Moreover, with a view to examining the effects of variation in the
steric bulk of the N-bound aryl substituents, we targeted
complexes featuring ligands 1Ph, 1Xyl and 1Dipp (Scheme 7).
Yields of the respective metal complexes (of the type [1R]MCl)
range from 50-80%, and each has been characterized by
standard spectroscopic techniques and by X-ray diffraction
(Figure 8).
deprotonation and with
a delocalized imino-amide ligand
description.[16,17] Thus for example, [4Mes]MgI(OEt2) features Mg-
N, C-N and C-C distances within the metal chelate ring of
2.026(2)/2.035(2), 1.345(3)/1.352(3) and 1.409(3)/1.414(3) Å,
respectively, while the related complex {[4Mes]H}MgI2 (obtained
as a minor side-product in the synthesis of [4Mes]MgI(OEt2); see
SI) which incorporates the fully protonated neutral ligand [4Mes]H,
features longer M-N and C-C [2.092(2)/2.082(3) and
1.527(4)/1.533(4) Å, respectively] and shorter N-C distances
[1.312(5)/1.319(5) Å] consistent with a non-conjugated diimine
formulation.
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H
H
Me2N
NMe2
centre out of the least-squares plane defined by the NC3N N-
nacnac chelate ring (e.g. by 0.99 Å for [1Ph]SnCl) and by a
complementary displacement of the N-bound aryl groups below
the same plane (with the ipso-carbons lying on average 0.91 Å
out of plane for [1Ph]SnCl). As the aryl groups become larger,
mutual steric repulsion forces them apart (Figure 9) with the
resulting disrotatory realignment of the N-M bonds dropping the
metal centre closer to the NC3N plane. Thus, in the sequentially
bulkier systems [1Xyl]SnCl and [1Dipp]SnCl, for example, the metal
centre lies 0.86 and 0.56 Å above the NC3N plane, and the ipso-
carbons are on average 0.68 and 0.52 Å below the plane. By
means of comparison, the structure of the corresponding
Nacnac system, {HC(MeCDippN)2}SnCl features a Sn(II) centre
which lies 0.66 Å out of the analogous ligand plane.[13c] These
factors – notably the drive for the larger N-aryl groups to lie
closer to the NC3N plane on steric grounds - exert a secondary
influence on the electronic properties of the [1Ph]-, [1Xyl]- and
[1Dipp]- ligands. Increasing congestion in the NC3N plane as the
aryl groups become larger forces the exo-cyclic NMe2 groups to
rotate out of the plane. Thus, in [1Ph]SnCl, [1Xyl]SnCl and
[1Dipp]SnCl the torsion angles between the NC3N chelate and
NC2 amino planes are 16.3/16.3o, 22.2/24.9o and 25.3/30.8o,
respectively, implying less efficient π-conjugation into the chelate
ring.
Me2N
NMe2
(i) nBuLi, toluene
(ii) SnCl2
N
N
R
R
Sn
N
N
R
R
Cl
[1R]SnCl: R = Ph, Xyl, Dipp
Scheme 7. Syntheses of N-nacnac-supported SnII chloride complexes.
Figure 8. Molecular structures of [1Ph]SnCl, [1Xyl]SnCl and [1Dipp]SnCl in the
solid state as determined by X–ray crystallography. Displacement ellipsoids
drawn at 50 % probability level; most H-atoms, minor disorder components
and solvate molecules omitted and N-substituents drawn in wireframe format
for clarity. Key metrical parameters are given in Table 4.
Me2N
NMe2
M
N
N
Ar
Ar
Table 4. Crystallographically determined bond lengths (Å) and angles
(o) for tin N-nacnac complexes. For comparison, data given in square
parentheses refer to the corresponding (backbone Me) Nacnac
complexes featuring the same N-aryl substituents.[13]
Figure 9. Structural realignment of the N-bound substituents of [N-nacnac]-
ligands as the bulk of the aryl groups increases.
Complex
d(M1-N1),a
d(M1-N2)
2.156(4)
2.156(4)
[2.170(9)]
d(N1-C1),
d(N2-C3)
1.362(6)
1.368(7)
[1.338(14)]
d(C1-C2),
d(C2-C3)
1.401(6)
1.406(5)
[1.348(17)]
∠(N1-M1-N2)
In broader terms, comparison of the structural parameters
determined for [1R]SnCl with the corresponding complexes of the
more well-established Nacnac ligand family reveals small but
significant differences. [1Dipp]SnCl, for example shows with a
marked widening of the N-Sn-N angle [89.8(2) vs. 85.2(1)o] and
an associated shortening of the Sn-N distances [2.161 (mean)
vs. 2.183 Å (mean)] compared to {HC(MeCDippN)2}SnCl.[13c]
Spectroscopically, the chemical shifts associated with the
backbone γ-CH proton are also consistent with a more electron
rich ligand framework in the N-nacnac complexes. The
respective signals are shifted significantly upfield compared to
their Nacnac analogues [e.g. 4.04 ppm for [1Dipp]SnCl vs. 5.05
ppm for {HC(MeCDippN)2}SnCl].[13c] Such an effect is consistent
with the well-documented effects of π-donor amino groups on
alkene resonances.[18]
The availability of the more sterically encumbered [1Dipp]SnCl
system allowed us to explore the possibilities for the synthesis of
the corresponding tin hydride. Accordingly, treatment with
K[Et3BH] in toluene led to the formation of the corresponding
metal hydride [1Dipp]SnH, which has been characterized by
spectroscopic and crystallographic methods (Scheme 8 and
Figure 10). This compound is thermally fragile, showing signs of
decomposition to tin metal over a period of ca. 12 h in C6D6
[1Ph]SnCl
84.4(1)
[84.9(3)]
[2.174(9)]
[1.379(15)]
[1.453(17)]
[1Xyl]SnCl
2.156(3)
2.148(2)
1.354(4)
1.352(3)
1.405(3)
1.402(4)
86.4(1)
[1Dipp]SnCl
2.167(4)
2.156(5)
[2.185(2)]
[2.180(2)]
1.355(7)
1.342(6)
[1.329(3)]
[1.344(3)]
1.410(8)
1.404(9)
[1.392(4)]
[1.401(3)]
89.8(2)
[85.2(1)]
[1Dipp]SnH
2.190(3)
2.194(4)
[2.198(2)]
[2.194(2)]
1.338(5)
1.338(6)
[1.326(3)]
[1.326(3)]
1.401(7)
1.416(6)
[1.404(3)]
[1.405(3)]
89.4(7)
[85.1(1)]
a See Fig. 6 for atom numbering scheme. Metric parameters given for
b
c
one of the molecules in the asymmetric unit.
bridging N atom.
Associated with a
The structures of these tin complexes allow for a systematic
appraisal of the steric and electronic effects brought about by
changes in the N-aryl substituents, and in particular as the bulk
of the aryl group is increased in the order Ph < Xyl < Dipp.[13a-c]
Thus, more ‘puckered’ complexes are associated with smaller
aryl groups, as manifested by greater projection of the metal
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solution, and over a period of several days in the solid state.
Spectroscopically, the 1H and 119Sn resonances for the Sn-H
moiety (δH = 13.42 ppm; δSn = -18 ppm) can be compared with
the corresponding data obtained for {HC(MeCDippN)2}SnH (δH =
13.96 ppm; δSn = -4.5 ppm).[13d] While these differences are
relatively small, divergence in the solid-state structures of the
two compounds again hints at underlying electronic differences.
Thus, while {HC(MeCDippN)2}SnH exists as a weakly bound
head-to-head dimer, featuring bridging Sn…H contacts of 4.01(3)
Å and a Sn…Sn separation of 3.71 Å,[13d] [1Dipp]SnH is more
obviously monomeric in the solid state (Figure 10). Although the
position of the tin-bound hydrogen atom could not be reliably
established by X-ray crystallography, the alignment of the
molecular units is in head-to-tail fashion, such that Sn-H…Sn
interactions are precluded. Conceivably, this phenomenon
signals a less polarized Sn-H bond, as a result of ligation by the
more electron-rich N-nacnac ligand. Steric factors might also be
expected to play a role, given the greater size of the backbone
NMe2 group (vs. Me), although this is presumably not a major
factor, given that the distance between the centroids of the
flanking Dipp rings changes little between the two systems.
Assimilation of either one or two equivalents of the N-nacnac
ligand is possible via iodide metathesis, leading to the formation
of compounds of composition {[1Dipp]Yb(µ-I)}2 and [1Dipp]2Yb,
respectively. Both compounds could be characterized by
standard spectroscopic and analytical techniques, and their
structures in the solid state determined by X-ray crystallography
(Figure 11). Interestingly, while the structures determined for s-
and p-block N-nacnac complexes reveal coordination modes
which strongly resemble those of the related ‘parent’ Nacnac
systems, those of {[1Dipp]Yb(µ-I)}2 and [1Dipp]2Yb show greater
Me2N
Dipp
I
N
Yb
(i) KCH2Ph
N
(ii) YbI2(thf)2
(1 equiv.)
Me2N
Dipp
2
K[1Dipp
]
[1Dipp]H
Me2N
Dipp
NMe2
Dipp
N
N
(i) KCH2Ph
(ii) YbI2(thf)2
(0.5 equiv.)
Yb
Me2N
Dipp
NMe2
Dipp
Me2N
Dipp
NMe2
Dipp
N
N
Me2
K[Et3BH], THF
Me2N
Dipp
N
Dipp
N
N
N
N
Sn
Sn
Scheme 9. Syntheses of homo- and heteroleptic YbII N-nacnac complexes.
H
Cl
[1Dipp]SnCl
[1Dipp]SnH
Scheme 8. Syntheses of a N-nacnac-supported SnII hydride.
Figure 10. Molecular structure of [1Dipp]SnH in the solid state as determined by
X–ray crystallography. Displacement ellipsoids drawn at 50 % probability level;
most hydrogen atoms, minor disorder components and solvate molecules
omitted and N-substituents drawn in wireframe format for clarity. Key metrical
parameters are given in Table 3.
Figure 11. Molecular structures of {[1Dipp]Yb(µ-I)}2 and [1Dipp]2Yb in the solid
state as determined by X–ray crystallography. Displacement ellipsoids drawn
at 50 % probability level; most hydrogen atoms omitted and N-substituents
drawn in wireframe format for clarity. The structure of {[1Dipp]Yb(µ-I)}2 is
centrosymmetric; only one of the two independent components in the
asymmetric unit is shown.
While Nacnac ligands have been employed effectively across
the Periodic Table, another area where they have found
particularly
widespread
application
is
in
f-element
structural differences. {[1Dipp]Yb(µ-I)}2, for example, features an
η4 mode of coordination of the N-nacnac ligand involving close
contacts with four of the five atoms of the N2C3 backbone [d(Yb-
C) = 2.734(5), 2.811(5) Å; d(Yb-N) = 2.337(5), 2.336(4) Å, for
one component of the asymmetric unit]. The other Yb…C contact
is somewhat longer [2.961(5) Å], and a description in terms of an
η3-azaallyl interaction augmented by the N-coordination of a
discrete imine donor (Scheme 8) is also in line with the N-C and
C-C distances within the N-nacnac backbone. Thus, the C-N
distance associated with the imine function [1.326(8) Å] is
chemistry.[2,19,20] In part this reflects the combination of steric
bulk and hard N-donor character allied to a chelating ligand
framework. With this in mind, we sought to further benchmark
our new N-nacnac ligands by synthesizing example of YbII
complexes, which again offer for like-for-like comparison with
existing Nacnac systems.[14] Thus, the reactions of in situ
.
potassiated N-nacnac reagents with YbI2 2(thf) were investigated
(Scheme 9).
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shorter than that in the azaallyl unit [1.363(9) Å], and the C-C
distance within the latter [1.383(8) Å] is shorter than the formal
single bond which links the two donor components [1.455(7) Å].
The corresponding product of the reaction of YbI2(thf)2 with
{HC(MeCDippN)2}K, by contrast generates a dimeric complex of
the type {(Nacnac)Yb(thf)(µ-I)}2, featuring the more common η2
N,N' mode of coordination of the β-diketiminate while retaining
one molecule of thf at each metal centre.[14b] Such differences
highlight the enhanced donor capabilities of the N-nacnac ligand
variant, in this case through the direct involvement of the more
electron rich ligand backbone.
however, observed in the complexes of the larger, harder YbII
ion, with azaallyl/imino and even azaallyl/NMe2 coordination
modes being demonstrated by X-ray crystallography. Such
observations hint at potential avenues for exploitation of this
ligand family in the near future.
Experimental Section
General considerations
The related bis(N-nacnac) complex [1Dipp]2Yb shows even
greater structural divergence from its Nacnac counterpart. Thus,
the solid-state structure (Figure 9) shows two distinct modes of
coordination: one N-nacnac ligand is coordinated in η4-fashion,
similar to the mode of ligation seen in {[1Dipp]Yb(µ-I)}2 [d(Yb-C) =
2.741(2), 2.776(2), 2.925(2) Å; d(Yb-N) = 2.369(1), 2.385(1) Å],
while the second ligand adopts a unique geometry, being bound
to the metal through one NDipp unit and one of the ‘backbone’
NMe2 groups. As such, a pendant imine function is projected
away from the metal centre, which allows for an alternative (less
sterically demanding) chelate geometry. The metal coordination
environment is completed by two Yb…H-C contacts involving the
hydrogens of isopropyl substituents from the two N-nacnac
ligands. By contrast, the solid state structure of
{HC(MeCDippN)2}2Yb reported by Harder features two
identically bound N,N'-chelating Nacnac ligands [d(Yb-N) =
2.381(1), 2.399(1) Å] and a metal centre with a close to
tetrahedral coordination geometry.[14a]
All manipulations were carried out using standard Schlenk line or dry-box
techniques under an atmosphere of argon. Solvents were degassed by
sparging with argon and dried by passing through a column of the
appropriate drying agent using a commercially available Braun SPS.
NMR spectra were measured in C6D6 or CDCl3 which were dried over
potassium or molecular sieves, respectively, and stored under argon in a
Teflon valve ampoule. NMR samples were prepared under argon in 5
mm Wilmad 507-PP tubes fitted with J. Young Teflon valves. NMR
spectra were measured on Varian Mercury-VX-300 or Bruker AVII-500
spectrometers; 1H and 13C NMR spectra were referenced internally to
residual protio-solvent (1H) or solvent (13C) resonances and are reported
relative to tetramethylsilane (δ = 0 ppm). 7Li, 27Al and 119Sn NMR spectra
3+
were referenced with respect to LiCl/D2O, Al(H2O)6
respectively. Chemical shifts are quoted in
constants in Hz. Elemental analyses were carried out at London
Metropolitan University. The syntheses of MesNC(Cl)NEt2,
and SnMe4,
δ
(ppm) and coupling
MesNC(Me)NEt2, MesNC(CH2Ph)NEt2, DippNC(Cl)NMe2, DippNC(Me)-
NMe2, 2 and 3 are described in the supporting information.
Syntheses of novel compounds
Generic synthesis of protio-ligands [1R]H via route (i): To a solution
of dichloromethylene-dimethylammonium chloride (15.00 g, 92.3 mmol)
in dichloromethane (100 mL) was added dropwise N,N-
dimethylacetamide (4.10 mL, 44.1 mmol) at room temperature, and the
reaction mixture refluxed for 6 h. After the removal of volatiles in vacuo,
chloroform was added (100 mL), followed by ArNH2 (100 mmol) via
syringe at 0oC. The reaction mixture was then refluxed for 12 h. After
cooling to room temperature, saturated KOH solution was added at 0oC
until the pH was ≥ 10, followed by water (100 mL). The aqueous layer
was washed twice with chloroform (100 mL each) and the organic layer
extracted, washed with brine (100 mL) and dried over MgSO4. The
resulting solution was filtered and volatiles removed in vacuo to give the
crude product. [1Ph]H: The solid crude product was washed with cold
hexane to yield a yellow solid as a spectroscopically pure material. Yield:
7.55 g, 56%. Crystals suitable for X-ray crystallography were obtained
from a saturated acetone solution at -26oC. 1H NMR (400 MHz, CDCl3):
δH 2.84 (s, 12H, (CH3)2N), 3.37 (s, 2H, N-nacnac backbone CH2), 6.57 (d,
Conclusions
The synthesis of a new class of amino-functionalized β-
diketiminato ligands (N-nacnacs) is reported, with two
approaches having been developed to protio-ligands bearing
backbone NMe2 or NEt2 groups and a range of N-bound aryl
substituents. In contrast to their (Nacnac)H counterparts, the
structures of these systems both in the solution and in the solid
state feature the bis(imine) tautomer and a backbone CH2 group.
Direct metallation with group 1, 2 or 13 metal alkyls allows
access to the respective metal complexes via deprotonation of
the methylene group. The structures of a range of Li, Mg and Al
compounds have been determined, and in each case are
consistent with a delocalized imino-amide ligand description.
Transmetallation has then been explored using lithium N-nacnac
complexes possessing varying steric profiles, with SnII
compounds being targeted (via metathesis) in order to provide
like-for-like comparison with the analogous Nacnac complexes.
While analogies can be drawn between N-nacnac and Nacnac
complexes along similar lines to those described previously for
guanidinate/amidinate systems, the degree of electronic
perturbation effected by introduction of the backbone NR2
groups appears to be restricted (particularly for more bulky N-
nacnac ligands) by the inability of the amino group to achieve
effective conjugation with the N2C3 heterocycle. Much more
radical divergence from the Nacnac structural norms are,
3
3JHH = 7.7 Hz, 4H, o-CH of Ph), 6.90 (t, JHH = 7.4 Hz, 2H, p-CH of Ph),
3
7.18 (t, JHH = 7.6 Hz, 4H, m-CH of Ph). 13C{1H} NMR (100 MHz, CDCl3):
δC 29.4 (N-nacnac backbone CH2), 38.6 ((CH3)2N), 122.0 (p-CH of Ph),
122.7 (o-CH of Ph), 129.1 (m-CH of Ph), 150.8 and 155.6 (ipso-C of Ph
and imine quaternary C). ESI-MS (m/z, %): 309.2, weak, [M+H]+;
accurate mass: calc. for C19H25N4 ([M+H]+) 309.2074, meas. 309.2075.
Elemental microanalysis: calc. for C19H24N4: C 73.99, H 7.84, N 18.17%,
meas. C 74.13, H 8.01, N 18.00%. Crystallographic data: C19H24N4, Mr =
308.43, trigonal, R-3, a = 26.6569(4), b = 26.6569(4), c = 12.9106(3) Å, V
= 7945.0(2) Å3, Z = 18, ρc = 1.160 g cm-3, T = 150 K, λ = 1.54180 Å.
10753 reflections collected, 3694 independent [R(int) = 0.077] used in all
calculations. R1 = 0.0419, wR2 = 0.1072 for observed unique reflections [I
> 2σ(I)] and R1 = 0.0451, wR2 = 0.1110 for all unique reflections. Max.
and min. residual electron densities 0.25 and -0.27 e Å -3. CCDC ref:
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1528016. [1Xyl]H: (NB. additional base (N-ethyl diisopropyl amine, 11.70
mL, 68.36 mmol) was added along with the aniline for the second reflux
step). The product was recrystallized from minimal acetone:hexane as
pale yellow crystals; additional crops could be obtained from the filtrate to
give an overall yield of 5.67 g (35%). 1H NMR (400 MHz, CDCl3): δH 1.98
(s, 12H, CH3 of Xyl), 2.86 (s, 12H, (CH3)2N), 3.13 (s, 2H, N-nacnac
Synthesis of [1Dipp]H via route (ii): To a solution of DippNC(Me)NMe2
(1.00 g, 4.06 mmol) was added nBuLi (2.66 mL of a 1.6 M solution in
hexane, 4.26 mmol) and TMEDA (0.52 g, 0.665 mL, 4.46 mmol) in
hexane (40 mL) at –78 °C. The reaction mixture was allowed to warm to
room temperature and stirred for 30 min, then cooled to –78 °C. In a
separate flask, DippNC(Cl)NMe2 (1.08 g, 4.06 mmol) was dissolved in
hexane (5 mL) and the resulting solution added dropwise to the reaction
mixture. After the addition, the mixture was allowed to warm to room
temperature, and stirred for 12 h. After heating at a gentle reflux for 1 h,
and cooling to room temperature, water (5 mL) was slowly added to the
reaction mixture, followed by dichloromethane (10 mL). The organic
fraction was then washed with water (2 x 10mL) and aqueous sodium
bicarbonate (10 mL, saturated). The organic fraction was dried (MgSO4)
and concentrated. The residue was recrystallised from boiling ethanol (10
mL) to give the product as a colourless solid. Yield: 0.69 g, 35%.
Spectroscopic and analytical data matched those measured for a sample
obtained via route (i).
3
3
backbone CH2), 6.80 (t, JHH = 9.1 Hz, 2H, p-CH of Xyl), 6.98 (d, JHH
=
7.4 Hz, 4H, m-CH of Xyl). 13C{1H} NMR (100 MHz, CDCl3): δC 18.6 (CH3
of Xyl), 31.4 (N-nacnac backbone CH2), 38.6 ((CH3)2N), 121.6 (p-CH of
Xyl), 128.0 (m-CH of Xyl), 128.9 (o-C of Xyl), 147.9 (ipso-C of xyl), 154.1
(imine quaternary C). ESI-MS (m/z, %): 365, weak, [M+H]+; accurate
mass: calc. for C23H33N4 365.2700, meas. 365.2698. Elemental
microanalysis: calc. for C23H32N4: C 75.78, H 8.85, N 15.37%, meas. C
75.65, H 9.01, N 15.25. Crystallographic data: C23H32N4, Mr = 364.53,
tetragonal, P 43212, a = 8.0421(1), b = 8.0421(1), c = 32.9265(6) Å, V =
2129.53(5) Å3, Z = 4, ρc = 1.137 g cm-3, T = 150 K, λ = 0.71073 Å. 4485
reflections collected, 1510 independent [R(int) = 0.035] used in all
calculations. R1 = 0.0428, wR2 = 0.1087 for observed unique reflections [I
> 2σ(I)] and R1 = 0.0592, wR2 = 0.1291 for all unique reflections. Max.
and min. residual electron densities 0.22 and -0.24 e Å-3. CCDC ref:
1528018. [1Dipp]H: (NB. additional base (N-ethyl diisopropyl amine, 26.53
mL, 155 mmol) was added along with the aniline for the second reflux
step). The crude product (a dark red oil) was dissolved in an
acetone/hexane mixture and stirred vigorously for 10 min. Filtration
followed by storage at -26oC overnight yielded the product as pale yellow
[4Mes]H was prepared from MesNC(Me)NEt2 and MesNC(Cl)NEt2 via
route (ii) in an analogous manner to that described above, and the crude
residue recrystallised from ethanol to give the product as a colourless
crystalline solid. Yield: 66% on a 1 - 2g scale. 1H NMR (400 MHz, C6D6):
δH 0.98 (br s, 12H, NCH2CH3), 2.07 (s, 12H, o-CH3 of Mes), 2.21 (s, 6H,
p-CH3 of Mes), 3.18 (br s, 8H, NCH2CH3), 3.31 (s, 2H, N-nacnac
backbone CH2), 6.88 (s, 4H, m-CH of Mes). 13C{1H} NMR (101 MHz,
C6D6): δC 13.1 (NCH2CH3), 18.4, 20.5 (CH3 of Mes), 29.9 (N-nacnac
backbone CH2), 41.6 (NCH2CH3), 128.5, 128.9, 130.1, 145.6 (Mes) 153.2
(imin quaternary C). EI-MS (m/z, %): 449.3, 100, [M+H]+; accurate mass:
crystals. Yield: 6.91 g, 33%. 1H NMR (400 MHz, C6D6): δH 1.12 (d, 3JHH
=
7.1 Hz, 12H, (CH3)2CH), 1.18 (d, 3JHH = 7.1 Hz, 12H, (CH3)2CH), 2.68 (s,
12H, (CH3)2N), 2.95 (br sept, 3JHH = ca. 7 Hz, 4H, (CH3)2CH), 3.21 (s, 2H,
N-nacnac backbone CH2), 7.05 (t, 3JHH = 7.5 Hz, 2H, p-CH of Dipp), 7.12
+
calc. for C29H45N4 ([M+H]+) 449.3639, meas. 449.3641. Elemental
3
(d, JHH = 7.5 Hz, 4H, m-CH of Dipp). 13C{1H} NMR (125 MHz, C6D6): δC
microanalysis: calc. for C29H44N4: C 78.10, H 10.15, N 11.75%; meas.: C
78.25, H 10.27, N 11.66%. Crystallographic data: C29H44N4, Mr = 448.68,
monoclinic, C 2/c, a = 12.142(2), b = 20.507(4), c = 10.584(2) Å, β =
91.35(3)o, V = 2634.6(9) Å3, Z = 4, ρc = 1.131 g cm-3, T = 100 K, λ =
0.71090 Å. 9834 reflections collected, 2453 independent [R(int) = 0.082]
used in all calculations. R1 = 0.0546, wR2 = 0.1418 for observed unique
reflections [I > 2σ(I)] and R1 = 0.0597, wR2 = 0.1461 for all unique
reflections. Max. and min. residual electron densities 0.58 and -0.28 e Å-3.
CCDC ref: 1528020.
22.5 ((CH3)2CH), 24.4 ((CH3)2CH-), 28.6 ((CH3)2CH), 32.0 (N-nacnac
backbone CH2), 38.5 ((CH3)2N), 122.7 (p-CH of Dipp), 123.2 (m-CH of
Dipp), 138.6 (o-C of Dipp), 146.0 (ipso-C of Dipp), 153.8 (imine
quaternary C). ESI-MS (m/z, %): 477.4, 100, [M+H]+; accurate mass: calc.
for C31H49N4 ([M
+
H]+) 477.3952, meas. 477.3949. Elemental
microanalysis: calc. for C31H48N4: C 78.10, H 10.15, N 11.75%, meas. C
78.27, H 10.06, N 11.85%. Crystallographic data: C31H48N4, Mr = 476.75,
monoclinic, P 21/c, a = 9.5453(1), b = 17.5799(2), c = 17.3757(2) Å, β =
91.7380(5)o, V = 2914.40(6) Å3, Z = 4, ρc = 1.086 g cm-3, T = 150 K, λ =
0.71073 Å. 12578 reflections collected, 6636 independent [R(int) = 0.019]
used in all calculations. R1 = 0.0480, wR2 = 0.1132 for observed unique
reflections [I > 2σ(I)] and R1 = 0.0637, wR2 = 0.1315 for all unique
reflections. Max. and min. residual electron densities 0.28 and -0.27 e Å-3.
CCDC ref: 1528010.
[5Mes]H: To a solution of MesNC(CH2Ph)NEt2 (2.47 g, 8.00 mmol) in Et2O
(20 mL) was added TMEDA (0.93 g, 1.2 mL, 8.0 mmol) and the solution
cooled to –78 °C. nBuLi (5.5 mL of a 1.6 M solution in hexane, 8.80
mmol) was then added and the reaction mixture warmed to room
temperature, resulting in a yellow heterogeneous mixture. After stirring
for a further 2 h, the mixture was cooled to –78 °C and MesNC(Cl)NEt2
(2.0 g, 1.7 mL, 8.00 mmol) added. The reaction mixture was again
warmed to room temperature, stirred for 16 and then refluxed for 1 h.
After cooling to room temperature, water (10 mL) was added followed by
dichloromethane (10 mL). The organic layer was extracted and washed
with water (2 x 10 mL) and aqueous sodium bicarbonate (10 mL). The
organic fraction was dried over MgSO4 and concentrated to yield an
orange oil, which was recrystallised from ethanol to give the product as
colourless crystalline material Yield: 2.80 g, 66% yield. 1H NMR (500
MHz, 298 K, C6D6): δH 0.70 (br, 12H, NCH2CH3), 2.24 (s, 6H, CH3 of
Mes), 2.33 (s, 6H, CH3 of Mes), 2.38 (s, 6H, CH3 of Mes), 2.99 (v br, 8H,
NCH2CH3), 5.38 (s, 1H, N-nacnac backbone CHPh), 6.84 (s, 2H, m-CH
[1tBu]H: To
a
dichloromethane solution of dichloromethylene-
dimethylammonium chloride (7.50 g, 46.15 mmol) was added dropwise at
room temperature N,N-dimethylacetamide (2.05 mL, 22.05 mmol), and
the reaction mixture refluxed for 12 h. After removal of volatiles in vacuo,
chloroform was added, followed by N-ethyldiisopropylamine (11.70 mL,
68.36 mmol) and tert-butylamine (5.24 mL, 50 mmol) - both dropwise via
syringe at 0 °C. The reaction mixture was then refluxed for a further 12 h.
After allowing the solution to cool to room temperature, the solvent was
removed in vacuo to give an orange solid, and the flask brought into the
glovebox where it could be opened and a spatula used to break up the
solid as much as possible. Subsequently, diethyl ether (100 mL) was
added and the solution stirred overnight. After filtration, the solvent
removed in vacuo to give a pale yellow spectroscopically pure solid.
Yield: 0.24 g, 4% yield. 1H NMR (400 MHz, C6D6) δH 1.36 (s, 18H,
C(CH3)3), 2.43 (s, 12H, (CH3)2N), 3.86 (s, 2H, N-nacnac backbone CH2).
3
of Mes), 6.88 (s, 2H, m-CH of Mes), 7.06 (t, JHH = 7.6 Hz, 1H, p-CH of
3
3
Ph), 7.20 (t, JHH = 7.6 Hz, 2H, p-CH of Ph), 7.65 (d, JHH = 7.6 Hz, 2H,
m-CH of Ph).1H NMR (300 MHz, 298 K, CDCl3): δH 0.74 (t, 3JHH = 7.0 Hz,
12H, NCH2CH3), 2.13 (s, 6H, CH3 of Mes), 2.18 (s, 6H, CH3 of Mes), 2.20
(s, 6H, CH3 of Mes), 3.04 (br m, 8H, NCH2CH3), 5.16 (s, 1H, N-nacnac
backbone CHPh), 6.73 (s, 2H, m-CH of Mes), 6.76 (s, 2H, m-CH of Mes),
t
13C{1H} NMR (101 MHz, C6D6) δC 29.9 (CH3 of Bu), 29.9 (N-nacnac
t
backbone CH2), 35.8 ((CH3)2N), 50.5 (quaternary C of Bu), 157.4 (imine
quaternary C). ESI-MS (m/z, %): 269, WEAK, [M+H]+; accurate mass:
3
3
7.21 (t, JHH = 7.6 Hz, 1H, p-CH of Ph), 7.30 (t, JHH = 7.6 Hz, 2H, o-CH
of Ph), 7.49 (d, 3JHH = 7.6 Hz, 2H, m-CH of Ph). 1H NMR (300 MHz, 333K,
calc. for C15H32N4 269.2700, meas. 269.2686.
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10.1002/chem.201700757
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3
CDCl3): δH 0.76 (t, JHH = 7.0 Hz, 12H, NCH2CH3), 2.11 (s, 6H, CH3 of
isolated as a white solid by filtration. Yield: 0.35 g, 50%. Single crystals
suitable for X-ray diffraction were obtained from diethyl ether. 1H NMR
(400 MHz, C6D6): δH 0.46 (br, 6H, OCH2CH3), 1.28 (br, 24H, (CH3)2CH),
2.30 (s, 12H, N(CH3)2), 3.51 (b, 4H, (CH3)2CH), 3.56 (s, 1H, N-nacnac
backbone CH), 4.10 (br, 4H, OCH2CH3), 7.14 (m, 6H, CH of Dipp).
13C{1H} NMR (100 MHz, C6D6): δC 11.3 (OCH2CH3), 24.2 ((CH3)2CH),
26.8 ((CH3)2CH), 28.5 ((CH3)2CH), 28.1 ((CH3)2CH), 41.1 (N(CH3)2), 60.0
(br, OCH2CH3), 74.6 (N-nacnac backbone CH), 123.8 (br, Dipp), 124.5
(br, Dipp), 142.7 (Dipp), 145.4 (Dipp), 164.4 (imine quaternary C). EI-MS
(m/z, %): 583.4, 100, [M-Et2O-{(CH3)2CH}]+. Elemental microanalysis:
calc. for C35H57N4MgO: C 59.96, H 8.20, N 7.99%; meas.: C 59.19, H
7.41, N 8.67%. Crystallographic data: C35H57IMgN4O, Mr = 701.06,
triclinic, P-1, a = 11.027(1), b = 16.357(1), c = 21.692(1) Å, α = 104.37(1),
β = 93.58(1), γ = 105.64(1)o, V = 3614.7(2) Å3, Z = 4, ρc = 1.288 g cm-3, T
= 100 K, λ = 0.71073 Å. 53066 reflections collected, 14178 independent
[R(int) = 0.026] used in all calculations. R1 = 0.0274, wR2 = 0.0648 for
observed unique reflections [I > 2σ(I)] and R1 = 0.0405, wR2 = 0.0726 for
all unique reflections. Max. and min. residual electron densities 0.57 and
-0.38 e Å-3. CCDC ref: 1528012.
Mes), 2.17 (s, 6H, CH3 of Mes), 2.19 (s, 6H, CH3 of Mes), 3.04 (d m, 3JHH
= 7.5 Hz, 8H, NCH2CH3), 5.18 (s, 1H, N-nacnac backbone CHPh), 6.72
(s, 2H, m-CH of Mes), 6.75 (s, 2H, m-CH of Mes), 7.18 (t, 3JHH = 7.6 Hz,
3
3
1H, p-CH of Ph), 7.28 (t, JHH = 7.6 Hz, 2H, o-CH of Ph), 7.48 (d, JHH
=
7.6 Hz, 2H, m-CH of Ph). 13C{1H} NMR (121 MHz, 298K, C6D6): δC 13.2
(NCH2CH3), 19.8, 20.5 (CH3 of Mes), 20.6 (N-nacnac backbone CHPh),
43.3 (NCH2CH3), 126.5 (Ph), 127.2 (Mes), 128.2 (Mes), 128.5 (Ph),
128.7 (Ph), 128.9 (Mes), 129.4 (Ph), 139.9 (Mes), 146.3 (imine
quaternary C). EI-MS, (m/z, %): 524.4, 3, [M]+; 509.5, 13, [M-CH3]+.
Elemental microanalysis: calc. for C34H48N4: C 80.10, H 9.22, N 10.68%;
meas. C 79.89, H 9.37, N 10.57%.
[1Dipp]Li(OEt2): To a solution of [1Dipp]H (2.00 mmol) in Et2O (25 mL) at -
78 0C was added a solution of nBuLi in hexane (0.88 mL of a 2.5 M
solution, 2.20 mmol); the reaction mixture was warmed to room
temperature and stirred for 12 h. Concentration to ca. 5 mL and storage
at -26oC yielded colourless crystals of the product as an analytically pure
1
3
material. Yield 0.69 g, 62%. H NMR (400 MHz, C6D6): δH 0.54 (t, JHH
=
3
7.0 Hz, 6H, CH3CH2O), 1.20 (d, JHH = 7.2 Hz, 12H, (CH3)2CH), 1.31 (d,
3JHH = 6.8 Hz, 12H, (CH3)2CH), 2.52 (s, 12H, (CH3)2N), 2.64 (q, 3JHH = 7.1
Hz, 4H, CH3CH2O), 3.51 (sept, 3JHH = 6.8 Hz, 4H, (CH3)2CH), 4.09 (s, 1H,
[4Mes]MgI(OEt2): MeMgI (2.99 mL of a 1.1 M solution in diethyl ether,
7.92 mmol) was added to a solution of [4Mes]H (2.96 g, 6.60 mmol) also in
diethyl ether (30 mL) at 0°C. The reaction mixture was allowed to warm
to room temperature and stirred for 30 min. The product was isolated as
3
N-nacnac backbone CH), 7.03 (t, JHH = 7.4 Hz, 2H, p-CH of Dipp), 7.15
(d, JHH = 7.6 Hz, 4H, m-CH of Dipp).13C{1H} NMR (100 MHz, C6D6): δC
3
1
13.6 (CH3CH2O), 23.7 ((CH3)2CH), 25.4 ((CH3)2CH), 28.1 ((CH3)2CH),
41.3 ((CH3)2N), 62.8 (CH3CH2O), 72.8 (N-nacnac backbone CH), 121.7
(p-CH of Dipp), 123.7 (m-CH of Dipp), 141.1 (o-C of Dipp), 149.5 (ipso-C
of Dipp), 166.2 (imine quaternary C). Crystallographic data: C35H57LiN4O,
Mr = 556.80, monoclinic, P 21/n, a = 9.80960(10), b = 25.6135(3), c =
14.2229(2) Å, β = 106.501(1)o, V = 3426.44(5) Å3, Z = 4, ρc = 1.079 g
cm-3, T = 150 K, λ = 0.71073 Å. 14549 reflections collected, 7740
independent [R(int) = 0.025] used in all calculations. R1 = 0.0573, wR2 =
0.1200 for observed unique reflections [I > 2σ(I)] and R1 = 0.0807, wR2 =
0.1409 for all unique reflections. Max. and min. residual electron
densities 0.71 and -0.45 e Å-3. CCDC ref: 1528011.
a white solid by filtration (3.05 g, 75 % yield). H NMR (400 MHz, C6D6):
3
3
δH 0.40 (br t, JHH = 6.8 Hz, 6H, OCH2CH3), 0.82 (t, JHH = 7.2 Hz, 12H,
NCH2CH3), 2.12 (s, 6H, CH3 of Mes), 2.24 (s, 6H, CH3 of Mes), 2.78 (s,
6H, CH3 of Mes), 2.94 (br q, 3JHH = 6.8 Hz, 4H, NCH2CH3), 3.04 (br q,
3
3JHH = 7.0 Hz, 4H, NCH2CH3), 3.27 (q, J = 7.2 Hz, 4H, OCH2CH3), 4.18
(s, 1H, N-nacnac backbone CH), 6.79 (s, 2H, m-CH of Mes), 6.82 (s, 2H,
m-CH of Mes). 13C{1H} NMR (100 MHz, C6D6): δC 11.1 (OCH2CH3), 11.3
(NCH2CH3), 18.3 (CH3 of Mes), 19.4 (CH3 of Mes), 21.8 (CH3 of Mes),
41.4 (NCH2CH3), 63.3 (OCH2CH3), 75.6 (N-nacnac backbone CH), 128.3
(Mes), 128.4 (Mes), 129.5 (Mes), 129.6 (Mes), 131.0 (Mes), 145.3 (Mes)
167.4 (imine quaternary C). EI-MS (m/z, %), 599.1, 1, [M-Et2O+H]+.
Elemental microanalysis: calc. for C33H53IMgN4O: C 58.89, H 7.94, N
{[4Mes]Li}2: To a solution of [4Mes]H (0.8 g, 1.8 mmol) in hexane (20 mL)
at -78oC was added nBuLi (1.23 mL of a 1.6 M solution, 1.96 mmol). The
reaction mixture was warmed to room temperature and stirred for 16 h.
After filtration, concentration and cooling to 4oC a pale yellow crystalline
material was obtained. Yield: 0.67 g, 81%. Crystals suitable for X-ray
crystallography were grown from a hexane solution stored at +5 °C. 1H
NMR (C6D6, 300 MHz): δH 0.87 (t, 3JHH = 6.8 Hz, 12H, NCH2CH3), 2.18 (s,
8.32%; meas.:
C 58.69, H 7.76, N 8.36%. Crystallographic data:
C33H53IMgN4O, Mr = 673.00, monoclinic, P21/c, a = 8.443(2), b =
40.607(8), c = 9.968(2) Å, β = 101.82(3)o, V = 3345.1(12) Å3, Z = 4, ρc =
1.336 g cm-3, T = 100 K, λ = 0.71090 Å. 52110 reflections collected, 6182
independent [R(int) = 0.082] used in all calculations. R1 = 0.0306, wR2 =
0.0775 for observed unique reflections [I > 2σ(I)] and R1 = 0.0313, wR2 =
0.0780 for all unique reflections. Max. and min. residual electron
densities 0.48 and -1.02 e Å-3. CCDC ref: 1528021.
3
12H, o-CH3 of Mes), 2.31 (s, 6H, p-CH3 of Mes), 2.98 (q, JHH = 6.8 Hz,
8H, NCH2CH3), 4.07 (s, 1H, N-nacnac backbone CH), 6.93 (s, 4H, m-CH
of Mes). 13C{1H} NMR (C6D6, 101 MHz): δC 12.3 (NCH2CH3), 19.3 (CH3 of
Mes), 20.8 (CH3 of Mes), 42.8 (NCH2CH3), 77.1 (N-nacnac backbone
CH), 128.9 (Mes), 129.2 (Mes), 130.6 (Mes), 149.7 (Mes), 166.7 (imine
quaternary C). 7Li NMR (C6D6, 156 MHz): δLi 0.43. EI-MS (m/z, %): 454.4,
2 [M]+; 448.5, 21, [M-Li+H]+; 433.4, 79, [M-Li-CH3]+. The highly air-
sensitive nature of {[4Mes]Li}2 meant that reliable microanalysis proved
impossible to obtain. Crystallographic data: C58H88Li2N8, Mr = 909.23,
triclinic, P-1, a = 13.617(3), b = 19.395(4), c = 22.395(5) Å, α = 75.23(3),
β = 72.90(3), γ = 78.96(3)o, V = 5422.6(19) Å3, Z = 4, ρc = 1.114 g cm-3, T
= 100 K, λ = 0.71080 Å. 92884 reflections collected, 20768 independent
[R(int) = 0.084] used in all calculations. R1 = 0.0644, wR2 = 0.1655 for
observed unique reflections [I > 2σ(I)] and R1 = 0.0906, wR2 = 0.1849 for
all unique reflections. Max. and min. residual electron densities 1.18 and
-0.48 e Å-3. CCDC ref: 1528023.
[1Ph]AlMe2 and [1Dipp]AlMe2: The two compounds were synthesized by a
common method: to a solution of [1Ph]H/[1Dipp]H (2.1 mmol) in toluene (25
mL) at -200C, was added a solution of AlMe3 also in toluene (1.05 mL of
a 2.0 M solution, 2.1 mmol) with rapid stirring. The reaction mixture was
slowly warmed to room temperature and volatiles removed in vacuo to
yield the product as a spectroscopically pure light yellow solid. Slow
evaporation of a saturated toluene solution produced crystals suitable for
1
X-ray crystallography. [1Ph]AlMe2: yield 0.98 g, 75%. H NMR (400 MHz,
C6D6): δH -0.28 (AlCH3), 2.26 (s, 12H, (CH3)2N-), 4.06 (s, 1H, N-nacnac
backbone CH), 6.82 (t, 3JHH = 7.4 Hz, 2H, p-CH of Ph), 6.98 (d, 3JHH = 7.2
3
Hz, 4H, o-CH of Ph), 7.07 (t, JHH = 7.8 Hz, 4H, m-CH of Ph). 13C{1H}
NMR (125 MHz, C6D6): δC -8.9 (AlCH3), 40.3 ((CH3)2N), 79.2 (N-nacnac
backbone CH), 122.4 (p-CH of Ph), 125.0 (o-CH of Ph), 129.1 (m-CH of
Ph), 149.1 (ipso-C of Ph), 166.4 (imine quaternary C). 27Al NMR (104
MHz, C6D6): δAl 166 (br). EI-MS: (m/z, %): 349.0, 100, [M-CH3]+; 304.0,
80 [M-2CH3]+; accurate mass: calc. for C20H26AlN4 ([M – CH3]+) 349.1967,
meas. 349.0262. Elemental microanalysis: calc. for C21H29AlN4: C 69.20,
H 8.02, N 15.37%, meas. C 69.04, H 7.89, N 15.39%. Crystallographic
data: C21H29AlN4, Mr = 364.46, monoclinic, P 21/c, a = 25.2085(10), b =
[1Dipp]MgI(OEt2): MeMgI (0.90 mL of a 1.10 M solution in diethyl ether,
0.99 mmol) was added dropwise to a solution of [1Dipp]H (0.40 g, 0.825
mmol) also in diethyl ether (10 mL) at 0°C. The reaction mixture was
warmed to room temperature and stirred for 30 min. The product was
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10.1002/chem.201700757
Chemistry - A European Journal
FULL PAPER
9.3862(3), c = 18.8139(7) Å, β = 110.086(4)o, V = 4180.3(3) Å3, Z = 8, ρc
= 1.158 g cm-3, T = 150 K, λ = 1.54184 Å. 30632 reflections collected,
8099 independent [R(int) = 0.109] used in all calculations. R1 = 0.0953,
wR2 = 0.2725 for observed unique reflections [I > 2σ(I)] and R1 = 0.1097,
wR2 = 0.2930 for all unique reflections. Max. and min. residual electron
densities 0.69 and -0.65 e Å-3. CCDC ref: 1528015. [1Dipp]AlMe2: yield
[R(int) = 0.000] used in all calculations. R1 = 0.0218, wR2 = 0.0468 for
observed unique reflections [I > 2σ(I)] and R1 = 0.0246, wR2 = 0.0492 for
all unique reflections. Max. and min. residual electron densities 0.53 and
-0.51 e Å-3. CCDC ref: 1528019. [1Dipp]SnCl: Yield 0.52 g, 78%. 1H NMR
3
(400 MHz, C6D6): δH 1.11 (d, JHH = 6.8 Hz, 12H, (CH3)2CH-), 1.13 (d,
3JHH = 6.4 Hz, 12H, (CH3)2CH-), 1.28 (d, 3JHH = 6.4 Hz, 12H, (CH3)2CH-),
3
0.94 g, 84%. 1H NMR (500 MHz, C6D6): δH -0.28 (AlCH3), 1.24 (d, 3JHH
=
1.59 (d, JHH = 6.8 Hz, 12H, (CH3)2CH-), 2.24 (s, 12H, (CH3)2N-), 3.02
6.7 Hz, 12H, (CH3)2CH), 1.40 (d, 3JHH = 6.7 Hz, 12H, (CH3)2CH), 2.27 (s,
(sept, JHH = 6.7 Hz, 2H, (CH3)2CH-), 4.03 (s, 1H, N-nacnac backbone
3
3
3
12H, (CH3)2N), 3.57 (sept, JHH = 6.7 Hz, 4H, (CH3)2CH), 3.83 (s, 1H, N-
CH), 4.47 (sept, JHH = 6.7 Hz, 2H, (CH3)2CH-), 7.05-7.15 (6H, aromatic
nacnac backbone CH), 7.16-7.20 (6H, aromatic CH). 13C{1H} NMR (125
MHz, C6D6): δC -8.09 (AlCH3), 24.1 ((CH3)2CH), 26.7 ((CH3)2CH), 28.4
((CH3)2CH), 41.0 ((CH3)2N), 76.5 (N-nacnac backbone CH), 124.7 (p-CH
of Dipp), 125.5 (m-CH of Dipp), 142.8 (ipso-C of Dipp), 144.5 (o-C of
Dipp), 166.8 (imine quaternary C). 27Al NMR (104 MHz, C6D6): δAl 157
(br). EI-MS: (m/z, %): 517.4, 40 [M-CH3]+; accurate mass: calc. for
C32H50AlN4 ([M–CH3]+) 517.3851, meas. 517.3889. Elemental
microanalysis: calc. for C33H53AlN4: C 74.39, H 10.03, N 10.52%, meas.
CH).13C{1H} NMR (100 MHz, C6D6): δC 24.0 ((CH3)2CH-), 24.2
((CH3)2CH-), 27.0 ((CH3)2CH-), 28.3 ((CH3)2CH-), 28.3 ((CH3)2CH-), 28.4
((CH3)2CH-), 41.3 (CH3)2N-), 79.9 (N-nacnac backbone CH), 124.5, 125.5,
126.3, 142.1, 144.5, 145.5 (aromatic C), 165.9 (imine quaternary C).
119Sn NMR (186 MHz, C6D6): δSn -192 ppm. EI-MS: (m/z, %): 630.3, 3
[M]+; 587.2, 30 [M-NMe2]+; accurate mass: calc. for C31H47ClN4116Sn (M+)
626.2507, meas. 626.2506. Crystallographic data: C31H47ClN4Sn, Mr =
629.88, monoclinic, C 2/c, a = 34.9244(8), b = 9.8094(3), c = 19.5389(4)
Å, β = 112.4405(14)o, V = 6186.9(3) Å3, Z = 8, ρc = 1.352 g cm-3, T = 150
K, λ = 0.71073 Å. 36739 reflections collected, 7035 independent [R(int) =
0.066] used in all calculations. R1 = 0.0440, wR2 = 0.0714 for observed
unique reflections [I > 2σ(I)] and R1 = 0.0932, wR2 = 0.1046 for all unique
reflections. Max. and min. residual electron densities 2.57 and -2.09 e Å-3.
CCDC ref: 1528013. CHN microanalysis measurements on the
compounds [1R]SnCl (R = Ph, Xyl, Dipp) – even those using single
crystalline samples – gave reproducibly low C analysis, while giving
acceptable data in each case for H and N.
C 74.59, H 10.04, N 10.44%. Crystallographic data: C33H53AlN4, Mr
=
532.79, monoclinic, P 21/c, a = 17.3795(3), b = 9.8573(1), c = 19.1009(3)
Å, β = 101.2023(6)o, V = 3209.92(8) Å3, Z = 4, ρc = 1.102 g cm-3, T = 150
K, λ = 0.71073 Å. 13688 reflections collected, 7303 independent [R(int) =
0.042] used in all calculations. R1 = 0.0470, wR2 = 0.0988 for observed
unique reflections [I > 2σ(I)] and R1 = 0.0871, wR2 = 0.1401 for all unique
reflections. Max. and min. residual electron densities 0.55 and -0.52 e Å-3.
CCDC ref: 1528009.
[1Ph]SnCl, [1Xyl]SnCl and [1Dipp]SnCl: The three compounds were
prepared by a common method. A solution of [1R]H (1.0 mmol, R = Ph,
Xyl, Dipp) in toluene (25 mL) was treated with nBuLi (1.05 equiv.) at -
780C, and the reaction mixture warmed slowly to room temperature and
stirred for 2 h. The resulting solution was added to a toluene solution (10
mL) containing SnCl2 (1.05 equiv.) at -78oC, and the resulting mixture
warmed to room temperature with stirring. After 12 h, volatiles were
removed in vacuo, and the resulting residue washed with cold hexane to
yield the product as near-white spectroscopically pure solid in each case.
X-ray quality crystals were obtained from a solution in toluene layered
with hexane and stored at -26oC. [1Ph]SnCl: Yield 0.51 g, 69%. 1H NMR
(400 MHz, C6D6): δH 2.29 (s, 12H, (CH3)2N-), 4.25 (s, 1H, N-nacnac
backbone CH), 6.77 (t, 3JHH = 7.0 Hz, 2H, p-CH of Ph), 6.84 (d, 3JHH = 8.0
[1Dipp]SnH: To a toluene solution (30 mL) of [1Dipp]SnCl (0.5 g, 0.8 mmol)
at -78oC was added a 1.0 M solution of K[HBEt3] in THF (1.05 equiv.)
over a period of 5 min. The reaction mixture was warmed to room
temperature and stirred for an additional 3 h before volatiles were
removed in vacuo. The residual solid was extracted into cold hexane;
storage at -26oC produced light yellow crystals suitable for X-ray
crystallography. Yield: 0.066 g, 14%. 1H NMR (400 MHz, C6D6): δH 1.19
3
3
(d, JHH = 6.3 Hz, 12H, (CH3)2CH-), 1.21 (d, JHH = 6.8 Hz, 12H,
3
3
(CH3)2CH-), 1.27 (d, JHH = 6.8 Hz, 12H, (CH3)2CH-), 1.54 (d, JHH = 6.8
3
Hz, 12H, (CH3)2CH-), 2.28 (s, 12H, (CH3)2N-), 3.30 (sept, JHH = 6.8 Hz,
2H, (CH3)2CH-), 3.72 (sept, JHH = 6.7 Hz, 2H, (CH3)2CH-), 4.02 (s, 1H,
3
N-nacnac backbone CH), 7.08-7.16 (6H, aromatic CH), 13.42 (s, 1H,
SnH).13C{1H} NMR (100 MHz, C6D6): δC 23.9 ((CH3)2CH-), 24.1
((CH3)2CH-), 26.7 ((CH3)2CH-), 27.8 ((CH3)2CH-), 28.3 ((CH3)2CH-), 28.4
((CH3)2CH-), 41.5 ((CH3)2N-), 78.8 (N-nacnac backbone CH), 124.4,
124.7, 125.5, 143.8, 144.3, 145.3 (aromatic C), 167.0 (imine quaternary
C). 119Sn NMR (186 MHz, C6D6): δSn -18 ppm. EI-MS: (m/z, %): 595.0,
weak [M-H]+. Crystallographic data: C31H48SnN4, Mr = 594.43, monoclinic,
P 21/c, a = 12.4032(4), b = 17.2188(5), c = 15.4106(4) Å, β = 103.675(3)o,
V = 3197.92(17) Å3, Z = 4, ρc = 1.235 g cm-3, T = 150 K, λ = 1.54180 Å.
18662 reflections collected, 6621 independent [R(int) = 0.064] used in all
calculations. R1 = 0.0634, wR2 = 0.1622 for observed unique reflections [I
> 2σ(I)] and R1 = 0.0728, wR2 = 0.1740 for all unique reflections. Max.
and min. residual electron densities 2.61 and -3.07 e Å-3. CCDC ref:
1528014.
3
Hz, 4H, o-CH of Ph), 7.01 (t, JHH = 7.6 Hz, 4H, m-CH of Ph). 13C{1H}
NMR (100 MHz, C6D6): δC 40.6 ((CH3)2N-), 82.9 (N-nacnac backbone
CH), 122.3 (p-CH of Ph), 123.6 (o-CH of Ph), 129.9 (m-CH of Ph), 148.9
(ipso-C of Ph), 165.1 (imine quaternary C). 119Sn NMR (186 MHz, C6D6):
δSn -169 ppm. EI-MS (m/z, %): 462.1, 6, [M]+; 426.1, 2 [M-Cl]+; accurate
mass: calc. for C19H23ClN4Sn ([M]+) 462.0633, meas. 462.0678.
Crystallographic data: C19H23ClN4Sn, Mr = 461.56, triclinic, P-1, a =
8.6350(2), b = 9.3350(3), c = 13.8133(5) Å, α = 104.8910(12), β =
100.1742(12), γ = 105.6759(15), V = 999.15(6) Å3, Z = 2, ρc = 1.534 g
cm-3, T = 150 K, λ = 0.71073 Å. 23131 reflections collected, 4552
independent [R(int) = 0.034] used in all calculations. R1 = 0.0386, wR2 =
0.0696 for observed unique reflections [I > 2σ(I)] and R1 = 0.0561, wR2 =
0.0878 for all unique reflections. Max. and min. residual electron
densities 1.77 and -1.24 e Å-3. CCDC ref: 1528017. [1Xyl]SnCl: Yield:
0.41 g, 59%. 1H NMR (400 MHz, C6D6): δH 2.02 (s, 6H, CH3 of Xyl), 2.21
(s, 12H, (CH3)2N), 2.77 (s, 6H, CH3 of Xyl), 4.01 (s, 1H, N-nacnac
backbone CH), 7.01 – 6.84 (overlapping m, 6H, p- and m-CH of Xyl).
13C{1H} NMR (101 MHz, C6D6): δC 19.4, 21.9 (CH3 of Xyl), 40.2 ((CH3)2N),
79.6 (N-nacnac backbone CH), 124.2 (p-CH of xyl), 129.2, 130.1 (m-CH
of Xyl), 133.5, 133.6 (o-C of Xyl), 146.2 (ipso-C of Xyl), 165.5 (imine
quaternary C). EI-MS (m/z, %): 510, 100, [M]+; accurate mass: calc. for
C23H31ClN4112Sn 510.1285, meas. 510.1264. Crystallographic data:
C23H31ClN4Sn, Mr = 517.67, orthorhombic, P 212121, a = 9.2745(1), b =
11.9112(1), c = 21.0381(2) Å, V = 2324.09(4) Å3, Z = 4, ρc = 1.479 g cm-3,
T = 150 K, λ = 0.71073 Å. 5289 reflections collected, 5289 independent
{[1Dipp]Yb(µ-I)}2: To a stirred solution of [1Dipp]H (0.439 g, 0.92 mmol) in
toluene (10 mL) was added KCH2Ph (0.120 g, 0.92 mmol). A white
precipitate started to form immediately and after stirring overnight at
room temperature a very thick white suspension was formed. At this point,
volatiles were removed in vacuo, and solid YbI2(thf)2 (0.527 g, 0.92
mmol) added, followed by thf (20 mL). The reaction mixture was stirred at
room temperature for 12 h, producing a dark brown-red suspension.
Volatiles were again removed in vacuo, and the residue extracted with
warm benzene (3 × 10 mL). The filtrate was slowly evaporated under
reduced pressure until only about 1 mL of liquid remained. The very dark
brown mother liquor was decanted via a cannula and the crystalline
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residue was washed with a small amount of cold benzene. Drying under
vacuum yielded maroon crystals of [1Dipp]Yb(µ-I)(THF). Yield: 0.34 g, 0.40
mmol, 43%. 1H NMR (C6D6, 400 MHz): δH 0.94 (br s, 4H, CH2 of THF),
(CH3)2N-), 2.40 (two s, 12H, (CH3)2N-), 2.83 (br s, 3H, (CH3)2N-), 2.85-
3.02 (overlapping septets, 4H, (CH3)2CH-), 3.06 (sept, 3JHH = 6.7 Hz, 1H,
3
(CH3)2CH-), 3.11 (br s, 3H, (CH3)2N-), 3.24 (sept, JHH = 6.7 Hz, 1H,
3
3
3
1.38 (d, JHH = 6.7 Hz, 12H, (CH3)2CH-), 1.41 (d, JHH = 6.7 Hz, 12H,
(CH3)2CH-), 3.26 (s, 1H, N-nacnac backbone CH), 3.37 (sept, JHH = 6.7
3
3
(CH3)2CH-), 2.49 (s, 12H, (CH3)2N-), 3.41 (br sept, JHH = ca. 7 Hz, 4H,
Hz, 1H, (CH3)2CH-), 3.64 (sept, JHH = 6.7 Hz, 1H, (CH3)2CH-), 6.75 (d,
3
(CH3)2CH-), 3.68 (br s, 4H, OCH2 of THF), 3.80 (s, 1H, N-nacnac
backbone CH), 7.02 (t, 3JHH = 7.6 Hz, 2H, p-CH of Dipp), 7.16 (m, 4H, m-
CH of Dipp + C6D5H). 13C{1H} NMR (C6D6, 100 MHz): δ 162.9 (imine
quaternary C), 147.5 (ipso-C of Dipp), 139.9 (o-C of Dipp), 124.3 (m-CH
of Dipp), 122.0 (p-CH of Dipp), 74.2 (N-nacnac backbone CH), 69.7
(OCH2 of THF), 40.7 ((CH3)2N-), 29.2 ((CH3)2CH-), 26.5 ((CH3)2CH-),
24.9 (CH2 of THF), 24.0 (CHMe2). Although single crystals of this
material could not be obtained, removal of THF was possible at elevated
temperatures to give samples of the donor-free dimer suitable for X-ray
crystallography. A sample of [1Dipp]Yb(µ-I)(THF) (0.149 g, 0.175 mmol)
was heated slowly with a heat-gun under full vacuum. At ~80 °C the
vacuum gauge showed vapour evolution, which continued over a period
of 2 h with the temperature in the range of 80 to 90 °C. The originally
maroon crystals turned into a red-orange material, and a small amount of
[1Dipp]H sublimed. The product was extracted with benzene (4 mL), the
red-orange solution decanted from a small amount of pale precipitate and
slowly evaporated at room temperature almost to dryness producing
large red crystals of {[1Dipp]Yb(µ-I)}2 (suitable for crystallography) which
were washed with a small amount of benzene and dried in vacuo. Yield:
0.105 g, 77%. 1H NMR (C6D6, 400 MHz): δH 1.32 (d, 3JHH = 6.7 Hz, 12H,
3JHH = 7.6 Hz, 1H, m-CH of Dipp), 6.86 (t, JHH = 7.6 Hz, 1H, p-CH of
Dipp), 6.90-7.19 (m, 8H, CH of Dipp), 7.32 (d, 3JHH = 7.6 Hz, 1H, m-CH of
3
Dipp), 7.36 (d, JHH = 7.6 Hz, 1H, m-CH of Dipp). 13C{1H} NMR (C6D6,
100 MHz): δC 21.5, 22.2, 22.4, 23.6, 24.1, 24.3, 24.4, 24.4, 24.5, 24.8,
25.9, 26.1, 26.2, 27.5 ((CH3)2CH-), 27.3, 28.3, 28.5, 28.6, 29.0, 29.3,
30.0, 30.2 ((CH3)2CH-), 39.8, 40.4, 40.7, 41.3, 41.8, 43.0 ((CH3)2N-), 66.2,
67.2 (N-nacnac backbone CH), 121.3, 121.5, 121.8, 122.4, 122.5, 123.6,
123.6, 123.8, 124.3, 124.5, 124.8, 125.2 (CH of Dipp); 137.6, 139.0,
139.2, 139.3, 139.5, 139.8, 134.0, 140.1 (o-C of Dipp); 146.1, 147.4,
148.0 (ipso-C of Dipp); 161.9, 162.9, 163.2 (imine quaternary C). A
sample of [1Dipp]2Yb for X-ray crystallography was prepared from [1Dipp]K
(0.051 g, 0.099 mmol) and YbI2(thf)2 (0.020 g, 0.035 mmol) using a
similar procedure. Crystallographic data: C62H94N8Yb, Mr = 1124.52,
orthorhombic, P 212121, a = 14.3829(1), b = 15.0030(1), c = 27.5152(2) Å,
V = 5937.41(7) Å3, Z = 4, ρc = 1.258 g cm-3, T = 150 K, λ = 1.54180 Å.
70955 reflections collected, 12348 independent [R(int) = 0.025] used in
all calculations. R1
= 0.0167, wR2 = 0.0431 for observed unique
reflections [I > 2σ(I)] and R1 = 0.0173, wR2 = 0.0434 for all unique
reflections. Max. and min. residual electron densities 0.30 and -0.43 e Å-3.
CCDC ref: 1528008.
3
(CH3)2CH-), 1.33 (d, JHH = 6.7 Hz, 12H, (CH3)2CH-), 2.42 (s, 12H,
3
(CH3)2N-), 3.19 (sept, JHH = 6.7 Hz, 4H, (CH3)2CH-), 3.71 (s, 1H, N-
Crystallography
nacnac backbone CH), 6.98 (t, 3JHH = 7.6 Hz, 2H, p-CH of Dipp), 7.11 (d,
3JHH = 7.6 Hz, 4H, m-CH of Dipp). 13C{1H} NMR (C6D6, 100 MHz): δC 22.8
((CH3)2CH-), 25.6 ((CH3)2CH-), 29.8 ((CH3)2CH-), 40.0 ((CH3)2N-), 71.2
(N-nacnac backbone CH), 121.8 (p-CH of Dipp), 124.0 (m-CH of Dipp),
138.7 (o-C of Dipp), 146.2 (ipso-C of Dipp), 161.8 (imine quaternary C).
Elemental microanalysis: calc. for C31H47N4Yb: C 48.00, H 6.11, N 7.22%,
meas. C 47.89, H 6.04, N 7.09%. Crystallographic data: C62H94I2N8Yb2
Mr = 1551.37, monoclinic, P 21/n, a = 20.2293(6), b = 17.2389(4), c =
20.7063(6) Å, β = 114.666(4)o, V = 6562.1(4) Å3, Z = 4, ρc = 1.570 g cm-3,
Diffraction data were collected using a Nonius Kappa CCD or Oxford
Diffraction (Agilent) SuperNova diffractometer at 150 K; data were
reduced using either DENZO, SCALEPACK or CrysAlisPro, and the
structures were solved with either SIR92, SuperFlip or SHELXT and
refined with full-matrix least squares within CRYSTALS or SHELXL-2014,
as described in the CIF.[21] Complete details of the X-ray analyses have
been deposited at The Cambridge Crystallographic Data Centre (CCDC
1528007-1528025).
T
= 150 K, λ = 1.54180 Å. 39921 reflections collected, 13613
independent [R(int) = 0.043] used in all calculations. R1 = 0.0419, wR2 =
0.0994 for observed unique reflections [I > 2σ(I)] and R1 = 0.0531, wR2 =
0.1082 for all unique reflections. Max. and min. residual electron
densities 3.12 and -2.44 e Å-3. CCDC ref: 1528007.
Computational Method
Geometry optimization were performed using the Amsterdam Density
Functional (ADF) 2014 software package. Calculations were performed
using the Vosko-Wilk-Nusair local density approximation with exchange
from Becke, and correlation correction from Perdew, and 3-dimension
dispersion effect (BP86-D3).[22] Slater-type orbitals (STOs) were used for
the triple zeta basis set with an additional set of polarization functions
(TZP). The full-electron basis set approximation was applied with no
molecular symmetry. General numerical quality was good. Run files for
each of the calculations are included in the SI.
[1Dipp]2Yb: To a mixture of [1Dipp]K (prepared in situ from [1Dipp]H (0.104 g,
0.22 mmol) and KCH2Ph (0.029 g, 0.22 mmol) in toluene and dried in
vacuo) and [1Dipp]Yb(µ-I)(THF) (0.185 g, 0.22 mmol) was added THF (ca.
5 mL) by vacuum transfer. The mixture was warmed to 55 °C and
agitated by hand until a dark brown suspension was formed. At this point,
volatiles were removed in vacuo, and the residue extracted with benzene
(2 mL) and transferred into a crystallisation tube. After drying in vacuo,
hexane (ca. 2 mL) was vacuum transferred into the tube, which was then
sealed. After gentle warming, the resulting dark brown solution was
decanted from the accompanying grey precipitate into the second part of
the tube, concentrated (to form viscous oil) and stored in a freezer at
−30°C for 2 d. This led to the formation of colourless crystals of [1Dipp]H
and nearly black crystals of [1Dipp]2Yb, which were washed with hexane
(once crystallised it was poorly soluble in this solvent) and dried in vacuo.
Yield: 0.095 g, 0.084 mmol, 38%. 1H NMR (C6D6, 400 MHz): δH 0.42 (d,
Acknowledgements
We acknowledge funding from the Jardine Foundation (DCHD),
the EPSRC (AP, grant number EP/L025000/1), EU Marie Curie
program (ELK, grant number PIEF-GA-2013-626441) and the
ARC (CJ, AS, SA). We also thanks Drs Jesus Campos and
Rémi Tirfoin for additional crystallography, and Reike Clauss for
additional synthetic work.
3
3JHH = 6.7 Hz, 3H, (CH3)2CH-), 0.60 (d, JHH = 6.7 Hz, 3H, (CH3)2CH-),
3
3
1.02 (d, JHH = 6.7 Hz, 3H, (CH3)2CH-), 1.05 (d, JHH = 6.7 Hz, 3H,
3
(CH3)2CH-), 1.17 (m, 15H, (CH3)2CH-), 1.20 (d, JHH = 6.7 Hz, 3H,
(CH3)2CH-), 1.23 (d, 3JHH = 6.7 Hz, 3H, (CH3)2CH-), 1.29 (d, 3JHH = 6.7 Hz,
3H, (CH3)2CH-), 1.35 (d, JHH = 6.7 Hz, 3H, (CH3)2CH-), 1.42 (d, JHH
6.7 Hz, 3H, (CH3)2CH-), 1.47 (d, JHH = 6.7 Hz, 3H, (CH3)2CH-), 1.53 (d,
3JHH = 6.7 Hz, 3H, (CH3)2CH-), 2.24 (br s, 3H, (CH3)2N-), 2.35 (s, 3H,
3
3
=
[1]
For early references, see: a) W. Bradley, I. Wright, J. Chem. Soc. 1956,
640-648; b) J. E. Parks, R. H. Holm, Inorg. Chem. 1968, 7, 1408–1416;
c) S. G. McGeachin, Can. J. Chem. 1968, 46, 1903–1912; d) C. L.
3
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10.1002/chem.201700757
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FULL PAPER
Honeybourne, G. A. Webb, Chem. Commun. (London) 1968, 739-740;
e) R. Bonnett, D. C. Bradley, K. J. Fisher, Chem. Commun. 1968, 886-
887.
H. V. R. Dias, Inorg. Chem. 2001, 40, 1000-1005; c) Y. Ding, H. W.
Roesky, M. Noltemeyer, H.-G. Schmidt, P. P. Power, Organometallics
2001, 20, 1190-1194; d) L. W. Pineda, V. Jancik, K. Starke, R. B.
Oswald, H. W. Roesky, Angew. Chem., Int. Ed. 2006, 45, 2602-2605.
[14] a) S. Harder, Angew. Chem. Int. Ed. 2004, 43, 2714-2718; b) P.B.
Hitchcock, A. V. Khvostov, M. F. Lappert, A. V. Protchenko, Dalton
Trans. 2009, 2383-2391.
[2]
[3]
L. Bourget-Merle, M. F. Lappert, J. R. Severn, Chem. Rev. 2002, 102,
3031-3066.
See, for example: a) M. S .Hill, P. B. Hitchcock, R. Pongtavornpinyo,
Science 2006, 311, 1904-1907; b) S. P. Green, C. Jones, A. Stasch,
Science 2007, 318, 1754-1757; c) M. M. Rodriguez, E. Bill, W. W.
Brenessel, P. L Holland, Science 2011, 334, 780-783.
[15] For a related lithium Nacnac derivative see: a) C. Cui, H. W. Roesky, H.
Hao, H.-G. Schmidt, M. Noltemeyer, Angew. Chem., Int. Ed. 2000, 39,
1815. Binuclear systems have been reported in association with aryl
groups bearing donor substituents: b) J. Liu, L. Vieille-Petit, A. Linden,
X. Luan, R. Dorta J. Organomet. Chem. 2012, 719, 80-86.
[4]
[5]
For selected recent reviews encompassing aspects of Nacnac
chemistry, see: a) M. Asay, C. Jones, M. Driess, Chem. Rev. 2011, 111,
354-396; b) Y. Tsai, Coord. Chem. Rev. 2012, 256, 722; c) C. Chen, S.
M. Bellows, P. L. Holland, Dalton Trans. 2015, 44, 16654-16670; d) C.
Camp, J. Arnold, Dalton Trans. 2016, 45, 14462-14498.
See, for example: a) D. T. Carey, E. K. Cope-Eatough, E. Vilapana-
Mafé, F. S. Mair, R. G. Pritchard, J. E. Warren, R. J. Woods, Dalton
Trans. 2003, 1083-1093; b) Y. Cheng, D. J. Doyle, P. B. Hitchcock, M.
F. Lappert; Dalton Trans. 2006, 4449-4460; c) M. P. Romero-
Fernández, M. Ávalos, R. Babiano, P. Cintas, J. L. Jiménez, M. E. Light,
J. C. Palacios, Org. Biomol. Chem. 2014, 12, 8997-9010. C6F5 groups
have also been employed as electron-withdrawing N-aryl groups: D.
Vidovic, J. N. Jones, J. A. Moore, A. H. Cowley, Z. Anorg. Allg. Chem.
2005, 631, 2888-2892.
[16] For related magnesium Nacnac derivatives see reference 3b.
[17] For related aluminium Nacnac derivatives, see: a) B. Qian, D. L. Ward,
M. R. Smith III, Organometallics 1998, 17, 3070-3076; b) C. E.
Radzewich, M. P. Coles, R. F. Jordan, J. Am. Chem. Soc. 1998, 120,
9384-9385.
[18] E. Pretsch, P. Bühlmann, M. Badertscher in Structure Determination of
Organic Compounds (eds. M. Badertscher, P. Bühlmann, E. Pretsch),
Springer-Verlag, Berlin, 2009, Chp. 5.
[19] See also: W. E. Piers, Coord. Chem. Rev. 2002, 233-234, 131-155.
[20] For early examples of f-element Nacnac chemistry see: a) P. B.
Hitchcock, S. A. Holmes, M. F. Lappert, S. Tian, J. Chem. Soc., Chem.
Commun. 1994, 2691-2692; b) D. Drees, J. Magull, Z. Anorg. Allg
Chem. 1994, 620, 814-818.
[6]
[7]
C. Jones, Coord. Chem. Rev. 2010, 254, 1273-1289.
P. T. K. Lee, Masters Thesis, St. Mary’s University, Halifax, Canada,
2009.
[21] a) J. Cosier, A.M. Glazer, J. Appl. Crystallogr. 1986, 19, 105-107; b) Z.
Otwinowski, W. Minor, in Methods Enzymol., Vol 276: Macromolecular
Crystallography, Part A (Eds.: C.W. Carter, Jr., R.M. Sweet) Academic
Press, New York, 1997, pp. 307-326; c) A. Altomare, G. Cascarano, C.
Giacovazzo, A. Guagliardi, J. Appl. Crystallogr. 1994, 27, 1045-1050; d)
L. Palatinus, G. Chapuis, J. Appl. Crystallogr. 2007, 40, 786-790; e)
P.W. Betteridge, J.R. Carruthers, R.I. Cooper, K. Prout, D.J. Watkin, J.
Appl. Crystallogr. 2003, 36, 1487; f) R.I. Cooper, A.L. Thompson, D.J.
Watkin, J. Appl. Crystallogr. 2010, 43, 1100-1107; g) A.L. Thompson, D.
J. Watkin, J. Appl. Crystallogr. 2011, 44, 1017-1022.
[8]
[9]
a) Z. Janousek, H. G. Viehe, Angew. Chem., Int. Ed. Engl. 1971, 10,
574-575; b) S. Brenner, H. G. Viehe, Tetrahedron Lett. 1976, 17, 1617-
1620.
See also: a) A. Albers, T. Bayer, S. Demeshko, S. Dechert, F. Meyer,
Chem.-Eur. J. 2013, 19, 10101-10106. For a very recent example of a
cationic carbene featuring a related backbone, see: b) V. Regnier, Y.
Planet, C.E. Moore, J. Pecaut, C. Philouze, D. Martin, Angew. Chem.
Int. Ed. 2017, 56, 1031-1035.
[10] M. Stender, R. J. Wright, B. E. Eichler, J. Prust, M. M. Olmstead, H. W.
Roesky, P. P. Power, Dalton Trans. 2001, 3465-3469.
[11] J. Emsley in The Elements 3rd edition, Clarendon Press, Oxford, 1998.
[12] J. Feldman, S. J. McLain, A. Parthasarathy, W. J. Marshall, J. C.
Calabrese, S. D Arthur, Organometallics 1997, 16, 1514.
[22] a) A. D. Becke, Phys. Rev. A 1988, 38, 3098-3100; b) J. P. Perdew,
Phys. Rev. B 1986, 33, 8822-8824; c) J. G. Snijders, P. Vernooijs, E. J.
Baerends, Atomic Data and Nuclear Data Tables, 1982, 26, 483-509.
[13] a) A. Akkari, J. J. Byrne, I Saur, G. Rima, H. Gornitzka, J. Barrau, J.
Organomet. Chem. 2001, 622, 190-198; b) A. E. Ayers, T. M. Klapötke,
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Entry for the Table of Contents (Please choose one layout)
Layout 1:
FULL PAPER
N-nacnac-ed
Dinh Cao Huan Do, Ailsa Keyser,
Andrey V. Protchenko, Brant Maitland,
Indrek Pernik, Haoyu Niu, Eugene L.
Kolychev, Arnab Rit, Dragoslav Vidovic,
Andreas Stasch,* Cameron Jones,* and
Simon Aldridge*
The synthesis and coordination
chemistry of electron-rich amino-
functionalized β-diketiminato (N-
nacnac) ligands are reported. Two
synthetic methodologies have been
developed for protio-ligands bearing
backbone NR2 groups, which react
with metal alkyls to access complexes
from groups 1, 2 and 13. SnII and YbII
systems can be prepared via trans-
metallation to allow direct comparison
with conventional Nacnac compounds.
Page No. – Page No.
Highly electron rich β-diketiminato
systems: Synthesis and coordination
chemistry of amino functionalized ‘N-
nacnac’ ligands
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