N,N′-Diamidonaphthalene as a Versatile Ligand to Stabilize Mono- and Bimetallic Complexes of Group 13

Article abstract of DOI:10.1002/ejic.201800297

Disubstituted 1,8-diamidonaphthalene complexes of B and Al were accessed via hydrogen or methane elimination reactions from readily available borane or trimethylaluminum. Trigonal planar borane complexes, HB[1,8-(NR)C₁₀H₆] (R = iPr,

Full text of DOI:10.1002/ejic.201800297

https://doi.org/10.1002/ejic.201800297
Full Paper
Organometallic Chemistry
N,N′-Diamidonaphthalene as a Versatile Ligand to Stabilize
Mono- and Bimetallic Complexes of Group 13
Sojung Lee,[a] Nawal Almalki,[a] Bulat Gabidullin,[a] and Darrin Richeson*[a]
Abstract: Disubstituted 1,8-diamidonaphthalene complexes of ray diffraction analyses and display puckered, four-membered
B and Al were accessed via hydrogen or methane elimination M2N2 rings with a bridging diamidonaphthalene ligand. With
reactions from readily available borane or trimethylaluminum. R = Ph, a monometallic aluminum complex, MeAl(OEt2)-
Trigonal planar borane complexes, HB[1,8-(NR)C10H6] (R = iPr, 4 [1,8-(PhN)2C10H6] (6), was isolated as a diethylether adduct. The
and R = Ph, 5), were observed to be air stable, a feature attrib- structural data suggested that the dialkyl and diaryl are
uted to B–N pπ–pπ bonding and supported by computations. stronger σ-bonding ligands compared to reported trimethylsilyl
Bimetallic Al complexes, [Al(CH3)2]2[(RN)2C10H6] (R = iPr, 7, R = analogues.
Ph, 8, or R = iPr/Np, 9), were documented by single-crystal X-
Introduction
ited by the electronic, steric and potential N-silyl reactivity of
these groups.
Boron hydrides and alkylaluminum species are core functional
groups in the chemistry of the group 13 elements. They can be
exploited from both fundamental and applied perspectives and
have been employed for their reactivity and as building blocks
in synthesis. Modulation of the chemistry of these and other
group 13 element functionalities can be achieved through
changes to the ligand environment. For example, the applica-
tion of ꢀ-diketiminate ligands has vitalized the synthetic chem-
istry of group 13 elements.[1–4] As supporting ligands, ꢀ-diket-
iminates exhibit strong and diverse binding modes combined
with adjustable steric demands through variation of the NR
substituents and these features have promoted their applica-
tion in group 13 and across the periodic Table These observa-
tions provided an impetus for our efforts to design and imple-
ment ligands that are reminiscent of the ꢀ-diketiminate scaffold
in both geometry and frontier orbital topology and this target
has led us to investigate the application of the dianions, N,N′-
disubstituted-1,8-diamidonaphthalene (“R2DAN2–”) as ligands in
group 13 chemistry. The R2DAN2– scaffold presents a rigid
dianionic ligand with delocalized π-electrons in a framework
with similarities to the ꢀ-diketiminate scaffold. Diamino-
naphthalene-based ligands have seen some application with
borohydride and alkylaluminum chemistry with particularly
noteworthy examples being silyl-substituted tetraminoperylene
and 1,8-bis(trialkylsilylamino)naphthalene group 13 compounds
represented by A–D.[5–9] Importantly, reports have been re-
stricted to trialkylsilyl, R3Si, substituents and are therefore lim-
Our desire is to explore the modification to the steric and
electronic features of the R2DAN2– framework by introduction
and variation of the N-substituents to include both alkyl and
aryl groups. We previously reported the syntheses of ligands 1–
3 (Scheme 1) through a multi-step reductive amination
method,[10] or using a Cu catalyzed coupling reaction,[11–13] re-
spectively. Furthermore, among the main group elements, this
framework has been successfully applied to group 14 divalent
species[10,14,15] and to low coordinate group 15 cations.[16,17] We
now wish to report the use three disubstituted 1,8-diamino-
naphthalene species 1–3[15] for the isolation and characteriza-
tion of monomeric, three coordinate borohydrides with unusual
air stability as well as mono- and dinuclear Al-Me complexes.
These new compounds make a substantial and fundamental
contribution to the limited number of compounds reported
with the 1,8-diamidonaphthalene-based scaffold and represent
potential building blocks for further synthetic chemistry of
these elements.
[a] Department of Chemistry and Biomolecular Sciences and Centre for
Catalysis Research and Innovation, University of Ottawa,
Ottawa, Ontario K1N6N5, Canada
E-mail: darrin@uottawa.ca
http://mysite.science.uottawa.ca/darrin/
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201800297.
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Scheme 1. Synthetic routes to ligands 1, 2 and 3.
Results and Discussion
Interestingly, both 4 and 5 are stable to air in both solid
state and in solution and NMR solutions of these compounds
can be prepared in the air using deuterated solvents directly
from the bottle as received from the supplier. These observa-
tions are in sharp contrast with the reactivity of the diazaborine
species A, which are sensitive in both solid state and solution.[8]
Similarly, five-membered 2-hydrido-1,3,2-diazaboroles are re-
ported to be colorless air- and moisture-sensitive solids.[18]
Definitive confirmation for the structural features of 4 and 5
was obtained from the single-crystal X-ray analyses and results
are summarized in Figure 1 and Figure 2 and selected bond
lengths and angles are given in Table 1. Both structures display
a diamidonaphthalene group chelating to a trigonal planar B
center. The NBN unit and naphthalene backbone are nearly co-
planar with the angle between these two planes being only
4.50 in 4 and 8.20 in 5. For both 4 and 5, the H atom bonded
to B were refined freely and yielded average B–H bond lengths
of 1.11 Å. Both compounds exhibited similar N–B–N bite angles
of 120.8(3)0 in 4 and 119.2(1)0in 5, a feature that is consistent
with sp2 hybridized B centers. Finally, the B centers are bonded
symmetrically to the ligand with 4 displaying two equal B–N
distances [1.405(5) and 1.409(5) Å] and 5 showing slightly
The diaminonaphthalene proligands 1–3 possess reactive NH
protons allowing for their direct reaction with inorganic and
organometallic compounds that possess basic groups. These
compounds include boron hydrides, with reactive BH groups,
and trimethylaluminum with strongly basic AlMe moieties. For
example, both 1 and 2 react directly with BH3(SMe2) as summa-
rized in Scheme 2. From these reactions, compounds 4 and 5
were isolated as colorless and light orange crystals, respectively.
The multi-nuclear NMR spectra of these two new 1,3,2-diaza-
borine species provide clear indications for the structures pro-
1
posed for 4 and 5. Specifically, both compounds exhibited H
and 13C NMR resonances indicating a symmetrical ligation for
the R2DAN2– group. A broad resonance for the BH group was
1
observed in each of the H NMR spectra at δ = 4.74 ppm (4)
and 4.26 ppm (5) with these values being comparable to silyl-
ated N,N′;N′′,N′′′-diborylene-3,4,9,10-tetraaminoperylenes (A),
which gave corresponding B-H resonances observed at δ =
4.71–4.75 ppm.[8] The 11B NMR spectra further support the pro-
posed formulations with compound 4 displaying a proton de-
coupled 11B resonance at δ = 28.4 ppm while compound 5
showed such a resonance at δ = 25.9 ppm. For comparison,
the perylene analogue A (R = Me) had a 11B resonance at δ =
29.8 ppm.[7] Although they are not completely analogous, the
monomeric species B, BX[(NSiMe3)2C10H6], gave 11B NMR reso-
nances at similar chemical shifts of 32.1 ppm (X = Cl) and
28.0 ppm (X = Br).[6] Finally, the microanalysis data on 4 and 5
was consistent with the suggested formulations.
longer but equivalent distances at 1.4163(16)
Å and
Figure 1. Structural representation of HB[1,8-(iPrN)2C10H6] (4). Carbon-bound
hydrogen atoms have been omitted for clarity. The thermal ellipsoids are
shown at 50 % probability level.
Scheme 2. Synthesis of compounds 4 and 5.
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1.4186(16) Å. These bond lengths are, in both cases, slightly experimental as well as the theoretical data agree with a signifi-
shorter than those reported for the tetraaminoperylene com- cant delocalization of the nitrogen 2p-centered lone electron
pounds A, which averaged 1.43 Å[8] Reported six-membered pairs into the vacant 2pz orbital of the boron atom in 4.
compounds with saturated rings, HB(RR′C6H3NCHMe)2CMe2
(R = R′ = iPr; R = iPr, R′ = H), displayed B–N distances that
ranged from 1.396(4) Å to 1.414(5) Å and these distances were
judged to optimize B–N pπ–pπ interactions.[19]
Figure 2. Structural representation of HB[1,8-(PhN)2C10H6] (5). Carbon-bound
hydrogen atoms have been omitted for clarity. The thermal ellipsoids are
shown at 50 % probability level.
Figure 3. The frontier orbitals (HOMO-2 to LUMO) representing the π-bonding
in 3 obtained from DFT [B3LYP, 6-311+G(d,p)] on compound 4.
Table 1. Selected bond lengths [Å] and angles [°] for HB[(iPrN)2C10H6] (4) and
HB[(PhN)2C10H6] (5).
The protonation reaction of trimethylaluminum with ligand
2 in ether offers an analogous method for introducing the 1,8-
2–
Compound 4
Compound 5
(PhN)2C10H6 group in aluminum chemistry as shown in
N(1)–B(1)
N(2)–B(1)
B(1)–H(1)
1.405(5)
1.409(5)
1.11(4)
B(1)–N(1)
B(1)–N(2)
B(1)–H(1)
1.4163(16)
1.4186(16)
1.112(13)
Scheme 3. The red crystalline product obtained from this reac-
tion gave H NMR spectroscopic data indicative of a 1:1 CH3Al/
1
ligand ratio and only nine aromatic carbon resonances in the
13C NMR consistent with a symmetrical ligand environment. A
1H resonance at δ = 0.24 ppm was assigned the Al–CH3 moiety
and is comparable to the only analogues in the literature, com-
pounds C and D, which displayed corresponding resonances,
assigned to Al–CH3, at δ = –0.55 ppm and –0.57 ppm, respec-
tively.[5,7]
N(1)–B(1)–N(2)
N(1)–B(1)–H(1)
N(2)–B(1)–H(1)
C(1)–N(1)–B(1)
C(1)–N(1)–C(11)
B(1)–N(1)–C(11)
C(9)–N(2)–B(1)
C(9)–N(2)–C(14)
B(1)–N(2)–C(14)
120.8(3)
123(2)
115(2)
120.6(3)
118.5(3)
120.6(3)
120.2(3)
119.2(7)
120.7(7)
N(1)–B(1)–N(2)
N(1)–B(1)–H(1)
N(2)–B(1)–H(1)
C(2)–N(1)–B(1)
C(2)–N(1)–C(11)
B(1)–N(1)–C(11)
C(10)–N(2)–B(1)
C(10)–N(2)–C(17)
B(1)–N(2)–C(17)
119.21(11)
119.5(7)
121.3(7)
120.84(10)
118.89(9)
120.27(10)
121.07(10)
119.49(9)
119.41(10)
The air stability of 4 and 5 as well as the observed B–N bond
lengths could be attributed to B–N π-bonding and in order to
further reveal the more detailed features of these interactions
we carried out a computational study on compound 4. Starting
with the crystal structure data, compound 4 was optimized us-
ing DFT and the Gaussian 09 program employing the B3LYP
functional and a 6-311+G(d,p) basis set.[20] The resulting struc-
ture was well aligned with the experimentally determined X-
ray data with comparison details provided in the Supporting
Information.
Scheme 3. Synthesis of compound 6.
The NMR spectra of 6 showed variable traces of Et2O and
this provided further motivation to perform the single-crystal
The frontier orbitals obtained from these computations show X-ray analysis on this species. The results of this analysis are
a clear NBN π bonding interaction as presented in Figure 3. summarized in Figure 4 with selected bond lengths and angles
While the HOMO and LUMO for 4 are non-bonding with respect in Table 2. Compound 6 was the anticipated mononuclear Al
the BN linkages, the occupied HOMO-2 and HOMO-1 orbitals species possessing one chelating N,N′-diphenyldiamido-
show the contribution to NBN π-bonding. Taken together the naphthalene ligand, one methyl group and a coordinated di-
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1
ethyl ether to give a pseudo-tetrahedral coordination geometry groups. Furthermore, the H NMR spectrum of 7 displayed two
for the Al center. The presence of coordinated ether is consist- equal integral doublet peaks at δ = 1.38 ppm and 1.28 ppm
ent with the fact that the crystals of 6 were removed from assigned to the methyl groups of the iPr substituents.
the mother liquor and immediately frozen in Paratone oil in
preparation for the data collection. The N(1) and N(2) centers
are planar with a sum of bond angles equal to 3600 in both
cases. Of the six angles around the Al center, the smallest is
represented by the ligand bite angle N(1)–Al(1)–N(2), 98.84(11)0
and the average of these six angles is 109.30 supporting a dis-
torted tetrahedral assignment. The four bond lengths associ-
ated with the Al center, C(23)–Al(1) = 1.939(3) Å, N(1)–Al(1) =
1.812(2) Å, N(2)–Al(1) = 1.816(2) Å, and Al(1)–O(1) = 1.895(2) Å,
are slightly shorter than in the analogue [1,8-(Me3SiN)2C10H6]-
Al(Me)thf (C) [Al–C 1.9482(16), av. Al–N = 1.830 Å, Al–O =
1.920 Å].[5] Further comparison can be made to the silylated
Scheme 4. Synthesis of compounds 7–9.
tetraaminoperylenes species, [AlMe(thf)]2[(Me3Si)4N4C20H8] (D),
Surprisingly, this product was the only isolated species re-
with Al–C = 1.954(3) Å, average Al–N = 1.826 Å, and Al–O =
gardless of the reaction stoichiometry between 1 and AlMe3
and an improved synthesis was achieved using 2 equiv. of Al-
Me3 to produce 7 which could be obtained as colorless crystals
from cold (–25 °C) ether. An X-ray diffraction study was per-
formed and confirmation of the connectivity was obtained with
the molecular structure shown in Figure 5. The corresponding
values for selected bond lengths and angles are provided in
Table 3.
1.910(2) Å.[7]
Figure 4. The molecular structure for MeAl(OEt2)[1,8-(PhN)2C10H6] (6).
Hydrogen atoms have been omitted for clarity. The thermal ellipsoids are
shown at 50 % probability level.
Table 2. Selected bond lengths [Å] and angles [°] for Al(CH3)(Et2O)-
[(PhN)2C10H6] (6).
C(23)–Al(1)
N(1)–Al(1)
1.939(3)
1.812(2)
N(2)–Al(1)
Al(1)–O(1)
1.816(2)
1.895(2)
Figure 5. The molecular structure for (AlMe2)2[1,8-(iPrN)2C10H6] (7). Hydrogen
atoms have been omitted for clarity. The thermal ellipsoids are shown at
50 % probability level.
C(1)–N(1)–Al(1)
C(11)–N(1)–Al(1)
C(9)–N(2)–C(17)
C(9)–N(2)–Al(1)
C(17)–N(2)–Al(1)
N(1)–Al(1)–N(2)
125.0(2)
118.01(18)
118.9(2)
124.79(19)
116.20(18)
98.84(11)
N(1)–Al(1)–O(1)
N(2)–Al(1)–O(1)
N(1)–Al(1)–C(23)
N(2)–Al(1)–C(23)
O(1)–Al(1)–C(23)
108.21(10)
103.83(10)
117.73(13)
119.84(13)
107.17(12)
Compound 7 is a bimetallic Al species, [μ-1,8-(iPrN)2-
C10H6](AlMe2)2, with each aluminum center possessing a four-
coordinate distorted tetrahedral geometry consisting of two
methyl groups, and the two nitrogens of a 1,8-diamidonaphth-
alene ligand. Each of the anionic nitrogen centers formally pos-
sesses two electron pairs and both of these are donated to the
two different Al centers. The result is a puckered, butterfly
shaped Al2N2 metallacycle with approximate C2v symmetry. A
The longer bond lengths for the N-silyl species parallels the
observations with the boron compounds 4 and 5 and these
features imply that ligands 1 and 2 may have slightly stronger
element–ligand bonding interactions.
The reaction of AlMe3 with ligand 1 followed a different path similar structure has been reported from the related trimethyl-
than for the synthesis of 6. The direct reaction of equimolar silyl ligand, [μ-1,8-(Me3SiN)2C10H6](AlMe2)2 (E).[9] The four Al–N
ratio of 1 and AlMe3 proceeded smoothly to yield the unantici- bond lengths in 7 range from 1.9710(15) Å to 1.9873(15) Å and
pated bimetallic product (AlMe2)2[1,8-(iPrN)2C10H6] (7) as shown are considerably longer than in the mononuclear species 6 yet
in Scheme 4. The first indication of a bimetallic species was the slightly shorter than in compound E with Al–N of 1.998(4) and
appearance of two equal intensity (6 H) proton NMR signals at 1.995(4) Å. The bimetallic core positions the two methyls on
δ = –0.10 ppm and –1.18 ppm consistent with four Al–CH3 each Al in inequivalent environments consistent with the NMR
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Table 3. Selected bond lengths [Å] and angles [°] for [Al(CH3)2]2[(iPrN)2C10H6]
(7).
Al(1)–C(21)
1.962(2)
Al(2)–C(19)
1.9554(19)
Al(1)–C(22)
Al(1)–N(12)
Al(1)–N(1)
1.9627(19)
1.9744(17)
1.9836(15)
Al(2)–C(20)
Al(2)–N(12)
Al(2)–N(1)
1.957(2)
1.9710(15)
1.9873(15)
C(21)–Al(1)–C(22)
C(21)–Al(1)–N(12)
C(22)–Al(1)–N(12)
C(21)–Al(1)–N(1)
C(22)–Al(1)–N(1)
N(12)–Al(1)–N(1)
C(21)–Al(1)–Al(2)
C(19)–Al(2)–C(20)
C(19)–Al(2)–N(12)
C(20)–Al(2)–N(12)
C(19)–Al(2)–N(1)
C(20)–Al(2)–N(1)
N(12)–Al(2)–N(1)
116.15(10)
112.00(8)
113.17(8)
115.90(8)
113.85(8)
80.74(6)
102.91(7)
114.93(9)
109.74(8)
114.90(8)
119.14(8)
112.81(8)
80.73(6)
C(2)–N(1)–C(13)
C(2)–N(1)–Al(1)
C(13)–N(1)–Al(1)
C(2)–N(1)–Al(2)
C(13)–N(1)–Al(2)
Al(1)–N(1)–Al(2)
C(10)–N(12)–C(16)
C(10)–N(12)–Al(2)
C(16)–N(12)–Al(2)
C(10)–N(12)–Al(1)
C(16)–N(12)–Al(1)
Al(2)–N(12)–Al(1)
114.34(14)
103.76(10)
117.48(12)
103.09(11)
122.91(11)
91.59(6)
119.72(15)
106.45(11)
114.31(11)
104.45(11)
115.74(12)
92.35(7)
Figure 7. The molecular structure for (AlMe2)2[1,8-(iPrN)(NpN)C10H6] (9).
Hydrogen atoms have been omitted for clarity. The thermal ellipsoids are
shown at 50 % probability level.
Table 4. Selected bond lengths [Å] and angles [°] for [Al(CH3)2]2[(PhN)2C10H6]
(8).
observations. Crystallographically there are four Al–C bond
lengths ranging from 1.9554(19) Å to 1.9627(19) Å. In 7 the two
N–Al–N bite angles were 80.74(6)0 and 80.73(6)0 which are
much smaller than the corresponding angle in 6 but only
slightly smaller than the angle of 83.0(2)° observed for com-
pound E.
C(1)–Al(1)
1.9544(16)
C(9)–N(1)
1.4633(16)
C(2)–Al(1)
C(3)–N(1)
1.9542(16)
1.4491(17)
N(1)–Al(1)
N(1)–Al(1)#1
1.9868(12)
1.9966(12)
C(2)–Al(1)–C(1)
C(2)–Al(1)–N(1)
C(1)–Al(1)–N(1)
C(2)–Al(1)–N(1)#1
C(1)–Al(1)–N(1)#1
N(1)–Al(1)–N(1)#1
118.16(8)
115.05(7)
111.38(6)
112.44(6)
114.29(6)
79.43(6)
C(3)–N(1)–Al(1)
C(9)–N(1)–Al(1)
C(3)–N(1)–Al(1)#1
C(9)–N(1)–Al(1)#1
116.05(8)
108.07(8)
119.73(8)
105.24(8)
Employing this same stoichiometric ratio but using ligand 2
or 3 generated the analogous bimetallic Al species 8 and 9
(Scheme 4). The appearance of two inequivalent, equal intensity
1
signals assigned to the Al–CH3 groups in the H NMR and the
13C NMR spectra was a clear indication of analogous dimetallic
structures. Furthermore, we were fortunate to obtain single
crystals of both complexes and their single-crystal X-ray analy-
ses confirmed that they displayed similar structures as repre-
sented in Figure 6 and Figure 7. The selected bond lengths and
angles for 8 and 9 are provided in Table 4 and Table 5, respec-
tively. Complexes 7–9 displayed parallel structural features with
small differences in bond lengths and bond angles.
Table 5. Selected bond lengths [Å] and angles [°] for [Al(CH3)2]2-
[(iPrN)(NpN)C10H6] (9).
C(19)–Al(1)
1.9544(17)
Al(1)–N(2)
1.9832(13)
C(20)–Al(1)
C(21)–Al(2)
C(22)–Al(2)
1.9680(17)
1.9570(16)
1.9603(16)
Al(1)–N(1)
Al(2)–N(2)
Al(2)–N(1)
1.9909(12)
1.9734(12)
1.9961(12)
C(19)–Al(1)–C(20)
C(19)–Al(1)–N(2)
C(20)–Al(1)–N(2)
C(19)–Al(1)–N(1)
C(20)–Al(1)–N(1)
N(2)–Al(1)–N(1)
C(1)–N(1)–C(11)
C(1)–N(1)–Al(1)
C(11)–N(1)–Al(1)
C(1)–N(1)–Al(2)
C(11)–N(1)–Al(2)
Al(1)–N(1)–Al(2)
115.04(8)
114.15(7)
109.85(7)
113.16(7)
118.84(7)
81.17(5)
116.27(11)
106.65(8)
125.22(9)
102.11(8)
111.32(8)
89.97(5)
C(21)–Al(2)–C(22)
C(21)–Al(2)–N(2)
C(22)–Al(2)–N(2)
C(21)–Al(2)–N(1)
C(22)–Al(2)–N(1)
N(2)–Al(2)–N(1)
C(9)–N(2)–C(16)
C(9)–N(2)–Al(2)
C(16)–N(2)–Al(2)
C(9)–N(2)–Al(1)
C(16)–N(2)–Al(1)
Al(2)–N(2)–Al(1)
115.81(8)
116.84(7)
111.79(6)
113.04(6)
113.41(7)
81.29(5)
119.99(11)
107.05(9)
113.44(9)
105.28(9)
116.08(9)
90.86(5)
Conclusions
Elimination of hydrogen or methane from borane or trimethyl-
aluminum when reacted with N,N′-disubstituted-1,8-diamino-
naphthalene has been documented as a versatile route to
dialkyl- and diaryl-1,8-diamidonaphthalene complexes for
group 13. This ligand array supports unexpectedly air-stable,
trigonal planar borane compounds HB[1,8-(NR)C10H6] (R = iPr, 4
Figure 6. The molecular structure for (AlMe2)2[1,8-(PhN)2C10H6] (8). Hydrogen
atoms have been omitted for clarity. The thermal ellipsoids are shown at
50 % probability level.
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Teflon screw cap. To this solution was added BH3·SMe2 (0.140 g,
1.84 mmol) pre-dissolved in toluene. The solution was heated to
60 °C overnight. The volatiles were removed under vacuum and the
crude product was crystallized by dissolving in hexane and cooling
to –25 °C. The product was isolated as colorless crystals and dried
under vacuum (0.397 g, 1.57 mmol, 95 %). 1H NMR (C6D6, 300 MHz):
with 11B decoupling δ = 7.20–7.22 (m, 4 H, CH), 6.36–6.41 (m, 2 H,
CH), 4.74 (s br, 1 H, BH), 3.67 (sep, 2 H, J = 6.03 Hz, CHMe2), 1.12 (d,
12 H, J = 6.54, CH3). 13C NMR (C6D6, 300 MHz): δ = 141.85, 137.28,
127.70, 127.10, 118.20, 102.97(C aromatic), 46.69 (CHMe2), 22.86
(CH3). 11B NMR (C6D6, 300 MHz): with 1H decoupling δ = 25.9 (s
BN2H).
and R = Ph, 5). Structural analysis combined with computations
point to significant B–N pπ–pπ bonding, a feature that we at-
tribute to the observed stability.
In the case of the trimethylaluminum reactions, the identity
of the products as mono- or bimetallic systems supported by
the 1,8-diamidonaphthalene dianion depended on stoichio-
metry as well as substituent identity. The different coordination
environments and ligand bonding features were documented
by single-crystal X-ray diffraction analyses and the unantici-
pated bimetallic complexes feature four-membered M2N2 rings
with puckered butterfly structures. The structural data sug-
gested that the dialkyl and diaryl are stronger σ-bonding li-
gands compared to trimethylsilyl analogues.
Compounds 4–9 represent interesting species as well as
building blocks for further group 13 chemistry. Our continuing
investigations are focused on variation of the ligand as well as
exploring changes to the bonding environment of the group
13 element.
Preparation of HB[1,8-(NC6H5)2C10H6] (5): The diamine
(C6H5NH)2C10H6 2 (0.320 g, 1.03 mmol) was dissolved in approxi-
mately 30 mL of toluene and transferred to a Schlenk vessel
equipped with a Teflon screw cap. To this solution was added
BH3·SMe2 (0.14 mL, 1.115 mmol) pre-dissolved in toluene. The solu-
tion was heated to 60 °C overnight. The volatiles were removed
under vacuum and the crude product was crystallized by dissolving
in ether and cooling to –25 °C. The product was isolated as light
orange color crystals and dried under vacuum (0.303 g, 0.95 mmol,
1
92 %). H NMR (CDCl3, 300 MHz): δ = 7.44–7.50 (m, 4 H, CH), 7.30–
Experimental Section
7.37 (m, 6 H, CH), 7.03–7.14 (m, 4 H, CH), 6.15 (dd, 2 H, CH), 4.26 (s
br, 1 H, BH). 13C NMR (CDCl3, 300 MHz): δ = 143.88, 142.97, 136.32,
129.90, 128.25, 127.06, 126.78, 120.32, 118.90, 106.15 (C aromatic).
General: All manipulations were carried out in either a nitrogen
filled dry box or under nitrogen using standard Schlenk techniques.
Reaction solvent (anhydrous diethyl ether) was sparged with nitro-
gen then dried by passage through column of activated alumina
using an apparatus purchased from Anhydrous Engineering. Deu-
terated benzene was purchased from Aldrich Chemical Company
and was dried by vacuum transfer from potassium. BH3·SMe2, and
AlMe3, anhydrous toluene, and anhydrous hexane were purchased
from Aldrich Chemical Company and used without further purifica-
tion. 1H, 13C, and 11B NMR spectra were run on either a Bruker
300 MHz or Bruker 600 MHz spectrometer using the residual pro-
tons of the deuterated solvent for reference. Elemental analyses
were performed by G.G. Hatch Stable Isotope Laboratory at the
University of Ottawa or Midwest Micro Lab in Indianapolis, IN, USA.
1
11B NMR (CDCl3, 300 MHz): with H decoupling δ = 28.4 (s, BN2H).
Preparation of [μ-1,8-C10H6(NC6H5)2](AlMe)(OEt2) (6): The
diamine (C6H5NH)2C10H6 2 (0.310 g, 1.0 mmol) was dissolved in
approximately 15 mL of diethyl ether in a round-bottomed flask
equipped with a stir bar. To the solution was added a 2.0
M hexanes
solution of AlMe3 (0.5 mL, 1.0 mmol). The solution was stirred over-
night and turned green, reddish brown, and finally red in color. The
volatiles were removed and the product was recrystallized from
1
ether at –25 °C, giving red crystals (0.314 g, 0.74 mmol, 0.74 %). H
NMR (CDCl3, 300 MHz): δ = 7.37 (dd, 2 H, CH, J = 8.16, 1.32 Hz),
7.13–7.11 (m, 2 H, CH), 6.93–7.07 (m, 6 H, CH), 6.67–6.73 (m, 6 H,
CH), 0.24(s, 3 H, CH3Al). 13C NMR (CDCl3, 300 MHz): δ = 144.93,
140.06, 137.45, 129.09, 126.01, 123.30, 121.10, 118.09, 116.92 (C aro-
matic), 1.39(CH3Al).
Structural Determinations: The crystals were mounted on thin
glass fibers using paraffin oil. Prior to data collection, crystals were
cooled to 200 2 K. Data were collected on a Bruker AXS single-
crystal diffractometer equipped with a sealed Mo tube source
(wavelength 0.71073 Å) and APEX II CCD detector. Raw data collec-
tion and processing were performed with Bruker APEX II software
package.[21] Semi-empirical absorption corrections based on equiv-
alent reflections were applied.[22] Systematic absences in the diffrac-
tion dataset and unit cell parameters were consistent with triclinic
Preparation of [μ-1,8-C10H6(NiPr)2](AlMe2)2 (7): The diamine
(iPrNH)2C10H6 1 (0.242 g, 1.0 mmol) was dissolved in approximately
15 mL of hexane in a round-bottomed flask equipped with a stir
bar. To the solution was added a 2.0
M hexanes solution of AlMe3
(1.0 mL, 2.0 mmol). The solution was stirred overnight as it turned
black, then brown. The volatiles were removed to yield a beige
solid. The product was recrystallized from ether at –25 °C, affording
colorless crystals (0.0174 g, 49 %). 1H NMR (C7D8, 300 MHz): δ =
7.31–6.68 (m, 6 H), 4.03 (sept, 2 H, J = 7.14 Hz), 3.58 (m, 1 H), 1.38
(d, 6 H, J = 7.05 Hz), 1.28 (d, 6 H, J = 6.33 Hz), –0.10 (s, 6 H), –1.18
(s, 6 H). 13C NMR (C6D6, 300 MHz): δ = 125.31, 123.25, 122.16, 119.74,
113.44, 111.66(C aromatic), 47.41(CHMe2), 47.13(CHMe2), 22.49(CH3),
19.08(CH3), –5.23(AlMe2), –10.95(AlMe2).
P1 (#2) for 7 and 9, monoclinic P2 /n (#14) for 6 and 3, and P2 /c
¯
1
1
(#14) for 5, monoclinic C2/c (#15) for 8, orthorhombic P212121 (#19)
for 4. The structures were solved by direct methods and refined
with full-matrix least-squares procedures based on F2, using
SHELXL[23] and WinGX.[24] All non-hydrogen atoms were refined
anisotropically. The hydrogen atoms were placed in idealized posi-
tions, except for H(1) in 4, H(1) in 5, and H(1A), H(2A) in 3 that were
located in the difference Fourier map and refined freely. In 4 one
of the isopropyl groups is disordered over two positions with
0.61(3):0.39(3) occupancy ratio. It was refined using enhanced rigid-
body restraints (RIGU) and constraints (EADP) applied to the atomic
displacement parameters. No additional restraints or constraints
were used for refinement of 3, and 5–9.
Preparation of [μ-1,8-C10H6(NC6H5)2](AlMe2)2 (8): The diamine
(C6H5NH)2C10H6 2 (0.105 g, 0.5 mmol) was dissolved in approxi-
mately 15 mL of diethyl ether in a round-bottomed flask equipped
with a stir bar. To this solution was added a 2.0
M hexanes solution
of AlMe3 (0.5 mL, 1.0 mmol). The solution was stirred overnight and
turned green, then red color. The volatiles were removed and the
product was recrystallized from ether at –25 °C, providing red crys-
1
Preparation of HB[1,8-(NiPr)2C10H6] (4): The diamine (iPrNH)2-
tals (0.135 g, 0.32 mmol, 65 %). H NMR (C6D6, 600 MHz): δ = 7.18–
C10H6 1 (0.40 g, 1.65 mmol) was dissolved in approximately 30 mL 7.28 (m, 9 H), 7.11–7.13 (m, 2 H), 6.93 (t, 3 H, J = 7.89 Hz), 6.36(dd,
of toluene and transferred to a Schlenk vessel equipped with a
J = 7.72, 1.00 Hz, 2 HHz), –0.37 (s, 6 H, AlMe2), –0.64 (s, 6 H, AlMe2).
Eur. J. Inorg. Chem. 0000, 0–0
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13C NMR (C6D6, 600 MHz): δ = 152.14, 144.11, 135.85, 130.99, 130.03,
126.96, 126.76, 123.39, 121.82, 118.04, 113.85 (C aromatic), –8.15
(CH3Al), –10.04 (CH3Al).
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Preparation of [μ-1,8-C10H6(NiPr)(NNp)](AlMe2)2 (9): The diamine
(iPrNH)(NpNH)C10H6 3 (0.300 g, 1.15 mmol) was dissolved in approx-
imately 15 mL of diethyl ether in a round-bottomed flask equipped
with a stir bar. To this solution was added a 2.0
M hexanes solution
of AlMe3 (1.15 mL, 2.30 mmol). resulting in a green solution. The
solution was stirred overnight and turned to a pinkish red color.
The volatiles were removed and the product was recrystallized from
ether at –25 °C, providing red crystals (0.25 g, 0.66 mmol, 57 %). 1H
NMR (C6D6, 300 MHz): δ = 7.22–6.89 (m, 6 H), 4.02 (sept, 1 H, J =
7.11 Hz), 3.29(s, 2 H), 1.28 (d, 6 H, J = 7.20 Hz), 0.95 (2, 9 H), –0.18
(s, 6 H), –1.09 (s, 6 H). 13C{H} NMR (C6D6, 300 MHz): δ = 147.79,
144.23, 136.02, 125.26, 125.16, 123.72, 123.19, 122.185, 113.63,
112.76 (C aromatic), 56.90(CH2Me3), 47.55(CHMe2), 30.75(CMe3),
18.99(CH3), 0.99(CH3), –7.70(AlMe2), –10.66(AlMe2)
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Acknowledgments
We thank the Natural Sciences and Engineering Research Coun-
cil (NSERC) of Canada, the Saudi Arabian Cultural Bureau, and
the Canada Research Chairs Program for funding as well as Ca-
nada Foundation for Innovation for computing resources.
[20] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.
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katsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G.
Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hase-
gawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A.
Montgomery Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Broth-
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chari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega,
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Revision A.02, Gaussian, Inc., Wallingford CT, 2016.
Keywords: Aluminum · Diaminonaphthalene · Boranes ·
Hydrides · Organometallic chemistry
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Received: March 6, 2018
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Full Paper
Organometallic Chemistry
S. Lee, N. Almalki, B. Gabidullin,
D. Richeson* ........................................ 1–8
N,N′-Diamidonaphthalene as a Ver-
satile Ligand to Stabilize Mono- and
Bimetallic Complexes of Group 13
Borohydride and alkylaluminum species are supported by disubstituted 1,8-di-
amidonaphthalene ligation.
https://doi.org/10.1002/ejic.201800297
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim