Bridging the gap: Attractive 3c-4e interactions in peri-substituted acenaphthylenes

Article abstract of DOI:10.1002/ejic.201301549

A series of peri-substituted acenaphthylenes that contain mixed halogen-chalcogen functionalities at the 5,6-positions in 1-6 [Acenapyl[X](EPh) (Acenapyl = acenaphthylene-5,6-diyl; X = Br, I; E = S, Se, Te)] and chalcogen-chalcogen moieties in 7-11 [Acenap(EPh)(E′Ph) (Acenap = acenaphthene-5,6-diyl; E/E′ = S, Se, Te)] have been prepared from their corresponding acenaphthene analogues A1-A11 by utilising 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) for the dehydrogenation of the ethane backbone. The related dihalide compounds 13 and 14 Acenapyl[XX′] (XX′ = BrBr, II) have also been prepared by following a similar procedure, and 1,2,5,6-tetrabromo-1,2-dihydroacenaphthylene A0 was prepared as an intermediate by following an alternative route to 13. The series of acenaphthylene compounds have remarkably similar molecular structures to their acenaphthene counterparts; they exhibit an expected increase in peri separation as heavier congeners occupy the close peri positions. The presence of the ethene bridge, however, naturally compresses the nearest bay angle as it increases the splay of the exocyclic peri atoms, thereby resulting in a minor increase in separation relative to equivalent acenaphthenes. The structures of 1-11, 13 and 14 are discussed and compared with previously reported analogous naphthalene and acenaphthene compounds. Similar to acenaphthene derivatives, aromatic ring conformations and the location of p-type lone pairs influences the geometry of the peri region. Under appropriate geometric conditions, quasi-linear three-body C_Ph-E...Z (E = Te, Se, S; Z = Br/E) fragments provide an attractive component for the E...Z interaction. DFT studies confirm the onset of formation of three-center, four-electron bonding, similar in extent to that observed in analogous acenaphthenes, despite an increase in the peri distances. peri-Substituted acenaphthylenes [Acenapyl(X)(EPh)] and [Acenapyl(EPh)(E′Ph)] have been prepared and molecular structures determined where possible. Comparison with analogous naphthalene and acenaphthene compounds reveals similar trends. Under appropriate geometric conditions, quasilinear C_Ph-E...Z (E = Te, Se, S; Z = Br/E) fragments exist to promote attractive 3c-4e interactions.

Full text of DOI:10.1002/ejic.201301549

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DOI:10.1002/ejic.201301549
Bridging the Gap: Attractive 3c–4e Interactions in peri-
Substituted Acenaphthylenes
Louise M. Diamond,[a] Fergus R. Knight,*[a]
Kasun S. Athukorala Arachchige,[a] Rebecca A. M. Randall,[a]
Michael Bühl,[a] Alexandra M. Z. Slawin,[a] and J. Derek Woollins[a]
Keywords: Arenes / Fused-ring systems / Noncovalent interactions / Density functional calculations / Chalcogens
A series of peri-substituted acenaphthylenes that contain
mixed halogen–chalcogen functionalities at the 5,6-positions
in 1–6 [Acenapyl[X](EPh) (Acenapyl = acenaphthylene-5,6-
separation as heavier congeners occupy the close peri posi-
tions. The presence of the ethene bridge, however, naturally
compresses the nearest bay angle as it increases the splay of
diyl; X = Br, I; E = S, Se, Te)] and chalcogen–chalcogen moie- the exocyclic peri atoms, thereby resulting in a minor in-
ties in 7–11 [Acenap(EPh)(EЈPh) (Acenap = acenaphthene-
5,6-diyl; E/EЈ = S, Se, Te)] have been prepared from their
corresponding acenaphthene analogues A1–A11 by utilising
2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) for the
dehydrogenation of the ethane backbone. The related dihal-
ide compounds 13 and 14 Acenapyl[XXЈ] (XXЈ = BrBr, II)
have also been prepared by following a similar procedure,
and 1,2,5,6-tetrabromo-1,2-dihydroacenaphthylene A0 was
prepared as an intermediate by following an alternative
route to 13. The series of acenaphthylene compounds have
crease in separation relative to equivalent acenaphthenes.
The structures of 1–11, 13 and 14 are discussed and com-
pared with previously reported analogous naphthalene and
acenaphthene compounds. Similar to acenaphthene deriva-
tives, aromatic ring conformations and the location of p-type
lone pairs influences the geometry of the peri region. Under
appropriate geometric conditions, quasi-linear three-body
CPh–E···Z (E = Te, Se, S; Z = Br/E) fragments provide an at-
tractive component for the E···Z interaction. DFT studies con-
firm the onset of formation of three-center, four-electron
remarkably similar molecular structures to their acenaphth- bonding, similar in extent to that observed in analogous ace-
ene counterparts; they exhibit an expected increase in peri
naphthenes, despite an increase in the peri distances.
that the bonding in these species, termed hypervalent,[4] was
now ionic rather than covalent in nature.[2]
Introduction
Understanding how atoms interact in different bonding
situations and the ability to quantify the extent of bonding
between two atoms is an ongoing challenge for chemists,
one which dates back to the origins of the electronic theory
of valence proposed by Lewis and Langmuir in the early
1900s.[1,2] The stability of molecules was originally ascribed
to their ability to pair valence electrons off in chemical
bonds to achieve “stable octets”, with the concept of coval-
ence introduced as “the number of pairs of electrons an
atom can share with its neighbor”.[1–3] Ambiguity over the
bonding in molecules of heavier main-block elements
(period 3 and higher), in which an “octet expansion” would
be required to conform to conventional Lewis 2c–2e cova-
lent bonding theory, was thus rationalised by the availabil-
ity of unfilled low-lying d orbitals.[1] Langmuir, however,
accounted for the legitimacy of the octet rule by suggesting
The advancement of molecular-orbital theory in the lat-
ter half of the last century led to a greater understanding
of the bonding in hypervalent compounds, which favoured
the octet rule rather than conventional Lewis 2c–2e theory
as a valid first approximation for the bonding in molecules
of the main block.[3] The concept of a three-centre, four-
electron bond (3c–4e) subsequently introduced by Rundle
et al.[5] and Pimental[6] was able to explain the bonding
without either violating the octet rule or invoking ionic
bonding and later evolved to include four- and five-centre,
six-electron bonds (4c–6e, 5c–6e).[7] With the help of in-
creasingly sophisticated calculations, novel bonding scenar-
ios are continuing to be uncovered.[8] However, identifying
synthetic routes to these systems is essential for corroborat-
ing theoretical predictions, which are not always unambigu-
ous.
The chemistry of 1,8-disubstituted naphthalenes is well
developed,[9] with many groups utilising the rigidity of the
backbone and close proximity of the substituted moieties
for studying weak noncovalent interactions in main-group
systems.[10,11] The geometric constraints unique to peri-sub-
stituted species allows large heteroatoms to occupy un-
[a] EaStCHEM, School of Chemistry, University of St Andrews,
St Andrews, Fife, KY16 9ST, UK
E-mail: frk@st-andrews.ac.uk
http://chemistry.st-and.ac.uk/staff/jdw/group/home.html
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201301549.
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usually close positions within van der Waals radii. The sub- metric configurations, 3c–4e-type interactions provide an
sequent nonbonded intramolecular interactions that result attractive component for the E···Z interaction, which be-
from the direct overlap of orbitals can either be repulsive comes less prominent for the lighter, second-row congeners.
owing to steric hindrance or attractive in the form of weak However, the variation in peri separation between com-
or strong bonding.[12,13] When electron density is delocal- pounds with different aromatic ring configurations can be
ised over formally nonbonded atoms, the degree to which correlated to the ability of frontier orbitals to take part in
the delocalisation contributes to the bonding between these attractive or repulsive interactions. In addition, the intro-
atoms is of particular interest.[8,14–19] Heavier third- and duction of the ethane linker ensures peri-substituted ace-
fourth-row peri substituents, susceptible to hypervalent naphthenes naturally display greater molecular distortion
bonding, can be forced to interact well within the sum of than corresponding naphthalene derivatives, thereby re-
van der Waals radii. However, the nature, size and number sulting in longer peri distances and less interaction between
of the substituents attached to the peri atoms and the the peri atoms.[17,18]
makeup of the rigid backbone can have a notable affect on
The ease of synthesising the valuable precursor 5,6-di-
the formally nonbonded peri separations. Such tendencies bromoacenaphthene[20] relative to the more laborious
are observed in naphthalenes N1–N12[18] and their ace- method for preparing the naphthalene equivalent[21] has
naphthene analogues A1–A12.[17] Under appropriate geo- seen an increasing rise in the use of the acenaphthene scaf-
fold for preparing peri-substituted species.[22–27] The related
acenaphthylene backbone that incorporates a C=C double
bond on the bridging moiety, however, has seen limited use.
Herein, we report the synthesis and structural characterisa-
tion of a series of halogen and chalcogen peri-substituted
acenaphthylenes 1–12, analogues of previously reported
naphthalenes N1–N12[18] and acenaphthenes A1–A12,[17]
along with 5,6-dihaloacenaphthylenes 13 (Br)[28,29] and 14
(I) (Figure 1).
Results and Discussion
Acenaphthylenes 1–11, 13[28,29] and 14 were synthesised,
with crystal structures determined for 2, 3, 5, 6, 8–10 and
13. In addition, 1,2,5,6-tetrabromo-1,2-dihydroacenaphthyl-
ene A0[28] was synthesised as an intermediate in the prepa-
ration of 13 and its crystal structure determined. The struc-
ture of 5,6-dibromoacenaphthene A13 is also reported for
completeness and for comparison with 13 and A0. All com-
pounds obtained (1–11, 13, 14 and A0) were characterised
by multinuclear magnetic resonance and IR spectroscopy
and mass spectrometry, and the homogeneity of the new
compounds was confirmed by microanalysis where possible.
77Se and 125Te NMR spectroscopic data can be found in
Table 1.
Previous work undertaken on analogous naphthalene[18]
and acenaphthene[17] compounds highlighted 5,6-dibromo-
acenaphthylene 13[28,29] as a potential starting material for
the preparation of chalcogen-substituted acenaphth-
ylenes 1–12. 1,8-Dibromonaphthalene N13 and 5,6-di-
bromoacenaphthene A13 both readily undergo lithium–
halogen exchange reactions to form mono- and dilithiated
precursors for many metal-substitution reactions, and have
Figure 1. Sterically crowded peri-substituted acenaphthylenes 1–14,
acenaphthenes A1–A12[17] and naphthalenes N1–N12.[18]
Table 1. 77Se and 125Te NMR spectroscopic data (δ values, ppm).[17,18]
2
N2
A2
5
N5
A5
8
N8
A8
10
N10
A10
peri atoms
Br,Se
448
3
Br,Te
723
Br,Se
448
N3
Br,Te
731
Br,Se
424
A3
Br,Te
696
I,Se
427
6
I,Te
687
I,Se
431
N6
I,Te
698
I,Se
401
A6
I,Te
662
Se,Se
427
9
Te,Te
618
Se,Se
429
N9
Te,Te
620
Se,Se
408
A9
Te,Te
586
Se,S
456
11
Te,S
951
Se,S
455
N11
Te,S
715
Se,S
434
A11
Te,S
689
77Se NMR
peri atoms
125Te NMR
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previously been shown to react with diphenyl dichalco- characteristic pair of doublets that represent the two CH
genides to form substituted chalcogen com- peaks of the ethene double bond were present [δ = 6.94 (d,
pounds.[17,18,30,31]
3
3
1 H, JH,H = 5.2 Hz, CH), 6.91 (d, 1 H, JH,H = 5.2 Hz,
Compound 13 was initially prepared by following a CH) ppm]. However, 1H NMR and heteronuclear single
modified version of the route reported by Meinwald and quantum coherence (HSQC) spectroscopy revealed that
Chiang.[28] A solution of 5,6-dibromoacenaphthene A13[32] peaks for only one phenyl group were present, thus indicat-
in chloroform was treated with N-bromosuccinimide (NBS; ing that only one chalcogen–phenyl group remained. In ad-
2.2 equiv.) and benzoyl peroxide (0.22 equiv.) and heated dition, no signal was observed in the 125Te NMR spectrum;
under reflux for five hours to afford A0 (yield 74%). Debro- however, the 77Se NMR spectrum displayed a singlet at δ =
mination to the target compound 13 was subsequently 446 ppm. Mass spectrometry confirmed the presence of a
achieved by treating A0 with five equivalents of zinc and mono-substituted selenium–phenyl acenaphthylene with a
heating to reflux in glacial acetic acid for four hours (yield mass/charge ratio of 307.0. Attempts to recrystallise the un-
86%; Scheme 1).[33] An alternative route to 13, reported by known product were unsuccessful, we speculate that the re-
Mitchell and co-workers,[34] converts 5,6-dibromoace- action has proceeded with the loss of PhTe to give ace-
naphthene A13 directly to the product in one step, using naphthyl(SePh).
2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in benz-
77Se and 125Te NMR spectroscopic data for the series
ene (24 h) heated under reflux conditions to dehydrogenate of acenaphthylene derivatives and their acenaphthene and
the ethane bridge (yield 25%, Scheme 1).
naphthalene analogues are displayed in Table 1. The ace-
naphthylene derivatives display NMR spectroscopic signals
with similar chemical shifts to their naphthalene counter-
parts. This is in contrast to equivalent acenaphthene com-
pounds, the signals of which lie noticeably upfield at much
lower chemical shifts. The exception is mixed tellurium–
sulfur derivative 11, which displays a significantly higher
chemical shift of δ = 952 ppm (cf. N11 δ = 715 ppm; A11 δ
= 589 ppm).
X-ray Investigations
Scheme 1. Alternative routes for the synthesis of 5,6-dibromoace-
naphthylene 13: (i) N-bromosuccinimide, benzoyl peroxide, chloro-
form, 80 °C, 5 h; (ii) zinc powder, glacial acetic acid, 120 °C, 4 h;
(iii) DDQ, benzene, 90 °C, 24 h.
Suitable single crystals were obtained for 2, 3, 5, 6, 8 and
13 by diffusion of hexane into a saturated solution of the
compound in dichloromethane. Crystals for 9 and 10 were
The preparation of 5,6-bis(phenylsulfanyl)acenaphthyl- obtained by slow evaporation of a saturated solution of the
ene 7 was initially attempted following the procedure out- product in dichloromethane and for A0 by evaporation of
lined previously for the synthesis of analogous 5,6-bis(phen- a saturated hexane solution. Compound 13 contains two
ylchalcogeno)acenaphthenes A7–A10.[17] Compound 13 nearly identical molecules in the asymmetric unit, in con-
was first treated with tetramethylethylenediamine trast to the remaining members of the series, which crystal-
(TMEDA) (2.7 equiv.) and n-butyllithium (2.4 equiv.) to lise with one molecule in the asymmetric unit. The molecu-
afford the corresponding 5,6-dilithioacenaphthylene· lar structures of 2, 3, 5, 6, 8–10 and 13 are analysed together
2TMEDA complex, which was subsequently treated with here and compared with the structures of naphthalene and
two equivalents of diphenyl disulfide. The reaction, how- acenaphthene derivatives previously reported.[17,18] The mo-
ever, was unsuccessful and an alternative route to ace- lecular structures of A0 and A13 are also discussed. Se-
naphthylenes 1–12 was explored.
lected interatomic bond lengths and angles are listed in
Prompted by the ease of conversion of A13 into ace- Tables 2 and 3. Further crystallographic information can be
naphthylene 13, it was decided to first prepare acenaphth- found in the Supporting Information.
enes A1–A12[17] and then treat them with DDQ to dehydro-
The molecular structures of acenaphthylenes 2, 3, 5, 6,
genate the ethane backbone and afford the desired ace- 8–10 and 13 (Figure 2) are remarkably similar to their ace-
naphthylenes 1–12. Compounds A1–A12 were thus treated naphthene counterparts (A2, A3, A5, A6, A8–10 and
with DDQ (1.5 equiv.) by following the same procedure A13);[17] they exhibit identical phenyl and “naphthalene”
outlined above for the preparation of 13,[34] with 5,6-di- ring configurations and have comparable degrees of molec-
iodoacenaphthene A14 converted to acenaphthylene 14 in a ular distortion between corresponding compounds. Natu-
similar fashion. Conversion to the corresponding ace- rally, the ethane and ethene backbones of the acenaphthene
naphthylene was successful in each case and in moderate to and acenaphthylene derivatives have a noticeable impact on
good yields (12–71%), except, surprisingly, for the reaction their molecular geometry relative to the equivalent substi-
of mixed tellurium–selenium compound A12, which was tuted naphthalenes (N2, N3, N5, N6, N8–10 and N13).[18]
unsuccessful. 1H NMR spectroscopy revealed that the reac- This is most apparent when contrasting the degree to which
tion had formed an unsymmetrical acenaphthylene, as the each set of compounds deviates from an ideal geome-
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Table 2. Selected interatomic distances [Å] and angles [°] for compounds 2, 3, 5, 6, 8–10.
2
3
5
6
X,E
Br,Se
Br,Te
I,Se
I,Te
peri-Region distances
X1···E1
3.189(2)
85
3.260(4)
83
3.3324(9)
86
3.366(3)
83
[a]
% ΣrvdW
peri-Region bond angles
X1–C1–C10 [°]
C1–C10–C9 [°]
124.0(8)
131.3(9)
121.2(7)
376.5(14)
16.5
109.0(9)
177.07(1)
122.6(18)
134(3)
118.0(18)
374.6(22)
14.6
109(3)
169.40(1)
125.4(3)
132.2(4)
121.7(3)
379.3(6)
19.3
109.5(4)
174.72(1)
121.2(12)
131.7(17)
126.5(14)
379.4(25)
19.4
109.0(2)
170.03(1)
E1–C9–C10 [°]
Σ of bay angles
Splay angle[b] [°]
C4–C5–C6 [°]
X1–E1–C13 [°]
Out-of-plane displacement
X1
E1
–0.217(1)
0.190(1)
–0.258(1)
0.382(1)
–0.245(1)
0.183(1)
0.357(1)
–0.417(1)
Central naphthalene ring torsion angles
C: (6)–(5)–(10)–(1) [°]
C: (4)–(5)–(10)–(9) [°]
–175.1(8)
179.8(8)
–174(2)
–178(2)
175.6(4)
–179.7(4)
177.4(19)
172.4(19)
8
9
10
X,E
Se,Se
Te,Te
Se,S
peri-Region distances
E1···E2
3.191(3)
84
3.393(3)
82
3.144(3)
85
[a]
ΣrvdW [%]
peri-Region bond angles
E1–C1–C10 [°]
C1–C10–C9 [°]
123.4(11)
130.5(12)
122.5(12)
376.4(20)
16.4
109.0(12)
84.47(1)
176.6(1)
124.5(10)
131.2(13)
124.1(10)
379.8(19)
19.8
108.7(13)
92.99(1)
174.06(1)
122.8(6)
129.9(6)
123.0(5)
375.7(10)
15.7
108.4(6)
172.72(1)
94.35(1)
E2–C9–C10 [°]
Σ of bay angles
Splay angle[b] [°]
C4–C5–C6 [°]
E2–E1–C13 [°]
E1–E2–C19 [°]
Out-of-plane displacement
X1
E1
–0.213(1)
0.245(1)
0.306(1)
–0.387(1)
0.276(1)
–0.260(1)
Central naphthalene ring torsion angles
C: (6)–(5)–(10)–(1) [°]
C: (4)–(5)–(10)–(9) [°]
–177.1(14)
–177.0(14)
177.5(8)
175.2(8)
178.5(6)
177.4(6)
[a] Van der Waals radii used for calculations: rvdW(Br) = 1.85 Å, rvdW(I) = 1.98 Å, rvdW(S) = 1.80 Å, rvdW(Se) = 1.90 Å, rvdW(Te) =
2.06 Å.[35] [b] Splay angle: Σ of the three bay region angles: 360°.
Table 3. Selected interatomic distances [Å] and angles [°] for compounds 13, A0 and A13 (values in parentheses are for independent
molecules).
13
A0
A13
X,X
Br,Br
Br,Br
Br,Br
peri-Region distances
X1···X2
3.3387(6) [3.3195(6)]
90 [90]
3.462(3)
94
3.3052(11)
89
[a]
ΣrvdW [%]
peri-region bond angles
Br1–C1–C10 [°]
C1–C10–C9 [°]
124.0(2) [123.6(2)]
133.3(3) [133.6(3)]
124.44(19) [123.5(3)]
381.74(19) [380.7(5)]
21.7 [20.7]
120.2(12)
142.2(13)
119.6(11)
382.0(21)
22.0
124.3(3)
132.5(4)
123.8(4)
380.6(6)
20.6
Br2–C9–C10 [°]
Σ of bay angles
Splay angle[b] [°]
C4–C5–C6 [°]
124.0(2) [123.6(2)]
120.2(12)
111.0(4)
Out-of-plane displacement
X1
X2
–0.006(1) [-0.011(1)]
0.042(1) [0.029(1)]
0.192(1)
–0.196(1)
0.028(1)
–0.061(1)
Central naphthalene ring torsion angles
C: (6)–(5)–(10)–(1) [°]
C: (4)–(5)–(10)–(9) [°]
178.7(3) [–178.5(2)]
–178.1(3) [179.7(2)]
179.3(12)
179.4(13)
179.8(3)
178.9(3)
[a] Van der Waals radii used for calculations: rvdW(Br) = 1.85 Å.[35] [b] Splay angle: Σ of the three bay region angles: 360°.
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try[36–38] upon the introduction of the large chalcogen and tively];[17,37,38] however, unlike the naphthalenes, the bonds
halogen heteroatoms. The substituted naphthalene systems, around C10 retain their ideal length (average 1.43 and
without the restriction of a semi-rigid linker, have greater 1.44 Å, respectively).[17,37,38] In addition, the presence of the
freedom to deform to reduce the steric crowding that occurs ethane and ethene bridges blocks any possible distortion of
within the peri region. Elongation of the bonds around C10 the C4–C5–C6 angle, which remains close to ideal in both
(average 1.44 Å relative to the ideal 1.42 Å),[18,36] close to sets of compounds (average 112 and 109°, respec-
the site of steric repulsion, is accompanied by a natural in- tively).[17,37,38] The rigidity of the organic linkers also helps
crease in the C1–C10–C9 angular splay (average 128° rela- to reduce the distortion that occurs within the acenaphth-
tive to the ideal 118°),[18,36] although this is offset by a ene and acenaphthylene carbon frameworks, with central
minor reduction in the C4–C5–C6 angle (average 118° rela- C–C–C–C torsion angles averaging only 3° relative to 5° in
tive to the ideal 122°).[18,36] The most conspicuous deviation the naphthalene derivatives.
from ideality in the naphthalene systems is the reduction in
Akin to their naphthalene and acenaphthene analogues,
planarity of the carbon framework, with central naphthal- substituted acenaphthylenes 2, 3, 5, 6, 8–10 and 13 experi-
ene C–C–C–C torsion angles indicating a significant buck- ence additional out-of-plane displacement, with the peri
ling of the ring system is taking place (average 5° relative atoms lying 0.18–0.42 Å from the mean plane depending
to the ideal 0°).[18,36]
upon the bulk of the peri substituents. Further separation
is provided by in-plane tilting of the exocyclic peri bonds
with angles around C1 and C9 averaging 123° relative to
120° in the ideal acenaphthylene structure.[38] This, coupled
with the natural increase in the C1–C10–C9 angular splay
from the inclusion of the ethene bridge, results in greater
bay-region angles in the acenaphthylene compounds than
analogous acenaphthenes and naphthalenes (average splay
angles 17, 16 and 14°, respectively).[17,18] This is reflected in
the magnitude of the peri distances observed in each set of
compounds, which increase in the order naphthalenes to
acenaphthenes to acenaphthylenes (3.06–3.31 Å in N2, N3,
N5, N6, N8–10 and N13;[18] 3.11–3.38 Å in A2, A3, A5, A6,
A8–10 and A13;[17] 3.14–3.39 Å in 2, 3, 5, 6, 8–10 and 13).
Nevertheless, peri separations are still shorter than the sum
of van der Waals radii [3.60–4.12 Å][35] for the two inter-
acting atoms in all of the compounds studied.
Figure 2. The molecular structure of 2 (hydrogen atoms omitted
for clarity). The structures of 3, 5 and 6 (which adopt similar con-
formations) are omitted here but can be found in the Supporting
Information (Figure S1).
Acenaphthylenes 2, 3, 5, 6, 8–10 adopt identical configu-
rations to their acenaphthene counterparts,[17] previously
characterised, along with the naphthalene series,[18] accord-
The introduction of bridging ethane/ethene organic link- ing to the related classification systems devised by Nakani-
ers at the 1- and 2-positions of the naphthalene skeleton in shi et al.[10] and Nagy et al.[39] The absolute conformation
acenaphthene and acenaphthylene results in a minor re- of each structure is calculated from torsion angles θ and γ
duction in the planarity of the carbon framework, and nat- (Tables 4 and 5; Figure 4 and Figure S4 in the Supporting
urally compresses the C4–C5–C6 angle (naphthalene 122°, Information), which describe the relative alignment of the
acenaphthene 112°, acenaphthylene 109°).[36–38] In both E(“naphthalene”) and E(phenyl) rings with respect to the
compounds this coincides with a significant widening of the C(ar)–E–C(ar) planes.[10,39]
bay region, augmented by an increase in the C1–C10–C9
The equatorial type B configuration adopted by mono-
angle (acenaphthene 127°, acenaphthylene 128°, cf. naphth- substituted acenaphthylenes 2, 3, 5 and 6 (Table 4, Fig-
alene 122°).[36–38] The exocyclic peri-hydrogen atoms are ure 4), in which the E–CPh bond aligns along the mean
thus divergent and no longer parallel, subsequently increas- plane of the molecule,[10,39] corresponds to the general trend
ing the ideal peri distance to approximately 2.7 Å in both observed for analogous Se and Te acenaphthene and
acenaphthene and acenaphthylene (cf. naphthalene naphthalene derivatives.[17,18] This promotes a quasi-linear
2.4 Å).[36–38] This natural increase in peri separation in the three-body fragment with X···E–CPh angles (ψ) in the range
unsubstituted compounds is reflected in the series of substi- 169–177° (Figure 4). Independent of the form of the
tuted acenaphthenes (A2, A3, A5, A6, A8–10 and A13)[17] “naphthalene” backbone, substitution of larger congeners
and acenaphthylenes (2, 3, 5, 6, 8–10 and 13), which exhibit into the congested peri region leads to a build up of steric
less deviation from ideality relative to analogous naphthal- pressure, which is alleviated by molecular distortion. In
ene derivatives. Nevertheless, in both series, and in line with each class of compounds, a steady increase in the peri dis-
their naphthalene analogues, substitution of the heavy halo- tance is observed as bromine and selenium are sequentially
gen and chalcogen moieties requires further widening of the replaced by iodine and tellurium, respectively [N2
C1–C10–C9 angle [average 131° (acenaphthene) and 132° 3.1136(6) Å to N6 3.3146(6) Å;[18] A2 3.1588(16) Å to A6
(acenaphthylene) relative to the ideal 127 and 128°, respec- 3.3721(17) Å;[17] 2 3.189(2) Å to 6 3.366(3) Å; Figure 3], in-
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Table 4. Torsion angles [°] categorising the acenaphthylene and phenyl ring conformations in 2, 3, 5 and 6.
Acenaphthylene ring conformations
Phenyl ring conformations
Torsion angle [°]
C10–C9–E1–C13
C9–E1–C13–C14
2
3
5
θ1 –167.8(7) Acenapyl1[a]: equatorial[d]
θ1 –161.4(17) Acenapyl1: equatorial
θ1 –167.7(3) Acenapyl1: equatorial
γ1 84.8(7) Ph1[b]: axial[c]
γ1 100.4(18) Ph1: axial
γ1 84.4(3) Ph1: axial
[a] Acenapyl1: acenaphthylene ring E1. [b] Ph1: E1 phenyl ring. [c] Axial: perpendicular to the C(ar)–E–C(ar) plane. [d] Equatorial: copla-
nar with the C(ar)–E–C(ar) plane.[39]
Table 5. Torsion angles [°] categorising the acenaphthylene and phenyl ring conformations in 8, 9 and 10.
Acenaphthylene ring conformations
Phenyl ring conformations
C1–E1–C13–C14 C9–E2–C19–C20
Torsion angle [°]
8
C10–C1–E1–C13
C10–C9–E2–C19
θ2 –174.0(12)
θ1 –75.7(13)
γ1 156.2(14)
Ph1[c]: equatorial
γ1 –159.2(8)
Ph1: equatorial
γ1 99.2(6)
γ2 84.6(10)
Ph2[d]: axial
γ2 86.1(10)
Ph2: axial
γ2 –165.8(5)
Ph2: equatorial
Acenapyl1[a]: axial[e]
θ1 78.8(7)
Acenapyl2[b]: equatorial[f]
θ2 166.2(7)
9
Acenapyl1: axial
θ1 161.9(5)
Acenap1: equatorial
Acenapyl2: equatorial
θ2 82.1(5)
Acenap2: axial
10
Ph1: axial
[a] Acenapyl1: acenaphthylene ring E1. [b] Acenapyl2: acenaphthylene ring E2. [c] Ph1: E1 phenyl ring. [d] Ph2: E2 phenyl ring. [e] Axial:
perpendicular to the C(ar)–E–C(ar) plane. [f] Equatorial: coplanar with the C(ar)–E–C(ar) plane.[39]
fluenced in part by an increasingly large and positive splay (Table 5, Figure 4).[17,18] The AB conformation positions
of the exocyclic X–CAcenapyl and E–CAcenapyl bonds (N2–N6 one of the E–CPh bonds perpendicular to the mean ace-
13–16°;[18] A2–A6 15–18°;[17] 2–6 17–19°). These figures also naphthylene plane whilst aligning the other E–CPh bond
reflect the influence of the ethane and ethene backbones, along the plane of the molecule, and gives rise to a quasi-
with significantly wider peri separations observed for the linear three-centre E···EЈ–CPh-type fragment. In all cases ψ
acenaphthenes and acenaphthylenes relative to their
naphthalene equivalents.
Figure 3. Independent of the backbone, increasing peri distances
are observed as larger heteroatoms occupy the close peri positions,
although acenaphthenes and acenaphthylenes display greater sepa-
rations than naphthalene derivatives (naphthalenes: diamonds; ace-
naphthenes: squares; acenaphthylenes: triangles).
The mutual axial–equatorial orientation of the ace-
naphthyl and phenyl rings, characteristic of the type AB
configuration,[10] gives the structures of 8–10 an “aircraft-
like” appearance, commonly associated with diaryl sulf-
Figure 4. The orientation of the E(phenyl) groups, the quasi-linear
arrangements and structural conformations of acenaphthylenes 2,
ides[39] and seen in previously reported bis- and mixed-
chalcogen naphthalene and acenaphthene analogues 3, 5, 6, 8–10.
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approaches 180° (173–177°), and nonbonded peri distances value of 0.14 for the bis-tellurium species A9.[17,18] Similar,
are within the sum of van der Waals radii for the two inter- attractive donor–acceptor 3c–4e-type interactions are pre-
acting chalcogen atoms. It is worth noting that 5,6-bis- dicted to occur in acenaphthylenes 2, 3, 5, 6, 8–10, all of
(phenyltelluro)naphthalene N9 is the one anomaly amongst which adopt either the type B or type AB configuration.
this group of compounds that choose to adopt the margin-
To complement our previous results on the naphthalene
and acenaphthene series, we optimised the ditelluride 9 in
ally different CC–t type configuration.[17]
Acenaphthylenes 8–10, which differ only by chalcogen both AB and CC-t conformations at the B3LYP/SDD/6-
type and not by configuration, conform to the accepted rule 31+G* level of density functional theory (DFT). At that
that increasing the bulk of the substituents that reside in the level, (chosen for compatibility with our previous calcula-
peri region will result in an increase in molecular distortion. tions on the naphthalene and acenaphthene series),[17] both
When compared in conjunction with their acenaphthene are very close in energy (within less than 1 kJmol–1), with
and naphthalene counterparts, this trend is extended to the AB form observed in the crystal being the more stable
each set of compounds irrespective of the backbone, with (see Table S14 in the Supporting Information). The trend
peri distances [N10 3.063(2) Å to N9 3.3287(1) Å; A10 towards longer Te···Te separations on going from N9 to 9
3.113(4) Å to A9 3.3674(19) Å; 10 3.144(3) Å to
9
is captured well in the computations (from 3.34 to 3.44 Å,
3.393(3) Å][17,18] and corresponding splay angles (N10 12.4° respectively, with A9 lying in between). However, the calcu-
to N9 15.0°; A10 12.7° to A9 18.4°; 10 15.7° to 9 19.8°)[17,18] lated WBI decreases only marginally, from 0.14 to 0.13,
steadily increasing in each case as the heavier congeners are within this series; the same trends are seen for the other
located in close proximity. This coincides with the expected dichalcogenides from the present study that have been
change in structural deformation across the series for corre- structurally characterised (see Table S14 in the Supporting
sponding compounds, with a notable increase in distortion Information). The donor–acceptor interaction from a lone
associated with changing the naphthalene backbone for pair on one Te into a σ*(Te–C) antibonding orbital of the
acenaphthene and acenaphthylene, respectively [N10 other TePh moiety, which was identified for A9,[17] is thus
3.063(2) Å, A10 3.113(4) Å, 10 3.144(3) Å; N8 3.1322(9) Å, present in the acenaphthylene derivative as well. According
A8 3.1834(10) Å,
3.3674(19) Å, 9 3.393(3) Å].[17,18]
Although the nature of the organic backbone and the tially the same in A9 and 9, namely, 47 kJmol–1.
size of the heteroatoms located at the peri positions play an An additional calculation on the elusive mixed Te–Se
8
3.191(3) Å; N9 3.287(1) Å, A9 to second-order perturbation analysis of the natural bond
orbitals (NBOs),[41] the energy of this interaction is essen-
important role in determining the molecular geometry of compound 12 furnished no apparent reason why it should
these systems, the number, size and location of the func- not be formed: structural properties are as expected [i.e., in
tional groups attached to the peri atoms are also highly in- between those of the bis-selenium and bis-tellurium conge-
fluential.[17] The conformation of the aromatic ring systems ners (see Table S14 in the Supporting Information)], and
and by inference the location and interaction of the chalco- the stability is comparable to the corresponding driving
gen and halogen lone pairs has been shown to dictate the force that leads to the Te–S species 11 [Equation (1)] relative
geometry of the peri region in naphthalenes N1–N12 and to the latter [Equation (2)], which can be isolated.[42]
acenaphthenes A1–A12.[18,17] The contrast observed in peri
C12H6(TePh)2 (9) + C12H6(SPh)2 (7)Ǟ2 C12H6(TePh)(SPh) (11),
separation between differing conformers of the peri-substi-
ΔE = –22.0 kJmol–1
(1)
tuted phenyl group can be correlated to the ability of the
frontier orbitals of the halogen or chalcogen atoms to take
part in attractive or repulsive interactions. Repulsion be-
tween p-type lone pairs was found to be less pronounced
when the conformation of the respective compound con-
formed to a type B or type AB configuration.[10,17,18,39]
C12H6(TePh)2 (9) + C12H6(SePh)2 (8)Ǟ2 C12H6(TePh)(SePh) (12),
ΔE = –15.6 kJmol–1
(2)
Similar to its acenaphthene analogue, bis-telluride 9
In this situation, torsion angles (θ) approach 180°, which packs with short intermolecular contacts between Te atoms
corresponds to an equatorial “naphthalene” ring conforma- of neighbouring molecules to construct Te4 parallelograms.
tion, and the axis of the p orbitals aligns parallel and verti- The strictly planar Te4 rhombus core contains two unequal
cal to the aromatic system.[39] In addition, the existence of Te···Te nonbonded distances and interior angles sum to
a quasi-linear G···E–CPh (G = Br, I, S, Se, Te) three-body 360°. The intermolecular Te···Te separation [3.843(1) Å] is
fragment exhibited by this type of configuration was shown longer than the nonbonded intramolecular peri distance
to provide an attractive component for the G···E interac- [3.393(3) Å]; however, both distances are shorter than twice
tion. Density functional studies confirmed these weak do- the van der Waals radius of tellurium (4.12 Å) (Figure 5).[35]
nor–acceptor interactions in type AB conformers, which No similar intermolecular arrangement is observed in SeSe
promoted the delocalisation of a p-type lone pair (G) to (8) or SeS (10) derivatives.
the antibonding σ*(E–C) orbital, thus forming an attractive
Compounds 13 and A0 were first prepared by Pretenko
three-centre four-electron (3c–4e)-type interaction.[16,17,18] et al.[29] in 1967, and despite their use in the years to follow,
This was shown to become more prevalent as heavier conge- no molecular structure data have yet been published. The
ners were introduced along the series, with increasingly structure of 13 is, at first sight, remarkably similar to its
large Wiberg bond index (WBI)[40] values obtained, up to a acenaphthene analogue A13,: a planar molecule that con-
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The substitution of two additional bromine atoms onto
the ethane bridge in 1,2,5,6-tetrabromoacenaphthene A0
dramatically transforms the geometry of the carbon frame-
work by inducing greater molecular distortion to accommo-
date the extra steric bulk (Figure 7). A marked expansion
of the C4–C5–C6 angle [120.2(12)° cf. A13 111.0(4)°] and
the C1–C10–C9 angular splay [142.2(13)° cf. A13 132.5(4)°]
naturally constricts the C5–C10 bond, which compresses to
1.239(18) Å, comparable in length to a standard C=C
double bond and much shorter than that found in A13
[1.418(6) Å]. The increased splay of the two exocyclic Br–
CAcenap bonds (22.0° cf. A13 20.6°), coupled with the dis-
placement of the peri-bromine atoms to opposite sides of
the mean acenaphthene plane (ca. 0.2 Å), increases the sep-
aration across the bay region to 3.462(3) Å [cf. A13
3.3052(11) Å], only 6% shorter than the sum of the van der
Waals radii (3.70 Å).[35] The presence of the two additional
bromine atoms, which occupy remote positions 2.114(1) Å
above (Br3) and 2.077(1) Å below (Br4) the plane, respec-
tively, causes the C11–C12 bond of the ethane bridge to
extend to 1.59(2) Å [cf. A13 1.561(8) Å]. Interestingly, the
Br3–C11 [2.066(15) Å] and the Br4–C12 [2.078(14) Å]
bonds are considerably longer than those associated with
the peri-bromine atoms [Br1–C1 1.724(17) Å; Br2–C9
1.694(14) Å].
Figure 5. Short intermolecular contacts between neighbouring mo-
lecules of 9 form planar Te4 parallelogram units with Te···Te sepa-
rations within the sum of van der Waals radii. The structures of 8
and 10, displaying similar AB configurations, can be found in the
Supporting Information.
tains negligible out-of-plane distortion in which the
bromine atoms are essentially located on the mean ace-
naphthylene plane (displacements Ͻ 0.1 Å; C–C–C–C tor-
sion angles Ͻ 2°; Figure 6). On closer inspection, structural
changes are observed within the carbon skeleton caused by
the presence of the C=C double bond {1.322(5) Å
[1.359(5) Å]}, which coincides with a greater in-plane dis-
tortion that occurs in the bay region.
Figure 7. The molecular structure of A0 (hydrogen atoms omitted
for clarity).
Figure 6. The structure of 13 contains two independent molecules
in the asymmetric unit (H atoms omitted for clarity). The corre-
sponding structure of A13 is omitted here but can be found in the
ESI (Figure S3 in the Supporting Information).
Conclusion
peri-Substituted acenaphthylenes [Acenapyl(X)(EPh)] (X
Contraction of the C4–C5–C6 angle [13 109.5(2)° = Br, I; E = S, Se, Te) 1–6, [Acenapyl(EPh)(EЈPh)] (E/EЈ =
[109.5(3)°]; A13 111.0(4)°] is accompanied by a natural in- S, Se, Te) 7–11 and [Acenapyl(X)2] (X = Br, I) 13, 14 have
crease in the C1–C10–C9 angular splay [13 133.3(3)° been prepared from corresponding acenaphthenes A1–A14
[133.6(3)°]; A13 132.5(4)°] with the C5–C10 bond reducing by using DDQ to perform the dehydrogenation of the eth-
accordingly from 1.418(6) in A13[17] to 1.410(4) Å ane backbone.[34] Crystal structures determined for 2, 3, 5,
[1.417(5) Å] in 13. Further widening of the exocyclic Br– 6, 8–10 were analysed and compared with previously re-
CAcenapyl bonds results in a larger observed splay angle (13 ported analogous naphthalenes N1–N12[18] and acenaphth-
21.7° [20.7°]; cf. A13 20.6°) and increases the separation be- enes A1–A12.[17] In addition, 1,2,5,6-tetrabromo-1,2-di-
tween the two bromine atoms that now lie 3.3387(6) Å hydroacenaphthylene A0[28] was synthesised as an interme-
[3.3195(6) Å] apart [cf. A13 3.3052(11) Å].
diate in the preparation of 13 and crystal structures deter-
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(1.30 g, 74%); m.p. 148–150 °C. 1H NMR (300 MHz, CDCl3,
mined for 13 and A0 were contrasted with the structure of
5,6-dibromoacenaphthene A13.
The series of acenaphthylenes are unremarkable and re-
veal similar trends to those found in acenaphthene ana-
logues, with increased molecular distortion associated with
an increase in steric bulk within the peri region. Under ap-
propriate geometric conditions, quasi-linear three-body
3
25 °C, Me4Si): δ = 8.00 [d, JH,H = 7.5 Hz, 2 H, Acenap 4,7-H],
3
7.42 [d, JH,H = 7.5 Hz, 2 H, Acenap 3,8-H], 5.86 (s, 2 H, Acenap
9,10-H) ppm. 13C NMR (75.5 MHz, CDCl3, 25 °C, Me4Si): δ =
141.5 (q), 137.0 (s), 136.7 (q), 127.7 (q), 124.2 (s), 119.3 (q), 53.2
(s) ppm. MS (ES+): m/z (%) = 309.76 (100) [M + H]. C12H6Br4: C
30.9, H 1.3; found C 31.1, H 1.3.
[Acenapyl(Br2)] (13): A solution of A0 (0.32 g, 0.69 mmol), zinc
powder (0.22 g, 3.43 mmol) and glacial acetic acid (50 mL) was
heated to reflux for 4 h, cooled and filtered. The yellow filtrate
was washed with saturated aqueous sodium hydrogen carbonate
(2ϫ50 mL), dried (MgSO4), filtered and concentrated under re-
duced pressure to give an orange solid. An analytically pure sample
was obtained by recrystallisation from hexane (0.18 g, 86%); m.p.
80–82 °C. 1H NMR (300 MHz, CDCl3, 25 °C, Me4Si): δ = 7.86 [d,
C
Ph–E···Z (E = Te, Se, S; Z = Br/E) fragments provide an
attractive component for the E···Z interaction. DFT studies
map the trend towards longer E···E separations on going
from naphthalenes to acenaphthenes to acenaphthylenes;
however, calculated WBIs decrease only marginally between
the series. DFT calculations also confirm the onset of for-
mation of 3c–4e bonding, with the donor–acceptor interac-
tion [from a Te lone pair into a σ*(Te–C) antibonding or-
bital of the neighbouring TePh] reported for A9,[17] also
identified in the acenaphthylene derivatives and similar in
extent, despite an increase in the peri distances.
3
3JH,H = 7.4 Hz, 2 H, Acenapyl 4,7-H], 7.39 [d, JH,H = 7.4 Hz, 2
H, Acenapyl 3,8-H], 6.91 (s, 2 H, Acenapyl 9,10-H) ppm. 13C NMR
(75.5 MHz, CDCl3, 25 °C, Me4Si): δ = 140.4 (q), 135.5 (s), 129.6
(q), 129.2 (s), 126.5 (q), 125.3 (s), 121.1 (q) ppm. MS (ES+): m/z
(%) = 310.89 (100) [M + H]. C12H6Br2: C 46.5, H 1.95; found C
46.4, H 2.0.
Experimental Section
An alternative route to 13 following a modification of the pro-
cedure described by Mitchell and co-workers:[34] DDQ (10.9 g,
48.1 mmol) was added to a stirred solution of 5,6-dibromoace-
naphthene A13 (10.0 g, 32.1 mmol) in benzene (250 mL) and the
mixture was heated under reflux conditions for 24 h. After cooling
to room temperature, pentane (200 mL) was added and the mixture
was filtered. The filtrate was passed through a short column of
silica with a pentane eluent. The resulting solution was then evapo-
rated under reduced pressure to yield the title compound as a yel-
low solid. An analytically pure sample was obtained by recrystalli-
sation from diffusion of hexane into a saturated solution of the
compound in dichloromethane to give yellow crystals (0.16 g,
20%).
General: All experiments were carried out under an oxygen- and
moisture-free nitrogen atmosphere using standard Schlenk tech-
niques and glassware. Reagents were obtained from commercial
sources and used as received. Dry solvents were collected with a
MBraun solvent system. Elemental analyses were performed by
Stephen Boyer at the London Metropolitan University. Infrared
spectra were recorded for solids as KBr discs and oils on NaCl
plates in the range 4000–300 cm–1 with a Perkin–Elmer System
2000 Fourier transform spectrometer. 1H and 13C NMR spectra
were recorded with a Bruker Avance 300 MHz spectrometer with
δ(H) and δ(C) referenced to external Me4Si. 77Se and 125Te NMR
spectra were recorded with a Jeol GSX 270 MHz spectrometer with
δ(Se) and δ(Te) referenced to external Me2Se and Me2Te respec-
tively, with a secondary reference for δ(Te) to diphenyl ditelluride
[Acenapyl(SPh)(Br)] (1): Compound 1 was synthesised by the
method described for 13 but with DDQ (1.05 g, 4.63 mmol) and
[Acenap(SPh)(Br)] A1 (1.00 g, 2.93 mmol) to yield a red solid
[δ(Te) = 428 ppm]. Assignments of 13C and H NMR spectra were
1
1
(0.48 g, 48%); m.p. 80–82 °C. H NMR (300 MHz, CDCl3, 25 °C,
made with the help of H–H COSY and HSQC experiments. All
measurements were performed at 25 °C. All values reported for
NMR spectroscopy are in parts per million. Coupling constants
(J) are given in hertz. Mass spectrometry was performed by the
University of St. Andrews Mass Spectrometry Service for 2, 3, 5,
6, 8–10 and A0. Electrospray mass spectrometry (ESMS) was car-
ried out with a Micromass LCT orthogonal accelerator time-of-
flight mass spectrometer. Mass spectrometry for 13 and 14 was
carried out at the EPSRC National Mass Spectrometry Service in
Swansea. The isotopic distribution patterns of the respective frag-
ment ions were confirmed using IsoPro 3.1 MS simulation soft-
ware;[43] however, in each case only the most abundant isotopic
peak for each fragment ion is reported. Acenaphthene precursors
(A1–A12,[17] 5,6-dibromoacenaphthene A13[20] and 5,6-diiodoace-
naphthene A14)[30] were prepared following standard literature pro-
cedures.
Me4Si): δ = 7.69 [d, 3JH,H = 7.4 Hz, 1 H, Acenapyl 4-H], 7.36–7.23
3
(m, 7 H, Acenapyl 3,8-H, SPh 12–16-H) 7.05 [d, JH,H = 7.4 Hz, 1
H, Acenapyl 7-H], 6.79 (s, 2 H, 2ϫCH) ppm. 13C NMR
(75.5 MHz, CDCl3, 25 °C, Me4Si): δ = 140.3 (q), 139.1 (q), 138.6
(q), 135.8 (q), 134.7 (s), 133.8 (s), 13.3 (q), 131.0 (s), 129.3 (s,
CHϫ2), 128.7 (s), 128.65 (s), 127.1 (q), 125.3 (s), 125.25 (s), 120.7
(q) ppm. MS (ES+): m/z (%) = 701.09 (100) [2M + Na], 260.12 (50)
[M – Br]. C18H11BrS (339.25): calcd. C 63.7, H 3.3; found C 63.7,
H 3.4.
[Acenapyl(SePh)(Br)] (2): Compound 2 was synthesised by the
method described for 13 but with DDQ (0.86 g, 3.81 mmol) and
[Acenap(SePh)(Br)] A2 (1.00 g, 2.59 mmol) to yield an orange so-
lid, which was recrystallised from evaporation of dichloromethane
to give yellow crystals (0.18 g, 18%); m.p. 100–102 °C. 1H NMR
3
(300 MHz, CDCl3, 25 °C, Me4Si): δ = 7.86 [d, JH,H = 7.2 Hz, 1
1,2,5,6-Tetrabromoacenaphthene (A0): A solution of 5,6-dibromo-
acenaphthene (1.18 g, 3.77 mmol), N-bromosuccinimide (1.48 g,
8.29 mmol), benzoyl peroxide (0.20 g, 0.83 mmol) and chloroform
(40 mL) was heated to reflux for 5 h under an atmosphere of nitro-
gen, cooled, washed with saturated aqueous sodium hydrogen carb-
H, Acenapyl 4-H], 7.84–7.82 (m, 2 H, SePh 12,16-H), 7.55–7.51
(m, 3 H, SePh 13–15-H), 7.43 [d, 3JH,H = 7.3 Hz, 1 H, Acenapyl 3-
3
3
H], 7.32 [d, JH,H = 7.6 Hz, 1 H, Acenapyl 7-H], 7.23 [d, JH,H
=
3
7.6 Hz, 1 H, Acenapyl 8-H], 6.97 [d, JH,H = 5.3 Hz, 1 H, CH],
3
6.94 [d, JH,H = 5.3 Hz, 1 H, CH] ppm. 13C NMR (75.5 MHz,
onate (3ϫ50 mL), dried (MgSO4), filtered and concentrated under CDCl3; 25 °C, Me4Si): δ = 140.6 (q), 138.7 (q), 137.6 (s), 137.1 (q),
reduced pressure to give an orange solid. The crude solid was puri-
fied by column chromatography with a hexane eluent and an ana-
lytically pure sample was obtained by recrystallisation from hexane
133.9 (s), 131.6 (q), 130.6 (s), 130.5 (q), 130.4 (s), 129.7 (s), 129.5
(s, CH), 128.2 (q), 128.1 (s, CH), 125.6 (s), 125.2 (s), 121.8 (q) ppm.
77Se NMR (51.5 MHz, CDCl3, 25 °C, MeSeSeMe): δ = 448 (s)
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ppm. MS (ES+): m/z (%) = 386.95 (50) [M + H]. C18H11BrSe
(386.15): calcd. C 56.0, H 2.9; found C 55.9, H 2.85.
(s), 130.6 (s), 129.6 (s, CH), 127.9 (s, CH), 125.6 (s), 120.7 (q),
118.8 (q), 97.7 (q) ppm. 125Te NMR (81.2 MHz, CDCl3, 25 °C,
MeTeTeMe): δ = 687 (s) ppm. MS (ES+): m/z (%) = 512.91 (95)
[M + OMe]. C18H11ITe (481.79): calcd. C 44.9, H 2.3; found C
44.9, H 2.3.
[Acenapyl(TePh)(Br)] (3): Compound 3 was synthesised by the
method described for 13 but with DDQ (0.57 g, 2.49 mmol) and
[Acenap(TePh)(Br)] A3 (0.73 g, 1.66 mmol) to yield an orange so-
lid, which was recrystallised by diffusion of hexane into a saturated
solution of the compound in dichloromethane to give red crystals
(0.17 g, 23%); m.p. 105–107 °C. 1H NMR (300 MHz, CDCl3,
[Acenapyl(SPh)2] (7): Compound 7 was synthesised by the method
described for 13 but with DDQ (0.93 g, 4.11 mmol) and [Acenap-
(SPh)2] A7 (1.04 g, 2.81 mmol) to afford a dark yellow solid (0.61 g,
25 °C, Me4Si): δ = 7.91–7.86 (m, 2 H, TePh 12,16-H), 7.67 [d, 3JH,H 58%); m.p. 169–171 °C. 1H NMR (300 MHz, CDCl3, 25 °C,
= 7.3 Hz, 1 H, Acenapyl 4-H], 7.42–7.36 (m, 1 H, TePh 14-H), Me4Si): δ = 7.38 [d, JH,H = 7.3 Hz, 2 H, Acenapyl 4,7-H], 7.33–
3
3
7.33–7.25 (m, 3 H, Acenapyl 3-H, TePh 13,15-H), 7.23 [d, JH,H
=
7.16 (m, 12 H, Acenapyl 3,8-H, SPh 12–16-H), 6.87 (s, 2 H, Acena-
pyl 9,10-H) ppm. 13C NMR (75.5 MHz, CDCl3, 25 °C, Me4Si): δ
= 148.2 (q), 136.4 (q), 132.6 (s), 132.4 (s), 131.1 (q), 129.8 (s), 129.6
(q), 129.0 (s, CHϫ2), 127.9 (s), 127.0 (q), 125.0 (s), 120.8 (q) ppm.
7.4 Hz, 1 H, Acenapyl 7-H], 7.08 [d, 3JH,H = 7.4 Hz, 1 H, Acenapyl
3
3
8-H], 6.81 [d, JH,H = 5.3 Hz, 1 H, CH], 6.74 [d, JH,H = 5.3 Hz, 1
H, CH] ppm. 13C NMR (75.5 MHz, CDCl3, 25 °C, Me4Si): δ =
141.9 (s), 141.1 (q), 139.3 (q), 135.0 (s), 133.1 (s), 131.8 (q), 130.6 MS (ES+): m/z (%) = 390.79 (100) [M + Na]. C24H16S2 (368.51):
(s), 129.7 (s), 129.5 (s), 127.8 (s, CH), 125.6 (s, CH), 125.0 (s), 123.4
(q), 121.8 (q), 118.8 (q), 30.5 (q) ppm. 125Te NMR (81.2 MHz,
CDCl3, 25 °C, MeTeTeMe): δ = 724 (s) ppm. MS (ES+): m/z (%)
= 466.87 (100) [M + OMe], 435.90 (40), [M + H]. C18H11BrTe
(434.79): calcd. C 49.7, H 2.6; found C 49.6, H 2.6.
calcd. C 78.2, H 4.4; found C 78.1, H 4.5.
[Acenapyl(SePh)2] (8): Compound 8 was synthesised by the method
described for 13 but with DDQ (0.74 g, 3.26 mmol) and [Acenap-
(SePh)2] A8 (1.01 g, 2.16 mmol) to yield an orange solid, which was
recrystallised from diffusion of hexane into a saturated solution of
the compound in dichloromethane to give orange crystals (0.53 g,
[Acenapyl(SPh)(I)] (4): Compound 4 was synthesised by the
method described for 13 but with DDQ (0.41 g, 1.81 mmol) and
[Acenap(SPh)(I)] A4 (0.46 g, 1.19 mmol) to yield a brown oil
1
53%); m.p. 82–84 °C. H NMR (300 MHz, CDCl3, 25 °C, Me4Si):
3
δ = 7.73–7.69 (m, 2 H, SePh 12,16-H), 7.67 [d, JH,H = 7.7 Hz, 2
(0.17 g, 37%). 1H NMR (300 MHz, CDCl3, 25 °C, Me4Si): δ = 8.38 H, Acenapyl 3,8-H], 7.50 [d, JH,H = 7.7 Hz, 2 H, Acenapyl 4,7-
3
[d, 3JH,H = 7.3 Hz, 1 H, Acenapyl 4-H], 7.60–7.38 (m, 7 H, Acena-
H], 7.46–7.44 (m, 3 H, SePh 13–15-H), 7.05 (s, 2 H, Acenapyl 9,10-
H) ppm. 13C NMR (75.5 MHz, CDCl3, 25 °C, Me4Si): δ = 140.3
(q), 135.05 (s), 134.7 (s), 134.3 (q), 133.6 (q), 131.4 (q), 131.2 (q),
130.2 (s), 129.2 (s, CHϫ2), 128.5 (s), 125.3 (s) ppm. 77Se NMR
(51.5 MHz, CDCl3; 25 °C, MeSeSeMe): δ = 428 (s) ppm. MS
(ES+): m/z (%) = 463.78 (100) [M + H]. C24H16Se2 (462.31): calcd.
C 62.4, H 3.5; found C 62.3, H 3.55.
3
pyl 7,8-H, SPh 12–16-H), 7.30 [d, JH,H = 7.3 Hz, 1 H, Acenapyl
3
3
3-H], 7.05 [d, JH,H = 5.3 Hz, 1 H, CH], 6.99 [d, JH,H = 5.3 Hz, 1
H, CH] ppm. 13C NMR (75.5 MHz, CDCl3, 25 °C, Me4Si): δ =
143.9 (s), 141.3 (q), 140.8 (q), 137.1 (q), 136.8 (q), 134.1 (s), 132.2
(s), 131.1 (q), 130.2 (s), 129.7 (q), 129.5 (s, CH), 129.4 (s, CH),
128.0 (s), 126.0 (s), 125.42 (s), 92.5 (q) ppm. MS (ES+): m/z (%) =
259.03 (100) [M – I]. C18H11BrS (339.25): calcd. C 56.0, H 2.9;
found C 55.9, H 2.8.
[Acenapyl(TePh)2] (9): Compound 9 was synthesised by the method
described for 13 but with DDQ (0.30 g, 1.32 mmol) and [Acenap-
(TePh)2] A9 (0.50 g, 0.89 mmol) to yield a red solid which was
recrystallised by evaporation of dichloromethane to afford red crys-
[Acenapyl(SePh)(I)] (5): Compound 5 was synthesised by the
method described for 13 but with DDQ (0.18 g, 0.78 mmol) and
[Acenap(SePh)(I)] A5 (0.22 g, 0.51 mmol) to yield an orange solid,
which was recrystallised by diffusion of hexane into a saturated
solution of the compound in dichloromethane to give yellow crys-
tals (0.08 g, 34%); m.p. 83–85 °C. 1H NMR (300 MHz, CDCl3,
1
tals (0.22 g, 45%); m.p. 123–125 °C. H NMR (300 MHz, CDCl3,
3
25 °C, Me4Si): δ = 7.80 [d, JH,H = 7.2 Hz, 2 H, Acenapyl 4,7-H],
7.69–7.62 (m, 2 H, TePh 12,16-H), 7.23–7.13 (m, 5 H, Acenapyl
3,8-H, TePh 13–15-H), 6.78 (s, 2 H, Acenapyl 9,10-H) ppm. 13C
NMR (75.5 MHz, CDCl3, 25 °C, Me4Si): δ = 141.4 (s), 138.6 (s),
3
25 °C, Me4Si): δ = 8.10 [d, JH,H = 7.3 Hz, 1 H, Acenapyl 4-H],
7.55–7.52 (m, 2 H, SePh 12,16-H), 7.32–7.23 (m, 3 H, SePh 13–15- 136.4 (q), 131.0 (q), 130.2 (s), 129.2 (s, CHϫ2), 128.6 (s), 125.3
H), 7.17–7.09 (m, 3 H, Acenapyl 3,7,8-H), 6.75 [d, 3JH,H = 5.3 Hz,
(s), 121.9 (q), 121.6 (q), 120.0 (q) ppm. 125Te NMR (81.2 MHz,
3
1 H, CH], 6.72 [d, JH,H = 5.3 Hz, 1 H, CH] ppm. 13C NMR CDCl3; 25 °C, MeTeTeMe): δ = 618 (s) ppm. 123Te NMR
4
(75.5 MHz, CDCl3, 25 °C, Me4Si): δ = 142.6 (s), 141.3 (q), 139.6
(q), 136.8 (s), 131.9 (s), 131.7 (q), 131.5 (q), 131.2 (q), 130.4 (s),
(70.7 MHz, CDCl3, 25 °C, MeTeTeMe): δ = 619 [s, J(123Te,125Te)
1706] ppm. MS (ES+): m/z (%) = 590.96 (100) [M + OMe], 484.93
129.3 (s, CH), 128.8 (s), 128.3 (s, CH), 125.6 (s), 125.4 (s), 30.2 (q) (62) [M – Ph]. C24H16Te2 (559.59): calcd. C 51.5, H 2.9; found C
ppm. 77Se NMR (51.5 MHz, CDCl3, 25 °C, MeSeSeMe): δ = 427
(s) ppm. MS (ES+): m/z (%) = 464.89 (100) [M + OMe]. C18H11IS
(386.25): calcd. C 49.9, H 2.6; found C 49.8, H 2.6.
51.2, H 3.0.
[Acenapyl(SePh)(SPh)] (10): Compound 10 was synthesised by the
method described for 13 but with DDQ (0.45 g, 1.98 mmol) and
[Acenap(SePh)(SPh)] A10 (0.52 g, 1.25 mmol) to yield an yellow
solid, which was recrystallised from evaporation of dichlorometh-
ane to give red crystals (0.16 g, 31%); m.p. 75–77 °C. 1H NMR
[Acenapyl(TePh)(I)] (6): Compound 6 was synthesised by the
method described for 13 but with DDQ (0.88 g, 3.85 mmol) and
[Acenap(TePh)(I)] A6 (1.22 g, 2.52 mmol) to yield an orange solid,
which was recrystallised by diffusion of hexane into a saturated
solution of the compound in dichloromethane to give orange crys-
3
(300 MHz, CDCl3, 25 °C, Me4Si): δ = 7.88 [d, JH,H = 7.2 Hz, 1
H, Acenapyl 4-H], 7.87–7.82 (m, 2 H, SePh 12,16-H), 7.68 [d, 3JH,H
= 7.2 Hz, 1 H, Acenapyl 3-H], 7.60–7.48 (m, 3 H, SePh 13–15-H),
1
tals (0.87 g, 71%); m.p. 134–136 °C. H NMR (300 MHz, CDCl3,
3
3
25 °C, Me4Si): δ = 8.03 [d, JH,H = 7.3 Hz, 1 H, Acenapyl 4-H],
7.48–7.30 (m, 7 H, Acenapyl 7,8-H, SPh 12–16-H), 7.12 [d, JH,H
3
3
7.85–7.83 (m, 2 H, TePh 12,16-H), 7.66 [d, JH,H = 7.3 Hz, 1 H,
= 5.3 Hz, 1 H, CH], 7.06 [d, JH,H = 5.3 Hz, 1 H, CH] ppm. 13C
Acenapyl 7-H], 7.41–7.21 (m, 4 H, acenapyl 8-H, TePh 13–15 H),
NMR (75.5 MHz, CDCl3, 25 °C, Me4Si): δ = 142.0 (q), 139.0 (q),
138.6 (q), 137.6 (s), 137.3 (s), 133.1 (q), 131.8 (q), 131.3 (q), 130.7
(s), 130.4 (s, CH), 130.2 (q), 129.8 (s), 129.6 (s), 129.4 (s), 129.0 (s),
128.2 (s, CH), 126.9 (s), 125.7 (s), 124.9 (s) 124.6 (q) ppm. 77Se
NMR (51.5 MHz, CDCl3, 25 °C, MeSeSeMe): δ = 456 (s) ppm.
3
3
7.14 [d, JH,H = 7.3 Hz, 1 H, Acenapyl 3-H], 6.74 [d, JH,H
=
3
5.3 Hz, 1 H, CH], 6.71 [d, JH,H = 5.3 Hz, 1 H, CH] ppm. 13C
NMR (75.5 MHz, CDCl3, 25 °C, Me4Si): δ = 141.9 (s), 141.5 (s),
141.1 (q), 140.0 (q), 139.3 (q), 136.0 (s), 135.0 (s), 133.8 (q), 133.1
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FULL PAPER
MS (ES+): m/z (%) = 416.01 (100) [M + H]. C24H16SSe (415.41):
calcd. C 69.4, H 3.9; found C 69.3, H 3.9.
(augmented with a set of d-polarisation functions) and 6-31+G(d)
basis elsewhere]. Wiberg bond indices[40] were obtained in an NBO
analysis[41] at the same level. See the Supporting Information for
more details.
[Acenapyl(TePh)(SPh)] (11): Compound 11 was synthesised by the
method described for 13 but with DDQ (0.78 g, 1.67 mmol) and
[Acenap(TePh)(SPh)] A11 (0.57 g, 2.53 mmol) to yield an oily yel-
low solid (0.09 g, 12%); m.p. 113–115 °C. 1H NMR (300 MHz,
CDCl3, 25 °C, Me4Si): δ = 8.36–8.32 (m, 2 H, TePh 12,16-H), 7.88
Supporting Information (see footnote on the first page of this arti-
cle): Full experimental details, crystallographic data and figures
and computational details.
3
3
[d, JH,H = 7.1 Hz, 1 H, Acenapyl 4-H], 7.83 [d, JH,H = 7.3 Hz, 1
3
H, Acenapyl 7-H], 7.61 [d, JH,H = 7.0 Hz, 1 H, Acenapyl 3-H],
Acknowledgments
7.58–7.42 (m, 4 H, Acenapyl 8-H, TePh 13–15-H), 7.22–7.14 (m, 5
H, SPh 12–16-H), 7.01 [d, 3JH,H = 5.3 Hz, 1 H, CH], 6.96 [d, 3JH,H
= 5.3 Hz, 1 H, CH] ppm. 13C NMR (75.5 MHz, CDCl3; 25 °C,
Me4Si): δ = 140.4 (s), 136.6 (s), 136.4 (q), 136.2 (s), 136.1 (s), 135.0
(q), 132.6 (q), 132.5 (q), 132.3 (s, CH), 132.0 (s), 130.7 (s, CH),
130.6 (q), 130.4 (s), 129.8 (s), 129.6 (q), 129.3 (s), 127.6 (s), 126.2
(q), 125.8 (s), 125.6 (q) ppm. 125Te NMR (81.2 MHz, CDCl3,
25 °C, MeTeTeMe): δ = 951 (s) ppm. MS (ES+): m/z (%) = 495.02
(95) [M + OMe].
Elemental analyses were performed by Stephen Boyer at the Lon-
don Metropolitan University. Mass spectrometry was performed
by Caroline Horsburgh at the University of St. Andrews Mass
Spectrometry Service and by the EPSRC National Mass Spectrom-
etry Service in Swansea. Calculations were performed using the
EaStCHEM Research Computing Facility maintained by Dr. H.
Früchtl. The work in this project was supported by the Engineering
and Physical Sciences Research Council (EPSRC). M. B. wishes to
thank the School of Chemistry, University of St Andrews (EaSt-
CHEM) for support.
[Acenapyl(I2)] (14): Compound 14 was synthesised by the method
described for 13 but with DDQ (0.94 g, 4.12 mmol) and [Acen-
ap(I2)] A14 (1.08 g, 2.67 mmol) to yield a yellow solid (0.16 g,
15%); m.p. 109–111 °C. 1H NMR (300 MHz, CDCl3, 25 °C,
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[4] J. I. Musher, Angew. Chem. 1969, 81, 68; Angew. Chem. Int. Ed.
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3
Me4Si): δ = 8.29 [d, JH,H = 7.4 Hz, 2 H, Acenapyl 4,7-H], 7.15 [d,
3JH,H = 7.4 Hz, 2 H, Acenapyl 3,8-H], 6.80 (s, CHϫ2) ppm. 13C
NMR (75.5 MHz, CDCl3, 25 °C, Me4Si): δ = 144.8 (s), 144.7 (q),
153.7 (q), 129.6 (q), 129.44 (s, CHϫ2), 125.9 (s), 125.5 (q) ppm.
MS (ES+): m/z (%) = 404.86 (100) [M + H]. C12H6I2 (403.99): calcd.
C 35.7, H 1.5; found C 35.6, H 1.6.
Crystal Structure Analyses: X-ray crystal structures for A0 and 6
were determined at –148(1) °C with the St Andrews Robotic Dif-
fractometer,[44] a Rigaku ACTOR-SM, and a Saturn 724 CCD area
detector with graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å). Data were corrected for Lorentz, polarisation and ab-
sorption. Data for compound 10 were collected at –148(1) °C with
a Rigaku MM007 high-brilliance RA generator (Mo-Kα radiation,
confocal optic) and Saturn CCD system. At least a full hemisphere
of data was collected using ω scans. Intensities were corrected for
Lorentz, polarisation, and absorption. Data for compounds 13 and
A13 were collected at –148(1) °C with a Rigaku SCXmini CCD
area detector with graphite-monochromated Mo-Kα radiation (λ
= 0.71073 Å). Data were corrected for Lorentz, polarisation and
absorption. Data for 2, 3, 5, 8 and 9 were collected at –180(1) °C
with a Rigaku MM007 high-brilliance RA generator (Mo-Kα radi-
ation, confocal optic) and a Mercury CCD system. At least a full
hemisphere of data was collected using ω scans. Data for the com-
plexes analysed was collected and processed using CrystalClear
(Rigaku).[45] Structures were solved by direct methods[46] and ex-
panded using Fourier techniques.[47] Non-hydrogen atoms were re-
fined anisotropically. Hydrogen atoms were refined using the riding
model. All calculations were performed using the CrystalStruc-
ture[48] crystallographic software package except for refinement,
which was performed using SHELXL-97.[49]
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Received: December 10, 2013
Published Online: February 24, 2014
Eur. J. Inorg. Chem. 2014, 1512–1523
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