Noncovalent interactions in peri-substituted chalconium acenaphthene and naphthalene salts: A combined experimental, crystallographic, computational, and solid-state NMR study

Article abstract of DOI:10.1021/ic301627y

Twelve related monocation chalconium salts [{Nap(EPh)(EPh)Me} ⁺{CF₃SO₃}^-] 2-4, [{Acenap(Br)(EPh)Me}{CF₃SO₃}^-] 5-7, and [{Acenap(EPh)(EPh)Me}⁺{CF₃SO₃}^-] 8-13 have been prepared and structurally characterized. For their synthesis naphthalene compounds [Nap(EPh)(EPh)] (Nap = naphthalene-1,8-diyl; E/E = S, Se, Te) N2-N4 and associated acenaphthene derivatives [Acenap(X)(EPh)]/[Acenap(EPh) (EPh)] (Acenap = acenaphthene-5,6-diyl; E/E = S, Se, Te; X = Br) A5-A13 were independently treated with a single molar equivalent of methyl trifluoromethanesulfonate (MeOTf). In addition, reaction of bis-tellurium compound A10 with 2 equiv of MeOTf afforded the doubly methylated dication salt [{Acenap(TePhMe)₂}²⁺{(CF₃SO₃) ₂}^2-}] 14. The distortion of the rigid naphthalene and acenaphthene backbone away from ideal was investigated in each case and correlated in general with the steric bulk of the interacting atoms located at the proximal peri positions. Naturally, introduction of the ethane linker in acenaphthene compounds increased the splay of the bay region compared with equivalent naphthalene derivatives resulting in greater peri distances. The conformation of the aromatic rings and subsequent location of p-type lone pairs has a significant impact on the geometry of the peri region, with anomalies in peri separations correlated to the ability of the frontier orbitals to take part in attractive or repulsive interactions. In all but one of the monocations a quasi-linear three-body C_Me-E...Z (E = Te, Se, S; Z = Br/E) fragment provides an attractive component for the E...Z interaction. Density functional studies confirmed these interactions and suggested the onset of formation of three-center, four-electron bonding under appropriate geometric conditions, becoming more prevalent as heavier congeners are introduced along the series. The increasingly large J values for Se-Se, Te-Se, and Te-Te coupling observed in the ⁷⁷Se and ¹²⁵Te NMR spectra for 1, 3, 4, 9, 10, and 13 give further evidence for the existence of a weakly attractive through-space interaction.

Full text of DOI:10.1021/ic301627y

Article
pubs.acs.org/IC
Noncovalent Interactions in Peri-Substituted Chalconium
Acenaphthene and Naphthalene Salts: A Combined Experimental,
Crystallographic, Computational, and Solid-State NMR Study
Fergus R. Knight,* Rebecca A. M. Randall, Kasun S. Athukorala Arachchige, Lucy Wakefield,
John M. Griffin, Sharon E. Ashbrook, Michael Buhl, Alexandra M. Z. Slawin, and J. Derek Woollins
̈
EaStCHEM, School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST, United Kingdom
S
* Supporting Information
ABSTRACT: Twelve related monocation chalconium salts [{Nap(EPh)(E′Ph)-
Me}+{CF3SO3}−] 2−4, [{Acenap(Br)(EPh)Me}{CF3SO3}−] 5−7, and [{Acenap-
(EPh)(E′Ph)Me}+{CF3SO3}−] 8−13 have been prepared and structurally
characterized. For their synthesis naphthalene compounds [Nap(EPh)(E′Ph)]
(Nap = naphthalene-1,8-diyl; E/E′ = S, Se, Te) N2−N4 and associated
acenaphthene derivatives [Acenap(X)(EPh)]/[Acenap(EPh)(E′Ph)] (Acenap =
acenaphthene-5,6-diyl; E/E′ = S, Se, Te; X = Br) A5−A13 were independently
treated with a single molar equivalent of methyl trifluoromethanesulfonate (MeOTf).
In addition, reaction of bis-tellurium compound A10 with 2 equiv of MeOTf afforded
the doubly methylated dication salt [{Acenap(TePhMe)2}2+{(CF3SO3)2}2−}] 14.
The distortion of the rigid naphthalene and acenaphthene backbone away from ideal
was investigated in each case and correlated in general with the steric bulk of the
interacting atoms located at the proximal peri positions. Naturally, introduction of
the ethane linker in acenaphthene compounds increased the splay of the bay region compared with equivalent naphthalene
derivatives resulting in greater peri distances. The conformation of the aromatic rings and subsequent location of p-type lone
pairs has a significant impact on the geometry of the peri region, with anomalies in peri separations correlated to the ability of the
frontier orbitals to take part in attractive or repulsive interactions. In all but one of the monocations a quasi-linear three-body
CMe−E···Z (E = Te, Se, S; Z = Br/E) fragment provides an attractive component for the E···Z interaction. Density functional
studies confirmed these interactions and suggested the onset of formation of three-center, four-electron bonding under
appropriate geometric conditions, becoming more prevalent as heavier congeners are introduced along the series. The
increasingly large J values for Se−Se, Te−Se, and Te−Te coupling observed in the 77Se and 125Te NMR spectra for 1, 3, 4, 9, 10,
and 13 give further evidence for the existence of a weakly attractive through-space interaction.
acenaphthene scaffold [{Acenap(X)(EPh)}/{Acenap(EPh)-
(E′Ph)} (X = Br, I; E = S, Se, Te)].21,22 These systems
constrain the bulky halogen and chalcogen congeners in
sterically demanding position, at distances closer than the sum
of their respective van der Waals radii, inducing direct overlap
of orbitals, leading to the onset of weakly bonding 3c-4e-type
interactions under appropriate geometric conditions.11,17,19,21
Evidence supporting weak noncovalent peri interactions in
these compounds is observed in the respective 77Se and 125Te
NMR spectra.17,21 Furukawa et al. identified a similar
interaction between telluronio−tellurenyl groups at the peri
positions of telluronium salt 1 (Figure 1) formed following
treatment of 1,8-bis(phenyltelluro)naphthalene [Nap(TePh)2]
N1 (Figure 1) with methyl trifluoromethanesulfonate
(MeOTf).23 The 125Te NMR spectrum of 1 showed two
peaks at δ = 656 (Te+) and 557 ppm (Te), each peak exhibiting
INTRODUCTION
■
Pioneering work on the electronic theory of the covalent bond
led to a greater understanding of strong bonding (covalent/
ionic),1 but ambiguity over the role of weak inter- and
intramolecular noncovalent interactions continues to intrigue
chemists.2−9 Designing structural architectures which invoke
novel and unusual bonding interactions is indispensable for
developing the theory of nonbonded forces and the chemical
bond and is therefore an intriguing field of study.10,11
In this context, we previously utilized the unique geometric
constraints associated with peri substitution and the rigidity of
the naphthalene12 and acenaphthene13 backbones to investigate
noncovalent forces occurring in mixed-donor ligands. Our early
work focused on naphthalene, synthesizing dichalcogenide
ligands,14 unusual phosphorus compounds,15 and mixed-donor
phosphorus−chalcogen systems.16 More recently, we prepared
a series of 1,8-disubstituted naphthalene derivatives that contain
chalcogen or halogen moieties at the peri positions [{Nap-
(EPh)(E′Ph)}/{Nap(X)(EPh)} (X = Br, I; E = S, Se,
Te)]17−20 and an analogous series employing the alternative
Received: July 25, 2012
Published: September 24, 2012
© 2012 American Chemical Society
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methyl trifluoromethanesulfonate (MeOTf). For the synthesis
of monocation chalconium salts 2−13 (Figure 1), methylation
reactions were carried out using a 1:1 molar ratio of MeOTf to
chalcogen derivative and run in dichloromethane under an
oxygen- and a moisture-free nitrogen atmosphere (yield 87−
96%). Under identical reaction conditions, treatment of 5,6-
bis(phenyltelluro)acenaphthene A1021 with 2 mol equiv of
MeOTf afforded the dication chalconium salt 14 (yield 54%).
Corresponding reactions of the remaining group of chalcogen
derivatives with a similar loading of methyl triflate exclusively
afforded the monocation chalconium salt in each case. All
compounds obtained (2−14) were characterized by multi-
nuclear magnetic resonance and IR spectroscopies and mass
spectrometry, and the homogeneity of the new compounds was
where possible confirmed by microanalysis. Solid-state and
solution 77Se and 125Te NMR spectroscopic data can be found
in Table 1 (and Table S1, Supporting Information).
The respective acenaphthene NMR signals for compounds 9,
10, and 13 display an upfield shift, lying at lower chemical
shifts, indicating the nuclei are more shielded than in equivalent
naphthalene salts 3, 1, and 4, respectively. The 125Te NMR
spectrum of 10 is comparable with the data reported for the
naphthalene telluronium salt 1 by Furukawa et al.:23 two peaks
at δ = 641 (Te+) and 522 ppm (Te), each peak exhibiting
satellites due to 125Te−125Te coupling. Indication of a strong
through-space peri interaction is observed between the
telluronio and the tellurenyl groups, with large coupling
constants (JTeTe = 946 Hz) of a similar magnitude to the
reported naphthalene derivative (1 JTeTe = 1093 Hz23).
Solution and Solid-State NMR Studies. In contrast, the
significantly smaller J values observed for 77Se−77Se coupling [3
(167 Hz); 9 (141 Hz)] in the 77Se NMR spectra for analogous
selenonium salts 3 [δ = 436 (Se+), 392 ppm (Se)] and 9 [δ =
422 (Se+), 366 ppm (Se)] implies a weaker through-space
interaction is occurring in each case. A more direct comparison
is possible through the corresponding reduced coupling
constants K, which decrease by ca. 60% on going from 1 (K
= 9.0.1021 kg m−2 s−2 A−2) to 3 (K = 3.8.1021 kg m−2 s−2 A−2).
As might be expected, the mixed-telluronio−selanyl com-
pounds 4 and 13 display properties in between those of the bis-
tellurium and bis-selenium analogues. The reciprocal 125Te
NMR and 77Se NMR spectra for both compounds exhibit single
peaks [4 δTe = 706 ppm, δSe = 347 ppm; 13 δTe = 679 ppm, δSe
= 322 ppm] with satellites attributed to 125Te−77Se coupling.
The relatively large J values [4 (429 Hz); 13 (382 Hz)], lying
between those of the telluronium salts (1, 10) and selenonium
salts (3, 9), indicate a potential weakly attractive through-space
interaction.
Figure 1. Monocation (1−13) and dication (14) chalconium salts
formed from the reaction of naphthalene N1−N4 and acenaphthene
A5−A13 derivatives with methyl trifluoromethanesulfonate (methyl
triflate).
satellites due to 125Te−125Te coupling with the large coupling
constants of JTeTe = 1093 Hz attributed to a peri interaction.23
The work presented here complements our earlier studies of
noncovalent interactions in naphthalene and acenaphthene
chalcogenides17,19,21 and the work initially undertaken by
Furukawa et al. on tellurium−tellurium peri interactions in 1,8-
ditelluronaphthalenes.23 Herein we report a complete synthetic
and structural study of associated monocation chalconium salts
2−13 and dication 14 formed from reaction of naphthalenes
N2−N417 and acenaphthenes A5−A1321 with MeOTf and an
investigation of the potential nonbonding interactions
associated with these types of systems (Figure 1).
RESULTS AND DISCUSSION
■
Synthesis of Chalconium Salts 2−14. Naphthalene
compounds [Nap(EPh)(E′Ph)] (Nap = naphthalene-1,8-diyl;
E/E′ = S, Se, Te) N2−N417 (Figure 1) and associated
acenaphthene derivatives [Acenap(Z)(EPh)] (Acenap =
acenaphthene-5,6-diyl; Z = Br, SPh, SePh, TePh; E = S, Se,
Te) A5−A1321 (Figure 1) were independently treated with
a
Table 1. 77Se and 125Te NMR Spectroscopy Data
N323
3
A621
6
A921
9
A1121
11
N417
4
A1321
13
peri atoms
Se, Se
429
Se+, Se
Se, Br
424
Se+, Br
Se, Se
408
Se+, Se
422, 366
427, 375
141
Se, S
434
Se+, S
Te, Se
363
Te+, Se
Te, Se
341
Te+, Se
77Se solution NMR
77Se solid-state NMR
J (solution NMR)
436, 392
420
431
347
323
426, 400
433
442
350
336, 319
382
167
429
N117
123
A721
7
A1021
10
A1221
12
14
peri atoms
Te, Te Te+, Te
620 656, 557 696
1093
Te, Br Te+, Br Te, Te
Te+, Te
Te, S Te+, S Te+, Te+
125Te solution NMR
J (125Te solution NMR)
125Te solid-state NMR
693 586
641, 522 689
946
694
677
688
−834
706
429
663
679
−716 382
595, 523 665, 551 705
695
684
706, 682
a
Solution spectra of parent compounds 3 and 4 were run in CDCl3; spectra of acenaphthene chalconium salts were run in CD3CN; δ (ppm), J (Hz).
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Figure 2. Thermal ellipsoid plots (50% probability) of chalconium salts 6, 10, and 12 (H atoms omitted for clarity). Structures of 5, 7, 8, 9, 11, and
13 (adopting conformations similar to 6, 10, and 12) are omitted here but can be found in the Supporting Information (Figure S4).
Solid-state NMR spectra were recorded for compounds A9−
A13 and 9−13, and chemical shifts are found to be close to the
solution-state values. It was not possible to determine J values
owing to the larger line widths obtained in the solid-state NMR
spectra. Deviations of up to 17.8 ppm for 77Se and 62.8 ppm for
125Te between the solution-state and the solid-state chemical
shifts result from the changes in geometry imposed by the
crystal structure in the solid state. DFT calculations of 77Se and
125Te NMR parameters were performed on fully geometry-
optimized structures (full details are given in the Supporting
Information). These enabled assignment of solid-state NMR
spectra which contain more than one resonance. For
compounds A9 and A10, the two chemically equivalent
selenium and tellurium atoms in each of the molecules are
crystallographically inequivalent in the solid state owing to the
conformation of the molecule. This results in the observation of
two 77Se and 125Te distinct resonances in the solid-state NMR
spectra for each compound. For the crystallographically
inequivalent sites in these compounds, the experimental
chemical shift differences of 51.6 (77Se) and 114.3 ppm
distinct selenium species in the structure have very similar local
bonding geometries, and DFT calculations predict only a 7.5
ppm difference in chemical shift between the two sites.
Furthermore, DFT calculations performed on a structure for
which only hydrogen positions were optimized predict a
smaller chemical shift difference of 3.8 ppm. Therefore, it is
likely that the two distinct selenium sites are unresolved in the
experimental solid-state 77Se NMR spectrum, where a line
width of 5 ppm was obtained. For compound 13, two 77Se and
two 125Te resonances are observed in the experimental solid-
state 77Se and 125Te NMR spectrum, indicating larger structural
differences between the two molecules in the asymmetric unit.
This could be related to the larger difference in phenyl ring
conformation between the two molecules in the crystal
structure for 13 (Table S2, Supporting Information), which is
known to be an important factor in determining 77Se chemical
shifts.24,25 Indeed, the structural differences between the two
crystallographically distinct molecules are reflected in the DFT
calculations, which predict chemical differences of 19.0 (77Se)
and 10.7 ppm (125Te).
(
125Te) for A9 and A10 show reasonable agreement with
X-ray Investigations. Suitable single crystals were obtained
for 2 and 4 by slow evaporation of a dichloromethane solution
of the product. Crystals for 3 and 5−14 were obtained by
diffusion of hexane into saturated solutions of the individual
compound in dichloromethane. Compounds 5, 8, 11, and 13
contain two nearly identical molecules in the asymmetric unit,
differences of 35.5 and 135.6 ppm predicted by the calculations.
Crystal structures of compounds 11 and 13 contain two
crystallographically distinct molecules per asymmetric unit. For
compound 11, only one isotropic resonance was observed in
the 77Se solid-state NMR spectrum. We note that the two
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in contrast to the remaining members of the series which
crystallize with one molecule in the asymmetric unit. Selected
interatomic bond lengths and angles are listed in Table 2.
Further crystallographic information can be found in the
Supporting Information.
within the sum of van der Waals radii for the two interacting
chalcogen atoms (8 3.093(3) Å [3.034(3) Å]; 9 3.2469(19) Å;
10 3.445(3) Å; 11 3.114(3) Å [3.073(4) Å]; 12 3.117(3) Å; 13
3.2089(14) Å [3.1718(14) Å]). In line with parent compounds
A8−A13,21 deformation of the natural acenaphthene geometry
in 8−13 through in-plane and out-of-plane distortions and
buckling of the carbon skeleton generally increases as larger
atoms occupy the proximal 5,6 positions. A notable increase in
the peri separation is observed as the heavier congeners are
substituted, with a marked lengthening from 3.093(3) Å
[3.034(3) Å] in 8 (ΣrvdW 3.60 Å)27 to 3.445(3) Å in 10 (ΣrvdW
4.12 Å).27 Naturally, the increased congestion of the peri space
causes a greater divergence of the E−CAcenap bonds within the
acenaphthene plane, with large positive splay angles in the
range 13.2−19.9°. This is accompanied by further displacement
of the peri atoms to opposite sides of the mean acenaphthene
plane (0.1−0.4 Å) and a reduction in the planarity of the
organic framework by 1−6°.
Nevertheless, it is interesting to note that the small
modification in orientation between the cis and the trans
configurations of the axial phenyl rings in B-AA-type
compounds (8−13) greatly affects the degree to which the
chalcogen frontier orbitals take part in attractive or repulsive
interactions. Despite an attractive 3c-4e-type interaction being
present in each compound, irregular nonbonded B-AAt peri
separations (8, 11−13) are observed with respect to the size of
the interacting atoms when compared with B-AAc (9, 10) and
B-A (5−7) systems (see Figure S6, Supporting Information),
similar to the trends observed for the parent species (type A/
AA vs B/AB).21 Greater lone pair−lone pair repulsion is
observed in compounds adopting type B-AAc and B-A
configurations, with larger than expected peri distances
compared to B-AAt systems where lone pair interactions are
less effective. This is highlighted by the Se···Se peri distance in
9 (B-AAc) [3.2469(19) Å; ΣrvdW 3.80 Å27] being longer than
the Te···E distances found in 12 (B-AAt) [3.117(3) Å; ΣrvdW
3.86 Å27] and 13 (B-AAt) [3.2089(14) Å (3.1718(14) Å);
ΣrvdW 3.96 Å27], accommodating heavier chalcogen congeners.
Similarly, the S···Br distance in 5 (B-A) [3.182(3) Å (3.181(3)
Å); ΣrvdW 3.65 Å27] is longer than the Se···S distance in 11 (B-
AAt) [3.114(3) Å (3.073(4) Å); ΣrvdW 3.70 Å27] and the
Te···Br distance in 7 (B-A) [3.2848(14) Å; ΣrvdW 3.91 Å27] is
longer than the Te···Se distance in 13 (B-AAt) [3.2089(14) Å
(3.1718(14) Å); ΣrvdW 3.96 Å27]. Nevertheless, B-AAc- and B-
A-type species behave as a related series, displaying a quasi-
linear relationship between peri distance versus collective peri
atom size (sum of van der Waals radii of the two peri atoms),
with an expected general increase in peri separation as larger
halogen or chalcogen congeners occupy the proximal 5,6
positions (Figure S6, Supporting Information).21 A similar
relationship is found for the series of compounds adopting the
B-AAt motif. To complement these findings, DFT calculations
were performed for acenaphthene derivatives 8−13, comparing
the cis and trans B-AA-type conformations and determining the
extent of three-center, four-electron-type interactions occurring
in the series (vide infra).
The molecular structures of chalconium monocation salts 2−
13 exhibit a range of structurally diverse configurations which
are notably different from those of the respective parent
derivatives N2−N417 and A5−A13.21 As we previously
reported,17,21 the conformation of the aromatic ring systems
and alignment of the aryl moieties dictates the final solid-state
structure, influencing the degree of repulsion between p-type
lone pairs (and hence the extent of molecular distortion) and
enabling attractive intramolecular peri interactions to occur
under appropriate geometric conditions. Similar to their parent
precursors,17,21 the absolute configuration of these systems can
be classified by the relative alignment of the naphthalene and
acenaphthene backbones and the aryl moieties with respect to
the C(ar)−E−C(ar) planes (see Figures S2 and S3 and Tables
S2 and S3, Supporting Information).11,17,19,21,26
The series of 5-bromo-6-(methyl)(phenyl)chalconium ace-
naphthenes 5−7 adopt the same equatorial−axial arrangement
(Figures 2 and S3, Supporting Information), in each case
positioning the E−CMe bond along the mean acenaphthene
plane and subsequently forcing the E−CPh bond to lie with a
perpendicular configuration (type B-A; Figure S3, Supporting
Information).11,17,19,21,26 The location of the methyl function-
ality provides the correct geometry for the existence of a quasi-
linear three-body Br···E−CMe fragment with potential 3c-4e
character11,21 (Br···E−C angles (ψ) in the range 166−176°;
Figure S3, Supporting Information). Naturally, the nonbonded
Br···E peri distances increase with increasing chalcogen size,
with separations lengthening from 3.181(3) Å [3.182(3) Å] in
5 to 3.2848(14) Å in 7 but still 13−16% shorter than the sum
of van der Waals radii (ΣrvdW) in each case. The natural bond
stretching and angle widening distortions of the acenaphthene
framework are insufficient to completely alleviate the steric
strain imposed by substitution of the bulky chalcogen and
halogen substituents in 5−7. Supplementary displacement of
the peri atoms away from the acenaphthene mean plane and a
greater divergence of the exocyclic bonds transpire to help
alleviate peri space crowding. Considerable distortion is
observed within the bay region, with large but comparable
angular splays observed for the E−CAcenap and X−CAcenap bonds
[5 17.2° [16.3°]; 6 17.8°; 7 17.2°]. The disposition of the peri
atoms to opposite sides of the acenaphthene ring ranges from
0.1 to 0.9 Å, and further deformation is achieved by a minor
buckling of the acenaphthene framework in each case (central
torsion angles 1−4°).
Methylation of bis-chalcogen compounds A8−A10 and
mixed-chalcogen derivatives A11−A13 affords a series of
comparable structures in which the E−CMe bond aligns along
the plane of the acenaphthene backbone, similar to 5−7. In
each case the two phenyl rings are located perpendicular to the
acenaphthene plane but with either a cis (9, 10) or a trans (8,
11−13) orientation (B-AAc/B-AAt; Figures 2 S3 and S4,
Supporting Information). This promotes a quasi-linear E···E′−
Interestingly, the three naphthalene compounds 2−4 adopt
different configurations compared to their acenaphthene
analogues (8, 9, and 13). In bis-selenide 3 (Figures S3 and
S5, Supporting Information), minor rotation around the
Se(9)−C(9) bond results in a twist orientation of the
respective phenyl ring, affording a B-ACc configuration (cf. B-
AAc adopted by acenaphthene 9), while in naphthalene 4
CMe three-atom fragment which may promote delocalization of
a chalcogen lone pair (G) to the antibonding σ* (E−C) orbital,
thus providing an attractive three-center four-electron (3c-4e)
type component for the E···E′ interaction.11,21 Evidence for this
is supported by E···E′−CMe angles (ψ) approaching 180°
(170−177°) and short nonbonded peri distances, 16−19%
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Figure 3. Thermal ellipsoid plots (50% probability) of naphthalene chalconium salts 2 and 4. Structure of 3 is omitted here but can be found in
Figure S5, Supporting Information.
(Figures 3, Supporting Information) the phenyl rings prefer to
align with a cis orientation (B-AAc), contrasting with the trans
configuration adopted by 13 (B-AAt). In both cases, the
equatorial methyl group completes a quasi-linear E···E′−CMe
fragment, similar to acenaphthenes 8−13, with short non-
bonded peri distances, ∼20% shorter than the respective sum of
van der Waals radii [3 3.077(3) Å; 4 3.177(1) Å] and E···E′−
CMe angles which approach 180° [3 ψ = 177.1°; 4 ψ = 171.2°].
The greatest disparity is observed in naphthalene 2 (Figures
3, Supporting Information) which adopts a C-CAc config-
uration (cf. 8 B-AAt) and is subsequently the only compound
of those studied in this project that does not align the E−CMe
bond along the plane of the backbone. Subsequently, no linear
fragment is found in 2, with the C-CAc conformation
accounting for a more acute S(2)···S(1)−C(17) angle of ψ =
100.7° and a larger relative peri separation than might be
expected from interactions between lighter Group 16 congeners
[3.006(2) Å: 84%].
Typically, naphthalene salts 2−4 display less molecular
Figure 4. Thermal ellipsoid plot (50% probability) of dication
chalconium salt 14 (H atoms omitted for clarity).
distortion and shorter peri distances compared with analogous
acenaphthene derivatives 8, 9, and 13,21 although significant
deformation of the naphthalene geometry is still required in
order to accommodate the large chalcogen atoms. Elongation
Te+···Te+ separation [3.5074(16) Å] compared with the
of the C−C bonds around C10 (mean 1.43 Å; cf. C5 bonds
telluronio−tellurenyl Te+···Te separation in monocation 10
1.42 Å) is supplemented by an increase in the C1−C10−C9
angular splay (mean 127°; cf. C4−C5−C6 120°). Additional
relaxation is afforded by the displacement of the peri atoms to
opposite sides of the naphthyl plane (0.2−0.5 Å) and the
divergence of the exocyclic bonds (splay angles 13.1−14.2°).
Considerable buckling of the usually rigid naphthalene unit is
also observed with central C−C−C−C torsion angles deviating
from planarity by 2−6°.
Treatment of 5,6-bis(phenyltelluro)acenaphthene A13 with
2 mol equiv of MeOTf resulted in methylation of both
tellurium centers, affording the dication salt [{Acenap-
(TePh)2(Me)2}2+(OTf−)2] 14 (Figure 4). The additional
electrostatic repulsion acting between the positively charged
cationic tellurium centers enhances the steric strain within the
peri region and leads to a greater deformation of the
acenaphthene carbon framework compared with monocation
10. The repulsive Te+···Te+ Coulombic interaction is
predominantly accommodated by a greater in-plane divergence
of the exocyclic Te−CAcenap bonds [splay angle for 14 23.4° and
10 19.9°], which leads to an increase in the nonbonding
[3.445(3) Å]. Nevertheless, the Te+···Te+ separation in 14
[3.5074(16) Å] is still 15% shorter than twice the van der
Waals radii for Te [4.12 Å].27
The conformation of dication 14 can be classified as type C-
CCc-C (Figures 4 and S3, Supporting Information). The two
Te−CMe bonds are displaced 151.14(1)° and 136.01(1)° from
the respective C(10)−C(1)−Te−CMe planes (Table S3,
Supporting Information), locating the methyl groups at
positions between an equatorial and an axial configuration,
corresponding to a twist conformation. The two methyl groups
subsequently point away from the center of the molecule and
are located on opposite sides of the acenaphthene ring.
Amassing the bulk of the substituents on one side of the
molecule (top half in Figure 5) leaves much open space on the
other. In the solid, this space is actually occupied by a water
molecule (see O(7) Figure 4), presumably introduced during
workup in air. Crystallization under anhydrous conditions
affords the same structure of the dication of 14, now with an O
atom from one of the triflate counterions at the position of this
water (the “anhydrous” structure still contains one water
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In order to assess the difference between the cis and the trans
structural motifs, a conformational search was undertaken
where all molecules 8−13 were optimized in the respective
other conformation. In each case the two possible B-AA
conformations were considered, with the phenyl groups
adopting either the cis (B-AAc) or the trans (B-AAt)
orientation. It is interesting to note that AAc conformations
could be optimized for all members of the group, contrasting
with a similar study of the parent compounds A8−A13 which
invariably optimized to AB forms (or intermediate structures
denoted AC or CC, where one or both of the dihedral angles θ
are close to 140°; Figure S2, Supporting Information).
In all cases the most stable conformer corresponded to the B-
AAt configuration, but the energy span between the two
conformations is remarkably small, ranging from 3.7 kJ/mol for
8 to 7.1 kJ/mol for 10 (Table S9, Supporting Information).
Formation of the B-AAc conformer for 9 and 10 in the solid is
likely to be due to intermolecular interactions or packing forces.
When the phenyl substituents are moved from a cis orientation
to a trans orientation, a small decrease in the peri distance is
observed. The extent of this decrease ranges from 0.002 Å for 8
to 0.031 Å for 10 (Table S9, Supporting Information) and is
more pronounced as the size of the interacting peri atoms
increases. The extent of covalent bonding in 8−13 was
investigated to assess whether the change in peri distance with
conformation is a result of specific bonding interactions. The
Wiberg bond index (WBI), which usually approaches a value of
one for a true single bond, was investigated for each conformer
in the series (8−13).
In general, there is a trend to higher WBIs as large atoms
occupy the proximal peri positions, independent of the
conformation of the aromatic rings. In all cases, WBIs for the
B-AAt conformer are slightly greater than for the equivalent B-
AAc structure by 0.004−0.011 units. As expected, very small
WBIs (0.052/0.041) are computed for the two conformers of 8
with a relatively large peri distance (86% ΣrvdW) between the
two small sulfur substituents. Significantly higher values are
obtained for the heavier members of the series with WBIs in the
range from 0.102 (9 SeSe) to 0.184 (10 TeTe), indicating the
onset of weak three-center, four-electron-type interactions,
which become more prevalent as heavier congeners are
introduced along the series. In the second-order perturbation
analysis of the natural bond orbitals (NBOs)30 of 10, weak
donor−acceptor interactions are apparent, involving the p-type
lone pair on the TePh group and the σ*(Te-CH3) antibonding
orbital on the other side. These interactions amount to ca. 60
kJ/mol, similar to the findings for the neutral precursor A10.21
Unsurprisingly, significantly lower WBIs are obtained for the
dication 14 (0.046) and its water adduct (0.039), cf. Figure 5.
These findings correlate with the 77Se and 125Te NMR data
and J coupling values. Considering the 125Te solid-state
chemical shifts for compounds 10, 12, and 13, a systematic
decrease in chemical shift of the Te+ species is observed as
heavier congeners are introduced on the adjacent peri site. This
indicates that as the adjacent atom becomes heavier, the Te+
species becomes more shielded due to increasing through-space
lone pair interactions between the two chalcogen congeners.
Similarly, the 77Se chemical shift for the Se+ species in
compound 9 is also lower than that for compound 11,
indicating that through-space interactions are increased for
compound 9, which contains the heavier congener on the
adjacent peri site. These observations are mirrored in the 77Se
and 125Te solution-state NMR chemical shifts, which follow the
Figure 5. B3LYP-optimized bare dication from 14 (top) and with one
water molecule added (bottom), including selected bond distances in
Angstroms (italics, from X-ray crystallography); organic H atoms
omitted for clarity.
molecule per two structural units, but this is more remote from
the Te atoms).
DFT Calculations. To assess the role of the water molecule
in 14, density functional theory (DFT) calculations were
performed. When an optimization is started for the pristine
dication from the crystal structure, a B-AB-A-type minimum is
obtained (top of Figure 5), reminiscent of related neutral
bis(phosphines).28 When the water molecule is retained, a
noticeably different conformation is obtained (bottom of Figure
5), about halfway between the pristine minimum and the
structure observed in the solid (note that dispersion forces
favoring π stacking are not accounted for at the level used).
The water is held in a position not too far from where it is
found in the solid, though not approaching the Te atoms quite
as closely (see the distances on the bottom of Figure 5). In the
starting structure, one of the H atoms of the water (which were
not refined in X-ray analysis) was placed pointing toward the
lone pair of the more distant Te atom but rotated away during
optimization. In the gas phase, this water molecule is bound
rather strongly (with a raw binding energy exceeding 40 kcal/
mol at the B3LYP level) and mostly through electrostatic
interactions between the positively charged Te atoms (+1.4e
according to natural population analysis) and the negatively
charged O atom.
Additional DFT calculations were performed for acenaph-
thene derivatives 8−13, comparing the cis and trans B-AA-type
conformations and determining the extent of three-center, four-
electron-type interactions occurring in the series. Selected
geometrical parameters for 8−13 together with the chalcogen−
chalcogen Wiberg bond indices (WBIs)29 are collated in Table
S9, Supporting Information. The latter are a probe for the
extent of covalent bonding, approaching a value close to one for
true single bonds.
Atomic coordinates obtained from X-ray crystallography
were reoptimized at the B3LYP level to ensure that the chosen
basis sets and effective core potentials (ECPs) are adequate for
the problem at hand. Interestingly, the optimized peri distances
between the chalcogens are noticeably shorter than those
observed in the solid, by up to 0.08 Å (overestimation is usually
a common DFT problem). Nevertheless, this appears system-
atic as an excellent linear correlation is found between DFT and
X-ray distances, with a slope of 0.88 and a correlation
coefficient of 0.96 (Figure S7, Supporting Information).
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a Micromass LCT orthogonal accelerator time-of-flight mass
spectrometer.
same trend, and evidence for through-space interactions is
supported by the J coupling values, which are substantially
larger for compounds containing heavier chalcogen pairs.
[{Nap(SPh2)Me}+{CFSO3}−] (2). To a solution of 1,8-bis-
(phenylsulfanyl)naphthalene (0.38 g, 1.11 mmol) in dichloromethane
(20 mL) was added methyl trifluoromethanesulfonate (0.13 mL, 1.11
mmol) at room temperature. The reaction mixture was stirred at this
temperature for 24 h, and the solvent was removed in vacuo. The
crude product was washed with diethyl ether, and the brown
precipitate which formed was collected by filtration. An analytically
pure sample was obtained by slow evaporation of a dichloromethane
CONCLUSION
■
Naphthalene compounds N2−N417 and associated acenaph-
thene derivatives A5−A1321 have been independently treated
with MeOTf, affording 12 monocation chalconium salts 2−13.
Reaction of bis-tellurium compound A10 with 2 equiv of
MeOTf additionally afforded the doubly methylated dication
salt [{Acenap(TePhMe)2}2+{(CF3SO3)2}2−}] 14. Where a
choice exists between potential methylation sites (mixed-
chalcogen derivatives, bromo−chalcogen species) reaction
occurs preferentially at the least electronegative chalcogen
atom or exclusively at the chalcogen atom in the case of the
bromine compounds. The molecular structures of 2−13 adopt
a variety of conformations which are notably different than their
parent derivatives. While a general increase in the peri distance
is observed when larger atoms occupy the proximal peri
positions, the conformation of the aromatic rings and
subsequent location of p-type lone pairs has a significant
impact on the geometry of the peri region, with anomalies in
peri separations correlated to the ability of the frontier orbitals
to take part in attractive or repulsive interactions. Compounds
adopting type B-AAc and B-A configurations experience greater
lone pair−lone pair repulsion and consequently exhibit larger
than expected peri distances relative to the size of the
interacting atoms compared to B-AAt systems. In the majority
of cases, an equatorial alignment of the E−CMe bond affords a
quasi-linear three-body CMe−E···Z (E = Te, Se, S; Z = Br/E)
fragment, providing an attractive component for the E···Z
interaction. Density functional studies confirmed these
interactions and suggested the onset of three-center, four-
electron-type bonding under appropriate geometric conditions,
becoming more prevalent as heavier congeners occupy the
proximal peri positions. These findings correlate with the 77Se
and 125Te NMR data and J coupling values.
1
solution of the product (0.45 g, 80%); mp 82−84 °C. H NMR (270
MHz, CDCl3, 25 °C, TMS) δ = 8.19 (1 H, d, 3J (H,H) = 7.9, Nap 4-
H), 8.06 (1 H, dd, 3J (H,H) = 8.3, 4J (H,H) = 1.2, Nap 5-H), 8.02 (1
3
4
3
H, dd, J (H,H) = 7.8, J (H,H) = 1.0, Nap 2-H), 7.95 (1 H, dd, J
4
3
(H,H) = 7.2, J (H,H) = 1.3, Nap 7-H), 7.71 (1 H, t, J (H,H) = 7.9,
Nap 3-H), 7.59 (1 H, t, 3J (H,H) = 7.8, Nap 6-H), 7.45−7.38 (5H, m,
S+Ph 12−16-H), 7.12−7.00 (3 H, m, SPh 19−21-H), 6.73−6.68 (2 H,
m, SePh 18,22-H), 3.48 (3 H, s, CH3). 19F NMR (376.5 MHz, CDCl3,
25 °C, CCl3F): −78.79(s). MS (ES+): m/z (%) 358.89 (100) [M+ −
OTf].
[{Nap(SePh2)Me}+{CFSO3}−] (3). Compound 3 was synthesized by
the method described for 2 but with [Nap(SePh)2] (0.14 g, 0.31
mmol) and MeOTf (0.04 mL, 0.31 mmol). An analytically pure
sample was obtained by recrystallization from diffusion of pentane into
a saturated dichloromethane solution of the product (0.17 g, 88%);
mp 94−96 °C. 1H NMR (270 MHz, CDCl3, 25 °C, TMS) δ = 8.25 (1
H, d, 3J (H,H) = 7.9, Nap 4-H), 8.17 (1 H, d, 3J (H,H) = 8.9, Nap 5-
H), 8.15 (1 H, d, 3J (H,H) = 10.0, Nap 7-H), 7.98 (1 H, d, 3J (H,H) =
7.3, Nap 2-H), 7.76 (1 H, t, 3J (H,H) = 7.9, Nap 3-H), 7.64 (1 H, t, 3J
(H,H) = 7.9, Nap 6-H), 7.50−7.38 (5H, m, Se+Ph 12−16-H), 7.16−
7.08 (3 H, m, SePh 19−21-H), 6.98−6.86 (2 H, m, SePh 18,22-H),
2
3.32 (3 H, s, J (H,Se) = 14.1 Hz, CH3). 77Se NMR (51.5 MHz,
4
4
CDCl3, 25 °C, Me2Se): δ = 436 (s, J (Se,Se) = 167), 392 (s, J
(Se,Se) = 167). 19F NMR (376.5 MHz, CDCl3, 25 °C, CCl3F):
−78.75(s). MS (ES+): m/z (%) 454.54 (100) [M+ − OTf].
[{Nap(TePh)(SePh)Me}+{CFSO3}−] (4). Compound 4 was synthe-
sized by the method described for 2 but with [Nap(TePh)(SePh)]
(0.10 g, 0.20 mmol) and MeOTf (0.02 mL, 0.20 mmol). An
analytically pure sample was obtained by slow evaporation of a
dichloromethane solution of the product (0.11 g, 89%); mp 130−132
1
°C. H NMR (270 MHz, CDCl3, 25 °C, TMS) δ = 8.15−8.08 (2 H,
m, Nap 4,5-H), 8.05 (1 H, d, 3J (H,H) = 8.2, Nap 2-H), 7.74 (1 H, d,
3J (H,H) = 7.4, Nap 7-H), 7.61−7.49 (2 H, m, Nap 3,6-H), 7.47−7.37
(3 H, m, Te+Ph 11−13-H), 7.35−7.27 (2 H, m, Te+Ph 10,14-H),
7.14−7.04 (3 H, m, SePh 18−20-H), 6.94−6.84 (2 H, m, SePh 17,21-
EXPERIMENTAL SECTION
■
2
H), 2.69 (3 H, s, J (H,Te) = 30.5, CH3). 77Se NMR (51.5 MHz,
All experiments were carried out under an oxygen- and a moisture-free
nitrogen atmosphere using standard Schlenk techniques and glassware.
Reagents were obtained from commercial sources and used as
received. Dry solvents were collected from a MBraun solvent system.
Elemental analyses were performed by the University of St. Andrews
School of Chemistry Microanalysis Service. Infrared spectra were
recorded as KBr discs in the range 4000−300 cm−1 on a Perkin-Elmer
System 2000 Fourier transform spectrometer. 1H and 13C NMR
spectra were recorded on a Jeol GSX 270 MHz spectrometer with
δ(H) and δ(C) referenced to external tetramethylsilane. 77Se and
125Te NMR spectra were recorded on a Jeol GSX 270 MHz
spectrometer with δ(Se) and δ(Te) referenced to external Me2Se
and Me2Te, respectively, with a secondary reference for δ(Te) to
diphenyl ditelluride (δ(Te) = 428 ppm). 19F NMR spectra were
recorded on a Bruker Ultrashield 400 MHz spectrometer with δ(F)
referenced to external trichlorofluoromethane. Assignments of 13C and
1H NMR spectra were 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 (ppm).
Coupling constants (J) are given in Hertz (Hz). Mass spectrometry
was performed by the University of St. Andrews Mass Spectrometry
Service. Electron impact mass spectrometry (EIMS) and Chemical
Ionization Mass Spectrometry (CIMS) was carried out on a
Micromass GCT orthogonal acceleration time-of-flight mass spec-
trometer. Electrospray mass spectrometry (ESMS) was carried out on
CDCl3, 25 °C, Me2Se): δ = 347(s). 125Te NMR (81.2 MHz, CDCl3,
25 °C, PhTeTePh): δ = 706 (4J (Te,Se) = 429). 19F NMR (376.5
MHz, CDCl3, 25 °C, CCl3F): −78.69(s). MS (ES+): m/z (%) 502.32
(100) [M+ − OTf].
[{Acenap(Br)(SPh)Me}+{CFSO3}−] (5). Compound 5 was synthe-
sized by the method described for 2 but with [Acenap(Br)(SPh)]
(0.24 g, 0.72 mmol) and MeOTf (0.08 mL, 0.72 mmol). An
analytically pure sample was obtained by recrystallization from
diffusion of hexane into a dichloromethane solution of the product
(0.32 g, 88%); mp 119−121 °C. 1H NMR (270 MHz, CD3CN, 25 °C,
TMS) δ = 8.13 (1 H, d, 3J (H,H) = 7.7, Acenap 4-H), 7.95 (1 H, d, 3J
(H,H) = 7.5, Acenap 7-H), 7.83−7.75 (2 H, m, S+Ph 13,15-H), 7.75−
7.71 (1 H, m, S+Ph 14-H), 7.71−7.60 (3 H, m, Acenap 3-H, S+Ph
3
12,16-H), 7.39 (1 H, d, J (H,H) = 7.5, Acenap 8-H), 3.62 (3 H, s,
CH3), 3.55−3.35 (4 H, m, 2 × CH2). 19F NMR (376.5 MHz, CD3CN,
25 °C, CCl3F): −79.77(s). MS (ES+): m/z (%) 354.91 (100) [M+ −
OTf]. Anal. Calcd for C20H16BrF3O3S2: C, 47.5; H, 3.2. Found: C,
47.2; H, 3.0.
[{Acenap(Br)(SePh)Me}+{CFSO3}−] (6). Compound 6 was
synthesized by the method described for 2 but with [Acenap(Br)-
(SePh)] (0.27 g, 0.70 mmol) and MeOTf (0.08 mL, 0.70 mmol). An
analytically pure sample was obtained by recrystallization from
diffusion of hexane into a dichloromethane solution of the product
(0.35 g, 90%); mp 150−152 °C. 1H NMR (270 MHz, CD3CN, 25 °C,
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TMS) δ = 7.92 (2 H, d, 3J (H,H) = 7.8, Acenap 4,7-H), 7.75−7.66 (3
H, m, Se+Ph 13−15-H), 7.66−7.56 (3 H, m, Acenap 8-H, Se+Ph 12,16-
H), 7.40 (1 H, d, 3J (H,H) = 7.6, Acenap 3-H), 3.55−3.41 (4 H, m, 2
× CH2), 3.38 (3 H, s, 2J (H,Se) = 13.2, CH3). 77Se NMR (51.5 MHz,
CD3CN, 25 °C, Me2Se): δ = 420 (s). 19F NMR (376.5 MHz, CD3CN,
25 °C, CCl3F): −79.77(s). MS (ES+): m/z (%) 402.84 (100) [M+ −
OTf]. Anal. Calcd for C20H16BrF3O3SSe: C, 43.5; H, 2.9. Found: C,
43.1; H, 2.9.
analytically pure sample was obtained by recrystallization from
diffusion of hexane into a dichloromethane solution of the product
1
(0.34 g, 96%); mp 92−94 °C. H NMR (270 MHz, CD3CN, 25 °C,
TMS) δ = 8.00 (1 H, d, 3J (H,H) = 7.3, Acenap 4-H), 7.91 (1 H, d, 3J
(H,H) = 7.7, Acenap 7-H), 7.65 (1 H, d, 3J (H,H) = 7.7, Acenap 8-H),
7.60 (1 H, d, 3J (H,H) = 7.3, Acenap 3-H), 7.58−7.43 (5 H, m, Se+Ph
12−16-H), 7.23−7.12 (3 H, m, SPh 20−22-H), 6.94−6.85 (2 H, m,
SPh 19,23-H), 3.62−3.50 (4 H, m, 2 × CH2), 3.20 (3 H, s, 2J (H,Se) =
13.5, CH3). 77Se NMR (51.5 MHz, CDCl3, 25 °C, Me2Se): δ = 431
(s). 19F NMR (376.5 MHz, CD3CN, 25 °C, CCl3F): −79.87(s). MS
(ES+): m/z (%) 432.84 (100) [M+ − OTf].
[{Acenap(Br)(TePh)Me}+{CFSO3}−] (7). Compound 7 was
synthesized by the method described for 2 but with [Acenap(Br)-
(TePh)] (0.22 g, 0.50 mmol) and MeOTf (0.06 mL, 0.50 mmol). An
analytically pure sample was obtained by recrystallization from
diffusion of hexane into a dichloromethane solution of the product
(0.26 g, 88%); mp 135−137 °C. 1H NMR (270 MHz, CD3CN, 25 °C,
TMS) δ = 7.88 (1 H, d, 3J (H,H) = 7.5, Acenap 4-H), 7.87 (1 H, d, 3J
(H,H) = 7.5, Acenap 7-H), 7.74−7.66 (2 H, m, Te+Ph 12,16-H),
7.64−7.58 (1 H, m, Te+Ph 14-H), 7.57−7.44 (3 H, m, Acenap 3-H,
[{Acenap(TePh)(SPh)Me}+{CFSO3}−] (12). Compound 12 was
synthesized by the method described for 2 but with [Acenap(TePh)-
(SPh)] (0.34 g, 0.72 mmol) and MeOTf (0.08 mL, 0.72 mmol). An
analytically pure sample was obtained by recrystallization from
diffusion of hexane into a dichloromethane solution of the product
(0.42 g, 87%); mp 166−168 °C. 1H NMR (270 MHz, CD3CN, 25 °C,
TMS) δ = 8.00 (1 H, d, 3J (H,H) = 7.3, Acenap 4-H), 7.86 (1 H, d, 3J
(H,H) = 7.5, Acenap 7-H), 7.66−7.57 (4 H, m, Acenap 3,8-H, Te+Ph
13,15-H), 7.57−7.51 (1 H, m, Te+Ph 14-H), 7.50−7.41(2 H, m, Te+Ph
12,16-H), 7.32−7.17 (3 H, m, SPh 20−22-H), 6.96−6.87 (2 H, m, SPh
3
Te+Ph 13,15-H), 7.37 (1 H, d, J (H,H) = 7.5, Acenap 8-H), 3.52−
3.44 (2 H, m, CH2), 3.44−3.34 (2 H, m, CH2), 2.86 (3 H, s, 2J (H,Te)
= 30.6, CH3). 125Te NMR (81.2 MHz, CD3CN, 25 °C, PhTeTePh): δ
= 693. 19F NMR (376.5 MHz, CD3CN, 25 °C, CCl3F): −79.80(s).
MS (ES+): m/z (%) 452.77 (100) [M+ − OTf]. Anal. Calcd for
C20H16BrF3O3STe: C, 39.9; H, 2.7. Found: C, 40.1; H, 2.6.
2
19,23-H), 3.62−3.49 (4 H, m, 2 × CH2), 2.66 (3 H, s, J (H,Te) =
31.5, CH3). 125Te NMR (81.2 MHz, CD3CN, 25 °C, PhTeTePh): δ =
694(s). 19F NMR (376.5 MHz, CD3CN, 25 °C, CCl3F): −79.78(s).
MS (ES+): m/z (%) 482.86 (100) [M+ − OTf]. Anal. Calcd for
C26H21F3O3S2Te: C, 49.6; H, 3.4. Found: C, 49.3; H, 3.1.
[{Acenap(SPh)2Me}+{CFSO3}−] (8). Compound 8 was synthesized
by the method described for 2 but with [Acenap(SPh)2] (0.25 g, 0.69
mmol) and MeOTf (0.08 mL, 0.69 mmol). An analytically pure
sample was obtained by recrystallization from diffusion of hexane into
a dichloromethane solution of the product (0.34 g, 92%); mp 107−
109 °C. 1H NMR (270 MHz, CD3CN, 25 °C, TMS) δ = 8.05 (1 H, d,
3J (H,H) = 7.3, Acenap 4-H), 7.95 (1 H, d, 3J (H,H) = 7.7, Acenap 7-
H), 7.69−7.60 (3 H, m, Acenap 3,8-H, S+Ph 14-H), 7.60−7.43 (4 H,
m, S+Ph 12,13,15,16-H), 7.29−7.13 (3 H, m, SPh 20−22-H), 6.95−
6.85 (2 H, m, SPh 19,23-H), 3.62−3.51 (4 H, m, 2 × CH2), 3.47 (3 H,
s, CH3). 19F NMR (376.5 MHz, CD3CN, 25 °C, CCl3F): −79.81(s).
MS (ES+): m/z (%) 384.95 (100) [M+ − OTf]. Anal. Calcd for
C26H21F3O3S3: C, 58.4; H, 3.9. Found: C, 58.4; H, 3.8.
[{Acenap(TePh)(SePh)Me}+{CFSO3}−] (13). Compound 13 was
synthesized by the method described for 2 but with [Acenap(TePh)-
(SePh)] (0.10 g, 0.20 mmol) and MeOTf (0.03 mL, 0.20 mmol). An
analytically pure sample was obtained by recrystallization from
diffusion of hexane into a dichloromethane solution of the product
(0.12 g, 92%); mp 138−140 °C. 1H NMR (270 MHz, CD3CN, 25 °C,
TMS) δ = 8.13 (1 H, d, 3J (H,H) = 7.2, Acenap 4-H), 7.87 (1 H, d, 3J
(H,H) = 7.5, Acenap 7-H), 7.65−7.50 (5 H, m, Acenap 3,8-H, Te+Ph
12,14,16-H), 7.50−7.39 (2 H, m, Te+Ph 13,15-H), 7.27−7.16 (3 H, m,
SePh 20−22-H), 7.08−6.98 (2 H, m, SePh 19,23-H), 3.61−3.48 (4 H,
[{Acenap(SePh)2Me}+{CFSO3}−] (9). Compound 9 was synthe-
sized by the method described for 2 but with [Acenap(SePh)2] (0.65
g, 1.39 mmol) and MeOTf (0.16 mL, 1.39 mmol). An analytically pure
sample was obtained by recrystallization from diffusion of hexane into
a dichloromethane solution of the product (0.80 g, 91%); mp 125−
127 °C. 1H NMR (270 MHz, CD3CN, 25 °C, TMS) δ = 8.12 (1 H, d,
3J (H,H) = 7.3, Acenap 4-H), 7.91 (1 H, d, 3J (H,H) = 7.7, Acenap 7-
2
m, 2 × CH2), 2.66 (3 H, s, J (H,Te) = 32.2, CH3); 77Se NMR (51.5
4
MHz, CD3CN, 25 °C, Me2Se): δ = 323(s, J (Se,Te) = 382). 125Te
NMR (81.2 MHz, CD3CN, 25 °C, PhTeTePh): δ = 679(s, 4J
(
125Te,Se) = 382). 19F NMR (376.5 MHz, CD3CN, 25 °C, CCl3F):
−79.85(s). MS (ES+): m/z (%) 528.83 (100) [M+ − OTf]. Anal.
Calcd for C26H21F3O3SSeTe: C, 46.12; H, 3.13. Found: C, 46.25; H,
2.68.
H), 7.62 (1 H, d, J (H,H) = 7.7, Acenap 8-H), 7.60−7.44 (6 H, m,
[{Acenap(TePh)2Me2}2+{CFSO3}22−] (14). Compound 14 was
synthesized by the method described for 2 but with [Acenap(TePh)2]
(0.28 g, 0.49 mmol) and MeOTf (0.22 mL, 1.97 mmol). An
analytically pure sample was obtained by recrystallization from
diffusion of hexane into a dichloromethane solution of the product
(0.24 g, 54%); mp 115−117 °C. 1H NMR (270 MHz, CD3CN, 25 °C,
TMS) δ = 8.03−7.95 (2 H, m, Acenap 4,7-H), 7.54−7.48 (2 H, m,
Acenap 3,8-H), 7.48−7.27 (10 H, m, Te+Ph 12−16,19−23-H), 3.44 (4
H, s, 2 × CH2), 3.02 (3 H, s, 2J (H,Te) = 26.5, CH3), 2.88 (3 H, s, 2J
(H,Te) = 26.7, CH3). 125Te NMR (81.2 MHz, CD3CN, 25 °C,
PhTeTePh): δ = 677(s). 19F NMR (376.5 MHz, CD3CN, 25 °C,
CCl3F): −79.84(s). MS (ES+): m/z (%) 740.71 (95) [M+ − OTf].
Anal. Calcd for C28H24F6O6S2Te2: C, 37.6; H, 2.7. Found: C, 37.6; H,
2.8.
3
Acenap 3-H, Se+Ph 12−16-H), 7.22−7.11 (3 H, m, SePh 20−22-H),
7.07−6.97 (2 H, m, SePh 19,23-H), 3.58−3.47 (4 H, m, 2 × CH2),
3.24 (3 H, s, 2J (H,Se) = 13.6, CH3). 77Se NMR (51.5 MHz, CD3CN,
4
4
25 °C, Me2Se): δ = 422 (s, J (Se,Se) = 141), 366 (s, J (Se,Se) =
141). 19F NMR (376.5 MHz, CD3CN, 25 °C, CCl3F): −79.74(s). MS
(ES+): m/z (%) 480.84 (100) [M+ − OTf]. Anal. Calcd for
C26H21F3O3SSe2: C, 49.7; H, 3.4. Found: C, 49.5; H, 3.3.
[{Acenap(TePh)2Me}+{CFSO3}−] (10). Compound 10 was synthe-
sized by the method described for 2 but with [Acenap(TePh)2] (0.24
g, 0.42 mmol) and MeOTf (0.05 mL, 0.42 mmol). An analytically pure
sample was obtained by recrystallization from diffusion of hexane into
a dichloromethane solution of the product (0.29 g, 95%); mp 155−
157 °C. 1H NMR (270 MHz, CD3CN, 25 °C, TMS) δ = 8.47 (1 H, d,
3J (H,H) = 7.1, Acenap 4-H), 7.91 (1 H, d, 3J (H,H) = 7.5, Acenap 7-
H), 7.65−7.58 (2 H, m, Te+Ph 12,16-H), 7.58−7.51 (2 H, m, Acenap
8-H, Te+Ph 14-H), 7.51−7.39 (3 H, m, Acenap 3-H, Te+Ph 13,15-H),
7.27−7.18 (3 H, m, TePh 20−22-H), 7.18−7.10 (2 H, m, TePh 19,23-
Solid-State NMR Experimental Details. Solid-state NMR
experiments were performed using a Bruker Avance III spectrometer
operating at a magnetic field strength of 9.4 T. Experiments were
carried out using a Bruker 4-mm probe at MAS rates of between 4 and
14 kHz (77Se and 125Te) and 12.5 kHz (13C). 77Se chemical shifts are
referenced to (CH3)2Se using the resonance of Na2SeO4 at 1058.7
ppm as a secondary reference. 125Te chemical shifts are references
relative to (CH3)2Te using the resonance of Te(OH)6 (site 1) at 692.2
ppm as a secondary reference. 13C chemical shifts are referenced
relative to tetramethylsilane using the CH3 resonance of L-alanine at
20.5 ppm as a secondary reference. Transverse magnetization was
2
H), 3.60−3.47 (4 H, m, 2 × CH2), 2.70 (3 H, s, J (H,Te) = 33.1,
CH3). 125Te NMR (81.2 MHz, CD3CN, 25 °C, PhTeTePh): δ =
641(s, 4J (125Te,125Te) 946), 522(s, 4J (Te,Te) 946). 19F NMR (376.5
MHz, CD3CN, 25 °C, CCl3F): −79.77(s). MS (ES+): m/z (%) 576.78
(100) [M+ − OTf]. Anal. Calcd for C26H21F3O3STe2: C, 42.7; H, 2.9.
Found: C, 42.8; H, 2.9.
[{Acenap(SePh)(SPh)Me}+{CFSO3}−] (11). Compound 11 was
synthesized by the method described for 2 but with [Acenap(SePh)-
(SPh)] (0.25 g, 0.60 mmol) and MeOTf (0.07 mL, 0.60 mmol). An
1
obtained by cross-polarization from H using optimized contact pulse
durations of 10−15 ms (77Se), 6−12 ms (125Te), and 1−3 ms (13C).
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Article
Two-pulse phase modulation 1H decoupling was applied during
acquisition. For compounds A9-A13, recycle intervals of 120 s were
used. For compounds 9−13, recycle intervals of 5 s were used.
Crystal Structure Analyses. X-ray crystal structures for 2, 3, 4, 8,
10, and 13 were determined at −148(1) °C on the St Andrews
Robotic Diffractometer31 a Rigaku ACTOR-SM, Saturn 724 CCD area
detector with graphite-monochromated Mo Kα radiation (λ = 0.71073
Å). Data was corrected for Lorentz, polarization, and absorption. Data
for compounds 5, 6, and 11 were collected at −148(1) °C using 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, polarization, and absorption. Data for compounds 7, 9, and
12 were collected at −148(1) °C on a Rigaku SCXmini CCD area
detector with graphite-monochromated Mo Kα radiation (λ = 0.71073
Å). Data were corrected for Lorentz, polarization, and absorption.
Data for 14 were collected at −180(1) °C using a Rigaku MM007
high-brilliance RA generator (Mo Kα radiation, confocal optic) and
Mercury CCD system. At least a full hemisphere of data was collected
using ω scans. Data for the complexes analyzed was collected and
processed using CrystalClear (Rigaku).32 Structures were solved by
direct methods33 and expanded using Fourier techniques.34 Non-
hydrogen atoms were refined anisotropically. Hydrogen atoms were
refined using the riding model. All calculations were performed using
the CrystalStructure35 crystallographic software package except for
refinement, which was performed using SHELXL-97.36 These X-ray
data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html or from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1EZ, UK; fax (+44) 1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk.
Computational Details. Geometries were fully optimized in the
gas phase at the B3LYP level37 using Curtis and Binning’s 962(d)
basis38 on Se, the Stuttgart−Dresden effective core potentials along
with their double-ζ valence basis sets for Te39 (augmented with d-
polarization functions with exponents of 0.237),40 and 6-31+G(d)
basis elsewhere. Wiberg bond indices41 and natural charges were
obtained in a natural bond orbital analysis42 at the same level.
Optimizations were started from two different conformers for each
compound 8−13, labeled B-AAt and B-AAc. Experimental structures
from X-ray crystallography were used as one of the starting
conformers. Computations were performed using the Gaussian 03
suite of programs.43 Selected relative energies were refined including
the empirical dispersion corrections according to Grimme (denoted
B3LYP-D3).44
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AUTHOR INFORMATION
Corresponding Author
*E-mail: frk@st-andrews.ac.uk.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Elemental analyses were performed by Stephen Boyer at the
London Metropolitan University. Mass spectrometry was
performed by Caroline Horsburgh. Calculations were per-
formed using the EaStCHEM Research Computing Facility
maintained by Dr. H. Fruchtl. The work in this project was
̈
supported by the Engineering and Physical Sciences Research
Council (EPSRC). M.B. wishes to thank EaStCHEM and the
University of St. Andrews for support.
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