Hypervalent adducts of chalcogen-containing peri -substituted naphthalenes; Reactions of sulfur, selenium, and tellurium with dihalogens

Inorg. Chem. 2010, 49, 7577–7596 7577

DOI: 10.1021/ic101086h

Hypervalent Adducts of Chalcogen-Containing peri-Substituted Naphthalenes;

Reactions of Sulfur, Selenium, and Tellurium with Dihalogens

€

Fergus R. Knight, Amy L. Fuller, Michael Buhl, Alexandra M. Z. Slawin, and J. Derek Woollins*

School of Chemistry, University of St. Andrews, St. Andrews, Fife, United Kingdom, KY16 9ST

Received May 29, 2010

A range of structurally diverse compounds 1-15 {Nap[SPh]₂Br₄(Nap = naphthalene-1,8-diyl); Nap[SePh]-

3

[EPh] Br₄(E = Se, S); Nap[SePh]₂I₂; Nap[SePh][EPh] 3/2I₂(E = Se, S); Nap[TePh][G] X₂(G = SePh, SPh,

3

Br, I; X = Br, I); and [Nap(PPh₂OH)(SPh)]^þBr₃^-} formed from the reactions between peri-substituted naphthalene

chalcogen donors D1-D8 {Nap[ER][E⁰R] (ER/E⁰R = SPh, SePh, TePh); Nap[TePh][X] (X = Br, I); and Nap[PPh₂]-

[SPh]} and dibromine and diiodine were characterized by X-ray crystallography and where possible by multinuclear

NMR, IR, and MS. X-ray data for 1-15 were analyzed by naphthalene ring torsions, peri-atom displacement, splay

angle magnitude, peri-distance, aromatic ring orientations, and quasi-linear three-body arrangements. The hyperva-

lent linear moieties are considered in the context of the charge-transfer model and the 3c-4e model introduced by

Pimentel and Rundle. In general, the conformation of the final products obeyed the rule based on charge-transfer that

“seesaw” (X-ER₂-X, 10-E-4) adducts arise when the halogen (X) is more electronegative than the chalcogen (E),

and if the converse is true then, CT “spoke” (X-X-ER₂, 8-E-3) adducts are formed. Upon treatment with dibromine,

selenium donor compounds D2 {Nap[SePh]₂} and D3 {Nap[SePh][SPh]} afford unusual tribromide salts of

bromoselenyl cations containing a hypervalent X-E E⁰3c-4e type interaction. Upon treatment with diiodine, D2

and D3 form “Z-shaped”, “extended spoke” adducts containing an uncommon 2:3 donor/chalcogen ratio and

incorporating chains of I₂held together by rare I I interactions. As expected, “seesaw” 10-E-4 adducts are formed

following the reaction of Te donors D4-D7 {Nap[TePh][X] (X = Br, I); Nap[TePh][EPh] (E = Se, S)} with the

dihalogens. Naphthalene distortion in general is comparable between respective donor compounds and products

1-15. Ionic species 2 and 3 display a noticeable reduction in molecular distortion explained by the relief of steric strain

via weak peri-interactions and the onset of 3c-4e bonding.

3 3 3

1. Introduction

2c-2e covalent bond but proposed that the bonding was

accompanied by an expansion of the octet.^2,5Conversely,

Langmuir favored the octet rule and argued that the bonding

was now ionic rather than covalent.^2,6

With the emergence of quantum mechanical theory, the

bonding inhypervalent compounds was generally assumed to

be covalent in nature and rationalized by the acceptance of

the supplementary electrons into the unfilled low-lying d

orbitals, thus violating the octet rule.^3,4,7-9The absence of 2d

orbitals therefore justified the lack of hypervalency in com-

pounds of period 2.^3,4With the advancement of molecular

orbital theory, Rundle and Pimentel developed the earlier

Hypervalency of the heavier main group elements has

attracted considerable attention due to the extraordinary

structures and reactivity their compounds exhibit. The ambi-

guity over the bonding in these species continues to intrigue

chemists and has been debated upon since the pioneering

work on the electronic theory of the covalent bond by Lewis

and Langmuir in the early 1900s.^1-4While elements of period

2 and atoms in their lowest valences conformed readily to the

octet rule, the bonding in molecules formed by heavier atoms

of the periodic table in their higher valences (e.g., PC1₅)

conflicted with this theory and was the topic of a contentious

debate.^2,4Lewis persisted with his traditional theory of the

(5) Lewis, G. N. In Valence and the Structure of Atoms and Molecules; The

Chemical Catalog Co.: New York, 1923; chapter 8.

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*To whom correspondence should be addressed. E-mail: jdw3@st-and.ac.uk.

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r

2010 American Chemical Society

Published on Web 07/15/2010

pubs.acs.org/IC

7578 Inorganic Chemistry, Vol. 49, No. 16, 2010

Knight et al.

work undertaken by Sugden¹⁰and introduced the notion of a

three-center, four-electron bond (3c-4e) to explain the

hypervalency in the trihalide ions.^7,11This concept has be-

come a favored method for explaining the existence of

hypervalency without violating the octet rule or invoking

ionic bonding.^12,13The four electrons occupy bonding and

nonbonding molecular orbitals;^2,7,11,14,15as only one bond-

ing pair is available for the two bonds, hypervalent bonds are

weaker than single electron pair bonds (2c-2e) between the

same elements. Bond orders of apical bonds in hypervalent

3c-4e species are typically less than one (∼0.5), with bond

halogen, the stoichiometry of the reactants, and the nature of

the donor atoms’ R group(s) all play a significant role.^15,22A

slight adjustment to any one of these variables could lead to

subtle modifications in molecular geometry, so it is unsur-

prising that a diverse combination of structures have been

synthesized: charge-transfer (CT) “spoke” and “extended

spoke” adducts, polyiodide, “seesaw”, ionic, “T-shaped”,

bent, mixed-valence, dication-bridged, and dimeric struc-

tural motifs.^15,22Ionic compounds, often accompanied

by counteranions of polyhalides adopting unusual and

sometimes complex structures are also known.^15,22,24-33

The neutral charge-transfer (CT) “spoke” adduct (R₂E-

X-Y, 8-E-3) and the “seesaw” (X-ER₂-Y, 10-E-4) inser-

tion adduct, characteristic of quasi-linear hypervalent E-

X-Y^{15,22,28,34,35}and X-E-Y^{14,15,22,28,31,36,37}fragments,

respectively, are the most common structural motifs gener-

ated from the reaction of diorganochalcogen donors [R₂E]

with inter- or dihalogens.

˚

distances predicted to be 0.18 A longer than for single

electron pair bonds with bond orders of 1.0.^7,9,11,14,15

In 1969, Musher classified “hypervalent” molecules as

those “formed by elements in Groups V-VIII of the periodic

table in any of their valences other than their lowest stable

chemical valence of 3, 2, 1, and 0 respectively.”³The pertinence

of the term “hypervalence” has recently been under dispute

following the advancement of quantum mechanical calcula-

tions which reinforce the 3c-4e theory proposed by Rundle

and Pimentel and conform to the octet rule.^2,7,11,13,16As

a consequence, the use of octet expansion of the heavier

main group elements has diminished from current bonding

descriptions.^13,16,17Nonetheless, hypervalency is a topic of con-

tinued interest to chemists with numerous compounds contain-

ing linear arrangements of three main group elements having

been well documented recently in the literature.^14,15,18-22The

nature of the bonding in these linear species can be described

by the Rundle-Pimentel 3c-4e model and a charge-transfer

model and has recently been thoroughly reviewed.²³

Organic molecules containing the group 16 donor atoms

sulfur, selenium, and tellurium react with dihalogens (Br₂, I₂)

and interhalogens (IBr, ICl) to form a variety of addition

complexes with wide structural diversity. Experimental con-

ditions control the pathway these reactions take and subse-

quently the structural motifs and geometry around the group

16 atoms in the final structure. Factors such as the type of

chalcogen donor atom, the form of the dihalogen or inter-

With variations in the reaction conditions affecting the

outcome of reactions between chalcogen donors [R₂E] with

di- and interhalogens, predicting the conformation of the

final solid state structures continues to be a challenge to

chemists. In solution, the CT “spoke” adduct and the “see-

saw” adduct of RR⁰E X₂type compounds are in equi-

3

librium.^14,38,39Husebye and co-workers suggested that all

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Article

Inorganic Chemistry, Vol. 49, No. 16, 2010 7579

at the halogen and the chalcogen sites of the [R₂E-X]^þ

cation affording the CT “spoke” and “seesaw” hypervalent

adducts, respectively.^14,15,22,41The structure of the final

product can therefore be predicted with a generalization

based on the degree of charge transfer between the nonbond-

ing orbitals of the chalcogen donor n(E) to the LUMO of the

di- or interhalogen acceptor σ*(X-X⁰).^14,39,42This can be

estimated from the electronegativity (χ) of the elements and

follows the loose rule that the “seesaw” adducts will be

formed if halide X is more electronegative than chalcogen

E [R₂E^δþ-X^δ-], while if the converse is true, then the CT

“spoke” adducts will predominate.^14,39,42This is exemplified

by the fact that no CT adducts are known for Te donors

[χ(Te) 2.08]⁴³with any di- or interhalogen [χ(F) 3.94, χ(I)

2.36].^14,15,22,43It must be recognized, however, that the

electronegativity of the chalcogen atom and the electronic

properties of R₂E can be affected by the R groups, thus

influencing the outcome of the reaction. Compounds with

bulky groups around E will favor the three-coordinate chal-

cogen environment of the CT “spoke” adduct over the more

congested four-coordinate atom in the “seesaw” form.^14,39

“Spoke” adducts are formed via the transfer of electron

density from nonbonding orbitals of the chalcogen donor

atom into the LUMO of the di- or interhalogen acceptor

molecule (and hence termed charge-transfer adducts). This

generally occurs when χ(E)>χ(X); i.e., the chalcogen atom

is a stronger donor and more electron density is available to

donate into the empty orbitals on X.^15,22The majority of

neutral CT “spoke” adducts reported in the literature are

formed by the reaction of organosulfur [χ(S) 2.58]⁴³donors

with diiodine [χ(I) 2.36],^{15,22,30,35,43,44}for example, benzyl

sulfide diiodine.⁴⁵

considerable increase in the iodine-iodine bond length from

free iodine [2.66 A]⁴⁸compared to similar sulfur compounds,

˚

showing that organoselenides are better donor molecules

than organosulfides [χ(Se) 2.35, χ(S) 2.58].^15,22,43Reaction

of dibromine with diorganosulfur and diorganoselenium

donors produces adducts of different geometries. Follow-

ing the general rule based on electronegativity values,

both R₂S [χ(S) 2.58]⁴³and R₂Se [χ(Se) 2.35]⁴³donors are

expected to form “seesaw” compounds [χ(X)>χ(E); χ(Br)

2.68].^{14,15,22,39,42,43}While all structurally reported diorg-

anoselenium dibromine compounds exclusively adopt “see-

saw” structures,^{14,15,22,47,49,50}diorganosulfur dibromine

compounds are known to adopt CT “spoke” arrange-

ments^{15,22,28,42,51,52}(“T-shaped” adducts have been reported

from the reaction of S-donor compounds with dibro-

mine).^41,53

Generally, when the halide species (X) is more electroneg-

ative than the chalcogen atom (E), “T-shaped” or “seesaw”

adducts are formed.^14,39,42Consequently, all the known

reactions between tellurium donors [χ(Te) 2.08]⁴³and di- or

interhalogens [χ(F) 3.94, χ(I) 2.36]⁴³form “T-shaped” or

“seesaw” adducts with no tellurium CT “spoke” adducts

known.^15,22,42Tellurium forms strong donor-strong accep-

tor systems with the dihalogens, strong enough to cleave the

X-X bond and oxidize tellurium.^14,15,22Subsequent nucleo-

philic attack occurring at the tellurium site of the [R₂Te-X]^þ

cation affords the “seesaw”/“T-shaped” hypervalent adduct

with a quasi linear X-Te-X alignment.^14,15,22

Partial negative charge acting on the terminal Y atom of

the R₂E-X-Y linear fragment can be sufficient for CT

“spoke” adducts to act as donors toward other acceptors

(A). This produces adducts which are structurally more

complex, known as CT “extended spoke” adducts [R₂E-

Organoselenium diiodine CT adducts are less com-

mon,^15,22,46,47but those reported in the literature exhibit a

X-Y A] (where A is normally another XY molecule and

3 3 3

XY A angles are typically close to 90°).^15,22The terminal

3 3 3

(41) (a) Aragoni, M. C.; Arca, M.; Demartin, F.; Devillanova, F. A.;

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3 3 3

Garau, A.; Isaia, F.; Lelj, F.; Lippolis, V.; Verani, G. Chem. Eur. J. 2001, 7,

;

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With an extremely strong Y A interaction, systems of the

3 3 3

type [RE-X]^þ[Y-A]^-can be envisaged (for example, the

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selone with IBr).^2,15

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2005, 44, 2710. (e) Aucott, S. M.; Kilian, P.; Robertson, S. D.; Slawin, A. M. Z.;

J. D. Inorg. Chem. 1966, 5, 522. (e) Jeske, J.; du Mont, W.-W.; Jones, P. G. Chem.

;

Eur. J. 1999, 5, 385. (f) Cristiani, F.; Demartin, F.; Devillanova, F. A.; Isaia, F.; Saba,

G.; Verani, G. J. Chem. Soc., Dalton Trans. 1992, 3553.

(47) Godfrey, S. M.; McAuliffe, C. A.; Pritchard, R. G.; Sarwar, S.

J. Chem. Soc., Dalton Trans. 1997, 1031.

Woollins, J. D. Chem. Eur. J. 2006, 12, 895. (f) Aucott, S. M.; Duerden, D.; Li,

;

Y.; Slawin, A. M. Z.; Woollins, J. D. Chem. Eur. J. 2006, 12, 5495.

;

7580 Inorganic Chemistry, Vol. 49, No. 16, 2010

Knight et al.

Scheme 1. Hypervalent Adducts Formed from the Reactions of Chalcogen-Containing peri-Substituted Naphthalenes D1-D8 with Dibromine and

Diiodine^a

^aconditions: (i-vii) X₂(X = Br, I), CH₂Cl₂, 2 h, RT; i (4 equiv), Br₂; ii (2 equiv), X₂; iii/iv (1 equiv), I₂; v/vi (1 equiv), X₂; vii (4 equiv), Br₂.

We have previously explored sterically crowded 1,8-disub-

stituted naphthalenes.^54,55Our early work focused on dichal-

cogenide ligands⁵⁴and unusual phosphorus compounds.⁵⁵

More recently, we have reported the synthesis and structu-

ral study of mixed phosphorus-chalcogen,⁵⁶chalcogen-

chalcogen,⁵⁷and halogen-chalcogen systems.⁵⁸During our

investigations of peri-substituted naphthalenes, we prepared

a number of chalcogen donors D1-D8 (Scheme 1).^57,58The

work reported here complements our previous study of

chalcogen-naphthalene derivatives,^56-58expanding the

knowledge of naphthalene distortion and contributing to the

exciting field of hypervalence that occurs in linear species

formed from the reactions between chalcogen donors and

dihalogens. Here, we present the reactions between chalco-

gen donors D1-D8 and dibromine and diiodine and a full

structural study of the geometrically diverse products

formed, 1-15 (Scheme 1).

(55) (a) Kilian, P.; Philp, D.; Slawin, A. M. Z.; Woollins, J. D. Eur. J.

Inorg. Chem. 2003, 249. (b) Kilian, P.; Slawin, A. M. Z.; Woollins, J. D. Chem.

;

Eur. J. 2003, 9, 215. (c) Kilian, P.; Slawin, A. M. Z.; Woollins, J. D. Chem.

Commun. 2003, 1174. (d) Kilian, P.; Slawin, A. M. Z.; Woollins, J. D. Dalton

Trans. 2003, 3876. (e) Kilian, P.; Milton, H. L.; Slawin, A. M. Z.; Woollins, J. D.

Inorg. Chem. 2004, 43, 2252. (f) Kilian, P.; Slawin, A. M. Z.; Woollins, J. D.

Inorg. Chim. Acta 2005, 358, 1719. (g) Kilian, P.; Slawin, A. M. Z.; Woollins,

J. D. Dalton Trans. 2006, 2175.

2. Results and Discussion

Compounds 1-15 were synthesized, and where possible

the derivatives were characterized by multinuclear NMR and

IR spectroscopy and mass spectrometry. The homogeneity

of the new compounds was confirmed by microanalysis. ³¹P,

⁷⁷Se, and ¹²⁵Te NMR spectroscopy data for compounds

4-15 are compared in Table 1 with those of donors

D2-D8.^57,58The tribromide salts 2 and 3 are insoluble in

all common NMR solvents; hence, no NMR spectroscopic

data for these compounds are given. Suitable single crys-

tals were obtained for 1-15 by diffusion of pentane into

(56) (a) Knight, F. R.; Fuller, A. L.; Slawin, A. M. Z.; Woollins, J. D.

Dalton Trans. 2009, 8476. (b) Knight, F. R.; Fuller, A. L.; Slawin, A. M. Z.;

Woollins, J. D. Chem. Eur. J. 2010, 16, 7617. (c) Knight, F. R.; Fuller, A. L.;

;

Slawin, A. M. Z.; Woollins, J. D. Polyhedron, 2010, 29, 1849, DOI: 10.1016/

j.poly.2010.02.033. (d) Knight, F. R.; Fuller, A. L.; Slawin, A. M. Z.; Woollins,

J. D. Polyhedron, 2010, 29, 1956, DOI: 10.1016/j.poly.2010.03.006.

€

(57) Knight, F. R.; Fuller, A. L.; Buhl, M.; Slawin, A. M. Z.; Woollins,

J. D. Chem. Eur. J. 2010, 16, 7503.

;

€

(58) Knight, F. R.; Fuller, A. L.; Buhl, M.; Slawin, A. M. Z.; Woollins,

J. D. Chem. Eur. J. 2010, 16, 7605.

;

Article

Inorganic Chemistry, Vol. 49, No. 16, 2010 7581

saturated solutions of the individual compound in dichlor-

omethane. All compounds 1-15 crystallize with one mole-

cule in the asymmetric unit. Selected interatomic distances,

angles, and torsion angles are listed in Tables 1-6. Further

crystallographic information can be found in Tables 8-11

and the Supporting Information.

Adducts formed from the reaction of diorganosulfur

compounds with dibromine are rare. The majority of those

reported and structurally characterized by single-crystal

X-ray diffraction adopt the CT “spoke” structure with a

S-Br-Br linear arrangement.^{15,22,28,42,51}Upon treatment of

1,8-bis(phenylsulfanyl)naphthalene D1 with dibromine, no

adduct is isolated, but electrophilic aromatic substitution do-

minates. Aromatic groups bearing -SR groups are strongly

activated by delocalization of resonance lone pairs into the

aromatic π system and are therefore highly reactive toward

electrophilic substitution.⁵⁹The delocalization of the lone

pair on sulfur into the aromatic system in D1 makes it un-

available for donation into the empty orbitals of the dibro-

mine molecule. The naphthalene ring system being less aro-

matic than the phenyl moieties thus makes it more susceptible

toward electrophilic substitution. The activating S(phenyl)

group donates electrons into the π system and directs

incoming electrophiles to the ortho or para positions. Attack

at the para position is sterically more favorable, placing the

large bromine atom further from the bulk of the molecule.⁵⁹

The second bromination is directed by the second S(phenyl)

moiety to the ortho (C7) position to avoid the inevitable steric

interaction between the bromine atoms upon para substitu-

tion. Final bromination of the phenyl rings occurs with the

sulfur atoms directing the substitution to the two para posi-

tions, away from the steric bulk of the molecule to produce

1,8-bis(4-bromophenylsulfanyl)-2,5-dibromonaphthalene 1

Table 1. ³¹P, ⁷⁷Se, and ¹²⁵Te NMR Spectroscopy Data [δ (ppm)] for Donors

D2-D8 and Adducts 4-15

D2

4

5

D3

6

peri atoms SeSe SeSe

X-Te-X

SeSe

Se-I-I I₂

SeS

Se-I-I I₂

Se-I-I

3 3 3

⁷⁷Se NMR 428.6 436.9, 436.7 445.1, 444.3 455.3 476.9

3 3 3

D4

7

9

D5

8

10

peri atoms TeS TeS

X-Te-X

TeS

Br-Te-Br I-Te-I

TeSe TeSe

TeSe

Br-Te-Br I-Te-I

362.8 500.0

687.6 941.4

⁷⁷Se NMR

428.8

747.0

¹²⁵Te NMR 715.2 958.9

790.9

D6

11

13

D7

12

14

peri atoms BrTe BrTe

X-Te-X

BrTe

Br-Te-Br I-Te-I

887.5

ITe ITe

Br-Te-Br I-Te-I

698.3 903.0 848.0

ITe

¹²⁵Te NMR 731.2 942.8

D8

15

peri-atoms

³¹P NMR

PS

-5.3

PS

52.5

˚

Table 2. Selected Interatomic Distances [A] and Angles [deg] for 1-5

compound

1

2

3

4

5

peri-region distances and subvan der Waals contacts

E(1) E⁰(1)

2.935(4)

0.665; 82

1.787(11)

1.780(11)

2.7619(7)

1.038; 73

1.957(6)

1.918(5)

2.721(2)

0.979; 74

1.955(8)

1.796(9)

3.1339(6)

0.666; 82

1.953(5)

1.933(5)

3.0756(14)

0.724; 81

1.948(8)

1.929(7)

3 3 3

a

Σr_vdW- E E⁰; % Σr_vdW

3 3 3

E(1)-C(1)

E⁰(1)-C(9)

naphthalene bond lengths

C(1)-C(2)

C(2)-C(3)

C(3)-C(4)

C(4)-C(5)

C(5)-C(10)

C(5)-C(6)

C(6)-C(7)

C(7)-C(8)

C(8)-C(9)

C(9)-C(10)

C(10)-C(1)

1.365(16)

1.388(16)

1.370(16)

1.417(15)

1.453(15)

1.438(16)

1.340(18)

1.386(16)

1.402(16)

1.431(15)

1.442(15)

1.372(8)

1.401(9)

1.352(9)

1.424(8)

1.430(8)

1.404(8)

1.357(9)

1.395(9)

1.374(8)

1.414(7)

1.427(7)

1.375(14)

1.390(15)

1.342(17)

1.424(14)

1.429(12)

1.422(16)

1.363(16)

1.404(15)

1.362(15)

1.395(13)

1.450(14)

1.366(7)

1.411(8)

1.383(8)

1.374(8)

1.451(7)

1.416(8)

1.350(8)

1.393(8)

1.379(7)

1.424(7)

1.435(6)

1.375(15)

1.410(12)

1.350(17)

1.428(16)

1.430(11)

1.406(14)

1.365(17)

1.411(13)

1.376(14)

1.412(14)

1.441(14)

peri-region bond angles

E(1)-C(1)-C(10)

C(1)-C(10)-C(9)

E⁰(1)-C(9)-C(10)

Σ of bay angles

splay angle^b

122.3(8)

126.0(10)

121.6(8)

369.9(18)

9.9

119.8(4)

126.2(5)

120.1(4)

366.1(9)

6.1

119.5(6)

126.0(8)

119.8(7)

365.3(15)

5.3

121.9(3)

128.4(4)

123.0(4)

373.3(7)

13.3

122.5(7)

126.9(7)

124.2(6)

373.6(14)

13.6

C(4)-C(5)-C(6)

121.0(10)

120.6(5)

119.0(8)

119.9(5)

119.2(8)

out-of-plane displacement

E(1)

E⁰(1)

-0.343(13)

0.343(13)

0.2887(66)

-0.0101(66)

0.112(11)

0.139(11)

-0.3290(74)

0.5359(73)

0.415(11)

-0.246(11)

central naphthalene ring torsion angles

C:(6)-(5)-(10)-(1)

C:(4)-(5)-(10)-(9)

176.1(10)

176.2(9)

-177.4(12)

-175.0(12)

179.3(8)

-179.2(8)

-172.7(7)

-176.2(7)

176.7(6)

174.8(7)

P

^avan der Waals radii used for calculations: r_vdW(S), 1.80 A; r_vdW(Se), 1.90 A;^{61 b}Splay angle:

of the three bay region angles - 360.

˚

7582 Inorganic Chemistry, Vol. 49, No. 16, 2010

Knight et al.

˚

Table 3. Selected Interatomic Distances [A] and Angles [deg] for 6-10

compound

6

7

8

9

10

peri-region distances and subvan der Waals contacts

E(1) E⁰(1)

2.9798(18)

0.720; 81

1.958(5)

1.773(5)

3.075(2)

0.785; 80

2.124(10)

1.782(11)

3.141(2)

0.819; 79

2.148(15)

1.933(14)

3.0767(17)

0.783; 78

2.138(6)

1.784(6)

3.137(2)

0.823; 79

2.14(2)

3 3 3

a

Σr_vdW- E E⁰; % Σr_vdW

3 3 3

E(1)-C(1)

E⁰(1)-C(9)

1.915(19)

naphthalene bond lengths

C(1)-C(2)

C(2)-C(3)

C(3)-C(4)

C(4)-C(5)

C(5)-C(10)

C(5)-C(6)

C(6)-C(7)

C(7)-C(8)

C(8)-C(9)

C(9)-C(10)

C(10)-C(1)

1.367(9)

1.411(8)

1.360(11)

1.416(10)

1.427(7)

1.432(10)

1.361(11)

1.399(9)

1.360(10)

1.424(9)

1.431(9)

1.355(15)

1.410(16)

1.393(15)

1.400(15)

1.421(14)

1.452(15)

1.343(15)

1.388(15)

1.362(15)

1.447(14)

1.427(13)

1.36(2)

1.37(2)

1.39(2)

1.45(2)

1.52(2)

1.28(2)

1.40(2)

1.34(2)

1.43(2)

1.42(2)

1.380(9)

1.395(10)

1.363(10)

1.411(10)

1.433(9)

1.420(9)

1.360(10)

1.405(10)

1.382(9)

1.447(9)

1.433(9)

1.43(2)

1.42(2)

1.37(3)

1.43(3)

1.41(3)

1.45(2)

1.36(2)

1.43(2)

1.36(3)

1.46(3)

1.43(2)

peri-region bond angles

E(1)-C(1)-C(10)

C(1)-C(10)-C(9)

E⁰(1)-C(9)-C(10)

Σ of bay angles

splay angle^b

121.7(4)

126.8(5)

122.4(4)

370.9(9)

10.9

123.1(7)

127.6(9)

121.3(7)

372.0(16)

12.0

122.2(10)

130.4(15)

120.9(13)

373.5(27)

13.5

122.5(4)

127.1(6)

122.7(5)

372.3(11)

12.3

122.6(14)

129.4(17)

120.4(14)

372.4(31)

12.4

C(4)-C(5)-C(6)

119.1(5)

117.7(9)

119.2(14)

119.4(6)

116.2(18)

out-of-plane displacement

E(1)

E⁰(1)

0.438(11)

-0.233(11)

-0.401(12)

0.250(12)

-0.444(1)

0.259(1)

-0.3690(82)

0.3007(77)

-0.372(8)

0.317(8)

central naphthalene ring torsion angles

C:(6)-(5)-(10)-(1)

C:(4)-(5)-(10)-(9)

176.8(4)

174.9(4)

-179.1(8)

-174.3(8)

-177.0(12)

-173.5(13)

-177.3(6)

-174.1(5)

179.7(14)

-174.7(13)

P

^avan der Waals radii used for calculations: r_vdW(S), 1.80 A; r_vdW(Se), 1.90 A; r_vdW(Te), 2.06 A.^{61 b}Splay angle: of the three bay region angles - 360.

˚

(Scheme 1).⁵⁹Varying the loading of dibromine (1-6 equiv)

produced 1 exclusively.

is reduced.⁶²Distortion away from the “ideal” naphthalene

geometry also helps alleviate steric strain and occurs via in-

plane and out-of-plane deviations of the exocyclic bonds and

buckling of the usually rigid backbone.^{56-58,60,61,63}X-ray

structural data play a fundamental role in determining naph-

thalene distortion and therefore assessing steric strain.^56-58

The structural geometry of compounds 1-15 can be

described by the orientation of the naphthyl and phenyl rings

relative to the C(ar)-G(1)-C(ar) and the C(ar)-Z(2)-CI

planes, calculated from torsion angles θ and γ, respectively

(see Table 7, Figure 1).⁶⁴When θ and γ approach 90°, the

orientation is categorized as axial, while an equatorial con-

formation is denoted by angles close to 180°.⁶⁴Conforma-

tions in between axial and equatorial are classified as twist.⁶⁴

For angle θ, axial conformations correspond to the “type A”

Substitution of the heavier main group elements at the peri

positions in naphthalene causes considerable steric hindrance,

giving rise to structurally distorted compounds with unusual

bonding and geometry.^56-58,60The bulky atoms are con-

strained in close proximity to the rigid backbone at a distance

shorter than the sum of van der Waals radii for the two

interacting atoms.^56-58Steric strain caused by the crowding

of substituents can be released through bond formation or if

weak attractive noncovalent interactions exist between tightly

packed atoms.^60,61As nonbonded distances decrease relative to

the sum of van der Waals radii, weak noncovalent interactions

become more covalent in nature and the steric interaction

structure presented by Nakanishi et al. (the G-C_Ph

/

(59) (a) Organic Chemistry; Clayden, J., Greeves, N., Warren, S., Wothers, P.,

Eds.; Oxford University Press: Oxford, U. K., 2001; chapter 22. (b) Organic

Chemistry Structure and Function, 3rd ed.; Vollhardt, K. P. C., Schore, N. E.,

Eds.; W. H. Freeman and Company: New York, 1999; chapter 16.

Z-C_Phbond lies perpendicular to the naphthyl plane).⁶⁵

(62) Hayashi, S.; Nakanishi, W. Bull. Chem. Soc. Jpn. 2008, 81(12), 1605.

(63) (a) Coulson, C. A.; Daudel, R.; Robertson, J. M. Proc. R. Soc.

London, Ser. A 1951, A207, 306. (b) Cruickshank, D. W. J. Acta Crystallogr.

1957, 10, 504. (c) Brock, C. P.; Dunitz, J. D. Acta Crystallogr., Sect. B: Struct.

Sci. 1982, B38, 2218. (d) Oddershede, J.; Larsen, S. J. Phys. Chem. A 2004, 108,

(60) Balasubramaniyan, V. Chem. Rev. 1966, 66, 567.

€

(61) (a) Schmidbaur, H.; Oller, H.-J.; Wilkinson, D. L.; Huber, B.;

€

Muller, G. Chem. Ber. 1989, 122, 31. (b) Fujihara, H.; Furukawa, N. J. Mol.

Struct. 1989, 186, 261. (c) Fujihara, H.; Akaishi, R.; Erata, T.; Furukawa, N.

J. Chem. Soc., Chem. Commun. 1989, 1789. (d) Handal, J.; White, J. G.; Franck,

R. W.; Yuh, Y. H.; Allinger, N. L. J. Am. Chem. Soc. 1977, 99, 3345. (e) Blount,

1057.

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(64) Nagy, P.; Szabo, D.; Kapovits, I.; Kucsman, A.; Argay, G.; Kalman,

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J. F.; Cozzi, F.; Damewood, J. R.; Iroff, D. L.; Sjostrand, U.; Mislow, K. J. Am.

A. J. Mol. Struct. 2002, 606, 61.

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Chem. Soc. 1980, 102, 99. (f) Anet, F. A. L.; Donovan, D.; Sjostrand, U.; Cozzi,

F.; Mislow, K. J. Am. Chem. Soc. 1980, 102, 1748. (g) Hounshell, W. D.; Anet,

F. A. L.; Cozzi, F.; Damewood, J. R., Jr.; Johnson, C. A.; Sjostrand, U.; Mislow,

(65) (a) Nakanishi, W.; Hayashi, S. J. Org. Chem. 2002, 67, 38.

(b) Hayashi, S.; Yamane, K.; Nakanishi, W. J. Org. Chem. 2007, 72, 7587.

(c) Nakanishi, W.; Hayashi, S.; Toyota, S. J. Am. Chem. Soc. 1998, 63, 8790.

(d) Nakanishi, W.; Hayashi, S.; Uehara, T. J. Phys. Chem. 1999, 103, 9906.

(e) Nakanishi, W.; Hayashi, S.; Uehara, T. Eur. J. Org. Chem. 2001, 3933.

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K. J. Am. Chem. Soc. 1980, 102, 5941. (h) Schrock, R.; Angermaier, K.; Sladek,

A.; Schmidbaur, H. Organometallics 1994, 13, 3399.

Article

Inorganic Chemistry, Vol. 49, No. 16, 2010 7583

˚

Table 4. Selected Interatomic Distances [A] and Angles [deg] for 11-15

compound 11

12

13

14

15

peri-region distances and sub van der Waals contacts

G(1) E(1)

3 3 3

3.2397(15)

0.670; 83

1.900(11)

2.153(10)

3.3810(7)

0.659; 84

2.117(9)

2.150(8)

3.1563(6)

0.754; 81

1.911(6)

2.150(6)

3.3608(11)

0.679; 83

2.097(11)

2.159(9)

3.165(2)

0.435; 88

1.796(11)

1.789(12)

a

Σr_vdW- G E; % Σr_vdW

3 3 3

G(1)-C(1)

E(1)-C(9)

naphthalene bond lengths

C(1)-C(2)

C(2)-C(3)

C(3)-C(4)

C(4)-C(5)

C(5)-C(10)

C(5)-C(6)

C(6)-C(7)

C(7)-C(8)

C(8)-C(9)

C(9)-C(10)

C(10)-C(1)

1.382(16)

1.413(16)

1.341(18)

1.423(17)

1.450(14)

1.427(18)

1.357(16)

1.390(15)

1.345(17)

1.441(16)

1.415(16)

1.361(13)

1.397(14)

1.376(14)

1.422(13)

1.453(12)

1.410(14)

1.352(14)

1.416(13)

1.374(14)

1.437(13)

1.406(13)

1.357(9)

1.390(10)

1.360(8)

1.409(10)

1.424(8)

1.419(7)

1.364(9)

1.405(8)

1.362(6)

1.444(8)

1.421(6)

1.384(17)

1.369(17)

1.36(2)

1.393(13)

1.391(17)

1.359(13)

1.423(14)

1.442(17)

1.415(13)

1.362(14)

1.414(18)

1.397(13)

1.420(12)

1.459(12)

1.392(16)

1.432(13)

1.423(16)

1.345(16)

1.400(15)

1.354(16)

1.450(14)

1.415(17)

peri-region bond angles

G(1)-C(1)-C(10)

C(1)-C(10)-C(9)

E(1)-C(9)-C(10)

Σ of bay angles

splay angle^b

121.3(8)

129.3(10)

122.5(8)

373.1(18)

13.1

122.0(6)

129.3(8)

124.6(6)

375.9(14)

15.9

121.5(4)

128.1(5)

122.8(3)

372.4(9)

12.4

126.3(7)

128.2(8)

124.2(7)

378.7(15)

18.7

126.2(7)

126.4(10)

122.9(7)

375.5(17)

15.5

C(4)-C(5)-C(6)

119.9(9)

119.8(8)

119.4(5)

120.5(10)

118.9(11)

out-of-plane displacement

G(1)

E(1)

-0.550(14)

0.641(15)

-0.644(14)

0.646(15)

0.312(14)

-0.614(14)

-0.410(14)

0.436(14)

0.436(11)

-0.466(11)

central naphthalene ring torsion angles

C:(6)-(5)-(10)-(1)

C:(4)-(5)-(10)-(9)

170.2(10)

174.0(10)

-168.7(8)

-175.5(8)

174.4(5)

176.5(5)

-175.2(9)

-176.8(9)

171.9(7)

174.9(7)

P

^avan der Waals radii used for calculations: r_vdW(P), 1.80 A; r_vdW(S), 1.80 A; r_vdW(Br), 1.85 A; r_vdW(I), 1.98 A; r_vdW(Te), 2.06 A.^{61 b}Splay angle: of

the three bay region angles - 360.

˚

-

˚

Table 5. Selected Interatomic X-E-E, E-X-X, and X₃distances [A] and angles [deg] for 2-6

compound

2

3

4

5

6

E-Se-X and Br₃^-distances and subvan der Waals contacts

Se-I-I and I₃^-distances and subvan der Waals contacts

Br(1)-Se(1)

Se(1)-E(2)

Br(2)-Br(3)

Br(3)-Br(4)

2.4878(8)

2.7619(8)

2.5170(8)

2.5668(8)

2.4232(15)

2.721(2)

2.5514(17)

2.5433(17)

I(1)-Se(1)

I(1)-I(2)

2.9795(8)

2.7987(6)

2.8497(9)

2.8672(8)

3.543(1)

2.7402(11)

3.8730(9)

2.8436(6)

2.8706(5)

3.526(1)

2.7418(7)

3.8527(13)

I(2) I(3)

I(3)-I(3)¹

3 3 3

I(1) E(2)

3 3 3

3.6956(7)

E-E-X and E-X-X bond angles

Br(1)-Se(1)-E(2)

Br(2)-Br(3)-Br(4)

172.10(3)

177.78(3)

176.34(1)

178.57(5)

I(2)-I(1)-Se(1)

177.637(15)

74.33(1)

178.09(3)

177.5(1)

176.3(1)

81.54(1)

179.04(2)

107.9(1)

108.0(1)

82.81(1)

I(2) I(3)-I(3)⁰

3 3 3

I(1)-I(2) I(3)

3 3 3

I(1)-Se(1)-E(2)

An equatorial conformation for θ aligns the G-C_Ph/Z-C_Ph

bond on or close to the plane (“type B”),⁶⁵and a twist

conformation relates to Nakanishi’s “type C” (Figure 1).^64,65

Compound 1 (Figure 2) displays a mixed equatorial-axial

and axial-equatorial conformation of naphthyl and phenyl

rings around the two individual sulfur atoms, matching that

observed for D1 and classified as the “AB-type” structure

(Figure 1).^57,65The sulfur atoms are displaced to even dis-

tances but to opposite sides of the naphthalene least-squares

plane with a deviation comparable to that displayed by D1.⁵⁷

The sulfur atoms are further accommodated by in-plane

distortions in the C-C-C group between the peri atoms

indicated by a positive splay angle of 9.9°. The resulting

˚

nonbonded S S peri distance [2.935(4) A] is 18% shorter

3 3 3

than the sum of the van der Waals radii for two sulfur atoms

66

˚

[3.60 A] and marginally shorter than that observed in D1

57

˚

[3.0036(13) A].

A more pronounced distortion of the naphthalene skeleton

is observed in 1, which exhibits larger maximum C-C-C-C

torsion angles [ca. 4°] compared to D1 [ca. 1-3°].⁵⁷Br(4) and

(66) Bondi, A. J. Phys. Chem. 1964, 68, 441.

7584 Inorganic Chemistry, Vol. 49, No. 16, 2010

Knight et al.

˚

Br(8) atoms lie 0.025(13) A and 0.103(11) A above the

to the extent that the Br(1)-Br(2) bond is cleaved, forming

the cation [RSe-Br]^þand a quasi-linear hypervalent 3c-4e

Br₃^-counteranion.¹⁵

˚

naphthyl plane, respectively, and Br-C [1.90-1.91 A] and

˚

S-C [1.79-1.76 A] bond lengths are within the usual ranges

˚

[1.90, 1.77 ( 0.05 A]. Intermolecular short contacts exist

The ionic “extended spoke” adducts 2 and 3 adopt a

similar conformation in their molecular structures (Figure 3).

The naphthyl and phenyl rings orient with an axial-

equatorial arrangement around each chalcogen peri atom

with both E-C_Phbonds aligning perpendicular to and on the

same side of the naphthyl plane (“AA-c type”, Figure 1).^64,65

The phenyl rings overlap in a face-to-face offset arrange-

1

˚

between bromine atoms [Br(4) Br(8) 3.63(1) A; Br(4)

3 3 3

Br(14)¹¹3.65(1) A; Br(14) Br(20)¹¹¹3.63(1) A], but no

˚

3 3 3

significant overlap of phenyl or naphthyl rings is observed.

All structurally reported adducts formed from the reaction

of diorganoselenium compounds with dibromine adopt the

“seesaw” geometry.^{14,15,22,47,49,50}The donor compounds 1,8-

bis(phenylselenyl)naphthalene D2 and 1-(phenylselenyl)-

8-(phenylsulfanyl)naphthalene D3 react with dibromine to

form similar tribromide salts of analogous bromoselenyl

cations, which can be represented by the formula [RSe-

˚

ment with centroid-centroid distances [2, 3.691(1) A; 3,

˚

3.79(1) A] within the usual range for typical π-π stack-

67

˚

ing [3.3-3.8 A]. Each adduct displays one quasi-linear

X-E E⁰arrangement of three atoms [2, 172.1°; 3,

3 3 3

Br]^þ[Br-Br₂]^-(Scheme 1).¹⁵The lower electronegativity

176.3°], the nature of the bonding that can be described by

3 3 3

and hence greater electron donor ability of selenium over

sulfur allows for a strong donor-strong acceptor system to

form with dibromine sufficient to cleave the Br-Br bond and

oxidize the selenium atom.^15,22,43In both D2 and D3, the

Se(1) atom reacts with the first molecule of Br₂simulta-

neously weakening the Br(1)-Br(2) bond. The partial nega-

tive charge acting on the terminal Br(2) atom could be

sufficient to act as a donor toward a second (acceptor)

molecule of Br₂. Delocalization of negative charge onto the

terminal Br(2) atom would strengthen the Se(1)-Br(1) bond

the Rundle-Pimentel 3c-4e model.^7,11The Se Se and

3 3 3

˚

Se S peri distances in 2 and 3 [2.7619(7) A; 2.721(2) A] are

3 3 3

27% and 26% shorter than the sum of van der Waals radii for

the two interacting atoms, respectively. These values lie

between those of a single electron pair Se-Se and Se-S

68,69

˚

bond [2.3639(5) A; 2.24(1) A]

and the nonbonding

˚

interactions observed in D2 and D3 [3.1332(9) A; 3.063(2) A],

respectively.⁵⁷

The significant reduction in the peri distance in both

adducts relative to D2 and D3 suggests that a weak attractive

noncovalent interaction is operating between the peri atoms,

thus decreasing steric hindrance. As expected, naphthalene

distortion in 2 and 3, although still influential due to the

absence of a strong peri-covalent bond,⁶⁸is notably dimin-

ishedcomparedwith D2 and D3, respectively. Theinclination

of the exocyclic E-C_Napbonds within the naphthyl plane is

minimal with small, but not negligible, positive splay angles

[2, 6.1°; 3, 5.3°] considerably reduced compared with donor

compounds D2 [13.9°] and D3 [12.4°]. The displacement of

the peri atoms from the naphthyl plane is relatively low in

both compounds, with the Se(2) atom of 2 lying virtually on

the plane. The peri atoms of 3 are displaced to the same side

of the plane. The naphthalene skeleton for 2 shows a minor

deviation from planarity with central naphthalene ring tor-

sion angles ca. 3-5°, while the backbone of 3 is essentially

planar ca. 0.7-0.8°.

˚

Table 6. Selected Interatomic X-E-X Distances [A] and Angles [deg] for 7-14

compound

7

8

9

10

X-E-X distances, sub van der Waals contacts, and bond angles

X(1)-Te(1)

Te(1)-X(2)

2.7072(11) 2.719(2)

2.6688(12) 2.671(2)

2.9457(6)

2.9073(6)

2.9538(17)

2.8943(17)

3.6136(16) 3.696(2)

X(1) G(1)^a

3.486(2)

3.542(2)

177.94(6) 176.81(2)

3 3 3

X(1)-Te(1)-X(2) 176.67(4)

179.59(6)

11

12 13

14

X(1)-Te(1)

Te(1)-X(2)

2.6664(13) 2.6578(10) 2.9343(5)

2.6686(13) 2.6779(11) 2.8952(4)

3.7079(17) 3.8497(11) 4.0089(6)

2.9480(7)

2.9042(7)

4.16(1)

X(1) G(1)^a

3 3 3

X(1)-Te(1)-X(2) 175.80(4)

176.55(3)

176.405(19) 177.27(3)

^aG(1) = S, 7, 9; Se, 8, 10; Br, 11, 13; I, 12, 14.

Table 7. Torsion Angles [deg] Categorizing the Naphthalene and Phenyl Ring Conformations in 1-15^a

naphthalene ring conformations

phenyl ring conformations

Nap₁: C(10)-C(1)-G(1)-C(11)

Nap₂: C(10)-C(9)-Z(9)-C(17)

Ph₁: C(1)-G(1)-C(11)-C(12)

Ph₂: C(9)-Z(9)-C(17)-C(18)

1

2

3

4

5

6

7

8

θ₁= 155.1(9): eq

θ₁= 99.8(4): ax

θ₁= 87.7(7): ax

θ₁= -155.6(5): eq

θ₁= 166.1(5): eq

θ₁= 166.8(3): eq

θ₁= -145.9(7): twist

θ₁= -147.1(12): twist

θ₁= -146.9(5): twist

θ₁= -148.0(12): twist

θ₁= 141.8(8): twist

θ₁= -140.3(8): twist

θ₁= 152.8(4): eq

θ₁= -157.3(7): eq

θ₁= 160.4(7) Nap₁: eq

θ₃= -84.7(8) Nap₃: ax

θ₂= -105.3(9): ax

θ₂= -101.4(4): ax

θ₂= -116.3(7): ax

θ₂= -88.9(5): ax

θ₂= 75.1(6): ax

θ₂= 75.2(4): ax

θ₂= 85.8(8): ax

θ₂= -86.4(13): ax

θ₂= -87.5(5): ax

θ₂= -86.8(13): ax

n/a

γ₁= -88.5(11): ax

γ₁= 167.7(4): eq

γ₂= 16.8(12): eq

γ₂= 164.4(4): eq

γ₂= -151.5(8): eq

γ₂= 170.2(4): eq

γ₂= 26.2(9): eq

γ₂= 23.2(7): eq

γ₂= 148.3(8): twist

γ₂= -29.5(16): twist

γ₂= 146.2(5): twist

γ₂= -21.8(17): twist

n/a

γ₁= -159.4(7): eq

γ₁= -116.5(5): ax

γ₁= -67.7(7): ax

γ₁= 117.0(4): ax

γ₁= -148.9(8): twist

γ₁= 40.5(14): twist

γ₁= -151.2(5): twist

γ₁= 42.8(15): twist

γ₁= 137.0(8): twist

γ₁= -136.5(7): twist

γ₁= 138.6(4): twist

γ₁= -135.7(8): twist

γ₁= 101.8(10) Ph₁: ax

γ₃= 153.6(6) Ph₃: twist

9

10

11

12

13

14

15

n/a

θ₂= 97.8(6) Nap₂: ax

n/a

γ₂= -168.1(7) Ph₂: eq

^aNap₁: naphthalene ring G(1). Nap₂: naphthalene ring Z(9). Nap₃: second naphthalene ring G(1). Ph₁: G(1) phenyl ring. Ph₂: Z(9) phenyl ring. Ph₃:

second G(1) phenyl ring. ax = axial: perpendicular to C(ar)-G/Z-C(ar) plane. eq = equatorial: coplanar with C(ar)-G/Z-C(ar) plane. twist:

intermediate between equatorial and axial.

Article

Inorganic Chemistry, Vol. 49, No. 16, 2010 7585

Table 8. Crystallographic Data for Compounds 1-4

compound

1

2

3

4

empirical formula

fw

C₂₂H₁₂Br₄S₂

660.07

C₁₆H₁₁Br₄Se₂

757.9

C₂₂H₁₆Br₄SSe

711

C₂₂H₁₆I₂Se₂

692.1

temperature (°C)

cryst color, habit

cryst dimensions (mm³)

cryst syst

-148(1)

yellow, prism

0.12 ꢀ 0.06 ꢀ 0.06

monoclinic

orange, block

0.12 ꢀ 0.12 ꢀ 0.12

monoclinic

orange, platelet

0.18 ꢀ 0.12 ꢀ 0.06

monoclinic

orange, prism

0.12 ꢀ 0.12 ꢀ 0.06

triclinic

˚

lattice params

a = 32.535(13) A

a = 9.293(3) A

b = 14.082(5) A

˚

c = 17.212(6) A

a = 13.555(2) A

b = 9.2381(13) A

˚

c = 18.663(3) A

a = 10.003(3) A

˚

b = 5.4833(18) A

˚

b = 10.453(2) A

˚

c = 27.215(9) A

˚

c = 11.749(3) A

R = 102.307(6)°

β = 84.68(3)°

γ = 93.395(4)°

V = 1089.3(5)

P1

2

2.11

644

62.337

11727

0.036

0.486-0.688

3715

β = 92.729(11)°

β = 97.177(9)°

β = 103.009(3)°

3

volume (A )

˚

V = 4850(3)

C2/c

8

1.808

2528

68.368

13347

0.068

0.406-0.664

4268

V = 2234.8(13)

P2₁/n

4

2.252

1424

104.897

13998

0.042

0.268-0.284

4524

V = 2277.0(6)

P2₁/c

4

2.074

1352

87.882

12771

0.064

0.294-0.590

3971

space group

Z value

Dcalc (g/cm³)

F000

μ(Mo Ka) (cm^-1

no. of reflns measd

)

Rint

min and max transmissions

independent reflns

obsd refln (no. variables)

refln/param ratio

3398(254)

16.8

0.0866

0.1144

0.2732

1.206

3974(254)

17.81

0.0435

0.054

0.1236

1.175

3489(254)

15.63

0.0699

0.0813

0.1938

1.15

3557(236)

15.74

0.0302

0.0359

0.1262

1.28

residuals: R₁(I>2.00σ(I))

residuals: r (all reflns)

residuals: wR₂(all reflns)

goodness of fit indicator

Flack param

3

˚

2.78 e/A

˚

1.32 e/A

˚

2.33 e/A

˚

1.44 e/A

maximum peak in final diff. map

minimum peak in final diff. map

3

˚

-1.00 e/A

-1.17 e/A

-1.18 e/A

-1.77 e/A

-

The linear Br₃counteranions present in both molecular

(Scheme 1). Iodine [χ(I) 2.36],⁴³unlike bromine [χ(Br)

2.68],⁴³has a similar electronegativity to selenium [χ(Se)

2.35]⁴³and accepts electron density from nonbonding orbi-

tals of the selenium donor to form the charge-transfer adduct.

This has the effect of lowering the bond order and conse-

structures exhibit a lengthening of the Br-Br distances

[2.52-2.57 A] compared to free bromine [2.28 A].⁴⁸This is

indicative of the three-center, four-electron bond (3c-4e)

model proposed by Rundle and Pimentel to explain hyper-

valency in the trihalide ions.^7,11The primary distinction

between the molecular structures of 2 and 3 derives from

˚

quently weakening the I-I bond, which extends from 2.66 A

(free iodine)⁴⁸to 2.7987(6) A.^15,22The partial negative charge

˚

differing intra- and intermolecular interactions and subse-

˚

delocalized on the terminal I(2) atom in the hypervalent

3c-4e Se(1)-I(1)-I(2) bond allows I(2) to act as a donor

toward a second molecule of diiodine to afford a CT

“extended spoke” adduct 5 (Scheme 1).¹⁵

quent molecular packing. Short Br(1) Br(2) [3.172(1) A]

3 3 3

and Se(2¹) Br(2) [3.555(1) A] contacts present in 2 lock

˚

3 3 3

two neighboring molecules together, forming a quasi-planar

rectangular arrangement of eight atoms (Figure 4). Two

further nonbonded intermolecular interactions are observed

Adduct 5 adopts a similar structure to that formed by the

reaction of triphenylphosphine sulfide with I₂.⁷⁰The terminal

iodine atoms of two molecules of adduct 4 (D2-I₂) act as

-

between a terminal Br(4¹¹) atom of a Br₃ion and the

11

˚

two selenium peri atoms [Se(1) Br(4 ) 3.250(1) A and

donors toward the same diiodine molecule, which bridges

˚

3 3 3

11

˚

Se(2) Br(4 ) 3.715(1) A]. The linear tribromide counter-

anion in 3 adopts a position above the peri atoms. There is no

Br(1) Br₃interaction but instead a nonbonded intra-

molecular interaction between Se(1) Br(2) [3.562(1) A].

Although a number of short contacts exist, there is no

significant overlap of phenyl or naphthyl rings in either

via soft-soft I I interactions [3.543(1) A], constructing a

3 3 3

“Z-shaped” system with a D2-I₂I₂I₂-D2 configura-

3 3 3 3 3 3

-

tion. Compounds with extended poly(I₂) chains held by weak

3 3 3

˚

I₂I₂interactions and adducts formed with a donor/diha-

3 3 3

logen composition greater than 1:1 are extremely rare.^15,71

The treatment of 1-(phenylselenyl)-8-(phenylsulfanyl)-

naphthalene D3 with two equivalents of diiodine produces

an analogous “Z-shaped” adduct to that of 5 (Scheme 1).

Two “spoke”-like adduct units constructed from the sele-

nium donor moiety of D3 and diiodine are bridged by the

adduct and no π π stacking.

3 3 3

Diorganoselenium compounds are known to form CT

“spoke” adducts upon treatment with diiodine.^15,22,46,47

1,8-Bis(phenylselenyl)naphthalene D2 reacts with one molar

equivalent of diiodine to form the neutral CT “spoke” adduct

4 containing a quasi-linear Se-I-I fragment [177.6(1)°]

same diiodine molecule with weak I I interactions of a

3 3 3

15

˚

similar magnitude as observed in adduct 5 [3.526(1) A].

The ⁷⁷Se NMR spectra for adducts 4 and 5 display a

downfield shift compared to D2 [δ = 428.6 ppm].⁵⁷Both

spectra exhibit two signals, each corresponding to a different

(67) (a) Roesky, H. W.; Andruh, M. Coordin. Chem., Rev. 2003, 236, 91.

(b) Koizumi, T.; Tsutsui, K.; Tanaka, K. Eur. J. Org. Chem. 2003, 9(18), 4528.

(c) Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885.

(68) Fuller, A. L.; Knight, F. R.; Slawin, A. M. Z.; Woollins, J. D. Eur. J.

Inorg. Chem. 2010, accepted,

(69) Meinwald, J.; Dauplaise, D.; Clardy, J. J. Am. Chem. Soc. 1977, 99

(23), 7743.

(70) (a) Schweikert, W. W.; Meyers, E. A. J. Phys. Chem. 1968, 72, 1561.

(b) Bransford, J. W.; Meyers, E. A. Cryst. Struct. Commun. 1978, 7, 697.

(71) Arca, M.; Demartin, F.; Devillanova, F. A.; Garau, A.; Isaia, F.;

Lippolis, V.; Verani, G. J. Chem. Soc., Dalton Trans. 1999, 3069.

7586 Inorganic Chemistry, Vol. 49, No. 16, 2010

Table 9. Crystallographic Data for Compounds 5-8

compound

Knight et al.

5

6

7

8

empirical formula

fw

C₄₄H₃₂I₆Se₄

1638

C₄₄H₃₂I₆S₂Se₂

1544.2

C₂₂H₁₆Br₂STe

599.84

C₂₂H₁₆Br₂SeTe

646.73

temperature (°C)

cryst color, habit

cryst dimensions (mm³)

cryst syst

-148(1)

-180(1)

red, prism

0.15 ꢀ 0.09 ꢀ 0.09

triclinic

red, prism

0.21 ꢀ 0.15 ꢀ 0.09

triclinic

yellow, prism

0.21 ꢀ 0.03 ꢀ 0.03

monoclinic

colorless, platelet

0.06 ꢀ 0.06 ꢀ 0.03

monoclinic

˚

lattice params

a = 9.6503(18) A

b = 11.3357(16) A

˚

c = 11.8269(16) A

a = 9.6066(17) A

b = 11.2528(14) A

˚

c = 11.8080(14) A

a = 18.873(10) A

˚

b = 15.452(7) A

˚

c = 13.922(6) A

a = 19.172(8) A

˚

b = 15.285(6) A

˚

c = 14.070(7) A

R = 65.996(10)°

β = 82.763(14)°

γ = 83.206(14)°

V = 1169.3(3)

P1

1

2.326

750

71.303

13845

0.043

0.336-0.526

4628

R = 65.855(9)°

β = 82.839(14)°

γ = 83.443(14)°

V = 1152.9(3)

P1

1

2.224

714

57.432

13510

0.038

0.403-0.596

4542

β = 100.423(11)°

β = 100.442(13)°

3

volume (A )

˚

V = 3993(3)

C2/c

8

1.995

2288

56.13

10797

0.082

V = 4055(3)

C2/c

8

2.119

2432

7.207

12736

0.1295

0.652-1.000

3669

space group

Z value

Dcalc (g/cm³)

F000

μ(Mo Ka) (cm^-1

no. of reflns measd

)

Rint

min and max transmissions

independent reflns

0.542-0.845

3510

obsd refln (no. variables)

refln/param ratio

4222(245)

18.89

0.0483

0.0569

0.1746

1.185

4336(245)

18.54

0.0429

0.0479

0.1587

1.148

2992(236)

14.87

0.0696

0.0876

0.1808

1.261

2284(236)

15.55

0.0947

0.1436

0.2625

1.077

residuals: R₁(I>2.00σ(I))

residuals: r (All reflns)

residuals: wR₂(all reflns)

goodness of fit indicator

Flack param

3

˚

1.32 e/A

˚

2.46 e/A

˚

1.50 e/A

˚

2.515 e/A

maximum peak in final diff. map

minimum peak in final diff. map

3

˚

-1.56 e/A

-1.98 e/A

-1.67 e/A

-1.557 e/A

Table 10. Crystallographic Data for Compounds 9-12

compound

9

10

11

12

empirical formula

fw

C₂₂H₁₆I₂STe

693.84

C₂₂H₁₆I₂SeTe

740.71

C₁₆H₁₁Br₃Te

570.57

C₁₆H₁₁Br₂ITe

617.58

temperature (°C)

cryst color, habit

cryst dimensions (mm³)

cryst syst

-148(1)

-180(1)

-148(1)

orange, prism

0.15 ꢀ 0.09 ꢀ 0.09

monoclinic

colorless, platelet

0.05 ꢀ 0.05 ꢀ 0.05

monoclinic

colorless, platelet

0.12 ꢀ 0.12 ꢀ 0.01

orthorhombic

yellow, prism

0.15 ꢀ 0.09 ꢀ 0.09

orthorhombic

˚

lattice params

a = 18.909(4) A

a = 19.723(9) A

a = 8.4839(18) A

˚

b = 12.041(2) A

˚

c = 15.592(3) A

a = 8.5238(18) A

˚

b = 12.165(3) A

˚

c = 15.780(3) A

˚

b = 15.954(3) A

˚

b = 15.191(6) A

˚

c = 14.282(3) A

˚

c = 14.463(6) A

β = 99.994(5)°

V = 4243.1(15)

P2/c

8

2.172

2576

44.16

12261

0.033

β = 100.692(12)°

V = 4258(3)

C2/c

8

2.311

2720

6.011

13494

0.1378

0.797-1.000

3836

3

volume (A )

˚

V = 1592.8(6)

Pca2₁

4

2.379

1056

94.028

4898

0.057

0.409-0.910

2459

V = 1636.3(6)

Pca2₁

4

2.507

1128

85.916

4932

0.04

0.290-0.462

2609

space group

Z value

Dcalc (g/cm³)

F000

μ(Mo Ka) (cm^-1

no. of reflns measd

)

Rint

min and max transmissions

independent reflns

0.487-0.672

4204

obsd refln (no. variables)

refln/param ratio

3961(236)

17.81

2117(236)

16.25

2353(182)

13.51

2579(182)

14.34

residuals: R₁(I>2.00σ(I))

residuals: r (all reflns)

residuals: wR₂(all reflns)

goodness of fit indicator

Flack param

0.0361

0.0429

0.1341

1.244

0.0823

0.1495

0.2132

0.992

0.0461

0.0503

0.0996

1.089

0.0313

0.0332

0.0967

1.206

3

˚

1.65 e/A

-1.63 e/A

˚

3.359 e/A

-1.375 e/A

˚

0.77 e/A

-1.09 e/A

˚

1.41 e/A

-1.50 e/A

maximum peak in final diff. map

minimum peak in final diff. map

3

˚

selenium environment [4, δ = 436.9, 436.7 ppm; 5, δ = 445.1,

444.3 ppm]. The ⁷⁷Se NMR spectrum for adduct 6 reveals a

similar downfield shift compared to D3 [δ = 455.3 ppm]⁵⁷

with a single peak at δ = 476.9 ppm.

Following the treatment of selenium donor D2 with

diiodine, no significant alteration to the naphthalene geo-

metry is observed upon the formation of the CT “spoke”

addition product 4 (Figure 5).⁵⁷The naphthyl and phenyl

rings orient with the same mixed equatorial-axial/axial-

equatorial conformation as observed forD2, with oneE-C_Ph

bond aligning perpendicular to the naphthyl plane and

one aligning with the plane (“AB-type”, Figure 1).^57,64,65

Article

Inorganic Chemistry, Vol. 49, No. 16, 2010 7587

Table 11. Crystallographic Data for Compounds 13-15

compound

13

14

15

empirical formula

fw

C₁₆H₁₁BrI₂Te

664.58

C₁₆H₁₁I₃Te

711.58

C₅₆H₄₃O₂P₂S₂Br₃

1113.73

temperature (°C)

cryst color, habit

cryst dimensions (mm³)

cryst syst

-148(1)

red, platelet

0.15 ꢀ 0.15 ꢀ 0.03

triclinic

orange, prism

0.12 ꢀ 0.03 ꢀ 0.03

triclinic

colorless, prism

0.12 ꢀ 0.09 ꢀ 0.09

triclinic

˚

lattice params

a = 8.221(2) A

a = 7.290(4) A

a = 9.1606(13) A

˚

b = 11.537(3) A

˚

c = 12.606(4) A

˚

b = 9.639(3) A

˚

b = 9.642(6) A

˚

c = 11.613(3) A

˚

c = 13.294(7) A

R = 105.274(8)°

β = 90.454(4)°

γ = 102.945(9)°

V = 863.0(4)

P1

2

2.557

600

76.13

9862

0.044

0.335 - 0.796

3384

R = 104.034(9)°

β = 92.232(12)°

γ = 103.475(12)°

V = 877.0(9)

P1

2

2.695

636

69.675

9605

0.071

0.632 - 0.811

3429

R = 83.21(5)°

β = 71.33(4)°

γ = 66.89(4)°

V = 1160.8(7)

P1

1

1.593

562

28.176

11962

0.105

0.511 - 0.776

4041

3

volume (A )

˚

space group

Z value

Dcalc (g/cm³)

F000

μ(Mo Ka) (cm^-1

no. of reflns measd

)

Rint

min and max transmissions

independent reflns

obsd refln (no. variables)

refln/param ratio

3262(182)

18.59

0.0373

0.0391

0.1186

1.144

3196(182)

18.84

0.0589

0.0675

0.1966

1.134

3185(296)

13.65

0.1109

0.1398

0.1854

1.241

residuals: R₁(I>2.00σ(I))

residuals: r (All reflns)

residuals: wR₂(all reflns)

goodness of fit indicator

Flack param

3

˚

1.43 e/A

˚

2.28 e/A

˚

0.93 e/A

maximum peak in final diff. map

minimum peak in final diff. map

3

˚

-1.29 e/A

-2.40 e/A

-0.79 e/A

Displacement of the peri atoms from the naphthalene mean

diiodine molecule held by weak I I interactions [5 3.543(1)

3 3 3

plane in 4 is comparable to D2 [ca. 0.3-0.5 A]⁵⁷and reveals

A; 6 3.526(1) A] (Figure 7). In both cases, the linear Se-I-I

fragment [5, 178.1(1)°; 6, 179.0(1)°] has the same orientation

as described for adduct 4: situated at 99.4(1)° and 99.3(1)° to

the Se(1)-C(11) bond and lying 80.4(1)° and 76.9(1)° from

the C(11)-Se(1)-C(1) plane, respectively. I(1) is positioned

˚

that steric strain operating between the selenium atoms in the

two compounds is of a similar magnitude. Deviation of the

peri atoms within the naphthyl plane also corresponds, with

the divergence of the exocyclic bonds illustrated by the splay

angle [4, 13.3°; D2, 13.9°].⁵⁷Despite the amount of naphtha-

˚

in the peri gap with I(1) E(2) separations [5, 3.8730(9) A; 6,

3.8527(13) A] within the sum of van der Waals radii.

3 3 3

66

˚

lene distortion, interatomic nonbonded Se Se separations

3 3 3

for 4 [3.1339(6)] and D2 [3.1332(9)]⁵⁷are 18% shorter than

double the van der Waals radii of selenium [3.80].⁶⁶Maxi-

mum C-C-C-C central naphthalene ring torsion angles in

the range 4-7° show that both naphthalene backbones are

significantly buckled.

The interaction between the terminal I(2) atom of the

“spoke” adduct and the second I₂molecule weakens and

˚

extends the I(1)-I(2) bond [5, 2.8672(8) A; 6, 2.8706(5) (cf. 4,

˚

2.7987(6) A)], concurrent with shortening the Se(1)-I(1)

15,22

˚

bond [5, 2.8497(9) A; 6, 2.8436(6) A (cf. 4, 2.9795(8) A)].

The hypervalent quasi-linear Se(1)-I(1)-I(2) fragment

[Se-I-I angle, 177.6°], characteristic of the weaker 3c-4e

I(1)-I(2) I₂angles [5, 107.9(1)°; 6, 108.0(1)°] are slightly

3 3 3

more obtuse than average values [90°] for known “extended

spoke” compounds.^15,22As expected, the I(3)-I(3¹) bond

length of the bridging diiodine molecule is extended in both

bond, displays an increase in the I(1)-I(2) bond length

48

˚

[2.7987(6) A] compared to free diiodine [2.66 A]. It is

situated at 97.0(1)° to the Se(1)-C(11) bond and lies quasi-

perpendicular to the C(11)-Se(1)-C(1) plane [76.6(1)°] due

to steric crowding around the selenium lone pairs.^72,73This

˚

adducts [5, 2.7402(11) A; 6, 2.7418(7) A] compared with free

48

˚

iodine [2.66 A] due to the existence of the weak I

interactions.

I

3 3 3

results in a close intramolecular I(1) Se(2) contact

The naphthalene components of each “Z-shaped” adduct

display a minor decrease in molecular distortion compared

with donor compounds D2 and D3, with a greater distortion

observed in adduct 5 compared with 6. In both compounds,

3 3 3

˚

[3.6956(7) A], which is within the sum of van der Waals radii

for interacting selenium and iodine atoms [3.88 A].⁶⁶Adduct

˚

4 also exhibits an intermolecular nonbonded interaction

between the I(2) and Se(2) atoms of neighboring molecules

˚

the nonbonded Se(1) E(2) distance [5, 3.0756(14) A; 6,

3 3 3

˚

(A and B) with an I(2A) Se(2B) distance of 3.663(1) A

(Figure 6).

2.9798(18) A] is 19% shorter than the sum of van der Waals

3 3 3

radii for the two interacting atoms [cf. D2, 18%; D3, 17%].⁵⁷

The CT “extended spoke” adducts 5 and 6 are character-

The displacement of the peri atoms from the naphthalene

ized by a “Z-shaped” D-I₂I₂I₂-D system con-

˚

mean plane [0.2-0.4 A] is comparable in the two adducts to

3 3 3 3 3 3

the out-of-plane distortion observed for D2 and D3.⁵⁷The

substitution of heavier elements in the bay region of 5

compared with 6 causes a larger positive splay of the two

E-C_Napbonds within the least-squares plane and thus exhi-

bits a greater splay angle [5, 13.6°; 6, 10.9°]. Maximum

structed from two “spoke”-like adduct units and a bridging

(72) Ouvrard, C.; Le Questel, J.-Y.; Berthelot, M.; Laurence, C. Acta

Crystallogr., Sect. B: Struct. Sci. 2003, 59, 512.

€

(73) Nather, C.; Bolte, M. Phosphorus, Sulfur Silicon Relat. Elem. 2003,

178, 453.

7588 Inorganic Chemistry, Vol. 49, No. 16, 2010

Knight et al.

Figure 3. Molecular structure of the ionic CT “extended spoke” adduct

2 formed from the reaction of D2 with dibromine (compound 3 adopts a

similar structure, see the Supporting Information).

afford “T-shaped”/“seesaw” adducts with no tellurium CT

“spoke” adducts having been reported.^15,22Tellurium forms

a strong donor-strong acceptor system with dihalogen

molecules sufficient to cleave the X-X bond and oxidize

tellurium.^15,22Nucleophilic attack occurring at the chalcogen

site of a diorganotellurium [R₂Te-X]^þcation affords a

“seesaw” hypervalent adduct containing the quasi linear

X-Te-X alignment.^15,22

Tellurium-donor compounds 1-(phenyltellurenyl)-8-(phenyl-

sulfanyl)naphthalene D4 and 1-(phenyltellurenyl)-8-(phenyl-

selenyl)naphthalene D5 react conventionally with dibromine

and diiodine, affording a series of “seesaw” insertion adducts

(Scheme 1). In all four reactions, the dihalogen reacts at the

larger, less electronegative tellurium atom due to its greater

electron donor ability over sulfur and selenium.^43,48

Figure 1. Orientation of the naphthyl and phenyl rings, the type of

structure, and the quasi-linear arrangements in compounds 1-14.⁶⁵

The formation of the X-Te-X fragment is confirmed by a

significant downfield shift in the ¹²⁵Te NMR spectra for

7-10 compared to D4 [δ = 715.2 ppm]⁵⁷and D5 [δ = 687.6

ppm].⁵⁷Single peaks are observed in all four spectra with the

signals for the bromine compounds 7 [δ = 958.9 ppm] and 8

[δ = 941.4 ppm] lying at expected higher chemical shifts

compared to their iodine analogues 9 [δ = 790.9 ppm] and 10

[δ = 747.0 ppm]. A downfield shift is also observed in the

⁷⁷Se NMR spectra of 8 and 10 compared to D5 [δ = 362.8

ppm],⁵⁷with single peaks at δ = 500.0 ppm and δ = 428.8

ppm, respectively.

The four adducts 7-10 are characterized by the well-

known “seesaw” structure and incorporate an asymmetric

linear X-Te-X fragment [7, 176.7(1)°; 8, 177.9(1)°; 9,

176.8(1)°; 10, 179.6(1)°] characterized by unequal X-Te

bond lengths (Figure 8).²³The central tellurium atom adopts

a distorted trigonal bipyramidal (TBP) geometry with angles

around tellurium for all four adducts in the range 87-98°.

The formation of the linear fragment is accompanied by a

minor adjustment to the naphthyl and phenyl ring conforma-

tions compared to the tellurium donor compounds D4 and

D5.⁵⁷A slight rotation round the Te(1)-C(1) bond positions

the Te-C_Phbond intermediate between perpendicular and

coplanar with the naphthyl plane, and both phenyl rings

adopt twist conformations.⁶⁴This affords a twist-twist and

axial-twist arrangement corresponding to the “AC-type”

Figure 2. Molecular structure of 1,8-bis(4-bromophenylsulfanyl)-2,5-

dibromonaphthalene 1.

C-C-C-C central ring torsion angles are in the range 3-5°

for both compounds, showing that the deviation of the

naphthalene backbones from planarity is comparable. The

conformation of the naphthyl and phenyl rings in both

adducts is comparable to donor compounds D2 and D3,

with an equatorial-axial/axial-equatorial orientation de-

scribed as an “AB-type” structure.^57,64,65

“Seesaw” and “T-shaped” adducts are formed if halide X

is more electronegative than chalcogen E [R₂E^δþ-X^δ-].

Consequently, all known reactions between tellurium donors

[χ(Te) 2.08]⁴³and di- or interhalogens [χ(F) 3.94, χ(I) 2.36]⁴³

Article

Inorganic Chemistry, Vol. 49, No. 16, 2010 7589

Figure 4. Intermolecular short contacts in the molecular structure of the ionic CT “extended spoke” adduct 2, producing a quasi-linear rectangular

arrangement of eight atoms.

Figure 7. Molecular structure of the CT “extended spoke” adduct 6

characterized by a “Z-shaped” D-I₂I₂I₂-D system (adduct 5

adopts a similar structure, see the Supporting Information).

3 3 3 3 3 3

Figure 5. Molecular structure of the neutral CT “spoke” adduct 4.

Figure 8. Molecular structure of the “seesaw” adduct 7 (adducts 8-10

display similar molecular structures, see the Supporting Information).

ing atoms [94-96%].⁶⁶Te-Br [2.67-2.72 A] and Te-I

˚

[2.89-2.95 A] bond lengths are within the usual ranges

74

˚

[2.68, 2.99 ( 0.05 A].

The naphthalene moieties of the “seesaw” adducts experi-

ence a similar degree of molecular distortion compared to

donor compounds D4 and D5.⁵⁷As expected, the deforma-

tion of the naphthalene unit is greater in adducts 8 and 10

(TeSe) compared with compounds 7 and 9 (TeS). Intramo-

Figure 6. Intermolecular nonbonded short contacts between two neigh-

boring molecules of adduct 4.

structure (Figure 1).^64,65The alignment of the “seesaw”

moiety positions one of the terminal halide atoms of

˚

X-Te-X in the peri gap and in close proximity to E(2).

lecular Te S [7, 3.075(2) A; 9, 3.0767(17) A] and Te Se

3 3 3

˚

Noncovalent X E(2) distances [7, 3.486(2) A; 8, 3.542(2)

[8, 3.141(2) A; 10, 3.137(2) A] peri distances are 20-22%

3 3 3

˚

A; 9, 3.6136(16) A; 10, 3.696(2) A] are marginally shorter

shorter than the sum of van der Waals radii for the two

than the sum of van der Waals radii for the two interact-

chalcogen atoms and comparable to the separations in the

57

˚

independent molecules of D4 [3.0684(13) A (3.0984(11) A)]

and D5 [3.1919(11) A (3.1580(12) A)],⁵⁷respectively. Devia-

˚

(74) CSD Version 5.31, Conquest 1.12 & Vista. http://www.ccdc.cam.ac.uk/

(accessed Jul 2010).

tion of the peri atoms within the naphthyl plane is marginally

7590 Inorganic Chemistry, Vol. 49, No. 16, 2010

Knight et al.

Figure 10. Molecular structure of the “seesaw” insertion adduct 11

(12-14 adopt identical arrangements, see Supporting Information).

Figure 9. Short intermolecular contacts between neighboring molecules

of the “T-shaped” adduct 7 form planar Te₂X₂square units (8, 9, and 10

adopt identical arrangements, see the Supporting Information).

The substitution of bulky halogen atoms at the second peri

position in 11-14 results in a greater degree of steric strain

and consequently naphthalene distortion compared with

adducts 7-10. Additionally, the deformation of the naphtha-

lene unit is greatest in adducts with an iodine peri atom, 12

and 14, compared with 11 and 13 (Br). The intramolecular

greater in the selenium compounds 8 and 10 with large

positive splay angles of the magnitude 13.5° and 12.4° [cf.

12.0° and 12.3° for 7 and 9]. Distortion out-of-the plane is

comparable throughout the series with atoms lying at dis-

˚

Te Br peri distance in 11 [3.2397(15) A] is larger than the

3 3 3

separation in the tellurium donor compound D6 [3.1909(10)

˚

tances between 0.3 and 0.4 A, and the deviation of the central

A],⁵⁸while the distance in 13 is marginally shorter [3.1563(6)

˚

naphthalene ring torsion angles from planarity is also con-

sistent, 0-7°. Short intermolecular contacts exist in each of

the four adducts between Te and X atoms of neighboring

molecules constructing planar Te₂X₂squares (Figure 9). In

˚

A]. Conversely, the Te I distances in 12 and 14 [3.3810(7)

3 3 3

˚

A; 3.3608(11) A] are longer than the separation in D7

58

˚

[3.3146(6) A]. In all cases, the Te X separation is less

than the sum of van der Waals radii for the two interacting

atoms by 16-19%.

3 3 3

all cases, the Te X distance is 93-95% of the sum of van

3 3 3

der Waals radii for the two interacting atoms.

The increased congestion in the peri region of adducts 12

and 14 causes a larger divergence of the Te-C and X-C

bonds within the naphthyl plane compared with 11 and 13.

Large positive splay angles are observed for all four adducts

with those for 11 and 13 [13.1°; 12.4°] similar in size to D6

[13.6°]⁵⁸and those for 12 and 14 [15.9°; 18.7°] comparable to

the splay in D7 [16.2°].⁵⁸Adducts 11 and 12 containing the

Br-Te-Br linear fragment display the greatest out-of-plane

The comparable reactions of 1-bromo-8-(phenyltellu-

renyl)naphthalene D6 and 1-iodo-8-(phenyltellurenyl)naph-

thalene D7 with dihalogens (Br₂, I₂) afforded a similar array

of “seesaw” insertion adducts 11-14 (Scheme 1). The ¹²⁵Te

NMR spectra for 11-14 show a similar trend to that

previously described for 7-10 with an expected downfield

shift compared to their respective donor compounds D6 [δ =

731.2 ppm]⁵⁸and D7 [δ = 698.3 ppm].⁵⁸Single peaks are

observed in all spectra, with bromine compounds 11 [δ =

942.8 ppm] and 12 [δ = 903.0 ppm] possessing higher chemi-

cal shifts compared to their iodine counterparts 13 [δ = 887.5

ppm] and 14 [δ = 848.0 ppm].

˚

distortion with atoms lying ∼0.6 A to opposite sides of the

naphthalene least-squares plane. Adducts 11 and 12 also

display a major distortion to the naphthalene ring system

with maximum central naphthalene ring torsion angles of

∼10-11°. Short intermolecular contacts between Te and I

atoms of neighboring I-Te-I units in 12 and 14 form similar

planar Te₂X₂square units to 7-10. Although a number of

short contacts exist in adducts 11 and 13, no similar inter-

molecular arrangement is observed.

Adducts 11-14 adopt similar “seesaw” geometries to

those observed for 7-10, but the linear X-Te-X fragments

are more symmetrical (Figure 10). Tellurium adopts a quasi-

trigonal bipyramidal conformation with angles around the

central atom in the range 87.4-99.4°. Adducts 11 and 12

containing Te and Br peri atoms adopt a twist-twist orienta-

tion of naphthyl and phenyl rings (“C-type”), while in

adducts 13 and 14 (TeI) the Te-C_Phbond aligns along the

naphthyl plane and the compounds display an equatorial-

twist conformation (“B-type”; Figure 1).^64,65The arrange-

ment of the linear species in all four adducts positions one of

We have recently reported the synthesis and structural

study of (8-phenylsulfanylnaphth-1-yl)diphenylphosphine

D8; a complete series of phosphorus(V) oxygen, sulfur, and

selenium chalcogenides; and a study of its coordination

chemistry.⁵⁶Treatment of D8 with excess dibromine in di-

chloromethane led to the formation of the air-stable phos-

phonium salt 15. Phosphorus forms a four-coordinate catio-

nic fragment via the addition of a hydroxyl group which is

the X atoms in the peri gap, but X X⁰separations in all

3 3 3

balanced by a linear Br₃^-counteranion (Scheme 1). The ³¹

P

cases are greater than the sum of van der Waals radii for the

˚

two interacting halogen atoms. Te-Br [2.66-2.68 A] and

NMR spectrum shows a single peak at δ = 52.48 ppm.

The molecular structure of 15 is shown in Figure 11. In the

asymmetric unit, two molecules of 15 share the proton

˚

Te-I [2.90-2.95 A] bond lengths are within the usual ranges

74

˚

[2.68, 2.99 ( 0.05 A].

Article

Inorganic Chemistry, Vol. 49, No. 16, 2010 7591

3. DFT Calculations

situated between the oxygen atoms and form a “Z-shaped”

P-O-H-O-P bridge. All five atoms lie on the same plane

with P-O-H angles of 131.2(1)° and an O-H-O angle of

180.0(1)°. P-O bond lengths are identical in both molecules

Of the compounds presented here, only 2 and 3 display a

reduction in naphthalene distortion and by inference the

degree of steric strain operating between the peri atoms,

compared with parent donor compounds (D2 and D3).⁵⁷

This can be rationalized by the presence of an attractive weak

interaction between the peri atoms, inferred by the noticeable

shrinkage of the peri distance in both adducts. In addition,

the two peri atoms align with one bromine atom to form

˚

[1.527(6) A] with a value in between the observed PdO bond

56

˚

length in the phosphine oxide of D8 (D8dO) [1.492(2) A]

and a standard single P-OH bond [1.56 A].⁷⁵This suggests

˚

that the structure is an average of a phosphine oxide and a

phosphonium cation, as depicted in Figure 12. The charge of

-

the cation is balanced by the presence of a linear Br₃

counteranion [180.00(6)°], which exhibits elongated Br-Br

bond lengths [2.5984(12) A] compared to free bromine

a quasi-linear Br(1)-Se(1) E(2) arrangement, suggesting

3 3 3

the nature of the bonding could be represented by the 3c-4e

˚

mode. To try and assess the possibility of direct Se(1) E(2)

3 3 3

48

˚

[2.28 A].

bonding interactions that would indicate an onset of 3c-4e

bonding in 2 and 3, density functional theory computations

were performed for the possible reaction products between

1,8-(SePh)₂-C₁₀H₆(D2) and Br₂, optimized at the B3LYP/

962(þd)/6-31þG* level (Figure 13).

The naphthalene component of the phosphonium salt 15

exhibits greater strain relief and naphthalene distortion

compared to phosphine D8 and its phosphine oxide

D8dO.⁵⁶The peri atoms are accommodated by an intramo-

˚

lecular nonbonded P S distance of 3.165(2) A, notably

Structure A (Figure 13) corresponds to that observed in the

solid for 2; A^þis the isolated cationic fragment of this ion

pair; B corresponds to the analogue where Se^ais replaced

with Te (8) and C to that where Br is replaced with I (4 and 5).

Optimizations starting from the two different conformations

found in the latter two solids converged to the same mini-

mum. Optimizations for A starting from the coordinates of 2

and its S-analogue 3 afforded two distinct minima, which

differ in the exact position of the Br₃moiety. Both are very

close in energy, within ca. 1 kcal/mol, and only the results for

the most stable conformer (derived from solid 3) will be

3 3 3

˚

larger than the separation in D8 [3.0330(7) A] and D8dO

[3.1489(9) A].⁵⁶The divergence of the P-C and S-C bonds

˚

within thenaphthyl plane is also more pronouncedin15, with

a large positive splay angle of 15.5° [cf. D8, 14.1; D8dO,

12.4].⁵⁶Additionally, the peri atoms are displaced to opposite

˚

sides of the mean naphthalene by 0.436(11) A (P) and

-0.466(11) A (S). The naphthalene backbone in the phos-

phonium salt displays a significant deformation from pla-

narity, with maximum C-C-C-C torsion angles lying in

the range 5-8°. One short intramolecular S O contact

exists with a separation 11% shorter than the sum of van der

Waals radii for the two atoms. Although a number of short

intermolecular interactions exist, there is no significant over-

lap of phenyl or naphthyl rings and no π-π stacking is

observed.

˚

3 3 3

discussed in the following. As expected, the Se Se contacts

3 3 3

are shortest in A and A^þ, with substantial bonding inter-

actions indicated by Wiberg bond indices (WBI)⁷⁶of ca.

0.3-0.4. For comparison, the fully covalent S-S single bond

in naphtho(1,8-cd)(1,2-dithiole) has a WBI of 0.99 at the

˚

same level. The optimized Se-Se distance for A, 2.807 A, is in

˚

very good agreement with that observed in solid 2, 2.762 A,

even though the Br₃moiety has moved somewhat closer

to the cationic fragment in the gas-phase optimization

(Se^aBr and Se^bBr of 3.42 A and 3.87 A, respectively),

˚

3 3 3

as compared to the solid (where Se^aBr and Se^bBr are

3 3 3

˚

3.55 A and 4.40 A, respectively). In B and C, the Se Se

3 3 3

distances are larger than in A and A^þ, and weaker but

still noticeable bonding is found (WBI ≈ 0.1). The refined

selenium-selenium distances for species 2 and 3 suggest that

3c-4e bonding is present in both cases.

Significant energetic driving forces are computed for all

products A-C already in the gas phase (cf. the negative

ΔE_rþ ZPE values). The largest such driving force is com-

puted for A, the actual, crystallized product, but compounds

B and C are only a few kilocalories per mole less stable.

Standard entropic and enthalpic corrections would reduce

the free energy of bromination to essentially zero for B and C

and would make formation of A endergonic (see ΔG_r^298K

values). Immersion in a polarizable continuum favors the

Figure 11. Molecular structure of hydroxydiphenyl[(8-phenylsulfa-

nyl)naphthalene-1-yl]phosphonium tribromide 15.

Figure 12. Crystal structure of 15. Two molecules share a proton to form a P-O-H-O-P bridge, explained by an average structure of a phosphine oxide

and a phosphonium cation.

7592 Inorganic Chemistry, Vol. 49, No. 16, 2010

Knight et al.

Figure 13. DFT computations performed at the B3LYP level for the possible reaction products between D2 and Br₂. ΔE_r, ΔE_rþ ZPE, and ΔG_r^298Kare

gas-phase relative energies, zero-point corrected energies, and free energies, respectively, relative to D2 þ nBr₂; ΔG_r(CH₂Cl₂) are free energies (at 298 K)

corrected for solvation effects.

formation of B and C slightly, by ca. -3 kcal/mol, and

stabilizes the highly polar ion pair A significantly, by ca.

-11 kcal/mol. Judging from the ΔG_r(CH₂Cl₂) values, for-

mation of all products is exergonic in a condensed phase, with

a slight preference for the observed product A. These results

therefore suggest that the occurrence of A may not be due to

its intrinsic stability but would rather arise from its favorable

interaction with the polar environment of the crystal. Not-

withstanding the crude nature of some approximations

involved (ideal-gas entropies, continuum solvation model),

the relative free energies in solution are computed to be rather

similar for all products. This would help to rationalize the

rather diverse chemistry encountered upon varying the chal-

cogen and/or the halogen in this system.

Because the relative free energies of the various products

appear to be rather closely spaced, it is conceivable that

complex equilibria rather than a single product might occur

in solution, and that, thus, the nature of the species present in

solution could be different from that in the solid state. This

is in agreement with the generally accepted mechanism

to describe the formation of adducts from the reaction of

diorganochalcogen donors with the dihalogens;^14,38,39in

sol_ꢁution the CT “spoke” and the “seesaw” adducts of type

diorganochalcogen donors [R₂E] with inter- or dihalo-

gens.^15,22In general, the reactions between D1-D8 and the

dihalogens conform to the charge-transfer rule and form

“seesaw” adducts when the halogen (X) species is more

electronegative than the chalcogen donor (E) [R₂E^δþ-X^δ-

]

and form CT “spoke” adducts if the converse is true.^20-22

Reactions between Te donors [χ(Te) 2.08]⁴³and any

dihalogen [χ(F) 3.94, χ(I) 2.36]⁴³explicitly afford “seesaw”

or “T-shaped” adducts with no CT adducts known for any

tellurium compound.^14,15,22,43Tellurium donor compounds

D4-D7 react conventionally to form strong donor-strong

acceptor systems with the dihalogens. The X-X bond is

cleaved, and the Te atom is oxidized.^14,15,22In each case,

nucleophilic attack occurs at the tellurium site of the

[R₂Te-X]^þcation, affording a series of “seesaw” hyperva-

lent adducts 7-14 characterized by the quasi-linear

X-Te-X alignment.^14,15,22

As expected from electronegativity values, all structurally

reported adducts formed from the reaction of diorganosele-

nium compounds [χ(Se) 2.35]⁴³with dibromine [χ(Br) 2.58]⁴³

adopt the “seesaw” geometry.^{14,15,22,47,49,50}The decrease

in the electronegativity difference between selenium and

iodine [χ(Br) 2.36]⁴³favors the formation of CT “spoke”

adducts.^15,22,46,47The selenium-donor compounds D2 and

D3 react to form strong donor-strong acceptor systems with

dibromine sufficient to cleave the Br-Br bond and oxidize

the selenium atom.^15,22The hypervalent 3c-4e interaction

RRE X₂are in equilibrium, and as reported by Husebye and

3

co-workers, all of the products in these reactions are derived

from a common intermediate species [R₂E-X]^þ.^15,22,40

4. Conclusions

operating between the quasi-linear Br-Se E arrangement

3 3 3

in both compounds blocks the nucleophilic attack at the

selenium site of the [R₂Se-X]^þcation, so no “seesaw” adduct

is formed. Instead, a hypervalent linear tribromide counter-

anion balances the charge, and the ionic tribromide salts 2

and 3 are formed, which can be represented by the formula

The structural conformation of the products formed from

the reactions between donor compounds D1-D8 and the

dihalogens is dependent on several factors, most importantly

the donor ability of the chalcogen atom, the acceptor abi-

lity of the dihalogen species, and the stoichiometry of the

reactants. When two donor atoms are available (D3, D4, D5),

reaction occurs explicitly between the dihalogen and the least

electronegative element. The neutral charge-transfer (CT)

“spoke” adduct and the “seesaw” insertion adduct, charac-

teristic of quasi-linear hypervalent E-X-Y^{15,22,28,34,35}and

X-E-Y^{14,15,22,28,31,36,37}fragments, respectively, arethe most

common structural motifs generated from the reaction of

[RSe-Br]^þ[Br-Br₂]^{-2 34}

.

3 3 3

D2 reacts conventionally with a single equivalent of diio-

dine to form the CT “spoke” adduct 4 characterized by the

quasi-linear Se-I-I alignment. Reaction with a higher

equivalent of diiodine (1:2) affords a structurally more

complex “extended spoke” adduct 5, incorporating I₂chains.

Two molecules of adduct 4 acting as donors interact with a

single bridging diiodine molecule via soft-soft I I inter-

3 3 3

actions to construct a “Z-shaped” system with a D-I₂

3 3 3

(75) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,

A. G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1.

(76) Wiberg, K. B. Tetrahedron 1968, 24, 1083.

I₂I₂-D configuration. D3 reacts to form a comparable

system, 6. These “Z-shaped” systems are of great interest, as

Article

Inorganic Chemistry, Vol. 49, No. 16, 2010 7593

compounds with extended poly(I₂) chains held by weak

techniques and glassware. Reagents were obtained from

commercial sources and used as received. Dry solvents were

collected from an MBraun solvent system. Elemental ana-

lyses were performedbytheUniversity of St. Andrews School

of Chemistry Microanalysis Service. Infrared spectra were

recorded as KBr discs in the range 4000-300 cm^-1on 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. ³¹P, ⁷⁷Se, and ¹²⁵Te NMR spectra were

recorded on a Jeol GSX 270 MHz spectrometer with δ(P),

δ(Se), and δ(Te) referenced to external phosphoric acid,

dimethylselenide, and diphenyl ditelluride, respectively.

I₂I₂interactions and also adducts formed with a donor/

3 3 3

dihalogen composition greater than 1:1 are extremely

rare.^15,71

Adducts formed from the reaction of organosulfur com-

pounds with dibromine are rare.^{15,22,28,42,51}Resonance lone

pairs on sulfur in D1 and D8 are delocalized into the aromatic

π system, reducing the donor ability of the compound for

reaction with the dihalogens. The aromatic groups in D1 are

strongly activated and highly reactive toward electrophilic

substitution.⁵⁹Upon treatment with dibromine, D1 under-

goes a standard electrophilic aromatic substitution reaction

which substitutes bromine atoms in the 4 and 8 positions on

the naphthyl ring and in the para positions on the two phenyl

rings. Phosphine D8 neither reacts to form an adduct nor

undergoes electrophilic aromatic substitution. Instead, treat-

ment with dibromine affords the tetravalent phosphonium

salt 15, which packs via a “Z-shaped” P-O-H-O-P bridge

and is charge-balanced by the presence of a tribromide

counteranion.

Aragoni et al. have recently reviewed the nature of the

bonding in linear three-body systems including the E-X-X

and X-E-X arrangements of the CT “spoke” and “seesaw”

adducts.²³They concluded that these linear moieties can be

accounted for by a charge-transfer model and the three-

center, four-electron bond (3c-4e) model introduced by

Rundle and Pimentel to explain the hypervalency in the

trihalide ions.^7,11The linear three-body systems present in

2-14 conform to the 3c-4e model and as such have weaker

and, by inference, longer bond lengths compared with the

distances between atoms in standard single electron pair 2c-2e

bonds. The tribromide anions present in compounds 2, 3, and

1

Assignments of ¹³C and H NMR spectra were made with

the help of H-H COSY and HSQC experiments. All mea-

surements were performed at 25 °C. All values reported

for NMR spectroscopy are in parts per million (ppm). Coupl-

ing 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)

were carried out on a Micromass GCT orthogonal acce-

leration time-of-flight mass spectrometer. Electrospray

mass spectrometry (ESMS) was carried out on a Micromass

LCT orthogonal accelerator time-of-flight mass spectro-

meter.

1,8-Bis(4-bromophenylsulfanyl)-2,5-dibromonaphthalene (1).

A solution of 1,8-diphenylsulfanylnaphthalene, D1 (0.22 g,

0.63 mmol), in dichloromethane (20 mL) was cooled to 0 °C

and slowly treated with bromine (0.2 g, 0.06 mL, 1.3 mmol). An

analytically pure sample was obtained by crystallization from

the diffusion of pentane into a dichloromethane solution of

the product (0.3 g, 75%). Anal. Found: C, 41.2; H, 1.8. Calcd for

C₂₂H₁₂S₂Br₄: C, 40.3; H, 1.8%. v_max(KBr disk)/cm^-1: 3401w,

3075w, 2920w, 2848w, 2362w, 1881w, 1570s, 1558s, 1470vs,

1400w, 1382s, 1320w, 1282s, 1268s, 1185s, 1083s, 1065s, 1018w,

1006vs, 805vs, 765w, 745s, 688w, 641w, 608w, 561w, 517w, 497w,

471s, 417w, 396w, 373w, 352w. δ_H(270 MHz, CDCl₃): 8.19 (1 H,

d, J 9.1Hz, nap 4-H), 7.80 (1 H, d, J 9.1 Hz, nap3-H), 7.46 (1 H, d,

J 8.2 Hz, nap 6-H), 7.33 (2 H, d, J 8.4 Hz, SPhBr3,5-H), 7.21(2 H,

d, J 8.6 Hz, SPhBr 9,11-H), 7.05 (2 H, d, J 8.4 Hz, SPhBr 2,6-H),

6.95 (1 H, d, J 8.2 Hz, nap 2-H), 6.74 (2 H, d, J 8.6 Hz, SPhBr

8,12-H). δ_C(67.9 MHz, CDCl₃): 135.4(s), 132.9(s), 132.5(s),

132.1(s), 131.8(s), 130.7(s), 128.3(s). m/z (EI^þ) 659.69 ([M]^þ,

100%, 347.80 ([M - 2(ArBr)]^þ, 98%).

Compound 2. A solution of 1,8-bis(phenylselenyl)naphthal-

ene, D2 (0.21 g, 0.47 mmol), in dichloromethane (20 mL) was

cooled to 0 °C and slowly treated with bromine (0.15 g, 0.05 mL,

0.93 mmol). An analytically pure sample was obtained by

crystallization from the diffusion of dichloromethane into a

pentane solution of the product (0.2 g, 57%). Anal. Found: C,

39.6; H, 1.3. Calcd for C₂₂H₁₆Se₂Br₄: C, 40.3; H, 2.5%. v_max

(KBr disk)/cm^-1: 3396w, 3050w, 2920w, 2848w, 2356w, 2325w,

1589w, 1566w, 1486s, 1470s, 1438s, 1346s, 1261w, 1212w, 1194w,

1176w, 1083w, 1047s, 1016w, 992s, 825s, 812vs, 757w, 744vs,

730vs, 679vs, 659w, 533w, 484w, 463s, 457s, 442w, 378w. m/z

(ES^þ) 539.11 ([M - Br₃þ Na]^þ, 100%).

˚

15 all display elongated Br-Br bond distances [2.52-2.60 A]

48

˚

compared to free dibromine [2.28 A] but within the

usual range for Br₃ions [2.5-2.6 A].⁷⁴Similarly, I-I bond

-

˚

lengths exhibit a noticeable lengthening in the Se-I-I frag-

˚

ments of compounds 4-6 [2.80-2.87 A] compared with free

diiodine [2.66 A].⁴⁸Te-Br and Te-I bond lengths in the linear

˚

Br-Te-Br and I-Te-I fragments of the “seesaw” insertion

adducts 7-14 are within the usual range.²³

Following treatment with dibromine and diiodine, the

degree of distortion and, by inference, the steric strain operat-

ing between the peri atoms in their addition products 2-15

(and the substitution product 1) in general appears unchanged.

The exceptions to this are the two tribromide salts of bromo-

selenyl cations (2, 3), which display a reduction in the distor-

tion of the naphthalene geometry compared to parent donor

compounds D2 and D3, respectively. This can be rationalized

by the existence of the quasi-linear Br(1)-Se(1) E(2) inter-

3 3 3

action in both compounds, which can be represented by the

3c-4e model. The attractive weak interaction between the peri

atoms, inferred by the noticeable shrinkage of the peri distance

in both adducts, reduces the steric hindrance and therefore the

required distortion of the naphthalene scaffold. From DFT

calculations performed on 2, the optimized Se-Se distance

Compound 3. A solution of 1-(phenylselenyl)-8-(phenyl-

sulfanyl)naphthalene, D3 (0.02 g, 0.051 mmol), in dichloro-

methane (5 mL) was cooled to 0 °C and slowly treated with

bromine (0.02 g, 0.005 mL, 0.10 mmol). An analytically pure

sample was obtained by crystallization from the diffusion of

dichloromethane into a pentane solution of the product (0.01 g,

33%). v_max(KBr disk)/cm^-1: 3447vs, 3418vs, 2924vs, 2848s,

2372w, 1985w, 1918w, 1773w, 1735s, 1718s, 1703s, 1686s, 1654s,

1636s, 1578s, 1543s, 1523w, 1459s, 1436s, 1383w, 1343w, 1261w,

1203w, 1177w, 1148w, 1087s, 1020w, 913w, 814vs, 751vs, 735vs,

692w, 602w, 541w, 456s, 398w. m/z (ES^þ): 422.83 ([M - Br₄þ

OMe]^þ, 97%), 391.83 ([M - Br₄]^þ, 100%).

˚

[2.746 A] is in excellent agreement with that observed in the

76

˚

solid [2.762 A], and the WBI value of 0.4 indicates a

considerable bonding interaction and the onset of 3c-4e

bonding in the quasi-linear three-body system.

5. Experimental Section

All experiments were carried out under an oxygen- and

moisture-free nitrogen atmosphere using standard Schlenk

7594 Inorganic Chemistry, Vol. 49, No. 16, 2010

Knight et al.

Compound 4. A solution of 1,8-bis(phenylselenyl)naphthal-

ene, D2 (0.23 g, 0.53 mmol), in dichloromethane (20 mL) was

cooled to 0 °C and slowly treated with iodine (0.13 g, 0.53

mmol). An analytically pure sample was obtained by crystal-

lization from the diffusion of dichloromethane into a pentane

solution of the product (0.2 g, 66%). Anal. Found: C, 39.5; H,

2.2. Calcd for C₂₂H₁₆Se₂I₂: C, 38.2; H, 2.3%. v_max(KBr disk)/

cm^-1: 3406w, 3050w, 2920w, 2848w, 2382w, 1690w, 1659w, 1573s,

1550w, 1473s, 1435s, 1331w, 1191w, 1137w, 1088w, 1060s, 1018s,

995w, 956w, 912w, 838w, 811vs, 750s, 737vs, 687vs, 662s, 613w,

471w, 453w. δ_H(270MHz, CDCl₃):7.82(2H, dd, J1.0 and 8.2 Hz,

nap 4,5-H), 7.72 (2 H, dd, J 1.2 and 7.4 Hz, nap 2,7-H), 7.47-7.37

(4 H, m, SePh 2,6-H), 7.36-7.20 (8 H, m, nap 3,6-H, SePh 3-5-H).

δ_C(67.9 MHz, CDCl₃) 136.2(s), 133.1(s), 130.1(s), 129.7(s),

128.0(s), 126.4(s). δ_Se(51.5 MHz, CDCl₃): 436.9, 436.7. m/z

(EI^þ): 565.99 ([M - I]^þ, 5%), 440.12 ([M - I₂]^þ, 100%).

Compound 5. A solution of compound 4 (0.24 g, 0.35 mmol)

in dichloromethane (20 mL) was cooled to 0 °C and slowly

treated with iodine (0.09 g, 0.35 mmol). An analytically pure

sample was obtained by crystallization from the diffusion of

dichloromethane into a pentane solution of the product. δ_H

(270 MHz, CDCl₃): 7.74 (2 H, dd, J 1.0 and 8.2 Hz, nap 4,5-H),

7.63 (2 H, dd, J 1.2 and 7.4 Hz, nap 2,7-H), 7.44-7.37 (4 H, m,

SePh 2,6-H), 7.28-7.20 (8 H, m, nap 3,6-H, SePh 3-5-H).

δ_Se(51.5 MHz, CDCl₃): 445.1, 444.3.

1651w, 1604w, 1572s, 1535w, 1475s, 1436s, 1378w, 1331s,

1209w, 1195w, 1177w, 1136w, 1081w, 1064w, 1049s, 1020w,

994s, 907w, 813vs, 755vs, 727vs, 680s, 613w, 555w, 526w, 446s,

314w. δ_H(270 MHz, CDCl₃): 8.32 (2 H, d, J 7.0 Hz, TePh 2,6-

H), 8.28 (1 H, d, J 7.2 Hz, nap 4-H), 8.21 (1 H, d, J 7.3 Hz, nap

5-H), 8.09 (1 H, d, J 7.6 Hz, nap 7-H), 8.05 (1 H, d, J 7.7 Hz, nap

2-H), 7.64-7.44 (5 H, m, nap 3,6-H, TePh 3-5-H), 7.36-7.29 (2

H, m, SePh 2,6-H), 7.24-7.17 (3 H, m, SePh 3-5-H). δ_C(67.9

MHz, CDCl₃): 141.1(s), 138.8(s), 136.7(s), 133.6(s), 132.3(s),

131.3(s), 130.7(s), 129.9(s), 129.6(s), 127.7(s), 127.2(s), 126.9(s).

δ

_Se(51.5 MHz, CDCl₃): 500.0. δ_Te(81.2 MHz, CDCl₃): 941.4.

m/z (ES^þ): 518.69 ([M - Br₂þOMe]^þ, 100%).

Compound 9. A solution of 1-(phenyltellurenyl)-8-(phenyl-

sulfanyl)naphthalene, D4 (0.032 g, 0.073 mmol), in dichloro-

methane (5 mL) was treated with iodine (0.018 g, 0.073 mmol).

An analytically pure sample was obtained by crystallization

from the diffusion of dichloromethane into a pentane solution

of the product (0.04 g, 80%. v_max(KBr disk)/cm^-1: 3448br s,

3045w, 2920w, 2371w, 2342w, 1720w, 1686w, 1652w, 1635w,

1578w, 1541w, 1524w, 1509w, 1475s, 1432s, 1381w, 1324s,

1261w, 1196w, 1156w, 1136w, 1073w, 1045w, 1022w, 991w,

928w, 905w, 813vs, 755vs, 734s, 723vs, 681vs, 617w, 563w,

535w, 478w, 446s, 350w. δ_H(270 MHz, CDCl₃): 8.37 (1 H, dd,

J 0.6 and 7.5 Hz, nap 4-H), 8.22 (2 H, d, J 7.5 Hz, TePh 2,6-H),

8.17 (1 H, d, J 7.2 Hz, nap 2-H), 8.13-8.04 (2 H, m, nap 5,7-H),

7.66 (1 H, t, J 7.8 Hz, nap 6-H), 7.59-7.48 (2 H, m, nap 3-H,

TePh 4-H), 7.43-7.34 (2 H, m, TePh 3,5-H), 7.23-7.15 (3 H, m,

SPh 3-5-H), 7.05-6.97 (2 H, m, SPh 2,6-H). δ_C(67.9 MHz,

CDCl₃): 140.1(s), 139.3(s), 138.2(s), 133.5(s), 132.6(s), 131.4(s),

130.1(s), 129.7(s), 128.1(s), 127.8(s), 127.6(s), 127.5(s). δ_Te(81.2

MHz, CDCl₃): 790.9. m/z (ES^þ): 470.86 ([M - I₂þ OMe]^þ,

100%).

Compound 6. A solution of 1-(phenylselenyl)-8-(phenylsul-

fanyl)-naphthalene, D3 (0.066 g, 0.17 mmol), in dichloro-

methane (5 mL) was treated with iodine (0.086 g, 0.34 mmol).

An analytically pure sample was obtained by crystallization

from the diffusion of dichloromethane into a pentane solution

of the product (0.07 g, 18%). Anal. Found: C, 34.6; H, 2.1. Calcd

for (C₂₂H₁₆SSeI₂)I: C, 34.2; H, 2.1%. v_max(KBr disk)/cm^-1

:

Compound 10. A solution of 1-(phenyltellurenyl)-8-(phenyl-

selenyl)naphthalene, D5 (0.13 g, 0.26 mmol), in dichloro-

methane (5 mL) was treated with iodine (0.065 g, 0.26 mmol).

An analytically pure sample was obtained by crystallization

from the diffusion of dichloromethane into a pentane solution

of the product (0.2 g, 85%). Anal. Found: C, 36.0; H, 1.7. Calcd

3434brs, 3040w, 1940w, 1880w, 1803w, 1720w, 1655w, 1575s,

1541w, 1473s, 1435s, 1350w, 1324s, 1301w, 1196s, 1139w, 1059w,

1019s, 996s, 968w, 900w, 815vs, 783s, 754s, 737vs, 687vs, 615w,

540w, 520w, 483w, 455s. δ_H(270 MHz, CDCl₃): 7.98-7.89 (2 H,

m, nap 2,4-H), 7.76 (1 H, dd, J 1.9 and 7.2 Hz, nap 5-H),

7.68-7.60 (2 H, m, SePh 2,6-H), 7.50 (1 H, t, J 7.7 Hz, nap

3-H), 7.43-7.33 (3 H, m, SePh 3-5-H), 7.28-7.15 (4 H, m, nap

6-H, SPh 3-5-H), 7.15-7.06 (1 H, m, nap 7-H), 7.06-6.97 (2 H,

m, SPh2,6-H). δ_C(67.9MHz, CDCl₃):139.2(s), 135.9(s), 132.3(s),

131.7(s), 131.6(s), 130.1(s), 129.6(s), 129.2(s), 127.4(s), 126.5(s),

126.4(s), 126.0(s). δ_Se(51.5 MHz, CDCl₃): 476.9. m/z (ES^þ):

391.89 ([M - I₂]^þ, 100%).

for C₂₂H₁₆TeSeI₂: C, 35.7; H, 2.2%. v_max(KBr disk)/cm^-1

:

3441br s, 3046w, 2273w, 1572w, 1474s, 1434s, 1328s, 1189w,

1064w, 1046w, 1017w, 991w, 834w, 810vs, 752vs, 722vs, 680vs,

610w, 523w, 438s, 314w. δ_H(270 MHz, CDCl₃): 8.12 (1 H, d,

J 7.0 Hz, nap 4-H), 8.04 (1 H, d, J 8.1 Hz, nap 2-H), 8.00 (2 H, d,

J 7.5 Hz, TePh 2,6-H), 7.68 (1 H, d, J 7.3 Hz, nap 5-H), 7.58 (2 H,

d, J 7.4 Hz, nap 3,7-H), 7.49-43 (1 H, m, TePh 4-H), 7.42-7.32

(4 H, m, TePh 3,5-H, SePh 2,6-H), 7.22-7.16 (4 H, m, nap 6-H,

SePh 3-5-H). δ_C(67.9 MHz, CDCl₃): 139.2(s), 135.7(s),

135.6(s), 133.4(s), 132.5(s), 131.6(s), 130.5(s), 129.5(s), 129.3(s),

127.7(s), 127.5(s), 126.1(s). δ_Se(51.5 MHz, CDCl₃): 428.8. δ_Te

(81.2 MHz, CDCl₃): 747.0. m/z (ES^þ): 518.66 ([M - I₂þ OMe]^þ,

100%).

Compound 11. A solution of 1-bromo-8-(phenyltellurenyl)-

naphthalene, D6 (0.10 g, 0.25 mmol), in dichloromethane (5 mL)

was treated with a 0.1 M solution of bromine in dichloro-

methane (0.25 mmol, 2.5 mL). An analytically pure sample

was obtained by crystallization from the diffusion of dichloro-

methane into a pentane solution of the product (0.1 g, 91%).

Anal. Found: C, 33.9; H, 2.2. Calcd for C₁₆H₁₁TeBr₃: C, 33.7; H,

2.0%. v_max(KBr disk)/cm^-1: 3424brs, 3051w, 2920w, 1655w,

1589w, 1569w, 1535w, 1470s, 1432s, 1330s, 1260s, 1186s, 1133w,

1048s, 993w, 945w, 917w, 897w, 806vs, 735vs, 681s, 453s. δ_H(270

MHz, CDCl₃): 8.45 (2 H, d, J 6.6 Hz, TePh 2,6-H), 8.08 (1 H, d,

J 6.7 Hz, nap 5-H), 8.01 (2 H, d, J 7.5 Hz, nap 4,7-H), 7.91 (1 H, d,

J 7.9 Hz, nap 2-H), 7.70-7.51 (3 H, m, TePh 3-5-H), 7.51-7.36

(2 H, m, nap 3,6-H). δ_C(67.9 MHz, CDCl₃): 137.2(s), 134.3(s),

133.5(s), 132.0(s), 130.2(s), 127.4(s), 126.9(s). δ_Te(81.2 MHz,

CDCl₃): 942.8. m/z (ES^þ): 442.76 ([M - Br₂þ OMe]^þ, 100%).

Compound 12. A solution of 1-iodo-8-(phenyltellurenyl)-

naphthalene, D7 (0.09 g, 0.20 mmol), in dichloromethane

Compound 7. A solution of 1-(phenyltellurenyl)-8-(phenyl-

sulfanyl)naphthalene, D4 (0.032 g, 0.073 mmol), in dichloro-

methane (5 mL) was treated with bromine (0.023 g, 0.007 mL,

0.15 mmol). An analytically pure sample was obtained by

crystallization from the diffusion of dichloromethane into a

pentane solution of the product (0.04 g, 80%). Anal. Found: C,

42.6; H, 2.7. Calcd for C₂₂H₁₆TeSBr₂: C, 44.0; H, 2.7%. v_max

(KBr disk)/cm^-1: 3441br s, 3052w, 2953w, 1944w, 1869w, 1578s,

1475s, 1437s, 1325w, 1261w, 1200w, 1180w, 1072w, 1049w,

1046w, 1023w, 991s, 907w, 814vs, 757vs, 738s, 726vs, 680vs,

619w, 564w, 538w, 480w, 448s. δ_H(270 MHz, CDCl₃): 8.26-

7.96 (6 H, m, nap 2,4,5,7-H, TePh 2,6-H), 7.70-7.40 (5 H, m,

nap 3,6-H, TePh 3-5-H), 7.32-7.00 (5 H, m, SPh 2-6-H);

δ_C(67.9 MHz, CDCl₃) 139.7(s), 138.1(s), 134.3(s), 133.5(s),

132.5(s), 131.5(s), 130.3(s), 130.1(s), 129.6(s), 128.8(s), 127.4(s),

127.3(s). δ_Te(81.2 MHz, CDCl₃): 958.9. m/z (ES^þ): 472.79 ([M -

Br₂þOMe]^þ, 100%).

Compound 8. A solution of 1-(phenyltellurenyl)-8-(phenyl-

selenyl)naphthalene, D5 (0.12 g, 0.24 mmol), in dichlorometh-

ane (5 mL) was treated with bromine (0.038 g, 0.01 mL, 0.24

mmol). An analytically pure sample was obtained by crystal-

lization from the diffusion of dichloromethane into a pentane

solution of the product (0.1 g, 75%). Anal. Found: C, 40.7;

H, 2.0. Calcd for C₂₂H₁₆TeSeBr₂: C, 40.9; H, 2.5%. v_max(KBr

disk)/cm^-1: 3441brs, 3052s, 1944w, 1869w, 1738w, 1721w,

Article

Inorganic Chemistry, Vol. 49, No. 16, 2010 7595

(5 mL) was cooled to 0 °C and slowly treated with a 0.1 M

solution of bromine in dichloromethane (2.0 mL, 0.20 mmol).

An analytically pure sample was obtained by crystallization

from the diffusion of dichloromethane into a pentane solution

of the product (0.1 g, 86%). v_max(KBr disk)/cm^-1: 3449br s,

3045w, 2954s, 2924s, 2851w, 1561w, 1532w, 1467w, 1432s,

1324w, 1260s, 1182w, 1094w, 1019w, 991w, 937w, 902w, 871w,

805vs, 766w, 746w, 731vs, 697w, 680s, 643w, 560w, 520w, 501w,

452s, 387w. δ_H(270 MHz, CDCl₃): 8.41-8.29 (3 H, m, nap 4-H,

TePh 2,6-H), 8.12 (1 H, d, J 7.2 Hz, nap 5-H), 7.96 (1 H, d, J 8.0

Hz, nap 7-H), 7.92 (1 H, d, J 7.4 Hz, nap 2-H), 7.63-7.46 (3 H,

m, TePh 3-5-H), 7.38 (1 H, t, J 7.7 Hz, nap 6-H), 7.28 (1 H, t,

J 7.7 Hz, nap 3-H). δ_C(67.9 MHz, CDCl₃): 142.2(s), 138.6(s),

137.2(s), 133.9(s), 131.8(s), 130.9(s), 130.1(s), 127.9(s), 126.6(s).

132.6(s), 131.5(d, J 10.4 Hz), 129.2(d, J 13.5 Hz), 128.7(s),

128.2(s), 128.1(s), 126.2(s), 125.7(s), 125.5(s). δ_P(109 MHz,

CDCl₃): 52.48. m/z (ES^þ): 458.85 ([M - Br₃þ Na]^þ, 100%).

5.1. Crystal Structure Analyses. X-ray crystal structures

determined for compounds 8 and 10 were collected at -180(1) °C

by using a Rigaku MM007 high brilliance RA generator

(Mo KR radiation, confocal optic) and Mercury CCD system.

At least a full hemisphere of data was collected using ω scans.

Intensities were corrected for Lorentz, polarization and absorp-

tion. Data for all other compounds [1-5, 7, 9-15] were collected

at -148(1) °C on the St. Andrews STANDARD system⁷⁷

Rigaku ACTOR-SM, Saturn 724 CCD area detector with

˚

confocal optic Mo KR radiation (λ = 0.71073 A). The data

were corrected for Lorentz, polarization, and absorption. The

data for the complexes analyzed were collected and processed

using CrystalClear (Rigaku).⁷⁸The structure was solved by

direct methods⁷⁹and expanded using Fourier techniques.⁸⁰

The non-hydrogen atoms were refined anisotropically. Hydro-

gen atoms were refined using the riding model. All calculations

were performed using the CrystalStructure⁸¹crystallographic

software package except for refinement, which was performed

using SHELXL-97.⁸²

δ

_Te(81.2 MHz, CDCl₃): 903.0. m/z (ES^þ): 488.71 ([M - Br₂þ

OMe]^þ, 100%).

Compound 13. A solution of 1-bromo-8-(phenyltellurenyl)-

naphthalene, D6 (0.039 g, 0.095 mmol), in dichloromethane

(5 mL) was treated with iodine (0.0024 g, 0.095 mmol). An

analytically pure sample was obtained by crystallization from

the diffusion of dichloromethane into a pentane solution of the

product (0.03 g, 54%). v_max(KBr disk)/cm^-1: 3433br s, 3040w,

2925w, 2371w, 1652w, 1638w, 1561w, 1532w, 1467s, 1432s,

1381w, 1327w, 1259w, 1207w, 1184w, 1130w, 1045s, 991w,

942w, 911w, 825w, 805vs, 746s, 729s, 680s, 603w, 526w, 446s,

432w. δ_H(270 MHz, CDCl₃): 8.48 (2 H, dd, J 1.1 and 8.5 Hz,

TePh 2,6-H), 8.15 (1 H, dd, J 1.1 and 7.7 Hz, nap 4-H), 8.07 (2 H,

m, nap 2,5-H), 7.92 (1 H, dd, J 0.8 and 8.3 Hz, nap 7-H),

7.67-7.59 (1 H, m, TePh 4-H), 7.53-7.42 (3 H, m, nap 6-H,

TePh 3,5-H), 7.40 (1 H, t, J 7.8 Hz, nap 3-H). δ_C(67.9 MHz,

CDCl₃): 139.7(s), 138.5(s), 134.2(s), 133.3(s), 131.8(s), 130.3(s),

130.1(s), 127.5(s), 127.1(s). δ_Te(81.2 MHz, CDCl₃): 887.5. m/z

(ES^þ): 442.76 ([M - I₂þ OMe]^þ, 100%).

5.2. Computational Details. Geometries were fully optimized

in the gas phase at the B3LYP level⁸³using Curtis and Binning’s

962(d) basis⁸⁴on Se and Br (augmented with a set of diffuse s

and p functions on Br) and 6-31þG(d) basis elsewhere, followed

by calculation of the harmonic frequencies to confirm the

minimum character of each stationary point and to evaluate

standard thermodynamic corrections at 1 atm and 298 K.

Wiberg bond indices⁷⁶were obtained in a natural bond orbital⁸⁵

€

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Compound 14. A solution of 1-iodo-8-(phenyltellurenyl)naph-

thalene, D7 (0.11 g, 0.25 mmol), in dichloromethane (5 mL) was

treated with iodine (0.063 g, 0.25 mmol). An analytically pure

sample was obtained by crystallization from the diffusion of

dichloromethane into a pentane solution of the product (0.1 g,

81%). Anal. Found: C, 27.5; H, 1.3. Calcd for C₁₆H₁₁TeI₃: C,

26.9; H, 1.6%. v_max(KBr disk)/cm^-1: 3430br s, 2959s, 2924vs,

2853s, 1735w, 1654w, 1529w, 1465w, 1430w, 1375w, 1363w,

1317w, 1261vs, 1177w, 1090vs, 1020vs, 866w, 802vs, 747w,

727w, 680w, 663w, 587w, 561w, 535w, 520w, 448w, 389w. δ_H

(270 MHz, CDCl₃): 8.38-8.29 (2 H, m, TePh 2,6-H), 8.27 (1 H,

dd, J 1.1 and 7.4 Hz, nap 4-H), 8.15 (1 H, dd, J 1.0 and 7.6 Hz,

nap 5-H), 7.93 (1 H, d, J 8.1 Hz, nap 7-H), 7.86 (1 H, dd, J 1.0

and 8.2 Hz, nap 2-H), 7.57-7.49 (1 H, m, TePh 4-H), 7.44-7.34

(2 H, m, TePh 3,5-H), 7.30 (1 H, t, J 7.8 Hz, nap 6-H), 7.23 (1 H,

t, J 7.8 Hz, nap 3-H). δ_C(67.9 MHz, CDCl₃): 142.1(s), 140.0(s),

139.4(s), 133.7(s), 131.6(s), 130.7(s), 130.2(s), 128.1(s), 126.9(s).

δ_Te(81.2 MHz, CDCl₃): 848.0. m/z (ES^þ): 490.68 ([M - I₂þ

OMe]^þ, 100%).

Compound 15. A solution of (8-phenylsulfanylnaphth-1-yl)-

diphenylphosphine, D8 (0.30 g, 0.71 mmol), in dichloromethane

(15 mL) was treated with bromine (0.45 g, 0.15 mL, 2.8 mmol).

An analytically pure sample was obtained by crystallization

from the diffusion of dichloromethane into a pentane solution

of the product (0.2 g, 32%). v_max(KBr disk)/cm^-1: 3430brs,

3069w, 3052w, 2691w, 2197w, 1968w, 1898w, 1814w, 1738w,

1636w, 1578s, 1543w, 1477vs, 1435vs, 1320s, 1264w, 1197s,

1151s, 1115vs, 1064w, 1023w, 988w, 921w, 887s, 825s, 765vs,

738vs, 718vs, 687vs, 625w, 613w, 581w, 561vs, 535vs, 503s, 468s,

413s, 346vs. δ_H(270 MHz, CDCl₃): 8.41 (1 H, d, J 8.0 Hz, nap

4-H), 8.25 (1 H, d, J 8.0 Hz, nap 5-H), 7.87 (2 H, d, J 6.8 Hz, nap

2,7-H), 7.69 (1 H, t, J 7.7 Hz, nap 6-H), 7.66-7.59 (1 H, m, nap

3-H), 7.57-7.42 (6 H, m, 2 ꢀ PPh₂3-5-H), 7.41-7.30 (4 H, m, 2

ꢀ PPh₂2,6-H), 6.96 (1 H, t, J 7.3 Hz, SPh 4-H), 6.92-6.83 (2 H,

m, SPh 3,5-H), 6.15 (2 H, d, J 7.5 Hz, SPh 2,6-H), 2.99 (1 H,

br s, -OH). δ_C(67.9 MHz, CDCl₃): 140.6(s), 137.3(s), 132.8(s),

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7596 Inorganic Chemistry, Vol. 49, No. 16, 2010

Knight et al.

analysis at the same level. The optimizations were started from

the experimental structures available from X-ray crystallo-

graphy, substituting chalcogens and halogens where necessary.

Additional single-point energy calculations were performed

using the polarizable continuum model (PCM) of Tomasi and

co-workers,⁸⁶employing the same basis sets on Se and Br as

before, and 6-311þG(d) elsewhere, together with the parameters

of CH₂Cl₂as a typical solvent. The resulting changes in relative

energies were added as increments to the gas-phase free energies,

affording the ΔG_r(CH₂Cl₂) values in Figure 13. Reaction en-

ergies have not been corrected for basis-set superposition error

(BSSE). An exploratory BSSE calculation for C using the

Counterpoise method⁸⁷(with D2 and Br₂fragments) indicated

a very small correction of just around 1 kcal/mol. The com-

putations were performed using the Gaussian 03 suite of

programs.⁸⁸

Acknowledgment. Elemental analyses were performed by

Sylvia Williamson, and Mass Spectrometry was performed by

Caroline Horsburgh. Calculations were performed 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. thanks EaStCHEM for support.

Supporting Information Available: Crystal structure illustra-

tions for compounds 3, 5, 8-10, and 12-14 and CIF data for

1-15. This material is available free of charge via the Internet at

http://pubs.acs.org.

Article Doi

Hypervalent adducts of chalcogen-containing peri -substituted naphthalenes; Reactions of sulfur, selenium, and tellurium with dihalogens

DOI: 10.1021/ic101086h

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Full text of DOI:10.1021/ic101086h

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