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New Ionic Isoelectronic Analogues of CO2 and CS2.

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R =
Certainly the advantages of binary coding will first be realized
fully in the synthesis of compound libraries of small organic
molecules.r8]The future of combinatorial chemistry promises to
be interesting.
Scheme 3. The synthetic receptor 1 labeled with an azo dye R.
Still et a]. have proved the viability of their concept with these
two e ~ a m p l e s , [ ~and
~ ' l have shown that combinatorial chemistry
is a useful tool for the study of supramolecular interactions.
German version Angen. C h m . 1994, 106. 1649
[l] Peptide libraries: G. Jung. A. G . Beck-Sickinger, Angew. Chem. 1992. 104. 357;
Angrw. Chem. In/. Ed. Engl. 1992, 31, 375; phage libraries: J. A. Wells, H. B.
Lowman, Curr. Opin. Bioterhnol. 1992, 3, 355; libraries of peptidomimetics:
R. N. Zuckermann, C u r . Opin. Slrurl. Bid. 1993. 3, 580; oligonucleotide Iibraries: M. Famnlok, J. W. Szostak, Angew. Chem. 1992. 104, 1001 : A n g w .
Chem. I n f . Ed. Engl. 1992. 31. 979; molecular diversity: M. R. Pavia. T. K.
Sawyer, W. H. Moss, Biuorg. M i d . Chcm. Lett. 1993.3. 3x7; W. H. Moos, G. D.
Green, M. P. Pavia. Annu. Rep. Med. Chrm. 1993. 28, 315.
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[3] A. Furka, F. Sebestyen, M. Asgedom, G . Diho. fnt. J. Pep/. Protein R m . 1991.
37,487; K. S. Lam, S. E. Salmon, E. M. Hersh, V. J. Hruby. W. M. Karmierski.
R. J. Kndpp, Nature 1991, 354, 82.
[4] J. Nielsen. S. Brenner. K. D. Janda. J. Am. Chern. Suc. 1993. lfS.9812.
[5] J. M. Kerr. S. C. Banville. R. N. Zuckermann. J Am. Chem. Suc. 1993. 115,
[6] M. H. J. Ohlmeyer, R. N. Swanson, L. W. Dillard, J. C. Reader. G. Asouline. R.
Kobayashi. M. Wigler, W. C. Still, Pfor. Nut/. A w d . Scl. U S A 1993. PO. 10922.
[7] A. Borchardt, W. C. Still, J. Am. Cl7em. Sur. 1994. 116. 373.
[XI C. Chen. L. A. A. Randall, R. B. Miller, A. D. Jones, M. J. Kurth, J A m Chcm.
Soc. 1994, 116, 2661.
New Ionic, Isoelectronic Analogues of CO, and CS,
Thomas M. Klapotke*
Several isoelectronic analogues of CO, have been known for
a long time and are well characterized. These include neutral
N,O ( C , " ) and the ionic species N; (Dm,,),C N i - (D%,,,),
NO: (D1;J.l'I In the last few years. in particular, great progress
has been made in the area of these simple 22-electron (16valence-electron) X = Y = Z species. Thus, all of the possible
X=Y=Z" systems that contain X, Y , and Z elements of the
second period and net charges ( - 4 2 n < + 4) have been computed by a b initio methods and many ions were predicted to be
locally stable.[21In meantime several of these unknown species
have been prepared and characterized, for example CBN4- and
C:-, and these species together with their heavier CS, analogues are highlighted here.
The structurally well-characterized ionic, isoelectronic analogues of CO, known to date are summarized in Table l together with three isoelectronic ions of CS,. the heavier homologue
of C 0 2 . Furthermore, the BAS:- anion, which is isoelectronic
to CSez. has been reported (dBAs
= 186.8 pm) .I3]
In all cases the bond lengths in the ions isoelectronic to CO,
and CS, are appropriate for bond orders greater than unity, and
Pri\.-Doz. Dr. T. M. Klapotke
Institut f u r Anorganische und Analytische Chemie der
Technischen Universitdt
S t r a s e des 17. J u n i 135, D-10623 Berlin ( F R G )
Telefax' Inr. code + (30)314-22168
Table 1. Bond lengths of CO, and CS2 and their ionic. isoelectronic analogues [a].
d,, [pm] d,, [pm] Ref.
[4] [h]
dxy[pm] (I,, [pm] Ref
15. 61
[9. 101
[ l l , 121
~ 3 1
[a] Ions that are isoelectronic or isovalence-electronic to OCS, for example SeCN
[I] are also known; however, they are not discussed here. Polymeric structures have
been proposed for the compounds Li,AIN,. Li,GaN,, Li,AIP,. and Li,AIAs, 13).
Formally isosteric transition metal species (e.g. [FeN,I4- isosteric to SiS,) have been
described see ref. [14]. [b] The fulminate ion C N O - isomeric to the cyanate ion is
also known [I].
therefore significant (p-p), bonding has to be considered. Even
in the recently published PCS- ion the C-S bond length
(162 pm) is significantly shorter than the value expected for a
typical single bond (cf. d,, (thioether) z 182 pm) .['I However,
the NBO (NBO = natural bond orbitals) analysis for the PCSion based on an a b initio calculation (HF 6-31 + G*),
= 157 pm, d,, = 164 pm) clearly indicates that P-C - S - is
the most favored Lewis structure (NBO charges [el: P -0.03,
C -0.63, S -0.34)."']
With the exception of the C:- ion all species quoted in
Table 1 can be regarded as linear within the reported standard
deviations. Interestingly, the C:- ion exhibits C,, symmetry
with a C-C-C bond angle of 169.0(6)-; the C - C distances of
134.6(4)pm are consistent with the expected value for C - C
double bonds of 135 ~ m . [ 'A~ comparison
of the experimentally determined structural parameters of the C:- ion with those
computed by a b initio methods showed that the unusual deviation fiom linearity can be explained by matrix effects caused by
the trigonal prismatic coordination of the C:- ion by C a 2 +
In all ions isoelectronic to CO, the most electropositive atom
always occupies the central Y position in the X = Y = Z species.
This is consistent with theoretical calculations which predict
that this isomer will always be the most stable.['']
Most of the anionic 16-valence-electron species that are
isoelectronic to CO, and CS, were synthesized by high-temperature solid-state reactions in sealed niobium or tantalum ampoules. For example, the compounds Sr3(BN2),[lo1 and
KIBP2'3Jwere prepared at 1000'T from strontium nitride and
BN or from K and BP, respectively. Ca3Br2CBN and
Sr,CI2CBN were synthesized at 950 ;C from the corresponding
metal, its dihalide, boron nitride, and graphite." In analogy,
Ca3C1,C, was formed from calcium, CaCI,. and graphite at
900'C.1'31The synthesis of the first compound containing an
isolated PCS- ion was achieved in solution by treatment of
lithium bis(trimethylsily1)phosphanide with equimolar amounts
of 0,O'-diethyl thiocarbonate [Eq. (a)] .['I
+ [(CH;),SI]~P-LI DME
[Eq. (f)], and polymeric sulfur nitride, (SN),, [Eq. (g)] demonstrate the synthetic potential of the SNS+ cation in main group
+ NaN,
+ SnCI,
+ 2AsF,
+ NaAsF, + N, + as8
+ SnCI,
(771 radical)
[ I ] N. N . Greenwood, A. Earnshaw, Chemistrj. of ihe Elements. Pergamon. Oxford. 1984, p. 337. 50Y: C k m i e der Elemen&. VCH. Weinheim, 1988, p. 375.
[2] P. Pyykkii. Y. Zhao, J. Phys. Chem. 1990. 94, 7753.
[3] H. G. von Schnering. M. Sorner. M. Hartweg. K Peters. Angrx Chem. 1990.
102. 63; .4ngrw. Chwis. I n / . Ed. Ens/. 1990. 29. 65; and references therein.
[4] A. F. Wells, Strurr~irulInorgunk C / i e m b t r j . , 5th ed., Clarendon. Oxford. 1984.
[5] R. Faggiani. R J. Gillespie. C. J. L. Lock, J. D. Tyrer, Inorg. Cheni. 1978. 17.
[6] S. Parsons, J. Passmore, Acc. Chem. Re.\. 1994. 27. 101.
[7] G Becker. K. Hubler. Z. Anorg. ANg. Cliem. 1994, 620. 405.
[8] M . G Down. M. J. Haley. P. Hubberstey. R. J Pulham. A. E Thunder. J
C/feni. Sor. Dulton Truns. 1978, 1407.
[9] H . Yamane. S. Kikkawa. H. Horiuchi, M. Koizumi, J. SolidStatc, Chrm. 1986.
6s. 6.
[lo] H. Woinelsdorf. H:J. Meyer, Z. Anorg. Allg. Chum 1994, 620. 262.
[ I l l H . Wornelsdorf. H:J. Meyer. 2. Anorg. Allg. Chem. 1994, 620, 258.
[I21 H.-J. Meyer. Z. Anorg. Allg. Cheni. 1991. 594, 113.
[I31 H:J. Meyer. Z . Anors. A&. Chem. 1991. 593. 185.
[14] N . Jansen, H. Spiering, P. Gutlich. D. Stahl. R. Kniep. V. Eyert. J. Kiibler, P. C.
Schmidt, Angeu.. Chrm. 1992. 104. 1632; Angrii. Chcm. Inr. Ed. Engl. 1992.31.
1624; A. Gudat. S. Haag. P. Hiihn, R. Kniep. W. Milius. A. Rabenau, J. Allojs
Compd. 1991, 177. L 17.
[15] A. Schulz, T. M . Klapotke. unpublished.
1161 B. M. Gimarc. J. A m . Chrm. Six. 1970, 92,266; J. K. Burdett, N . J. Lawerence,
J. J. Turner. InorK. Chem. 1984. 23. 2419.
[I71 B. Ayrez. A. J. Banister. P. D. Coates. M. I. Hansford. J. M. Rawson. C. E. F.
Rickard. M. B. Hursthouse. K . M. Abdul Malik, M. Motevalli, J. Chem. Soc.
Dulton Truns. 1992. 3097; A. J. Banister. R. G. Hey. G. K. MacLean, J. Passmore. Inorg. Cheni. 1982. 21. 1679.
The SNS+ ion is classically obtained by oxidation of a mixture of tetrasulfurtetranitride and sulfur with AsF, [Eq.
however, two new laboratory syntheses are more convenient
and do not involve the use of explosive S,N, [Eqs. (c) and
(d)] . [ I 'I
+ is, + 6 A s F ,
(hn aromatic)
German version: A n g r w C'hem. 1994. 106, 1651
(drne = 1,2-dirnethoxyethane)
Earlier this year the synthesis. isolation and characterization
of the CBN4- ion. an additional molecule isoelectronic to CO,,
was achieved. It had been predicted for many years on the basis
of quantum mechanical calculations that this anion should be
stable. This result should encourage the synthesis of new analogues of CO, and CS,. The most likely possible new anions
include: NCB4 isomeric to the experimentally characterized
CBN4-,c1 NCC3- and OBC3- isoelectronic with NBN","']
and OBN2- rtnalogous to the known NCN2-.'*] One particularly exciting challenge in this field that remains is the synthesis
of the highly charged cations analogous to CO,, namely O:+
and F N F 3 +; these are predicted to be locally
- 5 5
+ 2 H,C,OSi(CH,),
+ SN'
Of all the ions considered here so far, the SNS+ cation has
attracted the most interest as a starting material in preparative
inorganic chemistry. The preparation of new pseudoaromatic
S-N heterocycles [Eq. (e)], unusual, thermally stable radicals
VCH ~ ~ r l u j i s g e r l l . \ ~ h unihH,
0-69451 W m h e i m , 1994
0570-0R33:94:1515-1576 S 10.00+ .25:0
Angeu. Chrm. I n t . Ed. Enyl. 1994. 33. No. 15/16
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isoelectronic, ioni, cs2, co2, new, analogues
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