Synthesis, structure and reactivity of cyclopropenyl-1-ylidene stabilized S(ii), Se(ii) and Te(ii) mono- and dications

Article abstract of DOI:10.1039/c2cc36225b

The syntheses and structural characterization of carbene-stabilized chalcogen centred mono- and dications employing a reverse electron demand onio-substitutent transfer strategy are reported. The electronic structures of these compounds were determined by density functional calculations and their reactivity towards Pd(0) centres was evaluated.

Full text of DOI:10.1039/c2cc36225b

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Synthesis, structure and reactivity of cyclopropenyl-1-ylidene stabilized
S(II), Se(II) and Te(II) mono- and dicationswz
´
Agnes Kozma, Jekaterina Petuskova, Christian W. Lehmann and Manuel Alcarazo*
ˇ
Received 27th August 2012, Accepted 12th October 2012
DOI: 10.1039/c2cc36225b
The syntheses and structural characterization of carbene-stabilized
chalcogen centred mono- and dications employing a reverse
electron demand onio-substitutent transfer strategy are reported.
The electronic structures of these compounds were determined by
density functional calculations and their reactivity towards Pd(0)
centres was evaluated.
describe the extension of this methodology from phosphorus
to chalcogen-centred cations and some reactivity of the thus
obtained compounds.
By gentle heating of THF suspensions containing 1-chloro-2,
3-bis(diisopropylamino)cyclopropenium salts
PhSSiMe , PhSeSiMe or PhTeSiMe , the S, Se, or Te-centred
cations 3–5 were isolated as white or pale yellow solids
Scheme 2). Remarkably, the synthetic utility of our strategy
1 or 2 with
3
3
3
(
Main group polycations bearing a formal charge of +2 or
even larger at the central atom have attracted some attention
due to the ability of these highly electropositive centres to
could be further confirmed when the reaction with the
bis(silylated) species S(SiMe ) , Se(SiMe ) and Te(SiMe3)2
3 2
3 2
1
was conducted in the presence of two equivalents of 1 or 2.
The isolated crystalline materials were found to be salts 6–11
containing the desired dicationic chalcogen complexes supported
interact with small organic molecules or serve as strong
2
p-acceptor ligands for transition metals. Concerning chalcogens,
the main route for the synthesis of these compounds is based on
3
the onio-substituent strategy that involves the generation of a
by two 2,3-bis(diisopropylamino)cyclopropenyl-1-ylidene ligands
6
(Scheme 2).
2
transient ‘‘Ch(TfO) ’’ from the corresponding chlorides and
Single crystals suitable for X-ray diffraction analysis were
grown for most of the newly prepared compounds. As can be
seen in Fig. 1 the cationic part of 3–5 features comparable
structural parameters namely: (i) quite similar C–C bond
TMSTfO and subsequent trapping of the thus generated
cation by neutral two electron donor ligands such as pyridines,
4
bisimines, phosphines or carbenes.
Very recently we reported an alternative synthetic approach
that, inversely to the transformation described, makes use of
silylated phosphines and chlorocyclopropenium salts as starting
˚
lengths in the cyclopropenyl ring (1.376–1.425 A) suggesting
delocalization of the positive charge in this moiety and
(ii) slightly shorter Ch–C(carbene) bonds than the respective
Ch–C(Ph). This reveals a weak, but preferred, back-donation
from the chalcogen centre to the cyclopropenium ring. The
main geometric difference among compounds 3–5 is the
2a
materials (see Scheme 1). Thus, employing this unprecedented
‘reverse electron demand’’ onio-substitutent transfer
strategy, the isolation and structural characterization of the
‘
3+
elusive [(carbene) P] (carbene = 2,3-bis(diisopropylamino)-
3
5
cyclopropenyl-1-ylidene) species were possible. Herein, we
3+
Scheme 1 Synthesis of [L
3
P] cations by reaction of 1-chlorocyclo-
3 3
propenium salts and P(SiMe ) .
Max Planck Institut fu¨r Kohlenforschung, 45470-Mu¨lheim an der
Ruhr, Germany. E-mail: alcarazo@mpi-muelheim.mpg.de;
Fax: +49 208 3062994; Tel: +49 208 3062428
w This article is part of the ChemComm ‘Emerging Investigators 2013’
themed issue.
z Electronic supplementary information (ESI) available: Characteri-
zation data for all new compounds and further computation data.
CCDC 895891–895903. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c2cc36225b
+
2+
2
Scheme 2 Synthesis of [LChPh] and [L Ch] cations by reaction
of 1-chlorocyclopropenium salts with PhChSiMe
(Ch = S, Se, Te).
3 3 2
and Ch(SiMe )
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Fig. 1 Solid state structures of 3 (up, left), 4 (up, middle), 5 (up, right), 6 (down, left), 8 (down, middle) and 11 (down, right). All hydrogen atoms,
10
solvent molecules and anions have been omitted for clarity.
C(carbene)–Ch–C(Ph) angle (3, 103.41; 4, 98.51; 5, 95.01)
reflecting the well known tendency of the heavier elements of
a group to employ unhybridized atomic orbitals to form
the S and Se atoms of these compounds would exhibit Lewis
base properties. Thus, the coordination chemistry towards
electron rich metal-containing moieties was studied. In sharp
+
7
bonds. A similar trend could be observed for compounds 6,
8
contrast to the phosphorus-centred analogues [LPR
3+
2
]
and
8 and 11 (6, 100.11; 8, 97.31; 11, 95.41). In addition, short
contacts within the sum of the van der Waals radii were
[L
3
P] (L = 2,3-bis(diisopropyl-amino)cyclopropenyl-1-ylidene;
R = Ph), no reaction was observed by exposure of 3, 4, 6 or 8 to
2
a
observed between the chalcogen and the oxygen atoms of
9
the triflate counterions in the solid state structure of 7 and 11.
K
2
PdCl
equimolar amount of [Pt(Ph
the smooth precipitation of a yellow solid with concomitant
release of two equivalents of PPh . In addition, two new signals
4
or K
2
PtCl
4
.
More importantly, treatment of 3 with an
3
P) ] in refluxing toluene resulted in
4
The bonding situation in compounds 3–6, 8 and 10 was
evaluated using the B3LYP functional with the LANL2DZ
pseudopotential for S, Se and Te and the 6-31G* basis set
for all other atoms. Optimized structures closely match the
experimental data. Inspection of the frontier orbitals reveals
the presence of two lone pair orbitals with maximum coefficient
at the central chalcogen atom (see Fig. 2 and the ESIz).
Interestingly, according to natural population analysis, the
cyclopropenium moieties bear most of the positive charges in
S-based compounds while the central chalcogen centre gets
progressively more positively charged for the heavier analogues.
This whole set of findings support the idea that compounds 6, 8
and 10 should be considered as dicationic chalcogen-based
3
31
1 31 195
appeared in the P NMR spectrum (d = 16.5 ppm, J( P, Pt) =
2898.4 Hz, J( P, P) = 23.3 Hz; d = 20.1 ppm, J( P, Pt) =
2360.3 Hz, J( P, P) = 23.3 Hz) suggesting the formation of
2
31 31
1 31 195
2
31 31
a product that contains two PPh in a relative cis-position.
3
Extraction with Et O allowed the isolation of 12 in analyti-
2
cally pure form in 82% yield. The selenium derivative 4 reacts
analogously affording compound 13 in similar yield while 6
and 8 decompose under the same reaction conditions.
The structures of 12 and 13 were unambiguously confirmed
by X-ray crystallographic analysis. As depicted in Scheme 3
3 4
and Fig. 3 the oxidative insertion of [Pt(PPh ) ] into the C–S
1
1
analogues of carbodicarbenes and carbodiphosphoranes.
or C–Se bonds provides cyclopropenylidene complexes of
Pt(II) bearing two phosphines and an additional sulphide or
selenide ligand. Although the oxidative insertion of low valent
metals into appropriate halo-imidinium salts is a well known
process, the insertion into the C–S or C–Se bonds of cyclo-
propenium salts is, to the best of our knowledge, unprece-
Encouraged by the lone pair characteristics calculated for
the HOMO of 3–6, 8 and 10 we wished to ascertain whether
1
2
dented. Finally, when the same reaction is attempted
employing [Pd(PPh ] instead of [Pt(PPh ], the system
3
)
4
3 4
)
evolves in a different manner. Probably, after the oxidative
insertion step, dissociation of the phosphine trans to the
carbene produces a tricoordinated species that dimerises
affording dimetallic complexes 14 and 15. In these compounds
the sulphide or selenide moiety acts as a bridging ligand
Fig. 2 Molecular orbitals of 8: HOMO (left) and HOMO ꢀ 2 (right).
Chem. Commun.
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reaction of dicationic compounds with Pd(0) or Pt(0), under
the same conditions monocationic derivatives 3 and 4 cleanly
suffer from oxidative insertion of the low valent metal into the
C–Ch bonds.
Generous financial support from the Deutsche Forschungs-
gemeinschaft and the Fonds der Chemischen Industrie
´
is gratefully acknowledged. A.K. thanks the DAAD for
support.
Notes and references
1
2
D. D. Caleb and P. J. Ragogna, Inorg. Chem., 2010, 49, 8164.
(a) J. Petuskova, M. Patil, S. Holle, C. W. Lehmann, W. Thiel and
ˇ
M. Alcarazo, J. Am. Chem. Soc., 2011, 133, 20758; (b) M. P. Coles
and P. B. Hitchcock, Chem. Commun., 2007, 5229; (c) M. Azouri,
J. Andrieu, M. Picquet and H. Cattey, Inorg. Chem., 2009,
Scheme 3 Reactivity of 3 and 4 towards Pd(0) and Pt(0) species.
4
8, 1236; (d) I. Abdellah, C. Lepetit, Y. Canac, C. Duhayon and
R. Chauvin, Chem.–Eur. J., 2010, 16, 13095; (e) C. Maaliki,
C. Lepetit, Y. Canac, C. Bijani, C. Duhayon and R. Chauvin,
Chem.–Eur. J., 2012, 18, 7705.
3
4
(a) R. Weiss and S. Engel, Synthesis, 1991, 1077; (b) G. Bouhadir,
au and G. Bertrand, Heteroat. Chem., 1995,
R. W. Reed, R. Re
´
hlhafer and R. Weiss, Eur. J. Org. Chem., 2004,
6
, 371; (c) F. G. Pu
002.
¨
1
¨
(a) J. W. Dube, M. M. Hanninen, J. L. Dutton, H. M. Tuononen
and P. J. Ragogna, Inorg. Chem., 2012, 51, 8897; (b) J. L. Dutton
and P. J. Ragogna, Coord. Chem. Rev., 2011, 255, 1414;
(
c) J. L. Dutton, T. L. Battista, M. J. Sgro and P. J. Ragogna,
Chem. Commun., 2010, 46, 1041; (d) J. L. Dutton, H. M. Tuononen
and P. J. Ragogna, Angew. Chem., Int. Ed., 2009, 48, 4409;
´
(e) D. J. Williams, P. H. Poor, G. Ramırez and D. Vanderveer,
Inorg. Chim. Acta, 1989, 165, 167.
5
6
For the isolation of 2,3-bis(diisopropylamino)cyclopropenyl-1-ylidene
see: V. Lavallo, Y. Canac, B. Donnadieu, W. W. Schoeller and
G. Bertrand, Science, 2006, 312, 722.
For the synthesis of 6 and 8 as perchlorates see: (a) Z. Yoshida,
H. Konishi and H. Ogoshi, Isr. J. Chem., 1981, 21, 139;
Fig. 3 Solid state structure of 13. All hydrogen atoms, solvent
10
molecules and anions have been omitted for clarity.
(
1
b) R. Allmann, F. Kaiser, M. Krestel and G. Seitz, Angew. Chem.,
986, 98, 191.
7
8
9
We have also prepared, though by a different synthetic route, the
oxygen analogue of 3, (16). In this compound the
C(carbene)–Ch–C(Ph) angle is 117.61 (see the ESIz).
The oxygen analogue of 6 (17) has a C(carbene)–Ch–C(Ph) angle
of 117.61. See the ESIz and G. Maas and P. J. Stang, J. Org. Chem.,
1983, 48, 3038.
L. Pauling, The Nature of the Chemical Bond, Cornell University
Press, Ithaca, NY, 1960, p. 260.
0 CCDC 895892 (6), 895893 (8), 895894 (7), 895895 (11), 895896 (3),
1
8
95897 (14), 895898 (12), 895899 (13), 895900 (4), 895901 (15),
95903 (5), 895902 (16), 895891 (17) contain the supplementary
8
crystallographic data for this paper.
1
1 (a) C. A. Dyker, V. Lavallo, B. Donnadieu and G. Bertrand,
¨
Angew. Chem., Int. Ed., 2008, 47, 3206; (b) A. Furstner,
Fig. 4 Solid state structure of 15. All hydrogen atoms, anions and
M. Alcarazo, R. Goddard and C. W. Lehmann, Angew. Chem.,
Int. Ed., 2008, 47, 3210; (c) M. Alcarazo, C. W. Lehmann,
10
3
Ph groups from PPh ligands have been omitted for clarity.
A. Anoop, W. Thiel and A. Fu
d) I. Fernandez, C. Dyker, A. De Hope, B. Donnadieu,
G. Frenking and G. Bertrand, J. Am. Chem. Soc., 2009,
31, 11875; (e) M. Melaimi, P. Parameswaran, B. Donnadieu,
G. Frenking and G. Bertrand, Angew. Chem., Int. Ed., 2009,
¨
rstner, Nat. Chem., 2009, 1, 295;
(
´
between the two metal atoms formally donating two electron
pairs (Fig. 4 and the ESIz).
1
By the employment of a ‘‘reverse electron demand’’ onio-
substituent transfer strategy, the isolation and structural
¨
48, 4792; (f) W. Petz, F. Oxler, B. Neumu
¨
G. Frenking, Eur. J. Inorg. Chem., 2009, 4507; (g) B. Ine
ller, R. Tonner and
s, M. Patil,
2
+
+
´
characterization of [(carbene)
2
Ch]
and [(carbene)ChPh]
J. Carreras, R. Goddard, W. Thiel and M. Alcarazo, Angew.
Chem., Int. Ed., 2011, 50, 8400; (h) M. Alcarazo, Dalton Trans.,
2011, 40, 1839.
(
carbene = 2,3-bis(diisopropylamino)cyclopropenyl-1-ylidene;
Ch = S, Se and Te) species were possible. The electronic
structures of these compounds were calculated confirming the
presence of two non-shared lone pairs on the chalcogen centres
while most of the positive charges reside in the cycloprope-
nium rings. Although no product could be isolated from the
12 (a) D. Kremzow, G. Seidel, C. W. Kehmann and A. Fu
Chem.–Eur. J., 2005, 11, 1833; (b) Z. Yoshida, Pure Appl. Chem.,
982, 54, 1059; (c) N. J. Hardman, M. B. Abrams, M. A. Pribisco,
¨
rstner,
1
T. M. Gilbert, R. L. Martin, G. J. Kubas and R. T. Baker, Angew.
Chem., Int. Ed., 2004, 43, 1955.
This journal is c The Royal Society of Chemistry 2012
Chem. Commun.