Germylene and stannylene cleavage of Lawesson's reagent

Article abstract of DOI:10.1039/a706097a

Lawesson's reagent undergoes cleavage reactions with bis[bis(trimethylsilyl)amino]germanium(II) and bis[bis(trimethylsilyl)amino]tin(II) whilst with 1,3-di-tert-butyl-1,3,2-diazagermol-2-ylidene the product is a novel spirocyclic germanium derivative.

Full text of DOI:10.1039/a706097a

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Germylene and stannylene cleavage of Lawesson’s reagent
Claire J. Carmalt, Jason A. C. Clyburne, Alan H. Cowley,* Viviana Lomeli and Brian G. McBurnett
Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas, 78712, USA
Lawesson’s reagent undergoes cleavage reactions with
bis[bis(trimethylsilyl)amino]germanium(II) and bis[bis(tri-
methylsilyl)amino]tin(II) whilst with 1,3-di-tert-butyl-
1,3,2-diazagermol-2-ylidene the product is a novel spir-
ocyclic germanium derivative.
distance [2.1125(9) Å] is longer than that of the external P–S
bond [1.9315(9) Å]. Although the phosphorus and tin centres
are four-coordinate, there is considerable deviation of the bond
angles from the ideal tetrahedral value and the N–Sn–N angle in
3b [116.07(7)°] is larger than that in 2b [104.7(2)°].5
Lawesson’s reagent 1 is one of the most versatile thiation
reagents available and is highly effective, for example, for the
conversion of aldehydes and ketones to the corresponding thio
derivatives.1 However, much less information is available
regarding the interaction of 1 with transition metal2 or main
group reagents. Herein we describe the unusual reactions of 1
with some coordinatively unsaturated group 14 compounds.
2 Ar′PS2
4
1
Ar′ = C6H4OMe-p
Ar′PS + Ar′PS3
5
6
The mechanism of formation of 3a,b is not clear, but
plausible routes to these products include (i) oxidative addition
of 2a,b to 4, which results from symmetrical cleavage of 1,
followed by addition of sulfur to phosphorus, (ii) addition of
2a,b to an ArAPS3 (6) fragment resulting from unsymmetrical
cleavage of 1, and (iii) addition of sulfur to 2a,b followed by
reaction of the resulting germa- or stanna-thione with 4. In an
attempt to clarify this point, 7,6 which can be viewed as a cyclic
dimer of the requisite stanna-thione 8, was treated with an
equimolar quantity of 1 in CD2Cl2 or C6D6 solution at 25 °C.
SiMe3
SiMe3
Me3Si
Me3Si
N
M
N
Me3Si
Me3Si
N
S
S
S
1
M
P
N
SiMe3
SiMe3
OMe
2a M = Ge
b M = Sn
3a M = Ge
b M = Sn
NMR (31P and H) assay indicated quantitative conversion to
1
The reaction of 1 with stannylene 2b3 in THF solution
resulted in a > 90% isolated yield of 4b.† Interestingly, the
corresponding reaction of 1 with 2a3 produced a much smaller
yield (ca. 10%) of the Ge analogue 3a. 31P NMR and
HRMS(CI+) data were consistent with the formulae proposed
above for both compounds, and 1H and 13C NMR spectra
indicated the presence of one p-MeOC6H4 and two (non-
equivalent) N(SiMe3)2 groups.‡ However, in order to ascertain
the atom connectivity, it was necessary to appeal to X-ray
crystallography. Suitable single crystals of 3b were obtained
from CH2Cl2 solution. The central feature of the molecular
structure of 3b§ (Fig. 1) comprises a planar PS2Sn ring [sum of
angles = 360.00(3)°]. Such rings are rare as indicated by a
search of the Cambridge Data Base which revealed only one
previous example.4 As expected, the average P–Sring bond
3b. This observation is consistent with route (iii), and as such
would represent a novel formal [2 + 2] cycloaddition involving
PNS and SnNS bonds.7
SiMe3
SiMe3
SiMe3
Me3Si
Me3Si
N
N
SiMe3
Me3Si
Me3Si
N
S
S
[2+2]
2
3b
Sn
Sn
Sn
N
S
2
N
N
SiMe3
SiMe3
SiMe3
SiMe3
7
8
In sharp contrast to the results obtained with 2a, the cyclic
germylene 98 undergoes a completely different type of reaction
with 1 and affords 10 as the major product. Whilst not
appropriate as a mechanism, one way of thinking of this reaction
is to consider that the cyclic germylene 9 serves as a source of
Ge atoms for transfer to four ArAPS (5) moieties. As pointed out
above, 5 could arise via unsymmetrical cleavage of 1.
O(1)
Si(1)
OMe
MeO
Si(2)
C(1)
N(1)
S(3)
Sn
But
N
P
S(2)
N(2)
P
P
S
S
S
S
P
P
1
Ge
S(1)
Si(3)
Si(4)
Ge
N
But
Fig. 1 Molecular structure of 3b showing the atom numbering scheme.
Selected distances (Å) and angles (°): P–C(1) 1.804(2), P–S(1) 1.9315(9),
P–S(2) 2.1168(9), P–S(3) 2.1018(9), Sn–S(2) 2.4188(6), Sn–S(3)
2.4358(6), N(1)–Sn 2.015(2), N(2)–Sn 2.023(2), N–Si(1) 1.764(2), N–Si(2)
1.757(2), N(2)–Si(3) 1.757(2), N(2)–Si(4) 1.761(2); C(1)–P–S(1)
112.05(8), S(2)–P–S(3) 101.32(3), P–S(2)–Sn 87.17(3), P–S(3)–Sn
87.06(3), N(1)–Sn–N(2) 116.07(7), Sn–N(1)–Si(1) 122.83(10), Sn–
N(1)–Si(2) 115.15(9), Sn–N(2)–Si(3) 116.33(9), Sn–N(2)–Si(4)
120.37(10), Si(1)–N(1)–Si(2) 120.73(10), Si(3)–N(2)–Si(4) 121.35(10).
MeO
OMe
9
10
The X-ray crystal structure of 10 revealed an interesting
spirocyclic geometry (Fig. 2). Individual molecules of 10 reside
on a crystallographic twofold axis. The GeS2P2 rings are
slightly puckered and the dihedral angle between the S–Ge–S
planes is 81.7°. The geometry at Ge is essentially tetrahedral;
Chem. Commun., 1998
243

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yield based on 1), mp 200 °C (becomes opaque at 170 °C). HRMS:
calculated for C28H28GeO4P4S4 (M+), 754.9111; found 754.9125.
P(2A)
P(1A)
‡ Selected spectroscopic data: 3a: NMR (C6D6): 31P{1H} d 42.0; 1H d
8.02–8.08 (m, 2 H, aryl), 6.80–6.82 (m, 2 H, aryl), 8.85 (s, 3 H, OCH3), 0.47
[s, 18 H, Si(CH3)3], 0.34 [s, 18 H, Si(CH3)3]; 13C d 162.6 (s, p-Caryl), 132.2
(d, 3JPC 14 Hz, m-Caryl), 114.3 (d, 2JPC 16 Hz, o-Caryl), 54.9 (s, OCH3), 6.5
(s, SiCH3), 5.5 (s, SiCH3), ipso-Caryl not observed. HRMS (CI+): calc. for
S(2A)
S(1A)
Ge
C
19H43GeN2OPS3Si4 (M+), m/z 597.0826; found 597.0825.
S(2)
S(1)
3b: NMR (C6D6): 31P{1H} d 56.5, satellites due to coupling with 119Sn
observed (75 Hz); 119Sn{1H} d 2240 (d, 2JPSn 76 Hz); 1H d 8.17–8.26 (m,
2 H, aryl), 7.02–7.06 (m, 2 H, aryl), 3.91 (s, 3 H, OCH3), 0.49 [s, 18 H,
Si(CH3)3], 0.31 [s, 18 H, Si(CH3)3]; 13C d 161.6 (s, p-Caryl), 137.0 (d, 1JPC
94 Hz, ipso-Caryl), 132.2 (d, JPC 15 Hz, m-Caryl), 113.7 (d, JPC 17 Hz,
o-Caryl), 54.9 (s, OCH3), 6.2 (s, SiCH3), 5.7 (s, SiCH3). HRMS (CI+): calc.
for C19H43N2OPS3Si4Sn (M+), m/z 674.0374; found 674.0361.
P(2)
P(1)
3
2
Fig. 2 Molecular structure of 10 showing the atom numbering scheme.
Selected distances (Å) and angles (°): Ge–S(1) 2.222(1), Ge–S(2) 2.223(1),
P(1)–S(1) 2.103(2), P(2)–S(2) 2.098(2), P(1)–P(2) 2.220(2); S(1)–Ge–S(2)
105.89(4), P(1)–S(1)–Ge 104.69(5), S(1)–P(1)–P(2) 104.46(6), S(2)–P(2)–
P(1) 103.50(6), P(2)–S(2)–Ge 105.07(5).
10 NMR (C6D6): 31P{1H} d 45.6; 1H d 7.47–7.50 (m, 2 H, aryl),
6.92–6.95 (m, 2 H, aryl), 3.79 (s, 3 H, OCH3), 0.49 [s, 18 H, Si(CH3)3], 0.31
[s, 18 H, Si(CH3)3]; 13C d 161.6 (s, p-Caryl), 133.4 (d, 3JPC 15 Hz, m-Caryl),
114.6 (d, 2JPC 17 Hz, o-Caryl), 54.0 (s, OCH3), ipso-Caryl not observed.
§ Crystal data: 3b: C19H43N2OPS3Si4Sn, M = 673.75, monoclinic, space
group I2/a,
a
=
27.250(2),
=
b
=
11.542(1),
c
=
=
20.522(1) Å,
b
=
98.200(4)°, U
6388.6(8) Å3, Z
=
8, Dc
1.401 g cm23
,
however, the endocyclic S–Ge–S angles [105.89(4)°] are more
acute than the exocyclic angles [117.10(6)°]. The average Ge–S
[2.222(1) Å], P–S [2.100(2) Å] and P–P [2.220(2) Å] distances
each correspond to a bond order of unity. Finally, the R2P2S2
ligand does not appear to have been described previously;
although a phosphorus–sulfur heterocycle is known9 in which
the Ph2P2S2 ligand is associated with a PhP(S) moiety, i.e.
(PhPS)3.
F(000) = 2784, T = 183(2) K. 7313 independent reflections were collected
on a Siemens P4 diffractometer using graphite-monochromated Mo-Ka
radiation (l = 0.71073 Å, 2.01° < q < 27.50°, m = 4.35 cm21); an
absorption correction was applied: wR2
reflections with I > 2s(I).
= 0.0578, R = 0.0261 for
10: C28H28GeO4P4S4, M = 753.21, monoclinic, space group C2/c, a
24.248(6), b 7.931(1), c 20.152(5) Å, b 122.34(1)°,
=
=
=
=
U = 3274.5(1) Å3, Z = 4, Dc = 1.528 g cm23, F(000) = 1536, T = 293(2)
K. 3721 independent reflections were collected on an Enraf Nonius CAD4
diffractometer using graphite-monochromated Mo-Ka radiation
(l = 0.71073 Å, 2.39° < q < 27.50°, m = 14.19 cm21); an absorption
correction was applied: wR2 = 0.1243, R = 0.0499 for reflections with I >
2s(I). CCDC 182/691.
We thank the National Science Foundation, and the Robert A.
Welch Foundation for financial support.
Footnotes and References
* E-mail: cowley@mail.utexas.edu
1 For a review, see: M. P. Cava and M. I. Levinson, Tetrahedron, 1985, 41,
5061.
2 R. Jones, D. J. Williams, P. T. Wood and J. D. Woollins, Polyhedron,
1987, 6, 539; G. A. Zank and T. B. Rauchfuss, Organometallics, 1984, 3,
1191.
3 M. J. S. Gynane, D. H. Harris, M. F. Lappert, P. P. Power, P. Rivie`re and
M. Rivie`re-Baudet, J. Chem. Soc., Dalton Trans., 1977, 2004.
4 J. L. Lefferts, K. C. Molloy, M. B. Hossain, D. van der Helm and
J. J. Zuckerman, Inorg. Chem., 1982, 21, 1410.
5 T. Fjeldberg, H. Hope, M. F. Lappert, P. P. Power and A. J. Thorne,
J. Chem. Soc., Chem. Commun., 1983, 639.
6 P. B. Hitchcock, E. Jang and M. F. Lappert, J. Chem. Soc., Dalton Trans.,
1995, 3179.
7 [2 + 2] reactions have also been suggested for a ferrocenyl analogue of
Lawesson’s reagent: M. R. StJ. Foreman, A. M. Z. Slawin and
J. D. Woollins, Chem. Commun., 1997, 1269.
8 W. A. Herrmann, M. Denk, J. Behm, W. Scherer, F. R. Klingan, H. Bock,
B. Soluki and M. Wagner, Angew. Chem., Int. Ed. Engl., 1992, 31,
1485.
9 C. Lensch, W. Clegg and G. M. Sheldrick, J. Chem. Soc., Dalton Trans.,
1984, 723.
† Experimental procedure: 3a: compound 2a (0.81 g, 2.1 mmol) in 50 cm3
of THF was added to a stirred slurry of 1 (0.80 g, 2.0 mmol) in 10 cm3 of
THF. The solution was warmed to 60 °C for 20 min. The solvent was
removed in vacuo and the resulting yellow residue was dissolved in 30 cm3
of CH2Cl2. After filtration through Celite the filtrate was concentrated and
stored at 225 °C to afford a small quantity of yellow powder 3a (0.09 g,
0.15 mmol, 8%), mp 132–136 °C.
3b: compound 2b (1.25 g, 2.8 mmol) in 50 cm3 of THF was added to a
stirred slurry of 1 (1.15 g, 2.8 mmol) in 10 cm3 of THF. The solution was
warmed to 60 °C for 20 min. The solvent was removed in vacuo and the
resulting pale yellow powder was dissolved in 30 cm3 of CH2Cl2. After
filtration through Celite the filtrate was concentrated and stored at 225 °C
to afford pale yellow crystals of 3b (0.90 g, 1.3 mmol, 92% yield based on
1), mp 140–143 °C.
10: compound 9 (0.67 g, 2.80 mmol) was dissolved in 30 cm3 of toluene
and added to a stirred suspension of 1 (0.78 g, 1.94 mmol) in 40 cm3 of
toluene at 25 °C. Over a 20 min period, the originally yellowish solution
turned red as the solids dissolved. After 4 h a precipitate formed and the
reaction mixture was allowed to stir for an additional 12 h. After filtration,
the solvent and volatiles were removed from the filtrate and the residue was
dissolved in CH2Cl2 and this solution was covered with a layer of hexane.
Colourless crystals of 10 formed over a period of several days (0.15 g, 20%
Received in Bloomington, IN, USA, 19th August 1997; 7/06097A
244
Chem. Commun., 1998