The synthesis and complexation of a bis(phosphavinyl)tin compound

Article abstract of DOI:10.1039/b006407f

The first bis(phosphavinyl)tin and stannadiphosphabicyclo[2.1.0]pentane compounds, readily prepared from the reaction of a phosphavinyl Grignard reagent with SnMe2Cl2, have been used as ligands in the formation of two crystallographically characterised complexes. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b006407f

View Article Online / Journal Homepage / Table of Contents for this issue
The synthesis and complexation of a bis(phosphavinyl)tin
compound
Cameron Jones* and Anne F. Richards
Department of Chemistry, University of Wales, Cardiff, PO Box 912, Park Place, Cardiff,
UK CF10 3TB. E-mail: jonesca6@cardiff.ac.uk
Received 4th August 2000, Accepted 23rd August 2000
First published as an Advance Article on the web 8th September 2000
The first bis(phosphavinyl)tin and stannadiphospha-
bicyclo[2.1.0]pentane compounds, readily prepared from
the reaction of a phosphavinyl Grignard reagent with
SnMe2Cl2, have been used as ligands in the formation of
two crystallographically characterised complexes.
Main group vinyl complexes have been widely utilised as
reagents in both organic and organometallic synthesis.1 It
might be expected that main group phosphavinyl complexes, i.e.
[M{–C(R)᎐P(R)} ] 1, M = main group element, would have a
᎐
similar range ofn uses in organophosphorus and phospha-
organometallic synthesis, especially considering the close
analogy between phosphorus and the valence isoelectronic CR
fragment.2 We have recently reported the regio- and stereo-
selective syntheses of a range of substituted phosphavinyl
Grignard reagents, e.g. [Z-Mg(Cl){–C(But)᎐PCy}] 2 Cy =
᎐
cyclohexyl,3 which we saw as potential transfer reagents in the
synthesis of compounds of the type 1. In particular we are
interested in the preparation of phosphavinyl tin complexes
given the wide applicability of vinyl tin compounds to a number
of organic transformations which include the Stille reaction.4
To date there is only one example of a related phosphaalkenyl
tin complex, [Sn(NMe ){N(SiMe ) } {C(SiMe )᎐P(NR )}],
᎐
3
2
3
2
NR2 = 2,2,6,6-tetramethylpiperidino,5 2though the trans2ient
species, [SnR {–C(R)᎐PH}], R = alkyl or aryl, have been impli-
᎐
cated as inte3rmediates in the formation of several phospha-
organo-tin compounds.6 Herein, we report the outcome of the
reaction of 2 with SnMe2Cl2 which has afforded the first
examples of both a bis(phosphavinyl)tin compound and a
stannadiphosphabicyclo[2.1.0]pentane, the latter of which is
formed via an unexpected phosphavinyl coupling reaction.
Reaction of SnMe2Cl2 with two equivalents of 2 in diethyl
ether yields an oily mixture of products after stirring overnight.
A 31P NMR analysis of this mixture suggested that it was com-
prised of two major components which could not be separated
using standard techniques. Consequently, the mixture was
treated with an excess of [W(CO)5(THF)] in THF and the reac-
tion products chromatographed. Two partially overlapping
bands were collected from the column and recrystallised from
diethyl ether to afford orange crystals of 3 and yellow crystals
of 4 in low to moderate yields (Scheme 1). Both compounds are
thermally robust and can be handled in air indefinitely.
Scheme 1 Reagents and conditions: i, 1/2 SnMe2Cl2; ii, W(CO)5-
(THF).
that the two major products in the mixture are the bis(phos-
phavinyl)tin compound, 5 (δ 299), and the heterobicycle, 6
1
(δ 42, JPSn 194 Hz; δ Ϫ106). It could not be determined if 5
exists as the Z,Z- or E,E-isomer, both of which would give a
singlet in their 31P NMR spectra, though the Z,Z-form is the
more likely. In addition, we have not been able to elucidate
the mechanism of formation of 6 but it seems probable that this
involves one of the isomeric forms of 5 which undergoes a
phosphavinyl coupling reaction and subsequent rearrangement.
The molecular structures of 3 and 4 (Fig. 1 and 2)‡ are
consistent with their solution spectroscopic data and in the case
of 3 a novel mixed bonding mode exists in which the bis(phos-
phavinyl)tin ligand is coordinated to a W(CO)4 fragment in an
η1-fashion through P(1) and an η2-fashion through the P(2)–
C(14) double bond. As a result of the side-on coordination this
bond is considerably lengthened [1.754(5) Å] relative to normal
localised P–C double bonds, e.g. P(1)–C(3) [1.666(5) Å]. It is,
however, evident that the bis(phosphavinyl)tin ligand in 3 exists
as its E,Z-isomer and therefore 5 has undergone an isomeris-
ation upon coordination to the W(CO)4 fragment. This
isomerisation has precedent in metallophosphaalkene chem-
istry7 and is not surprising given the weakness of the
The most informative spectroscopic data come from their
31P{1H} NMR spectra† which for the major product, 3, shows
a two line pattern with the low field signal (δ 253.9) occurring in
the normal region for localised phosphaalkenyl fragments.7
This signal possesses 183W satellites with a coupling of 232 Hz
that is indicative of a one bond P–W interaction. The high field
signal (δ 77.6) is in the expected region for η2-coordinated
phosphaalkenyl moieties.7 The minor product, 4, also displays a
two line pattern in its 31P{1H} NMR spectrum, the low field
signal (δ 29.5) of which is clearly associated with the tungsten
coordinated phosphorus atom as it possesses both 117,119Sn and
183W satellites.
π-component of the P᎐C bond. The X-ray crystal structure of 4
᎐
is of low accuracy but does show it to possess a strained
stannadiphosphabicyclo[2.1.0]pentane core with all bond
lengths normal for single bonded interactions. From the angles
From an examination of the 31P NMR spectrum of the reac-
tion mixture prior to treatment with [W(CO)5(THF)] it is clear
DOI: 10.1039/b006407f
J. Chem. Soc., Dalton Trans., 2000, 3233–3234
This journal is © The Royal Society of Chemistry 2000
3233

View Article Online
elucidate the mechanism of formation of 6 and the use
of phosphavinyl tin compounds in Stille reactions will form
the basis of a forthcoming publication.
Acknowledgements
We gratefully acknowledge support from the EPSRC (student-
ship for A. F. R.).
Notes and references
† Synthesis and spectroscopic data for 3 and 4: A solution of 2 (0.50 g,
2.05 mmol) in Et2O (25 ml) was added to SnMe2Cl2 (0.24 g, 1.08 mmol)
in Et2O (25 ml) at Ϫ50 ЊC. The resulting solution was warmed slowly to
room temperature, stirred overnight and volatiles removed in vacuo to
yield a yellow oil which consisted of several inseparable phosphorus-
containing products (see text). The oil was dissolved in THF (5 ml) and
added to a solution of [W(CO)5(THF)] (1.9 mmol) in THF (50 ml).
After 18 h volatiles were removed in vacuo and the residue chrom-
atographed (Kieselgel, Et2O–hexane 50:50) and partially overlapping
yellow and orange fractions collected. These were concentrated in vacuo
to yield orange crystals of 3 (yield 42% approx., mp 123–126 ЊC on
single crystal) and yellow crystals of 4 (yield 18% approx., mp 163–
168 ЊC dec. on single crystal). Data for 3: 31P{1H} NMR (145.8 MHz,
C6D6) δ 77.6 (s, P(2)), 253.9 (s, P(1), 1JPW 232 Hz); 1H NMR (400 MHz,
C6D6) δ 0.48 (s, 3H, SnMe), 0.69 (s, 3H, SnMe), 0.95 (s, 9H, But), 1.22
(s, 9H, But) 0.71–2.12 (m, 22H, Cy); APCI-MS: m/z 783 (Mϩ Ϫ CO,
100%), 516 (Mϩ Ϫ W(CO)4, 73%); IR (Nujol, ν/cmϪ1) 2027 m, 1951 s,
1939 s; Data for 4: 31P{1H} NMR (145.8 MHz, C6D6) δ Ϫ108.7 (s, P(2)),
Fig. 1 Molecular structure of 3. Selected bond lengths (Å) and
angles (Њ): P(1)–C(3) 1.666(5), P(2)–C(14) 1.754(5), P(1)–W(1) 2.501(2),
P(2)–W(1) 2.6384(17), C(14)–W(1) 2.481(6); Sn(1)–C(3)–P(1) 108.7(3),
Sn(1)–C(14)–P(2) 120.0(3), C(3)–P(1)–W(1) 123.1(2), C(14)–W(1)–P(2)
39.91(12).
1
1
29.5 (s, P(1) JSnP 190, JPW 226 Hz); 1H NMR (400 MHz, C6D6)
δ 0.74 (s, 3H, SnMe), 0.82 (s, 3H, SnMe), 0.91 (s, 9H, But), 1.24 (s, 9H,
But), 0.76–1.95 (m, 22H, Cy); APCI-MS: m/z 516 (Mϩ Ϫ W(CO)5,
100%), 366 (P2Cy2C2But2, 44%); IR (Nujol, ν/cmϪ1) 2035 m, 1980 s,
1928 m; reproducible microanalyses proved difficult to obtain due to
the partial co-crystallisation of 3 and 4.
‡ Crystal data for 3: C28H46O4P2SnW, M = 811.13 triclinic, space group
¯
P1, a = 10.759(9), b = 11.445(8), c = 16.379(6) Å, α = 103.38(5), β =
98.22(5), γ = 112.86(7)Њ; V = 1746(2) Å3, Z = 2, Dc = 1.543 g cmϪ3
,
F(000) = 800, µ(Mo-Kα) = 41.25 cmϪ1, 150(2) K, 6261 unique reflec-
tions, R (on F) 0.0342, wR (on F2) 0.0919 (I > 2σI). 4: C29H46O5P2SnW,
M = 839.14, monoclinic, space group C2/c, a = 35.7212(10), b =
10.3448(12), c = 20.0542(15) Å, β = 90.239(11)Њ; V = 7410.5(10) Å3,
Z = 8, Dc = 1.504 g cmϪ3, F(000) = 3312, µ(Mo-Kα) = 38.92 cmϪ1
,
293(2) K, 4436 unique reflections, R (on F) 0.0997, wR (on F 2) 0.2474
(I > 2σI). All crystallographic measurements were made using an
Enraf-Nonius CAD4 diffractometer. The structure was solved by direct
methods and refined on F 2 by full matrix least squares (SHELX 97)8
using all unique data. All non-hydrogen atoms are anisotropic with H-
atoms included in calculated positions (riding model). Empirical
absorption corrections were carried out by the DIFABS method.9
CCDC reference number 186/2154.
Fig. 2 Molecular structure of 4. Selected bond lengths (Å) and
angles (Њ): Sn(1)–P(1) 2.506(6), Sn(1)–C(2) 2.17(2), P(1)–C(1) 1.90(2),
P(2)–C(1) 1.91(2), P(2)–C(2) 1.89(2); Sn(1)–P(1)–C(1) 81.4(6), P(1)–
Sn(1)–C(2) 73.9(5), P(1)–C(1)–C(2) 105.5(13), Sn(1)–C(2)–C(1)
98.6(12), C(1)–P(2)–C(2) 51.2(9).
1 Comprehensive Organometallic Chemistry II, ed. E. W. Abel, F. G. A.
Stone and G. Wilkinson, Pergamon, Oxford, 1995, vol. 11.
2 K. B. Dillon, F. Mathey and J. F. Nixon, in Phosphorus: The Carbon
Copy, Wiley, Chichester, 1998.
3 D. E. Hibbs, C. Jones and A. F. Richards, J. Chem. Soc., Dalton
Trans., 1999, 3531.
within the four membered ring it is safe to assume there is a
high degree of p-character to the bonding within the ring,
which would explain why no two-bond PP or SnP couplings are
observed in the 31P{1H} NMR spectrum of 4.
In related work we have investigated the reaction of 2 with
SnCl2 or SnCl4 in an attempt to form homoleptic phosphavinyl
tin compounds. Interestingly, however, both reactions lead to
an oxidative coupling of the phosphavinyl fragment and form-
ation of the highly strained 2,4-diphosphabicyclo[1.1.0]butane,
P2(Cy)2C2(But)2. The results of this study, our efforts to
4 J. Tsuji, Palladium Reagents and Catalysts, Wiley, Chichester, 1997,
ch. 4.
5 V. D. Romanenko, A. O. Gudima, A. N. Chernega and G. Bertrand,
Inorg. Chem., 1992, 31, 3493.
6 M. Schmitz, R. Göller, U. Bergsträsser, S. Leininger and M. Regitz,
Eur. J. Inorg. Chem., 1998, 227.
7 L. Weber, Angew. Chem., Int. Ed. Engl., 1996, 35, 271 and refs
therein.
8 G. M. Sheldrick, SHELX-97, University of Göttingen, 1997.
9 Z. Otwinowski and W. Minor, in Methods in Enzymology, ed. C. W.
Carter and R. M. Sweet, Academic Press, New York, 1996.
3234
J. Chem. Soc., Dalton Trans., 2000, 3233–3234