Stereoselective synthesis of 2-phosphino-1-zirconaindenes and related 2-phosphinophospholes and stiboles

Article abstract of DOI:10.1039/a606672k

2-Phosphinophospholes and stiboles are prepared from the reaction of benzynezirconocene with alkynylphosphines followed by addition either of dichlorophosphines or a dichlorostibene.

Full text of DOI:10.1039/a606672k

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Stereoselective synthesis of 2-phosphino-1-zirconaindenes and related
2-phosphinophospholes and stiboles
Y. Miquel,a A. Igau,a B. Donnadieu,a J.-P. Majoral,*a L. Dupuis,b N. Piriob and P. Meunier*b
a Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex, France
b Laboratoire de Synthe`se et d’Electrosynthe`se Organome´talliques associe´ au CNRS (UMR 5632), Universite´ de Bourgogne,
Faculte´ des Sciences Gabriel, 6 boulevard Gabriel, 21000 Dijon, France
2-Phosphinophospholes and stiboles are prepared from the
reaction of benzynezirconocene with alkynylphosphines
followed by addition either of dichlorophosphines or a
dichlorostibene.
of the 1-phenyl-3,4-dimethyl-2-thiophosphole followed by
addition of diphenylchlorophosphane.3
Treatment of the alkynylphosphine 1a with [ZrPh2(h-
C5H5)2] 2a in benzene at 80 °C for 6 h leads to the formation of
a phosphinozirconaindene 4a arising from insertion of the
carbon–carbon triple bond of 1a into a zirconium–carbon bond
of the transient benzyne zirconocene 3a. The reaction gave rise
to only one phosphorus species as indicated by 31P NMR
spectroscopy (4a, d 6.9) (Scheme 1). 4a was further charac-
terized by 1H and 13C NMR† but the spectroscopic data did not
distinguish between the two possible structures for 4a: the
2-phosphinozirconaindene form 4aA or the 3-phosphinozirco-
naindene form 4aB. In order to have a better knowledge of the
structure of 4a, exchange reactions with phenyl or tert-butyl
dichlorophosphanes were attempted. Addition of these di-
chlorophosphanes RPCl2 to a solution of 4a in thf afforded the
phosphinophosphol derivatives 5 (R = Ph) or 6 (R = But)
(Scheme 1). 31P NMR spectra exhibit as expected two doublets
[5, d 214 (PPh2), 10.6 (PPh); 6, d 212 (PPh2), 3.7 (PBut)] with
a large 2JPP of 50 Hz for 5 and 52 Hz for 6. Compounds 5 and
6 were fully characterized as their disulfide adducts 7 and 8 {7,
The development of new and practical methods of stereoselec-
tive synthesis of main-group element derivatives is currently
among the major objectives of a number of research groups
throughout the world. Our ongoing investigations concern the
study of interactions between group IV element and main-group
element species1 and are focused on the discovery of new
methodologies of ring formation, opening or expansion but also
on the preparation of ligands which have been regarded as
laborious to prepare by conventional means.
The present report deals with an efficient synthesis of
substituted zirconaindene compounds and their use as starting
reagents for the formation of a variety of 2-phosphinophos-
pholes and of a 2-phosphinostibole. Indeed phospholes2
continue to attract considerable attention because of their use in
different fields (e.g. catalysis, coordination chemistry) and
therefore there is a need to diversify ways of preparation of
these useful phosphorus heterocycles as well as the nature of
these derivatives. To the best of our knowledge only one report
described the preparation of a 2-thiophosphinophosphole which
was obtained via a sequence of reactions involving metallation
2
d(31P) 39.2 [P(S)Ph2], 51.4 [P(S)Ph], JPP 24.7 Hz; 8, d (31P)
38.9 [P(S)Ph2],† 78.6 [P(S)But], 2JPP 24.9 Hz}. Confirmation of
the identity of 8 was achieved by a single-crystal X-ray study‡
which shows that the 2- and not the 3-substituted thiophosphole
heat
[ZrPh2Cp2]
Cp2Zr
–PhH
2a, b
3a, b
Ph2P
R
1a, b
1a
R = H, b R = Ph
C(212)
2a, 3a Cp = η-C5H5
t
2b, 3b
Cp = η-C5H4Bu
C(216)
C(211)
C(4)
PPh2
R
R
C(226)
C(5)
C(3)
P(2)
Zr
Cp2
Zr
Cp2
PPh2
C(2)
C(1)
4a′′, b′′
4a′ Cp = η-C5H5, R = H
b′ Cp = η-C5H4But, R = Ph
C(221)
S(2)
C(6)
C(9)
C(222)
P(1)
S(1)
C(7)
H
H
S
S8
MCl2R
C(13)
4a′
C(10)
M
PPh2
P
PPh2
C(11)
S
C(12)
R
R
5, 6, 9
7, 8
Fig. 1 Molecular structure of 8 with crystallographic numbering scheme.
Selected bond lengths (Å) and angles (°): P(1)–C(1) 1.831(3), P(1)–C(9)
1.814(3), C(1)–C(2) 1.340(4), C(2)–C(3) 1.468(4), C(3)–C(9) 1.391(4),
P(2)–C(1) 1.804(3); C(1)–P(1)–C(9) 91.4(1), P(1)–C(1)–C(2) 109.2(2),
P(1)–C(1)–P(2) 130.7(2).
5, 7 M = P, R = Ph
6, 8 M = P, R = But
9 M = Sb, R = Ph
Scheme 1
Chem. Commun., 1997
279

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was formed. A molecule of 8 is shown in Fig. 1 and important
bond lengths and angles are summarized.
Therefore these results clearly demonstrate that the 2-phos-
phinozirconaindene form 4aA is selectively prepared when the
acetylenic phosphane 1a is treated with the benzynezirconocene
3a.
As a consequence the P–S bond length is found to be slightly
larger [2.005(1) Å] than those generally observed for thio-
phosphoryl groups (1.93–1.95 Å). Indeed, the P–S bond length
lies in between those of a single and a double P–S bond.
In conclusion, we have discovered a new and easy approach
to the synthesis of 2-phosphinophospholes and a related
2-phosphinostibole. The remarkable stereoselectivity in these
reactions arises from the strong interaction between the
phosphorus lone pair in 1a or 1b and zirconium in 3a or 3b.
Such an interaction has been already demonstrated to be the
driving force in many reactions involving phosphorus and
zirconium.6
A similar exchange reaction involving 4aA and phenyl-
dichlorostibene led to the formation of the corresponding
2-phosphinostibole 9 [d (31P) 22] (Scheme 1).
Remarkably such a stereoselective synthesis of 2-phosphino-
phospholes was also observed with more hindered acetylenic
phosphanes such as 1b and more hindered diphenylzircono-
cenes such as [ZrPh2(h-C5H4But)2] 2b.
Indeed treatment of 1b with 2b affords exclusively the
complex 4bA [d (31P) 227.1]. Addition of S8 to 4bA led to the
corresponding sulfide 10 [d (31P) 34.3]† (Scheme 2). Successful
X-ray diffraction analysis of a single crystal of 10‡ shows
several interesting features (Fig. 2). First, it corroborates that,
here also, the insertion reaction of the benzynezirconocene 3b
into the carbon–carbon triple bond of 1b is stereoselective and
leads to an a-substituted zirconaindene. Secondly the structure
reveals an interaction between zirconium and sulfur. The Zr–S
distance is 2.797(1) Å, and compares well, for example, with the
Zr–S bond lengths found in compounds with a chelating
dithiocarbamate ligand such as [ZrCl(S2CNEt2)(h-C5H5)2] [Zr–
S 2.635(2), 2.723(2) Å].4,5
Footnotes
† Satisfactory analytical and/or spectral data were obtained for all new
compounds. Selected spectroscopic data for compounds 8 and 10. For 8:
DCIMS, m/z 439 ([M + 1]+, 100%). NMR: dH (C6D6) 1.06 [d, 3J(HP) 18.2
Hz, 9 H, CH3], 6.80–7.14 (m, 8 H, CHPh), 7.45 (m, 1 H, CHPh), 7.80 [dd,
3
2J(HP) 35.5, J(HP) 17.6 Hz, 1 H, CH], 8.18, 8.24, 8.50, 8.58 (m, 1 H,
CHPh); dC 136.1 [dd, 1J(CP) 27.5, 1J(CP) 66.3 Hz, PCP], 138.1 [dd, 1J(CP)
78.9, 3J(CP) 3.2 Hz, CPBut], 140.9 [dd, J(CP) 17.2, J(CP) 22.0 Hz,
CCPBut], 157.1 [dd, 2J(CP) 10.2, 2J(CP) 6.2 Hz, CH].
For 10: DCIMS, m/z 727 ([M + 1]+, 100%). NMR: dH (C6D6) 1.14 (s, 18
H, C5H4But), 5.75 (m, 4 H, C5H4But), 5.87, 6.16 (2 pseudo q, 4 H,
C5H4But), 6.68 (m, 1 H, CHAr), 6.86–6.90 (m, 3 H, CHAr), 6.96–6.99 (m,
1 H, CHAr), 7.04–7.07 (m, 2 H, CHAr), 7.13–7.16 (m, 1 H, CHAr), 7.26–7.30
(m, 4 H, CHAr), 7.36–7.41 (m, 6 H, CHAr), 7.45–7.46 (m, 1 H, CHAr); dC
154.7 [d, 2J(CP) 6.3 Hz, ZrCNCPh], 154.8 [d, 1J(CP) 33.3 Hz, ZrCP], 170.5
[d, 3J(CP) 5.5 Hz, ZrCNC], 194.2 [d, 3J(CP) 6.5 Hz, ZrC].
Ph
S8
‡ Crystal data recorded on an IPDS STOE diffractometer using a f rotation
4b′
scan, Mo-Ka radiation was used (l
=
0.71073 Å). For 8:
Zr
PPh2
C
24H24P2S2·0.5C6H6, crystal dimensions 0.50 3 0.37 3 0.25 mm,
(η-C5H4But)2
S
monoclinic, space group I2/a, a = 19.156(4), b = 10.131(2), c = 28.391(6)
Å, b = 109.50(2)°, U = 5193.8 Å3; Dc = 1.22 g cm23, m = 3.29 cm21
,
10
number of reflections collected 16191, number of independent reflections
4100 (Rm = 0.049), R = 0.0429, Rw = 0.0445, GOF = 1.04.
Scheme 2
For 10: C44H35PSZr, crystal dimensions 0.60 3 0.50 3 0.50 mm,
monoclinic,spacegroupP21/c,a = 12.247(2),b = 19.746(4),c = 15.970(1)Å,
b
m
=
=
106.41(1)°,
U
=
3704.8 Å3; Dc
=
1.31
g
cm23
,
C(72)
4.16 cm21, number of reflections collected 23271, number of
C(70)
independent reflections 4163 (Rm = 0.047), R = 0.0314, Rw = 0.0364,
GOF = 0.8.
C(73)
C(15)
Atomic coordinates, bond lengths and angles, and thermal parameters
have been deposited at the Cambridge Crystallographic Data Centre
(CCDC). See Information for Authors, Issue No. 1. Any request to the
CCDC for this material should quote the full literature citation and the
reference number 182/340.
C(71)
C(16)
C(8)
C(6)
C(7)
C(126)
C(116)
C(9)
C(14)
C(17)
C(121)
C(122)
C(10)
C(13)
C(18)
References
C(12)
C(11)
Zr
1 See for example: J.-P. Majoral, M. Zablocka and A. Igau, Chem. Ber.,
1996, 129, 879 and references therein; A. Mahieu, A. Igau, J. Jaud and
J.-P. Majoral, Organometallics, 1995, 14, 944.
C(123)
C(111)
C(113)
S
C(1)
P
C(2)
C(112)
2 For a review see: F. Mathey, Chem. Rev., 1988, 88, 429; A. N. Hughes,
Handbook of Organophosphorus Chemistry, Marcel Dekker, New York,
1992, p. 483.
3 B. Deschamps and F. Mathey, Organometallics, 1992, 11, 1411.
4 S. L. Buchwald, R. B. Nielsen and J. C. Dervan, J. Am. Chem. Soc., 1987,
109, 1590.
C(5)
C(221)
C(31)
C(30)
C(3)
C(4)
C(226)
C(222)
5 The covalent Zr–S bond length was found to be 2.514(2) Å in a
germazirconaheterocycle: J. Bodiguel, P. Meunier, M. M. Kubicki,
P. Richard and B. Gautheron, Organometallics, 1992, 11, 1423.
6 M. Zablocka, A. Igau, N. Ce´nac, B. Donnadieu, F. Dahan, J.-P. Majoral
and K. M. Pietrusiewicz, J. Am. Chem. Soc., 1995, 117, 8083; N. Ce´nac,
M. Zablocka, A. Igau, J.-P. Majoral and A. Skowronska, Organome-
tallics, 1996, 15, 1208; N. Ce´nac, M. Zablocka, A. Igau, J.-P. Majoral and
A. Skowronska, J. Org. Chem., 1996, 61, 796.
C(33)
C(32)
Fig. 2 Molecular structure of 10 with crystallographic numbering scheme.
Selected bond lengths (Å) and angles (°): P–S 2.005(1), P–C(1) 1.749(3),
S–Zr 2.797(1), Zr–C(1) 2.490(4), Zr–C(8) 2.580(3), C(8)–C(3) 1.391(4),
C(3)–C(2) 1.406(5), C(1)–C(2) 1.389(6), Zr–C(1)–P 106.4(2), Zr–S–P
85.4(4).
Received, 30th September 1996; Com. 6/06672K
280
Chem. Commun., 1997