Versatile routes to selenoether functionalised tertiary phosphines

Article abstract of DOI:10.1039/c0dt00004c

New selenoether functionalised tertiary phosphines, based on aryl (2a, 2b) or alkyl (4) backbones, have been synthesised and characterised. P,Se-chelation has been achieved upon complexation to square-planar Pt^II (3a) or Pd^II (3b) me

Full text of DOI:10.1039/c0dt00004c

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www.rsc.org/dalton | Dalton Transactions
Versatile routes to selenoether functionalised tertiary phosphines†
Tom J. Cunningham, Mark R. J. Elsegood, Paul F. Kelly, Martin B. Smith* and Paul M. Staniland
Received 18th February 2010, Accepted 9th April 2010
First published as an Advance Article on the web 19th April 2010
DOI: 10.1039/c0dt00004c
New selenoether functionalised tertiary phosphines, based on
aryl (2a, 2b) or alkyl (4) backbones, have been synthesised
and characterised. P,Se-chelation has been achieved upon
complexation to square-planar PtII (3a) or PdII (3b) metal
centres. For 3a and 3b, weak non-covalent M ◊ ◊ ◊ Se contacts
were established using single crystal X-ray crystallography.
Tertiary phosphines continue to remain an integral tool in the
design and synthesis of new metal based complexes. Hybrid
tertiary phosphines, bearing additional donor atoms such as
oxygen, have frequently been described as hemilabile by virtue
of the soft/hard donor atom combination.1 Considerable re-
cent interest has focused on mixed P,O- and P,S-ligands for
their fascinating coordination chemistry,2 including water-soluble
macrocyclic complexes using a weak-link approach,3 and catalytic
applications.4 Tertiary phosphines with an additional selenium
Scheme 1 Preparative routes to 1a–3b.
donor centre have been very poorly developed in comparison
to their lighter Group 16 counterparts.5 In contrast, numerous
spectroscopy of 2a and 2b showed single phosphorus resonances at
6
d(P) -10.0 [3J(PSe) 139 Hz] and d(P) -34.6 ppm [3J(PSe) 201 Hz]
=
tertiary phosphine selenides (R3P Se) have been documented
and there has been much recent interest in phosphorus-selenium
chemistry e.g. Woollins’ reagent.7
respectively.
Crystals of 2b, suitable for X-ray crystallography, were grown
by vapour diffusion of Et2O into a CDCl3 solution.‡ The
molecular structure (Fig. 1) of 2b revealed crystallisation of
a single enantiomer and confirmed the ortho arrangement of
the bulky chiral phosphaadamantyl cage and selenoether group.
Metric parameters are broadly as anticipated and the transannular
We,8 and others9 have been interested in exploiting the
favourable stereoelectronic, solubility and crystalline properties
of the 6-phospha-2,4,8-trioxa-1,3,5,7-tetramethyladamantyl cage
group in the synthesis of new phosphine ligands. Herein we
describe the synthesis of a new, air-stable, selenoether phosphine
containing this diamondoid group, along with two further sele-
noether phosphines and their square-planar dichloropalladium
and platinum(II) complexes.
˚
P(1) ◊ ◊ ◊ Se(1) separation [3.230 A] suggests cis-co-ordination to
metal centres should be feasible. To the best of our knowledge we
believe this structure determination represents the first example of
a functionalised selenoether tertiary phosphine.
The synthetic procedure to the new selenoether modified
phosphines 2a and 2b was achieved using standard methodology
(Scheme 1). Following a known procedure for accessing bro-
mophosphine 1a,10 reaction of the parent cage phosphine, AdPH,
with 1-bromo-2-iodobenzene in dimethylacetamide (DMA) under
standard P–C coupling conditions afforded 1b in good yield (55%)
as an air-stable crystalline solid.† One noticeable difference in the
preparation of 1b, opposed to 1a, was the considerably shorter
reaction time to proceed to completion (typically 2 d for 1b; 5 d
1
for 1a). In the 31P{ H} NMR spectrum of 1b a single phosphorus
resonance was observed at d(P) -29.6 ppm, some 25 ppm upfield
with respect to 1a [d(P) -4.9 ppm]. Reaction of either 1a or 1b with
PhSeH and KOH, in DMA, for 5 d at ca. 160 ◦C afforded 2a or 2b
1
in reasonable yields (53% and 40% respectively). 31P{ H} NMR
Fig. 1 Molecular structure of 2b. All C–H hydrogen atoms are omitted
◦
˚
for clarity. Selected bond distances (A) and angles ( ): C(1)–Se(1) 1.919(3),
Se(1)–C(7) 1.925(3), C(8)–P(1) 1.844(3); C(1)–Se(1)–C(7) 102.41(14),
Se(1)–C(7)–C(8) 119.7(2), C(13)–P(1)–C(16) 92.40(14).
Department of Chemistry, Loughborough University, Loughborough, UK
LE11 3TU. E-mail: m.b.smith@lboro.ac.uk; Fax: +44 1509 223925;
Tel: +44 1509 222553
† Electronic supplementary information (ESI) available: Experimental
procedures, spectroscopic data and additional X-ray figures. CCDC
reference numbers 766945–766947. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c0dt00004c
To demonstrate the co-ordination potential of 2a and 2b,
reaction of 1 equiv. of each ligand with either PtCl2(cod) (cod =
cycloocta-1,5-diene) or PdCl2(PhCN)2 in CH2Cl2 at ambient
5216 | Dalton Trans., 2010, 39, 5216–5218
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temperature afforded the dichlorometal(II) complexes 3a and 3b
in good yields. Crystals of 3a and 3b were grown by vapour
diffusion of diethyl ether into either a CDCl3/(CH3)2SO or CH2Cl2
solution (Fig. 2).‡ In both cases, P,Se-chelation is clearly evident
with P(1)–M(1)–Se(1) bond angles of 90.28(3) and 87.902(12)◦.
Furthermore the M(1)–Se(1) bond lengths [Pt(1)–Se(1) 2.3561(5)
for 2a; Pd(1)–Se(1) 2.3656(2) for 2b] are consistent with selenoether
coordination.11 The M(1)–Se(1)–C(7)–C(8)–P(1) five-membered
˚
rings are essentially coplanar to within 0.046 A (for 3a) and
˚
0.104 A (for 3b). The interplanar angles for 3a and 3b, as
defined by the Se(1)/C(7)/C(8)/P(1) vs. Se(1)/M(1)/P(1) planes,
are 4.9◦ and 11.4◦ respectively indicating marginal folding along
the P(1) ◊ ◊ ◊ Se(1) vector. In addition, there is a clear change in
dihedral angle between the phenyl/phenylene rings attached to
Se(1) as a function of chelation. In the free ligand 2a, the dihedral
angle is 54.1◦ which expands to 87.0◦ (for 3a) and 82.1◦ (for 3b). As
a consequence, weak non-covalent M(1) ◊ ◊ ◊ Se(1) intermolecular
Scheme 2 Preparative routes to 4 and 5.
with coordination of both P and Se donor atoms to a single Pd(II)
metal centre.
˚
˚
contacts [Pt(1) ◊ ◊ ◊ Se(1) 3.709 A for 3a; Pd(1) ◊ ◊ ◊ Se(1) 3.787 A
for 3b] link adjacent molecules into dimer pairs.12 Although not
shown in Fig. 2, additional Se(1) ◊ ◊ ◊ Cl(1A) interactions are present
In summary, we have shown how established synthetic routes
can be used to access, hitherto unknown, selenoether modified
tertiary phosphines and demonstrated their ease of P,Se-chelation
at soft metal centres. Further coordination studies are in progress
and results from these will be reported in due course.
˚
˚
(3.445 A for 3a; 3.679 A for 3b). In the case of 3a this distance is
significantly less than the sum of the van der Waals radii for Se
13
˚
and Cl atoms (3.65 A).
Acknowledgements
We would like to thank the EPSRC and Loughborough University
for funding (PMS). Johnson Matthey are gratefully acknowledged
for the generous loan of precious metal salts.
Notes and references
‡ Crystal data: For 2b, C22H25O3PSe: Mr = 447.35, orthorhombic, space
˚
˚
˚
group P212121, a = 8.1752(5) A, b = 10.1189(6) A, c = 24.5004(14) A,
3
˚
˚
V = 2026.8(2) A , T = 150(2) K, Z = 4, l(Mo-Ka) = 0.71073 A, 17 792
data measured, 4890 unique (Rint = 0.0366), dc = 1.466 g cm-3, R1
=
0.0391 (for 4049 data with I > 2s(I)), wR2 = 0.0858 (all data), and
248 parameters. CCDC 766945. For 3a, C24H19Cl2PPtSe: Mr = 683.31,
˚
˚
monoclinic, space group P21/n,◦a = 11.2539(7) A, b = 13.4809(8) A, c =
3
˚
˚
14.7665(9) A, b = 101.0079(10) , V = 2199.0(2) A , T = 150(2) K, Z =
˚
4, l(Mo-Ka) = 0.71073 A, 19 234 data measured, 5350 unique (Rint
=
0.0357), dc = 2.064 g cm-3, R1 = 0.0276 (for 4130 data with I > 2s(I)),
Fig. 2 Molecular structures of (a) 3a and (b) 3b. All C–H hydrogen
atoms are omitted for clarity. For complex 3b the CH2Cl2 s◦olvate
wR2 = 0.0557 (all data), and 262 parameters. CCDC 766946. For 3b,
¯
C22H25Cl2O3PPdSe·CH2Cl2: Mr = 709.58, triclinic, space group P1, a =
◦
˚
˚
˚
˚
11.0639(5) A, b = 11.0640(5) A, c = 11.7858(5) A, a = 89.7421(7) , b =
˚
has been removed. Selected bond distances (A) and angles ( ) for
◦
◦
3
76.3793(7) , g = 68.4046(6) , V = 1298.32(10) A , T = 150(2) K, Z =
3a: Pt(1)–P(1) 2.2094(11), Pt(1)–Se(1) 2.3561(5), Pt(1)–Cl(1) 2.3668(11),
Pt(1)–Cl(2) 2.3142(11); P(1)–Pt(1)–Se(1) 90.28(3), P(1)–Pt(1)–Cl(2)
91.89(4), Se(1)–Pt(1)–Cl(1) 85.94(3), Cl(1)–Pt(1)–Cl(2) 92.04(4). For
3b: Pd(1)–P(1) 2.2615(4), Pd(1)–Se(1) 2.3656(2), Pd(1)–Cl(1) 2.3506(4),
Pd(1)–Cl(2) 2.3180(5); P(1)–Pd(1)–Se(1) 87.902(12), P(1)–Pd(1)–Cl(2)
98.800(17), Se(1)–Pd(1)–Cl(1) 84.577(14), Cl(1)–Pd(1)–Cl(2) 88.709(18).
˚
2, l(Mo-Ka) = 0.71073 A, 11 577 data measured, 6012 unique (Rint
=
0.0110), dc = 1.815 g cm-3, R1 = 0.0188 (for 5490 data with I > 2s(I)),
wR2 = 0.0464 (all data), and 302 parameters. CCDC 766947. All three
structures were determined routinely.
1 N. C. Gianneschi, M. S. Masar III and C. A. Mirkin, Acc. Chem. Res.,
2005, 38, 825.
2 (a) P. A. Ulmann, C. A. Mirkin, A. G. DiPasquale, L. M. Liable-Sands
and A. L. Rheingold, Organometallics, 2009, 28, 1068; (b) C. G. Oliveri,
P. A. Ulmann, M. J. Wiester and C. A. Mirkin, Acc. Chem. Res., 2008,
41, 1618; (c) C. G. Oliveri, S. T. Nguyen and C. A. Mirkin, Inorg.
Chem., 2008, 47, 2755; (d) A.-M. Valean, S. Go´mez-Ruiz, P. Lo¨nnecke,
I. Silaghi-Dumitrescu, L. Silaghi-Dumitrescu and E. Hey-Hawkins,
New J. Chem., 2009, 33, 1771; (e) T.-W. Chiou and W.-F. Liaw, Inorg.
Chem., 2008, 47, 7908.
3 M. J. Wiester and C. A. Mirkin, Inorg. Chem., 2009, 48, 8054.
4 (a) L. Diab, M. Gouygou, E. Manoury, P. Kalck and M. Urrutigo¨ıty,
Tetrahedron Lett., 2008, 49, 5186; (b) A. Dervisi, D. Koursarou, L.-l.
Ooi, P. N. Horton and M. B. Hursthouse, Dalton Trans., 2006, 5717;
(c) G. L. Moxham, H. E. Randell-Sly, S. K. Brayshaw, R. L. Woodward,
Having successfully demonstrated the preparation of aryl based
selenoether phosphines, we also found the ease by which an
alkyl backboned selenoether phosphine can be readily obtained.
Using an AIBN radical initiated hydroselenation,14 reaction of
=
Ph2PCH CH2 with PhSeH afforded solid 4 (Scheme 2) regios-
electively which has been characterised [d(P) -15.4].15 Reaction
of the anti-Markovnikov product 4 with PdCl2(cod) gave the five-
membered chelate complex 5 displaying the expected spectroscopic
and analytical properties. The significant downfield shift in the
1
31P{ H} NMR spectrum of 5 [d(P) 62.3 ppm] is fully consistent
This journal is
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A. S. Weller and M. C. Willis, Angew. Chem., Int. Ed., 2006, 45, 7618;
(d) R. Malacea, J.-C. Daran, S. B. Duckett, J. P. Dunne, C. Godard,
E. Manoury, R. Poli and A. C. Whitwood, Dalton Trans., 2006, 3350;
(e) J. R. Dilworth, C. A. Maresca von Beckh W. and S. I. Pascu, Dalton
Trans., 2005, 2151.
M. R. J. Elsegood, A. J. Lake, N. M. Sanchez-Ballester, M. B. Smith,
T. S. Varley and K. Blann, Eur. J. Inorg. Chem., 2007, 1405.
9 (a) J. Hopewell, P. Jankowski, C. L. McMullin, A. G. Orpen and
P. G. Pringle, Chem. Commun., 2010, 46, 100; (b) J. H. Downing, J.
Floure, K. Heslop, M. F. Haddow, J. Hopewell, M. Lusi, H. Phetmung,
A. G. Orpen, P. G. Pringle, R. I. Pugh and D. Zambrano-Williams,
Organometallics, 2008, 27, 3216.
10 P. Machnitzki, T. Nickel, O. Stelzer and C. Landgrafe, Eur. J. Inorg.
Chem., 1998, 1029.
11 (a) L. Vigo, M. Risto, E. M. Jahr, T. Bajorek, R. Oilunkaniemi, R. S.
Laitinen, M. Lahtinen and M. Ahlgre´n, Cryst. Growth Des., 2006, 6,
2376; (b) N. R. Champness, W. Levason, J. R. Quirk, G. Reid and C. S.
Frampton, Polyhedron, 1995, 14, 2753.
5 (a) D. K. Dutta, J. D. Woollins, A. M. Z. Slawin, D. Konwar, M.
Sharma, P. Bhattacharyya and S. M. Aucott, J. Organomet. Chem.,
2006, 691, 1229; (b) J. E. Aguado, S. Canales, M. C. Gimeno, P. G.
Jones, A. Laguna and M. D. Villacampa, Dalton Trans., 2005, 3005;
(c) S. E. Durran, M. R. J. Elsegood and M. B. Smith, New J. Chem.,
2002, 26, 1402; (d) J. Laube, S. Ja¨ger and C. Tho¨ne, Eur. J. Inorg. Chem.,
2001, 1983; (e) E. G. Hope, T. Kemmitt and W. Levason, J. Chem. Soc.,
Perkin Trans., 1987, 487; (f) S. K. Harbron, S. J. Higgins, E. G. Hope,
T. Kemmitt and W. Levason, Inorg. Chim. Acta, 1987, 130, 43; (g) G.
Dyer and D. W. Meek, J. Am. Chem. Soc., 1967, 89, 3983.
12 M. D. Milton, J. D. Singh and R. J. Butcher, Phosphorus, Sulfur Silicon
Relat. Elem., 2001, 169, 153.
13 A. Bondi, J. Phys. Chem., 1964, 68, 441.
´
6 (a) V. Cadierno, J. D´ıez, J. Garc´ıa-Alvarez and J. Gimeno, Dalton
14 (a) B. A. Trofimov, N. K. Gusarova, S. N. Arbuzova, N. I. Ivanova,
A. V. Artem’ev, P. A. Volkov, I. A. Ushakov, S. F. Malysheva and V. A.
Kuimov, J. Organomet. Chem., 2009, 694, 677; (b) N. K. Gusarova,
N. A. Chernysheva, S. V. Yas’ko, T. I. Kazantseva, I. A. Ushakov and
B. A. Trofimov, Synthesis, 2008, 2743.
15 For a recent alternative synthesis of 4 see: A. M. Spokoyny, M. S. Rosen,
P. A. Ulmann, C. Stern and C. A. Mirkin, Inorg. Chem., 2010, 49,
1577.
Trans., 2010, 39, 941; (b) C. Kling, H. Ott, G. Schwab and D. Stalke,
Organometallics, 2008, 27, 5038.
7 (a) G. Hua and J. D. Woollins, Angew. Chem., Int. Ed., 2009, 48, 1368;
(b) G. Hua, Y. Li, A. M. Z. Slawin and J. D. Woollins, Angew. Chem.,
Int. Ed., 2008, 47, 2857; (c) P. Kilian, S. Parveen, A. M. Fuller, A. M. Z.
Slawin and J. D. Woollins, Dalton Trans., 2008, 1908.
8 (a) T. J. Cunningham, M. R. J. Elsegood, P. F. Kelly, M. B. Smith and
P. M. Staniland, Eur. J. Inorg. Chem., 2008, 2326; (b) G. M. Brown,
5218 | Dalton Trans., 2010, 39, 5216–5218
This journal is
The Royal Society of Chemistry 2010
©