Preparation and structural characterization of ionic five-coordinate palladium(II) and platinum(II) complexes of the ligand Tris[2-(diphenylphosphino)ethyl]phosphine. Insertion of SnCl2 into M-Cl bonds (M = Pd, Pt) and hydroformylation activity of the Pt-SnCl3 systems

Article abstract of DOI:10.1021/ic020006k

The five-coordinate palladium(II) and platinum(II) complexes [M(PP₃)Cl]Cl [M = Pd (1), Pt (2)] (PP₃ = tris[2-(diphenylphosphino)ethyl]phosphine) were prepared by interaction of aqueous solutions of MCl₄^2- salts with PP₃ in CHCl₃. Complexes 1 and 2 undergo facile chloro substitution reactions with KCN in 1:1 and 1:2 ratios to afford complexes [M(PP₃)(CN)]Cl [M = Pt (3)] and [M(PP₃)(CN)](CN) [M = Pd (4), Pt (5)] possessing M-C bonds, both in solution and in the solid state. The reaction of 1 and 2 with SnCl₂ in CDCl₃ occurs with insertion of SnCl₂ into M-Cl bonds leading to the formation of [M(PP₃)(SnCl₃)](SnCl₃) [M = Pd (6), M = Pt (7)]. The isolation as solids of complexes 6 and 7 by addition of SnCl₂ to the precursors requires the presence of PPh₃ which activates the cleavage of M-Cl bonds, favors the SnCl₂ insertion, and does not coordinate to M in any observable extent. Solutions of 6 in CDCl₃ undergo tin dichloride elimination in higher proportion than solutions of 7. The reaction of complexes 1 and 2 with SnPh₂Cl₂ leads to [M(PP₃)Cl]₂[SnPh₂Cl₄] [M = Pd (8)]. Complexes 2, 5, 7, and 8 were shown by X-ray diffraction to contain distorted trigonal bipyramidal monocations [M(PP₃)X]⁺ [M = Pt, X = Cl^- (2), X = CN^- (5), X = SnCl₃^- (7); M = Pd, X = Cl^- (8)], the central P atom of PP₃ being trans to X in axial position and the terminal P donors in the equatorial plane of the bipyramids. The preformed catalyst 7 showed a relatively high aldehyde selectivity compared to most of the platinum catalysts.

Full text of DOI:10.1021/ic020006k

Inorg. Chem. 2002, 41, 4435−4443
Preparation and Structural Characterization of Ionic Five-Coordinate
Palladium(II) and Platinum(II) Complexes of the Ligand
Tris[2-(diphenylphosphino)ethyl]phosphine. Insertion of SnCl2 into M−Cl
Bonds (M ) Pd, Pt) and Hydroformylation Activity of the Pt−SnCl3
Systems
Damia´n Ferna´ndez,† M. Ine´s Garc´ıa-Seijo,† Tama´s Ke´gl,‡ Gyo1rgy Pet_ocz,§ La´szlo´ Kolla´r,§ and
,†
M. Esther Garc´ıa-Ferna´ndez*
Department of Inorganic Chemistry, UniVersity of Santiago de Compostela,
E-15782 Santiago de Compostela, Spain, Research Group for Petrochemistry of the Hungarian
Academy of Sciences, H-8200, Veszpre´m, Hungary, and Department of Inorganic Chemistry,
UniVersity of Pe´cs, H-7624 Pe´cs, P.O. Box 266, Hungary
Received January 2, 2002
The five-coordinate palladium(II) and platinum(II) complexes [M(PP3)Cl]Cl [M ) Pd (1), Pt (2)] (PP ) tris[2-
3
(diphenylphosphino)ethyl]phosphine) were prepared by interaction of aqueous solutions of MCl42- salts with PP in
3
CHCl3. Complexes 1 and 2 undergo facile chloro substitution reactions with KCN in 1:1 and 1:2 ratios to afford
complexes [M(PP )(CN)]Cl [M ) Pt (3)] and [M(PP )(CN)](CN) [M ) Pd (4), Pt (5)] possessing M−C bonds, both
3
3
in solution and in the solid state. The reaction of 1 and 2 with SnCl2 in CDCl3 occurs with insertion of SnCl2 into
M−Cl bonds leading to the formation of [M(PP )(SnCl3)](SnCl3) [M ) Pd (6), M ) Pt (7)]. The isolation as solids
3
of complexes 6 and 7 by addition of SnCl2 to the precursors requires the presence of PPh3 which activates the
cleavage of M−Cl bonds, favors the SnCl2 insertion, and does not coordinate to M in any observable extent.
Solutions of 6 in CDCl3 undergo tin dichloride elimination in higher proportion than solutions of 7. The reaction of
complexes 1 and 2 with SnPh2Cl2 leads to [M(PP )Cl]2[SnPh2Cl4] [M ) Pd (8)]. Complexes 2, 5, 7, and 8 were
3
shown by X-ray diffraction to contain distorted trigonal bipyramidal monocations [M(PP )X]+ [M ) Pt, X ) Cl- (2),
3
X ) CN- (5), X ) SnCl3- (7); M ) Pd, X ) Cl- (8)], the central P atom of PP being trans to X in axial position
3
and the terminal P donors in the equatorial plane of the bipyramids. The “preformed” catalyst 7 showed a relatively
high aldehyde selectivity compared to most of the platinum catalysts.
1. Introduction
(SnCl3)(chiral diphosphines) “preformed” catalysts,3-6 despite
their low activities compared to the rhodium analogues,
Tertiary phosphines are generally excellent ligating agents
to d8 metal ions and are very important constituents of
compounds for catalysis.1,2 Thus, platinum-chiral diphos-
phine complexes in the presence of tin(II) chloride and PtCl-
(3) (a) Botteghi, C.; Paganelli, S.; Schionato, A.; Marchetti, M. Chirality
1991, 3, 355. (b) Gladiali, S.; Bayo´n, J. C.; Claver, C. Tetrahedron:
Asymmetry 1996, 6, 1453. (c) Agbossou, F.; Carpentier, J.-F.;
Mortreux, A. Chem. ReV. 1995, 95, 2485.
(4) (a) Parinello, G.; Stille, J. K. J. Am. Chem. Soc. 1987, 109, 7122. (b)
Kolla´r, L.; Consiglio, G.; Pino, P. J. Organomet. Chem. 1987, 330,
305. (c) Kolla´r, L.; Bakos, J.; To´th, I.; Heil, B. J. Organomet. Chem.
1989, 370, 257. (d) Consiglio, G.; Nefkens, S. C. A.; Borer, A.
Organometallics 1991, 10, 2046. (e) Sturm, T.; Weissensteiner, W.;
Mereiter, K.; Ke´gl, T.; Jeges, G.; Pet_ocz, G.; Kolla´r, L. J. Organomet.
Chem. 2000, 595, 93.
(5) Farkar, E.; Kolla´r, L.; Moret, M.; Sironi, A. Organometallics 1996,
15, 1345.
(6) (a) Ke´gl, T.; Ko´llar, L.; Szalontai, G.; Kuzmann, E.; Ve´rtes, A. J.
Organomet. Chem. 1996, 507, 75. (b) Jedlicka, B.; Weissensteiner,
W.; Ke´gl, T.; Kolla´r, L. J. Organomet. Chem. 1998, 563, 37.
* Corresponding author. E-mail: qiegfq@usc.es. Phone: 34-981-563100/
14241. Fax: 34-981-597525.
† University of Santiago de Compostela.
‡ Research Group for Petrochemistry of the Hungarian Academy of
Sciences.
§ University of Pe´cs.
(1) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza, F.; Frediani, P.; Ram´ırez,
J. A. Organometallics 1990, 9, 226.
(2) Thaler, E. G.; Folting, K.; Caulton, K. G. J. Am. Chem. Soc. 1990,
112, 2664.
10.1021/ic020006k CCC: $22.00 © 2002 American Chemical Society
Published on Web 07/27/2002
Inorganic Chemistry, Vol. 41, No. 17, 2002 4435

Ferna´ndez et al.
proved to be efficient in enantioselective hydroformylation.
Especially, the hydroformylation of unsatured esters and
vinyl aromatics resulted in chiral building blocks and
compounds of pharmacological interest. The branched al-
dehydes obtained in hydroformylation of vinyl aromatics can
be further oxidized to the corresponding acids which are used
as effective nonsteroidal analgesics.7,8 The insertion of SnCl2
into the Pt-Cl bond of a PtCl2(P2) precursor (P2 ) two
monophosphines or chelating diphosphine) results in the
formation of a trichlorostannato ligand affording complexes
of the type PtCl(SnCl3)(P2).9 However, by addition of
monophosphine, the cleavage of the Pt-Sn bond occurs with
by using the PP3 ligand [Pd(PP3)X]+ (X ) Cl-, Br-, I-)16
demonstrating that the order of stabilization of the axial halo
ligand X is I- > Br- > Cl-. In the presence of free trimethyl
phosphite, the halo ligand substitution takes place with
formation of [Pd(PP3)(P(OCH3)3)]2+.17 These facts are con-
sistent with expectations that reduction of the electronic
repulsion is essential to give a higher coordination number
than that usually observed, such as five-coordinate for
palladium(II) complexes, and that only the donor orbitals
on the relatively higher energy levels can form effective σ
bonding in such complexes, compared with ordinary square-
planar ones. The higher selectivity of the axial coordination
site in [Pd(PP3)X]+ complexes for thiolate sulfur atoms
compared with the corresponding square-planar [Pd(P3)X]+
compounds18a (P3 ) linear triphosphine) can be applied to
separation of sulfur-containing amino acids from other amino
acids and selective determination of the reduced form of
glutathione, which is quite important in the biological redox
and detoxification systems.18b
-
formation of ionic complexes containing SnCl3 as coun-
teranion, [PtCl(P3)](SnCl3), [PtCl(P)(P2)](SnCl3).5 In conse-
quence, when a catalytic system such as PtCl2(COD)/PPh3/
SnCl2 is used in hydroformylation, the Pt/PPh3 ratio influences
the products of reaction.10 The addition of PPh3 to square-
planar compounds containing a tridentate triphosphine such
as [M(triphos)Cl]Cl (M ) Pd, Pt; triphos ) bis[2-(diphe-
nylphosphino)ethyl]phenylphosphine) in the presence of
SnCl2 leads to a chloro substitution reaction11 with formation
of the ionic complexes [M(triphos)(PPh3)](SnCl3)2. Likewise,
the σ-carbon donor ligand CN- is able to displace the chloro
ligand from the coordination sphere of M(II) affording new
M-C bonds in [M(triphos)(CN)]+ complexes which by
addition of another equivalent of CN- form neutral five-
coordinate compounds of the type [M(triphos)(CN)2].11
The kinetics for ligand substitution reactions in square-
planar palladium(II) and platinum(II) complexes have been
well established, and an associative mechanism via a trigonal
bipyramidal transition state has been generally proposed.12
Five-coordinate hydride species containing the tripodal
polyphosphine tris[2-(diphenylphosphino)ethyl]phosphine)
(PP3) and related ligands have been prepared with several
low spin d8 ions including Co(I), Ni(II), Pd(II), and Pt(II).13-15
Likewise, S. Funahashi et al. have prepared relatively stable
five-coordinate trigonal bipyramidal palladium(II) complexes
Following the investigations previously developed with
square-planar complexes, the present work deals with the
syntheses and characterization of trigonal bipyramidal com-
pounds of the type [M(PP3)(CN)]+ and [M(PP3)(SnCl3)]+ (M
) Pd, Pt) and the potential role of the Pt-SnCl3 systems in
the hydroformylation of styrene. We report an unusual
procedure for isolation of the solids [M(PP3)(SnCl3)](SnCl3)
starting from [M(PP3)Cl]Cl and SnCl2 in the presence of
PPh3. The behavior as a Lewis acid of SnPh2Cl2 versus
[M(PP3Cl]Cl just binding Cl- excludes the possibility of
formation of M-Sn bonds but provides a way for obtaining
well-ordered crystals containing trans [SnPh2Cl4]2- anions.
The crystal structures for [M(PP3)X]X (X ) Cl-, CN-,
-
SnCl3 ) and [Pd(PP3)Cl]2[SnPh2Cl4] are reported, and the
trans influence of the anionic ligands X is discussed.
2. Results and Discussion
2.1. Syntheses. Scheme 1 shows all complexes prepared
with tris[2-(diphenylphosphino)ethyl]phosphine (PP3). Com-
plexes 1 ([Pd(PP3)Cl]Cl) and 2 ([Pt(PP3)Cl]Cl) were prepared
as hydrates [(1)‚4H2O and (2)‚2H2O] starting from aqueous
(7) Andrieu, J.; Camus, J. M.; Poli, R.; Richard, P. New J. Chem. 2001,
25, 1015.
(8) Sonawane, H. R.; Bellur, N. S.; Ahuja, J. R.; Ulkarni, D. G.
Tetrahedron: Asymmetry 1992, 3, 163.
2-
solutions of MCl4 salts and following a variation19 of the
(9) (a) Clark, H. C.; Davies, J. A. J. Organomet. Chem. 1981, 213, 503.
(b) Bardi, R.; Piazessi, A. M.; Del Pra, A.; Cavinato, G.; Toniolo, L.
J Organomet. Chem. 1982, 234, 107. (c) Consiglio, G.; Pino, P.;
Flowers, L. I.; Pittmann, C. U., Jr. J. Chem. Soc., Chem. Commun.
1983, 612. (d) Kolla´r, L.; Bakos, J.; To´th, I.; Heil, B. J. Organomet.
Chem. 1989, 370, 257. (e) Ancillotti, F.; Lami, M.; Marchionna, M.
J. Mol. Catal. 1990, 58 (3), 345.
(10) (a) Cavinato, G.; De Munno, G.; Lami, M.; Marchionna, M.; Toniolo,
L.; Viterbo, D. J. Organomet. Chem. 1994, 466, 277. (b) Scrivanti,
A.; Berton, A.; Toniolo, L.; Botteghi, C. J. Organomet. Chem. 1986,
314 (3), 369.
method previously used by R. B. King et al.20
The reactions of 1 and 2 in CHCl3 with KCN in CH3OH
led to the formation of [Pt(PP3)(CN)]Cl (3) and [M(PP3)-
(CN)](CN) [M ) Pd (4), Pt (5)]. The solids of 4 and 5 were
obtained as chloroform solvates [(4)‚CHCl3 and (5)‚CHCl3].
Solutions of 1 and 2 in chloroform react under stirring (ca.
12 h) with SnCl2, added as a solid, to form complexes
[M(PP3)(SnCl3)](SnCl3) [M ) Pd (6), Pt(7)]. However, all
attempts to prepare complexes 6 and 7 quantitatively as solids
(11) Ferna´ndez, D.; Sevillano, P.; Garc´ıa-Seijo, M. I.; Castin˜eiras, A.;
Ja´nosi, L.; Berente, Z.; Kolla´r, L.; Garc´ıa-Ferna´ndez, M. E. Inorg.
Chim. Acta 2001, 312, 40.
(12) (a) Wilkins, R. G. Kinetics and Mechanism of Reaction of Transition
Metal Complexes, 2nd ed.; VCH: Weinheim, Germany, 1991; Chapter
4. (b) Khan, A. R.; Harvey, P. D.; Socol, S. M. Inorg. Chim. Acta
1996, 251, 89.
(13) (a) Bru¨ggeller, P. Inorg. Chim. Acta 1987, 129, L27. (b) Bru¨ggeller
P. Z. Naturforsch 1986, 41B (12), 1561.
(14) Hohman, W. H.; Kountz, D. J.; Week, D. W. Inorg. Chem. 1986, 25,
616.
(15) Gieren, V. A.; Bru¨ggeller, P.; Hofer, K.; Hu¨bner, T.; Ruiz-Pe´rez, C.
Acta Crystallogr. 1989, C45, 196.
(16) Aizawa, S.; Iida, T.; Funahashi, S. Inorg. Chem. 1996, 35, 5163.
(17) Aizawa, S.; Funahashi, S. Anal. Sci. 1996, 12, 27.
(18) (a) Aizawa, S.; Okada, M.; Kobayashi, K.; Yamada, S.; Nakamura,
N. Chem. Lett. 2000, 1412. (b) Flohe, L.; Benohr, H. Ch.; Sies, H.;
Waller, H. D.; Wendel, A. Glutathione; Academic Press: New York,
1974.
(19) de Assis, E. F.; Filgueiras, C. A. L. Transition Met. Chem. (Dordrecht,
Neth.) 1994, 19, 484.
(20) King, R. B.; Kapoor, P. N. Inorg. Chem. 1971, 10, 1851.
4436 Inorganic Chemistry, Vol. 41, No. 17, 2002

Tris[2-(diphenylphosphino)ethyl]phosphine Complexes
Table 1. 31P{1H} NMR Data (rt) in CDCl3 for (1)‚4H2O, (2)‚2H2O, 3,
3*, (4-7)‚CHCl3, and (8)‚4H2O and Reactions of 1 and 2
Scheme 1. Complexes Prepared with PP3 Showing Labels for Donor
Atoms
cmpd
δPeq a 1J(195Pt, 31Peq) δPax a 1J(195Pt, 31Pax)
(1)‚4H2O
29.5s
25.0s
26.4d
26.4dd
47.3s
30.6s
44.6sd
28.4se
29.2s
29.5s
25.0s
134.1s
118.3s
124.3q
124.3dq
154.3s
131.6s
160.0s
137.8se
141.5s
133.0s
118.3s
(2)‚2H2O
2590
2543
2543
2505
1811
1811
3b
3*b,c
(4)‚CHCl3
(5)‚CHCl3
(6)‚CHCl3
(7)‚CHCl3
(7)‚CHCl3
(8)‚4H2Og
(2)‚2H2O +
6 equiv SnPh2Cl2
(1)‚4H2O +
2539
1825
2450
2441
1695
2005
f
2590
2505
g
29.5s
25.0s
134.0s
118.3s
h
1 equiv PPh3
(2)‚2H2O +
1 equiv PPh3
2590
2505
h
a
b
c
See Scheme 1 for labeled atoms. 2J(31Peq, 31Pax) ) 4.5 Hz. 2J(31Peq,
13C) ) 15 Hz, 2J(31Pax, 13C) ) 102 Hz. 2J(117/119Sn, 31Peq) ) 339 Hz.e
d
2J(117/119Sn, 31Peq) ) 298 Hz, 2J(117/119Sn, 31Pax) ) 2609/2729 Hz.
f
Spectrum recorded in CDCl3/DMF (1/1), 2J(117/119Sn, 31Peq) ) 300 Hz.g
h
by reaction of the precursors 1 and 2 with SnCl2 in excess
were unsuccessful. The M-SnCl3 complexes were achieved,
as chloroform solvates [(6)‚CHCl3 and (7)‚CHCl3] using PPh3
as additive (M/PPh3 ) 1/1). Crystals of complex 8 ([Pd-
(PP3)Cl]2[SnPh2Cl4]) were obtained as hydrates (8)‚4H2O
from the reaction {[Pd(PP3)Cl]Cl (1) (CDCl3) and 6 equiv
of SnPh2Cl2 (CD3OD)}.
Complexes 1-7 were prepared in excellent yields (81-
92%), and the higher solubilities were found in coordinating
solvents such as DMSO or DMF. However, the cyano
complexes were not soluble in DMF.
Spectrum recorded in CDCl3/CD3OD (1/1). δP(PPh3) -7.3.
nuclear phosphine complexes containing square-planar Pt-
(II) centers (3000-3600 Hz).11,24-26 The proton decoupled
195Pt spectrum of 2 (Figure 2a) in DMSO-d6 consists of an
overlapped doublet of (1:3:3:1) quartets centered at δ -4373.
This resonance was strongly shifted toward a lower field
compared with the corresponding value of the analogous
hydrido complex [Pt(PP3)H]+ 13 (δ ) -5474) and also shifted
lower field compared with the values (δ ) -4858 to -4592)
for square-planar Pt(II) complexes.24-26 The only coupling
constant available from the multiplet is 1J(195Pt, 31Peq) ) 2590
Hz.
2.2. Mass Spectometry and Infrared Spectroscopy. The
FAB MS for complexes 1, 2, and 4-7 showed peaks
assigned to M(PP3)X fragments in all cases.
2.3.2. NMR Spectra for Complexes 3, 3*, and 4-8. The
31P NMR spectra for solutions in CDCl3 of [Pt(PP3)(CN)]Cl
(3) and [Pt(PP3)(13CN)]Cl (3*) (prepared by interaction of 3
and 1 equiv of K13CN) consist of two signals: a doublet
(3), a doublet of doublets (3*), at δ 26.4, and a quartet (3),
a doublet of quartets (3*), at δ 124.3. The signals were
assigned to the Peq and Pax atoms, respectively, in a trigonal
bipyramidal arrangement (Scheme 1). The couplings
The far-infrared spectra (400-100 cm-1) for complexes
1 and 2 show bands at 348 and 351 cm-1, respectively,
assigned to terminal M-Cl stretching vibrations. For com-
plexes 6 and 7, bands were detected at ∼320 cm-1 assignable
-
to Sn-Cl stretches of the SnCl3 ligand. The near-infrared
spectra (4000-500 cm-1) for complexes 3 and 5 show bands
around 2120 cm-1 characteristic of ν(CN) of the cyano
ligand.21,22 Likewise, the band at 2077 cm-1 observed for
complex 3* was assigned to ν(13CN).
1
1J(195Pt, 31Peq) ) 2543 Hz, J(195Pt, 31Pax) ) 1811 Hz, and
2J(31Peq, 31Pax) ) 4.5 Hz are in accordance with this structure.
The proton decoupled 13C NMR spectrum of 3* consists of
a doublet of quartets at δ 105.5 (Figure 1b) from which the
2.3. NMR Spectra. 2.3.1. NMR Characterization of
Complexes 1 and 2. The 31P{1H} NMR spectrum of
complexes 1 and 2 ([M(PP3)Cl]Cl) in CDCl3 (Table 1) shows
two signals with integration ratios 3:1 assignable to the
equatorial and axial phosphorus (Peq, Pax) of the ligand,
respectively, in a five-coordinate compound with a trigonal
bipyramidal structure (Scheme 1).16,18 The 1J(195Pt, 31P) values
of 2590 and 2505 Hz for 2 are in accordance with the
terminal and central P of PP3 occupying the equatorial
and axial positions, respectively,13,23 of the bipyramid. The
1J(195Pt, 31Pax) value of 2505 Hz is lower than the coupling
constants due to P trans to Cl in other homo- and hetero-
1
2
couplings J(195Pt, 13C) ) 911 Hz, J(31Pax, 13C) ) 102 Hz,
and 2J(31Peq, 13C) ) 15 Hz confirm again the trigonal
bipyramidal structure. The same structure can be proposed
on the basis of the 31P{1H} NMR data for solutions of [Pd-
(PP3)(CN)](CN) (4) and [Pt(PP3)(CN)](CN) (5) in CDCl3.
(23) Garc´ıa-Seijo, M. I.; Garc´ıa-Ferna´ndez, M. E.; Habtemariam, A.;
Murdoch, P. Del S; Gould, R. O.; Sadler, P. J. Presented at 34th ICCC,
Edinburgh, Scotland, 2000; Poster Abstract PO939.
(24) Sevillano, P.; Habtemariam, A.; Parsons, S.; Castin˜eiras, A.; Garc´ıa,
M. E.; Sadler, P. J. J. Chem. Soc., Dalton Trans. 1999, 2861.
(25) Sevillano, P.; Habtemariam, A.; Garc´ıa-Seijo, M. I.; Castin˜eiras, A.;
Parsons, S.; Garc´ıa, M. E.; Sadler, P. J. Aust. J. Chem. 2000, 53, 635.
(26) Review article on polyphosphine complexes: Garc´ıa-Seijo, M. I.;
Garc´ıa-Ferna´ndez, M. E. Recent Research DeVelopments in Inorganic
and Organometallic Chemistry; Research Signpost: Trivandrum, India,
2001; Vol. 1, pp 99-123.
(21) Khan, A. R.; Socol, S. M.; Meek, D. W.; Yasmeen, R. Inorg. Chim.
Acta 1995, 234, 109.
(22) (a) Balch, A. L.; Catalano, V. J. Inorg. Chem. 1992, 31, 3934. (b)
Yip, H.-K.; Lin, H.-M.; Cheung, K.-M.; Che, C.-M.; Wang, Y. Inorg.
Chem. 1994, 33, 1644.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4437

Ferna´ndez et al.
Figure 2. ORTEP diagram for 2 and 5.
(Table 1). The use of this procedure allowed the preparation
of complexes 6 and 7 as solids.
Figure 1. NMR spectra for solutions of (a) (2)‚2H2O in DMSO-d6, (b)
3* in CDCl3, and (c) (7)‚CHCl3 in CDCl3 at rt: (a) 195Pt, (b) 13C, (c)
31P{1H} (peaks and satellites are labeled as 2 for (2)‚2H2O and 9 for
(7)‚CHCl3).
The 31P{1H} NMR spectrum for 6 and 7 dissolved in
CDCl3 and the spectrum for 7 in CDCl3/DMF (1/1) show
two sets of two signals assignable to Pax and Peq in [M(PP3)-
Cl]+ and [M(PP3)(SnCl3)]+ complexes. This indicates that
the trichlorostannato ligand undergoes tin dichloride elimina-
tion to some extent (Figure 1c). The presence of M-Sn
bonds is evident from the couplings 2J(117/119Sn, 31Peq) ) 339
The insertion of SnCl2 into M-Cl bonds was observed in
solution by addition of SnCl2, as a solid, to solutions of 1
and 2 in CDCl3 under stirring.
Because the square-planar complexes [M(triphos)Cl]Cl
react with PPh3 in the presence of SnCl2 to form [M(triphos)-
(PPh3)](SnCl3)2 (prepared as solids),11 the analogous reaction
was carried out with [M(PP3)Cl]Cl. It was surprisingly
observed that when 1 and 2 (in CHCl3) react with 2 equiv
of SnCl2 (in CH3OH) in the presence of PPh3 (M/PPh3 )
1/1) the formation of complexes 6 and 7 occurs, respectively,
with there being no reaction between [M(PP3)Cl]+ and PPh3
2
Hz (M ) Pd) and 298 Hz (M ) Pt) as well as J(117/119Sn,
31Pax) ) 2609/2729 Hz and 1J(195Pt, 31Pax) ) 1695 Hz (M )
Pt). Despite the lower value of 1J(195Pt, Pax) in CDCl3 for 7
(1695 Hz) compared to 5 (1825 Hz), the facile elimination
-
of SnCl2 from SnCl3 ligand is indicative of weaker
-
coordinating behavior for SnCl3 versus CN-, and the
4438 Inorganic Chemistry, Vol. 41, No. 17, 2002

Tris[2-(diphenylphosphino)ethyl]phosphine Complexes
Table 2. SnCl2 Elimination for 6 and 7 and Insertion of SnCl2 into
M-Cl Bonds for 1 and 2 in CDCl3
cmpd
[M(PP3)(SnCl3)]+ (%) [M(PP3)Cl]+ (%)
[Pd(PP3)(SnCl3)](SnCl3) (6)
[Pt(PP3)(SnCl3)](SnCl3) (7)
[Pt(PP3)(SnCl3)](SnCl3) (7)a
[Pd(PP3)Cl]Cl (1) +
1 equiv SnCl2
75.4
90.0
45.0
24.6
10.0
55.0
0.0
100.0
[Pt(PP3)Cl]Cl (2) +
64.4
35.6
0.0
1 equiv SnCl2
[Pt(PP3)Cl]Cl (2) +
2 equiv SnCl2
100.0
a
CDCl3/DMF (1/1).
sequence proposed for the trans influence27 in complexes 1,
5, 7, and [Pt(PP3)H]+ (1J(195Pt,31P) ) 1467 Hz)13a is H- >
Figure 3. ORTEP diagram for 7.
-
CN- > SnCl3 > Cl-.
and one monoanion, crystals of 8 consist of two monocations
[Pd(PP3)Cl]+ symmetrically located in relation to one dianion
[SnPh2Cl4]2-, the tin atom being the center of symmetry.
The cations [M(PP3)X]+ adopt, in all cases, a slightly
distorted trigonal bipyramidal geometry where PP3 acts as a
tetradentate chelating ligand with the central phosphorus in
axial position (Pax) trans to the donor atom of the anionic
ligand X and the terminal phosphorus in the equatorial plane
(Peq) of the bipyramid. All M-Peq distances are longer than
the M-Pax for each complex. This can be attributed not only
to the strong σ interaction of the axial bond in the trigonal
bipyramidal geometry but also to the participation of the Pax
in three fused five-membered chelate rings to M. Similar
trends with different axial and equatorial bond distances were
observed in analogous d8 metal complexes such as [Co(PP3)-
(P(OCH3)3)]+ 16 and [Ni(PP3)(P(OCH3)3)]2+,14 and regardless
of geometry, the shortest metal-phosphorus distances for
other polyphosphine complexes ([RuCl2(tetraphos)],29 [Ni-
(Te-Te)(triphos)],30 [Pt(triphos)Cl]Cl24) also corresponded
to the P donor atoms involved in more than one chelate ring
to a metal center. For the present complexes, each M(II) in
[M(PP3)X]+ [M ) Pt (2, 5, 7), Pd (8)] is displaced by 0.161-
0.197 Å from the equatorial plane defined by the three
equatorial phosphorus atoms toward the X ligand, with the
sequence of this displacement being 8 > 7 > 5 > 2.
The broad signals observed at δ -65.4 and -66.6 in the
119Sn NMR spectra (CDCl3) for 6 and 7, respectively, did
-
not allow us to distinguish between SnCl3 ligand and
counterion.28
The 31P{1H} NMR spectra for (1 + 6 equiv SnPh2Cl2 )
8) and (2 + 6 equiv SnPh2Cl2) show signals (Table 1) in the
same position as those for precursors 1 and 2, respectively.
SnPh2Cl2 reacts here as general-type Lewis acid, just binding
Cl-, and the different behavior compared to SnCl2 (a specific
complexing reagent for platinum group metals) is probably
because of steric and electronic factors.
2.3.3. Elimination of SnCl2 for Complexes 6 and 7 and
Insertion of SnCl2 into M-Cl Bonds for Complexes 1 and
2. Table 2 shows the percentages of [M(PP3)(SnCl3)]+ versus
[M(PP3)Cl]+ detected by 31P{1H} NMR for solutions of 6
and 7 (“preformed” systems) and titrations of 1 and 2 with
SnCl2 (in situ systems) in CDCl3.
The tin dichloride elimination from 6 dissolved in CDCl3
occurs in higher proportion (24.6%) than from 7 (10%). The
use of the solvent mixture CDCl3/DMF (1/1) for dissolving
7, as expected, increases this elimination (55%).
The total insertion of SnCl2 into the M-Cl bonds requires
the addition of 1 and 2 equiv of SnCl2 to solutions in CDCl3
of 1 and 2, respectively.
The Pt-Pax bond distances for 2, 5, and 7 [2.2214(2),
2.259(5), and 2.294(3) Å, respectively] increase ca. 0.035
Å from 2 to 5 and from 5 to 7. The unexpected increase for
7 compared to 5 (CN- is stronger trans ligand)27 can be
Thus, palladium(II) complexes 1 and 6 undergo more facile
tin dichloride insertion and elimination reactions in CDCl3
than platinum(II) compounds 2 and 7, respectively, undergo.
2.4. Structural Characterization of 2, 5, 7, and 8 by
X-ray Diffraction. Suitable crystals for X-ray diffraction
studies of 2, 5, and 8 were obtained as hydrates (2)‚H2O,
(5)‚H2O, and (8)‚4H2O. Crystals of 7 were obtained as the
chloroform solvate (7)‚CHCl3. Crystal parameters, data
collection, and refinement for all crystal structures are given
in Table 3. The ORTEP diagrams with numbering schemes
for complexes 2 and 5 are given in Figure 2, and for 7 and
8, in Figures 3 and 4, respectively. Selected bond distances
and angles for all crystals are listed in Table 4. While crystals
of 2, 5, and 7 are made up of discrete units [Pt(PP3)X]X [X
) Cl- (2), CN- (5), SnCl3- (7)] containing one monocation
-
attributed to a steric effect with the SnCl3 coordinated
complex, leading to more distortion of the tetrapod ligand
chelate rings. Likewise, the lower trans effect of the axial
-
ligand SnCl3 compared with H- results in a Pt-Pax bond
distance for 7 higher than the same distance for the hydrido
complex [Pt(PP3)H](BPh4) [2.266(1) Å]15, the general trend
(on the basis of 31P{1H} NMR data) being in the opposite
sense. The Pd-Pax bond distance for complex 8, 2.217(2)
Å, is shorter than the same distance for complex 1 (2.237-
(3) Å).16 The Pt-Peq bond lengths are in the same range
2.340(1)-2.400(1) Å for all three complexes 2, 5, and 7 and
(27) (a) Parshall, G. W. J. Am. Chem. Soc. 1966, 88, 704. (b) Parshall, G.
W. J. Am. Chem. Soc. 1964, 86, 5367. (c) Parshall, G. W.; Stolberg,
U. G. J. Am. Chem. Soc. 1965, 87, 658.
(29) Rivera, A. V.; De Gil, E. R.; Fontal, B. Inorg. Chim. Acta 1985, 98,
153.
(30) Di Vaira, M.; Peruzzini, M.; Stoppioni, P. Angew. Chem. 1987, 26,
(28) McFarlane, W.; Rees, N. H. J. Chem. Soc., Dalton Trans. 1990, 3211.
916.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4439

Ferna´ndez et al.
Figure 4. ORTEP diagram for 8.
Table 3. Summary of Crystal Parameters, Data Collection, and Refinement for (2)‚6H2O, (5)‚H2O, (7)‚CHCl3, and (8)‚4H2O
(2)‚6H2O
(5)‚H2O
(7)‚CHCl3
(8)‚4H2O
empirical formula
fw
C42H42P4Cl2O5.5Pt
1024.63
293(2)
C44H42N2OP4Pt
933.77
293(2)
C43H42Cl9P4PtSn2
1434.17
293(2)
0.71073
0.62 × 0.09 × 0.08
yellow/needles
monoclinic
P21/c
12.514(3)
42.380(11)
10.552(3)
90
113.165(4)
90
C48H47Cl3P4PdSn0.5O2
1051.83
293(2)
temp (K)
wavelength (Å)
cryst size (mm3)
color/habit
cryst syst
space group
a (Å)
0.71073
0.71073
0.71073
0.33 × 0.20 × 0.06
orange/prisms
triclinic
0.38 × 0.29 × 0.02
yellow/plates
triclinic
0.34 × 0.17 × 0.07
red/plates
triclinic
P1h
P1h
P1h
10.275(2)
10.630(2)
20.770(4)
80.244(4)
86.006(4)
75.924(4)
2167.7(8)
2
10.306(4)
10.488(4)
21.012(8)
80.411(6)
86.458(6)
76.204(6)
2174.2(15)
2
10.112(2)
12.028(3)
21.282(5)
92.903(4)
101.721(4)
111.854(4)
2329.4(9)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
5145(2)
4
1.851
4.298
Z
calcd d (Mg/m3)
1.570
3.551
1020
1.426
3.408
932
1.500
1.008
1066
abs coefft (mm-1
F(000)
)
2764
θ range for
data collection (deg)
index ranges
1.00-26.44
0.98-26.44
0.96-26.41
0.99-26.42
-12 e h e 12
-13 e k e 13
0 e l e 25
24811
8840 [Rint ) 0.0363]
0.8152 and 0.3870
-12 e h e 12
-12 e k e 13
0 e l e 26
24054
8834 [Rint ) 0.0724]
0.9350 and 0.3575
-15 e h e 15
-35 e k e 52
-13 e l e 11
33126
10514 [Rint ) 0.0767]
0.7249 and 0.1758
-12 e h e 12
-15 e k e 15
0 e l e 26
17131
9339 [Rint ) 0.0515]
0.9420 and 0.6488
reflns collected
indep reflns
max and min
transmission
data/restraints/params
8840/0/493
0.980
8834/0/421
1.251
10514/0/532
0.992
9339/0/519
0.958
GOF on F2
final R indices
R1 ) 0.0302
wR2 ) 0.0672
0.716 and -0.796
R1 ) 0.1126
wR2 ) 0.2920
7.443 and -4.948
R1 ) 0.0658
wR2 ) 0.1363
1.401 and -2.168
R1 ) 0.0566
wR2 ) 0.1384
1.157 and -1.701
largest diff. peak
and hole (e‚Å-3
)
are slightly longer than the analogous distances for the
hydrido complex [2.313(1)-2.343(1) Å]. Pd-Peq bond
distances for 8 are similar to those for complex 1.16 The Pt-
Cl and Pd-Cl bond distances for 2 and 8, respectively, are
coincident and slightly longer than Pt-Cl (2.364(2) Å) and
Pd-Cl (2.358(2) Å) distances in square-planar complexes
of the type [M(triphos)Cl]2[SnPh2Cl4] (M ) Pd, Pt).31 The
Pt-C distance for 5 is in the same range of distances found
for other heterobimetallic cyano complexes such as [PtRh-
(µ-dppm)2(CNBut)2(CN)2](PF6) and [AgPt(dppm)2(CN)2(CF3-
SO3)] [dppm ) bis(diphenylphosphino)methane] [2.02(2)-
2.035(2) and 2.00(2) Å].22 The C-N distances in CN- ligand
and counterion are 1.14(2) and 0.96(6) Å, respectively,
revealing, as expected, a decrease in the CN bond order for
CN- ligand compared with the counteranion. This is a
consequence of the significant π-acceptor ability of the
ligand.
The Pt-Sn bond length for 7 (2.5741(2) Å) is longer than
the average axial Pt-Sn distances in [Pt(SnCl3)5]3- (2.553
Å), almost coincident with the average equatorial Pt-Sn
lengths (2.572 Å) in the same five-coordinate complex32a and
slightly shorter than the Pt-Sn bonds in square-planar
complexes such as trans-[PtH(SnCl3)(PPh3)2] (2.601(1) Å)32b
(32) (a) Nelson, J. H.; Alcock, N. W. Inorg. Chem. 1982, 21, 1196. (b)
Go´mez, M.; Muller, G.; Sainz, D.; Sales, J. Organometallics 1991,
10, 4036.
(31) Garc´ıa-Seijo, M. I.; Castin˜eiras, A.; Mahieu, B.; Ja´nosi, L.; Berente,
Z.; Kolla´r, L.; Garc´ıa-Ferna´ndez, M. E. Polyhedron 2001, 20, 855.
4440 Inorganic Chemistry, Vol. 41, No. 17, 2002

Tris[2-(diphenylphosphino)ethyl]phosphine Complexes
Table 4. Selected Distances (Å) and Angles (deg) for Complexes
(2)‚6H2O, (5)‚H2O, (7)‚CHCl3, and (8)‚4H2O
Table 5. Hydroformylation of Styrene with Pt Complexes Containing
PP3
a
(2)‚6H2Oa (5)‚H2Oa,b
(7)‚CHCl3
(8)‚4H2Oa
a
catalyst
R time (h) conversion (%) Rc (%)b
R
br (%)c
d
M(1)-P(1)
2.2214(2) 2.259(5) 2.294(3)
2.3404(2) 2.377(5) 2.382(3)
2.4008(2) 2.359(4) 2.378(3)
2.3672(2) 2.344(5) 2.362(3)
2.4201(2) 2.029(2) 2.5741(2)
2.217(2)
2.419(2)
2.400(2)
2.469(2)
2.4202(2)
[Pt(PP3)Cl]Cl + SnCl2
140
110
50
2
11
12
38
42
99
63
62
75
d
M(1)-P(2)
[Pt(PP3)Cl]Cl + 5 SnCl2
[Pt(PP3)(SnCl3)](SnCl3)
M(1)-P(3)
M(1)-P(4)
a
M(1)-Xa
Reaction conditions: Pt/styrene ) 1/4000; 100 °C; p(CO/H2 ) 1/1)
b
Sn(1/2)-Cl(1/4)
Sn(1/2)-Cl(2/5)
Sn(1/2)-Cl(3/6)
Sn(1)-C(43)
2.355(4)/2.494(4)
) 100 bar; toluene solvent. Rc ) Chemoselectivity toward hydroformy-
c
2.370(4)/2.479(5) 2.608(3)
2.344(4)/2.506(5) 2.566(2)
2.145(9)
lation: (B + C)/(B + C + D) × 100. Rbr ) regioselectivity toward
d
branched aldehyde: B/(B + C) × 100. ∼30% of the substrate (styrene)
polymerized.
P(1)-M(1)-P(2)
P(1)-M(1)-P(3)
P(1)-M(1)-P(4)
P(2)-M(1)-P(3)
P(2)-M(1)-P(4)
P(3)-M(1)-P(4)
P(1)-M(1)-Xa
84.40(4) 84.22(2) 84.34(2)
83.40(8)
84.29(8)
83.59(7)
129.67(8)
112.68(8)
114.09(8)
178.56(9)
96.87(7)
94.46(7)
83.59(7)
84.59(5) 84.96(17) 84.21(2)
85.40(4) 84.06(2) 83.75(2)
119.01(4) 119.51(2) 117.46(2)
124.80(4) 123.06(2) 120.13(2)
113.74(4) 114.60(2) 119.28(2)
177.30(5) 178.4(5) 178.44(8)
tetrahedral geometry. The pyramidalization of SnCl3- coun-
teranion is evident from its Cl-Sn-Cl angles which are
below 95°.
The dianion [SnPh2Cl4]2- for 8 shows a trans-octahedral
geometry with the phenyl rings in coplanarity. The angles
trans C-Sn-C or Cl-Sn-Cl [180.00(11)°], and C-Sn-
Cl [∼90.0°], confirm this trans-octahedral arrangement.
2.5. Hydroformylation of Styrene with Pt Complexes
Containing PP3 as Catalysts. Styrene (A) as the model
substrate was reacted either in the presence of the platinum
precursor complex [Pt(PP3)Cl]Cl (2) and anhydrous tin(II)
chloride or in the presence of the “preformed” catalyst [Pt-
(PP3)(SnCl3)](SnCl3) (7) with CO/H2 (1/1) at 100 °C and a
pressure of 100 bar (Table 5).
P(2)-M(1)-Xa
93.13(4) 97.2(5)
97.57(5) 95.1(5)
95.16(5) 94.6(5)
96.30(8)
96.74(9)
94.70(8)
P(3)-M(1)-Xa
P(4)-M(1)-Xa
Pt(1)-Sn(1)-Cl(1)
Pt(1)-Sn(1)-Cl(2)
Pt(1)-Sn(1)-Cl(3)
Cl(1/4)-Sn(1/2)-Cl(2/5)
Cl(1/4)-Sn(1/2)-Cl(3/6)
Cl(2/5)-Sn(1/2)-Cl(3/6)
Cl(2)-Sn(1)-Cl(2)#
C(43)-Sn(1)-C(43)#
C(43)-Sn(1)-Cl(2)
C(43)-Sn(1)-Cl(3)
119.09(2)
118.62(2)
120.53(1)
97.57(2)/92.15(2)
99.40(2)/93.48(2)
96.80(2)/94.41(2) 90.23(9)
180.00(2)
180.0(7)
90.3(3)
89.7(3)
a
M ) Pt (2, 5, 7), M ) Pd (8); X ) Cl(1) (2, 8), X ) C(43) (5), X )
b
Sn (1) (7). C(43)-N(1) ) 1.14(2) Å, C(44)-N(2) ) 0.96(6) Å.
CO/H2
PhCHdCH2
8
and PtI(SnCl3)(bdpp) [bdpp ) 2,4-bis(diphenylphosphino)-
pentane] (2.6113(2) Å).5 This metal-tin bond is shorter than
the sum of the appropriate atomic radii, in agreement with
similar trends observed for other metal-SnCl3 [metal ) Ru-
A
PhCH CH CHO PhC H
5
PhCH(CH )CHO
+
+
2
2
2
3
C
D
B
-
(II), Ir(I), Pd(I)] complexes.32a All Sn-Cl distances in SnCl3
The highest activity among the systems was found for the
“preformed” catalyst [Pt(PP3)(SnCl3)](SnCl3) (7) followed
by the in situ prepared catalyst (2 + 5 equiv of SnCl2). (It
has to be mentioned that the hydroformylation under harsh
conditions and elevated reaction times is accompanied by
polymerization of the substrate, as well as the dimerization
of the aldehyde regioisomers B and C (in smaller extent)
resulting in low reproducibility of the reaction.) The regio-
and chemoslectivities were rather low when in situ systems
were used. However, excellent aldehyde selectivity was
obtained in the presence of the “preformed” catalyst 7.
In general, Pt-PP3 systems show very low catalytic
activities compared to those of platinum-diphosphine tin-
(II) chloride systems4,32 and especially to those of widely
used rhodium-containing systems.33 It is presumably due to
the four phosphorus donor atoms of the ligand blocking the
coordination sites. The absence of easily available vacant
sites substantially hinders the facile activation of the reactants
(carbon monoxide, olefin).
-
ligand are shorter than those corresponding to SnCl3
counteranion. Despite the high calculated density for 7 (1.851
Mg/m3) compared to 2, 5, and 8 (1.570, 1.426, and 1.500
Mg/m3, respectively), the crystal packing does not impose
any unusual platinum-tin or tin-tin intermolecular contacts.
The Sn-Cl and Sn-C distances for [SnPh2Cl4]2- in 8 are
in agreement with the values found in [Pd(triphos)Cl]2[SnPh2-
Cl4].
The average value for P-M-P angles involving Pax
(84.30°) and Peq (119.0°) reveals in all structures a light
distortion from the trigonal bipyramidal geometry. The
chelate bite angles Pax-M-Peq below 90° are presumably a
consequence of the chelate strain of the five-membered
P-C-C-P chelate rings formed. The angles P(1)-M(1)-
P(3) (84.21(2)°) and P(1)-M(1)-P(4) (83.75(2)°) for 7 are
smaller than the same angles for 5 (and 2). This is in
accordance with phosphorus donors P(3) and P(4) (and their
phenyl rings) bent back more in the more sterically bulky
The hydrofomylation activity of the coordinatively satu-
rated 18-electron complex, [Pt(PP3)(SnCl3)]+, can be ex-
plained by two reasons. (i) The complete dissociation10b of
the trichlorostannate ligand provides a vacant coordination
site. This fact is known from mechanistic studies carried out
-
SnCl3 coordinated complex producing the unexpected
increase in the Pt-Pax distance. The averages for P-M-X
angles (X ) Cl, C, Sn) (178.20° and 94.62° for Pax-M-X
and Peq-M-X, respectively) are also in accordance with a
certain distortion. While the Pt-Sn-Cl angles for 7 are ca.
120°, the Cl-Sn-Cl angles for SnCl3- ligand are above 95°
showing a distortion for the PtSnCl3 moiety from the
(33) Ojima, I.; Tsai, Ch-I.; Tzamarioudaki, M.; Bonafoux, D. The hydro-
formylation reaction. In Organic Reactions; Overman, L. E., Ed.;
Wiley & Sons: New York, 2000; Vol. 56, Chapter 1, pp 1-354.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4441

Ferna´ndez et al.
-
by high-pressure NMR.34 The importance of the SnCl3
Nicolet IMPACT 400 with a DTGS detector and a Mattson Cygnus
100 spectrophotometer. The bands are reported as s ) strong, m
) medium, b ) broad. 31P{1H}, 195Pt, and 119Sn NMR spectra were
recorded on a Bruker AMX500 spectrometer at 202.46, 107.52,
and 186.5 MHz, respectively. 13C and some 31P{1H} NMR spectra
were recorded on a Varian Inova 400 spectrometer at 100.6 and
161.9 MHz, respectively. Chemical shifts are reported relative to
external standard SiMe4 (13C), 85% H3PO4 (31P), 1 M Na2PtCl6
acting as a counterion has been proved in elementary steps
such as carbon monoxide activation, insertion to Pt-alkyl
bond, and aldehyde forming step. (However, to the best of
our knowledge, the role of SnCl2 “cocatalyst” in olefin
activation is still uncertain, and no mechanistic evidence has
been reported.) (ii) The “arm off” dissociation of the PP3
ligand leads to vacant coordination site(s), too. This effect
has been observed in case of HRh(CO[η3-MeC(CH2PPh2)3]
precursor under even less severe conditions (30 bar, room
temperature).35 The branched selectivities of 60-75% typical
for various Pt-diphosphine systems, obtained also by the
Pt-PP3 systems, might be due to the dissociation of two
phosphorus donors, that is, PP3 acting as a bidentate ligand
in square-planar catalytic intermediates.
In case of the in situ systems, the insertion of SnCl2 into
the Pt-Cl bond is not quantitative in noncoordinating toluene
solvent; so, lower activity and different activation modes for
the reactants could be expected. Although in DMF complete
dissociation of SnCl3 can be observed, much less active
systems have been obtained because of solvent coordination.
(
195Pt), and SnMe4 (119Sn); δ ) chemical shift in ppm, s ) singlet,
d ) doublet, t ) triplet, dd ) doublet of doublets, dt ) doublet of
triplets, q ) quartet, dq ) doublet of quartets, m ) multiplet, bs
) broad signal, J ) coupling constant in hertz. Conductivities were
measured at 25 °C using 10-3 M solutions in DMF on a WTW
model LF-3 instrument.
4.2. Preparations and Titrations. Preparation of [Pd(PP3)-
Cl]Cl (1). Complex 1 was prepared as (1)‚4H2O. A suspension of
PdCl2 (0.0158 g, 0.2922 mmol) and NaCl (0.0342 g, 0.5844 mmol)
in H2O (14 mL) was heated on a water bath (80 °C) until a clear
solution was obtained. This was allowed to cool to room temper-
ature, and a solution of PP3 (0.1959 g, 0.2922 mmol) in CHCl3 (30
mL) was added dropwise. The mixture was stirred for 24 h at room
temperature, and CHCl3 was removed in vacuo to leave a red
precipitate in the aqueous phase. It was filtered off, washed with
H2O and Et2O, and dried in vacuo. Yield: 92%, mp 260 °C.
Found: C, 55.0; H, 5.4. C42H50P4O4PdCl2 requires: C, 55.6; H,
-
3. Conclusions
5.6%. IR νmax/cm-1: (Pd-Cl) 348m. MS (FAB): m/z 811 (M+
-
The five-coordinate complexes [M(PP3)Cl]+ (M ) Pd, Pt)
exhibit a trigonal bipyramidal structure both in solution and
solid state where PP3 acts as tetradentate chelating ligand
with the central phosphorus in axial position trans to Cl and
the terminal ones in the equatorial plane of the bipyramid.
The reactions of these chloro complexes with KCN or SnCl2
maintain their geometries leading to the formation of new
M-C or M-Sn bonds in the axial positions. However, the
reactions of [M(PP3)Cl]Cl with SnPh2Cl2 occur with forma-
tion of [SnPh2Cl4]2- anions. The isolation of complexes
[M(PP3)(SnCl3)](SnCl3) as solids by addition of SnCl2 to the
precursors requires the presence of PPh3. The tin dichloride
insertion and elimination in chloroform was more favored
for Pd(II) than for Pt(II). Although the catalytic activity for
solutions of the “preformed” complex [Pt(PP3)(SnCl3)]-
(SnCl3) in the hydroformylation of styrene is very low, the
potential formation of a vacant site by dissociation may be
responsible for its excellent aldehyde selectivity.
Cl, 55.6%); 776 (M+ - 2Cl, 2.0%); 563 (M+ - 2Cl -C2H4PPh2,
3.3%). 31P{1H} NMR (CDCl3): See Table 1. Λ(DMF) ) 77.1
ohm-1 cm2 mol-1
.
4.3. Preparation of [Pt(PP3)Cl]Cl (2). Complex 2 was obtained
as (2)‚2H2O. To a solution of K2PtCl4 (0.1729 g, 0.4160 mmol) in
H2O (15 mL) was added dropwise a solution of PP3 (0.2793 g,
0.4160 mmol) in CHCl3 (30 mL), and the mixture was stirred for
12 h. CHCl3 was removed in vacuo to leave a yellow precipitate
in the aqueous phase which was filtered off, washed with H2O and
Et2O, and dried in vacuo. Suitable crystals for X-ray diffraction
were obtained from a solution of the complex in CHCl3. Yield:
85%, mp 281 °C. Found: C, 51.4; H, 4.7. C42H46P4O2PtCl2
requires: C, 51.8; H, 4.7%. IR νmax/cm-1: (Pt-Cl) 351m. MS
(FAB): m/z 900 (M+ - Cl, 45.1%); 865 (M+ - 2Cl, 1.3%); 652
(M+ - 2Cl -C2H4PPh2, 1.2%). 31P{1H} NMR (CDCl3): See Table
1. 195Pt NMR (DMSO-d6): δ -4373 (m) (overlapped dq). Λ(DMF)
) 72.1 ohm-1 cm2 mol-1
.
4.4. Titrations of (1)‚4H2O and (2)‚2H2O with KCN, SnCl2,
SnPh2Cl2, and PPh3. To a solution of complexes (1)‚4H2O and
(2)‚2H2O in CDCl3 were added solutions of KCN and SnPh2Cl2 in
CD3OD or PPh3 in CDCl3 in different stoichiometric ratios. The
31P{1H} NMR spectra were recorded after each addition. Tin
dichloride was added as a solid to 13 × 10-3 M solutions of (1)‚
4H2O and (2)‚2H2O in CDCl3, and the 31P{1H} NMR spectra were
recorded after stirring for 12 h. The results for titrations with SnPh2-
Cl2 and PPh3 are given in Table 1 and with SnCl2 in Figures S1-
S2 (Supporting Information).
4.5. Preparation of [Pt(PP3)(CN)]Cl [CN ) 12CN (3); 13CN
(3*)]. Complex [Pt(PP3)Cl]Cl‚2H2O (0.4683 g, 0.5 mmol) was
added to a solution of KCN (3) or K13CN (3*) (0.5 mmol) dissolved
in CH3OH (15 mL). The powder did not dissolve completely but
was kept in suspension at 50 °C with constant stirring for 10 h.
The white powderlike crystals were filtered, washed with water,
methanol, and ether, and dried. The crystallization was carried out
in a benzene/methanol mixture. Yield: 90%, mp 276 °C. Found:
C, 56.0; H, 4.8; N, 1.6. C43H42NP4PtCl requires: C, 55.7; H, 4.6;
N, 1.5%. IR νmax/cm-1: (12CN) 2123m, (13CN) 2077m. 31P{1H}
4. Experimental Section
4.1. General Procedures. Dichloromethane was redistilled under
nitrogen over CaCl2. Potassium tetrachloroplatinate(II), palladium-
(II) chloride, and tin(II) chloride were purchased from Strem
Chemicals, and tris[2-(diphenylphosphino)ethyl]phosphine and
diphenyltin(IV) chloride, from Aldrich. Potassium cyanide was
purchased from Panreac, and potassium cyanide-13C, from Cam-
bridge Isotope Laboratories. Microanalyses were performed on a
Fisons Instrument EA 1108 CHNS-O. Fast atom bombardment
(FAB) mass spectra were obtained in a Micromass Autospec
spectrometer using 3-nitrobenzyl alcohol as the matrix. Infrared
spectra were recorded at ambient temperature as KBr pellets (4000-
500 or 4000-400 cm-1) and Nujol mulls (500-100 cm-1) on a
(34) To´th, I.; Ke´gl, T.; Elsevier, C. J.; Kolla´r, L. Inorg. Chem. 1994, 33,
5708.
(35) Kiss, G.; Horva´th, I. T. Organometallics 1991, 10, 3798.
4442 Inorganic Chemistry, Vol. 41, No. 17, 2002

Tris[2-(diphenylphosphino)ethyl]phosphine Complexes
NMR (CDCl3): See Table 1. 13C NMR (CDCl3) (3*): δ 105.5
equiv) in CD3OD. Suitable crystals for X-ray diffraction of (8)‚
4H2O appeared in the mixture solution after some days. 31P{1H}
NMR (CDCl3/CD3OD ) 1/1): See Table 1.
1
2
2
(dq), J(195Pt, 13C) ) 911 Hz, J(31Pax, 13C) ) 102 Hz, J(31Peq,
13C) ) 15 Hz.
4.6. Preparation of [Pd(PP3)(CN)](CN) (4). This compound
was prepared as (4)‚CHCl3. To a solution of [Pd(PP3)Cl]Cl‚4H2O
(0.1068 g, 0.1259 mmol) in CHCl3 (25 mL) was added a solution
of KCN (0.0164 g, 0.2519 mmol) in CH3OH (16 mL), and
immediately, the color of the solution changed from bright red to
yellow. The mixture was stirred for 24 h at ambient temperature,
and after that, Et2O (80 mL) was added to precipitate a yellow
solid, which was filtered off and dried in vacuo. Yield: 91%, mp
285 °C. Found: C, 57.5; H, 4.5; N, 3.1. C45H43N2P4PdCl3
requires: C, 57.0; H, 4.6; N, 3.0%. IR νmax/cm-1: (CN) 2124m.
MS (FAB): m/z 802 (M+ - CN, 24.4%). 31P{1H} NMR (CDCl3):
See Table 1.
4.11. X-ray Crystallography. Orange prisms of (2)‚6H2O,
yellow plates of (5)‚H2O, yellow needles of (7)‚CHCl3, and red
plates of (8)‚4H2O were mounted on glass fibers and used for data
collection. Crystals data were collected at 293(2) K, using a Bruker
SMART CCD 1000 diffractometer. Crystals of (5)‚H2O were of
lower quality than those of (2)‚6H2O, (7)‚CHCl3, and (8)‚4H2O;
this lowered the precision of the crystal structure, which can be
taken to establish chemical connectivity. Graphite monochromated
Mo KR radiation was used throughout. The data were processed
with SAINT,36 and empirical absorption correction was made using
SADABS.37 The structures were solved by direct methods using
the program SIR9238 and refined by full-matrix least-squares
techniques aginst F2 using SHELXL-97.39 Positional and anisotropic
atomic displacement parameters were refined for all non-hydrogen
atoms. Hydrogen atoms were placed geometrically, and positional
parameters were refined using a riding model. Atomic scattering
factors were obtained with the use of International Tables for X-ray
Crystallography.40 Molecular graphics were obtained from ORTEP-3
for Windows.41
4.12. Hydroformylation Experiments. In a typical experiment,
a solution of 0.025 mmol of [Pt(PP3)Cl]Cl and 0.125 mmol of SnCl2
in 30 mL of toluene containing 0.1 mol of styrene was transferred
under argon into a 150 mL stainless steel autoclave. The reaction
vessel was pressurized to 100 bar total presure (CO/H2 ) 1/1) and
placed in an oil bath kept at 100 °C, and the mixture was stirred
with a magnetic stirrer. The pressure was monitored throughout
the reaction. After cooling and venting of the autoclave, the pale
yellow solution was removed and immediately analyzed by GC.
The same procedure was used for hydroformylation experiments
with [Pt(PP3)Cl]Cl/SnCl2 in 1/1 ratio and with [Pt(PP3)(SnCl3)]-
(SnCl3).
4.7. Preparation of [Pt(PP3)(CN)](CN) (5). The complex was
obtained as (5)‚CHCl3. To a solution of [Pt(PP3)Cl]Cl‚2H2O (0.1095
g, 0.1169 mmol) in CHCl3 (30 mL) was added a solution of KCN
(0.0152 g, 0.2338 mmol) in CH3OH (15 mL) dropwise, and
immediately, the color of the solution turned from yellow to
colorless. The mixture was stirred for 12 h, and after that, Et2O
was added to precipitate a white solid, which was filtered off and
dried in vacuo. Suitable crystals for X-ray diffraction were obtained
from a mixture of [Pt(PP3)Cl]Cl‚2H2O and KCN in CDCl3/CD3-
OD. Yield: 82%, mp > 300 °C. Found: C, 52.0; H, 4.0; N, 2.6.
C45H43N2P4PtCl3 requires: C, 52.1; H, 4.2; N, 2.7%. IR νmax/cm-1
:
(CN) 2122m. MS (FAB): m/z 891 (M+ - CN, 47.5%). 31P{1H}
NMR (CDCl3): See Table 1. 195Pt NMR (DMSO-d6): δ -4768
(brs).
4.8. Preparation of [Pd(PP3)(SnCl3)](SnCl3) (6). The compound
was prepared as (6)‚CHCl3. To a solution of [Pd(PP3)Cl]Cl‚4H2O
(0.1080 g, 0.1274 mmol) in CHCl3 (25 mL) was added a solution
of PPh3 (0.0241 g, 0.1274 mmol) in CHCl3 (5 mL). After that, a
solution of SnCl2 (0.0668 g, 0.2548 mmol) in CH3OH (15 mL)
was added, and the mixture was stirred for 24 h during which an
orange precipitate was formed. Et2O (100 mL) was added to
precipitate completely the solid that was filtered off and dried in
vacuo. Yield: 81%, mp 212 °C. Found: C, 38.8; H, 3.4. C43H43P4-
Sn2PdCl9 requires: C, 38.3; H, 3.2%. IR νmax/cm-1: (Sn-Cl)as
290m,br, 249m,br; (Sn-Cl)coord 322s. MS (FAB): m/z 1003 (M+
- SnCl3, 0.5%); 503 (M+ - 2SnCl3 -C2H4PPh2, 1.6%). 31P{1H}
NMR (CDCl3): See Table 1. 119Sn NMR (CDCl3): δ -65.4 (brs).
Acknowledgment. We thank Xunta de Galicia (Spain)
for financial support and the Unidade de Raios X (RIAIDT)
of the University of Santiago de Compostela (Spain) for the
performance of intensity measurements of crystals for
complexes 2, 5, 7, and 8. L.K. thanks the Hungarian Research
Foundation for financial support (OTKA 0335047).
Supporting Information Available: A crystallographic infor-
mation file (CIF), containing structural data for 2, 5, 7, and 8.
Figures S1 and S2 showing the titrations of complexes 1 and 2
with 1 and 2 equiv of SnCl2. Figure S3 showing the 31P{1H} NMR
spectrum for solutions in CDCl3 + DMF of the solid obtained from
the reaction (2 + 4 equiv SnCl2). This material is avaliable free of
charge via the Internet at http://pubs.acs.org.
Λ(DMF) ) 77.0 ohm-1 cm2 mol-1
.
4.9. Preparation of [Pt(PP3)(SnCl3)](SnCl3) (7). Complex 7
was isolated as (7)‚CHCl3. To a solution of [Pt(PP3)Cl]Cl‚2H2O
(0.1380 g, 0.1473 mmol) in CHCl3 (35 mL) was added a solution
of PPh3 (0.0386 g, 0.1473 mmol) in CHCl3 (6 mL). After that, a
solution of SnCl2 (0.0559 g, 0.2946 mmol) in CH3OH (8 mL) was
added, and the mixture was stirred for 24 h during which a yellow
precipitate was formed. Et2O (90 mL) was added to precipitate
completely the solid that was filtered off and dried in vacuo. Suitable
crystals for X-ray diffraction were obtained from a CDCl3 solution.
Yield: 90%, mp 250 °C. Found: C, 35.4; H, 3.2. C43H43P4Sn2-
PtCl9 requires: C, 35.9; H, 3.0%. IR νmax/cm-1: (Sn-Cl)as 290m,b,
247m,b; (Sn-Cl)coord 323s,b. MS (FAB): m/z 563 (M+ - 2SnCl3
-C2H4PPh2, 0.1%). 31P{1H} NMR (CDCl3 or CDCl3/DMF )
1/1): See Table 1. 119Sn NMR (CDCl3) ) δ -66.6 (brs). Λ(DMF)
IC020006K
(36) SMART and SAINT, Area Detector Control and Integration Software;
Bruker Analytical X-ray Instruments Inc.: Madison, WI, 1997.
(37) Sheldrick, G. M. SADABS, Program for Empirical Absorption
Correction of Area Detector Data; University of Goettingen: Goet-
tingen, Germany, 1997.
(38) Altomare, A.; Cascatano, G.; Giacovazzo, C.; Guagliardi, A. SIR92.
J. Appl. Crystallogr. 1993, 26, 343.
(39) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal
Structures; University of Goettingen: Goettingen, Germany, 1997.
(40) International Tables for X-ray Crystallography; Kluwer Academic
Publishers: Dordrecht, The Netherlands, 1995; Vol. C.
) 75.0 ohm-1 cm2 mol-1
.
4.10. Preparation of [Pd(PP3)Cl]2[SnPh2Cl4] (8). To a solution
of (1)‚4H2O in CDCl3 was added a solution of SnPh2Cl2 (6 mol
(41) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4443