the protonated or alkylated pta ligands are stretched compared to
the unsubstituted pta (average 1.495 Å in 8, 9 and 10 as opposed
to 1.473 Å), while the other two (P)C–N distances are not affected
by the protonation or alkylation (1.472 Å vs. 1.473 Å). Based on
these data it can be concluded that protonation or alkylation of one
of the nitrogen atoms in pta led to the same slight distortion of the
phosphatriazaadamantane skeleton.
to KI standard solutions). Purification included precipitation of
ptaMe+tos− by addition of 15 mL ethyl acetate to a solution of 2.2 g
of the raw product in 3 mLof methanol with stirring (97% recovery)
followed by another ion exchange as above. The product of the
second ion exchange procedure contained no iodide above the ICP
detection limit (0.05 ppm). 1H-NMR (D2O, rt): /ppm 2.35 (s, 3H,
CH3, tos); 2.68 (s, 3H, CH3, ptaMe); 3.73–3.94 (m, 4H, P–CH2–N);
4.25 (d, 2H, P–CH2–N+), 2JP–H = 5.4 Hz; 4.36–4.55 (m, 2H, N–CH2–
N); 4.74–4.88 (m, 4H, N–CH2–N+); 7.35 (d, 2H,–CH–C(−)–CH3),
−
3JH–H = 7.2 Hz; 7.6 Hz (d, 2H,–CH–C(−)–SO3 ), 3JH–H = 7.2 Hz. 31P-
NMR (D2O, r.t.): /ppm −83.30 (s).
trans-[Ru(H2O)4(ptaMe)2](tos)4·2H2O, 8. This was obtained by
slow crystallization at room temperature from a solution of 400 mg
(1.91 mmol) ptaMe+tos− and 180 mg (0.33.mmol) [Ru(H2O)6](tos)2
in 3 mL H2O; the pH was adjusted to 5.5 by addition of Htos. The
solution was stirred for 3 min and then left to stand for one day. The
yellow-brown crystals (307 mg, 75.9%) were isolated by filtration
and submitted for X-ray structure determination. 31P-NMR (H2O,
rt): /ppm −23.3 (s). Analysis for RuC42H70P2N6S4O18, M = 1238.30
(found/required): C 40.81/40.74, H 5.84/5.70, N 6.61/6.79.
Scheme 4 Structure of ptaMe+.
Relevance to catalysis. In situ formation of homogeneous
catalysts from suitable metal-containing precursors and ligands
(often phosphines) is a widely used practice in catalysis. For
example, in a study on the hydrogenation of benzaldehyde the
catalyst was prepared by mixing solutions of [Ru(H2O)6]2+ and
pta in several molar ratios and mechanistic conclusions were
drawn from the dependence of the reaction rate on the [pta]:[Ru]
ratios.15 Similarly, hydrodehalogenation reactions were catalysed
with mixtures of [Ru(H2O)6]2+ and pta or mtppms.16 In the present
study we have shown that in the case of the sulfonated triphenyl-
phosphine complexes the catalytically important [Ru(H2O)5L]2+
and [Ru(H2O)4L2]2+ complexes are formed instantaneously from
[Ru(H2O)6]2+ and an excess of L. Conversely, the reaction of
[Ru(H2O)6]2+ and pta first leads mainly to [Ru(H2O)5(pta)]2+ which
is only slowly replaced by cis- and trans-[Ru(H2O)4(pta)2]2+ and
those remain by far the major species even in a large excess of
pta. Although under the catalytic conditions applied in refs.15
and 16 the complex formation equilibria may be shifted relative
to the conditions of this study, the formation of higher coordinated
species must be dealt with care. In situ preparation of the catalysts
starting with [Ru(H2O)6]2+ and water-soluble phosphines can be
practical but the actual composition of the catalytic species may not
be directly related to the [metal]:[ligand] ratio employed in their
synthesis.
trans-[Ru(H2O)4(ptaH)2](tos)4·2H2O, 9. This was obtained by
reacting 300 mg (1.91 mmol) pta in 3 mL H2O acidified to pH 4
(Htos) with 180 mg (0.33 mmol) [Ru(H2O)6](tos)2. The reaction
mixture was stirred for 3 min then left to stand for one day, after
which 347 mg (88%) of the yellow-brown crystals were collected.
X-ray quality yellow crystals were deposited during long standing
of a strongly acidic (Htos) solution of the complex. 31P-NMR
(D2O, rt): /ppm −31.4 (s). Analysis for RuC40H66P2N6S4O18,
M = 1210.25, (found/required): C 39.96/39.70, H 5.46/5.50, N
7.04/6.94.
trans-mer-[RuI2(H2O)(ptaMe)3]I3·2H2O, 10. The following
procedure is faster and yields a cleaner product than the previously
published23 method. 488 mg (1.63 mmol) ptaMe+I− and 108 mg
(0.65 mmol) KI in 6 mLwater was reacted with 180 mg (0.33 mmol)
[Ru(H2O)6]2+(tos)2 at room temperature. The solution was stirred
for 3 min then left to stand for one day yielding 351 mg (82%) of
the product as strongly pink crystals. 31P-NMR (D2O, rt): /ppm
2
2
10.6 (t), JP–P = 33.8 Hz; −37.1 (d), JP–P = 34.5 Hz. Analysis for
RuC21H51P3N9I5O3, M = 1306.29 (found/required): C 19.31/18.11,
H 3.94/3.56, N 9.65/9.07.
Experimental
[Ru(H2O)6](tos)2,11 pta,33 (ptaMe+I−),33 mtppms-Na,26 ptppms-K34
and mtppts-Na335 have been prepared according to the literature. All
reagents were high purity products of Aldrich and used as received.
Manipulations with the air-sensitive Ru-complexes were done in an
inert atmosphere using Schlenk-techniques. NMR measurements
were run on Bruker AC 200 MHz, Bruker AM 360 MHz and
Bruker DRX 400 MHz spectrometers. The spectra were referenced
to 2,2-dimethyl-2-silapentane-5-sulfonate (dss) sodium salt (1H)
and to 85% H3PO4 (31P) and were analyzed by the WINNMR
software. 17O spectra were obtained using 10% 17O-enriched water
(Cambridge Isotope Laboratories). Microanalyses were carried out
by Analytische Laboratorien (Lindau, Germany) and Analytical
Services, ICMB, EPFL (Lausanne).
pH-potentiometric studies. The acid dissociation constant of
ptaH+ was determined by titration with 0.2113 M HCl of solutions
of approximately 30 mg pta in 10 mL 0.01 M KCl under inert
atmosphere at 25.0 °C using an ABU 91 autoburette (Radiometer).
The data were analyzed with the SUPERQUAD36 program resulting
in a pKa = 5.89 ± 0.01.
X-ray structural determinations. Data collection was
performed using an Enraf Nonius MACH3 diffractometer at room
temperature with Mo-K radiation ( = 0.71069 Å). Structures
were determined using direct methods with the SIR-92 package37
and refined using the SHELX9738 program. Hydrogen atoms
were placed into geometric positions in the case of C–H atoms or
found at the difference electron density map in the case of O–H
and N–H atoms. Remaining electron densities are close to heavy
atoms i.e. iodine or ruthenium. All structures are stabilized by
extensive hydrogen bond networks. In structure 2 the phenyl rings
in symmetry related tosylates are disordered perpendicular to each
other and the coordinated water molecules are also disordered over
two positions with an occupancy of 60/40. These disorders resulted
in remaining errors i.e. acceptor contacts in the final refinement. The
publication material was prepared using the WINGX suite,39 and
analysis of H-bond network and other crystallographic calculations
were performed using the PLATON program.40
Preparation of ligand and Ru(II) complexes
ptaMe-p-toluenesulfonate (ptaMe+tos−). This was obtained
by ion exchange of ptaMe+I− on a Molselect DEAE-25 (Reanal,
Hungary) column in tosylate form. 1 g of ptaMe+I− was dissolved
in 10 mL H2O and passed very slowly through a column of 2.5 g
Molselect DEAE-25 tosylate. The column was eluted with a further
50 mL of H2O. The pH of the combined eluates was adjusted
to neutral with a few drops of aqueous Htos. This solution was
concentrated to 2–5 mL on a rotary evaporator and added drop by
drop to 50 mL of rapidly stirred acetone; stirring was continued
for 2 h. The resulting white precipitate was filtered, washed with
acetoneanddried.Yield980 mg(85%).Thiscompoundstillcontains
0.93% w/w I− as shown by ICP-AAS determinations (Perkin Elmer
OPTIMA 3300 DV, = 182.976 nm and 206.163 nm, calibrated
CCDC reference numbers 236511–236513.
graphic data in CIF or other electronic format.
D a l t o n T r a n s . , 2 0 0 4 , 2 3 3 6 – 2 3 4 0
2 3 3 9
Kovacs, Jozsef
