Synthesis and characterization of [RuCl3(P-P)(H2O)] complexes; P-P = achiral or chiral, chelating ditertiary phosphine ligands

Article abstract of DOI:10.1021/ic990130c

The reaction of the dinuclear [RuCl₂(dppb)]₂(μ-dppb) (dppb = 1,4-bis(diphenylphosphino)butane) with Cl₂ in MeOH for ～30 min at room temperature gives the bright-red solid mer-RuCl₃dppb)(H₂O) (1); Cl₂ treatment for ～10 min affords the red-brown, mixed valence complex [RuCl(dppb)]₂(μ-Cl)₃ (2). Controlled bulk coulometric reduction of 50% of the content of a CH₂Cl₂ solution of 1 also produces 2, formed by the reaction of 1 with RuCl₂(dppb) produced in situ during the electrolysis. Complexes 1 and 2 were characterized by spectroscopic techniques [including electron spin resonance (ESR)], magnetic moments and cyclic voltammetry, and the structure of 1 was determined by X-ray diffraction. The structure shows that the aquo ligand forms hydrogen bonds with two cis-chlorine ligands of the neighboring molecule of the complex; this interaction gives rise to exchange coupling between two Ru(III) centers that is reflected in the ESR spectrum. A species 3 analogous to 1 has been obtained with the diop ligand [diop = (2R,3R)- or (2S,3S)-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane], on using RuCl₂(diop)(PPh₃) or [RuCl(diop)]2(μ-Cl)₃ as precursors. The RuCl₃(P-P)L complexes (P-P = dppb, diop; L = dimethyl sulfoxide, MeOH) are readily synthesized from 1 or 3.

Full text of DOI:10.1021/ic990130c

Inorg. Chem. 1999, 38, 5341-5345
5341
Synthesis and Characterization of [RuCl3(P-P)(H2O)] Complexes; P-P ) Achiral or Chiral,
Chelating Ditertiary Phosphine Ligands
Luis R. Dinelli,† Alzir A. Batista,*,† Karen Wohnrath,† Marcio P. de Araujo,†
Salete L. Queiroz,‡ Marcos R. Bonfadini,‡ Glaucius Oliva,‡ Otaciro R. Nascimento,‡
Paul W. Cyr,§ Kenneth S. MacFarlane,§ and Brian R. James*,§
Departamento de Qu´ımica, Universidade Federal de Sa˜o Carlos, CEP 13565-905,
Sa˜o Carlos (SP), Brazil, Instituto de F´ısica e Qu´ımica, Universidade de Sa˜o Paulo, CEP 13560-970,
Sa˜o Carlos (SP), Brazil, and Department of Chemistry, The University of British Columbia,
Vancouver, BC, V6T 1Z1, Canada
ReceiVed January 29, 1999
The reaction of the dinuclear [RuCl2(dppb)]2(µ-dppb) (dppb ) 1,4-bis(diphenylphosphino)butane) with Cl2 in
MeOH for ∼30 min at room temperature gives the bright-red solid mer-RuCl3(dppb)(H2O) (1); Cl2 treatment for
∼10 min affords the red-brown, mixed valence complex [RuCl(dppb)]2(µ-Cl)3 (2). Controlled bulk coulometric
reduction of 50% of the content of a CH2Cl2 solution of 1 also produces 2, formed by the reaction of 1 with
“RuCl2(dppb)” produced in situ during the electrolysis. Complexes 1 and 2 were characterized by spectroscopic
techniques [including electron spin resonance (ESR)], magnetic moments and cyclic voltammetry, and the structure
of 1 was determined by X-ray diffraction. The structure shows that the aquo ligand forms hydrogen bonds with
two cis-chlorine ligands of the neighboring molecule of the complex; this interaction gives rise to exchange
coupling between two Ru(III) centers that is reflected in the ESR spectrum. A species 3 analogous to 1 has been
obtained with the diop ligand [diop ) (2R,3R)- or (2S,3S)-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphos-
phino)butane], on using RuCl2(diop)(PPh3) or [RuCl(diop)]2(µ-Cl)3 as precursors. The RuCl3(P-P)L complexes
(P-P ) dppb, diop; L ) dimethyl sulfoxide, MeOH) are readily synthesized from 1 or 3.
Introduction
reported was the hydrogenation of prochiral functionalized
olefins such as (Z)-acetamidocinnamic acid to 97% enantiomeric
excess using [RuCl(P-P)]2(µ-Cl)2 (P-P ) chiraphos, diop)
species.7 Subsequently, many “Ru(P-P)”-containing complexes
(but with more emphasis on P-P ) binap), such as Ru2Cl4-
(P-P)2(NEt3),2,8 Ru(OAc)2(binap),9 [RuCl(arene)(P-P)]+,10 [RuH-
(P-P)(solvent)3]+,11 Ru(P-P)(π-allyl)2,12 RuCl2(RCN)2(P-P),6,8e,13
[RuX(P-P)]2(µ-X)2 (X ) halogen),2,6,14,15 and [RuX(P-P)]2(µ-
For Ru complexes containing chelating ditertiary phosphine
ligands, the 1:1 “RuII(P-P)” moiety has been identified as the
active component of catalysts within hydrogenation reactions,
and this has motivated our ongoing interest in synthesizing Ru
complexes that contain a single diphosphine ligand per metal
center and examining their activities for the catalytic hydrogena-
tion of unsaturated organics.1,2 In cases where the catalyst
precursor contains two chelating diphosphines per Ru, the active
species in solution has been shown to contain a Ru(P-P) moiety,
and indeed the excess (P-P) ligand inhibits the catalysis.3 There
are many examples of achiral and chiral “Ru(P-P)” catalyst
systems. The [RuCl(dppb)]2(µ-Cl)2 complex catalyzes the
hydrogenation of styrene,4 the transfer hydrogenation (from
propan-2-ol) of acetophenone,5 and the H2-hydrogenation of
imines.6 The first “Ru(P-P)” enantioselective catalyst system
(7) James, B. R.; Pacheco, A.; Rettig, S. J.; Thorburn, I. S. Ball, R. G.;
Ibers, J. A. J. Mol. Catal. 1987, 41, 147.
(8) For example: (a) Ikariya, T.; Ishii, Y.; Kawano, H.; Arai, T.; Saburi,
M.; Yoshikawa, S.; Akutagawa, S. J. Chem. Soc., Chem. Commun.
1985, 922. (b) Kitamura, M.; Ohkuma, T.; Inoue, S.; Sayo, N.;
Kumobayashi, S.; Akutagawa, S.; Ohta, T.; Takaya, H.; Noyori, R. J.
Am. Chem. Soc. 1988, 110, 629. (c) Kawano, H.; Ikariya, T.; Ishii,
Y.; Saburi, M.; Yoshikawa, S.; Uchida, Y.; Kumobayashi, H. J. Chem.
Soc., Perkin Trans. I. 1989, 1571. (d) Taber, D. F.; Silverberg, L. J.
Tetrahedron Lett. 1991, 32, 4227. (e) Shao, L.; Takeuchi, K.; Ikemoto,
H.; Kawai, T.; Ogasawara, H.; Takeuchi, H.; Kawano, H.; Saburi, M.
J. Organomet. Chem. 1992, 435, 133. (f) Ohta, T.; Tonomura, Y.;
Nozaki, K.; Takaya, H.; Mashima, K. Organometallics 1996, 15, 1521.
(9) (a) Noyori, R.; Ikeda, T.; Ohkuma, T.; Widhalm, M.; Kitamura, M.;
Takaya, H.; Akutagawa, S.; Sayo, N.; Kumobayashi, H. J. Am. Chem.
Soc. 1989, 111, 9134. (b) Ohta, T.; Takaya, H.; Noyori, R. Tetrahedron
Lett. 1990, 31, 7189. (c) Ashby, M. T.; Halpern, J. J. Am. Chem. Soc.
1991, 113, 589.
(10) (a) Mashima, K.; Kusano, K.; Ohta, T.; Noyori, R.; Takaya, H. J.
Chem. Soc., Chem. Commun. 1989, 1208. (b) Fogg, D. E.; James, B.
R. J. Organomet. Chem. 1993, 462, C21.
(11) (a) Wiles, J. A.; Lee, C. E.; McDonald, R.; Bergens, S. H. Organo-
metallics 1996, 15, 3782. (b) Wiles, J. A.; Bergens, S. H. Organo-
metallics 1998, 17, 2228.
(12) (a) Geˆnet, J. P.; Mallart, S.; Pinel, C.; Juge, S.; Laffite, J. A.
Tetrahedron: Asymmetry 1991, 2, 43. (b) MacFarlane, K. S.; Rettig,
S. J.; Liu, Z.; James, B. R. J. Organomet. Chem. 1998, 557, 213.
(13) Fogg, D. E.; James, B. R. Inorg. Chem. 1997, 36, 1961.
* To whom correspondence should be addressed.
† Federal University of Sa˜o Carlos.
‡ University of Sa˜o Paulo.
§ University of British Columbia.
(1) ) Queiroz, S. L.; Batista, A. A.; Oliva, G.; Gambardella, M. T. do P.;
Santos, R. H. A.; MacFarlane, K. S.; Rettig, S. J.; James, B. R. Inorg.
Chim. Acta 1998, 267, 209 and references therein.
(2) MacFarlane, K. S.; Thorburn, I. S.; Cyr, P. W.; Chau, D. E. K.-Y.;
Rettig, S. J.; James, B. R. Inorg. Chim. Acta 1998, 270, 130.
(3) (a) James, B. R.; McMillan, R. S.; Morris, R. H.; Wang, D. K. W.
AdV. Chem. Ser. 1978, 167, 127. (b) James, B. R.; Wang, D. K. W.
Can. J. Chem. 1980, 58, 245.
(4) Joshi, A. M.; MacFarlane, K. S.; James, B. R. J. Organomet. Chem.
1995, 488, 161.
(5) Joshi, A. M.; James, B. R. J. Chem. Soc., Chem. Commun. 1989, 1785.
(6) Fogg, D. E.; James, B. R.; Kilner, M. Inorg. Chim. Acta 1994, 222,
85.
10.1021/ic990130c CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/27/1999

5342 Inorganic Chemistry, Vol. 38, No. 23, 1999
Dinelli et al.
1
shifted H NMR signal of CHCl3.24 Cyclic voltammetry (CV) experi-
X)3,2,14,16 have been used as catalysts, and these have been
synthesized generally via RuII precursors having Ru(arene),10
Ru(diene),8c,17,18 or Ru(η3-allyl) moieties,12,15,19 or via RuCl2-
(PR3)32,6,14,16 or RuCl3(PR3)2(N,N-dimethylacetamide) (R ) Ph,
p-tolyl).2,14,16 Such types of complexes are extremely effective
precursors for catalytic asymmetric hydrogenation of function-
alized prochiral olefins, dienes, and ketones,20,21 and certain
prochiral imines.22 The synthesized “RuII(P-P)” species are
typically air-sensitive in solution, and clearly it would be
advantageous for application in organic syntheses to use more
air-stable complexes as catalyst precursors. We have noted, for
example, the preferred use of the air-stable, Ru(III)/Ru(II)
mixed-valence complex [RuCl(P-P)]2(µ-Cl)3, which under H2
is reduced to the true RuII catalyst precursor [RuCl(P-P)]2(µ-
Cl)2.6 The number of reported, isolated “RuIII(P-P)” species is
very limited,16 and outside of the mixed-valence type, we are
unaware of any containing chiral, chelating diphosphines.
In this paper, we report the synthesis of RuCl3(P-P)L
complexes [L ) H2O, MeOH, dimethyl sulfoxide (DMSO), P-P
) dppb or diop], a new class of “RuIII(P-P)” species, and include
the structure of RuCl3(dppb)(H2O) (1). A new route to the
known, binuclear, mixed-valence [RuCl(dppb)]2 (µ-Cl)3 complex
(2)14,16 from [RuCl2(dppb)]2(µ-dppb)14,23 is also described.
Controlled potentiometric coulometry of 1 also produces 2.
ments were carried out at room temperature in CH2Cl2 containing 0.10
M Bu4N+ClO4 (TBAP) (Fluka Purum) using a BAS-100B/W Bio-
-
analytical Systems Instrument; the working and auxiliary electrodes
were stationary Pt foils, and the reference electrode was Ag/AgCl, 0.10
M TBAP in CH2Cl2, a medium in which ferrocene is oxidized at 0.43
V (Fc+/Fc). In the controlled potentiometric coulometry, a Pt mesh
was used as working electrode and the auxiliary electrode was separated
from the solution by a sintered glass disk. Elemental analyses were
performed in the Chemistry Departments at either the University of
Sa˜o Paulo or British Columbia.
mer-RuCl3(dppb)(H2O) (1). All reactions with Cl2 were performed
in air in a well-Ventilated fume hood. Cl2 was generated by dropwise
addition of concentrated HCl (10 mL) to ∼6.0 g of magnetically stirred,
solid KMnO4 in a three-necked flask equipped with a 50-mL addition
funnel, a stopper, and a rubber septum; the generated Cl2 was vented
through a Tygon tube equipped with a 1-mL syringe (with an 18G
needle) at each end, one end being inserted through the septum. The
syringe tip on the outlet end of the tubing was fitted to a short piece of
plastic tubing which was inserted into the reaction mixture to prevent
contamination by metal from the syringe. The bubbling rate was
maintained by adding one drop of concentrated HCl and allowing the
released Cl2 to bubble through the mixture before adding another drop
of acid. Bubbling of Cl2 through a suspension of Ru2Cl4(dppb)3 (97
mg, 0.06 mmol) in MeOH (10 mL) for 30 min at room temperature
generated a bright red precipitate, which was collected by filtration,
washed with Et2O (3 × 10 mL), and dried under vacuum (72 mg; 92%).
Anal. Calcd for C28H30OCl3P2Ru: C, 51.59; H, 4.64; Cl, 16.31.
Found: C, 51.5; H, 4.7; Cl, 16.6. UV-vis (CH2Cl2): 534 (1650), 420
(1290), 352(1750). IR: νOH 3053 s, δOH 1620 s, νRu-Cl 340, 303, 263.
ESR: see text. µeff 2.19 µB. Crystals suitable for X-ray analysis were
grown by slow diffusion of Et2O into a CH2Cl2 solution of the complex.
Complex 1 was also made by bubbling Cl2 through a suspension of
Ru2Cl5(dppb)2 (2) (see below; 28 mg, 0.023 mmol) in MeOH (3 mL)
for ∼10 min. Concentration of the red suspension in vacuo and filtration
gave a bright red solid, which was washed with Et2O (5 × 1 mL) and
dried under vacuum (15.5 mg; 52%).
[RuCl(dppb)]2(µ-Cl)3 (2). Use of the procedure described above,
but bubbling Cl2 for 10 min through a C6H6 or CH2Cl2 solution (10
mL) of the Ru2Cl4(dppb)3, gave a red-brown solution, which was then
reduced in volume to ∼1 mL; addition of Et2O (10 mL) produced a
red-brown product, which was filtered off, washed with hexanes, and
vacuum-dried (66 mg; 90%). Anal. Calcd for C56H56Cl5P4Ru2: C, 54.57;
H, 4.59; Cl, 14.38. Found: C, 54.5; H, 4.6; Cl, 14.6. UV-vis/NIR
(CDCl3): 374 (9400), 436 (sh, 7300), 550 (sh, 4700), 980 (900), 2050
(1200).
RuCl3(dppb)(DMSO). Complex 1 (100 mg, 0.153 mmol) and
DMSO (25 µL, 0.352 mmol) were stirred in CH2Cl2 (25 mL) at room
temperature for 4 h; the solution volume was reduced to ∼2 mL, when
addition of Et2O (10 mL) precipitated a red solid, which was collected,
washed well with Et2O, and dried under vacuum (88 mg, 79%). Anal.
Calcd for C30H34OCl3P2SRu: C, 50.61; H, 4.81, S, 4.50. Found: C,
50.32; H, 4.92; S, 4.37. UV-vis (CH2Cl2): 532 (1670), 420 (1330),
356 (1750). IR: νSO 944 vs, νRu-Cl 336, 261. ESR: g1 2.974, g2 1.985,
g3 1.518. µeff 2.08 µB.
Experimental Section
Materials and Instrumentation. Except for the oxidation using Cl2,
manipulations were carried out under purified Ar using standard Schlenk
techniques. Reagent grade solvents were appropriately distilled and dried
before use. The dppb was used as received from Aldrich. RuCl3‚3H2O
(∼40% Ru) was obtained on loan from Johnson Matthey Ltd. or
Colonial Metals Inc., or purchased from Degussa S.A. (Sa˜o Paulo).
[RuCl2(dppb)]2(µ-dppb) (written subsequently as Ru2Cl4(dppb)3),3a,23
14,16
[RuCl(P-P)]2(µ-Cl)3
(written subsequently as Ru2Cl5(P-P)2, where
P-P ) dppb or diop), and RuCl2(diop)(PPh3)13,14 were prepared
according to literature procedures.
IR spectra (cm-1) were recorded as CsI pellets in the 4000-200
cm-1 region, on a Bomen-Michelson 102 instrument; UV-visible
(UV-vis) and near-infrared (NIR) spectra were recorded in solution
on Hewlett-Packard 8452A diode array or Cary 500 spectrophotometers,
respectively, and are presented as λmax or shoulder (nm)/ꢀmax (M-1cm-1).
ESR spectra were measured at - 160 °C using a Varian E-109
instrument operating at the X band frequency, within a rectangular
cavity (E-248) fitted with a temperature controller. Effective magnetic
moments (µeff) were determined at room temperature (∼25° C) by the
Gouy method, or by the Evans method using the paramagnetically
(14) Joshi, A. M.; Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chim.
Acta 1992, 198-200, 283.
(15) Geˆnet, J. P.; Oinel, C.; Rutovelomanana-Vidal, V.; Mallart, S.; Pfister,
X.; Cano De Andradez, M. C.; Laffitte, J. A. Tetrahedron: Asymmetry
1994, 5, 665.
(16) Thorburn, I. S.; Rettig, S. J.; James, B. R. Inorg. Chem. 1986, 25,
234.
(17) Brown, J. M.; Brunner, H.; Leitner, W.; Rose, M. Tetrahedron:
Asymmetry 1991, 2, 331.
(18) Ohta, T.; Noyori, R.; Takaya, H. Inorg. Chem. 1988, 27, 566.
(19) Alcock, N. W.; Brown, J. M.; Rose, M.; Wienand, A. Tetrahedron:
Asymmetry 1991, 2, 47.
(20) (a) Noyori, R.; Takaya, H. Acc. Chem. Res. 1990, 23, 345. (b) Takaya,
H.; Ohta, T.; Noyori, R. In Catalytic Asymmetric Synthesis; Ojima,
I., Ed.; VCH: Oxford, 1993; p 1. (c) Ager, D. J.; Laneman, S. A.
Tetrahedron: Asymmetry 1997, 8, 3327.
(21) Noyori, R. Chem. Soc. ReV. 1989, 18, 187; Science 1990, 248, 1194;
ChemTech 1992, 360; Tetrahedron 1994, 50, 4259; Asymmetric
Catalysis in Organic Synthesis; Wiley: New York, 1994; Acta Chem.
Scand. 1996, 50, 380.
(22) (a) Oppolzer, W.; Wills, M.; Starkenmann, C.; Bernardinelli, G.
Tetrahedron Lett. 1990, 31, 4117. (b) James, B. R. Catal. Today 1997,
37, 209.
RuCl3(dppb)(MeOH). Complex 1 (100 mg, 0.153 mmol) was
refluxed in 10 mL of CH2Cl2/MeOH (1:1) for 8 h. The solution volume
was reduced to ∼2 mL, when addition of Et2O precipitated a dark red
solid, which was collected, washed with ether, and dried under vacuum
(72 mg; 71%). Anal. Calcd for C29H32OCl3P2Ru: C, 52.30; H, 4.84.
Found: C, 52.4; H, 4.6. UV-Vis (CH2Cl2): 530 (1780), 420 (1470),
356 (1900). IR: δOH 1634, νRu-Cl 351, 266. ESR: g1 2.828, g2 2.106,
g3 1.645.
RuCl3(diop)(H2O) (3). Bubbling of Cl2 through a solution of
RuCl2(diop)(PPh3) (273 mg, 0.29 mmol) in CH2Cl2 (30 mL) for ∼30
min at room temperature generated a red solution, which was then
evaporated to dryness; the solid was then dissolved in Et2O (30 mL)
and the solution filtered to remove a small amount of the mixed
(24) (a) Evans, D. F. J. Chem. Soc. 1959, 2003. (b) Crawford, T. H.;
Swanson, J. J. Chem. Educ. 1971, 48, 382.
(23) Bressan, M.; Rigo, P. Inorg. Chem. 1975, 14, 2286.

Characterization of [RuCl3(P-P)(H2O)] Complexes
Inorganic Chemistry, Vol. 38, No. 23, 1999 5343
Table 2. Selected Bond Lengths (Å) and Angles (deg)a
Table 1. Crystallographic Data for mer-RuCl3(dppb)(H2O) (1)a
formula
fw
space group
a, Å
C28H30OCl3P2Ru
651.88
Ru-P(1)
2.286(2)
2.384(2)
2.402(2)
1.037(5)
0.953(5)
Ru-Cl(2)
2.304(2)
2.348(2)
2.216(5)
2.484(2)
3.346(3)
Ru-P(2)
Ru-Cl(3)
orthorhombic, Pbca
14.932 (2)
18.133 (3)
20.594 (2)
5576.0(1)
8
1.553
25
9.850
2648
Ru-Cl(1)
O(W)‚‚‚H(O1)
O(W)‚‚‚H(O2)
Ru-O(W)
Cl(3)‚‚‚H(O1)
Cl(3)‚‚‚O(W)
b, Å
c, Å
P-C 1.830(8)-1.843(8)
V, Å3
Z
P(1)-Ru-P(2)
P(1)-Ru-Cl(1)
P(1)-Ru-Cl(2)
P(1)-Ru-Cl(3)
93.53(7) Cl(1)-Ru-O(W)
92.09(7) Cl(2)-Ru-Cl(3)
95.66(8) Cl(2)-Ru-O(W)
96.43(7) Cl(3)-Ru-O(W)
82.6(2)
167.32(8)
82.8(2)
F
calc, g/cm3
T, °C
µ (Mo KR), cm-1
F(000)
85.4(1)
P(1)-Ru-O(W) 174.4(2)
P(1)-C(1)-C(2)
115.9(5)
114.4(7)
116.5(7)
117.3(6)
no. of refined params
R1 [I > 2σ(I)]
wR2
316
0.046
0.094
P(2)-Ru-Cl(1)
P(2)-Ru-Cl(2)
P(2)-Ru-Cl(3)
P(2)-Ru-O(W)
Cl(1)-Ru-Cl(2)
Cl(1)-Ru-Cl(3)
174.37(7) C(1)-C(2)-C(3)
89.14(7) C(2)-C(3)-C(4)
86.31(7) P(2)-C(4)-C(3)
a R1 ) Σ||Fo| -|Fc||/Σ|Fo|, wR2 ) [Σw(Fo - Fc2)2/Σw(Fo )2]1/2
.
2
2
91.8(2)
P(1)-C(111)-C(112) 116.6(6)
90.55(8) P(1)-C(111)-C(116) 124.8(6)
92.83(7) H(O1)-O(W)-H(O2) 100.0(4)
phosphine precursor. The red solution was concentrated to ∼1 mL and
hexanes (20 mL) were added to precipitate the product, which was
collected, and dried under vacuum (53 mg; 25%). Anal. Calcd for
C31H34O3Cl3P2Ru: C, 51.43; H, 4.73. Found: C, 51.17; H, 4.76. UV-
vis (CH2Cl2): 534 (1720), 428 (1480), 356 (1800). IR: νOH 3058 s,
δOH 1596 s, νRu-Cl 313, 274. ESR: g1 2.782, g2 2.137, g3 1.721. µeff
2.21 µB. Complex 3 was also made by bubbling Cl2 through a solution
of Ru2Cl5(diop)2 (25.5 mg, 0.018 mmol) in CH2Cl2 (10 mL) for 10
min. Concentration of the red solution in vacuo to ∼2 mL, followed
by addition of hexanes (10 mL) precipitated a dark red solid, which
was filtered off, washed with hexanes (3 × 3 mL) and dried under
vacuum (13.3 mg; 50%).
O(W)-H(O1)-Cl(3)
140.0(3)
C-P-C 102.1(3)-103.0(3)
a Estimated standard deviations are given in parentheses.
table of atomic coordinates and equivalent isotropic thermal parameters,
crystallographic data, hydrogen atom parameters, anisotropic thermal
parameters, bond lengths, and bond angles are included as Supporting
Information.
Results and Discussion
RuCl3(diop)(DMSO). Complex 3 (22.3 mg, 0.031 mmol) and
DMSO (5 µL, 0.070 mmol) were stirred in CH2Cl2 (10 mL) at room
temperature for 6 h, when the solution changed from dark red to pink.
The volume was reduced to ∼1 mL and hexanes (20 mL) were added
to precipitate a solid, which was filtered off, washed with hexanes (3
× 3 mL), and dried in vacuo (13 mg, 58%). Anal. Calcd for
C33H38O3Cl3P2SRu requires: C, 50.55; H, 4.88. Found: C 50.21; H,
4.99. UV-vis (CH2Cl2): 530 (1680), 424 (1390), 358 (1750). IR: νSO
948 vs, νRu-Cl 325, 260. ESR: g1 2.982, g2 2.031, g3 1.584.
The Ru(III) aquo, chelating diphosphine complexes of the
type RuCl3(P-P)(H2O), where P-P ) dppb (1) or diop (3), are
readily synthesized by Cl2-oxidation of the Ru(II) precursors
Ru2Cl4(P-P)3 or RuCl2(P-P)(PPh3), or the Ru(II)Ru(III) dinuclear
species Ru2Cl5(P-P)2; the source of the water for the aquo ligand
could be the solvent or the Cl2 supply. That the syntheses from
Ru2Cl4(P-P)3 proceed via Ru2Cl5(P-P)2 is apparent via visible
monitoring of the reaction because the mixed valence species
are red-brown, whereas 1 and 3 are bright red; also, during the
synthesis of 3 from RuCl2(diop)(PPh3), in situ monitoring in
the NIR region revealed the charge-transfer bands at 950 and
2050 cm-1, characteristic of Ru2Cl5(diop)2.16 Finally, if the Cl2-
oxidation procedure is carried out for a shorter time scale, the
Ru2Cl5(dppb)2 complex (2) can be isolated in high yield on using
Ru2Cl4(dppb)3 as reactant.
X-ray analysis of RuCl3(dppb)(H2O) (1) reveals a distorted
octahedral structure with a mer-configuration of the Cl atoms
with the aquo ligand necessarily trans to a P atom (Figure 1).
Of interest, the aquo ligand forms H-bonds with two cis-chlorine
ligands of the neighboring molecule of the complex, which is
related by an inversion center. The water H atoms were
identified from difference maps and were refined isotropically;
the O-H(O1) and O-H(O2) distances are 1.037(5) and 0.953(5)
Å, respectively, whereas the H(O1)‚‚‚Cl(3) hydrogen-bonding
distance is 2.484(2) Å. The distance of the O atom of one
molecule to the Cl(3) from the centrosymmetrically related
molecule is 3.346(3) Å, and the corresponding O-H(O1)‚‚‚
Cl(3) angle is 140.0(3)°. The H(O1)-O-H(O2) angle is
100.0(4)°. There is also a much weaker H-bonding interaction
between H(O2) and Cl(1) with a separation of 3.217 Å. The
Ru-Cl distances (2.304-2.402 Å) appear in the normal, well-
established range for Ru(III) complexes29-31; the longest one
is reasonably the bond trans to the P atom, whereas the Ru-
Cl(3) of length 2.348(2) Å is possibly weakened compared with
Ru-Cl(2), 2.304(2) Å, because of the H-bonding interaction
with Cl(3). The Ru-P(1) and Ru-P(2) bonds, 2.286(2) Å and
2.384(2) Å, are trans to water and Cl, respectively, and are
X-ray Crystallographic Analysis of 1. Selected crystallographic
data appear in Table l together with some experimental details. A single
crystal of approximate dimensions 0.12 × 0.30 × 0.60 mm was used
for data collection and unit cell determination on an Enraf-Nonius
CAD-4 diffractometer at room temperature with graphite monochro-
matized Mo KR radiation (λ ) 0.710 73 Å). Unit-cell parameters were
obtained from a least-squares refinement of the setting angles of 25
reflections in the range θ ) 10.2-18.9°. Intensity data were collected
in the ω-2θ scan mode up to θmax ) 24.97°, with a scan rate range
6.7-20° min-1. The data were corrected for Lorentz and polarization,
and the absorption effects were corrected empirically by a standard
procedure.25 The structure was solved by Patterson methods and
difference Fourier techniques. Scattering factors for non-H atoms were
taken from Cromer and Mann,26a with corrections for anomalous
dispersion from Cromer and Liberman26b and for H atoms from Stewart
et al.27 All calculations were performed with the program SHELX-
97.28 All non-H atoms of the structure were refined with anisotropic
thermal parameters. The aromatic and methylene H atoms were set
isotropic with a thermal parameter 20% greater than the equivalent
isotropic displacement parameter of the associated C atom. All H atoms
were stereochemically positioned and refined with the riding model.28
The aromatic and CH2 bond lengths were set equal to 0.93 and 0.97
Å, respectively, and the aromatic rings were treated as rigid groups.
Selected bond lengths, and bond angles appear in Table 2. A complete
(25) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.
(26) (a) Cromer, D. T.; Mann, J. B. Acta Crystallogr., Sect. A: Fundam.
Crystallogr. 1968, 24, 321. (b) Cromer, D. T.; Liberman, D. J. Chem.
Phys. 1970, 53, 1891.
(27) Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J. Chem. Phys. 1965,
42, 3175.
(28) Sheldrick, G. M. SHELX-97. Programs for Crystal Analysis (Release
97-2). University of Go¨ttingen, Germany, 1997.

5344 Inorganic Chemistry, Vol. 38, No. 23, 1999
Dinelli et al.
Figure 2. ESR spectra (X-band frequency) of RuCl3(dppb)L complexes
(L ) H2O, DMSO, MeOH) at -160 °C in the solid state.
Figure 1. X-ray structure of mer- RuCl3(dppb)(H2O) (1), showing 50%
probability thermal ellipsoids for the nonhydrogen atoms.
O-bonded sulfoxide.34 Dissolution of 1 or 3 in MeCN gives
UV-vis changes consistent with replacement of the aquo ligand
by MeCN (see below).
comparable to the Ru-P bond length in mer-RuCl3(PPh3)(1-
methylimidazole)2, 2.326(2) Å, where the PPh3 is trans to the
methylimidazole.30 As expected, for a relatively hard Ru(III)
center, the Ru-OH2 distance [2.216(5) Å] is shorter than the
Ru-P distances, and being trans to a P-donor, the bond is longer
than that of 2.101(4) Å found in RuCl3(dmtp)2(H2O), where
dmtp is a N-donor pyrimidine derivative, and the aquo ligand
is trans to a Cl atom.31
The magnetic moments of 1 and 3 (2.19 and 2.21 µB,
respectively), although somewhat high for low-spin d5 (S ) 1/2)
systems, are not unusual for Ru(III) complexes.32 Within these
aquo complexes, the IR spectra show a sharp δOH band of
coordinated water in the 1600 cm-1 region.33 Three bands seen
in the 340-260 cm-1 range for 1 with mer-geometry could be
associated with νRu-Cl stretches. For 3, two stronger bands in
this range are evident, but there are also several weaker bands
that might be due to νRu-Cl; whether 3 is mer or fac is not known
unambiguously, but similarities in UV-vis spectra of 1 and 3
imply a mer-configuration. The far-IR data for these particular
complexes [or RuCl3(P-P)L, where L is another coordinating
solvent, see below] do not readily distinguish between the mer-
and fac-geometries.
Complexes 1 and 3, and the RuCl3(P-P)L species, in CH2Cl2
all show very similar UV-vis spectra having three bands in
the 350-540 nm region with the middle band of somewhat
lower intensity (see Figure S1). The spectra correspond closely
to those reported earlier by one of our groups for dissolution of
the dinuclear complex [RuCl3(dppb)]2 in DMSO or MeCN,16
consistent with formation of the corresponding RuCl3(dppb)L
species. The new Ru(III) chemistry described here also partly
clarifies the nature of the earlier suggested disproportionation
of Ru2Cl5(dppb)2 in coordinating solvents into “RuCl3(dppb)”
and “RuCl2(dppb)”.16
The solid-state ESR spectrum measured for RuCl3(dppb)(H2O)
(1) is markedly different from those determined for the
corresponding DMSO and MeOH complexes (Figure 2). Those
of the last two, with three g values in the 2.9, 2.0, and 1.5
regions, are typical of Ru(III) species with rhombic distortions,30
whereas the spectrum of 1 shows a signal close to zero magnetic
field, which is characteristic of complexes with coupling
between paramagnetic species.35 Presumably, such an interaction
in 1 occurs via a pathway involving the intermolecular H-
bonding of the coordinated water molecule with the Cl atoms
of the neighboring molecule of the complex, as noted in the
discussion of the crystal structure. The observed ESR spectrum
is consistent with a spin-spin interaction giving a zero-field
splitting energy (J value) of 0.309 cm-1. A conceptually similar
exchange coupling between two Cu(II)-containing molecules
via a very weak H-bond between a coordinated Cl atom and
the NH proton of a pyrazole ligand (where Cl‚‚‚H ) 3.72 Å,
compared with H‚‚‚Cl ) 2.48 Å within 1) realized a J value
about 100 times smaller.35 The ESR of a frozen CH2Cl2 solution
of 1 (at -160 °C) shows the more typical three g value spectrum
(g ) 2.81, 2.11, and 1.71), implying the absence of coupling
evident in the solid state. The ESR spectrum for 3, the aquo/
diop complex, is that of a typical Ru(III) species, implying the
absence of strong H-bonding interactions in the solid-state
structure; the ESR spectrum of a frozen MeCN solution of
The aquo ligand in 1 and 3 is readily displaced by other
solvent ligands (L) such as DMSO, MeOH, and MeCN.
Complexes with DMSO and MeOH have been isolated; they
show correct elemental analyses for the formulation RuCl3(P-
P)L, and they have been partially characterized by spectroscopic
and sometimes µeff data. Similarities in UV-vis data to those
of 1 again suggest mer-geometries. The νSO values for the dppb/
DMSO and diop/DMSO complexes (944 and 948 cm-1) suggest
(29) (a) Che, C. M.; Kwong, S. S.; Poon, C. K.; Lai, T. F.; Mak, T. C. W.
Inorg. Chem. 1985, 24, 1359. (b) Hambley, T. W.; Lay, P. A. Inorg.
Chem. 1986, 25, 4553. (c) Keppler, B. K.; Wehe, D.; Endres, R. Inorg.
Chem. 1987, 28, 844. (d) Sheldrick, W. S.; Exner, R. Inorg. Chim.
Acta 1992, 195, 1. (e) Rack, J. J.; Gray, H. B. Inorg. Chem. 1999, 38,
2.
(30) Batista, A. A.; Polato, E. A.; Queiroz, S. L.; Nascimento, O. R.; James,
B. R.; Rettig, S. J. Inorg. Chim. Acta 1995, 230, 111.
(31) Velders, A. H.; Pazderski, L.; Ugozzoli, F.; Biagini-Cingi, M.; Manotti-
Lanfredi, A. M.; Haasnoot, J. G.; Reedijk, J. Inorg. Chim. Acta 1998,
273, 259.
(34) (a) Rochon, F. D.; Kong, P., Girad, L. Can. J. Chem. 1986, 64, 1897.
(b) James, B. R.; Morris, R. H. Can. J. Chem. 1980, 58, 399.
(35) (a) Goslar, J.; Hilczer, W.; Hoffmann, S. K. Phys. Status Solidi b 1993,
175, 465. (b) Hoffmann, S. K.; Goslar, J.; Hilczer, W.; Krupski, M.
Inorg. Chem. 1993, 32, 3554.
(32) (a) Cotton, F. A.; Torralba, R. C. Inorg. Chem. 1991, 30, 4392. (b)
Taqui Khan, M. M.; Reddy, K. V. J. Coord. Chem. 1982, 12, 71.
(33) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coor-
dination Compounds, 3rd ed.; Wiley: New York, 1978; p 226.

Characterization of [RuCl3(P-P)(H2O)] Complexes
Inorganic Chemistry, Vol. 38, No. 23, 1999 5345
2 (Figure 3). Controlled bulk coulometry to 50% reduction of
1 readily allows for isolation of 2; this was accomplished by
evaporating the product solution to dryness, dissolving the red-
brown residue in CH2Cl2, filtering off the TBAP, and adding
Et2O to precipitate the mixed-valence complex. The air-sensitive
Ru2Cl4(dppb)2 complex has been made previously by H2-
reduction of 2,2,14 and presumably could be made electrochemi-
cally (eq 3). The CV behavior of RuCl3(diop)(H2O) (3) is very
similar to that of 1; peaks corresponding to those of a-d are
seen at 0.20, 0.14, 0.66, and 0.82 V, respectively, the consis-
tently higher values revealing slight, relative stabilization of the
Ru(II) state in the diop vs corresponding dppb species.
The two peaks at E1/2 0.52 and 0.73 V (points c and d,
respectively) are attributed to Ru(III)/Ru(II) Ru(III)/Ru(III)
couples, one implication being that, in this solution, 2 could
exist as two isomers. Earlier, UV-vis and NIR data from one
of our groups16 had been interpreted in terms of the existence
of two isomers within complexes such as 2, such a conclusion
being based partly on the presence of two charge-transfer bands
in the NIR region solution spectra; for example, 2 in CDCl3
shows bands at 970 and 2050 nm of comparable intensity (ꢀ )
890 and 1180, respectively). Heath’s group more recently has
shown that the single isomer, mixed valence, cationic, triply
choro-bridged complexes [Ru2Cl3L6]2+ (where L is a terminal,
monodentate, tertiary phosphine) exhibit two bands in this region
of the spectrum but, in contrast to 2, the higher energy band
has much stronger intensity.37 The closeness of the two E1/2
values argues for the existence of isomers within the solution
of 2. These potentials are about 1.0 V below the corresponding
one of the dicationic species,38 which seems reasonable con-
sidering the 2+ difference in charges on the complexes;
comparison of each Ru environment in the two types of
complexes shows that 2 has a terminal Cl atom versus a terminal
PR3 ligand in the dications, a factor that again will relatively
stabilize Ru(III) and lead to a lower potential.38 Both types of
complexes are of the delocalized classification.16,37 An alterna-
tive explanation for the presence of the c and d peaks (suggested
by one of the reviewers) is that the second isomer is generated
via a redox-initated process after generation of the species giving
rise to peak c; further CV studies on these dinuclear Ru species
are needed to unravel these details.
Figure 3. Cyclic voltammograms of RuCl3(dppb)(H2O) (1) (2), and
Ru2Cl5(dppb)2 (2) (- - -); 0.001 M in CH2Cl2 with 0.10 M TBPA;
scan rate 100 mV/s.
RuCl3(diop)(MeCN) formed in situ from 3 was essentially
identical with that of 3.
1
Cursory examination of the H NMR spectra of several of
the isolated RuCl3(P-P)L complexes revealed relatively weak,
paramagnetically upfield-shifted, broad signals that could be
attributed generally to the phenyl or alkyl protons, but the NMR
studies were not pursued, although such data on such low-spin
d5 Ru species have been reported.31,36
Cyclic voltammetric measurements on [RuCl3(dppb)(H2O)]
(1) (Figure 3) show the intermediacy of Ru2Cl5(dppb)2 (2) in
the overall reduction to “RuCl2(dppb)”, which exists as the
known dimer [RuCl(dppb)]2(µ-Cl)2.2,14 The CV data are readily
rationalized in terms of eqs 1-3:
RuCl3(dppb)(H2O) (1) + 1 e- f
“RuCl2(dppb)” + Cl - + H2O (1)
RuCl3(dppb)(H2O) + “RuCl2(dppb)” f
Ru2Cl5(dppb)2 (2) + H2O (2)
Acknowledgment. We thank CNPq, CAPES, FINEP, and
FAPESP in Brasil, and NSERC of Canada, for financial support,
and Johnson Matthey Ltd. and Colonial Metals Inc. for loans
of ruthenium.
Ru2Cl5(dppb)2 (2) + 1 e- f Ru2Cl4(dppb)2 + Cl-
(3)
Supporting Information Available: Complete tables of crystal-
lographic data, final atomic coordinates and equivalent isotropic
parameters, hydrogen atom parameters, anisotropic thermal parameters,
bond lengths and bond angles for 1. This material is available free of
charge via the Internet at http://pubs.acs.org.
The CV reveals an irreversible Ru(III)/Ru(II) process with
Epc 0.14 V (point a), which is attributed to eq 1; this peak is
absent in subsequent cycles because the electrochemistry is
followed by the formation of 2 according to eq 2. The process
at 0.06 V (point b) is due to reduction of the Ru(III) center of
2, as confirmed by CV on a chemically synthesized sample of
IC990130C
(37) Yeomans, B. D.; Humphrey, D. G.; Heath, G. A. J. Chem. Soc., Dalton
Trans. 1997, 4153.
(36) Baird, I. R.; Rettig, S. J.; James, B. R.; Skov, K. A. Can. J. Chem.
1998, 76, 1379.
(38) Heath, G. A.; Lindsay, A J.; Stephenson, T. A.; Vattis, D. K. J.
Organomet. Chem. 1982, 233, 353.