An Easy Entry to Dimers [{RuX(μ-X)(CO)(P down curve sign P)} 2] (X = Cl, Br; P down curve sign P = 1,1′ Bis(diphenylphosphino)ferrocene, 1,1′-Bis(diisopropylphosphino)ferrocene)

Article abstract of DOI:10.1021/om030530e

Complexes [RuX(η³-2-C₃H₄R)(CO)(P down curve sign P)] (X = Cl, Br; R = H, Me; P down curve sign P = dppf, dippf) (2a-d and 3a-d) have been prepared by reaction of the η ³-allylruthenium(II) derivatives [RuX(η

Full text of DOI:10.1021/om030530e

5226
Organometallics 2003, 22, 5226-5234
An Ea sy En tr y to Dim er s [{Ru X(µ-X)(CO)(P kP )}2] (X ) Cl,
Br ; P kP ) 1,1′-Bis(d ip h en ylp h osp h in o)fer r ocen e,
1,1′-Bis(d iisop r op ylp h osp h in o)fer r ocen e) fr om
η3-Allylr u th en iu m (II) Der iva tives
[Ru X(η3-2-C3H4R)(CO)(P kP )] (R ) H, Me): Efficien t
Ca ta lyst P r ecu r sor s in Tr a n sfer Hyd r ogen a tion of
Keton es§
Victorio Cadierno,*,† Pascale Crochet, J osefina D´ıez,
Sergio E. Garc´ıa-Garrido, and J ose´ Gimeno*,‡
Departamento de Qu´ımica Orga´nica e Inorga´nica, Instituto Universitario de Qu´ımica
Organometa´lica “Enrique Moles” (Unidad Asociada al CSIC), Facultad de Qu´ımica,
Universidad de Oviedo, E-33071 Oviedo, Spain
Santiago Garc´ıa-Granda
Departamento de Qu´ımica Fı´sica y Anal´ıtica, Facultad de Qu´ımica, Universidad de Oviedo,
E-33071 Oviedo, Spain
Received J uly 9, 2003
Complexes [RuX(η3-2-C3H4R)(CO)(PkP)] (X ) Cl, Br; R ) H, Me; PkP ) dppf, dippf) (2a -d
and 3a -d ) have been prepared by reaction of the η3-allylruthenium(II) derivatives [RuX-
(η3-2-C3H4R)(CO)3] (1a -d ) with 1 equiv of the appropriate diphosphine. Treatment of 2a -d
and 3a -d with HX allows the high-yield preparation of the dimeric compounds [{RuX(µ-
X)(CO)(PkP)}2] (PkP ) dppf, X ) Cl (4a ), Br (4b); PkP ) dippf, X ) Cl (5a ), Br (5b)). Complex
[{RuCl(µ-Cl)(CO)(dppf)}2] reacts with neutral ligands, via chloride bridge cleavage, affording
the mononuclear derivatives [RuCl2(CO)(L)(dppf)] (L ) CO (6a ), BzNC (6b), Py (6c), PhNH2
(6d )). The structures of compounds [RuCl(η3-C3H5)(CO)(dppf)] (2a ), [{RuCl(µ-Cl)(CO)(dppf)}2]
(4a ), and [RuCl2(CO)(Py)(dppf)] (6c) have been confirmed by X-ray crystallography. The
catalytic activity of dimers 4a ,b and 5a ,b in transfer hydrogenation of ketones by propan-
2-ol has also been studied.
In tr od u ction
tate phosphines, i.e., PPh3, PMePh2, and PMe2Ph among
others.3 To the best of our knowledge, no five-coordinate
complexes containing chelate diphosphines have been
reported, and only three dimers, namely, [{RuCl(µ-Cl)-
(CO)(o-C6H4(PMePh)2)}2],4 [{RuCl(µ-Cl)(CO)(tBu2P(CH2)2-
PtBu2)}2],5 and [{RuCl(µ-Cl)(CO)(Cy2P(CH2)4PCy2)}2],6
have been described to date. Due to this fact, along with
the scarce catalytic studies involving this type of deriva-
tives,7 we believed it of interest to prepare novel dimeric
species and to explore their catalytic activity in transfer
hydrogenation of ketones.
The chemistry of carbonyl-halide-phosphine com-
plexes of ruthenium(II) has been largely explored.1 A
wide series of six-coordinate mononuclear compounds
of general formula [RuX2(CO)2(PR3)2] and [RuX2(CO)-
(PR3)3] (several stereoisomers have been described for
each of them) belong to this type of derivatives.1 In
contrast, only a limited number of five-coordinate 16-
electron complexes [RuX2(CO)(PR3)2] or their halide-
bridged dimers [{RuX(µ-X)(CO)(PR3)2}2] are known.2,3
The competitive formation of [RuX2(CO)(PR3)2] versus
[{RuX(µ-X)(CO)(PR3)2}2] is apparently influenced by the
steric and electronic properties of the phosphine ligands.
Thus, the bulky and electron-rich phosphines PCy3,
PtBu2Me, and PiPr3 appear to favor the formation of
unsaturated monomers,2 while the dimeric species
contain relatively less sterically demanding monoden-
(2) For references dealing with the chemistry of five-coordinate
complexes [RuX2(CO)(PR3)2] see: (a) Moers, F. G.; Ten Hoedt, R. W.
M.; Langhout, J . P. J . Organomet. Chem. 1974, 65, 93. (b) Moers, F.
G.; Langhout, J . P. J . Inorg. Nucl. Chem. 1977, 39, 591. (c) Moers, F.
G.; Buerskens, P. T.; Noordik, J . H. Cryst. Struct. Commun. 1982, 11,
1655. (d) Gaffney, T. R.; Ibers, J . A. Inorg. Chem. 1982, 21, 2062. (e)
Moers, F. G. J . Coord. Chem. 1984, 13, 215. (f) Werner, H.; Tena, M.
A.; Peters, K.; von Schnering, H. G. Chem. Ber. 1995, 128, 41. (g)
Huang, D.; Folting, K.; Caulton, K. G. Inorg. Chem. 1996, 35, 7035.
(h) Huang, D.; Heyn, R. H.; Bollinger, J . C.; Caulton, K. G. Organo-
metallics 1997, 16, 292. (i) Huang, D.; Streib, W. E.; Bollinger, J . C.;
Caulton, K. G.; Winter, R. F.; Scheiring, T. J . Am. Chem. Soc. 1999,
121, 8087. (j) Katayama, H.; Tanaguchi, K.; Kobayashi, M.; Sagawa,
T.; Minami, T.; Ozawa, F. J . Organomet. Chem. 2002, 645, 192. (k)
Werner, H.; Gruenwald, C.; Stueer, W.; Wolf, J . Organometallics 2003,
22, 1558. (l) Katayama, H.; Nagao, M.; Moriguchi, R.; Ozawa, F. J .
Organomet. Chem. 2003, 676, 49.
§ Dedicated to Prof. J ose´ Vicente on the occasion of his 60th birthday.
† E-mail: vcm@sauron.quimica.uniovi.es.
‡ E-mail: jgh@sauron.quimica.uniovi.es.
(1) (a) Seddon, E. A.; Seddon, K. R. In The Chemistry of Ruthenium;
Elsevier: Amsterdam, 1984. (b) Schro¨der, M.; Stephenson, T. A. In
Comprehensive Coordination Chemistry; Wilkinson, G., Ed.; Pergamon
Press: Oxford, 1987; Vol. 4, p 277. (c) Hill, A. F. In Comprehensive
Organometallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson,
G., Eds.; Pergamon: New York, 1995; Vol. 7, p 299.
10.1021/om030530e CCC: $25.00 © 2003 American Chemical Society
Publication on Web 11/11/2003

Dimers [{RuX(µ-X)(CO)(PkP)}2] (X ) Cl, Br)
Organometallics, Vol. 22, No. 25, 2003 5227
Sch em e 1
former procedure was effective in the preparation of
compounds [{RuCl(µ-Cl)(CO)(o-C6H4(PMePh)2)}2]4 and
[{RuCl(µ-Cl)(CO)(tBu2P(CH2)2PtBu2)}2],5 attempts to pre-
pare [{RuCl(µ-Cl)(CO)(Cy2P(CH2)4PCy2)}2] by decar-
bonylation of [RuCl2(CO)2(Cy2P(CH2)4PCy2)] proved un-
successful, being instead obtained by reaction of [Ru-
Cl2(CO)(PPh3)2(DMF)] with Cy2P(CH2)4PCy2.6
F igu r e 1. Structure of dimers [{RuX(µ-X)(CO)(PkP)}2]
reported in this paper.
Thus, in the present work we report the systematic
synthesis of the ruthenium(II) dimers [{RuX(µ-X)(CO)-
(PkP)}2] (X ) Cl, Br; see Figure 1) containing the chelate
diphosphine ligands 1,1′-bis(diphenylphosphino)fer-
rocene (dppf) and 1,1′-bis(diisopropylphosphino)ferro-
cene (dippf).8 They have been prepared starting from
the η3-allyl complexes [RuX(η3-2-C3H4R)(CO)(PkP)]
(X ) Cl, Br; R ) H, Me; PkP ) dppf, dippf), which
readily undergo the releasing of the allyl units in the
presence of the corresponding hydrogen halide. This
unprecedented synthetic methodology allows an easy
and efficient entry to the scarcely known dimeric
carbonyl-halide-diphosphine ruthenium(II) complexes.
Some of these species are shown to be highly efficient
catalysts in transfer hydrogenation of ketones by pro-
pan-2-ol.
We have designed an alternative synthetic approach
that allows us to check the ability of the relatively bulky
diphosphines dppf and dippf to stabilize halide-bridged
dimeric derivatives [{RuX(µ-X)(CO)(PkP)}2]. These com-
plexes can be accessible from the readily available
species [RuX(η3-allyl)(CO)(PkP)] (X ) Cl, Br; PkP )
dppf, dippf) by releasing of the η3-allyl fragment in the
presence of the corresponding hydrogen halide. The role
of η3-allyl groups to act as labile ligands generating free
coordination sites in acidic media is well-documented.9
Syn th esis of th e P r ecu r sor Com p lexes [Ru X(η3-
2-C3H4R)(CO)(P kP )] (X ) Cl, Br ; R ) H, Me; P kP )
d p p f, d ip p f). Treatment of tricarbonyl complexes [RuX-
(η3-2-C3H4R)(CO)3] (R ) H, Me; X ) Cl, Br; 1a -d )10 with
1 equiv of the appropriate diphosphine in refluxing
toluene (2a ,b and 3a ,b) or tetrahydrofuran (2c,d and
3c,d ) generates the monocarbonyl derivatives [RuX(η3-
2-C3H4R)(CO)(PkP)] (R ) H, Me; X ) Cl, Br; PkP )
dppf, dippf; 2a -d and 3a -d ), which have been isolated
as yellow-orange air-stable solids in 69-82% yield
(Scheme 1).
Resu lts a n d Discu ssion
The most general synthetic approaches to [RuX2(CO)-
(PR3)2] in their monomeric and dimeric forms are (i) the
thermal or photochemical decarbonylation of [RuX2-
(CO)2(PR3)2] species3e,f,i,m and (ii) the treatment of
alcoholic solutions of RuCl3‚nH2O with carbon monoxide
and the appropriate phosphine.2a,f,3i,n Although the
1
Spectroscopic data (IR and H, 31P{1H}, and 13C{1H}
(3) For references dealing with the chemistry of dimers [{RuX(µ-
X)(CO)(PR3)2}2] see: (a) Prince, R. H.; Raspin, K. A. J . Chem. Soc. (A)
1969, 612. (b) Ruiz-Ram´ırez, L.; Stephenson, T. A.; Switkes, E. S. J .
Organomet. Chem. 1973, 49, C77. (c) Ruiz-Ram´ırez, L.; Stephenson,
T. A. J . Chem. Soc., Dalton Trans. 1974, 1640. (d) Armit, P. W.;
Stephenson, T. A. J . Organomet. Chem. 1974, 73, C33. (e) Barnard,
C. F. J .; Daniels, J . A.; J effery, J .; Mawby, R. J . J . Chem. Soc., Dalton
Trans. 1976, 953. (f) Barnard, C. F. J .; Daniels, J . A.; Holland, P. R.;
Mawby, R. J . J . Chem. Soc., Dalton Trans. 1980, 2418. (g) Paz-
Sandoval, M. A.; Powell, P. J . Organomet. Chem. 1983, 252, 205. (h)
Sa´nchez-Delgado, R. A.; Thewalt, U.; Valencia, N.; Andriollo, A.;
Ma´rquez-Silva, R. L.; Puga, J .; Scho¨llhorn, H.; Klein, H. P.; Fontal, B.
Inorg. Chem. 1986, 25, 1097. (i) Krassowski, D. W.; Nelson, J . H.;
Brower, K. R.; Hauenstein, D.; J acobson, R. A. Inorg. Chem. 1988, 27,
4294. (j) Krassowski, D. W.; Nelson, J . H. J . Organomet. Chem. 1988,
356, 93. (k) Vac, R.; Nelson, J . H.; Milosavljevic´, E. B.; Solujic´, L. Inorg.
Chem. 1989, 28, 3831. (l) Pandey, K. K.; Tewari, S. K. Polyhedron 1989,
8, 1149. (m) Sun, Y.; Taylor, N. J .; Carty, A. J . Inorg. Chem. 1993, 32,
4457. (n) Bustelo, E.; J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P.
J . Chem. Soc., Dalton Trans. 1999, 2399. (o) Marchenko, A. V.;
Huffman, J . C.; Valerga, P.; J ime´nez-Tenorio, M.; Puerta, M. C.;
Caulton, K. G. Inorg. Chem. 2001, 40, 6444.
NMR) and elemental analyses for complexes 2a -d and
3a -d are in agreement with the proposed formulations
(details are given in the Experimental Section). Rele-
vant spectroscopic features are the following: (i) (IR)
the presence of a strong ν(CO) absorption band in the
range 1907-1926 cm-1, (ii) (31P{1H} NMR) the appear-
ance of a singlet signal at ca. 35 (2a -d ) or 41 (3a -d )
ppm, (iii) (1H NMR) typical resonances for the syn- and
anti-H of the η3-allyl ligands (δ 3.57-3.72 and 2.07-
2.47 ppm, respectively) as well as for the central
hydrogen (2a ,b, 3a ,b) or methyl (2c,d , 3c,d ) substitu-
ents (δ 4.69-4.91 and 2.05-2.12 ppm, respectively), and
(iv) (13C{1H} NMR) a characteristic downfield signal (δ
202.98-205.78 ppm) for the carbonyl ligand which
appears as a triplet (2J CP ) 14.3-16.1 Hz) due to the
coupling with the two equivalent phosphorus nuclei of
the ferrocenyl ligands. Since allyl groups in complexes
2a -d and 3a -d may adopt an endo or exo arrangement
(see Figure 2), the observation of only one set of
(4) Grocott, S. C.; Wild, S. B. Inorg. Chem. 1982, 21, 3535.
(5) Gottschalk-Gaudig, T.; Folting, K.; Caulton, K. G. Inorg. Chem.
1999, 38, 5241.
(6) Drouin, S. D.; Amoroso, D.; Yap, G. P. A.; Fogg, D. E. Organo-
metallics 2002, 21, 1042.
(7) Hydrosilylation of alkynes: see refs 2j and 2l. Hydrogenation of
olefins: see refs 3j and 3k. Hydrogenation of ketones and ortho-
olefination of arenes (Murai catalysis): see ref 6.
(8) For reviews on the chemistry of ferrocenyl-phosphines see: (a)
Gan, K. S.; Hor, T. S. A. In Ferrocenes: Homogeneous Catalysis,
Organic Synthesis and Material Science; Togni, A., Hayashi, T., Eds.;
VCH: Weinheim, 1995; p 3. (b) Bandoli, G.; Dolmella, A. Coord. Chem.
Rev. 2000, 209, 161. (c) Colacot, T. J . Platinum Metals Rev. 2001, 45,
22.
(9) See for example: (a) Braterman, P. S. In Reactions of Coordi-
nated Ligands; Braterman, P. S., Ed.; Plenum Press: New York, 1986;
Vol. 1, p 103. (b) Ratovelomanana-Vidal, V.; Geneˆt, J . P. J . Organomet.
Chem. 1998, 567, 163, and references therein. (c) Katayama, H.;
Ozawa, F. Organometallics 1998, 17, 5190.
(10) (a) Sbrana, G.; Braca, G.; Piacenti, F.; Pino, P. J . Organomet.
Chem. 1968, 13, 240. (b) Kondo, T.; Ono, H.; Satake, N.; Mitsudo, T.;
Watanabe, Y. Organometallics 1995, 14, 1945.

5228 Organometallics, Vol. 22, No. 25, 2003
Cadierno et al.
Sch em e 2
F igu r e 2. Exo and endo isomers of complexes [RuX(η3-2-
C3H4R)(CO)3] (1a -d ).
for the η3-C3H5 unit the average position for the
terminal carbons C(2) and C(2a) is shown, while for the
central carbon C(1′) one of the two possible positions is
represented). The molecular structure shows a pseu-
dooctahedron geometry around the ruthenium atom
with the η3-allyl fragment formally occupying two
coordination sites. Interligand angles around ruthe-
nium, in the range 67-104°, reveal the distortions
caused by the geometric restrictions of the allyl ligand.
The Ru-C(1′) and Ru-C(2) bond lengths of 2.22(3) and
2.267(7) Å, respectively, are consistent with the η3-
coordination mode of the allyl group. These values,
together with the C(1′)-C(2) distance (1.31(2) Å) and
the internal C(2)-C(1′)-C(2a) angle (132.0(2)°), com-
pare well to those reported in the literature for other
(η3-allyl)-ruthenium(II) complexes.10b,12
Syn th esis of Ha lid e-Br id ged Dim er s [{Ru X(µ-X)-
(CO)(P kP )}2] (X ) Cl, Br ; P kP ) d p p f, d ip p f). In
accordance with the well-known lability of the η3-allyl
groups in acidic media,9 we have found that the treat-
ment of complexes [RuX(η3-C3H5)(CO)(PkP)] (PkP )
dppf, X ) Cl (2a ), Br (2b); PkP ) dippf, X ) Cl (3a ), Br
(3b)) with a slight excess (ca. 1.5 equiv) of the appropri-
ate HX acid, in dichloromethane at room temperature,
affords the dimeric species [{RuX(µ-X)(CO)(PkP)}2]
(PkP ) dppf, X ) Cl (4a ), Br (4b); PkP ) dippf, X ) Cl
(5a ), Br (5b)), via propene releasing (83-88% yield;
Scheme 2). Alternatively, these compounds can also be
obtained in similar yield starting from the correspond-
ing (η3-2-methylallyl)-ruthenium(II) complexes [RuX(η3-
2-C3H4Me)(CO)(PkP)] (PkP ) dppf, X ) Cl (2c), Br (2d );
PkP ) dippf, X ) Cl (3c), Br (3d )).
F igu r e 3. ORTEP-type view of the structure of [RuCl(η3-
C3H5)(CO)(dppf)] (2a ) showing the crystallographic labeling
scheme. Atoms labeled with an “a” are related to those
indicated by a crystallographic 2-fold symmetry axis.
Hydrogen atoms are omitted for clarity, and only the ipso-
carbons of the phenyl rings of the Ph2P groups are shown.
Thermal ellipsoids are drawn at 20% probability level.
Selected bond distances (Å) and angles (deg): Ru-C(1′) )
2.22(3); Ru-C(2) ) 2.267(7); Ru-P(1) ) 2.387(1); Ru-Cl-
(1a) ) 2.532(5); Ru-C(20) ) 1.744(15); C(1′)-C(2) ) 1.31-
(2); C(20)-O(1) ) 1.028(19); Fe-C* ) 1.641(1); P(1)-Ru-
P(1a) ) 103.11(7); P(1)-Ru-Cl(1a) ) 88.64(14); P(1)-Ru-
C(20) ) 87.5(4); P(1)-Ru-C(2) ) 161.78(19); P(1)-Ru-
C(2a) ) 95.06(19); C(2)-Ru-Cl(1a) ) 90.3(3); C(2)-Ru-
C(20) ) 93.6(5); C(2)-Ru-C(2a) ) 66.8(4); C(2)-Ru-C(1′)
) 33.9(6); C(2)-C(1′)-C(2a) ) 132.0(2); C(20)-Ru-Cl(1a)
) 176.1(4); Ru-C(20)-O(1) ) 177.2(14). C* ) centroid of
the cyclopentadienyl ring (C(3), C(4), C(5), C(6), C(7)).
Compounds 4a ,b and 5a ,b have been isolated as air-
stable yellow-orange solids. They have been character-
ized by elemental analyses and IR and NMR spectros-
copy, which confirm the releasing of the allyl groups (see
the Experimental Section for details). 31P{1H} and 13C-
{1H} NMR data are useful for the structural elucidation.
In particular, the carbonyl resonances in the 13C{1H}
NMR spectra (δ 200.07-202.10 ppm), which appear as
resonances for both the proton and carbon nuclei of the
η3-allyl units seems to indicate that in solution only one
isomer is present.11
Although a single-crystal X-ray diffraction study on
[RuCl(η3-C3H5)(CO)(dppf)] (2a ) was carried out, no endo/
exo structural elucidation was achieved since the car-
bonyl, chloride, and allyl ligands are disordered in ca.
50/50 as a consequence of the opposite orientations
adopted by the molecules in the crystal lattice. An
ORTEP view is shown in Figure 3 (selected bond
distances and angles are listed in the caption). This
disorder is clearly reflected by the appearance of a
crystallographic 2-fold symmetry axis that contains the
ruthenium and iron atoms (in Figure 3 only one disposi-
tion of the mutually trans CO and Cl ligands is shown;
2
a doublet of doublets signal with J CP values in the
range 15.4-17.1 Hz, reveal a cis arrangement of the
carbonyl groups with respect to both phosphorus nuclei
of the diphosphines. The 31P{1H} NMR spectra, which
(12) See for example: (a) Smith, A. E. Inorg. Chem. 1972, 11, 2306.
(b) Schoonover, M. W.; Eisenberg, R. J . Am. Chem. Soc. 1977, 99, 8371.
(c) Hsu, L. Y.; Nordman, E.; Gibson, D. H.; Hsu, W. L. Organometallics
1989, 8, 241. (d) Braun, T.; Gevert, O.; Werner, H. J . Am. Chem. Soc.
1995, 117, 7291. (e) Esteruelas, M. A.; Liu, F.; On˜ate, E.; Sola, E.; Zeier,
B. Organometallics 1997, 16, 2919. (f) MacFralane, K. S.; Rettig, S.
J .; Liu, Z.; J ames, B. R. J . Organomet. Chem. 1998, 557, 213. (g) Six,
C.; Gabor, B.; Go¨rls, H.; Mynott, R.; Philipps, P.; Leitner, W. Organo-
metallics 1999, 18, 3316. (h) Nakanishi, S.; Sasake, H.; Takata, T.
Chem. Lett. 2000, 1058. (i) Older, C. M.; Stryker, J . M. Organometallics
2000, 19, 2661. (j) Smith, D. C.; Cadoret, J .; J afarpour, L.; Stevens, E.
D.; Nolan, S. P. Can. J . Chem. 2001, 79, 626. (k) Sasabe, H.; Nakanishi,
S.; Takata, T. Inorg. Chem. Commun. 2002, 5, 177.
(11) It has been reported that complexes [RuX(η3-C3H5)(CO)3] (X )
Cl, Br) exist in solution in a conformational equilibrium between endo
and exo isomers: Wrighton, M. S.; Wuu, Y. M. Organometallics 1988,
7, 1839. Variable-temperature 31P{1H} and 1H NMR experiments (from
-60 to 60 °C) were carried out with a THF-d8 solution of complex
[RuCl(η3-C3H5)(CO)(dppf)] (2a ). No changes were observed in the NMR
spectra, discarding the possibility of a dynamic equilibrium between
endo and exo species in solution.

Dimers [{RuX(µ-X)(CO)(PkP)}2] (X ) Cl, Br)
Organometallics, Vol. 22, No. 25, 2003 5229
Sch em e 3
Sch em e 4
F igu r e 4. ORTEP-type view of the structure of [{RuCl-
(µ-Cl)(CO)(dppf)}2] (4a ′) showing the crystallographic label-
ing scheme. Atoms labeled with an “a” are related to those
indicated by a crystallographic center of symmetry. Hy-
drogen atoms are omitted for clarity, and only the ipso-
carbons of the phenyl rings of the Ph2P groups are shown.
Thermal ellipsoids are drawn at 20% probability level.
Selected bond distances (Å) and angles (deg): Ru-Cl(1) )
2.446(1); Ru-Cl(1a) ) 2.489(1); Ru-Cl(2) ) 2.446(1); Ru-
P(1) ) 2.319(1); Ru-P(2) ) 2.355(1); Ru-C(35) ) 1.892-
(5); C(35)-O(1) ) 1.047(5); Fe-C* ) 1.640(1); Fe-C** )
1.643(1); P(1)-Ru-Cl(1) ) 86.93(3); P(1)-Ru-Cl(2) )
94.06(3); P(1)-Ru-C(35) ) 89.70(12); P(1)-Ru-P(2) )
101.32(3); P(1)-Ru-Cl(1a) ) 167.27(3); Cl(1)-Ru-C(35)
) 91.74(12); Cl(1)-Ru-Cl(1a) ) 80.80(3); Cl(1)-Ru-Cl-
(2) ) 85.86(3); Cl(1)-Ru-P(2) ) 168.45(3); P(2)-Ru-Cl-
(2) ) 85.53(3); P(2)-Ru-C(35) ) 96.30(12); P(2)-Ru-
Cl(1a) ) 91.29(3); Cl(2)-Ru-C(35) ) 175.42(12); Ru-
C(35)-O(1) ) 177.7(4); C*-Fe-C** ) 177.90(1). C* and
C** ) centroids of the cyclopentadienyl rings (C(1), C(2),
C(3), C(4), C(5) and C(6), C(7), C(8), C(9), C(10), respec-
tively).
nuclei of the diphosphine in 4a ′. Upon warming to room
temperature, this signal gradually disappears while new
signals of the AB spin system of 4a (δ 46.39 and 53.69
ppm; d, 2J PP ) 24.9 Hz) appear (ca. 4a ′/4a ratio 8:1, 1:1,
and 1:4 at -10, 0, and 10 °C, respectively). After ca. 1
h at room temperature the spectrum displays only the
AB pattern. In addition, starting from a solution of
complex 4a in CD2Cl2 at room temperature and then
cooling to -20 °C the reverse transformation is ob-
served. After a few minutes, the spectrum displays the
signals both of the starting complex (4a ) and of the
singlet at 45.65 ppm due to the presence of the stereo-
isomer 4a ′, along with other minor unassigned reso-
nances. These data are consistent with the existence in
solution of an equilibrium between both stereoisomers
(Scheme 3), which probably interconvert through a
chloride bridge cleavage process, involving the formation
of a transient five-coordinate species. A similar isomer-
ization process has been recently described for the
related dimeric species [{RuCl(µ-Cl)(CO)(PiPr2Me)2}2] by
Caulton, Puerta, and co-workers.3o,14
display a typical AB pattern (δ 46.39-64.90 ppm;
2J PP ) 16.6-24.9 Hz), are also fully consistent with the
structural proposal.13
Moreover, the formation of dimeric species was un-
ambiguously confirmed by a X-ray diffraction study of
the complex [{RuCl(µ-Cl)(CO)(dppf)}2] (4a ). A drawing
of the molecular structure is depicted in Figure 4.
Selected bond distances and angles are listed in the
caption; since they can be compared to those observed
for other chlorocarbonyl derivatives, no further com-
ments are deserved.1-6
The coordination geometry around each ruthenium
center can be described as a distorted octahedron in
which the carbonyl group and one chloride ligand occupy
axial positions and the phosphorus atoms of the ferro-
cenyl-diphosphine and two bridging Cl ligands occupy
the equatorial sites. The most relevant feature of this
structure is the anti arrangement of the two metallic
units (transoid-CO isomeric form). Since this dimeric
structure has equivalent phosphorus nuclei, it cannot
correspond to the initial products isolated, indicating
that an isomerization has occurred during the crystal-
lization process. To obtain information on this isomer-
ization, we have examined the 31P{1H} NMR spectra of
a crystalline sample of [{RuCl(µ-Cl)(CO)(dppf)}2] (4a ′)
in CD2Cl2 at variable temperature. Thus, at -20 °C the
spectrum shows a singlet signal at 45.65 ppm, as
expected for the chemically equivalent phosphorus
Rea ctivity of Ha lid e-Br id ged Dim er [{Ru Cl(µ-
Cl)(CO)(d p p f)}2] (4a ): Syn th esis of Mon on u clea r
Com p ou n d s [Ru Cl2(CO)(L)(d p p f)] (L ) CO, BzNC,
P y, P h NH2). Complexes 4a is prone to undergo addition
of two electron donor ligands in accordance with the
observed spontaneous cleavage of the chloride bridges.
Thus, when carbon monoxide is bubbled through a
refluxing THF solution of [{RuCl(µ-Cl)(CO)(dppf)}2]
(4a ), the dicarbonyl complex cis,cis,cis-[RuCl2(CO)2-
(dppf)] (6a ) is formed (89% yield; Scheme 4). IR and
NMR spectroscopic data are consistent with a cis
arrangement of the chloride and carbonyl ligands.
Characteristic features are (a) the two strong ν(CO)
absorption bands that appear at 2009 and 2070 cm-1
in the IR spectrum, (b) the AB pattern of the phosphorus
2
resonances at δ 15.34 and 38.78 ppm; d, J PP ) 25.3
Hz, and (c) the doublet of doublets carbonyl resonances
at 189.15 (dd, 2J CP ) 123.4 and 9.7 Hz) and 195.21 (dd,
2J CP ) 13.8 and 11.8 Hz) ppm.15
(13) Although a monomeric five-coordinate structure [RuX2(CO)-
(PkP)] could be also proposed for complexes 4a ,b and 5a ,b, it has been
discarded on the basis of steric deshielding of the ruthenium atom.
See ref 5.
Analogous cis,cis-[RuCl2(CO)(L)(dppf)] complexes
(L ) BzNC (6b), Py (6c), PhNH2 (6d )) have also been

5230 Organometallics, Vol. 22, No. 25, 2003
Cadierno et al.
obtained (85-95% yield) by treatment of [{RuCl(µ-Cl)-
(CO)(dppf)}2] (4a ) with an excess of benzyl isocyanide,
pyridine, or aniline, respectively (Scheme 4). These
compounds have been characterized by means of stan-
1
dard spectroscopic techniques (IR and H, 31P{1H}, and
13C{1H} NMR) and elemental analyses, all data being
fully consistent with the proposed formulations (see the
Experimental Section for details). Remarkable spectro-
scopic features are (i) (IR) the presence of one ν(CO)
absorption band in the range 1944-1977 cm-1, (ii) (31P-
{1H} NMR) the appearance of a pattern typical of the
AB spin system (δ 17.35-47.11 ppm; 2J PP ) 25.7-28.9
Hz), indicative of unequivalent phosphorus nuclei of the
dppf ligand, and (iii) (13C{1H} NMR) a characteristic
downfield signal (δ 198.23-201.76 ppm) for the carbonyl
2
group that appears as a doublet of doublets with J CP
values of 12.3-15.3 Hz. Moreover, the structure of the
complex cis,cis-[RuCl2(CO)(Py)(dppf)] (6c) has been
unequivocally confirmed by a single-crystal X-ray dif-
fraction study. An ORTEP view of the molecular struc-
ture is shown in Figure 5; bond distances and angles
around the metal are listed in the caption, all of them
being in the expected range.1a
F igu r e 5. ORTEP-type view of the structure of cis,cis-
[RuCl2(CO)(py)(dppf)] (6c) showing the crystallographic
labeling scheme. Only one disposition of the disordered and
mutually trans CO and Cl ligands is shown. Hydrogen
atoms are omitted for clarity, and only the ipso-carbons of
the phenyl rings of the Ph2P groups are shown. Thermal
ellipsoids are drawn at 20% probability level. Selected bond
distances (Å) and angles (deg): Ru-Cl(1) ) 2.427(3); Ru-
Cl(3) ) 2.459(1); Ru-N(1) ) 2.175(4); Ru-P(1) ) 2.342-
(1); Ru-P(2) ) 2.359(1); Ru-C(40) ) 1.795(11); C(40)-O(1)
) 1.134(15); Fe-C* ) 1.642(1); Fe-C** ) 1.643(1); P(1)-
Ru-P(2) ) 95.47(4); P(1)-Ru-C(40) ) 87.3(3); P(1)-Ru-
Cl(3) ) 172.34(4); P(1)-Ru-N(1) ) 90.33(11); P(1)-Ru-
Cl(1) ) 95.41(6); P(2)-Ru-C(40) ) 91.6(3); P(2)-Ru-Cl(3)
) 90.48(4); P(2)-Ru-Cl(1) ) 90.30(6); P(2)-Ru-N(1) )
172.94(11); Cl(1)-Ru-C(40) ) 176.5(3); Cl(1)-Ru-Cl(3) )
89.35(6); Cl(1)-Ru-N(1) ) 85.14(12); N(1)-Ru-C(40) )
92.7(3); N(1)-Ru-Cl(3) ) 84.08(11); C(40)-Ru-Cl(3) )
87.7(3); Ru-C(40)-O(1) ) 175.1(9); C*-Fe-C** ) 176.77-
(1). C* and C** ) centroids of the cyclopentadienyl rings
(C(1), C(2), C(3), C(4), C(5) and C(6), C(7), C(8), C(9), C(10),
respectively).
Ca ta lytic Tr a n sfer Hyd r ogen a tion of Keton es.
Following our interest in ruthenium-catalyzed transfer
hydrogenation of ketones by propan-2-ol,16 we decided
to explore the catalytic activity of the dimeric com-
pounds [{RuX(µ-X)(CO)(PkP)}2] (PkP ) dppf, X ) Cl
(4a ), Br (4b); PkP ) dippf, X ) Cl (5a ), Br (5b)) in
transfer hydrogenation of acetophenone (see Scheme
5).17 Our present interest was mainly motivated by the
recent observation that a hydride species obtained from
the analogous dimeric compound [{RuCl(µ-Cl)(CO)(Cy2P-
(CH2)4PCy2)}2] is a highly active catalyst in the hydro-
genation of ketones.6 In addition, increasing activity was
expected with respect to conventional octahedral chlo-
ride derivatives since the formation of transient five-
coordinate species in solution can readily provide the
required vacant site for coordination of the substrate.
Thus, in a typical experiment, the ruthenium catalyst
precursors 4a ,b and 5a ,b (0.2 mol %, i.e., 0.4 mol % of
Ru) and NaOH (9.6 mol %) were added to a 0.1 M
Sch em e 5
i
solution of acetophenone (5 mmol) in PrOH at 82 °C,
the reaction being monitored by gas chromatography.
(14) A dimer/monomer equilibration has been also proposed by
Caulton and Puerta for the isomerization of complex [{RuCl(µ-Cl)(CO)-
(PiPr2Me)2}2]. Other mechanisms for the 4a /4a ′ stereochemical equili-
bration (involving halide or phosphine arm dissociation) cannot be
totally discarded.
(15) As expected, complex 6a undergoes a decarbonylation process
in refluxing THF (ca. 3 h), regenerating the chloro-bridged dimer
[{RuCl(µ-Cl)(CO)(dppf)}2] (4a ).
(16) (a) Crochet, P.; Gimeno, J .; Garc´ıa-Granda, S.; Borge, J .
Organometallics 2001, 20, 4369. (b) Cadierno, V.; Crochet, P.; Garc´ıa-
AÄ lvarez, J .; Garc´ıa-Garrido, S. E.; Gimeno, J . J . Organomet. Chem.
2002, 663, 32. (c) Crochet, P.; Gimeno, J .; Borge, J .; Garc´ıa-Granda,
S. New J . Chem. 2003, 27, 414. (d) Cadierno, V.; Crochet, P.; D´ıez, J .;
Garc´ıa-AÄ lvarez, J .; Garc´ıa-Garrido, S. E.; Gimeno, J .; Garc´ıa-Granda,
S.; Rodr´ıguez, M. A. Inorg. Chem. 2003, 42, 3293. (e) Cadierno, V.;
Crochet, P.; D´ıez, J .; Garc´ıa-AÄ lvarez, J .; Garc´ıa-Garrido, S. E.; Garc´ıa-
Granda, S.; Gimeno, J .; Rodr´ıguez, M. A. Dalton Trans. 2003, 3240.
(17) For reviews on transition-metal-catalyzed transfer hydrogena-
tion of ketones see: (a) Zassinovich, G.; Mestroni, G.; Gladiali, S. Chem.
Rev. 1992, 92, 1051. (b) Noyori, R.; Hashiguchi, S. Acc. Chem. Res.
1997, 30, 97. (c) Palmer, M. J .; Wills, M. Tetrahedron: Asymmetry
1999, 10, 2045. (d) Noyori, R.; Yamakawa, M.; Hashiguchi, S. J . Org.
Chem. 2001, 66, 7931. (e) Ba¨ckvall, J . E. J . Organomet. Chem. 2002,
652, 105. (f) Carmona, D.; Lamata, M. P.; Oro, L. A. Eur. J . Inorg.
Chem. 2002, 2239. (g) Everaere, K.; Mortreux, A.; Carpentier, J . F.
Adv. Synth. Catal. 2003, 345, 67.
All the complexes have proven to be efficient catalysts,
leading to nearly quantitative conversions of acetophe-
none into 1-phenylethanol within 10 h (Figure 6). The
following features are worth noting: (i) the catalytic
performances shown by dimers containing the bulkier
and more basic dippf ligands 5a ,b are higher than those
of their corresponding dppf counterparts 4a ,b (the
nature of the halide bridges has little influence on the
reaction rate), and (ii) the exceptional high activity of
complexes [{RuX(µ-X)(CO)(dippf)}2] (5a ,b), which reach
very good conversions within 5 min (97% (5a ; X ) Cl)
and 86% (5b; X ) Br)), is retained at lower catalyst
loadings. As an example, using 0.05 mol % of 5a ,
acetophenone (0.1 M solution in iPrOH; ketone/Ru/
NaOH ratio: 1000/1/24) can be reduced in 97% yield
within 5 h. It is interesting to note that initially the
transformation is very rapid, giving rise to a yield of
73% in 1 min (TOF 43600 h-1).

Dimers [{RuX(µ-X)(CO)(PkP)}2] (X ) Cl, Br)
Organometallics, Vol. 22, No. 25, 2003 5231
Ta ble 1. Ca ta lytic Tr a n sfer Hyd r ogen a tion of
Keton es by Com p lex 5a a
F igu r e 6. Catalytic transfer hydrogenation of acetophe-
none by dimers 4a ,b and 5a ,b. Conditions: reactions were
carried out at 82 °C using 5 mmol of acetophenone (0.1 M
in iPrOH). Ketone/Ru/NaOH ratio: 250/1/24. Yield of
1-phenylethanol determined by GC.
The most active complex, [{RuCl(µ-Cl)(CO)(dippf)}2]
(5a ), has also been tested as catalyst in the hydride
transfer hydrogenation of other ketones (see Table 1).
Thus, it has shown to be very efficient in the reduction
of dialkyl ketones (see entries 1-4), although the
presence of bulky substituents in the ketone signifi-
cantly reduces its catalytic activity (i.e., Me(Et)CO vs
Me(tBu)CO; entry 3 vs 4). As observed for acetophenone,
fast reductions have also been found for its ortho-, meta-,
and para-substituted derivatives (see entries 5-11).
Nevertheless, the catalytic performance of 5a is reduced
when an electron-donor group (OMe) is introduced at
the para position of the aromatic ring (see entry 9).18
Assuming that these catalytic transformations proceed
through the well-established pathway in which the
ketone coordinates on mononuclear hydride-ruthenium
intermediates,17,19 the observed effect seems to indicate
that the hydride transfer from the metal to the coordi-
nated ketone is the turnover-limiting step (rather than
the ketone complexation) in the catalytic cycle.20 The
high catalytic efficiency of 5a is also clearly shown in
the transfer hydrogenation of R-tetralone (entry 12),
1-indanone (entry 13), and propiophenone (entry 14)
since the reduction of such substrates is usually dif-
ficult.17
a
Conditions: reactions were carried out at 82 °C using 5 mmol
of ketone (0.1 M in iPrOH). Ketone/Ru/NaOH ratio: 250/1/24.
b
Yield of the corresponding alcohol after 5 min. GC determined.
c Yield after 24 h in parentheses. Yield after 1 h in parentheses.
d
e Yield after 3 h in parentheses.
particular, [{RuCl(µ-Cl)(CO)(dippf)}2] (5a ) has proven
to be a catalyst precursor comparable to the five- or six-
coordinate ruthenium(II) species [RuCl2(PPh3)3],21 [Ru-
Cl2(PPh3)(PkN)] (PkN ) iminophosphines, aminophos-
phines, oxazolinylferrocenylphosphine),16a,c,22 [RuX-
(PPh3)(PkCkP)] (X ) Cl, CF3SO3; PkCkP ) 2,6-
C6H3(CH2PPh2)2),23 [RuCl2(PPh3)(PkNkO)] (PkNkO )
1-(diphenylphosphino)-2-ethoxy-1-(2-pyridyl)ethane),24
Con clu sion s
A novel synthetic route to dimers [{RuX(µ-X)(CO)-
(PkP)}2] (X ) Cl, Br; PkP ) 1,1′-bis(diphenylphosphino)-
ferrocene, 1,1′-bis(diisopropylphosphino)ferrocene), based
on the HX-promoted releasing of the η3-allyl units in
complexes [RuX(η3-2-C3H4R)(CO)(PkP)], has been dis-
covered. These dimers provide synthetically valuable
precursors not only to octahedral mononuclear ruthe-
nium(II) derivatives but also to extremely active cata-
lytic species for transfer hydrogenation reactions. In
[RuCl2(PPh3)(NkPkN)](NkPkN
) bis(oxazolin-2-yl-
methyl)phenylphosphine),25 or [{RuCl(µ-Cl)(NkPkN)}2]
(NkPkN ) bis(oxazolinyl)phenylphosphonite).26 It is
interesting to note that dimers 4a ,b and 5a ,b belong to
(18) Substrate reactivity is not attenuated when the methoxy
substituent is introduced in ortho position (see entry 10). This rate
enhancement can be attributed to chelate binding of o-methoxyac-
etophenone to the metal center. See for example: Evans, D. A.; Nelson,
S. G.; Gagne´, M. R.; Muci, A. R. J . Am. Chem. Soc. 1993, 115, 9800.
(19) Attempts to isolate any catalytic intermediate by reacting 5a
(21) Chowdhury, R. L.; Ba¨ckvall, J .-E. J . Chem. Soc., Chem. Com-
mun. 1991, 1063.
(22) Nishibayashi, Y.; Takei, I.; Uemura, S.; Hidai, M. Organome-
tallics 1999, 18, 2291.
(23) Dani, P.; Karlen, T.; Gossage, R. A.; Gladiali, S.; van Koten, G.
Angew. Chem., Int. Ed. 2000, 39, 743.
i
with NaOH, in PrOH and in the presence of acetophenone, have been
unsuccessful.
(24) Yang, H.; Alvarez, M.; Lugan, N.; Mathieu, R. J . Chem. Soc.,
Chem. Commun. 1995, 1721.
(25) Braunstein, P.; Fryzuk, M. D.; Naud, F.; Rettig, S. J . J . Chem.
Soc., Dalton Trans. 1999, 589.
(20) See for example: (a) Faller, J . W.; Lavoie, A. R. Organometallics
2001, 20, 5245. (b) Faller, J . W.; Lavoie, A. R. Organometallics 2002,
21, 3493.

5232 Organometallics, Vol. 22, No. 25, 2003
Cadierno et al.
3
2.94 (m, 2H each, CH(CH3)2), 3.72 (d, 2H, J HH ) 4.9 Hz,
the limited series of efficient catalysts containing ligands
with no N-H functionalities. As it is well-known, the
presence of an NH group is required to achieve efficient
ketone transfer hydrogenations.17b,d,f,g,27 The synthesis
of related dimers containing optically active diphos-
phines to use in asymmetric catalysis is currently in
progress.
CHH(syn)), 4.36 (br, 6H, C5H4), 4.69 (m, 1H, CH), 4.81 (br, 2H,
C5H4) ppm. 13C{1H} NMR (CD2Cl2): δ 19.69, 20.25, 20.60, and
21.08 (s, CH(CH3)2), 30.21 and 30.52 (d, J CP ) 19.3 Hz, CH-
(CH3)2), 55.62 (m, CH2), 70.69, 71.69, 73.98, and 75.51 (br, CH
of C5H4), 82.31 (d, J CP ) 34.2 Hz, C of C5H4), 98.64 (s, CH),
204.45 (t, J CP ) 15.3 Hz, CO) ppm. 3b: yield 82% (0.548 g).
1
1
2
Anal. Calcd for FeRuC26H41P2BrO: C, 46.73; H, 6.18. Found:
C, 46.51; H, 6.29. IR (KBr, cm-1): ν 1911 (CtO). 31P{1H} NMR
Exp er im en ta l Section
(CD
2Cl2): δ 40.74 (s) ppm. 1H NMR (CD2Cl2): δ 1.32 (m, 24H,
3
3
CH(CH3)2), 2.32 (dd, 2H, J HH ) 12.5 Hz, J HP ) 5.3 Hz,
The manipulations were performed under an atmosphere
of dry nitrogen using vacuum-line and standard Schlenk
techniques. Solvents were dried by standard methods and
distilled under nitrogen before use. All reagents were obtained
from commercial suppliers and used without further purifica-
tion with the exception of compounds [RuX(η3-2-C3H4R)(CO)3]
(R ) H, X ) Cl (1a ),10a Br (1b);10a R ) Me, X ) Cl (1c),10a Br
(1d )10b) and [Fe(η5-C5H4PR2)2] (R ) Ph (dppf),28 iPr (dippf)29),
which were prepared by following the methods reported in the
literature. Infrared spectra were recorded on a Perkin-Elmer
1720-XFT spectrometer. The C, H, and N analyses were
carried out with a Perkin-Elmer 2400 microanalyzer. NMR
spectra were recorded on a Bruker DPX-300 instrument at 300
MHz (1H), 121.5 MHz (31P), or 75.4 MHz (13C) using SiMe4 or
85% H3PO4 as standard. DEPT experiments have been carried
out for all the compounds reported. Abbreviations used: s,
singlet; br, broad singlet; d, doublet; dd, doublet of doublets;
t, triplet; m, multiplet.
CHH(anti)), 2.44 and 2.94 (m, 2H each, CH(CH3)2), 3.71 (dd, 2H,
3
3J HH ) 5.3 Hz, J HP ) 2.0 Hz, CHH(syn)), 4.36 (br, 6H, C5H4),
4.69 (m, 1H, CH), 4.80 (br, 2H, C5H4) ppm. 13C{1H} NMR (CD2-
Cl2): δ 19.69, 20.25, 20.61, and 21.08 (s, CH(CH3)2), 30.21 and
1
30.51 (d, J CP ) 19.5 Hz, CH(CH3)2), 55.62 (m, CH2), 70.70,
1
71.09, 73.99, and 75.51 (br, CH of C5H4), 82.30 (d, J CP ) 34.6
2
Hz, C of C5H4), 98.63 (s, CH), 204.45 (t, J CP ) 15.3 Hz, CO)
ppm.
Syn th esis of [Ru X(η3-2-C3H4Me)(CO)(P kP )] (P kP
)
d p p f, X ) Cl (2c), Br (2d ); P kP ) d ip p f, X ) Cl (3c), Br
(3d )). Gen er a l P r oced u r e. The corresponding diphosphine
(1 mmol) was added at room temperature to a solution of [RuX-
(η3-2-C3H4Me)(CO)3] (1c,d ) (1 mmol) in 30 mL of tetrahydro-
furan. The reaction mixture was heated under reflux for 2 h
(3c,d ) or 7 h (2c,d ) and then evaporated to dryness. The solid
residue was dissolved in dichloromethane (ca. 3 mL) and the
resulting solution transferred to an Al2O3 (neutral; activity
grade I) chromatography column. Elution with methanol gave
a yellow-orange band, from which complexes 2c,d and 3c,d
were obtained by solvent removal. 2c: yield 75% (0.581 g).
Anal. Calcd for FeRuC39H35P2ClO: C, 60.52; H, 4.56. Found:
C, 60.37; H, 4.43. IR (KBr, cm-1) ν 1921 (CtO). 31P{1H} NMR
Syn t h esis of [R u X(η3-C3H 5)(CO)(P kP )] (P kP ) d p p f,
X ) Cl (2a ), Br (2b); P kP ) d ip p f, X ) Cl (3a ), Br (3b)).
Gen er al P r ocedu r e. The corresponding diphosphine (1 mmol)
was added at room temperature to a solution of [RuX(η3-C3H5)-
(CO)3] (1a ,b) (1 mmol) in 30 mL of toluene. The reaction
mixture was heated under reflux for 40 min (3a ,b) or 3 h (2a ,b)
and then evaporated to dryness. The solid residue was dis-
solved in dichloromethane (ca. 3 mL) and the resulting solution
transferred to an Al2O3 (neutral; activity grade I) chromatog-
raphy column. Elution with methanol gave a yellow-orange
band, from which complexes 2a ,b and 3a ,b were obtained by
solvent removal. 2a : yield 75% (0.570 g). Anal. Calcd for
FeRuC38H33P2ClO: C, 60.06; H, 4.38. Found: C, 59.85; H, 4.13.
IR (KBr, cm-1): ν 1926 (CtO). 31P{1H} NMR (CD2Cl2): δ 34.31
1
(CD2Cl2): δ 35.45 (s) ppm. H NMR (CD2Cl2): δ 2.06 (s, 3H,
3
CH3), 2.11 (d, 2H, J HP ) 5.1 Hz, CHH(anti)), 3.57 (s, 2H,
CHH(syn)), 4.18, 4.39, 4.55 and 5.41 (br, 2H each, C5H4), 7.25-
7.65 (m, 20H, Ph) ppm. 13C{1H} NMR (CD2Cl2): δ 26.19 (s,
CH3), 59.52 (m, CH2), 72.06, 72.28, 75.08, and 76.32 (br, CH
1
of C5H4), 82.51 (d, J CP ) 45.1 Hz, C of C5H4), 118.94 (s, C),
2
127.15-138.40 (m, Ph), 204.55 (t, J CP ) 15.0 Hz, CO) ppm.
2d : yield 76% (0.622 g). Anal. Calcd for FeRuC39H35P2BrO:
C, 57.23; H, 4.31. Found: C, 57.42; H, 4.70. IR (KBr, cm-1): ν
1920 (CtO). 31P{1H} NMR (CD2Cl2): δ 35.27 (s) ppm. 1H NMR
3
(s) ppm. 1H NMR (CD2Cl2): δ 2.09 (dd, 2H, J HH ) 8.9 Hz,
3J HP ) 5.0 Hz, CHH(anti)), 3.69 (d, 2H, 3J HH ) 5.8 Hz, CHH(syn)),
4.20, 4.39, 4.55 and 5.40 (br, 2H each, C5H4), 4.91 (m, 1H, CH),
7.30-7.65 (m, 20H, Ph) ppm. 13C{1H} NMR (CD2Cl2): δ 58.80
(m, CH2), 72.05, 72.34, 75.14, and 76.39 (br, CH of C5H4), 82.54
3
(CD2Cl2): δ 2.12 (s, 3H, CH3), 2.18 (d, 2H, J HP ) 5.6 Hz,
CHH(anti)), 3.63 (s, 2H, CHH(syn)), 4.24, 4.45, 4.61, and 5.47 (br,
2H each, C5H4), 7.30-7.70 (m, 20H, Ph) ppm. 13C{1H} NMR
(CD2Cl2): δ 25.89 (s, CH3), 59.23 (m, CH2), 71.76, 71.99, 74.77,
and 76.02 (br, CH of C5H4), 82.23 (d, 1J CP ) 43.6 Hz, C of C5H4),
1
(d, J CP ) 45.0 Hz, C of C5H4), 101.28 (s, CH), 127.25-138.55
2
(m, Ph), 202.98 (t, J CP ) 14.3 Hz, CO) ppm. 2b: yield 80%
2
118.65 (s, C), 127.00-138.15 (m, Ph), 204.26 (t, J CP ) 14.2
(0.644 g). Anal. Calcd for FeRuC38H33P2BrO: C, 56.74; H, 4.13.
Found: C, 56.41; H, 4.02. IR (KBr, cm-1): ν 1926 (CtO). 31P-
{1H} NMR (CD2Cl2): δ 34.55 (s) ppm. 1H NMR (CD2Cl2): δ
Hz, CO) ppm. 3c: yield 69% (0.440 g). Anal. Calcd for
FeRuC27H43P2ClO: C, 50.83; H, 6.79. Found: C, 50.91; H, 6.87.
IR (KBr, cm-1): ν 1908 (CtO). 31P{1H} NMR (CD2Cl2): δ 41.08
3
3
2.07 (dd, 2H, J HH ) 12.8 Hz, J HP ) 5.1 Hz, CHH(anti)), 3.69
1
(s) ppm. H NMR (CD2Cl2): δ 1.38 (m, 24H, CH(CH3)2), 2.05
3
(d, 2H, J HH ) 7.4 Hz, CHH(syn)), 4.18, 4.39, 4.55 and 5.39 (br,
(s, 3H, CH3), 2.45 (m, 4H, CHH(anti) and CH(CH3)2), 3.04 (m,
2H, CH(CH3)2), 3.62 (s, 2H, CHH(syn)), 4.36, 4.41, 4.45, and 4.83
(br, 2H each, C5H4) ppm. 13C{1H} NMR (CD2Cl2): δ 19.41,
20.12, 20.26, and 20.88 (s, CH(CH3)2), 25.45 (s, CH3), 29.73
and 29.75 (d, 1J CP ) 21.2 Hz, CH(CH3)2), 56.65 (m, CH2), 70.43,
2H each, C5H4), 4.90 (m, 1H, CH), 7.30-7.65 (m, 20H, Ph) ppm.
13C{1H} NMR (CD2Cl2): δ 58.75 (m, CH2), 72.07, 72.35, 75.13,
and 76.36 (br, CH of C5H4), 82.46 (d, 1J CP ) 45.0 Hz, C of C5H4),
2
101.24 (s, CH), 127.25-138.50 (m, Ph), 202.99 (t, J CP ) 14.3
Hz, CO) ppm. 3a : yield 70% (0.437 g). Anal. Calcd for
FeRuC26H41P2ClO: C, 50.05; H, 6.62. Found: C, 50.12; H, 6.71.
IR (KBr, cm-1): ν 1913 (CtO). 31P{1H} NMR (CD2Cl2): δ 41.03
1
70.72, 73.38, and 75.26 (br, CH of C5H4), 82.27 (d, J CP ) 34.1
2
Hz, C of C5H4), 115.06 (s, C), 205.78 (t, J CP ) 16.1 Hz, CO)
1
ppm. 3d : yield 77% (0.525 g). Anal. Calcd for FeRuC27H43P2-
BrO: C, 47.52; H, 6.35. Found: C, 47.21; H, 6.14. IR (KBr,
cm-1): ν 1907 (CtO). 31P{1H} NMR (CD2Cl2): δ 41.04 (s) ppm.
1H NMR (CD2Cl2): δ 1.36 (m, 24H, CH(CH3)2), 2.05 (s, 3H,
CH3), 2.47 (m, 4H, CHH(anti) and CH(CH3)2), 3.03 (m, 2H,
CH(CH3)2), 3.61 (s, 2H, CHH(syn)), 4.41, 4.45, 4.51, and 4.82
(br, 2H each, C5H4) ppm. 13C{1H} NMR (CD2Cl2): δ 19.40,
20.13, 20.25, and 20.88 (s, CH(CH3)2), 25.47 (s, CH3), 29.72
and 29.74 (d, 1J CP ) 21.8 Hz, CH(CH3)2), 56.64 (m, CH2), 70.44,
(s) ppm. H NMR (CD2Cl2): δ 1.31 (m, 24H, CH(CH3)2), 2.32
3
3
(dd, 2H, J HH ) 12.2 Hz, J HP ) 4.9 Hz, CHH(anti)), 2.44 and
(26) Braunstein, P.; Naud, F.; Pfaltz, A.; Rettig, S. J . Organometal-
lics 2000, 19, 2676.
(27) Noyori, R.; Ohkuma, T. Angew. Chem., Int. Ed. 2001, 40, 40.
(28) Bishop, J . J .; Davison, A.; Katcher, M. L.; Lichtenberg, D. W.;
Merrill, R. E.; Smart, J . C. J . Organomet. Chem. 1971, 27, 241.
(29) Butler, I. R.; Cullen, W. R.; Kim, T. J . Synth. React. Inorg. Met.-
Org. Chem. 1985, 15, 109.

Dimers [{RuX(µ-X)(CO)(PkP)}2] (X ) Cl, Br)
Organometallics, Vol. 22, No. 25, 2003 5233
1
70.72, 73.38, and 75.26 (br, CH of C5H4), 82.25 (d, J CP ) 34.1
Yield: 89% (0.696 g). Anal. Calcd for FeRuC36H28Cl2O2P2: C,
55.27; H, 3.61. Found: C, 55.21; H, 3.54. IR (KBr, cm-1): ν
2009 and 2070 (CtO). 31P{1H} NMR (CD2Cl2): δ 15.34 and
38.78 (d, 2J PP ) 25.3 Hz) ppm. 1H NMR (CD2Cl2): δ 4.23, 4.30,
4.36, and 4.66 (br, 2H each, C5H4), 7.40-8.25 (m, 20H, Ph)
ppm. 13C{1H} NMR (CD2Cl2): δ 71.70, 72.27, 73.09, and 77.33
2
Hz, C of C5H4), 115.04 (s, C), 205.78 (t, J CP ) 16.1 Hz, CO)
ppm.
Syn th esis of [{Ru X(µ-X)(CO)(P kP )}2] (P kP ) d p p f, X
) Cl (4a ), Br (4b ); P kP ) d ip p f, X ) Cl (5a ), Br (5b)).
Gen er a l P r oced u r e. A solution of complexes [RuX(η3-C3H5)-
(CO)(PkP)] (2a ,b and 3a ,b) or [RuX(η3-2-C3H4Me)(CO)(PkP)]
(2c,d and 3c,d ) (1 mmol) in 50 mL of dichloromethane was
treated at room temperature with the appropriate HX acid (1.5
mL of a 1.0 M solution in diethyl ether;30 1.5 mmol). The
reaction mixture was stirred at room temperature for 30 min
and then evaporated to dryness. The resulting yellow-orange
solid residue was washed with diethyl ether (3 × 50 mL) and
vacuum-dried. 4a : yield 88% (0.664 g). Anal. Calcd for Fe2-
Ru2C70H56Cl4P4O2: C, 55.73; H, 3.74. Found: C, 55.47; H, 3.51.
IR (KBr, cm-1): ν 1987 (CtO). 31P{1H} NMR (CD2Cl2): δ 46.39
and 53.69 (d, 2J PP ) 24.9 Hz) ppm. 1H NMR (CD2Cl2): δ 4.30-
4.55 (m, 16H, C5H4), 7.20-7.90 (m, 40H, Ph) ppm. 13C{1H}
NMR (CD2Cl2): δ 72.70, 73.15, 74.76, and 75.40 (d, 2J CP ) 6.2
2
(d, J CP ) 5.9 Hz, CH of C5H4), 74.48, 75.82, 77.47, and 78.05
(d, 3J CP ) 8.9 Hz, CH of C5H4), 76.79 and 77.57 (d, 1J CP ) 53.8
Hz, C of C5H4), 127.55-136.90 (m, Ph), 189.15 (dd, 2J CP ) 123.4
2
and 9.7 Hz, CO), 195.21 (dd, J CP ) 13.8 and 11.8 Hz, CO)
ppm.
Syn th esis of cis,cis-[Ru Cl
2(CO)(L)(d p p f)] (L ) BzNC
(6b), P y (6c), P h NH
2 (6d )). Gen er a l P r oced u r e. A solution
of complex [{RuCl(µ-Cl)(CO)(dppf)}
2] (4a ) (0.755 g, 0.5 mmol)
in 30 mL of dichloromethane was treated, at room tempera-
ture, with the appropriate ligand (5 mmol) for 2 h. After
removing the solvent under reduced pressure, hexane (50 mL)
was added to the residue, yielding the precipitation of a yellow
solid, which was filtered off, washed with hexane (2 × 50 mL),
and vacuum-dried. 6b: yield 85% (0.741 g). Anal. Calcd for
3
Hz, CH of C5H4), 76.10, 76.21, and 77.05 (d, J CP ) 8.8 Hz,
1
CH of C5H4), 77.67 and 79.01 (d, J CP ) 55.9 Hz, C of C5H4),
FeRuC43H35Cl2P2NO: C, 59.26; H, 4.05; N, 1.61. Found: C,
2
126.90-135.60 (m, Ph), 200.07 (dd, J CP ) 16.2 and 16.2 Hz,
59.15; H, 3.98; N, 1.60. IR (KBr, cm-1
): ν 1977 (CtO), 2221
2
(CtN).
31P{1H} NMR (CD2Cl2): δ 17.35 and 42.83 (d, J PP
)
CO) ppm. 4b: yield 86% (0.725 g). Anal. Calcd for Fe2-
Ru2C70H56Br4P4O2: C, 49.85; H, 3.35. Found: C, 49.62; H, 3.21.
IR (KBr, cm-1): ν 1978 (CtO). 31P{1H} NMR (CD2Cl2): δ 46.96
and 52.72 (d, 2J PP ) 21.1 Hz) ppm. 1H NMR (CD2Cl2): δ 4.05-
4.80 (m, 16H, C5H4), 7.20-7.95 (m, 40H, Ph) ppm. 13C{1H}
NMR (CD2Cl2): δ 73.11, 73.72, 74.58, and 76.31 (d, 2J CP ) 6.6
25.7 Hz) ppm. 1
H NMR (CD2Cl2): δ 4.18, 4.25, 4.29, 4.41, and
4.55 (br, 2H each, C
5H4 and NCH2), 7.20-8.30 (m, 25H, Ph)
ppm. 13
C{1H} NMR (CD2Cl2): δ 48.09 (s, NCH2), 71.19, 71.72,
72.04, and 76.70 (d,
77.17, and 78.16 (d,
2J CP ) 5.1 Hz, CH of C5H4), 74.44, 75.01,
3J CP ) 8.7 Hz, CH of C5H4), 79.31 and
3
79.70 (d,
1J CP ) 53.0 Hz, C of C5H4), 126.95-137.00 (m, Ph
Hz, CH of C5H4), 75.96, 76.75, and 77.47 (d, J CP ) 8.2 Hz,
1
CH of C5H4), 78.45 and 79.49 (d, J CP ) 54.8 Hz, C of C5H4),
and CtN), 198.23 (dd,
2J CP ) 12.3 and 12.3 Hz, CO) ppm. 6c:
2
127.35-136.40 (m, Ph), 201.09 (dd, J CP ) 15.4 and 15.4 Hz,
yield 95% (0.792 g). Anal. Calcd for FeRuC40H33Cl2P2NO: C,
CO) ppm. 5a : yield 87% (0.538 g). Anal. Calcd for Fe2-
Ru2C46H72Cl4P4O2: C, 44.68; H, 5.87. Found: C, 44.51; H, 5.78.
IR (KBr, cm-1): ν 1959 (CtO). 31P{1H} NMR (CD2Cl2): δ 63.40
and 64.90 (d, 2J PP ) 18.1 Hz) ppm. 1H NMR (CD2Cl2): δ 0.75-
1.85 (m, 48H, CH(CH3)2), 2.56, 2.65, 2.92 and 3.46 (m, 2H each,
CH(CH3)2), 4.35-4.95 (m, 16H, C5H4) ppm. 13C{1H} NMR (CD2-
Cl2): δ 17.39, 18.88, 19.34, 20.03, 20.33, 20.79, 21.65, and 22.19
57.64; H, 3.99; N, 1.68. Found: C, 57.47; H, 3.71; N, 1.65. IR
(KBr, cm-1
): ν 1961 (CtO). 31P{1H} NMR (CD2Cl2): δ 35.54
1
and 44.52 (d,
2J PP ) 26.8 Hz) ppm. H NMR (CD2Cl2): δ 4.22,
4.30, 4.61, and 4.69 (br, 2H each, C
Ph and C
5H4), 6.90-8.80 (m, 25H,
5H5N) ppm. 13C{1H} NMR (CD2Cl2): δ 71.14, 71.22,
71.81, and 76.72 (d,
78.19, and 79.25 (d,
83.70 (d,
2J CP ) 6.1 Hz, CH of C5H4), 74.37, 75.10,
3J CP ) 8.6 Hz, CH of C5H4), 78.73 and
1
1J CP ) 52.9 Hz, C of C5H4), 124.30-138.45 (m, Ph
(s, CH(CH3)2), 28.49 (d, J CP ) 25.6 Hz, CH(CH3)2), 28.51 (d,
1J CP ) 29.4 Hz, CH(CH3)2), 29.10 (d, 1J CP ) 28.4 Hz, CH(CH3)2),
and C5H5N), 154.35 (s, C5H5N), 201.54 (dd, J CP ) 15.3 and
15.3 Hz, CO) ppm. 6d : yield 87% (0.737 g). Anal. Calcd for
2
1
29.71 (d, J CP ) 21.8 Hz, CH(CH3)2), 70.38, 70.63, 71.24, and
2
73.60 (d, J CP ) 5.8 Hz, CH of C5H4), 70.83, 71.76, 74.91, and
FeRuC41H35Cl2P2NO: C, 58.11; H, 4.16; N, 1.65. Found: C,
3
75.35 (d, J CP ) 8.5 Hz, CH of C5H4), 79.14 and 79.74 (d,
58.27; H, 4.28; N, 1.63. IR (KBr, cm-1
): ν 1944 (CtO), 3343
2
2
1J CP ) 48.3 Hz, C of C5H4), 201.07 (dd, J CP ) 17.1 and 17.1
(N-H). 31P{1H} NMR (CD2Cl2): δ 41.32 and 47.11 (d, J PP
)
28.9 Hz) ppm.
(br, 2H, NH
1H NMR (CD2Cl2): δ 4.29 (br, 8H, C5H4), 6.71
2), 7.10-8.20 (m, 25H, Ph) ppm. 13C{1H} NMR
Hz, CO) ppm. 5b: yield 83% (0.587 g). Anal. Calcd for Fe2-
Ru2C46H72Br4P4O2: C, 39.06; H, 5.13. Found: C, 39.14; H, 5.02.
IR (KBr, cm-1): ν 1965 (CtO). 31P{1H} NMR (CD2Cl2): δ 62.69
and 63.68 (d, 2J PP ) 16.6 Hz) ppm. 1H NMR (CD2Cl2): δ 0.75-
1.85 (m, 48H, CH(CH3)2), 2.68 (m, 4H, CH(CH3)2), 2.93 and
3.35 (m, 2H each, CH(CH3)2), 4.35-4.90 (m, 16H, C5H4) ppm.
13C{1H} NMR (CD2Cl2): δ 18.67, 18.74, 19.88, 19.96, 20.88,
2
(CD
CH of C
CH of C
2Cl2): δ 71.39, 72.11, 74.07, and 76.74 (d, J CP ) 5.4 Hz,
3
5H4), 74.11, 75.87, 77.68, and 78.12 (d, J CP ) 8.6 Hz,
1
5H4), 82.59 and 82.85 (d, J CP ) 51.7 Hz, C of C5H4),
127.90-135.65 (m, Ph), 201.76 (dd,
CO) ppm.
2J CP ) 15.1 and 15.1 Hz,
1
21.55, 21.96, and 22.47 (s, CH(CH3)2), 29.73 (d, J CP ) 26.6
Gen er a l P r oced u r e for Ca ta lytic Tr a n sfer Hyd r oge-
n a tion of Keton es. Under inert atmosphere, the ketone (5
mmol), the ruthenium catalyst precursor (0.01 mmol, 0.4 mol
% of Ru), and 45 mL of propan-2-ol were introduced into a
Schlenk tube fitted with a condenser and heated at 82 °C for
15 min. Then NaOH was added (5 mL of a 0.096 M solution
in propan-2-ol, 9.6 mol %), and the reaction monitored by gas
chromatography. The corresponding alcohol and acetone were
the only products detected in all cases. The identity of the
alcohols was assessed by comparison with commercially avail-
able (Aldrich Chemical Co. or Acros Organics) pure samples.
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of Com p lexes
2a , 4a ′, a n d 6c. Crystals suitable for X-ray diffraction analysis
were obtained, in all the cases, by slow diffusion of pentane
in a saturated solution of the complex in dichloromethane. The
most relevant crystal and refinement data are collected in
Table 2. The crystal of complex 2a possessed monoclinic
symmetry with systematic absences corresponding to either
space group C2/c or its noncentrosymmetric equivalent, Cc.
Subsequent solution and refinement confirmed the centrosym-
1
Hz, CH(CH3)2), 30.11 (d, J CP ) 29.7 Hz, CH(CH3)2), 30.49 (d,
1J CP ) 28.7 Hz, CH(CH3)2), 31.35 (d, 1J CP ) 21.5 Hz, CH(CH3)2),
2
71.91, 72.10, and 74.63 (d, J CP ) 6.1 Hz, CH of C5H4), 72.63,
3
76.49, and 76.51 (d, J CP ) 9.2 Hz, CH of C5H4), 79.76 and
1
2
79.81 (d, J CP ) 48.1 Hz, C of C5H4), 202.10 (dd, J CP ) 16.4
and 16.4 Hz, CO) ppm.
Syn th esis of cis,cis,cis-[Ru Cl2(CO)2(d p p f)] (6a ). Carbon
monoxide was bubbled through a solution of [{RuCl(µ-Cl)(CO)-
(dppf)}2] (4a ) (0.755 g, 0.5 mmol) in 70 mL of tetrahydrofuran
at 65 °C for 5 h. After removing the solvent under reduced
pressure, diethyl ether (50 mL) was added to the residue,
yielding the precipitation of a yellow solid, which was filtered
off, washed with diethyl ether (2 × 50 mL), and vacuum-dried.
(30) Anhydrous HCl (1.0 M solution in diethyl ether) is commercially
available from Aldrich Chemical Co. The 1.0 M solution of HBr in
diethyl ether was prepared as follows: HBr(g) (prepared in situ by slow
addition of 54 mL of H2SO4 (95%, 17.83 M; 0.963 mol) to 16 g of KBr
(0.134 mol)) was bubbled through 80 mL of diethyl ether at rt. The
resulting solution (ca. 1.5 M) was diluted with 40 mL of diethyl ether.

5234 Organometallics, Vol. 22, No. 25, 2003
Ta ble 2. Cr ysta llogr a p h ic Da ta for Com p lexes 2a , 4a ′, a n d 6c
Cadierno et al.
2a
4a ′
6c
chemical formula
fw
C
38H33P2ClOFeRu
C70H56Cl4P4O2Fe2Ru2‚4CH2Cl2
1848.37
C40H33Cl2P2NOFeRu‚CH2Cl2
918.36
759.95
T (°C)
wavelength (Å)
space group
a, Å
b, Å
c, Å
-153(2)
1.54180
C2/c (No. 15)
13.626(1)
14.878(1)
15.694(1)
90
91.191(6)
90
4
-123(2)
-153(2)
1.54180
P1h (No. 2)
11.1871(5)
11.2331(7)
16.938(1)
83.097(4)
74.654(3)
65.867(3)
2
1.54180
P1h (No. 2)
12.3336(7)
12.7635(7)
13.2492(8)
90.154(4)
103.397(3)
113.446(3)
1
R, deg
â, deg
γ, deg
Z
V, Å3
3180.9(5)
1.587
9.462
1850.9(2)
1.658
11.492
1873.0(2)
1.628
10.081
F
calcd, g cm-3
µ, cm-1
weight function (a, b)
R1a [I > 2σ(I)]
wR2a [I > 2σ(I)]
R1 (all data)
0.0600, 7.2573
0.0554
0.1221
0.0860, 1.1692
0.0495
0.1317
0.1034, 1.5616
0.0517
0.1414
0.0744
0.0552
0.0653
wR2 (all data)
0.1319
0.1376
0.1527
R1 ) ∑(|Fo| - |Fc|)/∑|Fo|; wR2 ) {∑[w(Fo - Fc2)2]/∑[w(Fo2)2]}1/2
.
a
2
metric choice C2/c. The crystals of compounds 4a ′ and 6c
possessed triclinic symmetry, space group P1h (ascertained from
structure determination). Data collections were performed on
a Nonius Kappa CCD single-crystal diffractometer using Cu
KR radiation with a crystal-detector distance fixed at 29 mm,
using the oscillation method, φ- and ω-scans with 2° oscillation,
and 50 s (2a and 6c) or 40 s (4a ′) exposure time per frame.
Data collection strategy was calculated with the program
Collect.31 Data reduction and cell refinement were performed
with the programs HKL Denzo and Scalepack.32 Absorption
correction was applied by means of XABS233 (2a and 6c) or
SORTAV34 (4a ′).
All the structures were solved by Patterson interpretation
and phase expansion using DIRDIF.35 Isotropic least-squares
refinement on F2 using SHELXL97 was performed.36 During
the final stages of the refinements, all the positional param-
eters and the anisotropic temperature factors of all the non-H
atoms were refined (except the mutually trans Cl and CO
ligands in 2a and 6c, and C1 and C1′ atoms of the allyl ligand
in 2a ; these highly disordered groups were found and isotro-
pically refined). The coordinates of H atoms in 2a were found
from difference Fourier maps and included in a refinement
with isotropic parameters (with the exception of those con-
nected to C1, C1′, and C2, which were geometrically located
and their coordinates were refined riding on their parent
atoms). For 4a ′ and 6c, the H atoms were geometrically located
and their coordinates were refined riding on their parent
atoms. The function minimized was [∑w(Fo - Fc2)/∑w(Fo2)]1/2
2
where w ) 1/[σ2(Fo2) + (aP)2 + bP] (a and b values are shown
in Table 2) with σ2(Fo2) from counting statistics and P )
(max(Fo2, 0) + 2Fc2)/3. Atomic scattering factors were taken
from the International Tables for X-ray Crystallography.37
Geometrical calculations were made with PARST.38 The
crystallographic plots were made with PLATON.39
Ack n ow led gm en t. This work was supported by the
Ministerio de Ciencia y Tecnolog´ıa (MCyT) of Spain
(Projects BQU2000-0227, BQU2000-0219, and CAJ AL-
01-03) and the Gobierno del Principado de Asturias
(Project PR-01-GE-4). S.E.G.-G. thanks the MCyT for
the award of a Ph.D. grant.
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic files, in CIF and PDF format, for the structure
determinations of complexes 2a , 4a ′, and 6c. This material is
available free of charge via the Internet at http://pubs.acs.org.
(31) Collect; Nonius BV: Delft, The Netherlands, 1997-2000.
(32) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307.
(33) Parkin, S.; Moezzi, B.; Hope, H. J . Appl. Crystallogr. 1995, 28,
53.
(34) Blessing, R. H. Acta Crystallogr. Sect. A 1995, 51, 33.
(35) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garc´ıa-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF Program System; Technical Report of the Crystallographic
Laboratory; University of Nijmegen: Nijmegen, The Netherlands,
1999.
(36) Sheldrick, G. M. SHELXL97: Program for the Refinement of
Crystal Structures; University of Go¨ttingen: Go¨ttingen, Germany,
1997.
OM030530E
(37) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1974; Vol. IV (Present distributor: Kluwer Aca-
demic Publishers: Dordrecht, The Netherlands).
(38) Nardelli, M. Comput. Chem. 1983, 7, 95.
(39) Spek, A. L. PLATON: A Multipurpose Crystallographic Tool;
University of Utrecht: The Netherlands, 2000.