Syntheses, structures, and reactivity studies of half-open ruthenocenes and their oxodienyl analogues

Article abstract of DOI:10.1021/om010735s

Improved synthetic routes to Cp*Ru(Pdl) complexes (Pdl = 2,4-dimethylpentadienyl and various oxodienyl ligands) including Cp*Ru(η⁵-2,4-Me₂-C₄ H₃O) (1), Cp*Ru[η⁵-2,4-(t-Bu)₂-C₄ H₃O] (1'), and Cp*ru(η⁵-2,4-Me₂-C₅ H₅) (1″) were developed. When chelating, diphosphines were used as coligands and reactions with O₂, Cl₂ or H₂ led to oxidative addition. A carbon-carbon bond activation was reported.

Full text of DOI:10.1021/om010735s

592
Organometallics 2002, 21, 592-605
Articles
Syn th eses, Str u ctu r es, a n d Rea ctivity Stu d ies of
Ha lf-Op en Ru th en ocen es a n d Th eir Oxod ien yl An a logu es
M. Elena Navarro Clemente, Patricia J ua´rez Saavedra,
Marisol Cervantes Va´squez, and M. Angeles Paz-Sandoval*
Departamento de Quı´mica, Centro de Investigacio´n y de Estudios Avanzados del IPN,
Apartado Postal 14-740, Me´xico 07000, D.F., Me´xico
Atta M. Arif and Richard D. Ernst
Department of Chemistry, University of Utah, 315 S. 1400 E., Room 2020,
Salt Lake City, Utah 84112-0850
Received August 10, 2001
Improved synthetic routes to Cp*Ru(Pdl) complexes (Pdl ) 2,4-dimethylpentadienyl and
various oxodienyl ligands) including Cp*Ru(η5-2,4-Me2-C4H3O) (1), Cp*Ru[η5-2,4-(t-Bu)2-
C4H3O] (1′), and Cp*Ru(η5-2,4-Me2-C5H5) (1′′) have been developed, and the relative
reactivities of the resulting complexes toward oxidative addition or ligand addition reactions
have been examined. Thus, the oxopentadienyl complexes 1 and 1′ and the 2,4-dimethyl-
pentadienyl complex 1′′ were found to undergo oxidative addition of SnCl4, Me2SnCl2, I2,
Cl2 (via CHCl3), and O2, yielding Cp*Ru[η3-CH2C(R)CHC(R)O](X1)(X2) [R ) Me, X1 ) Cl, X2
) SnCl3 (2); R ) Me, X1 ) X2 ) I (3); R ) t-Bu, X1 ) X2 ) I, (3′); R ) Me, X1 ) X2 ) Cl (4);
R ) t-Bu, X1 ) X2 ) Cl (4′)] or Cp*Ru[η3-CH2C(Me)CHC(Me)CH2](X1)(X2) [(X1) ) Cl, (X2) )
SnClMe2 (2a ′′); (X1) ) (X2) ) I2 (3′′); (X1) ) (X2) ) Cl2 (4′′)] and a peroxide Cp*Ru[η3-CH2C-
(Me)CHC(Me)O](O2) (5) readily, the oxodienyl products having η3-oxodienyl coordination
occurring preferentially through an all-carbon allylic fragment, in line with ruthenium’s
soft nature. The O2 reaction was of additional interest in that it also led to a product in
which oxidation of the Cp* ligand to a C5Me4(CHO) ligand had occurred, giving (η5-C5Me4-
CHO)Ru[η5-CH2C(Me)CHC(Me)O] (6). In contrast to the above, reactions of the 2,4-di(tert-
butyl)oxodienyl or 2,4-dimethylpentadienyl ligand complexes were much less favorable,
occurring much more slowly, if at all. For the reaction of CHCl3 with the 2,4-dimethylpen-
tadienyl complex, a small amount of an η6-toluene complex, [Cp*Ru(η6-C7H8)][Cp*RuCl3]
(11), was formed, apparently as a result of a carbon-carbon bond activation, giving a
rearrangement of the dienyl ligand. The additions of Lewis bases to the oxodienyl complexes,
leading to Cp*Ru[η3-CH2C(Me)CHC(Me)O]L species [L ) PPh3 (7), PHPh2 (8), PMe3 (9), CO
(10)], were most facile for small donors such as PMe3, while PPh3 and CO additions were
more reversible. Structural data have been obtained for representative examples of the above,
i.e., complexes 1, 1′, 2, 5, 6, 7, and 11.
In tr od u ction
nitrogen into the dienyl fragments. Thus, we have
reported previously the syntheses of several η4-amino-
pentadiene, η3- and η5-azapentadienyl, and η5-oxopen-
tadienyl ruthenium Cp* complexes.1-3
Because of the interesting chemistry displayed by the
oxodienyl complexes, and especially their major differ-
ences relative to the simple dienyl4 and azadienyl2
complexes, it was of particular interest to study the
reactivities of such species toward addition and oxida-
Half-open ruthenocene complexes have proven to be
quite versatile, as it has been found to be straightfor-
ward to incorporate into their pentadienyl ligands a
wide variety of substituents, including alkyl, aryl, CF3,
and siloxy groups.1 Additionally, it has also been pos-
sible to incorporate heteroatoms such as oxygen or
* Corresponding author. E-mail: mpaz@mail.cinvestav.mx.
(1) (a) Trakarnpruk, W.; Arif, A. M.; Ernst, R. D. Organometallics
1992, 11, 1686. (b) Trakarnpruk, W.; Rheingold, A. L.; Haggerty, B.
S.; Ernst, R. D. Organometallics 1994, 13, 3914. (c) Kulsomphob, V.;
Ernst, K. A.; Lam, K.-C.; Rheingold, A. L.; Ernst, R. D. Inorg. Chim.
Acta 1999, 296, 170. (d) Kulsomphob, V.; Turpin, G. C.; Lam, K.-C.;
Youngkin, C.; Trakarnpruk, W.; Carroll, P.; Rheingold, A. L.; Ernst,
R. D. J . Chem. Soc., Dalton Trans. 2000, 3086.
(2) Gutierrez, J . A.; Navarro, M. E.; Paz-Sandoval, M. A.; Arif, A.
M.; Ernst, R. D. Organometallics 1999, 18, 1068.
(3) Trakarnpruk, W.; Arif, A. M.; Ernst, R. D. Organometallics 1994,
13, 2423.
(4) (a) Ernst, R. D. Chem. Rev. 1988, 88, 1255. (b) Bosch, H. W.;
Hund, U.; Nietlispach, D.; Salzer, A. Organometallics 1992, 11, 2087.
10.1021/om010735s CCC: $22.00 © 2002 American Chemical Society
Publication on Web 01/19/2002

Half-Open Ruthenocenes
Organometallics, Vol. 21, No. 4, 2002 593
Sch em e 1
tive addition reactions, especially for the mesityl oxide
derivative Cp*Ru(η5-2,4-Me2-C4H3O) (1), the bulky
Cp*Ru[η5-2,4-(t-Bu)2-C4H3O] (1′), and the hydrocarbon
analogue Cp*Ru(η5-2,4-Me2-C5H5) (1′′).
In fact, electrochemical oxidations of compound 1
under argon and oxygen atmospheres have already been
described, providing evidence of the formation of Ru-
(III) as a reactive chemical species,5 ultimately leading
to the Ru(IV) compound Cp*Ru[η3-CH2C(Me)CHC(Me)O]-
(O2) (5) more efficiently than through the corresponding
chemical reaction (70 vs 57%). A number of other d4
ruthenium(IV) complexes had even earlier been syn-
thesized and studied, particularly regarding their acti-
vation of small molecules.6-14 Recently, increasing
attention has been given to the chemistry of precursors
containing half-sandwich [Cp*Ru(L)2]+ moieties, with
L ) tertiary phosphines or L2 ) bidentate phos-
phines15-17 or diamines.18 In this regard, intramolecular
activation of the pentamethylcyclopentadienyl ligand’s
C-H bonds has also been observed, for both neutral and
cationic Cp*Ru complexes.19-24 Not uncommonly, meth-
yl ring C-H activations have been found to occur therm-
ally or under the influence of strong bases.22 However,
there is more recent evidence that oxygen-induced
methyl C-H activation can occur with surprising facility
in Cp*Ru(III) complexes under ambient conditions,19,23-24
leading to Ru(II) complexes of tetramethylfulvene as
products, which exhibit unusual reactivity patterns of
their own, as described in detail by Maitlis et al.19-24
In particular, the stable cationic 16-electron complex
[Cp*Ru(Me2NCH2CH2NMe2)]+ has been reported to
undergo conversion to a Ru(III) complex, and this inter-
mediate eventually activates a methyl C-H bond of the
Cp* ligand, giving rise to a hydroxoruthenium tetra-
methylfulvene complex, [Ru(η6-C5Me4CH2)(Me2NCH2-
CH2NMe2)(OH)]{B[C6H3(CF3)2]4}.18
In contrast, when chelating diphosphines are used as
coligands, reactions with O2, Cl2, or H2 lead to oxidative
addition, thereby forming Cp*Ru(IV) complexes, which
showed in all cases strong binding between the ruthe-
nium atom and the corresponding activated coordinated
molecule.15-17 An interesting carbon-carbon bond ac-
tivation was even reported by Moro-oka, which resulted
in the 6-methylfulvene complex [Cp*Ru(C5H4CHCH3)]-
(BF4) upon stirring Cp*Ru(norbornadiene)Cl25 in dichlo-
romethane.
In this report, we describe improved synthetic proce-
dures for compounds 1 and 1′′, which involve a reaction
between the tetramer [Cp*RuCl]4 and either the lithium
oxopentadienide or the trimethyltinpentadiene reagent,
respectively, instead of directly using mesityl oxide or
potassium pentadienide, as previously described.1a
A
(5) Navarro-Clemente, M. E.; Chazaro, L. F.; Gonzalez, F. J .; Paz-
Sandoval, M. A. J . Electroanal. Chem. 2000, 480, 18.
(6) Nagashima, H.; Mukai, K.; Shiota, Y.; Ara, K.; Itoh, K.; Suzuki,
H.; Oshima, N.; Moro-oka, Y. Organometallics 1985, 4, 1314.
(7) Nagashima, H.; Mukai, K.; Shiota, Y.; Yamaguchi, K.; Ara, K.;
Fukahori, T.; Suzuki, H.; Akita, M.; Moro-oka, Y.; Itoh, K. Organome-
tallics 1990, 9, 799.
(8) Gemel, C.; Mereiter, K.; Schmid, R.; Kirchner, K. Organometal-
lics 1996, 15, 532.
(9) Gemel, C.; Kalt, D.; Mereiter, K.; Sapunov, V. N.; Schmid, R.;
Kirchner, K. Organometallics 1997, 16, 427.
comparative study of the reactivities of 1, 1′, and 1′′ has
also been undertaken, and the molecular structures of
1, 1′, and the functionalized pentamethylcyclopenta-
dienyl complex 6, the ligand adduct Cp*Ru[η3-CH2C-
(Me)CHC(Me)O] (PPh3) (7), and ruthenium(IV) com-
plexes Cp*Ru[η3-CH2C(Me)CHC(Me)O](Cl)(SnCl3) (2)
and Cp*Ru[η3-CH2C(Me)CHC(Me)O](O)2 (5) are also
discussed.
(10) Itoh, K.; Masuda, K.; Ikeda, H. Organometallics 1993, 12, 2752.
(11) Kirchner, K.; Mereiter, K.; Schmid, R. J . Chem Soc., Chem.
Commun. 1994, 161.
(12) Kirchner, K.; Mereiter, K.; Umfahrer, A.; Schmid, R. Organo-
metallics 1994, 13, 1886.
Resu lts a n d Discu ssion
(13) Mauthner, K.; Mereiter, K.; Schmid, R.; Kirchner, K. Organo-
metallics 1994, 13, 5054.
(14) Gemel, C.; Mereiter, K.; Schmid, R.; Kirchner, K. Organome-
tallics 1995, 14, 1405.
(15) Kirchner, K.; Mauthner, K.; Mereiter, K.; Schmid, R. J . Chem.
Soc., Chem. Commun. 1993, 892.
(16) J ia, G.; Ng, W. S.; Chu, H. S.; Wong, W.-T.; Yu, N.-T.; Williams
I. D. Organometallics 1999, 18, 3597, and references therein.
(17) Rios, I.; J imenez-Tenorio, M.; Padilla, J .; Puerta, M. C.; Valerga,
P. J . Chem Soc., Dalton Trans. 1996, 377.
(18) Gemel, C.; Mereiter, K.; Schmid, R.; Kirchner, K. Organome-
tallics 1997, 16, 5601.
(19) Fan, L.; Turner, M. L.; Adams, H.; Bailey, N. A.; Maitlis, P. M.
Organometallics 1995, 14, 676.
(20) Knowles, D. R. T.; Adams, H.; Maitlis, P. M. Organometallics
1998, 17, 1741.
(21) Guzev, O. V.; Morozova, L. N.; Peganova, T. A.; Antipin, M. Y.;
Lyssenko, K. A.; Noels, A. F.; O’Leary, S. R.; Maitlis, P. M. J .
Organomet. Chem. 1997, 536, 191.
The oxopentadienyl compounds 1 and 1′ were formed
cleanly at -78 °C from the corresponding lithium oxo-
pentadienides and [Cp*RuCl]4 in 80 and 88% yields,
respectively (Scheme 1). The original synthesis of com-
pound 1 utilized mesityl oxide and presumably entailed
a Cp*RuCl(η4-mesityl oxide) intermediate, which lost
HCl in the presence of a mild base in hot THF, giving
1 in ∼65% yield.1a The hydrocarbon analogue Cp*Ru-
(η5-2,4-C7H11) (1′′) has been previously reported,1a,4b and
we now report an alternate and useful synthetic pro-
cedure using [Cp*RuCl]4 and C7H11SnMe3 at -78 °C,
which led to 1′′ in 79% yield (Scheme 1). The constitu-
tions of 1 and 1′ have been confirmed by X-ray structure
determinations (Figures 1 and 2, vide infra). A com-
parative study of the reactivities of compounds 1, 1′, and
of the hydrocarbon analogue 1′′ gave evidence of the
(22) Fan, L.; Wei, C.; Aigbirhio, F. I.; Turner, M. L.; Gusev, O. V.;
Morozova, L. N.; Knowles, D. R. T.; Maitlis, P. M. Organometallics
1996, 15, 98, and references therein.
(23) Fan, L.; Turner, M. L.; Hursthouse, M. B.; Abdul Malik, K. M.;
Gusev, O. V.; Maitlis, P. M. J . Am. Chem. Soc. 1994, 116, 385.
(24) Wei, C.; Aigbirhio, F.; Adams, H.; Bailey, N. A.; Hempstead, P.
D.; Maitlis, P. M. J . Chem Soc., Chem. Commun. 1991, 883.
(25) Suzuki, H.; Kakigano, T.; Fukui, H.; Tanaka, M.; Moro-oka, Y.
J . Organomet. Chem. 1994, 473, 295.

594 Organometallics, Vol. 21, No. 4, 2002
Navarro Clemente et al.
The iodine and chlorine derivatives were found to
exist as mixtures of endo,anti and exo,syn isomers 3n a ,
3xs, and 4n a , 4xs, respectively (see Schemes 2 and 3).
However, while both chlorine isomers were present at
room temperature, for the iodine derivative the reaction
initially yielded as a kinetic product the endo,anti-
oxopentadienyl isomer 3n a , and only at elevated tem-
peratures was there evidence of isomerization to the
thermodynamically favored exo,syn 3xs (Scheme 3).
After 24 h at 45 °C in CDCl3, these were observed in a
0.05:0.95 ratio according to their respective Cp* signals
at 1.96 and 1.95 ppm. After a total of 15 days and 4
months, respectively, three different compounds were
easily detected from the corresponding Cp* signals
observed at 1.96, 1.95, and 1.69 ppm in 0.54:0.33:0.13
and 0.12:0.36:0.52 ratios, and these were assigned to
3n a , 3xs, and [Cp*RuI2]2.26 It was also demonstrated
that the pure chlorine isomer 4n a underwent partial
isomerization, in a sealed NMR tube in CDCl3 after 4
and 15 days at 60 °C, to the 4xs isomer in 50:50 and
17:83 ratios, accompanied by a small amount of
[Cp*RuCl2]2 and traces of Cp*2Ru. After 56 days, 4n a
had been completely consumed, giving evidence of the
corresponding kinetic and thermodynamic species. Simi-
lar endo to exo isomerizations have also been described
for [CpFe(η3-CH2CR1CR2R3)(CO)] [R1 ) H, Me; R2 ) R3
) OMe, Cl, H, or OPh],27 Co(η3-CH2C(Me)CHC(Me)-
CH2)(PMe3)3,28 and CpRu(η3-CH2C(Me)CH2)(CO).29 It
should be noted that analogous halogen derivatives such
as Cp*Ru(η3-allyl)(X)2 (X ) I,6 Br,6,7 Cl7), Cp*Ru(η3-
F igu r e 1. Structure of Cp Ru[η5-CH2C(Me)CHC(Me)O] (1).
8
oxopentadienyl)(Br)2,8 and Cp*Ru(η3-pentadienyl)(Br)2
have previously been reported.
Along with isomers 4n a and 4xs, the reaction be-
tween 1 and CHCl3 gave three other compounds. This
nonselective reaction produced five fractions after thin-
layer chromatography, corresponding to [Cp*RuCl2]2 [1H
NMR (CDCl3) δ = 5.00 (br)], (Cp*)2Ru (δ ) 1.84 ppm),
4n a , 4xs, and a dark green solid, which was not fully
characterized.30 In fact, a number of other activation
reactions, in particular when C-C bonds have been
involved, have led to the formations of intense green
solutions, and various mononuclear,31 binuclear,3 or
cluster32a compounds have been isolated.
F igu r e 2. Structure of Cp Ru[η5-CH2C(t-Bu)CHC(t-Bu)O]
(1′).
Surprisingly, in the presence of traces of air, a THF
solution of compound 1, BF3‚OEt2, and t-BuNH2 at -78
higher reactivity of the oxo-derivative 1 toward oxidative
additions, as well as in simple ligand addition reactions.
(a ) Oxid a tive Ad d ition Rea ction s. Oxop en ta d i-
en yl Com p ou n d s. As shown in the oxidative addition
reactions described in Scheme 2, new Cp*Ru(IV)(η3-
oxopentadienyl)(X1)(X2) compounds 2-5 can be synthe-
sized, under very mild conditions, through reactions of
Cp*Ru(II)(η5-2,4-Me2C4H3O) (1) with SnCl4, I2, CHCl3,
and O2 respectively. Addition of other potential oxidizing
agents, such as CH3I (1:100) or Me3SnCl (1:2), to 1 did
not lead to reaction even with an excess of reactant and
(26) (a) For Cp*RuI2 dimer: 1H δ ) 1.71 (s), 13C δ ) 12.98, 99.01
ppm in CDCl3. For Cp*RuCl2 dimer: 1H δ ) 5.075-4.85 (broad), 13C
δ ) not observed. (b) Koelle, U.; Kossakowski, J . J . Organomet. Chem.
1989, 362, 383.
(27) Fish, R. W.; Giering, W. P.; Marten, D.; Rosenblum M. J .
Organomet. Chem. 1976, 105, 101.
(28) Bleeke, J . R.; Peng W.-J . Organometallics 1984, 3, 1422.
(29) Gibson, D. H.; Hsu, W.-L.; Steinmetz, A. L.; J ohnson B. V. J .
Organomet. Chem. 1981, 208, 89.
(30) The same green powder was formed from reactions of 1, 1′, and
1′′ with CHCl3. The presence of cationic [(Cp*RuCl)3CH] is proposed
according to NMR [1H NMR (CDCl3) δ ) 1.69 (Cp*) and 19.9 (CH)
ppm; 13C NMR (CDCl3) δ ) 11.6 and 97.5 (Cp*) and 342.1 (CH) ppm]
and mass spectrum [FAB (glycerol and CHCl3): 828(9), 521(10), 277-
(15), 185(100)]. This compound, perhaps accompanied by a Cp*RuCl3
counterion, is analogous to a previously reported salts.32a Separation
of 4n a ′ from the green soluble product can be carried out chromato-
graphically on alumina by elution with ethanol.
1
strong refluxing conditions. The H and 13C NMR data
of complexes 1-5 are summarized in Tables 1 and 2.
The formation of the Sn-Ru bonded compound from
the oxidative addition of SnCl4 to 1 at room temperature
proceeded in 76% yield. Immediately after addition of
the Lewis acid one could observe an orange precipitate
of compound 2, Cp*Ru[η3-CH2C(Me)CHC(Me)O](Cl)-
(SnCl3), partially soluble in CH2Cl2, CHCl3, and acetone.
The structure of 2 was determined through a single-
crystal X-ray diffraction study (Figure 3, vide infra).
(31) Rios, I.; J imenez-Tenorio, M.; Padilla, J .; Puerta, M. C.; Valerga,
P. Organometallics 1996, 15, 4565.
(32) (a) Rondon, D.; Delbeau, J .; He, X.-D.; Sabo-Etienne, S.;
Chaudret, B. J . Chem. Soc., Dalton Trans. 1994, 1895, and references
therein. (b) Chaudret, B. Bull. Soc. Chim. Fr. 1995, 132, 268. (c)
Rondon, D.; He, X.-D.; Chaudret B. J . Organomet. Chem. 1992, 433,
C18. (d) Rondon, R.-D.; Chaudret, B.; He, X.-D.; Labroue, D. J . Am.
Chem. Soc. 1991, 113, 5671, and references therein.

Half-Open Ruthenocenes
Organometallics, Vol. 21, No. 4, 2002 595
Sch em e 2
Ta ble 1. 1H NMR Da ta a for P en ta d ien yl or Oxop en ta d ien yl Ru Cp * Com p ou n d s 1-10
compound
H1 anti
H1 syn
H3
H(C5)
H(C6)
Cp*
1
2.28
3.25
(3.10)
3.59
(3.46) (d, 1.1)
2.16
(1.97) (d, 2.2)
4.40
3.48
3.40
4.35
(4.40)
4.16
4.29 (d, 2.0)
2.60
(3.00)
4.10
3.80
4.04 (d, 2.0)
3.40
4.68
(4.80)
5.53
(5.43)
4.78
(4.84)
5.10
4.08
3.90
5.40
(5.40)
2.49
5.79 (d, 2.0)
4.25
(4.16)
4.90
2.80
5.52 (d, 2.0)
3.90
1.96
(1.99)
1.14
(1.08)
1.73
(1.77)
2.10
2.10
2.20 (d,1.3)
1.59
(2.10)
2.41
1.48
2.10
(1.95)
2.07
2.40
1.43
2.18
1.62
1.86
1.48
(1.54)
1.35
(1.23)
1.73
(1.77)
2.30
2.52
2.44
2.80
(2.70)
2.77
1.20
2.78
(2.50)
2.44
2.60
1.15
2.44
1.81
1.31
1.59
(1.68)
1.71
(1.79)
1.68
(1.79)
1.80
1.75
1.55
1.55
(1.90)
1.96
1.92
1.40
(1.78)
1.60
1.61
1.52
1.55
1.27
1.78, 1.73, 1.35,
1.26, 10.29 (CHO)
1.39
J P-H ) 1.3
1.55
J P-H ) 2.6
1.58
J P-H ) 1.5
1.52
(1.58)b
2.12
1′
(1.48)b
0.36
1′′c
(-0.02) (d, 2.2)b
3.80
2b
2′′b,d
2a ′′b,d
3n a
2.40
2.36
3.78
(3.78)b
1.89
3xsb
3n a ′b
3n a ′′d
3.98
1.35
(1.85)e
3.88
4n a b
4xsb
4n a ′
4n a ′′b,d
5
2.17
4.10
1.9
3.40
3.45
3.34
4.40
4.54
6
2.37
7f
8f
9f
10
1.00
J P-H ) 19.0
0.97
J P-H ) 20.5
0.78
J P-H ) 18.3
2.60
2.10
2.10
1.77
3.40
1.48
J P-H ) 15.4
1.07
J P-H ) 15.8
1.38
J P-H ) 15.8
3.10
1.99
1.68
1.88
1.54
2.60
2.62
2.65
2.00
a
In C6D6. δ values are in ppm and J values in hertz. For numbering, see oxopentadienyl ligand in any crystal structure figure or
Scheme 2. In CDCl3. c References 1a and 4b. Vinylic protons, 2′′: 5.21(s), 5.54 (s); 2a ′′: 5.08 (d, J ) 2.0), 5.50 (t, J ) 2.0); [SnClMe2:
1.25 (J SnH ) 8.2), 1.20 (J SnH ) 6.7)]; 3n a ′′: 5.0 (s), 5.27 (s); 4n a ′′: 5.1 (s), 5.5 (t, J ) 1.5). e In CD2Cl2. f Aromatic hydrogens for compounds:
7, 7.0-7.9 ppm; 8, 6.9-7.6 ppm; methyl hydrogens for compound 9, 0.87 ppm (J P-H ) 7.4).
b
d
°C afforded, after evaporation of THF, the previously
reported complex Cp*Ru[η3-CH2C(Me)CHC(Me)O](O2)
(5), in a very low yield (3%), as orange crystals.33a The
molecular structure of 5 (Figure 4) is described below.
In an attempt to avoid polymerization due to the BF3‚
OEt2, and thereby improve the synthesis of 5, we
replaced THF by CH2Cl2. However, from a stoichiomet-
ric mixture of compounds 1, BF3‚OEt2, and t-BuNH2, a

596 Organometallics, Vol. 21, No. 4, 2002
Navarro Clemente et al.
Ta ble 2. 13C NMR Da ta a for P en ta d ien yl or Oxop en ta d ien yl Ru Cp * Com p ou n d s 1-10
compound
C1
C2
101.2
C3
C4
C5
C6
CCp*
MeCp*
10.6
1
1′
54.8
48.5
84.0
71.7
135.0
151.1
23.2
31.2
25.1
29.4
87.1
87.7
117.2
11.9
(td, J CH ) 150)
(dd, J CH ) 150)
(q, J CH ) 126)
35.9
(q, J CH ) 126)
37.8
(q, J CH ) 126)
1′′b
45.0
92.3
91.5
(d, J CH ) 155)
66.8
87.6
85.7
63.7
66.8
92.3
25.9
(q, J CH ) 127)
34.8
17.4
18.3
36.0
33.8
25.9
(q, J CH ) 127)
22.8
24.5
24.7
26.4
24.2
89.6
10.9
(q, J CH ) 124)
9.3
9.5
9.4
11.9
11.8
12.0
(t, J CH ) 154)c
55.1
2c
117.8
109.4
108.0
111.5
n.o.
205.3
142.5
144.4
207.2
205.8
216.0
104.7
102.8
103.3
104.0
n.o.
2′′c,d
2a ′′c,d
3n a
64.7
65.7
58.5
61.3
3xsc
3n a ′c
50.1
130.6
52.0
29.7
26.4
104.7
40.8
24.4
(24.2)
36.2
34.7
47.4
26.3
(26.2)
20.4
18.4
3n a ′′d
59.3
104.7
(105.1)
115.8
110.1
132.7
82.4
(83.5)
70.5
70.1
62.4
145.2
(145.0)
207.3
205.7
216.0
100.4
(101.6)
106.8
106.5
107.5
11.3
(11.8)
9.5
9.5
9.8
(60.2)e
61.8
4n a c
4xsc
66.7
53.9
4n a ′c
31.8
26.7
(t, J CH ) 165.3)
(d, J CH ) 158)
(q, J CH ) 127)
40.5
(q, J CH ) 127)
47.4
4n a ′′c,d
5
6
65.7
51.8
56.2
108.0
114.4
103.8
85.7
61.0
83.0
144.5
205.6
139.9
18.4
33.1
23.4
24.7
18.1
24.5
103.4
102.7
9.4
8.5
9.3, 10.4,
190.0 (CHO)
9.6
7d,f
8d,f
9d,f
37.7
J P-C ) 6.6
37.9
J P-C ) 5.4
36.0
J P-C ) 6.8
41.0
88.1
J P-C ) 2.2
89.1
47.7
J P-C ) 3.3
51.0
202.0
201.7
200.6
200.5
34.7
30.6
30.8
29.0
20.1
J P-C ) 2.2
19.9
89.8
86.5
88.9
94.3
9.0
83.4
91.8
46.7
J P-C ) 3.6
58.0
20.2
24.7
9.8
10d
10.4
a
In C6D6. δ values are given in ppm and J values in hertz. For numbering see oxopentadienyl ligand in the crystal structure figures.
References 1a and 4b. c In CDCl3. 13C NMR data for compounds: 2′′, 124.2 (-RCdCH2); 2a ′′, 122.6 (-RCdCH2), 12.4, 13.7 (-SnClMe2);
b
d
3n a ′′, 121.5 (-RCdCH2); 4n a ′′, 121.9 (-RCdCH2); 7, 135.3 (d, 8.8 Hz,i), 132.2 (d, 10.8 Hz,o), 129.0 (s,p), 127.1 (d, 10.6 Hz, m); 8, 135.1
(s, i), 132.7 (d, 9.2 Hz, o), 129.5 (s, p), 128.7 (s, m); 9, 18.3 ppm (J P-C ) 26.5 Hz); 10, 209.9 ppm. e In CD2Cl2. 31P NMR data for compound:
f
7, 69.9 ppm; 8, 56.0 ppm, J P-H ) 328 Hz; 9, 7.7 ppm.
Sch em e 3
clopentadienyl complexes are not uncommon and, as
already mentioned, can be induced by the presence of
oxygen, leading to tetramethylfulvene or other types of
functionalized polyalkylated cyclopentadienyl complexes
(vide supra), such as the aldehyde derivatives [(η5-C5-
Me4CHO)Ru(CO)2X] (X ) Cl,Br, I, SCN).20
F igu r e 3. Structure of Cp Ru[η3-CH2C(Me)CHC(Me)O]-
(Cl)(SnCl3) (2).
new product mixture was obtained which again con-
tained complexes 1 and 5, but also an additional
product, 6, which spectroscopic and crystallographic
data revealed to be the previously reported aldehyde
derivative [η5-C5Me4CHO]Ru[η5-CH2C(Me)CHC(Me)O]
(6) (Figure 5) resulting from a ring-methyl activation
reaction.5 Ring-methyl activations in pentamethylcy-
(33) (a) Initial elution of the product mixture on alumina using 1:1
hexane/ether led to a 55% recovery of 1. Subsequent elution with ether
led to two orange bands, the second of which was 5. (b) We were
expecting that compound 1 in the presence of primary tert-butylamine
would afford, by nucleophilic attack, an azapentadienyl complex,
analogous to complex 1, in a similar manner as the one reported for
(oxopentadienyl)Mn(tricarbonyl) complexes.33c (c) Cheng, M.-H.; Cheng,
C.-Y.; Wang, S.-L.; Peng, S.-M.; Liu, R.-S. Organometallics 1990, 9,
1853.

Half-Open Ruthenocenes
Organometallics, Vol. 21, No. 4, 2002 597
dependent on the absence or presence of oxygen in the
acetonitrile solutions.5
It is important to mention that exposure of compound
1 in CH3NO2 to air also gave evidence of formation of
5, while addition of pure O2 allowed isolation of complex
5 in 57% yield, even without electrolysis. It was further
confirmed that a slow chemical reaction in CH3CN
between [Cp*Ru(CH3CN)3]PF6 and 5 led to the activa-
tion of the Cp* ligand in 5 giving compound 6.5 Most of
the previously reported complexes having an oxygen
molecule coordinated to ruthenium atoms have been
cationic species, such as [Cp*Ru(IV)(η2-O2)L2]+ (L2
)
dppe,15,16 dppm,16 dippe17) in which the O2 coordination
has appeared strong enough to render the complexes
relatively unreactive, except when a nitrogen chelate
was present (L2 ) Me2NCH2CH2NMe2),18 giving in that
case a tetramethylfulvene complex (vide supra), for
which [Cp*Ru(IV)(η2-O2)L2]+ was tentatively proposed
to be an intermediate, although the dioxygen ligand was
considered more likely to be a superoxo than a peroxo
species.18
F igu r e 4. Structure of Cp*Ru[η3-CH2C(Me)CHC(Me)O]-
(O)2 (5).
On the basis of the above, interesting chemistry
should be expected from neutral compound 5. It has
already been demonstrated that this complex is remark-
ably stable at room temperature and that it can also
release, under not unduly harsh conditions, the acti-
vated oxygen molecule, which could therefore take part
in selective oxidation reactions. In fact, passing 5
through a chromatographic column regenerated com-
pound 1, while activation of the Cp* ligand in compound
5 to give the aldehyde derivative 6 was already evident
after heating in C6D6 for 20 h at 40 °C. After 10 days at
this temperature there was a complete conversion of 5
into 6 and 1 in an approximate 1:0.8 ratio. In an effort
to understand this reaction we undertook 1H NMR
studies of the interaction of compound 1 with 1 equiv
of BF3‚OEt2 in C7D8. The resulting spectra gave evi-
dence, at low temperature, of the formation of the
presumed adduct Cp*Ru(OEt2)(η3-CH2C(Me)CH(Me)-
COfBF3). At -50, -30, and -10 °C there was no
evidence of compound 1, but new signals at 5.7(s, 1H),
4.2(s, Hsyn), 3.6(s, Hanti) 2.3(s, 3H), 1.6(s, 3H), 1.3(s, 15H),
3.2(q, Et2O), and 1.2(t, Et2O) suggested the formation
of an η3-oxopentadienyl complex, due to the coordination
to BF3 by the oxygen atom in compound 1. Above -10
°C the η3-oxopentadienyl complex began to eliminate the
BF3‚OEt2 adduct, and once again the signals from
F igu r e 5. Structure of (η5-C5Me4CHO)Ru[η5-CH2C(Me)-
CHC(Me)O] (6).
In Scheme 4 a tentative mechanism is proposed for
the formation of compound 6, having compound 5 as an
intermediate. The presence of a tetramethylfulvene
derivative is in agreement with Maitlis’ results for
similar ruthenium complexes.19,22-24 In our case we did
not observe a fulvene intermediate, which presumably
could lead to immediate regeneration of the aromatic
ring functionalized by a hydroperoxide group, and after
subsequent loss of water could afford the corresponding
aldehyde derivative 6.
1
compound 1 began to appear in the H NMR spectrum.
Finally, at room temperature there were signals for
compound 1 (1.92, 4.6, 1.45, 3.18, 2.1, 1.58, see Table
1), along with the corresponding signals for Cp*Ru-
(OEt2)(η3-CH2C(Me)CH(Me)COfBF3) in a 1:0.9 ratio.
As a result of the apparent ease of η5 f η3 f η5
interconversions of the oxopentadienyl ligand in com-
pounds 1, 5, and 6, respectively (see Scheme 4), as well
as the redox susceptibility of the ruthenium centers [Ru-
(II) f Ru(IV) f Ru(II)] in each case, we decided to
attempt the electrosynthesis of compound 5. After
several modifications of the experimental conditions, we
found that electrochemical oxidation of compound 1
under an oxygen atmosphere indeed offered a better
synthetic route, providing compound 5 in a yield of 70%.
The anodic oxidation of 1 was performed in acetonitrile
or nitromethane on a glassy carbon electrode. The
electrochemical behavior was found to be strongly
In the case of the oxopentadienyl compound 1′, with
bulky tert-butyl groups present on C2 and C4, the
corresponding oxidative addition reactions proceeded
much more slowly than those with just methyl group
substituents, such as 1 and 1′′. The reaction of 1′ with
I2 and CHCl3 led to the isolable compounds 3n a ′ and
4n a ′ (analogous to 3n a and 4n a in Scheme 2) in 63%
and 25% yields, respectively. The 1H and 13C NMR data
for 3n a ′ and 4n a ′ are listed in Tables 1 and 2. As had
been observed for compounds 3 and 4, compounds 3n a ′
and 4n a ′, in CDCl3 solution, were found to occur as
inseparable mixtures with the corresponding [Cp*RuX2]2

598 Organometallics, Vol. 21, No. 4, 2002
Navarro Clemente et al.
Sch em e 4
1
molecules [X ) Cl, H NMR (CDCl3) δ ≈ 5.0 (br) (vide
low stability of 2a ′′ prevented its characterization by
elemental analysis. No reaction was observed for the
less acidic Me3SnCl.
infra), X ) I, H NMR (CDCl3) δ 1.71 (s), 13C NMR δ
1
13.1, 96.0],26 while there was also evidence of the free
R,â-unsaturated ketone [t-BuC(O)CHC(Me)t-Bu]. As
was the case for 1 and CHCl3, the reaction of 1′ with
Stirring compound 1′′ in CHCl3 at room temperature
afforded 4n a′′, along with the paramagnetic [Cp*RuCl2]2,
and a deep green solid,30 which was recrystallized from
CHCl3/Et2O, yielding a mostly green powder, in which
a few red crystals were observed. The red crystals
corresponded to a novel and interesting C-C coupling
product in which the pentadienyl ligand was converted
to an η6-toluene molecule coordinated to the Cp*Ru
fragment. This cationic complex is accompanied by a
paramagnetic Cp*RuCl3 counterion. The formation of
[Cp*Ru(η6-C7H8)][Cp*RuCl3] (11) (Figure 6, vide infra)
along with the Cp*RuCl2 dimer in the same reaction
suggested an equilibrium between the dimer and chlo-
ride ions, forming the anionic fragment, which is favored
in the presence of the large and very stable cation
[Cp*Ru(η6-C7H8)+]. A high affinity for aromatic hydro-
carbons has been previously reported for the Cp*Ru+
fragment,8,34,35 and aromatization of hydrocarbons by
the electrophilic “Cp*Ru+” fragment has also been
observed.32,34 The mechanism for the cyclization of the
2,4-dimethylpentadienyl fragment through C-C activa-
tion is unclear. Recently, Salzer36 et al. reported the
isolation of [Cp*Ru(toluene)]+ from attempts to prepare
Cp*Ru(2,4-dimethylpentadienyl) complexes in EtOH.
While they proposed that formation of this cationic
complex was due to the presence of traces of toluene in
the EtOH, it is also possible, if not more likely, that the
toluene ring was formed in situ, as in the case of
compound 11, which was prepared in chloroform.
The higher yields for the isolation of the Ru(IV)
derivative Cp*Ru[η3-CH2C(R1)CHC(R1)R2](Cl)(X) [R1 )
Me, R2 ) O, X ) SnCl3], 2, as compared to the R1 ) Me,
R2 ) CH2; X ) SnCl3, 2′′, or SnMe2Cl, 2a ′′, analogues,
and the lack of formation of the corresponding derivative
for R1 ) t-Bu, R2 ) O, and X ) SnCl3, may be attributed
1
CHCl3 was found through H NMR to lead to a complex
mixture of 4n a ′ and [Cp*RuCl2]2, along with other spe-
cies that were not characterized, but displayed a sharp
singlet at 1.69 ppm30 and a broad singlet at 1.78 ppm.
Monitoring the reaction of 1′ and Me2SnCl2 in benzene
or THF showed that there was no oxidative addition;
instead, and after only 2 days, there was evidence of
free R,â-unsaturated ketone [t-BuC(O)CHC(Me)t-Bu],
along with starting materials. After 70 h at 40-45 °C,
there was a 1:0.85 ratio of free ketone and 1′, respec-
tively. In contrast, 1′ and SnCl4 gave a bright orange
solution at -78 °C, but as soon as the temperature
increased, the product became dark brown, and several
attempts to isolate the orange product at low temper-
ature failed. Although not all of these reactions led to
isolable products, it may in any case be recognized that
the presence of bulky tert-butyl substituents consider-
ably reduced the reactivity of the oxopentadienyl com-
pound 1′ compared to 1.
P en ta d ien yl Com p ou n d s. Analogous pentadienyl
compounds 2′′, 3n a ′′, 4n a ′′, and Cp*Ru[η3-CH2C(Me)-
CHC(Me)CH2](Cl)(SnMe2Cl) (2a ′′) were formed by the
oxidative additions of SnCl4, I2, CHCl3, and Me2SnCl2
with Cp*Ru[η5-CH2C(Me)CHC(Me)CH2] (1′′). Compara-
tively, 1′′ reacted more slowly than the corresponding
oxopentadienyl compound 1. The previously described
oxodienyl products 2, 3n a , 3xs, 4n a , and 4xs were
relatively easily isolated compared to their correspond-
ing pentadienyl complexes. Of these, only 3n a ′′ could
be isolated and fully characterized, while the formula-
tions of other species have had to rely on spectroscopic
data (see Tables 1 and 2). Also, it was observed that
attempts, even in chloroform, to recrystallize samples
of 2′′ afforded every time less soluble species, which
suggested that reactive species are involved and that
they undergo transformation during the purification
process. Seven milligrams of compound 2a ′′ was iso-
lated, and this sample was found to convert in chloro-
form solution to the corresponding compound 4n a ′′,
suggesting a labile Ru-Sn bond. The small quantity and
(34) (a) Carreno, R.; Urbanos, F.; Dahan, F.; Chaudret, B. New J .
Chem. 1994, 18, 449. (b) Masuda, K.; Ohkita, H.; Kurumatani, S.; Itoh,
K. Organometallics 1993, 12, 2221.
(35) (a) Fagan, P. J .; Ward, M. D.; Caspar, J . V.; Calabrese, J . C.;
Krusic, P. J . J . Am. Chem. Soc. 1988, 110, 2981. (b) Fagan, P. J .; Ward,
M. D.; Calabrese, J . C. J . Am. Chem. Soc. 1989, 111, 1698.
(36) Bauer, A.; Englert, U.; Geyser, S.; Podewils, F.; Salzer A.
Organometallics 2000, 19, 5471.

Half-Open Ruthenocenes
Organometallics, Vol. 21, No. 4, 2002 599
F igu r e 6. Structure of [Cp*Ru(η6-C7H8)][Cp*RuCl3] (11).
F igu r e 7. Structure of Cp*Ru[η3-CH2C(Me)CHC(Me)O]PPh3 (7).
to the higher reactivity of the Cp*Ru(η5-2,4-dimethyl-
oxopentadienyl) complex. This fact can be explained by
an increase in facility of the η5 T η3 interconversion for
the harder, more electronegative oxopentadienyl ligand.
The lack of formation of the corresponding derivatives
for R1 ) t-Bu, R2 ) O, and X ) SnCl3 may be traced to
the increased steric effects of the tert-butyl substituents.
(b) Ad d ition Rea ction s. Oxop en ta d ien yl Com -
p ou n d s. The addition of phosphines, PR3 (R ) Ph, Me
or R3 ) HPh2), in cyclohexane to compound 1 led to the
formation of compounds 7-9 as described in Scheme 2.
The complexes are air-stable in the solid state but
readily oxidized in solution. The addition reactions
generally proceed much more slowly than the oxidative
additions. For example, 1 equiv of triphenylphosphine
in a cyclohexane solution of compound 1 was heated
under reflux for 7.5 h, but after workup (see Experi-
mental Section), only a 13% yield of Cp*Ru[η3-CH2C-
(Me)CHC(Me)O]PPh3 (7) was obtained (Figure 7). Even
with prolonged reaction times (22 h), excesses of PPh3
(2:1), or a change in solvent (THF), the yields were not
improved, and in each case, significant quantities of
compound 1 remained, necessitating an inconvenient
separation of 1 and 7, whether through recrystallization
1
or sublimation, even after chromatography. Through H
and 31P NMR studies of pure compound 7 in C6D6 the
facile dissociation of PPh3 became evident, along with
the consequent formation of compound 1. After 24 h at
45 °C one could clearly observe from 31P NMR the
presence of free phosphine, compound 7, and a new
compound with a signal at δ ) 41 ppm, which was not
1
characterized. H NMR demonstrated that compounds
1 and 7 were present in an 8:2 ratio, which changed to

600 Organometallics, Vol. 21, No. 4, 2002
Ta ble 3. Cr ysta l Da ta for 1, 1′, 2, 5, 6, 7, a n d 11
Navarro Clemente et al.
C16H24ORu
C22H36ORu
C16H24OCl4SnRu
C16H24O3Ru
C16H22O2Ru
C34H39OPRu
(7)
C27H38Cl3Ru2
(1)
(1′)
(2)
(5)
(6)
(11)
mol wt
cryst syst
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
333.42
P212121
10.485(2)
11.720(2)
12.401(2)
90.00
90.00
90.00
1523.9(5)
4
417.58
P212121
11.604(2)
13.304(3)
13.488(3)
90.00
90.00
90.00
2082.3(8)
4
593.941
P21/n
8.829(2)
15.605(3)
15.274(3)
90.00
96.64(2)
90.00
2090.31
4
365.42
P21/n
8.829(2)
8.526(2)
21.244(4)
90.00
99.98(3)
90.00
1575.0(6)
4
347.41
P21/n
595.69
P21/n
671.06
P21/n
9.841(3)
13.594(4)
11.172(12)
90.000(12)
92.89(6)
90.00(6)
1492.7(17)
4
18.380(2)
9.6947(7)
18.467(2)
90.000(2)
117.628(10)
90.000(10)
2915.4(5)
4
8.4583(10)
26.5482(10)
12.5414(10)
90.0000(10)
90.781(10)
90.000(10)
2815.9(4)
4
Z
cryst size (mm)
0.31 × 0.3 ×
0.22 × 0.22 ×
0.31 × 0.28 ×
0.4 × 0.4 ×
0.5 × 0.4 ×
0.4 × 0.3 ×
0.17 × 0.17 ×
0.28
0.11
0.25
0.3
0.23
0.2
0.11
abs coeff (mm-1
)
1.016
1.453
0.758
1.332
2.4271
1.887
1.000
1.541
1.046
1.546
0.617
1.357
1.371
1.583
D
calcd (g cm-3
)
scan type
total no. of data
total no. of
ω/2θ
ω/2θ
θ/2θ
ω/2θ
ω/2θ
ω/2θ
ω/2θ
2704
2142
4088
2852
1472
6956
5547
1345
2082
3670
2770
1400
6361
4921
unique data
total no. of obsd
data, F>4σ(F)
final R1
final wR2
no. of variables
1154
1769
3109a
1971
1400
4361
2454
0.0326
0.0766
164
0.0412
0.1120
218
0.0205
0.0356
209
0.0330
0.0835
181
0.0367
0.0951
172
0.0329
0.0895
340
0.0461
0.1261
289
a
(Fo)2 > 3σ(Fo)2.
9:1 after 15 days, but thereafter remained constant for
at least 3 months.
7 (Figure 7) is described below. Phosphine derivatives
7-9 were observed exclusively as the exo-syn deriva-
tives, probably due to the harsh experimental conditions
required to obtain the addition products. Similar at-
tempts with triphenyl phosphite did not lead to clean
reactions.
A stoichiometric reaction between compound 1 and
PPh3 in THF, under UV irradiation with a medium-
pressure lamp, was carried out for 4.5 h, producing four
signals in the 31P NMR spectrum at 67.2, 56.3, 39.4, 26.6
ppm in a 0.57:0.65:1.0:0.58 ratio, respectively. Purifica-
tion by chromatography afforded only one phosphine
complex, accompanied by compound 1; the former
compound was characterized as the PHPh2 complex 8
(Scheme 2; δ ) 56.3 ppm, J P-H ) 329 Hz), formed via a
P-C bond cleavage reaction.
The addition of CO, at atmospheric pressure, to a
solution of compound 1 in refluxing THF gave after 10
h evidence by IR of decoordination by the CO of the
oxopentadienyl ligand (1668 cm-1, THF). An IR spec-
trum of a hexane solution of unreacted 1 and product
10 (Cp*Ru[η3-CH2C(Me)CHC(Me)O]CO) revealed the
presence of a carbonyl ligand in 10 (1962 cm-1, hexane).
The similar solubilities of compounds 1 and 10 did not
allow for the separation of these two compounds, which,
The stoichiometric photochemical reaction of 1 with
the PHPh2 ligand in THF solution was found to be less
selective than the corresponding reaction with PPh3.
After 4.5 h of irradiation and removal of solvent in a
vacuum, the reaction mixture gave a brown solid and
an oily fraction after washing with hexane. The brown
solid appeared, by 31P NMR, to be composed of at least
six different species (δ ) 66.3, 53.8, 36.5, 31.5, 21.4, and
-5.7 ppm). Additionally, a broad band was observed
between 47.9 and 21.4 ppm, while the oily fraction
showed three signals at 64.9, 53.9, and -15.8 ppm. After
chromatography on silica gel with ether as the eluant,
there were two signals at 66.7 and 56.0 ppm. Sublima-
tion under reduced pressure at 70 °C partially removed
compound 1, and the remaining product, which did not
1
by H NMR, were present in an approximate ratio of
1
0.56:0.44. The H and 13C NMR data for compound 10
are reported in Tables 1 and 2. Similar compounds, such
as CpRu(η3-CH2CRCH2)(CO) (R ) H, Me), have been
reported to arise from the phase transfer reaction of allyl
bromides or chlorides with CpRu(CO)2X (X ) Cl, Br).29
The chloride derivative gave a mixture of endo and exo
isomers in a 1:1 ratio, while the addition of CO to
compound 1 under THF reflux gave only the exo-syn
isomer.
Neither the oxopentadienyl compound 1′ nor the
hydrocarbon analogue 1′′ underwent addition reactions
even after at least 13 h with PPh3 under THF reflux,
PMe3 or CO.
sublime, was compound 8 (31P δ ) 55.5 ppm, J P-H
328 Hz) contaminated with 1.
)
A stoichiometric reaction between compound 1 and
PMe3 under reflux for 6 h in cyclohexane yielded an
orange product, which could be isolated after chroma-
tography and sublimation or recrystallization (see Ex-
perimental Section), although it appeared to have
limited stability in solution. The product Cp*Ru[η3-
CH2C(Me)CHC(Me)O]PMe3 (9) was obtained in the
highest (70%) yield of all the phosphine adducts,
likely due to the basicity and small size of PMe3. The
1H, 13C, and 31P NMR data for compounds 7-9 are
reported in Tables 1 and 2, and the crystal structure of
Str u ctu r a l Stu d ies. Crystal data for compounds 1,
1′, 2, 5, 6, 7, and 11 are provided in Table 3. The
structures of 1 and 1′ are presented in Figures 1 and 2.
These are generally similar to those of related species.1a
Some relevant data are provided in Table 4. The solid
state structures of the oxidative addition products 2, 5,
and 11 and the PPh3-coordinated complex 7 are pre-
sented in Figures 3, 4, 6, and 7, respectively, while
various bonding parameters are contained in Tables 5
and 6. The solid state structure of compound 6 is

Half-Open Ruthenocenes
Organometallics, Vol. 21, No. 4, 2002 601
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
in accommodating extra SnCl3 and Cl ligands, as
opposed to either a single O2 or PPh3 ligand. Each
complex contains an η3-oxodienyl ligand, coordination
preferentially being observed through carbon atoms (I)
rather than through an oxoallyl (II) (Scheme 5). Such
is to be expected based on the soft nature of Ru(II) and
is consistent with observations made for related η3-
oxodienyl and η4-dienal ligands.37 The bonding param-
eters within the ligands are quite similar, with an
average delocalized C-C distance of 1.410(4) Å, and an
average CdO distance of 1.215(5) Å, similar to the value
of 1.184(10) Å for the aldehyde substituent in 6 (vide
supra).
The Ru-Sn and Ru-Cl bond distances in compound
2, 2.6002(4) and 2.4002(9) Å, are longer and shorter,
respectively, than those in Ru(II) compounds such as
Cp*RuSnCl3(COD)38 [2.5855(4) Å] and CpRuX(Ph2PCH-
(Me)CH2PPh2] [X ) Cl,39 2.444(2) Å; X ) SnCl3,39 2.551-
(1) Å], or LRuCl(PHPh2)(PPh3) [L ) Cp 2.434(2); L )
Cp* 2.462(2) Å].40 Similar Ru-Cl distances have been
observed for Ru(IV) compounds such as [Cp*RuCl2-
(Ph2PCH2CH2PPh2)]CF3SO341 [2.397(1) and 2.390(1) Å]
and CpRuCl2(η3-C4H4OMe)42 [2.403(1) Å].
(d eg) for Com p ou n d s 1, 1′, a n d 6
1
1′
6
Bond Lengths
Ru-C1
Ru-C2
Ru-C3
Ru-C4
Ru-C7
Ru-C8
Ru-C9
Ru-C10
Ru-C11
Ru-O1
O1-C4
O2-C17
C1-C2
2.160(8)
2.161(10)
2.180(8)
2.170(7)
2.170(8)
2.158(7)
2.143(6)
2.172(7)
2.204(8)
2.167(5)
1.348(11)
2.142(7)
2.210(8)
2.227(7)
2.223(7)
2.237(8)
2.192(7)
2.155(7)
2.148(8)
2.176(8)
2.161(6)
1.333(9)
2.176(7)
2.178(7)
2.188(7)
2.196(7)
2.219(7)
2.182(7)
2.151(7)
2.141(8)
2.183(7)
2.152(5)
1.294(8)
1.184(10)
1.383(10)
1.413(10)
1.425(10)
1.491(10)
1.500(11)
1.427(4)
1.499(4)
1.346(15)
1.424(14)
1.398(13)
1.494(15)
1.500(17)
1.423(5)
1.344(12)
1.436(10)
1.439(10)
1.516(10)
1.525(12)
1.423(5)
C2-C3
C3-C4
C4-C5
C2-C6
C-C (Cp*)
C-Me (Cp*)
1.497(5)
1.500(5)
Bond Angles
C1-C2-C3
C1-C2-C6
C2-C3-C4
C3-C2-C6
C3-C4-C5
121.0(12)
120.5(13)
126.0(11)
117.1(7)
121.2(7)
119.8(7)
120.3(8)
124.6(7)
119.5(8)
119.3(7)
121.3(7)
121.4(7)
125.2(7)
117.1(7)
121.2(7)
In compound 5 the dioxygen is symmetrically bound
to ruthenium (Ru-O ∼1.993(3) Å) with an O2-O3
distance of 1.416(5) Å, which is much longer than that
in the superoxide KO2 (1.28 Å),43a but slightly shorter
than that in H2O2 (1.46 Å).43b The O-O and two Ru-O
distances are longer and shorter, respectively, compared
to those observed for many cationic dioxygen com-
plexes such as [Cp*Ru(O2)L2][X] {L2 ) Ph2PCH2CH2-
presented in Figure 5, and bonding parameters are
given in Table 4.
The bonding for the oxodienyl ligands in 1 and 6
appears similar, with respective average values for the
Ru-C(1-4) and Ru-O bonds being 2.168(6), 2.170(6),
2.184(6), 2.183(5), and 2.160(4) Å. The corresponding
distances for 1′ (Table 4) reflect a significant steric effect
of the tert-butyl substituents, as the values for the
internal ligand atoms (C2-4) are lengthened, while the
values for the C1 and O1 do not experience significant
lengthening. It appears that the steric interaction also
has affected the bonding for the cyclic ligand as well,
as the average Ru-C(Cp*) distance for 1′ is 2.182 Å, vs
an average of 2.172 Å for 1 and 6. One further point of
interest relates to the potential for disorder for the open
oxodienyl ligands. The fact that identical substituents
are present on the carbon atoms in the 2 and 4 positions
might be expected to favor such a possibility, although
the well-behaved refinements and general lack of mirror
plane symmetry in bonding parameters for the open
ligands indicate that any disorder is minor. Nonetheless,
the O1-C4 distance in 6 is at least slightly shorter than
those in 1 and 1′, and it is possible that the presence of
a polar substituent on the cyclic dienyl ligand in 6 could
have played a role in reducing the extent of disorder,
whether through inter- or intramolecular interactions.
The CHO group in the cyclic ligand of complex 6
displays a typical CdO bond length of 1.184(10) Å, along
with significant shortening for the C-CHO bond [1.456-
(10) Å] compared to 1.504(9) Å for the C-CH3 bonds in
the Cp* fragment of compound 1.
16
PPh2, X ) BPh4 [1.37(1), 2.003(9), and 2.002(9) Å], X
15
) PF6 [1.398(5), 2.040(3), and 2.023(3) Å], X )
17
BPh4
[1.37(1), 2.028(9), and 2.021(9) Å], L2 )
44
Ph2PCpFeCpPPh2 (dppf), X ) BF4 [1.381(11), 2.036-
(8), and 2.029(8) Å], and [RuH(O2)(dippe)2][BPh4]45,46
[1.36(1), 2.04(1), and 2.00(1) Å]. A similar O-O bond
length has been observed, however, for [Rh(O2)(dppe)2]-
[PF6] (1.418(11) Å).47
The crystal structure of compound 11 confirms the
susceptibility of the electrophilic fragment “Cp*Ru+” to
coordination by aromatic ligands,34,35 as well as by
chlorine atoms. The compound consists of two frag-
ments: the cationic [Cp*Ru(η6-toluene)]+ sandwich and
the anionic half-sandwich [Cp*RuCl3]-, both with crys-
tallographic mirror symmetry. The structure of the
anionic fragment corresponds to a piano stool geometry.
(37) (a) Benyunes, S. A.; Day, J . P.; Green, M.; Al-Saadoon, A. W.;
Waring, T. L. Angew. Chem., Int. Ed. Engl. 1990, 29, 1416. (b)
Trakarnpruk, W. Ph.D. Thesis, University of Utah, 1993.
(38) Moreno, B.; Sabo-Etienne, S.; Dahan, F.; Chaudret, B. J .
Organomet. Chem. 1995, 498, 139.
(39) Consiglio, G.; Morandini, F.; Ciani, G.; Sironi, A.; Kretschmer,
M. J . Am. Chem. Soc. 1983, 105, 1391.
(40) Torres-Lubian, R.; Rosales-Hoz, M. J .; Arif, A. M.; Ernst, R.
D.; Paz-Sandoval M. A. J . Organomet. Chem. 1999, 585, 68.
(41) Mauthner, K.; Mereiter, K.; Schmid, R.; Kirchner, K. Inorg.
Chim. Acta 1995, 236, 95.
(42) Albers, M. O.; Liles, D. C.; Robinson, D. J .; Shaver, A.; Singleton
E. Organometallics 1987, 6, 2347.
The structural parameters for 2, 5, and 7 correspond
in general fairly closely to each other, despite the fact
that the first two are Ru(IV) complexes, while the last
is Ru(II). In fact, the Ru-C bond distances in 2 are those
which stick out, being generally longer than those of 5
or 7 (e.g., Ru-C(Cp*) ) 2.258, 2.233, and 2.234 Å,
respectively). This may reflect a greater steric problem
(43) (a) Valentine, J . S. Chem. Rev. 1973, 73, 235. (b) Savariault,
J .-M.; Lehmann M. S. J . Am. Chem. Soc. 1980, 102, 1298.
(44) Sato, M.; Asai, M. J . Organomet. Chem. 1996, 508, 121.
(45) J imenez-Tenorio, M.; Puerta, M. C.; Valerga P. Inorg. Chem.
1994, 33, 3515.
(46) J imenez-Tenorio, M.; Puerta, M. C.; Valerga P. J . Am. Chem.
Soc. 1993, 115, 9794.
(47) McGinnety, J . A.; Payne, N. C.; Ibers J . A. J . Am. Chem. Soc.
1969, 91, 6301.

602 Organometallics, Vol. 21, No. 4, 2002
Navarro Clemente et al.
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles (d eg) for Com p ou n d s 2, 5, a n d 7
compound 2
compound 5
compound 7
Bond Lengths
Sn-Ru
Sn-Cl2
Sn-Cl3
Sn-Cl4
Ru-Cl1
Ru-C1
Ru-C2
Ru-C3
Ru-C7
Ru-C8
Ru-C9
Ru-C10
Ru-C11
O1-C4
C1-C2
C2-C3
C3-C4
C4-C5
C2-C6
C-C (Cp*)
2.6002(4)
2.359(1)
2.360(1)
2.380(1)
2.4002(9)
2.218(4)
2.216(4)
2.266(4)
2.233(3)
2.282(3)
2.296(3)
2.278(3)
2.203(3)
1.214(5)
1.400(6)
1.411(6)
1.489(6)
1.512(6)
1.505(6)
1.431(3)
1.490(3)
Ru-O2
Ru-O3
O2-O3
1.994(3)
1.991(3)
1.416(5)
Ru-P1
2.3205(8)
1.842(3)
1.836(3)
1.857(3)
P1-C17
P1-C23
P1-C29
2.156(5)
2.150(4)
2.199(4)
2.182(4)
2.172(4)
2.252(4)
2.313(4)
2.253(4)
1.211(7)
1.414(6)
1.423(6)
1.479(8)
1.514(8)
1.494(7)
1.425(3)
1.496(3)
2.189(3)
2.145(3)
2.223(3)
2.254(3)
2.226(3)
2.211(3)
2.243(3)
2.251(3)
1.220(4)
1.407(5)
1.431(5)
1.460(5)
1.504(6)
1.509(5)
1.422(2)
1.507(2)
C-Me (Cp*)
Bond Angles
Ru-Sn-Cl2
Ru-Sn-Cl3
Ru-Sn-Cl4
C1-C2-C3
C2-C3-C4
C3-C4-C5
C1-C2-C6
C3-C2-C6
O1-C4-C3
O1-C4-C5
Cl2-Sn-Cl3
Cl2-Sn-Cl4
Cl3-Sn-Cl4
Sn-Ru-Cl1
122.83(4)
121.22(3)
116.13(3)
118.0(4)
125.0(4)
115.5(4)
121.5(4)
120.4(4)
124.4(4)
119.9(4)
95.61(5)
97.14(5)
98.57(5)
77.45(3)
O3-Ru-O2
Ru-O3-O2
Ru-O2-O3
C1-C2-C3
C2-C3-C4
C3-C4-C5
C1-C2-C6
C3-C2-C6
O1-C4-C3
O1-C4-C5
41.64(14)
69.3(2)
69.1(2)
116.9(4)
124.9(5)
113.0(6)
122.1(4)
120.6(4)
124.6(5)
122.2(6)
Ru-P1-C17
Ru-P1-C23
Ru-P1-C29
C1-C2-C3
C2-C3-C4
C3-C4-C5
C1-C2-C6
C3-C2-C6
O1-C4-C3
O1-C4-C5
C17-P1-C23
C17-P1-C29
113.76(10)
117.40(10)
120.05(10)
115.8(3)
126.5(3)
115.3(3)
120.2(3)
123.9(4)
126.1(4)
118.4(4)
104.46(15)
100.53(13)
Ta ble 6. Selected Bon d Len gth s (Å) a n d An gles (d eg) for Com p ou n d 11
Ru1-C1
Ru1-C2
Ru1-C3
Ru1-C4
Ru1-C5
Ru1-C11
Ru1-C12
Ru1-C13
Ru1-C14
Ru1-C15
Ru1-C16
Ru2-Cl1
Ru2-Cl2
Ru2-Cl3
Ru2-C18
Ru2-C19
Ru2-C20
Ru2-C21
Ru2-C22
2.147(8)
2.178(7)
2.167(7)
2.149(8)
2.167(7)
2.208(8)
2.215(8)
2.219(8)
2.210(8)
2.213(8)
2.182(7)
2.405(3)
2.410(2)
2.381(2)
2.149(7)
2.194(9)
2.187(8)
2.163(8)
2.169(9)
C1-C2
1.395(17)
1.422(12)
1.510(11)
1.438(13)
1.379(12)
1.439(11)
1.375(13)
1.385(11)
1.487(14)
1.380(15)
1.393(15)
1.411(13)
1.402(12)
1.468(15)
1.420(14)
1.474(12)
1.402(13)
1.394(13)
1.363(12)
C1-Ru1-C2
38.1(3)
64.4(3)
39.0(3)
C1-C5
C1-Ru1-C3
C1-C6
C4-Ru1-C5
C3-Ru1-C5
C2-C3
64.2(3)
C3-C4
C1-Ru1-C11
C2-Ru1-C11
C4-Ru1-C11
C5-Ru1-C14
Cl1-Ru2-Cl2
Cl1-Ru2-Cl3
Cl3-Ru2-Cl2
Cl1-Ru2-C21
Cl1-Ru2-C18
Cl1-Ru2-C22
Cl2-Ru2-C22
Cl3-Ru2-C18
Cl3-Ru2-C19
Cl3-Ru2-C22
Ru1-C11-C17
116.6(3)
108.9(3)
167.4(3)
115.7(3)
89.45(9)
94.11(10)
89.35(10)
116.3(3)
104.0(3)
92.6(2)
145.9(3)
154.5(2)
123.7(4)
124.4(3)
129.6(7)
C4-C5
C11-C12
C11-C16
C11-C17
C12-C13
C13-C14
C14-C15
C15-C16
C18-C19
C18-C22
C18-C23
C19-C20
C20-C21
C21-C22
Sch em e 5
Su m m a r y
As a result of these studies, it is apparent that the
reactivities of the half-open ruthenocenes and their
oxodienyl analogues are strongly influenced by steric
and electronic properties of both the metal complex and
the incoming reactant, whether simple coordination or
oxidative addition is involved. Perhaps the clearest
observation to be made from this work is that while the
oxodienyl complexes undergo reactions similar to their
all-carbon analogues, the oxodienyl species generally
appear more reactive, a feature that can be traced to
the expected weaker coordination by the hard oxygen
center as compared to the softer carbon centers. A par-
As expected, the Ru-C distances for the arene ligand
are somewhat longer than those for the C5Me5 ligands
in either the cationic or anionic portions, the respective
averages being 2.208(3) vs 2.162(4) and 2.172(5) Å. The
Ru-Cl distances [2.405(3), 2.410(2), and 2.381(2) Å]
have typical values for Ru(IV) compounds.41,42 A similar
but not isomorphous compound, [Cp*Ru(η6-C6H6)]-
[Cp*RuBr3], has been previously reported.8

Half-Open Ruthenocenes
Organometallics, Vol. 21, No. 4, 2002 603
mmol) solution was added to a cold (-78 °C) THF solution (1.0
mL) of diisopropylamine (0.156 mL, 1.1 mmol). The solution
was stirred with slow warming to room temperature. After 15
min the solution was cooled to -78 °C, and 2,2,5,6,6-penta-
methyl-4-hepten-3-one (0.25 mL, 1.1 mmol) was added drop-
wise. After the solution was warmed to room temperature and
stirred for 15 min, a light yellow solution was observed. The
resulting (oxopentadienyl)lithium salt was slowly added drop-
wise to a cold (-78 °C) solution of [Cp*RuCl]4 (300 mg, 1.1
mmol) in 60 mL of THF. After the solution was warmed to
room temperature and stirred for 2 h, the volatiles were
removed under vacuum. Compound 1′′ was then extracted
from the remaining residue with diethyl ether, and the
resulting solution was concentrated and then chromato-
graphed on a 42 × 2 cm neutral alumina column with a 9:1
mixture of hexane/diethyl ether as the eluant. A yellow band
was collected and, after evaporation, recrystallization from cold
hexane, and filtration at -78 °C, a bright yellow solid was
obtained in 88% yield (410 mg, 0.98 mmol). Mp: 68-70 °C.
Crystals suitable for X-ray analysis were deposited from -5
°C hexane solutions. Anal. Calcd for C22H36ORu: C, 63.26; H,
8.72. Found: C, 63.32, H, 8.87. MS: 418(100)[M+], 399(7), 359-
(16), 331(25), 315(9), 233(42).
Syn th esis of Cp *Ru [η5-CH2C(Me)CHC(Me)CH2] (1′′). To
a THF solution (20 mL) containing 146 mg of [Cp*RuCl]4 (0.54
mmol) at -78 °C was added C7H11SnMe3 (136 mg, 0.54 mmol)
in 7 mL of THF. The addition resulted in a change in color
from dark brown to yellow and then red-brown. The solution
was allowed to warm slowly to room temperature and was then
filtered. After removal of the volatiles, the oily residue was
extracted with hexane and the solution evaporated. After
chromatography under silica gel and eluting with hexane, a
pale yellow solid was obtained in 79% yield (140 mg, 0.42
mmol). Spectroscopic data and physical properties have been
previously reported.1a
Syn th esis of Cp*Ru [η3-CH2C(Me)CHC(Me)O](Cl)(Sn Cl3)
(2). To a pentane solution (25 mL) containing 100 mg of
compound 1 (0.30 mmol) was added 0.10 mL (221 mg, 0.85
mmol) of SnCl4 with continuous stirring at room temperature.
Immediately an orange precipitate was observed. After 30 min
the reaction mixture was filtered and the orange residue
washed twice with 20 mL portions of pentane. The solvent was
removed in vacuo, and the crude product was recrystallized
from CH2Cl2/pentane at -78 °C to give 135 mg (0.23 mmol,
76%) of 2 as a red solid, which does not melt below 250 °C.
Single crystals were obtained by recrystallization from acetone
at -15 °C. Anal. Calcd for C16H24OCl4SnRu: C, 32.34; H, 4.04.
Found: C, 32.70; H, 3.99. IR (CHCl3, cm-1): 1689(vs). MS: 330
[M+ - SnCl4].
ticularly interesting illustration of this is the formation
of the neutral aldehyde derivative 6 from 5, a transfor-
mation not observed to date for the more common, cat-
ionic O2 complexes. Interestingly, azadienyl complexes
have been found to display behavior sometimes similar
to that of their isoelectronic pentadienyl and oxodienyl
complexes, but at other times different. Further studies
to gain a better understanding of the relationships
between these types of compounds are continuing.
Exp er im en ta l Section
Standard inert-atmosphere techniques were used for all
syntheses and sample manipulations. The solvents were dried
by standard methods (hexane and pentane with CaH2, diethyl
ether and THF with Na/benzophenone, CH2Cl2 and CHCl3 with
CaCl2, benzene and toluene with Na, CH3CN with P2O5) and
distilled under argon prior to use. Compounds [Cp*RuCl]4,35b
[Cp*Ru(CH3CN)3]+,35b,48 5,5 and 2,2,5,6,6-pentamethyl-4-hep-
ten-3-one49 were prepared according to literature procedures.
Iodine was resublimed and mesityl oxide distilled under
reduced pressure. All other chemicals were used as purchased
from Sigma-Aldrich, Strem Chemicals, Merck, and J . T. Baker.
Elemental analyses were performed by Robertson Microlit
Laboratories, Inc., Madison, NJ , and E&R Microanalytical
Labs. Solution IR spectra were recorded on a Perkin-Elmer
6FPC-FT spectrophotometer using a CHCl3 or CCl4 solution
cell with NaCl plates. 1H, 13C, and 31P NMR spectra were
recorded on J EOL 90 MHz, J EOL GSX-270, J EOL Eclipse-
400 MHz, or Bruker 300 MHz spectrometers in deoxygenated,
deuterated solvents. NMR chemical shifts are reported relative
to TMS and 31P NMR chemical shifts relative to 85% H3PO4.
Mass spectra were obtained with a Hewlett-Packard HP-
5990A, Finnigan MAT95 (FAB), or Finnigan LCQ ion trap
instrument. Ionization was by electrospray from a solution of
MeOH/H2O/acetic acid, 50:49:1 vol %, or a Micromass ZAB-
SE magnetic sector instrument. Ionization was by FAB with
xenon atoms at 6 keV energy (Washington University, St.
Louis, MO); m/z values are given relative to 102Ru, 35Cl, and
119Sn isotopes. Melting points were determined using a Mel-
Temp apparatus and are not corrected.
Syn th esis of Cp *Ru [η5-CH2C(Me)CHC(Me)O] (1). Under
a nitrogen atmosphere, a n-BuLi (1.0 mL, 1.6 M, 1.6 mmol)
solution was added to a cold (-78 °C) THF solution (1.0 mL)
of diisopropylamine (0.224 mL, 1.6 mmol). The solution was
stirred with slow warming to room temperature. After 15 min
the solution was cooled to -78 °C and mesityl oxide (157 mg,
0.182 mL, 1.6 mmol) was added dropwise. The solution was
then warmed to room temperature and stirred for 15 min, after
which a light yellow solution was observed. The resulting
(oxopentadienyl)lithium salt was slowly added dropwise to a
cold (-78 °C) solution of [Cp*RuCl]4 (434 mg, 1.6 mmol) in 20
mL of THF. After the solution was warmed to room temper-
ature and stirred for 2 h, the volatiles were removed under
vacuum. Compound 1 was then extracted from the remaining
residue with hexane, and the resulting solution was concen-
trated and then chromatographed on an Al2O3 (grade 1, 5 ×
1.5 cm) column with a mixture of hexane/diethyl ether (8:2)
as the eluant. A yellow band was collected. The solvent was
removed in vacuo, and the crude product was crystallized from
hexane at -78 °C to give 425 mg (1.28 mmol, 80%) of 1 as a
yellow powder. Spectroscopic data were consistent with those
reported previously. Single crystals were obtained by recrys-
tallization from hexane at -15 °C.
Syn t h esis of Cp *R u [η3-CH2C(Me)CHC(Me)CH2](Cl)-
(Sn Cl3) (2′′). The synthesis was carried out similarly to that
described for 2a ′′ (vide infra), but attempts to purify it were
unsuccessful, and thereby prevented its isolation. Its formula-
tion is therefore based upon NMR data (see Tables 1 and 2) of
the crude reaction product.
Syn t h esis of Cp *R u [η3-CH2C(Me)CHC(Me)CH2](Cl)-
(Sn ClMe2) (2a ′′). To a THF solution (30 mL) containing 100
mg of compound 1′′ (0.35 mmol) at -78 °C was added 70 mg
(0.35 mmol) of Me2SnCl2 with continuous stirring. After 2 h
at -78 °C, the mixture was allowed to warm to room temper-
ature and was stirred for an additional 24 h. The reaction
mixture was filtered and the cherry-red residue washed three
times with 3 × 5 mL hexane, leading to the extraction of 1′′
from the solid. The remaining red solid was recrystallized from
toluene/pentane at -78 °C to give 7 mg (0.013 mmol, 4%) of
2a ′′ as a red solid, which decomposes without melting at 65
°C. MS: 330 [M+ - SnMe2Cl2]. The small quantity and low
stability of 2a ′′ prevented its characterization by elemental
analysis.
Syn t h esis of Cp *R u [η5-CH2C(t-Bu )CH C(t-Bu )O] (1′).
Under a nitrogen atmosphere, a n-BuLi (0.70 mL, 1.6 M, 1.1
(48) Schrenk, J . L.; McNair, A. M.; McCormick, F. B.; Mann, K. R.
Inorg. Chem. 1986, 25, 3501.
(49) Ernst, R. D.; Freeman, J . W.; Swepston, P. N.; Wilson, D. R. J .
Organomet. Chem. 1991, 402, 17.
Syn th esis of Cp *Ru [η3-CH2C(Me)CHC(Me)O](I)2 (3). To
a hexane solution (20 mL) containing 100 mg of compound 1

604 Organometallics, Vol. 21, No. 4, 2002
Navarro Clemente et al.
(0.30 mmol) at -78 °C was added a toluene solution (10 mL)
of 76 mg of resublimed I2 (0.3 mmol). The yellow solution
immediately became dark. The reaction mixture was left for
30 min at -78 °C and then was slowly warmed to room
temperature. The solvent was removed in vacuo, and the crude
product was washed twice with hexane (20 mL). Recrystalli-
zation of the dark solid from acetone/hexane gave 146 mg
(0.25 mmol, 83%) of compound 3, which did not melt below
250 °C. Anal. Calcd for C16H24I2ORu: C, 32.7; H, 4.08; I, 43.2.
Found: C, 33.0; H, 4.05; I, 41.9. IR (CHCl3, cm-1): 1676(vs).
MS: 587(5) [M+], 461(100), 439(25), 401(22), 385(17).
After addition of hexane (∼8 mL) ca. 45 mg of a green solid
was isolated by filtration.30 4n a ′: IR (CHCl3, cm-1): 1666(vs).
HRMS: calc for C22H36Cl2ORu, 488.1180; found 488.1165; [M
- Cl2]: 418.1803, found 418.1800.
Syn t h esis of Cp *R u [η3-CH2C(Me)CH C(Me)CH2](Cl)2
(4n a ′′) a n d [Cp *Ru (η6-C7H8)][Cp *Ru Cl3] (11). A chloroform
solution (30 mL) containing 100 mg of compound 1′ (0.35
mmol) was stirred for 65 h at room temperature. The light
yellow solution turned yellow-brown. After filtration and
evaporation of the solvent, the dark brown oily residue was
extracted with Et2O, giving an orange solution, which, after
having its volume reduced to ∼15 mL, led to a mixture of
yellow and dark orange precipitates of 4n a ′′. Attempts to
purify the solid through chromatography or recrystallization
were unsuccessful due to the reactivity of the mixture in
solution. The fraction insoluble in Et2O gave 30 mg of a green
solid,30 which after recrystallization from CHCl3/Et2O afforded
at 5 °C a green solid, along with a few red crystals, which were
removed manually. These crystals do not melt below 210 °C.
An X-ray diffraction study revealed this to be compound 11.
MS for 11: 635(24) [M+ - Cl], 598(9.5), 545(93), 466(100), 271-
(25), 236(20).
Syn th esis of Cp *Ru [η3-CH2C(t-Bu )CHC(t-Bu )O](I)2 (3′).
To a hexane solution (15 mL) containing 135 mg of compound
1′ (0.33 mmol) at -78 °C was added a toluene solution (5 mL)
of 82 mg of resublimed I2 (0.33 mmol). The bright yellow
solution immediately turned brown. After approximately 45
min, the reaction mixture reached room temperature, yielding
a deep wine-red solution. The solvent was removed in vacuo,
and the crude product was washed twice with hexane (2 × 10
mL). The product was dissolved in CHCl3 and filtered. After
immediate evaporation compound 3′ was obtained as a deep
grape-purple solid (137 mg, 0.20 mmol, 63%), which did not
melt below 250 °C. 1H NMR spectroscopy always revealed the
presence of the dimer [Cp*RuI2]2 in solution in a ratio of 17:1
(3′:dimer). IR (CHCl3, cm-1): 1663(vs). MS (20 eV): 421(12),
420(53), 419(22), 418(100), 417(55), 416(44), 415(36), 412(15),
331(10), 329(11), 251(67), 180(20), 166(10), 165(77), 125(29),
124(49), 57(30). HRMS: [M - I2] 418.1803; found 418.1802.
Syn th esis of Cp *Ru [η3-CH2C(Me)CHC(Me)CH2](I)2 (3′′).
To a hexane solution (20 mL) containing 100 mg of compound
1′′ (0.30 mmol) at -78 °C was added a toluene solution (10
mL) of 76.6 mg of resublimed I2 (0.35 mmol). The yellow
solution immediately became dark. The reaction mixture was
kept for 30 min at -78 °C, and then on warming slowly to
room temperature it went from red-brown to wine-red. The
solvent was removed in vacuo, and the crude product was
washed twice with hexane (2 × 10 mL). Recrystallization of
the wine-red solid from acetone gave 142 mg (0.25 mmol, 81%)
of deep wine-red 3′′, which decomposes without melting at 160
°C. Anal. Calcd for C17H26I2Ru: C, 34.89; H, 4.44; I, 43.38.
Found: C, 34.91; H, 4.33; I, 42.91. IR (CHCl3, cm-1): 1600-
(CdC, w). LRFAB (matrix 3-NBA): 332 [M+].
Syn th esis of Cp *Ru [η3-CH2C(Me)CHC(Me)O](Cl)2 (4).
A light yellow chloroform solution (20 mL) containing 100 mg
of compound 1 (0.30 mmol) was refluxed for 2 h, whereupon it
became dark brown. After filtration and evaporation of the
solvent, the amber residue was purified by thin-layer chro-
matography, using silica gel and CHCl3 as eluent. There were
five bands, and the two most intense orange bands were
separated and extracted with chloroform, giving 25 mg and 6
mg of the corresponding amber isomers 4n a (0.06 mmol, 18%)
and 4xs (0.014 mmol, 4%). Both samples did not melt even at
250 °C. Anal. Calcd for 4n a : C16H24Cl2ORu: C, 47.52; H, 5.94;
Cl, 17.57. Found: C, 47.75; H, 6.16; Cl, 17.06. IR (CHCl3, cm-1):
4n a 1664(vs), 4xs 1692(vs). MS for 4n a : 404(1.3) [M+], 369-
(7.5), 334(100), 302(46), 289(27), 236(67), 97(91).
Ch em ical Syn th esis of Cp*Ru [η3-CH2C(Me)CHC(Me)O]-
(O2) (5). A nitromethane solution (10 mL) containing 68 mg
of compound 1 (0.20 mmol) was bubbled with pure O2 (19.2
mg, 0.6 mmol at 297 K and 585 mm Hg), and the Schlenk
vessel was closed. The initial light yellow solution turned
yellow-amber after 10 min. After continuous stirring for 1.5 h
at room temperature, the reaction mixture was evaporated
until dryness and the amber residue extracted with Et2O (3
× 5 mL). Filtration of the black residue, complete evaporation
of the filtered amber solution, and recrystallization at room
temperature from 10 mL of Et2O, after reducing the volume
until ∼2 mL, gave an amber solid 5 (42.4 mg, 0.12 mmol) after
filtration in 57% yield. Mp: 110-112 °C. Single crystals were
obtained by recrystallization from diethyl ether at -20 °C. IR
(KBr, cm-1): 1667(vs); 937(s), 894 (s). MS: 348 [M+ - O].
Electr och em ica l Syn th esis of Cp *Ru [η3-CH2C(Me)-
CHC(Me)O](O2) (5) a n d (η5-C5Me4CHO)Ru [η5-CH2C(Me)-
CHC(Me)O] (6).5 The electrolysis at 0.35 V of a mixture of a
2 mM solution of compound 1 (16.7 mg) in 25 mL of MeCN
and 0.1 M Bu4NPF6 (969 mg) was carried out until the starting
material was completely consumed. Evaporation of the solvent
and extractions with diethyl ether gave an oil, which was
purified by chromatography on neutral alumina using diethyl
ether as eluent. Evaporation of the solvent afforded 12.9 mg
of compound 5 in 70% yield. If the initial reaction mixture was
allowed to stand for at least 24 h, the formation of compound
6 also occurred, as observed from chromatography, carried out
as described above. In this case, three bands were observed.
The first was eluted with hexane, while the second and third
were eluted with diethyl ether, giving compounds 1, 5, and 6,
respectively. Compound 6 was isolated together with another
uncharacterized organometallic complex. A second chromato-
graphic procedure for the latter mixture using neutral alumina
and diethyl ether afforded pure compound 6. Mp: 133-136
°C. Single crystals were obtained from recrystallization in
diethyl ether at -15 °C. IR (CCl4, cm-1): 1670 (s). MS: 348
[M+]. Spectroscopic data for 5 and 6 were consistent with those
previously reported.
Syn t h esis of Cp *R u [η3-CH2C(t-Bu )CH C(t-Bu )O](Cl)2
(4′). A chloroform solution (30 mL) containing 300 mg of
compound 1′ (0.72 mmol) was maintained at reflux for 8 h.
The light yellow solution turned dark green. After filtration
and evaporation of the solvent, the green oily residue was
washed twice with pentane (2 × 10 mL). The pentane-insoluble
fraction was dissolved in dry EtOH (10 mL), and an orange
precipitate was immediately observed. After filtration, the
orange powder was washed with EtOH (∼35 mL) until the
washings were no longer green. The orange solid 4n a ′ was
obtained (88 mg, 0.18 mmol, 25%) and decomposes without
melting at 180 °C. The green ethanolic solution was purified
through chromatographic separation on an alumina column
with elution by EtOH. A green band was collected and its
volume was reduced (∼2 mL) by evaporation under vacuum.
Syn th esis of Cp *Ru [η3-CH2C(Me)CHC(Me)O]P P h 3 (7).
To a cyclohexane solution (40 mL) containing 150 mg of
compound 1 (0.45 mmol) was added 236 mg (0.90 mmol) of
PPh3. After the solution was refluxed 7.5 h, the solvent was
removed and the yellow residue was dissolved in a minimum
amount of hexane and then chromatographed on a silica gel
column (5 × 1.5 cm) with a mixture of hexane/diethyl ether
(9:1), leading first to recovery of starting material 1, while a
second fraction eluted with hexane/diethyl ether (8:2) afforded
35 mg of compound 7 as an orange powder (0.06 mmol, 13%).
Mp: 139-143 °C. Crystals suitable for X-ray analysis were

Half-Open Ruthenocenes
Organometallics, Vol. 21, No. 4, 2002 605
deposited from room-temperature hexane solutions whose
volumes had been reduced under vacuum. Anal. Calcd for 7:
C, 68.55; H, 6.60. Found: C, 67.94; H, 6.70. IR (KBr, cm-1):
1640(s). MS: 596(2.4) [M+], 501(6), 334(14), 252(6), 235(56),
57(100).
and the yellow residue was chromatographed with a mixture
of hexane/diethyl ether (8:2). Even though some starting
material could be removed, the complete separation of com-
pounds 10 and 1 could not be achieved. According to a H NMR
spectrum of the mixture, compound 10 was present ap-
1
Syn t h esis of Cp *R u [η3-CH2C(Me)CH C(Me)O]P H P h 2
(8). To a THF solution (250 mL) containing 250 mg of
compound 1 (0.75 mmol) was added 0.13 mL (140 mg, 0.75
mmol) of PHPh2. The solution was filtered into a photochemical
reactor and irradiated for 4.5 h with continuous stirring. The
solution changed from light yellow to orange-yellow. Filtration
and evaporation of the solvent under vacuum gave an amber
oil, which was extracted with diethyl ether. After the solvent
was concentrated and chromatographed on a silica gel column
(5 × 1.5 cm) with 1:1 hexane/diethyl ether, a mixture of
compounds 1 and 8 was obtained. Several attempts to remove
1 were unsuccessful.
proximately to the extent of 44%.
X-r a y Str u ctu r e Deter m in a tion for 1, 1′, 2, 5-7, a n d
11. Crystal data and experimental details are given in Table
3. X-ray data were collected on Enraf-Nonius four-circle or
rotating anode diffractometers using graphite-monochromated
Mo KR (λ ) 0.7107 Å) radiation. Final positional parameters
are available as Supporting Information.
Ack n ow led gm en t. M.A.P.S. and R.D.E. would like
to acknowledge the support of Conacyt and National
Science Foundation Bilateral Program (No. INT-
9202989). M.A.P.S. would like to thank Conacyt for
financial support through the project 26352-E, as well
as for the X-ray diffractometer (No. F0084), and Wash-
ington University Mass Spectrometry Research Re-
source (NIH, No. P41RR0954) for recording some of the
mass spectra. Thanks to Marco Antonio Leyva for
helping us with some X-ray diffraction studies. R.D.E.
would like to thank the NSF for partial support of this
research.
Syn th esis of Cp *Ru [η3-CH2C(Me)CHC(Me)O]P Me3 (9).
This yellow compound was prepared in the same manner as
the PPh3 adduct (7), using 50 mg (0.15 mmol) of 1, 15 mL of
cyclohexane, and PMe3 (20 µL, 0.19 mmol). The resulting
yellow oil was chromatographed using pentane/diethyl ether
(1:1), affording an orange band, which after reducing the
solvent volume gave 43 mg (0.11 mmol, 70%). The yellow
compound can be sublimed at ca. 90 °C under vacuum. Mp:
137-144 °C. Anal. Calcd for 9: C, 55.75; H, 8.07. Found: C,
56.03; H, 8.40. IR (KBr, cm-1): 1633(s). MS: 409(10) [M+], 394-
(6), 379(1), 364(1), 334(100), 302(35), 236(27).
Syn th esis of Cp *Ru [η3-CH2C(Me)CHC(Me)O]CO (10).
Carbon monoxide was bubbled for 10 h at atmospheric pres-
sure into a refluxing THF solution (25 mL) containing 100 mg
of compound 1 (0.3 mmol). Afterward, the solution was allowed
to cool to room temperature, the solvent was removed in vacuo,
Su p p or tin g In for m a tion Ava ila ble: X-ray complemen-
tary data and NMR spectra. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM010735S