Syntheses, structures, and spectro-electrochemistry of {Cp*(PP)Ru}C≡CC≡C{Ru(PP)Cp*} (PP = dppm, dppe) and their mono- and dications

Article abstract of DOI:10.1021/om030015g

The complexes {Cp*(PP)Ru}₂(μ-C≡CC≡C) (PP = dppm 5a, dppe 5b) have been synthesized from RuCl(PP)Cp* (1a/b) via the corresponding vinylidenes [Ru(=C=CH₂)(PP)Cp*]⁺ (2a/b), deprotonation (KOBu^t) to the ethynyls Ru(C≡CH)(PP)Cp* (3a/b), oxidative coupling ([FeCp ₂][PF₆]) to the bis(vinylidenes) [{Ru(PP)Cp*} ₂{μ-(=C=CHCH=C=)}]²⁺ (4a/b), and deprotonation [dbu (4a), KOBu^t (4b)]. Electrochemistry of 5a/b revealed the expected sequence of four le redox steps, which occurred at significantly lower E° values than found for the Ru(PPh₃)₂Cp analogue. Single-crystal X-ray structure determinations are reported for 1a/b, 2a/b, 3a/b, 4a/b, and 5a/b, together with the oxidized products [5b][PF₆] _n (n = 1, 2). In the monocation [5b][PF₆] the Ru-C(1) [1.931(2) A] and C-C distances [1.248-1.338(3) A] are intermediate between those found in 5b and the dication [5b]²⁺. The short Ru-C [1.857(5) A] and experimentally equal C-C distances [1.269-1.280(6) A] in [5b] [PF₆]₂ confirm the anticipated dicarbene-cumulene structure for the Ru=C=C=C=C=Ru bridge.

Full text of DOI:10.1021/om030015g

3184
Organometallics 2003, 22, 3184-3198
Syn th eses, Str u ctu r es, a n d Sp ectr o-electr och em istr y of
{Cp *(P P )Ru }CtCCtC{Ru (P P )Cp *} (P P ) d p p m , d p p e)
a n d Th eir Mon o- a n d Dica tion s†
Michael I. Bruce,*,‡ Benjamin G. Ellis,‡ Paul J . Low,§ Brian W. Skelton, and
Allan H. White
Department of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Department
of Chemistry, University of Durham, South Road, Durham DH1 3LE, England, and
Department of Chemistry, University of Western Australia, Crawley, Western Australia 6009
Received J anuary 9, 2003
The complexes {Cp*(PP)Ru}2(µ-CtCCtC) (PP ) dppm 5a , dppe 5b) have been synthesized
from RuCl(PP)Cp* (1a /b) via the corresponding vinylidenes [Ru(dCdCH2)(PP)Cp*]+ (2a /
b), deprotonation (KOBut) to the ethynyls Ru(CtCH)(PP)Cp* (3a /b), oxidative coupling
([FeCp2][PF6]) to the bis(vinylidenes) [{Ru(PP)Cp*}2{µ-(dCdCHCHdCd)}]2+ (4a /b ), and
deprotonation [dbu (4a ), KOBut (4b)]. Electrochemistry of 5a /b revealed the expected
sequence of four 1e redox steps, which occurred at significantly lower E° values than found
for the Ru(PPh3)2Cp analogue. Single-crystal X-ray structure determinations are reported
for 1a /b, 2a /b, 3a /b, 4a /b, and 5a /b, together with the oxidized products [5b][PF6]n (n ) 1,
2). In the monocation [5b][PF6] the Ru-C(1) [1.931(2) Å] and C-C distances [1.248-1.338-
(3) Å] are intermediate between those found in 5b and the dication [5b]2+. The short Ru-C
[1.857(5) Å] and experimentally equal C-C distances [1.269-1.280(6) Å] in [5b][PF6]2 confirm
the anticipated dicarbene-cumulene structure for the RudCdCdCdCdRu bridge.
In tr od u ction
dppe, dippe),7 Ru(PPh3)(L)Cp [L ) PPh3 (5c), PMe3
(5d )],8 Ru2(amp)4,9 Rh/IrHCl(PPri ) ,10 and PtCl(P-
3 2
Poly-ynyl and -diyl complexes are useful in the
assembly of multimetallic structures because of their
propensity to coordinate metals either by σ-bonding or
by π-bonding. This chemical behavior, together with
current interest in the properties of molecules contain-
ing metal-ligand fragments linked by unsaturated
chains (molecular wires),1 has resulted in the generation
of a wide variety of such complexes. A structurally
simple subset of poly-yndiyl compounds contains C4
chains linking electron-rich metal centers, {LnM}-Ct
CCtC-{MLn}, as found for MLn ) Mo/W(CO)2Tp,2 MnX-
(dmpe)2 (X ) I, CtCH),3 Re(NO)(PR3)Cp* (R ) aryl),4
Bu3)2.11 Several theoretical calculations have indicated
that the HOMOs of some of these complexes consist of
M-C antibonding orbitals lying above the remainder
of the orbital manifold, with ionization potentials low
enough to result in facile redox processes.3,8b,12 Various
reports have described the preparation of oxidized
derivatives containing n+ cations (n ) 1, 2, 3, or 4),
although crystallographic characterization of many of
these has proved difficult.
The valence structures A-E (Chart 1) can be used to
rationalize the structures of the M-C4-M bridges in
these materials. Each form conceals a variety of subtle
structural variations which can be related to more
detailed and sophisticated accounts of their electronic
structures. Ultimately, the structures are determined
by the degree of interaction between the metal center
and the carbon-based orbitals and are therefore a
Re(CO)3(But -bpy),5 Fe(CO)2Cp*,6 Fe(PP)Cp* (PP )
2
† Dedicated to our friend and colleague Professor Martin Bennett,
in recognition of his fine contributions to organometallic chemistry.
* Corresponding author. Fax:
michael.bruce@adelaide.edu.au.
‡ University of Adelaide.
+ 61 8 8303 4358. E-mail:
§ University of Durham.
University of Western Australia.
(1) Paul, F.; Lapinte, C. Coord. Chem. Rev. 1998, 178-180, 427.
(2) Woodworth, B. E.; White, P. S.; Templeton, J . L. J . Am. Chem.
Soc. 1997, 119, 828.
(3) (a) Kheradmandan, S.; Heinze, K.; Schmalle, H.; Berke, H.
Angew. Chem. 1999, 111, 2412; Angew. Chem., Int. Ed. 1999, 38, 2270.
(b) Fernandez, F. J .; Blacque, O.; Alfonso, M.; Berke, H. Chem.
Commun. 2001, 1266.
(4) (a) Zhou, Y.; Seyler, J . W.; Weng, W.; Arif, A. M.; Gladysz, J . A.
J . Am. Chem. Soc. 1993, 115, 8509. (b) Seyler, J . W.; Weng, W.; Zhou,
Y.; Gladysz, J . A. Organometallics 1993, 12, 3802. (c) Brady, M.; Weng,
W.; Zhou, Y.; Seyler, J . W.; Amoroso, A. J .; Arif, A. M.; Bo¨hme, M.;
Frenking, G.; Gladysz, J . A. J . Am. Chem. Soc. 1997, 119, 775. (d)
Meyer, W. E.; Amoroso, A. J .; Horn, C. R.; J aeger, M.; Gladysz, J . A.
Organometallics 2001, 20, 1115.
(7) (a) Le Narvor, N.; Lapinte, C. J . Chem. Soc., Chem. Commun.
1993, 357. (b) Le Narvor, N.; Toupet, L.; Lapinte, C. J . Am. Chem.
Soc. 1995, 117, 7129. (c) Le Narvor, N.; Lapinte, C. C. R. Acad. Sci.
Paris, Ser. IIc 1998, 745. (d) Guillemot, M.; Toupet, L.; Lapinte, C.
Organometallics 1998, 17, 1928.
(8) (a) Bruce, M. I.; Denisovich, L. I.; Low, P. J .; Peregudova, S. M.;
Ustynyuk, N. A. Mendeleev Commun. 1996, 200. (b) Bruce, M. I.; Low,
P. J .; Costuas, K.; Halet, J .-F.; Best, S. P.; Heath, G. A. J . Am. Chem.
Soc. 2000, 122, 1949.
(9) Ren, T.; Zhou, .; Alvarez, J . C. Chem. Commun. 2000, 1197.
(10) (a) Gil-Rubio, J .; Laubender, M.; Werner, H. Organometallics
2000, 19, 1365. (b) Gil-Rubio, J .; Laubender, M.; Werner, H. Organo-
metallics 1998, 17, 1202. (c) Werner, H.; Lass, R. W.; Gevert, O.; Wolf,
J . Organometallics 1997, 16, 4077.
(5) Yam, V. W.-W.; Lau, V. C.-Y.; Cheung, K.-K. Organometallics
1996, 15, 1740.
(6) Akita, M.; Chung, M.; Sakurai, A.; Moro-oka, Y. Chem. Commun.
2000, 1285.
(11) Sonogashira, K.; Ohga, K.; Takahashi, S.; Hagihara, N. J .
Organomet. Chem. 1980, 188, 237.
(12) Belanzoni, P.; Re, N.; Sgamellotti, A.; Floriani, C. J . Chem. Soc.,
Dalton Trans. 1998, 1825.
10.1021/om030015g CCC: $25.00 © 2003 American Chemical Society
Publication on Web 06/27/2003

{Cp*(PP)Ru}CtCCtC{Ru(PP)Cp*} (PP ) dppm, dppe)
Organometallics, Vol. 22, No. 16, 2003 3185
function of the particular metal-ligand combination
used to end-cap the carbon chain.
Resu lts
Syn th eses of {Cp *(P P )Ru }2(µ-CtCCtC) (P P )
d p p m , d p p e). We have previously shown that the
complex {Ru(PPh3)2Cp}2(µ-C4) is readily available via
a fluoride-catalyzed desilylation of Me3SiCtCCtCSiMe3
in the presence of RuCl(PPh3)2Cp.14 Although subse-
quently this reaction has been used to prepare several
related complexes,15 we have found that the analogous
reaction does not proceed to any appreciable extent with
RuCl(PP)Cp* (PP ) dppm 1a , dppe 1b). Consequently,
we have utilized the reaction sequence originally devised
by Lapinte and co-workers to make the analogous iron
diyndiyl complexes containing the Fe(dppe)Cp* group
(Scheme 1).7 These reactions, applied to RuCl(PP)Cp*,
are described in the Experimental Section and do not
require any detailed comment. All complexes have been
fully characterized by elemental microanalyses, IR,
NMR, and mass spectrometry and by single-crystal
X-ray structural studies, as summarized below.
Ch a r t 1
Accordingly, the chlorides 1a and 1b,16 which are
easily obtained from RuCl(PPh3)2Cp* and the diphos-
phine in refluxing toluene for 2 h, followed by column
chromatography, were prepared with isolated yields of
83 and 95%, respectively. Conversion to the light yellow
vinylidene complexes [Ru(dCdCH2)(PP)Cp*][PF6] (2a /
b) was achieved by reactions of 1a /b with HCtCSiMe3
in methanol in the presence of [NH4][PF6] in 96 and 95%
yields. If CH2Cl2 was used as the solvent for the
reaction, reaction times were considerably longer [5 days
(2a ), 24 h (2b)] with lower yields of 62 and 74%,
respectively. Deprotonation of 2a /b with KOBut afforded
the bright yellow neutral ethynyl derivatives Ru(Ct
CH)(PP)Cp* (3a /b) in essentially quantitative yield.
Oxidative coupling of the ethynyls to the bis(vi-
nylidene) complexes [{Cp*(PP)Ru}2(µ-CdCHCHdC)]-
[PF6]2 (4a /b) occurred upon stirring 3a /b with [FeCp2]-
[PF6] for 3 h at -78 °C. Slow addition of diethyl ether
to the reaction mixture results in crystallization of the
products as brick red crystalline solids in 91 and 85%
yields, respectively. Deprotonation (dbu or KOBut) then
afforded the desired butadiyndiyl compounds {Cp*(PP)-
Ru}2(µ-CtCCtC) (5a /b) as bright orange crystalline
solids in 90% yield in each case. Although deprotonation
of 4a with dbu gave 5a as the sole product, a mixture
of products was obtained when KOBut was used.
All complexes were readily identified from their
spectroscopic properties. Most informative in the IR
spectra were the bands found near 1625 [vinylidene ν-
(CdC)], 3265 and 1930 [ethynyl ν(≡CH) and ν(CtC)],
1600-1635 [vinylidene ν(CdC)], and 1970 cm-1 [ν(Ct
C)] for 2a /b, 3a /b, 4a /b, and 5a /b, respectively. Of
interest are the changes in the 13C resonances of the
carbon chain atoms as these conversions are realized.
In 2a /b, resonances for the vinylidene carbons are found
at δ 344.54 and 344.21 (triplets, CR) and at δ 102.26
and 102.65 (singlets, Câ). In the ethynyl derivatives,
both carbons resonate as triplets, with CR showing the
larger J (CP) at δ 120.26 (22.8 Hz) and 120.58 (22.9 Hz).
For 3a , Câ gives a poorly resolved triplet at δ 93.01,
whereas in 3b this resonance is at δ 92.99 with the
Others have examined the related chemistry of the
rhenium and iron complexes mentioned above with the
intriguing result that, while crystallographic and spec-
troscopic evidence favors a reduction in CtC bond order
and concomitant increase in C-C bond order as the
rhenium complex is oxidized,4c Mo¨ssbauer spectroscopy
and crystallographic studies of the iron complex suggest
that it retains the diacetylenic nature of the C4 ligand
while generating Fe(III) centers.7b In particular, the
trication in [{Fe(dippe)Cp*}2(µ-C4)][OTf]3 features two
Fe(III) centers and a carbon-centered (i.e., bridge-
centered) radical.7d More recent crystallographic studies
of the manganese system also gave results that are
consistent with the generation of a cumulenic C4 ligand
in the [{MnI(dmpe)2}2(µ-C4)]2+ dication,3a although in
this case, the diyndiyl nature of the C4 chain in the
neutral complex is not so evident.
In previous papers we have described the redox
chemistry of {Cp(PPh3)(L)Ru}2(µ-CtCCtC) [L ) PPh3,
PMe3] with the ultimate aim of characterizing a series
of products related by one-electron steps which might
exhibit the range of structures A-E.8 While four 1e
redox steps relating the 0/1+/2+/3+/4+ derivatives were
found, only the neutral complex with R ) Ph could be
crystallographically characterized (as cisoid and tran-
soid isomers).13,14 In seeking to obtain similar deriva-
tives that might be more readily accessible and therefore
more convenient for physical measurements, we have
increased the electron density at the ruthenium center
by using strongly electron-donating ligands, such as
pentamethylcyclopentadienyl (C5Me5, Cp*) and chelat-
ing diphosphines such as dppm and dppe. This paper
reports a comparative study of complexes containing the
Ru(PP)Cp* [PP ) dppm (series a ), dppe (series b)]
groups, including X-ray structure determinations of the
neutral and mono- and dications derived from the dppe
complex. These confirm the predicted trend of a reduc-
tion in CtC bond order and an increase in the C-C
bond order represented by the valence structures B and
C, respectively.
(13) Bruce, M. I.; Hinterding, P.; Tiekink, E. R. T.; Skelton, B. W.;
White, A. H. J . Organomet. Chem. 1993, 450, 209.
(14) Bruce, M. I.; Hall, B. C.; Kelly, B. D.; Low, P. J .; Skelton, B.
W.; White, A. H. J . Chem. Soc., Dalton Trans. 1999, 3719.
(15) Bruce, M. I.; Kelly, B. D.; Skelton, B. W.; White, A. H. J .
Organomet. Chem. 2000, 604, 150.
(16) Luo, L.; Zhu, N.; Zhu, N.-J .; Stevens, E. D.; Nolan, S. P.; Fagan,
P. J . Organometallics 1994, 13, 669.

3186 Organometallics, Vol. 22, No. 16, 2003
Bruce et al.
Sch em e 1
J (CP) coupling of 2.3 Hz being fully resolved. The bis-
(vinylidenes) 4a /b also exhibit the characteristic down-
field triplets at δ 348.59 and 348.08, with J (CP) of 15
and 17 Hz, respectively. In both cases, Câ resonated as
a singlet at δ ca. 103. In the 31P NMR spectra, reso-
nances between δ 4.76 and 18.0 are found for the dppm
complexes, while for the dppe derivatives, the signals
(3) Å with no apparent correlation with the diphosphine
or the charge. In contrast, in the cationic derivatives
2a /b, 4a /b, [5b][PF6], and [5b][PF6]2, the Ru-P dis-
tances [2.2756(5)-2.331(1) Å] are somewhat longer than
those found in the neutral complexes 3a /b and 5a /b
[2.2420(6)-2.2813(7) Å], probably because of reduced
back-bonding from the cationic metal center to the
phosphine ligand. The usual distorted octahedral struc-
ture is found for the ruthenium(II) center, with P-Ru-C
angles ranging between 78.90(7)° and 87.50(6)°, seem-
ingly independent of the nature of the ligands and
charge.
-
occur between δ 75.92 and 82.53; if the PF6 anion is
present, septet resonances at δ ca. -143 are present.
In the C4 (diyndiyl) complexes strong IR ν(CtC)
absorptions are found at 1966 (5a ) and 1973 (5b) cm-1
,
while in the 1H NMR spectrum, the Cp* methyl singlets
are at δ 1.89 (5a ) and 1.95 (5b). The CH2 protons of the
PP ligands resonate as multiplets at δ 4.23 (5a ) or 1.95
and 2.71 (5b). In the 13C NMR spectrum, the CR triplets
were found at δ 93.25 and 94.63 [J (CP) 27 Hz], while
Câ was upfield at δ 100.38 and 99.47 (both singlets),
respectively. There are again significant differences in
the 31P chemical shifts, with singlets at δ 17.50 (5a ) or
82.53 (5b). The ES mass spectra contain M+ ions at m/z
1290 and 1318, respectively, together with [Ru(PP)-
Cp*]+.
The Ru-C(1) distances reflect the nature of the
carbon ligand. For vinylidenes 2a /b, short Ru-C dis-
tances [between 1.834(4) and 1.848(2) Å] correspond to
a significant degree of multiple bonding between these
atoms. In contrast, the σ-bonded alkynyl ligands in 3a /b
and 5a /b are attached with longer Ru-C(1) distances,
between 2.001(3) and 2.019(2) Å. Within the carbon
ligands, C(1)-C(2) distances of 1.305(4) and 1.30(2) Å
in 2a /b and 1.338(7) and 1.323(5) Å in 4a /b are
consistent with the presence of formal CdC double
bonds, while diminution to between 1.202(3) and 1.223-
(3) Å in 3a /b and 5a /b confirms the presence of CtC
triple bonds in these complexes. The central C-C bond
lengths in 4a /b [1.448(7), 1.470(5) Å] or 5a /b [both
1.384(4) Å] are consistent with the conjugated structure
of the C4 ligands. The Ru-C(1)-C(2) angles are close
to linear, ranging between 170.6(2)° and 177.1(3)°. The
E configuration of the substituents on C(2)-C(3) in 4a /b
is also reflected in the torsion angles at these carbons
of -174.2(6)° (4a ) and -162.3(4)° (4b). Along the C4
chains in 5a /b, significant deviations from linearity
occur, with angles at the carbon atoms of between 170.6-
(2)° and 179.1(2)°. The bending at each carbon is
cumulative in each half of the molecule, with a total
deviation from linearity of 3.2° (5a ) or 5.1° (5b). This
feature has been discussed elsewhere and results both
Molecu la r Str u ctu r es. Figures 1-3 contain plots of
single molecules or cations of each of the complexes
studied, while selected structural parameters are col-
lected in Table 1. In 1a /b, the major difference is found
in the Ru-C(Cp*) distances, which average 2.20(2) and
2.24(1) Å, respectively, the result of the more compact
diphosphine ligand in the former, also reflected in the
smaller bite angle P(1)-Ru-P(2) of 71.53(6)° versus
82.15(2)° for the dppe analogue. The Ru-P distances
are similar in both complexes [range 2.2812(5)-2.294-
(2) Å].
Similar differences in the P(1)-Ru-P(2) angles are
found for the other complexes, with values for P(1)-
Ru-P(2) ranging between 70.71(2)° and 71.74(2)° (dppm)
and 81.50(3)° and 83.6(1)° (dppe). However, the average
Ru-C(Cp*) distances all fall in the range 2.24(2)-2.29-

{Cp*(PP)Ru}CtCCtC{Ru(PP)Cp*} (PP ) dppm, dppe)
Organometallics, Vol. 22, No. 16, 2003 3187
F igu r e 1. Projections of single molecules of (a) RuCl(dppm)Cp* (1a ), (b) RuCl(dppe)Cp* (1b), (c) Ru(CtCH)(dppm)Cp*
(3a ), and (d) Ru(CtCH)(dppe)Cp* (3b).
from facile bending modes at C(sp) carbons and from
contributions of different hybridized carbons in the
metal-bonded systems.17-19 In 5a /b, the Ru-C4-Ru
chains approach a transoid configuration. The torsion
angles between the Ru-Cp* axes are 69.9° and -46.9°.
Red ox Ch em istr y. The redox potentials for com-
plexes 1-4 are listed in Table 2. Single irreversible
oxidation processes were found for 2a /b at +1.71/+1.65
V and for 3a /b at +0.225/+0.31 V (possibly correspond-
ing to oxidative coupling to 4a /b, although characteristic
waves for the latter were not observed), while two
reversible waves were found for both 4a /b at +1.00,
+1.26 V, respectively. The neutral complexes 1 and 3
with dppm are more readily oxidized than their dppe
analogues, although the peak separations of the two
differ. In the case of the chloro complexes, formation of
a solvento cation by ionization of the Cl in solution
cannot be ruled out, and this species may give rise to
the irreversible wave found at higher potentials. Oxida-
tion of 3 may result in irreversible formation of 4,
although no waves for 4 were found at higher potential.
As expected, cationic complexes 2 and 4 are oxidized at
higher potentials than the neutral species; in these
cases, the dppe compounds are more easily oxidized. An
irreversible process is found for 2, whereas the lower of
the two found for 4 is reversible. No reduction is found
for any of the complexes within the solvent limit.
The rationale for this work is the search for Ru-C4-
Ru systems, which not only have lower oxidation
potentials than previously described examples8 but also
afford more stable oxidized complexes which could be
obtained in a crystalline form. Consequently, we have
obtained cyclic voltammograms for 5a and 5b (Figure
4), and these results are summarized in Table 3,
together with corresponding data for some related
complexes. In the case of 5a the first two oxidation
processes are fully reversible [ia/ic ) 1; current propor-
(17) Dembinski, R.; Lis, T.; Sazfert, S.; Mayne, C. L.; Bartik, T.;
Gladysz, J . A. J . Organomet. Chem. 1999, 578, 229.
(18) (a) Peters, T. B.; Bohling, J . C.; Arif, A. M.; Gladysz, J . A.
Organometallics 1999, 18, 3261. (b) Mohr, W.; Stahl, J .; Hampel, F.;
Gladysz, J . A. Inorg. Chem. 2001, 40, 3263. (c) Bohling, J . C.; Peters,
T. B.; Arif, A. M.; Hampel, F.; Gladysz, J . A. In Coordination Chemistry
at the Turn of the Century; Ondrejovic, G., Sirota, A., Eds.; Slovak
Technical Press: Bratislava, Slovakia, 1999; p 47.
(19) Bruce, M. I.; Costuas, K.; Halet, J .-F.; Hall, B. C.; Low, P. J .;
Nicholson, B. K.; Skelton, B. W.; White, A. H. J . Chem. Soc., Dalton
Trans. 2002, 383.

3188 Organometallics, Vol. 22, No. 16, 2003
Bruce et al.
F igu r e 2. Projections of the cations of (a) [Ru(dCdCH2)(dppm)Cp*][PF6] (2a ), (b) [Ru(dCdCH2)(dppe)Cp*][PF6] (2b)
(two independent molecules), (c) [{Cp*(dppm)Ru}2(dCdCHCHdCd)][PF6]2 (4a ), and (d) [{Cp*(dppe)Ru}2(dCdCHCHd
Cd)][PF6]2 (4b).
tional to (scan rate)1/2]. The 2+/3+ oxidation wave in
5a is only partially reversible (ia/ic ) 0.7), while the 3+/
4+ oxidation is chemically irreversible. In 5b, the first
three oxidations are reversible ia/ic ) 1; current propor-
tional to (scan rate)1/2], with the 3+/4+ process being
partially chemically reversible (ia/ie ) 0.7).
As can be seen from Table 3, the first oxidation
potentials for 5a and 5b, at -0.48 and -0.43 V,
respectively, are lower than those determined for {Cp-
(PPh3)(L)Ru}2(µ-C4) [L ) PPh3 (5c), PMe3 (5d )], as
expected. Comparison with the analogous iron complex
shows that the 0/1+ potential of the latter, measured
under the same conditions, occurs at an even lower
value (-0.68 V). Similar comments apply to the second
oxidation potentials (1+/2+) of these four complexes.
However, as oxidation proceeds, the 2+/3+ couples are
essentially identical for the four ruthenium compounds,
while the 3+/4+ couples of 5a and 5b (at +1.41, +1.51

{Cp*(PP)Ru}CtCCtC{Ru(PP)Cp*} (PP ) dppm, dppe)
Organometallics, Vol. 22, No. 16, 2003 3189
F igu r e 3. Projections of single molecules of (a) {Ru(dppm)Cp*}2(µ-C4) (5a ) and (b) {Ru(dppe)Cp*}2(µ-C4) (5b) and the
cations of (c) [{Ru(dppe)Cp*}2(µ-C4)][PF6] ([5b]+) and (d) [{Ru(dppe)Cp*}2(µ-C4)][PF6]2 ([5b]2+).
V) bracket the value for 5d [+1.46 V (irr.)]. The 3+/4+
couple has not been found in any related iron system
to date.
In the case of the dppm complex 5a , an unexpected
peak (0.72 V) was observed in the cathodic sweep, which
was found to decrease at higher scan rates. This is most
likely due to a product resulting from the decomposition
of the higher oxidized species under the conditions used
in the experiment and is presently uncharacterized.
The high thermodynamic stability of the oxidized
species [5]n + (n < 4) is evidenced by the significant
separations of each redox process, giving rise to large
comproportionation constants, KC (5a : n ) 1, KC ) 4.46
× 1010; n ) 2, KC ) 1.11 × 1015; n ) 3, KC ) 1.80 × 106.

3190 Organometallics, Vol. 22, No. 16, 2003
Ta ble 1. Selected Str u ctu r a l Da ta
Bruce et al.
1a
1b
2a
2ba
3a
3b
dppm-Cl
dppe-Cl
dppm-CCH2
dppe-CCH2
dppm-CtCH
dppe-CtCH
Bond Distances (Å)
2.2966(5)
2.2975(6)
Ru-P(1)
2.282(2)
2.294(2)
2.185(9)-2.22(1)
2.2882(5)
2.2812(5)
2.219-2.252(2)
2.320(3), 2.318(3)
2.317(3), 2.308(3)
2.27-2.30(1),
2.2731(5)
2.2756(6)
2.219-2.263(2)
2.2649(5)
2.2592(6)
2.215-2.269(2)
Ru-P(2)
Ru-C(Cp*)
2.248-2.286(2)
2.27-2.32(1)
(av)
Ru-C(1)
C(1)-C(2)
2.20(2)
2.434(2) [Cl]
2.24(1)
2.4532(5) [Cl]
2.27(2)
1.848(2)
1.305(4)
2.28(1), 2.28(2)
1.85(1), 1.84(1)
1.31, 1.29(2)
2.24(2)
2.015(2)
1.202(3)
2.25(2)
2.015(2)
1.202(3)
Bond Angles (deg)
71.74(2)
88.18(7)
85.54(7)
93.6(1)
P(1)-Ru-P(2)
P(1)-Ru-C(1)
P(2)-Ru-C(1)
P(1)-C(0)-P(2)
Ru-C(1)-C(2)
71.53(6)
82.15(2)
81.93(2) [Cl]
90.93(2) [Cl]
82.75(9), 83.6(1)
83.5(3), 84.5(3)
92.8(3), 92.3(4)
70.71(2)
87.97(6)
80.86(7)
90.78(9)
171.7(2)
82.71(2)
87.50(6)
85.27(6)
83.25(7) [Cl]
87.59(7) [Cl]
92.7(3)
176.2(2)
172.9(9), 172(1)
173.7(2)
4a
4bb
[dppm-C4H2]2+
[dppe-C4H2]2+
Bond Distances (Å)
2.308(1)
2.313(1)
Ru-P(1)
2.331(1), 2.331(1)
2.310(1), 2.306(1)
2.251-2.324(4),
2.268-2.311(4)
2.29, 2.28(3)
Ru-P(2)
Ru-C(Cp*)
2.262-2.312(5)
(av)
2.28(2)
Ru-C(1)
C(1)-C(2)
C(2)-C(3)
1.834(5)
1.338(7)
1.448(7)c
1.837, 1.834(4)
1.323, 1.324(5)
1.470(5)
Bond Angles (deg)
71.10(4)
88.1(2)
84.5(2)
93.4(2)
P(1)-Ru-P(2)
P(1)-Ru-C(1)
P(2)-Ru-C(1)
P(1)-C(0)-P(2)
Ru-C(1)-C(2)
C(1)-C(2)-C(3)
82.38, 83.33(4)
94.1, 91.0(1)
80.9, 82.0(1)
173.7(4)
170.9, 174.2(3)
123.5, 123.6(4)
122.3(5)c
5a b
dppm-C4
5bb
dppe-C4
[5b]+
[dppe-C4]+
[5b]2+ b
[dppe-C4]2+
Bond Distances (Å)
2.2556, 2.2420(8)
2.2465, 2.2531(9)
2.219-2.278(3),
2.223-2.275(3)
2.25, 2.25(2)
2.001, 2.003(3)
1.223, 1.218(4)
1.382(4)
Ru-P(1)
Ru-P(2)
2.2633, 2.2697(6)
2.2813, 2.2684(7)
2.226-2.259(2),
2.228-2.243(2)
2.24(1), 2.234(6)
2.017, 2.019(2)
1.216, 1.223(3)
1.385(3)
2.2756(5)
2.3001(5)
2.232-2.291(2)
2.319, 2.312(1)
2.311, 2.330(1)
2.260-2.300(4),
2.262-2.309(3)
2.27, 2.28(2)
1.858, 1.856(5)
1.280, 1.269(7)
1.294(7)
Ru-C(Cp*)
(av)
2.26(2)
Ru-C(1)
C(1)-C(2)
C(2)-C(3)
1.931(2)
1.248(3)
1.338(3)
Bond Angles (deg)
81.50, 83.09(3)
81.69, 82.54(8)
84.25, 80.70(9)
P(1)-Ru-P(2)
P(1)-Ru-C(1)
P(2)-Ru-C(1)
P(1)-C(0)-P(2)
Ru-C(1)-C(2)
C(1)-C(2)-C(3)
70.72, 71.20(2)
83.63, 80.14(7)
78.90, 79.57(6)
91.02, 91.06(9)
175.2, 170.6(2)
179.1(2), 177.7(3)
81.89(2)
83.38(6)
93.45(6)
83.18, 81.93(4)
85.0, 82.8(2)
86.7, 92.5(1)
176.6, 177.1(3)
176.9, 178.0(3)
165.6(2)
178.0(2)
175.6(5), 170.1(4)
176.7, 174.2(6)
a
b
Values for molecules 1, 2 given. Values involve Ru(1,2), C(1,4), C(2,3) as appropriate. c For C(3), read C(2′).
Ta ble 2. Red ox P oten tia ls for 1-4a
of chemical stability on the CV time scale; nevertheless
we regarded the oxidized species [5]n+ (n ) 1-3) to be
viable synthetic targets.
complex
E1/2
RuCl(dppm)Cp* 1a
RuCl(dppe)Cp* 1b
[Ru(dCdCH2)(dppm)Cp*][PF6] 2a
[Ru(dCdCH2)(dppe)Cp*][PF6] 2b
Ru(CtCH)(dppm)Cp* 3a
Ru(CtCH)(dppe)Cp* 3b
[{Ru(dppm)Cp*}2(µ-CdCHCHdC))2][PF6]2 4a +1.00, +1.26
[{Ru(dppe)Cp*}2(µ-CdCHCHdC))2][PF6]2 4b
+0.245, +1.12b
+0.275, +1.34b
+1.71b
Chemical oxidation of 5b occurs with the marked color
changes observed previously with 5c/d . Treatment of
the orange neutral compound with 1 or 2 equiv of
[FeCp2][PF6] affords the dark green monocation and
intense dark blue dication. The former was obtained as
the microcrystalline hexafluorophosphate, which is
sensitive to air when in solution. As an odd-electron
species, only broad resonances in the NMR spectra were
observed, as expected, and these were assigned on the
basis of their relative intensities: the C5Me5 resonance
is at δ 10.72, while the methylene protons of the dppe
ligand are found at δ 13.54. The phenyl protons appear
+1.65b
+0.225b
+0.31b
+1.00, +1.26
a
b
CH2Cl2 solution, 0.1 M [NBu4]BF4. Irreversible.
5b: n ) 1, KC ) 9.70 × 1010; n ) 2, KC ) 7.26 × 1013;
n ) 3, KC ) 8.80 × 107). The CV data give estimates of
thermodynamic stability and provide only an indication

{Cp*(PP)Ru}CtCCtC{Ru(PP)Cp*} (PP ) dppm, dppe)
Organometallics, Vol. 22, No. 16, 2003 3191
F igu r e 4. Cyclic voltammograms of {Ru(dppm)Cp*}2(µ-C4) (5a ) and {Ru(dppe)Cp*}2(µ-C4) (5b), both taken at 200 mV
s-1
.
as a set of broad multiplets between δ 6.46 and 7.92.
In the 31P NMR spectrum a slightly broadened singlet
is seen at δ 117.89, while the PF6 septet is observed at
δ -143.20. The higher chemical shift of the P(dppe)
nuclei, compared with 5b (δ 82.53), is consistent with
the removal of some electron density from the metal
centers.
No signal was observed in the 31P NMR spectrum.
-
We have isolated and characterized the PF6 salt of
[5b]2+ as a dark blue solid, which exhibits a ν(CC) band
at 1769 cm-1, consistent with a further lowering of the
1
CC bond order. In the H NMR spectrum recorded in
acetone-d6, a sharp singlet for the Cp* protons is found
at δ 1.94, while a broad singlet at δ 3.01 is assigned to
the methylene protons of the dppe ligand. The phenyl
protons appear in the expected region between δ 7.15
and 7.79. In the 13C NMR spectrum, the Cp* carbons
are singlets at δ 10.38 and 112.28, while multiplets at
δ 27.79 and between δ 129.80 and 133.79 are assigned
to the CH2 and Ph carbons of the dppe ligand, respec-
tively. Resonances for the C4 moiety were not observed
even with concentrated solutions and long delay times.
Figure 5 compares the ν(CC) bands of 5b, recorded
in CH2Cl2 as solvent, as oxidation proceeds. The neutral
species gives a single band at 1963 cm-1 (with a
shoulder at 1977 cm-1), consistent with the presence of
a CtC triple bond. Upon oxidation to [5b]+, a single
ν(CC) band is present at 1860 cm-1. In the spectrum of
[5b]2+ a single band at 1770 cm-1 is consistent with a
further reduction in CC bond order; a very weak
absorption at 1711 cm-1 is also present. In both oxidized
species, a ν(PF) band at 838 cm-1 results from the PF6

3192 Organometallics, Vol. 22, No. 16, 2003
Bruce et al.
Ta ble 3. Electr och em ica l Da ta for [{MLn }2(µ-C4)]n + (in CH2Cl2 u n less oth er w ise sta ted ; va lu es r efer en ced to
[F eCp 2]/[F eCp 2]+ ) 0.46 V)
E1
E2
E3
E4
KC
MLn
(0/1+)
(1+/2+)
∆E1/2
°
(2+/3+)
(3+/4+)
(0/1+/2+)
VAB/eV
ref
a
Mn(CtCH)(dmpe)2
MnI(dmpe)2
Re(NO)(PPh3)Cp*
Re(NO){P(tol)3}Cp*
Fe(dippe)Cp*
-1.46
-0.655
+0.01
-0.22
-0.97
-0.675
-0.48
-0.43
-0.23
-0.26
-0.89
-0.020
+0.54
+0.31
-0.18
+0.045
+0.15
+0.22
+0.41
+0.33
0.57
0.64
0.53
0.53
0.79
0.72
0.63
0.65
0.64
0.59
7.5 × 109
3b
3a
4d
4d
7d
a
5.4 × 1010
1.1 × 109
1.1 × 109
d
+0.81
+0.95
+1.04
+1.04
+1.03
+0.97
2.25 × 1013
1.60 × 1012
4.46 × 1010
9.70 × 1010
1.5 × 1011
2.1 × 1010
Fe(dppe)Cp*
0.47
0.63
0.63
0.71
0.69
7a, 7b, 7d
this work
this work
8b
Ru(dppm)Cp* 5a
Ru(dppe)Cp* 5b
Ru(PPh3)2Cp 5c
+1.41b
+1.51c
+1.68c
+1.46c
Ru(PMe3)(PPh3)Cp 5d
8b
MeCN. Partially reversible. c Irreversible. Values of 0.69, 0.61, 0.51 eV obtained from three absorption bands in NIR region (λmax
891, 1020, 1225 nm, respectively).
a
b
d
tional studies at the DF level, which suggest that
electrons are removed from the HOMO, which is es-
sentially Ru-C antibonding and delocalized over the
Ru-C4-Ru unit.8b
Crystals of the oxidized complexes [5b][PF6] (from
CH2Cl2/hexane) and [5b][PF6]2 (from ethanol) suitable
for X-ray studies were obtained (see Figure 3, Table 1).
The geometries of the cations are similar to those of the
neutral complex, but detailed examination of the Ru-
C4-Ru bridges shows significant differences. In [5b]-
[PF6] the structure of the centrosymmetric six-atom
Ru-C4-Ru chain is intermediate between the 1,3-
diyndiyl structure found in neutral 5b and the cumu-
lenic structure in [5b][PF6]2. In particular, the bond
distances found in [5b][PF6] for Ru-C(1) [1.931(2) Å],
C(1)-C(2) [1.248(3) Å], and C(2)-C(3) [1.338(3) Å] are
equal to the averages of the corresponding values found
in 5b and [5b][PF6]2. In the case of [5b][PF6]2, the Ru-
C(1) distances have decreased markedly to 1.858(4),
1.856(5) Å, while the C(1)-C(2) distances have in-
creased to 1.280, 1.269(6) Å and the C(2)-C(2′) separa-
tion has decreased to 1.294(7) Å. These data are
consistent with a change in electron distribution from
the diyndiyl formulation A in 5b to the cumulenic form
C in [5b][PF6]2. Comparison with previous structural
studies of [{MLn}2(µ-C4)]2+ cations (Table 4) shows that
[5b][PF6]2 provides the closest example so far to the pure
cumulenic form anticipated for these group 8 systems,
the C-C distances of [5b][PF6]2 in particular being
identical within 3σ. The dimensions are similar to those
found in the manganese analogue [{MnI(dmpe)2}2(µ-
C4)]2+, in which the C-C separations along the bridge
are 1.289, 1.295, and 1.298(5) Å, respectively.3a We note,
F igu r e 5. IR ν(CC) absorptions (in CH2Cl2) for (a) 5b, (b)
[5b][PF6], and (c) [5b][PF6]2.
anion. The significant lowering of the ν(CC) absorption
in these cations parallels the changes previously re-
ported for the IR ν(CC) spectra of {Ru(PPh3)2Cp}2(µ-
C4) (5c) and the mixed-ligand complex {Ru(PMe3)(PPh3)-
Cp}2(µ-C4) (5d ) as oxidation proceeds. These changes
are consistent with a decrease in C(1)-C(2) bond order.
In turn, these results are anticipated from computa-
Ta ble 4. Som e Bon d P a r a m eter s for [{MLn }2(µ-C4)]x+ Com p lexes
C(1)-C(2),
C(3)-C(4)
M-C(1)-C(2),
M-C(4)-C(3)
C(1)-C(2)-C(3),
C(2)-C(3)-C(4)
MLn
x
M-C(1), M-C(4)
C(2)-C(3)
ref
MnI(dmpe)2
0
1
2
0
2
0
1
0
1
2
1.798(15)
1.763(2)
1.263(17)
1.275(3)
1.33(3)
176(1)
179(1)
177(1)
179(1)
3a
3a
3a
4a, 4c
4a, 4c
1.313(5)
1.295(5)
1.389(5)
1.305(10)
1.37(1)
1.768(4), 1.770(4)
2.037(5)
1.909(7), 1.916(7)
1.889(9), 1.885(8)
1.830(8)
2.001, 2.003(3)
1.931(2)
1.858, 1.856(5)
1.289, 1.298(5)
1.202(7)
1.263, 1.260(10)
1.22, 1.22(1)
1.236(9)
1.223, 1.218(4)
1.248(3)
1.280, 1.269(7)
171.9(5), 174.5(4)
174.4(5)
168.5, 171.4(7)
175, 179(1)
167.0(6)
176.6, 177.1(3)
165.6(2)
175.6, 170.1(4)
173.9(4), 175.9(5)
176.8(6)
177.8, 175.4(9)
177, 176(1)
177(1)
176.9, 178.0(3)
178.0(2)
176.7, 174.2(6)
Re(NO)(PPh3)Cp*
Fe(dppe)Cp*
a
1.36(1)
7a, 7b
Ru(dppe)Cp* (5b)
1.382(4)
1.338(3)
1.294(7)
this work
this work
this work
a
Lapinte, C. Private communication (2002).

{Cp*(PP)Ru}CtCCtC{Ru(PP)Cp*} (PP ) dppm, dppe)
Organometallics, Vol. 22, No. 16, 2003 3193
Ta ble 5. Nea r -In fr a r ed a n d UV-Vis Sp ectr a l Da ta
for [5a /b]n + (n ) 1, 2)
νmax (cm-1) ꢀ (M-1 cm-1) ∆V (cm-1) ∆V calcda VAB (eV)b
[5a ]+
[5b]+
[5a ]2+
[5b]2+
10 165
12 100
14 215
10 195
12 240
14 000
15 385
17 452
21 598
15 152
17 241
21 505
14 000
9500
3500
9850
6600
2200
17 600
5800
4350
24 500
8000
4600
2036
2456
3720
2440
2600
3800
4846
5287
5730
4853
5317
5687
0.63
0.63
a
b
Calculated from eq 2. Calculated from eq 1.
however, that in the neutral manganese complex, the
CtC bonds are already long [at 1.263(17) Å] and the
central C-C bond short [at 1.33(3) Å].
Despite the changes in C-C bond lengths found in
the ruthenium complexes, the angles at individual
carbon atoms are closely similar in all cases and lie in
the range 170.1-176.7(4)°, the complexes having tran-
soid configurations. In [5b]+ the torsion angle between
the two vectors joining the Ru atoms with their Cp*
rings is 180°, whereas in [5b]2+, this angle is -39.7°.
Note that an undistorted cumulenic C4 chain would be
expected to have a torsion angle of either 0° or 180°, so
that the observed twisting is probably the result of
packing effects. Other changes to the coordination about
the ruthenium are minor, for example, the lengthening
of the Ru-P distances [to 2.311, 2.319(1) Å] being
comparable with those found in the other cations
reported above. Progressive oxidation results in a steady
decrease in the Ru‚‚‚Ru separations from 7.821(1) (5b)
to 7.6293(8) ([5b]+) and 7.4757(1) Å ([5b]2+).
UV/Vis/NIR Sp ectr oscop y. To follow the oxidation
processes, we undertook a UV/vis/NIR spectro-electro-
chemical study of the redox series [5]n+. Samples were
generated electrolytically in an OTTLE cell of design
similar to that employed in our previous work.8b Not
surprisingly, the electronic spectra of [5a ]n+ and [5b]n+
are similar, not only to each other but also to those of
[5c]n+ and [5d ]n+. The discussion that follows refers to
the compounds derived from 5a , but the spectra and
interpretation for 5b are essentially the same (Table 5,
Figure 6). Upon oxidation of 5a to [5a ]+, a set of rather
intense, overlapping broad bands are seen to grow in
the NIR region, with discernible maxima at 810 and 965
nm. The observation of multiple bands in the NIR region
has been reported previously for this class of complex.4c,20
These bands were deconvoluted by fitting Gaussian
plots, which allowed extraction of the parameters listed
in Table 5. Higher energy shoulders observed for both
5c and 5d indicate that multiple bands are also present
in the NIR spectra of these 35-electron half-sandwich
ruthenium diyndiyl complexes.
F igu r e 6. UV/vis/near-IR spectra of {Ru(dppm)Cp*}2(µ-
C4) (5a ) as oxidation proceeds: (a) 5a to [5a ]+; (b) [5a ]+ to
[5a ]2+
.
similar underlying structures. Electrolytic reduction of
these 34e dications proceeded smoothly and with com-
plete chemical reversibility through the corresponding
35e monocations to the parent 36-electron species.
However, while cyclic voltammetry indicated the high
thermodynamic stability of the trications [5a ]3+ and
[5b]3+ with respect to disproportionation, these species
proved to have significantly greater chemical reactivity
than [5c]3+ and [5d ]3+. Attempts to collect spectra from
electrogenerated [5a ]3+ and [5b]3+ within the OTTLE
cell were unsuccessful as a result of rapid decomposition
of the electrogenerated material, even at -30 °C.
Discu ssion
Application of the sequence of reactions outlined in
Scheme 1 to the Ru(PP)Cp* series has allowed the
synthesis and isolation of two new C4 complexes, {Ru-
(PP)Cp*}2C4 (5a /b). X-ray structural characterization
of all these complexes has been achieved. There are no
exceptional features in the various precursors; further
comments about the various forms of the C4 complexes
5 are made below.
Of most interest is the redox behavior of these
systems, which has been studied in detail using 5b. CV
data confirm the occurrence of four redox processes that
relate the five species [{Ru(dppe)Cp*}2C4]n+ (n ) 0-4)
through a series of 1e steps. IR studies of the ν(CC)
frequencies have confirmed a decrease in C(1)-C(2)
bond order as n increases from 0 to 2, the latter being
consistent with a cumulenic arrangement. The NMR
spectra confirm that the n ) 0 species is diamagnetic
and n ) 2 predominantly so, whereas the monocation
is paramagnetic. The somewhat broadened 31P NMR
Further oxidation results in the collapse of this set
of NIR bands, with concomitant growth of new higher
energy features at ca. 650, 573, and 463 nm, ac-
companied by an isosbestic point near 700 nm. This
profile was found earlier for [5c]2+ and [5d ]2+ and
clearly points to all of the dications [5]2+ having very
(20) Meyer, W. E.; Amoroso, A. J .; Horn, C. R.; J aeger, M.; Gladysz,
J . A. Organometallics 2001, 20, 1115.

3194 Organometallics, Vol. 22, No. 16, 2003
Bruce et al.
signal for the dppe ligand in [5b]2+ possibly indicates
that a small amount of the triplet state is in equilibrium
with the singlet form. The predominantly singlet state
of [5b][PF6]2 is in marked contrast with the iron
analogue.7c Of note in the present case is the significant
reduction in E(3+/4+), compared with 5c/d . Although
the CV data indicate only thermodynamic stabilities,
we have been encouraged by these results to extend the
preparative studies to these more highly charged spe-
cies, which will be described elsewhere.
Consequently, mixed-valence complexes often give rise
to a low-energy electronic transition that is found in the
NIR region. In the case of class II materials, this band
is usually termed the intervalence charge transfer
(IVCT) band and corresponds to the optically excited
electron transfer between the two interacting redox
centers.22,25 More recently, the shapes of these potential
energy surfaces have been the source of a large amount
of detailed discussion.24,25 The heavily overlapping NIR
transitions in the present examples prevent our observ-
ing the low-energy side of the NIR bands and preclude
a detailed analysis of the band shape. However, the
classical analysis of the IVCT band maximum and shape
in class II materials derived by Hush and others permits
calculation of the electronic coupling parameter VAB (or
Symmetric odd-electron binuclear complexes are usu-
ally described as “mixed-valence” compounds, which in
the case of the radical cations [5]+ and [5]3+ would
formally contain Ru(II/III) (or d6/d5) and Ru(III/IV) (or
d5/d4) centers, respectively. Similar mixed-valence com-
plexes have been obtained by oxidation of the diyndiyl
complexes containing Mn, Re, Fe, and Ru metal cen-
ters.3,4,7,8 Mixed-valence compounds featuring multiple
redox centers linked by some bridging ligand have been
classified by Robin and Day21 as belonging to one of
three classes, distinguished by the degree of interaction
between the redox centers. In class I materials, the
redox centers are essentially independent and behave
as such. Class II complexes display an intermediate
degree of coupling between the redox centers and give
rise not only to properties derived from the superposi-
tion of the valence-localized states but also to some
unique spectroscopic features arising from electron
transfer between the redox centers. The redox centers
in class III materials are so strongly coupled that the
system is better described in MO terms with a delocal-
ized ground state. The spectroscopic properties of class
III materials are unique and do not include the char-
acteristics of the valence-localized limiting forms. Class
II materials have been the subject of detailed theoretical
treatments,22 and recently the behavior of compounds
that fall at the class II/III boundary have attracted a
considerable degree of interest.23-27
H
AB) from the band maximum (or energy) and the shape
of the band on the high-energy side.22-27
For class III materials, in which the odd electron is
delocalized over the redox centers, the coupling param-
eter VAB is simply related to the energy of the NIR band.
VAB ) νmax/2
(1)
We are not the first to consider the term “inter-valence
charge transfer” applied to class II mixed-valence
complexes to be unduly cumbersome and potentially
misleadingwhen appliedtodelocalizedclassIIIcomplexes.4c,25
However, in the absence of a more precise term, and in
keeping with the current trends in the literature, we
shall refer to the NIR absorption band in these systems
using established IVCT terminology.
A simple test that is applied to distinguish class II
and class III materials entails a comparison of the
observed bandwidth v1/2 of the lowest energy electronic
transition with the value determined from the relation-
ship
1/2
v1/2 ) (2310νmax
)
(2)
Classical analyses of symmetric mixed-valence ma-
terials consider the construction of a potential energy
surface from two parabolic functions representing the
noninteracting centers. Electronic coupling between the
centers results in an avoided crossing at the intersection
of these parabolic functions. While a detailed description
of the two adiabatic surfaces that result is beyond the
scope of the present article (for an excellent discussion
see ref 22), it is important to recognize that photoexci-
tation from the lower surface to the upper will result
in an electronic absorption band, which corresponds to
a transition from the (HOMO - 1) to the SOMO.
derived by Hush for class II complexes.26 Class II
materials usually give rise to IVCT bands that are
either in good agreement with or broader than the Hush
analysis predictions, while class III materials give rise
to relatively sharp transitions. However, in the case of
[5a /b]+ the presence of multiple, overlapping NIR
absorptions, which can be deconvoluted to three closely
spaced Gaussian absorptions, complicates this analysis.
Nevertheless, the observation of electronic, vibrational,
and NMR spectral profiles for [5]+ that are not simple
superpositions of the spectra of 5 and [5]2+ strongly
suggests that a class III description is appropriate for
these complexes. The resolved profile has been used here
to calculate the values of VAB given in Table 5, which
are comparable with other data reported earlier.
(21) Robin, M. B.; Day, P. Adv. Inorg. Chem. Radiochem. 1967, 10,
247.
(22) Creutz, C. Prog. Inorg. Chem. 1989, 30, 1.
(23) Demadis, K. D.; Hartshorn, C. M.; Meyer, T. J . Chem. Rev. 2001,
101, 2655.
In the case of [5]+ the SOMO and (HOMO - 1) are
orthogonal, and the IVCT band originates from one of
the lower lying, predominantly metal-centered filled
orbitals, to the SOMO. For the model system [{Ru-
(PH3)2Cp}2(µ-C4}}]+ we have previously calculated the
energy gap between the nest of lower lying metal-
centered orbitals and the SOMO to be ca. 1.4 eV, which
(24) (a) Nelsen, S. F. Chem. Eur. J . 2000, 6, 581. (b) Nelsen, S. F.;
Tran, H. Q. J . Phys. Chem. A 1999, 103, 8139. (c) Nelsen, S. F.;
Ismagilov, R. F.; Gentilr, K. E.; Powell, D. R. J . Am. Chem. Soc. 1999,
121, 7108. (d) Nelsen, S. F.; Tran, H. Q.; Nagy, M. N. J . Am. Chem.
Soc. 1998, 120, 298. (e) Nelsen, S. F.; Ismagilov, R. F.; Powell, D. R. J .
Am. Chem. Soc. 1997, 119, 10213.
(25) Lambert, C.; No¨ll, G. J . Am. Chem. Soc. 1999, 121, 8434.
(26) Brunschwig, B. S.; Creutz, C.; Sutin, N. Chem. Soc. Rev. 2002,
31, 168.
(27) (a) Coropceanu, V.; Malagoli, M.; Andre, J . M.; Bre´das, J . L. J .
Am. Chem. Soc. 2002, 124, 10519. (b) Coropceanu, V.; Malagoli, M.;
Andre, J . M.; Bredas, J . L. J . Chem. Phys. 2001, 115, 10409. (c) Risko,
C.; Barlow, S.; Coropceanu, V.; Halik, M.; Bredas, J .-L.; Marder, S. R.
Chem. Commun. 2003, 194.
corresponds well to the energies of the NIR bands.8b
A
referee has noted that the difference in energy between
the two lower energy resolved band maxima approxi-
mates the vibrational evergy of the ν(CC) bands, and

{Cp*(PP)Ru}CtCCtC{Ru(PP)Cp*} (PP ) dppm, dppe)
Organometallics, Vol. 22, No. 16, 2003 3195
while vibrational structure has been observed in only a
few class III systems, it is possible that the band profiles
in the present systems result from vibrational fine
structurerather than distinct electronictransitions.24d,27c,28,29
measured for the analogous Cp derivatives 5c and 5d
[∆E°(2+/3+) ) 0.64, 0.62 V]8b and indicate the greater
thermodynamic stabilities of the dications derived from
5a and 5b relative to the corresponding trications.
Our earlier computational work suggested that the
frontier orbital of this species should be essentially
delocalized over the six-atom Ru2C4 fragment.8b Analy-
sis of the Hirshfield atomic charges across a series of
[{Cp′L2Ru}2C4]n+ complexes suggested that there are
more or less equivalent distributions of the fractional
electronic charges among the atoms of the Ru-C4-Ru
bridge for n ) 0, 1, 2. However, the more electron-rich
(i.e., Cp*) tricationic systems (n ) 3) have a greater
portion of the fractional electron charge on the carbon
chain than the Cp analogues.
In conclusion, we have shown that for half-sandwich
ruthenium diyndiyl complexes, the use of strongly
electron-donating ligands gives rise to complexes for
which their higher oxidized systems are more readily
available for voltammetric study than found earlier.
However, the decreased chemical stability of these very
highly oxidized complexes renders these species difficult
to obtain on a preparative or semipreparative scale.
These experiments further serve to highlight the influ-
ence of subtle variations in electronic structure, which
can be engineered through control of the metal-ligand
environment, have on the electronic structures of
diyndiyl, and by analogy, poly-yndiyl, complexes.
One of the goals of this work was to investigate the
effects of supporting ligand(s) in a family of diyndiyl
complexes 5 upon the extent to which metal and carbon
orbitals are mixed. The magnitude of the compropor-
tionation constant, KC, is often taken as an indication
of the strength of the coupling between the redox
centers, and for class III complexes in which the effects
of solvation on the shape and energy of the NVT band
are minimal, comparison of the magnitudes of VAB is
also possible. In the present series, KC and VAB are
similar for both the Cp*/PP derivatives [5a /b]+ and the
Cp/PR3 complexes [5c/d ]+ (Table 3). Thus it appears
that despite the increase in electron density resulting
from the introduction of the Cp* and PP ligands, there
has been no significant increase in the interaction
between the metal centers through the C4 bridge.
However, while there is little variation in the coupling
parameters within the family of complexes 5, it should
be noted that these Ru-based complexes display the
largest coupling parameters observed to date in the
diyndiyl series. In addition, the more highly oxidized
species [5a /b]3+/4+ undergo reversible redox processes,
indicating that they are more stable than the analogous
[5c/d ]3+/4+ cations studied previously.8b
The single-crystal X-ray structure determinations of
the neutral and mono- and dicationic species 5b, [5b]-
[PF6], and [5b][PF6]2 are of considerable interest in
connection with assignments of their electronic struc-
tures. As summarized in Table 1, these data confirm
the expected shortening of the Ru-C(1) and C(2)-C(3)
bonds and lengthening of the C(1)-C(2) separation,
consistent with the respective changes in bond order as
electrons are successively removed from the HOMO,
which has M-C antibonding character.8b This interpre-
tation is also consistent with the infrared ν(CC) data
and suggests that the 2e oxidation results in formation
of the dimetalla-cumulene (C), as found previously in
the series [{MLn}2(µ-C4)]n+ [n ) 0-2; MLn ) MnI-
(dmpe)2,3a Re(NO)(PPh3)Cp* 4]. In general, the dimen-
sions and geometry of the Ru-C4-Ru moiety in [5b]+
are intermediate between those of the neutral and
dicationic species and point to smooth changes in these
parameters as oxidation proceeds.
For the iron-based analogues of 5, an increase in the
electron density at the metal centers leads to an
increased iron-iron interaction, which has been at-
tributed to a greater overlap of metal- and carbon-based
orbitals in the frontier orbitals.7b For the Ru systems
which we have studied, electrochemical evidence sug-
gests a more complex trend. While the first and second
oxidation potentials of 5a and 5b are expectedly lower
than those of 5c and 5d , more revealing is an examina-
tion of the values of ∆E° between adjacent redox steps.
While ∆E°(1+/2+) across the series 5a -d is fairly
constant (0.59-0.65 V), the ∆E°(2+/3+) values are
larger (0.82 and 0.89 V, respectively). These differences
are significantly larger than the corresponding values
Exp er im en ta l Section
Gen er a l Meth od s. All reactions were carried out under
dry, high-purity nitrogen using standard Schlenk techniques.
Solvents were dried, distilled, and degassed before use.
Elemental analyses were from either the Canadian Microana-
lytical Service, Delta, B.C, Canada, or the Chemical and Micro-
Analytical Services, Belmont, Victoria, Australia.
In str u m en ta tion . Infrared: Perkin-Elmer FT-IR 1920x.
Solution spectra were obtained using a 0.5 mm path length
solution cell fitted with NaCl windows. Nujol mull spectra were
collected from samples mounted between NaCl disks. NMR:
Samples were dissolved in CDCl3 (Aldrich) unless otherwise
stated using 5 mm sample tubes. Spectra were recorded using
either Varian Gemini 2000 (1H at 300.13 MHz, 13C at 75.47
MHz, 31P at 121.105 MHz) or Varian Gemini 200 (1H at 199.98
MHz, 13C at 50.29 MHz) spectrometers. Electrospray (ES) mass
spectra were measured with a Finnigan LCQ instrument,
solutions in MeOH being directly infused. Cyclic voltammo-
grams were recorded for 1.0 mM solutions in CH2Cl2, with 0.1
M [NBu4][BF4] as supporting electrolyte, using a Maclab 400
instrument. A three-electrode system was used, consisting of
a platinum-dot working electrode and Pt counter and pseudo-
reference electrodes. Potentials are given in V vs SCE, the
ferrocene-ferricinium couple being used as internal calibrant
for the measured potentials (E0 ) 0.46 V vs SCE).30
Rea gen ts. The compounds HCtCSiMe3,31 RuCl(PPh3)2-
Cp*,32 and [FeCp2][PF6]30 were prepared by standard literature
methods. New syntheses of the complexes RuCl(PP)Cp* are
given below. All other reagents were used as purchased from
Aldrich.
P r ep a r a tion of Ru Cl(P P )Cp *. A solution of RuCl(PPh3)2-
Cp* and 1.5 equiv of the appropriate diphosphine was heated
in refluxing toluene for 2 h. The hot solution was then loaded
(30) Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877.
(31) Holmes, A. B.; Sporikou, C. N. Organic Syntheses; Wiley: New
York, 1993; Collect. Vol. 8, p 606.
(32) Morandini, F.; Dondana, A.; Munari, I.; Pilloni, G.; Consiglio,
G.; Sironi, A.; Moret, M. Inorg. Chim. Acta 1998, 282, 163.
(28) Lindeman, V.; Rosokha, S. V.; Sun, D.; Kochi, J . K. J . Am.
Chem. Soc. 2002, 124, 843.
(29) Launay, J .-P. Chem. Soc. Rev. 2001, 30, 387.

3196 Organometallics, Vol. 22, No. 16, 2003
Bruce et al.
directly onto a 10 × 3 cm silica column. Elution with toluene
removed any free phosphine ligands. The bright orange band
was eluted with 1:9 acetone/hexane, and the solvent removed
to give an orange crystalline solid, which was recrystallized
from CH2Cl2/hexane mixtures.
× 1H, CH2), 7.26-7.65 (m, 20H, Ph). 13C NMR: δ 10.82 (s,
3
Cp*), 50.41 [t, J (CP) 20.1, CH2], 91.27 [t, J (CP) 3.7 Hz, Cp*],
93.01 (s, Câ), 120.26 [t, 2J (CP) 22.8 Hz, CR], 127.27-132.83
(m, Ph). 31P NMR: δ 17.99 (s). ES mass spectrum (m/z): 647,
[Ru(C2H)(dppm)Cp* + H]+, 621, [Ru(dppm)Cp*]+.
Com p ou n d 1a . RuCl(PPh3)2Cp* (100 mg, 0.12 mmol) and
dppm (69 mg, 0.18 mmol) in toluene (20 mL) gave RuCl(dppm)-
Com p ou n d 3b. 2b (628 mg, 0.78 mmol) and KOBut (90 mg,
0.78 mmol) in thf (30 mL) gave bright yellow Ru(CtCH)(dppe)-
Cp* (3b) (490 mg, 95%). Anal. Calcd (C38H40P2Ru): C, 69.18;
H, 6.11. Found: C, 68.79; H, 6.63. IR (Nujol, cm-1): ν(tCH)
1
Cp* (1a ) (68 mg, 83%), identified from its H NMR spectrum:
δ 1.92 [t, 4J (HP) 2.7 Hz, Cp*], 4.49, 5.16 (2 × m, 2 × 1H, CH2),
7.53-7.78 (m, 20H, Ph) [lit. values were measured in a
different solvent (d8-thf):16 δ 1.66 (s), 4.18 (m), 4.94 (m), 7.27-
7.53 (m)]. Further spectroscopic details: 13C NMR: δ 10.78
1
4
3269, ν(CtC) 1925. H NMR: δ 1.54 [t, J (HP) 1.6 Hz, 15H,
4
Cp*], 1.57 [t, J (HP) 2.6 Hz, 1H, tCH], 2.08, 2.76 (2 x m, 2 ×
2H, PCH2), 7.09-7.83 (m, 20H, Ph). 13C NMR: δ 10.69 (s, Cp*),
29.90 (m, PCH2), 92.29 [t, 3J (CP) 2.3 Hz, Cp*], 92.99 [t, 3J (CP)
1
(s, Cp*), 49.09 [t, J (CP) 19 Hz, CH2], 88.61 (s, Cp*), 128.00-
134.80 (m, Ph). 31P NMR: δ 12.48 (s). ES mass spectrum (m/
z): 621, [M - Cl]+.
2.3 Hz, Câ], 120.58 [t, J (CP) 22.9 Hz, CR], 127.68-137.97 (m,
2
Ph). 31P NMR: δ 82.15 (s). ES mass spectrum (m/z): 661, [Ru-
(C2H)(dppe)Cp* + H]+; 635, [Ru(dppe)Cp*]+.
Com p ou n d 1b. RuCl(PPh3)2Cp* (100 mg, 0.12 mmol) and
dppe (72 mg, 0.18 mmol) in toluene (20 mL) gave RuCl(dppe)-
Cp* (1b) (76 mg, 95%). The complex was identified from its
1H NMR spectrum: δ 1.43 (s, 15H, Cp*), 2.13, 2.65 (2 × m, 2
× 2H, CH2P), 7.18-7.68 (m, 20H, Ph) [lit. values were
measured in a different solvent (d8-thf):16 δ 1.41 (s), 2.14 (m),
2.66 (m), 7.20-7.69 (m)]. Further spectroscopic details: 13C
NMR: δ 9.59 (s, C5Me5), 28.44 [t, J (CP) 32, CH2], 89.00 (s,
C5Me5), 127.38-139.03 (m, Ph). 31P NMR: δ 76.25 (s). ES mass
spectrum (m/z): 635, [M - Cl]+.
P r ep a r a tion of [Ru (dCdCH2)(P P )Cp *][P F 6]. To a sus-
pension of RuCl(PP)Cp* and NH4PF6 (2 mol equiv) in methanol
was added HCtCSiMe3 (5 mol equiv), and the solution was
heated at reflux point for 1 h. The resulting suspension was
left to cool to room temperature before being filtered on a
sintered glass frit and washed with diethyl ether (2 × 10 mL)
to give a yellow crystalline solid, which was dried under
vacuum.
P r ep a r a tion of [{Cp *(P P )Ru }2(dCdCHCHdCd)][P F6]2.
A solution of Ru(CtCH)(PP)Cp* in CH2Cl2 was cooled to -78
°C. [FeCp2][PF6] (0.9 mol equiv) was added, and the mixture
was stirred for 3 h at -78 °C. The product was crystallized
directly from the reaction by slow addition of diethyl ether and
collected by vacuum filtration, washed with further portions
of diethyl ether until all excess ferrocene was removed, and
dried under vacuum.
Com p ou n d 4a . 3a (940 mg, 1.44 mmol) in CH2Cl2 (20 mL)
and [FeCp2][PF6] (450 mg, 1.38 mmol) followed by addition of
diethyl ether (50 mL) gave crystalline brick red [{Cp*(dppm)-
Ru}2(dCdCHCHdCd)][PF6]2 (4a ) (1032 mg, 91%). The com-
plex was recrystallized from CH2Cl2/hexane mixtures. Anal.
Calcd (C74H76F12P6Ru2): C, 56.21; H, 4.84. Found: C, 56.02;
1
H, 4.71. IR (Nujol, cm-1): ν(CC) 1634, ν(PF) 840. H NMR: δ
1.78 (s, 30H, Cp*), 3.72 (s, 2H, dCH), 4.08, 5.00 (2 × m, 2 ×
2H, CH2), 6.99-7.43 (m, Ph). 13C NMR: δ 10.51 (s, Cp*), 47.04
[t, 1J (CP) 29.3 Hz, CH2], 95.63 (s, Cp*), 102.87 (s, Câ), 128.63-
134.52 (m, Ph), 348.59 [t, 2J (CP) 15.1 Hz, CR]. 31P NMR: δ
4.76 (s), -143.6 (septet, PF6). ES mass spectrum (m/z): 1436,
[{Cp*(dppm)Ru}2C4H2]+; 621, [Ru(dppm)Cp*]+.
Com p ou n d 2a . RuCl(dppm)Cp* (1375 mg, 2.12 mmol),
NH4PF6 (694 mg, 4.25 mmol), and HCtCSiMe3 (1030 mg, 10.5
mmol) in methanol (25 mL) gave bright yellow [Ru(dCdCH2)-
(dppm)Cp*][PF6] (2a ) (1570 mg, 96%). Anal. Calcd (C37H39F6P3-
Ru): C, 56.13; H, 4.96. Found: C, 56.49; H, 4.96. IR (Nujol,
cm-1): ν(CdC) 1627, ν(PF) 834. 1H NMR: δ 1.77 [t, 4J (HP)
Com p ou n d 4b. From 3b (660 mg, 1.17 mmol) in CH2Cl2
(30 mL) and [FeCp2][PF6] (348 mg, 1.05 mmol, 0.9 mol eq),
addition of diethyl ether (40 mL) crystallized brick red [{Cp*-
(dppe)Ru}2(dCdCHCHdCd)][PF6]2 (4b) (685 mg, 85%). The
complex was recrystallized from acetone/hexane mixtures.
Anal. Calcd (C76H80F12P6Ru2): C, 56.72; H, 5.01. Found: C,
56.77; H, 5.11. IR (Nujol, cm-1): ν(CC) 1600, ν(PF) 841. 1H
NMR: δ 1.66 (s, 30H, Cp*), 2.57-2.78 (m, 8H, CH2), 3.13 (s,
2H, dCH), 7.00-7.56 (m, 40H, Ph). 13C NMR: δ 10.13 (s, Cp*),
28.73 (m, CH2), 93.95 (s, Cp*), 103.22 (s, Câ), 128.79-134.41
4
1.8 Hz, 15H, Cp*], 3.03 [t, J (HP) 3.2, 2H, CH2], 4.63, 5.18 (2
× m, 2 × 1H, CH2), 7.13-7.46 (m, 20H, Ph), 13C NMR: δ 10.19
(s, Cp*), 48.24 [t, J (CP) 27.5, CH2], 95.23 (s, Cp*), 102.26 (s,
Câ), 127.48-135.63 (m, Ph), 344.54 [t, 2J (CP) 14.6, CR]. 31P
NMR: δ 6.56 (s), -143.6 (septet, PF6). ES mass spectrum (m/
z): 647, [Ru(CCH2)(dppm)Cp*]+; 621, [Ru(dppm)Cp*]+.
Com p ou n d 2b. RuCl(dppe)Cp* (2450 mg, 3.70 mmol), NH4-
PF6 (1210 mg, 7.42 mmol), and HCtCSiMe3 (1813 mg, 18.50
mmol) in methanol (25 mL) gave bright yellow [Ru(dCdCH2)-
(dppe)Cp*][PF6] (2b) (2333 mg, 95%). Anal. Calcd (C38H41F6P3-
Ru): C, 56.64; H, 5.12. Found: C, 56.74; H, 5.27. IR (Nujol,
2
(m, Ph), 348.08 [t, J (CP) 17.8 Hz, CR]. 31P NMR: δ 75.92 (s),
-143.70 (septet, PF6). ES mass spectrum (m/z): 1465, [{Cp*-
(dppe)Ru}2C4H2]+; 635, [Ru(dppe)Cp*]+.
1
4
cm-1): ν(CC) 1621, ν(PF) 835. H NMR: δ 1.59 [t, J (HP) 1.2,
P r ep a r a tion of {Cp *(d p p m )Ru }2(µ-CtCCtC) (5a ). To
a solution of 4a (640 mg, 0.4 mmol) in CH2Cl2 (20 mL) was
added dbu (0.6 mL, 4 mmol). The solution was stirred for 15
min, after which the solvent was removed under vacuum. The
oily residue was extracted with hot hexane until no more
bright orange complex could be removed. The extracts were
filtered and the solvent removed to give an orange crystalline
solid. Trituration with cold methanol (5 mL) followed by
collecting the solid on a glass sinter and washing with cold
methanol (5 mL) gave {Cp*(dppm)Ru}2(µ-CtCCtC) (5a ) (467
mg, 90%). The analytical sample was obtained from CH2Cl2/
hexane. Anal. Calcd (C74H74P4Ru2‚CH2Cl2): C, 65.54; H, 5.57.
4
15H, Cp*], 2.58, 2.94 (2 × m, 2 × 2H, PCH2), 2.99 [t, J (HP)
1.8 Hz, 2H, CH2], 7.09-7.57 (m, 20H, Ph). 13C NMR: δ 9.76 (s,
Cp*), 29.00 (m, PCH2), 93.11 (s, Cp*), 102.65 (s, Câ), 128.61-
133.75 (m, Ph), 344.21 [t, 2J (CP) 16.4, CR]. 31P NMR: δp 77.28
(s), -143.6 (septet, PF6). ES mass spectrum (m/z): 661, [Ru-
(CCH2)(dppe)Cp*]+; 635, [Ru(dppe)Cp*]+.
P r ep a r a tion of Ru (CtCH)(P P )Cp *. To a solution of [Ru-
(dCdCH2)(PP)Cp*][PF6] in thf was added KOBut (1 mol
equiv), and the solution was stirred at room temperature for
30 min. The solvent was removed under vacuum, and the solid
was extracted in a minimum of CH2Cl2 and loaded onto a short
(5 cm) column of basic alumina. Elution with 3:7 acetone/
hexane gave a bright yellow solution, which was concentrated
to give a bright yellow crystalline solid.
Com p ou n d 3a . 2a (550 mg, 0.694 mmol) and KOBut (78
mg, 0.694 mmol) in thf (20 mL) gave bright yellow Ru(CtCH)-
(dppm)Cp* (3a ) (420 mg, 94%). Anal. Calcd (C37H38P2Ru): C,
68.82; H, 5.93. Found: C, 69.03; H, 5.70. IR (Nujol, cm-1): ν-
(tCH) 3279, ν(CtC) 1932. 1H NMR: δ 1.52 [t, 4J (HP) 2.7, 1H,
CtCH], 1.88 [t, J (HP) 1.8 Hz, 15H, Cp*], 4.35, 4.70 (2 × td, 2
1
Found: C, 65.51; H, 5.70. IR (Nujol, cm-1): ν(CtC) 1966. H
NMR (C6D6): δ 1.89 (s, 30H, Cp*), 4.23 (m, 4H, CH2), 7.01-
7.64 (m, 40H, Ph). 13C NMR (C6D6): δ 11.37 (s, Cp*), 51.20 [t,
1J (CP) 22 Hz, CH2], 91.33 (s, Cp*), 93.25 [t, 2J (CP) 27 Hz, CR],
100.38 (s, Câ), 127.46-139.32 (m, Ph). 31P NMR (C6D6): δ 17.50
(s). ES mass spectrum (m/z): 1290, [M]+; 621, [Ru(dppm)Cp*]+.
P r ep a r a tion of {Cp *(d p p e)Ru }2(µ-CtCCtC) (5b). To a
solution of 4b (600 mg, 0.37 mmol) in thf (30 mL) was added
KOBut (103 mg, 0.92 mmol) and the reaction stirred at room

{Cp*(PP)Ru}CtCCtC{Ru(PP)Cp*} (PP ) dppm, dppe)
Organometallics, Vol. 22, No. 16, 2003 3197
Ta ble 6. Cr ysta l Da ta a n d Refin em en t Deta ils
1a
1b
2a
2b
3a
3b
formula
C
35H37ClP2Ru
C36H39ClP2Ru
C37H39F6P3Ru‚
CH2Cl2
876.63
C38H41F6P3Ru
C37H38P2Ru
C38H40P2Ru
MW
656.15
670.18
805.73
645.73
679.75
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
orthorhombic
P212121
9.8817(9)
15.210(1)
20.698(2)
monoclinic
P21/ n
11.115(1)
17.767(2)
16.714(2)
triclinic
P1h
orthorhombic
Pca21
23.4660(1)
16.131(1)
18.969(1)
monoclinic
P21/ n
8.8642(3)
32.1486(1)
11.3776(4)
monoclinic
P21/ n
12.4509(8)
19.046(1)
13.8966(8)
8.8548(6)
11.6736(9)
19.309(1)
97.216(2)
96.030(2)
102.584(2)
1914
109.131(1)
107.923(1)
104.440(2)
3111
4
1.401
7.2
3118
4
1.422
7.2
7180
8
1.490
6.3
3084
4
1.390
6.4
3191
4
1.415
6.2
Z
2
Dc, g cm-3
1.521
7.3
µ, cm-1
cryst size, mm 0.40 × 0.15 × 0.07 0.45 × 0.37 × 0.19 0.35 × 0.10 × 0.06 0.35 × 0.30 × 0.10 0.32 × 0.07 × 0.05 0.18 × 0.15 × 0.06
Tmin,max
2θmax, deg
Ntot
0.42, 0.84
58
63982
4610 (0.090)
4160
0.70, 0.86
58
29751
7677 (0.018)
6857
0.74, 0.86
75
39689
19734 (0.030)
15336
0.57, 0.77
58
148895
9729 (0.090)
7684
0.74, 0.86
75
64997
16262 (0.073)
10026
0.76, 0.88
75
67466
16848 (0.083)
9102
Nr (Rint
No
)
R
0.048
0.025
0.048
0.060
0.042
0.041
Rw
0.055
0.033
0.055
0.070
0.035
0.028
4a
4b
5a
5b
[5b][PF6]
[5b][PF6]2
formula
C74H76F12P6Ru2‚
4.5CH2Cl2
1963.58
orthorhombic
C2221
21.716(1)
24.068(2)
16.913(1)
C76H80F12P6Ru2‚
4C3H6O
1841.76
monoclinic
P21/c
24.010(3)
12.082(2)
29.331(4)
C74H74P4Ru2‚
C3H6O
1347.52
monoclinic
P21/ n
14.6636(7)
24.461(1)
20.042(1)
C76H78P4Ru2‚
C6H14
1403.67
triclinic
P1h
10.984(2)
17.860(3)
17.880(3)
88.906(3)
85.485(3)
88.576(3)
3495
C76H78F6P5Ru2
C76H78F12P6Ru2‚
2H2O
1643.45
triclinic
P1h
13.2874(9)
15.241(1)
20.520(1)
77.496(2)
89.899(2)
67.948(2)
3746
MW
1462.46
monoclinic
P21/n
8.6472(8)
20.001(2)
19.291(2)
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
90.795(2)
111.435(1)
90.794(2)
8840
4
1.475
7.9
8508
4
1.438
5.4
6692
4
1.377
5.9
3336
2
1.456
6.3
Z
2
2
Dc, g cm-3
1.334
5.7
1.457
6.1
µ, cm-1
cryst size, mm 0.25 × 0.23 × 0.13 0.18 × 0.08 × 0.05 0.20 × 0.15 × 0.12 0.40 × 0.30 × 0.10 0.35 × 0.14 × 0.11 0.20 × 0.15 × 0.12
Tmin,max
2θmax, deg
Ntot
0.75, 0.83
75
92460
12389 (0.051)
8288
0.74, 0.84
58
82999
21381 (0.056)
14399
0.74, 0.86
75
139241
35201 (0.087)
18901
0.74, 0.86
58
40040
16857 (0.024)
13880
0.73, 0.86
75
51431
17354 (0.053)
11199
0.75, 0.86
58
72643
19889 (0.046)
14537
Nr (Rint
No
)
R
0.051
0.048
0.044
0.039
0.042
0.057
Rw
0.072
0.053
0.039
0.048
0.048
0.064
temperature for 30 min. The solvent was removed under
vacuum and the crude solid extracted with hexane to give a
bright orange solution, which was filtered through cotton wool
and concentrated to give a bright orange crystalline solid.
Trituration with cold ethanol (5 mL) followed by collecting on
a glass sinter and washing with cold ethanol (5 mL) gave {Cp*-
(dppe)Ru}2(µ-CtCCtC) (5b) (438 mg, 90%) as a hemi-hexane
solvate. Anal. Calcd (C76H78P4Ru2.0.5C6H14): C, 69.74; H, 6.29.
Found: C, 69.79; H, 6.40. IR (Nujol, cm-1): ν(CtC) 1973; (CH2-
Cl2): 1963. 1H NMR (C6D6): δ 1.68 (s, 30H, Cp*), 1.95, 2.72 (2
× m, 2 × 4H, CH2), 7.04-8.05 (m, 40H, Ph). 13C NMR (C6D6):
δ 10.09 (s, Cp*), 29.11 (s, CH2), 92.26 (t, Cp*), 94.63 [t, 2J (CP)
27 Hz, CR], 99.47 (s, Câ), 127.32-140.46 (m, Ph). 31P NMR
(C6D6): δ 82.53 (s). ES mass spectrum (m/z): 1318, [M]+; 635,
[Ru(dppe)Cp*]+.
P r ep a r a t ion of [{Cp *(d p p e)R u }2(CtCCtC)][P F 6]n
([5b]n +). n ) 1. To a solution of 5b (50 mg, 0.038 mmol) in
CH2Cl2 (20 mL) was added [FeCp2][PF6] (11.9 mg, 0.036 mmol),
causing an immediate color change to bright green, after which
the solution was stirred for 30 min. The solvent was concen-
trated under vacuum ca. 5 mL and added dropwise to hexane
(250 mL) to give [{Ru(dppe)Cp*}2(µ-C4)][PF6] ([5b][PF6]) (48
mg, 91%) as a light green microcrystalline solid. Anal. Calcd
(C76H78P5F6Ru2‚CH2Cl2): C, 59.70; H, 5.21. Found: C, 59.80;
H, 5.21. IR (Nujol, cm-1): ν(CtC) 1859, ν(PF) 841; (CH2Cl2)
1
1860. H NMR: δ 6.46-7.92 (m, br, 40H, Ph), 10.72 (br, 30H,
Me), 13.54 (br, 8H, CH2P). ES mass spectrum (m/z): 1318,
[{Ru(dppe)Cp*}2C4]+; 635, [Ru(dppe)Cp*]+.
n ) 2. To a solution of 5b (50 mg, 0.038 mmol) in CH2Cl2
(20 mL) was added [FeCp2][PF6] (25 mg, 0.076 mmol) to give
an immediate color change to deep blue, after which the
solution was stirred for 30 min. The solvent was concentrated
under vacuum (ca. 5 mL) and added dropwise to hexane (250
mL) to give [{Cp*(dppe)Ru}2(CtCCtC)][PF6]2 ([5b][PF6]2) (47
mg, 79%) as a dark blue solid. Anal. Calcd (C76H78P6F12Ru2):
C, 56.79; H, 4.89. Found: C, 57.00; H, 5.02. IR (Nujol, cm-1):
ν(CC) 1769, ν(PF) 841; (CH2Cl2) 1770m, 1711vw. 1H NMR
(acetone-d6): δ 1.94 (s, 30H, C5Me5), 3.01 [s (br), 8H, CH2],
7.17-7.79 (m, 40H, Ph). 13C NMR (acetone-d6): δ 10.38 (s,
C5Me5), 27.79 (m, CH2), 112.28 (s, C5Me5), 129.80-133.97 (m,
Ph). 31P NMR (acetone-d6): δ 117.89 [s (br), dppe], -143.20
(septet, PF6). ES mass spectrum (m/z): 1463, [{Ru(dppe)-
Cp*}2C4 + PF6]+; 1318, [{Ru(dppe)Cp*}2C4]+; 659, [{Ru(dppe)-
Cp*}2C4]2+
.
Str u ctu r e Deter m in a tion s. Full spheres of diffraction
data were measured at ca. 153 K using a Bruker AXS CCD
area-detector instrument. Ntot reflections were merged to N
unique (Rint quoted) after “empirical”/multiscan absorption

3198 Organometallics, Vol. 22, No. 16, 2003
Bruce et al.
correction (proprietary software), No with F > 4σ(F) being used
in the full matrix least squares refinement. All data were
measured using monochromatic Mo KR radiation, λ ) 0.71073
Å. Anisotropic thermal parameter forms were refined for the
4a . Anion 2 was modeled as disordered about a crystal-
lographic 2-axis; certain solvent molecules were similarly
modeled as disordered. xabs refined to -0.03(4).
4b. Anion 2 was modeled as rotationally disordered about
an F-P-F axis, the two sets of components of the four
equatorial fluorines having occupancies refining to 0.881(6)
and complement.
non-hydrogen atoms, (x, y, z, Uiso
)
being constrained at
H
estimated values. Conventional residuals R, Rw on |F| are given
[weights: (σ2(F) + 0.0004F2)-1]. Neutral atom complex scat-
tering factors were used; computation used the XTAL 3.7
program system.33 Pertinent results are given in Figures 1-3
(which show non-hydrogen atoms with 50% probability am-
plitude displacement ellipsoids and hydrogen atoms with
arbitrary radii of 0.1 Å) and Tables 1 and 6.
5b. Solvent residues were modeled in terms of hexane, C(1-
3) disordered over two sets of sites, occupancies 0.5.
5b-+. (x, y, z, Uiso
) refined.
H
5b-2+. Difference map residues were modeled as a pair of
water molecule oxygen atoms, O‚‚‚O 2.84(1) Å.
Crystallographic data for the structure determinations have
been deposited with the Cambridge Crystallographic Data
Centre as CCDC 190604-190615. Copies of this information
may be obtained free of charge from: The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, England (fax: +44-1223-
336033, e-mail: support@ccdc.cam.ac.uk, or www: http://
www.ccdc.cam.ac.uk).
Va r ia ta . 1a . Friedel data were retained distinct, xabs refin-
ing to 0.06(5). Displacement amplitudes are unreasonably high
throughout the structure, suggestive of unresolved disorder
or lower symmetry (etc.).
1b. The structure is isomorphous with its molybdenum
analogue34 and was refined with the same cell and coordinate
setting. (x, y, z, Uiso
) refined.
H
2a . Extensive disorder is found throughout the anion and
solvent moieties, each being described in terms of pairs of
components, occupancies set at 0.5 after trial refinement. (x,
Ack n ow led gm en t. This work was supported by the
Australian Research Council (M.I.B.) and the EPSRC
(P.J.L.). B.G.E. held an Australian Post-graduate Award.
We thank J ohnson Matthey plc, Reading, England, for
a generous loan of RuCl3‚nH2O.
y, z, Uiso
) refined meaningfully for the dCH2 hydrogen atoms.
H
2b. The dCH2 hydrogen atoms are postulated from the
refinement behavior and chemistry. xabs refined to 0.19(5).
3a . (x, y, z, Uiso
3b. (x, y, z, Uiso
)
refined.
) refined.
H
H
Su p p or tin g In for m a tion Ava ila ble: X-ray structural
data for 1a /b, 2a /b, 3a /b, 4a /b, 5a /b, [5b]+, and [5b]2+. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(33) Hall, S. R.; du Boulay, D. J .; Olthof-Hazekamp R.; Eds. The
XTAL 3.7 System; University of Western Australia, 2000.
(34) Abugideiri, F.; Fettinger, J . C.; Keogh, D. W.; Poli, R. Organo-
metallics 1996, 15, 4407.
OM030015G