Synthesis and reactivity studies of dicationic dihydrogen complexes bearing sulfur-donor ligands: A combined experimental and computational study

Article abstract of DOI:10.1002/ejic.201201022

A series of dihydrogen complexes trans-[Ru(η²-H ₂){SC(SR)H}(dppe)₂][X][BF₄] (R = CH ₃, X = OTf; R = C₆H₅CH₂, X = BPh₄; R = H₂C=CHCH₂, X = BPh₄; dppe = Ph₂PCH₂CH₂PPh₂) bearing sulfur-donor ligands has been synthesized by protonation of the (alkyl dithioformate)hydrido complexes trans-[Ru(H){SC(SR)H}(dppe)₂][X] by using HBF₄·Et₂O. Competitive substitution reactions between H₂ and SC(SR)H in trans-[Ru(η²-H ₂){SC(SR)H}(dppe)₂][X][BF₄] have been studied by treatment with CH₃CN, CO, and P(OCH₃)₃. These resulted in the expulsion of SC(SR)H from the metal center, thus indicating that the alkyl dithioformate ligand is more labile than H ₂. Bonding of alkyl dithioformate ligands (sulfur-donor ligands) trans to H₂ have been studied by comparing the H-H distances and chemical-shift values (¹H NMR spectroscopy) of the various dihydrogen complexes bearing different trans ligands. This study qualitatively suggests that the alkyl dithioformate ligands in these trans-dihydrogen complexes show a poor π effect, and it is further supported by density functional theory calculations. The first example of a dihydrogen complex bearing dithioformic acid, trans-[Ru(η²-H₂){SC(SH)H}(dppe) ₂][BF₄]₂, was obtained by protonation of trans-[Ru(H){SC(S)H}(dppe)₂] by using HBF₄·Et ₂O. Copyright

Full text of DOI:10.1002/ejic.201201022

FULL PAPER
DOI:10.1002/ejic.201201022
Synthesis and Reactivity Studies of Dicationic Dihydrogen
Complexes Bearing Sulfur-Donor Ligands: A Combined
Experimental and Computational Study
Thirumanavelan Gandhi,*[a] Subramani Rajkumar,[a]
V. Prathyusha,[b] and U. Deva Priyakumar*[b]
Keywords: Ruthenium / Dihydrogen ligands / S ligands / Phosphane ligands / Density functional calculations
A
series of dihydrogen complexes trans-[Ru(η2-H2){SC-
H2. Bonding of alkyl dithioformate ligands (sulfur-donor li-
(SR)H}(dppe)2][X][BF4] (R = CH3, X = OTf; R = C6H5CH2, X =
BPh4; R = H2C=CHCH2, X = BPh4; dppe = Ph2PCH2CH2PPh2)
bearing sulfur-donor ligands has been synthesized by pro-
tonation of the (alkyl dithioformate)hydrido complexes trans-
gands) trans to H2 have been studied by comparing the H–
H
troscopy) of the various dihydrogen complexes bearing dif-
ferent trans ligands. This study qualitatively suggests that
distances and chemical-shift values (1H NMR spec-
[Ru(H){SC(SR)H}(dppe)2][X] by using HBF4·Et2O. Competi- the alkyl dithioformate ligands in these trans-dihydrogen
tive substitution reactions between H2 and SC(SR)H in trans-
[Ru(η2-H2){SC(SR)H}(dppe)2][X][BF4] have been studied by
treatment with CH3CN, CO, and P(OCH3)3. These resulted
in the expulsion of SC(SR)H from the metal center, thus indi-
cating that the alkyl dithioformate ligand is more labile than
complexes show a poor π effect, and it is further supported
by density functional theory calculations. The first example
of a dihydrogen complex bearing dithioformic acid, trans-
[Ru(η2-H2){SC(SH)H}(dppe)2][BF4]2, was obtained by proton-
ation of trans-[Ru(H){SC(S)H}(dppe)2] by using HBF4·Et2O.
the JH,D values of its η2-HD isotopomer. The groups of
Sellmann[8,9] and Morris[10] prepared dihydrogen transition-
metal complexes that bear sulfur-donor ligands, which are
biologically relevant to enzyme hydrogenases and nitroge-
nases. Sellmann et al.[8] reported dihydrogen complexes with
sulfur-rich coordination spheres. [Ru(η2-H2)(“S4”)(PCy3)]
{“S4”2– = 1,2-bis[(2-mercaptophenyl)thioethane]2–} and its
η2-HD isotopomer were obtained by treatment of
[Ru(H)(“S4”)(PCy3)]– with CH3OH and CD3OD, respec-
tively, and its JH,D value was found to be 32 Hz. In another
report, Sellmann and co-workers[9] reported the preparation
of the dihydrogen complex [Ru(η2-H2)(“N2Me2S2”)(PR3)]
Introduction
The chemistry of dihydrogen complexes that bear co-
ligands, especially ligands trans to H2, such as CO,[1] hal-
ides,[2] phosphanes, phosphites,[3] cyanides,[4] and nitriles,[5]
has been well established. On the contrary, dihydrogen com-
plexes bearing sulfur-donor ligands have not been well ex-
plored. Esteruelas and co-workers[6] reported the first ex-
amples of dihydrogen complexes containing sulfur-donor li-
gands. They treated [Os(H)2Cl2(PiPr3)2] with K[EtOCS2] to
obtain the dihydrogen complexes [Os(η2-H2){η2-S2C-
(OMe)}(Cl)(PiPr3)2] and [Os(η2-H2)(PiPr3)2(EtOCS2){η2-
S2C(OEt)}], and their H–H distances were determined from
the spin–lattice relaxation time measurements. Albéniz et
al.[7] have shown that the dihydrogen complex [Os(η2-
H2)(CO)(η2-S2CH)(PiPr3)2][BF4] could be prepared by pro-
tonation of [Os(H)(CO)(η2-S2CH)(PiPr3)2] with HBF4·
Et2O in CD2Cl2. The H–H distance in [Os(η2-H2)(CO)(η2-
S2CH)(PiPr3)2][BF4] was calculated from the T1(min.) and
[“N2Me2S2”
=
1,2-ethanediamine-N,NЈ-dimethyl-N,N-
bis(2-benzenethiolate)2–; R = iPr, Cy] by substitution of N2
in [Ru(N2)(“N2Me2S2”)(PR3)] with H2. Schlaf et al.[10] re-
ported the synthesis of dihydrogen complexes bearing sul-
fur-donor ligands of the type [M(η2-H2)(CO)(L)(PPh3)2]-
[BF4] (M = Ru, Os; L = pyridine-2-thiolate, quinoline-8-
thiolate) by protonating their precursor hydrido complexes
with HBF4·Et2O. They prepared trans-[Os(η2-H2)(HSPh)-
(dppe)2][BF4]2 (dppe = Ph2PCH2CH2PPh2) by protonation
of the trans-[Os(H)(HSPh)(dppe)2][BF4] complex by using
HBF4·Et2O.[10] Here we present the synthesis and properties
of new (dihydrogen)ruthenium complexes bearing sulfur-
donor ligands of the type trans-[Ru(η2-H2){SC(SR)H}-
(dppe)2][X][BF4] (R = CH3, X = OTf; R = C6H5CH2, X =
BPh4; R = CH2=CHCH2, X = BPh4; R = H, X = BF4).
Computational tools have been shown to be indispens-
able in studying the structural and energetic properties of
[a] Materials Chemistry Division,
School of Advanced Sciences, VIT University,
Vellore 632014, India
E-mail: velan.g@vit.ac.in
Homepage: http://vit.ac.in/sas/faculty.asp
[b] Centre for Computational Natural Sciences and Bioinformatics,
International Institute of Information Technology,
Hyderabad 500032, India
E-mail: deva@iiit.ac.in
http://www.iiit.ac.in/people/faculty/deva
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201201022.
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transition-metal complexes in general.[11] Density func- NMR spectroscopy since attempts to isolate these deriva-
tional studies were used to investigate and predict the geo- tives in the solid state resulted in their decomposition. The
metries, metal–ligand bonding,[12] and JH,D values in molec- bound H2 appears as a broad singlet in the range δ = –8.55
1
ular dihydrogen complexes.[13] Furthermore, it supports the to –8.71 ppm in the H NMR spectrum. These signals are
H2 activation mechanism,[14] exchange processes between shifted downfield with respect to the starting hydrido com-
M(H)(H2),[15] and the acidity of the dihydrogen com- plexes. The 31P{1H} NMR spectra of the dihydrogen com-
plexes.[16] In this paper, we have used hybrid density func- plexes comprise only a singlet resonance, thus indicating
tional calculations at the B3LYP level of theory to study equivalent phosphorus nuclei with a trans geometry for the
the Ru2+ complexes. The Ph2P(CH2)2PPh2 ligand has been dihydrogen and the alkyl dithioformate/dithioformic acid li-
replaced by the H2P(CH2)2PH2 ligand for computational gands.
studies. The substitution of the phenyl group in the ligand
by a hydrogen atom is commonplace in computational
studies and has been shown to have only a moderate effect
on the structural properties of the system under consider-
ation.[17–19] Similarly, PH3 and PMe3 have been shown to
satisfactorily model the PPh3 ligand.[20,21] Additionally, we
have performed natural bond orbital (NBO) and atoms-in-
molecules (AIM) analyses to specifically study the nature
of bonding between the Ru2+ ion and ligands, especially
how the behavior of the dihydrogen ligand changes with
respect to the ligand present trans to H2.
Results and Discussion
Synthesis and Characterization of trans-[Ru(η2-H2){SC(SR)-
H}(dppe)2][X][BF4] (R = CH3, X = OTf; R = C6H5CH2,
X = BPh4; R = CH2=CHCH2, X = BPh4; R = H, X = BF4)
The protonation of hydrido complexes trans-
[Ru(H){SC(SR)H}(dppe)2][X] (R = CH3, X = OTf; R =
C6H5CH2, X = BPh4; R = CH2=CHCH2, X = BPh4; R =
H, X = BF4) with 54% HBF4·Et2O (5 equiv.) afforded the
corresponding
dihydrogen
complexes
trans-[Ru(η2-
Figure 1. Stack plot of the 1H NMR spectra of the reaction of
trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf][BF4] (1) with CH3CN
in CDCl3. (1) trans-[Ru(H){SC(SCH3)H}(dppe)2][OTf]; (2) trans-
[Ru(H){SC(SCH3)H}(dppe)2][OTf] + 54% HBF4·Et2O; (3) trans-
[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf][BF4] + CH3CN. (a) trans-
[Ru(H){SC(SCH3)H}(dppe)2][OTf]; (b) trans-[Ru(η2-H2){SC-
H2){SC(SR)H}(dppe)2][X][BF4] [R = CH3, X = OTf (1); R
= C6H5CH2, X = BPh4 (2); R = CH2=CHCH2, X = BPh4
(3); R = H, X = BF4 (4)] [Equation (1)]. Addition of less
than 5 equiv. of 54% HBF4·Et2O to complexes 1, 2, 3, and
4 led to incomplete protonation of the hydrides, and equi-
librium is thereby established between the hydrido and its
corresponding dihydrogen complexes. A broad peak at δ =
(SCH3)H}(dppe)2][OTf][BF4];
(c)
trans-[Ru(η2-H2)(CH3CN)-
(dppe)2][OTf][BF4]; and (d) SC(SCH3)H.
1
11.50 ppm in the H NMR spectra corroborates the pres-
The dihydrogen complexes bearing sulfur-donor ligands
such as thiolates,[8–10] thiols,[22] η2-dithioformates,[7] xan-
thate derivatives, and thiocarboxylate derivatives[6] have
been reported; however, dihydrogen complexes bearing
alkyl dithioformates and dithioformic acid are unknown.
Complex 4 is the first example of a dicationic dihydrogen
complex bearing the unstable dithioformic acid as the trans
ligand.[23] Dithioformic acid is an unstable species; it has
been studied extensively by theoretical methods,[24] micro-
wave spectroscopy,[25] and IR spectroscopy.[26]
ence of an excess amount of HBF4·Et2O (Figure 1). These
reactions were carried out in CD2Cl2 under argon. The di-
hydrogen complexes were characterized in solution by using
Reactivity of trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf]-
[BF4] with CH3CN
Treatment of a solution of 1 in CDCl3 with CH3CN
(2 equiv.) afforded the dicationic dihydrogen complex trans-
(1) [Ru(η2-H2)(CH3CN)(dppe)2][OTf][BF4] by means of the eli-
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mination of the trans-SC(SCH3)H ligand [Equation (2)]. occurs to yield the hydrido derivative, and a proton equiva-
This is surprising since the bound H2 ligand would be ex- lent is released, which migrates to an external Lewis base
pected to be more labile than the methyl dithioformate moi- or an ancillary ligand or anion.[31] Mezzetti and co-workers
ety. The progress of this substitution reaction was moni- observed trans-[Ru(η2-H2)(CO)(dppp)2][OTf][BPh4] at only
1
tored by both H and 31P NMR spectroscopy. Addition of 233 K by protonation of trans-[Ru(H)(CO)(dppp)2][BPh4]
1 equiv. of CH3CN to 1 resulted in the formation of trans- with HOTf.[1c] The bound H2 ligand in this derivative was
[Ru(η2-H2)(CH3CN)(dppe)2][OTf][BF4] and free SC- shown to be highly activated toward heterolysis.
(SCH3)H, as shown in the Figure 1. It was found from the
1H NMR spectra that treatment of 1 with CH3CN yielded
only 80% of trans-[Ru(η2-H2)(CH3CN)(dppe)2][OTf][BF4].
The 1H NMR spectrum of trans-[Ru(η2-H2)(CH3CN)-
(dppe)2][OTf][BF4] shows
a
broad singlet at
δ
=
–10.77 ppm, which is comparable to that of the reported
trans-[Ru(η2-H2)(CH3CN)(dppe)2][BF4]2.[5] The other pos-
sible product is CH3CN trans to methyl dithioformate {i.e.,
trans-[Ru(CH3CN){SC(SCH3)H}(dppe)2][OTf][BF4]} with
the expulsion of H2; this species was not observed because
of steric crowding generated by trans ligands CH3CN and
methyl dithioformate. There have been only very few exam-
ples in the literature in which the dihydrogen ligand stays
intact with the metal center, and other coligands undergo a
substitution reaction. Esteruelas and co-workers[27] re-
ported that the η2-H2 ligand of [Os1{C6H4(O1)CH3}(η2-
H2)(H2O)(PiPr3)(Os1–O1)][BF4] stays intact upon addition
of acetone oxime. However, the aqua ligand is replaced by
Scheme 1.
acetone
oxime
to
yield
[Os1{C6H4(O1)CH3}(η2-
derivative.
This reactivity pattern (Scheme 1) was studied by using
H2){N(OH)=C(CH3)2}(PiPr3)(Os1–O1)][BF4]
NMR spectroscopy. Figure 2 [see plot (2)] shows the forma-
tion of 1 by protonation of trans-[Ru(H){SC(SCH3)H}-
(dppe)2][OTf] with HBF4·Et2O. Purging CO through the
solution of 1 resulted in the decrease in concentration of 1,
with a concomitant increase in the concentration of trans-
[Ru(H)(CO)(dppe)2][OTf]/[BF4] as shown in Figure 2 [see
plot (3)] and the reaction is complete in 15 min [see
plot (4)]. The hydrido ligand of trans-[Ru(H)(CO)(dppe)2]-
The methyl dithioformate binds to the metal atom through
the lone pair of electrons present on the sulfur atom as in
thioethers[28] and thioureas.[29] The bonding of the alkyl di-
thioformate to the metal atom will be discussed in detail in
the latter part of this article. It is instructive to note from
this result that the alkyl dithioformate ligand is more labile
than the bound H2.
(2)
Reactivity of trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf]-
[BF4] (1) with CO
Purging CO gas at a steady rate through a solution of 1
in CDCl3 for 2 min led to the formation of trans-
[Ru(H)(CO)(dppe)2][OTf]/[BF4] accompanied by the elimi-
nation of methyl dithioformate and a proton equivalent
(Scheme 1). The product trans-[Ru(H)(CO)(dppe)2][OTf]/
[BF4][30] presumably formed through the intermediacy of
trans-[Ru(η2-H2)(CO)(dppe)2][OTf][BF4], the bound H2 li-
gand of which is expected to be highly acidic. Heterolytic
Figure 2. Stack plot of the 1H NMR spectra of the reaction of
trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf][BF4] (1) with CO in
CDCl3. (1) trans-[Ru(H){SC(SCH3)H}(dppe)2][OTf]; (2) trans-
[Ru(H){SC(SCH3)H}(dppe)2][OTf] + 54% HBF4·Et2O; (3) trans-
[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf][BF4] + CO; (4) plot (3) +
15 min. (a) trans-[Ru(H){SC(SCH3)H}(dppe)2][OTf]; (b) trans-
[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf][BF4]; (c) trans-[Ru(H)-
cleavage of H2 in trans-[Ru(η2-H2)(CO)(dppe)2][OTf][BF4] (CO)(dppe)2][OTf]/[BF4]; and (d) SC(SCH3)H.
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[OTf] shows a quintet at δ = –7.22 ppm (JH,P = 19.6 Hz)
due to coupling with 4 equivalent phosphorus nuclei. The
outcome of this reaction is also surprising since SC-
(SCH3)H is replaced by CO instead of η2-H2. This reaction
also demonstrates that the methyl dithioformate is more la-
bile than the bound H2 ligand.
Reactivity of trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf]-
[BF4] with P(OCH3)3
When P(OCH3)3 (3 equiv.) was added to a solution of 1
in CDCl3, instant deprotonation of the dihydrogen ligand
was observed to yield the trans-[Ru(H){SC(SCH3)H}-
(dppe)2][OTf]/[BF4] hydrido complex [Figure 3; plot (3)
matches plot (1)] and protonated [HP(OCH3)3]+ in a small
quantity that was unobservable [Scheme 2 (a)]. Sub-
sequently, the excess amounts of P(OCH3)3 and HBF4·Et2O
participate in the substitution of SC(SCH3)H from trans-
[Ru(H){SC(SCH3)H}(dppe)2][OTf]/[BF4] to yield trans-
[Ru(H){P(OCH3)3}(dppe)2][OTf]/[BF4] and conversion of
P(OCH3)3 to PF(OCH3)2, respectively, both in coordinated
and noncoordinated form (Scheme 2).
1
Figure 3. Stack plot of the H NMR spectra of the reaction of 1
with P(OCH3)3 in CDCl3. (1) trans-[Ru(H){SC(SCH3)H}-
(dppe)2][OTf]; (2) trans-[Ru(H){SC(SCH3)H}(dppe)2][OTf] + 54%
HBF4·Et2O; (3) trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf][BF4]
+ P(OCH3)3; (4) plot (3) + 30 min. (a) trans-[Ru(H){SC(SCH3)-
H}(dppe)2][OTf]; (b) trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf]-
[BF4]; (c) trans-[Ru(H){P(OCH3)3}(dppe)2][OTf]/[BF4]; (d) trans-
[Ru(H){PF(OCH3)2}(dppe)2][OTf]/[BF4]; and (e) SC(SCH3)H.
Scheme 2.
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The excess amount of P(OCH3)3 present in the solution Table 1. Variable-temperature spin–lattice relaxation times (T1)
(400 MHz) of the η2-H2 ligand in trans-[Ru(η2-H2){SC(SR)H}-
(dppe)2][X][BF4] complexes in CD2Cl2. Italicized data indicate
undergoes the following reactions:
(a)ItdisplacesSC(SCH3)Hfromtrans-[Ru(H){SC(SCH3)H}-
T1(min.)
.
(dppe)2][OTf]/[BF4] to yield trans-[Ru(H){P(OCH3)3}-
(dppe)2][OTf]/[BF4][3d] and free SC(SCH3)H [Scheme 2 (b)],
T [K]
T1 [ms]
T1 [ms]
T1 [ms]
T1 [ms]
1
2[a]
3
4[a]
1
which was monitored both by H and 31P{1H} NMR spec-
301
293
283
273
263
253
243
233
223
213
16.5
15.1
15.1
15.1
15.1
15.1
15.1
15.8
17.3
18.7
troscopy;
trans-[Ru(H){SC(SCH3)H}(dppe)2][OTf]/[BF4]
15.8
15.8
15.8
15.8
15.1
15.8
15.8
17.3
18.7
7.2
7.2
8.6
11.5
14.4
17.3
20.2
21.6
30.3
15.8
15.8
15.8
15.8
15.8
15.8
17.3
18.7
20.2
exhibits a quintet at δ = –12.72 ppm for the hydrido ligand
[as shown in Figure 3; plot (3) matches plot (1)], and trans-
[Ru(H){P(OCH3)3}(dppe)2][OTf]/[BF4] appears as a doub-
let of quintets centered at δ = –9.19 ppm for the hydrido
ligand as shown in Figure 3 [see plot (4)].
(b) It reacts with HBF4·Et2O (an excess amount of
HBF4·Et2O was used to stabilize 1) to yield free PF-
(OCH3)2. The 31P{1H} NMR spectrum exhibits a doublet
centered at δ = 132.0 ppm for free PF(OCH3)2.[32]
[a] No T1(min.) was observed.
(c) Furthermore, trans-[Ru(H){P(OCH3)3}(dppe)2][OTf]/
[BF4] with an excess amount of HBF4·Et2O yields trans-
H–D Isotopomers
[Ru(H){PF(OCH3)2}(dppe)2][OTf]/[BF4]
The driving force for the formation of trans-
[Ru(H){PF(OCH3)2}(dppe)2][OTf]/[BF4] from trans-
[Scheme 2 (d)].
Deuterium was incorporated into the η2-H2 ligand by
bubbling HD gas (generated from the reaction of NaH and
D2O) through solutions of 1, 2, 3, and 4 in CD2Cl2 for
5 min. The η2-HD isotopomers trans-[Ru(η2-HD){SC-
(SR)H}(dppe)2][X][BF4] {R = CH3, X = OTf ([D]1); R =
C6H5CH2, X = BPh4 ([D]2); R = CH2=CHCH2, X = BPh4
([D]3); and R = H, X = BF4 ([D]4)} were thus obtained.
Albeniz et al.[34] proposed that isotopic scrambling occurs
due to a combination of the lability and the acidity of the
H2 ligand. The η2-HD signals were observed in the 1H
NMR spectra by nullifying the resonance due to the η2-H2
ligand by the inversion recovery method using the relation-
ship T1 = τnull/ln2 and the known T1 values of the dihydro-
gen complexes at room temperature.[22,35,36] The JH,D values
together with the H–H distances for these complexes are
summarized in Table 2. JH,D values for all the η2-HD deriv-
atives are 28.4 Hz, and the corresponding dH–H is 0.94 Å,
[Ru(H){P(OCH3)3}(dppe)2][OTf]/[BF4] is the cone-angle re-
duction of the trans-phosphite ligand as reported by Ma-
thew et al.[3d] In this reaction, the OCH3 group is likely
to be protonated followed by the elimination of CH3OH.
–
Consequently, the BF4 counterion provides the F– for the
phosphite to result in the PF(OCH3)2 ligand. trans-
[Ru(H){P(OCH3)3}(dppe)2][OTf]/[BF4]
and
trans-
[Ru(H){PF(OCH3)2}(dppe)2][OTf]/[BF4] appear as a doub-
let of quintets and doublet of sextets centered at δ = –9.19
and –8.22 ppm, respectively, for the hydrido ligands as
shown in Figure 3 [see plot (4)]. The 31P{1H} NMR spec-
trum exhibits a doublet of quintets centered at δ =
134.6 ppm for trans-[Ru(H){PF(OCH3)2}(dppe)2][OTf]/
[BF4]. All the above reactions are complete in 30 min. Thus,
the methyl dithioformate moiety in trans-[Ru(H){SC-
(SCH3)H}(dppe)2][OTf]/[BF4] was easily replaced by
P(OMe)3 [Scheme 2 (b)], and we were led to conclude that
methyl dithioformate is a labile ligand.
which was calculated by using the equation dH–H
=
–0.0167JH,D + 1.42 developed by Morris.[35b] Similar dH–H
values for complexes [D]1 to [D]4 corroborate that there is
no significant change in electronics at the metal center by
changing the R group in the alkyl dithioformate moiety.
Sellmann and co-workers observed JH,D values of 32 Hz for
dihydrogen complexes bearing sulfur-donor ligands of the
type [Ru(η2-H2)(PCy3)(“S4”)] {“S4”2– = 1,2-bis[(2-mercap-
tophenyl)thioethane]2–}, which is larger than the coupling
constants obtained in our complexes.[8]
1H NMR Spectroscopy T1 Measurements
The variable-temperature spin–lattice relaxation times
(T1) for η2-H2 of trans-[Ru(η2-H2){SC(SR)H}(dppe)2][X]
[R = CH3, X = OTf (1); R = C6H5CH2, X = BPh4 (2); R
= CH2=CHCH2, X = BPh4 (3); and R = H, X = BF4 (4)]
were determined in CD2Cl2. T1 data were obtained in the
temperature range 213–301 K and are summarized in
Table 1. T1 values reach minima at 15.1 ms at 253 and
263 K for complexes 1 and 3, respectively. For complexes 2
and 4, T1(min.) values were not observed. The H–H distances
can be calculated from the T1 minima values.[33] Thus, the
Table 2. H–H distances of the η2-H2 ligand of complexes trans-
[Ru(η2-H2){SC(SR)H}(dppe)2][X][BF4] obtained from JH,D
.
R (compound)
JH,D [Hz]
dH–H [Å]
CH3 ([D]1)
C6H5CH2 ([D]2)
CH2=CHCH2 ([D]3)
H ([D]4)
28.4
28.4
28.4
28.4
0.94
0.94
0.94
0.94
The η2-HD resonances of complexes [D]1, [D]2, [D]3,
H–H distances are 1.06 and 0.84 Å, respectively, for the and [D]4 experience downfield shifts relative to their η2-H2
1
slow and the fast rotation regimes of the H2 ligand for 1 counterparts in the H NMR spectra, and these shifts are
and 3.
of the order of 134–186 ppb. The η2-HD isotopomers of
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many dihydrogen complexes reported in the literature exhi- from the density functional theory calculations and the dis-
bit upfield shifts relative to their η2-H2 analogues. On the cussion of the bonding in these complexes determined on
contrary, the ones that show downfield shifts are very the basis of the results.
few.[37] These small chemical-shift differences are essentially
The H–H bond lengths of the dihydrogen ligand in each
independent of temperature, thereby suggesting that there of the complexes were calculated, and compared with the
is only one structure for these dicationic complexes.[38]
estimates obtained by using the NMR spectroscopic chemi-
A
rapid equilibrium between a dihydrido and a dihydrogen cal-shift values (Table 4). The distance between the two hy-
structure would likely lead to temperature-dependent iso- drogen atoms obtained using experimental data is the maxi-
tope effects that result from isotopic perturbation of equi- mum for the π-donor ligand (Cl–), and the minimum for
librium.[39]
the π-acceptor ligand (CO). For the other ligands, the dis-
tances were found to be intermediate between the two val-
ues. Such a trend of the change in the bond lengths with
respect to the nature of the ligand is accurately captured by
the computational methods used here. The η2-H2 bond
length seems to depend on the trans ligand bound to the
metal center. For a π-donor (Cl–) ligand, the π back-do-
nation from the d(M) orbital to the σ*(η2-H2) increases re-
sulting in a longer H–H distance. On the other hand, when
the ligand bound trans to H2 is a π-acceptor (e.g., CO), then
the π back-donation from the d(M) orbital to σ*(η2-H2)
decreases, thereby resulting in a shorter H–H bond. Such
an electronic effect is further confirmed on the basis of
NBO and AIM analyses (see below). Comparison of the
experimental and the computed bond lengths reveals that
the B3LYP/LANL2DZ method seems to underestimate the
bond lengths in general, which might be because of one or
more of the following two reasons: (a) the computations
were performed in the gas phase, and the experiments were
performed in the presence of a solvent; (b) the bidentate
ligand Ph2PCH2CH2PPh2, which was used in the experi-
mental study, has been replaced by H2PCH2CH2PH2. Irre-
spective of such quantitative differences, the qualitative
trends, and hence the conclusions from the computational
study are not expected to change with respect to the change
in the conditions or the level of theory used. The pKa value
that corresponds to the SH group of the ligand is expected
Bonding of S Ligands to the Metal Atom in the
trans-[Ru(η2-H2){SC(SR)H}(dppe)2][X][BF4] Complexes
[R = CH3, X = OTf (1); R = C6H5CH2, X = BPh4 (2);
R = CH2=CHCH2, X = BPh4 (3); R = H, X = BF4 (4)]:
Experimental and Computational Studies
Bonding of H2 to a metal atom is described by the σ(η2-
H2) donation of electron to the empty d(M) orbital and π
back-donation from the filled d(M) orbital to the σ*(η2-
H2) orbital. The properties and reactivity of the metal-
bound H2 molecule greatly depend on the ligand bound
trans to it. If the trans ligand is a π-donor (Cl–), it favors
the σ(η2-H2) donation to the d(M) orbital and increases the
π back-donation from the d(M) orbital to the σ*(η2-H2)
orbital, which results in a long H–H bond. If the trans li-
gand is a π-acceptor [CO, PF(OR)2, PF3], it reduces the π
back-donation from the d(M) orbital to the σ*(η2-H2) or-
bital, which results in either a short H–H bond or hetero-
lytic cleavage. If the trans ligand is a strong σ-donor (H–),
there is a powerful trans labilizing effect that reduces σ(η2-
H2) donation, which once again weakens the M–(η2-H2)
binding and contracts dH–H
[40]
.
Table 3 shows a comparison of chemical shifts and H–H
bond lengths of our complexes and others. One thing com-
mon to all these complexes (listed in Table 3) is that dihy-
drogen is bound to the ruthenium atom and has the same
diphosphane (dppe) ligand except for a CO complex
(dppp), but the variable is the trans ligand. The chemical-
shift values and the H–H bond lengths of dihydrogen com-
plexes bearing trans-sulfur ligands (alkyl dithioformate/di-
thioformic acid) lie in between those that have the π-donor
(Cl–), and π-acceptor [CO, PF3, PF(OR)2] and σ-donor li-
gands (H–) (Table 3). This qualitatively suggests that the
sulfur ligands trans to η2-H2 in complexes 1, 2, 3, and 4 are
both good π-donor and π-acceptor ligands, thus showing a
synergistic effect. The following section provides the results
Table 4. Experimental estimates of the H–H bond length [Å] and
interaction energies corresponding to the π back-donation from Ru
to the dihydrogen moiety calculated by using the second-order per-
turbation analysis with the NBO method.
trans Ligand
dH–H [Å]
π Back-donation (RuǞH2)
Exp.
B3LYP
[kcalmol–1]
Cl–
SC(SCH3)H
H–
0.98
0.94
0.88
0.85
0.843
0.825
0.797
0.793
21.10
15.77
11.25
7.98
CO
Table 3. Chemical-shift values and H–H bond lenghts of trans-[Ru(η2-H2)(L)(diphos)2]2+
.
trans-Ligand (L)
Ancillary ligand (diphos)
Chemical shift (δ) of H2 [ppm]
dH–H [Å][35a] (from T1)
Cl–[2a]
dppe
dppe
dppe
dppe
dppe
dppp
–12.3
–8.55 to –8.71
–5.12 to –5.63
–4.33
0.98
0.94
0.94 to 0.97
0.92
SC(SR)H
[a][3e]
PF(OR)2
[3a]
PF3
H–[33]
–4.6
–2.5
0.88
0.85
CO[1c]
[a] R = Me, Et, OiPr.
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to be low. To confirm this phenomenon, the proton affin- extent of back-donation, there is a correlation between the
ities of the dithioformate anion and that of the Ru complex nature of the ligand and the calculated bond orders. Al-
were calculated at the B3LYP level. The proton affinity of though NBO analysis gives an interpretation about the
the dithioformate anion was found to be approximately bonding in terms of orbital interactions, the topological
340 kcalmol–1. Interestingly, the proton affinity that corre- analysis of electron density calculated using Bader’s AIM
sponded to the dithioformate moiety coordinated to the Ru approach[43] results in a rigorous definition of chemical
complex was found to have decreased to 251 kcalmol–1.
bonding using molecular graphs. In these graphs, the atoms
The bonding between the ligand and the metal ion and that are bonded are linked by bond paths, and the minimum
their electronic manifestations on the dihydrogen moiety electron density along a bond path is termed as the bond
were analyzed by using the second-order perturbative inter- critical point.[44] AIM analysis was performed, and the
action energies between natural bond orbitals obtained with bond critical points were located in a way that corre-
the NBO analysis. The CO ligand was found to be the sponded to all the bonds. In all the complexes, the Ru cen-
strongest π-acceptor (RuǞCO) among the ligands consid- ter is bonded to the η2-H2 ligand through two bond critical
ered here with an interaction energy of about points (BCPs), and these are intersected by two ring critical
23.6 kcalmol–1, whereas the chlorido ligand acts as a π-do- points (RCPs). In addition to this, there is also a bond criti-
nor (ClǞRu) with an interaction energy of about cal point observed between the two hydrogen atoms in the
5.4 kcalmol–1. Interestingly, the sulfur-based ligand, η2-H2 ligand. The electron density at the BCP (ρ), the La-
SC(SCH3)H, was found to act both as a π-acceptor and placian of the electron density (V2ρ), and the bond ellipicity
as a π-donor. The corresponding interaction energies were (ε) values were obtained and compared with the experimen-
calculated to be 1.5 (RuǞS=C) and 7.9 kcalmol–1 (RuǟS), tal NMR spectroscopic chemical shifts given in Table 3.
respectively. The effect of the change in these ligands on the The correlation between several parameters calculated by
bonding of the dihydrogen moiety to Ru was examined by using computational methods, and the chemical-shift values
analyzing the π back-donation from Ru to the σ* orbital are presented in Figure 4. Linear correlations were obtained
of H2 (Table 4). The second-order perturbation interaction
energies between the corresponding orbitals decreased as
we moved from π-donor to π-acceptor and σ-donor ligands.
In case of π-donor ligands, the back-donation from Ru to
η2-H2 is high, thereby resulting in large interaction energies.
This trend illustrates the decrease in π back-donation along
the series, thus further confirming the electronic effect dis-
cussed above. Notably, the interaction energy values for the
SC(SCH3)H ligand lies between those of π-donor and π-
acceptor ligands, which shows dual character. Wiberg bond
indices[41] and overlap-weighted natural atomic orbital
(NAO) bond orders[42] were calculated, and those of select
bonds are presented in Table 5. With respect to the change
in the ligand trans to H2, there seems to be no significant
change in the bond orders/indices that correspond to the
four Ru–P coordinations (Ru–P1, Ru–P2, Ru–P3, and Ru–
P4 in Table 5). However, the bond orders between Ru and
H2, and between the two hydrogen atoms of the dihydrogen
ligand (Ru–H2 and H1–H2, respectively) change consider-
ably with respect to the ligand. Similar to the trend in the
Table 5. Wiberg bond indices and overlap-weighted NAO bond or-
ders for the Ru and the atoms to which it is bonded along with the
bond orders for (η2-H2) H–H atoms.
trans Ligand
Wiberg bond index
Ru–P1 Ru–P2 Ru–P3 Ru–P4 Ru–H2 H1–H2
Cl–
SC(SCH3)H
H–
0.771
0.781
0.785
0.769
0.772
0.767
0.790
0.771
0.772
0.766
0.790
0.771
0.771
0.782
0.785
0.769
0.670
0.621
0.49
0.549
0.573
0.682
0.647
Figure 4. (a) Correlations of the interaction energies corresponding
to the π back-donation from Ru to H2 calculated by using the sec-
ond-order perturbation analysis with NBO. (b) Wiberg index corre-
sponding to the Ru–H2 bond. (c) NAO bond order corresponding
to the Ru–H2 bond. (d) Wiberg index corresponding to the H–H
bond. (e) NAO bond order corresponding to the H–H bond. (f)
Electron density at the bond critical point corresponding to H–H.
(g) Laplacian of the electron density at the bond critical point of
H–H. (h) H–H bond ellipticity against the NMR spctroscopic
chemical-shift values of the dihydrogen moiety.
CO
0.517
NAO bond order
Cl–
SC(SCH3)H
H–
0.766
0.765
0.793
0.737
0.763
0.744
0.795
0.738
0.763
0.745
0.796
0.738
0.766
0.762
0.793
0.737
0.872
0.843
0.735
0.767
0.546
0.565
0.623
0.608
CO
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for all the correlations with correlation coefficient values chemical shifts that correspond to the dihydrogen moiety
ranging from 0.83 to as good as 0.99. The trans-directing and the calculated parameter, which furthers our under-
capability of the ligands under study [Cl–, SC(SCH3)H, H–, standing of the bonding in this class of compounds.
CO] depends on the polarizability. Softer ligands have a re-
markable trans-directing capability due to their high polar-
izability. The softer ligands like CO, H–, and RSH have
good trans-directing ability when bound to the soft acid
Ru+2, because soft–soft interactions are favorable according
to the hard/soft acid/base (HSAB) theory. The hard ligand
Cl–, which has a low polarizability, has the least trans-di-
recting ability. Bonding of the alkyl dithioformate ligand
could be compared with the bonding of thiourea and thio-
ketone to the metal atom. Fairlie et al.[29] showed that thio-
urea in [(NH3)5Ru{SC(NH2)2}](S2O6)3/2·H2O is a good π-
donor ligand. Setkina and co-workers[28] reported that the
Experimental Section
General Procedures: All reactions except those that involve the di-
hydrogen complexes were carried out under dry and purified nitro-
gen at room temperature by using standard Schlenk[45] and inert-
gas techniques unless otherwise specified. Manipulations that in-
volved dihydrogen complexes were carried out under argon. Sol-
vents used for the preparation of dihydrogen complexes were thor-
oughly saturated with argon just before use. 1H and 31P{1H} NMR
spectroscopic data were acquired with a Bruker Avance 400 MHz
spectrometer. The shifts of the residual protons of the deuterated
solvents were used as internal reference. Variable-temperature 1H
spin–lattice relaxation time measurements were carried out at
400 MHz by using the inversion recovery method (180°-τ-90° pulse
sequence at each temperature). The T1 data are summarized in
Table 1. 31P{1H} NMR spectroscopic chemical shifts have been
measured relative to 85% H3PO4 (aqueous solution) as an external
standard in CD2Cl2. trans-[Ru(H){η1-SC(S)H}(dppe)2][46] and
trans-[Ru(H){SC(SR)H}(dppe)2][X][23] (R = CH3, X = OTf; R =
H2C=CHCH2, X = BPh4; R = C6H5CH2, X = BPh4) were prepared
according to literature methods.
thiobenzylcyclopentadienyl
ligand
in
[(η5-C5H5)-
(CO)2MnǟS=C(Ph)(C5H4)Mn(CO)3] complexes shows
both acceptor and donor properties. Hence the alkyl di-
thioformate/dithioformic acid bound to the metal atom is
presumed to be a good π-acceptor and π-donor ligand. Our
future plan is to study the lability and its mechanistic as-
pects, and the acidity of these dihydrogen ligands trans to
sulfur-donor ligands.
The numbering scheme for the compounds reported in this work
is summarized in Table 6.
Conclusion
The protonation reactions of the hydrido complexes
trans-[Ru(H){SC(SR)H}(dppe)2][X] (R = CH3, X = OTf; R
= C6H5CH2, X = BPh4; R = CH2=CHCH2, X = BPh4; R
= H, X = BF4) with HBF4·Et2O result in new dicationic
Table 6. Numbering scheme for the compounds.
L
dihydrogen
complexes,
trans-[Ru(η2-H2){SC(SR)H}-
(dppe)2][X][BF4]. H–H distances of all these dihydrogen
complexes are of the order of 0.94 Å, thereby suggesting
that there is no significant effect on the dH–H value with a
change in the electronics of the sulfur ligand. The reactivity
of these dihydrogen complexes toward ligands such as
CH3CN and CO showed that the sulfur ligands are more
labile than the bound H2. The combined experimental and
computational studies suggest that the sulfur ligands pres-
ent in these trans-[Ru(η2-H2){SC(SR)H}(dppe)2][X][BF4]
dihydrogen complexes exhibit a poor π effect. The weak
metal donor–acceptor interactions in the Ru–S bond could
be further corroborated by the facile replacement of the sul-
fur ligand by H2. The results from the density functional
theory calculations and from the detailed analysis provide
CH3
C6H5CH2
H2C=CHCH2
H
1[a]
2[b]
3[b]
4[c]
[D]1[a]
[D]2[b]
[D]3[b]
[D]4[c]
[a] X = OTf. [b] X = BPh4. [c] X = BF4; [Ru] = Ru(dppe)2 fragment.
Preparation of trans-[Ru(η2-H2){SC(SR)H}(dppe)2][X][BF4] [R =
CH3, X = OTf (1); R = C6H5CH2, X = BPh4 (2); R =
CH2=CHCH2, X = BPh4 (3); R = H, X = BF4 (4)]: A 5 mm NMR
spectroscopy tube charged with trans-[Ru(H){SC(SR)H}-
(dppe)2][X] (0.02 g) was evacuated and filled with Ar in three cycles.
The hydrido complex was then dissolved in CD2Cl2 (0.6 mL), and
54% HBF4·Et2O (5 equiv.) was added to this solution. The 1H and
an excellent correlation between the NMR spectroscopic 31P{1H} NMR spectra revealed the formation of the dihydrogen
1
Table 7. H and 31P{1H} NMR spectroscopic data (δ) [ppm] of trans-[Ru(η2-H2){SC(SR)H}(dppe)2][X][BF4] complexes in CD2Cl2.
R (compound)
Ru(η2-H2)
R [SC(SR)H]
CH2CH2 (dppe)
Ph (dppe)
P (dppe)
CH3 (1)
–8.68 (br. s, 2 H)
2.76 (s, 3 H, CH3), 7.83 [s, 1 H, SC(SCH3)H]
2.59 (m, 4 H), 3.17 (m, 4 H) 6.63–7.44 (m, 40 H)
52.4 (s)
52.4 (s)
C6H5CH2 (2) –8.68 (br. s, 2 H) 4.43 [s, 2 H, SC(SH2CC6H5)H], 6.65–7.64 [m, 5 H, 2.59 (m, 4 H), 3.17 (m, 4 H) 6.65–7.64 (m, 40 H)
SC(SH2CC6H5)H], 7.83 [s, 1 H, SC(SH2CC6H5)H]
–8.71 (br. s, 2 H)
3.85 [d, J(Hd,Hc) = 6.8 Hz, 2 H, Hd], 5.70 [d,
J(Hb,Hc) = 4.9 Hz, 1 H, Hb], 5.73 [d, J(Ha,Hc) =
5.9 Hz, 1 H, Ha], 5.92 (m, 1 H, Hc), 7.83 [s, 1 H,
SC(SH2CCH=CH2)H]
2.60 (m, 4 H), 3.16 (m, 4 H) 6.65–7.64 (m, 40 H)
52.3 (s)
(3)
H (4)
–8.55 (br. s, 2 H)
6.01 [d, JH,H = 12.7 Hz, 1 H, SC(SH)H], 7.80 [d, 2.58 (m, 4 H), 3.19 (m, 4 H) 6.82–7.42 (m, 40 H)
JH,H = 12.7 Hz, 1 H, SC(SH)H]
52.5 (s)
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complexes trans-[Ru(η2-H2){SC(SR)H}(dppe)2][X][BF4] [R = CH3,
X = OTf (1); R = C6H5CH2, X = BPh4 (2); R = CH2=CHCH2, X
= BPh4 (3); R = H, X = BF4 (4)]. The NMR spectroscopic data of
these derivatives are summarized in Table 7.
Ph2PCH2CH2PPh2, JP,P = 32.0 Hz], 134.6 [dquint, JP,F = 1148.5,
JP,P = 32.0 Hz, PF(OCH3)2] ppm.
Computational Methods: Full geometry optimizations were carried
out on a series of dihydrogen complexes bearing ligands [Cl–,
SC(SCH3)H, H– and CO were chosen as model systems] that are
Observation of HD Isotopomers trans-[Ru(η2-HD){SC(SR)H}-
(dppe)2][X][BF4] {R = CH3, X = OTf ([D]1); R = C6H5CH2, X =
BPh4 ([D]2); R = CH2=CHCH2, X = BPh4 ([D]3); R = H, X = BF4
([D]4)}: These derivatives were prepared in the following manner:
Each of the hydrido complexes 1, 2, 3, 4 (0.02 g) was dissolved in
CD2Cl2 (0.6 mL) in a 5 mm NMR spectroscopy tube under Ar.
Then 5 equiv. of 54% HBF4·Et2O was added. The 1H NMR spectra
revealed the complete conversion of the hydrido into the corre-
sponding dihydrogen complexes [D]1, [D]2, [D]3, and [D]4. HD gas
(generated from NaH and D2O) was bubbled into the same solu-
present trans to η2-H2 by using the density functional B3LYP[47]
/
Genecp level (6-31G* basis set for C, H, O, P, S, Cl atoms and
LANL2DZ[48] basis set for Ru atoms) with the Gaussian 09 pro-
gram.[49] The data for the complexes at the B3LYP level using the
Los Alamos effective core potential LANL2DZ basis set on all
the atoms of the complexes considered are given in the Supporting
Information. In all the calculations, the phenyl groups attached to
the phosphorus atoms in the bidentate ligand were replaced by hy-
drogen atoms and were used as model systems. NBO analysis was
performed to examine the bond orders, and the second-order per-
turbative energies for the donor–acceptor interactions. The NBO
program 3.1[41] included in the Gaussian 09 suite of programs was
used for the analysis. The topological analysis of the electron den-
sity of these complexes was carried out by using the AIM method
implemented in the AIMALL program.[43] The anions surrounding
the complex ions were not taken into account during optimization
of these complexes at the B3LYP level.
1
tion for 5 min. The H–D isotopomer formed was observed by H
NMR spectroscopy.
Reaction of trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf][BF4] (1)
with CH3CN: CH3CN (2 equiv., 2 μL, 0.034 mmol) was added to a
solution of 1 (0.02 g, 0.017 mmol) in CDCl3. The yellow solution
1
became pale. The H and 31P NMR spectra revealed the complete
conversion of 1 into trans-[Ru(η2-H2)(CH3CN)(dppe)2][OTf][BF4]
accompanied by the elimination of SC(SCH3)H. The yield of trans-
[Ru(η2-H2)(CH3CN)(dppe)2][OTf][BF4] was 80% as ascertained
from the 1H NMR spectrum. 1H NMR (CDCl3) spectroscopic data
of trans-[Ru(η2-H2)(CH3CN)(dppe)2][OTf][BF4]:[5b] δ = –10.76 [br.
s, 2 H, Ru-(η2-H2)], 1.57 (s, 3 H, CH3CN), 2.43 (br. m, 4 H,
Ph2PCH2CH2PPh2), 3.01 (br. m, 4 H, Ph2PCH2CH2PPh2), 6.49–
7.99 (m, 40 H, Ph2PCH2CH2PPh2) ppm. 31P{1H} NMR (CDCl3):
δ = 56.6 (s, Ph2PCH2CH2PPh2) ppm.
Supporting Information (see footnote on the first page of this arti-
cle): Experimental estimates of the H–H bond length and the inter-
action energy corresponding to π back-donation (Table S1); Wiberg
bond indices and overlap-weighted NAO bond orders (Table S2);
correlations of the interaction energies, Wiberg indices, NAO bond
order, electron density, Laplacian values, and bond ellipticity (Fig-
ure S1); and Cartesian coordinates.
Reaction of trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf][BF4] (1)
with CO: CO gas was purged for 2 min through a solution of 1
(0.02 g, 0.017 mmol) in CDCl3. The yellow solution became paler.
Acknowledgments
1
The H and 31P NMR spectra revealed the complete conversion of
We thank the Department of Science and Technology, New Delhi
(India) (no. SR/FT/CS-135/2011) for financial support. T. G. is very
grateful to Prof. Balaji R. Jagirdar, IISc, Bangalore, India, for intel-
lectual discussions. V. P. thanks the Department of Science and
Technology (DST) for an INSPIRE fellowship.
1 into trans-[Ru(H)(CO)(dppe)2]+ accompanied by the elimination
of SC(SCH3)H.[30] NMR spectroscopy evidenced the complete dis-
appearance of the dihydrogen complex and the formation of trans-
[Ru(H)(CO)(dppe)2]+. 1H NMR (CDCl3) spectroscopic data for
trans-[Ru(H)(CO)(dppe)2]+: δ = –7.25 ppm (quint, 1 H, JH,P
=
19.6 Hz, Ru–H), 2.16 (br. m, 4 H, Ph2PCH2CH2PPh2), 2.47 (br. m,
4 H, Ph2PCH2CH2PPh2), 6.95–7.41 (m, 40 H, Ph2PCH2CH2PPh2).
[1] a) K. D. Welch, W. G. Dougherty, W. S. Kassel, D. L. DuBois,
R. M. Bullock, Organometallics 2010, 29, 4532; b) S. Bolano,
J. Bravo, F. Fernandez-Garcia, S. Garcia-Fontan, C. M. M.
Del, J. Organomet. Chem. 2009, 694, 2994; c) E. Rocchini, A.
Mezzetti, H. Rueegger, U. Burckhardt, V. Gramlich, Z. A. Del,
P. Martinuzzi, P. Rigo, Inorg. Chem. 1997, 36, 711.
13C{1H} NMR (CDCl3):
δ = 32.2 (quint, JC,P = 13.0 Hz,
Ph2PCH2CH2PPh2), 128.4–133.7 (m, Ph2PCH2CH2PPh2), 200.5 (s,
Ru–CO) ppm. 31P{1H} NMR (CDCl3):
Ph2PCH2CH2PPh2) ppm.
δ
=
63.9 (s,
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Reaction of trans-[Ru(η2-H2){SC(SCH3)H}(dppe)2][OTf][BF4] (1)
with P(OCH3)3: P(OCH3)3 (3 equiv., 6 μL, 0.052 mmol) was added
to a solution of 1 (0.02 g, 0.017 mmol) in CDCl3. The color of the
solution changed from yellow to orange. The 1H and the 31P NMR
spectra indicated the deprotonation of
1
to trans-
[Ru(H){SC(SCH3)H}(dppe)2][OTf]/[BF4]. Then further P(OCH3)3
(2 equiv., 4 μL, 0.033 mmol) was added to this solution; the 1H and
the 31P NMR spectra revealed the formation of trans-
[Ru(H){PF(OCH3)2}(dppe)2][OTf]/[BF4], SC(SCH3)H and a small
amount of trans-[Ru(H){P(OCH3)3}(dppe)2][OTf]/[BF4]. The com-
pounds SC(SCH3)H, trans-[Ru(H){PF(OCH3)2}(dppe)2][OTf]/
[BF4], and trans-[Ru(H){P(OCH3)3}(dppe)2][OTf]/[BF4] are present
in a relative ratio of 1.00:0.77:0.23. 1H NMR (CDCl3) spectro-
scopic data for trans-[Ru(H){PF(OCH3)2}(dppe)2][OTf]/[BF4]:[3d]
δ
= –8.22 (dsext, 1 H, JH,P = 136.0, JH,P = 20.0, JH,F = 20.0 Hz,
trans
Ru–H], 2.33 (m,
4
H, Ph2PCH2CH2cPis Ph2), 2.71 (m,
4 H,
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Ph2PCH2CH2PPh2), 2.87 [d, 6 H, PF(OCH3)2], 6.58–7.81 (m, 40
H, Ph2PCH2CH2PPh2) ppm. 31P{1H} NMR (CDCl3): δ = 63.1 [d,
Eur. J. Inorg. Chem. 2013, 1434–1443
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
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Published Online: February 1, 2013
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim