Half-sandwich benzylidene ruthenium complexes bearing phosphanyl-pyridine ligands: Reactivity towards nucleophiles and electrophiles

Article abstract of DOI:10.1002/ejic.200901162

The chelating hemilabile phosphanyl-pyridines PiPr₂XC ₅-H₄N (X = NH, the previously described, diisopropylphosphanyl-pyrid-2-ylamine, 1a; X = S, the novel diisopropyl- phosphanylmercaptopyridine, 1b) have been prepared to be used as ligands in the synthesis of the new half-sandwich chloro complexes [Ru(η⁵-C ₅Me₅)(κ²-P,N-PiPr₂XC ₅H₄N)Cl] (X = NH, 2a; S, 2b). These versatile starting compounds react with phenyldiazomethane to yield the novel carbene ruthenium complexes [Ru(η⁵-C₅Me₅) (κ²-P,N-PiPr₂XC₅H₄N)(=CHC ₆H₅)][BAr′₄] (Ar′ = 3,5-C ₆H₃(CF₃)₂; X. = NH, 3a; S 3b); 3a has been characterized, by X-ray crystallography. Compound 3a reacts as a Bransted base with an excess amount of triflic acid to give [Ru(η ⁵-C₅Me₅)(κ²-P,N-PiPr ₂NHC₅H₄N)-(η²-CH ₂C₆H₅)][CF₃SO₃] ₂ (4a), the first example of a structurally characterized. η²-benzylruthenium complex. The benzylidene complex 3a can also be deprotonated by bases, KOtBu or KN(SiMe₃)₂, thereby yielding neutral complex [Ru(η⁵C₅Me ₅)(κ²-P,N-PiPr₂NC₅H ₄N)(=CHC₆H₅)] (5a). The cationic complex [Ru(η⁵-C₅Me₅)(κ²-P,N- PiPr₂NHC₅H₄N)(PMe₃)]- [BAr′₄] (6a) has been prepared from 3a by straightforward and quick reaction with trimethylphospharie. Compound 3a also shows characteristic carbene reactivity against nucleophiles like NaBH₄/CH₃OH to afford alkyl compound [Ru(η⁵-C₅Me ₅)(κ²-P,N-PiPr₂NHC₅H ₄N)(η¹-CH₂C₆H₅)] (7a). The reaction of carbene complex 3b with LiCH₃ yields the neutral alkyl complex [Ru(η⁵-C₅Me₅) (κ²-P,N-PiPr₂SC₅H₄N) (η¹-CH₂-CH₂C₆H₅)] (8b), which contains a ss hydrogen atom.

Full text of DOI:10.1002/ejic.200901162

FULL PAPER
DOI: 10.1002/ejic.200901162
Half-Sandwich Benzylidene Ruthenium Complexes Bearing
Phosphanyl-Pyridine Ligands: Reactivity towards Nucleophiles and
Electrophiles
Ignacio Macías-Arce,[a] M. Carmen Puerta,*[a] and Pedro Valerga*[a]
Keywords: Carbenes / Ruthenium / Half-sandwich complexes / P,N ligands / β-Elimination
The chelating hemilabile phosphanyl-pyridines PiPr2XC5-
H4N (X = NH, the previously described diisopropylphos-
phanyl-pyrid-2-ylamine, 1a; X = S, the novel diisopropyl-
phosphanylmercaptopyridine, 1b) have been prepared to be
used as ligands in the synthesis of the new half-sandwich
chloro complexes [Ru(η5-C5Me5)(κ2-P,N-PiPr2XC5H4N)Cl] (X
= NH, 2a; S, 2b). These versatile starting compounds react
with phenyldiazomethane to yield the novel carbene ruthe-
ally characterized η2-benzylruthenium complex. The benzyl-
idene complex 3a can also be deprotonated by bases, KOtBu
or KN(SiMe3)2, thereby yielding neutral complex [Ru(η5-
C5Me5)(κ2-P,N-PiPr2NC5H4N)(=CHC6H5)] (5a). The cationic
complex
[Ru(η5-C5Me5)(κ2-P,N-PiPr2NHC5H4N)(PMe3)]-
[BArЈ4] (6a) has been prepared from 3a by straightforward
and quick reaction with trimethylphosphane. Compound 3a
also shows characteristic carbene reactivity against nucleo-
philes like NaBH4/CH3OH to afford alkyl compound [Ru(η5-
C5Me5)(κ2-P,N-PiPr2NHC5H4N)(η1-CH2C6H5)] (7a). The re-
nium
complexes
[Ru(η5-C5Me5)(κ2-P,N-PiPr2XC5H4N)-
(=CHC6H5)][BArЈ4] (ArЈ = 3,5-C6H3(CF3)2; X = NH, 3a; S 3b);
3a has been characterized by X-ray crystallography. Com- action of carbene complex 3b with LiCH3 yields the neutral
pound 3a reacts as a Brønsted base with an excess amount
of triflic acid to give [Ru(η5-C5Me5)(κ2-P,N-PiPr2NHC5H4N)-
(η2-CH2C6H5)][CF3SO3]2 (4a), the first example of a structur-
alkyl complex [Ru(η5-C5Me5)(κ2-P,N-PiPr2SC5H4N)(η1-CH2-
CH2C6H5)] (8b), which contains a β hydrogen atom.
with regards to its electrophilicity or nucleophilicity. There
is a broad range of reactivities in which Schrock and Fi-
scher types are only particular cases.[15]
Introduction
Transition-metal chemistry can be greatly expanded by
the use of polydentate ligands that contain significantly dif-
ferent chemical functionalities (hybrid ligands).[1] Among
these compounds, phosphanyl-pyridines[2,3] have emerged
as one powerful alternative to P,P or N,N ligands; 2-(di-
phenylphosphanyl)pyridine is the most studied member of
this family.[4] This ligand can be used to stabilize binuclear
complexes, especially heterobinuclear ones. However, the
short bite angle makes its mononuclear chemistry some-
what limited. To override this disadvantage, spacer groups
can be introduced between phosphanyl and pyridyl groups.
In our case, the selected spacer groups were amino[5–10] and
sulfur, with consequent changes in steric and electronic do-
nor properties of the ligands.
Ruthenium carbene complexes have been thoroughly
studied for their potential ability to catalyse olefin metathe-
sis, as shown by Grubbs carbene complexes.[15] In spite of
these works, there are few reported examples of half-sand-
wich ruthenium carbene complexes with non-Fischer-type
carbene ligands.[16] In this context, it seems reasonable that
the presence of functionalized phosphanylpyridine ligands
can stabilize carbene moieties and extend their reactivity.
In this work, new ruthenium chloro complexes that con-
tain phosphanyl-pyridine ligands are reported, and their
ability to form carbene complexes is studied. Additionally,
several derivatives produced by electrophilic or nucleophilic
attack on the carbene complex [Ru(η5-C5Me5)(κ2-P,N-
PiPr2NHC5H4N)(=CHC6H5)]+ are also studied.
Carbene complexes offer a wide variety of useful organic
transformations.[11–14] Usually their chemical behaviour is
summarized in Schrock and Fischer types, according to
metal class and nature of the substituents on the carbenic
atom. Often it is not possible to classify a carbene complex
Results and Discussion
Despite several existing reports[17–19] that describe the
synthesis of PiPr2NHC5H4N, (diisopropylphosphanyl)-
(pyrid-2-yl)amine (1a), we have used a previously unde-
scribed preparation that involves the well-known lithiation
of 2-aminopyridine and subsequent reaction with PiPr2Cl
to create the P–N bond.[20] An analogous procedure with
2-mercaptopyridine has been used in the synthesis of the
[a] Departamento de Ciencia de los Materiales e Ingeniería Met-
alúrgica y Química Inorgánica, Facultad de Ciencias, Uni-
versidad de Cádiz,
Campus del Río San Pedro, Puerto Real (Cádiz) 11510, Spain
Fax: +34-956-016-288
E-mail: carmen.puerta@uca.es
pedro.valerga@uca.es
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FULL PAPER
previously unreported PiPr2SC5H4N, 2-(diisopropylphos-
The NMR spectra are very similar to those of 2a, except
phanyl)mercaptopyridine (1b). This compound has been for the absence of an NH signal. Both 31P{1H} spectra dis-
obtained as a yellow viscous oil.
play notable downfield shifts, 124.4 (2a) and 129.9 ppm
The direct reaction of [{(η5-C5Me5)RuCl}4] with phos- (2b), in relation to the values found for 1a and 1b, as ex-
phanyl pyridines 1a and 1b gives neutral half-sandwich pected for metal-bonded P atoms. However, in terms of the
complexes [Ru(η5-C5Me5)(κ2-P,N-PiPr2NHC5H4N)Cl] (2a) differences among related complexes,[7,8] there are no sig-
and [Ru(η5-C5Me5)(κ2-P,N-PiPr2SC5H4N)Cl] (2b), which nificant changes in the chemical shifts of protons in the
have been isolated as orange and reddish-orange microcrys- pyridine ring.
talline solids, respectively. Compound 2a is almost insoluble
There are scarce examples of carbene complexes with for-
in nonpolar solvents and moderately soluble in polar sol- mula [Ru(C5R5)(=CRЈRЈЈ)(L)(LЈ)] (R = H, CH3; RЈ, RЈЈ
vents like dichloromethane or acetone. The most remark- = H, alkyl, aryl; L, LЈ = Cl, phosphanes, stibanes). The
able feature in its NMR spectra is the dependence of NH preparation of complex [Ru(η5-C5H5)(=CPh2)(PPh3)Cl] re-
resonance on solvent. Accordingly, in CD2Cl2 it appears at quires strong conditions (an excess of diazo compound and
5.7 ppm as a wide singlet, whereas in CD3COCD3 it shows relatively high temperatures).[24] Alternatively, a multistep
a doublet (JP,H = 5 Hz) at 7.5 ppm.
synthetic sequence that involves the formation of labile
In the same way, compound 2b is almost insoluble in compounds
[Ru(C5H5)Cl(C2H4)(PPh3)][25]
or [Ru-
nonpolar solvents, but it is a bit more soluble than 2a in (C5H5)(κ2-CH3CO2)(PPh3)][26] is feasible. Complexes [Ru-
polar solvents like dichloromethane or acetone. Suitable (C5H5)Cl(=CHPh)(PPh3)] and [Ru(C5Me5)Cl(=CHPh)-
single crystals of 2b for X-ray diffraction analysis were ob- (PPh3)] have been already prepared by using their respective
tained by slow diffusion of petroleum ether into a saturated labile ethylene complexes as precursors.[25] In the same way,
dichloromethane solution of the complex. An ORTEP view similar compounds that contain rhodium[27] or iridium[28]
of 2b is displayed in Figure 1.
have been synthesized. Nevertheless, the related osmium
compound [Os(C5H5)Cl(PiPr3)(=CHPh)] has been obtained
by direct reaction between [Os(C5H5)Cl(PiPr3)2] and phen-
yldiazomethane.[29]
In our case, the reaction between [Ru(C5Me5)Cl-
(PiPr2NHC5H4N)] and phenyldiazomethane has been car-
ried out in the presence of NaBArЈ4 [ArЈ = 3,5-bis(trifluoro-
methyl)phenyl] to avoid some disadvantages of this straight-
forward method, especially low yields and scant reprodu-
cibility. It is likely that the formation of a highly reactive
16e– intermediate promotes the immediate reaction with
phenyldiazomethane, thereby releasing N2(g). A change of
colour occurs in the solution from the initial orange to
greyish-blue. After workup, the benzylidene ruthenium
complex
[Ru(η5-C5Me5)(κ2-P,N-PiPr2NHC5H4N)(=CH-
C6H5)][BArЈ4] (3a) was obtained as a greenish-grey micro-
crystalline powder in 95% yield (Scheme 1).
Figure 1. Molecular structure of 2b. Thermal ellipsoids are drawn
at the 50% probability level. Atoms that correspond to disordered
groups in minor orientations and hydrogen atoms have been omit-
ted for clarity. Selected bond lengths [Å] and angles [°] with esti-
mated standard deviations in parentheses: Ru(1)–cyclopentadienyl-
(centroid) 1.818(5), Ru(1)–Cl(1) 2.444(1), Ru(1)–P(1) 2.269(2),
Ru(1)–N(1) 2.111(5), S(1)–P(1) 2.157(2), S(1)–C(11) 1.756(7);
Cl(1)–Ru(1)–P(1) 97.74(5), Cl(1)–Ru(1)–N(1) 85.44(15), P(1)–
Ru(1)–N(1) 82.08(14), P(1)–S(1)–C(11) 96.6(3).
It shows a “three-legged piano stool” geometry, analo-
gous to that found in related half-sandwich chlororuthe-
nium complexes that contain
P and N as donor
centres.[21–23] Ru–P and Ru–Cl bond lengths are comparable
to those found for [Ru(Ph-ind-ptpy)(PPh3)Cl] {Ph-ptpy-ind
= η5-κN-3-phenyl-1-[2-(2-pyridyl)-4-tolyl]indenyl}.[23] Re-
garding this complex, the most distinctive features are
Scheme 1. Preparation of benzylidene complexes.
Recrystallization in fluorobenzene/petroleum ether pro-
shorter Ru–ring centroid distance [1.818(5) vs. 1.849(3) Å], vides green crystals suitable for single-crystal X-ray diffrac-
Ru–N bond length [2.111(5) vs. 2.169(3) Å], and a smaller tion. The structure of the cation in 3a is shown in Figure 2.
P–Ru–N angle [82.08(14) vs. 95.88(7)°], due to a large ex-
tent to the bulkiness of the ligands in [Ru(Ph-ind- where the ruthenium atom is formally six-coordinated. The
ptpy)(PPh3)Cl] and the P–N connection in 2b. Ru=C bond-length value of 1.916(7) Å is similar to those
The molecule has a “three-legged piano stool” geometry,
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Hybrid Ligand Ruthenium Complexes
Cy
=
cyclohexyl],[15] [RuCl2(PCy3)(SIMes)(=CHPh)]
[1.836 Å; SIMes = 1,3-bis(mesityl)imidazolidin-2-ylidene][32]
and [RuCl2(PCy3)(IMes)(=CHPh)] [1.840 Å; IMes = 1,3-
bis(2,4,6-trimethylphenyl)imidazol-2-ylidene].[33]
The benzylidene compound 3b of formula [Ru(η5-
C5Me5)(κ2-P,N-PiPr2SC5H4N)(=CHC6H5)][BArЈ4]
has
been prepared in the same way. Both compounds present
similar spectroscopic data. The 31P{1H} NMR spectra of
compounds 3a and 3b in CD2Cl2 displayed one singlet at
room temperature that showed the lack of appreciable re-
strictions in rotation around the Ru=C bond under these
1
conditions. In the H NMR spectra, the most noteworthy
feature is the appearance of highly deshielded carbenic pro-
ton signals at 16.26 ppm for 3a and 17.14 ppm for 3b,
respectively. These chemical shifts are similar to those de-
scribed for related compounds, 17.25 ppm for [Ru(C5H5)-
Cl(PPh3)(=CHPh)] and 17.28 ppm for [Ru(C5Me5)Cl-
Figure 2. ORTEP view of cation complex [Ru(η5-C5Me5)(κ2-P,N-
PiPr2NHC5H4N)(=CHC6H5)]+ in 3a. Thermal ellipsoids are drawn
at the 50% probability level. Hydrogen atoms have been omitted
for clarity. Selected bond lengths [Å] and angles [°] with estimated (PPh3)(=CHPh)].[25] In the 13C{1H} NMR spectra, carbenic
standard deviations in parentheses: Ru(1)–cyclopentadienyl(cen-
troid) 1.933(6), Ru(1)–P(1) 2.294(2), Ru(1)–N(1) 2.124(5), Ru(1)–
C(11) 1.916(7), P(1)–N(2) 1.712(6), N(2)–C(18) 1.379(9); P(1)–
Ru(1)–N(1) 78.9(2), P(1)–Ru(1)–C(11) 91.8(2), N(1)–Ru(1)–N(1)
82.9(3), P(1)–N(2)–C(18) 117.7(5).
carbon signals appear as doublets at δ = 305.8 ppm for 3a
2
and 316.1 ppm for 3b, with coupling constants JP,C
=
16 Hz in both cases. These data are in agreement with those
reported for other related benzylidene complexes, δ =
327.5 ppm (2JP,C = 16 Hz) for [Ru(C5H5)Cl(PPh3)(=CHPh)]
and δ = 317.2 ppm (2JP,C = 13 Hz) for [Ru(C5Me5)Cl-
found in related complexes like [Ru(C5H5)Cl- (PPh3)(=CHPh)].[25]
(PPh3)(=CPh2)] (1.916 Å)[30] and [Ru(C5H5)(CO)(PPh3)-
Some acid–base reactions of complex 3a were studied.
(=CPh2)][PF6] [1.973(4) Å][25] or in other heteroatom-sub- The summary is shown in Scheme 2.
stituted alkylidene complexes like [Ru(C5H5)Cl(PPh3)-
Alkylidene complexes are susceptible to protonation pro-
(=C(COPh)Ph)] (1.933 Å)[25] and [CpRu(PMe3)(=CPhNH- cesses. In this way, the addition of an excess of trifluoro-
py)] (1.959 Å; Cp = cyclopentadienyl).[31] As expected, this methanesulfonic acid to complex 3a and further crystalli-
Ru=C value is longer than those found for pentacoordinate zation from acetone leads to an acetone adduct of
“Grubbs catalysts”: [RuCl2(PCy3)2(=CHPh)] [1.838(2) Å; compound
[Ru(η5-C5Me5)(κ2-P,N-PiPr2NHC5H4N)(η2-
Scheme 2. Chemical reactivity of 3a.
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I. Macías-Arce, M. C. Puerta, P. Valerga
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CH2C6H5)][CF3SO3]2 (4a) as red needle crystals. The struc-
The NMR spectroscopic data are in agreement with
ture of 4a·Me2CO has been elucidated by means of single- those reported for other transition-metal complexes that
crystal X-ray analysis. The structure of the cation in 4a is contain η2-benzyl ligands. Methylene protons are dia-
shown in Figure 3.
stereotopic and appear as two multiplets: one at δ =
2.71 ppm and the other as a double doublet at δ =
5.00 ppm. In particular, this last value shows a clear differ-
ence from an alkyl hydrogen and is closer to a olefin hydro-
gen. However, the methylene carbon appears at δ =
49.1 ppm, which is clearly out of range for alkyl carbon
atoms (20–30 ppm) or for free olefin carbon atoms (around
120 ppm). In the 1H NMR spectrum, the five phenyl hydro-
gen atoms are inequivalent, and the same occurs in the
13C{1H} NMR spectrum for the six carbon atoms. Equiva-
lence on the NMR spectroscopic scale can be introduced in
η2- and η3-benzyl complexes by fluxionality: in the case of
[Mo(C5H5)(NO)(η2-CH2Ph)Cl], a change in hapticity (η2–
η1–η2) and the rotation of the phenyl ring were invoked to
account for the observed equivalence at room tempera-
ture.[40] In [Ni(η3-CH2C6H5)Cl(PMe3)] and [Ni(η1-
CH2C6H5)Cl(PMe3)2], the equivalence was explained by
fast exchange of phosphane and fast suprafacial rearrange-
Figure 3. ORTEP view of cation complex [Ru(η5-C5Me5)(κ2-P,N-
PiPr2NHC5H4N)(η2-CH2C6H5)]2+ in 4a·Me2CO. Thermal ellip-
soids are drawn at the 50% probability level. Hydrogen atoms have
been omitted for clarity. Selected bond lengths [Å] and angles [°]
with estimated standard deviations in parentheses: Ru(1)–cyclopen-
tadienyl(centroid) 1.922(4), Ru(1)–P(1) 2.334(1), Ru(1)–N(2)
2.111(3), Ru(1)–C(11) 2.163(4), Ru(1)–C(12) 2.332(4), P(1)–N(1)
1.711(3), N(1)–C(18) 1.379(5), C(11)–C(12) 1.445(6); P(1)–Ru(1)–
N(2) 76.81(10), P(1)–Ru(1)–C(11) 84.76(12), P(1)–Ru(1)–C(12)
99.94(12), N(2)–Ru(1)–C(11) 128.33(15), N(2)–Ru(1)–C(12)
99.21(15), C(11)–Ru(1)–C(12) 37.26(16), Ru(1)–C(11)–C(12)
77.7(2), Ru(1)–C(12)–C(11) 1 65.0(2).
1
ment.[43] Unfortunately, although H and 13C{1H} NMR
spectroscopic benzylic chemical shifts disregard a η1-benzyl
ligand, our NMR spectroscopic data do not allow us to
discern between metal-bonded η2- and η3-benzyl in solu-
tion.
Several examples of reactions of phenylcarbene com-
plexes with Brønsted acids have been reported.[27,28,44] They
lead to η1-benzyl (alkyl) or η3-benzyl products depending
on the nature of the anion present in the acid. For instance,
The crystallographic study reveals a dicationic complex treatment of the osmium complex [Os(C5H5)Cl-
[Ru(η5-C5Me5)(κ2-P,N-PiPr2NHC5H4N)(η2-CH2C6H5)]2+ (PiPr3)(=CHPh)] with HBF4 affords η3-benzyl complex
,
which represents a protonated form of complex [Ru(η5- [Os(C5H5)Cl(PiPr3)(η3-C6H5CH2)][BF4].[29]
C5Me5)(κ2-P,N-PiPr2NHC5H4N)(=CHC6H5)]+ in 3a. Bond
Regarding the mechanism that operates in these transfor-
lengths and angles are in agreement with the η2 coordina- mations, Werner pointed out two routes. In the first one,
tion of the benzyl ligand. The angle Ru–Cbenzylic–Cipso of the nucleophilic carbenic atom can suffer a straightforward
77.7(2)° is much lower than the tetrahedral value expected addition of H+, followed by the coordination of benzyl li-
for a η1-alkyl coordination. Also, the η2 instead of η3 inter- gand. Alternatively, the second possibility consists of the
action is shown by the bond lengths [Ru–Cbenzylic
=
electrophilic attack on the rich metal centre and further
2.163(4) Å, Ru–Cipso = 2.332(4) Å] and much longer Ru– transfer to the α-carbon atom. In our case, transient hydride
Cortho distances: Ru(1)–C(17) 2.717(4) Å and Ru(1)–C(13) species were detected through in situ NMR spectroscopic
3.214(5) Å. These data are quite different from those re- experiments that gave support to the second possibility.
ported for [Ru(PMe3)3{η4-OC(O)C6H4CH2}] in which a η3- However, there were other unknown intermediates detected,
benzyl ligand shows a much shorter Ru–Cortho bond length, which suggests that the real operating mechanism can be
2.411(2) Å.[34] The bond length C(11)–C(12) [1.445(6) Å] is quite complex. We have been unable to find any evidence
shorter than a single C–C bond, likely due to some π delo- about NH participation, but this issue cannot be disre-
calization from the phenyl ring and to the fact that it is not garded.
very different from a metal-activated double bond. How-
The analogous reaction with carbene 3b gives unclear re-
ever, these data do not exactly match those of an activated sults. A reaction monitored by in situ NMR spectroscopy
π olefin, and some σ-alkyl interaction of the benzyl ligand showed some differences from the previously discussed re-
is indicated by the asymmetric η2 coordination that was action of carbene 3a. Several intermediates, metastable hy-
found. Other η2-benzyl complexes have been previously re- dride species in higher concentration than for 3a etc. were
ported, usually containing an early transition metal,[35–41] detected. They evolved to a complex mixture of products.
but, as far as we are aware, this is the first structurally char-
Deprotonation of carbene complexes has been observed
acterized example of a ruthenium complex that contains a in both nucleophilic and electrophilic compounds. The pres-
η2-benzyl ligand. In our case, in contrast to complexes ence of a chelating phosphanyl-pyridine ligand offers alter-
[(C5H5)2Zr(CH2-Ar)]+,[42] η2 coordination does not require native possibilities for the reaction with bases. Treatment of
the contribution of one solvent molecule as coligand.
a solution of 3a in THF with an excess of base, potassium
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Hybrid Ligand Ruthenium Complexes
tert-butoxide or potassium bis(trimethylsilyl)amide, pro- trum, which displays a strongly coupled double doublet
duced [Ru(η5-C5Me5)(PiPr2NC5H4N)(=CHC6H5)] (5a; (2JP,PЈ = 42 Hz). This unexpected outcome is due mainly to
Scheme 3). It has been obtained as a green-coloured pow- the severe steric congestion around the carbenic atom.
der that is quite soluble in nonpolar solvents like petroleum Steric congestion in 3a at Cα is also illustrated by the lack
ether and benzene. The most relevant feature in its NMR of reactivity towards Grignard reagent CH3MgCl. The sub-
spectra is the presence of characteristic carbenic low-field stitution of carbene by phosphane is favoured by the rela-
1
resonances for both H (16.22 ppm) and 13C (288.0 ppm). tive weakness of Ru=C in ambivalent carbenes. In accord
These data, together with the absence of a signal attribut- with theoretical studies, complexes with characteristics be-
able to the NH proton, suggest that deprotonation takes tween Schrock and Fischer types present weakened bonds
place on NH and thus the carbene moiety remains intact. by the energy used in matching the multiplicities of metallic
Moreover, the rest of the spectroscopic data shows no and carbene fragments.[47] The use of harder and unhin-
change of connectivity between atoms, thereby keeping the dered nucleophiles like hydride partially solved these incon-
chelating ligand in a κ2-P,N mode of coordination. How- veniences, but they could not completely eliminate unde-
ever, some noticeable changes in pyridyl-ring signals reveal sired reactions. When NaH is used as the hydride-transfer
an alteration in the electronic structure, especially the dis- agent, the deprotonated compound was the major product.
placement of the pyridyl carbon atom (2) signal to lower On the other hand, the reaction of 3a with weaker hydride-
field as expected (156.9 ppm) and the unusually high cou- tranference reagents like LiHBEt3 or NaBH4/CH3OH af-
pling constant of the pyridyl carbon atom (3) (3JP,C
23 Hz).
=
forded η1-benzyl complex [Ru(η5-C5Me5)(PiPr2NH-
C5H4N)(η1-CH2Ph)] (7a). Complex [Ru(η5-C5Me5)(PiPr2-
NHPy)H] was also detected, likely formed as a minor sub-
product by the nucleophilic substitution of the carbene li-
gand by hydride. This compound will be properly reported
in the near future.
Compound 7a was obtained as an oily orange solid, solu-
ble in petroleum ether and nonpolar solvents, unlike its par-
ent compound. Unambiguous characterization was pro-
vided by NMR spectra: 1H NMR spectroscopy showed two
resonances at δ = 2.46 and 3.10 ppm that corresponded to
nonchemically equivalent CH2 protons of the benzyl ligand.
Scheme 3. Proposed structure of 5a.
Deprotonation of carbene 3b cannot be carried out by The first of them appears as a virtual triplet (2JH,P = 9 Hz)
using THF as solvent because an immediate reaction with and the second one, better resolved, as a double doublet
this solvent occurs even at room temperature. Reactivity of (2JH,P = 9 Hz, JH,H = 2 Hz). The 13C{1H} NMR spectrum
THF towards metal complexes can proceed through radical displays the benzylic carbon as a doublet at δ = 12.1 ppm
1
1
C–H activation or double dehydrogenation of an α-methyl- (2JP,C = 11 Hz). H-1H gCOSY and H-13C gHSQC spec-
ene compound to form an oxacyclocarbene complex.[45] troscopy have properly correlated these signals.
Unfortunately, after some in situ NMR spectroscopic ex-
Our results are in good agreement with other examples
periments, we could not establish the nature of this process. of η1-benzyl ruthenium complexes.[48,49] In this context,
Attempts to deprotonate carbene 3b in diethyl ether were Bianchini and co-workers have isolated and characterized
unsuccessful. This compound proved to be unreactive mer-[(PNP)RuCl(CO)(η1-CH2Ph)] as an intermediate in C–
towards NaH. The use of potassium bis(trimethylsilyl)- C bond-cleavage reactions of terminal alkynes by water and
amide leads to the disappearance of carbene signals and the mediated by Ru compounds.[50] Whereas NMR spec-
formation of a mixture that contains several unidentified troscopy has not allowed us to distinguish between η2 and
compounds.
η3 coordination for 4a in solution, in the case of 7a, η1
Although nucleophilic addition on the carbenic atom is benzyl coordination has been unambiguously characterized
a well-known reaction of Fischer carbenes, in our case, re- by the chemical shift of the α-carbon atom being in the
activity studies of carbene complexes towards nucleophiles range of an alkyl, and the aromatic nuclei, which remain
present several difficulties on account of the existence of almost unaltered in relation to a nonbonded phenyl ring.
competitive reactions. Casey tested the electrophilic nature
An analogous reaction of hydrides with carbene 3b pro-
of the carbenic atom in [Re(C5H5)(CO)2- ceeded with the formation of a complex mixture of several
{=CHCH2CH2C(CH3)3}] by means of the reaction with compounds that contained the η1 benzyl complex [Ru(η5-
P(CH3)3 to afford the zwitterionic compound C5Me5)(PiPr2SC5H4N)(η1-CH2Ph)] (analogous to 7a), two
[Re(C5H5)(CO)2{=CH[P(CH3)3]CH2CH2C(CH3)3}].[46] In hydride complexes and other unidentified compounds. In
contrast to this rhenium carbene complex, 3a reacts with this case, the presumably greater stability of hydride inter-
P(CH3)3 to afford quantitatively and immediately a yellow mediates from 3b with respect to 3a results in no clear reac-
compound characterized as [Ru(η5-C5Me5){P(CH3)3}- tions.
(PiPr2NHC5H4N)][BArЈ4] (6a), the result of nucleophilic
Treatment of a solution of carbene complex 3b in ethyl
substitution of the benzylidene ligand at the metal centre ether with methyllithium gave a pink solution and micro-
1
by the phosphane, as indicated by the 31P{1H} NMR spec- crystalline solid. Extensive analysis, particularly by H and
Eur. J. Inorg. Chem. 2010, 1767–1776
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1771

I. Macías-Arce, M. C. Puerta, P. Valerga
FULL PAPER
13C{1H} NMR spectroscopy, gCOSY, DEPT, gHSQC and behaviour has been shown by reaction with H+ to yield a
gHMBC allows its unequivocal characterization as [Ru(η5- η2-benzyl ligand. There are some previously described ex-
C5Me5)(PiPr2SC5H4N)(–CH2CH2C6H5)] (8b). 1H NMR amples of this coordination mode for early transition-metal
spectroscopy shows two pairs of protons at 1.38/1.83 and benzylidene complexes, but it represents the first one in the
1.89/1.92 ppm and does not display any hydride or carbene case of ruthenium complexes. The electrophilic behaviour
signal. These protons correlated with corresponding doub- of [Ru(η5-C5Me5)(κ2-P,N-PiPr2XC5H4N)(=CHC6H5)]+ has
let carbon signals at δ = 15.0 and 40.9 ppm. Quite different been shown by reaction with H–, thereby giving rise to a
results have been previously reported for reactions of sim- η1-benzyl complex. Normally, NMR spectroscopic studies
ilar carbene complexes with methyllithium. Indeed, they af- allow for the unambiguous characterization of the η1 coor-
forded hydride–olefin complexes, this being the result ra- dination of a benzyl ligand. However, especially for late
tionalized by a β elimination on a 16-electron alkylmetal transition-metal complexes, the distinction between the usu-
intermediate. To explain our result in relation to earlier lit- ally disregarded η2, and the generally considered η3 mode
erature data, we postulate the mechanism shown in has been revealed to be difficult. We propose, from this
Scheme 4.
study, that the presence of a η2-benzyl ligand in metal com-
plexes should not be ruled out only based on their
NMR spectra. Reaction of [Ru(η5-C5Me5)(κ2-P,N-
PiPr2SC5H4N)(=CHC6H5)]+ with LiCH3 gives a 2-phenyl-
ethyl ruthenium complex stable towards β elimination,
which is likely formed through β elimination on an interme-
diate 1-phenylethyl complex followed by hydride migration
or, formally, alkene insertion.
Experimental Section
General Procedures: All synthetic operations were performed under
a dry dinitrogen or argon atmosphere by following conventional
Schlenk techniques. Tetrahydrofuran, diethyl ether and petroleum
ether (boiling range 40–60 °C) were obtained oxygen- and water-
free with an Innovative Technology Inc. solvent purification appa-
ratus. Dichloromethane, toluene, acetone and fluorobenzene were
of anhydrous quality and used as received. All solvents were deoxy-
genated immediately before use. Phenyldiazomethane (in
Scheme 4. Proposed mechanism for reaction of 3b with LiCH3.
[55]
toluene)[54] and NaBArЈ4
were prepared according to the re-
In the first step, a branched alkyl complex is formed by
direct nucleophilic attack on the carbenic atom, although
an attack on the metal centre, as previously suggested,[16]
cannot be disregarded. For the subsequent β elimination,
the creation of a vacant site, likely by decoordination of a
pyridyl group, is essential. In the η2-alkene-hydride interme-
diate, a hydride transfer results in a formal alkene insertion
to afford the final phenylethyl complex stable towards β eli-
mination. Some other 2-phenyl-ethyl ruthenium complexes
have already been reported, [TpRu(CO)(NCCH3)-
ported procedures.
IR spectra were recorded in Nujol mulls with a Perkin–Elmer
FTIR Spectrum 1000 spectrophotometer. NMR spectra were taken
with Varian Inova 400 MHz, Varian Inova 600 MHz or Varian
Gemini 300 MHz equipment. Chemical shifts are given in ppm
from SiMe4 (1H and 13C{1H}) or 85% H3PO4 (31P{1H}). H and
1
13C{1H} NMR spectroscopic signal assignments were confirmed
by 1H-gCOSY, 135-DEPT and gHSQC (1H-13C) experiments when
–
required. Chemical-shift NMR spectra obtained for BArЈ4 and
–
CF3SO3 are coincident with those found in their respective salts
and they will not be listed. Microanalyses were performed with a
LECO CHNS-932 elemental analyzer at the Servicio Central de
Ciencia y Tecnología, Universidad de Cádiz.
(CH2CH2Ph)],[51]
Ph)}2][52]
and
[{(C5Me5)Ru(µ2-SiPr-S,S)(CH2CH2-
[Br(CH2CH2Ph){(C5Me5)Ru(µ2-SiPr-
S,S)}2],[53] all of them obtained by reaction with the corre-
sponding halide or Grignard reagent containing
CH2CH2Ph.
Syntheses of PiPr2XC5H4N (X = NH, 1a; S, 1b): 2-Aminopyridine
(or 2-mercaptopyridine) was suspended in ethyl ether and cooled
to 0 °C. A stoichiometric amount of BuLi was added dropwise to
the suspension and it was stirred for 1 h at room temperature. The
solution was then cooled again to 0 °C and a stoichiometric
amount of PiPr2Cl was added dropwise. After addition, the solu-
tion was stirred at room temperature and filtered to eliminate LiCl.
The solvent was removed under vacuum. Compound 1a was iso-
lated as a white solid, whereas 1b was obtained as a yellow viscous
oil.
Conclusion
In summary, the syntheses of a new phosphanyl-pyridine
ligand, PiPr2SC5H4N, two half-sandwich chloro complexes
of ruthenium that contain PiPr2NHC5H4N or
PiPr2SC5H4N and their respective benzylidene complexes
are reported. The ambiphilic carbene character of [Ru(η5-
C5Me5)(κ2-P,N-PiPr2XC5H4N)(=CHC6H5)]+ versus nucleo-
Compound 1a: Yield 6.96 g (92%). 31P{1H} NMR (161.8 MHz,
CDCl3, 298 K): δ = 49.61 (s) ppm. 1H NMR (400 MHz, CDCl3,
298 K): δ = 1.01–1.08 (m, 12 H, CH3-iPr), 1.76 (m, 2 H, CH-iPr),
philes and electrophiles has been studied. Its nucleophilic 4.64 (d, JH,P = 11 Hz, NH), 6.62 (m, 1 H, 5), 7.06 (d, JH,H = 8 Hz,
1772 Eur. J. Inorg. Chem. 2010, 1767–1776
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Hybrid Ligand Ruthenium Complexes
1 H, 3), 7.42 (t, JH,H = 8 Hz, 1 H, 4), 8.01 (d, JH,H = 5 Hz, 1 H, under vacuum. The resulting residue was washed with petroleum
6) ppm. 13C{1H} NMR (75.45 MHz, CDCl3, 298 K): δ = 17.1 (d,
JP,C = 8 Hz, CH3-iPr), 18.6 (d, JP,C = 20 Hz, CH3-iPr), 26.3 (d, JP,C
= 11 Hz, CH-iPr), 108.6 (d, JP,C = 18 Hz, 3), 114.1 (s, 4), 137.5 (d,
JP,C = 2 Hz, 4), 147.8 (s, 6), 160.8 (d, JP,C = 19 Hz, 2) ppm. IR
ether (2ϫ10 mL), thereby affording a greenish-blue solid.
Compound 3a: Yield 0.67 g (95%). 31P{1H} NMR (161.8 MHz,
1
CD2Cl2, 298 K): δ = 137.3 (s) ppm. H NMR (400 MHz, CD2Cl2,
298 K): δ = 0.65, 0.97, 1.24 (m, 12 H, CH3-iPr), 1.70 [d, JP,H
1 Hz, 15 H, C5(CH3)5], 2.23 (m, 1 H, CH-iPr), 2.48 (m, 1 H, CH-
iPr), 5.67 (d, JP,H = 3 Hz, 1 H, NH), 6.64 (t, 1 H), 7.00 (d, JH,H
=
(Nujol): ν = 3201 [ν(N–H)], 1602 [ν(C=N)], 908 [ν(P–N)] cm–1.
˜
C11H19N2P (210.26): calcd. C 62.84, H 9.11, N 13.32; found C
62.88, H 9.15, N 13.27.
=
8 Hz, 1 H), 7.20–7.30, 7.49 (d, 2 H), 16.26 (s, 1 H, Ru=CH) ppm.
Compound 1b: Yield 1.36 g (75%). 31P{1H} NMR (161.8 MHz,
13C NMR (75.45 MHz, CD2Cl2, 298 K): δ = 10.8 [s, C5(CH3)5],
CDCl3, 298 K): δ = 58.7 (s) ppm. 1H NMR (400 MHz, CDCl3,
16.5 (d, JP,C = 8 Hz, CH3- iPr), 16.9 (m, CH3-iPr), 28.6 (d, JP,C
=
298 K): δ = 1.08–1.16 (m, 12 H, CH3-iPr), 2.03 (m, 2 H, CH-iPr), 19 Hz, CH-iPr), 30.7 (d, JP,C
=
34 Hz, CH-iPr), 101.7 [s,
6.94 (t, JH,H = 5 Hz, 1 H, 5), 7.42 (t, JH,H = 8 Hz, 1 H, 4), 7.55 (d,
JH,H = 8 Hz, 1 H, 3), 8.34 (d, JH,H = 5 Hz, 1 H, 6) ppm. 13C{1H}
NMR (100.5 MHz, CDCl3, 298 K): δ = 18.7 (d, JP,C = 8 Hz, CH3-
iPr), 19.4 (d, JP,C = 19 Hz, CH3-iPr), 25.4 (d, JP,C = 20 Hz, CH-
iPr), 119.9 (s, 5), 124.0 (d, JP,C = 12 Hz, 3), 136.2 (s, 4), 149.3 (s,
C5(CH3)5], 110.4 (d, JP,C = 6 Hz, 3), 117.4 (s, 5), 126.8–131.5, (s,
C6H5), 139.5 (s, 4), 155.6 (s, 6), 162.4 (s, 2), 305.8 (d, 2JP,C = 16 Hz,
Ru=C) ppm. C60H52BF24N2PRu (1399.90): calcd. C 51.48, H 3.74,
N 2.00; found C 51.75, H 3.80, N 1.96.
Synthesis of [Ru(η5-C5Me5)(PiPr2SC5H4N)(=CHC6H5)][BArЈ4]
(3b): Freshly prepared phenyldiazomethane (3 mmol in toluene)
was added to a solution of complex 2b in fluorobenzene (0.25 g,
0.5 mmol). A solution of NaBArЈ4 in fluorobenzene (0.5 mmol in
5 mL) was immediately added. The orange-red solution thus ob-
tained became dark green with abundant N2(g) evolution. It was
stirred for 5 min and filtered through anhydrous Na2SO4. After
filtration the solvent was removed under vacuum. The resulting
residue was washed with petroleum ether (4ϫ10 mL), thereby af-
fording a dark green solid.
6), 160.0 (d, JP,C = 14 Hz, 2) ppm. IR (Nujol): ν = 1572 [ν(C=N)]
˜
cm–1. C11H18NPS (227.30): calcd. C 58.13, H 7.98, N 6.16; found
C 58.17, H 8.01, N 6.10.
Syntheses of [Ru(η5-C5Me5)(PiPr2XC5H4N)Cl] (X = NH, 2a; S, 2b):
To prepare compound 2a, [(η5-C5Me5)RuCl]4 (1 g) and a stoichio-
metric amount of 1a were dissolved in petroleum ether (30 mL)
and stirred at room temperature for 45 min. The resulting orange
suspension was filtered and the recovered solid was washed with
cold petroleum ether (10 mL) and dried. An orange powder was
obtained. Compound 2b was prepared in the same way but by using
1b instead of 1a. It was isolated as a reddish-orange powder.
Compound 3b: Yield 0.60 g (84.6%) 31P{1H} NMR (161.8 MHz,
1
CD2Cl2, 298 K): δ = 131.3 (s) ppm. H NMR (400 MHz, CD2Cl2,
Compound 2a: Yield 1.60 g (90%). 31P{1H} NMR (161.8 MHz,
298 K): δ = 0.79–0.94, 1.26–1.39 (m, 12 H, CH3-iPr), 1.56 [d, JH,P
CD3COCD3, 298 K): δ = 124.4 (s) ppm. 1H NMR (400 MHz, = 1 Hz, 15 H, C5(CH3)5], 2.55 (m, 2 H, CH-iPr), 7.12 (t, JH,H
=
CD3COCD3, 298 K): δ = 1.24–1.33 (m, 12 H, CH3-iPr), 1.64 [d,
JP,H = 2 Hz, 15 H, C5(CH3)5], 2.49 (m, 1 H, CH-iPr), 2.95 (m, 1
H, CH-iPr), 6.48 (m, 1 H, 5), 6.82 (d, JH,H = 8 Hz, 1 H, 3), 7.23
(t, JH,H = 8 Hz, 1 H, 4), 7.52 (d, JH,H = 5 Hz, 1 H, NH), 8.37 (d,
7 Hz, 1 H), 7.58 (m), 7.73 (d, JH,H = 8 Hz), 7.40 (m), 7.50 (d, JH,H
= 8 Hz), 8.05 (m), 8.22 (d, JH,H = 6 Hz), 17.14 (s, Ru=CH) ppm.
13C{1H} NMR (100.5 MHz, CD2Cl2, 298 K):
10.3 [s,
δ
=
C5(CH3)5], 18.4, 18.5 (s, CH3-iPr), 19.0 (d, JP,C = 3 Hz, CH3-iPr),
JH,H = 6 Hz, 1 H, 6) ppm. 13C{1H} NMR (75.45 MHz, CD2Cl2, 19.9 (s, JP,C = 4 Hz, CH3-iPr), 29.7 (d, JP,C = 16 Hz, CH-iPr), 33.1
298 K): δ = 10.8 [s, C5(CH3)5], 17.9 (s, CH3-iPr), 18.1 (s, CH3-iPr), (d, JP,C = 16 Hz, CH-iPr), 100.9 [d, JP,C = 2 Hz, C5(CH3)5], 118.0
3
18.7 (s, CH3-iPr), 19.0 (d, JP,C = 7 Hz, CH3-iPr), 29.1 (d, JP,C
21 Hz, CH-iPr), 30.0 (d, JP,C = 21 Hz, CH-iPr), 83.6 [s, C5(CH3)5],
108.2 (s, 2), 114.6 (s, 5), 136.0 (s, 4), 153.9 (s, 6), 162.1 (d, JP,C
=
(d, JP,C = 4 Hz, 3), 123.9 (d, JP,C = 4 Hz), 126.5, 126.9, 128.6,
2
128.6, 129.0–129.9 (s, C6H5), 167.3 (d, JP,C = 6 Hz, 2), 316.1 (d,
=
2JP,C = 16 Hz, Ru=C) ppm. C60H51BF24NPRuS (1416.95): calcd. C
7 Hz, 2) ppm. IR (Nujol): ν = 3386 (wide) [ν(N–H)], 1604 [ν(C=N)] 50.85, H 3.63, N 0.99; found C 50.90, H 3.69, N 0.96.
˜
cm–1. C21H34ClN2PRu (482.01): calcd. C 52.35, H 7.10, N 5.83;
found C 52.9, H 7.05, N 5.71.
Synthesis of [Ru(η5-C5Me5)(PiPr2NHC5H4N)(η2-CH2C6H5)]-
[CF3SO3]2 (4a): A solution of compound 3a (0.7 g, 0.5 mmol) in
dichloromethane was treated with an excess amount of trifluoro-
methanesulfonic acid. Immediately the reaction mixture became
Compound 2b: Yield 1.51 g (82%). 31P{1H} NMR (161.8 MHz,
CDCl3, 298 K): δ = 129.9 (s) ppm. 1H NMR (400 MHz, CDCl3,
298 K): δ = 1.10–1.41 (m, 12 H, CH3-iPr), 1.48 [d, JP,H = 1.5 Hz, red and was stirred over 30 min at room temperature. The solution
15 H, C5(CH3)5], 2.62 (m, 1 H, CH-iPr), 2.66 (m, 1 H, CH-iPr), was then filtered through sodium sulfate and the solvent was re-
6.80 (t, JH,H = 6 Hz, 1 H, 5), 7.22 (t, JH,H = 8 Hz, 1 H, 4), 7.38 (d,
JH,H = 8 Hz, 1 H, 3), 8.83 (d, JH,H = 6 Hz, 1 H, 6) ppm. 13C{1H}
NMR (75.45 MHz, CDCl3, 298 K): δ = 9.9 [s, C5(CH3)5], 19.1 (d,
JP,C = 2 Hz, CH3-iPr), 19.4 (d, JP,C = 3 Hz, CH3-iPr), 19.7 (d, JP,C
moved under vacuum. Addition of acetone to the resulting oil
caused the precipitation of red crystals, which were washed with
petroleum ether and diethyl ether. The compound was obtained as
an acetone adduct.
= 2 Hz, CH3-iPr), 20.2 (d, JP,C = 2 Hz, CH3-iPr), 30.3 (d, JP,C
14 Hz, CH-iPr), 31.3 (d, JP,C = 5 Hz, CH-iPr), 84.3 [d, JP,C = 3 Hz,
C5(CH3)5], 119.7 (s, 5), 120.9 (d, JP,C = 3 Hz, 3), 133.6 (s, 4), 155.3
=
Compound 4a·CH3COCH3: Yield 0.45 g (66.7%). 31P{1H} NMR
(161.8 MHz, CD2Cl2, 298 K): δ = 122.7 (s) ppm. 1H NMR
(400 MHz, CD2Cl2, 298 K): δ = 0.75 (m, 3 H, CH3-iPr), 1.47–1.62
(m, 9 H, CH3-iPr), 1.85 [s, 15 H, C5(CH3)5], 2.11 (s, CH3COCH3),
(d, JP,C = 3 Hz, 6), 166.2 (d, JP,C = 9 Hz, 6) ppm. IR (Nujol): ν =
˜
1574 [ν(C=N)] cm–1. C21H33ClNPRuS (499.06): calcd. C 50.54, H
2.55 (m, 2 H, CH-iPr), 3.28 (m, 1 H, Ru-CH), 5.00 (dd, JH,H
=
6.66, N 2.81; found C 50.59, H 6.69, N 2.80.
Synthesis of [Ru(η5-C5Me5)(PiPr2NHC5H4N)(=CHC6H5)][BArЈ4] JH,H = 8 Hz, 1 H), 6.81 (d, JH,H = 8 Hz, 1 H), 7.21 (t, JH,H = 8 Hz,
11 Hz, JH,P = 4 Hz, Ru-CH), 6.07 (d, JH,H = 8 Hz, 1 H), 6.78 (t,
(3a): Freshly prepared phenyldiazomethane (3 mmol in toluene)
was added to a solution of NaBArЈ4 in fluorobenzene (0.5 mmol
in 5 mL). Complex 2a (0.5 mmol) was immediately added to the
resulting orange-red solution. The solution became deep blue-green
with abundant N2(g) evolution and was stirred for 5 min and fil-
tered through Na2SO4. After filtration, the solvent was removed
1 H), 7.31 (t, JH,H = 8 Hz, 1 H), 7.35 (d, JH,H = 8 Hz, 1 H), 7.52
(t, JH,H = 7 Hz, 1 H), 7.76 (t, JH,H = 7 Hz, 1 H), 7.86 (d, JH,H
=
8 Hz, 1 H), 8.80 (s, NH) ppm. 13C NMR (75.45 MHz, CD3COCD3,
298 K): δ = 10.5 [s, C5(CH3)5], 17.1 (d, JP,C = 2 Hz, CH3-iPr), 18.2
(d, JP,C = 4 Hz, CH3-iPr), 18.7 (d, JP,C = 4 Hz, CH3-iPr), 19.1 (d,
JP,C = 2 Hz, CH3-iPr) (methinic carbon atoms from isopropyl
Eur. J. Inorg. Chem. 2010, 1767–1776
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1773

I. Macías-Arce, M. C. Puerta, P. Valerga
FULL PAPER
groups overlap with those from acetone), 49.1 (d, JP,C = 4 Hz, Ru-
CH2), 103.4 [s, C5(CH3)5], 110.5 (s), 113.6 (d, JP,C = 7 Hz), 120.9
(s), 129.0 (s), 134.2 (s), 136.2 (s), 142.3 (s), 143.1 (s), 153.1 (s), 162.0
Compound 7a: Yield 0.081 g (20%). 31P{1H} NMR (161.8 MHz,
C6D6, 298 K): δ = 136.7 (s) ppm. 1H NMR (400 MHz, C6D6,
298 K): δ = 1.03 (m, 3 H, CH3-iPr), 1.13 (m, 3 H, CH3-iPr), 1.24
(m, 3 H, CH3-iPr), 1.38 (m, 3 H, CH3-iPr), 1.86 [d, J = 1 Hz, 15
2
(d, JP,C = 7 Hz, 2) ppm. IR (Nujol): ν = 3399 [ν(N–H)], 1613
˜
[ν(C=N)] cm–1. C33H47F6N2O7PRuS2 (893.90): calcd. C 44.34, H H, C5(CH3)5], 2.10 (m, 1 H, CH-iPr), 2.46 (vt, J = 9 Hz, 1 H, Ru-
5.30, N 3.13; found C 44.53, H 5.39, N 3.08.
CH), 2.82 (m, 1 H, CH-iPr), 3.10 (dd, JH,H = 9 Hz, JH,P = 2 Hz, 1
H, Ru-CH), 5.94 (d, J = 8 Hz, 3), 6.10 (m, 5), 7.0–7.5 (Ph), 7.77
(d, J = 6 Hz, 6), 7.84 (br. s, NH), 8.55 (t, unresolved, 4) ppm. 13C
NMR (75.45 MHz, C6D6, 298 K): δ = 11.3 [s, C5(CH3)5], 12.1 (d,
J = 11 Hz, Ru-CH2), 17.8 (d, JP,C = 3 Hz, CH3-iPr), 17.8 (d, JP,C
Synthesis of [Ru(η5-C5Me5)(PiPr2NC5H4N)(=CHC6H5)] (5a):
Complex 3a (0.7 g, 0.5 mmol) was dissolved in tetrahydrofuran
(8 mL). An excess amount of base, potassium tert-butoxide or po-
tassium bis(trimethylsilyl)amide (1 mmol), was added to this solu-
tion. The solution was then stirred at room temperature over 5 min.
The solvent was removed and the residue was extracted with petro-
leum ether (2ϫ10 mL). The resulting green solution was filtered
through sodium sulfate and cooled, thereby affording green micro-
crystals.
= 4 Hz, CH3-iPr), 18.5 (d, JP,C = 7 Hz, CH3-iPr), 19.1 (d, JP,C
9 Hz, CH3-iPr), 28.1 (d, JP,C = 24 Hz, CH-iPr), 32.0 (d, JP,C
15 Hz, CH-iPr), 86.6 [d, JP,C = 4 Hz, C5(CH3)5], 106.2 (d, JP,C
=
=
=
6 Hz, 3), 114.2 (s, 5), 126.1–131.1 (Ph), 137.8 (s, 4), 154.5 (d, JP,C
= 2 Hz, 6), 161.0 (d, JP,C = 13 Hz, 2) ppm. C28H41N2PRu (539.66):
calcd. C 62.53, H 7.70, N 5.21; found C 62.65, H 7.29, N 5.10.
Compound 5a: Yield 0.11 g (41.1%). 31P{1H} NMR (161.8 MHz,
C6D6, 298 K): δ = 132.5 (s) ppm. 1H NMR (400 MHz, C6D6,
298 K): δ = 0.76 (m, 3 H, CH3-iPr), 0.88 (m, 3 H, CH3-iPr), 1.04
(m, 3 H, CH3-iPr), 1.26 (m, 3 H, CH3-iPr), 1.45 [d, JH,P = 1 Hz,
15 H, C5(CH3)5], 1.81 (m, 1 H, CH-iPr), 2.42 (m, 1 H, CH-iPr),
5.70 (m, 1 H, 4), 6.88 (m, 1 H, 4), 7.01 (m, 3 H, Ph + 6), 7.12 (m,
2 H, Ph + 3), 7.45 (m, 2 H, Ph), 16.27 (br. s, 1 H, Ru=CH) ppm.
13C NMR (100.6 MHz, C6D6, 298 K): δ = 10.6 [s, C5(CH3)5], 16.8
(d, JP,C = 6 Hz, CH3-iPr), 17.2 (s, CH3-iPr), 17.4 (d, JP,C = 3 Hz,
CH3-iPr), 19.3 (d, JP,C = 1 Hz, CH3-iPr), 29.0 (d, JP,C = 30 Hz, CH-
iPr), 31.4 (d, JP,C = 43 Hz, CH-iPr), 99.4 [d, JP,C = 1 Hz, C5(CH3)5],
106.7 (s, 5), 114.1 (d, JP,C = 23 Hz, 3), 126.7–128.9 (Ph), 135.3 (d,
JP,C = 3 Hz, 4), 152.4 (d, JP,C = 3 Hz, 6), 156.9 (s, ipso-Ph), 175.6
(s, 2), 288.0 (d, JP,C = 10 Hz, Cα) ppm. C28H39N2P1Ru (535.67):
calcd. C 62.78, H 7.34, N 5.23; found C 62.85, H 7.66, N 5.02.
Synthesis of [Ru(η5-C5Me5)(PiPr2NHC5H4N)(PMe3)][BArЈ4] (6a):
Compound 3a (0.7 g, 0.5 mmol) was dissolved in dichloromethane
(8 mL). An excess amount of PMe3 was added. Immediately the
bluish reaction mixture became orange. The solution was stirred
over 20 min at room temperature and the solvent was removed. The
remaining solid residue was washed with petroleum ether
(3ϫ10 mL) and dried under vacuum to afford a pale yellow micro-
crystalline solid.
Synthesis of [Ru(η5-C5Me5)(PiPr2SC5H4N)(–CH2CH2C6H5)] (8b):
A green solution of carbene complex 3b (0.25 g, 0.17 mmol) was
treated with methyllithium (0.2 mL, 0.3 mmol, 1.6  in diethyl
ether). The reaction mixture became red. After 10 min of reaction
at room temperature, the solvent was removed until dryness and the
resultant oil was extracted in petroleum ether and filtered through
anhydrous sodium sulfate. Then, the pink solution was concen-
trated to 5 mL and cooled to –20 °C, thereby affording after several
days tiny pink microcrystals. They were separated by decantation.
Compound 8b: Yield 0.035 g (35%). 31P{1H} NMR (161.8 MHz,
C6D6, 298 K): δ = 151.0 (s) ppm. 1H NMR (600 MHz, C6D6,
298 K): δ = 1.06–1.16 (m, 12 H, CH3-iPr), 1.38 (m, 1 H, Ru-CH2),
1.69 [d, J = 1 Hz, 15 H, C5(CH3)5], 1.73 (m, 1 H, Ru-CH2), 1.89
(m, 1 H, Ru-CH2-CH2), 2.14 (m, 1 H, CH-iPr), 2.52–2.60 (m, 2 H,
CH-iPr, Ru-CH2-CH2), 6.06 (t, JH,H = 7 Hz, 1 H, 5), 6.43 (t, JH,H
= 8 Hz, 1 H, 4), 7.03 (t, JH,H = 7 Hz, 1 H, p-Ph), 7.12 (d, JH,H
8 Hz, 1 H, 3), 7.20 (t, JH,H = 7 Hz, 2 H, m-Ph), 7.24 (d, JH,H
=
=
8 Hz, 2 H, o-Ph), 8.35 (d, JH,H = 7 Hz, 1 H, 6) ppm. 13C NMR
(100.5 MHz, C6D6, 298 K): δ = 10.7 [s, C5(CH3)5], 15.0 (d, JP,C
13 Hz, Ru-CH2), 17.5 (d, JP,C = 4 Hz, CH3-iPr), 19.3 (d, JP,C
3 Hz, CH3-iPr), 19.5 (vt, JP,C = 3 Hz, CH3-iPr), 30.3 (d, JP,C
=
=
=
18 Hz, CH-iPr), 31.8 (d, JP,C = 9 Hz, CH-iPr), 40.9 (d, JP,C = 3 Hz,
Ru-CH2-CH2), 88.8 [d, JP,C = 4 Hz, C5(CH3)5], 118.8 (s, 3), 121.1
(d, JP,C = 4 Hz, 3), 124.3 (s, p-Ph), 128.1 (s, o-Ph), 128.2 (s, m-Ph),
129.4 (s, 4), 150.6 (d, JP,C = 1 Hz, i-Ph), 154.7 (d, JP,C = 4 Hz, 6),
Compound 6a: Yield 0.61 g (88%). 31P{1H} NMR (161.8 MHz,
CD2Cl2, 298 K): δ = 130.4 (d, JP,P = 42 Hz, PiPr2NHC5H4N), 4.6
(d, JP,P = 42 Hz, PMe3) ppm. 1H NMR (400 MHz, CD2Cl2,
298 K): δ = 0.93 (m, 3 H, CH3-iPr), 1.07 [d, JH,P = 8 Hz,
P(CH3)3], 1.27–1.53 (m, 9 H, CH3-iPr), 1.69 [t, JH,P = 1.5 Hz, 15
H, C5(CH3)5], 2.23 (m, 1 H, CH-iPr), 2.44 (m, 1 H, CH-iPr), 6.54
(dt, JH,H = 6.5 H, 1 Hz, 4), 7.19–7.53 (m) ppm. 13C NMR
2
165.0 (d, JP,C = 9 Hz, 2) ppm. C29H42NPRuS (568.76): calcd. C
61.24, H 7.44, N 2.46; found C 61.25, H 7.46, N 2.45.
Crystal Structure Analysis: Suitable single crystals of 2b, 3a and 4a
were obtained. Each crystal was mounted on a glass fibre and then
transferred to the cold nitrogen gas stream of a Bruker Smart
APEX CCD three-circle diffractometer (T = 100 K) with a sealed-
tube source and graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å) at the Servicio Central de Ciencia y Tecnología de la
Universidad de Cádiz. Crystal data and experimental details are
given in Table 1. In each case, four sets of frames were recorded
over a hemisphere of the reciprocal space by omega scan with δ(ω)
0.30° and exposure of 10 s per frame. Correction for absorption
1
(100.6 MHz, CD2Cl2, 298 K): δ = 7.5 [d, JP,C = 56 Hz, P(CH3)3],
9.9 [s, C5(CH3)5], 15.4 (d, JP,C = 8 Hz, CH3-iPr), 16.4 (d, JP,C
=
8 Hz, CH3-iPr), 17.6 (s, CH3-iPr), 18.0 (d, JP,C = 8 Hz, CH3-iPr),
29.6 (d, JP,C = 19 Hz, CH-iPr), 30.5 (d, JP,C = 50 Hz, CH-iPr), 90.4
[s, C5(CH3)5], 109.4 (d, JP,C = 6 Hz, 3), 115.1 (s, 5), 136.4 (s, 4),
2
151.6 (s, 6), 162.1 (d, JP,C = 11 Hz, 2) ppm. IR (Nujol): ν = 3402
˜
[ν(N–H)], 1606 [ν(C=N)] cm–1. C56H55BF24N2P2Ru (1385.86):
calcd. C 48.53, H 4.01, N 2.02; found C 49.02, H 4.11, N 1.96.
Synthesis of [Ru(η5-C5Me5)(PiPr2NHC5H4N)(η1-CH2C6H5)] (7a): was applied by scans of equivalents using the SADABS program.[56]
Complex 3a (1.05 g, 0.75 mmol) and NaBH4 (1.5 mmol) were dis-
An insignificant crystal decay correction was also applied. The
solved in tetrahydrofuran (8 mL) and methanol (2 mL) was added.
structures were solved by direct (2b, 4a·Me2CO) or Patterson (3a)
The reaction mixture became orange-red during treatment with methods, completed by subsequent difference Fourier syntheses
bubbling H2. It was then stirred over 20 min at room temperature
and the solvent was removed. The remaining residue was extracted
with petroleum ether (4ϫ20 mL). The resulting solution was fil-
tered through sodium sulfate. After filtration, petroleum ether was
removed to afford an orange oil.
and refined on F2 by full-matrix least-squares procedures using the
programs contained in the SHELXTL package.[57] Some disorder
was found in 2b for the pyridyl ring and one isopropyl group. The
disorder was modelled by splitting several atoms in two positions.
Most non-hydrogen atoms were refined with anisotropic displace-
1774
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 1767–1776

Hybrid Ligand Ruthenium Complexes
Table 1. Crystal data and experimental details.
2b
3a
4a·Me2CO
Formula
Formula weight
C21H33ClNPRuS
499.03
C60H52BF24N2PRu
1399.89
C33H47F6N2O7PRuS2
893.89
Crystal system
Space group
a [Å]
monoclinic
P21/c (no.14)
17.229(3)
monoclinic
P21/c (no.14)
13.210(3)
triclinic
P1 (no.2)
11.196(2)
¯
b [Å]
c [Å]
8.979(2)
15.953(3)
27.972(6)
16.697(3)
12.754(3)
14.847(3)
α [°]
β [°]
90.00
111.68(3)
90.00
105.41(3)
67.11(3)
84.96(3)
γ [°]
90.00
2293.(8)
90.00
5948(2)
81.58(3)
1931.0(7)
V [Å3]
Z
4
4
2
Dcalcd. [gcm–3]
µ (Mo-Kα) [mm–1]
F(000)
1.445
0.967
1032
1.563
0.407
2824
1.537
0.632
920
Crystal size [mm]
T [K]
0.27ϫ0.09ϫ0.09
100(2)
0.71073
1.000, 0.718
1.3, 25.0
–20:20; –10:10; –18:18
15356, 4025, 0.0544
3704
0.37ϫ0.17ϫ0.05
100(2)
0.71073
1.000, 0.869
1.8, 23.8
–13:14; –31:31; –18:18
36735, 9049, 0.065
8243
0.26ϫ0.09ϫ0.08
100(2)
0.71073
1.000, 0749
1.8, 25.0
–13:13; –15:14; –15:17
10195, 6700, 0.039
5970
λ [Å] (Mo-Kα)
Absorption correction (Tmax, Tmin
θmin – θmax [°]
Dataset (h,k,l limits)
Total, unique data, R(int)
Observed data [I Ͼ 2σ(I)]
)
Number of reflections, parameters
R, wR2 [I Ͼ 2σ(I)]
R, wR2 (all)
w
4025, 239
0.0567, 0.1073
0.0641, 0.1108
1/[σ2(Fo2) + (0.160P)2 +
12.2948P][a]
1.084
9049, 811
0.0785, 0.1789
0.0900, 0.1877
1/[σ2(Fo2) + (0.0839P)2 +
66.0316P][a]
0.943
6700, 480
0.0542, 0.1033
0.0633, 0.1080
1/[σ2(Fo2) + (0.0309P)2 +
4.2884P][a]
1.047
GOF
Max., average shift/error
0.001, 0.000
–0.812, 1.003
0.001, 0.000
–1.240, 0.707
0.001, 0.000
–0.569, 0.940
Min., max. residual density [eÅ–3]
2
2
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Acknowledgments
This work was supported by Ministerio de Ciencia y Tecnología
(MCYT), Dirección General de Investigación Ciencia y Técnica
(DGICYT), project CTQ2007 60137/BQU) and Junta de Andal-
ucía (PAIDI FQM188, PAI05_FQM_00094, P08-FQM-03538).
I.M. is grateful for a research fellowship from Junta de Andalucía
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Received: December 1, 2009
Published Online: February 11, 2010
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Eur. J. Inorg. Chem. 2010, 1767–1776