Reactivity of the Dimer [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (C10H16 = 2,7-Dimethylocta-2,6-diene-1,8-diyl) toward Guanidines: Access to Ruthenium(IV) and Ruthenium(II) Guanidinate Complexes

DOI: 10.1021/acs.organomet.5b00070

Source and publish data:

Organometallics p. 2796 - 2809 (2015)

Update date:2022-08-16

Topics:

Authors:

Menéndez-Rodríguez, Lucía

Tomás-Mendivil, Eder

Francos, Javier

Crochet, Pascale

Cadierno, Victorio

Anti?olo, Antonio

Fernández-Galán, Rafael

Carrillo-Hermosilla, Fernando

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Article abstract of DOI:10.1021/acs.organomet.5b00070

The novel bis(allyl)ruthenium(IV) guanidinate complexes [RuCl{κ²(N,N′)-C(NR)(NⁱPr)-NHⁱPr}(η³:η³-C₁₀H₁₆)] (C₁₀H₁₆ = 2,7-dimethylocta-2,6-diene-1,8-diyl; R = Ph (3a), 4-C₆H₄F (3b), 4-C₆H₄Cl (3c), 4-C₆H₄Me (3d), 3-C₆H₄Me (3e) 4-C₆H₄^tBu (3f)) have been synthesized by treatment of the dimeric precursor [{RuCl(μ-Cl)(η³:η³-C₁₀H₁₆)}₂] (1) with 4 equiv of the corresponding guanidine (ⁱPrHN)₂C=NR (2a-f). The easily separable guanidinium chloride salts [(ⁱPrHN)₂C(NHR)][Cl] (4a-f) are also formed in these reactions. Attempts to generate analogous Ru(IV) guanidinate complexes from (ⁱPrHN)₂C=NR (R = 2-C₆H₄Me (2g), 2,4,6-C₆H₂Me₃ (2h), 2,6-C₆H₃ⁱPr₂ (2i)) failed, due probably to the steric hindrance associated with the aryl group in these guanidines. On the other hand, the reaction of the dimer [{RuCl(μ-Cl)(η³:η³-C₁₀H₁₆)}₂] (1) with (ⁱPrHN)₂C=N-4-C₆H₄C≡N (2j) led to the selective formation of the mononuclear derivative [RuCl₂(η³:η³-C₁₀H₁₆){N≡C-4-C₆H₄-N=C(NHⁱPr₂)₂}] (5), in which the guanidine coordinates to ruthenium through the pendant nitrile unit. This result contrasts with that obtained by employing the related Ru(II) dimer [{RuCl(μ-Cl)(η⁶-p-cymene)}₂] (6), whose reaction with 2j afforded the expected guanidinate complex [RuCl{κ²(N,N′)-C(N-4-C₆H₄C≡N)(NⁱPr)-NHⁱPr}(η⁶-p-cymene)] (7). Treatment of 7 with dimer 1 yielded the dinuclear Ru(II)/Ru(IV) derivative 8, via cleavage of the chloride bridges of 1 by the C≡N group of 7. Reductive elimination of the 2,7-dimethylocta-2,6-diene-1,8-diyl chain in [RuCl{κ²(N,N′)-C(NR)(NⁱPr)-NHⁱPr}(η³:η³-C₁₀H₁₆)] (3a-f) readily took place in the presence of an excess of 2,6-dimethylphenyl isocyanide, thus allowing the high-yield preparation of the octahedral ruthenium(II) compounds mer-[RuCl{κ²(N,N′)-C(NR)(NⁱPr)-NHⁱPr}(CN-2,6-C₆H₃Me₂)₃] (9a-f). The structures of [RuCl{κ²(N,N′)-C(N-4-C₆H₄Me)(NⁱPr)-NHⁱPr}(η³:η³-C₁₀H₁₆)] (3d), [RuCl{κ²(N,N′)-C(N-4-C₆H₄C≡N)(NⁱPr)-NHⁱPr}(η⁶-p-cymene)] (7), and mer-[RuCl{κ²(N,N′)-C(N-4-C₆H₄^tBu)(NⁱPr)-NHⁱPr}(CN-2,6-C₆H₃Me₂)₃] (9f), as well as those of the guanidinium chloride salts 4a-c, were unequivocally confirmed by X-ray diffraction methods. In addition, the catalytic behavior of the guanidinate complexes 3a-f and 9a-f in the redox isomerization of allylic alcohols was also explored.

Full text of DOI:10.1021/acs.organomet.5b00070

Article

pubs.acs.org/Organometallics

Reactivity of the Dimer [{RuCl(μ-Cl)(η :η ‑C H )} ] (C H = 2,7-

10 16 2

10 16

Dimethylocta-2,6-diene-1,8-diyl) toward Guanidines: Access to

Ruthenium(IV) and Ruthenium(II) Guanidinate Complexes

†

‡

†

Lucıa

Menendez-Rodrıguez, Eder Tomas-Mendivil, Javier Francos, Pascale Crochet,

†

,§

Victorio Cadierno,* Antonio Antin

́ ́

olo,* Rafael Fernandez-Galan, and Fernando Carrillo-Hermosilla

†

Laboratorio de Compuestos Organometal

ORFEO-CINQA), Departamento de Quım

ica, Universidad de Oviedo, Julian

Department of Pure and Applied Chemistry, WestCHEM, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, U.K.

icos y Catal

isis (Unidad Asociada al CSIC), Centro de Innovacion

ica e Inorganica, Instituto Universitario de Quımica Organometal

Claverıa 8, E-33006 Oviedo, Spain

en Quım

ica Avanzada

(

ica Organ

ica “Enrique

Moles”, Facultad de Quım

‡

Centro de Innovacion

en Quım

ica Avanzada (ORFEO-CINQA), Departamento de Quım

s Quımicas-Campus de Ciudad Real, Universidad de Castilla-La Mancha, Campus Universitario,

́ ́

ica Inorganica, Organica y Bioquımica,

́ ́

Facultad de Ciencias y Tecnologıa

E-13071 Ciudad Real, Spain

S Supporting Information

ABSTRACT: The novel bis(allyl)ruthenium(IV) guanidinate

complexes [RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(η :η -

C H )] (C H = 2,7-dimethylocta-2,6-diene-1,8-diyl; R =

10 16

Ph (3a), 4-C H F (3b), 4-C H Cl (3c), 4-C H Me (3d), 3-

C H Me (3e) 4-C H Bu (3f)) have been synthesized by

treatment of the dimeric precursor [{RuCl(μ-Cl)(η :η -

C H )} ] (1) with 4 equiv of the corresponding guanidine

(

PrHN) CNR (2a−f). The easily separable guanidinium

chloride salts [( PrHN) C(NHR)][Cl] (4a−f) are also formed

in these reactions. Attempts to generate analogous Ru(IV)

guanidinate complexes from (PrHN) CNR (R = 2-C H Me

(

2g), 2,4,6-C H Me (2h), 2,6-C H Pr (2i)) failed, due

6 2 3 6 3 2

probably to the steric hindrance associated with the aryl group in these guanidines. On the other hand, the reaction of the dimer

[

{RuCl(μ-Cl)(η :η -C H )} ] (1) with (PrHN) CN-4-C H CN (2j) led to the selective formation of the mononuclear

derivative [RuCl (η :η -C H ){NC-4-C H -NC(NH Pr ) }] (5), in which the guanidine coordinates to ruthenium

2 10 16 6 4 2 2

through the pendant nitrile unit. This result contrasts with that obtained by employing the related Ru(II) dimer [{RuCl(μ-

Cl)(η -p-cymene)} ] (6), whose reaction with 2j aﬀorded the expected guanidinate complex [RuCl{κ (N,N′)-C(N-4-C H C

N)(N Pr)-NH Pr}(η -p-cymene)] (7). Treatment of 7 with dimer 1 yielded the dinuclear Ru(II)/Ru(IV) derivative 8, via

cleavage of the chloride bridges of 1 by the CN group of 7. Reductive elimination of the 2,7-dimethylocta-2,6-diene-1,8-diyl

chain in [RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(η :η -C H )] (3a−f) readily took place in the presence of an excess of 2,6-

dimethylphenyl isocyanide, thus allowing the high-yield preparation of the octahedral ruthenium(II) compounds mer-

[

(

{

RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(CN-2,6-C H Me ) ] (9a−f). The structures of [RuCl{κ (N,N′)-C(N-4-C H Me)-

2 3

i i 3 3 2 i i 6

N Pr)-NH Pr}(η :η -C H )] (3d), [RuCl{κ (N,N′)-C(N-4-C H CN)(N Pr)-NH Pr}(η -p-cymene)] (7), and mer-[RuCl-

κ (N,N′)-C(N-4-C H Bu)(N Pr)-NH Pr}(CN-2,6-C H Me ) ] (9f), as well as those of the guanidinium chloride salts 4a−c,

2 3

were unequivocally conﬁrmed by X-ray diﬀraction methods. In addition, the catalytic behavior of the guanidinate complexes 3a−f

and 9a−f in the redox isomerization of allylic alcohols was also explored.

INTRODUCTION

A large number of metal guanidinate complexes of types B

and C from across the periodic table have been described to

date, and their utility in homogeneous catalysis and materials

■

Guanidinate monoanions have emerged in recent years as

versatile and highly modular N,N′-donor ligands, mainly

because of their easy access and the wide range of derivatives

science has been demonstrated. In this context, we have

recently reported the preparation of a series of half-sandwich

available through substitution at the terminal nitrogen atoms.

(

η -arene)ruthenium(II) derivatives with symmetrically and

Although some examples of monodentate metal complexes A

are known, the coordination chemistry of these heteroallyl

ligands is largely dominated by the chelating and bridging

asymmetrically substituted guanidinate ligands (D in Figure 2),

Received: January 25, 2015

binding modes B and C, respectively (Figure 1).

XXXX American Chemical Society

DOI: 10.1021/acs.organomet.5b00070

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Figure 1. Guanidinate ligands and their coordination modes.

Figure 2. Structures of the mononuclear ruthenium complexes with monoanionic guanidinate ligands described in the literature.

Figure 3. Structure of the ruthenium(IV) dimer 1 and the guanidinate complexes described in this work.

which proved to be catalytically active in the base-free redox

isomerization of allylic alcohols. Compounds D represent rare

was not explored, a fact that contrasts with the chemistry of

related mononuclear ruthenium amidinate systems, which have

examples of mononuclear ruthenium guanidinate complexes

found several applications in homogeneous catalysis.

since, in addition to the closely related species E and F, only

Another signiﬁcant diﬀerence between the ruthenium

−

the octahedral ruthenium(II) (G and H ) and ruthenium(III)

chemistry of amidinates [(RN) CR] and guanidinates

−

(

I ) derivatives have been quoted so far in the literature. A

[(RN) CNR ] is that, to date, ruthenium(IV) representatives

are only known for the former. This fact, along with the

continuous interest of our respective groups in the chemistry of

the bis(allyl)ruthenium(IV) dimer [{RuCl(μ-Cl)(η :η -

C H )} ] (C H = 2,7-dimethylocta-2,6-diene-1,8-diyl; 1

in Figure 3) and that of metal guanidinate complexes,

mononuclear ruthenium(II) complex with a coordinated

guanidinate dianion, namely [Ru{κ (N,N′)-C(NAc) NAc}-

(

η -p-cymene)(PPh )], was also described by Henderson and

co-workers. The rest of the ruthenium guanidinate compounds

currently known are paddlewheel-type dinuclear species

containing Ru₂(n = 5, 6) cores, in which the nitrogenated

monoanions adopt a bridging coordination (C in Figure 1). It

10 16

prompted us to explore the reactivity of [{RuCl(μ-Cl)(η :η -

C H )} ] (1) toward guanidines. As a result of this study, we

is worth noting that the catalytic potential of complexes E−I

report herein the preparation of the ﬁrst examples of

DOI: 10.1021/acs.organomet.5b00070

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Scheme 1. Synthesis of the Bis(allyl)ruthenium(IV) Guanidinate Complexes [RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(η :η -

C H )] (3a−f)

ruthenium(IV) guanidinate complexes, namely [RuCl-

excess guanidine present in the medium) and chelation of the

resulting guanidinate anion.

{

κ (N,N′)-C(NR)(N Pr)-NH Pr}(η :η -C H )] (3a−f), as

well as a new family of octahedral ruthenium(II) derivatives

Both the ruthenium complexes 3a−f and the guanidinium

with the formula mer-[RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}-

salts 4a−f were isolated as air-stable solids and characterized by

(CN-2,6-C H Me ) ] (9a−f) (see Figure 3). The latter were

elemental analysis and IR and NMR ( H and C{ H})

spectroscopy (details are given in the Experimental Section),

the data obtained being fully consistent with the proposed

formulations. In particular, for complexes 3a−f, the IR spectra

showed a characteristic ν(N−H) absorption band in the 3320−

2 3

easily generated from 3a−f through the reductive elimination of

the 2,7-dimethylocta-2,6-diene-1,8-diyl chain, a process that

takes place cleanly in the presence of an excess of 2,6-

dimethylphenyl isocyanide. The catalytic behavior of complexes

341 cm⁻region. For their part, the H NMR spectra of 3a−f

a−f and 9a−f in the redox isomerization of allylic alcohols is

also brieﬂy discussed.

displayed a four-line pattern for the terminal allylic protons

H , H , H , and H ) and two separated signals for the methyl

(

RESULTS AND DISCUSSION

substituents of the 2,7-dimethylocta-2,6-diene-1,8-diyl unit,

indicative of inequivalent axial sites on the trigonal-bipyramidal

■

Following a synthetic procedure similar to that used in the

preparation of compounds D and E (Figure 2), the novel

ruthenium atom. The C{ H} NMR spectra of these

complexes also showed clearly that the halves of the bis(allyl)

C H ligand are in inequivalent environments, since 10

ruthenium(IV) guanidinate complexes [RuCl{κ (N,N′)-C-

(

NR)(N Pr)-NH Pr}(η :η -C H )] (3a−f) could be synthe-

diﬀerent signals were observed in all cases (see the

Experimental Section). The expected resonances for the

guanidinate ligands were also observed in the NMR spectra,

sized in high yield (70−84%) by the bridge-splitting reaction of

the violet dimer [{RuCl(μ-Cl)(η :η -C H )} ] (1) with 4

equiv of the corresponding guanidine ( PrHN) CNR (R =

the most signiﬁcant features being (i) ( H NMR) a doublet

Ph (2a), 4-C H F (2b), 4-C H Cl (2c), 4-C H Me (2d), 3-

signal ( J = 9.9−10.8 Hz) at δ 3.12−3.37 ppm, attributed to

C H Me (2e) 4-C H Bu (2f)) (Scheme 1). These guanidines

the NH proton, and (ii) ( C{ H} NMR) a downﬁeld singlet

for the central CN carbon at ca. δ 161 ppm. The spectra also

were obtained in high yields by a straightforward process of

direct addition of anilines to diisopropylcarbodiimide, catalyzed

showed the chemical inequivalence of all the methyl and

methynic units of the isopropyl substituents.

by ZnEt₂.

The reactions proceeded cleanly at room

temperature in THF to give red solutions containing the

In order to conﬁrm unequivocally the structure of complexes

3a−f, a single-crystal X-ray diﬀraction study on [RuCl-

desired complexes 3a−f, along with the respective guanidinium

chloride salts [( PrHN) C(NHR)][Cl] (4a−f). The diﬀerent

solubility proﬁles of 3a−f and 4a−f in pentane allowed their

easy separation at the end of the reactions (details are given in

the Experimental Section). Although no intermediates could be

detected, it is assumed that these reactions proceed through the

initial cleavage of the chloride bridges of 1 and coordination of

the guanidine to ruthenium through the more basic iminic

nitrogen, followed by release of HCl (which is trapped by the

{κ (N,N′)-C(N-4-C

Me)(N Pr)-NH Pr}(η :η -C10

16)]

(3d) was undertaken. Diﬀraction-quality crystals were obtained

by cooling at −10 °C a saturated solution of the complex in a

hexane/CH Cl mixture. The crystal structure determination

2 2

revealed the existence of two independent molecules in the

asymmetric unit (see Figure S1 in the Supporting Information).

However, these molecules are structurally almost identical, and

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for clarity only one will be discussed here. An ORTEP view,

along with selected bonding parameters, is shown in Figure 4.

Å, respectively) fall within the upper limit found in the crystal

structures of other mononuclear ruthenium guanidinate

complexes previously described in the literature (2.076−2.149

−6

Å).

Furthermore, as observed in other structures containing

the “Ru(η :η -C H )” unit, the 2,7-dimethylocta-2,6-diene-

,8-diyl chain shows a local C symmetry with no signiﬁcant

variation in the Ru−C distances (in the range 2.191(3)−

.226(3) Å). A striking feature of the structure is the small

N(1)−Ru−N(3) bond angle of 61.97(9)°, which deviates

signiﬁcantly from the ideal 90°. This value reﬂects a high strain

in the four-membered metallacycle as a consequence of the

small “bite” of the guanidinate ligand. The sum of angles

around the central carbon atom of the CN skeleton (359°)

indicates the planarity of the guanidinate anion, for which a

signiﬁcant contribution of the resonance form K (see Figure 5)

to its bonding is observed. This bonding description, which is

supported by the shorter C(1)−N(1) bond length (1.302(4)

Å) in comparison with the C(1)−N(2) and C(1)−N(3)

lengths (1.352(4) and 1.376(4) Å, respectively), contrasts with

that previously found in the related ruthenium(II) complex

[

RuCl{κ (N,N′)-C(N-4-C H Bu)(N Pr)-NH Pr}(η -p-cym-

ene)] (D in Figure 2) previously described by us, where the

delocalized form J dominated over the alternative resonance

Figure 4. ORTEP type view of the structure of the ruthenium(IV)

complex 3d with the crystallographic labeling scheme. Hydrogen

atoms, except that on N(2), have been omitted for clarity. Thermal

ellipsoids are drawn at the 30% probability level. Selected bond

distances (Å) and angles (deg): Ru−C* = 1.9664(2); Ru−C** =

forms K−M.

On the other hand, we note at this point that, although the

coordination of the guanidinate anions derived from 2a−f to

the [RuCl(η :η -C H )] fragment could also lead to the

10 16

formation of isomeric species of type N and O (Figure 6),

.9369(2); Ru−Cl(1) = 2.4534(8); Ru−N(1) = 2.146(2); Ru−N(3) =

.141(2); Ru−C(15) = 2.219(3); Ru−C(16) = 2.226(3); Ru−C(17)

2.222(3); Ru−C(20) = 2.191(3); Ru−C(21) = 2.196(3); Ru−

C(22) = 2.195(3); C(1)−N(1) = 1.302(4); C(1)−N(2) = 1.352(4);

C(1)−N(3) = 1.376(4); C(15)−C(16) = 1.409(4); C(16)−C(17) =

.417(4); C(20)−C(21) = 1.418(4); C(21)−C(22) = 1.410(4); C*−

Ru−Cl(1) = 90.76(2); C*−Ru−N(1) = 115.92(7); C*−Ru−N(3) =

7.34(6); C*−Ru−C** = 127.261(12); C**−Ru−Cl(1) =

7.543(19); C**−Ru−N(1) = 115.57(7); C**−Ru−N(3) =

6.68(7); Cl(1)−Ru−N(1) = 92.70(7); Cl(1)−Ru−N(3) =

54.46(7); N(1)−Ru−N(3) = 61.97(9); Ru−N(1)−C(1) =

4.45(18); Ru−N(3)−C(1) = 92.50(18); N(1)−C(1)−N(3) =

10.0(3); N(1)−C(1)−N(2) = 127.8(3); N(2)−C(1)−N(3) =

21.2(3); C(15)−C(16)−C(17) = 114.6(3); C(20)−C(21)−C(22)

113.0(3). C* and C** denote the centroids of the allyl units (C(15),

C(16), C(17), and C(20), C(21), C(22), respectively).

Figure 6. Structures of isomeric ruthenium(IV) complexes N and O

and the guanidines 2g−i.

The geometry about the ruthenium atom is best described as

a distorted trigonal bipyramid by considering the allyl groups as

monodentate ligands bound to the metal through their

respective centers of mass (C* and C**). The guanidinate

ligand is coordinated edge-on to the ruthenium atom through

complexes 3a−f were the only ruthenium-containing products

observed by NMR in the crude reaction mixtures. The higher

one of the N Pr units, which resides in an equatorial position

steric repulsion between the bulkier N Pr unit located in an

along with the allyl groups, and the N(p-tolyl) unit which is

trans to the chloride ligand in an axial position. The Ru−N(1)

and Ru−N(3) bond lengths observed (2.146(2) and 2.141(2)

axial position and the octadienediyl chain in isomers N and O

could explain the selective formation of complexes 3a−f. In

complete accord with this, dimer 1 was found to be completely

Figure 5. Resonance forms of the coordinated guanidinate ligands.

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Figure 7. ORTEP type views of the structures of the guanidinium chloride salts 4a (left), 4b (middle), and 4c (right) with the crystallographic

labeling schemes. Thermal ellipsoids are drawn at the 30% probability level. Selected bond distances (Å) and angles (deg) for 4a: C(1)−N(1) =

.322(2); C(1)−N(2) = 1.337(2); C(1)−N(3) = 1.353(2); N(1)−C(1)−N(2) = 118.9(2); N(1)−C(1)−N(3) = 122.7(2); N(2)−C(1)−N(3) =

18.4(2); C(1)−N(1)−C(2) = 126.5(1); C(1)−N(2)−C(5) = 124.7(2); C(1)−N(3)−C(8) = 125.9(2). Selected bond distances (Å) and angles

(

deg) for 4b: C(1)−N(1) = 1.328(2); C(1)−N(2) = 1.333(2); C(1)−N(3) = 1.357(2); N(1)−C(1)−N(2) = 121.7(2); N(1)−C(1)−N(3) =

19.8(2); N(2)−C(1)−N(3) = 118.6(1); C(1)−N(1)−C(2) = 124.5(2); C(1)−N(2)−C(5) = 126.5(2); C(1)−N(3)−C(8) = 124.8(1). Selected

bond distances (Å) and angles (deg) for 4c: C(1)−N(1) = 1.338(2); C(1)−N(2) = 1.323(2); C(1)−N(3) = 1.353(2); N(1)−C(1)−N(2) =

20.7(2); N(1)−C(1)−N(3) = 120.2(2); N(2)−C(1)−N(3) = 119.1(2); C(1)−N(1)−C(2) = 124.7(2); C(1)−N(2)−C(5) = 126.3(2); C(1)−

N(3)−C(8) = 124.5(2).

Scheme 2. Reactivity of the Ruthenium(IV) Dimer [{RuCl(μ-Cl)(η :η -C H )} ] (1) toward Guanidine 2j

unreactive toward the ⁱPr-trisubstituted guanidine

were obtained in all cases by slow diﬀusion of pentane into a

saturated solution of the salt in THF. ORTEP plots of the

structures are shown in Figure 7; selected bonding parameters

(

PrHN) CN Pr. In this same line, the steric hindrance

associated with the substitution in an ortho position of the aryl

substituents in guanidines 2g−i (see Figure 6) may also be

behind the lack of reactivity found for the Ru(IV) dimer 1 with

these guanidines. Attempts to synthesize the corresponding

complexes [RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(η :η -

C H )] by reacting dimer 1 with a 2-fold excess of the

are given in the caption. As observed in the structures of

other guanidium salts previously described in the literature,

the central CN fragment of the cations is perfectly planar (sum

of NCN angles 360°) with very similar C−N distances

(1.322(2)−1.357(2) Å). These values are intermediate between

those of pure carbon−nitrogen single (1.41 Å) and double

lithium salts generated by deprotonation of 2g−i with Li Bu

also failed. A complex mixture of products was formed in this

case.

bonds (1.27 Å), suggesting a large electronic delocalization

within the π system of the CN core. Also of note is that, in the

Concerning the characterization of the novel guanidinium

three structures, the chloride anions establish a series of strong,

charge-assisted, hydrogen-bonding interactions with the NH

groups of the guanidinium cations, which dominate the

extended structures (details are given in the Supporting

Information).

chloride salts 4a−e, their most relevant spectroscopic features

are (i) (IR) the presence of two characteristic strong N−H

−

absorption bands at 3159−3250 cm , (ii) ( H NMR) two

broad singlets at δ 7.49−7.67 (2H) and 9.71−10.04 (1H)

ppm, which were assigned to the N−H protons of the PrNH

and ArNH groups, respectively, and (iii) ( C{ H} NMR) a

singlet resonance at ca. 154.5 ppm corresponding to the carbon

atom of the central CN₃core. Moreover, the molecular

structures of compounds 4a−c were determined by X-ray

diﬀraction methods. Single crystals suitable for X-ray analysis

On the other hand, an interesting result was obtained when

the dimer [{RuCl(μ-Cl)(η :η -C H )} ] (1) was reacted with

10 16 2

the 4-cyanobenzene-substituted guanidine ( PrHN) CN-4-

C H CN (2j). Instead of the expected guanidinate complex,

the reaction led to the selective formation of the mononuclear

derivative [RuCl (η :η -C H ){NC-4-C H -NC-

10 16

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Scheme 3. Reactivity of the Ruthenium(II) Dimer [{RuCl(μ-Cl)(η -p-cymene)} ] (6) toward Guanidine 2j

(

NH Pr ) }] (5), in which the guanidine 2j coordinates to

imine unit being preferred in the case of the harder

ruthenium through the pendant nitrile unit (Scheme 2). The

reaction, which proceeded rapidly in THF at room temperature

with only 2 equiv of 2j, aﬀorded 5 in an excellent 91% isolated

yield. Coordination of the guanidine through the CN unit

was supported by a downﬁeld shift of the nitrile carbon

resonance (δ 127.5 ppm) in comparison with that shown by

the free guanidine 2j (δ 120.2 ppm). The rest of the chemical

shifts of the protons and carbons of the coordinated guanidine

in complex 5 were almost identical with those found in the

NMR spectra of the free ligand 2j. Furthermore, the proposed

axial coordination of the guanidine to the ruthenium center was

bis(allyl)Ru fragment.

The novel compounds 7 and 4j were characterized by

elemental analysis and IR and NMR ( H and C{ H})

spectroscopy, all data being fully consistent with the proposed

formulations (details are given in the Experimental Section). In

addition, the structure of complex 7 was unequivocally

conﬁrmed by means of an X-ray diﬀraction analysis. As in the

case of 3d, X-ray-quality crystals were obtained by cooling at

−

10 °C a saturated solution of the complex in a hexane/

CH Cl mixture. An ORTEP view of the molecule is shown in

Figure 8; selected bonding parameters are given in the caption.

As is usual for this compound class, a pseudooctahedral

three-legged piano-stool geometry around the metal center is

observed. Similarly to the case of the Ru(IV) complex 3d, the

sum of angles around the central carbon atom C(1) of the

guanidinate ligand (359.9°) indicates again the strict planarity

fully supported by the appearance in the H NMR spectrum of

four terminal allyl and two methyl resonances for the 2,7-

dimethylocta-2,6-diene-1,8-diyl chain, evidencing inequivalent

environments for the halves of the bis(allyl) ligand (see the

Experimental Section). This is also clearly reﬂected in the

of the CN unit. In addition, a detailed inspection of the C−N

C{ H} NMR spectrum of 5, which showed 10 separate signals

bond lengths also suggests for 7 an important contribution of

the resonance form K (see Figure 5) to the bonding. Thus, the

C(1)−N(1) distance of 1.313(6) Å was found to be

signiﬁcantly shorter than the C(1)−N(2) and C(1)−N(3)

distances (1.365(6) and 1.366(6) Å, respectively). The

presence of the electron-withdrawing 4-cyanophenyl substitu-

ent on N(3), capable of stabilizing a negative charge on this

nitrogen atom, appears to be responsible for these structural

for the C H unit.

Remarkably, the behavior of the Ru(IV) dimer [{RuCl(μ-

Cl)(η :η -C H )} ] (1) toward guanidine 2j diﬀered

signiﬁcantly from that shown by the related (arene)ruthenium-

II) dimer [{RuCl(μ-Cl)(η -p-cymene)} ] (6). Thus, as

previously described with other guanidines, the reaction of

with an excess of 2j resulted in the high-yield formation of the

(

expected guanidinate complex [RuCl{κ (N,N′)-C(N-4-

features since, in the analogous complex [RuCl{κ (N,N′)-C(N-

C H CN)(N Pr)-NH Pr}(η -p-cymene)] (7), along with

4-C H Bu)(N Pr)-NH Pr}(η -p-cymene)] (D in Figure 2)

6 4

the corresponding guanidinium chloride salt 4j (Scheme 3).

previously described by us, the bonding of the guanidinate

ligand to ruthenium was best described through the delocalized

resonance form J (see Figure 5).

Analysis of the crude reaction mixture by H NMR spectros-

copy did not show the presence of any byproduct resulting

from the coordination of the CN group of 2j to the

Interestingly, the coordinative properties of the pendant

cyano group remained intact in the ruthenium(II) complex 7,

since its treatment with 1/2 equiv of the dimer [{RuCl(μ-

[

RuCl (η -p-cymene)] fragment. It seems therefore that the

coordination of this guanidine is governed by the electronic

properties of the metal center, coordination of the nitrile vs

Cl)(η :η -C H )} ] (1) resulted in the high-yield formation

DOI: 10.1021/acs.organomet.5b00070

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(

[

4j), and a new complex that could correspond to

RuCl (η :η -C H ){NC-4-C H -NHC(NH Pr ) }]-

10 16

2 2

[Cl], was also formed when a THF solution of dimer 6 was

treated with 4 equiv of 5. However, all attempts to isolate 8 in

pure form from this mixture failed.

In another vein, one of the most interesting aspects in the

chemistry of (2,7-dimethylocta-2,6-diene-1,8-diyl)ruthenium-

(

IV) complexes deals with its use as precursors of ruthenium-

II) species, via reductive elimination of the bis(allyl) chain.

In this context, we have found that treatment of the complexes

[

RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(η :η -C H )] (3a−f)

with an excess of 2,6-dimethylphenyl isocyanide, in toluene at

room temperature, results in the clean formation of the novel

octahedral ruthenium(II) guanidinate derivatives mer-[RuCl-

{

(

κ (N,N′)-C(NR)(N Pr)-NH Pr}(CN-2,6-C H Me ) ] (9a−f)

2 3

Scheme 5), which were isolated as air-stable yellow solids in

Figure 8. ORTEP type view of the structure of the ruthenium(II)

complex 7 with the crystallographic labeling scheme. Hydrogen atoms,

except that on N(2), have been omitted for clarity. Thermal ellipsoids

are drawn at the 30% probability level. Selected bond distances (Å)

and angles (deg): Ru−C* = 1.6566(4); Ru−Cl(1) = 2.424(2); Ru−

N(1) = 2.114(4); Ru−N(3) = 2.100(4); C(1)−N(1) = 1.313(6);

C(1)−N(2) = 1.365(6); C(1)−N(3) = 1.366(6); C(14)−N(4) =

5−87% yield. The reactions were completely stereoselective,

no isomeric species being detected by NMR in the crude

reaction mixtures.

The identity and stereochemistry of these compounds were

unambiguously established by a single-crystal X-ray diﬀraction

study on 9f. An ORTEP type drawing of the molecular

structure, along with selected bonding parameters, is depicted

in Figure 9. The ruthenium atom is in a distorted-octahedral

environment, being bonded to three 2,6-dimethylphenyl

isocyanide molecules disposed in a mer fashion, two nitrogen

atoms of the guanidinate monoanion, and one chloride ligand

.136(6); C*−Ru−Cl(1) = 128.0(1); C*−Ru−N(1) = 135.8(1);

C*−Ru−N(3) = 135.9(1); Cl(1)−Ru−N(1) = 85.8(1); Cl(1)−Ru−

N(3) = 85.7(1); N(1)−Ru−N(3) = 62.2(1); Ru−N(1)−C(1) =

4.9(3); Ru−N(3)−C(1) = 93.9(3); N(1)−C(1)−N(2) = 127.9(4);

N(1)−C(1)−N(3) = 108.5(4); N(2)−C(1)−N(3) = 123.5(4);

C(11)−C(14)−N(4) = 179.6(6). C* denotes the centroid of the p-

cymene ring (C(15), C(16), C(17), C(18), C(19), and C(20)).

disposed trans with respect to the N Pr unit. As expected, all the

isocyanide ligands are bound to ruthenium in a nearly linear

fashion (Ru−C−N angles within the range 173.4(4)−

176.9(4)°) with metal−carbon bond distances of 1.891(4)−

1.993(4) Å. These bonding parameters ﬁt well with those

reported in the literature for other ruthenium(II) 2,6-

of the dinuclear Ru(II)/Ru(IV) derivative 8 (Scheme 4).

Although all attempts to crystallize this compound failed, the

elemental analysis and IR and NMR data obtained were in full

accord with the proposed formulation (see the Experimental

Section). In particular, the coordination of the nitrile unit to the

dimethylphenyl isocyanide complexes. As observed for 3d,

the small “bite” of the planar guanidinate ligand (sum of angles

around C(1) of 359.9°) results in a relatively small value for the

N(1)−Ru−N(3) angle (61.51°). However, in contrast to the

case of 3d and 7, the C(1)−N(1) and C(1)−N(3) bond

distances (1.323(5) and 1.343(5) Å) were now both shorter

than the C(1)−N(2) distance (1.363(5) Å), suggesting in this

case a major contribution of the delocalized resonance form J

(see Figure 5) to the bonding. Signiﬁcant diﬀerences between

the Ru−N(1) and Ru−N(3) bond lengths were also observed

(2.080(3) and 2.168(3) Å, respectively), probably as a result of

the diﬀerent trans inﬂuences of the chloride and isocyanide

ligands.

[

(

RuCl (η :η -C H )] fragment was supported by (i)

2 10 16

C{ H} NMR) the appearance of a singlet resonance at δ_C

27.5 ppm for the CN carbon in the spectrum, a chemical

shift identical with that found for complex 5 and slightly

deshielded in comparison to that of 7 (δ 120.4 ppm), and (ii)

−1

(

IR) a change in the CN absorption band (2239 cm ) with

−1

respect to that of 7 (2213 cm ). We stress the point that, to

our knowledge, no previous examples of the use of guanidine 2j

to generate bimetallic complexes have been published in the

literature. The bimetallic compound 8, along with [{RuCl(μ-

Cl)(η :η -C H )} ] (1), [( PrHN) C(NH-4-C H CN)][Cl]

Scheme 4. Synthesis of the Dinuclear Ru(II)/Ru(IV) Complex 8

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Scheme 5. Reactivity of the Ruthenium(IV) Guanidinate Complexes 3a−f toward 2,6-Dimethylphenyl Isocyanide

As noted in the Introduction, the (arene)ruthenium(II)

guanidinate complexes D (see Figure 2) had shown a

remarkable activity in the redox isomerization of allylic alcohols

TOF up to 1000 h⁻in THF at 80 °C). It is worth noting

(

that, in contrast to the vast majority of ruthenium catalysts

known for this catalytic transformation, these species were

able to operate under base-free conditions. This fact

prompted us to explore the catalytic potential of the novel

guanidinate complexes [RuCl{κ (N,N′)-C(NR)(N Pr)-

NH Pr}(η :η -C H )] (3a−f) and mer-[RuCl{κ (N,N′)-C-

NR)(N Pr)-NH Pr}(CN-2,6-C H Me ) ] (9a−f) using 1-

(

2 3

octen-3-ol as model substrate. For comparative purposes, the

catalytic reactions were performed in THF at 80 °C without the

addition of an external base. Thus, using a metal loading of 0.5

mol %, we found that the Ru(IV) complexes 3a−f were all able

to provide quantitatively the desired octan-3-one in a short

amount of time (see Table 1).

Figure 9. ORTEP type view of the structure of the ruthenium(II)

complex 9f with the crystallographic labeling scheme. Hydrogen

atoms, except that on N(2), have been omitted for clarity. Thermal

ellipsoids are drawn at the 30% probability level. Selected bond

distances (Å) and angles (deg): Ru−Cl(1) = 2.439(1); Ru−N(1) =

Table 1. Catalytic Isomerization of 1-Octen-3-ol into Octan-

-one using the Ru(IV) Complexes [RuCl{κ (N,N′)-

i i 3 3

C(NR)(N Pr)-NH Pr}(η :η -C H )] (3a−f) as Catalysts

.080(3); Ru−N(3) = 2.168(3); Ru−C(18) = 1.993(4); Ru−C(27) =

.891(4); Ru−C(36) = 1.982(4); C(1)−N(1) = 1.323(5); C(1)−

N(2) = 1.363(5); C(1)−N(3) = 1.343(5); C(18)−N(4) = 1.158(5);

C(27)−N(5) = 1.164(6); C(36)−N(6) = 1.147(5); Cl(1)−Ru−N(1)

TOF (h⁻¹

)

entry

catalyst

time

yield (%)

163.8(1); Cl(1)−Ru−N(3) = 102.34(9); Cl(1)−Ru−C(18) =

35 min

50 min

1.5 h

>99

343

240

5.9(1); Cl(1)−Ru−C(27) = 92.1(1); Cl(1)−Ru−C(36) = 91.9(1);

N(1)−Ru−N(3) = 61.5(1); N(3)−Ru−C(27) = 165.5(2); C(18)−

Ru−C(36) = 177.1(2); Ru−N(1)-C(1) = 96.9(2); Ru−N(3)−C(1) =

133

10 min

15 min

10 min

1200

800

2.3(3); N(1)−C(1)−N(3) = 109.2(3); N(1)−C(1)−N(2) =

25.4(4); N(2)−C(1)−N(3) = 125.3(4); Ru−C(18)−N(4) =

73.4(4); Ru−C(27)−N(5) = 176.7(4); Ru−C(36)−N(6) =

76.9(4); C(18)−N(4)−C(19) = 172.3(5); C(27)−N(5)−C(28) =

63.8(5); C(36)−N(6)−C(37) = 174.0(4).

1200

Reactions were performed at 80 °C, under an argon atmosphere,

using 1 mmol of 1-octen-3-ol (0.2 M solutions in THF). Yields

determined by GC. Turnover frequencies (((mol of product)/(mol

of Ru))/time) were calculated at the time indicated in each case.

The NMR data obtained for 9a−f were in fully accord with

the stereochemistry found in the solid-state structure of 9f

(

details are given in the Experimental Section), the most

The best results in terms of activity were obtained with

complexes 3d−f, featuring an N-aryl unit substituted with an

electron-releasing group, which were able to complete the

reaction in only 10−15 min (entries 4−6). In general, the

noticeable spectroscopic features being those associated with

the guanidinate CN and isocyanide carbons, which resonate at

ca. 159 ppm, and in the range 164.8−171.5 ppm (two singlet

signals with intensity ratio 2:1), respectively. The IR spectra

also showed the expected ν(CN) absorptions for the

isocyanide ligands (three independent bands in the ranges

−1

turnover frequencies (TOF) reached with 3e,f (800−1200 h )

compare favorably with those previously obtained for the same

reaction catalyzed by the (arene)ruthenium(II) guanidinate

−1

−1 28

041−2068, 2104−2108, and 2156−2166 cm ).

complexes D (TOF = 400−1000 h ). On the other hand,

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the higher reactivity of 3d−f vs 3a−c (entries 4−6 vs 1−3) can

be rationalized in terms of the easier dissociation of the chloride

ligand in the former. Such a dissociation process, which would

generate the required vacant position for substrate binding, is

expected to be favored with the greater electron density on the

metal center.

Finally, concerning the octahedral Ru(II) derivatives mer-

Reactions of the Dimer [{RuCl(μ-Cl)(η :η -C10

16)}

] (1) with

[

(

RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(CN-2,6-C H Me ) ]

2 3

Guanidines ( PrHN) CNR (R = Ph (2a), 4-C H F (2b), 4-C H Cl

(2c), 4-C H Me (2d), 3-C H Me (2e) 4-C H Bu (2f)). A solution of

6 4 6 4 6 4

3 3

6 4

9a−f), in marked contrast to 3a−f, they were completely

inactive in the isomerization of 1-octen-3-ol, even when the

[{RuCl(μ-Cl)(η :η -C10H16)} ] (1; 0.308 g, 0.5 mmol) in 20 mL of

tetrahydrofuran was treated with the appropriate guanidine 2a−f (2

mmol) at room temperature for 5 h. A gradual color change from

violet to red was observed. The solution was then evaporated to

dryness, and 40 mL of pentane was added to the resulting oily residue,

leading to the appearance of a white solid precipitate of the

corresponding guanidinium chloride salt [( PrHN) C(NHR)][Cl]

reactions were performed in the presence of a base (KO Bu) or

the chloride abstractor AgSbF . Although the electronic eﬀects

associated with the strong π-acceptor character of the

isocyanide ligands cannot be discarded, the high steric

congestion around the metal center imposed by the bulky

(

4a−f). The suspension was then ﬁltered using a cannula and, once

2,6-dimethylphenyl groups, which would prevent the coordi-

separated, the white solid was washed with hexanes (2 × 10 mL) and

diethyl ether (5 mL) to aﬀord 4a−f in pure form. The ﬁltrate was

stored in freezer at −10 °C for 48 h, leading to the precipitation of the

nation of the allylic alcohol, are possibly responsible for this

disappointing result.

complexes [RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(η :η -C H )]

3a−f) as orange-red solids, which were separated, washed with cold

(

CONCLUSION

■

pentane (3 mL), and vacuum-dried.

Characterization data for complexes 3a−f are as follows.

a: yield 0.353 g (72%). Anal. Calcd for RuC H N Cl: C, 56.25;

H, 7.39; N, 8.56. Found: C, 56.42; H, 7.44; N, 8.71. IR (KBr, cm ): ν

3336 (s, N−H). H NMR (C D ): δ 7.08 (m, 2H, CH_a_r_o_m), 6.94 (m,

1H, CH ), 6.82 (d, 2H, J = 7.2 Hz, CH_a_r_o_m), 5.05, 4.71, 4.61, and

.85 (s, 1H each, H , H , H and H ), 4.50 and 2.62 (m, 1H each, H

1 2 9 10

and H ), 4.11 and 3.05 (m, 1H each, CHMe ), 3.22 (d, 1H, J

In summary, we have prepared and fully characterized the ﬁrst

23 36 3

examples of ruthenium(IV) complexes, namely [RuCl-

−1

{

κ (N,N′)-C(NR)(N Pr)-NH Pr}(η :η -C H )] (3a−f), con-

taining heteroallyl guanidinate monoanions as ligands. As

previously observed with related half-sandwich (η -arene)-

ruthenium(II) derivatives, these Ru(IV) complexes are

arom HH

0.5 Hz, NH), 2.45 and 2.08 (s, 3H each, Me of C H ), 2.37 and

10 16

catalytically active in the base-free redox isomerization of allylic

alcohols. In addition, they have also been shown to be useful

precursors for the preparation of a new family of octahedral

.12 (m, 1H and 3H respectively, H , H , H and H ), 1.73 (d, 3H,

4 5 6 7

J_H_H= 6.0 Hz, CHMe ), 1.62 (d, 3H, J = 6.9 Hz, CHMe ), 0.87 (d,

3H, JHH = 6.6 Hz, CHMe

), 0.62 (d, 3H, JHH = 6.8 Hz, CHMe

)

ppm. ¹³C{ H} NMR (C D ): δ 160.9 (s, CN ), 149.1 (s, C_a_r_o_m), 128.8,

ruthenium(II) guanidinate complexes, i.e. mer-[RuCl{κ (N,N′)-

²⁵^.⁴^,^aⁿ^d¹²¹^.⁶⁽^s^,^C^Harom), 120.5 and 110.6 (s, C and C ), 95.4 and

1.4 (s, C and C ), 78.2 and 73.0 (s, C and C ), 47.6 and 44.4 (s,

CHMe ), 33.8 and 31.2 (s, C and C ), 23.5, 23.4, 23.1, and 22.3 (s,

2 7

C(NR)(N Pr)-NH Pr}(CN-2,6-C H Me ) ] (9a−f), via reduc-

2 3

tive elimination of the 2,7-dimethylocta-2,6-diene-1,8-diyl

ligand (C H ). Remarkably, despite the fact that several

isomers are possible within both families of compounds, the

reactions proceeded in all cases with complete stereoselectivity.

CHMe

), 19.9 and 19.0 (s, Me of C10H16) ppm.

b: yield 0.381 g (75%). Anal. Calcd for RuC H N ClF: C, 54.27;

−1

H, 6.93; N, 8.25. Found: C, 54.41; H, 6.78; N, 8.40. IR (KBr, cm ): ν

320 (s, N−H). F{ H} NMR (C D ): δ −120.9 (s) ppm. H NMR

6 6 arom arom

(C D ): δ 6.75 (m, 2H, CH ), 6.60 (m, 2H, CH ), 5.04, 4.68,

EXPERIMENTAL SECTION

4.12, and 2.74 (s, 1H each, H

, H

and H10), 4.59 and 2.50 (m, 1H

■

each, H and H ), 4.05 and 2.95 (m, 1H each, CHMe ), 3.12 (d, 1H,

Synthetic procedures were performed under an atmosphere of dry

argon using vacuum-line and standard Schlenk techniques. Solvents

were dried by standard methods and distilled under argon before use.

All reagents were obtained from commercial suppliers and used

without further puriﬁcation, with the exception of the dimeric

J_H_H= 9.9 Hz, NH), 2.52 and 2.12 (m, 1H and 3H respectively, H₄,

H , H and H ), 2.46 and 2.08 (s, 3H each, Me of C H ), 1.71 (d,

10 16

H, J = 6.3 Hz, CHMe ), 1.61 (d, 3H, J = 6.0 Hz, CHMe ), 0.97

HH 2 HH 2

(d, 3H, J = 6.1 Hz, CHMe ), 0.63 (d, 3H, J = 6.4 Hz, CHMe )

ppm. ¹³C{ H} NMR (C

): δ 160.8 (s, CN ), 158.1 (d, JCF = 241.5

^H^z^,^Carom), 144.9 (d, J ⁼²^.⁸^H^z^,^Carom), 126.4 (d, J = 7.4 Hz,

complexes [{RuCl(μ-Cl)(η :η -C H )} ] (1) and [{RuCl(μ-Cl)-

CH_a_r_o_m), 120.2 and 110.3 (s, C and C ), 115.4 (d, J = 21.6 Hz,

CHarom), 95.4 and 91.2 (s, C

(

η -p-cymene)} ] (6) and the guanidines ( PrHN) CNR (2a−

and C ), 78.2 and 72.9 (s, C and C ),

6 1 8

j), which were prepared by following the methods reported in the

literature. Infrared spectra were recorded on a PerkinElmer 1720-XFT

spectrometer. GC measurements were made on a Hewlett-Packard

HP6890 apparatus (Supelco Beta-Dex 120 column, 30 m length, 250

μm diameter). Elemental analyses were provided by the Analytical

7.7 and 44.5 (s, CHMe ), 33.7 and 31.1 (s, C and C ), 23.4 (s, 2C,

2 4 5

CHMe ), 23.1 and 22.3 (s, CHMe ), 19.9 and 19.1 (s, Me of C H )

10 16

ppm.

3c: yield 0.368 g (70%). Anal. Calcd for RuC H N Cl : C, 52.57;

−1

H, 6.71; N, 8.00. Found: C, 52.64; H, 6.65; N, 8.21. IR (KBr, cm ): ν

Service of the Instituto de Investigaciones Quım

icas (IIQ-CSIC) of

3331 (s, N−H). H NMR (C

): δ 7.05 and 6.59 (d, 2H each, JHH

.6 Hz, CH ), 5.00, 4.66, 4.55, and 2.70 (s, 1H each, H , H , H and

Seville. NMR spectra were recorded on Bruker DPX300 and AV400

instruments. The chemical shift values are given in parts per million

and are referenced to the residual peak of the deuterated solvent

arom 1 2 9

H ), 4.59 and 2.50 (m, 1H each, H and H ), 4.05 and 2.96 (m, 1H

each, CHMe ), 3.16 (d, 1H, J = 10.2 Hz, NH), 2.44 and 1.97 (s,

H each, Me of C H ), 2.35 and 2.07 (m, 1H and 3H respectively,

10 16

employed ( H and C) or the CFCl₃standard ( F). DEPT

experiments have been carried out for all of the compounds reported

in this paper. The numberings employed for the protons and carbons

of the 2,7-dimethylocta-2,6-diene-1,8-diyl skeleton are as follows:

H , H , H and H ), 1.69 (d, 3H, J = 6.6 Hz, CHMe ), 1.59 (d, 3H,

J_H_H= 6.5 Hz, CHMe ), 0.84 (d, 3H, J = 5.7 Hz, CHMe ), 0.59 (d,

3H, J = 7.0 Hz, CHMe ) ppm. C{ H} NMR (C D ): δ 160.7 (s,

CN ), 147.8 and 126.4 (s, C_a_r_o_m), 128.9 and 126.1 (s, CH_a_r_o_m), 120.6

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and 110.7 (s, C and C ), 95.6 and 91.4 (s, C and C ), 78.1 and 72.8

3244 (vs, N−H), 3193 (vs, N−H). H NMR (CDCl ): δ 10.04 (broad

(

s, C and C ), 47.7 and 44.4 (s, CHMe ), 33.7 and 31.2 (s, C and

s, 1H, NH), 7.67 (broad s, 2H, NH), 7.31 and 7.22 (d, 2H each, J

8.8 Hz, CH_a_r_o_m), 3.96 (broad s, 2H, CHMe ), 1.21 (d, 12H, J = 6.4

Hz, CHMe ) ppm. C{ H} NMR (CDCl ): δ 154.5 (s, CN ), 135.8

2 3 3

C ), 23.5, 23.3, 23.1, and 22.2 (s, CHMe ), 20.0 and 19.0 (s, Me of

2 HH

C H ) ppm.

d: yield 0.409 g (81%). Anal. Calcd for RuC H N Cl: C, 57.07;

and 131.2 (s, C_a_r_o_m), 129.7 and 123.8 (s, CH_a_r_o_m), 46.1 (s, CHMe₂),

−1

H, 7.58; N, 8.32. Found: C, 57.01; H, 7.64; N, 8.24. IR (KBr, cm ): ν

332 (s, N−H). H NMR (C D ): δ 6.93 and 6.78 (d, 2H each, J

.1 Hz, CH ), 5.06, 4.71, 4.44, and 2.87 (s, 1H each, H , H , H and

22.6 (s, CHMe ) ppm.

4d: yield 0.186 g (69%). Anal. Calcd for C H N Cl: C, 62.32; H,

14 24

−1

8.97; N, 15.57. Found: C, 62.40; H, 8.88; N, 15.54. IR (KBr, cm ): ν

3239 (vs, N−H), 3201 (vs, N−H). H NMR (CDCl ): δ 9.77 (broad

s, 1H, NH), 7.49 (broad s, 2H, NH), 7.06 (broad s, 4H, CH ), 3.96

arom

H ), 4.62 and 2.63 (m, 1H each, H and H ), 4.14 and 3.11 (m, 1H

each, CHMe ), 3.26 (d, 1H, J = 10.8 Hz, NH), 2.46 and 2.13 (s,

H each, Me of C H ), 2.35 and 2.18 (m, 1H and 3H respectively,

arom

(broad s, 2H, CHMe ), 2.28 (s, 3H, Me), 1.12 (d, 12H, J = 6.6 Hz,

H , H , H and H ), 2.12 (s, 3H, Me), 1.75 (d, 3H, J = 6.3 Hz,

CHMe ) ppm. C{ H} NMR (CDCl ): δ 154.5 (s, CN ), 135.5 and

CHMe ), 1.64 (d, 3H, J = 6.6 Hz, CHMe ), 0.92 (d, 3H, J = 5.4

Hz, CHMe ), 0.65 (d, 3H, J = 6.9 Hz, CHMe ) ppm. C{ H}

134.5 (s, C_a_r_o_m), 130.1 and 123.0 (s, CH_a_r_o_m), 45.8 (s, CHMe ), 22.5

(s, CHMe ), 20.9 (s, Me) ppm.

NMR (C D ): δ 161.1 (s, CN ), 146.1 and 130.9 (s, C_a_r_o_m), 129.6 and

4e: yield 0.208 g (77%). Anal. Calcd for C H N Cl: C, 62.32; H,

14 24

−1

25.4 (s, CH_a_r_o_m), 120.2 and 110.2 (s, C and C ), 95.4 and 91.4 (s, C

8.97; N, 15.57. Found: C, 62.29; H, 9.11; N, 15.69. IR (KBr, cm ): ν

and C ), 78.1 and 73.0 (s, C and C ), 47.7 and 44.4 (s, CHMe ), 33.7

3242 (vs, N−H), 3227 (vs, N−H). H NMR (CDCl ): δ 9.71 (broad

and 31.1 (s, C and C ), 23.5, 23.2, 22.7, and 22.3 (s, CHMe ), 20.7 (s,

s, 1H, NH), 7.56 (broad s, 2H, NH), 7.21 (t, 1H each, J = 7.5 Hz,

Me), 20.0 and 19.1 (s, Me of C H ) ppm.

CH_a_r_o_m), 7.02 (m, 3H, CH ), 3.98 (broad s, 2H, CHMe ), 2.33 (s,

arom

e: yield 0.424 g (84%). Anal. Calcd for RuC H N Cl: C, 57.07;

3H, Me), 1.20 (d, 12H, J = 6.1 Hz, CHMe ) ppm. C{ H} NMR

HH 2

−

H, 7.58; N, 8.32. Found: C, 57.15; H, 7.61; N, 8.14. IR (KBr, cm ): ν

(CDCl ): δ 154.6 (s, CN ), 139.8 and 137.0 (s, C_a_r_o_m), 129.4, 126.7,

3 3

325 (s, N−H). H NMR (C D ): δ 7.03 (t, 1H, J = 7.8 Hz,

123.4, and 119.8 (s, CH_a_r_o_m), 46.0 (s, CHMe ), 22.6 (s, CHMe ), 21.4

CH ), 6.77 (m, 1H, CH ), 6.70 (d, 1H, J = 7.8 Hz, CH_a_r_o_m),

(s, Me) ppm.

Synthesis of [RuCl (η :η -C

arom

.07, 4.72, 4.45, and 2.90 (s, 1H each, H , H , H and H ), 4.63 and

10 16

){NC-4-C H -NC-

.69 (m, 1H each, H and H ), 4.13 and 3.15 (m, 1H each, CHMe ),

(NH Pr

)

}] (5). A solution of the dimer [{RuCl(μ-Cl)(η :η -

C H16)} ] (1; 0.308 g, 0.5 mmol) in 20 mL of tetrahydrofuran was

10 2

.27 (d, 1H, J = 9.9 Hz, NH), 2.46 and 2.20 (s, 3H each, Me of

C H ), 2.33 and 2.16 (m, 1H and 3H respectively, H , H , H and

H ), 2.14 (s, 3H, Me), 1.74 (d, 3H, J = 6.6 Hz, CHMe ), 1.63 (d,

treated with the guanidine ( PrHN)

CN-4-C

CN (2j; 0.244 g,

1 mmol) at room temperature for 15 min. An immediate color change

from violet to orange was observed. The solution was then evaporated

to dryness, and the resulting orange solid was washed twice with 3 mL

of cold pentane and vacuum-dried. Yield: 0.503 g (91%). Anal. Calcd

H, J = 6.0 Hz, CHMe ), 0.90 (d, 3H, J = 6.5 Hz, CHMe ), 0.65

HH 2 HH 2

(

d, 3H, J = 6.3 Hz, CHMe ) ppm. C{ H} NMR (C D ): δ 161.1

HH 2 6 6

(

s, CN ), 148.9 and 138.2 (s, C_a_r_o_m), 128.8, 127.1, 126.0, and 122.6 (s,

CH_a_r_o_m), 120.5 and 110.4 (s, C and C ), 95.3 and 91.6 (s, C and C ),

for RuC24

: C, 52.17; H, 6.57; N, 10.14. Found: C, 52.21; H,

−1

8.1 and 73.0 (s, C and C ), 47.7 and 44.5 (s, CHMe ), 33.8 and 31.3

6.62; N, 10.20. IR (KBr, cm ): ν 3306 (m, N−H), 2237 (m, CN).

(

s, C and C ), 23.6, 23.5, 23.2, and 22.3 (s, CHMe ), 21.2 (s, Me),

H NMR (CD

): δ 7.39 and 6.89 (d, 2H each, JHH = 8.7 Hz,

0.0 and 19.1 (s, Me of C H ) ppm.

CH_a_r_o_m), 5.11 (m, 1H, H or H ), 5.06, 4.91, 4.61, and 4.03 (s, 1H

10 16

f: yield 0.443 g (81%). Anal. Calcd for RuC H N Cl: C, 59.27;

each, H , H , H and H ), 4.58 (m, 3H, H or H and NH), 3.72 (m,

1 2 9 10 3 8

−

H, 8.11; N, 7.68. Found: C, 59.16; H, 8.24; N, 7.77. IR (KBr, cm ): ν

H ), 4.61 and 2.68 (m, 1H each, H and H ), 4.18 and 3.11 (m, 1H

each, CHMe ), 3.37 (d, 1H, J = 9.9 Hz, NH), 2.42 and 2.17 (s, 3H

2H, CHMe ), 3.08 and 2.53 (m, 2H each, H , H , H and H ), 2.41

2 4 5 6 7

341 (s, N−H). H NMR (C D ): δ 7.19 and 6.84 (d, 2H each, J

and 2.38 (s, 3H each, Me of C H ), 1.15 (d, 12H, J = 5.7 Hz,

10 16 HH

.5 Hz, CH ), 5.03, 4.69, 4.45, and 2.87 (s, 1H each, H , H , H and

CHMe ) ppm. C{ H} NMR (CD Cl ): δ 157.2 (s, CN), 151.9

and 98.9 (s, C_a_r_o_m), 133.9 and 122.6 (s, CH ), 127.9 and 125.0 (s,

arom

C and C ), 127.5 (s, CN), 98.7 and 91.8 (s, C and C ), 83.2 and

79.6 (s, C and C ), 43.7 (s, CHMe ), 37.6 and 36.8 (s, C and C ),

1 8 2 4 5

each, Me of C H ), 2.36 and 2.15 (m, 1H and 3H respectively, H ,

H , H and H ), 1.74 (d, 3H, J = 5.7 Hz, CHMe ), 1.65 (d, 3H,

22.8 (s, CHMe ), 20.5 and 20.0 (s, Me of C H ) ppm.

2 10 16

J_H_H= 5.6 Hz, CHMe ), 1.30 (s, 9H, CMe ), 0.93 (d, 3H, J = 6.6

Synthesis of [RuCl{κ (N,N′)-C(N-4-C H CN)(N Pr)-NH Pr}(η -

] (6;

6 4

Hz, CHMe ), 0.67 (d, 3H, J = 6.7 Hz, CHMe ) ppm. C{ H}

NMR (C D ): δ 161.2 (s, CN ), 146.1 and 144.2 (s, C_a_r_o_m), 125.6 and

p-cymene)] (7). A solution of [{RuCl(μ-Cl)(η -p-cymene)}

0.306 g, 0.5 mmol) in 20 mL of tetrahydrofuran was treated with the

25.1 (s, CH_a_r_o_m), 120.3 and 110.3 (s, C and C ), 95.1 and 91.6 (s, C

guanidine ( PrHN)

CN-4-C

CN (2j; 0.489 g, 2 mmol) at

and C ), 78.0 and 72.9 (s, C and C ), 47.7 and 44.5 (s, CHMe ), 34.0

room temperature for 3 h. The solution was then evaporated to

(

s, CMe ), 33.8 and 31.3 (s, C and C ), 31.2 (s, CMe ), 23.6, 23.5,

3.2, and 22.3 (s, CHMe ), 20.0 and 19.1 (s, Me of C H ) ppm.

dryness, and 60 mL of pentane were added to the resulting oily

3 4 5 3

residue, leading to the appearance of a white solid precipitate of the

10 16

Characterization data for the novel guanidinium chloride salts

corresponding guanidinium chloride salt [( PrHN)

C(NH-4-C

C

[

(PrHN) C(NHR)][Cl] (4a−e) are as follows.

N)][Cl] (4j). The suspension was then ﬁltered using a cannula and,

once separated, the white solid was washed with hexanes (2 × 10 mL)

and diethyl ether (5 mL) to aﬀord 0.208 g of 4j (74% yield). The

4a: yield 0.187 g (73%). Anal. Calcd for C H N Cl: C, 61.04; H,

13 22 3

−1

.67; N, 16.43. Found: C, 60.99; H, 8.62; N, 16.41. IR (KBr, cm ): ν

240 (vs, N−H), 3187 (vs, N−H). H NMR (CDCl ): δ 9.78 (broad

ﬁltrate was stored in freezer at −10 °C for 48 h, leading to the

s, 1H, NH), 7.55 (broad s, 2H, NH), 7.39−7.19 (m, 5H, CH ), 3.93

precipitation of the complex [RuCl{κ (N,N′)-C(N-4-C

CN)-

arom

(

broad s, 2H, CHMe ), 1.24 (d, 12H, J = 6.3 Hz, CHMe ) ppm.

(N Pr)-NH Pr}(η -p-cymene)] (7) as an orange solid, which was

C{ H} NMR (CDCl ): δ 154.5 (s, CN ), 137.2 (s, C_a_r_o_m), 129.5,

separated, washed with cold pentane (3 mL), and vacuum-dried. Yield:

.427 g (83%). Anal. Calcd for RuC H N Cl: C, 56.07; H, 6.47; N,

25.7, and 122.7 (s, CH_a_r_o_m), 45.8 (s, CHMe ), 22.4 (s, CHMe ) ppm.

24 33 4

−1

0.90. Found: C, 56.18; H, 7.42; N, 10.98. IR (KBr, cm ): ν 3337 (m,

b: yield 0.191 g (70%). Anal. Calcd for C H N ClF: C, 57.03; H,

13 21 3

−1

N−H), 2213 (s, CN). H NMR (CD Cl ): δ 7.46 and 7.14 (d, 2H

.73; N, 15.35. Found: C, 55.88; H, 7.72; N, 15.29. IR (KBr, cm ): ν

each, J = 9.0 Hz, CH ), 5.41, 5.19, 5.12, and 5.10 (d, 1H each,

250 (vs, N−H), 3159 (vs, N−H). F{ H} NMR (C D ): δ −115.7

arom

^JHH = 5.7 Hz, CH of cymene), 3.55 (d, 1H, J = 10.8 Hz, NH), 3.35

(

s) ppm. H NMR (CDCl ): δ 10.00 (broad s, 1H, NH), 7.56 (broad

s, 2H, NH), 7.25 (m, 2H, CH ), 7.05 (m, 2H, CH_a_r_o_m), 3.97 (broad

s, 2H, CHMe ), 1.20 (d, 12H, J = 6.4 Hz, CHMe ) ppm. C{ H}

NMR (CDCl ): δ 160.5 (d, J = 246.7 Hz, C_a_r_o_m), 154.7 (s, CN ),

and 3.17 (m, 1H each, NCHMe

), 2.58 (m, 1H, CHMe

of cymene),

) ppm.

C{ H} NMR (CD Cl ): δ 160.7 (s, CN ), 155.0 and 100.5 (s,

2 2 3

arom

2.20 (s, 3H, Me of cymene), 1.32−0.96 (m, 18H, CHMe

33.0 (s, C_a_r_o_m), 124.8 (broad s, CH_a_r_o_m), 116.5 (d, J = 22.8 Hz,

C_a_r_o_m), 132.6 and 121.1 (s, CH_a_r_o_m), 120.4 (s, CN), 98.9 and 97.8

(s, C of cymene), 80.5, 79.3, 79.2, and 78.3 (s, CH of cymene), 45.9

and 45.4 (s, NCHMe ), 31.3 (s, CHMe of cymene), 25.2, 24.5, 24.0,

CH_a_r_o_m), 45.9 (s, CHMe ), 22.6 (s, CHMe ) ppm.

c: yield 0.217 g (75%). Anal. Calcd for C H N Cl : C, 53.80; H,

13 21 3 2

−1

.29; N, 14.48. Found: C, 51.48; H, 7.15; N, 13.53. IR (KBr, cm ): ν

22.4, 22.2, and 22.1 (s, CHMe ), 18.8 (s, Me of cymene) ppm.

DOI: 10.1021/acs.organomet.5b00070

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

(s, CH_a_r_o_m), 122.6 (d, ³J_C_F= 9.7 Hz, CH_a_r_o_m), 114.0 (d, ²J_C_F= 22.6 Hz,

CH_a_r_o_m), 45.2 (s, 2C, CHMe ), 24.3 and 23.3 (s, CHMe ), 19.1 and

Characterization data for [( PrHN) C(NH-4-C H CN)][Cl]

4j) are as follows. Anal. Calcd for C H N Cl: C, 59.88; H, 7.54;

14 21 4

(

−1

N, 19.95. Found: C, 59.93; H, 7.61; N, 20.10. IR (KBr, cm ): ν 3189

18.6 (s, C H Me ) ppm.

6 3 2

(

vs, N−H), 2227 (s, CN). H NMR (CDCl ): δ 10.2 (broad s, 1H,

9c: yield 0.130 g (80%). Anal. Calcd for RuC H N Cl : C, 61.37;

40 46 6 2

−1

NH), 7.96 (broad s, 2H, NH), 7.56 and 7.37 (broad s, 2H each,

H, 5.92; N, 10.74. Found: C, 61.46; H, 6.04; N, 10.91. IR (KBr, cm ):

CH ), 3.93 (broad s, 2H, CHMe ), 1.19 (broad s, 12H, CHMe )

ν 3329 (m, N−H), 2164 (m, CN), 2108 (vs, CN), 2050 (vs, C

arom

ppm. ¹C{ H} NMR (CDCl ): δ 154.1 (s, CN ), 142.3 and 107.8 (s,

N). H NMR (CD Cl ): δ 7.35 (d, 2H, J = 8.4 Hz, CH ), 7.20−

arom

C_a_r_o_m), 133.6 and 121.2 (s, CH_a_r_o_m), 118.3 (s, CN), 46.7 (s,

7.01 (m, 11H, CH ), 3.53 (m, 2H, CHMe and NH), 3.40 (sept,

arom 2

CHMe ), 22.6 (s, CHMe ) ppm.

1H, J = 6.0 Hz, CHMe ), 2.55 (s, 6H, C H Me ), 2.42 (s, 12H,

Synthesis of the Dinuclear Ru(II)/Ru(IV) Complex 8. A

C H Me ), 1.14 (d, 6H, J = 6.0 Hz, CHMe ), 1.07 (d, 6H, J

solution of the complex [RuCl{κ (N,N′)-C(N-4-C H CN)(N Pr)-

4.0 Hz, CHMe ) ppm. C{ H} NMR (CD Cl ): δ 170.8 and 164.8 (s,

NH Pr}(η -p-cymene)] (7; 0.100 g, 0.194 mmol) in 10 mL of

dichloromethane was treated with the dimer [{RuCl(μ-Cl)(η :η -

CN), 158.8 (s, CN ), 149.8, 135.3, 134.3, 130.3, 126.3, and 122.3 (s,

), 128.0, 127.7, 127.5, and 123.0 (s, CH ), 45.2 and 45.1 (s,

arom arom

C H )} ] (1) (0.060 g, 0.097 mmol) at room temperature for 30

CHMe ), 24.1 and 23.2 (s, CHMe ), 19.1 and 18.6 (s, C H Me ) ppm.

min. The solution was then evaporated to dryness, and the resulting

yellow solid was washed twice with 5 mL of diethyl ether and vacuum-

dried. Yield: 0.147 g (92%). Anal. Calcd for Ru C H N Cl : C,

9d: yield 0.124 g (81%). Anal. Calcd for RuC H N Cl: C, 64.59;

41 49 6

−1

H, 6.48; N, 11.02. Found: C, 64.48; H, 6.53; N, 11.13. IR (KBr, cm ):

ν 3335 (m, N−H), 2163 (m, CN), 2106 (vs, CN), 2042 (s, C

N). H NMR (CD Cl ): δ 7.25 and 6.96 (d, 2H each, J = 8.4 Hz,

2 2 HH

34 49

9.66; H, 6.01; N, 6.81. Found: C, 49.59; H, 6.06; N, 6.92. IR (KBr,

−1

cm ): ν 3307 (m, N−H), 2239 (m, CN). H NMR (CD Cl ): δ

CH_a_r_o_m), 7.20−7.01 (m, 9H, CH ), 3.52 (m, 2H, CHMe and NH),

arom

.37 and 7.10 (d, 2H each, J = 8.4 Hz, CH ), 5.41 (d, 1H, J

3.43 (sept, 1H, J = 6.4 Hz, CHMe ), 2.55 (s, 6H, C H Me ), 2.44

arom

HH 2 6 3 2

.7 Hz, CH of cymene), 5.16−5.08 (m, 5H, CH of cymene, H or H ,

(s, 12H, C H Me ), 2.27 (s, 3H, Me), 1.13 (d, 6H, J = 7.6 Hz,

6 3 2

and H , H , H or H ), 4.94, 4.63, and 4.05 (s, 1H each, H , H , H or

H ), 4.59 (m, 1H, H or H ), 3.50 (d, 1H, J = 10.8 Hz, NH), 3.33

CHMe ), 1.05 (d, 6H, J = 6.4 Hz, CHMe ) ppm. C{ H} NMR

2 HH 2

(CD Cl ): δ 171.5 and 165.4 (s, CN), 158.7 (s, CN ), 147.8, 134.3,

arom

(

m, 1H, NCHMe ), 3.19−2.96 (m, 4H, NCHMe , CHMe of cymene,

130.4, 128.6, 127.8, and 127.7 (s, C ), 135.4 128.4, 127.9, 127.6,

and H , H , H or H ), 2.53 (2H, H , H , H or H ), 2.20 (s, 6H, Me

127.5, and 122.1 (s, CH_a_r_o_m), 45.2 and 45.1 (s, CHMe ), 24.3 and 23.3

of C H ), 2.20 (s, 3H, Me of cymene), 1.31−1.00 (m, 18H, CHMe )

(s, CHMe ), 20.4 (s, C H Me), 19.1 and 18.6 (s, C H Me ) ppm.

ppm. C{ H} NMR (CD Cl ): δ 160.5 (s, CN ), 156.6 and 99.1 (s,

9e: yield 0.120 g (79%). Anal. Calcd for RuC H N Cl: C, 64.59;

41 49 6

−

C_a_r_o_m), 133.3 and 120.9 (s, CH_a_r_o_m), 127.8 and 124.8 (s, C and C ),

H, 6.48; N, 11.02. Found: C, 64.65; H, 6.50; N, 11.17. IR (KBr, cm ):

27.5 (s, CN), 98.5 and 91.6 (s, C and C ), 98.2 and 97.8 (s, C of

ν 3343 (m, N−H), 2166 (m, CN), 2108 (vs, CN), 2068 (s, C

cymene), 83.3 and 79.7 (s, C and C ), 80.5, 79.4, 79.1, and 78.1 (s,

CH of cymene), 46.1 and 45.6 (s, NCHMe ), 37.6 and 36.9 (s, C and

C ), 31.4 (s, CHMe of cymene), 25.0, 24.4, 24.0, 22.4, 22.3, and 22.1

N). H NMR (CD Cl ): δ 7.21−7.01 (m, 12H, CH ), 6.56 (d, 1H,

arom

= 8.7 Hz, CH ), 3.54 (m, 2H, CHMe and NH), 3.40 (sept,

HH arom 2

1H, J = 6.6 Hz, CHMe ), 2.55 (s, 6H, C H Me ), 2.44 (s, 12H,

C H Me ), 2.23 (s, 3H, Me), 1.13 (d, 6H, J = 6.6 Hz, CHMe₂),

6 3 2 HH

1.05 (d, 6H, J = 5.4 Hz, CHMe ) ppm. C{ H} NMR (CD Cl ): δ

HH 2 6 3 2

(

s, CHMe ), 20.5 and 20.0 (s, Me of C H ), 18.8 (s, Me of cymene)

10 16

ppm.

HH 2 2 2

Synthesis of mer-[RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(CN-2,6-

171.5 and 165.4 (s, CN), 158.8 (s, CN ), 150.5, 137.2, 135.4, 134.4,

C H Me ) ] (R = Ph (9a), 4-C H F (9b), 4-C H Cl (9c), 4-

C H Me (9d), 3-C H Me (9e), 4-C H Bu (9f)). A solution of the

2 3

130.5, and 127.8 (s, C ), 127.9, 127.6, 127.5, 127.4, 126.3, 122.7,

arom

119.8, and 119.3 (s, CH_a_r_o_m), 45.2 (s, 2C, CHMe ), 24.2 and 23.2 (s,

corresponding ruthenium(IV) guanidinate complex [RuCl{κ (N,N′)-

CHMe ), 21.2 (s, C H Me), 19.1 and 18.6 (s, C H Me ) ppm.

C(NR)(N Pr)-NH Pr}(η :η -C H )] (3a−f; 0.2 mmol) in 10 mL of

9f: yield 0.135 g (84%). Anal. Calcd for RuC H N Cl: C, 65.69;

44 55 6

toluene was treated with an excess of 2,6-dimethylphenyl isocyanide

0.314 g, 2.4 mmol) at room temperature for 12 h. A gradual color

−1

H, 6.89; N, 10.45. Found: C, 65.61; H, 7.02; N, 10.60. IR (KBr, cm ):

(

ν 3334 (m, N−H), 2162 (m, CN), 2105 (vs, CN), 2041 (vs, C

change from red to yellow was observed. Concentration of the

resulting solution (ca. 3 mL) followed by the addition of hexanes (ca.

N). H NMR (CD Cl ): δ 7.32−7.27 (m, 2H, CH ), 7.20−7.08 (m,

arom

1H, CH ), 3.55 (m, 2H, CHMe and NH), 3.43 (sept, 1H, J

arom

0 mL) precipitated a yellow solid, which was washed with hexanes (3

.3 Hz, CHMe ), 2.55 (s, 6H, C H Me ), 2.42 (s, 12H, C H Me ),

10 mL) and diethyl ether (5 mL) and vacuum-dried.

.33 (s, 9H, CMe ), 1.14 (d, 6H, J = 6.3 Hz, CHMe ), 1.06 (d, 6H,

3 HH 2

Characterization data for mer-[RuCl{κ (N,N′)-C(NR)(N Pr)-

J_H_H= 5.7 Hz, CHMe ) ppm. C{ H} NMR (CD Cl ): δ 171.5 and

NH Pr}(CN-2,6-C H Me ) ] (9a−f) are as follows.

2 3

65.4 (s, CN), 158.9 (s, CN ), 147.9, 140.9, 135.4, 134.3, 130.4, and

a: yield 0.130 g (87%). Anal. Calcd for RuC H N Cl: C, 64.20;

40 47 6

26.2 (s, C ), 127.9, 127.8, 127.6, 127.5, 124.5, and 121.6 (s,

−1

arom

H, 6.33; N, 11.23. Found: C, 64.31; H, 6.24; N, 11.47. IR (KBr, cm ):

CH_a_r_o_m), 45.2 and 45.1 (s, CHMe ), 33.9 (s, CMe ), 31.4 (s, CMe ),

ν 3326 (m, N−H), 2156 (m, CN), 2104 (vs, CN), 2055 (vs, C

4.3 and 23.3 (s, CHMe ), 19.1 and 18.7 (s, C H Me ) ppm.

General Procedure for the Catalytic Isomerization of 1-

2 6 3 2

N). H NMR (CD Cl ): δ 7.38−7.34 (m, 2H, CH ), 7.20−7.06 (m,

arom

1H, CH ), 6.72 (m, 1H, CH ), 3.54 (m, 2H, CHMe and NH),

arom arom 2

Octen-3-ol. In a Teﬂon-capped sealed tube under an argon

atmosphere, the corresponding ruthenium complex (0.01 mmol; 0.5

mol % of Ru) was added to a solution of 1-octen-3-ol (2 mmol) in

tetrahydrofuran (10 mL), and the resulting mixture was stirred at 80

°C for the indicated time (see Table 1). The course of the reaction was

monitored by regularly taking ca. 10 μL samples, which after dilution

with THF (3 mL) were analyzed by GC. The identity of the resulting

octan-3-one was assessed by comparison of its retention time with that

of a commercially available pure sample (Aldrich Chemical Co.).

X-ray Crystal Structure Determination of Compounds 3d,

4a−c, 7, and 9f. Crystals of the ruthenium complexes 3d, 7, and 9f

suitable for X-ray diﬀraction analysis were obtained by cooling (−10

°C) a saturated solution of the corresponding complex in hexane with

some drops of dichloromethane. Crystals of the guanidinium chloride

salts 4a−c were grown by slow diﬀusion of pentane into saturated

solutions of the salts in THF. The most relevant crystal and reﬁnement

data are collected in Tables S1 and S2 (see the Supporting

Information). Data collection was performed with Oxford Diﬀraction

Xcalibur Nova and Oxford Diﬀraction Gemini single crystal

^.⁴²⁽^s^e^p^t^,¹^H^,^JHH = 6.4 Hz, CHMe ), 2.55 (s, 6H, C H Me ), 2.43

(

s, 12H, C H Me ), 1.13 (d, 6H, J = 6.4 Hz, CHMe ), 1.05 (d, 6H,

6 3 2 HH 2

^JHH = 5.7 Hz, CHMe ) ppm. C{ H} NMR (CD Cl ): δ 171.3 and

65.2 (s, CN), 158.8 (s, CN ), 150.7, 135.4, 134.3, 130.4, and 126.2

(

s, C ), 127.9, 127.8, 127.6, 127.5, 122.2, and 118.3 (s, CH ),

arom

5.2 and 45.1 (s, CHMe ), 24.3 and 23.3 (s, CHMe ), 19.1 and 18.6 (s,

C H Me ) ppm.

b: yield 0.115 g (75%). Anal. Calcd for RuC H N ClF: C, 62.69;

40 46 6

−1

H, 6.05; N, 10.97. Found: C, 62.76; H, 6.13; N, 11.10. IR (KBr, cm ):

ν 3331 (m, N−H), 2165 (m, CN), 2108 (vs, CN), 2053 (vs, C

N). ¹⁹F{ H} NMR (CD Cl ): δ −127.8 (s) ppm. H NMR (CD Cl ):

δ 7.33 (m, 2H, CH ), 7.21−7.09 (m, 9H, CH ), 6.85 (t, 2H, J

arom

9.0 Hz, CH_a_r_o_m), 3.51 (m, 2H, CHMe and NH), 3.39 (sept, 1H,

J_H_H= 6.6 Hz, CHMe ), 2.55 (s, 6H, C H Me ), 2.43 (s, 12H,

C H Me ), 1.05 (d, 6H, J = 5.4 Hz, CHMe ), 1.00 (d, 6H, J =

.6 Hz, CHMe ) ppm. C{ H} NMR (CD Cl ): δ 171.1 and 165.1 (s,

CN), 158.8 (s, CN ), 156.4 (d, J = 234.5 Hz, C_a_r_o_m), 147.0,

35.3, 134.3, 130.4, and 127.8 (s, C_a_r_o_m), 128.0, 127.6, 127.5, and 126.3

DOI: 10.1021/acs.organomet.5b00070

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

diﬀractometers, using Mo Kα radiation (λ = 0.71073 Å; 3d and 9f)

and Cu Kα radiation (λ = 1.5418 Å; 4a−c and 7), respectively. Images

were collected at a ﬁxed crystal−detector distance of 45 mm for 3d, 7,

and 9f, 100 mm for 4a, 63 mm for 4b, and 65 mm for 4c, using the

oscillation method, with 1° oscillation and variable exposure time per

image (37.22 s for 3d, 7.28−30 s for 4a, 1.5−2 s for 4b, 1.5−4 s for 4c,

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(

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ASSOCIATED CONTENT

Supporting Information

■

721. (c) Motoyama, Y.; Hanada, S.; Niibayashi, S.; Shimamoto, K.;

CIF ﬁles, tables, and ﬁgures giving crystallographic information

on compounds 3d, 4a−c, 7, and 9f. The Supporting

Information is available free of charge on the ACS Publications

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AUTHOR INFORMATION

■

Corresponding Authors

E-mail for V.C.: vcm@uniovi.es.

E-mail for A.A.: Antonio.Antinolo@uclm.es.

(

11) (a) Cadierno, V.; Crochet, P.; Garcıa-Garrido, S. E.; Gimeno, J.

Curr. Org. Chem. 2006, 10, 165−183 and references cited therein.

-Garrido, S. E.; Gimeno, J.; Varela-Alvarez, A.;

(

b) Cadierno, V.; Garcıa

Notes

Sordo, J. A. J. Am. Chem. Soc. 2006, 128, 1360−1370. (c) Cadierno, V.;

Garcıa

-Garrido, S. E.; Gimeno, J. J. Am. Chem. Soc. 2006, 128, 15094−

5095. (d) Cadierno, V.; Gimeno, J.; Nebra, N. Chem. - Eur. J. 2007,

3, 6590−6594. (e) Cadierno, V.; Francos, J.; Gimeno, J. Chem.

z, J.; Francos, J.;

The authors declare no competing ﬁnancial interest.

ACKNOWLEDGMENTS

■

Commun. 2010, 46, 4175−4177. (f) Cadierno, V.; Dıe

Gimeno, J. Chem. - Eur. J. 2010, 16, 9808−9817. (g) Cadierno, V.;

This work was ﬁnancially supported by the Ministerio de

Economıa y Competitividad (MINECO) of Spain (projects

Francos, J.; Gimeno, J. Organometallics 2011, 30, 852−862. (h) Varela-

Alvarez; Sordo, J. A.; Piedra, E.; Nebra, N.; Cadierno, V.; Gimeno, J.

CTQ2013-40591-P and CTQ2014-51912-REDC), the Gobier-

no del Principado de Asturias (project GRUPIN14-006), and

the Junta de Comunidades de Castilla-La Mancha (project

PEII-2014-041-P). L.M.-R. and E.T.-M. thank the MINECO,

the MECD, and the European Social Fund (ESF) for the award

of FPI and FPU fellowships, respectively.

Chem. - Eur. J. 2011, 17, 10583−10599. (i) Lastra-Barreira, B.;

Francos, J.; Crochet, P.; Cadierno, V. Green Chem. 2011, 13, 307−313.

(

j) Garcıa-Alvarez, R.; Garcıa-Garrido, S. E.; Dıez, J.; Crochet, P.;

́ ́ ́

Cadierno, V. Eur. J. Inorg. Chem. 2012, 4218−4230. (k) Tomas

-A z, J.;

́ ́

Mendivil, E.; Garcıa lvarez, R.; Garcıa-Garrido, S. E.; Dıe

Crochet, P.; Cadierno, V. J. Organomet. Chem. 2013, 727, 1−9.

DOI: 10.1021/acs.organomet.5b00070

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

(

l) Tomas

Commun. 2014, 50, 9661−9664.

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Otero, A.; Lopez-Solera, I.; Rodrıguez, A. M.; Antinolo, A.

Organometallics 2010, 29, 2789−2795. (b) Elorriaga, D.; Carrillo-

Hermosilla, F.; Antinolo, A.; Lopez-Solera, I.; Menot, B.; Fernandez-

Galan, R.; Villasenor, E.; Otero, A. Organometallics 2012, 31, 1840−

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13) A completely delocalized bonding was also observed in the

-Mendivil, E.; Suar

ez, F. J.; Dıe

z, J.; Cadierno, V. Chem.

salt Li[( PrN)( PrNH)CN-4-C H CN], generated in situ by

deprotonation of 2j with Li Bu in THF at −78°C, failed. A mixture

of products, including 3j and other unidentiﬁed ruthenium complexes

containing probably more than one coordinated guanidinate unit, was

formed. (b) The reaction of dimer 1 with 4 equiv of 2j (as in the case

of dimer 6) did not give 3j. The nitrile complex 5 was again formed

exclusively.

(21) Examples of dinuclear Ru(II)/Ru(IV) complexes combining

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unit [RuCl (η :η -C H )], through bridging halide, diphosphine,

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(

, A.;

2 10 16

Rooyen, P. H. J. Chem. Soc., Dalton Trans. 1991, 2693−2702.

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(

22) See, for example: (a) Head, R. A.; Nixon, J. F.; Swain, J. R.;

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(

N.; Roulet, R. J. Chem. Soc., Chem. Commun. 1988, 951−953.

(

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(

solid-state crystal structures of complexes [RuCl{κ (N,N′)-C(NR) -

NHR}(η -p-cymene)] (R = Pr, Ph, 4-C H Me, 2-C H Me, 2-

(

g) Ng, S. Y.; Tan, G. K.; Koh, L. L.; Leong, W. K.; Goh, L. Y.

Organometallics 2007, 26, 3352−3361. (h) Trofinova, E. A.; Perekalin,

D. S.; Loskutova, N. L.; Nelyubina, Y. V.; Kudinov, A. R. J. Organomet.

Chem. 2014, 770, 1−5.

C H OMe, 2,4-C H Me ), [RuH{κ (N,N′)-C(NPh) -NHPh}(CO)

(

[

PPh ) ], [Ru{κ (N,N′)-C(NPh) -NHPh} (CO)(PPh )], and

Ru{κ (N,N′)-C(NPh) -NHPh} ] containing symmetrically substi-

(

23) (a) Although the fate of the C H chain could not be

10 16

tuted guanidinate ligands. See refs 3−6.

determined, on the basis of previous observations made by Salzer and

co-workers (see ref 22c), we assume that it is eliminated as the cyclic

dioleﬁn 1,6-dimethyl-1,5-cyclooctadiene. (b) Attempts to generate

related tricarbonyl species by bubbling carbon monoxide into toluene

solutions of 3a−f, both at room temperature and at 60 °C, failed. In all

the cases, the starting materials were recovered unchanged.

(

14) Isomers O could result from the rearrangement of the

guanidinate ligand via a 1,3-hydrogen shift, a process known in the

chemistry of metal guanidinates. See, for example, ref 4b and:

(

a) Mullins, S. M.; Duncan, A. P.; Bergman, R. G.; Arnold, J. Inorg.

Chem. 2001, 40, 6952−6963. (b) Zhang, J.; Cai, R.; Weng, L.; Zhuo,

X. Organometallics 2004, 23, 3303−3308. (c) Qian, C.; Zhang, X.; Li,

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(

24) See, for example: (a) Cadierno, V.; Crochet, P.; Dıe

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́ ́

(

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(

c) Cadierno, V.; Dıe

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16) For [( PrHN) C(NHPh)][Cl] (4a) and [( PrHN) C(NH-4-

2 2

C H F)][Cl] (4b) two crystallographically independent cation−anion

pairs were found in the asymmetric unit with very similar structural

parameters (see Figures S2 and S3 in the Supporting Information).

For brevity, only one of these pairs is represented in Figure 7 and only

its bond distances and angles are presented.

17) See, for example: (a) Said, F. F.; Ong, T. G.; Yap, G. P. A.;

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(

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a) da Costa, A. P.; Mata, J. A.; Royo, B.; Peris, E. Organometallics

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(

A.; Richeson, D. Cryst. Growth Des. 2006, 6, 1848−1857. (d) Li, D.;

Wang, Y.; Zhang, W.-X.; Zhang, S.; Guang, J.; Xi, Z. Organometallics

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ligands L usually results in the formation of equatorial [RuCl (η :η -

C H )L] adducts (see ref 11a and references cited therein), in the

case of nitriles, an axial coordination has also been previously

(

010, 29, 1832−1838. (b) Azua, A.; Sanz, S.; Peris, E. Organometallics

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A.; Suar

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(

Organometallics 2014, 33, 6294−6297.

20) (a) We must note that attempts to synthesize the

(27) We must point here that, although the dimer [{RuCl(μ-Cl)

corresponding Ru(IV) guanidinate complex [RuCl{κ (N,N′)-C(N-4-

(η :η -C10H16)} ] (1) is itself one of the most active catalysts known

for the redox isomerization of allylic alcohols in water, its eﬀectiveness

in THF is very low. Indeed, in the absence of base, it was only able to

C H CN)(N Pr)-NH Pr}(η :η -C H )] (3j) by reacting the dimer

10 16

[

{RuCl(μ-Cl)(η :η -C H )} ] (1) with a 2-fold excess of the lithium

DOI: 10.1021/acs.organomet.5b00070

Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

reach a TOF value of 20 h⁻in the isomerization of 1-octen-3-ol. See

ref 11a.

(

28) (a) Other allylic alcohols, such as CH CHCH(OH)R (R =

H, Me, Et, Pr, Bu) and MeCHCHCH(OH)Me, were subjected to

the action of the complex [RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}

(

η :η -C H )] (3f) under identical reaction conditions, and

10 16

quantitative formation of the corresponding carbonyl compounds

was in all cases observed in short times (from 10 to 30 min; TOF =

−1

00−1200 h ). (b) In complete accord with our previous results

using compounds D, the novel (arene)ruthenium(II) complex 7 was

also active in the base-free redox isomerization of 1-octen-3-ol. Using a

ruthenium loading of 0.5 mol % and performing the catalytic reaction

in THF at 80 °C, quantitative formation of octan-3-one was observed

−1

after 15 min (TOF = 800 h ). (c) As previously observed with the

arene)ruthenium(II) complexes D, the activity of the Ru(IV)

(

complexes [RuCl{κ (N,N′)-C(NR)(N Pr)-NH Pr}(η :η -C H )]

(

performed in the presence of HCl. For example, 8 h was needed to

3a−f) decreases signiﬁcantly when the catalytic reactions are

quantitatively transform 1-octen-3-ol into octan-3-one with 3f (0.5 mol

) when 1 mol % of HCl (Et O solution) was introduced into the

reaction medium (10 min required under acid-free conditions; see

entry 6 in Table 1). This fact suggests that, as previously proposed for

complexes D (see ref 3), the pendant amino NH Pr group of the

guanidinate ligands acts as an internal base, facilitating the generation

of the more coordinating oxo-allyl anion by deprotonation of the

allylic alcohol.

(

29) Evidence for the proposed chloride dissociation during catalysis

has been gained by measuring the molar conductivities of complexes

a−f in THF/1-octen-3-ol (20/1 v/v) solvent mixtures. Thus, despite

their neutral nature, molar conductivity values ranging from 10 (3b) to

−

−1

8 (3d) Ω cm mol were observed. This fact strongly supports that

partial dissociation of the chloride ligand to form cationic species takes

place in solution.

(

30) (a) Porri, L.; Gallazzi, M. C.; Colombo, A.; Allegra, G.

Tetrahedron Lett. 1965, 47, 4187−4189. (b) Salzer, A.; Bauer, A.;

Geyser, S.; Podewils, F. Inorg. Synth. 2004, 34, 59−65.

(

31) Bennett, M. A.; Huang, T.-N.; Matheson, T. W.; Smith, A. K.

Inorg. Synth. 1982, 21, 74−78.

Pro

(

32) CrysAlis CCD & CrysAlis RED; Oxford Diﬀraction Ltd.,

Oxford, U.K., 2008.

(

33) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837−838.

34) Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.;

Cascarano, G. L.; Caro, L. D.; Giacovazzo, C.; Polidori, G.; Spagna, R.

J. Appl. Crystallogr. 2005, 38, 381−388.

(

35) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;

Burla, M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27,

35−436.

36) Sheldrick, G. M. SHELXL97: Program for the Reﬁnement of

Crystal Structures; University of Gottingen, Gottingen, Germany, 1997.

37) International Tables for X-Ray Crystallography; Kynoch Press:

(

Birmingham, U.K., 1974; Vol. IV (present distributor: Kluwer

Academic Publishers, Dordrecht, The Netherlands).

(38) Nardelli, M. Comput. Chem. 1983, 7, 95−97.

(39) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.

(40) Macrae, C. F.; Bruno, I. J.; Chisholm, J. A.; Edgington, P. R.;

McCabe, P.; Pidcock, E.; Rodriguez-Monge, L.; Taylor, R.; van de

Streek, J.; Wood, P. A. J. Appl. Crystallogr. 2008, 41, 466−470.

(

41) Persistence of Vision Ray Tracer (POV-Ray), version 3.6; www.

povray.org.

DOI: 10.1021/acs.organomet.5b00070

Organometallics XXXX, XXX, XXX−XXX

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Article Doi

Reactivity of the Dimer [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (C10H16 = 2,7-Dimethylocta-2,6-diene-1,8-diyl) toward Guanidines: Access to Ruthenium(IV) and Ruthenium(II) Guanidinate Complexes

DOI: 10.1021/acs.organomet.5b00070

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