Octahedral RuII complexes with [PNO] hydrazonic ligands: Synthesis, structure, reactivity and catalytic activity in the addition of benzoic acid to alkynes

FULL PAPER

DOI: 10.1002/ejic.200600016

Octahedral Ru^IIComplexes with [PNO] Hydrazonic Ligands: Synthesis,

Structure, Reactivity and Catalytic Activity in the Addition of Benzoic Acid to

Alkynes

Paolo Pelagatti,*^[a]Alessia Bacchi,^[a]Marcella Balordi,^[a]Sandra Bolaño,^[b][‡]

Francesca Calbiani,^[a]Lisa Elviri,^[a]Luca Gonsalvi,*^[b]Corrado Pelizzi,^[a]

Maurizio Peruzzini,^[b]and Dominga Rogolino^[a]

Keywords: Tridentate ligands / Ruthenium / Homogeneous catalysis / Enol esters / Mass spectrometry

A series of Ru^IIcomplexes containing [(H)PNO] hydrazonic

ligands were synthesised using different ruthenium sources

such as [Ru(PPh₃)₃Cl₂], [Ru(dmso)₄Cl₂] and [Ru(p-cymene)

Cl₂]₂. The complexes were characterised by ¹H NMR, ³¹P{¹H}

NMR, IR, FAB-MS, microanalysis and in some cases by X-

ray diffraction analysis on a single crystal. The ligands show

a great variety of different coordinating behaviours such as

κ³-(H)PNO, κ²-(H)PN, κ¹-(H)P and κ³-PNO, depending on

the ruthenium precursor and on the synthetic experimental

conditions. The complexes trans-[Ru(κ³-(H)PNO)(PPh₃)Cl₂]

reacted with dmso to give the bis-chelate complex [Ru(κ³-

PNO)₂], [Ru(dmso)₄]Cl₂, OPPh₃, HCl and Me₂S, through an

oxygen-transfer reaction from dmso to PPh₃. A catalytic ver-

sion of this reaction was also developed. The complexes ob-

tained from [Ru(PPh₃)₃Cl₂] were tested as homogeneous pre-

catalysts for the coupling between benzoic acid and terminal

alkynes to give the corresponding enol esters. High stereo-

and regio-selectivity, up to 100% (determined by ¹H NMR),

in favour of the (Z)-anti-Markovnikov products (Z)-alk-1-en-

1-yl benzoate was observed. An ESI-MS monitoring of the

catalytic couplings revealed that the enol ester formation oc-

curs through an intermolecular attack of an external carbox-

ylate anion onto a vinylidene–Ru intermediate of the type

[Ru(PNO)(PPh₃)(C=CH–C₄H₉)Cl].

Germany, 2006)

reactive the metal complex exerting, at the same time, a

control upon the accessibility at the metal for an incoming

substrate. This last feature can be determinant for the selec-

tivity of the catalytic process. When the [PNO] ligand is

protic, as in the case of the acyl hydrazones, a further con-

trol on the hemilability of the ligand, from a κ³-(H)PNO

coordination to a κ²-(H)PN one, as well as on the nucleo-

philicity of the metal, can be exerted as a function of the

anionic or neutral character of the ligand.^[5]

As our ongoing research on the use of protic [PNO] acyl

hydrazones as ligands in the synthesis of transition-metal-

containing complexes,^[5]we have undertaken a study on the

coordinating behaviour of 2-(diphenylphosphanyl)benzal-

dehyde benzoylhydrazone (Hbidf) and 2-(diphenylphos-

phanyl)benzaldehyde acetylhydrazone (Haidf) (Scheme 1),

towards Ru^II.

Introduction

The use of potentially tridentate [PNO] ligands in the

synthesis of transition-metal complexes is scarcely described

in the literature.^[1]However, Ru^IIcomplexes with [PNO] li-

gands have been shown to be active catalysts in the transfer

hydrogenation of ketones,^[2]and some of us have reported

that [Pd(PNO)(OAc)] and [Pd(PNO)Cl] complexes [PNO =

acylhydrazones] promote the catalytic homogeneous hydro-

genation of alkenes^[3]and the semi-hydrogenation of ter-

minal alkynes,^[4]respectively. The use of [PNO] ligands for

the preparation of homogeneous catalysts containing soft

transition metals, is based on two assumptions: i) that the

chelating PN unit stabilizes the metal fragment under the

catalytic conditions and ii) that the labile M–O bond makes

[a] Dipartimento di Chimica Generale ed Inorganica, Chimica An-

alitica, Chimica Fisica, Università degli Studi di Parma,

Parco Area delle Scienze 17/A, 43100 Parma, Italy

E-mail: paolo.pelagatti@unipr.it

[b] Istituto di Chimica dei Composti Organometallici, Consiglio

Nazionale delle Ricerche (ICCOM-CNR),

via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze,

Italy

E-mail: l.gonsalvi@iccom.cnr.it

[‡] Current address: Universidad de Vigo, Facultad de Ciencias

(Químicas), Campus Universitario, 36310 Lagoas Marcosende,

Vigo, Spain

Supporting information for this article is available on the

WWW under http://ww w .eurjic.org or from the author.

Scheme 1.

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Ru^IIComplexes with Hydrazonic Ligands

FULL PAPER

The two ligands have been reacted with [Ru(PPh₃)₃Cl₂] taining tridentate ligands for this particular coupling reac-

under different reaction conditions, in order to isolate neu- tion, we have decided to test the complexes deriving from

tral or ionic complexes containing the ligands in either pro- the combinations of Hbidf and Haidf with [Ru(PPh₃)₃Cl₂]

tonated or deprotonated form. All the complexes have been as pre-catalysts in the addition of benzoic acid to terminal

fully characterised by a number of analytical and spectro- alkynes. Aiming at detecting the organometallic intermedi-

scopic techniques and, in several cases, by X-ray diffraction ates involved in the catalytic cycle, an ESI-MS study has

analysis on a single crystal. In order to elucidate the reactiv- been performed. ESI-MS technique allows for the detection

ity shown by the complexes of the type [Ru(κ³- of species at low concentration in solution and this makes

HPNO)(PPh₃)Cl₂] with dmso, the syntheses and the charac- it attractive to define the mechanism of metal-promoted

terisations of various Ru complexes obtained by reactions catalytic transformations. It has been successfully employed

of Hbidf with [Ru(dmso)₄Cl₂] and [Ru(p-cymene)Cl₂]₂are in different reactions, such as the reduction of ketones,^[20]

also reported.

epoxidations,^[21]olefins polymerisation^[22]and C–H bonds

Ruthenium is certainly one of the mostly used transition activation.^[23]To the best of our knowledge, this is the first

metals in homogeneous catalysis.^[6]The Ru-promoted coup- report dealing with the application of such a technique for

ling between benzoic acid and terminal alkynes (Scheme 2) the study of the addition of carboxylic acids to alkynes.

is an elegant way to produce vinyl esters, which find indus-

trial applications as polymerising substrates^[7]and acylating

reagents for the synthesis of amides^[8]and halogenated

ketones;^[9]other applications include cyclopropanation,^[10]

1,3-dipolar cycloaddition,^[11]asymmetric hydrogenation^[12]

and hydroformylation reactions.^[13]

Results and Discussion

Selected spectroscopic data (³¹P{¹H}NMR, ¹H NMR

and FT-IR) of the complexes reported in this work are col-

lected in Table 1.

Ru Complexes Obtained from [Ru(PPh₃)₃Cl₂]

The free ligands Hbidf and Haidf react with a stoichio-

metric amount of [Ru(PPh₃)₃Cl₂] in dichloromethane at

room temperature, leading to the neutral dichloride com-

plexes trans-[Ru(κ³-(H)PNO)(PPh₃)Cl₂], which were iso-

lated as purple solids in good yields (1 and 2 in Scheme 3,

respectively).

The neutral hydrazones coordinate in a tridentate fash-

ion by means of the P, N_imineand O donors. The neutral

behaviour of the ligands is indicated by the IR stretching

bands of the N–H bonds (3148 and 3145 cm^–1for 1 and 2,

respectively), while the involvement of the carbonyl group

in the coordination is pointed out by the shift to lower

Scheme 2.

The first report describing this reaction dates back to wavenumbers of the C=O stretching band (1629 cm^–1for

1983^[14]and deals with the use of Ru₃(CO)₁₂in the coupling both complexes) with respect to the free ligands (1652 and

of aliphatic and aromatic carboxylic acids to di- and mono- 1678 cm^–1for Hbidf and Haidf, respectively). The octahe-

substituted acetylenes. Later on, the process has been devel- dral coordinations are completed by a PPh₃molecule and

oped by Mitsudo,^[15]Dixneuf^[16]and Verpoort,^[17]although by two chloride ligands. The FAB-MS spectra and the ele-

other groups have been and are still involved in the field.^[18]mental analyses confirm the proposed stoichiometries. The

From the literature it can be inferred that the combination complexes 1 and 2 are poorly soluble in chloroform, dichlo-

of monodentate phosphanes with different Ru sources gen- romethane, THF, toluene, acetonitrile and methanol, while

erally yields to the Markovnikov product,^{[15,16a,16b,19]}al- they readily dissolve in strongly coordinating solvents, like

though in some cases the selectivity can be switched to the dmso and dmf. Based on the reactivity of 1 observed in

anti-Markovnikov product by replacing inorganic bases warm acetonitrile (vide infra), we suppose that the solution

with organic (coordinating) ones, such as pyridine deriva- of 1 and 2 in dmso or dmf occurs by breaking of a Ru–Cl

tives.^[18]The same trend has been described by Dixneuf re- bond and formation of the cationic complexes [Ru(κ³-(H)-

placing mono- with chelating phosphanes^[16d]and by Ver- PNO)(PPh₃)(S)Cl]Cl (1a and 2a, S = dmso or dmf). The ¹H

poort adding phosphanes to N-heterocyclic carbene com- NMR spectra of the freshly prepared samples recorded in

plexes.^[17d]With this in our mind, we have argued that the [D₆]dmso show singlets belonging to the hydrazonic pro-

high chelation degree of the acyl hydrazones could induce tons at δ = 14.11 and 13.65 ppm for 1a and 2a, respectively,

a good selectivity towards the anti-Markovnikov products, while the HC=N protons give rise to doublets at δ =

thus leading to the formation of the less commonly ob- 9.14 ppm and 8.69 ppm, respectively. The somewhat high

tained isomer. In order to test this hypothesis and because ⁴J_PHvalues of 7.5 and 7.7 Hz for 1a and 2a, respectively,

of the lack of data concerning the use of pre-catalysts con- corresponding to the couplings between the iminic protons

Eur. J. Inorg. Chem. 2006, 2422–2436

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2423

P. Pelagatti, L. Gonsalvi et al.

IR [cm^–1]^[b]

FULL PAPER

Table 1. Selected spectroscopic signals of the Ru complexes.

Complex

³¹P{¹H} NMR^[a]

PPh₂

¹H NMR [δ]^[a]

N–H

PPh₃

²J_PP[Hz]

HC=N [⁴J_PH

]

ν(NH)

ν(C=O)

1

3148 (w)

1629 (s)

1a^[c]

1b^[c]

1c

2

63

49

54

39.1

32

34

32

26.5

30

14.11

9.14 (7.5)

9.14 (8.2)

3145 (w)

1629 (s)

2a^[c]

2b^[c]

3

65.3

53.1

56.1

54.9

59.3

56.4

57.9

55.5

54.8

50.4

57.7 (s)

45.5 (s)

61 (s)

29.6

40.8

33.9

38.6

37.4

40

35.6

38.3

37.7

38.3

30.8

31

28

24

29

27

24

28

22

br. s

13.65

8.69 (7.7)

–

9.06 (8.1)

8.85 (br)

9.24 (8.1)

8.88 (br)

9.12 (7.2)

7.69 (br)

9.04 (8.1)

8.87 (br)

9.18 (s)

absent

3168 (w)

3180 (w)

3259 (w)

3267 (w)

absent

3294 (w)

3156 (w)

3311 (w)

absent

1624 (s)

1625 (s)

1612 (m)

1630 (m)

absent

1674 (s)

1594 (s)

1696 (s)

4

5

n.d.

14.31

n.d.

10.53

–

11.24

10.34

10.31

6

7

8

9

10

12

13

14

15

9.15 (s)

8.53 (s)

9.08 (s)

[a] CD₂Cl₂. [b] KBr disks. [c] [D₆]dmso.

the other two pairs of doublets have diminished. Finally,

after 48 hours the spectrum shows only the singlets at δ =

2

55 and 29 ppm. The low J_PPvalues of the two transient

pairs of doublets indicate the formation of two labile Ru

complexes containing two mutually cis phosphanes, while

the final singlets are ascribable to OPPh₃(singlet at δ =

29 ppm^[25]) and to the bis-chelate complex [Ru(bidf)₂] (12,

singlet at δ = 55 ppm). The presence of 12 is confirmed by

ESI-MS analysis of the warm dmso solution by a cluster at

m/z = 917. Complex 12 can be prepared by reaction be-

tween [Ru(PPh₃)₃Cl₂] or [Ru(dmso)₄Cl₂] with a twofold ex-

cess of Hbidf (vide infra) in the presence of a base. Its

³¹P{¹H}-NMR spectrum shows a singlet at δ = 57.7 ppm,

which is in good agreement with the value observed for the

in situ formed complex. On the basis of the aforementioned

observations we propose that the 1 Ǟ 12 transformation

occurs in agreement with Scheme 4.

Scheme 3.

and the P atoms of the PPh₃(as established by heteronuc-

1

lear H-³¹P correlation), are indicative of a PPh₃molecule

trans to the HC=N function.^[24]The chloride ligand and

dmso occupy the apices of the octahedron. The stereoselec-

tivity of the reaction is indicated by ³¹P{¹H}-NMR spec-

troscopy by two doublets centred at 63 and 39.1 ppm for 1a

Although the detection of (CH₃)₂S is made difficult by

and 65.3 and 40.8 ppm for 2a. The more shielded signals its volatility, a singlet at δ = 2.08 ppm is observed during

are generated by the PPh₃ligands, while the signals at lower ¹H NMR monitoring of the reaction. The same technique

fields are generated by the hydrazonic phosphorus nuclei.^[24]has allowed the detection of [Ru(dmso)₄Cl₂]: by repeating

The small ²J_PPvalues of 32 and 31 Hz for 1a and 2a, respec- the 1 Ǟ 12 transformation in dmso, after the complete re-

1

tively, are in agreement with a cis arrangement of the two moval of the solvent, the H NMR spectrum of the solid

P atoms. The isolation of the cationic complexes 1a and 2a residue recorded in CDCl₃shows, apart from the signals

is not possible because of their reactivity with dmso, as ascribable to 12, singlets in the region 3.47–2.25 ppm, in-

shown by NMR spectroscopy. In fact, on keeping the NMR dicative of the presence of a mixture of trans- and cis-

sample of 1a at room temperature overnight, two additional [Ru(dmso)₄Cl₂].^[26]The 1 Ǟ 12 transformation must neces-

³¹P{¹H}-NMR doublets appear, centred at δ = 49 and sarily occur through the transfer of a PNO ligand from a

32 ppm (²J_PP= 26.5 Hz). Moreover, two small singlets at δ Ru nucleus to another one. Thus, the changes observed in

= 53 and 27 ppm are also visible (see Supporting Infor- the ³¹P{¹H}-NMR spectrum of 1a in dmso may be tenta-

mation; see also the footnote on the first page of this arti- tively explained as follows (Scheme 4): dmso reacts with 1a

cle). When the tube is warmed at 50 °C for 6 hours, the new causing the displacement of the C=O group of the ligand

signals grow at the expenses of those belonging to the start- giving rise to [Ru(κ²-(H)PN)(PPh₃)(dmso)₂Cl]Cl (1b). Com-

ing complex, and an additional pair of doublets centred at plex 1b gives rise to the pair of doublets at δ = 49 and

δ = 54 and 34 ppm (²J_PP= 30 Hz) appears. After 16 hours 32 ppm, where the more shielded signal is due to PPh₃while

at 50 °C, the main signals are still those of 1a, but the sing- the other is due to the PPh₂moiety. The chemical shift of

lets at δ = 53 and 27 ppm have grown considerably while 49 ppm is similar to that found for 13 (δ =45.5 ppm, vide

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Eur. J. Inorg. Chem. 2006, 2422–2436

Ru^IIComplexes with Hydrazonic Ligands

FULL PAPER

Scheme 4.

infra), where Hbidf coordinates in a (H)PN bidentate fash- indicated by ³¹P{¹H}-NMR spectroscopy (disappearance of

ion. The simple isomerisation of 1b due, for example, to the the PPh₃signal at –7.5 ppm in favour of the OPPh₃signal

shift of PPh₃from the plane to an apex of the octahedron at δ = 26.8 ppm). A similar behaviour is conjecturable also

is ruled out by the ¹H NMR monitoring of the process: the for complex 2, although its reactivity in dmso has not been

HC=N function of 1b gives rise to a doublet centred at δ = investigated in details. It is worth noting that this step-by-

9.14 ppm with a ⁴J_PHof 8.02 Hz, indicative of a PPh₃trans step ligand decoordination probably corresponds to the re-

to the imine function. The reaction continues with the deco- versed way the ligand approaches the metal, a process not

ordination of the imine nitrogen from ruthenium which is always easy to envision with polydentate ligands. The key-

replaced by an additional molecule of dmso (probably fav- role played by dmso in the 1 Ǟ 12 transformation is evi-

oured by the trans effect of PPh₃), with formation of com- denced by the different reactivity shown by 1 in acetonitrile

plex 1c in which the neutral ligand coordinates in an uni- at 50 °C. After 4 hours an almost clear solution has been

dentate fashion through the P atom, giving rise to the pair obtained and the work-up has led to the cationic mono-

of doublets at δ = 54 and 34 ppm. Although one would chelate complex [Ru(κ³-(H)PNO)(PPh₃)(CH₃CN)Cl]Cl

expect a decrease of the chemical shift on passing from 1b (11). The neutral character of the ligand is clearly pointed

1

to 1c due to the loss of the chelation ring,^[27]a chemical out by the IR and H NMR spectra with a weak band at

shift around 50 ppm is not unusual for Ru complexes con- 3173 cm^–1and a singlet at δ = 10.48 ppm, respectively. The

taining coordinated monophosphanes and dmso.^[28]More- coordinated acetonitrile gives rise to a weak IR band at

1

over, the ability of Hbidf to coordinate Ru in a P-mono- 2273 cm^–1and a singlet at δ = 1.31 ppm in the H NMR

dentate mode is confirmed by the complex [(η⁶-p-cymene)- spectrum. Complex 11 decomposes within 24 hours in solu-

Ru(κ¹-(H)P)Cl₂]·3/2CHCl₃(15, vide infra) obtained by the tion and within 24–48 hours in the solid state, without evi-

reaction of Hbidf with [Ru(p-cymene)Cl₂]₂. Finally, 1c fur- dencing the formation of 12.

ther transforms, through a not yet defined pathway, into

Treatment of a toluene suspension of 1 or 2 with an ex-

[Ru(dmso)₄Cl₂], OPPh₃, (CH₃)₂S, HCl and 12. PPh₃oxi- cess of triethylamine in the presence of acetonitrile, leads to

dation then occurs through the dmso reduction to dimethyl the isolation of the neutral monochloride complexes [Ru(κ³-

sulfide. The metal ion-mediated deoxygenation of coordi- PNO)(PPh₃)(CH₃CN)Cl] (3 and 4 in Scheme 5) as yellow

nated sulfoxides has been observed with different metals.^[29]solids in good yields. The reactions occur with the substitu-

The most intensively studied systems are based on oxorhen- tion of a chloride ligand (precipitated as Et₃NHCl) with an

ium^[30]and oxomolybdenum compounds,^[25,31]the last also acetonitrile molecule.

being good models of the enzymes belonging to the dmso

The anionic character of the ligand is indicated by the

reductase class.^[32]To the best of our knowledge, the only disappearance of the spectroscopic signals of the N–H and

article dealing with the deoxygenation of dmso promoted C=O bonds.^[5]The coupling constants between the P nuclei

by ruthenium has been reported by James, describing the are again small (24 Hz) to indicate a cis arrangement of the

reaction of RuCl₃·3H₂O with dmso at high temperatures PPh₃and PPh₂moieties, while the iminic protons give rise

in the presence of HCl or HBr;^[33]in those cases however, to doublets with appreciable J_PHvalues indicative of a

although dimethyl sulfide complexes were isolated, the na- HC=N group trans to a PPh₃(Table 1). The coordinated

4

[24]

ture of the reductants remained unknown. Interestingly, the acetonitrile gives a singlet at δ = 1.21 ppm in both com-

oxygen transfer from dmso to PPh₃promoted by 1 can be plexes. The FAB-MS spectrum of 3 shows a cluster centred

made catalytic by dissolving the complex in dmso and heat- at m/z = 806 corresponding to the [Ru(κ³-PNO)(PPh₃)Cl]⁺

ing the solution at 100 °C in the presence of a 100-fold ex- fragment, while in the FAB-MS spectrum of 4 the molecu-

cess of PPh₃; the reaction is complete within 20 hours as lar peak is visible at m/z = 786. By slow evaporation of a

Eur. J. Inorg. Chem. 2006, 2422–2436

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2425

P. Pelagatti, L. Gonsalvi et al.

FULL PAPER

in 4 the Ru–P bond is significantly longer [2.2951(3) Å], and

can accommodate for ring planarity. By contrast, even if

the Ru–O bond [2.1177(5) Å] is longer than the Pd–O bond

(2.065 Å) in the [Pd(aidf)(OAc)] analogue,^[3]the ligand

bond lengths along the five-membered chelation ring are

very close to those observed in the palladium complex,

from which they do not deviate by more than 0.013 Å. The

molecular association in the crystal is based on dimeric ag-

gregates composed by two complexes related by a crystallo-

graphic twofold axis, linked by two water molecules which

act as hydrogen-bond donors towards chloride and nitrogen

as shown in Figure 2 [O2···N2: 2.883(2) Å, O2–H···N2:

149.7(6)°; O2···Cl(i): 2.232(1) Å, O2–H···Cl(i): 152.6(4)°, i:

y, x, 1–z]. This pattern is conserved in the related structure

of 6.

The dichloride complexes 1 and 2 suspended in a dichlo-

romethane/acetonitrile mixture react with an excess of

KPF₆or NaBPh₄leading to the cationic monochloride

complexes [Ru(κ³-(H)PNO)(PPh₃)(CH₃CN)Cl][X] [HPNO

= Hbidf, X = PF₆(5), X = BPh₄(7); HPNO = Haidf, X =

PF₆(6), X = BPh₄(8)] and precipitation of KCl or NaCl,

respectively (Scheme 6).

Scheme 5.

dichloromethane/acetonitrile mixture of 4, crystals suitable

for X-ray diffraction have been collected, and the structure

of the complex has been unequivocally confirmed. Com-

pound 4 crystallises with the inclusion of two water mole-

cules in the asymmetric unit, which take part in the packing

interactions. In 4 the Ru atom is hexacoordinate by the tri-

dentate deprotonated PNO (aidf^–) ligand, one tri-

phenylphosphane, trans to the N donor, one chloride and

one acetonitrile molecule, trans each other, in an irregular

octahedral geometry. The molecular structure is shown in

Figure 1, along with the labelling scheme, while the most

relevant geometric features are collected in Table 2.

As can be inferred from Table 1, the spectroscopic char-

acterisation indicates that the ligands have not varied their

coordinating behaviour with respect to the dichloride pre-

cursors, and that the PPh₃ligands are still trans to the

HC=N moieties [the ³¹P{¹H}-NMR signals range from 55.5

to 59.3 ppm for the PPh₂moiety, and from 35.6 to 40.0 ppm

2

for the PPh₃ligand, with J_PPvalues ranging from 24.6 to

29 Hz; the ⁴J_PHvalues range from 7.2 to 8.1 Hz]. The apices

of the octahedron are occupied by the residual chloride and

by an acetonitrile molecule, whose presence is confirmed by

1

IR (stretching band in the region 2265–2281 cm^–1) and H

NMR spectroscopy (singlets ranging from 0.43 to

1.70 ppm). The [PF₆]^–anions originate, in the ³¹P{¹H}-

NMR spectra, multiplets centred at –141.1 and –145.5 ppm,

for 5 and 6, respectively, while in the IR spectra they give

rise to an intense band at 845 cm^–1. The presence of the

[BPh₄]^–anion in 7 and 8 is pointed out by IR bands at

about 850 cm^–1. The structure of 6 has been unequivocally

established by X-ray diffraction analysis conducted on a

single crystal grown in a CH₂Cl₂/n-pentane mixture. In

compound 6, the [Ru(Haidf)]⁺cation (Figure 3) is arranged

identically to the related deprotonated neutral complex 4.

The comparison between the two molecules (Figure 4,

Table 2) may help to investigate the effect of protonation

on [Ru(aidf)(PPh₃)(CH₃CN)Cl]. The protonation of the hy-

drazonic nitrogen N2 seems to localize a larger double-

bond character on the carbonylic bond, which shortens by

Figure 1. Perspective view and labelling scheme of compound 4.

Rings C16–C21 and C28–C33 are labelled only on the ipso carbon

for clarity. Thermal ellipsoids at the 50% level.

The tridentate PNO coordination of aidf^–gives rise to 0.055 Å, while at the same time the adjacent C(O)–N bond

two chelation rings, which are both planar within 0.06 Å. elongates by 0.016 Å. Moreover, in the cationic complex 6

The planarity of the six-membered chelation ring contain- the Ru–O bond is longer than in 4 by 0.028 Å, while Ru–P

ing P1 contrasts with the behaviour generally observed in bond is slightly shorter (0.017 Å). The shortening of the

the family of the similar Pd(aidf) and Pd(bidf) complex- Ru–P bond is accompanied by a slight distortion from plan-

es,^[3,5c]where the chelation ring is puckered and the phos- arity of the six-membered chelation ring, as P1 deviates by

phorus donor is remarkably out of the average ring plane 0.14 Å from the ring plane. The [Ru(Haidf)]⁺cations are

(values ranging between 0.38 and 0.52 Å). In fact, in the Pd assembled in dimeric units (Figure 5) by N–H···Cl hydrogen

series the Pd–P distances range from 2.184 to 2.212 Å, while bonds [N2···Cl(ii): 3.300(6) Å, N2–H···Cl(ii): 149(7)°,

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Ru^IIComplexes with Hydrazonic Ligands

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Table 2. Bond lengths [Å] and angles [°] for compounds 4, 6, 12·dmso·H₂O, 15·1.5CHCl₃, with standard uncertainties in parentheses. In

15·1.5CHCl₃C_Tdenotes the centroid of the p-cymene ring.

Compound 4

Ru–N(3)

Ru–N(1)

Ru–O(1)

Ru–P(1)

Ru–P(2)

Ru–Cl

N(1)–C(7)

N(1)–N(2)

N(2)–C(8)

O(1)–C(8)

1.995(2)

2.075(1)

2.118(1)

2.2950(5)

2.3688(5)

2.4222(5)

1.290(2)

1.406(2)

1.310(3)

1.295(2)

P(1)–C(1)

C(1)–C(6)

C(6)–C(7)

N(3)–Ru–N(1)

N(3)–Ru–O(1)

N(1)–Ru–O(1)

N(3)–Ru–P(1)

N(1)–Ru–P(1)

O(1)–Ru–P(1)

N(3)–Ru–P(2)

1.845(2)

1.405(3)

1.457(3)

89.26(6)

84.94(6)

77.13(5)

90.07(5)

92.97(4)

168.94(4)

90.10(5)

N(1)–Ru–P(2)

O(1)–Ru–P(2)

P(1)–Ru–P(2)

N(3)–Ru–Cl

N(1)–Ru–Cl

O(1)–Ru–Cl

P(1)–Ru–Cl

P(2)–Ru–Cl

166.42(4)

89.30(4)

100.60(2)

171.58(5)

85.66(4)

87.368(4)

96.89(2)

93.25(2)

Compound 6

Ru–N(3)

Ru–N(1)

Ru–O(1)

Ru–P(1)

Ru–P(2)

Ru–Cl

N(1)–C(7)

N(1)–N(2)

N(2)–C(8)

O(1)–C(8)

2.001(6)

2.073(5)

2.147(4)

2.278(2)

2.385(2)

2.398(2)

1.277(8)

1.411(7)

1.325(8)

1.241(7)

P(1)–C(1)

C(1)–C(6)

C(6)–C(7)

N(3)–Ru–N(1)

N(3)–Ru–O(1)

N(1)–Ru–O(1)

N(3)–Ru–P(1)

N(1)–Ru–P(1)

O(1)–Ru–P(1)

N(3)–Ru–P(2)

1.845(6)

1.410(9)

1.44(1)

87.0(2)

84.9(2)

77.6(2)

89.0(2)

91.3(1)

167.6(1)

94.4(2)

N(1)–Ru–P(2)

O(1)–Ru–P(2)

P(1)–Ru–P(2)

N(3)–Ru–Cl

N(1)–Ru–Cl

O(1)–Ru–Cl

P(1)–Ru–Cl

P(2)–Ru–Cl

165.2(1)

87.8(1)

103.48(6)

172.2(2)

86.7(1)

89.2(1)

95.72(6)

90.47(6)

Compound 12·dmso·H₂O

Ru–N(3)

Ru–N(1)

Ru–O(1)

Ru–O(2)

Ru–P(1)

2.030(3)

N(2)–C(8)

N(3)–C(33)

N(3)–N(4)

N(4)–C(34)

C(1)–C(6)

C(6)–C(7)

C(27)-C(32)

C(32)–C(33)

N(3)–Ru–N(1)

N(3)–Ru–O(1)

N(1)–Ru- = (1)

N(3)–Ru–O(2)

1.316(4)

1.288(4)

1.419(4)

1.310(4)

1.411(4)

1.463(5)

1.425(4)

1.458(5)

171.9(1)

96.3(1)

N(1)–Ru–O(2)

O(1)–Ru–O(2)

N(3)–Ru–P(1)

N(1)–Ru–P(1)

O(1)–Ru–P(1)

O(2)–Ru–P(1)

N(3)–Ru–P(2)

N(1)–Ru–P(2)

O(1)–Ru–P(1)

O(2)–Ru–P(2)

P(1)–Ru–P(2)

95.6(1)

2.034(3)

2.109(2)

2.120(2)

2.2503(9)

2.2553(9)

1.829(3)

1.826(3)

1.288(4)

1.292(4)

1.409(3)

80.65(9)

94.58(8)

90.67(8)

166.22(7)

93.35(7)

90.79(8)

94.90(8)

93.28(7)

166.49(7)

90.05(3)

Ru–P(2)

P(1)–C(1)

P(2)–C(27)

O(1)–C(8)

O(2)–C(34)

N(1)–C(7)

N(1)–N(2)

77.7(1)

78.0(1)

Compound 15·1.5CHCl₃

Ru–C_T

1.698(1)

P–C(21)

1.857(9)

1.231(16)

1.39(2)

1.31(3)

1.26(3)

1.35(2)

1.47(2)

C_T–Ru–P

132.3(1)

125.6(1)

85.0(2)

124.3(1)

89.1(2)

86.0(1)

Ru–C(31)

Ru–C(28)

Ru–P

Ru–Cl(2)

Ru–Cl(1)

P–C(1)

2.27(2)

2.28(2)

2.374(5)

2.380(4)

2.422(5)

1.81(2)

N(1)–C(7)

N(1)–N(2)

N(2)–C(8)

O–C(8)

C(1)–C(6)

C(6)–C(7)

C_T–Ru–Cl(2)

P–Ru–Cl(2)

C_T–Ru–Cl(1)

P–Ru–Cl(1)

Cl(2)–Ru–Cl(1)

ii: 1–x, –y, 1–z]; this arrangement recalls the one observed

in 4, where the insertion of a water molecule provides the

bridging element, here constituted by the protonated –NH.

In the case of 6 the dimer is centrosymmetric.

Repeated attempts aimed at obtaining the dicationic

complexes of the type [Ru(κ³-(H)PNO)(PPh₃)(CH₃CN)₂]-

[X₂] by removal of the second chloride from the complexes

5–8 using several halogen scavengers such as KPF₆,

NaBPh₄, AgCF₃SO₃and TlPF₆, have failed due to exten-

sive decompositions or isolation of unknown products, irre-

spective of the amount of scavenger employed.

However, bis-acetonitrile Ru complexes have been ob-

tained by treatment of the cationic mono-chloride com-

plexes 6 and 7 with an excess of Et₃N in the presence of

Figure 2. Association in dimers bridged by hydrogen-bonded water

molecules in the crystal structure of 4.

Eur. J. Inorg. Chem. 2006, 2422–2436

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2427

P. Pelagatti, L. Gonsalvi et al.

FULL PAPER

Figure 5. Association in hydrogen-bonded dimers in the crystal

structure of 6.

Scheme 6.

Scheme 7.

The disappearance of the spectroscopic signals of the N–

H and C=O bonds agrees with the anionic character of the

ligand, while the NMR spectroscopic data similar to those

of the precursors indicate that PPh₃has not moved from its

trans disposition with respect to the imine moiety (Table 1).

The entering of the second molecule of acetonitrile is indi-

Figure 3. Perspective view and labelling scheme of compound 6.

Rings C16–C21, C28–C33 and C34–C39 are labelled only on the

ipso carbon for clarity. Thermal ellipsoids at the 50% level. The

–

PF₆anion has been omitted.

1

cated by H NMR spectroscopy with the appearance of an

additional singlet at δ = 2.37 and 2.34 ppm for 9 and 10,

respectively. These complexes are significantly unstable

both in solution and in the solid state.

Ru Complexes Obtained from [Ru(dmso)₄Cl₂]

In order to understand the nature of the Ru species in-

volved in the 1 Ǟ 12 transformation observed in dmso, the

ligand Hbidf has been reacted with [Ru(dmso)₄Cl₂]. In re-

fluxing EtOH/NaOH [Ru(dmso)₄Cl₂] reacts with a twofold

excess of Hbidf leading to the formation of the bis-chelate

octahedral complex [Ru(bidf)₂] (12) in good yield

(Scheme 8). In complex 12 two deprotonated ligands coor-

dinate Ru in a PNO fashion.

Figure 4. Superimposition of the molecular structure of 4 (aidf^–,

grey) and 6 (Haidf, black) showing the geometric effects due to

protonation of the PNO ligand.

acetonitrile. This procedure leads to the neutral complexes

The disappearance of the spectroscopic signals of the N–

trans-[Ru(κ³-PNO)(PPh₃)(CH₃CN)₂][X] [PNO = bidf, X = H and C=O bonds is indicative of the deprotonation that

BPh₄(9); PNO = aidf, X = PF₆(10)] in good yields occurred in both ligands, while the presence of a singlet at

(Scheme 7).

δ = 57.7 ppm in the ³¹P{¹H}-NMR spectrum is in agree-

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Eur. J. Inorg. Chem. 2006, 2422–2436

Ru^IIComplexes with Hydrazonic Ligands

FULL PAPER

Scheme 8.

ment with two magnetically equivalent phosphorus nuclei. out at room temperature with a Ru/Hbidf = 1:1 molar ratio,

The HC=N proton resonates as a singlet at δ = 9.18 ppm a complex mixture of different products forms, whose sepa-

1

in the H NMR spectrum recorded in CDCl₃, as expected ration and identification has not been possible so far. A

in the absence of a PPh₃ligand. The CI-MS spectrum exhi- clearer picture is instead obtained when the reaction is per-

bits a cluster centred at m/z = 916 (molecular peak). The formed in refluxing ethanol. Two different Ru^IIcomplexes,

structure of 12 has been unequivocally established by X-ray [Ru(κ²-(H)PN)(dmso)₂Cl₂] (13) and [Ru(κ³-(H)PNO)-

diffraction analysis on a single crystal obtained from a (dmso)Cl₂] (14) form as shown in Scheme 8. In complex 13

dmso solution of 13 (vide infra) and is shown in Figure 6. the neutral ligand coordinates the metal in a PN bidentate

Compound 12 crystallises as a 1:1:1 dmso/H₂O solvate. The fashion, as evidenced by IR [ν(N–H) = 3249 cm^–1, ν(C=O)

1

principal geometric features are reported in Table 2. The = 1674 cm^–1] and HNMR (singlet at δ = 11.24 ppm) spec-

most relevant feature in the geometry of [Ru(bidf)₂] is that troscopy.^[4]Two chlorides and two dmso molecules com-

the steric hindrance due to the bis-chelation produces sig- plete the octahedron, as evidenced by the IR [two strong

nificant distortions in the planarity of the two coordinated bands at 1088 and 1019 cm^–1due to the ν(S=O) and δ(C–

1

[PNO] ligands. In fact in both ligands the P atom deviates H), respectively] and H NMR (four singlets in the region

remarkably from the chelation plane (0.64 and 0.59 Å, 3.65–2.84 ppm) spectra as well as by microanalysis. The

respectively), and the Ru–P distances are significantly ³¹P{¹H}-NMR spectrum shows a singlet at δ = 45.5 ppm.

shorter [Ru–P1: 2.2503(9), Ru–P2: 2.2553(9) Å] than in the From a dmso solution of 13 crystals suitable for X-ray

previous mono-chelated complexes (Table 2). By contrast, analysis have been collected. The diffractometric analysis

the five-membered chelation rings are planar within 0.09 Å, shows the formation of the bis-chelate complex 12; this fur-

and the bond lengths along the ring are in agreement with ther mono-chelate Ǟ bis-chelate transformation is not sur-

those observed in the neutral mono-chelate 4. The mutual prising, because compound 13 is structurally similar to 1b,

arrangement of the two ligands in 12·dmso·H₂O favours a a proposed intermediate in the dmso-promoted 1 Ǟ 12

remarkable intramolecular π–π stacking between the rings transformation.

belonging to the ligands main backbone and the diphenyl-

In complex 14 the neutral ligand coordinates in a PNO

phosphane rings, with C···C separation ranging between 3.3 fashion as clearly indicated by the IR bands of the N–H

and 3.9 Å.

(3156 cm^–1) and C=O (1594 cm^–1) groups. The hydrazonic

1

proton gives rise to a singlet at δ = 10.34 ppm in the H

NMR spectrum recorded in CDCl₃, while the ³¹P{¹H}-

NMR spectrum shows a singlet at δ = 61 ppm. The octahe-

dron is completed by two chlorides and a dmso molecule,

while a half dmso molecule is outside of the coordination

1

sphere [the H NMR spectrum recorded in CDCl₃shows

four singlets in the region 3.48–2.48 ppm, while the IR spec-

trum shows strong bands at 1095 and 1023 cm^–1, attribut-

able to the ν(S=O) and δ(C–H) of the dmso, respectively].

Owing to the lack of structural information, a detailed ste-

reochemical description of the complexes 13 and 14 is not

possible at present.

Ru Complex Obtained from [Ru(p-cymene)Cl₂]₂

Figure 6. Perspective view and labelling scheme of compound

12·dmso·H₂O. Rings C15–C20, C21–C26, C41–C46 and C47–C52

are represented only by the ipso carbon for clarity. Thermal ellip-

soids at the 50% level.

[Ru(p-cymene)Cl₂]₂reacts with Hbidf in chloroform at

room temperature, leading to the isolation of [(η⁶-p-cy-

mene)Ru(κ¹-(H)P)Cl₂]·3/2CHCl₃(15), where the ligand

uses only the P atom to bind to ruthenium. The pseudo-

The reaction between Hbidf and [Ru(dmso)₄Cl₂] has octahedral coordination is completed by a η⁶-coordinated

been repeated without a base. When the reaction is carried p-cymene molecule and by two chloride ligands. The IR

Eur. J. Inorg. Chem. 2006, 2422–2436

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P. Pelagatti, L. Gonsalvi et al.

FULL PAPER

spectrum shows the presence of the N–H and of the C=O veral

Ru-catalysts

containing

monodentate

li-

groups with two bands at 3311 and 1696 cm^–1, respectively. gands.^{[15,16a,b,19]}However, high selectivity towards (Z)-alk-

The neutral character of the ligand is further substantiated 1-en-1-yl benzoate (anti-Markovnikov product) has been

1

by H NMR spectroscopy with a singlet at δ = 10.31 ppm; achieved in the coupling of phenylacetylene with 1-hexyne

the HC=N proton corresponds to a singlet at δ = 9.08 ppm, using allyl–Ru^IIcomplexes containing chelating diphospha-

while the p-cymene protons resonate at the expected chemi- nes such as dppp or dppb.^[16d]The same type of selectivity

cal shifts (in the range 5.47–5.33 ppm). The ³¹P{¹H}-NMR has been achieved by adding coordinating bases, such as

spectrum recorded in CDCl₃shows a singlet at δ = pyridines, to half-sandwich Ru^IIcomplexes containing

29.6 ppm. The structure of 15 has been unambiguously elu- monodentate phosphanes,^[18]or adding monophosphanes

cidated by X-ray diffraction analysis conducted on a crystal to N-hetherocyclic carbene complexes.^[17d]As we wanted to

collected from a chloroform/diethyl ether mixture which test whether the chelation of the acyl hydrazones could de-

was cooled to –20 °C. The molecular structure is reported termine a good selectivity towards (Z)-alk-1-en-1-yl benzo-

in Figure 7, and the most important geometric parameters ate, we have tested the complexes 1–4, 6, 7, 9 and 10 as pre-

are listed in Table 2. The neutral Hbidf ligand is coordi- catalysts in the addition of benzoic acid to phenylacetylene.

nated to the Ru atom only by the P donor [Ru–P bond To the best of our knowledge, this is the first report dealing

2.376(5) Å], while the remaining potential N and O donors with Ru complexes containing tridentate ligands employed

point away from the metal. The NH is instead on the same as pre-catalysts in such a catalytic transformation. The ex-

side as the P atom, in the opposite conformation with re- perimental conditions have been kept constant for every

spect to the one observed in the tridentate complexes. The catalytic run: toluene as solvent (for concentrations of

Ru centre completes its pseudo-octahedral coordination by about 10^–3 all the complexes are perfectly soluble),

two chloride atoms and the η⁶-p-cymene. The conformation Na₂CO₃as base (Ru/base molar ratio = 1:5), T = 120 °C

of the neutral ligand allows for a favourable contact be- and 1% of catalyst loading. The yields of the reactions (re-

tween the NH and the CH group and one of the coordi- ferred to the isolated enol esters) have been checked after

nated Cl [(N2)H···Cl1: 2.910(5), (C7)H···Cl1: 2.655(5) Å], 16 hours. The catalytic results are collected in Table 3.

thus strongly differentiating the intramolecular environ-

ment of the two chloride atoms.

As can be deduced from Entries 1 and 2, the dichloride

complexes 1 and 2 are completely inactive in the coupling

between 1-hexyne and benzoic acid. This is not unexpected,

as it can be imputed to the strongly bound chloride li-

gands.^{[8,16a,b,19,34]}The substitution of a chloride with a

more labile acetonitrile molecule, like in the case of the

mono-chloride complexes 3 and 4, leads to a moderate cata-

lytic activity with 35% and 49% yields (Entries 3 and 4),

respectively. However, high stereo- and regio-selectivity in

favour of (Z)-alk-1-en-1-yl benzoate have been reached in

both cases (94% an 99%, respectively). The amount of the

Markovnikov product remains very low and no traces of

(E)-alk-1-en-1-yl benzoate have been detected. The cationic

complexes 6 and 7 (Entries 5 and 6) lead to similar yields,

but again accompanied by excellent selectivities towards the

Z-anti-Markovnikov product. Finally, the cationic com-

plexes 9 and 10 show catalytic activities comparable to

those of the mono-chloride complexes, with a slightly di-

minished selectivity (10% of the Markovnikov product has

been obtained in both cases, Entries 7 and 8). Under the

experimental conditions applied, with the only exception of

the dichlorides 1 and 2, the tested Ru complexes result more

active than [Ru(PPh₃)₃Cl₂] (Entry 13) which, moreover,

leads exclusively to the Markovnikov product. From an in-

spection of Entries 1–8 of Table 3, it can be inferred that

Figure 7. Perspective view and labelling scheme of the ball-and-

stick structure of 15·1.5CHCl₃. η⁶-Coordination of the p-cymene

ligand is represented by empty sticks.

Addition of Benzoic Acid to Terminal Alkynes

The Ru-catalysed coupling of alkynes with carboxylic ac- the removal of a chloride ligand is necessary to have cata-

ids (Scheme 2) is an elegant way to obtain enol esters, which lytic activity accompanied by a good selectivity (compare

are starting materials for several important chemical trans- Entries 1 and 2 with Entries 3 and 4), while the removal of

formations.^[7–13]One of the major goals of this catalysis is the second chloride ligands does not bring to any improve-

the development of stereo- and regio-selective processes ment of the final yield, but instead provokes a slight de-

leading exclusively to one of the three possible enol ester crease in selectivity (compare Entries 3–6 with Entries 7 and

isomers (Scheme 2), thus the preparation of selective cata- 8). The importance of having a vacant coordination site is

lysts is certainly desirable. Literature data show that the confirmed by the inertness of the complexes observed in

Markovnikov products are those usually produced using se- coordinating solvents such as dmso, dmf and acetonitrile;

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Ru^IIComplexes with Hydrazonic Ligands

FULL PAPER

Table 3. Catalytic results for the addition of benzoic acid to terminal alkynes.^[a]

Entry

Ru complex

Alkyne

Yield [%]^[b]

Z-anti-M [%]^[c]

M [%]^[c]

1

2

3

4

5

6

7

8

1

1-hexyne

–

2

3

35

49

44

53

56

49

36

33

25

56

19

94

99

100

95

90

81

98

86

94

–

6

1

–

4

6

7

5

9

10

19

2

14

6

10

9

7

phenylacetylene

p-tolylacetylene

tert-butylacetylene

1-octyne

10

11

12

13

7

[Ru(PPh₃)₃Cl₂]

1-hexyne

100

[a] Conditions: solvent = toluene; T = 120 °C; Ru/benzoic acid/alkyne/Na₂CO₃= 1:100:100:5. [b] Referred to the isolated product. [c]

1

Determined by H NMR spectroscopy.

no traces of enol esters have been detected even after tion^[22]and C–H bonds activation^[23]for the detection of

24 hours of reaction. From the lengthening of the Ru–O the metal-containing intermediates involved in the catalytic

bond observed in the solid structure of 6 with respect to cycles. To the best of our knowledge, no report dealing with

the same bond length found in 4, one could expect a higher the use of such a technique for the study of the addition of

catalytic activity for the complexes containing protonated carboxylic acids to alkynes has appeared in the literature.

ligands, such as 6 and 7, on the basis of a hemilabile behav- Mechanistic studies conducted on diphosphanes containing

iour of the acyl hydrazones, from a κ³-(H)PNO coordina- complexes,^[15d]have evidenced the formation of a vinylidene

tion to a κ²-(H)PN one. However, these pre-catalysts behave intermediate as active catalyst, which undergoes an inter-

similarly to the complexes containing anionic ligands 3, 4, molecular attack of a carboxylate anion to generate the fi-

9 and 10, and this suggests that the acyl hydrazones remain nal enol ester. We have therefore undertaken an ESI-MS

tridentate throughout the catalytic cycle. An explanation of study aimed at detecting the key intermediates involved in

this levelling effect could certainly reside in the deproton- the enol ester synthesis catalysed by our Ru–PNO com-

ation of the ligand induced by the excess of Na₂CO₃which plexes; complex 5 [Ru(Hbidf)(PPh₃)(CH₃CN)Cl][PF₆] has

forces the acyl hydrazones to an anionic PNO coordination been chosen as a model. Initially, we have collected the

in all cases.

ESI(+) spectrum of a 10^–3 toluene solution of 5 at room

The study of the catalytic behaviour of complex 7 has temperature; this shows a predominant cluster centred at

been extended to other terminal alkynes, such as 1-octyne, m/z = 813 accounting for [Ru(bidf)(PPh₃)(CH₃CN)]⁺, and

phenylacetylene, p-tolylacetylene and tert-butylacetylene.

minor clusters at m/z = 849 and m/z = 772 accounting for

Whereas with 1-octyne the catalytic performance is sim- [Ru(Hbidf)(PPh₃)(CH₃CN)Cl]⁺and [Ru(bidf)(PPh₃)]⁺,

ilar to the one observed with 1-hexyne (56% conversion respectively. The solution has then been heated at 120 °C

with 94% of Z-anti-Markovnikov product and 6% of Mar- for 40 minutes and a new ESI(+) spectrum has been col-

kovnikov product, Entry 12), conversions not higher than lected. This shows again the clusters centred at m/z = 813

36% and lower selectivities have been obtained with the aryl and 772, indicating that the complex is preserved under

alkynes, (Entries 9 and 10) and with the bulkier tBu-acetyl- these conditions (Figure 8, a). A small cluster at m/z = 917

ene (Entry 11). Whilst with tBu-acetylene the lower yield shows the presence of 12, although the isotope pattern

can be imputed to steric factors, more difficult is to explain points out the presence of a second unknown species with

the lower reactivity of the aryl alkynes. Noteworthy is the similar mass which tangles the signal up.

fact that traces of dimerisation products have been detected

To a freshly prepared toluene solution of 5 heated at

neither with phenylacetylene nor with p-tolylacetylene, as 120 °C benzoic acid and Na₂CO₃have been added (Ru/

instead described with Ru–alkylidene complexes bearing N- acid/Na₂CO₃= 1:5:5 molar ratio); the ESI(+) spectrum

heterocyclic carbene ligands.^[17c]A possible explanation shows the disappearance of the signal at m/z = 813 in favour

could reside in the bulkiness of the phenyl ring attached of a cluster centred at m/z = 894 corresponding to the frag-

to the triple C–C bond of the alkyne which hampers the ment [Ru(Hbidf)(PPh₃)(C₆H₅COO)]⁺, where a carboxylate

vinylidene formation (vide infra), but elucidation of this anion is coordinated to Ru; the clusters at m/z = 772 and

point needs further studies.

917 are still visible (Figure 8, b). Subsequently, to a freshly

prepared toluene solution of 5 heated at 120 °C 1-hexyne

has been added (Ru/alkyne = 1:5 molar ratio); the collected

ESI(+) spectrum shows the disappearance of the signal at

ESI-MS Study

ESI-MS technique has been successfully employed in se- m/z = 813 and the appearance of a cluster at m/z = 854,

veral metal-catalysed transformations like, for example, re- corresponding to [Ru(bidf)(PPh₃)(C=CH–C₄H₉)]⁺(Fig-

duction of ketones,^[20]epoxidations,^[21]olefins polymerisa- ure 8, c); the cluster at m/z = 800 can be tentatively assigned

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P. Pelagatti, L. Gonsalvi et al.

FULL PAPER

Figure 8. ESI(+) spectra of toluene solutions of 5: a) after one hour at 120 °C; b) after the addition of benzoic acid/Na₂CO₃; c) after the

addition of 1-hexyne.

to the loss of butadiene from the vinylidene species, with mation, through a not defined pathway, can in principle

formation of the cation [Ru(bidf)(PPh₃)(C₂H₄)]⁺. This last account for catalyst deactivation.

signal however quickly disappears leaving the signal at

m/z = 854. The formation of the vinylidene intermediate is

then independent from the presence of benzoic acid. In fact,

the addition of 1-hexyne to a toluene solution containing

Conclusions

the carboxylate intermediate leads to the immediate disap-

In this work we have reported the synthesis and the full

pearance of the signal at m/z = 894 in favour of that at characterisation of several new octahedral Ru^IIcomplexes

m/z = 854. Although the ESI-MS experiments does not give obtained by reaction of [Ru(PPh₃)₃Cl₂] with two protic

conclusive evidences of the reaction mechanism governing [PNO] ligands. Depending on the experimental conditions,

the studied catalytic process, several observations are in fav- different coordination modes to Ru can be created, giving

our of the intermolecular nucleophilic attack of the carbox- rise to neutral or cationic complexes of general formula

ylate anion onto the vinylidene complex [Ru(bidf)- trans-[Ru(κ³-HPNO)(PPh₃)Cl₂], [Ru(κ³-PNO)(PPh₃)(CH₃-

(PPh₃)(C=CH–C₄H₉)Cl], such as: i) the formation of the CN)Cl], [Ru(κ³-HPNO)(PPh₃)(CH₃CN)Cl][X] (X = PF₆or

vinylidene intermediate which occurs independently on the BPh₄) and [Ru(κ³-PNO)(PPh₃)(CH₃CN)₂][X]. The com-

presence of the carboxylate ion, ii) that the signal of the plexes of the type trans-[Ru(κ³-HPNO)(PPh₃)Cl₂] show an

carboxylate complex quickly disappears in favour of that of interesting reactivity with dmso which leads to the forma-

the vinilydene intermediate after the addition of the alkyne, tion of bis-chelate complexes of the type [Ru(κ³-PNO)₂].

and iii) that no signal deriving from vinylidene species con- Such unusual conversion, monitored by ³¹P{¹H} spec-

taining a carboxylate anion has been detected. Unfortu- troscopy, occurs through the stepwise decoordination of the

nately, repeated attempts aimed at the isolation or detection three donors of the [PNO] ligand induced by dmso. Then,

of [Ru(PNO)(PPh₃)(C=CH–C₄H₉)Cl] species have been so the initial detachment of the amide oxygen leads to the for-

far unsuccessful.

mation of intermediate species where the ligands are κ²-(H)-

The observation of ESI-MS signals attributable to the PN coordinated; subsequently, the nitrogen decoordination

bis-chelate complex 12 can be one of the reasons of the leads to P-monodentate behaviour and, finally, a PNO li-

incomplete conversion of the alkyne substrates, as its for- gand transfer from two different ruthenium atoms takes

2432

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Eur. J. Inorg. Chem. 2006, 2422–2436

Ru^IIComplexes with Hydrazonic Ligands

FULL PAPER

place with formation of the bis-chelate complex [Ru(κ³-

PNO)₂], [Ru(dmso)₄Cl₂], Me₂S, OPPh₃and HCl. The de-

oxygenation of dmso occurs by oxygen transfer to a PPh₃

molcule. Model systems of the spectroscopically detected

intermediates have been obtained by reaction of an HPNO

ligand with [Ru(dmso)₄Cl₂] and [Ru(p-cymene)Cl₂]₂. A

catalytic version of the oxygen transfer reaction from dmso

to PPh₃has also been developed.

Most of the complexes containing PPh₃promote the

catalytic coupling between benzoic acid and terminal al-

kynes in toluene/Na₂CO₃at 120 °C, with 1% of catalyst

loading. The reactions proceed with high stereo- and re-

gioselectivity, up to 100% as established by ¹HNMR,

towards the formation of the anti-Markovnikov product.

Important mechanistic details come from the ESI-MS study

applied for the first time to this ruthenium-catalysed coup-

ling reaction: the enol esters form thanks to an intermo-

lecular nucleophilic attack of a uncoordinated carboxylate

anion onto a Ru–vinylidene intermediate of the type [Ru-

(PNO)(PPh₃)(C=CH–C₄H₉)Cl].

M.p. 160 °C (dec.). C₄₄H₃₆Cl₂N₂OP₂Ru·CH₂Cl₂(927.642): calcd.

C 58.25, H 4.10, N 3.02; found C 58.85, H, 4.11, N 3.02. ¹H NMR

([D₆]dmso): δ = 8.02–6.94 (m, 34 H, Ph), 5.20 (s, 2 H, CH₂Cl₂)

ppm. FAB-MS: m/z = 842 [M – CH₂Cl₂]⁺, 807 [M – CH₂Cl₂– Cl^–]⁺.

trans-[Ru(Haidf)(PPh₃)Cl₂]·1/2CH₂Cl₂(2): As for 1 but using li-

gand Haidf (150 mg, 0.433 mmol). Yield: 310 mg (91%). M.p.

160 °C (dec.). C₃₉H₃₄Cl₂N₂OP₂Ru·1/2CH₂Cl₂(823.105): calcd. C

57.75, H 4.26, N 3.41; found C 58.38, H 4.16, N 3.40. ¹H NMR

([D₆]dmso): δ = 7.75–6.87 (m, 29 H, Ph), 5.21 (s, 1 H, CH₂Cl₂), 2.25

[s, 3 H, CH₃C(O)] ppm. FAB-MS: m/z = 780 [M – CH₂Cl₂+H⁺]⁺,

745 [M – CH₂Cl₂– Cl^–]⁺, 709 [M – CH₂Cl₂– HCl – Cl^–]⁺.

[Ru(bidf)(PPh₃)(CH₃CN)Cl] (3): Complex 1 (320 mg, 0.380 mmol)

was dispersed in 20 mL of toluene at room temperature. NEt₃

(262 µL, 1.900 mmol) and CH₃CN (1 mL) were added, and the

purple solution was stirred at room temperature overnight. A yel-

low solid was filtered off, washed with water and n-hexane and

then dried under vacuum. Yield: 260 mg (81%). M.p. 180 °C (dec.).

C₄₆H₄₁ClN₃OP₂Ru (850.325): calcd. C 62.25, H 4.52, N 4.96; found

C 65.90, H 4.98, N 4.65. ¹H NMR (CD₂Cl₂): δ = 8.16 (dd, 2 H,

Ph), 7.30 (t, 2 H, Ph), 7.28–7.14 (m, 28 H, Ph), 7.12 (t, 1 H, Ph),

6.58 (t, 2 H, Ph), 1.21 (s, 3 H, CH₃CN) ppm. FAB-MS: m/z = 806

[M – CH₃CN]⁺, 771 [M – CH₃CN – Cl]⁺.

[Ru(aidf)(PPh₃)(CH₃CN)Cl] (4): As for 3 but starting from complex

2. Yellow solid. Yield: 130 mg (81%). M.p. 174 °C (dec.).

C₄₁H₃₆ClN₃OP₂Ru (785.23): calcd. C 62.86, H 4.60, N 5.36; found

Experimental Section

General: All reactions were performed under dry nitrogen em-

ploying standard Schlenk techniques. Solvents were dried prior to

use and stored under nitrogen. Elemental analysis (C, H, N and S)

were performed with a Carlo Erba Mod. EA 1108 apparatus. Infra-

red spectra were recorded with a Nicolet 5PCFT-IR spectropho-

1

C 62.98, H 4.75, N 4.95. H NMR (CD₂Cl₂): δ = 7.80 (t, 2 H, Ph),

7.58–7.11 (m, 24 H, Ph), 6.95 (t, 1 H, Ph), 6.54 (t, 2 H, Ph), 2.36

[s, 3 H, CH₃C(O)], 1.21 (s, 3 H, CH₃CN) ppm. FAB-MS: m/z =

786 [M+H⁺]⁺, 744 [M – CH₃CN]⁺. For slow evaporation of a

dichloromethane/acetonitrile mixture, crystals suitable for X-ray

analysis were collected.

tometer in the 4000–400 cm^–1range by using KBr disks. H NMR

1

spectra were obtained with a Bruker 300 FT spectrometer using

SiMe₄as internal standard, while ³¹P{¹H} NMR spectra were re-

corded with a Bruker AMX 400 FT using H₃PO₄85% as external

standard. Heterocorrelated ³¹P-¹H NMR spectra were measured

with a Bruker Avance 400 MHz. All spectra were collected at

298 K. FAB-MS spectra were performed with a Micromass Autoes-

pec mass spectrometer, employing m-nitrobenzyl alcohol as matrix.

A Quattro LC triple quadrupole instrument (Micromass, Manches-

ter, UK) equipped with an electrospray interface and a Masslynx

v. 3.4 software (Micromass) was used for ESI-MS data acquisition

and processing. The nebulizing gas (nitrogen, 99.999% purity) and

the desolvation gas (nitrogen, 99.998% purity) were delivered at a

flow-rate of 80 and 500 L/h, respectively. ESI-MS analyses were

performed by operating the mass spectrometer in positive (PI) ion

mode, acquiring mass spectra over the scan range m/z 100–1300,

using a step size of 0.1 Da and a scan time of 1.2 seconds. The

operating parameters of the interface were as follows: source tem-

perature 70 °C, desolvation temperature 70 °C, ES(+) voltage

3.0 kV, cone voltage 30 and 50 V, rf lens 0.3 V.

[Ru(Hbidf)(PPh₃)(CH₃CN)Cl][PF₆] (5): Complex

1

(250 mg,

0.297 mmol) was dispersed in 45 mL of CH₂Cl₂at room tempera-

ture. After 15 minutes of stirring KPF₆(280 mg, 1.521 mmol) and

CH₃CN (1 mL) were added. The solution was stirred overnight at

room temperature, then filtered and the resulting orange solution

was concentrated under vacuum, treated with n-hexane and re-

frigerated at –18 °C. An orange powder was filtered off, washed

with n-hexane and dried under vacuum. Yield: 210 mg (71%). M.p.

170 °C (dec.). C₄₆H₃₉ClF₆N₃OP₃Ru (993.271): calcd. C 55.65, H

3.93, N 4.23; found C 55.34, H 3.89, N 4.31. IR (cm^–1): ν = 2281

˜

1

(w, CH₃CϵN), 845 (vs, PF). H NMR (CD₂Cl₂): δ = 8.01 (d, 2 H,

Ph), 7.70 (m, 1 H, Ph), 7.63–7.23 (m, 28 H, Ph), 7.18 (t, 1 H, Ph),

6.40 (t, 2 H, Ph), 1.63 (s, 3 H, CH₃CN) ppm. ³¹P{¹H}NMR

(CD₂Cl₂): δ = –141.1 (m, 1 P, PF₆) ppm. FAB-MS: m/z = 806 [M –

PF₆– CH₃CN]⁺, 771 [M – PF₆– CH₃CN – HCl]⁺.

[Ru(Haidf)(PPh₃)(CH₃CN)Cl][PF₆]·CH₂Cl₂(6): As for 5 but start-

ing from complex 2. Yield: 160 mg (69%). M.p. 170 °C (dec.).

C₄₁H₃₇ClF₆N₃OP₃Ru·CH₂Cl₂(1016.133): calcd. C 49.65, H 4.14,

N 4.14; found C 50.00, H 3.91, N 4.48. IR (cm^–1): ν = 2273 (w,

˜

2-(Diphenylphosphanyl)benzaldehyde benzoylhydrazone (Hbidf)

and 2-(diphenylphosphanyl)benzaldehyde acetylhydrazone (Haidf)

were synthesised as previously reported.^[4b][Ru(PPh₃)₃Cl₂] was syn-

thesised by a literature reported method.^[35]

CH₃CϵN), 845 (vs, PF). ¹H NMR (CD₂Cl₂): δ = 8.88 (br., 1 H,

CH=N), 7.88 (t, 2 H, Ph), 7.72–7.03 (m, 25 H, Ph), 6.33 (t, 2 H,

Ph), 5.20 (s, 2 H, CH₂Cl₂), 2.38 [s, 3 H, CH₃C(O)] 1.70 (s, 3 H,

CH₃CN) ppm. ³¹P{¹H}NMR (CD₂Cl₂): δ = –145.5 (m, 1 P, PF₆)

ppm. FAB-MS: m/z = 786 [M – CH₂Cl₂– PF₆]⁺, 745 [M –

CH₂Cl₂– PF₆– CH₃CN]⁺, 709 [M – CH₂Cl₂– PF₆– CH₃CN –

HCl]⁺. From a refrigerated dichloromethane /n-pentane mixture,

crystals suitable for X-ray analysis were collected.

trans-[Ru(Hbidf)(PPh₃)Cl₂]·CH₂Cl₂(1): The ligand (250 mg,

0.613 mmol) was dissolved in 15 mL of CH₂Cl₂at room tempera-

ture. After 10 minutes of stirring [Ru(PPh₃)₃Cl₂] (590 mg,

0.617 mmol) was added and the resulting purple solution was

stirred for 5 hours at room temperature. The solvent was partially

removed in vacuo, and the solution was cooled to –18 °C for a

night. A purple powder was filtered off, washed with n-hexane and

diethyl ether and then dried under vacuum. Yield: 430 mg (83%).

[Ru(Hbidf)(PPh₃)(CH₃CN)Cl][BPh₄] (7): As for 6 but starting from

complex 1 and using NaBPh₄instead of KPF₆. Yield: 180 mg

(81%). M.p. 146–148 °C. C₇₀H₅₉BClN₃OP₂Ru (1167.544): calcd. C

Eur. J. Inorg. Chem. 2006, 2422–2436

www.eurjic.org

2433

P. Pelagatti, L. Gonsalvi et al.

FULL PAPER

72.04, H 5.06, N 3.60; found C 72.45, H 5.74, N 3.48. IR (cm^–1):

cooling at –18 °C a yellow solid formed, which was filtered off,

washed with diethyl ether and vacuum dried. Yield: 99 mg (63%)

M.p. 253–258 °C. C₅₂H₄₀N₄O₂P₂Ru·2H₂O (951.966): calcd. C

65.60, H 4.65, N 5.88; found C 65.26, H 4.76, N 5.59. ¹H NMR

(CDCl₃): δ = 7.66 (d, 4 H, Ph), 7.19–6.77 (m, 38 H, Ph) ppm. CI-

MS: m/z = 916 [M – H₂O]⁺.

ν = 2269 (w, CH CϵN), 843 (w, BP). ¹H NMR (CD Cl ): δ = 8.03

˜

3

2

(d, 2 H, Ph), 7.83–6.84 (m, 50 H, Ph), 6.39 (t, 2 H, Ph), 1.23 (s, 3

H, CH₃CN) ppm. FAB-MS: m/z = 848 [M – BPh₄]⁺, 807 [M –

BPh₄– CH₃CN]⁺, 771 [M – BPh₄– CH₃CN – HCl]⁺.

[Ru(Haidf)(PPh₃)(CH₃CN)Cl][BPh₄] (8): As for 7 but starting from

complex

2.

Yield:

50 mg

(70%).

M.p.

152–154 °C.

[Ru(Hbidf)(dmso)₂Cl₂] (13) and [Ru(Hbidf)(dmso)Cl₂]·1/2dmso·H₂O

(14): [Ru(dmso)₄]Cl₂(59.3 mg, 0.122 mmol) was dissolved in etha-

nol (15 mL). An equimolar amount of Hbidf dissolved in ethanol

(15 mL) was added, and the resulting solution was refluxed for 1 h.

A yellow solid precipitated (13), which was filtered off, washed with

ethanol and vacuum dried for several hours. Yield: 31 mg (35%).

M.p. 227 °C (dec.). C₃₀H₃₃Cl₂N₂O₃PRuS₂(736.675): calcd. C

C₆₅H₅₇BClN₃OP₂Ru·1/4CH₂Cl₂(1171.747): calcd. C 69.65, H 5.03,

N 3.38; found C 69.68, H 5.15, N 3.74. IR (cm^–1): ν = 2265 (w,

˜

CH₃CϵN), 851 (w, BP). ¹HNMR (CDCl₃): δ = 7.83–6.84 (m, 47

H, Ph), 6.53 (t, 2 H, Ph), 2.23 [s, 3 H, CH₃C(O)], 0.43 (s, 3 H,

CH₃CϵN) ppm. FAB-MS: m/z = 786 [M – BPh₄]⁺, 745 [M –

BPh₄– CH₃CN]⁺, 709 [M – BPh₄– CH₃CN – HCl]⁺.

48.91, H 4.51, N 3.80, S, 8.70; found C 48.86, H 4.47, N 3.86; S,

trans-[Ru(bidf)(PPh₃)(CH₃CN₂)₂][BPh₄] (9): Complex 7 (110 mg,

0.094 mmol) was dissolved in 20 mL of tolune at room temperature.

To the resulting yellow solution acetonitrile (3 mL) and NEt₃

(75 µL, 0.539 mmol) were added and then it was left stirring at

room temperature overnight. The solvent was completely removed

under vacuum obtaining a sticky pale orange solid, which was

washed with water and repeatedly triturated with n-hexane. The

bright orange powder was finally filtered off, washed with diethyl

ether and dried under vacuum. Yield: 90 mg (82%). M.p. 150–

154 °C. Due to the instability of the complex, irreproducible micro-

1

8.78. IR (cm^–1): ν = 1088 (vs, S=O); 1019 (s, ρC–H)_dmso. H NMR

˜

(CDCl₃): δ = 7.92 (d, 2 H, Ph), 7.79–7.20 (m, 17 H, Ph), 3.65 (s, 3

H, dmso), 3.45 (s, 3 H, dmso), 3.03 (s, 3 H, dmso), 2.84 (s, 3 H,

dmso) ppm. By slow evaporation of a dmso solution of 13 crystals

of 12·dmso·H₂O suitable for X-ray analysis were collected (see crys-

tallograhic analysis).

After the filtration of 13, the resulting solution was treated with n-

hexane observing the precipitation of an orange solid (14), which

was filtered off, washed with n-hexane and vacuum dried. Yield:

34 mg (40%). M.p. 228 °C (dec.). C₂₉H₃₂Cl₂N₂O_3.5PRuS_1.5

(715.625): calcd. C 48.67, H 4.51, N 3.91, S 6.72; found C 48.21,

analyses have been obtained. IR (cm^–1): ν = 2273 (w, CH CϵN),

˜

3

1

873 (w, BP). H NMR (CD₂Cl₂): δ = 8.21 (d, 2 H, Ph), 7.70 (t, 1

H, Ph), 7.46–7.05 (m, 49 H, Ph), 6.55 (t, 2 H, Ph), 2.37 (s, 3 H,

CH₃CϵN), 1.29 (s, 3 H, CH₃CϵN) ppm. FAB-MS: m/z = 771 [M –

BPh₄– 2CH₃CN]⁺.

H 4.71, N 4.22, S 7.14. IR (cm^–1): ν = 1095 (vs, S=O), 1023 (s, ρC–

˜

.

1

H)_dmso. H NMR (CDCl₃): δ = 7.78–7.35 (m, 19 H, Ph), 3.48 (s, 3

H, dmso), 2.95 (s, 3 H, dmso) ppm.

trans-[Ru(aidf)(PPh₃)(CH₃CN₂)₂][PF₆] (10): As for 9 but starting

form complex 8. Yield: 50 mg (76%). M.p. 137–142 °C. Due to the

instability of the complex, irreproducible microanalyses have been

[Ru(Hbidf)(p-cymene)Cl₂]·2CHCl₃(15): Hbidf (50 mg, 0.122 mmol)

was dissolved in 40 mL of chloroform and [Ru(p-cymene)Cl₂]₂

(75 mg, 0.122 mmol) was added. The mixture was stirred at room

temperature for 2.5 hours obtaining a deep red solution, which was

reduced in volume and treated with diethyl ether. A brown solid

precipitated (25 mg) whose characterisation was not possible. From

the mother liquors refrigerated at –20 °C, brown crystals suitable

for X-ray analysis were collected. Yield: 46.5 mg (40%). M.p.

220 °C (dec.). C₃₆H₃₅Cl₂N₂OPRu·2CHCl₃(953.395): calcd. C

47.87, H 3.90, N 2.90; found C 48.20, H 3.80, N 2.30. ¹H NMR

(CDCl₃): δ = 8.07 (d, 2 H, Ph), 7.62–7.03 (m, 17 H, Ph), 5.47 (d,

2 H, p-cymene), 5.33 (d, 2 H, p-cymene), 2.94 [m, 1 H, CH-

(CH₃)₂], 1.75 [s, 3 H, CH(CH₃)₂], 1.28 [s, 3 H, CH(CH₃)₂] ppm.

obtained. IR (cm^–1): ν = 2281 (w, CH CϵN), 835 (vs, PF). ¹H

˜

3

NMR (CD₂Cl₂): δ = 7.72 (t, 2 H, Ph), 7.61 (t, 2 H, Ph), 7.48–7.12

(m, 22 H, Ph), 7.05 (t, 2 H, Ph), 6.51 (t, 2 H, Ph), 2.34 [s, 3 H,

CH₃C(O)], 1.44 (s, 3 H, CH₃CϵN), 1.27 (s, 3 H, CH₃CϵN) ppm.

³¹P{¹H}NMR (CD₂Cl₂): δ = –150 (m, 1 P, PF₆) ppm.

[Ru(Hbidf)(PPh₃)(CH₃CN)Cl]Cl (11): Complex

1

(100 mg,

0.12 mmol) was treated with CH₃CN and the mixture was heated

at 50 °C for 4 hours. The initial purple mixture became an almost

clear orange solution. After filtration the resulting orange solution

was dried under vacuum, obtaining an orange powder. Yield:

60 mg (57%). C₄₆H₃₇Cl₂N₃OP₂Ru (881.746): calcd. C 62.16, H

4.25, N 4.57; found C 62.38, H 4.46, N 4.57. IR (cm^–1): ν = 2273

X-ray Analysis: Mo-K_αradiation (λ = 0.71073 Å), T = 293 K, on

a SMART AXS 1000 diffractometer equipped with CCD detector

was used for compounds 4 and 6 and 12·dmso·H₂O, while Cu-

K_αradiation (λ = 1.54178 Å), T = 293 K, with a Siemens AED

diffractometer equipped with scintillation detector was employed

for 15·1.5CHCl₃, which showed a significant crystal decay over the

data collection (47% intensity loss, correction applied). Lorentz,

polarisation, and absorption corrections were applied.^[36]Struc-

tures were solved by direct methods using SIR97^[37]and refined by

full-matrix least-squares on all F²using SHELXL97^[38]im-

plemented in the WingX package.^[39]Hydrogen atoms were partly

located on Fourier difference maps and refined isotropically, partly

introduced in calculated positions. Anisotropic displacement pa-

rameters were refined for all non-hydrogen atoms in 4, 6 and

˜

1

(w, CH₃CϵN). H NMR (CD₂Cl₂): δ = 7.88–6.86 (m, 32 H, Ph),

6.55 (t, 2 H, Ph), 1.31 (s, 3 H, CH₃CϵN) ppm.

[Ru(bidf)₂]·2H₂O (12). Method A: Hbidf (100 mg, 0.244 mmol) was

dissolved in ethanol (25 mL) by warming. 1  NaOH solution was

added until a pH Ϸ 8 (checked by litmus paper), obtaining a pale

yellow solution. [Ru(dmso)₄Cl₂] (59.3 mg, 0.122 mmol) was dis-

solved in ethanol (10 mL) and added to the ligand solution. After

2 h of reflux the solvent was partially removed under vacuum and

the resultant clear solution was refrigerated at –20 °C. The so-

formed solid was filtered off, washed with cold ethanol and vacuum

dried. Yield: 84 mg (75%).

Method B: Hbidf (140 mg, 0.343 mmol) was dissolved in 5 mL of

CH₂Cl₂at room temperature. A KOH solution (3.75 mL , 0.21 ⁾ 12·dmso·H₂O, but only for Ru and its coordination environment

was added, and the resulting pale yellow solution was stirred at

room temperature for 1 hour. [Ru(PPh₃)₃Cl₂] (160 mg, 0.167 mmol)

previously dissolved in 15 mL of CH₂Cl₂was added, and the mix-

ture stirred at room temperature for 3 hours. The solution was then

filtered and the solvent partially removed under vacuum. After

for 15·1.5CHCl₃. In 12·dmso·H₂O the dmso presents a disorder on

the

S atom. Final geometries have been analysed with

SHELXL97^[36]and PARST97,^[40]and extensive use was made of

the Cambridge Crystallographic Data Centre packages.^[41]Table 4

summarises crystal data and structure determination results.

2434

www.eurjic.org

Eur. J. Inorg. Chem. 2006, 2422–2436

Ru^IIComplexes with Hydrazonic Ligands

FULL PAPER

Table 4. Crystal data and structure refinement for structure analyses.

4

6

12·dmso·H₂O

15·1.5CHCl₃

Empirical formula

Formula weight

Wavelength

Crystal system

Space group

C₄₁H₄₀ClN₃O₃P₂Ru

821.22

0.71073 Å

tetragonal

P4₃2₁2

C₄₁H₃₇ClF₆N₃OP₃Ru

931.17

0.71073 Å

orthorhombic

Pcab

C₅₄H₄₈N₄O₄P₂RuS

1012.03

0.71073 Å

monoclinic

P2₁/c

C₃₈H₃₇Cl_6.50N₂OPRu

900.16

1.54100 Å

hexagonal

R-3

Unit cell dimensions [Å, °]

a = 14.430(1)

b = 14.430(1)

c = 37.134(2)

7732.2(9)

8

1.411

0.599

3376

a = 18.334(1)

b = 20.599(1)

c = 21.621(1)

8165.4(7)

8

1.515

0.631

3776

a = 11.114(2)

b = 21.271(4) β = 95.89(1) b = 41.520(8)

c = 20.280(4)

4769(2)

4

1.410

0.491

2088

a = 41.520(8)

c = 13.270(4)

19811(8)

18

1.358

7.090

Volume [Å³]

Z

Density (calculated) [mg/m³]

Absorption coefficient [mm^–1

F(000)

]

8217

Θ range for data collection [°]

Reflections collected

1.51–27.10

84143

1.76–28.42

86434

1.39–28.49

28916

3.55–64.77

7243

Independent reflections

8525 [R(int) = 0.0314] 9617 [R(int) = 0.0720] 10731 [R(int) = 0.0523]

6370 [R(int) = 0.0835]

6370/5/222

0.780

Data/restraints/parameters

8525/6/480

1.180

9617/0/615

1.203

10731/2/775

0.875

Goodness-of-fit on F²

Final R indices [I Ͼ 2σ(I)] (R₁, wR₂)

R indices (all data) (R₁, wR₂)

0.0296, 0.0631

0.0343, 0.0655

0.472/–0.516

0.0709, 0.1465

0.1205, 0.1593

0.539/–0.518

0.0454, 0.0963

0.0918, 0.1114

0.981/–0.675

0.1135, 0.3044

0.2530, 0.3526

0.964/–0.506

Largest ∆F max./min. [e·Å^–3

]

CCDC-294363 (for 4), -294364 (for 6), -294365 (for 12·dmso·H₂O)

and -294366 (for 15·1.5CHCl₃) contain the supplementary crystal-

lographic data for this paper. These data can be obtained free of

charge from The Cambridge Crystallographic Data Centre via

www.ccdc.cam.ac.uk/data_request/cif.

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Catalytic Reactions

Addition of Benzoic Acid to Terminal Alkynes: A toluene solution

(7 mL) containing the catalyst (0.01 mmol) and the alkyne

(1 mmol) was added at room temperature to a toluene solution

(6 mL) of benzoic acid containing solid Na₂CO₃(0.05 mmol). The

resulting mixture was heated to 120 °C and stirred for 16 hours,

then dried under vacuum; the residual solid was treated with 5 mL

of CH₂Cl₂and the precipitate was filtered off. Solid NaHCO₃

(1 mmol) was added, and the mixture was washed with H₂O three

times; the organic layer was dried by anhydrous Na₂SO₄and re-

duced in volume by vacuum and then filtered through silica gel to

remove the catalyst. The solution was finally dried under vacuum

1

and analysed by H NMR spectroscopy.

[2]

Oxygen Transfer from Dmso to PPh₃: Compound 1 (11 mg,

0.012 mmol) was dissolved in 8 mL of nitrogen-saturated dmso and

PPh₃(326 mg, 1.243 mmol) was added. The yellow solution was

refluxed under nitrogen and small samples were withdrawn at regu-

lar intervals, added of CDCl₃and analysed by ³¹P{¹H}-NMR spec-

troscopy.

[3]

[4]

Supporting Information (see footnote on the first page of this arti-

cle): ³¹P{¹H}-NMR spectra of complex 1 recorded in [D₆]dmso.

a) A. Bacchi, M. Carcelli, M. Costa, P. Pelagatti, C. Pelizzi, G.

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Acknowledgments

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Dr P. Barbaro (ICCOM-CNR) is gratefully thanked for running

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MS measurements. SB thanks Xunta de Galicia for a postdoctoral

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for access to Bruker Avance 400 MHz and the Centro Interfacoltà

di Misure G. Casnati of the University of Parma for the instrument

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Received: January 9, 2006

Published Online: April 20, 2006

2436

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Eur. J. Inorg. Chem. 2006, 2422–2436

Article Doi

Octahedral RuII complexes with [PNO] hydrazonic ligands: Synthesis, structure, reactivity and catalytic activity in the addition of benzoic acid to alkynes

DOI: 10.1002/ejic.200600016

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