Preparation of mono- and bis-(hydrazine) complexes of ruthenium(II)

Article abstract of DOI:10.1039/a702712e

Hydrazine complexes [RuH(R¹NHNH₂)L₄]BPh₄ 1-3, [Ru(R¹NHNH₂)₂L₄][BPh ₄]₂ 4-6 [R¹ = H, Me, Ph, 4-MeC₆H₄ or 4-O₂NC₆H₄; L = P(OEt)₃, PPh(OEt)₂ or P(OMe)₃] were prepared by allowing the hydride species [RuH₂L₄] to react, first with triflic acid (CF₃SO₃H) and then with an excess of the appropriate hydrazine. The derivatives [RuH(Me₂NNH₂){P(OEt)₃}₄]BPh ₄ 1f, [Ru(η¹-OSO₂CF₃)(Me₂NNH ₂){P(OEt)₃}₄]BPh₄ 9 and [Ru(η²-PhCONHNH₂)L₄][BPh₄] ₂ 7,8 [L = P(OEt)₃ or PPh(OEt)₂] were also obtained. The formulation and geometry in solution of the compounds were established by infrared and ¹H and ³¹P NMR spectroscopy. The reaction of the bis(nitrile) complexes [Ru(R²CN)₂L₄][BPh₄]₂ [R² = Me or MeC₆H₄; L = P(OEt)₃ or PPh(OEt)₂] with hydrazines depends not only on the experimental conditions, but also on the nature of the phosphite and the hydrazine used. Thus, nitrilehydrazine [Ru(R¹NHNH₂)(R²CN)L₄][BPh ₄]₂10-13 [L = P(OEt)₃ or PPh(OEt)₂] or amidrazone derivatives [Ru{η²-NH=C(R²)N(R¹)NH₂} {P(OEt)₃}₄][BPh₄]₂ 14,15 (R¹ = H or Me) were obtained together with the bis(hydrazine) compounds [Ru(R¹NHNH₂)₂L₄][BPh ₄]₂. Reaction of the arylhydrazine complexes 1-6 and 10-13 with Pb(O₂CMe)₄ at -30°C in CH₂Cl₂ resulted in selective oxidation of the arylhydrazine ligand giving the aryldiazene derivatives [RuH(R¹N=NH)L₄]BPh₄, [Ru(R¹N=NH)₂L₄][BPh₄]₂ and [Ru(R¹N=NH)(R²CN)L₄][BPh₄] ₂ (R¹ = Ph, 4-MeC₆H₄ or 4-O₂NC₆H₄). Treatment of hydrazine NH₂NH₂ and methylhydrazine MeNHNH₂ complexes 1-6 with Pb(O₂CMe)₄, instead, afforded the acetate [Ru(η²-O₂CMe)L₄]BPh₄ derivatives which were characterised by a crystal structure determination of [Ru(η²-O₂CMe){P(OEt)₃}₄]BPh ₄. The co-ordination of ruthenium is distorted octahedral with approximate C2_v symmetry and the acetate is bidentate.

Full text of DOI:10.1039/a702712e

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Preparation of mono- and bis-(hydrazine) complexes of
ruthenium(II)†
Gabriele Albertin,*,a Stefano Antoniutti,a Alessia Bacchi,b Emilio Bordignon,a
Piero Matteo Dolcettia and Giancarlo Pelizzib
a Dipartimento di Chimica, Università di Venezia, Dorsoduro 2137, 30123 Venezia, Italy
b Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Centro
CNR di Strutturistica Diffrattometrica, Università di Parma, Viale delle Scienze, 43100 Parma,
Italy
Hydrazine complexes [RuH(R1NHNH2)L4]BPh4 1–3, [Ru(R1NHNH2)2L4][BPh4]2 4–6 [R1 = H, Me, Ph, 4-MeC6H4
or 4-O2NC6H4; L = P(OEt)3, PPh(OEt)2 or P(OMe)3] were prepared by allowing the hydride species [RuH2L4] to
react, first with triflic acid (CF3SO3H) and then with an excess of the appropriate hydrazine. The derivatives
[RuH(Me2NNH2){P(OEt)3}4]BPh4 1f, [Ru(η1-OSO2CF3)(Me2NNH2){P(OEt)3}4]BPh4 9 and [Ru(η2-Ph-
CONHNH2)L4][BPh4]2 7,8 [L = P(OEt)3 or PPh(OEt)2] were also obtained. The formulation and geometry in
solution of the compounds were established by infrared and 1H and 31P NMR spectroscopy. The reaction of the
bis(nitrile) complexes [Ru(R2CN)2L4][BPh4]2 [R2 = Me or MeC6H4; L = P(OEt)3 or PPh(OEt)2] with hydrazines
depends not only on the experimental conditions, but also on the nature of the phosphite and the hydrazine used.
Thus, nitrilehydrazine [Ru(R1NHNH2)(R2CN)L4][BPh4]2 10–13 [L = P(OEt)3 or PPh(OEt)2] or amidrazone
derivatives [Ru{η2-NH᎐C(R2)N(R1)NH }{P(OEt) } ][BPh ] 14,15 (R1 = H or Me) were obtained together with the
᎐
2
3
4
4 2
bis(hydrazine) compounds [Ru(R1NHNH2)2L4][BPh4]2. Reaction of the arylhydrazine complexes 1–6 and 10–13
with Pb(O2CMe)4 at Ϫ30 ЊC in CH2Cl2 resulted in selective oxidation of the arylhydrazine ligand giving the
aryldiazene derivatives [RuH(R1N᎐NH)L ]BPh , [Ru(R1N᎐NH) L ][BPh ] and [Ru(R1N᎐NH)(R2CN)L ]-
᎐
᎐
᎐
4
4
2
4
4 2
4
[BPh4]2 (R1 = Ph, 4-MeC6H4 or 4-O2NC6H4). Treatment of hydrazine NH2NH2 and methylhydrazine MeNHNH2
complexes 1–6 with Pb(O2CMe)4, instead, afforded the acetate [Ru(η2-O2CMe)L4]BPh4 derivatives which were
characterised by a crystal structure determination of [Ru(η2-O2CMe){P(OEt)3}4]BPh4. The co-ordination of
ruthenium is distorted octahedral with approximate C2v symmetry and the acetate is bidentate.
Transition-metal complexes containing aryldiazenido, aryl-
diazene or hydrazine ligands are currently of interest as possible
intermediates in the chemistry of co-ordinated dinitrogen and
its reduction to NH3 catalysed by nitrogenases.1 Although a
number of studies on the chemistry of ‘diazo’ derivatives have
been reported over the past 25 years, relatively few are con-
cerned with hydrazine complexes1 and therefore several aspects
of the co-ordination chemistry of NH2NH2 and substituted
hydrazines still remain unclear. Among them we can cite the
influence that the central metal and the ancillary ligand may
have in determining the co-ordination mode, i.e. η1, η2, µ, etc.,
of the hydrazine ligand and in which way the co-ordination to a
metal fragment may change the properties of the NH2NH2 or
RNHNH2 molecule towards reduction, oxidation and deproto-
nation reactions.
We are interested in the chemistry of partially reduced
dinitrogen ligands and have previously reported2 the synthesis
and the reactivity of some aryldiazenido and aryldiazene com-
plexes of transition metals stabilised by phosphite ligands. Now
we have extended these studies to include hydrazine and substi-
tuted hydrazines as ligands and in this report we describe the
synthesis, characterisation and some reactivity studies on
hydrazine derivatives of ruthenium().
NHMe)2{PPh(OMe)2}4][PF6]2 derivatives,3b,5 only recently the
phosphine complexes [{RuCl[P(OMe)3]2}2(µ-Cl)(µ-NH2NH2)-
(µ-S)]6 and [RuX(CO)2(NH2NH2)(PPh3)2]7 (X = Cl or Br) have
been prepared and fully characterised. It is therefore of interest
to report the synthesis of new hydrazine complexes of ruthen-
ium() together with some new properties shown by this class
of compounds.
Experimental
All synthetic work was carried out under an inert atmosphere
using standard Schlenk techniques or a Vacuum Atmospheres
dry-box. Once isolated, the complexes were relatively stable in
air, but were stored under an inert atmosphere Ϫ25 ЊC. All sol-
vents were dried over appropriate drying agents, degassed on a
vacuum line and distilled into vacuum-tight storage flasks. The
phosphites P(OMe)3 and P(OEt)3 (Aldrich) were purified by
distillation under nitrogen, while PPh(OEt)2 was prepared
by the method of Rabinowitz and Pellon.8 The hydrazines
MeNHNH2, PhNHNH2, 4-O2NC6H4NHNH2, PhCONHNH2
and Me2NNH2 were Aldrich products used as received. The
p-tolylhydrazine 4-MeC6H4NHNH2 was prepared by treating
under nitrogen the corresponding salt 4-MeC6H4NHNH3ϩClϪ
with a slight excess of NaOH in aqueous solution. A solid sep-
arated which, after 15 min of stirring, was filtered off, washed
with water and dried over P2O5 under vacuum for 24 h. It was
stored under nitrogen at Ϫ25 ЊC. Hydrazine NH2NH2 was pre-
pared by decomposition of hydrazine cyanurate (NH2NH2ؒ
C3H3N3O3) (Fluka) following the reported method.9 Other
reagents from commercial sources were of the highest available
purity and used as received. Infrared spectra were recorded on
a Nicolet Magna 750 Fourier-transform spectrophotometer,
NMR spectra (1H, 13C, 31P) on a Bruker AC200 spectrometer at
temperatures between Ϫ90 and ϩ30 ЊC, unless otherwise noted.
Mono- and di-nuclear hydrazine complexes of ruthenium()
are known and often contain a ‘diene’3 or a polydentate NS4-,
OS4- or OS5-type group4 as an ancillary ligand. With phosphine
or phosphite the reported compounds are very few and, apart
from the [RuX2(RNHNH2)L3], [{RuX2(N2H4)L2}2] (X = Cl or
Br; R = H or Ph; L = tertiary phosphine) and [Ru(NH2-
† Supplementary data available (No. SUP 57295, 3 pp.): physical and
spectroscopic characterisation data. See J. Chem. Soc., Dalton Trans.,
1997, Issue 1.
J. Chem. Soc., Dalton Trans., 1997, Pages 4435–4444
4435

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The SWANMR software package has been used in treating the
NMR data.10 Proton and 13C spectra are referred to internal
tetramethylsilane, 31P-{1H} chemical shifts with respect to 85%
H3PO4, downfield shifts being considered positive. The conduct-
ivities of 10Ϫ3 mol dmϪ3 solutions of the complexes in MeNO2
at 25 ЊC were measured with a Radiometer CDM 83 instru-
ment. Physical constants and elemental analyses for all the
complexes and spectroscopic data for the triflate, dinitrile and
aryldiazene complexes are available as SUP 57295.
[Ru(RNHNH2)2L4][BPh4]2 [L = P(OEt)3 4, PPh(OEt)2 5 or
P(OMe)3 6; R = H a, Me b or Ph c]. A solution of the appropri-
ate hydride [RuH2L4] (0.65 mmol) in toluene (10 cm3) was treat-
ed sequentially with 2 equivalents of CF3SO3H (0.65 mmol, 58
µl) in order to prepare a suspension of the triflate cation [Ru-
(η2-O2SOCF3)L4]ϩ. An excess of the appropriate hydrazine (3
mmol) was added and the mixture was stirred for 3 h and then
evaporated to dryness. The oil obtained was treated with eth-
anol (or methanol) (2 cm3) and an excess of NaBPh4 (2.6 mmol,
0.89 g) in alcohol (3 cm3) was added to the resulting solution,
giving a white solid which was filtered off and crystallised from
CH2Cl2 (2 cm3) and ethanol (or methanol) (5 cm3); yield у80%.
Synthesis of the complexes
The hydride species [RuH2L4] [L = P(OMe)3, P(OEt)3 or PPh-
(OEt)2] were prepared following previous methods.11
[Ru(ç2-PhCONHNH2)L4][BPh4]2 [L = P(OEt)3 7 or PPh-
(OEt)2 8]. These complexes were prepared following the method
reported above for the bis(hydrazine) derivatives 4–6. In this
case, an excess of solid benzoylhydrazine (1 mmol, 0.136 g) was
[Ru(ç2-O2SOCF3){P(OEt)3}4]BPh4. To
a
solution of
[RuH2{P(OEt)3}4] (0.26 mmol, 2 g) in toluene (10 cm3) cooled to
Ϫ78 ЊC was added an equivalent amount of CF3SO3H (0.26
mmol, 23 µl) and the mixture brought to 0 ЊC and stirred for 1
h. The solution was cooled again to Ϫ78 ЊC and another
equivalent of CF3SO3H (0.26 mmol, 23 µl) added. After room
temperature was reached the reaction mixture was stirred for 2
h and then evaporated to dryness. The oil obtained was treated
with ethanol (5 cm3) giving a pale yellow solution to which an
excess of NaBPh4 (1 mmol, 0.34 g) in ethanol (2 cm3) was
added. A white solid slowly separated which was filtered off
and crystallised from CH2Cl2 (2 cm3) and ethanol (5 cm3); yield
у90%.
added to
a
freshly prepared suspension of [Ru(η2-O2-
SOCF3)L4]ϩ (0.26 mmol) in toluene (10 cm3) and the reaction
mixture, after the addition of CH2Cl2 (10 cm3), stirred for 24 h.
After filtration, the solvent was removed under reduced pres-
sure to give an oil which was triturated with ethanol (3 cm3).
The addition of an excess of NaBPh4 (1 mmol, 0.342 g) in
ethanol (5 cm3) to the resulting solution gave a white solid
which was filtered off and crystallised from CH2Cl2 (3 cm3) and
ethanol (5 cm3); yield у60%.
[Ru(ç1-OSO2CF3)(Me2NNH2){P(OEt)3}4]BPh4 9. An excess
of N,N-dimethylhydrazine (1.2 mmol, 91 µl) was added to a
freshly prepared suspension of [Ru(η2-O2SOCF3)L4]ϩ (0.3
mmol) in toluene (10 cm3) and the reaction mixture stirred for
24 h. The solvent was removed under reduced pressure to give
an oily product which was treated with ethanol (4 cm3) contain-
ing an excess of NaBPh4 (2 mmol, 0.68 g). A white solid slowly
separated under vigorous stirring, which was filtered off and
crystallised from CH2Cl2 (2 cm3) and ethanol (5 cm3); yield
у70%.
[RuH(ç1-OSO2CF3){P(OEt)3}4]. An equimolar amount of
triflic acid (CF3SO3H) (0.26 mmol, 23 µl) was added to a solu-
tion of [RuH2{P(OEt)3}4] (0.26 mmol, 0.20 g) in ethanol (6 cm3)
cooled to Ϫ78 ЊC. The reaction mixture was brought to 0 ЊC,
stirred for 2 h and then the solvent removed under reduced
pressure. The oil obtained was treated with light petroleum (b.p.
40–60 ЊC) (3 × 3 cm3), filtered and the resulting solution
evaporated to dryness leaving an oily product. We were not
able to crystallise this oil, but the IR and NMR spectra indicate
the presence of only one, pure compound and confirm the
proposed formulation.
[Ru(RNHNH2)(MeCN)L4][BPh4]2 [L = P(OEt)3 10 or PPh-
(OEt)2 11; R = H a, Ph c or 4-O2NC6H4 e]. To a solution of
[Ru(MeCN)2L4][BPh4]2 (0.25 mmol) in CH2Cl2 (6 cm3) was
added an equimolar amount of the appropriate hydrazine (0.25
mmol) and the reaction mixture was stirred at room temper-
ature for 24 h. The solvent was removed under reduced pressure
giving an oil which was treated with ethanol (2 cm3) and vigor-
ously stirred at 0 ЊC until a white solid separated from the
resulting solution. The solid was filtered off and crystallised by
slow cooling to Ϫ25 ЊC of its solution prepared by dissolving
the compound in ethanol (5 cm3) and enough CH2Cl2 to obtain
a saturated solution at room temperature; yield у45%.
[Ru(4-MeC6H4CN)2L4][BPh4]2 and [Ru(MeCN)2L4][BPh4]2
[L = P(OEt)3 or PPh(OEt)2]. To a solution of the appropriate
hydride [RuH2L4] (0.5 mmol) in toluene (10 cm3) cooled to
Ϫ78 ЊC were sequentially added first one and then a second
equivalent of CF3SO3H in order to generate in solution the
[Ru(η2-O2SOCF3)L4]ϩ cation, as previously described. An
excess of the appropriate nitrile (2 mmol) was added to the
resulting solution, which was stirred for 4 h and then evapor-
ated to dryness. The oil obtained was treated with ethanol con-
taining an excess of NaBPh4 (2 mmol, 0.68 g) and the resulting
solution stirred until a white solid separated, which was filtered
off and crystallised from CH2Cl2 (3 cm3) and ethanol (8 cm3);
yield у80%.
[Ru(RNHNH2)(4-MeC6H4CN)L4][BPh4]2 [L = P(OEt)3 12
or PPh(OEt)2 13; R = Ph c or 4-MeC6H4 d]. These complexes
were prepared exactly like the related 10 and 11 by treating the
dinitrile complex [Ru(4-MeC6H4CN)2L4][BPh4]2 with an equi-
molar amount of the appropriate hydrazine in CH2Cl2 for 24 h;
yield у50%.
[RuH(RNHNH2)L4]BPh4 [L = P(OEt)3 1, PPh(OEt)2 2 or
P(OMe)3 3; R = H a, Me b, Ph c, 4-MeC6H4 d or 4-O2NC6H4 e].
An equimolar amount of CF3SO3H (0.26 mmol, 23 µl) was
added to a solution of the appropriate hydride [RuH2L4] in
ethanol (or methanol) (6 cm3) cooled to Ϫ78 ЊC and the reac-
tion mixture brought to 0 ЊC and stirred for 1 h. An excess of
the appropriate hydrazine (0.5 mmol) was added to the result-
ing solution, which was stirred at room temperature for a
period varying between 3 h, in the case of NH2NH2, and 5 h, in
the case of the arylhydrazines. The addition of an excess of
NaBPh4 (1.1 mmol, 0.376 g) caused the precipitation of a white
solid which was filtered off and crystallised from CH2Cl2
(3 cm3) and ethanol (7 cm3); yield from 50 to 80%.
[Ru(4-O2NC6H4NHNH2)(4-MeC6H4CN){P(OEt)3}4][BPh4]2
12e and [Ru(Me2NNH2)(4-MeC6H4CN){P(OEt)3}4][BPh4]2 12f.
To a solution of [Ru(4-MeC6H4CN)2{P(OEt)3}4][BPh4]2 (0.12
mmol, 0.20 g) in CH2Cl2 (20 cm3) was added an excess of the
appropriate hydrazine (0.30 mmol) and the reaction mixture
stirred for 24 h. The solvent was removed under reduced pres-
sure giving an oil which was triturated with ethanol (3 cm3). The
resulting solution was vigorously stirred until a solid separated
which was filtered off and crystallised from a mixture of
CH2Cl2 and ethanol. A typical crystallisation involved the
preparation of a solution of the compound by treating the solid
sample with ethanol (7 cm3) and enough CH2Cl2 to obtain a
[RuH(Me2NNH2){P(OEt)3}4]BPh4 1f. This complex was pre-
pared like 1–3 using a reaction time of 9 h; yield у70%.
4436
J. Chem. Soc., Dalton Trans., 1997, Pages 4435–4444

View Article Online
(i)
saturated solution at room temperature which was slowly
cooled to Ϫ25 ЊC giving microcrystals of the product; yield
у55%.
[RuH2L4]
[RuH(η1-OSO2CF3)L4]
(iii)
[RuH(RNHNH2)L4]ϩ
1,2,3
[Ru{ç2-NH᎐C(4-MeC H )NHNH }{P(OEt) } ][BPh ]
14
and [Ru{ç2-NH᎐C(Me)N(Me)NH }{P(OEt) } ][BPh ] 15. An
᎐
6
4
2
3
4
4 2
(ii)
᎐
[RuH2L4]
[Ru(η2-O2SOCF3)L4]ϩ
2
3
4
4 2
equimolar amount of the hydrazine NH2NH2 or MeNHNH2
(0.2 mmol) was added to a solution of the appropriate nitrile
complex [Ru(RCN)2{P(OEt)3}4][BPh4]2 (R = 4-MeC6H4 or Me)
(0.2 mmol) in CH2Cl2 (10 cm3) and the reaction mixture stirred
for 24 h. The solvent was removed under reduced pressure
giving an oil which was treated with ethanol (3 cm3) containing
an excess of NaBPh4 (0.3 mmol, 0.1 g). A white solid separated
from the resulting solution which was filtered off and fraction-
ally crystallised in order to separate the amidrazone complex
in pure form. A typical separation involved the addition of
ethanol (7 cm3) to the raw solid sample and enough CH2Cl2 to
obtain a saturated solution at room temperature. By slow cool-
ing to 0 ЊC a first fraction of the complex 14 or 15 was obtained.
Further cooling of the solution to Ϫ30 ЊC gave an impure frac-
tion which must be recrystallised. The total yield obtained of
the pure compound was about 35%.
(iii)
[Ru(RNHNH2)2L4]2ϩ
4,5,6
Scheme 1 L = P(OEt)3 1 or 4, PPh(OEt)2 2 or 5 or P(OMe)3 3 or 6;
R = H a, Me b, Ph c, 4-MeC6H4 d or 4-O2NC6H4 e or Me2-NNH2 f. (i)
One equivalent of CF3SO3H at Ϫ78 ЊC; (ii) 2 equivalents of CF3SO3H
at Ϫ78 ЊC; (iii) an excess of RNHNH2
standard reflection was monitored to check crystal decom-
position or loss of alignment. A decay (15%) was detected and a
correction applied during data reduction. Lorentz-polarisation
effects were also considered.
The structure consists of discrete [Ru(η2-O2CMe)-
{P(OEt)3}4]ϩ cations and BPh4Ϫ anions. The phase problem was
solved by direct methods12 and the structure refined by full-
matrix least squares based on F2 with non-hydrogen atoms
belonging to the cation allowed anisotropic vibration. All
hydrogen atoms were introduced in idealised positions and
refined riding on their attached atoms. To prevent overfitting,
the C᎐C and C᎐O bond distances were restrained to be similar
for all ethoxy groups, and the thermal motion of carbon atoms
was restrained to be approximately isotropic and to fulfil rigid-
bond requirements, as implemented in SHELXL 93.13 Neutral
scattering factors were employed and anomalous dispersion
terms were included for non-hydrogen atoms. Calculations were
performed on an ENCORE91 computer using the programs
SIR 92,12 SHELXL 93,13 PARST 9514 and ZORTEP.15 Use was
made of the Cambridge Structural Database16 facilities at the
Centro di Studio per la Strutturistica Diffrattometrica del
C.N.R. in Parma.
Oxidation reactions
The oxidation of the hydrazine complexes was carried out
at low temperature (Ϫ30 to Ϫ40 ЊC) using Pb(O2CMe)4 as an
oxidant. In a typical reaction a sample of the appropriate com-
plex (0.2 mmol) was placed in a three-necked flask (25 cm3)
fitted with a solid-addition sidearm containing an equimolar
amount or an excess of Pb(O2CMe)4. Dichloromethane was
added, the solution cooled to Ϫ30 or Ϫ40 ЊC and the Pb(O2-
CMe)4 added portionwise in about 20–30 min to the cold stirred
solution. Then the solution was filtered and the solvent
removed under reduced pressure giving an oil which was treated
with ethanol (5 cm3) containing an excess of NaBPh4 (0.4
mmol, 0.14 g). A yellow or white solid slowly separated which
was filtered off and crystallised.
CCDC reference number 186/719.
[Ru(ç2-O2CMe){P(OEt)3}4]BPh4 16. This complex was ob-
tained in high yield (у80%) as a white solid from the oxidation
of the [Ru(NH2NH2)2L4]2ϩ or the [Ru(MeNHNH2)2L4]2ϩ cation
(0.2 mmol) with Pb(O2CMe)4 (0.4 mmol, 0.177 g). The complex
was crystallised from ethanol.
Results and Discussion
Preparation of hydrazine complexes
Hydridehydrazine [RuH(RNHNH2)L4]BPh4 1–3 and bis(hydra-
zine) complexes [Ru(RNHNH2)2L4][BPh4]2 4–6 were prepared
by treating hydride species [RuH2L4] first with triflic acid and
then with the appropriate hydrazine, as shown in Scheme 1. The
reaction of [RuH2L4] with 1 equivalent of CF3SO3H at low
temperature proceeds with the formation of the dihydrogen
[RuH(PhN᎐NH){P(OEt) } ]BPh 18. The compound was
᎐
3
4
4
prepared by oxidation of [RuH(PhNHNH2){P(OEt)3}4]BPh4
(0.2 mmol, 0.24 g) with an equimolar amount of Pb(O2CMe)4
(0.2 mmol, 0.089 g). The reaction product also contains the
[Ru(η2-O2CMe){P(OEt)3}4]BPh4 complex which was removed
by fractional crystallisation from ethanol giving a pure sample
cations17 [RuH(η2-H2)L4]ϩCF3SO3 (detected by the H NMR
spectra of the solution) which slowly afford the final triflate
complexes [RuH(η1-OSO2CF3)L4] by substitution of the H2 lig-
and with the CF3SO3Ϫ ion. In the case of the P(OEt)3 coligand
the [RuH(η1-OSO2CF3){P(OEt)3}4] complex was also separated
as an oily product and characterised by IR and NMR spec-
troscopy. Treatment of the η1-triflate complexes with further
CF3SO3H probably results in the formation of new, unstable
dihydrogen derivatives [Ru(η2-H2)(η1-OSO2CF3)L4]ϩ which lose
H2 and give the η2-triflate [Ru(η2-O2SOCF3)L4]ϩ cations which
Ϫ
1
of [RuH(PhN᎐NH){P(OEt) } ]BPh ; yield у20%.
᎐
3
4
4
[Ru(PhN᎐NH) {P(OEt) } ][BPh ] 19. The compound was
᎐
2
3
4
4 2
prepared by oxidation of [Ru(PhNHNH2)2{P(OEt)3}4][BPh4]2
(0.2 mmol, 0.32 g) with Pb(O2CMe)4 (0.4 mmol, 0.177 g) in a
1:2 ratio. A mixture of [Ru(PhN᎐NH) {P(OEt) } ][BPh ] and
᎐
2
3
4
4 2
[Ru(η2-O2CMe){P(OEt)3}4]BPh4 was obtained from which the
bis(diazene) derivative was separated by fractional crystallis-
ation from ethanol; yield у25%.
Ϫ
can be isolated as BPh4 salts and characterised. The η2 co-
ordination of the CF3SO3 ligand in these monocationic18 com-
plexes is further supported by the symmetric A2B2 multiplet
observed in the 31P-{1H} NMR spectra. By treating both the
η1- and η2-triflate complexes with the appropriate hydrazine the
new ruthenium derivatives 1–6 can easily be prepared and
characterised.
Crystallography
Suitable crystals of complex 16 for X-ray analysis were
obtained by recrystallisation from ethanol. Automatic peak
search and indexing procedures carried out on a Siemens AED
diffractomer yielded a monoclinic primitive cell. Inspection of
systematic absences and E statistics indicated unambiguously
the space group as P21/n. Pertinent crystal data and basic
information about data collection and structure refinement are
given in Table 2. During data collection the intensity of one
Good analytical data were obtained for all the hydrazine
complexes 1–6 which are pale yellow or white solids, stable in
the air and soluble in polar organic solvents where they behave
as 1:1 (1–3) or 2:1 (4–6) electrolytes.18 Their infrared and
NMR data are reported in Table 1. The presence of the hydra-
J. Chem. Soc., Dalton Trans., 1997, Pages 4435–4444
4437

View Article Online
Table 1 Infrared and NMR data for the ruthenium complexes
IRb
1H NMRc,d
31P-{1H} NMRc,e
Spin system δ (J/Hz)
Compounda
ν /cmϪ1
Assignment
δ
Assignment
1a [RuH(NH2NH2)-
{P(OEt)3}4]ϩ
3376m
3338m
3273m
1879m
1592w
3348m
3322m
1839m
ν(NH)
4.20–3.78 (m)f
3.14 (br)
1.29 (t), 1.25 (t)
1.21 (t)
Ϫ7.68 to Ϫ8.68 (m) RuH
4.28–3.90 (m)
3.10 (m)
POCH2CH3
RuNH2
POCH2CH3
AB2Cf
δA 148.9, δB 142.5, δC 137.4
JAB = 62.7, JAC = 39.2,
JBC = 45.2
ν(RuH)
δ(NH2)
ν(NH)
1b [RuH(MeNHNH2)-
{P(OEt)3}4]ϩ
POCH2CH3
CH3NH
CH3NH
AB2C
δA 150.9, δB 143.9, δC 139.3
JAB = 62.7, JAC = 39.8,
JBC = 44.6
ν(RuH)
2.49 (d)
1.31 (t), 1.29 (t),
1.24 (t)
POCH2CH3
Ϫ7.60 to Ϫ8.60 (m) RuH
1c [RuH(PhNHNH2)-
{P(OEt)3}4]ϩ
3367m
3323m
3312m
1839m
1605m
ν(NH)
4.89 (m)g
C6H5NH
RuNH2
AB2Cg
δA 148.4, δB 141.4. δC 136.8
JAB = 62.8, JAC = 39.3,
JBC = 45.6
4.79 (m)
4.12–3.78 (m)
1.27 (t), 1.21 (t),
1.18 (t)
POCH2CH3
POCH2CH3
ν(RuH)
δ(NH2)
1d [RuH(4-MeC6H4NHNH2)-
{P(OEt)3}4]ϩ
3356w
3331w
3322w
1875m
1605m
ν(NH)
δA 150.0, δB 142.8, δC 138.3
JAB = 62.8, JAC = 39.5,
JBC = 45.4
ν(RuH)
δ(NH2)
1e [RuH(4-O2NC6H4NHNH2)- 3392m
ν(NH)
δA 149.2, δB 142.1, δC 137.7
JAB = 63.4. JAC = 40.4,
JBC = 45.5
{P(OEt)3}4]ϩ
3369m
3312m
1844m
1602m
ν(RuH)
δ(NH2)
Ϫ7.35 to Ϫ8.35 (m) RuH
1f [RuH(Me2NNH2)-
{P(OEt)3}4]ϩ
3316m
1879m
ν(NH)
ν(RuH)
4.30 (m, br)
4.26–3.95 (m)
2.50 (s)
RuNH2
POCH2CH3
N(CH3)2
AB2C
AB2Cf
AB2C
δA 151.6, δB 142.9, δC 137.4
JAB = 62.7, JAC = 36.2,
JBC = 47.1
1.31 (t), 1.26 (t)
POCH2CH3
Ϫ7.33 to Ϫ8.36 (m) RuH
2a [RuH(NH2NH2)-
{PPh(OEt)2}4]ϩ
3370w
3333w
3265w
ν(NH)
4.00–3.16 (m)f
3.44 (m, br)
1.25 (t), 1.22 (t),
1.18 (t), 0.88 (t)
POCH2CH3
RuNH2
POCH2CH3
δA 170.3, δB 165.0, δC 159.9
JAB = 46.6, JAC = 28.7,
JBC = 31.8
1922m(br) ν(RuH)
Ϫ7.43 to Ϫ8.33 (m) RuH
2b [RuH(MeNHNH2)-
{PPh(OEt)2}4]ϩ
3341w
3305 m
1942m
ν(NH)
4.26 (br)
4.10–3.25 (m)
3.60 (m)
RuNH2
POCH2CH3
CH3NH
δA 171.9, δB 166.0, δC 161.0
JAB = 46.8, JAC = 29.3,
JBC = 30.6
ν(RuH)
2.36 (d)
CH3NH
1.28 (t), 1.27 (t),
1.23 (t), 0.91 (t)
POCH2CH3
Ϫ7.32 to Ϫ8.22 (m) RuH
2c [RuH(PhNHNH2)-
{PPh(OEt)2}4]ϩ
3380w
3305w
3228w
1908m
1601m
ν(NH)
5.44 (br)
4.49 (br)
C6H5NH
RuNH2
AB2C
δA 171.4, δB165.7, δC 161.6
JAB = 46.8, JAC = 30.1,
JBC = 31.8
4.50–3.30 (m)
1.28 (t), 1.16 (t),
1.04 (t), 0.97 (t)
POCH2CH3
POCH2CH3
ν(RuH)
δ(NH2)
3a [RuH(NH2NH2)-
{P(OMe)3}4]ϩ
3365w
3340m
3279w
1875m
ν(NH)
AB2Cf
δA 154.0, δB 148.3, δC 142.2
JAB = 63.6, JAC = 40.0,
JBC = 44.4
ν(RuH)
Ϫ7.59 to Ϫ8.59 (m) RuH
f
4a [Ru(NH2NH2)2-
{P(OEt)3}4]2ϩ
3375m
3325w
3315 (sh)
3266w
1617m
3350w
3313w
3299w
1597w
ν(NH)
4.38 (br)f
RuNH2
POCH2CH3
NH2
A2B2
δA 130.2, δB 120.5
JAB = 61.8
4.20–3.90 (m)
2.90 (br)
1.33 (t), 1.29 (t)
POCH2CH3
δ(NH2)
ν(NH)
4b [Ru(MeNHNH2)2-
{P(OEt)3}4]2ϩ
4.98 (br)
4.45–4.20 (m)
2.90 (br)
RuNH2
POCH2CH3
CH3NH
A2B2
A2B2
δA 131.3, δB 121.3
JAB = 62.1
δ(NH2)
ν(NH)
2.68 (d)
CH3NH
1.42 (t), 1.37 (t)
6.65 (t, br)
5.85 (br)
POCH2CH3
C6H5NH
RuNH2
4c [Ru(PhNHNH2)2-
{P(OEt)3}4]2ϩ
3317m
3298w
3240w
1601w
δA 130.0, δB 120.6
JAB = 62.0
4.54–4.30 (m)
1.42 (t), 1.39 (t)
POCH2CH3
POCH2CH3
δ(NH2)
4438
J. Chem. Soc., Dalton Trans., 1997, Pages 4435–4444

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Table 1 (Continued )
IRb
1H NMRc,d
31P-{1H} NMRc,e
Compounda
ν /cmϪ1
Assignment
δ
Assignment
Spin system δ (J/Hz)
4.00–3.30 (m)f
3.95 (br)
2.86 (br)
POCH2CH3
RuNH2
NH2
A2B2
δA 159.6, δB 151.4
JAB = 48.0
f
5a [Ru(NH2NH2)2-
{PPh(OEt)2}4]2ϩ
3370w
3342w
3317w
3263w
1603m
3334w
3302w
3259w
ν(NH)
1.27 (t), 1.24 (t)
POCH2CH3
δ(NH2)
ν(NH)
5b [Ru(MeNHNH2)2-
{PPh(OEt)2}4]2ϩ
4.23 (br)
4.00–3.60 (m)
3.95 (br)
RuNH2
POCH2CH3
CH3NH
A2B2
δA 159.8, δB 152.0
JAB = 47.9
2.27 (d)
1.39 (t), 1.36 (t)
5.33 (br)
CH3NH
POCH2CH3
RuNH2
5c [Ru(PhNHNH2)2-
{PPh(OEt)2}4]2ϩ
3330w
3305w
3294w
1601m
3374w
3344w
3312m
3270m
1609m
3296m
3236w
3207w
1632m
1603m
3509w
3295w
1627m
1603m
3302m
3232w
1616m
ν(NH)
A2B2
A2B2
δA 159.3, δB 152.1
JAB = 47.4
4.30–3.70 (m)
1.36 (t), 1.26 (t)
POCH2CH3
POCH2CH3
δ(NH2)
ν(NH)
5.06 (br)h
3.82 (t), 3.68 (m, br) POCH3
2.48 (br)
RuNH2
δA 137.4, δB 126.6
JAB = 61.4
h
6a [Ru(NH2NH2)2-
{P(OMe)3}4]2ϩ
NH2
δ(NH2)
ν(NH)
7 [Ru(η2-PhCONHNH2)-
{P(OEt)3}4]2ϩ
7.60 (t, br)f
5.55 (m, br)
4.20–3.90 (m)
1.32 (t), 1.30 (t)
1.18 (t)
NH
RuNH2
POCH2CH3
POCH2CH3
ABC2
δA 134.9, δB 132.0, δC 119.7
JAB = 84.7, JAC = 60.0,
JBC = 59.9
ν(CO)
δ(NH2)
ν(NH)
8 [Ru(η2-PhCONHNH2)-
{PPh(OEt)2}4]2ϩ
5.20 (m, br)f
4.10–3.50 (m)
1.38 (t), 1.32 (t),
1.23 (t), 1.20 (t)
5.12 (m, br)
4.44–4.10 (m)
2.72 (s)
RuNH2
POCH2CH3
POCH2CH3
ABC2
ABC2
δA 160.0, δB 158.7, δC 148.0
JAB = 63.8, JAC = 45.2,
JBC = 45.2
f
ν(CO)
δ(NH2)
ν(NH)
9 [Ru(η1-OSO2CF3)(Me2-
NNH2){P(OEt)3}4]ϩ
RuNH2
POCH2CH3
N(CH3)2
δA 134.1, δB 129.8, δC 120.8
JAB = 75.5, JAC = 59.6,
JBC = 65.3
δ(NH2)
ν(NH)
δ(NH2)
ν(NH)
1.41 (t), 1.38 (t),
1.37 (t), 1.35 (t)
5.78 (br)
5.56 (br)
4.40–4.20 (m)
2.67 (s)
1.41 (t), 1.37 (t).
1.34 (t)
7.14 (m, br)
4.40–4.10 (m)
2.22 (s)
1.40 (t), 1.38 (t),
1.34 (t), 1.31 (t)
4.10–3.60 (m)f
2.24 (br)
1.34 (t), 1.31 (t),
1.28 (t)
POCH2CH3
10c [Ru(PhNHNH2)(MeCN)-
{P(OEt)3}4]2ϩ
3365w
3357w
3311w
1601m
C6H5NH
RuNH2
POCH2CH3
CH3CN
ABC2
δA 130.0, δB 125.5, δC 120.1
JAB = 71.6, JAC = 57.6,
JBC = 63.1
POCH2CH3
10e [Ru(4-O2NC6H4NHNH2)-
(MeCN){P(OEt)3}4]2ϩ
3390w
3289w
3235w
1635m
RuNH2
POCH2CH3
CH3CN
ABC2
ABC2
ABC2
δA 134.8, δB 132.6, δC 120.1
JAB = 74.5, JAC = 62.3,
JBC = 57.2
δ(NH2)
ν(NH)
POCH2CH3
f
11a [Ru(NH2NH2)(MeCN)-
{PPh(OEt)2}4]2ϩ
3371w
3316w
3265w
POCH2CH3
RuNH2
POCH2CH3
δA 158.5, δB 155.5, δC 149.7
JAB = 55.5, JAC = 41.9,
JBC = 47.9
0.87 (s)
CH3CN
C6H5NH
RuNH2
POCH2CH3
CH3CN
POCH2CH3
11c [Ru(PhNHNH2)(MeCN)-
{PPh(OEt)2}4]2ϩ
3373w
3292w
3225w
1601m
ν(NH)
δ(NH2)
ν(NH)
5.08 (m, br)
4.89 (m, br)
4.20–3.80 (m)
1.49 (s)
1.43 (t), 1.41 (t),
1.37 (t), 1.09 (t)
5.93 (m)
5.69 (m)
4.50–4.25 (m)
2.47 (s)
δA 158.6, δB 155.9, δC 149.8
JAB = 56.7, JAC = 42.4,
JBC = 47.4
12c [Ru(PhNHNH2)(4-Me-
C6H4CN){P(OEt)3}4]2ϩ
3360w
3311w
3245w
2260m
1602m
C6H5NH
RuNH2
POCH2CH3
CH3 p-tolyl
POCH2CH3
ABC2
δA 129.9, δB 125.2, δC 119.6
JAB = 71.6, JAC = 57.6,
JBC = 63.0
ν(CN)
δ(NH2)
1.41 (t), 1.37 (t),
1.33 (t)
12d [Ru(4-MeC6H4NHNH2)-
3358w
ν(NH)
5.78 (br)
5.62 (br)
4.45–4.25 (m)
2.46 (s)
2.26 (s)
1.40 (t), 1.32 (t)
4.42–4.20 (m)
2.29 (s)
1.41 (t), 1.36 (t),
1.33 (t)
4-CH3C6H4NH ABC2
RuNH2
POCH2CH3
δA 130.0, δB 125.2, δC 119.7
JAB = 71.6, JAC = 57.5,
JBC = 62.8
(4-MeC6H4CN){P(OEt)3}4]2ϩ 3313w
3247w
2260m
1604m
ν(CN)
δ(NH2)
4-CH3 (CN)
4-CH3 (NHNH2)
POCH2CH3
POCH2CH3
CH3 p-tolyl
POCH2CH3
12e [Ru(4-O2NC6H4NHNH2)-
3380w
ν(NH)
ABC2
δA 133.9, δB 132.2, δC 119.7
JAB = 74.0, JAC = 62.3,
JBC = 57.8
(4-MeC6H4CN){P(OEt)3}4]2ϩ 3290w
3237w
2263m
1609m
ν(CN)
δ(NH2)
J. Chem. Soc., Dalton Trans., 1997, Pages 4435–4444
4439

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Table 1 (Continued )
IRb
1H NMRc,d
31P-{1H} NMRc,e
Spin system δ (J/Hz)
Compounda
ν /cmϪ1
Assignment
δ
Assignment
12f [Ru(Me2NHNH2)-
3308w
ν(NH)
ν(CN)
δ(NH2)
4.68 (m, br)
4.50–4.20 (m)
2.69 (s)
2.46 (s)
1.41 (t), 1.40 (t),
1.38 (t)
RuNH2
POCH2CH3
N(CH3)2
CH3 p-tolyl
POCH2CH3
ABC2
δA 130.2, δB 124.0, δC 119.8
JAB = 67.2, JAC = 57.5,
JBC = 64.8
(4-MeC6H4CN){P(OEt)3}4]2ϩ 2264m
1603m
13c [Ru(PhNHNH2)(4-Me-
C6H4CN){PPh(OEt)2}4]2ϩ
3377w
3293w
2250m
1602m
ν(NH)
5.26 (br)
5.09 (br)
4.30–3.50 (m)
2.38 (s)
1.47 (t), 1.40 (t)
9.57 (br)
C6H5NH
RuNH2
POCH2CH3
CH3 p-tolyl
POCH2CH3
ABC2
ABC2
δA 158.9, δB 155.1, δC 149.9
JAB = 56.1, JAC = 41.9,
JBC = 48.0
ν(CN)
δ(NH2)
14 [Ru{η2-NH᎐C(4-MeC6H4)- 3397w
ν(NH)
NH᎐
δA 135.2, δB 133.1, δC 120.4
JAB = 73.1, JAC = 62.1,
JBC = 57.3
f
᎐
᎐
NHNH2}{P(OEt)3}4]2ϩ
3333w
3310w
1635m
7.50 (m, br)
NH
δ(NH2)
7.20 (br)f
NH᎐
᎐
5.83 (m, br)
5.52 (m, br)
4.20–3.90 (m)
2.39 (s)
1.32 (s), 1.28 (t),
1.22 (t)
RuNH2
NH
POCH2CH3
CH3 p-tolyl
POCH2CH3
15 [Ru{η2-NH᎐C(Me)-
3399w
3307w
1641m
ν(NH)
7.80 (br)
6.55 (br)
NH᎐
RuNH2
POCH2CH3
NCH3 ϩ CCH3
POCH2CH3
132–118 (m)
᎐
᎐
N(Me)NH2}{P(OEt)3}4]2ϩ
δ(NH2)
4.45–4.15 (m)
2.55 (s), 2.45 (s)
1.40 (t), 1.38 (t),
1.34 (t)
4.25–4.05 (m)
1.86 (s)
16 [Ru(η2-O2CMe)-
{P(OEt)3}4]ϩi
1524m
ν(CO)
POCH2CH3
CH3CO2
POCH2CH3
A2B2
δA 139.5, δB 126.4
JAB = 57.2
f
1.32 (t), 1.29 (t)
a All compounds are BPh4Ϫ salts. b In KBr pellets. c In (CD3)2CO. d Phenyl-proton resonances are omitted. e Positive shift downfield from 85% H3PO4.
f In CD2Cl2. g In CDCl3. h In (CD3)2SO. i 13C NMR: δ 187.8 (m, CO), 165–122 (m, Ph), 62.5 (t), 62.3 (t) (CH2), 24.3 (s, MeCO2), 16.5 (t), 16.3 (t) (CH3
of phosphite).
excess Me2NNH2
L
[Ru(η2-O2SOCF3)L4]ϩ
L
L
H
L
NH2NHR
NH2NHR
[Ru(η1-OSO2CF3)(Me2NNH2)L4]ϩ
Ru
Ru
L
NH2NHR
L
9
L
L
I
II
Scheme 2 L = P(OEt)3
zine ligand in all the compounds is confirmed by the IR spectra
which show the characteristic ν(NH) and δ(NH2) bands,
observed at 3392–3228 (weak) and at 1617–1592 (medium)
L
Ru
L
L
1
cmϪ1, respectively. Furthermore, in the H NMR spectra the
O
L
OSO2CF3
NH2NMe2
L
C
N
Ru
NH2 and NH proton signals of the hydrazine ligand have been
identified and properly attributed by accurate integration and
decoupling experiments, so confirming the co-ordination of the
RNHNH2 ligand. Finally, in the complexes 1a–6a containing
the NH2NH2 ligand both the signals of the co-ordinated and
L
L
N
H
L
H
H
III
IV
1
free NH2 protons appear in the H spectra, so excluding the
the case of L = P(OEt)3 and characterised as the new hydra-
zinetriflate complex [Ru(η1-OSO2CF3)(Me2NNH2)L4]BPh4
presence of a dimeric complex with NH2NH2 bridging.
9
The infrared spectra of the hydridehydrazine derivatives
(Scheme 2). The infrared spectrum shows two ν(NH) bands at
3302 and 3232 cmϪ1 and δ(NH2) at 1616 cmϪ1 indicating the
presence of the hydrazine ligand. One band at 1325 cmϪ1 seems
to confirm the η1-O co-ordination of the triflate ion.19 The
[RuH(RNHNH2)L4]ϩ 1–3 also show
a medium-intensity
ν(RuH) band at 1922–1839 cmϪ1. Furthermore, in the 1H NMR
spectra the hydride ligand appears as a multiplet between δ
Ϫ8.68 and Ϫ7.15. Finally, in the temperature range from ϩ30
to Ϫ90 ЊC the 31P-{1H} NMR spectra appear as a AB2C multi-
plet simulable with the parameters reported in Table 1 and
suggesting the existence in solution of a type I geometry with
the hydride and the hydrazine ligands in a mutually cis position.
The 31P-{1H} NMR spectra of the bis(hydrazine) [Ru-
(RNHNH2)2L4]2ϩ 4–6 cations appear as a symmetric A2B2
multiplet in agreement, in this case, with a cis arrangement
(geometry II) of the two hydrazine ligands.
1
complex is a diamagnetic, 1:1 electrolyte18 and the H NMR
spectrum confirms the presence of both the hydrazine (NH2
protons at δ 5.12) and the phosphite ligands. Furthermore, the
31P-{1H} NMR spectrum appears as an ABC2 multiplet which
excludes the presence of a bis(hydrazine) complex and suggests
a type III geometry with the triflate and the Me2NNH2 ligands
in a mutually cis arrangement. The exclusive formation of
monohydrazine complexes with the disubstituted Me2NNH2
ligand may be reasonably attributed to the greater steric hind-
rance of the latter as compared to monosubstituted hydrazines
which prevents the co-ordination of two ligands in a cis
position to the RuL4 fragment.
Treatment of the η2-triflate complexes [Ru(η2-OSO2CF3)-
L4]ϩCF3SO3Ϫ with an excess of the disubstituted N,N-dimethyl-
hydrazine Me2NNH2 did not afford the bis(hydrazine) deriv-
ative but, surprisingly, a compound separated as a white solid in
Benzoylhydrazine also reacts with the η2-triflate cations
4440
J. Chem. Soc., Dalton Trans., 1997, Pages 4435–4444

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PhCONHNH2
[Ru(R2CN)2L4]2+
R1NHNH2
3 H3
[Ru(η2-O2SOCF3)L4]ϩ
[Ru(η2-PhCONHNH2)L4]2ϩ
7,8
2+
2+
H
H
H
H(Me)
H
L
L
Ru
L
H2(Me)
N3
N
N
N
L
N2
C
L
Ru
L
Scheme 3
L
N1
H1
VI
L
R2
C
R1NHNH2
R2
[Ru(R2CN)2{PPh(OEt)2}4]2ϩ
[Ru(R1NHNH2)(R2CN){PPh(OEt)2}4]2ϩ
11,13
Scheme 5 L = P(OEt)3; R1 = H or Me; R2 = 4-MeC6H4 or Me
L
R1NHNH2
[Ru(R1NHNH2)2{PPh(OEt)2}4]2ϩ
L
NH2NHR1
NCR2
Ru
L
5
L
R1 = H, Me, Ph, 4-MeC6H4, 4-O2NC6H4
R2 = Me 11, 4-MeC6H4 13
V
hydrazine complexes 10 and 12 can be separated by fractional
crystallisation and characterised. With N,N-dimethylhydrazine,
instead, the reaction is slow and affords only the mono-
substituted nitrilehydrazine [Ru(Me2NNH2)(4-MeC6H4CN)-
{P(OEt)3}4][BPh4]2 12f derivative which was isolated and char-
acterised. Treatment of the [Ru(R2CN)2{P(OEt)3}4]2ϩ deriv-
atives with the hydrazine NH2NH2 and the methylhydrazine
MeNHNH2 does not give the nitrilehydrazine complexes but a
mixture containing the known bis(hydrazine) compounds 4 and
new complexes which were separated and characterised (see
R1NHNH2
[Ru(R2CN)2{P(OEt)3}4]2ϩ
[Ru(R1NHNH2)(R2CN){P(OEt)3}4]2ϩ
10,12
R1NHNH2
[Ru(R1NHNH2)2{P(OEt)3}4]2ϩ
4
R1 = Ph, 4-MeC6H4, 4-O2NC6H4
R2 = Me 10, 4-MeC6H4 12
below) as the amidrazone20 derivatives [Ru{η2-NH᎐C(R2)-
᎐
N(R1)NH2}L4][BPh4]2 (R1 = H or Me; R2 = 4-MeC6H4 or Me)
14 and 15.
R1NHNH2
[Ru(R2CN)2{P(OEt)3}4]2ϩ
[Ru{η2-NH᎐C(R2)N(R1)NH2}{P(OEt)3}4]2ϩ
The nitrilehydrazine complexes [Ru(R1NHNH2)(R2CN)L4]-
[BPh4]2 10–13 are white or pale yellow solids stable in air and
are 1:2 electrolytes.18 The spectroscopic properties, Table 1,
confirm their formulation and suggest that the hydrazine and
the nitrile ligands are in a mutually cis position as in a type V
geometry.
᎐
14,15
ϩ [Ru(R1NHNH2)2{P(OEt)3}4]2ϩ
4
R1 = H, Me
R2 = Me, 4-MeC6H4
The IR spectra of the amidrazone complexes [Ru{η2-
NH᎐C(R2)N(R1)NH }L ][BPh ] 14 and 15 (Table 1) display
᎐
2
4
4 2
ν(NH) and δ(NH2) bands at 3399–3307 and 1641–1635 cmϪ1
,
Scheme 4
respectively, but do not show any ν(CN) band of the RCN
[Ru(η2-OSO2CF3)L4]ϩ to give the corresponding complexes
[Ru(η2-PhCONHNH2)L4][BPh4]2 7 and 8 which were isolated
and characterised (Scheme 3). The spectroscopic data (Table 1)
support the formulation of the compounds and suggest an η2
co-ordination of the benzoylhydrazine ligand, as shown in the
type IV geometry.
group. In the 1H NMR spectrum of the complex [Ru-
{η2-NH᎐C(4-MeC H )NHNH }{P(OEt) } ][BPh ] 14 three
᎐
6
4
2
3
4
4 2
slightly broad signals of intensity ratio 1:2:1 are present at δ
7.20, 5.83 and 5.52 (CD2Cl2) which were assigned by homo-
decoupling experiments to the H1, H3 and H2 protons, respect-
ively, of the amidrazone ligand schematised in geometry VI.
Good elemental analyses were obtained for the two complexes
14 and 15, the 31P NMR spectra of which are consistent with a
type VI geometry.
New hydrazine complexes of ruthenium of the type [Ru-
(R1NHNH2)(R2CN)L4][BPh4]2 10–13 were prepared by treating
the bis(nitrile) complexes [Ru(R2CN)2L4][BPh4]2 with the
appropriate hydrazine. The reaction proceeds easily, but
depends on several factors, including the nature of the phos-
phite ligand and of the hydrazine and the reaction conditions,
as shown in Scheme 4. The reaction of the bis(nitrile) cations
The formation of an amidrazone complex from the reaction
of a bis(nitrile) derivative with hydrazine NH2NH2 or methyl-
hydrazine is not completely unexpected, taking into account
that a co-ordinated nitrile can undergo nucleophilic attack by
several reagents such as alcohols, amines and carbanions to give
iminoethers, amidines and imines,21–24 respectively. Therefore,
taking into account that the first step of the reaction of the
bis(nitrile) with hydrazine is probably the substitution of one
R2CN ligand to give the [Ru(R1NHNH2)(R2CN)L4]2ϩ cations
(see Scheme 4), the formation of the amidrazone complexes can
be explained according to a reaction course that involves a
nucleophilic attack of one end of R1NHNH2 on the cyanide
carbon atom of the co-ordinated nitrile followed by a hydrogen
shift, giving a five-membered metallacycle (Scheme 5). A simi-
lar reaction, giving an amidrazone complex, has been observed
by us in iron derivatives25 and therefore it seems certain that
also a hydrazine molecule can behave as a reagent for nucleo-
philic attack upon co-ordinated nitrile24 giving the amidrazone
complexes. However, this cyclisation reaction is influenced both
by the substituent on the hydrazine and by the nature of the
ancillary phosphine ligand. In fact, the cyclisation reaction does
not take place with any arylhydrazine R1NHNH2 (R1 = Ph,
containing PPh(OEt)2, [Ru(R2CN)2{PPh(OEt)2}4]2ϩ
,
with
hydrazines proceeds with the substitution of both the R2CN
ligands giving a mixture of mono [Ru(R1NHNH2)(R2CN)L4]2ϩ
11,13 and bis(hydrazine) derivatives [Ru(R1NHNH2)2L4]2ϩ 5.
However, also operating at a low [Ru(R2CN)2L4]2ϩ: R1NHNH2
ratio, a mixture containing both the two hydrazine complexes
(11 or 13 and 5) was always obtained, the separation of which
was rather difficult and laborious. In only three cases, 11a, 11c
and 13c, we were able to separate by fractional crystallisation
the nitrilehydrazine complexes in pure form.
Also the related bis(nitrile) complexes [Ru(R2CN)2-
{P(OEt)3}4][BPh4]2 containing the P(OEt)3 phosphite ligands
react quickly with hydrazines R1NHNH2, but the reaction
depends on the nature of the substituent on the same hydrazine
molecule. With arylhydrazine it proceeds to give a mixture of
mono- and bis-(hydrazine) derivatives [Ru(R1NHNH2)-
(R2CN)L4]2ϩ 10 and 12 and [Ru(R1NHNH2)2L4]2ϩ 4 (R1 = Ph,
4-MeC6H4 or 4-O2NC6H4), respectively, from which the nitrile-
J. Chem. Soc., Dalton Trans., 1997, Pages 4435–4444
4441

View Article Online
(i)
L
Ru
L
[Ru(R1NHNH2)(R2CN)L4]2ϩ
12,13
L
O
O
CMe
L
[Ru(R1N᎐NH)(R2CN)L4]2ϩ ϩ [Ru(η2-O2CMe)L4]ϩ
᎐
VII
16,17
pared by us2b from the reaction of the hydride [RuH2-
{P(OEt)3}4] with the benzenediazonium salt PhN2ϩBF4Ϫ, fur-
ther confirms the proposed formulation and emphasises that
aryldiazene complexes of ruthenium() can be obtained both
by the insertion reaction of RN2ϩ into a Ru᎐H bond and by the
oxidation of an arylhydrazine derivative.
(i)
[RuH(R1NHNH2)L4]ϩ
1,2
[RuH(R1N᎐NH)L4]ϩ ϩ [Ru(η2-O2CMe)L4]ϩ
᎐
18
16,17
(i)
Oxidation of hydrazine complexes giving stable diazene
derivatives has been reported in a few cases4c,7,27 and often
involves dinuclear complexes with a diazene bridging unit. It
can be finally noted that the presence of the acetate complex 16
and 17 in the final oxidation product is not surprising as it may
be formed by substitution of the diazene ligand with the acetate
ion present in solution owing to the use of Pb(O2CMe)4 as
oxidising agent.
[Ru(R1NHNH2)2L4]2ϩ
4,5
[Ru(R1N᎐NH)2L4]2ϩ ϩ [Ru(η2-O2CMe)L4]ϩ
᎐
19
16,17
[RuH(NH2NH2)L4]ϩ




(i)
[Ru(η2-O2CMe)L4]ϩ
16,17
[Ru(NH2NH2)2L4]2ϩ
The results obtained on the oxidation of arylhydrazine com-
plexes prompted us to extend these studies to the hydrazine
NH2NH2 and methylhydrazine MeNHNH2 derivatives in an



[Ru(MeNHNH2)2L4]2ϩ
attempt to prepare the corresponding 1,2-diazene NH᎐NH and
᎐
Scheme 6 L = P(OEt)3 1,4,12,16,18,19, PPh(OEt)2 2,5,13,17; R1 = Ph,
4-MeC6H4; R2 = 4-MeC6H4. (i) Pb(O2CMe)4, CH2Cl2, Ϫ30 ЊC
methyldiazene MeN᎐NH complexes of RuII. Unfortunately,
᎐
although the oxidation reaction proceeds easily with Pb(O2-
CMe)4, the only isolated products were the acetate [Ru(η2-
O2CMe)L4]BPh4 complexes in high yield. Probably, also in this
case, the oxidation reaction proceeds to give the diazene ligand
which is labile in the complexes and can be substituted by the
acetate ion giving [Ru(η2-O2CMe)L4]ϩ as the final product. We
also attempted to oxidise the hydrazine ligand using other
reagents such as O2, H2O2, ButO2H, but the formation of the
diazene complexes was not observed. Equimolar amounts of
the hydrazine complex and the oxidizing agent gave no reaction,
while the use of an excess of reagent or reflux conditions caused
decomposition of the complex. Therefore, it seems that only
Pb(O2CMe)4 can give selective oxidation of the co-ordinated
hydrazine affording the corresponding diazene which is rather
labile and can be substituted by the MeCO2Ϫ ion giving [Ru(η2-
O2CMe)L4]BPh4 as final product. The acetate complex has also
been obtained in pure form and fully characterised in the case
of [Ru(η2-O2CMe){P(OEt)3}4]BPh4 16 containing P(OEt)3 as
supporting ligand and its spectroscopic data are reported in
Table 1. Compound 16 is a white solid stable in the air and in
solutions of polar organic solvents where it behaves as a 1:1
electrolyte.18 In the IR spectrum the ν(CO) band of the acetate
ligand is observed at 1524 cmϪ1, while in the 1H NMR spectrum
the methyl protons of the MeCO2 group appear as a singlet at δ
1.86. Furthermore, in the 13C spectrum the carbonyl carbon
atom of the acetate ligand appears as a multiplet at δ 187.8
while the methyl carbon atom appears at δ 24.3. Finally, in the
temperature range between ϩ20 and Ϫ80 ЊC the 31P spectra
appear as a symmetric A2B2 multiplet consistent with the
formulation proposed containing a η2-acetate ligand28 and
schematised in geometry VII.
4-MeC6H4 or 4-O2NC6H4) and this absence of reactivity may be
reasonably attributed to the steric hindrance of the aryl
substituent of the co-ordinated hydrazine. Furthermore, the
amidrazone complexes are formed only with the P(OEt)3 lig-
and, while no evidence of such a reaction has been observed
with the nitrilehydrazine derivatives [Ru(NH2NH2)(R2CN)L4]2ϩ
and [Ru(MeNHNH2)(R2CN)L4]2ϩ containing PPh(OEt)2 as
ancillary ligands. Therefore, it seems that a nitrile bonded to
a Ru(RNHNH2)L4 fragment can undergo nucleophilic attack
on the cyanide carbon atom only when the phosphines are
good π-acceptor ligands such as P(OEt)3 and when a hydrazine
such as NH2NH2 or MeNHNH2 is used. With the less π-acidic
PPh(OEt)2,26 instead, the cyclisation reaction does not take
place, so emphasising the important influence that the ancillary
ligands have in the formation of the amidrazone complexes.
Oxidation reactions
Hydrazine complexes of ruthenium() react with Pb(O2CMe)4
in CH2Cl2 at Ϫ30 ЊC to give the corresponding diazene deriv-
atives and/or the acetate [Ru(η2-O2CMe)L4]BPh4 complexes as
shown in Scheme 6. Treatment of both mono- (1,2,12,13) and
bis-(arylhydrazine) (4,5) complexes with Pb(O2CMe)4 at
Ϫ30 ЊC results in the formation of the corresponding aryl-
diazenes which, however, can be isolated as a mixture of prod-
ucts containing also the acetate complex [Ru(η2-O2CMe)L4]-
BPh4 16 and 17 and the starting hydrazine compound. The
amount of the three products in the mixture depends on the
ratio between the hydrazine complexes and the Pb(O2CMe)4
and on the reaction time. In each case a mixture of products was
obtained from which the separation of pure samples of aryl-
diazene was rather difficult. However, although the presence of
Such a geometry is confirmed by a crystal structure
determination of compound 16 the asymmetric unit of which
1
Ϫ
the diazene complex can easily be detected by the H NMR
contains a [Ru(η2-O2CMe){P(OEt)3}4]ϩ cation and a BPh4
spectra, in the case of the oxidation of [Ru(PhNHNH2)2-
{P(OEt)3}4][BPh4]2 4c and [RuH(PhNHNH2){P(OEt)3}4]BPh4
1c we were able to separate by fractional crystallisation the
anion. A perspective view of the cation is shown in Fig. 1, along
with the labelling scheme. Relevant geometric parameters are
reported in Table 3. The ruthenium is co-ordinated to four
phosphorus and two oxygen atoms in a distorted octahedral
fashion. The acetate acts as a symmetric bidentate ligand
[Ru᎐O(13) 2.195(6), Ru᎐O(14) 2.221(6) Å] and lies in the plane
containing Ru, P(1) and P(4). The line defined by Ru, C(49) and
C(50) bisects the angle P(1)᎐Ru᎐P(4) [P(1)᎐Ru᎐C(49) 132,
P(4)᎐Ru᎐C(49) 136Њ]. If the ethoxy groups are neglected, the
geometry of the complex closely approximates the C2v point-
group symmetry, with the two-fold axis placed along the
compounds [Ru(PhN᎐NH) {P(OEt) } ][BPh ] 19 and [RuH-
᎐
2
3
4
4 2
(PhN᎐NH){P(OEt) } ]BPh 18 in pure form. Their character-
᎐
3
4
4
isation is supported by the characteristic high-frequency NH
1
signal at δ 15–14 observed in the H NMR spectra and by the
A2B2 and ABC2 multiplets, respectively, in the 31P spectra. Fur-
thermore, a comparison of their spectroscopic data with those
of the phenyldiazene complexes [Ru(PhN᎐NH) {P(OEt) } ]-
᎐
2
3 4
[BPh4]2 or [RuH(PhN᎐NH){P(OEt) } ]BPh , previously pre-
᎐
3
4
4
4442
J. Chem. Soc., Dalton Trans., 1997, Pages 4435–4444

View Article Online
in the compression of the angles P(3)᎐Ru᎐O and P(2)᎐Ru᎐O
Table 2 Crystal data and structure refinement for [Ru(η2-O2CMe)-
{P(OEt)3}4]BPh4 16
(average = 85.4Њ) with respect to P(3)᎐Ru᎐P and P(2)᎐Ru᎐P
(average = 93.7Њ). The steric origin of this deformation is con-
firmed by comparison of the above average values with those
(84.2 and 94.4Њ respectively) found in the structure of [Ru-
{P(OPh)(OMe)2}4(O2CMe)]PF6,29 where, in addition, the larger
repulsion due to the bulkier phosphite substituents increases
the angle P(1)᎐Ru᎐P(4) involving the groups trans to the acetate
(98.5 compared with 91.9Њ found in this work). The geometry of
the co-ordinated anion agrees well with the average structure
found for bidentate acetates bound to Ru (average values for 20
molecules in the Cambridge Structural Database: C᎐C 1.50,
C᎐O 1.27, Ru᎐O 2.19 Å; O᎐C᎐O 118.0, O᎐Ru᎐O 59.6Њ).
Empirical formula
M
C50H83BO14P4Ru
1143.99
T/K
Crystal system
Space group
293(2)
Monoclinic
P21/n
a/Å
b/Å
c/Å
13.472(3)
24.268(5)
18.965(4)
94.68(5)
β/Њ
U/Å3
6180(2)
Z
4
Dc/Mg mϪ3
1.224
0.412
µ/mmϪ1
F(000)
λ/Å
2396
0.710 69
Acknowledgements
The financial support of Ministero dell’ Università e della
Ricerca Scientifica e Tecnologica and the Consiglio Nazionale
della Ricerche, Rome, is gratefully acknowledged. We thank
Dr. G. Balacco (Menarini Ricerche S.p.A.) for use of his NMR
software SWANMR and D. Baldan for technical assistance.
θ Range for data collection/Њ
Index ranges
3 to 27
Ϫ17 < h < 17, 0 р k р 31,
0 р l р 24
13 871
13 478
13 478, 337, 537
1.025
Reflections collected
Independent reflections
Data, restraints, parameters
Goodness of fit on F2
Final R indices [I > 2σ(I)]
R1 = 0.0756, wR2 = 0.1993
0.672, Ϫ0.521
Largest ∆F peak and hole/e ÅϪ3
References
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Table 3 Selected bond distances (Å) and angles (Њ) with estimated
standard deviations in parentheses
Ru᎐P(1)
Ru᎐P(2)
Ru᎐P(3)
Ru᎐P(4)
Ru᎐O(13)
2.216(3)
2.342(3)
2.339(3)
2.222(3)
2.195(6)
Ru᎐O(14)
2.221(6)
O(13)᎐C(49)
O(14)᎐C(49)
C(49)᎐C(50)
1.277(13)
1.254(12)
1.493(14)
P(1)᎐Ru᎐P(2)
P(1)᎐Ru᎐P(3)
P(1)᎐Ru᎐P(4)
P(1)᎐Ru᎐O(13)
P(1)᎐Ru᎐O(14)
P(2)᎐Ru᎐P(3)
P(2)᎐Ru᎐P(4)
P(2)᎐Ru᎐O(13)
P(2)᎐Ru᎐O(14)
P(3)᎐Ru᎐P(4)
96.98(9)
95.05(10)
91.95(10)
102.54(17)
161.30(17)
167.52(9)
90.04(9)
87.78(17)
83.71(17)
92.90(9)
P(3)᎐Ru᎐O(13)
P(3)᎐Ru᎐O(14)
P(4)᎐Ru᎐O(13)
P(4)᎐Ru᎐O(14)
O(13)᎐Ru᎐O(14)
Ru᎐O(13)᎐C(49)
Ru᎐O(14)᎐C(49)
O(13)᎐C(49)᎐O(14) 117.8(10)
O(13)᎐C(49)᎐C(50) 120.2(9)
O(14)᎐C(49)᎐C(50) 121.9(8)
86.35(17)
83.82(17)
165.51(16)
106.75(18)
58.8(2)
92.0(5)
91.5(6)
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Fig. 1 An ORTEP view of [Ru(η2-O2CMe){P(OEt)3}4]ϩ with thermal
ellipsoids shown at 30% probability level. Ethoxy groups are omitted
for clarity
Ru᎐C(49)᎐C(50) vector, one mirror plane defined by the
acetate, Ru, P(1) and P(4) atoms and the second mirror plane
defined by Ru, P(3), P(2), C(49) and C(50). The Ru᎐P bonds
which are trans to the acetate are noticeably shorter than
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and 2.341 Å respectively. The angle P(2)᎐Ru᎐P(3) deviates by
more than 10Њ from 180Њ due to the steric hindrance among the
phosphite ethoxy groups which results in displacement of P(2)
and P(3) towards the acetate. This deformation is also reflected
J. Chem. Soc., Dalton Trans., 1997, Pages 4435–4444
4443

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