Tautomerization of methyldiazene to formaldehyde-hydrazone in ruthenium and osmium complexes

Article abstract of DOI:10.1021/ic050817z

Mixed-ligand hydrazine complexes [M(CO)(RNHNH₂)P ₄](BPh₄)₂ (1, 2) [M = Ru, Os; R = H, CH ₃, C₆H₅; P = P(OEt)₃] with carbonyl and triethyl phosphite were prepared by al

Full text of DOI:10.1021/ic050817z

Inorg. Chem. 2005, 44, 8947−8954
Tautomerization of Methyldiazene to Formaldehyde-Hydrazone in
Ruthenium and Osmium Complexes
Gabriele Albertin,*,† Stefano Antoniutti,† Alessia Bacchi,‡ Fabiola De Marchi,† and Giancarlo Pelizzi‡
Dipartimento di Chimica, UniVersita` Ca’ Foscari di Venezia, Dorsoduro, 2137,
30123 Venezia, Italy, and Dipartimento di Chimica Generale ed Inorganica,
Chimica Analitica, Chimica Fisica, UniVersita` degli Studi di Parma,
Parco Area delle Scienze, 17/a, 43100 Parma, Italy
Received May 20, 2005
Mixed-ligand hydrazine complexes [M(CO)(RNHNH2)P4](BPh4)2 (1, 2) [M
P(OEt)3] with carbonyl and triethyl phosphite were prepared by allowing hydride [MH(CO)P4]BPh4 species to react
first with HBF4 Et2O and then with hydrazines. Depending on the nature of the hydrazine ligand, the oxidation of
[M(CO)(RNHNH2)P4](BPh4)2 derivatives with Pb(OAc)4 at 30 C gives acetate [M(
1-OCOCH3)(CO)P4]BPh4 (3a),
phenyldiazene [M(CO)(C6H5N NH)P4](BPh4)2 (3c, 4c), and methyldiazene [M(CO)(CH3N NH)P4](BPh4)2 (3b, 4b)
derivatives. Methyldiazene complexes 3b and 4b undergo base-catalyzed tautomerization of the CH3N NH
ligand to formaldehyde-hydrazone NH2N CH2, giving the [M(CO)(NH2N CH2)P4](BPh4)2 (5, 6) derivatives. Complexes
5 and 6 were characterized spectroscopically and by the X-ray crystal structure determination of the [Ru(CO)-
(NH2N CH2) P(OEt)3 4](BPh4)2 (5) derivative. Acetone-hydrazone [M(CO) NH2N C(CH3)2 P4](BPh4)2 (7, 8)
complexes were also prepared by allowing hydrazine [M(CO)(NH2NH2)P4](BPh4)2 derivatives to react with acetone.
) Ru, Os; R ) H, CH3, C6H5; P )
‚
−
°
κ
d
d
d
d
d
d
{
}
{
d
}
Introduction
ization of a coordinate methyldiazene to give the hydrazone
[W(NH2NdCH2)(CO)2(NO)(PPh3)2]+ complex has also been
described,7 but no experimental data for this reaction and
The chemistry of coordinate diazene (NHdNH or
RNdNH) has been extensively developed in the past 20
years, and a number of related transition metal complexes
have been reported.1,2 Interest in these studies stems not only
from the different coordination modes and chemical reac-
tivities that this class of compounds may exhibit1,2 but also
from the possible relevance of coordinate diazenes in
inorganic and bioinorganic N2-reducing systems.3
In the free state, diazenes are reactive and thermally
unstable molecules which decompose with the evolution of
nitrogen at room temperature.4 Coordination on a metal
fragment strongly enhances their stability and often leads to
new properties.1,2 Among these, we can highlight the easy
(2) For some papers on coordinate diazene, see: (a) Sellmann, D.; Brandl,
A.; Endell, R. Angew. Chem., Int. Ed. Engl. 1973, 12, 1019. (b)
Albertin, G.; Antoniutti, S.; Pelizzi, G.; Vitali, F.; Bordignon, E. J.
Am. Chem. Soc. 1986, 108, 6627-6634. (c) Smith, M. R., III;
Hillhouse, G. L. J. Am. Chem. Soc. 1988, 110, 4066-4068. (d)
Sellmann, D.; Soglowek, W.; Knoch, F.; Moll, M. Angew. Chem.,
Int. Ed. Engl. 1989, 28, 1271-1272. (e) Collmann, J. P.; Hutchinson,
J. E.; Lopez, M. A.; Guilard, R.; Reed, R. A. J. Am. Chem. Soc. 1991,
113, 2794-2796. (f) Sellmann, D.; Ka¨ppler, J.; Moll, M.; Knoch, F.
Inorg. Chem. 1993, 32, 960-964. (g) Smith, M. R., III; Cheng, T.-
Y.; Hillhouse, G. L. J. Am. Chem. Soc. 1993, 115, 8638-8642. (h)
Cheng, T.-Y.; Ponce, A.; Rheingold, A. L.; Hillhouse, G. L. Angew.
Chem., Int. Ed. Engl. 1994, 33, 657-659. (i) Cheng, T.-Y.; Peters, J.
C.; Hillhouse, G. L. J. Am. Chem. Soc. 1994, 116, 204-207. (j)
Albertin, G.; Antoniutti, S.; Bacchi, A.; Bordignon, E.; Busatto, F.;
Pelizzi, G. Inorg. Chem. 1997, 36, 1296-1305. (k) Sellmann, D.; Engl,
K.; Heinemann, F. W.; Sieler, J. Eur. J. Inorg. Chem. 2000, 1079-
1089.
(3) (a) MacKay, B. A.; Fryzuk, M. D. Chem. ReV. 2004, 104, 385-401.
(b) Fryzuk, M. D.; Johnson, S. A. Coord. Chem. ReV. 2000, 200-
202, 379-409. (c) Hidai, M.; Mizobe, Y. Chem. ReV. 1995, 95, 1115-
1133. (d) Sellmann, D.; Sutter, J. Acc. Chem. Res. 1997, 30, 460-
469. (e) Malinak, S. M.; Coucouvanis, D. Prog. Inorg. Chem. 2001,
49, 599-662.
(4) (a) Wiberg, N.; Bachhuber, H.; Fischer, G. Angew. Chem., Int. Ed.
Engl. 1972, 11, 829. (b) Patai, S., Ed. The Chemistry of Hydrazo,
Azo, and Azoxy Groups; Wiley: New York, 1975.
deprotonation of the diazene hydrogen atom to give a
1a,2b,2j,5
‚‚‚
N
‚‚‚
diazenido [M]
NsR derivative
and the reduc-
tion to hydrazine or NH3 under mild conditions.1a,6 Tautomer-
* To whom correspondence should be addressed. E-mail: albertin@unive.it.
† Universita` Ca’ Foscari di Venezia.
‡ Universita` degli Studi di Parma.
(1) (a) Sutton, D. Chem. ReV. 1993, 93, 995-1022. (b) Kisch, H.;
Holzmeier, P. AdV. Organomet. Chem. 1992, 34, 67-109. (c)
Zollinger, H., Ed. Diazo Chemistry II; VCH: Weinheim, Germany,
1995.
10.1021/ic050817z CCC: $30.25
Published on Web 10/18/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 24, 2005 8947

Albertin et al.
tight storage flasks. RuCl3‚3H2O and (NH4)2OsCl6 salts were
Pressure (USA) products, used as received. Phosphine PPh(OEt)2
was prepared by the method of Rabinowitz and Pellon,10 while
P(OEt)3 was an Aldrich product purified by distillation under
nitrogen. Diazonium salts were prepared in the usual way.11
Hydrazine NH2NH2 was prepared by the decomposition of hydra-
zine cyanurate (Fluka), following the reported method.12 High-grade
(99.99%) lead(IV) acetate was purchased from Aldrich. The other
reagents were purchased from commercial sources in the highest
available purity and used as received. Infrared spectra were recorded
on Nicolet Magna 750 FT-IR or Perkin-Elmer Spectrum One
spectrophotometers. NMR spectra (1H, 31P, and 13C) were obtained
on AC200 or AVANCE 300 Bruker spectrometers at temperatures
between -90 and +30 °C, unless otherwise noted. The COSY,
NOESY, HMQC, and HMBC NMR experiments were performed
for the resulting hydrazone complex were provided. We now
report the first documented example of base-catalyzed
tautomerization of a coordinate methyldiazene to formalde-
hyde-hydrazone, giving the corresponding [M]sNH2NdCH2
derivative.
Our interest in the chemistry of “diazo” complexes has
been extensively devoted to the synthesis and the reactivity
of hydrazine and diazene complexes of the iron triad2b,8 stab-
ilized by P(OEt)3 and PPh(OEt)2 phosphite ligands of the
[M(RNHNH2)2P4]2+, [M(RNHNH2)P5]2+, [M(RNdNH)2P4]2+,
and [M(RNdNH)P5]2+ (M ) Ru, Os; R ) H, CH3, C6H5)
types. Recently,2j,6c,9 we have shown that Mn(I) and Re(I)
also form stable hydrazine and diazene complexes of the
[M(RNHNH2)(CO)nP5-n]+ and [M(RNdNH)(CO)nP5-n]+ (P
) phosphite; n ) 1-4) types which, in part, parallel the
chemistry of the isoelectronic d6 ruthenium and osmium
diazo species, while also exhibiting new properties, unknown
for the related Ru(II) and Os(II) derivatives. This unusual
reactivity of Mn(I) and Re(I) diazo complexes may be
attributed to the presence of the strong π-acceptor carbonyl
ligands, which modify the properties of the mixed-ligand
M(CO)nP5-n fragment bonded to the diazo molecule. We,
therefore, decided to extend our studies on diazo complexes
by introducing a carbonyl ligand into the chemistry of
Ru(II) and Os(II) derivatives with the aim of testing how
this ligand may change the properties of coordinate diazo
molecules.
1
using their standard programs. H and 13C spectra are referred to
internal tetramethylsilane; 31P{1H} chemical shifts are reported with
respect to 85% H3PO4 with downfield shifts considered positive.
The SwaN-MR software package13 was used to treat NMR data.
The conductivities of 10-3 mol dm-3 solutions of the complexes
in CH3NO2 at 25 °C were measured with a Radiometer CDM 83.
Syntheses of the Complexes. Hydrides RuH2P4 and OsH2P4 [P
) P(OEt)3, PPh(OEt)2] were prepared following previously reported
methods.14,15 The hydride-carbonyl [MH(CO)P4]BPh4 complexes
[M ) Ru, Os; P ) P(OEt)3] were prepared by a modification of
the method reported for the related [RuH(CO){PPh(OEt)2}4]BPh4
derivative,16 as follows:
(A) [RuH(CO){P(OEt)3}4]BPh4. An equimolar amount of triflic
acid (0.26 mmol, 23 µL) was added to a solution of RuH2[P(OEt)3]4
(0.26 mmol, 0.200 g) in 10 mL of ethanol cooled to -196 °C and
placed under a CO atmosphere (1 atm). The reaction mixture was
brought to room temperature and stirred for about 2 h, and then,
the solvent was removed under reduced pressure. The oil obtained
was triturated with ethanol (2 mL) containing an excess of NaBPh4
(0.52 mmol, 0.18 g). A white solid slowly separated out and was
filtered and crystallized from CH2Cl2 and ethanol. Yield g 90%.
Anal. Calcd for C49H81BO13P4Ru: C, 52.83; H, 7.33. Found: C,
53.05; H, 7.49. ΛM ) 50.4 Ω-1 mol-1 cm2. 1H NMR (CD2Cl2, 25
°C) δ: 7.40-6.85 (m, 20 H, Ph), 4.10-3.90 (m, 24 H, CH2), 1.33,
1.31 (t, 36 H, CH3), -8.52 to -8.95 (m, 1 H, RuH). 31P{1H} NMR
(CD2Cl2, 25 °C) δ: A2BC spin syst, δA 137.2, δB 136.3, δC 136.0,
JAB ) 43.7, JAC ) 65.5, JBC ) 50.5. IR (KBr) cm-1: 2032 s (νCO),
1890 s (νRuH).
The results of these studies, which involve the synthesis
of new hydrazine and diazene complexes and the first well-
characterized example of tautomerization of methyldiazene
to formaldehyde-hydrazone in a metal complex, are reported
here.
Experimental Section
General Comments. All synthetic work was carried out in an
appropriate atmosphere (Ar, N2) using standard Schlenk techniques
or a vacuum atmosphere drybox. Once isolated, the complexes were
found to be relatively stable in air but were stored in an inert
atmosphere at -25 °C. All solvents were dried over appropriate
drying agents, degassed on a vacuum line, and distilled into vacuum-
(B) [OsH(CO){P(OEt)3}4]BPh4. An equimolar amount of
methyltriflate, CF3SO3CH3 (0.26 mmol, 29 µL), was added to a
solution of OsH2[P(OEt)3]4 (0.26 mmol, 0.22 g) in 10 mL of
toluene cooled to -196 °C and placed under a CO atmosphere (1
atm). The reaction mixture was brought to room temperature and
stirred for about 2 h, and then, the solvent was removed under
reduced pressure. The oil obtained was triturated with ethanol
(2 mL) containing an excess of NaBPh4 (0.52 mmol, 0.18 g). A
white solid slowly separated out and was filtered and crystal-
lized from CH2Cl2 and ethanol. Yield g 90%. Anal. Calcd for
(5) (a) Haymore, B. L.; Ibers, J. A. Inorg. Chem. 1975, 14, 2784-2795.
(b) Laing, K. R.; Robinson, S. D.; Uttley, M. F. J. Chem. Soc., Chem.
Commun. 1973, 176-177.
(6) (a) Parshall, G. W. J. Am. Chem. Soc. 1967, 89, 1822-1826. (b)
Schrock, R. R.; Glassman, T. E.; Vale, M. G. J. Am. Chem. Soc. 1991,
113, 725-726. (c) Albertin, G.; Antoniutti, S.; Giorgi, M. T. Eur. J.
Inorg. Chem. 2003, 2855-2866.
(7) Smith, M. R., III; Keys, R. L.; Hillhouse, G. L.; Rheingold, A. L. J.
Am. Chem. Soc. 1989, 111, 8312-8314.
(8) (a) Albertin, G.; Antoniutti, S.; Pelizzi, G.; Vitali, F.; Bordignon, E.
Inorg. Chem. 1988, 27, 829-835. (b) Albertin, G.; Antoniutti, S.;
Bacchi, A.; Bordignon, E.; Pelizzi, G.; Ugo, P. Inorg. Chem. 1996,
35, 6245-6253. (c) Albertin, G.; Antoniutti, S.; Bacchi, A.; Bordignon,
E.; Dolcetti, P. M.; Pelizzi, G. J. Chem. Soc., Dalton Trans. 1997,
4435-4444. (d) Albertin, G.; Antoniutti, S.; Bacchi, A.; Bergamo,
M.; Bordignon, E.; Pelizzi, G. Inorg. Chem. 1998, 37, 479-489. (e)
Albertin, G.; Antoniutti, S.; Bacchi, A.; Boato, M.; Pelizzi, G. J. Chem.
Soc., Dalton Trans. 2002, 3313-3320.
(10) Rabinowitz, R.; Pellon, J. J. Org. Chem. 1961, 26, 4623-4626.
(11) Vogel, A. I. Practical Organic Chemistry, 3rd ed.; Longmans, Green
and Co.: New York, 1956.
(12) Nachbaur, E.; Leiseder, G. Monatsh. Chem. 1971, 102, 1718-1723.
(13) Balacco, G. J. Chem. Inf. Comput. Sci. 1994, 34, 1235-1241.
(14) Peet, W. G.; Gerlach, D. H. Inorg. Synth. 1974, 15, 38-42. Gerlach,
D. H.; Peet, W. G.; Muetterties, E. L. J. Am. Chem. Soc. 1972, 94,
4545-4549.
(15) Albertin, G.; Antoniutti, S.; Bordignon, E. J. Chem. Soc., Dalton Trans.
1989, 2353-2358.
(16) Amendola, P.; Antoniutti, S.; Albertin, G.; Bordignon, E. Inorg. Chem.
1990, 29, 318-324.
(9) (a) Albertin, G.; Antoniutti, S.; Bacchi, A.; Ballico, G. B.; Bordignon,
E.; Pelizzi, G.; Ranieri, M.; Ugo, P. Inorg. Chem. 2000, 39, 3265-
3279. (b) Albertin, G.; Antoniutti, S.; Bordignon, E.; Perinello, G. J.
Organomet. Chem. 2001, 625, 217-230. (c) Albertin, G.; Antoniutti,
S.; Bacchi, A.; Bordignon, E.; Giorgi, M. T.; Pelizzi, G. Angew. Chem.,
Int. Ed. 2002, 41, 2192-2194.
8948 Inorganic Chemistry, Vol. 44, No. 24, 2005

Methyldiazene and Formaldehyde-Hydrazone Ru and Os Complexes
C49H81BO13OsP4: C, 48.92; H, 6.79. Found: C, 48.74; H, 6.80.
25 °C) δ: 7.40-6.81 (m, 45 H, Ph), 5.60 (m, br, 1 H, NH), 5.19
(m, br, 2 H, NH2), 4.08 (m, 24 H, CH2), 1.36, 1.33 (t, 36 H, CH3).
31P{1H} NMR (CD2Cl2, 25 °C) δ: AB2C spin syst, δA 78.5, δB
1
ΛM ) 49.5 Ω-1 mol-1 cm2. H NMR (CD2Cl2, 25 °C) δ: 7.31-
6.87 (m, 20 H, Ph), 4.01 (m, 24 H, CH2), 1.31 (t, 36 H, CH3),
-10.61 (m, 1 H, OsH). 31P{1H} NMR (CD2Cl2, -70 °C) δ: ABC2
spin syst, δA 99.0, δB 98.0, δC 96.6, JAB ) 47.7, JAC ) 32.0, JBC
) 33.5. IR (KBr) cm-1: 2012 s (νCO).
76.6, δC 73.9, JAB ) 56.4, JAC ) 42.0, JBC ) 37.5. IR (KBr) cm-1
3318 w, 3298 m (νNH), 2040 s (νCO).
:
(D) [M(CO)(C6H5NdNH){P(OEt)3}4](BPh4)2 (3c, 4c) [M )
Ru (3), Os (4)]. A solid sample of the phenylhydrazine [M(CO)-
(C6H5NHNH2){P(OEt)3}4](BPh4)2 complex (0.135 mmol) was
placed in a three-necked 25-mL flask fitted with a solid-addition
sidearm containing Pb(OAc)4 (0.135 mmol, 60 mg). The apparatus
was evacuated, CH2Cl2 (10 mL) was added, the solution was cooled
to -30 °C, and Pb(OAc)4 was added portionwise over 10-20 min
to the cold stirring solution. The reaction mixture was then allowed
to warm to 0 °C and was stirred for 20 min, and then, the solvent
was removed under reduced pressure. The oil obtained was treated
at 0 °C with ethanol (2 mL) containing NaBPh4 (0.27 mmol, 92
mg). A white solid slowly separated out and was filtered and twice
crystallized from CH2Cl2 and ethanol. Yield g 65%. (3c) Anal.
Calcd for C79H106B2N2O13P4Ru: C, 61.68; H, 6.95; N, 1.82.
Found: C, 61.55; H, 7.03; N, 1.75. ΛM ) 116.4 Ω-1 mol-1 cm2.
1H NMR (CD2Cl2, 25 °C) δ: 13.19 (m, 1 H, NH), 7.80-6.88 (m,
45 H, Ph), 4.21-4.00 (m, 24 H, CH2), 1.38, 1.26 (t, 36 H, CH3).
31P{1H} NMR (CD2Cl2, 25 °C) δ: AB2C spin syst, δA 123.3, δB
112.3, δC 110.1, JAB ) 52.7, JAC ) 60.0, JBC ) 65.1. IR (KBr)
cm-1: 2065 s (νCO). (4c) Calcd for C79H106B2N2O13OsP4: C,
(C) [M(CO)(RNHNH2){P(OEt)3}4](BPh4)2 (1, 2) [M ) Ru (1),
Os (2); R ) H (a), CH3 (b), C6H5 (c)]. An excess of HBF4‚Et2O
(0.72 mmol, 104 µL of a 54% solution in diethyl ether) was added
to a solution of the appropriate [MH(CO){P(OEt)3}4]BPh4 hydride
(0.18 mmol) in 10 mL of CH2Cl2 cooled to -196 °C. A large excess
of the appropriate hydrazine RNHNH2 (1.8 mmol) was added, and
the solution was brought to room temperature and stirred for 24 h.
The solvent was removed under reduced pressure to give an oil
which was triturated with ethanol (2 mL) containing an excess of
NaBPh4 (0.54 mmol, 0.185 g). A white solid slowly separated out
and was filtered and crystallized from CH2Cl2 and ethanol. Yield
from 55 to 68%. (1a) Anal. Calcd for C73H104B2N2O13P4Ru: C,
59.88; H, 7.16; N, 1.91. Found: C, 59.79; H, 7.20; N, 1.95. ΛM
)
114.5 Ω-1 mol-1 cm2. H NMR (CD2Cl2, 25 °C) δ: 7.40-6.88
(m, 40 H, Ph), 4.10 (m, 24 H, CH2), 3.92 (m, br, 2 H, RuNH2),
2.45 (m, br, 2 H, NH2), 1.39, 1.37, 1.33 (t, 36 H, CH3). 31P{1H}
NMR (CD2Cl2, 25 °C) δ: AB2C spin syst, δA 124.1, δB 114.5, δC
111.6, JAB ) 51.6, JAC ) 58.3, JBC ) 65.4. IR (KBr) cm-1: 3342
m, 3322 m, 3260 sh, 3256 m (νNH), 2065 s (νCO). (1b) Calcd
for C74H106B2N2O13P4Ru: C, 60.13; H, 7.23; N, 1.90. Found: C,
1
58.30; H, 6.56; N, 1.72. Found: C, 58.15; H, 6.69; N, 1.75. ΛM
)
120.8 Ω-1 mol-1 cm2. 1H NMR (CD2Cl2, 25 °C) δ: 13.56 (m, br,
1 H, NH), 7.40-6.86 (m, 45 H, Ph), 4.10 (m, 24 H, CH2), 1.37,
1.35 (t, 36 H, CH3). 31P{1H} NMR (CD2Cl2, 25 °C) δ: AB2C spin
1
59.98; H, 7.26; N, 1.87. ΛM ) 120.2 Ω-1 mol-1 cm2. H NMR
(CD2Cl2, 25 °C) δ: 7.33-6.85 (m, 40 H, Ph), 4.37 (br, 2 H, NH2),
4.17, 4.05 (m, 24 H, CH2), 3.27 (q, br, 1 H, NH), 2.58 (d, 3 H,
CH3N, JHH ) 6 Hz), 1.38, 1.36, 1.34 (t, 36 H, CH3 phos). 31P{1H}
NMR (CD2Cl2, 25 °C) δ: AB2C spin syst, δA 123.5, δB 114.1,
δC 110.9, JAB ) 53.6, JAC ) 55.4, JBC ) 66.2. 13C{1H} NMR
(CD2Cl2, 25 °C) δ: 191.8 (m, CO), 165-122 (m, Ph), 65.5 (m,
CH2), 44.7 (s, CH3N), 16.3 (m, CH3 phos). IR (KBr) cm-1: 3316
m, 3296 m, 3263 m (νNH), 2060 s (νCO). (1c) Calcd for
C79H108B2N2O13P4Ru: C, 61.60; H, 7.07; N, 1.82. Found: C, 61.79;
H, 7.15; N, 1.75. ΛM ) 119.8 Ω-1 mol-1 cm2. 1H NMR (CD2Cl2,
25 °C) δ: 7.44-6.72 (m, 45 H, Ph), 5.16 (m, br, 1 H, NH), 5.12
(m, br, 2 H, NH2), 4.10 (m, 24 H, CH2), 1.34, 1.32 (t, 36 H, CH3).
31P{1H} NMR (CD2Cl2, 25 °C) δ: AB2C spin syst, δA 122.4, δB
113.8, δC 110.2, JAB ) 53.9, JAC ) 56.6, JBC ) 65.3. IR (KBr)
cm-1: 3337 m, 3304 w, 3275 m (νNH), 2063 s (νCO). (2a) Calcd
for C73H104B2N2O13OsP4: C, 56.45; H, 6.75; N, 1.80. Found: C,
syst, δA 79.6, δB 77.1, δC 75.4, JAB ) 55.8, JAC ) 43.6, JBC
)
38.6. IR (KBr) cm-1: 2042 s (νCO).
(E) [Ru(κ1-OCOCH3)(CO){P(OEt)3}4]BPh4 (3a). This complex
was obtained from the oxidation of the [Ru(CO)(NH2NH2)-
{P(OEt)3}4](BPh4)2 (1a) hydrazine complex with Pb(OAc)4 fol-
lowing the method reported above for the related C6H5NHNH2
derivatives. Yield g 70%. Anal. Calcd for C51H83BO15P4Ru: C,
52.27; H, 7.14. Found: C, 52.39; H, 7.22. ΛM ) 51.8 Ω-1 mol-1
cm2. 1H NMR (CD2Cl2, 25 °C) δ: 7.35-6.94 (m, 20 H, Ph), 4.22-
3.98 (m, 24 H, CH2), 1.92 (s, 3 H, CH3COO), 1.34, 1.31, 1.29 (t,
36 H, CH3 phos). 31P{1H} NMR (CD2Cl2, 25 °C) δ: ABC2 spin
syst, δA 129.5, δB 120.8, δC 120.7, JAB ) 62.7, JAC ) 54.2, JBC
)
53.2. IR (KBr) cm-1: 2058 s (νCO), 1615 m (νCOO).
(F) [M(CO)(CH3NdNH){P(OEt)3}4](BPh4)2 (3b, 4b) [M ) Ru
(3), Os (4)]. A solid sample of the methylhydrazine [M(CO)-
(CH3NHNH2){P(OEt)3}4](BPh4)2 complex (0.2 mmol) was placed
in a three-necked 25-mL flask fitted with a solid-addition sidearm
containing Pb(OAc)4 (0.2 mmol, 89 mg). The apparatus was
evacuated, CH2Cl2 (10 mL) was added, the solution was cooled to
-30 °C, and Pb(OAc)4 was added portionwise over 10-20 min to
the cold stirring solution. The reaction mixture was then allowed
to warm to 0 °C and was stirred for 20 min, and then, the solvent
was removed under reduced pressure at 0 °C. The oil obtained was
treated at the same temperature with ethanol (2 mL) containing
NaBPh4 (0.4 mmol, 137 mg). A pale-yellow solid slowly separated
out and was filtered and dried under vacuum. Crystallization by
cooling to -25 °C of a saturated solution of the solid in CH2Cl2
and ethanol prepared at 0 °C gave white microcrystals of pure
methyldiazene derivative. Yield g 60%. (3b) Anal. Calcd for
C74H104B2N2O13P4Ru: C, 60.21; H, 7.10; N, 1.90. Found: C, 60.18;
H, 7.22; N, 1.85. ΛM ) 118.6 Ω-1 mol-1 cm2. 1H NMR (CD2Cl2,
25 °C) δ: 13.04 (d, br, 1 H, NH), 7.40-6.89 (m, 40 H, Ph), 4.20-
4.00 (m, 24 H, CH2), 3.75 (s, 3 H, CH3N), 1.35, 1.32 (t, 36 H, CH3
phos). 31P{1H} NMR (CD2Cl2, 25 °C) δ: AB2C spin syst, δA 123.5,
1
56.55; H, 6.81; N, 1.85. ΛM ) 117.2 Ω-1 mol-1 cm2. H NMR
(CD2Cl2, 25 °C) δ: 7.36-6.87 (m, 40 H, Ph), 4.38 (m, br, 2 H,
OsNH2), 4.21-4.00 (m, 24 H, CH2), 2.64 (m, br, 2 H, NH2), 1.38,
1.36 (t, 36 H, CH3). 31P{1H} NMR (CD2Cl2, 25 °C) δ: AB2C spin
syst, δA 80.5, δB 77.9, δC 77.1, JAB ) 54.9, JAC ) 43.8, JBC
)
36.9. 13C{1H} NMR (CD2Cl2, 25 °C) δ: 176.1 (m, CO), 163-122
(m, Ph), 65.3, 64.5 (m, CH2), 16.2 (m, CH3). IR (KBr) cm-1: 3340
m, 3312 m, 3262 m (νNH), 2037 s (νCO). (2b) Calcd for
C74H106B2N2O13OsP4: C, 56.71; H, 6.82; N, 1.79. Found: C, 56.58;
H, 7.00; N, 1.75. ΛM ) 123.5 Ω-1 mol-1 cm2. 1H NMR (CD2Cl2,
25 °C) δ: 7.37-6.87 (m, 40 H, Ph), 4.84 (m, br, 2 H, NH2), 4.18
(m), 4.05 (qnt, 24 H, CH2), 3.35 (m, 1 H, NH), 2.56 (d, 3 H, CH3N,
JHH ) 6 Hz), 1.38, 1.35, 1.33 (t, 36 H, CH3 phos). 31P{1H} NMR
(CD2Cl2, 25 °C) δ: AB2C spin syst, δA 79.5, δB 77.4, δC 76.3,
JAB ) 54.7, JAC ) 43.7, JBC ) 37.3. 13C{1H} NMR (CD2Cl2,
25 °C) δ: 176.4 (m, CO), 163-122 (m, Ph), 65.7, 64.9 (m,
CH2), 44.9 (m, CH3N), 16.3 (m, CH3 phos). IR (KBr) cm-1: 3308
m, 3298 w, 3261 m (νNH), 2045 s (νCO). (2c) Calcd for
C79H108B2N2O13OsP4: C, 58.23; H, 6.68; N, 1.72. Found: C, 57.99;
H, 6.84; N, 1.70. ΛM ) 115.6 Ω-1 mol-1 cm2. 1H NMR (CD2Cl2,
Inorganic Chemistry, Vol. 44, No. 24, 2005 8949

Albertin et al.
δB 112.3, δC 109.7, JAB ) 52.8, JAC ) 58.3, JBC ) 65.6. 13C{1H}
NMR (CD2Cl2, 25 °C) δ: 191.3 (m, CO), 164-135 (m, Ph), 68.6
H, 6.91; N, 1.79. ΛM ) 118.0 Ω-1 mol-1 cm2. 1H NMR (CD2Cl2,
25 °C) δ: 7.40-6.85 (m, 40 H, Ph), 5.97 (s, br, 2 H, NH2), 4.12
(m, 24 H, CH2), 2.05, 1.86 (s, 6 H, (CH3)2Cd), 1.39, 1.37, 1.35 (t,
36 H, CH3 phos). 31P{1H} NMR (CD2Cl2, 25 °C) δ: AB2C spin
(s, CH3Nd), 65.5 (m, CH2), 16.4 (m, CH3 phos). IR (KBr) cm-1
:
2050 s (νCO). (4b) Calcd for C74H104B2N2O13OsP4: C, 56.78; H,
6.70; N, 1.79. Found: C, 56.91; H, 6.88; N, 1.75. ΛM ) 115.9
syst, δA 79.5, δB 77.0, δC 75.8, JAB ) 55.6, JAC ) 41.7, JBC
)
1
Ω-1 mol-1 cm2. H NMR (CD2Cl2, 25 °C) δ: 13.45 (s, br, 1 H,
38.5. 13C{1H} NMR (CD2Cl2, 25 °C) δ: 178.2 (m, CO), 168.4 (s,
NdC), 165-122 (m, Ph), 65.5 (m, CH2), 24.9, 16.1 (s, (CH3)2Cd),
16.2 (m, CH3 phos). IR (KBr) cm-1: 3314 m, 3240 w (νNH), 2039
s (νCO).
NH), 7.32-6.86 (m, 40 H, Ph), 4.10 (m, 24 H, CH2), 3.72 (s, 3 H,
CH3N), 1.38, 1.36, 1.34 (t, 36 H, CH3 phos). 31P{1H} NMR
(CD2Cl2, 25 °C) δ: AB2C spin syst, δA 82.9, δB 78.7, δC 74.2, JAB
) 51.1, JAC ) 40.5, JBC ) 39.0. 13C{1H} NMR (CD2Cl2, 25 °C)
δ: 171.2 (m, CO), 165-122 (m, Ph), 68.4 (s, CH3Nd), 65.8 (m),
63.8 (d, CH2), 16.3 (m, CH3 phos). IR (KBr) cm-1: 2037 s (νCO).
(G) [M(CO)(NH2NdCH2){P(OEt)3}4](BPh4)2 (5, 6) [M ) Ru
(5), Os (6)]. Triethylamine (0.03 mmol, 4 µL) was added to a
solution of [M(CO)(CH3NdNH){P(OEt)3}4](BPh4)2 (3b, 4b)
methyldiazene complex (0.135 mmol) in 10 mL of CH2Cl2 cooled
to -196 °C. The reaction mixture was then brought to 0 °C and
stirred for 30 min. The solvent was removed under reduced pressure,
giving an oil which was triturated with ethanol (2 mL) at 0 °C. A
pale-pink solid slowly separated out and was filtered and crystallized
from CH2Cl2 and ethanol. Yield g 92%. (5) Anal. Calcd for
C74H104B2N2O13P4Ru: C, 60.21; H, 7.10; N, 1.90. Found: C, 60.08;
H, 7.23; N, 1.95. ΛM ) 124.4 Ω-1 mol-1 cm2. 1H NMR (CD2Cl2,
25 °C) δ: 7.34-6.86 (m, 40 H, Ph), AB spin syst δA 6.74, δB
6.60, JAB ) 9.3 Hz (2 H, dCH2), 5.86 (s, br, 2 H, NH2), 4.12 (m,
24 H, CH2 phos), 1.38, 1.35 (t, 36 H, CH3). 31P{1H} NMR
(CD2Cl2, 25 °C) δ: AB2C spin syst, δA 124.0, δB 114.6, δC 111.4,
JAB ) 52.5, JAC ) 56.5, JBC ) 66.1. 13C{1H} NMR (CD2Cl2, 25
°C) δ: 193.5 (m, CO), 149.2 (s, dCH2), 165-122 (m, Ph), 65.0
(m, CH2 phos), 16.3 (m, CH3). IR (KBr) cm-1: 3310 m (νNH),
2064 s (νCO). (6) Calcd for C74H104B2N2O13OsP4: C, 56.78; H,
6.70; N, 1.79. Found: C, 56.59; H, 6.81; N, 1.78. ΛM ) 119.6
X-ray Crystal Structure Determination of [Ru(CO)-
(NH2NdCH2){P(OEt)3}4](BPh4)2 (5). Single crystals of 5 were
obtained by recrystallization from CH2Cl2 and ethanol. X-ray
diffraction data were collected with a SMART AXS 1000 CCD
diffractometer (Mo KR radiation, λ ) 0.71073 Å, T ) 293 K).
Lorentz, polarization, and absorption corrections were applied.17
The structure was solved by direct methods using SIR9718 and
refined by full-matrix least-squares analysis on all F2 using
SHELXL9719 as implemented in the WingX package.20 Hydrogen
atoms belonging to the formaldehyde-hydrazone ligand were located
on Fourier difference maps and refined isotropically, and all the
others were introduced in calculated positions. Anisotropic displace-
ment parameters were refined for all non-hydrogen atoms. The
Cambridge Crystallographic Data Centre packages21 were used for
the analysis of crystal geometry. Crystal data: 5‚0.5CH2Cl2,
C74.50H105B2ClN2O13P4Ru, FW ) 1518.62, 0.3 × 0.1 × 0.1 mm3,
orthorhombic, space group Pca21, a ) 22.239(1), b ) 19.041(1),
c ) 19.538(1) Å, V ) 8273.4(7) Å3, F ) 1.219 Mg m-3, 9553
unique reflections [R(int) ) 0.0687], 6881 observed (I > 2σ(I)),
824 parameters, R1 ) 0.0465, wR2 ) 0.1137 (I > 2σ(I)).
Results and Discussion
Preparation of the Hydrazine Complexes. The synthesis
of the hydrazine complexes of ruthenium(II) and osmium-
(II) of the [M(CO)(RNHNH2){P(OEt)3}4](BPh4)2 (1, 2) type
was achieved by reacting the [MH(CO){P(OEt)3}4]BPh4
hydride first with an excess of HBF4‚Et2O and then with
the appropriate hydrazine, as shown in Scheme 1. Treatment
of the hydride [MH(CO)P4]+ with an excess of HBF4‚Et2O
probably leads to the evolution22 of H2 and the formation of
1
Ω-1 mol-1 cm2. H NMR (CD2Cl2, 25 °C) δ: 7.33-6.85 (m, 40
H, Ph), AB spin syst δA 6.60, δB 6.49, JAB ) 9.1 Hz (2 H, dCH2),
6.26 (s, br, 2 H, NH2), 4.00 (m, 24 H, CH2 phos), 1.37, 1.35, 1.32
(t, 36 H, CH3). 31P{1H} NMR (CD2Cl2, 25 °C) δ: AB2C spin syst,
δA 79.7, δB 77.7, δC 74.8, JAB ) 55.3, JAC ) 42.6, JBC ) 37.5.
13C{1H} NMR (CD2Cl2, 25 °C) δ: 177.2 (m, CO), 150.6 (s,
dCH2), 165-122 (m, Ph), 65.7 (m), 64.9 (d, CH2 phos), 16.2 (m,
CH3). IR (KBr) cm-1: 3298 m, 3261 w (νNH), 2050 s (νCO).
Suitable crystals for X-ray analysis were obtained by slow
cooling from 20 to -25 °C of a solution of complex 5 (100 mg)
prepared by adding 10 mL of ethanol and enough CH2Cl2 to obtain
a saturated solution at room temperature.
a
Scheme 1
(H) [M(CO){NH2NdC(CH3)2}{P(OEt)3}4](BPh4)2 (7, 8) [M
) Ru (7), Os (8)]. A solution of the appropriate [M(CO)-
(NH2NH2){P(OEt)3}4](BPh4)2 (1a, 2a) hydrazine complex (0.14
mmol) in 10 mL of acetone was refluxed for about 12 h. The solvent
was removed under reduced pressure, giving an oil which was
triturated with ethanol (3 mL) containing an excess of NaBPh4 (0.28
mmol, 96 mg). A white solid slowly separated out and was filtered
and crystallized from CH2Cl2 and ethanol. Yield g 65%. (7) Anal.
Calcd for C76H108B2N2O13P4Ru: C, 60.68; H, 7.24; N, 1.86.
Found: C, 60.55; H, 7.30; N, 1.91. ΛM ) 120.2 Ω-1 mol-1 cm2.
1H NMR (CD2Cl2, 25 °C) δ: 7.35-6.85 (m, 40 H, Ph), 5.56 (s,
br, 2 H, NH2), 4.10 (m, 24 H, CH2), 2.00, 1.85 (s, 6 H, (CH3)2Cd),
1.36, 1.35, 1.34 (t, 36 H, CH3 phos). 31P{1H} NMR (CD2Cl2, 25
°C) δ: AB2C spin syst, δA 125.1, δB 115.4, δC 111.6, JAB ) 53.4,
JAC ) 54.9, JBC ) 67.3. 13C{1H} NMR (CD2Cl2, 25 °C) δ: 182.5
(m, CO), 166.3 (s, NdC), 165-122 (m, Ph), 65.5 (m), 65.0 (d,
CH2), 25.2, 16.2 (s, (CH3)2Cd), 16.3 (m, CH3 phos). IR (KBr)
a M ) Ru (1), Os (2); P ) P(OEt)3; R ) H (a), CH3 (b), C6H5 (c).
(17) (a) SAINT: SAX, Area Detector Integration; Siemens Analytical
Instruments INC.: Madison, WI, Bruker AXS Copyright 1997-
1999. (b) Sheldrick, G. SADABS: Siemens Area Detector Absorption
Correction Software; University of Go¨ttingen: Go¨ttingen, Germany,
1996.
(18) Altomare, A.; Burla, M. C.; Cavalli, M.; Cascarano, G.; Giacovazzo,
C.; Gagliardi, A.; Moliterni, A. G.; Polidori, G.; Spagna, R. Sir97: A
New Program for SolVing and Refining Crystal Structures; Istituto di
Ricerca per lo Sviluppo di Metodologie Cristallografiche CNR: Bari,
Italy, 1997.
(19) Sheldrick, G. Shelxl97. Program for structure refinement; University
of Go¨ttingen: Go¨ttingen, Germany, 1997.
(20) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837-838.
(21) (a) Allen, F. H.; Kennard, O.; Taylor, R. Acc. Chem. Res. 1983, 16,
146-153. (b) Bruno, I. J.; Cole, J. C.; Edgington, P. R.; Kessler, M.;
Macrae, C. F.; McCabe, P.; Pearson, J.; Taylor, R. Acta Crystallogr.
2002, B58, 389-397.
cm-1
: 3314 m (νNH), 2056 s (νCO). (8) Anal. Calcd for
C76H108B2N2O13OsP4: C, 57.29; H, 6.83; N, 1.76. Found: C, 57.24;
8950 Inorganic Chemistry, Vol. 44, No. 24, 2005

Methyldiazene and Formaldehyde-Hydrazone Ru and Os Complexes
a
a coordinatively unsaturated23 [M(CO)P4]2+ intermediate
which, by reaction with RNHNH2, gives the final hydrazine
complexes 1 and 2. It is worth noting that only with P(OEt)3
as a supporting ligand can the carbonyl-hydrazine complexes
1 and 2 be prepared. With the PPh(OEt)2 and PPh2OEt phos-
phines, which are bulkier than P(OEt)3, instead, the reaction
of the hydride [MH(CO)P4]+ cation first with HBF4‚Et2O
and then with hydrazine always gives decomposition prod-
ucts.
Scheme 2
Good analytical data were obtained for all the compounds
1-2, which are white solids that are stable in air and in
solutions of polar organic solvents where they behave like
1:2 electrolytes.24 The infrared and NMR data support the
proposed formulation. The IR spectra show one strong band
at 2065-2037 cm-1 attributed to the νCO of the carbonyl
ligand, while three or four medium-intensity bands, attribut-
able to the νNH of the hydrazine ligand, were observed in
the 3342-3256 cm-1 region. The presence of the RNHNH2
ligand, however, is confirmed by the 1H NMR spectra, which
show the characteristic NH and NH2, slightly broad signals
between 5.60 and 2.45 ppm. The decoupling experiments
and COSY spectra confirm the proposed attribution and also
indicate that the doublet at 2.58 ppm for 1b and at 2.56 ppm
for 2b is due to the methyl group of the CH3NHNH2 ligand.
The proton spectra also show that, in the case of NH2NH2
complexes 1a and 2a, two NH2 signals are present, suggest-
ing η1-coordination for the hydrazine ligand. Further-
more, in the 13C NMR spectra, the carbonyl carbon signal
appears as a multiplet at 192-176 ppm, while a singlet at
44.9-44.7 ppm of the methyl substituent of the CH3NHNH2
group is also observed for methylhydrazine complexes 1b
and 2b. Finally, in the temperature range between +20 and
-80 °C, the 31P{1H} NMR spectra of the hydrazine complex
appear as an AB2C multiplet, suggesting that a geometry (I,
Scheme 1) with the carbonyl and the hydrazine ligands in a
mutually cis position can reasonably be proposed for our
derivatives 1 and 2.
Oxidation Reactions. The reactivity of hydrazine com-
plexes 1 and 2 with Pb(OAc)4 at low temperatures was
studied, and the results are summarized in Scheme 2. The
reaction of the hydrazine [M(CO)(NH2NH2)P4]2+ (1a, 2a)
cations with Pb(OAc)4 at -30 °C in CH2Cl2 proceeds to
give a pale-yellow solution from which the κ1-acetate
[Ru(κ1-OCOCH3)(CO)P4]BPh4 (3a) complex was, in the case
of ruthenium, isolated in pure form and characterized. With
osmium, an intractable oily mixture was obtained. The
formation of the acetate complex may suggest that the
reaction with Pb(OAc)4 proceeds through the selective
oxidation of NH2NH2 to give the unstable 1,2-diazene
[M(CO)(NHdNH)P4]2+ derivative, which undergoes sub-
stitution of the labile NHdNH ligand with the CH3COO-
a M ) Ru (3), Os (4); P ) P(OEt)3.
to give the final species 3a. The reaction was also carried
out, either at a low temperature (-50 °C) or using less than
the stoichiometric amount of Pb(OAc)4, but only traces of
the diazene complex were detected in the reaction product.
However, since the starting hydrazine 1a and 2a compounds
do not react with the acetate ion, the formation of an unstable
1,2-diazene intermediate is plausible and is supported both
by several of the precedents1,2,6c,8e reported in the literature
and by the results obtained with substituted hydrazines (see
Scheme 2).
Phenylhydrazine [M(CO)(C6H5NHNH2)P4]2+ (1c, 2c) com-
plexes react with Pb(OAc)4 to give, in contrast with the
case of hydrazine, the related phenyldiazene [M(CO)-
(C6H5NdNH)P4](BPh4)2 (3c, 4c) derivatives, which are stable
and were isolated in good yield and characterized. The
stability of 3c and 4c toward decomposition of the diazene
ligand prompted us to attempt the synthesis of the same
aryldiazene 3c and 4c complexes following a different route
involving the insertion of aryldiazonium cations into the
M-H bond of the [MH(CO)P4]+ hydride precursor (Scheme
3). The reaction was studied extensively but, at room
temperature, did not proceed, and the starting hydride was
quantitatively recovered. This unreactivity toward the inser-
+
tion of ArN2 into the M-H bond may be attributed to the
positive charge of the complexes, although the influence of
the ancillary ligands must not be underestimated.
a
Scheme 3
a
M ) Ru, Os; P ) P(OEt)3.
+
The insertion of ArN2 does take place, as previously
(22) For reactions of hydride complexes with Brønsted acids, see: Kubas,
G. J. Metal Dihydrogen and σ-Bond Complexes; Kluwer Academic:
New York, 2001, and references therein.
reported by us, in cationic complexes such as the pentakis-
(phosphite) [MHP5]+ or the mixed-ligand [MH(N-N)P3]+
[M ) Fe, Ru, Os; N-N ) 1,2-bipyridine, 1,10-phenanthro-
line; P ) P(OEt)3] derivatives,8e,25 giving stable and isolable
phenyldiazene complexes. The unreactivity of our [MH(CO)-
P4]+ derivatives is somewhat unexpected and may be
(23) The intermediate formed by reacting [MH(CO)P4]+ with HBF4‚Et2O
may also contain a labile BF4- ligand of the [M(BF4)(CO)P4]+ type.
However, an agostic interaction between the metal center and the C-H
bond of the ethyl group of one P(OEt)3 ligand to stabilize the [M(CO)-
P4]2+ intermediate is also plausible.
(24) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81-122.
Inorganic Chemistry, Vol. 44, No. 24, 2005 8951

Albertin et al.
a
Scheme 4
attributed to the presence of stronger π-acceptor ligands such
as CO, which probably decreases the hydridic character of
the M-H group, preventing the insertion of the ArN2+ cation
to give the ArNdNH aryldiazene group. It seems, therefore,
that only the oxidation of arylhydrazine allows the synthesis
of aryldiazene ligands bonded to the M(CO)P4 fragment in
complexes of the type 3c and 4c.
a M ) Ru (3b, 5), Os (4b, 6); P ) P(OEt)3.
Methylhydrazine [M(CO)(CH3NHNH2)P4](BPh4)2 (1b, 2b)
complexes react with Pb(OAc)4 at -30 °C to give, after
workup, a pale-yellow solid. Crystallization from CH2Cl2 and
ethanol yielded white microcrystals of pure methyldiazene
[M(CO)(CH3NdNH)P4](BPh4)2 (3b, 4b) derivatives in about
60% yield.
the diazene ligands in a type III or IV geometry can
reasonably be proposed for the diazene derivatives 3b, 3c,
4b, and 4c.
Tautomerization of Methyldiazene to Formaldehyde-
Hydrazone. The addition of traces of base (NEt3) to a
dichloromethane solution of the methyldiazene [M(CO)-
(CH3NdNH)P4](BPh4)2 (3b, 4b) complexes leads to the
tautomerization of the coordinate methyldiazene to formal-
dehyde-hydrazone, yielding the [M(CO)(NH2NdCH2)P4]-
(BPh4)2 (5, 6) derivatives, which were isolated with an
excellent yield (g92%) and characterized (Scheme 4). The
complexes are stable pale-pink solids which were character-
ized by standard spectroscopic methods (IR and NMR) and
by a single-crystal X-ray diffraction study of the [Ru(CO)-
(NH2NdCH2){P(OEt)3}4](BPh4)2 (5) derivative.
Both the phenyldiazene (3b, 4b) and the methyldiazene
(3c, 4c) complexes were isolated as white or pale-yellow
solids that are stable in air and in solutions of polar organic
solvents, where they behave like 2:1 electrolytes.24 The
acetate complex 3a is also stable both in the solid state and
in solution, where it behaves like a 1:1 electrolyte. Analytical
and spectroscopic data support the proposed formulation for
the compounds.
The IR spectra of the acetate [Ru(κ1-OCOCH3)(CO)P4]-
BPh4 (3a) complex show a strong band at 2058 cm-1 due to
the CO ligand and a medium-intensity absorption at 1615
cm-1 attributed to νCO of the coordinate acetate ion. The pres-
ence of the CH3COO- ligand is confirmed by the 1H NMR
spectrum, which shows, besides the signals of the phosphite
and the BPh4 anion, a singlet at 1.92 ppm attributable to the
methyl group of the acetate ligand. In the temperature range
between +20 and -80 °C, the 31P{1H} specta appear as a
ABC2 multiplet, suggesting the mutually cis position of the
carbonyl and the acetate ligands. On the basis of these data,
a geometry of type II (Scheme 2) can reasonably be
proposed.
The infrared spectra show the νCO band at 2064 (5) and at
2050 cm-1 (6), while the νNH of the hydrazone appears at
1
3310-3261 cm-1. The H NMR spectra show a slightly
broad signal at 5.86 (5) and 6.26 ppm (6) attributed to the
NH2 group of the NH2NdCH2 ligand, while the methylene
protons, which are not magnetically equivalent, appear as
an AB quartet (JAB ) 9.3 Hz) at 6.67 (5) and at 6.54 ppm
(6). The 13C NMR spectra show, besides the signals of the
-
P(OEt)3 ligands and the BPh4 anion, a multiplet at 177-
193 ppm attributed to the carbonyl carbon resonance and a
singlet at 149.2 (5) and at 150.6 ppm (6), which splits into
a doublet of doublets in the proton-coupled 13C spectra (1J
13CH
The 1H NMR spectra of both the methyldiazene (3b, 4b)
and the phenyldiazene (3c, 4c) complexes show, in the high-
frequency region, a slightly broad signal at 13.56-13.04 ppm
attributed to the NH proton of the substituted diazene ligand.
In the spectra of the methyldiazene complexes 3b and 4b, a
singlet at 3.75-3.72 ppm of the methyl substituent is also
present, which correlates (1H COSY) to the broad NH signal
near 13 ppm, which in turn is in agreement with the presence
of the diazene ligand. A NOESY experiment was also carried
out and indicated a cis arrangement of the CH3NdNH group.
In the 13C NMR spectra, one singlet at 68.6-68.4 ppm
appears and was attributed to the CH3 group of the meth-
yldiazene, while the multiplet between 191.3 and 171.2 ppm
was attributed to the carbonyl carbon resonance. The infrared
spectra of all the diazene complexes show a strong absorp-
tion at 2065-2037 cm-1 attributed to νCO of the carbonyl
ligand. In the temperature range between +20 and -80 °C,
the 31P{1H} NMR spectra appear as AB2C multiplets which
can be simulated with the reported parameters. On the basis
of these data, a mutually cis position of the carbonyl and
) 163 Hz). This signal at 149-150 ppm is correlated, in
the HMQC experiments, to the proton signal at 5.86-6.26
ppm and was attributed to the methylene carbon resonance
of the NH2NdCH2 ligand. In the temperature range between
+20 and -80 °C, the 31P{1H} NMR spectra of the
formaldehyde-hydrazone complexes 5 and 6 appear as AB2C
multiplets, suggesting a cis arrangement of the CO and the
hydrazone ligand, in agreement with a geometry (V) similar
to that of the solid state.
Compound 5 crystallizes as a [Ru(CO)(NH2NdCH2)-
(P(OEt)3)4](BPh4)2‚1/2CH2Cl2 solvate. The molecular structure
and labeling scheme are reported in Figure 1. The relevant
geometrical data of the octahedral cation are in Table 1. The
NH2NdCH2 and the CO ligands are in a cis position, and
the N-N bond is perfectly eclipsed with respect to the
CsO bond (C25sRusN1sN2 ) 10.3(5)°), while the
NdCH2 bond is practically perpendicular to the plane
containing the equatorial ligands P3, P4, C25, O13, N1, and
N2 (RusN1sN2sC26 ) -113.1(8)°). In the cation, the
Ru-P bond distances are in accord with the trans influence
of the ligands, where the one trans to the hydrazone moiety
is the shortest (Ru-P4 ) 2.270(2) Å). This is the first
structural example of a coordinated formaldehyde-hydrazone.
(25) (a) Albertin, G.; Antoniutti, S.; Bortoluzzi, M. Inorg. Chem. 2004,
43, 1328-1335. (b) Albertin, G.; Antoniutti, S.; Pizzol, S. J.
Organomet. Chem. 2004, 689, 1639-1647.
8952 Inorganic Chemistry, Vol. 44, No. 24, 2005

Methyldiazene and Formaldehyde-Hydrazone Ru and Os Complexes
Scheme 6
tion a simple but elusive molecule28 such as CH2NdNH2
formaldehyde-hydrazone. This species, in fact, has been
prepared in solution from the reaction of CH3OCH2OH with
hydrazine28 and is stable in the free state only below -30
°C. The tautomerization of methyldiazene establishes a
further method for the preparation of this molecule, which,
in this case, is stabilized by coordination, can be isolated as
a coordination compound, and is the first well-characterized
example of a formaldehyde-hydrazone complex. It may also
be noted that substituted hydrazone derivatives of ruthenium
and osmium are rare1a and were obtained from the reaction
of hydrazine [M]sNH2NH2 complexes29 with acetone,
yielding the [M]sNH2NdC(CH3)2 final species.
A possible mechanism, which requires the 1-3 shift of
one hydrogen atom, may be considered to explain the
tautomerization reaction (Scheme 6). This involves the direct
deprotonation of the methyl group of CH3NdNH to give a
coordinate methylenehydrazido(1-) [M]sNHsNdCH2 [A]
intermediate, which can undergo protonation to the basic N1
nitrogen atom with BH+ to yield the final 5 and 6 species
(Scheme 6). To obtain information on the reaction path, we
monitored the reaction at -80 °C by NMR techniques, but
the reaction was very fast even at this temperature, preventing
the observation of any intermediate species. The formation
of an intermediate of type A, however, is plausible and is
supported by numerous precedents30,31 reported in the
literature on coordinate hydrazido(1-) complexes. The
protonation of this intermediate to the N1 nitrogen atom
should easily afford the final formaldehyde-hydrazone
molecule.
Figure 1. Molecular structure of cis-[Ru(CO)(NH2NdCH2){P(OEt)3}4]2+
(5). The ethoxy groups are omitted for clarity.
Table 1. Relevant Bond Lengths (Å) and Angles (deg) for Compound
5‚1/2CH2Cl2
Ru-C(25)
1.90(1)
2.226(7)
2.270(2)
2.343(2)
2.347(2)
2.369(2)
1.454(9)
1.22(1)
89.7(3)
87.0(2)
175.8(2)
90.7(2)
86.3(2)
P(4)-Ru-P(1)
C(25)-Ru-P(2)
N(1)-Ru-P(2)
P(4)-Ru-P(2)
P(1)-Ru-P(2)
C(25)-Ru-P(3)
N(1)-Ru-P(3)
P(4)-Ru-P(3)
P(1)-Ru-P(3)
P(2)-Ru-P(3)
N(2)-N(1)-Ru
91.16(8)
89.9(2)
86.6(2)
Ru-N(1)
Ru-P(4)
Ru-P(1)
96.01(8)
172.83(8)
177.4(2)
87.9(2)
95.44(7)
90.31(8)
88.76(8)
112.5(4)
Ru-P(2)
Ru-P(3)
N(1)-N(2)
N(2)-C(26)
C(25)-Ru-N(1)
C(25)-Ru-P(4)
N(1)-Ru-P(4)
C(25)-Ru-P(1)
N(1)-Ru-P(1)
C(26)-N(2)-N(1) 115.8(9)
Scheme 5
A comparison with the Ru complexes of the related acetone-
hydrazone ligand26 shows that the NdCH2 bond (1.22(1)
Å) is remarkably shorter than the one observed for the
RusNH2sNdC(CH3)2 system (1.27-1.28 Å), while the
NsN bond is not significantly different.
Coordinate diazene [{M}sNHdNR]+ is known to un-
dergo a deprotonation reaction in the presence of a base to
give a diazenido derivative,1a,2b,2j,5 as shown in Scheme 5.
The reaction is reported2b,2j to involve the rearrangement of
the RN2- ligand to RN2+ with concurrent 2 e- reduction of
the metal center and consequent dissociation of one ligand.
A different behavior is shown by the metal-bonded
methyldiazene27 group in our complexes 3b and 4b, which
undergoes base-catalyzed tautomerization to hydrazone. The
reaction also allows one to prepare and stabilize by coordina-
The path of Scheme 6 entails the coordination of the
methyldiazene to the M(CO)P4 fragment to activate the
(28) Heaton, B. T.; Jacob, C.; Monks, G. L.; Hursthouse, M. B.; Ghatak,
I.; Somerville, R. G.; Heggie, W.; Page, P. R.; Villax, I. J. Chem.
Soc., Dalton Trans. 1996, 61-67.
(29) (a) Ashworth, T. V.; Singleton, E.; Hough, J. J. J. Chem. Soc., Dalton
Trans. 1977, 1809-1815. (b) Oosthuizen, H. E.; Singleton, T.; Fields,
J. S.; Van Niekerk, G. G. J. Organomet. Chem. 1985, 279, 433-446.
(30) (a) McCleverty, J. A.; Rae, A. E.; Wolochowicz, I.; Bailey, N. A.;
Smith, J. M. A. J. Chem. Soc., Dalton Trans. 1983, 71-80. (b)
Sellmann, D.; Kern, W.; Pohlmann, G.; Knoch, F.; Moll, M. Inorg.
Chim. Acta 1991, 185, 155-162. (c) Chatt, J.; Dilworth, J. R.;
Dahlstrom, P. L.; Zubieta, J. J. Chem. Soc., Chem. Commun. 1980,
786-787. (d) Glassman, T. E.; Vale, M. G.; Schrock, R. R. J. Am.
Chem. Soc. 1992, 114, 8098-8109.
(26) (a) Nolte, M. J.; Singleton, E. J. Chem. Soc., Dalton Trans. 1974,
2406-2410. (b) Day, V. W.; Everspacher, T. A.; Klemperer, W. G.;
Planalp, R. P.; Schiller, P. W.; Yagasaki, A.; Zhong, B. Inorg. Chem.
1993, 32, 1629-1637.
(27) Free methyldiazene, CH3NdNH, is reported to decompose upon
warming to give N2 and CH4. Decomposition via a CH2dNNH2
intermediate was also proposed, but only methane was detected:
Ackermann, M. N.; Ellenson, J. L.; Robison, D. H. J. Am. Chem. Soc.
1968, 90, 7173-7174.
(31) (a) Nicholson, T.; Zubieta, J. J. Chem. Soc., Chem. Commun. 1985,
367-368. (b) Barrientos-Penna, C. F.; Gilchrist, A. B.; Klahn-Oliva,
A. H.; Hanlan, A. J. L.; Sutton, D. Organometallics 1985, 4, 478-
485.
Inorganic Chemistry, Vol. 44, No. 24, 2005 8953

Albertin et al.
a
Scheme 7
The IR spectra of the hydrazone complexes 7 and 8 show
a strong absorption at 2056-2039 cm-1 due to the νCO of
the carbonyl ligand, while the bands of medium intensity at
3314-3240 cm-1 are attributed to νNH of the NH2NdC-
(CH3)2 group. The presence of the hydrazone ligand,
however, is confirmed by the proton NMR spectra, which
show a slightly broad signal at 5.56 (7) and at 5.97 ppm (8)
attributed to the NH2 of the NH2NdC(CH3)2 moiety. Two
singlets at 2.00 and 1.85 ppm for 7 and at 2.05 and 1.86
ppm for 8 are also present in the spectra; these are due to
the methyl substituents of the hydrazone. Curiously, only
one of these singlets correlates in the COSY experiment with
the broad signal between 6 and 5 ppm of the NH2 moiety.
The 13C NMR spectra further support the formulation of the
complexes showing a multiplet at 182.5 (7) and 178.2 ppm
(8) of the carbonyl carbon atom, one singlet at 166.3 (7)
and at 168.4 ppm (8) of the hydrazone carbon atoms, and
two singlets between 25 and 16 ppm of the methyl substit-
uents of the NH2NdC(CH3)2 ligand. The HMQC and HMBC
experiments confirm the attribution of these signals. In the
temperature range between +20 and -80 °C, the 31P{1H}
NMR spectra appear as AB2C multiplets, suggesting the
mutually cis position of the carbonyl and the hydrazone
ligands. A type VI geometry (Scheme 7) can therefore be
proposed for the acetone-hydrazone derivatives.
a M ) Ru (7), Os (8); P ) P(OEt)3.
methyl CH bond to give the final NH2NdCH2 molecule, and
this activation is probably attributable to the introduction of
a carbonyl ligand into the coordination sphere of the
methyldiazene derivatives. Comparable methyldiazene com-
plexes8c-e of Ru and Os of the [M(CH3NdNH)2P4](BPh4)2
and [M(CH3NdNH)(CH3NHNH2)P4](BPh4)2 [P ) P(OEt)3]
types, in fact, are very stable in the presence of a base, and
the methyldiazene does not show any trend of tautomeriza-
tion to formaldehyde-hydrazone. Introducing a strong π-ac-
ceptor ligand (CO) beside the P(OEt)3 decreases the elec-
tronic density on the metal center and probably makes the
M(CO)P4 fragment able to activate the CH3NdNH group
toward the tautomerization.
It can be noted that the presence of the CO ligand,
however, activates neither the methyldiazene nor the phe-
nyldiazene toward the deprotonation of the NH group to give
a diazenido derivative (see Scheme 5). Treatment of the
phenyldiazene complexes 3c and 4c with an excess of NEt3,
in fact, did not give any reactions, and the starting complexes
were recovered unchanged. The excess of base, instead,
caused exclusive tautomerization in the methyldiazene 3b
and 4b derivatives. Therefore, the properties of our M(CO)-
P4 fragment seem to involve the activation of the methyl
substituent instead of the NH group of the methyldiazene to
give the final formaldehyde-hydrazone complex.
Acetone-Hydrazone Complexes. The stability of form-
aldehyde-hydrazone complexes 5 and 6 prompted us to test
whether other hydrazone complexes containing the M(CO)-
P4 fragment can be prepared. We, therefore, reacted hydra-
zine [M(CO)(NH2NH2)P4](BPh4)2 (1a, 2a) derivatives with
acetone and observed that the reaction proceeded to give the
corresponding hydrazone [M(CO){NH2NdC(CH3)2}P4](BPh4)2
(7, 8) complexes, which were isolated as white solids and
characterized (Scheme 7). Hydrazone complexes of ruthe-
nium and osmium stabilized by the M(CO)P4 fragment can
therefore be prepared not only by the tautomerization of
methyldiazene but also by the reaction of coordinate hydra-
zine with a ketone.
Conclusions
In this paper, we have reported the synthesis of a series
of hydrazine complexes of ruthenium and osmium stabilized
by the mixed-ligand M(CO)P4 fragment with phosphites
and carbonyls. The introduction of the CO group in the
diazo chemistry of ruthenium and osmium induces new
properties on the diazo molecule. Among these, we can high-
light the first documented example of base-catalyzed tau-
tomerization of coordinate methyldiazene, CH3NdNH, to
formaldehyde-hydrazone, giving the [M(CO)(NH2NdCH2)-
P4](BPh4)2 derivatives. Furthermore, acetone-hydrazone
[M(CO){NH2NdC(CH3)2}P4](BPh4)2 derivatives can also be
prepared from the reaction of hydrazine complexes with
acetone.
Acknowledgment. The financial support of MIUR
(Rome)sPRIN 2004sis gratefully acknowledged. We thank
Daniela Baldan for technical assistance.
Supporting Information Available: Crystallographic data: CIF
and PDF files of Tables S1-S5 and Figures S1 and S2 for complex
5. This material is available free of charge via the Internet at
http://pubs.acs.org.
The complexes are stable in the solid state and in solutions
of polar organic solvents, where they behave like 2:1
electrolytes.24 The analytical and spectroscopic data support
the proposed formulation.
IC050817Z
8954 Inorganic Chemistry, Vol. 44, No. 24, 2005