Mono- and Bis(hydrazine) Complexes of Osmium(II): Synthesis, Reactions, and X-ray Crystal Structure of the [Os(NH2NH2)2{P(OEt) 3}+4](BPh4)2 Derivative

Article abstract of DOI:10.1021/ic970463e

Reaction of OsH₂P₄ [P = P(OEt)₃, PPh(OEt)₂, PPh₂OEt] with methyl triflate followed by the treatment with hydrazines gave the [OsH(RNHNH₂)P₄]BPh₄ (1-3) (R = H, CH₃, C₆H₅, 4-NO₂C₆H₄) derivatives. Instead, the reaction of OsH₂P₄ first with methyl triflate, then with triflic acid, and finally with an excess of the appropriate hydrazine affordged the bis(hydrazine) [Os(RNHNH₂)₂P₄](BPh₄)₂ (4, 5) (R = H, CH₃, C₆H₅) complexes. Also the [Os(NH₂NH₂){P(OEt)₃}₅](BPh ₄)₂ (7) derivative was prepared. All the hydrazine complexes were fully characterized by IR and ¹H and ³¹P NMR spectra, and a single-crystal X-ray structure determination of the complex [Os(NH₂NH₂)₂{P(OEt)₃} ₄](BPh₄)₂·C2H5OH (4a) is reported. The compound crystallizes in the space group P2₁/c with a = 20,550(4) A?, b = 19.663(4) A?, c = 20.843(4) A?, β= 99,84(9)°, and Z = 4. The coordination around the osmium atom is octahedral and the orientation of the ligands in the [Os(NH₂NH₂)₂{P(OEt)₃} ₄]²⁺ cation is determined by several strong hydrogen bonds involving hydrazine nitrogen and phosphite oxygen atoms. Amidrazone complexes [Os{η²-NH=C(R1)N (R)NH₂}{P(OEt)₃}₄](BPh₄)₂ (8, 9) (R = H, CH₃; R1 = CH₃, 4-CH₃C₆H₄) were prepared by allowing nitrile complexes [Os(R1CN)₂P₄](BPh₄)₂ to react with hydrazine NH₂NH₂ or methylhydrazine CH₃NHNH₂. Reaction of complexes containing substituted hydrazine ligands of the type [OsH(RNHNH₂)P₄]BPh₄ and [Os(RNHNH₂)₂P₄](BPh4)2 [P = P(OEt)₃; R = CH₃, C₆H₅] with Pb(OAc)₄ at -30 °C results in the selective oxidation of the hydrazine affording the corresponding diazene [OsH(RN=NH)P₄]BPh₄ (10) and [Os(RN=NH)₂P₄](BPh₂)₄ (11) derivatives. The first bis(methyldiazene) complex [Os-(CH₃N=NH)₂{P(OEt)₃}₄]BPh ₄)₂ (11b) was thus prepared.

Full text of DOI:10.1021/ic970463e

Inorg. Chem. 1998, 37, 479-489
479
Mono- and Bis(hydrazine) Complexes of Osmium(II): Synthesis, Reactions, and X-ray
Crystal Structure of the [Os(NH2NH2)2{P(OEt)3}4](BPh4)2 Derivative
Gabriele Albertin,*,† Stefano Antoniutti,† Alessia Bacchi,‡ Massimo Bergamo,†
Emilio Bordignon,† and Giancarlo Pelizzi‡
Dipartimento di Chimica, Universita` di Venezia, Dorsoduro 2137, 30123 Venezia, Italy, and
Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Centro CNR di
Strutturistica Diffrattometrica, Universita` di Parma, Viale delle Scienze, 43100 Parma, Italy
ReceiVed April 24, 1997
Reaction of OsH2P4 [P ) P(OEt)3, PPh(OEt)2, PPh2OEt] with methyl triflate followed by the treatment with
hydrazines gave the [OsH(RNHNH2)P4]BPh4 (1-3) (R ) H, CH3, C6H5, 4-NO2C6H4) derivatives. Instead, the
reaction of OsH2P4 first with methyl triflate, then with triflic acid, and finally with an excess of the appropriate
hydrazine afforded the bis(hydrazine) [Os(RNHNH2)2P4](BPh4)2 (4, 5) (R ) H, CH3, C6H5) complexes. Also
the [Os(NH2NH2){P(OEt)3}5](BPh4)2 (7) derivative was prepared. All the hydrazine complexes were fully
characterized by IR and 1H and 31P NMR spectra, and a single-crystal X-ray structure determination of the complex
[Os(NH2NH2)2{P(OEt)3}4](BPh4)2‚C2H5OH (4a) is reported. The compound crystallizes in the space group P21/c
with a ) 20.550(4) Å, b ) 19.663(4) Å, c ) 20.843(4) Å, â ) 99.84(9)°, and Z ) 4. The coordination around
the osmium atom is octahedral and the orientation of the ligands in the [Os(NH2NH2)2{P(OEt)3}4]2+ cation is
determined by several strong hydrogen bonds involving hydrazine nitrogen and phosphite oxygen atoms.
Amidrazone complexes [Os{η2-NHdC(R1)N(R)NH2}{P(OEt)3}4](BPh4)2 (8, 9) (R ) H, CH3; R1 ) CH3,
4-CH3C6H4) were prepared by allowing nitrile complexes [Os(R1CN)2P4](BPh4)2 to react with hydrazine NH2-
NH2 or methylhydrazine CH3NHNH2. Reaction of complexes containing substituted hydrazine ligands of the
type [OsH(RNHNH2)P4]BPh4 and [Os(RNHNH2)2P4](BPh4)2 [P ) P(OEt)3; R ) CH3, C6H5] with Pb(OAc)4 at
-30 °C results in the selective oxidation of the hydrazine affording the corresponding diazene [OsH(RNdNH)-
P4]BPh4 (10) and [Os(RNdNH)2P4](BPh4)2 (11) derivatives. The first bis(methyldiazene) complex [Os-
(CH3NdNH)2{P(OEt)3}4](BPh4)2 (11b) was thus prepared.
Introduction
(COD)(NH2NH2)3]BPh4 and [Os(COD)(NH2NH2)4](BPh4)2 and
on the carbonyl compound3b [OsBr(CO)2(NH2NH2)(PPh3)2]-
The chemistry of transition metal complexes containing
diazenido RN2, diazene RNdNH, hydrazine RNHNH2, and
other partially reduced dinitrogen ligands continues to arouse
interest not only for their relationship with the intermediates of
the dinitrogen fixation process but also for the diverse reactivity
modes and structural properties that the diazo complexes
exhibit.1,2 However, although a large number of studies have
been reported over the past 25 years, relatively few of them are
concerned with hydrazine or substituted hydrazine complexes.1-3
Furthermore, the osmium compounds containing NH2NH2 or
RNHNH2 ligands are rare3b,4,5 and include, apart from the
pioneering work on [OsCl2(RNHNH2)P3] and [OsCl2P2]2(µ-NH2-
NH2)2 (R ) H, Ph; P ) tertiary phosphine) derivatives,4 only
two papers on the cycloocta-1,5-diene (COD) complexes5 [OsCl-
CF3SO3.
Coordinate hydrazine NH2NH2 has been proposed as a
possible intermediate in the nitrogen fixation process, has been
shown to be a substrate6 as well as a product of functioning
nitrogenase, and has been isolated by quenching the enzyme.7
In this context, however, much remains to be known about the
chemistry of coordinate hydrazine and therefore it should be of
interest to report some new results on the synthesis and on the
reactivity of hydrazine derivatives.
In previous papers8 we have reported on the synthesis and
on the properties of both mono and bis forms of aryldiazene
(3) For recent papers on hydrazine complexes see: (a) Demadis, K. D.;
Malinak, S. M.; Coucouvanis, D. Inorg. Chem. 1996, 35, 4038. (b)
Cheng, T.-Y.; Ponce, A.; Rheingold, A. L.; Hillhouse, G. L. Angew.
Chem., Int. Ed. Engl. 1994, 33, 657. (c) Sellmann, D.; Ka¨ppler, J.;
Moll, M.; Knoch, F. Inorg. Chem. 1993, 32, 960. (d) Glassman, T.
E.; Vale, M. G.; Schrock, R. R. J. Am. Chem. Soc. 1992, 114, 8098.
(e) Kawano, M.; Hoshino, C.; Matsumoto, K. Inorg. Chem. 1992, 31,
5158. (f) Vogel, S.; Barth, A.; Huttner, G.; Klein, T.; Zsolnai, L.;
Kremer, R. Angew. Chem., Int. Ed. Engl. 1991, 30, 303.
(4) Chatt, J.; Leigh, G. J.; Paske, R. J. J. Chem. Soc. A 1969, 854.
(5) Oosthuizen, H. E.; Singleton, E.; Field, J. S.; Van Niekerk, G. C. J.
Organomet. Chem. 1985, 279, 433.
(6) (a) Burgess, B. K.; Wherland, S.; Stiefel, E. I.; Newton, W. E.
Biochemistry 1981, 20, 5140. (b) Davis, L. C. Arch. Biochem. Biophys.
1980, 204.
† Dipartimento di Chimica, Universita` Ca’Foscari di Venezia.
‡ Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica,
Chimica Fisica, Universita` di Parma.
(1) (a) Zollinger, H. In Diazo Chemistry II; VCH: Weinheim, Germany,
1995. (b) Sutton, D. Chem. ReV. 1993, 93, 995. (c) Kisch, H.;
Holzmeier, P. AdV. Organomet. Chem. 1992, 34, 67. (d) Johnson, B.
F. G.; Haymore, B. L.; Dilworth, J. R. In ComprehensiVe Coordination
Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.;
Pergamon Press: Oxford, U.K., 1987; Vol. 2, p 130. (e) Henderson,
R. A.; Leigh, G. J.; Pickett, C. J. AdV. Inorg. Chem. Radiochem. 1983,
27, 197. (f) Nugent, W. A.; Haymore, B. L.; Coord. Chem. ReV. 1980,
31, 123. (g) Bottomley, F. Q. ReV. 1970, 24, 617.
(7) (a) Dilworth, M. J.; Eady, R. R. Biochem. J. 1991, 277, 465. (b)
Thorneley, R. N.; Lowe, D. J. Biochem. J. 1984, 224, 887. (b) Evans,
D. J.; Henderson, R. A.; Smith, B. E. In Bioinorganic Catalysis;
Reedijk, J., Ed.; Marcel Dekker Inc.: New York, 1993. (d) Thorneley,
R. N.; Eady, R. R.; Lowe, D. J. Nature (London) 1978, 272, 557.
(2) (a) Hidai, M.; Mizobe, Y. Chem. ReV. 1995, 95, 1115. (b) Eady, R.
R.; Leigh, G. J. J. Chem. Soc., Dalton Trans. 1994, 2739. (c) Sellmann,
D. Angew. Chem., Int. Ed. Engl. 1993, 32, 64.
S0020-1669(97)00463-1 CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/10/1998

480 Inorganic Chemistry, Vol. 37, No. 3, 1998
Albertin et al.
6.80; N, 3.06. ΛM ) 54.7 Ω-1 mol-1 cm2. Anal. Calcd for 2a: C,
and aryldiazenido complexes of the iron family of the type [MH-
(ArNdNH)P4]+, [M(ArNdNH)2P4]2+, [M(ArN2)P4]+, and
[M(ArN2)2P3]2+ (M ) Fe, Ru, Os; P ) phosphite).8 Now, we
have extended9 these studies to include hydrazine and substituted
hydrazines as ligands, and in this paper we report the synthesis
and the characterization of mono- and bis(hydrazine) complexes
of osmium(II) together with some reactivity studies and an X-ray
crystal structure determination.
57.57; H, 6.42; N, 2.10. Found: C, 57.36; H, 6.55; N, 1.99. ΛM
)
54.0 Ω-1 mol-1 cm2. Anal. Calcd for 2b: C, 57.86; H, 6.50; N, 2.08.
Found: C, 57.51; H, 6.60; N, 2.03. ΛM ) 58.4 Ω-1 mol-1 cm2. Anal.
Calcd for 2c: C, 59.57; H, 6.36; N, 1.98. Found: C, 59.70; H, 6.26;
N, 1.90. ΛM ) 56.3 Ω-1 mol-1 cm2.
[OsH{(CH3)2NNH2}P4]BPh4 [P ) P(OEt)3 (1e), PPh(OEt)2 (2e)].
These complexes were prepared exactly like the related compounds 1
and 2 using an excess of (CH3)2NNH2 as a reagent; yield g65%. Anal.
Calcd for 1e: C, 48.62; H, 7.26; N, 2.27. Found: C, 48.79; H, 7.30;
N, 2.15. ΛM ) 54.8 Ω-1 mol-1 cm2. Anal. Calcd for 2e: C, 58.15;
H, 6.58; N, 2.05. Found: C, 58.40; H, 6.45; N, 2.12. ΛM ) 55.6 Ω-1
mol-1 cm2.
[OsH(RNHNH2)(PPh2OEt)4]BPh4 (3) [R ) CH3 (b), C6H5 (c)].
These complexes may be prepared by reacting the dihydride OsH2(PPh2-
OEt)4 first with methyl triflate and then with the appropriate hydrazine
as reported for the related P(OEt)3 (1) and PPh(OEt)2 (2) derivatives.
However, in order to obtain larger yields and pure compounds, an
alternative procedure can be used, such as the following. An excess
of the appropriate hydrazine (1 mmol) was added to a solution of the
[OsH(η2-H2)(PPh2OEt)4]BPh4 complex13 (0.10 mmol, 0.14 g) in 10 mL
of CH2Cl2, and the reaction mixture was stirred at room temperature
for about 24 h. The solvent was removed under reduced pressure giving
an oil which was treated with 2 mL of ethanol containing an excess of
NaBPh4 (0.2 mmol, 0.07 g). The resulting solution was cooled to -10
°C and vigorously stirred until a white solid separated out, which was
filtered out and crystallized from CH2Cl2 (1 mL) and ethanol (3 mL);
yield g50%. Anal. Calcd for 3b: C, 65.85; H, 5.94; N, 1.90.
Found: C, 66.02; H, 5.90; N, 1.85. ΛM ) 57.0 Ω-1 mol-1 cm2. Anal.
Calcd for 3c: C, 67.09; H, 5.83; N, 1.82. Found: C, 66.88; H, 5.76;
N, 1.70. ΛM ) 56.1 Ω-1 mol-1 cm2.
Experimental Section
All synthetic work was carried out under an appropriate atmosphere
(Ar, H2) using standard Schlenk techniques or a Vacuum Atmosphere
drybox. Once isolated, the complexes were found to be relatively stable
in air but were stored under an inert atmosphere at -25 °C. All solvents
were dried over appropriate drying agents, degassed on a vacuum line
and distilled into vacuumtight storage flasks. The (NH4)2OsCl6 salt
was a Johnson Matthey product, used as received. Triethyl phosphite,
P(OEt)3 (Aldrich), was purified by distillation under nitrogen, while
PPh(OEt)2 and the PPh2OEt were prepared by the method of Rabinowitz
and Pellon.10 The hydrazines CH3NHNH2, C6H5NHNH2, 4-NO2C6H4-
NHNH2, C6H5CONHNH2, and (CH3)2NNH2 were Aldrich products used
as received. Hydrazine, NH2NH2, was prepared by decomposition of
hydrazine cyanurate (Fluka) by following the reported method.11 Other
reagents were purchased from commercial sources in the highest
available purity and used as received. Infrared spectra were recorded
on a Nicolet Magna 750 FT-IR spectrophotometer. NMR spectra (1H,
31P) were obtained on a Bruker AC200 spectrometer at temperatures
varying between -90 and +30 °C, unless otherwise noted. 1H spectra
are referred to internal tetramethylsilane, while 31P{1H} chemical shifts
are reported with respect to 85% H3PO4, with downfield shifts
considered positive. The SwaN-MR software package12 has been used
in treating the NMR data. The conductivities of 10-3 M solutions of
the complexes in CH3NO2 at 25 °C were measured with a Radiometer
CDM 83 instrument.
Synthesis of Complexes. The hydrides OsH2P4 [P ) P(OEt)3,
PPh(OEt)2, PPh2OEt] were prepared as previously reported.8f,13
[OsH(RNHNH2)P4]BPh4 (1, 2) [P ) P(OEt)3 (1), PPh(OEt)2 (2);
R ) H (a), CH3 (b), C6H5 (c), 4-NO2C6H4 (d)]. Methyl triflate (0.10
mmol, 11 µL) was added to a solution of the appropriate hydride OsH2P4
(0.10 mmol) in 10 mL of toluene cooled to -196 °C. The reaction
mixture was brought to room temperature and stirred for 90 min, and
then an excess of the appropriate hydrazine (0.15 mmol) was added.
After 1 h of stirring, the solvent was removed under reduced pressure
giving an oil which was treated with 2 mL of ethanol containing an
excess of NaBPh4 (0.30 mmol, 0.10 g). A white or pale-yellow solid
slowly separated out from the resulting solution, which was filtered
out and crystallized from CH2Cl2 (1 mL) and ethanol (3 mL); yield
g70%. Anal. Calcd for 1a: C, 47.76; H, 7.10; N, 2.32. Found: C,
47.34; H, 7.18; N, 2.20. ΛM ) 60.2 Ω-1 mol-1 cm2. Anal. Calcd for
1b: C, 48.20; H, 7.18; N, 2.29. Found: C, 48.40; H, 6.92; N, 2.12.
ΛM ) 55.7 Ω-1 mol-1 cm2. Anal. Calcd for 1c: C, 50.54; H, 6.99;
N, 2.18. Found: C, 50.25; H, 7.01; N, 2.12. ΛM ) 53.0 Ω-1 mol-1
cm2. Calcd for 1d: C, 48.83; H, 6.68; N, 3.16. Found: C, 48.66; H,
[Os(RNHNH2)2P4](BPh4)2 (4, 5) [P ) P(OEt)3 (4), PPh(OEt)2 (5);
R ) H (a), CH3 (b), C6H5 (c)]. To a solution of the appropriate hydride
OsH2P4 (0.10 mmol) in 10 mL of toluene cooled to about -196 °C
was added an equimolar amount of methyl triflate (0.10 mmol, 11 µL)
and the reaction mixture brought to room temperature. After about 90
min of stirring, the solution was cooled again to -196 °C and a slight
excess of triflic acid (0.11 mmol, 9.7 µL) added. The reaction mixture
was then brought to room temperature and stirred for about 5 h. An
excess of the appropriate hydrazine (1 mmol) was added to the solution,
which was stirred for 24 h and then evaporated to dryness under reduced
pressure. The oil obtained was dissolved in 2 mL of ethanol, and an
excess of NaBPh4 (0.40 mmol, 0.14 g) in 2 mL of ethanol was added.
A white solid immediately separated out which was filtered out and
crystallized from CH2Cl2 (2 mL) and ethanol (3 mL); yield g80%.
Anal. Calcd for 4a: C, 55.53; H, 6.99; N, 3.60. Found: C, 55.68; H,
7.03; N, 3.49. ΛM ) 104.5 Ω-1 mol-1 cm2. Anal. Calcd for 4b: C,
56.06; H, 7.12; N, 3.53. Found: C, 56.20; H, 7.15; N, 3.40. ΛM
)
101.7 Ω-1 mol-1 cm2. Anal. Calcd for 4c: C, 59.02; H, 6.84; N,
3.28. Found: C, 59.21; H, 6.69; N, 3.19. ΛM ) 107.2 Ω-1 mol-1
cm2. Anal. Calcd for 5a: C, 62.71; H, 6.46; N, 3.32. Found: C,
62.53; H, 6.40; N, 3.23. ΛM ) 112.9 Ω-1 mol-1 cm2. Anal. Calcd
for 5b: C, 63.08; H, 6.59; N, 3.27. Found: C, 62.88; H, 6.35; N,
3.36. ΛM ) 115.4 Ω-1 mol-1 cm2. Anal. Calcd for 5c: C, 65.36; H,
6.36; N, 3.05. Found: C, 65.35; H, 6.29; N, 3.01. ΛM ) 109.6 Ω-1
mol-1 cm2.
(8) (a) Albertin, G.; Antoniutti, S.; Lanfranchi, M.; Pelizzi, G.; Bordignon,
E. Inorg. Chem. 1986, 25, 950. (b) Albertin, G.; Antoniutti, S.; Pelizzi,
G.; Vitali, F.; Bordignon, E. J. Am. Chem. Soc. 1986, 108, 6627. (c)
Albertin, G.; Antoniutti, S.; Bordignon, E. Inorg. Chem. 1987, 26,
3416. (d) Albertin, G. Antoniutti, S.; Pelizzi, G.; Vitali, F.; Bordignon,
E. Inorg. Chem. 1988, 27, 829. (e) Albertin, G.; Antoniutti, S.;
Bordignon, E. J. Am. Chem. Soc. 1989, 111, 2072. (f) Albertin, G.;
Antoniutti, S.; Bordignon, E. J. Chem. Soc., Dalton Trans. 1989, 2353.
(g) Amendola, P.; Antoniutti, S.; Albertin, G.; Bordignon, E. Inorg.
Chem. 1990, 29, 318. (h) Albertin, G.; Antoniutti, S.; Bacchi, A.;
Bordignon, E.; Pelizzi, G.; Ugo, P. Inorg. Chem. 1996, 35, 6245.
(9) Albertin, A.; Antoniutti, S.; Bordignon, E.; Pattaro, S. J. Chem. Soc.,
Dalton Trans. 1997, 4445.
[Os{(CH3)2NNH2}2{P(OEt)3}4](BPh4)2 (4e). This compound was
prepared exactly like 4 and 5; yield g55%. Anal. Calcd: C, 56.58;
H, 7.25; N, 3.47. Found: C, 56.69; H, 7.11; N, 3.34. ΛM ) 116.3
Ω-1 mol-1 cm2.
[Os(η2-C6H5CONHNH2){P(OEt)3}4](BPh4)2 (6). This complex was
prepared by a slight modification to the method used for 4 and 5, as
follows. Methyl triflate (0.10 mmol, 11 µL) was added to a cooled
solution (-196 °C) of OsH2[P(OEt)3]4 (0.10 mmol, 0.086 g) in 10 mL
of toluene, and the reaction mixture brought to room temperature and
then stirred for about 90 min. Triflic acid (0.10 mmol, 8.8 µL) was
then added to the solution cooled again to about -196 °C, and the
resulting mixture was brought to room temperature and stirred for 5 h.
The flask was open to the air and an excess of solid C6H5CONHNH2
(0.5 mmol, 0.067 g) added to the solution together with 5 mL of CH2-
Cl2. The suspension was stirred for 24 h and then filtered to remove
(10) Rabinowitz, R.; Pellon, J. J. Org. Chem. 1961, 26, 4623.
(11) Nachbaur, E.; Leiseder, G. Monatsh. Chem. 1971, 102, 1718.
(12) Balacco, G. J. Chem. Inf. Comput. Sci. 1994, 34, 1235.
(13) Albertin, G.; Antoniutti, S.; Baldan, D.; Bordignon, E. Inorg. Chem.
1995, 34, 6205.

Mono- and Bis(hydrazine) Complexes of Os(II)
Inorganic Chemistry, Vol. 37, No. 3, 1998 481
the excess benzoylhydrazine. The resulting solution was evaporated
to dryness giving an oil which was treated with 2 mL of ethanol
containing an excess of NaBPh4 (0.4 mmol, 0.14 g). A white solid
slowly separated out, which was filtered out and crystallized from CH2-
Cl2 (2 mL) and ethanol (3 mL); yield g55%. Anal. Calcd: C, 58.23;
H, 6.68; N, 1.72. Found: C, 58.40; H, 6.52; N, 1.70. ΛM ) 108.2
Ω-1 mol-1 cm2.
crystallized from ethanol; yield g55%. Anal. Calcd for
[OsH{P(OEt)3}5]BPh4: C, 48.36; H, 7.21. Found: C, 48.41; H, 7.15.
ΛM ) 51.5 Ω-1 mol-1 cm2. IR (KBr): 1990 [m, ν(OsH)] cm-1 1H
.
NMR (CD2Cl2, 25 °C; δ): 7.30-6.70 (m, 20 H, Ph), 3.96 (m, 30 H,
CH2), 1.25 (t, 45 H, CH3), -11.16 to -11.92 (m, 1 H, hydride).
31P{1H} NMR (CD2Cl2, -90 °C; δ): spin system AB4, δA ) 105.7,
δB ) 99.3, JAB ) 34 Hz. Anal. Calcd for OsCl2[P(OEt)3]4: C, 31.14;
H, 6.53. Found: C, 31.16; H, 6.84. 1H NMR (CD2Cl2, 25 °C; δ):
[Os(η2-O2SOCF3){PPh(OEt)2}4]BPh4. To a solution of OsH2[PPh-
(OEt)2]4 (0.32 mmol, 0.32 g) in 5 mL of toluene cooled to about -196
°C was added an equimolar amount of CF3SO3CH3 (0.32 mmol, 36
µL), and the reaction mixture was brought to room temperature and
stirred for 90 min. An excess of CF3SO3H (0.96 mmol, 86 µL) was
then added to the resulting solution previously cooled to about -196
°C. After the reaction mixture was brought to 20 °C, it was stirred for
3 h and then the solvent removed under reduced pressure. The oil
obtained was treated with ethanol (4 mL), and then an excess of NaBPh4
(1 mmol, 0.34 g) in 3 mL of ethanol was added to the resulting solution.
A white solid slowly separated out, which was filtered out and
crystallized fractionally from ethanol to separate the triflate complex
[Os(η2-O2SOCF3)P4]BPh4 from the dihydrogen [OsH(η2-H2)P4]BPh4
compound present in the solid obtained; yield g40%. Anal. Calcd:
C, 53.79; H, 5.56. Found: C, 53.49; H, 5.80. ΛM ) 53.4 Ω-1 mol-1
cm2. 1H NMR (CD2Cl2, 25 °C; δ): 7.60-6.70 (m, 40 H, Ph), 3.88
(m, br, 16 H, CH2), 1.24 (t, 24 H, CH3). 31P{1H} NMR (CD2Cl2, 25
°C; δ): spin system A2B2, δA ) 118.1, δB ) 77.8, JAB ) 31 Hz.
[Os(RCN)2P4](BPh4)2 [R ) CH3, 4-CH3C6H4; P ) P(OEt)3 and
PPh(OEt)2]. To a solution of the appropriate hydride OsH2P4 (0.5
mmol) in 10 mL of toluene cooled to about -196 °C was added an
equimolar amount of methyl triflate (0.5 mmol, 55 µL) and the reaction
mixture, brought to room temperature, stirred for 90 min. An excess
of the appropriate nitrile (25 mmol) and then an excess of triflic acid
(1.5 mmol, 132 µL) were added to the solution cooled again to -196
°C, which was brought to room temperature and stirred for 24 h. The
solvent was removed under reduced pressure giving an oil which was
treated with 5 mL of ethanol. The addition of an excess of NaBPh4 (2
mmol, 0.68 g) in 3 mL of ethanol caused the precipitation of a white
solid, which was filtered out and crystallized from CH2Cl2 (4 mL) and
ethanol (5 mL); yield g80%. Anal. Calcd for R ) CH3 and P )
P(OEt)3: C, 57.94; H, 6.78; N, 1.78. Found: C, 58.10; H, 6.63; N,
1.70. ΛM ) 115.2 Ω-1 mol-1 cm2. 1H NMR (CD2Cl2, 25 °C; δ):
7.40-6.80 (m, 40 H, Ph), 4.15-3.90 (m, 24 H, CH2), 1.72 (s, 6 H,
CH3 nitrile), 1.29, 1.26 (t, 36 H, CH3 phos). 31P{1H} NMR (CD2Cl2,
25 °C; δ): spin system A2B2, δA ) 81.0, δB ) 73.4, JAB ) 44.1 Hz.
Anal. Calcd for R ) CH3 and P ) PPh(OEt)2: C, 64.86; H, 6.27; N,
1.64. Found: C, 64.80; H, 6.31; N, 1.68. ΛM ) 117.7 Ω-1 mol-1
cm2. 1H NMR [(CD3)2CO, 25 °C; δ]: 7.90-6.70 (m, 60 H, Ph), 4.25-
4.00 (m, 16 H, CH2), 1.75 (s, 6 H, CH3 nitrile), 1.45, 1.44 (t, 24 H,
CH3 phos). 31P{1H} NMR (CD2Cl2, 25 °C; δ): spin system A2B2, δA
) 112.5, δB ) 107.4, JAB ) 33.6 Hz. Anal. Calcd for R ) 4-CH3C6H4
and P ) P(OEt)3: C, 61.18; H, 6.65; N, 1.62. Found: C, 60.94; H,
6.41; N, 1.58. ΛM ) 108.4 Ω-1 mol-1 cm2. IR (KBr): 2263 [m, ν-
4.19 (m, 24 H, CH2), 1.22 (t, 36 H, CH3). 31P{1H} NMR (CD2Cl2, 25
31 187
°C; δ): 83.5 s (J
) 293.4 Hz).
P
Os
[Os(NH2NH2){P(OEt)3}5](BPh4)2 (7). To a solution under hydrogen
(1 atm) of [OsH{P(OEt)3}5]BPh4 (0.10 mmol, 0.134 g) in 10 mL of
CH2Cl2 was added an equimolar amount of HBF4‚Et2O (0.10 mmol,
15 µL of a 54% solution in Et2O) and the reaction mixture stirred for
24 h. An excess of NH2NH2 (1 mmol, 32 µL) was added, and after
the H2 atmosphere was replaced with an argon one, the solution was
stirred for about 3 h. The solvent was removed under reduced pressure
giving an oil which was treated with ethanol (2 mL) containing an
excess of NaBPh4 (0.20 mmol, 0.068 g). A white solid slowly separated
out, which was filtered out and crystallized from CH2Cl2 (2 mL) and
ethanol (3 mL); yield g60%. Anal. Calcd: C, 55.39; H, 7.09; N,
1.66. Found: C, 55.54; H, 6.91; N, 1.58. ΛM ) 108.0 Ω-1 mol-1
cm2.
[Os{η2-NHdC(R1)N(R)NH2}{P(OEt)3}4](BPh4)2 (8, 9) [R1 ) CH3
(8), 4-CH3C6H4 (9); R ) H (a), CH3 (b)]. An excess of the appropriate
hydrazine (1.2 mmol) was added to a solution of [Os(R1CN)2P4](BPh4)2
(0.15 mmol) in 15 mL of 1,2-dichloroethane and the reaction mixture
refluxed for 3 h. The solvent was removed under reduced pressure
giving an oil which was treated with 3 mL of ethanol. The addition of
a slight excess of NaBPh4 (0.2 mmol, 68 mg) to the resulting solution
caused the precipitation of a white solid, which was filtered out and
crystallized from CH2Cl2 (2 mL) and ethanol (4 mL); yield g50%.
Anal. Calcd for 8a: C, 56.74; H, 6.89; N, 2.68. Found: C, 56.64; H,
6.65; N, 2.50. ΛM ) 112.5 Ω-1 mol-1 cm2. Anal. Calcd for 8b: C,
57.00; H, 6.95; N, 2.66. Found: C, 57.13; H, 6.90; N, 2.54. ΛM
)
116.6 Ω-1 mol-1 cm2. Anal. Calcd for 9a: C, 58.50; H, 6.81; N,
2.56. Found: C, 58.72; H, 6.67; N, 2.40. ΛM ) 121.4 Ω-1 mol-1
cm2. Anal. Calcd for 9b: C, 58.73; H, 6.88; N, 2.54. Found: C,
58.48; H, 6.71; N, 2.49. ΛM ) 113.9 Ω-1 mol-1 cm2.
[Os(CH3NdNH)2{P(OEt)3}4](BPh4)2 (11b). A sample of [Os(CH3-
NHNH2)2{P(OEt)3}4](BPh4)2 (0.10 mmol, 0.16 g) was placed in a three-
necked 25-mL round-bottomed flask fitted with a solid-addition side
arm containing an excess of Pb(OAc)4 (0.30 mmol, 0.14 g). Dichlo-
romethane (10 mL) was added, the solution cooled to -30 °C, and the
Pb(OAc)4 added portionwise over 20-30 min to the cold stirred
solution. The solution was then brought to room temperature and
filtered, and the solvent was removed under reduced pressure giving
an oil. The addition of ethanol (3 mL) containing an excess of NaBPh4
(0.2 mmol, 0.068 g) caused the separation of an orange solid, which
was filtered out and crystallized from CH2Cl2 (2 mL) and ethanol (3
mL); yield g60%. Anal. Calcd: C, 56.20; H, 6.88; N, 3.54. Found:
C, 56.32; H, 6.93; N, 3.44. ΛM ) 114.2 Ω-1 mol-1 cm2.
(CN)] cm-1 1H NMR [(CD3)2CO, 25 °C; δ]: 7.85-6.70 (m, 48 H,
.
Ph), 4.45-4.20 (m, 24 H, CH2), 2.44 (s, 6 H, CH3 nitrile), 1.37, 1.34
(t, 36 H, CH3 phos). 31P{1H} NMR [(CD3)2CO, 25 °C; δ]: spin system
A2B2, δA ) 84.0, δB ) 77.4, JAB ) 44.0 Hz. Anal. Calcd for R )
4-CH3C6H4 and P ) PPh(OEt)2: C, 67.31; H, 6.19; N, 1.51. Found:
C, 67.55; H, 6.03; N, 1.55. ΛM ) 110.0 Ω-1 mol-1 cm2. IR (KBr):
[OsH(C6H5NdNH){P(OEt)3}4]BPh4 (10c) and [Os(C6H5NdNH)2
{P(OEt)3}4](BPh4)2 (11c). These complexes were prepared by oxida-
tion with an excess of Pb(OAc)4 of the corresponding hydrazine
complexes [OsH(C6H5NHNH2){P(OEt)3}4]BPh4 and [Os(C6H5NHNH2)2-
{P(OEt)3}4](BPh4)2, respectively, following the same procedure reported
for the methylhydrazine [Os(CH3NHNH2)2{P(OEt)3}4](BPh4)2 deriva-
tive; yield g65%. Anal. Calcd for 10c: C, 50.62; H, 6.84; N, 2.19.
Found: C, 50.86; H, 6.89; N, 2.11. ΛM ) 53.5 Ω-1 mol-1 cm2. Anal.
Calcd for 11c: C, 59.16; H, 6.62; N, 3.28. Found: C, 59.41; H, 6.49;
N, 3.17. ΛM ) 107.1 Ω-1 mol-1 cm2.
2258 [m, ν(CN)] cm-1 1H NMR [(CD3)2CO, 25 °C; δ]: 8.00-6.70
.
(m, 68 H, Ph), 4.20-3.90 (m, 16 H, CH2), 2.40 (s, 6 H, CH3 nitrile),
1.45, 1.38 (t, 24 H, CH3 phos). 31P{1H} NMR [(CD3)2CO, 25 °C; δ]:
spin system A2B2, δA ) 108.9, δB ) 104.3, JAB ) 33.4 Hz.
[OsH{P(OEt)3}5]BPh4 and OsCl2[P(OEt)3]4. A 50-mL three-
necked round-bottomed flask was charged with 0.5 g (1.2 mmol) of
(NH4)2OsCl6, 20 mL of anhydrous ethanol, 3.7 mL (24 mmol) of
P(OEt)3, and about 1 g (15 mmol) of zinc dust. The reaction mixture
was refluxed for 14 h and filtered, and then the solvent was removed
under reduced pressure. The oil obtained was treated with ethanol (5
mL) giving a pale-yellow solution which separated a small amount
(about 7-8%) of a yellow solid characterized as OsCl2[P(OEt)3]4. After
filtration, an excess of NaBPh4 (2 mmol, 0.68 g) in 2 mL of ethanol
was added and the resulting solid formed was filtered out and
[Os(η2-O2CCH3){P(OEt)3}4]BPh4 (12). This complex was obtained
by the oxidation reaction with Pb(OAc)4 of both the hydrazine [OsH-
(NH2NH2){P(OEt)3}4]BPh4 and [Os(NH2NH2)2{P(OEt)3}4](BPh4)2 de-
rivatives. In a typical preparation a solution of [Os(NH2NH2)2{P(OEt)3}4]-
(BPh4)2 (0.10 mmol, 0.16 g) in 10 mL of CH2Cl2 cooled to -30 °C is
oxidized with solid Pb(OAc)4 (0.20 mmol, 0.089 g) added portionwise
over a 20-30 min period. The solution was then filtered and the solvent
removed under reduced pressure giving an oil. This oil was treated
with 4 mL of ethanol containing an excess of NaBPh4 (0.2 mmol, 0.068

482 Inorganic Chemistry, Vol. 37, No. 3, 1998
Albertin et al.
Table 1. Crystal and Structure Refinement Data for
[Os(NH2NH2)2{P(OEt)3}4](BPh4)2‚C2H5OH (4a)
corrected for Lorentz and polarization effects. The phase problem was
solved by direct methods, using SIR92,14 which allowed one to retrieve
all non-hydrogen atoms. Neutral atomic scattering factors were
employed, those for non-hydrogen atoms being corrected for anomalous
dispersion. Hydrogen atoms were placed at idealized positions, riding
on their carrier atoms, with the exception of those belonging to
hydrazine, whose presence and geometry were to be confirmed
experimentally. Several cycles of full-matrix least-squares refinement
were performed on F2 till the isotropic model had reached convergence,
using SHELXL96.15 A total of 12 anisotropic scaling factors were
then refined to model an empirical absorption surface according to the
method of Parkin, Moezzi, and Hope,16 as implemented in SHELXL96.
The validity of this absorption correction was supported by the
improvement of the rms R factor (wR2) from 0.468 to 0.452 upon the
introduction of the 12 parameters. This was also checked with the
cross-validation method implemented in SHELXPRO17 by refining the
12 parameters of the absorption model on a set of about 14 000
reflections and calculating the consequent R-factor drop on the
remaining 1600 “unbiased free reflections”. The resultant “local free-
R” dropped from 0.379 to 0.363 confirming the significance of the
correction. The values of the 12 anisotropic scaling factors refined
with the isotropic model on all reflections were held fixed in the
subsequent structure refinements to prevent instability due to their
correlation with atomic anisotropic thermal motion. Anisotropic thermal
displacement parameters were introduced and refined for all non-
hydrogen atoms; at this stage a careful inspection of the Fourier density
map allowed us to locate the hydrazinic hydrogens, which were
restrained to maintain correct geometry and realistic thermal factors
during the subsequent refinements. In order to improve the observation
to parameter ratio, phenyl rings were constrained to rigid group
behavior, and rigid bond and isotropicity restraints were applied on
the thermal motion of all carbons. The final model includes also a
highly mobile ethanol molecule, which was detected in the last stages
of the refinement. The final geometry was analyzed by the program
PARST95,18 and the drawings were made with ZORTEP.19 All the
calculations were performed on ENCORE91 computer at the Centro
di Studio per la Strutturistica Diffrattometrica del CNR in Parma, Italy.
Besides the use of data from the original literature, data for comparison
with other compounds were retrieved and analyzed by the software
packages of the Cambridge Structural Database.20 Table 2 reports final
fractional atomic coordinates for non-hydrogen atoms.
empirical formula
fw
temp
C74H114B2N4O13OsP4
1603.45
20(2) °C
wavelength
cryst system
space group
unit cell dimens
1.541 84 Å
monoclinic
P21/c
a ) 20.550(4) Å
b ) 19.663(4) Å, â ) 99.84(9)°
c ) 20.843(4) Å
V
8298(3) Å3
Z
4
D(calcd)
abs coeff
1.283 g/cm3
4.096 mm-1
F(000)
3344
3-70°
θ range for data collcn
index ranges
reflcns collcd
indepdt reflcns
refinement method
data/restraints/params
goodness-of-fit on F2
-25 e h e 24, 0 e k e 23, 0 e l e 25
16 177
15 738 [R(int) ) 0.1307]
full-matrix least-squares on F2
15738/927/815
0.842
final R indicesa [I > 2σ(I)] R1 ) 0.0909, wR2 ) 0.2168
R indices (all data)
largest ∆F peak and hole
R1 ) 0.3598, wR2 ) 0.3906
0.548 and -1.903 e/Å3
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) {∑[w(Fo2 - Fc2)2]/∑[w(Fo )2]1/2
,
2
w ) 1/{σ2(Fo ) + [0.17(2Fc2 + Fo )/3]2}.
2
2
Table 2. Fractional Atomic Coordinates (×104) and Equivalent
Isotropic Displacement Parameters (Å2 × 104) (One-Third Trace of
the Diagonalized Matrix), with Esd’s in Parentheses for Relevant
Non-Hydrogen Atoms
atom
x/a
y/b
z/c
Ueq
Os
P1
P2
P3
2164.5(4)
2802(3)
2886(3)
1442(3)
2614(3)
1471(7)
786(11)
1685(8)
1167(12)
2717(6)
3556(6)
2565(7)
3304(8)
2602(8)
3388(8)
1034(8)
907(6)
60.7(4)
2244.3(5)
1442(3)
2809(3)
2976(3)
2753(4)
1576(8)
1653(10)
1689(9)
1168(12)
958(8)
912(4)
971(23)
923(24)
972(26)
-22(3)
779(3)
185(3)
-886(3)
-572(8)
-569(10)
925(7)
787(10)
626(7)
-111(7)
-612(8)
1193(8)
1345(8)
372(11)
-455(7)
773(6)
P4
1045(30)
1054(77)
1523(119)
1095(81)
1592(119)
1230(73)
1178(66)
1448(84)
1713(94)
1808(110)
1993(101)
1331(77)
1179(67)
1551(93)
1301(76)
1304(72)
1581(93)
N1
N2
N3
N4
O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O11
O12
1642(7)
947(8)
Results and Discussion
2419(8)
3164(10)
3350(8)
3054(7)
2725(7)
3684(10)
3491(8)
2456(7)
2623(10)
Mono- and Bis(hydrazine) Complexes. Hydride-hydrazine
complexes [OsH(RNHNH2)P4]BPh4 (1-3) were prepared by
treating hydride species OsH2P4 first with methyl triflate and
then with an excess of the appropriate RNHNH2 ligand. Bis-
(hydrazine) derivatives [Os(RNHNH2)2P4](BPh4)2 (4, 5), instead,
can be obtained by sequential reaction of the hydrides OsH2P4
first with methyl triflate, then with triflic acid and, finally, with
an excess of the appropriate hydrazine as shown in Scheme 1.
The reaction of the hydride species OsH2P4 with CF3SO3CH3
proceeds with evolution of CH4 (by 1H NMR) and the probable
formation of the triflate complex21 OsH(η1-OSO2CF3)P4 which
1669(8)
2625(7)
2150(6)
3281(8)
467(9)
-919(6)
-1513(6)
-1160(8)
g), and the resulting solution was vigorously stirred at 0 °C until a
white solid separated out, which was filtered out and crystallized from
ethanol; yield g65%. Anal. Calcd: C, 48.70; H, 6.78. Found: C,
48.92; H, 6.60. ΛM ) 50.7 Ω-1 mol-1 cm2.
-
affords, by substitution of the CF3SO3 ligand, the final
X-ray Crystallography. The X-ray diffractometric analysis was
performed on a colorless crystal with a CAD4 diffractometer. Cu KR
radiation (λ ) 1.541 84 Å) was used because the crystal was expected
to diffract poorly, even in the presence of heavy scatters, due to possible
radiation damage and solvent loss. Automatic peak search, centering,
and indexing procedures established a monoclinic primitive lattice, and
systematic extinctions together with centric intensities statistics identi-
fied unambiguously the space group as P21/c. The intensity of a
reference reflection was measured periodically throughout data col-
lection to monitor crystal decay. Intensity loss of more than 50% was
detected, and data were rescaled accordingly. Table 1 reports crystal
data and details of data collection and structure refinement. The
intensity data were processed with a peak-profile procedure and
hydrazine complexes 1-3. Compounds 3, containing the PPh2-
(14) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla,
M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435.
(15) Sheldrick, G. SHELXL96, University of Goettingen, Germany, 1996.
(16) Parkin, S.; Moezzi, B.; Hope, H. J. Appl. Crystallogr. 1995, 28, 53.
(17) Sheldrick, G. SHELXPRO, University of Goettingen, Germany, 1996.
(18) Nardelli, M. J. Appl. Crystallogr. 1995, 28, 659.
(19) Zsolnai, L.; Pritzkow, H. ZORTEP. ORTEP original program modified
for PC, University of Heidelberg, Germany, 1994.
(20) Allen, F. H.; Kennard, O. Chem. Design Automation News 1993, 8, 1
and 31-37.
(21) Albertin, G.; Antoniutti, S.; Bordignon, E. J. Chem. Soc., Dalton Trans.
1989, 719.

Mono- and Bis(hydrazine) Complexes of Os(II)
Inorganic Chemistry, Vol. 37, No. 3, 1998 483
Scheme 1
(RNHNH2)P4]+ (1-3) cations appear, for all the complexes
except 2a,b, as A2BC or AB2C multiplets, which can be
simulated with the parameters reported in Table 3 and suggest
the existence of a cis geometry I. This geometry is also
confirmed by the presence, in the 1H NMR spectra, of a
complicated multiplet between -7.36 and -9.72 ppm for the
hydride ligand. Surprisingly, in the temperature range between
+30 and -90 °C, the 31P NMR spectra of the [OsH(NH2NH2)-
{PPh(OEt)2}4]BPh4 (2a) and [OsH(CH3NHNH2){PPh(OEt)2}4]-
BPh4 (2b) derivatives appear as sharp singlets, suggesting that
the hydride and the hydrazine ligands are in a mutually trans
position as in type II structure. This different geometry
observed in the two compounds 2a,b with respect to the other
monohydrazine compounds is, in some aspects, rather difficult
to explain taking also into account that the two compounds were
prepared exactly as the other derivatives 1-3 and that no
isomerization was observed in solution for all the monohydra-
zine derivatives. A steric influence of the ancillary phosphite
ligands in determining the geometry of the two complexes 2a,b
seems to be unprobable, because the steric hindrance (cone
angle)23 of the PPh(OEt)2 ligand is just intermediate between
those of the P(OEt)3 and of the PPh2OEt, whose related
hydrazine and methylhydrazine [OsH(RNHNH2)P4]+ (1a, 3a;
1b, 3b) derivatives show a cis geometry. However, also the
electronic properties23 of the PPh(OEt)2 ligand are intermediate
between those of P(OEt)3 and PPh2OEt, while, instead, NH2-
NH2 and CH3NHNH2 are different from the other arylhydra-
zines. Probably, a combination of steric and electronic factors
of both the phosphite and the hydrazine ligands favor a cis or
a trans arrangement of the ligands, as observed in our hydrazine
derivatives. As a result, both the N,N-dimethylhydrazine
complexes [OsH{(CH3)2NNH2}P4]BPh4 (1e, 2e) containing the
P(OEt)3 and the PPh(OEt)2 ligands show a type-I cis geometry.
Furthermore, on the basis of the A2B2 multiplets observed in
the 31P{1H) NMR spectra, a cis arrangement (III) of the two
OEt phosphine ligand, can also be obtained by substitution with
hydrazines of the η2-H2 ligand in [OsH(η2-H2)(PPh2OEt)4]+
cations.13
Treatment of the η1-triflate OsH(η1-OSO2CF3)P4 complex
with triflic acid may result in a protonation reaction giving the
dihydrogen intermediate [Os(η2-H2)(η1-OSO2CF3)P4]+ CF3SO3
-
which, by loss of H2, affords the η2-triflate [Os(η2-O2SOCF3)P4]+-
CF3SO3 derivative. Although the presence of a dihydrogen
-
complex was not detected in the reaction mixture, its formation
is plausible on the basis of the known properties8g,13 of the
osmium hydrides containing phosphite ligands. Furthermore,
the achievement and the characterization of the η2-triflate
[Os(η2-O2SOCF3){PPh(OEt)2}4]BPh4 complex seems to support
the proposed reaction path. Substitution of the η2-triflate with
RNHNH2 is easy and gives the bis(hydrazine) [Os(RNHN-
H2)2P4]2+ cations which can be separated as BPh4 salts and
characterized. It is worth noting that also the N,N-dimethyl-
hydrazine complexes [OsH{(CH3)2NNH2}P4]BPh4 (1e, 2e) and
[Os{(CH3)2NNH2}2P4](BPh4)2 (4e) can be obtained by following
the method reported in Scheme 1.
Good analytical data were obtained for all the hydrazine
complexes 1-5, which are white solids stable in the air and in
solutions of polar organic solvents, where they behave as 1:1
(1-3) or 2:1 (4, 5) electrolytes.22 The IR and NMR data (Table
3) support the proposed formulation and allow a geometry in
solution to be established.
The presence of the hydrazine ligand in all the complexes
1-5 is confirmed by the IR spectra, which show the charac-
teristic ν(NH) and δ(NH2) bands at 3386-3219 and at 1618-
1593 cm-1, respectively. Furthermore, in the [OsH(RNHNH2)-
P4]BPh4 (1-3) derivatives the absorption due to the ν(OsH) is
RNHNH2 ligands can also be proposed in solution for all the
bis(hydrazine) [Os(RNHNH2)2P4](BPh4)2 (4, 5) complexes,
except for 5a,b. Such a cis geometry was also observed in the
solid state (X-ray, see below) for the [Os(NH2NH2)2{P(OEt)3}4]-
(BPh4)2 (4a) derivative and is shown in Figure 1.
For the related [Os(NH2NH2)2{PPh(OEt)2}4](BPh4)2 (5a) and
[Os(CH3NHNH2)2{PPh(OEt)2}4](BPh4)2 (5b) complexes, in-
stead, the 31P NMR spectra indicate the presence of a trans
geometry (IV) (sharp singlet at 108.1 and 108.2 ppm) in
agreement with the presence, for the bis(hydrazine) derivative
also observed at 2078-1926 cm-1
.
The 1H NMR spectra confirm the presence of the hydrazine
ligand showing the characteristic NH and NH2 signals, which
were clearly assigned by accurate integration and homodecou-
pling experiments and are reported in Table 3. The spectra also
show that, in the case of NH2NH2 complexes, two NH2 proton
signals are present for all the mono- and bis(hydrazine)
complexes suggesting the presence of a η1-coordination for the
hydrazine ligand. Furthermore, the 31P{1H} NMR spectra allow
one to assign a geometry in solution for all the osmium
compounds. In particular, the 31P spectra of the [OsH-
(23) (a) Tolman, C. A. Chem. ReV. 1977, 77, 313. (b) Rahman, M. M.;
Liu, H.-Y.; Eriks, K.; Prock, A.; Giering, W. P. Organometallics 1989,
8, 1.
(22) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81.

484 Inorganic Chemistry, Vol. 37, No. 3, 1998
Albertin et al.
Table 3. IR and NMR Spectroscopic Data for the Osmium Complexes
compound
IRa
1H NMRb,c
(ppm)
spin
syst
31P{1H} NMRb,d
(ppm; J, Hz)
no.
formula
(cm-1
)
assgnt
assgnt
1a
[OsH(NH2NH2){P(OEt)3}4]BPh4
3374 m
3330 m
3273 m
1956 m
1593 m
ν(NH)
4.67 m, br
3.33 m, br
4.20-3.75 m
1.30, 1.25, 1.21 t
-8.55 to -9.54 m
OsNH2
NH2
CH2
CH3
H hydride
A2BC
A2BC
AB2C
AB2C
A2BC
δA ) 103.6
δB ) 103.6
δC ) 97.5
JAB ) 34.0
JAC ) 42.6
JBC ) 27.3
δA ) 103.7
δB ) 103.5
δC ) 98.0
JAB ) 34.1
JAC ) 43.0
JBC ) 27.7
δA ) 102.8
δB ) 102.6
δC ) 96.4
JAB ) 34.8
JAC ) 27.5
JBC ) 43.1
δA ) 104.1
δB ) 103.7
δC ) 96.7
JAB ) 34.9
JAC ) 28.2
JBC ) 43.4
δA ) 102.7
δB ) 101.4
δC ) 97.8
JAB ) 36.1
JAC ) 43.0
JBC ) 25.2
125.8 s
ν(OsH)
δ(NH2)
1b
1c
1d
1e
2a
2b
[OsH(CH3NHNH2){P(OEt)3}4]BPh4
[OsH(C6H5NHNH2){P(OEt)3}4]BPh4
[OsH(4-NO2C6H4NHNH2){P(OEt)3}4]BPh4
[OsH{(CH3)2NNH2}{P(OEt)3}4]BPh4
[OsH(NH2NH2){PPh(OEt)2}4]BPh4
[OsH(CH3NHNH2){PPh(OEt)2}4]BPh4
3348 m
3314 m
1927 m
ν(NH)
4.59 m, br
2.77 m, br
4.15-3.75 m
2.44 d, br
1.29, 1.25, 1.21 t
-8.73 to -9.72 m
5.35 m, br
OsNH2
NH
CH2
CH3NH
CH3
H hydride
OsNH2
NH
ν(OsH)
3363 m
3314 w
3301 m
1930 m
1604 m
ν(NH)
4.85 br
4.18-3.80 m
1.28, 1.24, 1.19 t
-8.54 to -9.53 m
CH2
CH3
H hydride
ν(OsH)
δ(NH2)
e
3386 m
3365 m
3301 m
1926 m
1601 m
ν(NH)
6.33 m, br
5.79 m, br
4.32-3.93 m
1.35, 1.28, 1.22 t
-8.21 to -9.21 m
NH
OsNH2
CH2
CH3
H hydride
ν(OsH)
δ(NH2)
3308 m
1963 m
ν(NH)
ν(OsH)
4.63 m, br
4.13-3.80 m
2.41 s
1.27, 1.25, 1.21 t
-8.55 to -9.31 m
OsNH2
CH2
(CH3)2N
CH3
H hydride
3370 m
3334 m
3317 m
3259 w
2063 m
1603 m
3328 m
3304 w
3256 w
2078 m
1611 m
ν(NH)
4.80 m, br
3.14 m, br
4.02-3.47 m
1.14, 1.12 t
-18.07 qi
JPH ) 18 Hz
4.64 m, br
3.19 m
4.02-3.40 m
2.42 d
OsNH2
NH2
CH2
CH3
H hydride
ν(OsH)
δ(NH2)
ν(NH)
OsNH2
NH
CH2
125.9 s
ν(OsH)
δ(NH2)
CH3NH
JHH ) 6.4 Hz
1.13 t
CH3
-18.02 qi
JPH ) 18 Hz
5.39 t, br
H hydride
e
2c
2e
3b
3c
[OsH(C6H5NHNH2){PPh(OEt)2}4]BPh4
3375 w
3293 m
3219 w
1983 m
1600 m
ν(NH)
NH
AB2C
A2BC
A2BC
A2BC
δA ) 126.3
δB ) 124.7
δC ) 115.9
JAB ) 23.6
JAC ) 21.0
JBC ) 28.4
δA ) 124.8
δB ) 122.7
δC ) 116.2
JAB ) 25.6
JAC ) 28.7
JBC ) 15.0
δA ) 98.7
δB ) 94.9
δC ) 91.9
JAB ) 17.7
JAC ) 22.0
JBC ) 19.0
δA ) 100.7
δB ) 97.4
δC ) 93.0
JAB ) 16.1
JAC ) 22.4
JBC ) 17.9
δA ) 84.6
δB ) 77.9
JAB ) 43.2
5.04 m, br
OsNH2
CH2
4.10-3.30 m
1.26, 1.15, 1.13,
1.03, 0.97 t
-7.98 to -8.70 m
4.35 br
4.00-3.50 m
2.35 s
1.27, 1.20, 1.13,
0.95 t
-8.06 to -8.79 m
3.70-2.90 m
2.41 m
1.53 d
1.22, 1.10, 1.03,
0.64 t
-8.02 to -8.75 m
5.20 br
4.60 m, br
3.40-3.00 m
0.85, 0.76, 0.59 t
-7.36 to -8.09 m
ν(OsH)
δ(NH2)
CH3
H hydride
OsNH2
CH2
[OsH{(CH3)2NNH2}{PPh(OEt)2}4]BPh4
3326 m
3282 m
2005 m
1607 m
ν(NH)
ν(OsH)
δ(NH2)
(CH3)2N
CH3
H hydride
CH2
NH
CH3NH
[OsH(CH3NHNH2)(PPh2OEt)4]BPh4
3334 w
3268 m
2045 m
ν(NH)
ν(OsH)
CH3
H hydride
NH
OsNH2
CH2
CH3
e
[OsH(C6H5NHNH2)(PPh2OEt)4]BPh4
3359 m
3327 w
3259m
2045 m
1611 m
ν(NH)
ν(OsH)
δ(NH2)
H hydride
4a
4b
[Os(NH2NH2)2{P(OEt)3}4](BPh4)2
[Os(CH3NHNH2)2{P(OEt)3}4](BPh4)2
3372 m
3315 m
3299 m
3266 m
1617 m
3345 m
3304 m
3290 m
1596 m
ν(NH)
4.81 br
4.15-3.90 m
2.97 br
OsNH2
CH2
NH2
A2B2
A2B2
1.33, 1.28 t
CH3
δ(NH2)
ν(NH)
5.03 br
4.20-3.90 m
2.57 d
JHH ) 6 Hz
1.34, 1.29 t
OsNH2
CH2
CH3NH
δA ) 83.6
δB ) 77.0
JAB ) 43.2
δ(NH2)
CH3

Mono- and Bis(hydrazine) Complexes of Os(II)
Inorganic Chemistry, Vol. 37, No. 3, 1998 485
Table 3 (Continued)
compound
IRa
1H NMRb,c
(ppm)
spin
syst
31P{1H} NMRb,d
(ppm; J, Hz)
no.
formula
(cm-1
)
assgnt
assgnt
OsNH2
CH2
CH3
e
4c
[Os(C6H5NHNH2)2{P(OEt)3}4](BPh4)2
3309 m ν(NH)
3285 m
3229 m
1601 m δ(NH2)
3326 m ν(NH)
3301 m
6.38 br
A2B2
δA ) 85.8
δB ) 76.7
JAB ) 42.9
4.55-3.30 m
1.40, 1.38 t
e
4e
5a
[Os{(CH3)2NNH2}2{P(OEt)3}4](BPh4)2
[Os(NH2NH2)2{PPh(OEt)2}4](BPh4)2
5.45 br
4.43-4.20 m
OsNH2
CH2
(CH3)2N
CH3
OsNH2
CH2
A2B2
δA ) 83.2
δB ) 77.6
JAB ) 44.1
1607 m δ(NH2) 2.67 s
1.41, 1.37 t
3349 m ν(NH)
3313 w
3289 w
3259 m
4.80 m, br
3.90-3.60 m
2.26 m, br
1.25, 1.22 t
108.1 s
NH2
CH3
1616 m δ(NH2)
3350 m ν(NH)
3314 m
5b
[Os(CH3NHNH2)2{PPh(OEt)2}4](BPh4)2
5.01 m, br
4.10-3.70 m
3.85 br
OsNH2
CH2
108.2 s
3260 m
NH
1618 m δ(NH2) 2.32 d
CH3NH
JHH ) 6
1.27 t
CH3
NH
OsNH2
CH2
CH3
NH
OsNH2
CH2
5c
6
[Os(C6H5NHNH2)2{PPh(OEt)2}4](BPh4)2
[Os(η2-C6H5CONHNH2){P(OEt)3}4](BPh4)2
3326 m ν(NH)
3297 m
3273 m
6.37 br
A2B2
δA ) 113.9
δB ) 102.9
JAB ) 31.9
5.45 br
3.80-3.20 m
1601 m δ(NH2) 1.21, 1.10 t
3271 m ν(NH)
7.30 br
6.12 m
4.17-3.96 m
A2BC
δA ) 88.9
δB ) 84.2
δC ) 71.3
JAB ) 40.6
JAC ) 41.1
JBC ) 42.0
δA ) 81.9
δB ) 79.0
JAB ) 40.3
3206 w
1633 m ν(CO)
1601 w δ(NH2) 1.32, 1.30, 1.17 t CH3
7
[Os(NH2NH2){P(OEt)3}5](BPh4)2
3366 w ν(NH)
3318 w
3270 w
4.90 br
3.52 m, br
4.20 m
1.50, 1.45 t
6.40 br
5.58 br
3.98 m
OsNH2
NH2
CH2
CH3
NHdC
NH2 and NH
CH2
C(CH3)
CH3
AB4
8a
[Os{η2-NHdC(CH3)NHNH2}{P(OEt)3}4](BPh4)2
3395 m ν(NH)
3333 m
3290 m
AB2C
δA ) 85.4
δB ) 83.0
δC ) 81.0
JAB ) 41.5
JAC ) 42.9
JBC ) 43.4
1647 m δ(NH2) 1.35 s
1.29, 1.26 t
9.29 br e
7.08 br
4.20 m
2.24 s
NHdC
OsNH2
CH2
C(CH3)
1.35, 1.34, 1.32 t CH3
6.26 m, br
5.76 br
8b
[Os{η2-NHdC(CH3)N(CH3)NH2}{P(OEt)3}4](BPh4)2
[Os{η2-NHdC(4-CH3C6H4)NHNH2}{P(OEt)3}4](BPh4)2
3399 m ν(NH)
3313 w
3264 m
OsNH2
ABC2
AB2C
AB2C
δA ) 84.8
δB ) 81.7
δC ) 81.6
JAB ) 40.3
JAC ) 39.2
JBC ) 42.8
δA ) 86.0
δB ) 84.8
δC ) 84.1
JAB ) 41.1
JAC ) 43.8
JBC ) 42.8
δA ) 84.9
δB ) 81.7
δC ) 81.1
JAB ) 40.8
JAC ) 42.7
JBC ) 43.3
δA ) 82.7
δB ) 76.5
JAB ) 43.3
NHdC
CH2
4.10-3.90 m
1640 m δ(NH2) 2.57, 1.67 s
CH3
1.31, 1.27, 1.26 t CH3 phos
e
9a
3395 m ν(NH)
3330 m
3292 m
9.79 br
7.42
4.24 br
NHdC
OsNH2
CH2
1636 m δ(NH2) 2.38 s
CH3C6H4
1.37, 1.36, 1.32 t CH3
9b
[Os{η2-NHdC(4-CH3C6H4)N(CH3)NH2}{P(OEt)3}4](BPh4)2 3397 m ν(NH)
6.49 m, br
6.06 m, br
4.04 m
OsNH2
NHdC
CH2
3273 m
3230 w
1625 m δ(NH2) 2.63, 2.45 s
CH3
1.34, 1.30, 1.27 t CH3 phos
11b [Os(CH3NdNH)2{P(OEt)3}4](BPh4)2
14.0 s,br
3.97 m
3.71 s
1.30, 1.23 t
4.04 m
1.78 s
1.29, 1.25 t
NH
A2B2
A2B2
CH2
CH3N
CH3
CH2
CCH3
CH3
12
[Os(η2-O2CCH3){P(OEt)3}4]BPh4
1523 m ν(CO)
δA ) 100.4
δB ) 78.0
JAB ) 38.7
a In KBr. b In CD2Cl2 at 25 °C. c Phenyl proton resonances are omitted. d Positive shift downfield from 85% H3PO4. e In (CD3)2CO at 25 °C.
too, of a trans arrangement of the NH2NH2 and the CH3NHNH2
ligands in complexes containing the PPh(OEt)2 as an ancillary
ligand.
Treatment of the dihydride OsH2P4 first with methyl triflate,
then with triflic acid, and finally with an excess of benzoylhy-
drazine gives the [Os(η2-C6H5CONHNH2){P(OEt)3}4]2+ (6)
cation, which was separated as BPh4 salt and characterized. As
for the related hydrazine complexes, the infrared spectrum shows
the bands due to the ν(NH) at 3271 and 3206 cm-1 and that
due to the δ(NH2) at 1601 cm-1 of the NHNH2 group. At 1633
cm-1 is also present a medium-intensity band attributed to the
1
coordinated carbonyl group of the benzoylhydrazine. The H
NMR spectrum confirms the proposed formulation showing,
apart from the resonances of the P(OEt)3 and the BPh4- protons,

486 Inorganic Chemistry, Vol. 37, No. 3, 1998
Albertin et al.
Monohydrazinepentakis(phosphite)[Os(NH2NH2){P(OEt)3}5]-
(BPh4)2 (7) complex was also prepared by reacting the hydride
[OsH{P(OEt)3}5]BPh4 first with an equivalent amount of HBF4‚
Et2O and then with an excess of hydrazine, as shown in Scheme
2. Protonation reaction of [OsHP5]+ with HBF4‚Et2O results
in the formation of an η2-H2 complex which is thermally
1
unstable and cannot be isolated. The H NMR spectra of the
CD2Cl2 solution, however, confirm the presence of the dihy-
drogen complex showing a broad signal at -7.0 ppm with a
T1(min)24 of 8 ms (210 K) at 200 MHz. Substitution of the
labile η2-H2 ligand with hydrazine affords the [Os(NH2NH2)-
{P(OEt)3}5]2+ derivative which was isolated as the BPh4 salt
-
Figure 1. ORTEP view of the [Os(NH2NH2)2{P(OEt)3}4]2+ cation of
4a. Ethyl groups are omitted for clarity. Thermal ellipsoids are drawn
at the 50% probability level. Intramolecular hydrogen bonds are
evidenced as dashed lines.
and characterized (Table 3). The 1H NMR spectrum shows two
NH2 signals at 4.90 and 3.52 ppm in agreement with a
η1-coordination of the NH2NH2 ligand. Furthermore, the IR
spectrum confirms the presence of the hydrazine group showing
the characteristic ν(NH) bands at 3366-3270 cm-1. Finally,
the 31P{1H} NMR spectrum appears as an AB4 multiplet in
agreement with the presence of a type-VI geometry for the
complex.
Scheme 2
X-ray Crystal Structure of [Os(NH2NH2)2{P(OEt)3}4]-
(BPh4)2 (4a). The asymmetric unit contains one [Os(NH2NH2)2-
{P(OEt)3}4]2+ cation, displayed in Figure 1, two BPh4- anions,
and one ethanol molecule. Relevant parameters regarding the
cation geometry are listed in Table 4. The metal coordination
is octahedral and involves four phosphorus atoms and two
nitrogens, the latter in cis each other. The two Os-P bonds
situated in trans to the hydrazine ligands (Os-P2 ) 2.232(6)
Å, Os-P4 ) 2.260(6) Å) are slightly shorter than those
involving P1 and P3 (Os-P1 ) 2.300(6) Å, Os-P3 ) 2.316(7)
Å), which are in trans to each other, due to different electronic
influence of the two kinds of ligands. The angles between cis
phosphorus atoms fall in the range 91.1-95.3°, while the angles
between phosphorus and nitrogens are smaller, ranging from
83.5 to 93.4°, due to the steric hindrance of the P(OEt)3 groups
and to intramolecular hydrogen bonds, as discussed later on.
The average Os-N bond length is 2.196 Å, slightly longer than
the one found in [OsBr(NH2NH2)(CO)2(PPh3)2]CF3SO3,3b where
the nitrogen atom is placed at 2.181 Å from the metal and trans
to a carbonyl group. This is the only other osmium-hydrazine
complex whose crystal structure has been determined so far. In
both compounds hydrazine approaches the metal at an angle
very close to 120°, while the remaining angles on N1 and N3
are close to tetrahedral values, reflecting the sp3 hybridization
of the nitrogen atoms bonded to the metal. Hydrazines form a
network of intramolecular hydrogen bonds: N2‚‚‚N4 ) 3.00(3)
Å, N2-H‚‚‚N4 ) 105(8)°, N1‚‚‚O3 ) 2.79(2), N1-H‚‚‚O3 )
104(3)°, N1‚‚‚O11 ) 2.80(2) Å, N1-H‚‚‚O11 ) 144(6)°, N3‚‚‚-
O1 ) 2.87(2), N3-H‚‚‚O1 ) 129(9)°, N3‚‚‚O8 ) 2.91(2), N3-
H‚‚‚O8 ) 101(9)°. As a result, the approximate directions of
the lone pairs belonging to N2 (lp2) and N4 (lp4) are differently
oriented with respect to the Os-N bond, with Os-N1-N2-
lp2 ) -60° and Os-N3-N4-lp4 ) 20°.
Table 4. Most Relevant Bond Distances (Å) and Angles (deg) with
Esd’s in Parentheses
Distances
Os-P1
Os-P2
Os-P3
Os-P4
P1-O1
P1-O2
P1-O3
P2-O4
P2-O5
P2-O6
2.300(6)
2.232(6)
2.316(7)
2.260(6)
1.615(16)
1.544(13)
1.573(17)
1.516(19)
1.507(19)
1.607(18)
P3-O7
P3-O8
P3-O9
P4-O10
P4-O11
P4-O12
Os-N1
Os-N3
N1-N2
N3-N4
1.536(16)
1.620(13)
1.57(2)
1.536(19)
1.615(14)
1.538(19)
2.200(14)
2.193(15)
1.446(28)
1.412(27)
Angles
N1-Os-N3
P4-Os-N3
P4-Os-N1
P3-Os-N3
P3-Os-N1
P3-Os-P4
P2-Os-N3
P2-Os-N1
P2-Os-P4
P2-Os-P3
P1-Os-N3
P1-Os-N1
P1-Os-P4
P1-Os-P3
P1-Os-P2
85.4(6)
175.3(4)
90.0(4)
89.2(5)
93.4(4)
92.0(2)
89.2(4)
172.6(4)
95.3(2)
91.6(2)
86.0(5)
83.5(4)
92.6(2)
174.4(2)
91.1(2)
Os-P1-O3
Os-P1-O2
Os-P1-O1
Os-P2-O6
Os-P2-O5
Os-P2-O4
Os-P3-O9
Os-P3-O8
Os-P3-O7
Os-P4-O12
Os-P4-O11
Os-P4-O10
Os-N1-N2
Os-N3-N4
112.2(7)
118.7(6)
112.6(6)
110.1(7)
116.6(7)
116.3(7)
122.4(8)
109.8(5)
113.9(7)
120.7(7)
106.3(5)
116.0(6)
117.7(12)
118.0(13)
one broad signal at 6.12 ppm and one, partially masked by the
phenyl protons, at 7.30 ppm attributed to the NH2 and NH
protons, respectively, of the C6H5CONHNH2 ligand. Finally,
the 31P NMR spectrum appears as a A2BC multiplet, in
agreement with the presence of a chelate benzoylhydrazine
ligand of the type schematized in geometry V.
Nitrogens are not involved in any intermolecular contact
shorter than 3.8 Å. The ethanol molecule found in the crystal
does not participate in any close contact with either cations or
anions; this justifies its high thermal mobility and suggests that
the crystal decomposition observed during data collection is due
to solvent loss.
Amidrazone complexes. The results obtained on the syn-
thesis of mono- and bis(hydrazine) complexes of osmium(II)
1-7 prompted us to extend these studies to other osmium
(24) Albertin, G.; Antoniutti, S.; Bordignon, E. Manuscript in preparation.

Mono- and Bis(hydrazine) Complexes of Os(II)
Inorganic Chemistry, Vol. 37, No. 3, 1998 487
Scheme 3
Scheme 4
derivatives with the aim to verify whether new hydrazine
derivatives may be prepared. We therefore prepared the new
bis(nitrile) derivatives [Os(R1CN)2P4](BPh4)2 and studied their
reaction with hydrazines RNHNH2 observing that the same
reaction depends on the nature of the substituent R on the
hydrazines, as shown in Scheme 3. While with arylhydrazines
such as C6H5NHNH2 the reaction proceeds in reflux conditions
to give a mixture of unidentified products, with hydrazine NH2-
NH2 or methylhydrazine CH3NHNH2, instead, the reaction
afforded a white solid which was characterized as an amidra-
zone25 complex of the type [Os{η2-NHdC(R1)N(R)NH2}P4]-
(BPh4)2 (8, 9) whose geometry is schematized in VII. However,
amines, and carbanions to give iminoethers, amidines, and
imines is well established,26-28 and therefore, a similar reaction
is expected to take place also with hydrazine as a nucleophilic
reagent.29 Finally, related amidrazone complexes [Fe{η2-
NHdC(R1)NHNH2}P4](BPh4)2 were previously obtained by us9
from hydrazine-nitrile [Fe(NH2NH2)(R1CN)P4]2+ cations, prob-
ably through a nucleophilic attack of an end of coordinated NH2-
NH2 to the cyanide carbon atom of the coordinated nitrile,
followed by a H-shift, giving a five-membered metallacycle.
On these bases, the formation of an amidrazone complex by
reacting a bis(nitrile) complex of osmium with hydrazine or
methylhydrazine is plausible, although doubt remains on the
probable reaction path. Treatment of [Os(R1CN)2P4]2+ with
RNHNH2 (R ) H, CH3) can result in the substitution of only
one R1CN ligand affording the [Os(RNHNH2)(R1CN)P4]2+
intermediate. By nucleophilic attack of one end of the
coordinated RNHNH2 on the nitrile carbon atom of the
coordinate nitrile followed by a H-shift, the amidrazone
complexes may be obtained (Scheme 4). Since excess of
hydrazine is used, base-catalyzed proton transfer can also be a
reasonable mechanism for the intramolecular H-shift.
only with the P(OEt)3 ligand the amidrazone complexes were
prepared in pure form, while with the related PPh(OEt)2
compounds only intractable oils or mixtures of difficult separa-
tion were always obtained. The compounds 8 and 9 are white
solids stable in the air and in solution of polar organic solvents
where they behave as 2:1 electrolytes.22 The elemental analyses
and the IR and NMR spectra (Table 3) support the proposed
formulation. In particular, the infrared shows the ν(NH) and
the δ(NH2) bands of the amidrazone ligand as weak- or medium-
intensity absorptions at 3399-3230 cm-1 and at 1647-1625
cm-1, respectively. The 1H NMR spectra show, apart from the
signals of the phosphites and of the BPh4-, two or three NH
signals which were assigned, by homodecoupling experiments
and accurate integration, to the H1, H2, and H3 protons (Table
3) of the chelate amidrazone ligand of the type of geometry
VII. The 31P{1H} NMR spectra confirm such a geometry
showing for all the compounds an AB2C or ABC2 multiplet
which can be easily simulated with the parameters reported in
Table 3.
However, the hydrazine can also react directly (without being
bonded to the osmium) with the coordinated R1CN group of
[Os(R1CN)2P4]2+ giving the η1-amidrazone ligand which, by
substitution of the other R1CN, can then give the final chelate
(26) (a) Maresca, L.; Natile, G.; Intini, F. P.; Gasparrini, F.; Tiripicchio,
A.; Tiripicchio-Camellini, M. J. Am. Chem. Soc. 1986, 108, 1180. (b)
Fanizzi, F. P.; Intini, F. P.; Natile, G. J. Chem. Soc., Dalton Trans.
1989, 947. (c) Cini, R.; Fanizzi, F. P.; Intini, F. P.; Maresca, L.; Natile,
G. J. Am. Chem. Soc. 1993, 115, 5123. (d) Paul, P.; Nag, K. Inorg.
Chem. 1987, 26, 1586. (e) Thorn, D. L.; Calabrese, J. C. J. Organomet.
Chem. 1984, 272, 283.
(27) (a) Amodio, C. A.; Nolan, K. B. Inorg. Chim. Acta 1986, 113, 27. (b)
Syamala, A.; Chakravarty, A. R. Inorg. Chem. 1991, 30, 4699. (c)
Feng, S. G.; White, P. S.; Templeton, J. L. Organometallics 1993,
12, 1765. (d) Fairlie, D. P.; Jackson, W. G. Inorg. Chem. 1990, 29,
140.
(28) (a) Uchiyama, T.; Takagi, K.; Matsumoto, K.; Ooi, S.; Nakamura,
Y.; Kawaguchi, S. Chem. Lett. 1979, 1197; Bull. Chem. Soc. Jpn. 1981,
54, 1077. (b) Kanda, Z.; Nakamura, Y.; Kawaguchi, S. Inorg. Chem.
1978, 17, 910. (c) Michelin, R. A.; Mozzon, M.; Berin, P.; Bertani,
R.; Benetollo, F.; Bombieri, G.; Angelici, R. J. Organometallics 1994,
13, 1341. (d) Braunstein, P.; Matt, D.; Dusausoy, Y.; Fischer, J.
Organometallics 1983, 2, 1410. (e) Vicente, J.; Chicote, M.-T.;
Fernandez-Baeza, J.; Lahoz, F. J.; Lopez, J. A. Inorg. Chem. 1991,
30, 3617.
The formation of an amidrazone complex from the reaction
of a coordinated nitrile with an hydrazine or methylhydrazine
molecule is not surprising taking into account the well-known
reaction25 of nucleophilic attack of hydrazine on activated nitriles
giving, as primary product, an amidrazone molecule. Further-
more, nucleophilic attack upon coordinated nitrile by alcohols,
(25) Watson, K. M.; Neilson, D. G. In The Chemistry of Amidines and
Imidates; Patai, S., Ed.; J. Wiley & Sons: London, 1975; p 491.
(29) Michelin, R. A.; Mozzon, M.; Bertani, R. Coord. Chem. ReV. 1996,
147, 299.

488 Inorganic Chemistry, Vol. 37, No. 3, 1998
Albertin et al.
Scheme 5
conditions [large excess of Pb(OAc)4 or higher temperature]
lead only to decomposition products.
Both the mono [OsH(RNHNH2)P4]+ and the bis [Os-
(RNHNH2)2P4]2+ derivatives of osmium(II) containing substi-
tuted hydrazine can be easily oxidized by Pb(OAc)4 to give the
corresponding substituted diazene complexes 10 and 11, which
were isolated and characterized. Confirmation of the presence
of the diazene ligand in these complexes is given by the high-
frequency signal of the NH groups at 12-15 ppm observed in
1
the H NMR spectra. However, the formulation of the phe-
nyldiazene complexes 10c and 11c is also confirmed by a
comparison of their spectroscopic properties with those of the
same derivatives [OsH(C6H5NdNH)P4]BPh4 and [Os(C6H5-
NdNH)2P4](BPh4)2 previously prepared by us from the reaction
of hydride species OsH2P4 with the phenyldiazonium cation.8f
Interesting, in this context, is the reaction of the methylhy-
drazine derivative with Pb(OAc)4 which allows the synthesis
of a rare example30 of methyldiazene complex which, of course,
cannot be obtained from the reaction of a methyldiazonium
cation. Oxidation of [Os(CH3NHNH2)2{P(OEt)3}4](BPh4)2 af-
forded, in fact, [Os(CH3NdNH)2{P(OEt)3}4](BPh4)2 (11b),
which was isolated as a yellow-orange solid and characterized.
Also the hydride [OsH(CH3NHNH2)P4]BPh4 can be oxidized
by Pb(OAc)4 to give an orange solid whose 1H NMR spectrum
shows a NH signal at 14.4 ppm suggesting the presence of a
diazene ligand. The thermal unstability of the complex,
however, prevented its complete characterization. Oxidation
of hydrazine complexes giving stable diazene derivatives is
reported in a few cases3b,c,30,31 and often involves dinuclear
complexes with a diazene bridging unit.
Scheme 6
The bis(methyldiazene) complex [Os(CH3NdNH)2{P(OEt)3}4]-
(BPh4)2 (11b) is stable both as a solid and in solutions of polar
organic solvents where it behaves as a 2:1 electrolyte.22 Good
analytical data were obtained for the compound whose 1H NMR
spectrum shows the characteristic, slightly broad diazene signal
at 14.0 ppm (Table 3). In the proton spectrum also the signal
of the methyl substituent of the CH3NdNH ligand is present
as a sharp singlet at 3.71 ppm together with the P(OEt)3 and
BPh4 signals. Furthermore, the 31P spectrum appears as a
symmetric A2B2 multiplet suggesting that the two diazene
ligands are in a mutually cis position as in a type-X geometry.
complex. In this case the reaction with methylhydrazine, which
possesses two possible sites for an attack, might give the two
compounds VIII and IX (Scheme 5). Furthermore, if the
reaction on coordinated nitrile parallels that of free R1CN, the
N1-substituted amidrazone VIII would be the predominant
product. The exclusive formation of the compound IX (geom-
etry VII) in our case seems, therefore, to suggest a reaction
path that involves the substitution of one R1CN followed by
the nucleophilic attack as shown in Scheme 4. Although a
nitrile-hydrazine [Os(RNHNH2)(R1CN)P4]2+ intermediate was
not detected, such a mechanism is also supported by the results
previously reported on the reaction of the related bis(nitrile)-
iron(II) complexes9 with hydrazine.
The results obtained on the reaction of substituted hydrazine
with Pb(OAc)4 prompted us to extend these studies to the related
NH2NH2 complexes in an attempt to prepare the 1,2-diazene
OsNHdNH derivative. Unfortunately, the reaction of both the
[OsH(NH2NH2)P4]+ (1a) and [Os(NH2NH2)2P4]2+ (4a) cations
with an excess of Pb(OAc)4 proceeds to give a pale-yellow
Oxidation Reactions. Hydrazine complexes of osmium(II)
1-5 react with Pb(OAc)4 at -30 °C in CH2Cl2 to give, in some
cases, the corresponding diazene derivatives and in other the
acetate complex [Os(η2-O2CCH3)P4]BPh4, as shown in Scheme
6. Studies on these reactions showed, first of all, that only the
Os complexes containing the P(OEt)3 phosphite ligand react with
Pb(OAc)4 to give the diazene or the acetate complexes. The
PPh(OEt)2 or PPh2OEt derivatives, instead, do not react with
Pb(OAc)4 at low temperature (-30 °C) and the use of different
(30) Smith, M. R., III; Keys, R. L.; Hillhouse, G. L.; Rheingold, A. L. J.
Am. Chem. Soc. 1989, 111, 8312. Ackermann, M. N. Inorg. Chem.
1971, 10, 272.
(31) (a) Smith, M. R., III; Cheng, T.-Y.; Hillhouse, G. L. J. Am. Chem.
Soc. 1993, 115, 8638. (b) Sellmann, D.; Soglowek, W.; Knoch, F.;
Moll, M. Angew. Chem., Int. Ed. Engl. 1989, 28, 1271. (c) Sellmann,
D.; Bo¨hlen, E.; Waeber, M;; Huttner, G.; Zsolnai, L. Angew. Chem.,
Int. Ed. Engl. 1985, 24, 981. (d) Sellmann, D.; Jo¨dden, K. Angew.
Chem., Int. Ed. Engl. 1977, 16, 464. (e) Ackermann, M. N.; Dobmeyer,
D. J.; Hardy, L. C. J. Organomet. Chem. 1979, 182, 561.

Mono- and Bis(hydrazine) Complexes of Os(II)
Inorganic Chemistry, Vol. 37, No. 3, 1998 489
solution from which no diazene derivative was separated but
only a white solid characterized as the acetate [Os(η2-O2CCH3)-
{P(OEt)3}4]BPh4 (12) complex (Scheme 6). The use of an
equimolar amount of Pb(OAc)4 instead of an excess results in
the formation only of a mixture of starting materials and of the
acetate complex 12. As the starting compounds 1a and 4a are
unreactive toward the substitution of the NH2NH2 ligand by
the acetate ion, it is probable that also in this case the reaction
with Pb(OAc)4 proceeds with the oxidation of the NH2NH2
group to give the corresponding diazene NHdNH ligand. This
ligand, however, must be rather labile in cations of the type
[OsH(NHdNH)P4]+, [Os(NHdNH)2P4]2+, or [Os(NHdNH)(NH2-
NH2)P4]2+ and can be easily substituted by the acetate ion
affording the found chelate [Os(η2-O2CCH3)P4]BPh4 derivative.
We also attempted to oxidize the NH2NH2 ligands in 1a and
4a with different reagents such as O2, H2O2, or (CH3)3COOH,
but we obtained either the starting complexes or decomposition
products which did not show any diazene compound. Further-
more, it can be noted that the acetate complex 12 was also
obtained by treating the amidrazone complexes 8 and 9 with
Pb(OAc)4. Finally, the formulation of the complex 12 as an
acetate complex comes from the analytical and the spectroscopic
data. In particular, the infrared spectrum shows the ν(CO) of
Conclusions. In this contribution we have reported a method
for the facile synthesis of mono- and bis(hydrazine) derivatives
of osmium of the type [OsH(RNHNH2)P4]+, [Os(RNHNH2)-
P5]2+, and [Os(RNHNH2)2P4]2+ stabilized by phosphite ligands.
The first structural parameters for a bis(hydrazine) complex,
[Os(NH2NH2){P(OEt)3}4](BPh4)2, are also reported. The reac-
tion of nitrile complexes with hydrazine also allows amidrazone
[Os{η2-NHdC(R1)N(R)NH2){P(OEt)3}4](BPh4)2 derivatives to
be prepared. Among the properties shown by the new osmium
hydrazine complexes we can emphasize the easy oxidation of
the substituted hydrazine RNHNH2 ligand by lead tetraacetate
to give the corresponding substituted diazene [OsH(RNdNH)-
P4]+ and [Os(RNdNH)2P4]2+ cations, including the first [Os-
(CH3NdNH)2P4](BPh4)2 bis(methyldiazene) derivative.
Acknowledgment. The financial support of MURST and
the CNR, Rome, is gratefully acknowledged. We thank Daniela
Baldan for technical assistance.
the CH3COO ligand as a medium-intensity band at 1523 cm-1
,
while in the 1H NMR spectrum the methyl protons of CH3COO-
group appear as a sharp singlet at 1.78 ppm in CD2Cl2 at 25
°C. Furthermore, the 31P{1H} NMR spectrum shows an A2B2
multiplet, in agreement with the formulation proposed and
schematized in XI.
Supporting Information Available: X-ray crystallographic files,
in CIF format, for compound 4a are available on the Internet only.
Access information is given on any current masthead page.
IC970463E