Ruthenium tris(pyrazolyl)borate diazo complexes: Preparation of aryldiazenido, aryldiazene, and hydrazine derivatives

Article abstract of DOI:10.1021/ic0497275

Tris(pyrazolyl)borate aryldiazenido complexes [RuTpLL′(ArN ₂)](BF₄)₂ (1-3) [Ar = C₆H ₅, 4-CH₃C₆H₄; Tp = hydridotris(pyrazolyl)borate; L = P(OEt)₃ or PPh(OEt)₂, L′ = PPh₃; L = L′ = P(OEt)₃] were prepared by allowing dihydrogen [RuTp(η²-H₂)LL′]⁺ derivatives to react with aryldiazonium cations. Spectroscopic characterization (IR, ¹⁵N NMR) using the ¹⁵N-labeled derivatives strongly supports the presence of a linear [Ru]-N≡N-Ar aryldiazenido group. Hydrazine complexes [RuTp(RNHNH₂)LL′]BPh₄ (4-6) [R = H, CH₃, C₆H₅, 4-NO₂C ₆H₅, 4-NO₂C₆H₄; L = P(OEt)₃ or PPh(OEt)₂, L′ = PPh_3i L = L′ = P(OEt)₃] were also prepared by reacting the [RuTp(η²-H₂)LL′]⁺ cation with an excess of hydrazine. The complexes were characterized spectroscopically (IR and NMR) and by X-ray crystal structure determination of the [RuTp(CH ₃NHNH₂){P(OEt)₃}(PPh₃)]BPh ₄ (4d) derivative. Tris(pyrazolyl)borate aryldiazene complexes [RuTp(ArN=NH)LL′]BPh₄ (7-9) (Ar = C₆H₅, 4-CH₃C₆H₄) were prepared following three different methods: (i) by allowing hydride species RuHTpLL′ to react with aryldiazonium cations in CH₂Cl₂; (ii) by treating aryldiazenido [RuTpLL′(ArN₂)](BF₄)₂ with LiBHEt₃ in CH₂Cl₂; (iii) by oxidizing arylhydrazine [RuTp(ArNHNH₂)LL′]BPh₄ complexes with Pb(OAc)₄ in CH₂Cl₂ at -30 °C. Methyldiazene complexes [RuTp(CH₃N=NH)LL′]BPh₄ were also prepared by the oxidation of the corresponding methylhydrazine [RuTp(CH ₃NHNH₂)LL′]BPh₄ with Pb(OAc)₄.

Full text of DOI:10.1021/ic0497275

Inorg. Chem. 2004, 43, 4511−4522
Ruthenium Tris(pyrazolyl)borate Diazo Complexes: Preparation of
Aryldiazenido, Aryldiazene, and Hydrazine Derivatives
,†
Gabriele Albertin,* Stefano Antoniutti,† Marco Bortoluzzi,† Jesus Castro-Fojo,‡ and
Soledad Garcia-Fonta´n‡
Dipartimento di Chimica, UniVersita` Ca’ Foscari di Venezia, Dorsoduro 2137,
30123 Venezia, Italy, and Departamento de Quimica Inorganica, UniVersidade de Vigo,
36200 Vigo, Spain
Received March 3, 2004
Tris(pyrazolyl)borate aryldiazenido complexes [RuTpLL′(ArN )](BF ) (1−3) [Ar ) C H , 4-CH C H ; Tp) hydridotris-
2
4 2
6
5
3 6 4
(pyrazolyl)borate; L ) P(OEt)3 or PPh(OEt)2, L′ ) PPh3; L ) L′ ) P(OEt)3] were prepared by allowing dihydrogen
[RuTp(η2-H )LL′]+ derivatives to react with aryldiazonium cations. Spectroscopic characterization (IR, 15N NMR)
2
using the 15N-labeled derivatives strongly supports the presence of a linear [Ru]sNtNsAr aryldiazenido group.
Hydrazine complexes [RuTp(RNHNH )LL′]BPh4 (4−6) [R ) H, CH , C H , 4-NO C H ; L ) P(OEt)3 or PPh(OEt)2,
2
3
6
5
2 6 4
L′ ) PPh3; L ) L′ ) P(OEt)3] were also prepared by reacting the [RuTp(η2-H )LL′]+ cation with an excess of
2
hydrazine. The complexes were characterized spectroscopically (IR and NMR) and by X-ray crystal structure
determination of the [RuTp(CH NHNH ){P(OEt)3}(PPh3)]BPh4 (4d) derivative. Tris(pyrazolyl)borate aryldiazene
3
2
complexes [RuTp(ArNdNH)LL′]BPh4 (7−9) (Ar ) C H , 4-CH C H ) were prepared following three different
6
5
3 6 4
methods: (i) by allowing hydride species RuHTpLL′ to react with aryldiazonium cations in CH Cl2; (ii) by treating
2
aryldiazenido [RuTpLL′(ArN )](BF ) with LiBHEt3 in CH Cl2; (iii) by oxidizing arylhydrazine [RuTp(ArNHNH )LL′]-
2
4 2
2
2
BPh4 complexes with Pb(OAc)4 in CH Cl2 at −30 °C. Methyldiazene complexes [RuTp(CH NdNH)LL′]BPh4 were
2
3
also prepared by the oxidation of the corresponding methylhydrazine [RuTp(CH NHNH )LL′]BPh4 with Pb(OAc)4.
3
2
Introduction
ligands, whose studies involve mainly Ti,4 Mo,5 and W5
complexes. No examples of diazo compounds of the iron
triad containing (pyrazolyl)borates as supporting ligands have
ever been reported.
The interest for this class of compounds is motivated not
only by the relationship that the diazo complexes may have
with the intermediates of the dinitrogen fixation process but
also by the different reactivity modes, dynamic behavior,
and structural properties that these complexes may exhibit.1,2
Of particular interest should be the geometry types (linear
or singly or doubly bent) that the aryldiazenido may exhibit
as a function of steric and electronic factors of the ligand
set. Also, the stabilization of diazene and hydrazine on the
The chemistry of aryldiazenido, diazene, and hydrazine
complexes has developed extensively in the past 30 years,
using mainly π-acceptors such as carbonyl, phosphine, and
cyclopentadienyl as ancillary ligands.1,2 Less attention has
been devoted to the use of N-donor molecules, such as bis-
(pyrazolyl)borate (Bp) and tris(pyrazolyl)borate3 (Tp) as
* To whom correspondence should be addressed. E-mail: albertin@unive.it.
† Universita` Ca’ Foscari di Venezia.
‡ Universidade de Vigo.
(1) (a) Sutton, D. Chem. ReV. 1993, 93, 995-1022. (b) Kisch, H.;
Holzmeier, P. AdV. Organomet. Chem. 1992, 34, 67-109.
(2) (a) Zollinger, H. Diazo Chemistry II; VCH: Weinheim, Germany,
1995. (b) 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.
(4) (a) Hughes, D. L.; Leigh, G. J.; Walker, D. G. J. Chem. Soc., Dalton
Trans. 1989, 1413-1416. (b) Hughes, D. L.; Leigh, G. J.; Walker, D.
G. J. Chem. Soc., Dalton Trans. 1988, 1153-1157.
(3) (a) Trofimenko, S. J. Am. Chem. Soc. 1966, 88, 1842-1844. (b)
Trofimenko, S. Chem. ReV. 1993, 93, 943-980. (c) Slugovc, C.;
Schmid, R.; Kirchner, K. Coord. Chem. ReV. 1999, 185, 109-126.
(d) Pettinari, C.; Santini, C. In ComprehensiVe Coordination Chemistry
II; McCleverty, J. A., Meyer, T. J., Eds.; Elsevier Pergamon: Oxford,
U.K., 2003; Vol. 1. (e) Special issue on scorpionate and related ligands:
Polyhedron 2004, 23, 195-508.
(5) (a) King, R. B.; Bisnette, M. B. J. Am. Chem. Soc. 1964, 86, 5694-
5695. (b) Trofimenko, S. J. Am. Chem. Soc. 1970, 92, 5118-5126.
(c) McCleverty, J. A.; Rae, A. E.; Wolochowicz, I.; Bailey, N. A.;
Smith, J. M. A. J. Chem. Soc., Dalton Trans. 1983, 71-80. (d) Deane,
M. E.; Lalor, F. J.; Ferguson, G.; Ruhl, B. L.; Parvez, M. J. Organomet.
Chem. 1990, 381, 213-231. (e) Sellmann, D.; Kern, W.; Pohlmann,
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10.1021/ic0497275 CCC: $27.50 © 2004 American Chemical Society
Published on Web 06/16/2004
Inorganic Chemistry, Vol. 43, No. 14, 2004 4511

Albertin et al.
following the reported method.12 High-grade (99.99%) lead(IV)
acetate was purchased from Aldrich. 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, 13C, 15N) were
obtained on AC200 or AVANCE 300 Bruker spectrometers at
temperatures between -90 and +30 °C, unless otherwise noted.
1H and 13C spectra are referred to internal tetramethylsilane. 31P-
(1H) chemical shifts are reported with respect to 85% H3PO4, while
15N is reported with respect to CH315NO2; in both cases, downfield
shifts are considered positive. The COSY, HMQC, and HMBC
NMR experiments were performed using their standard programs.
The SwaN-MR software package13 was used to treat NMR data.
The conductivity of 10-3 M solutions of the complexes in CH3-
NO2 at 25 °C was measured with a Radiometer CDM 83.
Synthesis of the Complexes. The hydrides RuHTpLL′ [L )
P(OEt)3 or PPh(OEt)2; L′ ) PPh3] and RuHTp{P(OEt)3}2, the
dihydrogen complexes [RuTp(η2-H2)LL′]BF4 and [RuTp(η2-H2)-
{P(OEt)3}2]BF4, and the aquo-complex [RuTp(H2O){P(OEt)3}-
(PPh3)]BF4 were prepared by following the reported methods.14
[RuTpLL′(ArN2)](BF4)2 (1, 2, 3) [L ) P(OEt)3, L′ ) PPh3
(1); L ) PPh(OEt)2, L′ ) PPh3 (2); L ) L′ ) P(OEt)3 (3); Ar
) C6H5 (a), 4-CH3C6H4 (b)]. Method 1: From the Hydride. An
equimolar amount of HBF4‚Et2O (0.1 mmol, 14 µL of a 54%
solution in Et2O) was added to a solution of the appropriate hydride
RuHTpLL′ (0.1 mmol) in CH2Cl2 (10 mL) which had been cooled
to -196 °C. The reaction mixture was brought to 0 °C, stirred for
30 min, and then transferred by needle into a three-necked, round-
bottomed 25-mL flask containing an excess of the appropriate
aryldiazonium salt (0.3 mmol) cooled to -196 °C. The reaction
mixture was brought to room temperature and then stirred for about
2 h. The solution was filtered to remove the unreacted diazonium
salt and then concentrated under reduced pressure to about 3 mL.
By slow addition of a large amount (10-20 mL) of diethyl ether,
red-orange microcrystals separated out and were filtered and dried
under vacuum; yield g 70%.
metal center and their reactivity toward oxidation and
reduction are important aspects of this chemistry.
We have previously reported6,7 on the synthesis and
reactivity of aryldiazenido, diazene, and hydrazine complexes
of the iron triad of the [M(ArN2)P4]+, [M(ArN2)(CO)2P2]+,
[M(ArNdNH)2P4]2+, and [M(RNHNH2)2P4]2+ (M ) Fe, Ru,
Os; P ) phosphites) types containing phosphites and
carbonyls as ancillary ligands. Now, we have extended these
studies with the aim of introducing tris(pyrazolyl)borate in
the diazo chemistry of the iron triad, and in this paper, we
report the synthesis and reactivity of unprecedented diazo
complexes of ruthenium8 stabilized by the tris(pyrazolyl)-
borate ligand.
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-
tight storage flasks. RuCl3‚3H2O salt was a ChemPur (U.S.A.)
product, used as received. Potassium hydridotris(pyrazolyl)borate
(KTp) was prepared according to a published procedure.9 Phen-
yldiethoxyphosphine, 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 The related bis(diazonium) salt [N2-
Ar-ArN2](BF4)2 (Ar-Ar ) 4,4′-C6H4-C6H4) was prepared by
treating the amine precursors H2NAr-ArNH2 with NaNO2, as
described in the literature for common mono(diazonium) salts. The
labeled diazonium tetrafluoroborates, (C6H5Nt15N)BF4 and [4,4′-
15NtNC6H4sC6H4Nt15N](BF4)2, were prepared from Na15NO2
(99% enriched, CIL) and the appropriate amine. Hydrazine, NH2-
NH2, was prepared by decomposition of hydrazine cyanurate (Fluka)
Method 2 for [RuTp{P(OEt)3}(PPh3)(ArN2)](BF4)2 (1): From
the Aquo-Complex. Solid samples of [RuTp(H2O){P(OEt)3}-
(PPh3)]BF4 (100 mg, 0.12 mmol) and of the appropriate aryldia-
zonium salt [ArN2]BF4 (0.36 mmol) were placed into a 25-mL three-
necked, round-bottomed flask. After cooling to -196 °C, CH2Cl2
(10 mL) was added, and the reaction mixture, brought to room
temperature, was stirred for about 4 h. The solution was filtered to
remove the unreacted diazonium salt and then concentrated under
reduced pressure to about 3 mL. The addition of diethyl ether (10-
20 mL) under vigorous stirring caused the separation of red-orange
microcrystals which were filtered and dried under vacuum; yield
g 70%. Found: C, 45.63; H, 4.51; N, 11.10. C39H45B3F8N8O3P2-
Ru (1a) requires: C, 45.87; H, 4.44; N, 10.97%. ΛM ) 181.5 Ω-1
mol-1 cm2. Found: C, 46.60; H, 4.49; N, 10.69. C40H47B3F8N8O3P2-
Ru (1b) requires: C, 46.41; H, 4.58; N, 10.82%. ΛM ) 182.3 Ω-1
mol-1 cm2. Found: C, 49.76; H, 4.37; N, 10.64. C44H47B3F8N8O2P2-
Ru (2b) requires: C, 49.51; H, 4.44; N, 10.50%. ΛM ) 179.9 Ω-1
mol-1 cm2. Found: C, 35.22; H, 4.78; N, 12.25. C27H45B3F8N8O6P2-
Ru (3a) requires: C, 35.05; H, 4.90; N, 12.11%. ΛM ) 177.8 Ω-1
mol-1 cm2. Found: C, 35.70; H, 4.97; N, 11.81. C28H47B3F8N8O6P2-
Ru (3b) requires: C, 35.81; H, 5.04; N, 11.93%. ΛM ) 182.8 Ω-1
mol-1 cm2.
(6) (a) Albertin, G.; Antoniutti, S.; Pelizzi, G.; Vitali, F.; Bordignon, E.
J. Am. Chem. Soc. 1986, 108, 6627-6634. (b) Albertin, G.; Antoniutti,
S.; Pelizzi, G.; Vitali, F.; Bordignon, E. Inorg. Chem. 1988, 27, 829-
835. (c) Albertin, G.; Antoniutti, S.; Bordignon, E. J. Am. Chem. Soc.
1989, 111, 2072-2077. (d) Albertin, G.; Antoniutti, S.; Bordignon,
E. J. Chem. Soc., Dalton Trans. 1989, 2353-2358.
(7) (a) Albertin, G.; Antoniutti, S.; Bacchi, A.; Bordignon, E.; Pelizzi,
G.; Ugo, P. Inorg. Chem. 1996, 35, 6245-6253. (b) Albertin, G.;
Antoniutti, S.; Bacchi, A.; Bordignon, E.; Dolcetti, P. M.; Pelizzi, G.
J. Chem. Soc., Dalton Trans. 1997, 4435-4444. (c) Albertin, G.;
Antoniutti, S.; Bacchi, A.; Bergamo, M.; Bordignon, E.; Pelizzi, G.
Inorg. Chem. 1998, 37, 479-489. (d) Albertin, G.; Antoniutti, S.;
Bacchi, A.; Barbera, D.; Bordignon, E.; Pelizzi, G.; Ugo, P. Inorg.
Chem. 1998, 37, 5602-5610. (e) Albertin, G.; Antoniutti, S.; Bacchi,
A.; Boato, M.; Pelizzi, G. J. Chem. Soc., Dalton Trans. 2002, 3313-
3320.
(8) For some papers on ruthenium diazo complexes see the following:
(a) Fan, L.; Einstein, F. W. B.; Sutton, D. Organometallics 2000, 19,
684-694. (b) Sellmann, D.; Engl, K.; Heinemann, F. W.; Sieler, J.
Eur. J. Inorg. Chem. 2000, 1079-1089. (c) Cheng, T. Y.; Ponce, A.;
Rheingold, A. L.; Hillhouse, G. L. Angew. Chem., Int. Ed. Engl. 1994,
33, 657-659. (d) Sellmann, D.; Ka¨ppler, J.; Moll, M.; Knoch, F. Inorg.
Chem. 1993, 32, 960-964. (e) Ashworth, T. V.; Singleton, E.; Hough,
J. J. J. Chem. Soc., Dalton Trans. 1977, 1809-1815. (f) Haymore, B.
L.; Ibers, J. A. Inorg. Chem. 1975, 14, 2784-2795, 3060-3070. (g)
McCleverty, J. A.; Seddon, D.; Whiteley, R. N. J. Chem. Soc., Dalton
Trans. 1975, 839-844. (h) McArdle, J. V.; Schultz, A. J.; Corden, B.
J.; Eisenberg, R. Inorg. Chem. 1973, 12, 1676-1681.
[RuTp{P(OEt)3}(PPh3)(C6H5Nt15N)](BF4)2 (1a1) and [RuTp-
{P(OEt)3}2(C6H5Nt15N)](BF4)2 (3a1). These complexes were
(9) Trofimenko, S. J. Am. Chem. Soc. 1967, 89, 3170-3177.
(10) Rabinowitz, R.; Pellon, J. J. Org. Chem. 1961, 26, 4623.
(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) Albertin, G.; Antoniutti, S.; Bortoluzzi, M. Manuscript in preparation.
4512 Inorganic Chemistry, Vol. 43, No. 14, 2004

Ruthenium Tris(pyrazolyl)borate Diazo Complexes
prepared exactly like the related unlabeled complexes 1a and 3a,
following method 1 and using (C6H5Nt15N)BF4 as a reagent; yield
g 65%.
mL) with a half-equimolar amount of (4,4′-Ν2C6H4-C6H4N2)(BF4)2
(0.05 mmol, 19 mg) bis(aryldiazonium) salt. The reaction mixture
was stirred for 4 h, and the solid obtained was crystallized from
CH2Cl2 and ethanol; yield g 75%. Found: C, 64.69; H, 5.72; N,
9.48. C126H130B4N16O6P4Ru2 requires: C, 64.85; H, 5.61; N, 9.60%.
ΛM ) 126 Ω-1 mol-1 cm2.
[{RuTp[P(OEt)3](PPh3)}2(µ-4,4′-15NHdNC6H4sC6H4Nd15NH)]-
(BPh4)2 (7f1). This complex was prepared exactly like the related
unlabeled 7f using (4,4′-15NtNC6H4sC6H4Nt15N)(BF4)2 as a
reagent; yield g 70%.
[RuTp(RNHNH2)LL′]BPh4 (4, 5, 6) [L ) P(OEt)3, L′ ) PPh3
(4); L ) PPh(OEt)2, L′ ) PPh3 (5); L ) L′ ) P(OEt)3 (6); R )
C6H5 (a), 4-NO2C6H4 (c), CH3 (d), H (e)]. To a solution of the
appropriate hydride RuHTpLL′ (0.2 mmol) in 10 mL of CH2Cl2,
cooled to -196 °C, was added an equivalent amount of CF3SO3H
(0.2 mmol, 18 µL). The reaction mixture was brought to 0 °C and
stirred for 30 min and then an excess of the appropriate hydrazine
(0.6 mmol) added. After 2 h of stirring, the solvent was removed
under reduced pressure to give an oil which was triturated with
ethanol (3 mL) containing an excess of NaBPh4 (0.4 mmol, 137
mg). A pale yellow solid separated out, which was filtered and
crystallized from CH2Cl2 and ethanol; yield g 80%. Found: C,
64.46; H, 5.89; N, 9.44. C63H68B2N8O3P2Ru (4a) requires: C, 64.68;
H, 5.86; N, 9.58%. ΛM ) 53.1 Ω-1 mol-1 cm2. Found: C, 62.42;
H, 5.52; N, 10.27. C63H67B2N9O5P2Ru (4c) requires: C, 62.28; H,
5.56; N, 10.38%. ΛM ) 54.5 Ω-1 mol-1 cm2. Found: C, 62.60; H,
5.93; N, 10.26. C58H66B2N8O3P2Ru (4d) requires: C, 62.88; H, 6.00;
N, 10.11%. ΛM ) 55.4 Ω-1 mol-1 cm2. Found: C, 62.41; H, 5.79;
N, 10.10. C57H64B2N8O3P2Ru (4e) requires: C, 62.59; H, 5.90; N,
10.24%. ΛM ) 50.9 Ω-1 mol-1 cm2. Found: C, 66.70; H, 5.76; N,
9.24. C67H68B2N8O2P2Ru (5a) requires: C, 66.95; H, 5.70; N,
9.32%. ΛM ) 56.8 Ω-1 mol-1 cm2. Found: C, 65.08; H, 5.74; N,
9.76. C62H66B2N8O2P2Ru (5d) requires: C, 65.33; H, 5.84; N,
9.83%. ΛM ) 49.6 Ω-1 mol-1 cm2. Found: C, 65.21; H, 5.80; N,
9.79. C61H64B2N8O2P2Ru (5e) requires: C, 65.08; H, 5.73; N,
9.95%. ΛM ) 56.2 Ω-1 mol-1 cm2. Found: C, 57.22; H, 6.32; N,
10.51. C51H68B2N8O6P2Ru (6a) requires: C, 57.05; H, 6.38; N,
10.44%. ΛM ) 58.0 Ω-1 mol-1 cm2.
[RuTp(ArNdNH)LL′]BPh4 (7, 8, 9) [Ar ) C6H5 (a),
4-CH3C6H4 (b); L ) P(OEt)3, L′ ) PPh3 (7); L ) PPh(OEt)2,
L′ ) PPh3 (8); L ) L′ ) P(OEt)3 (9)]. Method 1: From the
Hydride. In a 25-mL three-necked, round-bottomed flask were
placed solid samples of the appropriate hydride RuHTpLL′ (0.1
mmol) and an excess of aryldiazonium tetrafluoroborate [ArN2]-
BF4 (0.3 mmol). The flask was cooled to -196 °C and CH2Cl2 (7
mL) added. The reaction mixture was brought to room temperature
and stirred for 2 h and then the solvent removed under reduced
pressure. The oil obtained was treated with ethanol (2 mL)
containing an excess of NaBPh4 (0.2 mmol, 68 mg). A yellow-
orange solid slowly separated out from the resulting solution, which
was filtered and crystallized from CH2Cl2 and ethanol; yield g 85%.
Found: C, 64.60; H, 5.66; N, 9.71. C63H66B2N8O3P2Ru (7a)
requires: C, 64.79; H, 5.70; N, 9.59%. ΛM ) 55.0 Ω-1 mol-1 cm2.
Found: C, 65.22; H, 5.68; N, 9.37. C64H68B2N8O3P2Ru (7b)
requires: C, 65.04; H, 5.80; N, 9.48%. ΛM ) 55.7 Ω-1 mol-1 cm2.
Found: C, 67.23; H, 5.77; N, 9.10. C68H68B2N8O2P2Ru (8b)
requires: C, 67.28; H, 5.65; N, 9.23%. ΛM ) 56.6 Ω-1 mol-1 cm2.
Found: C, 56.96; H, 6.18; N, 10.35. C51H66B2N8O6P2Ru (9a)
requires: C, 57.15; H, 6.21; N, 10.46%. ΛM ) 57.2 Ω-1 mol-1
cm2. Found: C, 57.40; H, 6.26; N, 10.17. C52H68B2N8O6P2Ru (9b)
requires: C, 57.52; H, 6.31; N, 10.32%. ΛM ) 58.4 Ω-1 mol-1
cm2.
[RuTp(ArNdNH)LL′]BPh4 (7, 8, 9) [L ) P(OEt)3, L′ ) PPh3,
Ar ) C6H5 (7a); L ) PPh(OEt)2, L′ ) PPh3, Ar ) 4-CH3C6H4
(8b); L ) L′ ) P(OEt)3, Ar ) C6H5 (9a)]. Method 2: From the
Aryldiazenido. An equimolar amount of LiBHEt3 (0.1 mmol, 100
µL of a 1 M solution in THF) was added to a solution of the
appropriate aryldiazenido [ReTpLL′(ArN2)](BF4)2 (0.1 mmol) in
10 mL of CH2Cl2 which was cooled to -196 °C. The reaction
mixture was brought to 0 °C and stirred for 2 h. The solvent was
removed under reduced pressure to give an oil which was treated
with ethanol (2 mL) containing an excess of NaBPh4 (0.2 mmol,
68 mg). A yellow-orange solid slowly separated out from the
resulting solution, which was filtered and crystallized twice from
CH2Cl2 and ethanol; yield g 45%. Found: C, 64.60; H, 5.67; N,
9.68. C63H66B2N8O3P2Ru (7a) requires: C, 64.79; H, 5.70; N,
9.59%. ΛM ) 59.5 Ω-1 mol-1 cm2. Found: C, 67.21; H, 5.56; N,
9.16. C68H68B2N8O2P2Ru (8b) requires: C, 67.28; H, 5.65; N,
9.23%. ΛM ) 58.1 Ω-1 mol-1 cm2. Found: C, 57.39; H, 6.14; N,
10.35. C51H66B2N8O6P2Ru (9a) requires: C, 57.15; H, 6.21; N,
10.46%. ΛM ) 59.7 Ω-1 mol-1 cm2.
[RuTp(C6H5NdNH)LL′]BPh4 (7a, 9a) [L ) P(OEt)3, L′ )
PPh3 (7); L ) L′ ) P(OEt)3 (9)]. Method 3: Oxidation of the
Hydrazine. A solid sample of the appropriate hydrazine complexes
4, 6 (0.2 mmol) was placed in a 25-mL three-necked, round-
bottomed flask fitted with a solid-addition sidearm containing a
slight excess of Pb(OAc)4 (0.22 mmol, 97 mg). Dichloromethane
(10 mL) was added, the solution cooled to -30 °C and the Pb-
(OAc)4 added portionwise over 20-30 min to the cold, stirring
solution. The solution was warmed to room temperature and stirred
for 15 min and then the solvent removed under reduced pressure.
The oil obtained was treated with ethanol (3 mL) containing an
excess of NaBPh4 (0.4 mmol, 137 mg), and the yellow-orange solid
was filtered and recrystallized from CH2Cl2 and ethanol; yield g
65%. Found: C, 64.60; H, 5.81; N, 9.43. C63H66B2N8O3P2Ru (7a)
requires: C, 64.79; H, 5.70; N, 9.59%. ΛM ) 56.8 Ω-1 mol-1 cm2.
Found: C, 57.28; H, 6.17; N, 10.32. C51H66B2N8O6P2Ru (9a)
requires: C, 57.15; H, 6.21; N, 10.46%. ΛM ) 60.4 Ω-1 mol-1
cm2.
[RuTp(CH3NdNH){P(OEt)3}(PPh3)]BPh4 (7d). These com-
plexes were prepared by oxidation of the methylhydrazine com-
plexes with Pb(OAc)4, following the method used for the related
phenyldiazene 7a, 9a derivatives (method 3). The pale-yellow solid
obtained was twice crystallized from CH2Cl2 and ethanol at 0 °C;
yield g 30%. Found: C, 62.89; H, 5.75; N, 10.27. C58H64B2N8O3P2-
Ru requires: C, 63.00; H, 5.83; N, 10.13%. ΛM ) 56.7 Ω-1 mol-1
cm2.
[RuTp(C6H5Nd15NH){P(OEt)3}(PPh3)]BPh4 (7a1) and [RuTp-
(C6H5Nd15NH){P(OEt)3}2]BPh4 (9a1). These complexes were
prepared exactly like the related unlabeled 7a and 9a using
(C6H5Nt15N)BF4 as a reagent; yield g 80%.
[{RuTp[P(OEt)3](PPh3)}2(µ-4,4′-NHdNC6H4sC6H4NdNH)]-
(BPh4)2 (7f). This complex was prepared following the method used
for the related compounds 7a and 7b by allowing the hydride
RuHTp{P(OEt)3}(PPh3) (74 mg, 0.1 mmol) to react in CH2Cl2 (10
X-ray Crystal Structure Determination of [RuTp(CH3NHNH2)-
{P(OEt)3}(PPh3)]BPh4 (4d). The data were collected on a SI-
EMENS Smart CCD area-detector diffractometer with graphite-
monochromated Mo KR radiation. Absorption correction was
carried out using SADABS.15 The structure was solved by direct
methods and refined by full-matrix least squares based16 on F2.
All non-hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were included in idealized positions
Inorganic Chemistry, Vol. 43, No. 14, 2004 4513

Albertin et al.
Scheme 1a
Table 1. Crystal Data and Structure Refinement for
[RuTp(CH3NHNH2){(POEt)3}(PPh3)]BPh4 (4d)
compound
empirical formula
fw
[RuTp(CH3NHNH2){(POEt)3}(PPh3)]BPh4
C58H66B2N8O3P2Ru
1107.82
temp
293(2) K
wavelength
cryst syst
space group
unit cell dimensions
0.710 73 Å
orthorhombic
Pbca
a ) 14.2119(19) Å
b ) 27.294(4) Å
c ) 29.490(4) Å
114 39(3) Å3
vol
Z
8
density (calcd)
abs coeff
1.287 Mg/m3
0.380 mm-1
F(000)
cryst size
θ range for data collection
index ranges
reflns collected
independent reflns
4624
0.37 × 0.22 × 0.08 mm3
1.38-28.10°
-9 e h e 18, -36 e k e 35, -38 e l e 38
54 280
13 531 [R(int) ) 0.1685]
completeness to θ ) 28.10° 97.0%
abs correction
multiscan
max and min transmission
data/restraints/params
GOF on F2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and hole
1.0000 and 0.7863
13 531/0/679
0.680
R1 ) 0.0447, wR2 ) 0.0438
R1 ) 0.3060, wR2 ) 0.0839
0.427 and -0.358 e Å-3
a L ) P(OEt)3, L′ ) PPh3 1, 4; L ) PPh(OEt)2, L′ ) PPh3 2, 5; L ) L′
) P(OEt)3 3, 6; Ar ) C6H5 a, 4-CH3C6H4 b; R ) C6H5 a, 4-NO2C6H4 c,
CH3 d, H e.
We have also obtained crystals of 1b, but their poor quality
prevented any X-ray structure determination. The IR spectra
show, beside the absorptions of the Tp and the phosphine
ligands, a broad medium-intensity band at 2095-2073 cm-1
attributed to the ν(N2) of the aryldiazenido ligand. This
assignment was confirmed by the 15N isotopic substitution
of the ArN2 ligand. A shift of this absorption to lower
wavenumbers, by 25-29 cm-1, was observed in the labeled
1a1 and 3a1 derivatives. The ν(N2) value of our complexes
1-3 also suggests20 a near-linear structure (Chart 1) for the
and refined with isotropic displacement parameters, except those
attached to nitrogen atoms of the hydrazine molecule, which were
located and refined with isotropic displacement parameters. Atomic
scattering factors and anomalous dispersion corrections for all atoms
were taken from International Tables for X-ray Crystallography.17
Data collection and refinement results are summarized in Table 1.
Results and Discussion
Aryldiazenido Complexes. Dihydrogen complexes14,18
[RuTp(η2-H2)LL′]BF4 [L ) P(OEt)3 and PPh(OEt)2; L′ )
PPh3] react with aryldiazonium cations in CH2Cl2 to give
the aryldiazenido [RuTpLL′(ArN2)](BF4)2 (1, 2, 3) deriva-
tives (Scheme 1).
RuNNAr group when compared to literature data.8a The 15
N
NMR spectra confirm this hypothesis showing a multiplet
at -70.7 (1a1) and -75.3 (3a1) ppm, which falls in the range
of linear aryldiazenido ligands.8a,21
The reaction proceeds with the replacement of the η2-H2
ligand, giving the dicationic complexes 1-3 which were
isolated in good yield (g70%) and characterized. The [RuTp-
{P(OEt)3}(PPh3)(ArN2)](BF4)2 (1) compounds can also be
prepared by substituting the H2O ligand in the [RuTp(H2O)-
{P(OEt)3}(PPh3)]BF4 complex with aryldiazonium cations
in CH2Cl2 as the solvent. The reaction is slower than that
with the η2-H2 precursor, but it also gives the dicationic
complexes 1 in good yield (Scheme 2).
Good analytical data were obtained for the crystallized
samples of aryldiazenido complexes 1-3, which are red-
orange solids stable in air and in a solution of polar organic
solvents, where they behave as 2:1 electrolytes.19 The IR
and NMR data (Table 2) support the proposed formulation.
1
The H NMR spectra of 1-3 support their formulation,
showing the characteristic signals of the Tp ligand and the
phosphine groups. In the spectra of 1b, 2b, and 3b, the singlet
of the methyl substituent of the 4-CH3C6H4NtN ligand at
2.54-2.51 ppm is also observed. In a temperature range
between -80 and +20°C, the 31P{1H} NMR spectra of
[RuTpL(PPh3)(ArN2)](BF4)2 (1, 2) appear as AB quartets due
to the presence of two different phosphine ligands. Coupling
with 15N was also observed in the spectrum of the labeled
1a1 complex, which appeared as an ABX (X ) 15N) multiplet
15
with the two JP N of 6.5 and 3.5 Hz, respectively. The spectra
of the [RuTp{P(OEt)3}2(ArN2)](BF4)2 (3) phosphite deriva-
tives, instead, appear as sharp singlets due to the magnetic
equivalence of the two phosphite ligands. A doublet with
15N
JP of 6.7 Hz was observed in the spectra of the labeled
(15) Sheldrick, G. M. SADABS, An Empirical Absorption Correction
Program for Area Detector Data; University of Go¨ttingen: Germany,
1996.
[RuTp{P(OEt)3}2(C6H5Nt15N)](BF4)2 (3a1) derivative.
(16) Sheldrick, G. M. SHELX-97, Program for the Solution and Refinement
of Crystal Structures; University of Go¨ttingen: Germany, 1997.
(17) International Tables for X-ray Crystallography; Kluwer: Dordrecht,
The Netherlands, 1992; Vol. C.
(19) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81-122.
(20) (a) Bowden, W. L.; Little, W. F.; Meyer, T. J. J. Am. Chem. Soc.
1973, 95, 5084-5085. (b) Bowden, W. L.; Little, W. F.; Meyer, T. J.
J. Am. Chem. Soc. 1977, 99, 4340-4345.
(21) Haymore, B. L.; Hughes, M.; Mason, J.; Richards, R. C. J. Chem.
Soc., Dalton Trans. 1988, 2935-2940.
(18) The dihydrogen complexes [RuTp(η2-H2)LL′]BF4 used in these studies
were prepared in solution by treating the hydrides RuHTpLL′ with
an equimolar amount of HBF4‚Et2O.
4514 Inorganic Chemistry, Vol. 43, No. 14, 2004

Ruthenium Tris(pyrazolyl)borate Diazo Complexes
Scheme 2a
a Ar ) C6H5 a, 4-CH3C6H4 b; R ) C6H5 a, 4-NO2C6H4 c, CH3 d, H e.
Chart 1
aryldiazenido ligand. This precedent supports the hypothesis
of the geometry of our complexes 1-3 (Chart 1) and shows
that either Cp or Tp as ancillary ligand gives the strictly
comparable aryldiazenido [RuCp(PPh3)2(ArN2)](BF4)2 and
[RuTpLL′(ArN2)](BF4)2 (1-3) derivatives. Although a com-
plete comparison cannot be made for the absence of mixed-
ligand [RuCpLL′(ArN2)]2+ species, the spectroscopic prop-
erties suggest that the introduction of phosphite ligands in
RuTp chemistry makes the [RuTpLL′] fragment able to bind
the aryldiazenido group and is strictly comparable to the
[RuCp(PPh3)2] one. Furthermore, as previously observed in
related dicationic8a,20 [RuCp(PPh3)2(ArN2)](BF4)2 and [RuCl-
(bpy)2(ArN2)](PF6)2 compounds, the linear arrangement of
the ArNN ligand seems to be strongly dependent on the
formal 2+ charge of the complexes.
On the basis of these data, a geometry of the type reported
in Scheme 1 can reasonably be proposed for our aryldiaz-
enido derivatives.
Aryldiazenido complexes of the iron triad are re-
ported1,2,6-8,20 with several supporting ligands such as tertiary
phosphine, carbonyl, cyclopentadienyl, and 2,2′-bipyridine.
With hydrido-tris(pyrazolyl)borate, instead, the chemistry of
organo-diazo complexes appears to be largely unexplored,
and complexes 1-3 are, to the best of our knowledge, the
first tris(pyrazolyl)borate diazo complexes of the iron triad.
The use of mixed-ligand dihydrogen [RuTp(η2-H2)LL′]BF4
complexes with phosphite and Tp as precursors appears to
be an easy entry into this chemistry. The high value of ν-
(N2) (2095-2073 cm-1) and the value of δ 15N (ap-
proximately -70 ppm) for 1-3 suggest the presence of a
linear ArN2 group in our complexes. The comparable [RuCp-
(PPh3)2(ArN2)](BF4)2 complexes,8a containing cyclopentadi-
enyl instead of Tp as supporting ligand, showed similar
values for ν(N2) and δ 15N, and an X-ray crystal structure
indicated a near-linear Ru-N-N-C geometry for the
Hydrazine Complexes. Hydrazine, RNHNH2, can replace
the dihydrogen ligand in [RuTp(η2-H2)LL′]+ cations to give
[RuTp(RNHNH2)LL′]+ (4, 5, 6) derivatives, which were
isolated as BPh4 salts and characterized (Scheme 1). The
reaction easily proceeds at room temperature in CH2Cl2
yielding a series of hydrazine complexes of the type 4-6.
Also, the aquo-complex [RuTp(H2O){P(OEt)3}(PPh3)]+ can
be used as a precursor, by replacing H2O with hydrazine, to
give the final derivatives 4 (Scheme 2).
The hydrazine complexes 4-6 were isolated as white or
pale-yellow solids stable in air and in a solution of polar
organic solvents, where they behave as 1:1 electrolytes.19
Their characterization is supported by analytical and spec-
troscopic data (Table 2) and by the X-ray crystal structure
determination of the methylhydrazine complex 4d. The
ORTEP drawing of the [RuTp(CH3NHNH2){P(OEt)3}-
(PPh3)]+ cation (4d+) is shown in Figure 1.
The ruthenium atom has a slightly distorted octahedral
arrangement of donor atoms. Selected bond distances and
angles are displayed in Table 3. The shortest angle in the
octahedron is not due to the chelating effect of the scorpi-
onate ligand Tp, but the value of the N(15)-Ru-N(1) angle
is only 80.87(17)°, indicating a displacement of the hydrazine
ligand. Also, the equatorial plane containing the atoms
labeled as N(11), N(13), P(2), and N(1) shows both a poor
planarity (rms of 0.0314) when compared with the other two
planes of the octahedron (rms of 0.0125 and 0.0026) and
that the N(1) atom lies 0.128(8) Å out of the plane formed
by the other three donor atoms N(11), N(13), and P(2).
Figure 1. ORTEP diagram (30% probability level) of the cation [RuTp-
(CH3NHNH2){P(OEt)3}(PPh3)]+ (4d+). The phenyl groups have been
omitted for the sake of clarity.
The Ru-P bond distances show a difference between them
of 0.923 Å due to the different nature of the phosphine
Inorganic Chemistry, Vol. 43, No. 14, 2004 4515

Albertin et al.
Table 2. IR and NMR Data for Ruthenium Complexes
IRa
1H NMRb
δ, J/Hz
31P{1H} NMRb,c
δ, J/Hz
compound
ν/cm-1
assgnt
assgnt
spin system
AB
1a
[RuTp{P(OEt)3}(PPh3)(C6H5NtN)](BF4)2
(2523) w
(2079) m
ν(BH)
ν(NN)
8.29-6.26 m
3.92 m
Ph + Tp
CH2
δ
δ
A 103.1
B 25.9
3.63 m
JAB ) 49.0
1.14 t
CH3
d
1a1
[RuTp{P(OEt)3}(PPh3)(C6H5Nt15N)](BF4)2
(2523) w
(2050) m
ν(BH)
8.30-6.28 m
Ph + Tp
ABX
δ
δ
A 103.8
B 26.2
ν(15NN)
3.91 m
CH2
(X ) 15N)
3.63 m
1.15 t
JAB ) 48.9
JAX ) 6.50
JBX ) 3.50
CH3
e
1b
2b
[RuTp{P(OEt)3}(PPh3)(4-CH3C6H4NtN)](BF4)2
(2519) w
(2084) m
ν(BH)
ν(NN)
8.54-6.25 m
3.85 m
3.60 m
2.54 s
1.14 t
8.53-6.14 m
4.16 m
4.08 m
3.62 m
Ph + Tp
CH2
AB
AB
δ
δ
A 104.2
B 26.4
JAB ) 49.4
CH3 p-tol
CH3 phos
Ph + Tp
CH2
[RuTp{PPh(OEt)2}(PPh3)(4-CH3C6H4NtN)](BF4)2
(2529) w
(2073) m
ν(BH)
ν(NN)
δ
δ
A 137.2
B 26.1
JAB ) 41.0
3.08 m
2.52 s
CH3 p-tol
1.54 t
CH3 phos
0.96 t
3a
[RuTp{P(OEt)3}2(C6H5NtN)](BF4)2
(2490) w
(2087) m
ν(BH)
ν(NN)
8.55-6.10 m
Ph + Tp
CH2
CH3
Ph + Tp
CH2
CH3
Ph + Tp
CH2
CH3 p-tol
CH3 phos
Ph + Tp
RuNH2
A2
106.2 s
3.66 m
1.19 t
8.55-6.10 m
3.66 m
1.19 t
8.51-6.10 m
3.90 m
2.51 s
1.25 t
7.98-6.11 m
4.91 m
3.96 m
4.50 m
3.64 m
3.34 m
1.04 t
8.01-6.03 m
5.49 m
4.62 m
3.98 m
3.65 m
3.35 m
1.03 t
8.08-6.09 m
3.61 m
3.36 m
3.56 m
3.37 m
f
3a1
3b
[RuTp{P(OEt)3}2(C6H5Nt15N)](BF4)2
(2492) m
(2062) m
ν(BH)
A2X
δA 106.8
JAX ) 6.7
ν(15NN)
(X ) 15N)
[RuTp{P(OEt)3}2(4-CH3C6H4NtN)](BF4)2
[RuTp(C6H5NHNH2){P(OEt)3}(PPh3)]BPh4
(2498) m
(2095) m
ν(BH)
ν(NN)
A2
107.0 s
4a
4c
4d
3360 sh
3348 m
3283 m
2493 m
1608 m
ν(NH)
AB
δ
δ
A 132.9
B 48.7
JAB ) 56
ν(BH)
δ(NH2)
NH
CH2
CH3
Ph + Tp
NH
[RuTp(4-NO2C6H4NHNH2){P(OEt)3}(PPh3)]BPh4
3385 w
3327 w
3267 w
2488 m
1601 m
ν(NH)
AB
AB
δ
δ
A 131.4
B 47.0
JAB ) 55
RuNH2
ν(BH)
δ(NH2)
CH2
CH3
Ph + Tp
CH2
g
[RuTp(CH3NHNH2){P(OEt)3}(PPh3)]BPh4
3346 m
3271 m
3196 w
2480 m
ν(NH)
ν(BH)
δ
δ
A 132.9
B 48.9
JAB ) 56
RuNH2
3.06 m
NH
2.11 d
NCH3
JHH ) 6
1.04 t
CH3 phos
Ph + Tp
RuNH2
4e
5a
[RuTp(NH2NH2){P(OEt)3}(PPh3)]BPh4
3374 br, m
3305 br, w
3276 br, m
2486 m
ν(NH)
ν(BH)
8.06-6.09 m
3.85 m
AB
AB
δ
δ
A 132.8
B 48.8
JAB ) 55
3.43 m
3.64 m
3.32 m
2.77 t, br
1.05 t
8.01-5.81 m
5.95 m
3.80 m
4.31 t, br
4.15 m
CH2
NH2
CH3
Ph + Tp
RuNH2
[RuTp(C6H5NHNH2){PPh(OEt)2}(PPh3)]BPh4
3342 br, m
3283 w
2493 m
ν(NH)
δ
δ
A 169.7
B 47.7
ν(BH)
δ(NH2)
JAB ) 51
1605 m
NH
CH2
3.84 m
3.48 m
3.13 m
1.65 t
CH3
0.88 t
4516 Inorganic Chemistry, Vol. 43, No. 14, 2004

Ruthenium Tris(pyrazolyl)borate Diazo Complexes
Table 2. (Continued)
IRa
1H NMRb
δ, J/Hz
31P{1H} NMRb,c
δ, J/Hz
compound
ν/cm-1
assgnt
assgnt
spin system
AB
h
5d
[RuTp(CH3NHNH2){PPh(OEt)2}(PPh3)]BPh4
3340 m
3267 m
3248 sh
2482 m
ν(NH)
7.99-5.81 m
4.11 m
3.85 m
3.46 m
3.08 m
Ph + Tp
CH2
δ
δ
A 169.5
B 49.2
JAB ) 52
ν(BH)
3.69 m
NH
3.58 m
RuNH2
3.18 m
2.23 d
NCH3
JHH ) 6
1.58 t
CH3 phos
0.86 t
5e
[RuTp(NH2NH2){PPh(OEt)2}(PPh3)]BPh4
3364 m
3294 w
3284 m
2488 m
ν(NH)
ν(BH)
7.96-5.83 m
Ph + Tp
CH2
AB
δ
A 169.5
B 49.0
JAB ) 52
4.02 m
δ
3.76 m
3.44 m
3.06 m
3.48 m
3.08 m
RuNH2
NH2
1.52 t
CH3
0.88 t
6a
[RuTp(C6H5NHNH2){P(OEt)3}2]BPh4
3356 m, br
3288 w
2478 m
ν(NH)
7.87-6.19 m
5.29 m, br
4.94 t, br
3.62 m
Ph + Tp
NH
RuNH2
CH2
A2
135.6 s
ν(BH)
δ(NH2)
1601 m
1.17 t
CH3
7a
[RuTp(C6H5NdNH){P(OEt)3}(PPh3)]BPh4
2488 m
2486 m
ν(BH)
13.87 s, br
8.00-6.08 m
3.68 m
3.38 m
1.06 t
NH
Ph + Tp
CH2
AB
ABX
δ
A 128.8
B 41.9
JAB ) 55
δ
CH3
NH
i
7a1
[RuTp(C6H5N)15NH){P(OEt)3}(PPh3)]BPh4
ν(BH)
ABXY spin syst
δ
δ
A 129.1
B 41.9
(Y ) H, X ) 15N)
δY 13.86
JAB ) 55
JAX ) 4.40
JBX ) 2.80
JXY ) 64.9
JAY ) 3.68
JBY ) 1.26
8.02-6.08 m
3.69 m
JAX ) 4.40
JBX ) 2.80
Ph + Tp
CH2
3.40 m
1.07 t
CH3
NH
Ph + Tp
CH2
j
7b
7d
[RuTp(4-CH3C6H4NdNH){P(OEt)3}(PPh3)]BPh4
[RuTp(CH3NdNH){P(OEt)3}(PPh3)]BPh4
13.70 s, br
8.00-6.05 m
3.68 m
AB
AB
δ
A 128.7
B 41.5
JAB ) 56
δ
3.35 m
2.38 s
1.06 t
13.52 s, br
8.00-5.95 m
3.62 m
CH3 p-tol
CH3 phos
NH
Ph + Tp
CH2
δ
δ
A 132.9
B 47.5
JAB ) 55
.
3.30 m
3.04 s
1.02 t
13.98 m, br
8.00-6.08 m
3.68 m
NCH3
CH3 phos
NH
Ph + Tp
CH2
7f
[{RuTp[P(OEt)3](PPh3)}2
(µ-4,4′-NHdNC6H4-C6H4NdNH)](BPh4)2
2488 m
ν(BH)
ν(BH)
AB
δ
A 128.8
B 41.7
JAB ) 55
δ
3.38 m
1.08 t
CH3
NH
7f1
[{RuTp[P(OEt)3](PPh3)}2
2486 m
ABXY spin syst
ABX
δ
A 128.7
k
(µ-4,4′-15NHdNC6H4-C6H4N)15NH)](BPh4)2
(Y ) H, X ) 15N)
δB 41.8
δY 14.00
JAB ) 55.0
JAX ) 4.80
JBX ) 2.60
JAX ) 4.80
JBX ) 2.60
JXY ) 64.8
JAY ) 3.45
JBY ) 0.81
8.05-6.10 m
3.75 m
Ph + Tp
CH2
3.42 m
1.11 t
CH3
Inorganic Chemistry, Vol. 43, No. 14, 2004 4517

Albertin et al.
Table 2. (Continued)
IRa
ν/cm-1
1H NMRb
δ, J/Hz
13.46 s, br
8.01-5.92 m
3.77 qnt
31P{1H} NMRb,c
δ, J/Hz
compound
[RuTp(4-CH3C6H4NdNH){PPh(OEt)2}(PPh3)]BPh4
assgnt
assgnt
NH
Tp + Ph
CH2
spin system
AB
8b
2484 m
ν(BH)
δ
δ
A 161.3
B 38.9
JAB ) 45
3.33 qnt
2.38 s
CH3 p-tol
1.32 t
CH3 phos
0.89 t
9a
[RuTp(C6H5NdNH){P(OEt)3}2]BPh4
2478 m
2478 m
ν(BH)
ν(BH)
14.44 s, br
8.01-6.28 m
3.65 m
NH
Ph + Tp
CH2
CH3
NH
A2
130.5 s
1.19 t
l
9a1
[RuTp(C6H5N)15NH){P(OEt)3}2]BPh4
A2XY spin syst
A2X
δA 130.3
JAX ) 5.2
(Y ) H, X ) 15N)
δY 14.47
JAX ) 5.2
JAY ) 3.6
JXY ) 66.0
8.04-6.28 m
3.68 m
Ph + Tp
CH2
1.19 t
CH3
9b
[RuTp(4-CH3C6H4NdNH){P(OEt)3}2]BPh4
2492 m
ν(BH)
14.30 t, br
JPH ) 4.0
8.51-6.26 m
3.68 m
NH
A2
130.9 s
Ph + Tp
CH2
2.40 s
1.17 t
CH3 p-tol
CH3 phos
a In KBr pellets and (CH2Cl2). b In CD2Cl2 at 25 °C, unless otherwise noted. c Positive shift downfield from 85% H3PO4. d 15N NMR: ABX spin system
(X ) 15N), δX -70.7, JAX ) 6.50, JBX ) 3.50 Hz. e 13C NMR: 151-108 m Ph + Tp, 66.1 d CH2, 22.7 s CH3 p-tolyl, 15.9 d CH3 phos. f 15N NMR: A2X
spin system (X ) 15N), δX -75.3, JAX ) 6.7 Hz. g 13C NMR: 165-127 m Ph + Tp, 62.4 d CH2, 42.3 s NCH3, 16.1 d CH3 phos. h 13C NMR: 165-106
1
m Ph + Tp, 66.0 d, 65.9 d CH2, 42.5 s NCH3, 16.9 d, 16.1 d CH3 phos. i 15N NMR: ABXY spin system (X ) 15N, Y ) H), δX -10.9, JAX ) 4.40, JBX
) 2.80, JAY ) 3.68, JBY ) 1.26, JXY ) 64.9 Hz. j 13C NMR: 165-106 m Ph + Tp, 62.7 d CH2, 21.5 s CH3 p-tolyl, 16.1 d CH3 phos. k 15N NMR: ABXY
1
spin system (X ) 15N, Y ) H), δX -12.1, JAX ) 4.80, JBX ) 2.60, JAY ) 3.45, JBY ) 0.81, JXY ) 64.8 Hz. l 15N NMR: A2XY spin system (X ) 15N,
1
Y ) H), δX -15.2, JAX ) 5.2, JAY ) 3.6, JXY ) 66.0 Hz.
Table 3. Selected Bond Lengths [Å] and Angles [deg] for 4d
Table 4. Selected Hydrogen Bondsa
D-H
Ru-N(13)
Ru-N(15)
Ru-P(1)
2.085(4)
2.123(4)
2.2348(16)
1.437(5)
Ru-N(11)
Ru-N(1)
Ru-P(2)
2.111(4)
2.154(3)
2.3271(15)
1.461(6)
H‚‚‚A
D‚‚‚A
(DHA)
N(2)-H(2)‚‚‚O(3)
1.01(6)
0.90
0.90
0.97
0.93
2.01(6)
2.50
2.71
2.44
2.53
2.926(7)
2.775(6)
3.590(4)
2.837(7)
3.091(7)
3.093(7)
150(6)
98.2
166.5
104.4
119.5
124.0
N(1)-H(1A)‚‚‚N(15)
N(1)-H(1B)‚‚‚Cgb
C(6)-H(6A)‚‚‚O(1)
C(14)-H(14)‚‚‚O(2)
C(66)-H(66)‚‚‚N(15)
N(1)-N(2)
N(2)-C(1)
N(13)-Ru-N(11)
N(11)-Ru-N(15)
N(11)-Ru-N(1)
N(13)-Ru-P(1)
N(15)-Ru-P(1)
N(13)-Ru-P(2)
N(15)-Ru-P(2)
N(2)-N(1)-Ru
87.0(2)
N(13)-Ru-N(15)
89.00(18)
168.00(19)
94.57(6)
91.29(13)
98.05(12)
174.09(14)
94.55(12)
110.8(4)
82.18(17) N(13)-Ru-N(1)
85.31(18) P(1)-Ru-P(2)
91.28(13) N(11)-Ru-P(1)
173.44(13) N(1)-Ru-P(1)
92.19(14) N(11)-Ru-P(2)
91.96(13) N(1)-Ru-P(2)
0.93
2.48
a With esd’s except riding H. b Cg represents the centroid of the phenyl
ring labeled as 8.
distortion can be found in the angles around the boron atom
(N-B-N angles) (Table 3). We can infer from these values
that the pyrazolyl ring containing N(15) and N(16) atoms is
deviated from its natural position, probably because of the
hydrogen bonds in which this ring(s) is implied (vide infra).
Although there are not substantial intermolecular interac-
tions, the molecular arrangement is stabilized by some
intramolecular classic and nonclassic hydrogen bonds. Clas-
sic ones involve both nitrogen atoms of the hydrazine ligand
with N(15) of one pyrazolyl ligand and O(3) of the phosphite
ligand (Table 4). The nonclassic ones involve both
C-H‚‚‚N or C-H‚‚‚O as well as N-H‚‚‚π. This last one
involves the NH2 group of the hydrazine ligand and the
π-cloud of a phenyl ring of the phosphine ligand (Figure 2).
The mean values of these bond distances fall within the range
previously observed.23
123.2(3)
N(1)-N(2)-C(1)
N(14)-B(1)-N(16) 110.1(6)
O(1)-P(1)-O(2)
O(2)-P(1)-O(3)
C(61)-P(2)-C(81)
N(14)-B(1)-N(12) 108.1(6)
N(16)-B(1)-N(12) 107.0(6)
103.1(2)
107.2(2)
102.3(3)
O(1)-P(1)-O(3)
C(61)-P(2)-C(71)
C(81)-P(2)-C(71)
98.9(2)
97.9(3)
103.6(3)
ligands.22b The Ru-N bond distances from the Tp ligand in
trans orientation to the phosphine ligands are slightly shorter
than the values expected under a trans influence of the
phosphine ligands.22 The Ru-N(13) bond length is shorter,
because the hydrazine ligand is in the trans position.
The dihedral angles between the pyrazolyl rings are 120.6-
(2)°, 125.7(2)°, and 113.7(2)° (expected 120°), and a similar
(22) (a) Jime´nez Tenorio, M. A.; Jime´nez Tenorio, M.; Puerta, M. C.;
Valerga, P. J. Chem. Soc., Dalton Trans. 1998, 3601-3607. (b)
Conner, D.; Jayaprakash, K. N.; Gunoe, T. B.; Boyle, P. D. Inorg.
Chem. 2002, 41, 3042-3049. (c) Buriez, B.; Burns, I. D.; Hill, A. F.;
White, A. J. P.; Williams, D. J.; Wilton-Ely, J. D. E. T. Organome-
tallics 1999, 18, 1504-1516.
All other structural parameters in the ligands, as well as
-
in the BPh4 anion, are in the normal range.
4518 Inorganic Chemistry, Vol. 43, No. 14, 2004

Ruthenium Tris(pyrazolyl)borate Diazo Complexes
Hydrazine complexes of ruthenium are reported with
several supporting ligands, such as arene, diene, phosphine,
phosphite, and isocyanide.7b,25-29 Attempts were also made
to prepare complexes with cyclopentadienyl (Cp), by reacting
[CpRu(CO)3]+ with hydrazines, but the reaction occurred at
the coordinated CO to give isocyanate complexes.30
The use of [RuTp(η2-H2)L(PPh3)]+ and [RuTp(η2-H2)-
{P(OEt)3}2]+ as precursors allows the first tris(pyrazolyl)-
borate ruthenium hydrazine complexes to be prepared.
Aryldiazene Complexes. Aryldiazene complexes [RuTp-
(ArNdNH)L(PPh3)]BPh4 (7, 8) [L ) P(OEt)3 and PPh-
(OEt)2] and [RuTp(ArNdNH){P(OEt)3}2]BPh4 (9) can be
prepared following three different methods: (i) the insertion
+
of aryldiazonium cations, ArN2 , into the [Ru]-H bond of
the RuHTpLL′ hydride, (ii) the reduction of aryldiazenido
[Ru]sNtNAr (1-3) with LiBHEt3, (iii) the oxidation of
arylhydrazine [Ru]-NH2NHR (4-6) with Pb(OAc)4, as
shown in Scheme 3.
Both the RuHTpL(PPh3) and RuHTp{P(OEt)3}2 hydrides
react quickly with aryldiazonium cations in CH2Cl2 to give
the [RuTp(ArNdNH)L(PPh3)]BPh4 (7, 8) and [RuTp(ArNd
NH){P(OEt)3}2]BPh4 (9) aryldiazene derivatives, which were
separated as BPh4 salts and characterized. The reaction was
also extended to bis(aryldiazonium) [N2Ar-ArN2]-
(BF4)2 cations leading to the binuclear bis(aryldiazene)
[{RuTp[P(OEt)3](PPh3)}2(µ-4,4′-NHdNC6H4sC6H4NdNH)]-
(BPh4)2 (7f) derivative (Scheme 4). The same aryldiazene
complexes 7-9 were obtained by reacting the aryldiazenido
[RuTpL(PPh3)(ArN2)](BF4)2 (1, 2) and [RuTp{P(OEt)3}2-
(ArN2)](BF4)2 (3) with LiBHEt3 in CH2Cl2 at 0 °C. Studies
using the labeled [Ru]s15NtNPh (1a1) complex confirm that
the reduction takes place on the N(1) nitrogen atom, giving
the aryldiazene [Ru]s15NHdNPh (7a1) derivatives. Further-
more, the reaction of arylhydrazine [RuTp(ArNHNH2)L-
(PPh3)]BPh4 (4a) and [RuTp(ArNHNH2){P(OEt)3}2]BPh4
(6a) complexes with Pb(OAc)4 at -30 °C leads to the
selective oxidation of the ArNHNH2 group to give the
corresponding aryldiazene [Ru]sNHdNAr (7, 9) derivatives.
Figure 2. View of the cation 4d+ showing the intramolecular H-bonds.
One of the phenyl groups has been omitted.
The IR spectra of all the complexes 4-6 show the
characteristic absorptions of the Tp, the phosphine ligands,
-
and the BPh4 anion. In the 3385-3196 cm-1 region,
furthermore, three or four weak bands are present, attributed
to the ν(NH) of the hydrazine ligands. The presence of the
1
RNHNH2 group is confirmed by H NMR spectra, which
show the NH and NH2 resonances as slightly broad multiplets
between 5.95 and 2.77 ppm (Table 2).
Unexpectedly, for the mixed-ligand phosphine-phosphite
[RuTp(RNHNH2)L(PPh3)]BPh4 (4, 5) complexes, three NH
resonances were observed for the coordinated RNHNH2
ligands, with 1:1:1 intensity ratio (1:1:2 ratio for NH2NH2
in 4a and 5a). The attributions were confirmed by homo-
decoupling experiments and 1H COSY spectra, which
indicated that the two hydrogens of the coordinated NH2
group fall at different chemical shift values. This is probably
due to the coordination of the NH2 group of hydrazine to
the [RuTpL(PPh3)] fragment, which makes the two NH2
hydrogen atoms prochiral, with different chemical shift
values. Values of 8-10 Hz for the 2JHH of the two prochiral
NH2 protons were also determined.24
These results highlight one of the important properties that
the Tp ligand may have in diazo chemistry, namely, being
able to stabilize aryldiazenido, aryldiazene, and arylhydrazine
molecules bonded to the same [RuTpLL′] fragment. The
facile synthesis of aryldiazene complexes through three
different reactions is also an interesting and novel result in
this chemistry, which includes the mixed-ligand [RuTpLL′]
The 1H NMR spectra of the phosphite [RuTp(C6H5-
NHNH2){P(OEt)3}2]BPh4 (6a) derivative, however, show
only one broad multiplet for the NH2 as well as one for the
NH protons of the coordinated hydrazine ligand.
(24) For prochiral CH2 protons, the 2JHH values fall in the 10-15 Hz range.
See: (a) Bovey, F. A. Nuclear Magnetic Resonance Spectroscopy;
Academic Press: New York, 1969. (b) Abraham, R. J.; Loftus, P.
Proton and carbon-13 NMR spectroscopy; Heyden: London, 1980.
(25) Crabtree, R. H.; Pearman, A. J. Organomet. Chem. 1977, 141, 325-
333.
In the temperature range between +20 and -80 °C, the
31P{1H} NMR spectra of the [RuTp(RNHNH2)L(PPh3)]BPh4
(4, 5) complexes appear as AB quartets, while only one
singlet is present in the spectra of the [RuTp(C6H5NHNH2)-
{P(OEt)3}2]BPh4 (6a) derivative. On the basis of these data,
a geometry like the one determined in the solid state for 4d
can be proposed for all the hydrazine derivatives.
(26) Hough, J. J.; Singleton, E. J. Chem. Soc., Chem. Commun. 1972, 371-
372.
(27) Ashworth, T. V.; Reimann, R. H.; Singleton, E. J. Chem. Soc., Dalton
Trans. 1978, 1036-1039.
(28) Ashworth, T. V.; Nolte, M. J.; Reimann, R. H.; Singleton, E. J. Chem.
Soc., Dalton Trans. 1978, 1043-1046.
(29) Singleton, E.; Swanepoel, H. E. Inorg. Chim. Acta 1982, 57, 217-
221.
(23) Braga, D.; Grepioni, F.; Tedesco, E. Organometallics 1998, 17, 2669-
(30) Kruse, A. E.; Angelici, R. J. J. Organomet. Chem. 1970, 24, 231-
239.
2672 and references therein.
Inorganic Chemistry, Vol. 43, No. 14, 2004 4519

Albertin et al.
Scheme 3a
a L ) P(OEt)3, L′ ) PPh3 7; L ) PPh(OEt)2, L′ ) PPh3 8; L ) L′ ) P(OEt)3 9; Ar ) C6H5 a, 4-CH3C6H4 b.
Scheme 4a
a L ) P(OEt)3, L′ ) PPh3.
fragment with Tp and phosphite. A comparison with the
related ruthenium-cyclopentadienyl [RuCp(PPh3)2] fragment8a
shows that, also in this case, an aryldiazene cation of the
[RuCp(PPh3)2(NHdNC6H4OMe)]+ type can be obtained
NH2NH2 complexes (4e, 5e), instead, did not give any stable
complexes from the reaction with Pb(OAc)4. A color change
of the solution was observed, but only an intractable oil was
separated, which (by NMR) contained neither the starting
NH2NH2 complex nor the expected 1,2-diazene [RuTp(NHd
NH)LL′]BPh4 derivatives. Probably, the oxidation of the
hydrazine takes place in this case as well, but the instability
of the 1,2-diazene [Ru]sNHdNH formed prevents the
isolation of stable species.
All the diazene complexes 7-9 were isolated as stable
white or yellow solids, stable in air and in a solution of polar
organic solvents, where they behave as 1:1 electrolytes.19
The analytical and spectroscopic data (Table 2) support the
proposed formulation. In particular, the presence of the
diazene ligand is indicated by the characteristic high-
frequency (13-15 ppm), slightly broad signal of the NH
-
from the reaction of the aryldiazenido with BH4 , but it is
stable only at -80 °C. Our tris(pyrazolyl)borate aryldiazene
complexes 7-9, instead, are very stable and can be isolated
in the solid state. The ability of our [RuTpLL′] fragment to
stabilize the diazo complexes, however, may be due to the
peculiar properties of the Tp ligand and also to the presence
of the phosphite, which contributes to making the RuTpLL′
group suitable for diazo chemistry.
The result of the oxidation of arylhydrazine complexes
prompted us to extend the study to the other hydrazines, and
the results are shown in Scheme 5.
The methylhydrazine complexes (4d, 5d) react with Pb-
(OAc)4 at -30 °C to give the methyldiazene [RuTp(CH3Nd
NH)LL′]+ cations which, in the case of 7d, can be isolated
as BPh4 salts in pure form and characterized. The related
(31) (a) Laing, K. R.; Robinson, S. D.; Uttley, M. F. J. Chem. Soc., Dalton
Trans. 1973, 2713-2722. (b) Carrol, J. A.; Sutton, D.; Xiaoheng, Z.
J. Organomet. Chem. 1982, 244, 73-86.
4520 Inorganic Chemistry, Vol. 43, No. 14, 2004

Ruthenium Tris(pyrazolyl)borate Diazo Complexes
Scheme 5
(PPh3)]BPh4 (7, 8) appear as an AB quartet, while only one
singlet is observed in the spectra of the [RuTp(C6H5NdNH)-
{P(OEt)3}2]BPh4 (9a) derivative. On the basis of these data,
a geometry like those reported in Schemes 3-5 can reason-
ably be proposed for our diazene derivatives.
Reactivity studies on ArNdNH complexes 7-9 were
performed toward deprotonation and reduction reactions, and
the results showed that the aryldiazenes are robust complexes
which do not react either with bases (NEt3 or OH-) or with
-
-
reducing agents such as H2 (1 atm) or BHEt3 and BH4 .
The stability toward a base of [M]sNHdNAr group is
somewhat unexpected, owing to the known acidity of the
coordinate diazene which often undergoes deprotonation
giving the aryldiazenido [M]-N2Ar complexes.1a,6a,7a How-
ever, the unreactivity of our diazene complexes may be
explained by taking into account that a doubly bent aryldia-
-
zenido (ArN2 ) complex should be formed by first depro-
tonating a [Ru]sNHdNAr species (Scheme 6).
A rearrangement of this doubly bent ArN2- ligand to singly
+
bent ArN2 should involve a 2e- reduction of the central
metal to Ru(0), followed by the concurrent dissociation of
one ligand to give a final pentacoordinate aryldiazenido
complex.6a,b,7a,d The reluctance to dissociate any ligands in
the [RuTpLL′] fragment probably prevents the formation of
aryldiazenido derivatives by deprotonation of the corre-
sponding aryldiazene.
diazene proton. This attribution is confirmed, in the case of
the aryldiazene species, by the spectra of the labeled [Ru]s
15NHdNAr (7a1, 7f1, 9a1) complexes, which show the split
of the NH signal into one well-resolved doublet of multiplets
1
15NH
with the value for J
of 64-66 Hz, in agreement with
Conclusions
the presence of the diazene group.1,2,7,8,31 Further support
comes from the 15N NMR spectra of 7a1, 7f1, and 9a1, which
appear as ABXY (7a1, 7f1) and A2XY (9a1) (X ) 15N, Y )
1H) multiplets and which were simulated with the parameters
reported in Table 2 confirming the proposed formulation for
the complexes.
A facile route for the synthesis of tris(pyrazolyl)borate
diazo complexes of ruthenium has been developed using
classical and nonclassical RuHTpLL′ and [RuTp(η2-H2)LL′]+
hydrides as precursors. The exceptionally high value of ν(N2)
and the 15N NMR data for the dicationic aryldiazenido
[RuTpLL′(ArN2)](BF4)2 complexes strongly suggest a near-
linear arrangement of the Ru-bonded ArN2 ligand. The
structural parameters for a tris(pyrazolyl)borate methylhy-
drazine complex are also reported. Finally, the synthesis of
stable aryldiazene [RuTp(ArNdNH)LL′]BPh4 complexes has
been achieved through three different paths, involving one
The 1H NMR spectra of the diazene complexes 7-9 also
show the signals of the methyl substituent of the CH3Nd
NH and 4-CH3C6H4NdNH groups, beside the characteristic
resonaces of Tp and phosphine ligands and those of the BPh4
anion. In the temperature range between +20 and -80 °C,
the 31P{1H} NMR spectra of [RuTp(RNdNH){P(OEt)3}-
Scheme 6
Inorganic Chemistry, Vol. 43, No. 14, 2004 4521

Albertin et al.
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
of the following types of reactions: insertion, reduction, or
oxidation.
Acknowledgment. The financial support of MIUR (Rome),
PRIN 2002, is gratefully acknowledged. We thank Daniela
Baldan for technical assistance.
IC0497275
4522 Inorganic Chemistry, Vol. 43, No. 14, 2004