Ruthenium cyclopentadienyl aryldiazenido complexes. Synthesis of [Cp′Ru(PR3)2(N2C6H 4OMe)][BF4]2 and [Cp′RuCl(PPh3)(N2C6H 4OMe)][BF4] (Cp′ = Cp, Cp*) and x-ray crystal structure of [CpRu(PPh3)2

Article abstract of DOI:10.1021/om990761e

The neutral ruthenium complexes Cp′Ru(PR₃)₂Cl [Cp′ = Cp, PR₃ = PPh₃, PMe3, or 1/2 dppe; Cp′ = Cp*, PR₃ = PMe₃] react with [p-MeOC₆H₄N₂][BF₄] in acetone to give new cyclopentadienyl ruthenium aryldiazenido dicationic complexes [Cp′Ru(PR₃)₂(N₂C₆H ₄OMe)]-[BF₄]₂ [Cp′ = Cp, PR₃ = PPh₃ (1), PMe₃ (2), or 1/2 dppe (3); Cp′ = Cp*, PR₃ = PMe₃ (4)] in good yields. The dicationic complexes 1-3 may also be conveniently isolated in better yield by treatment of the acetonitrile ruthenium complexes [CpRu(PR₃)₂(NCMe)][BF₄] with the arenediazonium salt. When the reaction of Cp′Ru(PPh₃)₂Cl (Cp′ = Cp or Cp*) with [p-MeOC₆H₄N₂][BF₄] is carried out in toluene, the product is instead the cyclopentadienyl ruthenium aryldiazenido monocationic complex [Cp′RuCl(PPh₃)(N₂C₆H ₄OMe)][BF₄] [Cp′ = Cp (5) or Cp* (6)]. Further, if the reaction of Cp*Ru(PPh₃)₂Cl with diazonium salt is carried out in acetone, the binuclear complex [Cp*RuCl(N₂C₆H₄OMe)]₂[Cl] ₂ (7) can be isolated in low yield in addition to 6. All new complexes 1-7 were fully characterized by NMR, FT-IR, and mass spectroscopies. The structure of [CpRu(PPh₃)₂(N₂C₆H ₄OMe)][BF₄]₂·0.93CHCl₃ (1· 0.93CHCl₃) was determined by single-crystal X-ray diffraction. The structure exhibits a near-linear Ru-N-N-C geometry for the coordinated aryldiazenido group, with the NNC angle having a value of 159°, compared to the sp² value of approximately 120° commonly exhibited by other singly bent aryldiazenido complexes. On the basis of NMR spectroscopic data, 1 reacts with NaBH₄ at low temperature to give an arylhydrazido(2-) complex [CpRu(PPh₃)₂-{NN(H)C₆H₄OMe}][BF ₄], which readily converts to the corresponding aryldiazene complex [CpRu(PPh₃)₂(NH=NC₆H₄OMe)][BF ₄] by a hydrogen shift; at room temperature, the only product is the hydrido complex CpRuH(PPh₃)₂.

Full text of DOI:10.1021/om990761e

684
Organometallics 2000, 19, 684-694
Ru th en iu m Cyclop en ta d ien yl Ar yld ia zen id o Com p lexes.
Syn th esis of [Cp ′Ru (P R3)2(N2C6H4OMe)][BF 4]2 a n d
[Cp ′Ru Cl(P P h 3)(N2C6H4OMe)][BF 4] (Cp ′ ) Cp , Cp *) a n d
X-r a y Cr ysta l Str u ctu r e of
[Cp Ru (P P h 3)2(N2C6H4OMe)][BF 4]2, a n Ar yld ia zen id o
Com p lex w ith a La r ge N-N-C(a r yl) An gle a n d
Nea r -Lin ea r Ru -N-N-C(a r yl) Sk eleton
Li Fan, Frederick W. B. Einstein, and Derek Sutton*
Department of Chemistry, Simon Fraser University, Burnaby,
British Columbia, Canada V5A 1S6
Received September 28, 1999
The neutral ruthenium complexes Cp′Ru(PR3)2Cl [Cp′ ) Cp, PR3 ) PPh3, PMe3, or 1/2
dppe; Cp′ ) Cp*, PR3 ) PMe3] react with [p-MeOC6H4N2][BF4] in acetone to give new
cyclopentadienyl ruthenium aryldiazenido dicationic complexes [Cp′Ru(PR3)2(N2C6H4OMe)]-
[BF4]2 [Cp′ ) Cp, PR3 ) PPh3 (1), PMe3 (2), or 1/2 dppe (3); Cp′ ) Cp*, PR3 ) PMe3 (4)] in
good yields. The dicationic complexes 1-3 may also be conveniently isolated in better yield
by treatment of the acetonitrile ruthenium complexes [CpRu(PR3)2(NCMe)][BF4] with the
arenediazonium salt. When the reaction of Cp′Ru(PPh3)2Cl (Cp′ ) Cp or Cp*) with
[p-MeOC6H4N2][BF4] is carried out in toluene, the product is instead the cyclopentadienyl
ruthenium aryldiazenido monocationic complex [Cp′RuCl(PPh3)(N2C6H4OMe)][BF4] [Cp′ )
Cp (5) or Cp* (6)]. Further, if the reaction of Cp*Ru(PPh3)2Cl with diazonium salt is carried
out in acetone, the binuclear complex [Cp*RuCl(N2C6H4OMe)]2[Cl]2 (7) can be isolated in
low yield in addition to 6. All new complexes 1-7 were fully characterized by NMR, FT-IR,
and mass spectroscopies. The structure of [CpRu(PPh3)2(N2C6H4OMe)][BF4]2‚0.93CHCl3 (1‚
0.93CHCl3) was determined by single-crystal X-ray diffraction. The structure exhibits a near-
linear Ru-N-N-C geometry for the coordinated aryldiazenido group, with the NNC angle
having a value of 159°, compared to the “sp2” value of approximately 120° commonly exhibited
by other “singly bent” aryldiazenido complexes. On the basis of NMR spectroscopic data, 1
reacts with NaBH4 at low temperature to give an arylhydrazido(2-) complex [CpRu(PPh3)2-
{NN(H)C6H4OMe}][BF4], which readily converts to the corresponding aryldiazene complex
[CpRu(PPh3)2(NHdNC6H4OMe)][BF4] by a hydrogen shift; at room temperature, the only
product is the hydrido complex CpRuH(PPh3)2.
In tr od u ction
ligands PR3.4,9 The rhenium complex [Cp*Re(PMe3)2(p-
N2C6H4OMe)]+ has been shown to be dynamic on the
NMR time scale, with the singly bent aryldiazenido
ligand undergoing inversion or rotation at the carbon-
bound nitrogen atom Nâ, resulting in exchange of the
inequivalent PMe3 ligands.4 By contrast, the corre-
sponding iridium complex of similar formula, [Cp*Ir-
(PMe3)2(p-N2C6H4OMe)]+, exhibits a doubly bent aryl-
diazenido ligand, as expected from the difference in
electron-donating properties of these ligands (a doubly
bent neutral N2Ar ligand is a formal one-electron donor,
while the neutral singly bent ligand is a formal three-
electron donor).9 While these Cp* complexes with two
PMe3 ligands could be synthesized, corresponding ones
with two triphenylphosphine ligands could not be. This
is undoubtedly due to the steric congestion afforded by
the presence of bulky Cp* and PPh3 ligands. To further
explore the relationship between compounds of this
type, we have now turned our attention to the metals
of the intervening group 8, in the present case specifi-
The syntheses, structures, dynamic behavior, and
reactions of cyclopentadienyl and pentamethylcyclopen-
tadienyl aryldiazenido complexes of selected metals of
group 7 (i.e., Mn and Re)1-5 and group 9 (i.e., Ir)6-9 have
been studied in detail in our laboratory. Our recent
interest has involved ones with triorganophosphine
(1) Barrientos-Penna, C. F.; Klahn-Oliva, A. H.; Sutton, D. Orga-
nometallics 1985, 4, 367.
(2) Garcia-Minsal, A.; Sutton, D. Organometallics 1996, 15, 332.
(3) Cusanelli, A.; Sutton, D. Organometallics 1995, 14, 4651.
(4) Cusanelli, A.; Batchelor, R. J .; Einstein, F. W. B.; Sutton, D.
Organometallics 1994, 13, 5096.
(5) Barrientos-Penna, C. F.; Einstein, F. W. B.; Sutton, D.; Willis,
A. C. Inorg. Chem. 1980, 19, 2740.
(6) Yan, X.; Batchelor, R. J .; Einstein, F. W. B.; Zhang, X.;
Nagelkerke, R.; Sutton, D. Inorg. Chem. 1997, 36, 1237.
(7) Yan, X.; Batchelor, R. J .; Einstein, F. W. B.; Sutton, D. Inorg.
Chem. 1996, 35, 7818.
(8) Yan, X.; Einstein, F. W. B.; Sutton, D. Can. J . Chem. 1995, 73,
939.
(9) Kim, G. C.-Y.; Batchelor, R. J .; Yan, X.; Einstein, F. W. B.;
Sutton, D. Inorg. Chem. 1995, 34, 6163.
10.1021/om990761e CCC: $19.00 © 2000 American Chemical Society
Publication on Web 01/21/2000

Ru Cyclopentadienyl Aryldiazenido Complexes
Organometallics, Vol. 19, No. 4, 2000 685
at 10% V and a cesium ion beam accelerated at 12 keV. The
sample matrix was m-nitrobenzyl alcohol. FAB mass spectra
were obtained by G. Owen at SFU using a Hewlett-Packard
model 5985 GCMS instrument with a fast atom bombardment
probe (xenon source, Phrasor Scientific, Inc., accessory) for
samples dispersed in m-nitrobenzyl alcohol. Masses quoted
correspond to the most intense peak in the observed or
calculated isotopic pattern. Microanalyses were performed by
M. K. Yang of the Microanalytical Laboratory of Simon Fraser
University.
Ch a r t 1
The p-methoxybenzenediazonium tetrafluoroborate was
prepared by the standard procedure using p-methoxyaniline
(Aldrich) and sodium nitrite and was purified before use by
recrystallization from acetone and diethyl ether. The diazo-
nium salt substituted with 15N at the terminal nitrogen atom
(NR) was prepared by using Na15NO2 (95% 15N, MSD Isotopes)
and was employed for the synthesis of 15N-labeled compounds.
The starting complexes CpRu(PR3)2Cl [PR3 ) PPh3,17,18 PMe3,19,20
or 1/2 dppe20] and Cp*Ru(PR3)2Cl [R ) Ph or Me]20 were
synthesized according to the literature.
[CpRu (P P h 3)2(NCMe)][BF4]. This was prepared by slightly
modifying the literature procedure given for the PF6 salt.20,21
CpRu(PPh3)2Cl (1) (0.30 g, 0.41 mmol) and NaBF4 (0.10 g, 0.91
mmol) were dissolved in acetonitrile (20 mL) and refluxed for
10 h. The solvent was removed in a vacuum, and the residue
was extracted with dichloromethane (15 mL). Addition of
diethyl ether (30 mL) precipitated a yellow solid, which was
recrystallized from acetone/diethyl ether (1:5) to give [CpRu-
(PPh3)2(NCMe)][BF4] as yellow crystals in 95% yield (0.32 g).
IR (KBr): ν(CN) 2280 (w) cm-1, ν(BF4) 1051 (s) cm-1. 1H NMR
(CDCl3): δ 2.28 (br, 3H, NCMe), 4.50 (s, 5H, Cp), 7.00-7.60
(m, 30H, PPh3). 31P{H} NMR (acetone-d6): δ 43.68. 13C{H}
NMR (acetone-d6): δ 4.4 (NCMe), 84.2 (Cp), 129.2, 130.9, 132.7,
134.3 (PPh3), 136.8 (t, NCMe, J C-P ) 22 Hz). LSIMS-MS (m/
z): 691 [M(cation) - NCMe]+, 429 [M(cation) - NCMe -
PPh3]+. Anal. Calcd for C43H38BNP2F4Ru: C, 63.08; H, 4.65;
N, 1.71. Found: C, 63.13; H, 4.54; N, 1.75. [Cp Ru (P Me3)2-
(NCMe)][BF 4] and [Cp Ru (d p p e)(NCMe)][BF 4] have been
reported previously19,20 and were synthesized by a similar
procedure.
cally ruthenium. Although workers in this field had an
early interest in the aryldiazenido complexes of ruthe-
nium,10-16 it seems that cyclopentadienyl derivatives
have been overlooked. One obvious question posed by
the previous Re and Ir chemistry is whether one could
successfully synthesize mononuclear complexes of simi-
lar composition, namely, [Cp′Ru(PR3)2(p-N2C6H4OMe)]n+
(where Cp′ ) Cp or Cp*). For n ) 2 the complex would
presumably possess a singly bent N2Ar ligand, but the
neutral complex would have the ligand doubly bent. In
this paper we report the successful synthesis of some
examples of the dicationic complex and characterization
of the stereochemistry of the N2Ar ligand. Also reported
are some examples of the monocationic aryldiazenido
complexes [Cp′RuCl(PR3)(N2Ar)]+ and a binuclear com-
plex formulated to be [Cp*RuCl(N2C6H4OMe)]2[Cl]2.
These new compounds are shown in Chart 1.
[CpRu (P P h 3)2(N2C6H4OMe)][BF4]2 (1) an d [CpRu (P P h 3)2-
(
15NNC6H4OMe)] [BF 4]2 (1-15Nr). Meth od 1. F r om Cp Ru -
(P P h 3)2Cl. Twice the stoichiometric amount of [p-MeOC6H4N2]-
[BF4] or [p-MeOC6H4N15N][BF4] (60 mg, 0.27 mmol) was added
as a solid to a stirred suspension of CpRu(PPh3)2Cl (100 mg,
0.14 mmol) in acetone (10 mL). The mixture was heated to 40
°C for 3 h. The color of the solution changed gradually from
orange to red. The volume was reduced to 5 mL, and diethyl
ether (15 mL) was added to give a red oil. After recrystalliza-
tion twice from acetone/diethyl ether (1:5), [CpRu(PPh3)2-
(N2C6H4OMe)][BF4]2 (1) or [CpRu(PPh3)2(15NNC6H4OMe)]-
[BF4]2 (1-15NR) was obtained as a red solid in 73% yield (100
mg). IR (KBr): ν(NN) 2074 cm-1; ν(15NN) 2044 cm-1. 1H NMR
(acetone-d6): δ 4.00 (s, 3H, OMe), 5.93 (s, 5H, Cp), 7.16 (d, 2H
C6H4), 7.60 (d, 2H, C6H4), 7.22-7.62 (m, 30H, PPh3). 31P{H}
Exp er im en ta l Section
All manipulations were carried out under an atmosphere
of nitrogen using standard Schlenk techniques. Solvents were
dried over the appropriate reagents and distilled under
nitrogen prior to use. Some of the routine 1H NMR spectra
were recorded at 100 MHz by using a Bruker SY-100 spec-
trometer. The remaining 1H, 31P{H}, 13C{H}, and 15N NMR
spectra were obtained by M. M. Tracey in the NMR service of
Simon Fraser University on a Bruker AMX-400 instrument.
15N NMR chemical shifts are reported with reference to
nitromethane. IR data were recorded on a Bomem Michelson
model 120 FT-IR instrument. Liquid secondary ion mass
spectra (LSIMS) were obtained courtesy of D. McGillivray of
the MS service at the University of Victoria, Victoria, British
Columbia, using a Kratos Concept H double-focusing mass
spectrometer at 8 keV accelerating voltage. Scan conditions
were 20-2600 amu at 8 s/d using a resolving power of 2000
15
NMR (acetone-d6): δ 34.07 (s, PPh3, or d, PPh3, J P- ) 4.5
N
Hz). 13C{H} NMR (acetone-d6): δ 56.7 (OMe), 96.6 (Cp), 97.4,
117.0, 130.8, 166.5 (C6H4), 113.9, 129.8-133.2 (m, PPh3). 15N
NMR (acetone-d6): δ -64.52 (br, 15NR). LSIMS: (m/z) 913 [M
- BF4-]+, 826 (v. weak) [M - BF4 - BF4]+, 691 [CpRu-
-
(PPh3)2]+, 429 [CpRu(PPh3)]+. Anal. Calcd for C48H42B2N2P2-
OF8Ru: C, 57.66; H, 4.20; N; 2.80. Found: C, 57.40; H, 4.25;
N, 2.98.
(10) McCleverty, J . A.; Whiteley, R. N. J . Chem. Soc., Chem.
Commun. 1971, 1159.
(11) McCleverty, J . A.; Seddon, D.; Whiteley, R. N. J . Chem. Soc.,
Dalton Trans. 1975, 839.
(12) McArdle, J . V.; Schultz, A. J .; Corden, B.; Eisenberg, R. Inorg.
Chem. 1973, 12, 1676.
(13) Haymore, B. L.; Ibers, J . A. Inorg. Chem. 1975, 14, 3060.
(14) Haymore, B. L.; Ibers, J . A. Inorg. Chem. 1975, 14, 2784.
(15) Laing, K. R.; Robinson, S. D.; Uttley, M. F. J . Chem. Soc., Chem.
Commun. 1973, 176.
(17) Bruce, M. I.; Hameister, C.; Swincer, A. G.; Wallis, R. C. Inorg.
Synth. 1990, 28, 270.
(18) Bruce, M. I.; Windsor, N. J . Aust. J . Chem. 1977, 30, 1601.
(19) Treichel, P. M.; Komar, D. A. Synth. React. Inorg. Met.-Org.
Chem. 1980, 10, 205.
(20) Treichel, P. M.; Komar, D. A.; Vincenti, P. J . Synth. React. Inorg.
Met.-Org. Chem. 1984, 14, 383.
(16) Laing, K. R.; Robinson, S. D.; Uttley, M. F. J . Chem. Soc., Dalton
Trans. 1973, 2713.
(21) Blackmore, T.; Bruce, M. I.; Stone, F. G. A. J . Chem. Soc. A.
1971, 2377.

686 Organometallics, Vol. 19, No. 4, 2000
Fan et al.
Meth od 2. F r om [Cp Ru (P P h 3)2(NCMe)][BF 4]. The sto-
ichiometric amount of solid [p-MeOC6H4N2][BF4] (15 mg, 0.068
mmol) was added to a solution of [CpRu(PPh3)2(NCMe)][BF4]
(50 mg, 0.06 mmol) in acetone (10 mL). The solution was
refluxed for 5 h. The volume was reduced to 5 mL, and diethyl
ether (15 mL) was added to give a red oil. Crystallization from
acetone/diethyl ether gave red crystals of 1 in 88% yield (53
mg). Anal. Calcd for C48H42B2N2P2OF8Ru: C, 57.66; H, 4.20;
N, 2.80. Found: C, 57.41; H, 4.40; N, 2.70.
Meth od 3. Fr om CpRu (P P h 3)2I. The stoichiometric amount
of solid [p-MeOC6H4N2][BF4] (14 mg, 0.063 mmol) was added
to CpRu(PPh3)2I (50 mg, 0.061 mmol) and NaBF4 (13.5 mg,
0.12 mmol) in acetone (10 mL). The mixture was stirred at
room temperature for 1.5 h. The solvent was removed in a
vacuum, and the residue was extracted with CH2Cl2. Recrys-
tallization from acetone/diethyl ether gave fine orange-red
crystals of 1 in 80% yield (40 mg). Anal. Calcd for C48H42B2N2P2-
OF8Ru: C, 57.66; H, 4.20; N, 2.80. Found: C, 57.90; H, 4.25;
N, 2.61.
[BF4] (55 mg, 0.25 mmol) was dissolved in acetone (5 mL) and
added to a solution of Cp*Ru(PMe3)2Cl (50 mg, 0.12 mmol) in
acetone (10 mL) at -78 °C. The mixture was stirred at -78
°C for 1 h, and an orange-red solid precipitated. The solvent
was removed in a vacuum at 0 °C, and the residue was
recrystallized from acetone/diethyl ether (1:5) to give the
product as an orange-red solid in 89% yield (75 mg). IR
(KBr): ν(NN) 1815 cm-1; ν(15NN) 1780 cm-1. 1H NMR (acetone-
d6): δ 1.99 (virtual doublet, 18H, PMe3, J app ) 10.7 Hz), 2.21
(t, 15H, Cp*, J P-H ) 1.6 Hz), 3.95 (s, 3H, OMe), 7.25 (d, 2H
C6H4), 7.77 (d, 2H C6H4). 31P{H} NMR (acetone-d6): δ 2.52 (s,
PMe3). 13C{H} NMR (acetone-d6): δ 10.8 (Cp*), 18.6 (m, PMe3),
56.8 (OMe), 110.2 (Cp*), 115.0, 118.1, 130.0 166.0 (C6H4). 15N
NMR (acetone-d6): δ -24.32 (s, 15NR). FABMS: m/z 389
[Cp*Ru(PMe3)2]+, 311 [Cp*Ru(PMe3)]+.
[Cp Ru Cl(P P h 3)(N2C6H4OMe)][BF 4] (5) a n d [Cp Ru Cl-
(P P h 3)(15NNC6H4OMe)][BF 4] (5-15NR). Meth od 1. In Tolu -
en e. Twice the stoichiometric amount of solid [p-MeOC6H4N2]-
[BF4] or [p-MeOC6H4N15N][BF4] (38 mg, 0.17 mmol) was added
to a stirred suspension of CpRu(PPh3)2Cl (60 mg, 0.083 mmol)
in toluene (10 mL). The mixture was heated to 40 °C for 3 h.
The solution changed gradually from orange to yellow. The
solvent was removed in a vacuum, and the residue was
extracted with acetone. After recrystallization from acetone/
diethyl ether (1:5) the product was obtained as a greenish solid
in 88% yield (50 mg). IR (KBr): ν(NN) 1794; ν(15NN) 1761
[Cp R u (P Me3)2(N2C6H 4OMe)][BF 4]2 (2) a n d [Cp R u -
(P Me3)2(15NNC6H4OMe)][BF 4]2 (2-15NR). Meth od 1. F r om
Cp Ru (P Me3)2Cl. Twice the stoichiometric amount of [p-Me-
OC6H4N2][BF4] or [p-MeOC6H4N15N][BF4] (65 mg, 0.29 mmol)
was dissolved in acetone (5 mL) and added to the solution of
CpRu(PMe3)2Cl (50 mg, 0.14 mmol) in acetone (10 mL) at -78
°C. The mixture was stirred at -78 °C for 1 h, and the color
changed from yellow to orange-red. The solution was warmed
to 0 °C, and the volume was reduced to 5 mL by vacuum.
Addition of diethyl ether (15 mL) at room temperature gave
the product as an orange solid, which was recrystallized from
acetone/diethyl ether (1:5) to give orange-red crystals in 69%
1
cm-1. H NMR (acetone-d6): δ 3.92 (s, 3H, OMe), 6.14 (d, 5H,
Cp, J P-H ) 0.6 Hz), 7.11 (d, 2H C6H4), 7.39 (d, 2H C6H4), 7.55
(m, 15H, PPh3). 31P{H} NMR (acetone-d6): δ 40.06 (s, PPh3,
or d, PPh3, J P- ) 5.1 Hz). 13C{H} NMR (acetone-d6): δ 56.6
15
N
(OMe), 99.3 (Cp), 117.3, 132.9, 165.0 (C6H4), 129.9-137.1 (m,
15
PPh3). 15N NMR (acetone-d6): δ -18.55 (d, NR, J
) 5.1
yield (60 mg). IR (KBr): ν(NN) 1877 cm-1; ν(15NN) 1832 cm-1
.
15
N-P
Hz). LSIMS: m/z 599 [M(cation)]+, 464 [M(cation) - N2C6H4-
OMe]+, 429 [CpRu(PPh3)]+. Anal. Calcd for C30H27BN2POClF4-
Ru: C, 52.48; H, 3.94; N, 4.08. Found: C, 52.69; H, 3.94; N,
4.40.
1H NMR (acetone-d6): δ 2.07 (virtual doublet, 18H, PMe3, J app
) 11.5 Hz), 3.95 (s, 3H, OMe), 6.39 (s, 5H, Cp), 7.23 (d, 2H
C6H4), 7.84 (d, 2H C6H4). 31P{H} NMR (acetone-d6): δ 10.56
(s, PMe3). 13C{H} NMR (acetone-d6): δ 20.4 (m, PMe3), 56.9
(OMe), 97.2 (Cp), 116.0, 118.0, 130.6 165.7 (C6H4). 15N NMR
(acetone-d6): δ -29.65 (s, 15NR). LSIMS: m/z 541 [M - BF4-]+,
Meth od 2. In Aceton e. The stoichiometric amount of
[p-MeOC6H4N2][BF4] (30 mg, 0.14 mmol) was added to a stirred
suspension of CpRu(PPh3)2Cl (100 mg, 0.14 mmol) in acetone
(10 mL). The mixture was heated to 40 °C for 3 h. The color
changed from orange to red in the first 15 min and then
gradually turned to yellow. The solvent was removed in a
454 [M - BF4 - BF4]+ and 453 [M - BF4 - HBF4]+
(overlapping, v. weak), 319 [CpRu(PMe3)2]+, 243 [CpRu-
(PMe3)]+. Anal. Calcd for C18H30B2N2OP2F8Ru: C, 34.45; H,
4.78; N, 4.47. Found: C, 34.40; H, 4.69; N, 4.47.
-
-
1
Meth od 2. F r om [Cp Ru (P Me3)2(NCMe)][BF 4]. The sto-
ichiometric amount of solid [p-MeOC6H4N2][BF4] (25 mg, 0.11
mmol) was added to a solution of [CpRu(PMe3)2(NCMe)][BF4]
(50 mg, 0.11 mmol) in acetone (10 mL). The solution was
refluxed for 15 h. The volume was reduced to 5 mL, and diethyl
ether (15 mL) was added to give a red oil, which was
crystallized from acetone/diethyl ether to give 2 as a red solid
in 87% yield (60 mg).
vacuum, and a H NMR spectrum on the residue showed that
[CpRuCl(PPh3)(N2C6H4OMe)][BF4] (5) and [CpRu(PPh3)2-
(N2C6H4OMe)][BF4]2 (1) were formed in an approximate 4:1
ratio.
[Cp *Ru Cl(P P h 3)(N2C6H4OMe)][BF 4] (6), [Cp *Ru Cl-
(P P h 3)(15NNC6H4OMe)][BF 4] (6-15NR), [Cp *Ru Cl(N2C6H4-
OMe)]2[Cl]2 (7), a n d [Cp *Ru Cl(15NNC6H4OMe)]2[Cl]2 (7-
15NR). Meth od 1. In Tolu en e. Twice the stoichiometric
amount of solid [p-MeOC6H4N2][BF4] or [p-MeOC6H4N15N]-
[BF4] (55 mg, 0.25 mmol) was added to a stirred suspension
of Cp*Ru(PPh3)2Cl (100 mg, 0.12 mmol) in toluene (10 mL).
The mixture was heated to 40 °C for 3 h, and the solution
changed gradually from orange to yellow. The solvent was
removed in a vacuum, and the residue was extracted with
dichloromethane. After recrystallization from acetone/diethyl
ether (1:5), 6 or 6-15NR was obtained as a greenish-yellow solid
in 78% yield (70 mg). IR (KBr): ν(NN) 1771; ν(15NN) 1736
[CpRu (dppe)(N2C6H4OMe)][BF4]2 (3) an d [CpRu (dppe)-
(
15NNC6H4OMe)][BF 4]2 (3-15NR). Meth od 1. F r om Cp Ru -
(d p p e)Cl. A procedure analogous to that used for 1 gave 3 or
3-15NR as a red solid in 86% yield. IR (KBr): ν(NN) 2066-
1929 (br); ν(15NN) 2038-1900 (br) cm-1 1H NMR (acetone-
.
d6): δ 3.55 (m, 4H, CH2), 3.91 (s, 3H, OMe), 6.01 (s, 5H, Cp),
6.90 (AA′BB′q, 4H, C6H4), 7.60-8.20 (m, 20H, Ph). 31P{H}
NMR (acetone-d6): δ 71.97 (s, dppe). 13C{H} NMR (acetone-
d6): δ 28.6 (t, CH2, J C-P ) 22 Hz), 57.1 (OMe), 96.0 (Cp), 114.7,
117.2, 129.8 166.0 (C6H4), 129.8-134.1 (m, Ph). 15N NMR
(acetone-d6): δ -58.54 (s, 15NR). LSIMS: m/z 787 [M - BF4-]+,
1
cm-1. H NMR (CDCl3): δ 1.66 (d, 15H, Cp*, J P-H ) 1.7 Hz),
3.88 (s, 3H, OMe), 6.91 (d, 2H C6H4), 7.34 (d, 2H C6H4), 7.43
700 [M - BF4 - BF4]+ and 699 [M - BF4 - HBF4]+
-
-
(m, 15H, PPh3). 31P{H} NMR (CDCl3): δ 37.49 (s, PPh3, or d,
(overlapping, v. weak), 565 [Ru(dppe)]+. Anal. Calcd for
PPh3, J P- ) 6.0 Hz). 13C{H} NMR (CDCl3): δ 9.5 (s, Cp*),
15
N
C
38H36B2N2OP2F8Ru: C, 52.23; H, 4.12; N, 3.21. Found: C,
55.9 (OMe), 109.9 (Cp*), 95.1, 116.1, 131.7, 166.8 (C6H4),
124.3-134.8 (m, PPh3). 15N NMR (CDCl3): δ -4.77 (d, 15NR,
52.21; H, 4.20; N, 3.40.
15
J
) 6.0 Hz). LSIMS: m/z 669 [M(cation)]+, 534 [M(cation)
Meth od 2. F r om [Cp Ru (d p p e)(NCMe)][BF 4]. A proce-
dure analogous to that used for 2 gave 3 as a red solid in 79%
yield.
[Cp *Ru (P Me3)2(N2C6H4OMe)][BF 4]2 (4) a n d [Cp *Ru -
(P Me3)2(15NNC6H4OMe)][BF 4]2 (4-15NR). Twice the stoichio-
metric amount of [p-MeOC6H4N2][BF4] or [p-MeOC6H4N15N]-
N-P
- N2C6H4OMe]+, 499 [Cp*Ru(PPh3)]+.
Meth od 2. In Aceton e. The reaction was carried out as
above, but in acetone at 40 °C for 3 h. The solution changed
gradually from orange to yellow. The solvent was removed in
a
vacuum, and the residue was extracted with dichlo-

Ru Cyclopentadienyl Aryldiazenido Complexes
Organometallics, Vol. 19, No. 4, 2000 687
Ta ble 1. Cr ysta llogr a p h ic Da ta for th e Str u ctu r e
aryldiazenido dicationic complex [CpRu(PPh3)2(N2C6H4-
OMe)][BF4]2 (1), formed by replacement of the Cl ligand,
and the new monocationic complex [CpRuCl(PPh3)-
(N2C6H4OMe)][BF4] (5), formed by replacement of a
PPh3 ligand (Scheme 1). The ratio of the dication and
the monocation formed varied with the amount of
diazonium salt added. A stoichiometric amount of di-
azonium salt gave an approximate 1:4 ratio of 1 to 5.
This ratio increased to about 4:1 when more than 2
equiv of the diazonium salt was used. The dicationic
complex 1 can be separated from 5 as a red powder by
three recrystallizations from acetone/diethyl ether. Re-
crystallization from chloroform-diethyl ether gave or-
ange crystals suitable for X-ray structure analysis. The
dicationic complex [CpRu(PPh3)2(N2C6H4OMe)][BF4]2 (1)
is more conveniently formed by replacement of the
MeCN ligand in [CpRu(PPh3)2(NCMe)][BF4] with a
stoichiometric amount of the diazonium salt in acetone.
In this case, only 1 is formed and is isolated as orange
crystals in high yield (∼90%). Thus, this is a preferred
method for the preparation of the dication, although it
takes a longer time to complete the reaction. The
reaction of CpRu(PPh3)2Cl with diazonium salt was also
carried out in other solvents, such as methanol, CH2-
Cl2, or THF, but neither 1 nor 5 appeared to be formed,
and only a mixture of unidentified products was ob-
served, so it seems that acetone is the ideal solvent for
the preparation of these dicationic complexes from
CpRu(PR3)2Cl.
Deter m in a tion of 1‚0.93CHCl3
formula
fw
RuP2F8ON2C48.93B2H42.93Cl2.78
1104.5
cryst syst
space group
cell dimens
triclinic
P1h
a 10.5910(10) Å
b 13.2210(10) Å
c 18.8130(15) Å
R 100.121(8)°
â 100.126(8)°
γ 105.461(8)°
2414.9(4) Å3
2
V
Z
F(000)
1122.14
cryst dimens (mm)
0.42 × 0.20 × 0.16
D
calc (g cm-3
)
1.527
µ (mm-1
)
0.45
0.70930
54.0
0.041
λ (Mo KR) (Å)
2ϑ(max) (Mo KR)
RF
RwF
0.046
diffractometer
no. reflns measd
no. unique reflns
no. reflns with
Nonius CCD
35 189
8606
7601
Inet > 2.5σ(Inet
)
romethane. After recrystallization from acetone/diethyl ether,
[Cp*RuCl(PPh3)(N2C6H4OMe)][BF4] (6) or [Cp*RuCl(PPh3)(15N-
NC6H4OMe)][BF4] (6-15NR) was obtained as a greenish-yellow
solid in 67% yield. The mother liquid was kept at -4 °C for a
week, and [Cp*RuCl(N2C6H4OMe)]2[Cl]2 (7) or [Cp*RuCl-
(15NNC6H4OMe)]2[Cl]2 (7-15NR) was obtained as a black solid
in ca. 10% yield. Data for 7 IR (KBr): ν(NN) 1753; ν(15NN)
Complex 1 has been fully characterized by elemental
analysis, spectroscopy, and an X-ray structure. The IR
spectrum of 1 displays the expected absorption for the
organic and BF4 groups, and ν(NN) appears as a broad
moderately strong absorption at 2074 cm-1. The assign-
ment of ν(NN) was confirmed by 15N isotopic substitu-
tion at NR of the diazenido ligand. A shift of this
absorption to lower wavenumber by 30 cm-1 was
1722 cm-1 1H NMR (CDCl3): δ 1.74 (s, 15H, Cp*), 3.88 (s,
.
3H, OMe), 6.91 (d, 2H C6H4), 7.60 (d, 2H C6H4). 15N NMR
(CDCl3): -24.67 (s, 15NR,). LSIMS: m/z 851 [M - Cl]+, 714 [M
- Cl - N2C6H4OMe]+, 579 [Cp*RuCl2(N2C6H4OMe)2]+, 407
[Cp*RuCl(N2C6H4OMe)]+, 379 [Cp*RuCl(C6H4OMe)]+.
X-r ay Cr ystal Str u ctu r e Deter m in ation for 1‚0.93CHCl3.
Crystals were grown from chloroform-diethyl ether. A sum-
mary of the crystallographic data is given in Table 1. Complete
details of the crystal data, X-ray data collection, and structure
solution are provided as Supporting Information.
1
observed. In the H NMR spectrum, a singlet at δ 5.93
was observed for the Cp ligand, rather than the triplet
expected if the Cp protons are observably coupled to the
two equivalent phosphorus ligands. Similarly, a singlet
at δ 96.6 ppm was also observed for the Cp ligand in
the 13C{H} NMR spectrum. The 31P{H} NMR spectrum
displayed a singlet resonance at room temperature and
at -80 °C, in the normal region for a coordinated
phosphine, and indicated the two triphenylphosphines
to be equivalent on the NMR time scale at these
temperatures. However, in the 31P{H} NMR of 1-15NR
Rea ction of [Cp Ru (P P h 3)2(N2C6H4OMe)][BF 4]2 (1) w ith
Na BH4. (a ) At 0 °C. NaBH4 (25 mg, 0.63 mmol) was added to
a solution of 1 (30 mg, 0.030 mmol) in acetone (20 mL) at 0 °C
and stirred for 15 min. The mixture was allowed to reach room
temperature and stirred for 2 h. The solvent was removed in
a vacuum, and the residue was extracted with diethyl ether.
Addition of hexane (30 mL) precipitated yellow CpRu(PPh3)2H
in 43% yield (9 mg).22 1H NMR (C6D6): δ -11.61 (t, 1H, J P-H
) 32 Hz), 4.56 (s, 5H, Cp), 7.0-7.5 (m, 30H, Ph).
(b) At -90 °C. A solution of [CpRu(PPh3)2(15NNC6H4OMe)]-
[BF4]2 (1-15NR, 20 mg, 0.020 mmol) in acetone-d6 (1 mL) was
transferred by syringe into a 5 mm NMR tube at -80 °C which
contained NaBH4 (0.76 mg, 0.020 mmol). The NMR tube was
then placed immediately in the NMR instrument probe, which
had been cooled to -90 °C. The 1H, 31P{H}, and 15N NMR
spectra were recorded from -90 to -60 °C.
15
the resonance was a doublet at δ 34.1 (J P- ) 4.5 Hz),
N
resulting from coupling with NR. The 15N NMR spec-
trum of 1-15NR showed a broad singlet resonance at δ
-64.52 ppm, which is in the typical chemical shift range
for a singly bent aryldiazenido ligand.23 Signals due to
the singly charged ion pair resulting from loss of one
-
BF4 anion and the fragments formed by further loss
Resu lts
of the aryldiazenido ligand and one of the phosphines
were observed in the LSIMS spectrum.
1. Syn th esis a n d Ch a r a cter iza tion of Dica tion ic
Com p lexes [Cp Ru (P R3)2(N2C6H4OMe)][BF 4]2 (R )
P h (1), Me (2); P R3 ) 1/2 d p p e (3)) a n d [Cp *Ru -
(P Me3)2(N2C6H4OMe)][BF 4]2 (4). Reaction of CpRu-
(PPh3)2Cl with [p-MeOC6H4N2][BF4] in acetone at 40 °C
for 3 h gave a mixture of the new singly bent ruthenium
Reaction of Cp′Ru(PMe3)2Cl (Cp′ ) Cp or Cp*) with 2
equiv of diazonium salt in acetone at -78 °C gave the
dicationic complexes [Cp′Ru(PMe3)2(N2C6H4OMe)][BF4]2
[Cp′ ) Cp (2) or Cp* (4)] (Scheme 2). It should be noted
that the reaction temperature is crucial to successfully
(22) Bruce, M. I.; Humphrey, M. G.; Swincer, A. G.; Wallis, R. C.
Aust. J . Chem. 1984, 37, 1747.
(23) Haymore, B. L.; Hughes, M.; Mason, J .; Richards, R. L. J . Chem.
Soc., Dalton Trans. 1988, 2935.

688 Organometallics, Vol. 19, No. 4, 2000
Fan et al.
Sch em e 1
Sch em e 2
synthesizing 2 and 4. During the reaction, an orange
solid precipitates at -78 °C, but as the temperature is
allowed to rise, this redissolves, and the solution ap-
pears to slowly decompose (it becomes purple) when left
too long at room temperature. The isolation and crystal-
lization of the product can be successfully achieved at
room temperature, if carried out quickly, but only 2
yielded a satisfactory CHN analysis. However, 2 can
also be easily prepared from the reaction of [CpRu-
(PMe3)2(NCMe)][BF4] with diazonium salt in acetone at
refluxing temperature for 10 h with no difficulty. The
IR spectra of 2 and 4 in KBr disks exhibited a strong
band for ν(NN) at 1877 and 1815 cm-1. Both assign-
ments were confirmed by 15N isotopic substitution at
NR of the aryldiazenido ligand, where significant shifts
to lower wavenumbers were observed for both 2 and 4.
1
In the H NMR spectrum of 2, the Cp resonance is a
singlet, but in the spectrum of 4 the Cp* resonance is a
triplet from coupling to the two equivalent phosphorus
atoms with J H-P ) 1.6 Hz. The resonances assigned to
the PMe3 ligands were observed to be virtual (filled-in)
doublets. The apparent coupling constant J app ) (2J H-P
+
4J H-P), given by the separation between the two
outside peaks, was 11.5 Hz in 2 and 10.7 Hz in 4. The
31P{H} NMR spectra of 2 and 4 displayed a singlet
resonance at room temperature and at -90 °C, indicat-

Ru Cyclopentadienyl Aryldiazenido Complexes
Organometallics, Vol. 19, No. 4, 2000 689
Sch em e 3
ing the phosphine ligands to remain equivalent over this
temperature range. The 15N NMR spectrum showed a
singlet resonance at δ -29.6 for 2 and δ -24.3 for 4, so
these compounds showed no observable 31P-15N cou-
pling in either the 15N or the 31P{H} NMR spectra. The
LSIMS or FABMS spectra of 2 and 4 showed fragmen-
tation patterns analogous to those observed for 1.
The reaction of CpRu(dppe)Cl with 2 equiv of the
diazonium salt in acetone gave [CpRu(dppe)(N2C6H4-
OMe)][BF4]2 (3) as a red powder. There was no evidence
of formation of the possible monocationic complex
[CpRuCl(dppe)(N2C6H4OMe)][BF4], which, if analogous
to 5, would necessitate a monodentate (dangling) dppe.
Again, the dicationic complex can also be isolated in
good yield from the reaction of [CpRu(dppe)(NCMe)]-
[BF4] with the diazonium salt in acetone at refluxing
temperature (Scheme 3). The IR spectrum of 3 displays
monocationic complex 5 was formed. Recrystallization
from acetone and diethyl ether gave 5 as yellow-green
crystals in high yield. Similarly, Cp*Ru(PPh3)2Cl re-
acted with a stoichiometric amount of diazonium salt
in toluene at 40 °C to give the monocationic complex
[Cp*RuCl(PPh3)(N2C6H4OMe)][BF4] (6), which was iso-
lated as a yellow-green powder. When this reaction was
carried out in acetone, 6 was again the major product,
but now a minor product (<10%) could also be isolated,
which was formulated on the basis of spectroscopy and
elemental analysis as the binuclear aryldiazenido com-
plex [Cp*RuCl(N2C6H4OMe)]2[Cl]2 (7) (Scheme 4). No-
tably, by comparison with the corresponding reactions
in acetone for all the other cases just described, no
formation of any corresponding dicationic complex
[Cp*Ru(PPh3)2(N2C6H4OMe)][BF4]2 could be detected by
1H NMR spectroscopy.
ν(NN) as a very broad absorption at 2066-1929 cm-1
,
For the monocationic complexes [Cp′RuCl(PPh3)-
(N2C6H4OMe)][BF4] (5, 6), the IR spectra display the
expected absorption for the organic and BF4 groups and
a broad absorption at 1794 cm-1 (KBr disk) for 5 and
1771 cm-1 for 6, which fall within the range generally
associated with ν(NN) for a terminally coordinated
singly bent aryldiazenido ligand. The assignment was
confirmed by using their 15NR isotopomers, which showed
a shift to lower wavenumber by ∼35 cm-1. In the 1H
NMR spectra of the monocationic complexes [Cp′RuCl-
(PPh3)(N2C6H4OMe)][BF4], the Cp or Cp* resonances
were in both cases phosphorus-coupled doublets with
J P-H ) 0.6 Hz for 5 and 1.7 Hz for 6. The 13C{1H} NMR
spectrum shows a singlet resonances for the Cp in 5 or
the Cp* in 6 and no coupling of these carbons to
phosphorus. The 31P{H} NMR spectra of 5 or 6 dis-
played a singlet resonance at room temperature in the
normal region for a coordinated phosphine. However,
which is lower than that in 1. The assignment of ν(NN)
was confirmed by 15N isotopic substitution at NR, which
gave a shift to lower wavenumber by 28 cm-1. In the
1H NMR spectrum of 3, the Cp resonance occurred as a
singlet, with no observable coupling to phosphorus, and
the 31P{H} NMR spectrum gave a singlet resonance at
room temperature, indicating the NMR equivalence of
the two phosphorus atoms at this temperature, consis-
tent with bidentate coordination of the dppe ligand. The
15N NMR spectrum of 3-15NR showed a singlet resonance
at δ -58.54 and the absence of observable 31P-15N
coupling.
Syn th esis a n d Ch a r a cter iza tion of Mon oca tion ic
Com plexes [Cp ′Ru Cl(P P h 3)(N2C6H4OMe)][BF4] (Cp′
) Cp or Cp *). As stated above, the reaction of CpRu-
(PPh3)2Cl with a stoichiometric amount of diazonium
salt in acetone gave a mixture of the monocationic
complex [CpRuCl(PPh3)(N2C6H4OMe)][BF4] (5) and the
dicationic complex [CpRu(PPh3)2(N2C6H4OMe)][BF4]2 (1)
in an approximate 4:1 ratio. It is very difficult to
separate and isolate the monocation from the dication
analytically pure by recrystallizations. However, when
the reaction was conducted in toluene at 40 °C, only the
for the 15N-substituted compounds, the resonances in
15
the 31P{H} and
N NMR spectra were doublets with
J P-N ) 5.1 Hz for 5 and 6.0 Hz for 6. The LSIMS spectra
of 5 and 6 exhibited very strong patterns for [M-
(cation)]+, and fragments formed by loss of the aryl-
diazenido ligand and then chlorine are observable.

690 Organometallics, Vol. 19, No. 4, 2000
Fan et al.
Sch em e 4
In the IR spectrum of the binuclear complex [Cp*RuCl-
(N2C6H4OMe)]2[Cl]2 (7), ν(NN) appeared as a broad
moderately intense absorption at 1753 cm-1, which
indicates that the two aryldiazenide ligands are coor-
dinated to ruthenium as terminal ligands with a singly
represent the legs. The Cp ligand is bonded to the
ruthenium in the typical η5 coordination mode. The N2-
Ar ligand is “singly bent”, that is to say the Ru-N-N
part is essentially linear (angle 175.4°) and the N-N-
C(aryl) part is bent (angle 158.9°). However, this latter
angle is so large that the aryldiazenide ligand adopts
almost a linear coordination to ruthenium in this
structure. The plane of the aryldiazenide ligand makes
an angle of 35.2° with the Cp plane. Thus, there is no
plane of symmetry in the dication, and the two phos-
phine ligands are strictly inequivalent. The bond dis-
tances and angles of interest for the dication are listed
in Table 2.
1
bent geometry. The H NMR spectrum of 7 showed a
single peak at δ 1.74 for Cp* protons and a typical
AA′BB′ pattern at δ 6.90-7.60 for the aromatic hydro-
gens of the diazonium ligand. Microanalysis for C, H,
and N suggested the empirical formula Cp*Ru(N2C6H4-
OMe)Cl2. However, LSIMS showed a highest mass peak
at m/z 851 with an isotopic pattern matching that
calculated for a dinuclear species [Cp*2Ru2(N2C6H4-
OMe)2Cl3]+. It is difficult to formulate this as a discrete
cation without violating the 18-electron rule. However,
formulation as a dichloro-bridged ion pair [Cp*2Ru2(N2-
C6H4OMe)2Cl2]2+Cl- presents no such problem. This
suggests that 7 should be formulated as the dinuclear
complex [Cp*2Ru2(N2C6H4OMe)2Cl2][Cl]2. The LSIMS
showed a fragment at m/z ca. 714-716 corresponding
to further loss of N2C6H4OMe or Cp*, which are not
distinguishable at this resolution. The fragment at m/z
ca. 579 did not exhibit the correct pattern for [Cp*2Ru2-
Cl3]+ (calcd 581) but approximately matched [Cp*Ru-
(N2C6H4OMe)2Cl2]+ or [Cp*2Ru(N2C6H4OMe)Cl2]+ (calcd
577). The patterns observed at m/z 407 and 379 closely
matched the theoretical patterns for mononuclear frag-
ments [Cp*RuCl(N2C6H4OMe)]+ (or [Cp*2RuCl]+) and
[Cp*RuCl(C6H4OMe)]+, respectively. A dinuclear ruthe-
nium aryldiazenido complex and a polynuclear complex
given the formulas [Ru2Cl3(PPh3)3(N2Ar)2][PF6] and
[RuCl2(PPh3)(N2Ar)]n[PF6]n have been reported previ-
ously.11 All the new ruthenium diazenido complexes are
air-sensitive in solution but air-stable in the solid state.
They are insoluble in hexane and diethyl ether, slightly
soluble in acetone and chloroform, and very soluble in
acetonitrile and nitromethane.
4. Reaction s of [CpRu (P P h 3)2(N2C6H4OMe)][BF4]2
(1). [CpRu(PPh3)2(N2C6H4OMe)][BF4]2 reacted with an
excess of NaBH4 in acetone at 0 °C to give the known
ruthenium hydride CpRuH(PPh3)2 in 50% yield. When
this reaction was carried out at -78 °C, CpRuH(PPh3)2
was isolated in lower yield (∼20%). The low-temperature
1
reaction was monitored by H, 31P{H}, and 15N NMR
spectroscopy. The 1H NMR spectrum at -80 °C in
acetone-d6 showed the expected triplet at δ 11.62 and
singlet at δ 4.50 for the hydride and Cp protons of the
hydrido complex,22 but also a weak peak at δ 15.9, which
may be assigned to N-H in an aryldiazene complex,
presumably [CpRu(PPh3)2(NHdNC6H4OMe)][BF4].3,24
To confirm the assignment, the reaction was repeated
1
using 1-15NR. In this case the H NMR spectrum was
recorded more immediately at -80 °C and showed a
15N-H
doublet at δ 15.79 with J
) 67 Hz, confirming the
assignment, but now there was observed an additional
singlet of comparable intensity at δ 16.65, which exhib-
ited irreversible temperature-dependent behavior (see
below and Figure 2) that suggested it should be assigned
to the corresponding arylhydrazido(2-) complex [CpRu-
(PPh3)2{15NN(H)C6H4OMe}][BF4].25-27 Thus, spectra
recorded 25 min and 1 h later at -80 °C showed a
3. Cr ysta l Str u ctu r e of [Cp Ru (P P h 3)2(N2C6H4-
OMe)][BF 4]2‚0.93CHCl3 (1‚0.93CHCl3). The structure
of the dicationic complex 1 was confirmed by an X-ray
structural study. The geometry of the dication is shown
in Figure 1 and can be described as a three-legged piano-
stool structure where the N2Ar and two PPh3 ligands
(24) Barrientos-Penna, C. F.; Einstein, F. W. B.; J ones, T.; Sutton,
D. Inorg. Chem. 1982, 21, 2578.
(25) Carroll, J . A.; Sutton, D. Inorg. Chem. 1980, 19, 3137.
(26) Einstein, F. W. B.; J ones, T.; Hanlan, A. J . L.; Sutton, D. Inorg.
Chem. 1982, 21, 2585.
(27) Dilworth, J . R.; Harrison, S. A.; Walton, D. R. M.; Schweda, E.
Inorg. Chem. 1985, 24, 2594.

Ru Cyclopentadienyl Aryldiazenido Complexes
Organometallics, Vol. 19, No. 4, 2000 691
F igu r e 1. View of the cation [CpRu(PPh3)2(N2C6H4-
OMe)]2+ of 1‚0.93CHCl3. Phenyl rings of PPh3 groups have
been omitted for clarity.
Ta ble 2. Selected Bon d Len gth s (Å) a n d In ter bon d
An gles (d eg) for 1‚0.93CHCl3
Ru1-P1
Ru1-P2
Ru1-N1
Ru1-C1
Ru1-C2
Ru1-C3
Ru1-C4
Ru1-C5
N1-N2
2.4088(10)
2.3676(10)
1.8561(23)
2.225(3)
2.257(3)
2.259(4)
2.246(4)
2.243(4)
1.146(3)
N2-C10
C10-C20
C10-C60
C20-C30
C30-C40
C40-C50
C50-C60
O1-C40
O1-C70
1.390(4)
1.389(5)
1.376(6)
1.376(5)
1.387(6)
1.392(5)
1.383(5)
1.352(4)
1.439(6)
F igu r e 2. Variable-temperature 1H NMR in the NH region
for the low-temperature reaction of 1-15NR with NaBH4. The
singlet at δ 16.65 is assigned to the unlabeled NH group
of the arylhydrazido(2-) complex [CpRu(PPh3)2{15NN(H)-
C6H4OMe}][BF4]. The doublet, due to coupling with 15N,
is assigned to the 15NH group of the aryldiazene complex
[CpRu(PPh3)2(15NHdNC6H4OMe)][BF4].
Ru1-N1-N2
P1-Ru1-N1
P1-Ru1-P2
P2-Ru1-N1
N1-N2-C10
O1-C40-C30
O1-C40-C50
175.4(3)
97.02(10)
96.93(3)
90.59(10)
158.9(4)
116.1(3)
122.9(4)
C40-O1-C70
C10-C20-C30
C10-C60-C50
C20-C10-C60
C20-C30-C40
C30-C40-C50
C40-C50-C60
118.3(3)
118.0(4)
119.4(3)
122.4(3)
120.4(3)
121.0(3)
118.8(4)
of synthesizing 1 from CpRu(PPh3)2X and the diazonium
ion. However, the reaction with NaCl afforded the
aryldiazenido monocationic complex [CpRuCl(PPh3)-
(N2C6H4OMe)][BF4] (5) instead of the expected CpRu-
(PPh3)2Cl, so in this case Cl- has substituted a PPh3
group. Since 1 reacted with Cl- or I- in these two
different ways, we were prompted to investigate the
reaction of CpRu(PPh3)2I, instead of the chloride, with
a stoichiometric amount of aryldiazonium salt in the
presence of NaBF4. The dicationic complex [CpRu-
(PPh3)2(N2C6H4OMe)][BF4]2 (1) was isolated, and no
evidence of formation of the corresponding monocationic
complex [CpRuI(PPh3)(N2C6H4OMe)][BF4] was observed,
in contrast to the situation when the chloride, CpRu-
(PPh3)2Cl, is employed.
decrease in the intensity of the singlet relative to the
doublet, and at -70 °C the singlet had disappeared, but
the doublet remained. Similarly, two unequal reso-
nances were initially observed for the cyclopentadienyl
protons assigned to the diazene (δ 4.98) and the hy-
drazido(2-) complex (δ 4.94), and these exhibited
comparable changes. This behavior is consistent with a
transformation of the hydrazido(2-) complex to the
diazene complex by migration of the hydrogen from Nâ
to NR. The 15N NMR recorded on the same sample at
-80 and -70 °C exhibited a doublet at δ -27.1 with
J NH ) 69.8 Hz, which is clearly attributable to the
diazene complex. However, the upfield peak of the
doublet was somewhat more intense, and since no other
resonance could be located for the hydrazido complex,
it is possible that the expected singlet occurs coincident
with this peak. The diazene complex was unstable, and
further NMR spectra indicated complete decomposition
by -60 °C. We were unable to isolate either of the
postulated aryldiazene or arylhydrazido(2-) complexes.
Complex 1 reacted with KX (X ) Br or I) in acetone
to give the known complexes CpRu(PPh3)2X in good
yield. In this reaction, halide substitutes the N2Ar
ligand; that is, the reaction is the reverse of the method
Discu ssion
Syn th esis of Ru th en iu m Ar yld ia zen id o Com -
p lexes. The organodiazo chemistry of cyclopentadienyl
ruthenium derivatives appears to be largely unex-
plored.28 Specifically, we can find few previous refer-
ences to reactions with arenediazonium ions. Bruce and
co-workers reacted the σ-acetylide complex CpRu-
(PPh3)2(C2Ph) with ArN2+, but observed only electro-
philic attack at the acetylide ligand, to generate an
(28) Sutton, D. Chem. Rev. 1993, 93, 995.

692 Organometallics, Vol. 19, No. 4, 2000
Fan et al.
aryldiazovinylidene complex.29,30 When [CpRu(CO)3]+
was reacted with hydrazines, reaction occurred at
coordinated CO to give isocyanate complexes.31 There
have been a few studies of azobenzene reactions with,
for example, Cp′2Ru2(CO)4 (Cp′ ) Cp, Cp*), CpRuMe-
(PMe3)2, or Cp*RuMe(CO)2, generally leading to cyclo-
metalated (phenylazo)phenyl complexes.32-35
To our knowledge, no cyclopentadienyl ruthenium
aryldiazenido complexes have previously been synthe-
sized. As an entry into this chemistry, the complex
CpRu(PPh3)2Cl appeared to be an attractive possibility.
The complex readily undergoes substitution of a PPh3
ligand by other two-electron donors such as CO, phos-
phines, phosphites, and isocyanides, and furthermore
it is also possible to substitute the Cl ligand.21,36 It was
encouraging to find that the dicationic nitrosyl com-
plexes [Cp′Ru(PR3)2(NO)]2+ (Cp′ ) Cp, R ) Ph or Me;
Cp′ ) Cp*, R ) Ph) had already been prepared by
substitution of chloride in the complexes Cp′Ru(PR3)2-
Cl with the nitrosonium ion [NO]+ by using [NO][BF4]
or [NO][PF6].19,37,38 In view of the often parallel behavior
in the reactions of nitrosonium and aryldiazonium
salts,39 corresponding reactions with [ArN2][BF4] were
undertaken.
The reaction between CpRu(PPh3)2Cl and p-methoxy-
benzenediazonium tetrafluoroborate in the polar solvent
acetone gave the corresponding dicationic complex
[CpRu(PPh3)2(N2C6H4OMe)][BF4]2 (1) as the main prod-
uct (resulting from Cl substitution), but, in addition, a
minor product was the monocationic complex [CpRu-
(PPh3)(N2C6H4OMe)Cl][BF4] (5), formed by competing
phosphine substitution. It is well-known that CpRu-
(PPh3)2Cl (and the Cp* analogue) exhibit different
substitution behavior in polar and nonpolar solvents.
Polar solvents support preferential substitution of the
chloride ion, whereas substitution of the bulky PPh3
ligand is favored in nonpolar solvents.19,40,41 Correspond-
ingly, a high yield of 5 was obtained instead when the
reaction was performed in toluene. However, the reac-
tion of the more bulky pentamethylcyclopentadienyl
analogue Cp*Ru(PPh3)2Cl proceeded even in acetone
only with PPh3 loss to give the monocationic complex
[Cp*RuCl(PPh3)(N2C6H4OMe)][BF4] (6), and no corre-
sponding chloride-loss dicationic complex has been
observed in this case. This inability to synthesize the
highly crowded Cp* analogue of 1 is thus in accord with
the previously mentioned results with M ) Re and Ir,
where the similarly crowded complexes [Cp*M(PPh3)2(N2-
Ar)]+ could not be obtained. The additional formation
of the binuclear complex [Cp*RuCl(N2C6H4OMe)]2[BF4]2
(7) in this reaction can be rationalized by noting that
complex 6 still has a rather crowded geometry and loss
of the remaining PPh3 ligand may occur readily to form
7. We presume that this contamination contributes to
the inability to obtain reliable microanalysis data for 6
and 7.
The alternative synthesis of the dications 1-3 from
the reaction of the acetonitrile complex [CpRu(PR3)2-
(NCMe)][BF4] with diazonium salt in acetone gives an
improved yield but needs a longer reaction time. Indeed,
the relative reaction times and temperatures required
in these syntheses compare well with the known elec-
trophilic character of the diazonium ion and its prefer-
ential reaction with relatively electron-rich metal sites
in complexes.8 The cationic complex [CpRu(PPh3)2-
(NCMe)]+ is expected to be less electron-rich than
neutral CpRu(PPh3)2Cl, and the reaction is slower. (No
reaction was observed for the presumably even less
electron-rich cationic acetone complex [CpRu(CO)(PPh3)-
(OCMe2)][BF4].) On the other hand, CpRu(PMe3)2Cl is
more electron-rich than CpRu(PPh3)2Cl,38 and in this
case the reaction is completed even at low temperatures.
The product distribution of 1 and 5 resulting from the
reaction of CpRu(PPh3)2Cl with diazonium ion in ace-
tone was greatly dependent on the reaction stoichiom-
etry, with a 2:1 excess of diazonium ion changing the
ratio of 1:5 from 1:4 to 4:1, in favor of the dicationic
complex 1. In the proposed mechanism (Scheme 5), we
suggest that the ruthenium atom attacks [N2Ar]+ to first
give the unobserved doubly bent aryldiazenido inter-
mediate [CpRuCl(PPh3)2(N2Ar)][BF4]. (This step is simi-
lar to that proposed previously to account for the rapid
substitution of C2H4 by N2Ar+ in Cp*Ir(C2H4)2.)8 This
intermediate can then either dissociate chloride ion to
give the resulting complex dication of 1 as the mixed
chloride/tetrafluoroborate salt [CpRu(PPh3)2(N2C6H4-
OMe)][Cl][BF4] or dissociate a PPh3 ligand to give 5. A
further possibility is that the Cl- counterion of the salt
may reattack the dication and substitute a bulky PPh3
ligand to give 5, and this was indeed observed in the
reaction of 1 with NaCl. Experiments conducted in an
attempt to qualitatively investigate the mechanism gave
the following results. (1) When the reaction of CpRu-
(PPh3)2Cl with a 1:1 amount of [p-MeOC6H4N2][BF4] in
acetone was monitored by 1H NMR, it was observed that
the dication was formed at an early stage, but the
amount of monocationic complex 5 increased relative to
the dication as the reaction progressed, with complete
consumption of the starting materials. This is in agree-
ment with the idea that excess diazonium ion at an early
stage promotes the formation of 1 by consuming chloride
as relatively un-ionized ArN2Cl, but as all sources of
diazonium ion become depleted by reaction and the Cl-
concentration increases, the formation of 5 becomes
competitive. (2) When the reaction of CpRu(PPh3)2Cl
with a stoichiometric amount of [p-MeOC6H4N2][BF4]
in acetone was carried out in the presence of an excess
of NaBF4, the relative proportion of 1:5 was unchanged
at 1:4, indicating that the observed effect of additional
(29) Bruce, M. I.; Humphrey, M. G.; Liddell, M. J . J . Organomet.
Chem. 1987, 321, 91.
(30) Bruce, M. I.; Dean, C.; Duffy, D. N.; Humphrey, M. G.;
Koutsantonis, G. A. J . Organomet. Chem. 1985, 295, C40.
(31) Kruse, A. E.; Angelici, R. J . J . Organomet. Chem. 1970, 24, 231.
(32) Garn, D.; Knoch, F.; Kisch, H. J . Organomet. Chem. 1993, 444,
155.
(33) Bruce, M. I.; Gardner, R. C. F.; Stone, F. G. A. J . Chem. Soc.,
Dalton Trans. 1976, 81.
(34) Bruce, M. I.; Iqbal, M. Z.; Stone, F. G. A. J . Chem. Soc. A 1971,
2820.
(35) Bruce, M. I.; Iqbal, M. Z.; Stone, F. G. A. J . Chem. Soc. A 1970,
3204.
(36) Bruce, M. I.; Wong, F. S.; Skelton, B. W.; White, A. H. J . Chem.
Soc., Dalton Trans. 1981, 1398.
(37) (a) Conroy-Lewis, F. M.; Simpson, S. J . J . Organomet. Chem.
1987, 322, 221. (b) Conroy-Lewis, F. M.; Redhouse, A. D.; Simpson, S.
J . J . Organomet. Chem. 1990, 399, 307.
(38) Bruce, M. I.; Tomkins, I. B.; Wong, F. S.; Skelton, B. W.; White,
A. H. J . Chem. Soc., Dalton Trans. 1982, 687.
(39) Sutton, D. Chem. Soc. Rev. 1975, 4, 443.
(40) Bruce, M. I.; Hall, B. C.; Zaitseva, N. N.; Skelton, B. W.; White,
A. H. J . Chem. Soc., Dalton Trans. 1998, 1793.
(41) Bruce, M. I.; Hall, B. C.; Zaitseva, N. N.; Skelton, B. W.; White,
A. H. J . Organomet. Chem. 1996, 522, 307.

Ru Cyclopentadienyl Aryldiazenido Complexes
Organometallics, Vol. 19, No. 4, 2000 693
Sch em e 5
diazonium salt in increasing the relative proportion of
dication 1 formed is unlikely to be simply due to the
increase in [BF4]-. It therefore appears probable that
the additional diazonium salt acts not just by supplying
the extra [BF4]- required for the stoichiometry of 1. It
acts to promote formation of 1 relative to 5 by consum-
ing chloride as ArN2Cl (which may irreversibly decom-
pose to p-MeOC6H4Cl and N2 at the temperature of the
reaction). (3) However, when the reaction with a sto-
ichiometric amount of [p-MeOC6H4N2][BF4] in acetone
was carried out in the presence of excess NaBF4 and 1
equiv of TlOAc, chloride was consumed as TlCl, and now
only the dicationic complex 1 was observed, as expected.
(4) The iodo complex CpRu(PPh3)2I is more prone to
halide substitution than is the chloride, and when
reacted with a stoichiometric amount of [p-MeOC6H4N2]-
[BF4] in acetone in the presence of NaBF4, this yielded
only the dicationic complex 1.
that observed in the majority of aryldiazenido complexes
(near 1.25 Å),43 though is probably not significantly
different from the values in [RhCl(PPh3)2(p-N2C6H4-
OMe)][BF4]‚2CH2Cl2 (1.157 Å) and RuCl3(p-N2C6H4Me)-
(PPh3)2. Free [p-MeOC6H4N2][BF4] has ν(NN) near 2250
cm-1 in the IR spectrum, and from the near-linear
structure and short N-N bond length of the N2Ar
skeleton in 1 one would anticipate that ν(NN) for 1
might occur abnormally high compared with most other
singly bent aryldiazenido complexes, which usually have
values in the 1600-1800 cm-1 range.43 And so it does.
The value for 1 (2074 cm-1) is far above this range and
well exceeds the value in RuCl3(p-N2C6H4Me)(PPh3)2
(1882 cm-1 14
and [RhCl(PPh3)2(p-N2C6H4OMe)][BF4]‚
)
42
2CH2Cl2 (1982 cm-1). Similarly, ν(NN) for the PMe3
complex [Cp*Ru(PMe3)2(N2C6H4OMe)][BF4]2 (4) (1780
cm-1) is much greater than for the isoelectronic rhenium
monocationic complex [Cp*Re(PMe3)2(N2C6H4OMe)]-
[BF4] (ν(NN) ) ca. 1620 cm-1) of similar composition
and structure.4 Many years ago, a class of ruthenium
aryldiazenido complexes with 2,2′-bipyridine ligands
was reported having the formula [RuCl(bipy)2(N2Ar)]-
[PF6]2. These complexes were remarkable at the time
Molecu la r Str u ctu r e of 1. The most interesting
feature of the X-ray structure of 1 is the near-linear Ru-
N-N-C skeleton, with the N-N-C angle opened up
from the 120° sp2 angle, commonly exhibited by singly
bent N2Ar ligands, to 158.9°. To our knowledge, this is
the largest N-N-C angle to be observed in an aryl-
diazenido complex. There are other examples of aryl-
for displaying ν(NN) values in the region of 2080 cm-1
,
and it was suggested that the complexes might best be
considered to have the aryldiazenido ligand bound as
arenediazonium (N2Ar)+.45,46 Unfortunately, to our knowl-
edge, no X-ray structure of these complexes has been
reported. (The complex [RuCl(NH3)4(N2Ph)]Cl2 has been
reported to have ν(NN) as high as 2121 cm-1.)47 From
the result for 1, it seems almost certain that these
complexes would also display an enlarged N-N-C
angle, in keeping with the high value of ν(NN). In a
simplistic but nevertheless useful valence bond repre-
sentation shown below it can be argued that the
lowering of ν(NN), lengthening of the N-N bond length,
and decrease in the N-N-C angle in the coordinated
singly bent aryldiazenide ligand from the values in free
diazenido complexes with an opened N-N-C angle,
12,13
including RuCl3(p-N2C6H4Me)(PPh3)2
(137°) and
42
[RhCl(PPh3)2(p-N2C6H4OMe)][BF4]‚2CH2Cl2 (141.3°).
A compilation of the metrical details of aryldiazenido
complexes reported to about 1987 has been published.43
Although not an aryldiazenido complex, and not strictly
comparable for this and other reasons, a ruthenium
diazaborane derivative is known with an essentially
linear Ru-N-N-B skeleton and a N-N-B angle of
173°.44 The Ru-N bond length in 1 is somewhat longer
(1.853 Å) than that in RuCl3(p-N2C6H4Me)(PPh3)2 (1.784
Å), as expected if the structure is tending more to the
formal valence representation Ru-NtN-C. Also, the
N-N distance (1.145 Å) is correspondingly shorter than
(42) Einstein, F. W. B.; J ones, R. H.; Zhang, Y.; Sutton, D. Inorg.
Chem. 1988, 27, 1004.
(43) J ohnson, B. F. G.; Haymore, B. L.; Dilworth, J . R. In Compre-
hensive Coordination Chemistry; Wilkinson, G., Gillard, R. D., Mc-
Cleverty, J . A., Eds.; Pergamon Press: Oxford, 1987; Vol. 2, p 99.
(44) Schramm, K. D.; Ibers, J . A. J . Am. Chem. Soc. 1977, 16, 3287.
(45) Bowden, W. L.; Little, W. F.; Meyer, T. J . J . Am. Chem. Soc.
1973, 95, 5084.
(46) Bowden, W. L.; Little, W. F.; Meyer, T. J . J . Am. Chem. Soc.
1977, 99, 4340.
(47) Yuen, C. M. C.; Lau, T. C. Abstr. 31st Int. Conf. Coord. Chem.
1996, abstract 9P62.

694 Organometallics, Vol. 19, No. 4, 2000
Fan et al.
[N2Ar]+ derives substantially from the back-bonding
contribution.
going inversion or rotation at the carbon-bound nitrogen
atom Nâ, resulting in exchange of the inequivalent PMe3
ligands.4 In the present case, the 31P NMR spectra of 1,
2, and 4 indicated that the phosphine ligands remain
equivalent down to at least -80 °C. Thus, for the two
complexes where a direct comparison is possible, it
seems that the ruthenium dicationic complex [Cp*Ru-
(PMe3)2(p-N2C6H4OMe)]2+ (in 4) has a lower barrier to
rearrangement of the N2Ar group compared with the
corresponding monocationic rhenium complex [Cp*Re-
(PMe3)2(p-N2C6H4OMe)]+. The origin of this difference
seems likely to be related to the corresponding differ-
ences in the electronic structure and geometry of the
M-N2Ar group in these two situations, which are
manifested in the higher ν(NN) values and increased
NNC angle exhibited by the dicationic ruthenium
complexes in this study.
It is important to note that these bipyridine and
ammine complexes, and 1-3, are all dicationic com-
plexes. Thus, in addition to the effects of the ancillary
ligands, back-bonding will be much reduced in these
complexes because of the formal 2+ charge on the
cation, leading to higher than usual ν(NN) values and
correspondingly enlarged N-N-C angles. Indeed, there
have been relatively few other examples of dicationic
terminal aryldiazenido complexes synthesized.43 A fur-
ther factor that could cause the enlarged N-N-C angle
in 1 is the possibility of steric crowding of the singly
bent N2Ar ligand by the sterically demanding PPh3
groups.
Con clu sion
The values of ν(NN) for 1-4 show the expected
decrease as the phosphine or Cp′ becomes more basic,
and values are reduced further in the monocationic
complexes 5 and 6 compared to the corresponding
dications. The values of δ(15NR) for 1-4 range from
-64.52 to -24.32 and may be compared with the value
of -46.8 reported for RuCl3(PPh3)2(N2Ph).43 These
values also become less negative systematically with
increase in the basicity of the phosphine or Cp′, and 5
and 6 show still less negative values and the same
trend. The values of ν(NN) and δ(15N) for 7 support a
structure in which the N2Ar ligands are terminal, singly
bent, rather than bridging.
The solid-state structure of the dicationic complexes
1-4, exemplified by the crystal structure of 1‚0.93CHCl3,
follows a now familiar pattern for piano-stool geometry
Cp or Cp* aryldiazenido complexes with singly bent
aryldiazenido ligands.2,4,8,9 The aryldiazenido ligand is
oriented unsymmetrically with respect to a plane bisect-
ing the P-Ru-P angle, so that the plane of the aryl
ring is approximately perpendicular to that plane, and
the N2Ar ligand is bent toward one of the phosphine
ligands. The rhenium complex, [Cp*Re(PMe3)2(p-N2C6H4-
OMe)]+, of this type exhibits the expected two 31P NMR
resonances at low temperature, but these collapse to a
single resonance on increasing the temperature, at-
tributed to the singly bent aryldiazenido ligand under-
An entry into the field of cyclopentadienyl ruthenium
aryldiazenido complexes has been made through the
reactions of Cp′Ru(PR3)2Cl with arenediazonium salts.
Under the appropriate conditions, substitution of Cl
occurs to give new dicationic complexes such as 1-4,
or PPh3 substitution can occur to give monocationic
complexes such as 5 and 6. IR and NMR spectra show
these complexes have a terminally coordinated singly
bent N2Ar ligand. The X-ray structure of 1 demonstrates
that the N2Ar ligand is bound to ruthenium in a near-
linear geometry and has the largest known N-N-
C(aryl) angle for an aryldiazenido complex to date. This
geometry is compatible with the exceptionally high
value of ν(NN) observed in the IR spectrum.
Ack n ow led gm en t. Financial support from NSERC
Canada in the form of a research grant to D.S. is
gratefully acknowledged. We thank Scott Lovell, Uni-
versity of Washington, Seattle, for collecting the X-ray
data.
Su p p or tin g In for m a tion Ava ila ble: A listing of crystal
and data collection details and final parameters for 1‚
0.93CHCl3. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM990761E