Synthesis and properties of hydrotris(pyrazolyl)borate (Tp) ruthenium complexes with benzophenone imine: X-ray crystal structure of [TpRu(HN=CPh2)(PEt3)2][BPh4]

Article abstract of DOI:10.1016/S0020-1693(00)00002-5

The complexes [TpRuCl(dippe)] (dippe = 1,2-bis(diisopropylphosphino)ethane) and [TpRuCl(PEt₃)₂] react with HN=CPh₂ and NaBPh₄ in MeOH affording the cationic mononuclear imine derivatives [TpRu(HN=CPh₂)(dippe)][BPh₄] and [TpRu(HN=CPh₂)(PEt₃)₂][BPh₄], respectively. The X-ray crystal structure of the latter has been determined. The reaction of [TpRuCl(PMe(i)Pr₂)(MeCN)] with HN=CPh₂ led to the neutral imine derivative [TpRuCl(PMe(i)Pr₂)(HN=CPh₂)], which adds a second imine ligand upon chloride dissociation affording the cationic bis(imine) complex [TpRu(PMe(i)Pr₂)(HN=CPh₂)₂]⁺. The cationic complexes [TpRu(HN=CPh₂)(dippe)][BPh₄] and [TpRu(HN=CPh₂)(PEt₃)₂][BPh₄] react with KOBu(t) in tetrahydrofuran yielding the neutral metalated species [TpRu(σ-η¹-C₆H₄C(Ph)=NH)(dippe)] and the phenyl complex [TpRu(σ-η¹-C₆H₅)(PEt₃)₂], respectively. All compounds were characterized by IR, NMR and microanalysis. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(00)00002-5

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Inorganica Chimica Acta 300–302 (2000) 869–874
Synthesis and properties of hydrotris(pyrazolyl)borate (Tp)
ruthenium complexes with benzophenone imine: X-ray crystal
structure of [TpRu(HNꢀCPh2)(PEt3)2][BPh4]
Miguel Angel Jime´nez-Tenorio, Manuel Jime´nez-Tenorio, M. Carmen Puerta *,
Pedro Valerga
Departamento de Ciencia de Materiales e Ingenier´ıa Metalu´rgica y Qu´ımica Inorga´nica, Facultad de Ciencias, Uni6ersidad de Ca´diz,
Aptdo. 40, 11510 Puerto Real, Ca´diz, Spain
Received 1 December 1999; accepted 15 December 1999
Abstract
The complexes [TpRuCl(dippe)] (dippe=1,2-bis(diisopropylphosphino)ethane) and [TpRuCl(PEt3)2] react with HNꢀCPh2 and
NaBPh4 in MeOH affording the cationic mononuclear imine derivatives [TpRu(HNꢀCPh2)(dippe)][BPh4] and
[TpRu(HNꢀCPh2)(PEt3)2][BPh4], respectively. The X-ray crystal structure of the latter has been determined. The reaction of
[TpRuCl(PMeiPr2)(MeCN)] with HNꢀCPh2 led to the neutral imine derivative [TpRuCl(PMeiPr2)(HNꢀCPh2)], which adds a
second imine ligand upon chloride dissociation affording the cationic bis(imine) complex [TpRu(PMeiPr2)(HNꢀCPh2)2]+. The
cationic complexes [TpRu(HNꢀCPh2)(dippe)][BPh4] and [TpRu(HNꢀCPh2)(PEt3)2][BPh4] react with KOBut in tetrahydrofuran
yielding the neutral metalated species [TpRu(s-h1-C6H4C(Ph)ꢀNH)(dippe)] and the phenyl complex [TpRu(s-h1-C6H5)(PEt3)2],
respectively. All compounds were characterized by IR, NMR and microanalysis. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Imine complexes; Azavinylidene complexes; Hydrotris(pyrazolyl)borate; Ruthenium; Phosphine
1. Introduction
exchange [6]. Imines show a varied reactivity towards
transition metal complexes. Reactions of aromatic
imines with the in situ generated butatrienylidene ruthe-
nium cation [CpRuꢀCꢀCꢀCꢀCH2(PPh3)2]+ gives com-
plexes containing 4-ethynylquinoline or 1-azabuta-
1,3-diene ligands, the latter formed presumably by a
[2+2] cycloaddition of the CkꢀCl double bond of the
butatrienyliene moiety to the NꢀC of the imine [7]. The
five-coordinate osmium complex [Os(CꢂCPh)2(CO)-
(PiPr3)2] adds benzophenone imine yielding an isomeric
mixture of cis/trans-[Os(CꢂCPh)2(CO)(HNꢀCPh2)-
(PiPr3)2], which eliminates phenylacetylene thermally
furnishing the ortho-metalated compound [Os(CꢂCPh)-
(CO){HNꢀC(Ph)C6H4}(PiPr3)2] [8]. Despite all this rich
chemistry, monodentate nitrogen-bound imine com-
plexes are rare as result of the weak Lewis basicity
of the imine nitrogen atom [9]. We reported recently
that the X-ray crystal structure of [RuCl2(CO)-
(HNꢀCPh2)(PMeiPr2)2], which was prepared by the ad-
dition of benzophenone imine to the vacant coor-
A great deal of chemical transformations of organic
imines mediated by transitions metal complexes are
known. For instance, ruthenium hydrides have shown
to be efficient catalysts for the isomerization of imines
via [1,3] — hydrogen shift [1], for the transfer hydro-
genation of ketones and imines by isopropanol [2], or
for the addition of aromatic imines at the ortho —
CꢁH bonds to olefins [3]. Ruthenium complexes also
catalyze the asymmetric hydrosilylation of imines [4].
On the other hand, there is a growing interest in the
catalytic CꢀN bond formation by metal–imide medi-
ated imine metathesis [5], which may offer important
advantages over the conventional acid-catalyzed imine
* Corresponding author. Tel.: +34-956-016340; fax: +34-956-
016288.
E-mail address: carmen.puerta@uca.es (M.C. Puerta)
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00002-5

870
M.A. Jime´nez-Tenorio et al. / Inorganica Chimica Acta 300–302 (2000) 869–874
dination site of the 16-electron compound [RuCl2(CO)-
(PMeiPr2)2] [10]. In order to get a better understanding
of the coordination chemistry of benzophenone imine,
and its further transformations when bound to a metal
center, we have studied the reactivity of a series of
ruthenium phosphine complexes containing the ligand
hydrotris(pyrazolyl)borate (Tp) towards HNꢀCPh2.
These TpRu compounds are binding sites for a range of
small molecules including H2, N2 [11,12] and 1-alkynes
[13,14], and provide suitable metal centers for the coor-
dination of the weakly basic imine ligand.
(CD3COCD3): l 18.5, 19.3, 19.5 (s, P(CH(CH3)2)2);
20.5 m (PCH2); 24.9, 27.2 (m, P(CH(CH3)2)2); 105.9,
106.8, 135.4, 137.3, 144.9, 146.7 (s, B(C3H3N2)3); 125.9,
127.6, 127.7, 129.3, 129.7, 131.7 (HNꢀC(C6H5)2); 187.4
(s, HNꢀC(C6H5)2).
2.2. Preparation of [TpRu(HNꢀCPh2)(PEt3)2][BPh4] (2)
This compound was obtained following a procedure
analogous to that used for the preparation of 1, starting
from [TpRuCl(PEt3)2]. Yield: 80%. Anal. Calc. for
C58H71N7B2P2Ru: C, 66.3; H, 6.76; N, 9.3. Found: C,
66.6; H, 6.68; N, 8.9%. IR: w(NH) 3312 cm−1; w(BH)
2. Experimental
1
2467 cm−1. H NMR (CDCl3): l 0.77 (m, PCH2CH3),
1.88 (m, PCH2CH3); 5.93 t, 6.08 t, 7.45 d, 7.70 d, 7.72
d, 7.97 d (B(C3H3N2)3); 6.05 d, 6.79 t, 7.05 m, 7.42 m
(HNꢀC(C6H5)2); 10.34 (s, br, HNꢀ). 31P{1H} NMR: l
22.2 s. 13C{1H} NMR: l 5.2 (s, P(CH2CH3)3); 15.9 (t,
All synthetic operations were performed under a dry
dinitrogen or argon atmosphere following conventional
Schlenk or drybox techniques. Tetrahydrofuran, di-
ethylether and petroleum ether (boiling point range
40–60°C) were distilled from the appropriate drying
agents. All solvents were deoxygenated immediately
before use. 1,2-Bis(diisopropylphosphino)ethane [15],
JCP=14.8 Hz, P(CH2CH3)3); 102.6, 103.4, 132.8, 134.3,
141.7, 146.3 (s, B(C3H3N2)3); 122.0, 126.2, 126.9, 127.3,
130.1, 133.9 (HNꢀC(C6H5)2); 196.8 (s, HNꢀC(C6H5)2).
[TpRuCl(dippe)]
[11],
[TpRuCl(PEt3)2],
and
2.3. Preparation of [TpRuCl(HNꢀCPh2)(PMeiPr2)] (3)
[TpRuCl(PMeiPr2)(MeCN)] [12] were prepared accord-
ing to reported procedures. IR spectra were recorded in
Nujol mulls on a Perkin–Elmer FTIR Spectrum 1000
spectrophotometer. NMR spectra were taken on
Varian Unity 400 MHz or Varian Gemini 200 MHz
equipment. Chemical shifts are given in ppm from
SiMe4 (1H and 13C{1H}) or 85% H3PO4 (31P{1H}). The
phosphine protons of the dippe ligand appeared in the
1H NMR spectra of the corresponding compounds as a
series of overlapping multiplets in the range 0.5–3 ppm,
and were not assigned. Microanalysis were carried out
by Dr Manuel Arjonilla at the CSIC, Instituto de
Ciencias Marinas de Andaluc´ıa.
To a solution of [TpRuCl(PMeiPr2)(MeCN)] (0.15 g,
approximately 0.3 mmol) in toluene (10 ml), benzophe-
none imine (0.1 ml excess) was added. The mixture was
stirred at 70°C for 2 h. During this time, the color of
the solution changed from yellow to orange and then
finally red. The solvent was removed in vacuo, leaving
a red oil. This oil was treated with petroleum ether and
cooled to −20°C. A red–orange solid was obtained,
which was filtered off and dried in vacuo. Yield: 0.12 g,
62%. Anal. Calc. for C29H38N7BPRu: C, 52.5; H, 5.74;
N, 14.8. Found: C, 52.6; H, 5.89; N, 14.5%. IR: w(NH)
.
3206 cm−1; w(BH) 2466 cm−1 1H NMR (C6D6): l
0.06, 0.89, 0.92, 1.37 (m, P(CH(CH3)2)2); 1.58 (d, JHP
=
2.1. Preparation of [TpRu(HNꢀCPh2)(dippe)][BPh4] (1)
7.7 Hz, PCH3); 1.93, 2.11 (m, P(CH(CH3)2)2); 5.30 t,
5.88 t, 5.90 t, 6.54 d, 7.30 d, 7.47 d, 7.55 d, 7.90 d, 8.08
d (B(C3H3N2)3); 6.29 d, 6.67 d, 6.80 t, 6.97 m, 7.41 d,
7.17 t (HNꢀC(C6H5)2); 13.08 (s, br, HNꢀ). 31P{1H}
NMR: l 40.7 s. 13C{1H} NMR: l 4.45 (d, JCP=21.7
Hz, PCH3); 16.3, 16.4, 17.8, 18.0 (s, P(CH(CH3)2)2);
23.4, 28.6 (d, JCP=21 Hz, P(CH(CH3)2)2); 105.6, 105.7,
106.0, 134.0, 134.1, 135.5, 142.0, 146.9, 147.1 (s,
B(C3H3N2)3); 126.4, 128.1, 128.9, 129.1, 130.0, 138.1,
139.1 (HNꢀC(C6H5)2), 178.9 (s, HNꢀC(C6H5)2).
To a slurry of [TpRuCl(dippe)] (0.15 g, approxi-
mately 0.25 mmol) in MeOH (15 ml) an excess of solid
NaBPh4 (0.3 g) and benzophenone imine (0.1 ml, ex-
cess) was added. The mixture was heated using a warm
water bath for 30 min. A deep yellow color developed
during this time. The reaction mixture was stirred for a
further 2 h at room temperature (r.t.). Then it was
concentrated to approximately half of the volume and
cooled to −20°C. The yellow precipitate was filtered
off, washed with ethanol and petroleum ether and dried
in vacuo. Yield: 0.22 g, 85%. Anal. Calc. for
C60H73N7B2P2Ru: C, 66.9; H, 6.79; N, 9.1. Found: C,
66.6; H, 6.80; N, 8.8%. IR: w(NH) 3310 cm−1; w(BH)
2.4. Preparation of [TpRu(HNꢀCPh2)2(PMeiPr2)]-
[BPh4] (4)
1
2467 cm−1. H NMR (CDCl3): l 6.04 t, 6.16 t, 7.57 d,
A solution of 3 (0.1 g, 0.15 mmol) in MeOH (10 ml)
was treated with benzophenone imine (0.1 ml, excess)
and solid NaBPh4 (0.3 g, excess). The mixture was
heated gently using a warm water bath. After a few
7.63 d, 7.84 d, 7.89 d (B(C3H3N2)3); 6.00 d, 6.88 t, 7.11
t, 7.19 t, 7.47 t (HNꢀC(C6H5)2); 10.32 (s, br, HNꢀ).
31P{1H} NMR (CD3COCD3): l 74.3 s. 13C{1H} NMR

M.A. Jime´nez-Tenorio et al. / Inorganica Chimica Acta 300–302 (2000) 869–874
871
minutes, an orange crystalline precipitate was formed.
The mixture was stirred for 12 h at r.t. The yellow–or-
ange precipitate was filtered off, washed with ethanol
and petroleum ether and dried in vacuo. Yield: 0.15 g,
84%. Anal. Calc. for C66H69N8B2PRu: C, 70.3; H, 6.12;
N, 9.9. Found: C, 70.4; H, 6.03; N, 9.8%. IR: w(NH)
extracted with petroleum ether and the solution filtered
through Celite. Volume reduction to a few milliliters
using reduced pressure and cooling to −20°C gave an
orange solid, which was filtered and dried in vacuo.
Yield: 66%. Anal. Calc. for C36H52N7BP2Ru: C, 57.2;
H, 6.88; N, 12.9. Found: C, 57.3; H, 6.98; N, 13.1%.
1
3250 cm−1
(CD3COCD3): l 0.52, 1.36 (m, P(CH(CH3)2)2); 1.63 (d,
HP=7.3 Hz, PCH3); 2.32 (m, P(CH(CH3)2)2); 5.70 t,
;
w(BH) 2476 cm−1
.
1H NMR
IR: w(BH) 2472 cm−1; w(NH) 3320 cm−1. H NMR
(C6D6): l 5.77 t, 5.98 t, 6.68 d, 7.54 d, 7.56 d, 8.14 d
J
(B(C3H3N2)3); 6.94 t, 7.01 t, 7.08 t, 7.86
d
6.49 t, 7.20 d, 7.68 d, 7.84 d, 8.19 d (B(C3H3N2)3); 6.42
d, 6.92 t, 7.06 d, 7.15 t, 7.40 t, 7.49 t (HNꢀC(C6H5)2);
11.01 (s, br, HNꢀ). 31P{1H} NMR: l 33.7 s. 13C{1H}
NMR: l 5.7 (d, JCP=21 Hz, PCH3); 17.8, 18.3 (s,
P(CH(CH3)2)2); 26.4 (d, JCP=24 Hz, P(CH(CH3)2)2);
107.3, 108.4, 136.9, 138.1, 143.2, 147.1 (s, B(C3H3N2)3);
127.9, 128.7, 128.9, 129.7, 130.7, 131.8 (HNꢀC(C6H5)2);
188.2 (s, HNꢀC(C6H5)2).
(HNꢀC(C6H4)(C6H5)); 9.79 (s, br, HNꢀ). 31P{1H}
NMR: l 80.9 s. 13C{1H} NMR: l 18.7, 19.2, 19.8, 20.1
(s, P(CH(CH3)2)2); 21.0 (m, PCH2); 24.7, 25.5 (m,
P(CH(CH3)2)2); 105.2, 104.4, 134.6, 136.0, 143.2, 146.2
(s, B(C3H3N2)3); 127.5, 128.4, 129.3, 129.5, 130.4
(HNꢀC(C6H4)(C6H5); 138.9 (t, JCP=12.4 Hz, RuC);
177.1 (s, HNꢀC(C6H5)2).
2.6. Preparation of [TpRu(|-p1-C6H5)(PEt3)2] (6)
2.5. Preparation of [TpRu{|-p1-C6H4C(Ph)ꢀNH}-
(dippe)] (5)
A procedure analogous to that used for the prepara-
tion of 5 was used, starting from the imine adduct 2.
Yield: 60%. Anal. Calc. for C27H45N6BP2Ru: C, 51.7;
H, 7.18; N, 13.4. Found: C, 51.5; H, 6.98; N, 13.4%.
A solution of 1 in tetrahydrofuran was treated with
an excess of solid KOBut. The heterogeneous mixture
becomes orange gradually. It was stirred at r.t. for 15
min. Then solvent was removed in vacuo, the residue
1
IR: w(BH) 2464 cm−1. H NMR (C6D6): l 0.66 (m,
PCH2CH3), 1.73 (m, PCH2CH3); 5.80 t, 5.90 t, 7.47 d,
7.51 d, 8.20 br (B(C3H3N2)3); 7.29 t, 7.27 t, 8.09 br
(RuC6H5). 31P{1H} NMR: l 23.3 s. 13C{1H} NMR: l
Table 1
Summary of data for the crystal structure analysis of 2
8.0 (s, P(CH2CH3)3); 18.6 (t,
JCP=12 Hz,
P(CH2CH3)3); 105.2, 105.3, 136.2, 137.1, 144.7, 147.7
(s, B(C3H3N2)3); 122.4, 126.4, 128.3 (s, C6H5), 132.2 (t,
JCP=9.6 Hz, RuC).
Formula
C58H71B2N7P2Ru
1050.88
0.20×0.12×0.40
triclinic
Formula weight
Crystal size (mm)
Crystal system
Space group
(
P1 (no. 2)
2.7. Experimental for the X-ray structure determination
of compound 2
Cell parameters
,
a (A)
14.180(4)
14.936(4)
13.471(5)
101.76(3)
91.88(3)
78.29(2)
2735(3)
2
,
b (A)
,
c (A)
A crystal suitable for X-ray diffraction analysis was
mounted onto a glass fiber and transferred to an
AFC6S-Rigaku automatic diffractometer (T=290 K,
Mo Ka radiation, graphite monochromator, u=
h (°)
i (°)
k (°)
3
,
V (A )
,
0.71073 A). Accurate unit cell parameters and an orien-
Z
zcalc (g cm−3
)
1.276
tation matrix were determined by least-squares fittings
from the settings of 25 high-angle reflections. Crystal
data and details on data collection and refinements are
given in Table 1. Lorentz and polarization corrections
were applied. Decay was monitored by measuring three
standard reflections every 100 measurements. Decay
and absorption corrections were also applied. Reflec-
tions having I\3|(I) were used for structure refine-
ment. All calculations for data reduction, structure
solution, and refinement were carried out on a VAX
3520 computer at the Servicio Central de Ciencia y
Tecnolog´ıa de la Universidad de Ca´diz, using the
TEXSAN [16] software system and ORTEP [17] for plot-
ting. The structure was solved by the Patterson method,
and refined anisotropically by full-matrix least-squares
methods for all non-hydrogen atoms. The hydrogen
,
u (Mo Ka) (A)
v (Mo Ka) (cm−1
F(000)
0.71069
3.80
1104
0.93–1.00 („-scan method)
4.0
5.0B2qB50.1
8649
8325 [Rint=0.045]
4804
631
7.61
0.048
0.054
0.82
1.38
)
Transmission factors
Scan speed (ꢀ) (° min−1
2q interval (°)
Measured reflections
Unique reflections
Observed reflections [I\3|(I)]
Parameters
Reflection/parameter ratio
)
a
R
Rw (w=|F−2
Maximum D/| in final cycle
Goodness-of-fit
)
b
a R=ꢀ(ꢁFoꢁ−ꢁFcꢁ)/ꢀꢁFoꢁ.
b Rw=[(ꢀ w(ꢁFoꢁ−ꢁFcꢁ)2/ꢀ wFo2)]1/2
.

872
M.A. Jime´nez-Tenorio et al. / Inorganica Chimica Acta 300–302 (2000) 869–874
(dippe)][BPh4] (1) and [TpRu(HNꢀCPh2)(PEt3)2][BPh4]
(2). These products are yellow crystalline solids which
in their IR spectra display one medium band near 3300
cm−1, attributable to w(NH) in the imine ligand. The
1
imine proton appears in the H NMR spectra as one
broad signal at approximately 10.30 ppm, whereas
many resonances are observed in the aromatic region.
Signals for the phenyl protons of the benzophenone
imine ligand, six separate resonances for the pyrazole
protons of the Tp group, as well as the tetraphenyl-
borate protons all appear in the range 5.5–8.0 ppm,
making this part of the 1H NMR spectrum rather
complicated. The 31P{1H} NMR spectra consists of one
sharp singlet for both 1 and 2. We have observed that
the benzophenone imine is lost readily in solution. It
appears that a rapid dissociation equilibrium occurs
which leads to the formation of variable amounts of
free imine plus other species. These species have been
identified in some instances as solvent adducts, e.g.
[TpRu(Me2CO)(dippe)]+, which had been described
previously [11]. This behavior has been observed in
other imine complexes of ruthenium, as in the case of
[RuHCl(CO)(HNꢀCPh2)(PiPr3)2] [18], and hence in all
further operations for the purification of 1 and 2, an
excess of free imine was added to the liquor in order to
prevent decomposition by imine ligand dissociation.
Thus, single crystals of 2 suitable for X-ray structure
analysis were obtained by recrystallization of the crude
product from dichloromethane–petroleum ether con-
taining free benzophenone imine. The crystal structure
of compound 2 was determined. An ORTEP view of the
complex cation is shown in Fig. 1. Relevant bond
lengths and angles are listed in Table 2. The coordina-
tion around ruthenium is distorted octahedral, with
phosphines in a cisoid arrangement, with a P(1)ꢁ
Ru(1)ꢁP(2) angle of 99.28(7)°. The Ru(1)ꢁN(1) and
Fig. 1. ORTEP drawing of the complex cation [TpRu(HNꢀ
CPh2)(PEt3)2]+ in complex 2 with 50% probability thermal ellipsoids.
Hydrogen atoms, except that on the nitrogen atom of the imine
ligand, are omitted.
Table 2
,
Selected bond distances (A) and angles (°) for [TpRu(HNꢀ
CPh2)(PEt3)2][BPh4]
Ru(1)ꢁP(1)
Ru(1)ꢁP(2)
Ru(1)ꢁN(1)
Ru(1)ꢁN(12)
Ru(1)ꢁN(22)
2.364(2)
2.366(2)
2.095(5)
2.152(5)
2.091(5)
Ru(1)ꢁN(32)
N(1)ꢁC(1)
N(1)ꢁH(1)
C(1)ꢁC(2)
C(1)ꢁC(8)
2.140(5)
1.309(7)
0.9503
1.472(9)
1.485(9)
P(1)ꢁRu(1)ꢁP(2)
P(1)ꢁRu(1)ꢁN(1)
P(1)ꢁRu(1)ꢁN(12)
P(1)ꢁRu(1)ꢁN(22)
P(1)ꢁRu(1)ꢁN(32) 170.4(2)
P(2)ꢁRu(1)ꢁN(1) 92.3(1)
P(2)ꢁRu(1)ꢁN(12) 173.0(2)
P(2)ꢁRu(1)ꢁN(22)
P(2)ꢁRu(1)ꢁN(32)
N(1)ꢁRu(1)ꢁN(12) 89.8(2)
N(1)ꢁRu(1)ꢁN(22) 176.3(2)
99.28(7) N(1)ꢁRu(1)ꢁN(32)
92.3(2)
86.5(2)
83.2(2)
89.5(2)
87.4(2)
90.1(2)
N(12)ꢁRu(1)ꢁN(22)
N(12)ꢁRu(1)ꢁN(32)
N(22)ꢁRu(1)ꢁN(32)
Ru(1)ꢁN(1)ꢁC(1)
Ru(1)ꢁN(1)ꢁH(1)
C(1)ꢁN(1)ꢁH(1)
N(1)ꢁC(1)ꢁC(2)
87.5(2)
147.2(5)
106.3759
106.4386
119.9(6)
122.4(6)
117.7(6)
,
N(1)ꢁC(1) bond lengths of 2.095(5) and 1.309(7) A
correspond to single RuꢁN and double CꢀN bonds,
respectively. The Ru(1)ꢁN(1) separation is slightly
91.4(2)
90.1(2)
N(1)ꢁC(1)ꢁC(8)
shorter than that found in [RuCl2(HNꢀCPh2)(CO)-
i
C(2)ꢁC(1)ꢁC(8)
,
(PMe Pr2)2] (2.144(5) A) [10], being indicative of a
stronger metal–imine interaction in the case of 2. The
angles around C(2) indicate a sp2 hybridization as
expected. The phenyl rings of the imine ligand are
oriented in a way that their planes form 72.73°. A
similar value of 69.44° has been found for the angle
between the planes defined by the atoms Ru(1), N(1),
N(12), N(22) and P(2) and the atoms N(1), C(1), C(2)
and C(8) of the benzophenone imine ligand. All the
dimensions in the phosphine and Tp groups, as well as
in the [BPh4]− anion are in the normal range.
atoms were included at idealized positions and not
refined. Maximum and minimum peaks in the final
difference Fourier maps were +0.80 and −0.41 e
−3
,
A
.
3. Results and discussion
All attempts carried out to prepare the cationic imine
complex [TpRu(HNꢀCPh2)(PMeiPr2)2][BPh4] following
the same procedure used for the synthesis of 1 and 2 led
The complexes [TpRuCl(dippe)] and [TpRuCl(PEt3)2]
react smoothly with benzophenone imine and NaBPh4
in warm MeOH affording the corresponding mononu-
clear cationic imine complexes [TpRu(HNꢀCPh2)-
1
to the formation of mixtures. Using H and 31P{1H}
NMR spectroscopy, we monitored the reaction of the

M.A. Jime´nez-Tenorio et al. / Inorganica Chimica Acta 300–302 (2000) 869–874
873
dinitrogen complex [TpRu(N2)(PMeiPr2)2][BPh4] [12]
with an excess of benzophenone imine. Rapid substitu-
tion of dinitrogen and subsequent formation in situ of
the expected complex [TpRu(HNꢀCPh2)(PMeiPr2)2]-
[BPh4] was observed, but shortly afterwards, the
31P{1H} resonance attributed to this species disap-
peared and were replaced by two new signals, one of
which was due to the free PMeiPr2, and the other one
corresponding to a new species, which contains appar-
ently only one phospine ligand bound to the metal. The
lability of PMeiPr2 in bis(methyldiisopropylphosphine)
derivatives is well established, and this has allowed us
to access a range of neutral compounds resulting from
the substitution of one phosphine by neutral donors
[12,14]. Thus, the reaction of [TpRuCl(PMeiPr2)2], or
even more conveniently [TpRuCl(PMeiPr2)(MeCN)]
with benzophenone imine in toluene at 70°C led to the
substitution of either one phosphine or MeCN and the
formation of the red neutral imine derivative [TpRu-
Cl(HNꢀCPh2)(PMeiPr2)] (3), which was isolated upon
concentration and addition of petroleum ether. Ben-
zophenone imine is readily released from 3, and hence
free imine must be added in order to prevent dissocia-
tion and decomposition. Compound 3 reacts with fur-
ther benzophenone imine in MeOH in the presence of
NaBPh4 affording the cationic bis(imine) complex
[TpRu(HNꢀCPh2)2(PMeiPr2)][BPh4] (4), which was
identified as the final compound formed in the reaction
between [TpRu(N2)(PMeiPr2)2][BPh4] and HNꢀCPh2.
processes such as imine metathesis, or the coupling of
imines with alkynes and olefins. These possibilities are
currently under study.
In contrast with the well-documented chemistry of
vinylidene complexes [19], little is known about aza-
vinylidene complexes, formally related to the former,
containing one nitrogen atom at the a-position of the
unsaturated ligand [18]. Azavinylidene complexes of Os
and Ir have been prepared by the deprotonation of the
corresponding imine adducts, e.g. [(h6-C6H6)-
OsꢀNꢀCPh2(PMetBu2)][PF6] [20]. Azavinylidene com-
plexes of ruthenium, both mononuclear [21] and polinu-
clear [22], are also known. In an attempt to generate
neutral azavinylidene derivatives, we carried out the
deprotonation of 2 and 3 using KOBut. Unexpectedly,
no azavinylidene complexes were obtained. In both
cases, ortho-metalation of one of the phenyl rings of the
benzophenone imine took place, giving rise to species
containing a direct RuꢁC bond. Thus, the product of
the reaction of 1 with KOBut in tetrahydrofuran has
been identified as [TpRu{s-h1-C6H4C(Ph)ꢀNH}-
(dippe)] (5), in which the NH group of the imine is not
coordinated to ruthenium.
In the case of the deprotonation of 2, the reaction
goes further apparently, and the final product is the
s-aryl derivative [TpRu(s-h1-C6H5)(dippe)] (6), with
no evidence for the presence of the imine group. This
de-arylation reaction is feasible assuming that benzoni-
trile is released spontaneously from a species analogous
to 5.
Both 3 and 4 exhibit, in their IR spectra, bands
attributable to w(NH) as expected. The NH proton
appears in the H NMR spectra as one broad signal at
1
13.08 ppm for 3 and 11.01 ppm for 4. Apparently, this
resonance shifts to lower fields for a neutral complex,
by comparison with the values found in cationic com-
plexes. Complex 3 is a red–orange solid, very soluble in
most common organic solvents, where it dissociates
benzophenone imine easily, as seen above. Nine sepa-
rate pyrazole proton and carbon resonances are ob-
However, we have been unable to detect benzonitrile,
since it is lost during the work-up of the reaction
mixture, so this proposal must be taken with due
caution. It seems that the imine proton is abstracted by
KOBut for both 1 and 2, giving rise to an intermediate
azavinylidene complex, which rearranges possibly yield-
ing ortho-metalated derivatives, a reaction which has
precedents in ruthenium and osmium chemistry [8,18].
The de-arylation of the benzophenone imine leading to
the phenyl derivative 6 resembles the recently reported
1
served in the H and 13C{1H} NMR spectra for the Tp
ligand, resulting from the chemical and magnetic in-
equivalence of the three pyrazole rings, a feature that it
has been observed previously for other [TpRuCl-
(PMeiPr2)(L)] derivatives [12,14]. Compound 4 is a
yellow–orange, crystalline material, which constitutes a
rare example of a bis(imine) derivative. This sort of
compound may play an important role as a catalyst for

874
M.A. Jime´nez-Tenorio et al. / Inorganica Chimica Acta 300–302 (2000) 869–874
[4] (a) Y. Nishibayashi, I. Takei, S. Uemura, M. Hidai,
Organometallics 17 (1998) 3420. (b) R. Noyori, S. Hashiguchi,
Acc. Chem. Res. 30 (1997) 97.
[5] (a) G.K. Cautrell, T.Y. Meyer, J. Am. Chem. Soc. 120 (1998)
8035. (b) G.K. Cautrell, T.Y. Meyer, Organometallics 16 (1997)
5381.
[6] G. Toth, I. Pinter, A. Messmer, Tetrahedron Lett. 9 (1974) 735.
[7] M.I. Bruce, P. Hinterding, M. Ke, P.J. Low, B.W. Skelton, A.H.
White, Chem. Commun. (1997) 715.
[8] M.A. Esteruelas, F.J. Lahoz, A.M. Lo´pez, E. On˜ate, L.A. Oro,
Organometallics 14 (1995) 2496.
[9] (a) R.C. Mehrora, in: G. Wilkinson, R.D. Gillard, J.A. McClev-
erty (Eds.), Comprehensive Coordination Chemistry, vol. 2,
Pergamon, Oxford, 1987, p. 269. (b) S. Joss, P. Bigler, A. Ludi,
Inorg. Chem. 24 (1985) 3487. (c) W.D. Harman, H. Taube,
Inorg. Chem. 27 (1988) 3261.
[10] E. Bustelo, M. Jime´nez-Tenorio, M.C. Puerta, P. Valerga, J.
Chem. Soc., Dalton Trans. (1999) 2399.
[11] M. Jime´nez-Tenorio, M.A. Jime´nez-Tenorio, M.C. Puerta, P.
Valerga, Inorg. Chim. Acta 259 (1997) 77.
[12] M.A. Jime´nez-Tenorio, M. Jime´nez-Tenorio, M.C. Puerta, P.
Valerga, J. Chem. Soc., Dalton Trans. (1998) 3601.
[13] M.A. Jime´nez-Tenorio, M. Jime´nez-Tenorio, M.C. Puerta, P.
Valerga, Organometallics 16 (1997) 5528.
[14] M.A. Jime´nez-Tenorio, M. Jime´nez-Tenorio, M.C. Puerta, P.
Valerga, Organometallics (2000) in press.
[15] (a) M.D. Fryzuk, M.D. Jones, F.W.B. Einstein, Organometallics
3 (1984) 185. (b) T.A. Burt, J. Chatt, W. Hussain, G.J. Leigh, J.
Organomet. Chem. 182 (1979) 203.
decarbonylation of alcohols by [TpRuH(MeCN)-
(PPh3)], a process which yields alkyl- or aryl-TpRu car-
bonyl complexes of the type [TpRuR(CO)(PPh3)] [23].
Both 5 and 6 display one triplet resonance in their
13C{1H} NMR spectra attributable to the metal-bound
1
carbon atom of the phenyl ring. The H NMR spec-
trum of 5 displays one broad resonance at 9.79 ppm
due to the NH proton, consistent with the presence of
a weak w(NH) band at 3320 cm−1 in the IR spectrum.
1
At variance with this, the H NMR spectrum of 6 is
much simpler in the aromatic region, showing no evi-
dence for the presence of NH protons. We have also
tried to deprotonate the bis(imine) complex 4. A red
solid has been obtained, which also shows evidence for
ortho-metalation, being apparently binuclear, as in-
ferred from NMR spectroscopy. The full characteriza-
tion of this compound is still underway and will be
reported in due course. It appears clear from this study
that deprotonation of imine adducts is a complex pro-
cess which does not always lead to stable azavinylidene
derivatives.
Acknowledgements
[16] TEXSAN, version 5.0, Single-Crystal Structure Analysis Software,
Molecular Structure Corporation, The Woodlands, TX, 1989.
[17] C.K. Johnson, ORTEP, A Thermal Ellipsoid Plotting Program,
Oak Ridge National Laboratory, Oak Ridge, TN, 1965.
[18] C. Bohanna, M.A. Esteruelas, A.M. Lo´pez, L.A. Oro, J.
Organomet. Chem. 526 (1996) 73.
[19] (a) M.C. Puerta, P. Valerga, Coord. Chem. Rev. 193 (1999) 977.
(b) C. Brunneau, P.H. Dixneuf, Acc. Chem. Res. 32 (1999) 311.
(c) M.I. Bruce, Chem. Rev. 91 (1991) 197.
We wish to thank the Ministerio de Educacio´n y
Ciencia of Spain (DGICYT, Project PB97-1357) for
financial support. We also thank Johnson Matthey plc
for generous loans of ruthenium trichloride, and the
Royal Society of Chemistry for the award of grant for
International Authors (to M. Jime´nez-Tenorio)
[20] (a) T. Daniel, H. Mu¨ller, H. Werner, Inorg. Chem. 30 (1991)
3118. (b) H. Werner, W. Knaup, M. Dziallas, Angew. Chem.,
Int. Ed. Engl. 26 (1987) 248.
[21] H. Werner, T. Daniel, W. Knaup, O. Nu¨rmberg, J. Organomet.
Chem. 462 (1993) 309.
References
[22] (a) C. Bois, J.A. Cabeza, J.R. Franco, V. Riera, E. Saborit, J.
Organomet. Chem. 564 (1998) 201. (b) J.A. Cabeza, I. del R´ıo,
M. Moreno, V. Riera, F. Grepioni, Organometallics 17 (1998)
3027. (c) J.A. Cabeza, I. del R´ıo, V. Riera, D. Ardura, J.
Organomet. Chem. 554 (1998) 117.
[1] T. Yamagishi, E. Mizushima, H. Sato, M. Yamaguchi, Chem.
Lett. (1998) 1255.
[2] E. Mizushima, M. Yamaguchi, T. Yamagishi, Chem. Lett.
(1997) 237.
[3] F. Kakiuchi, M. Yamauchi, N. Chatani, S. Murai, Chem. Lett.
(1996) 111.
[23] Y.Z. Cheng, W.C. Chan, C.P. Lau, H.S. Chu, H.L. Lee, G. Jia,
Organometallics 16 (1997) 1241.
.
.