Preparation of bis(aryldiazene) and new aryldiazenido complexes of rhenium

Article abstract of DOI:10.1016/S0022-328X(03)00589-8

Mixed-ligand hydride ReH₂(NO)L(PPh₃)₂ complexes [L=P(OEt)₃ or PPh(OEt)₂] were prepared by allowing the ReH₂(NO)(PPh₃)₃ species to react with an excess of phosphite. Treatment of ReH₂(NO)L(PPh₃)₂ hydrides with an equimolar amount of aryldiazonium cations ArN₂⁺ gives the mono-aryldiazene [ReH(ArN=NH)(NO)L(PPh₃) ₂]BPh₄ complexes (Ar=C₆H₅, 4-CH₃C₆H₄), while treatment with an excess of ArN₂⁺ yields bis(aryldiazene) [Re(ArN=NH)₂(NO)L(PPh₃)₂] (BPh₄)₂ derivatives. Binuclear [{ReH(NO)L(PPh₃)₂}₂ (μ-HN=NAr-ArN=NH)](BPh₄)₂ and [{Re(4-CH₃C₆H₄N=NH)(NO)L (PPh₃)₂}₂(μ-HN=NAr=ArN=NH)] (BPh₄)₄ complexes (Ar-Ar=4,4′-C₆H₄-C₆H₄, 4,4′-C₆H₄-CH₂-C₆ H₄) were also prepared. The reaction of the triphenylphosphine ReH₂(NO)(PPh₃)₃ complex with aryldiazonium cations was studied and led exclusively to mono-aryldiazene [ReH(ArN=NH)(NO)(PPh₃)₃]BPh₄ and [{ReH(NO)(PPh₃)₃}₂ (μ-HN=NAr-ArN=NH)](BPh₄)₂ derivatives. The complexes were characterised spectroscopically (IR, NMR) using the ¹⁵N-labelled derivatives. The aryldiazenido [ReH(C₆H₅N₂){PPh(OEt)₂} ₄]BPh₄ complex was prepared by allowing trihydride ReH₃[PPh(OEt)₂]₄ to react with phenyldiazonium tetrafluoroborate. A reaction path involving the aryldiazene [ReH₂(C₆H₅N=NH) {PPh(OEt)₂}₄]⁺ intermediate was also proposed.

Full text of DOI:10.1016/S0022-328X(03)00589-8

Journal of Organometallic Chemistry 679 (2003) 208Á219
/
www.elsevier.com/locate/jorganchem
Preparation of bis(aryldiazene) and new aryldiazenido complexes of
rhenium
Gabriele Albertin *, Stefano Antoniutti, Fabio Bredariol
Dipartimento di Chimica, Universit a` Ca’ Foscari di Venezia, Dorsoduro 2137, 30123 Venezia, Italy
Received 22 April 2003; received in revised form 14 June 2003; accepted 18 June 2003
Abstract
Mixed-ligand hydride ReH
(NO)(PPh species to react with an excess of phosphite. Treatment of ReH
of aryldiazonium cations ArN2 gives the mono-aryldiazene [ReH(ArNÄ
2
(NO)L(PPh
3
)
2
complexes [Lꢀ
/
P(OEt)
3
or PPh(OEt)
(NO)L(PPh
NH)(NO)L(PPh ) ]BPh complexes (Arꢀ
2
] were prepared by allowing the Re-
hydrides with an equimolar amount
C H , 4-
H
2
3
)
3
2
3 2
)
ꢁ
/
/
3 2
4
6
5
ꢁ
CH
Binuclear [{ReH(NO)L(PPh
ArNÄNH)](BPh complexes (ArÃ
3
C
6
H
4
), while treatment with an excess of ArN
(m-HNÄNArÃ
Arꢀ4,4?-C
2
yields bis(aryldiazene) [Re(ArNÄ
NH)](BPh and [{Re(4-CH
CH ) were also prepared. The reaction of the
/NH)
2
(NO)L(PPh
3
)
2
](BPh
4
)
2
derivatives.
3
)
2
}
2
/
/
ArNÄ
/
4
)
2
3
C
H
6 4
NÄ/NH)(NO)L(PPh
3
)
2
}
2
(m-HNÄNArÃ
/
/
/
4
)
4
/
/
6
H
4
Ã
/
C
H
6 4
, 4,4?-C
H
6 4
Ã
/
2 6 4
C H
Ã
/
triphenylphosphine ReH (NO)(PPh ) complex with aryldiazonium cations was studied and led exclusively to mono-aryldiazene
2
3 3
[
characterised spectroscopically (IR, NMR) using the N-labelled derivatives. The aryldiazenido [ReH(C
ReH(ArNÄ
/
NH)(NO)(PPh
3
)
3
]BPh
4
and [{ReH(NO)(PPh
1
3
)
3
}
2
(m-HNÄ
/
NArÃ
/
ArNÄ
/
NH)](BPh
4
)
2
derivatives. The complexes were
){PPh(OEt) ]BPh
5
6
H
N
5 2
2
}
4
4
complex was prepared by allowing trihydride ReH [PPh(OEt) ] to react with phenyldiazonium tetrafluoroborate. A reaction path
3
2 4
ꢁ
involving the aryldiazene [ReH
#
2
(C
6
H
5
NÄ
/
NH){PPh(OEt)
2
}
4
]
intermediate was also proposed.
2003 Elsevier B.V. All rights reserved.
Keywords: Rhenium; Hydride complexes; Bis(aryldiazene); Aryldiazenido; Phosphite ligands
1
. Introduction
We have been active in this research area since 1984
and have reported several studies on the synthesis and
the reactivity of aryldiazene, aryldiazenido and hydra-
Although the diazo chemistry of rhenium has been
6
widely studied in the past 25 years, relatively few
complexes with the aryldiazene ArNÄNH ligand have
been reported [1Á3], and none containing two ArNÄNH
zine complexes of d -transition metals [6], including the
NH)-
/
preparation of mono-aryldiazene [Re(ArNÄ
/
/
/
(CO) L ]BPh (Lꢀphosphites, nꢀ1, 2, 3, 4) com-
/
/
n
5ꢂn
4
groups bonded to the same rhenium central metal have
plexes of rhenium [3]. The poor reactivity of these
diazene complexes along with the interesting properties
shown by the known bis(aryldiazene) derivatives [4]
prompted us to extend those studies to the preparation
of bis(aryldiazene) derivatives of rhenium. The strategy
we thought to use involved the reaction of rhenium
dihydrides with aryldiazonium salts, in an attempt to
ever been described. Bis(aryldiazene) compounds are
rare and were prepared [4] for the iron triad by double
ꢁ
insertion of two ArN2 into the MÃ
priate MH L hydrides.
/
H bond of appro-
2
4
Interest in the chemistry of these diazo complexes
stems not only from their relevance in the dinitrogen
fixation process [5], but also from the diverse reactivity
modes and structural properties that this class of
complexes may exhibit [1,2].
achieve a double insertion into the two ReÃ
However, since the known dihydride [7] Re-
(NO)(PPh does not give the bis(insertion) of
/H bonds.
H
)
3 3
2
ꢁ
2
ArN , we first investigated the synthesis of new
hydrides and then the reaction with aryldiazonium
cations. The results of these studies, which involve the
synthesis of bis(aryldiazene) and new aryldiazenido
complexes of rhenium, are reported here.
*
Corresponding author. Tel.: ꢁ
34-8917.
E-mail address: albertin@unive.it (G. Albertin).
/
39-041-234-8555; fax: ꢁ39-041-
/
2
0
022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00589-8

G. Albertin et al. / Journal of Organometallic Chemistry 679 (2003) 208Á
/219
209
2
. Experimental
from CH Cl and ethanol; yield ꢀ
/85%. For Re-
2
2
H (NO){P(OEt) }(PPh ) : Found: C, 55.6; H, 5.3; N,
1.5. C H NO P Re requires C, 55.50; H, 5.2; N, 1.5%.
42 47 4 3
2
3
3 2
2
.1. General considerations and physical measurements
For ReH (NO){PPh(OEt) }(PPh ) : Found: C, 58.9; H,
2
2
3 2
All synthetic work was carried out in an inert atmo-
5.1; N, 1.6. C H NO P Re requires C, 58.7; H, 5.0; N,
4
6
47
3 3
sphere using standard Schlenk techniques or a Vacuum
Atmosphere dry-box. Once isolated, the complexes were
found to be relatively stable in air, but were stored in an
1.5%.
2.2.2. [ReH(ArNÄ
2) [LꢀP(OEt) (1), PPh(OEt) (2), Arꢀ
4-CH C H (b)]
/
NH)(NO)L(PPh ) ]BPh (1 and
3
2
4
inert atmosphere at ꢂ
/
25 8C. All solvents were dried
/
/
C H (a),
6
3
2
5
over appropriate drying agents, degassed on a vacuum
line and distilled into vacuum-tight storage flasks.
Metallic rhenium was a Chempur product, used as
3
6
4
3
In a 25-cm three-necked round-bottomed flask were
placed solid samples of the appropriate hydride Re-
H (NO)L(PPh ) (0.1 mmol) and of the aryldiazonium
received. The phosphite P(OEt) (Aldrich) was purified
3
2
3 2
by distillation under nitrogen; PPh(OEt) was prepared
2
salt [ArN ]BF (0.1 mmol). The flask was cooled to ꢂ
/
2
4
3
by the method of Rabinowitz and Pellon [8]. Diazonium
salts were obtained in the usual way [9]. The related
196 8C and 10 cm of CH Cl added. The reaction
2
2
mixture was brought to 0 8C, stirred for 1 h and then the
solvent was removed under reduced pressure. The oil
obtained was treated with ethanol containing an excess
bis(diazonium) salts [N ArÃ
/
ArN ](BF ) (ArÃ
/
Arꢀ
/
2
2
4 2
4
,4?-C H Ã
/
C H , 4,4?-C H Ã
/
CH2Ã
/
C H ) were prepared
ArNH with
6
4
6
4
6
4
6
4
by treating the amine precursors H NArÃ
/
of NaBPh (0.2 mmol, 68 mg) and the resulting solution
4
2
2
NaNO as described for common mono-diazonium salts
stirred until a yellow solid separated out, which was
filtered and crystallised from CH Cl and ethanol; yield
2
[
[
(
9]. The labelled diazonium tetrafluoroborate
2
2
1
5
15
15
2
ꢂ1
C H NÅ
/
N]BF and [4,4?- NÅ
/
NC H Ã
/
C H NÅ
/
N]-
BF ) were prepared from Na NO (99% enriched,
ꢀ
/
65%; LM (S cm mol )ꢀ50.2 for 1a, 53.6 for 2a,
/
6
5
4
6
4
6
4
1
5
49.9 for 2b. Found: C, 65.0; H, 5.6; N, 3.2.
C H BN O P Re (1a) requires C, 64.9; H, 5.4; N,
4
2
2
CIL) and the appropriate amine. Alternatively, the
1
7
2
72
3
4 3
5
[
C H NH . Other reagents were purchased from com-
C H NÅ
/
N]BF salt was prepared from NaNO and
3.15. Found: C, 67.1; H, 5.45; N, 3.2%.
C H BN O P Re (2a) requires C, 66.9; H, 5.3; N,
6
5
4
2
1
5
6
5
2
76 72
3
3 3
ꢂ1
mercial sources in the highest available purity and used
as received. Infrared spectra were recorded on a Nicolet
Magna 750 FT-IR spectrophotometer. NMR spectra
3.1. IR (KBr, cm ): 1882 (w) n(ReH), 1674 (s) n(NO).
1
H-NMR (CD Cl -d , 25 8C, d): 13.08 (s, br), 11.50 (br)
2
2
2
(NH), 3.81 (JPH
ꢀ
/
8 Hz), 3.65 (JPH
3.31, 3.29 (qnt, CH ), 1.19, 0.78 (t, CH ) ppm. P{ H}-
ꢀ8 Hz) (q, ReH),
/
1
31
31
1
(
H, P) were obtained on a Bruker AC200 or an
AVANCE 300 spectrometers at temperatures varying
2 3
NMR (CD Cl -d , 25 8C, d): AB spin system, d 131.1
2
2
2
2
A
1
between ꢂ
/
90 and ꢁ
/
30 8C, unless otherwise noted. H
ppm, d 17.1 ppm, JABꢀ18.3 Hz; AB spin system, d
/
B
2 A
spectra are referred to internal tetramethylsilane. Phenyl
1
137.7 ppm, d 24.1 ppm, JABꢀ
/
10.8 Hz. Found: C, 67.2;
B
3
1
proton resonances are omitted. P{ H} chemical shifts
are reported with respect to 85% H PO , with downfield
H, 5.5; N, 3.20. C H BN O P Re (2b) requires C,
3 3
7
7
74
3
ꢂ1
67.05; H, 5.4; N, 3.05%. IR (KBr, cm ): 1871 (w)
1
n(ReH), 1682 (s) n(NO). H-NMR (CD Cl -d , 25 8C,
d): 12.89, 11.2 (s, br, NH), AB X spin system, d 3.83,
3
4
1
shifts considered positive. N spectra refer to external
5
2
2
2
1
3
5
CH NO , with downfield shifts considered positive.
2
2 X
ꢂ3
ꢂ3
The conductivity of 10
mol dm
solutions of the
JAX
3.67, JAX
2.37, 2.31 (s, CH ), 0.94, 0.78 (t, CH phos) ppm.
ꢀ/10.1 Hz, JBX
ꢀ/3.30 Hz; AB X spin system, d
2 X
complexes in CH NO at 25 8C was measured with a
ꢀ
/
JBX 7.1 Hz (ReH), 3.40Á3.00 (m, CH2),
ꢀ
/
/
3
2
Radiometer CDM 83 instrument.
3
3
3
1
1
P{ H}-NMR (CD Cl -d , 25 8C, d): AB spin system,
2
2
2
2
2
.2. Synthesis of complexes
dA 131.5 ppm, d 17.2 ppm, JABꢀ
/
18.3 Hz; AB spin
9.8 Hz.
B
2
system, d 137.7 ppm, d 24.1 ppm, JABꢀ
/
A
B
Hydrides ReH (NO)(PPh ) and ReH {PPh(OEt) }
2 3
2
3 3
3
15
/
were prepared following the methods previously re-
ported [7,10].
2.2.3. [ReH(C H NÄ
NH)(NO)L(PPh ) ]BPh
3 2
6
5
4
(1a and 2a ) [LꢀP(OEt) (1), PPh(OEt) (2)]
/
1
1
3 2
These complexes were prepared exactly like the
related unlabelled compounds 1a and 2a using
2
ReH (NO){PPh(OEt) }(PPh )
.2.1. ReH (NO){P(OEt) }(PPh ) and
3 2
2
3
1
5
[C H NÅ
/
N]BF as a reagent; yield ꢀ60%. For 2a :
/
2
2
3 2
6
5
4
1
ꢂ1
1
IR (KBr, cm ): 1883 (w) n(ReH), 1680 (s) n(NO). H-
An excess of the appropriate phosphite (6 mmol) was
added to a solution of ReH (NO)(PPh ) (1 mmol, 1.0 g)
1
NMR (CD Cl -d , 25 8C, d): 13.09 (dd, J
ꢀ
/
62 Hz,
61 Hz) (NH), 3.80
(m), 3.64 (q) (ReH), 3.29, 3.14 (m, CH ), 0.98, 0.81 (t,
2
3 3
2
2
2
15NH
3
in 20 cm of toluene and the reaction mixture refluxed
2
1
JPH
ꢀ
/
4 Hz), 11.49 (d, br, J
ꢀ
/
15NH
for 1 h. The solvent was removed under reduced
pressure to give an oil which was triturated with ethanol
2
3
1
1
CH ) ppm. P{ H}-NMR (CD Cl -d , 25 8C, d): AB Y
3
2
2
2
2
3
3 cm ). A yellow solid slowly separated out from the
(
resulting solution, which was filtered and crystallised
spin system, d 131.1 ppm, d 17.1 ppm, JABꢀ
/
18.1 Hz,
A
B
JAY
ꢀ/34.4 Hz, JBY
ꢀ1.6 Hz; AB Y spin system, d
/
2 A

210
G. Albertin et al. / Journal of Organometallic Chemistry 679 (2003) 208Á219
/
1
JBY
37.7 ppm, d 24.2 ppm, JABꢀ
/
10.2 Hz, JAY
ꢀ
/
3.7 Hz,
H, 5.7; N, 4.1. C102H B N O P Re (5a) requires C,
97 2 5 4 3
B
ꢀ/3.8 Hz).
69.70; H, 5.6; N, 4.0%. Found: C, 70.2; H, 5.8; N, 3.95.
C104H101B N O P Re (5b) requires C, 69.95; H, 5.70; N,
2
5
4 3
ꢂ1
2
.2.4. [{ReH(NO)L(PPh ) } (m-HNÄ
/
NArÃ
/
ArNÄ
/
3.9%. IR (KBr, cm ): 1730 (sh), 1726 (s), 1699 (s)
1
n(NO). H-NMR (CD Cl -d , 25 8C, d): 12.83, 12.69 (d,
3
2 2
NH)](BPh ) (3 and 4) [Lꢀ
/
P(OEt) (3),
4
2
3
2
2
2
PPh(OEt) (4), ArÃ
/
Arꢀ
/
4,4?-C H Ã
/
C H (c), 4,4?-
NH), 3.52 (m, CH ), 2.45, 2.42 (s, CH ), 1.07, 0.97 (t,
3
2
6
4
6
4
2 3
1
1
C H Ã
/
CH2Ã
/
C H (d)]
CH phos) ppm. P{ H}-NMR (CD Cl -d , 25 8C, d):
6
4
6
4
3
2
2
2
3
In a 25-cm three-necked round-bottomed flask were
placed solid samples of the appropriate hydride Re-
H (NO)L(PPh ) (0.1 mmol) and of the bis(aryldiazo-
AB spin system, d 104.7 ppm, d 4.58 ppm, JABꢀ24.7
/
2
A
B
Hz; AB spin system, d 104.4 ppm, d 4.08 ppm, JABꢀ
/
2
A
B
24.7 Hz; AB spin system, d 99.9 ppm, d ꢂ
/
0.17 ppm,
2
3 2
2
A
B
nium)tetrafluoborate [N ArÃ
/
ArN ](BF ) (0.05 mmol)
4 2
JAB
C106H B N O P Re (6a) requires C, 71.15; H, 5.5; N,
ꢀ
97
/
23.7 Hz. Found: C, 70.95; H, 5.6; N, 4.0.
2
2
and the flask was cooled to ꢂ
/
196 8C. Methylene
2
5
3 3
3
chloride (10 cm ) was added and the reaction mixture,
brought to 0 8C, was stirred for 4 h. The solvent was
removed under reduced pressure to give an oil, which
3.9%. Found: C, 71.4; H, 5.65; N, 3.9.
C108H101B N O P Re (6b) requires C, 71.3; H, 5.60;
2
5
3 3
ꢂ1
1
N, 3.85%. IR (KBr, cm ): 1716 (s, br) n(NO). H-
3
was treated with ethanol (3 cm ). The addition of
NMR (CD Cl -d , 25 8C, d): 12.88, 12.73 (d, NH), 3.63,
2
2
2
3
NaBPh (0.2 mmol, 68 mg) in 2 cm of ethanol caused
the separation of a yellow solid which was filtered and
3.35 (qnt, CH ), 2.39, 2.34 (s, CH ), 1.16, 0.99 (t, CH
2 3
4
3
3
1
1
phos) ppm. P{ H}-NMR (CD Cl -d , 25 8C, d): AB
2
2
2
2
crystallised from CH Cl and ethanol; yield ꢀ
/
65%; LM
121.5 for 3d, 127.3 for 4c, 123.9 for 4d.
Found: C, 64.9; H, 5.6; N, 3.2. C145H144B N O P Re
spin system, d 127.3 ppm, d 3.52 ppm, JABꢀ
/
20.0 Hz;
2
2
A
B
2
ꢂ1
(
S cm mol )ꢀ
/
AB spin system, d 122.0 ppm, d ꢂ
/
2.0 ppm, JAB
ꢀ
/
2
A
B
19.5 Hz; AB spin system, d 127.9 ppm, d 3.04 ppm,
B
2
6
8
6
ꢂ1
2
2
A
(
1
3d) requires C, 65.0; H, 5.4; N, 3.15%. IR (KBr, cm ):
1
JAB
ꢀ/20.0 Hz).
890 (w) n(ReH), 1695 (s) n(NO). H-NMR (CD Cl -d ,
2 2 2
1
5
2
JPH
5 8C, d): 12.88 (d, br), 11.5 (s, br) (NH), 3.98 (q,
2.2.6. [Re(C H NÄ
/
NH) (NO)L(PPh ) ](BPh )
2 3 2 4 2
6
5
2
ꢀ
/
8 Hz, ReH), 3.77, 3.35 (qnt, CH ), 1.03, 0.80 (t,
1
(5a and 6a ) [LꢀP(OEt) (5), PPh(OEt) (6)]
/
2
1
1
3 2
3
1
CH ) ppm. P{ H}-NMR (CD Cl -d , 25 8C, d): AB
These complexes were prepared exactly like the
related unlabelled compounds 5a and 6a using
3
2
2
2
2
spin system, d 107.0 ppm, d 18.4 ppm, JABꢀ
/24.1 Hz;
A
B
1
5
AB2 spin system, dA 113.5, dB 24.1, JAB
Found: C, 67.10; H, 5.4; N, 3.2. C152H142B N O P Re
2
ꢀ
/
12.6 Hz.
[C H NÅ
/
N]BF as a reagent; yield ꢀ
/
60%.
6
5
4
2
6
6
6
(
H, 5.5; N, 3.2. C153H144B N O P Re (4d) requires C,
4c) requires C, 66.9; H, 5.25; N, 3.1%. Found: C, 66.9;
2.2.7. [{Re(4-CH C H NÄ
/
NH)(NO)[P(OEt) ]-
3
3
6
4
(PPh ) } (m-4,4?-HNÄ
/
NC H Ã
/
C H NÄ
/NH)](BPh4)4
2
6
6
6
2
3 2 2
6
4
6
4
ꢂ1
6
7.00; H, 5.3; N, 3.1%. IR (KBr, cm ): 1890 (w)
1
(7)
3
n(ReH), 1684 (s) n(NO). H-NMR (CD Cl -d , 25 8C,
In a 25-cm three-necked round-bottomed flask were
placed 0.100 g (0.11 mmol) of ReH (NO){P(OEt) }-
2
2
2
d): 13.0, 11.4 (s, br, NH), 3.8 (m, ReH), 3.83 (s, CH2),
3
2
3
.31, 3.15 (qnt, CH phos), 1.15, 0.82 (t, CH ) ppm.
3
(PPh ) and 21 mg (0.055 mmol) of [4,4?-N C H Ã
/
2
3 2
2
6
4
3
1
1
P{ H}-NMR (CD Cl -d , 25 8C, d): AB spin system,
C H N ](BF ) . The flask was cooled to ꢂ
/
196 8C and
2
2
2
2
6
4
2
4 2
3
8 cm of CH Cl was added. The reaction mixture was
dA 131.0 ppm, d 17.2 ppm, JABꢀ
/
18.1 Hz; AB spin
9.6 Hz).
B
2
2
2
system, d 137.6 ppm, d 24.1 ppm, JABꢀ
/
brought to 0 8C, stirred for 4 h and then transferred, by
cannule, into a 25-cm three-necked flask cooled to
A
B
3
2
6
4
.2.5. [Re(ArNÄ
) [LꢀP(OEt) (5), PPh(OEt) (6), Arꢀ
-CH C H (b)]
/
NH) (NO)L(PPh ) ](BPh ) (5 and
ꢂ
/
196 8C and containing an excess of solid [4-
2
3 2
4 2
/
/
C H (a),
5
CH C H N ]BF (0.32 mmol, 66 mg) diazonium salt.
The resulting reaction mixture was brought to ꢂ10 8C
3
2
6
3
6
4
2
4
/
3
6
4
An excess of aryldiazonium tetrafluoroborate
ArN ]BF (0.4 mmol) and the appropriate hydride
ReH (NO)L(PPh ) (0.1 mmol) were placed as solid
and stirred for about 6 h. The solvent was removed
under reduced pressure, giving an oil which was
triturated with ethanol containing an excess of NaBPh4
(0.4 mmol, 0.137 g). A reddish-brown solid slowly
[
2
4
2
3 2
3
samples in a 25-cm three-necked round-bottomed flask.
The flask was cooled to ꢂ196 8C and dichloromethane
10 cm ) added. The reaction mixture was brought to
8C, stirred for 3 h and then the solvent removed under
/
separated out, which was filtered and crystallised from
2
3
(
CH Cl and ethanol; yield ꢀ
/
60%; L ꢀ284 S cm
/
2
ꢂ1
2
M
0
mol
.
Found: C, 70.15; H, 5.7; N, 4.1.
C206H196B N O P Re requires C, 69.9; H, 5.6; N,
reduced pressure. The oil obtained was treated with
3
ethanol (3 cm ) containing an excess of NaBPh (0.4
4
10
8
6
2
3.95%.
4
mmol, 0.137 g) and the resulting solution stirred for 30
min. A yellowish-orange solid slowly separated out,
which was filtered and crystallised from CH Cl and
2.2.8. [ReH(ArNÄ
/
NH)(NO)(PPh ) ]BPh (8)
3
3
4
[Arꢀ
/
C H (a), 4-CH C H (b)]
2
2
6 5 3 6 4
2
ꢂ1
3
ethanol; yield ꢀ
/
60%; LM (S cm mol )ꢀ/120.7 for 5a,
In a 25-cm three-necked round-bottomed flask were
placed 0.1 g (0.1 mmol) of ReH (NO)(PPh ) and an
1
14.8 for 5b, 122.3 for 6a, 117.5 for 6b. Found: C, 69.9;
2
3 3

G. Albertin et al. / Journal of Organometallic Chemistry 679 (2003) 208Á
/219
211
equimolar amount (0.1 mmol) of the appropriate
aryldiazonium tetrafluoborate [ArN ]BF and the flask
reaction mixture was brought to 0 8C, stirred for 4 h and
then the solvent removed under reduced pressure. The
oil obtained was triturated with ethanol containing an
2
4
3
was cooled to ꢂ196 8C. Dichloromethane (10 cm ) was
/
added and the reaction mixture, brought to 0 8C, was
stirred for 50 min. The solvent was removed under
reduced pressure to give a brown solid, which was
excess of NaBPh (0.2 mmol, 68 mg). A reddish-brown
4
solid separated out from the resulting solution, which
was filtered and crystallised from CH Cl and ethanol;
2
2
3
2
ꢂ1
treated with ethanol (5 cm ). The addition of an excess
of NaBPh (0.2 mmol, 68 mg) to the resulting solution
yield ꢀ
/
70%. LM (S cm mol )ꢀ125.1 for 9c, 138.5
/
4
for 9d. Found: C, 70.7; H, 5.1; N, 3.0.
caused the separation of a reddish-brown solid, which
was filtered and crystallised from CH Cl and ethanol;
C168H142B N O P Re (9c) requires C, 70.6; H, 5.0; N,
2
6
2
6
2
2
2
2.95%. Found: C, 70.8; H, 5.15; N, 3.1.
C169H144B N O P Re (9d) requires C, 70.70; H, 5.05;
2
ꢂ1
yield ꢀ
8
/
75%; LM (S cm mol )ꢀ
/
61.3 for 8a, 58.6 for
b. Found: C, 70.8; H, 5.20; N, 3.0. C H BN OP Re
2
6
2
6
2
8
4
72
3
3
ꢂ1
N, 2.95%. IR (KBr, cm ): 1830 (w) n(ReH), 1684 (s)
1
n(NO). H-NMR (CD Cl -d , 25 8C, d): 12.55, 11.35 (s,
(
H, 5.3; N, 3.05. C H BN OP Re (8b) requires C, 70.7;
8a) requires C, 70.6; H, 5.1; N, 2.95%. Found: C, 70.8;
2
2
2
8
5
74
3
3
br, NH), A BX spin system, d 3.37 ppm, JAXꢀ
2
/
JBX
ꢀ
/
ꢂ1
X
H, 5.15; N, 2.9%. IR (KBr, cm ): 1844 (m) n(ReH),
1
686 (s) n(NO). H-NMR (CD Cl -d , 25 8C, d): 12.50
6.86 Hz; A
BX spin system, d
31
3.67 ppm, JAX
Hz, JBX 15.6 Hz (ReH). P{ H}-NMR (CD Cl -d ,
ꢀ
/
34.6
2
X
1
1
2
2
2
ꢀ
/
2
2
2
(
d, JPH
ꢀ10 Hz), 12.25 (br) (NH), A BX spin system, d
/
2 X
2
5 8C, d): A B spin system, d 21.9 ppm, d 14.5 ppm,
2
A
B
3
ppm, J
.65 ppm, JAX
ꢀ
/
JBX
ꢀ7 Hz; A BX spin system, d 3.30
/
2 X
JAB
ppm, JAB
ꢀ
/
5.8 Hz; A B spin system, d 16.3 ppm, d 10.8
13.8 Hz.
2
A
B
ꢀ
/
15 Hz, JBX
ꢀ35 Hz (ReH), 2.33, 2.31 (s,
/
AX
1
3
1
ꢀ
/
CH3). P{ H} NMR (CD Cl -d , 25 8C, d): A B spin
2
2
2
2
system, d 16.5 ppm, d 11.0 ppm, JABꢀ
/
14.0 Hz; A B
A
B
2
spin system, d 21.6 ppm, d 14.2 ppm, JABꢀ
/
6.3 Hz.
A
B
1
5
2
.2.11. [{ReH(NO)(PPh ) } (m-4,4?-H NÄ
/
NC H Ã
/
3
3 2
6
4
15
/
1
5
2
.2.9. [ReH(C H NÄ
NH)(NO)(PPh ) ]BPh (8a )
1
6
1
5
3 3
4
C H NÄ
/
NH)](BPh ) (9c )
6
4
4 2 1
5
and [ReH(C H NÄ
/
NH)(NO)(PPh ) ]BPh (8a )
3 3 4 2
These complexes were prepared exactly like the
related unlabelled compound 8a using the labelled
6
5
This complex was prepared exactly like the related
1
5
unlabelled compound 9c using the [4,4?- NÅ
/
NC H Ã
/
6
4
15
C H NÅ
6
/
N](BF4)2 bis(aryldiazonium) salt; yield ꢀ
/
6
4
1
5
15
5
[
C H NÅ
/
N]BF4 and [C H NÅ
/N]BF , respectively,
4
ꢂ1
6
5
6
0%. IR (KBr, cm ): 1842 (w) n(ReH), 1684 (s)
1
n(NO). H-NMR (CD Cl -d , 25 8C, d): 12.71 (dd,
aryldiazonium salts; yield ꢀ
/65%. For 8a : IR (KBr,
1
2
2
2
ꢂ1
1
cm ): 1844 (w) n(ReH), 1684 (s) n(NO). H-NMR
1
1
J15NH
ꢀ
/
66 Hz), 11.5 (d, br, J15NH
ꢀ
/
63 Hz) (NH),
JBX 8 Hz,
.4 (m) (ReH). P{ H}-NMR (CD Cl -d , 25 8C, d):
1
(
CD Cl -d , 25 8C, d): 12.69 (dd, J
10 Hz), 11.46 (d, J15NH
system, dX 3.66 ppm, JAX
ꢀ
/
63 Hz, JPH
61 Hz) (NH), A BX spin
ꢀ
/
2
2
2
15NH
A BX spin system, d 3.67 ppm, JAX
ꢀ
/
ꢀ
/
2
X
ꢀ
/
31
1
2
3
2
2
2
ꢀ/JBX
ꢀ6.9 Hz; A BX spin
/
2
A BY spin system, d 16.2 ppm, d 10.9 ppm, JABꢀ
/
2
A
B
system, d 3.38 ppm, JAXꢀ
/
34.6 Hz, JBX
ꢀ15.6 Hz
/
X
1
3
1
14.0 Hz, JAY
ꢀ
/
1.8 Hz, JBY
ꢀ
/
28.5 Hz; A
2
BY spin
(
ReH). P{ H}-NMR (CD Cl -d , 25 8C, d): A BY
2
2
2
2
system, dA 22.1 ppm, dB 14.6 ppm, JAB
JAY 22.9 Hz, JBY 17.2 Hz.
ꢀ6.3 Hz,
/
spin system, d 16.2 ppm, d 10.8 ppm, JABꢀ
/
14.1 Hz,
28.1 Hz; A BY spin system, d 21.9
A
B
ꢀ
/
ꢀ
/
JAY
ꢀ
/
1.9 Hz, JBY
ꢀ
/
2
A
ppm, d 14.4 ppm, JABꢀ
/
6.3 Hz, JAYꢀ
/
4.3 Hz, JBY
ꢀ
/
B
ꢂ1
2
.3 Hz. For 8a : IR (KBr, cm ): 1844 (w) n(ReH),
684 (s) n(NO). H-NMR (CD Cl -d , 25 8C, d): 12.69
2
1
1
2.2.12. [ReH(C H N ){PPh(OEt) } ]BPh (11a)
6 5 2 2 4 4
2
2
2
2
d, br, J
(
ꢀ2.5 Hz), 11.47 (br) (NH), A BX spin
/
1
5NH
2
Solid samples of ReH {PPh(OEt) } (0.100 g, 0.102
3 2 4
system, dX 3.66 ppm, JAX
ꢀ
/
JBX
ꢀ6.9 Hz; A BX spin
/
2
mmol) and of an excess of [C H N ]BF (0.77 mg, 0.4
6 5 2 4
system, d 3.38 ppm, JAXꢀ
X
/
34.6 Hz, JBX
ꢀ
/
15.6 Hz
3
mmol) were placed in a 25-cm three-necked round-
3
1
1
(
ReH). P{ H}-NMR (CD Cl -d , 25 8C, d): A BY
2
2
2
2
bottomed flask and cooled to ꢂ196 8C. Dichloro-
/
spin system, d 16.2 ppm, d 10.8 ppm, JABꢀ
/
14.1 Hz,
3
A
B
methane (8 cm ) was added and the reaction mixture,
brought to 0 8C, was stirred for 2 h at this temperature
and then for other 4 h at about 22 8C. The solvent was
removed under reduced pressure giving an oil which was
treated with ethanol containing an excess of NaBPh4
JAY
dB 14.5 ppm, JAB
ꢀ
/
JBY
ꢀ
/
B1 Hz; A BY spin system, dA 21.9 ppm,
/
2
ꢀ
/
6.3 Hz, JAY
ꢀ/3.3 Hz, JBY
ꢀ5.4 Hz.
/
2
.2.10. [{ReH(NO)(PPh ) } (m-HNÄ
/
NArÃ
/
ArNÄ
/
3
3 2
NH)](BPh ) (9) [ArÃ
/
Arꢀ
/
4,4?-C H ÃC H (c), 4,4?-
/
4
2
6
4
6
4
(
0.14 g, 0.4 mmol). A reddish-brown solid slowly
separated out from the resulting solution, which was
filtered and crystallised from CH Cl and ethanol; yield
C H Ã
/
CH2Ã
/
C H (d)]
6
4
6
4
Solid samples of RuH (NO)(PPh ) (0.1 g, 0.1 mmol)
2
3 3
and the appropriate aryldiazonium tetrafluoborate
N ArÃArN ](BF ) (0.05 mmol) were placed in a 25-
cm three-necked round-bottomed flask. The flask was
2
2
2
[
/
ꢀ
/30%; L
M
ꢀ
/
62.7 S cm molꢂ1. Found: C, 60.1; H, 6.3;
H86BN O P Re requires C, 59.9; H, 6.15; N,
2 8 4
2
3
2
4 2
N, 2.0. C70
2.0%.
3
cooled to ꢂ196 8C and CH Cl (10 cm ) added. The
/
2
2

212
G. Albertin et al. / Journal of Organometallic Chemistry 679 (2003) 208Á219
/
1
5
2
(
.2.13. [ReH(C H NÅ
/
N){PPh(OEt) } ]BPh
2 4 4
On the basis of these data, a geometry of type I (Fig.
6
5
11a )
1), with the two hydride ligands in a mutually cis
position, can reasonably be proposed for the Re-
H (NO)L(PPh ) mixed-ligand derivatives.
1
This complex was prepared following the method
reported for the related unlabelled compound 11a using
2
3 2
1
5
[
C H NÅ
/
N]BF as a reagent; yield ꢀ30%.
/
6
5
4
3.2. Aryldiazene derivatives
3
. Results and discussion
The synthesis of bis(aryldiazene) complexes of rhe-
nium [Re(ArNÄ
/
NH) (NO)L(PPh ) ](BPh ) (5 and 6)
2 3 2 4 2
3
.1. Preparation of hydride complexes
was achieved by reacting the ReH (NO)L(PPh ) mixed-
2
3 2
ligand hydrides with an excess of aryldiazonium cations
in CH Cl , as shown in Scheme 2.
Studies on the reaction course revealed that the
The synthesis of bis(aryldiazene) complexes of rhe-
nium was achieved using the new ReH (NO)L(PPh )
2
2
2
3 2
[
Lꢀ
/
P(OEt) and PPh(OEt) ] mixed-ligand hydrides as
3
2
treatment of ReH (NO)L(PPh ) hydrides with an
2
3 2
precursors. The preparation of these mixed-ligand
hydrides deserves some further comments. Treatment
of ReH (NO)(PPh ) with an excess of phosphites gives
ꢁ
2
equimolar amount of ArN gives the [ReH(ArNÄ
/
ꢁ
NH)(NO)L(PPh ) ] monodiazene cations 1 and 2,
which further react with an excess of aryldiazonium
salt to give the final bis(aryldiazene) derivatives 5 and 6.
3
2
2
3 3
the ReH (NO)L(PPh ) derivatives, which were isolated
2
3 2
and characterised (Scheme 1).
The reaction proceeds with the replacement of only
2ꢁ
Bis(aryldiazonium) cations [N ArÃ
/ArN2]
also re-
act with ReH (NO)L(PPh ) dihydrides in a 1:2 ratio to
2
2
3 2
one PPh and with the exclusive formation of the mixed-
3
give binuclear complexes 3 and 4 with a di-diazene
bridging unit (Scheme 3).
These binuclear complexes 3 and 4 were treated with
ligand ReH (NO)L(PPh ) compounds. They are pale-
3 2
2
yellow solids stable in air and in a solution of common
organic solvents, where they behave as non-electrolytes.
Analytical and spectroscopic data (Table 1) support the
proposed formulation.
ꢁ
an excess of monodiazonium ArN2 cation in order to
test whether further insertion on the ReÃ/H bond can
take place to give bis(aryldiazene) species. In only one
case does the reaction proceed to give the binuclear
complex 7, which was isolated in pure form and
characterised (Scheme 4).
The infrared spectrum of each of the two hydride
ꢂ1
compounds shows one strong absorption at 1607 cm
due to the n(NO), and one medium-intensity slightly
,
broad band at 1823 and 1844 cmꢂ1, attributed to the
It is important to note that only the Re-
H (NO)L(PPh ) dihydride, containing mixed phos-
stretching of the ReÃ
/
H bond.
2
3 2
The proton NMR spectra confirm the presence of the
hydride ligands, showing a complicated multiplet be-
phiteÁ
/
phosphine ligands, undergoes insertion of two
ꢁ
ArN2 groups into the two ReÃ
bis(aryldiazene) complexes. The related triphenylpho-
/H bonds, yielding
tween ꢂ
/
0.46 and ꢂ3.46 ppm. Taking into account that
/
3
the P{ H}-NMR spectra display a AB multiplet, the
1
1
2
hydride pattern can be simulated using an AB XY
2
model (with Xꢀ
/
HA and YꢀH ) whose parameters
/
B
are reported in Table 1.
/
3 2
Scheme 1. LꢀP(OEt) and PPh(OEt) .
Fig. 1.
Scheme 2. Arꢀ
/C
6
H
5
3
(a), 4-CH C
6
H
4
/
3
(b); LꢀP(OEt) (1 and 5),
PPh(OEt) (2 and 6).
2
Scheme 4. Arꢀ
/
3
4-CH C
6
H
4
; ArÃ
/
Arꢀ/4,4?-C
6
H
4
Ã
/
C
6
H
4
/
3
; LꢀP(OEt) .
Scheme 3. ArÃ/Arꢀ/4,4?-C
6
H
4
Ã
/
C
6
H
4
(c), 4,4?-C
6
H
4
Ã
/
CH
2
Ã
/
C
6
H
4
/
3 2
(d); LꢀP(OEt) (3), PPh(OEt) (4).

Table 1
IR and NMR data for selected rhenium complexes
a
1
b,c
31
Spin system P{ H}-NMR
1
b,d
Compound
IR
(
n
Assgnt
H-NMR
d (J, Hz)
Assgnt
d (J, Hz)
ꢂ1
cm
)
e
3.68 (m) , 3.46 (m), 0.88 (t),
e
ReH (NO){PPh(OEt)
2
2
}(PPh
3
)
2
1823w,- n(ReH),
br, n(NO)
607s
CH , CH
ReH
2
3
,
AB
2
d
A
150.8, d
B
26.6, JAB
ꢀ/10.4
AB
2
XY spin syst, d
39.6, JAY
29.3, JBY 20.5, JXY
X
ꢂ
/
0.46, d
Y
1
ꢂ
/
3.07, JAX
ꢀ/
ꢀ/53.3,
J
BX
ꢀ/
ꢀ/
ꢀ
/
5
.4
ReH
2
(NO){P(OEt) }(PPh
3
3
)
2
1844m, n(ReH),
n(NO)
3.54 (qnt), 0.84 (t), AB
syst, d 0.48, d 3.46,
52.8, JAY 54.4, JBX
9.3, JBY 21.5, JXY 5.0
6, 11.60 (d, NH, ReH, AB
6, 4.10 (m), 3.51 CH , CH
qnt), 3.48 (qnt), 1.05 (t), 0.92 (t)
2
XY spin CH
2
, CH
3
,
AB
2
d
A
A
140.9, d
B
B
26.6, JAB
24.1, JAB
ꢀ
/
13.5
1
607s
X
ꢂ
/
Y
ꢂ
/
ReH
J
AX
ꢀ
/
ꢀ/
ꢀ/
2
ꢀ
/
ꢀ
/
3
1
a
a
[ReH(C
[ReH(C
6
6
H
5
5
NÄ
/
NH)(NO){P(OEt)
3
}(PPh
3
)
2
]BPh
4
1885w,
701s
n(ReH),
n(NO)
12.96 (d, br), JPH
ꢀ/
2
, AB
2
d
113.6, d
ꢀ/
12.9, d
A
3
1
br), JPH
ꢀ
/
2
3
107.2, d
B
18.2, JAB
ꢀ/23.7
(
15
1
1
1
H
NÄ
/
NH)(NO){P(OEt) }(PPh
3
3
)
2
]BPh
4
1886w,
701s
n(ReH),
n(NO)
12.95 (dm), J15NH
ꢀ
/
64, 11.60
64, 4.10 m, 3.48 CH
qnt), 3.51 (qnt), 1.05 (t), 0.92 (t)
NH, ReH, AB
2
Y,
Y
d
A
113.6, d
5.0, JBY
18.2, JAB 23.7, JAY
.9
B
24.0, JAB
ꢀ
/
12.9,
107.2, d
40.9, JBY
1
1
(dm), J15NH
ꢀ/
2
, CH
3
AB
2
J
AY
ꢀ/
ꢀ/4.3, d
A
B
(
ꢀ
/
ꢀ
/
ꢀ
/
2
4
5
c
[{ReH(NO){PPh(OEt)
f
2
}(PPh
3
)
2
}
2
(m-4,4?-HNÄ
/
NC
6
H
4
Ã
/
C
6
H
4
NÄ
/
1816w,
1684s
1730sh, n(NO)
n(ReH),
n(NO)
13.10 (d, br), 11.4 (s, br), 3.69
(m), 3.15 (m), 1.02 (t), 0.83 (t)
13.00 (d), 12.89 (d), 3.61 (qnt), NH, CH
NH, CH
CH
2
,
AB
2
, AB
2
2
d
A
125.0, d
131.6, d 18.4, JAB
99.6, d 0.46, JAB
B
11.4, JAB
ꢀ
/
18.1, d
A
NH)](BPh
4
)
2
3
B
ꢀ/
9.6
a
6
[Re(C H
5
NÄ/NH)
(NO){P(OEt) }(PPh
2 3
3
)
2
](BPh
4
)
2
2
,
AB
AB
2
, AB
,
d
A
B
ꢂ/
ꢀ
/24.4, d
A
1
1
717s,
701s
3.55 (qnt), 1.06 (t), 0.95 (t)
CH
3
2
104.4, d
104.1, d
B
B
4.43, JAB
ꢀ
ꢀ/
/
23.8, d
A
3.95, JAB
24.5
NÄ/15NH)
(NO){P(OEt)
}(PPh
)
)
1730sh, n(NO)
13.01 (dd), J15NH
1
ꢀ
/
64, 12.88
64, 3.60 (qnt), 3.54 CH
(qnt), 1.06 (t), 0.95 (t)
NH, CH
AB
AB
AB
Y ,
2
Y ,
2
Y
2
d
99.6, d
55.4, JBY
3.95, JAB 24.4, JAY
104.4, d 4.45, JAB
27.9, JBY 0.1
3.34, JAB
19.4
ꢂ
/
0.46, JAB
0.1, d
28.6, JBY
23.8,
ꢀ
/24.4,
5a
1
6
[Re(C H
5
2
3
3
2
](BPh
4
2
2
,
2
2
2
A
B
1
1
1
718s,
701sh
(dd), J15NH
ꢀ
/
3
J
AY
ꢀ/
ꢀ
/
A
104.0, d
B
ꢀ
/
ꢀ/
ꢀ
/
0
.1, d
A
B
ꢀ/
J
AY
ꢀ/
ꢀ/
6
a
a
[Re(C
6
H
H
5
NÄ
/
NH)
2
(NO){PPh(OEt)
2
}(PPh
3
)
2
](BPh
4
)
2
1730s,
n(NO)
n(NO)
13.06 (d), 3.46 (qnt), 3.32 (qnt), NH, CH
0.93 (t) CH
2
,
,
AB
2
, AB
2
d
A
126.9, d
B
ꢀ20.3, d
A
/
1
1
720s,
701sh
3
127.1, d
B
2.88, JAB
ꢀ/
NÄ/15NH)
(NO){PPh(OEt)
}(PPh
)
)
g
1730s,
701sh
13.05 (dd), J15NH
1
ꢀ
/
62, 12.90
64, 3.60 (qnt), 3.45 CH
qnt), 3.33 (qnt), 1.13 (t), 0.93 (t)
NH, CH
AB
AB
AB
Y ,
2
Y ,
2
Y
2
d
127.2, d
28.7, JBY
3.34, JAB 20.3, JAY
121.9, d 2.0, JAB
48.7, JBY 1.0
99.4, d 0.29, JAB
2.90, JAB
1.0, d
28.1, JBY
19.8,
ꢀ
/
19.4,
6
1
[Re(C
6
5
2
2
3
2
](BPh
4
2
2
2
2
2
A
B
1
1
(dd), J15NH
ꢀ
/
3
J
AY
ꢀ
/
ꢀ
/
A
126.9, d
B
(
ꢀ/
ꢀ/
ꢀ
/
1
.0, d
A
B
ꢂ
/
ꢀ/
J
AY
ꢀ/
ꢀ/
7
8
[{Re(4-CH
NC
3
C
6
H
4
NÄ
/
NH)(NO){P(OEt) }(PPh
3
3
)
2
}
2
(m-4,4?-HNÄ
/
1718s,br n(NO)
1844m, n(ReH),
12.9 (m), 3.52 (m), 2.44 (s), 2.40 NH, CH
(s), 1.06 (t), 0.95 (t) CH
phos
10, 11.46 (br), NH, ReH
BX spin syst, d 3.66, JAX
6.9, A BX spin syst, d
.38, JAX 34.6, JBX 15.6
2
,
AB
AB
2
,
,AB
d
A
B
ꢂ/
ꢀ
/26.0, d
A
6
H
4
Ã
/
C
6
H
4
NÄNH)](BPh
/
4
)
4
3
, CH
3
2
2
104.1, d
103.8, d
B
B
4.52, JAB
ꢀ
ꢀ/
/
20.0, d
A
4.08, JAB
25.0
a
[ReH(C
6
H
5
NÄ
/
NH)(NO)(PPh
3
)
3
]BPh
4
12.69 (d), JPH
ꢀ/
2
A B, A
2
B
d
A
16.2, d
B
10.8, JAB
ꢀ
/14.0, d
A
A
1
684s
n(NO)
A
2
X
ꢀ/
21.9, d
B
14.5, JAB
ꢀ/6.3
J
BX
ꢀ/
2
X
3
ꢀ/
ꢀ/
9
c
[{ReH(NO)(PPh
3
)
3
}
2
(m-4,4?-HNÄ
/
NC
6
H
4
Ã
/
C
6
H
4
NÄ
/NH)](BPh
4
)
2
1842w,
684s
n(ReH),
n(NO)
12.72 (d, br), 11.50 (s, br), A
spin syst, d 3.67, JAX
, 3.40 (m)
2
BX NH, ReH
2
A B, A
2
B
d
A
16.1, d
22.1, d 14.6, JAB
B
10.7, JAB
ꢀ
/14.0, d
1
X
ꢀ/
J
BX
ꢀ
/
B
ꢀ/
6.3
8

214
G. Albertin et al. / Journal of Organometallic Chemistry 679 (2003) 208Á219
/
sphine ReH (NO)(PPh ) compound, as well as the
2
3 3
tris(phosphite) ReH (NO)(PPh OEt) derivative [11],
2
2
3
instead, react with aryldiazonium cations yielding rather
the monoaryldiazene complexes, which can be isolated
and characterised (Scheme 5).
Also binuclear [{ReH(NO)(PPh ) } (m-HNÄ
/
NArÃ
NH)] complexes 9 can be prepared by reacting
ReH (NO)(PPh ) with a bis(aryldiazonium) salt in a
/
3
2 2
2
ꢁ
ArNÄ
/
2
3 3
1:2 ratio (Scheme 6).
All the aryldiazene complexes 1Á/9 were isolated as
yellow or orange solids stable in air and in a solution of
polar organic solvents, in which they behaved as 1:1 (1,
2
, 8), 2:1 (3, 4, 5, 6, 9) and 4:1 (7) electrolytes [12]. The
analytical and spectroscopic data, reported in Table 1,
support the proposed formulations. Furthermore, the
NMR spectra also show that the complexes were often
obtained as a mixture of two or more isomers that we
were not able to separate. Fractional crystallisation, for
example, gave only solid samples enriched in one
isomer, whereas the chromatography on silica gel or
alumina caused the decomposition of the complexes.
The IR spectra of monodiazene 1 and 2 complexes
showed a strong band in the n(NO) region at 1701Á
/
1674
cm due to the nitrosyl ligand and a medium-intensity
ꢂ1
ꢂ1
absorption at 1885Á
/
1871 cm attributed to the stretch-
ing of the ReÃH bond. The width of these bands,
/
however, does not allow us to emphasise the presence of
more isomers.
1
The H-NMR spectra of [ReH(ArNÄ
/
NH)(NO)-
L(PPh ) ] (1 and 2) cations, instead, show two NH
ꢁ
3
2
signals between 13.08 and 11.2 ppm, each of which are
split into two doublets in the labelled 1a and 2a1
1
1
compounds, with J
values of 61Á64 Hz, in agree-
/
NH
ment with the presence of two species containing the
diazene ligand [1,13]. Besides the signals of the phos-
ꢂ
phines and BPh4 anions, the resonances of the hydride
ligands are also present in the spectra, which appear
between 4.10 and 3.65 ppm as two well-separated
multiplets in some case or as two overlapping signals
in others. These resonances fall in an unusual region for
hydride ligands [14], probably owing to the presence of
the nitrosyl group in the cationic complexes. However,
heterodecoupling experiments emphasise the character-
istic coupling of the hydride with the phosphorus nuclei
of the phosphine thus confirming the assignment.
3
1
1
Furthermore, taking into account that the P{ H}-
NMR spectra of 1 and 2 show two well-separated AB2
multiplets, the two hydride patterns at 5Á/3 ppm may
also be simulated, in the case of both 2a and 2b, using
two AB X models (Xꢀ
/H), with the parameters re-
2
ported in Table 1.
The presence of two signals for the hydride, of two
3
NH resonances and of two P multiplets, suggests the
1
existence of two isomers for complexes 1 and 2, which
ꢁ
are probably formed by the insertion of the ArN2
group into the two non-equivalent ReÃ/H bonds of the

G. Albertin et al. / Journal of Organometallic Chemistry 679 (2003) 208Á
/219
215
several overlapping systems. The results may be ex-
plained on the basis of a restricted rotation of the
phosphorus ligand around the ReÃ
/
P bond, affording
/
6 5 3 6 4
Scheme 5. ArꢀC H (a), 4-CH C H (b).
more isomers with inequivalent phosphorus nuclei [15].
In order to test this hypothesis, we have registered the
3
1
P spectra between ꢁ
/
50 and ꢂ80 8C and observed no
/
significant variation in the spectra whose broad multi-
plets do not resolve with the changing temperature. We
have then used a different solvent and observed that
with CDCl CDCl , two well-resolved AB multiplets
2
2
2
appear in the spectra of 4c, which were easily simulated
with parameters reported in Table 1. These results show
that the nature of the solvent or rather the interaction of
our rhenium cations with the solvent are important in
Fig. 2.
3
1
determining the P-NMR spectra resolution.
ReH (NO)L(PPh ) precursors. Both hydrides are prob-
2
3 2
The infrared and NMR data, however, do not allow a
precise determination of the geometry in solution for the
two isomers present in the binuclear 3 and 4 complexes.
This is due to the nature of the hydride signals, which in
part overlap with the methylene multiplet thus prevent-
ing the determination of the JPH value. It can also be
noted that the reaction of ReH (NO)L(PPh ) with
ably reactive toward the insertion of the aryldiazonium
cation. The reaction of only one of the ArN 2ꢁ should
give rise to two different species with geometries of type
II and III of Fig. 2 as for example. In order to establish
that the geometry in solution of the two isomers are
really II and III, it is useful to examine the value of the
JPH between the hydride and phosphorus nuclei, and the
value J31P15N between the diazene and the phosphine in
the labelled 1a and 2a complexes (Table 1).
2
3 2
bis(aryldiazonium) salts should give four isomers of
type IIÁII, IIIÁIII, IIÁIII and IIIÁII (see Fig. 2) by
analogy with the monodiazonium species 1 and 2. These
/
/
/
/
1
1
In the case of 2b, the results showed that in one isomer
II) the two JPH have similar values, while in the other
III) one of the JPH is higher than the other, suggesting
are formed with different rates due to the different
2
(
(
ꢁ
ꢂ
reactivities towards [N ArÃ
/
ArN2]
of the two H
ligands in the ReH (NO)L(PPh ) precursor. One of the
2
2
3 2
the mutually trans position of the hydride and of one of
the phosphines. Also in one isomer (II), the diazene
ligand is trans to one phosphine. This can be deduced by
the higher J31P15N value of 40.9 or 34.4 Hz observed in
three isomers is probably formed so slowly to result
present only as traces.
Good analytical data were obtained for the bis(ar-
3
1
yldiazene) [Re(ArNÄ
/
NH) (NO)L(PPh ) ](BPh ) (5 and
2 3 2 4 2
one multiplet of the P spectra of the labelled 1a and
1
6
) complexes, which are orange solids stable in air and in
2
a1 complexes. It is therefore reasonable to propose the
II and III geometries for the two isomers present in our
mononuclear monodiazene
[ReH(ArNÄ
NH)(NO)L(PPh ) ]BPh (1 and 2) derivatives.
a solution of polar organic solvents, where they behave
as 1:2 electrolytes [12]. The IR and NMR data (Table 1)
support the proposed formulation and also indicate the
presence of more isomers. The IR spectra of complexes 5
and 6, which contain only one NO ligand, in fact show
two or three bands in the n(NO) region suggesting the
presence of more than one species.
/
3
2
4
Also in the related binuclear [{ReH(NO)L-
NH)](BPh4)2 (3 and 4)
complexes, the infrared spectra confirm the presence of
(
PPh ) } (m-HNÄ
/
NArÃ
/
ArNÄ
/
3
2 2
both the nitrosyl and the hydride ligands, showing the
ꢂ1
3
1
1
The P{ H}-NMR data confirm the presence of
more isomers, showing two or three AB multiplets in
the spectra, which can be simulated with the parameters
n(NO) at 1684Á
1
/
1695 cm
and the n(ReÃ
/
H) at 1890Á
/
ꢂ1
1
816 cm . The H-NMR spectra show the character-
2
istic signals of the diazene ligand in the high-frequency
region, which are seen as two well-separated broad
signals, suggesting the presence of two isomers in this
1
reported in Table 1. The H-NMR spectra also show the
presence of one or two doublets in the high-field region
attributed to NH resonances of the aryldiazene ligand.
Each of these doublets is split into a doublet of doublets
3
1
1
case as well. This is also confirmed by the P{ H}
spectra, which show two well-separated multiplets.
These multiplets are, however, slightly broad, and their
in the spectra of the labelled 5a
and 6a
64 Hz, in agreement with the
NH group [15].
complexes, with
1
1
1
simulation using a AB model is, in the case of complex
2
J
15NH values of 62Á
/
4
c, rather difficult, because the spectra seem to contain
presence of the ArNÄ
/
Scheme 6. ArÃ
/
/
6 4 6 4 6 4 2 6 4
Arꢀ4,4?-C H Ã/C H (c), 4,4?-C H Ã/CH Ã/C H (d).

216
G. Albertin et al. / Journal of Organometallic Chemistry 679 (2003) 208Á219
/
Fig. 4.
As reported above, only the mixed-ligand Re-
H (NO)L(PPh ) complexes allow bis(aryldiazene) to
2
3 2
be prepared. The related ReH (NO)(PPh ) hydride
2 3 3
exclusively gives the monoaryldiazene [ReH(ArNÄ
/
NH)(NO)(PPh ) ]BPh (8) complexes, which were iso-
3
3
4
lated and characterised in the usual way by analytical
and spectroscopic data (Table 1). The NMR data
suggest the presence of two isomers of geometry X and
XI type (Fig. 4) in this case as well. These are formed by
ꢁ
the insertion of only one ArN2 group into one of the
two hydrides of the ReH (NO)(PPh ) precursor. In the
2
3 3
temperature range between ꢁ
/
30 and ꢂ
/
80 8C, the
3
1
1
P{ H}-NMR spectra for each compound show, in
fact, two A B multiplets, while the proton spectra show
2
Fig. 3.
two NH signals between 12.69 and 11.25 ppm and two
hydride multiplets between 3.66 and 3.30 ppm. The
simulation of these multiplets using an A BX (XꢀH)
/
2
The geometry of the bis(aryldiazene) complexes 5 and
can be discussed in terms of the following six
model allows the JPH values to be calculated (Table 1),
and these suggest that in one isomer (XI) the hydride is
trans to one phosphine, while in the other it is in a
mutually cis position with all the phosphorus nuclei (X).
Furthermore, the values of the J31P15N determined for
6
structures, reported in Fig. 3.
3
However, taking into account that all the P multi-
1
plets observed in the spectra of 5 and 6 are of the AB2-
type, the geometries VII, VIII and IX can be excluded,
compound 8a1 seem to indicate that the ArNÄ
/
NH
3
1
because and ABC-type P spectrum must be expected.
Therefore, for the three isomers present in our samples
of 5 and 6, the three IV, V and VI geometries can be
ligand occupies the same position with respect to all
the phosphines in both the two isomers, in agreement
with the proposed X and XI geometries for complex 8.
1
ꢁ
reasonably proposed. It can also be noted that the H-
The monodiazene species 8 were treated with ArN2
NMR signals of the NH groups are less than those
expected for the presence of three isomers of IV, V and
VI geometries. An overlapping of the NH proton signals
is probably present. This is also observed in the
in an attempt to prepare bis(aryldiazene) complexes, but
only mixtures of unstable products were obtained whose
NMR spectra do not show the presence of diazenic
species.
1
5
1
N{ H}-NMR spectra of 6a , which show three doub-
1
Only the substitution of one PPh with either P(OEt)
3
3
lets of triplets (Table 1), instead of the four expected.
The analytical and spectroscopic data of the binuclear
or PPh(OEt)2 in ReH (NO)(PPh )
makes the
[Re(NO)L(PPh ) ] fragment able to stabilise two aryl-
2
3 3
3
2
[
{Re(4-CH C H NÄ
/
NH)(NO){P(OEt) }(PPh ) } (m-
diazene ligands bonded to the same central metal.
Binuclear complexes of the [{ReH(NO)(PPh ) } (m-
3
6
4
3
3 2 2
4
support its formulation. The diazene proton signals
,4?-NHÄ
/
NC H Ã
/
C H NÄ
/
NH)](BPh ) (7) compound
6
4
6
4
4 4
3 3 2
HNÄ
/
NArÃ
/
ArNÄ
/
NH)](BPh ) (9) type were also pre-
4 2
appear as a multiplet at 12.9 ppm, while two methyl
pared from the reaction of ReH (NO)(PPh ) with di-
2
3 3
2
N Ar] salts and their characterisa-
ꢁ
groups of the 4-CH C H NÄ
/
NH ligand appear as
1
diazonium [ArN
tion by NMR data (Table 1) indicate the formation of
2 2
Ã
/
3
6
4
3
1
singlets at 2.40 and 2.44 ppm. The P{ H}-NMR
spectra suggest the presence of more isomers in this
case as well, showing three AB multiplets which can be
more isomers in this case as well.
2
simulated using the parameters reported in Table 1.
These data, however, do not allow the unambiguous
determination of a geometry for the species present in
solution of this binuclear derivative.
3.3. Aryldiazenido complexes
The results obtained in the reaction of dihydride
species ReH (NO)L(PPh ) and ReH (NO)(PPh ) with
2
3 2
2
3 3

G. Albertin et al. / Journal of Organometallic Chemistry 679 (2003) 208Á
/219
217
/
2
Scheme 7. PꢀPPh(OEt) .
ArN 2ꢁ prompted us to extend the studies to other
polyhydrides and the results obtained with the trihy-
dride ReH P are reported in Scheme 7.
3
4
The ReH P hydride reacts with both an equimolar or
3
4
an excess amount of phenyldiazonium cation to give the
aryldiazenido complex 11a after workup, which was
then isolated and characterised. The reaction was also
studied by NMR spectroscopy, following the progress of
the reaction at variable temperatures in an NMR tube.
The spectra indicate that the aryldiazonium cation
Scheme 8.
presence of dihydrogen in the reaction mixture may
suggest the path of Scheme 8 for the formation of the
aryldiazenido complex 11a.
inserts into only one ReÃ
/
H bond to give the mono-
ꢁ
diazene [ReH (C H NÄ
/
NH)P4]
(10a) cation. This
species, however, is rather unstable and cannot be
2
6
5
The presence of molecular hydrogen in the reaction
mixture may be explained by taking the properties of
both the diazene and the hydride ligand in the rhenium
complexes [1,2,4,6,10,17], into account, i.e. the acidity of
the diazene hydrogen atom on one hand and the easy
isolated in pure form, but only as a mixture containing
1
0a and 11a and other unidentified compounds. The H
1
and P spectra, however, strongly support its formula-
3
1
tion showing a doublet at 13.95 ppm in the high-
frequency region, which is split into one doublet of
1
doublets ( J
protonation of the hydride ligand on the other, which
2
ꢀ62 Hz) in the spectra obtained using
/
1
5NH
1
5
ꢁ
potentially allow the formation of a h -H ligand. Thus,
2
the labelled C H NÅ
/
N
cation, in agreement with the
6
5
an intramolecular acidÁ/base reaction between the
presence of an aryldiazene ligand. In the proton spectra
of the reaction mixture, the disappearance of the
diazene proton of C H NÄ
/
NH and the ReÃH hydride
/
6
5
may give rise to a very unstable di-hydrogen intermedi-
ate [A] which, by the loss of its H and the rearrange-
hydride signal of the precursor ReH P at ꢂ
/
6.5 ppm
3.96 ppm can
also be observed. This signal is split into a doublet of
3
4
2
ꢁ
and the appearance of a new quintet at ꢂ
/
ꢂ
ment of the ArN2 ligand to ArN2 (see below), gives
rise to the final aryldiazenido complex 11a.
1
5
quintets owing to the coupling with N when the
1
5
ꢁ
The aryldiazenido complex 11a is a yellow solid,
stable in air and in a solution of polar organic solvents,
diamagnetic and 1:1 electrolyte. Analytical and spectro-
scopic data (Table 1) support its formulation. We also
attempted to determine the X-ray crystal structure, but
the poor quality of the obtained crystals prevented this
determination. The IR spectrum shows a medium-
labelled [C H NÅ
/
N] cation is used, in agreement
with the proposed formulation.
The hydride signal at ꢂ3.96 ppm does not change as
the temperature is lowered and appears always as a
sharp quintet even at ꢂ90 8C. Also the slightly broad
6
5
/
/
3
1
1
singlet of the related P{ H}-NMR spectra appears
unchanged in the temperature range from ꢁ20 to
90 8C, and these results prevent the determination of
a geometry in solution of this heptacoordinate complex
0a. The NMR data, however, strongly support its
formulation as an aryldiazene-hydride cation of the
/
ꢂ1
intensity band at 1680 cm , attributed to the n(NN)
ꢂ1
ꢂ
/
of the C H N ligand. This band shifts to 1653 cm in
6
5
2
1
5
the labelled [ReH(C H NÅ
/
N)P ]BPh (11a ) complex,
4 4 1
1
6
5
according to the proposed assignment. The value for the
NÃN stretching frequency is indicative of a singly-bent
aryldiazenido ligand [6d,18], which should be considered
ꢁ
/
[
ReH (C H NÄ
/
NH)P4] type. The spectra of the reac-
2
6
5
tion mixture also indicate that no other aryldiazene
species, besides 10a, is formed, even in the presence of an
excess of aryldiazonium cation, suggesting that the
ꢁ
2
formally present as an ArN
central metal must therefore be in a formal oxidation
state of ꢁ1 [Re(I)], according to geometry XII of
Scheme 8. In the temperature range between ꢁ20 and
80 8C, the P{ H}-NMR spectra of 11a is a sharp
group. The rhenium
ꢁ
insertion of only one ArN2 takes place on the
phosphite-containing ReH P trihydride derivative.
/
/
3
4
ꢁ
31
1
The [ReH (C H NÄ
/
NH)P4]
(10a) aryldiazene is
ꢂ
/
2
6
5
unstable in solution even at 0 8C and concurrent with
this decomposition its H-NMR spectrum shows the
singlet, suggesting the magnetic equivalence of the four
phosphite ligands, as expected for a geometry containing
1
appearance of a quintet at ꢂ
formation of the aryldiazenido [ReH(C H N )P ]
6
/
4.51 ppm due to the
ꢁ
the hydride and the ArN
position.
ligand in a mutually trans
2
5
2
4
(
also appears which decreases on shaking the NMR tube
11a) derivative. In the spectra, a singlet at 4.6 ppm
Aryldiazenido complexes of rhenium are known [19],
but none containing also a hydride ligand as in
compound 11a. We [6d] have previously prepared a
and may be attributed [16] to the signal of free H . The
2

218
G. Albertin et al. / Journal of Organometallic Chemistry 679 (2003) 208Á219
/
[
[
3] G. Albertin, S. Antoniutti, A. Bacchi, G.B. Ballico, E. Bordignon,
related complex of the [ReCl(PhN ){PPh(OEt) } ]BPh
4
2
2 4
ꢂ1
G. Pelizzi, M. Ranieri, P. Ugo, Inorg. Chem. 39 (2000) 3265.
4] (a) G. Albertin, S. Antoniutti, E. Bordignon, J. Chem. Soc.
Dalton Trans. (1989) 2353.;
type [n(NN)ꢀ
with hydrazine, but it contained Cl instead of the
hydride. The use of the trihydride ReH P as a precursor
/
1662 cm ] from the reaction of ReCl3P3
3
4
(b) G. Albertin, S. Antoniutti, G. Pelizzi, F. Vitali, E. Bordignon,
Inorg. Chem. 27 (1988) 829;
in the reaction with aryldiazonium cations allows the
synthesis of hydride-aryldiazenido complex of rhenium
to be easily achieved.
The preparation of the aryldiazenido complex 11a
from an aryldiazene prompted us to study the behaviour
(
c) G. Albertin, S. Antoniutti, G. Pelizzi, F. Vitali, E. Bordignon,
J. Am. Chem. Soc. 108 (1986) 6627.
5] (a) M.D. Fryzuk, S.A. Johnson, Coord. Chem. Rev. 200 (2000)
[
3
79;
b) A.E. Shilov, Metal Complexes in Biomimetic Chemical
Reactions, CRC Press, Boca Raton, FL, 1997;
(
of the diazene complexes 1Á9 towards a base, in order to
/
(
(
(
(
c) D. Sellmann, J. Sutter, Acc. Chem. Res. 30 (1997) 460;
d) R.L. Richards, Coord. Chem. Rev. 154 (1996) 83;
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test whether a deprotonation reaction can take place
affording new aryldiazenido derivatives. The results
show that, whereas the monoaryldiazenes 1Á
are unreactive towards a base, the bis(aryldiazene) 5 and
complexes react with triethylamine in CH Cl to give a
/
4, 8 and 9
f) M. Hidai, Y. Mizobe, Chem. Rev. 95 (1995) 1115.
[
6] (a) G. Albertin, S. Antoniutti, A. Bacchi, M. Boato, G. Pelizzi, J.
6
Chem. Soc. Dalton Trans. (2002) 3313.;
2
2
(
b) G. Albertin, S. Antoniutti, E. Bordignon, E. Visentin, Inorg.
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reddish-brown solution from which, however, no stable
aryldiazenido complex was isolated. The deprotonation
(
of both mono- and bis(aryldiazene) complexes 1Á9,
/
therefore, does not seem to be the way to obtain
aryldiazenido derivatives of rhenium.
(
(
3
.4. Conclusions
(
This contribution reports some new results on the
chemistry of ‘‘diazo’’ complexes of rhenium containing
nitrosyl as a supporting ligand. The first bis(aryldiazene)
(
Soc. Dalton Trans. (1997) 4445.;
(h) G. Albertin, S. Antoniutti, A. Bacchi, E. Bordignon, P.M.
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7] T.S. Cameron, K.R. Grundy, K.N. Robertson, Inorg. Chem. 21
complexes of rhenium of the [Re(ArNÄ
/
NH) (NO)L-
2
[
(PPh ) ](BPh ) type (Lꢀphosphites) were prepared
using the mixed-ligand hydrides ReH (NO)L(PPh ) as
/
3
2
4 2
(
1982) 4149.
2
3 2
[8] R. Rabinowitz, J. Pellon, J. Org. Chem. 26 (1961) 4623.
[9] A.I. Vogel, Practical Organic Chemistry, 3rd ed., Longmans &
Green, New York, 1956.
precursors. Mononuclear [ReH(ArNÄ
/
NH)(NO)L-
(
PPh ) ]BPh monodiazene and binuclear [{ReH(NO)L-
3 2 4
[
10] S. Garcia-Font a´ n, A. Marchi, L. Marvelli, R. Rossi, S. Anto-
niutti, G. Albertin, J. Chem. Soc. Dalton Trans. (1996) 2779.
11] G. Albertin, S. Antoniutti, B. Fregolent, in preparation.
12] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
(
aryldiazene as a bridging ligand, were also prepared by
PPh ) } (m-HNÄ
/
NArÃ
/
ArNÄ
/
NH)](BPh ) species, with
3
2 2
4 2
[
[
an analogous procedure.
The hydride-aryldiazenido [ReH(C H N ){PPh-
6
5
2
[13] (a) K.R. Laing, S.D. Robinson, M.F. Uttley, J. Chem. Soc.
Dalton Trans. (1973) 2713.;
(
OEt) } ]BPh complex was also obtained from the
2 4 4
(
b) J.A. Carrol, D. Sutton, Z. Xiaoheng, J. Organomet. Chem.
44 (1982) 73;
c) G. Albertin, S. Antoniutti, M. Lanfranchi, G. Pelizzi, E.
reaction of trihydride ReH3P4 with a aryldiazonium
cation.
2
(
Bordignon, Inorg. Chem. 25 (1986) 950.
14] (a) M. Peruzzini, R. Poli, Recent Advances in Hydride Chemistry,
Elsevier, Amsterdam, 2001;
[
[
[
Acknowledgements
(
b) A. Dedieu, Transition Metal Hydrides, WileyÁ
York, 1992;
c) S. Sabo-Etienne, B. Chaudret, Chem. Rev. 98 (1998)
077.
/
VCH, New
The financial support of MIUR (Rome)*
di Ricerca Scientifica di Rilevante Interesse Nazionale,
Cofinanziamento 2002Á2003*is gratefully acknowl-
edged. We thank Daniela Baldan for technical assis-
tance.
/
Programmi
(
2
/
/
15] (a) A.J. Deeming, S. Doherty, J.E. Marshall, N.I. Powell, J.
Chem. Soc. Chem. Commun. (1989) 1351.;
(
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(
Busatto, Organometallics 16 (1997) 4959.
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