Synthesis and reactivity of hydrazine complexes of iridium(III)

Article abstract of DOI:10.1039/a909404k

Hydride complexes IrHCl₂[PPh(OEt)₂]L₂1,3 and IrHCl₂[P(OEt)₃]L₂ 2,4(L = PPh₃ or AsPh₃) were prepared by substituting one phosphine or arsine ligand in IrHCl₂

Full text of DOI:10.1039/a909404k

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Synthesis and reactivity of hydrazine complexes of iridium(III)
Gabriele Albertin,* Stefano Antoniutti, Emilio Bordignon and Federica Menegazzo
Dipartimento di Chimica, Università Ca’ Foscari di Venezia, Dorsoduro, 2137, 30123 Venezia,
Italy
Received 29th November 1999, Accepted 25th January 2000
Published on the Web 8th March 2000
Hydride complexes IrHCl2[PPh(OEt)2]L2 1, 3 and IrHCl2[P(OEt)3]L2 2, 4 (L = PPh3 or AsPh3) were prepared by
substituting one phosphine or arsine ligand in IrHCl2L3 with the appropriate phosphite. Treatment of hydrides
1–4 first with triflic acid (CF3SO3H) and then with hydrazines gave [IrCl2(RNHNH2){PPh(OEt)2}L2]BPh4 5, 7
and [IrCl2(RNHNH2){P(OEt)3}L2]BPh4 6, 8 (R = H, Me, Ph or C6H4NO2-4). Hydride–hydrazine complexes
[IrH2(RNHNH2)(PPh3)3]BPh4 9 and [IrHCl(RNHNH2)(PPh3)2]BPh4 10 (R = H, Me or Ph) were also prepared by
allowing IrH3(PPh3)3 or IrH2Cl(PPh3)3 to react sequentially first with CF3SO3H or HBF4ؒEt2O and then with the
appropriate hydrazine. All complexes were fully characterised by IR and NMR spectroscopy and their geometry in
solution was also established. Oxidation with Pb(OAc)4 at Ϫ30 ЊC of arylhydrazines [IrCl2(ArNHNH2)LЈL2]BPh4
5–8 [LЈ = PPh(OEt) or P(OEt) ; Ar = Ph] afforded stable aryldiazene derivatives [IrCl (ArN᎐NH){PPh(OEt) }L ]-
᎐
2
3
2
2
2
BPh 11, 13 and [IrCl (ArN᎐NH){P(OEt) }L ]BPh 12, 14. By contrast, treatment with Pb(OAc) at Ϫ30 ЊC of
᎐
4
2
3
2
4
4
methylhydrazine complexes [IrCl2(MeNHNH2)LЈL2]BPh4 gave hydrides IrHCl2LЈL2. Aryldiazene complexes
[IrCl (ArN᎐NH)LЈL ]BPh 11–14 and [{IrCl LЈL } (µ-HN᎐NAr–ArN᎐NH)](BPh ) 15–18 [Ar = Ph or C H Me-4;
᎐
᎐
᎐
2
2
4
2
2
2
4
2
6
4
Ar–Ar = 4,4Ј-C6H4–C6H4 or 4,4Ј-(2-Me)C6H3–C6H3(Me-2)] were also prepared by allowing hydride species
IrHCl2LЈL2 1–4 to react with the appropriate aryldiazonium cations in acetone at Ϫ80 ЊC. Their characterisation
by IR and NMR spectroscopy (with 15N isotopic substitution) is discussed.
Transition metal complexes containing hydrazine and other
dry-box. Once isolated, the complexes were found to be
partially reduced dinitrogen ligands such as diazene RN᎐NH
stable in air and were stored at room temperature. All sol-
vents were dried over appropriate drying agents, degassed
on a vacuum line, and distilled into vacuum-tight storage
flasks. The IrCl3ؒ3H2O was a Pressure Chemical Co. product,
used as received. Triethylphosphite P(OEt)3 (Aldrich) was
purified by distillation under nitrogen; PPh(OEt)2 was prepared
by the method of Rabinowitz and Pellon.9 Hydrazines PhNH-
NH2, MeNHNH2, 4-NO2C6H4NHNH2 and Me2NNH2 were
Aldrich products used as received. Hydrazine NH2NH2
was prepared by decomposition of hydrazine cyanurate
NH2NH2ؒC3H3N3O3 (Fluka) following the reported method.10
᎐
and diazenido RN2 constitute a research area of current inter-
est, due not only to the relationship with intermediates of the
dinitrogen fixation process, but also to the diverse reactivity
modes and structural properties that these “diazo” complexes
exhibit.1,2 Numerous studies have been reported in the past 25
years on the synthesis, structure and reactivity of this class of
complexes, but relatively few of them have involved hydrazine
derivatives.1–3 Coordinated hydrazine NH2NH2 has been pro-
posed as possible intermediate in nitrogen fixation, has been
shown to be a substrate4 as well as a product of functioning
nitrogenase, and has been isolated by quenching the enzyme.5
However, much remains to be known about the chemistry of
coordinated hydrazine and it is therefore of interest to report
new results in this field, including the synthesis and reactivity of
the first hydrazine complexes of iridium. A glance through the
literature shows that the “diazo” chemistry of iridium involves
mainly aryldiazene, aryldiazenido and diazoalkane complexes,6
the coordination chemistry of hydrazine being practically
unexplored for this metal.
Ϫ
Diazonium salts [ArN2]ϩBF4 were obtained in the usual
way.11 The related bis(diazonium) [N2Ar–ArN2](BF4)2 [Ar–Ar =
4,4Ј-C6H4–C6H4 or 4,4Ј-(2-Me)C6H3–C6H3(Me-2)] salts were
prepared by treating the amine precursors H2NAr–ArNH2
with NaNO2, as described in the literature for common mono-
diazonium salts.11 Labelled diazonium tetrafluoroborates
15
15
15
᎐
᎐
᎐
[PhN᎐ N]BF and [4,4Ј- N᎐NC H –C H N᎐ N](BF ) were
᎐
᎐
᎐
4
6
4
6
4
4 2
prepared from Na15NO2 (99% enriched, CIL) and the appro-
priate amine. Alternatively, the [Ph N᎐N]BF salt was
15
᎐
᎐
4
In previous papers7 we reported the synthesis, structure and
reactivity of “diazo” complexes of several transition metals,
including hydrazine derivatives of the iron family8 of the type
[MH(RNHNH2)LЈ4]ϩ, [M(RNHNH2)2LЈ4]2ϩ and [M(RCN)-
(RNHNH2)LЈ4]2ϩ (LЈ = phosphite). We have now extended
these studies to other d6 transition metals, with the aim of first
establishing a method for synthesis, and then investigating the
properties of the hydrazine complexes of these metals. Results
on iridium, involving the synthesis of both hydrazine and
aryldiazene derivatives, are reported here.
obtained from NaNO2 and Ph15NH2. Triflic acid (Aldrich)
and HBF4ؒEt2O (54% solution in Et2O, Fluka) were used as
received. Other reagents were purchased from commercial
sources in the highest available purity and used as received.
IR spectra were recorded on a Nicolet Magna 750 FT-IR
spectrophotometer. NMR spectra (1H, 31P) were obtained
on a Bruker AC200 spectrometer at temperatures varying
1
between Ϫ90 and 30 ЊC, unless otherwise noted. H spectra
are referred to internal tetramethylsilane. 31P-{1H} chemical
shifts are reported with respect to 85% H3PO4, with
downfield shifts considered positive. The SwaN-MR soft-
ware package12 was used to treat NMR data. The con-
ductivities of 10Ϫ3 mol dmϪ3 solutions of the complexes in
MeNO2 at 25 ЊC were measured with a Radiometer CDM 83
instrument.
Experimental
All synthetic work was carried out under an inert atmosphere
using standard Schlenk techniques or a Vacuum Atmosphere
DOI: 10.1039/a909404k
J. Chem. Soc., Dalton Trans., 2000, 1181–1189
This journal is © The Royal Society of Chemistry 2000
1181

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Synthesis of complexes
(5 cm3) was added and, after 1 h of stirring, an excess of
NH2NH2 (13 µL, 0.40 mmol) was also added. The reaction
mixture was stirred for 2 h and the solvent was then removed
under reduced pressure, leaving an oily product which was
treated with ethanol (2 cm3). The addition of an excess of
NaBPh4 (0.137 g, 0.40 mmol) caused the separation of a white
solid which was filtered off and crystallised from CH2Cl2
(2 cm3)–ethanol (5 cm3); yield ≥65%; ΛM = 52.4 S cm2 molϪ1
(Found: C, 60.9; H, 5.35; N, 2.1; Cl, 5.2. C66H69BCl2IrN2O3P3
requires C, 60.7; H, 5.3; N, 2.15; Cl, 5.4%).
Hydrides mer-IrHCl2(PPh3)3, mer-IrHCl2(AsPh3)3, IrH2Cl-
(PPh3)3 and IrH3(PPh3)3 were prepared following the methods
previously reported.13a–c
IrHCl2[PPh(OEt)2](PPh3)2 1 and IrHCl2[P(OEt)3](PPh3)2 2.
An excess of the appropriate phosphite (4.75 mmol) was added
to a solution of IrHCl2(PPh3)3 (1 g, 0.95 mmol) in 30 cm3
of benzene and the reaction mixture refluxed for 2 h. The
solution was removed under reduced pressure, giving an oil
which was triturated with 3 cm3 of ethanol. A yellow solid
slowly separated out from the resulting solution, which was
filtered off and crystallised from benzene (3 cm3)–ethanol
(5 cm3); yield ≥60% (Found: C, 55.8; H, 4.6; Cl, 7.35. C46H46Cl2-
IrO2P3 1 requires C, 56.0; H, 4.70; Cl, 7.2. Found: C, 52.95;
H, 4.8; Cl, 7.20. C42H46Cl2IrO3P3 2 requires C, 52.8; H, 4.9; Cl,
7.4%).
[IrCl2(Me2NNH2){P(OEt)3}(PPh3)2]BPh4 6e. This complex
was prepared similarly to related compounds 6, but using a
large excess of Me2NNH2 (10:1 ratio) and a longer reaction
time (7–8 h); yield ≥30%; ΛM = 59.2 S cm2 molϪ1 (Found: C,
61.0; H, 5.6; N, 2.2; Cl, 5.5. C68H73BCl2IrN2O3P3 requires C,
61.3; H, 5.5; N, 2.10; Cl, 5.3%).
[IrCl2(RNHNH2){PPh(OEt)2}(AsPh3)2]BPh4 7 and [IrCl2-
(RNHNH2){P(OEt)3}(AsPh3)2]BPh4 8 (R ؍ H a, Me b or Ph c).
These complexes were prepared in the same manner as the
related triphenylphosphine complexes, with yields varying
between 40 and 60%; ΛM/S cm2 molϪ1 = 49.8 for 7a, 48.4 for 7c,
51.4 for 8a, 48.6 for 8b, 46.3 for 8c (Found: C, 59.2; H, 4.85;
N, 1.9; Cl, 5.15. C70H69As2BCl2IrN2O2P 7a requires C, 59.00;
H, 4.9; N, 2.0; Cl, 5.0. Found: C, 60.7; H, 5.0; N, 2.0; Cl, 4.6.
C70H73As2BCl2IrN2O2P 7c requires C, 60.8; H, 4.90; N, 1.9;
Cl, 4.7. Found: C, 56.75; H, 4.95; N, 2.1; Cl, 5.2. C70H69As2-
BCl2IrN2O2P 8a requires C, 56.9; H, 5.0; N, 2.0; Cl, 5.1. Found:
C, 57.4; H, 4.9; N, 2.1; Cl, 4.9. C67H71As2BCl2IrN2O3P 8b
requires C, 57.2; H, 5.1; N, 2.0; Cl, 5.0. Found: C, 59.1; H, 5.2;
N, 2.0; Cl, 4.9. C72H73As2BCl2IrN2O3P 8c requires C, 58.9;
H, 5.0; N, 1.9; Cl, 4.8%).
IrHCl2[PPh(OEt)2](AsPh3)2 3 and IrHCl2[P(OEt)3](AsPh3)2
4. An excess of the appropriate phosphite (4.22 mmol) was
added to a solution of IrHCl2(AsPh3)3 (1 g, 0.845 mmol) in
20 cm3 of benzene and the reaction mixture refluxed for 2 h.
The solvent was removed under reduced pressure, giving a
yellow solid which was treated with ethanol (15 cm3) containing
an excess of NaBH4 (0.15 g, 4.0 mmol). The resulting mix-
ture was refluxed for 1 h and the solvent was then removed
under reduced pressure. The residual solid material was
treated with ethanol (4 cm3) to give a yellow solution which was
vigorously stirred until a solid separated out. This was filtered
off and crystallised from benzene (2 cm3)–ethanol (4 cm3);
yield ≥45% (Found: C, 51.25; H, 4.3; Cl, 6.4. C46H46As2Cl2-
IrO2P 3 requires C, 51.40; H, 4.3; Cl, 6.60. Found: C, 48.6; H,
4.5; Cl, 6.7. C42H46As2Cl2IrO3P 4 requires C, 48.4; H, 4.45; Cl,
6.80%).
[IrH2(RNHNH2)(PPh3)3]BPh4 9 (R ؍ H a or Me b). To a solu-
tion of IrH3(PPh3)3 (0.150 g, 0.153 mmol) in 5 cm3 of toluene,
cooled to Ϫ80 ЊC, was added an equimolar amount of
CF3SO3H (13 µL, 0.153 mmol) and the reaction mixture
brought to room temperature. After the addition of 5 cm3 of
CH2Cl2, the reaction mixture was stirred for 1 h and then an
excess of the appropriate hydrazine (0.4 mmol) added. After 4 h
of stirring, the solvent was removed under reduced pressure,
and the resulting oil treated with 5 cm3 of ethanol. The addition
of an excess of NaBPh4 (0.103 g, 0.3 mmol) in 3 cm3 of ethanol
to the solution caused the precipitation of a white solid, which
was filtered off and crystallised from CH2Cl2 (3 cm3)–ethanol
(7 cm3); yield ≥55%; ΛM/S cm2 molϪ1 = 51.7 for 9a, 57.3 for 9b
(Found: C, 70.1; H, 5.3; N, 2.15. C78H71BIrN2P3 9a requires
C, 70.3; H, 5.4; N, 2.10. Found: C, 70.60; H, 5.4; N, 2.25.
C79H73BIrN2P3 9b requires C, 70.5; H, 5.5; N, 2.1%).
[IrCl2(RNHNH2){PPh(OEt)2}(PPh3)2]BPh4
5 and [IrCl2-
(RNHNH2){P(OEt)3}(PPh3)2]BPh4 6 (R ؍ H a, Me b, Ph c
or C6H4NO2-4 d). To a solution of the appropriate hydride (0.50
mmol) in 20 cm3 of CH2Cl2, cooled to Ϫ80 ЊC, was added an
equimolar amount of CF3SO3H (44 µL, 0.50 mmol) and the
reaction mixture, brought to room temperature, was stirred for
ca. 1 h. An excess of the appropriate hydrazine RNHNH2 (1.0
mmol for NH2NH2, 5 mmol for 4-NO2C6H4NHNH2) was
added and, after 2–3 h of stirring, the solvent was removed
under reduced pressure. The resulting oil was triturated with
ethanol (5 cm3) containing an excess of NaBPh4 (0.34 g,
1 mmol). A white solid slowly separated out, which was filtered
off and crystallised from CH2Cl2 (3 cm3)–ethanol (5 cm3); yield
60–70%: ΛM/S cm2 molϪ1 = 54.7 for 5a, 54.5 for 5b, 51.9 for
5c, 53.5 for 5d, 50.9 for 6b, 53.7 for 6c, 54.0 for 6d (Found: C,
62.7; H, 5.25; N, 2.0; Cl, 5.1. C70H69BCl2IrN2O2P3 5a requires
C, 62.9; H, 5.20; N, 2.1; Cl, 5.30. Found: C, 63.0; H, 5.05;
N, 2.0; Cl, 5.0. C71H71BCl2IrN2O2P3 5b requires C, 63.1;
H, 5.30; N, 2.1; Cl, 5.25. Found: C, 64.8; H, 5.1; N, 1.9; Cl, 5.2.
C76H73BCl2IrN2O2P3 5c requires C, 64.6; H, 5.20; N, 2.0; Cl, 5.0.
Found: C, 62.4; H, 4.90; N, 3.05; Cl, 5.1. C76H72BCl2IrN3O4P3
5d requires C, 62.60; H, 5.0; N, 2.9; Cl, 4.9. Found: C, 61.2; H,
5.30; N, 2.0; Cl, 5.3. C67H71BCl2IrN2O3P3 6b requires C, 61.00;
H, 5.4; N, 2.1; Cl, 5.4. Found: C, 62.45; H, 5.4; N, 1.9; Cl, 5.2.
C72H73BCl2IrN2O3P3 6c requires C, 62.6; H, 5.3; N, 2.0; Cl, 5.1.
Found: C, 60.8; H, 5.1; N, 3.0; Cl, 4.9. C72H72BCl2IrN3O5P3 6d
requires C, 60.6; H, 5.1; N, 2.95; Cl, 5.0%).
[IrHCl(RNHNH2)(PPh3)2]BPh4 10 (R ؍ H a, Me b or Ph c).
To a solution of IrH2Cl(PPh3)3 (0.102 g, 0.1 mmol) in 10 cm3 of
CH2Cl2, cooled to Ϫ80 ЊC, was added an equimolar amount
of HBF4ؒEt2O (13.5 µL, 0.1 mmol) and the reaction mixture,
brought to room temperature, was stirred for ca. 90 min. An
excess of the appropriate hydrazine (0.3 mmol) was added and,
after 3 h of stirring, the solvent was removed under reduced
pressure. The resulting solid was treated with 5 cm3 of ethanol
containing an excess of NaBPh4 (0.068 g, 0.2 mmol). The
solution was vigorously stirred until a white solid separated out,
which was filtered off and crystallised from CH2Cl2 (2 cm3)–
ethanol (6 cm3); yield ≥60%; ΛM/S cm2 molϪ1 = 53.9 for 10a,
50.4 for 10b, 52.5 for 10c (Found: C, 65.0; H, 5.2; N, 2.4; Cl, 3.2.
C60H55BClIrN2P2 10a requires C, 65.25; H, 5.0; N, 2.5; Cl, 3.2.
Found: C, 65.3; H, 5.0; N, 2.65; Cl, 3.3. C61H57BClIrN2P2 10b
requires C, 65.50; H, 5.1; N, 2.50; Cl, 3.2. Found: C, 66.9; H,
5.05; N, 2.3; Cl, 3.1. C66H59BClIrN2P2 10c requires C, 67.1; H,
5.0; N, 2.4; Cl, 3.00%).
[IrCl2(NH2NH2){P(OEt)3}(PPh3)2]BPh4 6a. This complex
was obtained by slight modification of the general method.
To a solution of IrHCl2[P(OEt)3](PPh3)2 (0.191 g, 0.20 mmol) in
10 cm3 of toluene, cooled to Ϫ80 ЊC, was added an equimolar
amount of CF3SO3H (18 µL, 0.20 mmol) and the reaction
mixture was brought to room temperature. Dichloromethane
1182
J. Chem. Soc., Dalton Trans., 2000, 1181–1189

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[IrCl (ArN᎐NH){PPh(OEt) }L ]BPh 11, 13 and [IrCl2-
Cl, 6.1. C106H104B2Cl4F8Ir2N4O4P6 requires C, 53.4; H, 4.40; N,
2.35; Cl, 5.95%).
᎐
2
2
2
4
(ArN᎐NH){P(OEt) }L ]BPh 12, 14 (Ar ؍ Ph c or C H Me-4 f;
᎐
3
2
4
6
4
L ؍ PPh3 11, 12 or AsPh3 13, 14). In a 25 cm3 three-necked
round-bottomed flask were placed the appropriate hydride
IrHCl2{PPh(OEt)2}L2 or IrHCl2{P(OEt)3}L2 (L = PPh3 or
AsPh3) (0.1 mmol) and the aryldiazonium salt ArN2ϩBF4Ϫ in an
equimolar amount (0.1 mmol). The flask was cooled to Ϫ80 ЊC
and dichloromethane (10 cm3) was slowly added. The reaction
mixture was brought to 0 ЊC, stirred at this temperature for 3 h,
and the solvent was then removed under reduced pressure. The
resulting oil was dissolved in 3 cm3 of ethanol and an excess
of NaBPh4 (0.068 g, 0.2 mmol) in 2 cm3 of ethanol added. A
yellow or orange solid slowly separated out from the stirred
solution, which was filtered off and crystallised from CH2Cl2
(3 cm3)–ethanol (7 cm3); yields varied between 55 and 70%;
ΛM/S cm2 molϪ1 = 56.4 for 11c, 57.9 for 11f, 55.4 for 12c, 58.6
for 12f, 55.4 for 13c, 54.3 for 14c, 51.9 for 14f (Found: C, 64.6;
H, 5.15; N, 1.9; Cl, 5.2. C76H71BCl2IrN2O2P3 11c requires C,
64.7; H, 5.1; N, 2.0; Cl, 5.0. Found: C, 64.85; H, 5.2; N, 2.05;
Cl, 5.1. C77H73BCl2IrN2O2P3 11f requires C, 64.9; H, 5.2; N, 2.0;
Cl, 5.0. Found: C, 62.9; H, 5.1; N, 2.1; Cl, 5.25. C72H71BCl2-
IrN2O3P3 12c requires C, 62.70; H, 5.2; N, 2.0; Cl, 5.1. Found:
C, 62.8; H, 5.4; N, 1.9; Cl, 5.2. C73H73BCl2IrN2O3P3 12f requires
C, 62.9; H, 5.3; N, 2.0; Cl, 5.1. Found: C, 61.5; H, 4.70; N,
1.85; Cl, 4.8. C76H71As2BCl2IrN2O2P 13c requires C, 60.9; H,
4.8; N, 1.9; Cl, 4.7. Found: C, 60.1; H, 5.0; N, 1.8; Cl, 4.9.
C72H71As2BCl2IrN2O3P 14c requires C, 58.9; H, 4.9; N, 1.9;
Cl, 4.8. Found: C, 59.4; H, 4.9; N, 2.00; Cl, 4.65. C73H73As2BCl2-
IrN2O3P 14f requires C, 59.20; H, 5.0; N, 1.9; Cl, 4.8%).
Oxidation of hydrazine complexes
Reactions were carried out in CH2Cl2 at Ϫ30 ЊC using Pb-
(OAc)4 as oxidising agent. In a typical reaction, solid samples
of the appropriate hydrazine complexes 5–10 (0.1 mmol) were
placed singly in a three-necked 25 cm3 round-bottomed flask
fitted with a solid-addition sidearm containing an excess of
Pb(OAc)4 (0.14 g, 0.30 mmol). Dichloromethane (10 cm3) was
added, the solution cooled to Ϫ30 ЊC, and the Pb(OAc)4 added
in portions over 20–30 min to the cold stirred solution. The
reaction mixture was then brought to room temperature and
filtered, and the solvent was removed under reduced pressure,
giving an oil. The addition of ethanol (3 cm3) containing an
excess of NaBPh4 (0.068 g, 0.2 mmol) led to the separation of
a solid, which was filtered off and crystallised from CH2Cl2
(2–3 cm3)–ethanol (4–6 cm3).
Results and discussion
Preparation of hydride complexes
The synthesis of hydrazine complexes of iridium was achieved
using as precursors the new hydrides IrHCl2[PPh(OEt)2]L2
1, 3 and IrHCl2[P(OEt)3]L2 2, 4 (L = PPh3 or AsPh3), the
preparation of which deserves some comment. Treatment of
the monohydride13a,c IrHCl2L3 with an excess of phosphite
gives the mixed-ligand species 1–4 as shown in Scheme 1.
[IrCl (PhN᎐15NH){PPh(OEt) }(PPh ) ]BPh 11c and [IrCl -
᎐
2
2
3
2
4
1
2
(Ph15N᎐NH){PPh(OEt) }(PPh ) ]BPh 11c2. These complexes
᎐
2
3
2
4
were obtained in the same manner as the related unlabelled
15
ϩ
Ϫ
15
ϩ
Ϫ
᎐
᎐
complex 11c using the PhN᎐ N BF or Ph N᎐N BF
᎐
᎐
4
4
phenyldiazonium salts; yield ≥70%.
[{IrCl [PPh(OEt) ]L } (ꢀ-4,4Ј-HN᎐NC H –C H N᎐NH)]-
᎐
᎐
4
2
2
2
2
6
4
6
(BPh ) 15c, 17c and [{IrCl [P(OEt) ]L } (ꢀ-4,4Ј-HN᎐NC H –
᎐
4
2
2
3
2
2
6
4
C H N᎐NH)](BPh ) 16c, 18c (L ؍ PPh 15, 16 or AsPh 17,
᎐
6
4
4
2
3
3
Scheme 1 L = PPh3 1, 2 or AsPh3 3, 4.
18). These complexes were prepared following the method used
for related mononuclear compounds 11–14 by reacting hydrides
IrHCl2[PPh(OEt)2]L2 and IrHCl2[P(OEt)3]L2 (0.1 mmol) with
the bis(aryldiazonium) [N2Ar–ArN2](BF4)2 salt (0.05 mmol)
in CH2Cl2; yield ≥40%; ΛM/S2 cm2 molϪ1 = 119.7 for 15c, 128.7
for 16c, 125.4 for 17c, 125.4 for 18c (Found: C, 64.8; H, 5.1;
N, 2.05; Cl, 4.8. C152H140B2Cl4Ir2N4O4P6 15c requires C, 64.7;
H, 5.00; N, 2.0; Cl, 5.0. Found: C, 62.9; H, 4.95; N, 1.9; Cl,
5.0. C144H140B2Cl4Ir2N4O6P6 16c requires C, 62.75; H, 5.1; N,
2.0; Cl, 5.1. Found: C, 60.8; H, 4.60; N, 1.9; Cl, 5.0.
C152H140As4B2Cl4Ir2N4O4P2 17c requires C, 60.9; H, 4.7; N, 1.9;
Cl, 4.7. Found: C, 59.2; H, 4.9; N, 1.8; Cl, 4.7. C144H140As4B2Cl4-
Ir2N4O6P2 18c requires C, 59.0; H, 4.8; N, 1.9; Cl, 4.8%).
The reaction proceeds with the replacement of only one
PPh3 or AsPh3 ligand, and the formation exclusively of mono-
phosphite species 1–4 which may be isolated as yellow solids
and characterised. The complexes are air-stable diamagnetic
solids, very soluble in aromatic hydrocarbons and slightly
in CH2Cl2 or THF, and non-electrolytes. The analytical and
spectroscopic data (Table 1) support the proposed formula-
tions. In the low frequency region, the 1H NMR spectra of PPh3
derivatives 1, 2 show one doublet of triplets at δ Ϫ10.49 for
1 and δ Ϫ10.38 for 2, attributed to the hydride ligand coupled
with the phosphorus nuclei. By contrast, in related AsPh3
1
compounds 3, 4, the H NMR hydride signal appears as only
[{IrCl [PPh(OEt) ](PPh ) } (ꢀ-4,4Ј-H15N᎐NC H –C H N᎐
one sharp doublet at δ Ϫ9.80 and Ϫ9.67, respectively, due to
coupling with only one phosphite ligand. For compounds 1 and
2, the 31P-{1H} NMR spectra show an AB2 pattern, formed of
a doublet at δ ca. Ϫ2 attributed to the PPh3, and a triplet at
δ 102.0 or 79.9 due to the PPh(OEt)2 or P(OEt)3 ligand. Only
one singlet at δ 82.0 or 85.6 ppm is observed, instead, in the
spectra of AsPh3 derivatives 3, 4. These spectroscopic data fit
the proposed formulations, but do not allow any geometry to
be unambiguously proposed. However, we identified14 ν(IrCl)
bands in the far-IR spectra of 1, appearing as two absorptions
of weak intensity at 333 and 326 cmϪ1 (Table 1), in accord with
the presence of two ClϪ ligands in a mutually cis position.
Taking into account the fact that the proton NMR spectra of
1–4 show high values (220–265 Hz) for one of the JPH coupling
constants, indicating a mutually trans position of the hydride
and of one phosphine ligand, a fac geometry (Fig. 1) may be
proposed for the hydride derivatives.
᎐
᎐
4
2
2
3
2
2
6
4
6
15NH)](BPh4)2 15c1. This complex was prepared in the same
manner as for the related unlabelled compound 15c using the
15
15
᎐
᎐
[4,4Ј- N᎐NC H –C H N᎐ N](BF ) bis(diazonium) salt.
᎐
᎐
6
4
6
4
4 2
[{IrCl [PPh(OEt) ](PPh ) } (ꢀ-4,4Ј-HN᎐N(2-Me)C H –
᎐
2
2
3
2
2
6
3
C H (Me-2)N᎐NH}](BF ) 15f. A 25 cm3 three-necked round
᎐
6
3
4 2
bottomed flask was charged with 0.100 g (0.10 mmol) of
IrHCl2[PPh(OEt)2](PPh3)2 and 0.020 g (0.05 mmol) of [4,4Ј-
N2(2-Me)C6H3–C6H3(Me-2)N2](BF4)2 and cooled to Ϫ80 ЊC.
Acetone (15 cm3) was added and the reaction mixture, slowly
brought to room temperature, was stirred for 8 h. The solution
was filtered and the solvent removed under reduced pressure.
The resulting reddish-brown oil was triturated with ethanol
(3 cm3) until a red solid separated out, which was filtered off
and crystallised from CH2Cl2 (2 cm3)–ethanol (5 cm3); yield
≥40%; ΛM = 184.7 S cm2 molϪ1 (Found: C, 53.2; H, 4.3; N, 2.25;
J. Chem. Soc., Dalton Trans., 2000, 1181–1189
1183

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Table 1 IR and NMR spectroscopic data for the iridium complexes
31P-{1H}
NMRb,d
IRa
1H NMRb,c
Compound
ν/cmϪ1
Assignment
δ(J/Hz)
Assignment Spin system
δ(J/Hz)
e
1
2
3
IrHCl2[PPh(OEt)2](PPh3)2
2116w
(333w) ν(IrCl)
(326w)
ν(IrH)
3.84 (m), 3.51 (m) CH2
AB2
AB2
Ae
δA 102.0
δB Ϫ2.4
JAB = 16
0.98 (t)
Ϫ10.49 (dt,
CH3
IrH
JPH = 220,
trans
JPH = 15)e
3.58 (qnt)
0.92 (t)
cis
e
IrHCl2[P(OEt)3](PPh3)2
2073w
2065w
2051w
ν(IrH)
ν(IrH)
CH2
CH3
IrH
δA 79.9
δB Ϫ1.66
JAB = 22
Ϫ10.38 (dt,
JPH = 262,
trans
JPH = 16)e
3.92 (m)
3.49 (m)
cis
IrHCl2[PPh(OEt)2](AsPh3)2
CH2
82.0 (s)
0.99 (t)
CH3
IrH
Ϫ9.80 (d,
JPH = 225)e
3.70 (qnt)
0.92 (t)
Ϫ9.67 (d,
JPH = 265)e
4.22 (br)
3.45 (m)
4
IrHCl2[P(OEt)3](AsPh3)2
ν(IrH)
ν(NH)
CH2
CH3
IrH
Ae
85.6 (s)
5a
[IrCl2(NH2NH2){PPh(OEt)2}(PPh3)2]BPh4
3342w
3276m
3263w
3226w
IrNH2
CH2
AB2
δA 63.4
δB Ϫ22.6
JAB = 22
3.07 (m, br)
1.18 (t)
NH2
CH3
(338m) ν(IrCl)
5b
5c
[IrCl2(MeNHNH2){PPh(OEt)2}(PPh3)2]BPh4
[IrCl2(PhNHNH2){PPh(OEt)2}(PPh3)2]BPh4
3329w
3248m
3240w
ν(NH)
3.98 (br)
3.80 (m)
3.38 (m)
1.56 (d, JHH = 8)
1.07 (t)
6.49 (br)
4.57 (br)
3.47 (m)
1.13 (t)
4.49 (br)
3.45 (m)
1.09 (t)
4.12 (m)
3.43 (qnt)
3.08 (br)
0.99 (t)
IrNH2
NH
CH2
CH3 hydraz
CH3 phos
NH
IrNH2
CH2
CH3
IrNH2
CH2
CH3
IrNH2
CH2
AB2
AB2
δA 62.2
δB Ϫ22.2
JAB = 21
3302w
3241m
3197w
1604m
3311m
3230m
1602m
3342m
3270m
3250(sh)
ν(NH)
δA 61.1
δB Ϫ22.7
JAB = 22
δ(NH2)
ν(NH)
5d
6a
[IrCl2(4-NO2C6H4NHNH2){PPh(OEt)2}-
(PPh3)2]BPh4
AB2
AB2
δA 59.9
δB Ϫ23.2
JAB = 22
δA 30.8
δB Ϫ18.7
JAB = 26
δ(NH2)
ν(NH)
[IrCl2(NH2NH2){P(OEt)3}(PPh3)2]BPh4
NH2
CH3
(327w) ν(IrCl)
6b
6c
[IrCl2(MeNHNH2){P(OEt)3}(PPh3)2]BPh4
3302m
3256m
3197m
ν(NH)
3.94 (m)
3.80 (m)
3.42 (qnt)
1.61 (d, JHH = 4)
0.99 (t)
6.40 (m)
4.45 (m)
3.44 (qnt)
1.00 (t)
4.40 (m)
3.47 (qnt)
1.01 (t)
4.12 (br)
3.55 (qnt)
2.39 (s)
IrNH2
NH
CH2
CH3 hydraz
CH3 phos
NH
IrNH2
CH2
CH3
IrNH2
CH2
CH3
IrNH2
CH2
CH3 hydraz
CH3 phos
IrNH2
CH2
NH2
CH3
NH
IrNH2
CH2
AB2
AB2
δA 28.7
δB Ϫ18.0
JAB = 26
[IrCl2(PhNHNH2){P(OEt)3}(PPh3)2]BPh4
3317m
3257m
3197w
1601m
3282m
3227w
1602m
3310w
3233m
1616m
ν(NH)
δA 28.1
δB Ϫ18.9
JAB = 26
δ(NH2)
ν(NH)
6d
6e
[IrCl2(4-NO2C6H4NHNH2){P(OEt)3}-
(PPh3)2]BPh4
AB2
AB2
δA 26.0
δB Ϫ19.5
JAB = 26
δA 21.5
δB Ϫ17.4
JAB = 20
δ(NH2)
ν(NH)
[IrCl2(Me2NNH2){P(OEt)3}(PPh3)2]BPh4
[IrCl2(NH2NH2){PPh(OEt)2}(AsPh3)2]BPh4
[IrCl2(PhNHNH2){PPh(OEt)2}(AsPh3)2]BPh4
δ(NH2)
ν(NH)
1.06 (t)
7a
7c
3340m
3271m
3263w
3223m
3299m
3242m
3197w
1597m
4.45 (m)
3.48 (qnt)
3.29 (m)
1.01 (t)
6.64 (m)
4.75 (t, br)
3.54 (qnt)
1.10 (t)
A
A
63.6 (s)
ν(NH)
61.4 (s)
δ(NH2)
CH3
(332w) ν(IrCl)
8a
8b
[IrCl2(NH2NH2){P(OEt)3}(AsPh3)2]BPh4
[IrCl2(MeNHNH2){P(OEt)3}(AsPh3)2]BPh4
3347w
3263m
3230m
3158w
3308w
3244m
3202w
1597m
ν(NH)
4.39 (m)
3.57 (m)
3.36 (m)
1.00 (t)
4.10 (m)
4.21 (m)
3.58 (qnt)
1.73 (d,
JHH = 6)
1.00 (t)
IrNH2
CH2
NH2
CH3
NH
IrNH2
CH2
CH3 hydraz
A
A
31.6 (2)
30.1 (s)
ν(NH)
δ(NH2)
(335w) ν(IrCl)
CH3 phos
1184
J. Chem. Soc., Dalton Trans., 2000, 1181–1189

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Table 1 (Contd.)
31P-{1H}
NMRb,d
IRa
1H NMRb,c
Compound
ν/cmϪ1
Assignment
δ(J/Hz)
Assignment Spin system
δ(J/Hz)
8c
9a
[IrCl2(PhNHNH2){P(OEt)3}(AsPh3)2]BPh4
3299w
3242m
3197m
1597m
3359w
3298m
3257m
2175w
(br)
ν(NH)
6.61 (m)
4.63 (m)
3.58 (m)
1.02 (m)
3.92 (m)
2.26 (m)
Ϫ12.04 (dtd,
NH
IrNH2
CH2
CH3
IrNH2
NH2
A
29.3 (s)
δ(NH2)
ν(NH)
[IrH2(NH2NH2)(PPh3)3]BPh4
A2B
δA 9.1
δB 4.1
JAB = 15
f
IrHB
ν(IrH)
JH = 5,
BHA
JPH = 120,
trans
JPH = 20)
cis
Ϫ20.86 (dtd,
IrHA
JH = 5,
AHB
JPH
JPH = 15)
=
cis
cis
9b
[IrH2(MeNHNH2)(PPh3)3]BPh4
3341w,
3284w
2176w
(br)
ν(NH)
ν(IrH)
3.70 (br)
1.92 (m, br)
1.58 (d,
JHH = 6)
Ϫ12.15 (dtd,
IrNH2
NH
CH3
A2B
δA 9.4
δB 3.9
JAB = 12
f
IrHB
JH = 5,
BHA
JPH = 120,
trans
JPH = 20)
cis
Ϫ20.76 (dtd,
IrHA
JH = 5,
AHB
JPH
JPH = 17)
=
cis
cis
10a
10b
[IrHCl(NH2NH2)(PPh3)2]BPh4
[IrHCl(MeNHNH2)(PPh3)2]BPh4
3334m, ν(NH)
4.38 (m, br)
2.64 (br)
Ϫ21.42 (t,
JPH = 18)
4.93 (br)
3.70 (br)
2.02 (br)
Ϫ20.98 (t,
JPH = 17)
5.14 (d, br)g
3.69 (br)
IrNH2
NH2
IrH
A2
A2
Ϫ4.4 (s)
Ϫ4.6 (s)
3248m
2267m
ν(IrH)
ν(NH)
ν(IrH)
3269w,
3210w
2245w
IrNH2
NH
CH3
IrH
IrNH2
NH
1.97 (d)
CH3
IrNH2
NH
10c
11c
[IrHCl(PhNHNH2)(PPh3)2]BPh4
3269m, ν(NH)
6.05 (t, br)
5.30 (m, br)
Ϫ20.43 (t,
JPH = 18)
12.49 (d,
A2
Ϫ4.4 (s)
3213m
2200w
1601m
ν(IrH)
δ(NH2)
IrH
h
[IrCl2(PhN᎐NH){PPh(OEt)2}(PPh3)2]BPh4
NH
AB2
δA 64.6
δB Ϫ20.0
JAB = 22
᎐
JPH = 12)
3.65 (m)
CH2
CH3
NH
1.17 (t)e
11c1 [IrCl2(PhN᎐15NH){PPh(OEt)2}(PPh3)2]BPh4
12.50 (ddt,
AB2Xh
δA 64.6
᎐
1
J
NH = 66,
(X = 15N)
δBϪ20.0
JAB = 21.7
JAX = 75.2
JBX = 3.6
15
JPH = 12,
JPH = 2)
3.71 (m)
1.18 (t)h
12.50 (dd,
CH2
CH3
NH
11c2 [IrCl2(Ph15N᎐NH){PPh(OEt)2}(PPh3)2]BPh4
AB2
δA 64.4
δB Ϫ20.0
JAB = 22
h
᎐
2
15
J
NH = 4,
JPH = 12)
3.71 (m)
1.18 (t)h
12.28 (d,
JPH = 12)
3.73 (m)
2.41 (s)
CH2
CH3
NH
h
11f
[IrCl2(4-MeC6H4N᎐NH){PPh(OEt)2}-
(342w) ν(IrCl)
AB2
δA 64.7
δB Ϫ19.9
JAB = 22
᎐
(PPh3)2]BPh4
CH2
CH3 p-tolyl
CH3 phos
NH
1.19 (t)h
12.36 (d,
JPH = 12)h
3.74 (qnt)
1.07 (t)
h
12c
12f
[IrCl2(PhN᎐NH){P(OEt)3}(PPh3)2]BPh4
AB2
δA 30.1
δB Ϫ15.9
JAB = 26
᎐
CH2
CH3
NH
h
[IrCl2(4-MeC6H4N᎐NH){P(OEt)3}-
(338w) ν(IrCl)
12.14 (d,
JPH = 12)
3.75 (m)
2.41 (s)
AB2
δA 30.6
δB Ϫ15.9
JAB = 26
᎐
(PPh3)2]BPh4
CH2
CH3 p-tolyl
CH3 phos
1.09 (t)h
J. Chem. Soc., Dalton Trans., 2000, 1181–1189
1185

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Table 1 (Contd.)
31P-{1H}
NMRb,d
IRa
1H NMRb,c
Compound
ν/cmϪ1
Assignment
δ(J/Hz)
Assignment Spin system
δ(J/Hz)
13c
14c
14f
[IrCl2(PhN᎐NH){PPh(OEt)2}(AsPh3)2]BPh4
12.64 (d,
JPH = 12)
3.58 (m)
1.11 (t)
NH
A
64.6 (s)
᎐
CH2
CH3
NH
[IrCl2(PhN᎐NH){P(OEt)3}(AsPh3)2]BPh4
12.90 (d,
JPH = 12)
3.88 (qnt)
1.04 (t)h
12.32 (d,
JPH = 12)
3.61 (qnt)
2.37 (s)
Ah
Ai
32.0 (s)
32.2 (s)
᎐
CH2
CH3
NH
[IrCl2(4-MeC6H4N᎐NH){P(OEt)3}-
(340w)
ν(IrCl)
᎐
(AsPh3)2]BPh4
CH2
CH3 p-tolyl
CH3 phos
NH
0.95 (t)i
h
15c
[{IrCl2[PPh(OEt)2](PPh3)2}2(µ-4,4Ј-
12.55 (d),
12.40 (d)
(JPH = 12)
3.72 (m)
1.18 (t),
AB2
AB2
δA 64.7
HN᎐NC6H4–C6H4N᎐NH)](BPh4)2
δB Ϫ20.0
JAB = 21.1
δA 64.3
δB Ϫ20.0
JAB = 21.1
δA 64.7
δB Ϫ19.9
JAB = 21.1
JAX = 73.3
JBX = 3.0
δA 64.3
δB Ϫ19.9
JAB = 21.1
JAX = 75.0
JBX = 3.0
δA 64.4
᎐
᎐
CH2
CH3
1.15 (t)h
12.55 (dd),
12.39 (dd)
15c1 [{IrCl2[PPh(OEt)2](PPh3)2}2(µ-4,4Ј-
H15N᎐NC6H4–C6H4N᎐15NH)](BPh4)2
NH
AB2Xh
(X = 15N)
᎐
᎐
15
(J NH = 66,
JPH = 12)
3.72 (m)
1.18 (t),
1.14 (t)h
CH2
CH3
AB2X
(X = 15N)
15f
[{IrCl2[PPh(OEt)2](PPh3)2}2{µ-4,4Ј-HN᎐N-
12.16 (d,
JPH = 12)
3.55 (m)
2.65 (s)
1.15 (t)
12.15 (d,
JPH = 12)
3.76 (qnt)
1.09 (t)h
NH
AB2
᎐
(2-Me)C6H3–C6H3(Me-2)N᎐NH}](BF4)2
δB Ϫ21.6
JAB = 22
᎐
CH2
CH3 p-tolyl
CH3 phos
NH
h
16c
17c
[{IrCl2{P(OEt)3}(PPh3)2}2(µ-4,4Ј-
AB2
δA 30.4
δB Ϫ15.8
JAB = 26
HN᎐NC6H4–C6H4N᎐NH)](BPh4)2
᎐
᎐
CH2
CH3
NH
[{IrCl2{PPh(OEt)2}(AsPh3)2}2(µ-4,4Ј-
HN᎐NC6H4–C6H4N᎐NH)](BPh4)2
13.05 (d),
12.89 (d)
(JPH = 12)
3.76 (m)
Ah
A
65.7 (s)
65.3 (s)
᎐
᎐
CH2
CH3
NH
1.15 (m)h
12.97 (d),
12.81 (d)
(JPH = 12)
3.86 (m)
18c
[{IrCl2{P(OEt)3}(AsPh3)2}2(µ-4,4Ј-
HN᎐NC6H4–C6H4N᎐NH)](BPh4)2
Ah
A
32.3 (s)
31.8 (s)
᎐
᎐
CH2
CH3
1.05 (t), 1.02 (t)h
a In KBr or (polyethylene). b In CD2Cl2 at 25 ЊC. c Phenyl proton resonances are omitted. d Positive shift downfield from 85% H3PO4. e In C6D6. f See
Fig. 3 in the text. g At Ϫ30 ЊC. h In (CD3)2CO. i In CDCl3.
Fig. 1 L = PPh3 or AsPh3, LЈ = PPh(OEt)2 or P(OEt)3.
Hydrazine complexes
Hydrazine complexes [IrCl2(RNHNH2)LЈL2]BPh4 5–8 were
prepared by treating the hydride species IrHCl2[PPh(OEt)2]L2
and IrHCl2[P(OEt)3]L2 first with triflic acid and then with
an excess of the appropriate RNHNH2 ligand, as shown in
Scheme 2.
Scheme 2 L = PPh3, LЈ = PPh(OEt)2 5a–d; L = PPh3, LЈ = P(OEt)3
6a–d; L = AsPh3, LЈ = PPh(OEt)2 7a,c; L = AsPh3, LЈ = P(OEt)3 8a–c;
R = H a, Me b, Ph c or C6H4NO2-4 d.
The reaction of hydrides 1–4 with CF3SO3H proceeds with
the evolution of H2 (1H NMR signal at δ 4.6)15 and the
probable formation of either the triflate Ir(η1-OSO2CF3)-
Cl2LЈL2 or the pentacoordinate [IrCl2LЈL2]ϩ complex, which
were not isolated. Treatment of these intermediates with an
excess of the appropriate hydrazine affords the final complexes
5–8, which were isolated as BPh4 salts and characterised. It
1186
J. Chem. Soc., Dalton Trans., 2000, 1181–1189

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Fig. 2 L = PPh3 or AsPh3, LЈ = PPh(OEt)2 or P(OEt)3.
Fig. 3 L = PPh3.
may be noted that hydrazine complexes can only be obtained
from mixed-ligand hydrides 1–4, whereas the use of IrHCl2-
(PPh3)3 or IrHCl2(AsPh3)3 as precursors affords only mix-
tures of products not containing coordinated hydrazine. The
nature of the ancillary ligands therefore plays an important role
in stabilising the coordination of the hydrazine molecule on the
central iridium atom.
HBF4ؒEt2O instead of CF3SO3H and then with RNHNH2,
pentacoordinate hydrazine complexes [IrHCl(RNHNH2)-
(PPh3)2]BPh4 10 were obtained in good yield after precipitation
with BPh4 salts (Scheme 3).
The reaction of IrH3(PPh3)3 with triflic acid proceeds with
1
the evolution of H2 (by H NMR) and the probable formation
Good analytical data were obtained for all hydrazine com-
plexes 5–8, which are white or yellow solids, stable in air and
in solutions of polar organic solvents, where they behave as
1:1 electrolytes.16 The spectroscopic data (IR and NMR,
see Table 1) support the proposed formulation and allow the
geometry in solution to be established. The IR spectra show the
characteristic ν(NH) and δ(NH2) bands of the hydrazine ligand
of either η1-OSO2CF3 or pentacoordinate [IrH2(PPh3)3]ϩ inter-
mediates which, on treatment with RNHNH2, afford the final
hydrazine complexes 9. Evolution of H2 was also observed in
the reaction of IrH2Cl(PPh3)3 with HBF4ؒEt2O, giving the
probable intermediate [IrHCl(PPh3)3]ϩ, which reacts with
hydrazine to give final complex 10. The reaction proceeds
with loss of one PPh3 ligand, affording the pentacoordinate
bis(phosphino) [IrHCl(RNHNH2)(PPh3)2]BPh4 derivative 10.
Good analytical data were obtained for both complexes 9
and 10, which are all air-stable white solids, diamagnetic,
and 1:1 electrolytes.16 The IR and NMR data are listed in
Table 1 and confirm the proposed formulation. In particular,
1
at 3347–3197 and 1616–1597 cmϪ1, respectively. The H NMR
spectra also confirm the presence of the metal-bonded
RNHNH2 ligand, showing slightly broadened NH2 and NH
signals, which were unambiguously assigned by accurate inte-
gration and homodecoupling experiments. The 13P-{1H} NMR
spectra of PPh3 derivatives 5, 6 show an AB2 multiplet (Table
1), in accord with the presence of two magnetically equivalent
phosphines which are different from the third. Only one singlet
appears in the spectra of AsPh3 derivatives 7, 8. Furthermore,
1
the H NMR spectra of [IrH2(RNHNH2)(PPh3)3]BPh4 deriv-
atives 9 display two sets of signals in the low frequency region,
each appearing as a doublet of triplets of doublets, due to the
coupling of two chemically inequivalent hydride ligands, HA
and HB (Fig. 3), with the phosphorus nuclei of the phosphine
ligands. The 31P-{1H} NMR spectra of 9 show A2B multiplets,
in agreement with two magnetically equivalent phosphines,
different from the third. Furthermore, the JPH values of
hydrides HA and HB are quite different, and the value of 120 Hz
observed in one case, compared with the other two, indicates
the mutually trans position of this hydride with one phosphine
ligand. On these bases, a mer-cis geometry of the type shown in
Fig. 3 may be proposed for our complexes 9.
the far-IR spectra show only one ν(IrCl) band at 338–327 cmϪ1
,
indicating the presence of two ClϪ ligands in a mutually trans
position. Although caution should be used with far-IR data,
a mer-trans geometry of the type shown in Fig. 2 may be
proposed for our hydrazine derivatives 5–8.
These results prompted us to extend the study to other
hydrides, in order to test the reaction for the synthesis of other
hydrazine derivatives. Results show that, whereas monohy-
drides IrHCl2(PPh)3 and IrHCl2(AsPh3)3 do not afford hydra-
zine complexes, the trihydride IrH3(PPh3)3 reacts first with triflic
acid and then with an excess of the appropriate hydrazine, to
The 1H NMR spectra of [IrHCl(RNHNH2)(PPh3)2]BPh4
10 show a triplet at δ ca. Ϫ21 in the low frequency region, due
to coupling of the hydride ligand with two chemically equiv-
alent phosphorus nuclei. The equivalence of the two PPh3
ligands is confirmed by the 31P-{1H} NMR spectra which,
between 30 and Ϫ90 ЊC, show only one singlet. However, the
spectroscopic data alone do not allow us to unambiguously
assign a geometry for these pentacoordinate hydrazine com-
plexes and, in the absence of an X-ray structure, no geometrical
assignment can be made.
give hydride–hydrazine cations [IrH2(RNHNH2)(PPh3)3]ϩ
9
which were isolated as BPh3 salts and characterised (Scheme 3).
Oxidation reactions
The oxidation reactions of hydrazine complexes 5–10 with
Pb(OAc)4 were studied extensively. The results are summarised
in Scheme 4.
Phenylhydrazine cations [IrCl2(PhNHNH2)LЈL2]ϩ 5c–8c react
with Pb(OAc)4 at Ϫ30 ЊC to give the corresponding phenyl-
diazene derivatives [IrCl (PhN᎐NH)LЈL ]ϩ 11c–14c, which
᎐
2
2
were isolated as yellow solids and characterised. Support for
their formulation comes from spectroscopic data and by com-
parisons with similar complexes prepared by reacting hydrides
IrHCl2LЈL2 1–4 with aryldiazonium cations (see below). The
related [IrCl2(NH2NH2)LЈL2]ϩ derivatives 5a–8a, react with
Pb(OAc)4 but do not yield any diazene derivatives as the solids
recovered from the reaction mixture only contain decom-
position products. Hydride–hydrazine complexes 9 and 10 also
give only decomposition products when treated with Pb(OAc)4,
and no traces of diazene species could be detected. Surprisingly,
the reaction of methylhydrazine complexes [IrCl2(MeNHNH2)-
LЈL2]BPh4 5b, 6b with Pb(OAc)4 at low temperature (Ϫ30 ЊC)
proceeds to give the hydrides IrHCl2[PPh(OEt)2](PPh3)2 or
Scheme 3 R = H a, Me b or Ph c.
Surprisingly, no hydrazine complexes were obtained by reacting
dihydride species IrH2Cl(PPh3)3 first with CF3SO3H and then
with RNHNH2. However, when IrH2Cl(PPh3)3 was treated with
J. Chem. Soc., Dalton Trans., 2000, 1181–1189
1187

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Fig. 4 L = PPh3 or AsPh3, LЈ = PPh(OEt)2 or P(OEt)3.
Scheme 4 LЈ = PPh(OEt)2 or P(OEt)3; L = PPh3 or AsPh3; R = H or
Me.
IrHCl2[P(OEt)3](PPh3)2 as final products. The formation of
a hydride species by oxidation of a methylhydrazine with
Pb(OAc)4 is rather unexpected, and may be explained on the
basis of the path in Scheme 5, which involves methyldiazene
Scheme 6 L = PPh3, LЈ = PPh(OEt)2 11, 15 (c,f); L = PPh3, LЈ =
P(OEt)3 12 (c–f), 16c; L = AsPh3, LЈ = PPh(OEt)2 13c, 17c; L = AsPh3,
LЈ = P(OEt)3 14 (c–f), 18c; Ar = Ph c or C6H4Me-4 f; Ar–Ar = 4,4Ј-
C6H4–C6H4 c or 4,4Ј-(2-Me)C6H3–C6H3(Me-2) f.
and during the course (0 ЊC) of the reaction. Otherwise, large
amounts of decomposition products or oily substances are
found in the final reaction products.
Scheme 5 [Ir] = IrCl2PL2.
Complexes 11–18 are yellow or orange solids, stable in air
and in solutions of polar organic solvents, where they behave as
1:1 or 2:1 electrolytes.16 The analytical and spectroscopic data
(Table 1) support the proposed formulation. Diagnostic for the
presence of the diazene ligand in both mono- and bi-nuclear
complexes is the high-frequency 1H NMR multiplet of the
NH proton at δ 13.05–12.14, which is split into a doublet
of multiplets in labelled compounds 11c1, 11c2, 15c1. The values
{[Ir]–NH᎐NMe}ϩ A as an intermediate. The methyldiazene
᎐
ligand may be unstable on the iridium centre and decompose,
transferring the hydride hydrogen atom to the metal and liber-
ating the unstable methyldiazonium MeN2ϩ species. This mech-
anism may seem inappropriate, since aryldiazonium cations
are generally inserted into the metal–hydride bond to give
aryldiazine species,1,2 whereas the path in Scheme 5 proposes a
reaction which is the reverse of an insertion. However, in our
case, an aliphatic diazene is involved, the properties of which
are very little known17,18 when compared with those of the
related aryldiazene.1,2 Furthermore, the precedent19 for the
formation of the hydride species ReH(CO)3(PPh3)2 by the reac-
2
for both 1J
and
J
NH, 66 and 4 Hz, respectively, were
15
15NH
also determined1,7,20 and agree with the proposed formulation.
It may also be noted that the spectra of three binuclear
complexes, i.e. 15c, 17c and 18c, show two sets of signals in the
NH region, which are each split into one doublet of multiplets
(15c1), in agreement with the presence of two diazene species.
As the 31P spectra of 15c, 17c and 18c also show two sets of
signals, the existence of two isomers of types II and III (Fig. 4)
may be invoked to explain the data of the three compounds.
Instead, only one isomer with trans-mer geometry, of types I
or II can be proposed for all the other mono- and bi-nuclear
aryldiazene complexes 11–18, except 15c, 17c and 18c. The
31P{1H} NMR spectra show only one AB2 multiplet for the
PPh3 derivatives and a sharp singlet for the AsPh3 ones, whereas
the 1H NMR spectra only show one signal for the diazene NH
proton. Furthermore, the far-IR spectra are consistent with
the presence of two ClϪ ligands in a mutually trans position
showing only one ν(IrCl) band at 342–338 cmϪ1, in agreement
with proposed geometries I and II.
tion of the 1,2-diazene complex [Re(CO) (NH᎐NH)(PPh ) ]ϩ
᎐
3
3 2
with base partly supports the proposed mechanism.
These results on the reactivity of hydrazine complexes of
iridium show that Pb(OAc)4 may be a selective oxidant of the
RNHNH2 molecule, but only in a few cases can the related
diazene complexes be isolated. Except in the phenyl PhNHNH2
species, in fact, the oxidation reactions of all hydrazine and
methylhydrazine complexes always give rise to products which
do not contain the diazene ligand.
Aryldiazene derivatives
The formation of aryldiazene complexes 11c–14c by oxidation
of arylhydrazine derivatives of iridium() prompted us to study
the reaction of hydrides IrHCl2LЈL2 1–4 with aryldiazonium
Lastly, it may be noted that the far-IR spectra of the three
compounds 15c, 17c and 18c show the presence of more than
one ν(IrCl) band (which partly overlap), in agreement with the
existence of a mixture of isomers of types II and III (Fig. 4) for
each compound.
cations, in order to test an alternative synthesis of {[Ir]–ArN᎐
᎐
NH}ϩ derivatives. The results are summarised in Scheme 6.
Both mono- ArN2 and bis- [N2Ar–ArN2]2ϩ aryldiazonium
ϩ
cations react with hydrides 1–4 to give aryldiazene com-
plexes [IrCl (ArN᎐NH)LЈL ]ϩ 11–14 and [{IrCl2LЈL2}2(µ-
᎐
2
2
NH᎐NAr–ArN᎐NH)]2ϩ 15–18, which were isolated as BPh4
᎐
᎐
Conclusions
salts and characterised. Crucial for the successful synthesis of
aryldiazene complexes is an exact stoichiometric ratio between
the reagents and a low temperature at the start (Ϫ80 ЊC)
This contribution reports data on a series of hydrazine
complexes of iridium of the type [IrCl2(RNHNH2)LЈL2]-
1188
J. Chem. Soc., Dalton Trans., 2000, 1181–1189

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6 X. Yan, R. J. Batchelor, F. W. B. Einstein, X. Zhang, R. Nagelkerke
BPh4, which may be prepared using the mixed-ligand hydrides
IrHCl2[PPh(OEt)2]L2 and IrHCl2[P(OEt)3]L2 as precursors.
Hydride–hydrazine derivatives [IrH2(RNHNH2)(PPh3)3]BPh4
and [IrHCl(RNHNH2(PPh3)2]BPh4 were also prepared by an
analogous procedure. Among the properties shown by these
hydrazine complexes is selective oxidation of the arylhydrazine
RNHNH2 ligand, giving the corresponding aryldiazene
and D. Sutton, Inorg. Chem., 1997, 36, 1237 and references therein;
M. Cowie, I. R. McKeer, S. J. Loeb and M. D. Gauthier,
Organometallics, 1986, 5, 860; M. Angoletta and G. Caglio,
J. Organomet. Chem., 1982, 234, 99; K. D. Schramm and J. A. Ibers,
Inorg. Chem., 1980, 19, 2435; A. B. Gilchrist and D. Sutton, J. Chem.
Soc., Dalton Trans., 1977, 677; J. A. Carroll, R. E. Cobbledick,
F. W. B. Einstein, N. Farrell, D. Sutton and P. L. Vogel, Inorg. Chem.,
1977, 16, 2462; M. Cowie, B. L. Haymore and J. A. Ibers, J. Am.
Chem. Soc., 1976, 98, 7608; F. W. B. Einstein and D. Sutton,
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1972, 94, 645; A. J. Deeming and B. L. Shaw, J. Chem. Soc. A, 1969,
1128.
complexes [IrCl (ArN᎐NH)LЈL ]BPh . The same aryldiazene
᎐
2
2
4
species [IrCl (ArN᎐NH)LЈL ]BPh may also be obtained
᎐
2
2
4
through the insertion of an aryldiazonium cation into the
Ir–H bond of hydrides IrHCl2LЈL2. This reaction also allows
the binuclear complexes [{IrCl LЈL } (µ-HN᎐NAr–ArN᎐NH)]-
᎐
᎐
2
2 2
7 G. Albertin, S. Antoniutti and E. Bordignon, J. Chem. Soc., Chem.
Commun., 1984, 1688; G. Albertin, S. Antoniutti, G. Pelizzi, F. Vitali
and E. Bordignon, J. Am. Chem. Soc., 1986, 108, 6627; G. Albertin
and E. Bordignon, J. Chem. Soc., Dalton Trans., 1986, 2551;
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3416; G. Albertin, S. Antoniutti and E. Bordignon, J. Am. Chem.
Soc., 1989, 111, 2072; G. Albertin, S. Antoniutti and E. Bordignon,
J. Chem. Soc., Dalton Trans., 1989, 2553; G. Albertin, P. Amendola,
S. Antoniutti and E. Bordignon, J. Chem. Soc., Dalton Trans., 1990,
2979; G. Albertin, S. Antoniutti, A. Bacchi, E. Bordignon, G. Pelizzi
and P. Ugo, Inorg. Chem., 1996, 35, 6245.
8 G. Albertin, S. Antoniutti, E. Bordignon and S. Pattaro, J. Chem.
Soc., Dalton Trans., 1997, 4445; G. Albertin, S. Antoniutti,
A. Bacchi, E. Bordignon, P. M. Dolcetti and G. Pelizzi, J. Chem.
Soc., Dalton Trans., 1997, 4435; G. Albertin, S. Antoniutti,
A. Bacchi, M. Bergamo, E. Bordignon and G. Pelizzi, Inorg. Chem.,
1998, 37, 479.
(BPh4)2 containing the bis(aryldiazene) bridging ligand to be
prepared.
Acknowledgements
The financial support of the Ministero della Ricerca Scientifica
e Tecnologica, Rome—Programmi di Ricerca Scientifica di
Rilevante Interesse Nazionale, Cofinanziamento 1998/99—
is gratefully acknowledged. We thank Daniela Baldan for
technical assistance.
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