Side-on bound complexes of phenyl- and methyl-diazene

Article abstract of DOI:10.1021/ic2027225

Treatment of trans-[FeCl₂(dmpe)₂] with phenylhydrazine and 1 equiv of base afforded the side-on bound phenylhydrazido complex cis-[Fe(η²-NH₂NPh)(dmpe)₂] ⁺. Further deprotonation of the phenylhydrazido complex afforded the side-on bound phenyldiazene complex cis-[Fe(η²-HN=NPh)(dmpe) ₂] as a mixture of diastereomers. Treatment of cis-[RuCl ₂(dmpe)₂] with phenylhydrazine or methylhydrazine afforded the end-on bound phenylhydrazine or methylhydrazine complexes cis-[RuCl(η¹-NH₂NHR)(dmpe)₂]⁺ (R = Ph, Me). Treatment of the substituted hydrazine complexes with base afforded the side-on bound phenylhydrazido complex cis-[Ru(η²-NH ₂NPh)(dmpe)₂]⁺ as well as the phenyldiazene and methyldiazene complexes cis-[Ru(η²-HN=NR)(dmpe)₂] (R = Ph, Me). cis-[RuCl(η¹-NH₂NHR)(dmpe) ₂]⁺ (R = Ph, Me), cis-[M(η²-NH ₂NPh)(dmpe)₂]⁺ (M = Fe, Ru) and cis-[Ru(η²-HN=NPh)(dmpe)₂] were characterized structurally by X-ray crystallography. cis-[Ru(η²-HN=NPh)(dmpe) ₂] is the first side-on bound phenyldiazene complex to be structurally characterized. In the structure of cis-[Ru(η²-HN= NPh)(dmpe)₂], the geometry of the coordinated diazene fragment is significantly nonplanar (CNNH angle 137°) suggesting that the complex is probably better described as a Ru(II) metallodiaziridine than a Ru(0) diazene π-complex.

Full text of DOI:10.1021/ic2027225

Article
pubs.acs.org/IC
Side-on Bound Complexes of Phenyl- and Methyl-diazene
Leslie D. Field,*,† Hsiu L. Li,† Scott J. Dalgarno,‡ and Ruaraidh D. McIntosh‡
†School of Chemistry, University of New South Wales, NSW 2052, Australia
‡School of EPS-Chemistry, Heriot-Watt University, Edinburgh, Scotland EH14 4AS, United Kingdom
S
* Supporting Information
ABSTRACT: Treatment of trans-[FeCl2(dmpe)2] with phe-
nylhydrazine and 1 equiv of base afforded the side-on bound
phenylhydrazido complex cis-[Fe(η2-NH2NPh)(dmpe)2]+.
Further deprotonation of the phenylhydrazido complex
afforded the side-on bound phenyldiazene complex cis-
[Fe(η2-HNNPh)(dmpe)2] as a mixture of diastereomers.
Treatment of cis-[RuCl2(dmpe)2] with phenylhydrazine or
methylhydrazine afforded the end-on bound phenylhydrazine or methylhydrazine complexes cis-[RuCl(η1-NH2NHR)(dmpe)2]+
(R = Ph, Me). Treatment of the substituted hydrazine complexes with base afforded the side-on bound phenylhydrazido complex
cis-[Ru(η2-NH2NPh)(dmpe)2]+ as well as the phenyldiazene and methyldiazene complexes cis-[Ru(η2-HNNR)(dmpe)2] (R =
Ph, Me). cis-[RuCl(η1-NH2NHR)(dmpe)2]+ (R = Ph, Me), cis-[M(η2-NH2NPh)(dmpe)2]+ (M = Fe, Ru) and cis-[Ru(η2-HN
NPh)(dmpe)2] were characterized structurally by X-ray crystallography. cis-[Ru(η2-HNNPh)(dmpe)2] is the first side-on
bound phenyldiazene complex to be structurally characterized. In the structure of cis-[Ru(η2-HNNPh)(dmpe)2], the geometry
of the coordinated diazene fragment is significantly nonplanar (CNNH angle 137°) suggesting that the complex is probably
better described as a Ru(II) metallodiaziridine than a Ru(0) diazene π-complex.
Although free phenyldiazene or methyldiazene can be
prepared in situ by a number of methods,7 the diazenes are
unstable species which readily decompose to give a range of
products including the corresponding hydrocarbon (benzene or
methane), dinitrogen, hydrazine, mono or disubstituted
hydrazines, and azobenzene (for phenyldiazene).8 Methyldia-
zene is also very oxygen sensitive and has been reported to
react explosively with oxygen at room temperature.9
INTRODUCTION
Recent studies of enzymatic dinitrogen reduction by nitro-
genase support an alternating pathway where N2Hx species
■
−
such as hydrazine (N2H4), hydrazide (N2H3 ), and diazene
(N2H2) are vital intermediates for reaction at iron of the active
site.1 In particular, the binding modes and the reactions by
which these species are interconverted are of interest because
they may provide a greater understanding of the mode of action
of nitrogenases. Given the general instability and reactive
nature of coordinated diazene, hydrazide, and hydrazine, we
have examined in this paper the synthesis and chemistry of
phenyl- and methyl-substituted N2HxR complexes as potentially
useful models for studying the potential diazene intermediates
in nitrogen fixation in either biological or synthetic systems.2
We previously reported the synthesis of the first side-on
bound diazene complex cis-[Fe(η2-NHNH)(dmpe)2] (dmpe
= 1,2-bis(dimethylphosphino)ethane) from the side-on bound
hydrazine complex cis-[Fe(η2-N2H4)(dmpe)2]2+ either by
reduction with potassium graphite3 or by deprotonation with
a strong base.4 The deprotonation route was also used to
synthesize the analogous Ru diazene complexes.5 The diazene
complexes, and in particular the Fe complex, are thermally
unstable, extremely air sensitive and fragile; they decompose
readily under most laboratory reaction conditions. However,
the diphenyldiazene (azobenzene) complex cis-[Fe(η2-NPh
NPh)(dmpe)2],6 is stable, and we initially targeted a synthesis
of side-on bound phenyldiazene and methyldiazene complexes
where an NH functionality remains (allowing for further
reaction) while the phenyl or methyl substituent potentially
confers some degree of stability to the resulting diazene
complexes.
Complexation to transition metals greatly increases the
stability of substituted diazenes, and there are now a number of
synthetic approaches to metal diazene complexes as well as a
number of different binding modes. The first reported route to
aryldiazene complexes was by insertion of an aryldiazonium
cation into a metal-hydride bond10 where the resulting
aryldiazene ligand is bound end-on, with a bent geometry
and with a proton on the metal-coordinated nitrogen atom
(Figure 1). Protonation at the coordinated nitrogen of
aryldiazenido complexes also afforded aryldiazene complexes.11
In a related method, the reaction of an aryldiazonium salt with a
platinum side-on bound phenylacetylene complex afforded the
bent, end-on bound aryldiazene complex containing an end-on
bound phenylacetylide ligand.12 In one example on rhenium,
protonation occurs on the noncoordinating nitrogen atom to
give the isomeric linear phenyldiazene complex.13 For several
examples of aryldiazenes on iridium, spontaneous hydro-
genation of aryldiazenido ligands can also occur via ortho-
metalation of the aryl ring.14 Aryl- and methyl-diazene
complexes have also been formed by the selective oxidation
Received: December 19, 2011
Published: March 6, 2012
© 2012 American Chemical Society
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Figure 2. ORTEP plot of cis-[Fe(η2-NH2NPh)(dmpe)2]+Cl− (1, 50%
displacement ellipsoids, chloride counterion, thf solvate, and carbon-
bound hydrogen atoms have been excluded for clarity). Selected bond
lengths (Å) and angles (deg): Fe1−N1 1.939(4), Fe1−N2 1.998(4),
N1−C13 1.352(6), N1−N2 1.400(5), N1−Fe1−N2 41.63(16), C13−
N1−N2 121.8(4), C13−N1−Fe1 161.4(4), N2−N1−Fe1 71.4(2).
Figure 1. Binding modes of aryl and alkyl substituted diazene
complexes.
bond in the azobenzene complex (1.391(3) Å). The phenyl
ring is nearly coplanar with the M−N−N plane as is also
observed for the bridging phenylhydrazido ligand in [(LFe)2(μ-
S)(μ-NH2NPh)] (L = (HC(CMeN(2,6-diisopropylphen-
yl))2)−)19 and side-on phenylhydrazido ligands in [Ti(Cp)-
Cl2(η2-NH2NPh)],20 [Ti(L′)Cl2(η2-NH2NPh)] (L′ = tris-
(pyrazolyl)borate),21 and [Zr(Cp*)2(OH)(η2-NH2NPh)]22
of the corresponding hydrazine complexes with Pb(OAc)4.15
Bridging phenyl- and methyldiazene complexes have also been
reported with both bent and linear (isodiazene) forms16 as well
as a simultaneously bridging and side-on phenyldiazene
complex of vanadium (Figure 1).17
There is only one report of a η2-HNNPh ligand on Co18
(although no crystal structure of the complex was reported)
and none reported for HNNMe.
23
although unlike that in [W(Cp)2(η2-NH2NPh)]+ where the
phenyl ring is bent out of the M−N−N plane. The coplanarity
of the phenyl group with the M−N−N plane as well as the
short N−C bond are consistent with sp2 hybridization of the
NPh nitrogen and partial delocalization of the nitrogen lone
pair through the π-system of the phenyl ring.
RESULTS AND DISCUSSION
■
Iron Phenylhydrazido(1-) and Phenyldiazene Com-
plexes. Addition of 1 equiv of strong base (KOtBu) to an
emerald green solution of trans-[FeCl2(dmpe)2] and phenyl-
hydrazine in tetrahydrofuran (thf) afforded red crystals of the
phenylhydrazido(1-) complex cis-[Fe(η2-NH2NPh)-
(dmpe)2]+Cl− (1) (Scheme 1), and these were characterized
by X-ray crystallography (Figure 2).
NMR data for cis-[Fe(η2-NH2NPh)(dmpe)2]+ (1) is entirely
consistent with the structure depicted in Figure 2. Four ddd
signals were observed in the 31P{1H} NMR spectrum,
characteristic of an octahedral complex containing two
bidentate dmpe ligands and two additional nonidentical ligands
in the remaining cis coordination sites. In the two-dimensional
1H-15N HSQC (Heteronuclear Single Quantum Coherence)
experiment, the two NH proton resonances at δ 5.46 and 3.80
correlate with a single 15N signal at δ −366.6 confirming that
both protons reside on the same nitrogen atom (NH2). A 15N
signal at δ −299.0 for NPh is observed when the ligand is 15N2-
labeled.
Scheme 1
Phenylhydrazido complex 1 could also be isolated as the
tetraphenylborate salt by counterion exchange in ethanol.
Treatment of the tetraphenylborate salt of 1 with KOtBu
afforded the side-on bound phenyldiazene complex cis-[Fe(η2-
HNNPh)(dmpe)2] (2) as the major product (Scheme 1).
Small amounts of byproducts including [Fe(N2)(dmpe)2]24
and [{Fe(dmpe)2}2(μ-dmpe)]6 are also formed, presumably
because of decomposition of the phenyldiazene complex.
The 31P{1H} NMR spectrum of cis-[Fe(η2-HNNPh)-
(dmpe)2] (2) is broad at room temperature but sharpens up at
low temperature showing two sets of resonances in a ratio of
approximately 2:1 (Figure 3) due to the presence of a pair of
diastereomers. Each diastereomer has an associated enantiomer,
and the four possible stereoisomers arise from the diazene
coordination to the metal with either face and the helical twist
that can be adopted by the bidentate dmpe ligands (Figure 4).
The phenylhydrazine is deprotonated only at NPh to give a
phenylhydrazido ligand which is coordinated side-on. The Fe−
NPh bond (1.939(4) Å) is shorter than the Fe−NH2 bond
(1.998(4) Å) and Fe−N bonds in side-on bound hydrazine cis-
[Fe(η2-N2H4)(dmpe)2]2+, diazene cis-[Fe(η2-NHNH)-
(dmpe)2], and azobenzene cis-[Fe(η2-NPhNPh)(dmpe)2]
complexes (1.981(2)−2.032(7) Å)3 as well as the Fe−NPh
bond in [(LFe)2(μ-S)(μ-NH2NPh)] (L = (HC(CMeN(2,6-
diisopropylphenyl))2)−)19 (1.990(4) Å). The relatively short
Fe−N bond probably arises from the nitrogen having a high
electron density (formal negative charge) leading to a strong
bond to the iron center. The geometry about the NPh nitrogen
is almost planar (sum of angles about N1 is 354.6°) and the
N−C bond (1.352(6) Å) is also shorter than the corresponding
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back-bonding from the metal to the diazene ligand causing a
large upfield shift of the signals.
An analogous reaction between trans-[FeCl2(dmpe)2] and
methylhydrazine in the presence of KOtBu did not give any
isolable complexes. In an attempt to access stable examples of
hydrazine and diazene complexes we further investigated
approaches to the synthesis of analogous ruthenium complexes.
Ruthenium Phenylhydrazine, Phenylhydrazido(1-),
and Phenyldiazene Complexes. Treatment of cis-
[RuCl2(dmpe)2] with excess phenylhydrazine in thf resulted
in the substitution of one chloride ligand with phenylhydrazine
to afford the phenylhydrazine complex cis-[RuCl(η1-
NH2NHPh)(dmpe)2]+ (3) as the chloride salt (Scheme 2).
The complex was isolated as the tetraphenylborate salt by anion
exchange with NaBPh4 in methanol. The four signals in the
31P{1H} NMR spectrum are characteristic of an octahedral
complex containing two bidentate dmpe ligands and two
additional nonidentical ligands in the remaining cis coordina-
tion sites. The large 298 Hz coupling between PC and PD
indicate that these two atoms are trans to each other in the
Figure 3. 31P{1H} NMR spectra of cis-[Fe(η2-HNNPh)(dmpe)2]
(2, toluene-d8, 243 MHz, * = [Fe(N2)(dmpe)2]; # = [{Fe-
(dmpe)2}2(μ-dmpe)]).
1
1
coordination sphere. In the H-15N HSQC experiment, the H
signal at δ 7.54 correlates to a 15N signal at δ −287.3 for NHPh
while the 1H signals at δ 5.16 and 4.55 correlate to a single 15
N
signal at δ −356.0 for the NH2 group. The coordination mode
of the phenylhydrazine ligand could not be determined
conclusively by NMR as all the NH protons exhibit only
weak coupling to P and while there are Nuclear Overhauser
Effect (NOE; through space) interactions with various CH3
protons, these could not be used to conclusively establish the
binding mode of the ligand.
Slow evaporation of a thf-d8 solution of 3 afforded colorless
crystals suitable for X-ray crystallographic analysis (Figure 5).
Figure 4. Diastereomers and enantiomers of [M(η2-HNNPh)-
(dmpe)] (M = Fe 2, Ru 5).
The observed dynamic behavior which interchanges the 31P
nuclei could result from face-to-face flip of the diazene on the
metal or a twist of the coordinated phosphine backbone or a
combination of the two.
1
A H-15N HSQC experiment at 200 K identified the 15N
resonances for the NH groups at δ −327.1 (major) and −324.5
(minor) correlating to 1H signals at δ 2.11 and 1.71,
respectively. Two 15N signals at δ −246.3 (minor) and
−254.3 (major) (200 K) for the 15N resonances for the NPh
−
Figure 5. ORTEP plot of cis-[RuCl(η1-NH2NHPh)(dmpe)2]+BPh4
(3, 50% displacement ellipsoids, BPh4 counterion, atoms of less than
50% occupancy and carbon bound hydrogen atoms have been
excluded for clarity). Selected bond lengths (Å) and angles (deg):
Ru1−N1 2.2504(19), N1−N2 1.436(3), N2−C25 1.412(3), N2−N1−
Ru1 117.17(13), C25−N2−N1 117.13(18).
1
groups are observed for the 15N-labeled analogue. The H and
15N chemical shifts for the side-on bound diazenes contrast to
literature data for end-on bound and bridging diazene
complexes,10,11,25,26 and this can be attributed to the significant
Scheme 2
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The phenylhydrazine is bound to Ru in an end-on fashion
through the NH2 group, and this binding mode is the most
common for phenylhydrazine.27,28 The phenylhydrazine ligand
is bent and the proton on the terminal nitrogen is relatively
close to protons on the dmpe methyl groups thus accounting
for the NOE interactions observed.
indicates a more sp3-like geometry for NPh with little or no
delocalization of the nitrogen lone pair into the phenyl ring.
The Ru−NPh bond (2.155(3) Å) is significantly longer than
the Ru−NH2 bond (2.126(3) Å) unlike all other reported
phenylhydrazide complexes where in general the M−NPh
bonds are shorter than the M−NH2 bonds. The N−N bond
length of 1.435(4) Å is almost the same length as that for the
phenylhydrazine complex 3 (1.436(3) Å) and is typical for an
N−N single bond.
Treatment of phenylhydrazine complex 3 or phenylhydrazide
complex 4 with excess base afforded the side-on bound
phenyldiazene complex cis-[Ru(η2-HNNPh)(dmpe)2] (5)
(Scheme 2), and crystals of 5 suitable for X-ray crystallography
were grown by layering a solution of 5 in benzene-d6 with
pentane (Figure 7). The phenyldiazene ligand is bound side-on
Treatment of the chloride salt of phenylhydrazine complex 3
with 1 equiv of KOtBu base in thf afforded a mixture of
unreacted starting material, the phenylhydrazide complex cis-
[RuCl(η2-PhNNH2)(dmpe)2]+Cl− (4), and the phenyldiazene
complex cis-[RuCl(η2-PhNNH)(dmpe)2] (5) as well as cis-
[RuCl2(dmpe)2] and free phenylhydrazine (probably because
of disassociation of phenylhydrazine from the starting material).
However, similar treatment of the tetraphenylborate salt of 3
with 1 equiv of base allowed the isolation of the singly
deprotonated phenylhydrazide complex cis-[RuCl(η2-
NH2NPh)(dmpe)2]+BPh4 (4). The signals in the 31P{1H}
−
NMR spectrum are heavily overlapped; however, the eight
1
singlets in the H{31P} NMR spectrum (for the dmpe methyl
protons) are characteristic of an octahedrally coordinated
complex containing two bidentate dmpe ligands and two
additional nonidentical ligands in the remaining cis coordina-
1
tion sites. In a H-15N HSQC experiment at 200 K, both NH
proton signals at δ 5.25 and 4.37 correlate to a single 15N signal
at δ −365.6 indicating that both protons are located on the
same nitrogen atom. The 15N signal at δ −287.0 (a doublet
with 20 Hz coupling to P) for NPh was observed on 15N
labeling, and this chemical shift is consistent with that observed
for the analogous iron complex 1 (δ −299.1).
Crystals of the ruthenium phenylhydrazide complex 4
suitable for X-ray diffraction analysis were grown by layering
a thf solution of the 15N-labeled complex with diethyl ether
(Figure 6). As for the analogous iron phenylhydrazide complex
Figure 7. ORTEP plot of cis-[RuCl(η2-HNNPh)(dmpe)2] (5, 50%
displacement ellipsoids, carbon bound hydrogen atoms have been
excluded for clarity). Selected bond lengths (Å) and angles (deg):
Ru1−N2 2.1238(16), Ru1−N1 2.1477(16), N1−N2 1.425(2), N2−
C13 1.383(2), N2−Ru1−N1 38.96(6), N2−N1−Ru1 69.61(9), C13−
N2−N1 114.74(15), C13−N2−Ru1 126.37(13), N1−N2−Ru1
71.42(9).
to Ru with an acute N2−Ru1−N1 angle of 38.96(6)°. The Ru−
N distances of 2.1238(16) and 2.1477(16) Å are longer than
the Ru−N distances of previously reported ruthenium η1-
aryldiazene complexes (2.080(11)−2.12(1) Å)25 although
within the range of Ru−N distances for the parent Ru η2-
diazene complexes [Ru(η2-NHNH)(PP)2] (PP = dmpe,
depe) (2.123(4)−2.1589(15) Å).5 The N−N distance of
1.425(2) Å is significantly longer than those reported for
end-on (including several iridium ortho-metalated aryldiazene
complexes),12−14,26 end-on bridging (μ-η1:η1)16 or side-on
bridging (μ-η2:η2)17 aryldiazene complexes (1.13(2)−1.373(5)
Å) although completely within the range of N−N distances for
the parent Ru η2-diazene complexes (1.414(5)−1.427(3) Å)
and slightly shorter than that for the phenylhydrazide complex
4 (1.435(4) Å). The long N−N bond is entirely consistent with
back-bonding from the filled d-orbitals of ruthenium to the
antibonding π* orbitals of the phenyldiazene ligand. Complex 5
is the first side-on bound phenyldiazene complex to be
structurally characterized.
−
Figure 6. ORTEP plot of cis-[Ru(η2-NH215NPh)(dmpe)2]+BPh4 (4,
50% displacement ellipsoids, BPh4 counterion and carbon bound
hydrogen atoms have been excluded for clarity). Selected bond lengths
(Å) and angles (deg): Ru1−N2 2.126(3), Ru1−N1 2.155(3), N1−C1
1.383(5), N1−N2 1.435(4), N2−Ru1−N1 39.16(11), C1−N1−N2
114.6(3), C1−N1−Ru1 129.0(2), N2−N1−Ru1 69.32(16), N1−N2−
Ru1 71.52(15).
1, the phenylhydrazide ligand is coordinated side-on and
deprotonated at NPh only. However, the phenyl ring is
distinctly bent out of the M−N−N plane compared with the
coplanar nature of the phenyl ring of the iron complex 1 and
other reported phenylhydrazido complexes.19−22 The out-of-
plane phenyl ring resembles that reported for [W(Cp)2(η2-
NH2NPh)]+,23 and the sum of angles about N1 (312.92°)
To date, there have been five side-on bound metal diazenes
that have been structurally characterized (Table 1). There is
always debate as to whether the metal diazenes are best
represented as π complexes of Mn or as metallodiaziridines
(metallo diazocyclopropanes) which would be Mn+2 hydrazides
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Table 1. NN Bond Lengths (Å) and RNNR (R = H, C) Dihedral Angles (deg) in Side-on Bound Metal Diazene Complexes
complex
N−N bond length (Å)
RNNR (R = H, C) dihedral angle (deg)
reference
3
cis-Fe(NHNH)(dmpe)2
1.427(7)
156(5)
149(5)
113.9(2)
162(2)
168(4)
137.2(2)
180
1.398(8)
cis-Fe(PhNNPh)(dmpe)2
cis-Ru(NHNH)(dmpe)2
cis-Ru(NHNH)(depe)2
cis-Ru(PhNNH)(dmpe)2
trans-NHNH
1.412(4)
3
1.427(3)
5
1.414(5)
5
1.425(2)
this work
1.247, 1.266, 1.28
1.173−1.259
34
35
trans-PhNNPh
180
(ML4N2H22−).29 Table 1 indicates that, in all cases, the N−N
bond is longer when diazene is complexed than it is in free
diazene. In cis-[Ru(PhNNH)(dmpe)2],(5), the torsional
angle C−N−N−H (137.2(2)°) deviates very significantly
from planarity suggesting that 5 should be viewed as more
like a metallodiaziridine than a π complex. However, in the
parent iron and ruthenium diazene complexes (Fe(NH
NH)(dmpe)2 and Ru(NHNH)(dmpe)2), the torsion angles
are closer to 180°3,5 (Table 1) suggesting that these are better
regarded as M(0)-π complexes. Theoretical calculations on
4
Fe(NHNH)(dmpe)2 were consistent with a π bonded
diazene, analogous to the π-bonding of alkenes to transition
metals and with little charge localization on the nitrogen atoms.
The coordination and bonding in metal π complexes has
been well-studied in alkene complexes, where the out of plane
distortions of the substituents on the coordinated alkene is a
measure of the metallocyclopropane character of an alkene
complex.30 The HCH angle in cyclopropane has been reported
to be 114.4° in liquid crystalline solution31 and 115.1 1° by
gas phase electron diffraction.32 The corresponding HCH angle
in aziridine is 115.72(1)°.33
It is likely that, as more side-on-bound complexes of diazene
and substituted diazenes are characterized, there will be a
continuum of structures ranging from those where the HNNH
torsional angle is closer to 180° (where the N atoms are
effectively sp2 hybridized) to those where the torsional angle
approaches the tetrahedral angle and the complexes are better
described as metallodiaziridines.
Figure 8. 31P{1H} NMR spectra of cis-[Ru(η2-HNNPh)(dmpe)2]
(5, toluene-d8, 243 MHz).
shift is consistent with the shifts reported for cis-[Fe(η2-NPh
NPh)(dmpe)2] (2, δ −246.3 and −254.3 for the minor and
major diastereomers respectively). The NPh 15N resonance
exhibits a 14 Hz coupling to 31P and in the 31P{1H} NMR
spectrum, PA exhibits the reciprocal coupling to 15N indicating
that PA is the signal for the phosphorus atom trans to NPh.
Ruthenium Methylhydrazine and Methyldiazene
Complexes. Treatment of cis-[RuCl2(dmpe)2] with excess
methylhydrazine in a mixture of thf and methanol afforded the
methylhydrazine complex cis-[RuCl(η1-NH2NHMe)(dmpe)2]+
(6) as the chloride salt (Scheme 2). Crystals suitable for X-ray
crystallography were obtained by layering the reaction mixture
with diethyl ether, and only one of the two independent
molecules in the unit cell is shown (Figure 9). The
methylhydrazine ligand is bound end-on to Ru through the
NH2 group, and this binding mode is the most common for
methylhydrazine.19,28,36
In the 1H{31P} NMR spectrum of phenyldiazene complex 5,
the eight singlets for the dmpe methyl groups are characteristic
of an octahedrally coordinated complex containing two
bidentate dmpe ligands and two additional nonidentical ligands
in the remaining cis coordination sites. In the 31P{1H} NMR
spectrum, three multiplets in the relative ratio 1:2:1 were
observed where the signals for PB and PC appear as a broad
multiplet at δ 38.7 (Figure 8). On lowering the temperature,
individual signals for PB and PC separate out and these signals
exhibit large 335 Hz couplings indicating that they are due to P
atoms trans to each other in the coordination sphere. In the
case of the Ru complex 5, only one diastereomer is observed at
low temperature unlike the iron complex 2 where two
diastereomers were observed. Again, the observed dynamic
behavior where the 31P nuclei are interchanged at higher
temperatures reflects fluxionality in the complex and could
result from face-to-face flip of the diazene on the metal or a
twist of the coordinated phosphine backbone or a combination
of the two.
The methylhydrazine complex 6 was isolated as the
tetraphenylborate salt by anion exchange with NaBPh4 in
methanol. In the 31P{1H} NMR spectrum, the four ddd signals
as well as the large coupling between PC and PD of 298 Hz are
similar to those for the phenylhydrazine complex 3. In the
1
1H-15N HSQC experiment, the H signal at 4.29 ppm, which
integrates to two protons, correlates to a 15N signal at −335.6
1
ppm for NH2 while the H signal at 4.04 ppm correlates to a
15N signal at −308.2 ppm for the NHMe group.
Attempted monodeprotonation of the methylhydrazine
complex 6 with 1 equiv of KOtBu afforded a complex mixture
of products. Treatment with excess KOtBu base, however,
afforded the side-on bound methyldiazene complex cis-
[RuCl(η2-HNNMe)(dmpe)2] (7) as the major product
and a small amount of [RuH2(dmpe)2]6 byproduct (Scheme
2). The 31P{1H} NMR spectrum contains multiplets that are
overlapping and severely distorted by second order effects. In
A low temperature (193 K) 1H-15N HSQC experiment for 5
showed a correlation between the NH proton resonance at δ
2.62 and a 15N signal at δ −324.4. The 15N signal for NPh
resonates at δ −251.5 for the 15N-labeled analogue, and this
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hydrazide and diazene complexes by stepwise deprotonation of
the parent hydrazine complexes. The phenyl- and methyl-
diazene complexes are the first known side-on bound
complexes of substituted diazenes. The complexes have been
thoroughly characterized by NMR spectroscopy (1H, 31P, and
15N) and by X-ray crystallography. Both iron and ruthenium
phenyldiazene complexes exhibit fluxional behavior consistent
with a facile twist of the diphosphines or face-to-face flip of the
coordinated diazenes. The ruthenium methyldiazene complex is
thermally unstable and decomposes in benzene-d6 to afford the
phenyl deuteride complex.
Now that there are several side-on bound diazenes that have
been structurally characterized, it is apparent that the structure
of the coordinated diazene can range from near planar to
significantly non-planar. The planar structure would be
expected for a complex where Fe(0) or Ru(0) is coordinated
to the π-system of a diazene where the nitrogens are effectively
sp2 hybridized and the nitrogen−nitrogen bond is effectively a
double bond. The structure where the diazene fragment is a
nonplanar structure would be anticipated for a complex where
Fe(II) or Ru(II) is coordinated to a diazide (RNNR)2‑ where
the nitrogens are effectively sp3 hybridized, and the structure is
better regarded as a metallodiaziridine.
Figure 9. ORTEP plot of cis-[RuCl(η1-NH2NHMe)(dmpe)2]+Cl− (6,
50% displacement ellipsoids, Cl counterion, carbon bound hydrogen
atoms have been excluded for clarity). Selected bond lengths (Å) and
angles (deg): Ru1−N1 2.1965(18), N1−N2 1.458(3), N2−C13
1.468(3), N2−N1−Ru1 119.57(14), N1−N2−C13 109.74(19).
1
the H{31P} NMR spectrum, there are seven resolved singlets
(including one which has twice the intensity of the others) for
1
the dmpe methyl groups. Of note in the H NMR spectrum is
the NMe resonance at δ 3.22 which exhibits a small coupling to
EXPERIMENTAL SECTION
■
P implying that the NMe group is coordinated to the metal
All manipulations of metal complexes and air-sensitive reagents were
carried out using standard Schlenk techniques or in nitrogen or argon
filled glove boxes. Solvents were dried and distilled under nitrogen or
argon from sodium/benzophenone (benzene, hexane), sodium
(heptane), diethoxymagnesium (ethanol), and dimethoxymagnesium
(methanol). Tetrahydrofuran (inhibitor free), diethyl ether, toluene,
and pentane were dried and deoxygenated using a Pure-Solv 400-4-
MD (Innovative Technology) solvent purification system. Deuterated
solvents were purchased from Cambridge Isotope Laboratories.
Tetrahydrofuran-d8, toluene-d8, and benzene-d6 were dried over and
distilled from sodium/benzophenone. Dichloromethane-d2 was dried
over, distilled from, and stored over activated molecular sieves.
Phenylhydrazine was purchased from Aldrich, distilled under vacuum,
and stored over activated molecular sieves under nitrogen.
Methylhydrazine was purchased from Aldrich, dried over barium
oxide, vacuum distilled, and stored over activated molecular sieves
under nitrogen. Potassium t-butoxide was sublimed twice and stored
under nitrogen or argon. trans-[FeCl2(dmpe)2] was prepared
according to the literature method.38 cis-[RuCl2(dmpe)2] was prepared
1
1
center. In the H-15N HSQC experiment at 193 K, the H
resonance at δ 3.9 correlates with a 15N signal at δ −289.5 for
NH (Figure 10a). Whereas in the H-15N HMBC (Hetero-
1
1
nuclear Multiple Bond Correlation) experiment, the NMe H
resonance correlates to two 15N signals at δ −286.7 and −277.3
ppm for NH and NMe respectively (Figure 10b). The
methyldiazene complex 7 is unstable in solution and
decomposes over several days in benzene-d6 to afford the
solvent activated complex [RuD(Ph-d5)(dmpe)2]37 (31P{1H} δ
45.8, 39.9, 33.2, 27.1) as the major product with concomitant
release of methane (1H δ 0.15, 13C δ −4.2 in benzene-d6) and
other unidentified products.
CONCLUSIONS
■
We have reported synthetic approaches to a series of side-on
bound iron and ruthenium phenyl and methyl-substituted
Figure 10. (a) 1H-15N HSQC spectrum (toluene-d8, 193 K, 400 and 41 MHz) (b) 1H-15N HMBC spectrum (thf-d8, 298 K, 500 and 51 MHz) of cis-
[RuCl(η2-HNNMe)(dmpe)2] (7).
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Table 2. Crystallographic Details for cis-[Fe(η2-NH2NPh)(dmpe)2]+Cl− (1), cis-[RuCl(η1-NH2NHPh)(dmpe)2]+BPh4 (3), cis-
−
−
[Ru(η2-NH215NPh)(dmpe)2]+BPh4 (4), cis-[Ru(η2-HNNPh)(dmpe)2] (5), and cis-[RuCl(η1-NH2NHMe)(dmpe)2]+Cl− (6)
1
3
4
5
6
formula
M (g mol−1
C22H47ClFeN2OP4
570.80
C46H78BClN2OP4Ru
946.31
C42H59BN2P4Ru
827.67
C18H38N2P4Ru
507.45
C26H76Cl4N4P8Ru2
1036.61
)
crystal morphology
size (mm3)
crystal system
space group
a (Å)
red plate
0.24 × 0.20 × 0.08
monoclinic
P21/c
colorless block
0.40 × 0.30 × 0.25
monoclinic
C2/c
yellow block
0.40 × 0.25 × 0.20
monoclinic
P21
yellow block
0.40 × 0.30 × 0.30
monoclinic
P21/c
colorless block
0.20 × 0.20 × 0.15
orthorhombic
P212121
17.260(2)
13.4299(16)
12.5230(14)
106.257(7)
2786.7(6)
4
39.212(3)
9.8714(7)
24.3607(17)
108.174(3)
8959.2(11)
8
10.0354(13)
16.150(2)
13.1828(19)
102.261(7)
2087.8(5)
2
14.5109(8)
8.6862(4)
18.9423(10)
102.279(2)
2333.0(2)
4
13.5246(6)
13.7540(6)
24.5580(11)
90.00
b (Å)
c (Å)
β (deg)
V (Å3)
4568.2(4)
4
Z
Dc (g/cm3)
1.360
1.403
1.317
1.445
1.507
μ (mm−1
)
0.884
0.591
0.560
0.952
1.199
F000
1216
4016
868
1056
2144
2θmax (deg)
58.1
51.4
54.7
52.7
54.4
reflections collected
independent reflections
observed reflections
final GOF
7171
57171
20297
17917
68743
7173 (Rint = 0.0464)
4115 [I > 2σ(I)]
1.010
8489 (Rint = 0.0398)
7337 [I > 2σ(I)]
1.049
9633 (Rint = 0.0401)
8610 [I > 2σ(I)]
1.052
4752 (Rint = 0.0261)
4329 [I > 2σ(I)]
1.019
9989 (Rint = 0.0348)
9326 [I > 2σ(I)]
1.029
R1
0.0714
0.0335
0.0444
0.0228
0.0226
wR2
0.1100
0.0770
0.0857
0.0522
0.0452
by heating a mixture of [{Ru(PMe2Ph)3}2(μ-Cl)3]+Cl− and dmpe at
200 °C and subsequent Soxhlet extraction with toluene.39 Phenyl-
hydrazine-15N2 was prepared by diazotization of aniline-15N with
sodium nitrite-15N and subsequent reduction with sodium sulfite.40
Ph15NNH2 was prepared in a similar manner with aniline-15N and
unlabeled sodium nitrite.
CH3), 1.58−1.40 (m, 2H, CH2), 1.27 (m, 3H, CH3), 1.25−1.11
(m, 9H, CH3), 0.92 (s, 3H, CH3). 1H{31P} NMR (CD2Cl2, 400
MHz): δ 6.97 (m, 2H, Ph), 6.70 (m, 2H, Ph), 6.44 (m, 1H,
Ph), 5.46 (br, 1H, NHH), 3.80 (br, 1H, NHH), 2.17−1.89 (m,
2H, CH2), 1.82 (m, 6H, CH3 and CH2), 1.75 (m, 4H, CH3 and
CH2), 1.63 (s, 3H, CH3), 1.58−1.40 (m, 2H, CH2), 1.27 (s, 3H,
CH3), 1.23 (s, 3H, CH3), 1.21 (s, 3H, CH3), 1.20 (s, 3H, CH3),
0.92 (s, 3H, CH3). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 65.6
(ddd, 2JAB 6.5 Hz, 2JAC 24.6 Hz, 2JAD 43.8 Hz, 1P, PA), 63.6 (ddd,
Air-sensitive NMR samples were prepared in argon or nitrogen
filled glove boxes or on a high vacuum line by vacuum transfer of
1
solvent into an NMR tube fitted with a concentric Teflon valve. H,
31P, and 15N NMR spectra were recorded on Bruker Avance III 600,
500, 400 or DPX300 NMR spectrometers at 298 K unless otherwise
stated. 1H NMR spectra were referenced to residual solvent resonances
while 31P spectra were referenced to external neat trimethyl phosphite
at δ 140.85 ppm. 15N NMR spectra were referenced to external neat
nitromethane at δ 0.0 ppm. Simulation of 31P spectra for cis-
unsymmetrical complexes were performed iteratively using the
simulation program NUMMRIT (SpinWorks 3), and the signs for
coupling constants are not implied. Infrared spectra were recorded on
a Nicolet Avatar 360 FTIR spectrometer as nujol mulls. Mass
spectrometric analysis for this work was carried out at the Bioanalytical
Mass Spectrometry Facility, UNSW. Microanalyses were carried out at
the Campbell Microanalytical Laboratory, University of Otago, New
Zealand, or on a Thermo Finnigan EA 1112 Series Flash Elemental
Analyzer at the Central Science Laboratory, University of Tasmania. X-
ray crystallography data were collected on a Bruker Nonius X8 Apex II
CCD diffractometer operating with MoKα radiation (λ = 0.71073) at a
temperature of 100(2) K. Crystallographic details are summarized in
Table 2.
2JBC 46.9 Hz, JBD 42.5 Hz, 1P, PB), 61.0 (ddd, JCD 151.2 Hz,
2
2
1P, PC), 60.4 (ddd, 1P, PD). 15N{1H} NMR (CD2Cl2, 41 MHz,
1
from HN-HSQC): δ −366.6 (corr with H δ 5.46 and 3.80,
NH2).
The 15N2-labeled analogue was prepared in a similar manner using
phenylhydrazine-15N2. 1H NMR (CD2Cl2, 400 MHz): 5.46 (br d, 1JHN
1
86 Hz, 1H, NHH), 3.80 (br d, JHN 79 Hz, 1H, NHH). 15N NMR
(CD2Cl2, 41 MHz): δ −299.0 (m, NPh), −366.8 (m, NH2).
The 15N-labeled analogue was prepared in a similar manner using
Ph15NNH2.
X = BPh4. Potassium t-butoxide (82 mg, 0.73 mmol) was added to a
solution of trans-[FeCl2(dmpe)2] (0.302 g, 0.707 mmol) and
phenylhydrazine (0.121 g, 1.12 mmol) in thf (4 mL) under nitrogen.
The resulting dark red solution was left to stand overnight in which
time a dark red crystalline solid precipitated. The solid cis-[Fe(η2-
NH2NPh)(dmpe)2]+Cl− was collected by filtration, washed with thf,
and dried in vacuo. The chloride salt was extracted with ethanol (3
mL, 3 × 1 mL), filtered through Celite then added to a solution of
sodium tetraphenylborate (0.250 g, 0.731 mmol) in ethanol (4 mL).
The resulting orange-red precipitate was collected by filtration, washed
with ethanol (3 × 1 mL) and methanol (3 × 1 mL), then dried under
vacuum (0.384 g, 0.491 mmol, 69% yield). C42H59BFeN2P4 (782.57)
cis-[Fe(η2-NH2NPh)(dmpe)2]+X− (1). X = Cl. Potassium t-
butoxide (36 mg, 0.32 mmol) was added to an emerald green
solution of trans-[FeCl2(dmpe)2] (0.118 g, 0.276 mmol) and
phenylhydrazine (0.130 g, 1.20 mmol) in thf (2 mL) under
nitrogen. The resulting dark orange-red solution was left to
stand overnight in which time a red crystalline solid
precipitated. The solid was collected by filtration, washed
1
requires C, 64.5; H, 7.6; N, 3.6; found, C, 64.2; H, 7.8; N, 3.2%. H
NMR (thf-d8, 300 MHz): δ 7.29 (m, 8H, o-PhB), 6.99−6.80 (m, 10H,
m-Ph and m-PhB), 6.72 (m, 4H, p-PhB), 6.54 (m, 2H, o-Ph), 6.40 (m,
1H, p-Ph), 3.80 (br s, 1H, NHH), 3.05 (br s, 1H, NHH), 2.07−1.70
1
2
with thf (4 mL), and dried in vacuo (0.125 g, 91% yield). H
(m, 5H, CH2), 1.67 (d, JHP 8 Hz, 3H, CH3), 1.64−1.46 (m, 3H,
NMR (CD2Cl2, 400 MHz): δ 6.97 (m, 2H, m-Ph), 6.70 (m,
2H, o-Ph), 6.44 (m, 1H, p-Ph), 5.46 (br, 1H, NHH), 3.80 (br,
1H, NHH), 2.17−1.89 (m, 2H, CH2), 1.88−1.78 (m, 6H, CH3
and CH2), 1.78−1.68 (m, 4H, CH3 and CH2), 1.63 (s, 3H,
CH2), 1.46−1.35 (m, 6H, CH3), 1.21−1.09 (m, 9H, CH3), 1.06 (m,
1
3H, CH3), 0.79 (m, 3H, CH3). H{31P} NMR (thf-d8, 300 MHz): δ
7.29 (m, 8H, o-PhB), 6.98−6.82 (m, 10H, m-Ph and m-PhB), 6.72
(m, 4H, p-PhB), 6.54 (m, 2H, o-Ph), 6.41 (m, 1H, p-Ph), 3.79 (br s,
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1H, NHH), 3.04 (br s, 1H, NHH), 1.95 (m, 1H, CH2), 1.83−1.70 (m,
4H, CH2), 1.67 (s, 3H, CH3), 1.65−1.47 (m, 3H, CH2), 1.43 (s,3H,
CH3), 1.41 (s, 3H, CH3), 1.164 (s, 3H, CH3), 1.157 (s, 3H, CH3),
1.13 (s, 3H, CH3), 1.06 (s, 3H, CH3), 0.79 (s, 3H, CH3). 31P{1H}
NMR (thf-d8, 122 MHz): δ 66.2 (m, 1P, PA), 64.2 (m, 1P, PB), 61.3
(m, 2P, PC and PD). 15N{1H} NMR (thf-d8, 30 MHz, from HN-
CH3), 1.19 (s, 3H, CH3). 31P{1H} NMR (thf-d8, 162 MHz): δ 50.8
2
(m, 1P, PA), 45.8 (m, 1P, PB), 40.9 (dm, JCD 298 Hz, 1P, PC), 33.5
(dm, 1P, PD). 15N{1H} NMR (thf-d8, 41 MHz, from HN-HSQC): δ
−287.3 (corr with 1H δ 7.54, NHPh), −356.0 (corr with 1H δ 5.16 and
4.55, NH2). IR: 3225 m, 3054 m, 3030 m, 1600 m, 1578 m, 1559w,
1497 m, 1426 m, 1304 m, 1284 m, 1250 m, 1200w, 1176w, 1153w,
1132w, 1079w, 1064w, 1033w, 1016w, 992w, 929s, 891 m, 838 m,
793w, 750s, 735s, 706s, 691 m, 651 m, 612s cm−1.
1
HSQC): δ −376.1 (corr with H δ 3.80 and 3.05, NH2). IR: 3305w,
3242w, 1942w, 1881w, 1823w, 1765w, 1587s, 1562 m, 1478s, 1427s,
1302s, 1281 m, 1265s, 1179 m, 1147w, 1123w, 1083w, 1068w, 1032w,
988w, 929s, 890s, 831 m, 802w, 757 m, 747s, 737s, 725s, 707s, 649 m,
624w, 613s cm−1.
−
cis-[Ru(η2-NH2NPh)(dmpe)2]+BPh4 (4). Potassium t-butoxide
(20 mg, 0.18 mmol) was added to a suspension of cis-[RuCl(η1-
−
NH2NHPh)(dmpe)2]+BPh4 (102 mg, 0.118 mmol) in thf (3 mL)
The 15N-labeled analogue was prepared in a similar manner using
cis-[Fe(η2-NH215NPh)(dmpe)2]+Cl−. 15N NMR (thf-d8, 30 MHz): δ
−299.1 (s, NPh).
under nitrogen. The initial dark blue suspension turned into a cloudy
yellow solution on stirring for 30 min. The reaction mixture was
filtered through Celite, the residue washed with thf (2 × 1 mL), and
the filtrate evaporated to dryness under vacuum. Diethyl ether (10
mL) and thf (0.5 mL) were added, and the mixture was left to stand
for 1 h. The yellow solid formed was collected by filtration, washed
with diethyl ether twice, and dried under vacuum (68 mg, 70% yield).
C42H59BN2P4Ru (827.79) requires C, 60.9; H, 7.2; N, 3.4; found, C,
60.5; H, 7.3; N, 3.3%. 1H NMR (thf-d8, 400 MHz): δ 7.29 (m, 8H, o-
PhB), 6.95 (m, 2H, m-Ph), 6.86 (m, 8H, m-PhB), 6.72 (m, 4H, p-
PhB), 6.56 (m, 2H, o-Ph), 6.40 (m, 1H, p-Ph), 4.75 (br, 1H, NHH),
3.92 (br, 1H, NHH), 2.01−1.75 (m, 3H, CH22), 1.71−1.47 (m, 5H,
cis-[Fe(η2-HNNPh)(dmpe)2] (2).41 Potassium t-butoxide (24
mg, 0.21 mmol) was added to a solution of cis-[Fe(η2-NH2NPh)-
(dmpe)2]+BPh4− (0.148 g, 0.189 mmol) in thf (2 mL) under nitrogen
and stirred for 20 min. The resulting red suspension was filtered
through Celite, the residue washed with thf (3 × 2 mL), and the
filtrate was evaporated to dryness under reduced pressure. The residue
was extracted with benzene (3 × 2 mL), filtered through Celite, and
evaporated to dryness under reduced pressure to afford a red solid
(44.3 mg, 51% yield). 1H NMR (toluene-d8, 600 MHz, 200 K): δ 7.88,
7.41, 7.37, 7.20, 6.82, 6.75 (m, Ph), 2.11, 1.71 (br s, NH), 1.50, 1.44,
1.15, 0.98, 0.86, 0.68, 0.66, 0.63, 0.61, 0.52, 0.38 (m, CH3), 1.64−0.73
(m, CH2). 31P{1H} NMR (toluene-d8, 243 MHz, 200 K): δ 71.5, 70.8,
65.9−64.3, 64.0, 63.4, 62.7, 54.5, 52.3 (m, P). 15N{1H} NMR
(toluene-d8, 61 MHz, from HN-HSQC, 200 K): δ −327.1, (corr with
2
CH2), 1.61 (d, JHP 8 Hz, 3H, CH3), 1.44 (d, JHP 5 Hz, 3H, CH3),
2
2
1.41 (d, JHP 8 Hz, 3H, CH3), 1.30 (d, JHP 8 Hz, 3H, CH3), 1.28 (d,
2JHP 8 Hz, 3H, CH3), 1.16 (d, 2JHP 7 Hz, 3H, CH3), 1.15 (d, 2JHP 6 Hz,
2
1
3H, CH3), 0.76 (d, JHP 5 Hz, 3H, CH3). H{31P} NMR (thf-d8, 400
MHz): δ 7.29 (m, 8H, o-PhB), 6.94 (m, 2H, m-Ph), 6.86 (m, 8H, m-
PhB), 6.72 (m, 4H, p-PhB), 6.56 (m, 2H, o-Ph), 6.40 (m, 1H, p-Ph),
4.75 (br, 1H, NHH), 3.92 (br, 1H, NHH), 1.92 (m, 1H, CH2), 1.76
(m, 1H, CH2), 1.67−1.47 (m, 6H, CH2), 1.61 (s, 3H, CH3), 1.44 (s,
3H, CH3), 1.41 (s, 3H, CH3), 1.30 (s, 3H, CH3), 1.28 (s, 3H, CH3),
1.16 (s, 3H, CH3), 1.15 (s, 3H, CH3), 0.76 (s, 3H, CH3). 31P{1H}
NMR (thf-d8, 162 MHz): δ 46.9 (m, 2P, PA and PB), 36.7 (m, 2P, PC
and PD). 15N{1H} NMR (thf-d8, 41 MHz, from HN-HSQC, 200 K): δ
−365.6 (corr with 1H δ 5.25 and 4.37, NH2). Note that NH 1H NMR
resonances shifted on cooling to 200 K. IR: 3320w, 3251w, 3054w,
1941w, 1882w, 1822w, 1764w, 1587s, 1562 m, 1478s, 1426s, 1416s,
1303s, 1282 m, 1263s, 1180 m, 1147w, 1125w, 1075w, 1067w, 1032w,
988w, 929s, 910 m, 890 m, 833 m, 802w, 756 m, 747s, 736s, 707s,
676w, 649 m, 624w, 613s cm−1.
1
1H δ 2.11, NH, major diastereomer), −324.5 (corr with H δ 1.71,
NH, minor diastereomer). IR: 3155w, 3050w, 3034w, 1605w, 1579s,
1548 m, 1415 m, 1358 m, 1316 m, 1291 m, 1281 m, 1272 m, 1244 m,
1150 m, 1121w, 1063w, 1018 m, 1008w, 978 m, 926s, 902 m, 884s,
831 m, 785w, 738 m, 716s, 705s, 694s, 640s, 628 m cm−1.
The 15N-labeled analogue was prepared in a similar manner using
−
cis-[Fe(η2-NH215NPh)(dmpe)2]+BPh4 . 15N NMR (toluene-d8, 40
MHz, 200 K): δ −246.3 (s, NPh, minor diastereomer), −254.3 (s,
NPh, major diastereomer).
cis-[RuCl(η1-NH2NHPh)(dmpe)2]+X− (3). X = Cl. Phenyl-
hydrazine (0.4 mL, 4 mmol) was added to a suspension of
cis-[RuCl2(dmpe)2] (0.148 g, 0.313 mmol) in thf (2 mL) under
nitrogen to give a pale yellow solution. Diethyl ether (10 mL)
was added, and the mixture left to stand overnight. The white
precipitate of cis-[RuCl(η1-NH2NHPh)(dmpe)2]+Cl− was
collected by filtration and washed with diethyl ether (0.173 g,
95% yield). The compound was used directly without further
purification.
The 15N-labeled analogue was prepared in a similar manner using
−
cis-[RuCl(η1-NH215NHPh)(dmpe)2]+BPh4 . 15N NMR (thf-d8, 30
2
MHz): δ −287.0 (d, JNP 20 Hz, NPh).
cis-[Ru(η2-HNNPh)(dmpe)2] (5). A suspension of cis-[RuCl(η1-
NH2NHPh)(dmpe)2]+Cl− (62 mg, 0.11 mmol) and potassium t-
butoxide (42 mg, 0.37 mmol) was stirred in thf (2 mL) under nitrogen
for 15 min. The initial blue-green suspension turned into a bright
yellow solution which was then evaporated to dryness in vacuo. The
residue was washed with hexane (3 × 2 mL) then extracted with
benzene (3 × 2 mL), filtered through Celite and the filtrate evaporated
to dryness under vacuum. The yellow-brown tacky solid was
recrystallized from benzene-d6 and pentane to afford cis-[Ru(η2-
PhNNH)(dmpe)2] as yellow-brown crystals (0.015 g, 27% yield).
C18H38N2P4Ru (507.53) requires C, 42.6; H, 7.6; N, 5.5; found, C,
The 15N-labeled analogue was prepared in a similar manner using
cis-[RuCl2(dmpe)2] (0.68 g, 1.4 mmol) and Ph15NHNH2 (0.17 g, 1.6
mmol), yield 80 mg (10%).
X = BPh4. A solution of NaBPh4 (35 mg, 0.10 mmol) in methanol
(0.5 mL) was added to a solution of cis-[RuCl(η1-NH2NHPh)-
(dmpe)2]+Cl− (34 mg, 59 μmol) in methanol (1.2 mL) under
nitrogen. The white precipitate of cis-[RuCl(η1-NH2NHPh)-
−
(dmpe)2]+BPh4 formed was collected by filtration, washed with
methanol (3 × 0.5 mL), and dried in vacuo (40 mg, 78% yield).
1
C42H60BClN2P4Ru (864.25) requires C, 58.4; H, 7.0; N, 3.2; found, C,
42.7; H, 7.8; N, 5.2%. H NMR (benzene-d6, 300 MHz): δ 7.72 (b,
1
58.2; H, 7.0; N, 3.1%. H NMR (thf-d8, 400 MHz): δ 7.54 (b, 1H,
1H, Ph), 7.38−6.95 (m, 3H, Ph), 6.65 (m, 1H, Ph), 2.89 (br, 1H,
NH), 1.48−1.32 (m, 1H, CH2), 1.41 (d, 2JHP 6 Hz, 3H, CH3), 1.36 (d,
2JHP 7 Hz, 3H, CH3), 1.32−1.05 (m, 6H, CH2), 1.09 (m, 3H, CH3),
NHPh), 7.28 (m, 8H, o-PhB), 7.22 (m, 2H, m-Ph), 6.90−6.81 (m,
9H, m- PhB and p-Ph), 6.79−6.68 (m, 6H, p-PhB and o-Ph), 5.16 (br,
1H, NHH), 4.55 (br, 1H, NHH), 2.01−1.74 (m, 4H, CH2), 1.69−1.57
(m, 1H, CH2), 1.57−1.52 (m, 4H, CH3 and CH2), 1.52−1.44 (m, 8H,
1.01 (m, 3H, CH3), 0.95−0.84 (m, 4H, CH2 and CH3), 0.82 (d, 2JHP
7
2
Hz, 3H, CH3), 0.81 (d, JHP 6 Hz, 3H, CH3), 0.78 (m, 3H, CH3).
1H{31P} NMR (benzene-d6, 300 MHz): δ 7.72 (b, 1H, Ph), 7.38−6.95
(m, 3H, Ph), 6.65 (m, 1H, Ph), 2.89 (br, 1H, NH), 1.48−1.32 (m, 1H,
CH2), 1.41 (s, 3H, CH3), 1.36 (s, 3H, CH3), 1.31−1.10 (m, 6H, CH2),
1.09 (s, 3H, CH3), 1.01 (s, 3H, CH3), 0.92−0.81 (m, 1H, CH2), 0.86
(s, 3H, CH3), 0.82 (s, 3H, CH3), 0.81 (s, 3H, CH3), 0.78 (s, 3H,
CH3). 31P{1H} NMR (benzene-d6, 122 MHz): δ 42.8 (m, 1P, PA),
38.9 (m, 2P, PB and PC), 34.1 (m, 1P, PD). 15N{1H} NMR (toluene-
d8, 41 MHz, from HN-HSQC, 193 K): δ −324.4 (corr with 1H δ 2.62,
NH). IR: 3143w, 3064w, 3034w, 1596w, 1578 m, 1549w, 1414w, 1342
2
2
CH3 and CH2), 1.40 (d, JHP 10 Hz, 3H, CH3), 1.36 (dd, JHP 8 Hz,
2JHP 2 Hz, 3H, CH3), 1.33−1.26 (m, 6H, CH3), 1.18 (d, 2JHP 8 Hz, 3H,
CH3). 1H{31P} NMR (thf-d8, 400 MHz): δ 7.53 (bt, 2JHH 3−4 Hz, 1H,
NHPh), 7.28 (m, 8H, o-PhB), 7.22 (m, 2H, m-Ph), 6.90−6.81 (m,
9H, m-PhB and p-Ph), 6.79−6.68 (m, 6H, p-PhB and o-Ph), 5.16 (dd,
2JHH 9 Hz, 2JHH 4 Hz, 1H, NHH), 4.55 (br, 2JHH 9 Hz, 2JHH 3 Hz, 1H,
NHH), 1.86 (m, 4H, CH2), 1.61 (m, 1H, CH2), 1.57−1.43 (m, 3H,
CH2), 1.55 (s, 3H, CH3), 1.50 (s, 3H, CH3), 1.49 (s, 3H, CH3), 1.40
(s, 3H, CH3), 1.36 (s, 3H, CH3), 1.31 (s, 3H, CH3), 1.29 (s, 3H,
3740
dx.doi.org/10.1021/ic2027225 | Inorg. Chem. 2012, 51, 3733−3742

Inorganic Chemistry
Article
m, 1290w, 1277 m, 1232w, 1148 m, 1064w, 1014w, 995w, 973w, 936
m, 923s, 895 m, 883 m, 865w, 826w, 787w, 743 m, 731 m, 716 m, 697
m, 688 m, 642 m, 630 m cm−1.
(toluene-d8, 41 MHz, from HN-HMBC, 193 K): δ −289.2 (corr with
1H δ 3.48, NH), −281.7 (corr with 1H δ 3.48, NCH3). 15N{1H} NMR
(thf-d8, 51 MHz, from HN-HMBC, 298 K): δ −286.7 (corr with 1H δ
The 15N-labeled analogue was prepared in a similar manner using
cis-[RuCl(η1-NH215NHPh)(dmpe)2]+Cl−. 15N NMR (benzene-d6, 51
1
2.77, NH), −277.3 (corr with H δ 2.77, NCH3). IR: 3172w, 2723w,
1767w, 1574w, 1415s, 1287 m, 1272s, 1213w, 1169w, 1121 m, 1055
m, 983w, 928s, 903s, 883s, 830s, 792 m, 720s, 701s, 684s, 642s cm−1.
MS (ESI, thf): m/z 996.1839 [25%], 908.0847 [30], 864.0952 [40],
547.1110 [40], 505.0890 [50], 447.0471 [100, (Ru(HNNMe)-
(dmpe)2H)+], 433.0319 [90], 403.0575 [43, (RuH(dmpe)2)+].
2
MHz): δ −251.5 (d, JNP 14 Hz, NPh). 15N{1H} NMR (benzene-d6,
2
51 MHz): δ −251.5 (d, JNP 14 Hz, NPh). 15N{1H, 31P} NMR
(benzene-d6, 51 MHz): δ −251.5 (s, NPh).
cis-[RuCl(η1-NH2NHMe)(dmpe)2]+X− (6). X = Cl. Methanol
(approximately 0.25 mL) was added to a suspension of cis-
[RuCl2(dmpe)2] (0.105 g, 0.222 mmol) in thf (2 mL) and
methylhydrazine (0.209 g, 4.54 mmol) under nitrogen to give a
pale yellow solution. Diethyl ether (10 mL) was added and the
mixture left to stand for 6 days. The white precipitate of cis-
[RuCl(η1-NH2NHMe)(dmpe)2]+Cl− was collected by filtration,
washed with diethyl ether, and dried under vacuum (90 mg,
78% yield). This compound was used directly without further
purification.
ASSOCIATED CONTENT
* Supporting Information
CIF files for 1, 3, 4, 5, and 6. This material is available free of
■
S
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: l.field@unsw.edu.au. Fax: +612 9385 8008. Phone:
+612 9385 2700.
■
X = BPh4. A solution of NaBPh4 (39 mg, 0.11 mmol) in methanol
(1 mL) was added to a solution of cis-[RuCl(η1-NH2NHMe)-
(dmpe)2]+Cl− (35 mg, 68 μmol) in methanol (1 mL) under nitrogen.
The white microcrystalline precipitate of cis-[RuCl(η1-NH2NHMe)-
ACKNOWLEDGMENTS
We thank the Australian Reseach Council and the University of
New South Wales for funding.
−
(dmpe)2]+BPh4 formed was collected by filtration, washed with
■
methanol (3 × 1.5 mL), and dried in vacuo (52 mg, 95% yield).
C37H58BClN2P4Ru (802.18) requires C, 55.4; H, 7.3; N, 3.5; found, C,
55.7; H, 7.5; N, 3.4%. 1H NMR (thf-d8, 400 MHz): δ 7.28 (m, 8H, o-
PhB), 6.86 (m, 8H, m-PhB), 6.71 (m, 4H, p-PhB), 4.29 (bm, 2H,
NH2), 4.04 (m, 1H, NHMe), 2.53 (d, 3JHH 6.4 Hz, 3H, NCH3), 1.91−
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1
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4
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