4d vs. 5d - Reactivity and fate of terminal nitrido complexes of rhodium and iridium

Article abstract of DOI:10.1002/ejic.201000899

The stability of (pyridinediimine)rhodium- and -iridium-azido complexes was studied by a combination of thermoanalytical methods (DTG/MS and DSC) and DFT calculations. On a preparative scale, the isolation and X-ray crystallographic characterization of th

Full text of DOI:10.1002/ejic.201000899

SHORT COMMUNICATION
DOI: 10.1002/ejic.201000899
4d vs. 5d – Reactivity and Fate of Terminal Nitrido Complexes of Rhodium
and Iridium
[a]
[a]
[a]
[a]
[a]
ˇ
ˇ
Julia Schöffel, Nevena Susnjar, Stefan Nückel, Daniel Sieh, and Peter Burger*
Dedicated to Jürgen Heck on the occasion of his 60th birthday
Keywords: C–H activation / Rhodium / Iridium / Nitrido complexes / Dinitrogen complexes
The stability of (pyridinediimine)rhodium– and -iridium–
azido complexes was studied by a combination of thermo-
analytical methods (DTG/MS and DSC) and DFT calcula-
tions. On a preparative scale, the isolation and X-ray crystal-
lographic characterization of the thermolysis products con-
firmed intramolecular C–H activation processes with con-
comitant reorganisation of C–C, C–N, N–H and Ir–N bonds
to yield tuck-in complexes with a different constitution of the
ligand framework for the Rh and Ir products. The tentatively
formed (Rh) or initially present (Ir) nitrido unit was converted
into either an amine (Rh) or amido (Ir) moiety. Furthermore,
the dimerization of the nitrido complexes to the correspond-
ing dinitrogen compounds, i.e. 2 LnMϵN Ǟ LnM–N2–MLn,
was investigated. Experimental evidence for the relevance of
this step was provided by the isolation and X-ray crystallo-
graphic characterization of a related dinuclear N2-bridged
(pyridinediimine)dirhodium complex. DFT calculations re-
vealed that the formation of dinitrogen complexes is thermo-
dynamically strongly favourable and evidenced that the pre-
vious isolation of a terminal iridium–nitrido complex was pos-
sible due to a high barrier for the dimerization process and a
sizeable barrier for the intramolecular C–H activation step.
bility and thermochemistry of 2-Ir and compare it to the
corresponding acclaimed 4d congener, the rhodium–nitrido
compound 2-Rh.
Introduction
In the last decade the status of the class of electron-rich
late transition complexes (Ͼ d4 configuration) with ter-
minal metal–heteroatom multiple bonds, i.e. M=XR and
M=X (X = N, O, S), changed from exotic to well-estab-
lished.[1,2] Imido complexes, LnM=NR (M = Co, Ni, Cu),
are among the most prominent representatives and display
a high reactivity in a variety of reactions, e.g. the aziridina-
tion of olefins.[3] For complexes with terminal unsubstituted
heteroatom ligands, M=X (e.g. metal–nitrido, –oxido, –sulf-
ido units), on the other hand, the situation has only little
changed. Apart from X-ray crystallographically charac-
terized metal–oxido complexes of the Pd, Pt and Au transi-
tion metals reported by Hill et al.[4] and the Pd–oxido com-
plex reported by Milstein et al.,[5] most compounds of this
type were proposed based on circumstantial experimental
evidence rather than their direct observation.[6] Recently, we
reported the synthesis and preliminary reactivity studies of
the first isolated d6-configured late transition nitrido exam-
ple, i.e. the square-planar complex 2-Ir, which displays a
terminal IrϵN unit.[7] Herein, we report on the thermal sta-
Results and Discussion
Our previous thermoanalytical study of the Ir–azido
complex 1-Ir revealed two consecutive exothermic steps: Ini-
tially, the nitrido complex 2-Ir is formed by N2 extrusion,
which then undergoes further conversion without further
mass loss to a previously unidentified product at elevated
temperature. From heating of either 1-Ir and 2-Ir at 150 °C
in the solid state, we were now able to isolate 3-Ir as the
product of the second thermolysis step in quantitative yield
(Scheme 1). The NMR spectroscopic and X-ray single-crys-
tal structure analysis of 3-Ir confirmed our previous sugges-
tion that a tuck-in amido complex is formed in this reaction
step by an apparent intramolecular C–H activation step of
one isopropyl methine C–H bond.
By contrast, the absence of a reaction up to 200 °C in
the TG/MS (Figure 1) and differential scanning calorimetry
(DSC) measurements of 1-Rh documented that the corre-
sponding rhodium–azido complex is thermally significantly
more robust than its iridium congener 1-Ir.[8] In the TG/MS
measurements an exothermic reaction sets in at T Ͼ 200 °C,
which is accompanied by a mass loss of 10% and a concom-
itant signature of m/z = 28 and 14 (N2+, N22+) in the mass
spectral trace evidencing extrusion of N2. The observed
[a] Institut für Angewandte und Anorganische Chemie,
Department Chemie, Universität Hamburg,
Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
Fax: +49-40-42838-6097
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000899.
View this journal online at
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4911

ˇ
J. Schöffel, N. Susˇnjar, S. Nückel, D. Sieh, P. Burger
SHORT COMMUNICATION
Scheme 1. Formation of rhodium and iridium tuck-in complexes
3-Ir and 3-Rh and ORTEP plots of 3-Ir and 3-Rh at the 50% prob-
ability level. Selected bond lengths [Å]: 3-Ir: Ir1–N1 1.853(6), Ir1–
N2 1.952(7), Ir1–N3 2.017(7), Ir1–N4 1.875(7), N4–C40 1.464(1),
C1–N2 1.314(11); 3-Rh: Rh1–N1 1.942(3), Rh1–N2 1.962(3), Rh1–
N3 2.014(3), Rh1–N4 2.148(3), N4–C40 1.537(5), C1–N2
1.512(11), C1–C43 1.590(5).[7]
Figure 1. DTGA/MS measurements for the transformations of 1-
Ir (top). Black: weight loss; light grey: DTG signal; grey: DTA
signal; black dots: ion current. (a) 1-Ir Ǟ 2-Ir Ǟ 3-Ir, ∆mcalcd.
=
3.9% (included for comparison),[7] reproduced with permission
from Angew. Chem.; (b) 1-Rh Ǟ 3-Rh, ∆mcalcd. = 4.5% (bottom).
mass loss is higher than the expected mass loss of 4.5%, of the double tuck-in rhodium compound 3-Rh. However,
caused by the thermal degeneration due to the chosen heat- even upon extended and elevated heating, there is no con-
ing rate.
version of 3-Ir to the iridium double tuck-in analogue of 3-
The DSC measurements of 1-Rh are in agreement with Rh. This circumstantial evidence suggests that the single
the TG/MS experiments and display only one strongly exo- tuck-in Rh analogue of 3-Ir is not a transient on the path-
thermic step with an enthalpy of ∆H = –36 kcal/mol. This way leading to 3-Rh.
compares to enthalpy values of ∆H = –6 and –21 kcal/mol
The formation of tuck-in complexes by reactive transi-
for the two consecutive transformations 1-Ir Ǟ 2-Ir and 2- tion metal complexes is a well-known process. Recently,
Ir Ǟ 3-Ir and a total ∆Htot value of –27 kcal/mol leading Power et al. reported for instance on the C–H activation in
to the nitrido and tuck-in iridium complexes. The identity a phenyl substituent of a putative two-coordinate manga-
of the thermolyis product 3-Rh could be established unam- nese complex.[9] Especially, in the chemistry of late transi-
biguously from an X-ray single-crystal structure analysis for tion metal complexes with terminal multiple-bonded π-do-
a recrystallized sample obtained from heating 1-Rh in the nor ligands, tuck-in formation is a well-known reaction
solid state at 200 °C (Scheme 1).[8]
While the formation of an anticipated rhodium tuck-in interactions.[10]
pathway, which allows to relax π–π metal–ligand repulsive
complex was indeed confirmed, to our surprise, its consti-
At present, we cannot offer a conclusive answer for the
tution differed from the one of the aforementioned iridium apparent disparity of the rhodium and iridium systems.
compound 3-Ir. In fact, two rather than just one isopropyl Even from extensive DFT calculations, in which open-shell
methine C–H bonds were activated yielding the amine– systems and different spin states were considered for the C–
amido complex 3-Rh. The 1-D and 2-D correlated NMR H activation processes in the Ir and Rh nitrido systems,
spectra of 3-Rh also document complete loss of symmetry only the following tentative explanations can be provided
upon thermolysis.
(Figure 2): We assume that the tuck-in formation for the
Upon inspection of the rhodium and iridium tuck-in rhodium system is initiated by the nitrido species. The ex-
complexes, it might be at first glance anticipated that the trusion of N2 for the rhodium complex is calculated to be
structure observed for the single tuck-in iridium derivative an uphill process by 15 kcal/mol, consistent with the ob-
3-Ir corresponds to an intermediate leading to an analogue served stability of the RhI–azido complex. The consecutive
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Terminal Nitrido Complexes of Rhodium and Iridium
Figure 2. Conceivable mechanisms for the formation of the tuck-in model complexes 3-Rhmodel and 3-Irmodel with DFT-calculated (BP86
functional) reaction barriers ∆Ea and total energies ∆Er (relative to 2-Mmodel) in kcal/mol.[8]
formation of the tuck-in complex may be initiated by hydro-
gen atom abstraction from the isopropyl methine group of
the nitrido unit to give the diradical imido (Rh=NH) inter-
mediate b (Figure 2). This view is supported by DFT calcu-
lations with the BP86 and B3LYP functionals for the model
Rh and Ir complexes, in which one of the iminoaryl substit-
uents was replaced by a hydrogen atom. The calculated en-
ergy differences revealed that this process is uphill by 21
(19) kcal/mol for the iridium system and only 15 (10) kcal/
Figure 3. ORTEP plots of 4-Rh (left) and 5-Rh (right) at the 50%
mol for the rhodium compound (B3LYP values are given
probability level. Selected bond lengths [Å] and angles [°]: 4-Rh:
in parentheses).[8] It seems therefore likely that radical path-
Rh1–N1 1.924(4), Rh1–N2 2.014(3), Rh1–N3 2.025(4), Rh1–N4
1.936(4), N4–N4Ј 1.130(7); 5-Rh: Rh1–N1 1.914(1), Rh1–N2
2.011(1), Rh1–N3 2.012(1), Rh1–N4 1.950(2), N4–N5 1.087(3),
Rh1–N4–N5 178.8(3).
ways are more prevalent for the tentative Rh–nitrido com-
plex 2-Rh. A possible scenario for the formation of 3-Rh is
depicted in Figure 2.
For the Ir system on the other hand, it is anticipated that
the initial C–H activation step proceeds by direct C–H bond
addition of the isopropyl methine group to the nitrido unit.
This would correspond to our previously proposed pathway
for the intermolecular addition of dihydrogen to the nitrido
unit yielding the amido complex ([Ir]ϵN + H2 Ǟ [Ir]-
NH2).[7] Finally, it deserves a special mention that the ex-
perimentally determined enthalpies for the formation of the
Rh and Ir tuck-in complexes are in good agreement with
the energy differences derived by DFT calculations.
Previous reports of Peters and Taube et al. of terminal
Fe– and Os–nitrido complexes to undergo dimerization to
more stable bridging N2 complexes according to 2 LnMϵN
Ǟ LnM–NϵN–MLn prompted us to look into similar path-
ways for the iridium–nitrido complex 2-Ir.[11] This was fur-
ther substantiated by the independent synthesis of the stable
dinuclear end-on bridging dinitrogen–Rh complex 4-Rh
with the sterically less demanding 2,6-dimethylphenyl sub-
stituent of the Nimine donor and the terminal dinitrogen–
Rh complex 5-Rh with the sterically more demanding 2,6-
diisopropylphenyl substituent (Figure 3). Both complexes 4-
Figure 4. Potential-energy scan for a colinear approach of two irid-
ium–nitrido model complexes (DFT, BP86).[8]
It deserves a special notion with this regard that our pre-
Rh and 5-Rh were obtained by reduction of the correspond- vious NBO analysis of the iridium–nitrido complex 2-Ir re-
ing RhI–chlorido or –methoxido precursors with sodium vealed sp hybridization for the nitrido N donor atom with
amalgam under dinitrogen.[12]
the lone pair located on the dimerization axis.[6] Therefore,
Initially, we studied the dimerization of the model this type of barrier was clearly expected based on a highly
iridium–nitrido complex depicted in Figure 4 under C2 unfavourable 4 electron/2 orbital situation for the direct
symmetry constraints, i.e a colinear approach of the two Ir– frontal attack. This parallels the findings for the dimeriza-
nitrido units. Whereas the overall process is thermodynami- tion of singlet carbenes, which dimerize by a so called “non-
cally very favourable with an energetic drop of –110 kcal/ least-motion pathway” that involves the attack of the occu-
mol, this process displays a substantial barrier of +35 kcal/ pied in-plane σ lone pair of one singlet carbene center on
mol (Figure 4).
the vacant out-of-plane pπ orbital of a second carbene (cf.
Eur. J. Inorg. Chem. 2010, 4911–4915
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SHORT COMMUNICATION
(400 MHz, [D8]THF, room temp.): δ = 8.47 [t, 3J = 8 Hz, 1 H,
Cpy(4)H], 7.87 [d, 2 H, Cpy(3,5)H], 7.08–7.20 (m, 6 H, CaromH),
3.06 [sept, 3J = 7 Hz, 4 H, CH(CH3)2], 1.65 (s, 6 H, N=CCH3),
1.14 [d, 3J = 7 Hz, 12 H, CH(CH3)2], 1.05 [d, 3J = 7 Hz, 12 H,
CH(CH3)2] ppm. 13C{1H} NMR (100 MHz, [D8]THF, room
temp.): δ = 166.6 (N=CCH3), 155.2 [Cpy(2,6)], 145.3 [Carom(1)],
139.5 [Carom(2,6)], 126.1 [Carom(3, 5 or 4)], 124.5 [Cpy(3,5)], 122.5
[Carom(3, 5 or 4)], 122.2 [Cpy(4)], 27.9 [CH(CH3)2], 22.7 [CH-
(CH3)2], 16.4 (N=CCH3) ppm.
Figure 5).[13] Finally, a spin-state change to a more stable
triplet from an initial S = 0 state during the dimerization
process shall be noted in passing (Figure 4).[8]
3-Rh: 55 mg (88 µmol) [Rh(iPr4N3)N3] (1-Rh) were placed as sol-
vent free solid in a teflon tapped Schlenk tube and heated under
vacuum at 150 °C for 5.5 d. After this time the solid changed its
1
color from green to violet and the H-NMR spectrum revealed a
quantitative conversion. Single crystals suitable for X-ray crystal
structure analysis were obtained from a concentrated toluene/di-
ethyl ether (2:1) solution at –35 °C. C33H43N4Rh (598.64): calcd. C
66.21, H 7.24, N 9.36; found C 66.16, H 7.15, N 8.85, 1H NMR
Figure 5. Frontier orbitals and nonleast-motion pathway for the
dimerization of iridium–nitrido complexes.
3
Next in our DFT study, we released the colinear con-
straints for the dimerization of the iridium model complex.
Based on the isolobal relation of the nitrido complex and
singlet carbenes a similar nonleast-motion pathway for di-
merization of the nitrido compounds was probed (Fig-
ure 5). This indeed revealed an essentially barrierless reac-
tion. We also investigated the dimerization of the corre-
sponding (unknown) iridium–nitrido complex with 2,6-di-
methylphenyl ketimine substituents, which also collapses
without barrier to the iridium anologue of the dinuclear
N2-bridged dirhodium compound 4-Rh.
(400 MHz, [D8]THF, room temp.): δ = 8.06 [d, J = 7.2 Hz, 1 H,
Cpy(3)H], 7.82–7.78 [m, 1 H, Cpy(4)H], 7.73–7.71 [m, 1 H, Cpy
-
(5)H], 7.31–7.17 [m, 3 H, Carom(3,4,5)HI], 6.71 [d, 3J = 7.0 Hz, 1
3
3
H, Carom(5)HK], 6.57 [d, J = 7.0 Hz, 1 H, Carom(3)HK], 5.95 [t, J
= 7.0 Hz, 1 H, Carom(4)HK], 4.23 (d, 3J = 11.2 Hz, 1 H, NH2), 3.93
(d, 3J = 11.2 Hz, 1 H, NH2), 3.52 [sept, 3J = 6.8 Hz, 1 H, CH-
(CH3)2], 2.79 [sept, 3J = 6.8 Hz, 1 H, CH(CH3)2], 1.82 [s, 3 H,
CC(CH3)2], 1.75 (s, 3 H, N=C-CH3), 1.56 [s, 3 H, NC(CH3)2], 1.46
[d, 3J = 6.8 Hz, 3 H, CH(CH3)2], 1.10 [s, 3 H, NC(CH3)2], 1.05–
1.04 [m, 6 H, CH(CH3)2], 0.95 [d, 3J = 6.8 Hz, 3 H, CH(CH3)2],
0.90 [s, 3 H, CC(CH3)2], 0.23 (s, 3 H, N-C-CH3) ppm.
3-Ir. (a) From Complex [Ir(iPr4N3)N3] (1-Ir): [Ir(iPr4N3)N3] (1-Ir)
(100 mg, 145 µmol) was placed as solvent-free solid in a Teflon®-
tapped Schlenk tube and heated under vacuum at 150 °C for 13 h.
The solid changed its color from green to violet. The 1H NMR
spectra showed an essentially quantitative conversion. Recrystalli-
zation was carried out from a concentrated THF/pentane (2:1)
solution at –35 °C. By the same procedure single crystals suitable
for X-ray crystal structure analysis were obtained. (b) Alternative
Synthesis from [Ir(iPr4N3)N] (2-Ir): Analogous to synthesis (a)
starting from [Ir(iPr4N3)N] (2-Ir). C33H43IrN4 (687.95): calcd. C
57.61, H 6.30, N 8.15; found C 57.66, H 6.68, N 7.41, 1H NMR
Conclusions
The observation of sizeable barriers for dimerization and
tuck-in formation provides an explanation for our previous
isolation of the exclusive nitrido complex 2-Ir. Nevertheless,
the presented system is viewed with mixed feelings. On the
one hand we are able to prevent dimerization of the nitrido
units through the proper choice of the ligand and can wit-
ness the desired, yet intramolecular, aptitude for C–H bond
activiation by the terminal nitrido unit. On the other hand,
new design rules for nitrido complexes are anticipated to
avoid the undesired step leading to tuck-in complexes and
are currently under investigation in our laboratory.
3
(400 MHz, [D8]THF, room temp.): δ = 8.53 [d, J = 7.8 Hz, 1 H,
3
3
Cpy(3 o. 5)H], 8.43 [d, J = 7.8 Hz, 1 H, Cpy(3 o. 5)H], 7.52 [t, J
3
= 7.8 Hz, 1 H, Cpy(4)H], 7.43 [d, J = 7.8 Hz, 1 H, Carom(3)HK],
7.33–7.29 [m, 3 H, Carom(3 or 5)HI, Carom(5)HK], 7.26–7.21 [m, 2
3
H, Carom(4, 3 or 5)HI and (NH)], 7.14 [t, J = 7.8 Hz, 1 H, Carom
-
3
3
(4)HK], 3.48 [sept, J = 6.8 Hz, 1 H, CH(CH3)2(K)], 2.88 [sept, J
= 6.8 Hz, 1 H, CH(CH3)2(I)], 2.76 [sept, 3J = 6.8 Hz, 1 H, CH-
(CH3)2I], 1.86 [s, 3 H, NC(CH3)2], 1.48 [d, 3J = 6.8 Hz, 3 H,
CH(CH3)2(K)], 1.39 (s, 3 H, N=C-CH3), 1.22–1.20 [m, 6 H,
NC(CH3)2, N=C-CH3] 1.17 [d, 3J = 6.8 Hz, 3 H, CH(CH3)2(I)],
Experimental Section
General: Synthetic and selected spectroscopic data for 1-Rh, 3-Rh,
3-Ir, 4-Rh, and 5-Rh are included here. The complete spectroscopic
and crystallographic data[14] as well as the used labelling scheme
for the assignment of the NMR resonances can be found in the
Supporting Information; the data for the starting materials can be
found in ref.[7,15]
3
3
1.11 [d, J = 6.8 Hz, 3 H, CH(CH3)2(I)], 1.08 [d, J = 6.8 Hz, 3 H,
CH(CH3)2(I)], 0.71 [d, J = 6.8 Hz, 3 H, CH(CH3)2(I)], 0.52 [d, J
3
3
= 6.8 Hz, 3 H, CH(CH3)2(K)] ppm.
¯
Crystallographic Data for 3-Ir: M = 760.04 g/mol, triclinic, P1 (no.
2), a = 11.6656(19), b = 12.176(2), c = 13.376(2) Å, α = 78.743(3)°
β = 103.168(2)°, γ = 76.307(3)°, V = 1670.2(5) Å3, Z = 2, ρcalcd.
=
1-Rh: To a solution of [Rh(iPr4N3)OMe] (428 mg, 695 µmol) in
THF (10 mL) was added Me3SiN3 (200 µL, 1.68 mmol). After stir-
ring at room temp. for 24 h, the solvent and the volatile side prod-
ucts were removed by vacuum distillation. The remainder was then
triturated with alternate pentane and vacuum treatment. The ob-
tained green product can be used without further purification. Cor-
rect elemental analysis data could not be obtained in several
attempts, even after repeated recrystallizations. 1H NMR
1.511 g/cm3, T = 153(2) K, λ(Mo-Kα) = 0.71073 Å. 7269 reflections
collected, which were used in all calculations. R1 = 0.0601, wR2 =
0.1265 for observed unique reflections [F2 Ͼ 2σ(F2)]. Max./min.
residual electron densities 3.548/–3.460 e/Å3.
4-Rh: A solution of [Rh(Me4N3)OMe] (84 mg, 167 µmol) in THF
(5 mL) was added quickly to NaHg (Na content 0.77%, 554 mg,
184 µmol), which was covered by THF (2 mL). The mixture was
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Terminal Nitrido Complexes of Rhodium and Iridium
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stirred under N2 at room temp. for 0.5 h. The color changed from
green to brown. The supernatant was decanted, filtered, and the
solvent was removed in vacuo. The resulting brown solid was
washed with pentane (2ϫ3 mL) and dried in vacuo. This crude
product was extracted with diethyl ether. The diethyl ether solution
was concentrated to 20% and cooled to –35 °C yielding a brown
microcrystalline solid. Alternatively, the material can be recrys-
tallized from THF/pentane. Yield: 53% (45 mg, 44.7 µmol) Single
crystals suitable for X-ray crystal-structure analysis were obtained
[4]
by recrystallization at –35 °C. C52H59N8O0.5Rh2 [4-Rh·(THF)0.5
]
(1009.3): calcd. C 61.84, H 5.89, N 11.10; found C 61.85, H 5.94,
1
N 10.95. H NMR (400 MHz, [D8]toluene, room temp.): δ = 4.94,
5.09, 16.76 (v. br.), 20.31 ppm; (400 MHz, C6D6, room temp.): δ =
1.11 (Et2O), 3.25 (Et2O), 5.01, 5.26, 17.16 (v. br.), 20.2 ppm. Ra-
man (solid): ν = 2059 (νNN) cm–1. ESR (toluene, room temp.): g =
˜
2 (3494 G).
[5]
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Details of the synthesis, characterization, thermoanalysis and
further information on the quantum chemical calculations of
the complexes are described in the Supporting Information.
The synthesis and characterization of the complexes 1-Ir and
3-Ir can be found in ref.[7]
5-Rh: [Rh(iPr4N3)Cl] (100 mg, 161 µmol) was dissolved in THF
(5 mL) and added to Na/Hg (0.77%, 550 mg, 183 µmol) covered
by a layer of THF. The mixture was stirred for 1.5 h, upon which
the color of the mixture changed from green to brown. The super-
natant brown solution was decanted and concentrated to dryness.
The solid residue was washed with pentane (2ϫ5 mL). After re-
moving the pentane in vacuo, the brown product was extracted into
toluene and filtered. The filtrate was then concentrated to dryness
in vacuo. Crystalline material was obtained from a toluene/pentane
solution at –35 °C. Yield: 76% (75 mg, 122 µmol). C33H43N5Rh
(612.64): calcd. C 64.70, H 7.07, N 11.43; found C 65.04, H 7.39,
[7]
[8]
1
N 9.59. H NMR (400 MHz, C6D6): δ = 2.28 (br.), 3.55 (br.), 5.60
(br.) ppm. IR (toluene): ν = 2139 (νNN) cm–1. ESR (toluene, room
˜
temp.): g = 1.99 (3500 G).
[9]
C. Ni, J. C. Fettinger, P. P. Power, Organometallics 2010, 29,
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Supporting Information (see footnote on the first page of this arti-
cle): Complete spectroscopic and thermoanalytical data, crystallo-
graphic and computational details of the DFTcalculations.
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Acknowledgments
Financial support of this research by Deutsche Forschungsgemein-
schaft is gratefully acknowledged.
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[12] The two dinitrogen complexes 4-Rh and 5-Rh are paramag-
netic. Their interesting electronic and magnetic properties will
be discussed elsewhere.
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[14] CCDC-777039 (3-Ir), -777040 (3-Rh), -777041 (4-Rh) and
-777042 (5-Rh) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
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Received: June 13, 2010
Published Online: September 28, 2010
Eur. J. Inorg. Chem. 2010, 4911–4915
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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