Reactions of [RhCl(diene)]2 with Bi- and terdentate nitrogen ligands. X-ray structures of five-coordinate complexes

Article abstract of DOI:10.1021/om960760b

Reaction of [RhCl(diene)]₂ (diene = 1,5-cyclooctadiene (COD) or bicyclo[2.2.1] hepta-2,5-diene (NBD)) with the N-N-N nitrogen ligands 2,6-(C(R¹)=N-R²)₂C₅H₃N in CD₂Cl₂ or CH₂Cl₂ yielded the five-coordinate complexes [RhCl(2,6-(C(H)=N-R²)₂C₅H₃N)(diene)] (diene = NBD; R² = i-Pr, t-Bu, and p-anisyl), which has been isolated for NBD but not for COD. A single-crystal X-ray determination showed that [RhCl(2,6-(C(H)=N-p-anisyl)₂C₅H₃N)(NBD)] has a distorted trigonal bipyramidal configuration with the pyridyl N-atom, one imine N-atom, and one alkene double bond in the equatorial plane, while the second alkene bond and the chloride atom occupy the axial positions. This conformation containing one noncoordinated imine moiety is clearly retained at 183 K in CD₂Cl₂, as is also the case for the other complexes. For the COD complexes, the reaction is more complicated, as the intermediates that are observed depend on the substituents R¹ and R² of the N-N-N nitrogen ligand. The five-coordinate complexes [RhCl(2,6-(C(R¹)=N-R²)₂C₅H ₃N)(COD)] could be observed at low temperatures for R¹ = H and R² = i-Pr, t-Bu, and p-anisyl, while for R¹ = Me and R² = p-anisyl, this intermediate could not be observed; instead, [Rh(2,6-(C(Me)=N-p-anisyl)₂C₅H₃N) ₂]⁺Cl^- was found, which shows the presence of one N-N-N ligand bonded as a bidentate ligand and one N-N-N ligand bonded as a terdentate ligand at low temperatures. Further reaction of [Rh(2,6-(C(Me)=N-p-anisyl)₂C₅H₃N) ₂]⁺Cl^- with [RhCl-(COD)]₂ afforded [RhCl(2,6-(C(Me)=N-p-anisyl)₂C₅H₃N)] and subsequently, via oxidative addition of CD₂Cl₂, the complex [RhCl₂(CD₂Cl)(2,6-(C(Me)=N-p-anisyl)₂C ₅H₃N)]. The dynamic properties of the five-coordinate diene complexes [RhCl(2-(C(H)=N-R²)-6-(Me)-C₅H₃N)(NBD)] (R² = i-Pr, t-Bu, and p-anisyl), which contain N-N nitrogen ligands, and of the new complexes [Rh(2-(C(H)=N-R²)-6-(Me)C₅H₃N)(NBD)]OTf (R² = i-Pr, t-Bu, and p-anisyl) and of [Rh(2,2′-bipyrimidine)(NBD)]OTf have been investigated. A single-crystal X-ray determination of [RhCl(2-(C(H)=N-i-Pr)-6-(Me)C₅H₃N)(NBD)] showed structural features which are analogous to those of [RhCl(2,6-(C(H)=N-p-anisyl)₂C₅H₃N)(NBD)].

Full text of DOI:10.1021/om960760b

54
Organometallics 1997, 16, 54-67
Rea ction s of [Rh Cl(d ien e)]2 w ith Bi- a n d Ter d en ta te
Nitr ogen Liga n d s. X-r a y Str u ctu r es of F ive-Coor d in a te
Com p lexes
Hendrikus F. Haarman,† Frank R. Bregman,† J an-Meine Ernsting,†
Nora Veldman,‡ Anthony L. Spek,‡ and Kees Vrieze*,†
J . H. van’t Hoff Research Institute, Laboratorium voor Anorganische Chemie, Universiteit van
Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, and Bijvoet
Center for Biomolecular Research, Vakgroep Kristal- en Structuurchemie, Universiteit Utrecht,
Padualaan 8, 3584 CH Utrecht, The Netherlands
Received September 3, 1996X
Reaction of [RhCl(diene)]2 (diene ) 1,5-cyclooctadiene (COD) or bicyclo[2.2.1] hepta-2,5-
diene (NBD)) with the N-N-N nitrogen ligands 2,6-(C(R1)dN-R2)2C5H3N in CD2Cl2 or
CH2Cl2 yielded the five-coordinate complexes [RhCl(2,6-(C(H)dN-R2)2C5H3N)(diene)] (diene
) NBD; R2 ) i-Pr, t-Bu, and p-anisyl), which has been isolated for NBD but not for COD. A
single-crystal X-ray determination showed that [RhCl(2,6-(C(H)dN-p-anisyl)2C5H3N)(NBD)]
has a distorted trigonal bipyramidal configuration with the pyridyl N-atom, one imine
N-atom, and one alkene double bond in the equatorial plane, while the second alkene bond
and the chloride atom occupy the axial positions. This conformation containing one
noncoordinated imine moiety is clearly retained at 183 K in CD2Cl2, as is also the case for
the other complexes. For the COD complexes, the reaction is more complicated, as the
intermediates that are observed depend on the substituents R1 and R2 of the N-N-N
nitrogen ligand. The five-coordinate complexes [RhCl(2,6-(C(R1)dN-R2)2C5H3N)(COD)] could
be observed at low temperatures for R1 ) H and R2 ) i-Pr, t-Bu, and p-anisyl, while for R1
) Me and R2 ) p-anisyl, this intermediate could not be observed; instead, [Rh(2,6-(C(Me)dN-
p-anisyl)2C5H3N)2]+Cl- was found, which shows the presence of one N-N-N ligand bonded
as a bidentate ligand and one N-N-N ligand bonded as a terdentate ligand at low
temperatures. Further reaction of [Rh(2,6-(C(Me)dN-p-anisyl)2C5H3N)2]+Cl- with [RhCl-
(COD)]2 afforded [RhCl(2,6-(C(Me)dN-p-anisyl)2C5H3N)] and subsequently, via oxidative
addition of CD2Cl2, the complex [RhCl2(CD2Cl)(2,6-(C(Me)dN-p-anisyl)2C5H3N)]. The
dynamic properties of the five-coordinate diene complexes [RhCl(2-(C(H)dN-R2)-6-(Me)-
C5H3N)(NBD)] (R2 ) i-Pr, t-Bu, and p-anisyl), which contain N-N nitrogen ligands, and of
the new complexes [Rh(2-(C(H)dN-R2)-6-(Me)C5H3N)(NBD)]OTf (R2 ) i-Pr, t-Bu, and
p-anisyl) and of [Rh(2,2′-bipyrimidine)(NBD)]OTf have been investigated. A single-crystal
X-ray determination of [RhCl(2-(C(H)dN-i-Pr)-6-(Me)C5H3N)(NBD)] showed structural
features which are analogous to those of [RhCl(2,6-(C(H)dN-p-anisyl)2C5H3N)(NBD)].
In tr od u ction
chloride atom was bent increasingly out of the plane of
the molecule, while the nitrogen ligand remained bonded
in a terdentate fashion. This distortion of the Cl-atom
out of the coordination plane could be correlated with
very large shifts of the 103Rh resonances to high parts
per million values owing to changes in the molecular
orbital sequence.2 In this context, it should be noted
that while we were unable to incorporate ethene or
cyclooctene in the product, alkene-containing rhodium
complexes with phosphine ligands have been reported,
e.g., by Burgess et al.3 and Binger et al.4 The Rh(III)
complexes [RhCl2(R3)(2,6-(C(R1)dN-R2)2C5H3N)] (R3 )
CH2Cl, CHCl2, CH2Ph, CHClPh, and Cl) resulting from
reactions of the Rh(I) complexes with the appropriate
substrates show the expected six-coordinate geometry.
However, for R1 ) Me and R2 ) i-Pr, it was shown by
variable temperature 1H NMR experiments that in
Recently we reported novel Rh(I) complexes which
were able to cleave C-Cl bonds of reagents such as
dichloromethane, chloroform, benzyl chloride, and R,R-
dichlorotoluene by oxidative addition.1 By employment
of N-N-N nitrogen ligands of the type 2,6-(C(R1)dN-
R2)2C5H3N (R1 ) H, R2 ) i-Pr, t-Bu, cyclohexyl, and
p-anisyl; R1 ) Me, R2 ) p-anisyl and i-Pr), we succeeded
in preparing very nucleophilic and very reactive Rh(I)
complexes via reaction of [RhCl(alkene)2]2 (alkene )
cyclooctene or ethene) with the above N-N-N ligands.
The molecular structures of [RhCl(2,6-(C(R1)dN-
R2)2C5H3N)] (R1 ) H, R2 ) i-Pr, t-Bu; R1 ) Me, R2 )
i-Pr) were determined by X-ray analysis. Interestingly,
by increasing the steric bulk of R1 and R2, the equatorial
* To whom correspondence should be addressed.
† J . H. van’t Hoff Research Institute.
(2) Haarman, H. F.; Kaagman, J . W. F.; Ernsting, J . M.; Wilms, M.;
Vrieze, K.; Elsevier, C. J . To be published.
(3) Burgess, K.; van der Donk, W. A.; Westcott, S. A.; Marder, T.
B.; Baker, R. T.; Calabrese, J . C. J . Am. Chem. Soc. 1992, 114, 9350.
(4) Binger, P.; Haas, J .; Glaser, G.; Goddard, R.; Kru¨ger, C. Chem.
Ber. 1994, 127, 1927.
‡ Bijvoet Center for Biomolecular Research.
X Abstract published in Advance ACS Abstracts, December 1, 1996.
(1) Haarman, H. F.; Ernsting, J . M.; Kranenburg, M.; Kooijman, H.;
Veldman, N.; Spek, A. L.; van Leeuwen, P. W. N. M.; Vrieze, K. To be
published.
S0276-7333(96)00760-1 CCC: $14.00 © 1997 American Chemical Society

Reactions of [RhCl(diene)]2
Organometallics, Vol. 16, No. 1, 1997 55
(5), t-Bu (6), and p-anisyl (7); R1 ) Me, R2 ) i-Pr (8) and
solution there is an equilibrium between a six-coordi-
nate Rh(III) species and an unusual five-coordinate
Rh(III) form which contains a bidentate bonded N-N-N
ligand and is the dominant species at higher tempera-
tures. Molecular modeling of the complexes with R1 )
Me, R2 ) i-Pr, and R3 ) CH2Cl, CHCl2, CH2Ph, CHClPh,
and Cl based on the data of the X-ray structures of
[RhCl(2,6-(C(R1)dN-R2)2C5H3N)] (R1 ) H, R2 ) i-Pr,
t-Bu; R1 ) Me, R2 ) i-Pr) and [RhCl2(CH2Cl)(2,6-
(C(H)dN-R2)2C5H3N)] (R2 ) i-Pr and cyclohexyl) showed
steric interactions between the methyl groups of the i-Pr
group (R2) and the methyl group (R1) and between the
i-Pr (R2) methyl groups and the chloride atom(s) or the
phenyl substituent of the R3 group. For R1 ) Me and
R2 ) i-Pr this led to the formation of the five-coordinate
Rh(III) complexes.
6
p-anisyl (9)), [RhCl(COD)]2 (COD ) 1,5-cyclooctadiene), and
6
[RhCl(NBD)]2 (NBD ) norbornadiene ) bicyclo[2.2.1]hepta-
2,5-diene) were synthesized according to literature procedures.
The ligands were purified by either sublimation or crystal-
lization, depending on the ligand.
[Rh (bp m )(NBD)]OTf (10). To a solution of 0.0660 g of
[RhCl(NBD)]2 (1.4 × 10-4 mol) in 5 mL of dichloromethane
was added 0.0737 g of AgOTf (2.9 × 10-4 mol). The resulting
suspension was stirred for 1 h and subsequently filtered giving
a clear yellow solution. A solution of 0.366 g of bpm (1, 2.8 ×
10-4 mol) in 5 mL of dichloromethane was added giving a red-
brown precipitate, which was filtered off, washed with dichloro-
methane (4 × 5 mL), and dried in vacuo. Yield: 0.10 g of 10
(85%). The complex is black-brown and dissolves only very
slightly, even in polar solvents. The analysis is slightly off
owing to solvent incorporation. However, the FABMS meas-
urement is conclusive.
In order to shed more light on the intimate pathways
by which the complexes [RhCl(2,6-(C(R1)dN-R2)2C5H3N)]
are formed from Rh(I)-alkene complexes, we directed
our attention to substitution reactions of [RhCl(diene)]2
(diene ) 1,5-cyclooctadiene (COD) or bicyclo[2.2.1]hepta-
2,5-diene (NBD)) with the N-N-N nitrogen ligands 2,6-
(C(R1)dN-R2)2C5H3N (R1 ) H, R2 ) i-Pr, t-Bu, and
p-anisyl; R1 ) Me, R2 ) i-Pr and p-anisyl). To facilitate
the characterization of the intermediate species, we
have studied the reaction of the N-N nitrogen ligands
2-(C(H)dN-R2)-6-(Me)C5H3N (R2 ) i-Pr, t-Bu, and
p-anisyl) and 2,2′-bipyrimidine with [RhX(NBD)]2 (X )
Cl, OTf). The results show that the substitution reac-
tions, the intermediates, and the dynamic behavior of
the intermediates critically depend on both the alkene
and the substituents R1 and R2 of the N-N-N ligand.
Anal. Calcd for C16H14F3N4O3RhS (10): C, 38.26; H, 2.81;
N, 11.15. Found: C, 37.77; H, 3.22; N, 10.53. FABMS for 10
(C16H14F3N4O3RhS) (obsd m/z, calcd m/z): 501.9738, 501.9786.
1H NMR of Mixtu r es of F r ee Liga n d 1 a n d Com p lex
10 a s a F u n ction of Tem p er a tu r e. 1H NMR spectra were
recorded at 183 and 293 K of a saturated solution of 10 in 0.5
1
mL of CD2Cl2. Subsequently, variable temperature H NMR
spectra were measured on the same solution to which 2 equiv
of free bpm ligand (1) had been added. As the signals of the
coordinated and noncoordinated bpm had coalesced, inter-
molecular exchange of bpm appeared to occur. It was unfor-
tunately not possible to study the kinetics of the reaction,
owing to insolubility of 10.
Syn th esis of [Rh (2-(C(H)dN-R2)-6-(Me)C5H3N)(NBD)]-
OTf (R2 ) i-P r (11), t-Bu (12), a n d p-An isyl (13)).
A
representative synthesis is given for complex 11. [RhCl-
(NBD)]2 (0.0946 g, 2.05 × 10-4 mol) was added to 0.11 g of
AgOTf (4.3 × 10-4 mol) in 20 mL of dichloromethane. The
resulting suspension was stirred for 1 h and subsequently
filtered giving a clear yellow-orange solution to which 80 µL
of the N-N ligand 2 (0.073 g, 4.5 × 10-4 mol) was added.
Dichloromethane was evaporated in vacuo giving a sticky
residue, and after the residue was washed with diethyl ether
(3 × 5 mL) and cold THF (2 × 1 mL) and dried in vacuo, the
product was isolated as a red powder. Yield: 0.174 g (84%).
The yield of 12 was 70% and that of 13 was 85%. Anal. Calcd
for C18H22F3N2O3RhS (11): C, 42.70; H, 4.38; N, 5.53. Found:
C, 42.61; H, 4.82; N, 4.59. Anal. Calcd for C19H24F3N2O3RhS
(12): C, 43.94; H, 4.47; N, 5.39. Found: C, 44.07; H, 4.78; N,
5.38. FABMS for 11 (C18H22F3N2O3RhS) (obsd m/z, calcd
m/z): 506.0393, 506.0358. FABMS for 12 (C19H24F3N2O3RhS)
(obsd m/z, calcd m/z): 520.0595, 520.0515. FABMS for 13
(C22H22F3N2O4RhS - CF3SO3) (obsd m/z, calcd m/z): 421.0746,
421.0780.
Exp er im en ta l Section
All experiments were carried out in a dry nitrogen atmo-
sphere using standard Schlenk techniques. Benzene, diethyl
ether, tetrahydrofuran (THF), and pentane were distilled
before use from sodium/benzophenone, dichloromethane and
chloroform were distilled from calcium hydride, and acetone
was distilled from KMnO4/Na2CO3. Molecular sieves, 3 Å,
were activated at 180 °C in vacuo for 24 h. Deuterobenzene
was dried over sodium and stored under nitrogen. Deuterated
chlorinated solvents were dried with molecular sieves, 3 Å,
and stored under nitrogen. The 1H and 13C NMR spectra were
recorded on a Bruker AMX 300 or AC 200 spectrometer. The
spectra were indirectly referenced to TMS using residual
solvent signals. Fast atom bombardment mass spectrometry
(FABMS) was carried out by the Institute for Mass Spectros-
copy of the University of Amsterdam using a J EOL J MS SX/
SX102A four-sector mass spectrometer coupled to a J EOL MS-
7000 data system. The samples were loaded in a matrix
solution (nitrobenzyl alcohol) onto a stainless steel probe and
bombarded with xenon atoms with an energy of 3 keV. During
the high-resolution FABMS measurements, a resolving power
of 5000 (10% valley definition) was used. CsI and/or glycerol
was used to calibrate the mass spectrometer. Elemental
analyses were carried out by Dornis und Kolbe, Mikro-
analytisches Laboratorium, Mu¨lheim a.d. Ruhr, Germany, and
by our Institute. The conductometric experiments were car-
ried out with a Consort K 720 conductometer equipped with a
Philips PW 9512/00 conductometric cell in a closed glass vessel.
2,2′-Bipyrimidine (bpm, 1) and AgOTf (OTf ) trifluoro-
methanesulfonate) were obtained from Aldrich and used as
received. The N-N nitrogen ligands5 2-(C(H)dN-R2)-6-(Me)-
C5H3N (R2 ) i-Pr (2), t-Bu (3), and p-anisyl(4)), the N-N-N
nitrogen ligands5 2,6-(C(R1)dN-R2)2C5H3N (R1 ) H, R2 ) i-Pr
1H NMR of Mixtu r es of F r ee Liga n d 2 a n d Com p lex
11 a s a F u n ction of Tem p er a tu r e. A NMR tube was filled
with 0.0061 g of 11 (1.2 × 10-5 mol, 0.022 mol/L) and 0.72 g of
CD2Cl2 (0.55 mL). 1H NMR spectra were recorded at 183 and
1
263 K. Subsequently, variable temperature H NMR spectra
were recorded on the same solutions to which 1.0 µL of the
free N-N ligand 2 (0.93 × 10-3 g, 0.58 × 10-5 mol) had been
added. Similar measurements were carried out after adding
excess free N-N ligand 2 as follows: 1.2 µL (0.71 × 10-5 mol,
1.0 equiv), 1.5 µL (0.84 × 10-5 mol, 1.8 equiv), and 1.7 µL (1.0
× 10-5 mol, 2.5 equiv). It was found that intermolecular
exchange of the free ligand took place. The reciprocal lifetime
(1/τ) values at 263 K were calculated by using the line widths
of the Me (H5, Scheme 1) signal of complex 11 as a function
of the free ligand concentration at 263 K. (c [mol/L], 1/τ [s-1]):
c ) 0.011, 1/τ ) 8.8; c ) 0.023, 1/τ ) 19.5; c ) 0.039, 1/τ )
34.9; c ) 0.057, 1/τ ) 51.5. These 1/τ values were also
calculated by using the line widths of the Me (H5) signal of
(5) Lavery, A.; Nelson, S. M. J . Chem. Soc., Dalton Trans. 1985,
1053.
(6) van der Ent, A.; Onderdelinden, A. L. Inorg. Synth. 1990, 28,
90.

56 Organometallics, Vol. 16, No. 1, 1997
Haarman et al.
the free ligand (0.010 mol/L) as a function of the concentration
of complex 11 at 263 K. (c [mol/L], 1/τ [s-1]): c ) 0.003, 1/τ )
1.3; c ) 0.006, 1/τ ) 3.8; c ) 0.012, 1/τ ) 7.8; c ) 0.015, 1/τ )
9.7.
Stu d y of th e in Situ F or m a tion of [Rh Cl(2,6-(C(H)dN-
R2)2C5H3N)(COD)] (R2 ) i-P r (20), t-Bu (21), a n d p-An isyl
(22)). A representative measurement is given for the yellow
complex 21. At 195 K, a NMR tube was filled with 0.0090 g
of [RhCl(COD)]2 (1.83 × 10-5 mol) and 0.0089 g of 6 (3.65 ×
10-5 mol) in 0.79 mL of deuterodichloromethane. 1H NMR
spectra were recorded between 183 and 293 K. At 223 K,
complex 21 was formed, while in the range of 233-273 K, the
equilibrium shifted toward [RhCl(COD)]2 and free ligand.
The red-orange complex 20 was formed at 230 K, and after
1 day at room temperature, the yellow-orange deuterochloro-
methyl complex [RhCl2(CD2Cl)(2,6-(C(H)dN-i-Pr)2C5H3N)]
(23)1 was produced. The purple complex 22 was formed at 230
K and decomposed after 24 h at room temperature. The
N-N-N ligand 8 did not react with [RhCl(COD)]2. The
intermediates 20, 21, and 22 could not be isolated.
Stu d y of th e in Situ F or m a tion of [Rh (2,6-(C(Me)dN-
p-a n isyl)2C5H3N)2]Cl (24). A NMR tube was filled at 195 K
with 0.0050 g of [RhCl(COD)]2 (1.0 × 10-5 mol) and 0.0081 g
of 9 (2.1 × 10-5 mol) in 1.0 mL of deuterodichloromethane. 1H
NMR spectra were recorded between 183 and 293 K. In the
range of 190-240 K, the dark green complex 24 was formed,
which could not be isolated. Increasing the temperature
caused 24 to react with excess [RhCl(COD)]2 to form the dark
green complex [RhCl(2,6-(C(Me)dN-p-anisyl)2C5H3N)] (25),
which was not isolated from the mixture but identified by
comparison with an authentic sample.1 Oxidative addition of
deuterodichloromethane to 25 took place at 298 K yielding
quantitatively the orange-yellow [RhCl2(CD2Cl)(2,6-(C(Me)dN-
p-anisyl)2C5H3N)] (26).
Con d u ctom etr y. A representative measurement is pre-
sented for complex 15. At 293 K, 0.0053 g of 15 (1.3 × 10-5
mol, 1.3 × 10-3 mol/L) was dissolved in 10.0 mL of distilled
dichloromethane and the conductivity was measured. The
molar conductivities of the other complexes were measured
for concentrations varying between 1.0 and 2.0 mmol/L in
dichloromethane at 293K. The conductivity values Λ (Ω-1 cm2
mol-1) at 293 K are as follows: 11, 69; 12, 56; 13, 52; 14, 2.2;
15, 1.3; and 16, 2.1.
Syn th esis of [Rh Cl(2-(C(H)dN-R2)-6-(Me)C5H3N)(NBD)]
(R2 ) i-P r (14), t-Bu (15), a n d p-An isyl (16)). A representa-
tive synthesis is presented for complex 16. To a solution of
0.025 g of [RhCl(NBD)]2 (5.0 × 10-5 mol) in 1 mL of dichloro-
methane was added a solution of 0.021 g of 4 (10 × 10-5 mol)
in 1 mL of dichloromethane at 195 K. After the red solution
was warmed to room temperature, dichloromethane was
evaporated giving a sticky residue, which was washed with
benzene (3 × 1 mL) and pentane (3 × 1 mL). The resulting
red powder, was dried in vacuo. Yield: 0.036 g (7.8 × 10-5
mol, 78%). The yield of 14 is 75% and that of 15 is 85%.
Anal. Calcd for C17H22ClN2Rh (14): C, 51.98; H, 5.65; N,
7.13. Found: C, 51.84; H, 5.66; N, 7.17. Anal. Calcd for
C
18H24ClN2Rh (15): C, 53.15; H, 5.95; N, 6.89. Found: C,
53.20; H, 6.04; N, 6.94. Elemental analysis of 16 was not
carried out, as 16 is completely analogous to 14 and 15.
FABMS for 14 (C17H22ClN2Rh) (obsd m/z, calcd m/z): 392.0500,
392.0519. FABMS for 15 (C18H24ClN2Rh) (obsd m/z, calcd
m/z): 406.0690, 406.0676. FABMS for 16 (C21H22ClN2ORh)
(obsd m/z, calcd m/z): 456.0450, 456.0468.
1H NMR of Mixtu r es of F r ee Liga n d 2 a n d Com p lex
14 a s a F u n ction of Tem p er a tu r e. A NMR tube was filled
with 0.0055 g of 14 (1.4 × 10-5 mol) which was dissolved in
1
0.83 g (0.63 mL) of CD2Cl2. At 294, 243, and 183 K, H NMR
spectra were measured. After 1.2 µL (7.0 × 10-6 mol) and 4.8
µL (28 × 10-6 mol) of free ligand 2 were added, 1H NMR
spectra were recorded at the same temperatures. Addition of
1
free ligand had no effect on the exchange rate, as the H NMR
signals of complex 14 and of the free ligand 2 were unaffected,
showing the absence of intermolecular exchange of the N-N
nitrogen ligand on the NMR time scale.
In ter m olecu la r Exch a n ge of Cl- betw een 11 a n d 14
a n d 12 a n d 15. A representative measurement is presented
for complexes 11 and 14. A NMR tube was filled with 0.0045
g of 11 (8.8 × 10-6 mol), 0.0035 g of 14 (8.9 × 10-6 mol), and
0.79 g (0.60 mL) of deuterodichloromethane. At 183 and 293
Ca lcu la tion of ∆Gq.7 The ∆Gq(coalescence) values are 37
( 2 kJ /mol for 11 (measured on H(12) at 195 K) and 46 ( 2
kJ /mol for 15 (measured on H(12) at 228 K). The values for
18 are 39 ( 2 kJ /mol (measured on H(4) at 218 K), 41 ( 2
kJ /mol (measured on H(7) at 208 K), and 41 ( 2 kJ /mol
(measured on H(12) at 208 K).
1
K, H NMR spectra were recorded. The signals of complexes
11 and 14 could not be observed separately. At 183 K, the
signals had already coalesced at the weighted mean, which
indicates very fast exchange of Cl- between 11 and 14. Similar
measurements for mixtures of 12 and 15 showed an analogous
behavior.
X-r a y Str u ctu r e Deter m in a tion of 14 a n d 19. Crystals
of 14 (orange) and 19 (red) were glued to the tip of a
Lindemann glass capillary (inert oil technique) and transferred
into the cold nitrogen stream of an Enraf-Nonius CAD 4 T
diffractometer on a rotating anode. Accurate unit-cell param-
eters were derived from a least-squares fit of the setting angles
of 25 reflections (SET4)8 in the range 11 < θ < 14°. The unit
cell was checked for higher lattice symmetry.9 Crystal data
and details on collection and refinement are presented in Table
1. An empirical correction for absorption was done with
DIFABS10 for both complexes. The structures were solved by
automated Patterson/Fourier techniques (DIRDIF92).11 The
Syn th esis of [Rh Cl(2,6-(C(H)dN-R2)2C5H3N)(NBD)] (R2
) i-P r (17), t-Bu (18), a n d p-An isyl (19)). A representative
synthesis is given for complex 19. To a solution of 0.22 g of
[RhCl(NBD)]2 (0.47 mmol) in 50 mL of dichloromethane was
added a solution of 0.32 g of the N-N-N ligand 7 (0.95 mmol)
in 5 mL of dichloromethane at 298 K affording a red colored
solution. The reaction mixture was concentrated to a small
volume, and pentane was added, after which fast crystalliza-
tion occurred. The product could be recrystallized from a small
volume of dichloromethane at -20 °C as block-shaped red
crystals. Yield: 0.42 g (0.87 mmol, 93%) of pure product. The
yields of the other compounds varied from 90 to 97%.
Anal. Calcd for C28H27ClN3O2Rh (19): C, 58.39; H, 4.72;
N, 7.29. Found: C, 58.04; H, 4.56; N, 7.25. FABMS for 17
(C20H31ClN3Rh) (obsd m/z - Cl, calcd m/z - Cl): 412.1243,
412.1253. FABMS for 18 (C22H31ClN3Rh) (obsd m/z, calcd
m/z): 475.1248, 475.1254. FABMS for 19 (C28H27ClN3O2Rh)
(obsd m/z, calcd m/z): 575.0905, 575.0840.
2
structures of F were refined by full-matrix least-squares
techniques (SHELXL93).12 Hydrogen atoms were taken into
account at calculated positions except for those on C(22), C(23),
C(25), and C(26) for 14, that were located from a difference
map, and their positional parameters were refined. The
(7) Faller, J . W. Adv. Organomet. Chem. 1977, 16, 211.
(8) de Boer, J . L.; Duisenberg, A. J . M. Acta Crystallogr. 1984, A40,
C410.
(9) Spek, A. L. J . Appl. Crystallogr. 1988, 21, 578.
(10) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.
(11) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF program system: Technical report of the crystallographic
laboratory.; Univerisity of Nijmegen: Nijmegen, The Netherlands,
1992.
1H NMR of Mixtu r es of F r ee Liga n d 6 a n d Com p lex
18 a s a F u n ction of Tem p er a tu r e. A NMR tube was filled
with 0.0037 g of 18 (7.7 × 10-6 mol) and 0.710 g of CD2Cl2
(0.500 mL). 1H NMR spectra were recorded at 183, 204, and
298 K. After 0.0010 g of the N-N-N ligand 6 (4.1 × 10-6
1
mol) was added, H NMR spectra were recorded at the same
temperatures. The addition of free ligand had no effect on the
1
widths and positions of the H NMR signals of 18 showing the
(12) Sheldrick, G. M. SHELXL93. Program for Crystal structure
refinement.; University of Go¨ttingen: Germany, 1993.
absence of intermolecular ligand exchange.

Reactions of [RhCl(diene)]2
Organometallics, Vol. 16, No. 1, 1997 57
Ta ble 1. Cr ysta llogr a p h ic Da ta for 14 a n d 19
14
Crystal Data
19
formula
C17H22ClN2Rh
392.73
orthorhombic
Pbca (no. 61)
8.5907(8)
C28H27ClN3O2‚3/2CH2Cl2
703.30
molecular weight
crystal system
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c (no. 14)
10.5446(7)
14.6353(7)
21.2040(7)
115.845(4)
2945.0(3)
1.586
12.9657(9)
29.014(5)
â (deg)
V (Å3)
3231.7(7)
1.614
8
D
Z
calc (g cm-3
)
4
F(000)
1600
12.2
0.10 × 0.38 × 0.63
1428
9.6
0.75 × 0.63 × 0.25
µ (Mo KR) (cm-1
)
crystal size (mm)
Data Collection
150
T (K)
175
θ
min, θmax
1.4, 27.4
0.710 73 (Mo KR)
ω
0.69 + 0.35 tan Θ
0:11; -13:16; 0:37
6270
1.8, 27.4
0.710 73 (Mo KR)
ω/2Θ
0.58 + 0.35 tan Θ
-13:13; -18:0; -27:20
9597
wavelength (Å)
scan type
∆ω (deg)
data set
total data
total unique data
total obsd [I > 2σ(I)]
DIFABS corr. range
3686 (Rint ) 0.062)
6719 (Rint ) 0.021)
2346
5432
0.69:1.57
0.91:1.11
Refinement
205
0.052
no. of refined params
345
0.040
0.103
a
final R1
b
final wR2
0.113
goodness of fit (S)
1.00
1.04
weighting schemec (w-1
)
σ2(Fo2) + (0.0327P)2
-0.80, 0.62
σ2(Fo2) + 0.049P2 + 3.19P
-0.79, 0.95
min and max residual density (e Å-3
)
a
b
2
R1 ) ∑(|Fo| - |Fc|)/∑|Fo|. wR2 ) {∑w(Fo - Fc2)2/∑w(Fï2)2}1/2
.
c P ) (max(Fo2, 0) + 2Fc2)/3.
F igu r e 1. Proposed structure of complex 10.
contribution of a disordered CHCl3 on an inversion center for
19 was taken into account following the BYPASS procedure13
as implemented as the SQUEEZE option in PLATON.14
Neutral atom scattering factors and anomalous dispersion
corrections were taken from the International Tables for
Crystallography.15 Geometrical calculations and illustrations
were performed by PLATON.14
F igu r e 2. 1H NMR spectra in the region 9.6-7.6 ppm of
10 at 183, 253, and 293 K.
3
ppm, with a J (H(2)-H(3)) coupling constant of 5.0 Hz,
and to H(2′) at 8.04 ppm, also with a 3J (H(2′)-H(3))
coupling constant of 5.0 Hz. At 253 K, the signals
disappeared in the base line and finally coalesced at 293
K. The temperature had no effect on the position of
H(3), since at 183 K, 253 K, and 293 K, H(3) resonates
at 7.77 ppm (Figure 2). We have found by measuring
the 1H NMR spectra of mixtures of complex 10 and bpm
at 183 K that in addition to this intramolecular ex-
change, intermolecular exchange of the bpm ligand
occurs. At this temperature, e.g., for a mixture of 2
equiv of bpm per equiv of complex 10, the signals of the
coordinated and noncoordinated bpm have coalesced.
Resu lts
Syn th esis a n d Ch a r a cter iza tion of [Rh (bp m )-
(NBD)]OTf (10). For compound 10 (Figure 1), which
1
was prepared from [RhOTf(NBD)] and bpm (1), the H
NMR spectra (Table 4, Figure 2) at 183 K showed two
signals from the bpm ligand belonging to H(2) at 9.16
(13) van der Sluis, P.; Spek, A. L. Acta Crystallogr. 1990, A46, 194.
(14) Spek, A. L. Acta Crystallogr. 1990, A46, C34.
(15) Wilson, A. J . C. International Tables for Crystallography;
Kluwer Academic Publishers: Dordrecht, The Netherlands, 1992; Vol.
C.

58 Organometallics, Vol. 16, No. 1, 1997
Ta ble 2. 1H NMRa Da ta of th e Liga n d s 2-9
Haarman et al.
ligand
H(2)
H(3)
H(4)
H(5)
H(6) H(8)
H(7)
2b
7.81 [d, 1H]
7.15 [d, 1H]
7.79 [d, 1H]
7.16 [d, 1H]
8.00 [d, 1H]
7.32 [d, 1H]
8.03 [d, 2H]
8.01 [d, 2H]
8.25 [d, 2H]
7.60 [d, 1H]
8.37 [s, 1H]
2.58 [s, 3H]
3.62 [sp 1H]
1.26 [d, 6H]
3c
4b
7.61 [t, 1H]
7.87 [t, 1H]
8.29 [s, 1H]
8.61 [s, 1H]
2.54 [s, 3H]
2.53 [s, 3H]
1.29 [s, 9H]
3.83 [s, 3H]
3.66 [sp, 2H]
3.86 [s, 6H]
7.33 [d, 2H]
6.94 [d, 2H]
1.29 [d, 12H]
1.31 [s, 18H]
6.97 [d, 4H]
7.36 [d, 4H]
1.24 [d, 12H]
6.84 [d, 4H]
6.95 [d, 4H]
5b,d
6c,d
7c,d
7.79 [t, 1H]
7.79 [t, 1H]
7.92 [t, 1H]
8.44 [s, 2H]
8.36 [s, 2H]
8.67 [s, 2H]
8b,d
9b,d
8.06 [d, 2H]
8.27 [d, 2H]
7.68 [t, 1H]
7.89 [t, 1H]
2.40 [s, 3H]
2.37 [s, 3H]
3.93 [sp, 2H]
3.84 [s, 6H]
a
b
1H NMR spectra were recorded at room temperature at 300.13 MHz; s ) singlet, d ) doublet, t ) triplet, sp ) septet. CDCl3.
c CD2Cl2. Taken from ref 1.
d
Ta ble 3. 13C NMR Da ta of th e Liga n d s 2-9
ligand
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
24.3
29.7
122.9, 114.8
24.5
30.0
115.0, 123.3
23.2
C(8)
55.8
2a,b
3a,b
4a,b
5b,d
6c,d
7c,d
8b,d
9b,d
158.3, 154.9
158.0, 155.5
159.3, 158.8
155.1
156.0
158.3
124.2, 118.2
123.9, 117.7
124.7, 118.7
122.6
122.0
123.0
136.8
136.7
137.0
137.5
137.6
137.7
136.3
137.3
159.8
156.9
159.2
159.6
156.8
158.3
163.5
167.9
24.4
24.3
24.5
61.7
65.9
154.8, 144.3
61.9
58.5
144.1,e 156.0f
51.3
56.0
56.0
156.4
156.8
120.8
122.7
13.1
16.7
144.3,e 156.3f
114.8, 121.4
a
b
d
13C NMR spectra were recorded at room temperature at 50.32 MHz. CD2Cl2. c CDCl3. 13C NMR spectra were recorded at room
temperature at 75.47 MHz and were taken from ref 1. e C(6). f Para-C(6′).
Ta ble 4. 1H NMRa of th e F ou r -Coor d in a te Ion ic Com p lexes 10-13
no.
(T (K))
H(2)
H(3)
H(4)d
H(5)
H(6)H(8)
H(7)
H(12)
H(13)
H(14)
10c (293) 8.67 [br s, 4H] 7.77 [t, 2H]
10c (183) 8.16 [dd, 2H] 7.78 [t, 2H]
8.04 [dd, 2H]
4.47 [s,e 4H]
4.49 [s,e 4H]
4.11 [s,e 2H] 1.26 [s,e 2H]
4.10 [s,e 2H] 1.48 [s,e 2H]
11c (293) 7.84 [d, 1H]
7.41 [d, 1H]
7.93 [t, 1H] 8.45 (2.6) [d, 1H] 2.26 [s, 3H] 3.14 [sp, 1H] 1.29g [d, 6H]
4.45 (2.1)d [dd, 4H]g 4.07 [s,e 2H] 1.46 [t, 2H]
11c (183) 7.36 [d, 1H]
7.74 [d, 1H]
7.91 [t, 1H] 8.36f [s, 1H]
2.16 [s, 3H] 2.99 [sp, 1H] 1.18g [br d, 6H] 4.64 [s,e 2H]g
4.02 [s,e 2H] 1.36 [s,e 2H]
4.08 [s,e 2H]g
4.55 (2.1)d [dd, 4H]g 3.95 [s,e 2H] 1.42 [t, 2H]
12c (293) 7.84 [d, 1H]
7.38 [d, 1H]
7.99 [t, 1H] 8.33 (2.4) [d, 1H] 2.28 [s, 3H]
1.29g [s, 9H]
1.18g [s, 9H]
12c (183) 7.57 [d, 1H]
7.33 [d, 1H]
13b (293) 7.99 [d, 1H]
7.34 [d, 1H]
7.95 [t, 1H] 8.20f [s, 1H]
2.17 [s, 3H]
4.47 [s,e 4H]g
3.95 [dd, 4H]
3.89 [s,e 2H] 1.32 [s,e 2H]
3.85 [s,e 2H] 1.25 [s,e 2H]
7.91 [t, 1H] 8.51 (2.1) [d, 1H] 2.50 [s, 3H] 3.83 [s, 3H] 7.32 [d, 2H]
6.92 [d, 2H]
a
1H NMR spectra were recorded at 300.13 MHz; s ) singlet, d ) doublet, dd ) double doublet, t ) triplet, sp ) septet, br ) broad.
CDCl3. c CD2Cl2. J (Rh-H). e No coupling observed. f Owing to line broadening, no J (103Rh-H(4)) could be observed. There is a clear
temperature dependent chemical shift varying between 0.08 and 0.36 ppm. J (H-H) in Hz.
b
d
g
h
Sch em e 1. Syn th esis of th e Ion ic Com p lexes
Syn t h esis a n d Ch a r a ct er iza t ion of [R h (2-
(C(H)dN-R2)-6-(Me)C5H3N)(NBD)]OTf (R2 ) i-P r
(11), t-Bu (12), a n d p-An isyl (13)). Complexes 11-
13 have been synthesized in quantitative yield in
dichloromethane by reaction of the corresponding N-N
ligands 2-4 with [RhOTf(NBD)], which was prepared
from [RhCl(NBD)]2 and AgOTf (Scheme 1). Coordina-
tion of NBD and the N-N ligands could be inferred from
the chemical shift differences between the free and
coordinated ligands (Table 2-5). The complexes 11-
13 could not be stored longer than 1 day, owing to
decomposition.
11-13a
At 183 K, as expected, the nonequivalent olefinic
hydrogen atoms H(12a) and H(12b) of 11 (Scheme 1)
have been observed as two signals, since 11 has Cs
symmetry, while at 195 K, the signals of H(12a) and of
H(12b) have coalesced. The nonequivalent olefinic
hydrogen atoms could only be observed as separate
signals when the compound and the solvents were
completely pure as traces of acetone or Cl- accelerated
the exchange. The ∆Gq of the exchange process, as
a
For the sake of clarity the rhodium atom has been omitted.
calculated at the coalescence temperature, is 37 ( 2 kJ /
mol (see the Experimental Section).
It is important to note that on the imine hydrogen
H(4) of complexes 11-13 a 3J (1H-103Rh) coupling
constant in the range of 2.1-2.6 Hz has been observed

Reactions of [RhCl(diene)]2
Organometallics, Vol. 16, No. 1, 1997 59
Ta ble 5. 13C NMR of th e F ou r -Coor d in a te Ion ic Com p lexes 11-13
no.
C(1)
C(2)
C(3)
C(4)
C(5)
23.7
C(6)
C(7)
24.9
C(8)
C(12)
C(13)
C(14)
11a,b
164.7
157.1
163.8
156.0
163.8
155.4
164.5
156.2
163.7
155.0
131.8
127.7
131.2
126.7
130.4
127.2
131.4
127.9
130.8
128.6
142.8
169.1
56.6 (3)c
65.6
(10)c
g
54.0
(3)c
53.3
65.4
(6)c
g
11b,f,h
12b,d
12b,f
13a,b
142.2
141.5
142.8
141.3
167.8
166.8
167.1
168.7
22.8
23.7
25.0
23.9
64.5
65.8
66.9i
24.5
29.9
30.6
61.3
(10)c
65.8
51.9e
53.1
64.5e
i
139.9 (2)c
155.0
115.1
123.1
56.0
63.5
52.2
(3)c
63.7e
(10)c
13C NMR spectra were recorded at room temperature at 50.32 MHz. CD2Cl2. c J (Rh-C) in Hz. 13C NMR spectra were recorded at
a
b
d
room temperature at 75.47 MHz. e No coupling observed. f 13C NMR spectra were recorded at 183 K at 75.47 MHz. g Has not been observed.
CF3SO3 has been observed at 127.6, 123.4, 119.1, and 114.9 ppm. C(6) and C(14) probably overlap.
h
i
Ta ble 6. 1H NMRa of th e Neu tr a l F ive-Coor d in a te Com p lexes 14-16
no. (T (K))
H(2)
H(3)
H(4)
H(5)
H(6) H(8)
H(7)
H(12)
H(13)
H(14)
14 (293) 7.47 [d, 1H] 7.75 [t, 1H] 8.34 [s, 1H] 3.61 [s, 3H] 4.33 [sp, 1H] 1.83 [d, 6H] 3.00 (2.3)b [br d, 4H]e 3.57 [s,c 2H] 1.06 [s,c 2H]
7.35 [d, 1H]
14 (183) 7.42 [d, 1H] 7.74 [t, 1H] 8.32 [s, 1H] 3.35 [s, 3H] 4.05 [sp, 1H] 1.68 [d, 6H] 2.96 [s,c 4H]e
3.50 [s,c 2H] 0.97 [s,c 2H]
7.39 [d, 1H]
15 (293) 7.48 [d, 1H] 7.72 [t, 1H] 8.37 [s, 1H] 3.74 [s, 3H]
1.88 [s, 9H] 2.92 (2.1)b [br d, 4H]e 3.57 [s,c 2H] 1.03 [s,c 2H]
7.35 [d, 1H]
15 (183) 7.48 [d, 1H] 7.74 [t, 1H] 8.28 [s, 1H] 3.65 [s, 3H]
1.79 [s, 9H] 2.89 [s,c 2H]e
2.67 [s,c 2H]e
3.49 [s,c 2H] 0.93 [s,c 2H]
7.35 [d, 1H]
16 (293) 7.47d [d, 2H] 7.73 [t, 1H] 8.49 [s, 1H] 3.62 [s, 3H] 3.92e [s, 3H] 8.36 [d, 2H] 2.97 (2.1)b [br d, 4H]e 3.41 [s,c 2H] 0.92 [s,c 2H]
16 (183) 7.43 [d, 1H] 7.58 [t, 1H] 8.53 [s, 1H] 3.48 [s, 3H] 3.86e [s, 3H] 8.32 [d, 2H] 2.87 [s,c 4H]e
7.38 [d, 1H] 7.01 [d, 2H]
3.42 [s,c 2H] 0.93 [s,c 2H]
a
b
1H NMR spectra were recorded in CD2Cl2 at 300.13 MHz; s ) singlet, d ) doublet, t ) triplet, sp ) septet, br ) broad. Residual
coupling. c No coupling observed. Accidental degenerate. e There is a clear temperature dependent chemical shift varying between 0.04
d
and 0.14 ppm.
Sch em e 2. Rea ction of th e Nitr ogen Liga n d s 2-4
(Table 4) at room temperature, for 12 the temperature
w ith [Rh Cl(NBD)]2 To F or m 14-16a
range is 193-298 K, which shows that the nitrogen
ligand remains coordinated on the NMR time scale.
Also, at room temperature, a coupling constant of 2.1
Hz was observed on the olefinic hydrogen H(12) signals
owing to coupling with 103Rh (Table 4). The 103Rh-
13C{1H} coupling constants for C(12) and C(13) of 11-
13, for C(14) of the NBD ligand for complex 11, and for
C(6) in the case of complexes 11 and 13, even at room
a
For the sake of clarity the rhodium atom has been omitted.
temperature, corroborate the intramolecular nature of
the exchange (Table 5).
Addition of N-N ligand 2 to complex 11 at 183 K
methyl atoms H(7), and the olefinic hydrogen atoms
caused extra line broadening of the H(12a) and H(12b)
signals of which the rate 1/τ, measured on these signals,
increased with increasing ligand concentration. How-
ever, no intermolecular ligand exchange occurred at 183
K, as the signals of the coordinated and noncoordinated
nitrogen ligand remained sharp. When we increase the
temperature, we also observe intermolecular exchange
of the N-N ligand. Concentration-dependent measure-
ments at 263 K showed that the rate 1/τ, measured on
the Me-substituent of both complex 11 and the N-N
ligand 2, is linearly dependent on the concentration of
the ligand and complex. The 1/τ (Me) of the complex
as a function of the ligand concentration goes through
zero, implying that 1/τ (complex) ) k[2].
H(12), methine hydrogen atoms H(13), and the meth-
ylene hydrogen atoms H(14) of the NBD ligand of 14-
16 are different from those of the ionic complexes 11-
1
13. From the relevant H and 13C NMR chemical shifts
collected in Tables 8 and 9 it is clear from the alkene
chemical shifts that complexes 14-16 have a trigonal
bipyramidal (TBP) structure in solution.
F lu xion a l P r ocesses. At 183 K, the olefinic hydro-
gen atoms H(12) of complex 15 appear as two signals
and not as four, as one might expect, since the olefinic
hydrogen atoms H(12a), H(12b), H(12c), and H(12d)
(Scheme 2) should all be inequivalent for a five-
coordinate TBP conformation if the geometry is analo-
gous to the solid state structure of 14 (Figure 3). This
is likely in view of the chemical shift values of the
olefinic atoms (Tables 8 and 9). Also, the methine
hydrogen atoms H(13a) and H(13b) appear as one signal,
although two signals might be expected. The olefinic
H(12) signals of complex 15 coalesced at 228 K with ∆Gq
) -46 ( 2 kJ /mol. In the case of complexes 14 and 16,
the olefinic hydrogen atoms H(12) already appeared as
one signal at 183 K, indicating very fast dynamic
processes even below this temperature.
Syn t h esis a n d Ch a r a ct er iza t ion of [R h Cl(2-
(C(H)dN-R2)-6-(Me)C5H3N)(NBD)]; R2 ) i-P r (14),
t-Bu (15), a n d p-An isyl (16). Complexes 14-16 have
been prepared in quantitative yield by reaction of the
corresponding ligands 2-4 with [RhCl(NBD)]2 in dichlo-
romethane (Scheme 2). Ligand coordination was obvi-
ous from the chemical shift differences between the free
and coordinated ligands for both the N-N and the NBD
ligands (Tables 2, 3, 6, and 7).
The chemical shifts of the pyridine methyl hydrogen
atoms H(5), the i-Pr hydrogen atoms H(6) and the i-Pr
The observed coalescence pattern for 15 at 183 K
shows fast exchange between the N and N* sites

60 Organometallics, Vol. 16, No. 1, 1997
Ta ble 7. 13C NMR of th e Neu tr a l F ive-Coor d in a te Com p lexes 14-16
Haarman et al.
no.
C(1)
C(2)
C(3)
C(4)
C(5)
27.6
C(6)
62.6
C(7)
25.1
C(8)
C(12)
C(13)
C(14)
14a,b
161.0
153.0
162.1
153.2
161.9
153.4
162.0
153.3
159.8
152.5
126.7
124.5
127.8
125.5
126.6
124.9
127.5
125.7
126.3
124.7
137.5
159.7
35.3 (9)c
47.5f
47.7f
47.8f
47.6f
46.9f
58.1 (6)c
14b,g
15b,e
15b,g
16a,d
138.3
137.6
138.5
136.8
160.6
158.5
159.3
156.4
27.7
27.9
28.7
27.1
62.3
62.0
62.7
25.5h
31.8
32.2
35.8h
i
58.5h
58.0h
35.1 (10)c
35.9f
57.8 (7)c
57.5 (6)c
131.3
142.6
124.2
114.1
55.3
a
b
d
13C NMR spectra were recorded at room temperature at 50.32 MHz. CD2Cl2. c J (Rh-C). CDCl3. e 13C NMR spectra were recorded
at room temperature at 75.47 MHz. f No coupling observed. g 13C NMR spectra were recorded at 183 K at 75.47 MHz. Broad. Has not
h
i
been observed.
Ta ble 8. Selected 1H NMR Ch em ica l Sh ifts (p p m ) for th e Olefin ic H(12), Meth in e H(13), a n d Meth ylen e
H(14) Hyd r ogen Atom s for Differ en t Geom etr ies
H(12)
H(13)
H(14)
Square Planar Complexes
11-13
3.95-4.65a
3.90-4.75
4.17d
3.85-4.07
3.50-3.80
3.77
1.18-1.45
1.05-1.45
1.39
[Rh(NBD)(monothio-â-ketonate)]b
[Rh(NBD)(PPh3)Cl]c
4.04d
3.60
1.13
e
[Rh(NBD){(pyrazolyl)2PhCH}]PF6
Square Pyramidal Complexes
[Rh(NBD)(dppp)(SnCl3)]f 298 K
[Rh(NBD)(dppp)(SnCl3)]f 243 K
[Rh(NBD)(dppb)(SnCl3)]f 298 K
[Rh(NBD)(dppb)(SnCl3)]f 243 K
3.80
3.40
3.47
3.26
3.23
1.40
1.40
1.26
1.26
3.81d
3.69d
3.73d
Trigonal Bipyramidal Complexes
14-16
2.47-3.07a
2.65-3.03
2.58d
3.42-3.57
3.35-3.56
3.14
0.93-1.06
0.91-1.05
0.91
17-19
[Rh(NBD)(PMe2Ph)2(Me)]g 300 K
[Rh(NBD)(PMePh2)2(Me)]g 253 K
[Rh(NBD)(PPh3)(Me)]g 238 K
2.76d
2.92d
0.82
3.20d
2.78d
0.93
3.54i
3.96i
1.45i
h
[Rh(NBD)(bis(indazol-1-yl)pyridin-2′-ylmethane)]PF6
A range is given. b Reference 29. c Reference 26. Average value. e Reference 35. f Reference 36. g Reference 37. Reference 21. i CDCl3.
a
d
h
Ta ble 9. 13C NMR Ch em ica l Sh ifts (p p m ) for th e C(12), C(13), a n d C(14) Ca r bon Atom s for Differ en t
Geom etr ies
vinyl C(12)
methine C(13)
methylene C(14)
Square Planar Complexesa
61.3-65.6b (10)c
57.0,h 57.6 (9.7)c
59.8
11-13
51.9-54.0 (3)d
50.8,h 50.6(2.0)c
50.2 (1.9)c
63.7-65.4 (6)d
62.7, 62.7 (6.1)c
62.0 (6.2)c
[Rh(NBD)(TpiPr, 4Br)]e-g
[Rh(NBD){(pyrazolyl)2PhCH}]PF6
i
Trigonal Bipyramidal Complexes
35.1-35.9 (9-10)b,d
14-16
46.9-47.6b,h
46.9-47.9 (2-3)b,d
48.9 (2.5)c
57.5-58.1 (6-7)b,c
57.4-58.6 (6-7)b,d
59.5 (6.6)c
17-19
35.2-37.0 (9-10)b,d
[Rh(NBD)(TpMe)]e,g
41.9 (broad)
i,j
[Rh(NBD)(bis(indazol-1-yl)pyridin-2′-ylmethane)]PF6
41.4 (13)c
47.9 (2.7)c
59.0 (6.6)c
Unfortunately, no 13C NMR chemical shift could be found in the literature for square pyramidal NBD complexes of Rh(I). A range
a
b
is given. c Rh-C coupling. Rh-C coupling is not in all cases observed. e Reference 20. f Two isomers, which differ in the positioning of
d
one noncoordinating pyrazolyl group, were observed. g The nomenclature for tris(pyrazolyl)borate ligands and their complexes, as proposed
h
i
j
by Trofimenko38 is used. No coupling observed. Reference 35. Reference 21.
rendering H(12a) and H(12b) (Scheme 2) equivalent as
well as H(12c) and H(12d) and of course H(13a) and
H(13b).
neutral five-coordinate complex 14 or 15, as the result-
ing spectra at 183 K and at room temperature showed
a weighted average of the spectra of 11 and 14 and of
12 and 15, respectively, instead of the spectra of the
separate species. It is clear that fast Cl- exchange must
occur either via dissociation of a small amount of Cl-
from the neutral complex or via an intermediate bi-
nuclear species with the Cl atom bridging between both
Rh(I) atoms. Since chloride exchange will equilibrate
all olefinic H(12) hydrogen atoms, it seems logical to
assume that this is the main cause of the coalescence
of the two olefinic H(12) signals to one in the temper-
ature range from 228 K to room temperature in the case
of complex 15, where R2 is the bulky t-Bu group. In
the case of the less bulky substituents i-Pr (complex 14)
and p-anisyl (complex 16), chloride exchange is clearly
Addition of free ligand 2 (0.5 and 2.0 equiv) to a
solution of complex 14 had no effect on the number and
1
line widths of the H NMR signals of the free ligand 2
and of complex 14 at 183-298 K. It is therefore clear
that in the case of these five-coordinate complexes, no
exchange occurs between free and coordinated ligand,
in contrast to what we have observed for the ionic four-
coordinate complex 11. Although complexes 14-16 are
nonconducting in dichloromethane (see the Experimen-
tal Section), the possibility of Cl- exchange has to be
taken into account for the higher temperature process.
This has been strikingly demonstrated for a 1:1 mixture
of the four-coordinate ionic complex 11 or 13 and the

Reactions of [RhCl(diene)]2
Organometallics, Vol. 16, No. 1, 1997 61
of complexex 14 and 19 lies 0.058(1) and 0.068(1) Å,
respectively, out of the N(1), N(2), C(22)dC(23) plane.
The angle between the line connecting the rhodium
atom with the center of the axial C(25)dC(26) bond and
the line connecting the rhodium atom with the Cl(1)
atom in the TBP is 16.0° in 14 and 13.9° in 19.
In Table 13 reported bond lengths have been collected,
for the sake of comparison, for square planar, square
pyramidal, and trigonal bipyramidal rhodium norbor-
nadiene complexes containing nitrogen ligands.
The Rh-Cl σ-bonds of 14 and 19, which are 2.3972(17)
and 2.3888(9) Å, respectively, are both shorter than
those reported for five-coordinate square pyramidal (SP)
rhodium chloride complexes.16 This indicates, as ex-
pected for a TBP structure,19 a stronger Rh-Cl σ-bond
in the TBP geometry than in the SP geometry.
F igu r e 3. An ORTEP plot of complex 14 at 50% prob-
ability level along with the adopted numbering scheme.
Also, it is clear that in complexes 14 and 19, the
π-back-bonding in the equatorial plane is stronger than
that in the axial position, as indicated by the shorter
Rh-C (olefinic) and longer C-C (olefinic) bonds for the
equatorial alkene bond when compared to the longer
Rh-C (olefinic) and shorter C-C (olefinic) bonds in the
axial position. These features have also been observed
for the TBP complexes [Rh(NBD)TpMe)]20 and [Rh-
Sch em e 3. Syn th esis of 17-19
21
(NBD)(bis(indazol-1-yl)pyridin-2′-ylmethane))]PF6
(Table 13).
The Rh-N bond lengths in complexes 14 and 19 lie
in the range from 2.248(4) to 2.283(3) Å and are
comparable to the ones observed for rhodium(I) norbor-
nadiene complexes with a TBP structure, but are 0.2 Å
longer than those found for four-coordinate rhodium(I)
norbornadiene compounds (Table 13). As in the case
of the five-coordinate palladium and platinum com-
plexes [(N-N)Pd(alkene)X2] reported by Albano et al.,22
the equatorial metal-nitrogen bonds in the TBP struc-
tures are longer than those in the corresponding four-
coordinate square planar complexes, which may be
ascribed to two factors.22 Firstly, the electronic satura-
tion of the metal atom in five-coordinate complexes
weakens σ-donation. Secondly, there is less favorable
overlap between the donor orbitals and the relevant
metal orbitals due to the N-metal-N angle.22
easier, as at 183 K all four olefinic H(12) signals have
already coalesced to one (Table 6).
Syn th esis a n d Ch a r a cter iza tion of [Rh Cl(2,6-
(C(H)dN-R2)2C5H3N)(NBD)]; R 2 ) i-P r (17), t-Bu
(18), a n d p -An isyl (19). The five-coordinate rho-
dium(I) complexes 17-19 have been prepared in virtu-
ally quantitative yield by adding the N-N-N ligands
5-7 to [RhCl(NBD)]2 at room temperature in dichloro-
methane (Scheme 3). Coordination of the ligand and
NBD was clear from chemical shift differences between
the free and coordinated ligands (Tables 2, 3, 10, and
11). These complexes did not react further at room
temperature, in contrast to the 1,5-cyclooctadiene com-
plexes (vide infra). Corresponding complexes with the
N-N-N ligands 8 and 9 could not be prepared.
Solid Sta te Str u ctu r es of 14 a n d 19. ORTEP plots
at 50% probability level of 14 and 19, along with their
adopted numbering scheme, are given in Figures 3 and
4, respectively. Selected bond distances and angles have
been collected in Table 12 for 14 and 19.
The geometries of 14 and 19 around rhodium may be
described as a distorted TBP, with the two nitrogen
donor atoms of the nitrogen ligand and one alkene bond
of norbornadiene in the equatorial plane. The chloride
atom and the second alkene bond of norbornadiene are
coordinated in the axial position. The N(1)-Rh(1)-N(2)
angles of 73.53(16)° for complex 14 and of 72.91(9)° for
complex 19 are both rather small when compared to
other metal diimine complexes.16-18 The rhodium atom
Str u ctu r e in Solu tion a n d F lu xion a l Beh a vior
of 17-19. At 183 K, in CD2Cl2, the N-N-N ligands
5-7 in the complexes 17-19 are coordinated as biden-
tate ligands, as observed for 19 (see Figure 4), which is
clear from the inequivalency of the meta pyridine
hydrogen atom H(2), the imine hydrogen atoms H(4),
and the H(6) and H(7) atoms of the i-Pr group. Also,
the shifts of the methyl hydrogen atoms of the t-Bu
group H(7) of complex 18 and the hydrogen atoms H(7)
and H(8) of the p-anisyl ring of complex 19 (see Table
10) indicate bidentate bonding with a dangling imine
side arm, in accord with the molecular structure (vide
supra). 13C NMR measurements for complex 17 at 183
K (Table 11) showed inequivalent imine side arms and
two 13C signals for C(12) and one 13C signal for C(13),
1
in agreement with the H NMR spectra at 183 K (Table
10).
(18) Zassinovich, G.; Bettella, R.; Mestroni, G.; Bresciani-Pahor, N.;
Geremia, S.; Randaccio, L. J . Organomet. Chem. 1989, 370, 187.
(19) Rossi, A. R.; Hoffmann, R. Inorg. Chem. 1975, 14, 365.
(20) Bucher, U. E.; Currao, A.; Nesper, R.; Ru¨egger, H.; Venanzi,
L. M.; Younger, E. Inorg. Chem. 1995, 34, 66.
(21) Lo´pez Gallego-Preciado, M. C.; Ballesteros, P.; Claramunt, R.
M.; Cano, M.; Heras, J . V.; Pinilla, E.; Monge, A. J . Organomet. Chem.
1993, 450, 237.
(22) Albano, V. G.; Natile, G.; Panunzi, A. Coord. Chem. Rev. 1994,
133, 67.
(16) Robertson, J . J .; Kadziola, A.; Krause, R. A.; Larsen, S. Inorg.
Chem. 1989, 28, 2097.
(17) Iglesias, M.; del Pino, C. J . R.; Blanco, S. G.; Carrera, S. M. J .
Organomet. Chem. 1988, 338, 89.

62 Organometallics, Vol. 16, No. 1, 1997
Ta ble 10. 1H NMRa of th e F ive-Coor d in a te Com p lexes 17-19
Haarman et al.
no. (T (K))
H(2)
H(3)
7.90b
H(4)
H(6) H(8)
H(7)
H(12)
H(13)
H(14)
17 (293)
17 (183)
7.90b [s, 3H]
8.11 [d, 1H]
7.60 [d, 1H]
9.51 [s, 2H] 4.22 [sp, 2H]
1.65 [d, 12H]
2.99c [sd, 4H] 3.54 [s,d 2H] 1.06 [s,d 2H]
7.92 [t, 1H] 10.37 [s, 1H] 4.14 [br sp, 1H] 1.74 [br d, 6H] 3.00c [sd, 2H] 3.46 [s,d 2H] 0.96 [s,d 2H]
8.40 [s, 1H] 3.96 [br sp, 1H] 1.30 [br d, 6H] 2.82c [sd, 2H]
18 (293)
18 (183)
7.91b [m, 3H] 7.91b
9.57 [s, 2H]
1.72 [s, 18H]
1.82 [s, 9H]
1.46 [s, 9H]
2.94c [sd, 4H] 3.55 [s,d 2H] 1.04 [s,d 2H]
2.97c [sd, 2H] 3.47 [s,d 2H] 0.93 [s,d 2H]
2.66c [sd, 2H]
8.18 [d, 1H]
7.57 [d, 1H]
8.11 [d, 2H]
7.90 [t, 1H] 10.66 [s, 1H]
8.36 [s, 1H]
7.98 [t, 1H]
19 (293)
19 (183)
9.79 [s, 2H] 3.91 [s, 6H]
8.04 [br d, 4H] 3.03c [sd, 4H] 3.41 [s,d 2H] 1.02 [s,d 2H]
7.10 [d, 4H]
8.36 [d, 1H]
7.67 [d, 1H]
7.79 [t, 1H] 11.01 [s, 1H] 3.88 [s, 3H]
8.59 [s, 1H] 3.84 [s, 3H]
7.04 [d, 4H]
7.67 [d, 2H]
8.41 [d, 2H]
2.93c [sd, 4H] 3.35 [s,d 2H] 0.93 [s,d 2H]
a
b
1H NMR spectra were recorded in CD2Cl2 at 300.13 MHz; s ) singlet, d ) doublet, t ) triplet, sp ) septet, br ) broad. H(2) and H(3)
overlap. c There is a clear temperature dependent chemical shift between 0.08 and 0.13 ppm. No coupling observed.
d
Ta ble 11. 13C NMR of th e F ive-Coor d in a te Com p lexes 17-19
no.
C(1)
C(2)
C(3)
C(4)
C(6)
C(7)
C(8)
C(12)
C(13)
C(14)
17a,b
17d,e
17b,g
154.6
154.0
155.6
153.2
154.8
156.5
153.7
154.8
125.8
125.4
128.8
124.6
125.5
129.1
124.3
126.4
137.9
137.3
139.1
160.2
159.5
161.9
159.8
157.4
159.1
158.2
158.0
62.6
62.1
63.8
63.6
57.4
63.3
60.2
160.4
143.5
24.8
24.4
26.5-
24.5h,i
30.5
32.1
30.2
124.5
36.6 (10)c
35.4 (10)c
36.2h 35.2h
47.6 (3)c
46.9 (2)c
47.9f
58.1 (7)c
57.7 (7)c
58.6f
18d,e
18b,g
137.2
139.0
35.3 (10)c
j
47.2f
48.1f
57.4 (6)c
56.0f
19a,b
138.1
114.9
37.0 (9)c
47.8f
58.5 (6)c
a
b
d
13C NMR spectra were recorded at room temperature at 50.32 MHz. CD2Cl2. c J (Rh-C). 13C NMR spectra were recorded at room
temperature at 75.47 MHz. e CDCl3. f No coupling visible. g 13C NMR spectra were recorded at 183 K at 75.47 MHz. Broad. Range.
Was not observed.
h
i
j
Ta ble 12. Selected Bon d Dista n ces a n d An gles of
Com p lex 14 a n d 19
14
19
Bond Distances (Å)
2.3972(17)
2.248(4)
Rh(1)-Cl(1)
Rh(1)-N(1)
Rh(1)-N(2)
Rh(1)-C(22)
Rh(1)-C(23)
Rh(1)- C(25)
Rh(1)-C(26)
C(22)-C(23)
C(25)-C(26)
2.3888(9)
2.283(3)
2.267(3)
2.057(3)
2.060(3)
2.120(4)
2.130(4)
1.420(5)
1.396(5)
2.255(5)
2.063(6)
2.063(6)
2.123(5)
2.127(6)
1.429(8)
1.404(8)
F igu r e 4. An ORTEP plot of complex 19 at 50% prob-
ability level along with the adopted numbering scheme. The
hydrogen atoms and the cocrystallized molecule of dichlo-
romethane have been left out for clarity.
Bond Angles (deg)
88.95(11)
89.34(12)
94.82(17)
93.87(18)
155.33(17)
158.26(17)
73.53(16)
123.47(19)
163.9(2)
Cl(1)-Rh(1)-N(1)
Cl(1)-Rh(1)-N(2)
Cl(1)-Rh(1)-C(22)
Cl(1)-Rh(1)-C(23)
Cl(1)-Rh(1)-C(25)
Cl(1)-Rh(1)-C(26)
N(1)-Rh(1)-N(2)
N(1)-Rh(1)-C(22)
N(1)-Rh(1)-C(23)
N(1)-Rh(1)-C(25)
N(1)-Rh(1)-C(26)
N(2)-Rh(1)-C(22)
N(2)-Rh(1)-C(23)
N(2)-Rh(1)-C(25)
N(2)-Rh(1)-C(26)
89.41(7)
89.97(7)
At this temperature of 183 K, the spectral features
of the diene ligand are similar to the ones observed for
complexes 14-16. In the case of complexes 17 and 18,
the olefinic hydrogen resonances H(12) have split into
two signals instead of four, while only one signal
appeared for the methine atoms H(13) instead of two.
In the case of 19, only one signal has been observed for
the olefinic hydrogen atoms H(12) at 183 K. The
fluxional processes that are responsible for this occur-
rence are clearly not due to intermolecular exchange of
the N-N-N ligands, as addition of 0.5 equiv of free
ligand to complex 18 had no effect at all on the 1H NMR
spectra in the range of 183-298 K.
95.02(13)
93.48(10)
154.79(11)
158.44(11)
72.91(9)
121.74(13)
162.04(12)
114.18(12)
89.98(12)
164.46(13)
124.76(12)
88.82(11)
110.41(12)
113.8(2)
90.4(2)
162.5(2)
122.3(2)
88.20(19)
111.3(2)
exchange of the coordinated and noncoordinated imine
moieties. As a result, a more subtle mechanism has to
occur (see the Discussion section).
In the temperature range of 183-218 K, the two
olefinic H(12) hydrogen signals coalesced to one signal,
while at the same time, the signals of the nonequivalent
side arms coalesced for both complex 17 and 18. At
room temperature, the 13C NMR spectra also show the
magnetic equivalence of the imine side arms and one
C(12) signal, in accord with the 1H NMR data. Fur-
thermore, we have found that the addition of chloride
anions caused the dissociation of the nitrogen ligands.
As the analogous triflate complexes could not be pre-
pared, it was not possible to investigate the existence
of chloride exchange in analogy to complexes 14 and 15.
Also, only chloride exchange would not explain the
In Situ NMR Stu d ies of th e Rea ction of [Rh Cl-
1
(COD)]2 w ith th e N-N-N Liga n d s 2,6-(C(R )dN-
R2)2C5H3N (R1 ) H, R2 ) i-P r (5), t-Bu (6), a n d
p-An isyl (7); R1 ) Me, R2 ) i-P r (8), a n d p-An isyl
(9)). Reactions between [RhCl(COD)]2 and the nitrogen
ligands 5-9 have been studied in situ because the
intermediates of the reactions could not be isolated,
owing to instability (Schemes 4 and 5).
When [RhCl(COD)]2 was added to the N-N-N ligand
5 at 230 K in deuterodichloromethane, the COD complex

Reactions of [RhCl(diene)]2
Organometallics, Vol. 16, No. 1, 1997 63
Ta ble 13. Selected Cr ysta llogr a p h ic Da ta of Squ a r e P la n a r , Squ a r e P yr a m id a l, a n d Tr igon a l Bip yr a m id a l
Str u ctu r es of Rh od iu m Nor bor n a d ien e Com p lexes Con ta in in g Nitr ogen Liga n d s
Rh-N (Å)
Rh-C olefinic (Å)
Rh-Cl (Å)
C-C olefinic (Å)
Square Planar Complexes
2.08-2.10
a
[Rh(NBD){(pyrazolyl)2PhCH}]PF6
2.07-2.09
2.101-2.125
2.125-2.139
1.33, 1.36
1.384, 1.401
1.390, 1.393
[Rh(NBD){(pyrazolyl)2PhCH}][RhCl2(NBD)]a,b
[Rh(NBD)(bpy)]Cl‚H2Oc
2.078-2.089
2.064-2.074
Square Pyramidal Complexes
2.094
[Rh(NBD)(bpy)Cl]c
2.098-2.123
2.159-2.118
2.590
2.4958
1.424
1.401, 1.415
[Rh(NBD)(2-(phenylazo)pyridine)Cl]c
2.055-2.042
Trigonal Bipyramidal Complexes
14
19
2.248-2.55 eq
2.063 eq
2.3972
2.3888
1.429 eq
1.404 ax
1.420 eq
1.396 ax
1.37 eq, 1.45 ax
1.38 eq
2.123-2.127 ax
2.057-2.057 eq
2.120-2.130 ax
1.95f eq, 2.05f eq
2.09-2.14 eq
2.267-2.283 eq
[Rh(NBD)(TpMe)]d
[Rh(NBD)(bis(indazol-1-yl)pyridin-2′-ylmethane)]PF6
2.25e eq, 2.147 ax
2.16-2.249 eq
2.166 ax
g
2.11-2.21 ax
1.34 ax
a
b
d
Reference 35. Only data of the [Rh(NBD){(pyrazolyl)2PhCH}] cation are given here. c Reference 16. Reference 20. e Avarage. f The
g
distance of Rh to the centers of the vinyl bonds are given here. Reference 21.
Sch em e 4. In Situ F or m a tion of Com p lexes 20-22
with the bulky t-Bu group, the olefinic hydrogen atoms
H(12) were observed as two signals at 223 K. Raising
the temperature to the range of 233-273 K caused the
equilibrium to move toward [RhCl(COD)]2 and free
ligand 6.
Addition of the N-N-N ligand 7 to [RhCl(COD)]2 at
230 K gave a fast reaction, as the mixture turned
instantly from yellow to purple affording complex [RhCl-
(2,6-(C(H)dN-p-anisyl)2C5H3N)(COD)] (22). At 243 K,
1
the H NMR spectrum of 22 (Table 14) is analogous to
the room temperature spectrum of 19 (Table 10),
indicating a similar structure. After 24 h at room
temperature, no oxidative addition of dichloromethane
had taken place, but instead, decomposition of 22 was
observed.
[RhCl(COD)]2 did not react with the N-N-N ligand
8, but did react with ligand 9 in two steps. It should
be noted that when in the temperature range of 190-
240 K, 2 equiv of ligand 9 was used for 1 equiv of [RhCl-
(COD)]2 and the dark green complex [Rh(2,6-(C(Me)dN-
p-anisyl)2C5H3N)2]Cl (24) was initially formed (Scheme
5, Table 15) with unreacted [RhCl(COD)]2 remaining in
solution.
Sch em e 5. Rea ction of [Rh Cl(COD)]2 w ith Liga n d
9 To F or m 24
At 240 K, fluxional processes occurred for 24, e.g., as
for H(7), a broad signal was observed. However, at 183
K, in the slow-exchange limit, one N-N-N ligand 9
coordinates as a terdentate ligand, as may be concluded
1
from the H NMR spectrum of H(2), which appeared as
a doublet, and of H(5), which appeared as a singlet. The
second N-N-N ligand 9 coordinates as a bidentate
ligand, as H(2) appeared as two separated doublets,
which is in accord with the observation that H(5) also
occurs as two well-separated signals (Table 15).
[RhCl(2,6-(C(H)dN-i-Pr)2C5H3N)(COD)] (20) was ini-
1
tially formed, as may be concluded from the H NMR
Increasing the temperature of the reaction mixture
to 273 K caused the dark green complex 24 to react with
excess [RhCl(COD)]2 to form the green square planar
rhodium complex [RhCl(2,6-(C(Me)dN-p-anisyl)2C5H3N)]
25 (Scheme 6), which was not isolated from the mixture
but identified by comparison with an authentic sample.1
13C NMR measurements could not be carried out
because of the instability of the relevant intermediates.
A further temperature increase to 298 K gave, as
expected, oxidative addition of dichloromethane yielding
the orange chloromethyl complex [RhCl2(CD2Cl)(2,6-
(C(Me)dN-p-anisyl)2C5H3N)] (26), of which the isola-
tion and characterization have been described else-
where.1 It should be noted that Rh(III) complexes
spectra at 230 K (Table 14). The chemical shifts of the
signals for the hydrogen atoms H(2), H(3), H(4), H(6),
and H(7) are comparable to those found for complex 17
(Table 10). Raising the temperature to room tempera-
ture gave conversion of 20 to the deuterochloromethyl
complex [RhCl2(CD2Cl)(2,6-(C(H)dN-i-Pr)2C5H3N)] (23)1
with concomitant formation of free COD.
When the reaction of [RhCl(COD)]2 with the N-N-N
ligand 6 was carried out in an NMR tube at 223 K, the
complex [RhCl(2,6-(C(H)dN-t-Bu)2C5H3N)(COD)] (21)
was formed, which is probably a five-coordinate species,
1
because the H NMR spectrum of 21 (Table 14) at 213
1
K resembled the room temperature H NMR spectrum
of 18 (Table 10). It should be noted that in this case,

64 Organometallics, Vol. 16, No. 1, 1997
Ta ble 14. 1H NMRa of th e F ive-Coor d in a te Com p lexes 20-22
H(3) H(4) H(6) H(8) H(7) H(12)
9.4 [br s, 2H] 4.27 [br m, 2H] 1.53 [d, 12 H]
Haarman et al.
no. T (K)
H(2)
H(14)
20
21
22
230
223
243
7.96 [m, 3H]b
b
b
2.99 [s,c 4H] 2.36 [s,c 4H]
1.6 [m, 4H]
7.96 [m, 3H]b
8.05 [d, 2H]
9.6 [br s, 2H]
1.56 [s, 18H]
3.87 [s,c 2H] 2.47 [s,c 2H] 2.21 [s,c 2H]
3.22 [s,c 2H] 1.56 [s,c 4H]
7.87 [t, 1H] 9.73 [s, 2H]
3.90 [s, 6H]
7.95 [br d, 4H] 3.62 [s,c 4H] 2.09 [s,c 4H]
7.04 [d, 4H]
1.42 [d, 4H]
a
b
1H NMR spectra were recorded at 300.13 MHz; s ) singlet, d ) doublet, t ) triplet, br ) broad, m ) multiplet. H(2) and H(3)
overlap. c No coupling observed.
Ta ble 15. 1H NMR of th e Com p lex 24a
T (K)
H(2)
H(3)
H(5)
H(7)c
H(8)c
240
183
7.85 [d, 4H]
7.89 [d, 1H]
7.81 [d, 1H]
7.93 [d, 2H]
8.07b [d, 2H]
7.64b [t, 1H]
8.15b [t, 1H]
1.79 [s, 12H]
2.19 [s, 3H]
1.14 [s, 3H]
1.86 [s, 6H]
6.57 [d, 8H], 6.28 [br d, 8H]
6.57 [s, 6H], 6.51 [s, 2H], 6.42 [d, 2H]
6.39 [d, 2H], 6.21[d, 2H] 5.71 [d, 2H]
3.74 [s, 12H]
3.70 [br d, 12H]
a
1H NMR spectra were recorded at 300.13 MHz; s ) singlet, d ) doublet, dd ) double doublet, t ) triplet, sp ) septet, br ) broad. The
numbers in italics refer to the bidentate coordinated ligand. There is a clear temperature dependent chemical shift. c Differentiation
b
between hydrogen atoms belonging to the terdentate ligand and to the bidentate coordinated ligand is not possible.
Sch em e 6. Rea ction of 24 w ith [Rh Cl(COD)]2 To
F or m 25 a n d Su bsequ en tly 26
also the N-N-N ligand in 19 is bonded as a bidentate
ligand with the pyridyl N-atom and one imine N-atom
bonded to Rh(I) in the equatorial plane. The NBD
ligand is bonded as a bidentate ligand with one alkene
bond in the equatorial plane and the other alkene bond
in an axial position; the other axial position is occupied
by the chloride atom. The long Rh-N bonds and the
small N-Rh-N bite angles are typical for these com-
plexes, although both N-atoms are in the equatorial
plane.22 It is clear that this five-coordinate geometry
is stabilized by steric bulk close to the coordinated
N-atoms, as rationalized extensively for Pd com-
plexes.22,23
Although fluxional movements (vide infra) occur in
all five-coordinate complexes reported here, it is clear
from the alkene chemical shifts at higher and lower
temperatures that the TBP geometry is the ground state
conformation also in solution (Table 8 and 9). It is
interesting to note that these five-coordinate NBD
complexes 17-19 did not react further, which allowed
us to study their dynamic behavior (vide infra).
However, in the case of reactions of [RhCl(COD)]2, it
turned out that the intermediates and products that
were observed depended strongly on the R1 and R2
substituents of the N-N-N ligands 5-9, as discussed
in the Results section.
[RhCl2(CD2Cl)(2,6-(C(R1)dN-R2)2C5H3N)] (R1 ) H, R2
) i-Pr, t-Bu, cyclohexyl, p-anisyl; R1 ) Me, R2
)
p-anisyl, i-Pr) have been prepared via [RhCl(2,6-
(C(R1)dN-R2)2C5H3N)] from [RhCl(alkene)2]2 (alkene )
ethene or cyclooctene) and the corresponding N-N-N
nitrogen ligands in CH2Cl2.1
Discu ssion
Previously, we have reported the synthesis of the
planar Rh(I) complexes [RhCl(2,6-(C(R1)dN-R2)2C5H3N)]
(R1 ) H, R2 ) i-Pr, t-Bu, cyclohexyl, p-anisyl; R1 ) Me,
R2 ) p-anisyl, i-Pr) by reacting [RhCl(alkene)2]2 (alkene
) ethene, cyclooctene) with the corresponding N-N-N
nitrogen ligands.1 These apparently highly nucleophilic
complexes rapidly underwent oxidative addition of
substrates containing C-Cl bonds.1 However, no reac-
tion was observed with H2 and alkenes, even under high
pressure, or when the complex contained good leaving
groups X-. We considered this rather remarkable and
focused our attention, therefore, on stabilizing rhodium-
alkene bonds by a different route. Since reaction of
[RhCl(ethene)2]2 with the N-N-N ligands easily led to
substitution of ethene, we used more strongly bonding
alkenes like COD and the more rigid NBD in the
starting compound so that rupture of the RhCl2Rh
bridge would dominate over alkene substitution. We
indeed observed that reaction (Scheme 3) of [RhCl-
(NBD)]2 with the N-N-N ligands 5-7 afforded 17-
19, which for 19 was shown to have a distorted TBP
structure in the solid state (Figure 4). From the single-
crystal X-ray studies on 14 (Figure 3) and 19 (Figure
4), it is clear that not only the N-N ligand in 14 but
In view of these and previous results,1 we suggest the
tentative general reaction scheme shown in Scheme 7.
In step i, the chloride bridge is ruptured with formation
of the five-coordinate NBD complexes 17-19 and COD
complexes 20-22. The reaction sequence now proceeds
with step ii, which involves substitution, but only for
COD, to give complex 24 with R1 ) Me and R2
)
p-anisyl which, in the presence of [RhCl(COD)]2 at 273
K, afforded the planar 25 (step iii), and subsequently
at 298 K converted to 26 (step iv).
F lu xion a l P r ocesses. In order to look more closely
into the origins of the dynamic behavior of complexes
17-19, the new compounds 14-16 (Scheme 2) have
been prepared, which turned out to have very similar
variable temperature 1H NMR spectra. In addition, the
ionic complexes 10-13 (Scheme 1 and Figure 1) have
been prepared, which contain asymmetric and sym-
metric bidentate N-N ligands. For the sake of simplic-
(23) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am. Chem. Soc.
1995, 117, 6414.

Reactions of [RhCl(diene)]2
Organometallics, Vol. 16, No. 1, 1997 65
Sch em e 7. Rea ction of Nitr ogen Liga n d s
Con ta in in g Th r ee N-Don or Atom s w ith
[Rh Cl(d ien e)]2 in CD2Cl2 To Give Ch lor om eth yl
Com p lexes
Sch em e 8. Mech a n ism for Exch a n ge of th e F ou r
N-Atom s in 10
mediates with monodentate ligands are also possible in
the light of mounting evidence for N-N ligands.24,25,31
When we increase the temperature, intermolecular
ligand exchange becomes feasible, but at lower rates
than the previous process. The intermolecular ligand
exchange could be measured quite precisely by studying
the inverse of the lifetime (1/τ) at 263 K on the signals
of the methyl substituent of the coordinated and non-
coordinated nitrogen ligand 2 as a function of the
concentrations of both ligand 2 and complex 11. The
1/τ (complex) versus ligand concentration line goes
through the zero point of this 1/τ axis, indicating the
virtual absence of a ligand independent pathway for
intermolecular ligand exchange (see the Results sec-
tion). At high ligand concentrations, a small signal of
the imine proton appears at 9.93 ppm. This species
might be [Rh(NBD)(2-(C(H)dN-i-Pr)-6-(Me)C5H3N)2]-
OTF with two monodentate bonded N-N ligands 2,
which are coordinated via the pyridine N-atoms. The
high-chemical shift value may be rationalized when the
imine protons of the two ligands are situated below and
above the coordination plane.31,32
ity, we commence our discussion with the ionic com-
plexes. The unusually dark colored compound 10 is
unfortunately rather insoluble, but it was possible to
observe for the bpm ligand that the H(2) and H(2′)
hydrogen atom signals, which are inequivalent at 183
K, merge and become magnetically equivalent at 293
K (Figure 2). This process may be due, if it is intramo-
lecular, to the mechanism proposed by Pregosin et al.24
and Ba¨ckvall and Gogoll,25 which involves intermediates
with monodentate bpm ligands as shown in Scheme 8.
We have also found that an intermolecular exchange of
bpm occurred when free bpm was added, but owing to
the low solubility, the kinetics of the reaction could not
be investigated.
Therefore, it was interesting to study the square
planar complex 11 with and without extra N-N ligand
2. At 183 K, the H(12a) and H(12b) signals of the NBD
ligand, which are already broadened, are observed
separately at 4.08 and 4.64 ppm (Table 4), while at 195
K, they have coalesced to one signal at 4.45 ppm. As
103Rh-H coupling is observed for the H-atom on the
imine C-atom between 195 and 293 K and on the H(12)
of NBD, an intramolecular process occurs in the absence
of free ligand. However, addition of free ligand at 183
K causes extra broadening of the H(12a) and H(12b)
signals; this process has been shown to be ligand
dependent, but without intermolecular ligand exchange,
as the ligand and free ligand signals remain sharp.
Therefore, it appears likely that the added N-N ligand
2 coordinates temporarily to the rhodium complex. The
resulting five-coordinate intermediate exchange of H(12a)
and H(12b) may now occur via Berry-type pseudo-
rotational processes. In this respect, it is interesting
that slight amounts of Cl- or acetone may also enhance
the alkene site-exchange rates of complex 2, probably
via five-coordinate intermediates.26-30 However, inter-
The five-coordinate complexes 15, which contains
N-N ligand 3, and 17 and 18, which contain the
N-N-N ligands 5 and 6, respectively, show only two
vinyl H(12) signals instead of four and one methine
1
H(13) signal instead of two (Tables 6 and 10) in the H
NMR spectra at 183 K. In all other cases (complexes
14, 16, and 19), only one H(12) signal has been observed
at 183 K indicating that we are dealing with very low
energy pathways. Although no 103Rh-H coupling con-
stant could be found on the imine hydrogen atom for
any of these five-coordinate complexes, we can exclude
intermolecular ligand exchange in the temperature
range from 183 to 298 K, as the free ligand signals
remain sharp for mixtures of the complex and the free
(27) Vrieze, K.; Volger, H. C.; Leeuwen, P. W. N. M. Inorg. Chim.
Acta Rev. 1969, 3, 109.
(28) Vrieze, K.; van Leeuwen, P. W. N. M. Prog. Inorg. Chem. 1971,
14, 1.
(24) Albinati, A.; Kunz, R. W.; Ammann, C. J .; Pregosin, P. S.
Organometallics 1991, 10, 1800.
(25) Gogoll, A.; O¨ rnebro, J .; Grennberg, H.; Ba¨ckvall, J .-E. J . Am.
Chem. Soc. 1994, 116, 3631.
(29) Heitner, H. I.; Lippard, S. J . J . Am. Chem. Soc. 1970, 92, 3486.
(30) Heitner, H. I.; Lippard, S. J . Inorg. Chem. 1972, 11, 1447.
(31) Crociani, B.; Di Bianca, F.; Paci, M.; Boschi, T. Inorg. Chim.
Acta 1988, 145, 253.
(26) Vrieze, K.; Volger, H. C.; Praat, A. P. J . Organomet. Chem.
1968, 14, 185.
(32) van der Poel, H.; van Koten, G.; Vrieze, K. Inorg. Chim. Acta
1981, 51, 253.

66 Organometallics, Vol. 16, No. 1, 1997
Haarman et al.
F igu r e 6. A possible exchange of N and imine N* sites in
complexes 17 and 18 via an intermediate with a monoden-
tate bonded ligand.
F igu r e 5. Exchange of N and N* sites in complexes 15,
17, and 18.
ligands (see the Experimental Section). Also, this low-
temperature process cannot be explained by Cl- ex-
change processes, as models show that the dissociation
of Cl- and the subsequent reassociation of the anion to
the ionic planar four-coordinate intermediates would
always lead to the equilibration of the four vinyl H(12)
protons, which is definitely not occurring for 15, 17, and
18 at 183 K. Although complex 14 with R2 ) i-Pr could
not be used for the study of the behavior of this group,
the four expected H(12) signals have already coalesced
to one signal at 183 K; we were fortunate to have
complex 17 with R2 ) i-Pr. It is very interesting to
observe that at 183 K, the N-N-N ligand of 17 is
bonded as a bidentate ligand (Scheme 3) with inequiva-
lent i-Pr groups. However, and this is important, the
two methyl groups on each i-Pr group are enantiotopic
on the NMR time scale, while four diastereotopic methyl
groups would have been expected for the TBP geometry,
which is clearly the ground state conformation in
solution (Scheme 3, Tables 8 and 10).
At this stage it is useful to consider some topological
points before the possible physical movements of the
ligands are explained. We may imagine, firstly, a
mirror plane through the Rh-Cl axis and the midpoints
of the coordinated alkene bonds that is caused by the
interchange of the N and N* sites on the NMR time
scale at 183 K (Figure 5). This site exchange would
equilibrate H(12a) with H(12b), H(12c) with H(12d), and
also the methine protons H(13a) and H(13b). When we
now consider the possible physical movements, we
should note that a simple turnstile rotation would give
two H(12) signals and one methine H(13) signal as
H(12a) interchanges with H(12c), H(12b) with H(12d),
and further H(13a) with H(13b). However, this would
not lead to the equilibration of diastereotopic Me groups
on each i-Pr substituent to enantiotopic Me groups, and
therefore, a turnstile rotation is not occurring.
F igu r e 7. Permutation of Cl and both alkene bonds in 15,
17, and 18.
ture NMR data can be rationalized by a process involv-
ing a monodentate coordinated nitrogen ligand. This
would lead, in principle, to two planar intermediates A
and B for 17 and 18 (Figure 6).
In the case of A, where the imine N*-atom remains
bonded to the Rh-atom, rotation of 180° about the Rh-
N* bond and association of the pyridyl N-atom to Rh
would indeed lead to N-N* exchange. Intermediate B
is not possible for 17 and 18 since, when the pyridyl
N-atom is only bonded to Rh, there would be two
dangling imine side arms which, as they have equal
chance to become bonded to Rh, would equilibrate both
side arms, which is definitely not observed for 17 and
18 at 183 K.
So, with the mirror plane through the Rh-Cl axis and
the midpoints of the coordinated alkene bonds, site
exchange of N and N* can only occur via a monodentate
bonded N-N* ligand via intermediate A in which only
the imine N is bonded (Figure 6).
As a second topological alternative, we may visualize,
on the NMR time scale, a mirror plane in the equatorial
plane (Figure 7). We must then have an exchange
between species C and D, which explains that the two
methyl groups on each i-Pr group are enantiotopic while
the two i-Pr groups remain inequivalent. It is obvious
that we do not need to assume an intermediate mono-
dentate nitrogen ligand, although this is not excluded.
However, the axial chloride atom must move to the
opposite axial position. A turnstile mechanism is again
not possible. A possible pathway has been described
by Shapley and Osborn,33 Scheme D in their publication,
which involves a permutation of the Cl-atom and both
alkene bonds via a movement of the Cl-atom from one
face to another of the pseudotetrahedral conformation
of the other ligands. In this way, the coalescence from
four to two signals may be rationalized and at the same
time the interchange of N and N* sites. This last
mechanism appears, however, to be a rather difficult
one, and therefore, we prefer the mechanism shown in
Figure 6 with A as the intermediate, which just involves
exchange of N and N* via a monodentate intermediate.
In light of the present knowledge24,25,34 and in view of
our results, this is a very reasonable mechanism.
It is very interesting to note that in the case of
[Rh(Me)(NBD)(PMe2Ph)2], which also has a TBP struc-
ture with the two phosphine ligands in the equatorial
plane, an axial-equatorial exchange of the alkene bonds
occurred via Berry pseudorotational movements or via
a turnstile mechanism.33 However, over the whole
temperature range studied, site exchange of the two
equivalent phosphines definitely did not occur, as the
two methyl groups on each P-atom remained dia-
stereotopic. This is, therefore, in contrast to our case
where the methyl groups on each inequivalent i-Pr
group became enantiotopic.
As for complex 17, neither a turnstile mechanism
around the arrow in Figure 5 nor the Berry pseudo-
rotational movement proposed by Shapley and Osborn
is possible,33 so we suggest that the variable tempera-
(34) Groen, J . H.; Elsevier, C. J .; Vrieze, K.; Smeets, W. J . J .; Spek,
A. L. Organometallics 1996, 15, 3445.
(35) Ballesteros, P.; Lo´pez, C.; Lo´pez, C.; Claramunt, R. M.; J ime´nez,
J . A.; Cano, M.; Heras, J . V.; Pinilla, E.; Monge, A. Organometallics
1994, 13, 289.
(33) Shapley, J . R.; Osborn, J . A. Acc. Chem. Res. 1973, 6, 305.

Reactions of [RhCl(diene)]2
Organometallics, Vol. 16, No. 1, 1997 67
F igu r e 8. Proposed chloride exchange via a binuclear
chloride species.
At higher temperatures, there is also a second dy-
namic process occurring in these five-coordinate com-
plexes 15, 17, and 18. In the case of complex 15
(Scheme 2), the two olefinic H(12) hydrogen atom
signals observed at 183 K coalesced to one signal at 228
K with a ∆Gq of 46 kJ /mol, while for 14 with R2 ) i-Pr
and 16 with R2 ) p-anisyl, the olefinic hydrogen atoms
H(12) appeared at 183 K as one signal already. We have
found that this equilibration is clearly due to chloride
exchange. This has been nicely corroborated by the
observation that a 1:1 mixture of ionic and five-
F igu r e 9. Intermediates in which the imine side arms
take up equivalent positions.
with apparently the same ∆Gq of 40 ( 2 kJ /mol, showing
that the bonded and nonbonded imine side arms inter-
change their sites. We have attempted to prepare ionic
triflate complexes but without any success; therefore,
we cannot provide evidence for chloride exchange. It
was not possible to study chloride exchange by adding
excess Cl- as the added Cl- replaced the N-N-N ligand
on the complexes. Even if we had evidence for chloride
exchange, e.g., via a binuclear intermediate of the type
shown in Figure 9, this would not explain the imine N
site exchange for 17 and 18, while it would only explain
the coalescence of the two olefinic H(12) signals to one.
Whatever the mechanism, it must involve intermediates
in which the imine side arms preferably take up
equivalent positions, as shown for the intermediates E
and F in Figure 9 where F is in fact the same as B in
Figure 6. The ionic five-coordinate intermediate E with
a terdentate bonded N-N-N ligand and a dissociated
chloride atom and the neutral four-coordinate inter-
mediate F with a monodentate bonded N-N-N ligand,
perpendicular to the coordination plane, and two dan-
gling side arms fulfill this requirement. At the present
time, we prefer intermediate E, as examples of dynamic
exchange between bi- and terdentate bonded N-N-N
ligands have been reported.1 Also, for complex 24,
which contains both a bi- and a terdentate bonded
N-N-N ligand, as demonstrated by 1H NMR (Table 15)
at 183 K, a dynamic exchange process occurs between
both coordination modes which equilibrates both ligands
at 240 K. Furthermore, intermediate F would lead to
equilibration of the side arms but not to equilibration
of the H(12) signals to one signal, but to two, if we do
not exchange the alkene positions at the same time.
1
coordinate complexes gave an H NMR spectrum at 183
K with signals appearing at the weighted mean of those
of the two complexes for both R2 ) t-Bu (12 and 15) and
R2 ) i-Pr (11 and 14) with one signal for the H(12)
protons. This chloride exchange probably proceeds via
a binuclear chloride species (Figure 8). The process is
faster for this 1:1 mixture of neutral 15 and ionic
complex 12 than for the neutral five-coordinate complex
15 only. This is obvious as the concentration of the
neutral chloride-donating complex is much higher for
the 1:1 mixture than the concentration of dissociated
Cl- when only neutral complex is present, as also
corroborated by the nonconductivity of complexes 14-
16 (see the Experimental Section).
In order to form the binuclear intermediate shown in
Figure 8, it appears logical to assume that the TBP
conformation of complex 15 converts to square pyrami-
dal conformation with the chloride atom on the axial
position. This can be done by taking one of the bonded
N-atoms as a pivot. After one pseudorotation, not only
the diene spans an equatorial and an axial site but also
the N-N* ligand. This will be a low-energy process as
the ideal angle in this conformation is 90° instead of
the 120° angle in the equatorial plane. If we now take
the chloride anion, which is now on an equatorial
position as a pivot, a square pyramidal intermediate
conformation will result with the chloride on the axial
position, as is needed for the formation of the binuclear
intermediate (Figure 8).
Ack n ow led gm en t. We would like to thank Profes-
sor P. W. N. M. van Leeuwen for stimulating discus-
sions, Dr. H.-W. Fru¨hauf for his interest in this work,
and K. Goubitz for assistance with the crystallographic
database.
In the case of the analogous complexes 17 and 18, the
two H(12) proton signals merge to one signal in the
range from 183 to 218 K. However, a crucial observa-
tion is also that the signals of the inequivalent protons
on the bidentate bonded N-N-N ligand coalesced, and
Su p p or tin g In for m a tion Ava ila ble: Further details of
the structure determinations, including coordinates, bond
lengths and angles, and thermal parameters for 14 and 19
(22 pages). Ordering information is given on any current
masthead page.
(36) Garralda, M. A.; Pinilla, E.; Monge, M. A. J . Organomet. Chem.
1992, 427, 193.
(37) Rice, D. P.; Osborn, J . A. J . Organomet. Chem. 1971, 30, C84.
(38) Trofimenko, S. Chem. Rev. 1993, 93, 943.
OM960760B