Complexes of heteroscorpionate trispyrazolylborate ligands. Part 10. Structures and fluxional behavior of rhodium(I) complexes with heteroscorpionate trispyrazolylborate ligands, Tp″Rh(LL) (LL = (CO)2 or COD)

Article abstract of DOI:10.1021/om020873x

Heteroscorpionate Tp″ ligands constructed of two 3-phenyl-5-methylpyrazolyl and a variable third pyrazolyl residue (3-methyl-5-phenyl-, 3,5-dimethyl-, and 3,5-diethylpyrazolyl) coordinate to rhodium(I) in a k² fashion to form Tp″Rh(LL) complexes (where LL = COD or (CO)₂). One of the two 3-phenyl-5-methylpyrazolyl and the less sterically hindered pyrazolyl coordinate through N(2) atoms, while the axially appended 3-phenyl-5-methylpyrazolyl is in side-on conformation. The Tp″Rh(COD) complexes possess C₁ symmetry in the solid state. The energy of activation of the exchange between coordinated and uncoordinated pyrazolyls was estimated from variable-temperature ¹H NMR measurements. Two ΔG? values were found for heteroscorpionate complexes. The ΔG?₁ - ΔG?₂ depends on a difference in steric demands of competing pyrazoles. For the homoscorpionate Tp^ph,MeRh(COD) complex two rotational isomers were identified by low-temperature ¹H NMR spectroscopy, which originate from slow rotation of the dangling 3-phenyl-5-methylpyrazolyl residue. All studied Tp′Rh-(COD) complexes were found to be catalytically active in regioselective polymerization of phenylacetylene.

Full text of DOI:10.1021/om020873x

1072
Organometallics 2003, 22, 1072-1080
Com p lexes of Heter oscor p ion a te Tr isp yr a zolylbor a te
Liga n d s. P a r t 10. Str u ctu r es a n d F lu xion a l Beh a vior of
Rh od iu m (I) Com p lexes w ith Heter oscor p ion a te
Tr isp yr a zolylbor a te Liga n d s, Tp ′′Rh (LL)
(LL ) (CO)2 or COD)
Tomasz Ruman,† Zbigniew Ciunik,‡ Anna M. Trzeciak,‡
Stanisław Wołowiec,*,†,‡ and J o´zef J . Zio´łkowski*,‡
Faculty of Chemistry, Rzeszo´w University of Technology, 6 Powstan´co´w Warszawy Avenue,
35-959 Rzeszo´w, Poland, and Faculty of Chemistry, University of Wrocław,
14 J oliot-Curie Street, 50-383, Wrocław, Poland
Received October 22, 2002
Heteroscorpionate Tp′′ ligands constructed of two 3-phenyl-5-methylpyrazolyl and a
variable third pyrazolyl residue (3-methyl-5-phenyl-, 3,5-dimethyl-, and 3,5-diethylpyrazolyl)
coordinate to rhodium(I) in a κ2 fashion to form Tp′′Rh(LL) complexes (where LL ) COD or
(CO)2). One of the two 3-phenyl-5-methylpyrazolyl and the less sterically hindered pyrazolyl
coordinate through N(2) atoms, while the axially appended 3-phenyl-5-methylpyrazolyl is
in side-on conformation. The Tp′′Rh(COD) complexes possess C1 symmetry in the solid state.
The energy of activation of the exchange between coordinated and uncoordinated pyrazolyls
1
was estimated from variable-temperature H NMR measurements. Two ∆Gq values were
found for heteroscorpionate complexes. The ∆Gq - ∆Gq depends on a difference in steric
1
2
demands of competing pyrazoles. For the homoscorpionate TpPh,MeRh(COD) complex two
rotational isomers were identified by low-temperature 1H NMR spectroscopy, which originate
from slow rotation of the dangling 3-phenyl-5-methylpyrazolyl residue. All studied Tp′Rh-
(COD) complexes were found to be catalytically active in regioselective polymerization of
phenylacetylene.
In tr od u ction
to undergo such borotropic shifts into 3-R2-5-R1-pyrazol-
1-yl has been recently explored in detail and eventually
used to obtain the chiral Tp* ligand with boron-centered
chirality: hydro(3,5-dimethylpyrazolyl)(3-isopropyl-5-
phenylpyrazolyl)(3-phenyl-5-isopropylpyrazolyl)borate
from synthetic Tp′′, hydrobis(3-phenyl-5-isopropylpyra-
zolyl)(3,5-dimethylpyrazolyl)borate.5 The goal has been
achieved by thermal conversion of the corresponding
Tp′′Co(NCS) complex under mild conditions. The Tp′′’s
are also interesting ligands for transition metal ions
which engage two nitrogen donors of these anions. In
such a case one may expect the preferential coordination
of two pyrazolyl residues with smaller steric hindrance
imposed by 3- and/or 5-substituents of Tp′′. In this paper
we have described the structures and fluxional behavior
of a series of Tp′′Rh(LL) complexes, where LL ) (CO)2
or COD. The Tp′′ ligands were constructed of two
3-phenyl-5-methylpyrazolyl residues and a variable
third one: 3,5-dimethyl-, 3,5-diethyl-, and 3-methyl-5-
phenylpyrazolyl. For comparison the previously known
TpPh,MeRh(COD) complex was also studied.
The chemistry of transition metal ion complexes with
the trispyrazolylborate anion (Tp) was initiated by
Trofimenko in 1966.1 Structural modifications of pyra-
zolyl residues (pz) by introducing various substituents
at the 3-5 positions of pz resulted in obtaining the
homoscorpionate ligands named second-generation
trispyrazolylborates (Tp′), which possess C3v symmetry,
and heteroscorpionates, ligands of Cs symmetry, con-
structed of two different pyrazolyl residues.2 The latter
will be called third-generation trispyrazolylborates (Tp′′)
hereafter. Heteroscorpionates are obtainable from asym-
metric 3-R1,5-R2pzH upon condensation with borohy-
dride (spontaneously formed Tp′′) or on the same route
with the use of two different pyrazoles (“synthetic”
heteroscorpionates). Transition metal ion compounds
with spontaneous Tp′′ can be prepared by ligation of
pure Tp′′ (usually sodium or thallium(I) salts of Tp′′ are
used) or by thermally induced intramolecular conversion
of homoscorpionate into heteroscorpionate in the com-
plex.3,4 The property of 3-R1-5-R2-pyrazol-1-yl residues
Resu lts a n d Discu ssion
† Rzeszo´w University of Technology.
Substituted tris(pyrazol-1-yl)borates (second-genera-
‡ University of Wrocław.
(1) Trofimenko, S. J . Am. Chem. Soc. 1966, 88, 1842.
(2) Trofimenko, S. Scorpionates: the coordination chemistry of
polypyrazolylborate ligands; Imperial College Press: London, U.K.,
1999.
tion scorpionates, Tp′)2 form Tp′Rh(LL) complexes, in
(4) Ruman, T.; -Lukasiewicz, M.; Ciunik, Z.; Wołowiec, S. Polyhedron
2001, 20, 2551.
(3) Trofimenko, S.; Calabrese, J . C.; Domaille, P. J .; Thompson, G.
S. Inorg. Chem. 1989, 28, 1091.
(5) Ruman, T.; Ciunik, Z.; Wołowiec, S. Eur. J . Inorg. Chem.,
submitted.
10.1021/om020873x CCC: $25.00 © 2003 American Chemical Society
Publication on Web 01/31/2003

Heteroscorpionate Trispyrazolylborate Ligands
Organometallics, Vol. 22, No. 5, 2003 1073
Sch em e 1
F igu r e 1. View of 1. Selected bond lengths (Å) and angles
(deg): Rh(1)-C(27), 1.852(2); Rh(1)-C(26), 1.862(2); Rh-
(1)-N(4), 2.0855(16); Rh(1)-N(2), 2.0957(16); C(27)-Rh-
(1)-C(26), 88.35(9); C(27)-Rh(1)-N(4), 94.79(8); C(26)-
Rh(1)-N(4), 174.79(7); C(27)-Rh(1)-N(2), 178.79(7); C(26)-
Rh(1)-N(2), 90.69(7); N(4)-Rh(1)-N(2), 86.11(6).
which they coordinate in κ2 fashion, when L1L2 ) (CO)2
or COD. The 1H NMR and IR studies of those complexes
in solution demonstrate that homoscorpionate Tp′ in-
terconverts between forms A, B, and C (Scheme 1). The
conversion B T C is fast on the 1H NMR time scale,
resulting in averaging of all pyrazolyl resonances,
whereas the A T B interconversion is relatively slower
F igu r e 2. View of 2. Selected bond lengths (Å) and angles
(deg): Rh(1)-N(2), 2.0950(15); Rh(1)-N(4), 2.1003(14); Rh-
(1)-C(38), 2.1344(19); Rh(1)-C(31), 2.1355(18); Rh(1)-
C(35), 2.1395(19); Rh(1)-C(34), 2.1457(17); N(2)-Rh(1)-
N(4), 82.60(6); N(2)-Rh(1)-C(38), 154.03(7); N(4)-Rh(1)-
C(38), 96.33(7); N(2)-Rh(1)-C(31), 167.48(7); N(4)-Rh(1)-
C(31), 92.93(6); N(2)-Rh(1)-C(35), 91.48(7); N(4)-Rh(1)-
C(35), 161.04(7); N(2)-Rh(1)-C(34), 98.68(6); N(4)-Rh(1)-
C(34), 160.85(7).
1
and the H NMR spectra indicate the presence of two
sets of resonances of 2:1 intensity ratio for A. In the solid
state the isomers A were evidenced by X-ray crystal-
lography barely in two cases, i.e., for TpPhRh(COD) and
TpMenthRh(CO)2.6,7 However in solution both of these
compounds indicate the presence of both A and averaged
B T C species at concentrations depending on temper-
ature and solvent. Here we have applied the heteroscor-
pionate Tp′′ ligands to construct Tp′′Rh(LL) complexes
and studied their properties in structural and fluxional
aspects.
Str u ctu r es of 1-4. The complex [HB(3-Ph,5-Mepz)2-
(3,5-diMepz)]Rh(CO)2 (1) was obtained by the procedure
used previously for the synthesis of TpPh,MeRh(CO)2,8
i.e., with Rh(acac)(CO)2 as starting material, whereas
[RhCl(COD)]2 was used for the synthesis of TpPh,MeRh-
(COD) (2), [HB(3-Ph,5-Mepz)2(3-Me,5-Phpz)]Rh(COD)
(3), and [HB(3-Ph,5-Mepz)2(3,5-diEtpz)] Rh(COD) (4),
where ([HB(3-Ph,5-Mepz)2(3,5-diMepz)] ) hydrobis(3-
phenyl-5-methylpyrazol-1-yl)(3,5-dimethylpyrazol-1-yl)-
borate, [HB(3-Ph,5-Mepz)2(3-Me,5-Phpz)] ) hydrobis(3-
phenyl-5-methylpyrazol-1-yl)(3-methyl-5-phenylpyrazol-
1-yl)borate, and [HB(3-Ph,5-Mepz)2(3,5-diEtpz)]
)
hydrobis(3-phenyl-5-methylpyrazol-1-yl)(3,5-diethylpyra-
zol-1-yl)borate. Monocrystals suitable for crystallo-
graphic studies were obtained for all complexes. A view
of 1 is presented at Figure 1. The 3,5-diMepz and one
of two 3-Ph,5-Mepz moieties of Tp′′ are coordinated by
N(4) and N(2) donors, respectively. The Rh-N(4) bond
is shorter by 0.01 Å in comparison with the Rh-N(2)
one. The nitrogen atom of appended 3-Ph,5-Mepz weakly
interacts with Rh(I) (2.84 Å). Its 3-phenyl substituent
is almost coplanar with the pyrazolyl ring and bisects
the OC-Rh-CO angle.
The molecular structure of 2 is presented in Figure
2. The Rh-N(3-Ph,5-Mepz) bond lengths in 2 are typical
for Tp′Rh(COD) complexes (about 2.10 Å, column 3 in
Table 1) and differ slightly from each other; Rh-N(4)
and Rh-N(2) distances are 2.100 and 2.095 Å, respec-
tively. The only reasonable explanation for this differ-
ence is the involvement of asymmetric arrangement of
the uncoordinated pyrazolyl moiety, the motif observed
in all homoscorpionate Tp′Rh(COD) complexes.
(6) Sanz, D.; Santa Maria, M. D.; Claramunt, R. M.; Cano, M.; Heras,
J . V.; Campo, J . A.; Ruiz, F. A.; Pinilla, E.; Monge A. J . Organomet.
Chem. 1996, 526, 341.
(7) Keyes, M. C.; Young, V. G.; Tolman, W. B. Organometallics 1995,
15, 4133.
(8) Moszner, M.; Wolowiec, S.; Tro¨sch., A.; Vahrenkamp, H. J .
Organomet. Chem. 2000, 595, 178.

1074 Organometallics, Vol. 22, No. 5, 2003
Ruman et al.
Ta ble 1. X-r a y Cr ysta llogr a p h ic Da ta a n d Metr ic P a r a m eter s for Tp ′Rh (L1L2) Com p lexes
complexref
Rh-N(pz) [Å]
2.099, 2.099, 3.694h 2.012, 2.012
2.107, 2.107 2.004, 2.004
Rh-X [Å]a
R [deg]b
D (g) [Å]c
ꢀ [deg]d
δ [deg]e ø[deg]f
1
2
3
4
[B(pz)4]Rh(COD)9,g
105.7
0.038 (0.000) 1.5, 1.5
0.098 (0.000) 9.9, 9.9
0.060 (0.067) 6.9, 19.7
0.064 (0.053) 23.5, 0.5
3.0
0.8
7.2
6.5
74.4
BpcodRh(COD)10
TpPh,MeRh(COD), 2j
2.086, 2.096, 3,767h 2.019, 2.027
109.5
107.9
77.4
76.6
[HB(3-Ph,5-Mepz)2(3-Me,5-Phpz)]Rh- 2.098, 2.100, 3.709h 2.014, 2.034
(COD), 3j
5
HB(3-Ph,5-Mepz)2(3,5-diEtpz)]Rh-
2.083, 2.095, 3.868h 2.019, 2.030
110.9
0.090 (0.117) 19.2, 15.2
11.9
79.7
(COD), 4j
6
7
8
9
TpiPr2Rh(COD)11
2.098, 2.133, 3.718h 2.025, 2.016
2.082, 2.133, 3.778h 2.011, 2.005
2.106, 2.120, 3.782h 2.026, 2.010
2.094, 2.094, 5.395n 2.024, 2.017
2.086, 2.096, 2.840h 1.852, 1.862
110.0
112.3
125.0
151.1
90.0
0.326 (0.149) 4.9, 10.5
0.028 (0.157) 5.4, 14.5
0.022 (0.169) 9.5, 15.0
0.164 (0.017) 8.9, 15.1
0.043 (0.029) 15.8, 21.4
12.5
13.1
14.1
12.6
4.2
74.4
75.3
76.2
171.3
81.0
TpMe,mt4Rh(COD)12,k
Tp4Bo,3MeRh(COD)113,m
TpPhRh(COD)6
10 [HB(3-Ph,5-Mepz)2(3,5-diMepz)]Rh-
(CO)2, 1j
14
11 Tpp-AnRh(CO)2
2.110, 2.107, 2.578h 1.824, 1.841
2.093, 2.091, 2.780h 1.855, 1.844
93.1
89.1
90.2
88.5
90.8
163.5
0.121 (0.054) 1.3, 1.4
0.045 (0.020) 6.1, 6.2
0.096 (0.015) 2.5, 10.1
0.064 (0.043) 5.6, 16.6
0.071 (0.061) 17.1, 17.7
0.065 (0.027) 2.6, 12.2
10.7
4.0
7.8
6.3
7.7
5.7
77.9
81.2
82.2
81.3
80.8
174.5
15,p
12 TpaRh(CO)2
2.109,2.105, 2.641h
1.851, 1.847
16
13 TpCF3,MeRh(CO)2
2.114, 2.115, 2.637h 1.824, 1.831
2.098, 2.102, 2.835h 1.851, 1.851
2.083, 2.104, 5.459n 1.853, 1.855
8
14 TpPh,MeRh(CO)2
7,r
15 TpMenthRh(CO)2
3
a
b
Rh-C or Rh-(center of CdC) distance. Boron-centered bite angle calculated as 2/3∑i)1Ri, where Ri is the angle between the Rh-B
and B-N(2) of pz lines. c Out-of-plane displacement of rhodium; the mean plane is defined by four donor atoms (or center of double bond
d
of COD ligand); the values in parentheses show the goodness of the plane. Pyrazole twist described by Rh-N(2)-N(1)-B dihedral
angles. e Metric parameter describing deformation of the coordination plane, the dihedral angle between (N)2-Rh and Rh-(C)2 (or Rh-
(center of CdC) planes. f Angle between Rh‚‚‚B axis and B-N(1) of the appended pyrazolyl moiety. g Bpcod ) (cyclooctane-1,5-diyl)bis(pyrazol-
1-yl)borate. Uncoordinated axial pyrazolyl moiety. j This work. k TpMe,mt4 ) tris(3-methyl-4,5-(1,3-butylene)pyrazol-1-yl)borate. Tp4Bo,3Me
h
m
) hydrotris(3-methylindazol-1-yl)borate. Uncoordinated equatorial pyrazolyl moiety. Tpa ) hydrotris(2H-benz[g]-4,5-dihydroindazol-
n
p
2-yl)borate, two independent molecules. TpMenth ) hydrotris(mentho(2,3-c)pyrazol-1-yl)borate.
r
F igu r e 3. View of 3‚CH2Cl2. Selected bond lengths (Å) and
angles (deg): Rh(1)-N(1), 2.098(2); Rh(1)-N(4), 2.100(2);
F igu r e 4. View of 4. Selected bond lengths (Å) and angles
Rh(1)-C(36), 2.129(3); Rh(1)-C(35), 2.130(3); Rh(1)-C(31),
(deg): Rh(1)-N(6), 2.0831(14); Rh(1)-N(4), 2.0953(15); Rh-
2.136(3); Rh(1)-C(32), 2.162(3); N(1)-Rh(1)-N(4), 82.58-
(1)-C(33), 2.1284(17); Rh(1)-C(36), 2.1377(17); Rh(1)-
(8); N(1)-Rh(1)-C(36), 95.37(10); N(4)-Rh(1)-C(36), 154.57-
C(32), 2.1425(17); Rh(1)-C(37), 2.1516(18); N(6)-Rh(1)-
(10); N(1)-Rh(1)-C(35), 92.03(10); N(4)-Rh(1)-C(35),
N(4), 81.55(6); N(6)-Rh(1)-C(33), 149.43(7); N(4)-Rh(1)-
166.57(10); N(1)-Rh(1)-C(31), 160.29(9); N(4)-Rh(1)-
C(33), 97.22(6); N(6)-Rh(1)-C(36), 89.90(6); N(4)-Rh(1)-
C(31), 92.30(10); N(1)-Rh(1)-C(32), 162.09(10); N(4)-Rh-
C(36), 161.81(7); N(6)-Rh(1)-C(32), 170.91(7); N(4)-Rh(1)-
(1)-C(32), 99.77(10).
C(32), 92.73(6); N(6)-Rh(1)-C(37), 102.06(6); N(4)-Rh(1)-
C(37), 160.15(7).
The molecular structures of 3‚CH2Cl2 and 4 are
presented in Figures 3 and 4, respectively. Both com-
plexes are built of Tp′′ ligands with two 3-Ph,5-Mepz
residues and a third one of lower steric hindrance (3-
borate, entries 1 and 2 in Table 1), in which the
mentioned differential factors do not operate.
Generally, for all Tp′Rh(COD) complexes with axially
Me,5-Phpz in 3‚CH2Cl2 and 3,5-diEtpz in the case of 4).
The Tp′′ ligands are coordinated in κ2 manner with side-
on appended 3-Ph,5-Mepz residues. The Rh-N(pyra-
zolyl) bond lengths differ slightly within the molecules
of 3‚CH2Cl2 and 4. There are three factors influencing
these bond lengths: a different steric hindrance imposed
by 3-R (and 5-R) substituents of coordinated pyrazolyl
residues, different electronic cis-trans effects resulting
from nonequivalent in-plane pyrazolyls, and conforma-
tion of uncoordinated 3-Ph,5-Mepz, as it was already
found in the molecule of 2. Those bond lengths are equal
within the complexes [B(pz)4]Rh(COD) and BpcodRh-
(COD) (where Bpcod ) cyclooctane-1,5-diylbis(pyrazolyl)-
appended pyrazolyl residues the uncoordinated pyra-
zolyls are arranged in a near side-on conformation,
which allows the N(2) of the pyrazole to interact weakly
with the rhodium(I) ion at a distance of 3.709-3.868 Å
(entries 3-8, column 3 in Table 1). Also the Rh(I)-(Cd
C) distances (measured in relation to the center of the
CdC bond, column 4) are slightly variable within the
2.005-2.027 Å range.
Similar relationships can be found for Tp′Rh(CO)2
complexes (entries 10-14), for which, however, the Rh-
(I)-N(2) axial uncoordinated pyrazole distance is con-
siderably shorter and varies within 2.578-2.840 Å,
whereas the Rh(I)-C bond lengths vary within the

Heteroscorpionate Trispyrazolylborate Ligands
Organometallics, Vol. 22, No. 5, 2003 1075
1.824-1.862 Å range. Thus, the ligands interact with
the rhodium(I) metal center more strongly in the case
of Tp′Rh(CO)2 than that in Tp′Rh(COD). This can also
be concluded on the basis of comparison of “bite” angle
R (column 5), which is considerably smaller for dicar-
bonyl complexes (for precise comparison see entries 3
and 14). These comparisons clearly indicate the involve-
ment of higher steric demands from COD ancillary
ligands in comparison with those of (CO)2.
The coordination sphere in both types of complexes
is slightly distorted from planarity; the rhodium metal
ion is 0.022-0.121 Å displaced out of the mean plane
with the exception of the high value for TpiPr2Rh(COD)
(0.326 Å, entry 6).
Close insight into the boat conformation of the
B-(N(1)-N(2))2-Rh fragment measured by the two
dihedral angles B-N(1)-N(2)-Rh (ꢀ, column 6), which
can be described as a pyrazole twist, indicates that
pyrazolyl substituents induce considerable distortions
of the boat. Consequently, the distortion of the coordi-
nation sphere around the central metal ion occurs, as
measured by the dihedral angle between two planes:
Rh-N(pz)2 and Rh-(CdC)2 in the case of Tp′Rh(COD)
or Rh-C in the case of Tp′Rh(CO)2 (angle δ in column
8). The values of δ are again larger for Tp′Rh(COD)
compounds than those for Tp′Rh(CO)2.
All the metric parameters are considerably different
in the case of Tp′Rh(L1L2) complexes with equatorial
uncoordinated pyrazole (entries 9 and 15). The angle ø
between the rhodium-boron axis and the boron-N(1)
bond of appended pyrazole distinguishes the conforma-
tion of the Tp′ ligand; for conformers B the value of ø
varies within 74.4-82.2°, whereas it is larger than 170°
in the case of Tp′ in conformation A.
TpiPr,iPrRh(COD),21 Tp4Bo,3MeRh(COD),13 TpPh,PhRh-
(COD),20 TpPh,MeRh(COD),15,17 and their Ir(I) ana-
logues.19 Exceptionally, the presence of pure B form at
ambient temperature was evidenced in the case of TpMs
-
Rh(COD), resulting in the appearance of two sets of
resonances from pyrazolyl moieties of 2:1 intensity
ratio,21 whereas two separate spectra of isomer A and
averaged B T C were observed for TpPhRh(COD)6 and
TppAnRh(COD)14 at a percentage depending on temper-
ature and solvent. In some cases the fluxional behavior
of Tp′Rh(L1L2) complexes was studied, indicating that
in the case of Tp′Rh(CO)2 the A T B T C was fast at
available low temperatures.8 Interestingly, in the highly
sterically hindered molecule of TpMenthRh(CO)2 two
separate spectra of B T C (one set of pz resonances)
and A (three sets of pz resonances due to C1 symmetry
of the species) were observed below the coalescence
temperature in toluene.7 In the case of heteroscorpi-
onate Tp′′M(COD) complexes (M ) Rh, Ir) two sets of
pyrazolyl resonances of 2:1 intensity ratio were observed
for [HB(3-iPr,4-Brpz)2(5-iPr,4-Brpz)]Rh(COD),17 [HB(3-
Mepz)2(5-iMez)]Ir(COD),19 and [HB(3-Mepz)(5-iMez)2]Ir-
(COD),19 although in the case of [HB(3-Mespz)2(5-
Mespz)]Rh(COD)21 three unexplained 4-H(pz) resonances
of 2:2:1 intensity ratio were found. Three resonances
from the ancillary COD ligand were present, consis-
tently with fast interconverting B T C or A T B T C
systems including the Tp′′Rh(COD) complexes, while
doubling of resonances for inert A species was observed
according to their Cs symmetry.
The 1H NMR spectrum of 1 comprises two 4-H
resonances at 6.33 and 6.02 ppm of 2:1 intensity ratio
attributed to 4-H(3-Ph,5-Mepz) and 4-H(3,5-diMepz),
respectively. The variable-temperature experiments
performed in toluene-d8 revealed that 1 remained in fast
exchange between B T C even at 190 K on the time
scale of the method. Similar behavior was found previ-
ously in the case of TpPh,MeRh(CO)2, whereas the slow,
solvent-dependent isomerization of average B T C
species into the A form has been found in the case of
TpPhRh(CO)2, resulting in evolution of the 1H NMR
spectrum of pure B T C species with a characteristic
broad 4-H singlet into two doublets of 2:1 intensity ratio
attributed to the A isomer.6 The isomer A was not found
for 1 in any common solvent used. On the basis of this
observation one may conclude that the presence of the
5-methyl substituent on pyrazolyl moieties destabilizes
conformation A.
1H NMR Stu d ies. Tp′Rh(L1L2) complexes (where
L1L2 ) diene or (CO)2) have been extensively studied
by NMR technique.8,11,13-21 The1H NMR spectra of
homoscorpionate complexes showed only one set of
resonances from pyrazolyl residues, evidencing the
presence of either exclusively B T C species in solution
or fast interconverting A T B T C. These kind of spectra
were observed at ambient temperature for TpRh-
(COD),17 TpMe,MeRh(COD),18 TpMe,Me,4ClRh(COD),17
TpCF3,MeRh(COD),17 TpCF3,CF3Rh(COD),16 TpiPrRh(COD),11
(9) Cocivera, M.; Ferguson, G.; Kaitner, B.; Lalor, F. J .; O’Sullivan,
D. J .; Parvez, M.; Ruhl, B. Organometallics 1982, 1, 1132.
(10) Bortolin, M.; Bucher, U. E.; Ru¨egger, H.; Venanzi, L. M.;
Albinati, A.; Lianza, F.; Trofimenko, S. Organometallics 1992, 11, 2514.
(11) Akita, M.; Ohta, K.; Takahashi, Y.; Hikichi, S.; Moro-oka, Y.
Organometallics 1997, 16, 4121.
(12) Rheingold, A. L.; Liable-Sands, L.; Trofimenko, S. Inorg. Chem.
2000, 39, 1333.
(13) Rheingold, A. L.; Haggerty, B. S.; Yap, G. P. A.; Trofimenko, S.
Inorg. Chem. 1997, 36, 5097.
(14) Santa Maria, M. D.; Claramunt, R. M.; Campo, J . A.; Criado,
R.; Heras, J . V.; Ovejero, P.; Pinilla, E.; Torres, M. R. J . Organomet.
Chem. 2000, 605, 117.
(15) Rheingold, A. L.; Ostrander, R. L.; Haggerty, B.; Trofimenko,
S. J . Am. Chem. Soc. 1994, 33, 3666.
(16) Del Ministro, E.; Renn, O.; Ru¨egger, H.; Venanzi, L. M.;
Burckhardt, U.; Gramlich, V. Inorg. Chim. Acta 1995, 240, 631.
(17) Bucher, U. E.; Currao, A.; Nesper, R.; Ru¨egger, H.; Venanzi,
L. M.; Younger, E. Inorg. Chem. 1995, 34, 66.
(18) Boaretto, R.; Ferrari, A.; Merlin, M.; Sostero, S.; Traverso, O.
J . Photochem. Photobiol. A 2000, 135, 179.
1
The H NMR spectrum of TpPh,MeRh(COD) (2, Figure
5) reveals the presence of averaged species B T C down
to 228 K in dichloromethane-d2, as demonstrated by the
presence of a 4-H singlet at 6.29 ppm. Also one set of
resonances from COD is observed at temperatures above
228 K. Below that point two resonances of 4-H(3-Ph,5-
Mepz) appear and simultaneously the number of reso-
nances from the COD ligand doubles. This situation
corresponds to a slow chemical exchange between
coordinated and dangling pyrazolyl residues. Surpris-
ingly, the molecule loses its Cs symmetry below the 207
coalescence point, resulting in the appearance of three
4-H(3-Ph,5-Mepz) resonances and 12 COD resonances.
The only reason responsible for further dissymmetry is
slow rotation of the dangling pyrazolyl residues around
the B-N(pz) bond. Estimated values for energy of
(19) Albinati, A.; Bovens, M.; Ru¨egger, H.; Venanzi, L. M. Inorg.
Chem. 1997, 36, 5991.
(20) Katayama, H.; Yamamura, K.; Miyaki, Y.; Ozawa, F. Organo-
metallics 1997, 16, 4497.
(21) Rheingold, A. L.; White, C. B.; Trofimenko, S. Inorg. Chem.
1993, 32, 3471.

1076 Organometallics, Vol. 22, No. 5, 2003
Ruman et al.
F igu r e 5. Selected regions of the 1H NMR spectra of 2
(dichloromethane-d2): the 4-H(pz) resonances (left column)
and 1′,2′,5′,6′-H(COD) resonances (right column).
F igu r e 6. Selected regions of the 1H NMR spectra of 3
(dichloromethane-d2): the 4-H(pz) resonances (left column)
and 1′,2′,5′,6′-H(COD) resonances (right column). The
4-H(pz) resonances from the minor DR isomer are labeled
with asterisks.
activation for pyrazolyl exchange and rotation of dan-
gling pyrazole were ∆Gq ) 43.2 kJ /mol and ∆Gq
)
BC
DR
43.9 kJ /mol, respectively (DR, dangling rotational iso-
mer). The COSY spectrum taken at 190 K for 2
indicated that scalar coupling occurs within olefinic
protons a T d and b T c (see assignments in bottom
trace of Figure 5), while EXSY cross-peaks were found
within all four sets of a T b T c T d of protons in the
NOESY spectrum at the same temperature. Thus, the
chemical shift nonequivalence caused by up-and-down
asymmetry in 2 is much larger (for individual pairs of
vicinal olefinic COD protons at 190 K: ∆δad ) δa - δd
) 0.72 ppm and ∆δbc ) δb - δc ) 0.32 ppm, and average
∆δBC ) (δa + δb)/2 - (δc + δd)/2 ) 0.52 and 0.51 ppm at
220 K) in comparison with that resulting from slowly
rotating asymmetric uncoordinated 3-Ph,5-Mepz (0.04
ppm, measured as ∆δDR ) (δa+ δd)/2 - (δb+ δc)/2).
resonances from 4-H(pz) and four resonances from
olefinic COD protons appear (trace D). Thus, two
separate chemical exchange processes corresponding to
(3-Ph,5-Mepz) T (3-Me,5-Phpz) and (3-Ph,5-Mepz)coord
T (3-Ph,5-Mepz)uncoord with the values of ∆GqBC1 ) 48.1
kJ /mol and ∆Gq
) 46.4 kJ /mol are observed, respec-
BC2
tively. This conclusion corroborates with 2D NMR COSY
and NOESY experiments performed at 190 K, which
showed the presence of both scalar and EXSY cross-
peaks between a T b and c T d. Further insight into
dynamic behavior of 3 is based on the observed three
minor peaks in the region of 4-H(pz) resonances (trace
E). Two sets of three 4-H(pz) resonances, as well as well-
resolved resonances from o-H (3-Ph,5-Mepz), appear at
the 88:12 intensity ratio at 190 K, and they correspond
to two DR isomers resulted from dangling 3-Ph,5-Mepz.
Their energies are different, consistent with the asym-
metry imposed by the rest of molecule, which was absent
in the case of 2.
1
The H NMR spectrum of 3 is composed of two sets
of pyrazolyl resonances of 2:1 intensity ratio, while one
set of COD resonances is observed, indicating that fast
pyrazolyl exchange takes place at room temperature in
dichloromethane-d2 (Figure 6, trace A). This situation
remains unchanged until 257 K, below which two
resonances from olefinic COD protons appear, whereas
the 2:1 pattern of 4-H(pz) is still present. This evidences
clearly the quenching of the (3-Ph,5-Mepz) T (3-Me,5-
Phpz) chemical exchange process leading to the in-plane
asymmetry of COD. The (3-Ph,5-Mepz)coord T (3-Ph,5-
Mepz)uncoord exchange remains fast on the time scale of
the method until 210 K, when simultaneously three
Finally, the in-plane asymmetry for the dominating
DR isomer in 3 consistent with different cis- and trans-
electronic and steric effects of two different coordinated
pyrazoles induced a 0.65 ppm chemical shift difference
(measured as ∆δBC1 ) (δa + δb)/2 - (δc + δd)/2), whereas
the up-and-down asymmetry resulted in the average
0.26 ppm chemical shift nonequivalence of olefinic COD

Heteroscorpionate Trispyrazolylborate Ligands
Organometallics, Vol. 22, No. 5, 2003 1077
Mepz) T (3,5-diEtpz) and (3-Ph,5-Mepz)coord T (3-Ph,5-
Mepz)uncoord are equal to ∆Gq
) 46.9 kJ /mol and
BC1
∆Gq
) 41.1 kJ /mol, respectively.
BC2
A detailed analysis of the spectra indicate that
average chemical shifts of the 4-H of uncoordinated and
coordinated 3-Ph,5-Mepz and that of 4-H of 3,5-diEtpz
remain unchanged upon slowing down the chemical
exchange. On the other hand, the difference of the
chemical shift of peripheral protons of 3-Ph,5-Mepz
between the coordinated and uncoordinated moiety is
rather large; the chemical shift difference of o-H(3-Ph)
is as large as 1.44 ppm, whereas that for 5-CH3 reaches
0.59 ppm. The chemical shift differences between COD
protons are quite large; the 1.14 ppm gap between pairs
of resonances corresponding to 1′,2′-H and 5′,6′-H (δAB
- δCD, trace E) attributed to different cis-trans sur-
roundings (no scalar cross-peaks were observed between
1′(2′) and 6′(5′) protons in the COSY spectrum) and the
1.10 ppm chemical shift difference between protons a
and b (0.93 ppm for c and d) related to up-and-down
asymmetry of the square planar complex were observed.
These observations suggest that the chemical shift
anisotropy in 4 originates from steric effects rather than
from different electronic properties of coordinated pyra-
zolyl residues.
The values of ∆Gq
in Tp′Rh(COD) complexes are
BC1
considerably lower in comparison with those observed
for TpPh,MeRh(CO)(PPh3)8 (76.5 kJ /mol), TpMe,MeRh(CO)-
(PMe3)22 (63 kJ /mol), and Tp(C2H4)(PPh3)23 (60 kJ /mol).
The (pz)coord T (pz)uncoord exchange, corresponding to the
mentioned B T C interconversion, proceeds via an
associative mechanism, with a pentacoordinate inter-
mediate, presumably with the rhodium center at tbp
geometry.24 Therefore, the larger steric hindrance of the
F igu r e 7. 1H NMR spectra of 4 dichloromethane-d2 at 300
K (A); 270 K (B); 230 K (C); 210 K (D); and 190 K (E). The
residual peaks from the solvent and trace HDO are labeled
with asterisks.
intermediate, the higher ∆Gq
can be expected. The
BC1
steric hindrance results both from Tp′ (Tp′′) and from
ancillary L1L2 ligands. In the case of L1L2 ) (CO)2 the
1
∆Gq is too small to be detected by H NMR spectros-
BC
protons (∆δab ) 0.31; ∆δcd ) 0.20 ppm, mean ∆δBC2
)
copy, while in the case when L2 ) PR3 the values of
0.25 ppm), which was considerably smaller than in the
case of 2.
∆Gq
are above 60 kJ /mol. The steric hindrance
BC
imposed by the symmetric COD ancillary ligand is
The 1H NMR spectrum of 4 recorded at 300 K is
composed of two 4-H resonances at 6.29 and 5.88 ppm
of 2:1 intensity ratio and one set of COD resonances
attributed to B or B T C fast interconverting species
(Figure 7, trace A). The assignment of resonances has
intermediate, and consequently the ∆Gq
values are
BC1
at the level of 43-47 kJ /mol (for 2-4). Due to C1
symmetry of the stable species for 3 and 4 at low
temperatures, the ∆Gq
values could be estimated.
corresponds to a difference in
BC2
The ∆Gq
- ∆Gq
BC1
BC2
1
been done on the basis of heteronuclear H-13C HMQC
steric hindrance between 3-Ph,5-Mepz and 3-Me,5-Phpz
in 3 and 3-Ph,5-Mepz and 3,5-diEtpz in 4. As one could
expect, the difference for 4 is larger (5.8 kJ /mol) in
comparison with that for 3 (2.3 kJ /mol). However, the
and HMBC experiments. Three resonances of the COD
ligand, each of the intensity corresponding to four
protons, are broad, which is rather typical for this kind
of complexes. Variable-temperature experiments in
dichloromethane-d2 indicated that primarily the (3-
Ph,5-Mepz) T (3,5-diEtpz) exchange became slow on the
time scale of the method at 255 K, resulting in the
appearance of two olefinic proton resonances below that
temperature with a preserved 2:1 pattern of 4-H(pz)
resonances (traces B and C). The slow (3-Ph,5-Mepz)coord
T (3-Ph,5-Mepz)uncoord exchange at temperatures below
223 K accounts for the appearance of three 4-H(pz) and
four olefinic proton resonances (labeled a-d in trace E).
The scalar couplings within the a T b and c T d pairs
of olefinic COD protons as cross-peaks in the COSY
spectrum and the same pattern of EXSY cross-peaks in
the NOESY spectrum are analogous to those for 3. The
values of activation energy corresponding to (3-Ph,5-
values of ∆Gq
and ∆Gq
depend on the values of
BC1
BC2
free energy of interconverting B forms, which bear
different coordinating and dangling pyrazolyls.
It has been shown that the strength of Rh-N(pz)
bonds can be largely differentiated, when two different
trans ligands are coordinated, as it was the case in the
molecule of TpPh,MeRh(CO)(PPh3), in which two stepwise
(3-Ph,5-Mepz)coord T (3-Ph,5-Mepz)uncoord equilibria were
observed with an energy gap of 21 kJ /mol.8 In the case
of 2-4 the symmetric COD ancillary ligand does not
(22) Chauby, V.; Serra Le Berre, C.; Kalck, P.; Daran, J .-C.;
Commenges, G. Inorg. Chem. 1996, 35, 6354.
(23) Oldham, W. J .; Heinekey, D. M. Organometallics 1997, 16, 467.
(24) Webster, C. E.; Hall, M. B. Inorg. Chim. Acta 2002, 330, 268.

1078 Organometallics, Vol. 22, No. 5, 2003
Ruman et al.
Sch em e 2
introduce an additional variable; therefore the results
on ∆Gq
- ∆Gq
seem to be reliable.
BC1
BC1
Ca ta lytic Tests. Catalytic activity in stereoregular
polymerization of phenylacetylene (PA) to cis-transoidal
poly(phenylacetylene) has been reported for the series
of Tp′Rh(COD) complexes.20 Following the same proce-
dure we have found that 2-4 were also highly active
as catalysts. Moreover, the catalysts were quite stable
under the applied reaction conditions (193 K, 24 h, 140-
1
fold excess of PA) and could be repeatedly used. The H
NMR monitoring of the catalytic reaction (12-fold excess
of PA was used) by the disappearance of resonances
from PA showed the absence of any other rhodium
complex in the mixture other than the starting one. In
addition, the release of the COD ligand was not noticed.
The complex TpPh,MeRh(CO)2 (entry 3), which was found
to be catalytically inactive, may be converted in situ by
addition of an equimolar amount of COD in the presence
of PA (entries 4, 5). The immediate formation of 2
accompanied by polymerization of PA took place as
followed by 1H NMR. A similar catalytic experiment was
performed with the use of a larger amount of COD
without losing catalytic activity of 2. The most efficient
catalyst was 4, for which the highest Mw values were
obtained in test reaction conditions (entry 9). Currently
we are studying the catalytic activity of Tp′Rh(L1L2)
complexes in copolymerization of acetylenes. Other
catalytic tests with 1 and [HB(3-Ph,5-Mepz)2(3,5-diMe-
pz)]Rh(CO)(PPh3), formed in situ by addition of 1-4
equiv of PPh3, indicated that complexes were inactive
Ta ble 2. Ca ta lytic Da ta
yield (%)a
Mw
Mw/Mn
b
c
entry
catalyst
1
2
3
4
5
6
7
8
9
2
96
86
0
72
100
98
83
100
100
47 000
39 300
2.38
2.77
2, reused
TpPh,MeRh(CO)2 (2′)
2′ + COD (2.5 equiv)
2′ + COD (5.0 equiv)
3
71 300
25 400
19 000
15 000
40 000
84 600
1.97
1.84
2.03
1.97
2.05
2.48
3, reused
3, reused second time
4
% of cis-poly(phenylacetylene) found by 1H NMR was 95-100.
Mw, molecular weight of polymer. c Mw/Mn, polydispersity.
a
b
0.60 mmol) in toluene (15 mL). The mixture was stirred for
20 h at room temperature. The precipitate of Na(acac) was
filtered off, and the filtrate was reconcentrated to a volume of
5 mL and left at 4 °C for 12 h. The resulting yellow precipitate
was collected by filtration, washed with ethanol and diethyl
ether, and vacuum-dried (250 mg, 0.43 mmol, 95% yield).
Crystals suitable for crystallographic measurement were
grown from concentrated toluene solution at 4 °C.
Anal. Calcd for C27H27N6O2BRh: C, 55.79; H, 4.68; N, 14.46.
Found: C, 56.10; H, 4.59; N, 14.68. IR (KBr): 2552 cm-1 (νB-H);
2070 (s), 2016 (s) cm-1 (νC-O). 1H NMR (toluene-d8; δ): 7.85
(d, J ) 7.1 Hz, 4H, o-H(3-Ph,5-Mepz)); 7.43-736 (m, 6H, m-
and p-H(3-Ph,5-Mepz)); 6.33 (s, 2H, 4-H(3-Ph,5-Mepz)); 6.02
(s, 1H, 4-H(3,5-diMepz)); 4.82 (m, J BH ) 150 Hz, B-H); 2.48,
2.47 (s, s, 3H, 3H, 3- and 5-CH3(3,5-diMepz)); 2.44 (s, 6H,
5-CH3(3-Ph,5-Mepz)).
2. The complex was synthesized at 83% yield (at the 0.21
mmol of NaTpPh,Me scale) according to a published procedure,
except benzene instead of dichloromethane10 or acetonitrile17
was used as the solvent for reaction between [RhCl(COD)]2
and NaTpPh,Me. Crystals of 2 were grown from a benzene-
hexane mixture. Satisfactory elemental analysis and IR and
1H NMR spectra confirmed the purity of 2.10
in hydrogenation and hydroformylation, in contrast to
+
[TpRu(PPh3)n(CH3CN)3-n
]
(where n ) 2 or 1), which
were evidenced to catalyze the hydrogenation of styrene
and in situ-generated TpRh(COD), the species probably
responsible for hydrogenative degradation of quino-
line.25,26
Exp er im en ta l Section
Gen er al P r ocedu r es. Syntheses of Tp′Rh(COD) and Tp′Rh-
(CO)2 complexes were performed under nitrogen atmosphere
using standard Schlenck and vacuum-line technique. The
anionic ligands were synthesized as sodium salts: Na[HB(3-
Ph,5-Mepz)2(3,5-diMepz)],27 Na[HB(3-Ph,5-Mepz)3],4 Na[HB-
(3-Ph,5-Mepz)2(3-Me,5-Phpz)],4 and Na[HB(3-Ph,5-Mepz)2(3,5-
diEtpz)],28 by previously described procedures. [RhCl(COD)]2
was synthesized according to published methods.29 The TpPh,Me
-
Rh(CO)2 was obtained as before.8 NMR experiments were
carried out on Bruker AMX 300 MHz and Bruker Avance 500
MHz instruments using standard parameters and pulse
sequences for 1H COSY and NOESY experiments and hetero-
nuclear 1H-13C HMQC and HMBC experiments. The assign-
ments of carbon resonances in 13C NMR spectra for Tp′′Rh-
(COD) complexes are in accordance with the numbering shown
in Scheme 2. The FT IR spectra were recorded on a Perkin-
Elmer 1725X instrument.
Anal. Calcd for C38H40N6BRh: C, 65.72; H, 5.81; N, 12.10.
Found: C, 66.17; H, 6.02; N, 12.06.
3. 3 was synthesized by stirring Na[HB(3-Ph,5-Mepz)2(3-
Me,5-Phpz)] (0.105 g, 0.207 mmol) with [RhCl(COD)] (0.045
g, 0.095 mmol) in 4 mL of benzene for 3 h at room temperature.
The precipitate of NaCl was filtered off, the filtrate was twice
concentrated under a stream of nitrogen, and the solution was
layered with ca. 2.5 mL of hexane. Yellow crystals of analyti-
cally pure 3 were collected (0.111 g, 0.160 mmol, 84% yield).
Crystals of 3‚CH2Cl2 suitable for X-ray crystallographic mea-
surement were obtained by recrystallization of 3 from a
dichloromethane-hexane solvent mixture.
Syn th eses of Com p lexes. 1. Na[HB(3-Ph,5-Mepz)2(3,5-
diMepz)] (200 mg, 0.45 mmol) dissolved in 15 mL of toluene
was added slowly to a solution of Rh(acac)(CO)2 (155.4 mg,
Anal. Calcd for C39H42N6Cl2BRh: C, 60.10; H, 5.43; N, 10.78.
Found: C, 60.16; H, 5.46; N, 10.38. IR (KBr): 2481 cm-1 (νB-H).
1H NMR (300 K, dichloromethane-d2; δ): 7.92 (d, J ) 7.1 Hz,
4H, o-H(3-Ph,5-Mepz)); 7.58 (d, J ) 7.1 Hz, 2H, o-H(3-Me,5-
Phpz)); 7.44-7.28 (m, 6H, m-, p-H(3-Ph,5-Mepz and 3-Me,5-
Phpz)); 6.29 (s, 2H, 4-H(3-Ph,5-Mepz)); 6.14 (s, 1H, 4-H(3-Me,5-
Phpz)); 3.80 (br s, 4H, 1′, 2′, 5′, 6′-H (COD)); 2.59 (s, 3H,
3-CH3(3-Me,5-Phpz)); 2.03 (s, 6H, 5-CH3(3-Ph,5-Mepz)); 1.85
(25) Chan, W.-C.; Lau, C.-P.; Che, Y.-Z.; Fang, Y.-Q.; Ng, S.-M.; J ia,
G. Organometallics 1997, 16, 34.
(26) Alvarado, Y.; Busolo, M.; Lopez-Linares, F. J . Mol. Catal. A
1999, 142, 163.
(27) L-ukasiewicz, M.; Ciunik, Z.; Ruman, T.; Sko´ra, M.; Wołowiec,
S. Polyhedron 2001, 20, 237.
(28) Ruman, T.; Ciunik, Z.; Wołowiec, S. Polyhedron 2002, 21, in
press (Part IX).
(29) Giordano, G.; Crabtree, R. H. Inorg. Synth. 1990, 28, 88.

Heteroscorpionate Trispyrazolylborate Ligands
Organometallics, Vol. 22, No. 5, 2003 1079
Ta ble 3. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
1
2
3‚CH2Cl2
4
empirical formula
fw
C
27H26BN6O2Rh
C38H40BN6Rh
694.48
C39H42BN6Cl2Rh
779.41
C35H42BN6Rh
660.47
581.27
T/K
100(2)
100(2)
100(2)
100(2)
λ/Å
0.71073
monoclinic
P21/c
12.6077(7)
19.6436(10)
11.2120(7)
0.71073
monoclinic
P21/c
11.5038(8)
15.1991(8)
19.1803(10)
0.71073
triclinic
P1h
0.71073
triclinic
P1h
cryst syst
space group
a/Å
b/Å
c/Å
12.872(2)
12.906(2)
12.9910(19)
107.272(14)
96.892(13)
113.646(13)
1816.0(5)
2
9.9159(7)
12.7807(8)
13.8793(12)
65.288(7)
76.741(7)
79.880(6)
1548.9(2)
2
R/deg
â/deg
105.554(5)
100.626(5)
γ/deg
V/Å3
2675.1(3)
4
1.443
0.674
1188
3296.1(3)
4
1.399
0.555
1440
Z
Dc/Mg‚m-3
1.425
0.655
804
1.416
0.587
688
µ/mm-1
F(000)
cryst size/mm
θ range for data collection/deg
ranges of h,k,l
0.19 × 0.16 × 0.13
3.51-28.51
-16f16,-25f20,
-14f14
0.18 × 0.18 × 0.10
3.34-28.50
-10f15,-20f20,
-24f25
0.18 × 0.15 × 0.13
3.31-28.45
-17f16,-12f17,
-16f17
0.17 × 0.14 × 0.12
3.58-28.30
-13f13,-15f15,
-18f14
9162
6163 (0.0192)
6163/556
1.040
no. of reflns collected
no. of ind reflns
18 275
22 423
12 679
6196 (0.0320)
6196/338
1.099
7734 (0.0269)
7734/575
1.091
7984 (0.0336)
7984/610
0.953
no. of data/params
GOF(F2)
final R1/wR2 indices (I>2σI)
largest diff peak/hole/e‚Å-3
0.0295/0.0694
1.011/-0.753
0.0293/0.0674
0.984/-0.591
0.0414/0.0603
0.761/-0.577
0.0242/0.0555
0.957/-0.472
(br m, 4H, 3′, 4′, 7′, 8′-Hexo (COD)); 1.33 (m, 4H, 3′, 4′, 7′, 8′-
endo (COD)). 13C NMR (300 K, dichloromethane-d2; δ): 153.2
(Mn and Mw) and polydispersity (Mn/Mw) with the use of a
Hewlett-Packard GPC system (CHCl3 solutions), a refractive
index detector, and a Plgel 10 m MIXED-B column The reuse
of catalysts tests was performed by stripping out the volatiles
from the filtrate and addition of CH2Cl2 and PA as in the
primary tests. Finally, the polymer samples were analyzed by
1H NMR spectroscopy in chloroform-d to establish the percent-
age of cis-poly(phenylacetylene) in accordance with published
procedures.30
In a separate experiment 3 mg of 2 and a 12-fold excess of
PA in dichloromethane-d2 were used, and the progress of the
reaction was monitored by 1H NMR spectroscopy. The progress
of polymerization was followed by the disappearance of the
substrate peak at 3.05 ppm and growing of the resonances from
poly(phenylacetylene) at 5.9, 6.7, and 6.9 ppm. Throughout 24
h of monitoring the PA resonance disappeared, while the
resonances from 2 remained unchanged. Formation of free
COD was not observed (absence of resonances at 2.4 and 5.6
ppm).
H
C-3(3-Ph,5-Mepz); 152.6 C-3(3-Me,5-Phpz); 150.9 C-5(3-Me,5-
Phpz); 146.6 C-5(3-Ph,5-Mepz); 135.7 C-6(3-Ph,5-Mepz); 133.7
C-6(3-Me,5-Phpz); 130.3 C-7(3-Me,5-Phpz); 129.0 C-7(3-Ph,5-
Mepz); 128.6 C-9(3-Me,5-Phpz); 128.5 C-8(3-Me,5-Phpz); 128.2
C-9(3-Ph,5-Mepz); 127.9 C-8(3-Ph,5-Mepz); 108.1 C-4(3-Me,5-
Phpz); 106.3 C-4(3-Ph,5-Mepz); 81.7 C-1′,2′,5′,6′ (COD); 30.1
C-3′,4′,7′,8′ (COD); 15.9 3-CH3(3-Me,5-Phpz); 13.4 5-CH3(3-
Ph,5-Mepz).
4. The complex was synthesized as 3 at the scale of 0.115 g
of Na[HB(3-Ph,5-Mepz)2(3,5-diEtpz) (0.24 mmol) and 0.049 g
of [RhCl(COD)]2 (0.10 mmol). Analytically pure 4 was obtained
by crystallization from benzene-hexane (yield 0.120 g, 0.182
mmol, 91% yield).
Anal. Calcd for C35H42N6BRh: C, 63.65; H, 6.41; N, 12.72.
Found: C, 63.47; H, 6.68; N, 12.59. IR (KBr): 2484 cm-1 (νB-H).
1H NMR (300 K, dichloromethane-d2; δ): 7.94 (d, J ) 7.1 Hz,
4H, o-H(3-Ph,5-Mepz)); 7.42-7.28 (m, 6H, m-, p-H(3-Ph,5-
Mepz)); 6.32 (s, 2H, 4-H(3-Ph,5-Mepz)); 5.93 (s, 1H, 4-H(3,5-
diEtpz)); 4.60 (m, J BH ) 140 Hz, 1H, B-H) 3.78 (br s, 4H, 1′,
2′, 5′, 6′-H (COD)); 2.80 (q, J ) 7.6 Hz, 2H, 3-CH2CH3(3,5-
diEtpz); 2.74 (q, J ) 7.6 Hz, 2H, 5-CH2CH3(3,5-diEtpz); 2.20
(s, 6H, 5-CH3(3-Ph,5-Mepz)); 1.79 (br s, 4H, 3′, 4′, 7′, 8′-Hexo
(COD)); 1.38 (t, 3H, 5-CH2CH3(3,5-diEtpz); 1.27 (m, 4H, 3′, 4′,
7′, 8′-Hendo (COD)); 1.23 (t, 3H, 3-CH2CH3(3,5-diEtpz). 13C NMR
(300 K, dichloromethane-d2; δ): 155.7 C-5(3,5-diEtpz); 152.7
C-3(3,5-diEtpz); 152.1 C-5(3-Ph,5-Mepz)); 145.6 C-3(3-Ph,5-
Mepz)); 135.0 C-6(3-Ph); 128.1 C-7(3-Ph); 127.1 C-8(3-Ph);
126.9 C-9(3-Ph); 103.3 C-4(3,5-diEtpz); 105.1 C-4(3-Ph,5-
Mepz); 80.5 C-1′,2′,5′,6′ (COD); 29.4 C-3′,4′,7′,8′ (COD); 22.1
5-CH2CH3(3,5-diEtpz); 21.1 3-CH2CH3(3,5-diEtpz); 14.5.
5-CH2CH3(3,5-diEtpz); 13.2 3-CH2CH3(3,5-diEtpz); 12.9 5-CH3-
(3-Ph,5-Mepz).
In another experiment 2 was generated in situ by addition
of an equimolar amount of COD into the solution of TpPh,Me
-
Rh(CO)2. The formation of 2 was observed immediately by
peaks of coordinated COD at 3.30, 1.60, and 1.09 ppm, which
remained unchanged over a period of 24 h, while the PA (added
at 12-fold excess together with COD) was totally consumed in
the catalytic reaction. The results of catalytic tests on the
polymerization of PA are summarized in Table 2.
Compound 1 and [HB(3-Ph,5-Mepz)2(3,5-diMepz)]Rh(CO)-
(PPh3) generated in situ by addition of 1 equiv of PPh3 were
tested for catalytic activity in the hydrogenation and hydro-
formylation of hex-1-ene in toluene (3-7 h, 353 K) and acetone
(72 h, 353 K). Standard conditions for catalytic runs were
0.01-0.02 g of catalyst, 1.5 mL of hexane, 1.5 mL of solvent,
and 10 atm pressure of H2/CO ) 1.
Ca ta lytic P r oced u r es. Complexes 1-4 were tested for
catalytic activity in the polymerization of phenylacetylene
(PA). In a typical experiment 0.013 mmol of catalyst was
dissolved in 0.5 mL of CH2Cl2, and 0.2 mL of PA (1.82 mmol)
was added. The mixture was stirred under nitrogen at 293 K
for 24 h, then the polymer was precipitated by addition of
methanol (2 mL), separated by microfiltration, washed with
methanol, weighed in order to determine the yield, and
analyzed for number- and weight-average molecular weights
Exp er im en ta l P r oced u r e for X-r a y Cr ysta llogr a p h y.
Suitable crystals of 1, 2, 3, and 4 were glued on top of a glass
fiber and transferred into the cold nitrogen stream on a Kuma
KM4CCD κ-axis diffractometer (graphite-monochromated Mo
KR radiation, λ ) 0.71073 Å). Crystals were positioned at 65
mm from the CCD camera. A total of 612 frames were
(30) Furlani, A.; Licoccia, S.; C.; Russo, M. V. J . Polym. Sci., Part
A: Polym. Chem. 1986, 24, 991.

1080 Organometallics, Vol. 22, No. 5, 2003
Ruman et al.
measured at 0.75° intervals with a counting time of 10-15 s.
Accurate cell parameters were determined and refined by
least-squares fit of 2700-5100 of the strongest reflections.
Data were corrected for Lorentz and polarization effects. No
absorption corrections were applied. Data reduction and
analysis were carried out with the Oxford Diffraction (Poland)
(formerly Kuma Diffraction Wrocław, Poland) programs. The
structures were solved by the heavy method (program
SHELXS9731) and refined by the full-matrix least-squares
method on all F2 data using the SHELXL97 programs.32 Non-
hydrogen atoms were refined with anisotropic displacement
parameters; hydrogen atoms were included from geometry of
molecules and/or ∆F maps. Their parameters were not refined
in 1, and in 2, 3, and 4 they were refined isotropically. Neutral
atom scattering factors were taken from Cromer and Waber.33
Final refinement details are collected in Table 1, and the
numbering schemes employed are shown in Figures 1, 2, 3,
and 4, which were drawn with ORTEP as 30% probability
ellipsoids.
Ad d ition a l Ma ter ia ls. Crystallographic data for the struc-
tures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre, CCDC no. 192815
for compound 1, CCDC no. 192816 for 2 , CCDC no. 192817
for 3‚CH2Cl2, and CCDC no. 192818 for 4. Copies of this
information may be obtained free of charge from the Director,
CCDC, 12 Union Rd., Cambridge 1EZ, UK (fax: +44-1223-
336033; e-mail: deposit@ccdc.cam.ac.uk or http://www.ccdc-
.cam.ac.uk).
Ack n ow led gm en t. This work was supported by
State Committee for Scientific Research KBN (Poland)
with Grants 3T09A 05219 to T.R., Z.C., A.T., and S.W.,
and PBZ KBN 15/T09/99/01D to A.T. and J .J .Z.
(31) Sheldrick, G. M. SHELXS97: Program for Solution of Crystal
Structures; University of Go¨ttingen, 1997.
(32) Sheldrick, G. M. SHELXL97: Program for Crystal Structure
Refinement; University of Go¨ttingen, 1997.
(33) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol. 4.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM020873X