Synthesis, structures, and characterization of benzildiimine complexes of rhodium(III) and iridium(I)

Article abstract of DOI:10.1016/j.ica.2009.11.027

The reactions of trans-[(PPh₃)₂M(CO)Cl] (M = Rh and Ir) with benzildiimine (H₂BDI = 2) derived from benzil-bis(trimethylsilyl)diimine (Si₂BDI) (1) in a 1:2 and 1:1 molar ratio afforded the cationic bis-benzildiiminato complexes [Rh(PPh₃)₂(HBDI)₂]Cl (3) and the mono-benzildiimine complex [Ir(PPh₃)₂(CO)(H₂BDI)]Cl (4), respectively. Both complexes are fully characterized using IR, FAB-MS, NMR spectroscopy and elemental analysis. The single crystal X-ray structure analysis reveals a distorted octahedral coordination geometry for the Rh(III) in 3 and a highly distorted square pyramidal geometry for Ir(I) in 4. In addition, the solid-state structure of Si₂BDI is reported here for the first time showing the substituents highly twisted because of steric reasons.

Full text of DOI:10.1016/j.ica.2009.11.027

Inorganica Chimica Acta 363 (2010) 723–728
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, structures, and characterization of benzildiimine complexes
of rhodium(III) and iridium(I)
*
Nadera Haque, Bernd Neumann, J. Nicolas Roedel, Ingo-Peter Lorenz
Munich/Germany, Ludwig-Maximilians University, Department of Chemistry and Biochemistry, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 July 2009
Received in revised form 11 November 2009
Accepted 19 November 2009
Available online 26 November 2009
The reactions of trans-[(PPh3)2M(CO)Cl] (M = Rh and Ir) with benzildiimine (H2BDI = 2) derived from ben-
zil-bis(trimethylsilyl)diimine (Si2BDI) (1) in a 1:2 and 1:1 molar ratio afforded the cationic bis-benzil-
diiminato complexes [Rh(PPh3)2(HBDI)2]Cl (3) and the mono-benzildiimine complex [Ir(PPh3)2(CO)-
(H2BDI)]Cl (4), respectively. Both complexes are fully characterized using IR, FAB-MS, NMR spectroscopy
and elemental analysis. The single crystal X-ray structure analysis reveals a distorted octahedral coordi-
nation geometry for the Rh(III) in 3 and a highly distorted square pyramidal geometry for Ir(I) in 4. In
addition, the solid-state structure of Si2BDI is reported here for the first time showing the substituents
highly twisted because of steric reasons.
Dedicated to Dr. Klaus Römer on the
occasion of his 70th birthday.
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Benzil-bis(trimethylsilyl)diimine
Benzildiimine
Crystal structures
Rhodium
Iridium
Triphenylphosphine
1. Introduction
and sometimes also to chlorinated solvents. After cleavage, the two
SiMe3 groups are replaced by two H atoms and then H2BDI (2 = tri-
During the past quarter of last century, 1,4-diazabutadienes (
a
-
methylsilyl substituted benzildiimine, Fig. 1) resembles a typical
1,2-diimine ligand with unsubstituted imino groups. In the present
study, we have chosen the benzildiimines 1 and 2 as the principal
ligands, not only because they carry the diimine chromophore but
also for their different coordination modes. However, only a few
metal complexes of 1 are known where the two trimethylsilyl
(SiMe3) groups stay attached with the ligand. Some complexes
with the general formula Mo(CO)4L (where L = 1 or similar phenyl-
imine ligands) were prepared by thermal substitution reaction of
Mo(CO)6 with the respective ligands in refluxing C6H6 [10]. Only
the magnetical and few spectrochemical properties of these com-
plexes were investigated, the molecular structures however were
not reported. In our prepared complexes (3 and 4), 1 as starting li-
gand changed into the diimine form 2 which is in good agreement
with the complexes synthesized from 1, but where the diimine
form resulted as final ligand in bis- and tris-chelate complexes
[11]. The complexes are of general formula of [M(HL)n] (ClO4)2
[HL = benzildiimine, phenanthrenequinonediimine (phi); n = 2,
M = Cu; n = 3, M = Fe, Ni] and [CoL(HL)2](ClO4)2 were prepared
from the corresponding metal salts and alcoholic HL or alcoholic
solution of the corresponding 1,2-bis(trimethylsilylimino) analog.
The complexes were characterized by elemental analysis, optical
spectra, and magnetic measurements. Similar Pd(HL)Cl2,
[Rh(HL)L]Cl2 and [Rh(HL)2]Cl3 complexes were also prepared with
diimines) have attracted considerable attention as useful reagents
in organometallic chemistry due to (i) their different types of coor-
dination modes and reactivity of their coordination complexes; (ii)
the applications of such complexes in organic synthesis and catal-
ysis; (iii) the utilization of such complexes as luminescence labels
for detection and photochemical cleavage of DNA [1–3]. Benzil-
bis(trimethylsilyl)diimine or 1,2-bis(trimethylsilylimino)-diphen-
ylethane (1 = Si2BDI, Fig. 1) is an interesting model from the view
point of the formation of heterocycles because it possesses two
imino groups in 1,4-relationship and two very labile Me3Si substit-
utents in the same molecule. A wide variety of heterocycles such as
B,N heterocycles, diazaheteroles, imidazoles, oxazolines and also
several coordination complexes were synthesized using 1 [4–7].
Si2BDI was prepared and characterized by means of IR, NMR and
elemental analysis, but no crystal structure of this compound
was reported [8,9]. Often it was observed that during the reactions
with metal complexes the two SiMe3 groups of 1 are easily cleaved
off as the N–SiMe3 group is very reactive and sensitive to moisture,
* Corresponding author. Address: Department Chemie und Biochemie, Ludwig-
Maximilians-Universität München, Butenandtstraße 5–13 (Haus D), D-81377 Mün-
chen, Germany. Tel.: +49 (0) 89 2180 77486; fax: +49 (0) 89 2180 77867.
E-mail address: ipl@cup.uni-muenchen.de (I.-P. Lorenz).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.11.027

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2.2. Synthesis of trans-[bis{(benzildiiminato-N,N0)
(triphenylphosphine)}rhodium(III)]-chloride (3)
A solution of (PPh3)2Rh(CO)Cl (0.052 g, 0.075 mmol) in 10 mL of
dichloromethane was added to
a dichloromethane solution
(10 mL) of Si2BDI (1) (0.053 g, 0.15 mmol). The resulting yellow
mixture was heated at 45 °C for 30 min forming a clear yellow
solution which was allowed to cool down to room temperature
and stirred continued for 1 day at room temperature. Then the
solution colour changed from yellow to reddish-brown. The solvent
was removed in vacuo. The solid product was washed with pen-
tane and dried under vacuum. Yield: 0.04 g (49.3%), reddish-brown
powder. M.p. 240 °C (decomp.). MS-FAB+: m/z (%) 1041 (1.4)
[M+ꢀCl], 779 (3.8) [M+ꢀClꢀPPh3], 573 (16) [Rh(H2BDI)(PPh3)]+.
1H NMR (CD2Cl2): d 12.94 (br, 2H, N–H), 7.89ꢀ7.81 (m, 12H,
RhꢀPh), 7.24ꢀ7.19 (m, 18H, RhꢀPh), 7.17ꢀ5.99 (m, 20H,
Fig. 1. Benzil-bis(trimethylsilyl)diimine (1) and benzildiimine (2).
the same ligands [12] and show considerable p-backbonding with-
in the chelates. Several types of diimine complexes of ruthe-
nium(II) and rhodium(III) of 9,10-phenanthrenequinone were
isolated [3b] which have been found to bind DNA avidly by inter-
calation between base pairs [13,14]. Rhodium(II) complexes con-
taining phi have found a particularly wide range of application as
photoactivated probes of local DNA helical conformation [3b].
In spite of these interesting properties, examples of transition
metal complexes of 1 as well as 2 are not widely reported and their
molecular structures are also unknown till date. So, we were inter-
ested to characterize the molecular structure of 1 and synthesize
and characterize fully rhodium(III) and iridium(I) complexes of 1
or if not possible, at least of 2. And indeed, we were successful in
the characterization of free 1, but not in finding 1 as ligand in
the complexes, where instead of 1 only 2 was found as bidentate
ligand. We present herein the results from the reactions of 2 with
Vaska’s and Vaska-type complexes trans-[(PPh3)2M(CO)Cl] (M = Ir,
Rh) and the characterization of the products by means of IR, mass,
1H, 13C, 31P NMR spectra, elemental analysis and X-ray diffraction.
In addition, the solid-state structure of 1 was determined here for
the first time by single crystal X-ray diffraction study.
2
H2BDIꢀPh). 13C{1H} NMR (CD2Cl2): d 172.37 (d, JRhꢀC = 51.9 Hz,
C@N), 135.51 (t, J = 5.2 Hz, PPh3ꢀCH), 131.89 (br, PPh3ꢀCH),
129.95 (s, PPh3ꢀCH), 128.13 (t, J = 5.2 Hz, PPh3ꢀCH),
134.93ꢀ126.88 (H2BDIꢀCH). 31P{1H} NMR (CD2Cl2): d 31.1 (d,
1JRhꢀP = 118.5 Hz, PPh3). IR (KBr): 3049 (w), 1589 (w), 1571 (w),
1482 (s), 1432 (s), 1096 (m), 938 (m), 745 (m), 692 (vs), 522 (s)
cmꢀ1. Anal. Calc. for C64H52ClN4P2Rh (1077.39): C, 71.34; H, 4.87;
N, 5.20. Found: C, 70.31; H, 4.63; N, 4.80%.
2.3. Synthesis of trans-[(benzildiimine-N,N0)-carbonyl-
bis(triphenylphosphine)iridium(I)]-chloride (4)
A solution of (PPh3)2Ir(CO)Cl (0.195 g, 0.25 mmol) in benzene
(15 mL) was added to
a benzene solution (5 mL) of Si2BDI
(0.088 g, 0.25 mmol). After 30 min the solution color changed from
yellow to reddish–brown. The resulting solution was stirred at
room temperature for 2 days. The solvent was then removed under
reduced pressure and the resulting residue was washed with pen-
tane (20 mL) and dried under vacuum. Yield: 0.075 g (30.4%), light
red powder. M.p. 175 °C (decomp.). MS-FAB+: m/z (%) 922 (1.6)
[M+ꢀ2HꢀCOꢀCl], 660 (6) [M+ꢀ2HꢀCOꢀClꢀPPh3], 400 (10)
[M+ꢀ2HꢀCOꢀClꢀ2PPh3]. 1H NMR (CD2Cl2): d 12.11 (br, 2H, NH),
2. Experimental
2.1. General
All reactions were carried out under argon using standard
Schlenk and vacuum-line techniques. Solvents were purified by
standard procedures; dichloromethane was distilled from calcium
hydride and n-pentane was distilled from sodium. All solvents
were stored under a dry argon atmosphere over 3 Å molecular
sieves. The complexes [MCl(CO)(PPh3)2] (M = Rh, Ir) [15] were pre-
pared and purified according to literature procedures. Si2BDI was
prepared according to the modified literature procedure from ben-
zil with two equivalents of sodium- or lithium-bis(trimethyl-
silyl)amide followed by quenching with chlorotrimethylsilane
[8,9]. The solution of benzil and sodium-bis(trimethylsilyl)amide
in benzene was stirred at 70 °C for 7 h. After the addition of chlo-
rotrimethylsilane the mixture was heated at 60 °C for 5 h. Then
the solution was filtered and the filtrate was vacuum distilled to
yield crystalline solid 1. It is well soluble in common polar sol-
vents, sparingly soluble in non polar solvents. Other reagents were
commercially available and used without further purification. NMR
spectra were measured with a Jeol Eclipse 270 spectrometer; the
chemical shifts are given relative to external standards (TMS and
85% H3PO4). Mass spectra were recorded with a Jeol MStation
JMS 700, NBA matrix (FAB+). IR spectra were recorded from KBr
pellets using a Perkin–Elmer Spectrum One FT-IR spectrometer.
The melting points, obtained with a Büchi Melting Point B-540 de-
vice, are uncorrected. Elemental analysis was performed by the
Microanalytical Laboratory of the Department of Chemistry and
Biochemistry, LMU, using a Hereaus Elementar Vario El apparatus.
7.97ꢀ6.75 (m, 40H, CHꢀPh). 13C{1H} NMR (CD2Cl2):
d
135.34ꢀ126.70 (m, CHꢀPh). 31P{1H} NMR (CD2Cl2): d 28.5 (s,
PPh3). IR (KBr): 3053 (m), 2957 (w), 2925 (w), 1962, 1597 (m),
1571 (w), 1483 (s), 1435 (vs), 1094 (vs), 998 (m), 942 (w), 747
(s), 721 (m), 693 (vs), 522 (s) cmꢀ1. Anal. Calc. for C51H42IrN2OP2Cl
(988.48): C, 61.96; H, 4.29; N, 2.83. Found: C, 60.05; H, 4.51; N,
2.68%.
2.4. X-ray data collection
Crystals of 1 suitable for X-ray analysis were isolated when the
vacuum distilled yellow liquid was allowed to cool to room tem-
perature after the synthesis. X-ray quality crystals of the com-
plexes 3 and 4 were grown by slow isothermic diffusion of
pentane into solutions of 3 or 4 in CH2Cl2 at room temperature
within 2 days. Single crystal X-ray diffraction data were collected
on a Nonius Kappa CCD diffractometer using graphite-monochro-
mated Mo Ka radiation. Single crystal X-ray structure analyses
were performed by direct methods using the SHELXS software and
refined by full-matrix least-squares with SHELXL-97 [16]. Selected
bond lengths and angles of 1, 3 and 4 are given in Tables 1–3,
respectively. Hydrogen bonds are given in Table 4. The crystal
data and details of the structural refinement can be found in
Table 5.

N. Haque et al. / Inorganica Chimica Acta 363 (2010) 723–728
725
Table 1
HBDI ligands within 1 day (Scheme 1). Interestingly, it contains
one hydrolyzed and one deprotonated nitrogen of each ligand 2 in-
stead of intact 1. Rh(I) is oxidized to Rh(III) after the coordination
of two ligands and forms the stable d6 low spin complex 3. One
NH hydrogen atom from each of the ligand 2 is deprotonated and
they are reduced to H2. Attempts to obtain the mono-H2BDI rho-
dium complex (analogous to 4) from the reaction using the molar
ratio 1:1 resulted also only in complex 3. As in the literature men-
tioned before, the two SiMe3 groups of 1 were replaced by two H
atoms in complex 3. Probably traces of H2O in solvent CH2Cl2
and sterical demands initiated the cleavage of bulky SiMe3 and
introduction of the H atoms to the bound ligand.
Selected bond lengths (Å) and angles (°) for 1.
N(1)ꢀC(1)
N(2)ꢀC(2)
C(1)ꢀC(2)
C(1)ꢀC(3)
C(2)ꢀC(9)
Si(1)ꢀN(1)
Si(2)ꢀN(2)
1.268(19)
1.270(19)
1.523(2)
1.490(2)
1.493(2)
1.737(14)
1.746(13)
C(1)ꢀN(1)ꢀSi(1)
C(2)ꢀN(2)ꢀSi(2)
N(1)ꢀC(1)ꢀC(3)
137.07(11)
133.17(11)
120.71(13)
123.0(13)
116.29(12)
121.53(13)
122.84(13)
115.62(12)
86.82(15)
N(1)ꢀC(1)ꢀC(2)
C(3)ꢀC(1)ꢀC(2)
N(2)ꢀC(2)ꢀC(9)
N(2)ꢀC(2)ꢀC(1)
C(9)ꢀC(2)ꢀC(1)
C(3)ꢀC(1)ꢀC(2)ꢀC(9)
N(1)ꢀC(1)ꢀC(2)ꢀN(2)
N(1)ꢀC(1)ꢀC(2)ꢀC(9)
C(3)ꢀC(1)ꢀC(2)ꢀN(2)
87.90(19)
ꢀ92.81(17)
ꢀ92.46(17)
The reaction of equivalent molars of 1 and IrCl(CO)(PPh3)2 in
benzene at ambient temperature afforded the cationic iridium
complex [Ir(PPh3)2(CO)(H2BDI)]Cl (4) with only one H2BDI ligand
within 2 days (Scheme 1). Attempts to obtain the bis-H2BDI irid-
ium complex analogous to 3 from a 1:2 metal complex: 1 ratio re-
sulted only in complex 4. Similar to 3 in complex 4 also both SiMe3
groups were replaced by two H atoms. But, unlike to the synthesis
of 3 the CO ligand remained intact in 4 after the reaction. Both
complexes are air stable and soluble in polar solvents and insoluble
in non polar solvents.
Table 2
Selected bond lengths (Å) and angles (°) for 3.
Rh(1)ꢀN(1)
Rh(1)ꢀN(2)
Rh(1)ꢀN(3)
Rh(1)ꢀN(4)
Rh(1)ꢀP(1)
Rh(1)ꢀP(2)
N(1)ꢀC(1)
N(2)ꢀC(2)
N(3)ꢀC(15)
N(4)ꢀC(16)
C(1)ꢀC(2)
2.028(3)
2.046(3)
2.038(3)
2.028(2)
2.351(8)
2.367(9)
1.285(4)
1.279(4)
1.284(4)
1.284(4)
1.501(5)
1.499(4)
1.487(4)
1.498(4)
1.496(5)
1.481(5)
0.83(4)
N(4)ꢀRh(1)ꢀN(3)
N(1)ꢀRh(1)ꢀN(2)
N(1)ꢀRh(1)ꢀN(4)
N(3)ꢀRh(1)ꢀN(2)
N(4)ꢀRh(1)ꢀN(2)
N(1)ꢀRh(1)ꢀN(3)
N(2)ꢀRh(1)ꢀP(2)
N(4)ꢀRh(1)ꢀP(2)
N(1)ꢀRh(1)ꢀP(2)
N(4)ꢀRh(1)ꢀP(1)
N(3)ꢀRh(1)ꢀP(1)
N(1)ꢀRh(1)ꢀP(1)
N(2)ꢀRh(1)ꢀP(1)
N(3)ꢀRh(1)ꢀP(2)
P(1)ꢀRh(1)ꢀP(2)
C(1)ꢀN(1)ꢀRh(1)
C(16)ꢀN(4)ꢀRh(1)
C(2)ꢀN(2)ꢀRh(1)
C(15)ꢀN(3)ꢀRh(1)
78.19(11)
78.37(11)
99.59(10)
103.85(12))
177.90(11)
177.48(11)
89.95(8)
89.52(7)
89.07(8)
88.44(7)
89.96(8)
88.78(7)
92.00(8)
92.09(8)
176.75(3)
114.5(2)
114.5(2)
117.4(2)
118.0(2)
3.1. Crystal structure analysis
3.1.1. X-ray structure of Si2BDI (1)
As shown in Fig. 2 the chemically equivalent bonds and angles
of the two equal parts of 1 have similar values of bond lengths and
angles and compare well with those found in structurally analo-
gous compounds [17,18]. The bond lengths CꢀN (N1ꢀC1
1.268(19) and N2ꢀC2 1.270(19) Å), SiꢀN (Si1ꢀN1 1.737(14) and
Si2ꢀN2 1.746(13)) and CꢀC (C1ꢀC2 = 1.523(2), C1ꢀC3 = 1.490(2),
C2ꢀC9 = 1.493(2) Å) fall within the expected range of ideal C@N
double, SiꢀN and CꢀC single bonds. The sum of angles around C1
and C2 is 359.99°, as expected for a sp2 hybridized carbon. The
phenyl ligands are planar (the sum of the angles around C3 and
C9 are 359.99° and 359.97°, respectively) and nearly perpendicular
to each other with a torsion angle C3ꢀC1ꢀC2ꢀC9 of 86.82(15)°.
The atoms N1 and N2 attached with the Si(CH3)3 groups are nearly
in the opposite side to each other and to the phenyl ring as re-
quired by the imposed steric interaction of the bulky groups (tor-
sion angles: N1ꢀC1ꢀC2ꢀN2 87.90, N1ꢀC1ꢀC2ꢀC9 ꢀ92.81,
C3ꢀC1ꢀC2ꢀN2 ꢀ92.46°). This may be the reason that 1 can not
act as bidentate ligand and is easily cleaved by hydrolysis to form
cissoidal 2 which can coordinate to metals as a chelating ligand.
C(15)ꢀC(16)
C(15)ꢀC(17)
C(16)ꢀC(23)
C(1)ꢀC(3)
C(2)ꢀC(9)
N(2)ꢀH(2)
N(3)ꢀH(3)
0.86(4)
Table 3
Selected bond lengths (Å) and angles (°) for 4.
Ir(1)ꢀN(2)
Ir(1)ꢀN(1)
Ir(1)ꢀC(15)
Ir(1)ꢀP(2)
Ir(1)ꢀP(1)
O(1)ꢀC(15)
N(1)ꢀC(1)
N(2)ꢀC(2)
C(1)ꢀC(2)
C(1)ꢀC(3)
C(2)ꢀC(9)
N(1)ꢀH(1)
N(2)ꢀH(2)
1.994(2)
2.032(2)
1.872(3)
2.327(10)
2.350(9)
1.145(3)
1.333(3)
1.340(3)
1.413(3)
1.484(3)
1.481(3)
0.82(3)
C(15)ꢀIr(1)ꢀN(2)
C(15)ꢀIr(1)ꢀN(1)
N(2)ꢀIr(1)ꢀN(1)
C(15)ꢀIr(1)ꢀP(2)
C(15)ꢀIr(1)ꢀP(1)
N(2)ꢀIr(1)ꢀP(2)
N(1)ꢀIr(1)ꢀP(2)
N(2)ꢀIr(1)ꢀP(1)
N(1)ꢀIr(1)ꢀP(1)
P(2)ꢀIr(1)ꢀP(1)
O(1)ꢀC(15)ꢀIr(1)
160.63(10)
96.31(10))
75.26(9)
92.06(8)
95.14(9)
88.61(7)
153.14(6)
103.07(7)
96.68(7)
107.96(3)
177.5(2)
3.1.2. X-ray structure of [Rh(HBDI)2(PPh3)2]Cl (3)
Complex 3 crystallizes with two molecules of disordered dichlo-
romethane as solvate. The coordination sphere of the Rh center can
be described as distorted octahedral (Fig. 3). The phosphine ligands
are mutually trans-disposed with slightly different RhꢀP distances
(Rh1ꢀP1: 2.351(8), Rh1ꢀP2: 2.367(9) Å). The two chelating H2BDI
ligands also occupy trans positions to each other with similar bite
angles (N4ꢀRh1ꢀN3 78.19(11) and N2ꢀRh1ꢀN1 78.37(11)). The
HBDI and the phosphine ligands are placed in axial positions
0.83(3)
Table 4
Hydrogen bonding for 3 and 4.
DꢀHꢁꢁꢁA
d(DꢀH)
d(HꢁꢁꢁA)
d(DꢁꢁꢁA)
<(DHA)
Compound 3
[(P1–Rh1ꢀP2
176.75(3)°,
N1ꢀRh1ꢀN3
177.48(11)°
and
N(2)ꢀH(2)ꢁꢁꢁCl(1)
0.83(4)
0.86(4)
2.60(4)
2.38(4)
3.317(3)
3.158(3)
145(3)
151(3)
N4ꢀRh1ꢀN2 177.90(11)°]. The rest of the angles between the me-
tal atom and the axial and equatorial donor atoms are in the range
of 78.19ꢀ103.85°. The four RhꢀN distances fall within the reported
range [19], two of them (Rh1ꢀN1 and Rh1ꢀN4 2.028(2) Å of two
different ligands located on the same side) are almost equal and
differ significantly from the other two (Rh1ꢀN3 2.038(3) and
Rh1ꢀN2 2.046(3) Å). The bond lengths RhꢀP are slightly longer
and those of RhꢀN are shorter than the bonds observed in other re-
ported examples [20,21]. The bonds N@C (1.279ꢀ1.285 Å) of 3 are
somewhat longer and those of C1ꢀC2 1.501(5) and C15ꢀC16
N(3)ꢀH(3)ꢁꢁꢁCl(1)
Compound 4
N(1)ꢀH(1)ꢁꢁꢁCl(1)
0.82(3)
2.44(3)
3.263(3)
174(2)
3. Results and discussion
Reaction of two molar equivalents of 1 with one molar equiva-
lent of RhCl(CO)(PPh3)2 in CH2Cl2 at room temperature afforded
the cationic rhodium complex [Rh(PPh3)2(HBDI)2]Cl (3) with two

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N. Haque et al. / Inorganica Chimica Acta 363 (2010) 723–728
Table 5
Crystal data and details of the structure refinement for 1, 3 and 4.
Compound
1
3
4
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C20H28N2Si2
352.62
200(2)
C66H56Cl5N4P2Rh
1247.29
195(2)
0.71073
monoclinic
P21/n
C105H90Cl8Ir2N4O2P4
2231.81
195(2)
0.71073
triclinic
0.71073
triclinic
ꢀ
ꢀ
P1
P1
9.2022(18)
10.195(2)
11.698(2)
30.177(6)
9.827(2)
13.190(3)
b (Å)
c (Å)
12.093(2)
17.812(7)
19.791(4)
a
(°)
82.22(3)
90
86.22(3)
b (°)
85.44(3)
108.33(3)
84.70(3)
c
(°)
69.06(3)
1049.2(4)
2
1.1162(4)
0.173
90°
5968.98(13)
4
1.3879(6)
0.608
71.72(3)
2423.6(10)
1
1.5292(5)
3.081
V (Å3)
Z
Calculated density (g cmꢀ3
)
l
(mmꢀ1
)
F(0 0 0)
380
2560
1114
Crystal size (mm3)
h Range (°)
0.28 ꢂ 0.16 ꢂ 0.09
3.27–26.00
ꢀ11 6 h 6 11,
ꢀ12 6 k 6 11,
ꢀ14 6 l 6 14
7694
0.23 ꢂ 0.11 ꢂ 0.10
3.15–26.00
ꢀ14 6 h 6 14,
ꢀ37 6 k 6 37,
ꢀ21 6 l 6 21
23 106
0.12 ꢂ 0.10 ꢂ 0.06
3.24–27.00
ꢀ12 6 h 6 12,
ꢀ16 6 k 6 16,
ꢀ25 6 l 6 25
21 056
Index ranges
Reflections collected
Independent reflections
Rint
4116
0.0197
11 706
0.0382
10 576
0.0218
Completeness to h (%)
Refinement method
99.8
99.8
99.8
full-matrix least-squares on F2
4116/0/223
1.047
full-matrix least-squares on F2
11 706/0/747
1.028
full-matrix least-squares on F2
10 576/0/585
1.056
Data/restraints/parameters
S on F2
Final R indices [I>2
r
(I)]
R1 = 0.0343, wR2 = 0.0894
R1 = 0.0433, wR2 = 0.0947
0.223 and ꢀ0.220
R1 = 0.0463, wR2 = 0.1106
R1 = 0.0733, wR2 = 0.1234
1.222 and ꢀ0.865
R1 = 0.0242, wR2 = 0.0526
R1 = 0.0293, wR2 = 0.0547
1.595 and ꢀ0.898
R indices (all data)
Largest difference peak/hole (e Åꢀ3
)
Scheme 1. Synthesis of the bis-HBDI (3) and mono-H2BDI complex (4) of rhodium(III) and iridium(I).
1.499(4) Å are slightly shorter compared to the respective bonds of
the free ligand 1 (N1ꢀC1 1.268(19), N2ꢀC2 1.270(19), C1ꢀC2
1.523(2) Å). One phenyl ring (C17ꢀC22) of H2BDI and one
torted trigonal bipyramidal as the bond angles around the metal
center are in the range of 75.26(9)ꢀ160.63(10)°. The arrangement,
however, resembles more to a highly distorted square pyramide,
caused by the strong steric interactions between the two PPh3 li-
gands and the two phenyl rings of H2BDI. Due to this steric repul-
sion the phosphine ligands forced from the trans position to almost
cis position [P2ꢀIrꢀP1 = 107.96(3)°] and the H2BDI ring strained
highly to form the small chelate bite angle N2ꢀIr1ꢀN1 = 75.26(9)°.
The N1 and N2 atoms are pseudo trans to the CO ligand
(C15ꢀIr1ꢀN2 160.63(10)°) and P2 of one PPh3 ligand (N1ꢀIr1ꢀP2
(C59ꢀC64) of the phosphine ligand are involved in
p–p stacking.
The distance between the centroids of stacked phenyl rings is
3.62 Å.
3.1.3. X-ray structure of [Ir(CO)(H2BDI)(PPh3)2]Cl (4)
Complex 4 was isolated as solid red crystals including dichloro-
methane as solvate. The molecular view is shown in Fig. 4. Its
geometry could be described as distorted square pyramidal or dis-
153.14(6)°), respectively. As the CO ligand is a better
r-donor–p-

N. Haque et al. / Inorganica Chimica Acta 363 (2010) 723–728
727
Fig. 2. Molecular structure of 1. The thermal ellipsoids are drawn at the 30%
probability level. Hydrogen atoms are omitted for clarity.
Fig. 4. Molecular structure of 4. The thermal ellipsoids are drawn at the 30%
probability level. Hydrogen atoms of phenyl groups and CH2Cl2 solvate molecules
are omitted for clarity.
3.2. Spectroscopy
The 1H NMR spectra of 3 and 4 show distinctive resonances due
to imine N–H hydrogen, which is well separated from other parts
of the spectrum. The relatively broad N–H resonances are observed
at 12.94 (3) and 12.11 (4) ppm, making it simple to determine pro-
tonation of the Si2BDI. The spectra of 3 and 4 also show signals in
the range 7.89ꢀ7.19 and 7.17ꢀ5.99 and 7.97ꢀ6.75 ppm, respec-
tively, indicating the presence of phenyl protons of PPh3 and
H2BDI ligands.
In the 13C NMR spectrum of 3 all phenyl carbons are well re-
solved [135.51ꢀ128.13 ppm (PPh3) and 134.9ꢀ126.8 ppm (Ph–
H2BDI)]. The C@N carbon is observed at 172.37 ppm as a doublet
by coupling with 103Rh. But, in the case of complex 4 overlapping
phenyl
carbon
signals
are
observed
in
the
range
135.34ꢀ126.70 ppm. There is
a very weak broad signal at
170ꢀ175 ppm indicating the C@N carbon, but a better assignment
was not possible.
The signals in both 1H and 13C NMR spectra are shifted further
upfield as compared to the free ligand (1), which suggests an elec-
tron enriched system, because of the more strongly electron donat-
ing PPh3 ligands. (1H: 7.80ꢀ7.32 ppm, 13C: 174.2 ppm (CN),
138.28ꢀ128.14 (PhꢀC) ppm, 1 recorded in CD2Cl2).
The 31P NMR spectra of 3 and 4 exhibit a doublet at 31.1 ppm
with a coupling constant of about 118.5 Hz (3) and a singlet at
28.5 (4) ppm respectively, indicating equivalent phosphine ligands
environment.
Fig. 3. Molecular structure of 3. The thermal ellipsoids are drawn at the 30%
probability level. Hydrogen atoms of phenyl groups and disordered CH2Cl2 solvate
molecules are omitted for clarity.
acceptor ligand than the PPh3 ligand, the Ir1ꢀN2 distance
(1.994(2) Å) trans to it is shorter than the Ir1ꢀN1 distance
(2.032(2) Å) in trans position to the PPh3 ligand. The Ir1ꢀP2 dis-
tance (2.327(10) Å) trans to the N2 atom is slightly shorter than
that of the Ir1ꢀP1 (2.350(9) Å), but both are consistent with
The IR spectra (KBr disc) of 3 and 4 exhibit weak vibrations
reported
values
[21,22].
The
C@N
bond
distances
within 3053ꢀ2925 cmꢀ1 assigned to the
m
(NꢀH) and
m
(CꢀH),
(N1ꢀC1 = 1.333(3) and C2ꢀN2 = 1.340(3) Å) are somewhat longer
and those of CꢀC (C1ꢀC2 = 1.413(3), C1ꢀC3 = 1.484(3) Å) and
C2ꢀC9 = 1.481(3) Å) are slightly shorter than the expected C@N
double and CꢀC single bonds. However, all the bond distances
are in the range observed for similar iridium complexes [23,24].
The phenyl rings of H2BDI in both complexes are essentially pla-
nar. As shown in Table 4, one molecule of the complexes (3 and 4)
is connected to the chloride anion by NꢀHꢁꢁꢁCl hydrogen bond,
involving one imine H atom of one H2BDI and the chloride anion
of another complex.
respectively. A significant low frequency of m(C@N) appearing at
1589, 1571(3) and 1597, 1571 (4) cmꢀ1 in comparison to the free
ligand 1 (1652 and 1646 cmꢀ1) suggests the involvement of imine
nitrogens of the (C@N) groups in coordination with the metal. The
m
(C@C) absorptions were observed between 1482 and 1432 cmꢀ1
.
The strong bands at 692, 522 (3) and 693, 522 (4) cmꢀ1 are indic-
ative of MꢀPPh3 ligation in the complexes [25].
In the positive-ion FAB mass spectrum of 3 the [M+ꢀCl] peak
was observed at m/z = 1041. Other peaks resulting from the frag-
mentation of 3 are observed at m/z = 779 and 573, assigned to

728
N. Haque et al. / Inorganica Chimica Acta 363 (2010) 723–728
[M+ꢀClꢀPPh3] and [Rh(H2BDI)(PPh3)]+, respectively. On the other
[3] (a) A.H. Krotz, L.Y. Kuo, J.K. Barton, Inorg. Chem. 32 (1993) 5963;
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(c) A.M. Pyle, J.K. Barton, Inorg. Chem. 26 (1987) 3820.
[4] J. Sundermeyer, H.W. Roesky, M. Noltemeyer, Can. J. Chem. 67 (1989) 1785.
[5] N. Weis, H. Pritzkow, W. Siebert, Eur. J. Inorg. Chem. 1 (1999) 7.
[6] I. Matsuda, T. Takahashi, Y. Ishii, Chem. Lett. 12 (1977) 1457.
[7] R. Neidlein, D. Knecht, Helv. Chim. Acta 70 (1987) 1076.
[8] G. Tuchtenhagen, K. Rühlmann, Liebigs Ann. Chem. 711 (1968) 174.
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[10] (a) D. Walther, M. Teutsch, Z. Chem. 16 (1976) 118;
hand, for complex
4 instead of the molecular peak, the
[M+ꢀ2HꢀCOꢀCl] peak was observed at m/z = 922. Other peaks
resulting from the successive loss of both PPh3 ligands are ob-
served at m/z = 660 and 400.
Supplementary material
(b) D. Walther, Z. Anorg. Allg. Chem. 8 (1974) 405.
CCDC 736240, 736241 and 736242 contain the supplementary
crystallographic data for 1, 3, and 4, respectively. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.
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[14] A.M. Pyle, E.C. Long, J.K. Barton, J. Am. Chem. Soc. 111 (1989) 4520.
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[16] G.M. Sheldrick, SHELX-97, an Integrated System for Solving and Refining Crystal
Structures from Diffraction Data, University of Göttingen, Germany, 1997.
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[18] S. Nishigaki, H. Yoshioka, K. Nakatsu, Acta Crystallogr. 34 (1978) 857.
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[20] M.T. Youinou, R. Ziessel, J. Organomet. Chem. 363 (1989) 197.
[21] L. Dahlenburg, M. Kuhnlein, Eur. J. Inorg. Chem. 9 (2000) 2117.
[22] R.D. Gilbertson, T.L.S. Lau, S. Lanza, H.P. Wu, T.J.R. Weakley, M.M. Haley,
Organometallics 22 (2003) 3279.
Acknowledgements
Financial support from the Bayerische Forschungsstiftung Mün-
chen (Nadera Haque) and the Dr. Klaus-Römer-Stiftung (Bernd
Neumann) are gratefully acknowledged.
References
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