Isomers of a dibismuthane, R2Bi-BiR2 [R = 2,6-(Me2NCH2)2C6H3], and unusual reactions with oxygen: Formation of [R2Bi]2(O 2)

Article abstract of DOI:10.1021/ic052160n

R₂Bi-BiR₂ [1; R = 2,6-(Me₂NCH ₂)₂C₆H₃], a dibismuthane that exists in different forms in the crystalline state, reacts in air with the formation of the peroxide [R₂Bi]₂(O₂) (2) and partial oxidation of the pendant (dimethylamino)-methyl groups, yielding the mononuclear bismuth complex R′R″Bi (3) [R′ = 2-(Me₂NCH ₂)-6-{Me₂N(O)CH₂}C₆H₃; R″ = 2-(Me₂NCH₂)-6-{O(O)C}C₆H ₃].

Full text of DOI:10.1021/ic052160n

Inorg. Chem. 2006, 45, 2341−2346
Isomers of a Dibismuthane, R2Bi
Unusual Reactions with Oxygen: Formation of [R2Bi]2(O2) and R
[R′ ) 2-(Me2NCH2)-6- Me2N(O)CH2
2-(Me2NCH2)-6- O(O)C C6H3]
−BiR2 [R ) 2,6-(Me2NCH2)2C6H3], and
′R′′Bi
{
}
}C6H3; R′′ )
{
Lucia Balazs,† Hans J. Breunig,*,† Enno Lork,† Albert Soran,‡ and Cristian Silvestru*,‡
UniVersita¨t Bremen, Fachbereich 2, D-28334 Bremen, Germany, and Facultatea de Chimie si
Inginerie Chimica, UniVersitatea “Babes-Bolyai” Cluj-Napoca, RO-400028 Cluj-Napoca, Romania
Received December 20, 2005
R2Bi
reacts in air with the formation of the peroxide [R2Bi]2(O2) (2) and partial oxidation of the pendant (dimethylamino)-
methyl groups, yielding the mononuclear bismuth complex R ′′Bi (3) [R′ ) 2-(Me2NCH2)-6- Me2N(O)CH2 C6H3;
′′ ) 2-(Me2NCH2)-6- O(O)C C6H3].
−BiR2 [1; R ) 2,6-(Me2NCH2)2C6H3], a dibismuthane that exists in different forms in the crystalline state,
′
R
{
}
R
{
}
Introduction
2-(Me2NCH2)C6H4,9 2,4,6-Me3C6H2,10 Me3Si;11 R2
)
(HCdCMe)212] with Bi-Bi bond lengths ranging from 2.990
to 3.066 Å.13
Tetraorganodibismuthanes, R2Bi-BiR2 (R ) alkyl, aryl),
are air-sensitive compounds, and many alkyl derivatives are
even self-igniting when exposed to air.1 It is, however,
possible to moderate the reactivity with oxygen, and sev-
eral reports on controlled oxidation reactions of dibismuth-
anes have appeared.2-7 Although as an initial step the
insertion of dioxygen into the Bi-Bi bond was proposed,
attempts failed to prove the existence of bis(diorganobis-
muthyl) peroxide.2 Only monoxides of the type (R2Bi)2O,5-7
or rearrangement products Bi2O3 and R3Bi,2,3 were isolated,
and bis(dimesitylbismuthyl) oxide was characterized by
X-ray crystallography.5,6 Dibismuthanes with known crys-
tal structures include R2Bi-BiR2 [R ) Ph,2 (Me3Si)2CH,8
We report here the synthesis, structures, and reactions of
R2Bi-BiR2 [1; R ) 2,6-(Me2NCH2)2C6H3], a tetraaryldibis-
muthane with protection by eight pendant amino groups.
Compound 1 reacts with air to form the peroxide [R2Bi]2-
(O2) (2) and R′R′′Bi [3; R′ ) 2-(Me2NCH2)-6-{Me2N(O)-
CH2}C6H3; R′′ ) 2-(Me2NCH2)-6-{O(O)C}C6H3], a mono-
nuclear bismuth complex where the pendant Me2NCH2
groups are partially oxidized.
Experimental Section
General Procedures. All syntheses and manipulations of the
air-sensitive compounds were carried out under argon using standard
Schlenk techniques. All solvents were dried and freshly distilled
under argon before use. The ligand 1,3-(Me2NCH2)2C6H4 was
synthesized according to a literature procedure.14 All other reagents
were commercially available. The NMR spectra were run on a
Bruker Avance DRX 600 instrument for R2BiCl and a Bruker DPX
200 instrument for the rest of compounds. Chemical shifts are
reported in δ units (ppm) referenced to C6D5H (7.15 ppm, 1H) and
* To whom correspondence should be addressed. E-mail:
breunig@chemie.uni-bremen.de (H.J.B.), cristi@chem.ubbcluj.ro (C.S.).
Tel: (+49)421-2182266 (H.J.B.), (+40)264-593833 (C.S.). Fax: (+49)-
421-2184042 (H.J.B.), (+40)264-590818 (C.S.).
† Universita¨t Bremen.
‡ Universitatea “Babes-Bolyai” Cluj-Napoca.
(1) Breunig, H. J.; Mu¨ller, D. Z. Naturforsch. 1983, 38b, 125.
(2) (a) Calderazzo, F.; Morvillo, A.; Pelizzi, G.; Poli, R. Chem. Commun.
1983, 507. (b) Calderazzo, F.; Poli, R.; Pelizzi, G. J. Chem. Soc.,
Dalton Trans. 1984, 2365. (c) Whitmire, K. H.; Cassidy, J. M. Acta
Crystallogr. 1992, C48, 917.
(9) Balazs, L.; Breunig, H. J.; Lork, E.; Silvestru, C. Eur. J. Inorg. Chem.
2003, 1361.
(3) Wieber, M.; Sauer, I. Z. Naturforsch. 1984, 39b, 887.
(4) Wieber, M.; Sauer, I. Z. Naturforsch. 1987, 42b, 695.
(5) Breunig, H. J.; Ebert, K. H.; Schulz, R. E.; Wieber, M.; Sauer, I. Z.
Naturforsch. 1995, 50b, 735.
(6) Li, X.-W.; Lorberth, J.; Ebert, K. H.; Massa, W.; Wocadlo, S. J.
Organomet. Chem. 1998, 560, 211.
(10) Balazs, L.; Breunig, H. J.; Lork, E. Z. Naturforsch. 2005, 60b, 180.
(11) Mundt, O.; Becker, G.; Ro¨ssler, M.; Witthauer, C. Z. Anorg. Allg.
Chem. 1983, 506, 42.
(12) Ashe, A. J., III; Kampf, J. W.; Puranik, D. B.; Al-Taweel, S. M.
Organometallics 1992, 11, 2743.
(13) Breunig, H. J. Z. Anorg. Allg. Chem. 2005, 631, 621.
(14) Yamamoto, Y.; Chen, X.; Kojima, S.; Ohdoi, K.; Kitano, M.; Doi,
Y.; Akiba, K.-Y. J. Am. Chem. Soc. 1995, 117, 3922.
(7) Breunig, H. J.; Mu¨ller, D. Z. Naturforsch. 1986, 41b, 1129.
(8) Balazs, G.; Breunig, H. J., Lork, E. Organometallics 2002, 21, 2584.
10.1021/ic052160n CCC: $33.50
Published on Web 02/09/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 5, 2006 2341

Balazs et al.
Table 1. Summary of Single-Crystal X-ray Diffraction Data for Compounds 1-3
1a‚CH3C6H5
1b/c‚Et2O
2‚Et2O
3
formula
fw
T/K
C48H76Bi2N8‚C7H8
1275.26
173(2)
C48H76Bi2N8‚C2H5O0.5
1220.19
173(2)
C52H86Bi2N8O3
1289.25
173(2)
C22H30BiN3O3
593.47
173(2)
cryst syst
space group
a/Å
b/Å
monoclinic
P21/c
12.276(2)
21.942(4)
21.119(4)
90
103.55(3)
90
5530.3(17)
4
1.522
6.396
0.0387
0.0902
2.085/-1.163
284976
triclinic
P1h
triclinic
P1h
monoclinic
P21/c
11.451(2)
11.096(1)
17.588(2)
90
94.53(1)
90
2227.8(5)
4
1.769
7.941
0.0508
0.0719
0.885/-0.839
284975
11.242(2)
21.154(4)
22.509(4)
95.49(2)
90.68(1)
98.20(1)
5272.1(17)
2
11.446(3)
12.012(5)
23.542(6)
85.28(3)
77.77(1)
62.15(2)°
2796.4(15)
2
c/Å
R/deg
â/deg
γ/deg
V/Å3
Z
Dc/g cm-1
1.540
6.704
0.0647
0.1134
1.685/-1.780
284977
1.531
6.330
0.0439
0.1004
2.095/-2.304
284974
µ(Mo KR)/mm-1
R1 [I > 2σ(I)]
wR2
largest diff peak and hole/e Å-3
CCDC no.
Scheme 1
C6D6 (128.0 ppm, 13C). Mass spectrometry (MS) and IR spectra
were recorded on a Finnigan MAT 8222 spectrometer and a Fourier
transform IR Spektrum 1000 instrument, respectively.
Synthesis of [2,6-(Me2NCH2)2C6H3]4Bi2 (1). Butyllithium (16.3
mL, 15% solution in hexane, 26 mmol) was added dropwise to a
solution of 1,3-(Me2NCH2)2C6H4 (5.2 g, 27 mmol) in 60 mL of
hexane. The reaction mixture was stirred under reflux for 12 h,
and removal of the solvent in a vacuum gives RLi as a white-
orange powder, which is dissolved in 80 mL of diethyl ether. This
solution was added dropwise at -80 °C to a solution of BiCl3 (4.1
g, 13 mmol) in 100 mL of diethyl ether. The mixture was warmed
to room temperature, stirred for 12 h, and then filtered. Removal
of the solvent gives 6.15 g (75%) of R2BiCl [R ) 2,6-(Me2-
slowly to a solution of 1 (0.2 g, 0. 16 mmol) in 15 mL of THF,
under argon, and slow diffusion was allowed to take place at room
temperature. Slow oxidation, at room temperature, resulted after
several weeks in the formation of colorless crystals of 3: IR (KBr,
cm-1) 1602 (COO), 1337 (NO); MS (EI, 70 eV, 200 °C) m/z (%)
577 (70) [M+ - O], 562 (25) [M+ - 2O], 534 (42) [M+ - COO
- O], 400 (100) [RBi+].
X-ray Crystallography. Table 1 lists crystal and refinement data.
The data were collected using a Stoe IPDS diffractometer for 1a‚
CH3C6H5 and a Siemens P4 four-circle diffractometer for 1b/c‚
Et2O, 2‚Et2O, and 3, respectively, using graphite-monochromated
Mo KR radiation (λ ) 0.710 73 Å). The structures were solved by
direct methods (full-matrix least squares on F 2). All non-hydrogen
atoms were refined with anisotropic thermal parameters. For
structure solution and refinement, the software package SHELX-
97 was used.15 The drawings were created using the DIAMOND
program by Crystal Impact GbR.16
1
NCH2)2C6H3] as a white solid [mp 155 °C; H NMR (600 MHz,
25 °C, CDCl3, TMS) δ 2.18 (12H, s, CH3), 3.62 (4H, s, CH2), 7.27
3
3
(1H, t, C6H3, JHH ) 7.5 Hz), 7.38 (2H, d, C6H3, JHH ) 7.4 Hz);
MS (EI, 70 eV, 200 °C) m/z (%) 591 (9) [R2Bi+], 435 (100)
[RBiCl+], 400 (61) [RBi+]]. A solution of R2BiCl (2.7 g, 4.30
mmol) in 30 mL of tetrahydrofuran (THF) was added dropwise
at -20 °C to magnesium (0.38 g, 15.7 mmol) activated with
1,2-dibromoethane (0.5 mL). The reaction mixture was stirred for
3 h, and then the temperature was raised to 10 °C. Removal of the
solvent in a vacuum, extraction with petroleum ether (80 mL), and
filtration and removal of the solvent to dryness give 1.6 g (67%)
of dark-red 1 (mp 60 °C). Crystals of 1a‚CH3C6H5 and 1b/c‚Et2O
are obtained from solutions of 1 in toluene or diethyl ether at
Results and Discussion
The dibismuthane 1 is obtained in a multistep procedure
including the arylation of BiCl3 with RLi and the reduction
of the resulting diarylbismuth monochloride with magnesium
in THF (Scheme 1).
-28 °C: 1H NMR (200 MHz, 25 °C, C6D6, TMS) δ 2.06 (12H, s,
2
CH3), AB spin system with A, 3.47, B, 3.60 (4H, CH2, JHH
)
3
13.6 Hz), 7.20 (2H, d, C6H3, JHH ) 7.5 Hz), 7.59 (1H, t, C6H3,
3JHH ) 7.5 Hz); MS (CIneg, NH3, 200 °C) m/z (%) 1181 (10) [M-
- H], 991 (45) [R2Bi-BiR-], 591 (100) [R2Bi-], 400 (97) [RBi-].
Heating a solution of 1 results in a new set of signals: 1H NMR
(200 MHz, 75 °C, C6D6, TMS) δ 2.04 (12H, s, CH3), AB spin
Compound 1 is a dark-red compound, both as a solid and
in solutions in hydrocarbons. Single crystals were grown at
-28 °C from solutions in toluene or diethyl ether. They
contain three different molecular forms of 1. Monoclinic
crystals in the space group P21/c consisting of 1a‚CH3C6H5
are obtained from toluene. The molecular structure of 1a is
depicted in Figure 1. Crystals obtained from diethyl ether
are triclinic (space group P1h). They contain two isomers,
1b and 1c, in the asymmetric unit. The structures of 1b and
2
system with A, 3.29, B, 3.76 (4H, CH2, JHH ) 11.7 Hz), 7.17
(3H, m, C6H3).
Synthesis of [2,6-(Me2NCH2)2C6H3]4Bi2(O2) (2). Slow access
of air into a solution of 1 in THF or diethyl ether at -28 °C gives
the peroxide 2 as a colorless, air-stable crystalline solid (mp
48 °C). Recrystallization from diethyl ether affords single crys-
tals of 2‚Et2O: MS (CIpos, NH3, 200 °C) m/z (%) 832 (28) [R2-
Bi2O2+], 591 (30) [R2Bi+], 401 (42) [RBi+ + H], 193 (100) [R+ +
2H].
(15) Sheldrik, G. M. SHELX-97; Universita¨t Go¨ttingen: Go¨ttingen, Ger-
many, 1997.
(16) DIAMONDsVisual Crystal Structure Information System; Crystal
Impact: Bonn, Germany, 2001.
Synthesis of [2-(Me2NCH2)-6-{Me2N(O)CH2}C6H3][2-(Me2-
NCH2)-6-{O(O)C}C6H3]Bi (3). Diethyl ether (25 mL) was added
2342 Inorganic Chemistry, Vol. 45, No. 5, 2006

Isomers of a Dibismuthane
elongations result from the increasing coordination by the
pendant-arm ligands.
In solution, the different types of coordination of the
pendant-arm ligands are not preserved. The 1H NMR
spectrum in C6D6 of 1 at +20 °C contains only one set of
signals for the 2,6-(Me2NCH2)2C6H3 groups, i.e., a singlet
signal for the methyl groups, an AB spin system for the CH2
protons, and the signals for the aromatic hydrogen atoms.
When the solution is warmed above room temperature, a
second set of rather broad 2,6-(Me2NCH2)2C6H3 signals
emerges, with increasing intensities on the cost of the signals
of 1. At +70 °C exclusively, the signals of the high-
temperature species are observed. The process is reversible,
and on cooling, the signals for 1 appear again. A possible
explanation for these findings is to consider the reversible
dissociation of 1 with the formation of the diarylbismuth
radical R2Bi• [R ) 2,6-(Me2NCH2)2C6H3] in solutions of 1.
Dissociative reactions of dibismuthanes have been proposed
several times, but even in the case of the sterically encum-
bered derivative, R2Bi-BiR2 [R ) (Me3Si)2CH], the forma-
tion of diorganobismuth radicals was not observed in solution
at room temperature.8,18 By contrast, the dissociation of
analogous diphosphanes or diarsanes with the formation of
R2P• or R2As• [R ) (Me3Si)2CH] is a well-established
process.19,20 Dissociation of 1 occurs also under the condi-
tions of electrospray ionization mass spectroscopy (EIMS),
and the R2Bi+ fragment ion is observed at highest mass. With
chemical ionization, however, the molecular ion of 1 can be
detected.
Figure 1. ORTEP-like representation of 1a in the crystal of 1a‚CH3C6H5.
The ellipsoids represent a probability of 30%. The hydrogen atoms are
omitted for clarity.
1c are shown in Figure 2. Selected interatomic distances and
angles are given in Table 2.
In all three forms, the dibismuthane molecules adopt the
trans conformation with dihedral angles lp-Bi-Bi-lp of
175.35(3)° (1a), 74.80(6)° (1b), and 80.37(6)° (1c) (lp )
assumed position of the lone pair of electrons on the bisector
of the obtuse C-Bi-C angle; the dihedral angle was
considered to be the angle between these bisectors). The
isomers have different types of coordination of the pendant
(dimethylamino)methyl arms. In 1a, four of the pendant Me2-
NCH2 arms, one per aryl group, are bonded through the
nitrogen atoms to both bismuth centers, which both display
a 3 + 2 coordination pattern with three normal covalent
bonds (Bi-Bi, 2 × Bi-C) and two dative bonds from the
pendant amino groups [Bi(1)-N(2) 3.241(7) Å, Bi(1)-N(4)
3.236(6) Å and Bi(2)-N(6) 3.284(8) Å, Bi(2)-N(8) 3.335-
(6) Å; compare the sum of covalent radii, ∑cov(Bi,N) ) 2.22
Å, and the van der Waals radii, ∑vdw(Bi,N) ) 3.94 Å,
respectively].14
In 1b, 3 + 2 coordination is also achieved for both bismuth
atoms; however, the origin of the amino groups is different;
i.e., at Bi(3), they originate from different aryl groups [Bi-
(3)-N(10) 3.241(12) Å and Bi(3)-N(12) 3.183(11) Å] like
in 1a, but at Bi(4), they belong to the same aryl group [Bi-
(4)-N(15) 3.370(10) Å and Bi(4)-N(16) 3.279(11) Å]. In
1c, the coordination number at Bi(2) is 3 + 3, with three of
the pendant arms involved in coordinative bonding [Bi(2)-
N(5) 3.351(9) Å, Bi(2)-N(6) 3.217(11) Å, and Bi(2)-N(7)
3.352(9) Å], whereas at Bi(1), 3 + 2 coordination occurs
[Bi(1)-N(1) 3.210(10) Å and Bi(1)-N(4) 3.233(10) Å]. For
all three forms of dibismuthane molecules, the N f Bi
intramolecular interactions are considerably longer than those
observed for the related R2Bi-BiR2 [R ) 2-(Me2NCH2)-
C6H4] [Bi-N 2.952(5)-3.170(4) Å].9 The different environ-
ments of the bismuth atoms lead to variations of the Bi-Bi
bond lengths [1a, 3.0992(6) Å; 1b, 3.1788(8) Å; 1c, 3.2092-
(8) Å]. These values are the longest known Bi-Bi bond
lengths in dibismuthanes, and there is little doubt that the
Slow access of air to a solution of 1 in THF or diethyl
ether at -28 °C gives the peroxide 2, a colorless, air-stable
crystalline solid. Solutions of 2 in organic solvents are
unstable at room temperature; they decompose with the
elimination of oxygen and the formation of (R2Bi)2O [mp
1
99-103 °C; H NMR (200 MHz, 25 °C, CDCl3, TMS) δ
1.99 (12H, s, CH3), AB spin system with A, 3.23, B, 3.49
(4H, s, br, CH2), 7.15 (3H, m, C6H3); MS (EI, 70 eV, 200
°C) m/z (%) 1007 (1) [R2BiOBiR+], 816 (1) [R2BiOBi+],
591 (100) [R2Bi+], 417 (80) [RBiOH+], 400 (77) [RBi+];
the same compound was isolated from hydrolysis of the
monochloride R2BiCl]. A reaction path leading to 2 is given
in Scheme 2.
Compound 2 crystallizes from diethyl ether as 2‚Et2O in
the space group P1h. The structure was determined by X-ray
diffraction. Selected interatomic distances and angles are
given in Table 3. The molecules of 2 consist of two R2Bi
units bridged by an O2 group, which adopts a position
intermediate between the end-on and side-on bridging
coordination (Figure 3). The O-O bond length [1.515(7)
Å] in 2 corresponds to a single bond and is only slightly
(17) Emsley, J. Die Elemente; Walter de Gruyter: Berlin, 1994.
(18) Ashe, A. J., III; Ludwig, E. G.; Oleksyszyn, J. Organometallics 1983,
2, 1859.
(19) Hinchley, S. L.; Morrison, C. A.; Rankin, D. W. H.; Macdonald, C.
L. B.; Wiacek, R. J.; Cowley, A. H.; Lappert, M. F.; Gundersen, G.;
Clyburne, J. A. C.; Power, P. P. Chem. Commun. 2000, 2045.
(20) Hinchley, S. L.; Morrison, C. A.; Rankin, D. W. H.; Macdonald, C.
L. B.; Wiacek, R. J.; Voigt, A.; Cowley, A. H.; Lappert, M. F.;
Gundersen, G.; Clyburne, J. A. C.; Power, P. P. J. Am. Chem. Soc.
2001, 123, 9045.
Inorganic Chemistry, Vol. 45, No. 5, 2006 2343

Balazs et al.
Figure 2. Structures of (a) 1b and (b) 1c in the crystal of 1b/c‚Et2O. The hydrogen atoms are omitted for clarity.
Table 2. Selected Interatomic Distances (Å) and Angles (deg) for 1
Molecule 1a
Table 3. Selected Interatomic Distances (Å) and Angles (deg) for 2
Bi(1)-O(1)
Bi(1)-C(1)
Bi(1)-C(13)
Bi(1)-N(1)
Bi(1)-N(2)
Bi(2)-O(2)
Bi(2)-C(25)
Bi(2)-C(37)
Bi(2)-N(5)
Bi(2)-N(6)
Bi(1)-O(2)
Bi(2)-O(1)
O(1)-O(2)
2.138(5)
2.285(6)
2.292(6)
3.148(7)
2.873(6)
2.171(5)
2.275(6)
2.305(7)
3.083(9)
2.848(5)
2.817 (5)
2.710(5)
1.515(7)
C(1)-Bi(1)-C(13)
O(1)-Bi(1)-C(1)
O(1)-Bi(1)-C(13)
C(25)-Bi(2)-C(37)
O(2)-Bi(2)-C(25)
O(2)-Bi(2)-C(37)
O(1)-Bi(2)-O(2)
O(1)-Bi(2)-C(25)
O(1)-Bi(2)-C(37)
O(2)-O(1)-Bi(1)
O(2)-O(1)-Bi(2)
Bi(1)-O(1)-Bi(2)
O(1)-O(2)-Bi(2)
101.3(2)
92.0(2)
88.0(2)
98.2(2)
98.2(2)
Bi(1)-Bi(2)
Bi(1)-C(1)
Bi(1)-C(13)
Bi(2)-C(25)
Bi(2)-C(37)
Bi(1)-N(2)
Bi(1)-N(4)
Bi(2)-N(6)
Bi(2)-N(8)
3.0992(6)
2.324(7)
2.303(6)
2.376(7)
2.300(7)
3.241(7)
3.236(6)
3.284(8)
3.335(6)
C(1)-Bi(1)-C(13)
C(1)-Bi(1)-Bi(2)
C(13)-Bi(1)-Bi(2)
C(25)-Bi(2)-C(37)
C(25)-Bi(2)-Bi(1)
C(37)-Bi(2)-Bi(1)
94.5(2)
104.38(17)
97.10(17)
99.0(2)
103.29(17)
97.80(18)
87.1(2)
33.93(16)
132.10(19)
81.97(19)
99.5(3)
53.1(2)
149.6(2)
93.0(3)
Molecule 1b
Bi(3)-Bi(4)
Bi(3)-C(49)
Bi(3)-C(61)
Bi(4)-C(73)
Bi(4)-C(85)
Bi(3)-N(10)
Bi(3)-N(12)
Bi(4)-N(15)
Bi(4)-N(16)
3.1788(8)
2.323(11)
2.331(10)
2.332(11)
2.306(11)
3.241(12)
3.183(112)
3.370(10)
3.279(11)
C(49)-Bi(3)-C(61)
C(49)-Bi(3)-Bi(4)
C(61)-Bi(3)-Bi(4)
C(73)-Bi(4)-C(85)
C(73)-Bi(4)-Bi(3)
C(85)-Bi(4)-Bi(3)
100.0(4)
101.5(3)
100.6(3)
101.6(4)
100.3(3)
108.3(3)
[2.817(5) Å] or Bi(2)-O(1) [2.710(5) Å] lie between the
values for single bonds and van der Waals contact distances
of the Bi and O atoms [compare the sum of covalent radii,
∑
cov(Bi,O) ) 2.16 Å, and the van der Waals radii, ∑vdw-
(Bi,O) ) 3.80 Å, respectively].17 The Bi(1)-O(1)-O(2) and
O(1)-O(2)-Bi(2) bond angles in 2 are 99.5(3) and 93.0-
(3)°, respectively. The Bi2O2 unit is folded [dihedral angles
Bi(1)-O(1)-Bi(2)/Bi(1)-O(2)-Bi(2) 44.1(6)° and O(1)-
Bi(1)-O(2)/O(1)-Bi(2)-O(2) 14.6(2)°], with wide Bi-O-
Bi [149.6(2) and 139.3(1)°] and acute O-Bi-O [32.05(15)
and 33.93(16)°] angles. The bonding of the peroxo bridge
can be described as a combination of normal covalent Bi-
(2)-O(2) and Bi(1)-O(1) and dative O(1) f Bi(2) and O(2)
f Bi(1) bonds. The C2BiO core at a metal center is
pyramidal with the bond angles at the Bi atoms [range 87.1-
(2)-101.3(2)°] generally more acute than in those in 1a
[range 94.5(2)-104.38(17)°]. For each metal center, two
intramolecular N-Bi interactions are established by nitrogen
atoms of the same aryl group; the shorter ones are trans to
an oxygen atom [Bi(1)-N(2) 2.873(6) Å, N(2)-Bi(1)-O(1)
153.7(1)° and Bi(2)-N(6) 2.848(5) Å, N(6)-Bi(2)-O(2)
159.9(1)°], while the longer ones are trans to a carbon atom
[Bi(1)-N(1) 3.148(7) Å, N(1)-Bi(1)-C(13) 153.1(2)° and
Bi(2)-N(5) 3.083(9) Å, N(5)-Bi(2)-C(37) 147.0(2)°; a
weaker interaction involving the disordered N(3) atom, Bi-
(1)-N(3B) 3.41(4) Å, can also be considered]. Almost
orthogonal to the Bi2O2 core lie the Bi-C bonds of the other
Molecule 1c
Bi(1)-Bi(2)
Bi(1)-C(1)
Bi(1)-C(13)
Bi(2)-C(25)
Bi(2)-C(37)
Bi(1)-N(1)
Bi(1)-N(4)
Bi(2)-N(5)
Bi(2)-N(6)
Bi(2)-N(7)
3.2092(8)
2.321(11)
2.297(10)
2.327(11)
2.338(10)
3.210(10)
3.233(10)
3.351(9)
C(1)-Bi(1)-C(13)
C(1)-Bi(1)-Bi(2)
C(13)-Bi(1)-Bi(2)
C(25)-Bi(2)-C(37)
C(25)-Bi(2)-Bi(1)
C(37)-Bi(2)-Bi(1)
100.2(4)
102.6(3)
103.0(3)
101.4(4)
103.9(3)
102.1(2)
3.217(11)
3.352(9)
Scheme 2
longer than the corresponding distances in H2O2 (1.475 Å)
or the peroxo cluster (Ph2SbO)4(O2)2 [1.461(4) and 1.466-
(5) Å].21 Also, the Bi(1)-O(1) [2.138(5) Å] and Bi(2)-O(2)
[2.171(5) Å] distances are consistent with single bonds; they
are, however, longer than those found for (Mes2Bi)2O [Bi-
O 2.075(8) and 2.064(7) Å].6 The distances Bi(1)-O(2)
(21) Breunig, H. J.; Kru¨ger, T.; Lork, E. J. Organomet. Chem. 2002, 648,
209.
2344 Inorganic Chemistry, Vol. 45, No. 5, 2006

Isomers of a Dibismuthane
Figure 3. (a) ORTEP-like representation at 40% probability of 2 in the crystal of 2‚Et2O (the hydrogen atoms are omitted for clarity). (b) Environment
around the Bi atoms in 2.
Scheme 3
pair of aryl substituents, where the amino groups are directed
away from the bismuth atoms. If the additional longer Bi-O
contacts are not considered, the coordination about the metal
centers is again tetragonal pyramidal [C(1) and C(25) atoms
in apical positions, respectively], with a higher degree of
distortion than that in 1a.
Figure 4. ORTEP-like representation at 50% probability of 3. The
hydrogen atoms are omitted for clarity.
When a THF/Et2O solution of the dibismuthane 1 is
exposed to air at room temperature, the oxidation proceeds
with cleavage of the Bi-Bi bond and formation of the
mononuclear diarylbismuth carboxylate 3. In the course of
the reaction, one of the pendant (dimethylamino)methyl
groups is transformed into an amine oxide and another one
is oxidized to a carboxyl group, which is intramolecularly
bonded to the bismuth center. An equation describing the
formation of 3 is proposed in Scheme 3. The side products
were not identified. A similar conversion to an amine oxide
derivative, i.e., Me2(O)N(CH2)3Sn(OCOCH2)3N, was ob-
served during the reaction of the oxidation of Me2N(CH2)3-
SnPh3 with N(CH2COOH)3 in dimethylformamide.22
It is very likely that the peroxide 2 is involved in the
oxidation process as a source of the oxygen atoms. Peroxides
are powerful oxidation agents that are also used for the
transformation of amines to amine oxides. Crystals of 3
belong to the monoclinic space group P21/c. They consist
of molecules containing bismuth bonded to a (C,O)-bidentate
chelating aryl carboxylato ligand derived from 3-[(dimethy-
lamino)methyl]benzoic acid and a second aryl group (Figure
4). Selected interatomic distances and angles are given in
Table 4.
Table 4. Selected Interatomic Distances (Å) and Angles (deg) for 3
Bi(1)-C(1)
Bi(1)-C(11)
Bi(1)-O(1)
Bi(1)-O(3)
Bi(1)-N(1)
Bi(1)-N(2)
O(1)-C(7)
O(2)-C(7)
O(3)-N(3)
2.274(8)
2.270(8)
2.395(6)
2.372(7)
3.019(8)
2.834(9)
1.295(10)
1.253(10)
1.404(9)
C(1)-Bi(1)-C(11)
C(1)-Bi(1)-O(1)
C(11)-Bi(1)-O(1)
C(1)-Bi(1)-O(3)
C(11)-Bi(1)-O(3)
O(1)-Bi(1)-O(3)
N(3)-O(3)-Bi(1)
O(3)-N(3)-C(20)
O(3)-N(3)-C(21)
O(3)-N(3)-C(22)
C(20)-N(3)-C(21)
C(20)-N(3)-C(22)
C(21)-N(3)-C(22)
102.9(3)
70.8(3)
77.5(2)
94.2(3)
80.6(3)
149.7(2)
125.3(5)
110.8(7)
108.2(7)
109.8(7)
108.6(8)
111.3(7)
108.1(8)
with two O-Bi-C angles considerably smaller than 90°
[O(1)-Bi(1)-C(1) 70.8(3)° and O(1)-Bi(1)-C(11) 77.5-
(2)°] and a C(1)-Bi(1)-C(11) angle of 102.9(3)°. The Bi-C
bond lengths [Bi(1)-C(1) 2.274(8) Å and Bi(1)-C(11)
2.270(8) Å] are comparable with the corresponding bonds
found in 1 or 2. The O(3) atom of the amine oxide pendant
arm is coordinated to the metal center, thus resulting in a
six-membered BiC3NO ring. The Bi-O bond lengths [Bi-
(1)-O(1) 2.395(6) Å and Bi(1)-O(3) 2.372(7) Å] are longer
than the values observed for the Bi-O single bond in (Mes2-
Bi)2O [Bi-O 2.095(18) and 2.117(19) Å5 and 2.075(8) and
2.064(7) Å6]. Similar values were observed for diphenyl-
bismuth N-benzoylglycinate, a polymeric diorganobismuth-
(III) carboxylate with bridging carboxylato groups [Bi-O
Because of the formation of the five-membered BiC3O
ring, the pyramidal geometry of the C2BiO core is irregular,
(22) Dakternieks, D.; Dyson, G.; Jurkschat, K.; Tozer, R.; Tiekink, E. R.
T. J. Organomet. Chem. 1993, 458, 29.
Inorganic Chemistry, Vol. 45, No. 5, 2006 2345

Balazs et al.
2.396(6) and 2.484(6) Å],23 or for the closely related
hypervalent mononuclear bismuth(III) species [2,6-(Me2-
NCH2)2C6H3]Bi[C6H4{C(CF3)2O}-2] [Bi-O 2.194(9) Å].14
The inner-coordination sphere around the bismuth center
of 3 can be described as distorted pseudo trigonal bipyra-
midal, with C(1) and C(11) in equatorial positions and O(1)
and O(2) in axial positions [O(1)-Bi(1)-O(3) 149.7(2)°].
Additional trans intramolecular Bi-N interactions [Bi(1)-
N(1) 3.019(8) and Bi(1)-N(2) 2.834(9) Å; N(1)-Bi(1)-
N(2) 142.1(2)°] are established by the two remaining
Me2NCH2 pendant arms, resulting in five-membered BiC3N
rings. When also the amino groups are considered, a distorted
octahedral coordination results.
different crystalline forms with remarkably long Bi-Bi bond
lengths, and a tendency to insert dioxygen from air probably
via the intermediate formation of diorganobismuth radicals
open interesting perspectives for applications of the dibis-
muthane oxygen system as a strong oxidant, which at room
temperature performs the transformation of a (dimethylami-
no)methyl group into a carboxyl group.
Acknowledgment. This work was supported by the
National University Research Council (CNCSIS, Romania;
Research Project Nos. A-1713 and TD-100/2004-2005) and
Deutsche Forschungsgemeinschaft (Research Project No.
436RUM 113/19/0-1). We also thank Universita¨t Bremen
for providing research facilities and financial support during
short-term research stays.
Conclusions
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
The formation of a new tetraaryldibismuthane with protec-
tion by eight pendant-arm amino ligands, which exist in
(23) Huber, F.; Domagala, M.; Preut, H. Acta Crystallogr. 1988, C44, 828.
IC052160N
2346 Inorganic Chemistry, Vol. 45, No. 5, 2006