The 2,2′-diindolylmethane dianion supporting scaffold for group 15 compounds

Article abstract of DOI:10.1016/j.ica.2012.06.019

Deprotonated 2,2′-diindolylmethane functions as a dianionic chelating ligand for the isolation and characterization of the group 15 species {ArCH(3-MeC₈H₄N)₂}PCl (2) and {ArCH(3-MeC ₈H₄N)₂}SbNMe₂ (6, Ar = p-C ₆H₄Br). The single crystal X-ray structure of 2 revealed a six-membered heterocycle featuring an N-P-N bonding motif and a terminal P-Cl function. The antimony complex 6 is a rare example of an N-heterocyclic aminostibine. DFT computations were used to examine the energies of isomers for these compounds and to describe the bonding features of the diindolyl fragment with the group 15 cation.

Full text of DOI:10.1016/j.ica.2012.06.019

Inorganica Chimica Acta 392 (2012) 5–9
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Note
The 2,20-diindolylmethane dianion supporting scaffold for group 15 compounds
⇑
Ian Mallov, Heather Spinney, Titel Jurca, Serge Gorelsky, Tara Burchell, Darrin Richeson
Department of Chemistry, Centre for Catalysis Research and Innovation, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, Canada K1N 6N5
a r t i c l e i n f o
a b s t r a c t
Deprotonated 2,20-diindolylmethane functions as a dianionic chelating ligand for the isolation and char-
acterization of the group 15 species {ArCH(3-MeC8H4N)2}PCl (2) and {ArCH(3-MeC8H4N)2}SbNMe2
(6, Ar = p-C6H4Br). The single crystal X-ray structure of 2 revealed a six-membered heterocycle featuring
an N–P–N bonding motif and a terminal P–Cl function. The antimony complex 6 is a rare example of an
N-heterocyclic aminostibine. DFT computations were used to examine the energies of isomers for these
compounds and to describe the bonding features of the diindolyl fragment with the group 15 cation.
Crown Copyright Ó 2012 Published by Elsevier B.V. All rights reserved.
Article history:
Received 18 April 2012
Received in revised form 30 May 2012
Accepted 3 June 2012
Available online 19 June 2012
Keywords:
2,20-Diindolylmethane
Phosphorus
Antimony
Aminostibine
DFT computations
1. Introduction
low
p-donating ability of the indole nitrogen atoms affords the pos-
sibility of synthesizing
p-acidic group 15 complexes and to probe
The alteration of the electronic and geometric environment of
transition metal and main group element centres can be achieved
through supporting ligand design, modification and substituent
variation. Indolate anions represent variants of amido ligands in
which the N centre resides in a fused, planar aromatic framework.
Like common amido ligands, these anions possess two potential
donor pairs of electrons. However, indolates differ from simple ami-
do ligands due to the fact that one of the nitrogen-centred lone elec-
their Lewis-acid/base properties. Furthermore, such species may
also serve as synthetic reagents, providing access to group 15 cations
or new metal complexes. Herein we present the first application of
deprotonated 2,20-diindolylmethane as dianionic chelating ligands
for the isolation and characterization of the group 15 species
{ArCH(3-MeC8H4N)2}PCl and {ArCH(3-MeC8H4N)2}SbNMe2 (Ar = p-
C6H4Br)
tron pairs is incorporated into the aromatic p-system which leads to
NH HN
N
N
2B
2BH+
reduced donating ability by the coordinated N centre. Bridging two
indoles at the 2-position with a single carbon linkage generates 2,20-
diindolylmethanes such as A [1]. Double deprotonation of the two
indole N–H functions of A would produce a dianionic species, B
(Eq. (1)), that is capable of chelate formation and generation of a
six-membered heterocycle compound. Despite the relatively direct
synthetic access to 2,20-diindolylmethane compounds, via the con-
densation of 3-methylindole with an aldehyde, examples of compre-
hensively reported complexes with these species as ligands are
scarce. Structurally characterized diindolylmethane complexes of
B are limited to the group 4 amido compounds (NEt2)2Ti[(NC8H4-
Me)2CHAr] and (NEt2)2(THF)Zr[(NC8H4Me)2CHAr] (Ar = C6H5, p-
C6H4Br) [2a,b], the group 4 metallocene compounds Cp2M[(NC8H4
Me)2CHAr] (M = Ti, Ar = C6H5; M = Zr, Ar = C6H5, p-C6H4(OCH3)) [3]
(1)
H
H
R
R
A
B
.
2. Results and discussion
The in situ deprotonation of di(3-methylindolyl)-4-bro-
mophenylmethane with dimethylaminopyridine (DMAP) in the
presence of PCl3 in CH2Cl2 yielded compound 2 in moderate yield
(55%) after removal of volatiles and extraction with THF (Eq. (2)).
The 1H and 13C NMR spectra of this product exhibited the resonances
for two diastereomeric compounds, in an approximate 5:1 ratio each
consistent with the proposed formulation of 2 and each possessing
doubly deprotonated 2,20-diindolylmethane substituents. These
features were further supported by the appearance of two 31P
NMR resonances at d90.3 ppm (major) and 96.0 ppm (minor). These
two isomers arise from the disposition of the P–Cl group and the
and
a single group 14 complex (C6H5)2Si[(NC8H4Me)2CHAr]
(Ar = p-C6H4OMe) [2a]. The steric bulk of the ligand and relatively
⇑
Corresponding author. Fax: +1 613 562 5170.
E-mail address: darrin@uottawa.ca (D. Richeson).
0020-1693/$ - see front matter Crown Copyright Ó 2012 Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.06.019

6
I. Mallov et al. / Inorganica Chimica Acta 392 (2012) 5–9
p-C6H4Br substituent relative to the six-membered heterocyclic
ring. Variation of the reaction stoichiometry did not result in an
appreciable reduction of the minor product in the NMR spectra
and gave poorer overall yields. Furthermore, attempts to separate
the isomers by extraction or recrystallization methods have not
met with success
and 1.6678(13) Å for 5 [6,7]. Furthermore, the P–Cl bond length
of 2.108(2) Å in 2 is slightly shorter than the P–Cl bond lengths
of 2.148(1) Å of 3, 2.1723(9) Å of 4, and 2.1993(6) Å of 5
Cl
NMe2
R
P
R
iPr
Sb
iPr
Cl
P
N
N
N
N
Ar
Ar
Cl
N
N
P
PCl3
5
NH HN
N
N
R = iPr, 3; Ph, 4
Ar = pMeOPh
DMAP
CH2Cl2
7
(2)
H
1
H
.
In order to explore the electronic structure and relative energies
of the two isomers of compound 2, DFT optimizations were carried
out using B3LYP and a mixed TZVP/DZVP basis set. The energy dif-
ference between the two isomers was found to be only 3.3 kcal/
mol with the crystallographically observed isomer being more sta-
ble. For comparison between the computed and experimental fea-
tures, selected structural parameters from the optimization are
presented alongside the crystallographic data in Table 1. Owing
to these computational results we propose that the crystallograph-
ically characterized isomer obtained for 2 is the major isomer ob-
served in the NMR spectra.
2
Br
Br
.
Compound 2 represents a new member of the 2-halo-1,3,2-
diazaphospholene class of compounds and possesses a unique
scaffold provided by the diindolylmethane framework. Although
these species have a rich history, the synthetic approaches to these
compounds have received significant current attention [4–7]. In
addition, most of these diaminophospholenes consist of five-mem-
bered cycles while compound 2 has the P centre in a six-membered
ring [4a,6–8]. As a result we obtained the single crystal X-ray struc-
ture of compound 2 using crystals that were prepared by slow dif-
fusion of hexanes into a saturated CH2Cl2 solution of 2. The results
of this analysis are summarized in Fig. 1 and Table 1. The trigonal
pyramidal P centre in 2 is defined by a stereochemically active lone
electron pair, the two N centres of the chelating di(indolyl)methane
ligand and a chloride group. In this structure the P–Cl group and the
p-C6H4Br substituent are oriented on the same side of the heterocy-
clic ring (‘‘cis’’ conformation). This relative orientation of the two
centres defines one of the possible isomers for the structure of com-
pound 2. The two tetrahedral centres P(1) and C(10) of the resulting
six-membered heterocycle are directed to the same side of the ring
plane to give a boat-like conformation.
The details of the bonding interactions between the dianionic
di(indolyl)methane ligand and the PCl dication fragments were
next examined. As expected,
a strong energy of interaction
(ꢀ709.8 kcal/mol) and high bond order (2.15) between these two
species were observed, which correspond to a charge transfer from
the diindolyl ligand to PCl fragment of 1.78 electrons. The di(indo-
lyl) ligand has four significant donor orbitals that interact with the
cation. The highest occupied fragment orbitals (HOFO) and their
relative contributions are HOFO, HOFO ꢀ 1, HOFO ꢀ 2, and
HOFO ꢀ 5 and are shown in Fig. 2. The P–Cl cation fragment accepts
this electron density into three lowest unoccupied fragment orbi-
tals LUFO, LUFO + 1 and LUFO + 2. The LUFO and LUFO + 1 orbitals
are dominated by phosphorus p orbital (80%) character. The
LUFO + 2 orbital is mixture of phosphorus p (63%) and Cl p (32%)
The P–N bond lengths of 2, at 1.689(6) and 1.676(6) Å are com-
parable to other previously reported structures of similar N-het-
erocyclic phosphines. For example, the six-membered
heterocyclic compound 3 displayed P–N bond lengths of 1.678(2)
and 1.681(2) and the bond distance of 4 was 1.670(2) Å [8a]. These
distances are slightly longer than the bond lengths of 1.6684(13)
and is essentially a
mix of
(LUFO with HOFO/HOFO-2 and LUFO + 2 with HOFO ꢀ 5)
and
(LUFO + 1 with HOFO ꢀ 1) in nature. In order to compare
r P–Cl orbital. The fragment interactions are a
r
p
the electronic interactions observed in 2 with the related com-
pound 3, similar DFT computations were carried out on
3(Fig. S1).1 Similar to 2, a strong energy of interaction between
the PCl and (iPrN)2C10H6 fragments and high bond order were ob-
tained. In the case of 3, the interaction energy and bond order were
larger than for 2 with values of ꢀ771.3 kcal/mol and 2.28, respec-
tively. These corresponded to a charge transfer of 1.83 electrons
from the diamido fragment to PCl. The diamidonapthalene ligand
fragment donates from the highest four occupied orbitals (relative
charge transfer in brackets): HOFO (11.7%), HOFO ꢀ 1 (17.3%),
HOFO ꢀ 2 (33.5%), HOFO ꢀ 3 (30.2%). These orbitals have analogous
spatial distributions to those seen for the di(indolyl)methane frag-
ment of 2. Furthermore, similar acceptor orbitals on the PCl frag-
ment were obtained from the fragment bonding analysis of 3.
Specifically the major acceptor orbitals were LUFO (34.8%),
LUFO + 1 (57.0%) LUFO + 2 (11.6%). There was a small acceptor con-
tribution from LUFO + 10 (4.0%) which is a P centred orbital with d
character.
Overall, the bonding analysis supports the experimental bond
lengths obtained from X-ray analysis. For example, compound 3
displayed slightly shorter P–N bond distances than 2. This appears
to be due largely to a reduced p-donation of the di(indolyl)meth-
1
Fig. 1. Thermal ellipsoid representation and numbering scheme for 2. Hydrogen
A figure providing the fragment orbitals for the interaction of the ligand and the
PCl2+ fragments, similar to Fig. 2, is provided in the supporting information.
atoms and a co-crystallized toluene molecule have been omitted for clarity.

I. Mallov et al. / Inorganica Chimica Acta 392 (2012) 5–9
7
Table 1
Selected bond distances and angles for 2 derived from single crystal X-ray analysis and computation.
Selected bonds
SSa BLb (Å)
Compc BLb (Å)
Selected angles
SSa angles (deg)
Compc angle (deg)
P–Cl
P–N1
P–N2
2.108(3)
1.689(6)
1.676(6)
2.154
1.725
1.725
N–P–N
96.8(3)
96.15
102.33
N1–P–Cl
N2–P–Cl
P–N1–C1
P–N2–C19
P–N1–C9
P–N2–C11
101.5(2)
101.0(2)
122.9(5)
123.5(5)
128.3(9)
129.5(5)
123.47
128.26
a
b
c
SS = solid state.
BL = bond lengths.
Comp = computed.
of the deprotonated and coordinated 2,20-diindolylmethane ligand.
Single resonances in the 1H and 13C NMR spectra were assigned to
the methyl protons and carbon atoms of the remaining dimethyl-
amido substituent. The proposed mononuclear structure is consis-
Å
tent with reported five-membered 2-X-1,3,2-stibolenes (X Cl, Br)
[9] and with the only reported stibolene with the Sb centre cap-
tured in a six-membered ring, 7 [8a,10]. Confirmation of the chem-
ical formula of 6 was obtained by elemental analysis
N(CH3)2
Sb
NH HN
N
N
Sb[N(CH3)2]3
(3)
toluene, -78 °C
- 2 HN(CH3)2
H
H
6
Br
Br
.
In spite of repeated attempts, crystals of 6 suitable for structural
elucidation were not forthcoming. The mononuclear structure of 6
was, therefore, modeled with a DFT computational study using the
B3LYP functional and the mixed DZVP/TZVP basis set. As observed
in the case of 2, isomers with two relative orientations of the Sb-
NMe2 to the ligand reached satisfactory minima with only a very
slight energy difference (2.1 kcal/mol). In contrast to the optimized
structure of 2, in this case the lower energy structure displayed the
Sb–NMe2 and the p-C6H4Br moieties in a ‘‘trans’’ conformation with
respect to the metallacyclic ring (Fig. S2). Examining the bonding
between the di(indolyl) anionic fragment and the SbNMe2 dication
revealed a high degree of interaction with a bond order of 1.97 and
charge transfer of 1.58 electrons from the ligand to the antimony-
amido fragment. This corresponded to a large energy of interaction
of ꢀ531.3 kcal/mol.
The in-depth bonding features of 6 displayed major donation
from five di(indolyl)methane donor orbitals to the SbNMe2 frag-
ment. As in the case of 2, the most significant were HOFO ꢀ 2 with
24.8% and HOFO ꢀ 5 with 38.6% donation respectively (Fig. S3). The
HOFO (5.1% donation), HOFO ꢀ 1 (7.4% donation) and HOFO ꢀ 3
(3% donation) each make important but smaller contributions to
Fig. 2. Fragment orbitals for optimized 2. The FOs with the largest contributions to
bonding are shown. The change in the orbital population (%) due to the fragment
interactions is provided by
the orbital.
DP values and indicate the relative charge transfer for
2+
bonding. The acceptor orbital array on the SbNMe2 fragment is
also similar to that observed with 2. However, there are some
interesting differences. Specifically, the Sb–NMe2 LUFO is the
ane ligand into the LUFO + 1 relative to the diamidonaphthalene li-
gand in 3. The slightly shorter P–Cl distance for 2 is consistent with
the lower degree of ligand donation into the LUFO + 2, an antibond-
ing P–Cl orbital.
In order to apply the di(indolyl)methane ligand scaffold to the
heavier congeners of group 15, Sb[N(CH3)2]3 was reacted with
{ArCH(3-MeC8H4NH)2} (Eq. (3)). This transamination reaction
was carried out at ꢀ78 °C in toluene, followed by gradual warming
to room temperature and removal of volatiles to produce the white
amidostibine 6 in 88% yield within 6 h. 1H and 13C NMR spectra
showed the expected resonances for the protons and carbon atoms
2+
largest accepting orbital (47.2%) and is an Sb-centred p orbital.
The LUFO + 1 is the next largest accepting orbital (34.5%) and is
dominated by Sb p orbital character (58.2%) but has very signifi-
cant N-centred p nature (29.3%). Like compound 2, the LUFO + 2 ac-
cepts a smaller percentage (3.8%) from the di(indolyl)methane
donor group. Furthermore, this orbital is a mix of 68.1% Sb p orbital
and 8.9% N p character and is Sb–NMe2 antibonding in nature. This
orbital is, in fact, the analogy to the LUFO + 2 of the PCl dication
fragment of 2. However, a significant difference in the nature of

8
I. Mallov et al. / Inorganica Chimica Acta 392 (2012) 5–9
this orbital arises from the fact that LUFO + 2 has 10.4% contribu-
tion from an antimony d orbital. Finally, the Sb amido cation ac-
cepts 3.1% of the electron density into the LUFO + 8, an orbital
that is predominantly of Sb d orbital character. This increased
importance of acceptor d orbitals would be an anticipated feature
of the heavier members of group 15.
mer). 1H NMR(C6D6, major isomer, ppm): 2.11 (s, 6H, 2 CH3), 5.60
[s, 1H CH(4-bromophenyl)(3-methylindolyl)2], 7.16 (d, 2H, HAr,
3
3JHH = 8.1 Hz) 7.22 (t, 2H, HAr, JHH = 8.1 Hz), 7.25 (m, 4H, HAr,
3
3JHH = 8.4 Hz), 7.53 (d, 2H, HAr, JHH = 7.8 Hz), 7.65 (m, 2H, HAr,
3JHH = 7.8 Hz) Minor isomer: 1H NMR(CDCl3, minor isomer, ppm):
2.17 (s, 6H, 2 CH3), 5.78 [s, 1H CH(4-bromophenyl)(3-methylindol-
yl)2], 7.08 (d, 2H, HAr, 3JHH = 8.1 Hz) 7.24 (t, 2H, HAr, 3JHH = 8.1 Hz),
3
3
7.38 (m, 4H, HAr, JHH = 8.4 Hz), 7.50 (d, 2H, HAr, JHH = 7.8 Hz),
3. Conclusion
3
7.81 (m, 2H, HAr, JHH = 7.8 Hz) 13C NMR (CDCl3, major isomer,
ppm): 9.03(CMe), 36.60 (CH(3-methylindolyl)2), 106.47 (CAr),
110.54 (CAr), (CAr), 115.84 (CAr), 115.92 (CAr), 119.15 (CAr),
122.29 (CAr), 123.68 (CAr), 129.31 (CAr), 129.23 (CAr), 130.76
(CAr), 138.28 (CAr), 139.57 Anal. Calc. for C25H19 N2BrPCl: C,
60.81; H, 3.88; N, 5.67. Found: C, 60.47; H, 3.79; N, 5.43.
This report expands on the small number of known di(indo-
lyl)methane compounds to include the first examples featuring
group 15 elements. Two new compounds of 2,20-diindolylmethane
have been obtained using two distinct synthetic methodologies; (i)
substitution of two chlorophosphine groups by di(indolyl)methane
in the presence of base and (ii) use of metal amido base to doubly
deprotonate the indolyl groups with concomitant coordination of
the resulting anionic ligand. One of the products, a six-membered
heterocycle featuring an N–P–N bonding motif and a terminal P–Cl
function, is an interesting material for further synthesis of phos-
phorus compounds. The antimony complex 6 is a rare example of
an N-heterocyclic aminostibine and provides the first definitive
evidence that diindolylmethane ligands can effectively support
heavier main-group elements to form stable compounds, and that
these compounds are obtainable in high yields. The intimate bond-
ing features of the diindolyl fragment with the group 15 cation
were revealed through computational analysis and several com-
mon aspects will assist in defining our future goals. Continued
exploration of the unique steric and electronic properties of the
di(indolyl)methane ligand promise to add significantly to chemis-
try of these chelating diamido ligands.
4.1.2. Di-(3-methylindol-2-yl)dimethylamidoantimony-4-
bromophenylmethane (6)
To
a Schlenk flask containing a suspension of 0.336 g
(0.783 mmol) di-(3-methylindolyl)-4-bromophenylmethane in
2 mL toluene cooled to ꢀ78 °C in a dry ice/acetone bath was added
a solution of 0.225 g (0.88 mmol) tris(dimethylamido)antimony in
2 mL toluene. The resultant white suspension was allowed to warm
to room temperature over a period of 3 h, with stirring, by which
point it had become a slightly cloudy, colourless solution. Volatiles
were then removed in vacuo and the resulting white solid was
washed with hexanes (2 ꢁ 1.5 mL) to yield 6 (0.407 g, 88% yield)
1H NMR (CDCl3, ppm): 2.48 (s, 6H, NCH3), 2.77 (s, 6H, 2 CH3), 5.84
[s, 1H CH(4-bromophenyl)(3-methylindolyl)2], 6.69 (d of quartets,
3
3
2H, HAr, JHH = 8.6 Hz), 7.16 (m, 4H, HAr, JHH = 8.1 Hz),), 7.31 (m,
3
3
4H, HAr, JHH = 7.9 Hz),), 7.63 (m, 2H, HAr, JHH = 8.6 Hz) 13C NMR
(CDCl3, ppm): 9.21 (CMe), 38.11 (NCH3), 41.02 (CH(3-methylindol-
yl)2), 110.95 (CAr), 111.43 (CAr), 118.68 (CAr), 119.21 (CAr), 119.60
(CAr), 121.30 (CAr), 121.84 (CAr), 129.76 (CAr), 131.46 (CAr),
132.00 (CAr), 137.04 (CAr), 141.31 (CAr) Anal. Calc. For
4. Experimental section
4.1. General Considerations
C
27H25BrN3Sb: C, 54.67; H, 4.35; N, 7.08. Found: C, 54.52; H, 4.34;
N, 7.01.
EI-MS m/z 593.03 [0.4%, M+], 547.97 [14%, C25H19BrN2
SbH+ = LSbH+], 546.98 [3.9%, C25H19BrN2Sb+ = LSb+], 428.09 [50%,
25H21BrN2+ = L+].
All manipulations were carried out under nitrogen atmosphere
employing standard drybox or Schlenk line techniques. Dichloro-
methane was distilled over CaH2 prior to use. All other solvents
were sparged with nitrogen and dried by passage through a col-
umn of activated alumina using an apparatus purchased from
Anhydrous Engineering. Deuterated benzene, chloroform and
dichloromethane were dried by addition of molecular sieves. Di-
C
4.3. Computations
Density Functional Theory (DFT) calculations have been per-
formed using the GAUSSIAN 09 package [11]. Wave function stability
calculations were performed to confirm that the calculated wave
functions corresponded to the electronic ground state. The struc-
tures of all species were optimized using the B3LYP exchange-
correlation (XC) functional with the mixed basis set (DZVP on Br
and Sb and TZVP on all other atoms). Tight SCF convergence criteria
(10ꢀ8 a.u.) were used for all calculations. Harmonic frequency cal-
culations with the analytic evaluation of force gradients were used
to determine the nature of the stationary points.
(3-methylindol-2-yl)-4-bromophenylmethane
was
prepared
according to a previously reported procedure [2a]. Tris(dimethyl-
amido)antimony was purchased from Strem Chemicals and used
as received. All other reagents were purchased from Aldrich and
used as received. NMR spectra were run on Bruker Avance 300
and 500 MHz spectrometers with deuterated benzene, chloroform
or dichloromethane as the solvent using residual protons of the
deuterated solvent for reference. Elemental analysis was per-
formed by Midwest Microlabs, Indianapolis, Indiana.
The analysis of the molecular orbital (MO) compositions in
terms of occupied and unoccupied orbitals of the fragment species
(HOFOs and LUFOs, respectively), the construction of MO diagram
(Figs. 2, S1and S3) and Mayer bond orders were calculated using
the AOMix program [12,13]. Atomic charges and Wiberg bond or-
ders in the natural atomic orbital basis were evaluated by using
the natural population analysis (NPA) [14].
4.1.1. Di-(3-methylindol-2-yl)chlorophosphine-4-bromophenylme
thane (2)
PCl3(0.050 mL, 0.57 mmol) was added dropwise to a solution of
di-(3-methylindolyl)-4-bromophenylmethane (0.189 g, 0.440
mmol in 2 mL dichloromethane), followed immediately by addi-
tion of 0.140 g (1.15 mmol) DMAP. The resulting clear yellow solu-
tion was allowed to stir for 72 h before removal of the solvent in
vacuo. The product was extracted with THF (3 ꢁ 1.5 mL), filtered
through a glass frit and solvent was removed in vacuo. The resul-
tant off-white solid was washed with hexanes (3 ꢁ 1.5 mL) and
diethyl ether (3 ꢁ 1.5 mL) and the resulting white solid was recrys-
tallized from dichloromethane at ꢀ22 °C. Yield: 0.119 g (54.8%)
31P{1H} NMR (C6D6, ppm): 90.3 (major isomer), 96.0 (minor iso-
4.4. Crystallography
Crystals of compound 2 were mounted on thin glass fibers using
paraffin oiland thesample were cooled to 200 °K prior to data collec-
tion. Data were collected on a Bruker AXS SMART (3-circle) single
crystal diffractometer equipped with a sealed Mo tube source

I. Mallov et al. / Inorganica Chimica Acta 392 (2012) 5–9
9
[3] M.R. Mason, D. Ogrin, B. Fneich, T.S. Barnard, K. Kirschbaum, J. Organomet.
Chem. 690 (2005) 157.
[4] (a) D. Gudat, Acc. Chem. Res. 43 (2010) 1308;
(wavelength 0.71073 Å) and SMART 1 K CCD detector. Raw data col-
lection and processing were performed with SMART software package
from BRUKER AXS (BRUKER AXS: SMART – Bruker Molekular Analysis
Research Tool, version 5.632, Bruker AXS Inc., Madison, WI, USA
1997)The crystals were weakly diffracting at high angles. Since the
R(sigma) was exceeding 35% beyong 1.1 Å resolution limit, the data
set was trimmed in order to improve signal to noise ratio and
achieve better refinement convergence.
(b) S. Burck, D. Gudat, M. Nieger, W.W. Du Mont, J. Am. Chem. Soc. 128 (2006)
3946;
(c) S. Burck, D. Gudat, K. Naettinen, M. Nieger, M. Niemeyer, D. Schmid, Eur. J.
Inorg. Chem. (2007) 5112.
[5] J.W. Dube, G.J. Farrar, E.L. Norton, K.L.S. Szekely, B.F.T. Cooper, C.L.B.
Macdonald, Organometallics 28 (2009) 4377.
[6] C.A. Caputo, J.T. Price, M.C. Jennings, R. McDonald, N.D. Jones, Dalton Trans.
(2008) 3461.
[7] B.E. Maryanoff, R.O. Hutchins, J. Org. Chem. 37 (1972) 3475. The first six-
membered diaminophospholene was reported here.
[8] (a) H.A. Spinney, I. Korobkov, G.A. Di Labio, G.P.A. Yap, D.S. Richeson,
Organometallics 26 (2007) 4972;
Acknowledgments
We thank the Natural Sciences and Engineering Research Coun-
cil (NSERC) of Canada for funding and Professor Tom Woo for ac-
cess to the Wooki Cluster for computations. TJ thanks NSERC for
a PGSD scholarship.
(b) H.A. Spinney, G.P.A. Yap, I. Korobkov, G.A. DiLabio, Organometallics 25
(2006) 3541.
[9] T. Gans-Eichler, D. Gudat, M. Nieger, Heteroatom. Chem. 16 (2005) 327.
[10] H.A. Spinney, I. Korobkov, D.S. Richeson, Chem. Commun. (2007) 1647.
[11] GAUSSIAN 09, Revision A.02, M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria,
M.A. Robb, J.R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson,
H. Nakatsuji, M. Caricato, X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G.
Zheng, J.L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J.A.
Montgomery, Jr., J.E. Peralta, F. Ogliaro, M. Bearpark, J.J. Heyd, E. Brothers,
K.N. Kudin, V.N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A.
Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. Millam, M.
Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, R.L.
Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth, P. Salvador, J.J. Dannenberg,
S. Dapprich, A.D. Daniels, Ö. Farkas, J.B. Foresman, J.V. Ortiz, J. Cioslowski, D.J.
Fox, GAUSSIAN, Inc., Wallingford CT, 2009.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ica.2012.06.019.
References
[1] M.R. Mason, T.S. Barnard, M.F. Segla, B. Xie, K. Kirschbaum, J. Chem. Crystallogr.
33 (2003) 531.
[2] (a) M.R. Mason, Chemtracts-Inorg. Chem. 16 (2003) 272;
(b) M.R. Mason, B.N. Fneich, K. Kirschbaum, Inorg. Chem. 42 (2003) 6592.
[12] S.I. Gorelsky, version 6.36 ed.; University of Ottawa: Ottawa, Canada, 2007.
[13] S.I. Gorelsky, A.B.P. Lever, J. Organomet. Chem. 635 (2001) 187.
[14] A.E. Reed, R.B. Weinstock, F.J. Weinhold, Chem. Phys. 83 (1985) 735.