Syntheses and crystal structures of organoindium(III) 1-D coordination polymers with bis(diphenylphosphino)alkane dioxides

Article abstract of DOI:10.1080/00958972.2018.1441404

Bromomethyl-dibromo-indium(III), Br₂InCH₂Br, obtained from indium monobromide and methylene dibromide, reacts with hard and soft donor ligands to afford the corresponding indium(III) organometallic complexes. In this work, we investigated the conditions to prepare adducts of Br₂InCH₂Br using bis(diphenylphosphino)alkane dioxides acting as hard ligands. We report here the synthesis and crystal structures of two 1-D coordination polymers with the hard donor ligands Ph₂P(O)(CH₂)_mP(O)Ph₂ (m?=?2, dppeO₂ and m?=?6, dpphO₂). Compounds 1 and 2 with formulas [Br₂In(CH₂Br)(dppeO₂)]_n (1) and [Br₂In(CH₂Br)(dpphO₂)]_n (2) were characterized by IR and Raman spectroscopy and elemental analysis. We also obtained an ionic indium(III) compound with dppeO₂ acting as a chelating ligand with formula [InBr₂(dppeO₂)₂][InBr₃(CH₂Br)] (3). The crystal structures were determined for 1–3 using single crystal X-ray diffractometry. The geometry around the In(III) can be described as a trigonal bipyramid in 1 and 2, and the chains were packed onto the plane giving layers that are stabilized mainly by intermolecular interactions. Compound 3 has a square bipyramidal In(III) cation with formula [Br₂L₂In]⁺ and tetrahedral organoindium(III) anion with formula [Br₃InCH₂Br]^–. Hirshfeld surface analysis employing 2-D fingerprint plots have been used to analyze intramolecular and intermolecular interactions present in the solid state of the structures.

Full text of DOI:10.1080/00958972.2018.1441404

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Syntheses and crystal structures of
organoindium(III) 1-D coordination polymers with
bis(diphenylphosphino)alkane dioxides
Clovis Peppe, Melina De Azevedo Mello, Felipe Terra Martins, Jaqueline Pinto
Vargas, Felipe Christoff Wouters, Robert Alan Burrow, Danielle Cangussu &
Rafael Pavão Das Chagas
To cite this article: Clovis Peppe, Melina De Azevedo Mello, Felipe Terra Martins, Jaqueline
Pinto Vargas, Felipe Christoff Wouters, Robert Alan Burrow, Danielle Cangussu & Rafael Pavão
Das Chagas (2018): Syntheses and crystal structures of organoindium(III) 1-D coordination
polymers with bis(diphenylphosphino)alkane dioxides, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2018.1441404
To link to this article: https://doi.org/10.1080/00958972.2018.1441404
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Journal of Coordination Chemistry, 2018
https://doi.org/10.1080/00958972.2018.1441404
Syntheses and crystal structures of organoindium(III) 1-D
coordination polymers with bis(diphenylphosphino)alkane
dioxides
Clovis Peppea, Melina De Azevedo Mellob, Felipe Terra Martinsc,
Jaqueline Pinto Vargasd, Felipe Christoff Woutersa, Robert Alan Burrowa,
Danielle Cangussuc and Rafael Pavão Das Chagasc
adepartamento de Química, universidade federal de santa maria, santa maria, Brazil; bColégio técnico
c
industrial de santa maria, universidade federal de santa maria, santa maria, Brazil; instituto de Química,
universidade federal de Goiás, Goiânia, Brazil; dCampus Caçapava do sul, universidade federal do Pampa,
Caçapava do sul, Brazil
ABSTRACT
ARTICLE HISTORY
received 17 october 2017
accepted 31 december 2017
Bromomethyl-dibromo-indium(III), Br2InCH2Br, obtained from indium
monobromide and methylene dibromide, reacts with hard and soft
donor ligands to afford the corresponding indium(III) organometallic
complexes. In this work, we investigated the conditions to prepare
adducts of Br2InCH2Br using bis(diphenylphosphino)alkane dioxides
acting as hard ligands. We report here the synthesis and crystal
structures of two 1-D coordination polymers with the hard donor
ligands Ph2P(O)(CH2)mP(O)Ph2 (m = 2, dppeO2 and m = 6, dpphO2).
Compounds 1 and 2 with formulas [Br2In(CH2Br)(dppeO2)]n (1) and
[Br2In(CH2Br)(dpphO2)]n (2) were characterized by IR and Raman
spectroscopy and elemental analysis. We also obtained an ionic
indium(III) compound with dppeO2 acting as a chelating ligand with
formula [InBr2(dppeO2)2][InBr3(CH2Br)] (3). The crystal structures were
determined for 1–3 using single crystal X-ray diffractometry. The
geometry around the In(III) can be described as a trigonal bipyramid
in 1 and 2, and the chains were packed onto the plane giving layers
that are stabilized mainly by intermolecular interactions. Compound
3 has a square bipyramidal In(III) cation with formula [Br2L2In]+ and
tetrahedral organoindium(III) anion with formula [Br3InCH2Br]–.
Hirshfeld surface analysis employing 2-D fingerprint plots have
been used to analyze intramolecular and intermolecular interactions
present in the solid state of the structures.
KEYWORDS
indium; organometallic
compounds; 1-d
coordination polymer;
bis(diphenylphosphino)
alkane dioxide; crystal
structure
CONTACT danielle Cangussu
danielle_cangussu@ufg.br; rafael Pavão das Chagas
rafael.pchagas@gmail.com
the supplemental data for this article can be accessed at https://doi.org/10.1080/00958972.2018.1441404.
© 2018 informa uK limited, trading as taylor & francis Group

2
C. PEPPE ET AL.
1. Introduction
The synthesis and characterization of coordination polymers (CPs) are of interest due to their
structures with different network topology, which open up possibilities of application in
many areas such as porous materials for gas storage, capture or separation, luminescent
materials, molecular recognition, catalysis, and molecular magnetism [1–5]. Despite the
growing number of reported CPs, there are far less examples of Group 13 metal-organic
coordination polymers compared to transition metals and lanthanides. Recent research
suggests promising applications for metal-organic frameworks containing metals of Group
13 and, therefore, the exploration of new indium structures has been of interest [6–11].
Most indium coordination polymers described have been inorganic or metallo-organic
involving N,O-donor ligands, mainly carboxylates or pyrazine ligands [12–16]. Among them,
there are a few examples of organometallic coordination polymers of indium, for instance,
with dicarboxylate [17], oximate [18], and amino carboxylate ligands [19]. To the best of our
knowledge, solid-state structural studies of organoindium coumpounds with 1,2-bis(diphe-
nylphosphino)alkanes dioxides have hitherto not been reported.
In the last two decades, some examples of coordination complexes of transition, main
group and lanthanide metal ions have been obtained with diphosphine dioxide-type ligands
of general formula Ph2P(O)–X–P(O)Ph2 (X=(CH2)m where m = 2, 4, and 6) which act as bidentate
chelating or bridging ligands [20–22]. The use of such ligands with variable X groups is
attractive to the supramolecular design of CPs with different structural motifs. This ligand
displays interesting characteristics, such as flexibility and increased chain length, which are
important to form multidimensional CPs. For example, reactions with diphosphine dioxide
ligands and Ln(III) [23–25], Ag(I) [26], Sn(II) [27], Pb(II) [28], Mn(II), and Fe(II) [29] may lead to
1-D, 2-D, and 3-D polymer structures. The flexible molecular backbone and ease of altering
the structural motif of bis(diphenylphosphino)alkanes dioxides, associated with the structural
and coordinative flexibility of indium, can lead to a variety of interesting new structures.
Our group has been investigating the coordination properties of the organoindium(III)
compound, Br2InCH2Br, produced from oxidative insertions of InBr into the carbon–halogen
bonds of methylene dibromide. This organometallic compound of indium(III) has been used
mainly as a model for coordination chemistry studies. Independently, it has been determined
that hard oxygen ligands, LH such as ethers, dimethylsulfoxide, and triphenylphosphine oxide
coordinate to the metallic center [30], while soft bases, LS displace bromide of the bromome-
thyl substituent to form ylides of general structure Br3InCH2LS (Scheme 1) [31–35].

JOURNAL OF COORDINATION CHEMISTRY
3
Scheme 1. Coordination behavior of organoindium compound Br2inCh2Br.
The simultaneous coordination of soft and hard ligands was also described, using
dialkylsulfides R2S (R=CH3, CH2Ph) as soft ligands (LS) and dimethylsulfoxide and triphe-
nylphosphine oxide acting as hard ones (LH) to produce compounds with general structure
X3(LH)nInCH2LS (X=halogen) [36]. The remarkable stability of the Br2InCH2Br compound allied
to its ability to coordinate to hard and soft bases through their two different electrophilic
sites suggest that the halogenomethylic complexes of indium are potential starting materials
to obtain metal-organic frameworks (MOFs). In view of this and aiming to design organoin-
dium MOFs, we turned our attention to finding ligands that could use the full coordination
ability to connect the Br2InCH2Br units to produce 1-D chains, 2-D lattices, or 3-D framework
structures. Accordingly, we have envisaged the possibility of using bis(diphenylphosphino)
alkanes as soft donor ligands to connect the units by binding into the methylene group and
bis(diphenylphosphino)alkanes dioxides as hard donor ligands to connect the units through
coordination to indium. In this article, we report our results involving the coordination of
bis(diphenylphosphino)alkane dioxides, Ph2PO(CH2)mPOPh2 (m = 2, dppeO2 and m = 6,
dpphO2), with Br2InCH2Br and describe the synthesis, characterization, and molecular struc-
tures of two new organoindium 1-D coordination polymers and one compound with dppeO2
acting as a chelating ligand giving a six-coordinate indium cation counterbalanced by an
anionic tetrahedral indium unit.
2. Experimental
2.1. Materials and measurements
All preparative work was carried out under dry nitrogen using standard Schlenk techniques,
up to the isolation of final products. All solvents were purified by standard procedures and
freshly distilled before use. 1,2-Bis(diphenylphosphino)ethane (dppe), triphenylphosphine,
and 1,6-dibromohexane were purchased from Sigma-Aldrich and used without purification.
Indium monobromide was prepared by heating indium metal and the corresponding indium
trihalide in a vacuum sealed tube at 450 °C. Methylene bromide (Aldrich) was dried over
Linde 4 Å molecular sieves. Infrared spectra were obtained using a Bruker Tensor 27 mid-IR
spectrometer. Raman spectra were obtained on a Bruker MultiRAM (1064 nm laser,
50–3500 cm−1). NMR spectra were recorded on a Bruker DPX-200 NMR spectrometer and
1
the chemical shifts (δ) are in ppm referenced to residual H solvent resonances. Indium
analysis was performed by back-titration of excess EDTA with thorium nitrate and bromide
analysis by the Volhard method [33]. Melting points were determined on a Microquimica
MQAPF-301 melting point apparatus and are uncorrected.

4
C. PEPPE ET AL.
2.2. Synthesis
2.2.1. Synthesis of 1,2-bis(diphenylphosphino)ethane dioxide (dppeO2)
The oxidation of dppe was carried out with dry dioxygen in a dichloromethane solution, in
the presence of SnI4, according to an adapted procedure previously described [37]. Yield:
66%. Melting point: 272–273 °C, lit. [38] 273–276 °C. IR (KBr)/cm−1: 3053 [ν(CH)Ar]; 2941
[νas(CH2)]; 2907 [νs(CH2)]; 1590, 1484, and 1438 [ν(C=C)]; 1175 [ν(P=O)]; 1071 and 1028
[δip(C=C–H)]; 730 and 694 [δop(C=C–H)] (δip and δop = in-plane and out-of-plane bending
modes, respectively). Raman (cm-1): 3056; 2930; 2900; 1591; 1575; 1187; 1164; 1107; 1030;
998; 787; 691; 618; 305; 244; 146; 96.
2.2.2. Synthesis of 1,6-bis(diphenylphosphino)hexane dioxide (dpphO2)
First, 1,6-dibromohexane (5 mmol) was dissolved in 20 mL of toluene in a 100 mL round
bottom flask equipped with a reflux condenser and triphenylphosphine (10 mmol) was
added to this solution. After 72 h of stirring under reflux, the white solid hexamethyleneb-
is(triphenylphosphonium bromide) produced was filtered and dried under vacuum. This
solid was then treated with aqueous sodium hydroxide solution (20 mL, 4 mol/L) for 24 h
with stirring at 100 °C. The solid obtained was recrystallized in EtOH. Yield: 81%. Melting
point: 193–196 °C, lit. [39] 196–198 °C. 1H NMR (CDCl3): δ = 1.26–1.39 (broad m, 4H), 1.41–1.57
(broad m, 4H), 2.07–2.29 (m, 4H), 7.31–7.53 (m, 12H), 7.59–7.76 (m, 8H). IR (KBr): 3050 [ν(CH)Ar];
2963 [νas(CH2)]; 2863 [νs(CH2)]; 1591, 1485 and 1437 [ν(C=C)]; 1183 [ν(P=O)]; 1072 [δip(C=C–H)];
719 and 694 [δop(C=C–H)]. Raman (cm−1): 3070; 3053; 2937; 2920; 2900; 2854; 1592; 1574;
1180; 1161; 1107; 1056; 1029; 1001; 687; 617; 300; 278; 251; 130; 106; 84.
2.2.3. Synthesis of [Br2In(CH2Br)(dppeO2)]n (1)
First, a solution of Br2InCH2Br was prepared by suspending 390 mg (1.0 mmol) of InBr in 1,4-dioxane
(8 mL) in a round flask under dry N2 atmosphere.To this suspension was added 0.35 mL (5.0 mmol)
of CH2Br2 and the mixture was kept stirring until complete dissolution of the red InBr solid. A
clear colorless solution was obtained and all volatiles were removed under high vacuum until
complete removal of excess CH2Br2.The resulting white solid (the bis-dioxane adduct of Br2InCH2Br)
was redissolved in 1,4-dioxane (10 ml) and dppeO2 (430 mg, 1.0 mmol) was added to the solution.
The reaction was kept under stirring for 4 h and the white solid product precipitated. The solid
was collected by filtration, dried under vacuum (yield 738 mg, 92%) and analyzed. Melting point:>
285 °C (decomp.). Anal. Calcd. (%) for C27H26Br3InO2P2: Br, 30.00; In, 14.37. Found: Br, 29.57; In,
14.14. IR (KBr)/cm−1: 3057 [ν(CH)Ar]; 2944 [νas(CH2)]; 2909 [νs(CH2)]; 1590, 1484, and 1437 [ν(C=C)];
1163 [ν(P=O)]; 1027 [δip(C=C–H)]; 728 and 692 [δop(C=C–H)]. Raman (cm−1): 3060; 2959; 2933; 2901;
1591; 1575; 1188; 1161; 1028; 999; 693; 617; 469; 244; 208; 157; 78. Colorless single crystals
suitable for X-ray analysis were obtained in a freezer after a few days of recrystallization in acetone.
2.2.4. Synthesis of [Br2In(CH2Br)(dpphO2)]n (2)
The organoindium compound Br2InCH2Br was prepared according to the procedure for 1.
In the second step, dpphO2 (486 mg, 1 mmol) was dissolved in 10 mL of hot 1,4-dioxane and
transferred to a solution of Br2InCH2Br in 1,4-dioxane (2 mL). The reaction was kept under
stirring for 12 h and the white solid product precipitated. The solid was collected by filtration,
dried under vacuum (yield 795 mg, 93%) and analyzed. Melting point: 260–262 °C. Anal.
Calcd (%) for C31H34Br3InO2P2: Br, 28.03; In, 13.43. Found: Br, 27.34; In, 12.65. IR (KBr)/cm−1:
3057 [ν(CH)Ar]; 2850 [νs(CH2)]; 1591, 1485, and 1438 [ν(C=C)]; 1155 [ν(P=O)]; 724 and 692

JOURNAL OF COORDINATION CHEMISTRY
5
[δop(C=C–H)]. Raman (cm−1): 3060; 2973; 2947; 2902; 2852; 1592; 1575; 1163; 1029; 999; 835;
687; 618; 467; 248; 206; 78. Colorless single crystals suitable for X-ray analysis were obtained
after a few days of recrystallization in ethanol in an open vessel.
2.2.5. Synthesis of [InBr2(dppeO2)2][InBr3(CH2Br)] (3)
The compound was prepared as 1, except that stoichiometry was adjusted to start with
98 mg (0.5 mmol) of InBr and after dppeO2 was added, the reaction mixture was kept under
stirring for 24 h at 60 °C. A white solid precipitated and was collected by filtration; we tried
to redissolve it in CHCl3. It was only partially soluble, then, it was filtered again and colorless
crystals were obtained from the filtrate after 3 days (230 mg, yield 58%). Melting point:
268–269 °C. Anal. Calcd (%) for C53H50Br6In2O4P4: Br, 30.27; In, 14.50. Found: Br, 30.50; In, 14.49.
2.3. X-ray crystallographic studies
Data were collected with a Bruker APEX II CCD area-detector diffractometer and graph-
ite-monochromated MoKα radiation (λ = 0.71073 Å). The structures of the compounds were
solved by direct methods implemented in SHELXS [40]. The structures were refined with
full-matrix least-squares on F2 using all data. The structures were refined with SHELXL using
anisotropic displacement parameters for all non-hydrogen atoms [40]. The hydrogens were
calculated in idealized positions and were not refined freely (riding model). Isotropic atomic
displacement parameters of hydrogens followed those of the bonded carbons
[Uiso(H) = 1.2Ueq(C)]. Crystallographic data and experimental details of the structure deter-
minations are listed in Table 1 with their deposit codes at the Cambridge Crystallographic
Data Center. CCDC numbers are 1572149 (1), 1572148 (2), and 1578960 (3). Selected bond
lengths and angles (Table S1) are available in the Supplemental Material.
3. Results and discussion
3.1. Synthesis of bis(diphenylphosphino)alkane dioxides
To avoid the oxidation of phosphines with hydrogen peroxide, we adapted described meth
-
ods to synthesize the 1,2-bis(diphenylphosphino)alkane dioxides. For dppeO2, we performed
an oxidation of 1,2-bis(diphenylphosphino)ethane with dioxygen in the presence of a
catalytic amount of SnI4 (Scheme 2). To synthesize dpphO2, we used a two-step synthetic
route involving the decomposition of a phosphonium salt in aqueous sodium hydroxide
(Scheme 2). Both dppeO2 and dpphO2 were readily produced with high yields.
3.2. Synthesis of organoindium(III) coordination polymers with
bis(diphenylphosphino)alkane dioxides
Two organoindium(III) coordination polymers were prepared by adding the diphosphine
dioxide ligands, Ph2PO(CH2)mPOPh2 (m = 2, dppeO2 and m = 6, dpphO2) to solutions of
Br2InCH2Br obtained from the oxidative insertion of InBr into a carbon–halogen bond of
CH2Br2 (Scheme 3).
Compounds 1 and 2 were produced as white solids in 92 and 93% yield, respectively. The
molecular formulas of both compounds were established by indium and bromide analysis.
These complexes are stable toward air and moisture in the solid state.

6
C. PEPPE ET AL.
Table 1. Crystal data and refinement statistics for 1–3.
1
2
3
structural formula
fW
Crystal system
space group
(C27h26Br3ino2P2)n
(C31h34Br3ino2P2)n
(C52h48Br2ino4P4)(Ch2Br4in)
798.97
triclinic
Pī
855.07
monoclinic
P21
1583.91
triclinic
Pī
Z
4
2
2
T (K)
100(2)
294(2)
296(2)
unit cell dimensions
a (Å)
b (Å)
c (Å)
α (°)
β (°)
13.4665 (13)
15.6090 (18)
16.6174 (17)
94.475 (6)
111.528
110.845
2947.9 (6)
1.800
7.82930(10)
21.6837(4)
9.7809(2)
90
96.6040(10)
90
1649.47(5)
1.722
4.473
11.7144(4)
12.5445(4)
22.3014(7)
92.934(2)
102.944(2)
112.509(2)
2916.30(17)
1.804
γ (°)
V (Å3)
Calculated density (mg/m3)
absorption coefficient (mm−1
absorption correction
Tmin/Tmax ratio
)
4.999
multi-scan
0.5696
5.052
multi-scan
0.6119
multi-scan
0.6894
θ range for data collection (°)
index ranges
2.68 – 30.55
−19 to 19
−22 to 22
−23 to 23
42,519
2.82 – 31.93
−11 to 9
−32 to 26
−14 to 13
23,978
3.56 – 30.54
−16 to 16
−17 to 17
−31 to 31
84,606
data collected
unique reflections
unique reflections with I >2σ(I)
symmetry factor (Rint
17,662
10,858
0.0553
10,043
7352
0.0495
17,665
10,558
0.0440
)
Completeness to θmax
F000
97.7
1552
99.7
840
99.0
1536
Parameters refined
Goodness-of-fit on F2
final R1 factor for I >2σ(I)
wR2 factor for all data
largest diff. peak / hole (e–/Å3)
CCdC deposit number
631
0.965
0.0475
0.0951
363
1.038
0.0355
0.0662
622
1.094
0.0503
0.1450
2.933/−1.660
1572149
0.614/−0.489
1572148
3.360/−1.873
1578960
Scheme 2. syntheses of bis(diphenylphosphino)alkane dioxides.
In the infrared spectra, the most significant stretching frequency is associated to the P=O
bond. As expected due to In–O bond formed upon coordination of the phosphine oxide to
indium, the P=O stretches in 1 and 2 (1163 and 1155 cm−1, respectively) appear at lower
wavenumbers in comparison with dppeO2 (1175 cm−1) and dpphO2 (1183 cm−1).

JOURNAL OF COORDINATION CHEMISTRY
7
Scheme 3. reactions of organoindium Br2inCh2Br with dppeo2 and dppho2.
Raman bands of the ligands moved very little upon coordination in 1 and 2.
Notwithstanding, in the spectra of both compounds appear bands attributed to In–O
(469 cm−1 for 1 and 467 cm−1 for 2) and In–Br stretching vibrations (208 cm−1 for 1 and
206 cm−1 for 2) [41].
Although solubilities of both compounds are limited, crystallization of 1 and 2 in acetone
and ethanol, respectively, furnished crystals suitable for X-ray crystallographic diffraction.
Indium(III) is a hard acid in the HSAB classification and, as expected, the hard donor oxygens
of bis(diphenylphosphino)alkane dioxides bind indium atoms of different Br2InCH2Br units
bringing about the organoindium(III) 1-D coordination polymers.
When performing reaction between Br2InCH2Br and dppeO2 under heating and for longer
time, we obtained an ionic compound (3) with dppeO2 acting as a chelating ligand to form
a square bipyramidal indium(III) cation and the anion is the tetrahedral organoindium
[Br3InCH2Br]– (Scheme 3). As previously described [30], this can be understood in terms of
the decomposition of the organoindium Br2InCH2Br when heated in dioxane. Intramolecular
bromide transfer in Br2InCH2Br gives the tautomeric structure Br3InCH2, which may be
responsible for the formation of the anion [Br3InCH2Br]– as well as its decomposition with
elimination of methylene group and chelation of dppeO2 may give rise to the cation
structure.
3.3. Description of structures of 1–3
Compound 1 crystallized in the centrosymmetric triclinic space group Pī with two Br2LInCH2Br
[L = 1,2-bis(diphenylphosphino)ethane dioxide] in the asymmetric unit, which gives two
crystallographically independent infinite polymeric chains shown in Figure 1. This figure was
prepared with MERCURY [42] as well as the other structural drawings. A summary of crystal
data collection and processing can be found in Table 1. The coordination geometry around
indium can be described as a trigonal bipyramid. The equatorial positions are occupied by
two bromides and the bromomethylene carbon onto a least-squares plane [root-mean
square deviations (RMSD) of the two bromides, the carbon and the indium are 0.0942 and
0.0245 Å for complexes labeled as A and B, respectively]. Oxygens from the ligand occupy
both apical positions. Bond lengths and angles around In(III) coordination sphere are shown
in Table S1.

8
C. PEPPE ET AL.
Figure 1. ellipsoid plot (50%) of the 1-d coordination polymer 1, constructed with building blocks a (right)
or B (left). atoms in the asymmetric unit are labeled, except for the phenyl carbons (labeling scheme of
phenyl rings is shown in turn). symmetry operators for atoms and phenyl rings which are not asymmetric
units: i = 1 − x, 2 − y, −z; ii = −x, 1 − y, −z; j = 2 − x, 2 − y, 1 − z; jj = 1 − x, 1 − y, 1 − z.
The presence of two crystallographically independent molecules in the asymmetric unit
of 1 can be understood through inspection of ligand conformations. Some similarities
between the two crystallographically independent ligand molecules can be pointed out,
such as: (1) the syn conformation of bromomethylene relative to one bromide [Br1–C1–In1–
Br11 and Br2–C2–In2–Br22 torsion angles are 11.8(3)° and 12.4(3)°]; (2) the anti conformation
of the ethane group [P1–C11–C11j–P1j, P2–C21–C21jj–P2jj, P3–C31–C31ii–P3ii, P4–C41–C41i–
P4i torsion angles measure 180.0(2)°, symmetry operators: i = 1 – x, 2 − y, −z; ii = −x, 1 − y,
−z; j = 2 − x, 2 − y, 1 − z; jj = 1 − x, 1 − y, 1 − z]; (3) the gauche conformations around all P–C
bond axes [C11j–C11–P1–O11, C21jj–C21–P2–O21, C31ii–C31–P3–O31, and C41i–C41–P4–
O41 torsion angles are 55.7(4)°, 64.6(4)°, 57.5(4)°, and 65.2(4)°]; and (4) the phenyl twists of
one diphenylphosphine [phenyl rings C and F are twisted by 12.3(2)°, as well as those labeled
as D and E are bent by 10.1(2)°]. However, the phenyl twists of another diphenylphosphine
differ significantly (Figure 2). If the best molecular overlay for the two building blocks are
taken (RMSD of the corresponding non-hydrogen atoms of 0.6635 Å), the least-square planes
calculated through the phenyl rings of the diphenylphosphine moieties which are not super-
imposed form angles of 62.3(2)° (A and H) and 38.4(2)° (B and G). Such conformational dif-
ference is consequence of the interaction patterns in the lattice (see below).
In the structure of 1, 1-D coordination chains form through bridging In-O bonds. Each
chain is constructed with inversion symmetry-related building blocks parallel to the [110]
direction, i.e., each chain has just one of the two In(III) coordination complexes which are
asymmetric units (Figure 3). Furthermore, chains made up of a crystallographically inde-
pendent coordination complex are packed side-to-side onto the (001) plane. This gives layers
of 1-D chains loading only one building block, which are alternately packed on top of each
other along the [001] direction (Figure 3). Such pillaring of the layers is stabilized mainly by
CH⋯Br and CH⋯π intermolecular interactions between crystallographically independent
coordination complexes belonging to neighboring chains (Figure 4). There are also CH⋯Br
and CH⋯π intramolecular interactions for all chains. However, the pattern of non-covalent
contacts changes slightly between the two conformationally distinct coordination complexes

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9
Figure 2. molecular overlay between building blocks a (red) or B (blue) of 1. labeling scheme of phenyl
rings is shown.
Figure 3. layers of coordination chains are assembled with just one crystallographically independent
building block of 1 (a or B) and alternately pillared on the top of each other.
present in the crystal structure of 1. This can be viewed in the fingerprint plots derived from
the Hirshfeld surfaces for each building block (Figure 4). The plots were generated by plotting
2-D grids of the (di,de) pairs measured on each individual spot of the calculated Hirshfeld
surface [43]. In these graphics, the d-values ranged from 0.4 to 2.6 Å. A color gradient from
blue to red represents the proportional contribution of the (di,de) pair to the global Hirshfeld
surface. This analysis allows probing of all regions of the coordination complex within the
crystal lattice. By analyzing Figure 4, one can find that the 2-D fingerprint plots of the crys-
tallographically independent coordination complexes of 1 are resembled. Both plots show
similar winged side areas referring to the presence of H⋯Br contacts. After the most abun-
dant general H⋯H contacts (61.5% and 57.9% for molecules A and B, respectively), H⋯Br
contacts have the largest contribution to the Hirshfeld fingerprints of both building blocks,
even though they occur more in molecules B (20.6%) than in A (19.4%). In turn, halogen⋯hal-
ogen contacts are found only in molecule A (0.5%). The H⋯C contacts, including C–H⋯π
interactions, are distributed over the central region of the fingerprints and also have different
proportions for the two crystallographically independent building blocks (14.8% and 16.9%

10
C. PEPPE ET AL.
Figure 4. main intramolecular and intermolecular non-covalent contacts for the coordination chains of 1.
notes: in this picture and in the next ones, the shown contact metrics refer to the h···a distance and the d–h···a angle (d and
a mean contact donor and acceptor, respectively). the term Cg denotes the centroid calculated through six phenyl carbons,
and only the contact donors and acceptors were labeled. the C–h···Br and C–h···π contacts are drawn as cyan and blue dotted
lines, respectively. full fingerprint graphics of the building blocks and most of the contacts filling them are shown. the blue
color indicates lower proportions of the (di,de) pair; green represents an intermediary frequency; red implies an upper limit
fraction greater than 0.1% of the surface points with the same (di,de) combination.
for molecules A and B, respectively). The other contact types represent less than 2% of the
fingerprint plots.
Compound 2 (Figure 5) has been solved in the non-centrosymmetric monoclinic space
group P21 with just one crystallographically independent building block of formula
Br2LInCH2Br [L = 1,2-bis(diphenylphosphino)hexane dioxide] (see Table 1 for summary of
data collection and treatment). Despite the chirality of this space group, the reliable refined
Flack parameter close to 0.5 [0.493(7)] reveals the crystallization of 2 as an inversion twin
(racemate). Its coordination geometry is similar to that of 1, with two bromides and the
bromomethylene carbon forming the trigonal bipyramid plane (RMSD for the least-square
plane calculated through In1, C1, Br2, and Br3 is 0.0127 Å) and both oxygens from the ligand
lying on apical positions (see table S1 for bond lengths and angles in the coordination envi-
ronment). Into the aliphatic spacer chain, the conformation around all C–C bond axes is anti,
except for that on the C12–C13 bond axes which is gauche (C11–C12–C13–C23 torsion is
72.6(5)°). The conformation of the two diphenylphosphine groups differs in 2. The torsion

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11
Figure 5. 50% ellipsoid plot of the 1-d coordination polymer 2.
notes: atoms in the asymmetric unit are labeled; except for the carbons from phenyl rings and the aliphatic spacer chain
(labeling scheme of phenyl rings is shown in turn). symmetry operators for atoms and phenyl rings which are not asymmetric
units: k = −1 + x, y, 1 + z.
Figure 6. (a) C–h···Br (cyan), π···π (green) and (b) C–h···π (blue) contacts found in the crystal packing of 2.
note: for the π···π interaction, the shown measurement refers to Cg···Cg distance.

12
C. PEPPE ET AL.
angles around P1–C11 [C12–C11–P1–O1 = −44.8(4)°] and P2–C21 [C22–C21–P2–O2 =
177.7(3)°] bond axes describe gauche and anti conformations, respectively. The bent angles
between the phenyl groups mean that planes are also different within the two diphenylphos-
phine groups [89.0(2)° between A and B and 65.8(2)° between C and D].
Similar to 1, oxygens from the same ligand are responsible for coordinating to different
indium atoms in 2, giving a 1-D coordination polymer made up of translation-symmetry-re-
lated building blocks joined together along the [−101] direction (Figure 5). Also, CH⋯Br and
CH⋯π contacts are the main non-covalent contacts in the crystal structure of 2 (Figure 6).
The first ones are found intramolecularly and intermolecularly, while CH⋯π and π⋯π inter-
actions work together to connect neighboring chains (Figure 6).
Compound 3 (Figure 7) has been solved in the triclinic centrosymmetric space group Pī
with one discrete cation [Br2L2In]+ [L = 1,2-bis(diphenylphosphino)ethane dioxide] and one
anion [Br3InCH2Br]– (see Table 1 for summary of data collection and treatment). To the best
of our knowledge, there is just one crystal structure of the [Br3InCH2Br]– anion [30] in the
Cambridge Structural Database (CSD version 5.38 with May 2017 update). The coordination
geometry of [Br3InCH2Br]– can be described as tetrahedral, as in its literature precedent [30],
while the cation assumes a square bipyramid environment. The octahedral basal plane is
formed with O1, O2, O3, Br2, and In1 and is slightly distorted (RMSD for the least-square
plane is 0.236 Å), while O4 and Br1 are in apical positions. The apical In1-O4 bond length is
much longer than the other In1-O bonds (see table S1 for bond lengths and angles in the
coordination environment). In the two ligand molecules, there are gauche conformations
around all P–C bond axes [C1–C1–P1–O1, C1–C2–P2–O2, C4–C3–P3–O3, and C3–C4–P4–O4
torsion angles are 66.5(4)°, 53.3(4)°, −54.2(4)°, and −64.4(4)°], as occurs in 1 built with the
same ligand. The ethane group in 1 adopts an anti configuration with torsion angles around
C1–C2 and C3–C4 ca. 90° [P1–C1–C2–P2 and P3–C3–C4–P4 torsion angles measure
−93.8(4) and 94.6(4)°]. The phenyl twists in the diphenylphosphine moieties are similar
Figure 7. ellipsoid plot (50%) of the discrete coordination polymer 3.
note: atoms in the asymmetric unit are labeled; except for the carbons from phenyl rings (labeling scheme of phenyl rings
is shown).

JOURNAL OF COORDINATION CHEMISTRY
13
[phenyl rings A and B, C and D, E and F, and G and H are twisted by 75.79(17)°, 84.29(19)°,
74.5(2)°, and 80.01(16)°, respectively]. Keeping the same packing trend of 1 and 2, 3 is sta-
bilized mainly by CH⋯Br and CH⋯π contacts (Figure 8). However, in this structure, CH⋯Br
contacts are established between neighboring species in the lattice, including a significant
engagement of the anion in such contacts as can be viewed in high contribution (42.7%) of
H···Br in the Hirshfeld fingerprint plot for [Br3InCH2Br]–, while CH⋯π ones help the intramo-
lecular stabilization of the cation (Figure 8). The contribution of H⋯C contacts, where there
are contacts CH⋯π, are significant in the Hirshfeld fingerprint plot for [Br3L2InCH2Br]+,
whereas they are absent in the anion (Figure 8).
Figure 8. C–h···Br (cyan) and (b) C–h···π (green) contacts found between anionic ([Br3inCh2Br]–) and
cationic ([Br2l2in]+) indium complexes present in 3.
note: full fingerprint graphics for [Br3inCh2Br]– (bottom) and [Br2l2in]+ (top) and most of the contacts filling them are also
shown.

14
C. PEPPE ET AL.
4. Conclusion
We have synthesized two new organoindium(III) 1-D coordination polymers with the hard
donor ligands dppeO2 and dpphO2 where indium ions are in a trigonal bipyramidal geometry
and one compound with a square bipyramid In(III) cation and a tetrahedral organoindium(III)
anion. The solid-state assemblies of 1–3 give supramolecular structures, mainly by intermo-
lecular interactions. The main non-covalent contacts in crystal structures are the CH⋯Br and
CH⋯π contacts, stabilizing the pillaring of the layers in 1 and 2. Hirshfeld 2-D fingerprint
plots were used for quantitative mapping of all the interactions. Despite the polymers not
being multi-dimensional, work is underway to investigate their potential as pre-constructed
building blocks for further multi-dimensional structures using the full coordinating ability
of the Br2InCH2Br, in reactions with bidentate soft and hard ligands.
Supplementary material
Supplementary material related to this article can be found on-line. Crystallographic data for the
structures have been deposited with the Cambridge Crystallographic Data Center under deposit codes
1572149 (1), 1572148 (2) and 1578960 (3). The data can be obtained free of charge from CCDC via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgment
FTM thanks CNPq for the research fellowship. The authors thank to Prof. Sailer S. dos Santos for
performing Raman spectroscopy analyses.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG) under
[grant number 201610267001033]; CNPq and CAPES.
ORCID
Danielle Cangussu
http://orcid.org/0000-0003-3388-6533
Rafael Pavão Das Chagas
http://orcid.org/0000-0002-4671-8697
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