Synthesis and structures of gallaarsenes LGaAsGa(X)L featuring a Ga-As double bond

Article abstract of DOI:10.1039/c9dt03998h

Three equivalents of LGa {L = HC[C(Me)N(2,6-i-Pr₂C₆H₃)]₂} react with AsX₃ (X = Cl, Br) by insertion into two As-X bonds, followed by the elimination of LGaX₂ and formation of LGaAsGa(Cl)L (1) and LGaAsGa(Br)L (2). According to single crystal X-ray analysis, 1 and 2 each exhibit one Ga-As single bond and one Ga-As double bond. The π-bonding contribution (9.71 kcal mol^-11 and 9.44 kcal mol^-12) was proved by variable temperature (VT) ¹H NMR spectroscopy, while the electronic structure of 1′ was studied by quantum chemical calculations.

Full text of DOI:10.1039/c9dt03998h

View Article Online
View Journal
Dalton
Transactions
An international journal of inorganic chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Schoening, L.
John, C. Wölper and S. Schulz, Dalton Trans., 2019, DOI: 10.1039/C9DT03998H.
Volume 46
Number 10
14 March 2017
Pages 3073-3412
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Dalton
Transactions
An international journal of inorganic chemistry
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
rsc.li/dalton
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
ISSN 0306-0012
COMMUNICATION
Douglas W. Stephen et al.
shall the Royal Society of Chemistry be held responsible for any errors
N-Heterocyclic carbene stabilized parent sulfenyl, selenenyl,
and tellurenyl cations (XH+, X = S, Se, Te)
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
rsc.li/dalton

Please do not adjust margins
Page 1 of 10
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT03998H
ARTICLE
Synthesis and Structure of Gallaarsenes LGaAsGa(X)L featuring a
Ga–As Double Bond
Juliane Schoening,a Lukas John,a Christoph Wölper,a Stephan Schulza,*
Received 00th January 20xx,
Accepted 00th January 20xx
Three equivalents of LGa {L = HC[C(Me)N(2,6-i-Pr2C6H3)]2} react with AsX3 by insertion into two As–X bonds, elimination of
LGaX2, and formation of LGaAsGa(Cl)L (1) and LGaAsGa(Br)L (2). According to single crystal X-ray analysis, 1 and 2 each exhibit
one Ga–As single bond and one Ga–As double bond. The π-bonding contribution (9.71 kcal/mol 1; 9.71 kcal/mol 2) was
DOI: 10.1039/x0xx00000x
1
proven by temperature variable (VT) H NMR spectroscopy, while the electronic structure of 1' was studied by quantum
chemical calculations.
([RMER']2), trimerize ([RMER']3) or oligomerize to form
heterocyclic (x = 2, 3) or cage-type complexes [RMER']x (x > 4).[9]
Sterically demanding substituents, which kinetically stabilize
Introduction
The number of p-block element compounds containing π-bonds
typically decreases with increasing atomic number within each
group. This observation was explained by the so-called "double
bond rule",[1] which is often addressed to the weak π-bond
interaction of heavier main group elements due to poor p-
orbital overlap. Luckily, substantial progress has been made
over the past years to develop fundamental concepts for the
electronic and/or kinetic stabilization of heavy main group
element compounds which feature multiple bonding or
delocalized π-bonding contribution.[2]
the monomeric unit (type A), as well as the addition of a Lewis
base and/or Lewis acid, which coordinates with the existing
Lewis acidic (M) and/or Lewis basic side (E), are both utilized to
suppress oligomerization reactions.[10] Moreover, coordination
of the group 13 metal by an N,N'-chelating β-diketiminate
ligand, which results in an increase of the coordination number,
was shown to effectively stabilize compounds with π-bonding
contribution (type B).
A large number of stable homonuclear group 14 compounds
with π-bonding interaction have been prepared since the initial
report by West and co-workers on the synthesis of Mes4Si2 (Mes
= 2,4,6-Me3-C6H2), which represents the first organosilicon
compound with a Si–Si double bond that was stable under
ambient conditions[3]. Heteronuclear group 13/15 compounds
with π-bonding contributions which are stable at ambient
conditions were almost limited to monomeric amino- and
phosphinoboranes R2EBR'2 (E = N, P),[4] as well as iminoboranes
RNBR',[5] whereas π-bonded compounds of the even heavier
elements remained almost unknown. The electronic structures
of such compounds were investigated to some extent by
quantum chemical calculations,[6] however structurally
characterizable compounds were limited to (base-stabilized)
boron-pnicogen compounds[7] and iminometallanes RMNR' (M
= Al, Ga, In; type A and B) (Scheme 1).[8] Monomeric
metallapnictenes of the general type RMER' (M = Al–Tl; E = N–
Bi) tend to form head-to-tail adducts due to the presence of
Lewis acidic and Lewis basic centres, hence they easily dimerize
Scheme 1. Structurally characterized group 13/15 compounds with π-bonding
contributions.
Despite the progress that has been made within the last
decades in the stabilization of π-bonded compounds of even
heavier main group elements, the number of stable group
13/15 compounds containing a double bond is still low. To the
best of our knowledge, LGaAsCp* C,[11] which was recently
synthesized in our group by reacting Cp*AsCl2 with two
equivalents of LGa, as well as [{Li(thf)3}2Ga2{As(SiiPr3)}4] D[12]
represents the only structurally characterized gallaarsenes
containing a Ga–As π-bond. In addition, we recently reported on
the synthesis and solid state structures of a series of
gallastibenes LGaSbGa(X)L of type E (X = F, Cl, Br, I),[13,14] as well
as LGaSbTer F (Ter = 2,6-Mes2-C6H3, Mes = 2,4,6-Me3-C6H2),[15]
which are the only structurally characterized compounds with
Ga-Sb π-bonds. Gallastibenes of type E are generally accessible
by reactions of SbX3 with three equivalents of LGa,[14] and
LGaSbGa(Cl)L was also formed by a single electron reduction
reaction of the stibanyl radical L(Cl)Ga)2Sb· with KC8 (Scheme
1).[13] In contrast, reactions of LGa with EX3 (X = halide, amide
NR2, alkoxide OR) in a 2:1 molar ratio yielded Ga-substituted
dipnictenes of the general type [L(X)GaE]2 containing As–As, Sb–
Sb, and Bi–Bi double bonds,[16] respectively. These compounds
a. Faculty of Chemistry, University of Duisburg-Essen and Center for
Nanointegration Duisburg-Essen (CENIDE); Universitätsstr. 7, S07 S03 C30, D-
45141 Essen; Fax: (+) 201-183 3830; E-mail: stephan.schulz@uni-due.de.
Electronic Supplementary Information (ESI) available: NMR and IR spectroscopic
data, crystallographic details and results from quantum chemical calculation. See
DOI: 10.1039/x0xx00000x.
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 2 of 10
ARTICLE
Journal Name
are largely stabilized by dispersion interactions as shown by exchange reaction between the Ga atoms or the rotation
View Article Online
quantum chemical calculation.[17]
around the Ga–As double bond. Experimentally we can't
DOI: 10.1039/C9DT03998H
The synthesis of LGaSbGa(Cl)L E by reactions of three distinguish between both processes. However, since any
equivalents of LGa with SbX3 prompted our interest to re- attempt to generate the corresponding cation [LGaEGaL]+ (E =
investigate reactions of LGa with AsX3, hence we herein report As, Sb) by halide abstraction reaction only proceeded with
on the synthesis of two gallaarsenes LGaAsGa(X)L E (X = Cl 1, Br complete decomposition of the compounds, we believe that the
2). 1 and 2 were spectroscopically characterized in solution, rotation around the Ga–As double bond is more likely. The
while the solid-state structure of 1 was determined by single rotation energy (G was calculated to 9.71 kcal mol-1 (1) and
crystal X-ray analysis. In addition, the structure and electronic 9.44 kcal mol-1 (2),[21] which agree very well with the π-bonding
nature of the bonding interaction in 1' was also investigated by contribution reported for LGaAsCp* (9.65 kcal mol-1)[11] and
quantum chemical calculations.
LGaSbGa(X)L E (G = 9.56 kcal mol-1 (x = Cl); 9.35 (x = Br)),[13,14]
whereas slightly stronger π-bond was reported for
a
PhP(GaTrip2)2 (G = 10.2 kcal mol-1, Trip = 2,4,6-i-Pr3C6H2).[22]
As observed for gallastibenes of type E, the i-Pr groups in 1 and
2 also split into three signals with a relative intensity of 1:1:2.
Solid state structure of 1.
Results and discussion
Synthesis and characterization of 1 and 2 in solution.
Reactions of three equivalents of LGa[18] with AsX3 at ambient
temperature yielded LGaAsGa(X)L (X = Cl 1, Br 2). 1H NMR
spectroscopy studies proved that the reactions occur with
double insertion of LGa into two As-X bonds, followed by
elimination of LGaX2 and formation of 1 and 2, which were
isolated as dark red, crystalline solids (Scheme 2). The insertion
of LGa into the As-X bond can be described as an oxidative
addition of AsX3 to a monovalent gallanediyl LGa, similar to
what has been observed by Braunschweig and co-workers in
reactions of AsCl3 with Pt(0) complexes PtL2, yielding trans-
[PtCl(AsCl2)L2] complexes.[19] Oxidative addition reactions of E-
Cl bonds of the heavier homologues (E = Sb, Bi) to Pt(0) centers
were also reported.[20]
Dark red crystals of 1 and 2 were obtained from solutions of 1
and 2 in n-hexane after storing for two days at ambient
temperature. Compound 1 crystallizes in the triclinic space
group P-1 while 2 in the monoclinic space group P21/n, each
with one molecule in the asymmetric unit. The Ga(1)–As(1) and
Ga(2)–As(1) bond lengths in 1 and 2 each differ by almost 9 pm
(1: Ga(2)–As(1) 2.2628(5) Å; Ga(1)–As(1) 2.35033(4) Å; 2 Ga(2)–
As(1) 2.2591(11) Å; Ga(1)–As(1) 2.3580(11) Å), clearly proving
the presence of a Ga–As single bond and a Ga–As double bond.
The Ga(1)–As(1) double bonds in 1 and 2, which represent the
shortest Ga–As bond ever reported, are almost identical to the
Ga–As double bond lengths recently reported for two
independent molecules observed in the crystal of LGaAsCp*
(2.2671(2), 2.2702(2) Å).[11] These values are well below the sum
of the calculated covalent double-bond radii (Ga 2.17 Å, As 1.14
Å),[23] clearly proving the π-bonding contribution in 1 and 2, but
Scheme 2. Synthesis of 1 and 2.
1 and 2 are air- and moisture-sensitive compounds. While 2 is compare very well to calculated Ga–As bond lengths in HGaAsR
reasonably soluble in both coordinating (THF, Et2O) and non- (R = H, 2.245 Å, 2.272 Å; Me, 2.251 Å) and XGaAsH (X = F, 2.283
coordinating solvents (n-hexane, benzene, toluene), the Å; Cl, 2.282 Å; Br, 2.284 Å; I, 2.285 Å), respectively.[24] In
solubility of 1 in these solvents is rather limited. Both contrast, the Ga–As bond in the dianion [Ga2{As(SiiPr3)}4]2-
D
compounds can be stored as isolated crystalline solids as well as (2.318(1) Å)[12] is 6 pm longer, and the intramolecularly base-
in solution in benzene under argon atmosphere for weeks stabilized diarsadigalletane [t-BuGaAsC6H3-2,6-(CH2NMe2)2]2,
without any sign of decomposition. The 1H NMR spectra of 1 and which forms a four-membered ring without any (p-p)π bonding
2 at ambient temperature each show only one set of resonances contribution, shows significantly longer Ga–As bonds of
for both β-diketiminate substituents: singlet resonances for the 2.457(3) Å.[25] This bond is even longer than the Ga(1)–As(1)
γ-CH proton (4.84 ppm (1); 4.90 ppm (2)) and both Me groups single bond in 1 (2.3503(4) Å) and 2 (2.3580(11) Å).
(4.18 ppm (1); 1.50 ppm (2)), as well as one septet for the
methine protons (3.16 ppm (1); 3.21 ppm (2)) and two doublets
Figure 1. Solid state structure of 1 including selected bond lengths (Å) and angles (°).
Displacement ellipsoids are displayed at 50% probability levels. Second orientation of
the disorder and hydrogen atoms omitted for clarity; As(1)–Ga(2) 2.2628(5), As(1)–Ga(1)
2.3503(4), Cl(1)–Ga(1) 2.2783(9), Ga(1)–N(2) 1.977(2), Ga(1)–N(1) 1.983(2), Ga(2)–N(3)
(1.18, 1.10 ppm (1); 1.26, 1.11 ppm (2)) for the methyl protons
of the i-Pr groups, respectively. The 13C spectra are in
accordance with 1H spectra and also show only one set of
1.922(3), Ga(2)–N(4) 1.957(2), Ga(2)–As(1)–Ga(1) 111.419(19), N(2)–Ga(1)–N(1)
94.04(10), N(2)–Ga(1)–As(1) 107.88(7), N(1)–Ga(1)–As(1) 117.33(7), N(3)–Ga(2)–N(4)
95.54(11), N(3)–Ga(2)–As(1) 150.79(8), N(4)–Ga(2)–As(1) 110.96(7).
resonances for both β-diketiminate substituents. Comparable
findings were previously reported for the Sb analogues
LGaSbGa(X)L.[13,14] Since the two β-diketiminate ligands in both
1 and 2 are in principle magnetically inequivalent, these findings
point to dynamic processes in solution. Cooling solutions of 1
and 2 in toluene-d8 to –80 °C forms two well-separated γ-CH
resonances for the two β-diketiminate ligands (Figs. S4, S8) with
a maximum peak separation of 18 Hz (1) and 36 Hz (2),
Figure 2. Solid state structure of 2 including selected bond lengths (Å) and angles (°).
Displacement ellipsoids are displayed at 50% probability levels. Hydrogen atoms omitted
for clarity; The model contains unresolvable twinning problems thus quantitative results
may be unreliable. As(1)–Ga(2) 2.2591(11), As(1)–Ga(1) 2.3580(11), Br(3)–Ga(1)
respectively. Two different processes are likely: halide anion
2.3986(11), Ga(1)–N(2) 1.994(6), Ga(1)–N(1) 2.020(6), Ga(2)–N(3) 1.910(6), Ga(2)–N(4)
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 10
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
1.957(6), Ga(2)–As(1)–Ga(1) 113.37(4), N(2)–Ga(1)–N(1) 94.4(2), N(2)–Ga(1)–As(1)
105.31(18), N(1)–Ga(1)–As(1) 120.12(17), N(2)–Ga(1)–Br(3) 103.96(18), N(1)–Ga(1)–
Br(3) 101.29(17), As(1)–Ga(1)–Br(3) 126.18(4), N(3)–Ga(2)–N(4) 95.4(2), N(3)–Ga(2)–
As(1) 153.88(17), N(4)–Ga(2)–As(1) 110.32(19).
and 1.88 electrons, respectively. As expected, the As atom
View Article Online
carries a more negative natural charge DoOfI:–110..010539(v/Cs9. D-0T0.73099)8iHn
comparison to the Sb analogues[13,14] due to its enhanced
electronegativity, which leads to an increased bond polarization
towards As. The HOMO of 1 (Fig. 3) corresponds to the As(1)–
Ga(2) -bond, which is mainly localized along the bond axis with
its core area on the As atom, and the two opposite lobes over
and under the Ga–As–Ga plane.
The Ga(1)–As(1) single bonds in 1 and 2 are also substantially
shorter compared to those found in four-membered
heterocycles of the type [R2GaAsR'2]x (av. 2.541(15) Å)[26] and
the six-membered heterocycles [Me2GaAs(i-Pr)2]3 [2.498(2)-
2.531(2) Å],[27] [H2GaAs(SiMe3)2]3 [2.4695(8)-2.4831(8) Å],[28]
[Br2GaAs(CH2SiMe3)2]3 [2.432(2)-2.464(1) Å].[29] t-Bu2GaAs(t-
Bu)2, which is the only structurally characterized monomeric
gallaarsane, also exhibits a roughly 10 pm longer Ga–As single
bond (2.466(3) Å).[30] These structural findings most likely
originate from the lower coordination number (2) of the As
atom in 1 and 2 compared to those in the monomeric (3) and
heterocyclic (4) compounds. The Ga(1)–As(1)–Ga(2) bond
angles (111.42(2)° 1, 113.37(4) 2) are comparable to the Ga–As–
C bond angles observed for C (110.92(5)°, 111.00(4)°) as well as
the Ga–Sb–Ga bond angles in compounds of type E, which range
from 107.37(1)° to 113.18(1)°,[13,14] whereas the Si(1)–As(1)–Ga
bond angle (103.34(6)°) observed in D was slightly smaller.[11]
The Ga(2)N2C3 metallacycles in 1 and 2 are almost planar (rms
deviation from best plane 0.067 Å (1) and 0.054 (2)), whereas
the Ga(1)N2C3 metallacycles significantly deviate from planarity
(rms deviation from best plane 0.158 Å (1) and 0.155 Å (2)) due
to the increased coordination number of the Ga atoms (4 vs. 3).
The N(1)–Ga(1)–N(2) angles of 94.03(2)° (1) and 94.4(2)° (2) are
slightly smaller than the N(3)–Ga(2)–N(4) angles of 95.55(2)° (1)
and 95.4(2)° (2). The Ga(2) atoms adopt almost perfect trigonal-
planar coordination spheres with the sums of bond angles
Σφ(Ga) being 357.3° (1) and 359.6° (2); these values further
indicate significant Ga-As π-bonding contribution.
Figure 3. HOMO and LUMO of 1'.
Experimental
General procedures.
Argon gas was dried by passing the gas through pre-heated
Cu2O pellets and molecular sieves columns. The reactions were
carried out using Schlenk and glove-box techniques. Toluene
and n-hexane were passed through the columns of MBraun
Solvent Purification System and collected in J-Young Schlenk
flasks and stored under argon atmosphere. Deuterated solvents
were dried over activated molecular sieves (4 Å) and degassed
prior to use. LGa (L = HC[C(Me)N(2,6-i-Pr2C6H3)]2)[18] was
prepared according to literature methods, while AsCl3 and AsBr3
were commercially available and freshly distilled and degassed
prior to use.
Materials and methods.
1H (300 MHz; 600 MHz) and 13C{1H} (75.5 MHz; 150.9 MHz) NMR
spectra were recorded using a Bruker Avance DPX-300
spectrometer or a Bruker Avance III HD spectrometer and
referenced to internal C6D5H (1H:  = 7.16; 13C:  = 128.06) or
C6D5CD2H (1H:  = 2.08; 13C:  = 20.43).[33] IR spectra were
recorded in a glovebox using an ALPHA-T FT-IR spectrometer
equipped with a single reflection ATR sampling module.
Microanalyses were performed at the elemental analysis
laboratory of University of Duisburg-Essen.
Quantum chemical calculations.
To gain a deeper understanding in the electronic structure of
the gallaarsenes, we computed the key geometries of 1' utilizing
density functional theory (DFT) approaches as implemented in
the ORCA quantum chemistry package (version 4.0).[31] We first
anchored our computational level with experiment by
comparing the computed structures of 1 with that found by
crystallography. DFT geometry optimized structures of 1'
(Cartesian coordinates summarized in Table S4) showed only
very small differences in the central Ga(1)–As(1) (2.3503(4) Å 1;
2.366 Å 1'), Ga(2)–As(1) (2.2628(5) Å 1; 2.259 Å 1'), Ga(1)–Cl(1)
(2.2783(9) Å 1; 2.231 Å 1'), Ga(1)–N(1/2) (1.983(2), 1.977(2) Å
1; 2.004, 2.005 Å 1') and Ga(2)–N(3/4) bond lengths (1.922(3),
1.957(2)Å 1; 1.962, 1.935 Å 1') as well as the Ga(1)–As(1)–Ga(2)
bond angles (111.419(19)° 1; 111.43° 1'), respectively.
Natural bond orbital (NBO) analysis of 1', which was performed
using the NBO 6.0 program,[32] reveals that the As(1)–Ga(2) -
bonding orbital is composed of a nearly sp hybridized orbital at
the Ga atom and a 85% p-character orbital at the As atom. An
almost exclusive p-character (99%) of the -bonding orbital at
both elements and a Mayer bond order of 1.70 lead to the
assumption of a covalent double bond. The -bond is slightly
polarized towards the As atom (64%), while the -bond is
strongly (86%) polarized. Both orbitals are populated by 1.89
Crystallography.
The crystals of 1 and 2 were mounted on nylon loops in inert oil.
Data were collected on a Bruker AXS D8 Kappa diffractometer
with APEX2 detector (monochromatic MoK radiation,  =
0.71073 Å) at 100(2) K. The structures were solved by Direct
Methods[34] and refined anisotropically by full-matrix least-
squares on F2.[35] Absorption corrections were performed semi-
empirically from equivalent reflections on basis of multi-scans
(Bruker AXS APEX2). Hydrogen atoms were refined using a
riding model or rigid methyl groups. As, Cl and
a
diisopropylphenyl (dipp) rest in 1 are disordered over two
positions. The corresponding bond lengths of the two
orientations of the dipp group were restrained to be equal
(SADI). The residual density near a second dipp group suggests
a disorder but refinement of the second orientation failed. The
site occupations factor obtained in the attempts were < 10%.
The crystal of 2 was non-merohedrally twinned and an
integration with two orientation matrices was attempted. The
best results yielded
a high percentage of unobserved
reflections. The resulting model showed improved R-values
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Dalton Transactions
Page 4 of 10
ARTICLE
Journal Name
3
13
(R1=0.0688, wR2=0.1528), slightly lower residual electron CH(CH3)2), 1.11 (d, JHH = 6.80 Hz, 24 H, CH(CH3)2). C NMR
View Article Online
density (still in unexpected places) and more reasonable (benzene-d6, 25 C, 75.5 MHz):  168.9D(ONIC: C10H.130)3,91/C449D.0T,03194928.H2
weighting scheme. However, the resulting adp were unrealistic (C6H3), 127.5, 124.8 (C6H3), 98.4 (-CH), 29.3 (CH(CH3)2), 26.7,
and in some cases anisotropic refinement was impossible even 24.8 (CH(CH3)2), 24.7 (NCCH3). UV/Vis (toluene): λ(ε) = 351 nm
with standard ISOR restraints. Neither model will give reliable (16395 M–1·cm–1).
quantitative results and any conclusions beyond the
connectivity should be carefully scrutinised.
Quantum chemical calculations.
Conclusions
Two gallaarsenes LGaAsGa(X)L (X = Cl 1, Br 2) were synthesized
by reactions of three equivalents of LGa with AsX3. This reaction
sequence has now established a general method for the
synthesis of gallaarsenes and -stibenes of the desired type. 1
and 2 exhibit the shortest Ga–As bond lengths ever reported,
which are roughly 5 pm shorter than the sum of the calculated
covalent double-bond radii (2.31 Å). The π-bonding
contributions of 1 and 2 were furthermore estimated by VT-
NMR spectroscopy (9.71 kcal mol-1 1, 9.44 kcal mol-1 2). These
findings undoubtedly prove the formation of Ga=As double
bonds in 1 and 2, which is also supported by results from
quantum chemical calculations only to reveal substantial π-
bonding contribution in 1'.
All quantum chemical calculations were employed with the
ORCA quantum chemistry package (version 4.0).[31] Ground-
state geometry optimizations were calculated with the PBE0
functional[36], the def2-SVP basis set on all C and H atoms and
the def2-TZVP basis set on As, Ga, Cl and N.[37] The atom-
pairwise dispersion correction with Becke-Johnson damping
scheme (D3BJ)[38] was used to account for dispersion
interactions. The RIJCOSX approximation was utilized to
accelerate the calculations in conjunction with the appropriate
auxiliary basis sets (def2/J).[39] Natural bond orbital analysis was
performed using the NBO 6.0 program.[32] Vibrational frequency
calculations were conducted to determine whether the
optimized geometries are local minima on the potential energy
surface.
Synthesis of LGaAsGa(Cl)L (1).
Conflicts of interest
There are no conflicts to declare.
A solution of LGa (200 mg, 0.411 mmol) and AsCl3 (24.8 mg,
0.137 mmol) in toluene (2.5 mL) was stirred for 2 days to yield
a dark red solution and a bright green solid (LGa(Cl)As)2.
(LGa(Cl)As)2 was filtered and all volatiles were removed in
vacuo. The resulting residue was dissolved in n-hexane (1.3 mL)
and stored at ambient temperature for several hours, to
crystallize LGaCl2. After the filtration, the mother liquor was
Acknowledgements
Financial support by the IMPRS RECHARGE of the MPI CEC (L.J.)
dissolved in n-hexane (0.3 mL) again to afford 1 as dark red and the DFG (SCHU 1069/22-1) is acknowledged.
crystals. Yield: 25 mg (0.023 mmol, 17 %). M.p. 242 °C. Anal.
Calcd. for C58H82AsClGa2N4: C, 64.20; H, 7.62; N, 5.16. Found: C,
62.70; H, 7.67; N, 4.95 %. IR (neat):  3061, 2959, 2923, 2864,
Notes and references
1524, 1435, 1368, 1318, 1255, 1175, 1088, 1019,931 859, 791,
‡
CCDC-1834971 (1) and CCDC-1958056 (2) contain the
1
757, 703, 636, 527, 439 cm-1. H NMR (toluene-d8, 25 C, 300
supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge
MHz):  7.05 (m, 12 H, aromatic H of Dipp group), 4.84 (s, 2 H,
3
-CH), 3.16 (sept, JHH = 6.83 Hz, 8 H, CH(CH3)2), 1.48 (s, 12 H,
Crystallographic
Data
Centre
via
3
3
www.ccdc.cam.ac.uk/data_request/cif.
NCCH3), 1.18 (d, JHH = 6.72 Hz, 24 H, CH(CH3)2), 1.10 (d, JHH
=
6.78 Hz, 24 H, CH(CH3)2). 13C NMR (toluene-d8, 25 C, 75.5 MHz):
 168.7 (NCCH3), 143.9, 142.1 (C6H3), 127.4, 124.5 (C6H3), 98.2
(-CH), 29.2 (CH(CH3)2), 26.3, 24.6 (CH(CH3)2), 24.5 (NCCH3).
Synthesis of LGaAsGa(Br)L (2).
1
2
3
W. E. Dasent, Non Existent Compounds - Compounds of Low
Stability; M. Dekker, New York, 1965; J. Goubeau, Angew.
Chem. 1957, 69, 77; K. S. Pitzer, J. Am. Chem. Soc. 1948, 70,
2140.
A solution of LGa (185 mg, 0.381 mmol) and AsBr3 (40 mg, 0.127
mmol) in toluene (3.5 mL) was stirred for 10 days to yield a red
solution and a bright green solid (LGa(Br)As)2. (LGa(Cl)As)2 was
filtered and all volatiles were removed in vacuo. The resulting
residue was dissolved in n-hexane (1.4 mL) and stored at
ambient temperature for 2l hours, to crystallize LGaBr2. After
the filtration, the mother liquor was dissolved in n-hexane (0.3
mL) again to afford 2 as red crystals. Yield: 16 mg (0.013 mmol,
10 %). M.p. 229 °C. Anal. Calcd. for C58H82AsBrGa2N4: C, 61.67;
H, 7.32; N, 4.95. Found: C, 60.20; H, 7.32; N, 4.44 %. IR (neat): 
3059, 2964, 2924, 2865, 1525, 1436, 1384, 1315, 1258, 1175,
D. J. Liptrot and P. P. Power, Nat. Rev. Chem. 2017, 1, 0004;
J.-D. Guo, D. J. Liptrot, S. Nagase and P. P. Power, Chem. Sci
2015, 6, 6235; R. C. Fischer and P. P. Power, Chem. Rev.
2010, 110, 3877; P. P. Power, Chem. Rev. 1999, 99, 3463.
S. Yao, Y. Xiong and M. Driess, Acc. Chem. Res. 2017, 50,
2026; E. Rivard, Chem. Soc. Rev. 2016, 45, 989; M. Driess and
C. Jones, Chem. Rev. 2011, 111, 354; G. H. Robinson, Main
Group: Multiple Bonding, In Encyclopedia of Inorganic and
Bioinorganic Chemistry, 1; R. A. Scott, J. Wiley & Sons, 2011;
R. West, M. J. Fink and J. Michl, Science 1981, 214, 1343.
J. A. Bailey and P. G. Pringle, Coord. Chem. Rev. 2015, 297-
298, 77; H. Nöth, Angew. Chem. Int. Ed. 1988, 27, 1603; P.
Paetzold, Adv. Inorg. Chem. 1987, 31, 123.
4
5
1
1104, 1055, 1018, 936, 870, 795, 757, 637, 530, 441 cm-1. H
a) A. Rosas-Sánchez, I. Alvarado-Beltran, A. Baceiredo, D.;
Hashizume, N. Saffon-Merceron, V. Branchadell and T. Kato,
Angew. Chem. Int. Ed. 2017, 56, 4814; J. A. Bailey and P. G.
Pringle, Coord. Chem. Rev. 2015, 297-298, 77; R. T. Paine and
H. Nöth, Chem. Rev. 1995, 95, 343; D. C. Pestana and P. P.
NMR (benzene-d6, 25 C, 300 MHz):  7.13 (m, 12 H, aromatic H
3
of Dipp group), 4.90 (s, 2 H, -CH), 3.21 (sept, JHH = 6.70 Hz, 8
H, CH(CH3)2), 1.50 (s, 12 H, NCCH3), 1.26 (d, 3JHH = 6.70 Hz, 24 H,
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 10
Dalton Transactions
Please do not adjust margins
Journal Name
ARTICLE
Power, J. Am. Chem. Soc. 1991, 113, 8426; P. P. Power,
Angew. Chem. Int. Ed. 1990, 29, 449.
24 A. Y. Timoshkin and H. F. Schaefer, Inorg. Chem. 2004, 43,
3080; A. Y. Timoshkin and G. Frenking, Inorg. ChVeiemw.A2rt0ic0le3O,nline
42, 60; C. W. Bock and M. Trachtman,DJ.OPI:h1y0s.1.0C3h9e/Cm9.D1T9093939,8H
97, 3183.
6
7
8
J.-S. Lu, M.-C. Yang and M.-D. Su, ACS Omega 2018, 3, 76; K.
K. Pandey, R. Vishwakarma and S. K. Patidar, Comp. Theoret.
Chem. 2016, 1076, 23; T.-W. Shih, M.-C. Li and M.-D. Su,
Inorg. Chem. 2015, 54, 5154; A. Y. Timoshkin and H. F.
Schaefer, III, J. Phys. Chem. A 2008, 112, 13180; A. Y.
Timoshkin, Coord. Chem. Rev. 2005, 249, 2094.
A. Rosas-Sánchez, I. Alvarado-Beltran, A. Baceiredo, D.
Hashizume, N. Saffon-Merceron, V. Branchadell and T. Kato,
Angew. Chem. Int. Ed. 2017, 56, 4814; A. N. Price, G. S.
Nichol and M. J. Cowley, Angew. Chem. Int. Ed. 2017, 56,
9953; E. Rivard, W. A. Merrill, J. C. Fettinger and P. P. Power,
Chem. Commun. 2006, 3800.
25 D. A. Atwood, A. H. Cowley, R. A. Jones and M. A. Mardones,
J. Organomet. Chem. 1992, 439, C33.
26 Cambridge Structural Database, Version 5.40, see also: Allen,
F. H. Applications of the Cambridge Structural Database in
chemical education. Acta Cryst. 2002, B58, 380. Search for
[R2GaAsR2]2 gave 7 hits (28 bonds) mean 2.541(15) Å range
from 2.518 to 2.574 Å.
27 A. H. Cowley, R. A. Jones, M. A. Mardones and C. M. Nunn,
Organometallics 1991, 10, 1635.
28 J. F. Janik, R. L. Wells, V. G. Young, Jr., A. L. Rheingold, and I.
A. Guzei, J. Am. Chem. Soc. 1998, 120, 532.
J. Li, X. Li, W. Huang, H. Hu, J. Zhang and C. Cui, Chem. Eur. J.
2012, 18, 15263; R. J. Wright, M. Brynda, J. C. Fettinger, A. R. 29 R. L. Wells, A. P. Purdy, A. T. McPhail, and C. G. Pitt, J.
Betzer and P. P. Power, J. Am. Chem. Soc. 2006, 128, 12498;
H. Zhu, J. Chai, V. Chandrasekhar, H. W. Roesky, J. Magull, D.
Vidovic, H.-G. Schmidt, M. Noltemeyer, P. P. Power and W.
A. Merrill, J. Am. Chem. Soc. 2004, 126, 9472; R. J. Wright, A.
D. Phillips, T. L. Allen, W. H. Fink and P. P. Power, J. Am.
Chem. Soc. 2003, 125, 1694; N. J. Hardman, C. Cui, H. W.
Roesky, W. H. Fink and P. P. Power, Angew. Chem. Int. Ed.
2001, 40, 2172.
B. Neumüller and E. Iravani, Coord. Chem. Rev. 2004, 248,
817. C. von Hänisch and F. Weigend, Z. Anorg. Allg. Chem.
2002, 628, 389-393. C. von Hänisch and B. Rolli, Z. Anorg.
Allg. Chem. 2002, 628, 2255.
Organomet. Chem. 1988, 354, 287.
30 K. T. Higa and C. George, Organometallics 1990, 9, 275.
31 F. Neese, The ORCA program system. Wiley Interdisciplinary
Reviews: Computational Molecular Science 2012, 2, 73.
32 NBO 6.0: E. D. Glendening, J. K. Badenhoop, A. E. Reed, J. E.
Carpenter, J. A. Bohmann, C. M. Morales, C. R. Landis and F.
Weinhold (Theoretical Chemistry Institute, University of
Wisconsin, Madison, WI, 2013); http://nbo6.chem.wisc.edu/.
33 R. K. Harris, E. D. Becker, S. M. Cabral de Menezes, R.
Goodfellow and P. Granger, Magn. Reson. Chem. 2002, 40,
489.
9
34 SHELXS-97; G. M. Sheldrick, Acta Crystallogr. 1990, A46, 467.
35 SHELXL-2014, G. M. Sheldrick, Acta Crystallogr. 2008, A64,
112; shelXle, C. B. Hübschle, G. M. Sheldrick and B. Dittrich, J.
Appl. Cryst. 2011, 44, 1281.
36 J. P. Perdew, M. Ernzerhof and K. Burke, J. Chem. Phys. 1996,
105, 9982.
10 K. Knabel, T. M. Klapötke, H. Nöth, R. T. Paine and I. Schwab,
Eur. J. Inorg. Chem. 2005, 1099; G. Linti, H. Nöth, K. Polborn
and R. T. Paine, Angew. Chem. Int. Ed. 1990, 29, 682.
11 C. Helling, C. Wölper and S. Schulz, J. Am. Chem. Soc. 2018,
140, 5053.
12 C. von Hänisch and O. Hampe, Angew. Chem. Int. Ed. 2002,
41, 2095.
13 C. Ganesamoorthy, C. Helling, C. Wölper, W. Frank, E. Bill, G.
E. Cutsail III and S. Schulz, Nat. Commun. 2018, 9, 87.
14 J. Krüger, C. Ganesamoorthy, L. John, C. Wölper and S.
Schulz, Chem. Eur. J. 2018, 24, 9157.
37 F. Weigend and R. Ahlrichs, Phys. Chem. Phys. 2005, 7, 3297.
38 S. Grimme, S. Ehrlich and L. Goerigk, J. Comp. Chem. 2011,
32, 1456.
39 F. Weigend, Phys. Chem. Chem. Phys. 2006, 8, 1057.
15 C. Helling, C. Wölper, Y. Schulte, G. Cutsail III and S. Schulz,
Inorg. Chem. 2019, 58, 10323.
16 L. Tuscher, C. Helling, C. Wölper, W. Frank, A. S. Nizovtsev
and S. Schulz, Chem. Eur. J. 2018, 26, 3241; J. Krüger, J.
Schoening, C. Ganesamoorthy, L. John, C. Wölper and S.
Schulz, Z. Anorg. Allg. Chem. 2018, 644, 1028; L. Tuscher, C.
Helling, C. Ganesamoorthy, J. Krüger, C. Wölper, W. Frank, A.
S. Nizovtsev and S. Schulz, Chem. Eur. J. 2017, 23, 12297; L.
Tuscher, C. Ganesamoorthy, D. Bläser, C. Wölper and S.
Schulz, Angew. Chem. Int. Ed. 2015, 54, 10657; G.
Prabusankar, C. Gemel, P. Parameswaran, C. Flener, G.
Frenking and R. A. Fischer, Angew. Chem. Int. Ed. 2009, 48,
5526.
17 L. Song, J. Schoening, C. Wölper, S. Schulz and P. R.
Schreiner, Organometallics 2019, 38, 1640.
18 N. J. Hardman, B. E. Eichler and P. P. Power, Chem. Commun.
2000, 1991.
19 J. H. Muessig, T. E. Stennett, U. Schmidt, R. D. Dewhurst, L.
Mailänder and H. Braunschweig, Dalton Trans. 2019, 48,
3547.
20 H. Braunschweig, R. D. Dewhurst, F. Hupp and J. Wolf, Chem.
Eur. J. 2015, 21, 1860. H. Braunschweig, P. Brenner, P.
Cogswell, K. Kraft and K. Schwab, Chem. Commun. 2010, 46,
7894; C. Tschersich, B. Braun, C. Herwig and C. Limberg,
Organometallics 2015, 34, 3782-3787.
21 D. Kost, E. H. Carlson and M. J. Raban, J. Chem. Soc. D 1971,
656.
22 M. A. Petrie and P. P. Power, Inorg. Chem. 1993, 32, 1309.
23 P. Pyykkö and M. Atsumi, Chem. Eur. J. 2009, 15, 12770.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Dalton Transactions
Page 6 of 10
View Article Online
DOI: 10.1039/C9DT03998H
Figure 1. Solid state structure of 1 including selected bond lengths (Å) and angles (°). Displacement
ellipsoids are displayed at 50% probability levels. Second orientation of the disorder and hydrogen atoms
omitted for clarity; As(1)–Ga(2) 2.2628(5), As(1)–Ga(1) 2.3503(4), Cl(1)–Ga(1) 2.2783(9), Ga(1)–N(2)
1.977(2), Ga(1)–N(1) 1.983(2), Ga(2)–N(3) 1.922(3), Ga(2)–N(4) 1.957(2), Ga(2)–As(1)–Ga(1)
111.419(19), N(2)–Ga(1)–N(1) 94.04(10), N(2)–Ga(1)–As(1) 107.88(7), N(1)–Ga(1)–As(1) 117.33(7),
N(3)–Ga(2)–N(4) 95.54(11), N(3)–Ga(2)–As(1) 150.79(8), N(4)–Ga(2)–As(1) 110.96(7).
905x868mm (96 x 96 DPI)

Page 7 of 10
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT03998H
Figure 2. Solid state structure of 2 including selected bond lengths (Å) and angles (°). Displacement
ellipsoids are displayed at 50% probability levels. Hydrogen atoms omitted for clarity; The model contains
unresolvable twinning problems thus quantitative results may be unreliable. As(1)–Ga(2) 2.2591(11),
As(1)–Ga(1) 2.3580(11), Br(3)–Ga(1) 2.3986(11), Ga(1)–N(2) 1.994(6), Ga(1)–N(1) 2.020(6), Ga(2)–N(3)
1.910(6), Ga(2)–N(4) 1.957(6), Ga(2)–As(1)–Ga(1) 113.37(4), N(2)–Ga(1)–N(1) 94.4(2), N(2)–Ga(1)–
As(1) 105.31(18), N(1)–Ga(1)–As(1) 120.12(17), N(2)–Ga(1)–Br(3) 103.96(18), N(1)–Ga(1)–Br(3)
101.29(17), As(1)–Ga(1)–Br(3) 126.18(4), N(3)–Ga(2)–N(4) 95.4(2), N(3)–Ga(2)–As(1) 153.88(17), N(4)–
Ga(2)–As(1) 110.32(19).
877x872mm (96 x 96 DPI)

Dalton Transactions
Page 8 of 10
View Article Online
DOI: 10.1039/C9DT03998H
Figure 3. HOMO and LUMO of 1'.
97x185mm (150 x 150 DPI)

Page 9 of 10
Dalton Transactions
View Article Online
DOI: 10.1039/C9DT03998H
Scheme 1. Structurally characterized group 13/15 compounds with π-bonding contributions.
1289x706mm (96 x 96 DPI)

Dalton Transactions
Page 10 of 10
View Article Online
DOI: 10.1039/C9DT03998H
Scheme 2. Synthesis of 1 and 2
973x265mm (96 x 96 DPI)