Stabilized Gallylene in a Pincer-Type Ligand: Synthesis, Structure, and Reactivity of PGaIP-Ir Complexes

Article abstract of DOI:10.1002/anie.201904968

Iridium complexes having a pincer-type gallylene ligand were successfully synthesized utilizing bis(phosphino)terpyridine as an efficient scaffold for the Ir?Ga^I bond. The stabilization of the gallylene moiety by the pincer-type structure enabled various reactions at Ir with keeping the gallylene ligand intact, leading to unique structures and reactivities of PGa^IP?Ir complexes.

Full text of DOI:10.1002/anie.201904968

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Accepted Article
Title: Stabilized Gallylene in a Pincer Type Ligand: Synthesis,
Structure, and Reactivity of PGaIP-Ir Complexes
Authors: Narumasa Saito, Jun Takaya, and Nobuharu Iwasawa
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201904968
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10.1002/anie.201904968
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Stabilized Gallylene in a Pincer Type Ligand: Synthesis, Structure,
and Reactivity of PGaIP-Ir Complexes
Narumasa Saito[a], Jun Takaya*[a,b], and Nobuharu Iwasawa*[a]
Abstract: Iridium complexes having a pincer-type gallylene ligand
were successfully synthesized utilizing bis(phosphino)terpyridine as
an efficient scaffold for the Ir–GaI bond. The stabilization of the
gallylene moiety by the pincer type structure enabled various
reactions at Ir with keeping the gallylene ligand intact, realizing
unique structures and reactivities of PGaIP-Ir complexes.
ligands on the group 13 metal and formally donating 2 electrons
to the transition metal. However, a group 13 metallylene-based
pincer-type ligand has remained unexplored in the pincer
chemistry. Although Langer recently reported synthesis and
property of iron and palladium complexes having pincer-type
borylene ligands,[8] there has been no report on the
corresponding heavier group 13 metallylene systems.
Herein we report synthesis, structure, and reactivity of iridium
Group 13 metallylenes (:EIR, E = Al, Ga, In, Tl), which are
neutral group 13 metal compounds having the +1 formal
oxidation state, have been attracting much attention as a new
type of supporting ligands in organometallic chemistry. They
coordinate to transition metals potentially through the σ-donation
and π-back donation with lone pair electrons and a vacant p-
orbital, behaving as isolobal species of PR3, CO, and carbene.
Numerous group 13 metallylene-ligated transition metal
complexes have been developed utilizing various mono- or
multidentate ligands on the group 13 metal such as Cp*, bulky
Ar and several nitrogen-containing compounds to stabilize the
metallylene (Figure 1, L = L-type ligand, X = X-type ligand).[1,2]
However, investigations on the reactivity of those metal
complexes are still limited despite their promising utility as new
transition metal catalysts in synthetic chemistry.[3] This is partly
due to the high reactivity of metallylenes and instability of the
monodentate coordination of the REI to transition metals, thus
resulting in easy loss of the metallylene moiety during
reactions.[4]
complexes having
a pincer-type gallylene ligand utilizing
bis(phosphino)terpyridine as an efficient scaffold for the Ir–GaI
bond. The pincer type structure enabled easy synthesis and
various reactions at Ir with keeping the gallylene moiety intact as
a supporting ligand, realizing unique structures and reactivities
of PGaIP-Ir complexes.
Previous examples –monodentate coordination–
(E = group 13 metals)
Me
Me
N
R
R
N
N
EI
R
R
[M]
EI
EI
EI
[M]
EI
Tp
[M]
N
Me
Me
X
[M]
[M]
(R = 2,4,6-iPr3C6H2)
(R = 2,6-iPr2C6H3)
(Tp = tris(pyrazolyl)borate)
(L2XGa)
(L2XGa)
(XGa)
(LXGa)
(L2XGa)
Problem: Loss of the group 13 metallylene moiety during reactions
This Work –group 13 metallylene in a pincer type ligand–
[Ir]
R2P
PR2
• The first synthesis of pincer-type gallylene ligand
• Facile synthesis by reduction of GaIII with IrI
One of the promising approaches to stabilize and utilize group
GaI
N
N
13 metallylenes as
incorporate the group 13 metal into
a
spectator supporting ligand is to
component of
Cl
R’
N
• Various reactions at [Ir] with keeping
the gallylene (GaI) moiety as a supporting ligand
a
a
multidentate ligand. Pincer type ligands seem to be suitable for
such a purpose because the pincer motif is advantageous for
introducing a variety of elements into the central position and
stabilizing the metal–element bonds while keeping sufficient
reactivity of the transition metal.[5] Several pincer-type group 13
metalloligands and their transition metal complexes have been
developed, in which the group 13 metal coordinates as a Z-type
ligand,[6] formally accepting 2 electrons in a vacant p-orbital from
the transition metal, or as an X-type ligand,[7] having two anionic
(L3XGa)
Figure 1. Group 13 metallylenes as a supporting ligand for transition metals
Recently, we have reported efficient synthesis and unique
catalysis of E–Pd bimetallic complexes (E = Al, Ga, In) utilizing a
6,6”-bis(phosphino)terpyridine derivative as a scaffold for the E–
Pd bonds, in which the group 13 metals coordinate as formally
anionic EI-metalloligands (Cl2EI).[9] We attempted to apply this
system to iridium with slight modification of substituents on the
phosphorus atoms and terpyridine. A newly designed 6,6”-
(iPr2P)2-terpyridine 1 having a mesityl group at the 4’-position
was synthesized in a gram scale through Pd-catalyzed cross
coupling reactions (see the Supporting Information for details).[10]
Treatment of 1 with 2.3 equivalent of GaCl3 afforded a cationic
terpyridine-GaCl2 complex 2 in 77% yield (Scheme 1). The
structure of 2 was identified by X-ray analysis (see the SI).
Introduction of Ir was achieved by the reaction of 2 and
[IrCl(cod)]2 in toluene at 80 ˚C, giving a Ga–Ir bimetallic complex
[a]
N. Saito, Dr. J. Takaya, and Prof. Dr. N. Iwasawa
Department of Chemistry
Tokyo Institute of Technology
O-okayama, Meguro-ku, Tokyo 152-8551 (Japan)
E-mail: niwasawa@chem.titech.ac.jp,
takayajun@chem.titech.ac.jp
[b]
Dr. J. Takaya
JST, PRESTO
Honcho, Kawaguchi, Saitama, 332-0012, Japan
Supporting information for this article is given via a link at the end of
the document.
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10.1002/anie.201904968
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COMMUNICATION
3, which can be regarded as a PGaP–pincer type Ir complex, as
a red solid in 78% yield.
complexes and could be a useful method to access a variety of
metallylene-coordinated late transition metal complexes.
a)
b)
–GaCl4
+
Cl(4)
iPr2P
PiPr2
iPr2P
PiPr2
Cl
Cl
Cl(3)
Ga
GaCl3
(2.3 equiv)
Ga
N
N
N
N
N
N
THF, rt, 10 h
Ga
Cl(1)
Ir
P(1)
Cl(1)
P(1)
P(2)
Ar
Ar
1
2
77%
Ir
P(2)
–GaCl4
Cl(2)
Cl(3)
+
iPr2P
iPr2P
Cl(2)
[IrCl(cod)]2
(0.5 equiv)
NBu4Cl
(1.5 equiv)
Cl
Cl
Cl
N
N
Cl
N
Ir
Ir
Ga
Ga
Cl
iPr2P
N
Toluene
80 ˚C, 2.5 h
THF, rt
11 h
Cl
Cl
Figure 2. ORTEP drawings of a) 3 and b) 4 at 50% probability level. [GaCl4]−
and hydrogen atoms are omitted for clarity. Selected bond lengths [Å] and
angles [deg]; 3: Ir–Cl(1), 2.310(1); Ir–Cl(2), 2.370(1); Ga–Cl(2), 2.725(1); Ir–
Ga, 2.3895(6); Ga–Cl(3), 2.226(1); Ir–P(1), 2.320(1); Ir–P(2), 2.327(1); P(1)–
Ir–P(2), 176.04(4); Cl(1)–Ir–Cl(2), 170.13(4).; 4: Ir–Cl(1), 2.3690(9); Ir–Cl(2),
2.5459(9); Ir–Cl(3), 2.3924(9); Ga–Cl(3), 2.8906(8); Ga–Cl(4), 2.2628(9); Ir–
Ga, 2.3970(7); Ir–P(1), 2.3426(9); Ir–P(2), 2.3350(9); P(1)–Ir–P(2), 172.13(3);
Cl(1)–Ir–Ga, 105.14(3); Cl(2)–Ir–Ga, 166.02(3); Cl(3)–Ir–Ga, 74.25(2).
iPr2P
Ar
Ar
N
N
3
78%
4
59%
(Ar = 2,4,6-Me3C6H2)
Scheme 1. Synthesis of Ir complexes having a pincer-type gallylene ligand.
The pincer-type structure enabled various reactions of the
Ga–Ir complex 3 at Ir without losing the gallylene ligand. The
reaction of 3 with 1.0 equivalent of tetrabutylammonium formate
afforded an IrIIIHCl2 complex 5 via ligand exchange and
decarboxylation, which was characterized by NMR and X-ray
analyses as described in the SI (Scheme 2). Moreover,
treatment of 3 with 2.3 equivalent of KC8 afforded a neutral IrI
monochloride complex 6 having the pincer-type gallylene ligand
in good yield through two electron reduction of IrIII (Scheme
2).[18] The structure of 6 was clarified by X-ray analysis of a
single crystal obtained from THF/Et2O (Figure 3). Interestingly,
the Ir possesses another Ga–metalloligand, a trivalent GaCl3, on
Ir as a Z-type ligand, which came from the counter anion
[GaCl4]– of 3. This is a rare example of having both L- and Z-
type Ga-metalloligands at a single metal center.[19] The Ir–Ga(1)
bond length is almost comparable to that of 3 (2.377(1) Å for 6,
2.3895(6) Å for 3). The Ga1–Ga2 distance of 3.010(1) Å is
longer than the sum of covalent radii (2.44 Å),[12] suggesting no
bonding interaction between these two gallium atoms. This was
also supported by the QTAIM analysis, in which no bond path
between Ga1 and Ga2 was observed. Several trials to dissociate
the GaCl3 from Ir by adding Lewis bases such as pyridine, 1,4-
diazabicyclo[2.2.2]octane (DABCO), and NH3 were unfruitful,
suggesting the dative interaction from Ir to GaCl3 is very strong.
Moreover, no exchange of the GaCl3 with the added AlCl3 was
also observed. This is in sharp contrast to the case of a pincer-
type carbene ligand, in which four-coordinate, 16e PCP-IrCl
complexes were stably formed and isolated.[20] This could be
attributed to the strong electron donating ability of the GaI-
metalloligand surrounded by three nitrogen atoms of terpyridine,
demonstrating unique electronic property of the pincer type
gallylene ligand.
The structure of 3 was fully determined by NMR and X-ray
analyses (Figure 2-a). The Ga–Ir complex 3 is cationic having
[GaCl4]– as a counter anion, and the geometry around iridium is
distorted square pyramidal with the PGaP-pincer type ligand.
The Ga–Ir bond length is 2.3895(6) Å, which is in a range of
previously reported values of Ga–Ir bonds (2.381(1) ~ 2.4689(5)
Å).[11] Importantly, the chloride ligand Cl(2) is seemingly bridging
between Ir and Ga, however, the distances to each metal are
substantially different. The Ir–Cl(2) distance of 2.370(1) Å is
similar to that of the Ir–Cl(1) (2.310(1) Å), whereas the Ga–Cl(2)
is 2.725(1) Å, which is much longer than the sum of covalent
radii (2.24 Å).[12] A quantum theory of atoms in molecules
(QTAIM) analysis showed the bond critical point (bcp) for the Ir–
Cl(2) bond, but not between Ga and Cl(2). These results clearly
indicate that the chloride ligand Cl(2) bonds to Ir, not to Ga.
Moreover, the cationic complex 3 was converted to a neutral
complex 4 by treatment with NBu4Cl (Scheme 1). The X-ray
structural analysis demonstrated the added chloride bonds to Ir,
not to Ga, to form the octahedral iridium trichloride complex
bearing a GaCl as a supporting ligand (Figure 2-b). The
coordination geometry of ligands on Ir except for the GaCl in 4 is
square pyramidal judged by the τ parameter (τ = 0.11), indicating
that the GaCl is a donor ligand to the Ir.[8c,13] Therefore, in these
complexes, the Ir can be described as an IrIII, and Ga as a
neutral GaI, gallylene, generated through two electron reduction
of 2 by the added IrI in terms of the formal oxidation state.[14]
Notably, the Ir–Cl(2) bond of 4 is elongated (2.5459(9) Å)
compared with that in the related pincer type IrIIICl complexes,
suggesting the strong trans influence of the GaI-metalloligand.[15]
Such a complexation-induced reduction of trivalent group 13
metals to metallylenes with neutral, late transition metals are
rather rare[16] whereas reactions with highly reactive, dianionic
carbonyl metalates such as K2[Fe(CO)4] with the group 13
chlorides were well developed to give XLnGaI–Fe(CO)4
complexes via double salt exchange.[17] This is the first example
of synthesis and structural analysis of gallylene-based pincer
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6model
HOMO
ORTEP of 5
iPr2P
Cl
HCOONBu4
(1.0 equiv)
H
N
Cl
Ga2Cl3
PiPr2
Ir
Ga
iPr2P
Cl
iPr2P
Ir
N
Cl
Ga1
[D8]THF
rt, 0.5 h
Ga1
Ar
N
N
N
Cl
N
5
3
Ga2
(Ar = 2,4,6-Me3C6H2)
([Ga] = GaCl3)
iPr2P
Ir
Cl
N
HOMO–2
HOMO–5
Cl
pyridine
DABCO
KC8 (2.2 equiv)
Ga
N
[Ga]
THF, rt, 11 h
iPr2P
Ar
NH3
AlCl3
N
76% (isolated)
Ga1
Ga1
6
no dissociation of GaCl3
Ga2
Ga2
Scheme 2. Various reactions of 3
Figure 4. Molecular orbitals of 6model at contour value = ±0.03 (B3PW91/6-
31G(d,p)/LANL2DZ).
Cl(2)
Finally, the Ga–Ir complex 6 was also found to react as a
PGaIP-IrI complex with keeping the Z-type ligand, GaCl3, intact.
The reaction of 6 with 30 equivalents of PhSiH3 in THF afforded
a dihydrido(silyl)IrIII complex 7 bearing both the PGaIP-pincer
ligand and GaCl3 Z-type ligand, which was characterized by X-
ray and 1H NMR analyses (Scheme 3, Figure 5). The Ir–Si bond
length (2.422(1) Å) is comparable to those of previously reported
silyliridium complexes.[21] The Ir–Ga(1) distance of 2.4616(6) Å is
clearly longer than those of 3 and 4 due to the strong trans
influence of the silyl ligand on 7. In 1H NMR, hydrogen atoms on
Ir and Si appeared at δ = –11.6 (1H, IrH), –8.9 (1H, IrH), and 5.0
(2H, SiH2) separately in [D2]dichloromethane, and no exchange
behavior among them was observed by 1H EXSY NMR,
supporting the Ir(silyl)H2 structure is maintained in the solution
Ga(1)
Ga(2)
P(1)
Ir
P(2)
Cl(1)
Figure 3. ORTEP drawing of 6 at 50% probability level. Hydrogen atoms are
omitted for clarity. Selected bond lengths [Å] and angles [deg]: Ir–Cl(1),
2.390(2); Ir–Ga(1), 2.377(1); Ir–Ga(2), 2.456(1); Ga(1)–Ga(2), 3.010(1);
Ga(1)–Cl(2), 2.258(2); Ir–P(1), 2.310(2); Ir–P(2), 2.316(2); P(1)–Ir–P(2),
168.50(8); Cl(1)–Ir–Ga(1), 140.26(6); Cl(1)–Ir–Ga(2), 142.71(6); Ga(1)–Ir–
Ga(2), 77.02(3).
without formation of
a σ-(Si–H) complex. The stretching
vibrations of the Si–H and Ir–H bonds were observed at 2085
and 2006 cm–1, respectively.[22] Furthermore, 6 immediately
reacted with
1 atm of CO to give a
six-coordinate IrI
monocarbonyl complex 8 having both PGaIP- and GaCl3 ligands.
The CO ligand vibrates at 2026 cm–1, which is close to the
values of standard IrIII complexes rather than IrI due to the strong
electron accepting nature of the GaCl3 ligand.[23] The high
stability of the GaCl3 on Ir during these transformations is
surprising and will be highly useful toward development of
cooperative molecular transformation with Ir, GaIII and GaI.
Further studies on the application of these complexes to
synthetic reactions are ongoing.
To gain further insights into the bonding situation, theoretical
calculations were performed on model complexes omitting the
mesityl group (Figure 4). The bonding character between Ir and
the gallylene ligand is mainly composed of a σ-bond between Ir
and Ga1 as seen in the HOMO–5. Additionally, a partial π-bond
is also found in the HOMO although this contribution is relatively
small. The Wiberg bond index (WBI) of 0.5553 for the Ir–Ga1
bond also supports these descriptions that there is almost no
double bond character. The HOMO–2 of 6model shows a σ-bond
between Ir and Ga2, in which the GaCl3 is accepting two
electrons as a Z-type ligand. The stabilization energy by the
coordination of GaCl3 in 6model is calculated to be 35.5 kcal/mol,
which supports the robustness of GaCl3 on Ir. Further
information on these theoretical calculations are described in the
supporting information.
iPr2P
Cl
H
N
PhH2Si
PhSiH3 (30 equiv)
THF, rt, 24 h
Ir
Ga
H
N
[Ga]
iPr2P
Ar
N
(isolated)
22%
7
6
iPr2P
Ir
Cl
Cl
OC
iPr2P
N
CO (1 atm)
Ga
N
[Ga]
CD2Cl2, rt, 0.5 h
Ar
N
(Ar = 2,4,6-Me3C6H2)
([Ga] = GaCl3)
8
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10.1002/anie.201904968
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COMMUNICATION
Scheme 3. Reaction of the GaI–IrI–GaIII complex 6.
[4] For examples of reactions at group 13 metallylenes with Cp* ligand, see; a)
ref 1a) and 1c); b) T. Steinke, C. Gemel, M. Cokoja, M. Winter, R.
Fischer, Angew. Chem. Int. Ed. 2004, 43, 2299; Angew. Chem. 2004, 116,
2349; c) T. Cadenbach, C. Gemel, R. Schmid, S. Block, R. Fischer, Dalton
Trans. 2004, 3171; d) T. Steinke, M. Cokoja, C. Gemel, A. Kempter, A.
Krapp, G. Frenking, U. Zenneck, R. Fischer, Angew. Chem. Int.
Ed. 2005, 44, 2943; Angew. Chem. 2005, 117, 3003; With diketiminate
ligand, see; e) A. Kempter, C. Gemel, N. Hardman, R. Fischer, Inorg.
Chem. 2006, 45, 3133; f) A. Doddi, C. Gemel, R. Seidel, M. Winter, R.
Fischer, J. Organomet. Chem. 2011, 696, 2635; g) T. Hooper, M. Garçon,
A. White, M. Crimmin, Chem. Sci. 2018, 9, 5435; With diamine ligand, see;
h) R. Fischer, M. Schulte, J. Weiss, L. Zsolnai, A. Jacobi, G. Huttner, G.
Frenking, C. Boehme, S. Vyboishchikov, J. Am. Chem. Soc. 1998, 120,
1237.
a)
b)
Cl
Cl(2)
Ga(1)
Ir
H(1)
P(1)
Cl(1)
Ga(1)
P(1)
P(2)
Ir
Ga(2)
Si
P(2)
H(2)
Ga(2)
C
O
[5] a) E. Peris, R. Crabtree, Chem. Soc. Rev. 2018, 47, 1959; b) L. Maser, L.
Vondung, R. Langer, Polyhedron 2018, 143, 28; c) Pincer and Pincer-Type
Complexs (Eds.: K. J. Szabó, O. F. Wendt,), Wiley-VHC, Weinheim,
Germany, 2014.
Figure 5. ORTEP drawings of a) 7 and b) 8 at 50% probability level. Hydrogen
atoms except SiH2 and IrH2 are omitted for clarity. H(1) and H(2) on Ir were
located in the final difference map and refined isotropically. Selected bond
lengths [Å] and angles [deg]; 7: Ir–Si, 2.422(1); Ir–Ga(1), 2.4616(6); Ir–Ga(2),
2.5497(5); Ga(1)–Ga(2), 3.1440(6); Ir–P(1), 2.3247(9); Ir–P(2), 2.3334(9); Ir–
H(1), 1.46(3); Ir–H(2), 1.54(4); P(1)–Ir–P(2), 163.70(3); Ga(1)–Ir–Ga(2),
77.69(1); Si–Ir–Ga(1), 154.06(3); 8: Ir–Cl(1), 2.503(2); Ir–C, 1.932(8); Ir–Ga(1),
2.484(1); Ir–Ga(2), 2.496(1); Ga(1)–Ga(2), 3.192(1); Ga(1)–Cl(2), 2.253(2); C–
O, 1.137(9); Ir–P(1), 2.353(2); Ir–P(2), 2.347(2); P(1)–Ir–P(2), 160.01(6),
Cl(1)–Ir–Ga(1), 111.68(5); Ga(1)–Ir–Ga(2), 79.72(3); Cl(1)–Ir–C, 84.1(2).
[6] a) M. Sircoglou, M. Mercy, N. Saffon, Y. Coppel, G. Bouhadir, L. Maron, D.
Bourissou, Angew. Chem. Int. Ed. 2009, 48, 3454; Angew. Chem. 2009,
121, 3506; b) T. Saito, N. Hara, Y. Nakao, Chem. Lett. 2017, 46, 1247.
[7] N. Hara, T. Saito, K. Semba, N. Kuriakose, H. Zheng, S. Sakaki, Y.
Nakao, J. Am. Chem. Soc. 2018, 140, 7070.
[8] a) L. Vondung, N. Frank, M. Fritz, L. Alig, R. Langer, Angew. Chem. Int.
Ed. 2016, 55, 14450; Angew. Chem. 2016, 128, 14665; b) M. Grätz, A.
Bäcker, L. Vondung, L. Maser, A. Reincke, R. Langer, Chem.
Commun. 2017, 53, 7230. c) L. Vondung, L. Alig, M. Ballmann, R. Langer,
Chem. Eur. J. 2018, 24, 12346.
In conclusion, we have achieved the first synthesis of Ir
complexes having a pincer-type gallylene ligand through the
complexation-induced reduction of GaIII by IrI. The stabilization
by the pincer type structure enabled various reactions at Ir with
keeping the gallylene ligand intact, which exerts high electron
donating nature and enables unique structures and reactivity.
This method is useful for preparation of analogous transition
metal complexes having a pincer-type metallylene ligand, which
would be promising catalysts in organometallic and synthetic
chemistry.
[9] J. Takaya, N. Iwasawa, J. Am. Chem. Soc. 2017,139, 6074.
[10] The mesityl group was necessary to increase solubility of Ir complexes in
standard organic solvents such as THF.
[11] a) M. Fryzuk, L. Huang, N. McManus, P. Paglia, S. Rettig, G. White,
Organometallics 1992, 11, 2979; b) S. Green, C. Jones, D. Mills, A.
Stasch, Organometallics 2007, 26, 3424; c) C. Durango-García, O.
Jiménez-Halla, M. López-Cardoso, V. Montiel-Palma, M. Muñoz-
Hernández, G. Merino, Dalton Trans. 2010, 39, 10588.
[12] B. Cordero, V. Gómez, A. Platero-Prats, M. Revés, J. Echeverría, E.
Cremades, F. Barragán, S. Alvarez, Dalton Trans. 2008, 2832.
[13] A. W. Addison, T. N. Rao, J. Chem. Soc. Dalton Trans. 1984, 1349.
[14] Theoretical calculation revealed that the neutral IrIIICl3 complex 4 is more
stable than the cationic complex 3 by 5.7 kcal/mol. Analyses on bonding
situation of the Ir–Ga bond are described in the SI.
Acknowledgements
[15] a) Y. Shi, T. Suguri, C. Dohi, H. Yamada, S. Kojima, Y. Yamamoto, Chem.
Eur. J. 2013, 19, 10672.
This research was supported by JSPS KAKENHI Grant Numbers
15H05800, 17H06143, 17H03019 (Gran-in-Aid for Scientific Research
(B)), 18H04646 (Hybrid Catalysis), and JST, PRESTO Grant Number
JY290145, Japan.
[16] Reactions of XEIIIH2 or InIIIMe3 with transition metal complexes to give
XEI–[M] are reported. See; a) J. Turner, J. Abdalla, J. Bates, R. Tirfoin, M.
Kelly, N. Phillips, S. Aldridge, Chem. Sci. 2013, 4, 4245; b) J. Abdalla, I.
Riddlestone, J. Turner, P. Kaufman, R. Tirfoin, N. Phillips, S.
Aldridge, Chem. Eur. J. 2014, 20, 17624; c) A. Caise, J. Abdalla, R. Tirfoin,
A. Edwards, S. Aldridge, Chem. Eur. J. 2017, 23, 16906; d) J. Abdalla, A.
Caise, C. Sindlinger, R. Tirfoin, A. Thompson, A. Edwards, S. Aldridge, Nat.
Chem. 2017, 9, 1256; e) ref 3b).
[17] Reduction of REIIIX2 with anionic transition metal complexes via salt
exchange has been widely utilized for the synthesis of REI–[M] complexes.
See; a) D. Reger, S. Mason, A. Rheingold, B. Haggerty, F. Arnold,
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Keywords: Gallylene • Gallium • Iridium • Pincer Ligand
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[18] The reduction using excess amount of KC8 with or without stabilizing
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complex.
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[19] M. Cokoja, C. Gemel, T. Steinke, F. Schröder, R. Fischer, Dalton T. 2005,
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Iridium complexes having a pincer-
type gallylene ligand were
successfully synthesized utilizing
bis(phosphino)terpyridine as an
Narumasa Saito, Jun Takaya*, and
Nobuharu Iwasawa*
[Ir]
R2P
PR2
GaI
N
N
Cl
N
Page No. – Page No.
efficient scaffold for the Ir–GaI bond.
The stabilization of the gallylene
moiety by the pincer type structure
enabled various reactions at Ir with
keeping the gallylene ligand intact,
realizing unique structures and
reactivities of PGaIP-Ir complexes.
Stabilized Gallylene in a Pincer Type
Ligand: Synthesis, Structure, and
Reactivity of PGaIP-Ir Complexes
Ar
gallylene in a pincer type ligand
• Facile synthesis
• Unique structures
• Various reactions at Ir
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Author(s), Corresponding Author(s)*
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Title
Text for Table of Contents
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