TY - JOUR
T1 - Isolobal Cationic Iridium Dihydride and Dizinc Complexes: A Dual Role for the ZnR Ligand Enhances H2 Activation
AU - Walsh, Amber M.
AU - Sotorrios, Lia
AU - Cameron, Rebecca G.
AU - Pécharman, Anne-Frédérique
AU - Procacci, Barbara
AU - Lowe, John P.
AU - Macgregor, Stuart A.
AU - Mahon, Mary F.
AU - Hunt, Neil T.
AU - Whittlesey, Michael K.
PY - 2024/12/2
Y1 - 2024/12/2
N2 - The reaction of [Ir(IPr)2H2][BArF4]
(1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; BArF4 =
B{C6H3(3,5-CF3)2}4) with
ZnMe2 proceeds with CH4 elimination to give
[Ir(IPr)(IPr′)(ZnMe)2H][BArF4] (3,
where (IPr′) is a cyclometalated IPr ligand). 3 reacts with H2 to
form tetrahydride [Ir(IPr)2(ZnMe)2H4][BArF4], 4,
that loses H2 under forcing conditions to form [Ir(IPr)2(ZnMe)2H2][BArF4], 5.
Crystallization of 3 also results in the formation of its
noncyclometalated isomer, [Ir(IPr)2(ZnMe)2][BArF4], 2,
in the solid state. Reactions of 1 and CdMe2 form
[Ir(IPr)2(CdMe)2][BArF4], 6,
and [Ir(IPr)(IPr′)(CdMe)2H][BArF4], 7,
which reacts with H2 to give [Ir(IPr)2(CdMe)2H4][BArF4], 8,
and [Ir(IPr)2(CdMe)2H2][BArF4], 9.
Structures of 2–8 are determined crystallographically.
Computational analyses show the various hydrides in 3–5 sit
on a terminal to bridging continuum, with bridging hydrides exhibiting greater
Znδ+···Hδ− electrostatic interaction. The isolobal
analogy between H and ZnMe ligands holds when both are present as terminal
ligands. However, the electrostatic component to the Znδ+···Hδ− unit
renders it significantly different to a nominally isolobal H···H moiety. Thus,
H2 addition to 3 is irreversible, whereas H2 addition
to 1 reversibly forms highly fluxional [Ir(IPr)2(η2-H2)2H2][BArF4], 11.
Computed mechanisms for cyclometalation and H2 addition
showcase the role of the bridging Znδ+···Hδ− moiety
in promoting reactivity. In this, the Lewis acidic ZnMe ligand plays a dual
role: as a terminal Z-type ligand that can stabilize electron-rich
Ir centers through direct Ir-ZnMe bonding, or by stabilizing strongly hydridic
character via Znδ+···Hδ− interactions.
AB - The reaction of [Ir(IPr)2H2][BArF4]
(1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; BArF4 =
B{C6H3(3,5-CF3)2}4) with
ZnMe2 proceeds with CH4 elimination to give
[Ir(IPr)(IPr′)(ZnMe)2H][BArF4] (3,
where (IPr′) is a cyclometalated IPr ligand). 3 reacts with H2 to
form tetrahydride [Ir(IPr)2(ZnMe)2H4][BArF4], 4,
that loses H2 under forcing conditions to form [Ir(IPr)2(ZnMe)2H2][BArF4], 5.
Crystallization of 3 also results in the formation of its
noncyclometalated isomer, [Ir(IPr)2(ZnMe)2][BArF4], 2,
in the solid state. Reactions of 1 and CdMe2 form
[Ir(IPr)2(CdMe)2][BArF4], 6,
and [Ir(IPr)(IPr′)(CdMe)2H][BArF4], 7,
which reacts with H2 to give [Ir(IPr)2(CdMe)2H4][BArF4], 8,
and [Ir(IPr)2(CdMe)2H2][BArF4], 9.
Structures of 2–8 are determined crystallographically.
Computational analyses show the various hydrides in 3–5 sit
on a terminal to bridging continuum, with bridging hydrides exhibiting greater
Znδ+···Hδ− electrostatic interaction. The isolobal
analogy between H and ZnMe ligands holds when both are present as terminal
ligands. However, the electrostatic component to the Znδ+···Hδ− unit
renders it significantly different to a nominally isolobal H···H moiety. Thus,
H2 addition to 3 is irreversible, whereas H2 addition
to 1 reversibly forms highly fluxional [Ir(IPr)2(η2-H2)2H2][BArF4], 11.
Computed mechanisms for cyclometalation and H2 addition
showcase the role of the bridging Znδ+···Hδ− moiety
in promoting reactivity. In this, the Lewis acidic ZnMe ligand plays a dual
role: as a terminal Z-type ligand that can stabilize electron-rich
Ir centers through direct Ir-ZnMe bonding, or by stabilizing strongly hydridic
character via Znδ+···Hδ− interactions.
UR - https://www.scopus.com/pages/publications/85209737100
U2 - 10.1021/acs.inorgchem.4c04058
DO - 10.1021/acs.inorgchem.4c04058
M3 - Article
C2 - 39564932
SN - 0020-1669
VL - 63
SP - 22944
EP - 22954
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 48
ER -