TY - JOUR
T1 - Structural preferences of cyclopentadienyl and indenyl rings in iridium(I) carbene complexes
AU - Prinz, Martina
AU - Veiros, Luís F.
AU - Calhorda, Maria José
AU - Romão, Carlos C.
AU - Herdtweck, Eberhardt
AU - Kühn, Fritz E.
AU - Herrmann, Wolfgang A.
PY - 2006/10/15
Y1 - 2006/10/15
N2 -
Cleavage of the [Ir(η
4
-COD)Cl]
2
dimer in the presence of the corresponding imidazolium salts and the strong base tBuO
-
leads to the formation of Ir(I) derivatives of N-heterocyclic carbenes. When halide is replaced by NaCp, a mixture of [Ir(η
4
-COD)(NHC
R
)(η
1
-Cp)] and [Ir(η
2
-COD)(NHC
R
)(η
5
-Cp)] is obtained. The latter is favored for R = Cy, while the former predominates for R = Me. Conversely, [Ir(η
4
-COD)(NHC
R
)(η
1
-Ind)] is the only product of the reaction with NaInd, despite the R substituent. DFT/B3LYP calculations confirmed that the η
1
coordination mode of the ring gives rise to the most stable structures, namely square planar complexes of 5d
8
Ir(I). The energy of the 18 electron species containing η
2
-COD and η
5
-Ind or Cp is higher by 13 and 5 kcal mol
-1
, respectively. The fluxional behaviour of indenyl, detected by NMR in the solutions of [Ir(η
4
-COD)(NHC
R
)(η
1
-Ind)], is associated to the low energy of the η
3
-Ind species required in the conversion process, and is not easily observed in the cyclopentadienyl derivatives, where a similar intermediate is disfavored.
AB -
Cleavage of the [Ir(η
4
-COD)Cl]
2
dimer in the presence of the corresponding imidazolium salts and the strong base tBuO
-
leads to the formation of Ir(I) derivatives of N-heterocyclic carbenes. When halide is replaced by NaCp, a mixture of [Ir(η
4
-COD)(NHC
R
)(η
1
-Cp)] and [Ir(η
2
-COD)(NHC
R
)(η
5
-Cp)] is obtained. The latter is favored for R = Cy, while the former predominates for R = Me. Conversely, [Ir(η
4
-COD)(NHC
R
)(η
1
-Ind)] is the only product of the reaction with NaInd, despite the R substituent. DFT/B3LYP calculations confirmed that the η
1
coordination mode of the ring gives rise to the most stable structures, namely square planar complexes of 5d
8
Ir(I). The energy of the 18 electron species containing η
2
-COD and η
5
-Ind or Cp is higher by 13 and 5 kcal mol
-1
, respectively. The fluxional behaviour of indenyl, detected by NMR in the solutions of [Ir(η
4
-COD)(NHC
R
)(η
1
-Ind)], is associated to the low energy of the η
3
-Ind species required in the conversion process, and is not easily observed in the cyclopentadienyl derivatives, where a similar intermediate is disfavored.
KW - Cyclopentadienyl
KW - DFT calculations
KW - Heterocyclic carbenes
KW - Indenyl
KW - Iridium complexes
KW - Ring hapticity
UR - http://www.scopus.com/inward/record.url?scp=33748886488&partnerID=8YFLogxK
U2 - 10.1016/j.jorganchem.2006.02.031
DO - 10.1016/j.jorganchem.2006.02.031
M3 - Article
AN - SCOPUS:33748886488
VL - 691
SP - 4446
EP - 4458
JO - Journal Of Organometallic Chemistry
JF - Journal Of Organometallic Chemistry
SN - 0022-328X
IS - 21
ER -