New Perspective on the Formation and Reactivity of Metal-Metal-Bonded Dinuclear Rhodium and Iridium Complexes
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- 作者：Cristina Tejel ; Miguel A. Ciriano ; José ; A. Ló ; pez ; Fernando J. Lahoz ; and Luis A. Oro
- 刊名：Organometallics
- 出版年：1997
- 出版时间：October 14, 1997
- 年：1997
- 卷：16
- 期：21
- 页码：4718 - 4727
- 全文大小：263K
- 年卷期：v.16,no.21(October 14, 1997)
- ISSN：1520-6041
文摘
Reactions of the binuclear complexes[{M(
-Pz)(CNBut)2}2](M = Rh (1), Ir (2); Pz =pyrazolate) with diiodine give the metal-metal-bonded complexes[{M(-Pz)(I)(CNBut)2}2](M = Rh (3), Ir (4)). A further reactionwith diiodine afford the complexes[{M(-Pz)(I)(CNBut)2}2(-I)]I, which reactcleanly with CF3SO3Me replacing theionic iodide by the triflategroup. The M(I) complexes 1 and 2 are easilyoxidized by mild oxidants such as[Cp2Fe]+ togive the metal-metal-bonded dications[{M(-Pz)(CNBut)2(MeCN)}2]2+,which add halideions yielding the neutral complexes[{M(-Pz)(X)(CNBut)2}2](M = Rh, X = Cl (7); M = Rh,Ir, X = I). These reactions indicate that the metal-metal bondformation has an electron-transfer character. Evidence of the nucleophilic attack by themetal-metal bond in complexes3 and 4 of small molecules such as diiodine isprovided by the reaction of [I(Py)2]BF4with7, which adds the electrophilic iodine(I) to give thebridging iodide complex [{Rh(-Pz)(Cl)(CNBut)2}2(-I)]+.In addition, an electrophile such asMeCF3SO3 abstracts one of theiodideligands trans to the metal-metal bond in 3 togive MeI and the cationic complex [Rh2(-Pz)2(I)(CNBut)4]CF3SO3.This cation adds complex 3, which behaves as ametalloligandthrough an iodide atom, to give the tetranuclear complex[{Rh2(-Pz)2(I)(CNBut)4}2(-I)]CF3SO3 (8). The X-ray structure of 8contains two metal-metal-bonded binuclear'Rh2(-Pz)2(I)(CNBut)4' units linked through aslightly asymmetric bridging iodine atom, showing anunusual Rh-I-Rh bond angle of 129.99(4)
. Reaction of3 with IC
C-Ph gives the acetylidecomplex[(CNBut)2(I)Rh(-Pz)2(-I)Rh(
1-CC-Ph)(CNBut)2]I.EHMO calculations on complexes[Rh2(-Pz)2(CNBut)4]2+,[Rh2(-Pz)2(I)(CNBut)4]+[A]+, and[{Rh(-Pz)(I)(CNBut)2}2]successfully explain the reactivity at the metal-metal bond, that ofthe iodide ligand in 3with electrophiles, and those of [A]+with nucleophiles. Complex 3 and the cation[Rh2(-Pz)2(I)(CNBut)4]+react with MeI in the presence of direct sunlight to give theoxidative-addition product[(CNBut)2(I)Rh(-Pz)2(-I)Rh(Me)(CNBut)2]+in high yield.
-Pz)(CNBut)2}2](M = Rh (1), Ir (2); Pz =pyrazolate) with diiodine give the metal-metal-bonded complexes[{M(-Pz)(I)(CNBut)2}2](M = Rh (3), Ir (4)). A further reactionwith diiodine afford the complexes[{M(-Pz)(I)(CNBut)2}2(-I)]I, which reactcleanly with CF3SO3Me replacing theionic iodide by the triflategroup. The M(I) complexes 1 and 2 are easilyoxidized by mild oxidants such as[Cp2Fe]+ togive the metal-metal-bonded dications[{M(-Pz)(CNBut)2(MeCN)}2]2+,which add halideions yielding the neutral complexes[{M(-Pz)(X)(CNBut)2}2](M = Rh, X = Cl (7); M = Rh,Ir, X = I). These reactions indicate that the metal-metal bondformation has an electron-transfer character. Evidence of the nucleophilic attack by themetal-metal bond in complexes3 and 4 of small molecules such as diiodine isprovided by the reaction of [I(Py)2]BF4with7, which adds the electrophilic iodine(I) to give thebridging iodide complex [{Rh(-Pz)(Cl)(CNBut)2}2(-I)]+.In addition, an electrophile such asMeCF3SO3 abstracts one of theiodideligands trans to the metal-metal bond in 3 togive MeI and the cationic complex [Rh2(-Pz)2(I)(CNBut)4]CF3SO3.This cation adds complex 3, which behaves as ametalloligandthrough an iodide atom, to give the tetranuclear complex[{Rh2(-Pz)2(I)(CNBut)4}2(-I)]CF3SO3 (8). The X-ray structure of 8contains two metal-metal-bonded binuclear'Rh2(-Pz)2(I)(CNBut)4' units linked through aslightly asymmetric bridging iodine atom, showing anunusual Rh-I-Rh bond angle of 129.99(4). Reaction of3 with ICC-Ph gives the acetylidecomplex[(CNBut)2(I)Rh(-Pz)2(-I)Rh(1-CC-Ph)(CNBut)2]I.EHMO calculations on complexes[Rh2(-Pz)2(CNBut)4]2+,[Rh2(-Pz)2(I)(CNBut)4]+[A]+, and[{Rh(-Pz)(I)(CNBut)2}2]successfully explain the reactivity at the metal-metal bond, that ofthe iodide ligand in 3with electrophiles, and those of [A]+with nucleophiles. Complex 3 and the cation[Rh2(-Pz)2(I)(CNBut)4]+react with MeI in the presence of direct sunlight to give theoxidative-addition product[(CNBut)2(I)Rh(-Pz)2(-I)Rh(Me)(CNBut)2]+in high yield.