ISSN:
1434-1948
Schlagwort(e):
Indenyl complexes
;
Cyclopentadienyl complexes
;
Molybdenocene
;
Ring slippage
;
Molybdenum
;
DFT calculations
;
Chemistry
;
General Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Reduction of [IndCpMo(L)Br]Br (L = 1a, CO; 2, NCMe) with Cp2Co in the presence of two equivalents of the ligand L′ gives the ring-slipped neutral complexes [(η3-Ind)CpMoL′2] (L′ = 5, CO; 6, 1/2 dppe; 7, PMe3; 8, P(OMe)3; 9, CNtBu) in good yield. Products 7, 8, and 9, but not [IndCpMoL′], are also formed in the presence of only 1 equivalent of L′ in modest yields. In the case of the reduction of [IndCpMo(L)Br]Br [L = 2, NCMe; 3a, CNtBu; 4, P(OMe)3] mixtures of the complexes, [(η3-Ind)CpMoL2] (8, 9) and [(η5-Ind)CpMoL] [L = 11, P(OMe)3; 12, CNtBu] were obtained. The only product of formal type [(η5-Ind)CpMoL] that could be prepared by these methods was the alkyne complex [(η5-Ind)CpMo(η2-PhC≡CPh)] (10). These results contrast with the well-known reductions of similar bis-cyclopentadienyl cations [Cp2Mo(L)Br]+, which produce [Cp2MoL] complexes under the same conditions. The reduction of the dications [Cp2MoL2][BF4]2 [L = CO; P(OMe)3] with Cp2Co is now reported to afford the neutral complexes [CpMo(η3-C5H5)(CO)2] (13) and [Cp2Mo(P(OMe)3)] (14), respectively, showing that the stability of the ring-slipped complexes is dependent on the other ligands. From DFT and EHMO calculations used to probe the bonding and the energetics of these ring slippage processes it is concluded that weak π acceptor ligands favour η5-Ind → η3-Ind slippage and disfavour η5-Cp → η3-Cp slippage at the CpMoL2 fragment. Redox-induced ring slippages involve very similar energies for both indenyl and cyclopentadienyl complexes and should be able to produce more examples of the otherwise rare η3-Cp coordination mode.
Zusätzliches Material:
1 Ill.
Materialart:
Digitale Medien
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