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Compared Reductive Chemistry of Molybdenocene and Indenyl‐Substituted Complexes
Author(s) -
Calhorda Maria J.,
Gamelas Carla A.,
Romão Carlos C.,
Veiros Luís F.
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(200002)2000:2<331::aid-ejic331>3.0.co;2-y
Subject(s) - chemistry , alkyne , ring (chemistry) , cyclopentadienyl complex , medicinal chemistry , ligand (biochemistry) , stereochemistry , yield (engineering) , organic chemistry , catalysis , biochemistry , materials science , receptor , metallurgy
Reduction of [IndCpMo(L)Br]Br (L = 1a , CO; 2 , NCMe) with Cp 2 Co in the presence of two equivalents of the ligand L′ gives the ring‐slipped neutral complexes [(η 3 ‐Ind)CpMoL′ 2 ] (L′ = 5 , CO; 6 , 1/2 dppe; 7 , PMe 3 ; 8 , P(OMe) 3 ; 9 , CN t Bu) 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 , CN t Bu; 4 , P(OMe) 3 ] mixtures of the complexes, [(η 3 ‐Ind)CpMoL 2 ] ( 8 , 9 ) and [(η 5 ‐Ind)CpMoL] [L = 11 , P(OMe) 3 ; 12 , CN t Bu] were obtained. The only product of formal type [(η 5 ‐Ind)CpMoL] that could be prepared by these methods was the alkyne complex [(η 5 ‐Ind)CpMo(η 2 ‐PhC≡CPh)] ( 10 ). These results contrast with the well‐known reductions of similar bis‐cyclopentadienyl cations [Cp 2 Mo(L)Br] + , which produce [Cp 2 MoL] complexes under the same conditions. The reduction of the dications [Cp 2 MoL 2 ][BF 4 ] 2 [L = CO; P(OMe) 3 ] with Cp 2 Co is now reported to afford the neutral complexes [CpMo(η 3 ‐C 5 H 5 )(CO) 2 ] ( 13 ) and [Cp 2 Mo(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 η 5 ‐Ind → η 3 ‐Ind slippage and disfavour η 5 ‐Cp → η 3 ‐Cp slippage at the CpMoL 2 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 η 3 ‐Cp coordination mode.