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Type: Artigo de periódico
Title: Synthesis And Structural Characterisation Of [ir4(co)8(ch3)(μ4-η 3-ph2pccph)(μ-pph2)] And Of The Carbonylation Product [ir4(co)8{c(o)ch3}(μ4-η 3-ph2pccph)(μ-pph2)]
Author: Braga D.
Fujiwara F.Y.
Grepioni F.
Pereira R.M.S.
Vargas M.D.
Abstract: Deprotonation of [(μ-H)Ir4(CO)10(μ-PPh2)], 1, gives [Ir4(CO)10(μ-PPh2)]- that reacts with Ph2PCCPh and CH3I to afford [Ir4(CO)8(CH3)(μ4-η 3-Ph2PCCPh)(μ-PPh2)], 2 (34%), besides [Ir4(CO)9(μ3-η3-Ph 2PC(H)CPh)(μ-PPh2)] and [(μ-H)Ir4(CO)9(Ph2PC≡CPh)(μ-PPh2)]. Compound 2 was characterised by a single crystal X-ray diffraction analysis and exhibits a flat butterfly of metal atoms, with the Ph2PCCPh ligand interacting with all four Ir atoms and the methyl group bonded terminally to a wingtip Ir atom. Carbonylation of 2 yields initially (25°C, 20 min) a CO addition product that, according to VT 31P{1H} and 13C{1H} studies, exists in solution in the form of two isomers 4A and 4B (8:1), and then (40°C, 7 h), the CO insertion product [Ir4(CO)8{C(O)CH3}-(μ4-η 3-Ph2PCCPh)(μ-PPh2)], 5. The molecular structure of 5, established by an X-ray analysis, is similar to that of 2, except for the acyl group that remains bound to the same Ir atom. The process is reversible at both stages. Treatment of 2 with PPh3 and P(OMe)3 affords the CO substitution products [Ir4(CO)7L(CH3)(μ4-η 3-Ph2PCCPh)(μ-PPh2)] (L = PPh3, 6 and P(OMe)3, 7), instead of the expected CO inserted products. According to the 1H and 31P{1H} NMR studies, the PPh3 derivative 6 exists in the form of two isomers (1:1) that differ with respect to the position of this ligand.
Rights: aberto
Identifier DOI: 
Date Issue: 1999
Appears in Collections:Unicamp - Artigos e Outros Documentos

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