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Type: Artigo de periódico
Title: Synthesis And Characterisation Of Derivatives Of [hir4(co)10(μ-pph2)] With Mono And Diphosphines; X-ray Molecular Structures Of [hir4(co)8→ph2p(ch2)npph2← (μ-pph2)] (n = 1 And 4)
Author: Ziglio C.M.
Vargas M.D.
Braga D.
Grepioni F.
Nixon J.F.
Abstract: The reactions of tdhe cluster compound [HIr4(CO)10(μ-PPh2)] (1) with a series of phosphines, PMe3 and PPh3, and diphosphines, Ph2P(CH2)nPPh2 (n = 1, dppm, n = 2, dppe and n = 4, dppb) and cis-PPh2CH=CHPPh2 (dppen), have been investigated. Reaction of 1 with PMe3 yielded the mono and di-substituted derivatives [HIr4(CO)10-n (PMe3)n(μ-PPh2)] (n = 1, 2 and n = 2, 3). 1H and 31P-NMR spectroscopy monitoring revealed that the two kinetic isomers 2b and 2c undergo conversion to the thermodynamic isomer 2a through a process, which apparently involves intra-molecular migration of the PMe3 ligand. In contrast, analogous kinetic isomers were not detected during the synthesis of the PPh3 derivative [HIr4(CO)9(PPh3)μ-PPh2)] (4). According to 1H and 31P-NMR data, compounds [HIr4(CO)8(L)2(μ-PPh2)] (L = PMe3 3 and PPh3 5) exist in solution in three isomeric forms 3a-3c and 5a-5c, respectively, at -60 °C. Compound 1 also reacts with diphosphines to give CO substitution products, whose composition depends on the size of the methylene chain. Whilst reaction with dppm and dppen yields only the bi-substituted species [HIr4(CO)8(dppm)(μ-PPh2)] (6) and [HIr4(CO)8(dppen)(μ-PPh2)] (7), respectively, with dppb, both the dimeric compound [{HIr4(CO)9(μ-PPh2)}2(dppb)] (8a) and the monomeric species [HIr4(CO)8(dppb)(μ-PPh2)] (8b) are formed, and with dppe, only the dimeric compound [{HIr4(CO)9(μ-PPh2)}2(dppe)] (9) is obtained. The dppm derivative exists in solution in the form of two inter-converting isomers 6a and 6b that differ with respect to the mode of coordination of the dppm and CO ligands. Isomerisation of 6a-6b is proposed to involve intra-molecular migration of dppm and carbonyl ligands. Structures were proposed for all compounds, on the basis of 1H and 31P[1H]-NMR studies and of correlations previously established for the phosphine and diphosphine derivatives of [Ir4(CO)12]; the molecular structures of compounds 5c, 6a and 8b were established by X-ray diffraction studies which confirmed the structures proposed based on spectroscopic data. © 2002 Elsevier Science B.V. All rights reserved.
Rights: fechado
Identifier DOI: 10.1016/S0022-328X(02)01583-8
Date Issue: 2002
Appears in Collections:Unicamp - Artigos e Outros Documentos

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