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Type: Artigo de periódico
Title: Synthesis and characterisation of derivatives of [HIr4(CO)(10)(mu-PPh2)] with mono and diphosphines; X-ray molecular structures of [HIr4(CO)(8)(PPh3)(2)(mu-PPh2)] and [HIr4(CO)(8){Ph2P(CH2)(n)PPh2}(mu-PPh2)] (n=1 and 4)
Author: Ziglio, CM
Vargas, MD
Braga, D
Grepioni, F
Nixon, JF
Abstract: The reactions of the cluster compound [HIr4(CO)(10)(mu-PPh2)] (1) with a series of phosphines, PMe3 and PPh3, and diphosphines, Ph2P(CH2)(n)PPh2 (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) (mu-PPh2)] (n = 1, 2 and n = 2, 3). H-1 and P-31-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)(mu-PPh2)] (4). According to H-1 and P-31-NMR data, compounds [HIr4(CO)(8)(L)(2)(mu-PPh2)] (L = PMe3 3 and PPh3 5) exist in solution in three isomeric forms 3a-3c and 5a-5c, respectively, at -60 degreesC. 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)(mu-PPh2)] (6) and [HIr4(CO)(8)(dppen)(mu-PPh2)] (7), respectively, with dppb, both the dimeric compound [{HIr4(CO)(9)(mu-PPh2)}(2)(dppb)] (8a) and the monomeric species [HIr4(CO)(8)(dppb)(mu-PPh2)] (8b) are formed, and with dppe, only the dimeric compound [{HIr4(CO)(9)(mu-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 H-1 and P-31[H-1]-NMR studies and of correlations previously established for the phosphine and diphosphine derivatives of [Ir-4(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. (C) 2002 Elsevier Science B.V. All rights reserved.
Subject: cluster
Country: Suíça
Editor: Elsevier Science Sa
Citation: Journal Of Organometallic Chemistry. Elsevier Science Sa, v. 656, n. 41671, n. 188, n. 198, 2002.
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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