Please use this identifier to cite or link to this item:
Type: Artigo de periódico
Title: Synthesis And X-ray Analysis Of The Tetranuclear Iridium Compounds Hir4(co)9(μ4-η3-ph 2pccph)(μ-pph2) And Ir4(co)7(μ-co)(μ3-η 2-hccph)(μ-pph2)2 And Multinuclear Nmr Studies Of The Latter Compound
Author: Benvenutti M.H.A.
Vargas M.D.
Braga D.
Grepioni F.
Mann B.E.
Naylor S.
Abstract: Reaction of HIr4(CO)10(μ-PPh2) (1) with Ph2PC≡CPh yields the CO-substituted compounds HIr4(CO)10-n(Ph2PC≡CPh) n(μ-PPh2), n = 1 (2) and 2 (3). The monosubstituted species (2) undergoes facile P-C bond cleavage, followed by acetylide insertion into the Ir-H bond to give Ir4(CO)7(μ3-η2-HC 2Ph)(μ-CO)(μ-PPh2)2 (4) in high yields, and under more forcing conditions, HIr4(CO)9(μ4-η3-Ph 2PCCPh)(μ-PPh2) (6) is also obtained. Compound 4 is also formed upon thermolysis of Ir4(CO)10(PPh2H)(Ph2PC≡CPh) (7), which is obtained from carbonyl substitution in Ir4(CO)11(PPh2H) (8) with Ph2PC≡CPh. Crystal data for 4: space group P21/n, a = 8.94(2) Å, b = 39.05(2) Å, c = 11.954(6) Å, β = 104.57(8)°, V = 4037.1 Å3, Z = 4, and final R (Rw) value 0.069 (0.073), for 2108 unique reflections [Fc > 4(Fo)]. Compound 4 exhibits a tetrahedral metal framework, with two elongated edges bridged by the μ-PPh2 ligands and a phenylacetylene bound to the cluster in the μ3-η2-∥ fashion. 1H, 13C{1H}, and 31P{1H} NMR spectroscopy studies have established that compound 4 is present in solution in the form of two isomers in a 1:2 ratio, which differ with respect to the orientation of the acetylene ligand and undergo two distinct dynamic processes: at low temperature, ca. 60° rocking of the acetylene with ΔG‡192 = 9.0 kcal mol-1, and estimated ΔG‡169 = 5.4 kcal mol-1, and interconversion of the two isomers at 82°C, with ΔG‡ = 21.8 kcal mol-1 via rotation of the acetylene by 120° steps. Crystal data for 6: space group P21/n, a = 11.840(3) Å, b = 18.745(9) Å, c = 18.695(8) Å, β = 100.63(3)°, V = 4077.9 Å3, Z = 4; final R(Rw) value 0.058 (0.060) for 2609 independent reflections observed [Fc > 4(Fo)]. Compound 6 exhibits a flat butterfly arrangement of metal atoms, with an elongated edge bridged by a PPh2 ligand and all metal atoms interacting with Ph2PCCPh, which acts as a 6-electron ligand. © 1993 American Chemical Society.
Rights: fechado
Identifier DOI: 
Date Issue: 1993
Appears in Collections:Unicamp - Artigos e Outros Documentos

Files in This Item:
File SizeFormat 
2-s2.0-0001045345.pdf1.43 MBAdobe PDFView/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.