449141-40-6Relevant academic research and scientific papers
Site-differentiated hexanuclear rhenium(III) cyanide clusters [Re6Se8(PEt3)n (CN)6-n]n-4 (n = 4, 5) and kinetics of solvate ligand exchange on the cubic [Re6Se8]2+ core
Gray, Thomas G.,Holm
, p. 4211 - 4216 (2002)
The site-differentiated, cyanide-substituted hexanuclear rhenium(III) selenide clusters cis- and trans-[Re6Se8(PEt3)4- (CN)2] and [Re6Se8(PEt3)5(CN)]+ have been prepared from heterogeneous reactions of the corresponding iodo clusters with AgCN in refluxing chloroform. Isolated yields are 68%, 46%, and 64% for cis-[Re6Se8(PEt3)4 (CN)2], trans-[Re6Se8(PEt3)4 (CN)2], and [Re6Se8(PEt3)5(CN)]+, respectively. The new compounds are air- and water-stable and are characterized by X-ray diffraction crystallography, 31P NMR and IR spectroscopies, and FAB mass spectrometry. In related work, the solvent exchange rates of two site-differentiated monosolvate clusters, [Re6Se8-(PEt3)5(MeCN)] (SbF6)2 and [Re6Se8(PEt3)5 (Me2SO)](SbF6)2, in neat solvents were measured by 1H NMR. These clusters are substitutionally inert; k ≈ 10-5-10-6 s-1 at 318 K. Activation parameters indicate a dissociative ligand exchange mechanism; ΔH? values obtained from least-squares fitting of temperature-dependent kinetics data exceed RT by a factor of ca. 50 over the temperature range studied. These results demonstrate that the substitutional lability encountered in a previous study of cluster photophysics (Gray, T. G.; Rudzinski, C. M.; Nocera, D. G.; Holm, R. H. Inorg. Chem. 1999, 38, 5932) cannot result from ground-state thermal reactions.
