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Title:Mobile metal-metal bonds in platinum metal sulfide clusters
Author(s):Venturelli, Anne
Doctoral Committee Chair(s):Rauchfuss, Thomas B.
Department / Program:Chemistry, Inorganic
Discipline:Chemistry, Inorganic
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
Abstract:The thesis presents experimental studies on platinum metal sulfido clusters.
The dicationic complex $\rm (C\sb5Me\sb5)\sb3Ir\sb3S\sb2\sp{2+}$ was obtained by treatment of $\rm \lbrack (\sb5Me\sb5)IrCl\sb2\rbrack \sb2$ with $\rm (Me\sb3Si)\sb2S$, followed by purification via aqueous ion exchange chromotography. The dication consists of a trigonal bypyramidal $\rm Ir\sb3S\sb2$ core with Ir-Ir bonds of 2.88 A. Cobaltocene reduction of the salt yielded the neutral clusters. This nido species likely consists of two metal-metal bonds amongst the three edges. Variable temperature $\sp1$H NMR measurements reveal dynamic behavior of the metal-metal bonds in solution. The $\sp1$H NMR spectrum consists of two signals in a 2:1 ratio at low temperatures, but only one symmetrical Ir environment at high temperatures. Analogous trinuclear nido clusters of (ring)$\rm \sb3M\sb3S\sb2$(ring = $\rm C\sb5Me\sb5$, M = Rh; ring = cymene, M = Os) were synthesized and exhibit similar dynamic behavior in solution.
A cuboidal cluster $\rm (C\sb5Me\sb5)\sb4Ir\sb4S\sb4\sp{2+}$ was also isolated from the reaction of $\rm \lbrack(C\sb5Me\sb5)IrCl\sb2\rbrack \sb2$ with $\rm (Me\sb3Si)\sb2S$. The tetrairidium dicationic cluster adopts a cubane structure consisting of interpenetrating Ir$\sb4$ and S$\sb4$ tetrahedra. The Ir$\sb4$ core is distorted from an idealized tetrahedrone by one Ir-Ir bond at 2.76 A. Variable temperature $\sp1$H NMR studies of $\rm (C\sb5Me\sb5)\sb4Ir\sb4S\sb4\sp{2+}$ indicate that the single metal-metal bond is fluxional in solution. From the dynamic NMR studies, we calculated a $\Delta$H$\sp\ddagger$ value for $\rm (C\sb5Me\sb5)\sb4Ir\sb4S\sb4\sp{2+}$ of 41 kJ/mol, and $\Delta$G$\sp\ddagger$ of 56 kJ/mol. These values can be compared to those found with $\rm(C\sb5Me\sb5)\sb4Rh\sb4S\sb4\sp{2+}$ in which $\Delta$H$\sp\ddagger$ is 43 kJ/mol, and $\Delta$G$\sp\ddagger$ is 37 kJ/mol. The $\Delta$H$\ddagger$ values for the barrier to single M-M bond migration in the Rh$\sb4$ and Ir$\sb4$ clusters are almost the same. DNMR experiments on $\rm (MeC\sb5H\sb4)\sb4Ru\sb4S\sb3(SMe)\sp+$ also demonstrate the mobility of the metal-metal bonds. The two bonds most likely move in a pairwise fashion. The $\Delta$H$\sp\ddagger$ value for $\rm (MeC\sb5H\sb4)\sb4Ru\sb4S\sb3(SMe)\sp+$ of 88 kJ/mol suggests that it is more difficult to move a pair of bonds as opposed to a single bond.
Hydrolysis of $\rm (C\sb5Me\sb5)Ir(C\sb4Me\sb4S)\sp{2+}$ with aqueous KOH gives the neutral acylthiolato complex concomitant with cleavage of a C-S bond. Thermolysis of solutions of the iridium acylthiolate led to cleavage of the second C-S bond with the formation of tetramethylfuran and $\rm (C\sb5Me\sb5)\sb4Ir\sb4S\sb4$.
Mixed metal $\rm M\sb3S\sb4$ clusters were obtained by the reaction of $\rm (C\sb5R\sb5)M(CH\sb3CN)\sb3\sp{2+}$ (M = Rh, Ir) with $\rm (C\sb5Me\sb5)\sb2Ru\sb2S\sb4$. The solid state structure of $\rm \lbrack (\sb5Me\sb5)\sb3RhRu\sb2S\sb4(CH\sb3CN)\rbrack \sp{2+}$ consists of an unsymmetrical $\rm RhRu\sb2S\sb4$ core containing an isosceles triangle of metal atoms with one Ru-Ru bond of 2.88 A. Variable temperature $\sp1$H NMR spectra reveal that the cluster is fluxional. $\rm \lbrack (C\sb5Me\sb5)\sb3RhRu\sb2S\sb4(CH\sb3CN)\rbrack \sp{2+}$ reacts with acetone to form the $\rm \lbrack (C\sb5Me\sb5)\sb3RhRu\sb2S\sb3(SCH\sb2COCH\sb3)\sp+$ species concomitant with cleavage of the C-H bond. This reaction is reversed by the addition of $\rm HO\sb3SCF\sb3$.
Issue Date:1996
Rights Information:Copyright 1996 Venturelli, Anne
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9702702
OCLC Identifier:(UMI)AAI9702702

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