Mobile metal-metal bonds in platinum metal sulfide clusters

Venturelli, Anne

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Description

Title

Mobile metal-metal bonds in platinum metal sulfide clusters

Author(s)

Venturelli, Anne

Issue Date

1996

Doctoral Committee Chair(s)

Rauchfuss, Thomas B.

Department of Study

Chemistry, Inorganic

Discipline

Chemistry, Inorganic

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Chemistry, Inorganic

Language

eng

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 $\rm HO\sb3SCF\sb3$.

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Copyright and License Information

Copyright 1996 Venturelli, Anne

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