Thermochemical studies of group VI metals by solution calorimetry

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)



First Committee Member

Carl D. Hoff, Committee Chair


The results of solution calorimetric studies have been used to measure the relative stabilities in solution of four related systems. Enthalpies of substitution for L$\sb1$Mo(CO)$\sb5$, cis L$\sb2$Mo(CO)$\sb4$ and (L-L)Mo(CO)$\sb4$, L$\sb3$M(CO)$\sb3$ where M = Cr, Mo and W as well as for L$\sb4$Mo(CO)$\sb2$ and (L-L)$\sb2$Mo(CO)$\sb2$ systems have been investigated for a wide range of mono and bi dentate ligands L: olefins, arenes, nitriles, isonitriles, phosphines, phosphites and carbon monoxide. Bond strength estimates have been reported for one of the systems. Comparison of a basic phosphine like PMe$\sb3$ to a phosphite has been made for these systems. It is interesting to note that depending upon the electronic requirements of the metal center, the relative order of affinity for the basic phosphine is reversed as one goes from the L$\sb1$Mo(CO)$\sb5$ system to the L$\sb4$Mo(CO)$\sb2$ system. The heats of reaction of H-Mo(CO)$\sb3$C$\sb5$H$\sb5$ with RSSR for R = p-Tolyl, Phenyl and Methyl producing RSH and RSMo(CO)$\sb3$C$\sb5$H$\sb5$ are reported. The reaction of the triple bonded dimer (Mo(CO)$\sb2$C$\sb5$H$\sb5$) $\sb2$ with RSSR to produce the (Mo(CO)$\sb2$SRCp) $\sb2$ dimer is reported. New synthetic routes to produce RSMo(CO)$\sb3$C$\sb5$H$\sb5$, (Mo(CO)$\sb2$CpSR)$\sb2$ and the double bonded dimer (Mo(CO)CpSR) 2 in gram quantities have been discovered. Reaction of these sulfur complexes with phosphines to produce RSMo(CO)$\sb2$C$\sb5$H$\sb5$PR$\sb3$ are reported, so that the relative stabilities between these sulfur complexes can be determined. Finally, the disproportionation reaction of the (Mo(CO)$\sb2$CpSR)$\sb2$ dimer to produce RSMo(CO)$\sb3$C$\sb5$H$\sb5$ and the double bonded dimer (Mo(CO)SR)$\sb2$ at 40$\sp\circ$C is reported. This analysis was done on the FT-IR. All these enthalpies have been used to construct a thermochemical cycle in order to predict important organometallic reactions.


Chemistry, Inorganic

Link to Full Text