Ring functionalized cyclopentadienyl derivatives of niobium and tantalum tetracarbonyl compounds, (eta(5)-C(5)H(4)R)M(CO)(4)

• Main Author: Gallagher, Skip
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1997
• Subjects: Chemistry; Inorganic chemistry
• ISBN: 0591646323; 9780591646320

The development of a number of synthetic routes has allowed the production of a wide variety of ring functionalized cyclopentadienyl derivatives of niobium and tantalum, $(\eta\sp5$-$\rm C\sb5H\sb4R)M(CO)\sb4$ where M = Nb and Ta. In the first route Na(M(CO)$\sb6\rbrack$ is reacted with a metal chloride (eg., Cu(I)Cl) to produce the bridging chloride, Na(M$\sb2(\mu$-Cl)$\rm\sb3(CO)\sb8\rbrack.$ The bridging species was reacted in situ with a variety of lithium, sodium and TMS cyclopentadienyl ligands to produce the desired metal carbonyl complex. In a second route iodine was used as both the oxidizing agent and the halogen donor to produce the bridging halide, Na (M$\sb2(\mu$-I)$\rm\sb3(CO)\sb8\rbrack$ which was reacted with a substituted cyclopentadienyl salt to produce ($\eta\sp5$-$\rm C\sb5H\sb4R)M(CO)\sb4.$ The difficulties associated with the synthesis of the metal hexacarbonyls promoted the development of a more direct route to larger quantities of the desired $(\eta\sp5$-$\rm C\sb5H\sb4R)M(CO)\sb4.$ Addition of a substituted cyclopentadienyl ring to MCl$\sb5$ was used to produce the tetrachloride, $(\eta\sp5$-$\rm C\sb5H\sb4R)MCl\sb4.$ Carbonylation under appropriate reducing conditions yielded the fully carbonylated complex. Attempts to produce the ring functionalized compounds under a variety of conditions using Friedel Crafts acylation or ring lithiation proved unsuccessful. The preparations reported here may be the only viable routes to this series of compounds. Molecular structures of $\rm(C\sb5H\sb4CH{=}CH\sb2)Nb(CO)\sb4,\ (C\sb5H\sb4CO\sb2Me)Nb(CO)\sb4,\ (C\sb5H\sb4C({=}O)CH\sb2C\sb6H\sb5)Nb(CO),\sb4,\ (C\sb5H\sb4C({=}O)CH\sb3)Nb(CO)\sb4,$ $\rm (C\sb5H\sb4CH\sb2C\sb5H\sb4)Nb\sb2(CO)\sb8,\ (C\sb5H\sb5)Nb(CO)\sb3PPh\sb3,\ (C\sb5H\sb5)Ta(CO)\sb4,\ (C\sb5H\sb4CO\sb2Me)Ta(CO)\sb4,\ (C\sb5H\sb4C({=}O)C\sb6H\sb5)Ta(CO)\sb4$ and $\rm (C\sb9H\sb7)Ta(CO)\sb4$ compounds have been determined. These are the first well-ordered structures reported for this family of half sandwich compounds.