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Synthesis, characterizations and reactions of low valent complexes of molybdenum containing (bis(2-diphenylphosphinoethyl)phenyl-phosphine), and, A nitrogen fixation approach
Abstract
High energy electron rich molybdenum phosphine complexes were synthesised by the reduction of (Mo(TRI)Cl$\sb3$) in THF with sodium amalgam in the presence of various ligands: arenes, cyclopentadiene, indene, dinitrogen, phosphines and phosphites; (TRI is (Bis(2-diphenylphosphinoethyl)phenylphosphine). The products are: i, (Mo($\eta\sp6$-arene)(TRI)), (arene = C$\rm\sb6H\sb6$, C$\rm\sb6H\sb5OCH\sb3$, C$\rm\sb6H\sb5CH\sb3$, C$\rm\sb{10}H\sb8$ or PPh$\sb3$); ii, (Mo($\eta\sp5$-C$\rm\sb5H\sb5$)(TRI)H); iii, (Mo($\eta\sp5$-C$\rm\sb9H\sb7$)(TRI)H); iv, fac- (Mo(N$\sb2$)(TRI)(PMe$\sb3)\sb2$); v, (Mo(N$\sb2)(\eta\sp3$-TRI)($\eta\sp2$-TRI)); vi, mer- (Mo(TRI)(P(OR)$\sb3)\sb3$), (R = Me or Et). When THF solvent was used and in the abscence of added ligands, the products are (Mo(TRI)(THF)$\sb3$) under argon and $\{$Mo(N$\sb2$)(TRI)(THF)$\}$x under dinitrogen. Heating fac- (Mo(N$\sb2$)(TRI)(PPhMe$\sb2)\sb2$) in THF with ethylene produced trans- (Mo(CH$\rm\sb2CH\sb2)\sb2$(TRI)(PPhMe$\sb2$). Heating trans- (Mo(N$\rm\sb2)\sb2(TRI)(PPh\sb3$)) in THF formed (Mo($\eta\sp6$-PhPPh$\sb2$)(TRI)) by rearrangement of $\sigma$- to $\eta\sp6$-bonded PPh$\sb3$. Reaction of (Mo($\eta\sp6$-arene)(TRI)) with strong acid formed (Mo($\eta\sp6$-C$\rm\sb6H\sb6$)(TRI)H) $\sp+$ and (Mo($\eta\sp6$-arene)(TRI)(H$\sb2\rbrack\sp{2+}$. The hydride complex (Mo($\eta\sp5$-C$\rm\sb5H\sb5$)(TRI)H) was also prepared by heating fac- (Mo(N$\sb2$)(TRI)(PMe$\sb3)\sb2$) with cyclopentadiene in heptane. The hydride complex reacted with CDCl$\sb3$ forming (Mo($\eta\sp5$-C$\rm\sb5H\sb5$)-(TRI)Cl) and (Mo($\eta\sp5$-C$\rm\sb5H\sb5$)(TRI)(CCl$\sb3$)) (Mass spectra: m + 1/z = 732 and 818 respectively). Mer- (Mo(TRI)(P(OR)$\sb3)\sb3$) isomerizes to fac- (Mo(TRI)(P(OR)$\sb3)\sb3$) both thermally and photochemically. Both Mer- (Mo(TRI)(P(OR)$\sb3)\sb3$) and (Mo($\eta\sp6$-arene)(TRI)) exhibit two oxidation waves in the cyclic voltammograms in THF. The first oxidation is reversible but the second oxidation is pseudoreversible. The reaction of HBr with trans- (Mo(N$\sb2)\sb2$(dppe)(PPh$\rm\sb2Me)\sb2$) in THF formed (Mo(NNH$\sb2$)(THF)(dppe)(PPh$\sb2$Me)Br) Br, (Mo(NNH$\sb2$)(dppe)-(PPh$\rm\sb2Me)\sb2$Br) Br and (Mo(NNH$\sb2$)(dppe)(PPh$\rm\sb2Me)Br\sb2$). The reaction of (Mo(NNH$\sb2$)(dppe)(PPh$\rm\sb2Me)(Br\sb2$) with pyridine formed the diamagnetic (Mo(NNH$\sb2$(dppe)(PPh$\rm\sb2Me(C\sb5H\sb5$N)Br) Br. In contrast, the reactions of (Mo(NNH$\sb2$)(dppe)(PPh$\rm\sb2Me)Br\sb2$) or (Mo(NNH$\sb2$)(dppe)-(PPh$\rm\sb2Me)\sb2$Br) Br with pyrazine formed the purple paramagnetic (Mo(NNH$\sb2$)(dppe)(PPh$\rm\sb2Me)(C\sb4H\sb4N\sb2$)Br) Br, (UV, $\lambda$ = 572 nm). A mechanism for ammonia and hydrazine production was proposed. It involves a series of electronation and protonation steps. Finally, the reactions of fac- (Mo(N$\sb2$)(TRI)(PMe$\sb3)\sb2$) and fac- (Mo(N$\sb2$)(TRI)(dppm)) produced the corresponding carbon dioxide complexes, IR (KBr), v(CO$\sb2$) = 1758.80 and 1779.98 cm$\sp{-1}$ respectively.
Subject Area
Chemistry
Recommended Citation
Hammud, Hassan Hasan, "Synthesis, characterizations and reactions of low valent complexes of molybdenum containing (bis(2-diphenylphosphinoethyl)phenyl-phosphine), and, A nitrogen fixation approach" (1994). ETD collection for University of Nebraska-Lincoln. AAI9507810.
https://digitalcommons.unl.edu/dissertations/AAI9507810