Reactivity of rigid bidentate phosphine ligands towards several multiply bonded complexes of dirhenium and dimolybdenum

Mohammed Abdel Qader Bakir, Purdue University

Abstract

The reactions of the rigid bidentate phosphine ligands Ph$\sb2$PC$\equiv$CPPh$\sb2$, o-C$\sb6$H$\sb4$(PPh$\sb2)\sb2$, cis- and trans-Ph$\sb2$PCH=CHPPh$\sb2$ with several multiply bonded complexes of dirhenium(II), dirhenium(III) and dimolybdenum(II) have been investigated. Reactions of (n-Bu$\sb4$N)$\sb2$Re$\sb2$Cl$\sb8$ with the bridging bidentate phosphine ligands L-L = Ph$\sb2$PC$\equiv$CPPh$\sb2$ or trans-Ph$\sb2$PCH=CHPPh$\sb2$ in methanol/conc. HCl give the salts (n-Bu$\sb4$N)$\sb2$((Re$\sb2$Cl$\sb7)\sb2\{\mu$-(L-L)$\}$), the first examples of quadruply bonded dirhenium(III) species of the type (Re$\sb2$Cl$\sb7$L) $\sp-$. The ligand cis-Ph$\sb2$PCH=CHPPh$\sb2$ reacts with multiply bonded complexes of dirhenium and dimolybdenum to form M$\sb2$X$\sb4$(dppee)$\sb2$, trans-MX$\sb2$(dppee)$\sb2$ (M = Mo or Re; X = Cl or Br), Mo$\sb2$I$\sb4$(dppee)$\sb2$ and (ReX$\sb2$(dppee)$\sb2$) X. The complexes M$\sb2$X$\sb4$(dppee)$\sb2$ have been isolated as their $\alpha$-(chelating phosphine ligands, eclipsed rotational geometry) and $\beta$-(bridging phosphine ligands, staggered rotational geometry) isomers. In the case of Re$\sb2$X$\sb4$(dppee)$\sb2$, these are the first examples of triply bonded dirhenium(II) species that have been isolated in both their $\alpha$- and $d\beta$-forms. The complexes $\beta$-M$\sb2$X$\sb4$(dppee)$\sb2$ (M = Re or Mo) constitute the first examples of this structural type which contain both C=C and Mo$\equiv$Mo or Re$\equiv$Re units within the same fused decaline-like ring system. The complexes $\alpha$-M$\sb2$X$\sb4$(dppbe)$\sb2$, trans- MX$\sb2$(dppbe)$\sb2$, (ReX$\sb2$(dppbe)$\sb2$) X$\cdot$nH$\sb2$O and (MoOX(dppbe)$\sb2$) X$\cdot$nH$\sb2$O have been isolated from the reactions of o-C$\sb6$H$\sb4$(PPh$\sb2)\sb2$ with multiply bonded complexes of dirhenium and dimolybdenum. There is no evidence for the formation of $\beta$-M$\sb2$X$\sb4$(dppbe)$\sb2$. The preparation of (MoOX(dppbe)$\sb2$) X$\cdot$nH$\sb2$O is the first time that oxo-molybdenum(IV) species have been isolated from the reactions of bidentate phosphine ligands with octahalodimolydate(II) anions. The ligand substitution reactions of the bidentate phosphine ligands L-L = cis-Ph$\sb2$PCH=CHPPh$\sb2$ and o-C$\sb6$H$\sb4$(PPh$\sb2)\sb2$ with Mo$\sb2$(O$\sb2$CCH$\sb3)\sb2$X$\sb2$(PPh$\sb3)\sb2$ in THF afford the complexes Mo$\sb2$(O$\sb2$CCH$\sb3)\sb2$X$\sb2$(L-L). These are the first examples of dimolybdenum(II) species that contain two bridging acetato groups and one bridging bidentate phosphine ligand. Oxidation of $\alpha$-Re$\sb2$Cl$\sb4$(L-L)$\sb2$ (L-L = dppee or dppp) with (Cp$\sb2$Fe)PF$\sb6$ in noncoordinating solvents afford the salts $\alpha$-(Re$\sb2$Cl$\sb4$(L-L)$\sb2$) PF$\sb6$.

Degree

Ph.D.

Advisors

Walton, Purdue University.

Subject Area

Chemistry

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