Reactions of phosphine and pyridine ligands with trinuclear rhenium(III) chloride and with acetato complexes of dinuclear rhenium(III) chloride

Sylvia Martha Veronica Esjornson, Purdue University

Abstract

The intermediacy of Re$\sb2$(O$\sb2$CCH$\sb3)\sb2$Cl$\sb4$ in the conversion of Re$\sb2$(O$\sb2$CCH$\sb3)\sb4$Cl$\sb2$ to Re$\sb3$Cl$\sb9$ was established, and the structure of Re$\sb2$(O$\sb2$CCH$\sb3)\sb2$Cl$\sb4$ was determined by X-ray crystallography. The Re-Re bond length was determined to be 2.2084(3) A. Mass spectral data for the complex Re$\sb2$(O$\sb2$CCH$\sb3)\sb2$Cl$\sb4$ are presented. The reaction of the trinuclear cluster Re$\sb3$Cl$\sb9$ with various phosphine ligands in ethanol have been used to prepare the new complexes Re$\sb3$Cl$\sb9$(PMe$\sb2$Ph)$\sb3$, Re$\sb3$CL$\sb9(\eta\sp1$-dppm)$\sb3$, Re$\sb3$Cl$\sb9$(dmpm)$\sb{1.5}$, Re$\sb3$Cl$\sb9(\eta\sp1$-arphos)$\sb3$ and Re$\sb3$Cl$\sb9$(arphos)$\sb{1.5}$, where dppm = Ph$\sb2$PCH$\sb2$PPh$\sb2$, dmpm = Me$\sb2$PCH$\sb2$PMe$\sb2$ and arphos = Ph$\sb2$PCH$\sb2$AsPh$\sb2$. Electronic absorption and low frequency IR data are tabulated for the series of complexes, and the $\sp1$H and $\sp{31}$P$\{$H$\}$ NMR spectra of several of these complexes and of Re$\sb3$Cl$\sb9$(PMe$\sb3)\sb3$ and Re$\sb3$Cl$\sb9$(PMePh$\sb2)\sb3$ are described, including studies of the dissociative ligand exchange in Re$\sb3$Cl$\sb9(\eta\sp1$-dppm)$\sb3$. Mass spectral studies on Re$\sb3$Cl$\sb9$(PMe$\sb3)\sb3$ are discussed. The structures of Re$\sb3$Cl$\sb9$(PMe$\sb3)\sb3$ and Re$\sb3$Cl$\sb9(\eta\sp1$-dppm)$\sb3$ have been established by X-ray crystallography. For both structures, the Re-Re bond distances span the range 2.471(1) A to 2.488(1) A. The Re-P bond lengths are 2.634(4) A for the Me$\sb3$P complex, and between 2.693(3) A and 2.727(3) A for Re$\sb3$Cl$\sb9(\eta\sp1$-dppm)$\sb3$; the presence of three monodentate dppm ligands is confirmed in the latter structure. Electronic absorption and $\sp1$H NMR spectroscopic evidence for the intermediate species (Re$\sb3$Cl$\sb6$(PMe$\sb3)\sb3$) $\sb{\rm n}$ in the reduction reaction of Re$\sb3$Cl$\sb9$ with phosphines is presented. The complexes Re$\sb2$Cl$\sb4$(PMe$\sb3)\sb4$ and ReCl$\sb3$(PMe$\sb3)\sb3$ resulting from the breakup of the cluster have been characterized by electronic absorption and $\sp1$H NMR spectroscopy and by cyclic voltammetry. The reactions between Re$\sb2$(O$\sb2$CCH$\sb3)\sb2$X$\sb4$L$\sb2$ (X = Cl or Br; L = H$\sb2$O or 4-methylpyridine) and 2-hydroxypyridine (Hhp) or 2-methyl-6-hydroxypyridine (Hmhp) in THF or acetone afford the diamagnetic dirhenium(III) complexes Re$\sb2$(hp)$\sb2$Cl$\sb4\cdot$Hhp$\cdot$THF and Re$\sb2$(mhp)$\sb2$X$\sb4\cdot$Hhp$\cdot$S (X = Cl or Br; S = THF or (CH$\sb3)\sb2$CO) in yields of ca. 70%. The complex Re$\sb2$(mhp)$\sb2$Cl$\sb4\cdot$Hmhp$\cdot$(CH$\sb3)\sb2$CO has been characterized by X-ray crystallography. The two mhp ligands are in a trans disposition to one another and are oriented so as to give a Re$\sb2$L$\sb8$ species that contains (ReCl$\sb2$O$\sb2$) and (ReCl$\sb2$N$\sb2$) units. The Hmhp ligand is bound through its oxygen atom to the rhenium atom that contains the (ReCl$\sb2$O$\sb2$) ligand set. The Re-Re quadruple bond distance is 2.210(1) A. The structure of trans-Re$\sb2$(O$\sb2$CCH$\sb3)\sb2$Cl$\sb2$(dppm)$\sb2$ was established by X-ray crystallography. The molecule contains trans dispositions of bridging acetate and dppm ligands. The Cl-Re-Re-Cl unit approaches linearity, with Re-Re-Cl angles of 175-76(6)$\sp\circ$. The Re-Re triple bond distance is 2.2763(7) A.

Degree

Ph.D.

Advisors

Walton, Purdue University.

Subject Area

Chemistry

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