Multiply-bonded dirhenium complexes that contain cis andtrans sets of two bridging diphosphine or diarsine ligands

Daniel Robert Derringer, Purdue University

Abstract

The dirhenium(III) complexes Re$\sb2$($\mu$-O$\sb2$CR)$\sb4$X$\sb2$ (R = CH$\sb3$, C$\sb2$H$\sb5$ C$\sb6$H$\sb5$; X = Cl, Br) react with dppm (Ph$\sb2$PCH$\sb2$PPh$\sb2$) to give the reduced species trans- (Re$\sb2$($\mu$-O$\sb2$CR)$\sb2$X$\sb2$($\mu$-dppm)$\sb2$) X (1), trans-Re$\sb2$($\mu$-O$\sb2$CR)$\sb2$X$\sb2$($\mu$-dppm)$\sb2$ (2), and cis-Re$\sb2$($\mu$-O$\sb2$CR)$\sb2$X$\sb2$($\mu$-dppm)$\sb2$ (3). These reactions proceed first to give the Re$\sb{2}\sp{5+}$ complexes 1 followed by the Re$\sb2\sp{4+}$ complexes 2 and 3. Complexes 2 and 3 can be oxidized to paramagnetic cis- (Re$\sb2$($\mu$-O$\sb2$CR)$\sb2$X$\sb2$($\mu$-dppm)$\sb2$) PF$\sb6$ and trans- (Re$\sb2$($\mu$-O$\sb2$CR)$\sb2$X$\sb2$($\mu$-dppm)$\sb2$) PF$\sb6$ by (($\eta$$\sp5$-C$\sb5$H$\sb5$)$\sb2$Fe) PF$\sb6$ and (C$\sb7$H$\sb7$)PF$\sb6$, respectively. The following compounds have been structurally characterized: cis-Re$\sb2$($\mu$-O$\sb2$CCH$\sb3$)$\sb2$Cl$\sb2$($\mu$-dppm)$\sb2$, trans-Re$\sb2$($\mu$-O$\sb2$CCH$\sb3$)$\sb2$Cl$\sb2$($\mu$-dppm)$\sb2$, and trans- (Re$\sb2$($\mu$-O$\sb2$CCH$\sb3$)$\sb2$Cl$\sb2$($\mu$-dppm)$\sb2$) PF$\sb6$. The dirhenium(III) halides (n-Bu$\sb4$N)$\sb2$Re$\sb2$X$\sb8$ (X = Cl, Br) react with dppm and a mixture of RCO$\sb2$H and (RCO)$\sb2$O (R = CH$\sb3$, C$\sb2$H$\sb5$) to give the reduced species Re$\sb2$($\mu$-O$\sb2$CR)X$\sb4$($\mu$-dppm)$\sb2$ (4). The dirhenium(III) complexes Re$\sb2$($\mu$-O$\sb2$CCH$\sb3$)$\sb2$X$\sb4$(H$\sb2$O)$\sb2$ (5, X = Cl, Br) react with dppa (Ph$\sb2$PNHPPh$\sb2$) to give reduced complexes that contain two, one, or zero acetate bridges. The Re$\sb2\sp{5+}$ complexes Re$\sb2$($\mu$-O$\sb2$CCH$\sb3$)X$\sb4$($\mu$-dppa)$\sb2$ (6) are produced in reactions of very short duration (3 min), while longer reaction times (15 min) favor trans- (Re$\sb2$($\mu$-O$\sb2$CCH$\sb3$)$\sb2$X$\sb2$($\mu$-dppa)$\sb2$) X (7). After several days, under these same reaction conditions, the Re$\sb2\sp{4+}$ complexes cis-Re$\sb2$($\mu$-O$\sb2$CCH$\sb3$)$\sb2$X$\sb2$($\mu$-dppa)$\sb2$ (8) are produced. While 6 can undergo reductive decarboxylation to give Re$\sb2$X$\sb4$($\mu$-dppa)$\sb2$ (9), the latter species do not appear to be important precursors to 8, as they are in an analogous system involving reactions of 5 with dppm. The most important reaction pathway to 8 is via the sequence 5 $\to$ 6 $\to$ 7 $\to$ 8. Complex 8 (X = Cl) reacts with (($\eta\sp5$-C$\sb5$H$\sb5$)$\sb2$Fe) PF$\sb6$ to produce paramagnetic cis- (Re$\sb2$($\mu$-O$\sb2$CCH$\sb3$)$\sb2$Cl$\sb2$($\mu$-dppa)$\sb2$) PF$\sb6$ (10). The redox pair 8 and 10 (X = Cl) and complex 9 (X = Cl) have been structurally characterized. (Abstract shortened with permission of author.)

Degree

Ph.D.

Advisors

Walton, Purdue University.

Subject Area

Chemistry

COinS