Reactions of rhenium polyhydride complexes with electrophiles and nucleophiles

Gregory Allen Moehring, Purdue University

Abstract

Reactions of ReH$\sb7$(PPh$\sb3$)$\sb2$ with L-L(L-L = 1,10-phenanthroline or 2,2-bipyridine) produce ReH$\sb3$(PPH$\sb3$)$\sb2$(L-L). These complexes react with acids in acetonitrile to form (ReH$\sb4$(PPh$\sb3$)$\sb2$(L-L)) BF$\sb4$ or (ReH$\sb2$(PPh$\sb3$)$\sb2$(L-L)(NCMe)) PF$\sb6$. The ligand 1,4-pyrazine (pyz) reacts with ReH$\sb7$(PPh$\sb3$)$\sb2$ to form ReH$\sb5$(PPh$\sb3$)$\sb2$(pyz), which reacts with further ReH$\sb7$(PPh$\sb3$)$\sb2$ to produce (ReH$\sb5$(PPh$\sb3$)$\sb2$) $\sb2$($\mu$-pyz). The complexes ReH$\sb7$(PPh$\sb3$)$\sb2$, ReH$\sb5$(PPh$\sb3$)$\sb2$L (L = py, Bu$\sp{\rm t}$NH$\sb2$, or CyNH$\sb2$), and ReH$\sb4$I(PPh$\sb3$)$\sb3$ react with HBF$\sb4\cdot$ET$\sb2$O in acetonitrile or propionitrile (RCN) to form (ReH(NCR)$\sb4$(PPh$\sb3$)$\sb2$((BF$\sb4$)$\sb2$, (ReH(NCR)$\sb3$(PPh$\sb3$)$\sb2$L) BF$\sb4$)$\sb2$, and (ReH(NCR)$\sb3$(PPh$\sb3$)$\sb3$) (BF$\sb4$)$\sb2$, respectively. The complexes (ReH(NCR)$\sb4$(PPH$\sb3$)$\sb2$) (BF$\sb4$)$\sb2$ react with Ph$\sb2$PCH$\sb2$CH$\sb2$PPh$\sb2$(dppe) to produce either (ReH(NCR)$\sb3$(PPh$\sb3$)(dppe)) (BF$\sb4$)$\sb2$ or (Re(NCR)$\sb2$(dppe)$\sb2$) BF$\sb4$. Interestingly, ReH$\sb5$(PPh$\sb3$)$\sb3$ reacts with HBF$\sb4\cdot$Et$\sb2$O/MeCN to form (ReH$\sb4$(PPh$\sb3$)$\sb3$(NCMe)) PF$\sb6$ (following metathesis with KPF$\sb6$). Several other products with this same stoichiometry, viz., (ReH$\sb4$(PPh$\sb3$)$\sb3$L) PF$\sb6$ (L = PPh$\sb3$, CNBu$\sp{\rm t}$, or CNXylyl), were prepared from reactions of ReH$\sb5$(PPh$\sb3$)$\sb3$ with C$\sb7$H$\sb7\sp+$PF$\sb6\sp-$ and L. Deprotonation of (ReH$\sb4$(PPh$\sb3$)$\sb3$(NCMe)) PF$\sb6$ and (ReH$\sb4$(PPh$\sb3$)$\sb3$(CNBu$\sp{\rm t}$)) -PF$\sb6$ was also accomplished. The deprotonation products, ReH$\sb3$(PPh$\sb3$)$\sb3$(NCMe) and ReH$\sb3$(PPh$\sb3$)$\sb3$(CNBu$\sp{\rm t}$), react with C$\sb7$H$\sb7\sp+$PF$\sb6\sp-$/MeCN to form (ReH$\sb2$(PPh$\sb3$)$\sb3$(NCMe)$\sb2$) PF$\sb6$ and (ReH$\sb2$(PPh$\sb3$)$\sb3$(NCMe)(CNBu$\sp{\rm t}$)) PF$\sb6$, respectively. The reaction of ReH$\sb5$(PPh$\sb3$)$\sb3$ with HBF$\sb4\cdot$Et$\sb2$O in dichloromethane affords (ReH$\sb6$(PPh$\sb3)\sb3$) BF$\sb4$; while (Au(PPh$\sb3$)) PF$\sb6$ forms the heterometallic cluster, (ReH$\sb5$(PPh$\sb3)\sb3$Au(PPh$\sb3$)) PF$\sb6$. This latter product reacts with NEt$\sb3$ to yield $\{$ReH$\sb4$(PPh$\sb3)\sb3$(Au(PPh$\sb3$)) $\sb2\}$PF$\sb6$. The product of the reaction of Re$\sb2$H$\sb8$(PPh$\sb3)\sb4$ with HBF$\sb4\cdot$Et$\sb2$O is (Re$\sb2$H$\sb9$(PPh$\sb3)\sb4$) BF$\sb4$, while (Re$\sb2$H$\sb8$(PPh$\sb3)\sb4$Au(PPh$\sb3$)) PF$\sb6$ and $\{$Re$\sb2$H$\sb8$(PPh$\sb3)\sb4$(Au(PPh$\sb3$)) $\sb2\}$(PF$\sb6$)$\sb2$, are formed from the reaction of Re$\sb2$H$\sb8$(PPh$\sb3)\sb4$ with (Au(PPh$\sb3$)) PF$\sb6$. Deprotonation with NEt$\sb3$ generates Re$\sb2$H$\sb7$(PPh$\sb3)\sb4$Au(PPh$\sb3$) and $\{$Re$\sb2$H$\sb7$(PPh$\sb3)\sb4$(Au(PPh$\sb3$)) $\sb2\}$PF$\sb6$ respectively. X-ray diffraction analysis of Re$\sb2$H$\sb7$(PPh$\sb3)\sb4$Au(PPh$\sb3$) has shown that this complex possesses an unsymmetrical triangular structure with Re-Au distances of 2.927(1)A and 2.720(1)A and a Re-Re distance of 2.571(1)A. The deprotonated products, Re$\sb2$H$\sb7$(PPh$\sb3)\sb4$Au(PPh$\sb3$) and $\{$Re$\sb2$H$\sb7$(PPh$\sb3)\sb4$(Au(PPh$\sb3$)) $\sb2\}$PF$\sb6$ are easily oxidized to their paramagnetic congeners.

Degree

Ph.D.

Advisors

Walton, Purdue University.

Subject Area

Chemistry

COinS