Structural and theoretical studies of organometallic complexes

• Main Author: Rosair, Georgina Margaret
• Published: University of the West of England, Bristol 1994
• Subjects: 547; Organic chemistry
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260221

This Thesis describes the X-ray structure determinations of six manganese cyanide, one rhenium cyanide and two rhodium triazenido complexes. An investigation of the trans influence using the Cambridge Structural Database and extended Hückel calculations is described in Chapter 4. Chapter 1 introduces the techniques and chemistry described in the rest of the Thesis. Chapter 2 describes the structures of two redox pairs, namely [Mn(CN)(CO)(dppm)2]z and [(OC)(dppm)2Mn(-CN)Rh(CO)2Cl]z (z = 0 or + 1). The major change on oxidation is an increase in the Mn-P bond lengths for both pairs, suggesting localised oxidation at manganese. Changed ligand stereochemistry at manganese in the trinuclear species, [{trans-(OC)2{(OEt)3P}(dppm)Mn(-CN)}2Rh(CO)2]+, led to different electronic behaviour, i.e. interaction between the manganese centres on oxidation. The composition of the HOMOs in a range of manganese carbonyl models was investigated by extended Hückel calculations. As seen in [{trans-(OC)2{(OEt)3P}(dppm)Mn(-CN)}2Rh(CO)2]+, where CN is cis to two trans CO ligands, the HOMO composition is such that electronic interaction can occur along the CN bridge on oxidation of the Mn(I) centre. The structure of [(OC)(dppm)2Mn(-CN)Fe(NO)2I] showed that the manganese cyanide unit could also be linked to a paramagnetic iron centre. The rhenium cyanide species [fac-(o-phen)(OC)3Re(-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)] shows that the photochemically active Re-phenanthroline centre is linked to the redox-active Ru-catecholate fragment via a cyanide bridge. Chapter 3 describes the X-ray structure of [Rh2(-CO)(dppe)(bipy)(-N1,3,N3-RNNNR)(-N1,N3-RNNNR)]2+ showing a previously unreported mode of triazenido co-ordination, a combination of bridging and chelating modes.