Aspects of the carbonyl chemistry of the group VII metals.

Abstract

This thesis describes the preparation and characterisation of various types of Group VII metal carbonyl complexes. The first chapter outlines the experimental techniques used in the work. The second chapter reviews the known types of cationic metal carbonyls and discusses the syntheses of cationic manganese and rhenium carbonyl complexes via substitution reactions of [M(CO)3(NCMe)3]+ClO4-. Substitution products isolated include tricarbonyl complexes of the types [M(CO)3(terdentate)]+, [M(CO)3(bidentate) (NCMe)]+, [M(CO)3 (monodentate) (NCMe)2]+, [M(CO)3(monodentate)2(NCMe)]+ and [M(CO)3(monodentate)3]+ as well as the dicarbonyl complex [Mn(CO)2(Ph3P)2(NCMe)2]+ClO4-. Cotton-Kraihanzel carbonyl stretching parameters for several of the complexes have been calculated and their value assessed. The third chapter concerns the photochemical substitution of carbonyl groups from (n5-MeC5H4)Mn(CO)3 by various bidentate ligands (arphos, dpae, dpam, dppa, dppe and dppm). Products of the types (n5-MeC5H4)Mn(CO) (L-L) with chelating ligands and [(n5-MeC5H4)Mn(CO)2]2(L-L) with bridging ligands were isolated. (n5-MeC5H4)Mn(CO)2PPh3 was similarly prepared. Considerable emphasis was placed upon the interpretation of the mass spectral fragmentation patterns of these products. The fourth chapter deals with the 31P nuclear magnetic resonance spectra of a number of the cationic and methylcyclo-pentadienyl complexes described in chapters 2 and 3. The anomalous 31P chemical shift behaviour of ditertiary phosphine chelate complexes previously noted for Group VI and Group VIII metals was also evident in the Group VII compounds. This behaviour can be used to distinguish between bidentate chelating and bidentate bridging coordination modes for ditertiary phosphine ligands. The final chapter describes some halogenation reactions of Group VI and Group VII transition metal carbonyl complexes. Part A of this chapter deals exclusively with products containing coordinated acetonitrile. A new convenient route to the preparations of MoC14(CH3CN)2, MoBr3(CH3CN)3, WX4(CH3CN)2 (X = C1, Br), and ReX4(CH3CN)2 (X = C1, Br) has been established. Part B discusses some halogenations of rhenium carbonyl complexes of the type fac-[Re(CO)3XL2]. Using mild conditions some seven-coordinate rhenium(III) complexes of the type Re(CO)2X3L2 have been isolated. More extreme reaction conditions afford six-coordinate rhenium(IV) halo-complexes.

Date of Award	1978
Original language	English
Awarding Institution	University of Bath