Abstract
M.Sc.
This study focussed on two areas of research in the field of organometallic chemistry. The first entails the preparation and characterisation of a number of Fischer-type carbene complexes of the general formula (C0) 5M(OR)(RI) (1 - 4). For the first group M = Cr, Mo or W, R = Et or Me and re = Ph or BiPh. A second, somewhat different group was prepared by deprotonating 4-
methylthiazol-2-methyltlfioether, reacting it with M(CO) 6, where M = Cr or W, and neutralising the resulting anion with methyltriflate. Both metals afforded only one product which could be successfully purified and characterised as M(C0),{C(OCH3)(C=C(CH3)N=C(SCH3)S) (6,7). The crystal structure of the tungsten complex was solved by single crystal X-ray techniques. A similar carbene complex preparation was carried out with 5-methylthiophenilyl-2-thiomethylether and M(C0)6, M = Cr or W, as starting reagents. In addition to the expected carbene complexes M(CO)5 (C(OCH3)(CH2SHCH=C(CH3)S)), M = Cr and W (9a, 10a), deprotonation of a ring carbon yielded M(C0) 5{C(OCH3)(6=C(SCH3)SC(CH3)=CH)) M = Cr and W (9b, 10b), whereas unreacted starting material afforded the sulfide W(C0) 54-SC(SCH3)=CHCH=C(CH3) (11). The second part of the thesis describes the preparation of pentacarbonyl thione and iminocomplexes,
as well as tricarbonyl imino-, sulphide and dinuclear re-sulphide complexes. 4-
Methylthiazoly1-2-thiolate were used for nucleophilic attack on (C0) 5Cr--C(OR)(12. 1) (1 and 4) to yield the thione complex Cr(C0) 54-S=CN(CH3)C(CH3)=CHS (13) upon methylation. Two other products were also obtained from these reactions : Cr(C0) 54-NC=CHSCH=C(CH3) (12) and Cr(CO) 54-N=C(CH3)SCH=C(CH3) (14), which indicates incomplete reaction with sulfur during the formation of the mentioned thiolate. Three beautiful electron ligand systems were produced by reacting 4-methylthiazol-2-disulphide
with (CO),W(THF) or Fe2(C0)) . A new "butterfly" bidentately coordinated tricarbonyl tungsten complex, [(C0)3 1/{N(S)SCH(CH3)) 2] (16) was obtained. The crystal structure of this complex shows many similarities to a known complex, (C0)3W(n2-PyS)2 that was prepared from ionic metalcarbonyl precursors. In addition to 16, a thione complex W(C0) 54-SHC(CIi )=CHS (17) also formed from the reaction with (CO) 5M(THF). The reaction between (CO),M(THF) and 4-methylthiazolyi-2-disulphide thus probably involves heterolytic bond cleavage and protonation on the silica gel. The reaction of Fe 2(CO)9 with the same disulphide resulted in the formation of the dinuclear compound Fe2(C0)6(SC=NC(CH3)=CHS)2 (18), possibly via the homolytic splitting of the disulphide bond. The crystal structure of this compound revealed the Fe-Fe-bond and eclipsed
configuration, typical of this type of Fe-cluster complex. Finally, two thione complexesM(C0)54—S(SMe)(eHCH(Me)S), (M= Cr and W; 20,21) were found to isomerise in solution to their sulphide analogues of which only the chromium complex Cr(C0)54— SC(Me)=CHCH=C(C(=S)(SMe)) (22) could be characterised.