The first chapter, -the intr-oducti-On contains-a-general-baGkground- concerning
the chemistry of molybdenum(II) and tungsten(II), their properties, and the synthesis and reactions of their complexes.
The second chapter describes the synthesis, reactions and characterisation of
the bis(3-hexyne)(EtC2Et) complexes of molybdenum(II) and tungsten(II), [Mlz(CO)
(NCMe)(rt2-EtC2Et)2]. The crystal structures of the bis(PPh3) complex [Wlz(CO)(PPh3)2 (112-EtC2Et)](4) and the PPhz(CH2)3PPh2 complex, [WI2(CO){Ph2P(CH2)3PPh2}(ri2-EtC2Et)](S) are discussed. The reaction of equimolar amounts [Moh(CO)(NCMe)(ri2-EtC2Et)2] and bipy to give the crystallographically characterised complex, [Moh(CO)(bipy)(ri2-EtC2Et)](l2) is also described.
The third chapter describes the reactions of the complexes [MI2(CO)
(NCMe)(ri2-EtC2Et)2] with one and two equivalents of phosphite ligands, P(OR)3 (R =Me, Et, ;Pr, 0Bu and Ph) to give [Moh(CO)(NCMe){P(OR)3}(ri2-EtC2Et)](R = Ph or
;Pr), [Wh(CO){P(OR)3}(ri2-EtC2Et)z](R = Me, Ph or ;Pr) and [Miz(CO){P(OR)3}i(ri
2-EtC2Et)](M = Mo, R = Me, Et, ;Pr, and 0Bu; M = W, R = Me, Et, ;Pr, 0Bu and Ph)
respectively. The reactions of the crystallographically characterised complex
[Moh(CO)(NCMe){P(OPh)3}(ri2-EtC2Et)](l3), with a series of neutral and anionic donor ligands is described. The crystal structures of one of the reaction products,
[Moh(CO)(dppe)(ri2-EtC2Et)](24) is discussed. The structures of [Mh(CO){P(O;Pr)3}z
(ri2-EtC2Et)] {M = Mo(31) and W(32)}, have also been crystallographically determined.
The fourth chapter is divided into two parts. The first part deals with the
synthesis and characterisation of tripodal triphos {MeC(CH2PPh2)3} seven-coordinate didentate phosphine complexes of molybdenum(II) and tungsten(II), namely [MI2(C0)3 {MeC(CH2PPh2)3-P,P '}] (36 and 37), which have the tripodal triphos ligand coordinated in a bidentate manner. The intramolecular rearrangement of 36 and 37 to give the dicarbonyl complexes, [MI2(C0)2{MeC(CH2PPh2)3-P,P ',P' '}] (38 and 39) is also
discussed. The reactions of 36 and 37 with [Ml2(C0)3(NCMe)2](M = Mo or W),
[MI2(C0)3(NCMe)L]{L = PPh3, AsPh3, SbPh3, P(OMe)3, P(OEt)3, P(OPh)3}, [Ml2(C0)3
{Ph2P(CH2)nPPh2} ](n = 1 or 2), [MI2(CO)(NCMe)(T12-EtC2Et)2], [MoX(C0)2(NCMe)i
(T13-C3RiR)] (X = Cl or Br; R = H, Me), [Fe2(C0)9] and [Fel(CO)i(Cp or Cp' )] to give a
wide range of multimetallic complexes is also described.
The fifth chapter describes the synthesis and characterisation of the sevencoordinate dichloro complex [WCh(CQ)3(NCMe)i], by reacting the complex
[Wii(CO)J(NCMe)i] with excess of NaCl in acetone/CH2Ch (50:50). The reaction of
[WCh(C0)3(NCMe)2] with 3-hexyne gives [WCh(CO)(NCMe)(T12 -EtC2Et)2](80), which reacts with a wide range of ligands, such as NPh3, PPh3, Ph2P(CH2)nPPh2, (n = 1 or 2), P(OPh)3, cis-Ph2PCH=CHPPh2, bipy and NaS2CNR2 (R = Me or Et) to give a series of new chloro 3-hexyne complexes of tungsten(II).
Chapter six gives full experimental details for Chapters two to five. In
conclusion, ninety seven new organomolybdenum and tungsten complexes containing a wide variety of ligands have been prepared and characterised, which form the main part of this thesis. Finally, an investigation of the catalytic activity of the complex [WCh (C0)3(NCMe)2] towards the polymerisation of phenylacetylene, PhC2H is briefly discussed.