BIMETALLIC COMPLEXES .3. SYNTHESIS AND REACTIONS OF C5H4PPH2-BRIDGED ZIRCONIUM-MOLYBDENUM AND ZIRCONIUM-TUNGSTEN COMPLEXES

The synthesis and reactions of bimetallic Zr-Mo and Zr-W complexes wit h bridging C5H4PPh2 ligands (henceforth abbreviated as Cp') are descri bed. Reaction of Cp-2'ZrCl2 (1) with organolithium or Grignard reagent s gives Cp-2'ZrR2 (R = Me (3), p-C6H4CH3 (5), CH,2SiMe3 (6)) while wit h AlMe3 the mono-exchange product Cp-2'Zr(Cl)Me (2) is formed Phenylli thium converts 2 into Cp-2'Zr(Me)Ph (4). From 1-3 the substitution pro ducts [(Cp-2'ZrMe)(2)(mu-O)] (7), Cp-2'Zr(SR)(2) (R = Me (8a), Ph (8b) , CH2C6H4Cl (8c)), Cp-2'Zr(Me)OR (R = CH2CF3 (9a), t-Bu (9b)), and Cp- 2'Zr(Cl)Ot-Bu (10) were obtained. Treatment of [Mo(CO)(4)(norbomadiene )3 with either 2, 4 or 9a gives the bis-Cp' bridged binuclear tetracar bonyl complexes [Cp-2'Zr(Me)(X)Mo(CO)(4)] (X = Cl (11), Ph (12), OCH2C F3 (13)). Binuclear complexes [Cp-2'Zr(X)(mu-Cl)M(CO)(3)] (X = Me, M = Mo, W (14a,b), X = Ot-Bu, M = Mo (16)) which contain an additional br idging chloride ligand were obtained similarly from [M(CO)(3)(cyclohep tatriene)] and the appropriate zirconium compound. The chloride bridge is readily opened by addition of either PMe3 or t-BuNC producing comp lexes [Cp-2'ZrCl2M(CO)(3)L] (L = PMe3 (18a,b), t-BuNC (19a,b)) and [Cp -2'Zr(Cl)(Me)M(CO)(3)PMe3] (20a,b; M = Mo (a), W (b)). Exchange of zir conium-bound chloride for organic groups is achieved by treatment of 1 8a,b or 19a,b with LiR which gives [Cp-2'ZrMe2M(CO)(3)L] (L = PMe3 (21 a,b), t-BuNC (22a,b), M = Mo (a), W (b)) as well as [Cp-2'ZrR2Mo(CO)(3 )PMe3] (R = Ph (23), Tol (24)). C-C coupling of two nitrile ligands wi th a Zr-bound methyl group to give a bridging 1,3-diiminato ligand tak es place upon reacting Cp'2ZrMe2 (3) with [W(CO)(3)(NCR)(3)]. The prod ucts [Cp-2'Zr(mu-HN-C(R) = CH-C(R) = N)W(CO)(3)] (R = Ph (25), CH2Ph ( 26)) were fully characterized by magnetic resonance including C-13-NMR of the doubly labelled derivative 26. Protonation of 26 using [PhMe2 NH]BPh4 gives the corresponding 1,3-diimine complex [Cp-2'Zr(mu-HN = C (R)-CH2-C(R) = N)W(CO)(3)]BPh4 (R = CH2Ph, 27). (C) 1997 Elsevier Scie nce S.A.