Bimetallic complexes III. Synthesis and reactions of C 5H 4PPh 2-bridged zirconium-molybdenum and zirconium-tungsten complexes

Abstract

The synthesis and reactions of bimetallic ZrMo and ZrW complexes with bridging C 5H 4PPh 2 ligands (henceforth abbreviated as Cp′) are described. Reaction of Cp′ 2ZrCl 2 ( 1) with organolithium or Grignard reagents gives Cp′ 2ZrR 2 (R  Me ( 3). p-C 6H 4CH 3 ( 5). CH 2SiMe 3 ( 6)) while with AlMe 3 the mono-exchange product Cp′ 2Zr(CI)Me ( 2) is formed. Phenyllithium converts 2 into Cp′ 2Zr(Me)Ph ( 4). From 1–3 the substitution products [(Cp′ 2ZrMe) 2(μ-O)]( 7). Cp′ 2Zr(SR) 2 (R Me ( 8a), Ph ( 8b), CH 2H 4Cl ( 8c)). Cp′ 2Zr(Me)OR (R  CH 2CF 3 ( 9a), t-Bu ( 9b), and Cp′ 2Zr(Cl)O t-Bu ( 10) were obtained. Treatment of [Mo(CO) 4(norabornadiene )]with either 2, 4 or 9a gives the bis-Cp′ bridged binuclear tetracarbonyl complexes [Cp′ 2Zr(Me)(X)Mo(CO) 4] (X  Cl ( 11), Ph ( 12). OCH 2CF 3 ( 13). Binuclear complexes [Cp′ 2Zr(X)(μ-Cl)M(CO) 3] (X  Me, M  Mo, W ( 14a,b), X = O t-Bu, M  Mo ( 16)) which contain an additional bridging chloride ligand were obtained similarly from [M(CO) 3(cycloheptatriene)] and the appropriate zirconium compound. The chloride bridge is readily opened by addition of either PMe 3 or t-BuNC producing complexes [Cp′ 2ZrCl 2M(CO) 3L] (L =PMe 3 ( 18a,b), t-BuNC ( 19a,b)) and [Cp′ 2Zr(Cl)(Me)M(CO) 3PMe 3] ( 20a,b; M  Mo ( a), W ( b)). Exchange of zirconium-bound chloride for organic groups is achieved by treatment of 18a,b or 19a,b with LiR which gives [Cp′ 2ZrMe 2M(CO) 3L](L  PMe 3 ( 21a,b), t-BuNC ( 22a,b), M  Mo ( a), W ( b)) as well as [Cp′ 2ZrR 2Mo(CO) 3PMe 3] (R  Ph ( 23) Tol ( 24)). CC coupling of two nitrile ligands with a Zr-bound methyl group to give a bridging 1,3-diiminato ligand takes palce upon reacting Cp′ 2ZrMe 3 ( 3) wityh [W(CO) 3(NCR) 3]. The products [Cp′ 2Zr(μ-HN-C (R)CH C(R)N)W(CO) 3] (R  Ph ( 25), CH 2Ph ( 26) were fully characterized by magnetiic resonance including 14C-NMR of the doubly labelled derivative 26. Protonation of 26 using [PhMe 2NH]BPh 4 gives the corresponding 1,3-diimine complex [Cp′ 2Zr(μ-HN C(R) CH 2 C(R)B)W(CO) 3]BPh 4 (R  CH 2Ph.27).