ABSTRACT
While B(C(6)F(5))(3) forms the adducts (CH(2))(4)CO(2)B(C(6)F(5))(3)1 and (CHMeCO(2))(2)B(C(6)F(5))(3)7 with δ-valerolactone and lactide, the frustrated Lewis pairs derived from B(C(6)F(5))(3) and phosphine or N-bases react with lactone to effect ring opening affording zwitterionic species of the form L(CH(2))(4)CO(2)B(C(6)F(5))(3) (L = tBu(3)P 2, Cy(3)P 3, C(5)H(3)Me(3)N 4, PhNMe(2) 5, C(5)H(6)Me(4)NH 6) while reaction with rac-lactide results in ring contraction to give salts [LH][OCCHMeCO(2)(CMe)OB(C(6)F(5))(3)] (L = tBu(3)P 8, Cy(3)P 9, C(5)H(3)Me(2)N 10, C(5)H(6)Me(4)NH 11). The mechanistic implications of these reactions are discussed.
ABSTRACT
The ZnMe complexes of bis-ferrocenyl-ß-diketiminate ligands are prepared and the reactions with [Ph(3)C][B(C(6)F(5))(4)] are found to yield the salts [H(Ph(3)C)C(MeC(N(C(5)H(4))FeCp)(2)ZnMe] [B(C(6)F(5))(4)] and [CH(2)=C(MeC(N(C(5)H(4))FeCp)(2)ZnMe][B(C(6)F(5))(4)], derived from electrophilic substitution and hydride abstraction.
ABSTRACT
Preparation of a N-ferrocenyl-amidinate complex was achieved by employing (TMEDA)Li[(CpFeC(5)H(4))NC(Ph)NSiMe(3)] (1) to prepare Cp*Zr[(CpFeC(5)H(4))NC(Ph)NSiMe(3)]Cl(2) (2). Complex 2 exhibited poor polymerization activity and thus a series of C-ferrocenyl bis(amidinate) complexes of the type M(L)(2)Cl(2) (M = Zr, 4; M = Ti, 5; L = (CyNC(CpFeC(5)H(4))NCy) were synthesized via reaction of ferrocenyl-amidine, H(L) and M(NMe(2))(2)Cl(2) (M = Ti, Zr·2THF). Half sandwich mono(amidinate) complexes, Cp'ZrLCl(2) (Cp' = Cp, 7; Cp' = Cp*, 8), were prepared by the reaction of Cp'ZrCl(3) with Li(L) and subsequently alkylated to give M(L)(2)Me(2) (M = Zr, 9; M = Ti, 11), CpZr(L)(CH(2)Ph)(2) (12) and Cp*Zr(L)Me(2) (10) with the appropriate alkylating agent. Abstraction of a methyl group from 7 with B(C(6)F(5))(3) and [Ph(3)C][B(C(6)F(5))(4)] proceeded cleanly to give [{CyNC(CpFeC(5)H(4))NCy}(2)ZrMe][MeB(C(6)F(5))(3)] 13 and [{CyNC(CpFeC(5)H(4))NCy}(2)ZrMe][B(C(6)F(5))(4)] 14, respectively. Similarly, the analogous CpZr and Cp*Zr derivatives LZr{CyNC(CpFeC(5)H(4))NCy}CH(2)Ph] [PhCH(2)B(C(6)F(5))(3)] L = Cp 15, Cp* 17 and [LZr{CyNC(CpFeC(5)H(4))NCy}CH(2)Ph][B(C(6)F(5))(4)] L = Cp 16, Cp* 18 were prepared. Cyclic voltammetry studies on the metal complexes containing ferrocenyl-amidinates reveal quasi reversible oxidation and reduction waves for the ferrocene/ferrocenium couple. The dichloride complexes (4-8) activated with MAO and dialkyl complexes (9,10) activated with B(C(6)F(5))(3) and [Ph(3)C][B(C(6)F(5))(4)] showed low ethylene polymerization activities.
Subject(s)
Amidines/chemistry , Coordination Complexes/chemistry , Ferrous Compounds/chemistry , Titanium/chemistry , Zirconium/chemistry , Coordination Complexes/chemical synthesis , Electrochemistry , Metallocenes , Molecular StructureABSTRACT
The direct synthesis of yttrium amidate complexes using the simple reaction of amide proligands and Y(N(SiMe3)2)3 results in the high-yielding preparation and isolation of crystalline, monomeric materials. The complex, tris(N-2',6'-diisopropylphenyl(naphthyl)amidate)yttrium mono(tetrahydrofuran) (4), was structurally determined to be a 7-coordinate C1 symmetric structure, maintaining one bound tetrahydrofuran molecule. Compound 4 (C12H17[NCO]C10H7)3Y(C4H8O) crystallized in the monoclinic space group P2(1)/c with a = 13.7820(11) A, b = 33.598(3) A, c = 16.0575(12) A, alpha = 90 degrees, beta = 98.762(3) degrees, gamma = 90 degrees, Z = 4. Solution phase NMR spectroscopic characterization of this same complex showed a highly symmetric species, consistent with a fluxional coordination environment for these compounds. Preliminary studies into the initiation of epsilon-caprolactone ring-opening polymerization using these complexes indicate high activity, producing high molecular weight polymer.
