Berg, David J.

The reaction of excess ArFNHLi with (ICH2CH2OCH2)2 affords the new diamines (ArFNHCH2CH2OCH2)2 (1, ArF = C6F5; 2, ArF = 3,5-C6H3(CF3)2) in moderate yield. Direct protonolysis of Zr(CH2Ph)nCl4-n (n = 2−4) or Zr[N(SiMe3)2]nCl4-n (n = 2, 3) with 1 or 2 (1 equiv) affords the zirconium complexes Zr(ArFNCH2CH2OCH2)2(X)(Y) (ArF = C6F5:  3, X = Y = Cl; 4, X = N(SiMe3)2, Y = Cl; 5, X = Cl, Y = CH2Ph; 6, X = Y = CH2Ph. ArF = 3,5-C6H3(CF3)2:  7, X = Y = Cl; 8, X = Y = CH2Ph). The structures of 1, 4, 5, and 7 were established by X-ray crystallography with the zirconium complexes 4, 5, and 7 all adopting a monocapped trigonal bipyramidal geometry in the solid state. However, in solution, these complexes display higher symmetry due to rapid ligand rearrangement. The silylamido complex 4 shows restricted rotation of the C6F5 rings in solution (ΔG⧧ = 49 ± 3 kJ mol-1). Abstraction of a benzyl group from 6 by B(C6F5)3 affords {Zr[CH2OCH2CH2N(C6F5)]2(CH2Ph)}+{(PhCH2)B(C6F5)3}- (9). This complex shows evidence for η2-benzyl coordination and does not polymerize ethylene at room temperature. Treatment of 3 with excess MAO (500 equiv) and ethylene (1 atm, 50 °C) affords polyethylene at a modest rate (3.2 kg mol-1 Zr h-1).

Photolysis of Zr(C6F5NCH2CH2OCH2)2(CH2Ph)2 at 435 nm results in formation of the metalated dimer {Zr[C6F4NCH2CH2OCH2CH2OCH2CH2NC6F5][CH2Ph]}2·(C7H8)2 (1), the bridging difluoride dimer {Zr[C6F5NCH2CH2OCH2CH2OCH2CH2NC6F5][F]}2[μ-F]2 (2), and bibenzyl. Complex 1 was characterized by NMR spectroscopy (1H, 19F, 13C) and X-ray crystallography. In the solid state 1 adopts a pentagonal bipyramidal geometry at each zirconium center with a η1-benzyl group occupying one of the axial positions. The bridging difluoride 2 was characterized by 1H and 19F NMR spectroscopy. For comparison purposes, Zr(C6F5NCH2CH2OCH2)2Me2 (3) was synthesized and characterized by NMR spectroscopy and X-ray crystallography. Photolysis of 3 at 435 nm does not result in any reaction.

The acid−base reaction of tetrabenzylzirconium with 1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (H2(CBC), 1) produces (CBC)Zr(CH2Ph)2, 2. Similarly, reaction of 2 with phenols yields (CBC)Zr(CH2Ph)(O-2,6-C6H3But2),3, and (CBC)Zr(O-2,6-C6H3Me2)2, 5. Prolonged heating of 3 leads to the metalated product (CBC)Zr[κ2(C,O)-OC6H3(6-But)(2-CMe2CH2)], 4. Reaction of ZrCl2[N(SiMe3)2]2 with H2(CBC) leads to (CBC)ZrCl2, 6, which subsequently affords (CBC)Zr(X)(Y) by salt metathesis (7, X = Cl, Y = N(SiMe3)2; 8, X = Y = CH3; 9, X = Y = CH2Si(CH3)3). Compounds 3 and 7 show restricted rotation about the Zr−O and Zr−N bonds, respectively, on the NMR time scale. For 3, the energy of activation for this process was determined to be 69 ± 1 kJ/mol. Neither 6 nor 8 shows ethylene polymerization activity when treated with 500 equiv of MAO. Reaction of 6 with 2 equiv of n-BuLi in the presence of excess diphenylacetylene leads to the zirconacyclopentadiene 10, (CBC)Zr(C4Ph4). The structures of 5, 9, and 10 have been determined by X-ray crystallography, and all three display distorted octahedral geometry.

A series of zirconium complexes supported by the chelating diamido ligand (C6F5NHCH2CH20CH2)2(H2(NOON)) have been prepared. These complexes include (NOON)Zr(CH2Ph)2, (NOON)ZrMe2, (NOON)ZrC12, and (NOON)ZrC1[N(SiMe3)2]. (NOON)ZrMe2 and (NOON)ZrC1[N(SiMe3)2] were crystallographically characterized and for all the complexes, the ligand NMR spectra were consistent with a fluxional process occurring in solution. When (NOON)Zr(CH2Ph)2was exposed to 435 nm light, a photochemical reaction occurred which resulted in C-F bond activation and the formation of (NOON)ZrF2and a metallated dimer. When (NOON)ZrC12was treated with MAO, it showed modest activity as an ethylene polymerization catalyst. A series of zirconium complexes supported by l , 4 , 8 , l l - tetraazabicyclo[6.6.2]hexadecane (H2(CBC)) have been prepared and characterized. ( C B C > Z ~ ( C H ~ P ~ ) N ( B U ' ) C ( H ) = C ( HC PB ~C , ) Z r ( O - 2 , 6 - C 6 H 3 M e 2 ) 2 , ( c B c ) z ~ ( o s ~ ( B u ' ) ~ H ) ~ , (CBC)Zr(CH2SiMe3)2, (CBC)ZrC4Ph4 were crystallographically characterized and (cBc)z~(cH~P~)(o-2,6-c~H~Bu'~), (CBC)Z~[K~(C,O)-OC~H~(~-RU')(~-CM~~CH~)] (CBC)ZrC12, (CBC)ZrC1[N(SiMe3)2] and (CBC)ZrMe2 were fully characterized. Treatment of (CBC)ZrMe2 with MA0 does not result in an active ethylene polymerization catalyst. The metallacycle (CBC)ZrC4Ph4reacts with thionyl chloride and dichlorophenylphosphine to yield tetraphenylthiophene oxide and pentaphenylphosphole respectively. Treatment of Yb[N(SiMe3)2]2(0Et2)2with H2(CBC) results in the sparingly soluble coordination polymer [(CBC)Yb], and two byproducts of this reaction were crystallographically characterized. One was the mixed valence salt { [ ( ~ - c B c ) Y ~ ] ~ ( ~ ~ - o))'{Y~[N(s~M~~)~w]~h}il-e,the other was { [ ( p - ~ ~ ~ ) ~ b-]o3)}(+pI-.3In both cases the cation is a trimer of ytterbium (111) ions bridged by an oxygen and three amido nitrogens from the (CBC) ligand.