94598-00-2Relevant academic research and scientific papers
Cationic Group 4 metal alkyl compounds containing aryloxide ligation: Synthesis, structure, reactivity and polymerization studies
Thorn, Matthew G.,Etheridge, Zac C.,Fanwick, Phillip E.,Rothwell, Ian P.
, p. 148 - 162 (2007/10/03)
A series of bis(alkyl) derivatives of titanium and zirconium [(ArO)2MR2] (M=Ti, Zr; R=Me, CH2Ph; ArO=various 2,6-di-substituted phenoxides) has been synthesized and their reactivity towards the Lewis acid [B(C6F5)3] examined. The benzyl compounds generate stable zwitterionic species such as [M(OC6HPh2-2,6-R2-3,5)2(CH 2Ph)][η6-C6H5CH 2B(C6F5)3] (M=Ti, R=H, 12; Me, 13: M=Zr, R=Me, 15). Structural studies of 12 and 15 show the boron anion π-bound to the metal center through the original benzyl phenyl ring. In contrast, treatment of the benzyl compound [Zr(OC6H3But2-2,6) 2(CH2Ph)2] with [B(C6F5)3] leads to the cyclometallated compound [Zr(OC6H3But-CMe2CH 2)(OC6H3But 2-2,6)][η6-C6H5CH 2B(C6F5)3] 16 which was structurally characterized. In contrast to this behavior the bis(methyl) species react with [B(C6F5)3] to produce unstable methyl cationic intermediates which decompose to a mixture of [Ti(OAr)2(CH3)(C6F5)] and [CH3B(C6F5)2]. The titanium zwitterionic benzyl compounds will react with alkynes and α-olefins to produce mono-insertion products such as [Ti(OC6H3Ph2-2,6)2{C(CH 3)C(Ph)CH2(η6-C6H 5)}][PhCH2B(C6F5)3] 24. In these compounds 1,2-insertion of olefins occurs followed by chelation of the original benzyl group to the metal center. Spectroscopic studies show the boron anion is non-coordinated to the metal center. Despite their thermal instability, the methyl cations can be generated in situ in the presence of olefins to produce polymers (ethene and propene) and oligomers (1-hexene). Studies show that the molecular weight of the polymers or oligomers increases systematically with the bulk of the aryloxide ligand. Spectroscopic studies of the polypropylene indicate 1,2-insertion is occurring with β-hydrogen abstraction to produce vinylidene end groups as the termination step.
The chemistry of sterically crowded aryl oxide ligands. 3. Crystal and molecular structure and spectroscopic properties of mixed benzyl-aryl oxide compounds of zirconium
Latesky, Stanley L.,McMullen, Anne K.,Niccolai, Gerald P.,Rothwell, Ian P.,Huffman, John C.
, p. 902 - 908 (2008/10/08)
The reaction between tetrabenzyl- or tetrakis(4-fluorobenzyl)zirconium, Zr(CH2Ph)4 or Zr(CH2PhF)4, and the sterically demanding ligand 2,6-di-tert-butylphenol (HOAr′) leads to two types of substitution products: Zr(OAr′)(CH2Ph)3 (Ia), Zr(OAr′)(CH2PhF)3 (Ib), and Zr(OAr′)2(CH2Ph)2 (IIa), Zr(OAr′)2(CH2PhF)2 (IIb). Addition of 4-methoxy-2,6-di-tert-butylphenol (HOAr′-OMe) to Ia generates the mixed aryl oxide Zr(OAr′)(OAr′-OMe)(CH2Ph)2 (IIc). Structural studies show that I contains a significant interaction between the zirconium atom and the aryl ring of one of the benzyl groups which is best described as approaching η3-bonding, whereas the ligands in II are purely σ-bound (η1). Spectroscopic evidence (1H and 13C NMR) suggests the possible retention of this type of interaction in solution. Compound Ia crystallizes in space group C2/c with a = 17.499 (10) A?, b = 10.566 (6) A?, c = 32.769 (12) A?, β = 95.79 (2)°, and Z = 8. Compound Ib crystallizes in space group P21/c with a = 9.480 (3) A?, b = 33.605 (19) A?, c = 10.608 (4) A?, β = 114.20 (2)°, and Z = 4. Compound IIc crystallizes in space group P21/n with a = 17.683 (9) A?, b = 11.342 (5) A?, c = 19.470 (1) A?, β = 101.01 (2)°, and Z = 4.
