Isolation and characterisation of transition and main group metal complexes supported by hydrogen-bonded zwitterionic polyphenolic ligandsElectronic supplementary information (ESI) available: full synthetic and spectroscopic details. See http://www.rsc.org/suppdata/cc/b3/b303618a/

Abstract

Reaction of Zr(O(i)Pr)4 or Sn[N(SiMe3)2]2 with the tris-phenol amine ligand H3L(Me/Me) results in the formation of zirconium or tin complexes containing the new C3-symmetric zwitterionic ammonium-trisphenolate ligand HL2-, while increasing the steric bulk of the ligand results in the isolation of a zirconium complex containing the known trianionic ligand L3-.

Polymetallic Group 4 Complexes: Catalysts for the Ring Opening Polymerisation of rac-Lactide

“…The Zr-O and Zr-N bond distances fall in line with literature examples at an average of 2.021(3) Å and 2.398(3) Å, respectively [37][38][39][40]. Bischelated Zr complexes, similar to 7, have previously been reported with amine bis and tris(phenolate) ligands, which feature relatively small steric bulk on the phenolate groups or on the Zr precursor [6,37,41,42]. Various bischelated Zr complexes have been reported in the literature, but to the best of our knowledge 7 is the first example of a bis(ABP) Zr complex, where the potentially coordinating ligand pendant arm remains unbound [37,39,40,42].…”

Titanium complexes supported by a sterically encumbering N-anchored tris-arylphenoxide ligand

“…1). 3 Upon inspection, the structure of 1-Cl reveals a titanium(IV) center disposed within a C 3 symmetric Nanchored tris-arylphenoxide scaffold. The Ti-O distances are similar ($1.80 Å ) and the Ti center lies in a trigonal bipyramidal environment with the N and Cl occupying the axial positions and with all Ad groups syn with respect to the Cl À group.…”

“…However, several examples of mononuclear systems supported by non-encumbering N-anchored tris-arylphenoxide ligands have been scarcely reported, thus hinting that electronic factors might also play a role in formation of mono versus polynuclear compounds [6]. Recent reports by Kol [2] Brown [4] and others [3,5,6] have demonstrated that the (O 3 N) 3À framework is highly compatible with Ti(IV), and depending on the steric nature of the tripodal ligand, these systems can have considerable resistance to hydrolysis. Given the high Ti-O bond enthalpy ($673 kJ/mol) [7] and stability of the N-anchored tris-arylphenoxide core, we decided to investigate the chemistry of Ti(IV) complexes supported with the sterically demanding ligand (O 3 N) 3À (O 3 N 3À = tris(2-O,3-Ad,5-tBubenzyl)amine, Ad = 1-adamantyl, Scheme 1).…”

“…These (O 3 N)Ti + cores are resistant to moisture and air, are mononuclear, and possess C 3 symmetry on the NMR timescale.Unlike the popularized triamido-amine ligands (N 3 N) 3À [1], N-anchored tris-arylphenoxide ligands of the type (O 3 N) 3À have received far less attention [2][3][4][5] despite these ancillary ligands being inherently more resistant to hydrolysis than the amide analogues. One major drawback of the (O 3 N) 3À is their ability to polymerize via bridging of the polyphenolic motifs [1a].…”

“…One major drawback of the (O 3 N) 3À is their ability to polymerize via bridging of the polyphenolic motifs [1a]. An obvious strategy to avoid this problem is to incorporate steric groups proximal to the hydroxyl motif, thereby disfavoring intermolecular interactions [2][3][4]. However, several examples of mononuclear systems supported by non-encumbering N-anchored tris-arylphenoxide ligands have been scarcely reported, thus hinting that electronic factors might also play a role in formation of mono versus polynuclear compounds [6].…”