Magnesium, calcium and zinc [NN'] heteroscorpionate complexes.

A new family of sterically demanding N2N' heteroscorpionate pro-ligands (HC(tBu2pz)2SiMe2N(H)R (R = iPr, tBu, Ph, Xyl)) has been prepared via a straightforward modular synthetic route. An extensive study into the synthesis and characterisation of lithium, magnesium, calcium and zinc complexes supported by both 3,5-tBu and 3,5-Me substituted N2N' ligand families has been conducted. Attempted deprotonation of the pro-ligands with nBuLi afforded the corresponding lithium salts Li{HC(tBu2pz)2SiMe2NR} (R = iPr (1), tBu (2), Ph (3) and Xyl (4)) but air- and thermal-sensitivity limited the yields of these potentially useful precursors; only the sterically encumbered ligand system allowed clean reactivity.

Cationic and charge-neutral calcium tetrahydroborate complexes and their use in the controlled ring-opening polymerisation of rac-lactide.

The first cationic main group tetrahydroborate complexes are reported. [Ca(BH(4))(THF)(5)][BPh(4)] and the charge neutral (Tp((t)Bu,Me))Ca(BH(4))(THF) are initiators for the living ring opening polymerization of rac-lactide, the latter producing PLA with high levels of heterotactic enrichment. These represent a new class of ROP initiators for main group metals.

Synthesis and ethylene trimerisation capability of new chromium(II) and chromium(III) heteroscorpionate complexes.

Reaction of (Me(2)pz)(2)CHSiMe(2)N(H)R (R = (i)Pr or Ph) or (Me(2)pz)(2)CHSiMe(2)NMe(2) with CrCl(3)(THF)(3) or CrCl(2)(THF)(2) gave Cr{(Me(2)pz)(2)CHSiMe(2)NR(1)R(2)}Cl(3) (R(1) = H, R(2) = (i)Pr (10) or Ph (11); R(1) = R(2) = Me (15)) or Cr{(Me(2)pz)(2)CHSiMe(2)NR(1)R(2)}Cl(2)(THF) (R(1) = H, R(2) = (i)Pr (12) or Ph (13); R(1) = R(2) = Me (16)), respectively. Compounds 10 and 11 were crystallographically characterized and the magnetic behaviour of all the new compounds was evaluated using SQUID magnetometry. Reaction of CrCl(3)(THF)(3) with Li{C(Me(2)pz)(3)}(THF) gave the zwitterionic complex Cr{C(Me(2)pz)(3)}Cl(2)(THF) (17) containing an apical carbanion.

Dicationic and zwitterionic catalysts for the amine-initiated, immortal ring-opening polymerisation of rac-lactide: facile synthesis of amine-terminated, highly heterotactic PLA.

Dicationic, zwitterionic and "conventional" yttrium compounds act as catalysts for the primary or secondary amine-initiated immortal ROP of rac-lactide; amine-terminated, highly heterotactic poly(rac-lactides) with narrow polydispersities and well-controlled molecular weights are prepared in this manner.

Sodium, magnesium and zinc complexes of mono(phenolate) heteroscorpionate ligands.

The reaction of bis(3,5-dimethylpyrazolyl)methylphenol N(2)O(Ar)H (1) with NaH in THF formed dimeric [Na(kappa(2)-N(2)O(Ar))(THF)](2) (2), which contains a kappa(2)(N,O)-bound bidentate N(2)O(Ar) ligand. The reaction of 1 with Mg(n)Bu(2) gave the four-coordinate monomeric butyl compound Mg(N(2)O(Ar))(n)Bu (3), whereas with (n)BuMgCl, a mixture of products was formed, including the six-coordinate homoleptic species Mg(N(2)O(Ar))(2) (4). The reaction of [Na(kappa(2)-N(2)O(Ar))(THF)](2) with (n)BuMgCl also gave 3, as did the redistribution reaction of Mg(n)Bu(2) with 4.

Synthesis, structures and reactivity of group 4 hydrazido complexes supported by calix[4]arene ligands.

Reaction of TiCl(2)(Me(2)Calix) with 2 equiv of LiNHNRR' afforded the corresponding terminal hydrazido(2-) complexes Ti(NNRR')(Me(2)Calix) (R = Ph, R' = Ph (1) or Me; R = R' = Me (3)) which were all structurally characterized. The X-ray structure of Ph(2)NNH(2) is reported for comparison. Compound 1 was also prepared from Na(2)[Me(2)Calix] and Ti(NNPh(2))Cl(2)(py)(3).