Robert C. Fay

Zirconium and hafnium

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Stereochemistry and molecular rearrangements of some six-, seven-, and eight-coordinate chelates of early transition metals☆

Abstract This article is a review of the stereochemistry and molecular rearrangements of selected six-, seven-, and eight-coordinate chelates of early transition metals: primarily, metal β-diketonates, dithiocarbamates, and monothiocarbamates. Dihalobis(β-diketonato)metal complexes M(dik) 2 X 2 (M = Ti, Zr, or Hf) generally have an octahedral cis configuration, but Ti(acac) 2 I 2 and V(dik) 2 X 2 exist in solution as an equilibrium mixture of cis and trans isomers. Nuclear magnetic resonance (NMR) line-shape studies show that the dialkoxy complexes cis -Ti(dik) 2 (OR) 2 rearrange by an intramolecular twisting mechanism whereas the closely related O , O −dimethyl dithiophosphates cis -Ti(Me 2 dtp) 2 (OR) 2 undergo metal-ligand bond rupture. The seven-coordinate complexes Zr(acac) 3 Cl, Ti(S 2 CNMe 2 ) 3 Cl, Ti(SOCNEt 2 )Cl, and CpM(S 2 CNMe 2 ) 3 (M = Ti, Zr, or Hf) have a pentagonal bipyramidal structure with the Cl or Cp ligand in an axial position. Eight-coordinate structures and stereoisomers are described

X-Ray crystal structure of tetrakis(8-quinolinolato)zirconium(IV), a dodecahedral M(AB)4 system

The structure of the title compound confirms previous suggestions that the stereochemistry of dodecahedral transition-metal complexes of the type M(AB)4 is dependent upon the electronic configuration of the metal ion.