- Synthesis, properties and structures of eight-coordinate zirconium(IV) and hafnium(IV) halide complexes with phosphorus and arsenic ligands
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Eight-coordinate [MX4(L-L)2] (M = Zr or Hf; X = Cl or Br; L-L =o-C6H4(PMe2)2 or o-C 6H4(AsMe2)2) were made by displacement of Me2S from [MX4(Me2S) 2] by three equivalents of L-L in CH2Cl2 solution, or from MX4 and L-L in anhydrous thf solution. The [MI 4(L-L)2] were made directly from reaction of MI 4 with the ligand in CH2Cl2 solution. The very moisture-sensitive complexes were characterised by IR, UV/Vis, and 1H and 31P NMR spectroscopy and microanalysis. Crystal structures of [ZrCl4{o-C6H4(AsMe2) 2}2], [ZrBr4{o-C6H 4(PMe2)2}2], [ZrI 4{o-C6H4(AsMe2)2} 2] and [HfI4{o-C6H4(AsMe 2)2}2] all show distorted dodecahedral structures. Surprisingly, unlike the corresponding Ti(iv) systems, only the eight-coordinate complex was found in each system. In contrast, the ligand o-C6H4(PPh2)2 forms only six-coordinate complexes [MX4{o-C6H4(PPh 2)2}] which were fully characterised spectroscopically and analytically. Surprisingly the tripodal triarsine, MeC(CH2AsMe 2)3, also produces eight-coordinate [MX 4{MeC(CH2AsMe2)3}2] in which the triarsines bind as bidentates in a distorted dodecahedral structure. There is no evidence for seven-coordination as found in some thioether systems.
- Levason, William,Matthews, Melissa L.,Patel, Bhavesh,Reid, Gillian,Webster, Michael
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