2 Homometallic Alkoxides

432 Alkoxo and Aryloxo Derivatives of Metals
Figure 5.21 Structure of [Fe12⊲ 6-O⊳2⊲ 3-
OMe⊳10⊲ -OMe⊳8⊲O2CCH2Cl⊳5.3Cl0.7⊲MeOH⊳4]
( D 6-oxo, ž D Fe; H atoms omitted).
The dodecanuclear mixed ligand mixed-valence iron oxo-alkoxides [Fe12⊲ 6-
O⊳2⊲OMe⊳18⊲OAc⊳6⊲MeOH⊳4] 177 and[Fe12⊲ 6-O⊳2⊲OMe⊳18⊲O2CCH2Cl⊳5.3Cl0.7⊲MeOH⊳4] 92
exhibit the interesting M12O34 framework (Fig. 5.21) which is related to the M10O28 framework
of the decanuclear manganese complex. 88 The two 6-oxo ligands link ten of the
twelve metal atoms in the dodecanuclear complexes. The mixed-ligand hexanuclear cation
[Fe6⊲ 4-O⊳⊲ -OMe⊳8⊲OMe⊳4⊲tren⊳2] 2 (tren D 2,2 0 ,2 00 -triaminotriethylamine) has a
centrosymmetric structure with octahedrally coordinated Fe(III). 90
5.8.2 Osmium
The mononuclear Os(VI) complex [Os⊲O⊳⊲OC2H4O⊳2] has a square pyramidal structure
with the terminal oxo-ligand occupying the apical site. Similarly in the binuclear complex
[Os2⊲O⊳2⊲ -O⊳2⊲OC2Me4⊳2] square pyramidal coordination of Os(VI) occurs. 178 Addition
of the strong base quinuclidine (C7H13N) produced a dimer exhibiting octahedral
Os(VI) [Os2⊲O⊳2⊲ -O⊳2⊲O2C6H10⊳2⊲C7H13N⊳2]. 77 The square pyramidal coordination
also occurs in the binuclear [Os2⊲O⊳2⊲ -O⊳2⊲OCMe2CH2Bu t ⊳2] 78 , whilst in the mononuclear
[Os⊲O⊳2fOCF⊲CF3⊳C⊲CF3⊳2Og⊲py⊳2] the octahedral Os(VI) atom has a linear
terminal dioxo osmium unit. 179
5.9 Oxo-alkoxides of Nickel, Copper, Aluminium, Tin, and Lead (Including
Heterometallic Compounds) (Table 5.9)
5.9.1 Nickel and Copper
Although no oxo-alkoxide structures involving cobalt or nickel appear to have been
reported there is an interesting octanuclear nickel antimony heterometallic compound
[Ni5Sb3⊲ 4-O⊳2⊲ 3-OEt⊳3⊲ -OEt⊳9⊲OEt⊳3⊲EtOH⊳4] in which the Ni(II) atoms are octahedrally
coordinated, one Sb is four-coordinated (lone pair in the vacant site of a