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2 Homometallic Alkoxides

2 Homometallic Alkoxides

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298 Alkoxo and Aryloxo Derivatives of Metals<br />

Figure 4.50 W4⊲ 3-O⊳2⊲ -O⊳4O10 core<br />

structure of [W4⊲ 3-OR⊳2⊲ -OR⊳4⊲OR⊳10]<br />

(R D Me, Et; R groups omitted).<br />

Figure 4.51 Structure of [W4⊲ -OPr i ⊳4⊲OPr i ⊳8]<br />

( D O; H atoms omitted).<br />

(distorted TBP) and two (bonded to pyridine) are distorted octahedral. 372 Without the<br />

coordinated pyridines all 4 W atoms are five-coordinated (TBP) in [W4⊲ 4-OPr i ⊳2⊲ 3, 2 -<br />

CO⊳2⊲OPr i ⊳10]. 333<br />

In [W4⊲ -OEt⊳6⊲ -CSiMe3⊳2⊲OEt⊳8] there is again a zig-zag chain of tungsten atoms<br />

with alternating short (2.51 ˚A) and long (3.51 ˚A) W–W distances. The outer two metal<br />

atoms are in confacial bi-octahedral units which are edge bridged by the -CSiMe3<br />

ligands. 364

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