2 Homometallic Alkoxides

X-Ray Crystal Structures of Alkoxo Metal Compounds 335
In the binuclear Cr(II) complex the bulky But 3CO ligand restricts the chromium
to three-coordination, 27 whilst in [Li⊲ -OCBu t 3⊳2MnfN⊲SiMe3⊳2g] the lithium is twocoordinated
and the Mn(II) is three-coordinated. 460 In the trinuclear bromo complex
[⊲thf⊳2Li⊲ -Br⊳2Mn⊲ -OCBu t 3⊳2Li] one Li is two-coordinated and the other is fourcoordinated
like the Mn(II). 460
In the Co(II) complex [⊲thf⊳3Li⊲ -Cl⊳Co⊲OCBu t 3⊳2] the Li is four-coordinated and the
Co three-coordinated (trigonal planar), but in [Li⊲ -OCBu t 3⊳2CofN⊲SiMe3⊳2g] with the
very bulky silylamide ligand the Li is two-coordinated and the Co three-coordinated. 393
Two trinuclear cobaltodisiloxanes have been reported. In [⊲tmeda⊳Lif -O⊲SiPh2O⊳2gCo-
-Li⊲tmeda⊳] the Co is in a distorted (flattened) tetrahedral configuration and the lithiums
are pseudo-tetrahedral, whilst in [⊲py⊳2Lif -O⊲SiPh2O⊳2g2⊲py⊳Co -CoCl⊲py⊳] one Co
is five-coordinated (distorted square pyramidal) with a pyridine ligand occupying the
apical position. 461
A centrosymmetrical molecule is given by [⊲PriOH⊳Lif , 2- OCH⊲Me⊳CH2NMe2g2NiCl]2 in which the lithiums are in distorted tetrahedral
configurations and the Ni(II) ions are five-coordinated (distorted square pyramidal)
by two chelating dimethylamino propanolate ligands and a terminal chloride. 462
The Cu(II)ionin[⊲py⊳2Lif , 2-O⊲SiPh2g2Cu -Li⊲py⊳2] is in a distorted square planar
configuration and the Li is pseudo-tetrahedral. 463 Square planar Cu(II) is also found in
the diolato complex [⊲H2O⊳2Lif , 2-O2⊲CH⊳2⊲CH2⊳2Og2Cu -Li⊲H2O⊳2] with pseudotetrahedral
lithium. 464 The preference of Cu(I) for linear two-coordination is evident
in [Li4Cu4⊲ 3-OBu t ⊳4⊲ -OBu t ⊳8] which has three-coordinated Li in a large structure
(Fig. 4.59). 465
Lithium also forms heterometal alkoxides with nontransition metals such as Al or
Sn. In [⊲Et2O⊳Lif -OC⊲Me⊳Ph2g⊲ -OC6H2But 2Me-2,4,6⊳AlMe⊲OC6H2But 2Me-2,4,6⊳] the Al is pseudo-tetrahedral and the Li three-coordinated, 466 whereas in [⊲thf⊳2Li⊲ -
OCEt3⊳2Al⊲OCEt3⊳Cl] the lithium is pseudo-tetrahedral. 467
In the Sn(II) complex [Li2⊲ 3-OBu t ⊳2⊲ -OBu t ⊳4Sn2] the lithiums are four-coordinated
but the tin atoms are three-coordinated (pyramidal) with a Li2O6Sn2 cage built from two
seco-norcubane Sn2Li2O3 units sharing a Li2O2 four-membered ring. 468 In the Sn(IV)
Figure 4.59 Structure of [Li4Cu4⊲ 3-
OBu t ⊳4⊲ -OBu t ⊳4] ( D Cu, D Li,
D O; H atoms omitted).