2 Homometallic Alkoxides

356 Alkoxo and Aryloxo Derivatives of Metals
Figure 4.62 Structure of [Laf , 4 -⊲OC2H4⊳3Ng2fNb⊲OPr i ⊳4g3]
( D O; H atoms omitted).
pp. 358–360). 508 In the trinuclear complex [f⊲Pr i O⊳2Ti⊲ -OPr i ⊳Ti⊲OPr i ⊳2g⊲ 3-OPr i ⊳2⊲ -
OPr i ⊳2CuCl] there is an isosceles triangle of metal atoms capped by ⊲ 3-OPr i ⊳ ligands
above and below the metal plane and bridged by three ⊲ -OPr i ) ligands in the plane. This
[MM 0 2 ⊲ 3-OR⊳2⊲ -OR⊳3] core is typically found in heterometallic and homometallic
alkoxide complexes (Figs 4.5 and 4.25). In this complex each six-coordinated Ti has
cis terminal alkoxo ligands whilst the five-coordinated (distorted TBP) Cu(II) has one
terminal chloride. 493
A similar structure was reported for [ICdfTi2⊲OPr i ⊳9g] with a five-coordinated Cd
atom. 495 Another example is found in the cationic complex [SnfTi2⊲OPr i ⊳9g] C ,inwhich
the Sn(II) atom has no terminal ligands but, assuming its lone pair of electrons occupies
an equatorial position, it has a pseudo-trigonal bipyramidal configuration. Interestingly
the Sn- 3-OR bond distances are shorter than the Sn- -OR bonds. 509
A very remarkable compound is the salt [Ti3⊲OPr i ⊳11] C [Sn2I6⊲OPr i ⊳3] which contains
discrete homometallic ions. The cation has the familiar [M3⊲ 3-OR⊳2⊲ -OR⊳3⊲OR⊳6]
structure whilst the anion has the confacial bi-octahedral structure [I3Sn⊲ -OR⊳3SnI3]. 509
In the pentanuclear complex [fTi⊲OPr i ⊳4gfOPb4⊲NBu t ⊳3g] the cubane-like [OPb4⊲ 3-
NBu t ⊳3] moiety is coordinated to the five-coordinated (TBP) titanium through its
oxygen so that strictly speaking it is a heterometallic oxoalkoxide. 510
3.4.2 Zirconium
The tetranuclear mixed ligand complex [Zr2Co2⊲ 3-OPr n ⊳2⊲ -OPr n ⊳4⊲OPr n ⊳4⊲acac⊳2]
contains distorted octahedral Zr(IV) and trigonal bipyramidal Co(II). It is a centrosymmetrical
molecule containing an edge-shared bi-octahedral [Zr2⊲ -OR⊳2⊲OR⊳8] unit
that incorporates two Co (acac) moieties, which are bridged by one 3-OR and two
-OR groups above and below the Zr2⊲ -OR⊳2 plane. 511