2 Homometallic Alkoxides

364 Alkoxo and Aryloxo Derivatives of Metals
3.8 Zinc, Cadmium, Indium, Thallium, Germanium, Tin, and Lead
Heterometallic Alkoxides
3.8.1 Zinc
The mixed ligand tetranuclear complex [Zn2Pb2⊲ , 2 -OC2H4OMe⊳4⊲ , 2 -O2CMe⊳4]
has a cyclic structure with alternating four-coordinated (tetrahedral) Zn and sixcoordinated
(distorted octahedral) Pb atoms (Table 4.22, pp. 365–366). 527
3.8.2 Cadmium
Cadmium and Ge(II) and Sn(II) give the trinuclear homoleptic alkoxides [M0⊲ -
OBu t ⊳3M⊲ -OBu t ⊳3M0 ](MDCd, M0 D Ge, Sn) with the typical structure reported
previously with six-coordinated M and three-coordinated M0 . 487 Cadmium is also
present in the trinuclear species [ICd (Sn2OPr i 9 )] which has the well-established core
structure MM0 2⊲ 3-OR⊳2⊲ -OR⊳3 found in numerous other trimetallic complexes. 495,525
3.8.3 Indium and Thallium
Indium(I) and thallium(I) are also involved in the structures of heterometallic alkoxides.
For example in the binuclear complex [Tl⊲ -OBu t ⊳3Sn] both metals are threecoordinated
(pyramidal). 528
Both [In⊲ -OBu t ⊳3Sn] and [Tl⊲ -OBu t ⊳3Sn] moieties can act as Lewis bases by
virtue of the electron lone pairs on each metal atom, which coordinate to other
metal carbonyls to give trimetallic and even tetrametallic mixed ligand heterometallic
alkoxides. 524 Some examples are [Tl⊲ -OBu t ⊳3Sn.Mo⊲CO⊳5], [⊲CO⊳5Mo.In⊲ -
OBu t ⊳3Ge.Mo⊲CO⊳5], [⊲CO⊳4Fe.In⊲ -OBu t ⊳3Sn.Fe⊲CO⊳4], [cis-⊲CO⊳4CrfIn⊲ -OBu t ⊳3
Geg2], [trans-⊲CO⊳4MofSn⊲ -OBu t ⊳3Tlg2], [cis-⊲CO⊳4CrfIn⊲ -OBu t ⊳3Sn.Cr⊲CO⊳5g2]
and [cis-⊲CO⊳4MofIn⊲ -OBu t ⊳3Sn.Cr⊲CO⊳5g2].
3.8.4 Germanium, Tin, and Lead
Several other heterometallic alkoxides involving Ge, Sn, or Pb have been reported.
The dimeric Ge2⊲ -OBu t ⊳2⊲OBu t ⊳2 is coordinated to Ni⊲CO⊳3 in the tetranuclear
[f⊲CO⊳3Nig⊲Bu t O⊳Ge⊲ -OBu t ⊳]2. The double -OBu t bridge is also present in the
dinuclear organometallic alkoxo compound [⊲Bu t O⊳Ge⊲ -OBu t ⊳2Sn, 1 -⊲C5H5⊳] in
which the 1 -C5H5 group and the terminal Bu t O ligand are cis with respect to
the GeO2Sn ring. 530 In the analogous complex [⊲Bu t O⊳Sn⊲ -OBu t ⊳2Pb⊲ 5 -C5H5⊳]
it is noteworthy that the cyclopentadienyl ligand is bonded in pentahapto mode to
the Pb atom. 522 The trinuclear homoleptic complexes [M 0 ⊲ -OBu t ⊳3M⊲ -OBu t ⊳3M 0 ]
(M D Pb, M 0 D Ge, Sn) have the typical structures characteristic of this class of
molecule. 487
Two novel examples of pentanuclear termetallic alkoxo carbonyl complexes are
[⊲Bu t O⊳2Ge⊲ -OBu t ⊳f -Fe⊲CO⊳4gPbf -Fe⊲CO⊳4g⊲ -OBu t ⊳Ge⊲OBu t ⊳2] in which the
inner Pb atom is four-coordinated by two bridging Fe⊲CO⊳4 and two bridging Bu t O
groups whereas the four-coordinated Ge has two terminal Bu t O groups. However, in
[Pbf -OBu t ⊳3Sn.Fe⊲CO⊳4g2] the central Pb atom is six-coordinated entirely by bridging
Bu t O groups and the Sn atoms are bonded to terminal Fe⊲CO⊳4 groups. 531