2 Homometallic Alkoxides

2.16.2 Silver and Gold
X-Ray Crystal Structures of Alkoxo Metal Compounds 331
Although several alkoxo complexes of Ag(I) andAu(I) have been prepared, usually
stabilized by organophosphine supplementary ligands, no X-ray structures have yet
been reported.
2.17 Alkoxides of Zinc, Cadmium, and Mercury
2.17.1 Zinc
The first organozinc alkoxo compound structurally characterized was the tetrameric
[Me4Zn4⊲ 3-OMe⊳4] (Fig. 4.56) which has the cubane-like Zn4O4 core with tetrahedrally
coordinated zinc (Table 4.16, p. 332). 437 The tert-butoxide has been shown to
adopt a similar structure in [Me4Zn4⊲ 3-OBu t ⊳4]. 438
In the heptanuclear molecule [Zn⊲ 3-OMe⊳6⊲ZnMe⊳6], which is centrosymmetric,
two Zn4O4 cubanes are fused through one octahedrally coordinated zinc giving a
dicubane structure. 439 The steric effect of bulky ligands led to the formation of the
dimer [Zn2⊲ -OCEt3⊳2fN⊲SiMe3⊳2g2] containing three-coordinated (trigonal planar)
zinc. 440 Using the tridentate functionalized alkoxo ligand the mononuclear octahedral
complex [Zn⊲1,4,7- 3 -OCHDCNMeCH2CH2NMe2⊳2] was obtained with the donor
oxygen atoms trans to one another. 440
The dimeric complex [EtZnf , 2 -OC⊲Me⊳DCHNEtBu t g2ZnEt] has four-coordinated
zinc. 441 The asymmetric dimer [f 2 -⊲Bu t O⊳3SiOgZnf -OSi⊲OBu t ⊳3gf , 2 -
OSi⊲OBu t ⊳3gZnfOSi⊲OBu t ⊳3g] is of interest in exhibiting four different coordinating
modes for the tri-tert-butoxy siloxo ligand (Fig. 4.57). 442
2.17.2 Cadmium
Two alkoxo cadmium structures have been reported. The bifunctional methoxyethoxo
ligand gave rise to the nonanuclear complex [Cd9⊲OC2H4OMe⊳18]⊲MeOC2H4OH⊳2
containing six-coordinated metal atoms. 443 The ligand is present in five different
coordination modes as in [Cd9⊲ 3, 2 -OR⊳6⊲ 3, 1 -OR⊳2⊲ , 2 -OR⊳6⊲ , 1 -OR⊳2⊲OR⊳2]
(OR D OC2H4OMe) with the hydrogen of two lattice alcohol molecules bonded
to the terminal alkoxo groups (Fig. 4.58). By using the bulky potentially
C C
C
Zn
O
C
C
O
Zn
Zn
C
O
Zn
Figure 4.56 Structure of [MeZn⊲ 3-
OMe⊳]4 (H atoms omitted).
O
C
C