2 Homometallic Alkoxides

X-Ray Crystal Structures of Alkoxo Metal Compounds 361
[W2Fe2⊲ 3-S⊳2⊲ -OPr i ⊳2⊲OPr i ⊳4⊲CO⊳5⊲py⊳] the four metal atoms form a planar rhomboidal
core (Fe–Fe, 2.648 ˚A; W–W, 2.714 ˚A; W–Fe, 2.648 ˚A, 2.699 ˚A). A 3-S ligand
caps each W2Fe and WFe2 triangle above and below the metal plane. In this unsymmetrical
molecule there is one W⊲ -OPr i ⊳W bridge and one W⊲ -OPr i ⊳Fe bridge.
One W has three terminal isopropoxo ligands and its neighbour has only one. 518 The
-C atom produces a linear W C–Ru system in [⊲Bu t O⊳3W C–Ru⊲CO⊳2⊲C5H5⊳] and
the three Bu t O ligands on tungsten are staggered with respect to the three ligands
on ruthenium. 519 The trinuclear complex [⊲C5H5⊳CoW2⊲ -OCH2Bu t ⊳2⊲OCH2Bu t ⊳4]
(W–W, 2.504 ˚A) has two W atoms bridged by two Bu t CH2O ligands and the Co
atoms of the cyclopentadienyl cobalt moiety. 520 A pentanuclear complex was formed
by bridging the Pt(II) atomintrans-Pt⊲PMe2Ph⊳2 to two W2⊲OBu t ⊳5 (W–W, 2.445 ˚A)
units by unsymmetrical , , 3 -C2 dicarbide fragments. 521
3.7 Manganese, Nickel, Copper, and Cobalt Heterometallic Alkoxides
3.7.1 Manganese
The tetranuclear homoleptic dimeric species [⊲Bu t O⊳M 0 ⊲ -OBu t ⊳2M⊲ -OBu t ⊳]2 (M D
Mn, M 0 D Sn; M D Co, M 0 D Ge, Sn; M D Ni, M 0 D Ge, Sn) all have similar
linear configurations with the inner two M atoms four-coordinated and the
outer two M 0 atoms three-coordinated (Table 4.21). 523 The homoleptic hexanuclear
complexes [M2⊲ 3-OEt⊳2⊲ -OEt⊳8Sb4⊲OEt⊳6] (MD Mn, Ni) have the same structure
as the magnesium analogue 488 with a core of two edge-sharing MO6 octahedra
with edge-bridging ⊲EtO⊳Sb⊲ -OEt⊳2 units chelating each M atom and tridentate
(EtO)Sb( 3-OEt)( -OEt) groups bridging the two M atoms. 522
3.7.2 Copper
The dinuclear complex [(acac) Cu⊲ -OSiMe3⊳2Al⊲OSiMe3⊳2] contains an unsymmetrical
Cu ( -OSiMe3⊳2 Al bridged unit with square planar Cu(II) and distorted tetrahedral
aluminium. 433 The mixed ligand complex [CuPb⊲ 3-OC2H4NMe2⊳⊲ -OC2H4NMe2⊳
⊲ -Cl⊳2]1 is a linear polymer formed by bridging centrosymmetrical dimer units
involving five-coordinated (distorted square pyramidal) Cu(II) atoms and distorted
octahedral Pb(II) atoms. The iodo analogue [CuPb⊲ 3-OC2H4NMe2⊳2⊲ -OC2H4NMe2⊳
⊲ -I⊳2]1 has a similar structure. 526
3.7.3 Cobalt
The hexanuclear dimeric mixed ligand termetallic alkoxo complex [⊲ -OBu t ⊳Co⊲ -
OBu t ⊳2Sn⊲OBu t ⊳Fe⊲CO⊳4]2 is of considerable interest. It has a linear array of
4-coordinated metals ⊲Bu t O⊳Sn⊲ -OBu t ⊳2Co⊲ -OBu t ⊳2Co⊲OBu t ⊳2Sn⊲OBu t ⊳ capped at
each end by metal–metal bonded Fe⊲CO⊳4 groups. 523