2 Homometallic Alkoxides

330 Alkoxo and Aryloxo Derivatives of Metals
being four-coordinated (compressed tetrahedral) and the outer ones three-coordinated
(trigonal planar). The trinuclear species [Cu3⊲OBu t ⊳4fOC⊲CF3⊳3g2] probably has a
linear structure too. 431 In the tetranuclear compound the bridging Cu–O bonds to the
three-coordinated Cu are shorter (1.86 ˚A) than those to the four-coordinated copper
(av. 1.95 ˚A). The mononuclear complexes [Cu⊲hfip⊳2(tmed)] and [Cu⊲hftb⊳2⊲tmed⊳]
(hfip D OCH⊲CF3⊳2, hftbD OC⊲Me⊳⊲CF3⊳2, tmedD Me2NC2H4NMe2) have distorted
square planar Cu(II) and are appreciably volatile. 432
The mixed ligand tetranuclear species [Cu4⊲ 3, 1 -OC2H4OPr i ⊳4⊲acac⊳4] has a
cubane-like Cu4O4 core and with the chelating acac ligand each Cu(II) is fivecoordinated
(distorted square pyramidal). 433
The tridentate ligand 1,1-bis-(2-pyridyl)-1-methoxy methoxide reacted with Cu(II)
in methanol in the presence of pyrazolate ions to form the tetranuclear complex
[Cu4L2⊲prz⊳4⊲MeOH⊳2] 2C ⊲ClO4⊳ 2 (L D MeOC⊲C5H4N⊳2O; prz D C3H3N2) inwhich
two coppers are square planar and two are square pyramidal (Fig. 4.55). The di-cation
is centrosymmetric, consisting of a dinuclear unit with two coppers bridged by the
bridging bis-chelating alkoxo ligand and one bridging pyrazolate ion, linked to another
dinuclear unit by two interdimer bridging pyrazolates. The five-coordinated Cu has a
coordinated methanol ligand. 434 The tridentate aminoalkoxo ligand (Me2NCH2⊳2CHO
which also acts as a bis-chelating bridging ligand forms the trinuclear complex
[Cu3f -OCH⊲CH2NMe2⊳2g4⊲MeOH⊳Cl2] inwhichthe3five-coordinated Cu(II) atoms
are in a nonlinear array. 435
A novel tetranuclear structure is exhibited by the mixed ligand complex
[Cu4⊲ -OMe⊳4⊲ , 2 -O2CMe⊳4]. The four copper atoms in a plane are alternately
double bridged by -OMe and , 2 -O2CMe ligands, and the molecule exhibits strong
antiferromagnetic behaviour. 436
Figure 4.55 Structure of [Cu4f -
OC⊲C5H4N⊳2⊲OMe⊳g2⊲ -N2C3H3⊳4⊲MeOH⊳2] 2C
( D Cu, D O; D N; H atoms omitted).