2 Homometallic Alkoxides

X-Ray Crystal Structures of Alkoxo Metal Compounds 329
2.16 Alkoxides of Copper, Silver, and Gold
2.16.1 Copper
The structures of various Cu(I) and Cu(II) alkoxo complexes have been reported
(Table 4.15).
The first homoleptic Cu(I) alkoxide structure determined was the tetranuclear tertbutoxide
[Cu4⊲ -OBu t ⊳4] which has a planar Cu4O4 ring (Fig. 4.54) with linear
two-coordinated copper rather than the cubane-like structure which might have been
anticipated. 420 Addition of PPh3 produced the dimer [Cu2⊲ -OBu t ⊳2⊲PPh3⊳2] with
three-coordinated copper. The Cu2P2O2 core is not coplanar owing to the dihedral
angle of 143.4 Ž about the O....Oaxis. 421 Likewise the triphenylsiloxo group gave
the tetranuclear [Cu4⊲ -OSiPh3⊳4] with linear two-coordinated Cu(I) and the dinuclear
[Cu2⊲ -OSiPh3⊳2⊲PMe2Ph⊳2]. 422 Even the very bulky ⊲Bu t O⊳2⊲Ph⊳SiO ligand produces
the tetranuclear [Cu4f -OSi⊲OBut⊳2Phg4] structure with the planar Cu4O4 core and
linear two-coordinated Cu(I). 423
Numerous structures of alkoxo copper(II) complexes have been determined.
The tridentate diolate ligands [O⊲CH2⊳4NDC⊲Me⊳CH2C⊲CF3⊳2O] 2 and
[O⊲CH2⊳3NDC⊲Me⊳CH2C⊲CF3⊳2O] 2 gave binuclear complexes [Cu2f -
O⊲CH2⊳nNDC⊲Me⊳CH2C⊲CF3⊳2Og2] (n D 4, 3). Each molecule has square planar
Cu(II) atoms with an essentially near planar ONCu⊲ -O⊳2CuNO framework. 424
In the dinuclear fluorinated iminoalkoxo complex [Cu2f -
OC⊲CF3⊳2CH2C⊲Me⊳DN⊲CH2⊳5NDC⊲Me⊳CH2C⊲CF3⊳2Og2], in which the tetradentate
ligands bridge the two copper(II) centres, the coordination around the metal
is distorted planar towards tetrahedral. 425 Other related Cu(II) complexes are
[CufOC⊲CF3⊳2CH2CHNHRg2] (RD menthyl), 426 ⊲PPh4⊳ C 2 [CufOC⊲CF3⊳2⊲OH⊳g4] 2 , 427
[CufO2C⊲CF3⊳2gL] (L D triazacyclododecene), 406 [CufOC⊲CF3⊳2OC⊲CF3⊳2Og
⊲Me2NC2H4NMe2⊳], 428 and [CufOC⊲CF3⊳2CH2C⊲O⊳DCHC⊲CF3⊳2OHg
⊲Me2NC2NMe2⊳]. 407 Bis-chelated complexes have been obtained using aminoalkoxo
ligands, e.g. [CufOCH2C⊲Me⊳2NH2g2], 429 [CufOCH⊲Me⊳CH2NMe2g2], and
[CufOCH2CH2N⊲Me⊳CH2CH2NMe2g2]. 430 In the latter compound the Cu(II) isfivecoordinated
(distorted square pyramidal) because one ligand is tridentate and the other
one bidentate. The mixed ligand complex [f⊲CF3⊳3COgCu⊲ -OBu t ⊳2Cu⊲ -OBu t ⊳2
Cu⊲ -OBu t ⊳2CufOC⊲CF3⊳3g] has a novel linear structure with the inner copper atoms
Figure 4.54 Structure of
[Cu4⊲ -OBu t ⊳4] (Hatoms
omitted).