2 Homometallic Alkoxides

X-Ray Crystal Structures of Alkoxo Metal Compounds 321
homoleptic triangulo-[Re3⊲ -OPr i ⊳3⊲OPr i ⊳6] 386 is in equilibrium with the hydride
[Re3⊲ -OPr i ⊳3⊲OPr i ⊳5H] and acetone. The hydride has the Re3 triangle (ReDRe,
2.368 ˚A) with the three bridging Pr i O groups in the same plane. The terminal
isopropoxide on the Re bonded to the hydride is bent towards the Re3⊲ -O⊳3 plane. 387
Four other Re cluster alkoxo complexes [Re3⊲ -OPr i ⊳3⊲H⊳⊲Cl⊳⊲OPr i ⊳4⊲PMe3⊳]
(Re–Re, 2.376 ˚A), [fRe3⊲ -OPr i ⊳3Cl⊲OPr i ⊳4g⊲ -Cl⊳2] (Re–Re, 2.384 ˚A), [Re3⊲ -
OCH2Bu t ⊳3⊲OCH2Bu t ⊳6⊲PMe3⊳] (Re–Re, 2.387 ˚A), and [Re3⊲ -OCH2Bu t ⊳2⊲ -
Cl⊳⊲OCH2Bu t ⊳4Cl⊲PMe3⊳2] (Re–Re, 2.449 ˚A) have also been reported. 533
2.13 Alkoxides of Iron and Osmium
Relatively few structures of the iron group alkoxo compounds have been reported. With
the bulky triphenylmethoxo ligand the mononuclear Fe(II) complex [Fe⊲OCPh3⊳2⊲thf⊳2]
was obtained. It has an irregular four-coordinate geometry with a very wide O�FeO
(alkoxo) angle (154.4 Ž ) and an acute O�FeO (THF) angle (93.6 Ž ). 377
The Os(IV) Schiff base alkoxo complex [Os⊲OPr i ⊳2⊲salen⊳] (salenD ethylene-bissalicylidineimine)
has the trans octahedral configuration (Table 4.13). 388 In the Os(VI)
nitrido chlorodiolato anions in the compounds ⊲PPh4⊳[OsNCl2⊲O2C2H4⊳] and
⊲PPh4⊳[OsNCl2⊲O2C2Me4⊳] the nitride atom occupies the apical position in a distorted
square pyramid with cis chlorines and the chelating diolate forming the base. 389 The
structures of numerous oxo alkoxo complexes of iron and osmium are detailed in
Chapter 5.
2.14 Alkoxides of Cobalt, Rhodium, and Iridium
2.14.1 Cobalt
The structure of the Co(II) derivative of glycerol [CofOCH2CH⊲O⊳CH2OHg]n
revealed a chain polymeric structure with the dinegative glycerolate
anion acting as a chelating and bridging ligand giving the cobalt ions
a TBP five-coordination. 390 Another mononuclear octahedral Co(II) complex
[CofOC⊲CF3⊳2CH2C⊲Me⊳DN⊲C2H4O⊳2C2H4NDC⊲Me⊳CH2C⊲CF3⊳2Og] was formed
by the template condensation of hexafluoro diacetone alcohol with 1,2-bis(2aminoethoxyethane).
The hexadentate ligand gave a distorted octahedral configuration
with alkoxo oxygens cis, imine nitrogen trans, and ether oxygens cis to one another. 391
The tridentate fluorinated sulphur-containing diol HOC⊲CF3⊳2CH2SCH2C⊲CF3⊳2OH
gavethefive-coordinated(TBP)Co(II)complex[CofOC⊲CF3⊳2CH2SCH2C⊲CF3⊳2Og⊲py⊳2]
with pyridine as supplementary ligands. The sulphur donor and one pyridine ligand occupy
the axial positions. 392
By using very bulky ligands the anionic complex [Co⊲OCBu t 3 ⊳2fN⊲SiMe3⊳2g]
was obtained with Co(II) in a planar three-coordinated configuration. 393 With the
triphenylmethoxo ligand the mononuclear four-coordinated [Co⊲OCPh3⊳2⊲thf⊳2] and
the dinuclear three-coordinated [Co2⊲ -OCPh3⊳2⊲OCPh3⊳2] neutral complexes were
characterized. The binuclear complexes [Co2f -OC⊲C6H11-c⊳3g2fOC⊲C6H11-c⊳3g2]and
[Co2( -OSiPh3⊳2⊲OSiPh3⊳2⊲thf⊳2] exhibited three-coordinated and four-coordinated
Co(II) respectively. 394