Sw. Schweiger et al., Studies of the alkylation of niobium and tantalum halides containing 2,6-diarylphenoxide ancillary ligation, J CHEM S DA, (13), 2001, pp. 2020-2031
Citations number
55
Categorie Soggetti
Inorganic & Nuclear Chemistry
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
The mixed halo(aryloxide) compounds [Nb{OC6H(C6H4Me-4)(2)-2,6-Ph-2-3,5}(2)C
l-3], [Ta(OC6HPh4-2,3,5,6)(2)Br-3] and [Nb(OC6HPh4-2,3,5,6)(2)I-3] have bee
n isolated and structurally characterized. Although the chloride and bromid
e compounds are square pyramidal with an axial aryloxide, the tris(iodide)
compound was determined to adopt a trigonal bipyramidal geometry in the sol
id state with trans, axial aryloxides. The reaction of the tantalum tris(ch
lorides) [Ta(OC6H3Ph2-2,6)(2)Cl-3] or [Ta(OC6HPh4-2,3,5,6)(2)Cl-3] with RMg
Cl (R = CH2Ph or CH2SiMe3) forms the corresponding mono-, bis- and tris-(al
kyls), all shown to adopt a trigonal bipyramidal geometry in the solidstate
with trans, axial aryloxides. In contrast the mono(cycloalkyl) compounds [
Ta(OC6H3Ph2-2,6)(2)(CnH2n+1)Cl] (n = 5, 6) were found to adopt square pyram
idal structures in the solid state with the alkyl group axial (metal pseudo
-equatorial) and mutually cis aryloxides. The alkylation of the correspondi
ng niobium substrate [Nb(OC6HPh4-2,3,5,6)(2)Cl-3] with Me3SiCH2MgCl produce
d a complex mixture of products. Careful analysis including the use of Si-2
9 NMR identified the d(0)-alkyl products [Nb(OC6HPh4-2,3,5,6)(2)Cl-2(CH2SiM
e3)], [Nb(OC6HPh4-2,3,5,6)(2)Cl(CH2SiMe3)(2)] and [Nb(OC6HPh4-2,3,5,6)(2)(C
H2SiMe3)(3)],the alkylidene compounds [Nb(OC6HPh4-2,3,5,6)(2)Cl(=CHSiMe3)]
and [Nb(OC6HPh4-2,3,5,6)(2)(CH2SiMe3)(=CHSiMe3)] and the d(1)-alkyl [Nb(OC6
HPh4-2,3,5,6)(2)(CH2SiMe3)(2)]. Treating a benzene solution of [Nb(OC6HPh4-
2,3,5,6)(2)(CH2SiMe3)(2)]/[Nb(OC6HPh4-2,3,5,6)(2)(CH2SiMe3)(=CHSiMe3)] and
PMe3 at 85 degreesC under 1200 psi of H-2 produced deep-green crystals of t
he d(1)-di(hydride) [Nb(OC6HCy2-2,6-Ph-2-3,5)(2)(H)(2)(PMe3)(2)].