380415-02-1Relevant articles and documents
The isolation and chemistry of niobium and tantalum dimethylamides containing mono- and di-aryloxide ancillary ligands
Schweiger, Scott W.,Tillison, Dana L.,Thorn, Matt G.,Fanwick, Phillip E.,Rothwell, Ian P.
, p. 2401 - 2408 (2007/10/03)
The salt complex [Me2NH2][Ta(NMe2)2Cl4] 4 has been isolated from the reaction of [Ta2Cl10] with Me2NH and the anion shown to contain mutually cis-dimethylamido ligands. 4 reacts with Me2NH and pyridine to produce the neutral adducts mer,cis-[Ta(NMe2)2Cl3(HNMe2)] 1 (known compound) and [Ta(NMe2)2Cl3(py)] 5. The solid state structure of [Ta(NMe2)2Cl3(py-4Ph)] 7 shows a mer,cis arrangement of Cl and NMe2 groups. The addition of 2,3,5,6-tetraphenyl- or 2,6-di-isopropyl-phenol (2 equiv) to solutions of 1 in benzene was found to produce a mixture of two isomers each containing a residual Ta-NMe2 and Ta-NHMe2 group. These were formulated as [Ta(OAr)2Cl2(NMe2)-(NHMe2)] with the coordinated amine trans to the Ta-NMe2 group and aryloxide ligands either mutually cis or trans. The cis isomer was found to thermally convert to the trans form. The trans isomers [M(OAr)2Cl2(NMe2)(NHMe2)] (M = Ta, OAr = 2,3,5,6-tetraphenyl- or 2,6-di-isopropyl-phenoxide; M = Nb, OAr = 2,3,5,6-tetraphenylphenoxide) are obtained in high yield by treatment of the corresponding tri(chlorides) [M(OAr)2Cl3] with excess Me2NH. The isomorphous/isostructural compounds [M(OC6HPh4-2,3,5,6)2Cl2(NMe2 )(py)] (M = Nb, Ta) were structurally characterized and shown to contain the pyridine ligand trans to the Ta-NMe2 group with mutually trans aryloxides. Addition of 2,2′-methylenebis(6-phenylphenol) {(HOC6H3Ph)2CH2} to 1 resulted in formation of the compound [Ta{(OC6H3Ph)2CH2}Cl2(NMe 2)(HNMe2)] 15. The solid state structure of 15 shows the nitrogen atoms to be mutually trans with cis aryloxide oxygen atoms. The eight-membered dioxametallacycle ring is puckered with the methylene bridge folded up towards the Ta-NMe2 group. The reaction pathways leading to these products are discussed.
