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(NMe2)(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.