Dialkylamides tantalum

Niobium and tantalum dialkylamides can easily undergo substitution or insertion reactions, as well as C—H activation. Substitution reactions have been used to obtain dialkylamides262 or dithiolenes.275 Aminolysis reactions, for instance, were assumed to occur via a simple associative mechanism (equation 6).276... 

A series of homoleptic Nbrv dialkylamido compounds has been obtained as highly air sensitive liquids by spontaneous reduction of [Nb(NR2)5] (R = Et, Pr", Bu" Table 41). Aminolysis of either Nbv or NbIV dialkylamides provided mixed species.256 The existence of quadrivalent tantalum dialkylamides is still questionable. [Ta(NEt2)4] was reported to have been detected during the thermolysis of [Ta(NEt2)5],263 which led predominantly to the Tav nitrene (2 Section 34.2.3.4.ii), but other workers could not find any evidence for its formation in a similar experiment.282 [Ta(NMeBu)4] has been reported to be formed in the decomposition of the corresponding pentavalent dialkylamide. 

A similar amine exchange on tantalum dialkylamides with primary amines again leads to an imido derivative (equation 40).6568... 

Under the attack of one equivalent OH in H2O, MeO in MeOH, or pure NH3 a silicon vertex was removed from the c/oso-cluster l.[21 A plausible mechanistic sequence for the degradation involves as the first step formation of an adduct consisting of the nucleophile and the c/oso-cluster. Afterwards this adduct should react with a protic solvent to give the isolated reaction product. In order to get indications for the expected adduct we studied the attack of nucleophiles in an aprotic solvent. Three types of nucleophiles were studied in this reaction. In the case of the dialkylamide nucleophile best results were achieved from the reaction of the close-cluster with transition metal amides of zirconium and tantalum,17,81 The anionic adduct cluster features a dialkylamide bridging both silicon centres of the silaborane cluster. 

Tantalum and niobium atoms were incorporated in the silaborate cluster by reaction of the dialkylamides with the silaborate 2. 

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