Amidouranium Tetraphenylborates

This is an area developed by Ephritikhine and coworkers the majority (66-71) of the salts are monoanionic U amides.The synthetic strategy was based on the amine elimination reactions of Equation (5.9), as summarised in Table 5.1. Erom Table 5.1 it is evident that NEt2 is more readily displaced from U than N(SiMe3)2 (67), Cp (68), cot (69,70,73), or Cl (71) upon protolysis. 

The uranium environment in each of the well separated cations of 66a, 68,69,72a, and 73 is distorted/ar-octahedral (66a),distorted trigonal bipyramidal (O-U-O, 157°) (68), ° five-coordinate with angles at U ranging from 73° (01 -U-02) to 133° (centroid of cot-U-N) (69a), pentagonal bipyramidal (5N atoms 0.33 A out of the mean plane) (72a), or distorted tetrahedral (73) ° each of Cp or cot is regarded as occupying a single coordination site. 

AmidoU tetraphenylborate Substrate X-ray structure/Comments References 

Using the same catalyst 66, the hydrosilylation of a terminal alkyne RC=CH with PhSiHa at ambient temperature afforded a mixture of cis- and rrani-RCH=C(H)Si(H)2Ph, CH2= C(R)Si(H)2Ph, RCH=CH2 and RCsCSi(H)2Ph at higher temperatures, the corresponding doubly hydrosilylated compounds RCH=C Si(H)2Ph 2 were also formedThe salt [UH(NEt2)2] [BPh4] (74) was implicated as a crucial intermediate  

The catalytic activity of 66 was also explored in the context of the dehydrocoupling of RNH2 (RR NH less reactive) with PhSiHa For the case of R = Pr Pr or Bu , the aminosilanes PhSi(H)3. N(H)R ( = 1, 2, or 3) were obtained 74 was again postulated 

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Two reactions of [U(NEt2)3][BPh4] (66) in thf-dg have been reported. Scheme 5.20, ° but the most extensive studies of reactivity of amidouranium tetraphenylborates have been of [U(cot)(NEt2)(thf)2] [BPl ] (69), Scheme 5.21 qq thebis-... 

The amidouranium tetraphenylborate [U(NEt2)3][BPh4] (66) was an effective catalyst for the selective dimerisation of terminal alkynes, as shown in Scheme 5.23 a suggested key intermediate was [U(C=CR)(NEt2)2(r 2-CH=CR)][BPh4]. ,io3... 

Table 5.1 Amidouranium tetraphenylborates from reactions of an amidoU compound with [NHEtjJfBPhJ in thf... 

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