Abstract-An efficient algorithm for recurrent neural network training is presented. The approach increases the training speed for tasks where a length of the input sequence may vary significantly. The proposed approach is based on the optimal batch bucketing by input sequence length and data parallelization on multiple graphical processing units. The baseline training performance without sequence bucketing is compared with the proposed solution for a different number of buckets. An example is given for the online handwriting recognition task using an LSTM recurrent neural network. The evaluation is performed in terms of the wall clock time, number of epochs, and validation loss value.

Carbene-stabilized complexes of substituted and unsubstituted phosphorus­(V) fluorides were obtained by oxidative addition of 2,2-difluorobis­(dialkylamines) to phosphorus­(III) halides. Octahedral and hydrolytically stable complexes were obtained in quantitative yields. All compounds were characterized in the solid state by single-crystal X-ray diffraction.

The P(CF(3))(3)CH(3)(+) ion is synthesized as P(CF(3))(3)CH(3)(+)AsF(6)(-) by methylation in a MeF/SO(2)/AsF(5) system or as P(CF(3))(3)CH(3)(+)Sb(2)F(11)(-) in a MeF/HF/SbF(5) system at low temperatures. In contrast to (CF(3))(3)(CH(3))P(+)AsF(6)(-), P(CF(3))(3)CH(3)(+)Sb(2)F(11)(-) is a stable, colorless crystalline solid. A crystal structure determination shows the presence of a slightly distorted tetrahedral phosphonium cation with P-C(F) distances of 188.1-188.7(4) and a P-C(H) bond length of 176.7(4) pm. The phosphonium salt (CF(3))(3)(CH(3))P(+)AsF(6)(-) was also obtained by abstraction of a fluoride ion from the anion [(CF(3))(3)(CH(3))PF(2)](-) salt using AsF(5).

Phosphoranides are interesting hypervalent species which serve as model compounds for intermediates or transition states in nucleophilic substitution reactions at trivalent phosphorus substrates. Herein, the syntheses and properties of stable trifluoromethylphosphoranide salts are reported. [K(18‐crown‐6)][P(CF3)4], [K(18‐crown‐6)][P(CF3)3F], and [NMe4][P(CF3)2F2] were obtained by treatment of trivalent precursors with sources of CF3− or F− units. These [P(CF3)4‐nFn]− (n=0–2) salts exhibit fluorinating (n=1–2) or trifluoromethylating (n=0) properties, which is disclosed by studying their reactivity towards selected electrophiles. The solid‐state structures of [K(18‐crown‐6)][P(CF3)4] and [K(18‐crown‐6)][P(CF3)3F] are ascertained by single crystal X‐ray crystallography. The dynamics of these compounds are investigated by variable temperature NMR spectroscopy.

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