New diorganoselenium(II) compounds and their behavior toward late transition metals

Hypervalent diorganoselenium(II) compounds of type 1-{2-[(2-(3,5-dimethyl-4,5-dihydro-1H-pyrazol-1-yl)ethyl)selanyl]phenyl}-N,N-dialkylmethanamine, [2-(R2NCH2)C6H4][(3,5-dmpz)CH2CH2]Se, [R = Me (1), Et (2), dmpz = dimethylpyrazole] were obtained by reacting 1-(2-bromoethyl)-3,5-dimethyl-1H-pyrazole [(3,5-dmpz)CH2CH2Br] with alkali metal aryl selenolates of type [2-(R2NCH2)C6H4]SeM (R = Me, M = Na; R = Et, M = Li) in a 1:1 molar ratio. The coordination ability of species 1, as well as that of bis[2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]selane, [(3,5-dmpz)CH2CH2]2Se (3) toward several late transition metals (Pd, Au, Ag) was investigated by reacting the neutral ligands 1 and 3 with PdCl2, AuCl(tht) and AgOTf in a 1:1 molar ratio. The neutral ligands 1–3, as well as the gold(I), silver(I) and palladium(II) adducts [2-(Me2NCH2)C6H4][(3,5-dmpz)CH2CH2)]SeAuCl (4), [(3,5-dmpz)CH2CH2)]2SeAuCl (5), [2-(Me2NCH2)C6H4][(3,5-dmpz)CH2CH2)]SeAgOTf (6), [(3,5-dmpz)CH2CH2)]2SeAgOTf (7) and [(3,5-dmpz)CH2CH2)]2SePdCl2 (8) were characterized by NMR spectroscopy (1H, 13C, 77Se) and mass spectrometry. The reaction between 1 and PdCl2 in a 1:1 molar ratio resulted in the formation of a complex reaction mixture of which the species [2-(Me2NCH2)C6H4SePdCl]2 (9) and 1-(2-chloroethyl)-3,5-dimethyl-1H-pyrazole [(3,5-dmpz)CH2CH2Cl] were unambiguously identified. Single crystal X-ray diffraction studies revealed a monomeric structure with a distorted T-shaped coordination geometry of type (C,N)SeC for the neutral ligand 1 and supramolecular associations based on dimeric units in case of species 9 and 9·0.5CH2Cl2·0.5THF.