title: Amidrazone complexes from a cascade platinum(II)-mediated reaction between amidoximes and dialkylcyanamides.
abstract: The aryl amidoximes R'C6H4C(NH2)═NOH (R' = Me, 2a; H, 2b; CN, 2c; NO2, 2d) react with the dialkylcyanamide platinum(II) complexes trans-[PtCl2(NCNAlk2)2] (Alk2 = Me2, 1a; C5H10, 1b) in a 1:1 molar ratio in CHCl3 to form chelated mono-addition products [3a-h]Cl, viz. [PtCl(NCNAlk2){NH═C(NR2)ON═C(C6H4R')NH2}]Cl (Alk2 = Me2; R' = Me, a; H, b; CN, c; NO2, d; Alk2 = C5H10; R' = Me, e; H, f; CN, g; NO2, h). In the solution, these species spontaneously transform to the amidrazone complexes [PtCl2{NH═C(NR2)NC(C6H4R')NNH2}] (7a-h; 36-47%); this conversion proceeds more selectively (49-60% after column chromatography) in the presence of the base (PhCH2)3N. The observed reactivity pattern is specific for NCNAlk2 ligands, and it is not realized for conventional alkyl- and arylnitrile ligands. The mechanism of the cascade reaction was studied by trapping the isocyanate intermediates [PtCl(NCO){NH═C(NR2)NC(C6H4R')NNH2}] (5a-h) and also by ESI-MS identification of the ammonia complexes [PtCl(NH3){NH═C(NR2)NC(C6H4R')NNH2}](+) ([6a-h](+)) in solution. The complexes [3a]Cl, [3c-h]Cl, 5a-h and 7a-h were characterized by elemental analyses, high resolution ESI-MS, IR, and (1)H NMR techniques, while 5b, 5d, 5g, 7b, and 7e were also studied using single-crystal X-ray diffraction.
authors.affiliation: Department of Chemistry, Saint Petersburg State University, Universitetsky Pr. 26, 198504 Stary Petergof, Russian Federation.
authors.forename: Dmitrii S
authors.initials: DS
authors.lastname: Bolotin
authors.forename: Nadezhda A
authors.initials: NA
authors.lastname: Bokach
authors.forename: Andreii S
authors.initials: AS
authors.lastname: Kritchenkov
authors.forename: Matti
authors.initials: M
authors.lastname: Haukka
authors.forename: Vadim Yu
authors.initials: VY
authors.lastname: Kukushkin
mesh_terms: D000577:Amides / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D009944:Organoplatinum Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010091:Oximes / Q000737:chemistry*
chemical_list: D000577:Amides; D009944:Organoplatinum Compounds; D010091:Oximes