Novel Tailoring Reaction for Two Adjacent Coordinated Nitriles Giving Platinum 1,3,5-Triazapentadiene Complexes

The tailoring reaction of the two adjacent nitrile ligands in cis-[PtCl2(RCN)2] (R = Me, Et, CH2Ph, Ph) and [Pt(tmeda)(EtCN)2][SO3CF3]2 (8·(OTf)2; tmeda = N,N,N′,N′-tetramethylethylenediamine) upon their interplay with N,N′-diphenylguanidine (DPG; NHC(NHPh)2), in a 1:2 molar ratio gives the 1,3,5-triazapentadiene complexes [PtCl2{NHC(R)NHC(R)NH}] (1–4) and [Pt(tmeda){NHC(Et)NHC(Et)NH}][SO3CF3]2 (10·(OTf)2), respectively. In contrast to the reaction of 8·(OTf)2 with NHC(NHPh)2, interaction of 8·(OTf)2 with excess gaseous NH3 leads to formation of the platinum(II) bis(amidine) complex cis-[Pt(tmeda){NHC(NH2)Et}2][SO3CF3]2 (9·(OTf)2). Treatment of trans-[PtCl2(RCN)2] (R = Et, CH2Ph, Ph) with 2 equiv of NHC(NHPh)2 in EtCN (R = Et) and CH2Cl2 (R = CH2Ph, Ph) solutions at 20–25 °C leads to [PtCl{NHC(R)NC(NHPh)NPh}(RCN)] (11–13). When any of the trans-[PtCl2(RCN)2] (R = Et, CH2Ph, Ph) complexes reacts in the corresponding nitrile RCN with 4 equiv of DPG at prolonged reaction time (75 °C, 1–2 days), complexes containing two bidentate 1,3,5-triazapentadiene ligands, i.e. [Pt{NHC(R)NC(NHPh)NPh}2] (14–16), are formed. Complexes 14–16 exhibit strong phosphorescence in the solid state, with quantum yields (peak wavelengths) of 0.39 (530 nm), 0.61 (460 nm), and 0.74 (530 nm), respectively. The formulation of the obtained complexes was supported by satisfactory C, H, and N elemental analyses, in agreement with FAB-MS, ESI-MS, IR, and 1H and 13C{1H} NMR spectra. The structures of 1, 2, 4, 11, 13, 14, 9·(picrate)2, and 10·(picrate)2 were determined by single-crystal X-ray diffraction.