The tailoring reaction of the two adjacent nitrile ligands in cis-[PtCl(2)(RCN)(2)] (R = Me, Et, CH(2)Ph, Ph) and [Pt(tmeda)(EtCN)(2)][SO(3)CF(3)](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 [PtCl(2){NHC(R)NHC(R)=NH}] (1-4) and [Pt(tmeda){NHC(Et)NHC(Et)NH}][SO(3)CF(3)](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 NH(3) leads to formation of the platinum(II) bis(amidine) complex cis-[Pt(tmeda){NH=C(NH(2))Et}(2)][SO(3)CF(3)](2) (9.(OTf)(2)). Treatment of trans-[PtCl(2)(RCN)(2)] (R = Et, CH(2)Ph, Ph) with 2 equiv of NH=C(NHPh)(2) in EtCN (R = Et) and CH(2)Cl(2) (R = CH(2)Ph, Ph) solutions at 20-25 degrees C leads to [PtCl{NH=C(R)NC(NHPh)=NPh}(RCN)] (11-13). When any of the trans-[PtCl(2)(RCN)(2)] (R = Et, CH(2)Ph, Ph) complexes reacts in the corresponding nitrile RCN with 4 equiv of DPG at prolonged reaction time (75 degrees 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 (1)H and (13)C{(1)H} 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.

The nucleophilic addition of N,N'-diphenylguanidine, HN=C(NHPh)(2) (DPG), to two adjacent dialkylcyanamide ligands in cis-[PtCl(2)(NCNR(2))(2)] (R = Me; R(2) = C(5)H(10), C(4)H(8)O) gives unusual eight-membered chelates [PtCl(2){NH=C(NR(2))N(Ph)C(=NH)N(Ph)C(NR(2))=NH}] (1-3) with trisguanidine as the cyclic ligand, in which the central guanidine =NH group remains uncoordinated. Treatment of trans-[PtCl(2)(NCNR(2))(2)] (R = R = Me; R(2) = C(5)H(10), C(4)H(8)O) with 1 equiv of HN=C(NHPh)(2) in a solution (R = R = Me; R(2) = C(5)H(10)) or in a suspension (R(2) = C(4)H(8)O) of CHCl(3) or MeNO(2) at 20-25 degrees C for 20 h results in the generation of the 1,3,5-triazapentadiene monochelates [PtCl{NH=C(NR(2))N(Ph)C(NH(2))=NPh}(NCNR(2))](Cl) (4-6). When any of trans-[PtCl(2)(NCNR(2))(2)] reacts with 2 equiv of DPG at 20-25 degrees C for 1-2 days or 4-6 are treated with 1 equiv more of HN=C(NHPh)(2) at the same temperature, the complexes bearing two chelate rings [Pt{NH=C(NR(2))N(Ph)C(NH(2))=NPh}(2)](Cl)(2) (7-9) are formed. The formulation of the obtained complexes was supported by satisfactory C, H, and N elemental analyses, agreeable ESI(+)-MS, IR and (1)H and (13)C{(1)H} NMR spectroscopies; the structures of 1 and 2 were determined by the single-crystal X-ray diffraction. Theoretical studies (at the B3LYP level of theory) revealed that the alkylnitrile eight-membered product is significantly less stable than the corresponding cyanamide species 1-3, and this fact, at least partially, explains why the former was not detected in the reaction between cis-dinitrileplatinum(II) complexes and DPG.

Two (1,3,5-triazapentadiene/ato)PtII complexes, [1][(Cl)2] and [2][(Cl)2], were synthesized by the previously reported platinum-mediated nitrile−amidine coupling. Both complexes crystallize as mixed chloroform−ethanol solvate [1][(Cl)2(CHCl3)7(EtOH)2] and [2][(Cl)2(CHCl3)6(EtOH)2] from the reaction mixture by slow evaporation of the commercial chloroform (containing ca. 1% of EtOH) taken as the solvent, while crystals of [2][(Cl)2(CHCl3)4] were obtained when distilled chloroform was employed. In the crystal structure of [1][(Cl)2(CHCl3)7(EtOH)2], [2][(Cl)2(CHCl3)6(EtOH)2], and [2][(Cl)2(CHCl3)4] solvates, the Cl− ion interacts with [1]2+ or [2]2+ by means of hydrogen bonding and via one hydrogen bridge, thus forming stacked arrays. The negatively charged cluster ions [Cl−(CHCl3) n ] (n = 2, 3) are stabilized via C−H···Cl− hydrogen bridges between the Cl− ion and CHCl3 molecules. In [1][(Cl)2(CHCl3)7(EtOH)2], two chloroform clusters dimerize to the [Cl−(CHCl3)3]2 species, where the halogen bonding between one Cl atom of CHCl3 and Cl− anion was detected. The halogen bonding was studied by theoretical methods (B3LYP, MP2), including the bond energy, AIM, and NBO charge transfer analyzes.

The cationic (1,3,5-triazapentadiene)Pt(II) complex [Pt{NH[double bond, length as m-dash]C(N(CH2)5)N(Ph)C(NH2)[double bond, length as m-dash]NPh}2]Cl2 ([]Cl2) was crystallized from four haloalkane solvents giving [][Cl2(CDCl3)4], [][Cl2(CHBr3)4], [][Cl2(CH2Cl2)2], and [][Cl2(C2H4Cl2)2] solvates that were studied by X-ray diffraction. In the crystal structures of [][Cl2(CDCl3)4] and [][Cl2(CHBr3)4], the Cl(-) ion interacts with two haloform molecules via C-DCl(-) and C-HCl(-) contacts, thus forming the negatively charged isostructural clusters [Cl(CDCl3)2](-) and [Cl(CHBr3)2](-). In the structures of [][Cl2(CH2Cl2)2] and [][Cl2(C2H4Cl2)2], cations [](2+) are linked to a 3D-network by a system of H-bondings including one formed by each Cl(-) ion with CH2Cl2 or C2H4Cl2 molecules. The lengths and energies of these H-bonds in the chloride-haloalkane clusters were analyzed by DFT calculations (M06 functional) including AIM analysis. The crystal packing noticeably affected the geometry of the clusters, and energy of C-HCl(-) hydrogen bonds ranged from 1 to 6 kcal mol(-1). An exponential correlation (R(2) > 0.98) between the calculated Cl(-)H distances and the energies of the corresponding contacts was found and used to calculate hydrogen bond energies from the experimental Cl(-)H distances. Predicted energy values (3.3-3.9 kcal mol(-1) for the [Cl(CHCl3)2](-) cluster) are in a reasonable agreement with the energy of the Cl3C-HCl(-) bond estimated using ATRFTIR spectroscopy (2.7 kcal mol(-1)).