Cu2+-Mediated Nucleophilic Addition of Different Nucleophiles to Dicyanamide - Synthesis, Structures, and Magnetic Properties of a Family of Mononuclear, Trinuclear, Hexanuclear, and Polymeric Copper(II) Complexes

The effect of anions in the synthesis and structure of pyrazolylamidino copper(II) complexes

Six new pyrazolylamidino Cu(II) complexes are synthesized directly from the reactions of Cu(X)₂ salts (X = ClO₄^-, BF₄^-, or Cl^-) and pyrazole (pzH) in nitrile solution (RCN, R = Me or Et) at 298 K via the metal-mediated coupling of RCN with pzH: [Cu(HNC(R)pz)₂(X)₂] (X = ClO₄^- or BF₄^-, R = Me, 1 or 7 and Et, 2 or 8, respectively) and dichloro Cu(II) complexes [Cu₂Cl₂(μ-Cl)₂(HNC(Me)pz)₂] (3) and [CuCl₂(HNC(Et)pz)] (4). Four more new complexes, [Cu₂(μ-Cl)₂(HNC(Me)pz)₂(pzH)₂][X]₂ (X = ClO₄^-, 5 and BF₄^-, 9) and [Cu₂(μ-Cl)₂(HNC(Et)pz)₂(pzH)₂(X)₂] (X = ClO₄^-, 6 and BF₄^-, 10), are obtained indirectly from the anion substitution reaction with Cl^- ions in 1 and 7, and 2 and 8, respectively. All complexes are characterized by EA, FTIR, UV-vis and EPR spectroscopy and X-ray crystallographic analyses. HNC(Et)pz or pzH is unobserved in both the nitrile-exchange reaction of 2 to d₆-1 and the anion-substitution reaction of 2 to d₆-5 in the CD₃CN solution. The ¹H NMR results reveal that the pzH-RCN coupling is intramolecular and reversible on a Cu(II) center. The crystal structures of these complexes show diverse supramolecular assemblies through imino NH⋯anion hydrogen bonds and pyrazolylamidino pz-pz (π⋯π) and pz-Cu(II) (π⋯metal) interactions. EPR results suggest weak magnetic couplings between Cu(II) centers in the polynuclear Cu(II) complexes. The yield and rate of the formation of 1 are higher in the reaction of Cu(ClO₄)₂ with a 4-fold molar excess of pzH compared with a 2-fold excess, indicating that [Cu(pzH)₄]²⁺ is the more active species for pzH-RCN coupling. The highest rate for the formation of 1 is achieved when [Cu(pzH)₄(ClO₄)₂] is used in MeCN solution. Thus, a plausible synthetic path for synthesizing pyrazolylamidino Cu(II) complexes is established. An intermediate species, [Cu(HNC(Me)pz)₂(pzH)₂][ClO₄]₂ (1a), is proposed for the synthetic process based on spectroscopic studies and DFT calculations. The reaction of [Cu(pzH)₄X₂] (X = ClO₄^-, Cl^-, NO₃^-, or BF₄^-) in MeCN solution suggests that the lability of coordinated anions upon nitrile substitution affects the rate of the formation of bis-pyrazolylamidino Cu(II) complexes.

Hexnuclear Cadmium(II) Cluster Constructed from Tris(2-methylpyridyl)amine (TPA) and Azides

A novel rare hexa nuclear cadmium(II)–azide cluster, [Cd6(TPA)4(μ3-1,1,3-N3)4(μ2-1,1-N3)6](ClO4)2·2H2O (1) was isolated and structurally characterized, in which the azide ligands reveal μ-1,1,3- and μ-1,1-N3 bridging modes.

An aminotetracyanocyclopentadienide system: light-induced formation of a thermally stable cyclopentadienyl radical

Crystals of the aminotetracyanocyclopentadienyl radical were obtained from the reaction of CaCl₂with Ag[C₅(CN)₄(NH₂)] and recrystallization in MeOH was performed in sunlight.

Structure, DFT Calculations, and Magnetic Characterization of Coordination Polymers of Bridged Dicyanamido-Metal(II) Complexes

Three coordination polymers of metal(II)-dicyanamido (dca) complexes with 4-methoxypyridine-N-oxide (4-MOP-NO); namely, catena-[Co(µ1,5-dca)2(4-MOP-NO)2] (1), catena-[Mn(µ1,5-dca)2(4-MOP-NO)2] (2), catena-[Cd(µ1,5-dca)2(4-MOP-NO)2] (3), and the mononuclear [Cu(κ1dca)2(4-MOP-NO)2] (4), were synthesized in this research. The complexes were analyzed by single crystal X-ray diffraction as well as spectroscopic methods (UV/vis, IR). The polymeric 1-D chains in complexes 1–3 were achieved by the doubly µ1,5-bridging dca ligands and the O-donor atoms of two axial 4-MOP-NO molecules in trans configuration around the distorted M(II) octahedral. On the other hand, the two “trans-axial” pyridine-N-oxide molecules in complexes 2 and 3 display opposite orientation (s-trans). The DFT (density functional theory) computational studies on the complexes 1–3 were consistent with the experimentally observed crystal structures. Compounds 1 and 2 display weak antiferromagnetic coupling between metal ions (J = −10.8 for 1 and −0.35 for 2).

Metal-mediated generation of triazapentadienate-terminated di- and trinuclear μ2-pyrazolate NiIIspecies and control of their nuclearity

Nuclearity control of nickel(ii)–azole systems for the generation of well-defined (azolate)₂Ni^IIspecies.

Solid-state Reaction of Azolium Hydrohalogen Salts with Silver Dicyanamide--Unexpected Formation of Cyanoguanidine-azoles, Reaction Mechanism and Their Hypergolic Properties

Cyanoguanidines as well as azoles are important bioactive groups, which play an important role in the medical application; meanwhile, the high nitrogen content makes them excellent backbones for energetic materials. A Novel and simple method that combined these two fragments into one molecular compound was developed through the transformation of dicyanamide ionic salts. In return, compounds 4–11 were synthesized, and fully characterized by IR, MS, NMR and elemental analysis. Meanwhile, the structures of compounds 4, 8 and 11 were confirmed by X-ray crystal diffraction. Detailed reaction mechanisms were studied through accurate calculations on the reaction energy profiles of the azolium cations and DCA anion, which revealed the essence of the transformation proceeding. Meanwhile, compound 8 exhibits excellent hypergolic property, which could be potentially novel molecular hypergolic fuel.

22-Azametallacrown-8 complex with a triazole-bridged ligand: synthesis, structure and magnetic properties

Reaction of Mn(OAc)2·4H2O with the H2L ligand affords a new manganese 22-MC-8 azametallacrown [Mn8(μ3-O)2(μ3-OH)2(μ2-OH)2(L)6(OAc)2(OH2)4]·2DMF (H2L = 3-(2-oxyphenyl)-5-(pyrazin-2-yl)-1,2,4-triazole). The structural analysis of the complex reveals that the azaMC ring possesses -[Mn-O-Mn-N-N-Mn-N-N-Mn-N-N]- connectivity. The magnetic behavior of the complex shows the dominant antiferromagnetic interactions between the manganese ions with S = 4 and the frequency-dependent out-of-phase signal.

Preparation and reactivity towards hydrazines of bis(cyanamide) and bis(cyanoguanidine) complexes of the iron triad

Bis(diethylcyanamide) [Fe(N≡CNEt2)2L4](BPh4)2 1a and bis(cyanoguanidine) [Fe{N≡CN(H)C(NH2)=NH}2L4](BPh4)2 1b [L = P(OEt)3] complexes were prepared by allowing iron(II) chloride to react first with an excess of P(OEt)3 and then of the appropriate cyanamide, followed by addition of an excess of NaBPh4. Instead, bis(complexes) of ruthenium and osmium [M(N≡CNEt2)2L4](BPh4)2 2a, 3a and [M{N≡CN(H)C(NH2)=NH}2L4](BPh4)2 2b, 3b (M = Ru 2, Os 3) were prepared by reacting hydrides MH2L4 first with either triflic acid HOTf or methyltriflate MeOTf and then with an excess of the appropriate cyanamide. Hydride-diethylcyanamide [MH(N≡CNEt2)L4]BPh4 4a, 5a and hydride-cyanoguanidine complexes [MH{N≡CN(H)C(NH2)=NH}L4](BPh4)2 4b, 5b (M = Ru 4, Os 5) were also obtained by reacting MH2L4 first with one equivalent of HOTf or MeOTf and then with the appropriate cyanamide. Treatment of bis(cyanamide) and bis(cyanoguanidine) complexes 1-3 with hydrazines RNHNH2 afforded hydrazinecarboximidamide derivatives [M{η(2)-N(H)=C(NEt2)N(R)NH2}L4](BPh4)2 6a-12a and [M{η(2)-N(H)=C[N=C(NH2)2]N(R)NH2}L4](BPh4)2 6b-12b (M = Fe 6-8, Ru 9, 10, Os 11, 12; R = H 6, 9, 11, Me 7, 10, 12, Ph 8). A reaction path involving nucleophilic attack by hydrazine on the cyanamide carbon atom is proposed. All the complexes were characterised by spectroscopy and X-ray crystal structure determination of [Os{η(2)-NH=C[N=C(NH2)2]N(CH3)NH2}{P(OEt)3}4](BPh4)2 12b.

Synthesis, Crystal Structures, and Magnetic Properties of Ternary M(II)-Dicyanamide-hydroxypyridine Complexes

Three two-dimensional (2D) and 3D supramolecular coordination architectures based on ternary M(II)-dicyanamide-2-hydroxypyridine systems, [Co(hmpH)2(dca)2] (1), [Cu(hmpH)2(dca)2] (2), and [Mn(hepH)2(dca)2] (3) (dca = dicyanamide, hmpH = 2-(hydroxymethyl)pyridine, hepH = 2-(hydroxyethyl)pyridine), have been synthesized. 1 is a mononuclear Co(II) complex. The mononuclear units are interlinked into a 2D (4,4) hydrogen-bonded layer via O–H⋯N hydrogen bonds between the hydroxyl groups and the noncoordinating nitrile ends. These 2D layers are further extended into a 3D supramolecular architecture via the interlayer pyridyl-pyridyl stacking interaction. 2 has a 1D coordination chain structure formed by the double 1,5-dca bridged dinuclear [Cu2(1,5-dca)2(hmpH)2] unit and the 1,3-dca bridges via weak Cu–N coordination, and these 1D coordination chains are further extended into 2D hydrogen-bonded layers via strong O–H⋯N hydrogen-bonding interaction between the hydroxyl groups and the noncoordinating nitrile ends. 3 is a 2D (4,4) coordination network made of 1D [Mn(hepH)(1,5-dca)] helical chain units and interchain double (1,5-dca) bridges. Pairs of [Mn(hepH)(1,5-dca)] helical chains are interlinked by the double (1,5-dca) bridges into a racemic coordination layer structure, which is further extended into a 3D hydrogen-bonded network. Magnetic studies reveal that weak antiferromagnetic exchange occurs in 3.

Syntheses, Crystal Structures, Magnetic Behaviours, and Thermal Properties of Three Hydrogen-Bonding Networks Containing Dicyanamide and 4-Hydroxypyridine

Three new dicyanamide-bridged polymeric complexes of{[Mn(dca)2(L)2]·2H2O}n(1),{[Cd(dca)2(L)2]·2H2O}n(2), and{[Co(dca)2(L)2]2(L)}n(3) (dca = dicyanamide, L = pyridinium-4-olate) have been synthesized and structurally characterized. In the three compounds, the protons of hydroxyl groups of 4-hydroxypyridine transfer to pyridyl nitrogen atoms. Compounds1and2are isomorphous forming one-dimensional[M(dca)2(L)2]nchains where metals are connected by double dca anions. These one-dimensional chains are extended into two-dimensional layers through weak C–H⋯N hydrogen bonds. Further, these layers are assembled into a three-dimensional supramolecular network through N–H⋯O, O–H⋯O hydrogen bonds. Complex3is a coordination layer of (4, 4) topology with octahedral metal centers linked by four singleμ1,5-bridges. These layers are interlocked by N–H⋯O, O–H⋯O hydrogen bonds from coordinated water molecules and free L molecules, which leads to a three-dimensional supramolecular architecture. The variable temperature magnetic susceptibilities measurement of compounds1and3shows the existence of weak antiferromagnetic interactions between the metal centers. The thermogravimetric analyses of the compounds1–3are also discussed.