Copper Complexes with a Hybrid Scorpionate Ligand Containing Pyridazine‐3‐thione

Synthesis and Structural Characterization of Copper Complexes Containing "R-Substituted" Bis-7-Azaindolyl Borate Ligands

The coordination chemistry of scorpionate ligands based on borates containing the 7-azaindole heterocycle is relatively unexplored. Thus, there is a requirement to further understand their coordination chemistry. This article outlines the synthesis and characterization of a family of complexes containing anionic flexible scorpionate ligands of the type [(R)(bis-7-azaindolyl)borohydride]^- ([^RBai]^-), where R = Me, Ph or naphthyl. The three ligands were coordinated to a series of copper(I) complexes containing a phosphine co-ligand to form the complexes, [Cu(^MeBai)(PPh₃)] (1), [Cu(^PhBai)(PPh₃)] (2), [Cu(^NaphthBai)(PPh₃)] (3), [Cu(^MeBai)(PCy₃)] (4), [Cu(^PhBai)(PCy₃)] (5) and [Cu(^NaphthBai)(PCy₃)] (6). Additional copper(II) complexes, namely, [Cu(^MeBai)₂] (7) and [Cu(^PhBai)₂] (8), were obtained during attempts to obtain single crystals from complexes 4 and 2, respectively. Complexes 7 and 8 were also prepared independently from CuCl₂ and two equivalents of the corresponding Li[^RBai] salt alongside an additional complex, namely, [Cu(^NaphthBai)₂] (9). The copper(I) and copper(II) complexes were characterized using spectroscopic and analytical methods. Furthermore, a crystal structure was obtained for eight of the nine complexes. In all cases, the boron-based ligand was found to bind to the metal centers via a κ³-N,N,H coordination mode.

Vapochromism and Magnetochemical Switching of a Nickel(II) Paddlewheel Complex by Reversible NH3 Uptake and Release

Reaction of [NiCl2 (PnH)4 ] (1) (PnH=6-tert-butyl-pyridazine-3-thione) with NiCl2 affords the binuclear paddlewheel (PW) complex [Ni2 (Pn)4 ] (2). Diamagnetic complex 2 is the first example of a PW complex capable of reversibly binding and releasing NH3 . The NH3 ligand in [Ni2 (Pn)4 (NH3 )] (2⋅NH3 ) enforces major spectroscopic and magnetic susceptibility changes, thus displaying vapochromic properties (λmax (2)=532 nm, λmax (2⋅NH3 )=518 nm) and magnetochemical switching (2: S=0; 2⋅NH3 : S=1). Upon repeated adsorption/desorption cycles of NH3 the PW core remains intact. Compound 2 can be embedded into thin polyurethane films (2P ) under retention of its sensing abilities. Therefore, 2 qualifies as reversible optical probe for ammonia. The magnetochemical switching of 2 and 2⋅NH3 was studied in detail by SQUID measurements showing that in 2⋅NH3 , solely the Ni atom coordinated the NH3 molecule is responsible for the paramagnetic behavior.

Synthesis and dye adsorption studies of the {dibromo(1,1′-(1,2-ethanediyl)bis(3-methyl-imidazole-2-thione)dicopper(i)}n polymer and its conversion to CuO nanospheres for photocatalytic and antibacterial applications

A new copper polymer was used as a dye adsorbent and CuO precursor. The CuO nanospheres showed good performances for photocatalytic and antibacterial applications.

Magnesium Stung by Nonclassical Scorpionate Ligands: Synthesis and Cone-Angle Calculations

A series of tris(pyrazolyl)alkane (RCTp) scorpionate ligands of the type RCTp^3-R' (R=Me, nBu, SiMe₃ ; R'=H, Me, Ph, iPr, tBu) were synthesized and their ability to coordinate methylmagnesium moieties was examined. The reaction of Mg(AlMe₄ )₂ with neutral proligands HCTp^3-Ph or Me₃ SiCTp^3-Me , containing a non-innocent backbone methine moiety, led to deprotonation/rearrangement and SiMe₃ /AlMe₃ exchange to afford [(Me₃ AlCTp^3-Ph )₂ Mg] and [(Me₃ AlCTp^3-Me )Mg(AlMe₄ )], respectively, with monoanionic tripodal ligands. Treatment of sterically less demanding RCTp^3-R' with Mg(AlMe₄ )₂ produced isostructural dicationic "metal-in-a-box" complexes of the type [(RCTp^3-R' )₂ Mg][AlMe₄ ]₂ (R=Me, nBu; R'=H, Me). Utilization of the superbulky ligands MeCTp^3-Ph and MeCTp^3-tBu gave monocationic complexes [(MeCTp^3-Ph )MgMe][AlMe₄ ] and [(MeCTp^3-tBu )MgMe][Al₂ Me₇ ] as separated ion pairs. The reaction of Mg(AlMe₄ )₂ with nBuCTp^3-Ph led to the formation of the dimagnesium complex [{(nBuCTp^3-Ph )Mg(AlMe₄ )}₂ (μ-CH₃ )], which features a bridging methyl moiety and terminal η¹ -coordinated tetramethylaluminato ligands. Isopropyl-substituted ligand MeCTp^3-iPr emerged from further fine-tuning of the steric and electronic parameters and, upon reaction with Mg(AlMe₄ )₂ , gave (MeCTp^3-iPr )Mg(AlMe₄ )₂ ; this represents the first example of a magnesium bis(alkyl) complex with an intact RCTp^3-R' ligand. The exact ligand cone angles Θ^° of all magnesium complexes were determined according to the mathematical analysis developed by Allen et al. [J. Comput. Chem. 2013, 34, 1189-1197].

{(Hydrogen 2,2′,2′′-boranetriyl)tris[6-tert-butyl-4-methylpyridazine-3(2H)-thione]-κ3H,S,S′}(triphenylphosphane-κP)copper(I) chloroform disolvate

In the title complex, [Cu(C27H40BN6S3)(C18H15P)]·2CHCl3, the CuIatom is surrounded in a trigonal-planar arrangement by the triphenylphosphane ligand and two of the three S atoms of the scorpionate ligand with an additional 3-center–2-electron B—H...Cu interaction, with the H atom as the apex of a pyramid [B—H = 1.140 (17) Å and Cu—H = 1.826 (16) Å].

Unusual C-N Coupling Reactivity of Thiopyridazines: Efficient Synthesis of Iron Diorganotrisulfide Complexes

The reaction of iron(II) triflate with 6-tert-butyl-3-thiopyridazine (PnH) and 4-methyl-6-tert-butyl-3-thiopyridazine (^MePnH) respectively led to iron bis(diorganotrisulfide) complexes [Fe(^RPnS₃Pn^R)₂](OTf)₂ [R = H (1a) and Me (2a)]. The corresponding perchlorate complexes were prepared by using the iron(II) chloride precursor and the subsequent addition of 2 equiv of NaClO₄, giving [Fe(^RPnS₃Pn^R)₂](ClO₄)₂ [R = H (1b) and Me (2b)]. The compounds were fully characterized including single-crystal X-ray diffraction analysis. All four compounds exhibit nearly perfect octahedral geometries with an iron center coordinated by four nitrogen atoms from two ^RPnS₃Pn^R ligands and by two sulfur atoms of the central atom in the S₃ unit. The diamagnetic complexes exhibit unusually high redox potentials for the Fe^2+/3+ couple at E_1/2 = 1.15 V (for 1a and 1b) and 1.08 V (for 2a and 2b) versus Fc/Fc⁺, respectively, as determined by cyclic voltammetry. Furthermore, the source of the extra sulfur atom within the S₃ unit was elucidated by isolation of C-N-coupled pyridazinylthiopyridazine products.

Heteroleptic metal(II) complexes of hydrotris(methimazolyl)borate and diimines: Synthesis, theoretical calculations, antimicrobial, antioxidant, in vitro cytotoxicity and molecular docking studies

A series of heteroleptic metal(II) complexes of formulation [M(Tm)(diimine)](ClO₄) (1-8), [Tm = hydrotris(methimazolyl)borate, diimine = 2,2'-bipyridyl or 1,10-phenanthroline and M = Mn(II), Ni(II), Cu(II) or Zn(II)] have been synthesized and characterized by spectroscopic methods. The geometric parameters of the complexes were determined using UV-Vis spectroscopy and DFT calculations. The analyses of HOMO and LUMO have been used to explain the charge transfer within the molecule. Antimicrobial activity of the synthesized heteroleptic complexes were evaluated against two Gram (-ve) (Escherichia coli and Klebsiella pneumoniae) and two Gram (+ve) (Bacillus cereus and Staphylococcus aureus) bacterial, and three fungal (Candida albicans, Candida glabrata and Candida krusei) strains with respect to the standard drugs erythromycin and amphotericin-B. The copper(II) complex 6 showed better scavenging activity against DPPH when compared to other complexes. The cytotoxic activity of copper(II) complexes 5 and 6 against MCF-7 cell line was assessed by MTT assay, which showed exponential responses toward increasing concentration of complexes. In the molecular docking studies, the complexes showed π-π, σ-π, hydrogen bonding, van der Waals and electrostatic interactions with FGFR kinase receptor.

Synthesis, structural and photo-physical studies of bismuth(III) complexes with Janus scorpionate and co-ligands

Some novel complexes of bismuth(III) with the Janus scorpionate ligand [HB(mtda(Me))3](-) (mtda(Me) = 2-mercapto-5-methyl-1,3,4-thiadiazolyl) were synthesised. Na[HB(mtda(Me))3] (1) was reacted with BiX3 (X = Cl, I, NO3) in the molar ratio 2 : 1 to afford the bismuth complexes {HB(mtda(Me))3}2BiCl (3), Na[{HB(mtda(Me))3}2BiI2] (4) and [{HB(mtda(Me))3}2Bi(NO3)]n (5). Two mixed complexes {HB(mtda(Me))3}Bi(phen)Cl2 (6) and {HB(mtda(Me))3}Bi(bipy)Cl2 (7) were obtained using Janus scorpionate as the primary ligand in the presence of 1,10-phenanthroline and 2,2'-bipyridyl, respectively, as co-ligands in the 1 : 1 ratio. The obtained complexes were characterised by (1)H, (13)C and diffusion NMR (DOSY), elemental analyses and mass spectrometry. Structures of the compounds NBu4[HB(mtda(Me))3] (2), 3, 4, 5, 6 and 7 were determined by single crystal X-ray diffraction. The molecular dynamic process in complex 3 was also studied by variable temperature NMR measurements. All bismuth complexes, except for the polymeric 5, are monomeric. Complexes 6 and 7 exhibit (B)H···Bi distances of 2.76(3) and 2.71(2) Å length, respectively. Compounds 2, 6 and 7 were screened for their luminescence activity. At 77 K in ethanol solution, complexes 6 and 7 exhibit phosphorescence from ligand-to-ligand charge transfer (LLCT) and the ligand-centred (LC) excited state, respectively.

Copper and silver complexes bearing flexible hybrid scorpionate ligand mpBm

The addition of flexible scorpionate ligand, [mpBm]⁻{i.e. HB(mt)2(mp), where mt = methyl-2-mercaptoimidazole and mp = 2-mercaptopyridine} to group eleven centres is reported for the first time. The coordination of this hybrid ligand to copper(I) and silver(I) centres in the presence of triphenylphosphine and trialkylphosphine co-ligands has been investigated. The trialkylphosphines coordinates to both copper and silver centres while the less basic triarylphosphine only successfully coordinates to the copper centre. Structural characterisation of [Cu{HB(mt)₂(mp)}(PPh₃)], [Cu{HB(mt)₂(mp)}(PCy₃)] and [Ag{HB(mt)₂(mp)}(PCy₃)] confirm κ³-SSH coordination modes for ligand where one of the mt 'arms' and the mp 'arm' of the scorpionate ligand are coordinated to the metal centre. The second mt 'arm' remains uncoordinated in all three complexes. A comparison has been made with the parent sulfur based scorpionate ligand, [Tm]⁻{HB(mt)₃}.

Synthesis and structural characterization of bis and tris(2-mercapto-1-methylbenzimidazolyl)hydroborato complexes: benzannulation promotes κ³-coordination

The benzannulated bis and tris(mercaptoimidazolyl)borohydride compounds, [BmMeBenz]Na and [TmMeBenz]Na, have been synthesized via the reactions of NaBH4 with two and three equivalents of 1-methyl-1,3-dihydro-2H-benzimidazole-2-thione, respectively. X-ray diffraction studies on the THF adducts, {μ-[BmMeBenz]Na(THF)₂}₂ and {[TmMeBenz]Na}₂(μ-THF)₃, indicate that both compounds are dinuclear but differ according to the nature of the bridging ligand. Specifically, {μ-[BmMeBenz]Na(THF)₂}₂ possesses bridging [BmMeBenz] ligands and terminal THF ligands, while {[TmMeBenz]Na}₂(μ-THF)₃ possesses terminal [TmMeBenz] ligands and bridging THF ligands. The tris(mercaptoimidazolyl)borohydride ligand of {[TmMeBenz]Na}₂(μ-THF)₃ coordinates in a κ³-manner, which is in marked contrast to the κ²-, κ¹- and κ⁰-modes that have been reported for various [TmMe]Na derivatives. Density functional theory (DFT) geometry optimization calculations of the anions [TmMeBenz]⁻ and [TmMe]⁻ in the gas phase indicate that the conformation required for κ³-S₃ coordination, i.e. one in which the three sulfur donors point away from the B-H group, is relatively more stable for [TmMeBenz]⁻ than for [TmMe]⁻, and thus provides a rationalization for the observation that benzannulation enables κ³-coordination of tris(mercaptoimidazolyl)borohydride ligand in {[TmMeBenz]Na}₂(μ-THF)₃. Furthermore, comparison of the molecular structure and IR spectroscopic properties of [TmMeBenz]Re(CO)₃ with those of [TmMe]Re(CO)₃ indicates that benzannulation reduces the electron donating properties of the ligand, but has little effect on its steric properties. {μ-[BmMeBenz]Na(THF)₂}₂ and {[TmMeBenz]Na}₂(μ-THF)₃ react with [Me₃PCuCl]₄ to give [BmMeBenz]CuPMe₃ and [TmMeBenz]CuPMe₃, the first pair of structurally related bis and tris(mercaptoimidazolyl)hydroborato copper(I) compounds.