Thiopyridazine-Based Copper Boratrane Complexes Demonstrating the Z-type Nature of the Ligand

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.

Automated oxidation-state assignment for metal sites in coordination complexes in the Cambridge Structural Database

The Cambridge Structural Database (CSD) currently contains over 400 000 transition-metal-containing entries, however many entries still lack curated oxidation-state assignments. Surveying and editing the remaining entries would be far too resource- and time-intensive to be carried out manually. Here, a highly reliable automated workflow for oxidation-state assignment in transition-metal coordination complexes via CSD Python API (application programming interface) scripts is presented. The strengths and limitations of the bond-valence sum (BVS) method are discussed and the use of complementary methods for improved assignment confidence is explored. In total, four complementary techniques have been implemented in this study. The resulting workflow overcomes the limitations of the BVS approach, widening the applicability of an automated procedure to more CSD entries. Assignments are successful for 99% of the cases where a high consensus between different methodologies is observed. Out of a total number of 54 999 unique metal atoms in a test dataset, the procedure yielded the correct oxidation state in 47 072 (86%) of cases.

Structural Mimics of Acetylene Hydratase: Tungsten Complexes Capable of Intramolecular Nucleophilic Attack on Acetylene

Bioinspired complexes employing the ligands 6-tert-butylpyridazine-3-thione (SPn) and pyridine-2-thione (SPy) were synthesized and fully characterized to mimic the tungstoenzyme acetylene hydratase (AH). The complexes [W(CO)(C2 H2 )(CHCH-SPy)(SPy)] (4) and [W(CO)(C2 H2 )(CHCH-SPn)(SPn)] (5) were formed by intramolecular nucleophilic attack of the nitrogen donors of the ligand on the coordinated C2 H2 molecule. Labelling experiments using C2 D2 with the SPy system revealed the insertion reaction proceeding via a bis-acetylene intermediate. The starting complex [W(CO)(C2 H2 )(SPy)2 ] (6) for these studies was accessed by the new acetylene precursor mixture [W(CO)(C2 H2 )n (MeCN)3-n Br2 ] (n=1 and 2; 7). All complexes represent rare examples in the field of W-C2 H2 chemistry with 4 and 5 being the first of their kind. In the ongoing debate on the enzymatic mechanism, the findings support activation of acetylene by the tungsten center.

Adding to the Family of Copper Complexes Featuring Borohydride Ligands Based on 2-Mercaptopyridyl Units

Borohydride ligands featuring multiple pendant donor functionalities have been prevalent in the chemical literature for many decades now. More recent times has seen their development into new families of so-called soft scorpionates, for example, those featuring sulfur based donors. Despite all of these developments, those ligands containing just one pendant group are rare. This article explores one ligand family based on the 2-mercaptopyridine heterocycle. The coordination chemistry of the monosubstituted ligand, [H3B(mp)]− (mp = 2-mercaptopyridyl), has been explored. Reaction of Na[BH3(mp)] with one equivalent of Cu(I)Cl in the presence of either triphenylphosphine or tricyclohexylphosphine co-ligands leads to the formation of [Cu{H3B(mp)}(PR3)] (R = Ph, 1; Cy, 2), respectively. Structural characterization confirms a κ3-S,H,H coordination mode for the borohydride-based ligand within 1 and 2, involving a dihydroborate bridging interaction (BH2Cu) with the copper centers.

Mono- and Hexanuclear Zinc Halide Complexes with Soft Thiopyridazine Based Scorpionate Ligands

Scorpionate ligands with three soft sulfur donor sites have become very important in coordination chemistry. Despite its ability to form highly electrophilic species, electron-deficient thiopyridazines have rarely been used, whereas the chemistry of electron-rich thioheterocycles has been explored rather intensively. Here, the unusual chemical behavior of a thiopyridazine (6-tert-butylpyridazine-3-thione, HtBuPn) based scorpionate ligand towards zinc is reported. Thus, the reaction of zinc halides with tris(6-tert-butyl-3-thiopyridazinyl)borate Na[TntBu] leads to the formation of discrete torus-shaped hexameric zinc complexes [TntBuZnX]6 (X = Br, I) with uncommonly long zinc halide bonds. In contrast, reaction of the sterically more demanding ligand K[TnMe,tBu] leads to decomposition, forming Zn(HPnMe,tBu)2X2 (X = Br, I). The latter can be prepared independently by reaction of the respective zinc halides and two equiv of HPnMe,tBu. The bromide compound was used as precursor which further reacts with K[TnMe,tBu] forming the mononuclear complex [TnMe,tBu]ZnBr(HPnMe,tBu). The molecular structures of all compounds were elucidated by single-crystal X-ray diffraction analysis. Characterization in solution was performed by means of 1H, 13C and DOSY NMR spectroscopy which revealed the hexameric constitution of [TntBuZnBr]6 to be predominant. In contrast, [TnMe,tBu]ZnBr(HPnMe,tBu) was found to be dynamic in solution.

5-Mercaptotetrazolyl-derived metallaboratranes

The reactions of 1-tert butyl-5-thiotetrazole (HtttBu) with Na[BH4] provides Na[H2B(tttBu)2] (Na[1]) or Na[HB(tttBu)3] (Na[2]) in refluxing THF or xylene, respectively. Treating [RuCl(Ph)(CO)(PPh3)2] with Na[2] affords the triply-buttressed ruthenaboratrane [Ru(CO)(PPh3){κ4-B,S,S',S''-B(tttBu)3}] (5) whilst Na[1] with [IrCl(CO)(PPh3)2] or [RuCl(Ph)(CO)(PPh3)2] provides rare examples of doubly-buttressed metallaboratranes [IrH(CO)(PPh3){κ3-B,S,S'-BH(tttBu)2}] (7) and [Ru(CO)(PPh3)2{κ3-B,S,S'-BH(tttBu)2}] (12), the latter via the isolable thiotetrazoylborate complex [Ru(Ph)(CO)(PPh3){κ3-H,S,S'-H2B(tttBu)2}] (11).

Ambient Stable Cyanomethylcopper(III) Complex: a Strong Cu-Csp3 Bond Supported by a PS3-Tripodal Chelator

An organocuprate(III) complex, [Cu(^TMSPS3)(CH₂CN)]^- (2), was identified along with a sequential derivative, [Cu(^TMSPS3)(CN)]^- (3), and an intermediate, [Cu(^TMSPS3)(HN═PPh₃)] (4), formed in a relative transformation. Apical ligands among these complexes all strongly associate with a robust trigonal copper(III) platform. The nature of the ligand binding was spectroscopically and computationally investigated through a series of copper(III) complexes. The bonding along the principal C₃ axis is adaptable, and σ interaction dominates the axial ligand coordination, where the cyanomethyl group exhibits the strongest bonding. Complex 2 is a scarce example of a thermostable aliphatic organocuprate(III) compound, which sheds some light on the organocopper(III) chemistry widely involved in many copper-mediated catalyses.

Synthesis and ligand substitution reactions of κ4-B,S,S′,S′′-ruthenaboratranes

Ruthenaboratranes of the form [Ru(CO)L{κ⁴-B(mt)₃}] (mt = N-methimazolyl) arise via substitution of the PPh₃ ligand in [Ru(CO)(PPh₃){κ⁴-B(mt)₃}] by L (L = PMe₂Ph, PMe₃, P(OMe)₃, P(OEt)₃, P(OPh)₃) or reactions of [RuCl(R)(CO)L_n] (R = Ph, CHCHPh; n = 2, L = PCy₃; n = 3, L = P(OMe)₃, PMe₂Ph) with Na[HB(mt)₃].

Methimazolyl based diptych bicyclo-[3.3.0]-ruthenaboratranes

The reactions of [RuCl(R)(CO)(PPh₃)₂] (R = CHCHPh, Ph) with Na[H₂B(mt)₂] (mt = N-methyl-2-mercaptoimidazolyl) transiently provide [Ru(R)(CO)(PPh₃){κ³-H,S,S′-H₂B(mt)₂}] which each evolve to the ruthenaboratrane [Ru(CO)(PPh₃)₂{κ³-B,S,S′-BH(mt)₂}](Ru→B)⁸.

(Acetamide-κO){2,2′,2′′-boranetriyltris[6-tert-butyl-4-methylpyridazine-3(2H)-thione]-κ4 B,S,S′,S′′}copper(I) trifluoromethanesulfonate chloroform disolvate

In the title solvated complex salt, [Cu(C27H39BN6S3)(C2H5NO)](CF3O3S)·2CHCl3, the CuI atom is coordinated by the three S atoms of the pyridazine-3-thione rings in the equatorial plane [Cu—S = 2.3072 (4)–2.3280 (4) Å] and the B atom of the scorpionate ligand and the O atom of an acetamide ligand as the apices of a trigonal bipyramid [Cu—B = 2.0456 (16) Å and Cu—O = 1.9957 (11) Å]. The amide group of the latter ligand is involved in a bifurcated hydrogen bond to the trifluoromethanesulfonate anion.

{(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].

Three-Fold-Symmetric Selenium-Donor Metallaboratranes of Cobalt and Nickel

A novel selenium-containing pyridazinyl-based soft scorpionate ligand (KTnse) was synthesized. It reacts with CoCl₂ and NiCl₂, yielding the first metallaboratrane complexes with selenium in their donor positions. Further substitution with Ag(OTf) or NaN₃ allows isolation of the respective triflate or azide complexes. Reaction with Ag(OTf) leads in the case of nickel to a dinuclear, dicationic complex with a short Ni-Ni distance, while cobalt gave a mononuclear cationic species. Substitution of the chloride by azide yields with both metals the respective azide complexes. All compounds were characterized via single-crystal X-ray diffraction analysis. Density functional theory calculations on the chloride species point to oxidized cobalt(III) and nickel(III) centers.

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.

1,3-N,O-Complexes of late transition metals. Ligands with flexible bonding modes and reaction profiles

1,3-N,O-Chelating ligands are ubiquitous in nature owing to their occurrence as α-chiral amino acids in metalloproteins.

Tris(6-tert-butyl-4-methylpyridazine-3-thiolato-κ2N,S)aluminium

The title complex, [Al(C9H13N2S)3], is composed of an aluminium atom coordinated by three bidentate thiopyridazine ligands in an octahedral environment. It has approximateC3symmetry, with Al—N distances in the range 1.9732 (17)–1.9794 (17) Å and three Al—S distances in the range 2.3961 (8)–2.4354 (8) Å. In the crystal, there are no significant intermolecular interactions present.