Synthese und Struktur von N,N,N‴,N‴‐Tetraisobutyl‐N′,N″‐isophthaloylbis(thioharnstoff) und Dimethanol‐bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato))dicobalt(II)

Synthesis and Structure of N,N,N?,N?‐Tetraisobutyl‐N′,N″‐isophthaloylbis(thiourea) and Dimethanol‐bis(N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato))dicobalt(II) The synthesis and the crystal structure of the ligand N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thiourea) and its Co^II‐complex are reported. The ligand co‐ordinates quadridentately forming a di‐bischelate. The donor atoms O and S are arranged in cis‐position around the central Co^II ions. In addition the co‐ordination geometry is determined by methanol molecules resulting in the co‐ordination number five. The complex crystallizes in the space group P1 (Z = 1) with two additional methanol molecules per formula unit. The free ligand crystallizes in the space group P1 (Z = 2) with one methanol molecule per formula unit. It shows the typical keto form of N‐acylthioureas with a protonated central N atom. The structures of both acylthiourea fragments come close to E,Z′‐configurations.     

Synthese,Strukturen, NMR‐ und EPR‐Untersuchungen der binuklearen Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(selenoureato))‐Komplexe des NiII und CuII

Synthesis, Structures, NMR and EPR Investigations of Binuclear Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(selenoureato)) Complexes of Ni^II and Cu^II The synthesis of binuclear Cu^II and Ni^II complexes of the quadridentate ligand N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(selenourea) and their crystal structures are reported. The complexes crystallize monoclinic, P2₁/c (Z = 2). In the EPR spectra of the binuclear Cu^II complex exchange‐coupled Cu^II‐Cu^II pairs were observed. In addition the signals of a mononuclear Cu^II species are observed what will be explained with the assumption of an equilibrium between the binuclear Cu^II‐complex (Cu^II‐Cu^II pairs) and oligomeric complexes with “isolated” Cu^II ions. Detailed ¹³C and ⁷⁷Se NMR investigations on the ligand and the Ni^II complex allow an exact assignment of all signals of the heteroatoms.     

Synthesis,Crystal Structure and Spectroscopic Properties of Bis(1‐(E)‐2‐formylpyridine semicarbazone)nickel(II) Diperchlorate Monohydrate

Pale‐green crystals of the title complex were prepared by reaction of 2‐formylpyridine semicarbazone (HCSpy) and nickel(II) perchlorate in boiling ethanol. The crystals are triclinic with the nickel ion in an octahedral arrangement, coordinated by two nitrogen atoms and one oxygen donor atom from each ligand molecule. The effect of coordination on bond lengths and angles was explored by comparison with the single‐crystal structure data of the free ligand HSCpy, which was collected as well. The assumed coordination mode was supported by ¹H and ¹³C NMR spectroscopic data. A detailed analysis of the electronic properties, including semi‐empirical quantummechanical calculations is presented. Furthermore, the data obtained from magnetic susceptibility and EPR measurements are in accordance with a low‐spin d⁸ nickel(II) complex.     

N,N′,N′′,N′′′‐Tetraethylterephthalamidinium bis(tetrazolate)

The crystal structure of the title 2:1 salt of tetrazole and a substituted terephthal­amidine, C₁₆H₂₈N₄²⁺·2CHN₄^?, contains an infinite network of hydrogen bonds, with short N?N distances of 2.820 (2) and 2.8585 (19) Å between the tetrazolate anion and the amidinium cation. Involvement of the lateral N atoms of the tetrazole in the hydrogen bonding appears to be a typical binding pattern for the tetrazolate anion.     

Syntheses and Spectroscopic Study of Some New N‐4‐Fluorobenzoyl Phosphoric Triamides; Crystal Structures of 4‐F‐C6H4C(O)N(H)P(O)R2, R = NH‐C(CH3)3, NH‐CH2C6H5, N(CH3)(CH2C6H5)

Some new N‐4‐Fluorobenzoyl phosphoric triamides with formula 4‐F‐C₆H₄C(O)N(H)P(O)X₂, X = NH‐C(CH₃)₃ ( 1 ), NH‐CH₂‐CH=CH₂ ( 2 ), NH‐CH₂C₆H₅ ( 3 ), N(CH₃)(C₆H₅) ( 4 ), NH‐CH(CH₃)(C₆H₅) ( 5 ) were synthesized and characterized by ¹H, ¹³C, ³¹P NMR, IR and Mass spectroscopy and elemental analysis. The structures of compounds 1 , 3 and 4 were investigated by X‐ray crystallography. The P=O and C=O bonds in these compounds are anti. Compounds 1 and 3 form one dimensional polymeric chain produced by intra‐ and intermolecular ‐P=O···H‐N‐ hydrogen bonds. Compound 4 forms only a centrosymmetric dimer in the crystalline lattice via two equal ‐P=O···H‐N‐ hydrogen bonds. ¹H and ¹³C NMR spectra show two series of signals for the two amine groups in compound 1 . This is also observed for the two α‐methylbenzylamine groups in 5 due to the presence of chiral carbon atom in molecule. ¹³C NMR spectrum of compound 4 shows that ²J(P,C_aliphatic) coupling constant for CH₂ group is greater than for CH₃ in agreement with our previous study. Mass spectra of compounds 1 ‐ 3 (containing 4‐F‐C₆H₄C(O)N(H)P(O) moiety) indicate the fragments of amidophosphoric acid and 4‐F‐C₆H₄CN⁺ that formed in a pseudo McLafferty rearrangement pathway. Also, the fragments of aliphatic amines have high intensity in mass spectra.     

N‐Benzoyl‐N′,N′‐dibutylselenourea and its palladium(II) complex

The crystal and molecular structures of N‐benzoyl‐N′,N′‐dibutylselenourea (HL), C₁₆H₂₄N₂OSe, and the corresponding complex bis(N‐benzoyl‐N′,N′‐dibutylselenoureato‐κ²Se,O)palladium(II), [Pd(C₁₆H₂₃N₂OSe)₂], are reported. The selenourea molecule is characterized by intermolecular hydrogen bonds between the selenoamidic H atom and the Se atom of a neighbouring molecule forming a dimer, presumably as a consequence of resonance‐assisted hydrogen bonding or π‐bonding co‐operativity. A second dimeric hydrogen bond is also described. In the palladium complex, the typical square‐planar coordination characteristic of such ligands results in a cis‐[Pd(L‐Se,O)₂] complex.     

Synthesis,Structure and Selective Chlorination of Bis(N‐borane‐dimethylaminopropyl)telluride

The reaction of Te powder, NaBH₄ and Me₂N(CH₂)₃Cl·HCl provided the title compound [H₃BNMe₂(CH₂)₃]₂Te ( 1 ), whose selective chlorination with SO₂Cl₂ lead to the formation of [ClH₂BNMe₂(CH₂)₃]₂TeCl₂ ( 2 ) and [Cl₃BNMe₂(CH₂)₃]₂TeCl₂ ( 3 ), respectively. Compounds 1 – 3 were characterized by multinuclear NMR spectroscopy and single crystal X‐ray diffraction.     

Relaxivity Study and X-ray Structure of Gd(III)-diethylenetriamine-N,N′,N′-triacetic-N,N″-bis(benzylamide). A Potential MRI Contrast Agent

The new bis(amide) derivatives of DTPA (diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid), diethylenetriamine-N,N′,N″-triacetic-N,N″-bis(benzylamide) (DTPA-BBA) have been synthesized. The crystal structure of gadolinium(III) complex of DTPA-BBA ([Gd(DTPA-BBA)]) has been determined by X-ray crystallography: C₂₈H₅₂GdN₅O₁₇, M_w = 889 g mol^?1, space group $ {\rm P}\bar 1 $ (#2) (triclinic), a = 12.645(4), b=14.125(8), c = 12.623(4) Å, α = 111.60(3), β = 114.79(3), γ = 88.39(4)°, V = 1881(1) ų, Z = 2, D_x = 1.569 g/cm³, λ(Mo Kα) =0.71069 Å, μ = 18.44 cm^?1, final R = 0.047, R_w = 0.046 for 3755 independent observed reflections at 23 °C. The coordination sphere of Gd(III) comprises three amine nitrogens, two amide oxygens, three carboxylic acid oxygens, and one water. The relaxivity of Gd(III) complex was determined to be R1 = 4.08(4) and R2 = 6.06(5) dm³ mmol^?1 s^?1 at pH = 7.0, 20 MHz, and 37(1) °C. Additionally, the R1 relaxivity for Gd(III) chelate was found to be invariant with respect to pH changes over the range of 2-10. This indicates that a constant inner-sphere hydration number is associated with the [Gd(DTPA-BBA)] complex. Hence the high stability of the complex is demonstrated.     

A 3-D Mn(II) complex containing N-isonicotinyl,N′,N′′-bis(hexamethylenyl) phosphoric triamide ligand: synthesis,structural characterization,and thermal studies

A new phosphoryl-containing ligand, N-isonicotinyl, N′,N′′-bis(hexamethylenyl) phosphoric triamide (1), was synthesized and characterized using IR, ¹H, ¹³C, and ³¹P NMR and UV–vis spectroscopy. Reaction of 1 with MnCl₂·4H₂O led to the formation of Mn(II) complex with the formula {Mn[4-NC₅H₄C(O)NHP(O)(NC₆H₁₂)₂]₂Cl₂}_n (2). Crystal structures of 1 and 2 were determined by X-ray crystallography, which reveals that 2 is centrosymmetric with two phosphoryl oxygens, chloride and nitrogen in trans positions. Coordination of bridged bidentate 1 through oxygen of the phosphoryl and nitrogen of the pyridine afforded a 3-D network extended by coordinative bonds. Compound 2 and its nano-sized particles prepared by sonochemical method were characterized by IR spectroscopy, X-ray powder diffraction, and thermal analysis and exhibited paramagnetic behavior at room temperature. Crystalline mixture of Mn₂P₂O₇ and Mn₂P₄O₁₂ was identified as a thermolysis product of 2.     

Two new thiophosphoramide structures: N,N′,N′′‐tricyclohexylphosphorothioic triamide and O,O′‐diethyl (2‐phenylhydrazin‐1‐yl)thiophosphonate

The compound N,N′,N′′‐tricyclohexylphosphorothioic triamide, C₁₈H₃₆N₃PS or P(S)[NHC₆H₁₁]₃, (I), crystallizes in the space group Pnma with the molecule lying across a mirror plane; one N atom lies on the mirror plane, whereas the bond‐angle sum at the other N atom has a deviation of some 8° from the ideal value of 360° for a planar configuration. The orientation of the atoms attached to this nonplanar N atom corresponds to an anti orientation of the corresponding lone electron pair (LEP) with respect to the P=S group. The P=S bond length of 1.9785 (6) Å is within the expected range for compounds with a P(S)[N]₃ skeleton; however, it is in the region of the longest bond lengths found for analogous structures. This may be due to the involvement of the P=S group in N—H...S=P hydrogen bonds. In O,O′‐diethyl (2‐phenylhydrazin‐1‐yl)thiophosphonate, C₁₀H₁₇N₂O₂PS or P(S)[OC₂H₅]₂[NHNHC₆H₅], (II), the bond‐angle sum at the N atom attached to the phenyl ring is 345.1°, whereas, for the N atom bonded to the P atom, a practically planar environment is observed, with a bond‐angle sum of 359.1°. A Cambridge Structural Database [CSD; Allen (2002). Acta Cryst. B 58 , 380–388] analysis shows a shift of the maximum population of P=S bond lengths in compounds with a P(S)[O]₂[N] skeleton to the shorter bond lengths relative to compounds with a P(S)[N]₃ skeleton. The influence of this difference on the collective tendencies of N...S distances in N—H...S hydrogen bonds for structures with P(S)[N]₃ and P(S)[O]₂[N] segments were studied through a CSD analysis.     

Structural and NMR Studies of the Hexameric Copper(I) Complex with N‐n‐butyl‐N′‐ethoxycarbonyl‐thioureate

The copper sulfide mineral flotation collector, N‐n‐butyl‐N′‐ethoxycarbonyl‐thiourea (H₂bectu), and the 1:1 hexameric copper(I) thioureate complex, [Cu(Hbectu)]₆, have been characterized by single crystal X‐ray diffraction. H₂bectu crystallizes in the triclinic space group with a = 5.2754(4), b = 9.0042(7), c = 12.6030(9) Å, α = 80.528(6), β = 90.173(6), γ = 76.472(7)°. An intramolecular N‐H···O hydrogen bond between the thioamide proton and carbonyl oxygen forms a planar six‐membered ring in the central core of the molecule with C=O, C=S and C‐N bond lengths in accord with those reported for other N‐alkyl/aryl‐N′‐acyl‐thiourea compounds. [Cu(Hbectu)]₆ crystallizes in the monoclinic space group C2/c with a = 23.269(5), b = 13.243(4), c = 23.037(7) Å, β = 91.81(2)° as discrete hexameric clusters disposed about a crystallographic centre of symmetry with a Cu₆S₆ core consisting of two Cu₃S₃ chair‐shaped rings linked by coordination of the deprotonated amide nitrogen atom to a copper atom in the adjacent ring. The six ligands assemble as a paddlewheel structure with the ethoxy and n‐butyl substituents packing in an alternating head to tail arrangement. Temperature dependent solution ¹H NMR spectroscopic studies show that the hexameric structure of the complex is maintained in solution.     

Bis[N,N′‐bis(2‐nitrocinnamaldehyde)phenylenediimine]copper(I) Perchlorate

The complex [Cu(nitroca₂ph)₂]ClO₄, where nitroca₂ph is N,N′‐bis(2‐nitrocinnamaldehyde)phenylenediimine, crystallizes in the triclinic space group with a = 13.167(1), b = 13.209(1), c = 14.465(1) Å, α = 83.209(9)°, β = 68.438(2)°, γ = 70.803(2)°, V = 2209.4(3) ų, Z = 2, D_calc = 1.527 mg/m³. The coordination polyhedron about the Cu(I) atom is best described as a distorted tetrahedron. 2‐nitroca₂en acts as a bidentate ligand coordinating via two N atoms to the copper. The four Cu–N distances are 2.04 (2), 2.038(2), 2.046(2), and 2.062(2) Å.     

Synthese,Struktur und einige Reaktionen [N-(N′,N′,N″,N″-tetramethyl)-guanidinyl]-substituierter Phosphorylverbindungen

Synthesis, Structure, and some Reactions of N-(N′,N′,N″,N″-tetramethyl)guanidinyl-substituted Phosphoryl Compounds The tetramethylguanidinyl-substituted phosphoryl compounds 1 – 10 were prepared in the reaction of the appropriate chlorophosphoryl compounds with either N′,N′,N″,N″-tetramethylguanidine (HTMG) or N-trimethylsilyl-(N′,N′,N″,N″-tetramethyl)guanidine (TMSTMG). With methyl iodide 1 reacted with N-alkylation to give the ammonium salt 11. 1 reacted with BF₃ · Et₂O at both imino nitrogen atoms with formation of the bis-BF₃-adduct 12 . The X-ray structure determination of phenylphosphonic acid-bis(N′,N′,N″,N″-tetramethylguanidinide) 3 shows shortened PN-bonds and widened PNC-angles, consistent with the partial double bond character of the PN-bond.     

Synthesis,Coordination, and Spectroscopic Properties of 2,2′‐Bipyridyldimesitylpalladium(II) and 6‐Mesityl‐2,2′‐bipyridyldimesitylpalladium(II)

The synthetic route to the dimesitylpalladium(II) complex [(bpy)PdMes₂] ( 1 ) (Mes = mesityl = 2,4,6‐trimethyl phenyl) does not only give the desired compound but also the 6‐mesityl‐2,2′bipyridyldimesitylpalladium [(6‐Mes‐bpy)PdMes₂] ( 2 ) complex and the free ligand 6,6′‐dimesityl‐2,2′‐bipyridine in reasonable yields. Single crystals of 2 were examined by X‐Ray diffraction. The compound reveals a sterically crowded molecular structure. An intramolecular π‐stacking interaction was found between the mesityl substituent on the bipyridine ligand and the adjacent mesityl ligand. The electrochemical behaviour of 1 and 2 together with a related compound was examined at various temperatures showing two reversible reduction reactions and reversible one‐electron oxidation steps at low temperatures. The latter are assigned to Pd^II/Pd^III couples.     

Synthesis,structural characterization,density functional theory calculations and biological evaluation of a new organotin(IV) complex containing N‐isonicotinyl‐N',N″‐diaryl phosphorictriamide as N‐donor ligand

A new diorganotin(IV) complex with the formula SnCl₂(CH₃)₂L₂ ( C_1a ), L = 4‐NC₅H₄CONHPO(NCH₃CH₂C₆H₅)₂, was synthesized and characterized using ¹H NMR, ¹³C NMR, ³¹P NMR, ¹¹⁹Sn NMR and infrared spectroscopies. The molecular structure of C_1a was determined using X‐ray crystallography, revealing that C_1a contains hexa‐coordinated Sn(IV) centres with trans‐configuration of donor atoms around them. Each Sn(IV) atom is positioned in the centre of inversion of an octahedron. C_1a forms one‐dimensional chains via two equal intermolecular P?O…H? N hydrogen bonds. These hydrogen bonds produce centrosymmetric rings as a supramolecular hydrogen‐bonded pattern. In order to compare the relative stability of C_1a (with N‐ligated configuration) and its possible O‐ligated isomer, C_1b , density functional theory calculations were performed, the results showing a preference of C_1a over C_1b from an energy point of view. Also, natural bond orbital analysis was carried out to obtain detailed information on the electronic features of the optimized structures. The theoretical results show that intermolecular hydrogen bonding in the crystal structure has a significant role in the stabilization of C_1a , and Sn(IV) interacts more strongly with the N_py atom than the P?O functional group. Furthermore, the free ligand and its complex were tested against three human cancer cell lines, i.e. human cervical carcinoma (HeLa), human prostate cancer (PC‐3) and human breast adenocarcinoma cancer (MCF‐7). C_1a displays moderate to good cytotoxicity towards all three cancer cell lines. Moreover, antibacterial tests were carried out using the disc‐diffusion method, in which C_1a shows high activity against selected Gram‐negative and Gram‐positive bacteria. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and Structure of New Trimethylplatinum(IV) Iodide Complexes of 2,2′‐Bipyridine Ligands

The synthesis and structural characterization of four new trimethylplatinum(IV) iodide complexes of 2,2′‐bipyridine ligands {[PtMe₃(4,4′‐Clbipy)I] ( 1 ), [PtMe₃(4,4′‐Brbipy)I] ( 2 ), [PtMe₃(4,4′‐CNbipy)I] ( 3 ) and [PtMe₃(4,4′‐NO₂bipy)I] ( 4 )} are reported. The ¹H NMR spectra of the complexes reveal the presence of two chemically distinct methyl groups in the complexes. X‐ray crystal structures of complexes 1 – 4 show that the platinum metal center in each of the complexes form distorted octahedral structure being surrounded by methyl groups, bipyridine ligand, and iodine atom. Furthermore, the crystal packing study shows that self‐assembly of the complexes are governed by weak hydrogen bonding and other non‐covalent interactions such as π ··· π, halogen ··· π and C–H ··· π interactions. Complex 1 exhibits infinite one‐dimensional zigzag chain structure and other three complexes form infinite ladder type structures.     

N,N′‐Bis(Salicylidene)‐1,2‐Cyclohexanediamine Lanthanide(III) Coordination Polymers: Syntheses,Crystal Structures,and Luminescence Properties

The salen‐type ligand H₂L [H₂L = N,N′‐bis(salicylidene)‐1,2‐cyclohexanediamine] was utilized for the synthesis of two lanthanide(III) coordination polymers [LnH₂L(NO₃)₃MeOH]_n [Ln = Eu ( 1 ) and Ln = Lu ( 2 )]. The single‐crystal X‐ray diffraction analyses of 1 and 2 revealed that they are isomorphous and exhibit one‐dimension neutral structure, in which H₂L effectively functions as a bridging ligand and give rise to a chain‐like polymer. The luminescent properties of polymers in solid state and in solution were investigated and 1 exhibits typical red luminescence of Eu^III ions in solid state and dichloromethane solution and 2 emits the ligand‐centered blue luminescence. The energy transfer mechanisms in these luminescent lanthanide polymers were described through calculation of the lowest triplet level of ligand H₂L.     

Magnetic Exchange Interactions in Dinuclear Copper(II) and Nickel(II) Complexes with μ‐Oxalato Bridges. The Structure of μ‐Oxalato(O,O′, O″, O‴)‐bis{[1, 8‐di(2‐pyridyl)‐3, 6‐dithiaoctane‐N,N′, S,S′]nickel(II)} Dinitrate Dihydrate

A copper(II) and two nickel(II) dinuclear oxalato‐bridged compounds of formulae [{Cu(bpdto)}₂(μ‐ox)](ClO₄)₂ ( 1 ), [{Ni(bpdto)]₂(μ‐ox)](ClO₄)₂( 2 ), and [{Ni(bpdto)}₂(μ‐ox)](NO₃)₂·2H₂O ( 3 ), where bpdto = 1, 8‐bis(2‐pyridyl)‐3, 6‐dithiaoctane and ox = oxalate = C₂O₄^2— anion, have been synthesized and characterized. The crystal structure of 3 was determined by single‐crystal X‐ray analysis. It is a dinuclear complex with i symmetry in which the oxalate ligand is coordinated in bis(didentate) fashion to the inversion centre‐related nickel atoms. The distorted octahedral environment of each nickel atom is completed by two sulphur atoms in the equatorial plane and by two pyridyl nitrogen atoms in axial positions. Magnetic susceptibility measurements over the range 5 — 299K, show antiferromagnetic interactions that are weak in 1 (J = —12.8 cm^—1) and strong in 2 and 3 (J = —37.8 and —40.9 cm^—1, respectively), which in the case of 3 is in keeping with the observed structural parameters.     

Synthesis,Spectroscopic Properties,and Crystal Structure of 2,2′‐Bipyridyldimesitylnickel(II)

The dimesitylnickel(II) complex [(bpy)NiMes₂] (Mes = mesityl = 2,4,6‐trimethylphenyl) was prepared and examined spectroscopically and electrochemically. The crystal and molecular structure was determined from single crystal X‐Ray diffraction experiments (monoclinic, P2₁/n, Z = 4, a = 8.3092(8) Å, b = 18.233(2) Å, c = 15.226(2) Å, β = 98.035(6)°). The nickel atom displays a distorted square planar environment. The axial positions of the square plane are shielded by each one of the methyl groups on the mesityl substituents. The complex shows electrochemical reduction processes that are mainly centered on the bpy ligand as inferred from spectroelectrochemical investigations (EPR and UV/Vis/NIR absorption) of the radical anion or dianion. The observed oxidation is assigned to a Ni^II/Ni^III couple. The title complex exhibits strongly solvatochromic longwavelength electronic absorptions.     

Zn(NCS)2‐3‐cyanopyridine Coordination Compounds: Synthesis,Crystal Structures,and Thermal Properties

The reaction of different stoichiometric amounts of Zn(NCS)₂ with 3‐cyanopyridine in different solvents leads to the formation of several new coordination compounds, which were structurally characterized and investigated for their thermal behavior. In Zn(NCS)₂(3‐cyanopyridine)₄ ( 1 ) and Zn(NCS)₂(3‐cyanopyridine)₂(H₂O)₂ · (3‐cyanopyridine)₂ ( 2 ) the zinc cations are octahedrally coordinated by two terminally N‐bonded thiocyanate anions and four 3‐cyanopyridine ( 1 ) or two 3‐cyanopyridine and two water molecules ( 2 ) within slightly distorted octahedra. Zn(NCS)₂(3‐cyanopyridine)₂ ( 3 ) and Zn(NCS)₂(3‐cyanopyridine)₂ · (H₂O)_0.5 ( 3‐H₂O ) also form discrete complexes but with tetrahedrally coordinated Zn cations. Upon heating compound 1 decomposes without the formation of any intermediate compound. In contrast, compound 2 loses the water molecules in the first step and transforms into compound 1 . Surprisingly, upon further heating a second TG step is observed, in which compound 3 is formed as an intermediate, which is not observed if compound 1 is heated directly. The tetrahedral complex 3 melts leading to the formation of an amorphous phase. If the hemihydrate 3‐H₂O is heated, it transforms into 3 via melting and crystallization but there are hints that a metastable phase might form as intermediate on water removal.