Structural studies of phosphor-1,1-diselenoato Mn(I) and Re(I) complexes

Mononuclear complexes of the type, M(CO)₄[Se₂P(OR)₂] (M = Mn, R = ⁱPr, 1a; Et, 1b; M = Re, R = ⁱPr, 3a; Et, 3b) can be prepared from either [-Se(Se)P(OⁱPr)₂]₂ (A) or [Se{-Se(Se)P(OEt)₂}₂] (B) with M(CO)₅Br. O,O′-dialkyl diselenophosphate ([(RO)₂PSe₂]^-, abbreviated as dsep) ligands generated from A and B act as a chelating ligand in these complexes. Upon refluxing in acetonitrile, these mononuclear complexes yield dinuclear complexes with a general formula of [M₂(CO)₆{Se₂P(OR)₂}₂] (M = Mn, R = ⁱPr, 2a; Et, 2b; M = Re, R = ⁱPr, 4a; Et, 4b). Dsep ligands display a triconnective, bimetallic bonding mode in the dinuclear compounds and this kind of connective pattern has never been identified in any phosphor-1,1-diselenoato metal complexes. Compounds 2b, 3b, and 4 are structurally characterized. Compounds 2b and 3b display weak, secondary Se?Se interactions in their lattices.     

Synthesis of two-coordinate iron aryloxides and their reactions with organic azide: Intramolecular C-H bond amination

The synthesis and reaction of homoleptic iron(II) complexes with 2,6-di-adamantyl-substituted aryloxides [OC₆H₂-2,6-Ad-4-R]⁻ ([OAr^AdR]⁻, Ad = adamantyl, R = Me, ⁱPr) are described. Monomeric two-coordinate iron aryloxides Fe(OAr^AdR)₂ (R = Me, 1; ⁱPr, 2) were synthesized by the reaction of Fe[N(SiMe₃)₂]₂ with 2 equiv of HOAr^AdR. Treatment of 1 and 2 with 1-azidoadamantane resulted in intramolecular insertion of an adamantyl nitrene into a methylene C-H bond of the aryloxide adamantyl substituent, yielding the corresponding amine-aryloxide complexes Fe(OAr^AdR)(OAr^AdR-NHAd) (R = Me, 3; ⁱPr, 4). Molecular structures of all these complexes are reported.     

Bimetallic nickel complexes of macrocyclic tetraiminodiphenols and their ethylene polymerization

Schiff’s base condensation of 2,6-diformyl-4-R-phenol and affords 34-membered macrocyclic tetraiminodiphenol compounds, (R = H and R′ = iPr, 1; R = Me and R′ = iPr, 2; R = F and R′ = iPr, 3; R = Me and R′ = Et, 4; R = F and R′ = Et, 5) in good yields (47-62%), from which dinuclear nickel complexes, (R = H and R′ =  iPr, 6; R = Me and R′ = iPr, 7; R = F and R′ = iPr, 8) are prepared. Molecular structures of 2, dipotassium salt of 1, and 7 were confirmed by X-ray crystallography. Addition of B(C₆F₅)₃ to a toluene solution of 6-8 gives insoluble precipitates which show good activity for ethylene polymerization.     

Synthesis, characterization, and norbornene polymerization of η-benzylnickel(II) complexes of N-heterocyclic carbenes

Neutral η¹-benzylnickel carbene complexes, [Ni(η¹-CH₂C₆H₅)(IiPr)(PMe₃)(Cl)] (3) (IiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) and [Ni(η¹-CH₂C₆H₅)(SIiPr)(PMe₃)(Cl)] (4) (SIiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazolin-2-ylidene), were prepared by the reaction between [Ni(η³-CH₂C₆H₅)(PMe₃)(Cl)] and an equivalent amount of the corresponding free N-heterocyclic carbene. The preparation of η³-benzylnickel carbene complexes, [Ni(η³-CH₂C₆H₅)(IiPr)(Cl)] (5) and [Ni(η³-CH₂C₆H₅)(SIiPr)(Cl)] (6) were carried out by the abstraction of PMe₃ from 3 and 4 by the treatment of B(C₆F₅)₃. The treatment of AgX on 5 and 6 produced the anion-exchanged complexes, [Ni(η³-CH₂C₆H₅)(NHC)(X)] (7, NHC = IiPr, X = O₂CCF₃; 8, NHC = IiPr, X = O₃SCF₃; 9, NHC = SIiPr, X = O₂CCF₃; 10, NHC = SIiPr, X = O₃SCF₃). The solid state structures of 3 and 10 were determined by X-ray crystallography. The η³-benzyl complexes of IiPr (5, 7, and 8) alone, in the absence of any activators such as borate and MAO, showed good catalytic activity towards the vinyl-type norbornene polymerization. The catalyst was thermally robust and the activity increases as the temperature rises to 130 °C.     

The (phosphino)tetraphenylborate ligand in ruthenium-arene chemistry

The synthesis of a series of anionic half-sandwich ruthenium-arene complexes [E][RuCl₂(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (E = Bu₄N⁺: R = Ph, 1a, ⁱPr, 1b or Cy, 1c; E = bis(triphenylphosphine)iminium or PNP⁺: R = Ph, 1a′, ⁱPr, 1b′ or Cy, 1c′) are reported. X-ray crystallographic studies of 1a′ and 1b′ confirmed the three-legged piano-stool coordination geometry. In solution, complexes 1a-c and 1a′-c′ are proposed to form monomer-dimer equilibria as a result of chloride ligand dissociation. Complexes 1a-c and 1a′-c′ also form the formally neutral zwitterionic complexes [RuCl(L)(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (L = pyridine: R = Ph, 2a, ⁱPr, 2b or Cy, 2c; L = MeCN: R = Ph, 3a, ⁱPr, 3b or Cy, 3c) via chloride ligand abstraction using AgNO₃ or MeOTf.     

Reaction of 1,2-dibromoethane with primary amines: formation of N,N′-disubstituted ethylenediamines RNH-CH2CH2-NHR and homologous polyamines RNH-[CH2CH2NR]n-H

The reaction of primary amines RNH₂ (R: Me, Et, iPr, tBu and Ph) with 1,2-dibromoethane gave N,N′-disubstituted ethylenediamines R-NH-CH₂CH₂-NH-R (1) in yields ranging from 10% (1a; R=Me) to 70% (1d, R=tBu; 1e, R=Ph). Piperazines and N-substituted polyethyleneimines were identified (¹H NMR, ¹³C NMR and EI-MS) as side products of the reaction and isolated by fractional distillation. The piperazines 2 are formed in yields of 3-10% and can be separated from the diamines 1 in all cases, except for R=Me and Ph. The polyamine homologues RNH-[CH₂CH₂NR]_n-H (3-5) were isolated in yields ranging from 0.1% (n=4, R=iPr) to 14% (n=2, R=iPr). The yields of 1 increase with the size of the substituent R, no obvious trend exists for the yields of the side products.     

Titanatranes containing tetradentate ligands with controlled steric hindrance

New monomeric titanatranes (Ar = 2,6-di-i-Pr-phenyl; x = 0, 5; x = 1, 6; x = 2, 7; x = 3, 8) were synthesized from the corresponding tetradentate ligands 1-4, respectively, using an equimolar mixture of Ti(O-i-Pr)₄ and 2,6-di-i-Pr-phenol. These compounds show the catalytic activity for the ring opening polymerization of l-lactide.     

Molecular structures and supramolecular association of chlorodiorganotin(IV) complexes with bis- and tris-dithiocarbamate ligand

Two series of di and trinuclear chlorodiorganotin(IV) complexes derived from bis- and tris-dithiocarbamate ligands have been prepared and structurally characterized. The dinuclear complexes 1-2 of the composition {(R₂SnCl)₂(bis-dtc)} (1, R = Me; 2, R = ⁿBu) have been obtained from R₂SnCl₂ (R = Me, ⁿBu) and the triethylammonium salt of N,N′-dibenzyl-1,2-ethylene-bis(dithiocarbamate). The trinuclear complexes 3-9 with the general formula {(R₂SnCl)₃(tris-dtc)} 3, R = Me, tris-dtc = tris-dtc-Me; 4, R = Me, tris-dtc = tris-dtc-ⁱPr; 5, R = Me, tris-dtc = tris-dtc-Bn; 6, R = ⁿBu, tris-dtc = tris-dtc-Me; 7, R = ⁿBu, tris-dtc = tris-dtc- ⁱPr; 8, R = ⁿBu, tris-dtc = tris-dtc-Bn; 9, R = ^tBu, tris-dtc = tris-dtc-Me) were prepared from R₂SnCl₂ (R = Me, ⁿBu, ^tBu) and the potassium dithiocarbamate salts of (tris[2-(methylamino)ethyl]amine) (tris-dtc-Me), (tris[2-(isopropylamino)ethyl]amine) (=tris-dtc-ⁱPr) and (tris[2-(benzylamino)ethyl]amine) (=tris-dtc-Bn). Compounds 1-9 have been analyzed as far as possible by elemental analysis, FAB⁺ mass spectrometry, IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy, and single-crystal X-ray diffraction analysis. The solid state and solution studies showed that the dtc ligands are coordinated to the tin atoms in the anisobidentate manner. In all cases the metal centers are five-coordinate. The coordination geometry is intermediate between square-pyramidal and trigonal-bipyramidal coordination polyhedra with τ-values in the range of 0.32-0.53. For the members of each series characterized in the solid state by X-ray diffraction analysis, different molecular conformations were found. The crystal structures show the presence of C-H?Cl, C-H?S, C-H?π, S?Cl, S?S, Cl?Sn and S?Sn contacts.     

Palladium(II)/allylpalladium(II) complexes with xanthate ligands: Single-source precursors for the generation of palladium sulfide nanocrystals

In an effort to find simple and common single-source precursors for palladium sulfide nanostructures, palladium(II) complexes, [Pd(S₂X)₂] (X = COMe (1), COⁱPr (2)) and η³-allylpalladium complexes with xanthate ligands, [(η³-CH₂C(CH₃)CR₂)Pd(S₂X)] (R = H, X = COMe (3); R = H, X = COEt (4); R = H, X = COⁱPr (5); R = CH₃, X = COMe (6)), have been investigated. The crystal structures of [Pd(S₂X)₂] (X = COMe (1), CoⁱPr (2)) and [(η³-CH₂C(CH₃)CH₂)Pd(S₂COMe)] (3) have been established by single crystal X-ray diffraction analysis. The complexes, 1, 2 and 3 all contain a square planar palladium(II) centre. In the allyl complex 3, this is defined by the two sulfurs of the xanthate and the outer carbons of the 2-methylallyl ligand, while in the complexes, 1 and 2 it is defined by the four sulfur atoms of the xanthate ligand. Thermogravimetric studies have been carried out to evaluate the thermal stability of η³-allylpalladium(II) analogues. The complexes are useful precursors for the growth of nanocrystals of PdS either by furnace decomposition or solvothermolysis in dioctyl ether. The solvothermal decomposition of complexes in dioctyl ether gives a new metastable phase of PdS which can be transformed to the more stable tetragonal phase at 320 °C. The nanocrystals obtained have been characterized by PXRD, SEM, TEM and EDX.     

Formation of 5-phenyl-1,2-dithiole-3-thione from molybdenum dithiopropiolato complexes

Molybdenum dithiopropiolato complexes, [(η⁵-C₅R₄R^′)Mo(CO)₂(η²-S₂CCCPh)] (R=H, R^′=Me 1a, R=R^′=H 1b; R=R^′=Me 1c) react with trimethylamine-N-oxide (TMNO · 2H₂O) under mild thermolysis to form 5-phenyl-1,2-dithiole-3-thione (2). The reaction proceeds through the formation of the oxo-complexes, [(η⁵-C₅R₄R^′)Mo(O)(η³-S₂CCCPh)] (R=H, R^′=Me 3a, R=R^′=H 3b; R=R^′=Me 3c). Direct reaction of 3a-c with TMNO · 2H₂O under thermolysis also results in formation of 2.     

Stereochemistry of the insertion of disubstituted alkynes into the metal aminocarbyne bond in diiron complexes

Terminal alkynes (HCCR^′) (R^′=COOMe, CH₂OH) insert into the metal-carbyne bond of the diiron complexes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCMe)(Cp)₂][SO₃CF₃] (R=Xyl, 1a; CH₂Ph, 1b; Me, 1c; Xyl=2,6-Me₂C₆H₃), affording the corresponding μ-vinyliminium complexes [Fe₂{μ-σ:η³-C(R^′)CHCN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R=Xyl, R^′=COOMe, 2; R=CH₂Ph, R^′=COOMe, 3; R=Me, R^′=COOMe, 4; R=Xyl, R^′=CH₂OH, 5; R=Me, R^′=CH₂OH, 6). The insertion is regiospecific and C-C bond formation selectively occurs between the carbyne carbon and the CH moiety of the alkyne. Disubstituted alkynes (R^′CCR^′) also insert into the metal-carbyne bond leading to the formation of [Fe₂{μ-σ:η³-C(R^′)C(R^′)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R^′=Me, R=Xyl, 8; R^′=Et, R=Xyl, 9; R^′=COOMe, R=Xyl, 10; R^′=COOMe, R=CH₂Ph, 11; R^′=COOMe, R=Me, 12). Complexes 2, 3, 5, 8, 9 and 11, in which the iminium nitrogen is unsymmetrically substituted, give rise to E and/or Z isomers. When iminium substituents are Me and Xyl, the NMR and structural investigations (X-ray structure analysis of 2 and 8) indicate that complexes obtained from terminal alkynes preferentially adopt the E configuration, whereas those derived from internal alkynes are exclusively Z. In complexes 8 and 9, trans and cis isomers have been observed, by NMR spectroscopy, and the structures of trans-8 and cis-8 have been determined by X-ray diffraction studies. Trans to cis isomerization occurs upon heating in THF at reflux temperature. In contrast to the case of HCCR^′, the insertion of 2-hexyne is not regiospecific: both [Fe₂{μ-σ:η³-C(CH₂CH₂CH₃)C(Me)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R=Xyl, 13; R=Me, 15) and [Fe₂{μ-σ:η³-C(Me)C(CH₂CH₂CH₃)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R=Xyl, 14, R=Me, 16) are obtained and these compounds are present in solution as a mixture of cis and trans isomers, with predominance of the former.     

Synthesis and structural studies of some titanium and zirconium complexes with chiral bis(amide), amidinate or bis(amidinate) ligands

Reaction of bis(amide) sodium Na₂[(1R,2R)-(−)-1,2-(NSiMe₃)₂-C₆H₁₀] (Na₂[L¹]) with Ti(OiPr)₂Cl₂ in different conditions gave mixed-ligand complexes [Ti(OiPr)Cl][L¹] (1) or [Ti(OiPr)₂Cl]₂[L¹] (2); 2 is a dinuclear titanium example in which Ti atoms are bridged by nitrogen and oxygen atoms simultaneously forming a distorted rhombic core. Reaction of the amine-amidinate ligand (1R,2R)-(−)-1-Li[NC(Ph)N(SiMe₃)]-2-(NHSiMe₃)-C₆H₁₀(Li[L²]) or rarely linked bis(amidinate) ligand Li₂[(1R,2R)-(−)-1,2-{NC(Ph)N(SiMe₃)}₂-C₆H₁₀](Li₂[L³]) with ZrCl₄ yielded the unbridged and bridged bis(amidinate) complexes ZrCl₂[L²]₂ (3) and [ZrCl₂(THF)][L³] (4), respectively; Moreover, the reaction of (1R,2R)-(−)-1-Li[NC(Ph)N(SiMe₃)]-2-Li(NSiMe₃)C₆H₁₀(Li₂[L²]) with Ti(OiPr)₂Cl₂ gave a new type of tridentate amido-amidinate product [Ti(OiPr)₂][L²] (6), which is a distinct model compared to [Ti(OiPr)₂Cl][L²] (5) yielded from Li[L²]. All the products have been characterized by X-ray crystallography and the structural studies are presented detailedly comparing with relevant compounds.     

A “sodium trap” based on benzo-15-crown-5 with an exocyclic N-(thiophosphoryl)thiourea moiety

For N-(thio)phosphorylthioureas of the common formula RC(S)NHP(X)(OiPr)₂HL^I (R = N-(4′-aminobenzo-15-crown-5), X = S), HL^II (R = N-(4′-aminobenzo-15-crown-5), X = O), HL^III (R = PhNH, X = S), HL^IV (R = PhNH, X = O), and (N,N′-bis-[C(S)NHP(S)(OiPr)₂]₂-1,10-diaza-18-crown-6) H₂L^V, salts LiL^I,III,IV, NaL^I–IV, KL^I–IVM₂L^V (M = Li⁺, Na⁺, K⁺), Ba(L^I,III,IV)₂, and BaL^V have been synthesized and investigated. Compounds NaL^I,II quantitatively drop out as a deposit in ethanol medium, allowing the separation of Na⁺ and K⁺ cations. This effect is not displayed for the other compounds. The crystal structures of HL^III and the solvate of the composition [K(Me₂CO)L^III] have been investigated by X-ray crystallography.     

Novel pentacoordinate silicon compounds bearing [Si-N-C-N-C-N] chelate ring derived from biguanide ligands

The reactions between secondary carbosilanes 1-3 and 1-propylbiguanide/1-phenylbiguanide, H₆bigR proceed via SiH/NH dehydrocoupling and afford 1,4-bis(silyl)-5-propyl/phenylbiguanides with the general formula (R¹R²₂SiCH₂CH₂SiMeH)₂·H₄bigR, [R¹=Ph, R²=Me, R=ⁿPr (4), R=Ph (5); R¹=Me, R²=Ph, R=ⁿPr (6), R¹=R²=Et, R=Ph (7)]. These compounds represent a new family of pentacoordinate silicon derivatives comprising of [Si-N-C-N-C-N] chelate ring and have been characterized by elemental analysis, FAB mass, IR and multinuclear (¹H, ¹³C and ²⁹Si) NMR spectral studies.     

Syntheses and crystal structures of di- and triorganotin derivatives with 2,5-dimercapto-1,3,4-thiodiazole

A series of organotin(IV) complexes with 2,5-dimercapto-1, 3, 4-thiodiazole (HHdmt) of the type (R_nSnCl_m)₂(dmt) (m=0, n=3, R=Ph 1, PhCH₂2, n-Bu 3; m=1, n=2, R=Ph 4) and [R₂Sn(dmt) · L]_n (L=0.5C₆H₆, R=CH₃5; L=0, n=5, R=n-Bu 6) have been synthesized. All complexes 1-6 were characterized by elemental analysis, IR, ¹H and ¹³C NMR spectra. And except for 3, complexes 1, 2, 4, 5 and 6 were also determined by X-ray crystallography. The tin atoms of complexes 1, 2, 3 and 4 are all five-coordinated. The geometries at tin atoms of 1, 2, 3 and 4 are distorted trigonal bipyramidal. The tin atoms of complexes 5 and 6 are six-coordinated and their geometries are distorted octahedral.     

Ruthenium piano-stool complexes containing mono- or bidentate pyrrolidinylalkylphosphines and their reactions with small molecules

Ruthenium piano-stool complexes incorporating the new bidentate aminoalkylphosphine ligand 1,2-bis(dipyrrolidin-1-ylphosphino)ethane (dpyrpe, I) or its monodentate counterpart bis(pyrrolidin-1-yl)methylphosphine (pyr₂PMe, II) have been prepared, [(C₅R₅)RuCl(PP)] (R = Me and PP = dpyrpe, 1; R = Me and PP = (pyr₂PMe)₂, 2; R = H and PP = dpyrpe, 3). Complexes 2 and 3 have been characterized by X-ray crystallography. Complexes 1 and 2 react with NaBAr₄^f in the presence of ligand L to yield [Cp^∗Ru(L)(dpyrpe-κ²P)][BAr^f₄] (L = MeCN, 4a; CO, 4b; N₂, 4c) and [Cp^∗Ru(L)(pyr₂PMe)₂][BAr₄^f] (L = MeCN, 5a; CO, 5b; N₂, 5c). Complex 4a was crystallographically characterized. The CO complexes 4b and 5b were examined using IR spectroscopy in an attempt to establish the electron-donating capabilities of I and II. Complex 1 oxidatively adds H₂ in the presence of NaBAr₄^f to yield the Ru(IV) dihydride [Cp^∗RuH₂(dpyrpe-κ²P)][BAr₄^f], 7.     

Mono and dinuclear half-sandwich platinum group metal complexes bearing pyrazolyl-pyrimidine ligands: Syntheses and structural studies

Reactions of 0.5 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = η⁶-C₆H₆, η⁶-p-ⁱPrC₆H₄Me) and [(Cp∗)M(μ-Cl)Cl]₂ (M = Rh, Ir; Cp∗ = η⁵-C₅Me₅) with 4,6-disubstituted pyrazolyl-pyrimidine ligands (L) viz. 4,6-bis(pyrazolyl)pyrimidine (L1), 4,6-bis(3-methyl-pyrazolyl)pyrimidine (L2), 4,6-bis(3,5-dimethyl-pyrazolyl)pyrimidine (L3) lead to the formation of the cationic mononuclear complexes [(η⁶-C₆H₆)Ru(L)Cl]⁺ (L = L1, 1; L2, 2; L3, 3), [(η⁶-p-ⁱPrC₆H₄Me)Ru(L)Cl]⁺ (L = L1, 4; L2, 5; L3, 6), [(Cp∗)Rh(L)Cl]⁺ (L = L1, 7; L2, 8; L3, 9) and [(Cp∗)Ir(L)Cl]⁺ (L = L1, 10; L2, 11; L3, 12), while reactions with 1.0 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ and [(Cp∗)M(μ-Cl)Cl]₂ give rise to the dicationic dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(L)]²⁺ (L = L1, 13; L2, 14; L3, 15), [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(L)]²⁺ (L = L1, 16; L2, 17; L3, 18), [{(Cp∗)RhCl}₂(L)]²⁺ (L = L1, 19; L2, 20; L3, 21) and [{(Cp∗)IrCl}₂(L)]²⁺ (L = L1 22; L2, 23; L3 24). The molecular structures of [3]PF₆, [6]PF₆, [7]PF₆ and [18](PF₆)₂ have been established by single crystal X-ray structure analysis.     

Fe Spin crossover materials based on dissymmetrical N4 Schiff bases including 2-pyridyl and 2R-imidazol-4-yl rings: Synthesis,crystal structure and magnetic and Mössbauer properties

The synthesis and characterization of new symmetrical Fe^II complexes, [FeL^A(NCS)₂] (1), and [FeL^Bx(NCS)₂] (2–4), are reported (L^A is the tetradentate Schiff base N,N′-bis(1-pyridin-2-ylethylidene)-2,2-dimethylpropane-1,3-diamine, and L^Bx stands for the family of tetradentate Schiff bases N,N′-bis[(2-R-1H-imidazol-4-yl)methylene]-2,2-dimethylpropane-1,3-diamine, with: R = H for L^B1 in 2, R = Me for L^B2 in 3, and R = Ph for L^B3 in 4). Single-crystal X-ray structures have been determined for 1 (low-spin state at 293 K), 2 (high-spin (HS) state at 200 K), and 3 (HS state at 180 K). These complexes remain in the same spin-state over the whole temperature range [80–400 K]. The dissymmetrical tetradentate Schiff base ligands L^Cx, N-[(2-R₂-1H-imidazol-4-yl)methylene]-N′-(1-pyridin-2-ylethylidene)-2,2-R₁-propane-1,3-diamine (R₁ = H, Me; R₂ = H, Me, Ph), containing both pyridine and imidazole rings were obtained as their [FeL^Cx(NCS)₂] complexes, 5–10, through reaction of the isolated aminal type ligands 2-methyl-2-pyridin-2-ylhexahydropyrimidine (R₁ = H, 5–7) or 2,5,5-trimethyl-2-pyridin-2-ylhexahydropyrimidine (R₁ = Me, 8–10) with imidazole-4-carboxaldehyde (R₂ = H: 5, 8), 2-methylimidazole-4-carboxaldehyde (R₂ = Me: 6, 9), and 2-phenyl-imidazole-4-carboxaldehyde (R₂ = Ph: 7, 10) in the presence of iron(II) thiocyanate. Together with the single-crystal X-ray structures of 7 and 9, variable-temperature magnetic susceptibility and Mössbauer studies of 5–10 showed that it is possible to tune the spin crossover properties in the [FeL^Cx(NCS)₂] series by changing the 2-imidazole and/or C2-propylene susbtituent of L^Cx.     

Cyclopentadienylaluminum thiolates - synthesis and structure

The dicyclopentadienylaluminum thiolates [Cp₂Al(μ-SR)]₂, where R = Et (1), ⁱPr (2), were obtained by reacting Cl₂AlSR with CpNa at the molar ratio 1:2, respectively. Use of CpLi instead of CpNa at the same molar ratio of reagents leads to the formation of cyclopentadienyl(chloro)aluminum thiolates [Cp(Cl)Al(μ-SR)]₂, exclusively, where R = Et (3), ⁱPr (4), ⁱBu (5), and ⁿBu (6). The compounds were characterized by ¹H, ¹³C, and ²⁷Al NMR spectroscopy. The structures of the compounds 1 and 4 were determined by X-ray crystallography.