Pyridine-2,6-dicarboxylate and perchlorate bridged hydrogen bonded 1D chains involving manganese(III)-cyclam moiety: synthesis, X-ray crystal structures and magnetic study

Two compounds H[Mn(cyclam)(pyridine-2,6-dicarboxylate)₂] · H₂O (1) and [Mn^III(cyclam)Cl₂]ClO₄ (2) (where cyclam=1,4,8,11-tetraazacyclotetradecane) have been synthesized and structurally characterized. The complex 1 crystallizes in the monoclinic space group P2(1)/c with a=11.4328(11), b=14.4275(14), c=8.5782(9) Å, , Z=2, R=0.0453. Complex 1 is octahedral in which [Mn(cyclam)]³⁺ unit occupies the basal plane having two pyridine-2,6-dicarboxylate anions in the axial positions. Molecular packing of the crystal is dominated by string of molecules along the b-axis. The strings are held together by extensive intermolecular hydrogen bonds involving N-H ? O, N-H ? N and O-H ? O which impart it an infinite 1D chain. Complex 2 on the other hand crystallizes in the space group P2₁2₁2₁ (No. 19) of the orthorhombic system. Mn(III) ions occupy the center of a distorted octahedron and two chloride ions occupy the axial positions. The packing diagram of 2 reveals that the complex is percholrate-bridged hydrogen bonded 1D chain along a-axis. Cyclic voltammogram of complex 1 shows a reduction wave at −0.25 V coupled to an oxidation wave at −0.05 V versus SCE in aqueous solution. The complex 2 is characterized by an irreversible reduction wave at −0.11 V versus SCE and is identical to that observed for [Mn^III(cyclam)Cl₂]Cl · 5H₂O. The magnetic measurements in the temperature range 1.9-300 K have been carried out for complex 1 which exhibits a very weak ferromagnetic interaction at low temperature. Complex 2 shows room temperature magnetic moment value of 4.92 BM consistent with the high spin d⁴ electronic configuration.     

Different coordination modes of Hdipic and dipic ligands to nickel(II) ions in a same environment (dipic = 2,6-pyridinedicarboxylate, dipicolinate)

Two new nickel(II) complexes of the composition [Ni(cyclam)(Hdipic)₂] · 2H₂O (1) and [Ni(cyclam)(H₂O)₂][Ni(dipic)₂] · 2.5H₂O (2) (cyclam = 1,4,8,11-tetraazacyclotetradecane) have been prepared and structurally characterized by a combination of analytical, spectroscopic, thermogravimetric, and crystallographic methods. The structure of 1 shows that the central nickel(II) ion is coordinated axially by two monodentate Hdipic ligands. The discrete neutral complex 1 further extends its structure by hydrogen bonding interactions to form a one-dimensional supramolecule. The structure of 2 consists of two independent nickel(II) centers. Water molecules instead of dipic ligands prefer to coordinate to the Ni1 ion forming a divalent cation [Ni(cyclam)(H₂O)₂]²⁺. Two dipic ligands coordinate to the second Ni2 ion forming a divalent anion [Ni(dipic)₂]²⁻. The divalent cations and anions are charge-balanced, resulting in a molecular salt. The divalent cations and anions are interconnected by multiple types of hydrogen bonding interactions.     

Sesquiterpene lactones from the endemic Cape Verdean Artemisia gorgonum

Leaves and flowers of Artemisia gorgonum (Asteraceae) collected in Fogo, Cape Verde islands, were phytochemically investigated and resulted in isolation and characterization of three guaianolides 1, 2, 5, and a secoguainolide 4, in addition to eight known guaianolides 6-11 and two known germacranolides 12, 13. Structures were elucidated by 1D and 2D NMR experiments. Careful examination of the ¹³C NMR spectrum led to revision of the structure of a previously described guaianolide from 2 to 3. Most compounds exhibited mild antiplasmodial activities, ridentin (13) being the most interesting with an IC₅₀ of 3.8 ± 0.7 μg ml⁻¹ against Plasmodium falciparum FcB1 and weak cytotoxicity in a vero cell line (IC₅₀ 71.0 ± 3.9 μg ml⁻¹).     

Palladium(II), platinum(II), ruthenium(II) and mercury(II) complexes of potentially tridentate Schiff base ligands of (E, N, O) type (E = S, Se, Te): Synthesis, crystal structures and applications in Heck and Suzuki coupling reactions

Schiff bases of 2-hydroxybenzophenone (HBP) (C₆H₅)(2-HOC₆H₄)CN(CH₂)_nEAr (L1/L2: E = S, Ar = Ph, n = 2/3; L3/L4: E = Se, Ar = Ph, n = 2/3; L5/L6: E = Te, Ar = 4-MeOC₆H₄, n = 2/3) and their complexes [PdCl(L-H)] (L = L1−L6; 1, 2, 3, 5, 7, 11), [PtCl(L3-H/L5-H)] (4/8), [PtCl₂(L4/L6)₂] (6/12), [(p-cymene)RuCl(L5/L6)]Cl (9/13) and [HgBr₂(L5/L6)₂] (10/14) have been synthesized and characterized by proton, carbon-13, selenium-77 and tellurium-125 NMR, IR and mass spectra. Single crystal structures of L1, 1, 3, 4, 5 and 7 were solved. The Pd-E bond distances (Å): 2.2563(6) (E = S), 2.3575(6)−2.392(2) (E = Se); 2.5117(5)−2.5198(5) (E = Te) are near the lower end of the bond length range known for them. The Pt-Se bond length, 2.3470(8) Å, is also closer to the short values reported so far. The Heck and Suzuki reaction were carried out using complexes 1, 3, 5 and 7 as catalysts under aerobic condition. The percentage yields for trans product in Heck reaction were found upto 85%.     

Molecular interactions of zinc(II) cyclams with polycarboxylato ligands

Four new zinc(II) cyclams of the composition {Zn(L)(tp²⁻) · H₂O}_n (1), {Zn(L)(H₂bta²⁻) · 2H₂O}_n (2), [Zn₂(L)₂(ox²⁻)] 2ClO₄ · 2DMF (3), and Zn(L)(H₂btc⁻)₂ · 2DMF (4), where L = cyclam, tp²⁻ = 1,4-benzenedicarboxylate ion, H₂bta²⁻ = 1,2,4,5-benzenetetracarboxylate ion, ox²⁻ = oxalate ion, DMF = N,N-dimethylformamide, and H₂btc⁻ = 1,3,5-benzenetricarboxylate ion, have been synthesized and structurally characterized by a combination of analytical, spectroscopic and crystallographic methods. The carboxylato ligands in the complexes 1-4 show strong coordination tendencies toward zinc(II) cyclams with hydrogen bonding interactions between the pre-organized N-H groups of the macrocycle and oxygen atoms of the carboxylato ligands. The macrocycles in 1, 2, and 4 adopt trans-III configurations with the appropriate R,R,S,S arrangement of the four chiral nitrogen centers, respectively. However, the complex 3 shows an unusual cis V conformation with the R,R,R,R nitrogen configuration. The finding of strong interactions between the carboxylato ligands and the zinc(II) ions may provide additional knowledge for the improved design of receptor-targeted zinc(II) cyclams in anti-HIV agents.     

Synthesis and characterization of CpMCl(PR3)(S or W-η-butadienesulfonyl) compounds of rhodium and iridium

A metathesis reaction of [Cp^∗MCl₂(PR₃)] [M = Rh, R = Ph (1), Me (3); M = Ir, R = Ph (2), Me (4)] takes place in the presence of potassium butadienesulfinate (SO₂CHCHCHCH₂)K (9) to afford the mononuclear compounds [Cp^∗M(Cl)(PR₃)(η¹-SO₂CHCHCHCH₂)] [M = Rh, R = Ph (11S), (11W); M = Rh, R = Me (13S), (13W)] and [M = Ir, R = Ph (12S); M = Ir, R = Me (14S), (14W)] under different reaction conditions. The addition of PR₃ (R = Ph, Me) to Cp^∗Ir(Cl)[(1,2,5-η)-SO₂CHCHCHCH₂] (7) affords the corresponding iridium isomers 12S, 12W and 14S, in a non-selective reaction, along with the corresponding dichloride compounds 2 or 4. The ¹H and ¹³C{¹H} NMR data are consistent with the butadienesulfonyl ligands coordinated exclusively through the sulfur atom, and they show the presence of two isomers, described as the S and W conformers, which can be isolated separately. There is clear evidence that these isomers correspond to the kinetic and thermodynamic derivatives, respectively.     

Preparation, spectroscopy, X-ray analysis, and water-solubility studies of the first bis-PTA (PTA = 1,3,5-triaza-7-phosphaadamantane) derivatives

The bis-phosphines, 1,1′-[1,2-phenylenebis(methylene)]bis-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1]decane dibromide (1), 1,1′-[1,3-arenebis(methylene)]bis-[3,5-diaza-1-azonia-7-phosphatricyclo [3.3.1.1]decane dibromide (arene = phenyl (2), tolyl (3), anisolyl (4)), and 1,1′-[1,4-phenylenebis(methylene)]bis-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1]decane dibromide (5) were prepared in over 90% yield by refluxing 1,2-bis(bromomethyl)benzene, 1,3-bis(bromomethyl)benzene, 1,3-bis(bromomethyl)-5-methyl-benzene, 1,3-bis(bromomethyl)-5-methoxy-benzene, and 1,4-bis(bromomethyl)benzene with 1,3,5-triaza-7-phosphaadamantane (PTA) in acetone or chloroform. Compounds 1-5 are the first phosphines reported that contain two PTA moieties. All five compounds were characterized by ESI-MS, elemental analysis, ¹H, ¹³C, and ³¹P NMR spectroscopy, while 3 and 4 were additionally analyzed via single crystal X-ray diffraction. The relative positions of the PTA units on the aromatic ring as well as the substituents of the ring had a pronounced effect on the water-solubilities of the systems. The ortho compound (1, 2000 mg/mL) was more than two orders of magnitude more soluble than the para compound (5, 12.5 mg/mL). The meta substituted phenyl (2) and tolyl (3) compounds had solubilities (810 mg/mL) that were more than triple that of PTA (235 mg/mL) while the anisolyl analog (4) was half as soluble (121 mg/mL).     

Syntheses, crystal structures and magnetic properties of trinuclear and [3 × 1 + 1 × 2] pentanuclear complexes derived from a compartmental ligand: Role of solvent on nuclearity and number of components

Reaction of [Cu^IIL⊂(H₂O)] (H₂L = N,N′-ethylenebis(3-ethoxysalicylaldimine)) with nickel(II) perchlorate in 1:1 ratio in acetone produces the trinuclear compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂ (1). On the other hand, on changing the solvent from acetone to methanol, reaction of the same reactants in same ratio produces the pentametallic compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)]·2MeOH (2A), which loses solvated methanol molecules immediately after its isolation to form [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)] (2B). Clearly, formation of 1 versus 2A and 2B is solvent dependent. Crystal structures of 1 and 2A have been determined. Interestingly, compound 2A is a [3 × 1 + 1 × 2] cocrystal. The cryomagnetic profiles of 1 and 2B indicate that the two pairs of copper(II)···nickel(II) ions in the trinuclear cores in both the complexes are coupled by almost identical moderate antiferromagnetic interaction (J = −22.8 cm⁻¹ for 1 and −26.0 cm⁻¹ for 2B).     

An efficient route to substituted 1-silacyclopent-2-enes and 1-silacyclohex-2-enes via consecutive 1,2-hydroboration and 1,1-organoboration

The reaction of alkyn-1-yl(vinyl)silanes R₂Si(CCR¹)CHCH₂ [R = Me (1), Ph (2); R¹ = ^tBu (a), Ph (b), SiMe₃ (c)] with 9-borabicyclo[3.3.1]nonane in a 1:1 ratio affords the 1-silacyclopent-2-ene derivatives 4a-c (R = Me) and 5a-c (R = Ph) as a result of selective intermolecular 1,2-hydroboration of the vinyl group, followed by intramolecular 1,1-organoboration of the alkynyl substituent. The analogous reaction sequence converts the alkyn-1-yl(allyl)dimethylsilanes 3a,c into the 1-silacyclohex-2-ene derivatives 7a,c. All reactions were monitored by ²⁹Si NMR spectroscopy and the structural assignment of the final products was based on multinuclear magnetic resonance data (¹H, ¹¹B, ¹³C and ²⁹Si NMR). The molecular structure of 6a was determined by X-ray analysis.     

Hybrid scorpionate/cyclopentadienyl titanium and zirconium complexes with alkoxide and imido ligands

The reactivity of hybrid scorpionate/cyclopentadienyl ligand-containing trichloride zirconium complexes [ZrCl₃(bpzcp)] (1) [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl] and [ZrCl₃(bpztcp)] (2) [bpztcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethylcyclopentadienyl] toward several lithium alkoxides has been carried out. Thus, alkoxide-containing complexes [ZrCl₂(OR)(bpzcp)] (R = Me, 3; Et, 4; ⁱPr, 5; (R)-2-Bu, 6), [ZrCl₂(OR)(bpztcp)] (R = Me, 7; Et, 8; ⁱPr, 9; (R)-2-Bu, 10) and [Zr(OR)₃(bpztcp)] (R = Et, 11; ⁱPr, 12) were prepared by deprotonation of the appropriate alcohol group with BuⁿLi followed by reaction with 1 or 2. In addition, the imido-complex [Ti(N^tBu)Cl(bpztcp)(py)] (13) were also prepared. The structures of these complexes have been proposed on basis of spectroscopic and DFT methods.     

The first metal complexes bearing ligated 3-iminoisoindolin-1-ones

The reaction between Zn(OAc)₂ · 2H₂O (1) and the 3-iminoisoindolin-1-ones H₂NCNC(O)C₆R¹R²R³R⁴ (R¹-R⁴ = H 2; R¹, R⁴ = H, R², R³ = Cl 3; R¹, R³, R⁴ = H, R² = Me 4) in EtCN at 70 °C for ca. 12 h affords the novel family of complexes [Zn{H₂NCNC(O)C₆R¹R²R³R⁴}₂(OAc)₂] (R¹-R⁴ = H 5; R¹, R⁴ = H, R², R³ = Cl 6; R¹, R³, R⁴ = H, R² = Me 7) in excellent (90% and 93% for 5 and 6, correspondingly) to good (64% for 7) yields. The isolated compounds were characterized by elemental analyses (C, H, N), IR, NMR and ESI⁺-MS. X-ray diffraction data for 2 and 5 indicate that both free (2) and ligated (5) 3-iminoisoindolin-1-ones exist in the zwitterionic form.     

Heterobimetallic Fe-Pd and Fe-Pt NCN pincer complexes (NCN = [C6H2(CH2NMe2)2-2,6])

The meta-diaminoaryl ferrocenes Fc-NCN-H (3) and Fc-CC-NCN-H (5) (Fc = (η⁵-C₅H₅)(η⁵-C₅H₄)Fe, NCN-H = C₆H₃(CH₂NMe₂)₂-3,5) can be used as precursors in the preparation of heterobimetallic transition metal complexes of structural type Fc-NCN-MX (NCN = [C₆H₂(CH₂NMe₂)₂-2,6]⁻; MX = PdCl (7), PtCl (8), PtI (9)) and Fc-CC-NCN-MX (MX = PdCl (11), PdI (12), PtCl (13)), respectively. They are accessible by applying different synthesis procedures, including oxidative addition and metallation-transmetallation processes.Cyclovoltammetric studies show that the ferrocene moieties in 3, 5, 7-9 and 11-13 can reversibly be oxidised. The potential of the Fe(II)/Fe(III) redox couple decreases with increasing electron density at the NCN pincer unit. The use of 8 as a possible (electro)chemical sensor in the detection of SO₂ is discussed as well.The solid-state structures of 8 and 13 are reported. The crystals of 8 contain two molecules of 8 in the asymmetric unit. The plane of the C₆H₂ moiety is with 27.2(3)° and 38.2(3)° tilted towards the C₅H₄ entity, while in 13 an angle of 45.9(3)° can be found. The d⁸-electron configured platinum atoms possess a somewhat distorted square-planar surrounding, setup by two Me₂NCH₂ortho-substituents, the NCN C_ipso carbon atom and the chloride ligand.     

Structures from powders: Diflorasone diacetate

Diflorasone diacetate, a steroid anti-inflammatory drug (marketed as Diacort^® or Florone^® by Pfizer) and used in the treatment of skin disorders, can be prepared as anhydrous form, DD1 (as deposited in the US pharmacopoeia), or as a monohydrated phase, DDW. Heating the DDW form above 90 °C, a mixture of DD1 and of a new anhydrous polymorph, DD2 is obtained. Further heating of this mixture, or of pure DD1, up to 230 °C (only a few degrees before melting!), generates an elusive anhydrous DD3 polymorph. Their crystal structures, determined uniquely from laboratory powder diffraction data, show the isomorphous character of the DDW and DD1 forms, while the DD2 and DD3 polymorphs crystallize with markedly different unit cells. Crystals of the DD1, DD2 and DDW forms are orthorhombic, P2₁2₁2₁, a = 29.386(1) Å; b = 10.4310(9) Å, c = 8.1422(7) Å, V = 2495.8(3) Å³ for DD1; a = 15.2639(10) Å; b = 11.7506(7) Å, c = 13.8931(11) Å, V = 2491.9(3) Å³ for DD2; a = 30.311(2) Å; b = 10.6150(9) Å, c = 7.9337(7) Å, V = 2552.7(4) Å³ for DDW; while the lattice parameters for the monoclinic P2₁DD3 species are a = 11.5276(10) Å; b = 13.8135(11) Å, c = 7.8973(7) Å, β = 103.053(6)°, V = 1225.0(2) Å³. These compounds have also been fully characterized by thermo analytical methods, as well by ¹³C, ¹⁹F, and ¹H NMR spectroscopy.     

Influence of the phosphine arrangement on the reactivity of palladium(II) and platinum(II) polyphosphine complexes with copper(I) chloride

The distorted square-planar complexes [Pd(PNHP)Cl]Cl (1) (PNHP = bis[2-(diphenylphosphino)ethyl]amine), [M(P₃)Cl]Cl [P₃ = bis[2-(diphenylphosphino)ethyl]phenylphosphine; M = Pd (2), Pt (3)] and [Pt(NP₃)Cl]Cl (5) (NP₃ = tris[2-(diphenylphosphino)ethyl]amine), coexisting in the later case with a square-pyramidal arrangement, react with one equivalent of CuCl to give the mononuclear heteroionic systems [M(L)Cl](CuCl₂) [L = PNHP, M = Pd (1a); L = P₃, M = Pd (2a), Pt (3a); L = NP₃, M = Pt (5a)]. The crystal structure of 3a confirms that Pt(II) retains the distorted square-planar geometry of 3 in the cation with P₃ acting as tridentate chelating ligand, the central P atom being trans to one chloride. The counter anion is a nearly linear dichlorocuprate(I) ion. However, the five-coordinate complexes [Pd(NP₃)Cl]Cl (4), [M(PP₃)Cl]Cl (M = Pd (6), Pt (7); PP₃ = tris[2-(diphenylphosphino)ethyl] phosphine) containing three fused five-membered chelate rings undergo a ring-opening by interaction with one (4, 6, 7) and two (6, 7) equivalents of CuCl with formation of neutral MCu(L)Cl₃ [L = NP₃, M = Pd (4a); L = PP₃, M = Pd (6a), Pt (7a)] and ionic [MCu(PP₃)Cl₂](CuCl₂) [M = Pd (6b), Pt (7b)] compounds, respectively. The heteronuclear systems were shown by ³¹P NMR to have structures where the phosphines are acting as tridentate chelating ligands to M(II) and monodentate bridging to Cu(I). Further additions of CuCl to the neutral species 6a and 7a in a 1:1 ratio resulted in the achievement of the ionic complexes 6b and 7b with ions as counter anions. It was demonstrated that the formation of heterobimetallic or just mononuclear mixed salt complexes was clearly influenced by the polyphosphine arrangement with the tripodal ligands giving the former compounds. However, complexes [M(NP₃)Cl]Cl constitute one exception and the type of reaction undergone versus CuCl is a function of the d⁸ metal centre.     

The influence of substituents (R) at N atom of thiophene-2-carbaldehyde thiosemicarbazones {(C4H3S)HCN-N(H)-C(S)NHR} on bonding, nuclearity and H-bonded networks of copper(I) complexes

The nuclearity, bonding and H-bonded networks of copper(I) halide complexes with thiophene-2-carbaldehyde thiosemicarbazones {(C₄H₃S)HC²N³-N(H)-C¹(S)N¹HR} are influenced by R substituents at N¹ atom. Thiophene-2-carbaldehyde-N¹-methyl thiosemicarbazone (HttscMe) or thiophene-2-carbaldehyde-N¹-ethyl thiosemicarbazone (HttscEt) have yielded halogen-bridged dinuclear complexes, [Cu₂(μ-X)₂(η¹-S-Htsc)₂(Ph₃P)₂] (Htsc, X: HttscMe, I, 1; Br, 2; Cl, 3; HttscEt, I, 4; Br, 5; Cl, 6), while thiophene-2-carbaldehyde-N¹-phenyl thiosemicarbazone (HttscPh) has yielded mononuclear complexes, [CuX(η¹-S-HttscPh)₂] (X, I, 7a; Br 8; Cl, 9) and a sulfur bridged dinuclear complex, [Cu₂(μ-S-HttscPh)₂(η¹-S-HttscPh)₂I₂] 7b co-existing with 7a in the same unit cell. These results are in contrast to S-bridged dimers [Cu₂(μ-S-Httsc)₂(η¹-Br)₂(Ph₃P)₂] · 2H₂O and [Cu₂(μ-S-Httsc)₂(η¹-Cl)₂(Ph₃P)₂] · 2CH₃CN obtained for R = H and X = Cl, Br (Httsc = thiophene-2-carbaldehyde thiosemicarbazone) as reported earlier. The intermolecular CH_Ph?π interaction in 1-3 (2.797 Å, 1; 3.264 Å, 2; 3.257 Å, 3) have formed linear polymers, whereas the CH_Ph?X and N³?HCH interactions in 4-6 (2.791, 2.69 Å, 5; 2.776, 2.745 Å, 6, respectively) have led to the formation of H-bonded 2D polymer. The PhN¹H?π, interactions (2.547 Å, 8, 2.599 Å, 9) have formed H-bonded dimers only. The Cu?Cu separations are 3.221-3.404 Å (1-6).     

Synthesis and reactivity with amines of new diiron alkynyl methoxy carbene complexes

The new diiron alkynyl methoxy carbene complexes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO){C(OMe)CCR′}(Cp)₂]⁺ (R = 2,6-Me₂C₆H₃ (Xyl), R′ = Tol, 3a; R = Xyl, R′ = Ph, 3b; R = Xyl, R′=Buⁿ, 3c; R = Xyl, R′=SiMe₃, 3d; R = Me, R′ = Tol, 3e; R = Me, R′ = Ph, 3f) are obtained in two steps by addition of R′CCLi (R′ = Tol, Ph, Buⁿ, SiMe₃) to the carbonyl aminocarbyne complexes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)₂(Cp)₂]⁺ (R = Xyl, 1a; Me, 1b), followed by methylation of the resulting alkynyl acyl compounds [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO){C(O)CCR′}(Cp)₂] (R = Xyl, R′ = Tol, 2a; R = Xyl, R′ = Ph, 2b; R = Xyl, R′ = Buⁿ, 2c; R = Xyl, R′ = SiMe₃, 2d; R = Me, R′ = Tol, 2e; R = Me, R′ = Ph, 2f). Complexes 3 react with secondary amines (i.e., Me₂NH, C₅H₁₀NH) to give the 4-amino-1-metalla-1,3-dienes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO){C(OMe)CHC(R′)(NMe₂)}(Cp)₂]⁺ (R = Xyl, R′ = Tol, 4a; R = Xyl, R′ = Ph, 4b; R = Me, R′ = Ph, 4c) and [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)CHC(Tol)(NC₅H₁₀)}(Cp)₂]⁺, 5. The addition occurs stereo-selectively affording only the E-configured products. Analogously, addition of primary amines R′NH₂ (R′ = Ph, Et, Prⁱ) affords the 4-(NH-amino)-1-metalla-1,3-diene complexes [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)CHC(R)(NHR′)}(Cp)₂]⁺ (R = Ph, 6a; Et, 6b; Prⁱ, 6c). In the case of 6a, only the E isomer is formed, whereas a mixture of the E and Z isomers is present in the case of 6b,c, with prevalence of the latter. Moreover, the two isomeric forms exist under dynamic equilibrium conditions, as shown by VT NMR studies. Complexes 6 are deprotonated by strong bases (e.g., NaH) resulting in the formation of the neutral vinyl imine complexes [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)CHC(NR)(Tol)}(Cp)₂] (R = Ph, 7a; Et, 7b; Prⁱ, 7c); the reaction can be reverted by addition of strong acids. X-ray crystal structures have been determined for 3a[CF₃SO₃] · Et₂O, 4c[CF₃SO₃], 6a[BF₄] · CH₂Cl₂, 6c[CF₃SO₃] · 0.5Et₂O and 7a · CH₂Cl₂.     

Synthesis and structure of dichloropalladium(II) complexes of heteroleptic N,S- and N,Se-donor ligands based on the 2-organochalcogenomethylpyridine motif, and Mizoroki-Heck catalysis mediated by complexes of N,S-donor ligands

Ligands containing the 2-organochalcogenomethylpyridine motif with substituents in the 4- or 6-position of the pyridyl ring, R⁴,R⁶-pyCH₂ER¹ [R⁴ = R⁶ = H, ER¹ = SMe (1), SeMe (2), SPh (6), SePh (7); R⁴ = Me, R⁶ = H, ER¹ = SMe (3), SPh (8), SePh (9); R⁴ = H, R⁶ = Me, ER¹ = SMe (4), SPh (10), SePh (11); R⁴ = H, R⁶ = Ph, ER¹ = SMe (5), SPh (12), SePh (13)] are obtained on the reaction of R⁴,R⁶-pyMe with LiBuⁿ followed by R¹EER¹. On reaction with PdCl₂(NCMe)₂, the ligands with a 6-phenyl substituent form cyclopalladated species PdCl{6-(o-C₆H₄)pyCH₂ER¹-C,N,E} (5a, 12a, 13a) with the structure of 13a (ER¹ = SePh) confirmed by X-ray crystallography; other ligands form complexes of stoichiometry PdCl₂(R⁴,R⁶-pyCH₂ER¹). Complexes with R⁶ = H are monomeric with N,E-bidentate configurations, confirmed by structural analysis for 3a (R⁴ = Me, ER¹ = SMe), 7a (R⁴ = H, ER¹ = SePh) and 9a (R⁴ = Me, ER¹ = SePh). Two of the 6-methyl substituted complexes examined by X-ray crystallography are oligomeric with trans-PdCl₂(N,E) motifs and bridging ligands, trimeric [PdCl₂(μ-6-MepyCH₂SPh-N,S)]₃ (10a) and dimeric [PdCl₂(μ-6-MepyCH₂SePh-N,Se)]₂ (11a). This behaviour is attributed to avoidance of the Me···Cl interaction that would occur in the cis-bidentate configuration if the pyridyl plane had the same orientation with respect to the coordination plane as observed for 3a, 7a and 9a [dihedral angles 8.0(2)-16.8(2)°]. When examined as precatalysts for the Mizoroki-Heck reaction of n-butyl acrylate with aryl halides in N,N-dimethylacetamide at 120 °C, the complexes exhibit the anticipated trends in yield (ArI > ArBr > ArCl, higher yield for electron withdrawing substituents in 4-RC₆H₄Br and 4-RC₆H₄Cl). The most active precatalysts are PdCl₂(R⁴-pyCH₂SMe-N,S) (R = H (1a), Me (3a)); complexes of the selenium containing ligands exhibit very low activity. For closely related ligands, the changes SMe to SPh, 6-H to 6-Me, and 6-H to 6-Ph lead to lower activity, consistent with involvement of both the pyridyl and chalcogen donors in reactions involving aryl bromides. The precatalyst PdCl₂(pyCH₂SMe-N,S) (1a) exhibits higher activity for the reaction of aryl chlorides in Buⁿ₄NCl at 120 °C as a solvent under non-aqueous ionic liquid (NAIL) conditions.     

Synthesis, photoluminescence and electrochemiluminescence of ruthenium(II) polypyridyl complexes based on bipyridine derivatives with carbazole moieties

Six complexes (1-6) with the type of [Ru(bpy)₂L]X₂ (1-3: L = L1-L3, X = Cl⁻; 4-6: L = L1-L3, X = PF₆⁻) were synthesized based on 2,2′-bipyridine and three 2,2′-bipyridine derivatives L1, L2 and L3 (L1 = 5,5′-dibromo-2,2′-bipyridine, L2 = 5-bromo-5′-carbazolyl-2,2′-bipyridine, L3 = 5,5′-dicarbazolyl-2,2′-bipyridine). The complexes 1-6 were characterized by ¹H NMR, MS(ESI) and IR spectra, along with the X-ray crystal structure analysis for 1, 5 and 6. Their photophysical properties and electrochemiluminescence (ECL) properties were investigated in detail. In the UV-Vis absorption spectra, all complexes 1-6 show strong intraligand (π → π^∗) transitions and metal-ligand charge transfer (MLCT, dπ (Ru) → π^∗) bands. Upon the excitation wavelengths at ∼508 nm, all complexes 1-6 exhibit typical MLCT emission of ruthenium(II) polypyridyl complexes. The introduction of carbazole moieties improves the MLCT absorption and emission intensity. The ruthenium(II) complexes 1-6 exhibit good electrochemiluminescence (ECL) properties in [Ru(bpy)₂L]²⁺/tri-n-propylamine (TPrA) acetonitrile solution and the complexes with PF₆⁻ showed higher ECL emission intensity than that of the complexes with Cl⁻ based on the same ligands.     

Reactions of triphenylphosphane-substituted ethoxycarbonylcarbene-bridged dicobalt carbonyl complexes with carbon monoxide or CO: An experimental and theoretical study

In CH₂Cl₂ solution and under a carbon monoxide atmosphere the cobalt complexes [μ₂-{ethoxycarbonyl(methylene)}-μ₂-(carbonyl)-bis(triphenylphosphanedicarbonyl-cobalt) (Co-Co)] (4) and [μ₂-{ethoxycarbonyl(methylene)}-μ₂-(carbonyl)-(tricarbonyl-cobalt)-(triphenylphosphanedicarbonyl-cobalt) (Co-Co)] (3) are in equilibrium. The equilibrium constant K = [3][PPh₃]/[4][CO] at 10 °C is 1.03 ± 0.11. The bridging and terminal CO ligands in complex 3 or 4 exchange with external ¹³CO simultaneously. In accord with that variable-temperature ¹³C NMR spectra reveal fluxional behavior for both complexes. The overall rate constant of ¹³CO-exchange for 3 at 10 °C is 17 × 10⁻³ s⁻¹ and for 4 at 10 °C is 26 × 10³ s⁻¹. In the case of complex 4 the concentration of PPh₃ has practically no influence on the rate of the ¹³CO-exchange reaction and on the rate of the reaction with CO. The coupling of the μ₂-ethoxycarbonylcarbene ligand and one of the coordinated carbon monoxide is at least one order of magnitude slower than the ¹³CO-exchange reactions, and is faster in complex 4 than in complex 3. The partial pressure of carbon monoxide has practically no effect on the coupling reaction.     

Syntheses, structures, and magnetic properties of 3d-4f heterometallic complexes constructed from pyrazole-bridged CuLn dinuclear units

A series of pyrazole-bridged heterometallic 3d-4f complexes, [CuDy(ipdc)₂(H₂O)₄] · (2H₂O)(H₃O⁺) (1) and [CuLn(pdc)(ipdc)(H₂O)₄] · H₃O⁺ (Ln = Ho (2), Er (3), Yb (4); H₃ipdc = 4-iodo-3,5-pyrazoledicarboxylic acid; H₃pdc = 3,5-pyrazoledicarboxylic acid), {[Cu₃Ln₄(ipdc)₆(H₂O)₁₆] · xH₂O}_n (Ln = Sm (5), x = 8.5; Ln = Eu (6), x = 7; Ln = Gd (7), Tb (8), x = 9), have been synthesized and structurally characterized. Ligand H₃ipdc was in situ obtained by iodination of ligand H₃pdc. Complexes 1-4 are pyrazole-bridged heterometallic dinuclear complexes, and 2-4 are isostructural. Complexes 5-8 are isostructural and comprised of an unusual infinite one-dimensional tape-like chain based on pyrazole-bridged heterometallic dinuclear units. The magnetic properties of compounds 1-4, 7 and 8 have been investigated through the magnetic measurement over the temperature range of 1.8-300 K.