Reaction of Ru(PPh3)3Cl2 with arylazoimidazoles: spectral characterisation and redox studies of [bis-{N(1)-alkyl-2-(arylazo)imidazole}-bis-(triphenylphosphine)]-ruthenium(II) perchlorate

Ru(PPh₃)₃Cl₂ reacts with N(1)-alkyl-2-(arylazo)imidazoles, p-RC₆H₄N=NC₃H₂N₂X, [RaaiX, R = H(a), Me(b), Cl(c); X = Me(1), Et(2), Bz(3)] under refluxing conditions in EtOH to give [Ru(RaaiX)₂(PPh₃)₂](ClO₄)₂ · H₂O complexes (4–6). RaaiX is a bidentate chelator (N, N) with N(imidazole), N and N(azo), N donor centres. Three isomers are present in the mixture in which the pairs of PPh₃, N and N occupy cis–cis–trans, cis–trans–cis and cis–cis–cis, positions respectively. The isomers were identified by ¹H-n.m.r. spectra. Four signals are observed in the aliphatic zone for N(1)-X; two are of equal intensity at higher and the other two signals at lower in the ratio 1:0.3:0.2 suggesting the presence of cis–cis–cis, cis–trans–cis and cis–cis–trans-geometry. The complexes display the allowed t ₂(Ru) ^*(RaaiX) transition. Cyclic voltammetry indicates two consecutive Ru^III/II couples along with azo reductions.     

Palladium azoimidazoles. Solvatochromic studies of catecholato complexes

N(1)-alkyl-2-(arylazo)imidazoles, p-RC₆H₄N=NC₃H₂ NN(1)X [RaaiX; X=Me(3), Et(4); R=H(a), Me(b), Cl(c)] have been synthesized and, upon reaction with Pd(MeCN)₂Cl₂, yield orange–red complexes Pd(RaaiX)Cl₂ (5),(6) which in turn were reacted with catechols in the presence of Et₃N to yield the ternary complexes Pd(RaaiX)(O,O) where O,O=pyrocatechol [cat, (7),(11)], 4-t-butylcatechol [tbcat,(8),(12)], 3,5-di-t-butylcatechol (dtbcat) (9),(13) and tetrachlorocatechol [tccat,a (10),(14). The complexes were characterized by elemental analysis, i.r., u.v.–vis. and ¹H-n.m.r. data. Electrochemical studies on (7)–(14) suggest four successive redox responses which are highly sensitive to the nature of the substituents. These complexes were found to exhibit a ligand-to-ligand charge transfer (l.l.c.t.) transition and a negative solvatochromic effect. The band position is largely dependent upon the substituent on the catechol frame and is qualitatively assigned as the 3b₁(cat)*(RaaiX) transition.     

Synthesis,Spectroscopic and Electrochemical Studies of Isomeric Dichloro-bis-[ N (1)-Alkyl-2-(Arylazo)Imidazole]-Osmium(II). Single Crystal X-ray Structures of Blue-Violet Dichloro-Bis-[ N (1)-Methyl-2-(Arylazo)Imidazole]-Osmium(II) Species

1-Alkyl-2-(arylazo)imidazoles (p-R-C₆H₄-N=N-C₃H₂N₂X, abbreviated as RaaiX, R = H(a), CH₃(b), Cl(c); X = N(1)-CH₃ (1), N(1)-CH₂-C₆H₅ (2)) have been reacted with (NH₄)₂[OsCl₆] and OsCl₂(RaaiX)₂ species isolated in two isomeric forms, blue-violet (3, 5) and red-violet (4, 6). IR spectra show two x (Os-Cl) modes and support a cis-OsCl₂ configuration. X-ray diffraction methods were used to determine structures of blue-violet isomers. In terms of the three coordination pairs around Os(II), Cl, Cl, N, N (N(imidazole), N) and N', N' (N(azo), N') the blue-violet isomers have a cis-trans-cis (ctc) configuration. ¹H NMR data for the red-violet complexes (isomers B) and results concerning analogous ruthenium(II) complexes indicate isomer B to have cis-cis-cis (ccc) configuration. Absorption spectra show an intense MLCT band at ca 580 nm along with two weak bands at 800 and 1000 nm. Cyclic voltammetry shows quasi-reversible Os(III)/Os(II) and Os(IV)/Os(III) couples at 0.4-0.6 V and 1.3-1.5 V versus SCE and ill-defined azo reductions. The X-Ray structures show unusually long N=N bond lengths, 1.31-1.32 Å, elongated by some 0.06 Å compared to the free ligand value. Os(II) prefers to bind N(azo) (Os-N(azo), 1.98 Å) rather than N(imidazole) (Os-N(imidazole), 2.03 Å). EHMO calculations of ctc-OsCl₂ (MeaaiMe) and comparison with the ruthenium(II) complex account for the MLCT transitions in terms of a metal-dominated HOMO to a ligand-dominated LUMO shift.     

Studies on the reactivity of cis-RuCl2 fragment in Ru(PPh3)2(TaiMe)Cl2 with N,N-chelators (TaiMe = 1-methyl-2-(p-tolylazo)imidazole). Spectral and electrochemical characterisation of the products

Dechlorination of Ru(PPh₃)₂(TaiMe)Cl₂ (TaiMe = p-Me-C₆H₄-N=N-C₃H₂NN(1)-Me (1), 1-methyl-2-(p-tolylazo)imidazole) has been carried out in acetone solution by Ag⁺ and reacted with N,N’-chelators to synthesise [Ru(PPh₃)₂ (TaiMe)(N,N’)]²⁺. The complexes have been isolated as their perchlorate salts. The N,N’ chelators are 1-alkyl-2-(phenylazo)imidazoles (PaiX, X = Me, Et, CH₂Ph); 2-(arylazo)pyridines, (Raap,p-R-C₆H₄-N=N-C₅H₄N; R = H, Me, Cl); 2-(arylazo)pyrimidines (Raapm,p-R-C₆H₄-N=N-C₃N₂H₂; R = H, Me, Cl); 2,2’-bipyridine (bpy) and 1,10-phenanthroline (o-phen). Unsymmetrical N,N’ chelators may give two isomers and this is indeed observed. The¹H NMR spectral data refer to the presence of two isomers in the mixture in different proportions. With consideration of coordination pairs in the order of PPh₃, PPh₃; N,N (N refers to N(immidazole)) and N’,N (N’ refers to N(azo)), the complexes have been characterised astrans-cis-cis andtrans-trans-trans configuration; the former predominates in the mixture. Electrochemical studies exhibit high potential Ru(III)/Ru(II) couple and quasireversible N=N reduction. Electronic spectra show high intensity (ε ∼ 10⁴) MLCT transition in the visible region (520 ±10) nm along with a shoulder (ε ∼ 10³) in the longer wavelength region.     

Ligand Substitution Reactions on Aquapentachloro‐ and Hexachloroplatinic Acid — Synthesis and Characterization of Tetrachloroplatinum(IV) Complexes with Heterocyclic N,N Donors

Reactions of aquapentachloroplatinic acid, (H₃O)[PtCl₅(H₂O)]·2(18C6)·6H₂O ( 1 ) (18C6 = 18‐crown‐6), and H₂[PtCl₆]·6H₂O ( 2 ) with heterocyclic N, N donors (2, 2′‐bipyridine, bpy; 4, 4′‐di‐tert‐butyl‐2, 2′‐bipyridine, tBu₂bpy; 1, 10‐phenanthroline, phen; 4, 7‐diphenyl‐1, 10‐phenanthroline, Ph₂phen; 2, 2′‐bipyrimidine, bpym) afforded with ligand substitution platinum(IV) complexes [PtCl₄(N∩N)] (N∩N = bpy, 3a ; tBu₂bpy, 3b ; Ph₂phen, 5 ; bpym, 7 ) and/or with protonation of N, N donor yielding (R₂phenH)₂[PtCl₆] (R = H, 4a ; Ph, 4b ) and (bpymH)⁺ ( 8 ). With UV irradiation Ph₂phen and bpym reacted with reduction yielding platinum(II) complexes [PtCl₂(N∩N)] (N∩N = Ph₂phen, 6 ; bpym, 9 ). Identities of all complexes were established by microanalysis as well as by NMR (¹H, ¹³C, ¹⁹⁵Pt) and IR spectroscopic investigations. Molecular structures of [PtCl₄(bpym)]·MeOH ( 7 ) and [PtCl₂(Ph₂phen)] ( 6 ) were determined by X‐ray diffraction analyses. Differences in reactivity of bpy/bpym and phen ligands are discussed in terms of calculated structures of complexes [PtCl₅(N∩N)]^— with monodentately bound N, N ligands (N∩N = bpy, 10a ; phen, 10b ; bpym, 10c ).     

Gold(I) complexes of thioamides

Summary Gold(I) forms linear [AuL₂]X complexes (X = Cl, Br, I or CIO₄) with thioacetamide and thiobenzamide, AuLX compounds with thiobenzamide (X = CI or Br),N, N-dimethylthioformamide (X = Cl, Br or 1) andN-dimethylthioacetamide (X = CI, Br or 1). Thev(AuS) vibrations are assigned in the 320-260 cm^–1 range. The i.r. spectra further suggest hydrogen bonding between the ligands and the anions. The conductivity measurements indicate dissociation of the [AuL₂]X complexes (X = halide) and coordination of X in solution.Presented in part at the XIX ICCC, Prague, 1978.     

Copper(II) complexes with derivatives of salen and tetrahydrosalen: a spectroscopic, electrochemical and structural study

Salen type complexes, CuL, the corresponding tetrahydrosalen type complexes, Cu[H₄]L, and N,N′-dimethylated tetrahydrosalen type complexes, Cu[H₂Me₂]L, were investigated using cyclic voltammetry, and electronic and ESR spectroscopy. In addition, the analogous copper(II) complexes with a derivative of the tetradentate ligand ‘salphen’ [salphen=H₂salphen=N,N′-disalicylidene-1,2-diaminobenzene] were studied. Solutions of CuL, Cu[H₄]L and Cu[H₂Me₂]L are air-stable at ambient temperature, except for the complex Cu(^tBu, Me)[H₄]salphen [H₂(^tBu, Me)[H₄]salphen=N,N′-bis(2-hydroxy-3-tert-butyl-5-methylbenzyl)-1,2-diaminobenzene]. Cu(^tBu, Me)[H₄]salphen interacts with dioxygen and the ligand is oxidatively dehydrogenated (–CH₂–NH–→–C=N–) to form Cu(^tBu, Me)[H₂]salphen and finally, in the presence of base, Cu(^tBu, Me)salphen. X-ray structure analysis of Cu(^tBu, Me)[H₂Me₂]salen confirms a slightly tetrahedrally distorted planar geometry of the CuN₂O₂ coordination core. The complexes were subjected to spectrophotometric titration with pyridine, to determine the equilibrium constants for adduct formation. It was found that the metal center in the complexes studied is only of weak Lewis acidity. In dichlormethane, the oxidation Cu(II)/Cu(III) is quasireversible for the CuL type complexes, but irreversible for the Cu[H₄]L and Cu[H₂Me₂]L type. A poorly defined wave was observed for the irreversible reduction Cu(II)/Cu(I) at potentials less than −1.0 V. The ESR spectra of CuL at both 77 K and room temperature reveal that very well resolved lines can be attributed to the interaction of an unpaired electron spin with the copper nuclear spin, ¹⁴N donor nuclei and to a distant interaction with two equivalent protons [A^Cu(iso)≈253 MHz, A^N(iso)≈43 MHz, A^N(iso)≈20 MHz]. These protons are attached to the carbon atoms adjacent to the ¹⁴N nuclei. In contrast to CuL, the number of lines in the spectra of the complexes Cu[H₄]L and Cu[H₂Me₂]L is greatly reduced. At room temperature, only a quintet with a considerably smaller nitrogen shf splitting constant [A^N(iso)≈27 MHz] is observed. Both factors, planarity and conjugation, are thus essential for the observation of distant hydrogen shf splitting in CuL. Due to the C=N bond hydrogenation, the coordination polyhedra of the complexes Cu[H₄]L and Cu[H₂Me₂]L is more flexible and more sensitive to ligand modification than that of CuL. The electron-withdrawing effect of the phenyl ring of the phenylenediamine bridge is reflected in a reduction of the copper hyperfine coupling constants in Cu(^tBu, Me)[H₄]salphen and Cu(^tBu, Me)[H₂Me₂]salphen complexes [A^Cu(iso)≈215 MHz].     

Preparation of novel palladium(II) complexes with dithiocarbimates from sulfonamides

Potassium N-R-sulfonyldithiocarbimates, K₂(RSO₂N=CS₂) (R = Me, Ph, 2-MeC₆H₄), react with Pd(OAc)₂ to yield complex anions bis(N-R-sulfonyldithiocarbimato)palladate(II), [Pd(RSO₂N=CS₂)₂]^2–, which were isolated as their n-Bu₄N⁺ salts. When the reaction was performed in the presence of Ph₃P in a 2:1 ratio with respect to Pd(OAc)₂, the N-R-sulfonyldithiocarbimatobis(triphenylphosphine)palladium(II) complexes were obtained. Elemental analyses, i.r. spectra and electronic spectra data were consistent with the formation of palladium–sulfur diamagnetic square planar complexes in the first case and mixed square planar complexes of palladium with Ph₃P and dithiocarbimates in the second case. The ¹H-n.m.r., ¹³C-n.m.r. and ³¹P-n.m.r. spectra showed the expected signals for the Bu₄N⁺ cation, Ph₃P and the dithiocarbimate moieties.     

Stabilization of a Silaaldehyde by its η2 Coordination to Tungsten

Treatment of pyridine‐stabilized silylene complexes [(η⁵‐C₅Me₄R)(CO)₂(H)W?SiH(py)(Tsi)] (R=Me, Et; py=pyridine; Tsi=C(SiMe₃)₃) with an N‐heterocyclic carbene ^MeIⁱPr (1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) caused deprotonation to afford anionic silylene complexes [(η⁵‐C₅Me₄R)(CO)₂W?SiH(Tsi)][H^MeIⁱPr] (R=Me ( 1‐Me ); R=Et ( 1‐Et )). Subsequent oxidation of 1‐Me and 1‐Et with pyridine‐N‐oxide (1 equiv) gave anionic η²‐silaaldehydetungsten complexes [(η⁵‐C₅Me₄R)(CO)₂W{η²‐O?SiH(Tsi)}][H^MeIⁱPr] (R=Me ( 2‐Me ); R=Et ( 2‐Et )). The formation of an unprecedented W‐Si‐O three‐membered ring was confirmed by X‐ray crystal structure analysis.     

Co(II)-Mediated and microwave assisted coupling between 2,6-diaminopyridine and nitriles. A new synthetic route to N-(6-aminopyridin-2-yl)carboximidamides

The Chinese-lantern-type Co₂(O₂CBu^t)₄{2,6-(NH₂)₂C₅H₃ N}₂ complex reacts with RCN (R = Me or Prⁿ) under microwave irradiation (MWI) to give the mononuclear amidine complexes Co(O₂CBu^t)₂{H₂N(C₅H₃ N)NHC(R)=NH} (R = Me (4a) or Prⁿ (4c)). Under microwave irradiation, the addition of 2,6-diaminopyridine to acetonitrile in the presence of the pivalate complexes Co₂(μ₂-OH₂)(O₂CBu^t)₄(HO₂CBu^t)₄ (1) or [Co(OH)_n(O₂CBu^t)_2−n ]_x (2) afforded complex 4a in higher yield compared to the corresponding reaction performed earlier without MWI. The use of MWI makes it possible to perform analogous reactions with nitriles RCN (R = Et, Prⁿ, or Ph) giving rise to complexes 4b—d, respectively. Compounds 4a—d were characterized by elemental analysis and IR spectroscopy. The structure of complex 4c was established by X-ray diffraction. Amidines H₂N(C₅H₃N)NHC(R)=NH, which formed in the coordination sphere of cobalt(II), were isolated in the free state from methanolic solutions of complexes 4a—d under the action of Na₂S and were characterized by electrospray mass spectrometry and ¹H and ¹³C{¹H} NMR spectroscopy. The reactions of 2-aminopyridine with both complexes 1 and 2 in acetonitrile under microwave irradiation produced the Co(O₂CBu^t)₂(H₂NC₅H₄N)₂ complex. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–42, January, 2006.     

Cyclooctenyl complexes of palladium(II) with multidentate N-heterocycles

[Pd(cod)(cotl)]ClO₄ (cod = 1,5-cyclooctadiene, cotl = cyclooctenyl, C₈H₁₃ ^–) undergoes substitutions with multidentate N-heterocycles: 1,3-bis(benzimidazolyl)benzene (L¹), 1,3-bis(1-methylbenzimidazol-2-yl)benzene (L²), 2,6-bis(benzimidazolyl)pyridine (L³) and 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (L⁴) to yield mono/binuclear complexes: [Pd(cotl)(L¹)(OClO₃)], [Pd(cotl)(L)]ClO₄ (L = L² or L³) and [Pd(cotl)₂(L⁴)](ClO₄)₂. Dihalobridged binuclear complexes [PdX(cotl)]₂ (X = Cl or Br) undergo halogen bridge cleavages with the multidentate N-heterocycles to form binuclear complexes of the type [PdX(cotl)₂L] (X = Cl or Br; L = L¹, L², L³ or L⁴). The complexes were characterized by elemental analyses, ¹H-, ¹³C-n.m.r., i.r., far-i.r. and FAB-mass spectral studies.     

Synthesis,spectroelectrochemical characterization and solvatochromic studies of arylazoimidazolepalladium(II) catecholates

The ternary complexes, [Pd(RaaiCH₂Ph)(OO)](4–6), where RaaiCH₂Ph = N(1)-benzyl-2-(arylazo)imidazole [p-RC₆H₄N=NC₃H₂N₂CH₂Ph (2), R = H (4), Me (5) and Cl (6)] and (OO) = catechol [catH₂,(a)], 4-t-butylcatechol [tbcatH₂, (b)], 3,5-di-t-butylcatechol [dtbcatH₂, (c)] and tetrachlorocatechol [tccatH₂, (d)], have been prepared and characterized by elemental analyses, i.r., u.v.-vis. and ¹H-n.m.r. data. Cyclic voltammograms suggest four successive redox responses that are highly sensitive to the nature of the substituents. The complexes exhibit a ligand-to-ligand charge transfer (LLCT) band and a negative solvatochromic effect. The position of the band is largely dependent on the substituent type on the catechol frame and is qualitatively assigned as the 3b ₁(cat) → π*(aai) transition. This revised version was published online in June 2006 with corrections to the Cover Date.     

Copper(I) complexes of neutral,deprotonated and protonated 4,6-dimethylpyrimidine-2 (1H)-thione

Summary The following copper(I) complexes of 4,6-dimethylpyrimidine-2(1H)-thione (HL), its protonated cation (H₂L⁺) and deprotonated anion (L^–) have been prepared: CuL, Cu(HL)X (X = Cl, Br or I), Cu(HL)₂X (X = C1 or Br), Cu₂(HL)₃Br₂, Cu(H₂L)X₂ (X = Cl or Br), Cu₃(HL)₂LA₂ (A = ClO₄ or BF₄ ). The i.r. spectra show that in all the HL and L^– complexes and in the Cu(H₂L)Br₂ complex, the ligands are S, N coordinated to the metal ion, while in Cu(H₂L)Cl₂ only the thiocarbonylic sulphur is coordinated, probably bridging two copper(I) atoms. Thev(CuN) (288–317 cm^–1 ) andv(CuS) (191–225 cm^–1 ) have uniform frequency values in all the complexes. The halide ions are, in all their complexes, wholly or in part coordinated giving twov(CuX) bands which may indicate an asymmetrical Cu-X Cu halide bridging bond.Author to whom all correspondence should be directed.     

Ruthenium(II)-Phthalocyaninate(2–): Darstellung und Eigenschaften von Acido(carbonyl)phthalocyaninato(2–)ruthenat(II), [Ru(X)(CO)Pc2−]− (X = Cl,Br, I,NCO, NCS,N3)

Ruthenium(II) Phthalocyaninates(2–): Synthesis and Properties of (Acido)(carbonyl)phthalocyaninato(2–)ruthenate(II), [Ru(X)(CO)Pc^2?]^? (X = Cl, Br, I, NCO, NCS, N₃) (ⁿBu₄N)[Ru(OH)₂Pc^2?] is reduced in acetone with carbonmonoxid to blue-violet [Ru(H₂O)(CO)Pc^2?], which yields in tetrahydrofurane with excess (ⁿBu₄N)X acido(carbonyl)phthalocyaninato(2–)ruthenate(II), [Ru(X)(CO)Pc^2?]^? (X = Cl, Br, I, NCO, NCS, N₃) isolated as red-violet, diamagnetic (ⁿBu₄N) complex salt. The UV-Vis spectra are dominated by the typical π-π* transitions of the Pc^2? ligand at approximately 15100 (B), 28300 (Q₁) und 33500 cm^?1 (Q₂), only fairly dependent of the axial ligands. v(C? O) is observed at 1927 (X = I), 1930 (Cl, Br), 1936 (N₃, NCO) 1948 cm^?1 (NCS), v(C? N) at 2208 cm^?1 (NCO), 2093 cm^?1 (NCS) and v(N? N) at 2030 cm^?1 only in the MIR spectrum. v(Ru? C) coincides in the FIR spectrum with a deformation vibration of the Pc ligand, but is detected in the resonance Raman(RR) spectrum at 516 (X = Cl), 512 (Br), 510 (N₃), 504 (I), 499 (NCO), 498 cm^?1 (NCS). v(Ru? X) is observed in the FIR spectrum at 257 (X = Cl), 191 (Br), 166 (I), 349 (N₃), 336 (NCO) and 224 cm^?1 (NCS). Only v(Ru? I) is RR-enhanced.     

Palladium(II) halide complexes with dithioesters derived from sarcosine

Summary The compounds EtO₂CCH₂(Me)NCS₂R (R = Me, ESDTM; R = Et, ESDTE) were prepared from sarcosine ethyl ester hydrochloride, CS₂ and alkyl iodide in EtOH-H₂O. These ligands react with palladium halides in benzene to yield the benzene solvates [Pd(ESDTR)X₂]·nC₆H₆ (R = Me or Et; X = Cl or Br; n < 1), in which the dithioester molecule coordinates through both sulphur atoms. Ligands and complexes have been characterized by i.r. and ¹H n.m.r. spectroscopy and by thermal analysis (t.g., d.t.g. and d.t.a.). The low stability of the adducts in both solution and solid phase is discussed on the basis of proton n.m.r. spectra. Thermal degradation of the 1∶1 complexes has been examined up to 1000° C. The first decomposition step involves release of alkyl halide to form the [Pd(ESDT)X] _n (X = Cl or Br) intermediates, which successively decompose, finally giving palladium.     

Front Cover: Small-Molecule Activation by Heteroleptic Metallasilylenes (Eur. J. Inorg. Chem. 2/2023)

We report on reactions of heteroleptic metallasilylenes L¹(Cl)MSiL² (M=Al 1 , Ga 2 , L¹=HC[C(Me)NDipp]₂, Dipp=2,6-ⁱPr₂C₆H₃; L²=PhC(N^tBu)₂) with CO₂, N₂O, and Me₃SiN₃, yielding the corresponding carbonate complexes L¹(Cl)MOSi(CO₃-κ²O,O−)L² (M=Al 3 , Ga 4 ), silanoic esters L¹(Cl)MOSi(O)L² (M=Al 5 , Ga 6 ), and silaimine L¹(Cl)GaSi(NSiMe₃)L² ( 8 ), whereas {L²Si[N(SiMe₃)Al(Cl)C(Me)NDipp][CHC(Me)N(Dipp)]} 7 was formed by C−C bond cleavage of the L¹ ligand. Compounds 3 – 8 were characterized by NMR (¹H, ¹³C) and IR spectroscopy, elemental analysis and single crystal X-ray diffraction.     

Tetradentate asymmetric Schiff bases and their Ni(II) and Fe(III) complexes

Three asymmetric Schiff-base tetradentate diimines H₂L¹, H₂L², and H₂L³ [(2-OH)C₆H₄N=CHC₆H₄2-N=CHC₆H₃(2-OH)(5-X), X?=?H, CH₃, Cl respectively] have been synthesized by a two step process. The reaction of 2-hydroxy aniline with 2-nitro-benzaldehyde in EtOH gave the starting Schiff base, 2-hydroxy-N-(2-nitrobenzylidene)aniline (SB-NO₂), which was reduced into the amino derivative (SB-NH₂) in solution. Reacting SB-NH₂ with 2-hydroxybenzaldehyde, 2-hydroxy-5-methylbenzaldehyde and 2-hydroxy-5-chlorobenzaldehyde gave the three new ligands H₂L¹, H₂L², and H₂L³ respectively. Their dimeric, binuclear metal complexes with Ni(II) and Fe(III) have also been synthesized. The ligands and their complexes were characterized by elemental analyses, LC–MS, IR, electronic, ¹H and ¹³C-NMR spectra, TGA, conductivity and magnetic measurements. All of the spectroscopic, analytical and other data indicate octahedral geometry M₂L₂(H₂O)X₂ (M: Ni,Co;X: Cl or H₂O), except for NiL² which is monomeric. Antimicrobial activities of the ligands and the complexes were evaluated against five bacteria. While the ligands and the Ni complexes are inactive towards Pseudomonas aeruginosa and Staphylococcus aureus, Fe complexes are active; only Fe complexes are inactive against Escherichia coli. All of the compounds have antimicrobial activities against Bacillus subtilis, and Yersinia enterecolitica.     

The coordination chemistry ofN,N′-ethylenebis(2-acetylpyridine imine) andN,N′-ethylenebis(2-benzoylpyridine imine); two potentially tetradentate ligands containing four nitrogen atoms

Summary New complexes of the general formulae [ML_A(H₂O)₂]-Cl₂ (M=Ni or Cu), [ML_AX₂] (M=Co or Cu; X=Cl or Br), [NiL_ABr₂]·H₂O, [ML_A] [MCl₄] (M=Pd or Pt), [NiL_B(H₂O)₂]Cl₂·2H₂O, [ML_BCl₂] (M=Co, Ni, Cu, Pd or Pt; X=Cl or Br) and [ML_B] [MCl₄] (M=Pd or Pt), where L_A=N,N-ethylenebis(2-acetylpyridine imine) and L_B=N, N-ethylenebis(2-benzoylpyridine imine), have been isolated. The complexes were characterized by elemental analyses, conductivity measurements, t.g./d.t.g. methods, magnetic susceptibilities and spectroscopic (i.r., far-i.r., ligand field,¹Hn.m.r.) studies. Monomeric pseudo-octahedral stereochemistries for the Co^II, Ni^II and Cu^II complexes andcis square planar structures for the compounds [ML_BX₂] (M=Pd or Pt; X=Cl or Br) are assigned in the solid state. The molecules L_A and L_B behave as tetradentate chelate ligands in the Co^II, Ni^II, Cu^II and Magnus-type Pd^II and Pt^II complexes, bonding through both the pyridine and methine nitrogen atoms. A bidentateN-methine coordination of the Schiff base L_B is assigned in the [ML_BX₂] complexes (M=Pd or Pt; X=Cl or Br). The anomalous magnetic moment values of the Co^II complexes are discussed.     

Seven-coordinate complexes of molybdenum(II) and tungsten(II) containing pyrazole as a ligand

Summary Equimolar quantities of [MI₂(CO)₃(NCMe)₂] (M = Mo or W) and C₃H₄N² (pyrazole) react in CH₂C1₂ at room temperature to give the iodo-bridged dimers [M(μ-I) (CO)₃(C₃H₄N²)]₂ (1) and (2). Two equivalents of C₃H₄N² react with [MI₂(CO)₃(NCMe)₂] (M = Mo or W) to give the bis(pyrazole) complexes [MI₂(CO)₃(C₃H₄N²)₂] (3) and (4) in good yield. Three and four equivalents of pyrazole react with [MoI₂(CO)₃(NCMe)₂] to give the cationic complexes [MoI(CO)₃(C₃H₄N²)₃]I (5) and [MoI(CO)₂(C₃H₄N²)₄]I (6), respectively. The mixed ligand complexes [MI₂(CO)₃(C₃H₄N²)L] (M = Mo or W; L = PPh₃, AsPh₃ or SbPh₃) (7)-(12) are prepared by reacting equimolar amounts of [MI₂(CO)₃(NCMe)₂] and L in CH₂C1₂ at room temperature, followed by an in situ reaction with one equivalent of C₃H₄N². The MoSnCl₃ complex [MoCl(SnCl₃)(CO)₃(C₃H₄N²)₂] (13) is prepared in an analogous manner using acetone as the solvent, whilst the mixed ligand compound [MoCl(SnQ₃)(CO) ₃(C₃H₄N²)(PPh₃)] (14) was prepared by treating the dimeric complex [Mo(μ-Cl)(SnCl₃)(CO)₃(PPh₃)]₂ with two equivalents of C₃H₄N². All the new complexes were characterised by elemental analysis (carbon, hydrogen and nitrogen), i.r. and ¹H n.m.r. spectroscopy.     

Synthesis and spectroscopic studies of homo- and heteroleptic N-arylsalicylaldiminates of titanium(IV), zirconium(IV) and chromium(III)

Homo- and heteroleptic N-arylsalicylaldiminate derivatives of Ti^IV and Zr^IV of the type, MX_4–x (OC₆H₄CH=NAr) _x (X = OPrⁱ, x = 2,3; X = Cl, x = 1,2,3,4; Ar = C₆H₃Me₂-2,6, C₆H₃Et₂-2,6) have been prepared by reactions in the desired molar ratios of: (i) Ti(OPrⁱ)₄/Zr(OPrⁱ)₄·PrⁱOH with N-arylsalicylaldimines in benzene, and (ii) MCl₄ (M = Ti, Zr) with Me₃SiOC₆H₄CH=NAr or HOC₆H₄CH=NAr in the presence of Et₃N as a base or the potassium salt of N-arylsalicylaldimines in benzene. The three homoleptic derivatives of Cr^III, Cr(OC₆H₄CH=NAr)₃ (Ar = C₆H₂Me₃-2,4,6, C₆H₃Et₂-2,6, C₆H₃Prⁱ ₂-2,6) have also been prepared by salt-elimination. All of these new derivatives have been characterized by elemental analyses, spectroscopic [i.r., ¹H and ¹³C-n.m.r. (Ti and Zr complexes), and electronic (for Cr complexes)] studies, as well as molecular weight measurements.