Synthesis and Characterization of β‐Diketiminate Aluminum Compounds and Their Use in the Ring‐Opening Polymerization of ε‐Caprolactone

Four aluminum alkyl compounds, [CH{(CH₃)CN‐2,4,6‐MeC₆H₂}₂AlMe₂] ( 1 ), [CH{(CH₃)CN‐2,4,6‐MeC₆H₂}₂AlEt₂] ( 2 ), [CH{(CH₃)CN‐2‐iPrC₆H₄}₂AlMe₂] ( 3 ), and [CH{(CH₃)CN‐2‐iPrC₆H₄}₂AlEt₂] ( 4 ), bearing β‐diketiminate ligands [CH{(Me)CN‐2,4,6‐MeC₆H₂}]₂ (L¹H) and [CH{(Me)CN‐2‐ⁱPrC₆H₄}]₂ (L²H) were obtained from the reactions of trimethylaluminum, triethylaluminum with the corresponding β‐diketiminate, respectively. All compounds were characterized by ¹H NMR and ¹³C NMR spectroscopy, single‐crystal X‐ray structural analysis, and elemental analysis. Compounds 1 – 4 were found to catalyze the ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) with good activity.     

Tetrylenes chelated by bifunctional β‐diketiminate ligand: structure and possible applications

The synthesis and structure of heteroleptic tetrylenes containing bifunctional β‐diketiminate ligand are reported. Compounds were prepared via a protolytic reaction of free β‐diketimine {N‐[(2‐MeO)C₆H₅]}N═C(Me)CH═C(Me)N(H){N′‐[(2‐MeO)C₆H₅]} (L^COH) and {N‐[(2‐MeO)C₆H₅]}N?CHCH?CHN(H){N′‐[(2‐MeO)C₆H₅]} (L^HOH), respectively, with corresponding bis(amide) – M[N(SiMe₃)₂]₂ (M = Ge, Sn, Pb) – in equimolar ratio or via the salt elimination route from lithium precursors generated from L^HOH/L^COH species and slight excess of SnCl₂ or GeCl₂.dioxane complex. Only heteroleptic complexes were obtained by the mentioned methods. Products were characterized by multinuclear NMR spectroscopy techniques and structures of four of them have been determined by X‐ray diffraction methods. Complexes L^HOGeCl and L^COSnN(SiMe₃)₂ crystallize as monomers with the three‐coordinated metal centres by one chloro or amido ligand and one bidentate β‐diketiminato unit, in contrast to the structure of L^COSnCl, which reveals a dimeric character and compound L^COPbN(SiMe₃)₂, where the central atom of lead is five‐coordinated by methoxy groups of the ligand. Complex L^COSnN(SiMe₃)₂ was tested as a catalyst for polymerization of various epoxides_. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and Structures of Gallium‐β‐Diketiminate Complexes: Isolation of a Dinuclear Gallium(II) Complex

The sterically demanding β‐diketiminate ligand L^dmp [L^dmp = HC{(CMe)N(dmp)}₂, dmp = C₆H₃‐2,6‐Me₂] was used to stabilize various gallium complexes in the formal oxidation states +II and +III. The reaction of in situ generated [L^dmpLi] with gallium chloride affords [L^dmpGaCl₂] ( 1 ), which was used as starting complex to synthesize a variety of gallium(III) compounds [L^dmpGaX₂] [X = F ( 2 ), I ( 3 ), H ( 4 ), and Me ( 5 )]. Synthesis of the dinuclear complex [L^dmpGaI]₂ ( 6 ), with gallium in the formal oxidation state +II was accomplished by converting “GaI” with in situ generated [L^dmpLi] in toluene. All compounds were characterized by elemental analyses, NMR spectroscopy, LIFDI‐TOF‐MS, and single‐crystal X‐ray diffraction. Additionally DFT calculations were performed for analysis of the bonding in 6 .     

Syntheses,characterization and anti‐microbial activities of palladium(II) and palladium(IV) complexes of 3,10‐C‐meso‐Me8[14]diene (L1) and its reduced isomeric anes (LA,LB and LC). Crystal and molecular structure of [PdL1][Pd(SCN)4]

The reactions of 3,10‐C‐meso‐3,5,7,7,10,12,14,14‐octamethyl‐1,4,8,11‐tetraazacyclotetradecadiene, L¹, and two isomers (L_B and L_C, differing in the orientation of methyl groups on the chiral carbon atoms) of its reduced form with PdCl₂ and K₂[Pd(SCN)₄], produce square‐planar tetrachloro‐ and tetrathiocyano‐palladium(II) complexes of general formulae [PdL′][PdCl₄] and [PdL′][Pd(SCN)₄] (L′ = L¹, L_B and L_C), respectively. By contrast, the third ane isomer, L_A, upon reaction with the same reagents, PdCl₂ and K₂[Pd(SCN)₄], formed octahedral tetrachloro‐ and tetrathiocyanato‐palladium(IV) complexes [PdL_ACl₂]Cl₂ and [PdL_A(SCN)₂](SCN)₂, respectively. The [PdL′][PdCl₄] and [PdL_ACl₂]Cl₂ complexes undergo substitution reactions with KSCN to form square‐planar and octahedral tetrathiocyanato complexes [PdL′][Pd(SCN)₄] and [PdL_A(SCN)₂](SCN)₂, respectively. All complexes have been characterized on the basis of analytical, spectroscopic, conductometric and magnetochemical data. The anti‐fungal and anti‐bacterial activities of these complexes have been studied against some phytopathogenic fungi and bacteria. The crystal structure of [PdL¹][Pd(SCN)₄] has been confirmed by X‐ray crystallography and shows with square‐planar PdN₄ and PdS₄ geometries [monoclinic, space group C2/c, a = 17.884(3) Å, b = 14.734(2) Å, c = 11.4313(18) Å, β = 104.054(5)° ]. Copyright © 2008 John Wiley & Sons, Ltd.     

From a Phosphaketenyl‐Functionalized Germylene to 1,3‐Digerma‐2,4‐diphosphacyclobutadiene

The first 4π‐electron resonance‐stabilized 1,3‐digerma‐2,4‐diphosphacyclobutadiene [L^H₂Ge₂P₂] 4 (L^H=CH[CHNDipp]₂ Dipp=2,6‐ⁱPr₂C₆H₃) with four‐coordinate germanium supported by a β‐diketiminate ligand and two‐coordinate phosphorus atoms has been synthesized from the unprecedented phosphaketenyl‐functionalized N‐heterocyclic germylene [L^HGe‐P=C=O] 2 a prepared by salt‐metathesis reaction of sodium phosphaethynolate (P≡C?ONa) with the corresponding chlorogermylene [L^HGeCl] 1 a . Under UV/Vis light irradiation at ambient temperature, release of CO from the P=C=O group of 2 a leads to the elusive germanium–phosphorus triply bonded species [L^HGe≡P] 3 a , which dimerizes spontaneously to yield black crystals of 4 as isolable product in 67 % yield. Notably, release of CO from the bulkier substituted [L^tBuGe‐P=C=O] 2 b (L^tBu=CH[C(^tBu)N‐Dipp]₂) furnishes, under concomitant extrusion of the diimine [Dipp‐NC(^tBu)]₂, the bis‐N,P‐heterocyclic germylene [DippNC(^tBu)C(H)PGe]₂ 5 .     

Novel nickel (II) complexes chelating β‐diketiminate ligands: synthesis and simultaneous polymerization and oligomerization of ethylene

Two novel nickel (II) complexes, CH{C(CF₃)NAr}₂NiBr ( 1 , Ar = 2,6‐ⁱPr₂C₆H₃ and 2 , 2,6‐Me₂C₆H₃), were synthesized by the reaction of the lithium salt of fluorinated β‐diketiminate backbone ligands with (1,2‐dimethoxyethane) nickel (II) bromide [(DME)NiBr₂]. The solid‐state structure of nickel (II) complex 2 as a dimer reveals four‐coordination and a tetrahedral geometry with bromide bridged by single crystal X‐ray measurement. Both complexes catalyze simultaneous polymerization and oligomerization of ethylene when activated by methylaluminoxane (MAO). It was found that the reaction temperature has a pronounced effect on the activity of ethylene polymerization and the molecular weight of obtained polyethylene. In addition, the nickel catalytic systems predominantly produce linear polyethylene with unsaturated end groups. Copyright © 2006 John Wiley & Sons, Ltd.     

Syntheses and Characterizations of Two Palladium(II) Complexes of 5‐Mercapto‐1‐methyltetrazole

Reaction of PdCl₂(CH₃CN)₂ with the sodium salt of 5‐mercapto‐1‐methyltetrazole (MetzSNa) in methanol solution affords an interesting dinuclear palladium complex [Pd₂(MetzS)₄ ] ( 1 ). However, treatment of PdCl₂(CH₃CN)₂ with neutral MetzSH ligand in methanol solution produces a mononuclear palladium complex [Pd(MetzSH)₄]Cl₂ ( 2 ). Both complexes were characterized by IR, ¹HNMR, UV‐Vis spectroscopy as well as X‐ray crystallography. Single‐crystal X‐ray diffraction analyses of two complexes lead to the elucidation of the structures and show that 1 possesses an asymmetric structure: one Pd atom is tetracoordinated by three sulfur atoms and one nitrogen atom to form PdS₃N coordination sphere, the other Pd atom is tetracoordinated by three nitrogen atoms and one sulfur atom to form PdSN₃ coordination sphere. The molecules of 1 are associated to 1‐D infinite linear chain by weak intermolecular Pd···S contacts in the crystal lattice. In 2 , the Pd atom lies on an inversion center and has a square‐planar coordination involving the S atoms from four MetzSH ligands. The two chloride ions are not involved in coordination, but are engaged in hydrogen bonding.     

Amidophosphine‐stabilized palladium complexes catalyse Suzuki–Miyaura cross‐couplings in aqueous media

We report a simple and efficient procedure for Suzuki–Miyaura reactions in aqueous media catalysed by amidophosphine‐stabilized palladium complexes trans‐{L³PPh₂}₂PdCl₂ ( 3 ), trans‐{L³PPhtBu}₂PdCl₂ ( 4 ), [Pd(η³‐C₃H₅)(L³PPh₂)Cl] ( 5 ) and {Pd[2‐(Me₂NCH₂)C₆H₄](L³PPh₂)Cl} ( 6 ). The acidity of the NH proton in complexes 3 , 4 , 5 , 6 plays an important role in their catalytic activity. In addition, the palladium complexes cis‐{L¹PPh₂}PdCl₂ ( 1 ) and trans‐{L²PPh₂}₂PdCl₂ ( 2 ) stabilized by phosphines containing Y,C,Y‐chelating ligands L^1,2 have also been found to be useful catalysts for Suzuki–Miyaura reactions in aqueous media. The method can be effectively applied to both activated and deactivated aryl bromides yielding high or moderate conversions. The catalytic activity of couplings performed in pure water increases when utilizing a Pd complex with more acidic NH protons. A decrease of palladium concentration from 1.0 to 0.5 mol% does not lead to a substantial loss of conversion. In addition, Pd complex 1 can be efficiently recovered using two‐phase system extraction. Copyright © 2016 John Wiley & Sons, Ltd.     

Quinine‐Derived Imidazolidin‐2‐imine Ligands: Synthesis,Coordination Chemistry,and Application in Catalytic Transfer Hydrogenation

Two new optically active bidentate N,N‐ligands, DMIQCI ( 3a ) and DMIQCD ( 3b ), containing a quinuclidine core and an imidazolidin‐2‐imine unit, were synthesized. The reaction of these ligands with [(η⁵‐C₅Me₅)RuCl]₄ afforded the brick‐red ruthenium(II) complexes [(η⁵‐C₅Me₅)Ru(DMIQCI)Cl] ( 4 ) and [(η⁵‐C₅Me₅)Ru(DMIQCD)Cl] ( 5 ), which were used as catalysts in the transfer hydrogenation of acetophenone in boiling 2‐propanol. The reactions of 3a and 3b with [(COD)PdCl₂] (COD = 1,5‐cycloocta‐diene) and with [(DME)NiBr₂] (DME = 1,2‐dimethoxyethane) afforded the square‐planar palladium(II) complexes [(DMIQCI)PdCl₂] ( 7 ) and [(DMIQCD)PdCl₂] ( 8 ) or the tetrahedral nickel(II) complexes [(DMIQCI)NiBr₂] ( 9 ) and [(DMIQCD)NiBr₂] ( 10 ), respectively. The X‐ray crystal structures of 4 , 7 , 9· THF, and 10 are reported.     

New CuII and CdII Metal‐organic Coordination Polymers with 1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazole Ligands: Syntheses,Structures and Luminescent Properties

Three new complexes {[Cu( L¹ )₂(NO₃)₂]?H₂O}_oo ( 1 ), {[Cu₄( L² )₂(OAc)₈]‐CH₃CH₂OH}_oo ( 2 ) and [Cd₂( L³ )₃(NO₃)₄(H₂O)₂]_oo ( 3 ) ( L¹= 4‐phenyl‐7‐(pyridine‐3‐yl)‐1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazole, L²= 4‐(pyridine‐3‐yl)‐7‐phenyl‐1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazole, and L³= 4‐(pyridine‐4‐yl)‐7‐phenyl‐1,2,4‐triazolo[3,4‐b]‐1,3,4‐thiadiazole) have been synthesized and characterized by elemental analyses, IR spectra and single crystal X‐ray diffraction. The structural analyses reveal that complex 1 is a neutral 2‐D network structure with a 4⁴ topology, 2 has a 1‐D neutral coordination chain with a [Cu₂(CH₃COO)₄] dinuclear structural unit bridged by four acetate ions, and 3 is a neutral rhombohedral grid structure. All the complexes are air stable at room temperature. Furthermore, the fluorescent properties of complex 3 and corresponding ligand L³ have been investigated and discussed.     

Zweikernige Palladium(II)‐, Platin(II)‐ und Iridium(III)‐Komplexe von Bis[imidazol‐4‐yl]alkanen

Dinuclear Palladium(II), Platinum(II), and Iridium(III) Complexes of Bis[imidazol‐4‐yl]alkanes The reaction of bis(1,1′‐triphenylmethyl‐imidazol‐4‐yl) alkanes ((CH₂)_n bridged imidazoles L(CH₂)_nL, n = 3–6) with chloro bridged complexes [R₃P(Cl)M(μ‐Cl)M(Cl)PR₃] (M = Pd, Pt; R = Et, Pr, Bu) affords the dinuclear compounds [Cl₂(R₃P)M–L(CH₂)_nL–M(PR₃)Cl₂] 1 – 17 . The structures of [Cl₂(Et₃P)Pd–L(CH₂)₃L–Pd(PEt₃)Cl₂] ( 1 ), [Cl₂(Bu₃P)Pd–L(CH₂)₄L–Pd(PBu₃)Cl₂] ( 10 ), [Cl₂(Et₃P)Pd–L(CH₂)₅L–Pd(PEt₃)Cl₂] ( 3 ), [Cl₂(Et₃P)Pt–L(CH₂)₃L–Pt(PEt₃)Cl₂] ( 13 ) with trans Cl–M–Cl groups were determined by X‐ray diffraction. Similarly the complexes [Cl₂(Cp*)Ir–L(CH₂)_nL–Ir(Cp*)Cl₂] (n = 4–6) are obtained from [Cp*(Cl)Ir(μ‐Cl)₂Ir(Cl)Cp*] and the methylene bridged bis(imidazoles).     

Reactivity of 6-(2-tolyl)- and 6-(2,6-xylyl)-2,2′-bipyridines with palladium(II) derivatives. Selective C(sp)H vs. C(sp)H activation

Two new 6-substituted 2,2′-bipyridines, L, 6-(2-tolyl)bipy, L¹, and 6-(2,6-xylyl)bipy, L², have been synthesized. Their reactions with Na₂[PdCl₄] or {Pd(OAc)₂} afford either 1:1 adducts [Pd(L)X₂] (X=Cl, OAc) or five-membered cyclometallated derivatives [Pd(L¹-H)X] arising from C(sp²)H activation. From the chloro-alkyl intermediates [Pd(L)(Me)Cl], in the presence of Na[BAr′₄] (Ar′=3,5-(CF₃)₂C₆H₃), cationic species [Pd(L)(Me)(S)]⁺ (L=L¹, L²; S=CH₃CN) can be obtained. At variance, in less coordinating solvents, e.g. dichloromethane, unexpected activation of a C(sp³)H bond occurs with loss of methane, to afford 6-membered cyclometallated derivatives. The latter species were isolated as [Pd(L-H)(PPh₃)][BAr′₄].     

Synthesis of N,N′,X‐tridentate 2‐iminomethylpyrrole‐coordinated palladium(II) complexes via N─H bond activation of pyrrole moiety

The reaction of [Pd(CH₃CN)₂Cl₂] with N ‐functional group‐substituted 2‐iminomethylpyrrole‐based ligands, namely N ¹‐((1H‐pyrrol‐2‐yl)methylene)‐N ³,N ³‐dimethylpropane‐1,3‐diamine (L_A), N ¹‐((1H‐pyrrol‐2‐yl)methylene)‐N ³‐methyl‐N ³‐phenylpropane‐1,3‐diamine (L_B), N ‐((1H‐pyrrol‐2‐yl)methylene)‐3‐(methylthio)propan‐1‐amine (L_C) and N ‐((1H‐pyrrol‐2‐yl)methylene)‐3‐methoxypropan‐1‐amine (L_D), resulted in [L_n PdCl] (L_n  = L_A–L_D) complexes in high yield via N─H bond activation of pyrrole moiety without use of base. [L_n PdCl] existed as monomeric four‐coordinated complexes with slightly distorted square planar geometries around the palladium metal center. The ligands show N ,N ′,X ‐tridentate binding mode to the palladium metal center to give two fused ring metallacycles. [L_BPdCl] gave the highest activity (3.29 × 10⁵ g PMMA (mol Pd)⁻¹ h⁻¹) for a methyl methacrylate (MMA) polymerization in the presence of modified methylaluminoxane at 60 °C compared to the other Pd(II) analogues, and resulted in PMMA with higher molecular weight (M _w = 7.16 × 10⁵ g mol⁻¹) and narrower polydispersity index. Syndiotactic‐enriched PMMA resulted in all cases.     

Pd(II) complexes of N(4)‐substituted phenylaminoacetohydrazone and biacetylmonooxime: synthesis,characterization, structures and catalytic behaviour towards Suzuki–Miyaura coupling reactions

The reaction of [PdCl₂(CH₃CN)₂] and N(4)‐substituted phenylaminoacetohydrazone ligands (LH) in methanol at room temperature afforded air‐ and moisture‐stable palladium(II) complexes of two types with general formulae [Pd(LH)Cl] and [Pd₂(LH)(L)]Cl. An unusual coordination mode of ligand LH is observed, in which the ligand coordinates through N(4)H nitrogen and without enolization of the carbonyl group of the hydrazone moiety in both mono‐ and bimetallic complexes. The crystal structure of the complexes reveals that the oxime LH reacts with [PdCl₂(CH₃CN)₂] presumably via the elimination of HCl from hydrazine NH. All the synthesized Pd(II) complexes were evaluated as catalysts in the Suzuki cross‐coupling reaction of aryl halides, activated 4‐bromoacetophenone and non‐activated bromobenzene, with phenylboronic acid in aqueous medium. In both cases, i.e. with activated and non‐activated aryl halides, all the complexes show moderate conversion leading to biaryls with yields in the range 50–65%. Copyright © 2016 John Wiley & Sons, Ltd.     

Ruthenium(II/III)‐Based Compounds with Encouraging Antiproliferative Activity against Non‐small‐Cell Lung Cancer

Hereby we present the synthesis of several ruthenium(II) and ruthenium(III) dithiocarbamato complexes. Proceeding from the Na[trans‐Ru^III(dmso)₂Cl₄] ( 2 ) and cis‐[Ru^II(dmso)₄Cl₂] ( 3 ) precursors, the diamagnetic, mixed‐ligand [Ru^IIL₂(dmso)₂] complexes 4 and 5 , the paramagnetic, neutral [Ru^IIIL₃] monomers 6 and 7 , the antiferromagnetically coupled ionic α‐[Ru^III₂L₅]Cl complexes 8 and 9 as well as the β‐[Ru^III₂L₅]Cl dinuclear species 10 and 11 (L=dimethyl‐ (DMDT) and pyrrolidinedithiocarbamate (PDT)) were obtained. All the compounds were fully characterised by elemental analysis as well as ¹H NMR and FTIR spectroscopy. Moreover, for the first time the crystal structures of the dinuclear β‐[Ru^III₂(dmdt)₅]BF₄ ? CHCl₃ ? CH₃CN and of the novel [Ru^IIL₂(dmso)₂] complexes were also determined and discussed. For both the mono‐ and dinuclear Ru^II and Ru^III complexes the central metal atoms assume a distorted octahedral geometry. Furthermore, in vitro cytotoxicity of the complexes has been evaluated on non‐small‐cell lung cancer (NSCLC) NCI‐H1975 cells. All the mono‐ and dinuclear Ru^III dithiocarbamato compounds (i.e., complexes 6 – 10 ) show interesting cytotoxic activity, up to one order of magnitude higher with respect to cisplatin. Otherwise, no significant antiproliferative effect for either the precursors 2 and 3 or the Ru^II complexes 4 and 5 has been observed.     

Pd(II) complexes bearing di‐ and monochelate fluorinated β‐ketonaphthyliminato ligand and their catalytic properties towards vinyl‐addition polymerization and copolymerization of norbornene and ester‐functionalized norbornene derivative

Fluorinated β‐ketonaphthyliminate ligand CF₃C(O)CHC[HN(naphthyl)]CH₃ ( L1 ) and Pd(II) complexes with dichelate fluorinated β‐ketonaphthyliminato ligand, {CF₃C(O)CHC[N(naphthyl)]CH₃}₂Pd ( C1 ), as well as with monochelate fluorinated β‐ketonaphthyliminato ligand, {CF₃C(O)CHC[N(naphthyl)]CH₃}Pd(CH₃)(PPh₃) ( C2 ), were synthesized and their solid‐state structures were confirmed using X‐ray crystallographic analysis. The Pd(II) complexes were employed as precursors to catalyze norbornene (NB) homo‐ and copolymerization with ester‐functionalized NB derivative using B(C₆F₅)₃ as a co‐catalyst. High activity up to 2.3 × 10⁵ g_polymer mol_Pd^?1 h^?1 for the C1 /B(C₆F₅)₃ system and 3.4 × 10⁶ g_polymer mol_Pd^?1 h^?1 for the C2 /B(C₆F₅)₃ system was exhibited in NB homopolymerization. Moreover, the Pd(II) complexes exhibited a high level of tolerance towards the ester‐functionalized MB monomer. In comparison with the C1 /B(C₆F₅)₃ system, the C2 /B(C₆F₅)₃ system exhibited better catalytic property towards the copolymerization of NB with 5‐norbornene‐2‐carboxylic acid methyl ester (NB‐COOCH₃), and soluble vinyl‐addition‐type copolymers were obtained with relatively high molecular weights (3.6 × 10⁴–7.5 × 10⁴ g mol^?1) as well as narrow molecular weight distributions (1.49–2.15) depending on the variation of monomer feed ratios. The NB‐COOCH₃ insertion ratio in all copolymers could be controlled in the range 2.8–21.0 mol% by tuning a content of 10–50 mol% NB‐COOCH₃ in the monomer feed ratios. Copolymerization kinetics were expressed by the NB and NB‐COOCH₃ monomer reactivity ratios: r_NB‐COOCH3 = 0.18, r_NB = 1.28 were determined for the C1 /B(C₆F₅)₃ system and r_NB‐COOCH3 = 0.19, r_NB = 3.57 for the C2 /B(C₆F₅)₃ system using the Kelen–Tüdõs method. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and Structural Characterization of β‐Ketoiminate‐Stabilized Gallium Hydrides for Chemical Vapor Deposition Applications

Bis‐β‐ketoimine ligands of the form [(CH₂)_n{N(H)C(Me)?CHC(Me)?O}₂] (LⁿH₂, n=2, 3 and 4) were employed in the formation of a range of gallium complexes [Ga(Lⁿ)X] (X=Cl, Me, H), which were characterised by NMR spectroscopy, mass spectrometry and single‐crystal X‐ray diffraction analysis. The β‐ketoimine ligands have also been used for the stabilisation of rare gallium hydride species [Ga(Lⁿ)H] (n=2 ( 7 ); n=3 ( 8 )), which have been structurally characterised for the first time, confirming the formation of five‐coordinate, monomeric species. The stability of these hydrides has been probed through thermal analysis, revealing stability at temperatures in excess of 200 °C. The efficacy of all the gallium β‐ketoiminate complexes as molecular precursors for the deposition of gallium oxide thin films by chemical vapour deposition (CVD) has been investigated through thermogravimetric analysis and deposition studies, with the best results being found for a bimetallic gallium methyl complex [L³{GaMe₂}₂] ( 5 ) and the hydride [Ga(L³)H] ( 8 ). The resulting films ( F5 and F8 , respectively) were amorphous as‐deposited and thus were characterised primarily by XPS, EDXA and SEM techniques, which showed the formation of stoichiometric ( F5 ) and oxygen‐deficient ( F8 ) Ga₂O₃ thin films.     

1, 9‐Dihydro‐purine‐6‐thione Derivatives of the d8–d10 Metal Ions (PdII,PtII, and CuI): Synthesis,Spectroscopy, and Structures

Reaction of 1, 9‐dihydro‐purine‐6‐thione (puSH₂) in presence of aqueous sodium hydroxide with PdCl₂(PPh₃)₂ suspended in ethanol formed [Pd(κ²‐N⁷,S‐puS)(PPh₃)₂] ( 1 ). Similarly, complexes [Pd(κ²‐N⁷,S‐puS)(κ²‐P, P‐L‐L)] ( 2 – 4 ) {L‐L = dppm (m = 1) ( 2 ), dppp (m = 3) ( 3 ), dppb (m = 4) ( 4 )} were prepared using precursors the [PdCl₂(L‐L)] {L‐L = Ph₂P–(CH₂)_m–PPh₂}. Reaction of puSH₂ suspended in benzene with platinic acid, H₂PtCl₆, in ethanol in the presence of triethylamine followed by the addition of PPh₃ yielded the complex [Pt(κ²‐N⁷,S‐puS)(PPh₃)₂] ( 5 ). Complexes [Pt(κ²‐N⁷,S‐puS)(κ²‐P, P‐L‐L)] ( 6 – 8 ) {L‐L = dppm ( 6 ), dppp ( 7 ), dppb ( 8 )} were prepared similarly. The 1, 9‐dihydro‐purine‐6‐thione acts as N⁷,S‐chelating dianion in compounds 1 – 8 . The reaction of copper(I) chloride [or copper(I) bromide] in acetonitrile with puSH₂ and the addition of PPh₃ in methanol yielded the same product, [Cu(κ²‐N⁷,S‐puSH)(PPh₃)₂] ( 9 ), in which the halogen atoms are removed by uninegative N, S‐chelating puSH^– anion. However, copper(I) iodide did not lose iodide and formed the tetrahedral complex, [CuI(κ¹‐S‐puSH₂)(PPh₃)₂] ( 10 ), in which the thio ligand is neutral. These complexes were characterized with the help of elemental analysis, NMR spectroscopy (¹H, ³¹P), and single‐crystal X‐ray crystallography ( 3 , 7 , 8 , 9 , and 10 ).     

Theoretical insights into the relative bonding of normal and abnormal N‐heterocyclic carbenes in [PdCl2(NHCR)2] and [PdCl2(NHCR)(aNHCR)] (R = H,Ph, Mes)

Quantum chemical insights into normal Pd‐C2(NHC^R) and abnormal Pd‐C5(aNHC^R) bonding, dominated by dispersion interactions in N‐hetereocyclic carbene complexes [PdCl₂(NHC^R)₂] ( I , R = H; II , R = Ph; III , R = Mes (2,4,6‐trimethyl)phenyl)) and [PdCl₂(NHC^R)(aNHC^R] ( IV , R = H; V , R = Ph; VI , R = Mes) have been investigated at DFT and DFT‐D3(BJ) level of theory with particular emphasis on the effects of the noncovalent interactions on the structures and the nature of Pd‐C2(NHC^R) and Pd‐C5(aNHC^R) bonds. The optimized geometries are good agreement with the experimental values. The Pd‐C bonds are essentially single bond. Hirshfeld charge distributions indicate that the abnormal aNHC^R carbene ligand is relatively better electron donor than the normal NHC^R carbene ligand. The C2 atom has larger %s contribution along Pd‐C2 bond than the C5 atom along Pd‐C5 bond. As a consequence the Pd‐C2(NHC^R) bonds are relative stronger than the Pd‐C5(aNHC^R) bonds. Thus, the results of natural hybrid orbital analysis support the key point of the present study. Calculations predict that for bulky substituent (R = Ph, Mes) at carbene, the Pd‐C2(NHC^R) bond is stronger than Pd‐C5(aNHC^R) bond due to large dispersion energy in [PdCl₂(NHC^R)₂] than in [PdCl₂(NHC^R)(aNHC^R)]. However, in case of non‐bulky substituent with small and almost equal contribution of dispersion energy, the Pd‐C2(NHC^R) bond is relative weaker than Pd‐C5(aNHC^R) bond. The bond dissociation energies are dependent on the R substituent, the DFT functional and the inclusion of dispersion interactions. Major point of this study is that the abnormal aNHCs are not always strongly bonded with metal center than the normal NHCs. Effects of dispersion interaction of substituent at nitrogen atoms of carbene ligand are found to play a crucial role on estimation of relative bonding strengths of the normal and abnormal aNHCs with metal center. © 2016 Wiley Periodicals, Inc.     

Organo‐Palladium(II)‐Verbindungen mit PdC4‐Koordination: Phenylethinyl‐ und Methylphenylethinylkomplexe

Tetrakis(p‐tolyl)oxalamidinato‐bis[acetylacetonatopalladium(II)] ([Pd₂(acac)₂(oxam)]) reacted with Li–C≡C–C₆H₅ in THF with formation of [Pd(C≡C–C₆H₅)₄Li₂(thf)₄] ( 1a ). Reaction of [Pd₂(acac)₂(oxam)] with a mixture of 6 equiv. Li–C≡C–C₆H₅ and 2 equiv. LiCH₃ resulted in the formation of [Pd(CH₃)(C≡C–C₆H₅)₃Li₂(thf)₄] ( 2 ), and the dimeric complex [Pd₂(CH₃)₄(C≡C–C₆H₅)₄Li₄(thf)₆] ( 3 ) was isolated upon reaction of [Pd₂(acac)₂(oxam)] with a mixture of 4 equiv. Li–C≡C–C₆H₅ and 4 equiv. LiCH₃. 1 – 3 are extremely reactive compounds, which were isolated as white needles in good yields (60–90%). They were fully characterized by IR, ¹H‐, ¹³C‐, ⁷Li‐NMR spectroscopy, and by X‐ray crystallography of single crystals. In these compounds Li ions are bonded to the two carbon atoms of the alkinyl ligand. 1a reacted with Pd(PPh₃)₄ in the presence of oxygen to form the already known complexes trans‐[Pd(C≡C–C₆H₅)₂(PPh₃)₂] and [Pd(η²‐O₂)(PPh₃)₂]. In addition, 1a is an active catalyst for the Heck coupling reaction, but less active in the catalytic Sonogashira reaction.