Copper and Silver Carbene Complexes without Heteroatom‐Stabilization: Structure,Spectroscopy, and Relativistic Effects

Salts of a copper and a silver carbene complex were prepared from dimesityl diazomethane, made possible by the steric shielding of the N‐heterocyclic carbene (NHC) ancillary ligand IPr**. The mint‐green complex [IPr**Ag=CMes₂]⁺[NTf₂]^? is the first isolated silver carbene complex without heteroatom donor substituents. Single‐crystal X‐ray diffraction provides evidence for a predominant carbenoid character, and supports the postulation of such reactive species as intermediates in silver‐catalyzed C? H activation reactions. The greenish yellow copper carbene complex [IPr**Cu=CMes₂]⁺[NTf₂]^? has spectroscopic properties in between the isostructural silver complex and the already reported emerald green gold carbene complex. A comparison in the Group 11 series indicates that relativistic effects are responsible for the strong σ bond and the significant π back‐bonding in the gold carbene moiety.     

A New Class of Remote N‐Heterocyclic Carbenes with Exceptionally Strong σ‐Donor Properties: Introducing Benzo[c]quinolin‐6‐ylidene

We make the case for benzo[c]quinolin‐6‐ylidene ( 1 ) as a strongly electron‐donating carbene ligand. The facile synthesis of 6‐trifluoromethanesulfonylbenzo[c]quinolizinium trifluoromethanesulfonate ( 2 ) gives straightforward access to a useful precursor for oxidative addition to low‐valent metals, to yield the desired carbene complexes. This concept has been achieved in the case of [Mn(benzo[c]quinolin‐6‐ylidene)(CO)₅]⁺ ( 15 ) and [Pd(benzo[c]quinolin‐6‐ylidene)(PPh₃)₂(L)]²⁺ L=THF ( 21 ), OTf ( 22 ) or pyridine ( 23 ). Attempts to coordinate to nickel result in coupling products from two carbene precursor fragments. The CO IR‐stretching‐frequency data for the manganese compound suggests benzo[c]quinolin‐6‐ylidene is at least as strong a donor as any heteroatom‐stabilised carbene ligand reported.     

Phenylimidorhenium(V) Complexes with 1,3‐Diethyl‐4,5‐dimethylimidazole‐2‐ ylidene Ligands

The phenylimidorhenium(V) complexes [Re(NPh)X₃(PPh₃)₂] (X = Cl, Br) react with the N‐heterocyclic carbene (NHC) 1,3‐diethyl‐4,5‐dimethylimidazole‐2‐ylidene (L^Et) under formation of the stable rhenium(V) complex cations [Re(NPh)X(L^Et)₄]²⁺ (X = Cl, Br), which can be isolated as their chloride or [PF₆]^? salts. The compounds are remarkably stable against air, moisture and ligand exchange. The hydroxo species [Re(NPh)(OH)(L^Et)₄]²⁺ is formed when moist solvents are used during the synthesis. The rhenium atoms in all three complexes are coordinated in a distorted octahedral fashion with the four NHC ligands in equatorial planes of the molecules. The Re–C(carbene) bond lengths between 2.171(8) and 2.221(3) Å indicate mainly σ‐bonding between the NHC ligand and the electron deficient d² metal atoms. Attempts to prepare analogous phenylimido complexes from [Re(NPh)Cl₃(PPh₃)₂] and 1,3‐diisopropyl‐4,5‐dimethylimidazole‐2‐ylidene (L^i?Pr) led to a cleavage of the rhenium‐nitrogen multiple bond and the formation of the dioxo complex [ReO₂(L^i?Pr)₄]⁺.     

Expanded‐Ring N‐Heterocyclic Carbenes Efficiently Stabilize Gold(I) Cations,Leading to High Activity in π‐Acid‐Catalyzed Cyclizations

A series of six‐ and seven‐membered expanded‐ring N‐heterocyclic carbene (er‐NHC) gold(I) complexes has been synthesized using different synthetic approaches. Complexes with weakly coordinating anions [(er‐NHC)AuX] (X^?=BF₄^?, NTf₂^?, OTf^?) were generated in solution. According to their ¹³C NMR spectra, the ionic character of the complexes increases in the order X^?=Cl^?<NTf₂^?<OTf^?<BF₄^?. Additional factors for stabilization of the cationic complexes are expansion of the NHC ring and the attachment of bulky substituents at the nitrogen atoms. These er‐NHCs are bulkier ligands and stronger electron donors than conventional NHCs as well as phosphines and sulfides and provide more stabilization of [(L)Au⁺] cations. A comparative study has been carried out of the catalytic activities of five‐, six‐, and seven‐membered carbene complexes [(NHC)AuX], [(Ph₃P)AuX], [(Me₂S)AuX], and inorganic compounds of gold in model reactions of indole and benzofuran synthesis. It was found that increased ionic character of the complexes was correlated with increased catalytic activity in the cyclization reactions. As a result, we developed an unprecedentedly active monoligand cationic [(THD‐Dipp)Au]BF₄ (1,3‐bis(2,6‐diisopropylphenyl)‐3,4,5,6‐tetrahydrodiazepin‐2‐ylidene gold(I) tetrafluoroborate) catalyst bearing seven‐membered‐ring carbene and bulky Dipp substituents. Quantitative yields of cyclized products were attained in several minutes at room temperature at 1 mol % catalyst loadings. The experimental observations were rationalized and fully supported by DFT calculations.     

Oxorhenium(V) Complexes with 1,3,4‐Triphenyl‐1,2,4‐triazol‐5‐ylidene

Reactions of the oxorhenium(V) complexes [ReOX₃(PPh₃)₂] (X = Cl, Br) with the N‐heterocyclic carbene (NHC) 1,3,4‐triphenyl‐1,2,4‐triazol‐5‐ylidene (L^Ph) under mild conditions and in the presence of MeOH or water give [ReOX₂(Y)(PPh₃)(L^Ph)] complexes (X = Cl, Br; Y = OMe, OH). Attempted reactions of the carbene precursor 5‐methoxy‐1,3,4‐triphenyl‐4,5‐dihydro‐1H‐1,2,4‐triazole ( 1 ) with [ReOCl₃(PPh₃)₂] or [NBu₄][ReOCl₄] in boiling xylene resulted in protonation of the intermediately formed carbene and decomposition products such as [HL^Ph][ReOCl₄(OPPh₃)], [HL^Ph][ReOCl₄(OH₂)] or [HL^Ph][ReO₄] were isolated. The neutral [ReOX₂(Y)(PPh₃)(HL^Ph)] complexes are purple, airstable solids. The bulky NHC ligands coordinate monodentate and in cis‐position to PPh₃. The relatively long Re–C bond lengths of approximate 2.1Å indicate metal‐carbon single bonds.     

Anionic Gold(I) Complexes—Twelve‐ and Ten‐Vertex Monocarba‐closo‐borate Anions with Carbon–Gold σ Bonds

The anionic gold(I) complexes [1‐(Ph₃PAu)‐closo‐1‐CB₁₁H₁₁]^? ( 1 ), [1‐(Ph₃PAu)‐closo‐1‐CB₉H₉]^? ( 2 ), and [2‐(Ph₃PAu)‐closo‐2‐CB₉H₉]^? ( 3 ) with gold–carbon 2c–2e σ bonds have been prepared from [AuCl(PPh₃)] and the respective carba‐closo‐borate dianion. The anions have been isolated as their Cs⁺ salts and the corresponding [Et₄N]⁺ salts were obtained by salt metathesis reactions. The salt Cs‐ 3 isomerizes in the solid state and in solution at elevated temperatures to Cs‐ 2 with ΔH_iso=(?75±5) kJ mol^?1 (solid state) and ΔH^≠=(118±10) kJ mol^?1 (solution). The compounds were characterized by vibrational and multi‐NMR spectroscopies, mass spectrometry, elemental analysis, and differential scanning calorimetry. The crystal structures of [Et₄N]‐ 1 , [Et₄N]‐ 2 , and [Et₄N]‐ 3 were determined. The bonding parameters, NMR chemical shifts, and the isomerization enthalpy of Cs‐ 3 to Cs‐ 2 are compared to theoretical data.     

Proton‐Induced Generation of Remote N‐Heterocyclic Carbene–Ru Complexes

The proton‐induced Ru?C bond variation, which was previously found to be relevant in the water oxidation, has been investigated by using cyclometalated ruthenium complexes with three phenanthroline (phen) isomers. The designed complexes, [Ru(bpy)₂(1,5‐phen)]⁺ ([ 2 ]⁺), [Ru(bpy)₂(1,6‐phen)]⁺ ([ 3 ]⁺), and [Ru(bpy)₂(1,7‐phen)]⁺ ([ 4 ]⁺) were newly synthesized and their structural and electronic properties were analyzed by various spectroscopy and theoretical protocols. Protonation of [ 4 ]⁺ triggered profound electronic structural change to form remote N‐heterocyclic carbene (rNHC), whereas protonation of [ 2 ]⁺ and [ 3 ]⁺ did not affect their structures. It was found that changes in the electronic structure of phen beyond classical resonance forms control the rNHC behavior. The present study provides new insights into the ligand design of related ruthenium catalysts.     

Nitrile‐functionalized Hg(II)‐ and Ag(I)‐N‐heterocyclic carbene complexes: synthesis,crystal structures,nuclease and DNA binding activities

Various nitrile‐functionalized benzimidazol‐2‐ylidene carbene complexes of Hg(II) and Ag(I) were synthesized by the interaction of 1‐benzyl/1‐butyl‐3‐(cyano‐benzyl)‐3 H‐benzimidazol‐1‐ium mono/dihexafluorophosphate with Hg(OAc)₂/Ag₂O in acetonitrile. Two of the benzimidazolium salts were structurally characterized by single crystal X‐ray diffraction technique. Structures of reported compounds were characterized by ¹ H, ¹³C NMR, FT‐IR, UV–visible spectroscopic techniques, and molar conductivity and elemental analyses. For bis‐benzimidazolium salt, dinuclear Hg(II)– and Ag(I)–carbene complexes were obtained. Nuclease activity and binding interactions of the synthesized benzimidazolium salts and their Ag(I)–carbene complexes with DNA were studied using agarose gel electrophoresis and, absorption spectroscopy and viscosity measurements, respectively. Ag(I)–carbene complexes showed higher DNA binding activity compared to their respective benzimidazolium salts. However, a benzimidazolium salt and two of the Ag(I) complexes showed remarkably higher nuclease activity both, in the presence and absence of an oxidizing agent. Copyright © 2012 John Wiley & Sons, Ltd.     

Copper–Carbene Intermediates in the Copper‐Catalyzed Functionalization of OH Bonds

Copper–carbene [Tp^xCu?C(Ph)(CO₂Et)] and copper–diazo adducts [Tp^xCu{η¹‐N₂C(Ph)(CO₂Et)}] have been detected and characterized in the context of the catalytic functionalization of O?H bonds through carbene insertion by using N₂?C(Ph)(CO₂Et) as the carbene source. These are the first examples of these type of complexes in which the copper center bears a tridentate ligand and displays a tetrahedral geometry. The relevance of these complexes in the catalytic cycle has been assessed by NMR spectroscopy, and kinetic studies have demonstrated that the N‐bound diazo adduct is a dormant species and is not en route to the formation of the copper–carbene intermediate.     

Synthetic and antimicrobial studies on new gold(I) complexes of imidazolidin‐2‐ylidenes

Six new 1,3‐diorganylimidazolidin‐2‐ylidene (NHC) gold(I) complexes of the type [Au(NHC)₂]⁺ (1–6), were synthesized by reacting [AuCl(PPh)₃] with 1,3‐dimesitylimidazolidin‐2‐ylidene or bis(1,3‐dialkylimidazolidin‐2‐ylidene). The complexes 1–6 were fully characterized by elemental analyses and spectroscopic data. The placement of mesityl or para‐substituted benzyl groups on the nitrogen atoms of the ring of the complexes leads to the particularly active antibacterial agents evaluated in this work. It is worth noting that the p‐methoxybenzyl derivative (2) inhibited the growth of Pseudomona aeruginosa, Staphylococcus epidermidis, Staphylococcus aureus and Enterococcus faecalis with minimum inhibitory concentration (MIC) values of 3.12 µg ml^?1, 6.25 µg ml^?1, 3.12 µg ml^?1 and 3.12 µg ml^?1 respectively. In contrast, the analogous p‐dimethylaminobenzyl derivative (3) is effective only against Escherichia coli (MIC = 3.12 µg ml^?1). Copyright © 2004 John Wiley & Sons, Ltd.     

New rhodium(I) water‐soluble complexes with 1‐alkyl‐1‐azonia‐3,5‐diaza‐7‐phospha‐adamantane iodides and their catalytic activity

The water‐soluble phosphine ligands, 1,3,5‐triaza‐7‐phosphatricyclo[3.3.1.1^3,7]decane (tpa) and 1‐alkyl‐1‐azonia‐3,5‐diaza‐7‐phosphatricyclo[3.3.1.1^3,7]decane iodides (Rtpa⁺I⁻), with alkyl=methyl(mtpa⁺I⁻), ethyl (etpa⁺I⁻) and n‐propyl, (ptpa⁺I⁻), and mtpa⁺Cl⁻ react with [Rh₂Cl₂(CO)₄] giving the rhodium(I) complexes [RhCl(CO)(tpa)₂], [RhI(CO)(Rtpa⁺I⁻)₂], [RhCl‐­(CO)(mtpa⁺Cl⁻)₃] and [RhI(CO)(Rtpa⁺I⁻)₃]. The properties and reactivities of the complexes have been investigated using ¹H and ³¹PNMR and IR spectroscopies. The five‐coordinate complexes in solutions show dynamic properties. The complexes are catalysts of the water‐gas shift reaction, the hydrogenation of CC and CO bonds, the hydroformylation of alkenes and the isomerization of unsaturated compounds. Copyright © 1999 John Wiley & Sons, Ltd.     

Efficient Room‐Temperature,Au+‐Mediated Coupling of a Carbene Ligand with Methane To Generate C2Hx (x=4, 6)

The thermal reactions of the closed‐shell, “naked” gold–carbene complex [Au(CH₂)]⁺ with methane have been explored by using FTICR mass spectrometry complemented by quantum chemical (QC) calculations at the CCSD(T)//BMK level of theory. Mechanistic aspects for this unprecedentedly efficient carbene insertion in the C? H bond of methane have been addressed and the origin of the counterintuitive high reactivity of [Au(CH₂)]⁺ towards this most inert hydrocarbon is discussed.     

Synthesis and Basic Coordination Properties of Side‐chain Functionalized Bis‐phosphonio‐benzophospholides

Salts containing bis‐phosphonio‐benzophospholide cations 2 a – d with an additional donor site in one of the phosphonio‐moieties were synthesized either via quaternisation of the Ph₂P moiety in the neutral phosphonio‐benzophospholide 3 , or via ring‐closure of the functionalized bis‐phosphonium ion 6 . The Ph₂P‐substituted cation 2 d formed chelate complexes [M(k²P,P′‐ 2 d )(CO)_n]⁺ with M(CO)_n = Ni(CO)₂, Fe(CO)₃, Cr(CO)₄. In the latter case, competition between formation of the chelate and a complex [Cr(kP‐ 2 d )₂(CO)₄]²⁺ was observed, and interpreted as a consequence of antagonism between the stabilizing chelate effect and destabilizing ligand–ligand repulsions. The formation of stable Pd^II and Pt^II complexes of 2 d suggests that the chelate effect may also overcome the kinetic inhibition which so far prevented isolation of complexes of these metals with bis‐phosphonio‐benzophospholides. The newly synthesized ligands and complexes were characterized by spectroscopic data, and an X‐ray crystal structure analysis of 2 a [Br]. The reactivity of chelate complexes towards Ph₃P indicates that the ring phosphorus atom is a weaker donor than the pendant Ph₂P‐group.     

The First Crystal Structure of a Reactive Dirhodium Carbene Complex and a Versatile Method for the Preparation of Gold Carbenes by Rhodium‐to‐Gold Transmetalation

The dirhodium carbene derived from bis(4‐methoxyphenyl)diazomethane and [Rh(tpa)₄]?CH₂Cl₂ (tpa=triphenylacetate) was characterized by UV, IR, and NMR spectroscopy, HRMS, as well as by X‐ray diffraction. The isolated complex exhibits prototypical rhodium carbene reactivity in that it cyclopropanates 4‐methoxystyrene at low temperature. Experimental structural information on this important type of reactive intermediate is extremely scarce and thus serves as a reference point for mechanistic discussions of rhodium catalysis in general. Moreover, dirhodium carbenes are shown to undergo remarkably facile carbene transfer on treatment with [LAuNTf₂] (L=phosphine). This formal transmetalation opens a valuable new entry into gold carbene complexes that cannot easily be made otherwise; three fully characterized representatives illustrate this aspect.     

The first example of a two‐coordinated AuI atom bonded to an FeII atom and an N‐heterocyclic carbene (NHC) ligand

The aurophilicity exhibited by Au^I complexes depends strongly on the nature of the supporting ligands present and the length of the Au–element (Au—E) bond may be used as a measure of the donor–acceptor properties of the coordinated ligands. A binuclear iron–gold complex, [1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene‐2κC²]dicarbonyl‐1κ²C‐(1η⁵‐cyclopentadienyl)gold(I)iron(II)(Au—Fe) benzene trisolvate, [AuFe(C₅H₅)(C₂₇H₃₆N₂)(CO)₂]·3C₆H₆, was prepared by reaction of K[CpFe(CO)₂] (Cp is cyclopentadienyl) with (NHC)AuCl [NHC = 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene]. In addition to the binuclear complex, the asymmetric unit contains three benzene solvent molecules. This is the first example of a two‐coordinated Au atom bonded to an Fe and a C atom of an N‐heterocyclic carbene.     

Two‐Photon Chemistry in Ruthenium 2,2′‐Bipyridyl‐Functionalized Single‐Wall Carbon Nanotubes

Ruthenium polypyridyl complexes are widely used as light harvesters in dye‐sensitized solar cells. Since one of the potential applications of single‐wall carbon nanotubes (SWCNTs) and their derived materials is their use as active components in organic and hybrid solar cells, the study of the photochemistry of SWCNTs with tethered ruthenium polypyridyl complexes is important. A water‐soluble ruthenium tris(bipyridyl) complex linked through peptidic bonds to SWCNTs (Ru‐SWCNTs) was prepared by radical addition of thiol‐terminated SWCNT to a terminal C?C double bond of a bipyridyl ligand of the ruthenium tris(bipyridyl) complex. The resulting macromolecular Ru‐SWCNT (≈500 nm, 15.6 % ruthenium complex content) was water‐soluble and was characterized by using TEM, thermogravimetric analysis, chemical analysis, and optical spectroscopy. The emission of Ru‐SWCNT is 1.6 times weaker than that of a mixture of [Ru(bpy)₃]²⁺ and SWCNT of similar concentration. Time‐resolved absorption optical spectroscopy allows the detection of the [Ru(bpy)₃]²⁺‐excited triplet and [Ru(bpy)₃]⁺. The laser flash studies reveal that Ru‐SWCNT exhibits an unprecedented two‐photon process that is enabled by the semiconducting properties of the SWCNT. Thus, the effect of the excitation wavelength and laser power on the transient spectra indicate that upon excitation of two [Ru(bpy)₃]²⁺ complexes of Ru‐SWCNT, a disproportionation process occurs leading to delayed formation of [Ru(bpy)₃]⁺ and the performance of the SWCNT as a semiconductor. This two‐photon delayed [Ru(bpy)₃]⁺ generation is not observed in the photolysis of [Ru(bpy)₃]³⁺; SWCNT acts as an electron wire or electron relay in the disproportionation of two [Ru(bpy)₃]²⁺ triplets in a process that illustrates that the SWCNT plays a key role in the process. We propose a mechanism for this two‐photon disproportionation compatible with i) the need for high laser flux, ii) the long lifetime of the [Ru(bpy)₃]²⁺ triplets, iii) the semiconducting properties of the SWNT, and iv) the energy of the HOMO/LUMO levels involved.     

Elevated Catalytic Activity of Ruthenium(II)–Porphyrin‐Catalyzed Carbene/Nitrene Transfer and Insertion Reactions with N‐Heterocyclic Carbene Ligands

Bis(NHC)ruthenium(II)–porphyrin complexes were designed, synthesized, and characterized. Owing to the strong donor strength of axial NHC ligands in stabilizing the trans M?CRR′/M?NR moiety, these complexes showed unprecedently high catalytic activity towards alkene cyclopropanation, carbene C? H, N? H, S? H, and O? H insertion, alkene aziridination, and nitrene C? H insertion with turnover frequencies up to 1950 min^?1. The use of chiral [Ru(D₄‐Por)(BIMe)₂] ( 1 g ) as a catalyst led to highly enantioselective carbene/nitrene transfer and insertion reactions with up to 98 % ee. Carbene modification of the N terminus of peptides at 37 °C was possible. DFT calculations revealed that the trans axial NHC ligand facilitates the decomposition of diazo compounds by stabilizing the metal–carbene reaction intermediate.     

Enhanced π‐Backdonation from Gold(I): Isolation of Original Carbonyl and Carbene Complexes

The specific electronic properties of bent o‐carborane diphosphine gold(I) fragments were exploited to obtain the first classical carbonyl complex of gold [(DPCb)AuCO]⁺ (ν(CO)=2143 cm^?1) and the diphenylcarbene complex [(DPCb)Au(CPh₂)]⁺, which is stabilized by the gold fragment rather than the carbene substituents. These two complexes were characterized by spectroscopic and crystallographic means. The [(DPCb)Au]⁺ fragment plays a major role in their stability, as substantiated by DFT calculations. The bending induced by the diphosphine ligand substantially enhances π‐backdonation and thereby allows the isolation of carbonyl and carbene complexes featuring significant π‐bond character.     

catena‐Poly[bis(μ‐2,2′‐bipyridin‐6‐olato)‐κ3N,N′:O;O:N,N′‐dicopper(I,II) [[tetrafluoridoniobium(V)]‐μ‐oxido]]

A novel copper–niobium oxyfluoride, {[Cu₂(C₁₀H₇N₂O)₂][NbOF₄]}_n, has been synthesized by a hydrothermal method and characterized by elemental analysis, EDS, IR, XPS and single‐crystal X‐ray diffraction. The structural unit consists of one C₂‐symmetric [NbOF₄]⁻ anion and one centrosymmetric coordinated [Cu₂(obpy)₂]⁺ cation (obpy is 2,2′‐bipyridin‐6‐olate). In the [NbOF₄]⁻ anion, each Nb^V metal centre is five‐coordinated by four F atoms and one O atom in the first coordination shell, forming a square‐pyramidal coordination geometry. These square pyramids are then further connected to each other via trans O atoms [Nb—O = 2.187 (3) Å], forming an infinite linear {[NbOF₄]⁻}_n polyanion. In the coordinated [Cu₂(obpy)₂]⁺ cation, the oxidation state of each Cu site is disordered, which is confirmed by the XPS results. The disordered Cu sites are coordinated by two N atoms and one O atom from two different obpy ligands. The [NbOF₄]⁻ and [Cu₂(obpy)₂]⁺ units are assembled via weak C—H...F hydrogen bonds, resulting in the formation of a three‐dimensional supramolecular structure. π–π stacking interactions between the pyridine rings [centroid–centroid distance = 3.610 (2) Å] may further stabilize the crystal structure.     

Pseudohalide‐directed Assembly of Two Zinc(II) Coordination Polymers with a 3,4‐Bis(3‐pyridyl)‐5‐(4‐pyridyl)‐1,2,4‐triazole Tecton

The zinc(II) pseudohalide complexes {[Zn(L³³⁴)(SCN)₂(H₂O)](H₂O)₂}_n ( 1 ) and [Zn(L³³⁴)(dca)₂]_n ( 2 ) were synthesized and characterized using the ligand 3,4‐bis(3‐pyridyl)‐5‐(4‐pyridyl)‐1,2,4‐triazole (L³³⁴) and ZnCl₂ in presence of thiocyanate (SCN^–) and dicynamide [dca, N(CN)₂^–] respectively. Single‐crystal X‐ray structural analysis revealed that the central Zn^II atoms in both complexes have similar octahedral arrangement. Compound 1 has a 2D sheet structure bridged by bidentate L³³⁴ and double μ_N,S‐thiocyanate anions, whereas complex 2 , incorporating with two monodentate dicynamide anions, displays a two‐dimensional coordination framework bridged by tetradentate L³³⁴ ligand. Structural analysis demonstrated that the influence of pseudohalide anions plays an important role in determining the resultant structure. Both complexes were characterized by IR spectroscopy, microanalysis, and powder X‐ray diffraction techniques. In addition, the solid fluorescence and thermal stability properties of both complexes were investigated.