Cyclometalated Iridium(III) and Rhodium(III) Complexes Containing Naphthyridine Ligands: Synthesis,Characterization and Biological Studies

The synthesis, crystal structure, and biological activity of new bis‐cyclometalated compounds [M(ptpy)₂(4‐chloro‐2‐methyl‐1,8‐naphthyridine)]PF₆ [M = Rh ( 1 ); M = Ir ( 2 ); ptpy = 2‐(p‐tolyl)pyridinato] and [M(ptpy)₂(2‐methyl‐1,8‐naphthyridine)]PF₆ [M = Rh ( 3 ); M = Ir ( 4 )] are described. The new compounds were prepared by the reaction of [{M(μ‐Cl)(ptpy)₂}₂] (M = Rh, Ir) with the corresponding naphthyridine ligands. The molecular structures of compounds 1 , 3 , and 4 were confirmed by single‐crystal X‐ray diffraction studies.     

Metal and Substituent Influence on the Cytostatic Activity of Cationic Bis-cyclometallated Iridium and Rhodium Complexes with Substituted 1,10-Phenanthrolines as Ancillary Ligands

Synthesis and characterization of the new cyclometalated complex salts [Rh(ptpy)₂(5.6-dimethyl-1,10-phenanthroline)]PF₆ ( 1a ) [Rh(ptpy)₂(2.9-dimethyl-4.7-diphenyl-1,10- phenanthroline)]PF₆ ( 2a ), [Rh(ptpy)₂(5-amino-1,10-phenanthroline)] PF₆ ( 3a ), and [M(ptpy)₂ (pyrazino-[2.3-f]-1,10-phenanthroline)]PF₆ (M = Rh, 4a ; M = Ir, 4b ), (ptpy = 2-(p-tolyl)pyridinato) are described. The molecular structures of compounds 1b and 4a in the solid state were determined by single-crystal X-ray diffraction. All these compounds and their already known Iridium counterparts 1b – 3b display significant cytotoxicity against human cancer cell lines MCF-7 (human breast adenocarcinoma) and HT-29 (colon adenocarcinoma) with IC₅₀ values in the low micromolar range.     

Cyclometalated Iridium(III) Complexes Containing Semicarbazone Ligands: Synthesis,Characterization, Photophysical and Biological Studies

The synthesis, crystal structure, photophysical properties, and biological activity of the novel bis‐cyclometalated complexes [Ir(ptpy)₂(vnsc)] ( 2 ) and [Ir(ptpy)₂(acsc)] ( 3 ) [ptpy = 2‐(p‐tolyl)pyridinato, vnsc = vanillin semicarbazone, acsc = acetone semicarbazone] are described. The new compounds were prepared by the reaction of [{Ir(μ‐Cl)(ptpy)₂}₂] ( 1 ) with the corresponding semicarbazone ligands under basic conditions. The molecular structure of compound 3 was confirmed by a single‐crystal X‐ray diffraction study. The complex crystallized from chloroform as a mono‐ solvate in the orthorhombic space group Pcab with eight molecules in the unit cell.     

Ein‐ und zweikernige Rhodiumkomplexe mit Arsino(phosphino)methanen in unterschiedlichen Koordinationsformen

Mono‐ and Dinuclear Rhodium Complexes with Arsino(phosphino)methanes in Different Coordination Modes The cyclooctadiene complex [Rh(η⁴‐C₈H₁₂)(κ²‐tBu₂AsCH₂PiPr₂)](PF₆) ( 1a ) reacts with CO and CNtBu to give the substitution products [Rh(L)₂(κ²‐tBu₂AsCH₂PiPr₂)](PF₆) ( 2 , 3 ). From 1a and Na(acac) in the presence of CO the neutral compound [Rh(κ²‐acac)(CO)(κ‐P‐tBu₂AsCH₂PiPr₂)] ( 4 ) is formed. The reactions of 1a , the corresponding B(Ar_F)₄‐salt 1b and [Rh(η⁴‐C₈H₁₂)(κ²‐iPr₂AsCH₂PiPr₂)](PF₆) ( 5 ) with acetonitrile under a H₂ atmosphere affords the complexes [Rh(CH₃CN)₂(κ²‐R₂AsCH₂PiPr₂)]X ( 6a , 6b , 7 ), of which 6a (R = tBu; X = PF₆) gives upon treatment with Na(acac‐f₆) the bis(chelate) compound [Rh(κ²‐acac‐f₆)(κ²‐tBu₂AsCH₂PiPr₂)] ( 8 ). From 8 and CH₃I a mixture of two stereoisomers of composition [Rh(CH₃)I(κ²‐acac‐f₆)(κ²‐tBu₂AsCH₂PiPr₂)] ( 9/10 ) is generated by oxidative addition, and the molecular structure of the racemate 9 has been determined. The reactions of 1a and 5 with CO in the presence of NaCl leads to the formation of the “A‐frame” complexes [Rh₂(CO)₂(μ‐Cl)(μ‐R₂AsCH₂PiPr₂)₂](PF₆) ( 11 , 12 ), which have been characterized crystallographically. From 11 and 12 the dinuclear substitution products [Rh₂(CO)₂(μ‐X)(μ‐R₂AsCH₂PiPr₂)₂](PF₆) ( 13 ‐ 16 ) are obtained by replacing the bridging chloride for bromide, hydride or hydroxide, respectively. While 12 (R = iPr) reacts with NaI to give the related “A‐frame” complex 18 , treatment of 11 (R = tBu) with NaI yields the mononuclear chelate compound [RhI(CO)(κ²‐tBu₂AsCH₂PiPr₂)] ( 20 ). The reaction of 20 with CH₃I affords the acetyl complex [RhI₂{C(O)CH₃}(κ²‐tBu₂AsCH₂PiPr₂)] ( 21 ) with five‐coordinate rhodium atom.     

Cyclometalation of Phenylpyridines by Rhodium(I) via Room‐temperature C–H Bond Activation

A convenient synthesis of cyclometalated complexes [{Rh(μ‐Cl)(C N)₂}₂] [C N = ppy, 2‐phenylpyridinato ( 2 ); C N = ptpy, 2‐(p‐tolyl)pyridinato ( 3 ); 4‐Clppy = 4‐chloro‐2‐phenylpyridinato ( 4 )] at room temperature is described. The compounds were obtained by the oxidative addition reaction of the corresponding 2‐phenylpyridines to [{Rh(μ‐Cl)(coe)₂}₂] ( 1 ) (coe = cis‐cyclooctene) in dichloromethane solution. The rate of the reaction seems to depend on the electronic influence of the substituents on the phenyl rings of the corresponding 2‐phenylpyridines. The analogous iridium complex of 1 reacted markedly only at higher temperatures in suitable solvents under cyclometalation. The molecular structure of the new compound 4 was additionally confirmed by an X‐ray diffraction study.     

Synthesis and Characterization of Polypiridine‐Based Rhenium(I) Complexes with Pyrazino[2,3‐f][1,10]phenanthroline

A series of tricarbonyl rhenium(I) complexes of the type fac‐[Re^I(CO)₃(ppl)(L)]^0/+, where ppl is pyrazino[2,3‐f][1,10]phenanthroline, and where L is Cl^?, TfO^?, 4‐(tert‐butyl)pyridine (^tBu‐py), 4‐methoxypyridine (MeO‐py), 4,4′‐bipyridyl (bpy), or 10‐(picolin‐4‐yl)phenothiazine (pptz), were synthesized and fully characterized. In all complexes, an increment in the electron‐acceptor properties of ppl compared to the free ligand was observed. This effect was more significant for pyridine‐type ligands, especially for pptz, compared to Cl^? or TfO^?. The properties of fac‐[Re(CO)₃(ppl)(pptz)]PF₆ were compared with those of the analogous compound fac‐[Re(CO)₃(dppz)(pptz)]PF₆, where dppz is dipyrido(3,2‐a : 2′,3′‐c)phenazine, the goal being to generate long‐lived excited charge‐transfer (CT) states. In this respect, fac‐[Re(CO)₃(ppl)(pptz)]PF₆ seems to be a promising candidate.     

Reversible Mechanical Interlocking of D‐Shaped Molecular Karabiners bearing Coordination‐Bond Loaded Gates: Route to Self‐Assembled [2]Catenanes

Complexation of 1,4‐phenylenebis(methylene) diisonicotinate, L1 , with cis‐protected Pd^II components, [Pd( L′ )(NO₃)₂], in an equimolar ratio yielded binuclear complexes, 1 a – d of [Pd₂( L′ )₂( L1 )₂](NO₃)₄ formulation where L′ stands for ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′‐bipyridine (bpy), and phenanthroline (phen). The combination of 4,4′‐bipyridine, L2 , with the cis‐protected Pd^II units is known to yield molecular squares, 2 a – d . However, 2 b – d coexist with the corresponding molecular triangles, 3 b – d . Combination of an equivalent each of the ligands L1 and L2 with two equivalents of cis‐protected Pd^II components in DMSO resulted in the D ‐shaped heteroligated complexes [Pd₂( L′ )₂( L1 )( L2 )](NO₃)₄, 4 a – d . Two units of the D ‐shaped complexes interlock, in a concentration dependent fashion, to form the corresponding [2]catenanes [Pd₂( L′ )₂( L1 )( L2 )]₂(NO₃)₈, 5 a – d under aqueous conditions. Crystal structures of the macrocycle [Pd₂(tmeda)₂( L1 )( L2 )](PF₆)₄, 4 b′′ , and the catenane [Pd₂(bpy)₂( L1 )( L2 )]₂(NO₃)₈, 5 c , provide unequivocal support for the proposed molecular architectures.     

The development of phosphinoamine–Pd(II)–imidazole complexes: implications in room‐temperature Suzuki–Miyaura cross‐coupling reaction

The reaction of N‐methylimidazole (N‐MeIm) and N‐butylimidazole (N‐BuIm) with the complexes [PdCl₂(PPh₂py–P,N)] and [PdCl₂(PPh₂Etpy–P,N)] in the presence of NH₄PF₆ under N₂ at room temperature afforded four new cationic Pd(II) complexes [PdCl(PPh₂py–P,N)(N‐MeIm)](PF₆) ( 1 ), [PdCl(PPh₂py–P,N)(N‐BuIm)](PF₆) ( 2 ), [PdCl(PPh₂Etpy–P,N)(N‐MeIm)](PF₆) ( 4 ) and [PdCl(PPh₂Etpy‐P,N)(N‐BuIm)](PF₆) ( 5 ) in good yields, where PPh₂py is 2‐(diphenylphosphino)pyridine and PPh₂Etpy is 2‐{2‐(diphenylphosphino)ethyl}pyridine). The complexes were fully characterized. The catalytic activities of these complexes were investigated for Suzuki–Miyaura cross‐coupling reactions at room temperature. Complex 2 exhibited excellent activity compared to other analogs. Copyright © 2013 John Wiley & Sons, Ltd.     

Structural Aspects of Palladium and Platinum Complexes With Chiral Diphosphinoferrocenes Relevant to the Regio‐ and Stereoselective Copolymerization of CO with Propene

A series of chiral diphosphinoferrocene ligands 3a – i , derived from josiphos (=(2R)‐1‐[(1R)‐1‐(dicyclohexylphosphino)ethyl]‐2‐(diphenylphosphino)ferrocene, formerly called {(R)‐1‐[(S)‐2‐(diphenylphosphino)ferrocenyl]ethyl}dicycloxexylphosphine) where the electronic properties of the ligand are systematically varied, were prepared. X‐Ray studies of five of these new ligands confirmed that these compounds display very similar conformations in the solid state and that no structural criteria could be found indicating the modified electronic properties. These ligands find application in the Pd‐catalyzed highly regio‐ and stereoselective CO/propene copolymerization reaction, where the electronic properties of the ligand show a great impact on the catalyst activity. Coordination‐chemical aspects of these diphosphinoferrocenes relevant to the CO/propene copolymerization reaction were addressed by the preparation and characterization of Pd‐ and Pt‐complexes of the general formula [PdCl₂(P−P)] ( 5 ), [PdMe₂(P−P)] ( 6 ), [PdClMe(P−P)] ( 7 ), [PdMe(MeCN)(P−P)]PF₆ ( 8 ), and [PtClMe(P−P)] ( 9 ) (P−P=chiral diphosphinoferrocene ligand ( 3a – h ), four of which were characterized by X‐ray crystallography.     

trans‐(Methanol)(methyl­di­phenyl­phosphine)­bis­(pentane‐2,4‐dionato)­cobalt(III) hexa­fluoro­phosphate hydrate

The title compound [Co(C₅H₇O₂)₂(C₁₃H₁₃P)(CH₄O)]PF₆·H₂O, (I), which was converted from trans‐[Co(acac)₂(PMePh₂)(H₂O)]PF₆ (acac is pentane‐2,4‐dionato) by recrystallization from aqueous methanol, has been confirmed as have a coordinated methanol ligand. The molecular structure of the complex cation, trans‐[Co(acac)₂(PMePh₂)(MeOH)]⁺, is similar to that of the above aqua complex found in the ClO₄ salt [Kashiwabara et al. (1995). Bull. Chem. Soc. Jpn, 68 , 883–888]. The Co—O bond length for the coordinated methanol is 2.059 (3) Å. There is an intermolecular hydrogen bond between the OH group of the coordinated methanol and one of the O atoms of the acac ligands in an adjacent complex cation [O5?O3′ = 2.914 (4) Å], giving a centrosymmetric dimeric dicationic complex.     

Syntheses and Structures of Ruthenium Complexes Containing a Ru‐H‐Tl Three‐Center–Two‐Electron Bond

Treatment of CpRuH(PP) (PP=dppm, dppe) with TlPF₆ produced [CpRu(H)(Tl)(PP)]PF₆. X‐ray diffraction and computational studies suggest that the complexes contain a Ru?H?Tl 3c–2e bond and can be viewed as the first σ‐complexes of period 6 main‐group hydrides [CpRu{η²‐(H?Tl)}(PP)]PF₆ or [Tl{η²‐H?RuCp(PP)}]PF₆. The complexes can be stored as a solid at room temperature for days without appreciable decomposition, but are unstable in solution and evolved to the trimetallic complexes [{CpRu(PP)}₂(μ‐Tl)]PF₆.     

Mononuclear Complexes of Platinum Group Metals Containing η6‐ and η5‐Cyclic Π‐Perimeter Hydrocarbon and Pyridylpyrazolyl Derivatives: Syntheses and Structural Studies

Piano‐stool‐shaped platinum group metal compounds, stable in the solid state and in solution, which are based on 2‐(5‐phenyl‐1H‐pyrazol‐3‐yl)pyridine ( L ) with the formulas [(η⁶‐arene)Ru( L )Cl]PF₆ {arene = C₆H₆ ( 1 ), p‐cymene ( 2 ), and C₆Me₆, ( 3 )}, [(η⁶‐C₅Me₅)M( L )Cl]PF₆ {M = Rh ( 4 ), Ir ( 5 )}, and [(η⁵‐C₅H₅)Ru(PPh₃)( L )]PF₆ ( 6 ), [(η⁵‐C₅H₅)Os(PPh₃)( L )]PF₆ ( 7 ), [(η⁵‐C₅Me₅)Ru(PPh₃)( L )]PF₆ ( 8 ), and [(η⁵‐C₉H₇)Ru(PPh₃)( L )]PF₆ ( 9 ) were prepared by a general method and characterized by NMR and IR spectroscopy and mass spectrometry. The molecular structures of compounds 4 and 5 were established by single‐crystal X‐ray diffraction. In each compound the metal is connected to N1 and N11 in a k² manner.     

A novel series of M(II) complexes of 6‐methylpyridine‐2‐carboxylic acid with 4(5)methylimidazole: Synthesis,crystal structures, α‐glucosidase activity,density functional theory calculations and molecular docking

Novel complexes of 6‐methylpyridine‐2‐carboxylic acid and 4(5)methylimidazole, namely [Mn(6‐mpa)₂(4(5)MeI)₂] ( 1 ), [Zn(6‐mpa)₂(4(5)MeI)₂] ( 2 ), [Cd(6‐mpa)₂(4(5)MeI)₂] ( 3 ), [Co(6‐mpa)₂(4(5)MeI)₂] ( 4 ), [Ni(6‐mpa)₂(4(5)MeI)(OAc)] ( 5 ) and [Cu(6‐mpa)₂(4(5)MeI)] ( 6 ), were synthesized for the first time. The structures of complexes 1 – 4 and complexes 5 and 6 were determined using X‐ray diffraction and mass spectrometric techniques, respectively. The experimental spectral analyses for these complexes were performed using Fourier transform infrared and UV–visible techniques. The α‐glucosidase inhibition activity values (IC₅₀) of complexes 1 – 6 were identified in view of genistein reference compound. Moreover, the DFT/HSEh1PBE/6‐311G(d,p)/LanL2DZ level was used to obtain optimal molecular geometry and vibrational wavenumbers for complexes 1 – 6 . Electronic spectral behaviours and major contributions to the electronic transitions were investigated using TD‐DFT/HSEh1PBE/6‐311G(d,p)/LanL2DZ level with conductor‐like polarizable continuum model and SWizard program. Finally, in order to investigate interactions between the synthesized complexes ( 1 – 6 ) and target protein (template structure S. cerevisiae isomaltase), a molecular docking study was carried out.     

Syntheses and Structures of Homo‐ and Heterobimetallic Complexes Containing a (Cyclopentadienone)rhodium(I) Fragment

The reaction of [RhCl(η⁴‐Ph₂R₂C₄CO)]₂ (R=Ph, 2‐naphthyl) with the dimeric complexes [RuCl₂(p‐cymene)]₂ p‐cymene=1‐methyl‐4‐(1‐methylethyl)benzene, [RuCl₂(1,3,5‐Et₃C₆H₃)]₂, [MCl₂(Cp*)]₂ (M=Rh, Ir; Cp*=1,2,3,4,5‐pentamethylcyclopenta‐2,4‐dien‐1‐yl), [RuCl₂(CO)₃]₂, [RuCl₂(dcypb)(CO)]₂ (dcypb=butane‐1,4‐diylbis[dicyclohexylphosphine]), [(dppb)ClRu(μ‐Cl)₂(μ‐OH₂)RuCl(dppb)] (dppb=butane‐1,4‐diylbis[diphenylphosphine]), and [(dcypb)(N₂)Ru(μ‐Cl)₃RuCl(dcypb)] was investigated. In all cases, mixed, chloro‐bridged complexes were formed in quantitative yield (see 5 – 8, 9 – 16, 18, 19, 21 , and 22 ). The six new complexes 5, 8, 9, 13, 15 , and 22 were characterized by single‐crystal X‐ray analysis (Figs. 1–3).     

Synthesis,characterization and hydroformylation activity of 7‐azaindolate‐bridged dinuclear rhodium(I)phosphines with pendant polar‐groups

New dinuclear Rh(I)–Phosphines of the types [Rh(µ‐azi)(CO)(L)]₂ ( 1,3 – 7 ) and [Rh(µ‐azi)(L)]₂ ( 8 ) with pendant polar groups, and a chealated mononuclear compound [Rh(azi‐H)(CO)(L)] ( 2 ) (where azi = 7‐azaindolate, L = polar phosphine) were isolated from the reaction of [Rh(µ‐Cl)(CO)₂]₂ with 7‐azaindolate followed by some polar mono‐ and bis‐phosphines ( L ₁ – L ₈ ). A relationship between Δδ³¹P‐NMR and ν(CO) values was considered to define the impact of polar‐groups on σ‐donor properties of the phosphines. These compounds were evaluated as catalyst precursors in the hydroformylation of 1‐hexene and 1‐dodecene both in mono‐ and biphasic aqueous organic systems. While the biphasic hydroformylations (water + toluene) gave exclusively the aldehydes, the monophasic one (aqueous ethanol) showed propensity to form both aldehydes and alcohols. The influence of bimetallic cooperative effects, and σ‐donor and hydrophilic properties of the phosphines with pendant polar‐groups in enhancing the yields and selectivity of hydroformylation products was emphasized. In addition, when strong σ‐donor phosphine was used, the π‐acceptor nature of pyridine ring of 7‐azaindolate spacer was found to be a considerable factor in facilitating the facile cleavage of CO group during hydroformylation and in supplementing the cooperative effects. Copyright © 2009 John Wiley & Sons, Ltd.     

Hydrothermal Synthesis of Five New Coordination Polymers Based on Benzophenone‐2, 4′‐dicarboxylic Acid and N‐Donor Spacers

Five new coordination polymers, namely, [Ni₂(L)₂(4, 4′‐bipy)₃)] · H₂O]_n ( 1 ), [Ni₂(L)₂(O) (bpp)₂]_n ( 2 ), [Zn(L)(bib)_0.5]_n ( 3 ), [Zn(L)(PyBIm)]_n ( 4 ), and [Zn₃(L)₂(OH)(im)]_n ( 5 ) [H₂L = benzophenone‐2, 4′‐dicarboxylic acid, 4, 4′‐bipy = 4, 4′‐bipyridine, bpp = 1, 3‐bis(4‐pyridyl)propane, PyBIm = 2‐(4‐pyridyl)benzimidazole, and im = imidazole] were synthesized under hydrothermal conditions. Structure determination revealed that compound 1 is a 3D network and exhibits a 4‐connected metal‐organic framework with (4².6³.8) topology, whereas compounds 2 , 3 , 4 , and 5 are two‐dimensional layer structures. In compounds 2 – 4 , dinuclear metal clusters are formed through carboxylic groups. In compound 5 , trinuclear metal clusters are formed through μ₃‐OH and carboxylic groups. The carboxylic groups exhibit three coordination modes in compounds 1 – 5 : monodentately, bidentate‐chelating, and bis‐monodentately. Furthermore, the luminescent properties for compounds 3 , 4 , and 5 were investigated.     

Triazole‐Functionalized N‐Heterocyclic Carbene Complexes of Palladium and Platinum and Efficient Aqueous Suzuki–Miyaura Coupling Reaction

Imidazolium salts bearing triazole groups are synthesized via a copper catalyzed click reaction, and the silver, palladium, and platinum complexes of their N‐heterocyclic carbenes are studied. [Ag₄(L1)₄](PF₆)₄, [Pd(L1)Cl](PF₆), [Pt(L1)Cl](PF₆) (L1=3‐((1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)methyl)‐1‐(pyrimidin‐2‐yl)‐1H‐imidazolylidene), [Pd₂(L2)₂Cl₂](PF₆)₂, and [Pd(L2)₂](PF₆)₂ (L2=1‐butyl‐3‐((1‐(pyridin‐2‐yl)‐1H‐1,2,3‐triazol‐4‐yl)methyl)imidazolylidene) have been synthesized and fully characterized by NMR, elemental analysis, and X‐ray crystallography. The silver complex [Ag₄(L1)₄](PF₆)₄ consists of a Ag₄ zigzag chain. The complexes [Pd(L1)Cl](PF₆) and [Pt(L1)Cl](PF₆), containing a nonsymmetrical NCN ′ pincer ligand, are square planar with a chloride trans to the carbene donor. [Pd₂(L2)₂Cl₂](PF₆)₂ consists of two palladium centers with CN₂Cl coordination mode, whereas the palladium in [Pd(L2)₂](PF₆)₂ is surrounded by two carbene and two triazole groups with two uncoordinated pyridines. The palladium compounds are highly active for Suzuki–Miyaura cross coupling reactions of aryl bromides and 1,1‐dibromo‐1‐alkenes in neat water under an air atmosphere.     

Syntheses and Structures of Terpyridine‐Metal Complexes

Seven complexes, [Ln(ctpy)(NO₃)₂]_n and M(ctpy)₂ · 4H₂O [Ln = Gd ( 1 ), Dy ( 2 ), Er ( 3 ); M = Co ( 4 ), Ni ( 5 ), Cu ( 6 ), Zn ( 7 )] with the ligand 2, 2′:6′,2′′‐terpyridine‐4′‐carboxylic acid (Hctpy) were hydrothermally synthesized. X‐ray diffractional analysis reveals that the isomorphous compounds 1 – 3 adopt one‐dimensional chain‐like structures, whereas 4 – 7 are isomorphic monomers. Luminescence spectroscopy measurements indicates that compound 7 exhibits photoluminescence in the solid state at room temperature.     

Generation and Reactivity of {(Ethane‐1,2‐diyl)bis[diisopropylphosphine‐κP]}‐{[2,4,6‐tri(tert‐butyl)phenyl]phosphino‐κP}rhodium ([Rh{PH(tBu3C6H2)}(iPr2PCH2CH2PiPr2)]): Catalytic C−P Bond Formation via Intramolecular C−H/P−H Dehydrogenative Cross‐Coupling

The complex [Rh(η³‐benzyl)(dippe)] ( 1 ; dippe=bis(diisopropylphosphino)ethane=(ethane‐1,2‐diyl)bis[diisopropylphosphine]) reacted cleanly with Mes*PH₂ ( 2 ; Mes*=2,4,6‐^tBu₃C₆H₂) to provide a new Rh species [Rh(H)(dippe)(L)] ( 3 ), L being the 2,3‐dihydro‐3,3‐dimethyl‐1H‐phosphindole ligand 4 (=^tBu₂C₆H₂(CMe₂CH₂PH)) (Scheme 1). Complex 3 was converted to the corresponding chloride [Rh(Cl)(dippe)(L)] ( 6 ) when treated with CH₂Cl₂, whereas the dimeric species [Rh₂{μ‐^tBu₂C₆H₂(CMe₂CH₂P)}(μ‐H)(dippe)₂] ( 7 ) was formed upon thermolysis in toluene (Scheme 2). The structures of 6 and 7 ⋅C₇H₈ were determined by X‐ray crystallography. Complexes 1 and 3 served as catalyst precursors for the dehydrogenative coupling of C−H and P−H bonds in the conversion of 2 to 4 (Scheme 3). Deuteration studies with Mes*PD₂ exposed a complex series of bond‐activation pathways that appear to involve C−H activation of the dippe ligand by the Rh‐atom (Schemes 4 and 5)     

Phenylene‐bridged β‐Ketoiminate Dilanthanide Aryloxides: Synthesis,Structure, and Catalytic Activity for Addition of Amines to Carbodiimides

The synthesis and reactivity of a series of bimetallic lanthanide aryloxides stabilized by a p‐phenylene‐bridged bis(β‐ketoiminate) ligand is presented. The reaction of 1,4‐diaminobenzene with acetylacetone in a 1:2.5 molar ratio in absolute ethanol gave the compound 1,4‐bis(4‐imino‐2‐pentanone)benzene ( 1 ) (LH₂) in high yield. Compound 1 reacted with (ArO)₃Ln(THF)₂ (ArO = 2,6‐tBu₂‐4‐MeC₆H₂O, THF = tetrahydrofuran) in a 1:2 molar ratio in THF, after workup, to give the corresponding dilanthanide aryloxides L[Ln(OAr)₂(THF)]₂ [Ln = Yb ( 2 ), Y ( 3 ), Sm ( 4 ), Nd ( 5 ), La ( 6 )] in high isolated yields. Compound 1 and complexes 2 – 6 were fully characterized, including X‐ray crystal structure analyses for complexes 2 , 3 , 5 , and 6 . Complexes 2 – 6 can be used as efficient pre‐catalysts for catalytic addition of amines to carbodiimides, and the ionic radii of the central metal atoms have a significant effect on the catalytic activity with the increasing sequence of La ( 6 ) < Nd ( 5 ) ≈ Sm ( 4 ) < Y ( 3 ) ≈ Yb ( 2 ). The catalytic addition reaction with 2 showed a good scope of substrates including primary and secondary amines.