Zur Reaktivität von Titanocenkomplexen [Ti(Cp′)2(η2‐Me3SiC≡CSiMe3)] (Cp′ = Cp,Cp*) gegenüber Benzoldicarbonsäuren

On the Reactivity of Titanocene Complexes [Ti(Cp′)₂(η²‐Me₃SiC≡CSiMe₃)] (Cp′ = Cp, Cp*) towards Benzenedicarboxylic Acids Titanocene complexes [Ti(Cp′)₂(BTMSA)] ( 1a , Cp′ = Cp = η⁵‐C₅H₅; 1b , Cp′ = Cp* = η⁵‐C₅Me₅; BTMSA = Me₃SiC≡CSiMe₃) were found to react with iodine and methyl iodide yielding [Ti(Cp′)₂(μ‐I)₂] ( 2a / b ; a refers to Cp′ = Cp and b to Cp′ = Cp*), [Ti(Cp′)₂I₂] ( 3a / b ) and [Ti(Cp′)₂(Me)I] ( 4a / b ), respectively. In contrast to 2a , complex 2b proved to be highly moisture sensitive yielding with cleavage of HCp* [{Ti(Cp*)I}₂(μ‐O)] ( 7 ). The corresponding reactions of 1a / b with p‐cresol and thiophenol resulted in the formation of [Ti(Cp′)₂{O(p‐Tol)}₂] ( 5a / b ) and [Ti(Cp′)₂(SPh)₂] ( 6a / b ), respectively. Reactions of 1a and 1b with 1,n‐benzenedicarboxylic acids (n = 2–4) resulted in the formation of dinuclear titanium(III) complexes of the type [{Ti(Cp′)₂}₂{μ‐1,n‐(O₂C)₂C₆H₄}] (n = 2, 8a / b ; n = 3, 9a / b ; n = 4, 10a / b ). All complexes were fully characterized analytically and spectroscopically. Furthermore, complexes 7 , 8b , 9a ·THF, 10a / b were also be characterized by single‐crystal X‐ray diffraction analyses.     

Asymmetric diosmium sawhorse complexes

Three asymmetric diosmium(I) carbonyl sawhorse complexes have been prepared by microwave heating. One of these complexes is of the type Os₂(μ‐O₂CR)(μ‐O₂CR′)(CO)₄L₂, with two different bridging carboxylate ligands, while the other two complexes are of the type Os₂(μ‐O₂CR)₂(CO)₅L, with one axial CO ligand and one axial phosphane ligand. The mixed carboxylate complex Os₂(μ‐acetate)(μ‐propionate)(CO)₄[P(p‐tolyl)₃]₂, ( 1 ), was prepared by heating Os₃(CO)₁₂ with a mixture of acetic and propionic acids, isolating Os₂(μ‐acetate)(μ‐propionate)(CO)₆, and then replacing two CO ligands with two phosphane ligands. This is the first example of an Os₂ sawhorse complex with two different carboxylate bridges. The syntheses of Os₂(μ‐acetate)₂(CO)₅[P(p‐tolyl)₃], ( 3 ), and Os₂(μ‐propionate)₂(CO)₅[P(p‐tolyl)₃], ( 6 ), involved the reaction of Os₃(CO)₁₂ with the appropriate carboxylic acid to initially produce Os₂(μ‐carboxylate)₂(CO)₆, followed by treatment with refluxing tetrahydrofuran (THF) to form Os₂(μ‐carboxylate)₂(CO)₅(THF), and finally addition of tri‐p‐tolylphosphane to replace the THF ligand with the P(p‐tolyl)₃ ligand. Neutral complexes of the type Os₂(μ‐O₂CR)₂(CO)₅L had not previously been subjected to X‐ray crystallographic analysis. The more symmetrical disubstituted complexes, i.e. Os₂(μ‐formate)₂(CO)₄[P(p‐tolyl)₃]₂, ( 8 ), Os₂(μ‐acetate)₂(CO)₄[P(p‐tolyl)₃]₂, ( 4 ), and Os₂(μ‐propionate)₂(CO)₄[P(p‐tolyl)₃]₂, ( 7 ), as well as the previously reported symmetrical unsubstituted complexes Os₂(μ‐acetate)₂(CO)₆, ( 2 ), and Os₂(μ‐propionate)₂(CO)₆, ( 5 ), were also prepared in order to examine the influence of axial ligand substitution on the Os—Os bond distance in these sawhorse molecules. Eight crystal structures have been determined and studied, namely μ‐acetato‐1κO:2κO′‐μ‐propanoato‐1κO:2κO′‐bis[tris(4‐methylphenyl)phosphane]‐1κP,2κP′‐bis(dicarbonylosmium)(Os—Os) dichloromethane monosolvate, [Os₂(C₂H₃O₂)(C₃H₅O₂)(C₂₁H₂₁P)₂(CO)₄]·CH₂Cl₂, ( 1 ), bis(μ‐acetato‐1κO:2κO′)bis(tricarbonylosmium)(Os—Os), [Os₂(C₂H₃O₂)₂(CO)₆], ( 2 ) (redetermined structure), bis(μ‐acetato‐1κO:2κO′)pentacarbonyl‐1κ²C,2κ³C‐[tris(4‐methylphenyl)phosphane‐1κP]diosmium(Os—Os), [Os₂(C₂H₃O₂)₂(C₂₁H₂₁P)(CO)₅], ( 3 ), bis(μ‐acetato‐1κO:2κO′)bis[tris(4‐methylphenyl)phosphane]‐1κP,2κP‐bis(dicarbonylosmium)(Os—Os) p‐xylene sesquisolvate, [Os₂(C₂H₃O₂)₂(C₂₁H₂₁P)₂(CO)₄]·1.5C₈H₁₀, ( 4 ), bis(μ‐propanoato‐1κO:2κO′)bis(tricarbonylosmium)(Os—Os), [Os₂(C₃H₅O₂)₂(CO)₆], ( 5 ), pentacarbonyl‐1κ²C,2κ³C‐bis(μ‐propanoato‐1κO:2κO′)[tris(4‐methylphenyl)phosphane‐1κP]diosmium(Os—Os), [Os₂(C₃H₅O₂)₂(C₂₁H₂₁P)(CO)₅], ( 6 ), bis(μ‐propanoato‐1κO:2κO′)bis[tris(4‐methylphenyl)phosphane]‐1κP,2κP‐bis(dicarbonylosmium)(Os—Os) dichloromethane monosolvate, [Os₂(C₃H₅O₂)₂(C₂₁H₂₁P)₂(CO)₄]·CH₂Cl₂, ( 7 ), and bis(μ‐formato‐1κO:2κO′)bis[tris(4‐methylphenyl)phosphane]‐1κP,2κP‐bis(dicarbonylosmium)(Os—Os), [Os₂(CHO₂)₂(C₂₁H₂₁P)₂(CO)₄], ( 8 ).     

Copper(II) and Sodium(I) Complexes based on 3,7‐Diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide: Synthesis,Characterization, and Catalytic Activity

The reaction of 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane (DAPTA) with metal salts of Cu^II or Na^I/Ni^II under mild conditions led to the oxidized phosphane derivative 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide (DAPTA=O) and to the first examples of metal complexes based on the DAPTA=O ligand, that is, [Cu^II(μ‐CH₃COO)₂(κO‐DAPTA=O)]₂ ( 1 ) and [Na(1κOO′;2κO‐DAPTA=O)(MeOH)]₂(BPh₄)₂ ( 2 ). The catalytic activity of 1 was tested in the Henry reaction and for the aerobic 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO)‐mediated oxidation of benzyl alcohol. Compound 1 was also evaluated as a model system for the catechol oxidase enzyme by using 3,5‐di‐tert‐butylcatechol as the substrate. The kinetic data fitted the Michaelis–Menten equation and enabled the obtainment of a rate constant for the catalytic reaction; this rate constant is among the highest obtained for this substrate with the use of dinuclear Cu^II complexes. DFT calculations discarded a bridging mode binding type of the substrate and suggested a mixed‐valence Cu^II/Cu^I complex intermediate, in which the spin electron density is mostly concentrated at one of the Cu atoms and at the organic ligand.     

Site‐Selective Ligand Exchange on a Heteroleptic TiIV Complex Towards Stepwise Multicomponent Self‐Assembly

A series of heteroleptic [Ti 1 ₂X]^? complexes have been selectively constructed from a mixture of Ti^IV ions, a pyridyl catechol ligand (H₂ 1 ; H₂ 1 =4‐(3‐pyridyl)catechol), and various bidentate ligands (HX) in the presence of a weak base, in addition to a previously reported [Ti 1 ₂(acac)]^? (acac=acetylacetonate) complex. Comparative studies of these Ti^IV complexes revealed that [Ti 1 ₂(trop)]^? (trop=tropolonate) is much more stable than the [Ti 1 ₂(acac)]^? complex, which allows the replacement of acac with trop on the [Ti 1 ₂(acac)]^? complex. This Ti^IV‐centered site‐selective ligand exchange reaction also takes place on a heteronuclear Pd^II? Ti^IV ring complex with the preservation of the Pd^II‐centered coordination structures. Intra‐ and intermolecular linking between two Ti^IV centers with a flexible or a rigid bis‐tropolone bridging ligand provided a tetranuclear and an octanuclear Pd^II? Ti^IV complex, respectively. These higher‐order structures could be efficiently constructed only through a stepwise synthetic route.     

Oxovanadium(IV,V) Complexes with 2‐Acetylpyridine‐2‐furanoylhydrazone (Hapf) as Ligand. X‐Ray Crystal Structures of [VO2(apf)] and [V2O2(μ‐O)2(apf)2]

The preparation of oxovanadium(IV, V) coordination compounds with 2‐acetylpyridine‐2‐furanoylhydrazone (Hapf) is described. [VO(apf)(acac)] was prepared from oxovanadium(IV) diacetylacetonate [VO(acac)₂] by reaction with Hapf in methanol or dichloromethane. The complex is paramagnetic and its EPR spectrum is consistent with an octahedral coordination for the vanadium(IV) atom. Voltammetry studies of [VO(apf)(acac)] indicate an irreversible oxidation, in agreement with the chemical behavior of the compound in solution. The vanadium(IV) complex undergoes slow oxidation in alcoholic solution, losing the acetylacetonate ligand to form [VO₂(apf)] and [V₂O₂(μ‐O)₂(apf)₂]. The crystal structures of these last compounds were determined by X‐ray diffraction methods. [V₂O₂(μ‐O)₂(apf)₂] crystallizes monoclinic [P2₁/c, Z = 2, a = 817.400(10), b = 1650.90(3), c = 984.70(2) pm, β = 112.7190(10)°]. The crystal structure consists of dimeric units, in which two μ‐oxo ligands subtend asymmetric bridges between the vanadium atoms in a very distorted octahedral coordination. In the crystal of [VO₂(apf)], orthorhombic [Pnma, Z = 4, a = 1630.000(10), b = 675.10(4), c = 1136.40(2) pm], the vanadium(V) atom is pentacoordinated.     

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.     

Tandem β‐Boration/Arylation of α,β‐Unsaturated Carbonyl Compounds by Using a Single Palladium Complex To Catalyse Both Steps

Diphenyl(3‐methyl‐2‐indolyl)phosphine (C₉H₈NPPh₂, 1 ) gives stable dimeric palladium(II) complexes that contain the phosphine in P,N‐bridging coordination mode. On treating 1 with [Pd(O₂CCH₃)₂], the new complexes [Pd(μ‐C₉H₇NPPh₂)(NCCH₃)]₂ ( 2 ) or [Pd(μ‐C₉H₇NPPh₂)(μ‐O₂CCH₃)]₂ ( 3 ) were isolated, depending on the solvent used, acetonitrile or toluene, respectively. Further reaction of 3 with the ammonium salt of 1 led to the substitution of one carboxylate ligand to afford [Pd(μ‐C₉H₇NPPh₂)₃(μ‐O₂CCH₃)] ( 4 ), in which the bimetallic unit is bonded by three C₉H₇NPPh₂^? moieties and one carboxylate group. Using this methodology, [Pd₂(μ‐C₆H₄PPh₂)₂(μ‐C₉H₇NPPh₂)(μ‐O₂CCX₃)] (X=H ( 7 ); X=F ( 8 )) were synthesised from the ortho‐metalated compounds [Pd(C₆H₄PPh₂)(μ‐O₂CCX₃)]₂ (X=H ( 5 ); X=F ( 6 )). Complexes 3 , 4 , 7 , and 8 have been found to be active in the catalytic β‐boration of α,β‐unsaturated esters and ketones under mild reaction conditions. Hindrance of the carbonyl moiety has an influence on the reaction rate, but quantitative conversion was achieved in many cases. More remarkably, when aryl bromides were added to the reaction media, complex 7 induced a highly successful consecutive β‐boration/cross‐coupling reaction with dimethyl acrylamide as the substrate (99 % conversion, 89 % isolated yield).     

Palladium‐MOP Chemistry: Pseudo‐cis‐Allyl MOP Complexes and Flexible Olefin Bonding. Preliminary Communication

We show that both palladium(0) and palladium(II) metal centers are capable of coordinating two monodentate MOP (=(R)‐2‐(diarylphosphino)‐1,1′‐binaphthalene) ligands in a pseudo‐cis orientation, despite published statements to the contrary. In addition to [Pd(η³‐C₃H₅)(MeO? MOP)₂]BF₄ (MeO? MOP=(R)‐2‐(diphenylphosphino)‐2′‐methoxy‐1,1′‐binaphthalene), the first examples of chiral bis κC¹‐prop‐2‐enyl (η¹‐CH₂CH?CH₂) complexes [cis‐Pd(κC¹‐C₃H₅)₂(MeO? MOP or MOP)₂], are shown to be relatively stable. Further, coordinated MOP and MeO? MOP both show stronger propensity towards novel intramolecular π‐olefin complexation than the CN? MOP analogue. The solid‐state structure of [Pd(fumaronitrile)(MOP)₂] is reported.     

Structural models of vanadate-dependent haloperoxidases and their reactivity

Vanadium(V) complexes with hydrazone-based ONO and ONN donor ligands that partly model active-site structures of vanadate-dependent haloperoxidases have been reported. On reaction with [VO(acac)₂] (Hacac = acetylacetone) under nitrogen, these ligands generally provide oxovanadium(IV) complexes [VO(ONO)X] (X = solvent or nothing) and [VO(acac)(ONN)], respectively. Under aerobic conditions, these oxovanadium(IV) species undergo oxidation to give oxovanadium(V), dioxovanadium (V) or μ-oxobisoxovanadium(V) species depending upon the nature of the ligand. Anionic and neutral dioxovanadium(V) complexes slowly deoxygenate in methanol to give monooxo complexes [VO(OMe)(MeOH)(ONO)]. The anionic complexes [VO₂(ONO)]^- can also be convertedin situ on acidification to oxohydroxo complexes [VO(OH)(HONO)]⁺ and to peroxo complexes [VO(O₂)(ONO)]^-, and thus to the species assumed to be intermediates in the haloperoxidases activity of the enzymes. In the presence of catechol (H₂cat) and benzohydroxamic acid (H₂bha), oxovanadium (IV) complexes, [VO (acac)(ONN)] gave mixed-chelate oxovanadium(V) complexes [VO(cat)(ONN)] and [VO(bha)(ONN)] respectively. These complexes are not very stable in solution and slowly convert to the corresponding dioxo species [VO₂(ONN)] as observed by⁵¹V NMR and electronic absorption spectroscopic studies.     

Diverse structures and magnetism of cobalt(II) and manganese(II) compounds with mixed azido and carboxylato bridges induced by methylpyridinium carboxylates

Herein we present a systematic study of the structures and magnetic properties of six coordination compounds with mixed azide and zwitterionic carboxylate ligands, [M(N₃)₂(2‐mpc)] (2‐mpc=N‐methylpyridinium‐2‐carboxylate; M=Co for 1 and Mn for 2 ), [M(N₃)₂(4‐mpc)] (4‐mpc=N‐methylpyridinium‐4‐carboxylate; M=Co for 3 and Mn for 4 ), [Co₃(N₃)₆(3‐mpc)₂(CH₃OH)₂] ( 5 ), and [Mn₃(N₃)₆(3‐mpc)₂] ( 6 ; 3‐mpc=N‐methylpyridinium‐3‐carboxylate). Compounds 1 – 3 consist of one‐dimensional uniform chains with (μ‐EO‐N₃)₂(μ‐COO) triple bridges (EO=end‐on); 5 is also a chain compound but with alternating [(μ‐EO‐N₃)₂(μ‐COO)] triple and [(EO‐N₃)₂] double bridges; Compound 4 contains two‐dimensional layers with alternating [(μ‐EO‐N₃)₂(μ‐COO)] triple, [(μ‐EO‐N₃)(μ‐COO)] double, and (EE‐N₃) single bridges (EE=end‐to‐end); 6 is a layer compound in which chains similar to those in 5 are cross‐linked by a μ₃‐1,1,3‐N₃ azido group. Magnetically, the three Co^II compounds ( 1 , 3 , and 5 ) all exhibit intrachain ferromagnetic interactions but show distinct bulk properties: 1 displays relaxation dynamics at very low temperature, 3 is an antiferromagnet with field‐induced metamagnetism due to weak antiferromagnetic interchain interactions, and 5 behaves as a noninnocent single‐chain magnet influenced by weak antiferromagnetic interchain interactions. The magnetic differences can be related to the interchain interactions through π–π stacking influenced by different substitution positions in the ligands and/or different magnitudes of intrachain coupling. All of the Mn^II compounds show overall intrachain/intralayer antiferromagnetic interactions. Compound 2 shows the usual one‐dimensional antiferromagnetism, whereas 4 and 6 exhibit different weak ferromagnetism due to spin canting below 13.8 and 4.6 K, respectively.     

Combining Topological and Steric Constraints for the Preparation of Heteroleptic Copper(I) Complexes

Heteroleptic copper(I) complexes have been prepared from a macrocyclic ligand incorporating a 2,9‐diphenyl‐1,10‐phenanthroline subunit ( M30 ) and two bis‐phosphines, namely bis[(2‐diphenylphosphino)phenyl] ether (POP) and 1,3‐bis(diphenylphosphino)propane (dppp). In both cases, the diphenylphosphino moieties of the PP ligand are too bulky to pass through the 30‐membered ring of M30 during the coordination process, hence the formation of C_2v‐symmetrical pseudo‐rotaxanes is prevented. When POP is used, X‐ray crystal structure analysis shows the formation of a highly distorted [Cu( M30 )(POP)]⁺ complex in which the POP ligand is only partially threaded through the M30 unit. This compound is poorly stable as the Cu^I cation is not in a favorable coordination environment due to steric constraints. By contrast, in the case of dppp, the bis‐phosphine ligand undergoes both steric and topological constraints and adopts a nonchelating coordination mode to generate [Cu₂( M30 )₂(μ‐dppp)](BF₄)₂. This compound exhibits metal‐to‐ligand charge transfer (MLCT) emission characterized by a very large Stokes’ shift (≈200 nm) that is not attributed to a dramatic structural distortion between the ground and the emitting states but to very weak MLCT absorption transitions at longer wavelengths. Accordingly, [Cu₂( M30 )₂(μ‐dppp)](BF₄)₂ shows unusually high luminescence quantum yields for Cu^I complexes, both in solution and in the solid state (0.5 and 7 %, respectively).     

Titanium(IV) and Zirconium(IV) Sulfato Complexes Containing the Kläui Tripodal Ligand: Molecular Models of Sulfated Metal Oxide Surfaces

Treatment of titanyl sulfate in about 60 mM sulfuric acid with NaL_OEt (L_OEt^?=[(η⁵‐C₅H₅)Co{P(O)(OEt)₂}₃]^?) afforded the μ‐sulfato complex [(L_OEtTi)₂(μ‐O)₂(μ‐SO₄)] ( 2 ). In more concentrated sulfuric acid (>1 M ), the same reaction yielded the di‐μ‐sulfato complex [(L_OEtTi)₂(μ‐O)(μ‐SO₄)₂] ( 3 ). Reaction of 2 with HOTf (OTf=triflate, CF₃SO₃) gave the tris(triflato) complex [L_OEtTi(OTf)₃] ( 4 ), whereas treatment of 2 with Ag(OTf) in CH₂Cl₂ afforded the sulfato‐capped trinuclear complex [{(L_OEt)₃Ti₃(μ‐O)₃}(μ₃‐SO₄){Ag(OTf)}][OTf] ( 5 ), in which the Ag(OTf) moiety binds to a μ‐oxo group in the Ti₃(μ‐O)₃ core. Reaction of 2 in H₂O with Ba(NO₃)₂ afforded the tetranuclear complex (L_OEt)₄Ti₄(μ‐O)₆ ( 6 ). Treatment of 2 with [{Rh(cod)Cl}₂] (cod=1,5‐cyclooctadiene), [Re(CO)₅Cl], and [Ru(tBu₂bpy)(PPh₃)₂Cl₂] (tBu₂bpy=4,4′‐di‐tert‐butyl‐2,2′‐dipyridyl) in the presence of Ag(OTf) afforded the heterometallic complexes [(L_OEt)₂Ti₂(O)₂(SO₄){Rh(cod)}₂][OTf]₂ ( 7 ), [(L_OEt)₂Ti(O)₂(SO₄){Re(CO)₃}][OTf] ( 8 ), and [{(L_OEt)₂Ti₂(μ‐O)}(μ₃‐SO₄)(μ‐O)₂{Ru(PPh₃)(tBu₂bpy)}][OTf]₂ ( 9 ), respectively. Complex 9 is paramagnetic with a measured magnetic moment of about 2.4 μ_B. Treatment of zirconyl nitrate with NaL_OEt in 3.5 M sulfuric acid afforded [(L_OEt)₂Zr(NO₃)][L_OEtZr(SO₄)(NO₃)] ( 10 ). Reaction of ZrCl₄ in 1.8 M sulfuric acid with NaL_OEt in the presence Na₂SO₄ gave the μ‐sulfato‐bridged complex [L_OEtZr(SO₄)(H₂O)]₂(μ‐SO₄) ( 11 ). Treatment of 11 with triflic acid afforded [(L_OEt)₂Zr][OTf]₂ ( 12 ), whereas reaction of 11 with Ag(OTf) afforded a mixture of 12 and trinuclear [{L_OEtZr(SO₄)(H₂O)}₃(μ₃‐SO₄)][OTf] ( 13 ). The Zr^IV triflato complex [L_OEtZr(OTf)₃] ( 14 ) was prepared by reaction of L_OEtZrF₃ with Me₃SiOTf. Complexes 4 and 14 can catalyze the Diels–Alder reaction of 1,3‐cyclohexadiene with acrolein in good selectivity. Complexes 2 – 5 , 9 – 11 , and 13 have been characterized by X‐ray crystallography.     

Activation of Molecular Hydrogen by Bis(η5,η1‐pentafulvene)‐titanium Complexes – Efficient Formation of Titanium(III)hydrides

The synthesis and crystal structures of two dinuclear titanocene hydride complexes are reported. Both complexes, namely bis(η⁵‐(di‐para‐tolylmethyl)cyclopentadienyl)titanium hydride dimer, [(η⁵‐C₂₀H₁₉)₂Ti(μ‐H)]₂ ( 2a ), and bis(η⁵‐2‐adamantylcyclopentadienyl)‐titanium hydride dimer, [(η⁵‐C₁₅H₁₉)₂Ti(μ‐H)]₂ ( 2b ), are formed via activation of molecular hydrogen by the corresponding bis(η⁵,η¹‐pentafulvene)titanium complexes 1a and 1b at ambient temperatures and pressures in high yields. The hydride complexes 2a and 2b exhibit planar [Ti₂H₂] cores and, as a result of the heterolytic cleavage of molecular hydrogen, substituted Cp Ligands were formed during the reaction.     

A Motif for Infinite Metal Atom Wires

A new motif for infinite metal atom wires with tunable compositions and properties is developed based on the connection between metal paddlewheel and square planar complex moieties. Two infinite Pd chain compounds, [Pd₄(CO)₄(OAc)₄Pd(acac)₂] 1 and [Pd₄(CO)₄(TFA)₄Pd(acac)₂] 2 , and an infinite Pd? Pt heterometallic chain compound, [Pd₄(CO)₄(OAc)₄Pt(acac)₂] 3 , are identified by single‐crystal X‐ray diffraction analysis. In these new structures, the paddlewheel moiety is a Pd four‐membered ring coordinated by bridging carboxylic ligands and μ₂ carbonyl ligands. The planar moiety is either Pd(acac)₂ or Pt(acac)₂ (acac=acetylacetonate). These moieties are connected by metallophilic interactions. The results showed that these one‐dimensional metal wire compounds have photoluminescent properties that are tunable by changing ligands and metal ions. 3 can also serve as a single source precursor for making Pd₄Pt bimetallic nanostructures with precise control of metal composition.     

Synthesis,Characterization, and Crystal Structures of Diruthenium Complexes Containing Bridging Salicylato Ligands

The thermal reaction of Ru₃(CO)₁₂ ( 1 ) with salicylic acid, in the presence of triphenylphosphine, pyridine, or dimethylsulfoxide, afforded the dinuclear complexes Ru₂(CO)₄(μ‐O₂CC₆H₄OH)₂L₂ ( 2 ) [L = PPh₃ ( 2a ). C₅H₅N ( 2b ); (CH₃)₂SO ( 2c )]. Complex 2b was further reacted with the aromatic dimmines 2,2′‐dipyridine or 1,10‐phenanthroline to give the cationic diruthenium complexes [Ru₂(CO)₂(μ‐CO)₂(μ‐O₂CC₆H₄OH)(N∩N)₂]⁺ ( 3 ) [(N∩N) = 2,2′‐dipyridine ( 3a ); 1,10‐phenanthroline ( 3b )], which were isolated as their tetraphenylborate salts. All five novel complexes were characterized spectroscopically and analytically. For 2a – 2b and 3a – 3b , single‐crystal X‐ray diffraction studies were also carried out.     

Zur Reaktivität von alkylthioverbrückten 44‐CVE‐triangularen Platinclustern: Umsetzungen mit bidentaten Phosphanliganden

On the Reactivity of Alkylthio Bridged 44 CVE Triangular Platinum Clusters: Reactions with Bidentate Phosphine Ligands The 44 cve (cluster valence electrons) triangular platinum clusters [{Pt(PR₃)}₃(μ‐SMe)₃]Cl (PR₃ = PPh₃, 2a ; P(4‐FC₆H₄)₃, 2b ; P(n‐Bu)₃, 2c ) were found to react with PPh₂CH₂PPh₂ (dppm) in a degradation reaction yielding dinuclear platinum(I) complexes [{Pt(PR₃)}₂(μ‐SMe)(μ‐dppm)]Cl (PR₃ = PPh₃, 3a ; P(4‐FC₆H₄)₃, 3b ; P(n‐Bu)₃; 3e ) and the platinum(II) complex [Pt(SMe)₂(dppm)] ( 4 ), whereas the addition of PPh₂CH₂CH₂PPh₂ (dppe) to cluster 2a afforded a mixture of degradation products, among others the complexes [Pt(dppe)₂] and [Pt(dppe)₂]Cl₂. On the other hand, the treatment of cluster 2a with PPh₂CH₂CH₂CH₂PPh₂ (dppp) ended up in the formation of the cationic complex [{Pt(dppp)}₂(μ‐SMe)₂]Cl₂ ( 5 ). Furthermore, the terminal PPh₃ ligands in complex 3a proved to be subject to substitution by the stronger donating monodentate phosphine ligands PMePh₂ and PMe₂Ph yielding the analogous complexes [{Pt(PR₃)}₂(μ‐SMe)(μ‐dppm)]Cl (PR₃ = PMePh₂, 3c ; PMe₂Ph, 3d ). NMR investigations on complexes 3 showed an inverse correlation of Tolmans electronic parameter ν with the coupling constants ¹J(Pt,P) and ¹J(Pt,Pt). All compounds were fully characterized by means of NMR and IR spectroscopy. X‐ray diffraction analyses were performed for the complexes [{Pt{P(4‐FC₆H₄)₃}}₂(μ‐SMe)(μ‐dppm)]Cl ( 3b ), [Pt(SMe)₂(dppm)] ( 4 ), and [{Pt(dppp)}₂(μ‐SMe)₂]Cl₂ ( 5 ).     

Mapping the Transformation [{RuII(CO)3Cl2}2]→[RuI2(CO)4]2+: Implications in Binuclear Water–Gas Shift Chemistry

The complete sequence of reactions in the base‐promoted reduction of [{Ru^II(CO)₃Cl₂}₂] to [Ru^I₂(CO)₄]²⁺ has been unraveled. Several μ‐OH, μ:κ²‐CO₂H‐bridged diruthenium(II) complexes have been synthesized; they are the direct results of the nucleophilic activation of metal‐coordinated carbonyls by hydroxides. The isolated compounds are [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)₂(μ‐OH)(NP^F‐Am)₂][PF₆] ( 1 ; NP^F‐Am=2‐amino‐5,7‐trifluoromethyl‐1,8‐naphthyridine) and [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)(μ‐OH)(NP‐Me₂)₂][BF₄]₂ ( 2 ), secured by the applications of naphthyridine derivatives. In the absence of any capping ligand, a tetranuclear complex [Ru₄(CO)₈(H₂O)₂(μ³‐OH)₂(μ:κ²‐C,O‐CO₂H)₄][CF₃SO₃]₂ ( 3 ) is isolated. The bridging hydroxido ligand in 1 is readily replaced by a π‐donor chlorido ligand, which results in [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)₂(μ‐Cl)(NP‐PhOMe)₂][BF₄] ( 4 ). The production of [Ru₂(CO)₄]²⁺ has been attributed to the thermally induced decarboxylation of a bis(hydroxycarbonyl)–diruthenium(II) complex to a dihydrido–diruthenium(II) species, followed by dinuclear reductive elimination of molecular hydrogen with the concomitant formation of the Ru^I? Ru^I single bond. This work was originally instituted to find a reliable synthetic protocol for the [Ru₂(CO)₄(CH₃CN)₆]²⁺ precursor. It is herein prescribed that at least four equivalents of base, complete removal of chlorido ligands by Tl^I salts, and heating at reflux in acetonitrile for a period of four hours are the conditions for the optimal conversion. Premature quenching of the reaction resulted in the isolation of a trinuclear Ru^I₂Ru^II complex [{Ru(NP‐Am)₂(CO)}{Ru₂(NP‐Am)₂(CO)₂(μ‐CO)₂}(μ₃:κ³‐C,O,O′‐CO₂)][BF₄]₂ ( 6 ). These unprecedented diruthenium compounds are the dinuclear congeners of the water–gas shift (WGS) intermediates. The possibility of a dinuclear pathway eliminates the inherent contradiction of pH demands in the WGS catalytic cycle in an alkaline medium. A cooperative binuclear elimination could be a viable route for hydrogen production in WGS chemistry.     

Tripropylarsane Complexes of Palladium(II) and Platinum(II) — Syntheses,Spectroscopy, and Structures

Several palladium(II) and platinum(II) complexes of tripropylarsanes (AsR₃; R = Pr, iPr) with the formulae, [MCl₂(AsR₃)₂], [M₂Cl₂(μ‐Cl)₂(AsR₃)₂], [Pd₂Me₂(μ‐Cl)₂(AsR₃)₂], [Pd₂X₂(μ‐Pz)₂(AsR₃)₂] (X = Cl or Me, Pz = pyrazolate), [Pd₂Cl₂(μ‐Y)₂(AsR₃)₂] (Y = OAc or SPh), [MCl(S₂CNEt₂)(AsR₃)] and [PdCp(Cl)(AsiPr₃)] (M = Pd or Pt) have been prepared. All the complexes have been characterised by elemental analyses, IR and ¹H NMR spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The structures of [Pd₂Me₂(μ‐X)₂(AsiPr₃)₂] (X = Cl or Pz) have been established by single crystal X‐ray diffraction analyses. Both of the complexes have sym‐trans configuration. Strong trans influence of the methyl group is reflected on the Pd—X bond distances.     

Umsetzungen von Cp*NbCl4 und Cp*TaCl4 mit Trimethylsilyl‐azid,Me3Si‐N3. Molekülstrukturen der bis(azido)‐oxo‐verbrückten Komplexe [Cp*NbCl(N3)(μ‐N3)]2(μ‐O) und [Cp*TaCl2(μ‐N3)]2(μ‐O) (Cp* = Pentamethylcyclopentadienyl)

Reactions of Cp*NbCl₄ and Cp*TaCl₄ with Trimethylsilyl‐azide, Me₃Si‐N₃. Molecular Structures of the Bis(azido)‐Oxo‐Bridged Complexes [Cp*NbCl(N₃)(μ‐N₃)]₂(μ‐O) and [Cp*TaCl₂(μ‐N₃)]₂(μ‐O) (Cp* = Pentamethylcyclopentadienyl) The chloro ligands in Cp*TaCl₄ (1c) can be stepwise substituted for azido ligands by reactions with trimethylsilyl azide, Me₃Si‐N₃ (A) , to generate the complete series of the bis(azido)‐bridged dimers [Cp*TaCl_3‐n(N₃)_n(μ‐N₃)]₂ ( n = 0 (2c) , n = 1 (3c) , n = 2 (4c) and n = 3 (5c) ). If the solvent CH₂Cl₂ contains traces of water, an additional oxo bridge is incorporated to give [Cp*‐TaCl₂(μ‐N₃)]₂(μ‐O) (6c) or [Cp*TaCl(N₃)(μ‐N₃)]₂(μ‐O) (7c) , respectively. Both 6c and 7c are also formed in stoichiometric reactions from [Cp*TaCl₂(μ‐OH)]₂(μ‐O) (8c) and A . Analogous reactions of Cp*NbCl₄ (1b) with A were used to prepare the azide‐rich dinuclear products [Cp*NbCl_3‐n(N₃)_n(μ‐N₃)]₂ (n = 2 (4b) , and n = 3 (5b) ), and [Cp*NbCl(N₃)(μ‐N₃)]₂(μ‐O) (7b) . The mononuclear complex Cp*Ta(N₃)Me₃ (10c) is obtained from Cp*Ta(Cl)Me₃ and A . All azido complexes were characterised by their IR as well as their ¹H and ¹³C NMR spectra; X‐ray crystal structure analyses are available for 6c and 7b .     

Facile Carbon–Fluorine Bond Activation and Subsequent Functionalisation of 1,1‐Difluoroethylene and Tetrafluoroethylene Promoted by Adjacent Metal Centres

The bridging fluoroolefin ligands in the complexes [Ir₂(CH₃)(CO)₂(μ‐olefin)(dppm)₂][OTf] (olefin=tetrafluoroethylene, 1,1‐difluoroethylene; dppm=μ‐Ph₂PCH₂PPh₂; OTf^?=CF₃SO₃^?) are susceptible to facile fluoride ion abstraction. Both fluoroolefin complexes react with trimethylsilyltriflate (Me₃SiOTf) to give the corresponding fluorovinyl products by abstraction of a single fluoride ion. Although the trifluorovinyl ligand is bound to one metal, the monofluorovinyl group is bridging, bound to one metal through carbon and to the other metal through a dative bond from fluorine. Addition of two equivalents of Me₃SiOTf to the tetrafluoroethylene‐bridged species gives the difluorovinylidene‐bridged product [Ir₂(CH₃)(OTf)(CO)₂(μ‐OTf)(μ‐C?CF₂)(dppm)₂][OTf]. The 1,1‐difluoroethylene species is exceedingly reactive, reacting with water to give 2‐fluoropropene and [Ir₂(CO)₂(μ‐OH)(dppm)₂][OTf] and with carbon monoxide to give [Ir₂(CO)₃(μ‐κ¹:η²‐C?CCH₃)(dppm)₂][OTf] together with two equivalents of HF. The trifluorovinyl product [Ir₂(κ¹‐C₂F₃)(OTf)(CO)₂(μ‐H)(μ‐CH₂)(dppm)₂][OTf], obtained through single C? F bond activation of the tetrafluoroethylene‐bridged complex, reacts with H₂ to form trifluoroethylene, allowing the facile replacement of one fluorine in C₂F₄ with hydrogen.