Evaluating the reducing power of 3-coordinate T-shaped Ni

The reactivity of (PNP)Ni^I, where PNP = (^tBu₂PCH₂SiMe₂)₂N, with oxidants was evaluated. Towards the nitroxyl TEMPO, a 1:1 adduct is formed which was shown to have η²-TEMPO bound through both N and O, with the consequence that one P of the PNP ligand is displaced, leaving the pincer ligand bidentate to Ni^II. DFT calculations show that the bidentate character of TEMPO is due to steric clash between ^tBu and TEMPO ring methyl groups. Reaction of (PNP)Ni with I₂, Br₂, C₂Cl₆ and even CH₂Cl₂ all yield (PNP)Ni^IIX, but never (PNP)Ni^IIIX₂. Excess Br₂ instead oxidizes one phosphorus, yielding the zwitterion [(Br^tBu₂PCH₂SiMe₂)N(SiMe₂CH₂P^tBu₂)]NiBr₂, whose structure is determined. DFT calculation of the species (PNP)Ni^III(Br)₂ yields reaction thermodynamics which show the reason for its absence, and also shows the low BDE of its Ni-Br bond. (PNP)Ni slowly catalyzes the polymerization of HCCR (R = H or Ph), but gives no detectable conversion to a new alkyne-derived nickel complex.     

Synthesis and characterization of η-cyclopentadienyl-silylallyl niobium and tantalum complexes

Reaction of the disilylcyclopentadiene 1,1-[SiMe₂(CH₂CHCH₂)]₂C₅H₄ with NbCl₅ gave the new allylsilyl-substituted monocyclopentadienyl niobium complex [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}Cl₄]. This compound was reacted with LiNHtBu or NH₂tBu to give the imido derivative [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}(NtBu)Cl₂], which was further alkylated to the imido alkyl complexes [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}(NtBu)R₂] (R = Me, CH₂Ph) and [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}(NtBu)Cl (CH₂Ph)]. Reaction of the imido complexes with the corresponding lithium cyclopentadienides gave the dicyclopentadienyl-imido complexes [M(η⁵-C₅R₅){η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}(NtBu)Cl] (M = Nb, Ta; R = H, Me). Metallocene dichlorides [M(η⁵-C₅R₅){η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}Cl₂] (M = Nb, Ta; R = H, Me) were easily prepared by reduction with Na/Hg and simultaneous transmetallation of [Ta(η⁵-C₅R₅)Cl₄] with Li[C₅H₄SiMe₂(CH₂CHCH₂)] and of [Nb{η⁵-C₅H₄SiMe₂(CH₂CHCH₂)}Cl₄] with Li(C₅R₅). All of the new compounds have been characterized by elemental analysis, and IR and NMR spectroscopy.     

Diphosphinoazine rhodium(III) and iridium(III) octahedral complexes

Rhodium(III) and iridium(III) octahedral complexes of general formula [MCl₃{R₂PCH₂C(Bu^t)NNC(Bu^t)CH₂PR₂}] (M = Rh, Ir; R = Ph, c-C₆H₁₁, Prⁱ, Bu^t; not all the combinations) were prepared either from the corresponding diphosphinoazines and RhCl₃ · 3H₂O or by the oxidation of previously reported bridging complexes [{MCl(1,2-η:5,6-η-CHCHCH₂CH₂CHCHCH₂CH₂)}₂{μ-R₂PCH₂C(Bu^t)NNC(Bu^t)CH₂PR₂}] with chlorine-containing solvents. Depending on the steric properties of the ligands, complexes with facial or meridional configuration were obtained. Crystal and molecular structures of three facial and two meridional complexes were determined by X-ray diffraction. Hemilability of ligand in the complex fac-[RhCl₃{(C₆H₁₁)₂PCH₂C(Bu^t)NNC(Bu^t)CH₂P(C₆H₁₁)₂}] consisting in reversible decoordination of the phosphine donor group in the six-membered ring was observed as the first step of isomerization between fac and mer isomers.     

Palladium complexes with PCP ligands.: Preparation and structural studies of two forms of [(PCP)Pd(OH2)]BF4

Abstraction of chloride from the Pd complex {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]PdCl with AgBF₄ in THF gives {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]Pd(THF)}⁺BF₄ ⁻. Attemped crystallization of this THF complex produced the aqua complex {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]Pd(OH₂)}⁺BF₄ ⁻. Crystal structures of two crystalline forms of this compound are reported. In {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]Pd(OH₂)}⁺BF₄ ⁻·THF, one hydrogen of the water is hydrogen bonded to the oxygen of the THF, and the other hydrogen is hydrogen bonded to an F of the BF₄ ⁻ anion. Another crystalline form has no THF, but has both of the hydrogens of water hydrogen bonded to different BF₄ ⁻ anions, such that two different BF₄ ⁻ anions bridge two {[η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]Pd(OH₂)}⁺ cations. A crystal structure is also reported for the palladium chloride complex [η³-2,6-(^tBu₂PCH₂)₂C₆H₃)]PdCl.     

Synthesis and characterization of metallatranes with phenyl substituents in atrane cage

A new series of mono- and diphenylsubstituted silatranes and boratranes N(CH₂CH₂O)₂(CHR³CR¹R²O)MZ (M = Si, Z = CH₂Cl, CCPh, H, OMenth, R¹, R², R³ = H, Ph; M = B, Z = nothing, R¹, R², R³ = H, Ph) have been synthesized. Both transalkoxylation and stepwise modification of a preformed metallatrane skeleton were used. The chloromethyl derivatives N(CH₂CH₂O)₂(CHRCHRO)SiCH₂Cl (R = H, Ph) react with tert-BuOK under intramolecular cycle expansion to give 1-tert-butoxy-2-carba-3-oxahomosilatranes N(CH₂CH₂O)(CH₂CH₂OCH₂)(CHRCHRO)SiO^tBu (R = H, Ph). The treatment of boratranes N(CH₂CH₂O)₂(CH₂CR¹R²O)B (R¹,R² = H, Ph) with triflic acid and trimethylsilyl triflate results in the products of electrophilic attack at the nitrogen atom. The molecular structures of four silatranes and one boratrane bearing phenyl groups in the atrane skeleton were determined by the X-ray structure analysis.     

Unexpected selectivity in electrophilic attack on (PNP)RuN

Protonation of (PNP)RuN, where PNP is (^tBu₂PCH₂SiMe₂)₂N, with HCl occurs at the amide nitrogen, with coordination of chloride to Ru^IV, while triflic acid protonates the same nitrogen, but has triflate anion hydrogen-bonded to the proton on the PNP amide nitrogen, not triflate coordinated to the metal. Methyl triflate however alkylates the nitride nitrogen, to give a C_2v symmetric product. DFT calculations show that the thermodyamic preference is for proton on amide nitrogen while alkyl favors nitride alkylation, even without the need for a hydrogen bond to reverse the H vs. alkyl preference. Alkylation at the amide nitrogen leads to nearly complete loss of the PN(R)P Ru/N bond in this unobserved isomer. These preferences among nucleophilic sites on (PNP)RuN are rationalized based on the frontier orbitals of this molecule.     

Synthesis and crystal structure of tetrameric silver(I) 3,5-di-tert-butyl-pyrazolate

A tetrameric [Ag(μ-3,5-^tBu₂pz)]₄ · CH₂Cl₂ (1 · CH₂Cl₂) has been prepared and structurally characterized. The four Ag-atoms are in an approximate rhombic arrangement with pyrazolato bridges alternating on either side of the Ag₄-plane. A ¹H NMR study shows partial decomposition of 1 to the mononuclear [Ag(3,5-^tBu₂pzH)₂]⁺ in solution.     

Hyponitrite complexes: Crystal and molecular structure of [Ru2(CO)4(μ-PBu2)(μ-Ph2PCH2PPh2)(μ-η-ONNOMe)]

The new trans-hyponitrite derivative complex [Ru₂(CO)₄(μ-P^tBu₂)(μ-dppm)(μ-η²-ONNOMe)] (2, dppm = Ph₂PCH₂PPh₂) was prepared by deprotonation of [Ru₂(CO)₄(μ-H)(μ-P^tBu₂)(μ-dppm)(μ-η²-ONNOMe)][BF₄] (1) with the base DBU (1.8-diazabicyclo[5.4.0]undec-7-ene). The latter complex salt has been obtained in an improved synthesis starting from the trans-hyponitrite complex [Ru₂(CO)₄(μ-H)(μ-P^tBu₂)(μ-dppm)(μ-η²-ONNO)]. Compound 2 has been characterized by spectroscopic methods as well as by X-ray diffraction and represents the first neutral complex bearing a deprotonated monoester of the hyponitrous acid as the bridging ligand.     

Preparation and characterization of macrocyclic dinickel complexes coligated by monoalkyl- and dialkylcarbamates

The dinuclear nickel(II) complex [Ni₂L(Cl)]⁺ (1), where (L)²⁻ represents a 24-membered binucleating hexamine-dithiophenolate ligand, reacts readily with primary and secondary amines RR′NH in the presence of CO₂ (1 bar) to give dinuclear monoalkyl- and dialkylcarbamate complexes [Ni₂L(O₂CNRR′)]⁺ (R = H, R′ = CH₂Ph (2), R = H, R′ = n-Bu (3), R = H, R′ = n-Oct (4), R = H, R′ = CH₂CH₂OH (5), R = R′ = Et (6), and R = R′ = CH₂CH₂OH (7)). Complexes 2-7 can also be prepared by the reaction of 1 with CO₂(air)/amine. The carbamate complexes are hydrolyzed in methanolic solution to give the known alkylcarbonate complex [Ni₂L(O₂COMe)]⁺ (8). These conversions are less rapid than the transesterification reactions of 8, due to a less electron-demanding carboxyl C(carbamate) atom. All new complexes were either isolated as perchlorate or tetraphenylborate salts and fully characterized by elemental analysis, UV/Vis, and IR spectroscopy. The structures of 2[BPh₄] and 7[BPh₄] have also been determined by X-ray crystallography. They confirm the presence of μ_1,3-bridging alkylcarbamate units in the products.     

sp C-H and sp C-H agostic ruthenium complexes: a combined experimental and theoretical study

Halide abstraction from the 18 electron Ru(II) complex RuCl(CO)₂[2,6-(CH₂P^tBu₂)₂C₆H₃] (2) with AgPF₆ results in the exclusive formation of the cationic complex {Ru(CO)₂[2,6-(CH₂P^tBu₂)₂C₆H₃]}⁺PF₆⁻ (3). The molecular structures of 2 and 3 were determined by complete single-crystal diffraction studies. X-ray crystallographic analysis of 3 reveals that the “open” coordination site is occupied by an agostic interaction between the metal center and an sp³ C-H bond of a tert-butyl substituent. DFT gas phase calculations (B97-1/SDD) show the necessity of two sterically demanding tert-butyl substituents on one P donor atom for the agostic interaction to occur. The reaction of 3 with H₂ results in the quantitative conversion to {Ru(H)(CO)₂[2,6-(CH₂P^tBu₂)₂C₆H₄]}⁺PF₆⁻ (4) where the aromatic C_ipso-H bond is η²-coordinated to the metal center. Treatment of the agostic complex 4 with Et₃N results in the formation of the neutral complex Ru(H)(CO)₂[2,6-(CH₂P^tBu₂)₂C₆H₃] (5). The mechanistic details of 3 + H₂ → 4 were investigated by DFT calculations at the B97-1/SDB-cc-pVDZ//B97-1/SDD level of theory.     

Reaction of [Pt3(μ-CO)3(PBu3)3] with activated olefins and alkynes: the X-ray-structure of [Pt(CO)(PBu3)(CF3CCCF3)]

The reactions of the triangulo-cluster [Pt₃(μ-CO)₃(P^tBu₃)₃] with activated olefins and alkynes have been examined under various conditions. At low temperature, cluster fragmentation occurs yielding the Pt(0) complexes [Pt(CO)(P^tBu₃)(olefin)] (olefin = maleic anhydride and maleimide), while di(tert-butyl)acetylenedicarboxilate reacts quantitatively giving the dinuclear Pt(0) complex [Pt₂(CO)₂(P^tBu₃)₂(μ-η²:η²-^tBuO₂CCCCO₂^tBu)]. At higher temperature and in the presence of alkyne in large excess, the latter dimer converts quantitatively to the monomers [Pt(CO)(P^tBu₃)(alkyne)] (alkyne = CF₃CCCF₃ and ^tBuO₂CCCCO₂^tBu). The stereochemistry of these complexes has been established by NMR and IR measurements. The structure of [Pt(CO)(P^tBu₃)(CF₃CCCF₃)] was confirmed by X-ray diffraction analysis.     

Synthesis and structures of copper and gold complexes of the P,N ligands RNC(Bu)C(H)RPPh2 (R = SiMe3, H)

The reaction of the chelating P,N ligand RNC(Bu^t)CH(R)PPh₂ (R = SiMe₃) (1) with CuCl and CuCl₂ (probably by way of reduction to Cu(I) by the phosphine ligand) or Cu(NCCH₃)₄ClO₄ yielded the dimeric 1:1 complex [Cu{PPh₂CH(R)C(Bu^t)NR}Cl]₂ (2) or the monomeric 2:1 complex [Cu{PPh₂CH(R)C(Bu^t)NR}₂]ClO₄ (3), respectively. The presence of trace amounts of water during the reaction resulted in the successive cleavage of the two trimethylsilyl groups of the ligand and the formation of the monomeric chelate complexes [Cu{PPh₂CH(R)C(Bu^t)NH}₂]ClO₄ (4) and [Cu{PPh₂CH₂C(Bu^t)NH}₂]ClO₄ (5). Oxidation of 5 by atmospheric oxygen led to small quantities of the blue Cu(II) complex [Cu{(O)PPh₂CH₂C(Bu^t)NH}₂](ClO₄)₂ (6). The dimeric gold complexes [Au{PPh₂CH₂C(Bu^t)NH}]₂X₂ (X = BF₄, ClO₄) (7) were similarly obtained from the previously described Au{PPh₂CH(R)C(Bu^t)NR}Cl by replacing the covalently bound chlorine with the weakly coordinating anions in the presence of small quantities of water. The solution and solid state structures (except 5) of all complexes were determined by NMR spectroscopy and X-ray crystallography.     

[S2], [S3], and [N3] coordination modes of hydrotris(thioxotriazolyl)borato. Zinc, nickel, cobalt, and bismuth complexes

The ligand hydrotris(1,4-dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazolyl)borato (Tr^Ph,Me) was synthetized as natrium salt and the complexes [Zn(Tr^Ph,Me)₂] · 7.5H₂O · 1.5CH₃CN (2a), [Zn(Tr^Ph,Me)₂] · 8DMF (2b), [Co(Tr^Ph,Me)₂] · 8DMF (3a), [Ni(Tr^Ph,Me)₂] · H₂O · 6DMSO (4a), [Bi(Tr^Ph,Me)₂]NO₃ (5), have been isolated and structurally characterized by X-ray diffraction. In the zinc derivatives the ligand adopts different denticity and coordination modes, η² and [S₂] for 2a and η³ and [N₃] for 2b, depending on the crystallization solvent, giving rise to tetrahedral and octahedral geometry, respectively. In the octahedral cobalt and nickel complexes the ligand is η³ and [N₃] coordinated whereas in the bismuth complex the η³ and [S₃] coordination is exhibited.     

Synthesis and coordination of the bifunctionalized ylides Ph2P(CH2)n(Ph)2PCHCOOMe (n = 1, 2) and ketenylidene Ph2P(CH2)2(Ph)2PCCO to Pd and Pt complexes

In this paper it is reported the synthesis of the phosphonium salts [Ph₂P(CH₂)_n(Ph)₂PCH₂COOMe]Br (n = 1 (1), 2 (2)) and [Ph₂P(CH₂COOMe)(CH₂)_n(Ph)₂PCH₂COOMe]Br₂ (n = 3 (3)) derived from the reactions of the diphosphines dppm, dppe and dppp with methyl bromoacetate. By reaction of the monophosphonium salt of dppm and dppe with the strong base Na[N(SiMe₃)₂] the corresponding carbonyl stabilized ylides Ph₂P(CH₂)_n(Ph)₂PCHCOOMe (n = 1 (4), 2 (5)) were obtained. The Ph₂P(CH₂)₂(Ph)₂PCHCOOMe (5) ylide was reacted with Pd(II) and Pt(II) substrates. From these reactions were isolated exclusively complexes in which the ylide was chelated to the metal through the free phosphine group and the ylidic carbon atom. A further reaction of the Ph₂P(CH₂)₂(Ph)₂PCHCOOMe (5) ylide with 1.5 equiv. of Na[N(SiMe₃)₂] gives the bifunctionalized ketenylidene Ph₂P(CH₂)₂(Ph)₂PCCO (6) system. This cumulenic ylide reacts with Pt(II) complexes to form a chelated derivative in which IR and NMR spectra suggest the breaking of the CC bond of the -CCO group.     

Silver(I) acetylides stabilized by η-alkynes: Synthesis, reaction chemistry and solid state structures

Individual synthetic routes to heterobimetallic Ti(IV)-Ag(I) acetylides of type {[Ti](μ-σ,π-CCR¹)₂}AgCCR² ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti: R¹ = SiMe₃: 6, R² = SiMe₃; 7, R² = Ph. R¹ = ^tBu: 8, R² = SiMe₃; 9, R² = Ph. [Ti] = (η⁵-C₅H₅)₂Ti): 10, R¹ = ^tBu, R² = SiMe₃) including (i) the reaction of {[Ti](μ-σ, π-CCR¹)₂}AgNO₃ ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti): 1, R¹ = SiMe₃; 2, R¹ = ^tBu. [Ti] = (η⁵-C₅H₅)₂Ti: 3, R¹ = ^tBu) with LiCCR² (4, R² = SiMe₃; 5, R² = Ph) and (ii) treatment of [Ti](CCSiMe₃)₂ ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti) (11) with [AgCCR²] (12, R² = SiMe₃; 13, R² = Ph) are described. The reactions of 1-3 with 4 or 5 appeared to be sensitive towards stoichiometry because an excess of 4 or 5 resulted in the formation of [(Ag(CCR²)₂)Li(OEt₂)]_n (14) and [Ti](CCR¹)₂. Coordination polymer 14 is also accessible, when, for example, [AgCCSiMe₃] (12) is treated with 1 eq. of LiCCSiMe₃ (4) in diethyl ether.The titanium(IV)-silver(I) acetylides 6-10 are stable in the dark and at low temperature, while on exposure to light and on heating they decompose to give R²CC-CCR² together with [Ti](CCR¹)₂ and elemental silver.Complexes 6-10 contain a mono-nuclear AgCCR² entity stabilized by the chelate-bonded organometallic π-tweezer molecule [Ti](CCSiMe₃)₂, which was evinced by structure determination of 7 in the solid state. In 14 linear [Me₃SiCC-Ag-CCSiMe₃]⁻ units are connected by [Li(OEt₂)]⁺ building blocks forming a coordination polymer.     

Syntheses, structure, and electrochemical properties of homo-metallic binuclear complexes containing ferrocenyl-ethynyl spacers

Structural determinations and electrochemical properties in the series of multinuclear ferrocenyl-ethynyl complexes with formula [(η⁵-C₅R₅)(P₂)M^II-CC-(fc)_n-CC-M^II(P₂)(η⁵-C₅R₅)] (fc = ferrocenyl; M = Fe(II), Ru(II), Os(II); R = H, CH₃; P₂ = Ph₂PCH₂CH₂PPh₂ (dppe), (C₂H₅)₂PCH₂CH₂P(C₂H₅)₂ (depe)) are reported. Complexes with more electron-rich ligand environment, such as [M(η⁵-C₅R₅)P₂] (R = CH₃ and P₂ = dppe, depe), were also prepared with regard to the understanding of electronic coupling mechanism. Structural determinations confirm that the ferrocenyl group is directly linked to the ethynyl linkage which is linked to the pseudo-octahedral [(η⁵-C₅R₅)(P₂)M] metal center. These complexes undergo sequential reversible oxidation events from 0.0 to 1.0 V referred to the Ag/AgCl electrode in anhydrous CH₂Cl₂ solution and the low-potential waves have been assigned to the two end-capped metallic centers. The magnitude of the electronic coupling between the two terminal metallic centers in the series of complexes was estimated by the electrochemical technique. Based on the correlation between the ΔE_1/2 values and the second redox potentials of the end-capping metallic centers in the series of complexes, a qualitative explanation for the difference of the electronic coupling is given.     

Palladium(II) amido complexes with an unsymmetrical PNP′ pincer-type coordination and a new (E,E)-tetradentate diphosphinoazine coordination mode

Cationic palladium(II) complexes [PdCl{PR₂CH₂C(Bu^t)NNC(Bu^t)CH₂PR₂}]Cl, where R = isopropyl, cyclohexyl or tert-butyl, were synthesized by the reactions of the corresponding diphosphinoazines with bis(acetonitrile)palladium(II) dichloride. When bis(benzonitrile)palladium(II) dichloride was used instead, in the molar ratio of 2:1 to the diphosphinoazine, a new complex was isolated with the isopropyl ligand showing a previously unknown (E,E) tetradentate coordination mode. Crystal and molecular structure was determined by X-ray diffraction. The solid complex was a racemate of two axially chiral enantiomers and the chirality was preserved in solution. Reactions of the cationic complexes with triethylamine gave complexes [PdCl{PR₂CHC(Bu^t)NNC(Bu^t)CH₂PR₂}], containing deprotonated diphosphinoazines in ene-hydrazone unsymmetrical pincer-like configuration. The complexes represent several of the still rare examples of Pd(II) amido bis(phosphine) complexes with a chlorine atom covalently bonded trans to the amide nitrogen.     

Synthesis and characterization of CpMCl(PR3)(S or W-η-butadienesulfonyl) compounds of rhodium and iridium

A metathesis reaction of [Cp^∗MCl₂(PR₃)] [M = Rh, R = Ph (1), Me (3); M = Ir, R = Ph (2), Me (4)] takes place in the presence of potassium butadienesulfinate (SO₂CHCHCHCH₂)K (9) to afford the mononuclear compounds [Cp^∗M(Cl)(PR₃)(η¹-SO₂CHCHCHCH₂)] [M = Rh, R = Ph (11S), (11W); M = Rh, R = Me (13S), (13W)] and [M = Ir, R = Ph (12S); M = Ir, R = Me (14S), (14W)] under different reaction conditions. The addition of PR₃ (R = Ph, Me) to Cp^∗Ir(Cl)[(1,2,5-η)-SO₂CHCHCHCH₂] (7) affords the corresponding iridium isomers 12S, 12W and 14S, in a non-selective reaction, along with the corresponding dichloride compounds 2 or 4. The ¹H and ¹³C{¹H} NMR data are consistent with the butadienesulfonyl ligands coordinated exclusively through the sulfur atom, and they show the presence of two isomers, described as the S and W conformers, which can be isolated separately. There is clear evidence that these isomers correspond to the kinetic and thermodynamic derivatives, respectively.     

Cationic induced assembly of two 2D zinc-terephthalate polymeric networks

Based on templates of [Ph₃PCH₂Ph]Cl and [Ph₄P]Cl ([Ph₃PCH₂Ph] = benzyltriphenylphosphonium, [Ph₄] = tetraphenylphosphonium), the hydrothermal reactions of zinc acetate dihydrate, H₂tp (tp = terephthalate) and water give rise to two new zinc-terephthalate coordination polymers, [Ph₃PCH₂Ph][Zn(tp)Cl] (1) and [Ph₄P][Zn(tp)(H₂O)₂·0.5tp] (2). X-ray single-crystal structural analysis reveals that both 1 (C₃₃H₂₆ClO₄PZn) and 2 (C₃₆H₃₀O₈PZn) crystallize in the 2D non-interpenetrating layered supramolecular networks with guest organophosphonium cations. Due to template effect of different guest cations, 1 presents an interesting 2D smectite-like lamellar framework that formed by the 4-linked (4,4) anionic zinc-terephthalate polymeric network and the interlayer [Ph₃PCH₂Ph]⁺ exchangeable cations, while 2 shows a 2D 3-linked (6,3) H-bonded anionic zinc-terephthalate polymeric brickwall network with encapsulated guest [Ph₄P]⁺ cations. Both compounds are stable up to about 300 °C, and exhibit intense fluorescent emission band at 446 nm (λ_exc = 328 nm) for 1 and 420 nm (λ_exc = 340 nm) for 2 in the solid state at room temperature.     

Unusual bond activation processes in the reaction of group 4 cyclopentadienyl alkyne complexes with azobenzene

The alkyne complexes [Cp′₂M(L)(η²-Me₃SiC₂SiMe₃)] (Cp′ = substituted or unsubstituted cyclopentadienyl; M = Ti, Zr, Hf; L = Py, THF) can serve as metallocene precursors by substitution of the alkyne molecule with other ligands. The reactions of the unsubstituted cyclopentadienyl complexes [Cp₂Zr(THF)(η²-Me₃SiC₂SiMe₃)] (1) and [Cp₂Ti(η²-Me₃SiC₂SiMe₃)] (2) with azobenzene were investigated. In the first case the diazene complex [Cp₂Zr(THF)(N₂Ph₂)] (3) was obtained by alkyne exchange. In the reaction of the titanium complex 2 a NN bond cleavage of azobenzene and a C-H activation of the cyclopentadienyl ligand were observed and the dinuclear imido bridged compound 4 was formed. This mixed valence complex is bridged additionally by a cyclopentadienyl ligand in a η¹:η⁵-coordination mode which is very unusual for titanium complexes. The molecular structures of both compounds were confirmed by X-ray crystallography and compared to former structural data shown in literature.