Complexes Trans Research Articles

Ferralactone formation from iron acetylides and carbon dioxide

CO2 reacts rapidly with the acetylide iron hydride trans- [FeH(C≡CH)(dmpe)2] by insertion into the metal hydride bond. However, this reaction is reversible and the final products of the reaction are the ferralactones cis- [Fe(OC(=O)CHCH-κ2C,O)(dmpe)2] and cis- [Fe(OC(=O)C(C(=O)OH)CH-κ2C,O)(dmpe)2] resulting from single and double CO2 addition to the β-carbon of the coordinated acetylene respectively, followed by cyclization. Reaction of the t-butylacetylide complex trans- [FeH(C≡CtBu)(dmpe)2] with CO2 affords the t‑butyl‑substituted ferralactone cis- [Fe(OC(=O)C(tBu)CH-κ2C,O)(dmpe)2]. Reaction of CO2 with trans- [FeH(C≡CPh)(dmpe)2] forms the phenyl-substituted ferralactone cis- [Fe(OC(=O)C(Ph)CH-κ2C,O)(dmpe)2] where the phenyl substituent is attached to the carbon adjacent to the carbonyl group of the metalalactone. Remarkably, reaction of CO2 with the side-on-bound complex Fe(η2-HC≡CPh)(dmpe)2] forms a different phenyl-substituted metalalactone cis- [Fe(OC(=O)CHC(Ph)-κ2C,O)(dmpe)2] where the phenyl substituent is attached to the metal-bound carbon of the metalalactone ring.

Azo-oximate metal-carbonyl to metallocarboxylic acid via the intermediate Ir(III) radical congener: quest for co-ligand driven stability of open- and closed-shell complexes.

The redox non-innocent behavior of the diaryl-azo-oxime ligand LNOH1 has been accentuated via the synthesis of metastable anion radical complexes of type trans-[Ir(LNO˙-)Cl(CO)(PPh3)2] 2 (CO is trans to azo group of the ligand) by the oxidative coordination reaction of 1 with Vaska's complex. The stereochemical role of co-ligands vis-à-vis the interplay of π-bonding has been found to be decisive in controlling the aptitude of the coordinated redox non-innocent ligand to accept or reject an electron. This has been clarified via the isolation of quite a few complexes as well as the failure to synthesize some others. The oxidized analogues of type trans-[Ir(LNO-)Cl(CO)(PPh3)2]+2+ (CO and azo group of the ligand are trans) as well as its cis isomer cis-[Ir(LNO-)Cl(CO)(PPh3)2]+3+ (CO and azo group of the ligand are cis) have been structurally characterized but the radical anion congener of the latter could not be synthesized. Furthermore, the closed shell complexes [Ir(LNO-)Cl2(PPh3)2] 4 and [Ir(LNO-)2Cl(PPh3)] 5 have been well characterized by diffraction as well as spectral techniques but their corresponding azo anion radical complexes could not be isolated and this is attributed to the trans influence of ancillary ligands. The anion radical complexes trans-[Ir(LNO˙-)Cl(CO)(PPh3)2] 2 may be rapidly transformed to the metallocarboxylic acids trans-[Ir(LNO-)Cl(CO2H)(PPh3)2] 6via a proton-coupled electron transfer (PCET) process, thereby demonstrating the role of odd electron over the coordinated ligand framework to trigger metal-mediated carbonyl to carboxylic acid functionalization. Complexes 6 are further stabilized via intramolecular -CO2H⋯ON- (carboxylic acid⋯oximato) H-bonding. The optoelectronic properties as well as the origin of transitions in the complexes were analyzed by TD-DFT and theoretical analysis, which further disclose that the odd electron in trans-[Ir(LNO˙-)Cl(CO)(PPh3)2] 2 is primarily azo-oxime centric with very low contribution from the iridium center.

Synthesis, structural and metal-to-metal charge transfer properties of cyanide-bridged compound [FeII/III-NC-RuII-CN-FeII/III

Cyanide-bridged mixed-valence complexes trans-[Cp(dppe)Fe(NC)RuII(tbupy)4(CN)Fe(dppe)Cp][PF6]n (n = 2, 3 and 4, respectively, 1–3) were systematically synthesized and characterized in three distinct redox states.

Thermally Controlled Synthesis of Octahedral Rhenium Clusters with 4,4′-Bipyridine and CN− Apical Ligands

The selective preparation, structural and spectroscopic study of two new rhenium cluster complexes trans-[Re6S8(bpy)4(CN)2] and trans-[Re6S8(bpy)2(CN)4]2− (bpy = 4,4′-bipyridine) obtained by reactions of corresponding hexarhenium cyanohalides with molten bpy are reported. The complexes were crystallized as solvates, displaying supramolecular structures based on cluster units linked by numerous weak interactions with bpy molecules. The molecular compound trans-[Re6S8(bpy)4(CN)2] (1) is insoluble in water and common organic solvents, while the ionic compound trans-Cs1.7K0.3[Re6S8(bpy)2(CN)4] (2) is somewhat soluble in DMSO, DMF and N-methylpyrrolidone. The presence of the redox-active ligand bpy leads to the occurrence of multi-electron reduction transitions in a solution of 2 at moderate potential values. The ambidentate CN− ligand is the secondary functional group, which has potential for the synthesis of coordination polymers based on the new cluster complexes. In addition, both new compounds show a weak red luminescence, which is characteristic of complexes with a {Re6S8}2+ cluster core.

The saga of rhodium(III) nitrate complexes and their speciation in solution: An integrated experimental and quantum chemical study

Rhodium(III) nitrate complexes trans-[(CH3)4N][Rh(H2O)2(NO3)4] (I), [(CH3)4N]Na2[Rh(H2O)6](NO3)6 (II), [(C2H5)4N]2[Rh(H2O)(NO3)5] (III) and [(CH3)4N]2[Rh(H2O)(NO3)5] (IV) were synthesized by the reactions of a “rhodium nitrate solution” with (CH3)4NNO3 and (C2H5)4NNO3. The complexes I, III and IV represent the first examples of soluble rhodium(III) complexes having four and five coordinated nitrato ligands, while II is the first example of a hexaaquarhodium(III) nitrate complex. Thermodynamic stability constants βi for the set of equilibria [Rh(H2O)6]3+ + iNO3− = [Rh(H2O)(6-i)(NO3)i](3−i) + iH2O were estimated using rhodium(III) solutions equilibrated for years. The constants decrease with the increase in the number of coordinated NO3− groups as follows: β1 ≈ 100, β2cis ≈ 10−1, β2trans ≈ 10−1 – 10−2, β3mer ≈ 10−2, β3fac ≈ 10−2, β4cis ≈ 10−4, β4trans ≈ 10−4. The kinetics and thermodynamics of NO3− ligands substitution with H2O molecules have been thoroughly studied by DFT calculations for a series of [Rh(NO3)x(H2O)6–x](3−x) complexes (x = 0–6). The high solubility of the synthesized complexes increases their synthetic significance and opens up new horizons in various practical applications such as homogeneous catalysis, photo- and electrochemistry, drug discovery and bioinorganic chemistry.

Electronic Structure and Magnetic Properties of a Low-Spin CrII Complex: trans-[CrCl2(dmpe)2] (dmpe = 1,2-Bis(dimethylphosphino)ethane).

Octahedral coordination complexes of the general formula trans-[MX2(R2ECH2CH2ER2)2] (MII = Ti, V, Cr, Mn; E = N, P; R = alkyl, aryl) are a cornerstone of both coordination and organometallic chemistry, and many of these complexes are known to have unique electronic structures that have been incompletely examined. The trans-[CrCl2(dmpe)2] complex (dmpe = Me2PCH2CH2PMe2), originally reported by Girolami and co-workers in 1985, is a rare example of a six-coordinate d4 system with an S = 1 (spin triplet) ground state, as opposed to the high-spin (S = 2, spin quintet) state. The ground-state properties of S = 1 systems are challenging to study using conventional spectroscopic methods, and consequently, the electronic structure of trans-[CrCl2(dmpe)2] has remained largely unexplored. In this present work, we have employed high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy to characterize the ground-state electronic structure of trans-[CrCl2(dmpe)2]. This analysis yielded a complete set of spin Hamiltonian parameters for this S = 1 complex: D = +7.39(1) cm-1, E = +0.093(1) (E/D = 0.012), and g = [1.999(5), 2.00(1), 2.00(1)]. To develop a detailed electronic structure description for trans-[CrCl2(dmpe)2], we employed both classical ligand-field theory and quantum chemical theory (QCT) calculations, which considered all quintet, triplet, and singlet ligand-field states. While the high density of states suggests an unexpectedly complex electronic structure for this "simple" coordination complex, both the ligand-field and QCT methods were able to reproduce the experimental spin Hamiltonian parameters quite nicely. The QCT computations were also used as a basis for assigning the electronic absorption spectrum of trans-[CrCl2(dmpe)2] in toluene.

Fluorination Reactions at a Platinum Carbene Complex: Reaction Routes to SF3 , S(=O)F and Fluorido Complexes.

The electron‐rich Pt complex [Pt(IMes)2] (IMes: [1,3‐bis(2,4,6‐trimethylphenyl)‐2‐imidazolinylidine]) can be used as precursor for the syntheses of a variety of fluorido ligand containing compounds. The sulfur fluoride SF4 undergoes a rapid oxidative addition at Pt0 to yield trans‐[Pt(F)(SF3)(IMes)2]. A photolytic reaction of SF6 at [Pt(IMes)2] in the presence of IMes gave the fluorido complexes trans‐[Pt(F)2(IMes)2] and trans‐[Pt(F)(SF3)(IMes)2] along with trans‐[Pt(F)(SOF)(IMes)2] and trans‐[Pt(F)(IMes’)(IMes)] (IMes’: cyclometalated IMes ligand), the latter being products produced by reaction with adventitious water. trans‐[Pt(F)(SOF)(IMes)2] and trans‐[Pt(F)2(IMes)2] were synthesized independently by treatment of [Pt(IMes)2] with SOF2 or XeF2. A reaction of [Pt(IMes)2] with a HF source gave trans‐[Pt(H)(F)(IMes)2], and an intermediate bifluorido complex trans‐[Pt(H)(FHF)(IMes)2] was identified. Compound trans‐[Pt(H)(F)(IMes)2] converts in the presence of CsF into trans‐[Pt(F)(IMes’)(IMes)].

Synthesis, coordination and catalytic use of phosphinoferrocene ligands bearing 6-phospha-2,4,6-trioxaadamantane P-donor moieties

1,1’-Bis(diphenylphosphino)ferrocene (dppf) and structurally related ferrocene bis-phosphines are indispensable ligands for coordination chemistry and catalysis. This contribution focuses on the coordination behaviour and catalytic properties of two dppf congeners bearing 1,3,5,7-tetramethyl-2,4,6-trioxa-8-phosphatricyclo[3.3.1.13,7]decane-8-yl groups (CgP) as the P-donor moieties, viz. Ph2PfcCgP (1) and its semi-homologous counterpart Ph2PfcCH2CgP (2; fc = ferrocene-1,1’-diyl). In reactions with a PdCl2 source, compound 1 produced exclusively the cis-chelate complex [PdCl2(1-κ2P,P’)], while the homologated ligand 2 afforded a complex mixture of compounds which equilibrated upon heating in methanol in favour of the symmetrical dimeric complex trans-[(µ-2)PdCl2]2 as a mixture of racemic and meso isomers. Notably, in aqueous Pd-catalysed cyanation of aryl bromides and Suzuki-Miyaura-type cross-coupling of benzoyl chlorides with boronic acids producing benzophenones, catalysts generated in situ from bis-phosphine 1 and Pd(II) sources were often more active than their counterparts resulting from dppf and 2.

Synthesis and characterization of new platinum(II) complexes with cyclic iminoether-type ligands having the azomethine group out of cycle

The trans isomer of cisplatin, transplatin, is an inactive platinum drug; however, a number of analogues, such as trans complexes with iminoether, thiazole and isopropylamine ligands, demonstrate promising antitumor activity in vitro and in vivo. In the particular case of iminoether ligands, HN=C(R)OR′, due to the presence of a double bond, two configurations, E and Z, can exist and isomerization between the two forms has been observed sometime in solution. An attempt to stabilize the ligand configuration was to block the geometry of the ligand by inserting the iminic double bond into a cycle; this led to the synthesis of platinum complexes with 5-methoxy-3,4-dihydropyrrole, ▪, and 2-methyl-4,5-dihydro-1,3-oxazole, ▪, in which, however, the ligand is deprived of a proton on the coordinating iminic nitrogen considered to be a key feature for the interaction of the platinum drug with target DNA. In this paper we describe the synthesis and characterization of platinum complexes with the 2-iminotetrahydrofuran ligand, ▪, where the iminic nitrogen is outside the cycle and can keep its proton. Apart from the isolation of the pure E and Z isomers (compounds 2-E and 2-Z) we also prepared the diiodido derivative (compound 1) and the cis isomer (compound 3).

Syntheses and Structures of trans-bis(Alkenylacetylide) Ruthenium Complexes.

A series of ruthenium alkenylacetylide complexes trans-[Ru{C≡CC(=CH2 )R}Cl(dppe)2 ] (R=Ph (1 a), c C4 H3 S (1 b), 4-MeS-C6 H4 (1 c), 3,3-dimethyl-2,3-dihydrobenzo[b]thiophene (DMBT) (1 d)) or trans-[Ru{C≡C-c C6 H9 }Cl(dppe)2 ] (1 e) were allowed to react with the corresponding propargylic alcohol HC≡CC(Me)R(OH) (R=Ph (A), c C4 H3 S (B), 4-MeS-C6 H4 (C), DMBT (D) or HC≡C-c C6 H10 (OH) (E) in the presence of TlBF4 and DBU to presumably give alkenylacetylide/allenylidene intermediates trans-[Ru{C≡CC(=CH2 )R}{C=C=C(Me)}(dppe)2 ]PF6 ([2]PF6 ). These complexes were not isolated but deprotonated to give the isolable bis(alkenylacetylide) complexes trans-[Ru{C≡CC(=CH2 )R}2 (dppe)2 ] (R=Ph (3 a), c C4 H3 S (3 b), 4-MeS-C6 H4 (3 c), DMBT (3 d)) and trans-[Ru{C≡C-c C6 H9 }2 (dppe)2 ] (3 e). Analogous reactions of trans-[Ru(CH3 )2 (dmpe)2 ], featuring the more electron-donating 1,2-bis(dimethylphosphino)ethane (dmpe) ancillary ligands, with the propargylic alcohols A or C and NH4 PF6 in methanol allowed isolation of the intermediate mixed alkenylacetylide/allenylidene complexes trans-[Ru{C≡CC(=CH2 )R}{C=C=C(Me)}(dmpe)2 ]PF6 (R=Ph ([4 a]PF6 ), 4-MeS-C6 H4 ([4 c]PF6 ). Deprotonation of [4 a]PF6 or [4 c]PF6 gave the symmetric bis(alkenylacetylide) complexes trans-[Ru{C≡CC(=CH2 )R}2 (dmpe)2 ] (R=Ph (5 a), 4-MeS-C6 H4 (5 c)), the first of their kind containing the dmpe ancillary ligand sphere. Attempts to isolate bis(allenylidene) complexes [Ru{C=C=C(Me)R}2 (PP)2 ]2+ (PP=dppe, dmpe) from treatment of the bis(alkenylacetylide) species 3 or 5 with HBF4 ⋅ Et2 O were ultimately unsuccessful.

Platinum Indolylphosphine Fluorido and Polyfluorido Complexes: An Interplay between Cyclometallation, Fluoride Migration, and Hydrogen Bonding.

The reaction of [PtCl2(COD)] (COD=1,5‐cyclooctadiene) with diisopropyl‐2‐(3‐methyl)indolylphosphine (iPr2P(C9H8N)) led to the formation of the platinum(ii) chlorido complexes, cis‐[PtCl2{iPr2P(C9H8N)}2] (1) and trans‐[PtCl2{iPr2P(C9H8N)}2] (2). The cis‐complex 1 reacted with NEt3 yielding the complex cis‐[PtCl{κ 2‐(P,N)‐iPr2 P(C9H7 N)}{iPr2P(C9H8N)}] (3) bearing a cyclometalated κ 2‐(P,N)‐phosphine ligand, while the isomer 2 with a trans‐configuration did not show any reactivity towards NEt3. Treatment of 1 or 3 with (CH3)4NF (TMAF) resulted in the formation of the twofold cyclometalated complex cis‐[Pt{κ 2‐(P,N)‐iPr2 P(C9H7 N)}2] (4). The molecular structures of the complexes 1–4 were determined by single‐crystal X‐ray diffraction. The fluorido complex cis‐[PtF{κ 2‐(P,N)‐iPr2 P(C9H7 N)}{iPr2P(C9H8N)}] ⋅ (HF)4 (5 ⋅ (HF)4) was formed when complex 4 was treated with different hydrogen fluoride sources. The Pt(ii) fluorido complex 5 ⋅ (HF)4 exhibits intramolecular hydrogen bonding in its outer coordination sphere between the fluorido ligand and the NH group of the 3‐methylindolyl moiety. In contrast to its chlorido analogue 3, complex 5 ⋅ (HF)4 reacted with CO or the ynamide 1‐(2‐phenylethynyl)‐2‐pyrrolidinone to yield the complexes trans‐[Pt(CO){κ 2‐(P,C)‐iPr2 P(C9H7NCO)}{iPr2P(C9H8N)}][F(HF)4] (7) and a complex, which we suggest to be cis‐[Pt{C=C(Ph)OCN(C3H6)}{κ 2‐(P,N)‐iPr2 P(C9H7 N)}{iPr2P(C9H8N)}][F(HF)4] (9), respectively. The structure of 9 was assigned on the basis of DFT calculations as well as NMR and IR data. Hydrogen bonding of HF and NH to fluoride was proven to be crucial for the existence of 7 and 9.

Synthesis, Structure, and Ammonia Oxidation Catalytic Activity of Ru-NH3 Complexes Containing Multidentate Polypyridyl Ligands.

Ammonia (electro)oxidation with molecular catalysts is a rapidly developing topic with wide practical applications ahead. We report here the catalytic ammonia oxidation reaction (AOR) activity using [Ru(tda-κ-N3O)(py)2], 2, (tda2- is 2,2':6',2''-terpyridine-6,6''-dicarboxylate; py is pyridine) as a catalyst precursor. Furthermore, we also describe the rich chemistry associated with the reaction of Ru-tda and Ru-tPa (tPa-4 is 2,2':6',2''-terpyridine-6,6''-diphosphonate) complexes with NH3 and N2H4 using [RuII(tda-κ-N3O)(dmso)Cl] (dmso is dimethyl sulfoxide) and [RuII(tPa-κ-N3O)(py)2], 8, as synthetic intermediates, respectively. All the new complexes obtained here were characterized spectroscopically by means of UV-vis and NMR. In addition, a crystal X-ray diffraction analysis was performed for complexes trans-[RuII(tda-κ-N3)(py)2(NH3)], 4, trans-[RuII(tda-κ-N3)(N-NH2)(py)2], 5, cis-[RuII(tda-κ-N3)(py)(NH3)2], 6 (30%), and cis-[RuII(tda-k-N3)(dmso)(NH3)2], 7 (70%). The AOR activity associated with 2 and 8 as catalyst precursors was studied in organic and aqueous media. For 2, turnover numbers of 7.5 were achieved under bulk electrolysis conditions at an Eapp = 1.4 V versus normal hydrogen electrode in acetonitrile. A catalytic cycle is proposed based on electrochemical and kinetic evidence.

Blue-to-red light triggered nitric oxide release in cytotoxic/cytostatic ruthenium nitrosyl complexes bearing biomimetic ligands

The nitrosyl complexes trans(L,L)-[RuNO(L)2Cl3] (L = indazole (I) and imidazole (II)) were synthesized and comprehensively characterized including by single crystal X-ray diffraction. Both compounds exhibit light-induced NO release under blue or green light (445, 532 nm) irradiation of DMSO solutions, complex (I) also shows NO release under red 638 nm irradiation, which is in the range of phototherapeutic window (600–1100 nm). The photolysis was investigated by spectroscopic (UV–vis, IR, EPR) and electrochemical (CV) techniques, and it was shown that NO can be activated by both light excitation or electrochemically. Performed DFT calculations allow to reveal possible charge transfers responsible for the NO activation. The dynamics of ruthenium species after irradiation consists of a transformation of [Ru3+(DMSO)(L)2Cl3] complex to a more stable [Ru2+(DMSO)(L)2Cl3]− product. The cytotoxic test of both complexes against breast adenocarcinoma cell line MCF-7 shows, imidazole complex (II) exhibits cytostatic action at concentrations higher than 25 µM, while indazole complex (I) is highly cytotoxic with IC50 value of 3.1 ± 0.6 µM, which is an order of magnitude higher than the activity of cisplatin. New knowledge open the prospects for the design and synthesis of prominent compounds trans(L,L)-[RuNO(L)2Cl3], where the nature of L influences the photo-sensitive and cytotoxic properties of the resulted complexes.

Density Functional Theory Study on the 193Ir Mössbauer Spectroscopic Parameters of Vaska's Complexes and Their Oxidative Adducts.

In the present study, density functional theory (DFT) calculation was applied to Vaska's complexes of formula trans-[IrIX(CO)(PPh3)2] and their oxidative adducts with small molecules (YZ) including H2, i.e., trans-[IrIIIClYZ(CO)(PPh3)2], to successfully correlate the electronic states of the complexes with the corresponding 193Ir Mössbauer spectroscopic parameters. After confirming the reproducibility of the DFT methods for elucidating the equilibrium structures and 193Ir Mössbauer isomer shifts of the octahedral Ir complexes, the isomer shifts and quadrupole splitting values of Vaska's complexes and their oxidative adducts were calculated. A bond critical point analysis revealed that the tendency in the isomer shifts was correlated with the strength of the covalent interaction in the coordination bonds. In an electric field gradient (EFG) analysis of the oxidative adducts, the sign of the principal axis was found to be positive for the complex with YZ = Cl2 and negative for the complex with YZ = H2. This reversal of the sign of the EFG principal axis was caused by the difference in the electron density distribution for the coordination bonds between Ir and YZ, according to a density of states analysis.

Synthesis of mononuclear and dinuclear palladium (II) complexes containing oxadithioether ligands and their catalytic activities in norbornene polymerization

AbstractThe Pd (II) complexes trans‐[PdCl2(μ‐L)]2 and [Pd(acac)(L)][BF4] (L = RS(CH2)2O(CH2)2SR, R = Me, Et, nPr, iPr, nBu, iBu, n‐hexyl, benzyl) were obtained through the reaction of Pd(cod)Cl2 or [Pd(acac)(MeCN)2][BF4] with one equivalent of oxadithioether (L). The structural features of these complexes were analyzed by nuclear magnetic resonance (NMR) and Fourier‐transform infrared spectroscopy (FTIR), as well as electrospray ionisation mass spectrometry and density functional theory calculations. The complexes di‐μ‐(2,10‐dimethyl‐6‐oxa‐3,9‐dithiaundecane‐κ2S,S′)‐bis[trans‐dichloropalladium (II)] and (acetylacetonate‐κ2O,O′)(2,10‐dimethyl‐6‐oxa‐3,9‐dithiaundecane‐κ2S,S′)palladium (II) tetrafluoroborate were characterized by X‐ray diffractometry. The X‐ray structures of each complex indicate an axial M–O interaction formed by the endodentate conformation of the oxadithioether ligand. Palladium (II) dichloride complexes with oxadithioethers were demonstrated to have a 16‐membered dinuclear structure with a trans‐configured S2PdCl2 fragment. In the case of cationic palladium acetylacetonate complexes, only mononuclear complexes with a cis configuration of the oxadithioether fragment were observed. Variable temperature 1H and 13C NMR studies of the complexes demonstrate dynamic bonding of the oxadithioether ligands consistent with the presence of diastereoisomers that differ in the orientation of the S‐R groups along with both endodentate and exodentate bonding modes in solution. FTIR studies of the complexes indicate the presence of isomers in the solid state. The palladium catalyst precursors trans‐[PdCl2(μ‐L)]2 and [Pd (acac)(L)][BF4] were found to be active in the addition polymerization of norbornene. In the presence of cocatalysts, such as diisobutylaluminum chloride and boron trifluoride etherate, Pd (II) complexes exhibited activities in the range of 105 to 107 g of polymer (mol of Pd)−1 h−1. The catalyst systems showed good thermostability with a high activity of 1.43 × 107 g of polymer (mol of Pd)−1 h−1 at 75°C. These complexes are examples of Pd (II) complexes bearing thioether ligands, which are rarely observed in the field of olefin polymerization.

Tetrabromoethane as σ-Hole Donor toward Bromide Ligands: Halogen Bonding between C2H2Br4 and Bromide Dialkylcyanamide Platinum(II) Complexes

The complexes trans-[PtBr2(NCNR2)2] (R2 = Me21, (CH2)52) were cocrystallized with 1,1,2,2-tetrabromoethane (tbe) in CH2Cl2 forming solvates 1·tbe and 2·tbe, respectively. In both solvates, tbe involved halogen bonding, viz. the C–Br···Br–Pt interactions, were detected by single-crystal X-ray diffractions experiments. Appropriate density functional theory calculations (M06/def2-TZVP) performed for isolated molecules and complex-tbe clusters, where the existence of the interactions and their noncovalent nature were confirmed by electrostatic potential surfaces (ρ = 0.001 a.u.) for isolated molecules, topology analysis of electron density, electron localization function and HOMO-LUMO overlap projections for clusters.

Ni(II) and Cu(III) organometallic complexes of trans doubly N-confused porphodimethenes: Synthesis, spectroscopic and theoretical characterization

Synthesis, spectroscopic and theoretical investigations of hitherto unknown highly stable nickel, and copper organometallic complexes of trans-doubly N-confused porphodimethenes are reported. The distorted square planar Ni organometallic complex has been susceptible to trivial +2 oxidation state of Ni via single CH activation and another weak Ni-C bond with C-H agostic interaction while the diamagnetic near square planar copper complex exhibits the atypical +3 oxidation state of copper via double inner CH activation. The conformational preorganization and metallation induced conformational reorganization owing to the formation of M-C bond formations by both nickel and copper have been thoroughly investigated by various spectroscopic techniques and in-depth DFT level theoretical calculations.

Synthesis, structure and photophysical properties of mono- and di-nuclear platinum(II) acetylide complexes

The reactions of cis-[PtCl2{P(C6H4CH3-p)3}2] with HCC-C6H4R-p (R = NO2, CH3, OCH3), in the presence of CuCl catalyst, lead to the formation of mono-acetylide complexes trans-[PtCl{P(C6H4CH3-p)3}2(CC-C6H4R-p)] (R = NO21; R = CH32; R = OCH3, 3). These monochloro-acetylide complexes were further employed for the synthesis of symmetrical dinuclear platinum complexes. Thus, the reactions of HCC-C6H2(2,5-OC4H9)2-CCH with two molar equivalents of 1, 2 and 3, in the presence of CuCl catalyst, affords dinuclear complexes trans-trans-[Pt2{P(C6H4CH3-p)3}4(CC-C6H4R-p)2(CC-C6H2(OC4H9)2-CC)](R = NO24; R = CH35; R = OCH3; 6). All these mono- and dinuclear platinum complexes have been characterized by IR, 1H NMR, 31P NMR spectroscopy, and the molecular structures of 2 and 5 were unequivocally established by single crystal X-ray diffraction analyses. The thermal stability of these complexes has been studied by thermogravimetric analysis (TGA). The photophysical properties of these materials have been probed using electronic absorption and emission spectroscopy, and z-scan techniques.

Studies on the reactivity of Rh(I) complexes towards SF5Cl

Sulfur chloride pentafluoride reacts with the rhodium(I) NHC complexes (N-heterocyclic carbene) trans-[Rh(Cl)(CO)(IMes)2] (1) and trans-[Rh(F)(CO)(IMes)2] (5) to give the cationic square-pyramidal complexes trans,trans-[Rh(Cl)2(CO)(IMes)2][SF5] (2) and trans-[Rh(Cl)(F)(CO)(IMes)2][SF5] (6) at 183 K. The compounds convert into the fluorido complexes trans,trans-[Rh(Cl)2(F)(CO)(IMes)2] (4) and cis,trans-[Rh(Cl)(F)2(CO)(IMes)2] (7) at ambient temperatures. In the reaction of 1 the rhodium(III) fluoroacyl complex trans,trans-[Rh(Cl)2(COF)(IMes)2] (3) was identified as additional product. DFT calculations were carried out in order to determine the configurations of the complexes 2, 3 and 6. For comparison the phosphine complex, trans-[Rh(F)(CO)(PEt3)2] (8) was treated with SF5Cl to yield cis,trans-[Rh(F)2(Cl)(CO)(PEt3)2] (9) at 183 K. At 213 K the sulfanyl complex cis,trans-[Rh(F)2(SF3)(CO)(PEt3)2] (10) was also identified.

Ni-Catalyzed Borylation of Aryl Sulfoxides.

A nickel/N‐heterocyclic carbene (NHC) catalytic system has been developed for the borylation of aryl sulfoxides with B2(neop)2 (neop=neopentyl glycolato). A wide range of aryl sulfoxides with different electronic and steric properties were converted into the corresponding arylboronic esters in good yields. The regioselective borylation of unsymmetric diaryl sulfoxides was also feasible leading to borylation of the sterically less encumbered aryl substituent. Competition experiments demonstrated that an electron‐deficient aryl moiety reacts preferentially. The origin of the selectivity in the Ni‐catalyzed borylation of electronically biased unsymmetrical diaryl sulfoxide lies in the oxidative addition step of the catalytic cycle, as oxidative addition of methoxyphenyl 4‐(trifluoromethyl)phenyl sulfoxide to the Ni(0) complex occurs selectively to give the structurally characterized complex trans‐[Ni(ICy)2(4‐CF3‐C6H4){(SO)‐4‐MeO‐C6H4}] 4. For complex 5, the isomer trans‐[Ni(ICy)2(C6H5)(OSC6H5)] 5‐I was structurally characterized in which the phenyl sulfinyl ligand is bound via the oxygen atom to nickel. In solution, the complex trans‐[Ni(ICy)2(C6H5)(OSC6H5)] 5‐I is in equilibrium with the S‐bonded isomer trans‐[Ni(ICy)2(C6H5)(SOC6H5)] 5, as shown by NMR spectroscopy. DFT calculations reveal that these isomers are separated by a mere 0.3 kJ/mol (M06/def2‐TZVP‐level of theory) and connected via a transition state trans‐[Ni(ICy)2(C6H5)(η2‐{SO}‐C6H5)], which lies only 10.8 kcal/mol above 5.