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The chemically achiral title mol­ecule, [Ti(C4H10N)2(C21H16N2)], crystallizes in the chiral space group P21. All three N atoms coordinating to the TiIV atom adopt planar environments [sums of valence angles = 359.5 (6), 360.0 (7) and 360.0 (6)°], which is indicative of pπ–dπ donation from all of these N atoms to the metal and, thus, of the formal 18 e− nature of the complex. The overall coordination about the TiIV atom is distorted tetra­hedral, assuming the cyclo­penta­dienyl ring occupies one coordination site. The Ti—Nimidazole amide-type bond is longer by approximately 0.16 Å than the other two Ti—Namide bonds.

The dinuclear title complex, [Ti2(C10H15)2(C6F5O)4O], features two TiIV atoms bridged by an O atom, which lies on an inversion centre. The TiIV atom is bonded to a η5-penta­methyl­cyclo­penta­dienyl ring, two penta­fluoro­phenolate anions and to the bridging O atom. The environment around the TiIV atom can be considered as a distorted tetra­hedron. The cyclo­penta­dienyl ring is disordered over two sets of sites [site occupancy = 0.824 (8) for the major component].

In the title compound, [Ti(C8H13Si)(C11H21Si2)Cl2], the TiIV atom is bonded to two Cl atoms, one 1,3-bis­(trimethyl­sil­yl)cyclo­penta­dienyl (Si2Cp) and one (trimethyl­sil­yl)cyclo­penta­dienyl ring (SiCp). The Si2Cp centroid–titanium distance is 2.0763 (10) Å and the SiCp centroid–titanium distance is 2.0793 (10) Å. The angle subtended at the Ti atom by the centroids of both cyclo­penta­dienyl rings is 131.22 (4)° and the Cl—Ti—Cl angle is 94.14 (2)°.

The mol­ecular structure of the title compound, [Fe(C5H5)(C13H4F5)], consists of a ferrocenyl group and a 2,3,4,5,6-penta­fluoro­benzene group linked through an ethyne spacer. The crystal packing is dominated by inter­molecular C—H⋯F hydrogen bonds, C—F⋯π inter­actions between the penta­fluoro­benzene groups [F⋯centroid distances = 3.882 (2) and 3.884 (2) Å] and π–π inter­actions between the penta­fluoro­benzene and cyclo­penta­dienyl rings [centroid–centroid distance = 3.741 (1) Å].

A series of ferrocenyl ester complexes, varying the lipophilic character of the pendant groups, was prepared and characterized by spectroscopic and analytical methods. The syntheses of Fe(C5H4CO2CH3)2, Fe(CpCOOCH3) (CpCOO CH2CH3), and Fe(CpCOOCH2CH3)2 are reported. The solid-state structure of Fe(C5H4CO2CH3)2 has been determined by X-ray crystallography. Fe(C5H4CO2CH3)2 has the cyclopentadienyl rings virtually in an eclipsed conformation with the pendant groups not completely opposite to each other. Cyclic voltammetry characterization showed that the functionalized ferrocenes oxidize at potentials, Epa, higher than ferrocene as a result of the electro withdrawing effect of the pendant groups on the cyclopentadienyl ligand. The cytotoxicities of Fe(C5H4CO2CH2CH2OH)2, Fe(C5H4CO2CH2CH=CH2)2, Fe(C5H4CO2CH3)2, Fe(CpCOOCH3)(CpCOOCH2CH3), and Fe(CpCOOCH2CH3)2 in colon cancer HT-29 and breast cancer MCF-7 cell lines were measured by the MTT biological viability assay and compared to ferrocene and ferrocenium. Fe(C5H4CO2CH2CH=CH2)2 showed the best IC50 values, 180(10) μM for HT-29 and 190(30) μM for MCF-7 cell lines, with cytotoxicities similar to ferrocenium. The cytotoxic data suggest that as we increase the lipophilic character of the functionalized ferrocene, the cytotoxicity improves approaching to the cytotoxic activity of ferrocenium.

The title dinuclear titanocene, [Ti2(C8H9O)(C18H25Si)2Cl3O], contains one Ti atom tetra­hedrally coordinated by two Cl atoms, a bridging O atom and the substituted cyclo­penta­dienyl ligand, and another Ti atom tetra­hedrally coordinated by a Cl atom, a bridging O atom, the 2,6-dimethyl­phenolate ligand and the substituted cyclo­penta­dienyl ligand. The bridging O atom lies on a twofold rotation axis.

In the centrosymmetric title compound, [Er2(C5H5)4(C4H9O)2], each Er atom is in a distorted tetra­hedral coordination environment, coordinated by two cyclo­penta­dienyl rings and two tert-but­oxy groups, forming a dimeric complex bridged through the tert-but­oxy groups.

Reaction of the tricarbon­yl{η5-[2-(dimethyl­amino)eth­yl]cyclo­penta­dien­yl}molybdenum anion and dichlorido­diphenyl­stannane affords the title compound, [MoSn(C6H5)2Cl(C9H14N)(CO)3], which exhibits a four-legged piano-stool geometry with chlorido­diphenyl­stannyl ligands unperturbed by the pendant 2-(dimethyl­amino)ethyl groups. The Mo—Sn bond length [2.7584 (5) Å] and the distortion of the tetra­hedral tin coordination geometry are similar to those observed in related tin-substituted tricarbonyl­molybdenum and -tungsten complexes.

In the title compound, [Fe(C5H5)(C15H11N2O)], the cyclo­penta­dienyl rings are essentially eclipsed, and the dihedral angle between the cyclo­penta­dienyl ring planes is 0.632 (10)°. The Fe atom is slightly closer to the substituted cyclo­penta­dienyl ring, with an Fe–centroid distance of 1.6374 (3) Å [1.6494 (3) Å for the unsubstituted ring]. The amide group is essentially coplanar with the substituted cyclo­penta­dienyl ring, with an N—C(O)—C—C torsion angle of 2.3 (3)°.

In the crystal structure of the title substituted ferrocene complex, [Fe(C19H18O2P)2], the FeII atom lies on a twofold rotation axis, giving an eclipsed cyclo­penta­dienyl conformation with a ring centroid separation of 3.292 (7) Å and an Fe—C bond-length range of 2.0239 (15)–2.0521 (15) Å. In the ligand, the cyclo­penta­dienyl ring forms dihedral angles of 60.36 (6) and 82.93 (6)° with the two benzene rings of the diphenyl­phosphine group, while the dihedral angle between the benzene rings is 67.4 (5)°.

The title compound, [TiW(C5H5)2(C7H5O)Cl(CO)5], consists of two metal centres, with a (tungstenpenta­carbon­yl)oxy­phenyl­carbene unit coordinated by a titanocene chloride. The oxycarbene group is nearly planar, with the phenyl ring twisted by an angle of 39.1 (2)° with respect to this plane. One of the cyclo­penta­dienyl rings undergoes an offset face-to-face π–π inter­action [3.544 (6) Å] with the symmetry-related cyclo­penta­dienyl ring of a neighbouring mol­ecule.

Nine amide-functionalized titanocenyls have been synthesized and characterized by spectroscopic and analytical methods and the solid state structure of Cp(CpCO-NH-C6H4-OCF3)TiCl2 was determined by single crystal X-ray diffraction. X-ray analysis of Cp(CpCO-NH-C6H4-OCF3)TiCl2 showed that titanium is in a pseudo tetrahedral geometry and contains a Ti-O(amide) coordination. In principle, Ti-O coordination should provide more hydrolytic stability to the corresponding titanocenyls than titanocene dichloride. The cytotoxic activities of these amide-functionalized titanocenyls on HT-29 colon cancer cell line were determined by MTT assay to elucidate structure-activity relationship. All complexes were more cytotoxic than titanocene dichloride and there is no correlation between the para substituents on the phenyl ring and their cytotoxicities.

In the title compound, [Zr(C16H13P)Cl2], the geometry at the metal atom is distorted tetra­hedral; the Cl—Zr—Cl angle is 101.490 (16)° and the cyclo­penta­dienyl (Cp) centroids subtend an angle of 122.63 (3)° at the Zr atom. The P atom lies 0.474 (3) and 0.496 (3) Å out of the planes of the Cp rings. The C—P—C angle of 91.42 (7)° reflects the pincer effect of the two Cp rings. Three C—H⋯Cl, one C—H⋯P, one C—H⋯π and one Cl⋯P inter­action link the mol­ecules to form thick layers parallel to the bc plane.

In the title compound, [Fe(C20H21NPS)(C17H14PS)]·CH2Cl2, both cyclo­penta­dienyl (Cp) rings constituting the ferrocene unit are substituted by a sulfur-protected diphenyl­phosphine. One of the Cp ligands is additionally substituted by a dimethyl­amino­methyl group causing the chirality of the mol­ecule. Surprisingly, although the synthetic procedure yielded the title compound as a racemic mixture, the reported crystal is enanti­omerically pure with the R absolute configuration. The dimethyl­amino group is exo with respect to the Cp ring. Both diphenyl­thio­phosphine groups are trans with respect to the centroid–Fe–centroid direction. Weak intra­molecular C—H⋯S and C—H⋯π inter­actions between symmetry-related mol­ecules are observed. The contribution of the disordered solvent was removed from the refinement using SQUEEZE in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148–155].

The reactions of bis(cyclopentadienyl)titanium(IV) dichloride with a new class of thiosemicarbazone (LH2), derived by condensing isatin with different N(4)-substituted thiosemicarbazides, have been studied and products of type [Cp2Ti(L)] have been isolated. On the basis of various physico-chemical and spectral studies, five coordinate structures have been assigned to these derivatives. Toxicity studies of titanocene complexes at tbur different concentrations have been carried out against snail Lymnaea acuminata. The effect of most potent compounds on the activity of acetylcholinesterase enzyme, which inhibits the activity of enzyme, possibly by the formation of enzyme-inhibitor complex, was also studied.

The reaction of [Pd(MeCN)4](BF4)2 with 2,2′-bipyrimidine (bpm) in MeCN–CHCl3 afforded the title compound, [Pd(C8H6N4)2](BF4)2·C2H3N. The asymmetric unit contains two half complexes, with the PdII atoms both lying on a twofold axis. Each metal atom adopts a tetra­hedrally distorted square-planar geometry. In the crystal, [Pd(bpm)2] dications are linked by C—H⋯N hydrogen bonds, forming chains parallel to the b axis. The chains are further linked by C—H⋯F and C—H⋯N inter­actions involving the tetra­fluoro­borate anions and acetonitrile mol­ecules. In this way, each chain interacts with six surrounding chains to generate the observed three-dimensional structure.

In the title complex, [Ru(C7H8)(C10H15)]PF6, the cation lies on a mirror plane and the anion lies on an inversion center. The distance between the Ru atom and the centroid of the benzene ring is 1.706 (5) Å and the distance between the Ru atom and the cyclo­penta­dienyl ring is 1.811 (5) Å. The crystal structure is stabilized by weak C—H⋯F hydrogen bonds. The H atoms of the methyl groups which lie on the mirror plane are disordered over two sites with equal occupancies.

In the title four-coordinate complex, [Ti(C2H6N)2(C31H28O4)], two symmetry-independent mol­ecules are present in the asymmetric unit. The TiIV atom displays a distorted tetra­hedral geometry, with Ti—O bond lengths ranging from 1.805 (3) to 1.830 (3) Å and O—Ti—O ligand bite angles of 100.16 (12) and 101.36 (12)°. The short Ti—N bond distances, ranging from 1.877 (4) to 1.905 (4) Å, indicate strong bonding between the TiIV atom and the dimethyl­amide ligands.

In the title complex, [FeZn(C5H5)(C20H14N3)(C12H8N2)](ClO4)2·CH3CN, the ZnII atom is five-coordinated by a tridentate chelating 4′-ferrocenyl-2,2′:6′,2′′-terpyridine (fctpy) ligand and a bidentate chelating 1,10-phenanthroline (phen) ligand in a distorted square-pyramidal environment with a phen N atom located at the apical position [Zn—N = 2.259 (4) Å]. The terpyridyl motif in each fctpy ligand is coplanar, but the cyclo­penta­dienyl ring is twisted by 9.5 (2)° out of coplanarity with each central pyridine. The two cyclo­penta­dienyl rings of the ferrocenyl group are almost eclipsed with a deviation of 4.5 (1)°. In addition, inter­molecular π–π inter­actions [centroid–centroid distance 3.753 (2) Å] are present between the cyclo­penta­dienyl and outer pyridyl rings of the fctpy ligands. One of the perchlorate anions is equally disordered over two positions.

In the title compound, [FePdBr(C5H5)(C11H10N2)(C26H36NP)]·CH2Cl2, the Pd atom displays a distorted square-planar coordination environment. The five-membered metallacycle adopts an envelope conformation with the coordinated cyclo­penta­dienyl C atom 0.4222 (4) Å out of plane. The dihedral angle between the pyrimidinyl ring and substituted cyclo­penta­dienyl ring is 21.47 (2)°. In the crystal structure, the dimeric unit is generated through the C—H⋯π contact via a crystallographic inversion centre, while the C—H⋯Cl contacts in the dimeric centre link the dichlormethane mol­ecules with the Pd complex mol­ecules.

The racemic title compound, [FePdCl2(C5H5)(C36H29P2)]·2(CH3)2SO, features a Pd-chelating 1,3-diphosphine, which is substituted at a P-bearing asymmetric C atom by a ferrocenyl group. The PdII atom is in a distorted quadratic coordination by two P and two Cl atoms with bond lengths of 2.2414 (3) and 2.2438 (3) Å for Pd—P, and 2.3452 (3) and 2.3565 (3) Å for Pd—Cl. The conformation of the Pd complex is controlled by an intra­molecular slipped π–π stacking inter­action between a phenyl and a cyclo­penta­dienyl ring with corresponding C⋯C distances starting at 3.300 (2) Å and the distance between ring centroids being 3.674 (2) Å. The crystal structure is stabilized by C—H⋯Cl and C—H⋯O hydrogen bonds. The (CH3)2SO solvent mol­ecules are arranged in layers parallel to (101) and are linked in pairs by C—H⋯O inter­actions. One (CH3)2SO mol­ecule is orientationally disordered [occupancy ratio 0.8766 (17):0.1234 (17)] with sulfur in two positions at both sides of its C2O triangle.

The title compound, [Ru2(C13H15S)2(CO)4], is a centrosymmetric binuclear metal–carbonyl complex containing an Ru—Ru single bond [2.7511 (8) Å]. Each RuI atom is coordinated by two bridging carbonyl ligands, one terminal carbonyl ligand and one η5-cyclo­penta­dienyl group. The complex has a trans conformation and the two cyclo­penta­dienyl ring planes are parallel. The crystal structure involves weak C—H⋯O hydrogen bonds.

In the cobaltocenium group of the title compound, [AuCo(C5H5)(C17H14P)Cl]PF6, the substituted cyclo­penta­dienyl (Cps) and the unsubstituted cyclo­penta­dienyl (Cp) ring planes are almost parallel, making a dihedral angle of 3.1 (3)°. The C atoms in Cp and Cps are in an eclipsed conformation. The AuI atom is coordinated by a P atom from the diphenyl­phosphanyl group and a Cl atom in an almost linear arrangement [P—Au—Cl = 178.15–(7)°]. Two hexa­fluorido­phosphate anions are each located on a twofold rotation axis. In the crystal, the complex cations and hexa­fluorido­phosphate anions are linked via inter­molecular C—H⋯F hydrogen bonds.

The title compound, [Fe(C5H5)(C21H24NPS)]I·CHCl3, is built up from a (ferrocenylmeth­yl)trimethyl­ammonium cation, a iodine anion and a chloro­form solvent mol­ecule, all residing in general positions. The N atom of the ammonium group is displaced by 1.182 (2) Å from the plane of the substituted cyclo­penta­dienyl (Cp) ring towards the Fe atom, whereas the C atom attached to the same Cp ring is slightly below this plane by −0.128 (2) Å. These deviations might result from weak agostic interactions between the two H atoms of the CH2 group and the Fe atom.

19F NMR spectroscopy has proved to be a valuable tool to monitor functionally important conformational transitions of nucleic acids. Here, we present a systematic investigation on the application of 5-fluoro pyrimidines to probe DNA and RNA secondary structures. Oligonucleotides with the propensity to adapt secondary structure equilibria were chosen as model systems and analyzed by 1D 19F and 1H NMR spectroscopy. A comparison with the unmodified analogs revealed that the equilibrium characteristics of the bistable DNA and RNA oligonucleotides were hardly affected upon fluorine substitution at C5 of pyrimidines. This observation was in accordance with UV spectroscopic melting experiments which demonstrated that single 5-fluoro substitutions in double helices lead to comparable thermodynamic stabilities. Thus, 5-fluoro pyrimidine labeling of DNA and RNA can be reliably applied for NMR based nucleic acid secondary structure evaluation. Furthermore, we developed a facile synthetic route towards 5-fluoro cytidine phosphoramidites that enables their convenient site-specific incorporation into oligonucleotides by solid-phase synthesis.