Substituted Cp Ring Research Articles

Towards building blocks for metallosupramolecular structures: non-symmetrically-functionalised ferrocenyl compounds.

Metallosupramolecular architectures formed from metal ions and bridging ligands are increasing in popularity due to their range of applications and ease of self-assembly. Many are able to readily change their shape and/or function in response to an external stimulus and have the ability to encapsulate guest molecules within their internal cavities. Ferrocenyl groups (Fc) have been incorporated previously within the bridging ligands of metallosupramolecular structures due to their ideal attributes brought about by the structural and rotational flexiblity of the two cyclopentadienyl (Cp) rings coordinated to the Fe(II) centre. However, the majority of these Fc-based structures contain symmetrically substituted Cp rings. We report the synthesis and characterisation of non-symmetrically functionalised Fc-based ligands incorporating both N,N' and NHC-donor groups chosen for their differing coordination properties. Both substituents were designed to coordinate to a single metal centre with the dissimilar coordination properties of each donor group facilitating stimulus-induced dissociation/association of one of the substituents as an opening/closing mechanism. Preliminary investigations into the coordination of these Fc-based ligands to a [Ru(η6-p-cymene)]2+ moiety indicated complexation through a mixture of either a bi- or tridentate fashion, as alluded by 1H NMR spectroscopy and mass spectrometry. Density functional theory (DFT) calculations revealed the Fc-based ligands adopt a syn conformation driven by H-bonding and π-interactions between the two Cp substituents, which facilitate coordination of both donor groups towards the metal centre.

Crystal structure of (E)-1,2-diferrocenyl-1,2-bis(furan-2-yl)ethene.

The title compound, [Fe2(C5H5)2(C20H14O2)], is the product of a new synthetic route towards tetra-aryl/hetaryl-substituted ethenes that reduces the occurrence of side-products. In the crystal, the mol-ecule is centrosymmetric and the cyclo-penta-dienyl (Cp) rings are nearly coplanar and aligned slightly closer to a staggered conformation than to an eclipsed one. The ethene plane is tilted by 32.40 (18)° with respect to that of the substituted Cp ring and by 63.19 (19)° with respect to that of the furan ring. C-H⋯π inter-actions link the mol-ecules into a three-dimensional supramolecular framework.

Ferrocenecarboxylic anhydride: a redetermination

The title molecule, [Fe2(C5H5)2(C12H8O3)], briefly reported previously [Zhang (2015). Private Communication (CCDC reference 1056736). CCDC, Cambridge, England], comprises two ferrocenyl units connected by an acid anhydride bridge. Both ferrocene units have near coplanar [dihedral angles between the ring planes = 2.84 (4) and 1.74 (13)°] and eclipsed [pseudo torsion angles = 6.3 (2) and 5.1 (2)°] cyclopentadienyl (Cp) rings. A twist through the anhydride linkage results in a dihedral angle of 73.81 (8)° between the two substituted Cp rings planes. An intramolecular C—H...O hydrogen bond is also found. In the crystal, C—H...O hydrogen bonds link the molecules into a three-dimensional network.

Crystal structure of 16-ferrocenylmethyl-3β-hydroxy-estra-1,3,5(10)-trien-17-one: a potential chemotherapeutic drug.

A new ferrocene complex, 16-ferrocenylmethyl-3β-hy-droxy-estra-1,3,5(10)-trien-17-one dimethyl sulfoxide monosolvate, [Fe(C5H5)(C24H27O2)]·C2H6OS, has been synthesized and structurally characterized by single-crystal X-ray diffraction techniques. The mol-ecule crystallizes in the space group P21 with one mol-ecule of dimethyl sulfoxide. A hydrogen bond links the phenol group and the dimethyl sulfoxide O atom, with an O⋯O distance of 2.655 (5) Å. The ferrocene group is positioned in the β face of the estrone moiety, with an O-C-C-C torsion angle of 44.1 (5)°, and the carbonyl bond length of the hormone moiety is 1.216 (5) Å, typical of a C=O double bond. The average Fe-C bond length of the substituted Cp ring [Fe-C(Cp*)] is similar to that of the unsubstituted one [Fe-C(Cp)], i.e. 2.048 (3) versus 2.040 (12) Å. The structure of the complex is compared with those of estrone and eth-oxy-methyl-estrone.

N-Ferrocenymethyl-N-phenylacetamide

In the title compound, [Fe(C5H5)(C14H14NO)], the asymmetric unit comprises two unique molecules. The two cyclopentadienyl (Cp) rings of each ferrocene residue are nearly parallel to one another. In each substituted Cp ring, the CH2group carries anN-phenylacetamide residue. In the crystal, C—H...O hydrogen bonds stack molecules alonga.

Meso-Bis{η5-1-[1-(dimethylamino)ethenyl]-3-(trimethylsilyl)cyclopentadienyl}iron(II) and the cobalt(II) analogue

The two title crystalline compounds, viz. meso-bis{η(5)-1-[1-(dimethylamino)ethenyl]-3-(trimethylsilyl)cyclopentadienyl}iron(II), [Fe(C(12)H(20)NSi)(2)], (II), and meso-bis{η(5)-1-[1-(dimethylamino)ethenyl]-3-(trimethylsilyl)cyclopentadienyl}cobalt(II), [Co(C(12)H(20)NSi)(2)], (III), were obtained by the reaction of lithium 1-[1-(dimethylamino)ethenyl]-3-(trimethylsilyl)cyclopentadienide with FeCl(2) and CoCl(2), respectively. For (II), the trimethylsilyl- and dimethylaminoethenyl-substituted cyclopentadienyl (Cp) rings present a nearly eclipsed conformation, and the two pairs of trimethylsilyl and dimethylaminoethenyl substituents on the Cp rings are arranged in an interlocked fashion. In the case of (III), the same substituted Cp rings are perfectly staggered leading to a crystallographically centrosymmetric molecular structure, and the two trimethylsilyl and two dimethylaminoethenyl substituents are oriented in opposite directions, respectively, with the trimethylsilyl group of one Cp ring and the dimethylaminoethenyl group of the other Cp ring arranged more closely than in (II).

N-Ferrocenymethyl-N-phenylpropionamide

In the title compound, [Fe(C5H5)(C15H16NO)], the two cyclo­penta­dienyl (Cp) rings are nearly parallel to each other, forming a dihedral angle of 3.7 (1)°, and adopt a staggered conformation. The amide group is almost perpendicular to the plane of the substituted Cp ring, with a C—N—C—C torsion angle of 101.3 (2)°, and the N and O atoms in the ethanoyl group are coplanar, with a C—N—C—O torsion angle of −0.7 (3)°. Weak C—H⋯O hydrogen bonds link adjacent mol­ecules.

Ethyl 3-ferrocenyl-1-(pyridin-2-ylmeth-yl)-1H-pyrazole-5-carboxyl-ate.

The title compound, [Fe(C5H5)(C17H16N3O2)], crystallizes with an essentially eclipsed conformation of the cyclo­penta­dienyl (Cp) rings. The unsubstituted ring is disordered over two positions with the major component being present 90 (1)% of the time. The substituted Cp ring, the pyrazole ring and three atoms of the eth­oxy­carbonyl group form a conjugated π-system. These 13 atoms are coplanar within 0.09 Å.

1-[(Ferrocen-1-yl)meth-yl]-3-(naphthalen-1-yl)thio-urea.

In the title compound, [Fe(C5H5)(C17H15N2S)], the cyclo­penta­dienyl (Cp) rings are almost parallel and essentially eclipsed, with a dihedral angle between the Cp ring planes of 0.807 (11)°. The Fe atom is slightly closer to the substituted cyclo­penta­dienyl ring, with an Fe–centroid distance of 1.6510 (8) Å, compared with 1.6597 (8) Å for the unsubstituted ring. The bridging unit between the substituted Cp ring and the naphthyl ring system is planar within 0.0174 Å and makes dihedral angles of 59.032 (10) and 66.02 (2)°, respectively, with these two rings. The angle between the substituted Cp ring and the naphthyl ring system is 72.094 (18)°. The H atoms of the NH groups of the thio­urea moiety are positioned anti with respect to each other. In the crystal, mol­ecules form centrosymmetric dimers via pairs of N—H⋯S hydrogen bonds.

Acetylferrocene–2-chloro-1-ferrocenylethanone (1/1)

In the title co-crystal, [Fe(C5H5)(C7H6ClO)][Fe(C5H5)(C7H7O)], both substituted ferrocene mol­ecules show the expected sandwich structure. The crystal packing exhibits weak inter­molecular Cl⋯Cl contacts of 3.279 (4) Å, π–π inter­actions between the substituted Cp rings of two neighbouring 2-chloro-1-ferrocenyl­ethanone mol­ecules [centroid–centroid distance = 3.534 (3) Å], and weak inter­molecular C—H⋯O and C—H⋯Cl hydrogen bonds.

1-(Diphenylphosphinothioyl)-2-[(4-methylphenyl)methoxymethyl]ferrocene

Following our continuing inter­est in developing new chiral phosphine-containing ferrocenyl ligands, we synthesized the title compound, [Fe(C5H5)(C26H24OPS)], in which there are two nearly identical mol­ecules in the asymmetric unit. The conformation of the cyclo­penta­dienyl (Cp) rings in each ferrocenyl group are inter­mediate between eclipsed and staggered, with twist angles of 16.6 (2) and 8.9 (2)°. The protecting S atom is located endo with respect to the substituted Cp ring. In the crystal, mol­ecules are connected through inter­molecular C—H⋯π inter­actions.

Binding of a 2-pyridyl moiety to a B/Sn bidentate Lewis acid

Reaction of the bidentate Lewis acid 1,2-Fc(SnMe 2Cl)(B(Me)Cl) ( 1, Fc = 1,2-ferrocenylene) with 2-trimethylstannylpyridine gave a complex ( 2), in which the 2-pyridyl group forms a bridge between the Lewis acidic tin and boron centers. The structure of 2 was confirmed by multinuclear and two-dimensional NMR, single crystal X-ray diffraction, and elemental analysis. The crystal structure shows that the pyridyl moiety is positioned endo relative to the substituted Cp ring and UV–Vis spectroscopy revealed an enhancement of the ferrocene-centered dd transition in comparison to related complexes with pyridine as a terminal ligand.

Bis(1-ferrocenylmethylidene-4-phenylthiosemicarbazidato-κ2N1,S)zinc(II) monohydrate

In the title compound, [Fe2Zn(C5H5)2(C13H11N3S)2]·H2O, the ZnII ion is in a distorted tetra­hedral geometry being coordinated by two thio­semicarbazone ligands via N and S atoms. One of the Cp rings is disordered over two positions with occupancies of 0.55 and 0.45. The dihedral angle between the substituted Cp rings is 56.1 (5)° and the two phenyl rings are orientated at a dihedral angle of 41.7 (4)°. In the crystal structure, inter­molecular O—H⋯S, N—H⋯O and C—H⋯N hydrogen bonds link the mol­ecules into chains along the b axis. The structure is further consolidated by O—H⋯π inter­actions.

(R,R)-(N,N′-Diferrocenylcyclohexane-1,2-diyldiimino)dibenzonitrile

In the title compound, [Fe2(C5H5)2(C34H34N4)], two ferrocenes are bridged by a cyclo­hexane-1,2-diamine unit. The cyclo­penta­dienyl rings of the two ferrocene units are almost parallel [dihedral angles of 0.7 (4) and 1.0 (4)° in the two units] and eclipsed, as is typically found for similar monosubstituted ferrocene derivatives. The dihedral angle formed by the two benzene rings is 20.2 (3)°. The Fe—C bond lengths to the two substituted Cp rings vary from 2.014 (4) to 2.070 (3) Å, and are in the normal range. In the crystal, mol­ecules are linked by C—H⋯N inter­actions, forming an infinite two-dimensional network.

Palladium(II), Platinum(II), and Iridium(I) Complexes of 2-Phosphino-1-dimethylaminoferrocenes: A Survey of Structure and Catalysis

A series of PdCl2, PtCl2, and Ir(COD)BArF complexes bearing a rare class of racemic bidentate 2-phosphino-1-dimethylaminoferrocene ligands were prepared and characterized by NMR spectroscopy and X-ray crystallography. The new complexes displayed a structural trend relating a decrease in heteroatom-metal bond length with an increase in ligand bite angle on going from Ir to Pd and Pt. The PdCl2 and PtCl2 complexes were almost isostructural and featured MCl2 moieties in the plane of the substituted Cp ring of the ligand. In contrast, the Ir(COD)+ complex was distinguished by a bend of the Ir(COD) moiety toward the unsubstituted (Cp′) ring. The latter gave rise to a steric interaction that placed the Cp rings in almost eclipsed conformations. Ligand 8a (2-diphenylphosphino-1-dimethylaminoferrocene) was able to promote Pd-catalyzed Suzuki−Miyaura and Buchwald−Hartwig coupling of aryl chlorides in addition to Ir-catalyzed hydrogenation of electron-deficient and unactivated alkenes. A preliminary intramolecular hydroamination of a terminal alkene using 8a in conjunction with Ir(I) afforded the cyclized product in 64% yield.

Lithium and sodium cation binding of cyclopentadienyl anions: Electronic effects of cyclopentadienyl substitution

The Li + and Na + binding of substituted cyclopentadienyl (Cp) anions were investigated using computational techniques. The ring centroid-metal distances and the binding energies of the Cp-metal complexes correlate very well with the ∑ σ m of the substituted Cp ring. These properties also correlate well with the Cp Θ zz values. The trend in the correlations is the more electron-rich the Cp (negative ∑ σ m and Θ zz values values), the shorter the Cp-metal bond and the stronger the binding energy. The NBO metal charges correlate, though not very well in either case, with the Cp Θ zz and ∑ σ m values. However, there is a substantial increase in correlation when the sum of the absolute value of the Hammett σ m (∑| σ m|) is employed. The significantly improved correlation when the ∑| σ m| values are employed leads us to propose a model for substituted Cp charge transfer upon Li + or Na + complexation, and it also informs us that the Hammett substituent constant σ m contains information about substituent polarizabilities, at least in the case of Li +- and Na +-substituted Cp anions.

(S)-1-(1-Ferrocenylmethyl-1H-benzimidazol-2-yl)ethanol monohydrate

In the structure of the title compound, [Fe(C5H5)(C15H15N2O)]·H2O, the unsubstituted cyclo­penta­diene (Cp) ring is disordered over two positions, with site-occupancy factors of 0.636 (12) and 0.364 (12). The dihedral angles between the planes of the substituted Cp ring and the major and minor components of the disordered ring are 0.8 (3) and 3.4 (6)°, respectively. The crystal packing is stabilized by inter­molecular O—H⋯O hydrogen bonds, forming zigzag chains running parallel to the a axis.

(Z)-3-Ferrocenyl-2-phenylacrylonitrile

In the structure of the title compound, [Fe(C5H5)(C14H10N)], the unsubstituted cyclo­penta­diene (Cp) ring is disordered over two positions, with site-occupancy factors 0.76 (2) and 0.24 (2). The dihedral angles between the substituted Cp ring and the major and the minor components of the disordered ring are 0.9 (5) and 6(2)°, repectively. The plane of the acrylonitrile unit makes dihedral angles of 6.1 (18) and 6.5 (4)° with the substituted Cp ring and the phenyl ring planes, respectively.

Ethyl 1-(2-bromoethyl)-3-ferrocenyl-1H-pyrazole-5-carboxylate

In the structure of the title compound, [Fe(C5H5)(C13H14BrN2O2)], the two cyclopentadienyl (Cp) rings are in an eclipsed conformation and are parallel. The dihedral angle between the substituted Cp ring and the heterocyclic ring is 8.20°.

Synthesis and Crystal Structure of Bis(cyclomercurated) Bisferrocenylimines

The new complexes of bis(cyclomercurated) bisferrocenylimines were synthesised in good yields by the cyclomercuration of Schiff bases bearing acylferrocene and p‐phenylenediamine at room temperature. All the new compounds' identities were completely elucidated by various spectroscopic methods. The X‐ray crystal structure confirmed that the mercury was directed into the ortho‐position of substituted Cp ring and showed the presence of two N→Hg coordinations via two 5‐membered rings in these molecules.