Dicarbonylcyclopentadienyltellurophenyliron complexes as ligands

The reaction of CpFe(CO)₂TePh (I) with ferricinium hexafluorophosphate as an oxidant affords ionic complex {[CpFe(CO)₂]₂(μ-TePh)}⁺PF ₆ ^? (II) with the simultaneous formation of diphenylditellurium. The decarbonylation of compound II by Me₃NO followed by the addition of complex I affords trinuclear complex {[CpFe(CO)₂(μ-TePh)]₂Fe(CO)Cp}PF₆ (III). The corresponding tetrafluoroborate (IV) is synthesized similarly. The heating of compound I with PPh₃ gives CpFe(CO)(PPh₃)TePh (V) that reacts with ionic complex [CpMn(CO)₂(NO)]PF₆ (VI) to form binuclear heterometallic ionic complex [CpFe(CO)(PPh₃)(μ-TePh)Mn(CO)(NO)Cp]PF₆ (VII). A similar reaction of Cp′Fe(CO)₂TePh (Cp′ is methylcyclopentadienyl) with compound VI affords heterometallic [Cp′Fe(CO)₂(μ-TePh)Mn(CO)(NO)Cp]PF₆ (VIII). The structures of compounds II, IV, VII, and VIII are determined by X-ray diffraction analysis (CIF files CCDC 963285, 963286, 963288, and 963289, respectively).     

A morphotropic series of the cluster complexes [Ln(DMF)8][Re6Q7Br7] (Q = S, Se): Synthesis, structure, and thermal transformations

The reactions of the octahedral anionic complexes [Re₆Q₇Br₇]^3? (Q = S, Se) with lanthanide bromides in DMF were studied. The reactions gave a series of compounds [Ln(DMF)₈][Re₆Q₇Br₇] (Q = S, Se) containing [Ln(DMF)₈]³⁺ complex cations. The compounds were studied by single-crystal and powder X-ray diffraction and thermal analyses. The crystal structures of [Ln(DMF)₈][Re₆S₇Br₇] with Ln = La (I), Ce (II), Nd (III), Eu (IV), and Lu (V) and [Ln(DMF)₈][Re₆Se₇Br₇] with Ln = La (VI), Ce (VII), Pr (VIII), and Lu (IX) were determined. It was found that [Ln(DMF)₈][Re₆Q₇Br₇] (Q = S, Se) can be divided into three structural groups: I, II, and VI (type A), VII (type B), and III–V, VIII, IX (type C). The complex [Pr(DMF)₈][Re₆Se₇Br₇] was found to crystallize in two polymorphous modifications with type B and C structures. Presumably, the morphotropic transitions in the [Ln(DMF)₈][Re₆Q₇Br₇] series (Q = S, Se) are mainly related to the change in the configuration of the [Ln(DMF)₈]³⁺ cations, resulting in a change in the packing motif of large complex ions in the crystals. The compounds [Ln(DMF)₈][Re₆Se₇Br₇] decompose according to a stepwise pattern, which suggests an intermediate formation of the complexes [Ln(DMF)₆][Re₆Se₇Br₇] (this was proved for Ln = Yb, Lu) with subsequent more extensive transformations, which affect also the cluster anion.     

Synthesis and molecular and crystal structures of binuclear complexes of Sm(III), Eu(III), Gd(III), Tb(III), and Dy(III) nitrates with 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione

Binuclear complexes of Sm(III), Eu(III), Gd(III), Tb(III), and Dy(III) nitrates with 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione (C₁₁H₂₀N₄O₂, SC)—[Sm(NO₃)₃(SC)(H₂O)]₂(I), [Eu(NO₃)₃(SC)(H₂O)]₂ (II), [Gd(NO₃)₂(SC)(H₂O)₃)]₂(NO₃)₂ (III), [Tb(NO₃)₃(SC)(H₂O)]₂ (IV), [Dy(NO₃)₃(SC)(H₂O)]₂ (V), are synthesized, and their X-ray diffraction analyses are carried out. The crystals of complexes I–V are monoclinic: space group P2₁/n for III and P2₁/c for I, II, IV, and V. In centrosymmetric coordination complexes II, III, IV, and V, the Ln atoms are coordinated by two O(1) and O(2) atoms of two molecules of the SC ligands bound by a symmetry procedure (1 ? x, ?y, 1 ? z), three bidentate nitrate anions, and a water molecule. The coordination numbers of the metal atoms are equal to 9, and the coordination polyhedra are considerably distorted three-capped trigonal prisms, whose bases include the O(1), O(2), O(12) and O(3), O(7), O(9) atoms. The dihedral angle between the bases of the prism is 18°, and that between the mean planes of the side faces is 55°–71° for I, 17° and 55°–71° for II, 16° and 55°–70° for IV, and 16° and 55°–70° for V. The Sm...Sm distance in complex I is 9.44 Å, Eu...Eu in II is 9.42 Å, Tb...Tb in IV is 9.36Å, and Dy...Dy in V is 9.36Å. The gadolinium atom in complex III is coordinated by two oxygen atoms of two ligand molecules bound by a symmetry procedure (?x, ?y + 1, ?z + 1), two bidentate nitrate anions, and three water molecules. One of the nitro groups in compound III is localized in the external coordination sphere of the metal. The coordination number of gadolinium is 9, and the coordination polyhedron is a significantly distorted three-capped trigonal prism, whose base includes the O(1), O(2), O(7) and O(4), O(5), O(9) atoms. The dihedral angle between the bases of the prism is 22.8°, and that between the mean planes of the side faces is 53°–72°. The Gd...Gd distance in complex III is 9.17 Å.     

anti-syn and anti-anti coordination of the bridging CO 3 2− group in [Cu2(Phen)4(μ-CO3)]B10H10 binuclear complexes: Synthesis, structure, and magnetic properties

A redox reaction that occurs in the [Cu₂B₁₀H₁₀]/Phen system in CH₃CN/DMSO and CH₃CN/DMF in air yields a Cu(II) binuclear complex, [(Phen)₂Cu(CO₃)Cu(Phen)₂]²⁺. The [Cu₂(Phen)₄(μ-CO₃)]B₁₀H₁₀ · 2.5DMSO · 2H₂O (I) and [Cu₂(Phen)₄(μ-CO₃)]B₁₀H₁₀ · 4DMF (II) compounds have been isolated and studied by X-ray crystallography at 150 K and EPR at 295 K. Their magnetic properties have been studied in the range 300–2 K. In the cations of both compounds, the bridging CO ₃ ^2? group is bidentately coordinated to two Cu atoms. The cations in I and II have different spatial orientations of the Cu-O bonds: anti-syn and anti-anti, respectively. Compound I has weak magnetic interactions caused by a short Cu…Cu distance (4.441 Å) in the dimer. No exchange coupling is observed in II.     

Cationic methyl complexes of rhodium(III): synthesis, structure, and some reactions

Cationic methyl complex of rhodium(III), trans-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] (1) is prepared by interaction of trans-[Rh(Acac)(PPh₃)₂(CH₃)I] with AgBPh₄ in acetonitrile. Cationic methyl complexes of rhodium(III), cis-[Rh(Acac)(PPh₃)₂ (CH₃)(CH₃CN)][BPh₄] (2) and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] (3) (Acac, BA are acetylacetonate and benzoylacetonate, respectively), are obtained by CH₃I oxidative addition to rhodium(I) complexes [Rh(Acac)(PPh₃)₂] and [Rh(BA)(PPh₃)₂] in acetonitrile in the presence of NaBPh₄. Complexes 2 and 3 react readily with NH₃ at room temperature to form cis-[Rh(Acac)(PPh₃)₂(CH₃)(NH₃)][BPh₄] (4) and cis-[Rh(BA)(PPh₃)₂(CH₃)(NH₃)][BPh₄] (5), respectively. Complexes 1-5 were characterized by elemental analysis, ¹H and ³¹P{¹H} NMR spectra. Complexes 1, 2, 3 and 4 were characterized by X-ray diffraction analysis. Complexes 2 and 3 in solutions (CH₂Cl₂, CHCl₃) are presented as mixtures of cis-(PPh₃)₂ isomers involved into a fluxional process. Complex 2 on heating in acetonitrile is converted into trans-isomer 1. In parallel with that isomerization, reductive elimination of methyl group with formation of [CH₃PPh₃][BPh₄] takes place. Replacement of CH₃CN in complexes 1 and 2 by anion I⁻ yields in both cases the neutral complex trans-[Rh(Acac)(PPh₃)₂(CH₃)I]. Strong trans influence of CH₃ ligand manifests itself in the elongation (in solid) and labilization (in solution) of rhodium-acetonitrile nitrogen bond.     

Synthesis and crystal structure of Co(III) dioximates with the complex anion [SbF6]?

The complexes [Co(DioxH)₂L₂][SbF₆] · nH₂O, where DioxH is dimethylglyoxime monoanion (DioxH^?) or 1,2-cyclohexanedione dioxime (NioxH^?), L is aniline (An) or triphenylphosphine (PPh₃), were isolated from the CoX₂ · nH₂O-NaSbF₆-DioxH₂-L system (X = F or CH₃COO) in aqueous methanol. The complexes were studied by UV, IR, and NMR spectroscopy and by X-ray diffraction. The crystal structure of [Co(DH)₂(An)₂][SbF₆] · H₂O (I) and [Co(NioxH)₂(PPh₃)₂][SbF₆] (II) is stabilized by the electrostatic interactions between the Co(III) complex cations and outer-sphere fluorine-containing anions and by hydrogen bonds between structural units.     

Cyanido-bridged one-dimensional systems assembled from [ReIVCl4(CN)2]2? and [MII(cyclam)]2+ (M = Ni, Cu) precursors

Three new cyanido-bridged heterometallic Re^IVNi^II and Re^IVCu^II one-dimensional systems were synthesized and extensively characterized both structurally and magnetically. Single-crystal X-ray diffraction analysis revealed that these compounds display a common topology, with chains composed of alternating [Re^IVCl₄(CN)₂]^2? and [M^II(cyclam)]²⁺ (M = Ni in 1, Cu in 2) or [Cu^II(N,N??-dimethylcyclam)]²⁺ (in 3) building units. Two different chain orientations with a tilt angle of ca. 51° to 55° are present in the crystal packing of these compounds. The magnetic susceptibility measurements suggest the presence of intrachain ferromagnetic interactions between the S = 3/2 Re^IV centers and the 3d metal ions: S = 1 Ni^II or S = 1/2 Cu^II. At low temperature, a three-dimensional ordered magnetic phase induced by interchain antiferromagnetic interactions (antiferromagnetic for 1 and 2; canted antiferromagnetic for 3) is detected for the three compounds.     

New Co(III) dioximates with hexafluorophosphate ion as stimulators of the proteolytic activity of the micromycete Fusarium gibbosum CNMN FD 12

The coordination compounds [Co(DH)₂(An)₂][PF₆] (I) and [Co(NioxH)₂(Thio)₂][PF₆] · 0.5DMF · 0.5H₂O (II), where DH- and NioxH-are dimethylglyoxime and 1,2-cyclohexanedione dioxime monoanions, respectively; An is aniline; and Thio is thiourea, were synthesized. The composition and structure of the complexes were determined by elemental analysis, IR spectroscopy, and X-ray diffraction. Compounds I and II are ionic and consist of complex cations [Co(DioxH)₂(A)₂]⁺, where DioxH is the α-dioxime residue, A is neutral organic molecule (aniline or thiourea), and [PF₆]^? anions. The coordination polyhedra of the Co(III) complex cations are octahedra formed by the set of N6 donor atoms of monodeprotonated DH-residues and two An molecules (in I) or by the N₄S₂ atoms of two NioxH-anions and two Thio molecules (in II). The formation of the crystal structure of I and II is largely determined by the [PF₆]-anions in which the fluorine atoms serve as acceptors in various hydrogen bonds. The compounds were tested as stimulators of biosynthesis of extracellular proteases of the micromycete Fusarium gibbosum CNMN FD 12. The introduction of the test complexes in optimized concentrations into the nutrition medium for cultivation of the producing strain enhances the biosynthesis of acid and neutral proteases by 63.6 and 92.5%, respectively.     

Design and synthesis of two-dimensional pillared MOF layers by connecting infinite one-dimensional chains via 4,4′-bipyridine

Two novel metal-organic frameworks, [Cd(Bna)(DMF)₂(H₂O)₂] _n · nDMF (I) (Bna = 2,2′-dihydroxy-l,l′-dinaphthyl-3,3′-dicarboxylate) and [Cd(Bna)(Bipy)(DMF)₂] _n (II) (Bipy = 4,4′-bipyridine) have been synthesized under mild conditions and structurally characterized. Crystal structural analyses reveal that complex I adots a 1D spiral structure with DMF guest molecules in the spiral by hydrogen bondings. Complex II is constructed by -Cd-Bna-Cd- zigzag chains, which are further connected by Bipy into a 2D sheet. X-ray powder diffraction and thermogravimetric analyses for I and II show that they are highly themally stable in the solid state.     

Reactivity of cationic methyl rhodium(III) complexes cis-[Rh(β-diket)(PPh3)2(CH3)(CH3CN)][BPh4] toward ligands of different character: pyridine, carbon monoxide, and triphenylphosphine

Cationic methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(Py)][BPh₄] (1) as a single isomer with Py in the trans to PPh₃ position, is formed upon the reaction of cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] with pyridine in methylene chloride solution.Complex 1 was characterized by elemental analysis and by ³¹P{¹H} and ¹H NMR spectra.Cationic pentacoordinate acetyl complexes, trans-[Rh(Acac)(PPh₃)₂(COCH₃)][BPh₄] (2) and trans-[Rh(BA)(PPh₃)₂(COCH₃)][BPh₄] (3), are prepared by action of carbon monoxide on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄], respectively, in methylene chloride solutions.Complexes 2 and 3 were characterized by elemental analysis and by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR. According to NMR data, 2 and 3 in solution are non-fluxional trigonal bipyramids with β-diketonate and acetyl ligands in the equatorial plane and axial phosphines.In solutions, 2 and 3 gradually isomerize into octahedral methyl carbonyl complexes trans-[Rh(Acac)(PPh₃)₂(CO)(CH₃)][BPh₄] (4) and trans-[Rh(BA)(PPh₃)₂(CO)(CH₃)][BPh₄] (5), respectively.Complexes 4 and 5 were characterized by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR, without isolation.Upon the action of PPh₃ on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)] [BPh₄], reductive elimination of the methyl ligand as a phosphonium salt, [CH₃PPh₃][BPh₄], occurs to give square planar rhodium(I) complexes [Rh(Acac)(PPh₃)₂] and[Rh(BA)(PPh₃)₂], respectively. The reaction products were identified in the reaction mixtures by ³¹P{¹H} and ¹H NMR.     

Synthesis, crystal structures, and properties of [Ca(H2O)2(Dmf@CB[6])(Bdc)] · DMF · 4H2O and [Ca(H2O)3(Dmf@CB[6])]Cl2 · 2H2O

Complexes [Ca(H₂O)₂(Dmf@CB[6])(Bdc)] · DMF · 4H₂O (I) and [Ca(H₂O)₃(Dmf@CB[6])]Cl₂ · 2H₂O (II) are synthesized by the heating (95°C) of a mixture of calcium chloride and cucurbit[6]uril (CB[6]) in a mixture of dimethylformamide (DMF) and water with the addition of terephthalic acid (H₂Bdc) in the case of complex I or triethylamine for complex II. The compounds are characterized by X-ray diffraction analysis, IR spectroscopy, and thermogravimetric and elemental analyses. The luminescence spectra are also recorded. According to the X-ray diffraction data, the calcium atom is coordinated by the oxygen atoms of the cucurbit[6]uril molecule, water molecules, and terephthalate anion (for I). The internal cavity of the cavitand is occupied by DMF.     

Zn-containing double complex salts formed by Keggin type polyoxotungstates: Synthesis and crystal structure

Novel double complex salts, [Zn(DMF)₆]₂[SiW₁₂O₄₀] · 2H₂O (I) and [Zn(H₂O)₂(DMF)₄][Zn(DMF)₆]₂[PW₁₂O₄₀]₂ · 6DMF (II) (DMF = N,N-dimethylformamide), were prepared by the reaction of Zn²⁺ and heteropoly acids H_x[EW₁₂O₄₀] · xH₂O (E = P, X = 3, E = Si, X = 4) in DMF. Compounds I and II were studied by X-ray diffraction (СIF files CCDC nos. 1497570 (I) and 1497571 (II)) and IR spectroscopy.     

Synthesis and Characterisation of Diruthenium Paddlewheel Compounds Bearing 2,6-Di(p-tolyl)benzoate Ligands

The mixed carboxylate diruthenium complexes trans-[Ru ₂ ^II,III (O₂CCH₃)₂(O₂CAr)₂Cl] (I) and trans-[Ru ₂ ^II,II (O₂CCH₃)₂(O₂CAr)₂] (II) (O₂CAr = 2,6-di(p-tolyl)benzoate) have been synthesised along with [Ru ₂ ^II,III (O₂CAr)₄Cl] (III) and the homoleptic complex [Ru ₂ ^II,II (O₂CAr)₄] (IV). The structures trans-[Ru₂(O₂CCH₃)₂(O₂CAr)₂Cl(thf)]·(thf) and [Ru₂(O₂CAr)₄Cl(η ¹-CH₂Cl₂)] were determined by X-ray crystallography, and display the expected paddlewheel arrangement of the carboxylate ligands around the diruthenium core. The structure of III is a rare example of a structurally characterised dichloromethane complex, highlighting the Lewis acidic nature of the diruthenium axial position. The bulky ^?O₂CAr ligand protects the axial positions from intermolecular interactions in the absence of strong nucleophiles for III and IV, and the effect this has on the electronic structure of the diruthenium core in these complexes was investigated by cyclic voltammetry, electronic absorption spectroscopy and magnetic susceptibility studies.     

Structural organization and thermal behavior of the heteropolynuclear complex [Au2{S2CN(CH3)2}4][ZnCl4] and the heterovalent complex ([Au{S2CN(CH3)2}2][AuCl2]) n obtained in the chemisorption system [Zn2{S2CN(CH3)2}4]-Au3+/2 M HCl

Reactions of freshly precipitated binuclear zinc dimethyldithiocarbamate with [AuCl₄]^? anions in 2 M HCl were studied. The heteropolynuclear complex [Au₂{S₂CN(CH₃)₂}₄][ZnCl₄] (I) and the polymeric heterovalent complex ([Au{S₂CN(CH₃)₂}₂][AuCl₂]) _n (II) were preparatively isolated from the chemisorption system [Zn₂{S₂CN(CH₃)₂}₄]-Au³⁺/2 M HCl. The products were characterized by ¹³C MAS NMR data and by X-ray diffraction determination of crystal and molecular structures. The principal structural units of compounds I and II are the tetragonal planar complex cations [Au{S₂CN(CH₃)₂}₂]⁺ (in which the complex-forming ion coordinates two MDtc ligands in the S,S′-bidentate mode) and the anions, namely, the distorted tetrahedral anion [ZnCl₄]^2? in I and the linear [AuCl₂]^? anion in II. The further structural self-organization of complexes at the supramoleular level occurs through relatively weak secondary bonds Au?S and Au?Cl. The chemisorption capacities of zinc dimethyldithiocarbamate calculated from gold(III)-binding reactions are 644.1 and 1288.2 mg of gold per gram of the sorbent. Simultaneous thermal analysis studies of the thermal behavior of I and II were used to elucidate the conditions of gold recovery.     

Platinum and rhenium phosphine carbonyl thiolate complexes

The heterometallic complex (CO)₃(PPh₃)Re(μ-SPr)Pt(PPh₃)(CO) (I) was formed in the reaction of Re₂(μ-SPr)₂(CO)₈ with (PPh₃)₂Pt(C₂Ph₂), together with (CO)₃(PPh₃)Re(μ-SPr)₂Re(CO)₄ (II), which was also prepared by an alternative synthesis. Compounds I and II were characterized by X-ray diffraction. In I, the Re-Pt single bond, 2.7414(5) Å, is supplemented by a thiolate bridge with shortened bonds: Pt-S (2.336(2) Å) and Re-S (2.449(2) Å). The Re-P (2.469(2) Å) and Pt-P (2.329(2) Å) bonds are also shortened. Complex II resulting from replacement of one CO group in the starting rhenium complex by triphenylphosphine has no M-M bond, and the Re-S and Re-P bond lengths (2.511(2)–2.527(2) and 2.517(3) Å) are close to the length of single bonds. It is assumed that the platinum atom in I is attached to the formally double bond Re ? SPr arising upon dissociation of Re₂(μ-SPr)₂(CO)₈.     

The Staudinger reaction of platinum(II)- and palladium(II)-coordinated 2-(azidomethyl)phenyl isocyanide. X-ray structure of trans-[PtCl{(H)}(PPh3)2][BF4] · CDCl3 · H2O

2-(Azidomethyl)phenyl isocyanide, 2-(CH₂N₃)C₆H₄NC (AziNC), coordinates to some cationic Pt(II) and Pd(II) species to afford isocyanide complexes of the type trans-[MCl(AziNC)(PPh₃)₂][BF₄] (M=Pt, l; Pd, 2). AziNC is coordinated also in some neutral Pt(II) and Pd(II) species such as [MCl₂(AziNC)₂] (M=Pt, 3; Pd, 4) derived from the reactions of 2 equiv. of AziNC with [PtCl₂(COD)] and [PdCl₂(MeCN)₂], respectively. Complexes 1 and 2 react with 1 equiv. of PPh₃ affording the heterocyclic carbene complexes trans-[MCl{(H)}(PPh₃)₂][BF₄] (M=Pt, 5; Pd, 6). Complexes 3 and 4 react with 1 equiv. of PPh₃ displacing the isocyanide with the formation of the complexes cis-[MCl₂(AziNC)(PPh₃)] (M=Pt, 7; Pd, 8). These latter ones react with 2 equiv. of PPh₃ affording as the final products the cationic carbene species trans-[MCl{(H)}(PPh₃)₂][Cl] (M=Pt, 9; Pd, 10). Complex 5 was also characterized by single crystal X-ray diffraction. The carbene complex is square-planar and the angle formed between the platinum square plane and the heterocyclic carbene ligand is 87.9(2)°. The C(1)-N(1) and C(1)-N(2) bond distances in the latter of 1.32(2) and 1.30(2) Å, respectively, are short for a single bond and indicate extensive π-bonding between the nitrogen atoms and the carbene carbon.     

Crystal structures and luminescence of a series of cadmium(II) complexes based on isophorone derivative containing imidazolyl

Three new complexes, [CdL₂(CH₃COO)₂(H₂O)₂] (I), CdL₂Br₂ (II), CdL₂I₂ (III), have been successfully synthesized by self-assembly of corresponding metal salts with (E)-2-(3-(4-(1H-imidazole-1-yl)styryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile (L). The structures of the complexes were determined by single crystal X-ray diffraction analysis (CIF file CCDC nos. 957831 (I), 957792 (II), 957832 (III)). In complex I, central metal is six-coordinated and the crystal packing shows a 3D supramolecular framework. Complexes II and III display the similar 2D supramolecular structures in which the central metals are four-coordination. The luminescent properties were investigated.     

Xanthate complexes of {Nb2S4}4+

Alkyl xanthate complexes [Nb₂S₄(S₂COR)₄] (R = Et (I), iso-Pr (II), n-Bu (III), and iso-Am (IV)) are synthesized by the ligand exchange reaction in solutions from (Et₄N)₄[Nb₂S₄(NCS)₈] and the corresponding potassium salts in satisfactory yields. The X-ray diffraction analyses are carried out for the isopropyl xanthate (II) and butyl xanthate (III) complexes. From the view point of mutual arrangement of chelate cycles, complexes II and III exist in crystals as ΛΔ isomers. The niobium-niobium distances are 2.8789(4) Å in complex II and 2.8856(3) Å in complex III. The first example for the formation of short S...S contacts between the disulfide ligands of the {Nb₂S₄}⁴⁺ fragments in the crystal structure of III is found (3.146 Å).     

Trifluoroacetylacetonate rhodium(III) methyl complexes, cis-[Rh(TFA)(PPh3)2(CH3)(L)][BPh4] and cis-[Rh(TFA)(PPh3)2(CH3)(I)] (L = CH3CN, NH3, pyridine), in comparison with their acetylacetonate analogs

The oxidative addition of CH₃I to planar rhodium(I) complex [Rh(TFA)(PPh₃)₂] in acetonitrile (TFA is trifluoroacetylacetonate) leads to the formation of cationic, cis-[Rh(TFA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] (1), or neutral, cis-[Rh(TFA)(PPh₃)₂(CH₃)(I)] (4), rhodium(III) methyl complexes depending on the reaction conditions. 1 reacts readily with NH₃ and pyridine to form cationic complexes, cis-[Rh(TFA)(PPh₃)₂(CH₃)(NH₃)][BPh₄] (2) and cis-[Rh(TFA)(PPh₃)₂(CH₃)(Py)][BPh₄] (3), respectively. Acetylacetonate methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(I)] (5), was obtained by the action of NaI on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] in acetone at −15 °C. Complexes 1-5 were characterized by elemental analysis, ³¹P{¹H}, ¹H and ¹⁹F NMR. For complexes 2, 3, 4 conductivity data in acetone solutions are reported. The crystal structures of 2 and 3 were determined. NMR parameters of 1-5 and related complexes are discussed from the viewpoint of their isomerism.     

Synthesis,Characterization, and Crystal Structure of Tertiary Phosphine-Substituted Diiron Propanedithiolate Complexes

As the active site models of [FeFe]-hydrogenase, two new tertiary phosphine-substituted diiron propanedithiolate complexes [(μ-PDT)Fe₂(CO)₅L] (PDT = SCH₂CH₂CH₂S, L = P(PhMe-m)₃, 1; PPh₂(CH₂CH₂CH₃), 2) have been prepared through carbonyl substitution reactions of parent complex [(μ-PDT)Fe₂(CO)₆] (A) with P(PhMe-m)₃ or PPh₂(CH₂CH₂CH₃) in the presence of the decarbonylating agent Me₃NO·2H₂O in MeCN at room temperature. The new complexes 1 and 2 were fully characterized by elemental analysis, FT-IR, ¹H, ¹³C{¹H}, and ³¹P{¹H} NMR spectroscopy, as well as for 1 by X-ray crystallography. In addition, the crystal structure of 1 has indicated that the phosphorus atom of the P(PhMe-m)₃ ligand resides in an apical position of the pseudo-square-pyramidal geometry of the tertiary phosphine-coordinated Fe₂ atom.