High-spin carboxylate polymers [M(OOCCMe3)2]n of group VIII 3d metals

A coordination polymer of the general formula [Co(OOCCMe₃)₂]_n (2) was prepared by mild thermolysis of the coordination polymer of variable composition [(HOOCCMe₃)_xCo(OH)_n(OOCCMe₃)_2−n ]_m, the dinuclear cobalt complex Co₂(μ-H₂O)(OOCCMe₃)₄(HOOCCMe₃)₄, the tetranuclear cobalt cluster Co₄(μ₃-OH)₂(OOCCMe₃)₆(HOEt)₆, and the hexanuclear cluster [Co₆(μ₄-O)₂(μ_n-OOCCMe₃)₁₀(C₄H₈O)₃(H₂O)]·1.5(C₄H₈O) (7) in organic solvents. In the crystal, the polymer has a chain structure. Unlike thermolysis of cobalt pivalates, thermolysis of the dinuclear complex Ni₂(μ-H₂O)(OOCCMe₃)₄(HOOCCMe₃)₄ gave rise to the hexanuclear complex Ni₆(μ₂-OOCCMe₃)₆(μ₃-OOCCMe₃)₆ (3). The magnetic properties of compound 2 are substantially different from those of 3. Compound 2 undergoes the magnetic phase transition into the ordered state at T _c = 3.4 K (H = 1 Oe), whereas compound 3 exhibits antiferromagnetic properties. Solid-state decomposition of polymeric cobalt carboxylate 2 (below 350 °C) afforded the octanuclear cluster Co₈(μ₄-O)₂(μ₂-OOCCMe₃)₆(μ₃-OOCCMe₃)₆ (9) as the major product, which sublimes without decomposition. Decomposition of 3 gave nickel oxide as the final product. Pivalates 2 and 3 reacted with 2,3-lutidine in acetonitrile at 80 °C to form the isostructural dinuclear complexes (2,3-Me₂C₅H₃N)₂M₂(μ-OOCCMe₃)₄ (M = Co or Ni). The structures of compounds 3 and 7 were established by X-ray diffraction. The structure of polymer 2 was determined by powder X-ray diffraction analysis. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1841–1850, November, 2006.     

Synthesis, structures, and magnetic properties of binuclear carboxylate complexes with NiII and NiIII atoms

The reaction of NiCl₂·6H₂O with Me₃CCOOH and KOH taken in a molar ratio of 1:2:2 in water afforded the nonanuclear antiferromagnetic complex Py₂Ni₂(Me₃CCOOH)₂(OOCCMe₃)₂(μ-OOCCMe₃)₂(μ-OH₂), which apparently contains Ni^II and Ni^III atoms. The complex was isolated by extraction with CH₂Cl₂, benzene, or hexane. The reactions of this complex with pyridine bases (pyridine (Py), 3,4-lutidine (Lut), and nicorandil (Nic)) gave the adducts L₄Ni₂(OOCCMe₃)₂(μ-OOCCMe₃)₂(μ-OH) (L=Py, Lut, or Nic, respectively). According to magnetic measurements, intramolecular ferromagnetic exchange interactions in these adducts are complemented by intermolecular antiferromagnetic interactions. Pyrolysis of the pyridine adduct in air or under an inert atmosphere in xylene yielded the antiferromagnetic complex Py₂Ni₂(Me₃CCOOH)₂(OOCCMe₃)₂(μ-OOCCMe₃)₂(μ-OH₂), which contains Ni^II atoms. The structures of all the complexes synthesized were established by X-ray diffraction analysis. The electronic absorption spectra of these compounds are considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 725–738, April, 1998.     

Trimethylacetate nickel complexes

The present review is devoted to the chemistry of trimethylacetate Ni^II complexes with various nitrogen-containing ligands. Pathways of formation of complexes containing the Ni₂(μ-OH₂)(μ-OOCCMe₃)₂ and Ni₂(μ-OOCCMe₃)₄ fragments are discussed. Pathways of degradation of the nine-nuclear complex Ni₉(HOOCCMe₃)₄(μ₄-OH)₃(μ₃-OH)₃)₃(μ₄-OOCCMe₃)₁₂ under the action of primary amines (aniline or propargylamine) as well as the process of dehydration ofN-phenyl-o-phenylenediamine up to the bischelate mononuclear complex [1,2-(NH)(NPh)C₆H₄]₂Ni are demonstrated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 409–419, March, 1999.     

Study of the electronic structure of polynuclear cobalt trimethylacetate complexes by Co3<Emphasis Type="Italic">s</Emphasis> and Co3<Emphasis Type="Italic">p</Emphasis> X-ray photoelectron spectroscopy

The electronic structure of mono-, hexa-, and nonanuclear cobalt trimethylacetate complexes was studied by XPS. The Co3s- and Co3p X-ray photoelectron spectra of the complexes were recorded. The Co3p spectrum of bivalent cobalt was calculated in the isolated-ion intermediate-coupling approximation. Spectrum analysis showed that the [Co(N-Phobsqdi)2(η′-N-Ph-opda)(OOCCMe₃)] complex is a strong-field complex with Co(III) in the diamagnetic state; the [Co(dipy)₂(OOCCMe₃)₂], [Co(dipyam)(OOCCMe₃)₂], and [Co₉(μ₃-OH)₆(μ-OOCCMe₃)₁₂(OCMe₂)₄] are high-spin weak-field Co(II) complexes; and the [Co₆(μ₄-O)₂(OOCCMe₃)₁₀(THF)₄] complex contains both the Co(II) and Co(III) atoms. The energy position of major Co3s- and Co3p spectral maxima were found to be sensitive to the nature of the nearest environment of cobalt atoms. The data correlate well with X-ray crystallographic data.     

Formation and Transformations of Polynuclear Hydroxo- and Oxotrimethylacetate Complexes of Ni(II) and Co(II)

Transformations of polymeric trimethylacetate complexes [M(OH) _n (OOCCMe₃)_{2 – n} ] _m (M = Ni (I) and Co (II)) and clusters Ni₉(₄-OH)₃(₃-OH)₃(-O,O-OOCCMe₃)(-O,O"-OOCCMe₃)₇(₃-O,O,O"-OOCCMe₃)₃(₄-O,O,O",O"-OOCCMe₃)(HOOCCMe₃)₄(III) and Co₆(₃-OH)₂(-OOCCMe₃)₁₀(HOOCCMe₃)₄(VIII), which are formed from Iand IIupon their recrystallization from nonpolar solvents, were studied. It was shown that the action of N-phenyl-o-phenylenediamine (L) on Ior IIIresults, depending on the solvent, in different tetranuclear clusters with the hydroxo bridges. For example, in benzene, the L₂Ni₄(₃-OH)₂(HOOCCMe₃)₄(-OOCCMe₃)₆complex (IX) is formed; its L molecules are coordinated in a monodentate way, whereas in acetonitrile, they chelate to give the {[o-C₆H₄(NH₂)(NHPh)]₂Ni₄(₃-OH)₂(MeCN)₂(OOCCMe₃)₂(-OOCCMe₃)₄} compound (X). Heating of Xin the presence of atmospheric oxygen yields IX, the mononuclear bissemiquinonediimine [o-C₆H₄(NH)(NPh)]₂Ni complex (XI), and water. It was noted that the use of aniline in these reactions affords, independent of the nature of the solvent, only one (NH₂C₆H₅)₂Ni₄(₃-OH)₂(HOOCCMe₃)₄(-OOCCMe₃)₆cluster (VI); in acetonitrile, this cluster is formed as the solvate VI· 2HOOCCMe₃(VIa). When treated with ethanol, Iand IIIgive the Ni₄(EtOH)₆(₃-OH)₂(₂-OOCCMe₃)₄(OOCCMe₃)₂cluster (V), which is structurally close to the known cobalt-containing analog IV. Thermolysis of IVin decalin at 170° causes its dimerization, giving the octanuclear Co₈(₄-O)₂( _n -OOCCMe₃)₁₂complex (VII) with the tetradentate oxo bridges.     

Pivalate Bridged High Spin Manganese(II) and Iron(II) Polymers

Antiferromagnetic Mn(II) polymers of general formula {[L₂Mn(μ-OOCCMe₃)₂][Mn₂(μ-OOCCMe₃)₄]}_n (L = 1,2-phenylenediamine (3) and 4,5-dimethyl-1,2-phenylenediamine (4)) were synthesized from [Mn(μ-OOCCMe₃)₂(HOEt)] _n (1) polymer and arenediamines in MeCN solution. The tetranuclear cluster Fe₄(μ₃-OH)₂(μ-OOCCMe₃)₄(η²-OOCCMe₃)₂(EtOH)₆ (5) was prepared by reacting FeSO₄·7H₂O with KOOCCMe₃ in EtOH and was used as starting pivalate iron(II) agent in further reactions. The thermolysis of 5 in MeCN was shown to result in a ferromagnetic polymer [Fe(μ-OOCCMe₃)₂] _n (6) containing tetrahedral iron(II) atoms. Cluster 5 was found to react with o-phenylenediamine giving rise to ferrimagnetic polymer [Fe(μ-OOCCMe₃)₂(HOEt)]_n (7). The reaction 7 with 2,6-diaminopyridine in MeCN results in binuclear antiferromagnetic complex (2,6-(NH₂)₂C₅H₃N)₂Fe₂(μ-OOCCMe₃)₄· 4MeCN (8). However the reaction of 4,5-dimethyl-1,2-phenylenediamine with polymer 7 yields a polymer {[L₂Fe(μ-OOCCMe₃)₂][Fe₂ (μ-OOCCMe₃)₄]} _n (9), which is an analogue of the manganese polymer 4. All newly synthesized compounds were characterized by the by X-ray diffraction studies and magnetic measurement. Dedicated to Professor Ilya I. Moiseev in recognition of his outstanding contribution to cluster chemistry     

Role of metal center in reactions of polynuclear nickel(ii) and cobalt(ii) trimethylacetates with 8-amino-2,4-dimethylquinoline

The reactions of 8-amino-2,4-dimethylquinoline (L) (1) with polynuclear nickel(ii) and cobalt(ii) hydroxotrimethylacetato complexes under anaerobic conditions were studied. The nonanuclear cluster Ni₉(₄-OH)₃(₃-OH)₃(_n-OOCCMe₃)₁₂(HOOCCMe₃)₄ gave the mononuclear complex Ni(²-L)(²-OOCCMe₃)₂ (2). The tetranuclear complex Ni₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆ produced the mononuclear complex Ni(²-L)(²-OOCCMe₃)(OOCCMe₃)L (3). At room temperature, the cobalt-containing polynuclear trimethylacetates, viz., the polymer [Co(OH) _n (OOCCMe₃)_2–n ] _x and the tetranuclear complex Co₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆, were transformed into the trinuclear cobalt(ii) complex Co₃(₃-OH)(-OOCCMe₃)₄(²-L)₂(OOCCMe₃) (4). Meanwhile, at 80 °C these compounds generated the binuclear cobalt(iii) complex Co₂(₂²-(HN)C₉NMe₂)₂(-OOCCMe₃)(L)(OOCCMe₃)₃ (5). The structures of the resulting compounds were established by X-ray diffraction analysis. Compounds 2—4 exhibit the antiferromagnetic spin-spin exchange coupling, whereas compound 5 is diamagnetic.     

Synthesis and structures of nickel(II) trimethylacetate dimers with coordinated diamines

Thermal decomposition of the tetranuclear nickel(II) complex Ni₄lη²-o-(NH₂)(NHPh)C₆H₄|₂(MeCN)₂(μ-OOCCMe₃)₄(η²-OOCCMe₃)₂ (I) under an inert atmosphere (o-xylene, 140 °C) was investigated. Under these conditions, the asymmetric binuclear complex Ni|η²-o-(NH₂)(NHPh)C₆H₄‖(η¹-o-(NH₂))(NHPh)C₆H₄|(η²,η-O,O-OOCCMe₃)(η²-OOCCMe₃) (2) was formed at the first stage. Complex2 was converted into the symmetric dimer Ni|η¹-o-(NH₂)(NHPh)C₆H₄|(μ-OOCCMe₃)₄ (3) upon recrystallization from benzene. The structures of complexes2 and3 were established by X-ray diffraction analysis. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1915–1918, November, 2000.     

Thermal behavior of samarium binuclear pivalate and tris-pivalate

Kinetic analysis of the thermolysis of samarium pivalate [Sm₂(μ₂-OOCCMe₃)₄(OOCCMe₃)₂(HOOCCMe₃)₆] · HOOCCMe₃ (1) was carried out (the input data were differential scanning calorimetry (DSC) and thermogravimetry data), and a mathematic model of the process was developed that allowed us to optimize (by calculation) the conditions for formation of {Sm(OOCCMe₃)₃} _n (2) samarium tris-pivalate via thermal decomposition of complex 1. The results of the thermal study of samarium and gadolinium tris-pivalates in the temperature range of −50…+50°C are reported. Specific anomalies were found in the DSC curves and heat capacity versus temperature curves in the temperature range of 0–50°C.     

Unsymmetrical dinuclear cobalt and nickel trimethylacetate complexes

The reaction of the dinuclear complex Co₂(-OOCCMe₃)₂(²-OOCCMe₃)₂bpy₂ (1) with the polymer [Co(OH) _n (OOCCMe₃)_2–n ] _x afforded the unsymmetrical dinuclear complex bpyCo₂(₂-O,²-OOCCMe₃)(₂-O,O"-OOCCMe₃)₂(²-OOCCMe₃) (2). The reaction of 2,2"-dipyridylamine with [Co(OH) _n (OOCCMe₃)_2–n ] _x gave rise to the analogous complex [(C₅H₄N)₂NH]Co₂(₂-O,²-OOCCMe₃)(-OOCCMe₃)₂(²-OOCCMe₃) (3). The reaction of complex 1 with Ni₄(₃-OH)₂(-OOCCMe₃)₄(OOCCMe₃)₂(MeCN)₂[²-o-C₆H₄(NH₂)(NHPh)]₂ (4) produced an isostructural heterometallic analog of complex 2 with composition bpyM₂(₂-O,²-OOCCMe₃)(₂-O,O"-OOCCMe₃)₂(²-OOCCMe₃) (5) (M = Co, Ni; Co : Ni = 1 : 1) and the dinuclear heterometallic complex bpy(HOOCCMe₃)M(-OH₂)(-OOCCMe₃)₂M(OOCCMe₃)₂[o-C₆H₄(NH₂)(NHPh)] (6) (M = Co, Ni; Co : Ni = 0.15 : 1.85). Compounds 2 and 5 exhibit ferromagnetic spin-spin exchange interactions.     

Replacement of carboxylate bridges in polynuclear nickel pivalates with 2-hydroxy-6-methylpyridine anions

The reaction of 2-hydroxy-6-methylpyridine (HL, 1) with nonanuclear nickel trimethyl-acetate Ni₉(OH)₆(OOCCMe₃)₁₂(HOOCCMe₃)₄ (2) in MeCN with a ratio M: L = 1: 1 under mild conditions (20 °C, 15 min) led to degradation of the metal core to form the hexanuclear complex (HL)₂(μ ₂-HL)₂Ni₆(μ₃-OH)₂(μ₂-H₂O)₂(μ-OOCCMe₃)₈(η-OOCCMe₃)₂ (3). Further heating of 3 in acetonitrile at 80 °C for 4 h afforded the (HL)Ni₆(μ ₃-OH)(μ₃,η²-L)₃(μ,η²-L)(μ₃-L)(μ ₃-OOCCMe₃)(μ-OOCCMe₃)₄(η²-OOCCMe₃) complex. The reaction with the use of a 2: 1 THF-EtOH mixture instead of acetonitrile at 50 °C gave the decanuclear complex [Ni₁₀(μ ₃-O)₂(μ₃-OH)₄(μ-OOCCMe₃)₆(μ₃,η ²-L)₆(EtOH)₆](H₂O)₂, which is also produced from compounds 1 and 2 in ethanol. The structures of the resulting complexes were established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 908–917, May, 2007.     

Mono-and polynuclear CoII complexes with 2-hydroxy-6-methylpyridine

The reaction of 2-hydroxy-6-methylpyridine with Co(NO₃)₂·6H₂O or Co(F₃CSO₃)₂·6H₂O in the absence of a deprotonating agent produces the mononuclear complexes Co(HL)₄(NO₃)₂ or Co(HL)₄(F₃CSO₃)₂ (HL is 6-methyl-2-pyridone), respectively. In the presence of triethylamine, the reaction affords the trinuclear complex Co₃(HL)₂(L)₄(NO₃)₂ or the heptanuclear dicationic complex [Co₇L₁₂]·(F₃CSO₃)₂·4MeCN in the case of cobalt nitrate or cobalt trifluoromethanesulfonate, respectively. When HL is deficient, the replacement of the trimethylacetate anions in polymeric cobalt pivalate [Co(OH)_n(OOCCMe₃)_2−n ]_x gives rise to the hexanuclear complex Co₆(μ₃-OH)₂(η²,μ₃-L)₂(μ-OOCCMe₃)₈(HOOCCMe₃)₄, whereas the HLCo₆(μ₃-OH)(η²,μ₃-L)₃(η²,μ-L) (μ₃-L)(μ₃-OOCCMe₃)(μ-OOCCMe₃)₄(η²-OOCCMe₃) complex is generated when HL is present in excess. The structures of the reaction products were established by X-ray diffraction. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1851–1862, November, 2006.     

Reactions of pyrrole-2,5-dicarbaldehyde with 2-aminodiphenylamine in the presence of nickel and cobalt trimethylacetates

The reactions of pyrrole-2,5-dicarbaldehyde (1) with 2-aminodiphenylamine (3) taken in a ratio of 1 : 2 in the presence of polinuclear nickel(ii) and cobalt(ii) trimethylacetate complexes were studied in MeCN. The reaction with Ni₉(HOOCCMe₃)₄(₄-OH)₃(₃-OH)₃(OOCCMe₃)₁₂ (2) afforded the mononuclear complex Ni(OOCCMe₃)₂[(PhHN)C₆H₄NHCHC₄H₂NCHNC₆H₄(NHPh)] (4) with a new ligand, which is the product of condensation of one molecule 1 with two molecules 3 and contains two NHPh groups. By contrast, the reaction with the polymeric complex [Co(OH) _n (OOCCMe₃)_2–n ] _x (5, n = 0.05—0.1) gave rise to the tetranuclear complex Co₄(₄-O)(-OOCCMe₃)₄L₂ (6), where L is, apparently, the product of further oxidation of Schiff"s base to the benzimidazole derivative. The structures of compounds 4 and 6 were established by X-ray diffraction analysis.     

New antiferromagnetic tetranuclear pivalate complex containing Fe<Superscript>III</Superscript> and Fe<Superscript>II</Superscript> atoms

The interaction of [K₂Fe^III ₄(O)₂(OOCCMe₃)₁₀(HOOCCMe₃)₂(H₂O)₂]_n with 2-pyridinecarboxaldehyde results in a mixed-valence complex Fe^IIFe^III ₃(μ₃-O)₂(μ₂-OOCCMe₃)₇L₂··2.5MeCN·3H₂O (L = 2-NC₅H₄COOH_0.75K_0.25). The structure of the complex was established by X-ray analysis. The magnetic properties of the complex were studied. Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2145–2148, September, 2005.     

Reactions of ortho-Phenylenediamine with a Nickel Trimethylacetate Complex

Interaction of ortho-phenylenediamine with the nonanuclear nickel trimethylacetate cluster Ni₉(₄-OH)₃(₃-OH)₃( _n -OOCMe₃)₁₂(HOOCCMe₃)₄(I) in an amine deficiency yields the antiferromagnetic trinuclear complex [Ni₃{-N,N"-(NH₂)₂C₆H₄}₂(HCCOOCMe₃)₃(₃-OH)(-OOCCMe₃)₄]⁺(OOCCMe₃)^–(III) containing bridging diamine ligands. Reaction of excess diamine with Ior IIIleads to the formation of the paramagnetic monomer Ni{²-o-(NH₂)₂C₆H₄}₂(OOCCMe₃)₂(IV), which reacts with atmospheric oxygen to form the known bis(semiquinonediimine) complex Ni[1,2-(NH)₂C₆H₄]₂(V).     

Synthesis,molecular and crystal structure,magnetic properties,luminescence, and solid-phase thermolysis of binuclear Ln(III) pivalates with 2,2′-dipyridyl and 1,10-phenanthroline molecules

Methods of synthesis of binuclear pivalate complexes L₂Ln₂(μ-O,η²-OOCCMe₃)₂(μ₂-O,O′-OOCCMe₃)₂(η²-OOCCMe₃)₂, where Ln = Sm, Eu, Gd, or Er and L = 2,2′-dipyridyl (Bipy) or 1,10-phenanthroline (Phen), from the corresponding binuclear complexes Ln₂(μ₂-OOCCMe₃)₄(OOCCMe₃)₂(HOOCCMe₃)₆ · HOOCCMe₃(I–IV), as well as of coordination polymers {Ln(OOCCMe₃)₃} _n , were suggested. The compounds were characterized by X-ray crystallography and X-ray powder diffraction and their magnetic properties, solid-phase thermolysis, and the phase composition of solid decomposition products were studied. The structures of the metal carboxylate core and surrounding ligands were shown to have an effect on the thermal stability of the complexes. The luminescence properties of the Eu(III) complexes were analyzed.     

Formation of cobalt(iii) cations with semiquinonediimine ligands

The reactions of polynuclear cobalt(ii) trimethylacetates [Co(OH) _n (OOCCMe₃)_2–n ] _x , Co₆(₃-OH)₂(OOCCMe₃)₁₀(HOOCCMe₃)₄, or Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with an excess of N-phenyl-o-phenylenediamine (1) in toluene followed by treatment with atmospheric oxygen afforded the diamagnetic complex [Co{²-(NPh)(NH)C₆H₄}₂{¹-(NH₂)C₆H₄(NPhH)}]⁺(Me₃CCOO...H...OOCCMe₃)^– (3), whose cation contains the Co^III atom. The reaction of Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with a deficient amount of diamine 1 in acetonitrile under an argon atmosphere gave rise to the antiferromagnetic ionic complex [Co{²-(NPh)(NH)C₆H₄}₂MeCN]⁺[Co₂(₂,²-OOCCMe₃)(₂-OOCCMe₃)₂(²-OOCCMe₃)₂]^–·2MeCN (4), whose cation is an isoelectronic analog of the cation in complex 3. The structures of the new compounds were established by X-ray diffraction analysis.     

Chemical assembly of a new heterometallic trimethylacetate cluster with the Co6Ni2 core

Co-thermolysis of the tetranuclear trimethylacetate clusters M₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ (M = Co or Ni; the reagent ratio was 1 : 1) in decalin (2 h, 170 °C) afforded the octanuclear heterometallic cluster Co₆Ni₂(₄-O)₂(₂-OOCCMe₃)₆(₃-OOCCMe₃)₆, which exhibits ferromagnetic properties at 10—8 K.     

Dinuclear rhodium(II) pivalate complexes with N-donor ligands

Eight dinuclear rhodium(II) complexes containing various, (primarily, polyfunctional) N-donor ligands in the trans position with respect to the Rh-Rh bond were synthesized and characterized by X-ray diffraction. In the Chinese-lantern dinuclear rhodium(II) pivalates, Rh^II ₂ (μ-OOCCMe₃)₄(L)₂ (L is 2,3-diaminopyridine (2), 7,8-benzoquinoline (4), 2,2′:6′,2″-terpyridine (5), N-phenyl-o-phenylenediamine (7)), and Rh^II ₂ (μ-OOCCMe₃)₄L¹L² (3, L¹ is 2-phenylpyridine, L² = MeCN), the steric effects of the axial ligands are most strongly reflected in the Rh-N(L) and Rh-Rh bond lengths. The introduction of chelating ligands containing a conformationally rigid chelate ring leads to the cleavage of two carboxylate bridges to form the dinuclear double-bridged structure Rh^II ₂ (μ- OOCCMe₃)₂(OCCMe₃)₂(η²-L³)₂, where L³ is 8-amino-2,4-dimethylquinoline (6). The reaction of complex 7 containing coordinated N-phenyl-o-phenylenediamine with pyrrole-2,5-dialdehyde afforded the new Rh^II ₂(μ-OOCCMe₃)₄(L⁴)₂ complex (8) containing 5-(1-phenyl-1-H-benzimidazol-2-yl)-1H-pyrrole-2-carbaldehyde (L⁴) in the axial positions of the dirhodium tetracarboxylate fragment. The coordinated diamine differs in reactivity from the free diamine. The reaction of the former with the above dialdehyde affords the [1+1]-condensation product, viz., 5-{(E)-[(2-anilinophenyl)imino]methyl}-1-H-pyrrole-2-carbaldehyde, whereas the reaction of unsubstituted o-phenylenediamine gives 5-{(E)-[(2-aminophenyl)imino]methyl}-1-H-pyrrole-2-carbaldehyde (L⁵) . The reaction of the latter with Rh^II ₂(μ-OOCCMe₃)₄(H₂O)₂ affords the dinuclear complex Rh^II ₂(μ-OOCCMe₃)₂(OOCCMe₃)₂(η²-L⁵)₂ (9), which is an analog of complex 6 containing only two bridging carboxylate groups.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 581–591, March, 2005.     

Oxidative dehydrogenation of diaminomaleonitrile coordinated to the nickel and platinum atoms

The reactions of diaminomaleonitrile H₂NC(CN)=C(CN)NH₂ (1) with the nine-nuclear carboxylate nickel(II) complex Ni₉(HOOCCMe₃)₄(μ₄-OH)₃(μ_n-OOCCMe₃)₁₂ (under an inert atmosphere or in air) and with K₂[PtX₄] (in air) afforded the bis-chelate mononuclear complexes M[HNC(CN)C(CN)NH]₂ (M=Ni (2) and Pt (3), respectively). The structural features of compounds 1, 2, and 3, which were determined by X-ray diffraction analysis, are discussed.