Schiff-base derivatives of molybdenum carbonyl

Summary Reactions of five Schiff bases (SB),viz.,N,N-ethylenebis(benzalideneimine) (SB¹),N,N-ethylenebis(p-anisylideneimine) (SB²),N,N-ethylenebis(methylphenylketimine) (SB³),N,N-ethylenebis(diphenylketimine) (SB⁴) andN,N-ethylenebis (salicylideneimine) (SB⁵) with molybdenum hexacarbonyl have been studied. The first four Schiff bases yieldcis-disubstituted derivatives whereas a non-carbonyl complex is obtained for the last one (SB⁵). [(Ph₃E)Mo(CO)₅] (E = P or As) after reaction with SB give SB-bridged dinuclear [(Ph₃E)(CO)₄Mo--(SB)-Mo(CO)₄(Ph₃E)] derivatives. Halogen-oxidation and nitrosylation ofcis-[(SB)Mo(CO)₄] have also been studied.     

Some substituted thiourea complexes of molybdenum carbonyl

Preparation of monosubstituted thiourea complexes of molybdenum carbonyl [Mo(CO)₅L] both by thermal and UV irradiation methods have been described. The ligands (L) used were N,N′-dimethylthiourea (DMTU), N,N′-diphenylthiourea (DPTU), tetramethylthiourea (TMTU) and tetraethylthiourea (TETU). The complexes [Mo(CO)₅(L)] were characterised by NMR, IR, UV-visible and elemental analyses.     

Cobalt and molybdenum carbonyl clusters in immunology. Synthesis and binding properties of mycotoxin derivatives of zearalenone

Transition metal cluster haptens of zearalenone derivatives having high binding affinity values for antibodies specific for this mycotoxin series have been synthesised. This provides the basis for a new type of non-isotopic immunoassay.     

Glycylglycine derivatives of rhenium carbonyl

Conclusions A linear and a cyclic carbonyl compound of rhenium were synthesized, which contain glycylglycine as the ligand.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1647–1649, July, 1982.     

The lack of intramolecular carbonyl ligand rearrangement in the stereospecifically 13co labelled (diamine)molybdenum tetracarbonyl derivatives

The preparation and spectral characterization of stereospecifically, axially labelled Mo(CO)₃(¹³CO)(diamine) complexes (diamine  N,N,N′,N′-tetramethylethylenediamine and N,N,N′,N′-tetramethyl-1,3-diaminopropane) and the rigidity (or lack of fluxionality) of the carbonyl ligands during subsequent thermal reactions of these derivatives are reported.     

Diazabutadienes as σ,π-bridging ligands in binuclear molybdenum carbonyl complexes containing molybdenummolybdenum double bonds

Reduction of Mo(CO)₄ DAB (DAB = diazabutadiene) followed by oxidation with Mn(CO)₃BrDAB or HCl gives a small yield (15 to 25%) of complexes of the type Mo₂(CO)₆(DAB)₂, in which the two DAB ligands bridge a molybdenummolybdenum double bond and act as σ,π-donors.     

Chromium carbonyl nitrosyls: comparison with isoelectronic manganese carbonyl derivatives

Density functional methods indicate that the global minimum for Cr2(NO)2(CO)8 is a staggered D4d structure in accord with experiment and analogous to the isoelectronic Mn2(CO)10. For the unsaturated Cr2(NO)2(CO)n derivatives the lowest energy structures are very different from the lowest energy structures for the isoelectronic Mn2(CO)n+2 derivatives. Thus the global minimum for Cr2(NO)2(CO)7 is an unbridged structure with a Cr(NO)(CO)4 fragment linked to a Cr(NO)(CO)3 fragment through a Cr=Cr double bond. For Cr2(NO)2(CO)6 the global minimum is a structure with two bridging CO groups, whereas the global minimum for Mn2(CO)8 is an unbridged structure. For Cr2(NO)2(CO)5 both NO groups are bridging NO groups with one of them having a short enough Cr-O distance to be considered a formal five-electron donor eta2-mu-NO group. Thus the isoelectronic substitution of NO for CO with a necessary adjustment in the central metal atom can lead to significant shifts in the relative energies of various structural types of metal carbonyl nitrosyls, particularly for unsaturated molecules. For the mononuclear Cr(NO)2(CO)3 the theoretical structure differs from that deduced from matrix isolation experiments. Moreover, the nu(CO) and nu(NO) vibrational frequencies predicted here for Cr(NO)2(CO)3 correspond more closely with the unassigned species labeled "Cr(NO)(CO)x" in the experiments rather than the species claimed to be Cr(NO)2(CO)3.     

Manganese carbonyl nitrosyls: comparison with isoelectronic iron carbonyl derivatives

The manganese carbonyl nitrosyls Mn(NO)(CO)4, Mn2(NO)2(CO)n (n = 7, 6, 5, 4), and Mn3(NO)3(CO)9 have been studied by density functional theory (DFT) using the B3LYP and BP86 methods for comparison of their predicted structures with those of isoelectronic iron carbonyl derivatives. DFT predicts a trigonal bipyramidal structure for Mn(NO)(CO)4 with an equatorial NO group very close to the experimental structure. The predicted lowest energy structure for Mn2(NO)2(CO)7 has two bridging NO groups in contrast to the known structure of the isoelectronic Fe2(CO)9, which has three bridging CO groups. The structures for the unsaturated binuclear Mn2(NO)2(CO)n (n = 6, 5, 4) derivatives are similar to those of the corresponding binuclear iron carbonyls Fe2(CO)n+2 derivatives but always with a preference of bridging NO groups over bridging CO groups. The trinuclear Mn3(NO)3(CO)9 is predicted to have a structure analogous to the known structure for Fe3(CO)12 but with two bridging NO groups rather than two bridging CO groups across one of the metal-metal edges of the M3 triangle. The dark red solid photolysis product of Mn(NO)(CO)4 characterized by its nu(CO) and nu(NO) frequencies approximately 45 years ago is suggested by these DFT studies not to be the originally assumed Mn2(NO)2(CO)7 analogous to Fe2(CO)9. Instead, this photolysis product appears to be Mn2(NO)2(CO)5 with a Mn(triple bond)Mn formal triple bond analogous to (eta5-C5H5)2V2(CO)5 obtained from the photolysis of (eta5-C5H5)V(CO)4.     

Rhodium carbonyl derivatives containing Rh-O-Si bonds

Summary The following mono-, di- and tetra-nuclear rhodium carbonyl derivatives with silanolato and disilanolato ligands were prepared: Rh(CO)(PR₃)₂(OSiR₃), [Rh(CO)₂(OSiR₃)]₂, Rh₂(CO)₃ (PBu₃)(OSiR₃)₂ and Rh₄(CO)₈(OSiPh₂)₂ (R = Me or Ph; R = n-Bu or Ph). The complexes may serve as models for the bonding of transition metals on silica surfaces.     

Synthesis of carbonyl derivatives of 3-phenylthiophene

3-Phenyl-2-acetylthiophene was synthesized by the acetylation of 3-phenylthiophene with acetic anhydride in the presence of 56% perchloric acid. Previously undescribed , -unsaturated ketones were synthesized by the crotonic condensation of 3-phenyl-2-acetylthiophene with several aromatic and heterocyclic aldehydes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1365–1367, October, 1971.     

Ionization constants of carbonyl derivatives of pyrrole

The indicator ratios of 22 carbonyl derivatives of pyrrole in sulfuric acid solutions were determined by spectrophotometry. The investigated compounds are divided into three groups with respect to the magnitude of the slope of the dependence of the indicator ratio on the molar concentration of the acid (d log I°/dC_c). Carbethoxypyrroles are characterized by a medium d log I°/dC_c value (0.70), which is the same as that observed for a number of indoles (0.70). For 2- and 3-formyland 3-acetylpyrroles this value (0.53) is close to the value obtained for Hammett bases (0.48). 2-Acetylpyrroles form a separate group. The ionization constants of the investigated compounds were determined with the aid of the corresponding acidity functions (H₁ and H₀). The effects of substitution on the basicity of the pyrrole ring are discussed.     

Conformational flexibility of 1,4-dihydroazine carbonyl derivatives

Summary The molecular geometry of 4-oxo derivatives of 1,4-dihydropyridine, 1,4-dihydropyrimidine, 1,4-dihydropyridazine, and 1,4-dihydro-1,3,5-triazine has been calculated by the semi-empirical quantum-chemical AM1 method. It could be shown that the dihydrocycle in these compounds is not conformationally rigid. Changing the angle between the endocyclic double bond planes ±15° causes less than 1 kcal/mol increase of energy.

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Konformative Flexibilität von 1,4-Dihydroazin-carbonyl-Derivaten (Kurze Mitt.)

Zusammenfassung Die molekulare Geometrie von 4-Oxo-Derivaten von 1,4-Dihydropyridin, 1,4-Dihydropyrimidin, 1,4-Dihydropyridazin und 1,4-Dihydro-1,3,5-triazin wurde mittels der semiempirischen quantenchemischen AM1-Methode berechnet. Es konnte gezeigt werden, daß der zweifach hydrierte Ring in diesen Verbindungen nicht starr ist. Eine Änderung des Winkels zwischen den Ebenen der endocyclischen Doppelbindungen um ±15° bewirkt eine Energieerhöhung von weniger als 1 kcal/mol.

     

Ruthenium carbonyl derivatives of N-salicylidene-2-hydroxyaniline

The ruthenium tricarbonyl derivative [Ru(CO)₃(sha)] (1), was synthesized from reaction of [Ru₃(CO)₁₂] with N-salicylidene-2-hydroxyaniline (shaH₂) Schiff base. The corresponding reactions of the ruthenium cluster with shaH₂ in presence of a secondary ligand L,L?=?pyridine and triphenyl phosphine resulted in the formation of the dicarbonyl derivatives [Ru(CO)₂(shaH₂)(L)] (2, 3). In the presence of L?=?2-aminobenzimidazole or thiourea, two complexes [Ru(CO)₂(sha)(L)] (4, 5) were formed and the shaH₂ ligand bonded to ruthenium oxidatively. The bipyridine(bpy) derivative had the molecular formula [Ru(CO)₂(shaH)(bpy)] (6), with shaH coordinated bidentate. All complexes were characterized by elemental analysis and mass, IR, ¹H NMR and UV–Vis spectroscopy. The spectroscopic studies of these complexes revealed several structural arrangements and different tautomeric forms.     

A new type of benzotriazole coordination in carbonyl complexes of molybdenum

We report the synthesis of new complexes of molybdenum carbonyl with benzotriazole and 1-methylbenzotriazole in which heterocycles containing the NH or NCH₃ group still act as bidentate ligands.Crystals of the benzotriazole derivative were subjected to an X-ray study. Its structure is built of complex molecules (BtH)₃Mo₂(CO)₆ linked with THF molecules via hydrogen bonds. The molecule has the crystallographic symmetry C_s with the Mo atoms, two CO groups and one benzotriazole ligand in the symmetry plane.