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The Ni(II) triazenide complex, trans -( o -Tol)Ni(PEt 3 ) 2 N 3 Ar 2 (Ar= p -FC 6 H 4 ) ( 1 ), was synthesized by the reaction of trans -( o -Tol)Ni(PEt 3 ) 2 Br with Ar 2 N 3 Na. The crystal structure as well as the 1 H-, 19 F- and 31 P-NMR spectra in toluene- d 8 at different temperatures are reported. It was found that the triazenido group acts as a monodentate ligand. Complex 1 in solid state has a S - cis -structure with NiN(3) σ-bond and exists as a 3:1 mixture of two isomers with cisoid or transoid orientation of the Me group of the o -tolyl ligand relative to the N(1)N(2) bond. It was established that the N , N ′-migration of ( o -Tol)Ni(PEt 3 ) 2 group occurs in a solution of 1 . The migration rate increases with the temperature increase in the range from −104 to −45°C. However, a further increase in the temperature slows down the process.

The first η2-olefinic monocarbon metallacarbone closo-2-(Ph3P)-1-N,2-[μ-(η2-CH2CHCh2)]-1-N-(σ-CH2CHCH2)-2,1- RhCB10H10 has been prepared by the reaction of the dimeric anion {[Ph3PRhB10H10CNH2]2-μ-H}−[PPN]+ with allyl bromide and characterized by a combination of spectroscopic methods and a single-crystal X-ray diffraction study. The variable temperature 1H and 13C NMR studies revealed the fluxional behavior of the η2-olefinic complex in CD2Cl2 solution which is associated with the allyl side-chain exchange process.

Organocobalt(III) complexes with Schiff bases derived from a β -diketone bearing both an alkyl and an aryl group have been prepared. The template syntheses using benzoylacetone and ethylenediamine as complexing agents provide a route to alkylcobalt chelates with the corresponding tri- and tetradentate Schiff bases. However, if a β -diketone with two aryl groups, e.g. dibenzoylmethane, was employed as the starting ketoenol component, no organometallic products were detected; a new mixed-ligand ‘inorganic’ chelate of cobalt(II), [Co{O=C(Ph)CH=C(Ph)O} 2 (en)], was isolated instead. Its structure as well as that of one of the alkylcobalt complexes with a tridentate Schiff base composed of benzoylacetone and ethylenediamine have been established by X-ray techniques. The current scope of the template synthesis of alkylcobalt complexes with Schiff bases is summarized.

Reactions of acetylide clusters M3H(C⋮CFc)(CO)9 (1a, M = Ru; 1b, M = Os; Fc = ferrocenyl) with Ru3(CO)12 in refluxing hexane yield the tetranuclear clusters RuM3H(C⋮CFc)(CO)12 (2a,b) with a butterfly metal core. The μ4-acetylide ligand of these complexes undergoes migration, indicated by variable-temperature 1H and 13C NMR studies. Compounds 2a and 2b are relatively unstable in solution as well as in the solid state and decompose with formation of corresponding trinuclear acetylide precursors and Ru3(CO)12. The molecular structures of 1a and 2a were established by the X-ray diffraction study of a mixed crystal, which contains both clusters in a 1:1 ratio.

By reaction of [ ω -diphenylphosphinoalkyl]diphenylphosphine sulphides Ph 2 P(CH 2 ) n P(S)Ph 2 ( n = 2–4) (L 1 −L 3 ) with AgNO 3 in CH 3 CN crystalline complexes with the composition metal:ligand 1:1 [Ag(L 1 )NO 3 , Ag(L 2 )NO 3 , Ag(L 3 )NO 3 ] and 1:2 [Ag(L 1 ) 2 NO 3 , Ag(L 3 ) 2 NO 3 ] were isolated. According to the X-ray analysis data, the crystals of Ag(L 1 )NO 3 are constructed from centrosymmetric dimeric molecules based on the 12-membered macrocycle AgSPCH 2 CH 2 PAgSPCH 2 CH 2 P ¯ . Each of the neutral ligands L 1 is a bridge between two silver ions and each of the silver ions is coordinated by a chelating NO 3 group. According to the IR spectra, the other 1:1 complexes also have an analogous structure. In the 1:2 complexes the coordinated NO 3 groups of the 1:1 complexes are replaced by the phosphine sulphide ligand. The downfield shifts of the signals of P III and P V atoms in 31 P NMR spectra of 1:2 complexes in comparison with the free ligands L 1 and L 3 reflect a participation of the P III atom and P=S group in complex formation.

Novel 12-vertex closo-hydridometallacarboranes 3,1,2-[(PPh3)2OsHXC2B9H11] (1a,b: X = Cl, H) and 3,1,2-[(PPh3)2OsH2-1,2-Me2C2B9H9] (1c) have been synthesized via oxidative addition of K+ salts of the nido-carborane anions [nido-7,8-R2-7,8-C2B9H10]- (R = H, Me), respectively, to OsCl2(PPh3)3 and characterized by spectroscopic (NMR and IR) as well as by single-crystal X-ray diffraction studies of 1a,c.

Treatment of [nido-B10H12CH]-Cs+ with RuCl2(PPh3)3 in methanol under gentle reflux afforded the two novel 10-vertex monocarbon ruthenacarboranes 2-Cl-2,5-(Ph3P)2-2-H-3,9-(MeO)2-2,1-RuCB8H6 (3) and 2,2-(Ph3P)2-2-H-3,9-(MeO)2-2,1-RuCB8H7 (4) along with a small amount of the 8-vertex complex (PPh3)2HRuCB6H4(OMe)3 (6). The 10-vertex clusters 3 and 4 on the basis of their capped-tricapped-trigonal-prismatic geometry, established for 3 by a single-crystal X-ray diffraction study, and the formal Wadian electron-counting arguments can be regarded as hyper-closo species having n rather than n + 1 skeletal electron pairs.

Results of structural studies of polynuclear transition metal complexes containing the metallacyclopentadiene fragment are overviewed. The structural features of the complexes in relation to the nature of the substituents in the organic moiety of the metallacycles, the nature of the transition metals and their ligand environment are analysed. The main structural characteristics corresponding to different modes of coordination of metallacyclopentadienes to one or two additional metal centres are revealed. The bibliography includes 154 references.

The first representative of the 1,2,3,4-tetrazine-N-oxides, 5,7-dibromobenzo-1,2,3,4-tetrazine-1-N-oxide 4b, has been obtained by intramolecular reaction of o-(tert-butylazoxy)phenyldiazonium tetrafluoroborate 2b. Compound 4b has been characterized by NMR spectroscopy and an X-ray diffraction study and its transformation 4b→ 5b→ 6b investigated; o-azidonitrosobenzene 5b was isolated and characterized for the first time.

Benzo-l,2,3,4-tetrazine 1-N-oxide formation involves the intramolecular cyclization of 2-(tert-butyl-NNO -azoxy)phenyldiazonium tetrafluoroborates and the N→N migration of the tert-butyl group to afford 2-(tert-butyl)benzo-l,2,3,4-tetrazinium 4-N-oxides 3 followed by elimination of the tert-butyl group. Compounds 3 were hydrolysed to give a new heterocyclic system, viz. 2-alkyl-6-oxo-2,6-dihydrobenzo-l,2,3,4-tetrazine 4-N-oxides. For 2-(tert-butyl)-8-bromo-6-oxo-2,6-dihydrobenzo-l,2,3,4-tetrazine 4-N-oxide an X-ray diffraction study was carried out.

Monomeric isocyano complexes of rhodium(III) have been prepared from 1,2-dimethyl-3-isocyano- 2b and 3-isocyano-1,2-dicarba-closo-dodecaborane(12) 2a and rhodium dimer [(η5-C5Me5)RhCl2]2 1; the structure of the resulting carborane rhodium complex was determined by an X-ray diffraction study.

It has been shown that nucleophilic substitution in 6β-chloro-7,8-didehydro-4,5α-epoxy-3-rnethoxy-17-methylmorphinan and 8β-bromo-6,7-didehydro-4,5α-epoxy-3-rnethoxy-17-methylmorphinan is accompanied by allylic rearrangement with both a change in and retention of the orientation of the substituting group. X-Ray diffraction studies of 8α-phenyl-6,7-didehydro- 4,5α-epoxy-3-methoxy-17-methylmorphinan and 6β-phenyl-7,8-didehydro-4,5α-epoxy-3-rnethoxy-17-methylmorphinan have been carried out.

Addition of (OC)5MCCPh (M = Mn,Re) to HOs3(CO)10(µ,η2-CCPh) leads to the formation of carbon–carbon bonds under mild conditions to yield metal cluster compounds HOs3M(CO)14(C2Ph)2; the cluster HOs3Re(CO)14(C2Ph) has been characterized by an X-ray structure analysis.