Ruthenium trihalides

A correlation of isomer shift, electronic configuration, and calculated -electron densities for a number of ruthenium complexes in analogy to the Walker-Wertheim-Jaccarino diagram for iron compounds has been reported by Clausen et al. [ 127]. Also useful is the correlation between isomer shift and electronegativity as communicated by Clausen et al. [128] for ruthenium trihalides where the isomer shift appears to increase with increasing Mulliken electronegativity. 

The poor solubility of these ruthenium trihalide complexes in most organic solvents suggests that they have an oligomeric structure bridged by halogen atoms. 

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

Ruthenium forms the whole range of trihalides but only fluorides in higher states. 

Tetravalent ruthenium chloride, RuC14. and the hydroxy chloride, RuiOH)CE, are intermediate products when RuCh is prepared by evaporating the tetroxide in TIG. When the hydroxychloride in hot IIQ is treated with Q2. it is converted to the tetrachloride. The anhydrous tetrachloride also is known. The tetrabromide and tetraiodide have not been isolated attempts to prepare these compounds result 111 the formation of the respective trihalides. 

The starting material for preparation of these derivatives, [Ru2(00)4(11 -CsH5)2], has previously been obtained by the reaction of sodium cyclo-pentadienide with a dihaloruthenium(II) carbonyl [Ru(CO)2l2] (ref. 3) or [Ru(CO)3Cl2]2(ref. 4) prepared by carbonylation of the corresponding ruthenium(III) trihalide. A more facile synthesis was later reported, involving the reaction of triruthenium dodecacarbonyl with cyclopentadiene. The procedure described herein represents a modification of this second method, resulting in an improved yield. 

Pyridazine forms a stable adduct with iodine, with semiconductor properties. " Similar complexes were prepared from iodine mono-ehloride, bromine, and nickel(II) ethyl xanthate. Complexes of pyrida-zines with iron carbonyls and with iron carbonyls and triphenylphosphine have been prepared and investigated. " Complexes of pyridazines with boron trihalides, silver salts, mercury(I) salts, iridium salts, " ruthenium salts, and chromium carbonyls are re-... 

---