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The complex [VCl 2 (tmen) 2 ] (tmen = N,N,NЈ,NЈ-tetramethylethane-1,2-diamine) changes spontaneously into a triangulo-trinuclear species [V 3 (µ-Cl) 3 (µ 3 -Cl) 2 (tmen) 3 ] ϩ in solution in tetrahydrofuran upon addition of salts of suitable counter ions. The apical (µ 3 ) chlorides can be replaced by methoxide, and the tmen by diphosphines. Several related materials, all containing the triangulo-V 3 X 3 (X = Cl or Br) motif, were characterised by mass spectroscopy, X-ray diffraction and other techniques. These clusters are antiferromagnetic both in solution and in the solid state. Thermogravimetric analysis of trans-[VCl 2 (tmen) 2 ] and of [V(MeOH) 6 ]Cl 2 implied the formation of similar triangulo-V 3 Cl 3 species, which appear to be of common occurrence in vanadium() chemistry. 2)᎐V( 1)᎐Cl( 3) Cl( 2)᎐V( 1)᎐Cl( 4) Cl( 3)᎐V( 1)᎐Cl( 4) Cl( 2)᎐V(1)᎐Cl( 5) Cl( 3)᎐V( 1)᎐Cl( 5) Cl( 4)᎐V( 1)᎐Cl( 5) Cl( 2)᎐V( 1)᎐N( 11) Cl( 3)᎐V( 1)᎐N( 11) Cl( 4)᎐V( 1)᎐N( 11) Cl( 5)᎐V( 1)᎐N( 11) Cl( 2)᎐V( 1)᎐N( 12) Cl( 3)᎐V( 1)᎐N( 12) Cl( 4)᎐V( 1)᎐N( 12) Cl( 5)᎐V( 1)᎐N( 12) N( 11)᎐V( 1)᎐N( 12) Cl( 1)᎐V( 2)᎐Cl( 3) Cl( 1)᎐V( 2)᎐Cl( 4) Cl(3)᎐V( 2)᎐Cl( 4) Cl( 1)᎐V( 2)᎐Cl( 5) Cl(3)᎐V(2)᎐Cl( 5) Cl( 4)᎐V(2)᎐Cl( 5) Cl(1)᎐V(2)᎐N( 21) Cl(3)᎐V( 2) ᎐N(21)

From the variation of magnetic properties with temperature trans-bis[ 1,2-bis(diethylphosphino)ethane]di-iodochromium(ii) undergoes a sharp S = 2 to S = 1 spin-state transition between 165 and 175 K.

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The dihydrated chromium(l1) complex bromides M,[CrBr,(OH,),],where M = Cs, Rb, NH,, or Hpy (py = pyridine), are magnetically dilute, high-spin compounds. The ammonium salt is isomorphous with the analogous copper(l1) bromide which is known to contain frans-[C~Br,(OH,),]~-anions with two short and two long Cu-Br bonds.

The reaction of [VCI,( MeCN),] with SiMe,l in acetonitrile under reflux yielded a vanadium(l1) cation [V(MeCN)J2+ with a counter ion I : -.