Linear trichromium complexes with direct Cr to Cr contacts. 2. Compounds with Cr-3(dipyridylamide)(4)(3)+ cores

Seven compounds having in common a Cr-3(dpa)(4)(3+) core (dpa = di(2-pyridy l)amide ion) have been prepared and all shown to have an unsymmetrical chai n of three Cr atoms. This chain can be described as a pair of quadruply bon ded Cr-II atoms to which a Cr-III atom is attached. No symmetrical chain ha s been found, contrary to a previous preliminary report. The seven compound s have been well characterized crystallographically, and their short and lo ng Cr to Cr distances (Angstrom, in parentheses) are: 1 [Cr-3(dpa)(4)Cl-2]C l . 2CH(2)Cl(2). THF (2.12, 2.47), 2 [Cr-3(dpa)(4)Cl-2]AlCl4. CH2Cl2 (2.011 , 2.555), 3 [Cr-3(dpa)(4)Cl-2]FeCl4. CH2Cl2 (2.009, 2.562), 4 [Cr-3(dpa)(4) Cl-2]I-3. THF . 2H(2)O (2.08, 2.49), 5 [Cr-3(dpa)(4)Cl-2]PF6. 2CH(2)Cl(2) ( 2.08, 2.48), 6 [Cr-3(dpa)(4)(BF4)F]BF4. 2-CH2Cl2 (1.900, 2.595), 7 [Cr-3(dp a)(4)ClF]BF4. CH2Cl2. C6H14 (2.039, 2.507). Magnetic susceptibility measure ments on 1 and 2 reveal mu(eff) = 3.85 +/- 0.05 mu(B) from 10 to 300 K.