Ferromagnetic behavior of linear chain electron-transfer complexes. Decamethylferrocene electron-transfer salts of 2,5-disubstituted-7,7,8,8-tetracyano-p-quinodimethanes. Magnetic characterization of [Fe(C5Me5)2].cntdot.+[TCNQI2].cntdot.- and structures of [TCNQI2]n- (n = 0, 1, 2)