Consider reduction of the following cobalt complexes [Co(NH3)5(L)]3+ (L = pyridine (I), NC5H4-p-CH2NH2 (II), NC5H4-p-CONH2 (III)) by labile [Cr(OH2)6]2+. a). Which cobalt complex is least likely to be reduced by an inner-sphere mechanism? b). The reduction of III proceeds with a rate constant of k = 17.4, while the reduction of I proceeds with a rate constant of k = 4.0 × 10-3. What is a likely explanation of the difference?