The Electron Transfer Series [Mo III (bpy) 3 ] n ( n =3+, 2+, 1+, 0, 1−), and the Dinuclear Species [{Mo III Cl( Me bpy) 2 } 2 (μ 2 ‐O)]Cl 2 and [{Mo IV (tpy . ) 2 } 2 (μ 2 ‐MoO 4 )](PF 6 ) 2 ⋅4 MeCN

The electronic structures of the five members of the electron transfer series [Mo(bpy) 3 ] n ( n =3+, 2+, 1+, 0, 1−) are determined through a combination of techniques: electro‐ and magnetochemistry, UV/Vis and EPR spectroscopies, and X‐ray crystallography. The mono‐ and dication are prepared and isolated as PF 6 salts for the first time. It is shown that all species contain a central Mo III ion (4d 3 ). The successive one‐electron reductions/oxidations within the series are all ligand‐based, involving neutral (bpy 0 ), the π ‐radical anion (bpy . ) 1− , and the diamagnetic dianion (bpy 2− ) 2− : [Mo III (bpy 0 ) 3 ] 3+ ( S =3/2), [Mo III (bpy . )(bpy 0 ) 2 ] 2+ ( S =1), [Mo III (bpy . ) 2 (bpy 0 )] 1+ ( S =1/2), [Mo III (bpy . ) 3 ] ( S =0), and [Mo III (bpy . ) 2 (bpy 2− )] 1− ( S =1/2). The previously described diamagnetic dication “[Mo II (bpy 0 ) 3 ](BF 4 ) 2 ” is proposed to be a diamagnetic dinuclear species [{Mo(bpy) 3 } 2 (μ 2 ‐O)](BF 4 ) 4 . Two new polynuclear complexes are prepared and structurally characterized: [{Mo III Cl( Me bpy 0 ) 2 } 2 (μ 2 ‐O)]Cl 2 and [{Mo IV (tpy . ) 2 } 2 (μ 2 ‐Mo VI O 4 )](PF 6 ) 2 ⋅4 MeCN.