Deprotonation of a heterodinuclear transition-metal hydride complex and reactions of the anion with electrophiles: X-ray crystal structures of [(η5-C5H5)(OC)2Mo{µ-Ag(PPh3)}(µ-PPh2)Mn(CO)4] and [(η-C5H5)(OC)2Mo(µ-I)(µ-PPh2)Mn(CO)4]

Abstract

Deprotonation of [(η⁵-C₅H₅)(OC)₂Mo(µ-H)(µ-PPh₂)Mn(CO)₄] with base gives the heterodinuclear anion [(η⁵-C₅H₅)(OC)₂Mo(µ-PPh₂)Mn(CO)₄]^– which has been isolated as its [NEt₄]⁺ salt. This anion reacts with complexes of Group 1 B metals to give heterotrinuclear complexes of the type [(η⁵-C₅H₅)(OC)₂Mo(µ-ML)(µ-PPh₂)Mn(CO)₄][ML = Au(PPh₃), Au(PMe₂Ph), or Ag(PPh₃)]. A single-crystal X-ray diffraction study established the structure of the silver-containing complex. The metal atom triangle [Mo–Mn 3.190(2), Ag–Mn 2.664(2), and Ag–Mo 2.874(2)Å] is bridged by a PPh₂ group along the Mo–Mn edge [Mo–P 2.387(4) and Mn–P 2.272(4)Å]. The bridging phosphorus atom lies 0.3 Å out of the plane of the three metal atoms resulting in an angle between this plane and the Mo–Mn–(µ-P) plane of 7.59°. The phosphorus atom in the PPh₃ group lies 0.11 Å out of the Mo–Mn–Ag plane on the same side of the plane as the phosphido ligand. The heterodinuclear anion reacts with iodine to give, as the major product, the iodo-bridged compound [(η⁵-C₅H₅)(OC)₂Mo(µ-I)(µ-PPh₂)Mn(CO)₄] which has been characterised by a single-crystal X-ray diffraction study. The two metal atoms in this complex are 3.978(2)Å apart indicating the absence of a metal-metal bond and the angle between the planes defined by Mo–Mn–(µ-I) and Mo–Mn–(µ-P) is 145.0°. Loss of one molecule of CO during the reaction of the heterodinuclear anion with I₂ accounts for the formation of [(η⁵-C₅H₅)(OC)₂Mo(µ-I)(µ-PPh₂)Mn(CO)₃] which is obtained as a minor product. The major product is converted in near quantitative yield into the minor product on photolysis and the minor product is similarly converted into the major product on treatment with CO.