Organometallic precursors and related methods

A method for preparing a precursor comprising:

• combining a first arene and a mixture of bis (arene) metal complexes;
• heating the first arene and the mixture of bis (arene) metal complexes;
• cooling the first arene and the mixture of bis (arene) metal complexes to obtain a bis (first arene) metal complex;
• combining the bis (first arene) metal complex and a second arene;
• and
• heating the bis (first arene) metal complex and the second arene to obtain a bis (second arene) metal complex.

A composition comprising:

• a precursor comprising a bis (arene) metal complex of at least one of the following formulas:
• where:
• M is Cr, Mo, W, Fe, or V;
• Z is a bond, an alkyl, a heteroatom, or a heteroalkyl;
• Ar4 is an arene of the formula:
• where:
• Rg, Rh, Ri, Rj, Rk, and Rm are each independently a hydrogen, a halogen, a dialkylamino, an alkyl, an alkoxy, an aryl, or a cycloalkyl;
• Ar5 is an arene of the formula:
• where:
• Rn, Ro, Rp, Rq, and Rr are each independently a hydrogen, a halogen, a dialkylamino, an alkyl, an alkoxy, an aryl, or a cycloalkyl;
• Ar6 is an arene of the formula:
• where:
• Rs, Rt, Ru, Rv, and Rw are each independently a hydrogen, a halogen, a dialkylamino, an alkyl, an alkoxy, an aryl, or a cycloalkyl;
• wherein the precursor has a purity of 90% or greater.