X-ray Crystal Structures of Cp*Ni(PEt3)X [X = Br, O(p-C6H4Me), NH(p-C6H4Me), S(p-C6H4Me), OCH3, CH2C6H5, Me, H, PEt3+]. Understanding Distortions and Trans Influences in Cyclopentadienyl Complexes

The syntheses of Cp*Ni(PEt 3 )Me and Cp*Ni(PEt 3 )Br have been accomplished, starting from the useful starting material Cp*Ni(PEt 3 )(acac). The X-ray crystal structures of Cp*Ni(PEt 3 )X (X = Br, O( p -C 6 H 4 Me), NH( p -C 6 H 4 Me), S( p -C 6 H 4 Me), OCH 3, Me, CH 2 Ph, H, PEt 3 + ) have been determined, providing a large sample of similar structures for the analysis of ring distortions as well as a systematic variation of X in order to evaluate the trans influence felt by opposite sides of the cyclopentadienyl ring. Major advances include demonstration that Cp can reduce its electron donation to a metal without “slipping”, the rational analysis of cyclopentadienyl distortions, and a well-supported trans-influence series for cyclopentadienylmetal complexes. In sum, d 8 Cp*NiL 2 complexes are similar to d 8 NiL 4 square-planar complexes in terms of bond lengths, binding geometry, and trans influences.