Reactions of nickel(II) complexes containing arsine ligands with electron-deficient olefins. Dianionic and neutral olefin ligands in nickel(II) and nickel(III) complexes

Abstract

The reaction of [Ni₂(bdpa)₃(H₂O)][ClO₄]₄[bdpa = bis(3-dimethylarsinopropyl)phenylarsine] with tetracyanoethylene (tcne) in dichloromethane yields the diamagnetic planar [Ni₂(bdpa)₂(tcne)][ClO₄]₂ complex, from which can be obtained the BPh₄^– and PF₆^– derivatives. Infrared spectra and other measurements allow the assignment of a cis-bridging dianionic tcne^2– ligand. Reaction of [Ni₂(bdpa)₃(H₂O)][ClO₄]₄ with 7,7,8,8-tetracyanoquinodimethane (tcnq) in a 1:3 ratio gives the planar [Ni(bdpa)(tcnq)]ClO₄; this, and the BPh₄^– derivative, are diamagnetic and contain the cis-bridging tcnq^2– dianion. Employing greater amounts of tcnq in this reaction yields the d⁷ nickel(III) five-co-ordinate species [Ni₂(bdpa)₂(tcnq)₂][ClO₄]₂, which exhibits an isotropic e.s.r. signal, g= 2.05, and µ_eff.= 1.88 µ_β. Reaction of the five-co-ordinate [Ni(dmpae)₂X]ClO₄[dmpae = 1,2-bis(methylphenylarsino)ethane] with tcne yields either [Ni(dmpae)(tcne)X]ClO₄(X = Cl or NCS) or [Ni(dmpae)₂(tcne)₂]X[ClO₄](X = Cl, Br, or I). Both of these types of complexes are six-co-ordinate and contain N-bonded unidentate neutral tcne ligands. We have obtained no evidence for olefinic bonding in any of these complexes.