Heterobimetallic Nickel(II) Complexes of Ferrocenyldithiophosphonates. Molecular Structures of [{FcP(OR)S₂}₂Ni] [Fc = Fe(η⁵‐C₅H₄)(η⁵‐C₅H₅), R = Et, Pri, Bus, Bui]

The reaction of 2,4‐diferrocenyl‐1,3‐dithiadiphosphetane 2,4‐disulfide [FcPS(μ‐S)] 2 [Fc = Fe(η 5 ‐C 5 H 4 )(η 5 ‐C 5 H 5 )] with alcohols ROH gave the corresponding ferrocenyldithiophosphonic acids [FcPS(OR)(SH)], which were treated in situ with Ni(CH 3 COO) 2 ·4H 2 O in acetic acid to yield the square‐planar heterobimetallic trinuclear complexes [{FcP(OR)S 2 } 2 Ni] (R = Me ( 1 ), Et ( 2 ), Pr i ( 3 ), Bu s ( 4 ) and Bu i ( 5 )). Compounds 1‐5 were characterized by elemental analysis, MS, NMR ( 1 H, 13 C and 31 P), IR spectroscopy, and 2‐5 also by X‐ray crystallography. Cyclovoltammetric studies on the heterobimetallic nickel(II) complexes 1‐5 showed irreversible reduction to unstable nickel(I) complexes and an irreversible two‐electron oxidation of the sulfur‐containing nickel fragments, followed by a reversible one‐electron oxidation of the two ferrocenyl groups.