Alkyl Transfer Reactivity in the First Octahedral Isocyanide Complex of Nickel(II)

[Ni{S2P(OEt)2}2] (1) reacts with 2 equiv of CNXyl (Xyl = 2,6-dimethylphenyl) to afford
[Ni{S2P(OEt)2}2(CNXyl)2] (2), which, as confirmed by X-ray crystallography, is the first
octahedral isocyanide complex of Ni(II). Reaction of 2 with PCy3 (2 equiv) produces square-planar [Ni{S2P(O)(OEt)}(PCy3)(CNXyl)] (3). When 2 is reacted with only 1 equiv of PCy3,
the final product is the square-planar complex [Ni{S2P(O)(OEt)}(CNXyl)2] (4), containing
two isocyanide ligands. Compound 4 reacts with 2-fold excess PCy3 to give 3 via isocyanide
displacement. Both 3 and 4 contain one ethyldithiophosphate ligand, which is produced by
the transfer of one ethyl group from a coordinated diethyl dithiophosphate of complex 2 to
the leaving diethyl dithiophosphate ligand. Experimental evidence indicates that the
phosphine plays a significant role in the alkyl transfer. Moreover, reaction of 1 with 2 equiv
of N-p-tolyl-2-iminopyridine affords octahedral [Ni{S2P(OEt)2}{2-pyCHNC6H4-Me-4}2][S2P(OEt)2] (5), in which both free and coordinated diethyl dithiophosphate coexist without any
transfer of alkyl.