Synthesis and reactivity of mixed-ligand isocyanide–diphosphine iron(0) complexes. X-Ray crystal structure of cis-[Fe(dppe)(CNPh)2{N(Ph)C(Me)–CNPh}]ClO4

Abstract

Reduction of mer-[Fel(L–L)(CNR)₃]I [(1a), L–L = 1,2-bis(diphenylphosphino)ethane (dppe), R = Ph; (1b) L–L = dppe, R = C₆H₄Me-4; (1c), L–L = bis(diphenylphosphino)methane, R = Ph] with sodium amalgam in tetrahydrofuran gives the very air-sensitive complexes [Fe(L–L)(CNR)₃](2a)–(2c) respectively. Compound (2a) reacts with NH₄PF₆ to give mer-[FeH(dppe)(CNPh)₃]PF₆(3), which is readily transformed to its fac isomer (4) by heating. Reaction of (2a) with SnPh₃Cl yields the novel heterodimetallic cation mer-[Fe(SnPh₃)(dppe)(CNPh)₃]⁺(5). Addition of CH₃I to toluene solutions of complexes (2a)–(2c) gives the neutral compounds [[graphic omitted]NR}](6a)–(6c) respectively which possess a new chelating ligand. Compound (6a) reacts with phenyl isocyanide in the presence of AgClO₄ to give cis-[[graphic omitted]NPh}]ClO₄(7) and with carbon monoxide in the presence of TIPF₆ to give [[graphic omitted]NPh}]⁺. For complex (7), a single-crystal X-ray diffraction study was carried out. The iminic nitrogen in (6a) is easily protonated with HClO₄ affording the cationic complex [[graphic omitted]–NHPh}]ClO₄. Complex (2a) reacts with allyl bromide to give mainly the undesired mer-[FeBr(dppe)(CNPh)₃]⁺ and a small amount of the neutral complex [[graphic omitted]NPh}].