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)–C
NPh}]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}].