Disproportionation of Bis(phosphaethenyl)pyridine Iron(I) Bromide Induced by tBuNC

• Published in: Organometallics 2014-11, Vol.33 (22), p.6700-6703
• Main Authors: Lin, Ya-Fan, Ichihara, Nobuko, Nakajima, Yumiko, Ozawa, Fumiyuki
• Format: Article
• Language: eng ; jpn
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om500901a

Redox behavior of Fe(I) complexes bearing a PNP-pincer-type phosphaalkene ligand, 2,6-bis[1-phenyl-2-(2,4,6-tri-tert-butylphenyl)-2-phosphaethenyl]­pyridine (BPEP-Ph), is reported. The four-coordinate Fe(I) complex [FeBr(BPEP-Ph)] (1) readily reacts with 1 equiv of tBuNC in toluene at −35 °C to give [FeBr(tBuNC)(BPEP-Ph)] (2) with a 17e configuration. Complex 2 is fairly stable in neat benzene at room temperature, but smoothly undergoes disproportionation in the presence of added tBuNC to afford the Fe(0) complex [Fe(tBuNC)2(BPEP-Ph)] (3) and the Fe(II) complex [FeBr2(tBuNC)4] (4) along with free BPEP-Ph. The single-crystal X-ray diffraction studies of 3 and 4 reveal distorted trigonal bipyramidal and square pyramidal arrangements around Fe, respectively. The yield of 3 increases up to 50%/2 when 2 equiv of tBuNC is added to the system. A disproportionation process involving a 19e intermediate is proposed.