At 110 °C α-substituted [Fe2(CO)6(µ-PhC![[double bond, length half m-dash]](http://hg.y866.cn/compound/lib/scimg/usr/1/A804403A.jpg)
CH2)(µ-PPh2)] 1 is cleanly converted into the β-isomer [Fe2(CO)6(µ-HCCHPh)(µ-PPh2)] 2, a process which is accelerated in the presence of arylphosphines; with P(OMe)3 mono- and di-substituted adducts of 1 are isolated at 70 °C, which cleanly isomerise at higher temperatures.
