Synthesis of a phospha-arsene and a phosphastibene; the first compounds with phosphorus–arsenic and phosphorus–antimony double bonds

The reaction of (Me3Si)2CHMCl2(M = As or Sb) with (2,4,6-But3C6H2)PH2 in the presence of 1,5-diazabicyclo[5.4.0]undec-5-ene affords the double-bonded compounds, (2,4,6-But3C6H2)PMCH(SiMe3)2(M = As or Sb)