Calcium-mediated hydrophosphination of diphenylethyne and diphenylbutadiyne as well as crystal structure of 1,4-diphenyl-1,4-bis(diphenylphosphanyl)buta-1,3-diene

Hydrophosphination reactions of phenyl substituted alkynes are catalyzed effectively by [(thf)4Ca(PPh2)2] (1). The reactions of diphenylethyne and diphenylbutadiyne with diphenylphosphane in THF in the presence of catalytic amounts of 1 (approx. 5 mol%) yield quantitatively the cis-addition products trans-1,2-diphenyl-1-diphenylphosphanylethene (2) and 1,4-diphenyl-1,4-bis(diphenylphosphanyl)buta-1,3-diene (3), respectively. The phenyl groups in 3 are oriented nearly perpendicular to the butadiene backbone and therefore, the π-systems of the phenyl groups and the butadiene unit show no interaction with each other.