Synthesis and coordination chemistry of pyrimidine-substituted phosphine ligands

Reaction of PPh2H with UrI (Ur = uracil) in the presence of Pd(OAc)2 affords PPh2Ur. In the solid state, PPh2Ur crystallises as a methanol solvate in the monoclinic space group P21/c. Reaction of PPh2Ur with CuI in dry and deoxygenated THF solution results in the formation of [Cu4(μ3-I)4(PPh2Ur)4]. A single crystal X-ray diffraction study demonstrated that this species contains a distorted tetrahedral core of copper atoms, with facially-capping iodides. The uracil groups in the clusters are engaged in hydrogen bonding to groups on neighbouring molecules to form an extended array. A similar reaction between PPh2Ur and CuI in unpurified THF allows for the isolation of the phosphine oxide P(O)PPh2Ur. The synthesis of the benzyl-protected phosphine PPh2UrP is also described [UrP = 2,4-bis(benzyloxy)pyrimidine]. Reaction of PPh2UrP with [Ru(η5-C5H5)(NCMe)3]PF6 allows for isolation of [Ru(η5-C5H5)(NCMe)(PPh2UrP)2]PF6.