[Bis(tetrahydrofuran-O)-bis(1,3-dialkyl-2-diphenylphosphanyl-1,3-diazaal lyl)calcium] - Synthesis and Crystal Structures of Calcium Bis[phospha(III)guanidinates] and Investigations of Catalytic Activity

摘要

The reaction of [(thf)(4)Ca(PPh2)(2)] (1) with diisopropyl- and dicyclohexylcarbodiimides yields the phospha(III)guanidinates [(thf)(2)Ca(RNC(PPh2)NR}(2)] with R = isopropyl (2) and cyclohexyl (3). The metathesis reaction of K{RNC(PPh2)NR) with anhydrous Cal(2) also allows the synthesis of these phospha(III)guanidinate complexes 2 and 3. For 2 a cis arrangement is observed whereas 3 crystallizes as trans isomer. The phospha(III)guanidinates act as bidentate chelate bases with an average Ca-N distance of 242.5 pm. The C-P bond length between the PPh2 fragment and the 1,3-diazaallyl unit is with values above 190 pm very large, The complexes 2 and 3 show a moderate catalytic activity in hydrophosphanylation reactions of dialkylcarbodiimides with diphenylphosphane.