Arylboron complexes of the acids Ph2C(XH)CO2H (X = O, NH)

The acids Ph2C(XH)CO2H (X = O, NH) readily react with the triarylboron reagents BAr3 (Ar = Ph, C6F5) to form the complexes [Ph2C(O)CO2BPh] (1) and [Ph2C(NH2)CO2BPh2] (2), Ph2C(p-CH3C6H4)CO2H (3a) [in the presence of Et3N the complex HNEt3[Ph2C(OH)CO2B(C6F5)3] (3b) was formed], and [Ph2C(NH3)CO2B(C6F5)3] (4), respectively. The synthesis and crystal structures of 1–4 (synchrotron radiation was necessary for 2) are reported.