(Pyrazolylborate)zinc Organophosphate Complexes Resulting from Hydrolytic Cleavage of Phosphate Esters

Five different (pyrazolylborate)zinc hydroxide complexes Tp*Zn−OH (1) were used as hydrolytic reagents towards esters of various acids of phosphorus. Trimethyl phosphate and trimethyl phosphite could not be cleaved. Dimethyl and diphenyl phosphite yielded TptBu,MeZn−OPHO(OR) (2, 3). Triphenyl phosphate reacted slowly producing moderate yields of Tp*Zn−OPO(OPh)2 (4). Tris(p-nitrophenyl) phosphate was cleaved rapidly, forming Tp*Zn−OPO(OC6H4NO2)2 (5) and Tp*Zn−OC6H4NO2 (6). Alkylbis(p-nitrophenyl) phosphates showed intermediate reactivity, losing p-nitrophenolate upon hydrolysis and producing Tp*Zn−OPO(OR)(OC6H4NO2) (7, 8). When phosphorus acid diesters were employed, condensation between the Zn−OH and P−OH functions occurred. This proved to be the convenient way of preparing the organophosphate complexes Tp*Zn−OPO(Ph)2 (9), Tp*Zn−OPO(OPh)2 (4), and Tp*Zn−OPO(OC6H4NO2)2 (5). Six structure determinations showed the structural variability of the resulting complexes.