Metallacycle Transfer Routes to Main-Group Phosphacycles

Abstract

The employment of phosphazirconacycles in metallacycle transfer reactions is a facile method for the synthesis of main-group phosphacycles. Reactions of Cp2Zr(PPh)3 (1), Cp2Zr(P(R*)C(Ph)CPh) (2), and Cp2Zr(P(Mes)P(Mes)C(Ph)CPh) (3) with various main-group dihalides results in cleavage of TM−MG bonds and formation of new MG−MG bonds. Triphosphanato complex 1 reacts with PhPCl2 or tBu2SnCl2 to yield (PPh)4 (4) and (t-Bu)2Sn(PPh)3 (7), respectively. Reaction of phosphametallacyclobutene 2 with PhPCl2 results in the formation of the unsymmetrically substituted 1,2-diphosphetene P(Ph)P(R*)C(Ph)CPh (5), while reaction with PhBCl2 yields PH(C6H2-(2-CH2C(CH3)2)-4,6-t-Bu2)B(Ph)CPhCPh (8), the product of ring expansion via CH activation. Phosphametallacyclopentene 3 reacts with PhPCl2 to furnish the unsymmetrically substituted 1,2,3-triphospholene P(Ph)P(Mes)P(Mes)C(Ph)CPh (6). Advantages to such metallacycle transfer reactions include (i) facile accessibility of main-group derivatives where conventional syntheses are laborious, tedious, and/or fraught with safety issues, (ii) selective control over molecular fragments, and (iii) new routes to novel main-group compounds.