Metallacycle transfer routes to main-group phosphacycles
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)2-Sn(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)-CPh=CPh (8), the product of ring expansion via C-H 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.
Breen, Tricia L. and Stephan, Douglas W.. (1997). Metallacycle transfer routes to main-group phosphacycles. Organometallics, 16 (3), 365-369.