“…One possibility is the use of various ligands in conjunction with classical anionic initiators. r-Ligands, such as crown ethers 6) , cryptands 7,8) , tertiary amines 9,10) ; l-ligands, such as alkali alkoxides 11,12) halides 2, 13) , perchlorates 14,15) , aluminum alkyls [16][17][18][19] , and r, l-ligands, such as alkoxyalkoxides [20][21][22][23] , aminoalkoxides 24) , and silanolates [25][26][27] have been used with much success.…”