at least one r 2 is not hydrogen each r 3 is independently selected from r rco roco roco 2 or sr n r 2 op r 2 and op or 2 m is 0 when a is p or b and is 1 when a is sn si or c n is 0 to 4 depending on the number of available sites and p is 0 to 3 for the tin stabilizers and 0 to 2 for the boron stabilizers two r 1 or two r 2 groups or an r 1 group and an r 2 group can be bridged together to form a ring groups that can bridge r 1 or r 2 groups together to form a ring include r 4 u2014 hc u2550 ch u2014 u2014 ch 2 o u2014 u2014 ch 2 nh u2014 u2014 hc u2550 n u2014 and u2014 ch 2 s where r 4 is alkylene from c 1 to c 20 arylene from c 6 to c 20 aryl alkylene from c 7 to c 20 alkyl arylene from c 7 to c 20 alkanediyl from c 1 to c 20 aryl alkanediyl from c 7 to c 20 u2014 co alkylene co u2014 from c 1 to c 20 u2014 co arylene co u2014 from c 6 to c 20 u2014 co aryl alkylene co u2014 from c 7 to c 20 u2014 co alkyl arylene co u2014 from c 7 to c 20 si r 2.