The present invention relates to rubber compositions containing borate compounds of the formula wherein R1 and R2 are independently selected from the group consisting of alkoxy radicals having from 1 to 8 carbon atoms; R3 is selected from the group consisting of alkylene groups having from 1 to 15 carbon atoms and arylene and alkyl substituted arylene groups having from 6 to 10 carbon atoms; X is selected from the group consisting of —SH, —SCN, and —NH2; and Y is selected from the group consisting of Sx and Sex where x is an integer of from 1 to 8.