Abstract: A compound having the molecular formula: ##STR1## wherein, M is selected from the group consisting of pentavalent atoms of Group V of the Periodic Table; R.sub.1, R.sub.2 and R.sub.3 are selected from the group consisting of substituent groups bondable to M; X is an electron withdrawing group; A is a connecting group capable of undergoing either condensation or addition reactions with compatible function groups of other compounds; R.sub.4 is an optional connecting group between the X and A groups; B is selected from the group consisting of R.sub.1, R.sub.2, R.sub.3, O--X--R.sub.4).sub.n A and O--X--R.sub.5, and wherein R.sub.5 is selected from the group consisting of R.sub.1, R.sub.2 and R.sub.3 ; and n is the integer 0 or 1. These pentavalent atom-containing compositions may be reacted into polymers with monomers, prepolymers or polymers. The compositions and polymers have flame-retardant properties.

Abstract: A compound having the molecular formula: ##EQU1## wherein, M is selected from the group consisting of pentavalent atoms of Group V of the Periodic Table; R.sub.1, R.sub.2 and R.sub.3 are selected from the group consisting of substituent groups bondable to M; X is an electron withdrawing group; A is a connecting group capable of undergoing either condensation or addition reactions with compatible function groups of other compounds; R.sub.4 is an optional connecting group between the X and A groups; B is selected from the group consisting of R.sub.1, R.sub.2, R.sub.3, O--X--R.sub.4).sub.n A and O--X--R.sub.5, and wherein R.sub.5 is selected from the group consisting of R.sub.1, R.sub.2 and R.sub.3 ; and n is the integer 0 or 1. These pentavalent atom-containing compositions may be reacted into polymers with monomers, prepolymers or polymers. The compositions and polymers have flame-retardant properties.