Heptaphosphorus-derived compounds as flame retardants

A heptaphosphorus-derived (P7) compound selected from the group consisting of triazine heptaphosphide and trialkylheptaphosphine of the formula

• P7(Rx)3 (I),
• wherein Rx represents a group of the partial formula
• —CR1R2R3 (A),
• wherein
• a) one of R1, R2 and R3 represents hydrogen;
• one of R1, R2 and R3 represents C1-C4-alkyl, phenyl or C1-C4-alkyl substituted with phenyl;
• and
• one of R1, R2 and R3 represents the group of the partial formula
• —CH═CRaRb (B),
• wherein
• one of Ra and Rb represents (C1-C4alkyl)3silyl;
• and the other
• one of Ra and Rb represents C1-C4-alkyl, phenyl or C1-C4-alkyl substituted with phenyl;
• or
• b) one of R1, R2 and R3 represents hydrogen;
• one of R1, R2 and R3 represents C1-C4-alkyl, phenyl or C1-C4-alkyl substituted with phenyl;
• and
• one of R1, R2 and R3 represents the group of the partial formula
• —CH—C(═O)—Ra (C),
• wherein
• Ra represents C1-C4-alkyl, phenyl or C1-C4-alkyl substituted with phenyl;
• or
• wherein
• c) one of R1, R2 and R3 represents hydroxy;
• one of R1, R2 and R3 represents hydrogen;
• and
• one of R1, R2 and R3 represents C1-C4-alkyl, phenyl or C1-C4-alkyl substituted with phenyl;
• or
• d) one of R1, R2 and R3 represents hydroxy;
• and
• two of R1, R2 and R3 represent C1-C4-alkyl, phenyl or C1-C4-alkyl substituted with phenyl.