Compounds of the following formula: in which: - E is a linear C 1 to C 5 alkyl chain, - GF is a reactive group chosen from the vinyl and alkoxysilane groups the alkoxy chain of which is C 1 to C 5, linear or branched, saturated or unsaturated, optionally containing at least one heteroatom, preferably N and/or O; - R 1 is a phosphine group P(R 4) 2, - R 2 is H or a phosphine group P(R 6) 2, - X 1, X 2, X 3 and X 4 are identical or different and are chosen, independently of one another, from a hydrogen atom, a group P(R 8) 2, a group -C(CH 3) 2 -P(R 3) 2 or an amino group R 7 N(R 5) 2, - X 5 is either a group GF-E-C(CH 3) 2 - in which GF and E are identical to GF and E defined previously, or H, or a phosphine group P(R 10) 2 or an amino group R 11 N(R 9) 2, - R 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10 and R 11 are, independently of one another, chosen from a C 1 to C 30 alkyl group, preferably C 1 to C 10, more preferably C 1 to C 5, linear or branched, saturated or unsaturated, optionally containing at least one heteroatom, preferably an N and/or O atom, or an aryl group, or a cyclic or acyclic aliphatic group, C 3 to C 7, optionally containing a heteroatom, preferably an N and/or O atom and optionally substituted, preferably by at least one methyl, methoxy or halogen (F, Cl, Br, I) preferably F or Cl, or CF 3 group; they are preferably chosen from a -CH 2 -, ethyl (Et), isopropyl (i-Pr), cyclohexyl (Cy) or tert-butyl (t-Bu) group, or a phenyl (Ph) or furyl (Fu) group, optionally substituted, preferably by at least one methyl, methoxy, halogen (F, Cl, Br, I) preferably F or CL, or CF 3 group; more preferably R 3, R 4, R 6, R 8 and R 10, are a phenyl group, R 5 and R 9 are both an ethyl group, R 7, R 11 are both a -CH 2 - group. - E is a linear C 1 to C 5 alkyl chain, - GF is a reactive group chosen from the vinyl and alkoxysilane groups the alkoxy chain of which is C 1 to C 5, linear or branched, saturated or unsaturated, optionally containing at least one heteroatom, preferably N and/or O; - R 1 is a phosphine group P(R 4) 2, - R 2 is H or a phosphine group P(R 6) 2, - X 1, X 2, X 3 and X 4 are identical or different and are chosen, independently of one another, from a hydrogen atom, a group P(R 8) 2, a group -C(CH 3) 2 -P(R 3) 2 or an amino group R 7 N(R 5) 2, - X 5 is either a group GF-E-C(CH 3) 2 - in which GF and E are identical to GF and E defined previously, or H, or a phosphine group P(R 10) 2 or an amino group R 11 N(R 9) 2, - R 3, R 4, R 5, R 6, R 7, R 8, R 9, R 10 and R 11 are, independently of one another, chosen from a C 1 to C 30 alkyl group, preferably C 1 to C 10, more preferably C 1 to C 5, linear or branched, saturated or unsaturated, optionally containing at least one heteroatom, preferably an N and/or O atom, or an aryl group, or a cyclic or acyclic aliphatic group, C 3 to C 7, optionally containing a heteroatom, preferably an N and/or O atom and optionally substituted, preferably by at least one methyl, methoxy or halogen (F, Cl, Br, I) preferably F or Cl, or CF 3 group; they are preferably chosen from a -CH 2 -, ethyl (Et), isopropyl (i-Pr), cyclohexyl (Cy) or tert-butyl (t-Bu) group, or a phenyl (Ph) or furyl (Fu) group, optionally substituted, preferably by at least one methyl, methoxy, halogen (F, Cl, Br, I) preferably F or CL, or CF 3 group; more preferably R 3, R 4, R 6, R 8 and R 10, are a phenyl group, R 5 and R 9 are both an ethyl group, R 7, R 11 are both a -CH 2 - group.