The present invention relates to a composition comprising a phosphacycle-containing ligating compound represented as:

wherein:
P is phosphorus; X 1 is phosphorus; each of R 1 and R 2 is independently a substituted or
unsubstituted hydrocarbon derivative, a substituted or unsubstituted heterohydrocarbon derivative, or a substituted or unsubstituted heteroatom group having from one to 50 non-hydrogen atoms; m is 1; R 1 and R 2 are linked together to form a divalent moiety represented as

which together with P forms a cyclic structure (phosphacycle) containing from 3 to 10 ring atoms; each of R 3 and R 4 is independently hydrogen, halogen, a substituted or unsubstituted hydrocarbon derivative, a substituted or unsubstituted heterohydrocarbon derivative, or a substituted or unsubstituted heteroatom group having from one to 50 non-hydrogen atoms; R 3 and R 4 are optionally linked together to form a divalent moiety represented as

wherein the optional character of the linkage is depicted by a dashed connection, which together with X 1 forms a cyclic structure containing from 3 to 10 ring atoms; Y is a divalent linking group [L(R 5 ) q ] p between P and
X 1 containing from one to 50 non-hydrogen atoms; [L(R 5 ) q ] p is represented by:

wherein each L is independently selected from the group consisting of nitrogen; p is an integer number from 1 to 6; R 5 is independently hydrogen, halogen, substituted or unsubstituted hydrocarbon derivative, substituted or unsubstituted heterohydrocarbon derivative, or a substituted or unsubstituted heteroatom group; q is 0, 1, or 2; provided that the [L] p subunit of the divalent linking group [L(R 5 ) q ] p does not comprise an amidine (N-C=N) group; further provided that in at least one phosphacycle of the phosphacycle-containing ligating compound, both atoms directly bonded to P or X 1 are sp 3 hybridized; still further provided that one or two phosphacycles comprising P, R 1 , and R 2 , or comprising X 1 , R 3 , and R 4 , contain no P-N, P-O, or P-S bonds within the ring part of the phosphacycle; two R 5 groups attached to the same L atom may be optionally linked together to form a cyclic structure that contains from 3 to 10 ring atoms; from two to ten independently selected ligating compounds may be optionally linked together via their respective independently selected Y, R 1 , R 2 , R 3 , R 4 or R 5 groups to form a poly(ligating compound) species, and wherein the composition is not 8-aza -1-phosphatricylo[3.3.0.0 2,6 ]octane.