Activation of C-H bonds in acetylene and terminal alkynes by rhodium(I) species. Crystal structure of cis-(ethynyl)hydrie BPh4.1.5C4H8O (NP3 = N(CH2CH2PPh2)3)

Article abstract of DOI:10.1016/0022-328X(88)80146-3

The 16-electron fragment (NP3)Rh⁺ inserts in a highly stereospecific manner across C-H bonds from acetylene and 1-alkynes to give the octahedral cis-(alkynyl)hydrides <(NP3)Rh(H)(C=-CR)>BPh4 (R = H, Ph, COOEt).The structure of the cis-(ethynyl)hydride <(NP3)Rh(H)(C=-CH)>BPh4.1.5 THF has been established by X-ray diffraction.The trigonal bipyramidal rhodium(I) complex <(NP3)RhH>, reacts with terminal alkynes to give H2 and the neutral ?-acetylides <(NP3)Rh(C=-CR)> (R = Ph, COOEt).These undergo metathesis between terminal alkynes and the ?-acetylide ligand through a mechanism involving consecutive breaking and making of C-H bonds.