The η-H-C Hg agostic interactions in the mercury complexes of N-confused porphyrin

Six four-coordinated complexes of the chemical formulae [Hg(2-N CH 2 COOCH 2 CH 3 -21-H-NCTPP)X] with X = Cl ( 5 ), Br ( 6 ), I ( 7 ), [Hg(2-NCH 3 -21-H-NCTPP)Cl] ( 4 ) and [Hg(2-NCH 2 COOCH 2 C 6 H 5 -21-H-NCTPP)X] with X = Cl ( 8 ), I ( 9 ) are synthesized and structurally determined. The bond path for the weak η 1 -H(17)-C(17) Hg agostic interactions between the Hg center and H(17) in complexes 4-9 was a through-space interaction from Hg to agostic carbon [C(17)] followed by a through-bond interaction from C(17) to an agostic proton [H(17)]. The magnitude of J [Hg-H(17)] [or the agostic upfield shift Δ δ ago of the C(17)] for these complexes increases as the halide ligand varies from iodide to chloride, ranging from 33.2 Hz (or 14.3 ppm) for I − to 36 Hz (or 15.8 ppm) for Br − and 36.9 Hz (or 16.0 ppm) for Cl − . The plot of J [Hg-H(17)] for the agostic proton H(17) versus |Δ δ ago | for the agostic carbon atom C(17) in compounds 3-9 was linearly expressed as J [Hg-H(17)] = 2.29 |Δ δ ago | + 0.13. The bond path for the η 1 -H(17)-C(17) Hg agostic interactions in 4-9 was a through-space interaction [Hg C(17)] and a through-bond interaction [Hg H(17)].