trans Influence and Steric Effect on the Distortions in Planar NiS4, NiS2PN,and NiS2P2 Chromophores

The planar diamagnetic complexes Ni(achdtc)₂] ( 1 ),Ni(achdtc)(PPh₃)(NCS)] ( 2 ), and Ni(achdtc)(PPh₃)₂]ClO₄ · 0.5EtOAc ( 3 ) (achdtc = allylcyclohexylcarbodithioate) were prepared, characterized by elemental analysis, electronic, IR, NMR (¹H, ¹³C, and ³¹P) spectroscopy and the crystal structures were determined by single‐crystal X‐ray crystallography. The characteristic thioureide bands occur at 1478, 1503, and 1507 cm^–1 for 1 , 2 , and 3 , respectively and the corresponding ¹³C chemical shifts are observed at 207.67, 204.16, and 202.31 ppm. ³¹P chemical shifts are observed at δ = 29.24 and 22.73 ppm for 2 and 3 , respectively, indicating a strong interaction. Electronic spectral bands are observed at 480, 483, and 475 nm for 1 , 2 , and 3 , corresponding to d → d_xy/d transitions. Ni–S distances are asymmetric. The trans influence of PPh₃ elongates the Ni–S bonds. The decrease in the S–Ni–S bite angle in 2 78.80(16)°] and in 3 78.36(2)°] compared to that observed in 1 79.42(3)°] is due to the steric crowding of PPh₃ around the central metal atom. A comparison of the bond parameters of compounds 1 – 3 shows a change in the arrangement from a planar NiS₄ chromophore to distorted planar NiS₂P₂ chromophores. The observed distortion from planar to tetrahedral arrangement is influenced by the bulky triphenylphosphine ligand.