Palladium(II) Cyclometalated Thiosemicarbazone Compounds:  A New Class of Bidentate P,S Metallo Ligands

Abstract

Reaction of the tetranuclear compounds 1−4 with bis(diphenylphosphino)methane gave the mononuclear complexes 5−8, with the diphosphine ligand binding in a monodentate fashion. Compounds 5−8 are capable of bonding systematically to a second palladium atom through the noncoordinated phosphorus atom and the sulfur atom of the thiosemicarbazone moiety to give the dinuclear compounds 9−12, thus behaving as new bidentate P,S-metallo ligands. All of the compounds have been characterized by IR and NMR spectroscopy, and the molecular structure of 9 has been determined by X-ray crystallography.

Synthesis, Characterization, and Crystal Structure Analysis of the First Terdentate [C,N,S] Thiosemicarbazone Complex with a Six‐Membered Palladacycle: Influence of Steric Effects on Ring Size

“…The angles between adjacent atoms in the coordination sphere are close to the expected value of 90°. However, as opposed to previous results where the C-Pd-N bite angle was less than 90°, due to formation of a five-membered metallacycle, [25,26] the sixmembered ring in the present case allows a larger bite of the C,N chelate, thereby relieving strain on the angle at the metal; consequently, the C(1A)-Pd(1A)-N(1A) angle is 94.27°. On the other hand, inspection of the N(2A)-Pd(1A)-S(1A) bite angle of the five-membered Pd-N-N-C-S ring shows a similar value to that observed earlier in related complexes, with a value of 83.45°.…”

Synthesis, characterization and solid state structures of thiosemicarbazone palladacycles: Influence of hydrogen bonding in the molecular arrangement

“…Two unique features distinguish thiosemicarbazones form other terdentate [C, N, X] (X = N, O, P) ligands: (a) the strength of the Pd-S chelating bond, which hinders opening of the metallated and coordination rings at the metal center, thus making the ligands excellent pincer species which powerfully secure three of the four coordination positions of the metal, allowing only the fourth coordination site to undergo further reaction with nucleophiles; (b) metallation of the ligand yields tetrameric compounds bearing a central Pd 4 S 4 central core. Upon reaction of the tetranuclear species with tertiary diphosphines, compounds with bridging or with mono-coordinate diphophine are obtained, the strength of the Pd-S chelating bond preventing the chelating bidentate mode of the diphosphine ligand [23,24]; with g 1 -diphosphines the corresponding compounds may behave as bidentate [P, S] metalloligands as we have previously shown [29]. In the cases with bridging diphosphines the 1 H and 31 P NMR data suggest symmetrical arrangements across the phosphine ligand, the transoid geometry being preferred to the cisoid one, as steric effects are minimized, as solid structural analysis has shown [24,30] (Fig.…”

Bonding and structure trends of thiosemicarbazone derivatives of metals—An overview

“…The phenyl rings at C 2 carbon involve metallation in the dinuclear complexes [Pd 2 L 2 (dppm)]·CH 3 COCH 3 212 [103] (dppm = Ph 2 PCH 2 PPh 2 ), and [Pd 2 LCl 2 (dppm)] 213 [241]. The former has bridging dppm and the latter has both sulfur and dppm as bridging moieties.…”

“…Neutral thiosemicarbazone ligands coordinate via a S-donor atom in complexes 231-247. Complexes have either trigonal planar (231,232) or distorted tetrahedral geometry (233)(234)(235)(236)(237)(238)(239)(240)(241)(242)(243)(244)(245)(246)(247)(248)(249). The geometry of N 3 , S-chelated complex 248 is more distorted.…”