Formation, characterization, and structural studies of novel thiosemicarbazone palladium(II) complexes. Crystal structures of [{Pd[C6H4C(Et)NNC(S)NH2]}4], [Pd{C6H4C(Et)NN C(S)NH2}(PMePh2)] and [{Pd[C6H4C(Et)NNC(S)NH2]}2(μ-Ph2PCH2PPh2)]

Abstract

The reaction of thiosemicarbazones 4-MeC 6 H 4 C(Me)᎐ ᎐ NN(H)C(᎐ ᎐ S)NH 2 a, C 6 H 5 C(Et)᎐ ᎐ NN(H)C(᎐ ᎐ S)NH 2 b and 4-MeC 6 H 4 C(Me)᎐ ᎐ NN(H)C(᎐ ᎐ S)NHMe c with K 2 [PdCl 4 ] led to tetranuclear palladiumthe ligands are tridentate through the [C, N, S ] atoms and they are deprotonated at the NH group. The Pd-S chelating bond is sufficiently strong for the complexes to undergo reactions with nucleophiles without bond cleavage. The molecular structure of 1b has been determined by single-crystal diffraction, confirming the formation of the tetranuclear moieties. Hydrogen bonding N ؒ ؒ ؒ H and S ؒ ؒ ؒ H links Pd 4 clusters into strands in the solid state. Reaction of 1a and 1b with phosphines gave mono-and di-nuclear species, 2a, 2b, 3b and 5a, 5b, respectively. Treatment with 1,1Ј-bis(diphenylphosphino)ferrocene led to trimetallic compounds 6a and 6b. The molecular structure of 3b has been determined by X-ray crystallography; dimer units are present through N ؒ ؒ ؒ H hydrogen bonds. The reaction of 2b with hydrochloric acid resulted in a 1 : 1 electrolyte, 4b, with NH and C᎐ ᎐ S groups. Alternatively, treatment of 1a, 1b and 1c with strong chelating phosphines produced mononuclear compounds with only cleavage of the Pd-S bridging bonds, 7a, 7b, 7c and 8c with the diphosphine monodentate; 7a and 7b were obtained with the dinuclear species 7aЈ and 7bЈ, respectively, as impurities, where the bidentate phosphine ligand bridges two metallated units. The crystal structure of one such compound, 7bЈ, with a bridging bis(diphenylphosphino)methane ligand, is also described.

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°.…”

Tetranuclear Complexes of PdII with Tridentate [C,N,O] and [O,N,O] Ligands: Synthesis, Reactivity and Structural Isomerism

“…In the 1 H NMR spectrum the HC=N and 5-H resonances were high-field shifted, as compared to the uncoordinated ligand, by 1.43 and 0.9 ppm, respectively; the low δ values in these cases were due to the structure of the complexes, which puts the HC=N and 5-H protons in the proximity of the shielding zone of the phenyl rings of a neighbouring metallated ligand. [32,33,37,39] Likewise, absence of the OH resonance in the 1 H NMR spectrum confirmed deprotonation.…”

“…[25] Nevertheless, few examples of supramolecular species with cyclometallated building blocks have been reported, [26][27][28][29][30][31] many of which correspond to tetrameric assemblies derived from palladium(II) cyclometallated complexes with [C,N,X] (X = O, S) tridentate ligands. Thus, for the [C,N,S] species, thiosemicarbazones give tetranuclear structures with an eight-membered Pd 4 S 4 core, [32][33][34] and tetranuclear cluster complexes derived from benzothiazolines [35,36] are also known. As for the [C,N,O] derivatives, [37][38][39][40] they also exhibit an analogous tetranuclear structure with a Pd 4 O 4 core.…”

Synthesis, characterization and structural studies of palladium(II) complexes with N-(aroyl)-N′-(2,4-dimethoxybenzylidene)hydrazines

“…In each of these three complexes (1-3), the bianionic planar ligand (L 2À ) acts as tridentate C,N,O-donor and the PPh 3 satisfies the fourth coordination site. However, under the same reaction condition ortho-metallation does not occur when R = NO 2 and the complex isolated in 77% yield is trans-[Pd(HL)(PPh 3 ) 2 Cl] (4) where the monoanionic HL À acts as monodentate deprotonated amide N-donor (Scheme 1). The molecular structures of all the complexes (1-4) have been confirmed by X-ray crystallography (vide infra).…”

“…Thiosemicarbazones and semicarbazones of aromatic aldehydes are known to act as tridentate ligands for Pd(II) and Pt(II) via ortho-metallation and can yield cyclometallated complexes having two fused five-membered chelate rings at the metal centre [1][2][3][4]. Thiosemicarbazones can coordinate the metal ion as mono-or bianionic C,N,Sdonor ligand.…”