The reactions of 4-bromo-1-(2-chloroethyl)-1H-pyrazole prepared from 4-bromopyrazole with the in situ generated PhSNa, PhSeNa, Na(2)S and Na(2)Se have resulted in thio/selenoether ligands L1-L4 respectively. The complexes [PdL1/L2Cl(2)](1-2) and [PdL3/L4Cl]BF(4) (3-4) of these ligands have been synthesized by reacting them with [PdCl(2)(CH(3)CN)(2)] in CH(3)CN at 70 °C. The L1-L4 and their complexes (1-4) have been characterized with spectroscopic techniques viz.(1)H, (13)C{(1)H} and (77)Se{(1)H} NMR, IR and HR-MS. Single crystal structures of 1-4 determined by X-ray diffraction reveal nearly square planar geometry around Pd in each case. Thermally stable, moisture/air insensitive complexes 1-4 have been found to be efficient pre-catalysts for Suzuki-Miyaura coupling reactions (yield up to 96% in 2 h). Nano-particles (NPs) (size ~3-19 nm) were formed in the beginning of these reactions. They are composed of Pd and S or Se with more % of Pd. These NPs also catalyze Suzuki coupling and appear to play an important role in catalysis. Single source one pot synthesis of Pd(4)Se and PdSe NPs (size ranges ~8-26 nm), capped with trioctylphosphine (TOP), has been developed by thermolysis of 2 and 4 at 200-250 °C in TOP. HR-TEM, SEM, SEM-EDX and powder XRD have been used to authenticate these nano-particles. The NPs of PdP(2) are formed when attempts were made to prepare nano-sized phases of palladium-sulfide by thermolysis of 1 and 3 in TOP.

The complexes of composition fac-[(η6-C6H6)Ru(L)][PF6][X] (1−6; X = PF6 or Cl), formed by reacting 2-MeSC6H4CHNCH2CH2E-C6H4-4−R (L1−L3) and 2-MeSC6H4CH2-NHCH2CH2E-C6H4-4−R (L4−L6) (where E = S or Se, R = H; E = Te, R = OMe) with [{(η6-C6H6)RuCl(μ-Cl)}2] and NH4PF6, have been characterized by 1H, 13C{1H}, 77Se{1H}, and 125Te{1H} NMR spectroscopy and X-ray crystallography. The Ru−Se and Ru−Te bond lengths are in the ranges 2.4837(14)−2.4848(14) and 2.6234(6)−2.6333(7) Å, respectively. Complexes 1−6 have been found to be efficient catalysts for catalytic oxidation of alcohols with N-methylmorpholine-N-oxide, tBuOOH, NaOCl, and NaIO4 and transfer hydrogenation reaction of ketones with 2-propanol. The TON values are up to 9.9 × 104 and 9.8 × 104 for two catalytic processes, respectively. The oxidation probably involves the formation of intermediate species having Ru(IV)O. Complexes 1−3 are as efficient as 4−6 for transfer hydrogenation of ketones. In transfer hydrogenation, the mechanism does not appear to be dependent on the availability of hydrogen on nitrogen and probably involves Ru−H bond formation. The catalytic efficiency for both processes follows the order Te > Se > S, which may be due to the presence of a MeO group on Te.

Synthesis of Palladium Complexes [Pd(L2) 2 ].2ClO 4 −A solution of [Pd(L2)Cl 2 ] (0.0645 g, 0.1 mmol) made in 5 mL of methanol was mixed with L2 (0.0468 g, 0.1 mmol) and silver perchlorate (0.0410 g, 0.2 mmol) dissolved in methanol (5 mL) with vigorous stirring. An orange precipitate was obtained instantaneously which was filtered,

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1,2,4,5-Tetrakis(phenyselenomethyl)benzene (L) has been synthesized by reaction of in situ generated PhSe(-) with 1,2,4,5-tetrakis(bromomethyl)benzene in N(2) atmosphere. Its first bimetallic complexes and a bis-pincer complex having compositions [(η(3)-C(3)H(5))(2)Pd(2)(L)][ClO(4)](2) (1) [Pd(2)(C(5)H(5)N)(2)(L)][BF(4)](2) (2) and [(η(6)-C(6)H(6))(2)Ru(2)(L)Cl(2)][PF(6)](2) (3) have been synthesized by reacting L with [Pd(η(3)-C(3)H(5))Cl](2), [Pd(CH(3)CN)(4)][BF(4)](2) and [(η(6)-C(6)H(6))(2)RuCl(2)](2) respectively. The structures of ligand L and its all three complexes have been determined by X-ray crystallography. In 1 and 3, ligand L forms with two organometallic species seven membered chelate rings whereas in 2 it ligates in a bis-pincer coordination mode. The geometry around Pd in 1 or 2 is close to square planar whereas in 3, Ru has pseudo-octahedral half sandwich "Piano-Stool" geometry. The Pd-Se bond distances are in the ranges 2.4004(9)-2.4627(14) Å and follow the order 1 > 2, whereas Ru-Se bond lengths are between 2.4945(16) and 2.5157(17) Å. The 1 and 2 have been found efficient catalysts for Heck reaction of aryl halides with styrene and methyl acrylate. The 2 is superior to 1. The TON and TOF values (per Pd) are up to ~47500 and ~2639 h(-1) respectively.

The in situ generated ArE¯(E = S or Se) reacts with (2chloromethyl)pyridine in N 2 atmosphere, resulting in half-pincer (N, S/Se) ligands (2-arylchalcogenomethyl)pyridine (L1−L3; aryl = Ph/2-pyridyl for S, Ph for Se). Half-sandwich complexes [(η 5 -Cp*)Rh(L)Cl][PF 6 ] (1, 2), [(η 5 -Cp*)Rh(L2)CH 3 CN][PF 6 ] 2 (3), and [(η 5 -Cp*)Ir(L)Cl][PF 6 ] (4− 6), where L = L1−L3, have been synthesized by reacting L with [(η 5 -Cp*)RhCl(μ-Cl)] 2 and [(η 5 -Cp*)IrCl(μ-Cl)] 2 respectively. The ligands and complexes have been characterized by IR, HR-MS, and 1 H, 13 C{ 1 H}, and 77 Se{ 1 H} NMR spectra. The single-crystal structures of all the complexes (1−6) have been determined with X-ray crystallography [Rh−S, Rh−Se, Ir−S, Ir−Se bond distances: 2.383(2)/2.353(2), 2.4867(9), 2.343(2)/2.341(3), 2.453(1) Å, respectively]. Each metal has pseudo-octahedral half-sandwich "piano-stool" geometry. The PF 6 − ions in crystals are packed between half-sandwich complex molecules, resulting in various H•••F secondary interactions. Complexes 1−6 have been explored for catalysis of oxidation of secondary alcohols with N-methylmorpholine-N-oxide and transfer hydrogenation reaction of ketones with 2propanol and found very efficient, as revealed by TON values, which are up to 9.6 × 10 3 and 9.8 × 10 3 respectively for the two catalytic reactions. The formation of the M−H bond has been noticed in the intermediates of both the catalytic reactions. DFT calculations indicate a reactivity order for the complexes of Rh > Ir, which is also found for the two catalytic reactions experimentally. The calculated (DFT) and observed bond distances and angles of 1−6 are reasonably close.

The reactions of [{(η6‐C6H6)RuCl(μ‐Cl)}2] and [{(η6‐p‐cymene)RuCl(μ‐Cl)}2] with N‐[2‐(arylchalcogeno)ethyl]morpholines (L) (aryl = Ph/2‐pyridyl for S, Ph for Se, 4‐MeOC6H4 for Te) and NH4PF6 result in “piano‐stool” complexes of RuII of composition [RuCl(η6‐C6H6)(L)][PF6]/[RuCl(η6‐p‐cymene)(L)][PF6], which give characteristic 1H, 13C{1H}, 77Se{1H}, and 125Te{1H} NMR spectra. Some of them have also been characterized by X‐ray crystallography [Ru–S, Ru–Se, and Ru–Te bond lengths: 2.3815(12)/2.3742(14), 2.4837(14), and 2.6143(7) Å, respectively]. The cyclic voltammograms show that all the complexes undergo irreversible oxidation (E${1 \over 2}$ = 0.290–0.586 V). All the ruthenium complexes have been explored for their catalytic activity in the oxidation of primary and secondary alcohols with N‐methylmorpholine N‐oxide (NMO), tBuOOH, NaOCl, and NaIO4 (TON values upto 9.8 × 104). The efficiency of the catalytic oxidation reaction decreases in the order Te > Se > S. The intermediate species involved in the oxidation reactions appear to incorporate the RuIV=O group.

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