Zinc complexes supported by tertiary 1,3,5-triazapenta-1,3-dienate ligand (L 1 ) and N-benzoyl-N -arylbenzamidinate [aryl =2,6-diisopropylphenyl (L 2 ), phenyl (L 3 )] ligands have been synthesized and characterized. The reaction of L 1 H with ZnEt 2 affords a mononuclear zinc complex [L 1 ZnEt] (1) in good yield. Tetra nuclear zinc complex [(L 1 ) 2 Zn 4 O(OAc) 4 ] (2) is prepared by treating L 1 H with one equivalent of Zn(OAc) 2 in toluene. Further, dinuclear zinc complexes [L 2 ZnEt] 2 (3) and [L 3 ZnEt] 2(4) are obtained in good yields from L 2 H and L 3 H with ZnEt 2 in toluene respectively . The complexes 1-4 have been characterized by 1 H/ 13 C NMR spectroscopy and single crystal X-ray diffraction studies. All of the complexes have been explored for their catalytic activity toward the ring-opening polymerization (ROP) of εcaprolactone. It has been found that complex 1 is an active catalyst for the polymerization of ε-caprolactone in presence of a cocatalyst benzyl alcohol (BnOH). While complex 2 is as active as 1 there is no need for a cocatalyst for the polymerization to proceed. Dinuclear zinc complexes 3 and 4 show very high activity for the ROP of ε-caprolactone (CL) and rac-lactide (LA) without requiring a cocatalyst. The resultant polymers are found to have very high molecular weight (M n = 296 X 10 3 g mol −1 ) and relatively narrow polydispersity index compared to 1 and 2.
A β-diketimine ligand with vinylidene substitution at γ-carbon, CH 2 C(CH 3 CNAr) 2 (Ar = 2,6-diisopropylphenyl) (L 2 ), was synthesized by treating β-diketimine H 2 C(CH 3 CNAr) 2 with n-BuLi followed by paraformaldehyde. L 2 formed the homobimetallic ether-bridged β-diketiminate complex [O{(CH 2 -β-diketiminate) Pd(OAc)} 2 ] (1) with (PdOAc) 2 . It also gave complexes [L 2 PdCl 2 ] (2) and [L 2 NiBr 2 ] (3) when treated with PdCl 2 (CH 3 CN) 2 and NiBr 2 (dimethoxyethane), respectively. All the compounds were characterized using 1 H/ 13 C NMR spectroscopy and single-crystal X-ray diffraction studies. The catalytic activity of Pd and Ni complexes 1, 2 and 3 was explored in Heck coupling and alkyne trimerization reactions and it was found that they are very good catalysts. The results are reported in detail.
The Suzuki–Miyaura cross‐coupling (SMC) reactions of several heteroaryl chlorides, benzyl chlorides, and aryl acid chlorides with (hetero)arylboron reagents have been investigated in the presence of [Pd(HL1)(PPh3)Cl2] (I) [HL1 = 3‐[(2,6‐diisopropylphenyl)‐1‐imidazolio]‐2‐quinoxalinide] as catalyst and K2CO3 as base in neat water. The synthesis of the heterocycle‐containing biaryls required the addition of 2 mol‐% of a phosphine ligand (PPh3 or X‐Phos). A combination of more than 115 substrates were screened and it was found that I is a versatile catalyst that can produce heterocycle‐containing biaryls, diarylmethanes, and benzophenones in moderate‐to‐excellent yields.
Synthesis of dihydroisoquinolinone-4-methylboronic esters from N-allylcarboxamides and B2(Pin)2via domino Heck/borylation has been achieved by using a quinoxaline-based NHC-palladacycle [Pd(C∧C:)PPh3Cl].
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