The First Cyclopentadienylalkylphosphane Nickel Chelates: Synthesis, Structures, and Reactions

Abstract

The first cyclopentadienylalkylphosphane nickel chelate complexes are reported. The anionic ligand obtained by reaction of spiro[2.4]hepta-4,6-diene with lithium di-tert-butylphosphide was treated with NiCl2 to yield [eta(5):kappa(1)-(di-tert-butylphosphanylethyl)cyclopentadienyl]chloronickel(II). From this complex, some acetonitrile-stabilized cationic complexes were obtained by reaction with the respective silver salts in acetonitrile. Methyl- and alkynylnickel chelates were prepared by reaction of the chloronickel complex with methyllithium and by copper-mediated coupling with terminal alkynes, respectively. Some of the complexes prepared were investigated by X-ray crystallography or cyclic voltammetry. The alkynylnickel chelates undergo cycloaddition reactions with ethoxycarbonylisothiocyanate or tetracyanoethylene, and the cyclobutenes obtained undergo ring opening to the corresponding dienes. The study includes an NMR spectroscopic investigation of the two conformers of one of these dienes.

The First Late‐Transition‐Metal Cyclopentadienyl Chelate Complexes with Silylphosphane or Secondary Phosphane Tethers

“…This is based on a comparison with the data of related di- tert-butyl-substituted complexes 3 and 6, which show respective resonances around 90 ppm, [11,13] assuming a shielding effect of the silyl substituent as compared to a tert-butyl group. In the 31 P{H} NMR spectra, singlets at δ = 24.0, 24.9, and 25.4 ppm, respectively, were observed, indicating a coordinated silylphosphane tether with nickel.…”

“…Deprotonation, reaction with spiro[2.4]hepta-4,6diene, followed by treatment with nickel dihalide complexes www.eurjic.org FULL PAPER 1989; [9] 2 bears an internal amine ligand and was prepared by Hadjiliadis et al in 1998; [10] 3 represents a cyclopentadienylalkylphosphane nickel chelate and was prepared in our group in 2007; [11] 4 is a cationic chelate with sulfur coordination, which was prepared by Rauchfuss et al in 1985, [12] and alkene complex 5 was prepared by Okuda et al. Only a few representatives of such complexes with early-transition-metals are known.…”

“…The respective ligand system is generated by nucleophilic opening of spiro[2.4]hepta-4,6diene with lithium tert-butylphosphide. Cyclopentadienyl chelate complexes with anionic tethers.In the context of our interest in cyclopentadienylalkylphosphane chelates of late-transition-metals such as cobalt [17][18][19][20][21][22][23][24][25][26][27][28][29] and nickel, [11,13] we noticed that phosphido chelates such as 9 are comparatively rare and known only for early-transition-metals such as group 4 metals, [15,[30][31][32][33] lanthanides, [34] or niobium. Treatment of lithium tert-butylphosphide with tert-butylchlorodimethylsilane or with chlorotriisopropylsilane affords the respective secondary silylphosphanes.…”

New cyclopentadienylethylphosphane chelate complexes with unsymmetrical phosphane substitution

“…15,16 With the new tert-butylphenyl substituted ligand in hand, we prepared the respective nickel chelate rac-20 in 70% yield. rac-20 was characterized spectroscopically, all data are in accord with related complexes.…”

“…rac-20 was characterized spectroscopically, all data are in accord with related complexes. 15,16 Jolly et al reported the synthesis of cyclopentadienylchromium dichloride chelates with a phosphane tether and their application as catalysts in alkene oligo-and polymerization reactions. 76 The complexes reported bear identical substituents at phosphorus, crystal structure analyses of the diphenyl and the dicyclohexyl complexes were included.…”