Keywords: Arene ligands / Phosphane ligands / Transition metals / Chelates / NickelWhile phosphane-tethered cyclopentadienyl complexes with tertiary phosphane moieties have extensively been investigated for many metals, this is not the case for such complexes with a secondary phosphane tether. Only a few representatives of such complexes with early-transition-metals are known. Here, we report the first late-transition-metal cyclopentadienyl chelate complexes with silylphosphane or secondary phosphane tethers. The respective ligand system is generated by nucleophilic opening of spiro[2.4]hepta-4,6diene with lithium tert-butylphosphide. The anionic ligand is trapped with iron(II) chloride with formation of the respective ferrocene derivative. Treatment of lithium tert-butylphosphide with tert-butylchlorodimethylsilane or with chlorotriisopropylsilane affords the respective secondary silylphosphanes. 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. in 1992. [7] Compared with cyclopentadienylalkyphosphane chelate complexes, the corresponding indenyl chelates are much less common. Recently, we prepared chelate 6 as the first nickel complex of its kind. [13] While the tethers in chelates such as 1-6 bear electroneutral ligands, a smaller number of their anionic counterparts, alkoxido, amido, and phosphido chelates have also been reported. Representative examples include zirconium(IV) complex 7 as an alkoxido chelate, which was prepared by Hermann et al., [14] and amido chelate 8, which was prepared by Erker et al. [15] Finally, Miyoshi, Nakazawa et al. provided a phosphido example in the form of complex 9 as a hafnium(IV) chelate (Scheme 2). [16] Compared with complexes such as 1-6, complexes such as 7-9 have been investigated to a much lesser extent. Scheme 2. 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. [35] One molybdenum example has been published by Scheer et al. [36] In many cases, these complexes were prepared by reaction of the dianionic ligand system with a suitable complexation reagent.While the reaction of a lithiated primary or secondary phosphane with a fulvene affords a ligand system with one carbon atom between the cyclopentadienyl and the phosphane moieties, [15,30,37] the corresponding rea...

1,16‐Di‐tert‐butyl‐1,16‐diphospha[5.5]ferrocenophane was prepared in 76% yield by deprotonation of 1,1’‐di(2‐tert‐butylphosphanylethyl)ferrocene followed by treatment with 1,1’‐di(2‐bromoethyl)ferrocene. The ferrocenophane exists as a mixture of syn and anti diastereomers, which were separated by repeated precipitation of one of them. Reaction with borane afforded the respective borane adducts in 47% yield. Methylation with iodomethane gave the respective diphosphonium salt in quantitative yield. Oxidation with 1.0 or 5.0 equivalents of silver hexafloroantimonate gave a green and a blue material, respectively, presumably the mono and the diferrcenium salts. 1,16‐Di‐tert‐butyl‐1,16‐diphospha[5.5]ferrocenophane and its oxidation products were subjected to a temperature‐dependent Mössbauer effect (ME) study to elucidate their dynamical and paramagnetic relaxation characteristics. The ME data are consistent with the absence of spin averaging for the two distinct Fe sites in the monooxidation product over the temperature range 91

In continuation of our research in cyclopentadienylalkylphosphane nickel chelates with secondary phosphane tethers the first cationic representatives of this class of compounds are reported. These were obtained by reaction of the respective bromo complex with tris(4-trifluoromethylphenyl)phosphane as well as with a number of alkyl and aryl isonitriles in the presence of indium tribromide. This Lewis acid is crucial for the success of the reactions leading to the respective tetrabromoindate salts. The compounds were characterized spectroscopically, including rare 14 N, 13 C couplings being observed. Finally, deprotonation experiments are reported, which provide some evidence for deprotonation taking place, although the expected phosphinidene chelates could not be isolated due to rapid decomposition.

Treatment of cyclopentadienylnickel chloro or bromo chelates bearing either a tertiary 2‐(di‐tert‐butyl)phosphanylethyl or a secondary 2‐(2,4,6‐trimethylphenyl)phosphanylethyl tether with imidazolylidene (Arduengo carbene) ligands results in cationic or electroneutral carbene complexes with either a decoordinated or a chelated tether. The outcome depends on the nature of the carbene, the counter anion, and the reactant stoichiometry. The results are the basis of ongoing investigations directed towards a deprotonation of the chelated cationic complexes with a secondary phosphorus atom.