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

Abstract

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: Synthesis, Reactions and Mössbauer Spectroscopy

“…The same yield was obtained when the deprotonation of 6 was carried out by methyllithium in hexane at -78°C (6). [14] Scheme 3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 followed by addition of 1,1'-di(2-bromoethyl)ferrocene in THF.…”

“…In contrast, respective ligands with secondary phosphane moieties offer the additional option of reactions of the P–H groups. In order to gain an access to derivatives with secondary phosphane moieties, we recently showed that the nucleophilic ring opening of spiro[2.4]hepta‐4,6‐diene with lithium tert ‐butylphosphide ( 5 ) gives the respective cyclopentadienylalkylphosphanes in 80% yield . The in situ reaction of the anionic ring opening product with iron(II) chloride afforded the disubstituted ferrocene derivative 6 in 70% yield (Scheme ) .…”

“…[14] The in situ reaction of the anionic ring opening product with iron(II) chloride afforded the disubstituted ferrocene derivative 6 in 70% yield (Scheme 2). [14] Ferrocene derivative 6 is a promising substrate for the synthesis of dinuclear phosphaferrocenophanes.…”

New Reactions of Cyclopentadienylnickel Chelates with Secondary Phosphane Tethers

“…[2] In some cases, however, the cyclopentadienyl as well as the phosphane moieties have been the subject of variations, for example by replacement of the cyclopentadienyl by an indenyl or fluorenyl system. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] Variations at the phosphane part include unsymmetrical substitution patterns such as phenyl/alkyl, [5] alkyl/ silyl, [17] or rare cases of secondary phosphane moieties. [17,18] We have investigated complexes such as 2-5 with cobalt, nickel and iron as the metal centers for a long time (Scheme 2).…”

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16] Variations at the phosphane part include unsymmetrical substitution patterns such as phenyl/alkyl, [5] alkyl/ silyl, [17] or rare cases of secondary phosphane moieties. [17,18] We have investigated complexes such as 2-5 with cobalt, nickel and iron as the metal centers for a long time (Scheme 2). [4,5,17,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Here we report some new reactions of cyclopentadienylnickel complexes with a secondary phosphane tether.…”