Complexes of Platinum Group Elements Containing the Intrinsically Chiral Cyclopentadienide Ligand (Cp^C)⁻¹

Abstract

Cyclopentadienide derivatives possessing intrinsic helical chirality have only rarely been published in the past. The ligand Cp C H, which is well-accessible from inexpensive dibenzosuberenone, is paradigm for such a ligand. Here, the synthesis as well as the spectroscopic and structural characterization of a series of platinum group metal complexes containing this ligand are presented. While alkaline metal salts of Cp C H failed in transferring the (Cp C ) −1 unit to this type of metal sites, (Cp C )Tl turned out to be an excellent precursor for the synthesis of ruthenium ([(η 5 -Cp C )Ru(η 6 -arene)]PF 6 , [(η 5 -Cp C )Ru(NCCH 3 ) 3 )]PF 6 ), rhodium ((η 5 -Cp C )Rh(η 4 -COD)), and iridium ((η 5 -Cp C )Ir(η 4 -COD), [(η 5 -Cp*)Ir(η 5 -Cp C )]PF 6 ) complexes with Cp C ligands. EXSY NMR studies were carried out to obtain a deeper insight into the ligand dynamics of Cp C complexes.

Phosphine Functionalized CpC Ligands and Their Metal Complexes

“…13 -). 19 F NMR (376 MHz, CD 3 CN): δ −72.9 (d, 1 3): A total of 0.74 mL (1.18 mmol) wasadded at 0 °C to a solution of 716 mg (1.07 m reaction mixture was stirred for 2 h at this temperat room temperature. During this time, the precipitati which was dissolved by the addition of 1 mL of t mmol) of [2-(chloromethyl)phenyl](diphenyl)phosp uene wasadded slowly at 0 °C and the reaction mixt temperature, whereby its color changed from pink temperature, the mixture was stirred for further 18 h the organic phase was separated, washed three time over MgSO4.…”

“…In addition, the phosphine donor remains in the immediate vicinity of the metal center after dissociation, which has a further stabilizing effect. Among all phosphine functionalized cyclopentadienyl derivatives, ferrocenyl phosphines have probably attracted the most attention, in particular due to their use as monoor bidentate ligands in transition metal catalyzed reactions [6][7][8][9][10][11][12][13][14][15][16] Recently, we presented the C 2 -symmetric and thus chiral cyclopentadiene derivative (Cp C ) −1 (1 −1 ) as a ligand for early and late transition metal complexes [17][18][19]. The corresponding cyclopentadiene Cp C H (1) is accessible in a few steps with high yield from dibenzosuberenone.…”

A Novel Cyclopentadienone and its Ruthenium and Iron Tricarbonyl Complexes

“…Cp C H (1) was synthesized according to procedures published in the literature. [16] Cp C O (4) by oxidation of TlCp C : 2.00 g (3.35 mmol) of Cp C Tl [20] were dissolved in 100 mL of dry THF and stirred under air at room temperature. The solution turned from orange to deep red within about 3 min.…”

“…Since the thallium(I) salt TlCp C has turned out to be the most suitable precursor for the transfer of the (Cp C ) À ligand to late, electron-rich transition metal centers, [20] its reactivity towards oxygen was investigated first. Treatment of TlCp C in THF with air leads to an intense red coloration of the solution (Scheme 3).…”

“…While its barrier of inversion (~85 kJ • mol À 1 ) is much higher than the barrier of inversion of Dbf À 1 (~20 kJ • mol À 1 ), it is still too low to prevent slow racemization at room temp, which we were able to demonstrate by means of a detailed NMR spectroscopic study on two Cp C ruthenium(II) complexes. [20] It therefore seemed to be interesting to prove the formation of Cp C O (4) and evaluate its organometallic chemistry in more detail.…”