Discovery and Synthetic Value of a Novel, Highly Crowded Cyclopentadienylphosphane Ph₂P‐Cp^TMH and Its Ferrocenyl‐Bisphosphane dppf^TM

Abstract

Base‐catalysed condensation of Ph2P–C5H5 (1) with an excess of acetone leads to a fulvene‐like diphenyl(4,4,6‐trimethyl‐4,5‐dihydropentalen‐2‐yl)phosphane Ph2P‐C11H13 (3) as a product of double condensation. Carbometallation of 3 with MeLi, followed by aqueous work‐up, results in formation of a new cyclopentadienylphosphane bearing a highly sterically demanding, anellated 1,1,3,3‐tetramethylcyclopentane moiety (4, Ph2P‐CpTMH). It reacts with chalcogene oxidants (H2O2, S8, Se) to form the corresponding phosphane chalcogenides Ph2P(=X)CpTMH, X = O (5), S (6), Se (7) in high yields. Quaternization of 4 with MeI gives the phosphonium salt 8 as a single isomer in high yield. Dehydrohalogenation of 8 by reaction with nBuLi gives CpTM‐phosphonium ylide Ph2P(CpTM)Me (9). An alternative protocol towards 9 that includes deprotonation of 8 with benzylpotassium followed by P‐alkylation is superior and gives 9 in more than 95 % yield. Staudinger reaction of 4 with tBuN3 gives onlyP‐amino‐cyclopentadienylidenephosphorane Ph2P(CpTM)NHtBu (10), whereas with Me3SiN3 only the tautomeric P‐imino‐cyclopentadienylphosphane Ph2P(NSiMe3)CpTMH (11) was isolated. Hydrolysis of 11 with wet MeCN leads to the new parent P‐amino‐cyclopentadienylidenephosphorane Ph2P‐(CpTM)NH2 (12). Treatment of 4 with benzylpotassium followed by transmetallation with FeCl2 leads to the sterically most crowded ferrocenyl‐bisphosphane [{Ph2P‐CpTM}2Fe] (13, dppfTM) in high yield. Its X‐ray diffraction analysis reveals an anti‐orientation of phosphane functionalities at both cyclopentadienyl rings. However, upon reaction of dppfTM with [PdCl2(MeCN)2], a constrained syn‐orientation is achieved in the product [{dppfTM}PdCl2] (14). Halogen exchange by reaction of 14 with NaI leads to the corresponding [{dppfTM}PdI2] (15). Molecular structures of 4, 9, 13 and 15 have been confirmed by XRD studies.

Deprotonated P-ylides As Templates for Novel Cyclopentadienyl Phosphonioalkyl, -alkylidene, and -alkylidyne (CpPC) Constrained-Geometry Complexes

“…The phosphonium ylides shown in Scheme represent the ligand set used in this work ( 1a – d , Z = H). Compound 1a was synthesized by reaction of in situ generated (Me 2 N) 2 PC 5 Me 4 H with methyl iodide followed by dehydrodehalogenation with KH, as previously reported for 1c , d . ,, A modified literature method had to be applied for the synthesis of 1b , which was ascribed to the reluctance of the in situ generated bulky phosphane t Bu 2 PC 5 H 5 to undergo quaternization with methyl iodide (for details, including a single-crystal X-ray analysis of 1b , see the Supporting Information). The phosphonium ylides 1a – d cover a broad spectrum of electronic and steric properties ( 31 P NMR (C 6 D 6 ) δ 2.1 ( 1d ), 52.6 ( 1a ) ppm; high ( 1c ) or low ( 1b ) steric demand of the Cp moiety); thus, significant differences with respect to their coordination behavior may be expected.…”

“…Solvents were distilled under an inert atmosphere of nitrogen employing standard drying agents . Starting materials (KH, ZrCl 4 , LiCH 2 SiMe 3 , n BuLi) were purchased from commercial sources or prepared according to literature procedures (P(NMe 2 ) 2 Cl, LiC 5 Me 4 H, t Bu 2 PCl, NaC 5 H 5 , 1c , d , , 2d , [ZrCl 4 (THF) 2 ], ZrBn 4 , Zr(CH 2 SiMe 3 ) 4 , BnK). Preparations of samples for analytical measurements were exclusively carried out in an MBraun glovebox under nitrogen.…”

New Lithium Phosphonium Diylides: A Methylene and a Cyclopentadienyl Moiety as Ylidic Coordination Sites

“…The desired CpPC ligand systems can be derived from cyclopentadienyl-substituted phosphanes in a straightforward protocol. A variety of this small class of compounds is accessible with different substitution patterns both at the phosphorus atom and at the cyclopentadienyl moiety . This allows for tuning of the electronic and steric parameters of the future ligand system.…”

Tetrahydropentalenyl-phosphazene constrained geometry complexes of rare-earth metal alkyls

“…The following steps were carried out according to the literature, while spectroscopic features match perfectly with the reported ones. 24 Synthesis of ligand L Ad H. To a solution of phosphane 1 Cp™HPPh 2 (2.40 g, 6.93 mmol, 1.00 eq.) in 30 mL of toluene, AdN 3 (1.35 g, 7.62 mmol, 1.10 eq.)…”

“…The ligands were prepared by a Staudinger reaction (Scheme 2) of the novel phosphane Cp™HPPh 2 (1, diphenyl(4,4,6,6-tetramethyl-1,4,5,6-tetrahydropentalen-2-yl)phosphane) 24 with organic azides (AdN 3 and DipN 3 ; Dip = 2,6-di-iso-propylphenyl). It should be mentioned that compared to our previously published synthesis of 1 we could exchange the highly toxic TlCp by NaCp, which can easily be synthesized on a large scale out of Na and (CpH) 2 .…”