An Alternative Preparation of 1‐(N,N‐Dimethylaminomethyl)‐1′‐(diphenylphosphanyl)ferrocene: Synthesis and Structural Characterization of Au^I and Pd^II Complexes with this Hybrid Ligand

Abstract

1-(N,N-Dimethylaminomethyl)-1′-(diphenylphosphanyl)ferrocene (1) was synthesized in good yield by lithiation of 1-bromo-1′-(diphenylphosphanyl)ferrocene and subsequent reaction with Eschenmoser's salt (dimethylmethylideneammonium iodide). Making use of an easily accessible, nontoxic starting material, this procedure represents a convenient alternative to the original synthetic protocol based on stepwise lithiation/functionalization of 1,1′-bis(tributylstannyl)ferrocene and reductive amination [M. E. Wright, Organometallics 1990, 9, 853–856]. Compound 1 has typical hybrid-donor properties. When reacted with [AuCl(tht)] (tht=tetrahydrothiophene), it afforded the expected AuI phosphane complex [AuCl(1-κP)] (2). An attempted removal of the chloride ligand from 2 with AgClO4 produced an ill-defined material formulated as Au(1)ClO4. The uncoordinated amine substituent reacted with traces of hydrogen chloride formed by slow decomposition typically occurring in solution. In this manner, complexes [AuCl(Ph2PfcCH2NHMe2)]Cl (3, fc=ferrocene-1,1′-diyl) and [AuCl(Ph2PfcCH2NHMe2)]ClO4 (4) were isolated from crystallizations experiments with 2 and Au(1)ClO4, respectively. On a larger scale, complex 3 was prepared easily from 2 and hydrogen chloride. The course of reactions between [PdCl2(cod)] (cod=cycloocta-1,5-diene) and 1 were found to depend on the ligand-to-metal ratio. Whereas the reaction with two equivalents of 1 afforded bis(phosphane) complex trans-[PdCl2(1-κP)2] (5), that of a Pd:P ratio 1:1 produced ligand-bridged dimer [(μ-1)PdCl2]2 (6). With hydrogen chloride, complex 6 reacted to afford zwitterionic complex [PdCl3(1H-κP)] (7), which was also formed when ligand 1 and [PdCl2(cod)] were allowed to react slowly by liquid-phase diffusion of their chloroform solutions. The compounds were characterized by spectroscopic methods (multinuclear NMR and ESI–MS), and the molecular structures of complex 2–4, 6⋅2CHCl3 and 7⋅1.5CHCl3 were determined by single-crystal X-ray diffraction analysis.

Ferrocenylmethylation reactions with a phosphinoferrocene betaine

“…Amine 1 was prepared as reported previously. 10 Benzene and chloroform were dried by standing over sodium metal and CaH 2 , respectively, and distilled under argon. Dimethyl sulfoxide was distilled under vacuum.…”

“…Coordination preferences of the newly prepared phosphinoferrocene sulfones were studied in reactions of 6a as the model representative, with zinc(II) halides. These salts were chosen mainly due to the position of the Zn(II) ion at the borderline between hard and soft metal ions 27 and due to its closed (d 10 ) coordination sphere, which makes it structurally variable because of the absence of crystal-field stabilisation. 28 To our disappointment, repeated experiments aiming at the preparation of defined products by co-crystallisation of zinc(II) halides with 6a were unsuccessful.…”

“…The residue was purified by column chromatography on a silica-gel column. Elution with diethyl ether-hexane (1 : 10) resulted in a yellow band that contained compound 5, which was isolated in a 6% yield (44 mg) after evaporation. Subsequent elution with diethyl ether-hexane 2 : 1 led to the development of a major orange band due to alcohol 3, which was isolated as slowly crystallising orange oil upon evaporation under vacuum.…”

“…6 Therefore, the [1′-(diphenylphosphino)ferrocene-1-yl]methyl derivatives have typically been synthesised either indirectly (e.g., via late-stage lithiation/phosphinylation 7 ) or from P-protected building blocks, such as Ph 2 P(S)fcCH 2 OH 8 or the borane adduct Ph 2 PfcCH 2 OH•BH 3 . 9 In view of our recent work focusing on the preparation and coordination properties of 1′-(diphenylphosphino)-1-[(dimethylamino)methyl]ferrocene (1) 10,11 and other 1′-functionalised phosphinoferrocene derivatives possessing an inserted methylene group, 9,12 we wanted to extend the hitherto unexplored synthetic chemistry of the former compound, which led us to attempt the preparation of ammonium salts derived from 1 and study their prospective synthetic applications. In this contribution, we describe the selective synthesis and structural characterisation of the phosphinoferrocene betaine Ph 2 PfcCH 2 N + Me 2 (CH 2 ) 3 SO 3 − (2; fc = ferrocene-1,1′-diyl) and its utilisation in the preparation of the known and some new 1′-functionalised phosphinoferrocene donors such as 1′-[(diphenylphosphino)ferrocenyl]methyl sulfones Ph 2 PfcCH 2 SO 2 R. Furthermore, we report on the reactions of the representative ligand, Ph 2 PfcCH 2 SO 2 Me, with zinc(II) and alkali metal halides, leading to structurally unique mixed-metal coordination polymers.…”

Synthesis of Two Isomeric Ferrocene Phosphanylcarboxylic Acids and their PdII Complexes with and without Auxiliary ortho‐Metalated C,E‐Ligands (E = N and S)

“…This prompted us to focus on “semi‐homologous” congeners of dppf and the related asymmetric donor derivatives. So far, we have reported the preparation and coordination behavior of diphosphane B (Scheme ) and compounds bearing CH 2 FG fragments (where FG denotes a functional group) in the place of the CH 2 PPh 2 moiety, namely, the phosphanylferrocene pyridine C , amine D , ether E , sulfones F , ureas G , and guanidine H . Notable examples from other laboratories include the imidazolium salts I used to prepare structurally interesting P‐chelated N‐heterocyclic carbene (NHC) complexes and a phosphane donor bearing an axially chiral azepine moiety, compound J …”