Unsymmetrically Substituted Bis(phosphino)Ferrocenes Triggering Through-Space ³¹(P, P′)-Nuclear Spin Couplings and Encapsulating Coinage Metal Cations

Abstract

We describe unsymmetrically substituted di-tert-butylated 1,1'-bis(phosphino)ferrocenes, with phosphino substituents R = [5-methyl]-2-furyl = Fu, and R' = phenyl (4a), i-propyl (4b). A modular synthetic approach was applied from the di-tert-butylated ferrocene platform (1), which lead to the formation of new diphosphines by using 1,1'bis(diiodo)-3,3'-bis(tert-butyl)ferrocene (2) as synthetic precursor. In contrast to the cousin non-alkylated unsymmetrically substituted diphosphino-ferrocenes which were reported up to now, these diphosphines showed strong ( 31 P, P')nonbonded (" ug -p e") nuclear spin-spin coupling. The strength of such internuclear spin-spin coupling constant (SSCCs) J PP' ranges between 17 and 35 Hz, and as such, are not associated to traditional " ug -b d" 4 J PP. The characterizations of these ferrocene derivatives by X-ray diffraction in the solid state, and by multinuclear NMR in solution, evidence that the strong SSCCs are attributable to the conformational constraint which is imposed to ferrocene backbone by the introduction of alkyl substituents on this platform. The molecular structures resolved in the solid-state showed long P…P u u l ep up to 6.9168(8) Å, while in solution a (P, P')-phosphorus lone-pair overlap clearly occurs. This testifies to a sufficient degree of rotational flexibility of the alkylated ferrocene backbone. We examined the coordination chemistry of these diphosphines towards coinage metals: Cu, Ag and Au. The constraint unsymmetrically substituted diphosphines 4a and 4b allowed the selective formation of dinuclear two-coordinate linear gold(I) complexes with strong Au…Au aurophilic interactions. They also lead to rare tetrahedral homoleptic d 10 monocationic complexes, with all the coinage metals, by structuring the encapsulation of the cation in a highly constraint environment where the stacking interactions of the (hetero)aromatic substituents of the phosphino groups are decisive. The resulting AA'XX' 31 P NMR signature in solution of the complexes was simulated and analyzed, as well as the stacking interactions between the pairs of furyl rings that were illustrated by noncovalent interactions (NCI) computation.

Aryl Triflates in Phosphorus-Directed Rhodium(III)-Catalyzed C–H Activation

“…All rights reserved. [23] A round flask (50 ml) equipped with a magnetic stirring bas was charged with 1-diphenylphosphine HAP (0.055 mmol, 1 equiv) and gold chloride [(Me2S)AuCl] or copper chloride CuCl (0.055 mmol, 1 equiv) and CH2Cl2 (0.025 M, 2 ml). The solution was stirred at room temperature overnight, and the mixture was filtrated on Celite and washed with CH2Cl2.…”

“…[22] The coordination to gold and copper were achieved in CH2Cl2 by reacting the ligand with [(Me2S)AuCl] or CuCl respectively (Scheme 1) We then achieved the complexation of the polyaromatic phosphines 18 and 27 to coinage metals with gold(I) chloride and copper(I) chloride salts (Table 1, Scheme 1). [23,24] For fluoranthenyl diphenylphosphines 18 and 27, the reaction with [(Me2S)AuCl] quantitatively leads to complexes A and B that are characterized in 31 P NMR spectroscopy (CDCl3, 202 MHz) by a singlet at 24.5 ppm and 30.5 ppm, respectively (Scheme 1, and XRD of B in Figure 4, XRD for A is reported in the Supporting Information). The complexation with Cu(I)Cl quantitatively leads to complexes C and D, respectively, which were obtained in 73% and 76% isolated yields after precipitation, and are characterized in 31 P NMR spectroscopy (CDCl3, 202 MHz) by a broad signal at 24.5 ppm and 30.5 ppm, respectively (see Scheme 1; XRD for C, as a classical cubane structure, is reported in the Supporting Information).…”