Bidentate Phosphines of Heteroarenes: 4,6‐Bis(diphenylphosphino)dibenzofuran and 4,6‐Bis(diphenylphosphino)dibenzothiophene

Abstract

Twofold lithiation of dibenzofuran (6) and dibenzothiophene y1phosphino)dibenzofuran (11) and 4-(dipheny1phosphino)di-(12) with n-butyllithium/N,N,N',N'-tetramethylethylenedi-benzothiophene (15) were obtained analogously via the monoamine (TMEDA) in n-hexane or n-pentane followed by the lithium compounds 9 and 14 of the heteroarenes. In the case reaction with chlorodiphenylphosphine yielded the title com-of dibenzofuran (6), it was shown that mono-and dilithiation pounds 4 and 5, respectively. The monophosphines 4-(diphen-is controlled by temperature.In a previous communication3) we have reported on the synthesis of 1,8-bis(diphenylphosphino)anthracene (1) and preliminary studies of its behaviour as a ligand in metal complexation. By using the 1,8-disubstituted anthracene unit as a rigid carbon skeleton, it was intended that two phosphorus centres should be placed at a distance just too long to allow both to coordinate simultaneously to one metal nucleus. Alternatively, the formation of dimetallic complexes should bring two metal nuclei, each coordinated to one of the phosphorus centres, into close proximity, possibly introducing novel structural features and properties, especially with respect to catalytic processes. However, on reaction of 1 with nickel(I1) chloride and bis(benzonitrile)palladium(II) chloride the concomitant cyclometallation of the carbon-hydrogen bond in position 9 of anthracene led to the formation of the extremely stable, squareplanar monometallic chelat complexes 2 and 3, respectively3! In pursuing our concept of rigid bidentate phosphine ligands for the formation of binuclear metal complexes we have been interested in 4,6-bis(diphenylphosphino)dibenzofuran (4) and 4,6-bis(dipheny1phosphino)dibenzothiophene (5). The replacement of the 1,S-disubstituted anthracene skeleton of 1 by the 4,6-disubstituted heteroarenes dibenzofuran and dibenzothiophene in 4 and 5, respectively, not only causes a small increase of the intramolecular distance between the phosphorus centres, but more importantly, it also alters the angle between the phosphorus lone pairs in such a way that a formation of monometallic chelate complexes should be rendered less favoured. Furthermore, the cyclometallation reaction, wich in the case of 1 leads to thc formation of the very stable monometallic chelate complexes 2 and 3, cannot occur in 4 and 5, because the oxygen and sulphur heteroatoms are located in the position between the two phosphorus substituents.On the other hand, the dibenzofuran oxygen and the dibenzothiophene sulphur atoms possess two lone pairs which might contribute additional weak coordinative bonds to metal atoms complexed by the phosphorus centres. Depending on the hybridization of the ring heteroatom, two idealized alternatives might be considered for this additionid coordination: With sp2 hybridization one lone pair of the ring heteroatom is located in the p orbital perpendicular to the plane of the condensed ring system and contributes to the electron sextet of the five-membered heteroaromatic ring. Th...

Synthesis and Characterisation of 2,2‐Bis(hydroxymethyl)‐1,3‐diselenolato Metal(II) Complexes Bearing Various Phosphanes

“…Preparation of Starting Materials: For compounds 1 ,44 5 30a and 6 30a the literature procedures were modified considerably or were not satisfying, therefore, the synthetic details are given in the Supporting Information. PTA,36 4‐dppdbf,45 dppma,39 dppn,30 dppbe,46 dppo‐xyl,47 xantphos,48 [Ni(cod) 2 ],49 [NiCl 2 (dppe)],50 [PdCl 2 (NCPh) 2 ],51 [PdCl 2 (dppf)],52 [PtCl 2 (PTA) 2 ]53 and [PtCl 2 (PPh 3 ) 2 ]54 were synthesised following literature procedures. [PdCl 2 (dppe)] and [PtCl 2 (dppe)] were prepared in the same manner as reported for the synthesis of [PtCl 2 (PPh 3 ) 2 ]54 using dppe instead of PPh 3 and K 2 PdCl 4 or K 2 PtCl 4 , respectively.…”

Synthesis and Structural Diversity of ZnCl2 and Zn(C6F5)2 Complexes of a Phosphinimine Ligand

“…ZnCl 2 , Zn(C 6 F 5 ) 2 , and ZnEt 2 were purchased from commercial sources in high purity and used without additional purification. L Dipp was prepared as previously reported,7e while MesN 3 14 and 4‐(diphenylphosphanyl)dibenzofuran15 were prepared by the standard literature methods. NMR spectra [ 1 H (300.13 MHz), 13 C{ 1 H} (75.47 MHz), 31 P{ 1 H} (121.48 MHz), 19 F (282.42 MHz), and 11 B (96.29 MHz)] were collected with a Bruker Avance II NMR spectrometer equipped with a variable‐temperature unit.…”

Gold(I)—Phosphine Catalyst for the Highly Chemoselective Dehydrogenative Silylation of Alcohols.

“…Bis [2-(diphenylphosphino)phenyl] ether (DPEphos) 2 and 1,8-bis(diphenylphosphino)dibenzofuran (DBFphos) 2,3 were prepared according to the published procedure.…”