Hydrophosphination reactions with transition metal ferrocenylphosphine complexes

Abstract

The group 6 metal mono-, bis- and tris-ferrocenylphosphine complexes [M(CO)5(PH2Fc)] (1a, M = Cr; 1b, M = Mo; 1c, M = W), cis-[M(CO)4(PH2Fc)2] (2a, M = Cr; 2b, M = Mo; 2c, M = W) and fac-[M(CO)3(PH2Fc)3] (3a, M = Cr; 3b, M = Mo; 3c, M = W) [Fc = Fe(η(5)-C5H4)(η(5)-C5H5)] were prepared and fully characterised. IR and NMR spectroscopy and single-crystal X-ray diffraction analysis indicate that FcPH2 is as good a σ donor as PhPH2 but is easier to handle and furthermore has a redox-active ferrocenyl group. Complex 1c was employed in the hydrophosphination of acrylonitrile and methyl acrylate in the presence of catalytic amounts of KOtBu giving the secondary phosphine complexes [W(CO)5{PH(Fc)(CH2CH2CN)}] (4a) and [W(CO)5{PH(Fc)(CH2CH2C(O)OMe)}] (4b). In addition, FcP(CH2CH2CN)2 (5) was prepared by a similar method from FcPH2 and acrylonitrile. These hydrophosphination products represent a convenient method for the modification of phosphines.

Air-stable fluorescent primary phosphine complexes of molybdenum and tungsten

“…The furthest downfield peak at 213.1 ppm appears as a broad doublet of doublets and is attributable to the two carbonyls trans to the phosphine ligands. This is consistent with the assignment of the carbonyls in cis-[Mo(CO) 4 (FcPH 2 ) 2 ] [35] and cis-[Mo(CO) 4 (PhPH 2 ) 2 ] [40]. Similarly, the IR spectrum further supports the structure of 7 as the cis-isomer, showing four distinct bands for the two A 1 , B 1 , and B 2 stretching frequencies at 2029, 1947, 1919 and 1896 cm −1 , again comparing well with the aforementioned analogues.…”

“…The bond lengths and angles ( Figure 1) were found to be comparable with those in the related [W(CO) 5 (FcCH 2 CH 2 PH 2 )] [38]. [35]. e IR in THF, N , cis-7 (Scheme 2).…”

“…Furthermore [M(CO) 5 [35] gave a comparable 1 J PH coupling constant of 328.0 Hz. The 13 C NMR spectrum of 5 showed a doublet splitting of 24.2 Hz on the resonance at δ 208.8 ppm, which is attributable to the carbonyl trans to the phosphine ligand, by virtue of the larger 2 J CP coupling [35,36,37]. The equatorial carbonyls gave a peak at δ 204.7 ppm ( 2 J CP = 9.8 Hz), the lower chemical shift consistent with those for related complexes ( Table 2).…”

“…Mathey has shown that [W(CO) 5 (RPH 2 )] forms when 7-phosphanorbornadiene complexes of tungsten pentacarbonyl are reacted with dihydrogen under 20 bar pressure at 150 °C [32], and also that primary mono-phosphine complexes of both tungsten and molybdenum can be used to prepare metal-bound Phospha-Wittig reagents that react further to give phosphaalkenes [33]. Furthermore [M(CO) 5 [35] gave a comparable 1 J PH coupling constant of 328.0 Hz. The 13 C NMR spectrum of 5 showed a doublet splitting of 24.2 Hz on the resonance at δ 208.8 ppm, which is attributable to the carbonyl trans to the phosphine ligand, by virtue of the larger 2 J CP coupling [35,36,37].…”

Challenges in Catalytic Hydrophosphination

“…Recent developments with more earth‐abundant metals highlight the potential for further growth in this area. Iron is an attractive catalyst for hydrophosphination because it is both electron‐rich and earth abundant, and work with iron has already demonstrated its wide breadth of reactivity . For example, oxo‐bridged dimers have shown good reactivity and selectivity in the hydrophosphination of styrene derivatives, as reported by Webster and co‐workers .…”