Synthesis, Characterization, and Transition-Metal Complexes of 3,4-Diazaphospholanes

Abstract

The steric, electronic, and synthetic characteristics of 3,4-diazaphospholanes are reported. Crystallographic structures of free and metal-complexed 3,4-diazaphospholanes provide steric metrics (cone angle, solid angle, etc.). Diazaphospholanes span a wide range of sizes with cone angles varying from 135 to 188°. The electron-donating abilities of diazaphospholanes have been estimated using the carbonyl infrared stretching frequencies, ν(CO), of [trans-Rh(diazaphospholane) 2 (CO)Cl] complexes. Frequencies for the CO stretches range from 1975 to 2011 cm -1 , thus indicating that 3,4-diazaphospholanes may be as electron rich as dialkylarylphosphines or as electron deficient as trialkyl phosphites. Reduction of N,N′-phthalamido-3,4-diazaphospholanes with BH 3 ‚SMe 2 yields diazaphospholanes that not only are more electron rich but also show a reorientation of the phospholane substituents that may affect catalytic properties. Diazaphospholanes readily react with many Rh and Pd catalyst precursors to form complexes. Metal complexes of 3,4-diazaphospholanes exhibit reactivities different from those of common phosphine complexes, presumably due to the generally greater steric bulk and electron deficiency of 3,4-diazaphospholanes relative to phosphines. Cationic Rh(I) complexes of 3,4-diazaphospholanes abstract chloride ligands from chlorinated solvents to afford chloride-bridged dimers. The complex [(rac-17)Pd-(Me)Cl] rearranges in solutionsstereoselectively transferring methyl from palladium to phosphorus while simultaneously opening a diazaphospholane ring. Many of the 3,4-diazaphospholane-metal complexes have extremely close Cl‚‚‚H-C(P)(N) contacts, suggesting Cl‚‚‚H hydrogen bonding.

Synthesis and structure of ferrocenylmethylphosphines, their borane adducts, and some related derivatives

“…The results for the FcCH 2 P fragment were similar, but the new structure included a reduced HPH angle (110(2)°) and equivalent P-H bond lengths of 1.29(4) and 1.26(4) Å. However, the CPH angles of 98.2(16) and 114.5 (17)°were unexpectedly different, raising doubts about the reliability of the H atom positions, especially because HPH and Scheme 5. Synthesis of ferrocenylmethylphosphine(boranes) (PR 2 = PH 2 (2 and 6), PH(CH 2 Fc) (3 and 7), P(CH 2 Fc) 2 (4 and 8), P(CH 2 OSiMe 3 ) 2 (11 and 15)).…”

“…To provide more quantitative information on the properties of 4 as a ligand, its solid cone angle in 14 was found to be 139°, with the Pt-P bond length normalized to 2.28 Å [16]. In comparison to related phosphines whose solid cone angles were calculated by the same method, ligand 4 was bulkier than PPh 3 (128°), but not as large as P(t-Bu) 3 (157°) [17].…”

Synthesis and Characterization of Cationic Synphos‐Rhodium Complexes

“…This molecular arrangement is generally recognized as π – π ‐stacking24 and was described first by Noyori in 1982 25. The π–π ‐stacking interaction contributes to the stability of the system by about 1.5–3 kcal/mol 24a,26…”

Transition metal-mediated metathesis between P–C and M–C bonds: Beyond a side reaction

“…Landis and coworkers have witnessed a challenging P-alkyl/M-alkyl exchange during the development of 3,4-diazaphospholanes [66], a new, modular class of chiral phosphine [67] which proved to be effective for many metal-catalyzed asymmetric transformations. While the complexation of [Rh(cod)Cl]2 with bis(3,4-diazaphospholane) (rac-19) afforded the chloride-bridged dimer, the reaction of [(cod)Pd(Me)Cl] and rac-19 yielded the unexpected product of a methyl migration to the phosphine along with a ring opening of the diazaphospholane ring (20), accompanied by the formation of the desired complex, [(rac-19)Pd(Me)Cl] (21) (Scheme 24).…”