Generation and Decomposition of Li/OR Phosphinidenoid Complexes

Abstract

Reaction of the P-bifunctional phosphane complex 2 with LDA and 12-crown-4 yielded complex 4, featuring the unprecedented combination of a P–H and P–O–Li unit, via an unknown decomposition pathway. Strong spectroscopic evidence for the transient Li/OC(O)CH3 phosphinidenoid complex 5 possessing a P–Li bond was obtained through reaction of 2 with LDA in the absence of 12-crown-4.

Synthesis of Aminophosphane Complexes: Searching the Boundary between Phosphanide and Phosphinidenoid Complex Chemistry

“…For example, the latter complex with (E) configuration has J (W,P) = 268 Hz, which is larger than that of the former (Z)-diphosphene complex [J (W,P) = 116 Hz]. [17] As the singlet at δ = 39.1 ppm shows no tungstenphosphorus coupling but a large phosphorus-proton coupling [ 1 J (P,H) = 195. [16] The molecular structure of complex 6 was also confirmed by single-crystal X-ray diffraction (Figure 4).…”

“…[16] The molecular structure of complex 6 was also confirmed by single-crystal X-ray diffraction (Figure 4). Unfortunately, Although the phosphorus-lithium coupling constant [17,18] strongly suggests complex 7, the data of derivative 8 are similar to those of one of the very few 1,1Ј-bifunctional P-H phosphane derivatives, [(Me 3 Si) 2 HCP(H)-N(SiMe 3 ) 2 ] [δ = 5.9 ppm; 1 J (P,H) = 210.0 Hz], to have been reported previously. [16] The only hint of steric crowding can be derived from the two-fold s-trans conformation of the C-H and P-W bond [of CH(SiMe 3 ) 2 ] in 6.…”

P‐OR Functional Phosphanido and/or Li/OR Phosphinidenoid Complexes?

“…[11] The latter not only possess high electron-spin density at the phosphorus atom (70-85 %) but also underwent phosphorus-centered reactions thereby providing new perspectives in synthesis [11] as well as new insights into systems possessing very weak P-C bonds. [13] In contrast, the first attempts to synthesize Li/OAc (phosphinidenoid)tungsten complexes (OAc = CH 3 CO 2 ) resulted only in decomposition upon warming to ambient temperature, [14] whereas an Li/OPh (phosphinidenoid)tungsten complex was successfully used in P-C bond-forming reactions with acyl chlorides. The use of strong and sterically demanding organic bases enabled the synthesis of P-X and P-OR (phosphinidenoid) tungsten complexes possessing enhanced thermal stabilities.…”

New Access to and Reactions of P‐Functional Acylphosphane Complexes

“…(Li/X-phosphinidenoid)metal complexes 2a,b and Li/ RO-phosphanide complexes 2c,d were generated by lithiation of the corresponding P-H bifunctional phosphane complexes 1a, [12] 1b, [7b] and 1c,d [13] with LDA in the presence of 12-crown-4 at -80°C and allowed to react in situ with acyl chlorides 3a,b to give selectively the (acylphosphane)tungsten complexes 4a-f (Scheme 2). The reactivity of the complexes 2a-d depended largely on the nature of the substituent X bonded to the phosphorus atom and, in general, complexes 2c,d bearing alkoxy substituents at the phosphorus atom appeared to be less reactive than the halogen-substituted complexes 2a,b.…”

“…The signals of the carbonyl carbon atoms directly bonded to the phosphorus atom in the 13 C NMR spectra of complexes 4a-f appeared at δ = 202.3-216.6 ppm. Interestingly, in the case of the P-chloro-substituted acylphosphane complexes 4a,b these signals displayed surprisingly small P,C coupling constants (4a: J = 1.3 Hz; 4b: J = 1.9 Hz) compared with the other complexes (4c-f: J = 7.1-19.6 Hz).…”