Syntheses and Structures of 5‐Membered Heterocycles Featuring 1,2‐Diphospha‐1,3‐Butadiene and Its Radical Anion

Abstract

LGa(P2OC)cAAC 2 features a 1,2‐diphospha‐1,3‐butadiene unit with a delocalized π‐type HOMO and a π*‐type LUMO according to DFT calculations. [LGa(P2OC)cAAC][K(DB‐18‐c‐6)] 3 containing the 1,2‐diphospha‐1,3‐butadiene radical anion 3•⁻ was isolated from the reaction of 2 with KC8 and dibenzo‐18‐crown‐6. 3 reacted with [Fc][B(C6F5)4] (Fc = ferrocenium) to 2 and with TEMPO to [L‐HGa(P2OC)cAAC][K(DB‐18‐c‐6)] 4 containing the 1,2‐diphospha‐1,3‐butadiene anion 4⁻. The solid state structures of 2‐4 were determined by single crystal X‐ray diffraction (sc‐XRD).

Gallaphosphene L(Cl)GaPGaL: A novel phosphinidene transfer reagent

“…The four‐coordinated gallium atoms in 2 a and 2 b adopt distorted tetrahedral geometries with Ga1−P1−C30 bond angles of 100.60(4)° and 101.62(4)°, respectively, and the phosphorus atoms are two‐coordinate as is typical for base‐stabilized phosphinidenes [23,24] . The Ga1−P1 bond lengths in 2 a (2.2441(3) Å) and 2 b (2.2538(3) Å) are almost identical but slightly shorter than the sum of the calculated Ga−P single‐bond radii (Ga 1.24 Å; P 1.11 Å) [27] and Ga−P single bonds in gallaphosphene 1 (2.2688(5) Å), [16] phosphaalkene L(Cl)GaP(cAAC) (2.289(2) Å), [22] diphosphene [L(Cl)GaP] 2 (2.313(3) Å), [28a] and in 1,2‐diphospha‐1,3‐butadiene (2.2844(4) Å), [28b] which is consistent with the strong σ‐donor ability of R NHCs [23,29] . In marked contrast, the P1−C30 bonds in 2 a (1.8099(13) Å) and 2 b (1.8175(12) Å) are far longer than the P−C bonds in L(Cl)GaP(cAAC) (1.736(2) Å) [22] and in phosphaalkenes (1.65–1.67 Å), [30] but comparable to calculated P−C single‐bond radii (P 1.11 Å; C 0.75 Å) [27] and P−C single bonds (1.805(2)–1.861(1) Å) in metal‐substituted phosphinidenes [31] .…”