Synthesis, Structure, and Coordination Chemistry of P-Acyl-, P-Thiocarbamoyl-, and P-Dithiocarboxyl-Substituted Phosphaalkenes R(X)C−PC(NMe₂)₂ (R = Ph, tBu, SSiMe₃, N(Ph)SiMe₃; X = O, S)

Abstract

Reaction of Me3SiPC(NMe2)2 (1) with pivaloyl chloride and benzoyl chloride afforded the acylated phosphaalkenes RC(O)PC(NMe2)2 2a (R = tBu) and 2b (R = Ph). Carbon disulfide and phenyl isothiocyanate were inserted into the P−Si bond of 1 to give the functionalized phosphaalkenes R(X)C−PC(NMe2)2 2c [R(X)C = Me3Si−S(S)C] and 2d [R(X)C = Ph(Me3Si)N(S)C]. Heating 2c and 2d with (CO)5MBr (M = Mn, Re) in toluene at 50−80 °C led to complexes [X = 3c (M = Mn, X = S), 3d (M = Mn, X = NPh), 4c (M = Re, X = S), and 4d (M = Re, X = NPh). The X-ray structure analysis of 2c showed extensive π-delocalization of electron density from phosphorus into the CS group. The structure determination of 4d revealed the molecule as a tricyclic system with an anti orientation of the peripheric four-membered rings. The organophosphorus fragment serves as η2(P,S)-μ(P) bridging ligand, a coordination mode without precedence in phosphaalkene chemistry.

Phosphaalkenes with Inverse Electron Density

“…[21] Scheme 12. Acylation of 8a by tBuC(O)Cl and PhC(O)Cl Reaction of the chlorocarbyne complexes TpЈ(CO) 2 MϵCϪCl [M ϭ Mo, W; TpЈ ϭ HB(3,5-Me 2 C 3 HN 2 ) 3 ] with two molar equivalents of 8a in CH 2 Cl 2 led to the precipitation of the red carbyne complex functionalized phosphaalkenes 23a,b within 2 h (Scheme 13).…”

“…The PϭC double bond length in nonconjugated phosphaalkenes ranges from 1.65Ϫ1.67 Å [2] whereas in C-amino-functionalized phosphaalkenes PϪC distances of 1.70Ϫ1.76 Å are frequently measured [8] as is illustrated in 29a [1.709(5) Å ], [25] 29c [1.717(4) Å ] [ Figure 1, (c)], [16] 7d [1.740(1) Å ], [5b] and 37a [1.744(2) Å ] [21] [ Figure 1, (a)]. A prerequisite for this bond lengthening is an effective π-interaction with (nearly) coplanar dialkylamino groups.…”

“…[23] An increasing low-field shift as a function of X is observed as follows: 7d (X ϭ H; δ 31 P ϭ Ϫ62.6) Ͼ 8a (Me 3 Si; Ϫ47.1) Ͼ 23a [TpЈ(CO) 2 MoϵC; 62.3] Ͼ 7c (tBu; 91.9) Ͼ 29a [Cp*(CO) 2 Fe; 135.5]. Particularly interesting is the replacement of the hydrogen atom at phosphorus by functional groups, which are able to withdraw electron density from phosphorus by π-delocalization as observed in MeO 2 CPϭC(F)NMe 2 (43) (δ 31 P ϭ Ϫ23.4) [30] vs. (E,Z)-HPϭC(F)NMe 2 (39a) (δ 31 P ϭ Ϫ90.0 and Ϫ99.9) [29] or in (Me 2 N)CϭPϪC(S)SSiMe 3 (32) (δ 31 P ϭ 145) [21] vs. 7d.…”

“…In the IR spectra of the inversely polarized phosphaalkenes 22a and 22b, strong bands at ν ϭ 1563 and 1546 cm Ϫ1 respectively, indicate pronounced π-delocalization of electron density into the carbonyl group. [21] In MeO 2 CϪPϭ C(F)NMe 2 the ν(CO) vibration is observed at ν ϭ 1685 cm Ϫ1 and thus at a lower wavenumber than in Me-O 2 CP(H)CF 3 [ν(CO) ϭ 1738 cm Ϫ1 ]. [30] The CO frequencies of 21 are also bathochromically shifted (1590Ϫ1640 cm Ϫ1 ) in comparison with monoacylated phosphanes.…”

Structural studies of phosphor-1,1-diselenoato Mn(I) and Re(I) complexes

“…Four CO groups attached to a six-coordinate metal center where all carbonyl groups are in cis-disposition to form a C 2v local symmetry corresponding to 2A 1 + B 1 + B 2 vibrational modes give rise to such an infrared pattern [22]. On the other hand, the m(CO) region in the IR spectra (KBr) of each of the four dinuclear species 2a-b and 4a-b exhibits two strong bands (2a, 2014, 1920; 2b, 2004, 1927; 4a, 2016, 1918; 4b, 2021, 1903) which point to a facial assembly of three carbonyl ligands in an octahedrally coordinated metal center [22,23].…”