A Terminal Nitride‐to‐Phosphide Conversion Sequence Followed by Tungsten Phosphide Functionalization Using a Diphenylphosphenium Synthon

Abstract

Dedicated to Professor Philip P. PowerThe terminal, anionic niobium phosphide (P 3À ) complex Na [P Nb(N[Np]Ar) 3 ] (Na-1; Np= neopentyl, Ar = 3,5-Me 2 C 6 H 3 ) has served as a platform for the construction of multiply bonded, phosphorus-containing moieties as both complexed ligands and free entities. [1][2][3][4][5] Exemplifying the latter is the synthesis of phosphaalkynes (RCP) and [O Nb{N(Np) [5] We envisioned that a similar method could be employed to synthesize new transition-metal phosphide complexes, given the availability of a suitable reaction partner for Na-1. We recently reported an attractive candidate for this application: the tungsten oxide/chloride complex, [O(Cl)W{N(iPr)Ar} 3 ] (3).[6] In a reaction similar to Equation (1), complex 3 is prepared by treating the corresponding nitride complex [NW{N(iPr)Ar} 3 ] (4) with pivaloyl chloride (tBuC(O)Cl), and is quantitatively obtained as a blood-red, highly lipophilic solid of sufficient purity for further synthetic studies. We hypothesized that in the presence of Na-1, 3 would behave as an "inorganic acid chloride", engaging Na-1 by elimination of NaCl. With subsequent intermetal exchange of P and O ligands, the known oxidoniobium complex 2 would be generated as well as a new terminal phosphide complex [P W{N(iPr)Ar} 3 ] (5). Several examples of installing multiply bonded ligands (oxide, imide, and alkylidene) by intermetal ligand exchange have been reported; [7][8][9][10][11][12][13][14][15][16] herein, we extend this concept to the terminal phosphide functional group.Our hypothesis was tested by treating a yellow-orange, ethereal solution of Na-1 with a red, ethereal solution of 3 at À35 8C, following in situ preparation of 3 from 4 and removal of tBuCN. Upon stirring for two hours at 22 8C, an orangebrown, homogeneous solution was obtained. Following solvent removal under reduced pressure the product mixture was dissolved in C 6 D 6 . [17]Separation of 5 from NaCl was trivial; however, separation of 5 from coproduct 2 at first proved difficult, owing to their similar solubility properties. This was initially overcome by applying the Pasteur method, [18] whereby mixtures of crystalline 2 and 5 were manually separated.A more efficient method of separating 5 from coproduct 2 was achieved by in situ conversion of 2 to the bistriflate complex [(TfO) 2 Nb{N(Np)Ar} 3 ] (6, Tf = CF 3 SO 2 ), [5] a complex that is only sparingly soluble in common hydrocarbon solvents. Accordingly, treatment of a 1:1 mixture of 2 and 5 in Et 2 O with neat triflic anhydride (Tf 2 O, 1 equiv) at room temperature resulted in a color change from orange-brown to yellow-brown over several minutes as a yellow precipitate formed. Following solvent removal under reduced pressure, the product mixture was dissolved in C 6 D 6 . The 1 H NMR spectrum of the product mixture revealed clean and selective production of 6, with 5 remaining unperturbed. The 31 P{ 1 H} NMR spectrum displayed only the downfield signal associated with 5, thus confirming its role as a spectator in this react...

Reactivity of Phosphanylphosphinidene Complex of Tungsten(VI) toward Phosphines: A New Method of Synthesis of catena-Polyphosphorus Ligands

“…The short P1−P2 distance of 2.1065(17) Å is almost identical with the P−P distance of 2.101(3) Å in [Cl(ArN) 2 W(η 2 -iPr 2 PP) − ], 16 19 Formally, the tungsten atom is pentacoordinated, but the coordination geometry can also be described as distorted pseudotetrahedral (ligation by N1, N2, Cl1, and the P1−P2 bond).…”

Simple NUF3 and PUF3 Molecules with Triple Bonds to Uranium

“…Clearly, the N UF 3 and P UF 3 molecules reported herein represent uranium-Group 15 triple bonds as shown by the molecular orbital analysis, although the UP bond is weak. A final comparison with terminal WN and WP bond lengths of 1.67 and 2.12 in analogous organometallic complexes [41,42] shows that the triple-bond lengths computed herein for uranium are 5 and 13 % longer than their tungsten analogues. We see that the UP bond is clearly weaker in comparison than WP, which is in marked contrast to UN in comparison with WN.…”

Terminal Molybdenum Phosphides with d Electrons: Radical Character Promotes Coupling Chemistry

“…[2] Owing to both end-on and side-on reactivity, [2b] rarer still are isolable terminal transition-metal phosphides.I ndeed, since the initial reports of aP 1 ligand bearing aMPtriple bond two decades ago, [3] only ah andful of examples of such am otif have been described ( Figure 1). [4] These compounds all display d 0 group 5a nd 6m etals in at rigonal coordination environment. Reported herein are the first examples of isolable transition-metal complexes with both terminal phosphide ligands and delectrons.…”