Phosphorus and Arsenic Atom Transfer to Isocyanides to Form π‐Backbonding Cyanophosphide and Cyanoarsenide Titanium Complexes

Abstract

Decarbonylation along with E atom transfer from Na(OCE) (E=P, As) to an isocyanide coordinated to the tetrahedral TiII complex [(TptBu,Me)TiCl], yielded the [(TptBu,Me)Ti(η3‐ECNAd)] species (Ad=1‐adamantyl, TptBu,Me−=hydrotris(3‐tert‐butyl‐5‐methylpyrazol‐1‐yl)borate). In the case of E=P, the cyanophosphide ligand displays nucleophilic reactivity toward Al(CH3)3; moreover, its bent geometry hints to a reduced Ad−NCP3− resonance contributor. The analogous and rarer mono‐substituted cyanoarsenide ligand, Ad−NCAs3−, shows the same unprecedented coordination mode but with shortening of the N=C bond. As opposed to TiII, VII fails to promote P atom transfer to AdNC, yielding instead [(TptBu,Me)V(OCP)(CNAd)]. Theoretical studies revealed the rare ECNAd moieties to be stabilized by π‐backbonding interactions with the former TiII ion, and their assembly to most likely involve a concerted E atom transfer between Ti‐bound OCE− to AdNC ligands when studying the reaction coordinate for E=P.

Metal‐Ligand Cooperativity to Assemble a Neutral and Terminal Niobium Phosphorus Triple Bond (Nb≡P)

“…Starting from the transmetallation product [(PNP)NbCl(PCO)(N t BuAr)] ( A ), we performed density functional theory (DFT) calculations at the B3LYP‐D3/cc‐pVTZ(‐f)/LACV3P//6‐31G**/LACVP level of theory [19] to investigate how the complex 2 is generated (Figure 3). [14] We expected the reductive decarbonylation step to be promoted by the nucleophilic attack by one of the phosphine arms of [PNP] − to the phosphorus atom of [PCO] − akin to what we had found in previous DFT calculations, where an isocyanide undergoes coupling with the X atom of a coordinated XCO − (X=P or As) ligand in a paramagnetic Ti II species to form η 3 ‐cyanophosphide or ‐cyanoarside species [16a] . However, the sterically demanding N t BuAr (anilido) ligand renders the concerted P−P bond formation through the four‐membered metallacycle transition state to be prohibitively high (Figure S26), resulting instead in two likely scenarios: A direct ( A‐TS1 ) or an anilide‐assisted ( A‐TS2 ) CO extrusion pathway (Figure S27), both of which are thermally accessible (Figure 3), according to our calculations.…”

Cyano(triphenylsilyl)phosphanide as a Building Block for P,C,N Conjugated Molecules

“…Related structures have been observed in a lanthanide complex of the [SCP] À anion [22] and in a titanium complex of [Ad-NCP] À . [21] The reaction of Na(18-crown-6) [1] with one equivalent of chlorotriphenylsilane in toluene or C 6 D 6 produced instant precipitation of colorless NaCl and gave a single product 4 2). 29 Si satellites ( 1 J P,Si = 47 Hz) indicate a P À Si bond.…”

“…These are the phosphanyl phosphacyanide salt E and the bis(triphenylstannyl)phosphanyl cyanide F which can be used to synthesize phosphaallenes such as R À P = C = N = BR' 2 , metal complexes such as [(LAu) 3 PCN] + , or solutions of the parent phosphacyanamide H 2 PCN. [8] Other functionalised PCN and AsCN derivatives such as H, [20] G [9] and J, [21] were likewise reported lately.…”