Syntheses and studies of group 6 terminal pnictides, early-metal trimetaphosphate complexes, and a new bis-enamide ligand

Abstract

Investigated herein is the reactivity of the terminal-nitrido, trisanilide tungsten complex, NW(N[i- Pr]Ar)3 (Ar = 3,5-Me 2C6H3, 1). Nitride 1 has been shown to undergo an "N for (O)C1 metathesis with a variety of acid chlorides to form oxochloride (Ar[i-Pr]N) 3W(O)C1 (2) and the corresponding nitriles. The reaction of 1 with acid chlorides has been shown to proceed through an acylimido chloride intermediate. Furthermore, oxochloride 2 has been converted to a terminal phosphido trisanilide tungsten complex, PW(N[i-Pr]Ar)3 (9) by treatment with the anionic niobium phosphide complex [Na(OEt2)][PNb(N[Np]Ar) 31. Nitride 1 and oxochloride 2 have been converted to pseudo-octahedral complexes through the use of electrophilic reagents such as oxalyl chloride and phosphorus pentachloride. (Ar[i- Pr]N)3W(OCN)(Cl) 2 (10) and (Ar[i-Pr]N)3W(N=PCl3)(Cl) 2 (11) are synthesized by treating compound 1 with oxalyl chloride and PCl5, respectively. Similarly, (Ar[i-Pr]N) 3W(Cl) 3 (12) is formed by treatment of oxochloride 2 with PC15 with concomitant loss of oxyphosphorus trichloride. Reaction studies of trichloride 12 undertaken in the attempt to generate a low-coordinate tungsten species are also presented. Also reported presently is a new procedure for synthesis of the terminal phosphoryl complex (Ar[t-Bu]N)3MoPO (17) by treating phosphide (Ar[t-Bu]N) 3MoP (16) with the potent oxygen atom transfer (OAT) reagent mesitylnitrile oxide (MesCNO). In conjunction with collaborators, the thermodynamic and kinetic aspects of MesCNO as an OAT reagent with phosphide 16 and phosphines have been investigated. Density Functional Theory calculations of OAT reactions of MesCNO are also shown. In an effort to further develop the coordination chemistry of the trianionic, tridentate ligand trimetaphosphate, studies are described whereupon trimetaphosphate is metallated with molybdenum. (MeCN)3Mo(CO) 3 reacts with [PPN] 3[P30 9] -H20 ([PPN] = [Ph3P=N-PPh3]') to form the trimetaphosphate salt [PPN]3[(P30 9)Mo(CO) 3] ([PPN] 3[18]) in high yield. Efforts to generate trimetaphosphate vanadium oxo ((P30 9)V--O, 19) are also revealed. Finally, the synthesis of a new bis-enamide ligand class is described by the double addition of ketenimines to dilithium arylphosphanides. Formation of [Li(thf)]2 {PhP[C(CPh2)NPh] 21 ([Li(thf)] 2[20]) and [Li(thf)]2{MesP[C(CPh2)NPh] 2} ([Li(thf)]2[21]) are presented. The synthesis of tantalum species utilizing these new bis-enamide ligands is also demonstrated.