Li/X phosphinidenoid pentacarbonylmetal complexes: a combined experimental and theoretical study on structures and spectroscopic properties.

The synthesis of P-F phosphane metal complexes [(CO)5M{RP(H)F}] 2a–c (R = CH(SiMe3)2; a: M = W; b: M = Mo; c: M = Cr) is described using AgBF4 for a Cl/F exchange in P-Cl precursor complexes [(CO)5M{RP(H)Cl}] 3a–c; thermal reaction of 2H-azaphosphirene metal complexes [(CO)5M{RP(C(Ph)═N}] 1a–c with [Et3NH]X led to complexes 3a–c, 4, and 5 (M = W; a–c: X = Cl; 4: X = Br; 5: X = I). Complexes 2a–c, 3a–c, 4, and 5 were deprotonated using lithium diisopropylamide in the presence of 12-crown-4 thus yielding Li/X phosphinidenoid metal complexes [Li(12-crown-4)(Et2O)n][(CO)5M(RPX)] 6a–c, 7a–c, 8, and 9 (6a–c: M = W, Mo, Cr; X = F; 7a–c: M = W, Mo, Cr; X = Cl; 8: M = W; X = Br; 9: M = W; X = I). This first comprehensive study on the synthesis of the title compounds reveals metal and halogen dependencies of NMR parameters as well as thermal stabilities of 6a, 7a, 8, and 9 in solution (F > Cl > Br > I). DOSY NMR experiments on the Li/F phosphinidenoid metal complexes (6a–c; M = W, Mo, Cr) rule out that the cation a...