Access to Metal Complexes of the Elusive Imidobis(phosphaalkene) Anion by N–Si Bond Cleavage of a <i>N</i>‐Silylimino‐Bridged Bis(phosphaalkene)

Abstract

Abstract Metalation of the aminophosphaalkene ( i PrMe 2 Si) 2 C=PN(H)SiMe 3 ( 2 ) with lithium diisopropylamide (LDA) in THF solution, followed by the reaction of the lithium salt 3 with the P ‐chlorophosphaalkenes (RMe 2 Si) 2 C=PCl ( 1a , R = Me; 1b , R = i Pr; 1c , R = Ph), furnishes the first N ‐silylimino‐bridgedbis(phosphaalkenes) [( i PrMe 2 Si) 2 C=P] 2 NSiMe 3 ( 4a ) and [( i PrMe 2 Si) 2 C=P][(RMe 2 Si) 2 C=P]NSiMe 3 ( 4b , R = Me; 4c , R = Ph). The N–Si bond cleavage of 4a under very mild conditions with AuCl(THT) and with [RhCl(COD)] 2 provides binuclear Au I and Rh I complexes 5 , 6 of the P , P′ ‐coordinatedimidobis(phosphaalkene) anion [( i PrMe 2 Si) 2 C=P] 2 N – , the first case of elusive P=C ‐unsaturated congeners of the “classic” bis(phosphanyl)amide ligands. Solid 4a exists in a helically distorted S‐shaped structure with two inequivalent P=C groups, but 31 P‐NMR reveals the equivalence of both P=C groups in solution at the NMR time scale. The P=C and P–N bonds distances in 4a do not indicate significant conjugation within the C=P–N–P=C moieties whereas in complexes 5 and 6 the W‐shaped CPNPC heteropentadienide anion exhibits strong 5‐center‐6‐π conjugation according to DFT calculations and to the experimental P=C and P=N bond lengths.