Phenylimido derivatives of [Mo 6O 19] 2−: syntheses, X-ray structures, vibrational, electrochemical, 95Mo and 14N NMR studies

Abstract

Both [Mo 6O 18(NPh)] 2− and [Mo 6O 17(NPh) 2] 2− species are formed by reaction of (n-Bu 4N) 2[Mo 6O 19] with either 1 or 2 equiv. of Ph 3PNPh in pyridine or acetonitrile and have been isolated as mixtures. Single-crystal X-ray diffraction analyses have shown that [Mo 6O 18(NPh)] 2−, [Mo 6O 17(NPh) 2] 2− and [Mo 6O 19] 2− can be found together in the same crystal of average composition (n-Bu 4N) 2[Mo 6O 19− x (NPh) x]. The structural parameters of the averaged anions have been determined for x=1.16 (sample 1) and x=0.92 (sample 2). Crystal data for 1: a=12.684(4), b=22.750(4), c=19.483(3) Å, β=103.04(2)°, space group P2 1/ c, Z=4, R=0.048 and R w=0.051 for 3846 reflections with I⩾3σ( I). Crystal data for 2: a = 12.678(2), b=22.645(3), c=19.462(4) Å, β=104.16(2)°, space group P2 1/ c, Z=4, R=0.058 and R w=0.061 for 5243 reflections with I⩾3σ( I). The products have been studied in acetonitrile solution by 95Mo and 14N NMR spectroscopy, Raman spectrophotometry and electrochemistry. Each of these techniques has confirmed the presence of the mono- and bis-imido derivatives together with the parent species, and has allowed both the characteristics of the individual components and the composition of the solution to be determined; the results obtained by the different methods are in reasonable agreement.