Electronic effects in (CH3)nC6H6-nMn(CO)3+ complexes (n = 0-6) as evidenced by proton and carbon-13 NMR spectroscopy, manganese-55 NQR [nuclear quadrupole resonance] spectroscopy, and carbonyl ir spectroscopy

Abstract

A spectroscopic analysis of electronic effects and transmission of electron density in (CH3)"C6H6_rtMn(CO)3+ complexes in = 0-6) using 'H and 13C nmr of the aromatic ring atoms,55Mn nqr spectroscopy, and CO ir spectroscopy is reported. The nmr data for the complexes show substantial shielding of the ring nuclei compared to the free arenes, and this was ascribed to magnetic anisotropy of the ring caused by the metal. By comparison of the Mn(I) complexes to the isoelectronic Cr(0) systems, it was concluded that much more ring -> metal electron migration occurs with Mn(I) than Cr(0). The S5Mn nqr frequencies increase linearly with the number of methyl groups on the ring. The CSHS~ligand appears to be a much better electron donor than CSH6 based on the nqr spectra. Crystal lattice differences produced only 3% change in the 55Mn coupling constant for a series of five anions in the C6H6Mn(CO)3* salts. A larger effect (8%) was observed for the mesitylene salts. Only minute perturbations occur to the axial symmetry of the metal-ring bond in all salts as evidenced by small asymmetry parameters. The carbonyl ir frequencies show a linear correlation with ring substitution, and it is concluded that the electron density changes on the metal are transmitted in a corresponding fashion to the CO groups. All spectra are found to be internally consistent.

Metall‐π‐Komplexe von Benzolderivaten, XV. Bis(η6‐naphthalin)chrom(0): Röntgenstrukturbestimmung und kernresonanzspektroskopische Untersuchung

“…Feld und einer Abnahme der Protonenkopplungskonstanten. Als wesentlich fur Koordinationsverschiebungen werden vor allem die magnetische Anisotropie der Metall-Aren-Bindung und die Anderung der Elektronendichte im Aren beim Ubergang vom freien in den koordinierten Zustand betrachtet 16,[18][19][20][21][22][23][24]. Diese Konzepte konnen dazu dienen, den Gang der chemischen Verschiebungen der Ringprotonen des Naphthalins in verschiedenen (q-Naphtha1in)metall-Komplexen zu deuten.…”

Periodic trends in metal-metal bond character based on cobalt-59 nuclear quadrupole resonance spectroscopy

“…This work Tl[Co(CO)4]3 9.760(6) 16.83 (250) 25.67 (35) 120.3 0.20 This work 11.00 (6) 16. 25 (200) 25.18 (40) 118.7 0.31 This work 9.130(6) 16.66 (250) 25. 25 This work 10.24 (2) 18.26 (3) 27.75 (5) 129.9 0.175…”

“…25 (200) 25.18 (40) 118.7 0.31 This work 9.130(6) 16.66 (250) 25. 25 This work 10.24 (2) 18.26 (3) 27.75 (5) 129.9 0.175…”

A novel (.eta.5-cyclohexadienyl)tricarbonylchromium anion: the reaction between the dianion of (.eta.6-naphthalene)tricarbonylchromium and a proton source

“…Department of Chemistry, Iowa State University Ames, Iowa 50011 Received July 26,1983 Although the photochemistry of furans has been extensively studied1 since the initial report of Srinivasan,2 no synthetic interest has developed due to the fact that complex product mixtures and low yields have inevitably resulted from these photolyses. We report here that silyl substitution allows remarkably clean photoisomerization of furans.…”