6533b7d7fe1ef96bd12682d9

RESEARCH PRODUCT

Comparative multinuclear magnetic resonance spectroscopic study of transition metal (Cr, W and Mn) mesitylene tricarbonyls and transition metal (Ru and Co) carbonyl clusters

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Abstract Three mononuclear 1,3,5-trimethylbenzene (mesitylene) carbonyl transition metal complexes, mesitylene tricarbonyl chromium, (CH 3 ) 3 C 6 H 3 Cr(CO) 3 ( 1 ), mesitylene tricarbonyl tungsten, (CH 3 ) 3 C 6 H 3 W(CO) 3 ( 2 ), mesitylene tricarbonyl manganese tetra-fluoroborate, [(CH 3 ) 3 C 6 H 3 Mn(CO) 3 ]BF 4 ( 3 ); and three clusters, mesitylene nonacarbonyl tetracobalt, (CH 3 ) 3 C 6 H 3 Co 4 (CO) 9 ( 4 ), mesitylene carbido tetradecacarbonyl hexaruthenium, (CH 3 ) 3 C 6 H 3 Ru 6 C(CO) 14 ( 5 ) and carbido heptadecacarbonyl hexaruthenium, Ru 6 C(CO) 17 ( 6 ), have been studied by means of 1 H, 13 C and natural abundance 17 O NMR spectroscopy. Generally, the 1 H and 13 C NMR chemical shifts of the aromatic protons and carbons in the compounds studied show clearly shielded values when compared with those of uncomplexed mesitylene. The 13 C NMR chemical shifts of the carbonyl groups show an inverse relation with the corresponding 17 O chemical shifts in agreement with the effect of π-backbonding. 1 J (C, H) spin-spin coupling constants of aromatic carbons in mesitylene moiety of chromium and tungsten complexes show clearly increased values when compared with uncomplexed mesitylene. This can be explained by an increased s-character in the CH bond induced by the σ-effect of the bound metal. Of the NMR methods studied, 17 O NMR was shown to have very promising properties owing to the exceptionally high sensitivity and small line width of NMR signals.