Mono-, bi- and polynuclear complexes of dimethyldiphenylsilane, diphenylether and biphenyl with Cr, Co and Ru. Synthesis and 1H, 13C, 17O and 29Si NMR spectroscopic characterization

Abstract

Mono- and bimetallic transition metal carbonyls of dimethyldiphenylsilane, Ph 2Si(CH 3) 2 (L1), diphenylether, Ph 2O (L2) and biphenyl, Ph 2 (L3): Ph 2Si(CH 3) 2Cr(CO) 3 ( 1), Ph 2Si(CH 3) 2[Cr(CO) 3] 2 ( 2), Ph 2Si(CH 3) 2Co 4(CO) 9 ( 3), Ph 2Si(CH 3) 2[Co 4(CO) 9] 2 ( 4), Ph 2Si(CH 3) 2Cr(CO) 3Co 4(CO) 9 ( 5), Ph 2OCr(CO) 3 ( 6), Ph 2OCo 4(CO) 9 ( 7), Ph 2ORu 6C(CO) 14 ( 8), Ph 2OCr(CO) 3Co 4(CO) 9 ( 9) and Ph 2Ru 6C(CO) 14 ( 10) have been prepared and characterized by means of 1H, 13C, 17O and 29Si NMR spectroscopy. The same order of the shielding effects induced by the transition metal (Co < Ru < Cr) on the 1H NMR chemical shifts of the η 6-coordinated ring as observed earlier for diphenylmethane is also valid for the present bisarene aromatic ligands containing hetero-atoms in their structures. Differing from the behaviour of the 1H NMR chemical shifts of methylene protons of the diphenylmethane complexes, δ( 1H) of Si(CH 3) 2 group in dimethyldiphenylsilane always shows deshielded values consistent with π-coordination. Similarly, δ( 29Si) of Si(CH 3) 2 group is monotonously deshielded with the increasing degree of the complexation. As for diphenylmethane derivatives, δ( 17OC) of the present chromium tricarbonyl derivatives always shows easy-to-detect spectral characteristics, the shifts varying between 372.8 and 374.5 ppm. The only value obtained for tetracobalt nonacarbonyl derivatives was that of 7, δ( 17OC) = 349 ppm. The same order of δ( 17OC) as observed for the mesitylene transition metal carbonyls (Co < Cr < Ru) is also valid for the present polyarene compounds. The inverse relation between δ( 13CO) and δ( 17OC) in Ru and Co derivatives can be explained by the effect of π-backbonding. Diphenylether derivatives were not thermally stable enough to determine accurately δ( 17O) of the ethereal oxygen for all derivatives prepared. From the synthetic point of view, the present bisarene ligands were not so easily transformed to their π-coordinated derivatives as diphenylmethane.