Correlaiton of Hammett σ constants withNMR parameters for substituted phenylsilanes, phenylmethylsilanes and phenyldimethylsilanes

Anomalous reaction of an aryl silane with Co2(CO)8; characterisation of Me2NC6H4Si[Co(CO)4][OCCo3(CO)9]2

“…The reaction between Me 2 NC 6 H 4 SiH 3 and Co 2 (CO) 8 in toluene is clearly different from that of other RSiH 3 since the solution turns distinctly purple, in contrast to the more usual orange-brown. Work-up required chromatographic separation, which led to extensive decomposition on the column so material recovery was relatively low.…”

“…pMe 2 NC 6 H 4 SiCl 3 was prepared by combining the Grignard reagent from p-Me 2 NC 6 H 4 Br with excess SiCl 4 , and reducing the chloride with LiAlH 4 gave the silane [8].…”

“…The reaction of organosilanes with Co 2 (CO) 8 has long been known to give products with Si-Co bonds [1]. Thus Cl 3 SiH gives Cl 3 SiCo(CO) 4 [2], SiH 4 gives Si[Co 2 (CO) 7 ] 2 [3], and PhSiH 3 results in PhSi[Co(CO) 4 ][Co 2 (CO) 7 ] which decarbonylates to the closocluster PhSiCo 3 (CO) 9 [4].…”

“…Thus Cl 3 SiH gives Cl 3 SiCo(CO) 4 [2], SiH 4 gives Si[Co 2 (CO) 7 ] 2 [3], and PhSiH 3 results in PhSi[Co(CO) 4 ][Co 2 (CO) 7 ] which decarbonylates to the closocluster PhSiCo 3 (CO) 9 [4]. Reaction of silicon hydrides to give Si-Co bonds is involved in the hydrosilation of alkenes, catalysed by Co 2 (CO) 8 [5].…”

“…To see if there was a more specific route to these by-products we reacted p-Me 2 NC 6 H 4 SiH 3 with Co 2 (CO) 8 and now report that a completely different reaction takes place.…”