ORGANOTRANSITION-METAL METALLCARBORANES .23. (C5ME5)CO(ET2C2B3H4-R) METALLACARBORANE SANDWICH COMPLEXES AS VERSATILE SYNTHONS - INTRODUCTION OF ORGANOMETHYL FUNCTIONAL-GROUPS AT BORON

The air-stable complex (C5Me5)Co(Et2C2B3H5) (1), a synthon of demonstrated utility in the construction of multidecker sandwiches and organometallic polymers, was derivatized at B(5) (the middle boron on the C2B3 ring) via bridge-deprotonation and reaction of the 1- ion with organomethyl halides. This approach, previously developed in our laboratory for B-alkylation of nido-LM(R2C2B3H5) metallacarboranes (L = aromatic hydrocarbon; M = Fe, Ru, or Co; R = alkyl), was employed in the present work to prepare a series of (C5Me5)Co(Et2C2B3H4-5-CH2-R') complexes in which R' is an aryl, cyano, alkoxy, acyl, alkenyl, alkynyl, ester, fluoroalkyl, or fluoroaryl group. Organic transformations of several of these compounds afforded carboxylic acid, amino, amide, and hydroxy derivatives. These species, characterized via H-1, C-13, and B-11 NMR, IR, UV-visible, and mass spectra, represent the first organic derivatization of small metallacarboranes beyond alkyl or arylalkyl substitution and demonstrate that the cluster framework of 1 remains intact under a wide range of organic reaction conditions.