The insertion of alkyl and aryl isonitriles into the silicon-boron bond of silylboranes proceeded thermally to provide (boryl)(silyl)iminomethanes in moderate-to-good yields. The (boryl)(silyl)iminomethane reacted with borane (BH 3 ) to give the corresponding borane complex in good yield, whose crystal structure was determined by a single-crystal X-ray analysis.It is commonly known that multistep reactions of isonitriles with organoboranes involve the coordination of the isonitrile to the boron followed by alkyl migration from the boron to the isocyano carbon, leading to the formation of boron-and nitrogen-containing heterocycles. 1 A simple 1:1 insertion product of isonitrile with organoborane has been scarcely known, to our best knowledge. 2,3 Herein, we report a new insertion reaction of isonitriles into the silicon-boron bonds of silylboranes 4 to provide N-substituted (boryl)(silyl)iminomethanes in moderate-to-good yields. In contrast to our previous results involving silaborative reactions with carboncarbon multiple bonds, 5-7 our present research indicates that no transition-metal catalyst is needed for the silaboration of isonitriles. It is interesting to note that reactions of the N-substituted (boryl)(silyl)iminomethanes with BH 3 afforded chromatographically stable boraneimine complexes. The structure of the borane-imine complex was determined by a single-crystal X-ray analysis.The silylborane 1a was subjected to a reaction with an equimolar amount of tert-butyl isonitrile (2a) at room temperature. The product 3aa was isolated by bulb-to-(1) Casanova, J., Jr. In Isonitrile Chemistry; Ugi, I., Ed.; Academic Press: New York; 1971; p 109.(2) Reactions of isonitriles with B-H bonds of borazines and the B-B bond of tetrakis(dimethylamino)diborane were reported to afford monomeric (iminomethyl)borazines and iminobis(boryl)methanes, respectively: Meller, A.; Batka, H. Monatsh. Chem. 1970, 101, 648. (3) Monomeric imino(boryl)methanes were prepared by the reaction of (iminomethyl)lithium with chlorobis(dimethylamino)borane: Sicker,