The reaction of nido-1,2-(η-C5Me5Ru) 2(μ-H)2B3H7 (1) with the dichloroborane BHCl2·SMe2 results in the formation of three sets of B-Cl inserted metallaborane products: nido-1,2- (η5-C5Me5Ru)2(μ-H)B 4H7Cl2 (2), pileo-2,3-(η5-C 5Me5Ru)2(μ-H)B4H 5Cl2 (three geometric isomers, 3-5), and pileo-2,3-(η5-C5Me5Ru)2(μ-H) B4H4Cl3 (a pair of geometric isomers, 6 and 7). When the same reaction was carried out under more forcing conditions, three new metallaborane compounds, closo-1-(SMe2)-2,3-(η5- C5Me5Ru)2(μ3-H)B 5HCl3 (a pair of geometric isomers, 8 and 9) and closo-2,3-(η5C5Me5Ru)2B 6H3Cl3 (10), were isolated in low yield in addition to 2-7. Compounds 8 and 9 exhibit a capped-octahedral geometry, and 10 exhibits a seven-sep (skeletal electron pair) bicapped-octahedral geometry. Reaction of nido-2,4-(η5-C5Me5-Ru) 2B6H12 and nido-2,3-(η5-C 5Me5Ru)2B8H12 with BHCl2·SMe2 results in substitution of terminal H by Cl, producing nido-2,4-(η5-C5Me5Ru) 2B6H10Cl2 (11) and nido-2,3-(η5-C5Me5-Ru)2B 8H11Cl (12) in 82% and 75% yields, respectively. © 2005 American Chemical Society.