Studies of 2-(.eta.5-C5H5)CoB4H8, a cobaltaborane analog of pentaborane(9)

Metallaborane reaction chemistry. Part 10. Phenylacetylene incorporation via [4,4-(PMe2Ph)2-arachno-4-PtCB8H12] in a ‘converse’ metalladicarbaborane synthesis of [7,7-(PMe2Ph)2-isonido-7,6,8-PtC2B6H7-6-Ph]

“…Only very small single-crystals of 2 were obtainable (50 · 50 · 20 lm), but a rotating-anode Xray source gave sufficient diffraction intensities for a satisfactory diffraction analysis. 2 The results of NMR spectrometry and mass spectrometry were entirely consistent with the solid-state cluster structure thus determined, 3 confirming that the crystal was representative of the bulk sample. Although the yield of 2 was small in this preliminary experiment on this system, there is a clear demonstration of a converse metallacarbaborane synthesis using the readily made [12] metallanonaborane starting substrate 1 that has no carbon atoms in the cluster.…”

“…Although converse syntheses, by the incorporation of organic residues such as acetylene into pre-formed metallaboranes, were advocated some 20 years ago as general methods with enormous potential [1], examples of this route were then sparse. Of the few examples, it had been shown that addition of alkynes, accompanied by boron-vertex loss, to [2-(C 5 H 5 )-nido-2-CoB 4 H 8 ] gives [1-(C 5 H 5 )-nido-1,2,3-CoC 2 B 3 H 7 ] and Csubstituted derivatives [3], and that the addition of MeC"CMe into [1,1,1-(CO) 3 [4]. More recently, we and others became interested in these types of Ôconverse reactionsÕ of acetylenes with boron-containing clusters, using both metallaborane and heteroborane substrates [5][6][7][8][9][10][11].…”

Transition Metal—Main Group Cluster Compounds

“…Ouster type 4 is exemplified by 1,2,3-(CpCo )3B3H5, (66)(67)(68) 1,2,3-(CpCo MIL 3 -C0)B 3 H 3 ( Figure 15a)(69,70) and 1,2,3-(CpCo )2Fe(CO)~3H3 (Figure 15b). (71) The first two of these compounds have been characterized crystallographically and the C03 and B3-triangles are mutually staggered in each one. The metal-main group interaction may be considered in terms of a transition metal7r-complex involving a cycloborenyl ligand and, as such, would be analogous to that in mononuclear cyclopropenyl complexes of the type L,.M(71 3 -C 3 R 3 )Y2) Alternatively, the metalloboranes may be described as cluster compounds.…”

Metal fragment exchange from a molybdaborane to a tungstaborane

“…However, there have been relatively few studies of the reactivity of metallaboranes. Some metallaboranes have been used as synthons in the stepwise synthesis of heterometallaboranes (or polymetallaboranes) by further reaction with metal complexes: these studies have been limited mainly to reactions of transition-metal halides and the larger, more stable metallaborane anions [5][6][7][8][9][10][11][12][13][14][15]. Some years ago we prepared the molybdaborane arachno-2-[Mo(g-C 5 H 5 )(g 5 :g 1 -C 5 H 4 )B 4 H 7 ] (I) in gram quantities permitting a study of its reactivity [16].…”