METALLABORANE HETEROATOM INCORPORATION REACTIONS - METALLACARBORANES,METALLATHIABORANES, AND AN IRIDAAZABORANE FROM IRIDANONABORANE PRECURSORS

Formation of metallaheteroboranes by insertion of heteroatoms into an existing metallaborane cluster, rather than adding the metal moiety to the heteroborane which is normally the case, has been achieved in the cases of carbon, nitrogen, and sulfur to produce nine-, ten-, and ele ven-vertex metallaheteroborane clusters. Thus passage of acetylene thr ough refluxing p-xylene solutions of either arachno-[(PMe(3))(2)(CO)HI rB8H12] (1a) or nido-[(PMe(3))(2)(CO)IrB8H11] (2a) afforded the 11-ver tex cluster nido-[9,9,9-(PMe(3))(2)(CO)-9,7,8-IrC2B8H11] (5a) in up to 44% yield. With the cage substituted species arachno-[(PMe(3))(2)(CO) HIrB8H11Cl] (1b) in the analogous product is nido-[5-Cl-9,9,9-(PMe(3)) (2)(CO)-9,7,8-IrC2B8H10] (5b) and the position of the Cl substituent i n the product suggests that the acetylene moiety attacks across the op en face of the intermediate nido-iridanonaborane species and that cage rearrangement does not occur during the course of the reaction. Simil arly, reaction of 1a with H2S under identical conditions results in th e formation nido-[2,2,2-(PMe(3))(2)H-2,6-IrSB8H10] (9a), closo-[2,2,2- (PMe(3))(2)H-2,1-IrSB8H8] (10), and nido-[(PMe(3))(2)HIrS2B8H8] (11a) in overall yields of 13%, 7%, and 20%, respectively. Additionally, ref luxing a solution of la and anhydrous hydrazine in xylene afforded a 1 0% yield of the novel iridaazanonaborane nido-[2,2,2-(PMe(3))(3)-2,9-I rNB7H9](12). The compound is the first metallaazanonaborane cluster to be described, and its formation indicates that methods similar to tho se used to generate azaboranes may be used on metallaboranes to genera te metallazaboranes, In addition to characterization by a combination of H-1, P-31, and B-11 NMR and IR spectroscopy and high-resolution mas s spectrometry, single-crystal X-ray diffraction studies were carried out on compounds 5a, 9a, 10, and 12.