Metallaborane Heteroatom Incorporation Reactions:  Metallacarboranes, Metallathiaboranes, and an Iridaazaborane from Iridanonaborane Precursors

Abstract

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 eleven-vertex metallaheteroborane clusters. Thus passage of acetylene through refluxing p-xylene solutions of either arachno-[(PMe3)2(CO)HIrB8H12] (1a) or nido-[(PMe3)2(CO)IrB8H11] (2a) afforded the 11-vertex cluster nido-[9,9,9-(PMe3)2(CO)-9,7,8-IrC2B8H11] (5a) in up to 44% yield. With the cage substituted species arachno-[(PMe3)2(CO)HIrB8H11Cl] (1b), the analogous product is nido-[5-Cl-9,9,9-(PMe3)2(CO)-9,7,8-IrC2B8H10] (5b) and the position of the Cl substituent in the product suggests that the acetylene moiety attacks across the open face of the intermediate nido-iridanonaborane species and that cage rearrangement does not occur during the course of the reaction. Similarly, reaction of 1a with H2S under identical conditions results in the formation nido-[2,2,2-(PMe3)2H-2,6-IrSB8H10] (9a), closo-[2,2,2-(PMe3)2H-2,1-IrSB8H8] (10), and nido-[(PMe3)2HIrS2B8H8] (11a) in overall yields of 13%, 7%, and 20%, respectively. Additionally, refluxing a solution of 1a and anhydrous hydrazine in xylene afforded a 10% yield of the novel iridaazanonaborane nido-[2,2,2-(PMe3)3-2,9-IrNB7H9] (12). The compound is the first metallaazanonaborane cluster to be described, and its formation indicates that methods similar to those used to generate azaboranes may be used on metallaboranes to generate metallazaboranes. In addition to characterization by a combination of 1H, 31P, and 11B NMR and IR spectroscopy and high-resolution mass spectrometry, single-crystal X-ray diffraction studies were carried out on compounds 5a, 9a, 10, and 12.

Theisonido-Metalladicarbaborane [1,1,1-H{P(CH3)3}2-6-Cl-1,2,4-IrC2B8H9]

“…In the rhodium analogue, [(PEt3)2HRhC2B8HI0], which has a coordinatively unsaturated metal vertex, this process appears to be reversible (Jung & Hawthorne, 1980). Direct thermolysis of the unsubstituted analogue of compound (II) has been shown to give the corresponding isonido compound in ca 25% yield (Bould, Rath & Barton, 1996). The structural features of compound (II) are comparable to those of the unsubstituted cage species [(PPh3)aHIrC2BsHI0] reported previously (Nestor et al, 1989).…”

“…1), which was prepared as described in the Experimental section. The characterization of one of the two products obtained, nido- [9,9,2(CO) 7,, (I), is discussed elsewhere (Bould, Rath & Barton, 1996), but the second, with its yellow dagger-shaped crystals, which amounted to ca 30--40% of the total yield as estimated by l~B NMR spectroscopy, was characterized by a single-crystal X-ray diffraction study, the details of which are presented here.…”

Reactions of 11-Vertex Rhodathiaboranes with HCl: Synthesis and Reactivity of New Cl-Ligated Clusters

“…This structure, with a {Rh(1)S(2)B(4)B (7) 24 in which invariably the hydride ligand lies trans to the sulfur vertex.…”

Organometallic chemistry on rhodaheteroborane clusters: reactions with bidentate phosphines and organotransition metal reagents

“…NMR spectra for 7 at different temperatures suggest an intramolecular dynamic process, which resembles the fluxional behavior observed for the previously studied species, 1 and 10, the isoelectronic platinacarborane, [8,8- 20 It is thought that all these species undergo fluxional motion similar to that illustrated in Scheme 4 for compound 1, involving a closo-type transition state. The activation energy G ‡ calculated for the process observed for 7 at the coalescence temperature of 310 K in the 31 21,22 Further support for the closo-type transition state comes from the observation of the reversible nido to closo change that compound 1 undergoes on deprotonation, which is illustrated in Scheme 3. 9,12,13 When the reactions of compound 1 with dppe and dppp are carried out in 1 : 3 metallathiaborane to phosphine molar ratios, compounds 7 and 10 are formed together with the yellow nido-rhodathiaboranes, [8,8- by substitution reactions at the metal center, and the addition of a second ligand at the 9-position in the cluster.…”