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.