Nine-vertex polyhedral iridamonocarbaborane chemistry. Products of thermolysis of [(CO)(PPh₃)₂IrCB₇H₈] and emerging alternative cluster-geometry patterns

Polyhedral Dynamics and the Jahn–Teller Effect

“…Initially it was assumed that the deltahedra in metallaboranes would be the same as the deltahedra in isoelectronic metal-free boranes. However, as metallaborane chemistry was developed further, particularly by Kennedy and co-workers [58][59][60][61], a variety of deltahedral metallaborane structures were discovered based on deltahedra topologically distinct from the most spherical deltahedra found in simple metal-free boranes and carboranes (Figure 1.4). Of particular interest was the discovery of 9-and 10-vertex metallaboranes based on deltahedra with the transition metal at a degree 6 vertex whereas the metalfree borane has a most spherical deltahedral structure (Figure 1.4) with only degree 4 and 5 vertices.…”

“…The conversion of a most spherical borane n-vertex deltahedron to a deltahedron with a degree 6 vertex for a transition metal atom leads to a change in its skeletal electron count from 2n + 2 to simply 2n [58][59][60][61]. This has been attributed to a change in the skeletal bonding from a globally delocalized model with an n-center core bond to a more localized bonding model with two-center bonds along some of the deltahedral edges and three-center bonds in some of the deltahedral faces [62].…”

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]

“…The ÔisonidoÕ descriptor arises from the formal removal of a vertex of cluster-connectivity four from an isocloso C 3v 10-vertex polyhedron (schematic V) [15]. This geometry contrasts to the more common classical nido structure obtained by the removal of a five-connectivity vertex from the isogonal bi-capped square Archimedian antiprism of formal D 4d symmetry (schematic configuration VI) [15][16][17][18]. The isonido-type cluster structure of 2 is similarities to those observed previously for some related {PtC 2 B 6 } species obtained from more conventional syntheses involving addition of a low-valent platinum(0) complex to a preformed dicarbahexaborane species [19][20][21][22].…”

“…The cluster therefore exhibits an isonido nine-vertex structural character. The ÔisonidoÕ descriptor arises from the formal removal of a vertex of cluster-connectivity four from an isocloso C 3v 10-vertex polyhedron (schematic V) [15]. This geometry contrasts to the more common classical nido structure obtained by the removal of a five-connectivity vertex from the isogonal bi-capped square Archimedian antiprism of formal D 4d symmetry (schematic configuration VI) [15][16][17][18].…”

Macropolyhedral boron-containing cluster chemistry: two-electron variations in intercluster bonding intimacy. Contrasting structures of 19-vertex [(η5-C5Me5)HIrB18H19(PHPh2)] and [(η5-C5Me5)IrB18H18(PH2Ph)]

“…Rhodium and iridium metallaboranes have figured significantly in this regard, for example in terms of reactions, both catalytic and non-catalytic [3][4][5][6][7][8][9], in phenomena such as fluxionalities [10,11], and in the establishment of interesting cluster types, such as those of 'isocloso' and 'isonido' geometries [12][13][14][15]. Single-cluster borane, heteroborane and metallaborane chemistry is governed at present by an uppermost limit to cluster size of about fourteen vertices [16,17]: to extend beyond this horizon the clusters need to be linked or fused together to make bigger cluster assemblies.…”