Ten-vertex metallaborane chemistry. Aspects of the iridadecaborane closo→isonido→isocloso structural continuum

Abstract

Reaction of the arachno-[ B,H,,] -or nido-[ BsHIZ] -anions with [ lrCl( PPh,),] at ca. 298 K gives, in addition to previously reported species, pale violet [7,7,9-( PPh,),-isonido-7-IrB,H,,] 2 in yields of ca. 2%. Single crystal X-ray diffraction analysis and multinuclear NM R spectroscopy reveal a ten-vertex {IrB,} cluster of an 'isonido' type that is based upon the closo eleven-vertex structure of [BllHl,]Z-from which a fourconnected vertex is removed to generate a four-membered open face. There are two fluxional bridging hydrogen atoms associated with the open face. Thermolysisat ca. 355 K of solutions in 1,1,2,2-tetrachIoroethane of yellow [5,7-(PPh,),-5-H-5-(o-Ph,PC6H,)-nido-5-lr~,H,,-2] 4 result in loss of hydrogen and the formation of deep purple [8-Cl-7,9-(PPh,),-7-(o-Ph,PC6H,)-ison~do-7-lrBsH6-1 01 5 (0-5%) and royal blue [7,9-(PPh,),-7-(o-Ph,P~6H,)-~son~do-7-IrB,H,-l 0 1 6 (045%). Single-crystal X-ray

Macropolyhedral boron-containing cluster chemistry. Cluster assembly about a molybdenum centre. Formation of the 19-vertex [(CO)2MoB16H15C2Ph2]? anion

“…containing closo-type ten-vertex borane cluster species. 15 Other cluster interboron distances are in the range 1.733 (4) to 1.872(4) Å, with carbon-boron distances in the range 159.7(4) to 162.1(4) Å. The C(21)-Mo(2)-C (22) …”

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].…”

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.…”