Janet E. Crook

Facile thermally-induced cluster oxidations in metallaborane chemistry: arachno→nido→closo reaction sequences exhibited by iridanonaboranes and iridadecaboranes, and the stabilization of the iridium(V) oxidation state

Iridanonaboranes and iridadecaboranes which have adjacent open-face bridging H atoms and terminal Ir–H atoms readily lose H2 in formal cluster oxidations which involve stable isolable iridium (V) species.

A novel closo-type metallaundecaborane, [1,1-(PPh3)2-2,5-(OEt)2-1-RuB10H8], and its relationship to the ‘isocloso’ series of metallaborane clusters

Abstract The new ruthenaundecaborane [(PPh3)2RuB10H8 (OEt)2] may be considered as an eleven-vertex member of a previously unrecognised series of metallaboranes which are formally derived by the single capping of an arachno-type (rather than a nido-type) cluster geometry with a metal centre which can be thought of as contributing four orbitals to the cluster bonding schemes.

Molecular structure of the 17-vertex conjuncto-platinaheptadecaborane [(PMe2Ph){PtB16H18(PMe2Ph)}]: a 16-vertex η6-hexadecaboranyl ligand

The compound [7-(PMe2Ph){7-PtB16H18-9′-(PMe2Ph)]} is a complex of a macropolyhedral 16-vertex borane ligand based on the structure of an as yet unknown B6–B10conjuncto-borane; it is the first example of a contiguous 17-vertex cluster species, and has a number of other interesting features.

closo–nido-Cluster isomerism in metallacarbaboranes via a change of metal valency state: molecular structure of µ-1,2-acetato-2-hydrido-2,10-bis(triphenylphosphine)-closo-1,2-carbairidadecaborane

The iridium(III)closo-cluster structure of [µ-1,2-(MeCO·O)-2-H-2,10-(PPh3)2-closo-1,2-ClrB8H7], which also contains a novel acetate bridge, contrasts with the otherwise ostensibly isoelectronic iridium (V)iso-nido-cluster structure of [(PPh3)(Ph2P[graphic omitted]H6(OMe)C(OH)}]

Heterobimetallic B-frame compounds: systematic synthesis and molecular structure of the seven-vertex µ-HOs,Pt-nido-osmaplatinaborane [(Ph3P)2(CO)(Os)(PhMe2P)ClHPtB5H7]

The first structurally characterized polyhedral metallaborane osmium compound has a seven-vertex nido-osmaplatinaborane cluster structure based on the dodecahedron with one five-connected vertex missing, the metal atoms being located on adjacent (2,7) positions in the five-membered open face and linked via an Os–H–Pt bridging bond; important wider implications of the mechanism of formation are indicated.

Synthesis, molecular structures, and nuclear magnetic resonance properties of the macropolyhedral metallaboranes [(PMe2Ph)4Pt3B14H16] and [(PMe2Ph)PtB16H18(PMe2Ph)], and a discussion of the bonding at platinum in these and some related platinaborane clusters

Thermolysis of [4-(PMe2Ph)2-arachno-4-PtB8H12] in refluxing toluene solution gives the known yellow 14-vertex diplatinaborane [(PMe2Ph)2Pt2B12H18] plus two novel 17-vertex cluster compounds, viz. the green triplatinaborane [(PMe2Ph)4Pt3B14H16](1) and the red monoplatinaborane [(PMe2Ph)PtB16H18(PMe2Ph)](2). Crystals of (1), as its 1:1 solvate with CH2Cl2, are monoclinic, space group P21/c, with a= 1 249.0(3), b= 3 732.6(8), c= 1 072.0(2) pm, β= 104.92(2)°, and Z= 4; the structure was refined using 4 802 independent Fo with I > 2σ(I) to a final R= 0.049, R′= 0.045. Crystals of (2) are also monoclinic, space group P21, with a= 992.7(3), b= 1 067.2(2), c= 1 378.7(3) pm, β= 95.08(2)°, and Z= 2; the structure was refined using 1 992 independent Fo with I > 2σ(I) to a final R= 0.0216, R′= 0.0248. These two new macropolyhedral boranes have been further characterized by multielement, multiple resonance, and multidimensional n.m.r. spectroscopy. The metal-to-borane bonding is discussed in terms of the ‘non-conical’ nature of the platinum contribution to the cluster bonding schemes.

Ten-vertex metallaborane clusters: action as a B-frame support for heterobimetallic species: [7,7-(PMe3)2-9,9,9-H(PPh3)(Ph2P-ortho-] and related compounds

Abstract Reaction of the nido ten-vertex iridaborane [ sym -6,6,6-H(PPh 3 )(PPh 2 - ortho - C 6 H 4 )-nido-6-IrB 9 H 12 -5 ] ( 1 ) or its uncyclized analogue 2 with KH followed by cis -[PtCl 2 (PMe 3 ) 2 ] yields the orange-red air-stable complex [7,7- (PMe 3 ) 2 -9,9,9-H(PPh 3 )(Ph 2 P- ortho - C 6 H 4 )-nido-7,9-PtIrB 9 H 10 -4 ] ( 3 ) or the corresponding acyclic analogue ( 4 ). Compound 3 has been characterized by multi-element NMR spectroscopy and by X-ray crystallography. It crystallizes in the monoclinic space group C2/c with a = 4072.1(8), b = 1509.2(4), c = 1912.9(4) pm, β = 110.63(2)°, Z = 8, and the structure ( R = 0.047 from 5641 reflections) is that of an eleven-vertex nido -dimetallaundecaborane with non-adjacent metal atoms in its open face, and has similarities to the structures of related nido -mono- metallaundecaboranes. During the course of the reaction the starting compounds 1 and 2 are shown to undergo a cluster rearrangement that may also play a role in many hitherto ostensibly disparate ten-vertex cluster reactions.

The reactions of arachno-decaboranyl complexes L2B10H12(L = two-electron donor ligand) with some platinum(II) compounds; nuclear magnetic resonance studies and the crystal and molecular structure of [8-Cl-7,7-(PMe2Ph)2-nido-7-PtB10H11]

The reactions of arachno-6,9-(SMe2)2B10H12 and of arachno-6,9-(MeCN)2B10H12 with the complex cis-[PtCl2(PMe2Ph)2] give moderate yields of the nido-platinaundecaborane [8-Cl-7,7-(PMe2Ph)2-7-PtB10H11] which has been characterised by single-crystal X-ray diffraction analysis. Analogous reactions with the dimeric species [{PtCl2(PR3)}2](R3= Me3–nPhn, n= 0, 1, or 2), by contrast, give the nido-platinaundecaboranes [7-Cl-7-(PR3)-8-(SMe2)-7-PtB10H11] which have been characterized by single- and multiple-resonance n.m.r. spectroscopy. Additional products of the reactions include the arachno nine-vertex species 4-(MeCN)B9H13 and 4-(SMe2)B9H13.

Two unusual closo-type ruthenaboranes: preparation, molecular structure, and nuclear magnetic resonance properties of [1,1,1 -(PPh3)HCl-1-RuB9H7-3,5-(PPh3)2] and [1,1 -(PPh3)2-1 -RuB10H8-2,5-(OEt)2]

Reaction of arachno-[B9H14]–- with [RuCl2(PPh3)3] under mild conditions gives the orange 10 vertex ruthenadecaborane [1,1,1-(PPh3)HCl-1-RuB9H7-3,5-(PPh3)2] in ca. 40% yield. The molecular structure is based on an ‘isocloso’C3v 1 : 3 : 3: 3 RuB9 stack with the nine-co-ordinate metal occupying the unique six-connected apical position. The electronic structure may be interpreted either on the basis of a ‘PSEPT-deficient’ 2n-electron cluster with the metal having a straightforward ‘conical’ three-orbital contribution, or as a ‘PSEPT-precise’(2n+ 2)-electron cluster with the metal having a four-orbital involvement, also conical, with the cluster. Similar bonding considerations apply to the red 11-vertex ruthenaundecaborane [1,1-(PPh3)2-1-RuB10H8-2,5-(OEt)2] which is obtained in a yield of 80% from the reaction of [RuCl2(PPh3)3] with closo-[B10H10]2– in refluxing ethanolic chloroform. The molecular structure is based on that of a closo-type C2v 1 : 2 : 4 : 2 : 2 RuB10 stack again with the metal occupying the unique six-connected apical position. Both compounds can be considered as having ‘isocloso’ structures derived from the complete capping of the open face of an arachno geometry to give a completely closed deltahedral cluster.

A novel exo-bicyclic closo-six-vertex dimetalla-hexaborane : [1,1,2-(CO)3-1-(PPh3)-2,2-(Ph2PC6H4)2-close-(1,2-Ir2B4H2-3,5-)]. CH2Cl2

The molecular structure of the novel compound [1,1,2-(CO)3-1-(PPh3)-2,2-(Ph2P-ortho-[graphic omitted]4H2)], isolated as an advanced degradation product from the reaction of closoB-10H102– with trans-[Ir(CO)Cl(PPh3)2] in methanolic solution, is based on a closed {Ir2B4} octahedral cluster with the metal atoms occupying adjacent vertices.