Karl Nestor

Polyhedral metallacarbaborane chemistry: preparation, molecular structure, and nuclear magnetic resonance investigation of [3-(η5-C5Me5)-closo-3,1,2-MC2B9H11] (M = Rh or Ir)

Reaction between Cs[nido-7,8-C2B9H11] and [{M(η5-C5Me5)Cl2}2] (M = Rh or Ir) yielded orange-yellow, air-stable crystals of [3-(η5-C5Me5)-closo-3,1,2-RhC2B9H11] [compound (2), 34%] or [3-(η5-C5Me5)-closo-3,1,2-IrC2B9H11] [compound (3), 96%] both of which were characterized by their assigned 11B and 1H n.m.r. spectra and by single-crystal X-ray diffraction analyses. Crystals of (2) were orthorhombic, space group P212121, with a = 1 081.0(2), b = 1 278.2(1), c = 1 278.4(2) pm, and Z = 4; R = 0.0197, R′ = 0.0204 for 1 756 observed reflections [I > 2.0σ(I)]. Crystals of (3) were also orthorhombic, space group P212121, with a = 1 076.3(1), b = 1 282.9(1), c = 1 292.8(2) pm, and Z = 4; R = 0.0286, R′ = 0.0307, for 1 712 observed reflections [I > 2.0σ(I)]. The n.m.r. properties of the C2B9H11 fragments of (2) and (3) are compared with the 11B and hitherto unreported 1H n.m.r. characteristics of the corresponding fragments of [3-(η5-C5H5)-closo-3,1,2-CoC2B9H11] (4), closo-1,2-C2B10H12, nido-7,8-C2B9H13, and [nido-7,8-C2B9H12]−, in order to assess any n.m.r. shielding patterns that might reveal bonding trends. The unique endo/bridging open-face hydrogen atom in [nido-7,8-C2B9H12]− is discussed in the light of its n.m.r. properties.

Steric and metal-centre control of two-, three- and four-orbital carborane-metal interaction in tin and platinum complexes of the {C2B8H9X} ligand, where X H and Ph

Abstract The cluster 11B and 1H NMR properties of the cluster species [1,1-Me2-1,2,3-SnC2B8H10] (compound 1), [1,1-{P(OMe)3}2-1,2,3-PtC2B8H10 (compound 2) and [1,1-{P(OMe)3}2-1,2,3-PtC2B8H9-2-Ph] (compound 3), together with single-crystal X-ray diffraction analyses of the platinum compounds, show that the metal-to-cluster bonding is substantially different for each of these three species, occurring predominantly via two, three and four orbitals respectively. The differences between compounds 2 and 3 constitute a rare example of a sterically induced change in metal oxidation state.

Polyhedral iridamonocarbaborane chemistry. Two ten-vertex arachno-6,9-iridacarbadecaboranes and some related ten-vertex carbaborane chemistry. Comparative nuclear magnetic resonance studies and the molecular structure of [asym-9-(CO)-9,9-(PPh3)2-9-H-arachno-9,6-IrCB8H12]

Reaction of trans-[IrCl(CO)(PPh3)2] with [NMe4][nido-6-CB9H12] in solution resulted in the formation in low yields of two isomers (sym and asym) of [9-(CO)-9,9-(PPh3)2-9-H-arachno-9,6-IrCB8H12]. These new air-stable yellow compounds differ in the arrangement of the exopolyhedral {(CO)(PPh3)2H} ligand group on the metal atom. Single-crystal X-ray diffraction analysis on the asym isomer confirmed the molecular constitution. Crystals were monoclinic, space group Cc, with a= 1 112.7(2), b= 2 184.7(3), c= 1 553.2(2) pm, β= 94.06(1)°, and Z= 4; 3 265 observed data [I > 2.0σ(I)]; R= 0.0183, R′= 0.0187. The cluster structure is of arachno ten-vertex ‘boat’ configuration, with the {Ir(CO)(PPh3)2} and {CH2 centres occupying the “prow” positions 9 and 6, and with the Ir–H hydrogen atom being endo over the cluster open face. N.m.r. spectroscopy permits assignment of the cluster 11B and 1H parameters and thence comparison with the equivalent parameters of the analogues [B10H14]2–, [6-CB9H14]–, 6,9-C2B8H14, and [5-(η5-C5H5)-5,6,9-CoC2B7H11], in order to assess the comparative effects of replacement of boron by carbon and metal centres in the basic ten-vertex arachno[B10H14]2– cluster type. Preparative details for [arachno-6-CB9H14]– are given.

Heterobimetallic B-frame complexes: novel isonido eleven-vertex rhodairidaboranes with Rh–H–Ir and B–H–B bridges

Reaction between [(η5-C5Me5)RhCl2]2 and [6-(η5-C5Me5)-nido-6-lrB9 H13] in the presence of tetramethylnaphthalenediamine gives the novel isonido eleven-vertex cluster compounds [(η5-C5Me5)2RhHlrB9H10] and [(η5-C5Me5)2RhHlrB9H9Cl] which have quadrilateral open faces with Rh–H–lr and B–H–B bridges.

Polyhedral iridathiaborane chemistry. Reactions of nido-6-SB9H11 and of [arachno-6-SB9H12]– with [{Ir(η5-C5Me5)Cl2}2] to give nido-8,7-iridathiaundecarboranes. A nuclear magnetic resonance and structural study

The reaction of [{Ir(η5-C5Me5)Cl2}2] with nido-6-SB9H11 and a non-nucleophilic base yields [8-(η5-C5Me5)-nido-8,7-IrSB9H11]1, whereas with the [arachno-6-SB9H12]– anion it yields [8-(η5-C5Me5)-9-Cl-nido-8,7-IrSB9H10]2, [8-(η5-C5Me5)-10-Cl-nido-8,7-IrSB9H10]3 and [1-(η5-C5Me5)-closo-1,2-IrSB9H9]4. With [Ir(CO)Cl(PPh3)2], Cs[B9H12] yields a compound formulated as [exo-9-{Cl-trans-(PPh3)2-cis-H2Ir}-arachno-6-SB9H11] which, on thermolysis, yields 9-(PPh3)-arachno-6-SB9H11. The crystal and molecular structures of Cs[arachno-6-SB9H12] and compound 2 have been established by single-crystal X-ray diffraction analysis, and all the iridathiaboranes have been examined in detail by 1H and 11B single and multiple magnetic resonance spectroscopy.

Eleven-vertex polyhedral stannadicarbaborane chemistry. ‘naked tin’{closo-1,2,3-SnC2B8}-cluster compounds

Reaction of anhydrous SnCl2 with the nido ten-vertex anions [6,9-C2B8H10]2–, [6-Me-6,9-C2B8H9]2–, [6-Ph-6,9-C2B8H9]2– or [6,9-Me2-6,9-C2B8H8]2– in tetrahydrofuran solution results in the formation of [closo-1,2,3-SnC2B8H10](59%), [2-Me-closo-1,2,3-SnC2B8H9](34%), [2-Ph-closo-1,2,3-SnC2B8H9](21%) or [2,3-Me2-closo-1,2,3-SnC2B8H8](10%) respectively as volatile white solids. Their NMR properties suggest that the compounds are best regarded as true closo species analogous to closo-2,3-C2B9H11.

Polyhedral metallacarbathiaborane chemistry. Designed synthetic routes to nine-vertex mixed diheteromonometallaborane cluster compounds

Abstract The synthesis of nine-vertex metallacarbathiaboranes [5-(η 5 C 5 Me 5 )- arachno -5,4,6-MCSB 6 H 10 ], where M=Rh or Ir, can be engineered either from the ten-vertex substrate [ arachno -6,9-CSB 8 H 12 ] by a site-specific addition of the metal centre that is accompanied by the directed elimination of specified boron cluster vertices, or by the directed successive removal of two boron vertices from [ arachno -6,9-CSB 8 H 12 ], or of one vertex from [ arachno -4,6-CSB 7 H 11 ] prior to the site-specific addition of the metal centre.

Polyhedral organoiridaborane chemistry. The reaction of MeNC with [6-(η5- C5Me5)-nido-6-IrB9H13]. Nuclear magnetic resonance studies and the crystal and molecular structure of [4,4-(η5-C5Me5)(MeNC)-arachno-4-IrB8H12]

The reaction between MeNC and [6-(η5-C5Me5)-nido-6-IrB9H13] results in the formation of two new yellow air-stable arachno metallaboranes, the ten-vertex compound [6-(η5-C5Me5)-6-(endo-MeNC)-arachno-6-IrB9H11-9-(exo-MeNC)], and the nine-vertex compound [4-(η5-C5Me5)-4-(endo- MeNC)-arachno-4-IrB8H12]. Both new species are characterized by multielement and multiple resonance n.m.r. spectroscopy and the nine-vertex species also by single-crystal X-ray diffraction analysis. Crystals were monoclinic, space group P21/n, with a= 1 392.0(2), b= 1 010.6(2), c= 1 480.8(2) pm, β= 113.01(1)°, and Z= 4. The structure refined to R= 0.0210 R′= 0.0212. The endo-type hydrogen atoms on B(6) and B(8) were located and shown to have partial bridging character to B(7).

Comparative metallaborane chemistry: preparation and nuclear magnetic resonance studies of some nido-5-metalladecaboranes of rhodium, iridium, ruthenium, and osmium

The isolation, and characterisation by n.m.r. spectroscopy, of the new ten-vertex nido-metalladecaboranes [5-(η5-C5Me5)-nido-5-RhB9H13], [5-(η5-C5Me5)-nido-5-IrB9H13], [6-(η5-C5Me5)-nido-6-IrB9H13], [5-(η6-C6Me6)-nido-5-RuB9H13], and [5-(η6-C6Me6)-nido-5-OsB9H13] are described. The n.m.r. data of the nido-5-metalladecaboranes, together with those of the previously reported first-row transition element compounds [5-(η5-C5Me5)-nido-5-CoB9H13] and [5-(η6-C6H3Me3-1,3,5)-nido-FeB9H13] permit an examination of n.m.r. shielding trends for this compound type across two columns and down three rows of the periodic Table. Similarities within the periods are more marked than those within the groups. [6-(OH)-5-(η6-C6Me6)-nido-5-OsB9H12] was also tentatively identified during this work.