Mark Bown

Eleven-vertex polyhedral metalladicarbaborane chemistry. Reactions of neutral nido-5,6-C2B8H12 and the [nido-6,9-C2B8H10]2− anion to give formally closo isomeric 1-(arene) and 1-(cyclopentadiene)-1,2,4- and 1,2,3-metalladicarbaundecaboranes, and some substituent chemistry. Chiral separations, and crystal and molecular structures of [5-Br-1-(η6-C6Me6)-1,2,4-RuC2B8H9] and [2-Me-1-(η5-C5Me5)-1,2,3-RhC2B8H9]

Abstract Reactions between nido -5,6-C 2 B 8 H 12 ( 1 ) and the organometallic halides [{MLCl 2 } 2 ] ( 2 ) [where {ML}={Ru(η 6 -C 6 Me 6 )} ( 2a ), {Ru(η 6 - p -MeC 6 H 4 i Pr)} ( 2b ), {Rh(η 5 -C 5 Me 5 )} ( 2c ), and {Os(η 6 - p -MeC 6 H 4 i Pr)} ( 2d )] in the presence of N , N , N ′, N ′-tetramethylnaphthalene-1,8-diamine (tmnda) in dichloromethane or chloroform have generated a series of the corresponding metalladicarbaboranes [1-L-1,2,4-MC 2 B 8 H 10 ] ( 3 , closo 11-vertex numbering system) [where {ML}={Ru(η 6 -C 6 Me 6 )} ( 3a ), {Ru(η 6 - p -MeC 6 H 4 i Pr)} ( 3b ), {Rh(η 5 -C 5 Me 5 )} ( 3c ), and {Os(η 6 - p -MeC 6 H 4 i Pr)} ( 3d )] in yields of 48–94%. The substituted species, [5-Br-1-(η 6 -C 6 Me 6 )-1,2,4-RuC 2 B 8 H 9 ] ( 5-Br-3a ) and [ 7-Br-1 -(η 6 -C 6 Me 6 )-1,2,4-RuC 2 B 8 H 9 ] ( 7-Br-3a ) have been obtained from a similar reaction involving [7-Br- nido -5,6-C 2 B 8 H 11 ] ( 7-Br-1 ) (combined yield 75%, separated by preparative HPLC). Each of the compounds 5-Br-3a and 7-Br-3a has been resolved into its enantiomers by use of chiral HPLC separation techniques. Analogous reactions between [{MLCl 2 } 2 ] ( 2 ) and the [ nido -6,9-C 2 B 8 H 10 ] 2− anion (species 4 2− ) have produced a series of the isomeric symmetrical complexes [1-L- closo -1,2,3-MC 2 B 8 H 10 ] ( 5 ) [where {ML}={Ru(η 6 -C 6 Me 6 )} ( 5a ), {Ru(η 6 - p -MeC 6 H 4 i Pr)} ( 5b ), {Rh(η 5 -C 5 Me 5 )} ( 5c ) and {Os(η 6 - p -MeC 6 H 4 i Pr)} ( 5d )]; the 2-methyl substituted compound [2-Me-1-(η 5 -C 5 Me 5 )- closo -1,2,3-RhC 2 B 8 H 9 ] ( 2-Me-5c ) has been prepared similarly using the [6-Me- nido -C 2 B 8 H 9 ] 2− anion (species 2-Me-4 2− ) as the starting dicarbaborane. All these compounds are characterised by mass spectrometry and 11 B- and 1 H-NMR spectroscopy. Single-crystal X-ray diffraction studies have been carried out on compounds 5-Br-3a and 2-Me-5c as two representative examples of the compounds in series 3 and in series 5 . The {MC 2 B 8 } clusters of compounds 3 have four-membered open faces, generating an ‘ isonido ’ geometry, whereas those of compounds 5 approximate more to the classical closo cluster geometry. Thermolyses of the {1,2,4-MC 2 B 8 } compounds 3a – 3d cleanly generate their corresponding {1,2,3-MC 2 B 8 } isomers 5a – 5d .

Organo-ruthenaborane and -osmaborane cluster compounds: preparation and NMR studies of [6-(η6-C6Me6)-nido-6-MB9H13] (M = Ru, Os) and the rearranged cluster [5-(η6-C6Me6)-nido-5-RuB9H11-7-(PMe2Ph)]

Abstract Reaction of the versatile organometallaborane synthon [(η 6 -C 6 Me 6 )RuCl 2 ] 2 with arachno -[B 9 H 14 ] − affords [6-(η 6 -C 6 Me 6 )- nido -6-RuB 9 H 13 ] in 80% yield. An analogous reaction with [(η 6 -C 6 Me 6 )OsCl 2 ] 2 (here reported for the first time) gives [6-(η 6 -C 6 Me 6 )- nido -6-OsB 9 H 13 ] in 13% yield. Treatment of the nido -6-ruthenadecaborane cluster with tertiary phosphines results in rearrangement and formation of [5-(η 6 -C 6 Me 6 )- nido -5-RuB 9 H 11 -7-PR 3 ] (77% yield for PR 3  PMe 2 Ph; 54% yield for PPh 3 ). The metallaborane products are all yellow or orange-yellow air-stable crystalline compounds which have been characterized by elemental analysis, mass spectrometry, and multi-element, multiple resonance, and 2D NMR spectroscopy.

Hexamethylbenzene-ruthenaborane and -osmaborane chemistry

Abstract An extensive suite of polyhedral metalloborane structural types is readily synthesizable by the reactions of [η 6 -C 6 Me 6 )RuCl 2 ] 2 with polyhedral borane anions, and preliminary indications are that the osmium analogue [(η 6 -C 6 Me 6 )OsCl 2 ] 2 , prepared by a route analogous to that used for [(η 6 -C 6 Me 6 )RuCl 2 ] 2 , is an equally versatile metallaborane synthon.

Facile pathway-defined fluxional cluster isomerization in ten-vertex closo-2,1,6-metalladicarbaboranes of ruthenium and rhodium

Multi-element n.m.r. spectroscopy allied with deuterium labelling and single-crystal X-ray diffraction analysis revels fluxionality within [2-(η6-C6Me6)-closo-2,1,6-RuC2B7H9] and [2-(η5-C5Me5)-closo-2,1,6-RhC2B7H9] that results in enantiomeric exchange (between the 2,1,6 and 2,1,9 forms)via defined diamond–square–diamond pathways.

The isolation and characterisation of the 1- and 2-isomers of nido-[(η6-C6Me6)RuB9H13]—but is the 1-isomer nido or arachno?

Reaction between [(η6-C6Me6)RuCl2]2 and K[B6H11] yields a rare example of a 2-metalla nido-decaborane derivative, [2-(η6-C6Me6)-nido-2RuB9H 13], together with an unprecedented 1-ruthena isomer having the same empirical formula but a more open arachno-type structure.

Organoruthenaborane chemistry. Part 5. Products of the reaction between closo-[B10H10]2– and [(η6-C6Me6)ClRuB3H8]. Nuclear magnetic resonance studies and the crystal and molecular structure of [{(η6-C6Me6)2Ru2H4}RuB10H8(OEt)2]

Reaction of [{Ru(η6-C6Me6)Cl2}2] with Tl[B3H8] gives the yellow arachno four-vertex species [2-(η6-C6Me6)-2-Cl-2-RuB3H8](1) in a yield of 66%. Treatment of this with closo-[B10H10]2– in refluxing ethanol results in the formation of yellow [1-(η6-C6Me6)-isocloso-1-RuB9H8-2-(OEt)](2, ca. 2% yield), yellow [1-(η6-C6Me6)-isocloso-1-RuB10H9-2-(OEt)](3, ca. 5% yield), and the novel dark red triruthenium–decaboron double-cluster compound [1-{(η6-C6Me6)2Ru2H4}-isocloso-1-RuB10H8-2,3-(OEt)2](4, 32% yield). Compounds (1)–(4) are reasonably air-stable and are characterised by n.m.r. spectroscopy. A single-crystal X-ray diffraction analysis of compound (4) showed that the crystals were monoclinic, space group P21/c, with a= 1 081.7(1), b= 1 622.6(3), c= 2 120.4(3) pm, β= 102.07(1)°, and Z= 4. The (η6-C6Me6)2Ru3H4 sub-cluster of compound (4) exhibits novel features.

Quantitative thermal rearrangement of an eleven-vertex metalladicarbaborane to give the isomeric cluster nido-[2-(η6-C6Me6)-8,10-Me2-2,8,10-OsC2B8H8] with an unexpected BCBCB open face

The molecular structure of the title compound exhibits a five-membered [graphic omitted] open face and is thereby fundamentally different from the closo-nature previously assumed and generally accepted for this type of polyhedral metalladicarbaborane cluster compound.

Preparation, structure, and nuclear magnetic resonance properties of the nine-vertex nido-rhenaborane [(PMe2Ph)3H2ReB8H11] and some related chemistry

Thermolysis of [6,6,6-(PMe2Ph)3-6-H-nido-6-ReB9H12-9-(OEt)](1) in C2D2Cl4 solution gives the new, pale yellow air-stable compound [2,2,2-(PMe2Ph)3-2,2-H2-nido-2-ReB8H11](2) in 80% yield. Crystals of the CH2Cl2 hemisolvate of (2) are monoclinic, space group P21/c, with a= 1 130.0(3), b= 1 292.2(3), c= 2 424.0(5) pm, β= 94.15(2)°, and Z= 4; the molecular structure was refined to R= 0.0399, R′= 0.0454. The detailed n.m.r. behaviour of compound (2) together with data for previously reported rhodium and iridium analogues permits the location of the substituent site on previously unconfirmed [2-(CO)-2,2-(PMe3)2-nido-2-IrB8H10-3-Cl] and thence provides information on mechanistic pathways for the formation of these and related metallaboranes. Detailed n.m.r. data for the non-metalla analogues [B9H12]– and previously unassigned [3-ClB9H11]– provide information on their mechanism of formation and a comparison with the metallaborane analogues. The n.m.r. work includes extensive use of [11B–11B]-COSY and [1H–1H]-COSY experiments and establishes general points.

A novel eleven-vertex closo-type azametallaborane: [1-(η6-MeC6H4-4-Pri)-closo-1,2-RuNB9H10]

Reaction between nido-6-NB9H12 and [(η6-MeC6H4-4-Pri)RuCl2]2 in tetrahydrofuran yields a variety of azaruthenaboranes of which one is the novel closo-type eleven-vertex species [1-(η6-MeC6H4-4-Pri)-closo-1,2-RuNB9H10].

A double cluster of ruthenium and boron; [1-η2-{(η6-C6Me6)2Ru2H4}-isocloso-1-RuB10H8-2,3-(OEt)2]

The novel double cluster compound [{(η6-C6Me6)2Ru2H4}RuB10H8(OEt)2], obtained in 31% yield as an unexpected product from the reaction between the mononuclear ruthenium complex arachno-[(η6-C6Me6)ClRuB3H8] and closo-[B10H10]2– in ethanol, exhibits a unique (non-carbonyl containing) triangular {Ru3} cluster and a closo-type eleven-vertex {RuB10} cluster conjoined at a common Ru atom.