F. Gordon A. Stone

Hydroboration of carbontungsten triple bonds: Crystal structures of the η3-benzyl complexes (η-C5H5)(CO)2W{/gh3CH[B(C2H5)2]C6H4Me-4} and (η-C5Me5)(CO)2W{η3-CH[B(C2H5)2]C6H4Me-4}

Abstract The Fischer carbyne complexes [(η-C 5 R 5 )(CO) 2 WC( p -totyl)] (R = H ( 1c )) (R = Me ( 2c )) react with H 2 B 2 Et 4 to afford the boryl substituted η 3 -benzyl complexes [(η-C 5 R 5 ) (CO) 2 W(α,1,2-η 3 {α-BEt 2 }( p -methyl)benzyl)] (R = H ( 5b )) (R = Me ( 6b )). On a column of silica, 5b is slowly converted to the η 3 -benzyl complex [η-C 5 H 5 )(CO) 2 W(α, 1,2-η 3 -{( p -methyl)benzyl}] ( 7 ). Complex 5b crystallizes in the monoclinic space group P 2 1 / n with a = 8.930(4), b = 14.490(8), c = 14.022(7) A, β = 98.70° and Z = 4. The structure was refined to R = 0.026 using 2649 unique observed diffractometer data. Complex 6b crystallizes in the monoclinic space group P 2 1 / a with a = 16.124(3), b = 8.728(2), c = 18.190(3) A, β = 114.56(1)° and Z = 4. The structure was refined to R = 0.033 using 2064 unique observed diffractometer data. The gross structures of the two complexes are very similar, with α-BEt 2 -( p - methyl)benzyl ligands bound in an α,1,2-η 3 -enylic fashion to the tungsten atoms. In 6b , one of the ethyl substituents is disordered. In both derivatives there is a weak attractive interaction between the boron atom of the boryl group and the carbon atom of one of the carbonyl ligands. In solution, 5b exists as a mixture of two isomers. Extended Huckel (EH) and Fenske-Hall (FH) self-consistent field (SCF) molecular orbital (MO) calculations were conducted on several model complexes, [(η-C 5 H 5 )(CO) 2 W(α,1,2-η 3 -benzyl)] ( 9 ), [(η-C 5 H 5 )(CO) 2 W{α,1,2-η 3 -( anti -1-BH 2 )allyl}] ( 10 ) and [(η-C 5 H 5 ) (CO) 2 W{α,1,2-η 3 -( anti -α-BH 2 )benzyl}] ( 11 ) as well as on 5b . The bonding of the η 3 - benzyl ligand to the metal was found to be similar in all cases and comparable with [(η-C 5 H 5 )(CO) 2 W(α,1,2- η 3 -allyl)]. Bonding overlap between empty π orbitals on the boryl group and two of the four π* ligand group orbitals of the two CO molecules was found in 5b .

Synthesis, crystal structure and some reactions of the ruthenacarborane complex [Ru(CO)2(MeCCPh)(η5-7,8-C2B9H11],

Abstract The alkyne complex [Ru(CO)2(MeCCPh)(η5-7,8-C2B9H11] (3c) has been prepared and its structure determined by X-ray crystallography. The ruthenium is co-ordinated on one side by the nido-7,8-C2B9H11 fragment in a pentahapto manner, and on the other by the two CO molecules and the alkyne [Ru–Cav.=2.305, C–C=1.228(3) A. Treatment of 3c with PEt3 and Ph2PCH2PPh2 in CH2Cl2 affords the ylid complexes [Ru{C(Me)C(Ph)PEt3}(CO)2(η5-7,8-C2B9H11)] (4b) and [Ru{C(Me)C(Ph)P(Ph)2CH2PPh2}(CO)2(η5-7,8-C2B9H11)] (4c), respectively. The structure of 4b was established by an X-ray diffraction study which revealed that the PEt3 molecule was attached to the carbon atom of the CPh group. In contrast, reactions between 3c and the donor molecules AsPh3, SbPh3 and Ph2P(S)CH2P(S)Ph2 resulted in displacement of the alkyne and formation of the complexes [Ru(CO)2(L)(η5-7,8-C2B9H11)] (5a, L=AsPh3; 5b, L=SbPh3; 5c, L=Ph2P(S)CH2P(S)Ph2). Treatment of 4c with the Ru(CO)2(η5-7,8-C2B9H11) fragment yielded the diruthenium complex [Ru2(μ-Ph2PCH2PPh2)(CO)4(η5-7,8-C2B9H11)2] (6). The structure, based on the linking of two Ru(CO)2(η5-7,8-C2B9H11) groups by the ligand Ph2PCH2PPh2, was determined by X-ray crystallography. NMR data for the new complexes are reported.

Non-spectator behavior of carborane ligands in icosahedral metallacarboranes

Abstract Icosahedral metallacarboranes with closo -3,1,2-MC 2 B 9 frameworks are formally derived by η 5 coordination of the open face of a nido -7,8-C 2 B 9 cage to a metal atom. Recent work has established that the boron vertices of these faces readily form exo -polyhedral bonds of various kinds. These include linkages to other metal-ligand systems via either three-center two-electron BH ⇀ metal of two-center B-metal σ interactions, as well as attachments to organic groups with BC or BO bonds. Many new types of molecular structure have been identified, thereby opening a new domain of metallacarborane chemistry which merits further study.

Fluorocarbon metal compounds—role models in organotransition metal chemistry

Abstract Early studies on organo-transition metal complexes with fluorocarbon ligands are reviewed in a historical context in relation to the renaissance of organometallic chemistry which followed the discovery of ferrocene.

Allyl(carborane) complexes of the group 6 metals : protonation studies with aqueous HI

Abstract Treatment of CH 2 Cl 2 solutions of [N(PPh 3 ) 2 ][ closo -1,2-Me 2 -3-(η 3 -C 3 H 5 )-3,3-(CO) 2 -3,1,2-WC 2 B 9 H 9 ] with aqueous HI in the presence of CO affords [N(PPh 3 ) 2 ][ closo -1,8-Me 2 -2-I-2,2,2-(CO) 3 -2,1,8-WC 2 B 9 H 9 ] in virtually quantitative yield. In contrast, the reaction between [N(PPh) 3 ) 2 ][ closo -1,2-Me 2 -3-(η 3 -C 3 H 5 )-3,3-(CO) 2 -3,1,2-MoC 2 B 9 H 9 ] and aqueous HI gives initially [N(PPh 3 ) 2 ][ closo -1,2-Me 2 -3-I-3,3,3-(CO) 3 -3,1,2-MoC 2 B 9 H 9 ], but the latter undergoes a cage framework rearrangement to afford [N(PPh 3 ) 2 ][ closo -1,8-Me 2 -2-I-2,2,2-(CO) 3 -2,1,8-MoC 2 B 9 H 9 , which is slow at room temperature. Protonation of [NEt 4 ][ closo -1,2-Me 2 -3-(CC 6 H 4 Me-4)-3,3-(CO) 2 -3,1,2-MoC 2 B 9 H 9 ] with aqueous HI yields initially [NEt 4 ][ closo -1,2,-Me 2 -8-(CH 2 C 6 H 4 Me-4)-3-I-3,3,3-(CO) 3 -3,1,2-MoC 2 B 9 H 8 ], which isomerizes at room temperature to give [NEt 4 ][ closo -1,8-Me 2 -11-(CH 2 C 6 H 4 Me-4)-2-I-2,2,2-(CO) 3 -2,1,8-MoC 2 B 9 H 8 ]. The reaction between [N(PPh 3 )2][ closo -1,8-Me 2 -2,I-2,2,2-(CO) 3 -2,1,8-MoC 2 B 9 H 9 ] and [W(CC 6 H 4 Me-4)(CO) 2 (η-C 5 H 5 )] in CH 2 Cl 2 in the presence of TIPF 6 affords mainly [MoW(μ-CC 6 H 4 Me-4)(CO) 3 (η 5 - nido -2,8-Me 2 -2,8-C 2 B 9 H 9 )(η-C 5 H 5 )] together with some of its polytopal isomer [MoW(μ-CC 6 H 4 Me-4)(CO) 3 (η 5 - nido -7,8-Me 2 -7,8-C 2 B 9 H 9 )(η-C 5 H 5 )].

Synthesis of the complexes [N(PPH3)2][M(CO)2(η3-C3H5)-(η6-7, 9-C2B10H10Me2)](M = Mo or W): crystal structure of [N(PPH3)2][WBr(CO) 3(η6-7,9-C2B10H10Me2)]

Abstract Treatment of the compounds [MBr(CO)2(NCMe)2(η3-C3H5)] (M = Mo or W) with Na2[7,9-C2B10H10Me2] in tetrahydrofuran, followed by addition of [N(PPh3) 2]Cl, affords the salts [N(PPh3)2][M(CO)2(η3-C3H5)(η6-7,9-C2 B10H10Me2)]. Reactions of [N(PPh3)2]2[M(CO)3(η6-7,9-C2B10H 10Me2)] with an excess of allyl bromide generate the complexes [N(PPh3)2][MBr(CO)3 (η6-7,9-C2B10H10Me2)] via an allyl-coupling process. The structure of the latter (M = W) has been determined by X-ray diffraction. The preparation of the molybdenum salt [N(PPh3)2] [MoBr(CO)3(η6-7,9-C2B10H10Me2)] by this route was accompanied by the formation of small amounts of the complex [N(PPh3)2][MoBr(CO)3(η5-7,9-C2B9H9Me2)] resulting from ejection of a BH vertex from the cage. Indeed, it was observed that in CH2Cl2 solutions, the former species was slowly converted into the latter at ambient temperatures. Protonation (aqueous HBr) of the salts [N(PPh3)2][M(CO)2(η3-C3H5)(η6-7,9-C2B10H10Me2)] in the presence of an atmosphere of CO also yields the compounds [N(PPh3)2][MBr(CO)3(η6-7,9-C 2B10H10Me2)], but if the molybdenum compound is protonated in the absence of CO the complex [N(PPh3)2][MoBr(CO)3(η5-7,9-C2B9H9Me2)] is formed directly. The NMR data for the new compounds are reported and discussed, as are the possible pathways of their formation.

Nitrosyl-cobalt monocarbollide complexes

Abstract The carborane anion [closo-2-CB10H11]− undergoes a polyhedral expansion reaction with [Co(CO)3(NO)] in tetrahydrofuran (THF) to afford [2-CO-2-NO-closo-2,1-CoCB10H11]−, isolated as the [N(PPh3)2]+ salt 1a. An X-ray diffraction study confirmed that the NO group is linearly bonded to cobalt. The CO ligand in 1a is readily replaced by PPh3 in the presence of Me3NO, or by PEt3 or CNBut directly, to give the species [N(PPh3)2][2-L-2-NO-closo-2,1-CoCB10H11] [L=PPh3 (1b), PEt3 (1c), CNBut (1d)]. Reactions of these anionic complexes with electrophilic reagents are exemplified by treatment of 1c with CF3SO3Me in CH2Cl2–THF to give the neutral, zwitterionic B-THF species [2-NO-2-PEt3-7-O(CH2)4-closo-2,1-CoCB10H10] (3a), and by the reaction of 1b with [CuCl(PPh3)]4 and Tl[PF6] in THF to give bimetallic [2,7,11-{Cu(PPh3)}-7,11-(μ-H)2-2-NO-2-PPh3-closo-2,1-CoCB10H9] (4b). X-ray diffraction analysis of crystals of 4b confirmed the presence of a CoCu bond.

Synthesis and characterization of the first charge-compensated monocarbollide(octacarbonyl) triosmium complex

Abstract The trinuclear osmium complex [Os3(CO)8(η5-7-NMe3-7-CB10H10] (1) has been synthesized by heating [Os3(CO)12] with nido-7-NMe3-7-CB10H12 in bromobenzene. The structure has been established by X-ray diffraction.

Carborane complexes of ruthenium: studies on the chemistry of the Ru(CO) 2 (η 5 -7,8-Me-2-7,8-C 2 B 9 H 9 ) fragment and the X-ray crystal structure of [NEt 4 ][Ru 2 (μ-Tl(CO) 4 (η 5 -7,8-Me-2-7,8-C 2 B 9 H 9 ) 2 ]

Abstract Reactions between Tl[closo-1,2-Me2-3,1,2-TlC2B9H9] and [RuBr(CO)3(η3-C3H5)] in tetrahydrofuran (THF) affords mixtures of the compounds [Ru(CO)3(η5-7,8-Me2-7,8-C2B9H9)] (1b) and Tl[Ru2(μ-Tl)(CO)4(η5-7,8-Me2-7,8-C2B9H9)2] (2a) in a ratio 2:3. Treatment of the mixtures with [NEt4]I followed by I2 produces [NEt4][RuI(CO)2(η5-7,8-Me2-7,8-C2B9H9)] (3b) as the only product. Complex 2a, isolated as the [NEt4]+ salt 2b, was the subject of a single-crystal X-ray diffraction analysis. The compound crystallises in the orthorhombic space group Pbcn [a=23.164(2), b=13.780(2), c=11.560(6) A]. The structure of the anion consists of two Ru(CO)2(η5-7,8-Me2-7,8-C2B9H9) fragments linked together via a thallium atom, with the complex carrying an overall uninegative charge. The synthon [Ru(THF)(CO)2(η5-7,8-Me2-7,8-C2B9H9)] (4b) is readily generated from 3b by the addition of AgBF4 in THF. The same procedure in MeCN produces the complex [Ru(NCMe)(CO)2(η5-7,8-Me2-7,8-C2B9H9)] (4c). The removal of THF from 4b in vacuo gave the 16-electron complex [Ru(CO)2(η5-7,8-Me2-7,8-C2B9H9)] and a polymeric material postulated to be [Ru(CO)2(η5-7,8-Me2-7,8-C2B9H9)]n. Reaction of solutions of 4b in CH2Cl2 with 2-electron donor ligands yields the complexes [Ru(L)(CO)2(η5-7,8-Me2-7,8-C2B9H9)] (4d, L=PPh3; 4e, L=CNBut; 4f, L=NC5H5). Addition of alkenes and alkynes to CH2Cl2 solutions of 4b did not give stable η2-adducts, but the species [Ru(CO)2(η5-7,8-Me2-7,8-C2B9H9)] was observed in these reactions. The complex [Ru(CO)2(η2,η5-7,8-Me2-10-C(H)C(H)SiMe3-7,8-C2B9H9)] (5a) was isolated from the reaction between 4b and Me3SiCCH. The IR and NMR spectra of the new compounds are reported.

Reactions of the molybdenum alkylidyne complex [NEt4][Mo(CC6H4Me-4)(CO)2(η5-C2B9H9Me2)] with trimethylphosphine and with 1,2-bis(diphenylphosphino)ethane; crystal structure of the complex [Mo(CC6H4Me-4)(CO)(dppe){Ph2P(CH2)2PPh2O}][C2B9H10Me2]

Abstract The reaction between the alkylidyne compound [NEt4][Mo(CC6H4Me-4) (CO)2(η5-C2B9H9Me2)] and trimethylphosphine gives the η2-ketenyl complex [NEt4] [Mo{η2-C(C6H4Me-4)C(O)}(CO)(PMe3)(η5-C2B9H9Me2)]. Treatment of [NEt4][Mo(C C6H4Me-4)(CO)2(η5-C2B9H9Me2)] with 1,2-bis(diphenylphosphino)ethane affords the two products [Mo(CC6H4Me-4)(CO)(dppe)2][C2B9H10Me2] and [MO(CC6H4Me-4) (CO)(dppe){Ph2P(CH2)2PPh2O}][C2B9H10Me2]. The molecular structure of the latter has been established by an X-ray diffraction study, which shows that the carborane cage has been cleaved from the metal and is acting as the counter-ion in a protonated form, and one dppe ligand has been converted into a mixed phosphine/phosphine oxide ligand. The 1H, 13C{1H}, 31P{1H} and 11B{1H} NMR spectra of the new compounds are reported and discussed.