[Ir(PPh3)2(H)2(ClCH2CH2Cl)][BArF4]: a well characterised transition metal dichloroethane complex.

Reaction of [Ir(PPh(3))(2)(COD)][BAr(F)(4)] with H(2) in dichloroethane solution results in [Ir(PPh(3))(2)(H)(2)(ClCH(2)CH(2)Cl)][BAr(F)(4)], which has been fully characterised by X-ray crystallography, NMR spectroscopy and ESI-MS. Its activity towards alkene hydrogenation has been compared with analogous CH(2)Cl(2) complexes

catena-poly[[(tetrafluoroborato-kappa F)silver(I)]-mu-triphenylphosphine-kappa P-2 : C-3]

The title compound, [Ag(BF4)(C18H15P)] n, crystallizes from dichloromethane-pentane as a one-dimensional coordination polymer in which the Ag atom is bound to a phosphine P atom, one F atom of tetrafluoroborate and one C atom of a neighbouring triphenylphosphine ligand. © 2007 International Union of Crystallography All rights reserved

Rhodium phosphine olefin complexes of the weakly coordinating anions [BAr4F](-) and [1-closo-CB11H6Br6](-). Kinetic versus thermodynamic factors in anion coordination and complex reactivity

Solution and solid-state structures for the pair of complexes Rh{P(Cyp 2)(η2-C5H7)}{η6- (C6H3(CF3)2)BAr3F} and Rh{P(Cyp2)(η2-C5H 7)}(I-closo-CB11H6Br6), which contain bound weakly coordinating anions, are reported. While thermochemical data show that enthalpically [I-closo-CB11H6Br 6]- binds less strongly with the metal fragment and it is the large entropy loss for the overall process of coordination of the [BAr 4F]- anion that results in the latter anion being thermodynamically more weakly coordinating. Qualitative kinetic data arising from reaction with H2 indicates that the carborane anion is displaced more readily, attributable to the ability of the carborane to lift a Rh-Br interaction. © 2007 American Chemical Society

Reversible addition of water to the high-hydride-content cluster [Rh6(PiPr3)6H12][BArF4]2. Synthesis and Structure of [Rh6PiPr3)6H11(OH)][BArF4]2.

The hydroxyhydrido salt [Rh(6)(P(i)Pr(3))(6)H(11)(OH)][BArF(4)](2) results from the addition of water to [Rh(6)(P(i)Pr(3))(6)H(12)][BArF(4)](2). This reaction is reversible, and the addition of dihydrogen to [Rh(6)(P(i)Pr(3))(6)H(11)(OH)][BArF(4)](2) results in the elimination of water and the regeneration of the hydride cluster

A DFT based investigation into the electronic structure and properties of hydride rich rhodium clusters.

Density functional theory has been used to investigate the structures, bonding and properties of a family of hydride rich late transition metal clusters of the type [Rh(6)(PH(3))(6)H(12)](x) (x = 0, +1, +2, +3 or +4), [Rh(6)(PH(3))(6)H(16)](x) (x = +1 or +2) and [Rh(6)(PH(3))(6)H(14)](x) (x = 0, +1 or +2). The positions of the hydrogen atoms around the pseudo-octahedral Rh(6) core in the optimized structures of [Rh(6)(PH(3))(6)H(12)](x) (x = 0, +1, +2, +3 or +4) varied depending on the overall charge on the cluster. The number of semi-bridging hydrides increased (semi-bridging hydrides have two different Rh-H bond distances) as the charge on the cluster increased and simultaneously the number of perfectly bridging hydrides (equidistant between two Rh centers) decreased. This distortion maximized the bonding between the hydrides and the metal centers and resulted in the stabilization of orbitals related to the 2T(2g) set in a perfectly octahedral cluster. In contrast, the optimized structures of the 16-hydride clusters [Rh(6)(PH(3))(6)H(12)](x) (x = +1 or +2) were similar and both clusters contained an interstitial hydride, along with one terminal hydride, ten bridging hydrides and two coordinated H(2) molecules which were bound to two rhodium centers in an eta(2):eta(1)-fashion. All the hydrides were on the outside of the Rh(6) core in the lowest energy structures of the 14-hydride clusters [Rh(6)(PH(3))(6)H(14)] and [Rh(6)(PH(3))(6)H(14)](+), which both contained eleven bridging hydrides, one terminal hydride and one coordinated H(2) molecule. Unfortunately, the precise structure of [Rh(6)(PH(3))(6)H(14)](2+) could not be determined as structures both with and without an interstitial hydride were of similar energy. The reaction energetics for the uptake and release of two molecule of H(2) by a cycle consisting of [Rh(6)(PH(3))(6)H(12)](2+), [Rh(6)(PH(3))(6)H(16)](2+), [Rh(6)(PH(3))(6)H(14)](+), [Rh(6)(PH(3))(6)H(12)](+) and [Rh(6)(PH(3))(6)H(14)](2+) were modelled, and, in general, good agreement was observed between experimental and theoretical results. The electronic reasons for selected steps in the cycle were investigated. The 12-hydride cluster [Rh(6)(PH(3))(6)H(12)](2+) readily picks up two molecules of H(2) to form [Rh(6)(PH(3))(6)H(16)](2+) because it has a small HOMO-LUMO gap (0.50 eV) and a degenerate pair of LUMO orbitals available for the uptake of four electrons (which are provided by two molecules of H(2)). The reverse process, the spontaneous release of a molecule of H(2) from [Rh(6)(PH(3))(6)H(16)](+) to form [Rh(6)(PH(3))(6)H(14)](+) occurs because the energy gap between the anti-bonding SOMO and the next highest energy occupied orbital in [Rh(6)(PH(3))(6)H(16)](+) is 0.9 eV, whereas in [Rh(6)(PH(3))(6)H(14)](+) the energy gap between the anti-bonding SOMO and the next highest energy occupied orbital is only 0.3 eV. At this stage the factors driving the conversion of [Rh(6)(PH(3))(6)H(14)](+) to [Rh(6)(PH(3))(6)H(12)](2+) are still unclear

[Rh(C7H8)(PPh3)Cl]: an experimental charge-density study.

In order to gain a deeper understanding into the bonding situation in rhodium complexes containing rhodium-carbon interactions, the experimental charge-density analysis for [Rh(C(7)H(8))(PPh(3))Cl] (1) is reported. Accurate, high-resolution (sin theta/lambda = 1.08 A(-1)), single-crystal data were obtained at 100 K. The results from the investigation were interesting in relation to the interactions between the rhodium metal centre and the norbornadiene fragment and illustrate the importance of such analyses in studying bonding in organometallic complexes

Cationic rhodium mono-phosphine fragments partnered with carborane monoanions [closo-CB11H6X6]- (X = H, Br). Synthesis, structures and reactivity with alkenes.

Addition of the new phosphonium carborane salts [HPR(3)][closo-CB(11)H(6)X(6)] (R = (i)Pr, Cy, Cyp; X = H 1a-c, X = Br 2a-c; Cy = C(6)H(11), Cyp = C(5)H(9)) to [Rh(nbd)(mu-OMe)](2) under a H(2) atmosphere gives the complexes Rh(PR(3))H(2)(closo-CB(11)H(12)) 3 (R = (i)Pr 3a, Cy 3b, Cyp 3c) and Rh(PR(3))H(2)(closo-CB(11)H(6)Br(6)) 4 (R = (i)Pr 4a, Cy 4b, Cyp 4c). These complexes have been characterised spectroscopically, and for 4b by single crystal X-ray crystallography. These data show that the {Rh(PR(3))H(2)}(+) fragment is interacting with the lower hemisphere of the [closo-CB(11)H(6)X(6)](-) anion on the NMR timescale, through three Rh-H-B or Rh-Br interactions for complexes 3 and 4 respectively. The metal fragment is fluxional over the lower surface of the cage anion, and mechanisms for this process are discussed. Complexes 3a-c are only stable under an atmosphere of H(2). Removing this, or placing under a vacuum, results in H(2) loss and the formation of the dimer species Rh(2)(PR(3))(2)(closo-CB(11)H(12))(2) 5a (R = (i)Pr), 5b (R = Cy), 5c (R = Cyp). These dimers have been characterised spectroscopically and for 5b by X-ray diffraction. The solid state structure shows a dimer with two closely associated carborane monoanions surrounding a [Rh(2)(PCy(3))(2)](2+) core. One carborane interacts with the metal core through three Rh-H-B bonds, while the other interacts through two Rh-H-B bonds and a direct Rh-B link. The electronic structure of this molecule is best described as having a dative Rh(I) --> Rh(III), d(8)--> d(6), interaction and a formal electron count of 16 and 18 electrons for the two rhodium centres respectively. Addition of H(2) to complexes 5a-c regenerate 3a-c. Addition of alkene (ethene or 1-hexene) to 5a-c or 3a-c results in dehydrogenative borylation, with 1, 2, and 3-B-vinyl substituted cages observed by ESI-MS: [closo-(RHC[double bond, length as m-dash]CH)(x)CB(11)H(12-x)](-)x = 1-3, R = H, C(4)H(9). Addition of H(2) to this mixture converts the B-vinyl groups to B-ethyl; while sequential addition of 4 cycles of ethene (excess) and H(2) to CH(2)Cl(2) solutions of 5a-c results in multiple substitution of the cage (as measured by ESI-MS), with an approximately Gaussian distribution between 3 and 9 substitutions. Compositionally pure material was not obtained. Complexes 4a-c do not lose H(2). Addition of tert-butylethene (tbe) to 4a gives the new complex Rh(P(i)Pr(3))(eta(2)-H(2)C=CH(t)Bu)(closo-CB(11)H(6)Br(6)) 6, characterised spectroscopically and by X-ray diffraction, which show coordination of the alkene ligand and bidentate coordination of the [closo-CB(11)H(6)Br(6)](-) anion. By contrast, addition of tbe to 4b or 4c results in transfer dehydrogenation to give the rhodium complexes Rh{PCy(2)(eta(2)-C(6)H(9))}(closo-CB(11)H(6)Br(6)) 7 and Rh{PCyp(2)(eta(2)-C(5)H(7))}(closo-CB(11)H(6)Br(6)) 9, which contain phosphine-alkene ligands. Complex has been characterised crystallographically

Sequential dehydrogenative borylation/hydrogenation route to polyethyl-substituted, weakly coordinating carborane anions

Treatment of Rh(PPh3)2(1-H-closo-CB 11H11) with ethene results in dehydrogenative borylation to form the vinyl-borate complex Rh(PPh3)2(1-H-7/12- (H2C=CH)-closo-CB10H10) as a mixture of 7- and 12-isomers. Further dehydrogenative borylation does not occur; this is accounted for by the strong binding of the vinylcarborane to the {Rh(PPh 3)2}+ fragment through C=C and B-H interactions. Addition of H2 results in hydrogenation of the vinyl group and the quantitative formation of the B-ethylcarborane complex Rh(PPh 3)2(1-H-7/12-(Et)-closo-CB11H10). The crystal structure of the norbornadiene adduct of one the isomers, [Rh(PPh3)2(nbd)][1-H-12-(H2C=CH)-closo-CB 11H10], has been determined. Addition of ethene to the complex Rh(PPh3)2(1-H-12-Br-closo-CB11H 10), in which the 12-position on the cage is blocked, results in only one isomer: Rh(PPh3)2(1-H-7-(CH2=CH)-12-Br- closo-CB11H9). Sequential addition of ethene/H2 to Rh(PPh3)2(1-H-7/12-(Et)-closo-CB11H 10) results, after six cycles, in the pentaethyl-substituted complex (characterized as the nbd salt) [Rh(PPh3)2(nbd)][1-H-2,4, 8,10,12-(Et)5-closo-CB11H6]. The solid-state structure shows that the antipodal boron vertex, two lower pentagonal, belt vertices, and two upper-belt vertices have been functionalized, with no two adjacent vertices on the same pentagonal belt substituted. The degree of ethylation can be controlled. Replacing the hydrogen on the cage carbon with a bulkier substituent (methyl or SiiPr3) affords products in which only three B-H vertices have been substituted, and the solid-state structure of Rh(PPh3)2(1-Me-7,11,12-(Et) 3-closo-CB11H8) shows that the antipodal boron vertex and two lower pentagonal belt vertices have undergone dehydrogenative borylation. Mechanistic insight into the dehydrogenative borylation comes from addition of D2 to a CH2Cl2 solution of Rh(PPh3)2(closo-CB11H12), which results in H/D exchange of the B-H vertices, suggesting that the metal fragment reversibly inserts into a B-H bond of the cage anion to form a boryl species. Attempts to observe intermediates in the actual hydroboration process by addition of ethene to Rh(PPh3)2(1-H-closo-CB 11H11) resulted in the observation of the tris(ethene) complex [Rh(PPh3)2(η2-C2H 4)3][1-H-closo-CB11H11], which has been characterized crystallographically as the [closo-CB11H 6Br6] salt. © 2007 American Chemical Society