<i>trans</i>-Bromocarbonylbis(triphenylphosphine)rhodium

Steyl, Gideon; Kirsten, Leo; Muller, Alfred; Roodt, Andreas

doi:10.1107/s1600536806014619

Cited by 2 publications

(2 citation statements)

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“…The Rh−Br and Rh−S distances in molecules A and B of 2 are also notably different; Rh−Br is 2.4519(11) Å in molecule A and 2.5161(11) Å in molecule B, while Rh−S is 2.380(2) Å in molecule A and 2.304(2) Å in molecule B. The shorter Rh−Br distance in molecule A is similar to those in closely related [RhBr(CO)(PPh 3 ) 2 ] (2.453 Å) and [ n Bu 4 N][RhBr(NBD)( i Pr 2 P(C 6 H 4 )BPh 3 - p )] (NBD = norbornadiene) (2.465 Å) . However, Rh−Br in molecule B is more comparable with that in [RhBr(CO)(Me 2 carbox)] [Me 2 carbox = 1-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)-3-mesitylimidazol-2-ylidene] (2.507 Å) in which the bromo ligand experiences the high trans -influence of an N -heterocyclic carbene.…”

Section: Resultsmentioning

confidence: 62%

Diversity of Metal−Ligand Interactions in Halide (X = I, Br, Cl, F) and Halide-Free Ambiphilic Ligand Rhodium Complexes

Cowie¹,

Emslie²,

Jenkins

et al. 2010

Inorg. Chem.

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Reaction of the neutral ambiphilic ligand 2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene (TXPB) with [{Rh(mu-Cl)(CO)(2)}(2)] yields [RhCl(CO)(TXPB)] (1) (Emslie et al. Organometallics 2006, 25, 5835). Complex 1 is square planar with the TXPB ligand bound to rhodium via the phosphine and thioether donors (these are features common to complexes 2-5, vide infra). Treatment of 1 with Me(3)SiBr and Me(3)SiI allowed for halide substitution to afford [RhBr(CO)(TXPB)] (2) and [RhI(CO)(TXPB)] (3), respectively. The halide co-ligands in complexes 1 and 2 form a strong bridging interaction between rhodium and the borane group in TXPB. The presence of stronger borane-halide coordination in 1 is clearly illustrated by an (11)B NMR chemical shift of 12 ppm versus 27 ppm in 2. In contrast, the iodide ligand in 3 forms only a weak bridging interaction to boron, leading to a B...I distance of 3.125(7) A, and an (11)B NMR chemical shift of 56 ppm (versus 69 ppm for free TXPB). A lower carbonyl stretching frequency in 3 (2002 cm(-1)) versus 1 or 2 (2008 and 2013 cm(-1), respectively) could be attributed to weakening of the Rh-X bond in 1 and 2 as a consequence of halide-borane coordination and/or a shorter Rh-S bond in complex 3. [Rh(CO)(TXPB-F)] (4) and the halide-free cation [Rh(CO)(TXPB)][PF(6)] (5) were accessed by reaction of 1 with [NMe(4)]F and Tl[PF(6)], respectively. Complex 4 is zwitterionic with fluoride bound to boron [(11)B NMR delta 4 ppm; B-F = 1.445(6) A; Rh...F = 3.261(3) A] and an eta(2)-interaction between the cationic rhodium center and the ipso- and ortho-carbon atoms of a B-phenyl ring in TXPB-F. By contrast, rhodium in 5 engages in an eta(2)-interaction with boron and the ipso-carbon of one B-phenyl ring; Rh-B and Rh-C(ipso) bond lengths in 5 are 2.557(3) and 2.362(2) A, respectively. The long Rh-B distance and an (11)B NMR chemical shift of 57 ppm are consistent with only a weak Rh-B interaction in 5, and a CO stretching frequency of 2028 cm(-1) (Nujol), versus 2004-2013 cm(-1) for complexes 1-4, is indicative of greatly reduced electron density in 5, relative to 1-4.

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Section: Resultsmentioning

confidence: 62%

Diversity of Metal−Ligand Interactions in Halide (X = I, Br, Cl, F) and Halide-Free Ambiphilic Ligand Rhodium Complexes

Cowie¹,

Emslie²,

Jenkins

et al. 2010

Inorg. Chem.

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“…Specifically, square-planar ML 2 (CO)X compounds may exhibit disorder between pairs of mutually trans CO and X ligands and this type of disorder can result in an artificial apparent lengthening of the Ir–CO bond that is cis to the NHC ligand. ,, An illustration of the ability of disorder to influence the Ir–CO bond lengths in this system is provided by the fact that there are several derivatives that possess more than one crystallographically independent molecule in the asymmetric unit and, for these structures, the Ir–CO bond lengths for the ligands that are trans to Cl are significantly different. For example, the Ir–CO bond lengths for the carbonyl groups that are cis to the NHC ligand in the two crystallographically independent molecules of (SIPr)Ir(CO) 2 Cl differ considerably, namely 1.855(6) and 1.959(4) Å, whereas those that are trans to the NHC ligand are much more similar, namely 1.872(5) and 1.883(5) Å .…”

Section: Results and Discussionmentioning

confidence: 99%

N-Heterocyclic Carbene Complexes of Nickel, Palladium, and Iridium Derived from Nitron: Synthesis, Structures, and Catalytic Properties

et al. 2021

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The mesoionic compound (1,4-diphenyl-1,2,4-triazol-4-ium-3-yl)phenylazanide, commonly referred to as Nitron, has been employed as a "crypto-NHC" to afford 1,2,4-triazolylidene compounds of nickel, palladium, and iridium. Specifically, Nitron reacts with NiBr 2 , PdCl 2 , and [Ir(COD)Cl] 2 to afford the Nheterocyclic carbene complexes (Nitron NHC ) 2 NiBr 2 , (Nitron NHC ) 2 PdCl 2 , and (Nitron NHC )Ir(COD)Cl, respectively. The lattermost compound reacts with (i) CO to afford the dicarbonyl compound (Nitron NHC )Ir(CO) 2 Cl and (ii) CO, in the presence of PPh 3 , to afford the monocarbonyl compound (Nitron NHC )Ir(PPh 3 )-(CO)Cl. Structural studies on (Nitron NHC )Ir(COD)Cl and (Nitron NHC )Ir(CO) 2 Cl indicate that Nitron NHC has a stronger trans influence than does Cl; furthermore, IR spectroscopic studies on (Nitron NHC )Ir(CO) 2 Cl indicate that Nitron NHC is electronically similar to the structurally related Enders carbene but is less electron donating than imidazol-2-ylidenes with aryl substituents. Significantly, the Nitron NHC ligand affords catalytic systems, as illustrated by the ability of (Nitron NHC )Ir(CO) 2 Cl to effect (i) the dehydrogenation of formic acid, (ii) aldehyde hydrosilylation, (iii) dehydrocoupling of hydrosilanes and alcohols, and (iv) ketone reduction via transfer hydrogenation.

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trans-Bromocarbonylbis(triphenylphosphine)rhodium

Abstract: Key indicatorsSingle-crystal X-ray study T = 100 K Mean (C-C) = 0.002 Å Disorder in main residue R factor = 0.018 wR factor = 0.047 Data-to-parameter ratio = 19.5For details of how these key indicators were automatically derived from the article, see

Cited by 2 publications

References 12 publications

Diversity of Metal−Ligand Interactions in Halide (X = I, Br, Cl, F) and Halide-Free Ambiphilic Ligand Rhodium Complexes

Diversity of Metal−Ligand Interactions in Halide (X = I, Br, Cl, F) and Halide-Free Ambiphilic Ligand Rhodium Complexes

N-Heterocyclic Carbene Complexes of Nickel, Palladium, and Iridium Derived from Nitron: Synthesis, Structures, and Catalytic Properties

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