Reactions of bis(ditertiaryphosphine) complexes of rhodium(I) with carbon monoxide, dioxygen, dihydrogen, and hydrogen chloride

Abstract

BRIAN R. JAMES and DEVINDEK MAHAJAN. Can. J. Chem. 58,996 (1980). The products, resulting from addition under mild conditions of the gaseous molecules CO, 0,. H,, and HCI, to some rhodium(1)-bis(ditertiaryph0sphine) complexes, are described; the P? phosphines used were Ph,P(CH,),,PPh,, n = 1-4, and (+)-diop (diop = 2,3-0-isopropylidene 2.3-dihydroxy-l,4-bis(diphenylphosphino)butane). Monocarbonyls were isolated from addition of C O to Rh(PT),+BF,-complexes (n = 1 and 3), the reactions being reversible; there was no reaction with the n = 2 system, while t h e n = 4and diop systems absorbed > 1 mol of CO per Rh to give mixtures ofproducts. The same cation precursors add 0, to yield cis-Rh(P P),O,+BF,-adducts (n = 1-3), the binding being reversible for the rr = 2 system; pure products were not isolated with the rr = 4 cation which absorbs 3 mol O,/Rh; the diop system was unreactive toward 02. Reversible additions of 1 mol H2 yield isolable cis-H,Rh(P>),+BF,-complexes with the n = 3 and diop systems; the n = 1 and 2 R~(P-P),+ cations are unreactive toward H,, while a mixture of hydrides is formed from the n = 4 species. The chlorohydrido cations-HRh(P-P),CI+A-(A = CI, BF,, PF,, SbF,), n = 1-3, were prepared via routes involvingaddition ofgaseous HCI to precursor Rh(P P),CI complexes; however, the reactions with the tz = 4 and diop systems did not yield pure products.The solution structures of all the isolated five-and six-coordinate addition products have been determined using ' H and variable temperature "P nmr. The five-coordinate carbonyl with n = 1 shows equivalent phosphines from -50 to 2S°C, while the n = 3 system shows inequivalent phosphines resulting from a trigonal bipyramidal structure with an equatorial carbonyl. The HR~(P-P),CI+ cation, tz = 3, has cis geometry, while trans-structures are preferred for the rz = 1 and 2 species. BRIAN R. JAMES et DEVINDER MAHAJAN. Can. J. Chem. 58,996(1980). On dkcrit les produits resultant de I'addition, dans des conditions douces, de molecules de CO, 0,. H, et HCI a I'etat gazeux sur quelques complexes de rhodium(]) bis(ditertiaryphosphines). On a utilise les phosphines P> suivantes: Ph2P(CH2), PPh,, n = 1-4 et (+)-diop (diop = 0-isopropylidene-2.3 dihydroxy-2,3 bis(diphenylphosphino)-1,4 butane). On a isole des produits monocarbonylks resultant de I'addition reversible de C O sur les complexes R~(P-P),+BF,-(rl = 1 et 3). On n'obtient pas de reaction avec le systkme n = 2 tandis que dans les systemes oh n = 4 et ou le groupe diop absorb6 est > 1 mol de CO/Rh, on obtient un melange de produits. Les mcmes precurseurs cationiques additionnent de I'oxygene pour conduire a I'adduit R~( P~) , o , + B F , -cis (rz = 1-3); le mode de liaison est riversible dans le cas du systeme n = 2. On n'a pas isole de produits purs dans le cas du cation n = 4 qui absorbe 3 mol de_O,/Rh. L e systeme diop ne reagit pas avec I'oxygene. Les additions reversible~de 1 mol de H, donnent les complexes H,Rh(P P)2+BF4-cis que I'on peut isoler avec n = 3 et le systeme diop. Les cations Rh(P P),+ ou n...

PHOTOCHEMISTRY OF trans‐[Rh(BIS(DIPHENYLPHOSPHINO)ETHANE)2X2][PF6]: TRANSIENT ABSORBANCE KINETIC STUDIES OF METAL‐HALOGEN BOND HOMOLYSIS

“…The product of the photochemical reaction of 1 in acetonitrile also exhibits a simple rhodium split doublet in its 31P-NMR at 51.76 ppm (JRh-p = 94.3 Hz), indicating a symmetric structure. The 31P-NMR data for the photoproduct correspond to the reported 31P-NMR data for the rhodium hydride complex, [HRh(d~pe)~Brl[PF~] (James and Mahajan, 1980). This assignment is further supported by 'H-NMR and mass spectral results.…”

“…The 31P-NMR of 2 consists of a rhodium split doublet at 16.83 ppm (JP-Rh = 83.1 Hz). The 31P-NMR of the photoproduct of 2 in CH2C12 shows a doublet peak at 50.97 ppm (JP-Rh) = 93.6 Hz) and agrees well with the authentic hydride, [HRh(dppe)21][PF6], prepared by literature methods (James and Mahajan. 1980).…”

Rhodium(I) complexes containing a bulky pyridinyl N-heterocyclic carbene ligand: Preparation and reactivity

“…Thus reaction of 7 with two equimolar amount of bisphosphine gave [(bisphosphine) 2 Rh] + species (Scheme 5). The resulting bisphosphine complexes was subsequently oxidized with molecular oxygen to form [Rh(bisphosphine) 2 (O 2 )] + species [18,19]. …”

Recent Developments in Catalytic Asymmetric Hydrogenation Employing P‐Chirogenic Diphosphine Ligands

“…The structures of dihydride complexes of general formula [RhH 2 (Ph 2 P(CH 2 ) n PPh 2 ) 2 ] X À (n > 3) containing six-or seven-membered chelate rings are isolable, [56,115,116] and it has been suggested that partial ligand dissociation occurred in the dihydride [RhH 2 (DIOP) 2 ]BF 4 to free a coordinating site in the metal coordination sphere. [56] Because previously reported trials failed to produce any significant conclusions on the smaller corresponding ring chelates (n 1, 2), we undertook meticulous NMR and computational studies to understand the mechanism of rhodiumcatalyzed hydrogenation employing MiniPHOS.…”

“…Data suggested that the two hydrogen atoms bind to the metal in a cisfashion (cis-dihydride chelate 105) and that only one of the two possible diastereomers is produced (Scheme 27). [117] The relative stability of 105, as opposed to the failure in detecting other ring chelates of similar size, [56,115,116] can be attributed to the electron-rich character of this ligand, increasing the affinity of 51 to H 2 . [107,118] Intensive theoretical calculations carried out on the optimized geometries of the Rh-diphosphine complex suggested that the steric strain imposed by double close contacts of the bulky t-butyl groups in 105b is higher that in 105a.…”