A SF5 Derivative of Triphenylphosphine as an Electron-Poor Ligand Precursor for Rh and Ir Complexes.

The synthesis of the triarylphosphine, P(p-C6H4SF5)3 containing a SF5 group, has been achieved. The experimental and theoretical studies showed that P(p-C6H4SF5)3 is a weaker σ-donor when compared with other substituted triarylphosphines, which is consistent with the electron-withdrawing effect of the SF5 moiety. The studies also revealed a moderate air stability of the phosphine. The σ-donor capabilities of P(p-C6H4SF5)3 were estimated from the phosphorus-selenium coupling constant in SeP(p-C6H4SF5)3 and by DFT calculations. The behavior of P(p-C6H4SF5)3 as ligand has been investigated by the synthesis of the iridium and rhodium complexes [MCl(COD){P(p-C6H4SF5)3}], [MCl(CO)2{P(p-C6H4SF5)3}2] (M = Ir, Rh), or [Rh(µ-Cl)(COE){P(p-C6H4SF5)3}]2, and the molecular structures of [IrCl(COD){P(p-C6H4SF5)3}] and [Rh(µ-Cl)(COE){P(p-C6H4SF5)3}]2 were determined by single X-ray diffraction. The structures revealed a slightly larger cone angle for P(p-C6H4SF5)3 when compared to other para-substituted triarylphosphines.

Suzuki-Miyaura Cross-Coupling Reactions of Highly Fluorinated Arylboronic Esters: Catalytic Studies and Stoichiometric Model Reactions on the Transmetallation Step.

Fluorinated 4-aryl phenylalanine amino acid derivatives (aryl=2-C5 NF4 , 4-C6 H4 SF5 , 2-C6 H4 SCF3 , C6 F5 ) were obtained in Suzuki-Miyaura cross-coupling reactions of phenylalanine precursors with highly fluorinated aryl boronic acid and esters in the presence of CsF. PdII complexes that possessed phenyl alanine derived ligands, such as trans-[PdBr{4-C6 H4 CH2 CH{NHC(O)CH3 }CO2 Et}(PiPr3 )2 ], were used as catalysts. Stoichiometric model reactions indicate the intermediate generation of the boronate Cs[BF(2-C5 NF4 )(pin)] (pin=pinacolato=O2 C2 Me4 ). The transmetallation step with Cs[BF(4-C6 H4 SF5 )(pin)], [NMe4 ][BF(2-C5 NF4 )(pin)] and/or the fluorido complex trans-[PdF{4-C6 H4 CH2 C{NHC(O)CH3 }(CO2 Et)2 }(PiPr3 )2 ] was investigated. A comparison of the reactions of trans-[PdX{4-C6 H4 CH2 C{NHC(O)CH3 }(CO2 Et)2 }(PiPr3 )2 ] (X=Br, F) with 2-Bpin-C5 NF4 or [NMe4 ][BF(2-C5 NF4 )(pin)] revealed the remarkable high reactivity of the fluorido complex towards 2-BpinC5 NF4 . Low-temperature NMR studies indicated the ionic species trans-[Pd{4-C6 H4 CH2 C{NHC(O)CH3 }(CO2 Et)2 }(PiPr3 )2 ][BF(2-C5 NF4 )(pin)] to be a highly reactive intermediate.

Activation of SF6 at Platinum Complexes: Formation of SF3 Derivatives and Their Application in Deoxyfluorination Reactions.

The activation of SF6 at [Pt(PR3 )2 ] R=Cy, iPr complexes in the presence of PR3 led selectively and in an unprecedented reaction route to the generation of the SF3 complexes trans-[Pt(F)(SF3 )(PR3 )2 ]. These can also be synthesized from SF4 and the SF2 derivative trans-[Pt(F)(SF2 )(PCy3 )2 ][BF4 ] was characterized by X-ray crystallography. trans-[Pt(F)(SF3 )(PR3 )2 ] complexes are useful tools for deoxyfluorination reactions and novel fluorido complexes bearing a SOF ligand are formed. Based on these studies a process for the deoxyfluorination of ketones was developed with SF6 as fluorinating agent.

Hydrodealkoxylation reactions of silyl ligands at platinum: reactivity of SiH3 and SiH2Me complexes.

The platinum(ii) complex [Pt(H)2(dcpe)] (; dcpe = 1,2-bis(dicyclohexylphosphino)ethane) reacts with an excess of the dialkoxymethylsilanes (HSiMe(OR)2; R = Me, Et) to give the bis(silyl) complex [Pt(SiH2Me)2(dcpe)] () and trialkoxymethylsilanes by hydrodealkoxylation reactions. These rearrangements of the silyl ligands involve Si-O bond activations. The exchange of the alkoxy moieties against silicon-bound hydrogen atoms occurs stepwise. The intermediate complexes [Pt(H){SiMe(OEt)2}(dcpe)] (), [Pt{SiMe(OEt)2}2(dcpe)] (), [Pt{SiHMe(OEt)}2(dcpe)] () and [Pt{SiHMe(OMe)}2(dcpe)] () were detected. Treatment of the complex with an excess of dichloromethylsilane yields the bis(silyl) complex [Pt(SiMeCl2)2(dcpe)] (). The hydrido silyl complex [Pt(H)(SiMeCl2)(dcpe)] () was identified as an intermediate. The reactions of the complexes [Pt(SiH3)2(dcpe)] () and [Pt(SiH2Me)2(dcpe)] () with iodomethane lead to a transfer of the SiH3 and SiH2Me ligands. Methylsilane and dimethylsilane, respectively, as well as the platinum diiodo complex [Pt(I)2(dcpe)] () were identified as main products.

Synthesis of a rhodium(i) germyl complex: a useful tool for C-H and C-F bond activation reactions.

The dihydrido germyl complex cis,fac-[Rh(GePh3)(H)2(PEt3)3] (2) was synthesized by an oxidative addition of HGePh3 at [Rh(H)(PEt3)3] (1). Treatment of 2 with neohexene generated the rhodium(i) germyl complex [Rh(GePh3)(PEt3)3] (3). Alternatively, treatment of the methyl complex [Rh(CH3)(PEt3)3] (4) with HGePh3 furnished at room temperature also 3. Low-temperature NMR measurements revealed an initial formation of the oxidative addition product fac-[Rh(GePh3)(H)(CH3)(PEt3)3] (5), which transforms into the intermediate complex [Rh(GePh3)(H)(CH3)(PEt3)2] (6) by dissociation of a triethylphosphine ligand. The reductive elimination of methane and coordination of PEt3 afforded the germyl complex 3. Treatment of 3 with CO gave the biscarbonyl complex [Rh(GePh3)(CO)2(PEt3)2] (7). The molecular structures of the complexes 2, 3 and 7 were determined by X-ray crystallography. The germyl complex 3 reacted with 2,3,5,6-tetrafluoropyridine or pentafluorobenzene to furnish the C-H activation products [Rh(4-C5NF4)(PEt3)3] (8) and [Rh(C6F5)(PEt3)3] (9), respectively. The reaction of 3 with hexafluorobenzene or perfluorotoluene gave selectively the C-F activation products 9 and [Rh(4-C6F4CF3)(PEt3)3] (10). Treatment of 3 with pentafluoropyridine resulted in the formation of the C-F activation products 8 and [Rh(2-C5NF4)(PEt3)3] (11) in a 1 : 10 ratio. The two isomeric activation compounds [Rh{(E)-CF[double bond, length as m-dash]CF(CF3)}(PEt3)3] (12) and [Rh{(Z)-CF[double bond, length as m-dash]CF(CF3)}(PEt3)3] (13) were obtained in a 3 : 1 ratio by reaction of 3 with hexafluoropropene. On exposure to oxygen the highly air sensitive complex 12 reacts to yield the peroxido-bridged dirhodium complex [Rh{(E)-CF[double bond, length as m-dash]CF(CF3)}(µ-κ(1):η(2)-O2)(PEt3)2]2 (14). The molecular structure of 14 was determined by X-ray crystallography.

Reactivity of platinum alkyne complexes towards N-fluorobenzenesulfonimide: formation of platinum compounds bearing a ß-fluorovinyl ligand.

The platinum(0) alkyne complexes [Pt(L)(η(2)-PhC[triple bond, length as m-dash]CPh)] 1-4 were synthesized by reactions of [Pt(cod)2] with diphenylacetylene and a phosphine ligand precursor (1: L = dcpe, 2: L = xantphos, 3: L = κ(2)-(P,N)-iPr2PC3H6NMe2, 4: L = κ(2)-(P,N)-iPr2PC2H4NMe2). Treatment of 1 or 4 with NFSI gave the complexes [Pt(F){N(SO2Ph)2}(dcpe)] (5) and [Pt(PhC[double bond, length as m-dash]CFPh){N(SO2Ph)2}{κ(2)-(P,N)-iPr2PC2H4NMe2}] (8), whereas the reactivity of 2 and 3 towards NFSI led to product mixtures. The compounds [Pt(F){N(SO2Ph)2}(xantphos)] (6a) as well as [Pt(PhC[double bond, length as m-dash]CFPh){N(SO2Ph)2}{κ(2)-(P,N)-iPr2PC2H4NMe2}] (7a) and [Pt(PhC[double bond, length as m-dash]CFPh)(F){κ(2)-(P,N)-iPr2PC2H4NMe2}] (7b) were clearly identified. Ligand exchange reactions at 8 resulted in the formation of the ß-fluorovinyl platinum(ii) complexes [Pt(PhC[double bond, length as m-dash]CFPh){OC(O)CF3}{κ(2)-(P,N)-iPr2PC2H4NMe2}] (9), [Pt(PhC[double bond, length as m-dash]CFPh)(FHF){κ(2)-(P,N)-iPr2PC2H4NMe2}] (10) and [Pt(PhC[double bond, length as m-dash]CFPh)(F){κ(2)-(P,N)-iPr2PC2H4NMe2}] (11). Treatment of 8 with dihydrogen yielded the fluorinated olefin (Z)-(1-fluoroethene-1,2-diyl)dibenzene and [Pt{N(SO2Ph)2}(H){κ(2)-(P,N)-iPr2PC2H4NMe2}] (12).

Remarkable reactivity of a rhodium(I) boryl complex towards CO2 and CS2: isolation of a carbido complex.

The activation of CO2, CS2 as well as of PhNCO at [Rh(Bpin)(PEt3)3] led to C=X bond cleavage and the formation of {RhXBpin} species (X = O, S, N). Treatment of the boryl complex [Rh(Bpin)(PEt3)3] with 0.5 equivalents of CS2 resulted in the fragmentation of CS2 and the formation of the remarkable µ-carbido complex trans-[Rh2(µ-C)(SBpin)2(PEt3)4].

Rhodium-Mediated Oxygenation of Nitriles with Dioxygen: Isolation of Rhodium Derivatives of Peroxyimidic Acids.

Dioxygen is used as the oxygenation agent in the rhodium-mediated conversion of nitriles into amides. The characterization of intermediate species and model compounds as well as isotope-labeling studies provided an insight into the reaction mechanism. The conversions of rhodium hydroperoxido or methylperoxido complexes with nitriles into metallacyclic rhodium-κ(2)-(N,O)-peroxyimidate compounds represent essential key steps. The former are accessible from a rhodium(III) peroxido complex and the latter represent rhodium derivatives of Payne's reagent (peroxyimidic acids).

Synthesis and structure of rhodium(i) silyl carbonyl complexes: photochemical C-F and C-H bond activation of fluorinated aromatic compounds.

The rhodium(i) silyl carbonyl complexes [Rh{Si(OEt)3}(CO)(dippp)] () and [Rh{Si(OEt)3}(CO)(dippe)] () (dippp = 1,3-bis(diisopropylphosphino)propane, dippe = 1,2-bis-(diisopropylphosphino)ethane) were synthesized on treatment of the methyl compounds [Rh(CH3)(CO)(dippp)] () or [Rh(CH3)(CO)(dippe)] () with HSi(OEt)3 at low temperature. The methyl complexes and were prepared starting from the binuclear complexes [{Rh(µ-Cl)(dippp)}2] () and [{Rh(µ-Cl)(dippe)}2] (), respectively. The silyl complexes and as well as the precursors [{Rh(µ-I)(dippp)}2] (), [Rh(X)(CO)(dippp)] (: X = CH3, : X = I) and [Rh(X)(CO)(dippe)] (: X = CH3, : X = Cl) were characterized by NMR and IR spectroscopy and the structures in the solid state were determined by X-ray crystallography. The silyl complex converts into the carbonyl-bridged complex [{Rh(µ-CO)(dippp)}2] () above temperatures of -30 °C by loss of the silyl ligand, whereas is more thermally stable and a reaction to the binuclear complex [{Rh(µ-CO)(dippe)}2] () was observed at 50 °C. The silyl complex reacted under irradiation with hexafluorobenzene and pentafluoropyridine to give the C-F activation products [Rh(C6F5)(CO)(dippe)] () and [Rh(2-C5F4N)(CO)(dippe)] (), respectively. As additional products the silyl dicarbonyl complex [Rh{Si(OEt)3}(CO)2(dippe)] () and the cationic complex [Rh2(µ-H)(µ-CO)2(dippe)2](+)[SiF5](-) () were identified. Compound was synthesized independently by treatment of with gaseous CO. In a similar manner, the dippp analogue [Rh{Si(OEt)3}(CO)2(dippp)] () was also prepared starting from . Photochemical reaction of with pentafluorobenzene and 2,3,5,6-tetrafluoropyridine resulted selectively in C-H bond activation to afford and [Rh(4-C5F4N)(CO)(dippe)] (), respectively.