Rhodium(I) carbonyl complexes of ether‐phosphine ligands and their reactivity

The reactions of dimeric complex [Rh(CO)₂Cl]₂ with hemilabile ether‐phosphine ligands Ph₂P(CH₂) _nOR [n = 1, R = CH₃ (a); n = 2, R = C₂H₅ (b)] yield cis‐[Rh(CO)₂Cl(P ～ O)] (1) [P ～ O = η ¹‐(P) coordinated]. Halide abstraction reactions of 1 with AgClO₄ produce cis‐[Rh(CO)₂(P ∩ O)]ClO₄ (2) [P ∩ O = η ²‐(P,O)chelated]. Oxidative addition reactions of 1 with CH₃I and I₂ give rhodium(III) complexes [Rh(CO)(COCH₃)ClI(P ∩ O)] (3) and [Rh(CO)ClI₂(P ∩ O)] (4) respectively. The complexes have been characterized by elemental analyses, IR, ¹H, ¹³C and ³¹P NMR spectroscopy. The catalytic activity of 1 for carbonylation of methanol is higher than that of the well‐known [Rh(CO)₂I₂]^? species. Copyright © 2002 John Wiley & Sons, Ltd.     

Rhodium(I) complexes with bis(pyrazolyl)methane ligands. Crystal structure of [Rh(COD)(CH2(Pz)2)]ClO4·12 C2H4Cl2

The synthesis and properties of neutral and cationic complexes of general formulae [{RhCl(diolefin)}₂(CH₂(pz)₂)], [Rh(CO)₂ (CH₂(pz)₂)][RhCl₂(CO)₂], (Rh(diolefin)(CH₂(pz)₂)]ClO₂, [{Rh(diolefin)(PPh₃)}₂(CH₂(pz)₂)](ClO₄)₂, [Rh(CO)₂(CH₂(pz)₂)]ClO₄ and [Rh(CO)(CH₂(pz)₂)(PPh₃)]ClO₄ are described. The NMR spectra of [Rh(COD)(CH₂(pz)₂)]ClO₄ complexes are discussed. X-ray structural analysis of [Rh(COD)(CH₂(Pz)₂)]ClO₄ · $\text{1}\text{2}$C₂H₄Cl₂ is presented; the final R factor is 0.061 for 2436 observed data, recorded with Cu-K_α, not corrected for absorption and with the sample inside a capillary. The Rh atom presents a distorted square planar coordination in a mononuclear arrangement. The COD ring has a twisted boat conformation, and the two halves of the CH₂(Pz)₂ moiety, which are quite similar to one another, form an angle of 47.2(4)°.     

Rhodium(I) diolefin complexes with polycyclic π-arene ligands. Synthesis of bimetallic complexes with diphenylmethane as bridging ligand

Summary The preparation and properties of cationic arenerhodium(I) complexes of general formula [Rh(diolefin)(⁶arene)]ClO₄ (diolefin=1,5-cyclooctadiene, tetrafluorobenzobarrelene or trimethyltetrafluorobenzobarrelene; arene = biphenyl or diphenylmethane) are described. These complexes react with the solvated intermediate complex [Rh(diolefin)(Me₂CO)_x]ClO₄ to give homobimetallic [(diolefin)Rh(Ph₂CH₂)Rh(diolefin)](ClO₄)₂ derivatives. New heterobimetallic complexes of the type [(diolefin)Rh(Ph₂CH₂)Cr(CO)₃]ClO₄ have been synthesized by reaction of Cr(CO)₃(⁶-Ph₂CH₂) with the solvated complex [Rh(diolefin)(Me₂CO)_x]ClO₄ or, alternatively by treatment of [Rh(diolefin)(⁶-arene)]ClO₄ with the complex Cr(CO)₃(⁶Me₃B₃N₃Me₃) in chloroform solution.     

Carbonyl complexes of manganese(I) with chelating phosphino-alkyl or -acyl ligands. Crystal and molecular structure of [Ph2PCH2CH2(O)CMn(CO)2(dppm)l

The phosphine Ph₂PCH₂CH₂Cl reacts with fac-[XMn(CO)₃(dppm)] (X = Cl or Br) in refluxing toluene to give the complexes cis,cis-[XMn(CO)₂(dppm)(Ph₂PCH₂CH₂Cl)] (I). Treatment of those species with Na amalgam in THF leads to the alkyl complex [Ph₂$\text{PCH}{}_2\text{CH}{}_2\text{M}$n(CO)₂(dppm)] (II), which does not react with CO under normal conditions but can be converted into cis,cis-[ClMn(CO)₂(dppm)(PPh₂Et)] by reacting with HCl (g) in ether. If the reduction of I with Na/Hg is carried out in the presence of CO the compound cis-[Ph₂$\text{PCH}{}_2\text{CH}{}_2\text{(O)CM}$n(CO)₂(dppm)] (III) is obtained. The latter has also been prepared directly from fac-[BrMn(CO)3(dppm)], Ph₂PCH₂CH₂Cl, and Na/Hg in THF, and characterized by X-ray crystallography. The crystals are monoclinic, space group P2₁/n; refinement gave R = 0.053 for 2593 reflections with I ? 2.5σ(I). The reaction of the complex fac-[O₃ClOMn(CO)₃(dppm)] with Ph₂PCH₂CH₂Cl in Cl₂CH₂ gives the salt fac-[Mn(CO)₃(dppm)(Ph₂PCH₂CH₂Cl)]ClO₄ which isomerizes to mer-[Mn(CO)₃(dppm)(Ph₂PCH₂CH₂Cl)]ClO₄ in boiling butanol. Both cationic carbonyl complexes give the acyl species III upon reduction with Na amalgam.     

Rhodium and iridium complexes containing the anion of 1-phenyl-3-methyl-4-benzoyl- pyrazolone-5, a sophisticated analogue of β-diketones

Several (diolefin)M(A) complexes (M = Rh, Ir) were prepared, where AH is 1-phenyl-3-methyl- 4-benzoylpyrazolone-5, a very stable asymmetric analogue of acetylacetone. In these complexes the diolefin could be replaced by one mole of (Ph₂PCH₂CH₂)₂, two of CO or of PPh₃, or three of CNBu^t, while 1,10-phenanthroline displaced the chelating ligand to yield [(cyclooctadiene)Rh(phen)]⁺ (A)^?. Some compounds X?Y (X?Y = iodine or MeI) added oxidatively yielding the corresponding trivalent species. Using ³¹P NMR spectra the presence of the expected steric isomers was detected in (Ph₃P)(CO)Rh(A) and in (Ph₃P) (CO)Rh(A)(X)(Y).     

Bidentate amine N-oxides and phosphine oxides as ligands in rhodium(I) chemistry

Cationic rhodium(I) complexes of the general formula [Rh(COD)L₂]ClO₄ (L₂ = bipyO₂, phenO, dpeO₂ and dpmO₂) are prepared from the solvated species [Rh(COD)(Me₂CO)_x]⁺ and the appropriate ligand. Complexes of the type [Rh_n(COD)_n](ClO₄)_n (CNPyO = 4-cyano and 2-cyanopyridine N-oxide) are obtained similarly. Reaction of [RhCl(COD)]₂ with the potassium salt of 2-picolinic acid N-oxide leads to the neutral complex Rh(COOPyO)(COD). The mononuclear rhodium diolefinic compounds react with carbon monoxide to give complexes of the type [Rh(CO)₂L₂]ClO₄ and Rh(COOPyO)(CO)₂, which on treatment with triphenylphosphine yield monocarbonyl derivatives.The catalytic activities of the diolefin complexes and related derivatives in hydrogen-transfer catalytic reactions have been studied.     

Rhodium(I) indazole and indazolate complexes

The preparation of cationic indazole (HIdz) rhodium(I) complexes of the types [(diolefin)Rh(HIdz)₂]ClO₄ and [(CO)₂Rh(HIdz)₂]ClO₄ is described. Neutral binuclear rhodium(I) complexes of the type [Y₂Rh(μ-Idz)]₂ (Y₂  COD, TFB, NBD, (CO)₂ or (CO)(PPh₃)) are obtained by treating the corresponding complexes [Y₂RhCl]₂ with indazole and organic or inorganic bases. The cationic mononuclear derivatives react with the solvated species [Y₂Rh(acetone)_x]ClO₄ in the presence of triethylamine to give neutral binuclear complexes of the types [(CO)₂Rh(μ-Idz)₂Rh(diolefin)], [(Ph₃P)(CO)Rh(μ-Idz)₂Rh(diolefin)] and [(diolefin)Rh(μ-Idz)Rh(diolefin′)] (diolefin  COD, TFB or NBD; diolefin′  COD or TFB). Alternative methods for the synthesis of the binuclear complexes are also described.     

Synthesis,formation constants and reactions of cationic rhodium(I) complexes of nitriles

Reactions of Rh(ClO₄)(CO)(PPh₃)₂ with nitriles produce new cationic rhodium(I) complexes, [RhL(CO)(PPh₃)₂]ClO₄ [L = CH₃CN (1), CH₃CH₂CH₂CN (2) or C₆H₅CN (3)], whose spectral data suggest that the nitriles are coordinated through the nitrogen atom. Formation constants for the reaction Rh(ClO₄)(CO)(PPh₃)₂ + L ⇋ [RhL(CO)(PPh₃)₂]ClO₄, have been measured to be 1.01 × 10⁵ M⁻¹ (CH₃CN), 1.07 × 10⁵ M⁻¹ (CH₃CH₂CH₂CN) and 2.59 × 10⁴ M⁻¹ (C₆H₅CN) at 25°C in monochlorobenzene. The differences in the formation constants for the different nitriles seem to be predominantly due to differences in ΔH (not to differences in ΔS). The nitriles in 1–3 are readily replaced with nitrogen base ligands (unsaturated nitriles and pyridine) and PPh₃.     

Chemistry of transition‐metal complexes containing functionalized phosphines: synthesis and structural analysis of rhodium(I) complexes containing allyl and cyanoalkylphosphines

A series of related acetylacetonate–carbonyl–rhodium compounds substituted by functionalized phosphines has been prepared in good to excellent yields by the reaction of [Rh(acac)(CO)₂] (acac is acetylacetonate) with the corresponding allyl‐, cyanomethyl‐ or cyanoethyl‐substituted phosphines. All compounds were fully characterized by ³¹P, ¹H, ¹³C NMR and IR spectroscopy. The X‐ray structures of (acetylacetonato‐κ²O,O′)(tert‐butylphosphanedicarbonitrile‐κP)carbonylrhodium(I), [Rh(C₅H₇O₂)(CO)(C₈H₁₃N₂)] or [Rh(acac)(CO)(^tBuP(CH₂CN)₂}] ( 2b ), (acetylacetonato‐κ²O,O′)carbonyl[3‐(diphenylphosphanyl)propanenitrile‐κP]rhodium(I), [Rh(C₅H₇O₂)(C₁₅H₁₄N)(CO)] or [Rh(acac)(CO){Ph₂P(CH₂CH₂CN)}] ( 2h ), and (acetylacetonato‐κ²O,O′)carbonyl[3‐(di‐tert‐butylphosphanyl)propanenitrile‐κP]rhodium(I), [Rh(C₅H₇O₂)(C₁₁H₂₂N)(CO)] or [Rh(acac)(CO){^tBu₂P(CH₂CH₂CN)}] ( 2i ), showed a square‐planar geometry around the Rh atom with a significant trans influence over the acetylacetonate moiety, evidenced by long Rh—O bond lengths as expected for poor π‐acceptor phosphines. The Rh—P distances displayed an inverse linear dependence with the coupling constants J_P‐Rh and the IR ν(C[triple‐bond]O) bands, which accounts for the Rh—P electronic bonding feature (poor π‐acceptors) of these complexes. A combined study from density functional theory (DFT) calculations and an evaluation of the intramolecular H…Rh contacts from X‐ray diffraction data allowed a comparison of the conformational preferences of these complexes in the solid state versus the isolated compounds in the gas phase. For 2b , 2h and 2i , an energy‐framework study evidenced that the crystal structures are mainly governed by dispersive energy. In fact, strong pairwise molecular dispersive interactions are responsible for the columnar arrangement observed in these complexes. A Hirshfeld surface analysis employing three‐dimensional molecular surface contours and two‐dimensional fingerprint plots indicated that the structures are stabilized by H…H, C…H, H…O, H…N and H…Rh intermolecular interactions.     

Chemie polyfunktioneller Moleküle. 82. Neue Rhodium(I)-Chelatkomplexe mit N,N-Bis(diphenylphosphino)alkyl- und -arylaminen

Chemistry of Polyfunctional Molecules. 82. New Rhodium(1) Chelate Complexes with N,N-Bis(diphenylphosphino) alkyl- and -arylamines . [Rh(μ-Cl)(CO)₂]₂ ( 1 ) reacts with (Ph₂P)₂NR (2, a: R = C₆H₅, b: R = p-C₆H₄CH₃) in a molar ratio of 1:2 to give the square plane, ionic complexes [Rh{(PH₂P)₂NR}₂] [cis-Rh(CO)₂Cl₂] ( 3a, b ). By the reactions of [Rh(μ-Cl)(C₈H₁₂)]₂(C₈H₁₂ = 1.5-Cyclooctadiene) (4) with (Ph₂P)₂NR ( 2a–d ) (c: R = CH₃, d: R = C₂H₅) in the molar ratios of 1:4 the square plane 1:1 electrolytes [Rh{(Ph₂P)₂NR}₂]Cl ( 5a–d ) are obtained. Upon treatment of 5a–d in dichloromethane with CO the complexes [Rh(CO){(Ph₂P)₂NR}₂]Cl ( 6a–d ) are formed. They are only stable in solution and in CO atmosphere and were identified by infrared spectroscopy. The new complexes have been characterized, as far as possible, by conductometry, IR; FIR, Raman, ³¹P-NMR, and ¹H-NMR spectra.     

Oxidative addition of different electrophiles with rhodium(I) carbonyl complexes of unsymmetrical phosphine–phosphine monoselenide ligands

Dimeric chlorobridge complex [Rh(CO)₂Cl]₂ reacts with two equivalents of a series of unsymmetrical phosphine–phosphine monoselenide ligands, Ph₂P(CH₂)_nP(Se)Ph₂ {n = 1( a ), 2( b ), 3( c ), 4( d )}to form chelate complex [Rh(CO)Cl(P∩Se)] ( 1a ) {P∩Se = η²‐(P,Se) coordinated} and non‐chelate complexes [Rh(CO)₂Cl(P～Se)] ( 1b–d ) {P～Se = η¹‐(P) coordinated}. The complexes 1 undergo oxidative addition reactions with different electrophiles such as CH₃I, C₂H₅I, C₆H₅CH₂Cl and I₂ to produce Rh(III) complexes of the type [Rh(COR)ClX(P∩Se)] {where R = ? C₂H₅ ( 2a ), X = I; R = ? CH₂C₆H₅ ( 3a ), X = Cl}, [Rh(CO)ClI₂(P∩Se)] ( 4a ), [Rh(CO)(COCH₃)ClI(P～Se)] ( 5b–d ), [Rh(CO)(COH₅)ClI‐(P～Se)] ( 6b–d ), [Rh(CO)(COCH₂C₆H₅)Cl₂(P～Se)] ( 7b–d ) and [Rh(CO)ClI₂(P～Se)] ( 8b–d ). The kinetic study of the oxidative addition (OA) reactions of the complexes 1 with CH₃I and C₂H₅I reveals a single stage kinetics. The rate of OA of the complexes varies with the length of the ligand backbone and follows the order 1a > 1b > 1c > 1d . The CH₃I reacts with the different complexes at a rate 10–100 times faster than the C₂H₅I. The catalytic activity of complexes 1b–d for carbonylation of methanol is evaluated and a higher turnover number (TON) is obtained compared with that of the well‐known commercial species [Rh(CO)₂I₂]^?. Copyright © 2006 John Wiley & Sons, Ltd.     

Carbonyl cationic rhodium(I) and iridium(I) complexes with sulphur donor and triphenylphosphine ligands

Summary The reaction of previously reported Rh^I and Ir^I cationic complexes towards carbon monoxide and triphenylphosphine has been studied. Carbonyl rhodium(I) mixed complexes of the formulae [Rh(CO)L₂(PPh₃)]ClO₄, (L=tetrahydrothiophene(tht), trimethylene sulfide(tms), SMe₂, or SEt₂), [(CO)(PPh₃)Rh{-(L-L)}₂Rh(PPh₃)(CO)](ClO₄)₂ (L-L= 2,2,7,7-tetramethyl-3,6-dithiaoctane (tmdto), (MeS)₂(CH₂)₃ (dth), or 1,4-dithiacyclohexane (dt), [Rh(CO)L(PPh₃)₂]ClO₄ (L= tht, tms, SMe₂, or SEt₂), and carbonyl iridium(I) complexes of the formulae [Ir(CO)₂(COD)(PPh₃)]ClO₄, [Ir(CO)(COD)(PPh₃)₂]ClO₄, [(CO)(COD)(PPh₃) Ir{-(L-L)} Ir(PPh₃)(COD)(CO)](ClO₄)₂ (L-L = tmdto or dt), [(CO)₂ (PPh₃)Ir(-tmdto)Ir(PPh₃)(CO)₂](ClO₄)₂, [(CO)₂(PPh₃) Ir(-dt)₂Ir(PPh₃)(CO)₂](ClO₄)₂, were prepared by different synthetic methods.     

A nonrigid mixed-chelate complex of iron(0)

The reaction of Fe(CO)(CH₂ CHCHCH₂)₂ with (Ph₂ PCH₂)₂ results in formation of a $\text{4}\text{1}$ mixture of two isomers of Fe(CO)(CH₂ CHCHCH₂)-(Ph₂ PCH₂ CH₂ PPh₂). NMR studies concerning the structures of these isomers and their dynamic behavior in solution are described.     

Some cationic carbonyl complexes of rhodium(I)

A number of cationic rhodium(I) complexes of the type [Rh(CO)₂(NN)]ClO₄, [Rh(CO)₂L₃]ClO₄ and [Rh(CO)(NN)L₂]ClO₄, where (NN) is 2,2^′-bipyridine or 1,10-phenanthroline and L is a tertiary phosphine or arsine, have been isolated and their structures assigned. The configuration of the complexes ion [Rh(CO)₂L₃]⁺ appears to depend critically on the size of the ligand L.     

Thermally induced ortho-metalation of dicarbomethoxyacetylenebis(triphenylphosphine)platinum

Heating a toluene solution of dicarhomethoxyacetylenebis(triphenylphosphine)platinum(0) at 130°C gives the ortho-metalated complex (Ph₃P)(Ph₂$\text{PC}{}_6\text{H}{}_4\text{)P}$t-trans-(COOMe)CCHCOOMe.     

Synthese und Charakterisierung von 2‐O‐funktionalisierten Ethylrhodoximen und ‐cobaloximen

Synthesis and Characterization of 2‐O‐Functionalized Ethylrhodoximes and ‐cobaloximes 2‐Hydroxyethylrhodoxime and ‐cobaloxime complexes L—[M]—CH₂CH₂OH (M = Rh, L = PPh₃, 1 ; M = Co, L = py, 2 ; abbr.: L—[M] = [M(dmgH)₂L] (dmgH₂ = dimethylglyoxime, L = axial base) were obtained by reaction of L—[M]^— (prepared by reduction of L—[M]—Cl with NaBH₄ in methanolic KOH) with BrCH₂CH₂OH. H₂O—[Rh]^—, prepared by reduction of H[RhCl₂(dmgH)₂] with NaBH₄ in methanolic KOH, reacted with BrCH₂CH₂OH followed by addition of pyridine yielding py—[Rh]—CH₂CH₂OH ( 3 ). Complexes 1 and 3 were found to react with (Me₃Si)₂NH forming 2‐(trimethylsilyloxy)ethylrhodoximes L—[Rh]—CH₂CH₂OSiMe₃ (L = PPh₃, 4 ; L = py, 5 ). Treatment of complex 1 with acetic anhydride resulted in formation of the 2‐(acet oxy)ethyl complex Ph₃P—[Rh]—CH₂CH₂OAc ( 6 ). All complexes 1 — 6 were isolated in good yields (55—71 %). Their identities were confirmed by NMR spectroscopic investigations ( 1 — 6 : ¹H, ¹³C; 1 , 4 , 6 : ³¹P) and for [Rh(CH₂CH₂OH)(dmgH)₂(PPh₃)]·CHCl₃·1/2H₂O ( 1 ·CHCl₃·1/2H₂O) and py—[Rh]—CH₂CH₂OSiMe₃ ( 5 ) by X‐ray diffraction analyses, too. In both molecules the rhodium atoms are distorted octahedrally coordinated with triphenylphosphine and the organo ligands (CH₂CH₂OH and CH₂CH₂OSiMe₃, respectively) in mutual trans position. Solutions of 1 in dmf decomposed within several weeks yielding a hydroxyrhodoxime complex “Ph₃P—[Rh]—OH”. X‐ray diffraction analysis exhibited that crystals of this complex have the composition [{Rh(dmg)(dmgH) (H₂O)(PPh₃)}₂]·4dmf ( 7 ) consisting of centrosymmetrical dimers. The rhodium atom is distorted octahedrally coordinated. Axial ligands are PPh₃ and H₂O. One of the two dimethylglyoximato ligands is doubly deprotonated. Thus, only one intramolecular O—H···O hydrogen bridge (O···O 2.447(9)Å) is formed in the equatorial plane. The other two oxygen atoms of dmgH^— and dmg^2—, respectively, act as hydrogen acceptors each forming a strong (intermolecular) O···H′—O′ hydrogen bridge to the H′₂O′ ligand of the other molecule (O···O′ 2.58(2)/2.57(2)Å).     

A reactive rhodium(I) carbonyl dithiolate and the formation of acyl and hydride species

The rhodium(I) complex [Rh(CO)(PEt₃)(mnt)]^? (mnt = maleonitriledithiolate) reacts with a variety of alkyl halides to form acyl complexes isolated in the presence of excess PEt₃ as five-coordinate species of formula [Rh(COR)(PEt₃)₂(mnt)]. The structure of the complex for R = n-Pr has been determined by an X-ray analysis, and is found to be a square-based pyramid with the acyl group in the apical position. Addition of HClO₄ to the rhodium(I) anion in the presence of excess PEt₃ yields rhodium(III) hydride, [RhH(CO)(PEt₃)₂(mnt)], while addition of acid to the rhodium(I) complex in CH₃CN solution with ethylene present leads slowly to formation of an acyl complex which is isolated as [Rh(COEt)(PEt₃)₂(mnt)] upon phosphine addition. A novel alkyl group migration from the acyl carbon to a donor S atom is also observed in monophosphine systems.     

Dirhodium(II) dicarboxylato complexes containing carbonyl and C-bonded methoxycarbonyl ligands

Oxidation of rhodium(I) carbonyl chloride, [Rh(CO)₂Cl]₂, with copper(II) acetate or isobutyrate in methanol solutions yields binuclear double carboxylato bridged rhodium(II) complexes with RhRh bonds, [Rh(μ-OOCRκO)(COOMeκC)(CO)(MeOH)]₂, where R=CH₃ or i-C₃H₇. According to X-ray data, surrounding of each rhodium atom in these complexes is close to octahedral and consists of another rhodium atom, two oxygens of carboxylato ligands, terminal carbonyl group, C-bonded methoxycarbonyl ligand, and axial CH₃OH. Methoxycarbonyl ligand is shown to originate from CO group of the parent [Rh(CO)₂Cl]₂ and OCH₃ group of solvent. N- and P-donor ligands L (p-CH₃C₆H₄NH₂, P(OPh)₃, PPh₃, PCy₃) readily replace the axial MeOH yielding [Rh(μ-OOCRκO)(COOMeκC)(CO)(L)]₂. The X-ray data for the complex with R=i-C₃H₇, L=PPh₃ showed the same molecular outline as with L=MeOH. Electronic effects of axial ligands L on the spectral parameters of terminal carbonyl group are essentially the same as in the known series of rhodium(I) complexes (an increase of δ¹³C and a decrease of ν(CO) with strengthening of σ-donor and weakening of π-acceptor ability of L).     

Photocatalytic properties of new cyclopentadienyl and indenyl rhodium(I) carbonyl complexes with water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) and tris(2-cyanoethyl)phosphine

Reactions of [(η⁵-R)Rh(CO)₂] (R = cp, ind) with water-soluble phosphines (L = 1,3,5-triaza-7-phosphaadamantane and tris(2-cyanoethyl)phosphine) give the new rhodium(I) complexes of the types [Rh(η⁵-cp)(CO)(PTA)] (1), [Rh(η⁵-cp)(CO)(P(CH₂CH₂CN)₃)] (2), [Rh(η⁵-ind)(CO)(PTA)] (3) and [Rh(η⁵-ind)(CO)(P(CH₂CH₂CN)₃)] (4) in isolated yields of 52-75%. All these compounds have been fully characterized by IR, ¹H, ³¹P{¹H} and ¹³C{¹H} NMR, FAB-MS spectroscopies and elemental analyses. Reactivity for the substitution of phosphine is greater for [(η⁵-ind)Rh(CO)(L)] comparing to [(η⁵-cp)Rh(CO)(L)] because of a flexibility of the indenyl ligand to undergo facile η⁵-η³ coordinative isomerizations. The obtained complexes are active catalyst precursors for the dehydrogenation of propan-2-ol, octane and cyclooctane under photoassisted conditions without any organic hydrogen transfer acceptors, giving TOFs of 26-56 using 3 as precatalyst.     

1-[(π-Cyclopentadienyl)dicarbonyliron]-1-methylsilacyclobutane and related iron-substituted silacyclobutanes

Silicon-transition metallic silacyclobutanes CpFe(L₂)$\text{Si(Me)CH}{}_2\text{CH}{}_2\text{C}$H₂ [L = CO or Ph₂MeP; or L₂ = (CO)(Ph₂MeP)] have been prepared and their reactions (substitution at Si or Fe, Si—Fe cleavage, or ring-opening) studied.