P.M. Treichel

Transition Metal-lsocyanide Complexes

Publisher Summary This chapter discusses the field of transition-metal complexes of isocyanides developed slowly over more than a century to a respectable subarea in coordination chemistry and which, in the process, seems to have attracted very little attention. The valence-bond pictures for an isocyanide and carbon monoxide and for metal complexes of these ligands emphasize the similarities of both the ligands and their complexes. The insertion of a carbonyl group into a metal–alkyl or metal–aryl bond and the reverse reaction involving decarbonylation of an acyl complex have been studied from both the synthetic and mechanistic points of view. The reactions of nucleophilic reagents with cationic and uncharged metal carbonyl complexes have received much attention in the past, and it is not surprising that these studies have now been extended to isocyanide metal complexes. Perhaps the greatest excitement in the field of metal isocyanide complex chemistry has been generated by the observation that a variety of protonic substances (alcohols, thiols, amines, and hydrazine) add to the coordinated isocyanide ligand. A number of chemists have been interested in the chemistry of cobinamine and cobaloxime complexes of several ligands, including isocyanides.

Metal carbonyl complexes of phenylphosphine and diphenylphosphine

Abstract Reactions of various metal carbonyls or their derivatives and diphenylphosphine (L) or phenylphosphine (L′) lead exclusively to ligand (carbonyl or halide) replacement; the following complexes are reported: [C 5 H 5 Fe(CO) 2 L]Br, [C 5 H 5 ]Fe(CO) 2 L′]I, [C 5 H 5 Mo(CO) 3 L]PF 6 , C 5 H 5 Mo(CO) 2 LCl, Mn(CO) 3 L 2 Br, Mn(CO) 3 L′ 2 Br, Mn(CO) 4 LBr, Mn(CO) 4 L′Br, Mn(CO) 4 (L)C 6 H 5 , Cr(CO) 4 L′ 2 , Mo(CO) 3 L′ 3 . Deprotonations of several of these species using n-butyllithium or sodium methoxide (cations only) were carried out and reactions of the resulting species studied. Reactions of deprotonated species included alkylation by methyl iodide to give methylphenylphosphine complexes, dimerization via μ-phosphido groups with CO loss, and intramolecular rearrangements. In the latter category we observe that [C 5 H 5 Fe(CO) 2 P(C 6 H 5 )Li 2 ]PF 6 rearranges to give C 5 H 5 Fe(CO) 2 Li and LiPF 6 , and Mn(CO) 4 [P(C 6 H 5 ) 2 Li]Br and C 5 H 5 Fe(CO)[P(C 6 H 5 ) 2 Li]Br eliminate LiBr to give [Mn(CO) 4 P(C 6 H 5 ) 2 ] 2 and [C 5 H 5 Fe(CO)P(C 6 H 5 ) 2 ] 2 respectively. Finally, we have irradiated M(CO) 5 PR 2 H and M(CO) 5 PR 2 Li species (MCr, Mo, W; RC 6 H 5 ) and observe that dimerization with accompanying oxidation to give M 2 (CO) 8 (PR 2 ) 2 and ligand redistribution to M(CO) 4 (PR 2 H) 2 are often seen; the former reaction occurs more often with the lithio species.

Chemistry of the cyclopentadienylmetal Carbonyls V. (A) reactions of cyclopentadienylmolybdenum and-tungsten tricarbonyl halides with group va donor ligands : (B) cationic cyclopentadienylmolybdenum and -tungsten carbonyl derivatives with group va donor ligands

Abstract The reaction of C5H5Mo(CO)3Cl and triphenylphosphine gives a mixture of C5H5Mo(CO)2[(C6H5)3P]Cl and C5H5Mo(CO)[(C6H5)3P]2Cl; C5H5Mo(CO)3X (X = Br, I) and C5H5W(CO)3Cl react with triphenylphosphine giving monosubstitution only. With triphenylarsine and -stibine C5H5M(CO)3X (M = Mo, X = Cl, Br, I; M = W, X = Cl) monosubstitution is found to occur. The reaction of 1,2-bis(diphenylphosphino) ethane (diphos) and C5H5Mo(CO)3Cl gives C5H5Mo(CO)(diphos)Cl and C5H5Mo(CO)2(diphos)+Cl-. The reactions of C5H5Mo(CO)3I and C5H5W(CO)3Cl and diphos lead to C5H5M(CO)2(diphos)+X- and [C5H5M(CO)2X]2-μ-diphos. The reactions of C5H5Mo(CO)3X(X = Cl, Br, I) and C5H5W(CO)3Cl and bipyridine (bipy) or o-phenanthroline (o-phen) give C5H5M(CO)2+X- and C5H5M(CO)2(o-phen)+X- (M = Mo, W) as the only products of these reactions. It is suggested that the chelating ability of a ligand is sometimes important in determining whether an ionic derivative is to be formed. Reactions between the compounds C5H5M(CO)3Cl or C5H5M(CO)2LCl [M = Mo, W; L = (C6H5)3P, (C6H5)3As], a Group VA donor molecule or carbon monoxide, and AlCl3 have been studied. From such reactions the compounds C5H5M(CO)3L+ AlCl-4 and C5H5M(CO)2L+2AlCl-4 [M = Mo, W; L = (C6h5)3P, (C6H5)3As, CH3CN] were obtained. The compound C5H5Mo(CO)(CH3CN)[(C6H 5)3P]+2AlCl-4 was obtained from C5H5Mo(CO)[(C6H5)3P]2Cl, CH3CN and AlCl3. All cations were eventually characterized as hexafluorophosphate salts.

Preparation of Several Homologous Series of Cyclopentadienylruthenium Complexes and Their Solvolysis in Polar Solvents

Abstract The convenient synthesis of 11 members of a series of compounds RuCl(L)2(η-C5H5) (L = PPh20Me, PPh(OMe)2, P(OMe)3, PPh2Me, PMe(OMe)2, 1/2dppe, PMe3, PPhMe2, PPhEt2, P(OEt)3, P(OPri)3) was accomplished by reaction between an excess of the indicated ligand and RuC1(PPh3)2(η-C5H5) in toluene. Related pentamthylcyclopentadienyl complexes, RuC1(L)2(η-C5Me5) (L - P(to1P)3, 1/2dppe, PMe3, PPh2OMe, PPh(OMe)2, P(OMe)3) were prepared from RuC1(PPh3)2(η-C5Me5) in a similar manner. Exchange of C1− with other anionic groups (X− = Br−, I−, CN−, SCN−, OCN−) in both series was shown to occur in ethanol. Displacement of chloride ion from RUCL(L)2(η-C5H5) or RuCl(L)2(η-C5Me5) by CH3CN or DMSO also occurs in solution in methanol in the presence of NH4PP6, a halide acceptor. This procedure provides excellent yields of the cationic complexes [Ru(solv)(L)2(η-C5H5)]PF6.

New cyclopentadienyliron trimethylphosphine complexes

Abstract Preparations of [Fe(C5H5)(CO)3-n(PMe3)n]X complexes (n = 1, 2, 3) are described. Irradiation of [Fe(C5H5)(CO)(PMe3)2]BF4 in acetonitrile gave I, CN) and [Fe(C5H5)(PMe3)2(PPh3)]BF4. Reactions of Fe(C5H5)(CO)2X compounds with PMe3 gave Fe(C5H5)(CO)(PMe3)COMe or Fe(C5H5)(PMe3)2Me, depending on conditions. One electron oxidations of Fe(C5H5)(PMe3)2SPh, Fe(C5H5)(PMe3)2SnPh3 and [Fe(C5H5)(PMe3)3]PF6 produced 17 electron products which were isolable.

Manganese(I) isocyanide complexes

Abstract The reaction of methyl isocyanide (L) and MnBr(CO)5 in tetrahydrofuran gives several products, depending on the reaction conditions, including: MnBr(CO)3 L2 (room temperature, 48 h), MnBr(CO)2L3 (reflux, 6 h), and a mixture of MnBr(CO)2L3, MnBr(CO)L4, and [Mn(CO)L5]Br (reflux, 24 h). The monosubstituted product MnBr(CO)4L was obtained from Mn2Br2(CO)8 and L, and other ionic species, [Mn(CO)6−xLx]+ (x = 1–4), were obtained from MnBr(CO)5−xLx, AlCl3, and CO. The reactions of MnX(CO)5 (X = Cl, Br, I) and CNC6H5 in tetrahydrofuran were reinvestigated. The product distribution was dependent on reaction time and on the ratio of reactants. The compound previously reported as MnBr(CNC6H5)5 was shown to be a mixture of [Mn(CO)(CNC6H5)5]Br and [Mn(CNC6H5)6]Br, and the new complex MnCl(CNC6H5)5 was characterized. Chemical oxidation of [Mn(CO)L5]PF6 yielded [Mn(CO)L5](PF6)2. Electrochemical oxidations of various cationic species were recorded. The difficulty of oxidation (E 1 2 ) increased with increasing carbonyl substitution (i.e., decreasing values of x) in the series [Mn(CO)6-xLx]PF6, presumably a result of the higher net positive charge on the metal due to removal of electron density to the CO ligands. Oxidation of the phenyl isocyanide complexes [Mn(CO)6-x(CNC6H5)x]PF6 (x = 5,6) was more difficult than was oxidation of the corresponding methyl isocyanide species.

Synthesis and structural characterization of acetatobis(triphenylphosphine)dicarbonylmanganese(I), (CH3CO2)Mn(CO)2[P(C6H5)3]2: An organometallic complex containing a chelating acetate ligand

The accidental but intriguing synthesis of acetatobis(triphenylphosphine)dicarbonylmanganese(I), (CH 3 CO 2 )Mn(CO) 2 [P(C 6 H 5 ) 3 ] 2 , has been accomplished by the reaction of NaMn(CO) 5 with (CH 3 ) 3 SiCl followed by the addition of triphenylphosphine and acetic acid. A three-dimensional single-crystal X-ray diffraction analysis has shown an octahedral-like molecule containing a symmetrically oxygen-chelating acetate group, the first such group to be reported in a metal carbonyl complex. The two triphenylphosphine ligands occupy mutually trans positions with the two carbonyl ligands possessing the remaining cis sites in the octahedral complex. The compound crystallizes with four molecules in a monoclinic unit cell of space group symmetry and of dimensions a = 17.744(2) A, b = 9.692(1) A, c = 20.004(2) A, and β = 106.195(4)°. The relatively long MnO(acetate) bond lengths [2.066(6) and 2.069(7) A] and the relatively short MnCO bond lengths [1.701(12) and 1.760(13) A] and the relatively short MnP(C 6 H 5 ) 3 bond lengths [2.260(3) and 2.275(3) A], compared to the corresponding MnCO and MnP(C 6 H 5 ) 3 bond lengths in other manganese carbonyl triphenylphosphine complexes, are rationalized on the basis that the acetate ligand in this molecule functions primarily as a σ-donor.

The stereospecific ring protonation of diindenyliron

Abstract Reactions of protonic acids (HCl, CF 3 COOH) with diindenyliron give the h 5 -indenyl- h 6 -indeneiron(II) monocation, [Fe(C 9 H 7 )(C 9 H 8 )] + , which can be isolated as a hexafluorophosphate salt. Two deuterium labeling experiments, the reaction of Fe(C 9 H 7 ) 2 and DCl and the reaction 1,1′,3,3′-tetradeuteriobis(indenyl)iron with HCl, confirm that the products in this reaction have been formed by stereospecific addition of the proton to the indenyl ring. Because of the wealth of data on metal protonations, including data on the protonation of ferrocene at the iron atom, preference is indicated here for endo ring protonation which is proposed to occur via an intermediate protonated metal species. Protonation of Fe(C 5 H 5 )(C 9 H 7 ) is also reported. Deprotonation with n-butyllithium regenerates diindenyliron. However, data on these reactions suggest preferential loss of an exo -proton, which is perhaps realistic in view of the known attack of nucleophiles on the exo position of coordinated hydrocarbon rings.

New 17 electron complexes of iron

Abstract One electron oxidation reactions are predicted forFe(C 5 H 5 )(dpe)X compounds according to cyclic voltammetry. These oxidations have been carried out using AgPF 6 as an oxidant, and a number of 17e complexes of the formula [Fe(C 5 H 5 )(dpe)X]PF 6 (X = Cl, Br, I, H, Me, SnMe 3 , CN, SCN (N bonded isomer), SPh) has been isolated. The compound [Fe(C 5 H 5 )(dpe)SPh]BF 4 also is formed from addition of HBF 4 to the appropriate 18 electron precursor, while addition of a potentially stronger oxidizing agent NOPF 6 gives [Fe(C 5 H 5 )(dpe)NO](PF 6 ) 2 . The compound [Fe(C 5 H 5 ){P(OPh) 3 } 2 I]PF 6 has been isolated. The 17e species Fe(C 5 H 5 )(dpe)S 2 O 3 forms from [Fe(C 5 H 5 )(dpe)(MeCN)]PF 6 and Na 2 S 2 O 3 . This may be the first organometallic compound having an S 2 O 3 ligand. The 17e compounds are paramagnetic, with all but the CN compound having magnetic moments corresponding to oneunpaired electron; the magnetic moment of the CN − compound is abnormally low (0.55 BM).

Rhenium(I) isocyanide complexes

Two series of rhenium(I) isocyanide complexes having the general formulas Re(CO)5−nLnBr and [Re(CO)6−nLn]PF6 (L = CNMe, CNtol) are described. The former compounds are formed from Re(CO)5Br by direct carbonyl replacement using thermal or photolytic conditions, the extent of the reaction being determined by reaction temperature and time. An interesting conversion of fac-Re(CO)3L2Br to mer,trans-Re(CO)3L2Br on heating is noted. The third possible isomer having this stoichiometry, mer,cis-Re(CO)3L2Br, forms in photolytic reactions of Re(CO)5Br and L. Three possible Re(CO)2L3Br isomers were isolated, thermal reactions (toluene reflux) giving the mer,cis and fac isomers, photolytic reactions giving all three isomers. Isomers were generally separated by chromatography and their geometries ascertained from infrared data. More forcing reaction conditions eventually give Re(CO)L4Br, then ReL5Br and [ReL6]Br (L = CNtol only) or [Re(CO)L5]Br. The other ionic complexes are prepared from the substituted carbonyl halide, Re(CO)5−nLnBr, and added ligands in the presence of a halide acceptor. Generally, all reactions are much less facile than corresponding reactions in the manganese carbonyl series. Spectroscopic and electrochemical data are reported.