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The reaction of dialkyl(chloromethylene)ammonium chlorides (R2NCHCl)+Cl–, (R = Me, Et, Pri, or Bun), with RhI substrates [RhCl(PPh3)3], [RhCl(CO)PPh3]2, or [RhCl(CO)2]2 affords RhIII secondary carbene complexes, [L′RhCl3CHNR2]n[L′= CO, n= 2; L′=(PPh3)CO, n= 1; L′=(PEt3)2 or (PPh3)2, n= 1], via a three-fragment oxidative-addition reaction. The secondary carbene RhIII complexes are characterised by a high degree of CN double-bonding, greater than in tertiary carbene complexes or carboxylic acid dialkylamides. The Ccarb–H1H n.m.r. resonance is at low field (τca. –1), ν(Ccarb–H) at ca. 3050 cm–1, and ν(Ccarb[graphic omitted]N) at ca. 1600 cm–1; coupling of Ccarb–H resonances are identified: 2J(103Rh–1H), 3J(31P–1H), and cis- and trans-4J(C1H3N–1H). A single-crystal X-ray analysis of [RhCl3(PEt3)2CHNMe2] has been carried out to R= 0·050; the complex has an approximately octahedral Rh environment with mutually trans-phosphine ligands. Bond distances (A) are Rh–Ccarb= 1·961(11), Ccarb–N = 1·289(14), Ccarb–H = 1·14(4), Rh–P = 2·368(3) and 2·372(3), Rh–Cl (mutually trans)= 2·357(4) and 2·364(3), Rh–Cl (trans-carbene)= 2·445(4). The high trans-influence of the secondary carbene ligand is discussed in terms of X-ray, i.r., and n.m.r. data, and it appears to have the highest trans-influence of a neutral ligand of RhIII.

The reaction of an imidoyl chloride R1C(Cl):NR2 with the RhI complex [Rh(CO)2Cl]2 in the rigorous absence of hydrogen chloride affords the RhIII carbene chelate Cl3(OC)[graphic omitted]R2. The chloride ligands are replaceable by Br– or I–, and the chelate bridge is cleaved by reaction with a tertiary phosphine. A single-crystal X-ray analysis of (IV) I3(OC)[graphic omitted]Me by the heavy-atom method has been refined to R 0·047 for 2400 independent terms measured on a diffractometer: the complex has an approximately octahedral Rh environment, with Rh–C(carb) 1·968(13), C(carb)–N 1·328(16), Rh–N 2·047(9), Rh–I 2·662(4)—2·774(4), and Rh–C(O) 1·892(14)A. Crystals are monoclinic, a= 10·83(1), b= 17·24(2), c= 11·52(1)A, β= 97·3(2)°, Z= 4, space group P21/n.

Preparation et caracterisation de complexes de Fe(III) avec le coordinat du titre, FeX(P-N 4 ), avec X=cl, Br, OH, N 3 . Structure cristalline de Fe Cl (P-N 4 )CHCl 3 •H 2 O: affinement jusqu'a R=0,104 (cristallisation dans PZ 1 /c avec Z=4). Etude de susceptibilite magnetique, RPE et Mossbauer de differents complexes et interpretation. Comparaison avec le comportement en solution

Crystals of the title compound are monoclinic, space group C2/m, with a= 14.706(5), b= 7.866(3), c= 8.132(3)A, and β= 114.40(2). The molecule lies on a site of 2/m symmetry with both the carbene ligands in the crystallographic mirror plane (i.e they are not orthogonal). The structure was refined by full-matrix least squares to an R value of 0.027 for 87 variables (including isotropic hydrogen atoms) and 1 661 data. The Mo–Ccaro, distance of 2.232(2)A is ca. 0.06 A shorter than in the cis isomer. The Mo–CO length of 2.001(2)A compares with the Mo–CO (trans CO) and Mo–CO (trans carbene) lengths of 2.028(3) and 1.980(3)A respectively in the cis isomer. The activation energy (70.4 ± 2 kJ mol–1, or 74.7 ± 0.7 kJ mol–1 for the ethyl homologues) for the trans→cis isomerisation was measured in diethyl phthalate by differential scanning calorimetry, using digital data logging equipment and a computer program. The reaction is first order and the negative activation entropy is attributed to interaction with solvent molecules in the transition state.

A search for metal ion promoted hydrolysis of urea and the factors influencing linkage isomerization on a metal has led us to prepare and examine reactivities of N- and O-bound phenylurea complexes of pentaamminecobalt(III). The N-bonded isomer reacts in aqueous acid to yield principally [Co(NH3)6]3+, CO2, and anilinium ion (ca. 70%) but also via parallel paths leading to [(NH3)5CoOC(NH2)NHC6H5]3+ (linkage isomerization) and [(NH3)5CoOH2]3+ (aquation). The major path involves an elimination reaction of [(NH3)5CoNH2CONHC6H5]3+ to give anilinium ion and [(NH3)5CoNCO]2+. The latter complex, which has been isolated and characterized, is known to undergo rapid hydration (pH l 2) to [(NH3)5CoNH2CO2H]3+, which subsequently decomposes along three parallel paths to [Co(NH3)6]3+ and traces of [(NH3)5CoOH2]3+ and [(NH3)5CoOCONH2]3+. Kinetic data for the three parallel reactions of [(NH3)5CoNH2CONHC6H5]3+ in aqueous HCIO4 (1.0 M, 25.0 dC) are kelim= 1.04 X 10-2 s-1 (elimination), kNo = 2.39 X 10-3 s-1 (isomerization), and kaq = 1.13 X 10-3 s-1 (aquation). A single-crystal structure reveals that the urea exo C-N bond is 0.11 A longer than the endo C-N bond and, as in uncoordinated phenylurea, the electron-with-drawing phenyl ring is neither planar with nor conjugated to the urea moiety. These features are likely retained in the protonated form and account for the facility of the elimination path. By contrast, neither elimination nor hydrolysis of the O-bonded phenylurea complex was detected; instead it slowly undergoes parallel aquation and O- to N-linkage isomerization. Both processes are base-catalyzed, and each obeys a rate law of the form k(obsd) = ks + Koh[Oh-]. The equilibrium constant (K'No= Kno/Kon= 166) reflects the strong thermodynamic preference for the O rather than the N terminus of the neutral phenylurea molecule. However, the observed equilibrium is pH-dependent (K'(obsd) = K'NO[H+]/(Ka + [H+])); for pH g 3, the N-bonded isomer is more stable due to its selective deprotonation (K'NO(obsd) a 10n5, pH 6.2). The single-crystal structure determination of [(NH3)5CoNHCONHC6H5](C104)2-H20 shows the cobalt in an approximately octahedral environment with phenylurea bonded as its anion through the indicated nitrogen center. As observed for the free ligand, the phenyl substituent is twisted (37d) with respect to the approximately planar urea moiety. The compound crystallizes in the monoclinic system (b = 91.64d), with V = 1887.0 A3, space group C2/c, Z = 8, a = 15.751 (6) A, b = 12.277 (5) A, c = 9.762 A, and R = 0.046 and RW = 0.043 for 1381 diffractometer data (244 variables) with 1 g 3s(I), m = 105.47 cm-1, and F(000) = 1023.96.

Carbene–Moo complexes are obtained by the thermal reaction of an electron-rich olefin [graphic omitted]R]2, LR2, with (a)[Mo(CO)6]{yielding [Mo(CO)5LR] or cis-[Mo(CO)4(LR)2](R = Me, Et, or PhCH2)(the tricarbene complex is unstable)}, and (b)[Mo(CO)2(C5H5-η)NO]{yielding [Mo(CO)(C5H5-η(LR)NO](R = Me or p-tol)}. By contrast, with [Mo(CO)3(C5H5-η)H] or [{Mo(CO)3(C5H5-η)}2], the olefin reacts as a reducing agent, yielding the amidinium molybdate(0) complexes [HLR]+[Mo(CO)3(C5H5-η)]– or [LR2]2+[Mo(CO)3(C5H5-η)]–2(R = Me). The six-membered chelate olefin [C[graphic omitted]Me]2, L′Me2, behaves qualitatively in a similar fashion, but is less reactive, dicarbene–Moo complexes not being accessible. The cis-dicarbene–Moo complexes are isomerised photochemically to the trans-complexes, but the former are thermodynamically the more stable. Reaction of [Mo(CO)5LEt] with LMe2 yields cis-[Mo(CO)4(LEt)(LMe)], whereas [Mo(CO)5LMe)] with LEt2 affords also cis-[Mo(CO)4(LMe)2] and cis-[Mo(CO)4(LEt)2]. The redistribution reaction cis-[Mo(CO)4(LR)2]+[Mo(CO)6]⇌ 2[Mo(CO)5LR](R = Me or Et) is reversible. Other reactions of monocarbene complexes give cis-[Mo(CO)4(LR)Q][Q = C5H5N, PPh3, or P(C6H11)3, fac-[Mo(CO)3(LR)Q′2][Q′2={P(OMe)3}2 or diphos], or cis-[Mo(CO)4{C(OMe)Me}LR]. ν(CN2) is at 1 510—1 480 cm–1 for the carbene–Moo complexes, but at 1 700–1 640 cm–1 for the amidinium cations, and ν(CO) values are very low; 1H n.m.r. spectra provide information on conformational aspects; ΔG‡ for Mo–Ccarb rotation in cis-[Mo(CO)4(LR)2] is ca. 10 kcal mol–1. 13C Chemical shifts for Ccarb. and CO are comparable (but are distinguished by 1H decoupling and 1H off-resonance studies). Both are in the range 230–210 p.p.m. upfield from SiMe4, whereas for [HLMe]+ or [LMe2]2+ there is a further 50–60 p.p.m. upfield shift for δ[Ccarbonium ion]. A single-crystal X-ray analysis of (4)cis-[Mo(CO)4(LMe)2] shows octahedral Mo, with MO–CO mutually-trans bond lengths longer by 0.048(2)A than MO–CO trans to carbene [2.024(3) and 2.032(3)A]; Mo–Ccarb[2.293(3)A] is appropriate for single bonds. The dihedral angles between the carbene ligand planes and the co-ordination planes in which they are involved are ca. 45°, which is sterically the preferred conformation. It is concluded that the carbene ligand is a strong σ-donor but a poor π-acceptor.

The absolute configuration of (−) D -Ru(bpy) 3 (ClO 4 ) 2 has been determined to be the right-hand screw configuration Δ. CD spectra of M(bpy) 2+ 3 (M = Fe, Ru, Os) doped in a uniaxial host. Lattice lead to a new assignment of CD bands in the MLCT region. The CD arises from intrinsically allowed electronic and magnetic transition dipole moments, the latter coming from metal-centered transitions.

Crystals of the title compound are monoclinic, space group P21/n with Z= 2 in a cell of dimensions a= 7·189(8), b= 12·053(15), c= 12·028(14)A, β= 91° 10′(20). The structure was solved by Patterson and Fourier methods and refined by full-matrix least-squares techniques to R 9·9% for 1206 visually estimated reflections. The centro-symmetric molecules have bond angles at tin within 1·3° of 90°; Sn–P is 2·615(5)A, and Sn–Cl are 2·445(5) and 2·455(5)A. The bond lengths are compared with those in phosphine complexes of transition- and Group B metal chlorides. The results are consistent with an earlier suggestion from Mossbauer studies that the Sn–P bonds have high tin 5s-character, and an approximate analysis of Sn–P r.m.r. coupling constants further supports this. An explanation is offered for the different modes of variation of 1J(M–P) for complexes of the phosphines RnPhn–3P.

The stereochemistry of the aqua and hydroxo products fromed in the induced aquation (Hg2+, Ag+, NO+) and base hydrolysis reactions of anti-p, syn-p, and s-[Co(Metren)NH3X]n+ ions (n= 2 or 3; tren = 2,2′,2″-triaminotriethylamine; X = Cl, Br, N3, NH3; p = primary, s = secondary) show a dependence on leaving group, type of reaction, and reactant stereochemistry, thereby eliminating the formation of common intermediates.

The 1 : 1 adduct of the PtI–PtI dimer [Pt-µ-{o-C6H4P(Ph)CH2 CH2PPh2}]2 with methyl iodide is deprotonated by sodium methoxide to give a µ-methylenediplatinum(II) complex [Pt2-µ-{o-C6H4P(Ph)CH2CH2PPh2}2(µ-CH2)], characterised by single-crystal X-ray structural analysis; the latter complex reacts with [Me3O]PF6 to give an ethyldiplatinum(II) cation which retains the bridging cyclometallated dppe ligands.

Reaction of the electron-rich olefin [Et[graphic omitted]]2 with tellurium affords the thermally or photochemically labile Et[graphic omitted]Te which reacts with [M(CO)5(NCMe)](M = Cr, Mo, or W) or [NEt4][MnBr2(CO)4] to yield [M(CO)5{Te[graphic omitted]Et}] or cis-[Mn(Br)(CO)4{Te[graphic omitted]Et}]; the compound [Cr(CO)5{Te[graphic omitted]Et}] is readily detellurated to yield the carbenemetal complex [Cr(CO)5{[graphic omitted]Et}]; the molecule of the title compound lies on a crystallographic mirror plane with the carbene ligand perpendicular to this plane and Te–Cr = 2·765(4), Te–Ccarb= 2·12(2)A, and ∠ Cr–Te–Ccarb= 96·1(5)°.

The molecule (MeAlNMe)7 has a cage structure; each aluminium and nitrogen atom is four-co-ordinate, and is bound to one methyl group and three atoms within the cage.

Octaethylporphin, oepH2, and [RhCl(CO)2]2 react in hot chloroform to form a complex, which has been shown by chemical analysis, spectroscopic studies, and X-ray analysis to be [oepH4]2+2{cis-[RhCl2(CO)2]}–. Crystals are tetragonal, space group P4/n, Z= 4, with cell dimensions a= 24·604(3) and c= 8·231(1)A. The structure has been refined by Fourier and least-squares methods to R 0·089 for l439 diffractometric intensity data. A novel feature of the structure is the essential planarity of the [oepH4]2+ dication. Other new complexes to have been prepared are Co(oep)(PR3)2, [Co(oep)(PR3)2]+Br–, and Co{N:C(CF3)2}(oep).

Two rhodium(I) complexes, trans-Rh[N:C(CF3)2][C(NRCH2)2](PPh3)2, (I; R =p-MeC6H4) and (II; R = Me), containing both alkylideneamido- and substituted carbene ligands have been prepared. Variable temperature 19F n.m.r. spectra suggest a low barrier to planar inversion at N. It did not prove possible to rearrange these to aza-allyl/allene isomers. As a contribution to the mechanism of formation of the latter, the synthesis of a C-alkylideneamidocarbene complex (V) is reported. A PtII imidoyl complex Pt–C(R)NR′, prepared by an oxidative addition reaction, did not isomerise to the alkylideneamide Pt–NCRR′; but with HCI the former gave a 1 : 1 adduct, presumed to be the carbene complex Pt–C(R)NHR′. A single crystal X-ray analysis of (II) has been carried out to R 0·067 for 2853 independent terms : the complex has an approximately square planar Rh environment with disorder about N:C and Rh–N, 2·02(3); NC, l·27(3); Rh–P, 2·290(4) and 2·291(4); and Rh–Ccarb, 2·006(15)A, and RhNC = 152°. Noteworthy are the significant departure from linearity at N and the exceptionally short mutually trans-Rh–P bond lengths; the M–NO/M–N:NR analogy is extended to M–N:CR2.

An X-ray structural analysis of the title compound (I) has converged at R 0.080 based on 1 332 reflections measured by diffractometer. The cobalt atom has square pyramidal co-ordination and is 0.38 A above the plane of the corrole ligand which is disordered in the crystal. There is an intermolecular contact of 3.0 A from a hydrogen atom of a phenyl ring to the vacant sixth co-ordination site of the cobalt. The structure was determined by the heavy-atom method. Crystals are monoclinic, space group P21/n, with Z= 4, in a cell of dimensions: a = 21.432(9), b= 13.513(6), c = 10.005(5)A, β= 95.20(2)°.

The methyl group in the 1 : 1 adduct of methyl iodide with the PtI–PtI dimer [Pt-µ-{o-C6H4P(Ph)CH2CH2PPh2}]2 is either bridging or migrating rapidly on the n.m.r. time-scale between the metal atoms; the adduct reacts with methyl-lithium to give a symmetrical dimethyldiplatinum(II) complex in which the co-ordination geometry about platinum is severely distorted from planarity, as shown by single-crystal X-ray structural analysis.