Binuclear thiolato-bridged complexes of general formula [(η5-C5Me5)2Rh2(μ-Pz)(μ-SR)2]BF4 (Pz=pyrazolate; R=C6F5 (2a), p-C6F4H (2b), p-C6H4F (2c) or C6H5 (2d)) have been prepared by reacting the hydroxo–pyrazolato-bridged compound [(η5-C5Me5)2Rh2(μ-Pz)2(μ-OH)] BF4 with the corresponding thiol. Complexes 2a–d show two types of fluxionality: rotation around the thiol C–S bond and isomerization among the three possible isomers in which the thiols occupy axial and/or equatorial positions within the Rh2S2 metallacycle. These processes are studied by 1H and 19F NMR spectroscopies. The crystal structures of 2b and 2d were established by X-ray crystallography. Compound 2b crystallises in the monoclinic space group P21/n, with lattice parameters a=14.368(2), b=18.252(2), c=15.268(2) Å, β=109.79(1)° and Z=4. Complex 2d crystallises in a monoclinic lattice, space group C2/c, with a=48.723(5), b=8.7503(8), c=40.334(4) Å, β=112.620(5)° and Z=16. Both cationic dinuclear complexes exhibit very similar molecular structures with analogous pseudo-octahedral environments for the rhodium centres. Each metal is bonded to a terminal η5-C5Me5 group and to three bridging ligands: two monodentate thiolates (p-SC6F4H in 2b and SC6H5 in 2d) and a bidentate pyrazolate group. The main structural dissimilarity affects the relative configuration of the thiolate phenyl substituents giving rise to syn (2b) or anti (2d) structures.

Treatment of the metallo ligands [ML(pz)(2)(Hpz)] (pz = pyrazolate; L = C(5)Me(5), M = Ir (1); L = mesitylene, M = Ru (3)) with [M'Cl{HB(3-i-Pr-4-Br-pz)(3)}] (M' = Co (4), Ni (5)) yields heterodinuclear complexes of formula [LM(&mgr;-pz)(2)(&mgr;-Cl)M'{HB(3-i-Pr-4-Br-pz)(3)}] (L = C(5)Me(5); M = Ir; M' = Co (6), Ni (7). L = mesitylene; M = Ru; M' = Co (8)). The related complex [Ru(eta(6)-p-cymene)(pz)(2)(Hpz)] (2) reacts with equimolar amounts of 4 or 5 to give mixtures of the corresponding bis(&mgr;-pyrazolato) &mgr;-chloro complexes [(eta(6)-p-cymene)Ru(&mgr;-pz)(2)(&mgr;-Cl)M'{HB(3-i-Pr-4-Br-pz)(3)}] (M' = Co (9), Ni (10)) and the triply pyrazolato-bridged complexes [(eta(6)-p-cymene)Ru(&mgr;-pz)(3)M'{HB(3-i-Pr-4-Br-pz)(3)}] (M' = Co (11), Ni (12)). Complex 1 reacts with 5 in the presence of KOH to give the IrNi complex [(eta(5)-C(5)Me(5))Ir(&mgr;-pz)(3)Ni{HB(3-i-Pr-4-Br-pz)(3)}] (13) whereas its reaction with 4 and KOH rendered the bis(&mgr;-pyrazolato) &mgr;-hydroxo complex [(eta(5)-C(5)Me(5))Ir(&mgr;-pz)(2)(&mgr;-OH)Co{HB(3-i-Pr-4-Br-pz)(3)}] (14). The molecular structure of the heterobridged IrCo complex (6) and those of the homobridged RuNi (12) and IrNi (13) complexes have been determined by X-ray analyses. Compound 6 crystallizes in the monoclinic space group P2(1)/n, with a = 10.146(5) Å, b = 18.435(4) Å, c = 22.187(13) Å, beta = 97.28(4) degrees, and Z = 4. Complex 12 is monoclinic, space group P2(1), with a = 10.1169(7) Å, b = 21.692(2) Å, c = 11.419(1) Å, beta = 112.179(7) degrees, and Z = 2. Compound 13 crystallizes in the monoclinic space group Cc, with a = 13.695(2) Å, b = 27.929(6) Å, c = 13.329(2) Å, beta = 94.11(4) degrees, and Z = 4. All the neutral complexes 6, 12, and 13 consist of linear M.M'.B backbones with two (6) or three (12, 13) pyrazolate ligands bridging the dimetallic M.M' units and three substituted 3-i-Pr-4-Br-pz groups joining M' to the boron atoms. The presence in the proximity of the first-row metal M' of the three space-demanding isopropyl substituents of the pyrazolate groups induces a significant trigonal distortion of the octahedral symmetry, yielding clearly different M'-N bond distances on both sides of the ideal octahedral coordination sphere of these metals.

The reaction of [{Rh(C(5)Me(5))}(2)(mu-L)(mu-OMe)(2)]BF4 [L = pyrazolate (pt), 3-methylpyrazolate. 3,5-dimethylpyrazolate or 3(5)-bromo-5(3)-methylpyrazolate] with HPPh(2) has been studied. Complexes of general formulae [{Rh(C(5)Me(5))}2(mu-L)(mu-OH)(mu-PPh(2))]BF4, [{Rh(C(5)Me(5))}(2)(mu-L)(-PPh(2))2]BF4 and [{Rh(C(5)Me(5))}(2)(mu-OH)(2)(mu-PPh(2))]BF4 were prepared and characterized by analytical and spectroscopic means. The crystal structure of [{Rh(C(5)Me(5))}(2)(mu-pz)(mu-PPh(2))(2)]BF4 . CHCl3 was determined. The rhodium atoms show pseudo-octahedral geometry and are separated by 3.473(1) Angstrom. The mu-hydroxo complexes [{Rh(C(5)Me(5))}(2)(mu-L)(mu-OH)(mu-PPh(2))]BF4 react with hydrochloric acid affording the corresponding mu-chloride compounds [{Rh(C(5)Me(5))}(2)(mu-L)(mu-Cl)(mu-PPh(2))]BF4, which in turn have been also prepared from [{Rh(C(5)Me(5))}(2)(mu-OH)(3)]BF4, HL, HPPh(2) and HCl in 1:1:1:1 ratio. The crystal structure of [{Rh(C(5)Me(5))}2(mu-pz)(mu-Cl)(mu-PPh(2))]BF4 . CHCl3 has been determined. Two (C(5)Me(5))Rh moieties are connected by three different anionic ligands, pz, Cl and PPh(2). The rhodium atoms are separated by 3.432(1) Angstrom. Aged solutions of reaction mixtures of [{Rh(C(5)Me(5))}(2)(mu-L)(mu-OMe)(2)]BF4 and HPPh(2) contain [{Rh(C(4)Me(5))}(2)(mu-Ph(2)PO(2))(2)(mu-PPh(2))]BF4, the diphenylphosphinato ligands arising from Ph(2)P(O)OH, an oxidation product of HPPh(2). The crystal structure of the solvate has been established. Two Ph(2)PO(2) groups and a PPh(2) ligand bridge two (C(5)Me(5))Rh units. The rhodium-rhodium distance is 4.049(1) Angstrom. The mu-hydrido complex [{Rh(C(5)Me(5))}(2)(mu-H)(mu-pz)(mu-PPh(2))] has been prepared by treating [{Rh(C(5)Me(5))}(2)(mu-OH)(3)]BF4 with Hpz and HPPh(2) in refluxing propan-2-ol.

The behaviour of the ligand 2,5-bis(pyrazol-1′-yl)-1,4-dihydroxybenzene (H2LL) towards RhI, IrI, RhIII and IrIII complexes is reported. This compound with two OH groups might act as a neutral ligand (H2LL), as a monoanionic ligand (HLL−) or as a dianionic ligand (LL2−). Complexes of all the three kinds have been isolated. In the case of H2LL, the compounds are not organometallic complexes but clathrates. The crystal and molecular structure of the host-guest complex [{(η5-C5Me5)RhCl}2-(μ-Cl)2]-H2LL (6a) is reported. Both the host and the guest have crystallographic Ci symmetry. No metal-H2LL chemical bonds are present, and van der Waals interactions between host and guest molecules govern the crystal packing. An heterobimetallic derivative [IrRh(η5-C5Me5)Cl2(LL)] (7c) has been isolated.

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The complete 1 H and 19 F NMR analysis of TFB and Me 3 TFB has been carried out. Some new long distance coupling constants have been determined.

The behaviour towards RhI of a new ligand containing three linked pyrazoles (HLL) has been studied. Depending on which diolefin, COD or TFB, is used, mono or dinuclear complexes are obtained. The structures of the four complexes, [RHCl(COD)(HLL)], [{RhCl(TFB]}2(μ-HLL)], [Rh(LL)(COD)] and [{Rh(TFB)}2(μ-LL)BF4, have been established by 1H and 13C NMR spectroscopy. In most cases, the NMR spectra reveal fluxional processes involving not only the RhI metal but also the N-H proton and the diolefin.

AbstractThe preparation of the new mononuclear complexes (III), (IV), and (VI) containing unidentate pyridazine ligands is carried out according to the scheme.

The preparation and characterization of the new mononuclear complexes [Rh(C5Me5)Cl2(pydz)], [Rh(C5Me5)Cl(pydz)2][X], and [Rh(C5Me5)(acac)(pydz)][X](pydz = pyridazine, X = BF4 or ClO4, acac = acetylacetonate) are reported. The mononuclear complex [Rh(C5Me5)Cl2(pydz)] reacts with the solvated species [Rh(C5Me5)L3][X]2(L = acetone) to form [{Rh(C5Me5)}2(µ-Cl)2(µ-pydz)][X]2. The structure of the latter complex (X = ClO4) has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P21/n with Z= 4 in a unit cell of dimensions a= 22.2761(9), b= 7.940 7(1), c= 19.359 5(8)Å, and β= 109.824(3)°. The structure was solved by Patterson analysis and refined by full-matrix least-squares methods to R= 0.047 for 3 970 observed reflections. The cation consists of two Rh(C5Me5) moieties triply bridged by two chlorine atoms and a pyridazine group. The latter co-ordinates in an exo-bidentate manner through the two nitrogen atoms. The two rhodium atoms are separated by 3.397(1)Å. Attempts to isolate homovalent double-bridged complexes of general formula [Rh2(C5Me5)2Cl2(pydz)2]2+ or mixed-valence rhodium(III)-rhodium(I) complexes of formulae [(C5Me5)ClRh(µ-Cl)(µ-pydz)Rh(tfb)]+ or [(C5Me5)ClRh(µ-pydz)2Rh(tfb)]2+(tfb = 5,6,7,8-tetrafluoro-1,4-dihydro-1,4-ethenonaphthalene) have been unsuccessful.

The synthesis and properties of rhodium(I) complexes of formulae [“RhCl(diolefin)”2(L)] (or [Rh(Cl(diolefin)(L)]), and [Rh(diolefin)(L)]n(ClO4)n are reported. These complexes react with carbon monoxide to yield the related carbonyl derivatives. Ligands used were pyridazine, 4,6-dimethyl-pyrimidine, 4,6-bis(3,5-dimethylpyrazol-1-yl)pyrimidine, 3,6-bis(3,5-dimethylpyrazol-1-yl)pyridazine and 3-(3,5-dimethyl-pyrazol-1-yl)-6-chloropyridazine. Related iridium(I) and gold(I) compounds are also reported.

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 · 12C2H4Cl2 is presented; the final R factor is 0.061 for 2436 observed data, recorded with Cu-Kα, 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)°.

The preparation of cationic rhodium(I) complexes of the type [Rh(diolefin)L2]ClO4 (L = 4-NH2py, 2-NH2py, 4-NMe2py, 4-CNpy or 2-CNpy) and of polynuclear compounds of the type [Rhn(diolefin)n(L-L)n(ClO4)n (L-L = 4,4′-bipy, pyz or 4-CNpy), in which the metal centres are bridged by the nitrogen-donor ligands, are described. Related rhodium(I) mono- and polynuclear carbonyls are also reported.