O.G. Ellert

Antiferromagnetic complexes with metal-metal bonds: IX. Synthesis and molecular structures of methylcyclopentadienylchromium(III) sulfide diamagnetic tetramer and the antiferromagnetic copper(II) bromide adduct of the tetranuclear cluster (MeC5H4)4Cr4(μ3-O)(μ3-S)3

Abstract Reaction of (MeC5H4)2Cr with HSCMe3 gave (MeC5H4)2Cr2S(SCMe3)2 (I) in the form of violet antiferromagnetic crystals ( − 2J = 478 cm−1). Pyrolysis of I in xylene and its reaction with a CuBr2 solution in THF/Et3N (1/1) leads to readily-soluble black diamagnetic crystals of (MeC5H4)4Cr4S4(II). An oxygen-containing antiferromagnetic analog of complex II, (MeC5H4)4Cr4O4(III) was isolated on oxidation of (MeC5H4)2Cr with traces of oxygen in the presence of Ar. The reaction of I with CuBr2 in the absence of Et3N yielded black-green needle-like crystals of the antiferromagnetic adduct (MeC5H4)4Cr4S3O · CuBr2(IV) (μeff at room temperature is 3.91 BM). The structures of II and IV were established by X-ray crystallography. The molecule of II contains a metallotetrahedral Cr4 skeleton (CrCr 2.822(2) A) with faces centered at the μ3-bridged S atoms (CrS 2.248(2) A). Each Cr atom is bonded to a η5-MeC5H4 (CrCaver. 2.241(9) A). In IV the tetrahedral Cr4 skeleton is distorted owing to the μ3-O bridging ligand (CrCr 2.70(1)–2.78(1) A, CrSaver. 2.25(2) A, CrO 2.07(2)–2.12(2) A) and to CuBr2 coordination to a sulfur atom (CuBr 2.23(2) A, BrCuBr 163.9(8)°, Cu···S 320 A).

Antiferromagnetic complexes involving metal—metal bonds: V &. Synthesis, molecular structures and magnetic properties of an adduct, (CpCrSCMe3)2S·Mn2(CO)9, and a cluster, (CpCr)2(μ2-SCMe3)(μ3-S)2Co(CO)2, containing the CrCrCo metallocycle*

Summary The photochemical reaction of the antiferromagnetic binuclear complex (CpCrSCMe 3 ) 2 S (I, Cp=cyclopentadienyl) with Mn 2 (CO) 10 in THF yields the adduct (CpCrSCMe 3 ) 2 S·Mn 2 (CO) 9 (IV). According to X-ray diffraction data, the fragments in IV are linked through an Mn−S bond (2.448(2) A), and the geometry of I changes only insignificantly upon the addition of Mn 2 (CO) 9 : the Cr−Cr bond distance changes from 2.689(8) A in I to 2.740(8) A in IV, the Cr−S( sulphide ) bond length increases from 2.24(1) A (I) to 2.31(1) A (IV), whereas the Cr−S (thiolate) bond and CrSCr angles (72.7(3) and 71.4(3)°) remain almost unaffected. Accordingly, formation of the adduct has little affect on the magnetic properties of I (the exchange parameter, −2 J , value is equal to 440 cm −1 for IV and 430 cm −1 for I). Compound I reacts with Co 2 (CO) 8 in THF at 20°C without UV irradiation to give the trinuclear cluster, (Cp 2 Cr 2 SCMe 3 )-(μ 3 -S) 2 Co(CO) 2 (V). Compound V is antiferromagnetic (−2 J 530 cm −1 , the Co atom is diamagnetic) and, according to the X-ray structural data, contains the CrCrCo metallacycle (the bond lengths are: Cr−Cr, 2.617(1); Cr−Co, 2.579(1) and 2.592(1) A) and sulphide bridges above and below the metallacycle plane. The effect of the coordination number of M on the transformations of the adducts of the type (CpCrSCMe 3 ) 2 S·M 2 (CO) n is discussed.

Antiferromagnetic complexes involving metalmetal bonds. II. The conditions for observation and means of intented variation of antiferromagnetic properties of binuclear complexes involving CrCr and VV bonds

Abstract The complex (CpCrSCMe 3 ) 2 S (I), contains a CrCr bond (2.689 A) and at the same time shows antiferromagnetic properties (−2J = 430 cm −1 ). It reacts with PhEH (E is S, Se) or MeI to give binuclear complexes (CpCrEPh) 2 S or [(CpCrSCMe 3 ) 2 SMe] + I − characterized by exchange parameter, −2J, values of 496, 398, and 350 cm −1 , respectively. Reaction between Cp 2 Cr and PhEH yields the antiferromagnetic trimer [CpCr(SPh) 2 ] 3 (−2J = 194 cm −1 ) and dimer [CpCr(SePh) 2 ] 2 (−2J = 208 cm −1 ). CpV(CO) 4 reacts with PhEH to give dimeric complexes [CpV(EPh) 2 ] 2 one of which shows antiferromagnetic behaviour (E = Se, −2J = 700 cm −1 ) and the other one is a diamagnetic substance (E = S, −2J>> 1000 cm −1 ). The magnetic properties of the complexes are treated in terms of the exchange channel model. It is shown that antiferromagnetic behaviour (magnetic moment decreases with temperature) of binuclear complexes involving direct metalmetal bonds may be expected when the paramagnetic ions are in high-spin states (S ⩾ 1). In such complexes, variations in metalmetal bond strength caused by ligand substitution may be studied by the methods of magnetochemistry.

Antiferromagnetic complexes with a metal—metal bond: XII. Synthesis, molecular structures, and magnetic properties of the clusters (MeC5H4)2Cr2(μ-SCMe3)(μ3-S)2Co(CO)2 and (C5H5)2Cr2(μ-SCMe3)(μ3-S)2Mn(CO)3 with triangular Cr2M metal frames☆

Abstract The triangular cluster (MeC5H4)2Cr2(μ-SCMe3)(μ3-S)2Co(CO)2 V was obtained by reaction of the binuclear complex (MeC5H4)2Cr2(μ-SCMe3)2(μ3-S) (IV) with Co2(CO)8 in heptane. The structure of V was solved by an X-ray structural study. Crystals of V are monoclinic, space group P21, a 9.437(1), b 15.9460(8), c 7.2540(8) A, β 109.399(9), V 1029.6 A3, Z = 4, R = 0.047, Rw = 0.052. The main geometric parameters of V are close to those of its previously described cyclopentadienyl analogue (C5H5)2Cr2(μ-SCMe3)(μ3-S)2Co(CO)2 (III), however, the CrCr bonds in V are somewhat shorter (by 0.02–0.04 A) and the methylcyclopentadienyl rings are in a staggered conformation in contrast to the eclipsed conformation of the C5H5 ligands in III. A photochemical reaction of (C5H5)2Cr2(μ-SCMe3)2(μ3-S) (I) with Mn2(CO)10 with a reagent ratio of 2 1 in boiling benzene (3 h) yielded the heteronuclear cluster (C5H5)2Cr2(μ-SCMe3)(μ3-S)2Mn(CO)3 (VI), characterized by an X-ray study (space group C2, a 18.709(7), b 9.883(4), c 11.470(5) A, β 109.65(2)°, V 1997.3 A3 Z = 4). VI has a triangular metal frame Cr2Mn (CrCr 2.646(2), CrMn 2.828(2) and 2.716(2) A). The electronic and steric factors governing the formation of III, V and VI are discussed. I, III–VI exhibit antiferromagnetic properties with the exchange parameter (−2J) increasing on introduction of a methyl group into the cyclopentadienyl ligand, as well as with the formation of metal cycle Cr2M (−2J(CrCr) 430, 530, 478, 556, 654 cm−1, respectively).

Antiferromagnetic complexes involving metalmetal bonds IV. Synthesis, molecular structure and magnetic properties of the heterotrinuclear cluster, (C5H5Cr)2(μ2-SCMe3)(μ3-S)2Fe(CO)3, with direct and indirect exchange between CrIII and FeI centers ☆

Abstract The photochemical reaction between the antiferromagnetic complex (C5H5-CrSCMe3)2S (I) (containing a CrCr bond 2.689 A long) and Fe(CO)5 results in the elimination of two carbonyl groups and one tert-butyl radical to give (C5H5Cr)2(μ2-SCMe3)(μ3-S)2 · Fe(CO)3 (III). As determined by X-ray diffraction, III contains a CrCr bond of almost the same length as in I (2.707 A), together with one thiolate and two sulphide bridges. The latter are also linked with the Fe atom of the Fe(CO)3 moiety (average FeS bond length 2.300 A). Fe also forms a direct bond, 2.726 A long, with one of the Cr atoms, whereas its distance from the other Cr atom (3.110 A) is characteristic for non-bonded interactions. Complex III is antiferromagnetic, the exchange parameter, −2J, values for CrCr, Cr(1)Fe and Cr(2)…Fe are 380, 2600 and 170 cm−1, respectively. The magnetic properties of III are discussed in terms of the “exchange channel model”. The contributions from indirect interactions through bridging ligands are shown to be insignificant compared with direct exchange involving metalmetal bonds. The effects of steric factors and of the nature of the M(CO)n fragments on the chemical transformations of (C5H5CrSCMe3)2S · M(CO)n are discussed.

Antiferromagnetic complexes with metalmetal bonds: XVIII. The influence of electronic factors on geometry of heterometallospirane clusters. Molecular structure and magnetic properties of Cp2Cr2(μ-SCMe3)(μ3-S)2M(μ3-S)2Fe2(CO)6 (M = Fe, Rh) and (MeC5H4)2Cr2(μ-SCMe3)(μ3-S)2Co(μ3-S)2Fe2(CO)6☆

Reaction of Cp2Cr2(SCMe3)2S (I) with Fe3S2(CO)9 gives the novel metallospirane cluster Cp2Cr2(μ-SCMe3)(μ3-S)2Fe(μ3-S)2Fe2(CO)6 (II). Analogous clusters with Co and Rh as central ions (III and IV respectively) have been obtained from the reaction of (MeC5H4)2Cr2(μ-SCMe3)(μ3-S)2Co(CO)2 or Cp2Cr2(μ-SCMe3)(μ3-S)2RhL2 (L = CO, L2 = COD) with Fe2(CO)6S2. The X-ray diffraction study of II (space group P1, a 9.691(4), b 12.294(3), c 14.515(5) A, α 66.25(2), β 74.89(3), γ 78.61(3)°, V 1519.8 A3, Z = 2) reveals Cr2Fe and Fe3 triangles in the Cr2FeFe2 metallospirane core at a dihedral angle of 106.8°, and the geometry of dichromium disulfide thiolate fragment remains unchanged as compared to I, III and IV (CrCr 2.689; 2.610(2); 2.598(2); 2.608(5) A in IIV, respectively). II has strong CrFe bonds (2.717(2) and 2.727(2) A, but the two bonds between the central and peripheral Fe atoms (3.018(2) and 3.032(2) A) are relatively weak. The peripheral FeFe bond (2.503(2) A) is still rather short. Formal replacement of the Fe atom in II by the Co atom in III (space group Pnam, a 14.549(2), b 14.480(2), c 14.146(2) A, V 2980.1 A3, Z = 4) results in the rupture of the FeFe bond (Fe…Fe 3.399(2) A) and formation of the two single CoFe bonds (2.554 (2) and 2.538(2) A). The dihedral angle between the planes of the metal triangles Cr2Co and CoFe2 in III is 90°. The geometry of the Rh(S)2Fe2(CO)6 moiety in the Rh-containing metall-spirane IV (space group P21/n, a 9.800(2), b 12.983(3), c 22.606(5) A, β 97.05(2)°, V 2854.3 A3, Z = 4) is not significantly different from that of the Co(S)2Fe2(CO)6 fragment in III (RhFe 2.650(4) A, Fe…Fe 3.344(4) A), the main difference involves the dihedral angle between the Cr2Rh and RhFe2 planes, which is 129.1° in IV. This difference being due to the tendency of the RhI atom to form the square planar complexes on one hand, and to decreasing the repulsion between the S atoms and the strengthening the RhCr bonds in the nonplanar ligand environment of the Rh atom on the other.

Interaction of carbon dioxide with acetylene complexes of titanocene Cp2Ti(RC2R) (R Ph, SiMe3). Synthesis and structure of binuclear σ-alkenylcarboxylate complexes of titanium (III) Cp2TiC(R)C(R) COOTiCp2 and unexpected transformation of these complexes into titanafuranone metallacycles under the action of air oxygen

Abstract It has been shown that carbon dioxide reacts with acetylene complexes of titanocene Cp2Ti(RC2R) (RPh, SiMe3) at room temperature and atmospheric pressure to form binuclear σ-alkenylcarboxylate complexes of trivalent titanium Cp2TiC(R)C(R)COOTiCp2 containing two fused chelate cycles and a tricoordinated oxygen atom. The interaction of these binuclear carboxylate complexes with air oxygen at 20°C results in rapid formation of titanafuranone metallacycles Cp 2 Ti(R)=C(R)C(O)O . X-ray diffraction studies of complexes Cp2TiC(SiMe3)C(SiMe3)COOTiCp2 and Cp 2 Ti(Ph)=C(Ph)C(O)O have been carried out.

Antiferromagnetic complexes involving metalmetal bonds III. Synthesis, structure and magnetic properties of heterotrinuclear complexes of the type M(CO)5L (M Cr, Mo and w) containing [(C5H5CrSCMe3)2S] as unusual antiferromagnetic ligand L

Isostructural heterotrinuclear complexes (C 5 H 5 CrSCMe 3 ) 2 S · M(CO) 5 (II–IV) were isolated from photochemical reactions between the antiferromagnetic complex (C 5 H 5 CrSCMe 3 ) 2 S (I) (with the CrCr bond 2.689 A long and with the exchange parameter −2 J = 430 cm −1 ) and metal hexacarbonyls, M(CO) 6 , where M is Cr, Mo, or W. According to the X-ray structural data on III and IV, complex I plays the role of an unusual antiferromagnetic ligand L bound to M through the sulphide bridge (M–S 2.58(2) A). Its geometry remains practically unaffected by the complex formation (the CrCr bond length in III and IV is 2.73(1) A). The exchange parameter, −2 J (410, 440 and 440 cm −1 in II to IV, respectively), also shifts only insignificantly from that of I, which probably means that indirect exchange via the sulphide bridge in I is of minor importance compared with the direct CrCr exchange. The CrCr bond length may thus be correlated with the observed overall exchange coupling.

Synthesis, molecular structure, and magnetic properties of bis(3,6-di-tert-butyl-o-benzosemiquinone)nickel(II) and -copper(II)

The title complexes of Ni and Cu with symmetrical 3,6-di-tert-butyl-o-benzosemiquinone are synthesized. Their EPR spectra and magnetic properties are investigated. The x-ray structure studies [Siemens R3/PC diffractometer, λ MoKα, ϑ/20-scanning in the rang 2 ≤ 2ϑ ≤ 54°, 2084 reflections withF > 4σ(F),R = 0.034,Rw = 0.039, monoclinic crystals,a = 9.982(2),b = 11.548(2),c = 12.145(2) Å, β = 95.05(3)°,Z = 2,dcalc = 1.19 g/cm−3, space groupP2l/c) demonstrated that the complex is monomeric with square-planar coordination for the Ni with theo-semiquinone ligands. The Cu complex is isostructural with the Ni (a = 9.88,b = 11.60,c = 12.15 Å, β = 95°]. The dependence of the magnetic moment of the Cu complex on temperature is consistent with the presence in it of two pathways for exchange interaction. These are antiferromagnetic ligand-ligandJ12 = −179 cm−1 and ferromagnetic metal-ligandJ13 = 100 cm−1 (mean-square deviation 2%). The Ni complex is diamagnetic over the whole studied temperature range despite the fact that it contains free-radicalo-semiquinone ligands. Such an effect involving electrons belonging to the free-radical ligands is observed for the first time in the magnetochemistry ofd8- andd9-transition-metal complexes. It is explained by incorporation of vacantpz- and/or occupieddxz- anddyz-orbitals of Ni in molecular orbitals containing the π-MO of the semiquinone ligands.

Interaction of Heteronuclear chromium-containing clusters with carboxalic acids. Molecular structure of the paramagnetic tetrahedral cluster Cp3Cr3(μ3-S)4Fe(OOCCMe3)

Abstract The reaction of (CpCrSCMe 3 ) 2 S and the adducts (CpCrSCMe 3 ) 2 S·ML (ML = Cr(CO) 5 , Mn 2 (CO) 9 and cluster (CpCrS) 2 (SCMe 3 )·Fe(CO) 3 (I) (containing CrCrFe metal chain) with benzoic acid gives the respective antiferromagnetic μ 3 -thio-bridged carboxylates Cr 2 MS(OOCPh) 6 (M = Cr(II), Mn(II), Fe(II)) (II–IV). On the other hand the reaction of I with the weaker trimethylacetic acid yields the tetrahedral cluster Cp 3 Cr 3 (μ 3 -S) 4 Fe(OOCCMe 3 ) (V) containing two unpaired electrons (μ eff = 2.81 BM). Crystal structure of V was solved by means of X-ray analysis (sp. gr. C2)c, a = 28.905(2), b = 9.563(2), c = 23.789(2) A, β = 131.84(3)°, V = 4902.8(4) A 3 Z = 4). In the metal tetrahedral skeleton Cr 3 Fe the average bond lengths CrCr and FeCr are 2.838(3) and 2.759(3) A respectively. The μ 3 -bridged sulfur atom locates over each tetrahedron face (the average CrS and FeS distances are 2.258(4) and 2.218(4) A respectively). Each chromium atom is combined to η 5 -C 5 H 5 ligand (the average CrC and CC distances are 2.224(20) and 1.391(30) A). The iron atom is bound to a terminal trimethylacetate group (FeO 1.896(10), O(1)C(1) 1.318(13), O(2)C(1) 1.252(21) A).