G.Sh. Gasanov

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 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).

The effect of electron deficit on the geometry of sulphide bridged methylcyclopentadienylmetal tetrahedra. Synthesis, physicochemical characteristics, and molecular structures of Cp′3Cr3(μ3-S)4Co(CO), Cp′4Cr4(μ3-O)(μ3-S)3+ ZnCl3·C4H8O−, and Cp′4V4S4 (Cp′ = π-CH3C5H4)

Abstract A diamagnetic electron-saturated cluster, Cp′ 3 Cr 3 (μ 3 -S) 4 Co(CO) (I), was obtained by heating a heterotrinuclear cluster, Cp′ 2 Cr 2 SCMe 3 (μ 3 -S) 2 Co(CO) 2 (Cp′ = π-CH 3 C 5 H 4 ), in heptane in the presence of diphenylacetylene. The treatment of (Cp′CrSCMe 3 ) 2 S with anhydrous ZnCl 2 in THF led to an electron-deficient cationic cluster, Cp′ 4 Cr 4 (μ 3 -O)(μ 3 -S) + 3 (II), with one unpaired electron (ZnCl 3 · thf − is the anion). Interaction between Cp′ 2 V and t-butylmercaptan in boiling heptane gives Cp′ 4 V 4 S 4 (III) which is a new member in the family of cubane clusters, Cp 4 M 4 S 4 , and contains an electron-deficient metal tetrahedral skeleton with two unpaired electrons. The structure of compounds I–III was determined by an X-ray diffraction study. I contains the metal tetrahedral Cr 3 Co skeleton which is flattened down the axis joining Co and the centre of the Cr 3 base (CrCo 2.692(4), CrCr 2.816(3) A). The μ 3 -S bridge is located above each face (CoS average, 2.171(6) A; CrS average, 2.255(5) A). The Co atom is also linked to the terminal CO group (CoC 1.82(2) A). and each Cr atom is bonded to the π-CH 3 C 5 H 4 (CrC average, 2.29(2) A. The cationic cluster in II is a distorted tetrahedron in which the CrCr bonds at the sulphide bridge faces (average, 2.765(2) A) are longer than those at the oxygen bridge face (average, 2.687(2) A). The CrO bonds (average, 1.994(5) A) are shorter than the CrS bonds (average, 2.224(3) A), and both are shorter than their counterparts in the neutral cluster, Cp′ 4 Cr 4 (μ 3 -O)(μ 3 -S) 3 ·CuBr 2 described previously, presumably because of the enhancement of π-bonding in both OCr and SCr bonds. This interaction is particularly noticeable in III, which has a strongly electron-deficient metal V 4 skeleton (VS average, 2.292(3) A) which gives rise to short VV distances (average, 2.867(3) A). The molecule of III is sterically not strained, the VC distances (average, 2.28(1) A) being close to distances expected for ordinary bonds. The physicochemical properties of I–III and the specific features of bonding peculiar to these clusters in relation to the electron deficit of their metal skeletons are discussed.

Antiferromagnetic complexes with a metal-metal bond: XV. Antiferromagnetic heterometallospirane clusters [(CH3C5H4)2Cr2(μ-SCMe3)(μ3-S)2]2M (M = MnII, FeII): Synthesis and molecular structures☆

Abstract The reaction of (CH 3 C 5 H 4 CrSCMe 3 ) 2 S (Ia) with Cp 2 Mn in boiling toluene (containing some THF) has been used to prepare a pentanuclear cluster, [(CH 3 C 5 H 4 ) 2 Cr 2 (SCMe 3 )(μ 3 -S) 2 ]Mn (II), which is antiferromagnetic and crystallizes into the monoclinic crystal system: space group Cc , a 26.540(10), b 9.208(3), c 21.595(9) A; β 135.30(2)°, V = 3712.1 A 3 , Z = 4. According to X-ray analysis, cluster II contains a metallospirane core, Cr 4 Mn, which appears to be strongly distorted, compared to its earlier studied cyclopentadienyl analogue [Cp 2 Cr 2 SCMe 3 (μ 3 -S) 2 ] 2 Mn, due to the short intramolecular contacts CH 3 …S (2.9–3.1 A). The angle between the metal triangle planes of Cr 2 Mn is 109.60°. Here, the two long CrMn bonds (3.019(3) and 3.104(4) A) are combined with the shorter Cr Cr bond (2.651(6) A) in one triangle and, vice versa, the less extended CrMn bonds (2.839(4) and 2.967(3) A) are combined with a longer CrCr bond (2.726(6) A) in the other triangle of Cr 2 Mn. By the reaction of Ia with [CpFe(CO) 2 ] 2 (taken in the ratio of 2 1 ) in boiling toluene, the antiferromagnetic cluster [(CH 3 C 5 H 4 ) 2 Cr 2 (SCMe 3 )(μ 3 -S) 2 ] 2 Fe (III) has been synthesized in which the same distortions as in cluster II are present, as revealed by X-ray analysis. In the metallospirane core of the molecule of III, the Cr 2 Fe triangles make an angle of 113.84° with each other. In this cluster, the CrCr distances in the peripheral binuclear fragments (CH 3 C 5 H 4 ) 2 Cr 2 (μ-SCMe 3 )(μ 3 -S) 2 are practically equal (2.688(3) and 2.661(3) A), whereas the FeCr bond lengths are markedly different (2.749(2) and 2.827(2) A in on triangle and 2.910(2) and 2.969(2) A in the other). The dependence of the geometries of clusters II and III on the steric effects of the methyl substituents in the cyclopentadienyl ligands and on the electronic effect of the central metal atom (Mn II or Fe II ) is discussed.

Synthesis and molecular structure of diamagnetic heterometallic clusters (RC5H4)2Cr2(μ3-S)2(μ4-S)Co2(CO)4 with a Cr2Co2 “butterfly” frame

Abstract The interaction of (RC5H4)2Cr2(SCMe3)2(μ-S) (I, R = H; Ia, R = CH3) with Co2(CO)8 in a molar ratio of 1 1 gave the 62-electron, heteronuclear clusters (RC5H4)2Cr2(μ3-S)2(μ4-S)Co2(CO)4 (II and IIa respectively), which were characterized by X-ray crystallography. Crystals of Illa are monoclinic, space group C2/c, a 15.246(1), b 11.846(9), c 9.9434(6) A, β 100.965(6)°, V 1763 A3, Z = 4, R = 0.046, Rw = 0.057. Crystals of IIa are triclinic, space group P , a 9.9771(9), b 10.1120(10), c 11.0770(10) A, α 116.982(8), β 99.560(8), γ 82.054(8)° , V 979.5 A3, Z = 2, R = 0.064, Rw = 0.060. The two clusters have a Cr2Co2 “metal butterfly” framework. In II, the CrCr separation is 2.544(1) A and those of CrCo are 2.622(1) and 2.617(1) A, the dihedral angle between the Cr2Co wings of the butterfly is 124.2°. The μ3-sulphide bridge is situated below each wing whereas the μ4-sulphide bridge is located between the wings. The average distances are: Cr-(μ3-S), 2.258(2), Cr-(μ4-S), 2.326(2), CO-(μ3-S), 2.178(2), Co-(μ4-S) 2.205(2) A. The geometry of IIa differs from II in that it has the staggered ring conformation instead of the eclipsed, it has non-equivalent CoCr bonds (av. 2.634(2) and 2.614(2) A) and has slightly shortened Co-(μ4-S) bonds (av. to 2.193(3) A). The structures of II and IIa were compared with the geometries of previously studied clusters, viz. the 66-electron “metal chain” Cp2Cr2(μ3-S)2(μ4-S)Ni2Cp2 and 62-electron “metal butterfly” Cp2Mo2(μ3-S)2(μ4-S)Co2(CO)4.

Antiferromagnetic complexes with a metal—metal bond: XIII. Transformation of μ3-sulphide clusters containing chromium and cobalt atoms by treatment with pivalic acid. Molecular structures of the pseudotetrahedral cluster Cp3Cr3(μ3-S)3(μ3-O)Co(CO)3 · Me3CCOOH · 0.5C6H6, and the heterometallic “bow-tie” cluster (Cp2Cr2SCMe3)2(μ3-S)4Co

Abstract The influence of pivalic acid on the triangular metal cluster (Cp 2 Cr 2 SCMe 3 )(μ 3 -S) 2 Co(CO) 2 (II) and its unstable precursor with a probable structure (Cp 2 Cr 2 SCMe 3 ) 2 (μ 3 -S) 2 Co(CO) 3 (A) has been studied. An X-ray study has shown that A transforms into an antiferromagnetic ** pseudotetrahedral cluster Cp 3 Cr 3 (μ 3 -S) 3 (μ 3 -O)Co(CO) 3 · Me 3 CCOOH · 0.5C 6 H 6 (III). The base of the cluster is an isosceles metal triangle, Cp 3 Cr 3 , which is capped by the tridentate bridging sulphur atom (CrCr 2.692(7), 2.868(8) and 2.884(8) A, av. CrS 2.26(1) A). The short CrCr bond is bridged by an oxygen atom, and the long bonds have sulphide bridges which in their turn are weakly bonded to the Co(CO) 3 group (CoO 2.16(2), CoS 2.47(1) and 2.48(1) A). In addition, the μ 3 -O bridging atom forms a hydrogen bond with the HOOCCMe 3 molecule, while the Co atom is situated at weakly-bonding distances from the Cr III atoms (CoCr 3.216(6), 3.238(6) and 2.892(6) A). The transformation of cluster II in the reaction with Me 3 CCOOH leads to the antiferromagnetic cluster (Cp 2 Cr 2 SCMe 3 ) 2 (μ 3 -S) 4 Co (IV), which according to an X-ray structural study, has a distorted bow-tie framework Cr 4 Co with the central Co II atom surrounded also by four μ 3 -bridging sulphide atoms. The angle formed by the planes of the Cr 2 Co metal triangles is equal to 85.40°. The bond lengths between pairs of chromium atoms in different triangles are almost equal (2.679(2) and 2.665(2) A) and close to the length of the CrCr bond in the initial cluster II. At the same time, CoCr bonds in one of the triangles (2.776(2) and 2.774(2) A) are noticeably shorter than in the other (2.809(2) and 2.959(2); all these values exceed, however, the length of the ordinary CoCr bond (2.59 A) found in II. The CoS bonds are also elongated (up to 2.26 A). It is proposed that elongation of CoCr bonds in III and IV (as well as CoO in III) results from an excessive number of electrons in the metal framework as compared to the number of corresponding bonding orbitals.

Antiferromagnetic complexes with a metal-metal bond: XIV. Synthesis and molecular structure of the antiferromagnetic cluster [Cp2Cr2(SCMe3)(μ3-S)2]2Mn, containing a heterometallic “bow-tie” Cr4Mn framework☆☆☆

Abstract The antiferromagnetic cluster [Cp 2 Cr 2 (SCMe 3 )(μ 3 -S) 2 ] 2Mn (II) was obtained by reaction of (CpCrSCMe 3 ) 2 S with CpMn(CO) 3 (reagent ratio 2:1) under UV irradiation in boiling toluene. The structure of II was established by an X-ray structural study. Crystals of II are orthorhombic, space group F dd 2, a = 39.715(13), b = 21.127(7), c = 7.808(3) A, V = 6551.4 A 3 , Z = 8. The molecule of II has a symmetrical bow-tie metal framework Cr 4 Mn with short CrCr bonds (2.690(4) A) and elongated CrMn bonds (2.936(3) and 2.947(3) A). The angle between the planes of Cr 2 Mn triangles is equal to 90°. The central Mn II atom ( d 5 electron configuration) is situated on a crystallographic two-fold axis and, besides Cr atoms, is surrounded by four μ 3 -bridging sulphur atoms (MnS, 2.393(5) and 2.389(5) A). Both CrCr bonds are bridged by a tert-butylthiolate group (av. CrS 2.347(5) A).

Antiferromagnetic complexes with metal-metal bonds XXVI. Synthesis, molecular structure and magnetic properties of mixed-metal triangular clusters, Cp2Cr2(μ-SR)(μ3-S)2FeCp (R = CMe3 or Ph) and linear mixed-metal chain CpCr(μ-SPh)3Fe(μ-SPh)3CrCp

Abstract The antiferromagnetic triangular cluster Cp 2 Cr 2 (μ-SCMe 3 )(μ 3 -S) 2 FeCp ( II ) ( - 2 J = 520 cm −1 ) with a strongly bonded Cr 2 Fe metal core (CrCr 2.650(3), CrFe 2.666(3) and 2.675(2) A) was obtained by prolonged photochemical reaction of Cp 2 Cr 2 (μ-SCMe 3 ) 2 (μ-S) ( I ) and Cp 2 Fe 2 (CO) 4 in THF. It was shown that thermal reaction between complex I and Cp 2 Fe 2 (CO) 2 (μ-SPh) 2 yields two clusters, diamagnetic triangular Cp 2 Cr 2 (μ-SPh)(μ 3 -S) 2 FeCp ( III ) and antiferromagnetic metal chain CpCr(μ-SPh) 3 Fe(μ-SPh) 3 CrCp ( IV ) (μ eff . 5.29 (296 K) - 3.95 (77 K) μ B ). Complex III as well as II involves the strongly bonded metal core Cr 2 Fe (CrCr 2.637(3), CrFe 2.644(3) and 2.672(3) A), whereas the FeCr bonds in the linear chain of IV are considerably elongated (up to 2.996(3) and 2.969(3) A), which is in agreement with their reduced bond order (equal to 1/2).

Antiferromagnetic complexes with a metal—metal bond: XI. Synthesis and structure of the pentanuclear cyclopentadienyl-t-butylthiolate-sulphidechromium cluster [Cp2Cr2(μ2-SCME3)(μ3-S)2]2Cr with a “bow-tie” frame☆

Abstract The reaction of the binuclear complex Cp 2 Cr 2 (SCMe 3 ) 2 S (I) with C 6 H 6 Cr(CO) 3 in a benzene/heptane ( 1 2 ) mixture under UV irradiation yields black crystals of the cluster [Cp 2 Cr 2 (SCMe 3 )S 2 ] 2 Cr (II), which, according to X-ray data, contains a pentanuclear “bow-tie” frame with a central Cr II atom, the angle between the Cr 3 triangle planes being 90°. The bonds between the central and peripheral chromium atoms are oridinary (2.933(1) and 2.889(1) A), while two pairs of Cr II atoms are double-bonded (CrCr 2.655(1) A). Above and below each Cr 3 triangle is a μ 3 -sulphide bridge (average Cr (centr.) S 2.333(3), average Cr (periph.) S 2.305(3) A). Moreover, the peripheral Cr III atoms are bonded in pairs with a μ 2 -SCMe 3 bridge (average CrS 2.358(4) A), and every Cr III atom is coordinated by a π-cyclopentadienyl ligand (average CrC 2.26(1) A, average CC 1.43(2) A).

Synthesis and structure of the heterotrinuclear chromium-palladium clusters (RC5H4CrCl)2-(μ3S)(μ-SCMe3)2Pd(PPh3) with ferromagnetic exchange interactions over the CrSCr system

Abstract Reactions of (RC5H4)2Cr2(SCMe3)2S(I, R = H; II, R = Me) with (PPh3)2PdCl2 in benzene at 20°C gives trinuclear complexes (RC5H4)2Cr2Cl2(μ3-S)(μ-SCMe3)2Pd(PPh3)(III, R = H; IV, R = Me). The structure of IV as a monobenzene solvate is established by an X-ray analysis (black-green triclinic crystals space group P 1 with a = 11.403(4), b = 14.933(5), c = 14.131(5) A, α = 99.13(3), β = 112.72(3), γ = 95.65(3)°, V = 2201.6 A, Z = 2; IV·C6H6). The structure was solved by direct methods and refined in an anisotropic approximation to R = 0.046, Rw = 0.058 for 7643 reflections with I ⩾ 2σ(I). In the molecule of IV metal atoms are separated by non-bonding distances (Cr … Cr 4.079(I), Cr … Pd 3.230(I) and 3.380(I) A) but linked by the bridging tridentate sulphur atom (CrS 2.339(2) and 2.329(2), PdS 2.327(2) A), and two SCMe3 groups between Pd and Cr (CrS 2.396(2) and 2.403(2), PdS 2.350(2) and 2.381(2) A, CrŜPd 85.14(6) and 89.92(6)°). The Cl atoms are transferred from Pd to Cr atoms (CrCl 2.308(2) A) and being terminally coordinated are in trans-positions to each other (as well as η-CH3C5H4 rings) with respect to the Cr2Pd plane. Cr atoms in III and IV exhibit ferromagnetic exchange interactions over the CrŜCr system (+2J = 28 and 11 cm−1, respectively).