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.