In this review article, we discuss advances in the chemistry of metal carbonyl clusters (MCCs) spanning the last three decades, with an emphasis on the more recent reports and those involving groups 8–10 elements.

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Triangular clusters [{MFe­(CO)4}3]3– (M = Cu, 4; Ag, 5; Au, 6) were selectively obtained by heating Fe­(CO)4(MIMes)2 (M = Cu, 1; Ag, 2; Au, 3; IMes = C3N2H2(C6H2Me3)2). 1–3 were synthesized by reacting Na2[Fe­(CO)4]·2thf with 2 equiv of M­(IMes)­Cl. As previously described, the direct reactions of Na2[Fe­(CO)4]·2thf with one equivalent of M­(I) salts resulted in the triangular cluster [{CuFe­(CO)4}3]3– for Cu, whereas the square clusters [{MFe­(CO)4}4]4– were formed for Ag and Au. Thus, depending on the synthetic protocol adopted, both the triangular [{MFe­(CO)4}3]3– and square [{MFe­(CO)4}4]4– polymerization isomers can be selectively obtained, at least for Ag and Au. Polymerization isomerism, that is two compounds having the same elemental compositions but different molecular weights, was investigated in [{MFe­(CO)4} n ] n− (n = 3, 4; M = Cu, Ag, Au) by means of structural and theoretical methods and the role of metallophilic interactions was computationally studied by means of the atoms-in-molecules (AIM) approach.

The reaction of Collman's reagent Na 2 [Fe(CO) 4 ]·2thf with one equivalent of Au(NHC)Cl (NHC = IMes, IPr; IMes = C 3 N 2 H 2 (C 6 H 2 Me 3 ) 2 ; IPr = C 3 N 2 H 2 (C 6 H 3 iPr 2 ) 2 ) in dmso resulted in the [Fe(CO) 4 (AuNHC)] -(NHC = IMes, 1; IPr, 2) mono-anions. 1-2 further reacted with Au(NHC)Cl or Au(PPh 3 )Cl affording the neutral complexes Fe(CO) 4 (AuNHC) 2 (NHC = IMes, 3; IPr, 4), Fe(CO) 4 (AuIMes)(AuIPr) (5) and Fe(CO) 4 (AuNHC)(AuPPh 3 ) (NHC = IMes, 6; IPr, 7). 1-7 have been spectroscopically characterized by IR, 1 H, 13 C{ 1 H} and 31 P{ 1 H} NMR techniques. Moreover, the molecular structures of 1, 2, 4, 6 and 7 have been determined through single-crystal X-ray diffraction as their [NMe 4 ][Fe(CO) 4 -[a] Dipartimento

The reactions of [Pt(CO)] (n = 2-4) homoleptic Chini-type clusters with stoichiometric amounts of PhPCHCHPPh (dppe) result in the heteroleptic Chini-type clusters [Pt(CO)(dppe)], [Pt(CO)(dppe)], and [Pt(CO)(dppe)]. Their formation is accompanied by slight amounts of neutral species such as Pt(CO)(dppe), Pt(CO)(dppe), and Pt(dppe). A similar behavior was observed with the chiral ligand R-PhPCH(Me)CHPPh (R-dppp), and two isomers of [Pt(CO)(R-dppp)] were identified. All the new species were spectroscopically characterized by means of IR and P NMR, and their structures were determined by single-crystal X-ray diffraction. The results obtained are compared to those previously reported for monodentate phosphines, that is, PPh, as well as more rigid bidentate ligands, that is, CH═C(PPh) (P^P), CH(PPh) (dppm), and o-CH(PPh) (dppb). From a structural point of view, functionalization of anionic platinum Chini clusters preserves their triangular Pt units, whereas the overall trigonal prismatic structures present in the homoleptic clusters are readily deformed and transformed upon functionalization. Such transformations may be just local deformations, as found in [Pt(CO)(dppe)], [Pt(CO)(R-dppp)], [Pt(CO)(PPh)], and [Pt(CO)(PPh)]; an inversion of the cage from trigonal prismatic to octahedral, as observed in [Pt(CO)(dppe)] and [Pt(CO)(PPh)]; the reciprocal rotation of two trigonal prismatic units with the loss of a Pt-Pt contact as found in [Pt(CO)(dppe)].

Homologation of bio-ethanol to butanol and higher alcohols by means of Guerbet reaction has been performed with a novel ruthenium based bifunctional catalyst under homogeneous conditions in the presence of a basic co-catalyst. Reaction screening demonstrated that the new catalyst shows conversions and selectivity comparable with some of ruthenium based bifunctional catalysts recently reported in the literature. The reaction occurs in pure ethanol as well as in ethanol from wine wastes furnished by CAVIRO distillery with up to 46% conversion of ethanol and an overall selectivity to higher alcohols of 91% and a minor carbon loss. Based on the laboratory results, an industrialization study has been carried out in order to propose a viable technological solution. The experimental data consistency has been verified and the results have been up-scaled to design a reactor working in a batch or, potentially, semi-batch operation mode. Further analysis of the overall process, together with the introduction of dedicated figures of merit have allowed the estimation of the process performance both in mass and energetic terms, and the outcome has been integrated into a life cycle analysis. Although preliminary, the multidisciplinary approach has converged towards complementary results; more specifically, the adoption of the base co-catalyst NaOEt has showed similar performance in terms of specific alcohols production and energy demand compared to the NaOH case. Moreover this last case proves to be better from an environmental perspective (LCA).

Novel Ru–NHC complexes bearing cyclopentadienones/hydroxycyclopentadienyls are active and selective in transfer hydrogenation exploiting the cooperation of both classes of ligands.

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