Uranium rhodium bonding in heterometallic complexes

Abstract

The UIV–RhI intermetallic distances in the U2Rh2 complex (left, 2.7601(5) Å) and URh complex (right, 2.7630(5) Å) are very short and almost identical in the solid state even though solution electrochemistry suggests very different metal-based reduction processes.

A Very Short Uranium(IV)–Rhodium(I) Bond with Net Double‐Dative Bonding Character

“…However, examples with dative metal donors are few, since they lack a substantial electrostatic attractive force to pair the two metal ions. Notable examples include U−Al/−Ga complexes utilising [AlCp*] and [Ga(Cp*)],, a trio of Group 10 derivatives [(I)UM(μ‐OPAr) 3 ] (M=Ni, Pd, Pt; OPAr=C 6 H 2 ‐1‐PPh 2 ‐2‐O‐3‐Bu t ‐5‐Me), and two Group 9 derivatives [U(I)(μ‐I)Rh(μ‐OPAr) 3 ] and [U(I) 2 (μ‐OPAr) 2 Rh(μ‐I)] 2 , though in all cases these systems seem to be limited to polar single U−M bonds. Very recently, [UFe(CO) 3 ] − and [OUFe(CO) 3 ] − with covalent‐σ and double‐dative‐π bonds, were reported in the gas phase, which hints that novel U−M bonds might await discovery under normal experimental conditions.…”

“…When characterising metal–metal bonds, bond order is an intuitive and important metric to consider, but perhaps the best benchmark is the formal shortness ratio (FSR MM′ =MM′ distance/sum of MM′ covalent radii), because this enables comparisons to be drawn about the relative shortness of a metal–metal bond by normalising different metal covalent radii. Using Pyykkö’s values, the current state‐of‐the‐art for actinide–metal derivatives prepared under normal conditions is a FSR UNi value of 0.90 for [(I)UNi(μ‐OPAr) 3 ], whereas complexes with U−Re,,, U−Ru, U−Rh, and U−Co, bonds have average FSR UM values of 0.98, 1.01, 0.93, and 1.04, respectively. These FSR values are higher than often observed in stronger M−M′ bonding, where values less than 0.8 can be found for high M−M′ bond order species, and this highlights the knowledge gap in the field in terms of strongly and multiply bonded intermetallic bonds.…”

“…The U1−Rh1 distance of 2.5835(3) Å is very short, being about 0.37 Å shorter than the sum of the single bond covalent radii of U and Rh (2.95 Å), and about 0.2 Å shorter than the only two other structurally authenticated U−Rh bonds in [U(I)(μ‐I)Rh(μ‐OPAr) 3 ] [2.7630(5) Å] and [U(I) 2 (μ‐OPAr) 2 Rh(μ‐I)] 2 [2.7601(5) Å] . Interestingly, the sum of the covalent double‐bond radii of U and Rh (2.44 Å) is only about 0.14 Å shorter than the U−Rh distance in 2 .…”

Preparation and Characterization of Uranium–Iron Triple‐Bonded UFe(CO)3− and OUFe(CO)3− Complexes

“…[2][3][4][5] Thed iscovery of as table compound with fivefold chromium-chromium (Cr À Cr) bonding in 2005 [6] revived efforts to synthesize and characterize homoas well as hetero-metal-metal bonding compounds across the periodic table from the d-block transition metals to the fblock lanthanides and actinides. [7][8][9][10][11][12] Metal-metal bonding of f-block actinide elements is of particular interest in understanding of the electronic structures,e specially f-orbital participation. Theb onding scenario of actinide elements such as uranium is considerably more complex than that in the d-block metals because the 5f,6 d, 7s,a nd 7p orbitals are energetically close to one another,and thus,all are available in forming the chemical bonds.D espite the proclivity of multiply bonded metal-containing complexes to exhibit novel types of bonding and reactivity,c omplexes containing actinide-metal bonds are uncommon largely due to the extreme difficulties in experimental synthesis and characterization.…”

“…Only af ew compounds of weak actinide-metal single and double bonds have been structurally characterized. [7,[9][10][11][12] Although polarized covalent uranium-ligand triple bonding is quite common, [13][14][15] and theoretical investigations on actinide-metal diatomics and complexes suggest that actinide-metal multiple bonding could exist, [16][17][18][19][20][21] so far there are no examples of experimentally characterized compounds with actinide-metal triple bonds.H erein, we report the synthesis of the UFe(CO) 3 À and OUFe(CO) 3 À complexes in the gas phase.Infrared photodissociation spectroscopic and advanced quantum chemistry studies indicate that both species contain unprecedented uranium-iron triple bonds with one covalent s bond and two Fe-to-U dative p bonds.…”