Ligand-Enhanced CO Activation by the Early Lanthanide–Nickel Heterodimers: Photoelectron Velocity-Map Imaging Spectroscopy of LnNi(CO)_n^– (Ln = La, Ce)

Abstract

Heterobimetallic lanthanum-nickel and cerium-nickel carbonyls, LnNi(CO) (Ln = La, Ce; n = 2-5), were generated using a pulsed laser vaporization/supersonic expansion ion source. These compounds were characterized by photoelectron velocity-map imaging spectroscopy and quantum chemical calculations. The binding motif in the most stable isomers of the n = 2 and 3 clusters consists of one side-on-bonded carbonyl. A new building block of two side-on-bonded carbonyls is favored at n = 4, which is retained at n = 5, evidencing the increase of the number of extremely activated CO molecule in the larger clusters. The experimental and theoretical results demonstrate the ligand-enhanced CO activation by the early lanthanide-nickel heterodimers, which would have important implications for the design of alloy catalysts for activation of a molecular ligand.

XPu(CO)n (X = B, Al, Ga; n = 2 to 4): π Back-Bonding in Heterodinuclear Plutonium Boron Group Compounds with an End-On Carbonyl Ligand

“…The optimized bond lengths of Pu–B (2.559 Å) and Pu–C1 (2.387 Å) are located within the sum of Pyykkö single-bond covalent radii ( r S P , 2.57 and 2.47 Å, respectively), , and the bond lengths of B–C1 (1.380 Å) and B–C2 (1.408 Å) are much shorter than the sum of Pyykkö double-bond covalent radii ( r D P sum, 1.45 Å), indicating that there are significant bonding interactions between these atoms. In BPu­(CO) 3 , the third CO alternately terminates on Pu, in contrast to the growth regularity of CeNi­(CO) n – anions, where CO performs as a planar bridged carbonyl species between Ni and Ce . Pu–C3 exhibits the shortest Pu–CO bond length, which was predicted to be 2.336 Å, much shorter than the r S P sum of Pu–C single bonds. , Unexpectedly, affected by CO, the Pu–B and Pu–C bond lengths in cyclic [PuBCO] have been reduced by 0.01 and 0.1 Å, respectively.…”

“…In BPu(CO) 3 , the third CO alternately terminates on Pu, in contrast to the growth regularity of CeNi(CO) n − anions, where CO performs as a planar bridged carbonyl species between Ni and Ce. 49 Pu− C3 exhibits the shortest Pu−CO bond length, which was predicted to be 2.336 Å, much shorter than the r S P sum of Pu− C single bonds. 46,47 Unexpectedly, affected by CO, the Pu−B and Pu−C bond lengths in cyclic [PuBCO] have been reduced by 0.01 and 0.1 Å, respectively.…”

Photoelectron Velocity Map Imaging Spectroscopic and Theoretical Study of Heteronuclear MNi(CO)7– (M = V, Nb, Ta)

“…As for MNi­(CO) 7 – (M = Ti, Zr, Hf), these structures had three bridging carbonyls, three carbonyls terminally bonded to the M (M = Ti, Zr, Hf) atom and one carbonyl terminally bonded to the Ni atom . The early transition metal–nickel carbonyls MNi­(CO) n – (M = Sc, Y, La, Ce, Ti, Zr, Hf, V) were characterized to have three different types of CO bonding configurations (side-on-bonding, bridging, and terminal carbonyls), − and the heterobinuclear noble metal–nickel carbonyls MNi­(CO) n – (M = Cu, Ag) have revealed that the carbonyls were terminally bonded to the Ni atom. , The structural information for previous studies of homobinuclear Cr 2 (CO) 7 + , Ni 2 (CO) 7 + , Pd 2 (CO) 7 + , and Fe 2 (CO) 7 – and heterobinuclear CuFe­(CO) 7 – and CoZn­(CO) 7 + have indicated that they mainly possessed terminal carbonyl coordination modes. − However, the geometric investigations indicate that our present results of the MNi­(CO) 7 – (M= V, Nb, Ta) clusters are determined to have three bridging carbonyl modes and the other carbonyls are terminally bonded to the metal atoms, which are similar to the MNi­(CO) 7 – (M= Ti, Zr, Hf) clusters . It is demonstrated that various coordination modes are adopted so as to stabilize the different binuclear carbonyl complexes, by guaranteeing that at least one of two metallic centers satisfies the 18-electron rule.…”

“…The heteronuclear metal carbonyl anion MNi­(CO) 3 – (M = Mg, Ca, Al) has three terminal-bonded carbonyls on Ni atom to form the Ni­(CO) 3 motif, where Ni remains for 18-electron configuration for MgNi­(CO) 3 and CaNi­(CO) 3 but not for AlNi­(CO) 3 . The early transition metal–nickel carbonyl clusters MNi­(CO) 3 – (M = Sc, Y, La, Ce, Ti, Zr, Hf) are composed of three kinds of different CO modes (side-on-bonding, bridging, and terminal carbonyls). − As for later transition metal–nickel carbonyls, MNi­(CO) n – (M = Ag, Cu), the carbonyl groups are determined to be preferentially bonded to the nickel atom until the nickel center satisfies the 18-electron configuration then additional CO molecules start to bind with the copper atom. , …”

Spectroscopic characterization of heteronuclear iron–chromium carbonyl cluster anions

“…Recently, many hetero-dinuclear metal carbonyl cluster anions and cations have been produced in the gas phase and spectroscopically examined. 26–51 The FeM(CO) 8 + (M = Co, Ni, Cu) clusters were characterized to possess the (CO) 5 Fe–M(CO) 3 structures, and could be viewed as being formed via the interaction of a neutral Fe(CO) 5 fragment with an M(CO) 3 + fragment. 26 The square pyramid Fe(CO) 5 neutral with an 18-electron configuration acted as a two-electron donor in forming an σ-type Fe → M dative single bond.…”