Linear and Bent Nitric Oxide Ligand Binding in an Asymmetric Butterfly Complex: CoMoCo'

Paulina Guerrero-Almaraz; Manuel Quiroz; Joseph H Reibenspies; Marcetta Y Darensbourg

doi:10.1021/acs.inorgchem.1c00987

Linear and Bent Nitric Oxide Ligand Binding in an Asymmetric Butterfly Complex: CoMoCo'

Inorg Chem. 2021 Nov 1;60(21):15975-15979. doi: 10.1021/acs.inorgchem.1c00987. Epub 2021 Jun 22.

Authors

Paulina Guerrero-Almaraz¹, Manuel Quiroz¹, Joseph H Reibenspies¹, Marcetta Y Darensbourg¹

Affiliation

¹ Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States.

PMID: 34157221
DOI: 10.1021/acs.inorgchem.1c00987

Abstract

Two synthetic approaches to install metallodithiolate ligands on molybdenum centers using the synthons [Mo₂(CH₃CN)₁₀]⁴⁺ and (N₂S₂)Co(NO) [N₂S₂ = N,N-bis(2-mercaptoethyl)-1,4-diazacycloheptane and NO = nitric oxide], or [Mo(NO)₂(CH₃CN)₄]²⁺ (CH₃CN = acetonitrile) and [(N₂S₂)Co]₂ lead to a bis-nitrosylated, trimetallic dication, CoMoCo'. This unique asymmetric butterfly complex, with S = 1, has a bent NO within the small {Co(NO)}⁸ wing (denoted as Co), reflecting Co^III(NO^-), and is S-bridged to a linear {Mo(NO)}⁶ diamagnetic unit. The latter is further S-bridged to a pentacoordinate (N₂S₂)Co^III(CH₃CN) donor in the larger wing and is the origin of the two unpaired electrons, denoted as Co'. The asymmetry in Mo-Co distances, 3.33 Å in the Co wing and 2.73 Å in the Co' wing, indicated a Mo-Co' bonding interaction. The transfer of NO from (N₂S₂)Co(NO) in the former path is needed to cleave the strong quadruple bond in [Mo≣Mo]⁴⁺, with the energetic cost compensated for via a one-electron bond between Mo and Co', as indicated by natural bonding orbital analysis.