Andrew RE, Storey CM, Chaplin AB. Well-defined coinage metal transfer agents for the synthesis of NHC-based nickel, rhodium and palladium macrocycles.
Dalton Trans 2016;
45:8937-44. [PMID:
27157720 PMCID:
PMC5783018 DOI:
10.1039/c6dt01263a]
[Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 04/27/2016] [Indexed: 11/21/2022]
Abstract
With a view to use as carbene transfer agents, well-defined silver(i) and copper(i) complexes of a macrocyclic NHC-based pincer ligand, bearing a central lutidine donor and a dodecamethylene spacer [CNC-(CH2)12, 1], have been prepared. Although the silver adduct is characterised by X-ray diffraction as a dinuclear species anti-[Ag(μ-1)]2(2+), variable temperature measurements indicate dynamic structural interchange in solution involving fragmentation into mononuclear [Ag(1)](+) on the NMR time scale. In contrast, a mononuclear structure is evident in both solution and the solid-state for the analogous copper adduct partnered with the weakly coordinating [BAr(F)4](-) counter anion. A related copper derivative, bearing instead the more coordinating cuprous bromide dianion [Cu2Br4](2-), is notable for the adoption of an interesting tetranuclear assembly in the solid-state, featuring two cuprophilic interactions and two bridging NHC donors, but is not retained on dissolution. Coinage metal precursors [M(1)]n[BAr(F)4]n (M = Ag, n = 2; M = Cu, n = 1) both act as carbene transfer agents to afford palladium, rhodium and nickel complexes of 1 and the effectiveness of these precursors has been evaluated under equivalent reaction conditions.
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