Abstract
Treatment of K[N(SiMe3)2] with N,N′-bis(2,6-difluorophenyl)formamidine (DFFormH) in toluene, resulted in the formation of [K(DFForm)]∞ (1) as a poorly soluble material. Upon dissolution in thf and layering with n-hexane, 1 was crystallised and identified as a two-dimensional polymer, in which all fluorine and nitrogen atoms, and also part of one aryl group, bridge between four symmetry equivalent potassium ions, giving rise to a completely unique μ4-(N,N′,F,F′):(N,N′):η4(Ar-C(2,3,4,5,6)):(F″,F′′′) DFForm coordination. The two-dimensional nature of the polymer could be deconstructed to one dimension by crystallisation from neat thf at −35 °C, giving [K2(DFForm)2(thf)2]∞ (2), where the thf molecules bridge the monomeric units. Complete polymer dissociation was observed when 1 was crystallised from toluene/n-hexane mixtures in the presence of 18-crown-6, giving [K(DFForm)(18-crown-6)] (3), which showed unprecedented κ(N,Cispo,F) DFForm coordination, rather than the expected κ(N,N′) coordination.
Highlights
With the ability to adopt numerous coordination modes, flexible N,N 0 -bis(aryl)formamidinates have earned a special place in coordination chemistry [1,2,3,4,5]
The potential to form metal–arene interactions, such as η6 coordination, has been largely observed in group one chemistry [8,9,10,11,12,13], though some examples are known in f -block chemistry [14]
In almost all examples of this aromatic coordination, the phenyl rings contained alkyl-substituents in either the 2,6 positions, or in the 2,4,6 positions (e.g., Me). This is likely due to a combination of steric pressure, which starves the metal centre from coordination of additional donors, and increased electron donation from the aromatic ring caused by the alkyl substituents. Another means to engage the aromatic component in coordination is through the addition of donor functionalities (e.g., OMe, F), especially in the ortho-positions, thereby transforming the formamidinate ligand into a tri- [15,16,17], or tetra-dentate (e.g., N,N 0,X or N,N 0,X,X0 ) [17], chelate, with examples across a variety of different metal classes [18]
Summary
With the ability to adopt numerous coordination modes, flexible N,N 0 -bis(aryl)formamidinates (and by extension aryl-functionalised amidinates) have earned a special place in coordination chemistry [1,2,3,4,5]. In almost all examples of this aromatic coordination, the phenyl rings contained alkyl-substituents in either the 2,6 positions (e.g., iPr, Et, Me), or in the 2,4,6 positions (e.g., Me) This is likely due to a combination of steric pressure, which starves the metal centre from coordination of additional donors, and increased electron donation from the aromatic ring caused by the alkyl substituents. Another means to engage the aromatic component in coordination is through the addition of donor functionalities (e.g., OMe, F), especially in the ortho-positions, thereby transforming the formamidinate ligand into a tri- [15,16,17], or tetra-dentate (e.g., N,N 0 ,X or N,N 0 ,X,X0 ) [17], chelate, with examples across a variety of different metal classes [18]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
