eprintid: 35358 rev_number: 19 eprint_status: archive userid: 8417 dir: disk0/00/03/53/58 datestamp: 2024-09-02 14:16:42 lastmod: 2024-09-03 15:29:16 status_changed: 2024-09-02 14:16:42 type: doctoralThesis metadata_visibility: show creators_name: Ruppert, Heiko title: Calix[4]pyrrolato Tin Complexes: Augmented Reactivity of Structurally Constrained Sn(II) and Sn(IV) Centers subjects: ddc-540 divisions: i-120200 adv_faculty: af-12 abstract: Structural constraint represents a viable tool to influence the reactivity of p-block centers in molecular compounds. This dissertation for the first time reveals the influence of structural constraint on the nucleophilicity and donor strength of Sn(II) and the Lewis acidity of Sn(IV) centers based on experimental and quantum chemical data. The macrocyclic, tetraanionic meso-octaalkylcalix[4]pyrrolato ligand delivered the first tetraamido stannate(II) dianion [2Et]2−. Coordination of four nitrogen pi-donors constrained into a square-pyramidal environment pushed the energetically buried electron lone pair at Sn(II)to an extreme sigma-donor capacity surpassing those of electron-rich carbene and phosphine ligands. The increased nucleophilicity of [2Et]2− even allowed the direct substitution of hydride from benzaldehyde (Section 3.1). Investigation of meso-substituent and ligand conformation effects on the electronic structure of [2R]2− (R = Me, Et) enabled the fine tuning of their donor and reducing strengths (Section 3.2). The flexible and dynamic coordination chemistry of [2Et]2− was explored in bimetallic complexes with Ni(0), W(0), and Ru(II) centers featuring either a η1-coordination via Sn(II) or a η5-coordination via a pyrrolato unit, depending on the electronic structure of the transition metal fragment (Section 3.1). With Au(I) centers a novel, dynamic µ2-coordination of all four pyrrolato N-atoms was discovered (Section 3.3). Application of the augmented nucleophilicity of [2Et]2− granted access to elusive low-substituted acyclic aminocarbenes by the umpolung reaction with chloroiminium salts. The newly formed carbenes were bound in the coordination sphere of the in situ generated, square-planar Sn(IV) Lewis acid 2Et delivering ambient-air-stable adducts. Eventually, cooperativity of the calix[4]pyrrole ligand backbone completed the reaction sequence and facilitated the selective transmetalation of the acyclic carbenes onto copper(I) halides accessing novel carbene complexes (Section 3.4). Lastly, the chemistry of anti-van’t Hoff-Le Bel Sn(IV) Lewis acids 2R (R = Me, Et) was explored. In the absence of Lewis bases, ambiphilic 2R exist as dimers and showed marked differences compared to their Si and Ge counterparts. 2R enabled the element-ligand cooperative activation of Lewis basic substrates, which was limited by their dimerization. Synthesis of the novel, sterically demanding meso-octa(ortho-phenylene)calix[4]pyrrole H4[1oPhen] and its Sn(IV) complexes were explored as the first steps towards a monomeric, truly square-planar Sn(IV) Lewis acid (Section 3.5). date: 2025 id_scheme: DOI id_number: 10.11588/heidok.00035358 own_urn: urn:nbn:de:bsz:16-heidok-353585 date_accepted: 2024-08-08 advisor: HASH(0x55de57b319e8) language: eng bibsort: RUPPERTHEICALIX4PYRR full_text_status: restricted place_of_pub: Heidelberg citation: Ruppert, Heiko (2025) Calix[4]pyrrolato Tin Complexes: Augmented Reactivity of Structurally Constrained Sn(II) and Sn(IV) Centers. [Dissertation] document_url: https://archiv.ub.uni-heidelberg.de/volltextserver/35358/1/Dissertation_Heiko_Ruppert_2024.pdf