Chirale tripodliganden mit phosphor- uni schwefeldonoren. synthese und komplexchemie chiral tripod ligands with phosphorus and sulfur donors. Synthesis and complex chemistry

Article abstract of DOI:10.1002/cber.19961290119

Neopentane based tripod licands CH₃C(CH₂X)(CH₂Y)(CH₂Z) with mixed donor groups X,Y,Z (PR₂, SR, SH) are accessible via two different strategies. The functionalized thietane CH₃(CH₂X)tCH₂SCH₂ allows stepwise introduction of P or S donors by substitution of the mesylate function and subsequent nucleophilic cleavage of the thietane ring. Tripod ligands 5 [CH₃C(CH₂X)(CH₂Y)(CH₂Z)j with up to three different donor groups (X = SH; Y = PPh₂; Z = P;4-Tol)₂, SCH₂Ph, PPh₂ are thus available. As an alternative the neopentano aerivatives 8 [CH₃C;CH₂X)(CH₂Y)(CH₂C1)] which are easily assessible from CH₃C(CH₂OSO₂Me)(CH₂BrJ(CH ₂Cl) (7) by stepwise substitution with phosphides LiPAr₂ (Ar = aryl) may be transiormed to 9 [CH₃C(CH₂X)(CH₂Y)(CH₂SBzl)]. Under controlled condi-tions the S-benzyl bond of 9 is cleaved reductively without concomitant cleavage of P-Ar bonds. Ligand 5a [CH₃C(CH₂PPh.)₂(CH₂SH)] reacts with Ni;BF₄J₂6 H₂O to yield the dinuclear species [(CH₃C(CH₂PPh₂)₂(CH ₂S)Ni)₂]²⁺ (10). The two ligands are bonded in an equivalent way with each of the two nickel centers interacting with one of the two phosphane functions of the ligand; the thiolate functions form (i2-SR bridges between the two nickel atoms. The SCH₂ group at the four-membered S₂Ni₂ ring are in mutual cis position with the four-membered ring bent along the sulfur-sulfur axis by 70°. The internal strain in 10 is analyzed by comparing its structure with the ones of [(CH₃C(CH₂PPh₂)₂NiSPh) ₂j²⁺ (11) and i(CH₃C(CH₂OH)(CH₂PPh₂)₂. NiOH}₂]₂+ (12). VCK Venagsgcsci.schaf: mbH, 1996.