Sterically Encumbered Amidinates and Guanidinates of Calcium and Strontium. Issue 18 (10th May 2013)

• Record Type: Journal Article
• Authors: Glock, Carsten; Loh, Claas; Görls, Helmar; Krieck, Sven; Westerhausen, Matthias
• Is Part Of: European journal of inorganic chemistry. Issue 18(2013)
• Page Start: 3261
• Page End: 3269
• Publication Date: 2013-05-10
• Subjects: Calcium -- Strontium -- N li­gands -- Chelates -- Steric hindrance; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201300080
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: An attempt to prepare Tmp‐C(NDipp)2 Li by treatment of lithium tetramethylpiperidide (Li‐Tmp) with N, N′ ‐bis(2, 6‐diisopropylphenyl)carbodiimide (Dipp‐N=C=N‐Dipp) failed, and ether degradation occurred instead, allowing the isolation of a few crystals of O=CH–CH=C(NH‐Dipp)2 (1 ) after hydrolytic work‐up. We then investigated calcium and strontium compounds. Metalation of PrisoH [Priso = i Pr2 N–C(N‐Dipp)2 ] with [(thf)2 Ca{N(SiMe3 )2 }2 ] in refluxing hexane for 18 h yielded [{(Me3 Si)2 N}(thf)Ca(Priso)] (2 ). At room temperature, very few crystals of [Ca(Priso)2 ]· hexane (3 ) precipitated after several months from a saturated hexane solution of2 . KN(SiMe3 )2 was added to a THF solution of [(thf)4 CaI2 ] and PrisoH and heated to 60 °C for several hours yielding [(thf)Ca(Priso)(μ‐I)]2 (4 ). Metalation of PrisoH with [(thf)2 Sr{N(SiMe3 )2 }2 ] led to formation of [Sr(Priso)2 ] (5 ) regardless of the applied stoichiometry. The reaction of N, N′ ‐bis(2, 6‐diisopropylphenyl)benzamidine with KN(SiMe3 )2 and [(thf)4 CaI2 ] in THF followed by recrystallization from 1, 2‐dimethoxyethane (dme) solution yielded [(dme)Ca{(Dipp‐N)2 C–Ph}2 ] (6 ). The molecular structures of these compounds are discussed and compared with those of other encumbered complexes of divalent metal ions. Abstract : In N, N′ ‐bis(diisopropylphenyl)amidinates and guanidinates of calcium the metal center is effectively shielded. Therefore drastic reaction conditions are required, with the disadvantage that side reactions such as ether cleavage and subsequent reactions also occur.