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Syntheses of Four‐Membered Metallacyclic Complexes with Nitrosylruthenium and Their Ring‐Opening upon HCl Addition
Author(s) -
Arikawa Yasuhiro,
Ikeda Kenta,
Asayama Taiki,
Nishimura Yoshimasa,
Onishi Masayoshi
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601163
Subject(s) - chemistry , adduct , stereochemistry , ring (chemistry) , medicinal chemistry , diastereomer , reactivity (psychology) , regioselectivity , catalysis , organic chemistry , medicine , alternative medicine , pathology
Symmetrically disubstituted bis(3‐hydroxyalkynyl) complex [TpRu{CCCPh 2 (OH)} 2 (NO)] ( 1 ) (Tp = BH(pyrazol‐1‐yl) 3 ) and unsymmetrically mixed (arylalkynyl)(3‐hydroxyalkynyl) congener [TpRu(CCC 6 H 4 Me){CCCPh 2 (OH)}(NO)] ( 2 ) were newly prepared. Treatment of 1 or 2 with p ‐toluenesulfonic acid monohydrate was carried out to give unusual four‐membered metallacyclic complexes [TpRu{C(CCPh 2 )C(O)C(CPh 2 )}(NO)] ( 3 ) and [TpRu{C(CCPh 2 )C(O)CH(C 6 H 4 Me)}(NO)] ( 5 ), respectively, as major products. Formation mechanism of 3 and 5 would involve insertion of the generated allenylidene group (RuCCCPh 2 ) into the other RuC(alkynyl) bond, followed by hydration of the resulting α‐alkynylallenyl fragment. With regards to the chemical reactivity of their four‐membered metallacycles, treatment with aq. HCl in MeOH afforded the ring‐opened one‐HCl adducts, [TpRuCl{C(CCPh 2 )C(O)CHCPh 2 }(NO)] ( 7 ) and [TpRuCl{C(CCPh 2 )C(O)CH 2 (C 6 H 4 Me)}(NO)] ( 8 ). On the other hand, the use of CH 2 Cl 2 and THF as the reaction solvent gave another type of one‐HCl adducts [TpRu{CH(C(Cl)CPh 2 )C(O)C(CPh 2 )}(NO)] ( 9 a / 9 b ) and [TpRu{CH(C(Cl)CPh 2 )C(O)CH(C 6 H 4 Me)}(NO)] ( 11 a / 11 b ) as diastereomeric pairs, still retaining the four‐membered ring structure. Moreover, their kinetically controlled products 9 b and 11 b were treated with aq. HCl to afford the ring‐opened two‐HCl adducts [TpRuCl{C(C(Cl)CPh 2 )(H)C(O)CHCPh 2 }(NO)] ( 10 ) and [TpRuCl{CH(C 6 H 4 Me)C(O)CH 2 (C(Cl)CPh 2 )}(NO)] ( 12 ), respectively. In 10 and 12 , each one RuC bond is cleaved at mutually different positions in the ring. Protonation on the carbonyl group would trigger the formation of 7 – 12 .