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Hydroboration of Alkynes with Zwitterionic Ruthenium–Borate Complexes: Novel Vinylborane Complexes
Author(s) -
Anju R. S.,
Mondal Bijan,
Saha Koushik,
Panja Subir,
Varghese Babu,
Ghosh Sundargopal
Publication year - 2015
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.201501107
Subject(s) - hydroboration , agostic interaction , ruthenium , chemistry , boranes , borane , medicinal chemistry , ligand (biochemistry) , borylation , boron , thermal decomposition , stereochemistry , catalysis , metal , organic chemistry , biochemistry , aryl , receptor , alkyl
Building upon previous studies on the synthesis of bis(sigma)borate and agostic complexes of ruthenium, the chemistry of nido ‐[(Cp*Ru) 2 B 3 H 9 ] ( 1 ) with other ligand systems was explored. In this regard, mild thermolysis of nido ‐ 1 with 2‐mercaptobenzothiazole (2‐mbzt), 2‐mercaptobenzoxazole (2‐mbzo) and 2‐mercaptobenzimidazole (2‐mbzi) ligands were performed which led to the isolation of bis(sigma)borate complexes [Cp*RuBH 3 L] ( 2 a – c ) and β‐agostic complexes [Cp*RuBH 2 L 2 ] ( 3 a – c ; 2 a , 3 a : L=C 7 H 4 NS 2 ; 2 b , 3 b : L=C 7 H 4 NSO; 2 c , 3 c : L=C 7 H 5 N 2 S). Further, the chemistry of these novel complexes towards various diphosphine ligands was investigated. Room temperature treatment of 3 a with [PPh 2 (CH 2 ) n PPh 2 ] ( n =1–3) yielded [Cp*Ru(PPh 2 (CH 2 ) n PPh 2 )‐BH 2 (L 2 )] ( 4 a – c ; 4 a : n =1; 4 b : n =2; 4 c : n =3; L=C 7 H 4 NS 2 ). Mild thermolysis of 2 a with [PPh 2 (CH 2 ) n PPh 2 ] ( n =1–3) led to the isolation of [Cp*Ru(PPh 2 (CH 2 ) n PPh 2 )(L)] (L=C 7 H 4 NS 2 5 a – c ; 5 a : n =1; 5 b : n =2; 5 c : n =3). Treatment of 4 a with terminal alkynes causes a hydroboration reaction to generate vinylborane complexes [Cp*Ru(RCCH 2 )BH(L 2 )] ( 6 and 7 ; 6 : R=Ph; 7 : R=COOCH 3 ; L=C 7 H 4 NS 2 ). Complexes 6 and 7 can also be viewed as η‐alkene complexes of ruthenium that feature a dative bond to the ruthenium centre from the vinylinic double bond. In addition, DFT computations were performed to shed light on the bonding and electronic structures of the new compounds.