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Cycloaddition versus Cleavage of the C=S Bond of Isothiocyanates Promoted by Digallane Compounds with Noninnocent α‐Diimine Ligands
Author(s) -
Zhang Wei,
Dodonov Vladimir A.,
Chen Weixing,
Zhao Yanxia,
Skatova Alexandra A.,
Fedushkin Igor L.,
Roesky Peter W.,
Wu Biao,
Yang XiaoJuan
Publication year - 2018
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.201802469
Subject(s) - diimine , cycloaddition , chemistry , bond cleavage , metallacycle , cleavage (geology) , stereochemistry , medicinal chemistry , metal , yield (engineering) , x ray crystallography , catalysis , organic chemistry , physics , geotechnical engineering , materials science , fracture (geology) , diffraction , optics , metallurgy , engineering
Whereas the chemistry of single‐bond activation by compounds of the main group elements has undergone some development in recent years, the cleavage of multiple bonds remains underexplored. Herein, the reactions of two digallanes bearing α‐diimine ligands, namely, [L 1 Ga−GaL 1 ] ( 1 , L 1 =dpp‐dad=[(2,6‐ i Pr 2 C 6 H 3 )NC(CH 3 )] 2 ) and [L 2 Ga−GaL 2 ] ( 2 , L 2 =dpp‐bian=1,2‐[(2,6‐ i Pr 2 C 6 H 3 )NC] 2 C 10 H 6 ), with isothiocyanates are reported. Reactions of 1 or 2 with isothiocyanates in 1:2 molar ratio proceeded with [2+4] cycloaddition of the C=S bond across the C 2 N 2 Ga metallacycle with formation of C−C and S−Ga single bonds to afford [L 1 (RN=C−S)Ga−Ga(S−C=NR)L 1 ] ( 3 , R=Me; 4 , R=Ph) and [L 2 (RN=C−S)Ga−Ga(S−C=NR)L 2 ] ( 8 , R=allyl; 9 , R=Ph). In the cases of 8 and 9 , this cycloaddition is reversible. The digallanes reacted with 2 equiv of PhNCS in the presence of Na metal or at high temperatures through a unique reductive cleavage of the C=S bond to yield the disulfide‐bridged digallium species [Na(THF) 3 ] 2 [L 1 Ga(μ‐S) 2 GaL 1 ] ( 5 ), [L 2 Ga(μ‐S) 2 GaL 2 ] ( 10 ), and [Na(DME) 3 ][L 2 Ga(μ‐S) 2 GaL 2 ] ( 11 ). Moreover, products 4 and 5 can further react with an excess of isothiocyanate, through cleavage of the C=S bond or cycloaddition, to give the bis‐ or mono‐S‐bridged complexes [Na(THF) 2 ] 2 [L 1 (PhN=C−S)Ga(μ‐S) 2 Ga(S−C=NPh)L 1 ] ( 6 ) and [L 1 (PhN=C−S)Ga(μ‐S)Ga(S−C=NPh)L 1 ] ( 7 ). All the newly prepared compounds were characterized by elemental analysis, single‐crystal X‐ray diffraction, IR spectroscopy, NMR ( 3 – 9 ) or ESR spectroscopy ( 11 ), and DFT calculations.