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Insertion of Alkynes into the PtSi Bond of Silylplatinum Complexes Leading to the Formation of 4‐Sila‐3‐platinacyclobutenes and 5‐Sila‐2‐platina‐1,4‐cyclohexadienes
Author(s) -
Tanabe Makoto,
Osakada Kohtaro
Publication year - 2004
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.200305344
Subject(s) - chemistry , dimethyl acetylenedicarboxylate , intramolecular force , medicinal chemistry , reductive elimination , ligand (biochemistry) , stereochemistry , crystallography , catalysis , cycloaddition , organic chemistry , biochemistry , receptor
The reaction of dimethyl acetylenedicarboxylate (DMAD) with [Pt(SiHPh 2 ) 2 (PMe 3 ) 2 ] produces cis ‐[Pt(CZCZSiHPh 2 )(SiHPh 2 )(PMe 3 ) 2 ] ( cis ‐ 1 , Z = COOMe) and [P t(CZCZSi Ph 2 )(PMe 3 ) 2 ] ( 2 ) depending on the reaction conditions. cis ‐ 1 and 2 are equilibrated in solution at room temperature, and they are isolated by recrystallization of the mixtures. cis ‐ 1 is converted slowly in solution into trans‐ [Pt(CZCZSiHPh 2 )(SiHPh 2 )(PMe 3 ) 2 ] ( trans ‐ 1 ) via intermediate 2 followed by reaction with H 2 SiPh 2 . DMAD also reacts with [Pt(SiHPh 2 ) 2 (dmpe)] (dmpe = 1,2‐bis(dimethylphosphino)ethane) to afford [Pt(CZCZSiHPh 2 )(SiHPh 2 )(dmpe)] ( 3 ). Conversion of 3 into 4‐sila‐3‐platinacyclobutene [P t(CZCZSi Ph 2 )(dmpe)] ( 4 ) takes place, accompanied by formation of H 2 SiPh 2 , to give an equilibrated mixture of the two complexes. Crystallographic and spectroscopic data of cis ‐ 1 , trans ‐ 1 , and 3 suggest the presence of an intramolecular interaction between the SiH group of the 3‐sila‐1‐propenyl ligand and Pt via an SiHPt three‐center‐four‐electron bond in the solid state and in solution. DMAD reacts with 2 to give 5‐sila‐2‐platina‐1,4‐cyclohexadiene with π‐coordinated DMAD, [P t(CZCZSiPh 2 CZC Z)(DMAD)(PMe 3 ) 2 ] ( 5 ), which is also obtained from the reaction of excess DMAD with [Pt(SiHPh 2 ) 2 (PMe 3 ) 2 ]. Unsymmetrical six‐membered silaplatinacycles without π‐coordinated alkyne, [P t(CZCZSiPh 2 CHC X)(PMe 3 ) 2 ] ( 6 : X = COOMe; 7 : X = Ph), are prepared analogously from the respective reactions of phenyl acetylene and of methyl acetylene carboxylate with 2 . Methyl 2‐butynolate reacts with 2 at 50 °C to form a mixture of the regioisomers [P t(CZCZSiPh 2 CMeC Z)(PMe 3 ) 2 ] ( 8 ) and [P t(CZCZSiPh 2 CZC Me)(PMe 3 ) 2 ] ( 9 ).