Synthesis and structure of a pyridine-stabilized silanone molybdenum complex and its reactions with PMe3 and acetone†
Takako Muraoka,Yuzuki Suzuki,Masato Tsuchimoto,Gama Trigagema,Keiji Ueno,Shinji Koyama
Dalton Transactions Pub Date : 11/18/2022 00:00:00 , DOI:10.1039/D2DT02560D
Abstract

Silanones (O[double bond, length as m-dash]SiR2) are highly reactive species that readily convert to oligomeric siloxane (O–SiR2)n. The coordination of silanones to transition metal fragments to afford silanone-coordinated complexes is a reliable silanone stabilization method. Herein, a pyridine-stabilized silanone molybdenum complex Cp*(OC)2Mo{O[double bond, length as m-dash]SiMes2(py)}(SiMe3) (2b, Cp*: η5-C5Me5, Mes: 2,4,6-Me3C6H2, and py: pyridine) was synthesized by reacting the silyl(silylene) complex Cp*(OC)2Mo([double bond, length as m-dash]SiMes2)(SiMe3) (4b) with pyridine-N-oxide in pyridine. X-ray crystal structure analysis revealed that the geometry of complex 2b is similar to those of the previously synthesized DMAP-stabilized analogue Cp*(OC)2Mo{O[double bond, length as m-dash]SiMes2(DMAP)}(SiMe3) (2a, DMAP: 4-(dimethylamino)pyridine). The Si[double bond, length as m-dash]O and Mo–O bond distances in 2b are similar to those observed in 2a, but the N–Si coordination bond of 2b is slightly longer (approximately 0.05 Å) than that of 2a, indicating weaker pyridine coordination than that of DMAP. The reaction of 2a with excess PMe3 in C6D6 at room temperature for 28 h afforded Cp*(OC)2Mo(PMe3)(SiMe3) (5c) in a 43% NMR yield. In contrast, reacting 2b with excess PMe3 in C6D6 at room temperature for 9 h afforded 5c and the five-membered metallacyclic carbene complex Cp*(OC)Mo([double bond, length as m-dash]C(SiMe3)OSiMes2O)(PMe3) (6) in 10% and 41% NMR yields, respectively. The reactions of pyridine-stabilized silanone complexes Cp*(OC)2M(O[double bond, length as m-dash]SiMes2(py))(SiMe3) (M = Mo (2b) and W (1b)) with acetone proceeded via pyridine elimination, coordination of acetone to the Si center in the silanone ligand, and elimination of HSiMe3 to give Cp*(OC)2M{OSiMes2OC(Me)[double bond, length as m-dash]CH2} (M = Mo (8) and W (9)) in high yields.

Graphical abstract: Synthesis and structure of a pyridine-stabilized silanone molybdenum complex and its reactions with PMe3 and acetone