Synthesis and characterization of five-coordinate, 16-electron RuII complexes supported by tridentate bis(phosphino)silyl ligationElectronic supplementary information (ESI) available: Variable temperature NMR data for 9 and crystallographic data for 3, 4, 5, 9 and 11 (CIF). CCDC 1029415-1029419. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6dt01869f

The synthesis of 16-electron complexes of the type (Cy-PSiP)RuX(L) (Cy-PSiP = κ 3 -(2-Cy 2 P C 6 H 4 ) 2 Si Me) is reported. Treatment of (Cy-PSiP)H with one equiv. RuCl 2 (PPh 3 ) 3 in the presence of Et 3 N afforded a mixture of (Cy-PSiP)RuCl(PPh 3 ) ( 1 ) and [(Cy-PSiP)RuCl] 2 ( 2 ), which exists in a temperature-dependent equilibrium process involving reversible dissociation of PPh 3 from 1 to form 2 . While treatment of this equilibrium mixture with PMe 3 afforded (Cy-PSiP)RuCl(PMe 3 ) ( 3 ) cleanly, this product was more straightforwardly prepared by the addition of PMe 3 to 2 (97% yield). Attempts to form an alkyl complex of the type (Cy-PSiP)RuMe(PMe 3 ) via treatment of 3 with MeMgBr led to the dehydrogenation and cyclometalation of a cyclohexyl phosphino group to give the isolable 18-electron complex [MeSi(C 6 H 4 PCy 2 )(C 6 H 4 PCy(η 3 -C 6 H 8 ))]RuPMe 3 ( 4 , 78% yield). The hydrido complex (Cy-PSiP)RuH(PMe 3 ) ( 5 ) was identified as a minor by-product in this dehydrogenative process. Whereas simple 16-electron alkyl complexes of the type (Cy-PSiP)RuR(PMe 3 ) remained elusive, the isolable allyl complex (Cy-PSiP)Ru(η 3 -C 3 H 5 ) ( 9 ) was successfully prepared from 2 and (C 3 H 5 )MgCl (79% yield). Treatment of 3 with Me 3 SiN 3 or NaN 3 did not generate a five-coordinate azido species. However, the putative dinuclear complex [(Cy-PSiP)RuN 3 ] 2 ( 10 ) was observed to react with one equiv. of PMe 3 to afford the isolable five-coordinate azido complex (Cy-PSiP)Ru(N 3 )(PMe 3 ) ( 11 ; 94% yield). Crystallographic data for 3 , 4 , 5 , 9 and 11 are presented. New electronically and coordinatively unsaturated complexes of the type (Cy-PSiP)RuX(L) (Cy-PSiP = κ 3 -(2-Cy 2 P C 6 H 4 ) 2 Si Me) are reported, including examples of 16-electron allyl and azido Ru species.