Experimental and theoretical investigation of the reactivity of [(BDI)Ti(Cl){η-P(SiMe)-PPr}] towards selected ketones

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 5; no. 4; pp. 139 - 141
• Main Authors: Zió kowska, Aleksandra, Szynkiewicz, Natalia, Ponikiewski, ukasz
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 02.02.2021
• Subjects: Acetone; Crystallography; Cyclohexanone; Ketones; NMR spectroscopy; Oxidation; Silver chloride; Spectrum analysis; Titanium; X ray analysis
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d0dt04014b

In this work, we report a new type of reactivity of [(BDI*)Ti(Cl){η 2 -P(SiMe 3 )-P i Pr 2 }] ( 1 ) towards ketones (BDI* = 2,6-diisopropylphenyl-β-methyldiketiminate ligand). In the reaction of 1 with acetone, cyclopentanone or cyclohexanone, a ketone moiety is inserted into Ti-P phosphanyl or Ti-P phosphido bonds to form complexes with a new C-P-P moiety, providing [(BDI*)Ti(Cl){η 2 -P(SiMe 3 )-P i Pr 2 -C(Me) 2 O}] ( 2a ), [(BDI*)Ti(Cl){η 2 -OC(Me) 2 P(SiMe 3 )-P i Pr 2 }] ( 2b ), [(BDI*)Ti(Cl){η 2 -P(SiMe 3 )-P( i Pr) 2 -{C(CH 2 ) 4 }O}] ( 3a ), and [(BDI*)Ti(Cl){η 2 -P(SiMe 3 )-P( i Pr) 2 -{C(CH 2 ) 5 }O}] ( 4a ). Starting complex 1 reacts with cyclohexanone, yielding a monocrystalline complex [{(ArN&z.dbd;C(Me)CHC(Me)&z.dbd;NAr)C(CH 2 ) 5 O}Ti(Cl){P i Pr 2 -P(SiMe 3 )C(CH 2 ) 5 O}] ( 4d ) with the insertion of two ketone molecules. Interestingly, we found that monoinserted complexes 2a and 3a may be oxidized via a reaction with AgCl, leading to elimination of the -SiMe 3 group and oxidation of the titanium atom. This reaction led us to isolate the Ti( iv ) complex [(BDI*)Ti(Cl){η 2 -P-P( i Pr) 2 -{C(CH 2 ) 5 }O}] ( 5 ) in crystalline form. To identify the kinds of products that may be formed and determine which products are the most energetically favoured ones, we conducted a thermodynamic DFT study of 1 towards acetone, cyclopentanone and cyclohexanone. Structures 2a , 2b , 3a , 3e , 4a , 4d , and 5 were characterized by X-ray crystallography, and complex 5 was also identified by NMR spectroscopy. Reaction of [(BDI*)Ti(Cl){η 2 -P(SiMe 3 )-P i Pr 2 }] with acetone led to new titanium complexes with a C-P-P bond by insertion of one molecule of acetone into two different Ti-P bonds (involving the phosphanyl phosphorus and the phosphido phosphorus atom).