A Study of the Interaction of some cationic Transition-Metal compounds with Carbon Monoxide and Nucleophiles

  • M. B. H. Howlader

    Student thesis: Doctoral Thesis


    A number of novel cationic carbonyl complexes of ruthenium and rhodium have been synthesised and characterised. The work also investigates the attack of nucleophiles on such species and examines the feasibility of these reactions as a possible first step in the catalytic production of organic esters. Mono and dipositive species of ruthenium have been effectively prepared by the reaction of [RuCl 2 (CO) 2{PPh3) 2 ] with AgBF4.

    The cationic 2species [RuCl(CO) 2 (PPh3) 2 ] [BF4 ] . 1/2(CH2C1 2 ) and [Ru(CO) 2 (PPh3) 2 ] [BF4] 22£H2cl2jiave been prepared under nitrogea The compound [Ru(CO)3(PPh3)2] [BF4 ] 2 has been synthesised in the presence of CO. The compound, [RuCl(CO)2(PPh3)2] [BF4 ] . l/2(CH2Cl2) reacts with 0*30 under CO to give [RuCl(COOCH3J I (00)2^*13)2. The compounds [Ru(CO) 2 (PPh3 ) 2 r [BF4 ] 2.CH2C1 2 and [Ru(CO) 3 (PPh3 ) 2 ] [BP4 ] 2 effectively form cis-[Ru(COOCH3)2(CO)2(PPh3)2] by the reaction of CHsONa in the presence of CO at room temperature. This dialkoxycarbonyl compound preparation from the dipositive species are energetically more favourable than the cis-[RuCl2(CO)2(PPh3)2L where the2reaction takes place at CO high pressure. The compound [Ru(CO)2(PPh3)2] [BF4 ] 2. CH2C1 2 reacts with NaBH4, Nal, cone. HC1 and CHsCOONa to give the dihydrido, diiodo, dichloro and bisethanoato compounds respectively.

    Cationic complexes of rhodium have been synthesised by the reaction of trans-[RhCl(CO)(L)2], (L = PPhs, AsPhs, PCys) with AgBF4 in the absence and presence of CO to give [Rh(CO|(L)2]_[BF4]~. n CH2C12 [where n = 1/2 or 3/2] and trans- [Rh(CO) 2 (L) 2 ] [BF4J~ respectively. These cations react with PONa (R = CH3/ C2Hs) to give [Rh(OR) (CO) (L) 2 ] and [Rh(COOR)(CO)(L) 2 ], (R = CH3, L = PPh3/ PCy3 ). The alkoxycarbonyl compound, [Rh(COOR) (CO) 2 (L) 2 ] is formed by the reaction of sodium alkoxide in the presence of CO, (when R = CH3, C2Hs, C3H7, then L = PPh3 and when R = CH3 then L = AsPh3). The alkoxo compound, Rh(OCH3) (CO) (L) 2, (L = PPh3 ) oxidatively adds CH3I to give [Rh(OCH3) (CH3 )I(CO) (L) 2 ].

    The cation [Rh(CO)(L) 2 ] , reacts with RCOONa to give the carboxylato compounds, trans-[Rh(CCCR) (CO) (L) 2 L when L = PPh3 then R = CH3, when L = AsPh3 then R = H, CH3, C2H5_and when L = PCys then R = CH3. The compound [Rh(CO) 2 (SbPh3)3] [BF4J . CH2C12 has been formed from [RhCl(CO)(SbPh3)aJ with AgBF4 in the _presence of CO. The cation [Ru(CO) 2 (PPh3) 2 ] reacts with CH^p in the presence of CO (10 atmospheres) to give [Ru(CO)3(PPh3)2) and a trace amount of dimethylcarbonate. The same compound is obtained by using triethylamine in methanol under CO (10 atmospheres) at 65-70 C. Dimethylcarbonate rapidly reacts with Cl^ONa in contact with air to form a white
    precipitate, suggested to be Na2COj. Homogeneous solutions of [RuCl 2 (CO) 2 (PPh3 ) 2 ], [Ru(CO) 2 (PPh3 ) 2 r and [Rh(CO) (PPh3 ) 2 ] in dichloromethane produce benzene in the presence of CI^ONa in air. The cationic complexes of rhodium [Rh(CO)(L) 2 l , where L = PPh3, AsPh3, PCy3 and ruthenium complex [RuCl(CO) 2 (PPh3) 2 ] are effective catalysts for the hydrogenation of alkenes under hydrogen at atmospheric pressure and ambient temperature.

    The compounds .-have been characterised by analysis, infrared, H-NMR, P-NMR and C-NMR spectres copy and the organic products have been characterised by gas chromatography and in one case, GC/MS.
    Date of AwardJan 1993
    Original languageEnglish

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