# US 2018/0021766 A1 · Phenanthroline based pincer complexes useful as catalysts for the preparation of methanol from carbondioxide

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- Number: US 2018/0021766 A1
- Document ID: US20180021766A1
- Status: Published application
- Kind: A1
- Application number: 15/549,827
- Filed: 2016-02-10
- Published: 2018-01-25
- Earliest claimed: 2015-02-10
- Assignees: Council of Scientific and Industrial Research
- Applicants: Council of Scientific and Industrial Research
- Inventors: Ekambaram BALARAMAN; Vinod Gokulkrishna LANDGE; Siba Prasad MIDYA; Manoj Kumar SAHOO; Garima JAISWAL
- Web page: https://patentgrep.com/patent/US20180021766A1

## CPC

- B01J 31/189: {containing both nitrogen and phosphorus as complexing atoms, including e.g. phosphino moieties, in one at least bidentate or bridging ligand}
- B01J 31/1815: {with more than one complexing nitrogen atom, e.g. bipyridyl, 2-aminopyridine}
- B01J 31/183: {with more than one complexing nitrogen atom, e.g. phenanthroline}
- B01J 31/20: Carbonyls
- B01J 31/2404: {Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring}
- B01J 31/2447: {and phosphine-P atoms as substituents on a ring of the condensed system or on a further attached ring}
- C07F 15/0046: {Ruthenium compounds}
- B01J 2231/643: of R2C=O or R2C=NR (R= C, H)
- B01J 2231/648: Fischer-Tropsch-type reactions
- B01J 2231/763: of -CH-XH (X= O, NH/N, S) to -C=X or -CX triple bond species
- B01J 2531/0244: Pincer-type complexes, i.e. consisting of a tridentate skeleton bound to a metal, e.g. by one to three metal-carbon sigma-bonds
- B01J 2531/821: Ruthenium
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- C07F: ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM (metal-containing porphyrins C07D487/22)

## Abstract

The present invention relates to a novel phenonthroline based pincer complexes and process for preparation thereof. The present invention also provides a one pot process for the conversion of carbon dioxide to methanol in the presence of a molecularly defined pincer-type single-site Ru-catalyst and secondary amine. Further the present invention provides the use of phenonthroline based pincer complexes for the esterification of alcohols and hydrogenation of esters under mild conditions.

## Claims

### Claim 1

A phenanthroline based pincer catalyst complexes of Formula (I);
wherein
M is a noble metal, transition metal (1st, 2nd and 3rd row of elements), alkaline-earth—or rare-earth elements;
Y is selected from the group consisting of phosphine (PRaRb), phosphite P(ORa)(ORb), phosphinite P(ORa)(Rb), amine (NRaRb), imine, sulphide SRa, oxide ORa, sulfoxide S(O)Ra, sulphone SO2Ra, oxazoline, N-heterocyclic carbine, heteroaryl containing at least one heteroatom selected from nitrogen or Sulphur;
L is selected from the group consisting of CO, BH3, BH2, PRaRbRc, P(ORa)(ORb)(ORc), nitrile (RCN) or isonitrile (RNC);
R, Ra, Rb, and Rc are selected from the group consisting of alkyl, cycloalkyl, aryl which may be further substituted heterocyclyl, heteroaryl, alkylcycloalkyl, alkylaryl, alkylheterocyclyl, alkylheteroaryl.
A ligand used is aromatic or dearomatic is selected from the group consisting of H, halogen, OCOR, OCOCF3, OSO2R, OSO2CF3, CN, OR, N(R)2 and RS;
R1, represents hydrogen or one or two substituents wherein each such substituent is independently selected from the group consisting of alkyl (linear and branched), cycloalkyl, aryl, substituted aryl, heterocyclyl, heteroaryl, alkylcycloalkyl, alkylaryl, alkylheterocyclyl, alkylheteroaryl, halogen, triflurometyl, nitro, amide, ester (—CO2R), —OC(O)R, —OC(O)CF3, —OSO2R, —OSO2CF3) cyano, alkoxy, alkylamino (mono or di), arylamino (mono or di), —SR, an inorganic support or a polymeric moiety.
R2 and R3 form a 6 membered aromatic ring which is further substituted with one or two substituents wherein each such substituent is independently selected from the group consisting of alkyl (linear and branched), cycloalkyl, aryl, substituted aryl, heterocyclyl, heteroaryl, alkylcycloalkyl, alkylaryl, alkylheterocyclyl, alkylheteroaryl, halogen, triflurometyl, nitro, amide, ester (—CO2R), —OC(O)R, —OC(O)CF3, —OSO2R, —OSO2CF3) cyano, alkoxy, alkylamino (mono or di), arylamino (mono or di), —SR, an inorganic support or a polymeric moiety.
R3 and R4 form a six member aromatic ring which is further substituted with one or two substituents wherein each such substituent is independently selected from the group consisting of alkyl (linear and branched), cycloalkyl, aryl, substituted aryl, heterocyclyl, heteroaryl, alkylcycloalkyl, alkylaryl, alkylheterocyclyl, alkylheteroaryl, halogen, triflurometyl, nitro, amide, ester (—CO2R), —OC(O)R, —OC(O)CF3, —OSO2R, —OSO2CF3) cyano, alkoxy, alkylamino (mono or di), arylamino (mono or di), —SR, an inorganic support or a polymeric moiety.

### Claim 2 (depends on 1)

The phenanthroline based pincer complexes of formula (I) as claimed in claim 1, wherein said complex is selected from HCl(CO)Ru(Phen-(tBu)PNN) (3), H(CO)Ru-(Phen-(tBu)PNN) (4) and H(CO)Ru(η1BH4)(Phen-(tBu)PNN) (5).

### Claim 3 (depends on 1)

The phenanthroline based pincer complexes of formula (I) as claimed in claim 1, wherein the said catalyst is used for hydrogenation of lactones to diols and esters to alcohols

### Claim 4 (depends on 1)

The phenanthroline based pincer complexes of formula (I) as claimed in claim 1, wherein the said catalyst is used for dehydrogenation of diols to lactones, alcohol to esters and secondary alcohols to ketones.

### Claim 5 (depends on 1)

A process for the preparation of phenanthroline based pincer complexes of formula (I) as claimed in claim 1, wherein said process comprising the steps of:
a) adding solution of Lithium diisopropylamide and tBuOK in suitable solvent to a solution of 2-methyl-1,10-phenanthroline (1) in ether at a temperature in the range of 0 to 5° C. followed by stirring the reaction mixture for the period in the range of 30 to 40 min to obtain a solution;
b) adding a solution of di-tert-butylchlorophosphine in ether to the solution as obtained in step (a) and stirring for a period of 1 to 2 hr at a temperature in the range of −50 to −78° C. followed by stirring at temperature in the range of 25 to 30° C. for the period in the range of 12 to 14 hrs to obtain Phen-PNN(tBu) (2);
c) mixing the Phen-PNN(tBu) (2) as obtained in step (b), RuHCl(CO)(PPh3)3 and tetrahydrofuran heating at a temperature in the range of 60 to 70° C. for the period in the range of 5 to 6 hr under argon atmosphere to obtain HCl(CO)Ru(Phen-(tBu)PNN) (3);
d) adding Sodium bis(trimethylsilyl)amide to the compound of step (c) in C6H6 to obtain H(CO)Ru-(Phen-(tBu)PNN) (4);
e) stirring the reaction mixture comprising HCl(CO)Ru(Phen-(tBu)PNN) (3) and NaBH4 in toluene and ethanol at temperature in the range of 50 to 70° C. for the period in the range of 10 to 15 min followed by stirring at a temperature in the range of 25-30° C. for the period in the range of 4 to 6 hrs to obtain H(CO)Ru(η1BH4)(Phen-(tBu)PNN) (5a).

### Claim 6 (depends on 8)

The process as claimed in claim 8, wherein solvent used in step (a) is selected from hexane, heptane, tetrahydrofuran (THF), diethyl ether, toluene, and etheylbenzene.

### Claim 7 (depends on 1)

A phenanthroline based pincer complexes of Formula (I) as claimed in claim 1
wherein
M is a noble metal, transition metal (1st, 2nd and 3rd row of elements), alkaline-earth—or rare-earth elements;
Y is selected from the group consisting of phosphine (PRaRb), phosphite P(ORa)(ORb), phosphinite P(ORa)(Rb), amine (NRaRb), imine, sulphide SRa, oxide ORa, sulfoxide S(O)Ra, sulphone SO2Ra, oxazoline, N-heterocyclic carbine, heteroaryl containing at least one heteroatom selected from nitrogen or Sulphur;
L is selected from the group consisting of CO, BH3, BH2, PRaRbRc, P(ORa)(ORb)(ORc), nitrile (RCN) or isonitrile (RNC);
R, Ra, Rb, and Rc are selected from the group consisting of alkyl, cycloalkyl, aryl which may be further substituted heterocyclyl, heteroaryl, alkylcycloalkyl, alkylaryl, alkylheterocyclyl, alkylheteroaryl.
A ligand used is aromatic or dearomatic and is selected from the group consisting of H, halogen, OCOR, OCOCF3, OSO2R, OSO2CF3, CN, OR, N(R)2 and RS;
R1, represents hydrogen or one or two substituents wherein each such substituent is independently selected from the group consisting of alkyl (linear and branched), cycloalkyl, aryl, substituted aryl, heterocyclyl, heteroaryl, alkylcycloalkyl, alkylaryl, alkylheterocyclyl, alkylheteroaryl, halogen, triflurometyl, nitro, amide, ester (—CO2R), —OC(O)R, —OC(O)CF3, —OSO2R, —OSO2CF3) cyano, alkoxy, alkylamino (mono or di), arylamino (mono or di), —SR, an inorganic support or a polymeric moiety.
R2, R3=H;
R2 and R3 form a 6 membered aromatic ring which is further substituted with one or two substituents wherein each such substituent is independently selected from the group consisting of alkyl (linear and branched), cycloalkyl, aryl, substituted aryl, heterocyclyl, heteroaryl, alkylcycloalkyl, alkylaryl, alkylheterocyclyl, alkylheteroaryl, halogen, triflurometyl, nitro, amide, ester (—CO2R), —OC(O)R, —OC(O)CF3, —OSO2R, —OSO2CF3) cyano, alkoxy, alkylamino (mono or di), arylamino (mono or di), —SR, an inorganic support or a polymeric moiety;
R4, R5=H or C2H5;
R3 and R4 form a six member aromatic ring which is further substituted with one or two substituents wherein each such substituent is independently selected from the group consisting of alkyl (linear and branched), cycloalkyl, aryl, substituted aryl, heterocyclyl, heteroaryl, alkylcycloalkyl, alkylaryl, alkylheterocyclyl, alkylheteroaryl, halogen, triflurometyl, nitro, amide, ester (—CO2R), —OC(O)R, —OC(O)CF3, —OSO2R, —OSO2CF3) cyano, alkoxy, alkylamino (mono or di), arylamino (mono or di), —SR, an inorganic support or a polymeric moiety.
wherein the said catalyst is useful for the preparation of methanol from carbon dioxide and the said process comprising the steps of:
i. mixing catalyst, secondary amine in a ratio of (1: 500) in tetrahydrofuran to obtain a solution;
ii. adding potassium tert-butoxide (in case of catalysts 3 or 5 or 7 only) to the solution obtained in step (a) to obtain a solution;
iii. pressurizing the solution as obtained in step (ii) with carbon dioxide at 10 atmosphere followed by H2 atmosphere at 30-40 atm to obtain a solution;
iv. heating the solution as obtained in step (iii) at 110-120° C. and stirring for 12-14 hrs to obtain a solution;
v. removing excess gases from the solution as obtained in step (iv) to obtain N-formylated product of secondary amine;
vi. adding catalyst and potassium tert-butoxide (in case of catalysts 3 or 5 or 7 only) to the N-formylated product of secondary amine as obtained in step (v) to obtain solution;
vii. pressurizing the solution as obtained in step (vi) with H2 at 40-45 atmosphere followed by heating the solution at 110-120° C. and stirring for 18-20 hrs to obtain methanol and recyclable secondary amine.

### Claim 8 (depends on 1)

The process as claimed in claim 1, wherein catalyst of formula 1 used in step (i) is selected from HCl(CO)Ru(Phen-(tBu)PNN) (3); H(CO)Ru-(Phen-(tBu)PNN) (4); H(CO)Ru(η1BH4)(Phen-(tBu)PNN) (5a); HCl(CO)Ru(BPy-tPNN); [H(CO)Ru(BPy-tPNN−)]; and H(CO) Ru−(Py-tPNN)].

### Claim 9 (depends on 7)

The process as claimed in claim 7, wherein said steps (ii) and (vi) are absent when [H(CO)Ru(BPy-tPNN)] catalyst is used.

### Claim 10 (depends on 7)

The process as claimed in claim 7, wherein secondary amine used in step (i) is selected from A or B
wherein;
X is selected from the group consisting of NH, CH2, and O
R1 and R2 are the same or different and is selected from the group consisting of alkyl (linear, branched), cyclo (up to 7 membered, which may be further mono, di, tri or tetra substituted and selected from the group consisting of alkyl (linear and branced), aryl (further substituted), cycloalkyl, alkylaryl, alkylheterocyclyl, alkylheteroaryl, halogen, triflurometyl, nitro, alkoxy, dialkylamino, diarylamino, and —SR), cycloalkyl, aryl (which may be further mono, di, tri or tetra substituted), heterocyclyl, heteroaryl,