text: the catalysts of the invention comprise two proximate metal cations within a macrocyclic ligand comprising two chelating centers , each center chelating one of the cations . the ligands place two chelated metal cations of cu ( i ) at a distance one from the other such that , on exposure to oxygen , dioxygen is bound between the cations as has been observed in the art in analogous compounds . the ligands of the invention also permit access to the chelated cations of a substrate to be oxidized ; i . e ., the ligand is so selected as to permit , it is believed , the binding of a substrate , such as phenol , to the catalyst . suitable ligands for meeting these requirements are found , for example , among heteromacrocyclic compounds , many of which are known . such macrocycles comprise two chelating centers each containing two or three trivalent nitrogen donor atoms . the nitrogen donor atoms of the chelating centers are normally separated from each other by two or three methylene groups . thus the chelating centers , can be said to be derived from ethylenediamine , diethylenetriamine , propylenediamine , and dipropylenetriamine . combinations such as ethylenepropylenetriamine are also operable and the two centers need not be the same . the centers are joined by two bridges attached at the terminal nitrogen atoms of the chelating centers to form macrocycles of 16 to 28 members , preferably 20 to 24 . the bridges , perferably alkylene radicals , each containing two to five methylene groups , need not be the same and are selected to meet the criterian that the chelated cations be not more than about 7 å apart , as determined by a molecular model . ligands containing unsubstituted bridges , selected according to the above criteria , are operable . substituted bridges , providing the substituents are not overly bulky , are generally operable . however , bulky substituents may sterically interfere with the binding of a substrate . the molecule designer is advised , therefore , to examine the molecular model of the ligand with this in mind before proceeding to synthesis . similarly , the internitrogen methylene groups may be branched or substituted under the same constraints . for particular applications it may be useful to modify the physical properties of the catalysts , for example their solubility , by substitution . catalyst mixtures are also operable . the macrocyclic ligands in many cases are known compounds . they are readily prepared by the methods , or obvious modification thereof , of those taught by the art , for example , by martin et al in j . org . chem 1982 47 , 415 and by lehn et al in j . amer . chem . soc . 1977 99 , 6766 . some ligands containing nonalkylene bridges are also operable . for example , a -- ch 2 ch 2 och 2 ch 2 -- group can replace one or both of the preferred alkylene bridges . a macrocyclic ligand having two such bridges was taught by lehn et al supra and the corresponding di - cu ( ii ) chelate was prepared by caughlin et al supra . the latter compound is not known to be an oxidation catalyst although a dioxygen bridge between co ( ii ) cations is reported by martell supra . the novel di - cu ( i ) chelate is expected to be operable as an oxidation catalyst according to this invention . the cations may also be coordinated with so - called soft ligands such as co which stabilize the lower oxidation state . they are released in the invention process . the coodination geometry about the cations in the invention catalysts is thought to be similar to that found by x - ray crystallography by pasquali et al in their monocopper complexes . a number of suitable macrocyclic ligands can be summarized by the general formula : ## str1 ## wherein a = 2 - 5 fig1 and 2 illustrate structures of co - containing catalysts of the invention wherein each ligand comprises two chelating centers derived , in the former case from diethylenetriamine and , in the latter case , ethylenediamine . the former macrocycle is 1 , 4 , 7 , 13 , 16 , 19 - hexaazacyclotetracosane and the latter is 1 , 4 , 10 , 13 tetraazacyclooctadecane . shown on the drawings are the corresponding subscript values pertaining to the general macrocycle ligand formula supra . as shown in the drawings , two coordination sites are occupied by carbon monoxide . anions are generally selected for reasons such as ease of isolation in preparing the catalyst . anions are not shown in drawings . the preferred ligands comprise two diethylenetriamine chelating centers joined by alkylene bridges of three , four , and five methylene groups . the macrocycle ligand of lehn et al supra belongs to a group of useful ligands comprising nonalkylene bridges . the group can be summarized by the above general formula with slight modification of the bridges designation , as follows : ## str2 ## wherein m and q are bridges in which one or both are -- ch 2 ch 2 och 2 ch 2 --. if only one bridge is -- ch 2 ch 2 och 2 ch 2 --, the other is an alkylene group containing two to five carbon atoms . in the macrocycle ligand of lehn et al m = q =-- ch 2 ch 2 och 2 ch 2 --, b = x = 2 , c = y = 1 , and d = z = 2 . operability of the invention catalysts requires a lower oxidation state in the cation . catalyst containing the cation in a lower oxidation state can be prepared by beginning the synthesis with the cation in that state , or the cation can be reduced in the finished compounds using a reductant such as a borohydride or ascorbic acid . in some cases it appears that the substrate itself is capable of reducing the cation to the lower oxidation state . it appears that the combination of macrocycle ligands , cations and optionally soft ligands , selected and assembled as described , provide : ( a ) an interatomic distance between the cations not greater than about 7 å ; ( b ) a stable orientation of the cations such that two coordination sites , one on each cation , are generally oriented toward each other ; and cis thereto ( c ) two further sites , one on each cation , said sites being sterically capable of binding a substrate ; and ( d ) the sites of ( b ) and ( c ) being formally vacant or occupied by readily displaced entities . fig3 shows a hypothetical reaction sequence resulting in the oxidation of a phenol substrate to o - benzoquinone , according to the invention . the catalyst comprises two cu ( i ) cations , as is preferred , and two readily displaced soft ligand carbon monoxide molecules coordinated thereto . they are contained within a ligand structure as described supra , which is here represented as an arc . it will be noted that co is released early in the sequence and dioxygen forms a bridge between the cations . phenol is then bound to the cation at a site adjacent to the dioxygen - cation bond . the consequent close proximity of the dioxygen to the ortho position directs attack to that position . the intermediate thus formed breaks down to yield the product o - benzoquinone , water and catechol , not shown , by protonation of the intermediate . finely divided cuprous iodide was suspended in abs . methanol ( 20 ml ) under carbon monoxide at atmospheric pressure . during about 15 minutes a solution of ligand in abs . methanol ( 10 ml ) was decanted from anhyd . caso 4 and added to the stirred suspension . after about 30 minutes the mixture was filtered in the absence of air and sodium tetraphenylborate was added to the filtrate . the catalyst precipated as a white solid which was filtered , washed with methanol , and dried , first in a stream of carbon monoxide and then under vacuum . other precipitants such as hexfluorophosphate and tetrafluoroborate may be employed . the yield of the invention catalyst , isolated as the colorless bis - tetraphenylborate complex , was 47 % using 55 mg ( 0 . 289 mmole ) cui , 50 mg ( 0 . 146 mmole ) ligand , and 100 mg ( 0 . 292 mmole ) sodium tetraphenylborate . analysis calculated for c 68 h 82 n 6 o 2 b 2 cu 2 : c , 70 . 16 ; h , 7 . 10 ; n , 7 . 22 . found : c , 69 . 02 ; h , 6 . 46 ; n , 7 . 23 %. characteristic ir absorption bands were observed at 3305 ( m ) and 3250 ( m ) for ligand nh ; 2085 ( s ) for co ; and 710 ( s ) and 740 ( s ) cm - 1 for tetraphenylborate . manometric measurement of co released on addition of excess triphenylphosphine indicated the presence of two moles of co per mole of catalyst . the cationic moiety of the product is represented in fig1 . the yield of the invention catalyst , isolated as the colorless bis - tetraphenylborate complex , was 59 % when using 66 . 5 mg ( 0 . 349 mmole ) cui , 50 mg ( 0 . 175 mmole ) ligand , and 119 mg ( 0 . 349 mmole ) sodium tetraphenylborate . analysis calculated for c 64 h 74 n 6 o 2 b 2 cu 2 : c , 69 . 36 ; h , 6 . 73 ; n , 7 . 58 . found : c , 68 . 83 ; h , 6 . 51 ; n , 7 . 47 %. characteristic ir absorption bands were observed at 3305 ( m ) and 3245 ( m ) for ligand nh ; 2085 ( s ) for co ; and 740 ( s ) and 715 ( s ) cm - 1 for tetraphenylborate . manometric measurement of co released on addition of triphenylphosphine indicated the presence of two moles of co per mole of catalyst . phenol ( 2 . 2 mmole ) was added to a solution under nitrogen of triethylamine ( 4 . 4 mmole ) in ch 2 cl 2 ( 50 ml ) containing suspended therein caso 4 anhyd . ( 1 . 5 g ). catalyst of fig1 wherein a = w = 5 as the tetraphenylborate ( 0 . 02 mmole ) was added and excess oxygen was bubbled through the solution . after 24 hrs . at room temperature , the solvent was evaporated under reduced pressure . the residue was taken up in ether , filtered , and the ether was evaporated . the residue was analyzed by thin layer chromatrography ( tlc ) ( silica gel ), visible spectroscopy , 1 h nuclear magnetic resonance ( nmr ), and high performance liquid chromatography ( hplc ) and found to contain : the experiment of example 3 was repeated using the tetraphenylborate catalyst of fig1 wherein a = w = 3 with the following results : no p - diphenols or p - quinones could be detected by tlc nor hplc and no ring cleavage products such as muconic acid could be detected by infrared spectroscopy in the products of either example 3 or 4 . the unidentified fraction , probably related to o - quinone which is known to be highly reactive , appears to form after workup after the invention reaction .