| Abstract: | The crystal structures of three unusual chromium organophosphate complexes have been determined, namely, bis(μ‐butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl hydrogen phosphato‐κO:κO′)di‐μ‐hydroxido‐bis(butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl hydrogen phosphato‐κO)(butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl phosphato‐κO)chromium](Cr—Cr) heptane disolvate or {Cr2(μ2‐OH)2μ2‐PO2(OBu)(O‐2,6‐tBu2‐4‐MeC6H2)‐κO:κO′]2PO2(OBu)(O‐2,6‐tBu2‐4‐MeC6H2)‐κO]2HOPO(OBu)(O‐2,6‐tBu2‐4‐MeC6H2)‐κO]2}·2C7H16, Cr2(C19H32O4P)4(C19H33O4P)2(OH)2]·2C7H16, denoted ( 1 )·2(heptane), μ‐bis(2,6‐diisopropylphenyl) phosphato‐1κO:2κO′]bisbis(2,6‐diisopropylphenyl) phosphato]‐1κO,2κO‐chlorido‐2κCl‐triethanol‐1κ2O,2κO‐di‐μ‐ethanolato‐1κ2O:2κ2O‐dichromium(Cr—Cr) ethanol monosolvate or {Cr2(μ2‐OEt)2μ2‐PO2(O‐2,6‐iPr2‐C6H3)2‐κO:κO′]PO2(O‐2,6‐iPr2‐C6H3)2‐κO]2Cl(EtOH)3}·EtOH, Cr2(C2H5O)2(C24H34O4P)3Cl(C2H6O)3]·C2H6O, denoted ( 2 )·EtOH, and di‐μ‐ethanolato‐1κ2O:2κ2O‐bis{bis(2,6‐diisopropylphenyl) hydrogen phosphato‐κO]bis(2,6‐diisopropylphenyl) phosphato‐κO]chlorido(ethanol‐κO)chromium}(Cr—Cr) benzene disolvate or {Cr2(μ2‐OEt)2PO2(O‐2,6‐iPr2‐C6H3)2‐κO]2HOPO(O‐2,6‐iPr2‐C6H3)2‐κO]2Cl2(EtOH)2}·2C6H6, Cr2(C2H5O)2(C24H34O4P)2(C24H35O4P)2Cl2(C2H6O)2]·2C6H6, denoted ( 3 )·2C6H6. Complexes ( 1 )–( 3 ) have been synthesized by an exchange reaction between the in‐situ‐generated corresponding lithium or potassium disubstituted phosphates with CrCl3(H2O)6 in ethanol. The subsequent crystallization of ( 1 ) from heptane, ( 2 ) from ethanol and ( 3 ) from an ethanol/benzene mixture allowed us to obtain crystals of ( 1 )·2(heptane), ( 2 )·EtOH and ( 3 )·2C6H6, whose structures have the monoclinic P21, orthorhombic P212121 and triclinic P space groups, respectively. All three complexes have binuclear cores with a single Cr—Cr bond, i.e. Cr2O6P2 in ( 1 ), Cr2PO4 in ( 2 ) and Cr2O2 in ( 3 ), where the Cr atoms are in distorted octahedral environments, formally having 16 ē per Cr atom. The complexes have bridging ligands μ2‐OH in ( 1 ) or μ2‐OEt in ( 2 ) and ( 3 ). The organophosphate ligands demonstrate terminal κO coordination modes in ( 1 )–( 3 ) and bridging μ2‐κO:κO′ coordination modes in ( 1 ) and ( 2 ). All the complexes exhibit hydrogen bonding: two intramolecular Ophos…H—Ophos interactions in ( 1 ) and ( 3 ) form two {HPO2(OR)2]2} associates; two intramolecular Cl…H—OEt hydrogen bonds additionally stabilize the Cr2O2 core in ( 3 ); two intramolecular Ophos…H—OEt interactions and two O…H—O intermolecular hydrogen bonds with a noncoordinating ethanol molecule are observed in ( 2 )·EtOH. The presence of both basic ligands (OH? or OEt?) and acidic H(phosphate)2]? associates at the same metal centres in ( 1 ) and ( 3 ) is rather unusual. Complexes may serve as precatalysts for ethylene polymerization under mild conditions, providing polyethylene with a small amount of short‐chain branching. The formation of a small amount of α‐olefins has been detected in this reaction. |
