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)2[μ2-PO2(OBu)(O-2,6-tBu2-4-MeC6H2)-κO:κO′]2[PO2(OBu)(O-2,6-tBu2-4-MeC6H2)-κO]2[HOPO(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′]bis­[bis­(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)2[μ2-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)2[PO2(O-2,6-iPr2-C6H3)2-κO]2[HOPO(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\overline 1 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 {H[PO2(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.

Cite: Tavtorkin A.N. , Korchagina S.A. , Komarov P.D. , Vinogradov A.A. , Churakov A.V. , Nifant'ev I.E. , Minyaev M.E.
Chromium complexes bearing disubstituted organophosphate ligands and their use in ethylene polymerization
Acta Crystallographica Section C: Structural Chemistry. 2020. V.76. N1. P.93-103. DOI: 10.1107/s2053229619015699 WOS Scopus OpenAlex

Identifiers:

≡ Web of science:	WOS:000506846200012
≡ Scopus:	2-s2.0-85077697426
≡ OpenAlex:	W2995978572

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