ISOLATION OF CHROMIUM(0) THIOLS - MOLECULAR-STRUCTURE OF (BUTSH)CR(CO)5
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The synthesis and characterization of (RSH)Cr(CO)4L (L = CO, R = But, Pri, Et, Ph; L = PEt3, R = Ph, But) are reported as the first examples of thiols bound to zerovalent d6 metals. An X-ray crystal structure determination of (ButSH)Cr(CO)5 found minor distortions from octahedral geometry about the Cr; two carbonyls are bent below the equatorial plane by 6 in response to the bulky But group. The CrSC and CrSH angles are 121.3 (2) and 106, respectively, and the CrS distance of 2.439 (2) A is significantly shorter than that of the anion, (ButS)Cr(CO)5 (2.479 (1) A). The complex crystallized in the monoclinic space group P21/n, with a = 6.545 (2) , b = 10.918 (2) , c = 17.731 (4) , = 97.58 (2), V = 1256.0 3, and Z = 4. Restricted force field calculations (Cotton-Kraihanzel approximation) of the CO stretching force constants are used to contrast the RSH ligands with amines and phosphines according to their ability as -donating ligands (RSH < NR3 v PR3) and as -accepting ligands (NR3 < RSH < PR3). When RSH ligands bind to the Cr(CO)5 moiety, the acidity of the thiols is moderately increased. There is no indication of SH oxidative addition of isolated (ButSH)Cr(CO)5, (PhSH)Cr(CO)s, or cis-(ButSH)Cr- (CO)4(PEt3) in solution, under either photochemical or thermal conditions. The most easily accessible reaction path is RSH ligand loss. 1990, American Chemical Society. All rights reserved.
