ISOLATION OF CHROMIUM(0) THIOLS - MOLECULAR-STRUCTURE OF (BUTSH)CR(CO)5

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 ∠Cr–S–C and ∠Cr–S–H angles are 121.3 (2) and 106°, respectively, and the Cr–S 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) Å, b = 10.918 (2) ¶, c = 17.731 (4) Å, β = 97.58 (2)°, V = 1256.0 Å3, 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 σ-donating ligands (RSH < NR3 v PR3) and as π-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 S–H 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.