The crystal and molecular structure of thiocyanatobis(thiourea)silver(I)

The crystal structure of Ag[SC(NH2)2]2SCN was determined from three-dimensional diffractometer data and refined by least-squares to a conventional R factor of 0.044 for 1642 observed reflections. The compound is monoclinic (space group C2 c) with cell parameters a = 11.072(3), b = 13.838(4), c = 13.983(4) Å, β = 111.65(3)°, Z =8, dc = 2.123 g cm-3, dm = 2.11 g cm-3. Within one complex Ag(tu)2SCN unit, three S atoms of two thiourea molecules (AgS 2.482(2) and 2.462(2) Å) and of one SCN group (AgS 2.608(2) Å) are bonded to the central Ag with almost trigonal planar AgS3 coordination. One of the two thiourea S atoms is weakly coordinated to a second Ag center (AgS 3.111(2) Å), forming a dimeric complex [Ag (tu)2SCN]2 unit with Ci symmetry and with a central planar four-membered AgSAgS ring (Ag⋯Ag 3.097(1) Å, bond angles SAgS 113.9(1)° and AgSAg 66.1(1)°). The orientation of the bridging thiourea molecule suggests the contribution of electron pairs in pπ carbon-sulfur MO's besides those in sulfur sp2 orbitals to the AgS bonding system, all bridge bonds being two-electron two-center bonds. © 1976.