Treatment of fluorenone, 2,3-diphenylindenone, tetraphenylcyclopentadienone, or 2,5-diethyl-3,4-diphenylcyclopentadienone with ((trimethylsilyl)ethynyl)lithium gives, after hydrolysis, the analogous alkynol; subsequent addition of dicobalt carbonyl and then fluoroboric acid yields the corresponding fluorenyl, indenyl, or cyclopentadienyl cation stabilized by complexation to a tricarbonylcobalt moiety. Variable-temperature NMR data on these cluster cations, and on their bis(diphenylphosphino)methane derivatives, reveal that the barrier to migration of the cationic center between cobalt cluster vertices increases in the order fluorenyl < indenyl < cyclopentadienyl and suggest that the cations with more antiaromatic character have the greatest need for charge delocalization onto the metal center. Replacement of a Co(CO)3 cationic fragment by an Fe(CO)3 unit yields the mixed-metal species [((fluorenyl)CCSiMe3)FeCo(CO)6] (22) and [((2,3-diphenylindenyl)CCSiMe3)FeCo(CO)6] (27). In these structural models for the cationic complexes, the Fe−C(9) distance in 22 is 2.626(11) Å, while in the indenyl system 27 the Fe−C(1) distance is 2.347(7) Å, again indicating that the 8π indenyl cation interacts more strongly with the metal center than does the 12π fluorenyl cation.

In an article in the March issue of In Practice, James Dunn outlined a stepwise process for conducting clinical audits in first-opinion small animal practice. In this article, he and Frances Dunn describe how this process might be applied to a specific aspect of small animal practice, using the prescription of fluoroquinolones as an example.

Laser flash photolysis (UV-LFP, 308 nm) of suitably substituted oxadiazolines leads to cyclohexylidene (14a), 4-tert-butyl-cyclohexylidene (14b), 2-trifluoromethylcyclohexylidene (14d), 8-aza-8methyl[3.2.1]oct-3-ylidene (14e), diethylcarbene (14f), and ethyl(methyl)carbene (14h). Carbene intermediates were inferred from the products of steady state photolyses, and their pyridinium ylides were inferred from transient absorption spectra observed when pyridine was present. Yields of the pyridinium ylides 15a-h as a function of pyridine concentration gave the lifetimes (τ) for carbenes 14a-h in cyclohexane, cyclohexane-d 12 , and benzene solutions, at 22 °C. The intermediacy of cyclohexylidene (14a) was inferred from the observation of cyclohexene formed in both the LFP and steady state (SS) experiments. The major products from dual wavelength irradiation of the oxadiazolines (at 254 and 300 nm) were those of 1,2-migration of hydrogen (1,2-H) in the corresponding carbenes. 2-Trifluoromethylcyclohexylidene gave 3-trifluoromethylcyclohexene and 1-trifluoromethylcyclohexene in a 9.8:1 ratio. The kinetic data support the conclusion that 1,2-H in the cyclohexylidenes is accelerated, relative to 1,2-H in dimethylcarbene. A 4-tert-butyl substituent has a negligible effect on the rate constant for 1,2-H, but the CF 3 group at the R-position decelerates 1,2-H by roughly 10-fold, as inferred from the distribution of products.

Two hundred and eight adults who requested outpatient treatment at a community mental health center were asked to complete brief questionnaires immediately prior to and after their first therapy session. Questionnaires contained items that pertained to self‐predicted length of stay in psychotherapy, situational barriers to regular attendance, and past behavior in similar situations (e.g., appointment‐keeping with other health care professionals). Therapists also were asked to make predictions with regard to client length of stay. Questionnaire data were analyzed via a series of double cross‐validated multiple regression and discriminant function equations, and results indicated that client and therapist predictions of length of stay in therapy were the most stable and consistent correlates of attendance behavior.